KR20020046389A - Polypropylene-based resin composition - Google Patents

Abstract

PURPOSE: A polypropylene resin composition is provided, to improve the melting flowability, the stiffness, the impact resistance, the heat resistance and the formability without using an elastic polymer. CONSTITUTION: The polypropylene resin composition comprises 80-95 wt% of an ethylene-propylene block copolymer whose ratio of a propylene homopolymer component to an ethylene-propylene copolymer component is 75:25 to 50:50 by weight and which has a melting index of 20-60 g/10 min(ASTM D1238: 230 deg.C, 2.16 kg); and 5-20 wt% of talc. Preferably the ethylene-propylene block copolymer has an absolute viscosity of 2.0-6.0 dl/g and contains 30-60 wt% of ethylene. The talc has the chemical composition of 3MgO4SiO2H2O, purity more than 95%, Mohs hardness of 4-5, a melting point more than 1,200 deg.C, an aspect ratio of 2-50 and a mean particle size of 1-50 micrometers, and is plate-shaped.

Description

Polypropylene-based resin composition

The present invention relates to a polypropylene resin composition, and more particularly, the weight ratio of the propylene homopolymer portion to the ethylene-propylene copolymer portion is 75 to 25 to 50 to 50 and the melt index (ASTM D1238: 230 ° C, 2.16 kg) It relates to a polypropylene resin composition comprising 80 to 95% by weight of ethylene-propylene block copolymer having 20 to 60g / 10min, and 5 to 20% by weight of talc.

Since the olefin elastomer has the properties of elasticity and plastic at the same time, and has thermoplasticity, the molding and processing can be facilitated by using the same processing equipment as that used for ordinary thermoplastic olefin resin. Therefore, it has been widely used as an impact modifier of composite materials for plastic parts of automobiles.

However, the olefin-based elastomer has a problem of sharply lowering the rigidity and heat resistance when added in an excessive amount, in contrast to the effect of improving the impact resistance, and in particular, due to the high price, the material cost increases. In order to solve this problem, it is common to use a polypropylene resin blended with a variety of olefin elastomers (elastomer). However, the elastomer composition thus prepared has a disadvantage in that the melt flowability is poor due to the viscosity difference between the polypropylene resin and the elastomer, and as a result, the moldability is lowered.

To date, various studies have been conducted for the purpose of improving the moldability of the elastomeric composition. For example, in Japanese Patent No. 62-260846, an elastomer composition was prepared by blending ethylene-propylene random copolymer and styrene ethylene butadiene rubber. The composition has good moldability, but since it uses amorphous random copolymer, This has the disadvantage of deteriorating.

On the other hand, in US Patent Nos. 4,212,787 and 4,247,652, polypropylene resin, polyethylene resin, ethylene propylene rubber, polyisobutylene, and mineral oil are mixed with a chestnut mixer, and then the mixture is cut to form a crosslinking agent and a crosslinking aid. Disclosed is a method of kneading in an extruder and then cutting the kneaded again and kneading in an extruder with a polypropylene resin to produce an elastomeric composition. The composition prepared by the above method has good processability, physical properties, paintability, etc., but the manufacturing process is complicated and requires many steps, thus making it expensive, and uniformly blending the liquid type mineral oil with other solid components. There is a problem that is difficult.

In addition, US Pat. No. 5,240,983 and EP 0409542A2 prepare an elastomer composition by mixing polypropylene resin, ethylene propylene rubber, ethylene propylene diene rubber, organosilane, crosslinking agent and mineral oil. As with the methods of 4,212,787 and 4,247,652, liquid type mineral oils are used, which has the disadvantage that the blending between the components is difficult to be made uniformly.

On the contrary, Korean Patent Publication No. 1996-1009 discloses a polyolefin composition prepared by adding ethylene propylene rubber as an impact modifier to a polypropylene block copolymer and adding fine talc as a rigidity and heat resistance reinforcing agent. However, the polyolefin composition has a problem in that impact resistance is improved by adding an excess of ethylene propylene rubber, while rigidity and melt flowability are decreased, and rigidity and heat resistance are improved by excess talc filling, while the weight of the molded article is increased by increasing density. There is this.

An object of the present invention is to solve the problems of the prior art as described above, to provide a polypropylene resin composition excellent in stiffness and impact resistance, and excellent moldability without adding an elastomer.

That is, the present invention provides an ethylene-propylene block having a weight ratio of 75 to 25 to 50 to 50 and a melt index (ASTM D1238: 230 ° C., 2.16 kg) of 20 to 60 g / 10 min in terms of the weight ratio of the propylene homopolymer portion to the ethylene-propylene copolymer portion. It provides a polypropylene resin composition comprising 80 to 95% by weight of the copolymer, and 5 to 20% by weight of talc.

Hereinafter, the components of the polypropylene resin composition of the present invention will be described in more detail.

The ethylene-propylene block copolymer used in the present invention is a polypropylene resin having a melt index (ASTM D1238: 230 ° C., 2.16 kg) of 20 to 60 g / 10 minutes, and 50 to 75% by weight of the propylene homopolymer portion and ethylene-propylene. Copolymer portion 25 to 50% by weight.

When the melt index is less than 20, appearance defects such as flow marks and tiger marks are generated when a large product such as an automobile bumper or a complex shape such as an automobile grille is injected. When the melt index exceeds 60, moldability is excellent while impact resistance rapidly decreases. do. Further, if the propylene homopolymer portion is more than 75% by weight and the ethylene-propylene copolymer portion is less than 25% by weight, the impact resistance is lowered, which is not good.

The content of the ethylene-propylene block copolymer is preferably 80 to 95% by weight based on the total composition, it can not achieve the object of the present invention outside the above range.

The propylene homopolymer, which is a component of the ethylene-propylene block copolymer, is a high stereoregular homopolypropylene having an isotactic pentad fraction of 95%, which is a stereoregularity index on Nuclear Magnetic Resonance. As mentioned above, it is preferable that the ratio (Mw / Mn, hereinafter "molecular weight distribution") of the weight average molecular weight (Mw) and the number average molecular weight (Mn) by a gel permeation chromatography (GPC) method is 7-12. .

When the isotactic pentad fraction is less than 95%, heat resistance and rigidity are lowered, and thus, a complicated shape product used at a high temperature may cause a warp or warp during use of the product. In addition, if the molecular weight distribution is less than 7, even if the resin composition of the same melt index to make the melt flowability is worse, if it exceeds 12, the metering time during injection molding is long, productivity is lowered.

The ethylene-propylene copolymer, which is another component of the ethylene-propylene block copolymer, is a polymer obtained by copolymerizing ethylene and propylene in the polypropylene homopolymer, and has an ethylene content of 30 to 60 wt% and an absolute viscosity (135 ° C). ) Is preferably 2.0 to 6.0 dl / g. The absolute viscosity is the viscosity when the ethylene-propylene copolymer is extracted with n-decane and the extract is dissolved in decaline at 135 ° C.

If the ethylene content is less than 30% by weight, the crystalline propylene portion is increased and the impact resistance is insufficient. If the ethylene content is more than 60% by weight, the crystalline ethylene portion is increased and the impact resistance is lowered. In addition, when the absolute viscosity is less than 2.0 dl / g, the elasticity is weakened, so the impact resistance at low temperature is insufficient, and when the absolute viscosity is greater than 7,0 dl / g, the molecular weight is too large. And impact resistance is lowered.

On the other hand, the talc used in the present invention for the purpose of improving mold release properties, high temperature dimensional stability and stiffness has a chemical composition of [3MgO 4SiO ₂ H ₂ O], purity is 95% or more, collecting hardness is 4 to 5, melting point It is preferable that it is 1200 degreeC or more, aspack ratio is 2-50, it has a plate-shaped particle shape, and the average particle size is 1-50 micrometers.

If the aspac ratio is less than 2, there is a problem of lowering the rigidity, and if it exceeds 50, there is a problem of poor appearance and impact resistance of the molded article. In addition, if the average particle size is less than 1㎛ produce agglomeration of particles during extrusion process, the productivity is lowered, if it exceeds 50㎛ there is a problem of poor appearance and impact resistance of the molded article.

The content of the talc is preferably 5 to 20% by weight based on the total composition. If the content is less than 5% by weight, the effect of improving heat resistance cannot be obtained. If the content is more than 20% by weight, the density of the composition is increased to increase the weight of the injection molding, and the flow marks are generated during injection molding, resulting in deterioration in appearance characteristics and impact strength. Is not good because it is sharply lowered.

In addition, the polypropylene resin composition of the present invention, if necessary, various additives, reinforcing agents, fillers, such as dispersants, heat stabilizers, weather stabilizers, antistatic agents, lubricants, slip agents, nucleating agents, flame retardants, wollastonite, calcium carbonate, mica , Kaolin, clay, barium sulfate, calcium sulfate and the like can be added within a range not contrary to the object of the present invention. In particular, the dispersant is used for the purpose of dispersing the talc and the pigment contained in the resin composition of the present invention or neutralizing the catalyst residue, calcium stearate, zinc stearate, magnesium stearate ), Hydrotalcite, polyoxyethylene stearyl ester, fatty acid amide, or mixtures thereof can be used.

There is no restriction | limiting in particular in the method of manufacturing the resin composition of this invention, The normal polypropylene resin composition manufacturing method can be used. That is, after mixing each of the above components and other additives, kneading such as kneader, roll mill, bambury mixer, and kneading using a single or twin screw extruder, etc. Can be used.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Examples and Comparative Examples

The ethylene-propylene block copolymers used in the production of the polypropylene resin compositions of Examples and Comparative Examples have a melt index (ASTM D1238: 230 ° C., 2.16 kg) of 40 g / 10 min, and more detailed characteristics thereof are shown in Table 1 below.

After weighing each component as shown in Table 2 below, the mixture was mixed at 2000 rpm for 5 minutes using a mixer (Shinhwa Industrial SSM-75), and then the screw rotation speed was 240 rpm using a PCM30 extrusion machine. The pellets were prepared by extrusion at a feed rate of 30 rpm. At this time, the temperature distribution of the extruder was set to 100/140/170/190/200/200/200/200 ° C from the first hopper to the die.

The pellets thus obtained were dried in an oven at 80 ° C. for 2 hours in consideration of the deterioration of physical properties due to moisture absorption, and then specimens for evaluation of physical properties were prepared using a Samsung Klockner FCM-110 injection machine (molding force = 110 tons). At this time, the temperature distribution of the injection machine was set to 30/200/200/200/200 ℃ in the order of the nozzle in the feeding hopper, the mold temperature was set to 60 ℃, injection pressure 60 to 100 bar. The physical property evaluation results of each specimen thus prepared are shown in Table 2 below.

Example Comparative example One 2 3 4 One 2 3 4 5 Ethylene Propylene Block Copolymer Propylene Homopolymer Composition ratio (% by weight) 65 70 60 70 90 85 70 62 85 Stereogram (isotactic pentad fraction,%) 96 96 95 95.5 95 90 89 90 91 Molecular weight distribution 8 9 11 7 8 8 5 9 5 Ethylene-Propylene Copolymer Composition ratio (% by weight) 35 30 40 30 10 15 30 38 15 Ethylene Content (wt%) 40 45 35 35 40 40 65 40 35 Absolute Viscosity (㎗ / g) 3.2 3.0 2.7 4 3 3.3 8 2.5 4

Example Comparative example One 2 3 4 One 2 3 4 5 Polypropylene resin (% by weight) Ethylene Propylene Block Copolymer 90 95 85 80 90 90 95 100 70 Inorganic filler (% by weight) Talc (particle size: 2㎛) 10 5 15 20 10 10 5 - 30 Impact modifier (parts by weight) Ethylene Propylene Rubber - - - - - 10 10 - 25 Properties Melt Index (g / 10min) 35 36 30 28 35 27 28 38 10 Density (g / cm 3) 0.97 0.94 1.03 1.07 0.97 0.97 0.94 0.91 1.16 Flexural modulus (kgf / ㎠) 15000 14800 14500 20000 20000 17000 9000 6500 14000 Room temperature impact strength (23 ℃, kgf ㎝ / ㎝) 60 55 60 45 7 9 10 60 45 Low temperature impact strength (-20 ℃, kgf cm / cm) 11 10 12 9 4 5 6 10 9 Heat Deflection Temperature (℃) 115 113 118 127 124 118 110 90 120

[Property evaluation method]

* Melt Index: ASTM D1238 (230 ℃, 2.16kg)

* Density: ASTM D1505

* Flexural Modulus: ASTM D790

* Impact strength at room temperature: ASTM D256

* Low temperature impact strength: ASTM D256

* Heat Deflection Temperature: ASTM D648

As can be seen from Table 2, when the content of the ethylene-propylene copolymer in the ethylene-propylene block copolymer is less than 25% by weight (Comparative Examples 1 and 2), the impact resistance at room temperature and low temperature is lowered. Even if ethylene propylene rubber as an impact modifier is added, impact resistance hardly improves (Comparative Example 2).

In addition, even if the content of the ethylene-propylene copolymer in the ethylene-propylene block copolymer is 25% by weight or more, when the ethylene content in the ethylene-propylene copolymer exceeds 60% by weight and the absolute viscosity exceeds 6.0 dl / g The addition of ethylene propylene rubber does not improve the impact resistance (Comparative Example 3).

On the other hand, when the stereoregularity of the propylene homopolymer is too low, the flexural rigidity is lowered (Comparative Examples 3 and 4), and when the talc as the inorganic filler is not added, the heat resistance is significantly decreased (Comparative Example 4).

On the other hand, when excessively adding ethylene propylene rubber and talc as impact modifiers, impact resistance, rigidity and heat resistance are good, but fluidity is poor in injection molding of large parts, resulting in poor appearance such as flow marks, and too high density. The weight of the injection-molded article is high, thereby increasing (Comparative Example 5). In addition, excessive addition of expensive ethylene propylene rubber is uneconomical because the production cost increases.

As described in detail above, the polypropylene resin composition of the present invention is excellent in melt flow property and excellent in balance of physical properties such as stiffness, impact resistance and heat resistance, and thus is suitable for producing complex large injection molded articles.

Claims (4)

Ethylene-propylene block copolymer 80 to 95 having a weight ratio of propylene homopolymer portion to ethylene-propylene copolymer portion of 75 to 25 to 50 to 50 and melt index (ASTM D1238: 230 ° C., 2.16 kg) of 20 to 60 g / 10 minutes Polypropylene resin composition comprising 5% by weight, and 5 to 20% by weight talc. The method of claim 1, Polypropylene resin composition, characterized in that the isotactic pentad fraction of the propylene homopolymer is 95% or more and the molecular weight distribution is 7 to 12. The method of claim 1, Polyethylene-based resin composition, characterized in that the ethylene content of the ethylene-propylene copolymer is 30 to 60% by weight and the absolute viscosity is 2.0 to 6.0 dl / g. The method of claim 1, The talc has a chemical composition of [3MgO 4SiO ₂ H ₂ O], has a purity of 95% or more, a hardness of 4 to 5, a melting point of 1200 ° C or more, an aspac ratio of 2 to 50, and a plate-like particle shape. It has a polypropylene resin composition, characterized in that the average particle size of 1 to 50㎛.