JPH0354986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermosetting composition that exhibits excellent heat resistance, adhesiveness and electrical insulation properties when thermoset, and is particularly useful as a varnish.

Conventional technology Conventionally, in the field of electronic components such as printed circuit boards that require heat resistance and high electrical insulation, and in the field of structural materials such as glass or carbon fibers and cloth that require heat resistance and adhesive properties, Epoxy resin-based, phenolic resin-based, and melamine resin-based varnishes are used.

Furthermore, in recent years, varnishes using various polyimide resins are being developed.

Problems to be Solved by the Invention Particularly in the field of electronic components, demands for miniaturization and higher performance have recently increased, and conventional epoxy resin-based, phenolic resin-based, and melamine resin-based varnishes have insufficient heat resistance. It has drawbacks such as a decrease in insulation resistance (solid specific resistance value) in a high temperature region, and is no longer able to meet the needs.

In addition, polyimide resin varnishes have excellent heat resistance and electrical insulation properties in high temperature ranges, but have difficulty in adhesion, which requires special modification of the polyimide resin, and the heat curing temperature is 250°C. It requires high temperatures of ~350°C and is also expensive, so its uses are limited.

Means for Solving the Problems The present inventors aimed to provide a thermosetting composition that has excellent heat resistance, adhesiveness, and electrical insulation properties when thermoset, and is particularly useful as a varnish. As a result of intensive research, we found that a composition consisting of an epoxy resin and a curing agent having at least two or more epoxy groups in a specific polyparabanic acid molecule,
The present invention was completed after discovering that the object of the present invention can be achieved.

That is, the present invention provides (a) preferably 1 part by weight of polyparabanic acid consisting of the following repeating units; (b) Preferably 0.3 to 3 parts by weight of an epoxy resin having at least two or more epoxy groups in the molecule, and (c) Preferably a curing agent per 100 parts by weight of (a)+(b).
The gist is a thermosetting composition containing 0.2 to 10 parts by weight.

The polyparabanic acid [hereinafter referred to as polymer ()] used in the present invention is composed of the following repeating units, but desirably ηinh.=0.6 or less (0.5g/
100ml dimethylformamide (25°C).

This polymer () can be obtained by hydrolyzing a known polymer () having an imidazolidinedione-1,3-diyl ring consisting of the following repeating units.

Polymer (2) can be produced by the reaction of 4,4'-diphenylmethane diisocyanate and hydrogen cyanide, as described, for example, in Japanese Patent Publication No. 49-12360.

Hydrolysis of the polymer () is achieved by carrying out the hydrolysis in the presence of an aqueous solution of a Brønsted acid such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, or anhydrous hydrogen chloride, anhydrous hydrogen bromide, or the like.

The epoxy resin used in the present invention is not particularly limited as long as it has at least two or more epoxy groups in its molecule.

Specific examples of epoxy resins include epoxidized products such as conjugated or non-conjugated dienes, conjugated or non-conjugated cyclic dienes, and unsaturated carboxylic acid esters having conjugated or non-conjugated dienes, aliphatic diols, aliphatic polyhydric alcohols, Polyglucidyl ethers obtained by reacting bisphenols, phenol novolacs, cresol novolacs, etc. with epichlorohydrin or β-methylepichlorohydrin, polyglucidyl esters obtained by reacting dicarboxylic acids with epichlorohydrin or β-methylepichlorohydrin, etc. can be mentioned. Furthermore, flexible epoxy resins to which an elastomer such as NBR or polybutadiene is reacted and added to the terminals may also be used.

As the curing agent, curing agents, curing accelerators, radical reaction initiators, etc. for epoxy resins can generally be used, but it is particularly preferable to use one or more curing agents selected from dicyandiamide and imidazole compounds.

Further, a curing accelerator can be added as necessary, and examples thereof include metal chelates.

The composition of the present invention preferably contains 1 part by weight of the polyparabanic acid and preferably 1 part by weight of the epoxy resin.
It is obtained by mixing 0.3 to 3 parts by weight and a curing agent, preferably 0.2 to 10 parts by weight per 100 parts by weight of both components, but they may be mixed in the presence of a solvent.

Specific examples of the solvent include N-methyl-2
-pyrrolidone, dimethylformamide, dimethylacetamide, 1,4-dioxane, methyl cellosolve, butyl carbitol, etc., and two or more of these may be used. A composition mixed using these solvents can be used as it is, especially as a varnish, and a composition obtained by mixing without using a solvent can be heat-molded as a compound.

The composition of the present invention may contain other additives as necessary, such as inorganic fillers such as silica powder, titanium oxide powder, and alumina powder, elastomers such as NBR and polybutadiene, organic polymers such as fine polyimide resin powder, and colorants such as pigments. It is also possible to add various coupling agents such as a silane coupling agent, a titanium-based coupling agent, and the like.

Effects of the Invention The composition of the present invention has excellent heat resistance, and furthermore,
It exhibits a high insulation resistance value (volume specific resistance value) even in the high temperature range of 200℃ or higher, which is superior to existing epoxy resin varnishes.It has a lower curing temperature than polyimide resin varnishes, below 200℃. It cures sufficiently at a temperature of 100 mL, has the same adhesive properties as conventional epoxy resin varnishes, and has a sufficiently long pot life of over 1 month (at room temperature).

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 A solution consisting of 26 g of hydrogen cyanide and 300 ml of N-methylpyrrolidone (NMP), 250 g of 4,4'-
Diphenylmethane diisocyanate and 500ml
A solution consisting of NMP and 4.3 g of phenyl isocyanate (molecular weight regulator) were mixed. To this mixture was added 23 ml of NMP solution saturated with sodium cyanide, and the mixture was stirred for 30 minutes. The precipitated polymer was washed with methanol to obtain a polymer (). This polymer () was then dissolved in 37% hydrochloric acid,
After hydrolyzing at 60°C for 2 hours, the mixture was filtered, washed with water until neutral, further washed with methanol, and dried to produce a polymer () with ηinh.=0.20.

100 parts by weight of the polymer () obtained above and
67 parts by weight of NMP was mixed to form a solution. Next, bisphenol F type epoxy resin with an epoxy equivalent of 170 (manufactured by Yuka Ciel Epoxy Co., Ltd., trade name, Epicote)
807), 3 parts by weight of dicyandiamide as a curing agent, and 0.1 part by weight of aluminum acetylacetate as a curing agent accelerator were added to the above solution and stirred to prepare a colorless, transparent and viscous varnish.

The pot life of this varnish at room temperature was more than one month.

This varnish was screen printed on a stainless steel substrate (10cm x 10cm) and cured at 200℃ for 10 minutes.
A sample with a coating thickness of 40 μm was prepared. After applying a DC electric field of 100 KV/cm to this sample at room temperature for 30 minutes, the temperature was raised at a rate of 2.5 K/min while the DC electric field remained applied, and the resistance value was measured for each unit temperature. The results are shown in Figure 1.

In addition, in order to evaluate the heat resistance of the cured product of this varnish, the above varnish was placed in an aluminum cup for thermal analysis and cured at 200°C for 10 minutes. The weight of the varnish after curing was 40 mg. Thermogravimetric analysis was performed on this cured varnish at a heating rate of 10 K/min in an air atmosphere. The results are shown in Figure 2.

From the above results, it can be seen that the thermosetting composition of the present invention has excellent heat resistance and high insulation properties in a high temperature range.

Comparative Example 1 A varnish consisting of 100 parts by weight of the epoxy resin used in Example 1 and 56 parts by weight of Ketimine (manufactured by Yuka Ciel Epoxy Co., Ltd., trade name, Epicure H-3) as a hardening agent was screened in the same manner as in Example 1. It was printed and cured at 200°C for 10 minutes, and the resistance value was measured at each unit temperature. The results are shown in Figure 1.

The heat resistance of this varnish was also measured in the same manner as in Example 1, and the results are shown in FIG.

[Brief explanation of drawings]

FIG. 1 is a graph showing the temperature characteristics of the volume resistivity of the cured coating films of varnishes according to Examples and Comparative Examples, and FIG. 2 is a graph showing the thermogravimetric reduction rate characteristics of the cured coating films.

Claims (1)

[Claims] 1 (a) polyparabanic acid consisting of the following repeating unit, A thermosetting composition comprising (b) an epoxy resin having at least two epoxy groups in its molecule and (c) a curing agent.