SURFACE-TREATED TALC AND POLYMER COMPOSITIONS FOR HIGH-TEMPERATURE APPLICATIONS

Abstract

The present invention relates to a composition for high-temperature applications; more specifically, the present invention relates to a coated talc, a process for preparing the same, and its use as an additive in the production of polyolefin blended material; the polyolefin blended materials produced according to the process of the present invention exhibit high thermal stability and are useful in a wide range of high-temperature applications.

Description

SURFACE-TREATED TALC AND POLYMER COMPOSITIONS FOR HIGH-TEMPERATURE APPLICATIONS This application claims priority to U.S. Patent Application No. 15 / 708,608, filed on September 19, 2017, which claims the benefit of U.S. Patent Application No. 62 / 490,939 filed on April 27, 2017, and both of these applications are incorporated herein by reference. FIELD OF INVENTION The present invention relates to a composition and product exhibiting thermal stability in high-temperature applications. More specifically, the present invention relates to a composition of a polymer, a coated or surface-treated talc, and thermal stabilizers. The composition of the present invention is useful for parts in a wide range of high-temperature applications. BACKGROUND OF THE INVENTION Certain polymers, such as polyolefins, are useful particles for high-temperature applications due to their high thermal stability when used with thermal stabilizers. Parts in such applications, for example, under the hood of a car, are subjected to high temperatures well above ambient for minutes or hours at a time. Polyolefins can withstand such use for many hours before the onset of thermal instability, as evidenced by brittleness. However, polyolefins alone may lack sufficient rigidity for certain applications. Additionally, the cyclical nature of heat exposure results in expansion and contraction of the part, leading to dimensional instability—that is, the part's shape changes during use. What is needed is a polyolefin composition that has high thermal stability and at the same time high dimensional stability and high stiffness for a wide range of high-temperature applications. BRIEF DESCRIPTION OF THE INVENTION The embodiments of the present invention include a composition comprising; a polyolefin; inorganic mineral particles with a surface treatment that includes a coating of a surface treatment component, and thermal stabilizers, wherein the inorganic mineral is selected from the group consisting of talc, calcium carbonate, precipitated calcium carbonate, clay and silica, wherein the surface treatment component is selected from the group consisting of a functionalized polyether, and a carbon-based polymer, wherein the surface treatment component inhibits the adsorption of the thermal stabilizers on the particles, allowing the thermal stabilizers to remain distributed in the polyolefin and reducing the degradation of the composition due to exposure to a high-temperature environment. The above modalities may include any or a combination of the following features: wherein the inorganic mineral is talc; wherein the surface treatment component is polysorbate 20 (PO-20); wherein the ratio of PO-20 to talc is 0.1 to 5 wt%.; wherein the ratio of PO-20 to talc is 0.4 to 0.8 wt%.; wherein the thermal stabilizers are uniformly distributed throughout the polyolefin; and wherein the surface treatment component blocks sites on the particles that can adsorb the thermal stabilizers onto the polyolefin, thereby decreasing the polyolefin's resistance to deterioration of its properties as a result of exposure to a high-temperature environment; and wherein the surface treatment component improves the compatibility of the polyolefin and the particles. The embodiments of the present invention include a method for forming a composition, comprising: forming a surface treatment coating on the surfaces of inorganic mineral particles, wherein the inorganic mineral is selected from the group consisting of talc, calcium carbonate, precipitated calcium carbonate, clay, and silica, wherein the surface treatment coating is selected from the group consisting of a functionalized polyether and a carbon-based polymer;forming into compounds by melting particles coated with a polyolefin comprising thermal stabilizers to form a composition comprising the coated particles dispersed throughout a polyolefin matrix, wherein the surface treatment coating inhibits the adsorption of the thermal stabilizers onto the particles during compounding so that the thermal stabilizers are dispersed throughout the polyolefin matrix. The above modalities include any or a combination of the following features: wherein the inorganic mineral is talc; wherein the surface treatment coating is polysorbate 20 (PO-20); wherein the ratio of PO-20 to talc is 0.1 to 5 wt%.; wherein the ratio of PO-20 to talc is 0.4 to 0.8 wt%.; wherein the thermal stabilizers are uniformly distributed throughout the polyolefin matrix; and wherein the surface treatment component blocks sites on the particles that can adsorb the thermal stabilizers in the polyolefin matrix, thereby decreasing the polyolefin's resistance to deterioration of its properties as a result of exposure to a high-temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 represents the results of the Long-Term Thermal Aging (LTHA) tests for a polyolefin, an untreated talc, and talc coated with polysorbate 20. Figure 2 represents the results of the Long-Term Thermal Aging (LTHA) tests for a polyolefin, an untreated talc, and talc coated with polysorbate 20. Figure 3 represents the results of LTHA tests for a polyolefin, untreated talc, and talc coated with polysorbate 20 at a talc concentration of 20% by weight. Figure 4 represents the LTHA test results for a polyolefin, untreated talc, and talc coated with polysorbate 20 at a talc concentration of 40% by weight. DETAILED DESCRIPTION OF THE INVENTION The dimensional stability and stiffness of polyolefins can be improved by incorporating inorganic particles into the polyolefin polymer to form a composite polymer resin. Examples of inorganic materials include talc, calcium carbonate, precipitated calcium carbonate, clay, and silica. Certain inorganic mineral particles have both polar and nonpolar or hydrophobic regions or sites. The polar regions or sites tend to preferentially adsorb polar species, such as polymeric hindered amines, phenolic-based compounds, and thioethers, which are typically used as thermal stabilizers. Talc particles, for example, have a plate-like structure with nonpolar or hydrophobic surfaces and polar edges. Talc incorporated into a polymer adsorbs the thermal stabilizers added to the polyolefin, preferentially to the polar edges of the talc particles. It is important that the thermal stabilizers remain dispersed throughout the polyolefin polymer to provide thermal stability when exposed to high temperatures. The adsorption of thermal stabilizers by the talc present in the polyolefin for thermal stability decreases the polymer's resistance to thermal energy. Therefore, the adsorption of thermal stabilizers causes brittleness in a composite composition much sooner than if talc were not added to the polymer.This has been a long-term problem since the development of talc-reinforced polyolefin-based plastics in high-temperature environments. The problem of thermal stabilizer adsorption can be addressed by using more expensive engineered resins such as nylon or by increasing the amount of costly thermal stabilizers (such as polymeric hindered amines) to compensate for the amount adsorbed by the talc. However, these alternatives may not be a cost-effective way to mitigate the accelerated thermal degradation of talc-polyolefin composite materials for high-temperature applications. The present invention includes a surface treatment that adsorbs strongly enough onto talc to block the adsorption sites of the thermal stabilizers on the polyolefin polymer and is compatible with both the talc and the polyolefin matrix. This surface treatment allows the thermal stabilizers to remain in the polymer matrix, extending the service life of the part subjected to elevated temperatures significantly longer than if the surface treatment were not added to the talc prior to fusion compounding with the polyolefin. Fusion compounding is a process of melting the polymer blend with other additives.Developing such a surface treatment is challenging at least in part because a surface treatment must be identified that adsorbs strongly enough onto the polar edges of the undesorbed talc mineral during melt compounding and is still compatible with the polyolefin matrix. Aspects of the present invention include a composition comprising a polyolefin; inorganic mineral particles with a surface treatment comprising a coating of a surface treatment component and thermal stabilizers. The inorganic mineral is selected from the group consisting of talc, calcium carbonate, precipitated calcium carbonate, clay, and silica. The surface treatment component may be selected from the group consisting of a functionalized polyether and a carbon-based polymer. The surface treatment component inhibits the adsorption of the thermal stabilizers onto the particles, thereby enabling the thermal stabilizers to reduce degradation of the composition due to exposure to a high-temperature environment. In the above aspects, the coating partially or completely covers a surface of the particles. The thickness of the coating can be uniform over the surface of the talc particles. In the previous aspect, the thermal stabilizers are distributed throughout the polymer, rather than adsorbing preferentially onto the particle surface. It is believed that the surface treatment component blocks sites on the particles that can adsorb the thermal stabilizers onto the polymer, thus decreasing the polymer's resistance to thermal energy. As a result, the thermal stabilizers are able to improve heat resistance when exposed to heat in a high-temperature environment. A ratio of the surface treatment component to the particle can be 0.1 to 1% by weight. The amount or load of inorganic particles in the composition can be 0.1 to 1, 1 to 10% by weight, 10 to 20% by weight, 20 to 30% by weight, 30 to 40% by weight, or greater than 40% by weight. One surface treatment component is polyoxyethylenated sorbitan monolaurate or polysorbate 20 (PO-20). PO-20 is a nonionic surfactant with a nonpolar end and a polar end. The structure of PO-20 is: Common commercial forms of PO-20 include Croda's Tween™ 20 and BASF's TMAZ® 20. A preferred inorganic mineral is talc. The preferred coating level range is 0.4 to 0.8 wt% PO-20 / wt% talc. PO-20 acts as a compatibilizer between the talc particles and the polyolefin. As a result, this facilitates the uniform dispersion of the particles within the polyolefin. Additionally, PO-20 adsorbs onto the polar edges of the talc and blocks the adsorption of thermal stabilizers. The average particle size of talc particles can be 0.1 to 10 microns, or narrower, 0.5 to 1 micron, 1 to 1.5 microns, 1.5 to 2 microns, 2 to 3 microns, 3 to 5 microns, or 5 to 10 microns. Thermal stabilizers in polyolefin are generally added during resin manufacturing at concentrations typically ranging from 0.05 to 1.0% by weight. These stabilizers are most commonly selected from sterically hindered amines, phenol-based compounds, and thioethers, added alone or in combination. Thermal stabilizers may be present in the composition at concentrations of 0.02 to 1.0% by weight, or narrower concentrations such as 0.02 to 0.05%, 0.05 to 0.07%, or 0.07 to 1.0% by weight. The present invention is a cost-effective solution for using an engineered resin as an alternative to polyolefin, and is more cost-effective than adding additional and more expensive thermal stabilizers to compensate for the amount adsorbed by the talc. The present invention involves treating the source of the problem (the talc surface) instead of adding additional thermal stabilizers to compensate for adsorption on the talc surface. A high-temperature application refers to one where a part is exposed to high temperatures during use and throughout all or part of its service life. High-temperature exposure may consist of repeated exposures where each high-temperature exposure is followed by a decrease in temperature to near or at ambient temperature until the next high-temperature exposure. Alternatively, high-temperature exposure may occur continuously throughout the part's service life. The temperature range for high-temperature exposure depends on the specific application. High temperature can be any temperature above ambient temperature. Ambient temperature might be 20–25°C. More specifically, high temperature could refer to 40–50°C, 50–100°C, 100–120°C, or above 120°C. High-temperature applications include, but are not limited to, under-hood applications, inside car cabins, household appliances (washing machines, dryers, ovens, refrigerators), and aircraft engines. High-temperature exposure for under-hood applications is 100–120°C, and the exposure time varies from exposure to exposure, ranging from a few minutes to several hours. High-temperature exposure for car cabin applications is 40–120°C, and the exposure time also varies from exposure to exposure, ranging from a few minutes to several hours. Generally, the customer specifies the high-temperature application, including a customer-specified high-temperature range, exposure time periods, and exposure frequency. The properties of a part used in a high-temperature application tend to degrade over time during its service life. In particular, exposure to heat results in polymer brittleness. Brittleness refers to a loss of ductility in a material, making it fragile. Brittleness makes a part susceptible to fracture and failure, rendering it unusable. Exposure to high temperatures or heat thus reduces a part's service life. A part's resistance to high-temperature exposure can be characterized by the time to embrittlement when the part is exposed to a specific high temperature. Heat exposure testing is referred to as thermal aging. Accelerated thermal aging is commonly used. Accelerated aging is a procedure that aims to determine a part's response under normal operating conditions over a relatively long period by subjecting the product to exaggerated conditions for a much shorter time. Exaggerated conditions for thermal aging correspond to an aging temperature higher than that experienced during normal use. An aging factor can be determined and used to calculate the response (e.g., time to brittleness) under normal operating conditions from the response observed in the aging test. For example, a time to brittleness of 200 hours might be observed at an aging temperature of 150°C.For a normal operating temperature of 100-120°C, the time to brittleness may correspond to approximately 400 hours. The thermal stability of parts is determined through long-term heat aging (LTHA) testing. A part is placed in a convection oven and exposed to high temperatures for a period of time. The part's properties are monitored, and the exposure time required to make the part brittle is identified. An exemplary procedure is ASTM Standard Procedure D-3045 for Heat Exposure Guidelines for Polypropylene. The equipment used for the test is a Blue M electric convection oven with hood ventilation. The oven is set to a designated aging temperature, such as 150°C, and a sample is placed in the oven after a suitable heating time. One objective of the aging test may be to make a determination of the resistance rating to oxidation or other degradation when the sample is exposed to hot air for an extended period of time. Another objective is to determine the time to brittleness, which is found at the point of sample failure. The assessment of failure can be subjective, so for consistency, failure can be defined as (1) color change = observation of any oxidized area with a rust color or (2) brittle failure = visible cracks throughout the sample. A cold sample is held in one hand to inspect both sides of the flexible bar, and the bar is gently flexed to check for cracks / fissures. The samples can be checked periodically, such as twice a day, until all fail. As samples fail, they can be removed from the oven. The failure rate can be reported as the average failure time for the five samples per sample, reported as hours until failure. Thermal stabilizers may include, but are not limited to, classes of hindered amine light stabilizers such as Chimassorb® 2020 and Uvinol® 4050 produced by BASF, phenolic and hindered phenols such as pentaerythrityl tetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and octacetyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, or thioethers such as dilauryl thiodipropionate, distearyl thiodipropionate, and dioctadecyl disulfide. These classes of thermal stabilizers can be used alone or in combination to improve the thermal stability of polyolefin-based polymer systems. In some aspects, the surface treatment component includes polyethers and functionalized polyethers to reduce the adsorption of the heat stabilizer onto the talc. The general structural formula is: H-(OCHR(CH2)x,CHRi)n-OH where n is the number of repeating units (molecular weight), x is zero or an integer, R is an alkyl group, O is oxygen, C is carbon, H is hydrogen, and Ri is a functional group which may be, without limitation, an alkyl carboxylate, an alkylamine, an alkylamide, an alkylthiol, an alkyl sulfate, an alkylsulfonate, an alkyl phosphate or an alkylphosphonate and the like. Polyethers and functionalized polyethers useful for the surface treatment of talc may be selected from the group consisting of poly(ethylene glycol), poly(ethylene glycol) bis-(carboxymethyl) ether, poly(ethylene glycol) dimethyl ether, poly(ethylene glycol-400) distearate, and the like, and functionalized polyethers (alkyl carboxylate, alkylamine, alkylamide, alkyl sulfate, alkylthiol, alkylsulfonate, alkyl phosphate, alkylphosphonate), wherein the alkylcarboxylate functionality is preferred. There is no limitation on the method used to produce the polyethers and functionalized polyether polymers. Any combination of the foregoing may be used. The polyethers and functionalized polyethers of the present invention may be manufactured by ionic polymerization or radical polymerization and the like, or by any other process known for producing polyethers and functionalized polyethers. The molecular weight range of polyethers and functionalized polyethers is approximately 1,000 to approximately 10,000,000 amu, with a preferred range of approximately 1,000 to approximately 1,000,000 amu. Molecular weight can be determined using GPC. It can be expressed as weight-average or number-average molecular weight. An additional aspect of the present invention relates to the use of carbon-based polymer coatings for surface treatment of talc in order to lower the adsorption level of the thermal stabilizer. Maleic acid / olefin copolymers are also included in the definition of carbon-based polymers. Carbon-based polymers useful for the surface treatment of talc can be selected from the group consisting of functionalized polyolefins: maleic acid / olefin copolymer, maleic acid / styrene copolymer, with the maleic acid / styrene copolymer being preferred. Mineral oils of any boiling point and paraffin waxes of any melting point are also included in the group of carbon-based polymers. The x / y ratio can range from approximately 100:1 to approximately 1:100, with the preferred ratio being approximately 10:1 to approximately 1:10. C is carbon, O is oxygen, H is hydrogen, and R is a functional group. R can be any group capable of bonding to carbon. This includes, but is not limited to, alkylcarboxylates, alkylamines, alkylamides, alkylthiols, alkyl sulfates, alkylsulfonates, alkyl phosphates, and alkylphosphonates, and the like. The molecular weight of the carbon-based polymer can range from approximately 100 to approximately 10,000,000 amu, with a preferred range of approximately 200 to approximately 2,000,000 amu An additional aspect of the present invention relates to the use of a surface treatment component of a functionalized polydialkyl, preferably polydimethylsiloxane, having the structural formula: [Si(CH3)(R) - O - Si(CH3)(R) - O]n where n is the number of repeating units (molecular weight), CH3 is a methyl group, Si is silicon, O is oxygen, and R is a functionalized alkyl group. The alkyl group may, without limitation, be functionalized with carboxylate, amine, amide, thiol, sulfate, phosphate, and the like. The siloxane polymers useful in the present invention may be selected from the group consisting of functionalized alkyl polydimethylsiloxane (carboxylate, amine, amide, thiol, sulfate, phosphate), wherein the carboxylate is preferred, bis-(12-hydroxystearate) terminated polydimethylsiloxane (Aldrich Chemical Co., 1001 West Saint Paul Avenue, Milwaukee, WI 53233), and graft poly(dimethylsiloxane)-polyacrylates (Aldrich). There is no limitation on the method used to produce the siloxane polymers. The siloxane polymers of the present invention may be manufactured by ionic polymerization or radical polymerization and the like, or any other process known for producing siloxane polymers. The molecular weight scale of siloxane polymer is from approximately 1000 to approximately 1,000,000 atomic mass units (amu), preferably scales from approximately 1000 to approximately 100,000 amu. The molecular weight can be determined by gel permeation chromatography (GPC). The silanes useful in the present invention have the structural formula SI₄R₄, where Si is silicon, and R can be any group capable of forming a covalent bond with silicon (e.g., an alkyl group, an alkoxy group, a functionalized alkyl group, a functionalized alkoxy group, and any combination thereof). The following silanes may be useful in the present invention: Octyltriethoxysilane (Momentive Silquest.RTM. A-137 silane), functional triamino silane (Momentive Silquest.RTM. A-1130 silane), and Bis-(gamma-triethoxysilanepropyl)amine (Momentive Silquest.RTM. A-1170 silane), all of which are commercially available from Momentive Performance Materials. An inorganic mineral, such as talc, calcium carbonate, precipitated calcium carbonate, clay, or silica, that is receptive to surface treatment, can be coated with the polymers described herein. However, talc is the preferred inorganic mineral. Talcs that are particularly useful are those that are receptive to surface treatment and are suitable for subsequent use in the production of polyolefin films. An exemplary, but not limiting, talc would normally have an empirical formula of Mgs SU Ow (OH)2 and a specific gravity of approximately 2.6 to approximately 2.9. The preferred talc, without further limitations, could have a mean or average particle size of approximately 0.1 microns to approximately 10 microns, wherein the mean or average particle size is approximately 0.5 microns to approximately 7 microns. The talc can be coated with approximately 0.0.1 percent by weight to approximately 10 percent by weight of the polymers described herein, wherein the preferred treatment level for the coating is approximately 0.25 percent by weight to 2 percent by weight, based on the weight of the polymer. All polymer coatings described herein can be applied to talc by any convenient dry powder mixing operation. One method includes applying the polysorbate 20 surface treatment to the talc, combining the talc and polysorbate streams at the desired rates to allow the target surface treatment to be achieved, and adding light to high shear agitation to fully combine and distribute the coating over the talc surface. The temperature at which the coating is applied to the talc ranges from approximately 0°C to approximately 500°C, preferably from approximately 30°C to approximately 200°C, and more preferably from approximately 60°C to approximately 80°C. The application temperature should be higher if the specific coating requires melting. Once the talc is coated, a talc-polyolefin composite or blend can be formed. A melt processing method such as extrusion or melt compounding can be used to form a coated talc-polyolefin composite. Without limitations, the coated talc can be added to an extruder or added as a pre-composited masterbatch to an extruder. A pre-composited masterbatch means that the resin and coated talc are pre-mixed in a compounder at a higher concentration and then diluted to the target mineral concentration by melt compounding with a resin, for example, in an extruder. A part can be formed from the mixture by passing the melt through a die or by using injection molding, thermoforming sheet, blow molding, or rotational molding, as examples. The polyolefins considered suitable for the present invention may be any polyolefin, which may be clear and crystalline. Non-limiting examples include crystalline α-olefin homopolymers with carbon numbers ranging from 2 to 12, or a mixture of two or more crystalline copolymers, or ethylene-vinyl acetate copolymers with other resins. The polyolefin resin may also be high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-propylene copolymers, poly-1-butene, ethylene-vinyl acetate copolymers, etc., and low- and medium-density polyethylenes. Additional examples are represented by random or block copolymers of polyethylene, poly-r-methylpentene-1-propylene, and ethylene-propylene, and ethylene-propylene-hexene copolymers.Among these, ethylene-propylene copolymers and those containing 1 or 2 selected from 1-butene, 1-hexene, 1-4-methylpentene, and 1-octene (the so-called LLDPEs) are particularly suitable, as well as metallocene-catalyzed polymers. The method for producing the polyolefin resin used in the present invention is not limited. For example, it can be manufactured by ionic polymerization or radical polymerization. Examples of polyolefin resins obtained by ionic polymerization include homopolymers such as polyethylene, polypropylene, polybutene-2, and poly-4-methylpentene, and ethylene copolymers obtained by copolymerizing ethylene and alpha-olefins. Alpha-olefins having 3 to 18 carbon atoms, such as propylene, 1-butene, 1-4-methylpentene, 1-hexene, 1-octene, 1-decene, and 1-octadecene, are used as α-olefins. These α-olefins can be used individually or in combination with other types. Other examples include propylene copolymers such as propylene-1-butene copolymers. Examples of polyolefin resins obtained by radical polymerization include ethylene alone or ethylene copolymers obtained by copolymerization of ethylene and radically polymerizable monomers.Examples of radically polymerizable monomers include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic acid esters and their acid anhydrides, as well as vinyl esters such as vinyl acetate. Specific examples of unsaturated carboxylic acid esters include ethyl acrylate, methyl methacrylate, and glycidyl methacrylate. These radically polymerizable monomers can be used individually or in combination. EXAMPLES Long-term heat aging tests and talc compositions are performed. In an initial set of aging tests, compositions including talc coated with PO-20 (Tween 20) and compositions including uncoated talc were studied. The polyolefin was a polypropylene (PP) copolymer (cPP Flint 5325HS (melt index 20)) from Flint Hill Resources Polymers, LLC of Longview, TX. Two talcs were used. The first talc was Talcron® MP 15-38, supplied by Specialty Minerals Incorporated. MP 15-38 has an average particle size of 2.0 microns. The second talc, Microtuff AG 191 (MTAG 191), also supplied by Specialty Minerals Incorporated, has an average particle size of 1.8 microns. The coating used was PO-20. The following compositions were evaluated: (1) MP 15-38 talc untreated on PP copolymer, (2) MP 15-38 talc treated in the laboratory with PO-20 to a coating level of 0.25 wt% PO-20 / wt% talc in PP copolymer, (3) MP 15-38 talc treated in the laboratory with PO-20 to a coating level of 0.5 wt% PO-20 / wt% talc in PP copolymer, (4) MP 15-38 talc treated in the laboratory with PO-20 to a coating level of 1.0 wt% PO-20 / wt% talc in PP copolymer, (5) MTAG 191 talc treated in the production facility with PO-20 to a coating level of 0.5-0.8% in the PP copolymer. Three different talc loading levels in PP copolymer were evaluated: 20 wt%, 30 wt%, and 40 wt%. The samples were subjected to long-term heat aging according to the ASTM D-3045 standard procedure described herein. The LTHA results, showing the hours to failure or brittleness, are shown in Table 1 and Figure 1. At a 20 wt% talc loading level, a significant improvement in time to failure was observed for all coated talc compositions (2)–(5), with (5) showing the best performance. At 30 wt% talc, the relative improvement was less significant for composition (2); however, (5) still showed a dramatic improvement. At 40 wt%, composition (2) showed no improvement, while compositions (3)–(5) still showed relative improvement. The smaller improvement in time to fracture for lower coating levels indicates a sensitivity to the minimum coating concentration. TABLE 1 LHTA of PP copolymer v talc samples with talc coated v uncoated ινΐΛ / a / zuzz / uiu / o Sample ID cPP Flint 5325 (%) LTHA Mineral at 150°C Hours to Failure Description (o / o) 1 2 100 80 None 0 20 835 MP 15-38 24 3 70 MP 15-38 30 24 4 60 MP 15-38 40 28 5 80 MP 15-38 w / 0.25% Tween 20 20 232 6 70 MP 15-38 w / 0.25% Tween 20 30 46 7 60 MP 15-38 w / 0.25% Tween 20 40 24 8 80 MP 15-38 w / 0.50% Tween 20 20 500 9 70 MP 15-38 w / 0.50% Tween 20 30 224 10 60 MP 15-38 w / 0.50% Tween 20 40 101 11 80 MP 15-38 w / 1.0% Tween 20 20 473 12 70 MP 15-38 w / 1.0% Tween 20 30 270 13 60 MP 15-38 w / 1.0% Tween 20 40 176 14 80 MTAG 191 20 701 15 70 MTAG 191 30 442 16 60 MTAG 191 40 227 In a second set of aging tests, compositions including talc coated with PO 20 polymer were studied. The polyolefin was a polypropylene copolymer (cPP). The following compositions were evaluated: (6) Ultratalc 609, surface untreated talc (average particle size 0.8 microns), (7) Microtuff AG 609, surface treated with 0.8 wt% PO-20 in a production facility (average particle size 0.8 microns). Both talcs are from Specialty Minerals Incorporated. The talc concentrations studied in the cPP were 20 wt% and 40 wt%. The talc compositions were compared to the cPP polymer at 0 wt% talc concentration. Figure 2 shows the results of the thermal aging studies. At a 20 wt% loading, the improvement in hours to brittleness is significantly better for Microtuff AG 609 (talc coated with 0.8% PO-20) compared to Ultratalc 609, which has no surface treatment. At a 40 wt% loading, Microtuff AG 609 is still superior, although the hours to brittleness are reduced. In a third set of aging tests, compositions including polymer-coated talc were studied. The polyolefin was a polypropylene (PP) copolymer (cPP Flint 5325HS (melt index 20)) from Flint Hill Resources Polymers, LLC of Longview, TX. Three talcs, all from Specialty Minerals Incorporated, were studied: (8) Ultratalc 609 - average particle size of 0.8 microns, without surface treatment (9) Microtuff AG-609 (MTAG 609) - average particle size of 0.8 microns containing 0.8 wt% PO-20, surface treatment, (10) Flextalc 610 - average particle size of 1 micron, without surface treatment, Two talc loading levels were studied: 20 wt% and 40 wt%. The LTHA results are shown in Figures 3 and 4 for the respective talc concentrations. For the 20 wt% loading level, the surface treated with MTAG 609 yielded the best results. The FT610 and UT609 samples (untreated talc on the surface) showed significantly lower brittleness times. Similar results, in relative terms, are shown for the 40 wt% loading level. The foregoing description of the illustrated embodiments of the invention, including what is described in the abstract, is not intended to be exhaustive or to limit the invention to the precise embodiments described. While the specific embodiments and examples of the invention are described herein for illustrative purposes, various modifications within the scope of the invention are possible, as will be recognized by those skilled in the relevant art.

Claims

1. A composition characterized in that it comprises: a polyolefin; inorganic mineral particles comprising a surface treatment component; and a heat stabilizer; wherein the inorganic mineral comprises talc, calcium carbonate, precipitated calcium carbonate, clay, silica, or any combination of talc, calcium carbonate, precipitated calcium carbonate, clay and silica, and wherein the surface treatment component comprises a polysorbate.

2. The composition according to claim 1, further characterized in that the inorganic particles comprise an average particle size of 0.1 to 10 microns.

3. The composition according to claim 1, further characterized in that the inorganic mineral comprises talc.

4. The composition according to claim 1, further characterized in that the ratio of the weight percent of the surface treatment component in the composition to the weight percent of inorganic mineral in the composition is 0.1 to 5.

5. The composition according to claim 1, further characterized in that the weight percentage ratio of the surface treatment component in the composition to the weight percentage of inorganic mineral in the composition is 0.4 to 0.

8.

6. The composition according to claim 1, further characterized in that the surface treatment component blocks sites on the particles that can adsorb the thermal stabilizer, and wherein the thermal stabilizer constitutes 0.02 to 1.0 percent by weight of the composition.

7. A method for forming a composition, characterized in that it comprises: forming a surface treatment coating on surfaces of inorganic mineral particles, wherein the inorganic mineral comprises one or more members of the group consisting of talc, calcium carbonate, precipitated calcium carbonate, clay, and silica, wherein the surface treatment coating comprises a polysorbate; forming into composites by fusion the coated particles with a polyolefin comprising a heat stabilizer to form a composition comprising the coated particles dispersed throughout a polyolefin matrix, wherein the surface treatment coating inhibits the adsorption of the heat stabilizer onto the particles during composite formation so that the heat stabilizer is dispersed throughout the polyolefin matrix.

8. The method according to claim 7, because the inorganic mineral comprises talc.

9. The method according to claim 7, because a polysorbate to inorganic mineral ratio is 0.1 to 5% by weight.

10. The method according to claim 9, further characterized in that a polysorbate to inorganic mineral ratio is 0.4 to 0.8% by weight.

11. The method according to claim 7, further characterized in that the inorganic particles comprise an average particle size of 0.1 to 10 microns.

12. The method according to claim 7, further characterized in that the surface treatment coating blocks sites on the inorganic particles that can absorb the thermal stabilizer, and wherein the thermal stabilizer constitutes 0.02 to 1.0 percent by weight of the composition.