JPH0362735B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing prepregs used in the electrical and electronics industry, and more particularly to prepregs that are flame retardant, have a relatively long pot life even at high temperatures, and have dispersion stability. The present invention relates to a method for producing a prepreg using a solvent-free flame-retardant epoxy resin composition that provides a uniform cured product.

Epoxy resins are widely used in the electrical and electronic fields because they have excellent properties such as mechanical properties, electrical properties, thermal properties, chemical resistance, and adhesive properties. In the electrical and electronic fields, in recent years, varnishes have been made flame retardant to prevent fires during use, and solvent-free varnishes have been developed to improve working environments, solve pollution problems, and save resources. has become a major issue.

The present invention provides a method for producing a prepreg using a solvent-free flame-retardant epoxy resin composition that solves the above problems.

That is, in the present invention, an epoxy resin (A) that is liquid at room temperature and a compound (B) having at least two phenolic hydroxyl groups in the molecule are added to the epoxy resin (A) to form a phenolic hydroxyl group per epoxy group of the epoxy resin (A). is 0.05~0.5
The specific gravity at 25℃ is 1.33~
1.52, prepare a liquid mixture (C) with a bromine content of 16 to 32% by weight, and add an average particle size to the liquid mixture (C).
A fiber base material is impregnated with an epoxy resin composition (D) obtained by dispersing dicyandiamide finely ground to 50 μm or less in a solid state, heated, and the impregnated epoxy resin composition (D) is partially dispersed. The present invention relates to a prepreg manufacturing method characterized by reaction.

Epoxy resin that is liquid at room temperature used in the present invention
(A) is 2,2-bis(4-hydroxyphenyl)
Bis(4-hydroxyphenyl) such as propane (hereinafter referred to as bisphenol A), bis(4-hydroxyphenyl)methane (hereinafter referred to as bisphenol F), 1,1-bis(4-hydroxyphenyl)ethane, etc. diglycidyl ethers of alkanes,
Polyglycidyl ethers of polyhydric phenols such as phenol novolak and cresol novolak,
Polyglycidyl ethers of aliphatic polyhydroxy compounds such as ethylene glycol and polyethylene glycol, and mixtures thereof; further, these epoxy resins and a reactive diluent containing at least one epoxy group, such as butyl glycidyl ether, etc. It is a mixture of

In addition, bromine-containing epoxy resins include bis(4-hydroxyphenyl) alkanes such as bisphenol A and bisphenol F, which are liquid at room temperature;
Bromine-substituted bis(4-
Epoxy resin obtained by reacting hydroxyphenyl) alkanes with epihalohydrin such as epibromhydrin or epichlorohydrin. Brominated bis(4-hydroxyphenyl) is solid at room temperature but dissolves in liquid epoxy resin. ) Diglycidyl ethers obtained by reacting alkanes with epihalohydrin, bis(4-
Diglycidyl ethers obtained by reacting diglycidyl ethers of hydroxyphenyl) alkanes with bromine-substituted bis(4-hydroxyphenyl)alkanes, and further bromine-containing ethers such as dibromucresyl glycidyl ether. Also included are reactive diluents and the like.

Examples of the compound (B) having at least two phenolic hydroxyl groups in the molecule include catechol, resorcinol, bisphenol A, bisphenol F,
Dihydric phenols such as tetrabromobisphenol A, pyrogallol, phenol novolak resins,
It is a polyhydric phenol such as cresol novolac resin, polyparavinylphenol, bromine-substituted polyparavinylphenol, or a mixture thereof.

The blending ratio of the liquid mixture (C) of the epoxy resin (A), which is liquid at room temperature, and the compound (B) having a phenolic hydroxyl group, is such that the phenolic hydroxyl group is 0.05 to 1 epoxy group in the epoxy resin (A). Compound (B) having phenolic hydroxyl groups in the range of 0.5
It is preferable to mix.

When the number of phenolic hydroxyl groups is less than 0.05, the curing speed is slow, and the performance of the cured product improved by adding the compound, especially the improvement effect on bending strength, water resistance, etc., is almost negligible.
If the number of phenolic hydroxyl groups exceeds 0.5, curing proceeds before the solid dicyandiamide is completely dissolved, and dicyandiamide remains unreacted in the cured product, which may affect the properties of the cured product, especially the chemical resistance. , heat resistance etc. are poor, so it is necessary to mix so that the number of phenolic hydroxyl groups is in the range of 0.05 to 0.5 per epoxy group.

In addition, in determining the blending composition, in order to improve the dispersion stability of dicyandiamide, we decided to use a liquid mixture (C).
It is necessary to adjust the specific gravity at 25°C to be in the range of 1.33 to 1.52. For this reason, it is preferable to mix an epoxy resin containing bromine or a bromine-containing compound having a phenolic hydroxyl group so that the bromine content is about 16 to 32% by weight with respect to the liquid mixture (C). By adjusting the bromine content to 16 to 32% by weight, flame retardancy can be imparted to the composition at the same time.

The dicyandiamide used in the present invention can be produced using, for example, a “jet pulverizer” (manufactured by Nippon Neumatic Co., Ltd.).
Average particle size 50μ obtained by finely pulverizing with etc.
m or less. The reason why the average particle size is set to 50 μm or less is that if the average particle size exceeds 50 μm, the viscosity of the liquid mixture (C) decreases due to heating etc. even if the specific gravity of the mixture is in the range of 1.33 to 1.52, and dicyandiamide This is because sedimentation and floating of the resin are observed, resulting in uneven curing and poor properties of the cured product. In addition, in order for solid dicyandiamide to completely dissolve and react before curing is completed, it is more preferable for the particle size of dicyandiamide to be small, and from this point of view, it is preferable that the average particle size of dicyandiamide is 50 μm or less. is important.

The epoxy resin composition (D) used in the present invention is prepared by mixing the above-mentioned epoxy resin (A), which is liquid at room temperature, and the compound (B) having a phenolic hydroxyl group at room temperature to 200°C, and then adding an average It is produced by adding 1 to 5 parts by weight of dicyandiamide finely pulverized to a particle size of 50 μm or less to 100 parts by weight of the mixture, uniformly kneading with a three-roll mill, etc., and dispersing it into a solid state. Since the phenolic hydroxyl group slightly reacts with the epoxy resin during production, it is preferable to mix at as low a temperature as possible. Further, if the amount of dicyandiamide added is less than 1 part by weight, the effect will be insufficient, and if it exceeds 5 parts by weight, dicyandiamide will remain unreacted, resulting in a decrease in the properties of the cured product, especially the heat resistance. Furthermore, if it is necessary to increase the curing speed of the composition, a curing accelerator may be used in combination. As the curing accelerator, for example, aliphatic tertiary amines having an aromatic ring such as benzyldimethylamine, unsaturated ring tertiary amines such as pyridine, 3 (3
Urea compounds such as (chlorophenyl)-1,1-dimethylurea, boron trifluoride amine complexes, imidazoles, etc. can be used. In addition, the amount to be used must be determined with due care since the pot life of the composition will be shortened, but usually,
It is used in an amount of 1 part by weight or less based on the epoxy resin.

Epoxy resin composition (D) thus obtained
, glass, silicon carbide, mica, asbestos,
In the process of impregnating fiber cloth, nonwoven fabric, or paper made of carbon, aromatic polyamide, etc., the viscosity of the composition is lowered by heating it to 40 to 80°C in order to increase the impregnation rate. The fiber base material is impregnated by the dipping method etc.
Furthermore, the fiber base material impregnated with the composition is
The mixture is heated using a hot air oven or the like adjusted to a temperature of 0.degree. C. to cause a partial reaction and obtain a prepreg.

The term "partial reaction" used here refers to stopping the reaction to the extent that the resin can flow by heating the obtained prepreg to 150°C or higher. For example, Soxhlet extraction of the prepreg with acetone The remainder is preferably 50% by weight or less of the epoxy resin composition.

The epoxy resin composition (D) used in the present invention has good storage stability at low temperatures because it has dicyandiamide, which is a retention hardening agent, dispersed therein in solid form. By heating to the above temperature, the curing reaction proceeds rapidly. In addition, the average particle size of dicyandiamide is set to 50 μm or less, and the liquid mixture (C) is heated at 25°C.
By adjusting the specific gravity in the range of 1.33 to 1.52 to approximate that of dicyandiamide, the viscosity of the composition can be reduced not only at room temperature but also by heating to 40 to 80°C. The dispersion stability is good even when the average particle size of dicyandiamide is
Since the diameter is 50 μm or less, it penetrates even into the finer parts of the fiber base material and curing progresses uniformly, so the resulting cured product has excellent mechanical properties, electrical properties, thermal properties, chemical resistance, etc. Are better.

Example 1 84 g of bisphenol A, 109 g of tetrabromobisphenol A and 260 g of epichlorohydrin
were mixed and dissolved in a separable flask, sodium hydroxide was added as a reaction catalyst, and the reaction was carried out at 80°C for about 4 hours. Excess epichlorohydrin was removed in vacuo, and the produced sodium chloride was washed with water to form a bromine-containing solution. An epoxy resin having an amount of 24% by weight and an epoxy equivalent of 248 was obtained. 200 g of the obtained epoxy resin was placed in another separable flask, 45 g of bisphenol A was added thereto, and the mixture was stirred and mixed at 120° C. for about 30 minutes to obtain a uniform liquid mixture. of this liquid mixture
Specific gravity at 25℃ is 1.38, viscosity at 35℃
400 poise, and the bromine content was 19.5% by weight. For the resulting liquid mixture, an average particle size of 15μ
8 g of dicyandiamide powder and 0.5 g of benzyldimethylamine were added and kneaded using three rolls to obtain an epoxy resin composition.

The obtained composition was heated to 60° C. and impregnated into a glass nonwoven fabric (basis weight: 120 g/cm ³ ). The viscosity of the composition at this time was 14 poise, and after being left at this temperature for 5 hours, the viscosity increased slightly to 28 poise, but no precipitation of the dicyandiamide powder occurred.

A glass nonwoven fabric impregnated with the composition is heated in a hot air oven.
A prepreg was obtained by heating at 140°C for 10 minutes. When this prepreg was subjected to Soxhlet extraction with acetone for about 1 hour, the extraction residue was 10% by weight of the epoxy resin composition.

Example 2 AER331 (manufactured by Asahi Kasei Industries, Ltd., bisphenol A)
Diglycidyl ether, epoxy equivalent weight 190) 520
g, DER542 (manufactured by Dow Chemical, tetrabromo bisphenol A diglycidyl ether, epoxy equivalent 345, bromine content 48% by weight) 280 g, bisphenol A 120 g, phenol volak resin (average molecular weight 350) 20 g and as a reactive diluent.
60 g of BROC (manufactured by Nippon Kayaku Co., Ltd., dibromucresyl glycidyl ether) was placed in a separable flask and stirred and mixed at 120° C. for about 30 minutes to obtain a uniform liquid mixture. This liquid mixture had a specific gravity of 1.33 at 25°C, a viscosity of 160 poise at 35°C, and a bromine content of 16% by weight. To the resulting mixture, add 40% of dicyandiamide powder with an average particle size of 15 μm.
5 g of 3(3-chlorophenyl)-1,1-dimethylurea were added and kneaded with three rolls to obtain an epoxy resin composition.

The resulting composition was heated to 70°C and impregnated into a glass cloth (Style 7628, manufactured by Asahi Schuebel Co., Ltd.). The viscosity of the composition at this time was 4 poise, and the viscosity after standing at this temperature for 5 hours was 6 poise, but no precipitation of the dicyandiamide powder occurred.

A glass cloth impregnated with the composition was heated in a hot air oven for 140 minutes.
A prepreg was obtained by heating at °C for 8 minutes. When this material was subjected to Soxhlet extraction with acetone for about 1 hour, the extraction residue was 7% by weight of the epoxy resin composition.

Example 3 AER331 (manufactured by Asahi Kasei Industries, Ltd., bisphenol A)
Diglycidyl ether, epoxy equivalent 190) 650g
and 350 g of tetrabromobisphenol A were placed in a separable flask and stirred and mixed at 120° C. for about 1 hour to obtain a homogeneous mixture. 25 of this liquid mixture
Specific gravity at ℃ is 1.39, viscosity at 35℃ is 500
poise, and the bromine content was 20% by weight.
To the obtained liquid mixture, 30 g of dicyandiamide powder having an average particle size of 15 μm and 2 g of benzyldimethylamine were added, and the mixture was kneaded with three rolls to obtain an epoxy resin composition.

The resulting composition was heated to 60°C and impregnated into glass paper (GMC-00-100, manufactured by Honshu Paper Industries Co., Ltd.). The viscosity of the composition at this time was 18 poise, and after being left at this temperature for 5 hours, the viscosity increased to 35 poise, but no precipitation of the dicyandiamide powder occurred.

A prepreg was obtained by heating glass paper impregnated with the composition at 140°C for about 10 minutes in a hot air oven. When this product was subjected to Soxley extraction with acetone for about 1 hour, the extraction residue was 8% by weight of the epoxy resin composition.

Claims (1)

[Claims] 1. An epoxy resin (A) that is liquid at room temperature and a compound (B) having at least two phenolic hydroxyl groups in the molecule.
are mixed in a range of 0.05 to 0.5 phenolic hydroxyl groups per epoxy group of the epoxy resin (A),
Specific gravity at 25℃ is 1.33-1.52, bromine content is 16
An epoxy resin composition (D) obtained by preparing a liquid mixture (C) having properties of ~32% by weight and dispersing dicyandiamide finely ground to an average particle size of 50 μm or less in the liquid mixture (C) in a solid state. An epoxy resin composition (D) in which a fiber base material is impregnated, heated, and impregnated with
A method for producing prepreg, characterized by partially reacting. 2 The fiber base material is glass, silicon carbide, mica,
2. The method for producing prepreg according to claim 1, wherein the prepreg is fabric, nonwoven fabric, or paper made of fibers made of asbestos, carbon, aromatic polyamide, or the like.