JPS61287966A - Epoxy resin varnish - Google Patents

Abstract

PURPOSE:To provide the titled varnish giving prepregs which hardly suffer from formation of voids, by specifying a solvent to be used in the epoxy resin varnish. CONSTITUTION:An epoxy resin and a hardener (e.g. dicyandiamide) are dissolved in at least one solvent exhibiting an evaporation loss of 0.5mg/cm<2>.min or below under a pressure of 100mmHg, selected from among methylcellosolve, ethylcellosolve, butylcellosolve, dimethylformamide, diethylformamide and dimethylacetamide. Optionally, filler, reactive diluent, pigment, etc., may be added.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an epoxy resin varnish that is impregnated into a base material such as a fiber and cured to form a laminate, a multilayer board, or the like.

[Background technology]

BACKGROUND ART Conventionally, base materials such as fibers are impregnated with epoxy resin and semi-cured to form prepregs, which are then laminated and cured by heating to obtain laminates or multilayer plates. However, in laminates and multilayer boards created using this method, air bubbles trapped during impregnation with epoxy resin and air spaces trapped between the eyebrows when stacking prepregs can cause void defects after curing. This was often a problem. Therefore, in order to reduce the occurrence of void defects, attempts have been made to impregnate epoxy resin and stack prepregs under reduced pressure.

The method for impregnating with epoxy resin under reduced pressure is as follows.

First, fibers such as woven or nonwoven fabrics made of glass fibers or the like are placed under reduced pressure to remove air between the fibers. Then,
1. Impregnating the fibers with an epoxy resin varnish also placed under reduced pressure; After taking it out from under reduced pressure, adjust the amount of varnish as before.

A prepreg is obtained by semi-curing. Compared to conventional prepregs, the prepreg produced in this way has fewer air bubbles or unimpregnated areas caused by air bubbles, has better transparency, reduces the possibility of void generation, and has fewer voids. It will be possible to create laminates and multilayer bodies. However, conventional epoxy resin varnishes have
In order to dissolve the main components, such as solid epoxy resins, brominated epoxy resins, hardeners, etc., a large amount (usually 30 to 50% ). For this reason, if an epoxy resin varnish containing a large amount of these solvents is placed under reduced pressure, the solvents will rapidly evaporate even at room temperature.

As an example, the inventors investigated epoxy resin varnish containing a large amount of acetone, which has a low boiling point, and found that at room temperature,
0.5mg/c at normal pressure (20℃, '1at+I+)
The amount of solvent evaporated was 10°C.

2.5 mg/cm”-mm under reduced pressure of 100 mHg
The pressure increases to 40-90mmH by further reducing the pressure.
When I turned it down to g, it boiled. In this way, if the amount of solvent evaporation is high, the component ratio of the epoxy resin varnish will change over time, the solid content will increase, the temperature of the varnish will decrease, the viscosity will increase, and the viscosity will increase. The impregnation properties change, making it impossible to create a uniform prepreg. Not only that, but the evaporated solvent will fill the pressure reducing device, and there is a very high risk that it will catch fire and explode due to static electricity.

As described above, at present, there is no epoxy resin varnish suitable for impregnation under reduced pressure. It is an object of the present invention to provide an epoxy resin varnish that can be used in an impregnation method to create a prepreg with a low possibility of void generation.

[Disclosure of the invention]

In order to achieve the above object, the present invention provides an epoxy resin varnish that is impregnated into a base material under reduced pressure and cured,
The gist thereof is an epoxy resin varnish characterized in that the amount of evaporation of the solvent contained in the varnish under reduced pressure of 100,100 tons is 0.5 B/cm2·min or less.

This invention will be explained in detail below.

As the epoxy resin that is the main component, any type of epoxy resin that is normally used for varnishes can be used.

For example, bisphenol A type, brominated bisphenol A
Preferred epoxy resins of the present invention include those in which a solid epoxy resin such as a mold is the main ingredient, and a novolac type epoxy resin is added as necessary, but epoxy resins of other types and components may also be used. , of course it is possible.

Various types of curing agents can be used for epoxy resins, but in particular for laminates, it is generally used for laminates because the prepreg has good storage stability and good properties. It is preferable to use dicyandiamide (hereinafter referred to as rDicyJ).

In addition to the above epoxy resin and curing agent, add 100 m
The epoxy resin varnish of the present invention is constructed by adding a solvent (single substance or mixture) whose evaporation amount under mHg vacuum, preferably 30 mmHg vacuum, is 0.5 mg/crA-min or less. As mentioned above, the amount of evaporation of the solvent under a reduced pressure of 100 mmHg may be 0.5 mg/cfll-min or less, but it is not preferable that the amount of evaporation is extremely low, and it is necessary to dry the solvent sufficiently by appropriate drying after impregnation. Furthermore, it is preferable that the epoxy resin, curing agent, etc. have high solubility. Although not particularly limited, preferred solvents for this invention that satisfy the above conditions include ethers such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, and amides such as dimethylformamide, dimethylacetamide and diethylformamide. A solvent having an evaporation amount of 0.5 mg/ctA-min or less under a reduced pressure of 100 mmHg can be obtained by using the above compounds alone or by mixing two or more kinds. Moreover, the solvent used in this invention is 100 m
The total evaporation amount under mHgg pressure is 0°5 mg/
A small amount of acetone, MEK, etc., which have a high vapor pressure at room temperature, may be included as long as it is below ant-min. Thus, as long as the solvent used in the present invention satisfies the above conditions, it can be mixed according to the type of solid content such as the epoxy resin and curing agent to be dissolved, and even at room temperature, the solvent can It has high solubility, and the amount of evaporation can be reduced even under reduced pressure.

In addition to the above-mentioned components, the epoxy resin varnish of the present invention can be obtained by blending a filler 2-reactive diluent, a pigment, etc., if necessary.

The epoxy resin varnish obtained in the above manner is impregnated into a base material under reduced pressure, returned to normal pressure and semi-cured to create a prepreg, and then layered with metal foil etc. as necessary and cured. In this way, laminated plates and multilayer plates can be obtained.

The base material is generally glass cloth, but it may also be nonwoven fabric, or it may be made of a material other than glass, such as polyester.

Fibers such as aromatic polyamide may also be used.・The use of epoxy resin varnish is not limited to laminated boards and multilayer boards; as long as it is manufactured by impregnating fibers with varnish, it can be used for skis, fishing rods, rackets, etc.
In this case as well, by impregnating under reduced pressure, it is possible to produce a material with few bubbles and excellent physical properties.

As mentioned above, the epoxy resin varnish of this invention has 1
Evaporation amount under 00mmHg reduced pressure is o, 5mg/cn
Since the solvent is a compound that is less than or equal to Lmin, it can be used in an impregnation method under reduced pressure, making it possible to produce prepregs with less possibility of void generation, laminates, and multilayer plates with fewer voids.

Next, examples of the present invention will be described together with comparative examples.

(Example 1) A solution prepared by blending 250 g of methyl cellosolve as a solvent with 1000 g of brominated bisphenol A epoxy resin (YDB-500 manufactured by Tobu Kasei Co., Ltd.) was further mixed with 30 g of Dicy as a curing agent and 2-ethyl-4-methylimidazole (hereinafter referred to as r2E4MZ) and 150 g of methyl cellosolve and 150 g of dimethyl formamide as solvents were mixed to prepare an epoxy resin varnish. The viscosity of the finished epoxy resin varnish at 25° C. and the amount of evaporation under reduced pressure of 100 mmHg were measured. The results are shown in Table 1.

Glass cloth (7628 AS45 manufactured by Asahi Schwebel)
0) was placed in an airtight container, and the pressure inside the airtight container was reduced to 100 mmHg using a vacuum pump.

While maintaining a reduced pressure state, place the epoxy resin varnish that has been evacuated in advance into the same container and adjust the pressure to 100 mmHg.
The glass cloth was impregnated with this epoxy resin varnish for 3 minutes under reduced pressure, and the inside of the container was returned to normal pressure. The glass cloth impregnated with epoxy resin varnish was taken out from the container, excess varnish was removed with a bar, and then placed in a dryer and dried at 150°C for 4 minutes to obtain a resin content of 42 to 45.
% prepreg was obtained. When the obtained prepreg was observed with a magnifying glass, it was found that although there were some long air bubbles between the fibers, good impregnating properties were obtained. Furthermore, when a four-layer multilayer board was created using this prepreg, it was found that no voids were generated and the board had good moldability.

The molding conditions were as follows.

The prepreg obtained in this example was placed on the metal circuit side surface of a substrate in which a 18 μm metal circuit was formed on an insulating plate with a thickness of 0.1 fl, and an insulating plate with a thickness of 0.4111 mm was placed on top of it. A substrate with a 70 μm metal circuit formed thereon was superimposed on each side of the board, and another sheet of the same prepreg was superimposed on top of that, and a 0.1-thick substrate with a 18 μm metal circuit formed thereon, the same as the first one. The In substrates were stacked so that the surface on which the metal circuit was formed faced the previously stacked prepreg. This material was put into a press, and under a pressure of 40 kg/cri, first, 1
After heating at 30°C for 30 minutes, the temperature was raised and heating was performed at 170°C for 60 minutes to obtain a multilayer board.

(Examples 2 to 5) Epoxy resin varnishes were prepared using the component formulations shown in Table 1, and the same operations and observations as in Example 1 were performed. Viscosity of epoxy resin varnish at 25℃ and 100mmH
g:$i Table 1 shows the measurement results of the amount of evaporation under positive pressure. Furthermore, when the impregnating properties and moldability of the prepreg were observed, good results were obtained that were almost the same as in Example 1.

(Comparative Example) An epoxy resin varnish was prepared in the same manner as in Example 1, except that acetone, which has a high vapor pressure at normal pressure, was used as the main component of the solvent. Table 1 also shows the measurement results of the viscosity of the obtained epoxy resin varnish at 25°C and the amount of evaporation under reduced pressure of 100 mmHg.

As shown in Table 1, the epoxy resin varnish of this comparative example had an evaporation amount of 2-5 at a reduced pressure of 100 mmHg.
mg/an! -min, it was difficult to impregnate glass cloth under reduced pressure.

Therefore, in this comparative example, the glass cloth was impregnated with the epoxy resin varnish for about 1 minute at room temperature and pressure, and then dried to obtain a prepreg.

When the impregnation properties of the obtained prepreg were observed in the same manner as in the examples, it was found that there were many long air bubbles along the fibers between the fibers in each system forming the glass cloth, and that there were many long air bubbles along the fibers. There were also many spherical bubbles at the intersection with the prepreg, the transparency of the prepreg was poor, and the impregnability was not good. Furthermore, when a four-layer multilayer board was created using this prepreg in the same manner as in Example 1, voids were generated and a good molded product could not be created.

When the gel time at 160°C was measured for the above Examples and Comparative Examples, they were all within the range of 5 to 6 minutes, indicating that the epoxy resin varnish of the present invention can be used almost in the same way as ordinary epoxy resin varnishes. Although not shown in the examples above, even when each solvent other than acetone shown in Table 1 is used alone, sufficient physical properties can be obtained as an epoxy resin varnish impregnated under reduced pressure. Needless to say, it was.

〔Effect of the invention〕

The epoxy resin varnish of this invention is constructed as described above and can be used in an impregnation method under reduced pressure, making it possible to produce prepregs with less possibility of generating voids, and as a result, with fewer voids. It becomes possible to manufacture laminated boards and multilayer boards.

Claims (2)

[Claims] (1) An epoxy resin varnish that is impregnated into a base material and cured under reduced pressure, where 100 m of the solvent contained in the varnish is
Evaporation amount under mHg reduced pressure is 0.5mg/cm^2・
An epoxy resin varnish characterized by being less than or equal to min. (2) The epoxy resin varnish according to claim 1, wherein the solvent contains at least one compound selected from the group consisting of methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethylacetamide, and diethylformamide. .