JPH021666B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention particularly relates to a double-sided release sheet with excellent moisture-resistant dimensional stability and heat-resistant dimensional stability, and a prepreg material formed by supporting a reinforcing fiber prepreg on one side of such a release sheet. Release sheets are widely used in the manufacture of carbon fiber and other reinforcing fiber prepreg materials. For example, in the production of unidirectional carbon fiber prepreg materials, carbon fibers arranged parallel to each other in one direction in a sheet form are impregnated with a thermosetting resin, a release sheet is attached to this, and the resin is preliminarily applied. harden. When manufacturing fiber-reinforced resin materials, release sheet-attached prepregs, that is, prepreg materials, are cut into arbitrary shapes, the required number of sheets are laminated in a predetermined direction, excluding the release sheet, and the resin is cured by heating under pressure. . Release sheets used in the production of such prepreg materials are generally required to have the following properties. (a) have double-sided removability and exhibit appropriate temporary adhesion to prepreg; (b) withstand the heat encountered in the manufacturing process of prepreg materials (e.g., in the manufacturing process of epoxy resin-impregnated carbon fiber prepreg materials); (Can withstand heat of 100-170℃.) (c) Low thermal shrinkage and good heat-resistant dimensional stability. (d) Good moisture resistance and dimensional stability. Conventionally, there is no known release sheet that satisfies the above-mentioned requirements among the release sheets used in the manufacturing process of prepreg materials for reinforcing fibers. for example,
As a release sheet that has been widely used,
A known paper is made of kraft paper, a coating layer of an anchor material formed on both sides of the kraft paper, and a coating layer of a release agent formed on the surface of each coating layer. This release sheet is mainly composed of kraft paper, which easily absorbs moisture and has a low elastic modulus, so there is a possibility that the release sheet will stretch due to moisture absorption, or that the release sheet will be tensioned during the prepreg material manufacturing process and then released. The shrinkage caused by the release sheet is large, and the reinforcing fibers are lifted from the surface of the release sheet, or become loose (sagging) within the release sheet, resulting in disordered alignment. In the case where the prepreg material is a scrim cloth laminated prepreg material, the scrim cloth lifts up and separates from the reinforcing fibers. Furthermore, when the prepreg is peeled off from the release sheet during use, the prepreg becomes like a corrugated sheet, which makes it difficult to handle and makes it impossible to obtain a fiber-reinforced resin material with high physical properties. JP-A-56-10532 proposes a unidirectional prepreg material using a paper release sheet that has an elongation of 0.5% or less relative to its bone-dry dimensions under 60% relative humidity. However, as a result of studies conducted by the inventors, it is difficult to avoid curling and channeling during production even when using paper with good moisture-resistant dimensional stability. Satisfactory results cannot be obtained without a release sheet. The object of the present invention is to provide a release sheet that satisfies the above-mentioned requirements and, in particular, has both moisture-resistant dimensional stability and heat-resistant dimensional stability, and a prepreg prepared by supporting such a release sheet with reinforcing fiber prepreg. To provide the materials. Therefore, in one aspect, the present invention includes a metal foil base material, a paper base material bonded to both sides of this base material,
Provided is a double-sided release sheet characterized by having a coating layer of a release agent formed on the outer surface of each paper base material. In another aspect, the present invention provides a prepreg material comprising a reinforcing fiber prepreg supported on one side of a release sheet as described above. The accompanying drawing is a sectional view showing a typical example of the double-sided release sheet of the present invention. As shown in the figure, adhesive layers 3 and 3' are provided on both sides of the metal foil base material 2.
Paper base materials 1 and 1' are bonded to each other via. Further, coating layers 5 and 5' of a release agent are formed on the outer surface of each paper base material 1 and 1' via an undercoat layer 4 and 4'. The paper base material used in the present invention uses heat encountered in the manufacturing process of prepreg materials (generally 100 to 170
℃) and that does not undergo large dimensional changes upon moisture absorption. Generally, high-quality paper, kraft paper, glassine paper, roll paper, etc. with a basis weight of about 50 to 150 g/m ² are used. In particular, single-sided kraft paper with a thickness of about 0.05 to 0.2 mm is preferable because of its low elongation upon moisture absorption. Both surfaces of the paper base material are sealed with a hydrophilic polymeric substance such as starch, polyvinyl alcohol, or an anchor material such as polyethylene. That is, it is preferable to have a coating layer of the anchor material. As the metal foil, foils of metals such as copper, aluminum, tin, and iron are used. Among these, aluminum foil is preferred because it is lightweight and has good adhesion to the primer. The metal foil used has a thickness of 50 microns or less, generally 3 to 50 microns, preferably 5 to 20 microns. If the metal foil is too thick, the prepreg material will undergo plastic deformation. Paper base materials are attached to both sides of the metal foil using a heat-resistant adhesive such as acrylic resin. This pasting uses adhesive 1-20g/m ²
(in terms of solid content) by pressing with a roll coater or the like according to a conventional method, followed by drying and curing. A coating layer of a release agent is usually formed on both surfaces of the metal foil paper base bonded body through an undercoat layer. As the undercoat layer, a hydrophilic polymeric substance such as polyvinyl alcohol having good heat resistance and peelability may be used in the form of an emulsion or a solution. The application rate is about 1 to 20 g/m ² (solid content equivalent). As the release agent, commonly used silicone resins or non-silicone resins such as long chain alkyl acrylate polymer resins are used. A preferred release agent is a condensation reaction type or addition reaction type silicone resin of polydimethylsiloxane and polydimethylhydrodiene siloxane. The amount of the release agent applied may be about 0.30 to 2 g/m ² (in terms of solid content), and coating can be carried out according to a commonly used method. A reinforcing fiber prepreg is temporarily attached and supported on one surface of the double-sided release sheet produced as described above, that is, on the outer surface of one of the coating layers 5 and 5'. The reinforcing fibers are carbon fibers, glass fibers, organic high modulus fibers (eg, polyaramid fibers such as "KEVLAR" from DuPont, USA). Prepreg is made by pulling strands of reinforcing fibers with a number of single threads of several thousand in one direction, or by aligning them in one direction so that the fiber axes intersect with each other at any angle between 0 and 90 degrees. It is obtained by impregnating a thermosetting resin such as a B-stage epoxy resin, unsaturated polyester resin, phenolic resin, or polyimide resin into a multilayered structure. A scrim cloth made of carbon fiber, glass fiber, organic high elastic fiber, etc. may be attached to the surface thereof, that is, the surface opposite to the surface supported by the release sheet. The thickness of the prepreg is 0.02-1.0mm, preferably 0.03-0.5mm, and the reinforcing fiber content is 30
~85% by weight, preferably 40-80% by weight. When using scrim cloth, if it is made of glass fiber, the thickness should be 0.01 to 0.1
mm, preferably 0.02-0.05mm, weight 10-80g/
m ² , preferably 15 to 40 g/m ² , and in the case of carbon fibers or organic high elastic fibers, the thickness
0.02~0.15mm, preferably 0.03~0.1mm, area weight 10~
90g/ ^m2 , preferably 20-60g/ ^m2 . In the release sheet of the present invention, since the paper base material is pasted on both sides of the metal foil, the moisture absorption change of the paper base material is less likely to occur due to the interference with the metal foil, and the rate of moisture absorption can be slowed down. It is possible to prevent elongation due to Also, shrinkage due to dehumidification and thermal shrinkage are very small. Furthermore, since the release sheet has a symmetrical laminated structure of "paper-metal-paper," the release sheet itself does not warp even if it encounters changes in temperature and humidity. Additionally, metal foil has a higher modulus of elasticity than kraft paper or the like, and can withstand stress during the manufacturing process of prepreg materials. Therefore, it is possible to prevent looseness, sagging, or lifting of the scrim cloth, and it is possible to obtain a fiber-reinforced resin material that is not only easy to handle but also has high physical properties. Hereinafter, the present invention will be described in more detail with reference to Examples. Example: Paper base material was kraft paper (basis weight 80g/
^m2 , thickness 85μ) high quality paper (basis weight 80g/ ^m2 , thickness 85μ)
and Suemi kraft paper (basis weight 80g/m ² , thickness
85μ) were used. Use an acrylic adhesive (Cybinol RC-902, manufactured by Saiten Kagaku Co., Ltd.) as the adhesive, and apply the adhesive using a roll coater.
g/m ² (solid diameter) on both sides of Al aluminum) foil (thickness 7 μm). Each paper base material was attached to both sides of the Al foil and dried. Next, polyvinyl alcohol (Tenkapoval K-17E, manufactured by Denki Kagaku Kogyo Co., Ltd.) was applied to the outer surface of the obtained laminated base material.
2 g/m ² of each was applied and dried. Furthermore, 1 g of a light release silicone release agent (SRX-357, manufactured by Toray Silicone Co., Ltd.) was applied to one side, and 1 g of a heavy release silicone release agent (SRX-370, manufactured by Toray Silicone Company) was applied to the other side. /m ² (solid content) was coated using a roll coater and dried and cured (Samples Nos. 1, 2, and 3). In addition, as a comparative sample
Release sheets were manufactured by treating only the paper base material in the same manner as above without laminating Al foil (Samples Nos. 4, 5,
6). The heat resistance and humidity dimensional stability of the release sheet obtained by the above treatment were measured, and the results shown in Table 1 were obtained.

【table】

[Table] Carbon fiber "Torayka" T-300 manufactured by Toray Industries, Inc. (average single yarn system 7μ, number of single yarns 6000) is arranged in a sheet shape parallel to each other in one direction, and Yuka Ciel Co., Ltd. epoxy The resin "Epicote" 828, the same "Epicote" 1004, and boron trifluoride monoethylamine were dissolved in methyl ethyl ketone at a weight ratio of 10:10:1 to make the resin component 60% by weight, and then impregnated with a resin solution. This was placed on the heavy release agent coating layer of two types of release sheets, and heated to 150°C.
The carbon fibers were passed through a hot air drying oven to evaporate the methyl ethyl ketone, and then pressed between a pair of hot rolls with a surface temperature of 110°C to spread out the carbon fibers to produce a prepreg material. This prepreg material is
The thickness of the prepreg excluding the release sheet was about 0.12 mm, and the carbon fiber content was about 63% by weight.
Furthermore, on top of the above prepreg, a thickness of 0.03mm,
Glass fiber plain fiber scrim cloth with a basis weight of 25 g/m ² was laminated together. The above two types of release sheets are
In the table, they are katari kraft paper/Al/same paper (sample No. 1) and katari kraft paper (sample No. 4). Next, the above two types of prepreg materials were heated to 25
The samples were left in a room at 70% RH and 70% humidity, and changes in morphology over time were observed. The observation results are shown in Table 2.

[Table] From Table 2 above, it can be seen that the prepreg material of the present invention (sample No. 7) has very little curling or lifting of the scrim cloth.

[Brief explanation of drawings]

The figure is a sectional view showing a typical example of a double-sided release sheet according to the present invention. Reference numbers are as follows. 1,1'...Paper base material, 2...Metal foil base material, 3,
3'...Adhesive layer, 4, 4'...Undercoat layer, 5,
5'...Release agent coating layer.

Claims (1)

[Scope of Claims] 1. A double-sided product characterized by having a metal foil base material, a paper base material bonded to both sides of this base material, and a coating layer of a release agent formed on the outer surface of each paper base material. Peeling sheet. 2. In a prepreg material in which reinforcing fiber prepreg is supported on one side of a release sheet, the release sheet includes a metal foil base material, a paper base material laminated on both sides of this base material, and an outer layer of each paper base material. A prepreg material comprising a double-sided release sheet having a coating layer of a release agent formed on the surface.