JPS6399929A - Manufacture of electrically-conductive resin molding - Google Patents

Abstract

PURPOSE:To obtain a resin molding having excellent electrical conductivity and heat resistance suitable for a contact point material and a resistor such as a battery and a switch, by a method wherein after molding of polyphenylene sulfide resin containing a specific quantity of a carbon fiber is heat-treated under specific conditions. CONSTITUTION:An injection molding method is preferable as a molding method of polyphenylene sulfide with which a carbon fiber is compounded from viewpoints of productivity, dynamic properties and electrical characteristics. In a normal case, a fiber whose diameter is 10 mum or shorter and length is about 0.5-6mm is used for a form of the carbon fiber. It is essential that the compounding quantity of the carbon fiber is made into 10-70 wt%. In the case where the compounding quantity is less than 10 wt% electrical conductivity of a molding turns insufficient and in the case where the same exceeds 70 wt%, uniform dispersion of the resin and carbon fiber becomes hard and fluidity at the time of melting turns worse further and molding turns difficult. It is essential that heat treatment to be executed after the molding is performed at least at 80 deg.C and in the case where a heat treatment temperature is less than 80 deg.C, an improvement in electric conductivity due to repeating heat treatment is insufficient. The heat treatment is performed two times or more.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a resin molded article having excellent conductivity and heat resistance and suitable as a contact material for batteries, switches, etc., or as a resistor.

(Conventional O Technique) It has been widely practiced in the past to uniformly disperse carbon fibers in a thermoplastic resin to impart conductivity. In addition to being electrically conductive, carbon fiber has excellent performance as a reinforcing material, and is increasingly in demand as a material for mechanical parts that require rigidity and dimensional precision.

For example, JP-A-57-188155 ``Conductive resin''
has proposed a conductive resin with excellent conductive and mechanical properties, which is a thermoplastic resin mixed with ultrafine carbon fibers. Furthermore, in JP-A No. 58-46508 ``Electrically conductive materials and their manufacturing method'', conductive fibers such as carbon fibers and metal fibers and thermoplastic synthetic resin powder are mixed in a mixer with rotary blades at the bottom. It has been shown that a conductive resin molded product having excellent mechanical strength and sufficient electrical conductivity can be obtained by heating and press-molding the mixture.

(Problems to be Solved by the Invention) The electrical conductivity of carbon fibers is not good when compared with general metal materials, and therefore the electrical conductivity of plastic resins containing carbon fibers is not sufficient. I can't say that. Ninthly, there was a problem in that in order to obtain a high level of conductivity, it was necessary to increase the amount of carbon fiber blended. However, if the blending amount is increased, there will be problems such as poor fluidity during melting and a decrease in molding processability, and the breakage of carbon fibers during melt kneading or molding processing will become significant. However, no improvement in conductivity can be obtained with the increase.

On the other hand, to use it as a resistor for voltage drop.

There were problems with the thermal stability and heat resistance of the conductive material against the heat generated by energization.

(Means for Solving the Problems) The present inventors have conducted intensive research to solve the problems of the prior art, and as a result, have achieved the present invention.

That is, the method of the present invention is characterized in that a polyphenylene sulfide resin containing 10 to 70% carbon fiber is heat-treated at least twice at 80° C. after molding. It is.

The present invention will be explained in detail below.

Various carbon fibers such as acrylonitrile-based, pitch-based, cellulose-based, and lignin-based carbon fibers can be used as the carbon fibers used in the present invention, and r! There are no restrictions on A quality or graphite quality. In terms of conductivity and mechanical properties, p, 1.0-2Ω・
Specific electrical resistivity below cm, 1001Kg/mm2
It is preferable to use acrylonitrile-based or pitch-based carbon fibers having a tensile strength above.

There are no particular restrictions on the shape of carbon fiber, but in normal cases,
Use fibers with a diameter of 10 μm or less and a fiber length of about 0.5 to 6 mm. It is important that the amount of carbon fiber blended is 10 to 70% by weight, particularly preferably 15 to 60% by weight. If the blending amount is less than 1011%, the resulting molded product will have insufficient conductivity and the object of the present invention cannot be achieved. - If the force exceeds 70″IL ratio, it will be difficult to uniformly disperse the resin and carbon fibers, and furthermore, the fluidity during melting will be extremely poor, making it difficult to mold.

The polyphenylene sulfide resin used in the present invention is
A polymer consisting of alternating bonds of benzene rings and sulfur can be obtained by reacting paradichlorobenzene with sodium sulfide, for example.

Examples of molding methods for polyphenylene sulfide blended with carbon fibers include compression molding, injection molding, etc.
Injection molding is preferred in terms of productivity, mechanical properties, and electrical properties.

It is essential that the heat treatment carried out in the present invention be carried out at a temperature of at least 80°C, and in particular, a temperature of 100°C or higher is suitable for achieving the object of the present invention. If the heat treatment temperature is less than 80°C, the conductivity cannot be improved sufficiently by repeated heat treatments, and the object of the present invention cannot be achieved.

It is important to carry out the heat treatment two or more times, and it is particularly preferable to carry out the heat treatment eight or more times. If the number of heat treatments is one, sufficient improvement in conductivity cannot be obtained even if the treatment is performed at high temperatures and for a long time. That is.

The present inventors have discovered that the p-conductivity is significantly improved by repeating heat treatment, and have achieved the present invention.

The time for one heat treatment varies depending on the temperature, shape, size, etc. of the molded product, but is usually 1 minute or more, preferably 8 minutes or more. The heat treatment can be carried out in air, vacuum, gas such as argon gas, nitrogen gas, etc., and further under various atmospheres such as water, oil, etc.

In the present invention, in addition to carbon fibers, reinforcing materials such as carbon black, conductive filler exclusively for metal fibers, and glass fibers can also be used.

(Effects of the Invention) The conductive resin molded product according to the present invention has extremely low conductivity compared to conventional resin molded products containing carbon fiber, and can be used as a contact material for batteries, switches, etc. It is suitable as a resistor that requires heat resistance.

(Example) A more detailed explanation will be given below using examples.

Note that the physical properties shown in the Examples were measured by the following method.

(1) Tensile strength Measured according to ASTM D-688.

(2) Flexural modulus Measured according to ASTM D-790.

(3) Volume resistivity Measured according to ASTM D-257.

Example 1 Polyphenylene sulfide resin (manufactured by Phillips Vetroleum, Rydon P-4) and fiber diameter 7 μm
, polyacrylonitrile carbon fiber with a fiber length of 6 mm (manufactured by Toho Rayon Co., Ltd., Besphite ETA-as-
NR) were blended in the proportions shown in Table 1 and melt-kneaded to obtain pellets.

Next, injection molding was performed using the obtained pellet under the usual molding conditions for polyphenylene sulfide resin to prepare a test piece.

The obtained test pieces were heat-treated in air under the conditions shown in Table 1-2, and then their physical properties were measured. In addition, the heat-treated test piece is
Once cooled to room temperature, it was subjected to a first heat treatment.

The sample in Table I No. 5 had extremely poor fluidity during heating and melting and could not be pelletized.

Table-1 Table-2 Table-8

Claims (5)

[Claims] (1) After molding polyphenylene sulfide resin containing 10 to 70% by weight of carbon fibers, at least 80°C,
A method for producing a conductive resin molded article, which comprises performing heat treatment two or more times. (2) The method according to claim 1, wherein the carbon fiber content is 15 to 60% by weight. (3) The method according to claim 1, wherein the heat treatment is carried out at at least 100°C. (4) The method according to claim 1, wherein the heat treatment is performed at least three times. (5) The method according to claim 1, wherein one heat treatment is performed for at least 3 minutes.