JP2643335B2 - Polyolefin composition for injection molding - Google Patents

Description

The present invention relates to a polyolefin composition for injection molding containing a propylene / α-olefin block copolymer resin, and in particular, to a polyolefin composition on the extension of a gate when injection-molded. The present invention relates to a polyolefin composition for injection molding capable of preventing the occurrence of color unevenness called white streaks formed on the surface.

[Conventional technology]

Propylene / ethylene block copolymer resin has strength,
Because of its excellent mechanical properties such as impact resistance and formability, it is used for molded products such as bumpers, instrument panels, interior trims for automobiles, and other exterior parts. Such a propylene / ethylene block copolymer resin is blended with an inorganic filler such as talc in order to improve rigidity in addition to the above-mentioned properties, a pigment is blended for the purpose of coloring, and a molded article is formed by injection molding or the like. It has been.

However, when the propylene / ethylene block copolymer resin is injection-molded, color irregularities called almost linear white stripes occur on the outer surface on the extension of the gate immediately after the gate or in a portion where the thickness changes, Hurt the appearance. This color unevenness is formed as a remarkable white streak when an inorganic filler such as talc is blended, and when it is colored, it is particularly conspicuous when it is colored black, blue, grayish black, but inorganic fillers and pigments , Color unevenness due to the difference in glossiness is formed.

The streaky color unevenness as described above is different from the flow mark formed in a ripple shape around the gate,
The flow mark is formed even when the injection molding conditions are such that the flow mark is not formed, for example, when the flow velocity of the injection resin is low. In some cases, the flow mark and the white stripe may be formed simultaneously.

Conventionally, in order to prevent such streaky color unevenness, a polyolefin composition comprising a propylene / ethylene block copolymer and a multi-component pigment containing iron black (Japanese Patent Publication No.
No. 62-14576).

[Problems to be solved by the invention]

An object of the present invention is to propose a polyolefin composition for injection molding that can prevent the formation of streaky color unevenness during injection molding.

[Means for solving the problem]

The present invention has a propylene content of 40 to 99 mol%, and an MFR of 1 to 60.
0.1 to 5 parts by weight of a modified polyolefin having an acid value of 4 mg-KOH / g or more and an intrinsic viscosity [η] of 0.04 to 2d1 / g based on 100 parts by weight of a propylene / α-olefin block copolymer resin of g / 10 minutes. It is a polyolefin resin composition for injection molding characterized by containing.

The propylene / α-olefin block copolymer resin of the present invention is prepared so that the polypropylene component, the polyethylene component and / or the ethylene / propylene random copolymer component are present in a mixed state, and is commercially sold. And so-called block polypropylene resins.

The propylene / α-olefin block copolymer resin constituting the present invention contains 40 to 99 mol%, preferably 70 to 90 mol% of a propylene component, and the remaining components are α-olefins other than propylene. And the melt flow index MFR
(ASTM D 1238, (L)) can be used in an amount of 1 to 60 g / 10 minutes, preferably 5 to 40 g / 10 minutes.

As α-olefins other than propylene, ethylene,
Examples thereof include butene-1, hexene-1, and 4-methylpentene-1, with ethylene being preferred.

The modified polyolefin is a polyolefin having an acid group in the molecular structure, and specific examples thereof include the following.

(I) Oxidized polymers obtained by homo- or copolymerization of α-olefins such as ethylene, propylene, butene-1, 4-methylpentene-1 and octene-1 to introduce carboxyl groups.

(Ii) Acrylic acid, methacrylic acid,
Those obtained by graft polymerization of α, β-unsaturated carboxylic acids such as crotonic acid, maleic acid, and fumaric acid or anhydrides thereof.

(Iii) A random copolymer of the above α-olefin and the above α, β-unsaturated carboxylic acid, such as an ethylene / acrylic acid copolymer and an ethylene / methacrylic acid copolymer.

(Iv) A sulfonated product of the above polyolefin.

Among these, polyolefin oxide such as polyethylene oxide, polypropylene oxide, polybutene-1, and ethylene oxide / α-olefin copolymer, or maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, maleic anhydride-grafted ethylene / α Maleic anhydride grafted polyolefins such as olefin copolymers are preferred. These are one kind alone,
Alternatively, two or more kinds can be used as a mixture.

Such a modified polyolefin preferably has an acid value of 4 mg-KOH / g or more, preferably 10 to 100 mg-KOH / g, and an intrinsic viscosity [η] (measured at 135 ° C. in decalin) of 0.04 to 2 dl / g.

The amount of the modified polyolefin is 0.1 to 5 parts by weight based on 100 parts by weight of the propylene / α-olefin block copolymer resin.
Parts by weight, preferably 0.5 to 3 parts by weight.

The composition of the present invention may contain an inorganic filler and a pigment in addition to the above components. The inorganic filler is not particularly limited, and those generally used can be used, and examples thereof include talc, clay, silica, barium sulfate, calcium carbonate, glass fiber, and wood powder. These can be used alone or in combination of two or more. The inorganic filler is used to impart properties such as rigidity to the polyolefin composition, and the compounding amount is usually 1 to 100 parts by weight, preferably 1 to 100 parts by weight, based on 100 parts by weight of the propylene / α-olefin block copolymer resin. 50 parts by weight.

The pigment is not particularly limited and those generally used can be used, for example, carbon black, iron black, red iron oxide, titanium oxide, cadmium yellow, cadmium red, zinc white, ultramarine, cobalt blue, calcium carbonate, titanium yellow, Inorganic pigments such as lead white, lead red, graphite, navy blue and the like, and organic pigments such as quinacridone, polyazo yellow, anthraquinone yellow, polyazo red, azo lake yellow, berylene, phthalocyanine blue, phthalocyanine green, and isoindolinone yellow. . The amount of the pigment is usually 0.1 to 7 parts by weight, preferably 0.3 to 3 parts by weight, based on 100 parts by weight of the propylene / α-olefin block copolymer resin.

The composition of the present invention has an appropriate amount of another resin as desired,
Alternatively, additives such as a dispersant, an antioxidant and a lubricant can be blended.

As a method for producing the polyolefin composition according to the present invention,
A known method can be applied, and examples thereof include a method of mechanically blending the above components with an extruder, a kneader, or the like.

The polyolefin composition thus obtained is molded by a normal injection molding method to obtain a molded product.When injection molded, a streak-like color unevenness such as a white streak does not occur, and the appearance is good. Product.

〔The invention's effect〕

The polyolefin composition of the present invention is obtained by blending a small amount of a modified polyolefin with a propylene / α-olefin block copolymer resin, and does not impair the properties of the block copolymer resin. The occurrence of unevenness can be prevented, and an injection molded article having a good appearance can be obtained.

〔Example〕

Hereinafter, examples of the present invention will be described. However, parts indicate parts by weight.

Example 1 Maleic anhydride having an acid value of 30 mg / KOH / g and an [η] of 0.44 dl / g based on 100 parts of a propylene / ethylene block copolymer resin having a propylene content of 88 mol% and an MFR of _{230 ° C. at} 10 g / 10 min. 1 part of acid-grafted polypropylene and 2.2 parts of carbon black as a pigment were mixed and stirred with a Henschel mixer.
After mixing, the mixture was granulated while being kneaded by a two-wheel extruder (CIM-50, manufactured by Nippon Steel Works, trademark). Thereafter, a plate-shaped molded sample of 120 mm × 130 mm was prepared by injection molding, and the occurrence of streak-like color unevenness (white streaks) was visually observed. Table 1 shows the results
Shown in

Examples 2 to 3 and Comparative Examples 1 to 2 Samples were prepared in the same manner as in Example 1 with the compositions shown in Table 1 and observed. Table 1 shows the results.

In the first, propylene homopolymer is MFR _{230 ° C} 11g / 10 minutes,
Oxidized polyethylene wax I is acid 20 mg-KOH / g, [η]
0.2dl / g, oxidized polyethylene wax II has an acid value of 10mg-KOH
/ g, [η] 015 dl / g.

Claims (1)

(57) [Claims] 1. A propylene content of 40 to 99 mol%, and an MFR of 1 to 60
0.1 to 5 parts by weight of a modified polyolefin having an acid value of 4 mg-KOH / g or more and an intrinsic viscosity [η] of 0.04 to 2 dl / g with respect to 100 parts by weight of a propylene / α-olefin block copolymer resin of g / 10 minutes. A polyolefin resin composition for injection molding characterized by containing.