JPH0657824B2 - Conductive adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention particularly relates to a conductive adhesive that does not require a conductive aggregate, and more particularly the present invention relates to a conductive adhesive composed of a novel thermosetting resin. Is.

(Prior Art) Conventionally, as a conductive adhesive having a thermosetting resin as an adhesive, there is no example in which conductivity is exhibited without adding a conductive aggregate.

(Problems to be Solved by the Invention) All of the conventional conductive adhesives have the drawback that conductivity cannot be imparted without the presence of conductive aggregates such as silver, copper, graphite and carbon. .

(Means and Actions for Solving Problems) The present invention provides a conductive adhesive capable of imparting conductivity without the presence of a conductive aggregate such as silver, copper, graphite or carbon. The purpose is.

One of the present inventors at the 51st Annual Meeting of the Chemical Society of Japan held in Kanazawa, Japan on October 4, 1985, was mainly composed of condensed polycyclic aromatic compounds of two or more rings, hydroxymethyl group and halomethyl group. A thermosetting composition comprising an aromatic cross-linking agent having one or two or more aromatic rings having at least one group of two or more groups and an acid catalyst (hereinafter abbreviated as COPNA resin composition) Was announced. (Proceedings of Symposium Lecture Ip
539-542) The present invention is based on CO published by one of the present inventors.
Focusing on the fact that the PNA resin composition exhibits conductivity based on an aromatic conjugated system in the presence of a catalyst for promoting conductivity, and applying this as a conductive adhesive, there is substantially no conductive aggregate. The purpose of the present invention is to provide a conductive adhesive having conductivity, and the above object can be achieved by providing the conductive adhesive according to the claims.

Next, the present invention will be described in detail.

That is, the present invention shows that a cured product of a COPNA resin composition exhibits conductivity based on an aromatic conjugated system in the presence of a catalyst for promoting conductivity, and is excellent in heat resistance, water resistance, dimensional stability, strength, thermal conductivity, etc. It is a conductive adhesive.

Hereinafter, a condensed polycyclic aromatic compound which is a component of the COPNA resin composition constituting the conductive adhesive, an aromatic cross-linking agent,
The acid catalyst and the conductivity promotion catalyst will be described.

The condensed polycyclic aromatic compound of the present invention includes naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, acenaphthene, acenaphthylene, perylene, coronene, and one or more selected from derivatives having these as a main skeleton. Or a mixture of one or more selected from coal-based or petroleum-based heavy oils, tars, pitches, and derivatives thereof.

Next, the aromatic crosslinking agent of the present invention includes a hydroxymethyl group,
Aromatic compounds consisting of one or more aromatic rings having at least one group of at least one of halomethyl groups, such as p-xylylene dichloride, 1,4-benzenedimethanol (p-xylylene glycol), 9,
10-anthracene dimethanol and the like can be used.

Further, the acid catalyst of the present invention is one or two selected from Lewis acids such as aluminum chloride and boron fluoride, or protic acids such as sulfuric acid, phosphoric acid, organic sulfonic acid and carboxylic acid, and derivatives thereof. Mixtures of the above can be used.

Regarding the mixing ratio for using the condensed polycyclic aromatic compound, the aromatic cross-linking agent, and the acid catalyst as the adhesive, the aromatic cross-linking agent /
Condensed polycyclic aromatic compound = 0.5 to 4.0 (molar ratio); the amount of acid catalyst added is 0.5 to 10 wt% with respect to the aromatic crosslinker / condensed polycyclic aromatic compound mixture. Was experimentally confirmed to be a suitable range. Also, COP
The reaction temperature range for obtaining a thermosetting intermediate reaction product (B stage resin) having substantially thermoplasticity obtained by heating and reacting the NA resin composition is preferably in the range of 60 to 300 ° C. Confirmed experimentally.

The electroconductivity-accelerating catalyst of the present invention is selected from air, oxygen, ozone, sulfur, hydrogen peroxide, manganese dioxide, nitrous acid, nitric acid, permanganic acid, chromic acid, chloric acid and hypozinc acid. Oxidizing agent consisting of one kind or a mixture of two or more kinds, or one or two kinds selected from these oxidizing agents and aluminum chloride, boron fluoride, sulfuric acid, phosphoric acid, organic sulfonic acid, carboxylic acid, and derivatives thereof The combination with the above mixture is effective, and when the electroconductivity-accelerating catalyst is a gas at room temperature, it can be used in the presence thereof, and when it is a liquid or a solid, it can be added and used.

The amount of the conductivity-enhancing catalyst added is not particularly limited, but for the gas oxidizing agent, it is effective only by performing the adhering operation in the atmosphere. It is preferable to add about 0.01 to 3%.
When an acid is added, it is preferable to add the surface treatment agent and the additive in excess of the necessary amounts, or separately add about 0.01 to 1%.

In the case of an acid, the stronger the effect, the greater the effect, and the effect is further enhanced by the combined use with an oxidizing agent. It is considered that the mechanism of expressing conductivity in the present invention is as follows.

(A) The methylene directly bonded to the aromatic ring in the cured product of the COPNA resin composition that constitutes the adhesive is oxidized by an oxidizing agent, passes through hydroperoxide, and becomes a carbonyl group by dehydration. This carbonyl group has a conjugation relationship with the aromatic rings on both sides, so that conductivity is exhibited.

This is expressed as follows using pyrene as a model.

(B) Among the methylenes directly bonded to the aromatic ring in the cured product of the COPNA resin composition that constitutes the adhesive, the aromatic ring derived from the aromatic cross-linking agent is a sterically hindered position on the aromatic ring derived from the condensed polycyclic aromatic compound. (Part of A in the formula), the aromatic ring derived from the fused polycyclic aromatic compound undergoes electrophilic substitution with an acid, and as a result, the aromatic ring derived from the aromatic cross-linking agent in the sterically hindered position is electrophilic. Attack, and that part closes. At this time, the oxidant pulls out methylene hydrogen and hydrogen at the ring-closing position in a dehydrated form, whereby aromatization proceeds from a low temperature and conductivity by a conjugated system is developed. In addition, as another mechanism, by extracting one methylene hydrogen, a quinoid structure is formed and a similar conjugated system is established.

This is expressed as follows using pyrene as a model.

Next, post-curing is effective for the conductive adhesive of the present invention. The post-curing temperature is preferably 100 to 400 ° C., and the post-curing time is preferably 10 to 30 hours.
This post-curing promotes the development of the conjugated system and improves the conductivity.

As described above, a conductive adhesive having excellent heat resistance, water resistance, dimensional stability, strength and thermal conductivity can be obtained.

By the way, in the present invention, a conductive adhesive can be obtained without using a conductive aggregate, but carbon, graphite, a carbon precursor as a conductive aggregate in the COPNA resin composition adhesive of the present invention,
By mixing a metal such as silver or copper, greater conductivity can be obtained, and the same effect can be obtained by adding a very small amount of conductive aggregate as compared with the conventional thermosetting resin.

Further, among the COPNA resin composition adhesives of the present invention, those using a coal-based or petroleum-based heavy oil, tar, pitch, etc. as the condensed polycyclic aromatic compound have a remarkably high carbonization yield, Pitch-based COPNA resin composition After carbon, graphite, and carbon precursor are bonded with an adhesive, the adhesive is completely carbonized and graphitized by firing and graphitizing conventional carbon and graphite materials Can be greatly simplified and the cost can be reduced.

Further, a mixture of the COPNA resin composition adhesive of the present invention with a metal such as carbon, graphite, a carbon precursor, silver or copper as a conductive aggregate has excellent heat resistance, peeling strength, not only the adhesive. It can also be used as a conductive paint having heat conductivity and a varnish, and can be used for antistatic purposes, electromagnetic wave shielding, paint for radiator plates, surface heating elements and the like.

(Examples) Next, the present invention will be described in more detail with reference to Examples.

Example 1. A commercially available high-density and high-strength isotropic graphite material (trade name: T-6 manufactured by Ibiden Co., Ltd .: bending strength 1000 kg / cm ² )
Processed into a block of × 20 × 20mm, 400 ℃ in air
After heating for 3 hours with a functional group containing oxygen on the surface, a surface treatment agent consisting of an ethanol solution of p-xylylene glycol: 5 wt% and p-toluenesulfonic acid: 1 wt% is applied to the adhesive surface, This was heat-treated in air at 150 ° C. for 30 minutes and used as an adherend. As the pitch-based COPNA resin composition adhesive, a benzene-soluble component (average molecular weight 340) of petroleum-based pitch having a softening point of 80 ° C. and p-xylylene glycol are mixed at a molar ratio of 1: 2, and 1 wt. % P
-Toluenesulfonic acid was added to the mixture at 120 ° C at 40
B-stage resin reacted for minutes was used. This B-stage resin is melted in air at 130 ° C., applied to the adhesive surface of the adherends, adhered to each other and then fixed with a jig, and then in air 1
It was cured by heat treatment at 80 ° C. for 1 hour. Post-curing was carried out in air at 200 ° C. for 20 hours. For comparison, a commercially available two-component mixed epoxy adhesive (trade name Araldite: manufactured by Ciba Geigy) was used to bond an adherend, which was fixed with a jig and cured in air at 50 ° C. . For both of these, the specific resistance (four-terminal method), the electrical resistance (tester), and the thickness of the adhesive layer of the adhesive portion were measured. The results are shown in Table 1.

When the bending strength of the bonded portion of the bonded structure of Example 1 was measured, the base material ruptured and the bonded surface did not change.

Example 2. Commercially available mild steel and brass were processed into a block of 20 × 20 × 20 mm, and a surface treatment agent consisting of an ethanol solution of p-xylylene glycol: 5 wt% and p-toluenesulfonic acid: 1 wt% was applied to the adhesive surface, and air was applied. Heat treatment was performed at 150 ° C. for 30 minutes, and this was used as the adherend. As the pitch-based COPNA resin composition adhesive, petroleum-based pitch (average molecular weight 300) having a softening point of 49 ° C. and p-xylylene glycol are mixed at a molar ratio of 1: 2, and 1 wt% of p-toluene is mixed therein. A B-stage resin was used in which the mixture containing sulfonic acid was reacted at 120 ° C. for 40 minutes. This B-stage resin is melted in air at 130 ° C. and applied to the adhesive surface of the adherend,
After the adherends were adhered to each other, they were fixed with a jig and heat-treated in air at 180 ° C. for 1 hour to be cured. Post-curing was carried out in air at 200 ° C. for 20 hours. In order to examine the electric resistance of the bonding part of different adherends, a combination of mild steel-brass, mild steel-mild steel and brass-brass was measured with a tester. The results are shown in Table 2.

Example 3. A commercially available silicon carbide sintered body was heat-treated in air at 600 ° C. for 1 hour to introduce a functional group containing oxygen on the surface, and this was used as an adherend. As the COPNA resin composition adhesive, a benzene-soluble component (average molecular weight 360) of coal-based pitch having a softening point of 83 ° C. and p-xylylene dichloride are used in a molar ratio of 1: 2.
A B-stage resin was used which was prepared by mixing at a ratio of 1 wt. A mixture obtained by adding 0.5 wt% of anhydrous aluminum chloride to this B-stage resin as a catalyst for promoting conductivity is melted at 130 ° C. and applied onto a silicon carbide sintered body, and the silicon carbide sintered bodies are fixed with a jig. The adhesive was cured at 150 ° C. Subsequently, post-curing treatment was performed at 200 ° C. for 10 hours. For the purpose of investigating the heat resistance, the bonded structure was heated in nitrogen at a heating rate of 20 ° C./min to measure the weight loss. As a result, no weight loss was observed up to 450 ° C. Further, when a current of 10 A was applied to both ends of this bonded structure using a constant current power source for the purpose of examining conductivity, the voltage was 4 V and no local heat generation was observed.

Example 4. A commercially available graphite material is heat treated in air at 500 ° C. for 30 minutes,
After introducing a functional group containing oxygen to the surface, p-xylylene dichloride: 5 wt%, p-toluenesulfonic acid: 1 wt
% Ethanol solution, followed by heat treatment in air at 150 ° C. for 30 minutes to obtain an adherend. As the COPNA resin composition adhesive, naphthalene and p-xylylene glycol are mixed at a molar ratio of 1: 1.75, and a mixture obtained by adding 1 wt% of p-toluenesulfonic acid thereto at 130 ° C. in air. B reacted for 40 minutes
A stage resin was used. After adding 0.5 wt% of anhydrous aluminum chloride as a catalyst for promoting conductivity and 10 wt% of graphite powder crushed to 350 mesh or less as a conductive aggregate to the B-stage resin, they were melted in air at 140 ° C.
After the melt was cooled to room temperature, it was sandwiched between the adherends as powder and fixed with a jig, and the adhesive surface was tightened and cured by adhesion while heating at 150 ° C. Bonded structure 1 at 250 ℃
It was post-cured for 0 hours. It was measured with a tester to examine the electric resistance of the bonded portion. As a result, the adhesive portion showed an electrical resistance of 0.1Ω at an adhesive thickness of 40 μm.

Example 5. 20 × 2 of commercially available graphite material (pulling strength 250 kg / cm ² )
After processing to 0 × 20 mm and heat treatment in air at 500 ° C. for 30 minutes to introduce a functional group containing oxygen on the surface, p-xylylene glycol: 5 wt%, p-toluenesulfonic acid: 1
After soaking in a surface treatment agent consisting of wt% ethanol solution,
It was heat-treated in air at 150 ° C. for 30 minutes and used as an adherend. The softening point of the COPNA resin composition adhesive is 83
Benzene-soluble matter (average molecular weight 36
0) and p-xylylene glycol were mixed at a molar ratio of 1: 2, and 1 wt% of p-toluenesulfonic acid was added thereto, and the mixture was reacted at 130 ° C. for 40 minutes to use a B-stage resin. A mixture containing 0.5 wt% of anhydrous aluminum chloride as a catalyst for promoting conductivity in this B-stage resin was melted in air at 130 ° C. and applied to the adhesive surface of the adherend. Fixed with a tool and 180 ℃ in air
It was heat-treated for 1 hour and cured. Post-curing in air at 200 ° C
I went there for 20 hours. When the tensile strength was measured for the purpose of examining the adhesive strength, breakage occurred from the portion of the adherend and the adhesive surface did not change.

Example 6. After adding 5 wt% of commercially available silver powder (average particle size: 2 μm) to the COPNA resin composition adhesive in Example 1, adhesion was performed in the same manner as in Example 1. As a result, the electric resistance was 0.08 Ω when the adhesive thickness was 28 μm.

Example 7. The graphite material adhered in Example 5 was fixed to an electric discharge machine EP-60K (manufactured by Mitsubishi Electric Corp.) so that an electric current would flow through the adhesion surface, and a peak current of 20 in kerosene was used with mild steel as a counterpart material.
Electrical discharge machining was performed under the conditions of A and pulse width of 60 μsec. After that, a hole with a bottom of 20 × 20 × 10 mm was drilled in mild steel in 2 hours, but there was no change in the bonded portion.

Example 8. The bonded structure obtained in Example 1 was treated for 300 hours in boiling water, but no change was observed.

(Effects of the Invention) As described above, the conductive adhesive of the present invention is a thermosetting adhesive which is unprecedented and shows conductivity based on an aromatic conjugated system without requiring conductive aggregate. It is a conductive adhesive having excellent heat resistance, thermal conductivity, water resistance, dimensional stability, strength and the like.

This conductive adhesive with excellent heat resistance, thermal conductivity, water resistance, dimensional stability, strength, etc. is a structural material, heat resistant material, heat insulating material, electric / electronic material, sliding member, antistatic,
It can be used for applications such as electromagnetic wave shielding, and is considered to have an effect of greatly contributing to industry.

Claims (2)

[Claims] 1. A thermosetting composition comprising the following fused polycyclic aromatic compound, aromatic cross-linking agent, and acid catalyst reacted with each other, and a conjugated system exhibiting substantially electroconductivity by an electroconductivity-accelerating catalyst. A conductive adhesive characterized by being formed; the condensed polycyclic aromatic compound is naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene,
Acenaphthene, acenaphthylene, perylene, coronene,
And a mixture of one or more selected from the derivatives having these as the main skeletons, or one or two or more selected from the coal-based or petroleum-based heavy oil, tar, pitch and these derivatives A condensed polycyclic aromatic compound selected from a mixture, wherein the aromatic cross-linking agent is p-xylylene dichloride,
An aromatic cross-linking agent selected from 1,4-benzenedimethanol, (p-xylylene glycol), 9,10-anthracene dimethanol, etc., wherein the acid catalyst is aluminum chloride, boron fluoride, sulfuric acid,
Phosphoric acid, organic sulfonic acid, carboxylic acid, and an acid catalyst selected from one or a mixture of two or more selected from these derivatives, wherein the conductivity-enhancing catalyst is air, oxygen, ozone, Oxidizing agent consisting of one or a mixture of two or more selected from sulfur, hydrogen peroxide, manganese dioxide, nitrous acid, nitric acid, permanganic acid, chromic acid, chloric acid, hypochlorous acid, or the above oxidant Aluminum chloride, boron fluoride, sulfuric acid,
It is selected from the group consisting of phosphoric acid, organic sulfonic acid, carboxylic acid, and a mixture of one or more selected from derivatives thereof. 2. The conductive adhesive according to claim 1, wherein the adhesive is a mixture of the condensed polycyclic aromatic compound, the aromatic cross-linking agent and the acid catalyst, or thermosetting thereof. A conductive adhesive characterized in that at least one selected from the intermediate reaction products is thermally cured by a reaction.