JPS6134366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a non-cellular resin sheet reinforced with a fiber base material (hereinafter referred to as a non-cellular sheet), and its purpose is for insulation, adhesive protection materials, particularly electrical and electronic materials, etc. The present invention relates to a method for producing a non-cellular fiber-reinforced resin sheet that can be suitably used as a precision material.

Conventionally, this type of sheet has been manufactured using the so-called solution coating method, in which synthetic resin is dissolved in a solvent and then impregnated into the fiber base material, but this solution coating method is generally limited in that only resins that can be dissolved in the solvent can be used. When the viscosity of the solution increases, it becomes difficult to mix with the fiber base material, so the resin concentration cannot be increased.If you try to apply a resin containing an inorganic filler, the filler will settle in the solution and you will not be able to apply it. .

Therefore, there are many usage methods in which a resin containing no or almost no filler is dissolved in a solvent at a relatively low concentration and applied to the fiber base material. However, even with this method, when trying to obtain a sheet with a large amount of resin impregnated, the amount of solvent is large, so voids (voids, hereinafter the same) may occur due to volatilization of the solvent during the formation of the resin layer, or voids may occur even after the resin layer is formed. Volatile solvent remains in the layer and evaporates when the sheet is cured, causing damage to the sheet and causing voids.

In recent years, in response to the demand for a sheet manufacturing method that does not involve the volatilization of organic solvents from a hygienic standpoint, in order to replace the solution coating method, which has these drawbacks, resin powder has been coated directly onto fiber substrates without using solvents. A method for manufacturing a bubble-free sheet using a so-called powder coating method has been proposed, in which a powder layer of a predetermined thickness is first formed by disposing the powder layer on the base material, and then heated and melted to impregnate the inside of the base material.

However, this manufacturing method has the disadvantage that the flow of the resin cannot be suppressed because no external pressure is applied during the complete curing stage to form a bubble-free sheet, and as a result, voids occur.

The presence of voids in a bubble-free sheet is undesirable because it causes a decrease in the strength of the sheet itself and, when used in electronic materials, a decrease in sealing performance.

The present invention has been made to improve these drawbacks, and after coating both sides of a sheet-like fiber base material with thermosetting resin powder to make a powder-coated fiber base material, this powder-coated fiber base material is Release paper is attached to both sides of the engineered fiber base material and heated and melted using a heated roll press.
The present invention relates to a method for producing a bubble-free sheet, which is then completely cured under pressure.

The resin powder used in this invention is as follows:
It usually has a particle size of 300μ or less, preferably in the range of 250 to 50μ, and is made of a thermosetting resin or a mixture of this and a thermoplastic resin, and optionally contains an inorganic filler, various additives, or a trace amount of an organic solvent. Powders containing these can be preferably used, and specific resins include epoxy resins, polyesters, phenolic resins, polyethylene, nylon, and ethylene-vinyl acetate copolymers.

A method of placing the resin powder as described above on a fiber base material such as woven fabric, non-woven fabric, or mat made of natural organic, synthetic organic, or inorganic fibers is to place the resin layer with a uniform thickness. Any method may be used as long as it is possible, and the usual spray coating method, electrostatic coating method, spray coating method, and fluidized dip coating method are preferably used.

The resin powder placed on the fiber base material is heated as necessary to fix it to the base material.

This heat treatment can be omitted if the process of placing the resin powder on the substrate and the process of pressurizing and heating are performed continuously, but if the process of placing the resin powder on the substrate and the process of pressurizing and heating are performed separately. In this case, it is desirable to temporarily adhere the resin powder onto the fiber base material, that is, to process the resin powder at a low temperature around the melting point of the resin powder and for a short time, in order to make the sheet non-porous.

The resin layer placed or fixed on the fiber base material (powder-coated fiber base material) is coated with a release film on both sides of the upper and lower surfaces, and is heated to a pressure of 0.2 to 40 kg/cm ² using a heated roll press or the like. 50-200℃, within 12 minutes, preferably 0.5-5Kg/ ^cm2 , 80-180℃, within 5 minutes, conditions set appropriately depending on the properties of the resin used, especially for thermosetting resins. Heat treatment is performed while applying pressure under conditions that do not allow the curing reaction to proceed, thereby removing air bubbles in the resin and impregnating the base material with the resin to produce a prepreg sheet with release paper on both sides.

In this pressurized heat treatment step, the air bubbles between the resin powders and the air bubbles contained in the base material are first pushed out by the pressure treatment, and then the resin powder is gradually melted by the heat treatment performed at the same time. Melting begins under pressure, so at the same time as melting, the air bubbles contained in the powder are pushed out by external pressure and the resin penetrates into the already defoamed base material, resulting in a bubble-free double-sided product with good impregnating properties. It becomes a prepreg sheet with release paper.

The prepregs with release paper on both sides thus obtained are in close contact with each other, and are then completely cured under pressure to form a bubble-free sheet, which is the object of the present invention. It is preferable to adopt a tightening force pressurization method in which a long prepreg with release paper on both sides is wound around a core such as a drum many times and its ends are fixed with adhesive tape or the like.

By doing so, a long non-bubble sheet can be obtained.

Further, the heating at this time is performed under conditions that do not cause resin flow until the prepreg gels, and then leads to complete curing.

Generally, a method is adopted in which the temperature is gradually heated starting from the low temperature side.

In the process of obtaining a bubble-free sheet from prepreg with release paper on both sides, if the release paper and prepreg are not in close contact with each other or if the curing reaction proceeds rapidly, the resin will flow and air will be taken inside, making it difficult to obtain a bubble-free sheet. You can't get it.

As described above, according to the manufacturing method of the present invention, the sheet obtained is bubble-free and has a uniform thickness because it is manufactured under pressure.

Further, the sheet obtained according to the present invention can be particularly suitably used as precision materials such as electrical and electronic materials that require moisture resistance and tightness.

In the present invention, the sheet-like fiber base material can be used by subjecting it to a primer treatment in advance.

For example, soft resins (epoxy resin, phenolic resin, polyester resin, nylon, polybutyral resin, polysulfone resin, phenoxy resin,
The sheet-like fiber base material is pre-primed with a treatment liquid (solid content, 10 to 20% by weight) consisting of ethylene vinyl acetate copolymer, liquid rubber, etc.) and organic solvent (ketone, alcohol, trichlene, toluene, etc.). You can leave it there.

At this time, the soft resin is preferably one that is compatible with the thermosetting resin powder to be used later, and one that exhibits tackiness at room temperature.

Further, the amount of soft resin adhered to the primer-treated fiber base material is preferably 2 to 20% by weight of the total amount including the thermosetting resin powder to be coated later.

The present invention will be specifically explained below using examples.

Parts in the examples are parts by weight.

Example 1 Epoxy resin (Epicoat #1002 manufactured by Ciel Kagaku Co., Ltd.) 100 parts 2-undecyl imidazole 1 part Carbon black 3 parts The above ingredients were roll-kneaded at 100°C for 10 minutes, and the resulting resin was pulverized with a hammer mill. particle size
It was made into a resin powder of 80 to 200μ. When the gelation time of this powder was measured, it was 2 minutes and 30 seconds at 150°C.

Using this powder, glass cloth (trade name 216-AS308, manufactured by Asahi Schuebel Co., Ltd., 110 g/ ^m2 , 60 pieces vertically, 60 pieces horizontally)
58 pieces/inch) was coated on both sides using a gravure roll with slits so that the amount of resin powder was 100 g/m ² , and in this state was heated at 120° C. for 2 minutes to fix it. After that, a polyester release film (thickness 50μ) treated with silicone resin was placed on the top and bottom surfaces respectively, and a roll press was applied to
A laminated sheet having a length of 25 m and a width of 350 mm was obtained by pressure and heat treatment at 3 Kg/cm ² and 0.3 m/min.

Next, the obtained laminated sheet was wrapped around a core with a diameter of 350 mm while keeping the release film (release paper) in close contact with it, and the ends were secured with adhesive tape to prevent it from unrolling. ℃ for 3 days, 100℃
The curing reaction was gradually progressed for 1 day at 150° C. for 1 hour to obtain a bubble-free sheet having a uniform thickness and no bubbles.

Example 2 60 parts of epoxy resin (Epicoat #828 manufactured by Yuka Ciel Epoxy Co., Ltd.) and 40 parts of phenoxy resin (PKHH manufactured by Yukion Carbide Co., Ltd.) were dissolved in methyl ethyl ketone, and the resin content was 15% and the viscosity (25°C) was 10. ~20
Poise Primer A was created.

Next, a mixture consisting of 100 parts of epoxy resin (Epicoat #1002 manufactured by Yuka Ciel Epoxy Co., Ltd.), 1 part of 2-undecylimidazole (manufactured by Shikoku Kasei Co., Ltd.) and 3 parts of carbon black (manufactured by Mitsubishi Kasei Co., Ltd.) was added.
After kneading with a roll for 10 minutes at 100°C, the mixture was pulverized with a hammer mill to create a resin powder with an average particle size of 80 to 200μ. The gelation time of this powder is 2 minutes at 150℃30
It was hot in seconds.

Next, the primer A was coated with a glass cloth (product name 216-AS308 manufactured by Asahi Schuebel Co., Ltd.; 110g/
m ² , 60 vertical lines, 58 horizontal lines/inch), impregnated and coated on
The organic solvent was removed by air drying. The amount of primer applied was 7 g/m ² in terms of resin content. Thereafter, the resin powder was coated on both sides of the primer-treated glass cloth using a gravure roll with slits so that the amount of resin powder was 100 g/m ² .
It was fixed by heat treatment at ℃ for 2 minutes. In this treatment, the organic solvent in the primer was completely volatilized and removed.

After that, a polyester release film (thickness:
50μ) were placed on the upper and lower surfaces, respectively, and subjected to pressure and heat treatment using a roll press at 120°C, 3Kg/cm ² and 0.3m/min to obtain a laminated sheet with a length of 25m and a width of 350mm.

Next, the obtained laminated sheet was wrapped around a core with a diameter of 350 mm while keeping the release film (release paper) in close contact with it, and the ends were secured with adhesive tape to prevent it from unrolling. ℃ for 3 days, 100℃
The curing reaction was gradually progressed for 1 day at 150° C. for 1 hour to obtain a bubble-free sheet having a uniform thickness and no bubbles.

Claims (1)

[Claims] 1. After coating both sides of a sheet-like fiber base material with thermosetting resin powder to obtain a powder-coated fiber base material, release paper is attached to both sides of this powder-coated fiber base material, and a heated roll press is applied. A method for producing a bubble-free sheet, which comprises heating and melting the sheet, and then completely curing it under pressure.