JP6442064B2 - High rigidity polypropylene resin composition with excellent flowability, heat resistance and external shape - Google Patents

Description

  The present invention relates to a polypropylene resin suitable for injection molding. More specifically, the present invention relates to a polypropylene resin for injection products that is excellent in flowability and heat resistance, excellent in outer shape such as gloss and transparency, and excellent in moldability, physical properties, and outer shape. More specifically, propylene homopolymer and ethylene-propylene rubber polymer are stepwise based on high stereoregular high rigidity polypropylene resin with wide molecular weight distribution by Ziegler-Natta catalyst containing succinate internal electron donor. A polymerized ethylene-propylene block copolymer that contains an organometallic nucleating agent by adjusting the ethylene content of the ethylene-propylene block copolymer, the ethylene-propylene rubber content and the intrinsic viscosity of the ethylene-propylene rubber. The present invention relates to a high-rigidity polypropylene resin composition excellent in flowability, heat resistance and outer shape.

  Polypropylene resin is a material that is excellent in rigidity, chemical resistance, and moldability compared to other polyolefin resins, has a very wide range of industrial use, and is widely used. However, polypropylene obtained by polymerizing propylene alone is excellent in rigidity, hardness, and heat resistance, but has a limitation in use due to low impact strength. In order to improve such low impact strength, an ethylene-propylene block copolymer in which ethylene is copolymerized when polypropylene is polymerized has been developed. However, the impact characteristics of the ethylene-propylene block copolymer are improved by making it an ethylene-propylene rubber, but the rigidity and heat resistance are lower than that of the propylene homopolymer, and the rubber-like dispersion makes it opaque. There is a problem that gloss decreases. In Patent Document 1, etc., a composition in which an inorganic filler and rubber were blended with polypropylene resin to improve mechanical properties was presented, but the gloss was lowered by the filler, and the material cost and processing cost due to blending increased. It was way. Talc is also often used as a low-cost filler to improve the mechanical properties of polypropylene, especially heat resistance. Scratch is inferior and the outer shape is easily damaged by scratches. As a method for improving the gloss of polypropylene, Patent Document 2 discloses that an aluminum toning pigment is added and kneaded. However, the method of applying such an external additive depends on material costs and kneading. There are disadvantages that the processing cost increases and the manufacturing process becomes complicated.

JP-A-53-64257 Korean Patent Publication No. 2006-0104109

  In order to solve the above-mentioned problems, an object of the present invention is a polypropylene resin composition having excellent flowability suitable for molding large-sized injection products and products having complicated ribs with excellent heat resistance and mechanical strength. Thus, an object of the present invention is to provide a polypropylene resin composition having improved gloss and transparency by adjusting the composition and content and intrinsic viscosity of ethylene-propylene rubber.

  The polypropylene resin composition of the present invention is a polypropylene resin composition comprising an ethylene-propylene block copolymer having an ethylene content of 2 to 4% by weight and an organometallic nucleating agent, wherein the ethylene-propylene block copolymer comprises: (A) a propylene homopolymer, and (b) a copolymer obtained by polymerizing an ethylene-propylene rubber polymer, wherein (a) propylene homopolymer is added to 100 parts by weight of the ethylene-propylene block copolymer. 85 to 92 parts by weight of the polymer, and 8 to 15 parts by weight of the (b) ethylene-propylene rubber polymer, and the content of the organometallic nucleating agent is 100 parts by weight of the ethylene-propylene block copolymer. 0.05 to 0.3 parts by weight, the polydispersity index of the propylene homopolymer (a) is 6 to 15, and the ethylene The relative intrinsic viscosity of the solvent extract of propylene block copolymer ethylene - intrinsic viscosity ratio of the solvent-insoluble fraction of the propylene block copolymer is characterized in that it is a 0.5 to 1.6.

  The polypropylene resin according to the present invention is excellent in heat resistance and mechanical strength, and has excellent flowability suitable for molding large-sized injection products and products having complicated shapes. In addition, by adjusting the composition and content of ethylene-propylene rubber and the intrinsic viscosity without the application of additives to increase gloss, it exhibits superior gloss compared to existing resins, and improved transparency and excellent outer shape. Have.

Hereinafter, the present invention will be described in more detail.
The polypropylene resin composition of the present invention is a polypropylene resin composition comprising an ethylene-propylene block copolymer having an ethylene content of 2 to 4% by weight and an organometallic nucleating agent, wherein the ethylene-propylene block copolymer comprises: (A) a copolymer obtained by polymerizing a propylene homopolymer and (b) an ethylene-propylene rubber polymer, and (a) a propylene homopolymer based on 100 parts by weight of the ethylene-propylene block copolymer 85 to 92 parts by weight, and (b) 8 to 15 parts by weight of the ethylene-propylene rubber polymer, and the content of the organometallic nucleating agent is 0 with respect to 100 parts by weight of the ethylene-propylene block copolymer. 0.05 to 0.3 parts by weight, and the polydispersity index of the propylene homopolymer (a) is 6 to 15, and the ethylene- The ethylene for intrinsic viscosity of the solvent extract of b pyrene block copolymer - intrinsic viscosity ratio of the solvent-insoluble fraction of the propylene block copolymer is characterized in that it is a 0.5 to 1.6.

  In the present invention, the polypropylene resin composition is polymerized using a Ziegler-Natta catalyst containing a succinate-based internal electron donor, and comprises (a) a propylene homopolymer and (b) an ethylene-propylene rubber polymer. An ethylene-propylene block copolymer produced with an organometallic nucleating agent. More specifically, in the ethylene-propylene block copolymer, a propylene homopolymer and an ethylene-propylene rubber polymer are polymerized stepwise in a series of reactors.

  “Polymerization” in the present invention is used to mean not only homopolymerization but also copolymerization. The term “polymer” is used to mean not only a homopolymer but also a copolymer.

  The olefin polymerization catalyst referred to as a Ziegler-Natta catalyst in the present invention refers to a catalyst system comprising a combination of a main catalyst mainly composed of a transition metal compound, a cocatalyst composed of an organometallic compound, and an electron donor. And a solid catalyst component mainly composed of a halogen compound and an organoaluminum compound system as a promoter. The Ziegler-Natta catalyst can be used without particular limitation as long as it is used for general olefin polymerization.

<Component (a) Propylene Homopolymer>
In the present invention, the component (a) propylene homopolymer is polymerized by injecting propylene alone in a polymerization reactor. The method for polymerizing the polymer may be any conventional method known in the technical field, and is not particularly limited.

  In the present invention, the component (a) propylene homopolymer is 85 to 92 parts by weight with respect to 100 parts by weight of the ethylene-propylene block copolymer. If the content of the component (a) propylene homopolymer is less than 85 parts by weight, the degree of crystallinity is lowered and heat resistance and mechanical strength are lowered, and if it exceeds 92 parts by weight, impact resistance is lowered. It is not desirable.

  In the present invention, the molecular weight distribution of the propylene homopolymer (a) is 6 to 15 as a polydispersity index measured by a rheological method. If the polydispersity index is less than 6, there is a risk that the flowability will decrease and unmolded when molding large injection products or complex injection products, and the formation and orientation of odd nuclei due to high molecular weight will occur. Therefore, heat resistance and mechanical strength are reduced. If the polydispersity index exceeds 15, the metering time becomes longer at the time of injection, which leads to a decrease in productivity.

  In the present invention, the propylene homopolymer (a) is preferably a highly stereoregular polypropylene homopolymer having a stereoregularity index measured by a nuclear magnetic resonance method of 95% or more based on the pentad method. . If the stereoregularity index is less than 95% based on the pentad method, the heat resistance and mechanical strength of the polypropylene resin will decrease. The nuclear magnetic resonance method is a phenomenon in which a nucleus placed in an external magnetic field interacts with an electromagnetic wave having a specific frequency, and a substance utilizing the fact that this specific frequency changes minutely in the molecule depending on the environment of the atom. It is a method to analyze.

<Component (b) Ethylene-propylene rubber copolymer>
In the present invention, the component (b) ethylene-propylene rubber copolymer is polymerized from the component (a) propylene homopolymer and then continuously in the presence of the component (a) propylene homopolymer in a subsequent polymerization reactor. The component (b) ethylene-propylene rubber copolymer is polymerized at 8 to 15 parts by weight with respect to 100 parts by weight of the ethylene-propylene block copolymer. The method for polymerizing the rubber copolymer is not particularly limited, and is a conventional method known in the technical field. The content of ethylene copolymerized during the polymerization of the component (b) ethylene-propylene rubber copolymer is 2 to 4% by weight based on the ethylene-propylene block copolymer. If the ethylene content is less than 2% by weight, the elasticity of the rubber is reduced and the impact resistance is reduced. If it exceeds 4% by weight, the component (a) propylene homopolymer and the component (b) ethylene-propylene rubber Since the compatibility of the copolymer is lowered and the rubbery size is increased, the gloss and transparency are lowered, the dispersibility is lowered, and the impact strength is also lowered.

  As for content of the organometallic nucleating agent which comprises the polypropylene resin composition of this invention, it is desirable to add 0.05-0.3 weight part with respect to 100 weight part of ethylene-block copolymers. When the content of the organometallic nucleating agent is less than 0.05 parts by weight, it is difficult to obtain sufficient heat resistance, mechanical rigidity and transparency, and when it exceeds 0.3 parts by weight, further improvement in physical properties is achieved. do not become. As the organometallic nucleating agent, a conventionally known organometallic nucleating agent for polypropylene is used, and preferable examples include aluminum para-tert-butyl benzoic acid, sodium benzoate, and calcium benzoate.

  In the present invention, the intrinsic viscosity (xylene solvent) of the solvent extract of the component (b) ethylene-propylene rubber copolymer is preferably 1.0 to 2.0 dl / g. If the intrinsic viscosity is less than 1.0 dl / g, the size of the rubber component is reduced, the molecular weight of the rubber component is reduced, and the impact characteristics are deteriorated. When the intrinsic viscosity exceeds 2.0 dl / g, the size of the rubber component becomes large, a lump is generated, the gloss and transparency are lowered, and the outer shape is not excellent. In addition, since the rubber dispersion is caused by the difference in viscosity between the component (a) propylene homopolymer and the component (b) ethylene-propylene-rubber copolymer, the intrinsic viscosity ratio of the solvent insoluble matter and the intrinsic viscosity of the solvent extract. {(Intrinsic Viscosity of Solvent Extract) / (Intrinsic Viscosity of Solvent Insoluble Content)} is the solvent insoluble content in the ethylene-propylene block copolymer relative to the intrinsic viscosity of the solvent extract in the ethylene-propylene block copolymer. The intrinsic viscosity ratio is preferably 0.5 to 1.6. When the intrinsic viscosity ratio is less than 0.5, the size of the rubber component is reduced and the impact characteristics are deteriorated. When it exceeds 1.6, a lump of the rubber component is generated and the external characteristics are deteriorated.

  In the present invention, the polypropylene resin preferably has a melt index of 4 to 30 g / 10 min (ASTM D 1238). When the melt index is less than 4 g / 10 min, the flowability of the molten resin is lowered, and when processing a large or complicated injection, the flowability is insufficient and unmolding may occur, and 30 g / 10 Exceeding the minute is not desirable because the impact strength decreases rapidly.

  As the polypropylene resin of the present invention, various additives such as a neutralizing agent, an antioxidant, a heat stabilizer, a weather stabilizer, an antistatic agent, a lubricant, an antiblocking agent, a pigment, and a dye are included in the present invention. Can be added within a range not departing from the above.

The polypropylene resin of the present invention comprises a porous solid particle catalyst produced by reacting dialkoxymagnesium with a titanium compound and an internal electron donor in the presence of an organic solvent (hereinafter referred to as “propylene polymerization catalyst”). Can be manufactured using. More specifically, the catalyst first reacts dialkoxymagnesium with a titanium compound in the presence of an organic solvent, and then secondarily reacts the reaction product with the titanium compound and an internal electron donor in the presence of the organic solvent. Can be manufactured. The dialkoxymagnesium used for the production of the propylene polymerization catalyst is produced by reacting metal magnesium with an alcohol. The general formula Mg (OR ¹ ) ₂ (where R ¹ is an alkyl having 1 to 6 carbon atoms). Spherical particles, which are used as a carrier. Although there is no restriction | limiting in particular as a titanium compound used by the primary and secondary reaction in manufacture of the said catalyst for propylene polymerization, It is preferable to use a titanium halide compound, especially titanium tetrachloride. As the internal electron donor used in the production of the propylene polymerization catalyst, one or more compounds selected from dicarboxylic acid ester compounds can be mixed and used. Specific examples of the dicarboxylic acid ester compounds include dimethyl succinate, diethyl succinate, dinormal propyl succinate, diisopropyl succinate, 1,1-dimethyl-dimethyl succinate, 1,1-dimethyl-diethyl succinate. 1,1-dimethyl-dinormalpropyl succinate, 1,1-dimethyl-diisopropyl succinate, 1,2-dimethyl-dimethyl succinate, 1,2-dimethyl-diethyl succinate, ethyl-dimethyl succinate, Examples include ethyl-diethyl succinate. As the organic solvent used in the production of the propylene polymerization catalyst, an aliphatic hydrocarbon or aromatic hydrocarbon having 6 to 12 carbon atoms is used, preferably a saturated aliphatic hydrocarbon or aromatic having 7 to 10 carbon atoms. Group hydrocarbons are used, and specific examples thereof include octane, nonane, decane, toluene, xylene, and the like. The catalyst for propylene polymerization produced by the above method contains magnesium, titanium, an internal electron donor, and a halogen atom, and the content of each component is not particularly limited, but is preferably 15 to 25% by weight of magnesium, 1 to 1 of titanium. 5% by weight, internal electron donor 5 to 15% by weight, halogen atom 55 to 79% by weight. The polymerization of propylene using the propylene polymerization catalyst (A) is carried out by mixing with alkylaluminum (B) and an external electron donor (C) as a co-catalyst and reacting with propylene. The alkylaluminum (B) used for the propylene polymerization is a compound represented by the general formula Al (R ² ) ₃ (wherein R ² is an alkyl group having 1 to 4 carbon atoms), Specific examples include trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, triisobutylaluminum and the like. The external electron donor (C) used for the propylene polymerization preferably has the general formula R ³ _m Si (OR ⁴ ) _4-m (where R ³ is an alkyl group having 1 to 10 carbon atoms, cycloalkyl) R ⁴ is an alkyl group having 1 to 3 carbon atoms, m is 1 or 2, and a compound (C-1) represented by the chemical formula C ₂ H ₃ Si (OC ₂ H ₅ ) A mixture of vinyltriethoxysilane compounds (C-2) represented by ₃ , and specific examples of the compound (C-1) include n-C ₃ H ₇ Si (OCH ₃ ) _{3 , (n-C 3 H 7} ) 2 Si (OCH 3) 2, i-C 3 H 7 Si (OCH 3) 3, (i-C 3 H 7) 2 Si (OCH 3) 2, n-C 4 _{H 9 Si (OCH 3) 3} , (n-C 4 H 9) 2 Si (OCH _{) 2, i-C 4 H} 9 Si (OCH 3) 3, (i-C 4 H 9) 2 Si (OCH 3) 2, t-C 4 H 9 Si (OCH 3) 3, (t-C 4 _{H 9) 2 Si (OCH 3} ) 2, n-C 5 H 11 Si (OCH 3) 3, (n-C 5 H 11) 2 Si (OCH 3), ( _{cyclopentyl) Si (OCH 3) 3,} ( Cyclopentyl) ₂ Si (OCH ₃ ) ₂ , (cyclohexyl) Si (OCH ₃ ) ₃ , (cyclohexyl) ₂ Si (OCH ₃ ) ₂ , (cycloheptyl) Si (OCH ₃ ) ₃ , (cycloheptyl) ₂ Si (OCH _{3) 2,} (phenyl) Si _{(OCH 3)} 3, _{(phenyl) 2 Si (OCH 3) 2} , n-C 3 H 7 Si (OC 2 H 5) 3, (n-C 3 H 7) 2 Si (OC ₂ H ₅ ) _{2, i-C 3 H 7} Si (OC 2 H 5) 3, (i-C 3 H 7) 2 Si (OC 2 H 5) 2, n-C 4 H 9 Si (OC 2 H 5) 3, _{(n-C 4 H 9)} 2 Si (OC 2 H 5) 2, i-C 4 H 9 Si (OC 2 H 5) 3, (i-C 4 H 9) 2 Si (OC 2 H 5) 2 _{, t-C 4 H 9 Si} (OC 2 H 5) 3, (t-C 4 H 9) 2 Si (OC 2 H 5) 2, n-C 5 H 11 Si (OC 2 H 5) 3, ( _{n-C 5 H 11) 2} Si (OC 2 H 5) 2, ( _{cyclopentyl) Si (OC 2 H 5)} 3, ( _{cyclopentyl) 2 Si (OC 2 H 5} ) 2, ( cyclohexyl) Si _(OC 2 H _{5) 3, (cyclohexyl) 2 Si (OC 2 H 5} ) 2, ( cycloheptyl) Si (OC _{2 5) 3, (cycloheptyl) 2 Si (OC 2 H 5} ) 2 , (phenyl) Si _{(OC 2 H} 5), _{(phenyl) 2 Si (OC 2 H 5} ) 2 and the like are used, in particular, dicyclopentyl More desirable are dialkyl dialkoxysilane compounds such as dimethoxysilane, diisopropyldimethoxysilane, and dicyclohexyldimethoxysilane.

  The present invention can be more specifically understood by the following examples and comparative examples. The following examples are intended to illustrate the present invention and are not intended to limit the protection scope of the present invention.

Examples 1-2 and Comparative Examples 1, 3-5
Production of catalyst Into a glass reactor equipped with a 1 liter stirrer sufficiently substituted with nitrogen, 150 ml of toluene and diethoxymagnesium (spherical shape having an average particle diameter of 60 μm and a particle size distribution index of 0.86) The apparent density is 0.32 g / cc.) 25 g was charged and maintained at 10 ° C. After 25 ml of titanium tetrachloride was diluted with 50 ml of toluene and charged over 1 hour, the temperature of the reactor was raised to 60 ° C. at a rate of 0.5 ° C. per minute. After stirring the reaction mixture at 60 ° C. for 1 hour, the stirring was stopped and the solid product was allowed to precipitate, the supernatant was removed, 200 ml of new toluene was added, and the mixture was stirred for 15 minutes and then washed once. did.
In a state where 150 ml of toluene was added to the solid product treated with titanium tetrachloride and the temperature was maintained at 30 ° C., 50 ml of titanium tetrachloride was added at a constant rate over 1 hour while stirring at 250 rpm. After the addition of titanium tetrachloride was completed, 2.5 g of 1,2-diisobutyl-diethyl succinate was added and the reactor temperature was raised to 110 ° C. at a constant rate over 80 minutes (1 ° C. per minute). Temperature increase). When the temperature of the reactor reached 60 ° C. during the temperature raising process, 2.5 g of 1,2-isobutyl-diethyl succinate was further added. After maintaining the mixture at 110 ° C. for 1 hour, the temperature was lowered at 90 ° C., stirring was stopped to remove the supernatant, and then 200 ml of toluene was added and washed once. To this, 150 ml of toluene and 50 ml of titanium tetrachloride were added, the temperature was raised to 110 ° C., and maintained and aged for 1 hour. The slurry mixture after the aging process was washed twice with 200 ml of toluene each time, and washed with 200 ml each time at 40 ° C. with normal hexane to obtain a light yellow solid catalyst component. The titanium content in the solid catalyst component obtained by drying for 18 hours under a nitrogen flow was 2.72% by weight.

Production of Polypropylene Resin Polypropylene resin was produced with the composition shown in Table 1 by a polymerization method known to those skilled in the art using a Hypol polypropylene production process (Hypol Process) constituted of a bulk-gas phase polymerization reactor.

Comparative Example 2
Polypropylene resin was produced with the composition shown in Table 1 using a normal Ziegler-Natta catalyst containing a phthalate internal electron donor.

（４）エチレン含有量
赤外線吸収スペクトル（ＦＴ−ＩＲ）を使って、７２０、７３０ｃｍ^−１特性ピークを利用してエチレン含有量を測定した。
（５）固有粘度
１３５℃ デカリン（Ｄｅｋａｌｉｎ）溶液下で粘度測定器を利用して固有粘度を測定した。
（６）屈曲弾性率
ＡＳＴＭ Ｄ７９０方法により測定した。
（７）アイゾット（Ｉｚｏｄ）衝撃強さ
ＡＳＴＭ Ｄ２５６方法により常温で測定した。
（８）熱変形温度
ＡＳＴＭ Ｄ６４８方法により測定した。
（９）光沢度
ＡＳＴＭ Ｄ５２３−８９方法により測定した。
（１０）曇り度
ＡＳＴＭ Ｄ１００３方法により測定した。
（１１）流れ性
同一条件で射出したとき（射出温度２３０℃）、ポリプロピレン樹脂が最大に流れる長さで測定した。

Test Examples The experimental methods used in the present invention are summarized below.
Physical property measuring method (1) Melt index
Measurements were made at 230 ° C. and 2.16 kg load according to ASTM D1238 conditions.
(2) Stereoregularity (Isotactic index, II)
Stereoregularity was measured by measuring the directionality of propylene polymerized on polypropylene by the pentad method (Pentad) of a nuclear magnetic resonance spectrometer (Nuclear Magnetic Resonance Spectrometer, NMR).
(3) Polydispersity index (PI)
Measure storage modulus and loss modulus at a temperature of 200 ° C with a rheometrics dynamic spectrometer using rheological properties in a method of measuring molecular weight distribution And the polydispersity index was measured from the following formula | equation using the cross modulus (Cc) which is the intersection.

(4) Ethylene content Using infrared absorption spectrum (FT-IR), ethylene content was measured using 720 and 730 cm ^-1 characteristic peaks.
(5) Intrinsic Viscosity Intrinsic viscosity was measured using a viscometer under a Decalin solution at 135 ° C.
(6) Flexural modulus Measured by the ASTM D790 method.
(7) Izod Impact Strength Measured at room temperature by the ASTM D256 method.
(8) Thermal deformation temperature Measured by the ASTM D648 method.
(9) Glossiness Measured by the ASTM D523-89 method.
(10) Haze Measured by the ASTM D1003 method.
(11) Flowability When injected under the same conditions (injection temperature 230 ° C.), the flow was measured by the length at which the polypropylene resin flows to the maximum.

  As shown in Table 1 above, the polypropylene resin according to the present invention is excellent in flowability, excellent in balance of high heat resistance and mechanical properties, and excellent in glossiness and transparency as outer characteristics. Became clear. On the other hand, the polypropylene resin of Comparative Example 1 was found to have no organometallic nucleating agent, poor heat resistance and mechanical properties, and low transparency. In Comparative Example 2, a phthalate system was used as the internal electron donor of the catalyst, and since the molecular weight distribution of component (a) was narrow, it was found that heat resistance and mechanical strength were low and flowability was inferior. . In Comparative Example 3, the ethylene content was high during polymerization of the ethylene-propylene block copolymer and the mechanical strength was good, but the glossiness and transparency were inferior. In Comparative Example 4, it was found that the content of component (a) was low, the content of component (b) was high and the mechanical rigidity was low, and the glossiness and transparency were somewhat inferior. In Comparative Example 5, the heat resistance, mechanical rigidity, and flowability were good, but it was revealed that the intrinsic viscosity and intrinsic viscosity ratio of the solvent extract were high and the glossiness and transparency were very low.

  The polypropylene resin according to the present invention is excellent in heat resistance and mechanical strength, and has excellent flowability suitable for molding large-sized injection products and products having complicated shapes. In addition, by adjusting the composition and content of ethylene-propylene rubber and the intrinsic viscosity without the application of additives to increase gloss, it exhibits superior gloss compared to existing resins, and improved transparency and excellent outer shape. Have.

Claims (5)

In a polypropylene resin composition comprising an ethylene-propylene block copolymer having an ethylene content of 2 to 4% by weight and an organometallic nucleating agent,
The ethylene-propylene block copolymer is a copolymer obtained by polymerizing (a) a propylene homopolymer and (b) an ethylene-propylene rubber polymer,
(A) propylene homopolymer 85-92 parts by weight and (b) ethylene-propylene rubber polymer 8-15 parts by weight with respect to 100 parts by weight of the ethylene-propylene block copolymer,
The content of the organometallic nucleating agent is 0.05 to 0.3 parts by weight with respect to 100 parts by weight of the ethylene-propylene block copolymer.
The polydispersity index of the propylene homopolymer (a) is 6 to 15, and the polydispersity index is a storage modulus at a temperature of 200 ° C. using a rheometrics dynamic spectrometer. And the loss modulus (loss modulus) was measured from the following equation using the cross modulus (Gc) that is the intersection of the loss modulus and the loss modulus (loss modulus):

The intrinsic viscosity ratio of the solvent-insoluble component in the ethylene-propylene block copolymer to the intrinsic viscosity of the solvent extract in the ethylene-propylene block copolymer when measured at 135 ° C. in a decalin solution is 0.5. ～1.6 der is,
In the ethylene-propylene block copolymer, the inherent viscosity (xylene solvent) of the solvent extract is 1.0 to 2.0 dl / g .   2. The polypropylene resin composition according to claim 1, wherein a melt index of the ethylene-propylene block copolymer is 230 ° C. and 4 to 30 g / 10 minutes of ASTM D1238.   2. The polypropylene resin composition according to claim 1, wherein the (a) propylene homopolymer has a stereoregularity index of 95% or more in terms of a pentad fraction.   The polypropylene resin composition further includes at least one additive selected from a neutralizing agent, an antioxidant, a heat stabilizer, a weather stabilizer, an antistatic agent, a lubricant, an antiblocking agent, a pigment, and a dye. The polypropylene resin composition according to claim 1, comprising: a polypropylene resin composition according to claim 1. The polypropylene resin composition according to claim 1, wherein the organometallic nucleating agent is a metal salt selected from the group consisting of an aluminum salt, a sodium salt, and a calcium salt.