JPH06299040A - Thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To provide a thermoplastic resin compsn. the problem with flow mark in injection molding of which is overcome. CONSTITUTION:The compsn. comprises 50-75wt.% propylene-ethylene block copolymer obtd. by a multistage plymn., 20-35wt.% olefin elastomer, and 5-20wt.% inorg. filler provided that the block copolymer has a die swell ratio (at 210 deg.C, a shear rate of 10<3>s<-1> and an L/D of capillary of 40/0.8) of 1.4 or higher and contains propylene-ethylene random copolymer parts having an intrinsic viscosity of 4.0 or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin composition, and more particularly to a thermoplastic resin composition having improved flow marks during injection molding.

[0002]

BACKGROUND OF THE INVENTION Polypropylene is widely used in various fields because it is lightweight and has excellent mechanical strength and the like. However, since it is inferior in impact resistance, various rubbers such as ethylene-propylene copolymer rubber (EPR) and other inorganic fillers such as talc are added to the propylene-ethylene block copolymer for the purpose of improving the impact resistance. A polypropylene resin composition has been proposed.

JP-A-61-12742 discloses (a) ethylene content 2
~ 3 wt%, melt flow rate 40-45 g / 10 min propylene-ethylene block copolymer 62-57 wt%, (b)
Ethylene content 70-80% by weight, Mooney viscosity ML _{1 + 4} (100
℃) 55-58 ethylene-propylene copolymer rubber 26-28
% By weight, (c) density 0.955 to 0.960 g / cm ³ , high density polyethylene 2 to 3% by weight, melt flow rate 18 to 22 g / 10 min, (d) average particle size 1.8 to 2.2 μm, specific surface area 36000 to 42
000 cm ² / g of talc 10-12% by weight, melt flow rate 13-18 g / 10 min, density 0.950-0.980 g / cm ³ ,
Flexural modulus 11500 to 14000 kg / cm ² , linear expansion coefficient between 20 to 80 ° C 7 × 10 ^-5 to 10 × 10 ^-5 cm / cm / ° C and JIS-Z8741
Disclosed is a resin composition having a surface gloss of 55% or more by a 60 ° -60 ° method.

JP-A-1-149845 discloses that (a) 5 to 12% by weight of a boiling xylene-soluble component having an ethylene content of 20 to 60% by weight and an ethylene content of the whole polymer of 1 to 7% by weight. And 59-74% by weight of propylene-ethylene block copolymer having a melt flow rate of 15-50 g / 10 min, and (b) propylene content of 20-60% by weight and Mooney viscosity ML _{1 + 4} (100 ° C).
100-150 ethylene-propylene copolymer rubber
-20% by weight and (c) 3-6% by weight of talc having a specific surface area of 30,000 cm ² / g or more and an average particle size of 0.5 to 2.0 μm are disclosed.

However, JP-A-61-12742 and JP-A-61-12742
In the system such as the resin composition of 1-149845, which comprises propylene-ethylene block copolymer, ethylene-propylene copolymer rubber (adding high-density polyethylene etc. if necessary) and talc, propylene- By adjusting the ratio of ethylene and propylene, the molecular weight and the like in the ethylene block copolymer and the ethylene-propylene copolymer rubber, a composition having fluidity suitable for each use is obtained. However, the above composition has a problem that flow marks are likely to occur when injection molding.

Therefore, the flow marks are concealed by forming a grain on the surface of molding resistance or by applying a coating. However, these methods are sufficient especially when manufacturing a large injection molded product. It may not be possible to obtain the concealing effect of the flow mark, and these methods may not be adopted depending on the intended use.

Therefore, an object of the present invention is to provide a thermoplastic resin composition having improved flow marks during injection molding.

[0008]

In view of the above object, the present inventors have proposed a composition containing a multi-stage polymerized propylene-ethylene block copolymer, an olefin elastomer, and an inorganic filler such as talc. As a result of diligent research on what kind of physical property should be used to reduce the flow mark at the time of molding, as a propylene-ethylene block copolymer, a die swell ratio in a predetermined range and a predetermined range. It was found that flow marks hardly occur when a polymer having an intrinsic viscosity of the propylene-ethylene random copolymer part of is used, and the present invention was conceived.

That is, the thermoplastic resin composition of the present invention comprises (a) 50 to 75% by weight of a propylene-ethylene block copolymer obtained by multistage polymerization, and (b) 20 to 35% by weight of an olefin elastomer. (c) An inorganic filler containing 5 to 20% by weight, wherein the (a) propylene-ethylene block copolymer obtained by multistage polymerization is
Die swell ratio of 1.4 or higher (210 ° C, shear rate 10
³ s ⁻¹ , L / D of the capillary = 40 / 0.8), and the propylene-ethylene random copolymer portion in the propylene-ethylene block copolymer has an intrinsic viscosity of 4.0 or more. To do.

The present invention is described in detail below. [1] Composition component (a) Propylene-ethylene block copolymer The (a) propylene-ethylene block copolymer used in the present invention is synthesized by multistage polymerization.

The propylene-ethylene block copolymer synthesized by the above multi-stage polymerization is substantially composed of a crystalline homopolypropylene portion, a propylene-ethylene random copolymer portion and a small amount of a crystalline ethylene homopolymer portion. And each part may exist as a single polymer, or may be in a state where each part is bonded. The above-mentioned parts are basically composed of propylene and / or ethylene, but may contain a small amount of other α-olefin, diene-based monomer or the like.

Crystalline Propylene Homopolymer Part The propylene homopolymer part includes a propylene homopolymer or a propylene copolymer containing a small amount (about 5 mol% or less) of a comomer component. As the comonomer component, other α such as butene-1 and octene-1
-Olefin, diene-based monomers and the like can be mentioned.

The propylene homopolymer portion is 0.8 to
It preferably has an intrinsic viscosity [η] _H of 1.5 l / g. When the intrinsic viscosity is less than 0.8 dl / g, ductility is insufficient, and when it is 1.5 dl / g
When it exceeds, the fluidity of the composition becomes insufficient, which is not preferable.

Propylene-Ethylene Random Copolymerization Portion The propylene-ethylene random copolymerization portion is a low crystalline portion and preferably has an ethylene content of 25 to 65% by weight. Less than 25% by weight of ethylene or
If it exceeds 65% by weight, ductility is particularly insufficient, which is not preferable. Further, the propylene-ethylene random copolymer portion may contain a small amount (about 5 mol% or less) of a comonomer component. As a comonomer component, butene-
Other α-olefins such as 1, octene-1, diene-based monomers and the like.

The intrinsic viscosity [η] _CXS of the propylene-ethylene random copolymer portion is 4.0 or more, preferably 4.0.
It is ~ 10.0 dl / g. If the intrinsic viscosity of the propylene-ethylene random copolymer portion is less than 4.0 dl / g, flow marks are likely to occur. If the intrinsic viscosity exceeds 10.0 dl / g,
It is not preferable because the composition has insufficient fluidity.

Crystalline ethylene homopolymer part The ethylene homopolymer part is an optional component, and is a component which is slightly synthesized during the synthesis of the propylene-ethylene random copolymer part. Examples of the crystalline ethylene homopolymer portion include a homopolymer of ethylene or an ethylene copolymer containing a small amount (about 5 mol% or less) of a comomer component. Examples of the comonomer component include other α-olefins such as butene-1 and octene-1, and diene-based monomers.

The content of ethylene in the whole multistage propylene-ethylene block copolymer containing each of the above-mentioned moieties is 1 to 16% by weight, and particularly 2.0 to 1
It is preferably 2.5% by weight. Further, regarding the content of the crystalline propylene homopolymer portion and the propylene-ethylene random copolymer portion, the sum of + is 10
0% by weight of the crystalline propylene homopolymer part
It is preferably 75 to 95% by weight, and the propylene-ethylene random copolymerization portion is 5 to 25% by weight. If it is outside the above range, the balance of physical properties is deteriorated. When the crystalline ethylene homopolymer part is contained, its content is about 5% by weight or less.

The multi-stage polymerized propylene-ethylene block copolymer has a die swell ratio of 1.4 or more, preferably 1.4 to 2.4 (210 ° C., shear rate 10 ³ s ⁻¹ , L / D of the capillary = 40 / 0.8. ) Has. Die swell ratio
If it is less than 1.4, flow marks are likely to occur. If the die swell ratio exceeds 2.4, the moldability of the composition will be insufficient, which is not preferable.

Further, the melt flow rate (MFR, 230 ° C., multi-stage polymerized propylene-ethylene block copolymer,
2.16 kg load) is preferably 15 to 90 g / 10 minutes. M
If the FR value is less than 15 g / 10 minutes, the moldability of the resulting composition, particularly the injection moldability, will decrease, and if it exceeds 90 g / 10 minutes, the mechanical strength will decrease, such being undesirable.

The total melt flow rate of components other than the propylene-ethylene random copolymerization portion (crystalline propylene homopolymer + crystalline ethylene homopolymer) is preferably 20 to 220 g / 10 minutes.

The multi-stage polymerized propylene-ethylene block copolymer as described above is obtained by first polymerizing propylene in the presence of a Ziegler catalyst or the like to give a crystalline propylene homopolymer portion (which may contain a small amount of a comonomer component). ) Is produced and switched to ethylene + propylene in the next step to produce a random copolymerization moiety. The crystalline ethylene homopolymer portion is produced in a small amount in the step of synthesizing the random copolymer portion.

The crystalline propylene homopolymer portion, the propylene-ethylene random copolymer portion and the crystalline ethylene homopolymer portion are, for example, propylene-
The ethylene block copolymer is dissolved in boiling xylene, and after cooling, the crystalline propylene homopolymer part and the crystalline ethylene homopolymer part are separated as the insoluble part, and the insoluble part is reheated to 100 ° C. to remove the crystalline propylene homopolymer. The polymer portion can be separated as an insoluble portion.

(B) Olefin-based elastomer As the olefin-based elastomer, a copolymer rubber of two or more kinds of α-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and the above-mentioned mono Two types of olefin (preferably ethylene and propylene) and dicyclopentadiene, 1,4
-Hexadiene, cyclooctadiene, methylene norbornene, ethylidene norbornene and other non-conjugated dienes, or copolymer rubbers with conjugated dienes such as butadiene and isoprene, etc. may be mentioned. Typically, ethylene-propylene copolymer rubber (EPR), ethylene-butene copolymer rubber (EBR), ethylene-propylene-diene copolymer rubber (EPDM) and the like can be mentioned.

Ethylene-propylene copolymer rubber (EP
R) preferably has an ethylene content of 60 to 80 mol% and a propylene content of 20 to 40 mol%. A more preferable range is 72 to 78 mol% of ethylene and 22 of propylene.
~ 28 mol%. Such ethylene-propylene copolymer rubber has a content of 0.3 to 9.0 g / 10 min, especially 0.4 to 8.6 g.
It preferably has a melt flow rate (MFR, 230 ° C., 2.16 kg load) of / 10 minutes.

The ethylene-propylene-diene copolymer rubber (EPDM) is an olefin elastomer obtained by copolymerizing the ethylene-propylene copolymer rubber with a diene compound in an amount of 20 mol% or less. The ethylene-propylene-diene copolymer rubber is 0.3 to 3.
It preferably has a melt flow rate (MFR, 230 ° C., 2.16 kg load) of 0 g / 10 min, in particular 0.4 to 2.5 g / 10 min.

Ethylene-butene copolymer rubber (EBR)
Preferably has an ethylene content of 78 to 86 mol% and a butene-1 content of 14 to 22 mol%. Particularly, those having an ethylene content of 80 to 84 mol% and a butene-1 content of 16 to 20 mol% are preferable. Incidentally, the ethylene-butene copolymer rubber, in addition to ethylene and butene-1, hexene-1,
Other α-olefins such as octene-1 and diene compounds such as ethylidene norbornene and dicyclopentadiene may be contained in small amounts. Such ethylene-butene copolymer rubber has a content of 1.0 to 80 g / 10 min, especially 2.0 to 50 g / 10.
It preferably has a melt flow rate (MFR, 230 ° C., 2.16 kg load) of minutes.

(C) Inorganic Filler Examples of the inorganic filler used in the present invention include talc, mica, various whiskers, glass fibers, calcium carbonate and the like. Of these, talc is preferred.

The talc preferably has an average particle size of 3.0 μm or less. If the average particle diameter of talc exceeds 3.0 μm, mechanical strength such as bending elastic modulus and dimensional stability are deteriorated, which is not preferable. Particularly preferred average particle size of talc is 1.
It is 0 to 2.0 μm. The average particle size referred to here is
It is a particle size obtained by centrifugal sedimentation type particle size distribution measurement.

[2] Blending Ratio The blending ratio of the various components as described above is (a) 50 to 75% by weight of the multistage propylene-ethylene block copolymer,
It is preferably 55 to 70% by weight, (b) the olefinic elastomer is 20 to 35% by weight, preferably 20 to 30% by weight, and (c) the inorganic filler is 5 to 20% by weight, preferably 5 to
15% by weight.

(A) The rigidity of the resulting composition when the multistage propylene-ethylene block copolymer is less than 50% by weight,
Hardness and the like tend to decrease, while if it exceeds 70% by weight, ductility decreases.

(B) 20% by weight of olefin elastomer
If it is less than 35% by weight, tensile properties such as tensile elongation at break and impact strength are lowered, while if it exceeds 35% by weight, hardness and rigidity are lowered.

Further, if the content of the inorganic filler (c) is less than 5% by weight, the rigidity and heat distortion resistance are not sufficient, and if it exceeds 20% by weight, the ductility decreases.

[3] Other Components The thermoplastic resin composition of the present invention may have other additives such as a heat stabilizer and an antioxidant for the purpose of modifying the thermoplastic resin composition.
A light stabilizer, a flame retardant, a plasticizer, an antistatic agent, a release agent, a foaming agent, etc. can be added.

[4] Production Method The composition of the present invention is used at 180 to 220 ° C., preferably 190 to 21 ° C. by using an extruder such as a single screw extruder or a twin screw extruder.
It can be obtained by melt-kneading at 0 ° C.

[5] Physical Properties The thermoplastic resin composition of the present invention obtained as described above has a melt flow rate (MFR, 230 ° C., 2.16 kg) of 7 to 40 g / 10 min, especially 9 to 30 g / 10 min. Load). When the MFR value is less than 7 g / 10 minutes, the moldability of the obtained composition, especially the injection moldability is deteriorated.
If it exceeds 0 minutes, the mechanical strength is lowered, which is not preferable.

Further, the thermoplastic resin composition of the present invention comprises 1.
3 or more, particularly 1.3 to 2.3 die swell ratio (210 ° C., shear rate 10 ³ s ⁻¹ , capillary L / D = 40/0.
It is preferable to have 8). If the die swell ratio is less than 1.3, flow marks are likely to occur in the injection molded product, which is not preferable. If the die swell ratio exceeds 2.3, the formability is deteriorated, which is not preferable.

Further, the thermoplastic resin composition of the present invention comprises 5.
0 × 10 ^{2 to} 2.0 × 10 ³ poise, especially 7.0 × 10 ^{2 to} 1.5 ×
It preferably has a viscosity of 10 ³ poise (measured by capillograph). If the viscosity is less than 5.0 × 10 ² poise, flow marks are likely to occur in the injection molded product, while 2.0 ×
When it exceeds 10 ³ poise, the moldability of the composition, particularly the injection moldability, is deteriorated, which is not preferable.

[0038]

In the present invention, a multi-stage polymerized propylene-ethylene block copolymer, a composition containing a predetermined amount of an olefin elastomer, and an inorganic filler, as a multi-stage polymerized propylene-ethylene block copolymer, Since the one having a predetermined range of die swell ratio and a predetermined range of the intrinsic viscosity of the propylene-ethylene random copolymerization portion is used, the resulting composition has almost no flow mark when injection-molded. And has good mechanical strength.

Although the reason why such an effect is obtained is not always clear, the propylene-ethylene block copolymer having the above-mentioned physical properties is injection-molded when it is used as a composition with an olefin elastomer and an inorganic filler. It is considered that the composition obtained has a uniform resin fluidity at the time of injection molding because it acts so as to have a suitable melt viscosity.

[0040]

The present invention will be described in more detail by the following examples. The following resins and talc were used as raw materials. [1] Two-stage polymerization propylene-ethylene block copolymer

Table 1 Physical Properties BPP-1 BPP-2 BPP-3 BPP-4 BPP-5 MFR ⁽¹⁾ 30 70 40 60 80 Cv ⁽²⁾ 15 10 15 15 5 5 Gv ⁽³⁾ 50 30 50 50 50 50 [Η] _CXS ⁽⁴⁾ 4 6 6 3 4 MFR _HOMO ⁽⁵⁾ 90 180 180 140 140 140 Die swell ratio ⁽⁶⁾ 1.4 1.7 1.7 1.4 1.3

Note) (1) MFR: 230 according to ASTM D1238
Measured at 2.degree. C. under a load of 2.16 kg (unit: g / 10 minutes). (2) Cv: Content of the copolymerized portion (propylene-ethylene random copolymerized portion) in the propylene-ethylene block copolymer (unit is% by weight). (3) Gv: Content of ethylene in the propylene-ethylene random copolymerization portion (unit is% by weight). (4) [η] _CXS : Intrinsic viscosity (unit: dl / g) of the copolymerized portion (propylene-ethylene random copolymerized portion) in the propylene-ethylene block copolymer. (5) MFR _HOMO : Melt flow rate (MFR, 230 ° C., 2.16 kg load) of homo moieties (crystalline propylene homopolymer moiety and crystalline ethylene homopolymer moiety) in propylene-ethylene block copolymer; unit is g / Ten
Minutes). (6) Die swell ratio: 210 ° C., shear rate 10 ³ s ⁻¹ , capillary L / D = 40 / 0.8.
(Dimensionless quantity).

[2] Olefin-based elastomer EPR-1: [propylene content 26% by weight, melt flow rate (MFR, 230 ° C., 2.16 kg load) 3.2 g / 10
Min] EPR-2: [propylene content 23% by weight, melt flow rate (MFR, 230 ° C., 2.16 kg load) 0.8 g / 10
Min] EBR-1: [butene content 20% by weight, melt flow rate (MFR, 230 ° C, 2.16 kg load) 7.1 g / 10 min]

[3] Talc Talc-1: [LMF100 manufactured by Fuji Talc Co., Ltd., average particle size 1.8 μm] Talc-2: [LMS300 manufactured by Fuji Talc Co., Ltd., average particle size 1.2 μm]

Examples 1 to 6 and Comparative Examples 1 to 7 Multi-stage polymerized propylene-ethylene block copolymers (BPP-1 to BPP-7) and olefinic elastomers (EPR-1, EPR-) in proportions shown in Table 2. 2 or EBR-1) and talc (talc-1 or talc-2) are dry-blended with a super mixer, and then charged into a twin-screw extruder (45 mmφ) for 180-
Kneading was performed at 220 ° C. and a screw rotation speed of 200 rpm to obtain pellets.

Next, the obtained pellets were molded by an injection molding machine at an injection temperature of 210 ° C. and an injection pressure of 60 kg / cm ² into test pieces for measuring physical properties described later.

For the test piece thus obtained,
Melt flow rate, die swell ratio and viscosity measurement,
The presence / absence of flow marks, rigidity and impact resistance were evaluated. The results are shown in Table 3.

Table 2 Composition (parts by weight) Example 1 Example 2 Example 3 Example 4 Example 5 Type of BPP BPP-1 BPP-1 BPP-2 BPP-2 BPP-2 Compounding amount 60 65 60 60 65 Type of EPR or EBR EPR-1 EPR-1 EBR-1 EBR-1 EPR-2 Compound amount 30 25 30 30 25 25 Type of talc Talc-1 Talc-1 Talc-1 Talc-2 Talc-1 Compound amount 10 10 10 10 10

Table 2 (continued) Composition (parts by weight) Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 BPP type BPP-3 BPP-4 BPP-5 BPP-3 BPP-3 Blend Amount 70 60 60 45 45 70 EPR or EBR type EPR-1 EPR-1 EPR-1 EPR-1 EPR-1 Compounding amount 25 30 30 35 15 15 Talc type Talc-2 Talc-1 Talc-1 Talc- 1 compounding amount 5 10 10 20 15

[0050]

Third physical property Example 1 Example 2 Example 3 Example 4 Example 5 M FR ⁽¹⁾ 15 17 30 30 20 20 Die swell ratio ⁽²⁾ 1.3 1.3 1.6 1.6 1.6 Viscosity (× 10 ² ) ⁽³⁾ 9.0 8.5 7.0 7.0 8.0 Presence of flow mark ⁽⁴⁾ No No No No No Stiffness evaluation ⁽⁵⁾ ○ ○ ○ ○ ○ Impact resistance evaluation ⁽⁶⁾ ○ ○ ○ ○ ○

Table 3 (continued) Physical Properties Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 M FR ⁽¹⁾ 25 30 40 40 15 25 Die swell ratio ⁽²⁾ 1.6 1.3 1.2 1.4 1.6 Viscosity (× 10 ² ) ⁽³⁾ 7.5 7.0 6.0 9.0 8.0 Flow mark presence / absence ⁽⁴⁾ No Yes Yes Yes No Stiffness evaluation ⁽⁵⁾ ○ ○ ○ ○ ○ Impact resistance evaluation ⁽⁶⁾ ○ ○ ○ ○ ×

Table 3 (continued) Physical Properties Comparative Example 5 Comparative Example 6 Comparative Example 7 M FR ⁽¹⁾ 10 22 15 Die swell ratio ⁽²⁾ 1.4 1.6 1.4 Viscosity (× 10 ² ) ⁽³⁾ 10.0 8.0 9.0 Presence or absence of flow mark ⁽⁴⁾ No No No Stiffness evaluation ⁽⁵⁾ × × ○ Impact resistance evaluation ⁽⁶⁾ ○ ○ ×

(1) MFR: 230 ° C. according to ASTM D1238, 2.
It was measured under a load of 16 kg (unit: g / 10 minutes). (2) Die swell ratio: 210 ° C., shear rate 10 ³ s ⁻¹ , capillary L / D = 40 / 0.8
(Dimensionless quantity). (3) Viscosity: Measured under conditions of 210 ° C. and shear rate of 10 ³ s ⁻¹ (unit is poise). (4) Presence or absence of flow mark: An injection-molded product of 35 cm × 10 cm × 0.3 cm was prepared, and visually observing the surface of the product, the flow mark was found ^ Yes ", and the flow mark was not found"
^ No ". (5) Evaluation of rigidity: Flexural modulus (unit: kgf / cm ² ) is determined by ASTM
The measurement was performed according to D790, and those having a value of 6000 kgf / cm ² or more were evaluated as ◯, and those less than that were evaluated as x. (6) Impact resistance evaluation: Izod impact strength (unit: kgf-
cm / cm) is measured according to ASTM D256 using a test piece with a thickness of 6.4 mm at -30 ° C with a notch, and the value is 5 kg.
Those with f-cm / cm or more were evaluated as ○, and those less than f-cm / cm were evaluated as ×.

As is clear from Table 3, Examples 1 to 6
The composition (1) has a MFR value, a die swell ratio and a viscosity value suitable for injection molding, has no flow mark,
The rigidity and impact resistance were good. In contrast,
In the compositions of each comparative example, those without flow marks had insufficient rigidity and / or impact resistance, and those with good rigidity and impact resistance had flow marks.

[0056]

As described above in detail, in the present invention, a multi-stage polymerized propylene-ethylene block copolymer, an olefin elastomer, and an inorganic filler are contained in predetermined amounts, respectively. As the polymerized propylene-ethylene block copolymer, one having a predetermined range of die swell ratio and a predetermined range of propylene-ethylene random copolymerized intrinsic viscosity is used, and thus the obtained composition is Almost no flow marks are formed when injection-molded, and it has good mechanical strength.

The thermoplastic resin composition of the present invention as described above is suitable for large-sized injection-molded articles, especially for various exterior parts of automobiles such as bumpers, side moldings, spoilers and mat guards.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kichiyoshi Kitano 3-1, Chidori-cho, Kawasaki-ku, Kanagawa Prefecture Tonen Kagaku Co., Ltd. Technology Development Center

Claims (1)

[Claims] 1. A propylene-ethylene block copolymer obtained by multi-stage polymerization of 50 to 75% by weight, (b) an olefinic elastomer of 20 to 35% by weight, and (c) an inorganic filler of 5 to 20% by weight. A thermoplastic resin composition containing and wherein (a) the propylene-ethylene block copolymer obtained by multistage polymerization has a die swell ratio of 1.4 or more.
(210 ° C, shear rate 10 ³ s ^-1 , capillary L / D =
40 / 0.8), and the propylene-ethylene random copolymer portion in the propylene-ethylene block copolymer has an intrinsic viscosity of 4.0 or more.