Thermoplastic resin composition

Abstract: A thermoplastic resin composition comprising (A) a propylene/ethylene block copolymer, (B) a combination of a low-crystalline ethylene/butene random copolymer resin and an amorphous ethylene/butene random copolymer rubber, or a combination of an ethylene/octene copolymer rubber and an ethylene/propylene copolymer rubber, (C) a specific block elastomer, and (D) talc. This composition has good injection molding properties, can reveal excellent flexural modulus, heat resistance and surface hardness, and is suitable for producing such injection-molded products as interior automotive trims.

Description: BACKGROUND OF THE INVENTION This invention relates to a thermoplastic resin composition which comprises (A) a propylene/ethylene block copolymer, (B) a combination of a low-crystalline ethylene/butene random copolymer resin and an amorphous ethylene/butene random copolymer rubber, or a combination of an ethylene/octene copolymer rubber and an ethylene/propylene copolymer rubber, (C) a specific block elastomer, and (D) talc, which has good injection molding properties, which shows excellent flexural modulus, heat resistance and surface hardness, and which is suitable for producing such injection-molded products as interior automotive trims. Numerous attempts to improve impact resistance and rigidity have been hitherto made by incorporating ethylene/propylene copolymers or various ethylene copolymers and talc into polypropylene. For instance, compositions having high impact resistance have been known as described in Japanese Patent Publication No. 42929/1988, and Japanese Laid-Open Patent Publications Nos. 150/1989, 66263/1989 and 204946/1989. However, the composition described in the above-mentioned Japanese Patent Publication No. 42929/1988 can reveal neither sufficiently high flexural modulus nor heat resistance. This is because polypropylene having extremely high crystallinity is not used in this composition. The compositions described in Japanese Laid-Open Patent Publications Nos. 150/1989, 66263/1989 and 204946/1989 are fit for such uses as bumpers because their talc contents are low. However, they reveal flexural modulus extremely lower than the one required for trims. Furthermore, a composition containing an ethylene/alpha-olefin copolymer and a large amount of an inorganic filler is described in Japanese Patent Publication No. 159345/1992. This composition is, however, unfavorable from the viewpoint of weight-saving of automobiles because its specific gravity is high. On the other hand, in order to overcome the aforementioned shortcomings, a composition has been proposed in Japanese Laid-Open Patent Publication No. 53843/1995. In those fields which require low-pressure high-cycle molding, materials having higher fluidity are demanded. To meet such a severe demand, the composition proposed is still insufficient in fluidity. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, thereby providing a composition which has high fluidity and good molding properties, which can reveal good physical properties, and which is suitable for producing interior automotive trims such as installment panels. It has now been found that a composition having high fluidity, good molding properties and excellent physical properties can be obtained by blending, in a specific ratio, (A) a propylene/ethylene block copolymer in which the propylene homopolymer moiety has high fluidity and extremely high crystallinity; (B) the following combination (B-1) or (B-2) of two different copolymers: (B-1) a combination of a resinous ethylene/butene random copolymer containing crystalline segments in its molecule and a substantially elastomeric ethylene/butene random copolymer containing few crystalline segments in its molecule, and (B-2) a combination of an ethylene/octene copolymer rubber containing crystalline segments in its molecule and an ethylene/propylene copolymer rubber containing few crystalline segments in its molecule; (C) a specific block elastomer consisting essentially of polyethylene structure (crystalline moiety) and ethylene/1-butene copolymer structure (random elastomer moiety), and (D) talc. The present invention has been accomplished on the basis of this finding. Thus, the thermoplastic resin composition of the present invention comprises the following components (A) to (D): component (A) : 50 to 75% by weight of a propylene/ethylene block copolymer whose propylene homopolymer moiety has a melt flow rate (MFR: at 230°C under a load of 2.16 kg) of 20 to 200 g/10 min and an isotactic pentad rate of 0.98 or higher, the MFR of the block copolymer being 10 to 100 g/10 min (at 230°C under a load of 2.16 kg), the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the block copolymer being from 5 to 7; component (B) : the following combination (B-1) or (B-2) of two different copolymers: (B-1) : the following two copolymers (B-1-1) and (B-1-2) : (B-1-1) : 5 to 10% by weight of an ethylene/butene random copolymer resin having a melting temperature measured by a differential scanning calorimeter of 60 to 100°C and an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg), and (B-1-2) : 5 to 10% by weight of an ethylene/butene random copolymer rubber which does not have a melting temperature measured by a differential scanning calorimeter of higher than 30°C and has an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg), (B-2) : the following two copolymers (B-2-1) and (B-2-2) : (B-2-1) : to 15% by weight of an ethylene/octene random copolymer rubber having a melting temperature measured by a differential scanning calorimeter of 60 to 90°C and an MFR of 1.0 to 20 g/10 min (at 230°C under a load of 2.16 kg), and (B-2-2) : 1 to 5% by weight of an ethylene/propylene copolymer rubber having a melting temperature measured by a differential scanning colorimeter of lower than 30°C, being substantially amorphous, having an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg) ; component (C) : 0.3 to 5% by weight of a block elastomer represented by the following formula [I] or [II], having a melting temperature measured by a differential scanning calorimeter of 80 to 110°C and an MFR of 0.5 to 20 g/10 min (at 230°C under a load of 2.16 kg), consisting of 20 to 40% by weight of polyethylene crystalline moiety and 60 to 80% by weight of random elastomer moiety: polyethylene moiety · (ethylene/butene random elastomer moiety) · polyethylene moiety [I] polyethylene moiety · (ethylene/butene random elastomer moiety) [II]; and component (D): 15 to 25% by weight of talc having an average particle diameter of 5 micrometers or less and a specific surface area of 3.5 m 2 /g or more. DETAILED DESCRIPTION OF THE INVENTION [I] Components (A) Propylene/Ethylene Block Copolymer (Component (A)) A propylene/ethylene block copolymer having a melt flow rate (MFR: at 230°C under a load of 2.16 kg) of 10 to 100 g/10 min, preferably 20 to 80 g/10 min, particularly 30 to 60g/10 min is used as the component (A) of the thermoplastic resin composition of the present invention. When a propylene/ethylene block copolymer having an MFR lower than the above-described range is used, the resulting thermoplastic resin composition is insufficient in fluidity. It is therefore necessary to use a molder with strong clamping force, or to increase the molding temperature when such a thermoplastic resin composition is molded into thin-walled products. The productivity is thus adversely affected. On the contrary, when a propylene/ethylene block copolymer having an MFR higher than the above-described range is used, the resulting thermoplastic resin composition cannot reveal good properties such as impact resistance. The MFR of the above propylene/ethylene block copolymer can be adjusted during polymerization, or can be adjusted with an organic peroxide such as diacyl peroxide or dialkyl peroxide after polymerization. Further, it is necessary that the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the propylene/ethylene block copolymer, which shows the molecular weight distribution of the block copolymer, be in the range of 5 to 7, preferably in the range of 5.5 to 6.5. A propylene/ethylene block copolymer whose Mw/Mn ratio is not within the above-described range provides a thermoplastic resin composition which reveals decreased impact strength. The propylene homopolymer moiety of the propylene/ethylene block copolymer is required to have an MFR of 20 to 200 g/10 min, preferably 30 to 150 g/10 min, particularly 40 to 100 g/10 min, and an isotactic pentad rate of 0.98 or more, preferably 0.985 or more. When the MFR of the propylene homopolymer moiety of the propylene/ethylene block copolymer is lower than the above-described range, the final thermoplastic resin composition is insufficient in fluidity. On the other hand, when the MFR is in excess of the above-described range, the final thermoplastic resin composition cannot reveal high impact resistance. When the isotactic pentad rate (P) of the propylene homopolymer moiety of the propylene/ethylene block copolymer is lower than the above-described range, the final thermoplastic resin composition cannot reveal sufficiently high flexural modulus, so that such an isotactic pentad rate is not suitable. The "isotactic pentad rate (P) " as used herein means the rate of isotactic segments in polypropylene molecular chain determined in terms of pentad by means of 13 C-NMR. Further, the ethylene content of the above propylene/ethylene block copolymer is preferably from 2 to 8% by weight, and that of the elastomer moiety of the propylene/ethylene block copolymer is preferably from 30 to 50% by weight. When the ethylene content of the block copolymer is lower than this range, the final thermoplastic resin composition tends to reveal poor heat resistance. On the other hand, when the ethylene content is in excess of the above range, the final thermoplastic resin composition cannot reveal sufficiently high flexural modulus and surface hardness. A catalyst having high stereoregularity is used for the production of the above propylene/ethylene block copolymer. Examples of the method for preparing the catalyst include a method in which a titanium trichloride composition obtained by reducing titanium tetrachloride with an organoaluminum compound, and then treating the resulting compound with various electron donors and acceptors is combined with an organoaluminum compound and an aromatic carboxylic acid ester (see Japanese Laid-Open Patent Publications Nos. 100806/1981, 120712/1981 and 104907/1983); and a method in which titanium tetrachloride and various electron donors are brought into contact with a magnesium halide to obtain a catalyst supported on a carrier (see Japanese Laid-Open Patent Publications Nos. 63310/1982, 43915/1988 and 83116/1988). The propylene/ethylene block copolymer can be obtained by carrying out block copolymerization between propylene and ethylene in the presence of the above catalyst, by employing such a production method as the gas phase fluid bed, solution or slurry method. It is important to incorporate the above propylene/ethylene block copolymer into the thermoplastic resin composition of the present invention in an amount of 50 to 75% by weight, preferably 53 to 72% by weight, more preferably 55 to 70% by weight, most preferably 58 to 70% by weight of the composition. When the amount of the propylene/ethylene block copolymer is less than the above-described range, the thermoplastic resin composition cannot reveal high flexural modulus. On the contrary, when the amount of the block copolymer is more than the above-described range, the thermoplastic resin composition reveals impaired impact resistance. (B) Component (B) The combination (B-1) or (B-2) of two different copolymers, which will be hereinafter explained in detail, is used as the component (B) of the thermoplastic resin composition of the present invention. The combination (B-1) is a combination of two copolymers (B-1-1) and (B-2-1) as described below. Component (B-1-1) : The component (B-1-1) is an ethylene/butene random copolymer resin, and used in order to improve the impact resistance of the thermoplastic resin composition with its surface hardness maintained high. When the component (B-1-1) is used along with the component (B-1-2) and the component (C), which will be explained later, the resulting thermoplastic resin composition can have more well-balanced physical properties. An ethylene/butene random copclymer resin having a melting temperature measured by a differential scanning calorimeter (DSC) of 60 to 100°C, preferably 65 to 90°C, particularly 70 to 80°C is used as the component (B-1-1). An ethylene/butene random copolymer resin having a melting temperature lower than the above-described range has low crystallinity, so that such a copolymer resin cannot impart sufficiently high surface hardness to the thermoplastic resin composition. On the contrary, when an ethylene/butene random copolymer resin having a melting temperature higher than the above range is used, the resulting thermoplastic resin composition cannot reveal sufficiently high impact resistance. Any ethylene/butene random copolymer resin can be used for the present invention regardless of its butene cement as long as it has a melting temperature in the above-described range. An ethylene/butene random copolymer resin containing 15 to 25% by weight, particularly 17 to 23% by weight of butene is preferred from the viewpoints of both impact resistance and surface hardness. An ethylene/butene random copolymer resin having a melt flow rate (MFR: at 230°C under a load of 2.16 kg) of 0.5 to 10 g/10 min, preferably 1 to 8 g/10 min, particularly 2 to 7 g/10 min is used as the component (B-1-1). When an ethylene/butene random copolymer resin having an MFR either lower or higher than the above-described range is used, the resulting thermoplastic resin composition revealsimpaired impact resistance. Further, an ethylene/butene random copolymer resin having a density of lower than 0.90 g/cm 3 , particularly 0.87 to 0.89 g/cm 3 is preferable as the component (B-1-1) because, when such a random copolymer resin is used, the resulting thermoplastic resin composition can reveal improved impact resistance and surface hardness. It is not necessary that the above ethylene/butene random copolymer resin itself be of one type, and a mixture of two or more of the random copolymer resins can be used. The above ethylene/butene random copolymer resin can be obtained by copolymerizing ethylene and butene in the presence of an ion polymerization catalyst such as a Ziegler catalyst or Phillips catalyst, by employing such a production method as the gas phase fluid bed, solution or slurry method. It is important to incorporate the ethylene/butene random copolymer resin, the component (B-1-1), into the thermoplastic resin composition of the present invention in an amount of 5 to 10% by weight, preferably 6 to 9% by weight of the composition. When the amount of the ethylene/butene random copolymer resin is less than the above-described range, the thermoplastic resin composition reveals lowered Rockwell hardness. On the contrary, when the amount of the random copolymer resin is in excess of the above-described range, the thermoplastic resin composition reveals decreased flexural modulus. Component (B-1-2) : The component (B-1-2) is an ethylene/butene random copolymer rubber, and used in order to impart high impact resistance to the thermoplastic resin composition of the invention. An ethylene/butene random copolymer rubber which does not have a melting temperature measured by a differential scanning calorimeter (DSC) of higher than 30°C and which is a substantially amorphous elastomer is suitable as the component (B-1-2). The ethylene/butene random copolymer rubber may either have a melting temperature of lower than 30°C or have no melting temperature. When an ethylene/butene random copolymer rubber having a melting temperature of 30°C or higher is used, the resulting thermoplastic resin composition cannot reveal sufficiently high impact resistance. An ethylene/butene random copolymer rubber having a melt flow rate (MFR: at 230°C under a load of 2.16 kg) of 0.5 to 10 g/10 min, preferably 1 to 8 g/10 min, particularly 2 to 7 g/10 min is used as the component (B-1-2). When the MFR of the above random copolymer rubber is not within the above range, the final thermoplastic resin composition cannot reveal sufficiently high impact resistance. Further, an ethylene/butene random copolymer rubber having a density of less than 0.90 g/cm 3 , particularly 0.87 to 0.89 g/cm 3 is favorable from the viewpoint of the impact resistance of the final thermoplastic resin composition. It is not necessary that the above ethylene/butene random copolymer rubber itself be of one type, and a mixture of two or more of the random copolymer rubbers can be used. The above ethylene/butene random copolymer rubber can be obtained, like the above-described component (B-1-1), by copolymerizing ethylene and butene in the presence of an ion polymerization catalyst such as a Ziegler catalyst or Phillips catalyst, by employing such a production method as the gas phase fluid bed, solution or slurry method. Any ethylene/butene random copolymer rubber can be used regardless of its butene content as long as it is substantially amorphous and elastomeric. An ethylene/butene random copolymer rubber containing more than 25% by weight, particularly more than 30% by weight of butene is preferred because such a random copolymer rubber can impart improved impact resistance to the final thermoplastic resin composition. It is important to incorporate the above ethylene/butene random copolymer rubber into the thermoplastic resin composition of the present invention in an amount of 5 to 10% by weight, preferably 6 to 9% by weight of the composition. When the amount of the ethylene-butene random copolymer rubber is less than the above-described range, the thermoplastic resin composition reveals impaired impact resistance. On the contrary, when the amount of the random copolymer rubber is in excess of the above-described range, the thermoplastic resin composition reveals decreased flexural modulus. The combination (B-2) is a combination of two copolymers (B-2-1) and (B-2-2) as described below. Component (B-2-1) : The component (B-2-1) is an ethylene/octene random copolymer rubber, and used in order to improve the impact resistance of the thermoplastic resin composition of the invention with its surface hardness maintained high. When the component (B-2-1) is used along with the component (B-2-2) and the component (C), the resulting thermoplastic resin composition can reveal more well-balanced physical properties. An ethylene/octene random copolymer rubber having a melting temperature measured by a differential scanning calorimeter (DSC) of 60 to 90°C, preferably 60 to 85°C, particularly 60 to 70°C is suitable as the component (B-2-1). An ethylene/octene random copolymer rubber having a melting temperature lower than the above range has low crystallinity, so that such a rubber cannot impart sufficiently high surface hardness to the thermoplastic resin composition. On the contrary, when the melting temperature of the copolymer rubber is higher than the above range, the final thermoplastic resin composition cannot reveal sufficiently high impact resistance. An ethylene/octene random copolymer rubber having a density of 0.90 g/cm 3 or lower, preferably 0.86 to 0.89 g/cm 3 , particularly 0.865 to 0.880 g/cm 3 is suitable from the viewpoints of both impact resistance and surface hardness. Any ethylene/octene random copolymer rubber can be used regardless of its octane content as long as it has a melting temperature in the above-described range. An ethylene/octene random copolymer rubber containing 10 to 17 mol%, preferably 12 to 17 mol% of octene is preferred from the viewpoints of both impact resistance and surface hardness. The "octene content" as used herein is a value obtained by means of 13 C-NMR in accordance with the description in Macromolecules vol. 15, pp. 353-360 and pp. 1402-1406 (1982). The above ethylene/octene random copolymer rubber can be obtained by polymerization using a titanium compound such as a titanium halide, an organoaluminum-magnesium complex such as an alkyl aluminum-magnesium complex or an alkylalkoxy aluminum complex, an alkyl aluminum, a so-called Ziegler catalyst such as an alkyl aluminum chloride, or a metallocene compound as described in WO-91/04257. However, when the polymerization is carried out by using a metallocene compound, an ethylene/octene random copolymer rubber which is more effective can be obtained. The polymerization can be carried out by employing such a production method as the gas phase fluid bed, solution or slurry method. An ethylene/octene random copolymer rubber having a melt flow rate (at 230°C under a load of 2.16 kg) of 1.0 to 20 g/10 min, preferably 5 to 16 g/10 min, more preferably 7 to 13 g/10 min is used as the component (B-2-1). When the MFR of the random copolymer rubber is either lower or higher than the above-described range, the final thermoplastic resin composition cannot reveal high impact resistance. The amount of the above ethylene/octene random copolymer rubber incorporated into the thermoplastic resin composition is from 7 to 15% by weight, preferably from 8 to 12% by weight of the composition. When the amount of the random copolymer rubber is less than the above-described range, the thermoplastic resin composition cannot reveal sufficiently high impact resistance. On the contrary, when the amount of the random copolymer rubber is in excess of the above-described range, the thermoplastic resin composition cannot reveal sufficiently high flexural modulus. It is not necessary that the above ethylene/octene random copolymer rubber itself be of one type, and a mixture of two or more of the random copolymer rubbers can be used. Component (B-2-2) : The component (B-2-2) is an ethylene/propylene copolymer rubber, and used in order to impart high impact resistance to the thermoplastic resin composition. This component (B-2-2) is a substantially amorphous elastomer having a melting temperature measured by a differential scanning calorimeter (DSC) of lower than 30°C. When an ethylene/propylene copolymer rubber whose melting temperature is not within the above-described range is used, the resulting thermoplastic resin composition cannot reveal sufficiently high impact resistance, so that such a copolymer rubber is not suitable. An ethylene/propylene copolymer rubber having a density of 0.88 g/cm 3 or less, particularly 0.85 to 0.87 g/cm 3 is suitable from the viewpoint of impact resistance. The above ethylene/propylene copolymer rubber can be obtained by copolymerizing ethylene and propylene in the presence of an ion polymerization catalyst such as a Ziegler catalyst or Phillips catalyst, by employing such a production method as the gas phase fluid bed, solution or slurry method. Any ethylene/propylene copolymer rubber can be used regardless of its propylene content as long as it is substantially amorphous. An ethylene/propylene copolymer rubber containing 20 mol% or more, particularly 25 mol% or more of propylene is suitable from the viewpoint of impact resistance. The MFR (at 230°C under a load of 2.16 kg) of this ethylene/propylene copolymer rubber is from 0.5 to 10 g/10 min, preferably from 1 to 8 g/10 min, more preferably from 2 to 7 g/10 min. When the MFR of the above copolymer rubber is either lower or higher than this range, the impact-resistance-improving effect cannot be fully obtained. The amount of the above ethylene/propylene copolymer rubber incorporated into the thermoplastic resin composition is from 1 to 5% by weight, preferably from i to 4% by weight of the composition. When the amount of the copolymer rubber is less than the above-described range, the thermoplastic resin composition cannot reveal sufficiently high impact resistance. On the contrary, when the amount of the copolymer rubber is in excess of the above-described range, the thermoplastic resin composition cannot reveal sufficiently high flexural modulus. It is not necessary that the above ethylene/propylene copolymer rubber itself be of one type, and a mixture of two or more of the copolymer rubbers can be used. (C) Block Elastomer (Component (C)) A block elastomer, the component (C) of the thermoplastic resin composition of the present invention, is used so that the impact-resistance-improving effect of the above component (B) can be more effectively obtained. Even when only a small amount of the block elastomer is added, this effect can be fully obtained. The melting temperature of this block elastomer (component (C)) measured by a differential scanning calorimeter is from 80 to 110°C, preferably from 90 to 105°C. When a block elastomer whose melting temperature is not within the above-described range is used, the resulting thermoplastic resin composition cannot reveal sufficiently high impact resistance. Further, the melt flow rate (MFR: at 230°C under a load of 2.16 kg) of the block elastomer for use in the present invention is from 0.5 to 20 g/10 min, preferably from 0.5 to 15 g/10 min. When a block elastomer having an MFR either lower or higher than the above-described range is used, the resulting thermoplastic resin composition reveals decreased Izod impact strength. The block elastomer (component (C)) contains as essential constituents polyethylene structure and elastomer structure. When either one of these structures is not present in the elastomer, the above-described effect cannot be fully obtained. The block elastomer can be of triblock structure or of diblock structure represented by the following formula [I] or [II]: polyethylene moiety · (ethylene/butene random elastomer moiety)·polyethylene moiety [I] polyethylene moiety (ethylene/butene random moiety) [II] The proportion of the crystalline moiety of the above polyethylene structure is from 20 to 40% by weight, preferably from 23 to 35% by weight. Further, the proportion of the moiety of the elastomer structure, ethylene/butene random elastomer moiety, is from 60 to 80% by weight, preferably from 65 to 77% by weight. The butene content (the rate of 1,2-polymerization) of the elastomer structure is preferably from 60 to 90% by weight, particularly from 65 to 85% by weight. When any of these proportions is not within the above-described range, the final thermoplastic resin composition tends to reveal low impact resistance. There is no particular limitation on the method for producing the block elastomer. For instance, the elastomer can be prepared in the following manner, by using the method and procedure described in Japanese Laid-Open Patent Publication No. 34513/1993. For instance, after butadiene is 1,4-polymerized, the polymerization conditions are changed so that the 1,2-polymerization of butadiene can mainly occurr. Thus, the rate of 1,2-polymerization can be increased by controlling the polarity of a solvent, or the like. If hydrogenation is carried out at this stage, an elastomer of diblock structure represented by the formula [II] is obtained. If hydrogenation is carried out after the above product is subjected to a coupling treatment, an elastomer of triblock structure represented by the formula [I] can be obtained. The so-called living polymerization method can be employed as a method for carrying out the above polymerization. The polymerization can be carried out in the same manner as is employed for obtaining a styrene elastomer such as SEBS (styrene/ethylene/butylene/styrene copolymer). A block elastomer having a rate of 1,2-polymerization of 60 to 90% by weight, preferably 65 to 85% by weight is suitable as the component (C) for use in the present invention. When the rate of the 1,2-polymerization is not within the above-described range, there is a tendency that the block elastomer cannot fully bring about the above-described effect. The amount of the above block elastomer incorporated into the thermoplastic resin composition of the invention is from 0.3 to 5% by weight, preferably from 0.5 to 3% by weight, particularly from 0.75 to 3% by weight of the composition. When the amount of the block elastomer is in excess of the above-described range, the thermoplastic resin composition reveals decreased Rockwell hardness. On the contrary, when the amount of the block elastomer is less than the above-described range, the aforementioned effect cannot be obtained. (D) Talc (Component (D)) Physical Properties of Talc: Talc used as the component (D) of the thermoplastic resin composition of the present invention has an average particle diameter of 5 micrometers of less, preferably 0.5 to 3 micrometers, and a specific surface area of 3.5 m 2 /g or more, preferably 3.5 to 6 m 2 /g. When the average particle diameter and specific surface area are not within the above respective ranges, the final thermoplastic resin composition reveals decreased flexural modulus. The average particle diameter of the talc is a particle diameter at a cumulative quantity of 50% by weight on a particle size cumulative distribution curve which is obtained by a measurement carried out by the liquid layer sedimentation light transmission method (by using, for example, Model "CP" manufactured by Shimadzu Corp., Japan). Further, the specific surface area of the talc can be determined by the air transmission method (by using, for example, a constant-pressure-aeration-type specific surface area measuring apparatus, Model "SS-100" manufactured by Shimadzu Corp., Japan). The above defined talc can be generally prepared by means of dry grinding, followed by dry classification. Talc whose surface has been treated with any of various organic titanate coupling agents, silane coupling agents, fatty acids, metallic salts of a fatty acid, and fatty acid esters can also be used in order to improve the adhesion between the talc and the polymers or the dispersibility of the talc in the polymers. The amount of the talc incorporated into the thermoplastic resin composition of the invention is from 15 to 25% by weight, preferably from 17 to 23% by weight of the composition. When the amount of the talc is less than the above-described range, the final thermoplastic resin composition cannot reveal sufficiently high flexural modulus. On the other hand, when the amount of the talc is in excess of the above-described range, the final thermoplastic resin composition reveals decreased tensile elongation. (E) Additional Components (Optional Components) In addition to the above-described essential five components (A), (B-1-1), (B-1-2), (C) and (D), or five components (A), (B-2-1), (B-2-2), (C) and (D), other additional components (component (E)) can be added to the thermoplastic resin composition of the invention within such a limit that the effects of the present invention will not be remarkably marred. Examples of such additional components (component (E)) include antioxidants of phenol type and phosphorus type, deterioration-on-weathering inhibitors of hindered amine type, benzophenone type and benzotriazole type, nucleating agents such as aluminum compounds and phosphorus compounds, dispersing agents represented by metallic salts of stearic acid, coloring materials such as quinacridone, perylene, phthalocyanine and carbon black, fibrous potassium titanate, fibrous magnesium oxysulfate, fibrous aluminum borate, whisker of calcium carbonate, carbon fiber and glass fiber. [II] Process for Producing Thermoplastic Resin Composition (1) Kneading The thermoplastic resin composition of the present invention can be obtained by kneading, at a temperature of 180 - 250°C, the five components (A), (B-1-1), (B-1-2), (C) and (D), or the five components (A), (B-2-1), (B-2-2), (C) and (D), and, if necessary, the component (E) by a conventional extruder, Banbury mixer, roller, Brabender Plastograph or kneader. Of these, an extruder, especially a twin-screw extruder is preferably used for producing the composition of the present invention. (2) Molding There is no particular limitation on the method for molding the thermoplastic resin composition of the present invention. However, the injection molding method is most suitable when the effects of the present invention to be obtained are taken into consideration. [III] Thermoplastic Resin Composition (1) Physical Properties The thermoplastic resin composition of the present invention produced by the above-described method has good injection molding properties, and reveals the following excellent physical properties of flexural modulus, impact resistance, tensile elongation, surface hardness and heat resistance: (a) MFR: 20 g/10 min or more, preferably 25 g/10 min or more; (b) flexural modulus: 20,000 kg/cm 2 or more, preferably 23,000 to 28,000 kg/cm 2 ; (c) Izod impact strength (at 23°C) : 15 kg·cm/cm or more, preferably 18 kg·cm/cm or more; (d) tensile elongation: 400% or more, preferably 500% or more; (e) Rockwell hardness: 75 or more, preferably 80 or more; and (f) heat deformation temperature: 120°C or higher, preferably 130°C or higher. (2) Uses Since the thermoplastic resin composition of the present invention has the above-described good physical properties, it can be used for obtaining a variety of molded products. In particular, it is preferable to injection mold the thermoplastic resin composition into such products as interior automotive trims, especially installment panels, console boxes, and the like. (3) Effects of the Invention The thermoplastic resin composition of the present invention has good injection molding properties, can reveal excellent appearance, flexural modulus, tensile elongation, heat resistance, surface hardness and impact resistance, and is suitable for producing injection-molded products such as interior automotive trims. EXAMPLES The present invention will now be explained more specifically by referring to the following examples. However, the present invention is not limited to or limited by the following examples. [I] Measuring Methods (1) MFR: measured in accordance with ASTM-D1238, at a temperature of 230°C under a load of 2.16 kg. (2) Isotactic pentad rate (P): determined in accordance with the method described in Macromolecules, 8, 687 (1975), by using 13 C-NMR. (3) Melting temperature: A differential scanning calorimeter was used for the measurement. A sample was heated to a temperature of 180°C and melted. Thereafter, the sample was cooled to a temperature of -100°C at a rate of 10°C/min, and the temperature of the sample was then raised at a rate of 10°C/min, thereby obtaining a thermogram. The peak of the thermogram was taken as the melting temperature of the sample. (4) Flexural modulus: measured in accordance with ASTM-D790, at a temperature of 23°C and a bending rate of 2 mm/min. (5) Impact resistance: evaluated by the Izod impact strength at 23°C in accordance with ASTM-785. (6) Tensile elongation: A tensile test was carried out in accordance with ASTM-D638 at a temperature of 23°C and a stress rate of 10 mm/min, and the elongation was measured. (7) Surface hardness: evaluated by the Rockwell hardness (at 23°C) on the R-scale in accordance with ASTM-D785. (8) Heat deformation temperature: measured in accordance with ASTM-D523 under a load of 4.6 kg. (9) Ratio (Mw/Mn) of weight-average molecular weight to number-average molecular weight: determined by using GPC (gel permeation chromatography). [II] Examples Examples 1 to 15 & Comparative Examples 1 to 25 The components shown in Tables 1 to 5 were blended according to the formulations shown in Tables 6, 7 and 8. To each mixture were further added 0.1 parts by weight of tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate]methane and 0.4 parts by weight of magnesium stearate. The mixture was mixed by a super mixer (manufactured by Kawata Mfg. Co., Ltd., Japan) for 5 minutes, and the resultant was kneaded and granulated by a two-roll kneader ("FCM" manufactured by Kobe Steel, Ltd., Japan) set at 210°C. Thermoplastic resin compositions were thus obtained. Thereafter, the thermoplastic resin compositions were respectively molded, at a molding temperature or 210°C, into various types of specimens by using an injection molder with a clamping force of 100 tons, and the measurements were carried out by the above-described various methods. The results are shown in Tables 9 to 11. Ethylene/Propylene Block Copolymer Type Propylene Homopolymer Moiety Block Copolymer Molecular Weight Distribution Mw/Mn MFR (g/10 min) Isotactic Pentad Rate MFR (g/10 min) Ethylene Content (wt. %) PP-1 81 0.988 45 4.5 5.7 PP-2 125 0.983 68 4.3 5.8 PP-3 50 0.986 28 4.3 6.3 PP-4 238 0.981 120 3.9 5.2 PP-5 14 0.981 8 4.7 6.1 PP-6 77 0.963 43 4.1 5.5 PP-7 120 0.989 47 4.8 8.3 PP-8 53 0.985 49 4.2 4.4 Component (B-1-1) Type MFR (g/10min) Melting Temperature (°C) PEX-1 6.5 80 PEX-2 7.0 103 PEX-3 9.1 78 PEX-4 4.8 79 PEX-5 21 80 PEX-6 0.4 81 PEX-7 6.1 42 Component (B-1-2) Type MFR (g/10min) Melting Temperature (°C) PEX- 8 6.3 26 PEX- 9 9.2 28 PEX-10 4.9 28 PEX-11 23 26 PEX-12 0.3 26 PEX-13 5.9 53 Component (C) Type PE Moiety Elastomer Moiety MFR Melting Temperature Structure Proportion (wt. %) Proportion (wt. %) Rate of 1,2-Polymerization (wt. %) Elastomer-1 30 70 78 2.8 99.7 Triblock Elastomer-2 27 73 74 13 99.9 Triblock Elastomer-3 29 71 70 1.2 98.3 Triblock Elastomer-4 28 72 75 100 99.2 Triblock Elastomer-5 31 69 74 0.1 98 Triblock Elastomer-6 99 1 80 2.5 118 Triblock Elastomer-7 5 95 76 3.1 45 Triblock Elastomer-8 32 68 73 2.2 99.5 Diblock Component (D) Type Average Particle Diameter (µm) Specific Surface Area (m 2 /g) Talc-1 2.8 4.0 Talc-2 6.5 2.8 Examples 16 to 29 & Comparative Examples 26 to 46 The components shown in Tables 12 to 16 were blended according to the formulations shown in Tables 17, 18 and 19. To each mixture were further added 0.1 parts by weight of tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate]methane and 0.4 parts by weight of magnesium stearate. The mixture was mixed by a super mixer (manufactured by Kawata Mfg. Co., Ltd., Japan) for 5 minutes, and the resultant was kneaded and granulated by a two-roll kneader ("FCM" manufactured by Kobe Steel, Ltd., Japan) set an 210°C. Thermoplastic resin compositions were thus obtained. Thereafter, the thermoplastic resin compositions were respectively molded, at a molding temperature of 210°C, into various types of specimens by using an injection molder with a clamping force of 350 tons, and the measurements were carried out by the above-described various methods. The results are shown in Tables 20, 21 and 22.

Claims: A thermoplastic resin composition comprising the following components (A) to (D) : component (A): 50 to 75% by weight of a propylene/ethylene block copolymer whose propylene homopolymer moiety has a melt flow rate (MFR: at 230°C under a load of 2.16 kg) of 20 to 200 g/10 min and an isotactic pentad rate of 0.98 or higher, the MFR (at 230°C under a load of 2.16 kg) of the block copolymer being 10 to 100 g/10 min, the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the block copolymer being from 5 to 7; component (B): the following combination (B-1) or (B-2) of two different copolymers: (B-1) : the following two copolymers (B-1-1) and (B-1-2) : (B-1-1) : 5 to 10% by weight of an ethylene/butene random copolymer resin having a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of 60 to 100°C and an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg), and (B-1-2): 5 to 10% by weight of an ethylene/butene random copolymer rubber which does not have a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of higher than 30°C and has an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg), (B-2) : the following two copolymers (B-2-1) and (B-2-2) : (B-2-1) : 7 to 15% by weight of an ethylene/octene random copolymer rubber having a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of 60 to 90°C and an MFR of 1.0 to 20 g/10 min (at 230°C under a load of 2.16 kg), and (B-2-2) : 1 to 5% by weight of an ethylene/propylene copolymer rubber having a melting temperature measured by a differential scanning colorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of lower than 30°C, being substantially amorphous, having an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg) ; component (C): 0.3 to 5% by weight of a block elastomer represented by the following formula [I] or [II], having a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of 80 to 110°C and an MFR of 0.5 to 20 g/10 min (at 230°C under a load of 2.16 kg), consisting of 20 to 40% by weight of polyethylene crystalline moiety and 60 to 80% by weight of random elastomer moiety: polyethylene moiety·(ethylene/butene random elastomer moiety)·polyethylene moiety [I] polyethylene moiety · (ethylene/butene random elastomer moiety) [II]; and component (D) : 15 to 25% by weight of talc having an average particle diameter of 5 micrometers or less and a specific surface area of 3.5 m 2 /g or more. The thermoplastic resin composition according to claim 1, wherein the block elastomer, the component (C), is a hydrogenated product of a butadiene polymer, and the rate of 1,2-polymerization of butadiene in the ethylene/butene random elastomer moiety is from 60 to 90% by weight. The thermoplastic resin composition according to claim 1 or 2, having an MFR of 20 g/10 min or more, a flexural modulus (ASTM-D790) of 20,000 kg/cm 2 or more, an Izod impact strength (ASTM-785) of 15 kg·cm/cm or more, a tensile elongation (ASTM-D638) of 400% or more, a heat deformation temperature (ASTM-D523) of 120°C or higher and a Rockwell hardness (ASTM-D785) of 75 or more. A thermoplastic resin composition comprising the following components (A) to (D): component (A): 50 to 75% by weight of a propylene/ethylene block copolymer whose propylene homopolymer moiety has a melt flow rate (MFR: at 230°C under a load of 2.16 kg) of 20 to 200 g/10 min and an isotactic pentad rate of 0.98 or higher, the MFR (at 230°C under a load of 2.16 kg) of the block copolymer being 10 to 100 g/10 min, the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the block copolymer being from 5 to 7; component (B-1-1) : 5 to 10% by weight of an ethylene/butene random copolymer resin having a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of 60 to 100°C and an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg) ; component (B-1-2) : 5 to 10% by weight of an ethylene/butene random copolymer rubber which does not have a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of higher than 30°C and has an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg) ; component (C) : 0.3 to 5% by weight of a block elastomer represented by the following formula [I] or [II], having a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of 80 to 110°C and an MFR of 0.5 to 20 g/10 min (at 230°C under a load of 2.16 kg), consisting of 20 to 40% by weight of polyethylene crystalline moiety and 60 to 80% by weight of random elastomer moiety: polyethylene moiety · (ethylene/butene random elastomer moiety) · polyethylene moiety [I] polyethylene moiety · (ethylene/butene random elastomer moiety) [II]; and component (D) 15 to 25% by weight of talc having an average particle diameter of 5 micrometers or less and a specific surface area of 3.5 m 2 /g or more. The thermoplastic resin composition according to claim 4, wherein the block elastomer, the component (C), is a hydrogenated product of a butadiene polymer, and the rate of 1,2-polymerization of butadiene in the ethylene/butene random elastomer moiety is from 60 to 90% by weight. The thermoplastic resin composition according to claim 4 or 5, having an MFR of 20 g/10 min or more, a flexural modulus (ASTM-D790) of 20,000 kg/cm 2 or more, an Izod impact strength (ASTM-785) of 15 kg · cm/cm or more, a tensile elongation (ASTM-D638) of 400% or more, a heat deformation temperature (ASTM-D523) of 120°C or higher and a Rockwell hardness (ASTM-D785) of 75 or more. A thermoplastic resin composition comprising the following components (A) to (D) : component (A) : 50 to 75% by weight of a propylene/ethylene block copolymer whose propylene homopolymer moiety has a melt flow rate (MFR: at 230°C under a load of 2.16 kg) of 20 to 200 g/10 min and an isotactic pentad rate of 0.98 or higher, the MFR (at 230°C under a load of 2.16 kg) of the block copolymer being 10 to 100 g/10 min, the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the block copolymer being from 5 to 7; component (B-2-1) : 7 to 15% by weight of an ethylene/octene random copolymer rubber having a melting temperature measured by a differential scanning colorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of 60 to 90°C and an MFR of 1.0 to 20 g/10 min (at 230°C under a load of 2.16 kg); component (B-2-2) : 1 to 5% by weight of an ethylene/propylene copolymer rubber which does not have a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of higher than 30°C, being substantially amorphous, and has an MFR of 0.5 to 10 g/10 min (at 230°C under a load of 2.16 kg) ; component (C): 0.3 to 5% by weight of a block elastomer represented by the following formula [I] or [II], having a melting temperature measured by a differential scanning calorimeter (peak of the thermogram obtained by melting at 180°C and cooling at-100°C at a rate of 10°C/min) of 80 to 110°C and an MFR of 0.5 to 20 g/10 min (at 230°C under a load of 2.16 kg), consisting of 20 to 40% by weight of polyethylene crystalline moiety and 60 to 80% by weight of random elastomer moiety: polyethylene moiety · (ethylene/butene random elastomer moiety) · polyethylene moiety [I] polyethylene moiety · (ethylene/butene random elastomer moiety) [II] ; and component (D) : 15 to 25% by weight of talc having an average particle diameter of 5 micrometers or less and a specific surface area of 3.5 m 2 /g or more. The thermoplastic resin composition according to claim 7, wherein the block elastomer, the component (C), is a hydrogenated product of a butadiene polymer, and the rate of 1,2-polymerization of butadiene in the ethylene/butene random elastomer moiety is from 60 to 90% by weight. The thermoplastic resin composition according to claim 7 or 8, having an MFR of 20 g/10 min or more, a flexural modulus (ASTM-D790) of 20,000 kg/cm 2 or more, an Izod impact strength (ASTM-785) of 15 kg · cm/cm or more, a tensile elongation (ASTM-D638) of 400% or more, a heat deformation temperature (ASTM-D523) of 120°C or higher and a Rockwell hardness (ASTM-D785) of 75 or more.

Inventors: ISHII IZUMI, JAGAWA YASUTOSHI, NAGAI TAKAYUKI, NISHIO TAKEYOSHI, SANO HIRONARI, SATO HIROKI, TSUTSUMI IKUO, ZANKA YUKIHITO, ISHII, IZUMI, JAGAWA, YASUTOSHI, NAGAI, TAKAYUKI, NISHIO, TAKEYOSHI, SANO, HIRONARI, SATO, HIROKI, TSUTSUMI, IKUO, ZANKA, YUKIHITO, Ishii, Izumi, c/o Japan Polychem Corp., Sano, Hironari, c/o Misubishi Chemical Corporation, Sato, Hiroki, c/o Japan Polychem Corp., Tsutsumi, Ikuo, c/o Japan Polychem Corp., Zanka, Yukihito, c/o Japan Polychem Corp.
Applicants: JAPAN POLYCHEM CORP, TOYOTA MOTOR CO LTD, JAPAN POLYCHEM CORPORATION, TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1996
Main classification: C08L53
IPC codes: C08L53