Polyethylene compounds having non-migratory slip properties

Abstract

A masterbatch having functionalized silicone with an epoxy group or a secondary amine group as a slip additive, the polyethylene compound that the silicone-containing masterbatch has been let down into, and the plastic articles and films from such compounds having improved slip properties are disclosed. The improved slip properties are evidenced by essentially no migration of the slip additive 12 weeks after manufacturing and a dynamic coefficient of friction value of less than 0.4 and a static coefficient of friction 0.5 or less as measured within the first day of manufacturing according to the ASTM D1894-01 method.

Claims

1. A masterbatch for polyethylene, comprising in weight percent of the masterbatch: (a) from 40 to 90 weight percent of polyethylene carrier, (b) from 5 to 10 weight percent of functionalized polysiloxane, (c) from 5 to 40 weight percent of functionalized polyolefin, and (d) optionally, from 0 to 1 weight percent of other additives; wherein the functional group on the functionalized polysiloxane is an epoxy group or a secondary amine group, and wherein the functionalized polyolefin contains a maleic anhydride group and is a grafting agent for the functionalized polysiloxane.

2. The masterbatch of claim 1, wherein the functionalized polyolefin is ethylene ethyl acrylate maleic anhydride terpolymer.

3. A polyethylene compound comprising the masterbatch of claim 1 and polyethylene resin.

4. A polyethylene compound comprising: (a) polyethylene matrix and (b) slip additive comprising in weight percent of the slip additive (i) from 40 to 90 weight percent of polyethylene carrier, (ii) from 5 to 10 weight percent of functionalized polysiloxane, (ii) from 5 to 40 weight percent of functionalized polyolefin, and (iv) optionally, from 0 to 1 weight percent of other additives; wherein the functional group on the functionalized polysiloxane is an epoxy group or a secondary amine group, and wherein the functionalized polyolefin contains a maleic anhydride group and is a grafting agent for the functionalized polysiloxane.

5. The polyethylene compound of claim 4, wherein the functionalized polyolefin is miscible with the polyethylene matrix.

6. The polyethylene compound of claim 4, wherein the additive is selected from the group consisting of anti-blocking agents; adhesion promoters; biocides (antibacterials, fungicides, and mildewcides), anti-fogging agents; anti-static agents; bonding, blowing and foaming agents; dispersants; fillers and extenders; fire and flame retardants and smoke suppresants; impact modifiers; initiators; lubricants; micas; pigments, colorants and dyes; plasticizers; processing aids; other slip or release agents; silanes, titanates and zirconates; stabilizers; stearates; ultraviolet light absorbers; viscosity regulators; waxes; and combinations of them.

7. The polyethylene compound of claim 4, wherein one or more additives are added in the form of a masterbatch concentrate.

8. The polyethylene compound of claim 4, in the shape of a molded plastic article, an extruded plastic article, or a calendered plastic article.

9. A film having at least one layer comprised of the polyethylene compound of claim 4.

10. A laminate of the film of claim 9, wherein there is more than one film layer, and wherein each layer comprises same or different ingredients.

11. The laminate of claim 10, wherein there is a skin layer contacting one surface of a core layer also having an opposing surface, and wherein the skin layer has a thickness between about 0.5 microns and about 1 millimeter.

12. The laminate of claim 11, further comprising a second skin layer contacting the opposing surface of the core layer, wherein the core layer comprises polyolefin resin.

13. The laminate of claim 11, wherein the skin layer has dynamic coefficient of friction value of 0.4 or less and static coefficient of friction value of 0.5 or less, according to the ASTM D1894-01 method, within 1 day after manufacturing of the laminate.

14. The laminate of claim 11, wherein the change between static coefficient of friction and dynamic coefficient of friction values of the skin layer within 1 day after manufacturing and 20 days after manufacturing, according to the ASTM D1894-01 method, is 5% or less.

15. The laminate of claim 11, wherein there is essentially no migration of the slip additive from the skin layer into another film layer measured 12 weeks after manufacturing.

Description

EXAMPLES

(1) Table 2 shows a list of ingredient for the Comparative Examples A-D and Examples 1 and 2, including a description, brand name, manufacturer and function of each ingredient. Table 3 shows the recipes for Masterbatches (MBs) I-V.

(2) TABLE-US-00002 TABLE 2 Description of Ingredients Manu- Name Description Brand facturer Function Polyethylene Low density LDPE 100 Exxon Carrier polyethylene and film matrix resin Non-reactive High Multibase PolyOne Slip silicone MB molecular diluted into additive weight LDPE silicone gum (10%), Polyethylene (90%) Alkoxysilane Ethoxyl silyl 3-0247 ETE Dow Slip functionalized terminated POLYMER Corning additive polysiloxane polydimethyl (reactive siloxane silicone) Methoxy Methoxy SILRES Wacker Slip functionalized functional MSE-100 additive polysiloxane methyl (reactive polysiloxane silicone) Epoxy Epoxy TEGOMER Evonik Slip functionalized functional E-Si 2330 additive polysiloxane polysiloxane (reactive silicone) Secondary Secondary TEGOMER Evonik Slip amine amine A-Si 2330 additive functionalized functional polysiloxane polysiloxane (reactive silicone) Functionalized Ethylene ethyl LOTADER Arkema Grafting terpolymer of acrylate 8200 agent ethylene (2.8% maleic for the MAH) anhydride reactive terpolymer silicone (2.8% MAH) Amino- 3-Amino DYNASILAN Evonik Co-agent functionalized propyl AMEO with the silane trimethoxy reactive silane silicone Catalyst Tetra n-butyl TYZOR T- Dorf Ketal Silanol titanate nBT Chemicals catalyst Antiblock MB Polyethylene On Cap ABPE PolyOne Anti-block masterbatch MB additive of crosslinked poly(methyl methacrylate) beads

(3) TABLE-US-00003 TABLE 3 Masterbatch Recipes Ingredient Name (by Wt. Percent) MB I MB II MB III MB IV MB V Polyethylene carrier 90%  89%  88.5%   90%  90%  Alkoxysilane function- 5% 5% alized polysiloxane (reactive silicone) Methoxy silane 5% functionalized methyl polysiloxane (reactive silicone) Epoxy functionalized 5% polysiloxane (reactive silicone) Secondary amine 5% functionalized polysiloxane (reactive silicone) Functionalized 5% 5% 5% 5% 5% terpolymer of ethylene (2.8% MAH) Amino-functionalized 0.5%.sup.  silane Catalyst 1% 1% 100%  100%  100%  100%  100% 

(4) Masterbatches I-V were prepared by a continuous process using a BERSTORFF ZE25A co-rotating twin screw extruder having a screw length to diameter ratio of 60. Table 4 shows the mixing conditions of the twin screw extruder.

(5) TABLE-US-00004 TABLE 4 Extruder Mixing Conditions for Masterbatches I-V Extruder Type ZE25A twin screw extruder, with a screw size of 25 mm L/D = 60 Zone 1 20° C. Zone 2 140° C. Zone 3 200° C. Zone 4 210° C. Zone 5 220° C. - silicone injection Zone 6 220° C. Zone 7 220° C. Zone 8 220° C. Zone 9 230° C. Zone 10 240° C. Die Temperature 240° C. RPM 500 Pelletizer Strand pelletizer Pellet size 3 mm

(6) All of the ingredients for the masterbatches were fed into the throat of the extruder, except the silicone slip additives. The silicone slip additives were injected into the melt in zone 5 via injection ports.

(7) Pellets produced from the above described process were then blended into the polymer resin matrix to produce the polyethylene compound. Table 5 shows the recipes and Table 6 shows the film extrusion conditions for all the Comparative Examples and Examples.

(8) TABLE-US-00005 TABLE 5 Recipes (Wt. %) of Comparative Examples and Examples Example A B C D 1 2 Ingredient/ Masterbatch Polyethylene matrix 79% 79% 79% 79% 79% 79% MB I 20% MB II 20% MB III 20% MB IV 20% MB V 20% Non-reactive silicone 20% MB Antiblock MB 1% 1% 1% 1% 1% 1% Total 100% 100% 100% 100% 100% 100% % Silicone 1% 1% 1% 1% 1% 1% % Total functionalized 0% 1% 1% 1% 1% 1% polyolefin

(9) The polyethylene compounds were extruded into a 2-layer laminate film, overall A/B film thickness of 50 μm, of which the A side (slip layer) is 5 μm and the B side (virgin LDPE) is 45 μm, using a Labtech multilayer cast film line according to the conditions in Table 6, below.

(10) TABLE-US-00006 TABLE 6 Film Extrusion Conditions of All Comparative Examples and Examples Extruder Type Single screw extruder Zone 1 180° C. Zone 2 220° C. Zone 3 220° C. Zone 4 220° C. Distributor 220° C. Head 225° C./220° C./225° C. Die Slot die RPM Screw speed between 35 and 75 rpm to obtain thickness for film extrusion Chill Roll Chill roll at 20° C. and 6 m/min

(11) Evaluation of Polyethylene Films

(12) Non-reactive silicone was compared to four types of reactive silicones for effectiveness as slip additives in polyethylene-based films. The reactive silicones evaluated were 1) alkoxysilane functionalized polysiloxane, 2) methoxy functionalized polysiloxane, 3) epoxy functionalized polysiloxane, and 4) secondary amine functional polysiloxane. The Example formulations satisfied the required and preferred criteria described in Table 7. The results of the Comparative Examples and Examples are shown in Table 8.

(13) TABLE-US-00007 TABLE 7 Criteria and Testing Methods of Films Criteria Type Test Method (1) No observed Required Films were tested for 12 weeks (84 days), migration of after which migration would be unlikely silicone additive to occur. Additive migration of the slip additive was observed by measuring the COF values on the layer of the film that had no slip additive. If there was no migration, static and dynamic COF values were 1 or greater for the layer with no slip additive. If migration occurred, static and dynamic COF values decreased below 1. (2) COF values Required Threshold dynamic COF value of 0.4 or lower than the less and a static COF value of 0.5 or nonreactive less. silicone control film (3) Stability of Preferred Less than a 5% change in static and the slip additive dynamic COF values between the 1st day after manufacturing and: (i) 20 days after manufacturing, and (ii) thermal treatment at 60° C. for 7 days.

(14) The COF values were measured using the ASTM D1894 Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting. Haze and clarity were measured according to ASTM D1003: Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics using the BYK-GARDNER Haze Guard Plus.

(15) TABLE-US-00008 TABLE 8 Example A B C D 1 2 COF within 1 Day after Film Manufacturing (ASTM D1894) Static COF 0.56 0.35 0.45 0.62 0.39 0.35 Dynamic COF 0.46 0.27 0.39 0.57 0.35 0.29 COF 20 Days after Film Manufacturing (ASTM D1894) Static COF 0.48 0.36 0.5 0.66 0.38 0.34 Dynamic COF 0.41 0.28 0.44 0.59 0.33 0.26 Δ Static COF 0.08 −0.01 −0.05 −0.04 0.01 0.01 (COF Day 1/COF Day 20) Δ Dynamic COF 0.05 −0.01 −0.05 −0.02 0.02 0.03 (COF Day 1/COF Day 20) COF after thermal treatment at 60° C. for 7 days (ASTM D1894) Static COF 0.42 0.33 — 0.6 0.37 0.32 Dynamic COF 0.32 0.28 — 0.57 0.31 0.28 Δ Static COF 0.14 0.02 — 0.02 0.02 0.03 (COF Day 1/ COF at 60° C. for 7 days) Δ Dynamic COF 0.14 −0.01 — 0 0.04 0.01 (COF Day 1/COF at 60° C. for 7 days) Haze 15.7 10.9 10.3 24 12.6 20.4 (ASTM D1003) Clarity 83 85.1 90.6 62.5 77.8 70 (ASTM D1003) Additive migration Yes Yes Yes No No No to other film layer after 12 weeks (Yes/No) Additive migration 10 15 15 >84 >84 >84 observed after day Observations by No No No Gels No Gel No Gel microscope Gel Gel Gel formed (size = ~50 μm)

(16) The control film, Comparative Example A, contained the non-reactive silicone MB, which had a high molecular weight silicone gum as the slip additive. The polyethylene compound of Comparative Example A contained 1% silicone by weight. Comparative Example A exhibited moderate slip performance with static and dynamic COF values of 0.56 and 0.46 respectively, measured within the first day of manufacturing. Additive migration was observed within 10 days of manufacturing. Decreased COF values 20 days after manufacturing and after thermal treatment also evidenced migration of the non-reactive silicone in the control film.

(17) Comparative Examples B-D, and Examples 1 and 2 each tested a reactive silicone as the slip additive, replacing the non-reactive silicone of Comparative Example A. For comparison with the control film, the polyethylene compounds of Comparative Examples B-D, and Examples 1 and 2, were formulated to contain 1% silicone by weight of the compound.

(18) Masterbatches I and II tested ethoxy silyl terminated polydimethylsiloxane, also referred to as an alkoxysilane functionalized polysiloxane, as the slip additive. During production, the alkoxysilane functionalized polysiloxane hydrolyzed, producing silanol end groups on each chain. The silanol end groups then underwent a condensation reaction to create new Si—O bonds linking the polysiloxane to another polysiloxane, thereby forming a longer polysiloxane chain.

(19) Functional polyolefin having a maleic anhydride (MAH) group was also added to Masterbatches I and II to catalyze the silanol hydrolysis and condensation reactions. In addition, a silanol catalyst was added to Masterbatch II to promote the hydrolysis and condensation reactions.

(20) The resulting films of Masterbatches I and II, respectively Comparative Examples B and C, slowed the slip additive migration, but still evidenced additive migration after 15 days.

(21) Masterbatch III tested methoxy functional methyl polysiloxane as a slip additive. The methoxy group offers a hydrolyzable methoxy silyl structure which undergoes a similar reaction as the hydrolysis and condensation reactions described for Masterbatches I and II. Masterbatch III also had a silanol catalyst to promote the hydrolysis and condensation reactions.

(22) Additionally, Masterbatch III contained 3-aminopropyl trimethoxysilane, which reacted with the MAH group on the functionalized polyolefin to form a silane grafted polyethylene. Although Comparative Example D, produced from Masterbatch III, exhibited no migration of the slip additive after 84 days, gels of approximately ˜50 μm in size formed in the film. These gels likely resulted from grafting of the amino-functionalized silane to the MAH-grafted polyolefin, which created co-polymers that were incompatible to the overall polyethylene matrix. As a result, the film had a rough surface that negatively affected slip performance, so Comparative Example D demonstrated significantly worse slip performance compared to the control film, Comparative Example A.

(23) Masterbatch IV produced Example 1, which tested epoxy functionalized polysiloxane as a slip agent. Unexpectedly, Example 1 showed no migration of the slip additive after 12 weeks (84 days) and demonstrated improved static and dynamic COF values compared to the control film, Comparative Example A. The COF measured 20 days after manufacturing and after thermal treatment resulted in consistent values that evidenced good stability of the slip additive in the film. In addition, Example 1 showed excellent optical properties that were similar to the optical properties of the control film.

(24) Finally, Masterbatch V produced Example 2, which tested a secondary amine functional polysiloxane as a slip additive. Example 2 also showed no migration of the slip additive after 84 days and demonstrated improved static and dynamic COF values compared to the control film, Comparative Example A. In addition, good slip additive stability was evidenced by consistent COF values measured 20 days after manufacturing and after thermal treatment.

(25) Selection of the appropriate reactive silicone for different polyolefin-based compounds is difficult and unpredictable. Silicone's effectiveness as a non-migrating slip additive is affected by multiple variables, including the reactivity to, compatibility with, and surface energy of the reactive silicone relative to the polyolefin matrix.

(26) Comparative Examples B and C demonstrated that although the hydrolysis and condensation reactions of the polysiloxane formed longer silica chains, which increased the density of the polysiloxane, it did not prevent the migration of the polysiloxane. Comparative Example D showed that, in addition to forming the longer silica chains, reacting the MAH group of the functionalized polyolefin with an amino-functionalized silane immobilized the polysiloxane. However, the side product of the reaction between the functionalized polyolefin and amino-functionalized silane was incompatible with the polyethylene matrix, and created gels that compromised the film's slip performance.

(27) Examples 1 and 2 did not undergo any hydrolysis or condensation reactions. Instead, Examples 1 and 2 relied only on the reactivity of the epoxy group or secondary amine group of the polysiloxane with the functionalized polyolefin to create a linkage that, unexpectedly, immobilized the polysiloxane in the polyethylene matrix, while also achieving improved slip properties compared to the control film.

(28) The invention is not limited to the above embodiments. The claims follow.