KR101699589B1 - Stiff polypropylene resin composition having excellent flowability, heat resistance and good appearance - Google Patents

Abstract

The present invention relates to a high rigidity polypropylene resin composition excellent in flow properties and heat resistance and excellent in appearance such as gloss and transparency, and relates to an ethylene-propylene block copolymer in which a propylene homopolymer and an ethylene-propylene rubber polymer are polymerized stepwise . More specifically, the molecular weight distribution of the propylene homopolymer, the ethylene content of the ethylene-propylene block copolymer, the ethylene-propylene rubber content, and the intrinsic viscosity of the ethylene-propylene rubber are measured in the presence of a Ziegler-Natta catalyst containing a succinate- And a high rigidity polypropylene resin composition excellent in flow properties, heat resistance and appearance, which comprises an organometallic nucleating agent.

Description

[0001] The present invention relates to a high rigidity polypropylene resin composition having excellent flowability, heat resistance and appearance,

The present invention relates to a polypropylene resin suitable for injection molding. Specifically, it is a polypropylene resin for injection products having excellent flow and heat resistance, excellent appearance such as gloss and transparency, and excellent moldability, physical properties and appearance. More particularly, the present invention relates to a high-rigidity polypropylene resin having a high stereoregularity and a broad molecular weight distribution by a Ziegler-Natta catalyst containing a succinate-based internal electron donor, wherein the propylene homopolymer and the ethylene- Characterized in that the ethylene content of the ethylene-propylene block copolymer, the ethylene-propylene rubber content, and the intrinsic viscosity of the ethylene-propylene rubber are controlled with the ethylene-propylene block copolymer having an ethylene- To a high rigidity polypropylene resin composition excellent in appearance.

Polypropylene resin is widely used because it has excellent rigidity, chemical resistance, moldability and industrial use range compared with other polyolefin resins. However, polypropylene obtained by polymerizing propylene alone has excellent rigidity, hardness, and heat resistance, but its use is limited due to its low impact strength. In order to improve such low impact strength, an ethylene-propylene block copolymer in which ethylene is copolymerized when polymerizing polypropylene has been developed. However, the ethylene-propylene block copolymer has an improved impact property due to the ethylene-propylene rubber phase, but has a problem that rigidity and heat resistance are lowered than that of the propylene homopolymer and opaque and gloss is lowered due to dispersion of the rubber phase. Japanese Unexamined Patent Publication No. 53-64257 discloses a composition in which an inorganic filler and a rubber are blended in a polypropylene resin to improve mechanical properties. However, due to the filler, the gloss is lowered and the material cost and the processing cost due to blending are increased. Though talc is often used as a low-cost filler which improves physical properties, particularly heat resistance, gloss is also lowered and the hardness of the talc itself is low, so that the scratch resistance of the polypropylene resin filled with talc is poor and the appearance is easily damaged by scratches.

As a method of improving the luster of polypropylene, Korean Patent Laid-Open Publication No. 2006-0104109 proposes adding and kneading an aluminum coloring pigment. However, the method of applying such an external additive increases the processing cost due to material cost and kneading The manufacturing process becomes complicated.

In order to solve the above problems,

It is a polypropylene resin composition that has excellent heat resistance and mechanical strength and is suitable for forming a complex molded product having many large injection products or ribs. It is a polypropylene resin composition which is controlled by composition, content and intrinsic viscosity of ethylene- And to provide a propylene resin composition.

상기 에틸렌-프로필렌 블록 공중합체 중의 용제추출물의 고유점도에 대한 상기 에틸렌-프로필렌 블록 공중합체 중의 용제불용분의 고유점도의 비는 0.5~1.6인 것을 특징으로 하는 폴리프로필렌 수지 조성물에 관한 것이다.1. A polypropylene resin composition comprising an ethylene-propylene block copolymer having an ethylene content of 2 to 4 wt% and an organometallic nucleating agent, wherein the ethylene-propylene block copolymer comprises (a) a propylene homopolymer and (b) (A) 85 to 92 parts by weight of a propylene homopolymer and (b) 8 to 15 parts by weight of an ethylene-propylene rubber polymer, based on 100 parts by weight of the ethylene-propylene block copolymer, The content of the metal-based nucleating agent is 0.05 to 0.3 parts by weight based on 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 the Rheometrics Dynamic Specification The storage modulus and loss modulus were measured at a temperature of 200 ° C in a Rheometrics Dynamic Spectrometer, and the crossover modulus (Gc) Will from the measure,

Wherein the ratio of the intrinsic viscosity of the solvent insoluble matter in the ethylene-propylene block copolymer to the intrinsic viscosity of the solvent extract in the ethylene-propylene block copolymer is 0.5 to 1.6.

The polypropylene resin according to the present invention is excellent in heat resistance and mechanical strength and has excellent flow properties suitable for molding large-sized injection products and complicated shapes. In addition, the composition and content of ethylene-propylene rubber and the intrinsic viscosity can be controlled without application of additives to increase gloss, so that the resin exhibits excellent gloss compared to conventional resin, and transparency is improved.

Hereinafter, the present invention will be described in more detail.

1. A polypropylene resin composition comprising an ethylene-propylene block copolymer having an ethylene content of 2 to 4 wt% and an organometallic nucleating agent, wherein the ethylene-propylene block copolymer comprises (a) a propylene homopolymer and (b) (A) 85 to 92 parts by weight of a propylene homopolymer and (b) 8 to 15 parts by weight of an ethylene-propylene rubber polymer, based on 100 parts by weight of the ethylene-propylene block copolymer, The content of the metal-based nucleating agent is 0.05 to 0.3 parts by weight based on 100 parts by weight of the ethylene-propylene block copolymer. The propylene homopolymer (a) has a polydispersity index of 6 to 15, Wherein the ratio of the intrinsic viscosity of the solvent insoluble matter in the ethylene-propylene block copolymer to the intrinsic viscosity of the extract is from 0.5 to 1.6, To a phenolic resin composition.

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 block copolymer Containing organometallic nucleating agent.

More specifically, in the ethylene-propylene block copolymer, the propylene homopolymer and the ethylene-propylene rubber polymer are polymerized stepwise in a series of reactors.

In the present invention, the term " polymerization " means not only homopolymerization but also copolymerization, and the term " polymer " is used to mean not only a homopolymer but also a copolymer.

In the present invention, the catalyst for olefin polymerization, which is referred to as the Ziegler-Natta catalyst, refers to a catalyst system comprising a combination of a main catalyst, a promoter, an organometallic compound and an electron donor, which are the main components of the transition metal compound. Titanium, magnesium and a halogen compound A solid catalyst component and an organoaluminum compound system as a cocatalyst. The Ziegler-Natta catalyst can be used without any 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 into the polymerization reactor. The method of polymerizing the polymer is by a conventional method known in the art, and is not particularly limited in the present invention.

In the present invention, the propylene homopolymer (a) is 85 to 92 parts by weight in 100 parts by weight of the ethylene-propylene block copolymer.

If the content of the propylene homopolymer (a) is less than 85 parts by weight, the crystallinity is lowered and the heat resistance and mechanical strength are lowered. If the propylene homopolymer content exceeds 92 parts by weight, the impact resistance is lowered.

In the present invention, the molecular weight distribution of the propylene homopolymer (a) is 6-15 as a polydispersity index measured by a rheological method.

When the polydispersity index is less than 6, the flowability is lowered, and there is a risk of unforming when molding a large-sized article or a complex molded article, and since nucleation and orientation due to a high molecular weight portion do not occur, heat resistance and mechanical strength . When the polydispersity index is more than 15, the metering time at the time of injection becomes long, which causes a decrease in productivity, which is not preferable.

In the present invention, the propylene homopolymer (a) is preferably a highly stereoregular polypropylene homopolymer having a stereoregularity index, measured by nuclear magnetic resonance (NMR), of not less than 95% based on the pentadacting method. When the steric hindrance index is less than 95% based on the pentadec method, the heat resistance and mechanical strength of the polypropylene resin are lowered.

The nuclear magnetic resonance method is a phenomenon in which an atomic nucleus lying in an external magnetic field interacts with an electromagnetic wave having a specific frequency and analyzes the substance using the fact that the intrinsic frequency is finely changed by the environment of the atom in the molecule Method.

<Component (b) Ethylene-propylene rubber copolymer>

In the present invention, the component (b) ethylene-propylene rubber copolymer is preferably continuously polymerized in the presence of the component (a) propylene homopolymer in the subsequent polymerization reactor after polymerization of the component (a) propylene homopolymer, b) The ethylene-propylene rubber copolymer is polymerized in an amount of 8 to 15 parts by weight based on 100 parts by weight of the ethylene-propylene block copolymer.

The method of polymerizing the rubber copolymer is a conventional method known in the art, and is not particularly limited in the present invention.

The content of ethylene copolymerized in the polymerization of the ethylene-propylene rubber copolymer (b) is 2 to 4% by weight based on the ethylene-propylene block copolymer.

If the content of ethylene is less than 2% by weight, the elasticity of the rubber decreases to lower the impact resistance. If the content of ethylene exceeds 4% by weight, compatibility of the propylene homopolymer (a) and the ethylene-propylene rubber copolymer (b) The size of the rubber phase is lowered, so the gloss and transparency are lowered, the dispersibility is lowered, and the impact resistance is also lowered.

The content of the organometallic nucleating agent constituting the polypropylene resin composition of the present invention is preferably 0.05 to 0.3 parts by weight based on 100 parts by weight of the ethylene-block copolymer. If the content of the organometallic nucleating agent is less than 0.05 part by weight, it is difficult to obtain sufficient heat resistance, mechanical rigidity and transparency. If the content is more than 0.3 parts by weight, further improvement of the physical properties is not achieved.

As the organic metal-based nucleating agent, conventionally known organic metal-based nucleating agents for polypropylene may be used, and preferred examples thereof include aluminum parathetic butylbenzoate, sodium benzoate, calcium benzoate and the like.

In the present invention, the intrinsic viscosity (xylene solvent) of the solvent extract in 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 becomes smaller and the molecular weight of the rubber component becomes smaller, so that the impact property is lowered. If the intrinsic viscosity exceeds 2.0 dl / g, the size of the rubber component becomes larger and the rubber component becomes lumpy and the gloss and transparency deteriorate, so that the appearance is poor. Also, since the dispersion of the rubber is caused by the difference in viscosity between the propylene homopolymer (a) and the ethylene-propylene rubber copolymer (b), the intrinsic viscosity of the solvent insoluble matter and the intrinsic viscosity of the solvent extract (Intrinsic viscosity of solvent insoluble matter) / (intrinsic viscosity of solvent insoluble matter)} is preferably from 0.5 to 1.6 based on the intrinsic viscosity of the solvent insoluble matter in the ethylene-propylene block copolymer to the intrinsic viscosity of the solvent extract in the ethylene-propylene block copolymer.

If the intrinsic viscosity ratio is less than 0.5, the size of the rubber component becomes small to lower the impact characteristics. If the intrinsic viscosity ratio exceeds 1.6, the rubber component is clumped to deteriorate the appearance characteristics.

In the present invention, the polypropylene resin preferably has a melt index of 4 to 30 g / 10 min (ASTM D 1238).

If the melt index is less than 4 g / 10 min, the flowability of the molten resin is lowered, resulting in a lack of flowability when processing a large or complex injection, and when the melt index exceeds 30 g / 10 min, Which is undesirable.

Various additives such as neutralizing agents, antioxidants, heat stabilizers, weather stabilizers, antistatic agents, lubricants, anti-blocking agents, pigments, dyes and the like can be added to the polypropylene resin of the present invention within the range not detracting from the characteristics of the present invention.

The polypropylene resin of the present invention is produced by using a porous solid particle catalyst (hereinafter referred to as 'catalyst for propylene polymerization') prepared by reacting a dialkoxymagnesium with a titanium compound and an internal electron donor in the presence of an organic solvent More specifically, the catalyst may be prepared by first reacting a dialkoxymagnesium with a titanium compound in the presence of an organic solvent, and then reacting the reactant with a titanium compound and an internal electron donor in the presence of an organic solvent .

The dialkoxymagnesium used in the production of the propylene polymerization catalyst is a spherical compound represented by the general formula Mg (OR ¹ ) ₂ (wherein R ¹ is an alkyl group having 1 to 6 carbon atoms) which is produced by reacting magnesium metal with an alcohol As a carrier.

In the production of the propylene polymerization catalyst, the titanium compound used in the first and second reactions is not particularly limited, but a halogenated titanium compound, particularly titanium tetrachloride, is preferably used.

As the internal electron donor used for the production of the propylene polymerization catalyst, one or more compounds selected from dicarboxylic acid ester compounds may be used in combination. Specific examples of the dicarboxylic acid ester compound include dimethyl succinate, diethyl succinate, dinompropyl succinate, diisopropyl succinate, 1,1-dimethyl-dimethyl succinate, 1,1-dimethyl- Dimethyl-diisopropyl succinate, 1, 2-dimethyl-dimethyl succinate, 1, 2-dimethyl-diethyl succinate, Ethyl-dimethyl succinate, ethyl-diethyl succinate, and the like.

As the organic solvent used for the production of the propylene polymerization catalyst, an aliphatic hydrocarbon or an aromatic hydrocarbon having 6 to 12 carbon atoms can be used, and preferably a saturated aliphatic hydrocarbon or aromatic hydrocarbon having 7 to 10 carbon atoms can be used. Specific examples thereof include octane, nonane, decane, or toluene, xylene, and the like.

The propylene polymerization catalyst prepared by the above method contains magnesium, titanium, an internal electron donor, and a halogen atom. The content of each component is not particularly limited, but preferably 15 to 25 wt% of magnesium, 1 to 5 wt% of titanium 5 to 15% by weight of an internal electron donor, and 55 to 79% by weight of a halogen atom.

The polymerization of propylene using the catalyst (A) for propylene polymerization is carried out by mixing with alkyl aluminum (B) and external electron donor (C) as a cocatalyst and reacting with propylene.

The alkylaluminum (B) used in 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), and specific examples thereof include trimethylaluminum, Triethyl aluminum, tripropyl aluminum, tributyl aluminum, triisobutyl aluminum and the like.

The external electron donor (C) used in the propylene polymerization is preferably a compound represented by the general formula R ³ _m Si (OR ⁴ ) _4-m (wherein R ³ represents an alkyl group, a cycloalkyl group or an aryl group having 1 to 10 carbon atoms , R ⁴ is an alkyl group having 1 to 3 carbon atoms, and m is 1 or 2, and a vinyltriethoxysilane represented by the formula C ₂ H ₃ Si (OC ₂ H ₅ ) ₃ Specific examples of the compound (C-1) as a mixture of the compound (C-2) include nC ₃ H ₇ Si (OCH ₃ ) ₃ , (nC ₃ H ₇ ) ₂ Si (OCH ₃ ) ₂ , iC ₃ H _{7 Si (OCH 3) 3,} (iC 3 H 7) 2 Si (OCH 3) 2, nC 4 H 9 Si (OCH 3) 3, (nC 4 H 9) 2 Si (OCH 3) 2, iC 4 H _{9 Si (OCH 3) 3,} (iC 4 H 9) 2 Si (OCH 3) 2, tC 4 H 9 Si (OCH 3) 3, (tC 4 H 9) 2 Si (OCH 3) 2, nC 5 H _{11 Si (OCH 3) 3,} (nC 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 CH _{3) 2, (phenyl) Si (OCH 3) 3,} ( _{phenyl) 2 Si (OCH 3) 2} , nC 3 H 7 Si (OC 2 H 5) 3, (nC 3 H 7) 2 Si (OC 2 _{H 5) 2, iC 3 H} 7 Si (OC 2 H 5) 3, (iC 3 H 7) 2 Si (OC 2 H 5) 2, nC 4 H 9 Si (OC 2 H 5) 3, (nC 4 _{H 9) 2 Si (OC 2} H 5) 2, iC 4 H 9 Si (OC 2 H 5) 3, (iC 4 H 9) 2 Si (OC 2 H 5) 2, tC 4 H 9 Si (OC 2 _{H 5) 3, (tC 4} H 9) 2 Si (OC 2 H 5) 2, nC 5 H 11 Si (OC 2 H 5) 3, (nC 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 H _{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, and more preferably a dialkyldialkoxysilane compound such as dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, and dicyclohexyldimethoxysilane.

The present invention can be more specifically understood by the following examples and comparative examples. The following examples are only illustrative of the present invention and do not limit the scope of protection of the present invention.

Examples 1 and 2 and Comparative Examples 1 and 3 to 5

Preparation of Catalyst

Into a glass reactor equipped with a stirrer having a volume of 1 liter sufficiently substituted with nitrogen, 150 ml of toluene and 25 g of diethoxy magnesium (spherical having an average particle diameter of 60 탆, a particle size distribution index of 0.86 and an apparent density of 0.32 g / cc) And kept at 10 [deg.] C. 25 ml of titanium tetrachloride was diluted in 50 ml of toluene and added over 1 hour, and then the temperature of the reactor was raised to 60 ° C at a rate of 0.5 ° C per minute. The reaction mixture was stirred at 60 ° C for 1 hour, then the stirring was stopped to wait for the solid product to settle, the supernatant liquid was removed, 200 ml of fresh toluene was added, stirred for 15 minutes, and washed once.

150 ml of toluene was added to the solid product treated with titanium tetrachloride, and 50 ml of titanium tetrachloride was added thereto at a constant rate over 1 hour while stirring at 250 rpm while maintaining the temperature at 30 ° C. After the addition of titanium tetrachloride was completed, 2.5 g of 1,2-diisobutyl-diethyl succinate was added and the temperature of the reactor was elevated to 110 ° C. over a period of 80 minutes (at a rate of 1 ° C. per minute) . When the temperature of the reactor reached 60 占 폚 in the course of heating, 2.5 g of 1,2-isobutyl-diethyl succinate was further added. The mixture was maintained at 110 DEG C for 1 hour, then cooled to 90 DEG C, stirring was stopped, and the supernatant liquid was removed. Then, 200 mL of toluene was added and washed once. 150 ml of toluene and 50 ml of titanium tetrachloride were added thereto, the temperature was raised to 110 ° C, and the mixture was kept for 1 hour and aged. The aged slurry mixture thus obtained was washed twice with 200 ml of toluene per one time and washed with n-hexane at 40 ° C for five times with 200 ml each time to obtain a pale yellow solid catalyst component. The titanium content in the solid catalyst component obtained by drying in flowing nitrogen for 18 hours was 2.72% by weight.

Production of polypropylene resin

A polypropylene resin was prepared by a polymerization method known to those skilled in the art using a hypol polypropylene production process (Hypol Process) composed of a bulk-gas phase polymerization reactor and a composition as shown in Table 1.

Comparative Example 2

Using a conventional Ziegler-Natta catalyst containing a phthalate internal electron donor, a polypropylene resin was prepared with the composition shown in Table 1.

Test Example

The experimental method used in the present invention is summarized as follows.

How to measure property

(1) Melt Index

It was measured at 230 占 폚 under a load of 2.16 kg according to ASTM D1238 conditions.

(2) Isotactic index (II)

The degree of stereoregularity was measured by measuring the directionality of propylene polymerized on polypropylene with Pentad method (Nuclear Magnetic Resonance Spectrometer, NMR).

(3) Polydispersity index (PI)

The storage modulus and loss modulus were measured at a temperature of 200 ° C in a Rheometrics Dynamic Spectrometer using the rheological properties and the crossover modulus (Gc) The polydispersity index was measured from the food.

(4) Ethylene content

The ethylene content was measured using a 720, 730 cm- ¹ characteristic peak using an infrared absorption spectrum (FT-IR).

(5) Intrinsic viscosity

The intrinsic viscosity was measured using a viscosity meter in a 135 DEG C decalin solution.

(6) Flexural modulus

ASTM D790 method.

(7) Izod impact strength

It was measured at room temperature according to the ASTM D256 method.

(8) Heat deformation temperature

It was measured according to the ASTM D648 method.

(9) Glossiness

ASTM D523-89.

(10) Cloudiness

ASTM D1003 method.

(11) Flowability

When injected under the same conditions (injection temperature: 230 ° C), the length of the polypropylene resin was measured to the maximum.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 The internal electron donor of the catalyst Succinate system Succinate system Succinate system Phthalate system Succinate system Succinate system Succinate system Suzy
Furtherance Melt Index
(g / 10 min) 8 7 7 8 8 7 8 Component (a) stereoregularity diagram
Indices(%) 95.5 96 96 95.5 96 95.5 95.5 Component (a) Polydispersity
Indices 6.5 7.5 7.5 4.5 6.5 7.0 7.0 The content of component (a)
(Parts by weight) 90 86 86 90 86 79 85 The content of component (b)
(Parts by weight) 10 14 14 10 14 21 15 Ethylene content
(weight%) 2.5 3.5 3.5 2.5 5.0 3.5 2.3 Solvent
Intrinsic viscosity (dl / g) 1.6 1.3 1.3 1.7 1.5 1.6 2.3 Intrinsic viscosity ratio 0.94 0.76 0.76 1.0 0.88 1.0 1.7 Aluminum-based nucleating agent
(Parts by weight) 0.1 0.1 0 0.1 0.1 0.1 0.1 Mechanical properties Flexural modulus
(kg / cm ² ) 18,500 18,000 17,000 16,500 18,000 16,000 18,000 Izod impact strength, room temperature
(kgcm / cm) 9.0 9.5 7.5 9.0 8.0 10 9.0 Heat deformation temperature (캜) 133 132 117 128 133 130 132 Optical properties Glossiness
(60 °,%) 89 88 88 90 81 85 75 Cloudiness (%) 35 39 60 35 48 44 80 Processability Flow (cm) 130 135 135 110 135 130 135

As shown in Table 1, the polypropylene resin according to the present invention has excellent flowability, excellent balance of high heat resistance and mechanical properties, and excellent appearance and transparency.

  On the other hand, the polypropylene resin of Comparative Example 1 was poor in heat resistance and mechanical properties due to the organic metal-based nucleating agent and showed low transparency. Comparative Example 2 shows that the phthalate system was used as the internal electron donor of the catalyst, and the molecular weight distribution of the component (a) was narrow, so that the heat resistance and the mechanical strength were low and the flowability was poor. In Comparative Example 3, the ethylene content in the polymerization of the ethylene-propylene block copolymer was high and the mechanical strength was good, but the gloss and transparency were poor. In Comparative Example 4, the content of the component (a) is low and the content of the component (b) is high, so that the mechanical rigidity is low and the gloss and transparency are somewhat poor. In Comparative Example 5, although the heat resistance, the mechanical rigidity and the flowability were good, the intrinsic viscosity and the intrinsic viscosity ratio of the solvent extract were high, and the gloss and transparency were extremely low.

Claims (6)

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) 85 to 92 parts by weight of a propylene homopolymer and (b) 8 to 15 parts by weight of an ethylene-propylene rubber polymer based on 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 based on 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 determined by measuring a storage modulus and a loss modulus at a temperature of 200 ° C in a Rheometrics Dynamic Spectrometer, crossover modulus (Gc).

Wherein the ratio of the intrinsic viscosity of the solvent insoluble matter in the ethylene-propylene block copolymer to the intrinsic viscosity of the solvent extract in the ethylene-propylene block copolymer is 0.5 to 1.6.
The method according to claim 1,
Wherein the intrinsic viscosity of the solvent extract in the ethylene-propylene block copolymer is 1.0 to 2.0 dl / g.
The method according to claim 1,
Wherein the melt index of the ethylene-propylene block copolymer is 230 DEG C and 4 to 30 g / 10 minutes of ASTM D1238.
The method according to claim 1,
Wherein the propylene homopolymer (a) has a stereoregularity index of not less than 95% as a pentad fraction.
The method according to claim 1,
Wherein the polypropylene resin composition further comprises at least one additive selected from a neutralizer, an antioxidant, a heat stabilizer, a weather stabilizer, an antistatic agent, a lubricant, an anti-blocking agent, a pigment, and a dye.
The method 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.