JPS6364007B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conductive resin molded article having excellent physical properties such as a low surface resistance value. In the electric/electronic industry, conductive synthetic resin molded products are used for antistatic purposes, electromagnetic shielding, etc., but conventional methods for imparting conductivity include (1) silver powder, copper powder, aluminum powder, and nickel powder. Method of mixing metal powder such as powder, (2) Method of mixing carbon black and graphite, (3)
Methods that have been used include mixing carbonyl nickel powder with epoxy resin and curing it while applying a magnetic field. However, in the method (1) above, the 10 ⁹ to 10 ^-5 [Ω・
cm], it is necessary to mix a large amount of metal powder, and the price of metal powder is high.
As a result, physical properties deteriorate and costs increase. Furthermore, in the method (2) above, carbon black and graphite are cheaper than the metal powder mixed in the above (1), so the cost of the product itself can be kept low. However, the amount used is still large, and the physical properties are much worse than those mixed with metal powder. Furthermore, in the method (3) above, it is necessary to mix a large amount of carbonyl nickel powder in order to obtain the desired conductivity. In addition, with conventional methods, it is necessary to uniformly mix a substance that imparts conductivity into the molded product in order to reduce only the electrical resistivity of the surface, and even the inside of the molded product that does not require conductivity at all is conductive. The physical properties of the molded product are significantly deteriorated because the substance that imparts it is mixed in the same proportion as the surface. The present inventors have arrived at the present invention as a result of extensive research in view of the drawbacks of the above-mentioned conventional methods. That is, the present invention provides a synthetic resin composition containing powder obtained by coating triiron tetroxide or magnetic powder containing it as a main component with conductive powder of carbon black or graphite. The present invention provides a conductive resin molded product having excellent physical properties with a low surface electrical resistance value, which is characterized by being molded under the influence of a strong magnetic field perpendicular to the surface of the molded product in a molten or uncured state. be. In such molded products, a large amount of powder collects on the surface layer (plane perpendicular to the magnetic field) of the molded product, so the electrical resistance value is significantly lower than that inside the molded product, and even if the molded product has the same surface electrical resistance value, In comparison, compared to conventional products in which a conductive material is uniformly dispersed inside the molded product, it has the advantage of requiring less amount of conductive material (powder) and less deterioration in physical properties (strength). In the present invention, triiron tetroxide or a material containing it as a main component is used as the magnetic powder, and carbon black or graphite is used as the conductive powder. It is difficult to coat conductive powder with materials other than magnetic powder. Synthetic resins in the present invention include polyvinyl chloride, polyethylene, polyethylene oxide, polypropylene, polystyrene, high impact polystyrene, thermoplastic resins such as ABS resin and polymethyl methacrylate, thermosetting resins such as urea formaldehyde and phenol formaldehyde, and epoxy resins. Examples include resin and polyurethane. The stronger the magnetic field used in the present invention, the better the results. However, if the synthetic resin composition has a low viscosity when subjected to the influence of a magnetic field in a molten or uncured state, the present invention can be achieved with a viscosity of about 5000 Gauss. Examples of the present invention are shown below, but the present invention is not limited by the Examples. The molded article of the present invention may contain commonly used stabilizers, anti-aging agents and other additives. Example 1 Ferrous sulfate, _ferric sulfate and _carbon black (average particle size 0.1μ, oil absorption
While stirring the mixed aqueous solution (30cc/100gr), sodium hydroxide was gradually added to cause coprecipitation. Observation of the obtained black coprecipitate revealed that the triiron tetroxide was completely covered with carbon black and had sufficient coating strength. 4 parts by weight of the obtained coprecipitate and 96 parts by weight of epoxy resin were mixed, a curing agent was added, and the mixture was cured at 60° C. for 1 hour under the influence of a 5000 Gauss magnetic field to prepare a flat plate with a thickness of 1.0 cm. In this case, the magnetic lines of force act perpendicularly to the surface of the flat plate. A cube with a side length of 1.0 cm was created from the obtained flat plate. A conductive substance (silver paint) was applied to the sides of the cube parallel to each other, and after drying, lines were drawn with a cutter knife in a direction perpendicular to the lines of magnetic force to divide the silver paint into 1 mm intervals. Numbers were assigned from the top (surface when flat plate) No. 1 to No. 10. The electrical resistance values of the opposing numbers were measured. Comparative Example 1 was prepared by changing the strength of the magnetic field to 1500 Gauss. Comparative example 2 was prepared in the same manner as in the example except that no magnetic field was applied. The results are shown in Table 1.

[Table] Example 2 The impact strength of a flat plate obtained by the same method as Example 1 is shown below. The impact strength of a flat plate without any magnetic field applied was set as 1 for comparison. Example 1 (5000 Gauss) 2.03 Comparative Example 1 (1500 Gauss) 0.96 Comparative Example 2 (0 Gauss) 1.00 Example 3 6 parts by weight of the same black coprecipitate as in Example 1 and 94 parts by weight of polyethylene were mixed and heated at 160°C. A flat plate with a thickness of 1 cm was formed by applying a magnetic field of 8000 Gauss. A cube with sides of 1 cm was obtained from the obtained flat plate, silver paint was applied to the opposite sides, and after drying, parallel lines were drawn at 1 mm intervals from the top with a cutter knife. The numbers are No. 1 to No. 10 from the top. Comparative Example 3 was prepared in the same manner as in Example 3 except that the magnetic field was set to 3000 Gauss, and Comparative Example 4 was prepared in which no magnetic field was applied. The results are shown in Table 2.

[Table] Example 4 A flat plate was prepared in the same manner as in Example 3, and the impact strength was measured. The impact strength of a flat plate without any magnetic field applied was set as 1 for comparison. Example 3 (8000 Gauss) 1.45 Comparative Example 3 (3000 Gauss) 0.95 Comparative Example 4 (0 Gauss) 1.00

Claims (1)

[Claims] 1. A synthetic resin composition containing a powder obtained by coating triiron tetroxide or a magnetic powder containing it as a main component with conductive powder of carbon black or graphite is heated in a molten or uncured state. A conductive resin molded product having excellent physical properties with a low surface electrical resistance value, characterized by being molded under the influence of a strong magnetic field perpendicular to the surface of the molded product.