Title of Invention	POLYPROPYLENE RESIN COMPOSITION AND INJECTION MOLDED ITEM FOR AUTOMOBILE THEREFROM
Abstract	Provided are a polypropylene resin composition that excels not only in fluidity but also in balance between rigidity and impact resistance, and that can, when being molded into an automotive injection molded article, provide an automotive injection molded article excelling in weld appearance and flow mark appearance, and an automotive injection molded article made thereof. There is provided a polypropylene resin composition comprising 50 to 65 wt% of propylene-ethylene block copolymer (A-1) containing crystalline propylene homopolymer segment and propylene-ethylene random copolymer segment of 4.0 to 5.5 dl/g in intrinsic viscosity; 1 to 10 wt% of ethylene- a-olefin copolymer rubber (B) of 0.05 to 1 g/10 min in melt flow rate; 8 to 18 wt% of ethylene- a-olefin copolymer rubber (C) of 2 to 20 g/10 min in melt flow rate; and 18 to 25 wt% of inorganic filler (D), the sum of the rubbers (B) and (C) being 17 to 25 wt%. Further, an automotive injection molded article of the composition is provided.

Title of Invention

POLYPROPYLENE RESIN COMPOSITION AND INJECTION MOLDED ITEM FOR AUTOMOBILE THEREFROM

Abstract

Provided are a polypropylene resin composition that excels not only in fluidity but also in balance between rigidity and impact resistance, and that can, when being molded into an automotive injection molded article, provide an automotive injection molded article excelling in weld appearance and flow mark appearance, and an automotive injection molded article made thereof. There is provided a polypropylene resin composition comprising 50 to 65 wt% of propylene-ethylene block copolymer (A-1) containing crystalline propylene homopolymer segment and propylene-ethylene random copolymer segment of 4.0 to 5.5 dl/g in intrinsic viscosity; 1 to 10 wt% of ethylene- a-olefin copolymer rubber (B) of 0.05 to 1 g/10 min in melt flow rate; 8 to 18 wt% of ethylene- a-olefin copolymer rubber (C) of 2 to 20 g/10 min in melt flow rate; and 18 to 25 wt% of inorganic filler (D), the sum of the rubbers (B) and (C) being 17 to 25 wt%. Further, an automotive injection molded article of the composition is provided.

Full Text	DESCRIPTION POLYPROPYLENE RESIN COMPOSITION AND INJECTION MOLDED ITEM FOR AUTOMOBILE THEREFROM TECHNICAL FIELD [0001] The present invention relates to a polypropylene resin composition and to an injection 5 molded article thereof for automobiles. It relates more specifically to a polypropylene resin composition that excels not only in fluidity but also in balance between rigidity and impact resistance and that can provide an automotive article excellent in weld 10 appearance and flow mark appearance when being processed to form an automotive injection-molded article, to an automotive injection molded article formed thereof, and to a method for producing the automotive injection-molded article. 15 BACKGROUND ART [0002] Polypropylene resin compositions have been used widely for molded articles, e.g., automotive interior or exterior components and electric component 20 housings, because they are materials excellent in rigidity, impact resistance, and so on. [0003] For example, JP-A-3-20566 discloses automotive soft resin bumpers raade of propylene polymer compositions which contain a propylene polymer, an ethylene/a-olefin copolymer, talc and a specified propylene polymer containing a polar group or a combination of a specified conjugated diene copolymer having a hydroxy1 group at a molecular terminal and a specified propylene polymer graft-modified with an ethylenically unsaturated compound containing a carboxyl or acid anhydride group, the bumpers having a specified flexural modulus and a specified linear expansion coefficient, for the purpose of improving the appearance (weld and flow mark) and the dimensional stability (low linear expansion) of automotive soft resin bumpers, their balance between impact resistance at low temperature and flexibility, and their paintability. [0004] JP-A-9-71711 discloses a propylene resin composition comprising a propylene/ethylene block copolymer, an ethylene/a-olefin copolymer and talc, wherein the propylene/ethylene block copolymer contains a crystalline propylene homopolymer segment and an ethylene/propylene random copolymer segment containing ethylene at 20 to 80% by weight, and has a melt flow rate (MFR) of 25 to 140 g/10 minutes, and wherein the ethylene/a-olefin copolymer has an MFR of 0.5 to 15 g/10 minutes and an ethylene triad sequence fraction of Automotive exterior components, which have been required to have more improved quality, need still improvement even when the polypropylene resin compositions described above are used. A polypropylene resin composition is required to have still improved properties with respect to fluidity and balance between rigidity and impact resistance, and an injection-molded article thereof is required to be improved in weld appearance and flow mark appearance. In particular, an automotive bumper as a large-size injection-molded article is required to have good appearance and good balance between rigidity and impact resistance. [0007] Under such situations, it is an object of the present invention to provide a polypropylene resin composition excellent in fluidity and in balance between rigidity and impact resistance, and capable of giving an automotive injection-molded article excellent in weld appearance and flow mark appearance when being molded into an automotive injection-molded article, and present invention can solve the above problems, accomplishing the present invention. The present invention relates to a polypropylene resin composition containing 50 to 65% by weight of a polypropylene resin (A); 1 to 10% by weight of an ethylene/a-olefin copolymer rubber (B); 8 to 10% by weight of an ethylene/a-olefin copolymer rubber (C); and 18 to 25% by weight of an inorganic filler (D), wherein the combined content of the ethylene/a-olefin copolymer rubber (B) and the ethylene/a-olefin copolymer rubber (C) is 17 to 25% by weight, where the overall amount of the polypropylene resin composition is let be 100% by weight, wherein the polypropylene resin [A) is a propylene/ethylene block copolymer (A-1) having a crystalline propylene homopolymer segment and a propylene/ethylene random copolymer segment having an intrinsic viscosity of 4.0 to 5.5 dL/g, or is a propylene polymer mixture (A-3) containing the block copolymer (A-1) and a crystalline propylene homopolymer (A-2), contains an a-olefin of 4 to 12 carbon atoms and ethylene, and has a density of 0.850 to 0.870 g/cm and a melt flow rate of 2 to 20 g/10 minutes (determined at 230°C and under a load of 2.16 kg), and also relates to an automotive injection-molded article of the polypropylene resin composition and to a method for producing the automotive injection-molded article. ADVANTAGES OF THE INVENTION [0009] In accordance with the present invention, a polypropylene resin composition can be obtained which is excellent in fluidity and in balance between rigidity and impact resistance and which can give an automotive injectionmolded article excellent in weld appearance and flow mark appearance when being molded into an injection-molded article, and an automotive injection-molded article made thereof can also be obtained. THE BEST MODE FOR CARRYING OUT THE INVENTION [0010] crystalline propylene homopolyraer segment and a propylene/ethylene random copolymer segment. [0012] From the viewpoint of improving the balance between rigidity and impact resistance, the propylene/ethylene block copolymer (A-1) preferably contains 55 to 90% by weight of the crystalline propylene homopolymer segment and 10 to 45% by weight of the propylene/ethylene random copolymer segment, where the whole amount of the block copolymer is let be 100% by weight-[0013] The propylene/ethylene block copolymer {A-1) more preferably is a block copolymer containing 65 to 88% by weight of the crystalline propylene homopolymer segment and 12 to 35% by weight of the propylene/ethylene random copolymer segment, and still more preferably is a block copolymer containing 70 to 85% by weight of the crystalline propylene homopolymer segment and 15 to 30% by weight of the I The isotactic pentad fraction is the fraction of the propylene monomer unit existing at the center of the isotactic chain in the form of a pentad unit (i.e., the chain in which five propylene monomer units are continuously meso-linked) , determined by C-NMR, the procedure of which is described by A. Zambelli et al. (Macromolecules, 6, 925, 1973). NMR absorption peaks are assigned by the procedure described in Macromolecules, 8, 687, 1975, later published. [0016] More specifically, the isotactic pentad fraction is determined as an areal fraction of mmmm peaks to all the absorption peaks in the methyl carbon region in the -C-NMR spectral pattern. The isotactic pentad fraction of an NPL reference material (CRN No. M19-14 Polypropylene PP/MWD/2, supplied by UK's NATIONAL PHYSICAL LABORATORY) was determined by the above procedure to be 0.94 4. [0017] Moreover, the molecular weight distribution (Q value, Mw/Mn), as determined by gel permeation chromatography (GPC), of the crystalline propylene homopolymer segment in the block copolymer (A-1) preferably is 3 or more but less than 7, and more preferably is 3 to 5. [0019] From the viewpoint of realizing good balance between rigidity and Impact resistance, the propylene/ethylene random copolymer segment in the propylene/ethylene block copolymer (A-1) preferably has a propylene/ethylene weight ratio of 65/35 to 52/46, and more preferably 62/38 to 55/45, wherein the ratio is defined as the ratio of the weight of propylene-derived structural units (propylene content) to the weight of ethylene-derived structural units (ethylene content). [0020] From the viewpoint of making weld lines less noticeable to realize good weld appearance of an molded From the viewpoint of improving moldability and impact resistance, the block copolymer (A-11 preferably has a melt flow rate (MFR) of 10 to 120 g/10 minutes, more preferably 20 to 53 g/10 minutes. [0022] The propylene/ethylene block copolymer (A-1) may be produced by a known polymerization method using a catalyst system prepared by bringing (a) a solid catalyst component containing magnesium, titanium, a halogen and electron donor as essential components, (b) an organoaluminum compound and (c) an electron donor component into contact with each other. Examples of this type of catalyst system and a production method thereof include those disclosed in JP-A-1-315908, JP-A-7-216017 and JP-A-10-212319. [0023] The propylene/ethylene block copolymer (A-1) may be produced by a method which comprises at least two polymerization stages, wherein the crystalline propylene homopolymer segment is produced in the first Examples of polymerization methods include a bulk polymerization process, a solution polymerization process, a slurry polymerization process and a vapor-phase polymerization process. These processes may be carried out either batch-wide or continuously. These polymerization processes may optionally be combined with each other. From the viewpoint of being industrially and economically advantageous, a continuous vapor-phase polymerization process and a continuous bulk-vapor-phase polymerization process are preferred. [0025] More specific examples of a production method include: (1) a method in which, in the presence of the aforesaid catalyst system prepared by bringing (a) a solid catalyst component, (b) an organoaluminum compound and (c) an electron donor component into contact with each other, at least two polymerization tanks are placed in series, a crystalline propylene homopolymer segment is produced in the first tank/ the product is transferred to the second tank, and a propylene/ethylene random copolymer segment having an ethylene content of 35 to 48% by weight and an compound and (c) an electron donor component into contact with each other, at least four polymerization tanks are placed in series, a crystalline propylene homopolymer segment is produced in the first and second tanks, the product is transferred to the third tank, and a propylene/ethylene random copolymer segment having an ethylene content of 35 to 48% by weight and intrinsic viscosity of 4.0 to 5.5 dL/g is produced in the third and fourth tanks. [0026] A known method of handling catalysts may be adopted appropriately for determining the amounts of the (a) solid catalyst component, the (b) organoaluminum compound and the (c) electron donor component and how to supply the catalyst components into the polymerization tanks in the aforementioned polymerization methods. [0027] The polymerization temperature is ordinarily in a range from -30 to 300°C, preferably from 20 to 180°C. The polymerization pressure is ordinarily in a range from the atmospheric pressure to 10 MPa, preferably from 0.2 to 5 MPa. Hydrogen, for example, the known, preliminary polymerization method is a method in which a small amount of propylene is supplied and which is conducted in a slurry state using a solvent in the in the presence of a solid catalyst component (a) and an organoaluminum compound (b). [0029] The block copolymer (A-1) may, as required, be incorporated with various additives. Examples of such additives include antioxidant, UV absorber, lubricant, pigment/ antistatic agent, copper inhibitor, flame retardant, neutralizer, foaming agent, plasticizer, nucleating agent, antifoaming agent and crosslinking agent- Among such additives, an antioxidant or a 0V absorber is preferably added for improving heat resistance, weather resistance and stability against oxidation. [0030] Examples of the method for producing the block copolymer (A-1) include, in addition to the above-described methods in which the block copolymer is produced by using the above-described catalyst and the above-described polymerization methods, a method in polymer produced by the melt-kneading in the presence of a peroxide of a polymer obtained by the production method using the above-describe catalyst can be determined by measuring the intrinsic viscosity of a component of the polymer resulting from the melt-kneading which is soluble in xylene at 20°C. [0031] An organic peroxide is ordinarily used as the aforesaid peroxide, and examples of such an organic peroxide include alkyl peroxides, diacyl peroxides, peroxyesters and peroxycarbonates. The alkyl peroxides include dicumyl peroxide, di-tert-butyl peroxide, di-tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, tert-butylcumyl, 1,3-bis(t-butylperoxyisopropyl)benzene and 3,6,9-triethyl-3,6, 9-trimethyl-l,4, 7-triperoxonane. [0032] The diacyl peroxides include benzoyl peroxide, lauroyl peroxide and decanoyl peroxide. The peroxyesters include 1,1,3,3-tetramethylbutyl peroxyneodecanoate, a-ciomyl peroxyneodecanoate, tert-butyl peroxyneodecanoate. butyl peroxyhexahydroterephthalate, tert-amyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate and di-butyl peroxytrirrtethyladipate. [0033] The peroxycarbonates include di-3-raethoxybutyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di-isopropyl peroxydicarbonate, tert-butyl peroxyisopropylcarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate and dimyristyl peroxydicarbonate. [0034] When the polypropylene resin (A) to be used in the present invention is a propylene polymer mixture {A-3) containing a propylene/ethylene block copolymer (A-1) and a crystalline propylene homopolymer lA-2), the content of the block copolymer (A-l) in the propylene polymer mixture {A-3} is preferably 30 to 99% by vjeight and the content of the propylene homopolymer [A-2) is preferably 1 to 70% by weight. More preferably, the content of the block copolymer (A~l) is 45 to 90% by weight and the content of the propylene The propylene homopolymer (A-2) ordinarily has a melt flow rate (MFR, determined at 230°C and under a load of 2160 g) of 10 to 500 g/10 minutes, preferably 40 to 350 g/10 minutes. [0037] The propylene homopolymer (A-2) may be produced in a manner similar to that for producing the propylene/ethylene block copolymer (A-1). A method using the same catalyst system as that used for the production of the block copolymer (A-1) may be used. [0038] The ethylene/a-olefin copolymer rubber (B) for use in the present invention is an ethylene/a-olefin copolymer rubber which contains an a-olefin of 4 to 12 carbon atoms and ethylene. Examples of the a olefin of 4 to 12 carbon atoms include butene-1, pentene-1, hexene-1, heptene-1, octene-1 and decene. Butene-1, hexene-1 and octene-1 are preferable. [0039] From the viewpoint of increasing impact strength, especially impact strength at low temperature, the content of a-olefin in the copolymer Examples of the copolymer rubber (B) include ethylene/butene-1 random copolymer rubber, ethylene/hexene-1 random copolymer rubber and ethylene/octene-1 random copolymer rubber. Preferred is ethylene/octene-1 random copolymer rubber or ethylene/butene-1 random copolymer rubber. Two or more ethylene/a-olefin copolymer rubbers may be used in combination. [0041] From the viewpoint of obtaining good balance between rigidity and impact resistance, the copolymer rubber (B) has a density of 0.850 to 0.870 g/cm, preferably 0.850 to 0.865 g/cm. [0042] From the viewpoint of making weld lines less noticeable to realize good weld appearance of an molded article, making flow marks less visible to realize good flow mark appearance of a molded article, and realizing good balance between rigidity and impact resistance/ the copolymer rubber {B) has a melt flow rate (determined at 230°C and under a load of 2.16 kg) of 0.05 to 1 g/10 minutes, preferably 0.2 to 1 g/10 minutes. The known catalyst includes a catalyst system coniposed of a vanadium compound and an organoaluminum compound, a Ziegler-Natta catalyst system and a metallocene catalyst system, and the known polymerization process includes a solution polymerization process, a slurry polymerization process, a high-pressure ion polymerization process, or a vapor-phase polymerization process. [0044] The ethylene/a-olefin copolymer rubber (C) for use in the present invention is an ethylene/a-olefin copolymer rubber which contains an a-olefin of 4 to 12 carbon atoms and ethylene. Examples of the oc-olefin of 4 to 12 carbon atoms include butene-1, pentene-l, hexene-1, heptene-1, octene-1 and decene. Butene-1, hexene-1 and octene-1 are preferable. [0045] From the viewpoint of increasing impact strength, especially impact strength at low temperature, the content of a-olefin of 4 to 12 carbon atoms in the copolymer rubber [C) preferably is 20 to 50% by weight, more preferably 24 to 50% by weight, wherein the whole amount of the copolymer rubber (C) is ethylene/butene-1 random copolymer rubber. Two or more ethylene/a-olefin copolymer rubbers may be used in combination. [0047] From the viewpoint of obtaining good balance between rigidity and impact resistance, the copolymer rubber (C) has a density of 0.850 to 0.870 g/cm preferably 0.850 to 0.865 g/cm-. [0048] From the viewpoint of obtaining good balance between rigidity and impcct resistance, the copolymer rubber (C) has a melt flow rate (determined at 230°C and under a load of 2.16 kg) of 2 to 20 g/10 minutes, preferably 2.3 to 15 g/10 minutes, more preferably 2.5 to 10 g/10 minutes. [0049] The copolymer rubber (C) may be produced by the same method as that for producing the copolymer rubber (B). [0050] The inorganic filler (D) for use in the combination. [0051] Talc to be used as the inorganic filler (D) preferably is a product obtained by crushing hydrous magnesium silicate. The crystalline structure of a hydrous magnesium silicate molecule is a three-layered pyrophylite type structure, and talc is composed of a pile of this structure. Talc is more preferably in the form of tabular particles obtained by finely pulverizing crystals of a hydrous magnesium silicate molecule to a size as small as a unit layer. [0052] Talc preferably has an average particle diameter of 3 [jm or less. The average particle diameter of talc is a 50% equivalent particle diameter DsD determined on the basis of an integrated distribution curve measured by a minus sieve method while suspending talc in a dispersion medium, namely water or alcohol, using a centrifugal sedimentation type particle size distribution analyzer. [0053] silane coupling agents, titanium coupling agents, higher fatty acids, higher fatty acid esters, higher fatty acid amides and higher fatty acid salts. [0054] Fibrous magnesium sulfate to be used as the inorganic filler (D) preferably has an average fiber length of 5 to 50 jti, more preferably 10 to 30 urn, and preferably has an average fiber diameter of 0.3 to 2 \|jm, more preferably 0.5 to 1 urn . [0055] The content of the polypropylene resin (A) contained in the polypropylene resin composition of the present invention is 65 to 50% by weight, preferably is 63 to 55% by weight, and more preferably is 63 to 57% by weight, wherein the overall amount of the polypropylene resin composition is let be 100% by weight. If the content of the polypropylene resin (A) is less than 50% by weight, the rigidity may deteriorate. If the content is more than 65% by weight, the impact strength may deteriorate. [0056] If the content of the copolTner rubber (3) is less than 1?- by weight, weld lines and flow marks may be visible and the impact strength may deteriorate. If the content is more than 10 by weight, the fluidity may deteriorate and the impact strength may deteriorate. [0057] The content of the ethylene/a-olefin copolymer rubber (C) in the polypropylene resin composition of the present invention is 8 to 18% by weight, preferably 10 to 16% by weight. If the content of the copolymer rubber (C) is less than B% by weight, the impact strength may deteriorate. If the content is more than 18% by weight, the rigidity may deteriorate. [0058] The content of the inorganic filler (D) in the polypropylene resin composition of the present invention is 13 to 25% by weight, preferably 19 to 23% by weight. If the content of the inorganic filler (D) is less than 18% by weight, the rigidity may deteriorate. If the content is 25% by weight, the impact strength may deteriorate. If the combined content of the copolymer rubber (B) and the copolymer rubber (C) is less than 17% ]DY weight, the impact resistance may be insufficient. If the combined content is more than 25% by weight, the rigidity may be insufficient. [0060] From the viewpoint of making weld lines less visible to realize good weld appearance of an molded article, making flow marks less visible to realize good flow mark appearance of a molded article, and realizing good balance between rigidity and impact resistance, the ratio of the content of the copolymer rubber (B) (BK, % by weight) to that of the copolymer rubber (c) (Cw, % by weight), Bw/Cw/ is preferably in a range from 15/85 to 85/15 (% by weight/% by weight), more preferably from 20/80 to 45/55 (% by weight/% by weight). [0061] From the viewpoint of making weld lines less visible to realize good weld appearance of an molded article and making flow marks less visible to realize good flow mark appearance of a molded article, the The polypropylene resin composition of the present invention may be produced by a method comprising melt-kneading of ingredients. Examples of the method include a method using a kneader such as a single screw extruder, a twin screw extruder, a Bunbury mixer and a hot roll. The kneading temperature is ordinarily 170 to 250°C, and the kneading time is ordinarily 1 to 20 minutes. The ingredients may be kneaded either at one time or at separate times. [0063] Examples of the method of kneading the ingredient at separate times include the following methods (1), (2) and {3): (1) A method in which a block copolymer (A-1) is kneaded beforehand to form pellets, and then the pellets, a copolymer rubber (B), a copolymer rubber (C) and an inorganic filler (D) are kneaded together. (2} A method in which a block copolymer (A-l) is kneaded beforehand to form pellets, and then the pellets, a homopolymer {A-2), a copolymer rubber (B), a copolymer rubber (C) and an inorganic filler (D) are kneaded together. (3) A method in which a block copolymer (A-l), a and an inorganic filler (D) are kneaded together, and then a copolymer rubber (B) and a copolymer rubber (C) are added, followed by further kneading. In the methods (3) and (4), a crystalline homopolymer [A-2) may be added optionally. [0064] The polypropylene resin composition of the present invention may, as required, be incorporated with various additives. Examples of such additives include antioxidant, UV" absorber, lubricant, pigment, antistatic agent, copper inhibitor, flame retardant, neutralizer, foaming agent, plasticizer, nucleating agent, antifoaming agent and crosslinking agent. for improving heat resistance, weather resistance and stability against oxidation, it is preferable to add an antioxidant or a UV absorber. [00 65] For further improving balance between mechanical properties, the polypropylene resin composition of the present invention may be further incorpoiated with a rubber containing a vinyl aromatic compound. Examples of the rubber containiig a vinyl aromatic compound include a block copolymr;r composed of more, more preferably 351 or more, wherein the total amount of the double bonds in the conjugated diene portions is let be 100% by weight. [0066] The rubber containing a vinyl aromatic compound preferably has a molecular weight distribution (Q value), as determined by GPC (gel permeation chromatography), of 2.5 or less, more preferably of 1 to 2.3. [0067] The content of the vinyl aromatic compound in the rubber is 10 to 20% by weight, more preferably 12 to 19% by weight, wherein the whole amount of the rubber containing a vinyl aromatic compound is let be 100% by weight. I [0068] The rubber containing a vinyl aromatic compound preferably has a melt flow rate (MFR, determined in accordance with JIS-K-6753 at 230°C) of 0.01 to 15 g/10 minutes, more preferably 0.03 to 13 g/10 minutes. [0069] Examples of the rubber containing a vinyl aromatic compound include block copolymers, e.g.. copolymers obtained by hydrogenation of such block copolymers. Other examples include rubbers obtained by causing a vinyl aromatic compound such as styrene to react with an ethylene/propylene/nonconjugated diene rubber (EPDM). Two or more rubbers containing a vinyl aromatic compound niay be used in combination. [0070] The rubber containing a vinyl aromatic compound may be produced by a method in which a vinyl aromatic compound is bonded to an olefin copolymer rubber or a conjugated diene rubber by polymerization or a reaction. [0071] The polypropylene resin composition of the present invention can be used in the fields in which high quality is required, e.g., automotive interior or exterior components. The automotive injection-molded article of the present invention is an automotive injection-molded article made of the polypropylene resin composition of the present invention, and preferably is a relatively large automotive injection-molded article as large as 2000 m or more in projected area. Applications of such composition of the present invention is molded to form an automotive injection-molded article by using an injection molding machine and a mold having a plurality of gates. Examples [0072] The present invention is described with reference to Examples and Comparative Examples. The procedures for analyzing the properties of the polymers and the compositions used in these examples are described below. (1) Intrinsic viscosity (unit: dL/g} The reduced viscosity was measured using an Ubbelohde viscometer at three concentrations of 0.1, 0,2 and 0.5 g/dL. The intrinsic viscosity was determined by the calculation procedure described in "Polymer Solutions and Polymer Experiments 11", P. 491 (published by Kyoritsu Shuppan in Japan in 1982), namely a method wherein the reduced viscosity is plotted against the concentration and the viscosity is extrapolated to the zero concentration. Tetralin was used as a solvent and the viscosity was measured at crystalline propylene homopolymer segment in a crystalline propylene/ethylene block copolymer was determined by the procedure (1) described above after taking a polymer powder out of a polymerization tank after completion of the first step, namely the polymerization to the crystalline propylene homopolymer segment, in the- production of the crystalline propylene/ethylene block copolymer. [0074] (1-lb) Intrinsic viscosity of propylene/ethylene random copolymer segment : [TIJE? The intrinsic viscosity [T\|]EP of the propylene/ethylene random copolymer segment in a crystalline propylene/ethylene block copolymer was calculated from the following formula by using the weight ratio X of the propylene-ethylene random copolymer segment to the whole portion of the propylene-ethylene block copolymer after measuring the intrinsic viscosity [Ti]p of the propylene homopolymer segment and the intrinsic viscosity [IIIT of the whoje portion of the propylene/ethylene block copolymer by wherein the weight ratio X relative to the whole portion of the propylene-ethylene block copolymer was ) determined by the procedure (2) described below. [0075] The intrinsic viscosity of a component soluble in xylene at 20°C collected by the procedure described below was measured and used as the intrinsic j viscosity inlEP of the propylene/ethylene random copolymer segment in a crystalline propylene/ethylene block copolymer thermally decomposed in the presence of a peroxide. [Component soluble in xylene at 20°c] ) Five grams of the crystalline propylene/ethylene block copolymer was dissolved conpletely in 500 mL of boiling xylene, and then cooled to a temperature of 20°C, at which the solution was left at rest for 4 hours. It was then filtered to separate ) the portion insoluble in xylene at 20°C. The filtrate was concentrated and solidified to evaporate xylene, and then dried at 60°C under reduced pressure, thereby obtaining a polymer component soluble in xylene at 20°C. The weight ratio and the ethylene content were determined from a ""*C-NMR spectrum obtained under the following conditions, on the basis of the report made by Kakugo et al. (Macromolecules, 1982, 15, 1150-1152). A sample was prepared by homogeneously dissolving about 200 mg of a propylene/ethylene block copoly.mer in 3 mL of ortho-dichlorobenzene in a test tube which was 10 mm in diameter. The C-NMR spectrum of the sample was measured under the following conditions. Analysis temperature: 135°C Pulse interval; 10 seconds Pulse width: 45° Number of integrations: 2500 [0077] (3) Melt flow rate (MFR, unit: g/10 minutes) MFR was determined in accordance with JTS-K-6758 at a temperature of 230'C and a load of 2.16 kg. [0078] (4) Flexural modulus (FM, unit: MPa) (5) l2od impact strength (Izod, unit: kj/m") Izod impact strength was determined in I accordance with jlS-K-7110, wherein the measurement was conducted at a measurement temperature of 23°C or -30'C using a 6.4 mm thick injection-molded, notched specimen which was notched after molding. [0080] (6) Isotactic pentad fraction {[mmmm]) The fraction of the propylene monomer unit existing at the center of the isotactic chain in the form of a pentad unit{i.e., the chain in which five propylene monomer units are continuously meso-linked) in a polypropylene molecular chain measured by the method described by A. Zambelli et al. in Macromolecules, 6, 925 (1973) was determined as an isotactic pentad fraction. NMR absorption peaks were assigned on the basis of Macromolecules, 8, 687 (1975), later published. [0081] More specifically, the isotactic pentad fraction was determined as an areal fraction of the [Production-1 of injection-molded article] Specimens for the property evaluations (4) to (6) described above were prepared by injection molding using an injection molding machine (IS150E-V, manufactured by Toshiba Machine Co., Ltd.) at a molding temperature of 220°C, a mold cooling temperature of 50°C, an injection time of 15 seconds and a cooling time of 30 seconds. [0083] (7) Preparation of injection-molded article for evaluating development of weld lines and flow marks (7-1) Small flat plate A small injection-molded article, which served as a specimen for evaluating the development of weld lines and flow marks, was prepared by the following procedure. A flat molded article illustrated in Fig. 1 was prepared by executing molding with an injection molding machine SE180D having a clamping force of 180 tons, manufactured by Sumitomo Heavy Industries, Ltd. and a mold of 100 mm x 400 mm x 3.0 mm in size having (7-1-a) Development of weld lines Using a flat molded article prepared by the procedure (7-1), weld lines were visually observed. The length 3' and the visibility of the weld line illustrated in Fig. 1 were evaluated. In this evaluation, the shorter or the less visible the weld line is, the better in appearance the article is. [0085] (7-1-b) Development of flow marks Using a flat molded article prepared by the procedure (1-1), flow marks were visually observed. The distance 4' from the gated edge to the position where the flow marks shown in Fig. 1 started to develop/ namely the distance to the position A where the flow marks started to develop (the distance, measured at a side edge and expressed in mm, to the position where the flow marks started to develop) and the visibility of the flow marks were evaluated. In this evaluation, the longer the distance to the position where the flow marks started to develop is or the less visible the flow marks are, the better in appearance the article is. (7-2-a) Development of weld lines Using a flat molded article prepared by the procedure (7-2), a weld line was visually observed. The visibility of the weld line was observed in the same manner as that in (7-1-a) described above. In this evaluation, the less visible the weld line is, the better in appearance the article is. [0088] (7-2-b) Development of flow marks Using a flat molded article prepared by the procedure (7-2), flow marks were visually observed. In the same manner as that in the (7-1-b) described above, the distance 4' from the gated edge to the position where the flow marks started to develop, namely the distance to the position A where the flow marks started to develop (the distance, measured at a side edge and expressed in mm, to the position where the flow marks started to develop) and the visibility of the flow marks were evaluated. In this evaluation, the longer the distance to the position where the flow marks 280 mm X 3.0 mm-thick in size having a single gate were compared and evaluated with respect to their flow lengths (mm). [0090] The method for synthesizing the solid catalyst component {1} used in the preparations of the polymers used in Examples and Comparative Examples is described below. {!) Solid catalyst component (I) A 200-L cylindrical reactor (equipped with a stirrer having three paired blades of 0.35 m in diameter and four btffles of 0.05 m in width) was purged with nitrogen. It was charged with 54 L of hexane, 100 g of diisobutyl phthalate, 20.6 kg of tetraethoxysilane and 2.23 kg of titanium tetrabutoxide, and then was stirred. Then, to the resulting mixture under stirring, 51 L of a solution of butylmagnesium chloride in dibutyl ether (2.1 mol/L in concentration) was dropped over four hours while the reactor temperature was kept at 7°C. The stirring speed was set at 150 rpm. After the completion of the dropping, the mixture was stirred for one hour at 20°C diameter of 39 \im and contained a fine powdery component of 16 nm or less at an amount of 0.5% by weight. Then, toluene was removed so that the volxjine of the slurry would become 49.7 L, and the resulting slurry was stirred for one hour at 80°C and then was cooled to 40°C or lower. Under stirring, a mixed liquid composed of 30 L of titanium tetrachloride and 1.16 kg of dibutyl ether was charged, and further 4.23 kg of orthophthaloyl chloride was charged. The mixture was stirred for three hours while the reactor temperature was kept at 110°C, and then filtered. The resulting solid was washed with 90 L of toluene three times at 95°C, and then incorporated with toluene, giving a slurry. After being left at rest, toluene was removed so that the slurry would come to have a volume of 49,7 L, and then a mixed liquid composed of 15 L of titanium tetrachloride, 1.16 kg of dibutyl ether and 0.87 kg of diisobutyl phthalate was charged with stirring. The mixture was stirred for one hour while the reactor temperature was kept at 105°C, and then filtered. The resulting solid was washed with 90 L of toluene twice then filtered. The mixture was stirred for one hour while the reactor temperature was kept at 105°C, and then filtered. The resulting solid was washed with 90 L of toluene twice at 95°C, and then incorporated with toluene/ giving a slurry. After being left at rest/ toluene was removed so that the slurry would come to have a volume of 49.7 L. A mixed liquid composed of 15 L of titanium tetrachloride and 1.16 kg of dibutyl ether was charged with stirring. At 95°C, the resulting solid vjas washed with 90 L of toluene three times and with 90 L of hexane twice. The resulting solid component was dried to give a solid catalyst component. The solid catalyst component contained Ti at 2.1% by weight and a phthalic acid ester component at 10.8% by weight. This solid catalyst component is hereinafter referred to as solid catalyst component (I). [0091] [Preparation of polymers! (1) Preparation of propylene homopolymers (HP) (1-1) Preparation of HPP-1 A propylene homopolymer was prepared by (1-2) Preparation of HPP-2 A propylene homopolymer was prepared by conventional solvent polymerization in the presence of a catalyst disclosed in JP-A-10-212319, where the hydrogen concentration and the polymerization temperature in the system were controlled. The resulting polymer had an intrinsic viscosity [r\]p of 0.92 dL/g, an isotactic pentad fraction of 0.991, a molecular weight distribution, Q value (Mw/Mn), of 5.4, and an MFR of 111 g/10 minutes. [0093] (1-3) Preparation of HPP-3 A propylene homopolymer was prepared by conventional solvent polymerization in the presence of a catalyst disclosed in JP-A-10-212319, where the hydrogen concentration and the polymerization temperature in the system were controlled. The resulting polymer had an intrinsic viscosity ["HIF of 0.76 dL/g, an isotactic pentad fraction of 0.991, a (I), a propylene homopolymer segment was prepared in the first stage, and a propylene/ethylene random copolymer segment vjas prepared in the second stage. In the first stage the hydrogen concentration and the polymerization temperature were controlled. In the second stage, vapor-phase polymerization for foritiinq" the propylene-ethylene random copolymer segment was continued while propylene was continuously supplied so that the reaction temperature and the reaction pressure could be kept at constant levels and hydrogen and ethylene were supplied so that the hydrogen and ethylene concentrations in the vapor phase could be kept at constant levels. The propylene homopolymer prepared in the first stage ias sampled and analyzed to have an intrinsic viscosity [Ti]p of 0.93 dL/g and a stereoregularity (mmmm fraction) of 0.987, The finally-obtained propylene/ethylene block copolymer totally had an intrinsic viscosity [riJioTAL of 1.54 dL/g. An analysis revealed that the content of the propylene/ethylene randi_m copolymer {EP content) was (2-2) Preparation of BCCP-2 By a continuouSf two-stage solvent polymerization process using a catalyst disclosed in JP-K-7-216017, a propylene homopolymer segment was prepared in the first stage, and a propylene/ethylene random copolymer segment was prepared in the second stage. A propylene/ethylene block copolymer having a structure shown below was obtained by controlling the hydrogen concentration, the polymerization temperature and the ethylene/propylene concentrations in the system. The propylene horaopolymer prepared in the first stage was sampled and analyzed to have an intrinsic viscosity [T)]? of 0,93 dL/g and a stereoregularity (mmmm fraction) of 0.97-. The finally-obtained propylene/ethylene block copolymer totally had an intrinsic viscosity [TIITOTPT, of 1.39 dL/g. An analysis revealed that the content of the propylene/ethylene random copolymer (EP content) was 10% by weight. Therefore, the intrinsic viscosity [TIJEP of the propylene/ethylene random copolymer segment {EP polymer are given in Table 1. [0096] (2-3) Preparation of BCCP-3 The method for preparing BCPP-1 was repeated except for controlling and adjusting the hydrogen concentration, the polymerization temperature and the ethylene/propylene concentrations so that the polymer described in Table 1 could be obtained. The analytical results of the resulting polymer are given in Table 1. [0097] (2-4) Preparation of BCCP-4 The method for producing BCPP-2 was repeated except for using a catalyst disclosed in JP-A-10-212319 and controlling and adjusting the hydrogen concentration, the polymerization temperature and the ethylene/propylene concentrations so that the polymer described in Table 1 could be obtained. The analytical results of the resulting polymer are given in Table 1. [0098] Example 1 To 100 parts by weight of a propylene/ethylene block copolymer powder (BCCP-1) were added 0.0 5 parts by weight of calcium stearate (produced by NOF Corp.], 0.05 parts by weight of 3,9- of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite (ULTRANOX U626, GE Specialty Chemicals Inc.) as stabilizers, followed by forming pellets using an extruder. [0099] Forty percent by weight of the BCPP-1 pellets, 12% by weight of a propylene homopolymer (HPP-2) powder, 8% by weight of a propylene homopolymer (HPP-3) powder, 1% by weight of an ethylene/butene-1 random copolymer rubber EBR-1 (density: 0.861 g/cm, MFR (determined at 230°C and a load of 2.16 kg): 0.46 g/10 minutes) as the ethylene/a-olefin copolymer rubber (B), 12% by weight of an ethylene-octene-1 random copolymer rubber EOR-1 (density: 0.857 g/cm MFR (determined at 230'C and a load of 2.16 kg); 2.7 g/10 minutes) as the ethylene/a-olefin copolymer rubber (C) and 21% by weight of talc (average diameter: 2.7 \m.) as the inorganic filler (C) were compounded at these relative amounts, and then preliminarily mixed uniformly by a tumbler. Subsequently, the resulting mixture was kneaded and extruded by a twin screv. kneading/extruding machine (TEX44SS-30BW-2V, manufactured by the Japan Steel Works, Ltd.] under conditions including an extrusion rate of 50 kg/hour, 2300, and a screw properties and the result of weld appearance evaluation of an injection-molded article. [0100] EKample-2 Thirty two percent by weight of the BCPP-1 pellets, 11% by weight of BCPP-2 pellets resulting from pellitization in the same manner as that in the preparation of the BCPP-1 pellets, 3% by weight of a propylene homopolymer (HPP-2) powder, 14% by weight of a propylene homopolymer (HPP-3) powder, 6% by weight of an ethylene/butene-1 random copolymer rubber EBR-1 (density: 0.861 g/cm\ MFR (determined at 230°C and a load of 2.16 kg): 0.46 g/10 minutes) as the ethylene/a-olefin copolymer rubber (B), 13% by weight of an ethylene-octene-1 random copolymer rubber EOR-1 (density: 0.857 g/cm, MFR (determined at 230°C and a load of 2.16 kg): 2.7 g/10 minutes) as the ethylene/a-olefin copolymer rubber (C) and 21% by weight of talc (average diameter: 2.7 \im) as the inorganic filler (C) were compoianded at these relative amounts, and subjected to the same treatment as that in Example 1. Subsequently, the MFR and the properties of an injection-molded article were measured and the weld in the preparation of the BCPP-1 pellets, Hi by weight of BCPP-2 pellets, 18% by weight of a propylene homopolymer (HPP-1) powder, 15% by weight of an ethylene/butene-1 random copolymer rubber EBR-1 (density: 0.861 g/cm\ MFR (determined at 230°C and a load of 2.16 kg): 0.46 g/10 minutes) as the ethylene/a-olefin copolymer rubber (B), 5% by weight of an ethylene-octene-1 random copolymer rubber EOR-1 (density: 0.857 g/cm MFR (determined at 230°C and a load ol 2.16 kg): 2.7 g/10 minutes) as the ethylene/a-olefin copolymer rubber (C) and 21% by weight of talc (average diameter: 2.7 urn) as the inorganic filler (C) were compounded at these relative amounts, and subjected to the same treatment as that in Example 1. Subsequently, the MFR and the properties of an injection-molded article were measured and the weld appearance of an injection-molded article was evaluated. In Table 2, the evaluation results are shown. [0102] Comparative Example-2 olefin copolymei: r'-bber (B) , li% by weight of an sthylene/octene-1 random copolymer rubber EOR-2 (density: 0.870 g/cm MFR (determined at 230°C and a load of 2.16 kg); 11 g/10 minutes) as the ethylene/a-Dlefin copolymer rubber (C) and 16% by weight of talc (average diameter: 2.7 im) as the inorganic filler (C) -jere compounded at these relative amounts, and subjected to the same treatment as that in Example 1. Subsequently, the MFR and the properties of an injection-molded article were measured and the weld appearance of an injection-molded article was evaluated. In Table 2, the evaluation results are shown. It is also found that the polypropylene resin composition prepared in Comparative Example-1 is insufficient in flow mark appearance and fluidity because the intrinsic viscosity {[TIIP) of the 15 propylene/ethylene random copolymer segment in the block: copolymer (A-1) fails to satisfy the requirement of the present invention with respect to it and the content of the ethylene/a-olefin copolymer rubber (B) fails to satisfy the requirement of the present 20 invention with respect to it. [0107] It is also found that the polypropylene resin composition prepared in Comparative Example-2 is insufficient in weld appearance because the intrinsic 25 viscosity ([TIIE?) of the propylene/ethylene random copolymer segment in the block copolymer (A-1) fails to satisfy the requirement of the present invention with respect tc it and no ethylene/a-olefin copolymer rubber [0108] Brief Description of the Drawing Fig. 1 is a plan view of a flat molded article (small flat plate) for evaluating the 10 appearance. [0109] Description of Symbols 1: Gate 1 2: Gate 2 15 3: Weld line 4: Flow mark A 5: Flow mark B 3': Weld line length 4': Position A at which a flow mark develops CLAIMS (Amended claims filed on November 28, 2007 under PCT Article 34) 1. A polypropylene resin composition comprising: 50 to 65% by weight of a polypropylene resin (A); 1 to 10% by weight of an ethylene/a-olefin copolymer rubber (B); 8 to 10% by weight of an ethylene/a-olefin copolymer rubber (C); and 18 to 25% by weight of an inorganic filler (D), wherein the combined content of the ethylene/a-olefin copolymer rubber (B) and the ethylene/a-olefin copolymer rubber {C) is 17 to 25% by weight, where the overall amount of the polypropylene resin composition is let be 100% by weight, wherein the polypropylene resin (A) is a propylene/ethylene block copolymer (A-l) having a crystalline propylene homopolymer segment and a propylene/ethylene random copolymer segment having an intrinsic viscosity of 4.0 to 5.5 dL/g, or is a propylene polymer mixture (A-3) containing the block copolymer {A-l) and a crystalline propylene homopolyraer (A-2) , the ethylene/a-olefin copolymer rubber (B) contains an a-olefin of 4 to 12 carbon atoms and ethylene, and has a density of 0.850 to 0.870 g/cm3 and a melt flow rate of 0.05 to 1 g/lO minutes {determined at 230°C and under a load of 2.16 kg), and the ethylene/a-olefin copolymer rubber (C) contains an a-olefin of 4 to 12 carbon atoms and ethylene, and has a density of 0.350 to 0.870 g/cm2 and a melt flow rate of 2.3 to 15 g/10 minutes (determined at 230°C and under a load of 2.16 kg). 2. The polypropylene resin composition according to Claim 1, wherein the propylene/ethylene random copolymer segment in the propylene/ethylene block copolymer (A-1) has a propylene/ethylene weight ratio of 65/35 to 52/48, the ratio being defined as the ratio of the weight of propylene-derived structural units (propylene content) to the weight of ethylene-derived structural units (ethylene content). 3. The polypropylene resin composition according to Claim 1 or 2, wherein the crystalline propylene homopolymer segment in the propylene/ethylene block copolymer (A-1) or the component composed of the crystalline propylene homopolymer in the propylene polymer mixture (A-3) has an isotactic pentad fraction, as determined by 13c-NMR, of 0.98 or more. 4. The polypropylene resin composition according to any one of Claims 1 to 3, wherein the inorganic filler {D} is talc. 5. An automotive injection molded article made of the polypropylene resin composition according to any one of Claims 1 to 4. 6. A method for producing the automotive injection molded article according to Claim 5, comprising molding the polypropylene resin composition according to any one of Claims 1 to 4 to form an automotive injection molded article by the use of an injection molding machine and a mold having a plurality of gates.

Full Text

DESCRIPTION
POLYPROPYLENE RESIN COMPOSITION AND INJECTION
MOLDED ITEM FOR AUTOMOBILE THEREFROM
TECHNICAL FIELD [0001]
The present invention relates to a polypropylene resin composition and to an injection 5 molded article thereof for automobiles. It relates more specifically to a polypropylene resin composition that excels not only in fluidity but also in balance between rigidity and impact resistance and that can provide an automotive article excellent in weld 10 appearance and flow mark appearance when being processed to form an automotive injection-molded article, to an automotive injection molded article formed thereof, and to a method for producing the automotive injection-molded article.
15 BACKGROUND ART [0002]
Polypropylene resin compositions have been used widely for molded articles, e.g., automotive interior or exterior components and electric component 20 housings, because they are materials excellent in rigidity, impact resistance, and so on. [0003]

For example, JP-A-3-20566 discloses automotive soft resin bumpers raade of propylene polymer compositions which contain a propylene polymer, an ethylene/a-olefin copolymer, talc and a specified propylene polymer containing a polar group or a combination of a specified conjugated diene copolymer having a hydroxy1 group at a molecular terminal and a specified propylene polymer graft-modified with an ethylenically unsaturated compound containing a carboxyl or acid anhydride group, the bumpers having a specified flexural modulus and a specified linear expansion coefficient, for the purpose of improving the appearance (weld and flow mark) and the dimensional stability (low linear expansion) of automotive soft resin bumpers, their balance between impact resistance at low temperature and flexibility, and their paintability. [0004]
JP-A-9-71711 discloses a propylene resin composition comprising a propylene/ethylene block copolymer, an ethylene/a-olefin copolymer and talc, wherein the propylene/ethylene block copolymer contains a crystalline propylene homopolymer segment and an ethylene/propylene random copolymer segment containing ethylene at 20 to 80% by weight, and has a melt flow rate (MFR) of 25 to 140 g/10 minutes, and wherein the ethylene/a-olefin copolymer has an MFR of 0.5 to 15 g/10 minutes and an ethylene triad sequence fraction of

Automotive exterior components, which have been required to have more improved quality, need still improvement even when the polypropylene resin compositions described above are used. A polypropylene resin composition is required to have still improved properties with respect to fluidity and balance between rigidity and impact resistance, and an injection-molded article thereof is required to be improved in weld appearance and flow mark appearance. In particular, an automotive bumper as a large-size injection-molded article is required to have good appearance and good balance between rigidity and impact resistance. [0007]
Under such situations, it is an object of the present invention to provide a polypropylene resin composition excellent in fluidity and in balance between rigidity and impact resistance, and capable of giving an automotive injection-molded article excellent in weld appearance and flow mark appearance when being molded into an automotive injection-molded article, and

present invention can solve the above problems, accomplishing the present invention.
The present invention relates to a polypropylene resin composition containing 50 to 65% by weight of a polypropylene resin (A); 1 to 10% by weight of an ethylene/a-olefin copolymer rubber (B); 8 to 10% by weight of an ethylene/a-olefin copolymer rubber (C); and 18 to 25% by weight of an inorganic filler (D), wherein the combined content of the ethylene/a-olefin copolymer rubber (B) and the ethylene/a-olefin copolymer rubber (C) is 17 to 25% by weight, where the overall amount of the polypropylene resin composition is let be 100% by weight,
wherein the polypropylene resin [A) is a propylene/ethylene block copolymer (A-1) having a crystalline propylene homopolymer segment and a propylene/ethylene random copolymer segment having an intrinsic viscosity of 4.0 to 5.5 dL/g, or is a propylene polymer mixture (A-3) containing the block copolymer (A-1) and a crystalline propylene homopolymer (A-2),

contains an a-olefin of 4 to 12 carbon atoms and ethylene, and has a density of 0.850 to 0.870 g/cm and a melt flow rate of 2 to 20 g/10 minutes (determined at 230°C and under a load of 2.16 kg), and also relates to an automotive injection-molded article of the polypropylene resin composition and to a method for producing the automotive injection-molded article.
ADVANTAGES OF THE INVENTION [0009]
In accordance with the present invention, a polypropylene resin composition can be obtained which is excellent in fluidity and in balance between rigidity and impact resistance and which can give an automotive injectionmolded article excellent in weld appearance and flow mark appearance when being molded into an injection-molded article, and an automotive injection-molded article made thereof can also be obtained.
THE BEST MODE FOR CARRYING OUT THE INVENTION
[0010]

crystalline propylene homopolyraer segment and a propylene/ethylene random copolymer segment. [0012]
From the viewpoint of improving the balance between rigidity and impact resistance, the propylene/ethylene block copolymer (A-1) preferably contains 55 to 90% by weight of the crystalline propylene homopolymer segment and 10 to 45% by weight of the propylene/ethylene random copolymer segment, where the whole amount of the block copolymer is let be 100% by weight-[0013]
The propylene/ethylene block copolymer {A-1) more preferably is a block copolymer containing 65 to 88% by weight of the crystalline propylene homopolymer segment and 12 to 35% by weight of the
propylene/ethylene random copolymer segment, and still more preferably is a block copolymer containing 70 to 85% by weight of the crystalline propylene homopolymer segment and 15 to 30% by weight of the

I The isotactic pentad fraction is the fraction
of the propylene monomer unit existing at the center of the isotactic chain in the form of a pentad unit (i.e., the chain in which five propylene monomer units are continuously meso-linked) , determined by C-NMR, the procedure of which is described by A. Zambelli et al. (Macromolecules, 6, 925, 1973). NMR absorption peaks are assigned by the procedure described in Macromolecules, 8, 687, 1975, later published. [0016]
More specifically, the isotactic pentad fraction is determined as an areal fraction of mmmm peaks to all the absorption peaks in the methyl carbon region in the -C-NMR spectral pattern. The isotactic pentad fraction of an NPL reference material (CRN No. M19-14 Polypropylene PP/MWD/2, supplied by UK's NATIONAL PHYSICAL LABORATORY) was determined by the above procedure to be 0.94 4. [0017]

Moreover, the molecular weight distribution (Q value, Mw/Mn), as determined by gel permeation chromatography (GPC), of the crystalline propylene homopolymer segment in the block copolymer (A-1) preferably is 3 or more but less than 7, and more preferably is 3 to 5. [0019]
From the viewpoint of realizing good balance between rigidity and Impact resistance, the propylene/ethylene random copolymer segment in the propylene/ethylene block copolymer (A-1) preferably has a propylene/ethylene weight ratio of 65/35 to 52/46, and more preferably 62/38 to 55/45, wherein the ratio is defined as the ratio of the weight of propylene-derived structural units (propylene content) to the weight of ethylene-derived structural units (ethylene content). [0020]
From the viewpoint of making weld lines less noticeable to realize good weld appearance of an molded

From the viewpoint of improving moldability and impact resistance, the block copolymer (A-11 preferably has a melt flow rate (MFR) of 10 to 120 g/10 minutes, more preferably 20 to 53 g/10 minutes. [0022]
The propylene/ethylene block copolymer (A-1) may be produced by a known polymerization method using a catalyst system prepared by bringing (a) a solid catalyst component containing magnesium, titanium, a halogen and electron donor as essential components, (b) an organoaluminum compound and (c) an electron donor component into contact with each other. Examples of this type of catalyst system and a production method thereof include those disclosed in JP-A-1-315908, JP-A-7-216017 and JP-A-10-212319. [0023]
The propylene/ethylene block copolymer (A-1) may be produced by a method which comprises at least two polymerization stages, wherein the crystalline propylene homopolymer segment is produced in the first

Examples of polymerization methods include a bulk polymerization process, a solution polymerization process, a slurry polymerization process and a vapor-phase polymerization process. These processes may be carried out either batch-wide or continuously. These polymerization processes may optionally be combined with each other. From the viewpoint of being industrially and economically advantageous, a continuous vapor-phase polymerization process and a continuous bulk-vapor-phase polymerization process are preferred. [0025]
More specific examples of a production method include:
(1) a method in which, in the presence of the aforesaid catalyst system prepared by bringing (a) a solid catalyst component, (b) an organoaluminum compound and (c) an electron donor component into contact with each other, at least two polymerization tanks are placed in series, a crystalline propylene homopolymer segment is produced in the first tank/ the product is transferred to the second tank, and a propylene/ethylene random copolymer segment having an ethylene content of 35 to 48% by weight and an

compound and (c) an electron donor component into contact with each other, at least four polymerization tanks are placed in series, a crystalline propylene homopolymer segment is produced in the first and second tanks, the product is transferred to the third tank, and a propylene/ethylene random copolymer segment having an ethylene content of 35 to 48% by weight and intrinsic viscosity of 4.0 to 5.5 dL/g is produced in the third and fourth tanks. [0026]
A known method of handling catalysts may be adopted appropriately for determining the amounts of the (a) solid catalyst component, the (b) organoaluminum compound and the (c) electron donor component and how to supply the catalyst components into the polymerization tanks in the aforementioned polymerization methods. [0027]
The polymerization temperature is ordinarily in a range from -30 to 300°C, preferably from 20 to 180°C. The polymerization pressure is ordinarily in a range from the atmospheric pressure to 10 MPa, preferably from 0.2 to 5 MPa. Hydrogen, for example,

the known, preliminary polymerization method is a method in which a small amount of propylene is supplied and which is conducted in a slurry state using a solvent in the in the presence of a solid catalyst component (a) and an organoaluminum compound (b). [0029]
The block copolymer (A-1) may, as required, be incorporated with various additives. Examples of such additives include antioxidant, UV absorber, lubricant, pigment/ antistatic agent, copper inhibitor, flame retardant, neutralizer, foaming agent, plasticizer, nucleating agent, antifoaming agent and crosslinking agent- Among such additives, an antioxidant or a 0V absorber is preferably added for improving heat resistance, weather resistance and stability against oxidation. [0030]
Examples of the method for producing the block copolymer (A-1) include, in addition to the above-described methods in which the block copolymer is produced by using the above-described catalyst and the above-described polymerization methods, a method in

polymer produced by the melt-kneading in the presence of a peroxide of a polymer obtained by the production method using the above-describe catalyst can be determined by measuring the intrinsic viscosity of a component of the polymer resulting from the melt-kneading which is soluble in xylene at 20°C. [0031]
An organic peroxide is ordinarily used as the aforesaid peroxide, and examples of such an organic peroxide include alkyl peroxides, diacyl peroxides, peroxyesters and peroxycarbonates.
The alkyl peroxides include dicumyl peroxide, di-tert-butyl peroxide, di-tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, tert-butylcumyl, 1,3-bis(t-butylperoxyisopropyl)benzene and 3,6,9-triethyl-3,6, 9-trimethyl-l,4, 7-triperoxonane. [0032]
The diacyl peroxides include benzoyl peroxide, lauroyl peroxide and decanoyl peroxide.
The peroxyesters include 1,1,3,3-tetramethylbutyl peroxyneodecanoate, a-ciomyl peroxyneodecanoate, tert-butyl peroxyneodecanoate.

butyl peroxyhexahydroterephthalate, tert-amyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate and di-butyl peroxytrirrtethyladipate. [0033]
The peroxycarbonates include di-3-raethoxybutyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di-isopropyl peroxydicarbonate, tert-butyl peroxyisopropylcarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate and dimyristyl peroxydicarbonate. [0034]
When the polypropylene resin (A) to be used in the present invention is a propylene polymer mixture {A-3) containing a propylene/ethylene block copolymer (A-1) and a crystalline propylene homopolymer lA-2), the content of the block copolymer (A-l) in the propylene polymer mixture {A-3} is preferably 30 to 99% by vjeight and the content of the propylene homopolymer [A-2) is preferably 1 to 70% by weight. More preferably, the content of the block copolymer (A~l) is 45 to 90% by weight and the content of the propylene

The propylene homopolymer (A-2) ordinarily has a melt flow rate (MFR, determined at 230°C and under a load of 2160 g) of 10 to 500 g/10 minutes, preferably 40 to 350 g/10 minutes. [0037]
The propylene homopolymer (A-2) may be produced in a manner similar to that for producing the propylene/ethylene block copolymer (A-1). A method using the same catalyst system as that used for the production of the block copolymer (A-1) may be used. [0038]
The ethylene/a-olefin copolymer rubber (B) for use in the present invention is an ethylene/a-olefin copolymer rubber which contains an a-olefin of 4 to 12 carbon atoms and ethylene. Examples of the a olefin of 4 to 12 carbon atoms include butene-1, pentene-1, hexene-1, heptene-1, octene-1 and decene. Butene-1, hexene-1 and octene-1 are preferable. [0039]
From the viewpoint of increasing impact strength, especially impact strength at low temperature, the content of a-olefin in the copolymer

Examples of the copolymer rubber (B) include ethylene/butene-1 random copolymer rubber, ethylene/hexene-1 random copolymer rubber and ethylene/octene-1 random copolymer rubber. Preferred is ethylene/octene-1 random copolymer rubber or ethylene/butene-1 random copolymer rubber. Two or more ethylene/a-olefin copolymer rubbers may be used in combination. [0041]
From the viewpoint of obtaining good balance between rigidity and impact resistance, the copolymer rubber (B) has a density of 0.850 to 0.870 g/cm, preferably 0.850 to 0.865 g/cm. [0042]
From the viewpoint of making weld lines less noticeable to realize good weld appearance of an molded article, making flow marks less visible to realize good flow mark appearance of a molded article, and realizing good balance between rigidity and impact resistance/ the copolymer rubber {B) has a melt flow rate (determined at 230°C and under a load of 2.16 kg) of 0.05 to 1 g/10 minutes, preferably 0.2 to 1 g/10 minutes.

The known catalyst includes a catalyst system coniposed of a vanadium compound and an organoaluminum compound, a Ziegler-Natta catalyst system and a metallocene catalyst system, and the known polymerization process includes a solution polymerization process, a slurry polymerization process, a high-pressure ion polymerization process, or a vapor-phase polymerization process. [0044]
The ethylene/a-olefin copolymer rubber (C) for use in the present invention is an ethylene/a-olefin copolymer rubber which contains an a-olefin of 4 to 12 carbon atoms and ethylene. Examples of the oc-olefin of 4 to 12 carbon atoms include butene-1, pentene-l, hexene-1, heptene-1, octene-1 and decene. Butene-1, hexene-1 and octene-1 are preferable. [0045]
From the viewpoint of increasing impact strength, especially impact strength at low temperature, the content of a-olefin of 4 to 12 carbon atoms in the copolymer rubber [C) preferably is 20 to 50% by weight, more preferably 24 to 50% by weight, wherein the whole amount of the copolymer rubber (C) is

ethylene/butene-1 random copolymer rubber. Two or more ethylene/a-olefin copolymer rubbers may be used in combination. [0047]
From the viewpoint of obtaining good balance between rigidity and impact resistance, the copolymer rubber (C) has a density of 0.850 to 0.870 g/cm preferably 0.850 to 0.865 g/cm-. [0048]
From the viewpoint of obtaining good balance between rigidity and impcct resistance, the copolymer rubber (C) has a melt flow rate (determined at 230°C and under a load of 2.16 kg) of 2 to 20 g/10 minutes, preferably 2.3 to 15 g/10 minutes, more preferably 2.5 to 10 g/10 minutes. [0049]
The copolymer rubber (C) may be produced by the same method as that for producing the copolymer rubber (B). [0050]
The inorganic filler (D) for use in the

combination.
[0051]
Talc to be used as the inorganic filler (D) preferably is a product obtained by crushing hydrous magnesium silicate. The crystalline structure of a hydrous magnesium silicate molecule is a three-layered pyrophylite type structure, and talc is composed of a pile of this structure. Talc is more preferably in the
form of tabular particles obtained by finely pulverizing crystals of a hydrous magnesium silicate molecule to a size as small as a unit layer.
[0052]
Talc preferably has an average particle diameter of 3 [jm or less. The average particle diameter of talc is a 50% equivalent particle diameter DsD determined on the basis of an integrated distribution curve measured by a minus sieve method while suspending talc in a dispersion medium, namely water or alcohol, using a centrifugal sedimentation type particle size distribution analyzer.
[0053]

silane coupling agents, titanium coupling agents, higher fatty acids, higher fatty acid esters, higher fatty acid amides and higher fatty acid salts. [0054]
Fibrous magnesium sulfate to be used as the inorganic filler (D) preferably has an average fiber length of 5 to 50 jti, more preferably 10 to 30 urn, and preferably has an average fiber diameter of 0.3 to 2 |jm, more preferably 0.5 to 1 urn . [0055]
The content of the polypropylene resin (A) contained in the polypropylene resin composition of the present invention is 65 to 50% by weight, preferably is 63 to 55% by weight, and more preferably is 63 to 57% by weight, wherein the overall amount of the polypropylene resin composition is let be 100% by weight.
If the content of the polypropylene resin (A) is less than 50% by weight, the rigidity may deteriorate. If the content is more than 65% by weight, the impact strength may deteriorate. [0056]

If the content of the copolTner rubber (3) is less than 1?- by weight, weld lines and flow marks may be visible and the impact strength may deteriorate. If the content is more than 10 by weight, the fluidity may deteriorate and the impact strength may deteriorate. [0057]
The content of the ethylene/a-olefin copolymer rubber (C) in the polypropylene resin composition of the present invention is 8 to 18% by weight, preferably 10 to 16% by weight.
If the content of the copolymer rubber (C) is less than B% by weight, the impact strength may deteriorate. If the content is more than 18% by weight, the rigidity may deteriorate. [0058]
The content of the inorganic filler (D) in the polypropylene resin composition of the present invention is 13 to 25% by weight, preferably 19 to 23% by weight.
If the content of the inorganic filler (D) is less than 18% by weight, the rigidity may deteriorate. If the content is 25% by weight, the impact strength may deteriorate.

If the combined content of the copolymer rubber (B) and the copolymer rubber (C) is less than 17% ]DY weight, the impact resistance may be insufficient. If the combined content is more than 25% by weight, the rigidity may be insufficient. [0060]
From the viewpoint of making weld lines less visible to realize good weld appearance of an molded article, making flow marks less visible to realize good flow mark appearance of a molded article, and realizing good balance between rigidity and impact resistance, the ratio of the content of the copolymer rubber (B) (BK, % by weight) to that of the copolymer rubber (c) (Cw, % by weight), Bw/Cw/ is preferably in a range from 15/85 to 85/15 (% by weight/% by weight), more preferably from 20/80 to 45/55 (% by weight/% by weight). [0061]
From the viewpoint of making weld lines less visible to realize good weld appearance of an molded article and making flow marks less visible to realize good flow mark appearance of a molded article, the

The polypropylene resin composition of the present invention may be produced by a method comprising melt-kneading of ingredients. Examples of the method include a method using a kneader such as a single screw extruder, a twin screw extruder, a Bunbury mixer and a hot roll. The kneading temperature is ordinarily 170 to 250°C, and the kneading time is ordinarily 1 to 20 minutes. The ingredients may be kneaded either at one time or at separate times. [0063]
Examples of the method of kneading the ingredient at separate times include the following methods (1), (2) and {3):
(1) A method in which a block copolymer (A-1) is kneaded beforehand to form pellets, and then the pellets, a copolymer rubber (B), a copolymer rubber (C) and an inorganic filler (D) are kneaded together. (2} A method in which a block copolymer (A-l) is kneaded beforehand to form pellets, and then the pellets, a homopolymer {A-2), a copolymer rubber (B), a copolymer rubber (C) and an inorganic filler (D) are kneaded together. (3) A method in which a block copolymer (A-l), a

and an inorganic filler (D) are kneaded together, and then a copolymer rubber (B) and a copolymer rubber (C) are added, followed by further kneading.
In the methods (3) and (4), a crystalline homopolymer [A-2) may be added optionally. [0064]
The polypropylene resin composition of the present invention may, as required, be incorporated with various additives. Examples of such additives include antioxidant, UV" absorber, lubricant, pigment, antistatic agent, copper inhibitor, flame retardant, neutralizer, foaming agent, plasticizer, nucleating agent, antifoaming agent and crosslinking agent. for improving heat resistance, weather resistance and stability against oxidation, it is preferable to add an antioxidant or a UV absorber. [00 65]
For further improving balance between mechanical properties, the polypropylene resin composition of the present invention may be further incorpoiated with a rubber containing a vinyl aromatic compound.
Examples of the rubber containiig a vinyl aromatic compound include a block copolymr;r composed of

more, more preferably 351 or more, wherein the total amount of the double bonds in the conjugated diene portions is let be 100% by weight. [0066]
The rubber containing a vinyl aromatic compound preferably has a molecular weight distribution (Q value), as determined by GPC (gel permeation chromatography), of 2.5 or less, more preferably of 1 to 2.3. [0067]
The content of the vinyl aromatic compound in the rubber is 10 to 20% by weight, more preferably 12 to 19% by weight, wherein the whole amount of the rubber containing a vinyl aromatic compound is let be 100% by weight. I [0068]
The rubber containing a vinyl aromatic compound preferably has a melt flow rate (MFR, determined in accordance with JIS-K-6753 at 230°C) of 0.01 to 15 g/10 minutes, more preferably 0.03 to 13 g/10 minutes. [0069]
Examples of the rubber containing a vinyl aromatic compound include block copolymers, e.g..

copolymers obtained by hydrogenation of such block copolymers. Other examples include rubbers obtained by causing a vinyl aromatic compound such as styrene to react with an ethylene/propylene/nonconjugated diene rubber (EPDM). Two or more rubbers containing a vinyl aromatic compound niay be used in combination. [0070]
The rubber containing a vinyl aromatic compound may be produced by a method in which a vinyl aromatic compound is bonded to an olefin copolymer rubber or a conjugated diene rubber by polymerization or a reaction. [0071]
The polypropylene resin composition of the present invention can be used in the fields in which high quality is required, e.g., automotive interior or exterior components.
The automotive injection-molded article of the present invention is an automotive injection-molded article made of the polypropylene resin composition of the present invention, and preferably is a relatively large automotive injection-molded article as large as 2000 m or more in projected area. Applications of such

composition of the present invention is molded to form an automotive injection-molded article by using an injection molding machine and a mold having a plurality of gates.
Examples [0072]
The present invention is described with reference to Examples and Comparative Examples. The procedures for analyzing the properties of the polymers and the compositions used in these examples are described below. (1) Intrinsic viscosity (unit: dL/g}
The reduced viscosity was measured using an Ubbelohde viscometer at three concentrations of 0.1, 0,2 and 0.5 g/dL. The intrinsic viscosity was determined by the calculation procedure described in "Polymer Solutions and Polymer Experiments 11", P. 491 (published by Kyoritsu Shuppan in Japan in 1982), namely a method wherein the reduced viscosity is plotted against the concentration and the viscosity is extrapolated to the zero concentration. Tetralin was used as a solvent and the viscosity was measured at

crystalline propylene homopolymer segment in a crystalline propylene/ethylene block copolymer was determined by the procedure (1) described above after taking a polymer powder out of a polymerization tank after completion of the first step, namely the polymerization to the crystalline propylene homopolymer segment, in the- production of the crystalline propylene/ethylene block copolymer.
[0074]
(1-lb) Intrinsic viscosity of propylene/ethylene random copolymer segment : [TIJE?
The intrinsic viscosity [T|]EP of the propylene/ethylene random copolymer segment in a crystalline propylene/ethylene block copolymer was calculated from the following formula by using the weight ratio X of the propylene-ethylene random copolymer segment to the whole portion of the propylene-ethylene block copolymer after measuring the intrinsic viscosity [Ti]p of the propylene homopolymer segment and the intrinsic viscosity [IIIT of the whoje portion of the propylene/ethylene block copolymer by

wherein the weight ratio X relative to the whole portion of the propylene-ethylene block copolymer was
) determined by the procedure (2) described below. [0075]
The intrinsic viscosity of a component soluble in xylene at 20°C collected by the procedure described below was measured and used as the intrinsic
j viscosity inlEP of the propylene/ethylene random
copolymer segment in a crystalline propylene/ethylene block copolymer thermally decomposed in the presence of a peroxide. [Component soluble in xylene at 20°c]
) Five grams of the crystalline
propylene/ethylene block copolymer was dissolved conpletely in 500 mL of boiling xylene, and then cooled to a temperature of 20°C, at which the solution was left at rest for 4 hours. It was then filtered to separate
) the portion insoluble in xylene at 20°C. The filtrate was concentrated and solidified to evaporate xylene, and then dried at 60°C under reduced pressure, thereby obtaining a polymer component soluble in xylene at 20°C.

The weight ratio and the ethylene content were determined from a ""*C-NMR spectrum obtained under the following conditions, on the basis of the report made by Kakugo et al. (Macromolecules, 1982, 15, 1150-1152).
A sample was prepared by homogeneously dissolving about 200 mg of a propylene/ethylene block copoly.mer in 3 mL of ortho-dichlorobenzene in a test tube which was 10 mm in diameter. The C-NMR spectrum of the sample was measured under the following conditions.
Analysis temperature: 135°C
Pulse interval; 10 seconds
Pulse width: 45°
Number of integrations: 2500 [0077]
(3) Melt flow rate (MFR, unit: g/10 minutes)
MFR was determined in accordance with JTS-K-6758 at a temperature of 230'C and a load of 2.16 kg. [0078]
(4) Flexural modulus (FM, unit: MPa)

(5) l2od impact strength (Izod, unit: kj/m")
Izod impact strength was determined in I accordance with jlS-K-7110, wherein the measurement was conducted at a measurement temperature of 23°C or -30'C using a 6.4 mm thick injection-molded, notched specimen which was notched after molding. [0080]
(6) Isotactic pentad fraction {[mmmm])
The fraction of the propylene monomer unit existing at the center of the isotactic chain in the form of a pentad unit{i.e., the chain in which five propylene monomer units are continuously meso-linked) in a polypropylene molecular chain measured by the method described by A. Zambelli et al. in Macromolecules, 6, 925 (1973) was determined as an isotactic pentad fraction. NMR absorption peaks were assigned on the basis of Macromolecules, 8, 687 (1975), later published. [0081]
More specifically, the isotactic pentad fraction was determined as an areal fraction of the

[Production-1 of injection-molded article]
Specimens for the property evaluations (4) to
(6) described above were prepared by injection molding
using an injection molding machine (IS150E-V,
manufactured by Toshiba Machine Co., Ltd.) at a molding
temperature of 220°C, a mold cooling temperature of
50°C, an injection time of 15 seconds and a cooling time
of 30 seconds.
[0083]
(7) Preparation of injection-molded article for
evaluating development of weld lines and flow marks
(7-1) Small flat plate
A small injection-molded article, which served as a specimen for evaluating the development of weld lines and flow marks, was prepared by the following procedure.
A flat molded article illustrated in Fig. 1 was prepared by executing molding with an injection molding machine SE180D having a clamping force of 180 tons, manufactured by Sumitomo Heavy Industries, Ltd. and a mold of 100 mm x 400 mm x 3.0 mm in size having

(7-1-a) Development of weld lines
Using a flat molded article prepared by the procedure (7-1), weld lines were visually observed. The length 3' and the visibility of the weld line illustrated in Fig. 1 were evaluated. In this evaluation, the shorter or the less visible the weld line is, the better in appearance the article is. [0085] (7-1-b) Development of flow marks
Using a flat molded article prepared by the procedure (1-1), flow marks were visually observed. The distance 4' from the gated edge to the position where the flow marks shown in Fig. 1 started to develop/ namely the distance to the position A where the flow marks started to develop (the distance, measured at a side edge and expressed in mm, to the position where the flow marks started to develop) and the visibility of the flow marks were evaluated. In this evaluation, the longer the distance to the position where the flow marks started to develop is or the less visible the flow marks are, the better in appearance the article is.

(7-2-a) Development of weld lines
Using a flat molded article prepared by the procedure (7-2), a weld line was visually observed. The visibility of the weld line was observed in the same manner as that in (7-1-a) described above. In this evaluation, the less visible the weld line is, the better in appearance the article is. [0088] (7-2-b) Development of flow marks
Using a flat molded article prepared by the procedure (7-2), flow marks were visually observed. In the same manner as that in the (7-1-b) described above, the distance 4' from the gated edge to the position where the flow marks started to develop, namely the distance to the position A where the flow marks started to develop (the distance, measured at a side edge and expressed in mm, to the position where the flow marks started to develop) and the visibility of the flow marks were evaluated. In this evaluation, the longer the distance to the position where the flow marks

280 mm X 3.0 mm-thick in size having a single gate were compared and evaluated with respect to their flow lengths (mm). [0090]
The method for synthesizing the solid catalyst component {1} used in the preparations of the polymers used in Examples and Comparative Examples is described below. {!) Solid catalyst component (I)
A 200-L cylindrical reactor (equipped with a stirrer having three paired blades of 0.35 m in diameter and four btffles of 0.05 m in width) was purged with nitrogen. It was charged with 54 L of hexane, 100 g of diisobutyl phthalate, 20.6 kg of tetraethoxysilane and 2.23 kg of titanium tetrabutoxide, and then was stirred. Then, to the resulting mixture under stirring, 51 L of a solution of butylmagnesium chloride in dibutyl ether (2.1 mol/L in concentration) was dropped over four hours while the reactor temperature was kept at 7°C. The stirring speed was set at 150 rpm. After the completion of the dropping, the mixture was stirred for one hour at 20°C

diameter of 39 \im and contained a fine powdery component of 16 nm or less at an amount of 0.5% by weight. Then, toluene was removed so that the volxjine of the slurry would become 49.7 L, and the resulting slurry was stirred for one hour at 80°C and then was cooled to 40°C or lower. Under stirring, a mixed liquid composed of 30 L of titanium tetrachloride and 1.16 kg of dibutyl ether was charged, and further 4.23 kg of orthophthaloyl chloride was charged. The mixture was stirred for three hours while the reactor temperature was kept at 110°C, and then filtered. The resulting solid was washed with 90 L of toluene three times at 95°C, and then incorporated with toluene, giving a slurry. After being left at rest, toluene was removed so that the slurry would come to have a volume of 49,7 L, and then a mixed liquid composed of 15 L of titanium tetrachloride, 1.16 kg of dibutyl ether and 0.87 kg of diisobutyl phthalate was charged with stirring. The mixture was stirred for one hour while the reactor temperature was kept at 105°C, and then filtered. The resulting solid was washed with 90 L of toluene twice

then filtered. The mixture was stirred for one hour while the reactor temperature was kept at 105°C, and then filtered. The resulting solid was washed with 90 L of toluene twice at 95°C, and then incorporated with toluene/ giving a slurry. After being left at rest/ toluene was removed so that the slurry would come to have a volume of 49.7 L. A mixed liquid composed of 15 L of titanium tetrachloride and 1.16 kg of dibutyl ether was charged with stirring. At 95°C, the resulting solid vjas washed with 90 L of toluene three times and with 90 L of hexane twice. The resulting solid component was dried to give a solid catalyst component. The solid catalyst component contained Ti at 2.1% by weight and a phthalic acid ester component at 10.8% by weight. This solid catalyst component is hereinafter referred to as solid catalyst component (I).
[0091]
[Preparation of polymers!
(1) Preparation of propylene homopolymers (HP)
(1-1) Preparation of HPP-1
A propylene homopolymer was prepared by

(1-2) Preparation of HPP-2
A propylene homopolymer was prepared by conventional solvent polymerization in the presence of a catalyst disclosed in JP-A-10-212319, where the hydrogen concentration and the polymerization temperature in the system were controlled. The resulting polymer had an intrinsic viscosity [r\]p of 0.92 dL/g, an isotactic pentad fraction of 0.991, a molecular weight distribution, Q value (Mw/Mn), of 5.4, and an MFR of 111 g/10 minutes. [0093] (1-3) Preparation of HPP-3
A propylene homopolymer was prepared by conventional solvent polymerization in the presence of a catalyst disclosed in JP-A-10-212319, where the hydrogen concentration and the polymerization temperature in the system were controlled. The resulting polymer had an intrinsic viscosity ["HIF of 0.76 dL/g, an isotactic pentad fraction of 0.991, a

(I), a propylene homopolymer segment was prepared in the first stage, and a propylene/ethylene random copolymer segment vjas prepared in the second stage. In the first stage the hydrogen concentration and the polymerization temperature were controlled. In the second stage, vapor-phase polymerization for foritiinq" the propylene-ethylene random copolymer segment was continued while propylene was continuously supplied so that the reaction temperature and the reaction pressure could be kept at constant levels and hydrogen and ethylene were supplied so that the hydrogen and ethylene concentrations in the vapor phase could be kept at constant levels. The propylene homopolymer prepared in the first stage ias sampled and analyzed to have an intrinsic viscosity [Ti]p of 0.93 dL/g and a stereoregularity (mmmm fraction) of 0.987, The finally-obtained propylene/ethylene block copolymer totally had an intrinsic viscosity [riJioTAL of 1.54 dL/g. An analysis revealed that the content of the propylene/ethylene randi_m copolymer {EP content) was

(2-2) Preparation of BCCP-2
By a continuouSf two-stage solvent polymerization process using a catalyst disclosed in JP-K-7-216017, a propylene homopolymer segment was prepared in the first stage, and a propylene/ethylene random copolymer segment was prepared in the second stage. A propylene/ethylene block copolymer having a structure shown below was obtained by controlling the hydrogen concentration, the polymerization temperature and the ethylene/propylene concentrations in the system. The propylene horaopolymer prepared in the first stage was sampled and analyzed to have an intrinsic viscosity [T)]? of 0,93 dL/g and a stereoregularity (mmmm fraction) of 0.97-. The finally-obtained propylene/ethylene block copolymer totally had an intrinsic viscosity [TIITOTPT, of 1.39 dL/g. An analysis revealed that the content of the propylene/ethylene random copolymer (EP content) was 10% by weight. Therefore, the intrinsic viscosity [TIJEP of the propylene/ethylene random copolymer segment {EP

polymer are given in Table 1.
[0096]
(2-3) Preparation of BCCP-3
The method for preparing BCPP-1 was repeated except for controlling and adjusting the hydrogen concentration, the polymerization temperature and the ethylene/propylene concentrations so that the polymer described in Table 1 could be obtained. The analytical results of the resulting polymer are given in Table 1. [0097] (2-4) Preparation of BCCP-4
The method for producing BCPP-2 was repeated except for using a catalyst disclosed in JP-A-10-212319 and controlling and adjusting the hydrogen concentration, the polymerization temperature and the ethylene/propylene concentrations so that the polymer described in Table 1 could be obtained. The analytical results of the resulting polymer are given in Table 1. [0098] Example 1
To 100 parts by weight of a propylene/ethylene block copolymer powder (BCCP-1) were added 0.0 5 parts by weight of calcium stearate (produced by NOF Corp.], 0.05 parts by weight of 3,9-

of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite (ULTRANOX U626, GE Specialty Chemicals Inc.) as stabilizers, followed by forming pellets using an extruder.
[0099]
Forty percent by weight of the BCPP-1 pellets, 12% by weight of a propylene homopolymer (HPP-2) powder, 8% by weight of a propylene homopolymer
(HPP-3) powder, 1% by weight of an ethylene/butene-1 random copolymer rubber EBR-1 (density: 0.861 g/cm, MFR
(determined at 230°C and a load of 2.16 kg): 0.46 g/10 minutes) as the ethylene/a-olefin copolymer rubber (B), 12% by weight of an ethylene-octene-1 random copolymer rubber EOR-1 (density: 0.857 g/cm MFR (determined at 230'C and a load of 2.16 kg); 2.7 g/10 minutes) as the ethylene/a-olefin copolymer rubber (C) and 21% by weight of talc (average diameter: 2.7 \m.) as the inorganic filler (C) were compounded at these relative amounts, and then preliminarily mixed uniformly by a tumbler. Subsequently, the resulting mixture was kneaded and extruded by a twin screv. kneading/extruding machine (TEX44SS-30BW-2V, manufactured by the Japan Steel Works, Ltd.] under conditions including an extrusion rate of 50 kg/hour, 2300, and a screw

properties and the result of weld appearance evaluation
of an injection-molded article.
[0100]
EKample-2
Thirty two percent by weight of the BCPP-1 pellets, 11% by weight of BCPP-2 pellets resulting from pellitization in the same manner as that in the preparation of the BCPP-1 pellets, 3% by weight of a propylene homopolymer (HPP-2) powder, 14% by weight of a propylene homopolymer (HPP-3) powder, 6% by weight of an ethylene/butene-1 random copolymer rubber EBR-1 (density: 0.861 g/cm\ MFR (determined at 230°C and a load of 2.16 kg): 0.46 g/10 minutes) as the ethylene/a-olefin copolymer rubber (B), 13% by weight of an ethylene-octene-1 random copolymer rubber EOR-1 (density: 0.857 g/cm, MFR (determined at 230°C and a load of 2.16 kg): 2.7 g/10 minutes) as the ethylene/a-olefin copolymer rubber (C) and 21% by weight of talc (average diameter: 2.7 \im) as the inorganic filler (C) were compoianded at these relative amounts, and subjected to the same treatment as that in Example 1. Subsequently, the MFR and the properties of an injection-molded article were measured and the weld

in the preparation of the BCPP-1 pellets, Hi by weight of BCPP-2 pellets, 18% by weight of a propylene homopolymer (HPP-1) powder, 15% by weight of an ethylene/butene-1 random copolymer rubber EBR-1 (density: 0.861 g/cm\ MFR (determined at 230°C and a load of 2.16 kg): 0.46 g/10 minutes) as the ethylene/a-olefin copolymer rubber (B), 5% by weight of an ethylene-octene-1 random copolymer rubber EOR-1 (density: 0.857 g/cm MFR (determined at 230°C and a load ol 2.16 kg): 2.7 g/10 minutes) as the ethylene/a-olefin copolymer rubber (C) and 21% by weight of talc (average diameter: 2.7 urn) as the inorganic filler (C) were compounded at these relative amounts, and subjected to the same treatment as that in Example 1. Subsequently, the MFR and the properties of an injection-molded article were measured and the weld appearance of an injection-molded article was evaluated. In Table 2, the evaluation results are shown. [0102] Comparative Example-2

olefin copolymei: r'-bber (B) , li% by weight of an sthylene/octene-1 random copolymer rubber EOR-2 (density: 0.870 g/cm MFR (determined at 230°C and a load of 2.16 kg); 11 g/10 minutes) as the ethylene/a-Dlefin copolymer rubber (C) and 16% by weight of talc (average diameter: 2.7 im) as the inorganic filler (C) -jere compounded at these relative amounts, and subjected to the same treatment as that in Example 1. Subsequently, the MFR and the properties of an injection-molded article were measured and the weld appearance of an injection-molded article was evaluated. In Table 2, the evaluation results are shown.

It is also found that the polypropylene resin composition prepared in Comparative Example-1 is insufficient in flow mark appearance and fluidity because the intrinsic viscosity {[TIIP) of the
15 propylene/ethylene random copolymer segment in the
block: copolymer (A-1) fails to satisfy the requirement of the present invention with respect to it and the content of the ethylene/a-olefin copolymer rubber (B) fails to satisfy the requirement of the present
20 invention with respect to it. [0107]
It is also found that the polypropylene resin composition prepared in Comparative Example-2 is insufficient in weld appearance because the intrinsic
25 viscosity ([TIIE?) of the propylene/ethylene random
copolymer segment in the block copolymer (A-1) fails to satisfy the requirement of the present invention with respect tc it and no ethylene/a-olefin copolymer rubber

[0108]
Brief Description of the Drawing
Fig. 1 is a plan view of a flat molded article (small flat plate) for evaluating the 10 appearance. [0109]
Description of Symbols 1: Gate 1 2: Gate 2 15 3: Weld line 4: Flow mark A 5: Flow mark B 3': Weld line length 4': Position A at which a flow mark develops

CLAIMS
(Amended claims filed on November 28, 2007 under PCT Article 34)
1. A polypropylene resin composition comprising: 50 to 65% by weight of a polypropylene resin (A); 1 to 10% by weight of an ethylene/a-olefin copolymer rubber (B); 8 to 10% by weight of an ethylene/a-olefin copolymer rubber (C); and 18 to 25% by weight of an inorganic filler (D), wherein the combined content of the ethylene/a-olefin copolymer rubber (B) and the ethylene/a-olefin copolymer rubber {C) is 17 to 25% by weight, where the overall amount of the polypropylene resin composition is let be 100% by weight,
wherein the polypropylene resin (A) is a propylene/ethylene block copolymer (A-l) having a crystalline propylene homopolymer segment and a propylene/ethylene random copolymer segment having an intrinsic viscosity of 4.0 to 5.5 dL/g, or is a propylene polymer mixture (A-3) containing the block copolymer {A-l) and a crystalline propylene homopolyraer (A-2) ,
the ethylene/a-olefin copolymer rubber (B) contains an a-olefin of 4 to 12 carbon atoms and ethylene, and has a density of 0.850 to 0.870 g/cm3 and a melt flow rate of 0.05 to 1 g/lO minutes {determined at 230°C and under a load of 2.16 kg), and
the ethylene/a-olefin copolymer rubber (C) contains an a-olefin of 4 to 12 carbon atoms and

ethylene, and has a density of 0.350 to 0.870 g/cm2 and a melt flow rate of 2.3 to 15 g/10 minutes (determined at 230°C and under a load of 2.16 kg).
2. The polypropylene resin composition according to Claim 1, wherein the propylene/ethylene random copolymer segment in the propylene/ethylene block copolymer (A-1) has a propylene/ethylene weight ratio of 65/35 to 52/48, the ratio being defined as the ratio of the weight of propylene-derived structural units (propylene content) to the weight of ethylene-derived structural units (ethylene content).
3. The polypropylene resin composition according to Claim 1 or 2, wherein the crystalline propylene homopolymer segment in the propylene/ethylene block copolymer (A-1) or the component composed of the crystalline propylene homopolymer in the propylene polymer mixture (A-3) has an isotactic pentad fraction, as determined by 13c-NMR, of 0.98 or more.
4. The polypropylene resin composition according to any one of Claims 1 to 3, wherein the inorganic filler {D} is talc.
5. An automotive injection molded article made of the polypropylene resin composition according to any one of Claims 1 to 4.
6. A method for producing the automotive injection molded article according to Claim 5, comprising molding the polypropylene resin composition according to any one of Claims 1 to 4 to form an

automotive injection molded article by the use of an injection molding machine and a mold having a plurality of gates.

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Patent Number

269541

Indian Patent Application Number

6696/CHENP/2008

PG Journal Number

44/2015

Publication Date

30-Oct-2015

Grant Date

27-Oct-2015

Date of Filing

05-Dec-2008

Name of Patentee

SUMITOMO CHEMICAL COMPANY, LIMITED

Applicant Address

27-1, SHINKAWA 2-CHOME CHUO-KU TOKYO.

Inventors:

#	Inventor's Name	Inventor's Address
1	KANZAKI, SUSUMU	4-26-16, KONANDAI KISARAZU-SHI CHIBA.
2	INANAMI, HIROSHI	C/O TOYOTA JIDOSHA KABUSHIKI KAISHA 1, TOYOTA-CHO, TOYOTA-SHI, AICHI-KEN
3	INOUE, KAORU	C/O TOYOTA JIDOSHA KABUSHIKI KAISHA 1, TOYOTA-CHO, TOYOTA-SHI, AICHI-KEN

PCT International Classification Number

C08L53/00

PCT International Application Number

PCT/JP07/61296

PCT International Filing date

2007-06-04

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2006-155688	2006-06-05	Japan