JPH0547585B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a conductive resin composition, and more specifically, the present invention relates to a conductive resin composition that has excellent conductivity, particularly durable conductivity, excellent mechanical properties such as electromagnetic shielding properties and impact resistance, and A thermoplastic containing conductive fibers that has a good molded appearance and excellent moldability, and can be suitably used as a molding material for housings of electronic devices, office automation equipment, home appliances, etc. The present invention relates to a resin composition. [Prior art and its problems] In recent years, in the field of housings for electronic devices, OA office processing equipment, home appliances, etc., synthetic resins have been increasingly used in products. However, since electromagnetic waves emitted from electronic devices and the like pass through synthetic resins, electromagnetic interference such as noise generation and malfunction of elements and the like occur. As housing materials for preventing electromagnetic interference, there are known resin compositions that have conductive electromagnetic shielding properties by blending conductive fillers such as stainless steel fibers into resins such as thermoplastic resins (Unexamined Japanese Patent Publication No. Publication No. 129031 (1982), Japanese Unexamined Patent Publication (Kokai) No. 58-
(See Publication No. 150203). However, in conventional conductive resin compositions, when a small amount of conductive filler is blended,
Sufficient conductivity and electromagnetic shielding properties cannot be obtained. On the other hand, if a large amount is blended to improve conductivity and electromagnetic shielding properties, there are problems such as a significant decrease in the inherent physical properties of the resin, such as impact resistance, and a deterioration of the appearance of the molded product. In addition, there is a method of using metal fibers with a large aspect ratio to increase conductivity with the same blending amount, but in that case, there are problems such as fiber balls are likely to form and it is difficult to mix and knead uniformly. Ta. Furthermore, a conductive resin composition obtained by blending conductive fibers converged with resin such as AS resin and a thermoplastic resin described in JP-A No. 58-129031 solves the above problems. Although this problem has been solved to some extent, even if only partially, it is still far from satisfactory, and has serious drawbacks such as particularly low durable conductivity. Moreover, it is difficult to obtain uniform dispersion of the conductive filler.
There were problems such as the appearance of the molded product being damaged and not necessarily being satisfactory. [Object of the Invention] This invention has been made based on the above circumstances. The purpose of this invention is to solve the above-mentioned problems, to provide high conductivity and high electromagnetic wave shielding properties even though a significantly small amount of conductive filler is blended, and to have excellent durable conductivity. By providing a conductive resin composition that has excellent mechanical properties such as impact resistance, has high filler dispersibility, and has a good appearance when formed into a molded product, which is extremely useful in practical use. be. [Means for achieving the above object] As a result of intensive research to solve the above problems, the inventor used a specific resin as a sizing agent, and developed a fibrous material such as metal fibers converged with this sizing agent. The present invention was completed after discovering that a conductive resin composition comprising a conductive filler and a thermoplastic resin in a specific ratio is extremely effective in achieving the object of the present invention. That is, the present invention provides a conductive resin composition comprising a thermoplastic resin and a fibrous conductive filler, wherein the fibrous conductive filler is bound by a butyral resin, and the conductive filler is bound by a butyral resin. The present invention relates to a conductive resin composition characterized in that the blending ratio of the fibrous conductive filler is 0.1 to 2.0% by volume in the conductive resin composition. Examples of the thermoplastic resin in this invention include styrene resins such as polystyrene and copolymer resins thereof, polyphenylene resins, vinyl chloride resins and copolymer resins thereof, vinylidene chloride resins, vinyl acetate resins, polyamide resins, polyacetals, Commonly used resins for molding materials include engineering plastics such as polycarbonate, thermoplastic polyester resin, polyolefin oxide, noryl resin, and polysulfonate. Examples of the styrene resin include styrene homopolymer, rubber reinforced polystyrene, and ABS.
Examples include resin, SAN resin, ACS resin, etc. As the polyolefin resin, for example,
Ultra high density polyethylene, high density polyethylene,
Polyethylene such as medium and low density polyethylene, linear low density polyethylene, isotactic polypropylene, syndiotactic polypropylene,
Examples include polypropylene such as atactic polypropylene, polybutene, 4-methylpentene-1 resin, etc. In the present invention, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer Copolymers of olefins such as propylene-vinyl chloride copolymers can also be used. Examples of the vinyl chloride copolymer resin include vinyl chloride-vinyl acetate resin, vinyl chloride-vinyl acetate resin, and vinyl chloride-vinyl acetate resin.
Examples include vinylidene chloride copolymer resin and vinyl chloride-acrylonitrile copolymer resin. Examples of the vinyl acetate resin include vinyl acetate resin, polyvinyl acetal, polyvinyl butyral, and the like. Examples of the polyamide resin include nylon 6, nylon 8, nylon 11, nylon 66, and nylon 610. The polyacetal may be a single polymer or a copolymer. Examples of the polycarbonate include polycarbonate obtained from bisphenol A and phosgene, polycarbonate obtained from bisphenol A and diphenyl carbonate, and the like. Examples of the thermoplastic polyester resin include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and the like. Note that these thermoplastic resins can be of various grades such as general grade, flame retardant grade, and impact resistant grade. Since the composite resin composition according to the present invention is to be subjected to molding, the various thermoplastic resins may be appropriately selected and used as long as the thermoplastic resin has a moldable molecular weight. be able to. The various thermoplastic resins mentioned above can be used alone, but two or more types can also be mixed and used as a polymer blend. Of course, among the various thermoplastic resins mentioned above, styrenic resins are preferred, and particularly preferred are polybutadiene, ABS resin, SBS resin,
Polystyrene in which soft component particles are dispersed (so-called impact-resistant polystyrene), which is obtained by dissolving or mixing 2 to 20% by weight of rubber such as MBS resin or NAS resin in a styrene monomer and polymerizing the above styrene monomer; It is ABS resin. A fibrous conductive filler (hereinafter, this may be referred to as a converged conductive filler) constituting the fibrous conductive filler converged with the butyral resin (hereinafter, this may be referred to as a convergent filler). ), the fiber length is preferably 1 to 15 mm, more preferably 2 to 10 mm, and the aspect ratio is preferably 200 to 5,000, more preferably 300 to 1,000. If the fiber length is less than 1 mm, the conductivity may be insufficient in some cases, and the electromagnetic shielding property may be reduced, while if it exceeds 15 mm, the dispersibility may be insufficient in some cases. Otherwise, it may become difficult to knead. Further, the aspect ratio is less than 200,
If the content of the conductive filler is not increased, the improvement in conductivity may be small, while if it exceeds 5,000, fiber breakage may increase and dispersibility may become insufficient. Examples of the butyral resin include polyvinyl butyral, such as a synthetic resin obtained by reacting polyvinyl alcohol (PVA) with butyraldehyde. In addition, this butyral resin has a viscosity of 10~
Those within the range of 370 cps can be suitably used as a convergence agent. Specific examples of such butyral resins include butyral resin (Eslec B, manufactured by Sekisui Chemical Co., Ltd.), butyral resin (#3000K, manufactured by Denki Kagaku Kogyo Co., Ltd.), and the like. The blending ratio of the thermoplastic resin ([A] component) and the convergent filler ([B]) component in the conductive resin composition of the present invention is as follows: [A] component and [B] component
When the total of the components is 100% by volume, the content of component [B] is 0.1 to 2.0% by volume, preferably 0.5 to 1.8% by volume. If the proportion of component [B] is less than 0.1% by volume, the conductivity may be insufficient and the durable conductivity may decrease. On the other hand, if it exceeds 2.0% by volume, the impact resistance of the resin molded product may decrease, the appearance of the molded product may deteriorate, and the desired conductive resin may not be obtained. The convergent filler can be easily obtained by converging the conductive fibrous material with the butyral resin and, if necessary, cutting the obtained convergent body into a predetermined length. The conductive fibrous material has good conductivity, and has a fiber length at least within the above-mentioned preferable range.
There is no particular restriction as long as it can be made into a material with an aspect ratio, such as stainless steel, brass,
Examples include highly conductive metals (or alloys) such as aluminum and copper, highly conductive metal (or alloy) coatings such as nickel coated carbon, nickel coated glass, and nickel coated resin, and fibers or fibrous materials such as conductive carbon. Among them, the highly conductive metal (or alloy) fibers and the highly conductive metal (or alloy) coated fibers are preferred, and stainless steel fibers, nickel-coated carbon fibers, etc. are particularly preferred. Note that these conductive fibrous materials may themselves form a fiber bundle, or may be a single fiber. However, as will be described later, it is desirable to use these conductive fibers by converging them into a suitable fiber bundle. These conductive fibrous materials can be manufactured by known methods such as melt spinning, stretching, wire drawing, extrusion, and cutting. In addition, conductive fibrous materials coated with metal are
It can be obtained by a known metal coating method, such as subjecting the fibrous material obtained by the above method to electroless metal plating, electrolytic metal plating, metal vapor deposition, or the like. The method of converging the conductive fibrous material with the butyral resin to obtain the converged body is usually to collect 100 to 20,000 conductive fibers, preferably 500 to 500, with a diameter of 1 to 50 μm, preferably 5 to 25 μm.
A method can be adopted in which a fiber bundle consisting of 10,000 fibers is impregnated with a predetermined amount of a butyral resin solution dissolved in an appropriate solvent, the solvent is evaporated and removed, and if necessary, the fiber bundle is dried. At this time, the solvent to be used must be one that stably dissolves the butyral resin and is easy to remove by evaporation.
There are no particular limitations on the organic solvent as long as it does not impede the above impregnation/drying operations and does not impede the purpose of the present invention, and various organic solvents or mixtures thereof may be appropriately selected and used. As such a solvent,
Particularly suitable examples include non-reactive, low-boiling organic solvents such as chloroform. The conductive fibrous material and the butyral resin may be used alone or in combination of two or more. When converging the conductive fibrous material with butyral resin, it is usually desirable to perform a degreasing treatment in advance. Examples of degreasing include solvent degreasing, immersion degreasing,
These include alkaline degreasing and surfactant degreasing. Furthermore, when performing the impregnation with the butyral resin, a tackifier such as a terpene resin can be used in combination as necessary. The convergence body obtained as described above is cut into a predetermined length, and the convergence body is made of a conductive filler having a predetermined length and aspect ratio and condensed with butyral resin. This can lead to a convergent filler with properties. In this invention, the thermoplastic resin ([A] component)
The object of the present invention can be achieved by blending (mixing) with the specific convergent filler ([component B]). In addition to component A] and component [B], as long as they do not impede the effects of the present invention, suitable additives such as lubricants, flame retardants,
Various additives such as colorants, antioxidants, ultraviolet absorbers, plasticizers, adhesion promoters, inorganic fillers, and heat stabilizers can be added and blended. Examples of the lubricant include fatty acids, fatty acid esters, fatty acid amides, metal soaps, and alkyl betaines. Note that all of these lubricants are different from surfactants. Among the various lubricants mentioned above, preferred ones include:
For example, saturated alkyl fatty acids with 10 to 20 carbon atoms,
Examples include monoglycerides thereof, acid amides thereof, metal salts thereof, ethylene bisstearamide, alkyl betaines, etc., and particularly preferred ones include stearic acid, calcium stearate, stearic acid monoglyceride, ethylene bis stearoids, alkyl betaines, Examples include oleic acid amide. In the conductive resin composition according to this invention,
By appropriately selecting one or more of the above lubricants and blending them in an appropriate amount, it is possible to impart appropriate moisture to the resulting resin composition and improve workability during blending. , it is possible to achieve desirable effects such as improving the dispersibility of the fibrous conductive filler, and it is generally preferable to use it in this manner. The blending ratio of this lubricant ([C] component) is as follows:
When the sum of the [A] component, the [B] component, and the added [C] component is 100% by weight, the [C] component proportion is usually about 0.1 to 6% by weight, preferably 0.5%. The content is preferably 2.0% by weight. Examples of the flame retardant include tetrapromoethane, tetrabromobutane, decabromodiphenyl ether, hexabromodiphenyl ether, tetrabromobisphenol A, polybromophenylene oxide, hexabromocyclododecane, brominated polycarbonate, and the like. Can be mentioned. Among these, decabromodiphenyl ether and the like are preferred. The blending ratio of the flame retardant is usually 3 to 30 parts by weight per 100 parts by weight of the thermoplastic resin [A]. Further, as the coloring agent, a sparingly soluble azo dye,
Examples include red colorant, cadmium yellow, cream yellow, titanium white, etc. As the antioxidant, triazole-based, salicylic acid-based, and acrylonitrile-based antioxidants are used. As the ultraviolet absorber, hydroxybenzophenone type, hydroxybenzotriazole type, etc. are used. Examples of the plasticizer include phthalic acid diester, butanol diester, and phosphoric acid diester. Examples of the inorganic filler include carbonates such as calcium carbonate, magnesium carbonate, and dolomite, sulfates such as calcium sulfate and magnesium sulfate, sulfites such as calcium sulfite, talc, clay, mica, asbestos, glass fiber,
Glass beads, calcium silicate, montmorillonite, bentonite and other silicates, silicon carbide,
Examples include ceramics such as silicon nitride, whiskers thereof, carbon black, graphite, and carbon fibers. The conductive resin composition according to the present invention can be produced by blending the thermoplastic resin [A], the convergent filler, and, if necessary, the various additives such as the lubricant. There are no particular restrictions on the method of blending the components to obtain the conductive resin composition according to the present invention. For example, after preparing the thermoplastic resin, mix the resin and the convergent filler in a Henschel mixer. Dry blending may be carried out using a mixer such as, or melt kneading may be carried out using a Banbury mixer, roll mill, screw extruder, or the like. The various additives mentioned above may be added during this kneading. Also, before cutting the convergent body, if necessary, after contacting with the lubricant etc., the stainless steel fibers are cut to a predetermined size, mixed with a thermoplastic resin,
It may be kneaded. Alternatively, a masterbatch may be prepared by appropriately mixing and kneading the thermoplastic resin and, if necessary, the various additives mentioned above, and a convergent filler of a predetermined size may be dry blended into this masterbatch. Alternatively, a method may be used in which the conductive fiber bundles are bundled using a binder containing additives such as a lubricant, cut into predetermined dimensions, and mixed and kneaded with a thermoplastic resin. The conductive resin composition obtained in this way is
For example, it can be molded into various molded products by various molding methods such as injection molding, cast molding, extrusion molding, and press molding. In this way, the conductive resin composition has significantly improved conductivity without reducing the mechanical strength such as impact resistance of the molded product or deteriorating the appearance of the molded product. It also has excellent durability and conductivity, and also has excellent electromagnetic shielding properties, so it is suitable for use as housing materials and electromagnetic shielding materials for electronic equipment, OA office processing equipment, home appliances, etc., and is extremely useful as an industrial material. Useful. [Effects of the Invention] According to the present invention, since the thermoplastic resin and the fibrous conductive filler converged by a specific convergence agent are blended in a specific ratio, the following effects can be achieved. (1) Since the fibrous conductive filler is uniformly dispersed, this conductive resin composition has extremely good conductivity, extremely good durable conductivity, and excellent electromagnetic shielding properties. . (2) Since agglomerates of the fibrous conductive filler are difficult to form, the moldability and processability of various molded products obtained from this conductive resin composition are excellent, and the mechanical properties of the various molded products obtained are excellent. Mechanical properties such as strength are maintained at a high level, and the appearance of the molded product is excellent. (3) Therefore, this conductive resin composition is not only suitable as a housing material for shielding electromagnetic waves emitted from electronic devices and various elements, but also as an industrial material with a wide range of applications. Very advantageous. [Example] Next, the present invention will be explained in more detail by showing examples and comparative examples of the present invention. Production example 1 (Production example of convergent conductive fibrous filler) Butyral resin A as convergence agent [Sekisui Chemical Co., Ltd.
Prepare a chloroform solution (concentration 20% by weight) of Eslec BL-1 (low degree of polymerization type) manufactured by Co., Ltd., and insert stainless steel fibers (SUS 304, diameter 8 μm,
After soaking (5000 fiber bundles), the stainless steel fibers were dried and bundled. Thereafter, the obtained bundle was cut into lengths of 4 mm or 6 mm to obtain two types of stainless steel fiber bundles having different lengths. Note that these aggregates contained 12.5% by weight of butyral resin A. Example 1 0.93% by volume of the 4 mm long stainless steel fiber bundle obtained in Production Example 1 above and 99.07% by volume of impact-resistant polystyrene (MI 4.0g/10 min, density 1.05g/cm ³ )
After dry blending, injection molding was performed at a molding temperature of 240℃ to make a test piece (thickness: 3 mm, length: 70 mm, width: 70 mm).
We created and measured the volume resistivity before and after heat shock, the electromagnetic shielding property after heat shock, and the Izot impact strength. Further, regarding the appearance, a square plate having a thickness of 3 mm, a width of 10 cm, and a length of 10 cm was molded and visually judged. The results are shown in Table 1. Example 2 The 6 mm long stainless steel fiber bundle obtained in Production Example 1 was used instead of the 4 mm long stainless steel fiber bundle, the usage ratio was 0.87% by volume, and the usage ratio of polystyrene was 99.13% by volume. It was carried out in the same manner as in Example 1 except for the following. The results are shown in Table 1. Example 3 A test was carried out in the same manner as in Example 1 except that the proportions of the stainless steel fiber aggregate and polystyrene were changed. The results are shown in Table 1. Example 4 In place of butyral resin A in Production Example 1,
A stainless steel fiber bundle having a length of 4 mm was obtained in the same manner as in Production Example 1 using butyral resin B (manufactured by Sekisui Chemical Co., Ltd., Eslec BH-3 (high degree of polymerization type)). The experiment was carried out in the same manner as in Example 1 using this converging body. The results are shown in Table 1. Example 5 In Production Example 1, instead of using stainless steel fibers, 10,000 pieces of nickel-coated carbon fiber (manufactured by American Cyanamid Company - CYCOM MCG fiber: 8 μm diameter carbon fiber coated with 0.5 μm nickel) were used. A convergent body with a length of 4 mm was obtained in the same manner using a fiber bundle. The experiment was carried out according to Example 1 using this convergent body. The results are shown in Table 1. Production example 2 (Production example of convergent conductive fibrous filler) In production example 1, instead of using butyral resin as a convergence agent, polystyrene (PA-S), polyethylene teregutalate (PFT), and polyvinyl alcohol (PVA) were used. The procedure was the same as in Production Example 1 except that polycarbonate (PC) and polycarbonate (PC) were used, respectively, to obtain stainless steel fiber aggregates each having a length of 4 mm. Comparative Examples 1 to 4 The same procedure as in Example 1 was carried out, except that the stainless steel fiber bundles produced in Production Example 2 were used instead of the stainless steel fibers bundled with butyral resin. The results are shown in Table 1. Comparative Examples 5 and 6 The same procedure as in Example 1 was carried out except that the blending ratio of the stainless steel fiber bundle was changed. The results are shown in Table 1. Example 6 In Example 1, instead of polystyrene
It was carried out in the same manner except that ABS resin was used. The results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1. A conductive resin composition comprising a thermoplastic resin and a fibrous conductive filler, wherein the fibrous conductive filler is bound by a butyral resin, and the butyral resin is bound by the butyral resin. The blending ratio of the fibrous conductive filler in the conductive resin composition is from 0.1 to
A conductive resin composition characterized by having a content of 2.0% by volume. 2. The conductive resin composition according to claim 1, wherein the thermoplastic resin is a styrene resin.