# Patent

## Title
Processes to form ethylene-based polymers using asymmetrical polyenes

## Abstract

A process to form an ethylene-based polymer including polymerizing ethylene and at least one asymmetrical polyene comprising an “alpha, beta unsaturated-carbonyl end” (“α,β-unsaturated-carbonyl end”) and a “C—C double bond end,” wherein the polymerization takes place in the presence of at least one free-radical initiator; and wherein the polymerization takes place in a reactor configuration comprising at least two reaction zones, reaction zone 1 and reaction zone i (i>2), wherein reaction zone i is downstream from reaction zone 1.

## Background
REFERENCE TO RELATED APPLICATIONS
This application is a U.S. National Stage Application under 35 U.S.C. §371 of International Application No. PCT/US2014/072138 filed on Dec. 23, 2014, which claims the benefit of U.S. Provisional Application No. 61/920,899, filed Dec. 26, 2013, and incorporated herein by reference.


BACKGROUND
Conventional low density polyethylene (LDPE) has good processability; however, when used in film and/or extrusion coating applications, increased melt strength is still desired.
U.S. Publication No. 2008/0242809 discloses a process for preparing an ethylene copolymer, where the polymerization takes place in a tubular reactor at a peak temperature between 290° C. and 350° C. The comonomer is a di- or higher functional (meth)acrylate used in an amount of 0.008-0.200 mole percent relative to the amount of ethylene copolymer.
International Publication No. WO 2007/110127 discloses an extrusion coating composition comprising an ethylene copolymer obtained by polymerization in a tubular reactor at a peak temperature of 300−350° C. The comonomer is a bifunctional α,ω-alkadiene.
International Publication No. WO 97/45465 discloses an unsaturated ethylene copolymer, a method for producing it, and its use for producing crosslinked structures. The unsaturated ethylene copolymer comprises a polymer, obtained by radical polymerization through a high-pressure process, of ethylene and at least one monomer which is copolymerizable with ethylene and includes a diunsaturated comonomer of the formula (I): H2C═CH—O—R—CH═CH2, wherein R═—(CH2)m-O—, —(CH2CH2O)n-, or —CH2-C6H10-CH2-O—, m=2-10, and n=1-5. Preferably, the comonomer of formula (I) is 1,4-butanediol divinyl ether.
International Publication No. WO 2012/057975 describes the need for polymers comprising monomeric chain transfer agents (CTAS), and showing improved melt strength and a low soluble content. International Publication No. WO 2012/084787 describes simulated tubular reactions in which bi- and/or higher functional comonomers are used to increase the long chain branching (LCB) level in the polymer. These bi- and/or higher functional comonomers have at least one vinyl group and at least one CTA group, by which LCB or T-branches can be formed, after initial incorporation into the ethylene-based Polymer, by the first functionality, and further reaction of the remaining functionality.
International Application No. PCT/US13/029881 (now WO 2014/003837) discloses an ethylene-based polymer, formed from reacting ethylene and at least one asymmetrical polyene comprising an “alpha, beta unsaturated end” and a “C—C double bond end,” wherein the reaction takes place in the presence of at least one free-radical initiator.
The impact of the above-described multifunctional components on the final polymer through coupling and/or branching reactions is complex, and depends on the type and reactivity of the functional groups. A vinyl functional group will act as a comonomer and incorporate into a polymer chain/molecule. When involved, CTA functionality will either start the formation of a new polymer molecule, or initiate, after incorporation of the monomeric group, the formation of a LCB or T-branch. For a multi- and/or bifunctional component to impact polymer rheology, it is important that (1) at least two functional groups of the component molecule react and (2) effective branches are formed in the polymer.
H-branches are either intermolecular (between two molecules) or intra-molecular (within a molecule) and formed by reaction of two or more vinyl groups of the bi- and/or multifunctional component. The probability that functional groups will react, and contribute to a melt strength increase, depends on the reactivity of the functional groups, overall, and remaining conversion level, and molecular topology of the polymer, showing how the component is incorporated by its first reacting functionality. The impact of H-branch formation on melt strength will be (1) negligible with intra-molecular 11-branch formation, (2) low for intermolecular H-branch formation between two small polymer molecules, and (3) significant for intermolecular H-branch formation between two larger molecules. However, the latter (3) could lead to the formation of gels, especially when crosslinked networks are formed between and inside large polymer molecules.
Taking into account the reaction kinetic data reported by Ehrlich and Mortimer in Adv. Polymer Sci., Vol 7, pp. 386-448 (1970), and a typical ethylene conversion level in a tubular reactor of 25-35%, the following general remarks can be made: (i) the incorporation level per reactor pass is less than 50% for hydrocarbon dienes, while the probability of forming 11-branches is less than 10%; (ii) a monomeric CTA containing acrylate monomer functionality will have a high incorporation level per reactor pass, but further reaction would be required to form a T-branch; and (iii) the probability that the CTA functionality will react, depends on chain transfer activity and remaining conversion level. For compounds with a CTA functionality similar to typically used CTAs for the high pressure LDPE process, the amount of T-branching formed would be low. Di- or higher functional (meth)acrylate components will lead to almost complete incorporation in the polymer, and a very high level of secondary reaction. The high reactivity of the functional groups makes even distribution over the polymer formed in a tubular reactor difficult. Furthermore, coupling or H-branch formation, when the component is fed to the first reaction zone, will already occur in the first reaction zone, thus increasing the risk of initiating and/or forming product gels and fouling in the first reaction zone, with further exposure and deterioration in the remaining reaction/cooling zones if present.
International Publication No. WO2013/059042 describes the use of fresh ethylene and/or CTA feed distribution to broaden molecular weight distribution (MWD) and increase melt strength, while remaining all other process conditions constant.
Liu, J., et al., Branched Polymer via Free Radical Polymerization of Chain Transfer Monomer: A Theoretical and Experimental Investigation, J. Polym. Sci. Part A: Polym. Chem., (2007), 46, 1449-59, discloses a mathematical model for the free radical polymerization of chain transfer monomers containing both polymerizable vinyl groups and telogen groups. The molecular architecture of the polymer is disclosed as being prognosticated, according to the developed model, which was validated experimentally by the homopolymerization of 4-vinyl benzyl thiol (VBT), and its copolymerization with styrene.
Wu, P-C et al, Monte Carlo simulation of structure of Low-Density Polyethylene; Ind. Eng. Chem. Prod. Res. Develop., Vol. 11, No 3, 352-357 (1972) describes modeling polymer molecule formation through consecutive branching by applying a Monte Carlo simulation.
Iedema, P. D. et al., Rheological Characterization of Computationally Synthesized Reactor Populations of Hyperbranched Macromolecules; Bivarate Seniority-Priority Distribution of IdPE, Macromolcular Theory and Simulations, 13, 400-418 (2004) shows computationally obtained seniority and priority distributions, in order to characterize LDPE, using rheological quantities, in terms of comb-shaped and Cayley tree structures.
The continuous stirred tank reactor (CSTR), or autoclave, process typically leads to more Cayley tree structured molecular polymer topology, due to the inherent, more homogeneous LCB level and chain segment size distribution, while the residence time distribution creates very long and very short growth paths, leading to a broader MWD. Furthermore, a comonomer will be homogenously incorporated within a reaction zone regardless of its reactivity. The tubular reactor process typically leads to more comb-shaped molecular polymer topology, due to the low starting LCB level and the lower temperature conditions leading to long chain segments, while the MWD is narrowed, due to the more homogenous residence time distribution. However, the lack of back mixing, as present in a CSTR reactor, or axial mixing, leads to a comonomer incorporation distribution that is strongly affected by the reactivity of the comonomer and the changing composition of reactants along the tubular reactor. Comonomers with reactivity similar to ethylene, such as vinyl acetate, will lead to homogeneous copolymers, while highly reactive comonomers, such as acrylates, will lead to strongly inhomogeneous copolymers in a tubular reactor. Incorporation in a larger polymer molecule, at a position more inside the polymer molecule sphere (higher priority and seniority in Cayley tree structure), may affect reactivity and increase the probability for an intra-molecular reaction. Incorporation in smaller (lower gyration radius), and/or linear polymer molecules (comb like structure), and/or at a position more at the outer side of polymer molecule sphere (lower priority and seniority in a Cayley tree structure), may affect the reactivity less, and increase the probability for an intermolecular reaction.
The use of highly reactive multifunctional components is also subject to other process and/or polymer concerns, such as stability of the component, premature polymerization and fouling formation potential in the compression and preheating sections, reactor fouling, gel formation in polymer, process stability potentially leading to ethylene decomposition, and the like.
International Publication No. WO 2013/149699 describes improving the purity and/or stability of non-conjugated double bonds to reduce the percentage conversion in the so-called “zero conversion test.” The “zero conversion test” simulates the polymerization and fouling potential of a non-conjugated diene in a tubular reactor preheating section, prior to starting the reaction through injection/activation of an initiator.
International Publication No. WO2013/149698 describes using an inhibitor to prevent unwanted polymerization (i.e., premature polymerization) at the preheater walls, prior to addition of the free radical initiator, when applying a non-conjugated diene. International Publication No. WO2013/132011 describes preventing preheating fouling, by feeding the non-conjugated diene after preheating the ethylene, and before starting the reaction through injection/activation with an initiator.
There remains a need for such processes that can be used in combination with coupling and/or branching components with differentiated monomeric reactivity, to form ethylene-based polymers, such as LDPE, with improved melt strength, especially for film and extrusion coating applications. There is a further need for such processes that make optimal use of the coupling and/or branching component, while avoiding and minimizing preheater fouling and gel formation. These needs and others have been met by the following invention.
SUMMARY OF THE INVENTION
The invention provides a process to form an ethylene-based polymer, said process comprising polymerizing ethylene and at least one asymmetrical polyene comprising an “alpha, beta unsaturated-carbonyl end” (“α,β unsaturated-carbonyl end”) and a “C—C double bond end,” wherein the polymerization takes place in the presence of at least one free-radical initiator; and wherein the polymerization takes place in a reactor configuration comprising at least two reaction zones, reaction zone 1 and reaction zone i (i≧2), wherein reaction zone i is downstream from reaction zone 1.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a flow diagram for a LDPE process.
FIG. 2 shows the temperature profile for the tubular configuration used in comparative polymerizations 1-2 and inventive polymerizations 1-3;
FIG. 3 shows the temperature profile for the tubular configuration used in inventive polymerizations 4-6;
FIG. 4 shows the temperature profile for the tubular configuration used in comparative polymerization 3 and inventive polymerizations 7-8;
FIG. 5 shows the incorporation frequency of polyene (bifunctional component) into locally-formed polymer versus reactor length for comparative polymerizations 1-2 and inventive polymerizations 1-2;
FIG. 6 shows the incorporation frequency of polyene (bifunctional component) into locally-formed polymer versus reactor length for inventive polymerizations 3-5;
FIG. 7 shows the incorporation frequency of polyene (bifunctional component) into locally-formed polymer versus reactor length for inventive polymerizations 6-7;
FIG. 8 shows the incorporation frequency of polyene (bifunctional component) into locally-formed polymer versus reactor length for comparative polymerization 3 and inventive polymerization 8.
FIG. 9 shows the LCB frequency in locally-formed polymer versus reactor length for comparative polymerization 1 and inventive polymerizations 5-6.
FIG. 10 shows a flow diagram for the polymerizations used for Inventive Example A′ and inventive examples 1′, 2′ and 4′.
FIG. 11 shows a flow diagram for the polymerizations used for Inventive Example 3′.
FIG. 12 shows the “simulated incorporation frequency of PPG-AEMA into locally-formed polymer versus reactor length” for Inventive Examples 1′, 3′ and 4′.



DETAILED DESCRIPTION
As discussed above, the invention provides a process to form an ethylene-based polymer, the process comprising polymerizing ethylene and at least one asymmetrical polyene comprising an “α,β unsaturated-carbonyl end” and a “C—C double bond end,” wherein the polymerization takes place in the presence of at least one free-radical initiator; and wherein the polymerization takes place in a reactor configuration comprising at least two reaction zones, reaction zone 1 and reaction zone i (i≧2), wherein reaction zone i is downstream from reaction zone 1.
In a further embodiment, the total number of reaction zones=n. In a further embodiment, n is from 2 to 20, further from 2 to 10, and further from 2 to 6.
An inventive process may comprise a combination of two or more embodiments described herein.
Asymmetrical Polyene
In one embodiment, the asymmetrical polyene is an asymmetrical diene. In an embodiment, the asymmetrical diene has an “α,β unsaturated-carbonyl end” comprising a α,β unsaturation and a carboyl group and a “C—C double bond end” comprising carbon-carbon double bond.
In one embodiment, the “α,β unsaturated-carbonyl end” of the asymmetrical polyene is selected from the group consisting of the following:




wherein R1 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3);





wherein R2 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3); R3 is selected from H, CH3, or CH2CH3; R4 is selected from H, CH3, or CH2CH3; and n is from 1 to 50, or from 1 to 20, or further from 1 to 10;





wherein R5 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3);





wherein R′5 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3); and





In the structures a)-e) above, the notation “” represents a break at the center of a covalent bond between the “α,β unsaturated-carbonyl end” of the asymmetrical polyene and the remaining chemical structure of the asymmetrical polyene.
In one embodiment, the “a, 13 unsaturated-carbonyl end” of the asymmetrical polyene is selected from the group consisting of the following: a) through d), as shown above.
In one embodiment, the “C—C double bond end” of the asymmetrical polyene is selected from the group consisting of the following:




wherein R7 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3);





wherein R8 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3);





wherein R9 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3);





wherein R10 is selected from H or OH;





wherein m=1 to 20;





wherein R11 is selected from H or OH;





wherein p=1 to 20;





wherein R12 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3); R13 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3); and R14 is selected from H, a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3) or phenyl group (Ph); and





wherein R15 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3); R16 is selected from H or a C1-C6 alkyl (preferably a C1-C3 alkyl and more preferably CH3).

In the structures 1)-25) above, the “” notation represents a break at the center of a covalent bond between the “C—C double bond end” of the asymmetrical polyene and the remaining chemical structure of the asymmetrical polyene.
In one embodiment, the “C—C double bond end” of the asymmetrical polyene is selected from the group consisting of the following: 1), 2), 3), 4), 5), 6), 7), 8), 9), 10), 11), 12), 13), 14), 15), 16) and 17), each as shown above.
In one embodiment, the “C—C double bond end” of the asymmetrical polyene is selected from the group consisting of the following: 1), 2), 3), 4), 5), 6), 7), 8), 9), 10), 11), 12), and 17), each as shown above.
In one embodiment, the “C—C double bond end” of the asymmetrical polyene is selected from the group consisting of the following: 1), 2), 3), 12), and 17) each as shown above.
In one embodiment, the “C—C double bond end” of the asymmetrical polyene is selected from the group consisting of the following: 13), 14), 15) and 16), each as shown above.
In one embodiment, the “α,β unsaturated-carbonyl end” of the asymmetrical polyene is selected from the group consisting of the following: b) and c), each as shown above, and in a further embodiment, b) wherein R3 and R4 are both H; or when R3 is CH3 or CH2CH3, then R4 is H; or when R4 is CH3 or CH2CH3, then R3 is H.
In one embodiment, the “α,β unsaturated-carbonyl end” of the asymmetrical polyene is b) as shown above. In a further embodiment, the “α,β unsaturated-carbonyl end” of the asymmetrical polyene is b) as shown above, and in a further embodiment, b) wherein R3 and R4 are both H, or when R3 is CH3 or CH2CH3, and R4 is H, or when R4 is CH3 or CH2CH3, and R3 is H.
In one embodiment, the “α,β unsaturated-carbonyl end” of the asymmetrical polyene is c) as shown above.
The reactor configuration comprises at least one reactor. In one embodiment, the asymmetrical polyene is present in the reactor in an amount greater than or equal to 100 ppm by weight, based on the total amount by weight of ethylene in the reactor. In one embodiment, the asymmetrical polyene is present in an amount less than, or equal to, 10000 ppm by weight, or less than, or equal to, 5000 ppm, or less than, or equal to, 1000 ppm, based on the total amount by weight of ethylene in the reactor.
In one embodiment, the asymmetrical polyene is selected from the group consisting of the following:




wherein n is from 1 to 50, further from 1 to 20 and further from 1 to 10; Ra is selected from H or an alkyl (preferably ethyl or methyl and more preferably methyl); Rb is selected from H or an alkyl (preferably ethyl or methyl and more preferably methyl); and preferably wherein Ra and Rb are selected from the group consisting of (i) Ra and Rb are both H, (ii) when Ra is methyl, then Rb is H, (iii) when Ra is H, then Rh is methyl, and (iv) a combination of (ii) and (iii);





wherein m=1 to 20.

In one embodiment, the asymmetrical polyene is selected from the group consisting of i) through x), each as shown above.
In one embodiment, the asymmetrical polyene is selected from the group consisting of: i), ii), iii), iv) and v), each as shown above.
In one embodiment, the asymmetrical polyene is selected from the group consisting of: i) and v), each as shown above.
In one embodiment, the asymmetrical polyene is selected from the group consisting of: vi), vii), viii), ix) and x), each as shown above.
In one embodiment, the asymmetrical polyene is selected from the group consisting of i), as shown above.
In one embodiment, the asymmetrical polyene is polypropylene glycol allyl ether methacrylate (PPG-AEMA). (See experimental section.)
In one embodiment, the asymmetrical diene has 1H NMR signals from 3.0 to 6.5 ppm chemical shift.
In one embodiment, the “α,β unsaturated-carbonyl end” has a reactivity ratio (r1) equal to k11/k12, wherein k11, k12 and r1 are as described in Ehrlich and Mortimer, Adv. Polymer Sci., Vol. 7, pp. 386-448 (1970). In one embodiment, r1 is less than 0.8, or less than or equal to 0.5, or less than or equal to 0.3, or less than or equal to 0.1.
In one embodiment, the “C—C double bond end” has a reactivity ratio (r1) equal to k11/k12, wherein k11, k12 and r1 are as described in Ehrlich and Mortimer, Adv. Polymer Sci., Vol. 7, pp. 386-448 (1970). In one embodiment, r1 is less than 0.8, or less than or equal to 0.7, or less than or equal to 0.6, or less than or equal to 0.4.
In one embodiment, the ratio between the reactivity ratio of the “C—C double bond end” and the reactivity ratio of the “α,β unsaturated-carbonyl end” is less than 5, or less than or equal to 3, or less than or equal to 1, or less than or equal to 0.4.
In one embodiment, an inventive polymer is polymerized in the presence of at least two asymmetrical polyenes as disclosed herein. In a further embodiment, the at least two asymmetrical polyenes are asymmetrical dienes as disclosed herein.
An asymmetrical polyene may comprise a combination of two or more embodiments as described herein.
An asymmetrical diene may comprise a combination of two or more embodiments as described herein.
Ethylene-based Polymer
In one embodiment, the ethylene-based polymer is a modified low density polyethylene, comprising, in polymerized form, ethylene, and bonded chemical groups derived from the asymmetrical polyene. In a further embodiment, the modified LDPE comprises less than 2.0 wt %, further less than 1.0 wt %, of other comonomer(s), based on the weight of the modified LDPE.
In one embodiment, the ethylene-based polymer comprises at least one structure selected from the group consisting of the following A through D:




wherein n is from 1 to 50; R1 is selected from H or a C1-C6 alkyl; Ra is selected from H or methyl; Rh is selected from H or methyl; and

preferably wherein Ra and Rb are selected from the group consisting of (i) Ra and Rb are both H, (ii) when Ra is methyl, then Rb is H, (iii) when Ra is H, then Rb is methyl, and (iv) a combination of (ii) and (iii);




wherein R1 is selected from H or a C1-C6 alkyl;





wherein R1 is selected from H or a C1-C6 alkyl; and





wherein R1 is selected from H or a C1 to C6 alkyl.

In one embodiment, the ethylene-based polymer comprises at least one structure selected from structures A)-C), as shown above.
In one embodiment, the ethylene-based polymer comprises at least one structure selected from structures A) and B), as shown above.
In one embodiment, the ethylene-based polymer comprises at least one structure selected from structure A), as shown above.
In one embodiment, the ethylene-based polymer comprises at least one structure selected from structure B), as shown above.
In one embodiment, the ethylene-based polymer comprises at least one structure selected from structure C), as shown above.
In one embodiment, the ethylene-based polymer comprises at least one structure selected from structure D), as shown above.
In the above structures A) through D), the “” notation represents a break at the center of a covalent carbon-carbon bond in the hydrocarbon backbone of the ethylene-based polymer.
In one embodiment, the ethylene-based polymer comprises, in reacted form, greater than or equal to 0.015 moles of the asymmetrical polyene per 1000 moles of carbon atoms incorporated into the polymer, or, in other words, per 500 moles of ethylene units incorporated into the polymer. In a further embodiment, the asymmetrical polyene is an asymmetrical diene.
In one embodiment, the ethylene-based polymer comprises, in reacted form, less than or equal to 10 moles, or less than or equal to 5 moles, or less than or equal to 2 moles, or less than or equal to 1 mole of asymmetrical polyene per 1000 moles of carbon atoms incorporated into the polymer, or, in other words, per 500 moles of ethylene units incorporated into the polymer. In a further embodiment, the asymmetrical polyene is an asymmetrical diene.
In one embodiment, the ethylene-based polymer comprises, in reacted form, at least 0.03 weight percent of the asymmetrical polyene, based on the weight of the polymer. In a further embodiment, the asymmetrical polyene is an asymmetrical diene as described herein.
In one embodiment, the ethylene-based polymer has a melt index (I2) from 0.1 to 100 g/10 min, or from 0.1 to 50 g/10 min, or from 0.1 to 30 g/10 min. In one embodiment, the ethylene-based polymer has an I2 from 0.3 to 100 g/10 min, or from 0.3 to 50 g/10 min, or from 0.1 to 30 g/10 min, or from 0.3 to 30 g/10 min, or from 0.5 to 30 g/10 min, or from 1.0 to 10 g/10 min. In one embodiment, the ethylene-based polymer has an I2 from 0.3 to 100 g/10 min, or from 1 to 50 g/10 min, or from 2 to 20 g/10 min, or from 2 to 10 g/10 min.
In one embodiment the ethylene-based polymer has a density greater than or equal to 0.910, or greater than or equal to 0.914, or greater than or equal to 0.916 grams per cubic centimeter (g/cc or g/cm3).
In one embodiment the ethylene-based polymer has a density less than or equal to 0.940, or less than or equal to 0.935, or less than or equal to 0.932 g/cc.
In one embodiment the ethylene-based polymer has a density from 0.910 to 0.940. In one embodiment, the ethylene-based polymer has a density from 0.910 to 0.940, or from 0.915 to 0.935, or from 0.916 to 0.932 g/cc.
In one embodiment the ethylene-based polymer has a density from 0.912 to 0.940, or from 0.915 to 0.935, or from 0.920 to 0.930, or from 0.918 to 0.926 g/cc.
In one embodiment, the ethylene-based polymer has a density of from 0.916 to 0.940, or from 0.916 to 0.921, or from 0.920 to 0.924, or from 0.923 to 0.940 g/cc.
In one embodiment, the ethylene-based polymer has a density from 0.920 to 0.940 g/cc.
In one embodiment, the ethylene-based polymer has a density greater than, or equal to, 0.921 g/cc, further greater than, or equal to, 0.922 glee, further greater than, or equal to, 0.923 g/cc.
The invention also provides a composition comprising an inventive ethylene-based polymer, as described herein.
In one embodiment, the composition further comprises an ethylene/α-olefin interpolymer with a density less than or equal to 0.954 g/cc.
In one embodiment, the composition further comprises another ethylene-based polymer that differs from the inventive ethylene-based polymer in one or more properties, for example, density, melt index (I2), weight average molecular weight (Mw(abs)), number average molecular weight (Mn(conv)), and/or polydispersity index (Mw(abs)/Mn(conv)).
The invention also provides an article comprising at least one component formed from an inventive composition.
In one embodiment, the article is a film or a coating, for example, an extrusion coating.
In one embodiment, the article is a film. In another embodiment, the article is a coating.
In one embodiment, the article is a coating for a cable or wire. In one embodiment, the cable or wire is an electrical or telecommunications wire or cable.
In one embodiment, the article is a coated sheet, and in a further embodiment the sheet is selected from a metal, a paper, or another polymer substrate or combinations thereof. In a further embodiment, the coated sheet is used in a wire or cable configuration. In another embodiment, the coated sheet is used in a packaging application.
An inventive ethylene-based polymer may comprise a combination of two or more embodiments as described herein.
An inventive composition may comprise a combination of two or more embodiments as described herein.
An inventive article may comprise a combination of two or more embodiments as described herein.
Process
For producing a highly branched ethylene-based polymer, a high pressure free-radical initiated polymerization process is typically used. Two different high pressure free-radical initiated polymerization reactor types are known. In the first type, an agitated autoclave vessel having one or more reaction zones is used. The autoclave reactor normally has several injection points for initiator and/or monomer feeds. In the second type, a jacketed tube having one or more reaction zones is used as a reactor. Suitable, but not limiting, reactor lengths may be from 100 to 3600 meters (m), or from 1000 to 2800 m. The beginning of a reaction zone, for either type of reactor, is typically defined by the side injection of initiator of the reaction, ethylene, CTA (or telomer), or comonomer(s), and any combination thereof. A high pressure process can be carried out in autoclave or tubular reactors having one or more reaction zones, or in a combination of autoclave and tubular reactors, each comprising one or more reaction zones.
In an embodiment, the inventive process takes place in a reactor configuration comprising at least one autoclave and/or tubular reactor.
In one embodiment, the inventive process takes place in a reactor configuration comprising a tubular reactor.
In one embodiment, the inventive process takes place in a reactor configuration comprising a tubular reactor and an autoclave reactor. In one embodiment, the tubular reactor is downstream from the autoclave reactor.
Often a CTA is used to control molecular weight. In one embodiment, one or more CTAs are added to an inventive polymerization process. CTAs typically comprise at least one of the following groups: alkanes, aldehydes, ketones, alcohol, ether, esters, mercaptan or phosphine. In a further embodiment, a CIA comprises at least group of an alkane, an unsaturated hydrocarbon, a ketone, an aldehyde, an alcohol or ether. Preferably, a CTA is selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons, ketones, aldehydes, alcohols, ethers, esters, mercaptans and phosphines. More preferably, a CTA is selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons, ketones, aldehydes, alcohols and ethers. In an embodiment, a CTA is selected from the group consisting of saturated hydrocarbons, ketones, alcohols, ethers, esters, mercaptans and phosphines. Exemplary CTAs include, but are not limited to, propylene, isobutane, n-butane, 1-butene, methyl ethyl ketone, acetone, ethyl acetate, propionaldehyde, ISOPAR-C, -E, and -H (ExxonMobil Chemical Co.), and isopropanol; and further propylene, propionaldehyde, butane and isobutane. In one embodiment, the amount of CTA used is from 0.03 to 10 weight percent based on the weight of the total reaction mixture.
In one embodiment in which CTA is added to the polymerization, the ratio of the concentration of the CTA in the feed to reaction zone i, wherein i≧2 and reaction zone i is downstream from reaction zone 1, to the concentration of the CTA in the feed to reaction zone 1 is greater than or equal to than 1.0, or greater than 1.5, or greater than 2.
In one embodiment in which CTA is added to the polymerization, the ratio of the concentration of the CTA in the feed to reaction zone i, wherein i≧2 and reaction zone i is downstream from reaction zone 1, to the concentration of the CTA in the feed to reaction zone 1 is less than 1.0, or less than 0.8, or less than 0.6, or less than 0.4.
In one embodiment, the CTA is added to the polymerization in at least zones 1 and zone i, wherein i≧1, and wherein reaction zone i is downstream from reaction zone 1, and wherein the ratio of “the concentration of the CTA in the feed to reaction zone i” to “the concentration of the CTA in the feed to reaction zone 1” is greater than or equal to than 1.0. For example, CTA concentration units of wt % CTA, based on total weight of feed to the reaction zone.
In one embodiment, the process includes a high pressure and low pressure recycle loop to improve ethylene efficiency, since ethylene is only partially converted or consumed per reactor pass. Typically, the conversion level per reactor pass is between 12% and 40%, with conversion levels for tubular reactors being at the higher end of that range and conversion levels for autoclave reactors being at the lower end of that range.
In one embodiment, the polymerization may take place in a tubular reactor as described in international patent application PCT/US Ser. No. 12/059,469, filed Oct. 10, 2012. This patent application uses a multi-zone reactor and describes alternate locations of feeding fresh ethylene to control the ethylene to CTA ratio and therefore polymer properties. Fresh ethylene may be simultaneously added in multiple locations to achieve the desired ethylene to CTA ratio. In a similar way, addition of fresh CTA addition points may be carefully selected to control polymer properties as described in international patent application PCT/US12/064284, filed Nov. 9, 2012. Fresh CTA may be simultaneously added in multiple locations to achieve the desired CTA to ethylene ratio.
Likewise, the addition points and the amount of the fresh polyene (branching agent), as described in this application, may be controlled to control gels formation while maximizing the desired property of increased melt strength and performance in targeted applications. In one embodiment, fresh polyene may be simultaneously added in multiple locations to achieve the desired polyene to ethylene ratio (for example, a molar ratio). The use of a polyene (or branching and/or coupling agent) to broaden MWD and to increase the melt strength of the polymer will put further requirements on the distribution of the CTA and the polyene along a reactor system in order to achieve the desired change in product properties without or minimizing potential negative impacts like gel formation, reactor fouling, process instabilities, low efficiency of polyene, etc.
In one embodiment, the polymerization takes place in at least one tubular reactor. In a multi-reactor system, the autoclave reactor usually precedes the tubular reactor. The addition points and amounts of fresh ethylene, fresh CTA, and fresh polyene may be appropriately controlled to achieve the desired ratios of CTA to ethylene and polyene to ethylene in the feeds to and/or in the reaction zones.
In one embodiment, the polyene (branching agent) is an asymmetrical diene as described herein and added to the polymerization in an amount from 0.002 to 0.300 mole percent, or from 0.005 to 0.300 mole percent, based on the total moles of ethylene and asymmetrical diene added to the polymerization.
In one embodiment, the polymerization takes place in two reactors. In one embodiment, the polymerization takes place in one reactor with multiple or at least two reaction zones.
In one embodiment, the polymerization takes place in a reactor configuration comprising at least two reaction zones, reaction zone I and reaction zone i (i≧2) and wherein reaction zone i is downstream from reaction zone 1. In an embodiment, i is from 2-5, or from 2-4. In an embodiment, i=2.
In one embodiment, the total number of reaction zones=n. In a further embodiment, n is from 1 to 20, further from 1 to 10, and further from 1 to 6.
In a further embodiment, n is from 2 to 20, further from 2 to 10, and further from 2 to 6.
In one embodiment, more polyene, by mass, is added to reaction zone i as compared to the amount of polyene, by mass, added to reaction zone 1. As used above, the amount of polyene is determined based on the polyene added to a reaction zone in a fresh feed (i.e., not carry-over polyene).
In one embodiment, more polyene, by mass, is added to reaction zone 1 as compared to the amount of polyene, by mass, added to reaction zone i. As used above, the amount of polyene is determined based on the polyene added to a reaction zone in a fresh feed (i.e., not carry-over polyene).
In one embodiment, a greater concentration of polyene is added to reaction zone i as compared to the concentration of polyene added to reaction zone 1. For example, see “kg/hr amounts” in Table 9, or “wt % polyene distribution in Table 4.
In one embodiment, a greater concentration of polyene is added to reaction zone 1 as compared to the concentration of polyene added to reaction zone i. For example, see “kg/hr amounts” in Table 9, or “wt % polyene distribution in Table 4.
In one embodiment, polyene is added to both reaction zone 1 and reaction zone i.
In one embodiment, no polyene is added to reaction zone 1.
Depending on the reactivity ratios of the polyene and the distribution of polyene between reaction zones, the amount of polyene incorporated into the ethylene-based polymer in each reaction zone, and the end of the polyene (i.e., “α,β unsaturated-carbonyl end” or “C—C double bond end”) which incorporates into the ethylene-based polymer, may vary.
In one embodiment, the ratio of the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 1 to the concentration of polyene incorporated into the locally-formed polymer of reaction zone i (i≧2, or from 2 to 6, or from 2 to 5, or from 2 to 4, or equal to 2) is less than or equal to I, or less than 1, or Jess than or equal to 0.75, or less than or equal to 0.5. For example, see concentration ratios in Tables 6 and 12.
In one embodiment, the ratio of the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 1 to the concentration of polyene incorporated into the locally-formed polymer of reaction zone 2 (i=2) is less than or equal to 1, or less than 1, or less than or equal to 0.75, or less than or equal to 0.5. In a further embodiment, a majority amount of polyene incorporated into the ethylene-based polymer is incorporated through the “α,β unsaturated-carbonyl end.” For example, see concentration ratios in Tables 6 and 12.
In one embodiment, the ratio of the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 1 to the concentration of polyene incorporated into the locally-formed polymer of reaction zone i+1 (wherein I is from 2 to n−1, and n=the total number of reaction zones) is less than 1, or less than 1, or less than or equal to 0.75, or less than or equal to 0.5.
In one embodiment, the ratio of the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 1 to the concentration of polyene incorporated into the locally-formed polymer of reaction zone i (i=2 to n−1, wherein n is the total number of reaction zones) is less than or equal to 1, or less than 1, or less than or equal to 0.75, or less than or equal to 0.5, and the ratio of the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 1 to the concentration of polyene incorporated into the locally-formed polymer of reaction zone i+1 is less than 1, or less than 1, or less than or equal to 0.75, or less than or equal to 0.5. In a further embodiment, a majority amount of polyene incorporated into the ethylene-based polymer is incorporated through the “α,β unsaturated-carbonyl end.”
In one embodiment, the ratio of the concentration of the polyene incorporated into the locally-formed polymer of reaction zone i+1 (i is from 2 to n−1 and n is the total number of reaction zones) to the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 2 is less than or equal to 1, or less than 1, or less than or equal to 0.7, or less than or equal to 0.5. In a further embodiment, a majority amount of polyene incorporated into the ethylene-based polymer is incorporated through the “a, i3 unsaturated-carbonyl end.”
In one embodiment, prior to being fed into a reaction zone, polyene is fed through a compression stage of a secondary compressor. In an embodiment, polyene is fed through a compression stage of a secondary compressor prior to being fed into each reaction zone which receives polyene. In another embodiment, polyene is fed through a compression stage directly into a reaction zone or directly into the feed for a reaction zone. The choice of feed point into the reaction and/or a reaction zone depends on several factors, including, but not limited to, the solubility of the polyene in pressurized ethylene and/or solvent, the condensation of the polyene in pressurized ethylene, and/or the pre-heater fouling by premature polymerization of the polyene.
In an embodiment, the concentration of polyene in the total ethylene feed to the reactor is less than 0.2 mole percent, or less than 0.1 mole percent, or less than 0.05 mole percent, or less than 0.025 mole percent based on the total moles of ethylene fed to the reactor.
In one embodiment, the ethylene fed to the first reaction zone is at least 10 percent of the total ethylene fed to the polymerization. In one embodiment, the ethylene fed to the first reaction zone is from 10 to 100 percent, or from 20 to 80 percent, or from 25 to 75 percent, or from 30 to 70 percent, or from 40 to 60 percent of the total ethylene fed to the polymerization.
In one embodiment, the ethylene-based polymer comprises ethylene and one or more comonomers, and preferably one comonomer. Comonomers include, but are not limited to, α-olefins, acrylates, methacrylates and anhydrides, each typically having no more than 20 carbon atoms. The α-olefin comonomers, which have a combined monomer and CTA functionality, may have 3 to 10 carbon atoms, or in the alternative, the a-olefin comonomers may have 3 to 8 carbon atoms. Exemplary a-olefin comonomers include, but are not limited to, propylene, 1 butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 4 methyl-1-pentene and combinations thereof. Preferably, the a-olefin comonomers are selected from propylene, 1-butene and combinations thereof.
In one embodiment, the ethylene-based polymer comprises ethylene and at least one asymmetrical polyene as the only monomeric units.
In one embodiment, polyene is added prior to, or simultaneously with, the addition of free-radical initiator at the inlet of the reaction zone. Preferably, the polyene is added prior to the initiator addition to allow for a good dispersion of the polyene.
Free radical initiators are generally used to produce the inventive ethylene-based polymers. A free radical initiator, as used here, refers to a free radical generated by chemical and/or radiation means. Exemplary free radical initiators include organic peroxides including, but not limited to, cyclic peroxides, diacyl peroxides, dialkyl peroxides, hydroperoxides, peroxycarbonates, peroxydicarbonates, peroxyesters, and peroxyketals. Preferred initiators are t-butyl peroxy pivalate, di-t-butyl peroxide, t-butyl peroxy acetate and t-butyl peroxy-2-hexanoate, or mixtures thereof. In one embodiment, these organic peroxide initiators are used in an amount from 0.001 to 0.2 wt %, based upon the weight of polymerizable monomers.
In one embodiment, an initiator is added to at least one reaction zone and the initiator has a half-life temperature at one second greater than 255° C., preferably greater than 260° C. In a further embodiment, such initiators are used at a peak polymerization temperature from 320° C. to 350° C. In a further embodiment, the initiator comprises at least one peroxide group incorporated in a ring structure. Examples of such initiators include, but are not limited to, TRIGONOX 301 (3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonaan) and TRIGONOX 311 (3,3,5,7,7-pentamethyl-1,2,4-trioxepane), both available from Akzo Nobel, and HMCH-4-AL (3,3,6,6,9,9-hexamethyl-1,2,4,5-tetroxonane) available from United Initiators. See also International Publication Nos. WO 02/14379 and WO 01/68723.
In one embodiment, for the polymerization process described herein, the maximum (or peak) temperature for each reaction zone is from 150° C. to 360° C., or from 170° C. to 350° C., or from 200° C. to 340° C. In a further embodiment, the maximum temperature for each reaction zone which receives fresh polyene (i.e., new and/or recycled polyene, not including carry-over polyene) is from 260° C. to 330° C., or from 270° C. to 320° C., or from 280° C. to 310° C.
In one embodiment, the maximum temperature in the first reaction zone is greater than the maximum temperature for each subsequent or consecutive reaction zone.
In one embodiment, the maximum temperature in the first reaction zone is at least greater than 300° C., or at least greater than 310° C., or at least greater than 320° C.
In one embodiment, the maximum temperature in the first reaction zone is at least 10° C., or at least 20° C., or at least 30° C. greater than the maximum temperature of each consecutive reaction zone.
In one embodiment, the maximum temperature of the last reaction zone is less than the maximum temperature of each prior reaction zone.
In one embodiment, the polymerization pressure as measured at the first inlet of the reactor is from 1000 bar to 3600 bar, or from 1200 bar to 3500 bar, or from 1500 to 3400 bar, or from 2000 to 3200 bar.
In one embodiment, the polyene is subject to an “oxygen removal step” prior to being fed to a reaction zone.
In one embodiment, the polyene is stored in a feed vessel, and wherein the feed vessel has a “head-space gas” comprising less than 5.0 volume percent oxygen.
A process for forming an ethylene-based polymer may comprise a combination of two or more embodiments as described herein.
Additives
An inventive composition may comprise one or more additives. Additives include, but are not limited to, stabilizers, plasticizers, antistatic agents, pigments, dyes, nucleating agents, fillers, slip agents, fire retardants, processing aids, smoke inhibitors, viscosity control agents and anti-blocking agents. The polymer composition may, for example, comprise less than 10% of the combined weight of one or more additives, based on the weight of the inventive polymer.
In one embodiment the polymers of this invention are treated with one or more stabilizers, for example, antioxidants, such as IRGANOX 1010, IRGANOX 1076 and IRGAFOS 168. In general, the polymers are treated with one or more stabilizers before extrusion or other melt processes.
An inventive composition may further comprise at least one other polymer, in addition to an inventive ethylene-based polymer. Blends and mixtures of the inventive polymer with other polymers may be prepared. Suitable polymers for blending with the inventive polymers include natural and synthetic polymers. Exemplary polymers for blending include propylene-based polymers (both impact modifying polypropylene, isotactic polypropylene, atactic polypropylene, and random propylene/ethylene copolymers), various types of ethylene-based polymers, including high-pressure, free-radical LDPE, heterogeneously branched LLDPE (typically via Ziegler-Natta catalysis), homogeneously branched linear or substantially linear PE (typically via single-site, including metallocene catalysis), including multiple reactor PE (“in-reactor” compositions of heterogeneously branched PE and homogeneously branched PE, such as products disclosed in U.S. Pat. No. 6,545,088 (Kolthammer et al.); U.S. Pat. No. 6,538,070 (Cardwell, et al.); U.S. Pat. No. 6,566,446 (Parikh, et al.); U.S. Pat. No. 5,844,045 (Kolthammer et al.); U.S. Pat. No. 5,869,575 (Kolthammer et al.); and U.S. Pat. No. 6,448,341 (Kolthammer et al.)), ethylene-vinyl acetate (EVA), ethylene/vinyl alcohol copolymers, polystyrene, impact modified polystyrene, ABS, styrene/butadiene block copolymers and hydrogenated derivatives thereof (SBS and SEBS), and thermoplastic polyurethanes. Other ethylene-based polymers include homogeneous polymers, such as olefin plastomers and elastomers (for example, polymers available under the trade designations AFFINITY Plastomers and ENGAGE Elastomers (The Dow Chemical Company) and EXACT (ExxonMobil Chemical Co.)). Propylene-based copolymers (for example, polymers available under the trade designation VERSIFY Plastomers & Elastomers (The Dow Chemical Company) and VISTAMAXX (ExxonMobil Chemical Co.) can also be useful as components in blends comprising an inventive polymer.
Applications
The polymers, polymer blends and compositions of this invention may be employed in a variety of conventional thermoplastic fabrication processes to produce useful articles, including extrusion coating onto various substrates (for example, paper, cardboard, a metal); monolayer and multilayer films; molded articles, such as blow molded, injection molded, or rotomolded articles; coatings; fibers; and woven or non-woven fabrics.
An inventive polymer may be used in a variety of films, including but not limited to, clarity shrink films, collation shrink films, cast stretch films, silage films, stretch hood, sealants, and diaper backsheets.
Other suitable applications include, but are not limited to, wires and cables, gaskets and profiles, adhesives; footwear components, and auto interior parts.
DEFINITIONS
Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percents are based on weight, and all test methods are current as of the filing date of this application.
The term “composition,” as used herein, includes a mixture of materials, which comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.
The terms “blend” or “polymer blend,” as used, refers to a mixture of two or more polymers. A blend may or may not be miscible (not phase separated at molecular level). A blend may or may not be phase separated. A blend may or may not contain one or more domain configurations, as determined from transmission electron spectroscopy, light scattering, x-ray scattering, and other methods known in the art. The blend may be effected by physically mixing the two or more polymers on the macro level (for example, melt blending resins or compounding), or the micro level (for example, simultaneous forming within the same reactor).
The term “polymer” refers to a compound prepared by polymerizing monomers, whether of the same or a different type. The generic term polymer thus embraces the term homopolymer (which refers to polymers prepared from only one type of monomer with the understanding that trace amounts of impurities can be incorporated into the polymer structure), and the term “interpolymer” as defined below. Trace amounts of impurities may be incorporated into and/or within the polymer.
The term “interpolymer” refers to polymers prepared by the polymerization of at least two different types of monomers. The generic term interpolymer includes copolymers (which refers to polymers prepared from two different monomers), and polymers prepared from more than two different types of monomers.
The term “ethylene-based polymer” refers to a polymer that comprises a majority amount of polymerized ethylene, based on the weight of the polymer, and, optionally, at least one comonomer.
The term “ethylene-based interpolymer” refers to an interpolymer that comprises a majority amount of polymerized ethylene, based on the weight of the interpolymer, and at least one comonomer.
The term “ethylene-based copolymer” refers to a copolymer that comprises a majority amount of polymerized ethylene, based on the weight of the interpolymer, and a comonomer as the only monomer types.
The term “propylene-based polymer” refers to a polymer that comprises a majority amount of polymerized propylene, based on the weight of the polymer, and, optionally, at least one comonomer.
The term “polyene,” as used herein, refers to a poly-unsaturated compound having two or more carbon-carbon double bonds.
The terms “rheology modifier” or “rheology modifying agent,” as used herein, refer to the polyenes, as described herein, which are able to change the rheology of the polymer, for example, increase G′ and melt strength, when incorporated into the polymer.
The term “alkyl,” as used herein, refers to a saturated linear, cyclic, or branched hydrocarbon group. Nonlimiting examples of suitable alkyl groups include, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, i-butyl (or 2-methylpropyl), etc. In one embodiment, the alkyls have 1 to 20 carbon atoms.
The term “high pressure polymerization process,” as used herein, refers to a free radical polymerization process carried out at an elevated pressure of at least 1000 bar (100 MPa).
The term “mass fraction,” as used herein, refers to the mass ratio of one component in a mixture to the total mass of the mixture. Mass fraction can be determined by calculating the ratios between mass amounts or mass flows.
The terms “feed” or “feed stream,” as used herein, refer to fresh and/or recycled reactant added to a reaction zone at an inlet. A feed may consist of polyene or ethylene, comprise polyene or ethylene, or comprise polyene and ethylene.
The terms “side stream” or “side feed stream,” as used herein, refer to the ethylene-rich feed stream to sequential reaction zones.
The term “make-up,” when used herein in reference to a reactant (i.e., “make-up ethylene,” “make-up CTA,” “make-up polyene,” etc.), refers to the feed stream of the reactant needed to compensate for the converted and/or lost reactant in the high polymerization process.
The term “fresh,” when used herein in reference to a reactant (i.e., “fresh ethylene,” “fresh polyene”), refers to reactant provided from an external source(s) and not provided internally from a recycled source(s). For example, in an embodiment, fresh ethylene is used as “make-up ethylene” required to compensate for the ethylene consumed by the polymerization and/or lost through, for example, purge from the process and residual ethylene in the polymer.
The term “reaction zone,” as used herein, refers to a reactor zone where polymerization reaction is initiated or reinitiated by the addition of free radicals or components which dissociate into and/or generate free radicals. Typically, the reaction medium is heated and/or cooled by a heat transfer medium flowing through the jacket around the reactor. A reaction zone may also start with the addition of fresh ethylene and/or free radicals or components which dissociate into and/or generate free radicals.
The term “first reaction zone,” as used herein, refers to the first reactor zone where the polymerization is initiated by the addition of radicals or components which dissociate into and/or generate radicals. The first reaction zone ends at the point where there is a new feed of fresh and/or recycled ethylene, radicals, and/or components which dissociate into and/or generate radicals.
The terms “subsequent reaction zone,” or “sequential reaction zone,” as used herein, refer to a reactor zone which receives ethylene and polymer from a previous reactor zone, and where radicals or components which dissociate into and/or generate radicals are added at the inlet of the subsequent (or sequential) reactor zone. The subsequent (or sequential) reaction zone ends at the point where there is a new feed of fresh and/or recycled ethylene, radicals, and/or components which dissociate into and/or generate, radicals; however, the nth reaction zone ends at the position of a pressure control device of the reactor system. The number of subsequent (or sequential) reaction zones is (n−1), where n is the total number of reaction zones.
The terms “CTA activity” and “chain transfer activity coefficient (Cs value)” as used herein, refer to the ratio between the “rate of chain transfer” to the “rate of ethylene propagation.” See Mortimer references provided on page 34.
The Booster compressor (Booster) is a device that compresses the following: a) the low pressure recycle coming from the LPS (Low pressure Separator), and b) optionally, the recycled compressor packing leaks, each to the pressure level required at the inlet side of the Primary compressor. This compression can take place in one or multiple compression stages, and can be combined with intermediate cooling. A Booster can consist of single or multiple compressor frames, and can be potentially combined with Primary compressor frame(s).
The Primary compressor (Primary) is a device that compresses the following: a) the fresh incoming ethylene, and/or b) the low pressure recycle coming from the Booster, and/or c) the recycled compressor packing leaks, each to the pressure level required at the inlet side of the Hyper compressor. This compression can take place in one or multiple compression stages, and can be combined with intermediate cooling. The Primary can consist of single or multiple compressor frames, and can be potentially combined with Booster compressor frame(s).
Hyper compressor (Hyper), or Secondary compressor, is a device that compresses the following: a) the ethylene coming from the HPR (High Pressure Recycle), and/or b) the Primary, each to a pressure level required to feed the reactor at its inlet pressure set point. This compression can take place in one or multiple compression stages, and can be combined with intermediate cooling. The Hyper comprises a plunger reciprocating compressor, and can consist of single or multiple compressor frame(s).
The term “locally-formed polymer,” as used herein, refers to a polymer product produced in a given reaction location, for example, a given reaction zone. The locally-formed polymer may consist of new polymer molecules or new polymer added as long chain branches to already formed polymer molecules.
The terms “comprising,” “including,” “having,” and their derivatives, are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term “comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, “consisting essentially of” excludes from the scope of any succeeding recitation any other component, step, or procedure, excepting those that are not essential to operability.
The term “consisting of” excludes any component, step, or procedure not specifically delineated or listed.
Test Methods
Density—Samples that were measured for density were prepared according to ASTM D4703: Annex A: Method C. Samples were pressed at 190° C. and 3,000 psi for five minutes, 15 tons for two minutes, and then cooled, under pressure, at 15° C./min. Density measurements were made after conditioning at 23° C. and 50% R.H. for 40 hours, prior to testing, using ASTM D792 Method B.
Melt Index—Melt index, or 12, was measured in accordance by ASTM D 1238, Condition 190° C./2.16 kg, and was reported in grams eluted per 10 minutes. The 110 was measured in accordance with ASTM D 1238, Condition 190° C./10 kg, and was reported in grams eluted per 10 minutes.
GPC Method: Triple Detector Gel Permeation Chromatography (TDGPC)-Conventional GPC Data—A Triple Detector Gel Permeation Chromatography (3D-GPC or TDGPC) system consisting of a Polymer Laboratories (now Agilent) high temperature chromatograph Model 220, equipped with a 2-angle laser light scattering (LS) detector Model 2040 (Precision Detectors, now Agilent), an IR-4 infra-red detector from Polymer Char (Valencia, Spain), and a 4-capillary solution viscometer (DP) (Visotek, now Malvern) is used. Data collection is performed using Polymer Char DM 100 data acquisition box and related software (Valencia, Spain). The system is also equipped with an online solvent degassing device from Polymer Laboratories (now Agilent).
High temperature GPC columns consisting of four 30 cm, 20 urn mixed A LS columns from Polymer Laboratories (now Agilent) are used. The sample carousel compartment is operated at 140° C., and the column compartment is operated at 150° C. The samples are prepared at a concentration of 0.1 grams of polymer in 50 milliliters of solvent. The chromatographic solvent and the sample preparation solvent is 1,2,4-trichlorobenzene (TCB) containing 200 ppm of 2,6-di-tert-butyl-4methylphenol (BHT). The solvent is sparged with nitrogen. The polymer samples are gently stirred at 160° C. for four hours. The injection volume is 200 microliters. The flow rate through the GPC is set at 1.0 ml/minute.
Column calibration and sample molecular weight calculations are performed using Polymer Char “GPC One” software. Calibration of the GPC columns is performed with 21 narrow molecular weight distribution polystyrene standards. The molecular weights of the polystyrene standards range from 580 to 8,400,000 g/mol, and are arranged in 6 “cocktail” mixtures, with at least a decade of separation between the individual molecular weights.
The peak molecular weights of polystyrene standards are converted to polyethylene molecular weights using the following equation (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)): Mpolyethylene=A(Mpolystyrene)B. Here, B has a value of 1.0, and the experimentally determined value of A is around 0.38 to 0.44.
The column calibration curve is obtained by fitting a first order polynomial to the respective polyethylene-equivalent calibration points, obtained from the above equation to the observed elution volumes.
The conventional number and weight-average molecular weights (Mn(conv) and Mw(conv), respectively) are calculated according to the following equations:



  
    
      Mn
      _
    
    =
    
      
        
          ∑
          i
        
        ⁢
        
          Wf
          i
        
      
      
        
          ∑
          i
        
        ⁢
        
          (
          
            
              Wf
              i
            
            /
            
              M
              i
            
          
          )
        
      
    
  




  
    
      
        Mw
        _
      
      =
      
        
          
            ∑
            i
          
          ⁢
          
            (
            
              
                Wf
                i
              
              *
              
                M
                i
              
            
            )
          
        
        
          
            ∑
            i
          
          ⁢
          
            Wf
            i
          
        
      
    
    ,
  



where, Wfi is the weight fraction of the i-th component and Mi is the molecular weight of the i-th component. The molecular weight distribution (MWD) is expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn).

The A value is determined by adjusting the A value in the Williams and Ward Equation, until Mw, the weight average molecular weight, calculated using the above Equation, and the corresponding retention volume polynomial, agreed with the independently determined value of Mw, obtained in accordance with a linear polyethylene homopolymer reference, with known absolute weight-average molecular weight of 115,000 g/mol as measured by LALLS, in a manner traceable to standard homopolymer polyethylene NBS1475.
The absolute weight average molecular weight (Mw(abs)) is characterized by the LS detector and IR-4 concentration detector using the following equation:




  
    
      Mw
      ⁡
      
        (
        abs
        )
      
    
    =
    
      
        K
        LS
      
      *
      
        
          ∑
          
            (
            
              LS
              i
            
            )
          
        
        
          ∑
          
            (
            
              IR
              i
            
            )
          
        
      
    
  
  ,




wherein Σ(LSi) is the response area of the LS detector, Σ(IRi) is the response area of the IR-4 detector, and KLS is the instrument constant, which is determined using a standard NIST 1475 with known concentration and certificated value for the weight average molecular weight of 52,000 g/mol.

The absolute molecular weight at each elution volume is calculated using the following equation:




  
    
      M
      
        LS
        ,
        i
      
    
    =
    
      
        K
        LS
      
      *
      
        
          LS
          i
        
        
          IR
          i
        
      
    
  
  ,




wherein KLS is the determined instrument constant, LSi and IRi are the LS and IR detector responses of the same i-th elution component.

The absolute number average and zeta average molecular weight are calculated with the following equations:



  
    
      Mn
      ⁡
      
        (
        abs
        )
      
    
    =
    
      
        K
        LS
      
      ⁢
      
        
          ∑
          
            (
            
              IR
              i
            
            )
          
        
        
          ∑
          
            
              (
              
                IR
                i
              
              )
            
            /
            
              (
              
                
                  LS
                  i
                
                
                  IR
                  i
                
              
              )
            
          
        
      
    
  




  
    
      Mz
      ⁡
      
        (
        abs
        )
      
    
    =
    
      
        K
        LS
      
      ⁢
      
        
          
            ∑
            
              
                IR
                i
              
              *
              
                
                  (
                  
                    
                      LS
                      i
                    
                    
                      IR
                      i
                    
                  
                  )
                
                2
              
            
          
          
            ∑
            
              
                IR
                i
              
              *
              
                (
                
                  
                    LS
                    i
                  
                  
                    IR
                    i
                  
                
                )
              
            
          
        
        .
      
    
  



A linear extrapolation was performed on log MLS,i—elution volume plot, when the log MLS,i data scattered, caused by low LS or IR detector responses.
Standard Method for Hexane Extractables—Polymer pellets (from the polymerization pelletization process, without further modification; approximately 2.2 grams per press) are pressed in a Carver Press at a thickness of 3.0-4.0 mils. The pellets are pressed at 190° C. for 3 minutes at 40,000 lbf. Non-residue gloves (PIP* CleanTeam* CottonLisle Inspection Gloves, Part Number: 97-501) are worn to prevent contamination of the films with residual oils from the hands of the operator. Films are cut into “1-inch by 1-inch” squares, and weighed (2.5±0.05 g). The films are extracted for two hours, in a hexane vessel, containing about 1000 ml of hexane, at 49.5±0.5° C., in a heated water bath. The hexane used is an isomeric “hexanes” mixture (for example, Hexanes (Optima), Fisher Chemical, high purity mobile phase for HPLC and/or extraction solvent for GC applications). After two hours, the films are removed, rinsed in clean hexane, and dried in a vacuum oven (80±5° C.) at full vacuum (ISOTEMP Vacuum Oven, Model 281A, at approximately 30 inches Hg) for two hours. The films are then place in a desiccators, and allowed to cool to room temperature for a minimum of one hour. The films are then reweighed, and the amount of mass loss due to extraction in hexane is calculated. This method is based on 21 CRF 177.1520 (d)(3)(ii), with one deviation from FDA protocol by using hexanes instead of n-hexane.
Method for Collection of Soluble Fraction of Hexane Extractables for GPC and Nuclear Magnetic Resonance (NMR)—The above method for standard hexane extractables is used. For analytical calculations and soluble fraction preparation for GPC testing, 2.5 g of film is used as described above. For soluble fraction preparation for NMR, 7.5 g of film is used.
The remaining hexane, including hexane used for rinse, is reduced to collect the soluble fraction. Distillation, rotovapping or other equivalent techniques for removing solvent can be used. The hexane is reduced until 100-150 milliliters of solution remains.
The remaining hexane is transferred to a pre-weighed evaporation dish. The evaporation dish is heated slightly under nitrogen until dry. Once evaporated to dryness, the dish is transferred to a room temperature vacuum oven for at least 12 hours. The weight of the residue is calculated to determine the weight percent hexane extractables. The remaining residue is analyzed by GPC and NMR.
Rheological G′—The sample used in the G′ measurement is prepared from a compression molding plaque. A piece of aluminum foil is placed on a back plate, and a template or mold is placed on top of the back plate. Approximately 12 grams of resin is placed in the mold, and a second piece of aluminum foil is placed over the resin and mold. A second back plate is then placed on top of the aluminum foil. The total ensemble is put into a compression molding press run at the following conditions: 3 min at 150° C. and 10 bar, followed by 1 min at 150° C. and 150 bar, followed by a “1.5 min” quench cooling to room temperature at 150 bar. A 25 mm disk is stamped out of the compression-molded plaque. The thickness of the disk is approximately 2.0 mm.
The rheology measurement to determine G′ is done in a nitrogen environment at 170° C. and a strain of 10%. The stamped-out disk is placed between the two “25 mm” parallel plates located in an ARES-1 (Rheometrics SC) rheometer oven, which is preheated for at least 30 minutes at 170° C., and the gap of the “25 mm” parallel plates is slowly reduced to 1.65 mm. The sample is then allowed to remain for exactly 5 minutes at these conditions. The oven is then opened, the excess sample is carefully trimmed around the edge of the plates, and the oven is closed. The storage modulus (G′) and loss modulus (G′′) of the sample are measured via a small amplitude, oscillatory shear according to a decreasing frequency sweep form 100 to 0.1 rad/s (when able to obtain a G′′ value lower than 500 Pa at 0.1 rad/s), or from 100 to 0.01 rad/s. For each frequency sweep, 1-points (logarithmically spaced) per frequency decade are used.
The data are plotted (G′ (Y-axis) versus G′′ (X-axis)) on a log-log scale. The Y-axis scale covers the range from 10 to 1000 Pa, while the X-axis scale covers the range from 100 to 1000 Pa. The Orchestrator software is used to select the data in the region where G′′ is between 200 and 800 Pa (or using at least 4 data points). The data are fit to a log polynomial model using the fit equation Y=C1+C2 In(x). Using the Orchestrator software, G′ at G′′ equal to 500 Pa is determined by interpolation.
Melt Strength—Melt strength measurements are conducted on a Gottfert Rheotens 71.97 (Göettfert Inc.; Rock Hill, S.C.) attached to a Gottfert Rheotester 2000 capillary rheometer. A polymer melt is extruded through a capillary die with a flat entrance angle (180 degrees), with a capillary diameter of 2.0 mm, and an aspect ratio (capillary length/capillary diameter) of 15.
After equilibrating the samples at 190° C. for 10 minutes, the piston is run at a constant piston speed of 0.265 mm/second. The standard test temperature is 190° C. The sample is drawn uniaxially to a set of accelerating nips, located 100 mm below the die, with an acceleration of 2.4 mm/sec2. The tensile force is recorded as a function of the take-up speed of the nip rolls. Melt strength is reported, as the plateau force (cN), before the strand breaks. The following conditions are used in the melt strength measurements: plunger speed=0.265 mm/sec; wheel acceleration=2.4 mm/sec2; capillary diameter=2.0 mm; capillary length=30 mm; and barrel diameter=12 mm.
Gel Content Measurement—
1. Apparatus: The apparatus consists of a 4-zone laboratory extruder, Model OCS ME 20, with a “150 mm ribbon die (cast film die),” a CR-8 winding unit, an air knife, and an FS-3 line scan camera (50 micron resolution; available from OCS Optical Control Systems GmbH Hullener Feld 36, 58454 Witten, Germany, or an equivalent).
2. Material-specific settings for film-manufacturing: The temperature setting for the heating zones at cylinder and die is determined for an ethylene-based polymer according to MFR-ranges in two groups, as follows:
Group 1: MFR-range 1.5-3 g/10 min (190° C./2.16 kg), temperatures: 160 (first zone)/180/180/180/180° C. (die).
Group 2: MFR-range 3-6 g/10 min (190° C./2.16 kg), temperatures: 150/150/150/150/150° C.
Preset Parameters: Rotational speed (screw): 70 rpm; Haul-off speed: 4 m/min; the cast film thickness is 76 μm±5 μm.
3. Measurement: One analysis inspects 50 parcels, where a parcel is defined as “24.6 cm3” volume of film which corresponds to a “0.324 m2” surface area for a film thickness of 76 μm.
4. Analysis: G1200=the average sum of 50 parcels of “the areas of all gels greater than 200 μm in diameter in each parcel.” Diameter of gel is determined as the diameter of a circle having equivalent area.
EXPERIMENTAL
Polymerization Simulations
A polymerization simulation model with applied reaction scheme and kinetics is described by Goto et al., as discussed above. Other reactor and product modeling frameworks are available through Aspen Plus of Aspen Technology, Inc., Burlington, Mass., USA; and PREDICI of Dr. Wulkow Computing in Technology GmbH (CiT), Rastede, Germany. Process and product responses predicted by these model frameworks are determined by the reactor parameters and the applied reaction scheme and kinetic parameters. The applied reaction scheme and kinetic parameters are described below.
The polymerization simulations were achieved with Goto LDPE simulation model as described in the following: S. Goto et al; Journal of Applied Polymer Science: Applied Polymer Symposium, 36, 21-40, 1981 (Title: Computer model for commercial high pressure polyethylene reactor based on elementary reaction rates obtained experimentally).
The kinetic data used by Goto et al. was derived from high pressure free radical polyethylene polymerization experiments performed at varying temperature, pressure and polymer concentrations as described in the following: K. Yamamoto, M. Sugimoto; Rate constant for long chain-chain branch formation in free-radical polymerization of ethylene; J. Macromol. Science-Chem., A13 (8), pp. 1067-1080 (1979). The following elementary reaction steps are described by Goto et al.: i) propagation of ethylene, ii) termination of radicals, iii) backbiting or SCB formation, iv) transfer to polymer or LCB formation, v) beta elimination of secondary radicals leading to vinyl formation, and vi) beta elimination of tertiary radicals leading to vinylidene formation.
See Table 1 for kinetic data for main reactions, where ko is the pre-exponential or frequency factor; Ea is the activation energy, reflecting the temperature dependence; and ΔV is the activation volume, reflecting the pressure dependence. All kinetic constants are from Goto et al., except the ko, Ea and ΔV values for backbiting, which have been optimized to better reflect the level of methyl branches (as analyzed by C13 NMR technique) in high pressure polyethylene, as a function of pressure and temperature conditions.







TABLE 1







Kinetic Constants for Main Reactions










Reaction
ko
Ea
ΔV





Units
m3/hr/kmol
cal/mol
cc/mol


Propagation
5.63E+11
10520
−19.7


Termination
  3E+11
3000
13


Backbiting
 2.6E+12
12130
−14


Transfer to Polymer
1.75E+12
14080
4.4


Beta Elimination of sec rad
5.82E+11
15760
−22.6


Beta Elimination of tert rad
8.51E+10
14530
−19.7









The kinetic data for selected CTAs are given in Table 2. The kinetic constants haven been calculated with the help of the kinetic constants on the Cs-value (ks/kp), as determined by Mortimer (see references at page 34), and the ethylene propagation kinetics as given by Goto et al. (see Table 1).
The polyenes have been described, and modeled, through assigning kinetic r1 and r2 reactivity ratios (see Tables 2 and 3 below). The kinetic r1 and r2 reactivity ratios are, by definition, linked to the ethylene propagation kinetics for their temperature (Ea) and pressure (ΔV) dependencies. In the simulations, it was assumed that the polyenes do not exhibit additional chain transfer activity. Furthermore, for the total consumption, incorporation and H-branch (inter- and intra-molecular) formation, it has been assumed that, after incorporation of one functional group, the reactivity of the other functional group is not affected. In reality, the reactivity of second functional group will be decreased after incorporation of the polyene through its primary functional group in a polymer molecule. However, this assumption will not affect the first part of this study, as described in Tables 4 to 6. This study focuses on the optimal incorporation and positioning of the polyene through the reaction of the first functional group, in order to optimize the use and application of the polyene, in regard to enhancement of rheological properties, and prevention or reduction of reactor and preheater fouling and gel formation in the final product. The second part of the study, comprising actual polymerization results and simulations of these, focuses on the incorporation of the rheology modifier in the polymer, and the conversion to H-branches, in order to increase melt strength and G′ values of the formed polymer. The final impact of a formed H-branch will depend on its “build-in order” and place in the molecular topology. The impact of H-branch formation on melt strength will be as follows: (1) negligible with intra-molecular H-branch formation, (2) low for intermolecular H-branch formation between two small polymer molecules, and (3) significant for intermolecular H-branch formation between two larger molecules. It is assumed that ratio inter-molecular and intra-molecular H-branch is constant for one type of polyene, while (2) is promoted by feeding the polyene to the further down reaction zone(s), while (3) is promoted by feeding the polyene more to the front reaction zone(s).







TABLE 2







Kinetic Constants for Selected CTA's


and Polyenes (Bifunctional Components)










Chain Transfer to Modifier
Reactivity Ratios













kao
Ea
ΔV
r1
r2


Component
m3/hr/kgmol
cal/mol
cc/mol
(k11/k12)
(k22/k21)















Propylene
2.20E+11
13220
−16.7
3.10
0.77


(CTA)


Propional-
1.07E+11
9720
−8.4
0.00
0.00


dehyde


(CTA)


Isobutane
3.51E+11
14020
−16.7
0.00
0.00


(CTA)


Diene bond A
0
NA
NA
0.08
12.50


(Polyene)


Diene bond B
0
NA
NA
0.40
2.50


(Polyene)





NA—not applicable













TABLE 3







Reactivity Ratios for Polyenes (Bifunctional Model Components)









Reactivity Ratios












r1
r2



r1B/r1A
(k11/k12)
(k22/k21)

















Sym bi-
Bond A
1
0.08
12.50



acrylate
Bond B

0.08
12.50



Asym-
Bond A
5
0.08
12.50



acrylate
Bond B

0.40
2.50



Sym HC
Bond A
1
1
1



diene
Bond B

1
1







Sym bi-acrylate = symmetrical bi-acrylate



Asym-acrylate = asymmetrical acrylate



Sym HC diene = symmetrical hydrocarbon diene






Chain transfer activity and comonomer reactivity scheme data are described in the following: P. Ehrlich, G. A. Mortimer, Fundamentals of the free radical polymerization of ethylene, Adv. Polymer Sci., Vol 7, 386-448 (1970); G. Mortimer, Journal of Polymer Science: Part A-1; Chain transfer in ethylene polymerization; Vol. 4, p 881-900 (1966); G. Mortimer, Journal of Polymer Science: Part A-1, Chain transfer in ethylene polymerization. Part IV. Additional study at 1360 atm and 130° C.; vol 8, p1513-1523 (1970); G. Mortimer, Journal of Polymer Science: Part A-1, Chain transfer in ethylene polymerization. Part V. The effect of temperature; vol 8, p1535-1542 (1970); G. Mortimer, Journal of Polymer Science: Part A-1, Chain transfer in ethylene polymerization Part V. The effect of pressure, vol 8, p1543-1548 (1970); and G. Mortimer, Journal of Polymer Science: Part A-1, Chain transfer in ethylene polymerization VII. Very reactive and depleteable transfer agents, vol 10, pp. 163-168 (1972).
Description of Flow Diagram
FIG. 1 shows a generalized flow scheme of a simulated high pressure polymerization plant configuration containing a tubular reactor. Stream (1) is the fresh ethylene make-up, which is compressed together with the outlet of the Booster by the Primary to stream (2). Stream (2) is combined with high pressure recycle stream (18) and distributed over the suction inlets of the Hyper. The Hyper pressurizes the ethylene feed streams to a level sufficient to feed the high pressure tubular reactor (Reactor). Although not depicted, the flow scheme could include partial combination and/or distribution of the stream (2) and stream (18) over the inlets of the Hyper.
Stream (4) and/or (5) depicts the CTA system make-up feed. The CTA make-up can, in principle, be freely distributed over the main compression streams fed and/or distributed over the side stream (8) and front stream (9). CTA make-up streams (4) and/or (5) can be fed in the inlet(s), interstage(s), outlet(s) of the Hyper and/or inlet(s) of the reaction zones. The CTA system can consist of single and/or multiple components and include varying compositions.
Stream (6) and/or stream (7) depict the polyene feed. The polyene feed can, in principle, be freely distributed over the main compression streams fed to and/or distributed over the side stream (8) and/or front stream (9). Polyene streams (6) and/or (7) can be fed in the inlet(s), interstage(s), outlet(s) of the Hyper, individual ethylene feed streams to the reactor, and/or directly into the reaction zones. The discharge temperature of the Hyper is typically in the range of 60 to 100° C. The ethylene feed to the first reaction zone is typically preheated to a temperature from 130 to 180° C., while the ethylene of the side feed is fed to the reactor at the Hyper discharge temperature or cooled prior to feeding to the reactor.
The dimensions and configuration of the Reactor are given in Table 4. In the Reactor, the polymerization is initiated with the help of free radical initiation systems, injected and/or activated at the inlet of each reaction zone. The maximum temperature in each reaction zone is controlled at a set point by regulating the concentration and/or feed amount of initiation system at the start of each reaction zone. After finishing the reaction, and having applied multiple cooling steps, the reaction mixture is depressurized and/or cooled in (10), and separated in the high pressure separator (HPS). The HPS separates the reaction mixture into an ethylene rich stream (15), containing minor amounts of waxes and/or entrained polymer, and a polymer rich stream (11) which is sent for further separation to the LPS. Ethylene stream (15) is cooled and cleaned in stream (17). Stream (16) is a purge stream to remove impurities and/or inerts.
The polymer separated in LPS is further processed in (12). The ethylene removed (13) in the LPS is fed to the Booster, where, during the compression, condensables such as solvent, lubrication oil and others are collected and removed through stream (14). The outlet of the Booster is combined with make-up ethylene stream (1), and further compressed by the Primary.
General Polymerization Conditions Used in Comparative and Inventive Polymerizations
All comparative and inventive polymerizations have been simulated, with an overall concentration of 100 mole ppm branching agent (polyene), in the overall ethylene feed, while the melt index (I2) of the final product was kept at 4 dg/min by adjusting the CTA concentration in the simulations.
Reactor and Feed Configurations Used in Comparative and Inventive Polymerizations
Table 4 shows the reactor configuration (i.e., dimensions, lay-out, applied ethylene feed, polyene feed distribution) used for the simulated comparative and inventive polymerizations. The feed distributions show the percent of total ethylene or polyene feed stream fed to each reaction zone.
The notation “100/0/0/0” means that all the total ethylene or polyene feed is fed to the first reaction zone, while no fresh feed streams are fed to the second, third and fourth reaction zones. The ethylene or polyene received in the second, third and fourth reaction zones is carry-over from the previous reaction zones. Likewise, the notations “65/35/0/0” and “35/65/0/0” mean that 65% of the total ethylene or polyene feed is fed to the first reaction zone (or second reaction zone) and 35% of the total ethylene or polyene feed is fed to the second reaction zone (or first reaction zone) while no fresh feed streams are fed to the third and fourth reaction zones. The ethylene or polyene received in the third and fourth reaction zones is carry-over from previous reaction zones.
The notation “25/25/50/0/0” means that 25% of the total ethylene or polyene feed is fed to the first and second reaction zones and 50% of the total ethylene or polyene feed is fed to the third reaction zone, while no fresh feed streams are fed to the fourth and fifth reaction zones. The ethylene or polyene received in the fourth and fifth reaction zones is carry-over from previous reaction zones.
Further columns give information on pressure level and start temperature at the inlet of the first reaction zone, the ethylene feed temperature when a side ethylene feed stream is applied, and the maximum or peak temperatures in each reaction zone (Rx). The last columns of Table 4 indicate the type and the reactivity ratio of the simulated polyene.
The reactor temperature profiles are given in FIGS. 2 to 4. In these diagrams, all reaction zones have one cooling section; however, multiple cooling sections, with counter- or co-current heat transfer media, operating at differentiated inlet temperatures may be used.
Different cooling and/or heating media can be applied for the reactor cooling and/or preheating sections. The cooling/heating media comprise water, pressurized water (temperature level can be varied), condensate, boiling condensate, etc. The temperature of the cooling media is typically in the range of 0 to 220° C., while the temperature for preheating services is typically in the range of 100 to 250° C. The cooling/heating is applied through jackets around the high pressure tubes by co-current or counter-current flow. Single or multiple cooling and/or heating zones can be applied in the reactor or in a reaction zones. In the simulations the cooling/preheating was applied by counter-current and with one cooling section per reaction zone.
Discussion of Results:
Table 5 shows the simulated levels of ethylene and polyene (branching agent) conversion, the SCB and LCB frequency in polymer, and how the polyene is incorporated into the polymer. Incorporation through B functionality leads to an internal (available) double bond A (IDBA), while incorporation through A functionality leads to an internal (available) double bond B (IDBB).







TABLE 4







Reactor Configurations, Feed Modes, Process Conditions and Polyenes


Used in Comparative and Inventive Polymerizations


















Ethylene
Polyene

Start








feed
feed
Reactor
temp.
Temp. of
Max.





# of
distribution
distribution
inlet
in Rx-
Ethylene
temp. in





Rx-
over Rx-
over Rx-
pressure
zone 1
side feed
Rx-
Polyene




zones
zones (wt %)
zones (wt %)
(bar)
(° C.)
(° C.)
zones
functionality
r1B/r1A










Comparative Polymerizations (CP) 1-2 and Inventive Polymerizations (IP) 1-2:


Inside tube diameter (60 mm) and Rx-zone length (distribution): 1600 m (400-400-400-400 m)
















CP1
4
100/0/0/0
100/0/0/0
2500
150
—
All 290
Sym bi-
1










acrylate



CP2
4
100/0/0/0
100/0/0/0
2500
150
—
All 290
Sym HC
1










diene



IP1
4
100/0/0/0
100/0/0/0
2500
150
—
All 290
Asym-
5










acrylate



IP2
4
100/0/0/0
 50/50/0/0
2500
150
—
All 290
Asym-
5










acrylate








Inventive Polymerization (IP) 3:


Inside tube diameter 50-60-60-60 mm and Rx-zone length (distribution): 1600 m (300-500-400-400 m)
















IP3
4
 65/35/0/0
 0/100/0/0
2500
150
80
All 290
Asym-
5










acrylate








Inventive Polymerizations (IP) 4-6:


Inside tube diameter 40-60-60-60 mm and Rx-zone length (distribution): 1600 m (200-500-500-400 m)
















IP4
4
 35/65/0/0
 0/50/50/0
2500
150
80
All 290
Asym-
5










acrylate



IP5
4
 35/65/0/0
 0/100/0/0
2500
150
80
All 290
Asym-
5










acrylate



IP6
4
 35/65/0/0
 0/100/0/0
2500
150
80
330/290/
Asym-










290/290
acrylate
5







Comparative Polymerization (CP) 3 and Inventive Polymerizations (IP) 7-8:


Inside tube diameter 35-50-60-60-60 mm and Rx-zone length (distribution): 1700 m (150-150-500-500-400 m)
















CP3
5
 25/25/50/0/0
 25/25/50/0/0
2500
150
80
All 290
Sym bi-
1










acrylate



IP7
5
 25/25/50/0/0
 25/25/50/0/0
2500
150
80
All 290
Asym-
5










acrylate



IP8
5
 25/25/50/0/0
 0/100/0/0/0
2500
150
80
All 290
Asym-
5










acrylate
















TABLE 5







Predicted Conversion, Branching and Polyene Incorporation Levels





















Incorporation of





Reactor
Polyene


polyene
















Polyene

conversion
conversion
LCB
SCB*
as IDBA
as IDBB



functionality
r1B/r1A
(wt %)
(wt %)
(/1000 C.)
(/1000 C.)
(mol %)
(mol %)


















CP1
Sym bi-acrylate
1
32.6
99.95
3.54
24.4
50
50


CP2
Sym HC diene
1
32.7
45.3
3.56
24.4
50
50


CP3
Sym bi-acrylate
1
34.8
99.99
4
24.5
50
50


IP1
Asym-acrylate
5
32.6
99.74
3.55
24.4
16.7
83.3


IP2
Asym-acrylate
5
32.6
97.27
3.55
24.4
16.7
83.3


IP3
Asym-acrylate
5
32.9
98.95
3.62
24.3
16.7
83.3


IP4
Asym-acrylate
5
32.7
96.6
3.52
23.7
16.7
83.3


IP5
Asym-acrylate
5
32.7
99.43
3.51
23.7
16.7
83.3


IP6
Asym-acrylate
5
33.7
99.4
3.81
24.3
16.7
83.3


IP7
Asym-acrylate
5
34.8
98.34
4
24.5
16.7
83.3


IP8
Asym-acrylate
5
34.85
99.92
4.01
24.4
16.7
83.3





*ethyl/butyl branches by backbiting; polymers prepared in the absence of propylene or other olefinic CTAs






Comparative Polymerizations 1-2 and Inventive Polymerizations 1-2

CP1, CP2 and IP1 show the impact of the type and reactivity (distribution) of the polyene, when the polyene is added entirely to the first reaction zone. The impact of a changing feed distribution of the asym-acrylates is simulated in IP2 (compared to IP1). The distribution of asym-acrylates over reaction zones 1 and 2 slightly lowers the incorporation level of the polyene.
FIG. 5 shows the incorporation frequency of polyene into the polymer formed along the reactor for CP1, CP2, IP1 and IP2. The incorporation frequency is expressed as frequency of incorporation of the polyene per 1000 carbon atoms in the locally-formed polymer. In summary, the following remarks can be made.
CP1: Symmetrical bi-acrylates (sym bi-acrylate) have a high and inhomogeneous incorporation level, with equal formation of IDBA and IDBB, and equal chances for secondary reactions of the formed IDBA and IDBB groups in the formed and further reacting polymer. The probability for secondary reactions (H-branch formation) is very high and localized. Secondary reactions will mainly occur in polymer molecules originating from the first reaction zone, and will make part of the very high molecular weight fraction in the final polymer. The high probability for secondary reactions in the polymer originating from the first reaction zone will have adverse effects on reactor fouling and increase the probability that product gels are formed. Furthermore, the high reactivity and concentration can easily lead to premature polymerization and fouling in the reactor preheater.
CP2: Symmetrical hydrocarbon dienes (sym HC diene) have a very homogeneous, though low overall, incorporation level, equal formation of IDBA and IDBB, and equal but low chances for secondary reactions of the formed IDBA and IDBB groups in the formed and further reacting polymer. The probability for secondary reactions (H-branch formation) is very low due to low reactivity and very low levels of IDBA and IDBB formed.
IP1: Asymmetrical bifunctional acrylates (asym-acrylate), with differentiated reactivity, have an inhomogeneous and high incorporation level, with differentiated formation of IDBA and IDBB, and differentiated chances for secondary reactions for the formed IDBA and IDBB groups in the formed and further reacting polymer. The incorporation level for asym-acrylates is lower than that for sym bi-acrylates. The probability for secondary reactions (H-branch formation) to occur in the first reaction zone is strongly reduced, compared to CP1, due to the lower reactivity of the B-functionality, and therefore adverse effects originating from the first reaction zone, like reactor fouling and product gels, are unexpectedly reduced.
IP2: Distribution of asym-acrylate leads to a more homogeneous incorporation level, although the incorporation level is slightly lower. The probability for secondary reactions (H-branch formation) to occur in the first reaction zone is strongly reduced, compared to CP1 and IP1, due to the strongly reduced concentration level and/or the lower reactivity of the B-functionality. Adverse effects, like fouling of the preheater and the reaction zones, and product gels, are therefore, unexpectedly significantly reduced.
Inventive Polymerizations 3-6
IP3 and IP5 show the impact of ethylene distribution, when the polyene (asym-acrylate) is fed entirely to the second reaction zone. In IP5, less polymer (containing no polyene) is made in the first reaction zone, while the advantages of IP3, that is, not exposing the reactor preheater and the first reaction zone to polyene, are maintained.
The impact of changing feed distribution of asym-acrylate is simulated in IP4. Distribution of the asym-acrylate polyene over the second and third reaction zones leads to a more homogeneous incorporation, although at the cost of a reduced incorporation level and reduced secondary reactions.
FIG. 6 shows the incorporation frequency of the polyene in the polymer formed along the reactor for IP3-5. The incorporation frequency is expressed as frequency of incorporated polyene per 1000 carbon atoms in the locally-formed polymer.
IP3 and IP5 differ in ethylene feed distribution to the first and second reaction zones. It was surprisingly discovered that with the same polyene distribution, reducing the ethylene feed to the first reaction zone will improve polymerization conditions, by reducing the amount of homopolymer in the first reaction zone, increasing the incorporating level of the polyene in subsequent reaction zones, and maintaining the advantages of IP3, namely, not exposing the reactor preheater and first reaction zone to the polyene.
The impact of changing first reaction zone temperature is shown in IP6. The incorporation frequency of the polyene for IP6 is shown in FIG. 7. IP6 differs from IP5 in first reaction zone maximum temperature (330° C. versus 290° C.). The increased maximum temperature in the first reaction zone, results in more LCB formation in the first reaction zone and a higher LCB level in the overall polymer. The maximum temperature in the first reaction zone can be safely increased, due to the absence of the polyene in the first reaction zone. Alternatively, the higher level of LCB can be used to lower the feed level of the polyene, while maintaining the melt strength at a high level.
FIG. 9 shows the increased LCB frequency of Inventive 6 versus Inventive 5 and Comparative 1. As illustrated by IP6, not exposing the reactor preheater and first reaction zone to a polyene, allows raising the maximum temperature in the first reaction zone and the reactor conversion level, while the overall LCB level, and therefore product melt elasticity range, is enhanced, while reactor fouling and product gel issues are reduced or prevented.
Comparative Polymerization 3 and Inventive Polymerizations 7 and 8
CP3 and IP7 show the impact of the reactivity of polyene (sym bi-acrylate versus asym-acrylate), when the polyene is evenly distributed over the applied ethylene feed distribution.
IP8 show the impact of feeding all asym-acrylate to the second reaction zone. The incorporation frequency of the polyene in the polymer formed along the reactor for CP3, IP7 and IP8 is shown in FIGS. 7 and 8. The application of asym-acrylate gives a more homogeneous incorporation frequency, as compared to using sym bi-acrylate, while feeding asym-acrylate to the second zone gives an unexpectedly higher incorporation level, than the even distribution of asym-acrylate over the ethylene feed streams to first three reaction zones. Furthermore, the adverse consequences of adding polyene to the first reaction zone (i.e., contact of the polyene in the reactor preheater and first reaction zone) are avoided in IP8. Table 6 gives an overview of the ratios of incorporation levels of the polyene, or bifunctional component (BFC), for comparative and inventive polymerizations.







TABLE 6







Ratios of Concentrations of Polyene Incorporated per Rx-zone v. Polyene Structure, 


Distribution and Incorporation



























Ratio











Ratio 
Conc.










Ratio
Conc.
Polyene










Conc.
Polyene
incorp.














Ratio Conc. of Polyene Incorporated

More
polyene
incorp.
Rxi + 1/



in Rx-Zones

Polyene
incorp.
Rx1/Rxi + 1 ≦ 1
Rx2 ≦ 1 


















Rx1/
Rx2/
Rx3/
Rx4/
Rx5/
Asym-
to Rxi
Rx1/Rx2
(i is from 2
(i is from 2



Rx2
Rx2
Rx2
Rx2
Rx2
acrylate
(i ≧ 2)
(i = 2) ≦ 1
to n − 1)
to n − 1)




















CP1
22.1
1
0.14
0.0015
NA
No
No
No
No
No


CP2
1.12
1
0.92
0.85
NA
No
No
No
No
No


CP3
1.73
1
1.06
0.047
0.0048
No
No
No
No
No


IP1
5.7
1
0.32
0.1
NA
Yes
No
No
No
No


IP2
0.54
1
0.32
0.1
NA
Yes
Yes
Yes
Yes
Yes


IP3
0
1
0.2
0.057
NA
Yes
Yes
Yes
Yes
Yes


IP4
0
1
1.85
0.52
NA
Yes
Yes
Yes
Yes
No


IP5
0
1
0.146
0.041
NA
Yes
Yes
Yes
Yes
Yes


IP6
0
1
0.14
0.04
NA
Yes
Yes
Yes
Yes
Yes


IP7
1.62
1
1.03
0.17
0.048
Yes
Yes
Yes
Yes
Yes


IP8
0
1
0.057
0.0096
0.0026
Yes
Yes
Yes
Yes
Yes









In Table 6, “Rx” means “reaction zone” and the digit following indicates which reaction zone. “Rx1” therefore means reaction zone 1, and so forth. The concentration of polyene incorporated in a reaction zone is calculated by dividing the amount (in mass or moles) of polyene consumed in that reaction zone by the amount (in mass or moles) of polymer formed in that reaction zone. For example, concentration of polyene incorporated in Rx1 is therefore:




  (
  
    
      Amount
      ⁢
      
        
      
      ⁢
      of
      ⁢
      
        
      
      ⁢
      polyene
      ⁢
      
        
      
      ⁢
      consumed
      ⁢
      
        
      
      ⁢
      in
      ⁢
      
        
      
      ⁢
      R
      ×
      1
    
    
      Amount
      ⁢
      
        
      
      ⁢
      of
      ⁢
      
        
      
      ⁢
      polymer
      ⁢
      
        
      
      ⁢
      formed
      ⁢
      
        
      
      ⁢
      in
      ⁢
      
        
      
      ⁢
      R
      ×
      1
    
  
  )




The ratio of the concentration of polyene incorporated in a first reaction zone to the concentration of polyene incorporated in a second reaction zone is calculated by dividing the respective concentrations, resulting in a dimensionless ratio. For example, to determine the ratio of the concentration of polyene incorporated in Rx1 to the concentration of polyene incorporated in Rx2, the following equation is used:




  
    (
    
      
        Amount
        ⁢
        
          
        
        ⁢
        of
        ⁢
        
          
        
        ⁢
        polyene
        ⁢
        
          
        
        ⁢
        consumed
        ⁢
        
          
        
        ⁢
        in
        ⁢
        
          
        
        ⁢
        R
        ×
        1
      
      
        Amount
        ⁢
        
          
        
        ⁢
        of
        ⁢
        
          
        
        ⁢
        polymer
        ⁢
        
          
        
        ⁢
        formed
        ⁢
        
          
        
        ⁢
        in
        ⁢
        
          
        
        ⁢
        R
        ×
        1
      
    
    )
  
  
    (
    
      
        Amount
        ⁢
        
          
        
        ⁢
        of
        ⁢
        
          
        
        ⁢
        polyene
        ⁢
        
          
        
        ⁢
        consumed
        ⁢
        
          
        
        ⁢
        in
        ⁢
        
          
        
        ⁢
        R
        ×
        2
      
      
        Amount
        ⁢
        
          
        
        ⁢
        of
        ⁢
        
          
        
        ⁢
        polymer
        ⁢
        
          
        
        ⁢
        formed
        ⁢
        
          
        
        ⁢
        in
        ⁢
        
          
        
        ⁢
        R
        ×
        2
      
    
    )
  




Although the invention has been described in considerable detail in the preceding examples, this detail is for the purpose of illustration, and is not to be construed as a limitation on the invention as described in the claims. Furthermore the invention can be combined with other process elements, like ethylene and CTA make up feed distributions,
CTA selection, etc., in respect to further process optimization (conversion level, heat transfer, raw material costs, process stability, etc.) and further enhancement of product properties like gel content, MWD, density, and the like.
Description of Flow Diagram Used for Comparative Example A′ and Inventive Example 1′, 2′ and 4′′
FIG. 10 shows the flow scheme of the high pressure polymerization process with a tubular reactor used to produce comparative example A′ and inventive examples 1′, 2′ and 4. Stream (1), fresh ethylene make-up, is compressed together with the outlet of the Booster by two parallel Primary compressors A+B, both have similar capacity, resulting in flow (2) and flow (3). CTA is added through (22) to the feed of Primary compressor A. Stream (2) is combined with high pressure recycle stream (18), and distributed over flow (4) and flow (19). The Hyper compressor part feeding the front (9) of the reactor, receives from line (18) ethylene feed through line (19) and line (5). The Hyper compressor part feeding the side stream (8) receives ethylene feed through line (4). Line (4) receives ethylene feed from line (3) and additional ethylene from line (18). The Hyper pressurizes the ethylene feed streams to a level sufficient to feed the high pressure tubular reactor (Reactor).
Stream (6) and/or stream (7) depict the polyene feed. Information about the Reactor system can be found below. In the Reactor, the polymerization is initiated with the help of free radical initiation systems, injected and/or activated at the inlet of each reaction zone. The maximum temperature in each reaction zone is controlled at a set point by regulating the concentration and/or feed amount of initiation system at the start of each reaction zone. After finishing the reaction, and having applied multiple cooling steps, the reaction mixture is depressurized and/or cooled in (10), and separated in the high pressure separator (HPS). The HPS separates the reaction mixture into an ethylene rich stream (15), containing minor amounts of waxes and/or entrained polymer, and a polymer rich stream (11) which is sent for further separation to the LPS. Ethylene stream (15) is cooled and cleaned in stream (17). Stream (16) is a purge stream to remove impurities and/or inerts.
The polymer separated in LPS is further processed in (12). The ethylene removed (13) in the LPS is fed to the Booster, where, during the compression, condensables such as solvent, lubrication oil and others are collected and removed through stream (14). The outlet of the Booster is combined with make-up ethylene stream (1), and further compressed by the Primary compressors.
Description of Flow Diagram Used for Inventive Example 3′
FIG. 11 shows the flow scheme of the high pressure polymerization process with a tubular reactor, used to produce Inventive Example 3′. Stream (1), fresh ethylene make-up, is compressed together with the outlet of the Booster by Primary compressor system resulting in flow (2). Stream (2) is combined with high pressure recycle stream (19) and fed through line 5 to the Hyper compressor part feeding the front (9) of the Reactor. The Hyper compressor part feeding the side stream (8) receives ethylene feed through line (4). Line (4) receives ethylene feed from line (18). The CTA is fed through line (23). Line 22 is an optional line to feed a CTA component, but was not used in Example 3′. The Hyper pressurizes the ethylene feed streams to a level sufficient to feed the high pressure tubular reactor (Reactor).
Stream (6) and/or stream (7) depict the polyene feed. Information about the Reactor system can be found below. In the Reactor, the polymerization is initiated with the help of free radical initiation systems, injected and/or activated at the inlet of each reaction zone. The maximum temperature in each reaction zone is controlled at a set point by regulating the concentration and/or feed amount of initiation system at the start of each reaction zone.
After finishing the reaction, and having applied multiple cooling steps, the reaction mixture is depressurized and/or cooled in (10), and separated as discussed above for FIG. 10.
Additional Polymerizations—Example A′ (Comparative LDPE)
The polymerization was carried out in tubular reactor with three reaction zones. In each reaction zone, pressurized water was used for cooling and/or heating the reaction medium, by circulating this water through the jacket of the reactor. The inlet-pressure was 2220 bar, and the pressure drop over the whole tubular reactor system was about 300 bars. Each reaction zone had one inlet and one outlet. Each inlet stream consisted of the outlet stream from the previous reaction zone and/or an added ethylene-rich feed stream. The non-converted ethylene, and other gaseous components in the reactor outlet, were recycled through a high pressure recycle and a low pressure recycle, and were compressed and distributed through the booster, primary and hyper (secondary) compressor systems, according flow scheme shown in FIG. 10. Organic peroxides (see Table 7) were fed into each reaction zone. Iso-butane was used as a chain transfer agent (CTA), and it was present in each reaction zone inlet, originating from the low pressure and high pressure recycle flows (#13 and #15), as well as from freshly injected CTA make-up stream #22. The make-up ethylene is fed through stream #1.
After reaching the first peak temperature (maximum temperature) in reaction zone 1, the reaction medium was cooled with the aid of the pressurized water. At the outlet of reaction zone 1, the reaction medium was further cooled by injecting a fresh, cold, ethylene-rich feed stream (#20), and the reaction was re-initiated by feeding an organic peroxide system. This process was repeated at the end of the second reaction zone, to enable further polymerization in the third reaction zone. The polymer was extruded and pelletized (about 30 pellets per gram), using a single screw extruder, at a melt temperature around 230-250° C. The weight ratio of the ethylene-rich feed streams to the three reaction zones was 1.00:0.80:0.20. The internal process velocity was approximately 12.5, 9 and 11 in/sec for respectively the 1St, 2nd and 3rd reaction zones. Additional information can be found in Tables 8 and 9.
Example 1′ (Inventive Ethylene-based Polymer)
The polymerization was carried out in tubular reactor with three reaction zones, as discussed above for Comparative A′. All process conditions are the same as for Comparative Example A′, except the rheology modifier (PPG-AEMA=Polypropylene glycol allyl ether methacrylate) was added via stream #7 and #6. The amount can be found in Table 9. Additional information can be found in Tables 7-9.
PPG-AEMA resembles the polyene which is described in Table 3 as asymmetrical acrylate with the reactivity ratio r1b/r1a=5. Simulation results on this polyene can be found in Table 5. The structure and additional properties for PPG-AEMA can be found below:




Mn of about 280 g/mole; n from about 1 to about 10; isomeric oligomeric mixture, for each n, Ra═H and Rb═CH3, and Ra═CH3 and Rb═H).

Synthesis of Asymmetrical Diene Poly(Propylene Glycol) Allyl Ether Methacrylate (PPG-AEMA).

All methacrylate monomers in this application were prepared in accordance with the method of Example 1 in U.S. Pat. No. 4,916,255. In this case, XUS-13402.00, a polyglycol, commercially available from The Dow Chemical Company, was used to make the poly(propylene glycol) allyl ether methacrylate.
Example 2′ (Inventive Ethylene-based Polymer)
The polymerization was carried out in tubular reactor with three reaction zones, as discussed above for Inventive Example 1′. All process conditions are the same as for Example 1′, except propylene was used as CTA, and CTA was added via stream #22 (see FIG. 10), and the inlet pressure of reaction zone 1 was lowered. Additional information can be found in Tables 7-9.
Example 3′ (Inventive Ethylene-based Polymer)
The polymerization was carried out in tubular reactor with three reaction zones. See FIG. 11. The non-converted ethylene, and other gaseous components in the reactor outlet, were recycled through the high pressure recycle and low pressure recycle, and were compressed and distributed through the booster, primary and hyper (secondary) compressor systems, according to the flow scheme as shown in FIG. 11. This configuration leads to the lowest ratios of CTA concentration in the front ethylene-based feed versus the concentrations of CTA in sequential ethylene-based feed streams. While in Example A′, 1′, 2′ and 4′ the ratios of CTA concentration in the front ethylene-based feed versus the concentrations of CTA in sequential ethylene-based feed streams were higher, and above.
In each reaction zone, the polymerization was initiated with organic peroxides as described in Comparative Example A′. After reaching the first peak temperature in reaction zone 1, the reaction medium was cooled down with pressurized water. At the outlet of the first reaction zone, the reaction medium was further cooled by injecting a fresh, cold ethylene-rich feed stream (#20), and the reaction was initiated again, by feeding an organic peroxide system into the reaction zone. This process was repeated at the end of the second reaction zone, to enable further polymerization in the third reaction zone. The weight ratio of the ethylene-rich feed streams to the three reaction zones was 1.00:0.60:0.40. For the chain transfer agent, propionaldehyde (PA) was used, and it was present in each reactor inlet, originating from the low and high pressure recycle flows (#13  and #15), as well as from freshly injected CTA make-up stream #23. The make-up ethylene is fed through stream #1. Like Example 1′, the rheology modifier (PPG-AEMA) was added via stream #7 and #6. Additional information can be found in Tables 7-9.
Example 4′ (Inventive Ethylene-based Polymer)
The polymerization was carried out in tubular reactor with three reaction zones, as discussed above for Inventive Example 1′. All process conditions are the same as for Example 1′, except of the amount and feed-location of the rheology modifier. Additional information can be found in Tables 7-9.







TABLE 7







Initiators











Used in Rx-


Initiator
Abbreviation
zone 1/2/3





tert-Butyl peroxy-2-ethyl hexanoate
TBPO
yes/yes/no


Di-tert-butyl peroxide
DTBP
yes/yes/yes
















TABLE 8A







Pressure and temperature conditions of comparative and inventive examples



















reinitiation
reinitiation







Inlet-

temp.
temp.







pressure/
Start-
2nd zone/
3rd zone/
1st Peak
2nd Peak
3rd Peak


Ex.
Type
bar
temp./° C.
° C.
° C.
temp./° C.
temp./° C.
temp. /° C.





A’
Comp.
2220
140
150
207
294
292
294


1’
Inv.
2220
144
148
211
293
293
293


2’
Inv.
2155
145
148
217
293
293
294


3’
Inv.
2140
145
160
199
293
293
293


4’
Inv.
2220
140
148
213
294
293
294
















TABLE 8B







CTA Distribution










Mass fraction of Fresh Ethylene in
Wt Ratio of CTA concentration in



reaction zone Ethylene feed*
Ethylene reactor feeds**












Ex.
Rx-Z1
Rx-Z2
Rx-Z3
Rx-Z1/Rx-Z2
Rx-Z1/Rx-Z3





A′
0.17
0.39
0.39
1.36
1.36


1′
0.16
0.39
0.39
1.36
1.36


2′
0.16
0.39
0.39
1.38
1.38


3′
0.57
0.00
0.00
0.43
0.43


4′
0.16
0.39
0.39
1.36
1.36





*Mass fraction of fresh ethylene is the ratio of the amount of fresh ethylene in the feed stream to the total amount of the ethylene-based feed stream.


**Wt ratio of CTA is determined by mass balance calculations over the process flow streams, taking into account the conversions in the reactor and the location and/or distribution of the fresh ethylene flow stream and the location and/or distribution of the fresh CTA flow stream.













TABLE 9







Additional information of the comparative and inventive examples
















PPG-AEMA

Ratio







(mole ppm

CTA






PPG-AEMA
diene in

concentration 






flow kg 
ethylene-based

in front
Total





of diene 
feed stream

versus
Hyper
Polymer




per hour
in each

sequential 
throughput
output
Melt



(1st/2nd/3rd
reaction zone***)

feed
ton per
ton per
Strength


Ex.
zone)
(1st/2nd/3rd zone)
CTA
flows*
hour
hour**
cN





A’
 0/0/0
 0/0/0
Iso-butane
>1
54.2
15.0
4.3


1’
38/18/5
142/86/86
Iso-butane
>1
54.2
14.9
8.9


2’a
48/21/5
172/94/94
Propylene
>1
56.4
15.5
7.4


3’a
10/37/25
 34/219/219
PA
>1
56.2
15.9
8.0


4’
 0/50/13
 0/233/233
Iso-butane
>1
54.2
14.9
6.3





Note*:


Ratio(s) of CTA concentration in the front ethylene-based feed versus the concentrations of CTA in sequential ethylene-based feed streams.


Note**:


Polymer output was calculated from fresh ethylene (#1), CTA (#22 and or #23) and PPG-AEMA (#6 and or #7) intakes corrected for process purge stream (#16).


***Ethylene-based feed stream in each reaction zone refers to the feed stream compressed and fed by the hypercompressor, and containing a majority amount ethylene (for examples, greater than 80 wt % ethylene).


Other components, such as comonomer, CTA, peroxide dissociation products, solvent, etc., may also be present.


aPPG-AEMA was deoxygenated prior to injection into each reactor zone.






Simulation results are shown in Tables 10 and 12. Polymer properties are shown in Table 11.







TABLE 10







Simulated results on branching levels and conversions for the 


comparative and inventive examples

















PPG-
Conver- 







AEMA
sion
Simulated






conver-
to H-
H-branch



SCB
Methyl*
LCB
sion
branch**
level***


Ex.
#/1000 C.
#/1000 C.
#/1000 C.
%
%
#/1000 C.
















A’
26.5
0
3.74
0
0
0.0


1’
25.7
0
3.62
98.2
57.6
0.205


2’
25.5
2.2
3.67
98.1
57
0.239


3’
25.1
0
3.64
94.7
42.9
0.226


4’
25.8
0
3.66
95.4
42.7
0.198





Note*:


Methyl branches originate from propylene built-in as comonomer.


Note**:


Conversion to H-branches is conversion from PPG-AEMA fed to the reactor.


Note***:


Level of total simulated H-branches (inter-plus intra-molecular H-branches.













TABLE 11







Polymer properties of the examples
















GI-200


n-hexane




Mw 
unit = mm2
G’ (at 170° C.;

extract-



MI (I2)
(abs)
gel per 24.6
G” = 500 Pa)
Density
able 


Ex.
dg/min−1
g/mol
cm3 of film
unit = Pa
g/cm3
%





A’
4.0
118,100
 0.7
 89
0.9243
1.4


1’
3.9
159,200
22.7
137
0.9248
1.7


2’
4.1
161,700

124
0.9204
2.1


3’
3.8
153,000

122
0.9258
1.3


4’
3.7
136,400
56*
112
0.9243
1.5





*Average of two cast film runs.













TABLE 12







Simulated Ratios of the Concentrations of Polyene (PPG-AEMA) Incorporated


per Rx-zone for actual polymerizations A’, 1’, 2’, 3’ and 4’.





















Ratio Conc.
Ratio Conc.
Ratio Conc.








polyene
Polyene
Polyene incorp.
















More
incorp. into
incorp. into
into the final



Ratio Conc. of Polyene

Polyene
final
final polymer
polymer 



Incorporated in Rx-Zones

to
polymer
Rx1/Rxi + 1 ≦ 1
Rxi + 1/
















Rx1/
Rx1/
Rx3/
Asym-
Rxi
Rx1/Rx2
(i is from 2
Rx2 ≦ 1 (i is



Rx2
Rx3
Rx2
acrylate
(i ≧ 2)
(i = 2) ≦ 1
to n − 1)
from 2 to n-1)





A’
na
na
na
na
na
na
na
na


1’
2.9
7.8
0.37
Yes
No
No
No
Yes


2’
3.1
8.5
0.37
Yes
No
No
No
Yes


3’
0.57
0.5
0.72
Yes
Yes
Yes
Yes
Yes


4’
0
0
0.42
Yes
Yes
Yes
Yes
Yes









Summary of Results for Polymerizations A′ and 1′-4′

As shown in Table 11, the inventive ethylene-based polymers have significantly higher G′ values as compared to the comparative polymer, and these higher G′ values indicate higher melt strengths for the inventive polymers. See also Table 9. Higher melt strength provides for improved extrusion coating properties, for example reduced neck-in (shrinkage of web as compared to the die width; for example see US 2012/0252990 (page 11)) and better web stability during the extrusion coating process. The inventive examples using isobutane or propionaldehyde, as CTA (Examples 1′, 3′ and 4′), resulted in higher product densities, namely above 0.920 g/cc, and more specifically above 0.922 g/cc. The use of propylene, as CTA, resulted in product densities less than, or equal to, 0.920 g/cc.
Discussion of Actual Polymerization Results
The comparison of the Comparative Example A′ with the Inventive Examples 1′ to 4′ shows that the PPG-AEMA (rheology modifier; assymetrical diene) is an effective at increasing G′ and melt strength, by forming, predominantly, intermolecular branches. The results with iso-butane, as CTA, show the importance of the distribution of the rheology modifier over the reaction zones, to achieve a good balance between high G′ values and low Gel levels. The “GI-200 Gel-count” was measured on cast films, and provides an indication of the Gel levels in the final extrusion coating application; however due to significant higher temperatures and shear conditions in the extrusion coating process, the Gel levels in a coating would be significantly reduced, and thus, a coating formed from a modified ethylene-based polymer, described herein, would be comparable in appearance to a coating made from a conventional, un-modified ethylene-based polymer (for example, LDPE made in an autoclave process) with a similar density.
The results of the iso-butane as CIA, with reduced CIA-activity at inlet of the reactor and/or in the first reaction zone, versus using propylene as CTA, shows the importance to reduce the CTA-activity at the inlet of the reactor and/or in the first reaction zone over the CTA-activity in subsequent reaction zones. Replacing iso-butane by propylene resulted in lower densities, higher extractable levels and less effective use of the rheology modifier, as shown by a higher consumption rate of the rheology modifier.
Surprisingly, using PA (propionaldehyde), as CTA, and distributing its concentration and activity to the subsequent reaction zones, led to an effective use (high 0′ levels, low gel levels, and/or, in general, low consumption of the modifier) of the rheology modifier, and a high G′ value. The Gel level was visually lower despite the higher initial molecular weight in the front of the reactor due to the applied distribution of propionaldehyde to the subsequent reaction zones.
Comparison of Actual with Simulated Polymerization Results of Table 4, 5 and 6.
The simulated polymerizations, as described in Tables 4, 5 and 6, varied the ethylene feed (wt %) distribution over the reaction zones, namely 100/0/0/0, 65/35/0/0, 35/65/0/0 and 25/25/50/0/0. The actual polymerizations were carried in a three zone reactor with an ethylene feed (wt %) distribution of 50/40/10 and 50/30/20. Although the ethylene feed distributions differ between the actual and simulated polymerizations, the results of each can still be compared, to estimate the impact of the distribution of the modifying agent (asym-acrylate or PPG-AEMA) of the ethylene-based polymers formed from the actual polymerizations. The simulation results indicated that feeding all rheology modifying agent to the front is good for increasing the G′ of the polymer product, but increases the risk of Gel formation through localized inter- and intra-molecular H-branch formation. Furthermore, as shown in the simulated results, it was found that feeding the rheology modifying agent to the rear reaction zones, led to a better distribution of the agent, but should lead to a lower G′ of the polymer. Distributing the rheology modifying agent over the front and sequential reaction zones is preferred (see IP6). The incorporation of PPG-AEMA in the polymer for actual polymerizations was estimated through simulations. These simulations were carried out with a similar procedure used for CP 1 to CP 3 and IP 1 to IP 8, except for using actual reactor and feed conditions. These findings from the simulations are in agreement with the experimental and simulated polymerizations shown in Tables 10, 11, and 12, which show the best results for Inventive Examples 1′ and 3′ for high G′ values and sufficiently low gel levels. High G′ values and low Gel levels are indicative of a better distribution of the rheology modifying agent in the final polymer. Information on simulated branching levels in the polymer can be found in Table 10. This table contains furthermore information on incorporation level of PPG-AEMA in the polymer, and the conversion level of PPG-AEMA fed to the reactor to the H-branch level in the Polymer (inter-plus intra-molecular H-branches).
In summary for all actual inventive polymerizations, it was found that the PPG-AEMA (rheology modifying agent) is an effective rheology modifier. Its effectiveness is affected by the type and/or distribution of the CTA, and that the distribution of the rheology modifier needs to be carefully designed, to achieve an optimum balance between high G′ value and low gel-level. The examples also show that PPG-AEMA (rheology modifying agent) is an effective rheology modifier agent for producing products with high melt strengths and G′ values at higher product densities, namely above 0.920 g/cc, and more specifically above 0.922 g/cc. The use of propylene as CTA, results in product densities less than, or equal to, 0.921 g/cc. Furthermore it was found that the simulation results are in good in agreement with the actual polymerization findings. See Tables 10 and 12.

## Claims

1. A process to form an ethylene-based polymer, said process comprising polymerizing ethylene and at least one asymmetrical polyene, comprising an “alpha, beta unsaturated-carbonyl end” and a “C—C double bond end,” and
Wherein the polymerization takes place in the presence of at least one free-radical initiator; and
Wherein the polymerization takes place in a reactor configuration comprising at least two reaction zones, reaction zone 1 and reaction zone i (i≧2), wherein reaction zone i is downstream from reaction zone 1.

2. The process of claim 1, wherein more polyene is added to reaction zone i compared to the amount of polyene added to reaction zone 1.

3. The process of claim 1, wherein more polyene is added to reaction zone 1 as compared to the amount of polyene added to reaction zone i.

4. The process of claim 1, wherein the polyene is fed through a compression stage of a secondary compressor, prior to being fed to a reaction zone.

5. The process of claim 1, wherein the ratio of “the concentration of the polyene incorporated into the locally-formed polymer of the reaction zone 1” to “the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 2 (i=2)” is less than or equal to 1.

6. The process of claim 5, wherein the ratio of “the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 1” to “the concentration of the polyene incorporated into the locally-formed polymer of reaction zone i+1” is less than 1; and wherein i is from 2 to n−1, and n =the total number of reaction zones.

7. The process of claim 1, wherein the ratio of “the concentration of the polyene incorporated into the locally-formed polymer of reaction zone i+1” to “the concentration of the polyene incorporated into the locally-formed polymer of reaction zone 2” is less than or equal to 1, wherein i is from 2 to n−1, and n=the total number of reaction zones.

8. The process of claim 1, wherein the ethylene fed to the first reaction zone is from 10 to 100 percent of the total ethylene fed to the polymerization.

9. The process of claim 1, wherein the maximum temperature of the first reaction zone is greater than the maximum temperature of each consecutive reaction zone downstream from the first reaction zone.

10. The process of claim 1, wherein at least one CTA is added to the polymerization.

11. The process of claim 10, wherein the CTA comprises at least one of the following groups: alkanes, aldehydes, ketones, alcohol, ether, ester, mercaptan or phosphine.

12. The process of claim 1, wherein the process takes place in a reactor configuration that comprises at least one tubular reactor.

13. The process of claim 1, wherein the asymmetrical polyene is selected from the group consisting of the following:



wherein n is from 1 to 50; Ra is selected from H or alkyl; Rb is selected from H or alkyl;







wherein m=1 to 20.

14. The process of claim 1, wherein CTA is added to the polymerization in at least zones 1 and zone i, wherein i ≧1, and wherein reaction zone i is downstream from reaction zone 1, and wherein the ratio of “the concentration of the CTA in the feed to reaction zone i” to “the concentration of the CTA in the feed to reaction zone 1” is greater than or equal to than 1.0.