KR20040065079A - Polypropylene Resin Composition having Great Resistance to High Pressure, Impact Strength, and Transparency for Automotive applications - Google Patents

Abstract

PURPOSE: Provided is a polypropylene resin composition, which has excellent pressure resistance and impact resistance and high transparency and crystallinity suitable to be used as a material of a transparent container for cars. CONSTITUTION: The highly crystalline polypropylene resin composition comprises: (A) 30-74 wt% of a homopolypropylene resin having an isotactic pentad proportion of 95% or more and a molecular weight distribution index of 7-12; (B) 20-64 wt% of an ethylene-propylene random block copolymer having an absolute viscosity ratio of 0.8-1.2 based on the homopolypropylene resin; (C) 5-30 wt% of a C2-C8 alpha-olefin copolymer; and (D) 0.05-1.0 wt% of a nucleating agent.

Description

Polypropylene Resin Composition having Great Resistance to High Pressure, Impact Strength, and Transparency for Automotive applications}

The present invention relates to a highly crystalline polypropylene resin composition excellent in pressure resistance, impact resistance and transparency, and more particularly, for automobiles, including homo polypropylene resins and ethylene-propylene random block copolymers, alpha olefin copolymers and nucleating agents. The present invention relates to a polypropylene resin composition suitable as a material of a transparent storage container.

Polypropylene resin has excellent mechanical properties, chemical resistance, and moldability, and thus has a wide range of industrial applications such as automobile interior parts, home appliances parts, and industrial materials. In general, homo-propylene homopolymerized with propylene has excellent stiffness, hardness, tensile strength and heat resistance.However, when used as a material for injection molding products for automobiles and general liquids, low impact strength, especially low impact strength at low temperatures There were many restrictions. In addition, when the thickness is thicker than 2mm, the transparency is reduced, it is not suitable to apply to the transparent container that looks inside.

There are several methods to improve the impact properties of these polypropylenes, and a method of melt-blending rubber-based materials such as EPM (ethylene propylene copolymer) or EPDM (ethylene propylene diene copolymer) to polypropylene has been widely used. come. In this case, however, the transparency decreases due to the dispersibility control limit between the polypropylene and the rubber component, making it impossible to apply to the transparent storage container.

In order to improve transparency, Korean Patent Publication Nos. 2002-033562 and 2001-096295 disclose a block copolymer of a vinyl aromatic hydrocarbon compound in which hydrogen is added to a polypropylene resin, a styrene-ethylene-butylene-styrene (SEBS) block copolymer, and styrene. Although polypropylene resin compositions to which ethylene-propylene-styrene (SEPS) block copolymers and the like are applied have been proposed, they do not exhibit sufficient rigidity enough to reduce the crystallinity of polypropylene and to be molded into a storage container.

On the other hand, there is a method of applying a special nucleating agent to the block copolymer as a method to maintain a considerable level of rigidity and improve the impact characteristics. The method of adding an organic nucleating agent or an inorganic filler may be used as such a nucleation prescription technique, but there is a possibility of causing other physical properties to degrade.

The present invention is to improve the various problems as described above, to provide a polypropylene resin composition that can be applied to a transparent storage container for automobiles excellent in pressure resistance and impact resistance and excellent permeability There is this.

The present invention is (A) 30 to 74 wt% homopolypropylene resin having an isotactic pentad fraction of 95% or more and a molecular weight distribution of 7 to 12, (B) an absolute viscosity ratio of the homopolypropylene resin is 0.8 to 1.2 A polypropylene resin composition comprising 20 to 64% by weight of phosphorus ethylene-propylene random block copolymer, (C) 5 to 30% by weight of alpha olefin copolymer having 2 to 8 carbon atoms, and (D) 0.05 to 1.0% by weight of nucleating agent will be.

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

The homopolypropylene resin (A) used in the present invention is a high-stereoregular polypropylene having an isotactic pentad fraction, which is a stereoregularity index on Nuclear Magnetic Resonance, of 95% or more, and gel permeation chromatography. It is resin whose ratio (Mw / Mn, hereinafter molecular weight distribution) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) by a graph (GPC) method is 7-12. If the pentad fraction is less than 95%, there is a problem that the rigidity and heat resistance is lowered. If the molecular weight distribution is less than 7, the melt flowability deteriorates when the resin composition of the same melt index is produced. If the molecular weight distribution exceeds 12, the productivity decreases due to an increase in the metering time during injection molding. On the other hand, the content of the homo polypropylene resin is preferably 30 to 74% by weight. If the content is less than 30%, the stiffness and heat resistance required for the application to the storage container may not be expressed, and if the content is more than 74%, the impact characteristic is sharply lowered.

The ethylene-propylene random block copolymer (B) of the present invention is a polymer made by copolymerizing ethylene and propylene after (A) is made in a series of reactors, and has an intrinsic viscosity measured at 135 ° C. It is 0.8-1.2 level compared with the viscosity of (A) component. If the viscosity ratio is less than 0.8, the impact characteristic is drastically lowered, and if it is more than 1.2, the transparency is lowered. On the other hand, the content of the ethylene-propylene random block copolymer is preferably 20 to 64% by weight. If it is out of this content range, the balance between stiffness / heat resistance and impact resistance according to the relative proportion with (A) component is broken, and transparency is also reduced.

The alpha olefin copolymer (C) of the present invention is for expressing transparency and impact resistance, and possessing an appropriate level of optical / thermodynamic compatibility with the component (B), while being able to be dispersed to a fine level. Gives transparency In the alpha olefin copolymer usable as component (C), the carbon number of the alpha olefin is in the range of 2 to 8, which is for expression of impact resistance at low temperature. The content of component (C) is in the range of 5 to 30% by weight. When the content is less than 5% by weight, the impact properties and transparency reinforcement effect is insignificant, and when the content is more than 30% by weight, the relative physical property is lowered, which makes it impossible to express the rigidity and heat resistance for the storage container.

The nucleating agent as the component (D) used in the present invention is not particularly limited in its use, so that both the organic and inorganic nucleating agents can be used, and the amount of the nucleating agent used is preferably 0.05 to 1.0 wt%. More preferably, the organometallic nucleating agent such as aluminum parabutylbutyl benzoic acid, sodium benzoic acid, calcium benzoic acid or the like is more preferably 0.05 to 0.3% by weight, and more preferably 0.1 to 1.0% by weight of an inorganic nucleating agent such as talc. At this time, in the case of talc, the level whose average particle diameter is 1.0 micrometer and the maximum particle diameter is 6.0 micrometer or less is preferable. The content of the present nucleating agent is effective for the expression of stiffness and heat resistance at the time of application in the range of the above-mentioned range. When applied below the minimum content, the effect is insufficient, and when applied above the maximum content, no further expression occurs.

To the polypropylene resin composition according to the present invention, various additives such as antioxidants, neutralizers, heat stabilizers, antistatic agents, weather stabilizers, lubricants, slip agents, dispersants, and UV-stabilizers are added within a range not contradicting the characteristics of the present invention. Can be.

As a method for producing the polypropylene resin composition of the present invention, kneading using a twin screw extruder is preferable, and mixing at a polypropylene melting point or more is also possible using processing conditions for producing a generally known polypropylene resin composition.

The present invention can be understood in more detail by the following examples, which are only examples for illustrating the present invention, and are not intended to limit the protection scope of the present invention.

EXAMPLE

Test conditions for each test property are as follows.

1) Stereogram (isotactic pentad fraction)

C13-NMR was used to determine the isotactic fraction as pentad unit in the polypropylene molecular chain.

2) molecular weight distribution

The ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) was measured by gel permeation chromatography (GPC) method.

3) Absolute viscosity ratio of ethylene-propylene random block copolymer

The copolymer was extracted with n-decane solution, which was then decalin at 135 ° C.

Dissolved in Decaline to measure the viscosity.

4) Withstand pressure characteristics

After the external pressure was directly applied to the injection molding products for automobiles for a certain time, the appearance and deformation of the injection molding products were relatively compared and evaluated according to the following criteria:

( ◎ : Appearance state and no deformation at all, ○ : Appearance state and almost no deformation, × : Appearance state and deformation is severe due to lack of rigidity against external pressure).

5) Tensile strength and elongation

It was measured at room temperature by the method of ASTM D638.

6) impact strength

It was measured at room temperature by the method of ASTM D256.

7) Haze

It was measured at room temperature by the method of ASTM D1004.

8) Flexural modulus

It was measured at room temperature by the method of ASTM D790.

Examples 1 to 3

In the ingredients and blending ratios shown in Table 1 below, the homopolypropylene, ethylene-propylene random block copolymer, alpha olefin copolymer and nucleating agent were dry blended together with other additives in a Henschel mixer, and then introduced into a hopper of a twin screw kneading extruder. After melting and kneading together to produce the copper resin composition, injection is made with Samsung Kleukner FCM-110 (molding force = 110 tons) to produce specimens specified in ASTM standards, and the pressure resistance, tensile strength and elongation according to the method described above. , Impact strength, transparency, flexural modulus were measured. However, the injection molded product for evaluating the pressure resistance characteristics was injected by applying the storage container mold for automobiles. The results are shown in Table 1 together.

Comparative Examples 1 to 3

A resin composition was prepared in the same manner as in Example 1, except that a homo polypropylene, an ethylene-propylene random block copolymer, an alpha olefin copolymer, a nucleating agent, and other additives were used in the ingredients and blending ratios shown in Table 1 below. The specimen was fabricated using the specimen, and the pressure resistance, tensile strength, elongation, impact strength, transparency, and flexural modulus were measured according to the aforementioned method. However, the injection molded product for evaluating the pressure resistance characteristics was injected by applying the storage container mold for automobiles. The results are shown in Table 1.

Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Resin composition Homopolypropylene Content (% by weight) 47.5 45.0 40.0 47.5 50.0 45.0 Stereogram (isotactic pentad fraction, weight%) 96 96 96 92 96 96 Molecular weight distribution 7.5 7.5 7.5 5.5 7.5 7.5 Ethylene-propylene random block copolymer Content (% by weight) 47.5 45.0 40.0 47.5 50.0 45.0 Copolymer / homopolypropylene absolute viscosity ratio) 1.0 1.0 1.0 1.0 1.0 2.5 Alpha Olefin Copolymer Content (% by weight) 5 10 20 5 - 10 Carbon number 3 3 3 3 3 3 Organic nucleating agent 0.1 0.1 0.1 0.1 0.1 - Properties Pressure resistance ◎ ◎ ○ × ◎ × Tensile strength (yield, kg / cm ² ) 330 320 300 295 340 280 % Elongation 1,200 1,100 1,000 1,000 200 1,050 Impact Strength (kg.cm/cm) 30.0 40.0 65.0 28.5 6.5 36.0 Haze 40 45 46 42 43 65 Flexural modulus (kg / cm ² ) 12,000 11,000 10,500 11,500 13,000 10,500

From the table, it can be seen that

Comparative Example 1 was similar in impact characteristics and transparency compared to Example 1 to which homopolypropylene having a proper stereoregularity and molecular weight distribution, but withstand pressure characteristics due to the degradation of rigidity is significantly inferior. In Comparative Example 2, in which the alpha olefin copolymer was not applied, the impact characteristics were significantly reduced compared to Examples 1 to 3. In Comparative Example 3, the absolute viscosity ratio of the ethylene-propylene random block copolymer and the homopolypropylene was too high compared to Example 2, inferior in transparency and impact characteristics, and inferior in pressure resistance characteristics due to the stiffness deterioration due to the non-prescription of the nucleating agent.

As described in detail above, the highly crystalline polypropylene resin composition excellent in pressure resistance, impact resistance and transparency prepared according to the present invention is suitable for use as a material for transparent storage containers for automobiles. Simple modifications or variations of the present invention may be readily made by those skilled in the art, but such modifications or changes are all within the protection scope of the present invention, which may be clarified by the appended claims.

Claims (5)

(A) 30-74 wt% of homopolypropylene resin having an isotactic pentad fraction of 95% or more and a molecular weight distribution of 7-12, (B) an ethylene- having an absolute viscosity ratio of 0.8-1.2 with respect to the homopolypropylene resin. A high crystalline polypropylene resin composition comprising 20 to 64% by weight of propylene random block copolymer, (C) 5 to 30% by weight of alpha olefin copolymer having 2 to 8 carbon atoms, and 0.05 to 1.0% by weight of (D) nucleating agent. The high crystalline polypropylene resin composition according to claim 1, wherein the nucleating agent (D) is talc having an average particle diameter of 1.0 µm and a maximum particle diameter of 6.0 µm. The high crystalline polypropylene resin composition according to claim 1, wherein the (D) nucleating agent is a sorbitol organic nucleating agent. The method according to any one of claims 1 to 3, further comprising an antioxidant, a neutralizer, a heat stabilizer, an antistatic agent, a weather stabilizer, a lubricant, a slip agent, a dispersant, a UV-stabilizer, or a mixture thereof. Highly crystalline polypropylene composition. An automotive storage container manufactured by injecting the high crystalline resin composition according to any one of claims 1 to 3.