Polymer compositions

Abstract

A polymer composition is disclosed. The polymer composition includes a polyethylene and a plurality of inorganic fibers. The polymer composition can enhance the thermal oxidative stability and / or thermal dimensional stability of a polyethylene, including PE-RT polymers. The polymer composition can be used to form pipes, pipe fittings, and injected molded articles.

Description

[0001] POLYMER COMPOSITIONS

[0002] FIELD

[0003] Embodiments of the present disclosure relate to polymer compositions, to methods to improve physical properties of polymer compositions and to pipes and pipe fittings comprising polymer compositions.

[0004] INTRODUCTION

[0005] Pipes and pipe fittings are used for fluid distribution. Pipe fittings include elbows, joints, T-joints, Y-joints, manifolds, end caps, valves and adapters where pipes are attached. An assembled system of pipes and pipe fittings channels water or other fluids. Pipes and pipe fittings were traditionally made from metal, but metal is heavy and susceptible to corrosion. More recently, polymer pipes and fittings have become common.

[0006] A target application for polymer pipes has been for hot-water heating, by carrying heated water to floors and radiators to heat buildings. Certain polyethylenes, called “Polyethylene for Raised Temperature Resistance” or “PE-RT” have suitable hydrostatic strength and high thennal stability to carry hot water for long periods without bursting. Accelerated testing suggests that pipes made with PE-RT resins should be durable for up to 50 years for hot and cold water applications. However, it is desired to further reduce the thermal oxidation of polyethylenes, including PE-RT polymers. Further, polymer pipes, including PE-RT pipes, are known to expand and shorten when cold or hot water goes through the system (called “longitudinal reversion”). Repeated cycles of contraction and expansion may weaken joints in the pipe system and cause leaking.

[0007] It is desirable to find polyethylene-based pipe formulations that have improved thennal oxidative stability and / or reduced longitudinal reversion.

[0008] SUMMARY

[0009] Tire first aspect disclosed herein is a polymer composition. The polymer composition comprising: (a) a polyethylene; (b) a plurality of inorganic fibers; and (c) an additive selected from the group consisting of (i) an inorganic filler, or (ii) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone, or (iii) both (i) and (ii). For simplicity, these polymer compositions can be called “filled polyethylene” or “polymer composition.” Tire second aspect disclosed herein is a pipe. The pipe can carry fluid. The pipe comprises a layer of a polymer composition comprising: (a) a polyethylene; (b) a plurality of inorganic fibers; (c) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone; and (d) optionally, an inorganic filler.The third aspect disclosed herein is a pipe fitting. The pipe fitting comprises a polymer composition comprising: (a) a polyethylene; (b) a plurality of inorganic fibers; (c) an inorganic filler, and (d) optionally a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone.

[0010] The fourth aspect disclosed herein is a method to modify the thermal expansion and contraction of a polyethylene. The method comprises the step of compounding the polyethylene with: (a) a plurality of inorganic fibers; (b) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone; and (c) optionally, an inorganic filler.

[0011] The fifth aspect disclosed herein is a method to raise the thermal oxidative stability of a polyethylene. Tire method comprises the step of compounding the polyethylene with: (a) a plurality of inorganic fibers; (b) an inorganic filler, and (c) optionally a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone.

[0012] Tire polymer composition described herein in this disclosure can exhibit improved resistance to thermal oxidation or improved resistance to longitudinal reversion or both.

[0013] DETAILED DESCRIPTION

[0014] Definitions:

[0015] “Compatibilizer” means a graft copolymer comprising a non-polar polymer backbone and at least one grafted polar moiety.

[0016] “Graft Ratio” means the weight ratio of grafted polar moieties to non-polar polymer backbone in a compatibilizer.

[0017] “A plurality of inorganic fiber” means more than one inorganic fiber, where the fiber that comprises glass or other inorganic minerals. Examples of inorganic fibers include glass fibers, carbon fibers, and the fibers in rock wool and slag wool.

[0018] “Inorganic filler” means a particulate inorganic material that is inert with respect to the components of the polymer composition at temperatures up to at least 300°C.

[0019] “High Density Polyethylene” (HDPE) means a substantially linear, or linear, polyethylene homopolymer or ethylene / a-olefin copolymer which (i) comprises units derived from ethylene and optionally units derived from at least one C3-C10 a-olefm comonomer; and (ii) has a density from 0.940 g / cm3 to 0.980 g / cm3. Non-limiting examples of HDPE are sold under the DOW™ trademark.

[0020] “Linear Low Density Polyethylene” (LLDPE) means a substantially linear, or linear, ethylene / a-olefin copolymer containing homogeneous short-chain branching distribution which (i) comprises units derived from ethylene and units derived from at least one C3-C10 a-olefm comonomer; and (ii) has a densityfrom 0.910 g / cm3 to 0.940 g / cm3. Non-limiting examples of LLDPE are sold under the DOWLEX™ and ELITE™ trademarks.

[0021] ‘‘Polyethylene” means polyethylene homopolymer or ethylene / a-olefin interpolymer that comprises more than 50 weight percent (wt.%) repeating units derived from ethylene monomer. Hie term polyethylene includes high density polyethylene, low density polyethylene, linear low density polyethylene and ethylenebased plastomers.

[0022] “Polyethylene for Raised Temperature Resistance” or “PE-RT” means a polyethylene that meets ISO Standard 22391, as it is published as Edition 2 in 2009.

[0023] “Polyolefin” means polyethylene or polypropylene.

[0024] “Short Inorganic Fiber” means inorganic fiber having an average length of no more than 5 mm. Polymer Compositions

[0025] The polymer composition in this disclosure comprise a polyethylene, a plurality of inorganic fibers, and an additive selected from (i) an inorganic filler or (ii) a compatibilizer, or (iii) both (i) and (ii). In some embodiments, the polymer composition comprises an inorganic filler. In some embodiments, the polymer composition comprises compatibilizer. In some embodiments, the polymer composition comprises both inorganic filler and compatibilizer.

[0026] In some embodiments, the polymer composition comprises at least 50 weight percent (wt.%) of a polyethylene, based on the total weight of the polymer composition, or at least 55 wt.% or at least 60 wt.% or at least 65 wt.% or at least 70 wt.% or at least 75 wt.% or at least 78 wt.% or at least 80 wt.% or at least 82 wt.%. In some embodiments, the polymer composition comprises at most 95 wt.% of a polyethylene, or at most 92 wt.% or at most 90 wt.% or at most 88 wt.% or at most 85 wt.% or at most 83 wt.%.

[0027] In some embodiments, the inorganic fibers are short inorganic fibers (as defined above), such as “chopped” inorganic fibers. In some embodiments, the polymer composition comprises at least 1 wt.% of the inorganic fibers, based on the total weight of the polymer composition, or at least 3 wt.% or at least 5 wt.% or at least 8 wt.% or at least 10 wt.% or at least 12 wt.% or at least 14 wt.% or at least 15 wt.%. In some embodiments, tire polymer composition comprises at most 35 wt.% inorganic fibers or at most 30 wt.% or at most 25 wt.% or at most 22 wt.% or at most 20 wt.%oratmost 18 wt.%oratmost 16 wt.%oratmost 15 wt.%.

[0028] In some embodiments, the additive comprises at least 1 wt.% inorganic filler, based on the total weight of the polymer composition, or at least 2 wt.% or at least 3 wt.% or at least 4 wt.% or at least 5 wt.% or at least 6 wt.% or at least 7 wt.% or at least 8 wt.% or at least 9 wt.% or at least 10 wt.%. In some embodiments, the additive comprises at most 25 wt.% inorganic filler or at most 22 wt.% or at most 20 wt.% or at most 18 wt.% or at most 16 wt.% or at most 14 wt.% or at most 12 wt.% or at most 10 wt.%.

[0029] In some embodiments, the additive comprises at least 0.1 wt.% compatibilizer, based on the total weight of the polymer composition, or at least 0.2 wt.% or at least 0.3 wt.% or at least 0.5 wt.% or at least0.8 wt.% or at least 1.0 wt.%. In some embodiments, the additive comprises at most 5.0 wt.% compatibilizer or at most 4.0 wt.% or at most 3.5 wt.% or at most 3.0 wt.% or at most 2.8 wt.% or at most 2.6 wt.% or at most 2.4 wt.% or at most 2.2 wt.% or at most 2.0 wt.%.

[0030] In some embodiments, polyethylene and optionally the compatibilizer are the only polymers in the polymer composition. In some embodiments, the polymer composition comprises other polymers in addition to polyethylene and optionally the compatibilizer. Examples of polymers known for use in pipes include polypropylene, polystyrene, polystyrene, ABS and polyvinyl chloride. In some embodiments, other polymers in the composition form homogeneous blends with the polyethylene. Compatibilizer may help to form homogeneous blends between polyethylene and polymers that comprise polar moieties. In some embodiments, the polymer composition comprises at most 20 wt% polymer other than polyethylene, based on the total weight of the polymer composition, or at most 18 wt% or at most 15 wt% or at most 12 wt% or at most 10 wt% or at most 8 wt% or at most 5 wt% or at most 2 wt% or at most 1 wt%. In some embodiments, the polymer composition comprises 0 wt.% polymer other than polyethylene.

[0031] In some embodiments, tire inorganic filler or compatibilizer or both are the only additives in the polymer composition. In some embodiments, the polymer composition comprises additional additives. Examples of common additives include antistatic agents, dyes, lubricants, pigments, primary antioxidants, secondary antioxidants, processing aids, UV stabilizers, nucleators, slip agents such as erucamide, antiblock agents, and combinations thereof. Examples of common primary and secondary antioxidants that may be used in piping applications are sold under the Irganox and Irgafos trademarks, respectively. In some embodiments, the additional additives make up no more than 5 wt.% of the polymer composition or no more than 4 wt.% or no more than 3 wt.% or no more than 2 wt.% or no more than 1 wt.%. In some embodiments, the additional additives make up essentially 0 wt.% of the polymer composition.

[0032] The polymer composition can be made by compounding the polyethylene, inorganic fibers, inorganic fillers and / or compatibilizer and optionally other components using known techniques. Equipment for compounding polymers includes mixers, extruders and kneaders that melt the polymers with heat and / or mechanical energy and homogeneously blend the polymers and other ingredients. In some embodiments of the compounding process, the polymers achieve a peak temperature of at least 180°C or at least 190°C or at least 200°C or at least 210°C. In some embodiments of the compounding process, the polymers achieve a peak temperature of at most 240 °C or at most 220°C or at most 210°C or at most 200°C. In some embodiments, the compounded polymers are extruded as pellets, which are convenient for storage, transportation and use.

[0033] In some embodiments, the polymer composition has a density of at least 0.970 g / cm3or at least 0.975 g / cm3or at least 0.980 g / cm3or at least 0.985 g / cm3or at least 0.990 g / cm3or at least 0.995 g / cm3or at least 1.000 g / cm3. In some embodiments, the polymer composition has a density of at most 1.18 g / cm3or atmost 1.15 g / cm3or at most 1.12 g / cm3or at most 1.10 g / cm3or at most 1.08 g / cm3or at most 1.05 g / cm3or at most 1.02 g / cm3.

[0034] In some embodiments, the polymer composition has a melt index suitable for pipe extrusion and / or for multilayer co-extrusion. In some embodiments, the polymer composition has a melt index (I2) of at least 0.05 g / 10 min or at least 0.1 g / 10 min or at least 0.2 g / 10 min or at least 0.3 g / 10 min. In some embodiments, the polymer composition has a melt index (I2) of most 3.0 g / 10 min, or at most 2.5 g / 10 min or at most 2.0 g / 10 min or at most 1.5 g / 10 min or at most 1.2 g / 10 min or at most 1.0 g / 10 min or at most 0.8 g / 10 min or at most 0.5 g / 10 min. In some embodiments, the polymer composition has a melt index (I5) of at least 0.5 g / 10 min or at least 0.7 g / 10 min or at least 0.9 g / 10 min or at least 1.0 g / 10 min or at least 1.1 g / 10 min. In some embodiments, the polymer composition has a melt index (Is) of at most 3.0 g / 10 min, or at most 2.5 g / 10 min or at most 2.0 g / 10 min or at most 1.7 g / 10 min or at most 1.5 g / 10 min. Melt indices for polymer composition are measured at 190°C according to the Test Methods.

[0035] In some embodiments, the polymer composition has a melt index suitable for injection molding. In some cases, the desired range of melt indices for injection molding is higher than the desired range for pipe extrusion. In some embodiments, the polymer composition has a melt index (I2) at 190°C of at least

[0036] 1 g / 10 min or at least 2 g / 10 min or at least 3 g / 10 min. In some embodiments, the polymer composition has a melt index (I2) at 190°C of most 20 g / 10 min, or at most 15 g / 10 min or at most 10 g / 10 min or at most 8 g / 10 min or at most 5 g / 10 min.

[0037] Polyethylene

[0038] Tire polymer composition comprises a polyethylene. Some embodiments of polyethylene are homopolymers, which consist essentially of repeating units derived from ethylene.

[0039] Some embodiments of polyethylene are copolymers which comprise both repeating units derived from ethylene and repeating units are derived from one or more alpha-olefin comonomers. Suitable alpha-olefins may include those comprising from 3 to 10 carbon atoms (C3-C10). For example, the alpha-olefin may be a C4-C10 alpha-olefin, a C3-C6 alpha-olefin, a C4-C8 alpha-olefin, or a Ce-Cg alpha-olefin. In some embodiments, the alpha-olefin is selected from tire group consisting of propylene, 1 -butene, 1 -pentene, 1 -hexene, 4-methyl-1-pentene. 1-heptene, 1-octene, 1-nonene and 1-decene. In other embodiments, the alpha-olefin is selected from the group consisting of propylene, 1-butene, 1-hexene. and 1-octene. In further embodiments, the alphaolefin is selected from the group consisting of 1-hexene and 1-octene. For example, repeating units derived from comonomers may conform to Formula 2:

[0040] (2) 4CH2-CHR}-wherein R is an alkyl or substituted alkyl group comprising 1 to 8 carbon atoms. In some embodiments, R comprises 2 to 6 carbon atoms or 4 to 6 carbon atoms.In some embodiments, the polyethylene comprises a single polyethylene. In some embodiments, the polyethylene comprises a blend of two or more polyethylenes.

[0041] Polyethylene are commonly classified based on their density and their melt index (12).

[0042] In some embodiments, the polyethylene is HDPE. In some embodiments, the polyethylene is LLDPE. In some embodiments, the polyethylene has a density of at least 0.930 g / cm3, or at least 0.935 g / cm3or at least 0.938 g / cm3or at least 0.940 g / cm3or at least 0.941 g / cm3. In some embodiments, the polyethylene has a density of at most 0.950 g / cm3or at most 0.948 g / cm3or at most 0.945 g / cm3or at most 0.943 g / cm3or at most 0.942 g / cm3.

[0043] In some embodiments, the polymer composition has a melt index (12) that is lower than the polyethylene used to make it. In some embodiments, the melt index of the polyethylene is at least 1 0% of the melt index of the polymer composition or at least 170% or at least 190%. In some embodiments, the melt index of the polyethylene is at most 300% of the melt index of the polymer composition or at most 250% or at least 220%.

[0044] In some embodiments, the polyethylene is selected such that the polymer composition has a melt index suitable for pipe extrusion and / or for multilayer co-extrusion. In some embodiments, the polyethylene has a melt index (I2) at 190°C of at least 0.2 g / 10 min or at least 0.4 g / 10 min or at least 0.5 g / 10 min. In some embodiments, the polyethylene has a melt index (I2) at 190°C of most 4.0 g / 10 min, or at most 3.0 g / 10 min or at most 2.0 g / 10 min or at most 1.5 g / 10 min or at most 1.2 g / 10 min or at most 1.0 g / 10 min or at most 0.8 g / 10 min or at most 0.6 g / 10 min.

[0045] In some embodiments, polyethylene is selected such that the polymer composition has a melt index suitable for injection molding. In some embodiments, the polyethylene has a melt index (I2) at 190°C of at least 1 g / 10 min or at least 2 g / 10 min or at least 3 g / 10 min or at least 4 g / 10 min or at least 5 g / 10 min or at least 6 g / 10 min. In some embodiments, the polyethylene has a melt index (I2) at 190°C of most

[0046] 25 g / 10 min, or at most 20 g / 10 min or at most 15 g / 10 min or at most 10 g / 10 min or at most 8 g / 10 min or at most 6 g / 10 min.

[0047] In some embodiments, the polyethylene is a Polyethylene of Raised Temperature Resistance or PERT polymer.

[0048] Polyethylenes that are suitable for use in pipes and pipe fittings are known and commercially-available. Other suitable polyethylenes can be made by polymerization of ethylene monomer and optionally comonomers in the presence of a catalyst, according to known processes. Known processes include solution phase polymerization, slurry phase polymerization and gas phase fluidized bed polymerization. Known catalysts include Ziegler-Natta catalysts, metallocene catalysts and other single-site catalysts. Suitable catalysts and polymerization equipment are commercially available with instructions fortheir use.Inorganic Fibers

[0049] Tire polymer composition comprises a plurality of inorganic fibers. In some embodiments, the inorganic fibers are short inorganic fibers, which have an average length of no more than 5 mm. In some embodiments, the short inorganic fibers are chopped fibers.

[0050] In some embodiments, the inorganic fibers are glass fibers. In some embodiments the glass fibers comprise C glass. In some embodiments, the glass fibers comprise A glass. In some embodiments, the glass fibers comprise E glass. In some embodiments, the inorganic fibers are rock fiber, such those spun from igneous rocks such as diabase, basalt and olivine, and carbonate rocks containing 40-60% calcium and magnesium carbonates. In some embodiments, the inorganic fibers are slag fiber.

[0051] In some embodiments, the inorganic fibers are ceramic fibers, such as those spun from alumina, silica and other metal oxides. In some embodiments, the inorganic fibers are carbon fiber.

[0052] In some embodiments, the inorganic fibers have an average diameter of at least 2 microns or at least 3 microns or at least 5 microns or at least 8 microns or at least 10 microns or at least 12 microns. In some embodiments, the inorganic fibers have an average diameter of at most 30 microns or at most 25 microns or at most 20 microns or at most 18 microns or at most 15 microns. In some embodiments, the inorganic fibers have an average diameter from 3 to 25 microns or from 5 to 20 microns or from 8 to 17 microns or from 5 to 10 microns or from 10 to 15 microns.

[0053] In some embodiments, the inorganic fibers in tire polymer composition have an average length of at least 0.05 mm or at least 0.10 mm or at least 0.12 mm or at least 0.15 mm or at least 0.20 mm or at least 0.25 mm or at least 0.30 mm or at least 0.35 mm or at least 0.40 mm. In some embodiments, the inorganic fibers have an average length of at most 5 mm or at most 4 mm or at most 3 mm or at 2 mm or at most 1 mm or at most 0.8 mm or at most 0.7 mm or at most 0.6 mm or at most 0.5 mm or at most 0.40 mm or at most 0.35 mm or at most 0.30 mm or at most 0.25 mm or at most 0.20 mm.

[0054] Note that compounding equipment that melts and blends polymers though mechanical force can break up fibers, so that fibers in the polymer composition may be shorter than the raw material fibers added into the equipment. Tire fiber lengths above describe the fibers in the polymer composition, not the raw material fibers. In some embodiments, the raw fibers added to the compounding equipment have a length up to 10 mm or up to 8 mm or up to 6 mm or up to 5 mm, and have a length of at least 0.5 mm or at least 1 mm or at least 2 mm or at least 3 mm or at least 4 mm.

[0055] In some embodiments, the inorganic fibers comprise a coating called a sizing or a cladding. Sizing protects the fibers from abrading against each other during handling, processing and fabrication. In some cases, sizing also improves adhesion between the fiber and organic polymers that the fibers are blended with. Common examples of sizing comprise a film-forming polymer (called a ‘“film fonner”) and a coupling agent. Common film formers include polyvinyl acetates, polyurethanes, polyolefins, polyesters, epoxies and modifiedepoxies. In some embodiments, the film former is selected to enhance the compatibility of the fiber with polymers that the fiber will be blended with. In some embodiments, the film former enhances the compatibility of the inorganic fibers with polyethylene, such as a polyolefin film fonner. In some embodiments, the film former enhances the compatibility of the inorganic fibers with a compatibilizer used in the polymer composition, such as an acrylate film former. In some embodiments, the coupling agent is an organic silane. The silane coupling agent acts as a primer that enables tire film former to attach to the fiber and also adhere to the polymer.

[0056] Suitable inorganic fibers are commercially available, such as under the Owens Coming trademark. Others can be made by known techniques, such as by spinning molten glass or rock.

[0057] Inorganic Filler

[0058] In some embodiments of the polymer composition, additive (c) comprises an inorganic filler. The inorganic filler is a particulate inorganic material that is inert with respect to the components of the polymer composition at temperatures up to at least 300°C. In some embodiments, the inorganic filler is inert with respect to the components of the polymer composition at temperatures up to at least 400°C or at least 500°C or at least 600°C or at least 700°C or at least 800°C or at least 900°C or at least 1000°C.

[0059] Examples of common inorganic fillers used in polyethylene pipes include talc, carbon black, calcium carbonate and silica and mixtures of two or more of those materials. Talc can improve sound dampening and increase modulus in polyethylene pipes. Calcium carbonate can increase the durability, hardness, and strength of the polyethylene pipes. In some embodiments, the inorganic filler comprises talc or at least 50 wt.% talc, based on the total weight of the inorganic filler, or at least 60 wt.% talc or at least 70 wt.% talc or at least 80 wt.% talc or at least 90 wt.% talc. In some embodiments, the inorganic filler consists essentially of talc. In some embodiments, the talc is a high-aspect ratio talc. In some embodiments, the talc is a medium-aspect ratio talc.

[0060] In many cases, the inorganic filler is chosen to add thermal stability? to the polymer composition. In some embodiments, the inorganic filler has a loss on ignition at 625 °C of no more than 5 wt.% or no more than 4 wt.% or no more than 3 wt.% or no more than 2 wt.% or no more than 1 wt.%. In some embodiments, the inorganic filler has a loss on ignition at 625°C of 0 wt.%.

[0061] In some embodiments, the inorganic filler has a median particle diameter (D50) of at least 0.5 microns or at least 0.6 microns or at least 0.7 microns or at least 0.8 microns or at least 0.9 microns or at least 1.0 microns. In some embodiments, the inorganic filler has an average particle diameter of at most 2.0 microns or at most 1.5 microns or at most 1.2 microns or at most 1.0 microns or at most 0.8 microns.

[0062] In some embodiments, the inorganic filler has a maximum particle diameter (D95) of at most 20 microns or at most 15 microns or at most 10 microns or at most 8 microns or at most 6 microns or at most 5 microns or at most 4 microns or at most 3 microns. In some embodiments, the inorganic filler has amaximum particle diameter (D95) of at least 0.5 microns or at least 1.0 micron or at least 2.0 microns or at least 2.5 microns.

[0063] Suitable inorganic fillers are commercially available. Others can be made by known techniques, such as by crushing or grinding and sieving minerals.

[0064] Compatibilizer

[0065] In some embodiments of the polymer composition, additive (c) comprises a compatibilizer. As previously described, the compatibilizer is the graft copolymer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone. In some embodiments, the compatibilizer enhances compatibility and / or blending between the inorganic fibers and the polyethylene. For clarity, the compatibilizer is in addition to any sizing on the inorganic fibers, and sizing on the fibers is not part of the compatibilizer in this invention.

[0066] The nonpolar polymer backbone comprises on average at least 10 polymerized hydrocarbyl repeating units, such as ethylene, propylene units or butylene. In some embodiments, the non-polar polymer backbone of the compatibilizer comprises a polyolefin polymer. In some embodiments, the non-polar polymer backbone comprises a polyethylene. In some embodiments, the non-polar polymer backbone comprises a polypropylene polymer. In some embodiments, the polyolefin polymer comprises on average at least 11 repeating units or at least 12 repeating units or at least 15 repeating units or at least 20 repeating units.

[0067] In some embodiments, the grafted polar moieties comprise pendant acid groups or acid derivatives such as anhydride or ester groups. In some embodiments, the grafted polar moieties do not comprise maleamic acid moieties or derivatives. In some embodiments, the grafted polar moieties comprise maleic acid moieties or derivatives.

[0068] In some embodiments, the polar moiety is produced by grafting polar functional monomers onto the nonpolar backbone. Examples of suitable polar functional monomers include vinyl acetate, vinyl alcohol, and unsaturated monomers that have anhydride, amine, amide, or acrylate functional groups. In some embodiments, the polar functional monomers exclude maleimide or maleamic acid. For example, graft polymer segments may comprise units derived from acrylic acid, methacry lic acid or maleic acid or their ester or anhydride derivatives, hi some embodiments, the compatibilizer is a polyethylene grafted with maleic acid or its derivative such as maleic anhydride.

[0069] In some embodiments, the graft ratio of the compatibilizer is at least 0.1 wt.%, or at least 0.3 wt. % or at least 0.5 wt.% or at least 0.6 wt.% or at least 0.7 wt.% or at least 0.8 wt.%. In some embodiments, the graft ratio of the compatibilizer is at most 3 wt.%, or at most 2 wt.% or at most 1.8 wt.% or at most 1.6 wt.% or at most 1.4 wt.% or at most 1.2 wt.% or at most 1.0 wt.%.

[0070] In some embodiments, the melt index (12) of the compatibilizer is at least 0.5 g / 10 min or at least 0.7 g / 10 min or at least 0.9 g / 10 min or at least 1.0 g / 10 min. In some embodiments, the melt index (12) of thecompatibilizer is at most 20 g / 10 min or at most 15 g / 10 min or at most 12 g / 10 min or at most 10 g / 10 min or at most 8 g / 10 min or at most 6 g / 10 min or at most 4 g / 10 min or at most 2 g / 10 min or at most 2.0 g / 10 min.

[0071] In some embodiments, the density of the compatibilizer is at least 0.87 g / cc or at least 0.90 g / cc or at least 0.91 g / cc or at least 0.92 g / cc or at least 0.93 g / cc or at least 0.94 g / cc or at least 0.95 g / cc or at least 0.950 g / cc or at least 0.955 g / cc. In some embodiments, the density of the compatibilizer is at most 0.965 g / cc or at most 0.962 g / cc or at most 0.960 g / cc or at most 0.958 g / cc.

[0072] In some embodiments, the number average molecular weight of the compatibilizer is at least 410 Da or at least 450 Da or at least 500 Da or at least 600 Da or at least 620 Da or at least 650 Da or at least 700 Da or at least 800 Da or at least 900 Da or at least 1000 Da.

[0073] For clarity, the compatibilizer comprises a graft copolymer and is not an oligomer of less than 5 repeating units such as bis-maleamic acid.

[0074] Suitable compatibilizers are known and commercially available, such as under the AMPLIFY™ and BYNEL™ trademarks. Other compatibilizers can be made by known processes, such as by contacting polyolefin polymer with ethylenically unsaturated monomers, as previously described at a temperature of from 140°C-210°C in the presence of an organic peroxide.

[0075] Properties of the Polymer composition

[0076] In some embodiments, the polymer composition has a minimum required strength (MRS) at 20°C of at least 8.0 MPa or at least 9.0 MPa or at least 10.0 MPa or at least 11.2 MPa or at least 12.5 MPa. There is no maximum desired MRS, but in some embodiments, MRS greater than 15.0 MPa or 13.0 MPa is unnecessary.

[0077] In some embodiments, the polymer composition has athermal oxidative stability of at least 50 minutes or at least 55 minutes or at least 60 minutes or at least 65 minutes or at least 70 minutes or at least 75 minutes or at least 80 minutes or at least 85 minutes or at least 90 minutes or at least 95 minutes. There is no maximum desired thermal oxidative stability, but in some embodiments, stability greater than 120 minutes or 100 minutes is unnecessary.

[0078] In some embodiments, the polymer composition is a PE-RT polymer.

[0079] In some embodiments, the polymer composition has a flexural modulus of at least 1000 MPa or at least 1500 MPa or at least 2000 MPa or at least 2500 MPa or at least 2700 MPa or at least 2900 MPa. In some embodiments, the polymer composition has a flexural modulus of at most 4000 MPa or at most 3500 MPa or at most 3200 MPa or at most 3000 MPa.

[0080] Fabricated ProductsThe polymer composition can be made into fabricated products, such as pipes and fittings.

[0081] Pipes can be made by known methods such as pipe extrusion. In a pipe extrusion line, polyethylene is melted in an extruder and extruded through an annular die to form a tubular melt. The molten pipe then passes through a sizing or calibration device (which fixes its dimensions) and into a cooling trough. The cooled pipe may be coiled or cut to desired lengths. Printing devices in the line may mark the extruded pipes for identification.

[0082] Some embodiments of the pipes of this invention comprise a layer of polymer composition that comprises:

[0083] (a) a polyethylene;

[0084] (b) a plurality of inorganic fibers:

[0085] (c) a compatibilizer as previously described; and

[0086] (d) optionally an inorganic filler,

[0087] as previously described.

[0088] In some embodiments, the pipes are suitable for carrying heated fluid under pressure, such as pressure up to at least 6 bar or at least 8 bar or at least 10 bar. In some embodiments, the pipes are suitable for carrying unpressurized fluids, such as drainpipes. In some embodiments, the pipes are small pipes having an inner diameter from 10 mm to 14 mm and a wall thickness from 1.5 mm to 2 mm. In some embodiments, the pipes are medium pipes having an inner diameter from 16 mm to 63 mm and a wall thickness from 2 mm to 6mm. In some embodiments, the pipes are large pipes having an inner diameter of at least 65 mm and a wall thickness of at least 8 mm. In some embodiments, the large pipes have an inner diameter of at least 200 mm and a wall thickness of at least 3 mm. In some embodiments, pipes have a length of at least 1 m or at least 5 m or at least 8 m or at least 10 m or at least 20 m or at least 30 m or at least 40 m or at least 50 m or at least 100 m. In some embodiments, the pipes are extruded in an endless process and pipes of smaller diameter can be coiled to several hundred meters in length.

[0089] In some embodiments, the pipe comprises a monolayer structure, in which case the layer of filled polyethylene makes up essentially all of the pipe.

[0090] In some embodiments, the pipe comprises a multilayer structure, which has two or more concentric layers of polymer. In this case, one or more concentric layers of the pipe comprise the filled polyethylene. Other layers of the pipe may comprise other polymers. Common polymers to be used in other layers of the pipe include polyethylene, barrier polymers such as EVOH (ethylene-vinyl alcohol), and tie layers.

[0091] In some embodiments, tire layer comprising polymer composition makes up at least 10 % of the thickness of the pipe, or at least 20% or at least 25% or at least 30% or at least 35% or at least 40% or at least 45% or at least 50% or at least 60% or at least 70% or at least 80% or at least 90%. In some embodiments, the layer of filled polyethylene makes up 100 % of the thickness of the pipe. The thickness in these embodimentsis the thickness or wall thickness of the pipe. In some embodiments, the pipe is a pipe, and the layer comprising the polymer composition is at least 0.1 mm thick or at least 0.3 mm or at least 0.5 mm. In some embodiments, the pipe can be referred to as a medium pipe, and the layer comprising the polymer composition is at least 1 mm thick or at least 1.5 mm or at least 2 mm. In some embodiments, the pipe can be referred to as a large pipe, and the layer comprising a polymer composition is at least 2 mm thick or at least 3 mm or at least 5 mm.

[0092] In some embodiments, a pipe comprises an outer layer of PE100-RC polymer, a middle layer comprising or consisting of the polymer composition, and an inner layer of PE100-RC polymer. PE 100-RC polymer meets PE 100 strength requirements and also has enhanced resistance to stress cracking (slow crack growth) and rapid crack propagation. Examples of PE 100-RC polymer are commercially available from multiple sources. In some embodiments, the polymer composition layer(s) make up at least 25 percent of the wall thickness of tire pipe or at least 28 percent or at least 30 percent or at least 32 percent or at least 35 percent. In some embodiments, the polymer composition layer(s) make up at most 50 percent of the wall thickness of the pipe or at most 45 percent or at most 40 percent or at most 38 percent or at most 35 percent. In some embodiments, the PE 100-RC layer(s) make up at least 50 percent of the wall thickness of the pipe or at least 55 percent or at least 60 percent or at least 62 percent or at least 65 percent. In some embodiments, the PE 100-RC layer(s) make up at most 75 percent of the wall thickness of the pipe or at most 72 percent or at most 70 percent or at most 68 percent or at most 65 percent.

[0093] In some embodiments, the pipe has a longitudinal reversion, when tested according to the Test Methods, of less than 1.0% or no more than 0.9% or no more than 0.8% or no more than 0.7% or no more than 0.6% or no more than 0.5% or no more than 0.4% or no more than 0.3%. There is no minimum desired longitudinal reversion, but in some cases longitudinal reversion of less than 0.2% or 0.3% is unnecessary.

[0094] In some embodiments, the pipe is a PE 80 pipe or a PE 100 pipe or a PE-RT pipe. In some embodiments, the pipe has a minimum required strength (MRS) at 20°C of at least 8 MPa or at least 10 MPa or at least 11.2 MPa or at least 12.5 MPa.

[0095] Pipe fittings can be made by known processes, such as extrusion, injection molding or compression molding. Fittings are generally attached to pipes to redirect, redistribute or manage fluid flow. Examples of fittings include elbows, joints, T-joints, Y-joints, manifolds, end caps, valves and adapters.

[0096] Like pipes, in some embodiments, the pipe fittings can be suitable for carrying heated fluid under pressure, such as pressure up to at least 6 bar or at least 8 bar or at least 10 bar, and in some embodiments, the fittings are suitable for carrying unpressurized fluids. Fittings generally have a diameter suitable to flange onto a specific pipe. Unlike pipes, in many embodiments the longest dimension of a fitting is no more than 1 m or no more than 50 cm or no more than 25 cm or no more than 10 cm.

[0097] Some embodiments of the fittings of this invention comprise filled polyethylene that comprises: (a) a polyethylene;(b) a plurality of inorganic fibers;

[0098] (c) an inorganic filler; and

[0099] (d) optionally a compatibilizer as previously described.

[0100] The following illustrative embodiments list a few embodiments of the invention.

[0101] Illustrative Embodiments / Aspects

[0102] 1. A polymer composition comprising: (a) a polyethylene; (b) a plurality of inorganic fibers; and (c) an additive selected from the group consisting of (i) an inorganic filler, or (ii) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone, or (iii) both (i) and (ii).

[0103] 2. The polymer composition of aspect 1, wherein the polymer composition comprises 60 to 90 wt.% of the polyethylene, based on the total weight of the polymer composition, and the polyethylene is selected from HDPE or LLDPE.

[0104] 3. Tire polymer composition of aspect 2, wherein the polymer composition comprises from 3 to 25 wt.% of the plurality of inorganic fibers, based on the total weight of the polymer composition, and wherein the plurality of inorganic fibers have an average length from 0.10 mm to 1.0 mm and an average diameter from 5 microns to 20 microns.

[0105] 4. The polymer composition of aspect 3, wherein the additive (c) comprises from 2 wt.% to 20 wt.% of an inorganic filler selected from talc, calcium carbonate, carbon black, silica and combinations thereof, and wherein wt.% is based on the total weight of the polymer composition.

[0106] 5. A pipe fitting that comprises the polymer composition of aspect 4.

[0107] 6. The polymer composition of aspect 3. wherein the additive (c) comprises from 0.5 wt.% to 12 wt.% of the compatibilizer, wherein wt.% is based on the total weight of the polymer composition.

[0108] 7. The polymer composition of aspect 6, wherein the compatibilizer comprises a polyolefin polymer grafted with maleic anhydride polymer and has a graft ratio from 0.5 wt.% to 2.0 wt.%, based on the total weight of the polyolefin polymer.

[0109] 8. A pipe comprising the polymer composition of aspect 6.

[0110] 9. The pipe of aspect 8, wherein the pipe has a longitudinal reversion of less than 1.0%.

[0111] 10. The pipe of aspect 8, wherein the pipe comprises an inner layer of PE100-RC polymer, a middle layer comprising the polymer composition of claims 1-7, and an outer layer of PE100-RC polymer, w herein the PE100-RC polymer layers make up from 50 to 75 percent of the thickness of the pipe, and the middle layer make up from 25 to 50 percent of the thickness of the pipe.

[0112] 11. A polymer composition comprising: (a) from 60 to 90 wt.% of a polyethylene selected from EIDPE or LLDPE, and having a melt index (L) from 0.3 g / 10 min to 15.0 g / 10 min; (b) from 3 to 25 wt.% of aplurality of inorganic fibers that are glass fibers having an average length from 0.10 mm to 1.0 mm and an average diameter from 5 microns to 20 microns; and (c) an additive comprising from 2 wt.% to 20 wt.% of an inorganic filler selected from talc, calcium carbonate, carbon black and silica, wherein wt.% is based on the total weight of the polymer composition.

[0113] 12. The polymer composition of aspect 11, wherein the additive (c) further comprises from 0.5 wt.% to 12.0 wt.% of a compatibilizer based on the total weight of the polymer composition.

[0114] 13. Tire polymer composition, pipe fitting or pipe of any one of aspect 1 through 12, wherein when a compatibilizer is present, the compatibilizer has a melt index (I2) from 0.5 g / 10 min to 20.0 g / 10 min.

[0115] 14. The polymer composition, pipe fitting or pipe of aspect 13, wherein when a compatibilizer is present, the compatibilizer has a number average molecular weight of at least 620 Da.

[0116] 15. The polymer composition, pipe fitting or pipe of aspect 13, wherein the polymer composition has a density from 0.935 g / cm3to 0.950 g / cm3and a melt index (T) from 0.1 g / 10 min to 10.0 g / 10 min.

[0117] 16. A pipe comprising a layer of a polymer composition comprising: (a) a polyethylene; (b) a plurality of inorganic fibers; (c) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone; and (d) optionally, an inorganic filler.

[0118] A pipe for carrying fluid comprising a layer of polymer composition that comprises: (a) a polyethylene; (b) a plurality of inorganic fibers; (c) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone; and (d) optionally, an inorganic filler.

[0119] A fitting for carrying fluid comprising a polymer composition that comprises: (a) a polyethylene; (b) a plurality of inorganic fibers; (c) an inorganic filler, and (d) optionally a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone.

[0120] A method to modify the thermal expansion and contraction of a polyethylene comprising the step of compounding the polyethylene with: (a) a plurality' of inorganic fibers; (b) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone; and (c) optionally, an inorganic filler.

[0121] A method to raise the thermal oxidative stability of a polyethylene comprising the step of compounding the polyethylene with: (a) a plurality of inorganic fibers: (b) an inorganic filler, and (c) optionally? a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone w ith polar moieties grafted to the non-polar polymer backbone.Test Methods

[0122] Unless stated otherwise. measurements listed in this application are made using the following test methods:

[0123]

[0124] Examples

[0125] The following examples illustrate specific embodiments of the invention, but do not limit the broadest scope of the invention.

[0126] Tire materials in Table 1 are used for the Examples:

[0127] Table 1

[0128]

[0129] Preparation of Polymer composition

[0130] Tire materials in Table 1 are compounded in the proportions shown in Tables 2 and 3 to make the polymer composition compositions shown in Inventive Examples 1 to 9 (IE1 - IE9) and Comparative Examples 2-4. 6 and 7 (CE2-CE4. CE6 and CE7). Comparative Examples 1 and 5 (CE1 and CE5) are unfilled polyethylene, and so they are not compounded before use. The compounding is performed using a Buss Kneader MDK / E 46 L / D 15” that has 3 inlets. PE 1 and Comp 1 are added in the first inlet (longest residence time). GF1 and Filler 1 are added in the second inlet. The kneader is operated at 300 rpm, resulting in an output of 8kg / h for the samples. Tire melt temperatures in the kneader range from 140°C to 200°C. Tire resulting polymer composition is pelletized.

[0131] The polymer composition in IE1 to IE4 and CE1 to CE4 are tested for density, melt index, flexural modulus, abrasion resistance and thermal oxidation resistance as set out in the Test Methods. Results are shown in Table 2. Microscopic examination of fibers in the polymer composition shows that the fibers have an average fiber length of about 0.30 mm, as compared to the 4.5 mm length of the raw material fibers. Preparation of Pipes

[0132] The compositions in IE5 to IE9 and in CE5 to CE7 are coextruded with PE2 and EVOH to make pipes with the layers set out in Table 3. Pipe extrusion is perfonned using a 5 -layer machine from Extrudex GmbH. Extruder No. 1, for the innermost pipe layer has a diameter of 30 mm, an L / D ratio of 30 and a maximum output of 20 kg / h. Extruders No. 2 to 5, for pipe layers 2-5 respectively, have a screw diameter of 20 mm and a L / D ratio of 25 with a maximum output of 4 kg / h. Each extruder has five temperature zones that are set to the following profiles:

[0133]

[0134] The line can produce pipes in the size range of 8 to 32mm. It is set to make pipes with a diameter of 20 mm and a wall thickness of 2 mm. A line speed of 1.4 to 1.7 m / min is used for the extrusion.

[0135] When a 3-layer pipe is made, Extruders 1 and 2 both extrude the same polymer composition intended for the inner layer, and Extruders 4 and 5 both extrude the same polymer composition intended for the outer layer, while Extruder 3 extrudes the polymer composition for the middle layer. No demarcation between layers 1 and 2 or layers 4 and 5 is observed, and they each behave as a single layer.

[0136] The line has a two-zone vacuum calibration bath, with lengths of 750 mm and 1545 mm. A vacuum of 200 - 500 mbar is applied to calibrate the pipe.The resulting pipes have an external diameter of 20 mm and a wall thickness of 2 mm. Pipes are tested for hydrostatic strength at 20°C and stress levels of 10.9 MPa and at 95°C and stress levels of 4.0 to 4.4 MPa for long tenn and short temi hoop strength. Tire tests are made in accordance with the Test Methods The pipes are also tested for longitudinal reversion as described in the Test Methods. Results are shown in Table 3.Table 2 Resin Properties

[0137]

[0138] Table 3 Pipe Properties

[0139]

[0140]

[0141] a - Single specimen. Hours until test stopped without failure.

[0142] b - Two specimens. Hours until tests stopped without any failure.

[0143] c - Three specimens. Hours until tests stopped without any failure.

Claims

CLAIMS:We claim:

1. A polymer composition comprising: (a) a polyethylene; (b) a plurality of inorganic fibers; and (c) an additive selected from the group consisting of (i) an inorganic filler, or (ii) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone, or (iii) both (i) and (ii).

2. Tire polymer composition of claim 1, wherein the polymer composition comprises 60 to 90 wt.% of the polyethylene, based on the total weight of the polymer composition, and the polyethylene is selected from HDPE or LLDPE.

3. The polymer composition of claim 2, wherein the polymer composition comprises from 3 to 25 wt.% of the plurality? of inorganic fibers, based on the total weight of the polymer composition, and wherein the plurality of inorganic fibers have an average length from 0.10 mm to 1.0 mm and an average diameter from 5 microns to 20 microns.

4. The polymer composition of claim 3, wherein the additive (c) comprises from 2 wt.% to 20 wt.% of an inorganic filler selected from talc, calcium carbonate, carbon black, silica and combinations thereof, and wherein wt.% is based on the total weight of tire polymer composition.

5. A pipe fitting that comprises the polymer composition of claim 4.

6. Tire polymer composition of claim 3, wherein the additive (c) comprises from 0.5 wt.% to 12 wt.% of the compatibilizer, wherein wt.% is based on the total weight of the polymer composition.

7. The polymer composition of claim 6, wherein the compatibilizer comprises a polyolefin polymer grafted with maleic anhydride polymer and has a graft ratio from 0.5 wt.% to 2.0 wt.%, based on the total weight of the polyolefin polymer.

8. A pipe comprising the polymer composition of claim 6.

9. Tire pipe of claim 8, wherein the pipe has a longitudinal reversion of less than 1.0%.

10. Tire pipe of claim 8, w herein the pipe comprises an inner layer of PE100-RC polymer, a middle layer comprising the polymer composition of claims 1-7, and an outer layer of PE100-RC polymer, wherein the PE100-RC polymer layers make up from 50 to 75 percent of the thickness of the pipe, and tire middle layer make up from 25 to 50 percent of the thickness of the pipe.

11. A polymer composition comprising: (a) from 60 to 90 wt.% of a polyethylene selected from HDPE or LLDPE, and having a melt index (L) from 0.3 g / 10 min to 15.0 g / 10 min; (b) from 3 to 25 wt.% of a plurality of inorganic fibers that are glass fibers having an average length from 0.10 mm to 1.0 mm and an average diameter from 5 microns to 20 microns; and (c) an additive comprising from 2 wt.% to 20 wt.% ofan inorganic filler selected from talc, calcium carbonate, carbon black and silica, wherein wt.% is based on the total weight of the polymer composition.

12. The polymer composition of claim 11, wherein the additive (c) further comprises from 0.5 wt.% to 12.0 wt.% of a compatibilizer based on the total weight of the polymer composition.

13. The polymer composition, pipe fitting or pipe of any one of claims 1 through 12, wherein when a compatibilizer is present, the compatibilizer has a melt index (I2) from 0.5 g / 10 min to 20.0 g / 10 min.

14. Tire polymer composition, pipe fitting or pipe of claim 13, wherein when a compatibilizer is present, the compatibilizer has a number average molecular weight of at least 620 Da.

15. The polymer composition, pipe fitting or pipe of claim 13, wherein the polymer composition has a density from 0.935 g / cm3to 0.950 g / cm3and a melt index (I2) from 0.1 g / 10 min to 10.0 g / 10 min.

16. A pipe comprising a layer of a polymer composition comprising: (a) a polyethylene; (b) a plurality of inorganic fibers; (c) a compatibilizer that comprises a graft copolymer having a non-polar polymer backbone with polar moieties grafted to the non-polar polymer backbone; and (d) optionally, an inorganic filler.

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