JPS6155168A - Electrically conductive paint having excellent heat resistance - Google Patents

Abstract

PURPOSE:To provide an electrically conductive paint which has excellent heat resistance and does not cause a metallic damage to olefin resins, consisting of Ni-coated graphite and a binder component. CONSTITUTION:Nickel tetracarbonyl is thermally decomposed to deposit 10- 80wt% nickel on the surface of graphite having an average thickness of 0.1- 40mum, thus obtaining Ni-coated graphite (A). 90-30vol% component A and 10- 70vol% binder component (B) selected from among water-soluble silicate (e.g. sodium silicate), water-soluble polymer (e.g. PVA), thermoplastic resin (e.g. PE) and thermosetting resin (e.g. thermosetting acrylic resin) are dissolved or dispersed in water or an org. solvent (e.g. hexane).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides a conductive coating material particularly excellent in heat resistance.

[Prior art]

Conductive paints are usually made by mixing epoxy resin with silver powder, copper powder, or nickel powder and dissolving it in a solvent. Silver powder has high electrical conductivity (although it is excellent as an electrical conductor, it is expensive because it is a precious metal and is therefore less economical. Copper powder is a general-purpose metal and has high electrical conductivity as well as silver powder, so Although it is most widely used as a conductor, it is susceptible to oxidation (and has durability problems), and for example, if an olefin resin is used as a binder component, it will generate a paper trail and cause the resin to deteriorate.Also, if the binder component Even if olefin resin is not used as a component, similar problems will occur if olefin resin is used as a coating base material.Nickel powder is a commonly used metal along with copper, and like copper, olefin resin Although there is little risk of causing metal damage to the system resin, there is a problem in that it has poor heat resistance and, for example, when heated to 60° C. or higher, the electrical conductivity decreases surprisingly.

[Problem that the invention seeks to solve]

Therefore, the present inventors have conducted extensive research to find out whether it is possible to obtain a conductive coating material that has excellent heat resistance, does not cause metal damage to olefin resins, and is highly economical, and as a result has arrived at the present invention.

[Structure and outline of the invention]

That is, the present invention relates to a conductive paint with excellent heat resistance, which is characterized by comprising graphite (A) whose surface is coated with nickel and a binder component (B).

Graphite used as a conductor that is blended into the paint of the present invention to impart electrical conductivity is one whose surface is coated with nickel (hereinafter abbreviated as nickel-coated graphite). . The amount of nickel coated on the graphite surface is approximately 10% of the total amount of nickel-coated graphite.
~80% by weight. Further, it is preferable that the average diameter is about 10 to 1000 μm and the average thickness is about 0.1740 μm.

An example of manufacturing nickel-coated graphite is
Nickel tetracarbonyl N1(Co)4G thermal decomposition,
It can be manufactured by depositing nickel on the surface of graphite.

Binder component (B) All binder components that can be used in the paint field can be used.Binder components can be broadly divided into binder component (B1) used for water-soluble paint types and binder component (B1) used for oil-soluble paint types. It can be separated into a binder component (B2).

Representative examples of the binder component (B) include water-soluble silicates such as sodium silicate, potassium silicate, lithium silicate, ammonium silicate, ethyl silicate, water-soluble polymers such as carboxymethyl cellulose, polyvinyl alcohol, or mixtures thereof. .

Examples of the binder component (B2) include thermoplastic resins and thermosetting resins. As a thermosetting resin, there are two types: a two-component type that uses a hardening agent, and a one-component type that does not use a hardening agent.
There is a liquid type, but any type may be used as long as it is oil-soluble. In other words, in the case of a one-component type, if it has a hydrolyzable organic group such as an alkoxysilane in its polymer chain, it is oil-soluble, that is, soluble in organic solvents, before hydrolysis, but once the solvent evaporates, it becomes soluble in organic solvents. Then, the moisture in the air causes hydrolysis, crosslinking, and hardening. In such cases, the resin can be used at the point where it is soluble in the organic solvent before hydrolysis occurs. However, from the viewpoint of ease of handling, it is generally preferable for the thermosetting resin to be a two-component type.

Examples of the resin constituting the binder component (B2) include thermoplastic resins such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or ethylene;
Polyolefins such as random or block copolymers of α-olefins such as propylene, l-butene, and 4-methyl-1-pentene, ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, ethylene/vinyl alcohol Copolymers, ethylene/vinyl compound copolymers such as ethylene/vinyl chloride copolymers, polystyrene, acrylonitrile/styrene copolymers, ABS, methyl methacrylate/styrene copolymers, α-methylstyrene/
Styrenic resins such as styrene copolymers, polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinylidene chloride copolymers, polyvinyl compounds such as polymethyl acrylate and polymethyl methacrylate, nylon 6, nylon 6-6
, nylon 6-10. Any resin such as polyamide such as nylon 11 or nylon 12, thermoplastic polyester such as polyethylene terephthalate or polybutylene terephthalate, polycarbonate, polyphenylene oxide, or a mixture thereof may be used.

Examples of thermosetting resins include epoxy resins, urethane resins, thermosetting acrylic resins, and resol type phenolic resins.

Among the resins exemplified above, those that are particularly preferably used are olefin resins and acrylic resins. To explain the details of these resins again, examples of olefin resins include polyethylene, polypropylene, and poly(1-1).
Ethylene represented by butene, poly 3-methyl-1-butene, poly 4-methyl-1-pentene, ethylene/propylene copolymer, ethylene/1-butene copolymer, propylene/1-butene copolymer, α-Olefins such as propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-decene, 1-dodecene, etc. copolymers of α-olefins and conjugated dienes or non-conjugated dienes, such as ethylene-butadiene copolymers, ethylene-ethylidene norbornene copolymers, or ethylene-propylene-butadiene ternary copolymers. α- polymers, typified by ethylene/propylene/dicyclopentadiene ternary copolymer, ethylene/propylene/ethylidene norbornene ternary copolymer, ethylene/propylene/1,5-hexashuf ternary copolymer, etc. There are copolymers of two or more types of olefins and a conjugated diene or a non-conjugated diene. There are also copolymers of ethylene and vinyl acetate. Acrylic resins include methyl methacrylate, ethyl methacrylate, butyl methacrylate,
Hard type non-functional hexamers such as isobutyl methacrylate, soft type non-functional hexamers such as hexyl methacrylate, lauryl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, and conitylhexyl acrylate. carboxyl group-containing functional monomers such as acrylic acid and methacrylic acid; hydroxyl group-containing functional monomers such as hydroxyethyl methacrylate and hydroxyethyl methacrylate; and amide group-containing functional monomers such as acrylamide and methacrylamide. Glycidyl group-containing functional monomers, such as glycidyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, and if necessary, acrylic thread additives such as styrene. It is an acrylic polymer composed of polymerizable monomers.

[Form of conductive paint]

The form of the conductive paint of the present invention is graphite (A).
and a binder component (B), depending on the type of binder component (B), a water-soluble paint using water as a dispersion medium,
It can be divided into oil-soluble paints that use oil (organic solvent) as a dispersion medium. Still another form is one in which the resin is dispersed (not dissolved) in an aqueous phase or an oil phase in the form of an emulsion.

The coating material of the present invention may basically be in any of the above forms, but water-soluble and oil-soluble forms are particularly preferred, and oil-soluble forms are particularly preferred.

The organic solvent (C) used in the oil-soluble paint is one that dissolves the binder component and forms a liquid paint, and various organic solvents that can dissolve the binder component may be used. Among them, organic materials that are easy to paint (easy to dry, that is, have enough fluidity to be easily applied with a brush without causing any sagging during painting, and are volatile enough to evaporate quickly after application to form a cured coating) Solvents are preferred.

Examples of organic solvents include hexane, decane, 2.2
．． 5-) Aliphatic hydrocarbons such as remethylhexane and kerosene, aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, alicyclic hydrocarbons such as cyclohexane, and halogenated hydrocarbons such as carbon tetrachloride and trichloroethylene. , alcohols such as ethanol, propatool and butanol, phenols such as phenol, cresol and xylenol, ethers such as diethyl ether and diisopropyl ether, acetone,
Examples include ketones such as methyl ether ketone.

[Manufacture of conductive paint]

In order to obtain the conductive paint of the present invention, the volume ratio (A/B) of graphite (A) and binder component (B) is 90/1.
The ratio is adjusted to 0 to 30/70, preferably 85/15 to 40/60. In the case of oil-soluble paints, organic solvents (
C”) is 10-95% of the total volume and (30-90%
This can be obtained by placing a footstool to occupy the area. When A/B is within the above range, the conductivity of the coating material will be well balanced, the mechanical properties of the coating film, and the adhesion to the substrate will be good.

Furthermore, when the solvent (C) is within the above range, it becomes easy to apply as a paint and has excellent workability.

Furthermore, in producing the conductive paint of the present invention, various compounds that can be added to paints or resins may be used. That is, pigments, dyes, preservatives, thixotropic agents, heat stabilizers, weather stabilizers, etc. may be used.

〔Effect of the invention〕

Compared to conventionally used paints for the same purpose, the conductive paint of the present invention is: ■ There is no risk of metal damage even if an olefin resin is selected as a binder component; It is equally safe to use.

■ In the case of nickel powder, the electrical conductivity decreases rapidly when heated above about 60°C, and the electrical conductivity does not recover even after cooling, but in the case of nickel-coated graphite, it surprisingly The conductivity does not decrease even when heated above .degree. C., and therefore the electromagnetic wave shielding effect does not decrease even when applied to a high-temperature substrate or when a substrate coated with the coating of the present invention is used in a high-temperature atmosphere.

■ Nickel-coated graphite is chemically stable and does not deteriorate in performance when oxidized by air.
Maintains its initial performance as a conductive paint for a long time.

■It is economically superior and suitable as a general-purpose conductive paint.

It shows excellent effects such as:

[Embodiment]

As a preferred embodiment of the present invention, the binder component (B
), there are oil-soluble paints that use resins at least partially modified with unsaturated carboxylic acids.

In other words, by using a resin in which unsaturated carboxylic acid or its derivative is graft copolymerized as part of the resin used, the dispersibility of nickel-coated graphite in the resin is improved as described above, and the adhesion to the metal substrate is improved. be able to. Such unsaturated carboxylic acids or derivatives thereof include acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, nadic acid (endocys-
unsaturated carboxylic acids such as bicyclo(2,2,1)hept-5-ene-2,3-dicarboxylic acid) or derivatives thereof, such as acid halides, amides, imides, anhydrides, esters, etc. Examples include maleyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, and glycidyl maleate. Among these, unsaturated dicarboxylic acids or their acid anhydrides are preferred, and maleic acid, nadic acid, or their acid anhydrides are particularly preferred.

The grafting ratio of the unsaturated carboxylic acid or its derivative to the resin is 0.0 l-IQffi amount %, preferably 0.
．． The amount of the modified resin is 1 to 5% by weight, and at least the above-mentioned modified resin is present in the binder component (B) constituting the coating material of the present invention in an amount of 5% by weight or more, preferably 10% by weight or more.

[Usage form]

The conductive paint of the present invention is widely used in computer-related equipment, communication equipment such as radios and televisions, video tape recorders, medical equipment, and aircraft fields, such as conductive coating for cockpit canopies, conductive coating for preventing electric shock on helicopter rotor blades, etc. can be used.

〔Example〕

The content of the present invention will be explained below using preferred examples, but the present invention is not limited to these examples, and it goes without saying that the present invention can take any form as long as its purpose is not impaired.

Example 1 Nickel coated graphite contains nickel! 50% by weight,
(average diameter 100μ, average thickness 15μ): 35% by weight, consisting of a modified ethylene-propylene random copolymer grafted with 0.5% maleic anhydride and chlorinated polypropylene with a chlorination rate of 30% by weight. 1
A conductive paint was prepared by mixing 60 parts by weight of thinner with 100 parts by weight of a paint consisting of 00/60 mixed resin component: 27% by weight and an organic solvent mainly composed of toluene: 38% by weight.

A square plate having a thickness of 2 irises was formed by injection molding polypropylene (Mitsui Petrochemical Polypropylene 0J740), and a conductive paint was applied onto the square plate using a spray gun. then 85
The baking process was performed in an air oven at ℃ for 20 minutes. The coating thickness at this time was 100μ.

The electromagnetic wave shielding effect was tested using a device that combines a spectrum analyzer and a tracking generator with a shield box equipped with a transmitting antenna and a receiving antenna.
At megahertz, the received electric field strength L' with and without a test piece between both antennas is expressed in dB. The detailed contents of the measuring device are described in the following literature.

W, D, Na5on, Plastic Engine
ering, (1980, 4) P42-45 The heat aging test was conducted after leaving the sample in an air oven at 100°C for 30 days.

The adhesion of the coating film was evaluated by a substrate test based on UL-746C, and the tensile strength was determined based on ASTM D638. In the heat aging test for tensile strength, the tensile strength was determined to be 4 (4) after being left in an air oven at 150°C for 1000 hours.

The results are shown in Table 1.

Example 2 In the process of applying conductive paint on the polypropylene square plate of Example 1, the paint was applied with a spray gun onto the square plate previously heated to 80°C, and then heated in an air oven at 50°C for 20 minutes.
The minute baking was carried out in the same manner as in Example 1.

The coating thickness was 100μ.

The results are shown in Table 1.

Example 3 Nickel content 55% by weight, average diameter 50μ, average thickness 10μ
The same procedure as in Example 1 was conducted using nickel-coated graphite. The coating thickness was 100μ.

The results are shown in Table 1.

Example 4 The same conductive paint as in Example 1 except that polymethyl methacrylate was used as the resin component was used with ABS resin (JSR-
It was applied onto an injection molded square plate of ABS-10) using a spray gun, and baked in an air oven at 85° C. for 20 minutes. The coating thickness was lOOμ.

The results are shown in Table 1.

Example 5 A of Example 4 was used instead of the polypropylene square plate of Example 2.
A BS square plate was used, and the conductive paint of Example 4 was also used. The coating thickness was 100μ.

The results are shown in Table 1.

Comparative Examples 1 and 2 Comparative Examples 1 and 2 were carried out in the same manner as in Example 1 or 2 except that nickel powder (average diameter of about 40 μm) was used instead of nickel-coated graphite. The coating film thickness was 100μ in all cases. Table 1 shows the results.
Shown below.

Comparative Example 3 Comparative Example 1 was carried out in the same manner as in Comparative Example 1 except that the paint was baked in an air oven at 50° C. for 20 minutes. The coating thickness is 100
It was μ. The results are shown in Table 1.

Comparative Example 4 Copper powder (average diameter 4
The procedure was the same as in Example 1 except that 0μ) was used. The coating thickness was 100μ. The results are shown in Table 1.

Bisame Example 5 The same procedure as Example 5 was carried out except that nickel powder (average diameter 30 μm) was used instead of nickel coated graphite. The coating thickness was 100μ. The results are shown in Table 1.

As can be seen from this example, the electromagnetic shielding material of the present invention maintains its initial electromagnetic shielding effect even when left in a high-temperature atmosphere for a long period of time, and does not cause metal damage to olefin resins. Since there is no oxidation, the polypropylene used as the base material will not deteriorate.

Claims (6)

[Claims] (1) A conductive paint with excellent heat resistance, characterized by comprising graphite (A) whose surface is coated with nickel and a binder component (B). (2) The conductive paint according to claim 1, wherein the A/B volume ratio is from 90/10 to 30/70. (3) Claim 1 or 2 which is a water-soluble paint
Conductive paint as described in Section. (4) Claim 1 or 2 which is an oil-soluble paint
Conductive paints as described in Section. (5) The conductive paint according to claim 4, to which an organic solvent (C) is added. (6) The conductive paint according to claim 5, in which the organic solvent (C) accounts for 10 to 95% by volume of the entire paint component.