JP3138039B2 - Styrene 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 styrenic resin composition, and more particularly, to a molded article having excellent slidability and impact resistance and causing abrasion of a screw of a molding machine during molding. The present invention relates to a styrenic resin composition having no moldability and good moldability.

[0002]

2. Description of the Related Art In recent years, technological innovations in the field of light electrical equipment or electronics have been remarkable, and in the field of audio-related equipment and office automation-related equipment, various rotating bodies, keyboards, The tendency to apply plastic to gears or bearings has become remarkable.

[0003] Molded products in such fields are required to have various properties such as excellent slidability (surface lubricity), impact resistance, and abrasion resistance. Although plastic is used, it is urgently desired to reduce costs in the future as demand increases.

[0004] Styrene resins are one of general-purpose thermoplastic resins, and are widely used in daily necessities, toys, food containers and the like. Techniques for improving the slidability and abrasion resistance of a molded product by adding a polyorganosiloxane to a styrene resin are already known. For example, Japanese Patent Publication No. 52-43863 and Japanese Patent Publication No. -1
JP-A-5287 proposes a method for producing a composition containing a polyorganosiloxane having self-lubricating properties, and JP-A-60-217254 discloses a styrene-based resin composition containing a polyorganosiloxane. Has been proposed.

[0005]

However, the polyorganosiloxane-containing styrenic resin composition according to the prior art described above cannot withstand long-term use because the molded article has not yet been sufficiently slidable. Can not avoid the limitation of the application because it can not do. In addition, when molding the composition, burning occurs in the resin, which leads to undesirable situations such as contamination and deterioration of the product, and in continuous injection molding for a long time, the screw or cylinder of the molding machine is worn. There is a disadvantage that. The present invention overcomes the drawbacks of the conventional polyorganosiloxane-containing styrenic resin composition, provides a molded article having excellent slidability and impact resistance, and can cause abrasion of a molding machine screw and the like during molding. The object of the present invention is to provide a styrene resin composition having good moldability without any problem.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, by incorporating a specific copolymer containing an organosiloxane gum into a styrenic resin, It has been found that the object of the invention can be easily achieved, and the present invention has been completed. That is,
The gist of the present invention is that the content of the diene rubbery polymer is 15
100 parts by wt% or less of styrene resin, organo
Siloxane gum mixed with ethylene vinyl acetate copolymer
The styrenic resin composition is characterized by comprising 0.5 to 30 parts by weight of the grafted and grafted copolymer.

Hereinafter, the present invention will be described in detail. In the composition of the present invention, one raw material is a styrene resin having a diene rubber polymer content of 15% by weight or less. Such a styrene-based resin is obtained by polymerizing an aromatic vinyl monomer in the presence or absence of a dissolved diene-based rubbery polymer, or a vinyl-based monomer copolymerizable with an aromatic vinyl monomer. It is obtained by copolymerizing with the body.

Examples of the diene rubbery polymer include polybutadiene, butadiene-styrene copolymer rubber, natural rubber, polyisoprene rubber, styrene-isoprene copolymer rubber, and the like. These diene rubbery polymers are used alone or in combination of two or more. Examples of the aromatic vinyl monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, dimethylstyrene, α-methylstyrene, p-chlorostyrene, and the like.

The vinyl monomers copolymerizable with the aromatic vinyl monomers include, for example, acrylonitrile,
Acrylic esters, methacrylic esters, maleimides, N-methylmaleimides, N-phenylmaleimides and the like can be mentioned. These vinyl monomers are used in an amount of 30% by weight, preferably 10% by weight or less based on the aromatic vinyl monomer. The polymerization is suspension polymerization, emulsion polymerization,
It can be carried out according to a known method such as bulk polymerization or solution polymerization. Specific examples of the styrene resin include polystyrene resin (GPPS) and impact-resistant polystyrene resin (H
IPS).

[0010] In the present invention the composition, the other ingredients, Ol
Ganosiloxane gum kneaded with ethylene vinyl acetate
Is to graft copolymer der grafted is, kneading side
As the method , the following kneading method proposed in JP-B-56-1201 is particularly preferable.

That is, the kneading method proposed in Japanese Patent Publication No. 56-1201 discloses a method of mixing 10 to 175 parts by weight of a polydiorganosiloxane and 100 parts by weight of an ethylene vinyl acetate copolymer at a temperature of 170 to 235 ° C. 10 seconds
A homogeneous kneading at a shear rate greater than ^-1 and mechanically mixing for a time sufficient for the insoluble material in the xylene reflux to be at least 10% by weight of the total kneaded material, after which it is processable and stable Collecting objects. At this time, the ethylene-vinyl acetate copolymer is 8-35.
Weight percent copolymerized vinyl acetate, containing organosilicon
Xanthan gum is a toluene-soluble gum with a Williams plasticity greater than 0.020 inches and one silicon atom.
The ratio of organic groups per unit is about 2.0, and the organic groups are selected from methyl groups, phenyl groups, vinyl groups, and allyl groups. Those having a vinyl or allyl group and not more than 50% of the organic groups are phenyl groups.

The styrenic resin composition of the present invention is prepared by adding 100 parts by weight of the above-mentioned styrenic resin to the above organosiloxanes.
And 0.5 to 30 parts by weight of a copolymer containing gum . When the blending amount of the copolymer containing the organosiloxane gum is less than the above range, a styrene-based resin composition that gives a molded article having excellent slidability cannot be obtained, and
When the amount is more than the above range, a styrene resin composition which gives a molded article having excellent mechanical properties cannot be obtained. The compounding method may be a dry blending method or a melt kneading method using a kneading machine such as an extruder.

The styrenic resin composition of the present invention may contain, if desired, various additives conventionally used in styrenic resin compositions, such as lubricants, antioxidants, plasticizers, flame retardants, and light stabilizers. , A coloring agent, an antistatic agent and the like may be added, and further, a filler such as a fiber reinforcing agent such as a glass fiber and an inorganic filler may be filled.

The styrenic resin composition of the present invention has extremely excellent surface lubricity, slidability, and good moldability (there is no burning of a molded product and no screw abrasion of a molding machine).
Its application range is wide, including various light electrical equipment housings,
It can be suitably used to obtain molded articles such as OA equipment parts such as rotating bodies, gears and bearings. In particular,
Examples of the molded product include a cassette tape or a cassette reel in a VTR, a keyboard in a personal computer, a key top, and the like.

[0015]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the following, “parts” and “%” are all based on weight unless otherwise specified. The physical properties were measured by the following methods.

(1) Tensile strength: JIS
Compliant with K-7113 (2) Flexural strength and flexural modulus: JIS K-720
(3) Izod impact strength: JIS K-711
0 (4) Vicat softening point: JIS K-720
6 (5) Melt flow rate: JIS K-721
Conforms to 0

(6) Abrasion resistance: Injection molded sample (15
The abrasion test was performed by using a Taber abrasion tester (manufactured by Toyo Seiki Co., Ltd.) using a Taber abrasion tester (manufactured by Toyo Seiki Co., Ltd.) and rotating the abrasion wheel 1000 times at a rotation speed of 70 rpm under a load of 1 kg. Then, the sample wear amount (g) was displayed. (7) Static friction coefficient: A molded article similar to a soap box produced by injection molding was measured for a friction coefficient with an aluminum substrate using a Haydon 10-type static friction tester (manufactured by Shinto Kagaku).

(8) Check ring abrasion of screw of molding machine 5,000 shots are formed by a 1 oz. Injection molding machine, the degree of abrasion of the screw check ring is observed in an enlarged photograph, and wear of the check ring is reduced ( g) was measured. In other words, the check ring abrasion test is performed by setting a new check ring in a screw at several places with an iron brush, setting it on a screw, and taking an enlarged photograph (optical micrograph) of the injured part before and after molding. Observe. Further, the wear loss (g) is measured from the weight of the check ring before and after molding. The observation and evaluation of the degree of wear were performed according to the following criteria. ：: No damage was observed on the surface. X: The surface was scratched.

(9) Deterioration test of molded article burning: The molded article in the physical property measurement of the above (8) was visually observed for the presence or absence of burning (the occurrence of black stripes and discoloration in the molded article), and evaluated according to the following criteria. ：: Black streaks and discoloration were not observed. X: Black streaks and discoloration were observed.

[0020] melted and Examples 1-4 polybutadiene 5 wt% rubber-modified polystyrene resin and siloxane gum containing the ethylene-vinyl acetate copolymer graft copolymer obtained by grafting in an extruder at a ratio shown in Table 1 and kneaded Then, the styrene resin composition was pelletized. In each of the examples, the content of the siloxane gum containing dimethylpolysiloxane as a main component in the styrene resin composition was as follows: Example 1: 1.7%, Example 2:
2.9%, Example 3: 7.8%, Example 4: 13.8%
Met. Table 1 shows the results of measuring the physical properties of each of the above pellets.
Shown in

Table 2 shows the results of measurement of the physical properties of the following resin pellets as Comparative Examples 1 to 3. Comparative Example 1: Styrene-based resin used in Examples Comparative Example 2: Styrene-based resin used in Examples was melt-kneaded with 3 parts of silicone oil (dimethylpolysiloxane: 30,000 centistokes) using an extruder. Composition Comparative Example 3: Polyacetal resin (POM)

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

According to the present invention described above, styrene having good moldability without giving a molded article excellent in slidability and impact resistance and without causing abrasion of a screw of a molding machine at the time of molding. A resin composition is provided. Therefore,
The value of the present invention is great.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 51/04 C08L 25/04 C08L 51/08

Claims (1)

(57) [Claims] 1. An organosilic acid is added to 100 parts by weight of a styrene resin having a diene rubbery polymer content of 15% by weight or less.
Ethylene-vinyl acetate copolymer kneading process Rokisangamu
Has been styrenic resin composition characterized by comprising blending a graft copolymer 0.5 to 30 parts by weight of the graft.