JPS61183369A - Production of electrically conductive paint composition - Google Patents

Abstract

PURPOSE:To obtain the titled compsn. having low electrical resistance, by adding colloidal graphite powder alone or together with furnace black and/or acetylene black, forming a graft copolymer on the surfaces of the particles and producing a network structure. CONSTITUTION:Colloidal graphite powder alone or a mixture thereof with furnace black having a high structure and/or acetylene black is added to a copolymerization system contg. a reactive group-contg. vinyl monomer or a similar monomer. Polymn is carried out in the presence of a peroxide (e.g. cumene hydroperoxide) as a polymn. initiator to form a graft copolymer having a low degree of polymn. on the surfaces of the particles. An azo compd. (e.g. 2,2'-axobisisobutyronitrile) having a polymn.-initiating ability is added thereto to complete thepolymn. of the remaining monomer. A resin having epoxy groups and a hardener (e.g. polyamine) are added thereto, and the mixture is heat- treated to form a network structure over the whole structures of the graft polymer and a homopolymer formed in the reaction system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a conductive coating composition which has an extremely low electrical resistance value and which, when formed into a coating film, has a uniform resistance value in each part. fine colloidal graphite,
That is, by using graphite powder alone, or by using graphite powder as a component and adding furnace black with a high structure (oil absorption of 1 cc/g or more) or acetylene black, or in the coexistence of these three, the surface of the particles is A graft copolymer with a low degree of polymerization is applied to the coating film, and then a network structure is imparted to the entire graft copolymer and the homopolymer produced in the reaction system using a resin containing an epoxy group to create a conductive circuit in the coating film. The volume resistivity before curing is 106 to 1OrΩ・c.
0.1Ω by adding a mesh to the
- It has the characteristic that it can be set to a value of about cst or lower.

One of the monomer components used for grafting in the present invention is vinyl-based or similar, such as acrylic ester,
It includes methacrylic acid ester, acrylonitrile, vinyl acetate, styrene, etc., and can be used alone or in combination of two or more. On the other hand, the monomers used for copolymerization are those that have reactive groups such as carboxyl groups, amino groups, hydroxyl groups, or acid anhydrides in their structural composition, such as acrylic acid, methacrylic acid, glycidyl methacrylic acid, etc. These include acrylate, β-hydroxyethyl methacrylate, methacrylamide, and even maleic anhydride, but as long as they do not react with each other to form a gel, a combination of one or more of these, such as acrylic acid and methacrylic acid It can also be used in combination. Particularly for the purpose of imparting flexibility to the conductive coating material to be finally used, it is desirable to synthesize a multicomponent copolymerizable graft polymer in the coexistence of several monomers.

In addition to benzene-like rings, quinone groups, phenoxy radicals, hydroxyl groups, etc. are present on the particle surfaces of commercially available furnace blacks and acetylene blacks, and these are known to serve as reaction sites for free radicals and polymer radicals. . Moreover, the number of reaction points is said to be 1020/g or more. In addition, the graphite powder has a large number of reactive points distributed on its fractured surface similar to those of the carbon blank, which trap polymer radicals generated in the reaction system.

In the present invention, peroxides having the property of forming polymers with relatively small molecular weights, such as cumene hydroperoxide and t-butyl hydroperoxide, are used. It also has the characteristics of attacking the molecule, giving it a new unpaired electron, and becoming one of the grafting sites for the copolymer radical generated in the reaction system.

In other words, grafting using peroxide corresponds to the first stage reaction in the present invention, but since this reaction produces a graft copolymer with an extremely low degree of polymerization on the powder surface, the final heat curing is necessary. This has the advantage that processing can proceed efficiently. Following the first stage reaction, 2,2”
- An azo compound capable of initiating polymerization, such as azobisisobutyronitrile or 2,2′-azobis-2,4-dimethylvaleronitrile, is added to complete the polymerization of the remaining monomers, but this is the first step. This corresponds to a two-stage reaction.

The solvents used are tetrahydrofuran, dioxane,
It is desirable to use dimethylformamide, ethylene glycol monoether, etc. alone or in the form of a mixed solvent from among those that can serve as a solvent for the copolymer produced in the reaction system.

Previously, there has been an attempt (Patent No. 552,484) to create a resistor by graft copolymerizing an appropriate polymer onto the particle surface of highly structured furnace black or acetylene black to give it a network structure (Patent No. 552,484), but it has been difficult to increase the resistance value by several degrees. When the resistance was reduced to Ω·cIll, there was also a drawback that flexibility was lost. However, according to the present invention, it is also possible to create a coating film that has the advantage of maintaining flexibility even when a low resistance value is applied.

Next, examples of the present invention will be described.

Example 1 The reaction composition and synthesis conditions of the first stage are as follows.

Graphite (colloidal graphite) 2g carbon black (oil furnace black with oil absorption of 2cc/g) 8g acrylic acid (monomer with a reactive group) 4g butyl acrylate (monomer that can be the main component of the copolymer) 24 g t-butyl hydroperoxide (polymerization initiator) 0.5-1 g Tetrahydrofuran (solvent) 10 g Dioxane (solvent) 10 g First,
The first stage reaction composition is charged into a reaction vessel equipped with a stirring device, a backflow condenser, etc., and the reaction is continued for 1 hour while maintaining the temperature at 60 to 70°C.

Next, in the second stage reaction, 1 g of 2,2''-azobisisobutyronitrile dissolved in a mixture of 5 g of tetrahydrofuran and ethylene glycol monoether, such as 20 g of ethylene glycol monomethyl ether, is added, The remaining monomer is polymerized to nearly 100% in the reaction.The temperature is maintained at 60-80°C and the reaction is continued for 4-8 hours.

The method for producing a low resistance coating film from the above reaction product is as follows.

After cooling the reaction product to room temperature, 1 to 6 g of a resin containing an epoxy group, such as a bisphenol A type epoxy compound, and 0.1 to 0.3 g of an amine such as a polyamine are added to the entire volume, Stir vigorously.

The coating film is formed on the surface of a glass or porcelain plate, or a polyester film, etc., and after preliminary drying by a method such as infrared irradiation, the coating film is heated to 100 to 200°C, preferably 110 to 150°C.
Heat treatment for 3 to 5 hours. Here, a coating film with heat resistance, water resistance, and solvent resistance is obtained.

Note that the coating film obtained here can be given an arbitrary resistance value by adjusting the contents of graphite powder and carbon black therein. Further, it is also possible to adjust the magnitude of this resistance value by changing the amount of epoxy resin used or the temperature and time of the thermosetting treatment.

- For example, in a coating film containing 4 to 8% graphite powder in the total polymeric material and 30 to 35% oil furnace black with an oil absorption of 2 cc/g, when heat-cured at 150°C for 5 hours, the volume Resistance value: 0.1~10Ω・
cm can be obtained.

Example 2 Graphite powder (average particle size 1.56μ) 5g acetylene blank 5g methacrylic acid 3g methyl methacrylate
27g Cumene Hydroperoxide 0
．． 5g~1g Tetrahydrofuran 10
g Dioxane 20g Reaction temperature 60-70℃ Reaction time
The first stage reaction lasted for more than 1 hour, and then ethylene glycol monomethyl ether L containing 1 g of 2.2''-azobis-2,4-dimethylvaleronitrile was added.
After adding 100 ml of water, the polymerization reaction is continued for 5 to 8 hours while maintaining the temperature at 60 to 80°C.

The hardening process, that is, the reaction that creates the network, is carried out II.
Conforms to 1.

Example 3 Graphite powder (average particle size 2.15μ) 5g acetylene black 5g oil furnace black (oil absorption 2.3cc) 5g acrylic acid 2g methacrylic acid 1g butyl acrylate
30g cumene hydroperoxide 0
．． 5g~1g Tetrahydrofuran 10
g Ethylene glycol monomethyl ether 20g or more of the composition was reacted at 60-80°C for 30 minutes, then 2,2''
- Add 20 g of ethylene glycol monomethyl ether containing azobisisobutyronitrile Ig and complete the reaction at 60-80° C. for 5-8 hours.

The heat curing treatment is performed on a porcelain plate at 200° C. for 2 hours by adding 1 to 2 g of ethylene glycol.

Example 4 Graphite powder (average particle size 1.ssμ) 10g methacrylic acid 38 Ethyl methacrylate 30g Butyl acrylate
10g cumene hydroperoxide 0
．． 5g~1g Tetrahydrofuran 20
g Dioxane 10g Reaction temperature 60-80℃ Reaction time
After this reaction for 1 hour, a mixture of 10 g of ethylene glycol monomethyl ether containing 1 g of 2.2°-azobis-2,4-dimethylvaleronitrile and log of tetrahydrofuran was added, and the mixture was heated at 60-85°C for 5-8
Continue polymerization for hours.

Note that the curing treatment is based on Example 1.

Claims (1)

[Claims] Either colloidal graphite powder, furnace black or acetylene black having a high structure is made to coexist with colloidal graphite powder, or furthermore, in the coexistence of these three, a vinyl monomer having a reactive group is produced using peroxide as a polymerization initiator. A copolymer system containing monomers or similar monomers,
A method for producing a conductive coating composition capable of imparting a network structure by grafting onto the surface of the powder, then adding a curing agent and performing heat treatment.