JPS591574B2 - Prepreg sheet manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing prepreg sheets using thermosetting resin powder, and is suitable for use primarily as insulation and adhesive protection materials, particularly as precision adhesive materials for electrical and electronic materials. The present invention relates to a method for manufacturing a prepreg sheet with excellent corrugation processability.

Conventionally, this type of prepreg 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 generally only allows the use of resins that can be dissolved in the solvent. There are limitations, and if the solution viscosity increases, it will not be compatible with the coating process, so it is not possible to increase the resin concentration.If you try to coat a resin containing an inorganic filler, the filler will settle in the solution and you will not be able to coat it. There are drawbacks.

Therefore, it is common to use a resin that does not use filler or contains almost no filler, and dissolves it in a solvent at a relatively low concentration and applies it to the base material, but even with this method, it is not possible to obtain a prepreg sort with a large amount of resin impregnated. If the amount of solvent is large, boards (voids, the same hereinafter) may occur due to solvent volatilization during the resin layer formation, or unvolatilized solvent may remain in the layer even after the resin layer is formed, causing the moisture resistance of the sheet to deteriorate. This unvolatilized solvent may evaporate when the prepreg sheet is used, causing damage to the board.

In recent years, in response to the demand for a prepreg sheet manufacturing method that does not involve volatilization of organic solvents in place of the solution coating method, which has such drawbacks, and from a sanitary perspective, resin powder can be used as a fiber base material without using a solvent. A prepreg sheet manufacturing method has been proposed using the so-called powder coating method, in which a powder layer of a predetermined thickness is first formed on top of the base material, and then heated and melted to impregnate the inside of the base material.

In addition, in this method, if external pressure is applied when the resin is impregnated and integrated, that is, when it is heated and melted, the impregnation performance, sheet thickness accuracy, and bubble-free property are significantly improved compared to the case where no external pressure is applied. It is known to give good results. These powder coating methods can overcome the various drawbacks seen in conventional solution coating methods, and can therefore be said to be industrially advantageous.

However, when a thermosetting resin powder is specifically selected and used as the resin powder, there is a problem that the resin powder falls off during handling such as punching as a result of the sheet itself lacking in flexibility. For example, a prepreg sheet obtained by this method was punched and cut into small pieces of a predetermined shape.
Alternatively, if a tape-like slit is made, the resin near the cut will spill out, creating a missing part of the resin in the base material.
This has the disadvantage of causing poor adhesion, and contaminating the adherend when the resin is scattered to parts of the adherend that do not require adhesion.

As a result of intensive studies in light of the above circumstances, the inventors used a two-layer structure consisting of woven fabric and non-woven fabric as the base material, coated it with thermosetting resin powder, and melted and impregnated it. It was discovered that a prepreg sort with improved punching workability could be obtained by removing the unimpregnated resin layer exposed on the surface of the woven fabric using a specific method, which led to the completion of this invention. .

That is, in the present invention, after a thermosetting resin powder is placed on a fiber base material having a two-layer structure consisting of a woven fabric and a non-woven fabric, the thermosetting resin powder is placed on the woven fabric side so that the mold release treated surface is on the outside. The resin powder is melted and impregnated into the base material by applying heat and pressure through the single-sided release film and the double-sided release film provided on the nonwoven fabric side, and the unimpregnated resin layer on the woven fabric side surface is melted and impregnated into the base material. This relates to a method for manufacturing a prepreg sheet, characterized in that the above-mentioned single-sided release film is attached to and removed when the film is peeled off.

The reason that resin scatters and falls off when punching and cutting conventional prepreg sheets is mainly because unimpregnated resin layers are formed on both sides of the base material during resin impregnation, and this scatters and falls off. Even the resin impregnated inside is unlikely to cause scattering or falling off.

From this point of view, the gist of the invention is to devise ways to reduce the amount of unimpregnated resin layers on both sides of the prepreg sheet. In other words, in this invention, a fiber base material with a two-layer structure of woven fabric and non-woven fabric is used, and the thermosetting resin powder coated and placed on this is heated and pressurized through a release film to inside the base material. However, when impregnated in this way, the resin on the nonwoven fabric side firmly fills and adheres to the base material due to the entanglement effect of the nonwoven fabric fibers, which causes it to scatter and fall off when the prepreg sheet is cut. There's no fear.

On the other hand, on the woven fabric side, an unimpregnated surface resin layer is likely to be formed because the filling and adhesion of resin to this base material is poor. Therefore, by using a single-sided release film as the release film during heat and pressure, and arranging it so that the release-treated side is on the outside, this film can be Deposit and remove the surface resin layer. This also prevents the resin from scattering or falling off from the woven fabric. As described above, according to the present invention, it is possible to prevent the resin from scattering and falling off from the woven fabric side as well as from the nonwoven fabric side, so it is possible to obtain a prepreg sheet with greatly improved punching workability.

Further, by forming the fiber base material into a two-layer structure of woven fabric and non-woven fabric as described above, it is possible to prevent the resin from falling off during resin powder coating or melting and integration. This is because, if the fiber base material is made only of woven fabric, and this base material has a low density or is thin and coarse, a portion of the resin powder may slip through the base material during coating or melting and integration. There is. However, by adopting the above-mentioned two-layer structure, the nonwoven fabric effectively prevents the resin powder from slipping through, and it is possible to uniformly coat and impregnate the entire base material with a certain amount of the resin powder.
However, when using a base material made solely of nonwoven fabric without relying on the present invention, although some improvement in punching workability is observed, the effect is not as remarkable as that of the present invention. Moreover, in the case of nonwoven fabric alone, its rigidity and strength are low, resulting in poor mechanical strength as a prepreg sheet or its cured product, and there are problems with heat resistance, and when cured at high temperatures, the base material May shrink and deform. For this reason, the field of application is extremely limited and it lacks practicality. In this invention, thermosetting resin powder is first placed on a fiber base material made of woven fabric and nonwoven fabric. In this case, the resin powder may be placed on the woven fabric side or the nonwoven fabric side of the base material.
Alternatively, resin powder may be placed on a woven fabric and then this and a non-woven fabric are overlapped, or conversely, resin powder is placed on a non-woven fabric and then this and a woven fabric are overlapped. Good too. The thermosetting resin powder used here includes epoxy resin, phenol resin, silicone resin,
A resin composition is prepared by adding a curing agent and optional components such as an inorganic filler and pigment if necessary to a thermosetting resin such as polyimide resin or one containing a thermoplastic resin. Below, preferably 250 to 50
Powdered particles with a particle size in the μ range are used.

As the woven fabric and nonwoven fabric constituting the base material, those made of natural organic, synthetic organic, or inorganic fibers can be widely used.

The weight of the woven fabric is usually 30 to 2009/wl, and the weight of the nonwoven fabric is 12 to 759/m''.
The thickness of each base material is generally 0.05 to 0.18 m for woven fabric.
m1 non-woven fabric, 0.03-0.17mm, total thickness 0
．． The thickness is preferably about 1-0.4 mm. As a method for placing the resin powder on such a base material, a wide range of methods can be used as long as it can form a powder layer of uniform thickness, and generally, methods such as scattering coating method, electrostatic coating method, spray coating method, etc. is preferably adopted.

In this invention, after placing the thermosetting resin powder on the base material as described above, a single-sided release film is placed on the woven fabric side with the release-treated side facing outward, and a double-sided release film is placed on the non-woven fabric side. A release film is disposed, and the resin powder is melted and impregnated into the inside of the base material by applying heat and pressure through both release films.

When melting and impregnating with such a heating and pressurizing method, air bubbles between placed powders and air bubbles between fiber base materials are easily pushed out.
The resulting prepreg sheet is promoted to be air-free, and good results are obtained in terms of resin impregnation and sheet thickness accuracy. Note that the temperature conditions during heating and pressurization are selected such that the thermosetting resin powder does not harden (semi-hardening is sufficient). Further, prior to the heating and pressing described above, it is also possible to heat-fuse the material under pressure in a non-pressurized state and employ the heating and pressing method each time. Heat melting in a non-pressurized state gives good results in fixing the resin powder to the base material. As a double-sided release film to be placed on the nonwoven fabric side during heating and pressurization,
For example, any conventionally known base film, such as a base film such as a polyester film whose both sides are treated with a silicone resin, can be used. Similarly, as a single-sided release film provided on the woven fabric side, a base film such as a polyester film can be used. One side of which has been subjected to mold release treatment with silicone resin can be widely applied.

As a method of heating and pressing, for example, there is a method using a heated roll press or a heated press plate, and the pressure is usually 0.2 to 40 kg/CI
Ll5O~2000C112 minutes or less, preferably 0.5
It is sufficient to heat press under the conditions of ~5 kg/supply and 80 to 1800 C for 15 minutes.

During the heating and pressurization described above, the single-sided release film on the woven fabric side is peeled off while leaving the double-sided release film on the nonwoven fabric side as it is, but since this release film has been subjected to release treatment only on the outside, At the time of peeling, the unimpregnated resin layer on the surface of the woven fabric adheres to the film and is removed from the base material.

The amount of resin to be removed can be arbitrarily set by adjusting the temperature during peeling or selecting the material of the base of the single-sided release film.

Generally, a removal rate of about 1 to 30% by weight of the total amount of resin placed on the substrate is desirable. By setting such a moderate removal rate, it is possible to improve the punching workability without adversely affecting the adhesive performance inherent to the prepreg sheet. Note that since the release film on the nonwoven fabric side that is peeled off during use has been subjected to release treatment on both sides, the resin will not be attached or removed as described above when it is peeled off. EXAMPLES Below, examples of the present invention will be described in more detail.

In addition, below, parts and % shall mean parts by weight and weight 0t, respectively. Example 1 Epoxy resin (Epicoat # manufactured by Yuka Ciel Epoxy Co., Ltd.)
A mixture consisting of 100 parts of 1002), 1 part of 2-undecylimidazole (manufactured by Shikoku Kasei Co., Ltd.), and 3 parts of carbon black (manufactured by Mitsubishi Kasei Co., Ltd.) was roll-kneaded at 100°C for 10 minutes, and then pulverized with a hammer mill. and the particle size is 8
A resin powder of 0 to 200μ was obtained.

The gelation time of this powder was 2 minutes and 30 seconds at 15'C. This resin powder was applied to glass cloth with polyester nonwoven fabric (nonwoven fabric; manufactured by Nippon Vilene Co., Ltd., product name H-8101).
5. Thickness 0.04m77! , weight 15f! /M2, i glass cloth; Asahi Schuebel Co., Ltd. product name 216AS308
, thickness 0.10 mm 1 weight 1109/M2), the resin amount is 1009/M2 by gravure roll with slits.
2 from the glass cloth side, and was heat-treated at 12°C for 2 minutes to fix it to the substrate.

After that, a 50μ thick polyester release film treated on both sides with silicone resin was applied to the polyester non-woven fabric side, and a 50μ thick polyester release film treated on one side with silicone resin was applied to the glass cloth side, and in the case of the latter, release treatment was applied. Each was placed so that the surface facing outward, that is, the untreated surface was in contact with the glass cloth, and was heated at 120°C using a roll press from the resin powder-coated side to 3 kg/kg.
Heat pressing was performed at a speed of 0.5 m/min to 0.5 m/min.

Thereafter, the single-sided release film on the glass cloth side was peeled off at a temperature of 7°C to obtain the prepreg sheet of the present invention with the double-sided release film still provided on the nonwoven fabric side.

The amount of resin removed when peeling off the single-sided release film was 109.
/m”.Example 2 Epoxy resin (Epicoat #1 manufactured by Yuka Ciel Epoxy Co., Ltd.)
004) 40 parts, Epicote #1002 (mentioned above) 60 parts, phenol resin (manufactured by Gunei Kagaku Co., Ltd., trade name MPl2OHH)
) and 0.5 parts of 2-methylimidazole was roll-kneaded at 1000C for 10 minutes and then ground in a hammer mill to produce a resin powder with a particle size of 80 to 200 microns.

The gelation time of this powder was 3 minutes at 150°C. Next, glass cloth (product name 216-AS3O8 mentioned above)
The above-mentioned resin powder was coated on top using a gravure roll with slits so that the amount of resin powder was 120 g/M2, and was heat-treated at 120° C. for 2 minutes to fix it on the glass cloth.

After that, a polyester nonwoven fabric (product name H-8103 manufactured by Nippon Vilene Co., Ltd., thickness 0.07 mm, weight 309/d) was superimposed on the coated side, and the same as in Example 1 was applied to the glass cloth side and the polyester nonwoven fabric side. A single-sided release film and a double-sided release film are installed, and the following is done.
Hot pressing was carried out using the same method and conditions as in Example 1. Thereafter, the single-sided release film on the glass cloth side was peeled off at a temperature of 70°C to obtain the prepreg sheet of the present invention with the double-sided release film still provided on the nonwoven fabric side. However, the amount of resin removed when peeling off the single-sided release film was 159/
It was wl. Example 3 A blend consisting of 100 parts of epoxy resin (Epikote #1002 mentioned above), 0.5 parts of 2-wandecyl imidazole, and 50 parts of trihydrated alumina was roll-kneaded at 100° C. for 10 minutes and then milled in a hammer mill. Grind with a particle size of 80~
A 200μ resin powder was made.

The gelation time of this powder was 3 minutes and 20 seconds at 150°C. Next, polyester nonwoven fabric (product name H8lO mentioned above)
3) The above-mentioned resin powder was coated on top using a gravure roll with slits so that the amount of resin powder was 1009/I, and was heat-treated at 120° C. for 2 minutes to fix it on the nonwoven fabric.

After that, a glass cloth (manufactured by Asahi Schuebel Co., Ltd., product name 108-AS8ll, thickness 0.0
5 mm, weight 499/M2) were superimposed, and a single-sided release film and a double-sided release film similar to those in Example 1 were placed on the glass cloth side and the polyester nonwoven fabric side, and the following steps were performed in the same manner as in Example 1. It was heated and pressed using the following method and conditions. Thereafter, the single-sided release film on the glass cloth side was peeled off at a temperature of 70°C to obtain the prepreg sheet of the present invention with the double-sided release film still provided on the nonwoven fabric side. The amount of resin removed during peeling of the single-sided release film was 129/M2. Comparative Example 1 100 f! of the resin powder obtained in Example 1 was placed on glass cloth (trade name 216-AS3O8 mentioned above). /Rrl using a gravure roll with slits, and was heat-treated at 120'C for 2 minutes to fix it on the substrate.

Then, a double-sided release film was placed on both sides of the base material, and a 120-type C3kg/? , 0.5 m/min to obtain a prepreg sheet having release films on both sides. Comparative Example 2 The resin powder obtained in Example 2 was coated on a polyester nonwoven fabric (trade name H-8103 mentioned above) using a gravure roll with slits at a coating thickness of 1009/m''. A prepreg sheet was obtained by heat treatment at C for 3 minutes.

Comparative Example 3 On glass cloth (product name 108-AS8l mentioned above),
The resin powder obtained in Example 3 was coated with a gravure roll with slits to give a ratio of 909/M2.
It was heat-treated at 0° C. for 2 minutes to obtain a prepreg sheet.

In this case, not only during heat treatment but also during coating as shown in the table below, does the resin leak? The resin slipped through the base material, and the resin was extremely missing, making it impossible to obtain a prepreg sort that could be put to practical use. The results of examining the punching processability, resin powder coating status, and adhesion to adherends of the six types of prepreg sheets obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in the table below. It was a trigram when it came out.

The hexagram evaluation method was carried out using the following test method. <Punching workability> When the prepreg sheet is punched and cut into 10 mm square pieces using the Thomson method, it is visually observed to see if there is any resin falling off. The case where this occurred was evaluated as (△), and the case where there was significant falling off was evaluated as (x).

<Resin powder coating status> When the resin powder is placed on the base material, there is no slip-through of the resin (○), there is slight slip-through (△), and there is significant slip-through (X). ).

Adhesion> Adhesive sheet test pieces (adherend: rolled steel plate) were prepared according to JIS K685O.

The curing conditions were 1500C x 60 minutes. The tensile shear strength of the test piece was measured using an Instron type tensile tester UTM-1-5.
000B (manufactured by Toyo Portwin Co., Ltd.). As is clear from the above table, the prepreg sort of the present invention exhibits good punching workability, and even when the resin powder is applied, the resin does not slip through the base material and a certain amount of resin is uniformly distributed. It can be seen that satisfactory adhesive strength can be obtained even though a predetermined amount of the surface resin layer is removed using a single-sided release film.

Claims (1)

[Claims] 1. A single-sided release film that is placed on a fibrous base material with a two-layer structure consisting of a woven fabric and a non-woven fabric, and then placed on the woven fabric side with the release-treated surface facing outward. The resin powder is melted and impregnated into the inside of the base material by heating and pressurizing the resin powder through the double-sided release film provided on the non-woven fabric side, and the unimpregnated resin layer on the surface of the woven fabric is transferred to the single-sided release film. A method for producing a prepreg sheet, which is characterized in that the prepreg sheet is attached to and removed from the film when it is peeled off.