KR20090007044A - Ethylene-propylene block copolymer-based polypropylene resin composition having high flowability, stiffness and impact strength - Google Patents

Abstract

An ethylene-propylene block copolymer-based polypropylene resin composition is provided to mold a large sized and thin film injection molded product by not containing organic peroxide and having excellent mobility and post-processing property, and to ensure excellent rigidity and impact strength. An ethylene-propylene block copolymer-based polypropylene resin composition comprises polypropylene 100.0 parts by weight and nucleating agent 0.05~0.3 parts by weight and has a melt index of 80~120 g / 10 min. The polypropylene comprises (A) highly crystalline homo polypropylene 80~95 weight% having the isotactic pentad fraction of 96% or greater and (B) ethylenepropylene elastomeric copolymer 5~20 weight% having the molar ratio of ethylene / (ethylene + propylene) of 0.15~0.40. The absolute viscosity rate (A/B) of the highly crystalline homo polypropylene(A) and the ethylenepropylene elastomeric copolymer(B) is 0.09~0.33.

Description

Ethylene-propylene block copolymer-based polypropylene resin composition having high flowability, stiffness and impact strength

The present invention relates to a high rigid ethylene-propylene block copolymer-based polypropylene resin composition excellent in fluidity, rigidity and impact strength. More specifically, the present invention relates to a polypropylene resin composition comprising high crystalline homopolypropylene, an ethylene-propylene elastic copolymer, and a rigid nucleating agent, and has excellent fluidity and post-processability compared to conventional ethylene-propylene block copolymer-based polypropylene resins. The present invention relates to a highly rigid ethylene-propylene block copolymer-based polypropylene resin composition which is easily molded into a large molded article or a thin film product.

Since homopolypropylene in which propylene is homopolymerized has low impact strength, a technique of compensating impact strength by copolymerizing with an alpha olefin, for example ethylene, during polymerization is used. These ethylene-propylene block copolymers are widely used in injection molded products such as automobile parts, home appliances, industrial parts, daily necessities and packaging, packaging films and sheets due to their excellent rigidity and impact characteristics.

In the ethylene-propylene block copolymer-based polypropylene resin, the impact strength is increased when the content of the ethylene-propylene copolymer is increased, but there is a problem that the rigidity and the heat resistance are deteriorated. Therefore, various techniques have been proposed to improve the rigidity and heat resistance while maintaining a certain level of impact strength.

Japanese Laid-Open Patent Publication No. 55-81125 discloses a technique for producing high rigid polypropylene by raising isotacticity during polymerization.

In addition, the Republic of Korea Patent Publication No. 2001-0109721 is a nuclear magnetic resonance method, the stereoregularity index is 96% or more based on the pentad method, the molecular weight distribution is wide, consisting of an ethylene-propylene copolymer having an absolute viscosity of 3.0 ~ 6.5 dl / g Although a polypropylene resin composition having a melt index of 3 to 35 g / 10 min has been disclosed, there is a problem that the melt index is not much lower than 80 g / 10 min, which is the minimum melt index required for productivity, processability, and workability.

High-flow polypropylene resin products are indispensable for high-speed or large-size injection molding, and the viscosity of the resin used must be very low. In order to lower the viscosity of the resin, a method of setting the temperature at the time of injection may be considered very high, but in this case, problems such as color change, physical property degradation, and heat stability deterioration occur due to pyrolysis due to high temperature. In addition, when the injection molding does not have sufficient flowability, problems such as bending after forming or gas traces may occur due to excessive injection pressure and residual stress.

In order to solve this problem, a low-flow, highly crystalline ethylene-propylene block copolymer-based polypropylene resin is prepared, and then an organic peroxide is added to artificially cut the polypropylene chain, thereby lowering the molecular weight to improve the flowability of the resin. The method is used.

European Patent Nos. 1312617 and US Pat. No. 6,66,292 disclose a method for minimizing the decrease in rigidity and impact strength due to the addition of organic peroxides by adding specific organic peroxides to ethylene-propylene block copolymer-based polypropylene resins under specific conditions. Is being presented.

In addition, US Pat. No. 6,672,329 also proposes a method for producing a high flow propylene-ethylene block copolymer-based polypropylene resin by adding an organic peroxide to a specific ethylene-propylene copolymer.

However, when the organic peroxide is added to improve flowability, that is, the melt index of the polypropylene resin, workability is lowered due to a narrow molecular weight distribution, and there is a problem in that odor and poor paintability occur during post-processing.

Korean Patent Publication No. 2001-0109865 discloses a highly crystalline ethylene-propylene block copolymer-based polypropylene resin composition having a melt index of 80-120 g / 10min. The conditions for the optimization of the composition of the ethylene-propylene copolymer for preventing the degradation of the stiffness and the impact strength due to the high melt index are not disclosed, and the characteristics of the high stiffness and the high impact strength to the polypropylene resin composition In order to control the dispersion of the ethylene-propylene copolymer and the size of the copolymer, the ethylene-propylene copolymer can be controlled by controlling the interfacial tension of the homopolypropylene and ethylene-propylene copolymer and controlling the molecular weight of the ethylene-propylene copolymer. Although a fine distribution of is required, it has technical limitations in that nothing is disclosed.

The present invention is to solve the problems of the prior art as described above in order to form large and thin-film injection products with excellent fluidity and post-processability without artificially adding organic peroxide after ethylene-propylene block copolymer-based polypropylene resin production It is an object to provide a resin composition which is suitable and at the same time excellent in rigidity and impact strength.

Polypropylene resin composition according to the present invention 80-95 wt% of highly crystalline homopolypropylene (A) having an isotactic pentad fraction of at least 96% and ethylene-propylene elastomer (B) 5-20 having a molar ratio of ethylene / (ethylene + propylene) of 0.15-0.40 100 parts by weight of polypropylene having a ratio of absolute viscosity (component A / component B) of the highly crystalline homopolypropylene and the ethylene-propylene elastomer by 0.09 to 0.33, and the nucleating agent (C) 0.05 to 0.3 It relates to an ethylene-propylene block copolymer-based polypropylene resin composition having a melt index of 80 parts by weight.

The ethylene-propylene block copolymer-based polypropylene resin composition according to the present invention is a resin composition comprising a homopolypropylene (A), an ethylene-propylene copolymer (B) and a nucleating agent (C). Not only has excellent fluidity compared to block copolymer-based polypropylene resins, but also has excellent stiffness and impact strength due to the excellent properties of high-crystalline homopolypropylene and ethylene-propylene copolymers. It is suitable as a molding material for large products or thin film products.

The ethylene-propylene block copolymer-based polypropylene resin according to the present invention comprises homopolypropylene (A) as a matrix and ethylene-propylene copolymer (B) as a domain. The copolymer (B) is classified into an amorphous ethylene-propylene copolymer (Rubber) and a semicrystalline ethylene copolymer (semicrystalline ethylene copolymer) (B).

In order to impart high rigidity to the ethylene-propylene block copolymer-based polypropylene resin, the homopolypropylene (A) should be one having a high stereoregularity. That is, homopolypropylene having an isotactic pentad fraction of 96% or more, which is a stereoregularity index on Nuclear Magnetic Resonance, is required, and the melt index of the ethylene-propylene copolymer is determined by the melt index of the homopolypropylene. Since it is very large compared with the above, in order to give high fluidity to the ethylene-propylene block copolymer-based polypropylene resin, it is necessary to use a homopolypropylene (A) having a melt index that is much larger than the melt index of the ethylene-propylene copolymer.

The content, molecular weight, composition, particle size and distribution of the ethylene-propylene copolymer (B) are major factors influencing the physical properties of the polypropylene resin composition.

As the content of the ethylene-propylene copolymer (B) increases, impact strength increases, but stiffness such as tensile strength and stiffness decreases. In the polypropylene resin composition according to the present invention, when the content of the ethylene-propylene copolymer (B) is less than 5% by weight, the impact strength is weakened, and when the content is more than 20% by weight, the rigidity is deteriorated. do.

The molecular weight of the ethylene-propylene copolymer is determined according to the hydrogen concentration (Hydrogen Ratio, hydrogen / ethylene) in the composition injected into the gas phase reactor for polymerizing the ethylene-propylene copolymer, and measured in absolute viscosity. If the molecular weight of the ethylene-propylene copolymer (B) is small, the size of the ethylene-propylene copolymer, which is a domain, becomes small. The hydrogen concentration for producing an ethylene-propylene copolymer (B) having a molecular weight suitable for use in the present invention is preferably 0.005 to 0.030 in a hydrogen / ethylene molar ratio. If the hydrogen / ethylene molar ratio is greater than 0.030, the size of the ethylene-propylene copolymer is small enough to absorb shocks. If the hydrogen / ethylene molar ratio is less than 0.005, the size of the ethylene-propylene copolymer is large and even. There is a problem that the impact strength can be partially weakened because it is not dispersed.

However, there is a limit in controlling the size and distribution of the ethylene-propylene copolymer only by the molecular weight of the ethylene-propylene copolymer. Therefore, excellent stiffness and impact strength can be obtained by controlling the molecular weight of the ethylene-propylene copolymer, the ratio of the absolute viscosity of the ethylene-propylene copolymer (B) and the homopolypropylene (A), and the composition of the ethylene-propylene copolymer together. .

The ratio of the absolute viscosity of the ethylene-propylene copolymer (B) and the homopolypropylene (A) is a variable related to the compatibility between the parent homopolypropylene (A) and the ethylene-propylene copolymer (B) serving as a shock absorber. As for the absolute viscosity ratio (= absolute viscosity of component A / absolute viscosity of component B) of each component, 0.09-0.33 are preferable. If the absolute viscosity ratio is less than 0.09 or greater than 0.33, the ethylene-propylene copolymer (B) is agglomerated or homogeneously dispersed in the homopolypropylene (A), so that the ethylene-propylene block has excellent impact strength and rigidity. It becomes impossible to produce a copolymerized polypropylene resin.

The composition of the ethylene-propylene copolymer (B) is controlled by the molar ratio of ethylene / (ethylene + propylene). Larger proportions produce ethylene copolymers and smaller ones produce propylene random copolymers. As the propylene content of the ethylene-propylene copolymer increases, the interfacial tension between the homopropylene and the ethylene-propylene copolymer is weakened, so that the dispersion of the ethylene-propylene copolymer is good, so that the ethylene-propylene block copolymer-based polypropylene resin is excellent. It has stiffness and impact strength.

Specifically, in the ethylene-propylene copolymer, when the molar ratio of ethylene / (ethylene + propylene) is less than 0.10, the size of the ethylene-propylene copolymer is very small, so that the dispersion is good, but it is completely mixed (Perfect Mixing) Since there is a problem that the impact strength is weakened. Conversely, if the molar ratio of ethylene / (ethylene + propylene) is greater than 0.40, then due to the formation of semicrystalline ethylene copolymers and the interfacial tension between homopolypropylene and ethylene-propylene elastomers There is a problem that the impact strength is weakened.

In addition, it is preferable that the size of the ethylene-propylene copolymer is 0.5 to 2.0 microns. If the size of the ethylene-propylene copolymer is smaller than 0.5 microns or larger than 2.0 microns, the impact strength cannot be absorbed and the impact strength becomes poor. .

The nucleating agent (C) added to the polypropylene resin composition according to the present invention to supplement the mechanical strength of the finished product is dibenzylidene sorbitol, di (p-methyl benzylidene) sorbitol, dimethyl benzylidene sorbitol, alkyl benzoate aluminum salt, organic It can be selected from phosphorus metal salts and mixtures thereof, the content of the preferred nucleating agent is 0.05 to 0.3 parts by weight based on 100 parts by weight of polypropylene, if the nucleating agent is less than 0.05 parts by weight can not secure sufficient rigidity and heat resistance, 0.3 In the case of more than the weight part, no further improvement of the physical properties appears.

The resin composition according to the present invention may further include known additives such as antioxidants, neutralizers, stabilizers, etc., as necessary.

Polypropylene resins require Izod impact strength of 5.0 kg · cm / cm or more and tensile strength of 300 kg / cm² or more to be used for manufacturing automotive parts.Addition of inorganic additives such as talc It is not possible to achieve these levels of impact strength and tensile strength at the same time alone, and as shown in the present invention, stereoregularity of homopolypropylene, molecular weight and composition of ethylene-propylene copolymer, interfacial tension, size and distribution Through general control of the ethylene- propylene block copolymer-based polypropylene resin should be prepared.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited thereto. The method of evaluating the physical properties of the polypropylene prepared in Examples and Comparative Examples of the present invention is as follows.

1) Melt index: measured according to ASTM D1238 at a load of 2.16 Kg at 230 ° C.

2) Stereoregularity: The isotactic fraction was measured in pentad units of the homopolypropylene molecular chain using 13C-NMR.

3) Flexural modulus: measured by injection specimen according to ASTM D790.

4) Izod impact strength: The injection specimen was measured at 23 ° C according to ASTD D256.

5) Melting xylenes: A certain amount of sample obtained in the polymerization experiment is put into a round flask with a certain amount of xylene, added to the boiling point for about 1 hour, melted for about 1 hour, then cooled slowly to room temperature, and recrystallized. The percentage of remaining sample was measured by evaporation.

6) Absolute Viscosity: After dissolving the propylene-ethylene copolymer in decaline at 135 ° C, absolute viscosity was measured with a viscometer.

8) Spiral flow: The length of the injected specimen was measured by injection into a spiral mold at a temperature of 210 ° C. in a 150 ton injection machine.

9) electron microscopy; After the specimen was immersed in liquid nitrogen and cooled, the cross section was cut by a microtomer and placed in a cyclohexane solution, and left in an ultrasonic cleaner for 1 hour to dissolve the ethylene-propylene elastomer in the sample. The sample was deposited with gold and deposited with gold. The size and dispersion of the ethylene-propylene elastomer in the mixture was observed.

Compositions according to Examples and Comparative Examples were prepared in the following manner.

1. Preparation of component (A)

Hydrogen and propylene were injected into the polymerization reactor in order, and then the slurry bulk polymerization was carried out at 60 to 80 ° C. and 35 to 40 atm, and the melt index was controlled by the amount of hydrogen.

2. Preparation of Component (B)

After the completion of the polymerization of homopropylene as component (A) as above, unreacted propylene was removed, and the pressure was reduced to normal pressure. As a result, hydrogen was injected to continuously polymerize in the gas phase to obtain component (B) which is an ethylene-propylene copolymer.

In this step, the ethylene-propylene composition ratio in the elastic copolymer was controlled by the molar ratio of ethylene / (ethylene + propylene) shown in Table 1 below, and the absolute viscosity was controlled by the molar ratio of hydrogen / ethylene.

3. Pellet  And preparation of test specimens

In the resin composition obtained through the above step, pentaerythritol-derakis [3- (3,5-di-tert], a phenol-based (Hindered Phenol) antioxidant, was used as a primary antioxidant based on 100 parts by weight of the resin composition. 0.05 parts by weight of secondary antioxidant, Pentaerythrityl-terrakis [3- (3,5-di-tert.butyl-4-hydroxy-phenyl) -propionate]] 0.10 part by weight of tris (2,4-di-tert.butylphenyl) phosphate, a phosphorus antioxidant, and 0.05 part by weight of calcium stearate as a neutralizing agent After mixing 0.10 parts by weight of an alkyl benzoate aluminum salt as a nucleating agent to prepare pellets using a twin screw extruder, an injection test specimen of ASTM standard was prepared in a 150-ton injection machine of Dongshin Hydraulic and measured for physical properties. The results are shown in Table 1 below and FIGS. 1 to 3.

division Metric unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Component (A) composition Component (A) content wt.% 88 85 85 85 89 90 79 Pentad fraction wt.% 96 96 91 92 93 96 96  Component (B) composition Gas ratio mol / mol 0.18 0.30 0.50 0.45 0.38 0.46 0.30 H2 / C2 mol / mol 0.010 0.010 0.040 0.040 0.018 0.018 0.018 Component (B) content wt.% 12 15 16 16 12 11 21 Melt index g / 10min 110 85 95 82 90 100 98 Absolute Viscosity Ratio (A / B) - 0.20 0.28 0.45 0.47 0.27 0.27 0.20 Total ethylene content wt.% 4.0 7.0 8.0 8.0 5.5 4.2 12 Organic peroxide wt.ppm - - - adding adding - - Nucleating agent content wt.ppm 1,000 1,000 - 1,000 1,000 1,000 1,000 Properties The tensile strength kg / cm² 310 305 230 255 275 275 265 Flexural modulus kg / cm² 20,000 19,000 13,000 14,500 17,000 17,500 16,000 Izod impact strength kgcm / cm 5.5 5.9 8.6 8.2 6.1 4.8 7.5 Spiral flow mm 98 95 90 89 91 97 97 Odor and Finish (Paintability) - Great Good Bad Bad Bad Bad Bad

Note 1) Gas Ratio: molar ratio of ethylene / (ethylene + propylene).

Note 2) Absolute viscosity ratio: Absolute viscosity of component A / Absolute viscosity of component B

As can be seen in Table 1, Examples 1 and 2 are manufactured in the range of the absolute viscosity ratio of 0.09 ~ 0.33, whereas Comparative Example 1 and Comparative Example 2 is outside the absolute viscosity ratio of 0.09 ~ 0.33 In Comparative Example 3 and Comparative Example 4, the absolute viscosity ratio was prepared in the range of 0.09 to 0.33, but in the case of Comparative Example 3, the pentad fraction is less than 96%, and Comparative Example 4 is the ethylene-propylene elasticity in the gas phase reactor. The polymerization conditions of the copolymers differ from Examples 1 and 2 according to the invention. In the case of Comparative Example 5, all the conditions are the same as in Examples 1 and 2, but the content of component B is very high, 21wt%. In Comparative Examples 2 and 3, an organic peroxide was artificially added to the polymerized polypropylene to increase the melt index of the polypropylene resin.

As shown in the experimental results shown in Table 1, the compositions of Examples 1 and 2 according to the present invention is Izod (Izod) impact strength of 300 kg / cm ² or more 5.0 kg · cm / cm The tensile strength was shown above, and compared to Comparative Examples 1 to 5, it was possible to exhibit excellent post-processing properties such as mechanical properties, flowability, odor and paintability as a whole.

1 is an electron micrograph at 3000 times magnification of an ethylene-propylene block copolymer-based polypropylene resin composition according to Example 1 of the present invention.

FIG. 2 is an electron micrograph at 500 times the ethylene-propylene block copolymer-based polypropylene resin composition of Comparative Example 1 according to the prior art. FIG.

3 is an electron micrograph of a ethylene-propylene block copolymer-based polypropylene resin composition of Comparative Example 4 according to the prior art, which is enlarged by 2000 times.

Claims (5)

80-95% by weight of highly crystalline homopolypropylene (A) having an isotactic pentad fraction of 96% and ethylene-propylene elastomer (B) 5-20 having a molar ratio of ethylene / (ethylene + propylene) of 0.15-0.40 100 parts by weight of polypropylene made of a weight%, the absolute viscosity ratio (A / B) of the high crystalline homopolypropylene (A) and the ethylene-propylene elastomer (B) is 0.09 to 0.33, and the nucleating agent (C Ethylene-propylene block copolymer-based polypropylene resin composition having a melt index of 0.05 to 0.3 parts by weight, 80 to 120 g / 10 min. The ethylene-propylene block copolymer-based polypropylene resin composition according to claim 1, wherein the ethylene-propylene elastomer (B) is formed under a condition in which a hydrogen / ethylene molar ratio is 0.005 to 0.030. The ethylene-propylene block copolymer-based polypropylene resin composition according to claim 1, wherein the ethylene-propylene elastomer is uniformly dispersed in the resin composition in a size of 0.5 to 2.0 microns. According to claim 1, Izod (Izod) impact strength of the polypropylene resin composition is 5.0 kg · cm / cm or more, tensile strength 300 kg / cm ² The ethylene-propylene block copolymer type polypropylene resin composition characterized by the above. The method of claim 1, wherein the nucleating agent is selected from dibenzylidene sorbitol, di (p-methyl benzylidene) sorbitol, dimethyl benzylidene sorbitol, alkylbenzoic acid aluminum salts, organophosphorus metal salts and mixtures thereof. Propylene block copolymer-based polypropylene resin composition.

Images