KR100656829B1 - High-crystalline polypropylene resin composition having excellent melting flowability, stiffness and low temperature impact strength - Google Patents

Abstract

The present invention relates to a highly crystalline polypropylene resin composition having a significantly higher melt flow rate than a conventional polypropylene resin and excellent rigidity and impact strength, and is a problem caused when molding a molded article having a large size and a complicated shape. It is a composition that solves warping, unmolding and the like, and has excellent mechanical strength and simultaneously maintains impact strength even in a low temperature environment, and is made of a polypropylene, an ethylene propylene copolymer, and a nucleating agent.

The present invention can be used as a molding material for large products for electric, electronic, and automotive products, and the molded products can be used in both high and low temperature environments due to their excellent rigidity and impact resistance.

Melt flow, rigidity, low temperature impact strength, polypropylene, ethylene propylene copolymer, nucleating agent

Description

Highly crystalline polypropylene resin composition with excellent melt flow, stiffness and low temperature impact strength.

The present invention relates to a highly crystalline polypropylene resin composition having excellent melt flow properties and excellent rigidity and low temperature impact strength. More specifically, the present invention relates to a conventional polypropylene resin composition containing a polypropylene and an ethylene propylene copolymer and a nucleating agent. The present invention relates to a highly crystalline polypropylene resin composition having a wide range of use environments due to its excellent melt flow and easy molding of large molded articles, high crystallinity and appropriate rubber design, and improved rigidity and low temperature impact strength characteristics. .

Polypropylene resin is a material that has a wide range of industrial applications such as automotive interior parts and home appliances parts because it has superior rigidity, chemical resistance, and moldability compared to other polyolefin materials. Generally, homopolymerized with propylene homopolymer has excellent stiffness, hardness, tensile strength and heat resistance, but when used as a material for injection parts for automobile parts and general packaging, it is often used due to low impact strength, especially low impact strength at low temperatures. There has been a limitation. In order to modify such low impact resistance, a propylene ethylene block copolymer has been developed in which ethylene is added and copolymerized when polymerizing polypropylene. The propylene ethylene block copolymer has an effect on impact modification, but the stiffness and heat resistance are lowered compared to the existing polypropylene due to the characteristics of the copolymer. In particular, in order to replace ABS resin or high impact polystyrene with polypropylene, and to expand its use, a method for simultaneously improving impact resistance and rigidity is needed.

There are several ways to improve the impact properties of polypropylene. One of them is to melt and mix rubber-based materials such as EPM (ethylene propylene copolymer) or EPDM (ethylene propylene diene copolymer) to polypropylene. Has been used. However, in this case, the dispersion of EPM or EPDM can be a problem, and the price rises. Another method is to block-polymerize α-olefins, for example ethylene, in the aforementioned propylene polymerization, in which case the impact properties are increased as the ethylene content is increased, but there is a problem in that the rigidity and heat resistance are lowered. Several measures have been proposed to compensate for this drawback.

There is a method of using a special nucleating agent as an additive to increase the rigidity without lowering the impact characteristics. Nuclear refining techniques include the addition of organic nucleating agents and the use of inorganic fillers, there are disadvantages of price increases and other property deterioration. Thus, in order to produce high rigid polypropylene, there is a technique disclosed in Japanese Patent Application Laid-open No. 55-81125 for raising isotacticity during polymerization.                         

On the other hand, since polypropylene resin is a crystalline resin, shrinkage occurs when cooling after melting and molding. In the case of resin that does not exhibit sufficient flowability during injection molding, products with thin plate shape or thin rib-shaped products due to excessive injection pressure may cause warpage after molding, gas traces due to high resin temperature, and poor flowability. This results in problems such as unmolding of the ends of molded articles.

In order to solve this problem, a method of raising the melt index of the resin or adding a reinforcing material may be examined. However, when a resin having a high melt index is simply used, the melt flowability may be improved but the impact strength may be lowered. In addition, the method of reinforcing the inorganic filler is improved in bending and shrinkage after molding, but there is a cost caused by the appearance defects due to the filler, the specific gravity of the material rises, there is a disadvantage that the flow of the resin is worse by the filler.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has an object of developing a resin composition which is excellent in melting flow property of resin and is suitable for molding a complicated large-scale injection product, while maintaining rigidity and impact strength at the same time.

The resin composition of the present invention is an ethylene propylene copolymer having an isotactic pentad fraction of 95% or more, 60 to 95% by weight homopolypropylene (A) having a molecular weight distribution of 7 to 12, and an absolute viscosity of 1.5 to 6.0 dl / g. (B) 100 parts by weight of polypropylene polymer consisting of 5 to 40% by weight and 0.1 to 0.5 parts by weight of nucleating agent (C).

In addition, the melt index of the resin composition is preferably in the range of 80 to 120 g / 10 minutes. If the melt index is less than 80g / 10min, it is difficult to form large products, and if it exceeds 120g / 10min, the rigidity and impact resistance are inferior.

Homopolypropylene (A) used in the present invention is a high-stereoregular polypropylene, a resin having an isotactic pentad fraction, which is a stereoregularity index on Nuclear Magnetic Resnance, of 95% or more, and gel permeation. The ratio (Mw / Mn, hereinafter referred to as "molecular weight distribution") of the weight average molecular weight (Mw) and the number average molecular weight (Mn) by chromatography (GPC) method is resin of 7-12. When the isotactic pentad fraction of (A) is less than 95%, heat resistance and rigidity are lowered, and thus, in the case of a complicated shape product used at a high temperature, there is a disadvantage that the product is bent or twisted during use. In addition, if the molecular weight distribution of (A) is less than 7, the melt flowability is poor when the resin composition of the same melt index is made, and if it exceeds 12, the metering time is increased during injection molding, and the productivity is lowered.

In the resin composition of the present invention, the ethylene propylene copolymer (B) is a polymer made by copolymerizing ethylene and propylene after (A) is produced in a series of reactors, and the absolute viscosity measured at 135 ° C is 1.5 dl / g It is -6.0 dl / g. The weight ratio of components (A) and (B) is 5 to 40% by weight when the sum of (A) and (B) is 100, and the impact strength is lowered when the content of B is less than 5%. When it exceeds 40%, rigidity is inferior.

In the resin composition of the present invention, the nucleating agent (C) is not particularly limited, aluminum parabutyl benzoic acid, sodium benzoic acid, calcium benzoic acid and the like can be used. In the case of inorganic nucleating agents, talc nucleating agents are preferable, and talc having an average particle diameter of 2.0 mu, a minimum particle size of 1.0 mu or more, and a maximum particle diameter of 6 mu or less may be preferably used, and if the talc nucleating agent is less than 1.0 mu or more than 6 mu, The efficiency of the effect is lowered. In the case of the nucleating agent, 0.1 to 0.5 parts by weight, preferably 0.1 to 0.3 parts by weight based on 100 parts by weight of the polypropylene polymer, is difficult to obtain sufficient rigidity and heat resistance when the content of the nucleating agent is less than 0.1, and when it exceeds 0.5 parts by weight. No longer improves physical properties.

The resin composition of the present invention may be added various additives such as antioxidants, heat stabilizers, weather stabilizers, antistatic agents, lubricants, slip agents, flame retardants, pigments, dyes and the like.

There is no restriction | limiting in particular in the method of manufacturing the resin composition of this invention, The method of manufacturing the polypropylene resin composition generally known can be used. Each of the above components and other additives may be added in a required amount to knead using a kneader such as a kneader, a roll, a Bambury mixer, or a single or twin screw extruder.

The present invention will be described in detail through the following examples. However, these examples are for illustrative purposes only and the present invention is not limited thereto.

Examples 1-2 and Comparative Examples 1-4

The measurement method of the specimen physical properties in each Example and Comparative Example was as follows.

Stereoregularity diagram (isotactic pentad fraction): The isotactic fraction as a pentad unit in the polypropylene molecular chain using ¹³ C-NMR was measured.

Molecular weight distribution: The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography (GPC).

Absolute Viscosity of Ethylene Propylene Copolymer: The copolymer was extracted with n-decane solution, and the extract was dissolved in 135 ° C Decaline to measure the viscosity.

Melt flow index (MI): measured at 230 ° C. and 2.16 kg load according to the method of ASTM D1238.

Spiral flow: 110 ton injection machine, injection into the spiral mold at 235 ℃ to measure the length of the injected specimen.

Flexural modulus: According to ASTM D790 method.

Low temperature impact strength: injection molding the polymer into a sheet of 2mm thickness, dropping the weight from a certain height to measure the average breaking height.

Heat Deflection Temperature: According to ASTM D648 method.

The resin compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were prepared by kneading using a Bambari mixer kneader and a twin screw extruder by adding necessary amounts of the components and other additives in the ratios shown in Table 1 below.

ASTM Family No. 1 specimens were made to measure the flexural modulus, impact strength and yield point tensile strength using an injection machine to measure the physical properties of the resin compositions prepared above. The injection machine used was Samsung Klockner FM140TON, and the injection condition is fixed at 170, 200, 220, 230, 230 ℃ (temperature of nozzle), 60 ℃ (molding temperature) from the hopper, and the injection pressure is 50 ~. It carried out in the range of 120 atmospheres. The extruded specimens were placed in a room temperature of 23 ° C. for 72 hours and then physical properties were measured. Examples and comparative examples are shown in Table 1 below.

Table 1

As can be seen from Table 1, when Example 1 and Comparative Example 1 are compared, Example 1 and Comparative Example 1 are both highly crystalline polypropylene polymers, but all have excellent stiffness, but in Comparative Example 1 of the ethylene propylene copolymer The viscosity was too high, the low temperature shock was inferior to Example 1. Comparing Example 1 and Comparative Example 2, Example 1 was superior to Comparative Example 2 using a rigid polymer and resin flow properties of the general polymer as a high crystalline polypropylene polymer. Comparing Example 1 with Comparative Example 3, Comparative Example 3 uses only general homopolypropylene and slightly improves the rigidity / heat resistance, but the impact strength is lower than that of Example 1. Comparing Example 2 with Comparative Example 4, Example 2 is the addition of talc nucleating agent to the high crystalline polypropylene polymer, the stiffness / heat resistance / resin flow was excellent compared to Comparative Example 4 using the general polymer.

As described above, the highly crystalline polypropylene resin composition according to the present invention has excellent melt flow properties, which facilitates the molding of large products, as well as the rigidity and impact resistance of the molded products. It can be used over, and can be used as a molding material of large products for electric, electronic and automobiles.

Claims (3)

60 to 95 wt% of homopolypropylene (A) having an isotactic pentad fraction of 95% or more and a molecular weight distribution of 7 to 12, 5 to 40 ethylene propylene copolymer (B) having an absolute viscosity of 1.5 to 6.0 dl / g A high crystalline polypropylene resin composition comprising 100 parts by weight of a polypropylene polymer composed of% by weight and 0.1 to 0.5 parts by weight of the nucleating agent (C). 2. The highly crystalline polypropylene resin composition according to claim 1, wherein the melt index of the resin composition is in the range of 80 to 120 g / 10 minutes. The high crystalline polypropylene resin composition according to claim 1, wherein the nucleating agent is an inorganic nucleating agent, a talc having a minimum particle size of 1.0 mu and a maximum particle diameter of 6 mu.