JP2012149161A - Electroconductive resin composition, and conductive coating and conductive adhesive using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive resin composition that is excellent in conductivity, heat resistance, water resistance, adhesion with a substrate, and thermal conductivity.SOLUTION: The electroconductive resin composition includes: a resin component consisting of a resol type phenol resin (A) and a polyvinyl acetal resin (B); and carbon component consisting of a carbon nanotube (C) having 10-15,000 of an aspect ratio and a carbon black (D), wherein the content of the polyvinyl acetal resin (B) in the resin component is 5-30 mass%. The electroconductive resin composition is characterized by blending each of 20-70 parts by mass of the carbon nanotube (C) and 1-15 parts by mass of the carbon black (D) based on 100 parts by mass of the resin component.

Description

  The present invention relates to a conductive resin composition, a conductive paint containing the conductive resin composition, and a conductive adhesive.

  In recent years, conductive paints using a conductive resin composition, conductive adhesives, and the like are increasing from the viewpoints of weight reduction of products, environmental considerations, and manufacturing cost reduction. The conductive paint is, for example, screen-printed on a base film and widely used as a membrane circuit constituting a keyboard, a switch, and the like. The conductive adhesive is used as a substitute for solder. The conductive resin composition used for such applications is produced by, for example, dissolving a resin as a binder or matrix material in a solvent to form a varnish, and dispersing the conductive material in the varnish. The

  In the conductive resin composition, metals such as gold, silver, platinum, and palladium are used as fillers (conductive materials) for imparting conductivity, but when metals are used as the conductive materials. However, there are problems such as a decrease in reliability due to generation of dendrites under high humidity conditions, a decrease in conductivity due to oxidation of the metal surface, and an increase in manufacturing cost.

In order to solve such problems, research on conductive resin compositions using carbon-based conductive materials has been conducted.
For example, Patent Document 1 describes a conductive composition containing vapor grown carbon fiber, carbon black, a thermoplastic resin and / or a thermosetting resin.
Patent Document 2 discloses a conductive material in which a carbonaceous material for a conductive composition containing a vapor grown carbon fiber having a specific structure and graphite particles and / or amorphous carbon particles is blended in a resin component. Sex compositions are described.

JP-A-6-122785 JP 2004-221071 A

The conductive resin compositions described in Patent Documents 1 and 2 are stable against oxidation and corrosion, and can be reduced in cost compared to the case of using a metal-based conductive material. However, since the carbon-based conductive material has low dispersibility in the thermosetting resin and low stability after dispersion, the conductive resin composition using the carbon-based conductive material has conductivity, heat resistance, water resistance, There is a tendency for the adhesion and thermal conductivity of the resin to decrease, and improvements are desired.
An object of this invention is to provide the conductive resin composition which is excellent in electroconductivity, heat resistance, water resistance, adhesiveness with a base material, and heat conductivity in view of the said problem.
Another object of the present invention is to provide a conductive paint and a conductive adhesive containing the conductive resin composition.

The inventors of the present invention have made extensive studies to solve the above-mentioned problems. As a result, carbon that is a fibrous carbon having a specific aspect ratio with respect to a resin component composed of a resol-type phenol resin and a polyvinyl acetal resin. By blending a carbon component consisting of nanotubes and carbon black, which is powdered carbon, in a specific ratio, all of conductivity, heat resistance, water resistance, adhesion to the substrate, and thermal conductivity are excellent. The present inventors have found that a resin can be obtained and completed the present invention.
That is, the present invention is as follows.

[1] Carbon composed of a resin component composed of a resol type phenolic resin (A) and a polyvinyl acetal resin (B), carbon nanotube (C) having an aspect ratio of 10 to 15,000, and carbon black (D) The content of the polyvinyl acetal resin (B) in the resin component is 5 to 30% by mass, and the carbon nanotube (C) with respect to 100 parts by mass of the resin component 20 to 70 parts by mass and 1 to 15 parts by mass of carbon black (D) are blended.
[2] The resol type phenol resin (A) has a weight average molecular weight of 1,000 to 15,000, a methylol group equivalent of 148 to 344 g / eq, and the polyvinyl acetal resin (B) has a weight average molecular weight. The conductive resin composition according to [1], which is 30,000 to 500,000 and has a hydroxyl group equivalent of 90 to 120 g / eq.
[3] The molar ratio of the methylol group (methylol group / hydroxyl group) of the resol type phenol resin (A) to the hydroxyl group of the polyvinyl acetal resin (B) is 0.75 / 1 to 15/1, [1] or [2 ] The conductive resin composition of description.
[4] The conductive resin composition according to any one of [1] to [3], wherein the carbon fiber (C) has an average fiber diameter of 0.5 to 500 nm.
[5] The conductive resin composition according to any one of [1] to [4], wherein 25 to 70 parts by mass of a carbon component is blended with 100 parts by mass of the resin component.
[6] The conductive resin composition according to any one of [1] to [5], wherein the carbon nanotube (C) is heat-treated with a graphitization catalyst.
[7] A conductive paint comprising the conductive resin composition according to any one of [1] to [6].
[8] A conductive adhesive comprising the conductive resin composition according to any one of [1] to [6].

ADVANTAGE OF THE INVENTION According to this invention, the electroconductive resin composition which is excellent in electroconductivity, heat resistance, water resistance, adhesiveness with a base material, and heat conductivity can be provided.
Moreover, according to this invention, the conductive paint and conductive adhesive provided with the said characteristic can be provided.

[Conductive resin composition]
The conductive resin composition of the present invention comprises a resin component comprising a resol type phenol resin (A) and a polyvinyl acetal resin (B), a carbon nanotube (C) having an aspect ratio of 10 to 15,000, and carbon black. A conductive resin composition comprising a carbon component comprising (D), wherein the content of the polyvinyl acetal resin (B) in the resin component is 5 to 30% by mass, and 100 parts by mass of the resin component On the other hand, it is a conductive resin composition characterized by blending 20 to 70 parts by mass of carbon nanotubes (C) and 1 to 15 parts by mass of carbon black (D).

<Resin component>
The resin component in this invention consists of a resol type phenol resin (A) which is a thermosetting resin, and a polyvinyl acetal resin (B) which is a thermoplastic resin.

(Resol type phenol resin (A))
The resol type phenolic resin (A) has a weight average molecular weight of 1,000 to 1,000 from the viewpoint of dispersion stability of the carbon component as a filler, applicability when used as a paint or an adhesive, reactivity, and cure shrinkage. What is 15,000 is preferable, what is 3,000 to 10,000 is more preferable, and what is 5,000 to 8,000 is still more preferable. From the same viewpoint, those having a methylol group equivalent of 148 to 344 g / eq are preferred, those having 170 to 310 g / eq are more preferred, and those having 194 to 270 g / eq are even more preferred.

  Such a resol-type phenol resin (A) is obtained by heating and reacting phenols and aldehydes at a predetermined temperature in the presence of a basic catalyst, and then performing normal pressure concentration or vacuum concentration and taking out. be able to. In addition, since the resol type phenol resin (A) used in this invention has a methylol group, it can be bridge | crosslinked and hardened by heating this resin.

  Examples of phenols used in the synthesis of the resol type phenol resin (A) include phenol, various alkylphenols (for example, various butylphenols, various cresols, various xylenols), various phenylphenols, various methoxyphenols, 1,3-dihydroxybenzene, Bisphenol A, bisphenol F, etc. can be mentioned, and among these, phenol is preferred. Here, “various” means various structural isomers.

Examples of aldehydes include formaldehyde, paraformaldehyde, furfural, acetaldehyde, and benzaldehyde. Among these, formaldehyde and paraformaldehyde are preferable.
The said phenols and aldehydes may be used individually by 1 type, and 2 or more types may be mixed and used for them.
The molar ratio (aldehyde / phenol) of aldehydes to phenols when reacting aldehydes with phenols is preferably 0.6 / 1 to 3.0 / 1, preferably 1.1 / 1 to 2.5. / 1 is more preferable.

As the basic catalyst used for the synthesis of the resol type phenol resin (A), metal hydroxides, metal oxides, metal salts, amine compounds, and the like can be used.
As the metal hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide and the like can be used.
Examples of the metal oxide include magnesium oxide, calcium oxide, sodium oxide, and potassium oxide.
Examples of the metal salt include zinc acetate and lead acetate.
Examples of amine compounds include triethylamine, hexamethylenetetramine, dimethylethanolamine, and ammonia.
In the present invention, it is preferable to use a resol type phenol resin synthesized using an amine compound as a basic catalyst.

In the present invention, a modified resol type phenol resin having a carboxyl group and / or a glycidyl group in the molecule may be used as the resol type phenol resin (A). There is no restriction | limiting in particular as a modification | denaturation method, A well-known method is employable. For example, a method in which a carboxyl group-containing compound and / or a glycidyl group-containing compound is allowed to react with a part of the phenolic hydroxyl group or methylol group in the resol type phenol resin can be exemplified.
As a commercial item of a resole type phenol resin (A), Showa Denko Co., Ltd. "Shonol BKS-3823A", Sumitomo Bakelite Co., Ltd. "Sumilite resin PR" etc. can be mentioned, for example.

(Polyvinyl acetal resin (B))
As the polyvinyl acetal resin (B), those having a weight average molecular weight of 30,000 to 500,000 are preferable from the viewpoint of dispersion stability of the carbon component as a filler and applicability when used as a paint or an adhesive. What is 50,000-300,000 is more preferable, and what is 70,000-200,000 is still more preferable. From the same viewpoint, the hydroxyl equivalent is preferably 90 to 120 g / eq, more preferably 100 to 120 g / eq, and still more preferably 105 to 115 g / eq.

The polyvinyl acetal resin (B) can be obtained by formalizing a polyvinyl alcohol resin with an aldehyde compound. Examples of the aldehyde used in the formalization reaction include formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde. Among these, acetaldehyde and butyraldehyde are preferable. That is, the polyvinyl acetal resin (B) preferable in the present invention is a polyvinyl acetal resin obtained by formalizing a polyvinyl alcohol resin with acetaldehyde, and a polyvinyl butyral resin obtained by formalizing a polyvinyl alcohol resin with butyraldehyde. In addition, in the polyvinyl alcohol resin used as the raw material of the polyvinyl acetal resin (B), an acetyl group may remain in a part thereof, but when the acetyl group remains, the residual ratio of the acetyl group is 5 mol%. The following is preferable.
Examples of the commercially available polyvinyl acetal resin (B) include “Denka Butyral # 3000” manufactured by Denki Kagaku Kogyo Co., Ltd., “S Lec B” manufactured by Sekisui Chemical Co., Ltd., and the like.
The said polyvinyl acetal resin (B) may be used individually by 1 type, and 2 or more types may be mixed and used for it.

(Mixing ratio of resol type phenol resin (A) and polyvinyl acetal resin (B))
The resol type phenol resin (A) and the polyvinyl acetal resin (B) are mixed so that the content ratio of the polyvinyl acetal resin (B) in the resin component is 5 to 30% by mass. When the content ratio of the polyvinyl acetal resin (B) in the resin component is less than 5% by mass, the viscosity of the conductive resin composition is lowered, so that the dispersion stability of the filler is lowered. When the said content rate exceeds 30 mass%, the heat resistance of a conductive resin composition will fall. The content is more preferably 6 to 27% by mass, and still more preferably 7 to 23% by mass.
The molar ratio of the methylol group of the resol type phenol resin (A) to the hydroxyl group of the polyvinyl acetal resin (B) (methylol group / hydroxyl group) is preferably 0.75 / 1 to 15/1, and 1/1 to 10/1 is more preferable, and 1/1 to 6/1 is still more preferable. If the molar ratio of the methylol group to the hydroxyl group is within the above range, the carbon component is easily dispersed with respect to the resin component, and the stability after dispersion is also enhanced.

<Carbon component>
The carbon component in the present invention comprises carbon nanotubes (C) and carbon black (D).

(Carbon nanotube (C))
In the present invention, carbon nanotubes (C) having an aspect ratio (ratio of fiber length to fiber diameter) of 10 to 15,000 are used as carbon nanotubes (C) that are fibrous carbon. When the aspect ratio of the carbon nanotube (C) is less than 10, it is difficult to form a conductive path in the matrix, and it is difficult to improve conductivity. On the other hand, when the aspect ratio exceeds 15,000, the cohesive force between the fibers increases, and the dispersibility with respect to the resin component decreases. The carbon nanotube (C) has an aspect ratio of more preferably 20 to 1,000, still more preferably 30 to 500.
As an average fiber diameter of a carbon nanotube (C), 0.5-500 nm is preferable, 5-300 nm is more preferable, 10-180 nm is still more preferable. If an average fiber diameter is in the said range, a carbon nanotube (C) will become easy to disperse | distribute with respect to a resin component, and the conductive resin composition provided with the outstanding electroconductivity can be obtained.
In addition, there is no restriction | limiting in particular in the method of calculating | requiring an average fiber diameter, For example, 100-1,000 pieces of carbon nanotube samples are selected at random with a scanning electron microscope (SEM), and the fiber diameter of each sample is measured. , By calculating the average. Similarly, the aspect ratio is obtained by calculating from 100 to 1,000 carbon nanotube samples with a scanning electron microscope (SEM) and calculating the average fiber diameter and average fiber length. Can do.

  In this invention, 20-70 mass parts of carbon nanotubes (C) are mix | blended with respect to 100 mass parts of said resin components. When the compounding amount of the carbon nanotube (C) is less than 20 parts by mass, sufficient conductivity cannot be obtained, and when the compounding amount exceeds 70 parts by mass, the viscosity of the conductive resin composition is high. The dispersibility of the filler decreases. The compounding amount of the carbon nanotube (C) is more preferably 20 to 65 parts by mass, and further preferably 25 to 60 parts by mass.

The carbon nanotube (C) used in the present invention is produced by chemical vapor deposition (CVD), arc discharge, or the like, and a graphene sheet in which carbon atoms are regularly arranged in a hexagonal shape is rounded into a cylindrical shape. preferable.
In this specification, a single graphene sheet tube having a diameter of 1 to several nm and a length of about 1 to several μm is referred to as a single-walled carbon nanotube, and the graphene sheet tube is concentric. Those having a diameter of several nanometers to several tens of nanometers are called multi-walled carbon nanotubes. A graphene sheet rounded into a substantially conical shape is referred to as a carbon nanohorn, and includes a single-layer carbon nanohorn and a multi-layer carbon nanohorn. In the present invention, these are collectively referred to as carbon nanotubes.

The carbon nanotube (C) used in the present invention is preferably a vapor-grown carbon fiber produced by a vapor-phase growth method, has a linear fiber shape, and is a rigid fiber having an average value of bending index of 5 to 15 It is more preferable that The bending index indicates the rigidity of the vapor-grown carbon fiber, and the length (Lx) and the diameter (D) of the straight portions of a large number of vapor-grown carbon fibers taken by a microscope or the like are not bent. To Lx / D. Therefore, the vapor-grown carbon fiber having a small bending index indicates that the vapor-grown carbon fiber is bent at a short interval, and the vapor-grown carbon fiber having a large bending index has a long straight portion and is not bent.
Further, among multi-walled carbon nanotubes having a cylindrical shape formed by winding one surface (graphene sheet) of graphite having a carbon hexagonal mesh surface, it is preferable to use a rigid multi-wall vapor-grown carbon fiber having few bent portions. .

The method for producing the carbon nanotube having such properties is not particularly limited, and examples thereof include an arc discharge method, a vapor phase growth method, and a laser ablation method. Among these, the vapor phase growth method is preferable. . The vapor phase growth method is a method in which hydrocarbons such as benzene and toluene are thermally decomposed in the gas phase to synthesize vapor phase growth carbon fiber. More specifically, a fluid catalyst method, a zeolite supported catalyst method, and the like can be exemplified. . Vapor-grown carbon fiber is produced by subjecting an organic compound such as benzene, toluene or natural gas as a raw material to a thermal decomposition reaction at about 800 to 1,300 ° C. with hydrogen gas in the presence of a transition metal catalyst such as ferrocene. Obtainable.
In addition, as a commercial item of the carbon nanotube (C) which can be used for this invention, Showa Denko Co., Ltd. "VGCF", "VGNT" (trademark) etc. can be mentioned, for example.
In the present invention, one type of carbon nanotube may be used alone, or two or more types may be mixed and used.

The carbon nanotube produced by the above method may be dispersed as it is in the resin component without being treated, or may be dispersed in the resin component after being treated. As a treatment method, a method of treating at a low temperature (800 to 1,500 ° C.) under an inert gas atmosphere, or a method of treating at a high temperature (2,000 to 3,000 ° C.) under an inert gas atmosphere. From the viewpoint of improving the conductivity of the conductive resin composition, a method of performing the treatment at a high temperature (2,000 to 3,000 ° C.) is preferable.
The carbon nanotube (C) may be subjected to acid treatment with nitric acid, sulfuric acid, hydrochloric acid, or a mixed acid thereof from the viewpoint of improving the wettability to the resin and the dispersibility in the resin. You may perform the surface oxidation process by the heat processing in presence.

  In the present invention, for the purpose of improving conductivity, heat treatment may be performed in the presence of a graphitization catalyst to improve the crystallinity (graphitization degree) of the carbon nanotube. Examples of the heat treatment method using a graphitization catalyst include a method in which a graphitization catalyst is allowed to act on carbon nanotubes at 2,000 to 3,300 ° C. in an inert gas atmosphere such as argon.

Examples of the graphitization catalyst include boron, boron oxide (for example, B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₃ , B ₄ O _5, etc.), boron oxoacid (for example, orthoboric acid, metaboric acid, tetraborate and the like) and salts thereof, boron carbide (e.g., B ₄ C, B ₆ C, etc.), can be used boron nitride (BN), other boron compounds, in this, B ₄ C, B Boron carbides such as ₆ C and elemental boron are preferred. These graphitization catalysts may be directly added to or mixed with the carbon nanotubes, and the vapor generated by heating the graphitization catalyst is brought into contact with the carbon nanotubes without directly contacting the graphitization catalyst and the carbon nanotubes. May be.
The addition amount of the graphitization catalyst is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass, and still more preferably 1 to 8 parts by mass with respect to 100 parts by mass of the carbon nanotubes.

(Carbon black (D))
In the present invention, carbon black such as oil furnace black, channel black, acetylene black, and ketjen black is used as powdered carbon. Among these, from the viewpoint of conductivity, oil furnace black, acetylene black, and ketjen black are preferred, acetylene black and ketjen black are more preferred, and ketjen black is even more preferred.
Examples of the commercially available oil furnace black include “Dia Black” manufactured by Mitsubishi Chemical Corporation, “Seast” manufactured by Tokai Carbon Co., Ltd., and the like.
Moreover, as a commercial item of acetylene black, the Denka Black by Denki Kagaku Kogyo Co., Ltd. can be mentioned, for example.
Furthermore, as a commercial item of Ketjen Black, for example, “ECP 600JD” manufactured by Lion Corporation can be cited.

  In this invention, 1-15 mass parts of said carbon black (D) is mix | blended with respect to 100 mass parts of resin components. When the blending amount of the carbon black (D) is less than 1 part by mass, a conductive resin composition having sufficient conductivity cannot be obtained, and when the blending amount exceeds 15 parts by mass, the conductive resin Since the viscosity of the composition is increased, it is difficult to uniformly disperse the filler. As for the compounding quantity of carbon black (D) with respect to a resin component, 2-12 mass parts is more preferable.

Carbon black (D) may be dispersed in the resin component as it is without being treated, or may be dispersed in the resin component after being treated. As a treatment method, similarly to the treatment method of the carbon nanotube (C), a treatment method at a low temperature (800 to 1,500 ° C.) under an inert gas atmosphere, or a high temperature (2) under an inert gas atmosphere. , 3,000 to 3,000 ° C), but from the viewpoint of improving the conductivity of the conductive resin composition, the treatment is performed at a high temperature (2,000 to 3,000 ° C). Is preferred.
For the carbon black (D), from the viewpoint of improving wettability to the resin and dispersibility in the resin, acid treatment with nitric acid, sulfuric acid, hydrochloric acid or a mixed acid thereof, or in the presence of air Surface oxidation treatment by heat treatment may be performed.
Moreover, you may heat-process at 2,000-3,000 degreeC in presence of the said graphitization catalyst from a viewpoint of electroconductivity improvement and coating-film strength improvement.

The carbon black may be previously adjusted in particle size by pulverization or the like. For carbon black pulverization, high-speed rotary pulverizer (hammer mill, pin mill, cage mill), various ball mills (rolling mill, vibration mill, planetary mill), stirring mill (bead mill, attritor, distribution pipe mill, annular mill) Etc. can be used. Further, a screen mill, a turbo mill, a super micron mill, and a jet mill of a fine pulverizer can be used by selecting conditions.
The average particle size of carbon black is preferably 5 nm to 100 μm, more preferably 10 nm to 50 μm, and still more preferably 50 nm to 10 μm. When the average particle diameter is within the above range, carbon black (D) is easily dispersed in the resin component, and a conductive resin composition having excellent conductivity can be obtained.
There is no restriction | limiting in particular in the measuring method of an average particle diameter, It can measure by a well-known method. For example, it can be measured by a light scattering method, a laser Doppler method, or the like using a device such as a particle size distribution meter or a particle size measuring device.

(Blend ratio of resin component and carbon component)
25-70 mass parts is preferable, as for the compounding quantity of the said carbon component with respect to 100 mass parts of said resin components, 30-65 mass parts is more preferable, and 35-60 mass parts is still more preferable. If the blending amount of the carbon component relative to the resin component is within the above range, the conductivity of the conductive resin composition can be further improved, and the viscosity of the conductive paint and the like does not become too high. The filler can be sufficiently dispersed.

<Other ingredients>
In addition to the resin component and the carbon component, the conductive resin composition of the present invention includes a coupling agent, a leveling agent, a dispersant, a rheology control agent, an antifoaming agent, an antioxidant, and a plasticizer as necessary. Various additives such as these may be contained.
Moreover, you may contain the solvent used for manufacture of the below-mentioned conductive paint and conductive adhesive. Furthermore, a resin different from the resol type phenol resin (A) and the polyvinyl acetal resin (B) contained in the resin component may be used as the other resin as long as the object of the present invention is not impaired. When mix | blending other resin, 15 mass parts or less are preferable with respect to 100 mass parts of said resin components. Moreover, you may use the carbon compound different from the carbon nanotube (C) and carbon black (D) contained in the said carbon component as another carbon component. When mix | blending another carbon component, 10 mass parts or less are preferable with respect to 100 mass parts of resin components.

<Method for producing conductive resin composition>
The conductive resin composition of the present invention comprises a resin component composed of a resol type phenol resin (A) and a polyvinyl acetal resin (B), and a carbon component composed of carbon nanotubes (C) and carbon black (D). It can be manufactured by mixing at a mixing ratio of, and further adding other components as necessary and mixing them. A known mixing apparatus can be used for mixing. There is no restriction | limiting in the mixing | blending order of each component.

[Conductive paint, conductive adhesive]
The conductive paint and conductive adhesive of the present invention contain the conductive resin composition of the present invention, and are produced, for example, by mixing the conductive resin composition of the present invention, a solvent, and an additive. can do.
As the solvent used for the production of the conductive paint and the conductive adhesive, a general solvent can be used. For example, methyl ethyl ketone, N-methylpyrrolidone, glycol ether, glycol ester, terpene compound, and the like can be used. .
These solvents may be used alone or in a combination of two or more.
The conductive paint and conductive adhesive of the present invention may contain additives as necessary. Examples of the additive include a plasticizer, a drying regulator, and a surfactant.

  The conductive paint and the conductive adhesive can be produced by the same method as for ordinary paints and adhesives. For example, a resin component is dissolved in a solvent using a high-speed stirrer to produce a varnish. In the case of a large lot, the varnish and a carbon component are blended and premixed with a tank mixer, and this is mixed with a sand mill. And can be produced by continuously kneading and adjusting the viscosity. In the case of a small lot, for example, the carbon component and the varnish can be directly charged into an attritor and kneaded to adjust the viscosity. In addition, a ball mill or a three roll can be used instead of the sand mill or the attritor.

  Examples of methods for applying the conductive paint and the conductive adhesive to the substrate include a screen printing method, a dispenser method, a dipping method, a transfer method, an applicator method, a brush coating method, and a spray method. In addition, as a method of applying to a substrate or an electronic element, there are a screen printing method, a dipping method, and a transfer method. It is preferable to change the ratio of the conductive resin composition and the solvent in accordance with each coating method, and adjust the viscosity of the conductive paint and conductive adhesive.

  The conductive paint and conductive adhesive of the present invention are printed wiring electrical circuits for home appliances, industrial use, vehicles, communication information, air vessels, space / weapons, watches / photos, toys, etc. Can be suitably used.

  Examples The present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

The materials used in the examples and comparative examples are as follows. In addition, the physical property of each material was measured with the following method.
(Weight average molecular weight)
Measurement was performed by gel permeation chromatography. As a measuring apparatus, “Shodex GPC System-21 (columns: KF-802, KF-803, KF-805)” manufactured by Showa Denko KK was used. The measurement conditions were a column temperature of 40 ° C., an eluent of tetrahydrofuran, and an elution rate of 1 ml / min. The weight average molecular weight was expressed in terms of standard polystyrene equivalent molecular weight (Mw).

(Methylol group equivalent)
500 g of phenol, 250 ml of benzene, and 15 g of p-toluenesulfonic acid were placed in a flask in which a fractionating tube was set, respectively, and heated until boiling to remove water in the flask, and then cooled. Into this flask, 20 g of a measurement sample from which the solvent contained was removed by drying at a low temperature was added, the flask was heated to boil the contents, the amount of water produced thereby was measured, and the amount of water was expressed by the following formula: The methylol group equivalent was calculated by substitution. The “water content (% by weight) in the measurement sample” in the formula can be measured by the Karl Fischer titration method.
Methylol group equivalent (g / eq) = 18 × 100 / [amount of water produced (ml) × 100 / 20−moisture (% by weight) in measurement sample]

(Hydroxyl equivalent)
The measurement was performed according to JIS K 0070.
(Epoxy equivalent)
It measured based on JISK7236.

<Thermosetting resin>
(A-1) Resol type phenol resin
"Showonol BKS-3823A" manufactured by Showa Denko KK
Weight average molecular weight: 6,500
Methylol group equivalent: 258 g / eq
(A-2) 4,4′-methylenebis [N, N-bis (oxiranylmethyl) aniline]
“DTP-777” manufactured by Dalian Chemical Industry Co., Ltd.
Molecular weight: 370
Epoxy equivalent: 110 g / eq
(A-3) Bisphenol type epoxy resin
“JER 1004” manufactured by Mitsubishi Chemical Corporation
Weight average molecular weight: 5,200
Epoxy equivalent: 920 g / eq
(A-4) Novolac type phenolic resin
"Showon BRG-556" manufactured by Showa Denko KK
Weight average molecular weight: 1,200
Hydroxyl equivalent: 108 g / eq

<Thermoplastic resin>
(B-1) Polyvinyl acetal resin
Polyvinyl butyral manufactured by Denki Kagaku Kogyo Co., Ltd.
“Denkabuchiral # 3000”
Weight average molecular weight: 130,000
Hydroxyl equivalent: 109 g / eq
(B-2) Phenoxy resin
“YP-50S” manufactured by Nippon Steel Chemical Co., Ltd.
Weight average molecular weight: 55,000
Hydroxyl equivalent: 300 g / eq

<Fibrous carbon>
(C-1) Vapor growth carbon fiber (multi-walled carbon nanotube)
“VGCF” manufactured by Showa Denko KK
Average fiber diameter: 150 nm
Average fiber length: 8 μm
Aspect ratio: 53
(C-2) Graphitized vapor-grown carbon fiber produced by the following procedure Raw material obtained by heat-treating untreated vapor-grown carbon fiber (c-1) at 1,300 ° C. ₄ C) was added to 4 parts by mass of 100 parts by mass of vapor-grown carbon fiber, and mixed for 1 minute (rotation speed 15,000 r / min) with an absolute mill (manufactured by Osaka Chemical Co., Ltd.). The mixture was placed in a graphite crucible and subjected to graphitization for 30 minutes using a resistance heating type catalyst-added graphitization furnace (manufactured by Kurata Giken Co., Ltd.).
(C-3) Milled carbon fiber
“MLD-30” manufactured by Toray Industries, Inc.
Average fiber diameter: 7 μm
Average fiber length: 30 μm
Aspect ratio: 4.3

<Powdered carbon>
(D-1) Ketjen Black
“ECP 600JD” manufactured by Lion Corporation
Particle size: Aperture 75 μm pass 100%
: Aperture 44 μm pass 99.8%
Primary particle size: 34.0 nm
(D-2) Artificial graphite fine powder
“UF-G10” manufactured by Showa Denko KK
Particle size: 5μm

<Silver powder>
(E-1) Silver powder
“Agc-A” manufactured by Fukuda Metal Foil Industry Co., Ltd.

<Solvent>
(F-1) Butyl cell solve
“Butyl glycol” manufactured by Nippon Emulsifier Co., Ltd.
(F-2) Methanol:
"Methanol" manufactured by Wako Pure Chemical Industries, Ltd.

<Curing catalyst>
(G-1) 2-ethyl-4-methylimidazole
"2E4MZ" manufactured by Shikoku Chemicals Co., Ltd.

[Examples 1-8, Comparative Examples 1-15]
Samples used in each example and comparative example were prepared by the following method.
That is, according to the composition described in Tables 1 to 3, the raw materials were mixed so that the total weight of the mixture was 30 g, and the mixture was rotated and revolving mixer “Awatori Nerita ARE-310” (Sinky Co., Ltd.). After stirring for 30 seconds at 2,000 r / min (rotation / revolution), the mixture was stirred for 30 seconds at 2,200 r / min (revolution). This stirring operation was carried out four times, and the obtained conductive resin composition was applied on a glass plate so that the film thickness was 100 μm, and after heat-drying treatment at 80 ° C. for 30 minutes, 180 ° C. For 30 minutes to obtain a cured coating film. The physical property of the obtained cured coating film was measured by the following method.
In addition, the composition in Tables 1-3 is shown by "mass part", and the content rate of (b) component is shown by "mass%". The ratio of methylol group / hydroxyl group is indicated by "molar ratio".

(Conductivity test)
Measurement was performed by a four-end needle method using “Loresta-EP” (MCP-T360: manufactured by Dia Instruments Co., Ltd.) and an ASP probe. In this test, a case where the specific resistance value is 10.0 × 10 ⁻² Ω · cm or less is regarded as acceptable.
(Adhesion test)
On the surface of the cured coating film, 100 slits were cut in a grid pattern to provide 100 1 mm ² cut areas. After applying the cellophane tape on the 100 cut areas, the cellophane tape was peeled off, and the number of cut areas that did not adhere to the cellophane tape and did not peel off from the substrate was measured. In addition, in this test, the case where the number of the cut | interruption area | regions which did not peel from a base material is 95 or more is set as a pass.

(Adhesion test)
Two copper / copper (C100P) base materials each having a width of 14 mm, a length of 28 mm and a thickness of 9 mm were prepared, and the adhesive surfaces were each subjected to # 240 polishing treatment (finished by polishing to P240 according to JIS R6010). The two substrates, the film thickness, each coated with a conductive resin composition to be 100 [mu] m, dried 80 ° C. 60 min, bonded to overlap the coating surface of the two substrates, 2 kg / cm ² Adhesion was carried out at 180 ° C. for 30 minutes under the load of. The compression shear strength of the two bonded copper substrates was measured by COVER PRESS MODEL-C. In this test, the case where the compressive shear strength is 25 MPa or more is regarded as acceptable.
(Thermal conductivity test)
The conductive resin composition is coated on a tetrafluoroethylene sheet so as to have a thickness of 200 μm, dried by heating at 80 ° C. for 60 minutes to remove the solvent, and then peeled off from the tetrafluoroethylene sheet. A dried resin composition was obtained. Furthermore, this dried product was put into a 10 mm × 200 mm × 2 mm flat plate mold and cured by heating and pressing at 180 ° C. for 30 minutes to produce a molded plate having a thickness of 2 mm. The molded plate was subjected to measurement of thermal conductivity using a hot disk method thermophysical property measuring apparatus “TPS-2500s” manufactured by Kyoto Electronics Industry Co., Ltd. In this test, a case where the thermal conductivity is 8.0 W / k · m or more is regarded as acceptable.

(Heat resistance test)
In an atmosphere of 200 ° C., the compression shear strength was measured by the same method as in the above-mentioned adhesion test, and a pass (P) having a strength of 5 MPa or more was judged as pass (P), and a non-pass (F) was designated. .
(Water resistance test)
A conductive resin composition was applied on a glass plate so as to have a film thickness of 100 μm, heat-dried at 80 ° C. for 30 minutes, and further heated at 180 ° C. for 30 minutes to obtain a cured coating film. . This cured coating film is immersed in distilled water at 100 ° C. for 96 hours, and it is confirmed that there is no discoloration, deformation (bulging, peeling, etc.) and elution, and there is no discoloration, deformation (blowing, peeling, etc.) Was determined to be acceptable (P), and the others were unacceptable (F).

(Coating appearance test)
The appearance of the cured coating film was visually observed. Those in which no cracks, swells, blisters, peeling, etc. occurred were determined to be acceptable (P), and those that were not so were defined as unacceptable (F).
(Comprehensive evaluation)
In the conductivity test, adhesion test, adhesion test, thermal conductivity test, heat resistance test, water resistance test, and coating film appearance test, all satisfying the acceptance criteria (P), and other ( Evaluated as F).
Each measurement result is shown in Tables 1-3.

<Discussion>
The conductive resin compositions of Examples 1 to 8 have a specific resistance value of 10 × 10 ⁻² Ω · cm or less and a compressive shear strength of 30 MPa or more. It turns out that it has adhesiveness. In addition, the conductive resin compositions in Examples 1 to 8 showed no defects in the heat resistance test, the water resistance test, and the coating film appearance test as reliability tests.

In Comparative Example 1, the amount of the thermoplastic resin in the resin component is as small as 4.5% by mass, and the carbon component was insufficiently dispersed. Is considered to have occurred.
In Comparative Example 2, since the phenoxy resin was used as the thermoplastic resin, the resistance value was increased, and it was considered that the coating film after curing had cracks and cracks.
In Comparative Example 3, it is considered that the heat resistance was lowered because of the large amount of polyvinyl acetal resin.

In Comparative Example 4, since the tetrafunctional epoxy resin (a-2) and the novolac type phenol resin (a-4) were used as the thermosetting resin, the dispersion of the carbon component became insufficient and the resistance value increased. At the same time, it is considered that scratches and cracks occurred in the cured coating film.
In Comparative Example 5, since the high molecular weight bisphenol type epoxy resin (a-3) and the novolac type phenol resin (a-4) were used as the thermosetting resin, the dispersion of the carbon component became insufficient and the resistance value was high. At the same time, it is considered that the heat resistance has decreased.
In Comparative Example 6, since the resol type phenol resin was not used and only the polyvinyl acetal resin was used, it is considered that the heat resistance and water resistance were lowered.
Moreover, in Comparative Example 7, it was considered that the heat resistance and water resistance were low because a phenoxy resin was used without using a resol type phenol resin and a polyvinyl acetal resin.

In Comparative Example 8, since powdered carbon is not used, the resistance value is as high as 2.1 × 10 ⁻¹ Ω · cm. Further, in Comparative Example 9, since no fibrous carbon is used, the resistance value is as high as 1.4 × 10 ⁻⁰ Ω · cm.
In Comparative Example 10, since the amount of fibrous carbon was small, the resistance value was as high as 4.4 × 10 ⁻¹ Ω · cm.
In Comparative Examples 11 and 12, since the blending amount of powdered carbon was large, the viscosity of the conductive resin composition was high, and it was difficult to form a coating film by coating.

In Comparative Example 13, since a milled fiber having an aspect ratio of 4.3 was used as the fibrous carbon, the resistance value was as high as 1.0 × 10 ⁻⁰ Ω · cm.
In Comparative Example 14, since the artificial graphite powder was used as the powdery carbon, the resistance value was as high as 1.8 × 10 ⁻¹ Ω · cm.
In Comparative Example 15, since the metal conductive material (silver powder) was used as the conductive material instead of the carbon conductive material, discoloration, swelling and elution were observed after the water resistance test.

  Since the conductive resin composition of the present invention is excellent in conductivity, heat resistance, water resistance, adhesion to a substrate and thermal conductivity, it can be suitably used as a conductive paint and a conductive adhesive. In addition, the conductive paint and conductive adhesive of the present invention are used for industrial products such as integrated circuits, electronic components, optical components and various control components, wiring materials and connection materials with various devices, antistatic materials for various devices, electromagnetic waves, etc. It can be suitably used for shielding, electrostatic coating and the like.

Claims (8)

A resin component composed of a resol type phenol resin (A) and a polyvinyl acetal resin (B), and a carbon component composed of carbon nanotubes (C) and carbon black (D) having an aspect ratio of 10 to 15,000. A conductive resin composition comprising:
The content of the polyvinyl acetal resin (B) in the resin component is 5 to 30% by mass, the carbon nanotube (C) is 20 to 70 parts by mass, and the carbon black (D) is 100 parts by mass of the resin component. 1-15 mass parts of each is mix | blended, The conductive resin composition characterized by the above-mentioned.   The resol type phenol resin (A) has a weight average molecular weight of 1,000 to 15,000, a methylol group equivalent of 148 to 344 g / eq, and the polyvinyl acetal resin (B) has a weight average molecular weight of 30,000. The conductive resin composition according to claim 1, which is ˜500,000 and has a hydroxyl group equivalent of 90 to 120 g / eq.   The electroconductivity of Claim 1 or 2 whose molar ratio (methylol group / hydroxyl group) of the methylol group of the resol type phenol resin (A) to the hydroxyl group of the polyvinyl acetal resin (B) is 0.75 / 1 to 15/1. Resin composition.   The conductive resin composition in any one of Claims 1-3 whose average fiber diameter of a carbon nanotube (C) is 0.5-500 nm.   The conductive resin composition in any one of Claims 1-4 which mix | blends 25-70 mass parts of carbon components with respect to 100 mass parts of resin components.   The conductive resin composition according to any one of claims 1 to 5, wherein the carbon nanotube (C) is heat-treated with a graphitization catalyst.   A conductive paint comprising the conductive resin composition according to claim 1.   A conductive adhesive comprising the conductive resin composition according to claim 1.