JP3485756B2 - Polypropylene resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polypropylene resin composition having excellent injection moldability.

[0002]

2. Description of the Related Art Polypropylene is widely used in various fields because of its low density and good mechanical properties and moldability. However, since it is inferior in impact resistance and heat resistance, the ethylene-propylene block copolymer obtained by the multi-stage polymerization for the purpose of improving it has a rubber component such as ethylene-propylene copolymer rubber or ethylene-butene copolymer rubber. Various polypropylene-based resin compositions to which an inorganic filler such as talc and talc are added have been proposed.

For example, Japanese Patent Laid-Open No. 1-149845 discloses
(A) 5 to 12% by weight of a boiling xylene-soluble component having an ethylene content of 20 to 60% by weight, an ethylene content of the whole polymer of 1 to 7% by weight, and a melt flow rate of 15
Propylene-ethylene block copolymer 59 to 74% by weight, and (b) propylene content is 2 to 50 g / 10 min.
0-60% by weight and Mooney viscosity ML _{1 + 4} (100
35 to 20% by weight of ethylene-propylene copolymer rubber having a temperature of 100 to 150), and (c) a specific surface area of 30,000.
Disclosed is a resin composition containing 3 to 6% by weight of talc having a mean particle size of 0.5 to 2.0 μm at a cm ² / g or more.

[0004]

In order to improve the impact resistance of conventional polypropylene, the content of the ethylene-propylene copolymer part of the ethylene-propylene block copolymer as a polypropylene component is increased, and the polypropylene is also used. Increasing the amount of rubber components such as ethylene-propylene copolymer rubber and ethylene-butene copolymer rubber added later to the components causes a problem that the fluidity deteriorates. Further, the addition of a large amount of rubber component causes a problem that heat resistance and surface hardness are lowered.

On the other hand, in order to improve the production efficiency, the size and thickness of molded products are further advanced, and the demand for higher performance of molding materials is increasing. In order to meet such a demand, it is essential that the molding material has higher fluidity and higher performance, but in the conventional composite material of ethylene-propylene block copolymer and polyolefin elastomer, There was a limit to the improvement of physical properties. Therefore, an object of the present invention is to provide a polypropylene resin composition having excellent moldability and good mechanical properties.

[0006]

Means for Solving the Problems The present inventors have
As a result of earnest research to solve the problem, a specific wide-angle X-ray diffraction
Main component is polypropylene with diffraction peak intensity ratio
The composition has excellent mechanical properties and injection moldability, and
The present invention has been completed by finding that it exhibits a high surface hardness function.
I made it. That is, the polypropylene resin composition of the present invention
Thing(A) MFR with MFR of 50-100g / 10 minutes
-Propylene block copolymers,
The isotactic fraction (IPF) of the polypropylene part
98% or more of the ethylene-propylene copolymer part
Crystalline ethylene-propylene with a proportion of 1 to 10% by weight
Block copolymer 54-64% by weight, (B) less
Both types are represented by the following formula (I) or (II)
Two different types of len-based block copolymer elastomers
17-24% by weight of 17-18
24% by weight and (C) talc 15 having an average particle size of 5 μm or less
It is a polypropylene resin composition consisting of
The mechanical properties measured by the ASTM method are as follows.
AndWith injection molding ASTM No. 1 dumbbell center
Calculated from the intensity ratio of diffraction peaks obtained by recent wide-angle X-ray diffraction
Polypropylene resin with a degree of b-axis orientation of 720 or more
It is a composition.Flexural modulus ≧ 1800 MPa Tensile strength ≧ 20 MPa 23 ° C Izod impact strength ≧ 180 J / m -30 ° C Izod impact strength ≧ 30 J / m Rockwell hardness (R scale) ≧ 74 Heat distortion temperature (HDT 18.5kg) ≧ 73 ℃ Brittleness temperature ≤ -20 ° C MFR = 30 ± 10g / 10min

[Chemical 5]

[Chemical 6] (In the above formula, PS is a polystyrene block, PE
B is a polyethylene butene block, and m ≧ 1
)

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene resin composition of the present invention will be described in detail below. [1] Physical Properties of Polypropylene Resin Composition The polypropylene resin composition of the present invention needs to have a b-axis orientation of the diffraction peak intensity ratio by wide-angle X-ray diffraction near the center of ASTM No. 1 dumbbell by injection molding of 720 or more. is there. Here, the b-axis orientation strength ratio is expressed by the following equation.

[0008]

[Equation 1] (In the formula, I (040) is 2θ = 1 by wide-angle X-ray diffraction.
The peak intensity due to the (040) plane at 3.93 is shown, and I (110) is 2θ = by wide-angle X-ray diffraction.
The peak intensity resulting from the (110) plane at 16.68 is shown. ) If the degree of b-axis orientation is less than 720, the strength, embrittlement temperature, and hardness of the injection-molded product are poor, which is not preferable.

Further, the composition of the present invention is measured by the ASTM method.
Specified mechanical properties satisfy the following conditions. Flexural modulus ≧ 1800 MPa Tensile strength ≧ 20 MPa 23 ° C Izod impact strength ≧ 180 J / m -30 ° C Izod impact strength ≧ 30 J / m Rockwell hardness (R scale) ≧ 74 Thermal deterioration temperature (HDT 18.5 kg) ≧ 73 ° C Brittleness temperature ≤ -20 ° C MFR = 30 ± 10g / 10min Outside of these values, molded products with excellent injection moldability can be obtained.
I can't.

[2] Composition Component of Polypropylene Resin Composition The composition of the present invention comprises (A) a specific crystalline ethylene-propylene block copolymer, (B) a specific thermoplastic elastomer and (C) talc. Obtained by melt-kneading. Each component will be described above.

(A) Ethylene-Propylene Block Copolymer The ethylene-propylene block copolymer (A) used in the present invention is substantially composed of (a) a crystalline propylene polymer portion and (b) ethylene-propylene. Although it is composed of a copolymer part, it may contain a small amount of (c) a crystalline ethylene homopolymer part. Examples of the crystalline propylene polymer portion (a) include a propylene homopolymer and a propylene copolymer containing a small amount (about 5 mol% or less) of a comonomer component. As the comonomer component, other α such as butene-1 and octene-1
-Olefins. The isotactic pentad fraction (IPF) of the portion (a) is 98% or more. I
When the PF is low, the degree of b-axis orientation of the entire composition is low, the surface hardness is insufficient, and scratch resistance becomes a problem.

Here, the isotactic pentad fraction (IPF) means Macromolecules, 6 , 9
25 (1973), that is, ¹³ C-NMR.
Is the isotactic fraction in the pentad unit in the polypropylene molecular chain as measured by the method using. In other words, the isotactic pentad fraction is the fraction of propylene monomer units at the center of a chain in which four propylene monomer units are continuously meso-bonded. However,
For the assignment of peaks, see Macromolecule
s, 8 , 687 (1975). Specifically, the isotactic pentad unit was measured as the intensity fraction of the mmmm peak in all the absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum.

The ethylene-propylene copolymer portion (b) is an ethylene-propylene random copolymer portion having low crystallinity. The ethylene content of the ethylene-propylene copolymer portion is 25 to 80% by weight, and the ethylene-propylene copolymer portion contains a small amount (5 mol%
A third component), such as butene-1, octene-
It may further contain an α-olefin such as 1 or the like.

The content of the (a) crystalline propylene polymer portion and the (b) ethylene-propylene copolymer portion of the (A) ethylene-propylene block copolymer containing the above-mentioned respective portions is ( a) + (b) total 100
% Of (a) crystalline propylene polymer part is 9% by weight.
It is 0 to 99% by weight. On the other hand, the (b) ethylene-propylene copolymer portion is 1 to 10% by weight. If the amount of the copolymer is large, the surface hardness and HDT are lowered, and there is a problem that the product is easily scratched. Further, (A) the ethylene-propylene block copolymer melt flow rate (230
℃, load 2.16kg, hereinafter referred to as MFR), 50 ~
It is 100 g / 10 minutes, preferably 60 to 90 g / 10 minutes. When the MFR value is less than 50 g / 10 min, the fluidity of the composition is deteriorated, the moldability, particularly the injection moldability is deteriorated, and the moldability and scratch resistance are insufficient. On the other hand, MFR is 100g / 1
If it exceeds 0 minutes, the mechanical strength is lowered, which is not preferable.

The ethylene-propylene copolymer portion may be replaced with an olefinic elastomer satisfying the above-mentioned ethylene content, such as ethylene-propylene copolymer rubber or ethylene-butene copolymer rubber. . In this case, the MF of the composition mixed in the above mixing ratio
The crystalline propylene homopolymer may be blended so that R is 50 to 100 g / 10 minutes. Such an (A) ethylene-propylene block copolymer is, for example, a compound containing a (a) crystalline propylene polymer portion (a propylene homopolymer or a small amount of a comonomer component) in one or more steps of a conventional propylene polymerization method. After the polymerization of (), it can be obtained by a multi-stage polymerization in which the ethylene-propylene copolymer part (b) is subsequently polymerized in one or more steps, and can also be produced by a method such as a gas phase method or a slurry method.

Incidentally, (a) a crystalline propylene polymer portion (b) an ethylene-propylene copolymer portion and (c)
The crystalline ethylene homopolymer part is obtained by, for example, dissolving (A) an ethylene-propylene block copolymer in boiling xylene, and after cooling (a) the crystalline propylene polymer part and (c) the crystalline ethylene homopolymer part. As an insoluble part
The (b) ethylene-propylene copolymer part of the soluble part is separated, and the insoluble part is reheated to 100 ° C., and the (a) crystalline propylene polymer part is used as the insoluble part, which can be separately quantified. .

(B) Thermoplastic Elastomer The (B) thermoplastic elastomer used in the present invention is (1) a styrene block copolymer elastomer or (1) a styrene block copolymer elastomer and (2) ethylene-α-. Mixtures of olefin copolymers can be used. The (1) styrene block copolymer elastomer used in the present invention is represented by the following structural formula (I) or structural formula (II).

[0018]

[Chemical 7]

[Chemical 8] (In the above formula, PS is a polystyrene block, PE
B is a polyethylene butene block and m ≧ 1) Such a styrenic block copolymer comprises a monovinyl-substituted aromatic hydrocarbon, preferably styrene and a conjugated diene hydrocarbon, preferably 1,3-butadiene. A block copolymer is hydrogenated.

In the present invention, a hydrogenated block copolymer prepared by hydrogenating a block copolymer of a styrene polymer block and a 1,3-butadiene elastomer block is used. In the present invention, such a hydrogenated block copolymer has two or more blocks of PS blocks and PEB blocks, preferably three or more blocks of PS blocks, PEB blocks and PS blocks as described above. It is preferable as the physical property used.

The hydrogenated block copolymer is a styrene-ethylene-butene block copolymer elastomer (hereinafter also referred to as SEBS) or styrene-
It is also called an ethylene-butene copolymer elastomer (hereinafter also referred to as SEB). The hydrogenation amount of this SEBS or SEB is 90 mol% or more, and preferably one having no unsaturated bond is preferable from the viewpoint of weather resistance, recyclability and the like. The MFR of (1) styrene block copolymer elastomer is 0.5 to 15 g / 10.
Min, preferably 1 to 12 g / 10 min. When the MFR is less than 0.5, the fluidity is insufficient, the moldability is deteriorated, and the impact resistance is also insufficient. On the other hand, MFR is 15g / 10
Exceeding the minutes is not preferable because ductility and impact resistance are insufficient. Further, (1) the content of the polystyrene portion constituting the styrene block copolymer elastomer is 1
0 to 30% by weight is preferable. When the content of the polystyrene portion is less than 10% by weight, impact resistance is deteriorated, while when it exceeds 30% by weight, stretching is insufficient, which is not preferable.

The ethylene-α-olefin copolymer (2) used as the thermoplastic elastomer component of the present invention is M
FR is 0.5 to 10 g / 10 minutes, preferably 1 to 3 g /
In 10 minutes, the ethylene content is 50 to 90% by weight. α
Examples of the olefin include α-olefins such as propylene, butene-1, and octene-1. (2) The ethylene-α-olefin copolymer component can be used in an amount of 1 to 10% by weight based on the total polypropylene resin composition, and if it exceeds 10% by weight, surface hardness and HDT will be insufficient.
Not good for scratching the product.

(C) Talc The (C) talc used in the present invention has an average particle size of 5 μm measured by a laser diffraction / scattering particle size distribution analyzer.
m or less. If the average particle size of talc exceeds 5 μm, rigidity and dimensional stability become insufficient, which is not preferable. Further, talc is preferable when surface-treated with a modified silicone, a titanate coupling agent, or the like, because the rigidity and heat resistance of the composition can be further improved. It is also possible to use a part of the component (A) as a master batch in advance.

The polypropylene resin composition of the present invention is
Depending on its use, such as interior and exterior materials for automobiles, for each 100 parts by weight of the above components (A), (B) and (C), an antioxidant, a heat stabilizer and a light stabilizer may be further added. It is preferable to add about 0.01 to 2 parts by weight.
If the amount of each of the components is less than 0.01 parts by weight, the respective effects are not sufficient, while if it exceeds 2 parts by weight, not only there is no further effect but also the physical properties of the composition are deteriorated, which is not preferable.

In this case, examples of the antioxidant used include phenol type and phosphorus type. Examples of phenol compounds include tetrakis- [methylene-3
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate] methane, 2,6-di-t-butyl-4
-Methyl-phenol, tris (3,5-di-t-butyl-4-hydroxyphenyl) isocyanurate and the like can be mentioned.

Further, phosphorus-based compounds such as tris (2,4-di-t-butylphenyl) phosphite,
4,4'-butylidene-bis (3-methyl-6-t-butylphenyl-di-tridecyl) phosphite, 1,
1,3-tris (2-methyl-4-ditridecyl-phosphite-5-t-butyl) and the like can be mentioned.

Examples of the heat stabilizer include sulfur-based ones such as distearyl thiopropionate and dilauryl thiopropionate.

Further, examples of the light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidine) sebacate and dimethyl-1 (2-hydroxyethyl) -4.
-Hydroxyl-2,2,6,6-tetramethylpiperidine and succinic acid condensate, poly [{6- (1,1,3,
3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6 , 6-Tetramethyl-4-piperidyl)
Imino}], N, N'-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N-
Examples include (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate.

The polypropylene resin composition of the present invention is
In addition to the above, other additives such as a release agent, an antistatic agent, a plasticizer, a flame retardant, a lubricant, a copper anticorrosive agent, an organic or inorganic pigment and its dispersant, etc. are added for the purpose of its modification. You can The above-mentioned various additives and pigments are generally added at the time of mixing the respective components, but a high-concentration master batch may be prepared in advance and post-blended at the time of injection molding.

[3] Blending Ratio The blending ratio of the various components as described above is 54 to 64% by weight of (A) ethylene-propylene block copolymer and 17 to 24% by weight of (B) thermoplastic elastomer. And (C) talc is 15 to 25% by weight. When the content of the ethylene-propylene block copolymer (A) is less than 54% by weight, rigidity, heat resistance, hardness and the like of the resulting composition tend to be lowered, while when it exceeds 64% by weight, strength, ductility and the like are lowered. Further, (B) the thermoplastic elastomer is 17
If it is less than wt%, the embrittlement temperature is high and the impact resistance is lowered, while if it exceeds 24 wt%, the strength, rigidity, heat resistance, hardness and the like are lowered. Furthermore, when an ethylene-α-olefin copolymer is used in combination as the thermoplastic elastomer component, it is preferable to use 1 to 10% by weight of the total polypropylene resin composition. Further, if the talc (C) is less than 15% by weight, the rigidity and heat resistance are deteriorated, while if it exceeds 25% by weight, the ductility is deteriorated.

[4] Manufacturing Method The polypropylene resin composition of the present invention is preliminarily dry-blended with the above-mentioned various components and then fed to a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, etc.
It can be produced by melt-kneading at 0 to 300 ° C, preferably 190 to 210 ° C.

[0031]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited thereto. The following materials were used as the raw material resin, talc and additives.

[1] Ethylene-propylene block copolymer (BPP)

[Table 1] (1) MFR: 230 ° C according to ASTM D1238,
Measured under a load of 2.16 kg (unit: g / 10 minutes). (2) Cv: Content of ethylene-propylene copolymer portion (room temperature xylene-soluble portion) in the ethylene-propylene block copolymer (unit:% by weight). (3) Gv: ethylene content of the ethylene-propylene copolymer portion (unit: weight%). (4) IPF: ¹³ C-NMR spectrum analysis method.

[2] Thermoplastic elastomer (1) Styrenic block copolymer elastomer

[Table 2]

(2) Ethylene-α-olefin copolymer

[Table 3]

[0035] [3] Talc: AT164; Asada Flour Milling (Average particle size by laser scattering method                             = 3.6 μm)               LMS200; made by Fuji Talc (average particle size by laser scattering method                             = 4.7 μm)

Examples 1 to 10 and Comparative Examples 1 to 6 The above raw materials were blended in the proportions shown in Tables 4 to 6, dry blended in a super mixer, and then twin-screw extruder (P.
CM-45, L ・ D = 32) and put at 200 ℃, 200
The mixture was kneaded at rpm to obtain pellets. At the time of blending, Ir1010 (made by Ciba Geigy) and Mar as antioxidants
k2112 (manufactured by Asahi Denka Co., Ltd.) was added in an amount of 0.1 phr each.

Next, the obtained pellets were injected into an injection molding machine (TOSHIBA MACHINE IS-280E / cylinder temperature 210).
C., mold temperature 30.degree. C.) and injection-molded to obtain test pieces for measuring physical properties. For each test piece thus obtained, the following physical property measurement and each test were performed, and the results are shown in Table 4 to
It shows in Table 6. Furthermore, the results of the injection molding and the appearance after molding were evaluated using a metal mold for an automobile bumper of t = 3 mm (for the front: width of about 1.7 m) (Kobe Steel 3500 t vertical injection molding machine / cylinder temperature). 210
Table 4 to Table 6 show molding under the conditions of ℃ and mold of 30 ℃.

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

(1) MFR: measured according to ASTM D1238 at 230 ° C. under a load of 2.16 kg (unit: g / 10
Minutes). (2) Tensile strength at yield: measured by ASTM D638 (unit is MPa). (3) Flexural modulus: measured by ASTM D790 (unit is MPa). (4) Bending strength: measured by ASTM D790 (unit is MPa). (5) Izod impact strength: 2 according to ASTM D256
Measured at 3 ° C and -30 ° C (unit is J / m). (6) Heat distortion temperature (HDT): Measured by ASTM D648 at 18.5 kg / cm ² (unit: ° C). (7) Rockwell hardness: measured by ASTM D785 (scale is R). (8) Brittleness temperature: measured by ASTM D746 (unit: ° C). (9) b-axis orientation: Wide-angle X-ray diffraction is performed near the central portion of the ASTM No. 1 dumbbell test piece obtained by injection molding. It was calculated from the ratio of the peak intensity due to the (040) plane at 2θ = 13.93 and the peak intensity at 2θ = 16.68 due to the (110) plane in the scattering spectrum.

(10) Scratch resistance In order to evaluate the scratch resistance of an injection-molded article, a pencil hardness test is performed at 23 ° C. after injection molding on a sample left for 72 hours or more. Fix the sample on a horizontal table, hold a pencil at an angle of about 45 degrees, press it as strongly as possible (about 3 Kgf) on the surface of the sample so that the core does not break, and at a uniform speed (about The sample surface is scratched by extruding about 1 cm at 1 cm / s). After each scratch, the tip of the pencil core is newly sharpened, and the test is repeated 5 times with a pencil having the same hardness symbol. The pencil hardness of the material, which is one step lower than the other five times and has scratches (clear pencil traces), is the pencil hardness of the material. However, the test pencil is JIS S 60
The pencil hardness is 9 of the hardness code.
H is the hardest, 6B is the softest, and the hardest one is the upper rank. Also, sharpen the pencil and make the core cylindrical in about 3 m.
exposed, and then a hard, flat surface with abrasive paper (maximum particle size 4
(6 μm or less), apply a core at a right angle and gently grind while drawing a circle so that the tip is flat and the corner is sharp. Empirically, if the pencil hardness is 2B or more, it is judged that the scratch resistance is not a problem.

(11) Impact resistance In the drop weight impact test at -20 ° C as an evaluation of the impact resistance of the injection-molded article, a hemispherical wick having a weight of 10 kg and a diameter of 10 cm was dropped from a height of 1 m to destroy it. The morphology was confirmed.

As is clear from Tables 4 to 6, the compositions of Examples 1 to 10 of the present invention showed good mechanical properties with the b-axis being 720 or more after that, and the obtained injection molding produced large thin-walled parts. The moldability and appearance were good, and the surface hardness and impact strength of the molded product were also excellent.

On the other hand, the compositions of Comparative Examples have a b-axis orientation of less than 720 and are poor in surface hardness, HDT, scratch resistance, impact strength and the like. Particularly, in Comparative Example 1, when the copolymerization component of the ethylene-propylene block copolymer is as large as 12% by weight, the surface hardness and HDT are lowered, and the product is easily scratched (pencil hardness is less than 2B). . In Comparative Example 2, since the MFR of the ethylene-propylene block copolymer is low, the MFR of the composition decreases and the moldability deteriorates. For this reason, the surface hardness is low and the moldability and scratch resistance are insufficient. Comparative Example 3
However, since the ethylene-propylene block copolymer has low stereoregularity, the surface hardness is insufficient, and the scratch resistance of the product becomes a problem. Comparative Example 4 shows that when the proportion of the thermoplastic elastomer is too large, the strength, elastic modulus, surface hardness and HDT are affected, and the product is easily scratched. Comparative Example 5 shows that if the proportion of the ethylene-α-olefin copolymer in the thermoplastic elastomer is too large, the surface hardness and HDT will be insufficient, and the scratchability of the product will not be good. No. 6 shows that when the proportion of the thermoplastic elastomer is small, the brittle temperature is high and the impact resistance is poor.

[0046]

EFFECT OF THE INVENTION The polypropylene-based oily composition of the present invention is excellent in moldability and has a good balance of mechanical properties. Therefore, since the range of injection molding conditions can be widened, particularly thin and large-sized products can be easily molded. Therefore, it is useful in products obtained by injection molding of industrial materials such as interior / exterior materials for automobile parts and home electric appliance parts.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Fujita 1 Toho-cho, Yokkaichi-shi, Mie Nihon Polychem Co., Ltd. Yokkaichi Technical Center (72) Inventor Shinya Kawamura 1-cho, Toyota-cho, Aichi Prefecture Toyota Motor Corporation Stock In-company (72) Inventor Takao Nomura 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (56) References JP 9-241473 (JP, A) JP 9-68248 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 1/00-101/16 C08K 3/00-13/08

Claims (2)

(57) [Claims] 1.(A) MFR is 50 to 100 g / 10 minutes
Which is an ethylene-propylene block copolymer of
Isotactic fraction (I
PF) is 98% or more and ethylene-propylene copolymerization
Crystalline ethylene in which the proportion of the body part is 1 to 10% by weight
54 to 64% by weight of a propylene block copolymer,
(B) at least one type is represented by the following formula (I) or (II)
It is a styrene block copolymer elastomer represented by
Two or more different types of thermoplastic elastomers 17 to 24
17% to 24% by weight and (C) the average particle size is 5 μm or less
Polypropylene tree consisting of 15-25% by weight of talc
It is a fat composition and has low mechanical properties measured by the ASTM method.
As described above, andASTM No. 1 Dan by injection molding
Diffraction peak intensity ratio by wide-angle X-ray diffraction near the center of the bell
The degree of b-axis orientation obtained from
Pyrene-based resin composition.Flexural modulus ≧ 1800 MPa Tensile strength ≧ 20 MPa 23 ° C Izod impact strength ≧ 180 J / m -30 ° C Izod impact strength ≧ 30 J / m Rockwell hardness (R scale) ≧ 74 Heat distortion temperature (HDT 18.5kg) ≧ 73 ℃ Brittleness temperature ≤ -20 ° C MFR = 30 ± 10g / 10min [Chemical 1] [Chemical 2] (In the above formula, PS is a polystyrene block, PE
B is polyethylene butene Block, and m ≧ 1
) 2. The thermoplastic elastomer component (B) has a melt flow rate (1) of 0.5 to 15 g / 10.
Content of polystyrene and polystyrene part is 10 to 30% by weight
And has the following formula (I) or (II) [Chemical 4] (PS in the above formula is a polystyrene block, PEB
Is a polyethylene butene block and m ≧ 1)
And a styrene block copolymer elastomer of (2) having a melt flow rate of 0.5 to 10 g / 10
And an ethylene-α-olefin copolymer having an ethylene content of 50 to 90% by weight, and (2) the ethylene-α-olefin copolymer component is 10% by weight based on the total polypropylene resin composition. The polypropylene-based resin composition according to claim 1 , wherein: