1. A composition comprising: a polyolefin; particles of an inorganic mineral 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 polysorbate.

2. The composition of claim 1, wherein the inorganic particles have a median particle size of 0.1 to 10 microns.

3. The composition of claim 1, wherein the inorganic mineral comprises talc.

4. The composition of claim 1, wherein the ratio of the weight percent of the surface treatment component in the composition to the weight percent of the inorganic mineral in the composition is from 0.1 to 5.

5. The composition of claim 1, wherein the ratio of the weight percent of the surface treatment component in the composition to the weight percent of the inorganic mineral in the composition is from 0.4 to 0.8.

6. The composition of claim 1, wherein the surface treatment component blocks sites on the particles where a thermal stabilizer can be adsorbed, and wherein the thermal stabilizer comprises from 0.02 to 1.0 wt% of the composition.

7. A method of forming a composition, the method comprising: forming a surface treatment coating on a surface of particles of an inorganic mineral, 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 functionalized polyether, a carbon-based polymer, or both; melt compounding the coated particles with a polyolefin containing a thermal stabilizer to form a composition comprising the coated particles dispersed throughout a polyolefin matrix, wherein the surface treatment coating inhibits adsorption of the thermal stabilizer onto the particles during compounding such that the thermal stabilizer is dispersed throughout the polyolefin matrix.

8. The method of claim 7, wherein the inorganic mineral comprises talc.

9. The method of claim 7, wherein the surface treatment coating comprises polysorbate.

10. The method of claim 9, wherein the ratio of polysorbate to inorganic mineral in weight percent is 0.1 to 5.

11. The method according to claim 9, wherein the ratio of polysorbate to inorganic mineral in weight percent is 0.4 to 0.8.

Background

Certain polymers, such as polyolefins, are particularly useful for high temperature applications due to their high thermal stability when used with thermal stabilizers. Parts in such applications are, for example, at high temperatures well above ambient temperature every few minutes or hours of the parts under the hood of a motor vehicle. Polyolefins may undergo such use for several hours before thermal instability (e.g., manifested as embrittlement) begins. However, the stiffness possessed by polyolefins themselves may be insufficient for certain applications. In addition, the cyclic nature of the thermal exposure causes the part to expand and contract, which results in dimensional instability, i.e., the shape of the part changes during use.

What is needed is a polyolefin composition having high thermal stability while also having high dimensional stability and high stiffness for use in a wide range of high temperature applications.

Disclosure of Invention

Embodiments of the invention include compositions comprising: a polyolefin; a surface treated inorganic mineral particle having a coating comprising a surface treatment component, and a thermal stabilizer, 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 functionalized polyethers, and carbon based polymers, wherein the surface treatment component inhibits absorption of the thermal stabilizer onto the particle to allow the thermal stabilizer to remain distributed in the polyolefin and reduce degradation of the composition due to exposure to high temperature environments.

The above embodiments may include any one or 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 from 0.1 to 5 wt%; wherein the ratio of PO-20 to talc is from 0.4 to 0.8 wt%; wherein the heat stabilizer is uniformly distributed in the polyolefin matrix; and wherein the surface treatment component blocks sites on the particle that can adsorb thermal stabilizers in the polyolefin, such adsorption reducing the polyolefin's resistance to deterioration of its properties due to exposure to high temperature environments; and wherein the surface treatment component increases the compatibility of the polyolefin and the particle.

Embodiments of the present invention include a method of forming a composition comprising forming a surface treatment coating on the surface 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 functionalized polyethers, and carbon-based polymers; melt compounding the coated particles with a polyolefin containing a thermal stabilizer to form a composition comprising the coated particles dispersed in a polyolefin matrix, wherein the surface treatment coating inhibits adsorption of the thermal stabilizer onto the particles during compounding such that the thermal stabilizer is dispersed in the polyolefin matrix.

The above embodiments include any one or 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 from 0.1 to 5 wt%; wherein the ratio of PO-20 to talc is from 0.4 to 0.8 wt%; wherein the heat stabilizer is uniformly distributed in the polyolefin matrix; and wherein the surface treatment component blocks sites on the particles that can adsorb thermal stabilizers in the polyolefin matrix, such adsorption reducing the resistance of the polyolefin to degradation of its properties due to exposure to high temperature environments.

Drawings

Figure 1 depicts the Long Term Heat Aging (LTHA) test results for polyolefins, untreated talc, and talc coated with polysorbate 20.

Figure 2 depicts the Long Term Heat Aging (LTHA) test results for polyolefins, untreated talc, and talc coated with polysorbate 20.

Figure 3 depicts the results of the LTHA test for polyolefin, untreated talc, and talc coated with polysorbate 20 (talc concentration 20 wt%).

Figure 4 depicts the results of the LTHA test for polyolefin, untreated talc, and talc coated with polysorbate 20 (talc concentration 40 wt%).

Detailed Description

The dimensional stability and stiffness of polyolefins can be improved by including inorganic particles within the polyolefin polymer to form a composite polymer resin. Exemplary inorganic materials include talc, calcium carbonate, precipitated calcium carbonate, clay or silica. Some inorganic mineral particles have both polar and non-polar 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 typically used as thermal stabilizers.

Talc particles, for example, plate-like structures having non-polar or hydrophobic surfaces and polar edges. Talc incorporated into the polymer preferentially adsorbs the thermal stabilizer added to the polyolefin into the polar edges of the talc particles. It is important for thermal stabilizers to remain dispersed within the polyolefin polymer to provide thermal stability to the polymer when exposed to high temperatures. The adsorption of heat stabilizers present in polyolefins to provide thermal stability by talc reduces the resistance of the polymer to thermal energy. Thus, adsorption of the thermal stabilizer causes embrittlement of the composite composition for a much faster time than when talc is not added to the polymer. This has been a long-standing problem due to the development of talc-reinforced polyolefin-based plastic materials in high temperature environments.

The adsorption problem of the heat stabilizer can be solved by using more expensive engineering resins such as nylon or increasing the amount of expensive heat stabilizer (e.g., polymeric hindered amine) to compensate for the amount adsorbed by talc. However, these alternatives cannot be a cost effective way to mitigate the problem of accelerated thermal degradation of talc-polyolefin composites for high temperature environmental applications.

The present invention includes a surface treatment that adsorbs strongly enough onto talc to block sites that adsorb thermal stabilizers in polyolefin polymers and is compatible with both talc and polyolefin matrix. The surface treatment in turn allows the thermal stabilizer to remain in the polymer matrix, so that the service life of parts subjected to high temperatures is increased much longer than if no surface treatment had been added to the talc prior to melt compounding with the polyolefin. Melt compounding is a process of melt blending polymers with other additives. The challenge in the development of such surface treatments is at least in part because it must be determined that the surface treatment adsorbs strongly enough onto the polar edges of the talc mineral to not desorb during melt compounding and still be compatible with the polyolefin matrix.

Aspects of the invention include compositions comprising: a polyolefin; surface treated inorganic mineral particles having a coating comprising a surface treatment component, and a thermal stabilizer. The inorganic mineral is selected from talc, calcium carbonate, precipitated calcium carbonate, clay and silica. The surface treatment component may be selected from the group consisting of functionalized polyethers and carbon-based polymers. The surface treatment component inhibits the adsorption of the thermal stabilizer on the particles, which allows the thermal stabilizer to reduce degradation of the composition due to exposure to high temperature environments.

In the above aspect, the coating partially or completely covers the particle surface. The coating thickness may be uniform over the surface of the talc particles.

In the above aspect, the thermal stabilizer is distributed among the polymers rather than being preferentially adsorbed on the particle surface. It is believed that the surface treatment component blocks sites on the particles where thermal stabilizers in the polymer can be adsorbed, which would reduce the resistance of the polymer to thermal energy. Thus, the thermal stabilizer can improve thermal resistance to thermal exposure in a high temperature environment.

The ratio of surface treatment component to particles may be 0.1 to 1 wt%.

The content or loading of the inorganic particles in the composition can be 0.1 to 1, 1 to 10 wt%, 10 to 20 wt%, 20 to 30 wt%, 30 to 40 wt%, or greater than 40 wt%.

Preferred surface treatment components are polyoxyethylene (20) sorbitan monolaurate or polysorbate 20 (PO-20). PO-20 is a nonionic surfactant having a non-polar end and a polar end. The structure of PO-20 is:

typical commercially available forms of PO-20 include Tween from Croda^TM20 and from BASF20. The preferred inorganic mineral is talc, with a preferred coating amount ranging from 0.4 to 0.8 wt% PO-20/wt talc.

PO-20 acts as a compatibilizer between the talc particles and the polyolefin. Thus, it helps the particles to be uniformly dispersed in the polyolefin. In addition, PO-20 adsorbs on the polar edges of talc and blocks the thermal stabilizer adsorption.

The median particle size of the talc particles can be from 0.1 to 10 microns, or more narrowly, from 0.5 to 1 micron, from 1 to 1.5 microns, from 1.5 to 2 microns, from 2 to 3 microns, from 3 to 5 microns, or from 5 to 10 microns.

Heat stabilizers in polyolefins are usually added by resin manufacture, typically in concentrations ranging from 0.05 to 1.0 wt%. These heat stabilizers are most commonly selected from hindered amines, phenolic compounds, and thioethers added alone or in combination with each other. The heat stabilizer may be 0.02 to 1.0 wt% of the composition, or more narrowly, 0.02 to 0.05 wt%, 0.05 to 0.07 wt%, or 0.07 to 1.0 wt% of the composition.

The present invention is a cost effective solution to use alternative engineering resins to polyolefins and is more cost effective than adding additional more expensive thermal stabilizers to compensate for the amount adsorbed by talc. The present invention involves treating the source of the problem (talc surface) rather than adding additional heat stabilizer to compensate for adsorption onto the talc surface.

High temperature applications refer to applications in which a component is exposed to high temperatures during use and throughout all or a portion of its useful life. The high temperature exposure may correspond to repeated exposures in which the temperature drops to near or to ambient temperature after each high temperature exposure until the next high temperature exposure. Alternatively, the high temperature exposure may continue throughout the useful life of the component.

The temperature of the high temperature exposure depends on the particular application. The elevated temperature may be any temperature higher than the ambient temperature. The ambient temperature may be 20-25 ℃. More narrowly, elevated temperatures can mean temperatures of 40-50 deg.C, 50-100 deg.C, 100-120 deg.C, or greater than 120 deg.C.

High temperature applications include, without limitation, under the hood of an automobile, in the cabin of an automobile, electrical appliances (washer, dryer, oven, refrigerator), and aircraft engines. The high temperature exposure for under hood applications is 100-. The high temperature exposure for automotive compartment applications is 40-120 ℃, and the exposure periods vary and may last from minutes to hours. Generally, high temperature applications are custom made with a customer specified high temperature range, exposure time period, and exposure frequency.

The properties of components used in high temperature applications tend to degrade over time during their useful life. In particular, the thermal exposure causes embrittlement of the polymer. "embrittlement" means the loss of ductility in the material, rendering it brittle. Embrittlement makes the part susceptible to breakage and damage, rendering it unusable. The heat and high temperature exposure thus reduces the usable life of the component. The resistance of a component to high temperature exposure may be characterized by the time the component is exposed to a specified high temperature to embrittlement.

The test of heat exposure is called heat aging. Accelerated heat aging is typically used. Accelerated aging is a procedure intended to determine the response of a component over a longer period of time under normal use conditions by subjecting the product to the most adverse conditions over a much shorter period of time. The most adverse conditions for thermal aging correspond to aging temperatures that are higher than those encountered during normal use. The aging factor can be determined from the response observed in the aging test and used to calculate the response (e.g., time to embrittlement) under normal use conditions. For example, the time to embrittlement observed at an ageing temperature of 150 ℃ is 200 hours. The time to achieve embrittlement may correspond to about 400 hours for normal use temperatures of 100-.

The thermal stability of the parts was determined by long-term thermal aging (LTHA) testing. The part is placed in a convection oven and exposed to elevated temperatures for a period of time. The performance of the component is monitored and the exposure time required for embrittlement of the component is confirmed.

An exemplary procedure is ASTM Standard procedure No. D-3045 for thermal exposure guidance of Polypropylene. The equipment used for this test was a Blue M Electric Convection Oven (Electric connection Oven) with exhaust to a ventilation Hood (fune Hood). The oven is set to a specified aging temperature, e.g., 150 ℃, and after a suitable warm-up time, the sample is placed in the oven.

One purpose of the aging test may be to determine the degree of resistance of the sample to oxidation or other degradation when exposed to hot air for extended periods of time (ranking). Another object is to determine the embrittlement time which is determined by the damage to the test specimen. The assessment of damage can be subjective, for consistency, and damage can be defined as either (1) a color change-observing any oxidized areas with rust color, or (2) brittle damage-a visible crack throughout the specimen. The cooled test specimen was held in the hand to check both sides of the bent strip and the strip was gently bent to check for brittleness/cracking.

The specimen may be inspected periodically, for example twice daily, until all damage has occurred. When the sample is damaged, it can be removed from the oven. The rate of damage can be recorded as the average of the time to damage of five specimens per sample, which is recorded as the number of hours to reach damage.

The heat stabilizer may be, but is not limited to, a hindered amine light stabilizer, such as produced by BASF2020 and4050 phenols and hindered phenols, such as pentaerythritol tetrakis-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate and octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, or thioethers, such as dilauryl thiodipropionate, distearyl thiodipropionate, and dioctadecyl disulfide. These classes of thermal stabilizationThe agents may be used alone or in combination with each other to improve the thermal stability of the polyolefin-based polymer system.

In some aspects, the surface treatment component includes a polyether and a functionalized polyether to reduce adsorption of the thermal stabilizer onto the talc. The general structure is as follows:

H-(OCHR(CH2)_x,CHR₁)_n-OH

wherein n is the number of repeating units (molecular weight), x is 0 or an integer, R is alkyl, O is oxygen, C is carbon, H is hydrogen, and R is₁Is a functional group which can be, but is not limited to, an alkyl carboxylate, an alkyl amine, an alkyl amide, an alkyl thiol, an alkyl sulfate, an alkyl sulfonate, an alkyl phosphate, or an alkyl phosphonate, and the like.

The polyethers and functionalized polyethers useful for the surface treatment of talc may be selected from 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 carboxylates, alkylamines, alkylamides, alkyl sulfates, alkylthiols, alkyl sulfonates, alkyl phosphates, alkyl phosphonates), with alkyl carboxylate functionality being preferred. There is no limitation on the method used to produce the polyether and functionalized polyether polymers. Any combination of the above may be used. The polyethers and functionalized polyethers of the present invention may be made by ionic or free radical polymerization or the like, or by any other method known to produce polyethers and functionalized polyethers.

The molecular weight of the polyether and functionalized polyether ranges from about 1000 to about 10,000,000a.m.u., with a preferred range of about 1,000 to about 1,000,000 a.m.u.. The molecular weight can be determined by GPC. The molecular weight may refer to a number average molecular weight or a weight average molecular weight.

A further aspect of the invention relates to the use of a carbon based polymer coating for surface treating talc in order to reduce the adsorption level of heat stabilizers. Also included in the definition of carbon-based polymer are maleic acid/olefin copolymers.

The carbon-based polymer useful for surface treating talc may be selected from functionalized polyolefins: maleic acid/olefin copolymer, maleic acid/styrene copolymer, among which maleic acid/styrene copolymer is preferable. Also included in the group of carbon-based polymers are mineral oils of any boiling point and paraffins of any melting point. The ratio of x/y may range from about 100:1 to about 1:100, with a preferred range of about 10:1 to about 1: 10. C is carbon, O is oxygen, H is hydrogen, and R is a functional group. R may be any group that can form a chemical bond with carbon. It includes, without limitation, alkyl carboxylates, alkylamines, alkylamides, alkylthiols, alkyl sulfates, alkyl sulfonates, alkyl phosphates, alkyl phosphonates, and the like.

The molecular weight of the carbon-based polymer may range from about 100 to about 10,000,000a.m.u., and preferably ranges from about 200 to about 2,000,000 a.m.u..

A further aspect of the invention relates to a surface treatment component of a functionalized polydialkyl, preferably polydimethylsiloxane having the following structural formula:

[Si(CH₃)(R)-O-Si(CH₃)(R)-O]_n

wherein n is the number of repeating units (molecular weight), CH₃Is methyl, Si is silicon, O is oxygen, and R is a functionalized alkyl. The alkyl group may be functionalized with, without limitation, carboxylic acid esters, amines, amides, thiols, sulfates, and phosphates, among others.

The silicone polymers useful in the present invention may be selected from functionalized alkyl polydimethylsiloxanes (carboxylic esters, amines, amides, thiols, sulfates, phosphates), of which carboxylic esters, bis- (12-hydroxystearate) -terminated polydimethylsiloxanes (Aldrich Chemical Co. -1001West Saint Paul Avenue, Milwaukee, Wis.53233), poly (dimethylsiloxane) -graft-polyacrylates (Aldrich) are preferred. There is no limitation on the method used to produce the silicone polymer. The silicone polymer of the present invention can be made by ionic polymerization, radical polymerization, or the like, or any other method known to produce silicone polymers.

The molecular weight of the siloxane polymer ranges from about 1000 to about 1,000,000 atomic mass units (a.m.u.), with a preferred range being from about 1000 to about 100,000 a.m.u.. The molecular weight can be determined by Gel Permeation Chromatography (GPC).

Silanes useful in the present invention have the formula SiR₄Wherein Si is silicon and R may be an oxygen atomAny group that forms a covalent bond with silicon (e.g., alkyl, alkoxy, functionalized alkyl, and functionalized alkoxy, and any combination thereof). The following silanes may be used in the present invention: octyl triethoxysilane (Momentive Silquest. RTM. A-137 silane), triamino-functional silane (Momentive Silquest. RTM. A-1130 silane), bis- (gamma-trimethoxysilylpropyl) amine (Momentive Silquest. RTM. A-1170 silane), all of which are commercially available from Moentive Performance Materials.

Any inorganic mineral that can receive a surface treatment, such as talc, calcium carbonate, precipitated calcium carbonate, clay or silica, can be coated with the polymers described herein. However, talc is a preferred inorganic mineral. Particularly useful talcs are those that can be subjected to a surface treatment and can subsequently be used in the production of polyolefin films. An exemplary, but not limiting, talc typically has an empirical formula of Mg₃Si₄O₁₀(OH)₂And a specific gravity of about 2.6 to about 2.9. The preferred talc, without further limitation, may have an average or median particle size of from about 0.1 microns to about 10 microns, with a preferred average or median particle size of from about 0.5 microns to about 7 microns. Talc may be coated with from about 0.01 wt% to about 10% of the polymer described herein, with a preferred treatment level of coating being from about 0.25 wt% to 2 wt%, based on the weight of the polymer.

All of the polymer coatings described herein may be applied to the talc by any convenient dry powder mixing operation. The method includes applying a polysorbate 20 surface treatment agent to the talc, combining the talc with the polysorbate stream at a desired rate to allow the targeted surface treatment to be achieved, and adding mild to high shear agitation to thoroughly combine and distribute the coating on the talc surface.

The temperature at which the coating is applied to the talc ranges from about 0 ℃ to about 500 ℃, preferably from about 30 ℃ to about 200 ℃, and more preferably from about 60 ℃ to about 80 ℃. If a particular coating requires melting, the application temperature should be adjusted to a higher level.

Once coated, a composition or composite of talc and polyolefin can be formed. Melt processing methods, such as extrusion or melt compounding, can be used to form a composite of the coated talc and polyolefin. Without limitation, the coated talc may be added to the extruder or added to the extruder as an already compounded masterbatch. Compounded masterbatch means that the resin and coated talc are premixed at a higher concentration in a mixer and diluted to the target mineral concentration by melt compounding with the resin, for example, in an extruder.

The part may be formed from the mixture by passing the melt through a die or by using, for example, injection molding, thermoforming a sheet, blow molding, or rotational molding.

The polyolefins considered suitable for the present invention may be any polyolefin, which may be transparent crystalline. Non-limiting examples include crystalline homopolymers of alpha-olefins having carbon numbers in the range of 2 to 12, or blends 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 copolymer, poly-1-butene, ethylene-vinyl acetate copolymer, etc., as well as low and medium density polyethylene. Additional examples are represented by polyethylene, polypropylene, poly-r-methylpentene-1, and random or block copolymers of ethylene-propylene, and ethylene-propylene-hexene copolymers. Of these, copolymers of ethylene and propylene and those containing one or two selected from butene-1, hexene-1, 4-methylpentene-1, and octene-1 (so-called LLDPE) are particularly suitable, as well as metallocene-catalyzed polymers.

The production method of 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 the polyolefin resin obtained by ion polymerization include homopolymers such as polyethylene, polypropylene, polybutene-2 and poly-4-methylpentene, and ethylene copolymers obtained by copolymerizing ethylene and alpha-olefin, using alpha-olefin having 3 to 18 carbon atoms such as propylene, butene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1 and octadecene-1 as alpha-olefin. These alpha-olefins may be used alone or in two or more types. Other examples include propylene copolymers, such as copolymers of propylene and butene-1. Examples of the polyolefin resin obtained by radical polymerization include ethylene alone or an ethylene copolymer obtained by copolymerizing ethylene and a radical polymerizable monomer. Examples of the radical polymerizable monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic acid esters, and anhydrides thereof, and vinyl esters such as vinyl acetate. Specific examples of the unsaturated carboxylic acid ester include ethyl acrylate, methyl methacrylate and glycidyl methacrylate. These radically polymerizable monomers may be used alone or in two or more types.

Examples

Long-term heat aging tests of polyolefin and talc compositions were performed.

In a first set of aging tests, compositions containing talc coated with PO-20(Tween 20) and compositions containing uncoated talc were investigated. The polyolefin is a polypropylene copolymer (PP) obtained from Flint Hill Resources Polymers, LLC of Longview, TX (cPP Flint 5325HS (20 melt index)). Two talcs were used. The first talc is supplied by Specialty Minerals IncorporatedMP15-38 talc. The median particle size of MP15-38 was 2.0 microns. A second talc, Microtuff AG 191(MTAG 191), also available from Specialty Minerals Incorporated, having a median particle size of 1.8 microns. The coating used was PO-20. The following compositions were tested:

(1) MP15-38 talc not surface treated in PP copolymer,

(2) in PP copolymer, MP15-38 talc treated with PO-20 in a laboratory, coating level was 0.25 wt% PO-20/wt% talc,

(3) in PP copolymer, MP15-38 talc treated with PO-20 in a laboratory, coating level was 0.5 wt% PO-20/wt% talc,

(4) in PP copolymer, MP15-38 talc treated with PO-20 in a laboratory, coating level was 1.0 wt% PO-20/wt% talc,

(5) MTAG 191 talc treated with PO-20 in the manufacturing facility was coated at a level of 0.5-0.8% in PP copolymer.

Three different talc loadings in PP copolymer were tested: 20 wt%, 30 wt% and 40 wt%. The samples were heat aged for long periods of time according to ASTM Standard procedure No. D-3045, described herein. The LTHA results expressed in terms of the number of hours to failure or embrittlement are shown in Table 1 and FIG. 1.

All of the coated talc compositions (2) - (5) showed significant improvement in the number of hours to failure for a loading level of 20 wt% talc, with (5) being the best. The relative improvement of composition (2) is not significant for 30 wt% talc, however (5) still shows a significant improvement. Composition (2) showed no improvement for 40 wt%, while compositions (3) - (5) still showed relative improvements. A smaller improvement in the number of hours to failure for a lower coating level indicates sensitivity to minimum coating concentration.

TABLE 1 LHTA of PP copolymer with coated and uncoated talc and talc samples

In a second set of aging tests, compositions containing talc coated with PO-20 polymer were studied. The polyolefin is a polypropylene copolymer (cPP). The following compositions were tested:

(6) ultratalc 609, an untreated talc (median particle size 0.8 microns),

(7) microtuff AG 609, surface treated with 0.8 wt% PO-20 (median particle size 0.8 microns) in a manufacturing facility.

Both of these talcs are available from Specialty Minerals Incorporated. The talc concentrations studied in cPP were 20 wt% and 40 wt%. Talc compositions were compared to cPP polymers at a talc concentration of 0 wt%.

Figure 2 depicts the results of a thermal aging study. At 20 wt% loading, Microtuff AG 609 (talc coated with 0.8% PO-20) improved significantly better in the number of hours to achieve embrittlement compared to Ultratalc 609 without surface treatment. At 40 wt% load, Microtuff AG 609 is still superior, but the number of hours to achieve embrittlement is reduced.

In a third set of aging tests, compositions containing polymer coated talc were investigated. The polyolefin is a polypropylene (PP) copolymer (cPP Flint 5325HS (20 melt index)) obtained from Flint Hill Resources Polymers, LLC of Longview, TX. Three talcs were studied, all from Specialty Minerals Incorporated:

(8) ultratalc 609-median particle size 0.8 microns without surface treatment

(9) Microtuff AG-609(MTAG 609) -median particle size 0.8 microns, containing 0.8 wt% PO-20 surface treatment,

(10) flextalc 610-median particle size 1 micron, no surface treatment.

Two talc loadings, 20 wt% and 40 wt%, were investigated. The results of LTHA for the respective talc concentrations are shown in FIGS. 3 and 4. The surface treated MTAG 609 provided the best results for a 20 wt% loading. The FT610 and UT609 (talc without surface treatment) samples provided significantly lower hours to embrittlement. Similar results in the relative terms are shown for a loading of 40 wt%.

The above description of illustrated embodiments of the invention, including those described in the abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.

In particular, the invention also relates to the following items:

item 1. a composition comprising:

a polyolefin;

particles of a surface-treated inorganic mineral having a coating comprising a surface treatment component, and

a heat stabilizer,

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 functionalized polyethers and carbon-based polymers,

wherein the surface treatment component inhibits adsorption of the thermal stabilizer on the particles, such inhibition allowing the thermal stabilizer to remain distributed in the polyolefin and reduce degradation of the composition due to exposure to high temperature environments.

Item 2. the composition of item 1, wherein the inorganic mineral is talc.

Item 3 the composition of item 1, wherein the surface treatment component is polysorbate 20 (PO-20).

Item 4. the composition of item 3, wherein the ratio of PO-20 to talc is 0.1 to 5 wt%.

Item 5 the composition of item 4, wherein the ratio of PO-20 to talc is 0.4 to 0.8 wt%.

Item 6. the composition of item 2, wherein the surface treatment component is polysorbate 20 (PO-20).

Item 7 the composition of item 6, wherein the ratio of PO-20 to talc is 0.1 to 5 wt%.

Item 8 the composition of item 7, wherein the ratio of PO-20 to talc is 0.4 to 0.8 wt%.

Item 9 the composition of item 1, wherein the surface treatment component blocks sites on the particle that can adsorb internal thermal stabilizers of the polyolefin, which adsorption reduces the resistance of the polyolefin to deterioration of its performance due to exposure to high temperature environments.

Item 10 the composition of item 1, wherein the surface treatment component is a hydrophilic and lipophilic component that improves the compatibility of the polyolefin and the particles.

Item 11. a method of forming a composition, the method comprising:

forming a surface treatment coating on the surface 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 functionalized polyethers and carbon based polymers,

melt compounding the coated particles with a polyolefin containing a thermal stabilizer to form a composition comprising the coated particles dispersed throughout a polyolefin matrix, wherein the surface treatment coating inhibits adsorption of the thermal stabilizer onto the particles during compounding such that the thermal stabilizer is dispersed throughout the polyolefin matrix.

Item 12 the method of item 11, wherein the inorganic mineral is talc.

Item 13 the method of item 11, wherein the surface treatment coating is polysorbate 20 (PO-20).

Item 14 the method of item 13, wherein the ratio of PO-20 to talc is 0.1 to 5 wt%.

Item 15 the method of item 14, wherein the ratio of PO-20 to talc is 0.4 to 1.0 wt%.

Item 16 the method of item 12, wherein the surface treatment coating is polysorbate 20 (PO-20).

Item 17 the method of item 16, wherein the ratio of PO-20 to talc is 0.1 to 5 wt%.

Item 18 the method of item 17, wherein the ratio of PO-20 to talc is 0.4 to 1.0 wt%.

Item 19 the method of item 11, wherein the surface treatment component blocks sites on the particle that can adsorb thermal stabilizers within the polyolefin matrix, which adsorption reduces the resistance of the polyolefin to degradation of its properties due to exposure to high temperature environments.