Thermoplastic resin composition containing polytetrafluoroethylene powder mixture

Abstract: A polytetrafluoroethylene-containing powder mixture comprising polytetrafluoroethylene particles (A) with a particle size 10 µm or smaller and organic polymer particles (B), thermoplastic resin compositions containing it, and molded articles obtained therefrom. The polytetrafluoroethylene-containing powder mixture provides higher dispersibility for polytetrafluoroethylene in thermoplastic resins, and is effective for improving the molding workability and mechanical properties of thermoplastic resins.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin composition comprising polytetrafluoroethylene-containing powder mixture containing polytetrafluoroethylene particles with a particle size 10 µm or smaller (A) and organic polymer particles (B), to a thermoplastic resin composition including the mixture and to molded articles made therefrom. 2. Description of the Related Art Polytetrafluoroethylene (PTFE) has excellent heat resistance, chemical resistance and electrical insulating properties and is widely used as a coating material because of its special surface characteristics including water and oil repellent, non-adhesive and self-lubricating properties. Also, its high crystallinity and low intramolecular force give it a nature suitable to forming fibers with only minimal stress, and when combined with thermoplastic resins it is possible to achieve better molding workability and mechanical properties, allowing it to be used as an additive for thermoplastic resins. EP0166187 describes highly dispersed PTFE particles for thermoplastic moulding additives, produced by mixing and coagulating PTFE and substrate polymer dispersions. Japanese Unexamined Patent Publications No. 5-214184 and No. 6-306212, for example, disclose resin compositions wherein polytetrafluoroethylene is combined with polyolefins. Also, Japanese Unexamined Patent Publication No. 7-324147 discloses a process for producing polyolefin-based resin compositions whereby polytetrafluoroethylene prepared by mixing polytetrafluoroethylene with a powdered dispersion medium under high shear action is first made into fibers and then mixed with a polyolefin. A drawback exists, however, in that polytetrafluoroethylene has poor dispersibility in common thermoplastic resins which contain no halogen atoms, and fails to uniformly disperse with only simple blends as described in Japanese Unexamined Patent Publications No. 5-214184 and No. 6-306212, thus notably impairing the surface appearance of resulting molds. Furthermore, it is difficult to convert all of the polytetrafluoroethylene to fibers with shearing force by the process described in Japanese Unexamined Patent Publication No. 7-324147, and even the polytetrafluoroethylene fibers aggregate in the matrix resin making it impossible to obtain a uniform composition. In other words, the dispersibility of polytetrafluoroethylene in matrix resins constitutes a problem in all of these processes, and therefore large amounts of the polytetrafluoroethylene have been necessary in order to exhibit the aforementioned useful properties. SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermoplastic resin composition comprising a polytetrafluoroethylene-containing powder mixture which is effective for increasing the dispersibility of polytetrafluoroethylene in thermoplastic resins and improving the molding workability and mechanical characteristics of the thermoplastic resins. As a result of diligent research aimed at solving the problems described above, the present invention has been completed upon the finding that satisfactory molding workability and mechanical characteristics and molded articles with excellent outer appearances can be obtained by adding to thermoplastic resins a polytetrafluoroethylene-containing powder mixture comprising polytetrafluoroethylene particles with a particle size of 10 µm or smaller and organic polymer particles. The present invention thus provides a thermoplastic resin composition comprising a polytetrafluoroethylene-containing powder mixture comprising polytetrafluoroethylene particles (A) with a particle size of 10 µm or smaller and organic polymer particles (B) containing at least 20 wt.-% of a long chain alkyl (methacrylic) acid ester monomer with 12 or more carbon atoms, and moulded articles obtained therefrom. Compositions containing at least 50 wt.-% of the long chain alkyl ester are especially preferred and molded articles obtained therefrom. DESCRIPTION OF THE PREFERRED EMBODIMENTS The polytetrafluoroethylene particles (A) used according to the invention must not form aggregates of particles of size exceeding 10 µm, and particles of size 0.05-1.0 µm are preferred. Such polytetrafluoroethylene particles are dispersed in water containing an emulsifier and the like, and an aqueous dispersion of the polytetrafluoroethylene particles can be obtained by polymerizing tetrafluoroethylene monomer by emulsion polymerization using a fluorine-containing surfactant. In emulsion polymerization for producing the polytetrafluoroethylene particles, there may be used one or more copolymerizable components which may be a fluorine-containing olefin such as hexafluoropropylene, chlorotrifluoroethylene; fluoroalkylethylene, perfluoroalkylvinyl ether or a fluorine-containing alkyl (meth)acrylate such as perfluoroalkyl (meth)acrylate, so long as it does not impair the properties of the polytetrafluoroethylene. The content of the copolymerizable components is preferably no more than 10 wt% based on the tetrafluoroethylene. As commercially available polytetrafluoroethylene particle dispersions there may be mentioned Fluon AD-1 and AD-936 by Asahi ICI Fluoropolymers, Polyflon D-1 and D-2 by Daikin Industries and Teflon 30J by Mitsui-DuPont Fluorochemicals. The organic polymer particles (B) used according to the invention have affinity for thermoplastic resins from the standpoint of dispersibility of the polytetrafluoroethylene when combined with the thermoplastic resin. As examples of co-monomers for producing the organic polymer particles there may be mentioned styrene monomers such as styrene, p-methylstyrene, o-methylstyrene, p-chlorostyrene, o-chlorostyrene, p-methoxystyrene, o-methoxystyrene, 2,4-dimethylstyrene and α-methylstyrene, (meth)acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, dodecyl acrylate, dodecyl methacrylate, tridecyl acrylate, tridecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, vinyl ether monomers such as vinyl methyl ether and vinyl ethyl ether, vinyl carboxylate monomers such as vinyl acetate and vinyl butyrate, olefinic monomers such as ethylene, propylene and isobutylene, and diene monomers such as butadiene, isoprene and dimethylbutadiene. These monomers may be used alone or in combinations of 2 or more. The method of producing the aqueous dispersion of the organic polymer particles used for the invention is not critical, and for example, emulsion polymerization using an ionic emulsifying agent or soap-free emulsion polymerization using an ionic polymerization initiator may be employed. The ionic emulsifying agent may be any anionic, cationic or ampholytic emulsifying agent. If desired a nonionic emulsifying agent may also be used in combination with the ionic emulsifying agent. As examples of anionic emulsifying agents there may be mentioned fatty acid salts, higher alcohol sulfuric acid ester salts, liquid fatty oil sulfuric acid ester salts, fatty amine and fatty amide sulfuric acid salts, fatty alcohol phosphoric acid ester salts, sulfonic acid salts of dibasic fatty acid esters, fatty acid amide sulfonic acid salts, alkylallyl sulfonic acid salts and naphthalenesulfonic acid salts of formalin condensates. As examples of cationic emulsifying agents there may be mentioned fatty amine salts, quaternary ammonium salts and alkylpyridinium salts. As examples of ampholytic emulsifying agents there may be mentioned alkylbetaines. As examples of ionic polymerization initiators there may be mentioned persulfates (for example, potassium persulfate and ammonium persulfate), azobis(isobutyronitrilesulfonate), 4,4'-azobis(4-cyanovaleric acid), and other anionic polymerization initiators, and 2,2'-azobis(amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobisisobutylamide dihydrate and other cationic polymerization initiators. The particle size [d] of the organic polymer particles (B) used for the invention is not critical, but from the standpoint of stability in an aggregated state with the polytetrafluoroethylene it is preferably in the range of the following inequality with respect to particle size D of the polytetrafluoroethylene particles. 0.1 D < d < 10 D The polytetrafluoroethylene-containing powder mixture of the invention is obtained by mixing the polytetrafluoroethylene particle dispersion and organic polymer particle dispersion and then solidifying or spray drying to make a powder, and it contains aggregated particles which have aggregated and simple particles which remain without aggregating, due to the difference in surface charges of the polytetrafluoroethylene particles and organic polymer particles. The aggregated particles have structures wherein the polytetrafluoroethylene particles and organic polymer particles are integrated, and their morphology can differ depending on the mixing ratio and particle sizes of both particle types. There exist, for example, a configuration in which the organic polymer particles surrounds the polytetrafluoroethylene particles, a configuration in which the polytetrafluoroethylene particles surrounds the organic polymer particles, and a configuration in which a plurality of particles are aggregated around a single particle. Aggregation of only the polytetrafluoroethylene particles which produces aggregates of 10 µm or greater is not preferred from the standpoint of dispersibility in the thermoplastic resin. For a lower aggregation speed during mixing, a nonionic emulsifying agent may be adsorbed onto the surface of the polytetrafluoroethylene particles and/or (co)polymer particles of (meth)acrylic acid ester units with alkyl groups of at least 4 carbon atoms, prior to mixing. There is no specific criticality on the nonionic emulsifying agent, and as examples there may be mentioned polyoxyethylene alkyl ether, polyoxyethylene alkylallyl ether, dialkylphenoxypoly(ethyleneoxy) ethanol, polyvinyl alcohol, polyacrylic acid and alkylcellulose. The polytetrafluoroethylene-containing powder mixture of the invention may also be obtained by emulsion polymerization of a monomer with ethylenically unsaturated bonds in a dispersion prepared by mixing the polytetrafluoroethylene particle dispersion and organic polymer particle dispersion, followed by solidifying or spray drying to make a powder. The ethylenically unsaturated monomer used for emulsion polymerization in the mixed dispersion will depend on the use of the polytetrafluoroethylene-containing powder mixture, and may be selected from styrene monomers such as styrene, p-methylstyrene, o-methylstyrene, p-chlorostyrene, o-chlorostyrene, p-methoxystyrene, o-methoxystyrene, 2,4-dimethylstyrene and α-methylstyrene; acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, dodecyl acrylate, dodecyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; vinyl ether monomers such as vinyl methyl ether and vinyl ethyl ether; vinyl carboxylate monomers such as vinyl acetate and vinyl butyrate, olefinic monomers such as ethylene, propylene and isobutylene; and diene monomers such as butadiene, isoprene, prene and dimethylbutadiene. These monomers may be used alone or in combinations of 2 or more. The content of the polytetrafluoroethylene in the polytetrafluoroethylene-containing powder mixture of the invention is preferably 0.1 wt% to 90 wt%. The polytetrafluoroethylene-containing powder mixture of the invention may be obtained by pouring the aqueous dispersion thereof into hot water which has dissolved a metal salt such as calcium chloride or magnesium sulfate, and then drying after salting out and aggregation, or spray drying, to produce powder. Although most polytetrafluoroethylene fine powder cannot be easily dispersed in a uniform manner in thermoplastic resins because of production of aggregates of 100 µm or greater during the process of recovering the powder from the powder dispersion, the polytetrafluoroethylene-containing powder mixture of the present invention has very excellent dispersibility in thermoplastic resins because the polytetrafluoroethylene alone does not form domains exceeding a particle size of 10 µm. As the thermoplastic polyolefin resin (C) used according to the invention there may be mentioned polyolefin resins such as polyethylene, polypropylene and ethylene-propylene copolymer. Polypropylene resin is particularly preferred. As a more detailed explanation of the polyolefin resin to be used according to the invention, it includes polypropylene, polyethylene, poly-1-butene, polyisobutylene, random or block copolymers of propylene with ethylene and/or 1-butene in a desired proportion, ethylene-propylene-diene terpolymers with the ethylene and propylene in a desired proportion and no more than 50 wt% of the diene component, polymethylpentene, and random, block or graft copolymers of ethylene or propylene with no more than 50 wt% of a monomer other than an olefin with an ethylenically unsaturated group such as vinyl acetate, (meth)acrylic alkyl ester, aromatic vinyl compounds, etc. As preferred polyolefins there may be mentioned propylene-based polyolefins containing at least 50 wt% of propylene and mixtures of 100 parts by weight of a propylene-based polyolefin containing at least 50 wt% of propylene and 0.1-100 parts by weight of an ethylene-based polyolefin containing at least 50 wt% of ethylene; preferred for their high melt tension and excellent workability are those with a melt flow rate of 10 g/10 minutes or lower according to ASTM D1238. The melt flow rate is measured according to ASTM D1238, at 230°C, 2.16 kg load for propylene-based polyolefins and at 190°C, 2.16 kg load for ethylene-based polyolefins. According to the invention, mixture of the polytetrafluoroethylene-containing powder mixture with the thermoplastic resin results in increased tension of the melt during working of the thermoplastic resin composition, provides improved draw-off during calendering, drawdown of the melt during heat molding or blow molding and continuous foaming during foam molding, and improved workability for calendering, heat molding, blow molding and foam molding. In addition, for extrusion molding it improves the discharge rate and the surface condition of extrusion molds including sheets and films, and also improves the extrusion workability. According to the invention, the amount of the polytetrafluoroethylene-containing powder mixture used is 0.001 to 50 parts by weight per 100 parts by weight of the thermoplastic polyolefin resin (C). The amount of the polytetrafluoroethylene is preferably in the range of 0.001 to 40 parts by weight per 100 parts by weight of the thermoplastic resin. A filler may also be added to the thermoplastic resin composition according to the invention. The amount of filler added is preferably 0.1 to 400 parts by weight per 100 parts by weight of the thermoplastic polyolefin resin (C), and addition of the filler increases the rigidity and heat resistance while improving the workability, which includes preventing adhesion to roll surfaces during calendering, with costs reductions as well. If the amount is less than 0.1 part by weight the rigidity-improving effect is insufficient, and if it is greater than 400 parts by weight there is a tendency toward lower surface characteristics. The range is more preferably 1 to 350 parts by weight, and even more preferably 1 to 300 parts by weight. As examples of fillers to be used according to the invention there may be mentioned calcium carbonate, talc, glass fibers, carbon fibers, magnesium carbonate, mica, kaolin, calcium sulfate, barium sulfate, titanium white, white carbon, carbon black, ammonium hydroxide, magnesium hydroxide and aluminum hydroxide. Calcium carbonate and talc are preferred. If necessary, an additive such as a stabilizer, lubricant or flame retardant may also be added to the thermoplastic resin composition of the invention. As stabilizers there may be mentioned phenolic stabilizers such as pentaerythritol-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] and triethyleneglycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], phosphoric stabilizers such as tris(monononylphenyl) phosphite and tris(2,4-di-t-butylphenyl) phosphite and sulfuric stabilizers such as dilaurylthiodipropionate; as lubricants there may be mentioned sodium, calcium or magnesium salts of lauric acid, palmitic acid, oleic acid or stearic acid; and as flame retardants there may be mentioned phosphoric acid ester compounds including trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, cresylphenyl phosphate, octyldiphenyl phosphate, diisopropylphenyl phosphate, tris(chloroethyl) phosphate, and polyphosphates, such as alkoxy-substituted bisphenol A bisphosphate, hydroquinone bisphosphate, resorcin bisphosphate, trioxybenzene triphosphate, halogen-containing compounds such as tetrabromobisphenol A, decabromodiphenyl oxide, hexabromocyclodecane, octabromodiphenyl ether, bistribromophenoxyethane, ethylene bistetrabromophthalimide, tribromophenol, halogenated epoxy oligomers obtained by reaction between halogenated bisphenol A and epichlorohydrin, carbonate oligomers with halogenated bisphenol A as a constituent, halogenated polystyrene, chlorinated polyolefins and polyvinyl chloride; and metal hydroxides, metal oxides, sulfamic acid compounds, etc. The thermoplastic resin composition of the invention is obtained by mixing the aforementioned thermoplastic resin with the polytetrafluoroethylene-containing composite powder and if necessary a filler. The mixing method may be any conventionally known method, such as extrusion kneading or roll kneading. Also, a portion of the thermoplastic resin may be mixed with the polytetrafluoroethylene-containing powder mixture to prepare a master batch, and then the remaining thermoplastic resin may be added and mixed therewith later for multistage mixture. The thermoplastic resin composition of the invention has excellent dispersibility of the polytetrafluoroethylene, and therefore the workability, rigidity and surface appearance thereof is vastly improved, allowing production of molded articles by many different processes to provide useful molded products. The process used for working the thermoplastic resin composition of the invention may be calender molding, extrusion molding, heat molding, blow molding, injection molding, foam molding or melt spinning. As useful molded products to be obtained using the thermoplastic resin composition of the invention there may be mentioned sheets, films, thermoforms, blow molds, injection molds, foam molds and fibers. The present invention will be further illustrated below by way of examples, with the understanding that the invention is not limited to these examples. Throughout the descriptions, "parts" refers to parts by weight and "%" indicates percent by weight. Synthesis of polytetrafluoroethylene-containing powder mixture and mixture with polyolefin resin Measurement of the physical properties described in Reference Example 1, Examples 1-20 and Comparative Examples 1-15 was accomplished according to the following methods. (1) Solid portion concentration: Determined by drying the particle dispersion at 170°C for 30 minutes. (2) Particle size distribution and weight average particle size: A sample solution of the particle dispersion diluted with water was measured by the dynamic light scattering method (ELS800 by Otsuka Electronics, temperature: 25°C, scattering angle: 90°). (3) ζ potential: A sample solution of the particle dispersion diluted with a 0.01 mol/l aqueous NaCl solution was measured by electrophoresis (ELS800 by Otsuka Electronics, temperature: 25°C, scattering angle: 10°). (4) Melt tension: Pellets of the resin composition were extruded at a constant extrusion rate (falling speed: 20 mm/min) using a falling flow tester (capillograph by Toyo Precision Instruments), and the strands were taken up at a constant rate (1 m/min) and subjected to melt tension measurement. The L/D of the die was 10.0 mm/Φ2.0 mm and the measuring temperature was 200°C. (5) Swelling ratio: Pellets of the resin composition were extruded at a constant extrusion rate (falling speed: 1.5 mm/min) using a falling flow tester (capillograph by Toyo Precision Instruments), the strand diameter (D) was measured at a position 5 mm under the nozzle, and calculation was made with the following equation. The L/D of the die was 10.0 m/Φ2.0 mm and the measuring temperature was 190°C. (Swelling ratio) = D (mm)/2.0 (6) Melt flow rate: Measured according to ASTM D1238 at 230°C, 2.16 kg using pellets of the resin composition. (7) Flexural modulus: Measured according to ASTM D790 after obtaining test pieces by injection molding of the resin composition pellets. (8) Roll sheet appearance: Judged based on visual appearance of roll sheets during roll kneading using pellets of the resin composition. o - no surface irregularities and excellent luster Δ - some surface irregularities and slightly impaired luster x - notable surface irregularities and poor luster (9) Drawdown: Pellets of the resin composition were used for molding of a sheet 100 mm square and 1.5 mm thick, and after anchoring with a clamp with a 75 mm square opening, the drawdown of the sheet in a 190°C oven for 30 minutes was measured. (10) Evaluation of foam molded products: 1.0 part of azodicarbonamide (foaming agent) was mixed with 100 parts by weight of the resin composition pellets and used for injection molding to form a foam molded product, after which the condition of cross-sectional cells thereof was judged visually. o - fine and uniform Δ - slightly nonuniform x - nonuniform (11) Measurement of weight average molecular weight The weight average molecular weight was determined by gel permeation chromatography using standard samples of polymethyl methacrylate. Reference Example 1 <Production of polydodecyl methacrylate particle dispersion (P-1)> A 0.1 part portion of azobisdimethylvaleronitrile was dissolved in 100 parts of dodecyl methacrylate. To this was then added a mixture of 2.0 parts sodium dodecylbenzenesulfonate and 300 parts of distilled water, and after 2 minutes of stirring with a homomixer at 10,000 rpm, it was passed through a homogenizer twice at a pressure of 300 kg/cm 2 to obtain a stable dodecyl methacrylate preliminary dispersion. This was then charged into a separable flask equipped with a stirring blade, condenser, thermocouple and nitrogen inlet, and the mixture was raised to an internal temperature of 80°C under a nitrogen gas flow and stirred for 3 hours for radical polymerization, to obtain a polymer particle dispersion (hereunder referred to as P-1). The weight average molecular weight of the polymer was 650,000. The solid concentration of P-1 was 25.2%, the particle size distribution showed a single peak, the weight average particle size was 195 nm and the surface potential was -38 mV. Example 1 <Production of polytetrafluoroethylene-containing powder mixture (M-1)> After charging 160 parts of F-1 an aqueous PTFE particle dispersion containing 25% polytetrafluoroethylene particles and 1.2% polyoxyethylene nonyl phenyl ether (40 parts of polytetrafluoroethylene) and 119.0 parts of P-1 (30 parts of polydodecyl methacrylate) into a separable flask equipped with a stirring blade, condenser, thermocouple and nitrogen inlet, 82.9 parts of distilled water was added and the mixture was stirred for one hour at room temperature under a nitrogen gas flow. The internal temperature was then raised to 80°C, and then after adding a mixed solution of 0.001 part iron (II) sulfate, 0.003 part disodium ethylenediamine tetraacetate, 0.24 part Rongalite salt and 10 parts of distilled water, a mixture of 30 parts methyl methacrylate and 0.6 part tert-butyl peroxide was added dropwise over one hour, and after the dropwise addition the internal temperature was kept at 80°C for one hour to complete radical polymerization. No separation of solids was observed throughout the series of procedures, and a uniform particle dispersion was obtained. The solid concentration of the resulting particle dispersion was 24.9%, the particle size distribution was relatively broad, and the weight average particle size was 242 nm. After loading 400 parts of this particle dispersion into 800 parts of hot water at 70°C containing 10 parts of calcium chloride, the solids were separated, filtered and dried to obtain 99 parts of a polytetrafluoroethylene-containing powder mixture (M-1). The dried M-1 was shaped into a thin strip with a press molding machine at 200°C and then cut into super thin sections with a microtome, and these were observed with a transmission electron microscope while unstained. The polytetrafluoroethylene was observed as dark portions, but no aggregates or fibrils exceeding 10 µm were found. Example 2 <Production of polytetrafluoroethylene-containing powder mixture (M-2)> In the same manner as Example 1 there was obtained 99 parts of the polytetrafluoroethylene-containing powder mixture (M-2), except that 80 parts of F-1 (20 parts of polytetrafluoroethylene) was used and 198.4 parts of P-1 (50 parts of polydodecyl methacrylate) was used. No separation of solids was found in the particle dispersion prior to hardening, the solid concentration was 24.8%, the particle size distribution was relatively broad, and the weight average particle size was 220 nm. The dried M-2 was shaped into thin strip with a press molding machine at 200°C and then cut into super thin sections with a microtome, and these were observed with a transmission electron microscope while unstained. The polytetrafluoroethylene was observed as dark portions, but no aggregates or fibrils exceeding 10 µm were found. Example 3 <Production of polytetrafluoroethylene-containing powder mixture (M-3)> There was obtained 97 parts of the polytetrafluoroethylene-containing powder mixture (M-3) in the same manner as Example 1, except that 240 parts of F-1 (60 parts of polytetrafluoroethylene) was used and 39.7 parts of P-1 (10 parts of polydodecyl methacrylate) was used. No separation of solids was found in the particle dispersion prior to hardening, the solid concentration was 24.8%, the particle size distribution was relatively broad, and the weight average particle size was 269 nm. The dried M-3 was shaped into a thin strip with a press molding machine at 200°C and then cut into super thin sections with a microtome, and these were observed with a transmission electron microscope while unstained. The polytetrafluoroethylene was observed as dark portions, but no aggregates or fibrils exceeding 10 µm were found. Examples 4-15 Homopolypropylene pellets (melt flow rate: 5.0 g/10 min) used as the polyolefin were hand blended with the polytetrafluoroethylene-containing powder mixtures M-1, M-2, and M-3 in the proportions shown in Table 1, and then a twin-screw extruder (ZSK30, product of WERNER & PFLEIDERER Co.) was used for melt kneading at a barrel temperature of 200°C and a screw rotation rate of 200 rpm for shaping into pellets. Measurement of the physical properties of the resulting pellets gave the results shown in Tables 1 and 2. Comparative Examples 1-5 For comparison, evaluation was made in the same manner as Example 4 using pellets (Comparative Example 1) obtained by extrusion of a polyolefin under the same conditions as Example 4, and pellets (Comparative Examples 2-5) obtained by extrusion under the same conditions as Example 4 after adding powdered polytetrafluoroethylene to the powdered polyolefin, stirring and mixing at room temperature and high speed with a Henschel mixer while applying shear force to prepare polytetrafluoroethylene fibers. The results are shown in Tables 1 and 2. Homopolypropylene pellets (Comparative Example 1) or powdered polypropylene (Comparative Examples 2-5) were used as the polyolefin (all with a melt flow rate of 5.0 g/10 min), and Fluon CD123 by Asahi ICI Fluoropolymers was used as the powdered polytetrafluoroethylene. CD123 exists as aggregates of a few 100 µm resulting from aggregation of polytetrafluoroethylene primary particles of particle size 0.2-0.3 µm. Example No. Composition PTFE in composition (%) MT (g) SR MFR (g/10 min) PP (parts) Additive (parts) Type of additive 4 100 10 M-1 3.6 61 2.4 0.9 5 100 5 M-1 1.9 38 2.4 2.4 6 100 1 M-1 0.4 19 2.1 3.2 7 100 0.5 M-1 0.2 9 1.8 4.1 8 100 10 M-2 1.8 54 2.4 0.9 9 100 5 M-2 1.0 32 2.3 2.4 10 100 1 M-2 0.2 11 2.1 3.4 11 100 0.5 M-2 0.1 7 1.9 4.2 12 100 10 M-3 5.5 64 2.4 0.8 13 100 5 M-3 2.9 37 2.3 2.3 14 100 1 M-3 0.6 12 2.0 3.3 15 100 0.5 M-3 0.3 8 1.9 4.1 Comp. Example 1 100 0 0 3 1.3 5.0 2 100 3.7 CD123 3.6 5 1.5 0.8 3 100 1.9 CD123 1.9 5 1.5 2.1 4 100 0.4 CD123 0.4 4 1.4 3.0 5 100 0.2 CD123 0.2 3 1.3 4.1 Flexural modulus (kg/cm 2 ) Roll sheet appearance Drawdown (mm) Foam mold evaluation 4 13000 ○ 0 ○ 5 13500 ○ 0 ○ 6 14000 ○ 0 ○ 7 14000 ○ 2 ▵ 8 13000 ○ 0 ○ 9 13500 ○ 0 ○ 10 14000 ○ 0 ○ 11 14000 ○ 2 ▵ 12 13200 ▵ 0 ○ 13 13800 ▵ 0 ○ 14 14000 ○ 0 ○ 15 14000 ○ 2 ○ Comp. Example 1 14000 ○ 90 x 2 14000 x 20 x 3 14000 x 20 x 4 14000 x 40 x 5 14000 x 80 x PP: polypropylene (melt flow rate: 5.0 g/10 min) MT: melt tension SR: swelling ratio MFR: melt flow rate CD123: powdered polytetrafluoroethylene (Fluon CD123 by Asahi ICI Fluoropolymers) The compositions of the invention which included polytetrafluoroethylene-containing composite particles had significantly higher values for the melt tension and swelling ratio which were indicators of the draw-off properties for calender working, the heat moldability, blow moldability and foam moldability, compared to the comparative examples with the same PTFE contents, thus confirming their satisfactory molding workability. On the other hand, they also had low reduction in the melt flow rate, confirming that the extrusion moldability was not impaired. In addition, the roll sheet appearance, draw-down and foam moldability were also confirmed to be very excellent. Examples 16-18 Homopolypropylene pellets (melt flow rate: 5.0 g/10 min) and low density polyethylene pellets (melt flow rate: 0.3 g/10 min) were mixed and used as the polyolefin and were hand blended with the polytetrafluoroethylene-containing powder mixture M-1 in the proportions shown in Table 3, for shaping into pellets in the same manner as Example 4. Measurement of the physical properties of the pellets gave the results shown in Tables 3 and 4. Comparative Examples 6-11 Extruded mixtures of homopolypropylene pellets and low density polyethylene pellets (Comparative Examples 6-8), and extruded mixtures of powdered homopropylene, powdered low density polyethylene and powdered polytetrafluoroethylene which had been mixed with a Henschel mixer (Comparative Examples 9-11) were evaluated in the same manner as Example 4. The results are shown in Tables 3 and 4. Example No. Composition PTFE in composition (%) MT (g) SR PP (pts) PE (pts) Additive (parts) Type of additive Example 16 100 20 2 M-1 0.66 19 2.0 17 100 50 2.5 M-1 0.66 25 2.2 18 100 100 3.3 M-1 0.65 38 2.3 Comp. Example 6 100 20 0 - 0 3 1.3 7 100 50 0 - 0 4 1.4 8 100 100 0 - 0 6 1.5 9 100 20 0.8 CD123 0.66 4 1.4 10 100 50 1.0 CD123 0.66 5 1.6 11 100 100 1.3 CD123 0.65 8 1.6 MFR (g/10 min) Flexural modulus (kg/cm 2 ) Roll sheet appearance Drawdown (mm) Foam mold evaluation Example 16 3.2 12000 ○ 0 ○ 17 3.3 9000 ○ 0 ○ 18 3.4 7000 ○ 0 ○ Comp. Example 6 5.0 12000 ○ 40 x 7 5.0 9000 ○ 30 x 8 5.0 7000 ○ 30 x 9 3.0 12000 x 20 x 10 3.2 9000 x 20 x 11 3.3 7000 x 10 x PP: polypropylene (melt flow rate: 5.0 g/10 min) PE: low density polyethylene (melt flow rate: 0.3 g/10 min) MT: melt tension SR: swelling ratio MFR: melt flow rate CD123: powdered polytetrafluoroethylene (Fluon CD123 by Asahi ICI Fluoropolymers) Examples 19-20 Homopolypropylene pellets (melt flow rate: 5.0 g/10 min), low density polyethylene pellets (melt flow rate: 0.3 g/10 min), polytetrafluoroethylene-containing composite particle dry powder M-1 and light calcium carbonate of particle size 0.15 µm which had been surface-treated with fatty acid were hand blended in the proportions shown in Table 5, and then shaped into pellets in the same manner as Example 5. Measurement of the physical properties of the pellets gave the results shown in Tables 5 and 6. Comparative Examples 12-15 Pellets were shaped in the same manner as Example 4 from mixtures of powdered homopolypropylene (melt flow rate: 5.0 g/10 min), powdered low density polyethylene (melt flow rate: 0.3 g/10 min) and light calcium carbonate (Comparative Examples 12-13) and from extruded mixtures with which powdered polytetrafluoroethylene was further combined and mixed with a Henschel mixer (Comparative Examples 14-15). The results of evaluating the physical properties are shown in Tables 5 and 6. Composition PTFE in composition (%) MT (g) PP (pts) FE (pts) CC (pts) Additive (pts) Type of additive Example 19 100 - 50 2 M-1 0.53 24 20 100 50 50 2.5 M-1 0.49 25 Comp. Example 12 100 - 50 0 - 0 4 13 100 50 50 0 - 0 4 14 100 - 50 0.8 CD123 0.53 5 15 100 50 50 1.0 CD123 0.50 5 SR MFR (g/10 min) Flexural modulus (kg/cm 2 ) Roll sheet appearance Drawdown (mm) Example 19 2.1 3.2 16000 ○ 0 20 2.2 3.3 11000 ○ 0 Comp. Example 12 1.3 5.0 16000 ○ 90 13 1.4 5.0 11000 ○ 30 14 1.5 3.0 16000 x 30 15 1.6 3.2 11000 x 20 PP: polypropylene (melt flow rate: 5.0 g/10 min) PE: low density polyethylene (melt flow rate: 0.3 g/10 min) CC: light calcium carbonate of particle size 0.15 µm surface treated with fatty acid MT: melt tension SR: swelling ratio MFR: melt flow rate CD123: powdered polytetrafluoroethylene (Fluon CD123 by Asahi ICI Fluoropolymers)

Claims: A thermoplastic resin composition comprising a mixture of (i) a polytetrafluoroethylene-containing powder mixture comprising polytetrafluoroethylene particles (A) with a particle size 10 µm or smaller and organic polymer particles (B), wherein the organic polymer is a polymer obtained from a monomer containing at least 20 wt% of a long-chain alkyl (meth)acrylic acid ester monomer with 12 or more carbon atoms, with (ii) a thermoplastic polyolefin resin (C). The thermoplastic resin composition according to claim 1, wherein the polytetrafluoroethylene-containing powder mixture is obtained by a process, wherein a 0.05-1.0 µm particle-size polytetrafluoroethylene particle aqueous dispersion and an organic polymer particle aqueous dispersion are mixed and then subjected to solidifying or spray drying to make a powder. The thermoplastic resin composition according to claim 1, wherein the polytetrafluoroethylene-containing powder mixture is obtained by a process, wherein a monomer with an ethylenically unsaturated bond is subjected to emulsion polymerization in a dispersion prepared by mixing a 0.05-1.0 µm particle-size polytetrafluoroethylene particle aqueous dispersion and an organic polymer particle aqueous dispersion, and then solidifying or spray drying is accomplished to make a powder. The thermoplastic resin composition according to claim 1, which further contains a filler. A foam product which comprises a thermoplastic resin composition according to any one of claims 1 to 4. A heat-molded sheet which comprises a thermoplastic resin composition according to any one of claims 1 to 4. Fibers which comprise a thermoplastic resin composition according to any one of claims 1 to 4.

Inventors: KOSHIRAI ATSUNORI, TAKAYAMA NOBUHISA, YANAGASE AKIRA, KOSHIRAI, ATSUNORI, TAKAYAMA, NOBUHISA, YANAGASE, AKIRA, Koshirai, Atsunori, c/o Corporate Research Lab., Takayama, Nobuhisa, c/o Corporate Research Lab., Yanagase, Akira, c/o Corporate Research Lab.
Applicants: MITSUBISHI RAYON CO, MITSUBISHI RAYON COMPANY LTD.
Application year: 1997
Main classification: C08L27
IPC codes: C08L67, C08L33, C08L23, C08L27