JPH03273031A - Conductive molding and its production - Google Patents

Abstract

PURPOSE:To facilitate the formation of a molding having good and stable conductivity by coating particles of a curable thermoplastic substance with a conductive substance, optionally adding a curing agent to them, and molding and curing the mixture under applied pressure and heat. CONSTITUTION:Particles of a curable thermoplastic substance (e.g. epoxy resin particles or crosslinkable acrylic resin particles) are prepared. A layer of a conductive substance (e.g. a silver plating or a nickel plating) is formed on the surface of each particle by electroless plating or the like. A curing agent (e.g. dicyandiamide) is optionally added to the particles, and the resulting mixture is molded and cured under applied pressure and heated to obtain a conductive molding. This molding does not undergo any change in it conductivity with temperature, humidity, stress, etc., and can be desirably used for a conductive disc or the like.

Description

Detailed Description of the Invention "Object of the Invention" [Industrial Application Field] The present invention is directed to a conductive material that can be molded by applying pressure and/or heat and exhibits good and stable conductivity. This invention relates to a molded product and its manufacturing method.

[Conventional technology]

Conventionally, the surface of resin or ceramics was coated with a conductive material,
In particular, conductive powder coated with metal is used as filler for conductive bases, filler for electromagnetic shielding materials, and the like. These materials are usually used by dispersing the conductive powder in a binder.

Compared to the case where metal fine particles are used as a filler, these materials require a small amount of metal per unit volume and have a small difference in specific gravity with the binder, so they have superior dispersion stability, but they do not cause agglomeration or sedimentation of the particles. It is difficult to completely prevent this. Further, since conductivity or electromagnetic wave shielding properties are obtained through contact between the particles in the binder, the above-mentioned characteristics change depending on the way the particles come into contact with each other. Therefore, the above characteristics change depending on the environment in which it is used, such as temperature, humidity, stress, or deterioration of the binder resin, making it difficult to exhibit stable electrical or magnetic characteristics. This makes conductive fine particles non-alt.
This phenomenon is considered to be unavoidable in the method of fixing the conductive particles with a binder and maintaining conductivity by contacting the conductive fine particles with each other.

[Problem to be solved by the invention]

The present invention was developed as a result of extensive research aimed at ensuring effective and stable contact between conductive material layers and obtaining conductive molded products that are less susceptible to the effects of the external environment. Binds fine particles such as curable resin on the surface,
We have discovered a new conductive molded product and its manufacturing method.

"Structure of the Invention" [Means for Solving the Problems] The present invention provides a molded product that can easily exhibit good electrical conductivity and a method for producing the same, in which fine particles made of a curable thermoplastic substance are used to A conductive molded product obtained by coating with a material layer, adding a curing agent as necessary, molding and crosslinking by applying pressure and heating, and a metal layer in which the conductive material layer is formed by electroless plating. A conductive molded product that is
Furthermore, it is a conductive molded article in which the curable resin is an epoxy compound and/or an acrylic polymer. The present invention also relates to a method for manufacturing a conductive molded article.

That is, it is applied to the surface of fine particles made of a curable resin.
After forming the sexual substance layer, the fine particles are fused under heat and pressure, and the resin inside the particles is further cured by a crosslinking reaction, thereby providing a robust conductive molded product.

In the case of this molded product, unlike those in which conductive fine particles are fixed with a non-conductive binder, conduction is ensured by contact at the particle interface, and at the same time, the resins inside the fine particles are fused together and strengthened by crosslinking reaction. This is a molded product that forms a continuous structure and maintains the conductive bus. Therefore, conductivity is always ensured at the grain boundaries, making it possible to reduce the influence of external factors. Such a structure can also be formed by using thermoplastic resin as the fine particles on which the conductive material layer is to be provided, but if heat resistance, solvent resistance, mechanical strength, etc. are required, resin may be used. It may become unusable due to softening, dissolution, etc., and in such cases, it is effective to obtain a molded product by the method disclosed in the present invention.

The details of the present invention will be sequentially explained below.

The curable thermoplastic substance used in the present invention is not particularly limited as long as it is solid at room temperature and can be cured by heating, etc., such as thermosetting resins, low molecular weight organic substances, etc. . Note that the curing agent may or may not be included in advance. Examples of these substances include epoxy resins, crosslinkable (meth)acrylic resins, crosslinkable vinyl/(meth)acrylic copolymer resins, crosslinkable polyester resins, and block polyurethane resins. . As the epoxy resin, bisphenol A type epoxy resin, novolak type epoxy resin, alicyclic epoxy resin, etc. can be used singly or as a mixture of two or more types, and as the curing agent, it is usually used for curing the epoxy resin. There is no particular restriction as long as it is solid at room temperature, such as aromatic amines, dicyandiamide,
Dihydrazides, acid anhydrides, imidazole derivatives, etc. can be used, but the curing agent is not limited to those mentioned above. A tri-blend of curing agent and curing agent fine particles may be used. Crosslinkable (meth)acrylic resins and crosslinkable vinyl/(meth)acrylic copolymer resins include (meth)acrylic acid, (meth)acrylic acid esters, vinyl monomers, etc., and glycidyl groups such as glycidyl methacrylate. Nanatsuma and N with
-Copolymers with acrylamide derivatives such as -methylol acrylamide, N-methoxymethyl acrylamide, N-butoxymethyl acrylamide, etc. can be used, and a curing agent can also be used in combination if necessary. Ionic crosslinking using polyvalent metals can also be used.

As the crosslinkable polyester resin, those that can be crosslinked by methods such as melamine curing, blocked isocyanate curing, acid anhydride curing 3-epoxy curing, and peroxide curing of unsaturated polyester can be used. Block-type polyurethanes are stabilized by reacting active hydrogen compounds such as amides, carboxylic acids, phenol monobisulfites, etc. with the isocyanate groups of polyurethane prepolymers having isocyanate groups at the terminals or side chains. They can be selected and used as appropriate in consideration of the softening temperature of the resin, the dissociation temperature of the block, etc. Further, a curing agent may be used in combination as necessary. Incidentally, the above-mentioned items are merely examples, and the invention is not limited thereto.

The fine particles made of a curable thermoplastic substance used in the present invention preferably have a particle size of 1 μm or more and 1 mm or less. If the particle size is too small, a large amount of conductive material will be required to provide a conductive material layer with a practical thickness on the particle surface, resulting in poor economic efficiency. In addition, if the particle size is too large, the deformation of the 8 fine particles caused by pressurization and heating will become too large, making it impossible for the conductive material layer to follow the deformation, causing large-scale destruction of the conductive material layer, and causing conductive It becomes difficult to ensure sex. To obtain fine particles with such a particle size, mechanical pulverization or reprecipitation method in which a solution is poured into a poor solvent can be used, and if necessary, a classification operation can be used. It's okay.

Next, the conductive material layer provided on the surface of the fine particles obtained as described above will be described below. The conductive material layer used in the present invention is not particularly limited, and examples thereof include a metal layer obtained by electroless metal plating, a conductive layer formed by vapor deposition of a conductive metal oxide, etc. From the standpoint of material flexibility, it is more preferable to use an electroless metal plating layer. Cobalt is a metal that can be electrolessly plated.

Nickel, copper, silver, gold, platinum, and these metals with each other or with boron, nitrogen, phosphorus, vanadium, manganese, iron, zinc, molybdenum, tin, tungsten,
Examples include eutectoids with rhenium, tellurium, etc. When performing electroless plating on fine particles made of a hardenable thermoplastic substance, it is natural to perform the usual pretreatment, but the degreasing process, etching process, and sensitizing process that are usually performed as pretreatments are necessary. , the catalystizing process, and the accelerating process, the degreasing process and the etching process may be omitted.

In addition, when performing surface treatment on fine particles, particle agglomeration often becomes a problem, and to prevent this,
A small amount of a water-soluble organic solvent such as a surfactant or alcohol may also be present.

Further, in the case where the fine particles are aggregated into a lump with fine air bubbles as the nucleus, defoaming may be performed by reducing the pressure in addition to the above-mentioned measures. In addition, in order to form a uniform electroless metal layer on the fine particles, it is necessary that the particles are well wetted by the plating solution. It is preferable to carry out a reduction treatment by, for example, adding a reducing agent after sufficiently immersing the material.

Next, the method of coating fine particles of a hardenable thermoplastic substance with a conductive material layer in the present invention will be explained using an electroless plating method as an example, but the method is not limited thereto. .

[Pretreatment of hardenable thermoplastic fine particles] Fine particles of a hardenable thermoplastic substance are pretreated in the following procedure.

(1) Sensitizing process 5nCIz 2Hz0 5~20 g/j! HC1
Immerse in an aqueous solution of 5 to 50 g/l for 1 to 10 minutes while stirring (2) Wash with water.
At this time of filtration, it is better not to dry it for better dispersibility in the next step.

(3) Catalyzing process PdCl 20.5~Ig/l? Immersion in an aqueous solution of 10 to 200 g/1 HCl for 1 to 10 minutes while stirring (4) Washing and filtration At this time, not drying will result in better dispersibility in the next step.

(5) Accelerating process H2SO410~100g/j! Soak in an aqueous solution for 1 to 10 minutes while stirring (6) Wash with water.
At this time of filtration, it is better not to dry it for better dispersibility in the next step.

[Formation of metal layer]

(1) Immersion in the plating solution The pre-treated resin particles are immersed in the plating solution under conditions that prevent the reduction reaction from proceeding, and if necessary, add a surfactant, a water-soluble organic solvent, or defoam by reducing the pressure. Let's do it.

(2) Reduction operation The suspension is subjected to treatments such as addition of a reducing agent and heating to advance the reduction reaction and deposit a metal layer.

(3) Washing and filtration (4) Drying Fine particles of a hardenable thermoplastic material that has been pretreated using the methods exemplified above can be coated with conductive particles by applying a commonly used electroless plating method. It is possible to form a sexual material layer. There is no particular restriction on the thickness of the plating film, but it may be adjusted as appropriate depending on the desired specific resistance value. - For example, if you want to obtain a specific resistance value of about 10'Ω・C11 or less, you should form a metal layer of 10 g or more for 90 g of hardenable thermoplastic fine particles, although it depends on the particle size. is desirable.

Next, a method for fixing curable thermoplastic fine particles having a conductive material layer on the surface will be explained.

The fine particles are fixed by applying pressure and heating,
There are no particular limitations on the method as long as it does not impair the conductivity of the resulting coadherent. When fixing by applying pressure,
The pressure to be applied is appropriately selected depending on the hardness of the fine particles, the shape of the fine particles, the thickness of the conductive material layer, etc. Also, at this time, it is possible to simultaneously heat and adhere, but the heating temperature is
It is determined by considering the softening temperature, melt viscosity, etc. of the resin. If the molten resin becomes fluid by heating to a temperature that significantly exceeds its softening temperature, the surface of the molded product may be covered with a layer of molten resin and may not exhibit electrical conductivity.

Furthermore, if the heating temperature is too low, the fusion of the fine particles or the deformation of the fine particles may be insufficient, and fixation may not take place. When heating is performed, it is necessary to adjust the heating temperature appropriately depending on the softening temperature of the curable thermoplastic fine particles, melt viscosity, shape of the fine particles, thickness of the conductive material layer, etc.

Further, the conductive molded product of the present invention can be obtained by fixing only fine particles having a conductive material layer on the surface, but curable fine particles having a conductive material layer only on the surface of the molded product. It can also be obtained by making it exist and fixing it. For example, by forming a layer of fine particles of a thermoplastic substance having a conductive substance layer inside a molding mold and then molding the thermoplastic fine particles, a molded product having conductivity only on the surface can be obtained. I can do it.

In this case, what should become the inside of the molded product does not necessarily have to be curable thermoplastic fine particles having a conductive material layer, but may be anything that can adhere to the curable thermoplastic fine particles. Further, a layer made of thermoplastic fine particles having a conductive material layer on the surface is provided as the first layer, a layer made of a substance that can be fixed to the first layer by pressure and/or heating is provided as the second layer, and a third layer is provided. It is also possible to obtain a plate-like or film-like molded product with a conductive surface by providing a layer of thermoplastic fine particles with a conductive material layer on the surface and fixing them to each other by applying pressure and/or heating. It is.

Next, a detailed explanation of the present invention will be shown in Examples, but the present invention is not limited in any way by the following Examples. In addition,
"Parts" used in the examples indicate parts by weight in all cases. [Example] Example 1 Epicoat 1007 (manufactured by Yuka Shell Epoxy Co., Ltd.) was pulverized using a turbo mill to obtain fine particles with an average size of about 50 μm. 100 parts of these fine particles were pretreated by the method described above, and then stirred and dispersed in an aqueous solution having the following composition.

Silver nitrate 18 parts water
300 parts 35X ammonia water Add ethyl alcohol until brown precipitate dissolves
50 partsNext, in order to further improve the dispersibility of the epoxy resin fine particles, the pressure was reduced using a water aspirator to defoam. The pressure was returned to normal, and 100 parts of an aqueous solution containing 10 parts of 35% formalin was gradually added while sufficiently stirring with a magnetic star, and the centrifugal reaction was allowed to proceed for about 20 minutes. Dissolved salts were removed by decantation with water several times, and the mixture was heated and dried to obtain silver-plated epoxy resin particles.

1-cyanoethyl-2-methylimidazole (Curesol 2 manufactured by Shikoku Kasei Co., Ltd.) was added to 100 parts of the fine particles as a curing agent.
1 part of MZ-CN) o was triblended, and 1 part of this mixture was pressure-molded at a press pressure of about 100 kg-f/cm2 to obtain a disk-shaped press-molded product with a thickness of about 2.5 mm.

Next, this disk-shaped molded product was heated at 150° C. for 1 hour to undergo a hardening treatment, thereby obtaining a conductive disk. This disk was immersed in methyl ethyl ketone for 15 minutes and changes were observed.

Example 2 Epicoat 1007 (manufactured by Yuka Shell Epoxy Co., Ltd.) was pulverized using a turbo mill to obtain fine particles with an average size of about 50 μ-. 100 parts of these fine particles were pretreated by the method described above, and then stirred and dispersed in an aqueous solution having the following composition.

Nickel chloride 39 parts Sodium citrate 142 parts Sodium hypophosphite 27 parts Boric acid
77 parts Water 800 parts Ethyl alcohol 100 parts Next, in order to further improve the dispersibility of the epoxy resin fine particles, the pressure was reduced using a water aspirator to perform defoaming.

The pressure was returned to normal, and the distant reaction was allowed to proceed for about 30 minutes in a water bath at 80° C. while sufficiently stirring with a magnetic stirrer. After the reaction was completed, dissolved salts were removed by decantation with water several times, and nickel-plated epoxy fine particles were obtained by heating and drying. This fine particle 1
00 parts and 1-cyanoethyl-2-methylimidazole (Curezol 2MZ-CN manufactured by Shikoku Kasei Co., Ltd.) as a curing agent.
0. One part was triblended and one part of this mixture was pressed at a pressure of about 50 kg-f/cm2. It was heated and pressure molded at 75°C to obtain a film-like molded product with a thickness of about 0.3 mm.

Next, this film-shaped molded product was heated at 150° C. for 1 hour to perform a curing treatment to obtain a conductive film. This film was immersed in methyl ethyl ketone for 15 minutes and changes were observed.

Example 3 21 Put 660 parts of toluene into a separable flask and
Heat to 0° C. and continue stirring for about 30 minutes while blowing N2 gas. To this, 4 parts of azobisisobutyronitrile,
140 parts of methyl methacrylate, 1 part of lobate acrylate
A mixture of 40 parts of N-methoxymethylacrylamide and 20 parts of N-methoxymethylacrylamide is gradually added via a dropping tube over a period of about 2 hours. Liquid temperature 8
The reaction was allowed to proceed for about 2 hours while being maintained at 0°C, 20 parts of toluene in which 1 part of azobisisobutyronitrile was dissolved was added, and the reaction was allowed to proceed for 2 hours, after which 1 part of azobisisobutyronitrile was dissolved. 20 parts of toluene was added thereto, and the reaction was further allowed to proceed at 80° C. for 2 hours to obtain a polymer solution with a nonvolatile content of 30% by weight. This polymer solution was appropriately diluted with toluene and gradually added to methanol to perform reprecipitation to obtain fine resin particles. 100 parts of these fine particles were pretreated by the method described above, and then stirred and dispersed in an aqueous solution having the following composition.

Silver nitrate 40 parts Water 300 parts 35
χ Aqueous ammonia Added 50 parts of ethyl alcohol until the brown precipitate was dissolved.Next, in order to further improve the dispersibility of the resin particles, the pressure was reduced using a water aspirator to defoam. The pressure was returned to normal, and while stirring sufficiently with a magnetic stirrer, 100 parts of an aqueous solution containing 22 parts of 35% formalin was gradually added, and the centrifugal reaction was allowed to proceed for about 20 minutes. Dissolved salts were removed by decanting with water several times, and the mixture was dried by heating to obtain silver-plated acrylic resin fine particles. One part of these fine particles was pressed at a pressure of about 100 kg-f/c.
m" to obtain a disk-shaped press-molded product with a thickness of about 2.5+ea+. Next, this disk-shaped molded product was heated at 100°C
A conductive disk was obtained by heating and curing for a period of time. This disk was immersed in methyl ethyl ketone for 15 minutes and changes were observed.

Comparative example 1 1I! Put 378 parts of toluene in a separable flask,
Heat to 80°C while blowing N2 gas.

To this, 320 parts of styrene, 60 parts of acrylic M2-hydroxyethyl, 20 parts of acrylic acid, and AI
A mixture of 2 parts of BN is added dropwise with stirring over about 2 hours. After the dropwise addition was completed, 10 parts of toluene containing 10% by weight of AIBN was added twice every 3 hours, and the reaction was continued for an additional 2 hours to obtain a resin solution containing about 50% by weight of Furen fraction. 25 parts of silver powder (manufactured by F-14 Demetron) was added to 200 parts of this resin solution and dispersed to obtain a silver dispersed paste. This paste was cast on a Teflon plate, and after most of the toluene was volatilized, it was dried at 100° C. for 30 minutes to obtain a film. This film was immersed in methyl ethyl ketone for 15 minutes and changes were observed.

Comparative Example 2 The resin solution synthesized in Comparative Example 1 was added to methanol and reprecipitated to obtain resin fine particles. This fine particle 100
The sample was pretreated by the method described above, and then stirred and dispersed in an aqueous solution having the composition shown below.

Silver nitrate 40 parts Water 300 parts 35
χ Aqueous ammonia Added 50 parts of ethyl alcohol until the brown precipitate was dissolved.Next, in order to further improve the dispersibility of the resin particles, the pressure was reduced using a water aspirator to defoam. The pressure was returned to normal, and while stirring sufficiently with a magnetic stirrer, 100 parts of an aqueous solution containing 22 parts of 35% formalin was gradually added, and the centrifugal reaction was allowed to proceed for about 20 minutes. Dissolved salts were removed by decantation with water several times, and the mixture was heated and dried to obtain silver-plated acrylic resin fine particles. One part of these fine particles was pressed at a pressure of about 100 kg-f/
ca+! A disc-shaped press-molded product with a thickness of about 2.5 m was obtained. Next, this disc-shaped molded product was heated at 100°C for 1
A conductive disk was obtained by heating for a period of time and performing a fusion treatment. This disk was immersed in methyl ethyl ketone for 15 minutes and changes were observed.

The specific resistance values of the molded products obtained in the above Examples and Comparative Examples and the changes caused by immersion in methyl ethyl ketone are summarized below.

Claims (4)

[Claims] 1. A conductive material made of fine particles made of a hardenable thermoplastic substance, coated with a conductive material layer, a hardening agent added if necessary, molded and hardened by applying pressure and heating. Sex moldings. 2. The conductive molded article according to claim 1, wherein the conductive material layer is a metal layer formed by electroless plating. 3. 3. The conductive molded article according to claim 1, wherein the curable resin is an epoxy compound or an acrylic polymer. 4. Conductive molding characterized by coating fine particles made of a curable thermoplastic substance with a layer of conductive material, adding a curing agent if necessary, molding and curing by applying pressure and heating. method of manufacturing things