Patent Description:
Such kind of polypropylene compositions is widely used for making films in the packaging field, especially in the food packaging field, but also for the packaging non-food products and for the production of non-packaging items.

Packaging examples are the primary packaging of hygienic items, textile articles, magazines, mailing films, secondary collation packaging, shrink packaging films and sleeves, stretch packaging films and sleeves, form-fill-seal packaging films for portioning various types of articles such as bags, pouches or sachets, vacuum formed blisters.

Examples of form-fill-seal applications are the packaging of peat and turf, chemicals, plastic resins, mineral products, food products, small size solid articles.

The above applications and, in general, all the applications involving use of plastic films for packaging are included in the general definition of "flexible plastic packaging".

Non packaging items are for example synthetic clothing articles or medical and surgical films, films which are formed into flexible conveying pipes, membranes for isolation and protection in soil, building and construction applications, films which are laminated with nonwoven membranes.

An important feature of this kind of films is the sealing initiation temperature that it is preferred to be very low, without losing other features of the films such as hot tack.

<CIT> relates to heat-sealable polyolefin films comprising an heterophasic propylene copolymer and a butene-<NUM> (co)polymer having a content of butene-<NUM> derived units of <NUM> wt% or more and a flexural modulus (MEF) of <NUM> MPa or less.

<CIT> relates to a polyolefin composition comprising a random copolymer of propylene and a polymer of <NUM>-butene wherein preferably the <NUM>-butene polymer is a <NUM>-butene copolymer having a <NUM>-butene derived units content lower than <NUM> wt%.

<CIT> discloses polyolefin compositions comprising: A) a propylene ethylene copolymer, B) a propylene ethylene <NUM>-butene terpolymer. Also disclosed are films and multilayer films made with said composition.

The applicant found that it is possible to lower the sealing initiation temperature of a particular propylene composition by using a <NUM>-butene copolymer having particular features.

Thus an object of the present disclosure is a polymer composition comprising:.

The term "copolymer" as used in the present patent application refers to polymers containing only two comonomers such as propylene and ethylene or <NUM>-butene and ethylene, the term propylene ethylene <NUM>-butene terpolymer is defined as containing only propylene, ethylene and <NUM>-butene comonomers.

The polymer composition (A) herein disclosed can be prepared by a process comprising polymerizing propylene with ethylene and propylene with ethylene and <NUM>-butene, in the presence of a catalyst comprising the product of the reaction between:.

The particles of solid component have substantially spherical morphology and average diameter ranging between <NUM> and <NUM>, preferably from <NUM> to <NUM> and more preferably from <NUM> to <NUM>. As particles having substantially spherical morphology, those are meant wherein the ratio between the greater axis and the smaller axis is equal to or lower than <NUM> and preferably lower than <NUM>.

In general the amount of Mg preferably ranges from <NUM> to <NUM>% more preferably from <NUM> wt% to <NUM> wt%.

Generally, the amount of Ti ranges from <NUM> wt% to <NUM> wt% and more preferably from <NUM> wy% to <NUM> wt%.

Internal electron donor compounds are <NUM>,<NUM>-diethers of formula:
<CHM>
wherein RI and RII are the same or different and are C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> cycloalkyl or C<NUM>-C<NUM> aryl radicals; RIII and RIV are the same or different and are C<NUM>-C<NUM> alkyl radicals; or are the <NUM>,<NUM>-diethers in which the carbon atom in position <NUM> belongs to a cyclic or polycyclic structure made up of <NUM>, <NUM>, or <NUM> carbon atoms, or of <NUM>-n or <NUM>-n' carbon atoms, and respectively n nitrogen atoms and n' heteroatoms selected from the group consisting of N, O, S and Si, where n is <NUM> or <NUM> and n' is <NUM>, <NUM>, or <NUM>, said structure containing two or three unsaturations (cyclopolyenic structure), and optionally being condensed with other cyclic structures, or substituted with one or more substituents selected from the group consisting of linear or branched alkyl radicals; cycloalkyl, aryl, aralkyl, alkaryl radicals and halogens, or being condensed with other cyclic structures and substituted with one or more of the above mentioned substituents that can also be bonded to the condensed cyclic structures; one or more of the above mentioned alkyl, cycloalkyl, aryl, aralkyl, or alkaryl radicals and the condensed cyclic structures optionally containing one or more heteroatom(s) as substitutes for carbon or hydrogen atoms, or both.

Ethers of this type are described in published <CIT> and <CIT>.

Representative examples of said diethers are <NUM>-methyl-<NUM>-isopropyl-<NUM>,<NUM>-dimethoxypropane, <NUM>,<NUM>-diisobutyl-<NUM>,<NUM>-dimethoxypropane, <NUM>-isopropyl-<NUM>-cyclopentyl-<NUM>,<NUM>-dimethoxypropane, <NUM>-isopropyl-<NUM>-isoamyl-<NUM>,<NUM>-dimethoxypropane, <NUM>,<NUM>-bis (methoxymethyl) fluorene.

The Mg/Ti molar ratio is preferably equal to, or higher than, <NUM>, preferably in the range <NUM>-<NUM>, and more preferably from <NUM> to <NUM>. Correspondingly, the Mg/donor molar ratio is preferably higher than <NUM> more preferably higher than <NUM> and usually ranging from <NUM> to <NUM>.

The preparation of the solid catalyst component can be carried out according to several methods.

According to one method, the solid catalyst component can be prepared by reacting a titanium compound of formula Ti(OR)q-yXy, where q is the valence of titanium and y is a number between <NUM> and q, preferably TiCl<NUM>, with a magnesium chloride deriving from an adduct of formula MgCl<NUM>•pROH, where p is a number between <NUM> and <NUM>, preferably from <NUM> to <NUM>, and R is a hydrocarbon radical having <NUM>-<NUM> carbon atoms. The adduct can be suitably prepared in spherical form by mixing alcohol and magnesium chloride, operating under stirring conditions at the melting temperature of the adduct (<NUM>-<NUM>). Then, the adduct is mixed with an inert hydrocarbon immiscible with the adduct thereby creating an emulsion which is quickly quenched causing the solidification of the adduct in form of spherical particles. Examples of spherical adducts prepared according to this procedure are described in <CIT> and <CIT>. The so obtained adduct can be directly reacted with Ti compound or it can be previously subjected to thermal controlled dealcoholation (<NUM>-<NUM>) so as to obtain an adduct in which the number of moles of alcohol is generally lower than <NUM>, preferably between <NUM> and <NUM>. The reaction with the Ti compound can be carried out by suspending the adduct (dealcoholated or as such) in cold TiCl<NUM> (generally <NUM>); the mixture is heated up to <NUM>-<NUM> and kept at this temperature for <NUM>-<NUM> hours.

The treatment with TiCl<NUM> can be carried out one or more times. The internal electron donor compound can be added in the desired ratios during the treatment with TiCl<NUM>.

The alkylaluminum compound (ii) is preferably chosen among the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides, such as AlEt<NUM>Cl and Al<NUM>Et<NUM>Cl<NUM>, possibly in mixture with the above cited trialkylaluminums. The Al/Ti ratio is higher than <NUM> and is generally comprised between <NUM> and <NUM>.

Suitable external electron-donor compounds include silicon compounds, ethers, esters, amines, heterocyclic compounds and particularly <NUM>,<NUM>,<NUM>,<NUM>-tetramethylpiperidine and ketones.

A preferred class of external donor compounds is that of silicon compounds of formula (R<NUM>)a(R<NUM>)bSi(OR<NUM>)c, where a and b are integers from <NUM> to <NUM>, c is an integer from <NUM> to <NUM> and the sum (a+b+c) is <NUM>; R<NUM>, R<NUM>, and R<NUM> are alkyl, cycloalkyl or aryl radicals with <NUM>-<NUM> carbon atoms optionally containing heteroatoms. Particularly preferred are the silicon compounds in which a is <NUM>, b is <NUM>, c is <NUM>, at least one of R<NUM> and R<NUM> is selected from branched alkyl, cycloalkyl or aryl groups with <NUM>-<NUM> carbon atoms optionally containing heteroatoms and R<NUM> is a C<NUM>-C<NUM> alkyl group, in particular methyl. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane (C donor), diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane (D donor), diisopropyldimethoxysilane, (<NUM>-ethylpiperidinyl)t-butyldimethoxysilane, (<NUM>-ethylpiperidinyl)thexyldimethoxysilane, (<NUM>,<NUM>,<NUM>-trifluoro-n-propyl)-(<NUM>-ethylpiperidinyl)-dimethoxysilane, methyl(<NUM>,<NUM>,<NUM>-trifluoro-n-propyl)dimethoxysilane. Moreover, the silicon compounds in which a is <NUM>, c is <NUM>, R<NUM> is a branched alkyl or cycloalkyl group, optionally containing heteroatoms, and R<NUM> is methyl are also preferred. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane and thexyltrimethoxysilane.

The electron donor compound (iii) is used in such an amount to give a molar ratio between the organoaluminum compound and said electron donor compound (iii) of from <NUM> to <NUM>, preferably from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

The polymerization process can be carried out according to known techniques for example slurry polymerization using as diluent an inert hydrocarbon solvent, or bulk polymerization using the liquid monomer (for example propylene) as a reaction medium. Moreover, it is possible to carry out the polymerization process in gas-phase operating in one or more fluidized or mechanically agitated bed reactors.

The polymerization is generally carried out at temperature of from <NUM> to <NUM>, preferably of from <NUM> to <NUM>. When the polymerization is carried out in gas-phase the operating pressure is generally between <NUM> and <NUM> MPa, preferably between <NUM> and <NUM> MPa. In the bulk polymerization the operating pressure is generally between <NUM> and <NUM> MPa, preferably between <NUM> and <NUM> MPa. Hydrogen is typically used as a molecular weight regulator.

The polymer composition (A) is commercially available in the market such as Adsyl 5C <NUM> F sold by Lyondellbasell.

Component B) is a <NUM>-butene ethylene copolymer commercially available, such as Koattro DP <NUM> sold by LyondellBasell and can be prepared according to processes known in the art by using Ziegler Natta catalysts.

The polymer composition of the present disclosure can be prepared by mechanically blending component A) and component B) in accordance with processes well known in the art.

The polymer composition of the present disclosure can be advantageously used for the preparation of films, in particular multilayer films wherein the sealing layer comprises the <NUM>-butene copolymer composition of the present disclosure.

Thus a further object of the present disclosure is a film comprising the polymer composition of the present disclosure in particular a further object of the present disclosure is a multilayer film wherein the sealing layer comprises the polymer composition of the present disclosure.

The multilayer films of the present disclosure are characterized by having at least the sealing layer comprising The polymer composition of the present disclosure. The remaining layers can be formed of any material known in the art for use in multilayer films or in laminated products. Thus, for example, each layer can be formed of a polypropylene homopolymer or copolymer or polyethylene homopolymer or copolymer or other kind of polymers such as EVA.

The combination and number of the layers of the multilayer structure is not particularly limited. The number is usually from <NUM> to <NUM> layers or even more, preferably <NUM> to <NUM> layers, and more preferably <NUM> to <NUM> layers, and more preferably <NUM> to <NUM> layers and combinations including C/B/A, C/B/C/B/A, C/B/C/D/C/B/A are possible, provided that at least one sealing layer A comprises the <NUM>-butene copolymer composition of the present disclosure.

Preferred layers of the multilayer film of the present disclosure are <NUM> or <NUM> wherein at sealing layer comprises, preferably consists of the <NUM>-butene copolymer composition of the present disclosure.

The polymer composition of the present disclosure can further contain additives used in the art.

The polymer composition of the present disclosure can be advantageously used as sealing layer in a multilayer film, it allows to seal the film at lower temperature.

Preferably the polymer composition of the present disclosure consists essentially of components A) and B) as above described.

Preferably component A) consists essentially of components A1) and A2).

Wherein the term "consists essentially of' means that specific further components can be present, namely those not materially affecting the essential characteristics of the compound or composition. In particular no further polymers especially polyolefins are present in the composition.

The following examples are given to illustrate but not limit the present disclosure.

Melt Flow Rate: measured according to ISO <NUM> - <NUM> (<NUM>, <NUM> or <NUM>, <NUM>).

Tensile Modulus was measured according to ISO <NUM>-<NUM>, and ISO <NUM>-<NUM> on injection moulded sample.

Density was measured according to ISO <NUM>-<NUM>.

The density of samples was measured according to ISO <NUM>-<NUM> (ISO <NUM>-<NUM> method A "Methods for determining the density of non-cellular plastics- Part <NUM>: Immersion method, liquid pyknometer method and titration method"; Method A: Immersion method, for solid plastics (except for powders) in void-free form). Test specimens were taken from compression moulded plaques conditioned for <NUM> days before carrying out the density measure.

The melting temperature TmI is the melting temperature attributable to the crystalline form I of the copolymer. In order to determine the TmI, the copolymer sample is melted and then cooled down to <NUM> with a cooling rate of <NUM>/min. , kept for <NUM> days at room temperature, and then subjected to differential scanning calorimetry (DSC) analysis by cooling to -<NUM> and then heating to <NUM> with a scanning speed corresponding to <NUM>/min. In this heating run, the peak in the thermogram is taken as the melting temperature (Tml).

The content of comonomers was determined by infrared spectroscopy by collecting the IR spectrum of the sample vs. an air background with a Fourier Transform Infrared spectrometer (FTIR). The instrument data acquisition parameters were:.

Sample Preparation - Using a hydraulic press, a thick sheet was obtained by compression molding about g <NUM> of sample between two aluminum foils. A small portion was cut from this sheet to mold a film. The film thickness was set in order to have a maximum absorbance of the CH<NUM> absorption band recorded at ~<NUM>-<NUM> of <NUM> a. (% Transmittance > <NUM>%). Molding conditions were <NUM>±<NUM> (<NUM>°F) and pressure was around <NUM>/cm<NUM> (<NUM> PSI) for about one minute. The pressure was then released, the sample removed from the press and cooled to room temperature. The spectrum of pressed film sample was recorded in absorbance vs. wavenumbers (cm-<NUM>). The following measurements were used to calculate ethylene (C<NUM>) and <NUM>-butene (C<NUM>) contents:.

The ratio AC2 / At is calibrated by analyzing ethylene-<NUM>-butene standard copolymers of known compositions, determined by NMR spectroscopy. In order to calculate the ethylene (C<NUM>) and <NUM>-butene (C<NUM>) content, calibration curves were obtained by using samples of known amount of ethylene and <NUM>-butene detected by <NUM>C-NMR.

Calibration for ethylene - A calibration curve was obtained by plotting AC2/At versus ethylene molar percent (%C2m), and the coefficient aC2, bC2 and cC2 then calculated from a "linear regression".

Calibration for <NUM>-butene - A calibration curve was obtained by plotting FCRC4/At versus butane molar percent (%Cam) and the coefficients aC4, bC4 and CC4 then calculated from a "linear regression".

The spectra of the unknown samples are recorded and then (At), (AC2) and (FCRC4) of the unknown sample are calculated.

The ethylene content (% molar fraction C2m) of the sample was calculated as follows: <MAT>.

The <NUM>-butene content (% molar fraction C4m) of the sample was calculated as follows: <MAT>.

The comonomers content has been determined by infrared spectroscopy by collecting the IR spectrum of the sample vs. an air background with a Fourier Transform Infrared spectrometer (FTIR); the instrument data acquisition parameters are:.

Using a hydraulic press, a thick sheet is obtained by pressing about <NUM> of sample between two aluminum foils. If homogeneity is in question, a minimum of two pressing operations are recommended. A small portion is cut from this sheet to mold a film. Recommended film thickness ranges between <NUM> and0. <NUM> (<NUM> - <NUM> mils).

Pressing temperature is <NUM>±<NUM> (<NUM> °F) and about <NUM>/cm<NUM> (<NUM> PSI) pressure. After about <NUM> minute the pressure is released and the sample is removed from the press and cooled to room temperature.

The spectrum of a pressed film of the polymer is recorded in absorbance vs. wavenumbers (cm-<NUM>). The following measurements are used to calculate ethylene and <NUM>-butene content:.

In order to calculate the ethylene and <NUM>-butene content calibration straights lines for ethylene and <NUM>-butene obtained by using samples of known amount of ethylene and <NUM>-butene are needed.

Calibration straight line GC2 is obtained by plotting AC2 /At versus ethylene molar percent (%C2m). The slope of GC2 is calculated from a linear regression.

Calibration straight line GC4 is obtained by plotting DC4 /At versus <NUM>-butene molar percent (%C4m). The slope of GC4 is calculated from a linear regression.

Spectrum of the unknown sample is recorded and then (At), (AC2) and (DC4) of the unknown sample are calculated. The ethylene content (% molar fraction C2m) of the sample is calculated as follows: <MAT>.

The <NUM>-butene content (% molar fraction C4m) of the sample is calculated as follows: <MAT>.

The propylene content (molar fraction C3m) is calculated as follows: <MAT>.

The ethylene, <NUM>-butene contents by weight are calculated as follows: <MAT> <MAT>.

Some films with a thickness of <NUM> are prepared by extruding each test composition in a single screw Collin extruder (length/diameter ratio of screw <NUM>:<NUM>) at a film drawing speed of <NUM>/min and a melt temperature do <NUM>-<NUM>.

Each resulting film is superimposed on a <NUM> thick film of a propylene homopolymer having a xylene insoluble fraction at <NUM> of <NUM> wt% and a MFR L of <NUM>/<NUM>.

The superimposed films are bonded to each other in a Carver press at <NUM> under a <NUM> load, which is maintained for <NUM> minutes.

The resulting laminates are stretched longitudinally and transversally, i.e. biaxially, by a factor <NUM> with a Karo <NUM> Brueckener film stretcher at <NUM>, thus obtaining a <NUM> thick film (<NUM> homopolymer+<NUM> test).

Film Strips, <NUM> wide and <NUM> length are cut from the center of the BOPP film he film was superimposed with a BOPP film made of PP homopolymer. The superimposed specimens are sealed along one of the <NUM> sides with a Brugger Feinmechanik Sealer, model HSG-ETK <NUM>. Sealing time is <NUM> seconds at a pressure of <NUM> MPa (<NUM> psi). The starting sealing temperature is from about <NUM> less than the melting temperature of the test composition. The sealed strip is cut in <NUM> specimens <NUM> wide long enough to be claimed in the tensile tester grips. The seal strength <NUM> FE7234-EP-P1 is tested and load cell capacity <NUM> N, cross speed <NUM>/min and grip distance <NUM>. The results is expressed as the average of maximum seal strength (N). from are left to cool and then their unsealed ends are attached to an Instron machine where they are tested at a traction speed of <NUM>/min.

The test is than repeated by changing the temperature as follows:
If seal strength <NUM> N then decrease the temperature. Temperature variation must be adjusted stepwise, if seal strength is close to target select steps of <NUM> if the strength is far from target select steps of <NUM>.

The target seal strength (SIT) is defined as the lowest temperature at which a seal strength higher or equal to <NUM> N is achieved.

hot tack measurement after sealing by Brugger HSG Heat-Sealer (with Hot Tack kit). Samples obtained from BOPP film need to be cut at a minimum length of <NUM> and <NUM> width and tested at the following conditions:
Set the temperature from no sealing to <NUM> with an increase of <NUM> steps; at each temperature set the weight necessary to break the film in the neighborhood of the seal.

The specimen is consider break when <NUM>% or more of the seal part is open after the impact.

<NUM> of copolymer and <NUM><NUM> of o-xylene are placed in a glass flask fitted with a condenser and a magnetic stirrer. The temperature is increased to the boiling point of the solvent over <NUM>. The clear solution thus formed is left at reflux with stirring fora further <NUM>. The closed flask is then placed in a bath of ice-water for <NUM> and then in a bath of water thermostatically adjusted to <NUM>° C. The solid formed is then filtered off on filter paper at a high filtration rate. <NUM><NUM> of the liquid obtained from the filtration are poured into a preweighed aluminium container, which is placed on a hot-plate to evaporate off the liquid under a stream of nitrogen. The container is then placed in an oven at <NUM>° C. and maintained under vacuum <NUM> until a constant weight is obtained. From the amount of filtrate the amount of polymer soluble in xylene is calculated.

Component A is a commercial product sold by Lyondelbasell under the tradename Adsyl 5C 90F. Component B is a commercial product sold by Lyondelbasell under the tradename Koattro DP <NUM>.

The features of component A are reported on table <NUM>.

The features of component B are reported on table <NUM>.

Various amount of component B have bene blended with component A. A two layers BOPP film has been produced for each blend. The two layers being made by the same component. The seal initiation temperature has been measured. Table <NUM> reports the SIT for each sample.

Comparative component B1 is a <NUM>-butene ethylene copolymer sold by Lyondellbasell under the tradename Toppyl PB <NUM>. the features of this polymer are reported on table <NUM>.

Various amount of component B1 have bene blended with component A. A two layers BOPP film has been produced for each blend. The two layers being made by the same component. The seal initiation temperature has been measured. Table <NUM> reports the SIT for each sample.

By comparing table <NUM> and table <NUM> it is clear that component B according to the invention is more efficient in lowering the SIT of the composition.

The hot tack of the films of example <NUM> and example <NUM> has been measured at various temperature. The results are reported on table <NUM>.

Claim 1:
A polymer composition comprising:
A) from <NUM> wt% to <NUM> wt% of a propylene composition comprising:
A1) from <NUM> wt% to <NUM> wt% of a propylene ethylene copolymer having an ethylene derived units content ranging from <NUM> wt% to <NUM> wt%;
A2) from <NUM> wt% to <NUM> wt% of a propylene ethylene <NUM>-butene terpolymer having an ethylene derived units content ranging from <NUM> wt% and <NUM> wt% and <NUM>-butene derived units content of between <NUM> wt% and <NUM> wt%;
the sum of the amount of component A1) and A2) being <NUM>;
the composition being characterized by a xylene soluble fraction at <NUM>/<NUM> comprised between <NUM> wt% and <NUM> wt%;
the sum of the amounts of A1) and A2) being <NUM> wt%;
B) from <NUM> wt% to <NUM> wt% of a copolymer of <NUM>-butene and ethylene containing from <NUM> wt% to <NUM> wt% of ethylene derived units; said copolymer of <NUM>-butene and ethylene having:
- a Melt Flow Rate: measured according to ISO <NUM>-<NUM> -(<NUM>, <NUM>) ranging from <NUM> to <NUM>/<NUM>;
flexural modulus measured according to ISO <NUM> ranging from <NUM> MPa to <NUM> MPa;
the melting temperature measured according to Iso <NUM>-<NUM> ranging from <NUM> and <NUM>, form I.
the sum of the amounts of A) and B) being <NUM> wt%.