JP7406922B2 - Polypropylene resin composition - Google Patents

Description

The present invention relates to a polypropylene resin composition that can be used to produce a molded article that is used, for example, as an automobile exterior member, and that has suppressed appearance defects, has a low coefficient of linear expansion, and has high dimensional stability.

Molded products obtained by injection molding polypropylene resin compositions are widely used in automobile parts, home appliance parts, etc. due to their excellent mechanical properties and moldability, as well as their relatively advantageous cost performance compared to other materials. Its use in various fields is progressing.

In the automotive parts field, in addition to using polypropylene alone, polypropylene is also used in combination with ethylene-propylene copolymer (EPR), ethylene-butene copolymer (EBR), ethylene-octene copolymer (EOR), and styrene-butadiene copolymer. (SBR), materials with improved impact resistance by adding rubber components such as polystyrene-ethylene/butene-polystyrene triblock copolymer (SEBS), and materials with improved impact resistance by adding inorganic fillers such as talc, mica, and glass fiber. Improved materials are used, as well as blended polymers that have well-balanced mechanical properties by adding both a rubber component and an inorganic filler.

In recent years, there has been an increasing need to develop materials with excellent dimensional stability (low coefficient of linear expansion) while maintaining high mechanical properties (mainly rigidity), mainly for use as a substitute for metal materials. Material development research has begun to be carried out to achieve this goal. However, polypropylene molded products generally have a large dimensional change (linear expansion coefficient) with respect to temperature, so when used in environments with large temperature differences, such as for automobile exterior panels, gaps may form at the joints of parts, or They had problems such as poor installation performance during assembly, the so-called defective gap quality problem. Therefore, in this field, the high design quality and excellent cost effectiveness of polypropylene molded products have not yet been fully enjoyed.

As a measure to improve the dimensional stability of polypropylene molded products, various propylene resin compositions have been proposed in which polypropylene is blended with components such as inorganic fillers typified by talc and elastomer components. For example, a method for producing a low linear expansion material characterized by the combination of a propylene block copolymer containing crystalline polypropylene with a melt flow rate of 500 g/10 minutes or more and a low molecular weight polyolefin (Patent Document 1), a propylene block A resin composition in which a specific ethylene-butene-1 copolymer is blended with a copolymer (Patent Document 2), characterized by specifying the blending ratio and viscosity of the amorphous part and crystal part of the propylene block copolymer. (Patent Document 3), a resin composition characterized by using talc with an average particle size of 3 μm or less and having an excellent painted appearance after injection molding (Patent Document 4), and a resin composition manufactured using a Ziegler catalyst. A resin composition comprising a propylene resin and a specific shape of talc (Patent Document 5), a resin composition characterized by using two types of propylene block copolymers with different melt flow rates and a specific shape of talc (Patent Document 5) There is Patent Document 6).

Furthermore, a resin composition containing a specific propylene polymer, a specific ethylene/α-olefin copolymer, and an inorganic filler having an average particle size of more than 3.0 μm and less than 5.0 μm (Patent Document 7) is also known. It is being This resin composition has a low coefficient of linear expansion, high dimensional stability, and excellent surface impact resistance at low temperatures.

Japanese Patent Application Publication No. 2010-77396 Japanese Patent Application Publication No. 5-051498 Japanese Patent Application Publication No. 2000-95919 Japanese Patent Application Publication No. 2007-91789 Japanese Patent Application Publication No. 2013-159709 Japanese Patent Application Publication No. 2014-58614 JP2017-88742A

When injection molding the above resin compositions, poor appearance (flow marks, etc.) may occur on the surface of the molded product due to unstable flow of the resin composition within the mold. . Such poor appearance becomes a fatal defect in products such as automobile parts and home appliance parts. In particular, resin compositions containing inorganic fillers such as talc are likely to have poor appearance during injection molding. The present inventors focused on the need to provide a resin composition that satisfies the demand for further improvement in dimensional stability and is less likely to cause such appearance defects.

That is, an object of the present invention is to provide a polypropylene resin composition from which a molded article can be produced which suppresses appearance defects, has a low coefficient of linear expansion, and has high dimensional stability.

As a result of intensive studies to solve the above problems, the present inventors have developed a propylene resin composition having a specific composition containing an inorganic filler having a relatively large specific average particle diameter and a relatively large specific aspect ratio. They found that this is very effective and completed the present invention. That is, the present invention is specified by the following matters.

[1] 5 to 47 parts by mass of a propylene polymer (A) having a melt flow rate (230° C., 2.16 kg load) of 50 to 150 g/10 minutes and a decane soluble content of 6% by mass or more,
0 to 30 parts by mass of a propylene homopolymer (B) having a melt flow rate (230 ° C., 2.16 kg load) of 10 to 500 g/10 minutes,
It is a random copolymer of ethylene and α-olefin having 4 to 8 carbon atoms, with a density of 0.850 to 0.890 g/cm ³ and a melt flow rate (230°C, 2.16 kg load) of 0. 23 to 30 parts by mass of ethylene/α-olefin copolymer (C) having a rate of 5 to 30 g/10 minutes, and
30 to 40 parts by mass of an inorganic filler (D) having an average particle diameter of more than 8 μm and an aspect ratio of more than 9.0 [However, the total amount of components (A) to (D) is 100 parts by mass. ]
Contains
A polypropylene resin composition whose melt flow rate (230°C, 2.16 kg load) of the entire composition is 25 to 60 g/10 minutes.

[2] The polypropylene resin composition according to [1], wherein the inorganic filler (D) has an average particle diameter of more than 10 μm.

[3] The polypropylene resin composition according to [1] or [2], wherein the propylene polymer (A) is a block copolymer obtained from propylene and ethylene.

[4] The polypropylene resin composition according to any one of [1] to [3], which is used for automobile exterior parts.

[5] An automobile exterior member obtained by injection molding or press molding the polypropylene resin composition according to [4].

According to the polypropylene resin composition of the present invention, it is possible to produce a molded article that suppresses appearance defects, has a low coefficient of linear expansion, and has high dimensional stability. Such molded bodies are suitable for various uses, such as automobile exterior parts, for example.

3 is a photograph of the appearance of injection molded products of Example 3 and Comparative Example 3.

<Propylene polymer (A)>
The propylene polymer (A) used in the present invention is a propylene polymer having a melt flow rate (230°C, 2.16 kg load) of 50 to 150 g/10 minutes and a decane soluble content of 6% by mass or more. be.

The propylene polymer (A) substantially contains 6% by mass or more of a decane soluble portion (a1) and 94% by mass or less of a decane insoluble portion (a2). Decane-insoluble portion (a2) is a component that is generally insoluble in n-decane solvent at room temperature (23°C), and is usually a propylene homopolymer portion (propylene homopolymer component) that occupies the propylene polymer (A). ) is equivalent to The decane soluble portion (a1) is equivalent to a portion other than the propylene homopolymer portion, and is preferably a copolymer portion of propylene and ethylene (ethylene/propylene copolymer component).

The propylene polymer (A) usually contains 6% by mass or more of a decane soluble part (a1) and 94% by mass or less of a decane insoluble part (a2), preferably 6 to 20% by mass of a decane soluble part. (a1) and 80 to 94% by mass of a decane-insoluble part (a2), more preferably 6 to 15% by mass of a decane-soluble part (a1) and 85 to 94% by mass of a decane-insoluble part (a2). , particularly preferably contains 7 to 12% by mass of the decane soluble part (a1) and 88 to 93% by mass of the decane insoluble part (a2) [where the sum of the content of (a1) and the content of (a2)] is 100% by mass].

The propylene polymer (A) is preferably a propylene block copolymer obtained from propylene and ethylene. The intrinsic viscosity [η] of the decane-soluble portion (A) of this propylene-based block copolymer is preferably 2 to 9 dl/g, more preferably 3 to 8 dl/g.

The melt flow rate (230°C, 2.16 kg load) of the propylene polymer (A) is 50 to 150 g/10 minutes, preferably 50 to 130 g/10 minutes, more preferably 60 to 120 g/10 minutes, especially Preferably it is 70 to 110 g/10 minutes.

The propylene polymer (A) can be produced by a known method. For example, propylene can be polymerized using an olefin polymerization catalyst containing a solid titanium catalyst component (I) and an organometallic compound catalyst component (II) as described below, and then copolymerized with propylene and ethylene. A block copolymer is obtained.

[Solid titanium catalyst component (I)]
The solid titanium catalyst component (I) constituting the olefin polymerization catalyst contains, for example, titanium, magnesium, halogen, and, if necessary, an electron donor. For this solid titanium catalyst component (I), known components can be used without limitation.

In preparing the solid titanium catalyst component (I), magnesium compounds and titanium compounds are often used.

Specific examples of magnesium compounds include magnesium halides such as magnesium chloride and magnesium bromide; alkoxymagnesium halides such as methoxymagnesium chloride, ethoxymagnesium chloride, and phenoxymagnesium chloride; ethoxymagnesium, isopropoxymagnesium, butoxymagnesium, and 2-ethyl Examples include alkoxymagnesiums such as hexoxymagnesium; aryloxymagnesiums such as phenoxymagnesium; and magnesium carboxylates such as magnesium stearate. One type of magnesium compound may be used alone, or two or more types may be used in combination. Further, the magnesium compound may be a complex compound with other metals, a composite compound, or a mixture with other metal compounds.

Among these, magnesium compounds containing halogen are preferred, and magnesium halides, particularly magnesium chloride, are more preferred. In addition, alkoxymagnesiums such as ethoxymagnesium are also preferred. The magnesium compound may also be one derived from another substance, such as a compound obtained by contacting an organomagnesium compound such as a Grignard reagent with a compound such as titanium halide, silicon halide, or halogenated alcohol. .

Examples of the titanium compound include tetravalent titanium compounds represented by the following formula.
Ti(OR) _g X _4-g
(In the formula, R is a hydrocarbon group, X is a halogen atom, and g is 0≦g≦4.)

Specific examples of titanium compounds include tetrahalogenated titanium such as TiCl ₄ and TiBr ₄ ; Ti(OCH ₃ )Cl ₃ , Ti(OC ₂ H ₅ )Cl ₃ , Ti(O-n-C ₄ H ₉ )Cl ₃ , Ti(OC ₂ H ₅ ) Br ₃ , Ti(O-i-C ₄ H ₉ )Br ₃ and other trihalogenated alkoxy titanium; Ti(OCH ₃ ) ₂ Cl ₂ , Ti(OC ₂ H ₅ ) ₂ Dihalogenated alkoxytitanium such _{as Cl2 ;} monohalogenated alkoxytitanium such as Ti( _OCH3 ) _3Cl , Ti(O-n- _C4H9 ) _3Cl , Ti( _OC2H5 ) _3Br ; Ti( Examples include tetraalkoxytitaniums such as OCH ₃ ) ₄ , Ti(OC ₂ H ₅ ) ₄ , Ti(OC ₄ H ₉ ) ₄ , and Ti(O-2-ethylhexyl) ₄ . One type of titanium compound may be used alone, or two or more types may be used in combination. Among these, titanium tetrahalide is preferred, and titanium tetrachloride is more preferred.

As the magnesium compound and titanium compound, for example, compounds described in detail in JP-A-57-63310 and JP-A-5-170843 can also be used.

Specific examples of preferred methods for preparing the solid titanium catalyst component (I) used in the present invention include the following methods (P-1) to (P-4).
(P-1) A solid adduct consisting of a magnesium compound and an electron donor component (1) such as alcohol, an electron donor component (2) described below, and a liquid titanium compound are mixed in an inert hydrocarbon solvent. A method of contacting in a suspended state in coexistence.
(P-2) A method in which a solid adduct consisting of a magnesium compound and an electron donor component (1), an electron donor component (2), and a liquid titanium compound are contacted in multiple steps.
(P-3) A solid adduct consisting of a magnesium compound and an electron donor component (1), an electron donor component (2), and a liquid titanium compound are suspended in the coexistence of an inert hydrocarbon solvent. A method in which contact is made in a state in which the contact is made, and the contact is made in multiple steps.
(P-4) A method of bringing a liquid magnesium compound consisting of a magnesium compound and an electron donor component (1) into contact with a liquid titanium compound and an electron donor component (2).

The reaction temperature when preparing the solid titanium catalyst component (I) is preferably -30 to 150°C, more preferably -25 to 130°C, particularly preferably -25 to 120°C.

The solid titanium catalyst component (I) can also be prepared in the presence of a known medium, if necessary. Specific examples of the medium include slightly polar aromatic hydrocarbons such as toluene, and known aliphatic hydrocarbons or alicyclic hydrocarbon compounds such as heptane, octane, decane, and cyclohexane. Among these, aliphatic hydrocarbons are preferred.

As the electron donor component (1) used to form solid adducts and liquid magnesium compounds, known compounds that can solubilize magnesium compounds in the temperature range of room temperature to about 300°C are preferred, such as alcohols, aldehydes, etc. , amines, carboxylic acids and mixtures thereof are preferred. Examples of these compounds include those described in JP-A-57-63310 and JP-A-5-170843.

Specific examples of alcohols that can solubilize magnesium compounds include methanol, ethanol, propanol, butanol, isobutanol, ethylene glycol, 2-methylpentanol, 2-ethylbutanol, n-heptanol, n-octanol, and 2-ethylhexanol. , aliphatic alcohols such as decanol and dodecanol; alicyclic alcohols such as cyclohexanol and methylcyclohexanol; aromatic alcohols such as benzyl alcohol and methylbenzyl alcohol; aliphatic alcohols having alkoxy groups such as n-butyl cellosolve; Can be mentioned.

Specific examples of carboxylic acids include organic carboxylic acids having 7 or more carbon atoms such as caprylic acid and 2-ethylhexanoic acid. Specific examples of aldehydes include aldehydes having 7 or more carbon atoms such as capric aldehyde and 2-ethylhexyl aldehyde. Specific examples of amines include amines having 6 or more carbon atoms, such as heptylamine, octylamine, nonylamine, laurylamine, and 2-ethylhexylamine.

As the electron donor component (1), the above-mentioned alcohols are preferred, and ethanol, propanol, butanol, isobutanol, hexanol, 2-ethylhexanol, and decanol are particularly preferred.

The composition ratio of magnesium and electron donor component (1) in the resulting solid adduct or liquid magnesium compound varies depending on the type of compound used, so it cannot be unconditionally defined, but it is On the other hand, the electron donor component (1) is preferably 2 mol or more, more preferably 2.3 mol or more, particularly preferably 2.7 mol or more and 5 mol or less.

Particularly preferred examples of electron donors optionally used in the solid titanium catalyst component (I) include aromatic carboxylic acid esters and/or compounds having two or more ether bonds via multiple carbon atoms ( (hereinafter referred to as "electron donor component (2)").

As the electron donor component (2), known aromatic carboxylic acid esters and polyether compounds that have been preferably used in conventional olefin polymerization catalysts, such as those disclosed in JP-A-5-170843 and JP-A-2001-354714, are used. The compounds described in can be used without limitation.

Specific examples of the aromatic carboxylic acid ester include aromatic carboxylic acid monoesters such as benzoic acid ester and toluic acid ester, as well as aromatic polyvalent carboxylic acid esters such as phthalic acid esters. Among these, aromatic polycarboxylic acid esters are preferred, and phthalic acid esters are more preferred. As the phthalate esters, phthalate alkyl esters such as ethyl phthalate, n-butyl phthalate, isobutyl phthalate, hexyl phthalate, and heptyl phthalate are preferred, and diisobutyl phthalate is particularly preferred.

Specific examples of the polyether compound include compounds represented by the following chemical structural formula (1).

In the above formula (1), m is an integer of 1≦m≦10, more preferably an integer of 3≦m≦10, and R ¹¹ to R ³⁶ are each independently a hydrogen atom, or carbon, hydrogen, or oxygen. , fluorine, chlorine, bromine, iodine, nitrogen, sulfur, phosphorus, boron, and silicon. When m is 2 or more, a plurality of R ¹¹ and R ¹² may be the same or different. Any of R ¹¹ to R ³⁶ , preferably R ¹¹ and R ¹² may jointly form a ring other than a benzene ring.

Specific examples of such compounds include 1-substituted dialkoxy compounds such as 2-isopropyl-1,3-dimethoxypropane, 2-s-butyl-1,3-dimethoxypropane, and 2-cumyl-1,3-dimethoxypropane. Propanes; 2-isopropyl-2-isobutyl-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2-methyl- 2-cyclohexyl-1,3-dimethoxypropane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1 ,3-dimethoxypropane, 2,2-diisobutyl-1,3-diethoxypropane, 2,2-diisobutyl-1,3-dibutoxypropane, 2,2-di-s-butyl-1,3-dimethoxypropane , 2-substituted dialkoxy such as 2,2-dineopentyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane, etc. Propanes; 2,3-dicyclohexyl-1,4-diethoxybutane, 2,3-dicyclohexyl-1,4-diethoxybutane, 2,3-diisopropyl-1,4-diethoxybutane, 2,4-diphenyl -1,5-dimethoxypentane, 2,5-diphenyl-1,5-dimethoxyhexane, 2,4-diisopropyl-1,5-dimethoxypentane, 2,4-diisobutyl-1,5-dimethoxypentane, 2,4 -Dialkoxyalkanes such as diisoamyl-1,5-dimethoxypentane; 2-methyl-2-methoxymethyl-1,3-dimethoxypropane, 2-cyclohexyl-2-ethoxymethyl-1,3-diethoxypropane, 2 -trialkoxyalkanes such as -cyclohexyl-2-methoxymethyl-1,3-dimethoxypropane; and the like. One type of polyether compound may be used alone, or two or more types may be used in combination. Among these, 1,3-diethers are preferred, particularly 2-isopropyl-2-isobutyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, and 2-isopropyl-2-isopentyl-1. ,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, and 2,2-bis(cyclohexylmethyl)1,3-dimethoxypropane are preferred.

In the solid titanium catalyst component (I), the halogen/titanium (atomic ratio) (that is, the number of moles of halogen atoms/the number of moles of titanium atoms) is from 2 to 100, preferably from 4 to 90, and the electron donor component (1)/titanium atom (molar ratio) is 0 to 100, preferably 0 to 10, and electron donor component (2)/titanium atom (molar ratio) is 0 to 100, preferably 0 to 10. The magnesium/titanium (atomic ratio) (ie, number of moles of magnesium atoms/number of moles of titanium atoms) is from 2 to 100, preferably from 4 to 50.

As more detailed preparation conditions for the solid titanium catalyst component (I), it is preferable to use, for example, the conditions described in EP585869A1 and JP-A-5-170843, except for the use of the electron donor component (2). can.

[Organometallic compound catalyst component (II)]
The organometallic compound catalyst component (II) is a component containing a metal element selected from Groups 1, 2, and 13 of the periodic table. For example, a compound containing a Group 13 metal (such as an organoaluminum compound), a complex alkylated product of a Group 1 metal and aluminum, or an organometallic compound of a Group 2 metal can be used. Among these, organic aluminum compounds are preferred.

Specifically, as the organometallic compound catalyst component (II), organometallic compound catalyst components described in known documents such as the aforementioned EP585869A1 can be suitably used.

In addition to the electron donor component (1) and electron donor component (2) described above, a known electron donor component (3) may be used in combination as long as the object of the present invention is not impaired.

As the electron donor component (3), an organosilicon compound is preferable. This organosilicon compound is, for example, a compound represented by the following formula.
R _n Si(OR') _4-n
(In the formula, R and R' are hydrocarbon groups, and n is an integer of 0<n<4.)

Specific examples of organosilicon compounds represented by the above formula include diisopropyldimethoxysilane, t-butylmethyldimethoxysilane, t-butylmethyldiethoxysilane, t-amylmethyldiethoxysilane, dicyclohexyldimethoxysilane, and cyclohexylmethyldimethoxysilane. , cyclohexylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, t-butyltriethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, cyclohexyltrimethoxysilane, cyclopentyltrimethoxysilane, 2-methylcyclopentyltrimethoxysilane , cyclopentyltriethoxysilane, dicyclopentyldimethoxysilane, dicyclopentyldiethoxysilane, tricyclopentylmethoxysilane, dicyclopentylmethylmethoxysilane, dicyclopentylethylmethoxysilane, and cyclopentyldimethylethoxysilane. Among them, vinyltriethoxysilane, diphenyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, and dicyclopentyldimethoxysilane are preferred.

Further, a silane compound represented by the following formula described in International Publication No. 2004/016662 pamphlet is also a preferable example of the organosilicon compound.
Si(OR ^a ) ₃ (NR ^b R ^c )

In the above formula, R ^a is a hydrocarbon group having 1 to 6 carbon atoms. For example, it is an unsaturated or saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms, and a hydrocarbon group having 2 to 6 carbon atoms is particularly preferred. Specific examples include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, n-pentyl group, iso-pentyl group, cyclopentyl group, n -hexyl group and cyclohexyl group. Among these, ethyl group is particularly preferred.

R ^b is a hydrocarbon group having 1 to 12 carbon atoms or hydrogen. For example, it is an unsaturated or saturated aliphatic hydrocarbon group having 1 to 12 carbon atoms or hydrogen. Specific examples include hydrogen atom, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, n-pentyl group, iso-pentyl group, cyclopentyl group. group, n-hexyl group, cyclohexyl group, and octyl group. Among these, ethyl group is particularly preferred.

R ^c is a hydrocarbon group having 1 to 12 carbon atoms. For example, it is an unsaturated or saturated aliphatic hydrocarbon group having 1 to 12 carbon atoms. Specific examples include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, n-pentyl group, iso-pentyl group, cyclopentyl group, n -Hexyl group, cyclohexyl group, and octyl group. Among these, ethyl group is particularly preferred.

Specific examples of the organosilicon compound represented by the above formula include dimethylaminotriethoxysilane, diethylaminotriethoxysilane, diethylaminotrimethoxysilane, diethylaminotri-n-propoxysilane, di-n-propylaminotriethoxysilane, methyl n- Examples include propylaminotriethoxysilane, t-butylaminotriethoxysilane, ethyl n-propylaminotriethoxysilane, ethyl iso-propylaminotriethoxysilane, and methylethylaminotriethoxysilane.

Further, other examples of organosilicon compounds include compounds represented by the following formulas.
RNSi( ^ORa ) ₃

In the above formula, RN is a cyclic amino group. Specific examples include perhydroquinolino group, perhydroisoquinolino group, 1,2,3,4-tetrahydroquinolino group, 1,2,3,4-tetrahydroisoquinolino group, and octamethyleneimino group. It will be done. R ^a is the same as above.

Specific examples of organosilicon compounds represented by the above formula include (perhydroquinolino)triethoxysilane, (perhydroisoquinolino)triethoxysilane, (1,2,3,4-tetrahydroquinolino)triethoxy Examples include silane, (1,2,3,4-tetrahydroisoquinolino)triethoxysilane, and octamethyleneiminotriethoxysilane.

Each of the organosilicon compounds described above may be used in combination of two or more.

[polymerization]
A propylene/ethylene block copolymer, which is a preferred embodiment of the propylene polymer (A), can be produced, for example, by polymerizing propylene in the presence of the above-mentioned olefin polymerization catalyst, and then copolymerizing propylene and ethylene, or by pre-copolymerizing propylene and ethylene. It can be produced by polymerizing propylene in the presence of a prepolymerized catalyst obtained by polymerization, and then copolymerizing propylene and ethylene.

The prepolymerization is carried out by prepolymerizing the olefin in an amount of usually 0.1 to 1000 g, preferably 0.3 to 500 g, particularly preferably 1 to 200 g per 1 g of the olefin polymerization catalyst. In the prepolymerization, a catalyst can be used at a higher concentration than the catalyst concentration in the system in the main polymerization.

The concentration of the solid titanium catalyst component (I) in the prepolymerization is usually 0.001 to 200 mmol, preferably 0.01 to 50 mmol, more preferably 0.1 to 50 mmol in terms of titanium atoms per liter of liquid medium. It is 20 mmol.

The amount of organometallic compound catalyst component (II) in the prepolymerization is such that usually 0.1 to 1000 g, preferably 0.3 to 500 g of polymer is produced per 1 g of solid titanium catalyst component (I). The amount is generally 0.1 to 300 mol, preferably 0.5 to 100 mol, more preferably 1 to 50 mol, per mol of titanium atom in solid titanium catalyst component (I).

In the prepolymerization, the above-mentioned electron donor components can be used if necessary, and in this case, these components are usually 0.1 to 50 mol per mol of titanium atom in the solid titanium catalyst component (I), The amount is preferably 0.5 to 30 mol, more preferably 1 to 10 mol.

Prepolymerization can be carried out under mild conditions by adding the olefin and the catalyst components described above to an inert hydrocarbon medium. If an inert hydrocarbon medium is used, the prepolymerization is preferably carried out batchwise.

Specific examples of inert hydrocarbon media include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, dodecane, kerosene; cyclopentane, methylcyclopentane, cyclohexane, cycloheptane, methylcycloheptane; , alicyclic hydrocarbons such as cyclooctane; aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as ethylene chloride and chlorobenzene; or mixtures thereof. Among these, aliphatic hydrocarbons are preferred.

Prepolymerization can also be carried out using the olefin itself as a solvent. Prepolymerization can also be carried out in a substantially solvent-free state. In this case, it is preferable to carry out the preliminary polymerization continuously.

The olefin used in the prepolymerization may be the same as or different from the olefin used in the main polymerization described later. Propylene is particularly preferred as the olefin.

The temperature during prepolymerization is usually -20 to 100°C, preferably -20 to 80°C, more preferably 0 to 40°C.

Next, main polymerization carried out after or without passing through preliminary polymerization will be explained.

This polymerization is divided into a step of producing a propylene homopolymer component and a step of producing a propylene-ethylene copolymer component.

The main polymerization (and prepolymerization) can be carried out by any of liquid phase polymerization methods such as bulk polymerization, solution polymerization, and suspension polymerization, or gas phase polymerization. The process for producing the propylene homopolymer component is preferably liquid phase polymerization such as bulk polymerization or suspension polymerization, or gas phase polymerization. The process for producing the propylene-ethylene copolymer component is preferably liquid phase polymerization such as bulk polymerization or suspension polymerization, or gas phase polymerization, and more preferably gas phase polymerization.

When the main polymerization takes the form of slurry polymerization, the reaction solvent may be the inert hydrocarbon used in the above-mentioned prepolymerization, or an olefin that is liquid at the reaction temperature and pressure.

In this polymerization, the solid titanium catalyst component (I) is usually used in an amount of 0.0001 to 0.5 mmol, preferably 0.005 to 0.1 mmol, in terms of titanium atoms per liter of polymerization volume. used. Further, the organometallic compound catalyst component (II) is used in an amount of usually 1 to 2000 mol, preferably 5 to 500 mol, per 1 mol of titanium atom in the prepolymerized catalyst component in the polymerization system. When an electron donor component is used, it is usually 0.001 to 50 mol, preferably 0.01 to 30 mol, more preferably 0.05 to 20 mol, per 1 mol of organometallic compound catalyst component (II). Used in molar amounts.

If the main polymerization is carried out in the presence of hydrogen, the molecular weight of the resulting polymer can be adjusted (lowered) and a polymer with a high melt flow rate (MFR) can be obtained. The amount of hydrogen required to adjust the molecular weight varies depending on the type of manufacturing process used, polymerization temperature, and pressure, and may be adjusted as appropriate.

In the process of producing the propylene homopolymer component, the MFR can be adjusted by adjusting the polymerization temperature and hydrogen amount. Furthermore, in the process of producing the propylene-ethylene copolymer component, the intrinsic viscosity can be adjusted by adjusting the polymerization temperature, pressure, and amount of hydrogen.

In the main polymerization, the polymerization temperature of the olefin is usually 0 to 200°C, preferably 30 to 100°C, more preferably 50 to 90°C. The pressure (gauge pressure) is usually normal pressure to 100 kgf/cm ² (9.8 MPa), preferably 2 to 50 kgf/cm ² (0.20 to 4.9 MPa).

In the production of a propylene/ethylene block copolymer, which is a preferred embodiment of the propylene polymer (A), polymerization can be carried out in any of the batch, semi-continuous, and continuous methods. Further, the shape of the reactor can be either a tubular type or a tank type. Furthermore, the polymerization can be carried out in two or more stages by changing the reaction conditions. In this case, the tubular type and the tank type can be combined.

In order to obtain the propylene/ethylene copolymer portion in the propylene/ethylene block copolymer, which is a preferred embodiment of the propylene polymer (A), the ethylene/(ethylene + propylene) gas ratio must be adjusted in the polymerization step 2 described below. Control. The ethylene/(ethylene+propylene) gas ratio is usually 5 to 80 mol%, preferably 10 to 70 mol%, more preferably 15 to 60 mol%.

For example, by continuously carrying out the following two polymerization steps 1 and 2, a propylene/ethylene block copolymer, which is a preferred embodiment of the propylene polymer (A), can be obtained.
(Polymerization step 1)
A process of polymerizing propylene in the presence of a solid titanium catalyst component to produce a propylene homopolymer component (propylene homopolymer production process).
(Polymerization step 2)
A process of copolymerizing propylene and ethylene in the presence of a solid titanium catalyst component to produce an ethylene-propylene copolymer component (copolymer rubber production process).

In particular, it is more preferable to perform the polymerization step 1 in the first stage and the polymerization step 2 in the latter stage. Each polymerization step 1 and 2 can also be carried out using two or more polymerization tanks. The content of the decane soluble portion (a1) can be adjusted by the polymerization time (residence time) of polymerization step 1 and polymerization step 2. Further, the first stage polymerization step 1 may be performed in two or more stages of polymerization vessels connected in series. In that case, the ratio of propylene to hydrogen in each stage may be different for each polymerization vessel.

<Propylene homopolymer (B)>
The propylene homopolymer (B) used in the present invention is a propylene homopolymer having a melt flow rate (230° C., 2.16 kg load) of 10 to 500 g/10 minutes.

The propylene homopolymer (B) may be a polymer obtained by polymerizing substantially only propylene. For example, a homopolymer obtained by polymerizing only propylene, or a crystalline polymer obtained by copolymerizing propylene with another α-olefin in an amount of 6 mol % or less, preferably 3 mol % or less can be used. Among these, a homopolymer obtained by polymerizing only propylene is preferable.

The propylene homopolymer (B) can be produced by polymerizing monomers mainly containing propylene by a known method. For example, an olefin polymerization catalyst containing the solid titanium catalyst component (I) and an organometallic compound catalyst component (II) as described above, or a catalyst containing titanium trichloride and an alkyl aluminum compound, which is usually called a Ziegler-Natta type catalyst. It is obtained by polymerizing monomers based on propylene in the presence of a combination catalyst. The polymerization reaction may be carried out continuously or batchwise. Further, for example, it can be suitably produced by performing only the polymerization step 1 described above.

In the polymerization reaction, the polymerization temperature is usually 0 to 200°C, preferably 30 to 100°C, more preferably 50 to 90°C. The pressure (gauge pressure) is usually normal pressure to 100 kgf/cm ² (9.8 MPa), preferably 2 to 50 kgf/cm ² (0.20 to 4.9 MPa).

The melt flow rate (230°C, 2.16 kg load) of the propylene homopolymer (B) is 10 to 500 g/10 minutes, preferably 10 to 300 g/10 minutes, more preferably 20 to 250 g/10 minutes. .

The propylene homopolymer (B) may be one type of polymer, or two or more types of propylene homopolymers may be arbitrarily combined within a range that satisfies the above melt flow rate as a whole.

<Ethylene/α-olefin copolymer (C)>
The ethylene/α-olefin copolymer (C) used in the present invention is a random copolymer of ethylene and an α-olefin having 4 to 8 carbon atoms, and has a density of 0.850 to 0.890 g/cm. ^3. An ethylene/α-olefin copolymer having a melt flow rate (230°C, 2.16 kg load) of 0.5 to 30 g/10 minutes. This ethylene/α-olefin copolymer (C) is expected to contribute to improving the dimensional stability (reducing the coefficient of linear expansion) of the molded product through a synergistic effect with other components, as well as improving other physical properties. It also contributes to the improvement of properties, resulting in a molded product with a high balance of physical properties.

The α-olefin having 4 to 8 carbon atoms constituting the ethylene/α-olefin copolymer (C) is preferably 1-butene, 1-hexene, or 1-octene. One type of α-olefin may be used alone, or two or more types may be used in combination. As the ethylene/α-olefin copolymer (C), particularly preferred are ethylene-octene copolymers and ethylene-butene copolymers.

The melt flow rate (230°C, 2.16 kg load) of the ethylene/α-olefin copolymer (C) is 0.5 to 30 g/10 minutes, preferably 1 to 25 g/10 minutes, more preferably 2 ~20g/10 minutes. If this melt flow rate is 0.5 g/10 minutes or more, a decrease in the fluidity of the polypropylene resin composition and poor dispersion during kneading are unlikely to occur, resulting in a decrease in physical properties such as impact resistance and a change in the surface appearance of the molded product. There is a tendency for deterioration to occur less easily. Moreover, if the melt flow rate is 30 g/10 minutes or less, the molded article tends to have sufficient impact resistance.

The density of the ethylene/α-olefin copolymer (C) is 0.850 to 0.890 g/cm ³ , preferably 0.850 to 0.880 g/cm ³ , more preferably 0.855 to 0.880 g/cm 3 . It is 875g/ ^cm3 .

<Inorganic filler (D)>
The inorganic filler (D) used in the present invention has an average particle diameter of more than 8 μm and an aspect ratio of more than 9.0.

Specific examples of the inorganic filler (D) include talc, calcium carbonate, natural mica, synthetic mica, wollastonite, and montmorionite. The inorganic filler (D) may be used alone or in combination of two or more. Among them, talc is preferred.

The average particle size of the inorganic filler (D) exceeds 8 μm, preferably exceeds 10 μm. The upper limit of the average particle diameter range is preferably 15.0 μm or less, more preferably 13.0 μm or less. It is preferable to use an inorganic filler (D) having such an average particle diameter, for example, from the viewpoint of suppressing appearance defects and improving dimensional stability. This average particle size is a value measured by laser diffraction method. Specifically, it is the particle size at 50% of the integrated value in the particle size distribution determined by a particle size distribution meter such as a laser diffraction scattering particle size distribution meter. Examples of measuring devices include MT3300EXII manufactured by Microtrac and LA- manufactured by Horiba. An example is the 920 type.

The aspect ratio of the inorganic filler (D) exceeds 9.0. It is preferably greater than 9.0 and less than 20.0, more preferably 12.0 to 18.0. It is preferable to use an inorganic filler (D) having such an average particle diameter, for example, from the viewpoint of suppressing appearance defects and improving dimensional stability. The aspect ratio is a value representing the ratio between the major axis and the thickness of the filler, or the ratio between the long side and the short side. This aspect ratio is a value determined from the ratio of average particle diameter/average thickness by taking a photograph using an electron microscope, measuring the major axis and thickness of the powder, and determining the average value.

The inorganic filler (D) contributes to improving the dimensional stability (reducing the coefficient of linear expansion) of the molded article, and also contributes to improving mechanical properties such as rigidity and impact strength. Since the inorganic filler (D) has the above-mentioned specific average particle size (and aspect ratio), it has particularly excellent dimensional stability due to the synergistic effect with other components, and has excellent rigidity and impact strength. A high degree of physical property balance is achieved, and appearance defects during injection molding are suppressed.

As the inorganic filler (D), any shape of inorganic filler such as plate, rod, fiber, whisker, etc. can be used as long as it satisfies the above average particle diameter and aspect ratio. Moreover, inorganic fillers commercially available as fillers for polymers can also be used. Furthermore, in addition to the general roving shape, a chopped strand shape or the like that is more convenient to handle can also be used.

The inorganic filler (D) may be a mixture of two or more types of inorganic fillers as long as they satisfy the above average particle size and aspect ratio as a whole.

The method for producing the inorganic filler (D) is not particularly limited, and it can be produced by various known methods. When using, for example, talc as the inorganic filler (D), talc having a specific average particle size and aspect ratio can be produced by pulverization or granulation. Specifically, for example, there is a method in which talc raw stone is pulverized with an impact pulverizer or a micron mill type pulverizer, and then further pulverized with a jet mill, and then classified and adjusted with a cyclone, a micron separator, or the like. The aspect ratio and average particle size of talc can be appropriately adjusted by changing the grinding device and grinding time, and if necessary, talc with a controlled shape can be obtained by classification.

As the inorganic filler (D), one obtained by pulverizing raw stone may be used directly, or one that has been at least partially surface-treated may be used. For surface treatment, various surface treatment agents such as organic titanate coupling agents, organic silane coupling agents, modified polyolefins grafted with unsaturated carboxylic acids or their anhydrides, fatty acids, fatty acid metal salts, and fatty acid esters are used. Can be used. One type of surface treatment agent may be used alone, or two or more types may be used in combination.

<Nucleating agent (E)>
The polypropylene resin composition of the present invention may further contain a nucleating agent (E) as necessary, within a range that does not impair the object of the present invention.

The nucleating agent (E) is used, for example, for the purpose of further improving the dimensional stability (reducing the coefficient of linear expansion) and improving the impact strength of the polypropylene resin composition and its molded product. Specific examples of the nucleating agent (E) include compounds represented by the chemical structural formula (2) below, and various nucleating agents such as inorganic, sorbitol, carboxylic acid metal salts, and organic phosphates. It will be done.

(In formula (2), n is an integer of 0 to 2, R ¹ to R ⁵ may be the same or different from each other, and hydrogen atoms or alkyl groups having 1 to 20 carbon atoms, alkenyl groups, alkoxy group, carbonyl group, halogen group, or phenyl group, and R ⁶ is an alkyl group having 1 to 20 carbon atoms.)

Furthermore, examples of the inorganic nucleating agent include silica. Examples of sorbitol-based nucleating agents include 1,3,2,4-dibenzylidene-sorbitol, 1,3,2,4-di-(p-methyl-benzylidene)sorbitol, and 1,3,2,4-di- (p-ethyl-benzylidene) sorbitol, 1,3,2,4-di-(2',4'-di-methyl-benzylidene) sorbitol, 1,3-p-chlorobenzylidene-2,4-p-methyl -benzylidene-sorbitol and 1,3,2,4-di-(p-propylbenzylidene) sorbitol. Examples of carboxylic acid metal salt-based nucleating agents include aluminum mono-hydroxy-di-pt-butyl benzoate, sodium benzoate, and calcium montanate. Examples of organic phosphate nucleating agents include sodium bis(4-t-butylphenyl) phosphate, sodium-2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate, and lithium- 2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate is mentioned. The nucleating agent (E) may be used alone or in combination of two or more.

Among these, the compound represented by the chemical structural formula (2) is preferred from the viewpoint of improving dimensional stability (reducing linear expansion coefficient) and improving impact strength. Further, n is an integer of 0 to 2, R ¹ , R ² , R ⁴ and R ⁵ are hydrogen atoms, R ³ and R ⁶ may be the same or different from each other, and have 1 to 2 carbon atoms. More preferred are compounds with 20 alkyl groups. Further, n is an integer of 0 to 2, R ¹ , R ² , R ⁴ and R ⁵ are hydrogen atoms, and R ³ is -CH ₃ , -CH ₂ CH ₃ , -CH ₂ CH ₂ CH ₃ , -CH ₂ CH ₂ CH ₂ CH ₃ , -CH ₂ CH=CH ₂ , -CH(CH ₃ )CH=CH ₂ , -CH ₂ CH(X ¹ )-CH ₂ (X ² ), -CH ₂ CH (X ³ )-CH ₂ CH ₃ , -CH ₂ CH(X ⁴ )-CH ₂ OH, or -CH ₂ (OH)-CH(OH)-CH ₂ OH (X ¹ to X ⁴ are each independent) is a halogen group), and R ⁶ is an alkyl group having 1 to 20 carbon atoms.

The content of the nucleating agent (E) is not particularly limited, but is usually 0.05 to 0.5 parts by mass, preferably 0.1 to 0.5 parts by mass, based on a total of 100 parts by mass of components (A) to (D). 4 parts by mass. When the content of the nucleating agent (E) is 0.05 part by mass or more, the effect of reducing the coefficient of linear expansion tends to be more pronounced. Moreover, if it is 0.5 part by mass or less, the impact strength and economical efficiency of the molded article tend to be less likely to decrease.

The polypropylene resin composition may contain heat stabilizers, antistatic agents, weather stabilizers, light stabilizers, anti-aging agents, antioxidants, fatty acid metal salts, softeners, dispersants, fillers, Other additives such as colorants, lubricants, pigments, etc. can be incorporated within the range that does not impair the purpose of the present invention. The order of mixing the additives is arbitrary; they may be mixed at the same time, or a multi-stage mixing method may be used, such as mixing some components and then mixing other components.

<Polypropylene resin composition>
The polypropylene resin composition of the present invention comprises 5 to 47 parts by mass of a propylene polymer (A), 0 to 30 parts by mass of a propylene homopolymer (B), and 23 to 30 parts by mass of an ethylene/α-olefin copolymer (C). parts by mass, and 30 to 40 parts by mass of the inorganic filler (D) [however, the total amount of components (A) to (D) is 100 parts by mass. ] Contains.

The polypropylene resin composition of the present invention preferably contains 7 to 35 parts by mass of a propylene polymer (A), 10 to 30 parts by mass of a propylene homopolymer (B), and ethylene/α-olefin copolymer (C). 23 to 28 parts by mass, and 30 to 38 parts by mass of the inorganic filler (D) [However, the total amount of components (A) to (D) is 100 parts by mass. ] Contains.

The polypropylene resin composition of the present invention more preferably contains 8 to 28 parts by mass of a propylene polymer (A), 15 to 30 parts by mass of a propylene homopolymer (B), and ethylene/α-olefin copolymer (C ) 24 to 28 parts by mass, and 32 to 38 parts by mass of the inorganic filler (D) [However, the total amount of components (A) to (D) is 100 parts by mass. ] Contains.

The polypropylene resin composition of the present invention particularly preferably contains 10 to 22 parts by mass of a propylene polymer (A), 20 to 30 parts by mass of a propylene homopolymer (B), and an ethylene/α-olefin copolymer (C ) 24 to 27 parts by mass, and 32 to 36 parts by mass of the inorganic filler (D) [However, the total amount of components (A) to (D) is 100 parts by mass. ] Contains.

The polypropylene resin composition of the present invention can be produced by blending each of the above-mentioned components (A) to (D), and if necessary, component (E) and other optional components. Each component may be blended sequentially in any order, or may be mixed simultaneously. Alternatively, a multi-step mixing method may be adopted in which some components are mixed and then other components are mixed. Specifically, for example, after first blending components (A) to (C), which are resin components (organic compound components) in a polypropylene resin composition, component (D) and optionally component ( It can also be produced by adding and blending E).

As a method for blending each component, for example, a method of mixing or melt-kneading each component simultaneously or sequentially using a mixing device such as a Banbury mixer, single-screw extruder, twin-screw extruder, high-speed twin-screw extruder, etc. Can be mentioned.

The melt flow rate (MFR) (230° C., 2.16 kg load) of the entire polypropylene resin composition of the present invention is 25 to 60 g/10 minutes, preferably 30 to 60. It is preferable to set the MFR within such a range, particularly to set the MFR relatively high, from the viewpoint of, for example, moldability.

The method for molding the polypropylene resin composition of the present invention is not particularly limited, and various known methods can be used as methods for molding the resin composition. In particular, the molded article obtained from the polypropylene resin composition of the present invention has excellent dimensional stability with little dimensional change due to temperature changes. Injection molding and press molding are particularly preferred as the molding method.

The polypropylene resin composition of the present invention can be suitably used in various fields such as interior and exterior parts of automobiles (particularly exterior parts of automobiles) and household appliance parts.

<Automotive exterior parts>
The automobile exterior member of the present invention is a molded article obtained by injection molding or press molding the polypropylene resin composition of the present invention.

The automobile exterior member (and molded article for other uses) of the present invention preferably has linear expansion coefficients of 2.5×10 ⁻⁵ /°C or more in both the flow direction (MD) and the orthogonal direction (TD) to 3. .0×10 ⁻⁵ /°C or less. This coefficient of linear expansion is a value determined by measurement using the TMA method in a measurement range of -30°C to 90°C.

The molded article obtained from the polypropylene resin composition of the present invention is suitable for applications such as automobile interior and exterior parts, particularly automobile exterior parts. Specific examples of automobile exterior members include bumpers, side moldings, back doors, fenders, and back panels.

Hereinafter, the present invention will be explained in more detail based on Examples. However, the present invention is not limited to these examples. In Examples , Reference Examples , and Comparative Examples, each physical property was measured and evaluated by the following method.

<Melt flow rate (MFR) (g/10 minutes)>
Measurement was carried out in accordance with ISO 1133 under the conditions of a test load of 2.16 kg and a test temperature of 230°C.

<Decane soluble portion amount (D _sol ) and insoluble portion amount (D _insol )>
In a glass measuring container, approximately 3 g of the sample [component (A)] (measured to the nearest 10 ^-4 g. This mass was expressed as x ₂ (g) in the formula below), 500 ml of n-decane, A small amount of a heat-resistant stabilizer soluble in n-decane was charged, and the temperature was raised to 150 °C for 2 hours under nitrogen atmosphere while stirring with a stirrer to dissolve the sample. After holding at 150 °C for 2 hours, It was slowly cooled to 23°C over 8 hours. The obtained precipitate-containing liquid was filtered under reduced pressure using a 25G-4 standard glass filter manufactured by Iwata Glass Co., Ltd. 100 ml of the filtrate was collected and dried under reduced pressure to obtain a portion of the decane soluble component, and its mass was measured to the nearest 10 ^-4 g (this mass was expressed as x ₁ (g) in the formula below). did). Using this measured value, the amount of decane soluble portion (D _sol ) and the amount of insoluble portion (D _insol ) at room temperature (ie, 23° C.) were determined by the following formula.
D _sol (mass%) = 100×(500×x ₁ )/(100×x ₂ )
D _insol (mass%) = 100-D _sol

[Intrinsic viscosity [η]]
Approximately 20 mg of the sample was dissolved in 15 ml of decalin, and the specific viscosity η _sp was measured in an oil bath at 135°C. This decalin solution was diluted by adding 5 ml of decalin solvent, and then the specific viscosity η _sp was measured in the same manner. This dilution operation was repeated two more times, and the value of η _sp /C when the concentration (C) was extrapolated to 0 was determined as the intrinsic viscosity [η].
[η]=lim(η _sp /C) (C→0)

<Average particle size of inorganic filler>
In accordance with JIS R1620 and JIS R1622, the particle size value at a cumulative amount of 50% by mass read from a particle size cumulative curve measured by laser diffraction method was defined as the average particle size.

<Aspect ratio of inorganic filler>
Photographs were taken using an electron microscope, the long axis and thickness of the powder were measured, the average value was determined, and the aspect ratio was determined from the ratio of average particle size/average thickness.

<Bending elastic modulus (MPa)>
Flexural modulus (MPa) was measured according to ISO 178 under the following conditions.
Temperature: 23℃
Test piece: 80mm (length) x 10mm (width) x 4mm (thickness)
Bending speed: 2.0mm/min
Between spans: 64cm

<Linear expansion coefficient ( ^10-5 /℃)>
Evaluation was performed using the TMA method (measurement ranges -30 to 20°C and 20 to 90°C) in accordance with JIS K 7197. Specifically, a flat plate was obtained by injection molding at a resin temperature of 210°C and a mold temperature of 40°C using a mold cavity with a length of 240 mm, a width of 80 mm, and a thickness of 3 mm. A test piece was cut out in the shape of , and the linear expansion coefficient of -30 to 20°C and 20 to 90°C was measured for this test piece after heat treatment at 90°C for 20 minutes before the test.

<Appearance evaluation (flow mark)>
The appearance of the molded product was visually observed and evaluated based on the following criteria.
"○": There were almost no flow marks.
"×": Flow marks were clearly confirmed.

In Examples , Reference Examples , and Comparative Examples, the following components were used.

<Component (A)>
"A-1": Propylene-ethylene block copolymer (MFR = 85 g/10 min, n-decane soluble portion amount = 9.0 mass%, n-decane soluble portion ethylene content = 40 mol%, n - Intrinsic viscosity of decane soluble part [η] = 7.5 dl/g)

<Component (B)>
"B-1": Propylene homopolymer (manufactured by Prime Polymer Co., Ltd., Prime Polypro (registered trademark) J13B, MFR = 200 g / 10 minutes, density = 0.89 g / cm ³ )
"B-2": Propylene homopolymer (manufactured by Prime Polymer Co., Ltd., Prime Polypro (registered trademark) J137G, MFR = 30 g/10 minutes, density = 0.89 g/cm ³ )

<Component (C)>
"C-1": Ethylene-butene-based random copolymer (manufactured by Mitsui Chemicals, Inc., Tafmer (registered trademark) A-4050S, ethylene content = 80 mol%, 1-butene content = 20 mol%, MFR = 7 g/ 10 minutes, density = 0.862g/cm ³ )
"C-2": Ethylene-octene random copolymer (manufactured by Dow Chemical, ENGAGE (registered trademark) EG8137, ethylene content = 85 mol%, 1-octene content = 15 mol%, MFR = 26 g / 10 minutes, Density=0.864g/ ^cm3 )

<Component (D)>
"T-1": Talc (manufactured by Imerys, trade name HAR 3G77L, average particle size (laser diffraction method) = 11.8 μm, aspect ratio (SEM measurement) = 15.3)
"T-2": Talc (manufactured by Imerys, trade name Jetfine 3CA, average particle size (laser diffraction method) = 4.5 μm, aspect ratio (SEM measurement) = 9.0)

[Examples 1 to 3, Reference Example 4, Comparative Examples 1 to 3]
The propylene polymer (A), propylene homopolymer (B), ethylene/α-olefin copolymer (C), inorganic filler (D), and nucleating agent (E) were mixed in the amounts shown in Table 1 (by weight). ) and extruded using a twin-screw extruder (manufactured by Japan Steel Works, Ltd., TEX (registered trademark) 30α) at a cylinder temperature of 180°C, screw rotation of 750 rpm, and extrusion rate of 60 kg/h to obtain a polypropylene resin composition. I got something.

Table 1 shows the physical properties of injection molded articles produced from each of the obtained polypropylene resin compositions. Further, external photographs of the injection molded bodies of Example 3 and Comparative Example 3 are shown in FIG.

As is clear from the results shown in Table 1, in Examples 1 to 3 and Reference Example 4, in which talc (D-1) with large particle size and high aspect ratio was used as the inorganic filler (D), There were almost no flow marks and the coefficient of linear expansion was low.

On the other hand, in Comparative Examples 1 to 3 in which talc (D-2) with a small particle size and low aspect ratio was used as the inorganic filler (D), flow marks were clearly confirmed on the molded products, and the coefficient of linear expansion was also low. It was relatively expensive.

For example, Example 1 and Comparative Example 1 are compositions having the same composition except that the type of inorganic filler (D) is different. Therefore, by comparing Example 1 and Comparative Example 1, it can be seen that Example 1, which uses talc (D-1) with a large particle size and high aspect ratio, is superior in terms of appearance and coefficient of linear expansion. .

Further, Example 2 is an example in which the fluidity was adjusted by changing the blending ratio of the two propylene homopolymers (B-1) and (B-2) of Example 1. Example 3 is an example in which the rubber properties were increased by increasing the amount of the ethylene-butene random copolymer (C-1). Reference Example 4 is an example in which fluidity was increased by changing the type and amount of the ethylene/α-olefin copolymer (C) and the amount of the propylene homopolymer (B-1).

Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 are compositions having the same composition except that the type of inorganic filler (D) is different. Therefore, by comparing the evaluation results of Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, it was found that Examples 2 and 3 using talc (D-1) with large particle size and high aspect ratio It can be seen that this material is superior in terms of appearance and coefficient of linear expansion.

The polypropylene resin composition of the present invention is useful as a molded material in various fields such as automobile interior and exterior parts such as bumpers, side moldings, back doors, fenders, and back panels, household goods, and home appliance parts. In particular, it can be suitably used for automobile exterior parts.

Claims (5)

10 to 22 parts by mass of a propylene polymer (A) having a melt flow rate (230 ° C., 2.16 kg load) of 50 to 150 g/10 minutes and a decane soluble content of 6% by mass or more,
20 to 30 parts by mass of a propylene homopolymer (B) having a melt flow rate (230 ° C., 2.16 kg load) of 10 to 500 g/10 minutes,
It is a random copolymer of ethylene and α-olefin having 4 to 8 carbon atoms, with a density of 0.850 to 0.890 g/cm ³ and a melt flow rate (230°C, 2.16 kg load) of 0. 24 to 27 parts by mass of ethylene/α-olefin copolymer (C) having a rate of 5 to 30 g/10 minutes, and
32 to 36 parts by mass of an inorganic filler (D) having an average particle diameter of more than 8 μm and an aspect ratio of more than 9.0 [However, the total amount of components (A) to (D) is 100 parts by mass. ]
Contains
The α-olefin of the ethylene/α-olefin copolymer (C) is 1-butene,
A polypropylene resin composition whose melt flow rate (230°C, 2.16 kg load) of the entire composition is 25 to 60 g/10 minutes. The polypropylene resin composition according to claim 1, wherein the inorganic filler (D) has an average particle diameter of more than 10 μm. The polypropylene resin composition according to claim 1 or 2, wherein the propylene polymer (A) is a block copolymer obtained from propylene and ethylene. The polypropylene resin composition according to any one of claims 1 to 3 , which is used for automobile exterior parts. An automobile exterior member obtained by injection molding or press molding the polypropylene resin composition according to claim 4 .