KR101165494B1 - Polypropylene Resin Composition Comprising Ethylene-alpha-olefin Copolymer - Google Patents

Abstract

The present invention (a) 85 to 97 parts by weight of ethylene-propylene copolymer having a content of 2 to 5% by weight of ethylene and a melt index (230 ° C., 2.16 kg) of 10 to 30 g / 10 minutes; And (b) an ethylene-alphaolefin copolymer 3 having an ethylene content of 60 to 90 wt%, a density of 0.85 to 0.92 g / cm ³ , and a melt index (190 ° C., 2.16 kg) of 2 to 5 g / 10 minutes. To about 15 parts by weight, the ratio of the melt index of the (b) ethylene-alpha olefin copolymer to the melt index of the (a) ethylene-propylene copolymer relates to a polypropylene resin composition for injection molding, 0.1 to 0.4, The impact modifier (b) is characterized in that the transparency and impact resistance of the polypropylene resin injection molded product is improved by controlling the density and melt index of the ethylene-alpha olefin copolymer.

Polypropylene, ethylene-propylene, ethylene-alpha olefin, impact modifier, density, melt index, impact resistance, transparency.

Description

Polypropylene Resin Composition Comprising Ethylene-α-olefin Copolymer

The present invention relates to a polypropylene resin composition, more specifically, injection molding poly having excellent impact resistance and transparency by controlling the density and melt index of the ethylene-alpha olefin copolymer mixed with the ethylene-propylene copolymer as an impact modifier. It relates to a propylene resin composition.

Propylene polymers are versatile plastics that are used for a wide range of applications because of their excellent formability and mechanical strength and low cost. Recently, with the development of catalyst and process technology, the product range is gradually expanded to automobile parts and transparent materials. Propylene polymers used in a wide range of applications have a great deal of effort to improve their properties such as stiffness, transparency and high cycle injection moldability without compromising the inherent properties of propylene polymers depending on the application. Are being done.

As a catalyst capable of producing polyolefin having high stereoregularity, a Ziegler-Natta catalyst composed of a titanium catalyst component and an organoaluminum compound is widely used. Among them, a catalyst using a magnesium chloride-supported titanium catalyst is known to have high polymerization activity and high stereoregularity. In order to produce polyolefins having higher stereoregularity, magnesium chloride-supported titanium catalyst components and organoaluminum compounds, and at the same time, catalysts using electron donors are widely used.

In addition to the improved method using a catalyst, it is known that the properties can be improved by reducing the crystallization temperature and rate rise and crystal grain size of the propylene polymer to improve transparency.

To this end, an external nucleating agent is added during the extrusion process after propylene polymerization to increase the crystallization temperature and crystallization rate of the propylene polymer, and to reduce the crystal sphere size. Representative nucleating agents include aluminum salts of aromatic carboxylic acids, dibenzylidene sorbitol and substituted dibenzylidene sorbitol.

U.S. Pat. By prescribing these nucleating agents, the crystallization rate increases in the process of polypropylene being cooled from the molten state to solid state due to the presence of the nucleating agent, and the crystal spherical crystal size is refined so that light scattering is suppressed to improve transparency, glossiness, and molding cycle. A shorter performance improvement can be obtained. However, since these nucleating agents are low molecular weight materials and require a large amount of prescription, they may be volatilized during product molding to contaminate odors and molds or may leak to the product surface after molding, causing surface defects and odor problems.

Japanese Patent Laid-Open Nos. 53-64256 and 53-64257 disclose a method of mixing an inorganic filler or a rubber component with a talc component to mix and reinforce a polypropylene resin in order to improve rigidity and impact resistance. Incorporation of inorganic fillers into polypropylene resins causes problems such as poor appearance and cost incurred due to the increase in specific gravity of the material, and poor resin fluidity during molding, resulting in poor pigment dispersion and unmolded complex products. It is very likely to occur. In addition, when the rubber component and the talc component are mixed and blended with the polypropylene resin, only the rubber component is added, but the impact strength is improved, but the rigidity is decreased, and when only the talc component is added, the rigidity is improved, but the impact is lowered. Proper formulation of rubber and talc components to balance impact strength and stiffness has become a very important issue.

Korean Patent Laid-Open Publication No. 2004-0041727 is an ethylene-propylene random copolymer produced in a loop reactor is passed to a gas phase reactor, and the ethylene-propylene elastomer produced at this time is blended in-situ with an ethylene-propylene random copolymer. A method of preparing a transparent resin having excellent chemical resistance and impact resistance is disclosed, and a method of controlling physical properties by the absolute viscosity of an ethylene-propylene elastomer is disclosed. However, this value cannot be extended to all product ranges.

Korean Patent No. 361550 discloses a case where the ethylene-propylene random copolymer is melt mixed with an ethylene-alpha olefin copolymer elastomer, but the transparency improvement effect is insufficient, and a control method for improving transparency and impact strength is proposed. Is not clear and very limited.

The present invention is to solve the above problems, by adjusting the density and melt index of the ethylene-alpha olefin pin copolymer included in the ethylene-propylene copolymer as an impact modifier, to improve the impact resistance and transparency of the propylene polymer For the purpose of

The present invention provides a means for solving the above problems, (a) ethylene-propylene copolymer 85 having an ethylene content of 2 to 5% by weight and a melt index (230 ° C., 2.16 kg) of 10 to 30 g / 10 minutes. To 97 parts by weight; And (b) an ethylene-alphaolefin copolymer 3 having an ethylene content of 60 to 90 wt%, a density of 0.85 to 0.92 g / cm ³ , and a melt index (190 ° C., 2.16 kg) of 2 to 5 g / 10 minutes. To provide a polypropylene resin composition for injection molding comprising 15 to 15 parts by weight, wherein the ratio of the melt index of the (b) ethylene-alpha olefin copolymer to the melt index of the (a) ethylene-propylene copolymer is 0.1 to 0.4.

It is preferable that the said (a) ethylene-propylene copolymer has a melting temperature of 140-150 degreeC.

In addition, the (a) ethylene-propylene copolymer is preferably prepared using a Ziegler-Natta catalyst.

The (b) ethylene-alpha olefin copolymer is preferably prepared using a metallocene catalyst.

In addition, the (b) ethylene-alpha olefin copolymer is preferably an ethylene-butene copolymer or an ethylene-octene copolymer.

The present invention provides another injection molding product made of the polypropylene resin composition for injection molding as another means for solving the above problems.

The polypropylene resin composition for injection molding according to the present invention by controlling the density and melt index of the ethylene-alpha olefin pin copolymer included in the ethylene-propylene random copolymer as an impact modifier, It exhibits excellent impact and transparency.

The present invention (a) 85 to 97 parts by weight of ethylene-propylene copolymer having a content of 2 to 5% by weight of ethylene and a melt index (230 ° C., 2.16 kg) of 10 to 30 g / 10 minutes; And (b) an ethylene-alphaolefin copolymer 3 having an ethylene content of 60 to 90% by weight, a density of 0.85 to 0.90 g / cm ³ , and a melt index (190 ° C., 2.16 kg) of 2 to 5 g / 10 minutes. It includes to 15 parts by weight, the ratio of the melt index of the (b) ethylene-alpha olefin copolymer to the melt index of the (a) ethylene-propylene copolymer relates to a polypropylene resin composition for injection molding of 0.1 to 0.4. The present invention is characterized in that the impact and transparency of the polypropylene injection-molded product is improved by including the ethylene-alpha olefin copolymer having a controlled density and melt index without changing the physical properties of the ethylene-propylene copolymer.

(a) Ethylene-propylene copolymer

The polypropylene resin composition for injection molding according to the present invention is an ethylene-propylene copolymer as a main resin, and the ethylene-propylene copolymer has an ethylene content of 2 to 5% by weight, and a melt index (230 ° C., 2.16 kg). ) Is 10 to 30 g / 10 minutes.

The ethylene-propylene copolymer preferably has an ethylene content of 2 to 6% by weight, more preferably 3.5 to 4.5% by weight.

If the content is less than 2% by weight, the impact resistance and transparency may be insignificant. If the content exceeds 6% by weight, it is difficult to manufacture the injection molded product due to difficulty in operating the reactor when the viscosity of the copolymer is increased.

In addition, the ethylene-propylene copolymer preferably has a melt index (230 ° C., 2.16 kg) of 10 to 30 g / 10 minutes, and more preferably 13 to 15 g / 10 minutes.

In addition, the ethylene-propylene copolymer preferably has a melting temperature of 140 to 150 ℃. If the melting temperature is less than 140 ℃ may cause problems in the strength of the injection molded product, if it exceeds 150 ℃ because of the low ethylene content, which is the cause of impact resistance and transparency deterioration.

That is, when using an ethylene-propylene copolymer in which the ethylene content, the melt index, and the melting temperature fall within the above ranges, it is possible to mold a transparent and durable injection product.

The ethylene-propylene copolymer having the above physical properties does not change even when the ethylene-alpha olefin copolymer having a density and melt index is adjusted.

The ethylene-propylene copolymer is not limited thereto, but is preferably polymerized using a Ziegler-Natta catalyst.

The Ziegler-Natta catalyst may be used without particular limitation as long as it is used for general olefin polymerization, but preferably includes a transition metal compound containing an element belonging to Group 4, 5 or 6 of the periodic table as a main catalyst, As a cocatalyst, the thing containing the organometallic compound containing the element which belongs to group 13 of a periodic table can be used.

The transition metal compound may use a solid titanium catalyst containing magnesium, titanium, a halogen element and an internal electron donor. As the internal electron donor, for example, a diether compound, a phthalate compound, or a mixture thereof may be used. Specifically, diisobutyl phthalate may be used.

An organoaluminum compound can be used as the organometallic compound, and examples of the organometallic compound include Al (C ₂ H ₅ ) ₃ , Al (C ₂ H ₅ ) ₂ H, Al (C ₃ H ₇ ) ₃ , Al (C ₃ H ₇ ) ₂ H, Al (i- C ₄ H ₉ ) ₂ H, Al (C ₈ H ₁₇ ) ₃ , Al (C ₁₂ H ₂₅ ) ₃ , Al (C ₂ H ₅ ) (C ₁₂ H ₂₅ ) ₂ , Al (iC ₄ H ₉ ) (C ₁₂ H ₂₅ ) ₂ , Al (iC ₄ H ₉ ) ₂ H, Al (iC ₄ H ₉ ) ₃ , (C ₂ H ₅ ) ₂ AlCl, (iC ₃ H ₉ ) ₂ AlCl, or (C ₂ H ₅ ) ₃ Al ₂ Cl ₃ can be used.

The organometallic compound may also be a mixture of organoaluminum compounds, and organometallic compounds belonging to Periodic Tables 1, 2 and 13 may be used, in particular mixtures of different organoaluminum compounds. For example, the organoaluminum compound may be a mixture of Al (C ₂ H ₅ ) ₃ and Al (iC ₄ H ₉ ) ₃ ; A mixture of Al (C ₂ H ₁₇ ) ₃ , Al (C ₂ H ₅ ) ₃ and Al (C ₈ H ₁₇ ) ₃ ; A mixture of Al (C ₄ H ₉ ) ₂ H and Al (C ₈ H ₁₇ ) ₃ ; A mixture of Al (iC ₄ H ₉ ) ₃ and Al (C ₈ H ₁₇ ) ₃ ; A mixture of Al (C ₂ H ₅ ) ₃ and Al (C ₁₂ H ₂₅ ) ₃ ; A mixture of Al (iC ₄ H ₉ ) ₃ and Al (C ₁₂ H ₂₅ ) ₃ ; A mixture of Al (C ₂ H ₅ ) ₃ and Al (C ₁₆ H ₃₃ ) ₃ ; Mixtures of Al (C ₃ H ₇ ) ₃ and Al (C ₁₈ H ₃₇ ) ₂ (iC ₄ H ₉ ), and the like can be used.

The ethylene-propylene copolymer according to the present invention is preferably polymerized together with the Ziegler-Natta catalyst in the presence of an external electron donor. Examples of the external electron donor include substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, substituted or unsubstituted aryl groups having 6 to 30 carbon atoms, substituted or unsubstituted cycloalkyl groups having 5 to 30 carbon atoms, and substituted or unsubstituted groups. An organosilane compound containing at least one or more functional groups selected from the group consisting of alkoxy groups having 1 to 20 carbon atoms and containing at least one oxygen atom may be used. For example, examples of the external electron donor include aromatic organic silane compounds such as diphenyldimethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane, or phenylmethyldimethoxysilane; Methoxytrimethylsilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, diisopropyldimethoxysilane, di-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, dish Aliphatic organic silane compounds such as clohexyldimethoxysilane; Or mixtures thereof.

The polymerization of ethylene and propylene is carried out in the presence of the Ziegler-Natta catalyst and the external electron donor. The polymerization reaction proceeds in the same manner as in the polymerization of propylene using a conventional Ziegler-Natta catalyst. In particular, the reaction is preferably carried out substantially in the absence of oxygen and water. It may also be carried out under a pressure of 1 to 100 atm, preferably about 2 to 50 atm, at a temperature of 20 to 200 ° C, preferably 50 to 100 ° C.

(b) ethylene-alpha olefin copolymer

The polypropylene resin composition for injection molding according to the present invention includes 3 to 15 parts by weight of the ethylene-alphaolefin copolymer as an impact modifier for 85 to 97 parts by weight of the main resin (a) ethylene-propylene copolymer. The ethylene-alpha olefin copolymer has an ethylene content of 60 to 90% by weight, a density of 0.85 to 0.92 g / cm ³ , and a melt index (190 ° C., 2.16 kg) of 2 to 5 g / 10 min. .

Ethylene-alpha olefin, which is an impact reinforcing material, preferably contains 3 to 15 parts by weight, more preferably 5 to 8 parts by weight. If the content is less than 3 parts by weight, the impact resistance may be weakened. If the content is more than 15 parts by weight, the transparency may be lowered.

If the content of ethylene contained in the ethylene-alpha olefin copolymer as the impact reinforcing material is less than 60% by weight, the stiffness may be reduced. If the content of the ethylene content exceeds 90% by weight, the impact resistance may be lowered.

The ethylene-alpha olefin copolymer preferably has a density of 0.85 to 0.92 g / cm ³ , and more preferably 0.87 to 0.90. Transparency was improved by using a range similar to the density of the main resin ethylene-propylene copolymer. When the density of the said ethylene-alpha olefin copolymer is less than 0.85 g / cm <^3>, transparency may fall, and when it exceeds 0.92 g / cm < ³ >, impact resistance may fall.

 In addition, the ethylene-alpha olefin copolymer preferably has a melt index (190 ° C., 2.16 kg) of 2 to 5 g / 10 minutes, and more preferably 4 to 5 g / 10 minutes. If the melt index of the ethylene-alpha olefin copolymer is adjusted in the above range, the impact strength and transparency can be improved at the same time. When the melt index is less than 2 g / 10 minutes, the impact resistance and transparency may be degraded, and when the melt index exceeds 6 g / 10 minutes, the molecular weight of the final polymer may be lowered.

Further, the ratio of the melt index of the (b) ethylene-alpha olefin copolymer to the melt index of the (a) ethylene-propylene copolymer is preferably 0.1 to 0.4. Controlling the melt index ratio will control the size of the ethylene-alphaolefin copolymer. As the melt index ratio is close to 0.1, the size of the ethylene-alpha olefin copolymer is increased, thereby decreasing transparency and impact resistance. The closer the melt index ratio is to 0.4, the more the impact strength can be improved. The smaller size also improves transparency. It is possible to control the transparency and impact resistance of the polypropylene injection molded product within the above range. If the melt index ratio is less than 0.1, the size of the ethylene-alpha olefin copolymer may be excessively large, and the impact strength and transparency may be very low. If the melt index ratio is greater than 0.6, the molecular weight of the ethylene-alpha olefin copolymer may be decreased, thereby changing the physical properties of the final polymer. There is concern.

The ethylene-alpha olefin copolymer is a copolymer of ethylene and alpha olefin. Examples of the alpha olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene or 4-methyl-1-pentene, 1-octene. Etc., and these may be included alone or in combination of two or more, more preferably 1-butene or 1-octene.

The ethylene-alphaolefin copolymer used in the present invention can be polymerized using a metallocene catalyst. Polymerization using a metallocene catalyst has a narrower molecular weight distribution than polymerization using a Ziegler-Natta catalyst, thereby contributing more to transparency improvement.

The present invention also relates to an injection molded article made of the polypropylene resin composition. The polypropylene resin composition can be produced in a small amount of the stereoregularity is improved.

The injection molding method can use any conventional method used in the art without limitation. For example, the polypropylene powder or pellet resin is injected into the injection machine through the injection port. The injected resin is heated and melted in the barrel of the injection machine. When the melt is injected into the mold at a high pressure, and the polymer melt injected into the mold is solidified by cooling or crosslinking, the mold is opened and the molded article can be separated from the mold. The injection molded product is not particularly limited, and a product that requires excellent transparency and impact resistance can be produced.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, which are intended to help a specific understanding of the present invention, and the scope of the present invention is not limited by the Examples.

Example 1

Ziegler-Natta catalyst production

25.25 g of magnesium compound (MgCl ₂ -2.8C ₂ H ₅ OH) and 150 ml of anhydrous heptane were added to a 500 ml glass reactor under a nitrogen atmosphere at 0 DEG C, followed by stirring. Stirred. Thereafter, 100 ml of 0 ° C. TiCl ₄ was added thereto, and the mixture was reacted at room temperature for 1 hour. Further, 150 ml of TiCl ₄ was added dropwise, and the reaction mixture was heated to 100 ° C. for 2 hours. Then, the supernatant was separated and 200 ml of TiCl ₄ was added dropwise and reacted at 120 ° C. for 2 hours. After the reaction, TiCl ₄ was removed and washed 6 times with heptane at 80 ° C. to obtain a solid titanium catalyst.

(a) Preparation of ethylene-propylene copolymer

Using this catalyst, ethylene-propylene random polymerization was carried out using triethylaluminum as a promoter and dicyclopentyldimethoxysilane as an external electron donor at a dicyclopentyldimethoxysilane to catalyst molar ratio of 40 and 70 ° C. An ethylene-propylene random copolymer having a melt flow index of 13 ± 1 g / 10 min and an ethylene content of 3.7 ± 0.2 wt% was obtained.

(b) Blending with Ethylene-Alphaolefin

6 wt% of an ethylene-octene copolymer (melt index 5 g / 10 min, density: 0.870 g / cm ³ ) prepared by using a metallocene catalyst was blended into the ethylene-propylene copolymer obtained above to prepare a polymer.

Example 2

After the ethylene-propylene copolymer was prepared in the same manner as in Example 1, 6 wt% of an ethylene-octene copolymer (melt index: 2.2 g / 10 min, density: 0.898 g / cm ³ ) made using a metallocene catalyst was blended. To prepare a polymer.

Example 3

After the ethylene-propylene copolymer was prepared in the same manner as in Example 1, 6 wt% of an ethylene-butene copolymer (melt index 5.0 g / 10 min, density: 0.875 g / cm ³ ) made using a metallocene catalyst was blended. To prepare a polymer.

Example 4

After the ethylene-propylene copolymer was prepared in the same manner as in Example 1, 6 wt% of an ethylene-butene copolymer (melt index 2.1 g / 10 min, density: 0.883 g / cm ³ ) made using a metallocene catalyst was blended. To prepare a polymer.

Comparative Example 1

After the ethylene-propylene copolymer was prepared in the same manner as in Example 1, 6 wt% of an ethylene-octene copolymer (melt index 1.0 g / 10 min, density: 0.870 g / cm ³ ) made using a metallocene catalyst was blended. To prepare a polymer.

Comparative Example 2

After the ethylene-propylene copolymer was prepared in the same manner as in Example 1, 6 wt% of linear low density polyethylene (melt index: 4.4 g / 10 min, density: 0.914 g / cm ³ ) made using Ziegler-Natta catalyst was blended to obtain a polymer. Prepared.

Comparative Example 3

Comparative Example 3 was used in the ethylene-propylene copolymer prepared in Example 1 not containing any impact modifier.

Test Example

Injection specimens were prepared from the polymers prepared in Examples and Comparative Examples, and their properties were measured in the following manner, and the results are shown in Table 1 below.

(1) Melt Flow Index

The melt flow index was measured using a weight of 2.16 kg for the ethylene-propylene random copolymer used as matrix according to ASTM D1238 at a temperature of 230 ° C. and for the ethylene-alpha olefin copolymer used for the blending process at a temperature of 190 ° C. , In terms of weight (g) of polymer melted for 10 minutes (g / 10 min).

(2) stereoregularity

% Stereoregularity of the polymer is the weight ratio of the polymer that is not extracted in boiling o -xylene for 1 hour in weight percent. The stereoregularity measurement of the polymer is described in detail as follows. First, 200 ml xylene is prepared in a flask and then filtered with 200 mm No. 4 extraction paper. The aluminum pan was dried in an oven at 150 ° C. for 30 minutes, then cooled in a desiccator and weighed. Next, 100 ml of filtered o -xylene was collected by a pipette, transferred to an aluminum pan, and heated to 145 to 150 ° C to evaporate all o -xylene. The aluminum pan was then vacuum dried for 1 hour under a temperature of 100 ± 5 ° C. and a pressure of 1 hr, 13.3 kPa. After the aluminum pan was cooled in a desiccator, the above procedure was repeated twice, and the o -xylene-only blank test was completed within a weight error of 0.0002 g. Next, the polymer obtained in the examples was dried (70 ° C., 13.3 kPa, 60 minutes, vacuum dried), and then 2 g ± 0.0001 g of the cooled polymer sample in a desiccator was placed in a 500 ml flask, and 200 ml o − Xylene was added. The flask was connected to nitrogen and cooling water and the flask was heated to reflux o -xylene for 1 hour. After placing the flask in air for 5 minutes to cool the temperature below 100 ° C, the flask was shaken and placed in a thermostat (25 ± 0.5 ° C) for 30 minutes to precipitate insoluble matters. The resultant solution in which the precipitate was formed was filtered repeatedly until it was clean with 200 mm No. 4 extraction paper. After drying at 150 ° C. for 30 minutes, 100 ml of the filtered solution was added to a pre-weighed aluminum pan after cooling in a desiccator, and the aluminum pan was heated to 145 to 150 ° C. to evaporate o -xylene. The evaporated aluminum pan was vacuum dried for 1 hour at a temperature of 70 ± 5 ° C. and a pressure of 13.3 kP, and the weight was measured within an error of 0.0002 g by repeating the cooling in a desiccator twice.

The weight percent (Xs) of the o -xylene dissolved in the polymer is obtained by the following equation, and the weight ratio (= 100-Xs) of the polymer not extracted from o -xylene is obtained from The castle was made.

From here,

[Xs = o -xylene dissolved in the polymer (% by weight),

Vbo = volume of initial o -xylene in ml,

Vb1 = o -volume (ml) taken from the polymer dissolved in xylene,

Vb2 = volume of collected o -xylene (ml) used in the blank test,

W2 = sum of the weight of the polymer remaining in the aluminum pan (g) after evaporating the aluminum pan and o -xylene,

W1 = weight of aluminum pan (g),

Wo = weight of initial polymer in grams

B = average value of remaining residues in aluminum pan in ball test (g)]

XI = 100- Xs (weight ratio of polymer not extracted to o-xylene)

(3) Haze

The final copolymer was added with 1000 ppm of calcium stearate, 1000 ppm of phenolic antioxidants, 1000 ppm of phosphite antioxidants, 600 ppm of antistatic agents, and 2000 ppm of solitol-based nucleating agents. After manufacture, it was measured by ASTM D 1003.

(4) Izod impact strength and flexural modulus

After extruding the final copolymer obtained by adding the additive as described above, using a hydraulic injection molding machine to produce a specimen of 3mm thickness and measured the Izod impact strength according to ASTM D 256, after the specimen of 6mm thickness produced ASTM D790 The flexural modulus was measured by

(5) ethylene content

The ethylene content of the ethylene-propylene random copolymer is FT-IR (Bio-Rad FTS 3000), and the height of the 4800-3500 cm ^-1 peak and the ethylene component reflecting the specimen thickness in the IR absorption spectrum of the prepared specimen. It calculates by measuring the area of 790-660 cm <^-1> peak which is a peak by. The ethylene content of the known standard is divided by the area of the 790-660 cm ^-1 peak divided by the height of 4800-3500 cm ^-1 to obtain the ethylene content in the copolymer.

Referring to Table 1, Examples 1 to 4 hardly changed the melt index of ethylene-propylene, and are excellent in transparency and impact strength.

More specifically, the impact strength was improved while showing a level of transparency equivalent to that of Comparative Example 3 without using the impact modifier.

In addition, when comparing Example 1 and Comparative Example 1, the impact strength of Example 1 using the same ethylene-octene copolymer used as an impact modifier but having a higher melt index (low molecular weight) The transparency of the ethylene-alpha olefin copolymer dispersed after blending was lowered due to a higher melt index (smaller molecular weight).

Comparative Example 2 is a case of using a linear low-density polyethylene using a Ziegler-Natta catalyst due to the high density, but improved transparency, but the impact strength was not improved compared to Examples 1 to 4.

Claims (6)

(a) 85 to 97 parts by weight of an ethylene-propylene copolymer having an ethylene content of 2 to 5% by weight, a melt index (230 ° C., 2.16 kg) of 10 to 30 g / 10 minutes, and a melting temperature of 140 to 150 ° C. ; And (b) Ethylene-alpha olefin copolymer 3 to ethylene content of 60 to 90% by weight, density of 0.85 to 0.92 g / cm ³ , and melt index (190 ° C., 2.16 kg) of 2 to 5 g / 10 min. Including 15 parts by weight, The polypropylene resin composition for injection molding wherein the ratio of the melt index of the (b) ethylene-alpha olefin copolymer to the melt index of the (a) ethylene-propylene copolymer is 0.1 to 0.357. It is 0 degreeC, The polypropylene resin composition for injection molding. delete The method of claim 1, Wherein (a) ethylene-propylene copolymer is a polypropylene resin composition for injection molding, characterized in that prepared using a Ziegler-Natta catalyst. The method of claim 1, (B) The ethylene-alpha olefin copolymer is a polypropylene resin composition for injection molding, characterized in that prepared using a metallocene catalyst. The method of claim 1, (B) The ethylene-alpha olefin copolymer is an ethylene-butene copolymer or an ethylene-octene copolymer, polypropylene resin composition for injection molding. An injection molded article made of the polypropylene resin composition for injection molding according to claim 1.