Polypropylene compounds having non-migratory slip properties

Abstract

A masterbatch having epoxy-functionalized silicone as a slip additive, the polypropylene 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 (1) essentially no migration of the slip additive 12 weeks after manufacturing, (2) a dynamic coefficient of friction value of less than 0.4 and a static coefficient of friction 0.6 or less within the first day of manufacturing according to the ASTM D1894-01 method, and (3) less than 15% change in the dynamic and static coefficient of friction values between the first day of manufacturing and 20 days after manufacturing.

Claims

1. A masterbatch for polypropylene, comprising in weight percent of the masterbatch: (a) from 45 to 81 weight percent of polypropylene carrier, (b) from 5 to 10 weight percent of epoxy functionalized polysiloxane, (c) from 9 to 45 weight percent of functionalized polyolefin, and (d) optionally, from 0 to 10 weight percent of other additives; wherein the functionalized polyolefin contains a maleic anhydride group and is a grafting agent for the epoxy functionalized polysiloxane.

2. The masterbatch of claim 1, wherein the functionalized polyolefin is selected from the group consisting of maleic anhydride grafted polypropylene, maleic anhydride polypropylene copolymer, ethylene ethyl acrylate maleic anhydride terpolymer, and combinations of them.

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

4. A polypropylene compound comprising: (a) polypropylene matrix and (b) a slip additive comprising in weight percent of the slip additive (i) from 45 to 81 weight percent of polypropylene carrier, (ii) from 5 to 10 weight percent of epoxy functionalized polysiloxane, (ii) from 9 to 45 weight percent of functionalized polyolefin, and (iv) optionally, from 0 to 10 weight percent of other additives; wherein the functionalized polyolefin contains a maleic anhydride group and is a grafting agent for the epoxy functionalized polysiloxane.

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

6. The polypropylene 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 suppressants; 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 polypropylene compound of claim 4, wherein one or more additives are added in the form of a masterbatch concentrate.

8. The polypropylene 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 polypropylene 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 0.6 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 15% 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 1-3, including a description, brand name, manufacturer and function of each ingredient. Table 3 shows the recipes for Masterbatches (MBs) I-VI.

(2) TABLE-US-00002 TABLE 2 Description of Ingredients Name Description Brand Manufacturer Function Polypropylene Polypropylene PKS359 Ineos Carrier and film copolymer matrix resin Non-reactive High molecular weight Pearlene SIPP Momentive Slip additive silicone MB silicone gum (50%), MB-01 Polypropylene (50%) Alkoxysilane Ethoxy silyl terminated 3-0247 ETE Dow Corning Slip additive functionalized polydimethylsiloxane POLYMER polysiloxane (reactive silicone) Epoxy Epoxy functional TEGOMER E- Evonik Slip additive functionalized polysiloxane Si 2330 polysiloxane (reactive silicone) Functionalized Maleic anhydride PRIEX25093 Solvay Grafting agent for Polypropylene (MAH) grafted the reactive (0.2% MAH) polypropylene (0.2% silicone MAH; Melt flow index = 93 @ 230° C.) Functionalized Maleic anhydride PRIEX25097 Solvay Grafting agent for Polypropylene (MAH) grafted the reactive (0.45% MAH) polypropylene (0.45% silicone MAH; Melt flow index = 97 230° C.) Functionalized Ethylene ethyl acrylate LOTADER Arkema Grafting agent for terpolymer of maleic anhydride 8200 the reactive ethylene (2.8% terpolymer silicone MAH) (2.8% MAH) Functionalized Maleic anhydride BHX-10016 Baker Petrolite Grafting agent for polypropylene propylene copolymer reactive silicone copolymer (containing MAH) Amino- 3-Aminopropyl DYNASILAN Evonik Co-agent with the functionalized trimethoxysilane AMEO reactive silicone silane Catalyst Tetra n-butyl titanate TYZOR T-nBT Dorf Ketal Silanol catalyst Chemicals Antiblock MB Polypropylene On Cap AB PP PolyOne Anti-block additive masterbatch of MB 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 MB VI Polypropylene carrier 90% 89% 88% 45% 67.5% 81% Alkoxysilane functionalized 5% 5% 5% polysiloxane (reactive silicone) Epoxy functionalized 10%   10% 10% polysiloxane (reactive silicone) Functionalized polypropylene 5% 5% 5% 4.5%  (0.2% MAH) Functionalized polypropylene 45% (0.45% MAH) Functionalized terpolymer of 22.5% ethylene (2.8% MAH) Functionalized polypropylene 4.5%  co-polymer (containing MAH) Amino-functionalized silane 1% Catalyst 1% 1% 100% 100% 100% 100%  100% 100% 

(4) Masterbatches I-VI 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-VI 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 polypropylene 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 3 Polypropylene 94% 76% 76% 76% 86% 86% 86% matrix Non-reactive 2% silicone MB MB I 20% MB II 20% MB III 20% MB IV 10% MB V 10% MB VI 10% Antiblock MB 4% 4% 4% 4%  4%  4%  4% Total 100% 100% 100% 100% 100%  100%  100%  % Silicone 1% 1% 1% 1%  1%  1%  1% % Total 0% 1% 1% 1% 4.5%  2.25%   0.9%  functionalized polyolefin

(9) The polypropylene compounds were extruded into a 2-layer laminate film, each layer having a thickness of 25 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 1 200° C. Zone 2 240° C. Zone 3 240° C. Zone 4 240° C. Distributor 240° C. Head 245° C./240° C./245° 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 Polypropylene Films

(12) Non-reactive silicone was compared to two types of reactive silicones for effectiveness as slip additives in polypropylene-based films. The reactive silicones evaluated were alkoxysilane functionalized polysiloxane and epoxy functionalized polysiloxane. The Example formulations satisfied the required 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 for Films Criteria Type Test Method (1) No Required Films were tested for 12 weeks, after which observed migration would be unlikely to occur. migration of Additive migration of the slip additive was silicone observed by measuring the COF values on additive 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 less lower than the and a static COF value of 0.6 or less. Control containing nonreactive silicone (3) Stability of Required Less than 15% change in the static and the slip dynamic COF values, individually, from the additive 1st day after manufacturing and 20 days after manufacturing.

(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 3 COF within 1 Day after Film Manufacturing (ASTM D1894) Static COF 0.87 0.63 0.85 1.41 0.46 0.6 0.59 Dynamic COF 0.72 0.56 0.66 1.3 0.37 0.36 0.37 COF 4 Days after Film Manufacturing (ASTM D1894) Static COF — 0.58 — — 0.61 0.57 0.53 Dynamic COF — 0.37 — — 0.35 0.34 0.32 COF 20 Days after Film Manufacturing (ASTM D1894) Static COF 0.89 0.6 0.48 — 0.52 0.54 0.7 Dynamic COF 0.8 0.39 0.39 — 0.33 0.33 0.37 Δ Static COF −0.02 0.03 0.37 N/A −0.06 0.06 −0.11 (COF Day 1/COF Day 20) Δ Dynamic COF −0.08 0.17 0.27 N/A 0.04 0.03 0 (COF Day 1/COF Day 20) Haze (ASTM D1003) 2.5 3 7 9.5 1.5 3.5 2 Clarity (ASTM 98.6 98.4 94.8 74.4 96.9 94.3 98.7 D1003) Additive migration to No No No No No No No other film layer after 12 weeks (Yes/No) Observations by No No No Gels No No No microscope Gel Gel Gel Form Gel Gel Gel

(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 polypropylene compound of Comparative Example A contained 1% silicone by weight. Comparative Example A exhibited moderate slip performance with static and dynamic COF values of 0.87 and 0.72 respectively, measured within the first day of manufacturing. No migration of the silicone additive was observed 12 weeks after manufacturing.

(17) The Comparative Examples B-D and Examples 1-3 each tested a reactive silicone as the slip additive, replacing the non-reactive silicone of Comparative Example A. For comparison with the control film, Comparative Examples B-D and Examples 1-3 were also formulated to contain 1% silicone by weight of the compound.

(18) Replacing the silicone gum as slip additive, Masterbatches I, II and III contained ethoxy silyl terminated polydimethylsiloxane, also referred to as an alkoxysilane functionalized polysiloxane, in addition to a functional polyolefin containing maleic anhydride (MAH). 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) The anhydride of the grafted polypropylene (0.2% MAH) in Masterbatches I, II and III assisted to catalyze the silanol hydrolysis and condensation reactions.

(20) Masterbatches II and III contained an additional silanol catalyst to catalyze the hydrolysis and condensation reactions. In addition, Masterbatch III contained an amino functionalized silane, which reacted with the maleic anhydride (MAH)-grafted polypropylene.

(21) The resulting films of Masterbatches I, II and III, respectively Comparative Examples B, C and D showed no migration of the silicone slip additive after 12 weeks. Although Comparative Examples B and C showed improved COF values at manufacturing, both formulations evidenced instability indicated by a change greater than 15% in the COF values 20 days after manufacturing.

(22) For Comparative Example D, much higher COF values were measured after manufacturing compared to Comparative Example A, so no further testing was conducted. The higher COF values were due to the formation of gels from the 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 of the gels, the film had a rough surface that negatively affected slip performance.

(23) Masterbatches IV, V, and VI tested the second type of reactive silicone as a slip agent, epoxy functionalized polysiloxane. Each masterbatch also included one or more functionalized polyolefins containing MAH. The films of Examples 1-3, contained 10% of Masterbatches IV, V, and VI respectively. These films unexpectedly demonstrated improved static and dynamic COF values compared to the Control, Comparative Example A, and showed less than a 15% change in both COF values 20 days after manufacturing. No migration of the silicone additive was observed in Examples 1-3 after 12 weeks. Films of Examples 1-3 showed excellent optical properties within 5% of the haze and clarity measurements of the Control film according to ASTM D1003. Experiments conducted of films containing 5% by weight of Masterbatches IV, V, and VI also showed similar success.

(24) 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.

(25) 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, these formulations were not stable over longer periods of time. Comparative Example D showed that adding an amino functionalized silane to react with the MAH group, created gels rather than leading to increased stability.

(26) Examples 1-3 did not undergo any hydrolysis or condensation reactions. Instead, Examples 1 and 2 relied only on the reactivity of the epoxy group of the polysiloxane with the functionalized polyolefin to create a linkage that, unexpectedly, immobilized the polysiloxane in the polypropylene matrix, while also achieving improved slip properties compared to the control film.

(27) Therefore, whereas the alkoxysilane functionalized polysiloxanes did not represent an improvement from the non-reactive silicone used in the control film, epoxy functionalized polysiloxanes unexpectedly satisfied all of the required criteria in Table 7 compared to the Control.

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