JPH048463B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conductive thermoplastic resin composition, and more particularly to a conductive thermoplastic resin composition formulated as a powdered phosphorus conductive agent. In recent years, with the rapid advancement of electronics, the malfunction of electronic devices due to electromagnetic waves has come to the fore as a social problem. This is due to the rapid transition from metal materials to insulating plastic materials for the housings (cases) that house electronic devices. For this reason, in order to suppress electromagnetic wave interference from computers, electronic games, etc., shielding electronic devices from electromagnetic waves was introduced in 1988 by the United States (FCC regulations), West Germany (FTZ regulations), etc. One after another, it is required by law. In order to shield electromagnetic waves, it is considered necessary to make the plastic at least electrically conductive, similar to conventional housings made of metal materials. Methods for making plastic conductive include coating the molded product with conductive paint or post-processing methods such as zinc spraying, manufacturing the molded product using sheets laminated with metal foil, and adding metal powder or metal to the plastic. There are methods of blending and molding conductive materials such as flakes, metal fibers, carbon black, graphite, and carbon fibers. However, both of these methods have problems. In other words, the method of coating with conductive paint is to mix metal powder (silver, copper, nickel) with paint resin and apply it by spraying, but in addition to requiring painting equipment, the metal in the coating layer may oxidize. It has drawbacks such as being easily corroded and the coating layer easily peeling off during use. In addition, zinc spraying is a method in which metal is melted with arc heat and sprayed with high-pressure air, but it has drawbacks such as requiring expensive equipment and problems with adhesion and zinc toxicity. There is. The method of manufacturing a molded article using a metal foil laminated sheet has the drawback that it is impossible to integrally mold a molded article with a complicated shape, and is lacking in versatility. On the other hand, the method of integrally molding a resin composition blended with conductive materials is promising because it does not require special equipment and there is no risk of the conductive layer peeling off. There are various problems with these agents. For example, carbon black, graphite, etc. have the disadvantage that they have insufficient electrical conductivity and also significantly reduce the mechanical properties of plastics. Furthermore, metal powders such as copper powder, iron powder, and aluminum powder are easily oxidized, pose a risk of powder explosion during handling, and have the disadvantage that uniform dispersibility is difficult. On the other hand, metal fibers such as copper, iron, and stainless steel slightly improve the mechanical and thermal properties of plastics, but the fibers become entangled and are difficult to disperse uniformly, and metal fibers are expensive. It has the following disadvantages. Conductive fibers such as carbon fibers and aluminum-deposited glass fibers have the advantage of improving the mechanical strength of plastics, but they also cause directional conductivity and anisotropy in the shrinkage rate of molded products. It has disadvantages such as warpage and deformation easily occurring and fiber cost being extremely high. The inventors of the present invention have found that they have a large electrical conductivity effect, improve the mechanical and thermal properties of thermoplastic resins, are easy to disperse in thermoplastic resins, have little shrinkage anisotropy in molded products, are inexpensive, and are safe to handle. As a result of intensive research to develop a conductive filler and a thermoplastic resin composition containing the conductive filler, the composition of the present invention was arrived at. That is, the present invention is a conductive thermoplastic resin composition for electromagnetic shielding, which is characterized by containing powdered iron phosphorus in polyester and/or polyamide. The iron phosphorus referred to here is an alloy of phosphorus and iron represented by Fe ₂ P, also known as ferrophosphorus, and is usually obtained as a by-product when manufacturing phosphorus from phosphate rock, and usually contains some silicon, manganese, etc. as impurities. May contain. Conventionally, iron phosphorus has been used as an additive to increase the fluidity of castings and as an additive in the manufacture of steel ingots for thin iron plates, but there are no known examples of its use in which it is blended into thermoplastic resins and its effects. It has not been done. The composition according to the present invention has good handling properties and mixing and dispersing properties of each composition during kneading, and has excellent operability, and molded products obtained from the composition have excellent conductivity and extremely good electromagnetic shielding properties. Furthermore, it does not inhibit the moldability of thermoplastic resins, it does not cause warping or deformation in molded products, it improves the mechanical properties of molded products, and phosphorous iron has excellent chemical stability. It has many features such as stable performance even after long-term use. Examples of the polyamide in the present invention include nylon 6, nylon 6,6, nylon 12, polyether amide, polyester ether amide, etc., and examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, polyester polyether block copolymer, and polyester polylactone. Examples include block copolymers. Phosphate iron is usually amorphous particles, and from the viewpoint of dispersibility in thermoplastic resins, mechanical properties, electrical conductivity, etc., those with an average particle size of 30 μm or less are preferable, and those with an average particle size of 5 μm or less are particularly preferable. In addition, from the viewpoint of electromagnetic shielding properties, the blending amount is relative to the total amount of thermoplastic resin.
From the viewpoint of mechanical properties, it is preferably 20% by weight or more, and 90% by weight or less based on the total amount with the thermoplastic resin, and more preferably about 30 to 85% by weight.
However, when other conductive agents such as metal powder, carbon black, carbon fiber, charge transfer complex, polyacetylene, etc. or an antistatic agent are used in combination, antistatic effects, conductive effects, etc. can be obtained with a smaller amount of iron phosphorus. The kneading of the iron phosphorus and the thermoplastic resin can be carried out according to the usual method of kneading a filler and a thermoplastic resin. Further, in order to improve the wetting of the iron phosphorus and the resin, a treatment using a surface treatment agent similar to that used for ordinary fillers can be performed. In addition, the distribution of the conductive agent can be controlled by using polyalkylene glycols, polymers having polyoxyalkylene chains, anionic surfactants, or polymers containing anionic groups, or by kneading with the auxiliary agent in advance and then kneading with the thermoplastic resin. It is also possible to impart antistatic properties and conductivity with a smaller amount by changing the amount. Particularly when the thermoplastic resin is polyester, polyamide, etc., the effect of this method is great. Preferably, the polyalkylene glycols and polymers having oxyalkylene chains have relatively high molecular weights and are incompatible with thermoplastic resins. The composition according to the invention may optionally contain further reinforcing agents, such as glass fibers, boron carbide fibers, silicon carbide fibers, whiskers, aramid fibers, etc.
Alternatively, other fillers such as talc, mica, wollastonite, clay, silica, glass powder, calcium carbonate, etc. can also be used in combination. Further, conductive fillers such as carbon black, graphite, carbon fiber, aluminum powder, aluminum fiber, brass fiber, copper fiber, iron powder, copper powder, brass powder, etc. can also be used in combination. Furthermore, antioxidants, ultraviolet absorbers, hydrolysis stabilizers, dyes and pigments, flame retardants, flame retardant aids, lubricants, plasticizers, mold release agents, sliding properties improvers, which are blended into thermoplastic resins for molding. Impact modifiers, foaming agents, crystal nucleating agents, polyfunctional crosslinking agents, and other compounding agents can be blended as appropriate. In particular, when the thermoplastic resin is polyester, higher fatty acids, higher fatty acid esters, high molecular weight aliphatic polycarboxylic acids, carboxylic acid group-containing ethylene polymers, compatible polyalkylene ethers, polyhydric alcohol esters, Moldability and surface properties can be improved by using an organic crystallization accelerator such as polycarboxylic acid esters or polyepoxide. Molded articles made from the composition of the present invention have excellent antistatic properties, conductivity, electromagnetic shielding properties, etc.
In addition to improved mechanical properties, sliding properties, thermal conductivity, etc. are also improved. The composition according to the present invention can be applied to fibrous materials, tape-like materials,
Used as a molding material for extrusion molded products such as film-like products, injection molded products such as various molded parts, blow molded products, etc., as a molding material that is formed into a sheet shape and then air pressure or vacuum molded, and as a coating material. You can also do that. It can also be used as a composite material with other materials, such as an impregnated material such as cloth, a laminated material with a film, a metal plate, etc., as a carpet lining agent. It is particularly suitable as an injection molding material or a blow molding material. The present invention will be explained below with reference to Examples. In addition, the production of the composition in the Examples, the molding of injection molded specimens, and the physical properties of the obtained molded products were conducted according to the following methods. (1) Production of composition A predetermined amount of thermoplastic resin and phosphorous iron powder is melt-kneaded using a PCM-30 twin-screw extruder manufactured by Ikegai Tekko Co., Ltd. using the usual kneading conditions used for various resins to produce pellets. did. (2) Manufacture of molded products After drying the pellets using a vacuum dryer, using an injection molding machine (model FS-75 manufactured by Nissei Jushi Kogyo Co., Ltd.),
Under normal injection conditions used for various resins, a flat plate with a length and width of 200 mm and a thickness of 3 mm and ASTM
A test piece was molded. (3) Characteristic evaluation of test piece Γ Electromagnetic shielding property Magnetic field was measured using a flat test piece using the Optimal System Study Group (Institute of Industrial Science, University of Tokyo) method. Γ Heat distortion temperature ASTM D-648 using ASTM test piece
Measured at a load of 18.6 kg/cm. Γ Bending strength ASTM D-648 Example 1 After obtaining pellets by melt-kneading powdered iron phosphorus with an average particle size of 3 microns and nylon 6 (Toyobo Co., Ltd. nylon T102), a test piece was formed and its properties were evaluated. evaluated. The results are shown in Table 1.

[Table] As is clear from Table 1, a blend of 15% by weight of iron phosphorus does not provide sufficient electromagnetic shielding properties, and an excessively large blend has the disadvantage that physical properties such as bending strength decrease. The preferred amount is about 20 to 90% by weight. Of course, when used in combination with other conductive agents such as carbon black, excellent electromagnetic shielding properties can be obtained with a phosphorous iron content of 15% by weight or less. Example 2 Nylon 6 (Nylon T102, Toyobo Co., Ltd.) and iron phosphorus having various average particle sizes were used as thermoplastic resins and pelletized in the same manner, then molded and their properties were evaluated. The results are shown in Table 2.

[Table] As is clear from Table 2, if the average particle size of the iron phosphorus to be blended is too large, physical properties such as bending strength will deteriorate, so the average particle size is preferably about 30 microns or less. Example 3 Iron phosphorus having an average particle size of 3 microns and various thermoplastic resins were melted and kneaded into pellets, and then test pieces were molded and their properties were evaluated. Table 3 shows the results.
and shown in Table 4.

[Table] As a result, excellent electromagnetic shielding properties were obtained with the addition of iron phosphorus. In particular, thermoplastic resins such as polyamide and polyester have the advantage that bending strength, heat distortion temperature, etc. can be significantly improved.

Claims (1)

[Claims] 1. A conductive resin composition for electromagnetic shielding, characterized by containing powdered iron phosphorus in polyester and/or polyamide.