JPH02191650A - Self-lubricative styrenic resin composition - Google Patents

Abstract

PURPOSE:To provide a styrenic resin composition capable of forming molded products having good self-lubricity and not producing any black streak by compounding a styrenic resin with specific amounts of a silicone oil and a specified stearate ester, respectively. CONSTITUTION:(A) 100 pts.wt. of a styrenic resin (e.g. rubber-reinforced polystyrene, acrylonitrile-styrene copolymer) is mixed with (B) 0.5-10 pts. of a silicone oil comprising a linear polymer having a polysiloxane bond (preferably polydimethyl siloxane) preferably having a viscosity of 1000-30000CS (25 deg.C), especially 10000-30000CS, and (C) 0.1-3 pts.wt. of an ester prepared from stearic acid and a 1-10C, preferably 1-4C, alcohol by the use of a Henschel mixer, etc., hollowed by melt-kneading the mixture with a twin-screw extruder, etc., to provide a self-lubricate styrenic resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a self-lubricating resin composition in which a styrene resin contains silicone oil to provide sliding properties. This composition has the advantage of being less likely to produce black streaks on molded products when exposed to high shear forces during injection molding.

(Prior art) The technology of adding silicone oil to thermoplastic resins such as styrene resins to impart self-lubricating properties is known, for example, from JP-A No. 6
This method is known from Japanese Patent Application Laid-open No. 0-171117, Japanese Patent Application Laid-Open No. 62-39610, and the like.

Furthermore, in fact, this self-lubricating resin composition is widely used in sliding members such as VTR reel hub materials and office automation equipment as a substitute for polyacetal, which has been used for a long time as sliding members.

(Problem to be Solved by the Invention) However, when this self-lubricating resin composition is melted and molded with high shear force during injection molding, black streaks called "black streaks" appear on the molded product. It has the disadvantage of producing marks. These black streaks are treated as a serious molding defect in applications where uncolored products are used, such as VTR reel hubs, and molded products with black streaks can no longer be used as products, resulting in a major manufacturing problem. Become.

The cause of these black streaks is that the silicone oil in the styrene resin composition is not compatible with the resin, so when the resin is exposed to extremely high shear conditions during resin melting, it separates from the resin, causing the screws and cylinders of the molding machine to It is thought that this is to pick up a trace amount of gold m¥A that was generated between the inner wall and the inner wall. In other words, the problem is caused by the amount of silicone oil added and the shear state of the resin, so it is possible to reduce the amount of silicone oil added or change the molding machine and screw shape so that the high shear state does not occur when melting the resin. It is possible to eliminate the clause.

However, the above solution is not practical, and reducing the amount of silicone oil added does not provide self-lubricating properties, and changing the molding machine and screw will be expensive, so it is difficult to solve the problem. Until now, no inexpensive solution was known.

(Means for solving the problem) The inventor added a stearic acid ester composed of stearic acid and an alcohol having 1 to 10 carbon atoms to a self-lubricating resin composition in which a specific amount of silicone oil is added to a styrene resin. By adding a specific amount of , a self-lubricating styrenic resin composition which solves the above problems and does not generate black streaks was obtained, and the present invention was completed.

That is, the present invention provides styrenic resin 1. A self-lubricating product characterized by containing 045 to 10 parts by weight of silicone oil and 0.1 to 3 parts by weight of a stearic acid ester consisting of stearic acid and an alcohol having 1 to 10 carbon atoms per 0 parts by weight. It is a styrene-based resin composition with properties.

The present invention will be further explained below.

The styrenic resin used in the present invention is a resin obtained by polymerizing an aromatic vinyl compound represented by styrene alone or with other copolymerizable compounds in the presence or absence of a rubber such as polybutadiene.

Examples of the rubber include those having rubber elasticity such as polybutadiene, styrene-butadiene rubber, and acrylonitrile-butadiene rubber.

Examples of aromatic vinyl compounds other than styrene include α-methylstyrene and the like.

Other copolymerizable compounds include acrylonitrile,
Examples include non-aromatic compounds having a vinyl group such as metalrylonitrile and methyl methacrylate.

More specifically, polystyrene (
ps), rubber-reinforced polystyrene (Hl-PS), acrylonitrile-styrene copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS), and styrene-methyl methacrylate copolymer (MS). .

The silicone oil used in the present invention is limited in the amount added to the resin, but there is no particular restriction on its type, and it is a linear polymer having polysiloxane bonds as shown in the formula below, and is generally called silicone oil. Use what is available.

However, in the formula, X and Y represent an alkyl group, a phenyl group, a haloalkyl group, a herophenyl group, etc., and n is the number of repeating units.

As the silicone oil, it is preferable to use polydimethylsiloxane, in which X and Y in the above formula are methyl groups, because it is cheap and easily available (and has a high self-lubricity imparting effect, although it is not particularly specified. The viscosity of the silicone oil is preferably from 1000 to 3000 Qcs (25°C), especially from 10000 to 30Qcs (25''C), considering its processing performance, when considering addition to the resin.

In the present invention, the amount of silicone oil added is 0.5 to 10 parts by weight per 100 parts by weight of styrene resin.

This is because if the amount is less than 0.5 parts by weight, the resin composition will not have self-lubricating properties, and if it exceeds 10 parts by weight, the processability during production of the resin composition will be hindered and the mechanical properties of the molded product will deteriorate. This is because it would not be of practical use. Furthermore, the desirable addition amount of silicone oil is 2 to 5 parts by weight per 100 parts by weight of the resin from the viewpoint of processability, self-lubricating property, and mechanical properties.
Parts by weight.

The stearic acid ester added as a solution to the problem of black streaks in molded products in the present invention is an ester composed of stearic acid and an alcohol having 1 to 10 carbon atoms, and the amount added is Styrene resin 10
The amount is 0.1 to 3 parts by weight relative to 0 parts by weight. Added amount is 0
．． If it is less than 1 part by weight, it will not be possible to prevent the formation of black streaks, and if it exceeds 3 parts by weight, the physical properties of the resin composition will deteriorate and it will no longer be of practical use.

Specific examples of alcohols having 1 to 10 carbon atoms constituting the ester body include methyl alcohol having 1 carbon number;
Examples include lower alcohols such as ethyl alcohol having 2 carbon atoms and higher alcohols such as decyl alcohol having 10 carbon atoms. Furthermore, among the above alcohols, alcohols with a small number of carbon atoms are preferable because they cause less deterioration of physical properties even when added as an ester, and specifically, methyl alcohol, ethyl alcohol, propyl alcohol with 1 to 4 carbon atoms are preferable. Particular mention may be made of alcohol and butyl alcohol.

On the other hand, when using an alkyl ester other than stearic acid or a stearic acid ester with an alcohol having more than 10 carbon atoms, there are no particular limitations on the method for producing the styrenic resin composition of the present invention that can solve the black streaks. Specifically, styrene early resin, silicone oil, and stearic acid ester are mixed in a mixer such as a Henschel mixer, and then melted and kneaded in a kneading machine such as an axle or twin-screw extruder. There is a method in which stearic acid ester is mixed with silicone oil and uniformly dispersed and added to the process of melting and kneading styrenic resin in a mixer such as an axle or twin-screw extruder.

(Examples) The effects of the present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples unless it deviates from the gist thereof.

Example 1.2 and Comparative Examples 1 to 5 After premixing paddy wood with the formulation shown in Table 1 using a Henschel mixer, it was melt-kneaded using a co-directional twin-screw extruder at a cylinder temperature of 220°C. and got a beret.

Table 1 Mixing disposal (parts by weight) 'IL x 1 to 1 ton = 1-141 kj a H
l-R-5fit+m type pu)mi9''yo1ν10R-2
000 Methyl stearate Decyl stearate Butyl behenate Polydimethylsiloxane (viscosity at 25°C 125
00 C3) Next, the obtained pellet was molded at a molding temperature of 2 using a screw injection molding machine with an injection capacity of about 3 ounces.
A test piece was obtained by molding at a mold temperature of 20°C and 50°C to evaluate the tensile strength and wear amount relative to a homogeneous material.

The obtained test piece was subjected to a tensile test in accordance with ASTM D-638, and the wear amount relative to a homogeneous material was measured using a bottle-on-disk type wear tester manufactured by Tokyo Shikenki Seisakusho.

A specific method for measuring specific wear amount is as follows. First, place the previously formed φ120x2mm disc on the bottom.
A load of 10 kgf was applied to the bottle with the 0 mm bottle facing upward, and the bottle was brought into contact with the disc. After that, the disk was rotated at a rotational speed of 500 rpm (2rt+/5ec) with the bottle in contact until the total wear distance of the bottle reached 1km, and at this time the wear 1
(mm') was measured. Finally, the unit of wear is w1mcikgf), and the specific wear amount [ms'/(kg
f-km) ].

The black streaks were evaluated using the injection molding machine described above at a molding temperature of 1.
80℃, screw rotation speed 20Orpm, 5″xo, 5
"xo, 125" (2-point gate) test pieces were molded and visually evaluated.

Specifically, the degree of black streaks in 20 molded products was visually checked one by one. Test pieces with no black streaks were marked [○], and test pieces with thin black streaks were marked [△]. A test piece with black streaks was rated as [x]. And out of 20 molded products [0
] is 15 or more and there is no [×], A, [01 and [Δ
] are 15 or more in total, B, other [×]
The molded product with a large amount of black streaks was designated as C, and the degree of occurrence of black streaks in the molded product was indicated.

The evaluation results of tensile strength, wear amount relative to homogeneous material, and black streaks were evaluated in the second
Shown in the table.

Table 2 Evaluation Results From the results summarized in Table 2, an ester of stearic acid and an alcohol having 1 to 10 carbon atoms was added to a styrenic resin composition to which silicone oil was added to give -C self-lubricating properties. appropriate! It is clear that when added, a molded product without black streaks can be obtained even if the resin is melted and molded with high shear force during injection molding.

(Effects of the Invention) The styrenic resin composition of the present invention has self-lubricating properties and can provide molded products without black streaks.

Procedural amendment 12th and 7th, 1986

Claims (1)

[Claims] 0.5 to 10 parts by weight of silicone oil and stearic acid with 1 to 1 carbon number per 100 parts by weight of styrene resin
1. A styrenic resin composition having self-lubricating properties, characterized in that it contains 0.1 to 3 parts by weight of a stearic acid ester composed of alcohol.