JP2006316106A - Polypropylene resin composition and injection molding method using the same and molded form - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene resin composition capable of producing, using a multipoint gate, a molded form good in weld appearance and flow-mark appearance and also good in mechanical properties and flowability. <P>SOLUTION: The polypropylene resin composition comprises a total of 100 pts.wt. of (A) 40-84 pts.wt. of a crystalline propylene-ethylene block copolymer, (B) 1-30 pt(s).wt. of an elastomer and (C) 15-30 pts.wt. of an inorganic filler. This resin composition is such that the weight-average molecular weight (Mw) of the 0°C elution component by cross fractionation chromatography is 100,000-800,000. An injection molding method and a molded product each using the above resin composition are also provided, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polypropylene resin composition for obtaining a molded article excellent in weld appearance and flow mark appearance, and an injection molding method and molded article using the same.

  Molded articles obtained by injection molding a polypropylene resin composition are used in various fields such as automobile parts and household appliance parts. In particular, molded articles used for automobile parts are relatively large and have many complicated shapes. When injection molding such a large and complex shaped body, if the number of gates is small, the flow length from the gate to the end becomes longer, and the appearance of a striped pattern called a flow mark tends to occur near the end of the flow. Become. On the other hand, when injection molding is performed using a mold having a multi-point gate, the flow length from one gate is shortened, so the flow mark is reduced, but many boundary lines of resin flow called welds occur. This also becomes an appearance defect of the molded body.

Weld and flow mark are phenomena that are closely related not only to the size and shape of the molded body or the number of gates but also to the properties of the polypropylene resin composition. Patent Documents 1 and 2 disclose materials with excellent appearance performance such as welds and flow marks from the viewpoint of dealing with large molded products, but the flow length from one gate is short and many welds are generated. Therefore, it cannot be said that a welded product is sufficiently secured in a molded product formed by a multipoint gate.
JP 2003-41088 A JP 2000-838 A

  In the prior art, when the weld performance is improved, the flow mark performance is significantly lowered. In addition, when trying to achieve both, a significant decrease in component rigidity (flexural modulus) occurs. This is particularly noticeable when a large molded product is manufactured by injection molding. This is because the best matching of polypropylene, elastomer, and talc component in the resin composition has not been found.

  An object of the present invention is to provide a polypropylene resin composition that can produce a molded article having excellent weld appearance and flow mark appearance and having good mechanical properties and fluidity by a multipoint gate.

The present invention includes the following inventions.
(1) (A) crystalline propylene-ethylene block copolymer 40-84 parts by weight, (B) elastomer 1-30 parts by weight, and (C) inorganic filler 15-30 parts by weight ((A), (B) And the total amount of (C) is 100 parts by weight.), And the weight average molecular weight (Mw) of the components eluted by cross-fractionation chromatography at 0 ° C. is 100,000 to 800,000.
(2) The crystalline propylene-ethylene block copolymer (A) has a melt flow rate (MFR; 230 ° C., load 2.16 kg) of 10 to 200 g / 10 min, and is a crystalline propylene-ethylene block copolymer. It contains 1 to 30 parts by weight of n-decane solubles per 100 parts by weight, and the intrinsic viscosity ([η]; 135 ° C. in decalin) of the n-decane solubles is 1 to 6 dl / g. The polypropylene resin composition as described in said (1).
(3) The melt flow rate (MFR; 230 ° C., load 2.16 kg) of the polypropylene resin composition is 15 g / 10 min or more and the flexural modulus (ASTM D790) is 1500 MPa or more (1) or (2) The polypropylene resin composition described in 1.
(4) Using an injection molding machine having three or more injection cylinders or injection plungers of the polypropylene resin composition according to any one of (1) to (3) and having three or more gates. An injection molding method of polypropylene resin, wherein the molding is performed at a clamping pressure of 1000 to 2000 tons.
(5) The injection molding method according to (4), wherein the number of injection cylinders or injection plungers is 4-6.
(6) The injection molding method according to (4) or (5), wherein the mold clamping pressure is 1400 to 1800 ton.
(7) A polypropylene molded body obtained by the injection molding method according to any one of (4) to (6).
(8) The molded body according to (7), wherein the polypropylene molded body is an automotive part.
(9) The molded article according to (8), wherein the automotive part is a bumper.

  By using the polypropylene resin composition of the present invention, it is possible to produce a molded article having excellent weld appearance and flow mark appearance, and good mechanical properties and fluidity by a multipoint gate.

  The weight average molecular weight (Mw) of the component eluted at 0 ° C. in the fractionation chromatography of the polypropylene resin composition of the present invention is 100,000 to 800,000. Here, the cross-fraction chromatography 0 ° C. elution component corresponds to the n-decane soluble component in the crystalline propylene-ethylene block copolymer, and the main component of the cross-fraction chromatography 0 ° C. elution component is It is a propylene-ethylene random copolymer part. When the weight average molecular weight is less than 100,000, mechanical properties are deteriorated. On the other hand, when it exceeds 800,000, the weld appearance is deteriorated. The weight average molecular weight (Mw) of the cross fractionation chromatography 0 ° C. elution component is preferably 200,000 to 600,000.

  The polypropylene resin composition of the present invention comprises (A) crystalline propylene-ethylene block copolymer 40 to 84 parts by weight, (B) elastomer 1 to 30 parts by weight and (C) inorganic filler 15 to 30 parts by weight (( The total amount of A), (B) and (C) is 100 parts by weight. When the ratio is out of the above range, fluidity or mechanical properties deteriorate. The blending amount of the crystalline propylene-ethylene block copolymer is preferably 45 to 80 parts by weight, more preferably 50 to 75 parts by weight based on 100 parts by weight of the total of (A), (B) and (C). The amount of the elastomer is preferably 5 to 27 parts by weight, more preferably 10 to 25 parts by weight, and the amount of the inorganic filler is preferably 16 to 27 parts by weight, and more preferably 18 to 25 parts by weight.

  The crystalline propylene-ethylene block copolymer used in the present invention may be added with other crystalline polypropylene resins such as crystalline propylene homopolymer and crystalline propylene-ethylene random copolymer, if necessary. Good. The addition amount of these other crystalline polypropylene resins is preferably 50 parts by weight or less with respect to 100 parts by weight of the crystalline propylene-ethylene block copolymer.

  The crystalline propylene-ethylene block copolymer used in the present invention has a melt flow rate (MFR; 230 ° C., load 2.16 kg) of 10 to 200 g / 10 minutes, preferably from the viewpoint of balancing fluidity and mechanical properties. It is 20 to 70 g / 10 minutes, and preferably contains 1 to 30 parts by weight, preferably 3 to 25 parts by weight of n-decane solubles, based on 100 parts by weight of the crystalline propylene-ethylene block copolymer. And the intrinsic viscosity ([η]; 135 ° C. in decalin) of the n-decane soluble component is 1 to 6 dl / g, preferably 1.5 to 4.5 dl / g. Here, the n-decane soluble component means a component soluble in n-decane at room temperature, and is a main component of a propylene-ethylene random copolymer in a crystalline propylene-ethylene block copolymer. The crystalline propylene homopolymer and the crystalline propylene-ethylene random copolymer contain almost no n-decane-soluble component.

  As the elastomer used in the present invention, a thermoplastic elastomer is preferable. Examples of the thermoplastic elastomer include ethylene-α-olefin copolymers (for example, ethylene-propylene copolymers, ethylene-1-butene copolymers, ethylene-1-octene copolymers), ethylene-propylene-conjugated dienes. Copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, and styrene-ethylene-butylene-styrene block copolymers can be mentioned, and these can be used alone or in combination. . As the elastomer, an ethylene-1-octene copolymer and an ethylene-1-butene copolymer are preferable. As the elastomer, those having a melt flow rate (MFR; 190 ° C., load 2.16 kg) of 0.1 to 50 g / 10 min are preferable.

  Examples of the inorganic filler include talc, calcium carbonate, mica, barium sulfate, calcium silicate, clay, magnesium carbonate, alumina, silica, and glass fiber reinforcing agent. As the inorganic filler, talc is preferable.

  The polypropylene resin composition of the present invention is characterized in that the weight average molecular weight (Mw) of the component eluted at 0 ° C. is 100,000 to 800,000. In such a polypropylene resin composition, for example, the intrinsic viscosity ([η]; 135 ° C. in decalin) of the crystalline propylene-ethylene block copolymer soluble in n-decane is 1 to 6 dl / g. Can be obtained.

  In the polypropylene resin composition of the present invention, in addition to the components (A), (B) and (C), additives such as an antioxidant, an ultraviolet absorber, and the like are necessary as long as the effects of the present invention are not impaired. You may contain an antistatic agent, a lubricant, a pigment, a flame retardant, a nucleating agent, a dispersing agent, a plasticizer, etc. The compounding amount of these additives is usually 10 parts by weight or less with respect to the total of 100 parts by weight of the above (A), (B) and (C).

  The method for producing the polypropylene resin composition of the present invention is not particularly limited, and a method in which each component is blended in a predetermined amount and dry blended, and then melt-kneaded, or each component is quantitatively fed and directly melt-kneaded and granulated. The method to do is common. The temperature at the time of melt kneading is usually 160 to 350 ° C, preferably 170 to 260 ° C.

  The polypropylene resin composition of the present invention preferably has a melt flow rate (MFR; 230 ° C., load 2.16 kg) of 15 g / 10 min or more and a flexural modulus (ASTM D790) of 1500 MPa or more.

  Specifically, the molded article of the present invention includes interior parts and exterior parts such as automobile parts, in particular, bumpers, instrumental panels, fenders, trims, door panels, wheel covers, side protectors, console boxes, and column covers. In motorcycle parts, cowlings, muffler covers and the like are included. Also included are all molded bodies that form various welds for other uses.

  The molded body of the present invention is an injection molding machine having the polypropylene resin composition having 3 or more injection cylinders or injection plungers, preferably 4 to 6 and having 3 or more gates. It can be obtained by molding at a clamping pressure of 1000 to 2000 tons, preferably 1400 to 1800 tons.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.
The physical properties of each component of the polypropylene resin composition and the molded body were measured as follows.

[MFR]
MFR (melt flow rate): ASTM D1238
Measurement temperature 230 ℃
Measurement load 2.16kg

[Cross-fractionation chromatography (CFC; temperature elution fractionation)]
Cross-fractionation chromatography enables the analysis of the correlation between composition distribution and molecular weight distribution in a short time by directly connecting the temperature rising elution fractionation (TREF) part for composition fractionation and the GPC part for molecular weight fractionation. . The polymer dissolved at high temperature is cooled to form a thin polymer layer on the TREF column filled with inert support. First, the first section divided by TREF is injected online into the GPC, and the molecular weight of the section is measured. Meanwhile, elution is performed by raising the temperature to the next set temperature in the TREF section. When the molecular weight distribution measurement of the first section is finished, the second section is injected. Hereinafter, by repeating the same operation, detailed information on the molecular weight of each fraction of the composition distribution can be obtained.
Measurement model CFC T-150A (Mitsubishi Yuka)

[Method for measuring n-decane soluble content]
About 5 g of a polymer sample (the exact weight at this time is a) is obtained by adding 200 ml of n-decane and about 1% of BHT (3,5-di-t-butyl-4-hydroxytoluene) with respect to the sample amount. Along with this, put it in an Erlenmeyer flask. Heat to 145 ° C. and dissolve with stirring for 1 hour. After confirming that the sample is completely dissolved, it is allowed to cool for 1 hour. Thereafter, the polymer is precipitated while stirring with a magnetic stirrer for 1 hour. The precipitated polymer is suction filtered with a suction bottle and funnel (325 mesh screen). Acetone is added to the separated filtrate to make about 1 liter, and stirred for 1 hour to precipitate n-decane solubles. If the liquid does not become clear, add more acetone and continue stirring. The precipitate is filtered through a suction bottle and funnel (325 mesh screen). The collected precipitate is dried under reduced pressure at 105 ° C. and 20 mmHg or less for 1 hour. Let b be the amount of n-decane solubles recovered after drying.
The n-decane soluble content is calculated by the following formula.
n-decane soluble content (%) = (b / a) × 100
a: Weight of polymer sample (g), b: Recovered amount of soluble n-decane (g)

[Weld evaluation method]
An injection mold having a gate at the center (50 mm) having a width of 350 mm, a width of 100 mm, and a thickness of 2 mm and having a width of 100 mm was used (FIG. 1). A weir that prevents the flow of a resin having a diameter of 30 mm and a thickness of 2 mm centering on the point was provided at a position 50 mm immediately below the flow direction from the gate. The weld length was determined by measuring the length until the weld could not be discriminated by visual inspection of the weld generated after the weir when the mold was used for injection molding.
The injection molding was performed using the M200 injection molding machine (manufactured by Meiki Seisakusho) under the following conditions.
Number of injection cylinders: 1 Cylinder temperature: 210 ° C
Clamping pressure: 200ton
Mold temperature: 20 ℃
Injection pressure: 8.2 MPa
Cooling time: 20 seconds

[Flow mark evaluation method]
A flat plate having a length of 360 mm, a width of 150 mm, and a thickness of 3 mm can be formed, and an injection mold having a central portion (180 mm) having a length of 360 mm and gates at three points of 105 mm on both sides was used (FIG. 2). The injection molding was performed in the same manner as the weld evaluation method.
Evaluation 1 (one-point gate molding)
Injection molding was performed using a one-point gate other than the central portion, and the occurrence of flow marks was visually determined.
Evaluation 2 (3-point gate molding)
Injection molding was performed using all three gates, and the occurrence of flow marks was visually determined.

[Bending elastic modulus]
Flexural modulus: ASTM D790
Test piece size: 127 mm × 12.7 mm × 6.4 mmt
Distance between spans: 100mm
Bending speed: 2mm / min

[Components of polypropylene resin composition]
Each component of the polypropylene resin composition used in the examples is as follows.
(1) Crystalline propylene-ethylene block copolymer (PEBC-1)
-MFR: 105 g / 10 min- Propylene-ethylene random copolymer part: 10% by weight
Intrinsic viscosity [η]: 3.5 dl / g (measured at 135 ° C. in decalin; the same applies hereinafter)
(2) Crystalline propylene-ethylene block copolymer (PEBC-2)
-MFR: 135 g / 10 min- Propylene-ethylene random copolymer part: 7% by weight
Intrinsic viscosity [η]: 3.7 dl / g
(3) Crystalline propylene-ethylene block copolymer (PEBC-3)
-MFR: 75 g / 10 minutes- Propylene-ethylene random copolymer part: 14.5% by weight
Intrinsic viscosity [η]: 2.8 dl / g
(4) Crystalline propylene-ethylene block copolymer (PEBC-4)
-MFR: 95 g / 10 min- Propylene-ethylene random copolymer part: 9% by weight
Intrinsic viscosity [η]: 8 dl / g
(5) Ethylene-1-octene copolymer elastomer (EOR-1)
-MFR: 2 g / 10 min (190 ° C, load 2.16 kg)
-Octene content: 15 mol%
Density: 0.870 g / cm ³
(6) Ethylene-1-octene copolymer elastomer (EOR-2)
-MFR: 2 g / 10 min (190 ° C, load 2.16 kg)
-Octene content: 18 mol%
Density: 0.857 g / cm ³
(7) Ethylene-1-butene copolymer elastomer (EBR-1)
-MFR: 1.2 g / 10 min (190 ° C, load 2.16 kg)
-1-butene content: 21 mol%
Density: 0.860 g / cm ³
(8) Fine powder talc ・ Average particle size: 3.5μm

(Examples 1-4)
The components (1) to (8) are mixed with a Henschel mixer at the ratio shown in Table 1, and a twin screw extruder (TEX30α: manufactured by Nippon Steel Works; cylinder temperature: 200 ° C .; rotation speed: 1100 rpm; discharge amount) : 100 kg / hour) to obtain a polypropylene resin composition. Table 1 shows the weld and flow mark performance evaluation results of a molded product obtained by injection molding the obtained polypropylene resin composition.

(Comparative Example 1)
The components (4), (7) and (8) were mixed with a Henschel mixer at the ratio shown in Table 1, and granulated with a twin-screw extruder in the same manner as in Example to obtain a polypropylene resin composition. . Table 1 shows the weld and flow mark performance evaluation results of a molded product obtained by injection molding the obtained polypropylene resin composition.

フローマーク評価：
○：フローマークが認められない又はわずかに認められる。
△：フローマークが成形品表面積の５０％以上で認められる。

Flowmark evaluation:
○: A flow mark is not recognized or slightly recognized.
(Triangle | delta): A flow mark is recognized by 50% or more of a molded article surface area.

It is explanatory drawing of the metal mold | die for weld evaluation. It is explanatory drawing of the metal mold | die for flow mark evaluation.

Claims (9)

  (A) crystalline propylene-ethylene block copolymer 40-84 parts by weight, (B) elastomer 1-30 parts by weight and (C) inorganic filler 15-30 parts by weight ((A), (B) and (C ), And the weight average molecular weight (Mw) of the components eluted by cross fraction chromatography at 0 ° C. is 100,000 to 800,000.   The (A) crystalline propylene-ethylene block copolymer has a melt flow rate (MFR; 230 ° C., load 2.16 kg) of 10 to 200 g / 10 minutes, and 100 parts by weight of the crystalline propylene-ethylene block copolymer 2 to 30 parts by weight of an n-decane soluble component with respect to the intrinsic viscosity ([η]; 135 ° C. in decalin) of 1 to 6 dl / g. The polypropylene resin composition as described.   The polypropylene resin composition according to claim 1 or 2, wherein the polypropylene resin composition has a melt flow rate (MFR; 230 ° C, a load of 2.16 kg) of 15 g / 10 min or more and a flexural modulus (ASTM D790) of 1500 MPa or more. .   Clamping the polypropylene resin composition according to any one of claims 1 to 3 using an injection molding machine having three or more injection cylinders or injection plungers and having three or more gates. An injection molding method of polypropylene resin characterized by molding at a pressure of 1000 to 2000 tons.   The injection molding method according to claim 4, wherein the number of injection cylinders or injection plungers is 4-6.   The injection molding method according to claim 4 or 5, wherein the mold clamping pressure is 1400 to 1800 tons.   The polypropylene molded object obtained by the injection molding method of any one of Claims 4-6.   The molded article according to claim 7, wherein the polypropylene molded article is an automotive part.   The molded body according to claim 8, wherein the automotive part is a bumper.

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