IMPROVED PROCESS FOR MELT CUTTING ETHYLENE POLYMERS

Abstract: An improved process for melt cutting ethylene polymers is provided wherein the improvement comprises adding to the melt cutter water a small amount of non-ionic or anionic surfactants thereby significantly increasing the agglomeration temperature of the ethylene polymer. This allows for an increase in melt cutting capacity and productivity.

Description: TITLE Improved Process For Melt Cutting Ethylene Polymers BACKGROUND OF THE IFIENTION Field Of The Invention This invention relates to melt cutting and more specifically it relates to an improved process for the melt cutting of ethylene polymers. Description Of The Prior Art The use of surfactants is wide spread in many applications. For example, ethylene oxide and propylene oxide copolymer surfactants are disclosed in U.S.P. 3,422,049, and 3,432,483, as aiding the preparation of dispersions of polymers with particle sizes of below 10 microns to not greater than 25 microns and in U.S.P. 4,007,247 for the preparation of fibrils, i.e., short fibers having diameters less than 25 microns and preferably less than 10 microns. All three of these patents disclose water dispersion processes for polymer particle size reduction using high temperatures and pressures as well as high speed agitation and surfactants. U.S.P. 3,528,841 deals with reducing the tackiness of polymer pellets by applying a small particle size (less than 10 microns) polyolefin powder dispersed in water on the surface of the soft, sticky polymer to reduce its tackiness. In the alternative, the polyolefin powder coating can also be applied to the polymer by tumbling or by airveying. The purpose of applying this coating is to facilitate getting the product through the drying and purge steps of the production process and to supply a fre flowing product to the trade. Chemical Abstracts digest 37:153195p, Vol. 87, 1977 p. 48, entitled Agglomeration prevention during steam-stripping of solvents from rubber solutions" involves the use of a 1000-3000 molecular weight ethylene oxide/propylene oxide copolymer as a surfactant in a water/hydrocarbon solvent dispersion. Thus, a 20% solids butadiene rubber solution in hexane was steamstriped in a 0.005 weight percent solution of the above surfactant in water. This mixture forms a dispersion (oil in water at about 5 to 6 % solids) arc establishes the particle size of the rubber crumbs (average diameter 3@7mm). The surfactant's function is to make the to incompatible phases, namely, hexane and water ir.to one compatible phase. Steam stripping is used to obtain a single liquid (water) phase, ending up with an 88 solids slurry. The process involves forming a particle size in dispersion form from a solution of the rubber in a hydrocarbon solvent. SUMMARY OF THE INVENTION According to the present invention there is provided an improved process for melt cutting ethylene polymers, which process comprises extruding the molten thermoplastic polymer through one cr more orifices into water and cutting the extruded strand as it undergoes solidificatIon, wherein the Improvement comprises adding to the water from about 1 to aoout 1000 ppm by weight of at least one surfactant selected from the group consisting of non-ionic and anionic surfactants that will increase by at least lO2C the agglomeration temperature of an ethylene polymer that has an agglomeration temperature of from about 500C. to about 600C., said surfactant having a hydrophilic/lipophilic balance (HLB) range of from about 10 to about 45. Detailed Description Of The Invention Surprisingly it was found that the addition of small quantities of a non-ionic surfactant to the melt cutter water significantly increased the agglomeration temperature of soft ethylene/vinyl acetate copolymers. In the context of the present invention, the term "agglomeration temperature" means the agglomeration temperature of extruded, hot, cut pellets in water. Agglomeration temperature is determined by the process described below under "Laboratory Testing Procedure". This increase in the agglomeration temperature results in an increase in melt cutting capacity and productivity. Surfactants that are contemplated for use by the present invention are non-ionic and anionic surfactants that will increase by at least 100C the agglomeration temperature of an ethylene polymer that has an agglomeration temperature of from about 500C to about 60 C. Suitable surfactants have a hydrophilic/lipophilic balance (hub) range of from about 10 to about 50. Non-ionic surfactants are preferred and the preferred class of non-ionic surfactants are homo- and copolymers of olefin oxides wherein the olefin moiety contains up to 3 carbon atoms, such as ethylene and propylene oxide homo- and copolymers. The preferred (HLB) range is from about 20 to about 35. A high molecular weight "Pluronic" polyol, an a-hydro-omega-hydroxy-poly(oxyethvlene) poly (oxypropylene) poly(oxyethylene) block copolymer with an HLB range of about 10 to about 35 is the most preferred surfactant. Other non-ionic surfactants, however, such as oxyethylated straight chain alcohols, octyl phenoxy polyethoxy ethanol, ethylene oxide polymers and a reverse "Pluronic" 25R-8 [poly(oxypropylene)-poly(oxy ethylene)-poly(oxycropylene) block copolymer] also significantly raised the agglomeration temperature of ethylene polymers in water. At essentially equivalent EL3 values the higher molecular weight polymers appear to be most effective. The range of concentration for the melt cutter additive surfactant of the present invention is from about 1 to about 1000 parts per million (ppm) based upon the weight of the melt cutter water. The preferred range for the more effective surfactants is from about 1 to about 100 ppm. Although the increased agglomeration temperature obtained by the process of the present invention was discussed in terms of ethylene/vinyl acetate (EVA) copolymers it is to be understood that the present invention applies to other soft ethvlene polymers as well where tackiness and agglomeration are of concern. It is very important in the manufacture of polymers used in adhesives that the concentration of additives used in processing these polymers be as low as possible so as not to result in an adverse effect on critical adhesive properties. As illustrated below in the examples, surfactants of the present invention show no adverse affect on adhesion in the critical adhesion to aluminum test at concentrations of 20 ppm, as well as even up to 2000 ppm in some instances. Illustrative examples of commercially availabie surfactants are "Pluronic" F-98, "Pluronic" F-108, "Plurafac" A-38, "Pluronic" F-38, "Pluronic" 25R-8, "Sipon" L-22, "Carbowax" 20M, "Pluronic" P-104, "Triton" X-100. The following examples are given for the purpose of illustrating the present invention. All parts and percentages are by weight unless otherwise specified. Laboratory Testing Procedure These tests were made using a 10/1 water/ polymer ratio. Ethylene/vinyl acetate copolymer pellets were agitated in ambient temperature water using mild paddle-type agitation that will assure the movement of pellets in the water. The temperature of the water was gradually increased until significant agglomeration had occurred. In the case of untreated Elvax# 210, the first indication of tackiness occurred at approximately 50 C. (3 to 5 pellets agglomeration around the thermometer and agitator shaft). The second indicator was larger agglomerates (1/4" to 1/2") form- ing at a temperature of 540C. The third and final indicator was significant agglomeration (large clump 1" to 2" in diameter) occurring at a temperature of 58 C. This is the temperature considered as the agglomeration temperature of Elvaxe 210. In this study, the various melt-cutter additives were dissolved in the water prior to adding the ethylene/vinyl acetate copolymer pellets. Example 1 This example demonstrates the effect of "Carbowax" 20M, a very slightly crosslinked ethylene oxide copolymer (for further characterization see Table I), as a melt-cutter additive in laboratory tests to increase the agglomeration temperature of soft polymer grades of EVA [e.g., Elvaxe 40, (4q% VA, 57 M.I.), Elvax#, 150 (33% VA, 431.I.) and Elvax# 210 (282 VA, 400 M. I.)]. These tests were merely scouting tests without full attention being paid to the adequacy of agitation required to assure submersion of the pellets in the surfactant containing water. Accordingly the results are merely a rough indication of the effect of the surfactant. The tests involved the addition of 2500 ppm of "Carbowax" 20M (based on the weight of the water) agitated with a magnetic stirrer. mo agglomeration occurred at 700C. for Elvaxt 40 and and 150. Pellets of Elvax# 210 were about 60% agglomerated at 700C. Additional tests were run using Elvax# 40 at 1250 and 500 ppm based on the water, and these tests showed no agglomeration up to 700C. Example 2 This example demonstrates the effect of "Pluronic" F-98 and F-108, ethylene oxide-propylene oxide-ethvlene oxide block copolymers (for further characterization see Table I), as melt-ctter additives in laboratory tests to increase the agglomeration temperature of soft polymer grades of EVA (such as, Elvaxe 210). Following the same procedure described under Laboratory Testing Procedure, the following results were obtained: Melt-Cutter Agglomeration Melt-Cutter Additive Temperature Additive (ppm based on H2O) ( C.) Control 0 58 "Pluronic" 0.5 65 F-98 n 1.0 71 2.0 87 " 10.0 94 "Pluronic F-108 0.5 65 " 1.0 70 " 2.0 88 " 10.0 94 Examples 3- 6 and Comparative Examples 1-9 These examples represent the evaluation of samples from various classes of surfactants (e.g., nonionic, anionic, and cationic) in the laboratory melt-cutting study on Elvax# 40, 150 and 210. The results are shown in Tables I and II. TABLE I EFFECT OF MELT-CUTTER ADDITIVES ON AGGLOMERATION TEMPERATURE OF ELVAX# 210 EMI7.1 <tb> <SEP> Surface <tb> <SEP> Tension <tb> Exam- <SEP> Melt-Cutter <SEP> Chemical <SEP> Dynes/Cm. <tb> ples <SEP> Additive <SEP> Composition <SEP> 0.1%(3), <SEP> 25 C. <SEP> <tb> <SEP> No <SEP> Additive <tb> <SEP> Cl <SEP> (Control) <SEP> -- <SEP> - <tb> <SEP> 3 <SEP> "Pluronic" <SEP> F-108# <SEP> <SEP> &alpha; <SEP> <SEP> hydro-omega- <SEP> 41.2 <tb> <SEP> 4 <SEP> "Pluronic" <SEP> F-98 <SEP> hydroxy-poly(oxyethylene) <SEP> 43.0 <tb> <SEP> 5 <SEP> "Pluronic" <SEP> F-38 <SEP> poly(oxypropylene) <SEP> poly <SEP> 52.2 <SEP> <tb> <SEP> 6 <SEP> "Pluronic" <SEP> P-104 <SEP> (oxyethylene) <SEP> block <SEP> 33.1 <tb> <SEP> 7 <SEP> "Pluronic" <SEP> L-121(2)# <SEP> copolymer <SEP> <SEP> 39.6 <tb> <SEP> C2 <SEP> "Pluronic" <SEP> L-43 <SEP> ) <SEP> 47.3 <tb> <SEP> 8 <SEP> "Plurafac" <SEP> A-3 <SEP> < <SEP> Oxyethylated <tb> <SEP> Straight <SEP> Chain <tb> <SEP> Alcohol <SEP> 43.6 <tb> <SEP> 9 <SEP> "Triton"X-100 <SEP> Octylphenoxy <SEP> polyethoxy <tb> <SEP> ethanol <SEP> 31.0 <tb> <SEP> 10 <SEP> "Carbowax" <SEP> 2 <SEP> OM <SEP> Very <SEP> slightly <SEP> crosslinked <SEP> <tb> <SEP> ethylene <SEP> oxide <SEP> polymer <SEP> 52.0 <SEP> &commat; <tb> <SEP> 50% <SEP> by <SEP> wt. <SEP> <tb> <SEP> 11 <SEP> "Pluronic" <SEP> 25R-8 <SEP> a <SEP> hydro-omega-hydroxy- <SEP> <tb> <SEP> poly(oxypropylene) <SEP> poly <tb> <SEP> (oxyethylene) <SEP> poly(oxy <tb> <SEP> propylene) <SEP> block <SEP> copolymer <SEP> 46.1 <tb> <SEP> C3 <SEP> "Polyox"WSRN-10# <tb> <SEP> C4 <SEP> "Polyox"WSRN-750| <SEP> More <SEP> highly <SEP> crosslinked <SEP> <tb> <SEP> C5 <SEP> "Polyox"WSR-205 <SEP> ethylene <SEP> oxide <SEP> copolymer <tb> <SEP> C6 <SEP> "Polyox"WSR-1105# <tb> <SEP> 12 <SEP> "Sipon" <SEP> L-22 <SEP> Ammonium <SEP> Salt <SEP> of <SEP> Lauryl <tb> <SEP> Sulfate <tb> <SEP> C7 <SEP> "Atlas" <SEP> G-263 <SEP> n-cetyl-n-ethyl <SEP> morpho <tb> <SEP> lineum <tb> TABLE I (cont'd.) EFFECT OF MELT-CUTTER ADDITIVES ON AGGLOMERATION TEMPERATURE OF <RTI ID=8.1> ELVAX# 210 950C Agglomerz- tion Tempera Surfactant HLB Average ture(1) (ppm Examples Type Factor Mol. Wt. Based on Water) C1 - -- -- Agglomerates # 58 C. 3 Nonionic 27.0 14,000 13 4 Nonionic 27.5 13,500 13 5 Nonionic 30.5 5,000 30 6 Nonionic 13.0 5,850 30 7 Nonionic 0.5 4,400 75 C. &commat; 1000 ppm C2 Nonionic 13.5 1,850 670C. &commat; 1000 ppm 8 Nonionic 20 1,420 38 9 Nonionic 13.5 628 295 10 Nonionic 20 14,000- 440 20,000 11 Nonionic 30.3 9,000 465 C3 Nonionic 20 100,000 62 C. &commat; 1000 ppm C4 Nonionic 20 300,000 6300. &commat; 1000 ppm C5 Nonionic 20 600,000 630C. &commat; 1000 ppm C6 Nonionic 20 900,000 630C. &commat; 1000 ppm 12 Anionic 31 -- 875 C7 Cationic 30 -- 660C. &commat; ; 1000 ppm TABLE I (cont'd.) EFFECT OF MELT-CUTTER ADDITIVES ON AGGLOMERATION TEMPERATURE OF ELVAX# 210 Agglomeration Temperature ( C) at Indicated Surfactant Level (ppm) (4) Ex. O 0.3 1.0 2.0 2.5 5 10 20 Cl 58 -- -- -- -- -- -- - 3 58 63 70 88 -- -- 94 - 4 58 65 71 87 -- -- 94 - 5 58 -- -- -- -- -- 62 68 6 58 -- -- -- -- 67 90 - C2 53 -- -- -- -- -- -- - 7 58 I n s o l u b l e i n W a t e r 8 58 -- 65 -- -- -- 68 91 9 58 -- -- -- -- -- -- -10 58 -- -- -- -- -- -- 63 11 58 -- -- -- -- 63 -- -12 58 -- -- -- -- 61 -- - C3 58 60 60 62 -- -- 62 - C4 58 62 63 63 -- -- 63 - C5 58 63 63 63 -- -- 63 - C6 58 63 63 63 -- -- 63 - C7 58 -- -- -- -- 63 -- - TABLE I (cont'd.) EFFECT OF MELT-CUTTER ADDITIVES ON AGGLOMERATION TEMPERATURE OF ELVAX# 210 Agglomeration Temperature ( C) at Syndicated Surfactant Level (ppm) (4) Ex. 30 40 50 100 200 300 500 1000 CI -- -- -- -- -- -- -- - 3 -- -- -- -- - - -- -- - 4 -- -- -- -- -- -- -- - 5 > 97 -- -- -- -- -- -- - 6 -- -- -- > 97 -- -- > 97 > 97 C2 -- -- -- 65 -- -- 67 67 7 I n s o l u b l e i n W a t e r 8 -- -- -- -- -- -- -- - 9 -- -- -- 65 69 > 97 -- -10 -- -- 77 84 -- -- > 97 -11 -- -- 67 70 79 -- > 97 -12 -- -- 61 -- -- -- 67 > 97 C3 -- -- -- -- -- -- -- 60 C4 -- -- -- -- -- -- -- 60 CS -- -- -- -- -- -- -- 61 CE -- -- -- -- -- -- -- 64 C7 -- -- 63 -- -- -- 65 66 (1) except where indicated otherwise (2) limited solubility in water (3) wt. % concentration (4) based on water TABLE II Effect Of Melt-Cutter Additives On Agglomeration Temperature Of Elvax# 40 and 150 Agolomeration Te@@erature ( C) at indicated surfactant level (ppm)(1) Ex. Additive 0 0.5 1.0 2.0 2.5 5 10 20 C8 None 45 C9 None 55 - - - - - - - 13 "Pluronic" F-98 45 - - - - - - 14 " 55 - - - > 85 > 85 - 15 "Pluronic" F-108 45 - - - - - - 16 " 55 - - - 90 - 92 TABLE II (cont'd,) Effect Of Melt-Cutter Additives On Agglomeration Agglomeration Temperature ( C) at indicated surfactant level(ppm) Ex. 30 40 50 100 200 300 500 1000 C8 - - - - - - - C9 - - - - - - - 13 - - > 85 - - - - 14 - - - - - - - - 15 - - 96 - - - - 16 - - > 95 - - - - - (1) based on water Examples 17-22 The effect of the concentration of "Pluronic" F-98 in the melt-cutter water on the adhesive properties of Elvaxt 40 to aluminum foil was studied. The results summarized in Table III show that up to and including 2,000 ppmof additive based on the water) had little or no effect cn adhesion properties. Example 23 and Comparative example 10 The use of 20 ppm "Pluronic" F-98 as a melt-cutter additive was evaluated on a commercial scale in a continuous melt-cutter process for making one of the slower cutting grades of polymer, Elvaxe 210. This resulted in nearly a 50% increase in melt-cutting rates. This product, as well as a control product of Elvax# 210, was evaluated for color, odor, gel content, and adhesion to aluminum foil, both as is and after aging. The results were summarized in Table IV. "Pluronic" F-98 melt-cutter additive had no adverse effect on any of the above properties. @@@@@ ESCA (electron spectroscopy for chemical analysis) a.o.H @@@@@ c.v.m ## determination of the above Elvax# 210 processed using 20 ppm "Pluronic" F-9 8 based on the melt-cutter water: show 0.12 ppm surfactant on the polymer pellets on an 805 confidence level or 0.34 ppm based on 95% confidence level. Examples 24-27 and Comparative Examples 11-14 These examples show the effect of nonionic melt cutter additives on the agglomeration temperature of four soft ethylene terpolymer resins. The tests were run according to the Laboratory Testing Procedure described above. The data, summarized in Table V, show for the first three polymers that the addition of a nonionic surfactant (Pluronic# F-98), at a concentration of 20 parts per million (ppm) based on the water, significantly increased their agglomeration temperature. For the fourth polymer, E/MA/MAME, 50 ppm Pluronico F-108 based on the water, significantly increased the agglomera tion temperature of this terpolymer. TABLE III EFFECT OF CONCENTRATION OF "PLURONIC" F-98 ON ADHESIVE PROPERTIES OF FLVAXx 40 Peel Strength Data (lbs./inch) Melt- Heat Seal, 5-Mil Aluminum(2) Cutter 2480F. 3500F. Additive Std. Std. Ex. ppm ) Peel Deviation Peel Deviation C10 0 3.45 0.17 6.1 1.06 17 5 2.75 0.53 3.85 0.23 18 10 2,9 0.60 4.5 0.86 19 20 3.58 0.36 4.83 0.33 20 200 3.1 0.16 4.38 0.21 21 2,000 3.65 0.10 4,68 0.31 22 20,000 0.75 0.31 1.48 0.13 (1) Based on melt-cutter water. (2) Heat Seal Conditions: Pressure = 20 psi; Dwell Time = 6 seconds each side. TABLE IV Example C-10 23 20 ppm No Additive "Pluronic11 F-98 Pellet Appearance Normal Normal Peel Strength(1), 1bs./in. Initial Sealing Temp. 1200C. .47 Sealing Temp. 177 C. 3.8 5.3 Aged 1 Week Sealing Temp. 1200C .43 .73 Sealing Temp. 177 C. 4.0 3.6 (1) Sealed to aluminum foil 6 seconds, 20 psi. TABLE V EFFECT OF "PLURONIC" F-98 & F-108 MELT-CUTTER ADDITIVES ON THE AGGLOMERATION TEMPERATURE OF BTHYLEXE POLYMERS Melt Cutter Additive Compo- elt (ppm based Agg. Ex. Polymer sition Index on water) Temp. ( C) Cll E/VA/COt3) 61/29/10 35 0 52 24 E/VA/CO(3) 61/29/10 35 20(F-98) 93 C12 E/VA/MAA(4) 74/25/1 500 0 62 25 E/VA/MAA(4) 74/25/1 500 20*F-98) 92 C13 E/MA/CO(1) 64.2/22.7/ 81 0 60 13.1 26 E/MA/CO(1) 64.2/22.7/ 81 20(F-98) 95 13.1 C14 E/MA/MAME(2) 43/53/4 9 0 61 27 E/MA/MAME(2) 43/53/4 9 50(F-108) 97 (1) Ethylene/methyl acrylate/carbon monoxide copolymer. (2) Ethylene/methyl acrylate/monoethylester of maleic acid copolymer. (3) Ethylene/vinyl acetate/carbon monoxide copolymer. (4) Ethylene/vinyl acetate/methacrylic acid copolymer. Agglomeration temperatures or various Elvax# grades are indicated on Table VI below. TABLE VI Agglomeration Temperature of Elvaxt Grades Agglomeration Elvax# Melt Index Vinyl Acetate % Temperature (CC) 40 57 40 45 150 43 33 55 210 402 28 58 250 25 28 67 260 6 28 64 265 3 28 76 310 402 25 59 350 19.1 25 65 360 2 25 72 410 502 18 63 420 150 18 72 460 2.5 18 81

Claims: CLAIMS 1. An improved process for melt cutting ethylene polymers, which process comprises extruding molten thermoplastic polymer through one or more orifices into water and cutting the extruded strand as it undergoes solidification, wherein the improvement comprises adding to the water from about 1 to about 1000 wam by Weight-cefat least one surfactant selected from the group consisting of non-ionic and anionic surfactants that will increase by at least 10 C the agglomeration temperature of an ethylene polymer that has an agglomeration temperature of from about 500C. to about 60 C., said surfactant having a hydrophilic/lipophilic balance (HLB) range of from about 10 to about 45. 2. The process of Claim 1 wherein said surfactant is anionic surfactant. 3. The process of Claim 1 wherein said surfactant is non-ionic surfactant. 4. The process of Claim 3 wherein said nonionic surfactant is selected from the group consisting of ethylene oxide and propylene oxide homo- and copolymers. 5. The process of Claim 4 wherein the ELD range of said non-ionic surfactant is from about 20 to about 35. 6. The process of Claim 5 wherein said nonionic surfactant is selected from the group consisting o ethylene oxide and propylene oxide copolymers, oxyethylated straight chain alcohols and octyl phenoxy polyethoxy ethanol. 7. The process of Claim 6 wherein said nonionic surfactant iS selected from the group consIsting of ethylene oxide and propylene oxide copolymers. 8. The process of Claim 7 wherein said non-ionic surfactant is selected from the group consisting of &alpha;-hydro-omega-hydroxy-poly (oxyethylene) poly(oxypropylene) poly (oxyethylene) block copolymers. 9. The process of Claim 7 wherein said nonionic surfactant is selected from the group consisting of "Pluronic" F-98, "Pluronic" F-108, "Pluronic" P-104, 11Plurafac" A-38 and "Pluronic" F-38. 10. The process of Claims 3, 4, 6, 8 and 9 wherein said surfactant is present in an amount of from about 1 to about 100 ppm based upon the weight of the water.

Inventors: HALE, ALAN DONALD, MURPHY, CHARLES VINCENT
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1980
Main classification: B29B1
IPC codes: C08J3, B01J2, B29B9, B29K23