JPH0414844B2 - - Google Patents

Description

[Detailed description of the invention]

[Objective of the invention] (Industrial application field) The present invention provides a method for producing a conductive resin composition that has good dispersibility of conductive fibers, requires a small fiber filling rate, and has excellent conductivity of molded products. Regarding. (Prior Art) Conventionally, when preparing a conductive resin composition by filling and dispersing conductive fibers consisting of a large number of filaments in a thermoplastic resin, first, as shown in Japanese Patent Publication No. 60-54967, metal The fibers are converged using a thermoplastic resin solution or emulsion convergence agent, and then cut into lengths of 1 to 15 mm.Then, the cut convergent fibers are mixed with thermoplastic plastic and kneaded using an extruder. Disperse to make conductive plastic. Further, as disclosed in Japanese Patent Application Laid-Open No. 129031/1982, the kneaded and dispersed conductive plastic was cut into pellets using a pelletizer to facilitate injection molding. However, in the above conventional conductive resin composition, the metal fibers are kneaded and dispersed inside the heating cylinder of the extruder in the previous kneading and dispersion step.
The disadvantage is that the fibers are easy to break. In addition, in the subsequent pelletizing step, the pelletizing process is again cut, resulting in further cutting of the fibers, which has the disadvantage that the length of the fibers becomes much shorter than the initial length. and again,
When molded products are made using conventional conductive resin compositions, the conductivity decreases over time or the desired conductivity cannot be obtained, so it is necessary to increase the amount of conductive fibers filled. As a result, the moldability and physical properties of the molded product are impaired, and the cost is increased, which has become a problem. (Problems to be Solved by the Invention) The present invention has been made to eliminate the drawbacks of the conventional conductive resin compositions described above, and has good dispersibility of conductive fibers, even at a low fiber filling rate. The object of the present invention is to provide a method for producing a conductive resin composition that has excellent conductivity and does not impair the physical properties of the resin. [Structure of the Invention] (Means and Effects for Solving the Problems) As a result of extensive research to achieve the above object, the present invention has been developed to solve the problem of thermoplastic fibers, which is the main cause of cutting fibers and impairing conductivity. By omitting the kneading and dispersion process of the resin and conductive fibers using an extruder, and by using a chemical foaming agent as a sizing agent, the conductive fibers have good dispersibility in the thermoplastic resin during injection molding, resulting in low fiber filling. The present invention was completed based on the discovery that the material has excellent conductivity and does not impair the physical properties of the molded product. That is,
The present invention involves dissolving a binding agent containing a thermoplastic resin and a chemical foaming agent in a solvent, immersing conductive fibers in the binding agent, converging them, drying them to volatilize the solvent, and then cutting them into pellets. This is a characteristic method for producing a conductive resin composition. The conductive fibers used in the present invention include stainless steel fibers, aluminum fibers, copper fibers, carbon fibers, carbon fibers having a metal plating layer on the surface, glass fibers, and organic fibers, which may be used alone or in combination of two or more. can be used. The appropriate number of filaments of the conductive fibers to be converged with the convergent agent is about 500 to 20,000. The sizing agent used in the present invention contains a thermoplastic resin and a chemical blowing agent. The thermoplastic resins used here include vinyl chloride resin, ethylene vinyl acetate resin, polystyrene resin, AS resin, ABS resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, nylon resin,
Polycarbonate resin, modified polyphenylene oxide resin, polyphenylene sulfide resin,
Examples include polyether sulfone resin and polyetherimide resin, which may be used alone or in combination of two or more. Chemical blowing agents include azodicarbonamide (ADCA), azobisisobutyronitrile (AIBN), 4,4'-oxybisbenzenesulfonylhydrazide (OBSH), N,
Examples include N'-dinitrilopentamethylenetetramine (DPT), p-toluenesulfonyl semicarbazide (TSSC), p-toluenesulfonylhydrazide (TSH), trihydrazotriazine (THT), etc. Or 2
Used as a mixture of more than one species. Further, it is also possible to use a chemical foaming agent in which a foaming aid is added to these chemical foaming agents as necessary, and the foaming temperature and gas are adjusted. Examples of foaming aids include inorganic salts such as zinc white, tribasic lead sulfate, and white sulfur, metal soaps such as zinc stearate and lead stearate, and urea compounds, which may be used alone or in combination of two or more. used. Furthermore, thermoplastic resins prepared by adding chemical blowing agents in advance are commercially available, and these may also be added. It is desirable that the chemical blowing agent be blended in an amount of 2 to 30% by weight based on the thermoplastic resin contained in the sizing agent.
If the blending ratio is less than 2% by weight, the foaming gas pressure will be insufficient and the conductive fibers will be poorly dispersed, which is not preferable. 30 again
If it exceeds % by weight, the molded product itself becomes a foamed molded product, which is not preferable as a normal molded product. The method of coating and converging the conductive fibers with a sizing agent is not particularly limited and any method may be used, but the sizing agent may be dissolved in a solvent such as methylene chloride, tetrachloroethane, benzene, chloroform, etc.
The conductive fibers can be coated with a binding agent by dipping the conductive fibers in this solution, or by heating and melting the binding agent, extruding it from the extruder, and simultaneously passing a continuous conductive fiber through the center of the extruder die. A method that converges is preferably adopted. The amount of adhesion agent is
It is desirable that the amount is 5 to 40% by weight based on the conductive fibers; if it is less than 5% by weight, the foaming pressure will be insufficient and the dispersibility will be poor, and if it exceeds 40% by weight, the physical properties of the thermoplastic resin will be impaired. do not have. The conductive fibers are thus coated and converged with a binding agent, cooled, and then cut into pellets to obtain a conductive resin composition. The length of this pellet is preferably 3 to 12 mm, and the length is 3 mm.
If it is less than 12 mm, the conductivity will be low, and if it exceeds 12 mm, the dispersibility of the conductive fibers will be poor, and furthermore, during molding, the conductive fibers will not be filled into the details of the molded product, such as lattice parts, which is not preferable. When the thermoplastic resin of the matrix is made of polyethylene terephthalate, polybutylene terephthalate, nylon, etc., which has excellent solvent resistance, it is generally difficult to dissolve in solvents and is polar. This method is useful as a method that does not use strong solvents. After the extrusion coating is completed, the conductive fibers are dispersed by applying pressure flatly, and the conductive fibers are cut into pellets to obtain a conductive resin composition. This can be used as a molding material as it is, or it can be cut into pellets and used as a master pellet, and natural pellets made of thermoplastic resin can be blended therein and used as a molding material. In addition, thermoplastic resins containing chemical blowing agents include, for example, the product name manufactured by Engineer Plastics, FCJ-110 (for Noryl), FVC-60/65 (PBT
) and Eiwa Kasei Kogyo Co., Ltd. product name, polystyrene E1
There are 06, 105, 201, etc. These can be used alone or in combination of two or more. The chemical blowing agent contained in the sizing agent or natural pellets is heated in the cylinder of the injection molding machine, the chemical blowing agent decomposes, generates nitrogen gas and carbon dioxide gas, and foams, reducing the gas pressure. The conductive fibers are then dispersed using the injection molding machine and then dispersed and kneaded using an injection molding machine. Therefore, the conductive fibers are not cut by the injection molding machine and are well dispersed.
Moreover, a molded article with excellent conductivity can be obtained. (Examples) Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. In the following Examples and Comparative Examples, "%" means "% by weight". Example 1 3% of a chemical blowing agent azodicarbonamide (ADCA) was added to thermoplastic resin TFX-410 (ABS resin manufactured by Mitsubishi Monsanto Chemical Co., Ltd., trade name),
This was thoroughly stirred in twice the amount of methylene chloride to obtain a sizing agent. Carbon fiber with a nickel-metal layer in this solution (8 μm in diameter, 12,000 filaments)
was passed through and then dried to evaporate the solvent.
At this time, the proportion of ABS resin, carbon fiber with nickel plating layer, and ADCA was 67.9% by weight, 30
%, 2.1%. This was cut into 6 mm pellets to obtain a conductive resin composition. Injection molding was performed using this composition to obtain a molded article. The molded product was photographed by X-rays, and the dispersibility of the carbon fibers having a nickel plating layer was evaluated and the conductivity was tested, as shown in Table 1, and the excellent effects of the present invention were confirmed. Comparative Example 1 A carbon fiber (8 μm in diameter, 12,000 filaments) having a nickel plating layer was passed through a solution in which a thermoplastic ABS resin was dissolved in methylene chloride, and then dried to volatilize the solvent. At this time, the proportions of ABS resin and carbon fiber having a nickel plating layer were 70% and 30%. Make this length 6
A conductive resin composition was obtained by cutting into pellets of mm size. Injection molding was performed using this composition to obtain a molded article. This molded article was tested in the same manner as in the examples, and the results are shown in Table 1.

【table】

[Table] Evaluated. ○ mark is good, × mark is bad.
[Effect of the invention] As is clear from the above explanation and Table 1,
The method for producing the conductive resin composition of the present invention uses a chemical blowing agent as the fiber binding agent,
There is no need for a kneading and dispersion process using an extruder to disperse the thermoplastic resin and conductive fibers, and as a result, fewer long conductive fibers can be filled, resulting in excellent conductivity and without damaging the properties of the matrix resin. An electrically conductive resin composition with no oxidation can be obtained. Therefore, by using the method for producing a conductive resin composition of the present invention, a highly reliable molded article of electronic equipment can be obtained.

Claims (1)

[Claims] 1. A sizing agent containing a thermoplastic resin and a chemical foaming agent is dissolved in a solvent, conductive fibers are immersed in the sizing agent and converged, dried to volatilize the solvent, and then cut into pellets. A method for producing a conductive resin composition, characterized by: 2. The conductive resin composition according to claim 1, wherein the conductive fibers are stainless steel fibers, aluminum fibers, copper fibers, carbon fibers, or carbon fibers having a metal plating layer on the surface, glass fibers, or organic fibers. Production method. 3 The number of conductive fibers coated and bundled with a binding agent is
The method for producing a conductive resin composition according to claim 1 or 2, wherein the number of conductive resin compositions is 500 to 20,000. 4 The chemical blowing agent is azodicarbonamide, azobisisobutyronitrile, 4,4'-oxybisbenzenesulfonylhydrazide, p-toluenesulfonylhydrazide, trihydrazotriazine, p-toluenesulfonyl semicarbazine. Do,
or N,N'-dinitrosopentamethylenetetramine, the method for producing a conductive resin composition according to any one of claims 1 to 3. 5 Add a chemical blowing agent to the thermoplastic resin at a ratio of 2 to 30%.
A method for producing a conductive resin composition according to any one of claims 1 to 4, wherein the conductive resin composition is blended in a proportion of % by weight. 6 5 to 40% by weight of sizing agent based on the conductive fibers
A method for producing a conductive resin composition according to any one of claims 1 to 5, wherein the conductive resin composition is blended in a proportion of . 7. The method for producing a conductive resin composition according to any one of claims 1 to 6, wherein the pellets have a length of 3 to 12 mm.