JP3135321B2 - Colored styrenic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition having an excellent appearance which is useful as a material for housings of various electric appliances, office equipment and miscellaneous goods.

[0002]

2. Description of the Related Art Conventionally, styrenic resins have been used in moldability,
Because of the excellent balance of dimensional stability and mechanical strength,
Used in molding materials for various products. In particular, it is widely used for appearance parts such as various electric products, housings of office equipment and miscellaneous goods. And it is colored and used for design. For coloring styrenic resins used in these applications, titanium oxide is often used for coloring. Generally, titanium oxide and a fatty acid metal salt or the like are dispersed to uniformly disperse the titanium oxide in the resin. It is performed by kneading the resin with the agent. However, when a colored styrene-based resin is injection-molded using titanium oxide, a black streak-like pattern may be formed on a molded product even though a black-based colorant is not used. This black stripe pattern is called a black stripe.

[0003] Since the occurrence of the above-mentioned black stripes greatly reduces the commercial value, studies have conventionally been made. For example, 9,
10-dihydro-9-oxa-10-phosphananthrene-10-oxide, distearylpentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) 4,4′-biphenylenediphosphite, or , Boron trioxide is added to the styrenic resin,
The method described in JP-A-63-86743 for preventing the occurrence of black streaks and the method described in JP-A-2-88659 for preventing the occurrence of black streaks by using an alkylene-bis-fatty acid amide or zinc fatty acid as a coloring dispersant. The method is known. However, none of them was sufficient to completely prevent the occurrence of black stripes.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a black streak-like pattern (black stripe) generated on a molded product when injection-molded using a styrenic resin composition colored with a coloring agent containing titanium oxide. The purpose of the present invention is to solve the above-mentioned failure phenomenon.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that the object can be achieved by adding a specific compound, and have reached the present invention.

That is, the present invention relates to a styrene resin containing titanium oxide, wherein the maleic anhydride monomer is 0.05 to 8.0 parts by weight or the maleic anhydride monomer is 0.05 to 8.0 parts by weight with respect to 100 parts by weight of the styrene resin. A colored styrene-based resin composition comprising 0.05 to 50 parts by weight of a maleic anhydride-styrene copolymer containing at least 5.0 parts by weight of maleic anhydride and at least 5.0 parts by weight.

Hereinafter, the present invention will be described in detail.

The styrene resin used in the present invention includes, for example, a homopolymer of a styrene monomer (GPPS resin) and a copolymer of a styrene monomer and another copolymerizable monomer, for example, styrene-acrylonitrile. A copolymer resin (AS resin) or a polymer obtained by grafting them to a rubber component, such as a high impact polystyrene resin (HIPS resin);
An acrylonitrile-styrene-butadiene copolymer resin (ABS resin) is exemplified. Further, part or all of the styrene of these polymers is α-methylstyrene,
It may be replaced with a vinyl aromatic compound such as -methylstyrene, vinyltoluene and p-tert-butylstyrene. A part or all of acrylonitrile may be replaced with a vinyl cyanide compound such as methacrylonitrile. However, acrylonitrile-styrene-butadiene copolymer resin (ABS resin) is preferred.

The titanium oxide used in the present invention is not particularly limited as long as it is a commonly used one, and the average particle diameter is 0.1.
Particles of any size from 01 to 0.5 μm can be used. The crystal structure may be a rutile type or an anatase type. In addition, the surface may not be treated, but those treated in advance with aluminum oxide or the like are preferably used. The amount of titanium oxide added is usually 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the resin. .

The content of the maleic anhydride monomer is from 0.05 to 8.0 parts by weight, preferably from 0.1 to 3.0 parts by weight, based on 100 parts by weight of the styrene resin composition. When the amount of the maleic anhydride monomer is less than 0.05 part by weight, black streaks are liable to be generated on the surface of the injection-molded article. This is not preferable because a large amount of a low molecular weight substance centering on the styrene resin is generated, and the physical properties of the styrene resin, particularly the heat resistance, are remarkably reduced.

The maleic anhydride-styrene copolymer is a copolymer of a maleic anhydride monomer and a styrene monomer, and the styrene monomer is the styrene monomer used in the styrene resin. Styrene and α-methylstyrene are particularly preferred, and at least one or more of such styrene-based monomers are used. If desired, an acrylonitrile-based monomer, a maleimide-based monomer, an acrylate-based monomer or the like can be used in combination with the styrene-based monomer.

The proportion of maleic anhydride contained in the maleic anhydride-styrene copolymer (the proportion of maleic anhydride contained in the copolymer segment) is at least 5.
0% by weight or more, preferably 10.0% by weight.
% By weight or more. The proportion of maleic anhydride is 5.0% by weight
If the amount is less than that, black streaks easily occur in the injection molded article, which is not preferable.

The maleic anhydride-styrene copolymer can be modified with a rubbery polymer such as butadiene or a styrene-butadiene block copolymer.

The content of the maleic anhydride-styrene copolymer is from 0.05 to 50 parts by weight, particularly preferably from 0.5 to 10 parts by weight, based on 100 parts by weight of the styrene resin. If the content is less than 0.05 part by weight, black streaks are easily generated on the surface of the injection-molded article, and if the content is more than 50 parts by weight, the physical properties of the styrene resin, particularly the impact resistance, are undesirably reduced.

It is also possible to use an unsaturated dicarboxylic acid monomer such as maleic acid, fumaric acid, citraconic acid, metaconic acid, glutaconic acid, methylene succinic acid, allylmalonic acid in place of the maleic anhydride monomer. No improvement effect is obtained. On the other hand, an unsaturated dicarboxylic anhydride such as citraconic anhydride modified from maleic anhydride has an improving effect, but its effect is inferior to that of maleic anhydride.

Incidentally, a maleic anhydride monomer and a maleic anhydride-styrene copolymer may be used in combination.

The maleic anhydride-styrene copolymer used in the present invention can be obtained by known methods such as bulk polymerization, suspension polymerization, and emulsion polymerization.

The method for producing the resin composition of the present invention is not particularly limited. For example, titanium oxide, a maleic anhydride monomer or a maleic anhydride-styrene copolymer, and a styrene resin are mixed in advance with a Henschel mixer, tumbler or the like. Mixing, extruder, a method of pelletizing using a kneader or the like, mixing maleic anhydride-styrene copolymer during polymerization of the styrene resin, and pelletizing the obtained resin composition and titanium oxide. The method of mixing and pelletizing by the above method is performed.

In the present invention, if necessary, additives other than titanium oxide, for example, a coloring agent, an antistatic agent, an antioxidant, a plasticizer, and an ultraviolet absorber can be added.

[0020]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited to these examples.

Examples 1 to 4 Premixed according to the formulation shown in Table 1, and pelletized at a cylinder temperature of 220 ° C. using an extruder. Using an IS-80 EPN injection molding machine manufactured by Toshiba Machine Co., a cylinder of 240 ° C., a screw back pressure of 20 kg / cm 2, a screw rotation speed of 100 rpm, a mold temperature of 50 ° C., and 100 sheets of 50 × 150 mm flat plate were used. After molding, the number of black streaks was examined. Table 1 shows the results. No black stripes occurred in any case.

[0022]

[Table 1]

Comparative Examples 1 to 9 The number of black streaks was examined in the same manner as in Example except for the formulations shown in Table 2. Table 2 shows the results. Outside of the scope of the present invention, many black streaks were generated.

[0024]

[Table 2]

[0025]

According to the present invention, a molded article obtained by injection molding using the resin composition of the present invention does not produce black stripes, and is extremely useful for industrial use.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 35:00) (C08L 55/02 35:00) (56) References JP-A-2-194048 (JP, A) JP-A 63-240443 (JP, A) JP 49-46146 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 25/00-25/18 C08L 35/00-35 / 08 C08L 51/04 C08L 55/02 C08K 3/22 C08K 5/09-5/092

Claims (2)

(57) [Claims] In a styrene resin containing titanium oxide, 0.05 to 8.0 parts by weight of maleic anhydride monomer or 100 parts by weight of styrene resin, or maleic anhydride.
Maleic anhydride containing 0.05 to 8.0 parts by weight of an acid monomer and at least 5.0% by weight of maleic anhydride;
A colored styrene-based resin composition comprising 0.05 to 50 parts by weight of a styrene copolymer. 2. The colored styrene resin composition according to claim 1, wherein the styrene resin is an acrylonitrile-styrene-butadiene copolymer.