JPS6331383B2 - - 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 carrying 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 a sheet shape in one direction are impregnated with a thermosetting resin, a release sheet is attached to this, and the resin is preliminarily applied. harden. When producing a fiber-reinforced resin material, a release sheet-attached prepreg, that is, a prepreg material, is cut into an arbitrary shape, the required number of sheets are laminated in a predetermined direction excluding the release sheet, and the resin is cured by heating. Release sheets used in the production of such prepreg materials are generally required to have the following properties. (a) It should have removability on both sides and exhibit appropriate temporary adhesion to the prepreg. (b) To withstand the heat encountered in the manufacturing process of prepreg materials (for example, to withstand heat of 100-170°C in the manufacturing process of epoxy resin-impregnated carbon fiber prepreg materials). (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,
One known 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
Since it is mainly composed of kraft paper that easily absorbs moisture and has a low elastic modulus, the release sheet is prone to elongation due to moisture absorption, and is subject to significant shrinkage when the release sheet is tensed during the manufacturing process of the prepreg material and then released. The reinforcing fibers may float up from the surface of the release sheet (bouncing) or meander (sag) within the surface of the release sheet, resulting in disordered alignment.
Further, when the prepreg material is a scrim cloth bonded prepreg material, the scrim cloth will lift and separate from the reinforcing fibers. Therefore, when the prepreg is peeled off from the release sheet during use, the prepreg becomes like a corrugated sheet, which is not only difficult to handle, but also 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 material made by supporting such a release sheet with reinforcing fiber prepreg. is to provide. Therefore, in one aspect, the present invention includes a paper base material, a coating layer of a release agent formed on one side of the paper base material, an aluminum foil bonded to the other side of the paper base material, and a surface of the aluminum foil. Provided is a double-sided release sheet characterized by having a coating layer of a release agent formed on the surface of the sheet. 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, a release agent coating layer 5' is formed on one surface of the paper base material 1 via an undercoat layer 4', and an adhesive layer 3 is formed on the opposite surface of the paper base material 1. Aluminum foil (hereinafter referred to as "Al foil") 2 is pasted together through the film. Furthermore, a coating layer 5 of a release agent is formed on the surface of the Al foil with an undercoat layer 4 interposed therebetween. 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-glazed bleached 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. The thickness of Al foil is 50μ or less, generally 3 to 50μ,
Preferably, one with a diameter of 5 to 20 μm is used. If the Al foil is too thick, the prepreg material will undergo plastic deformation.
Al foil is attached to one side of the paper base using a heat-resistant adhesive such as acrylic resin. This adhesion may be carried out by using an adhesive of 1 to 20 g/m ² (in terms of solid content) and 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 Al 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 release agent may be applied in an amount of about 0.3 to 2 g/m ² (in terms of solid content), and coating can be carried out according to a commonly used method. The surface of the release sheet produced as described above opposite to the Al foil forming surface, that is, the coating layer 5'
A reinforcing fiber prepreg is temporarily attached and supported on top. The reinforcing fibers include carbon fibers, glass fibers, and organic high-modulus fibers (for example, polyaramid fibers such as "KEVLAR" manufactured by Dubon Co., Ltd. in the United States).
You may use a mixture of more than one species. 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. Layered in multiple layers,
B is applied to cross-shaped materials or laminated materials that are aligned in one direction and cross-shaped materials.
- It is impregnated with a thermosetting resin such as epoxy resin, unsaturated polyester resin, phenolic resin, or polyimide resin in a stage state. A scrim cloth made of carbon fiber, glass fiber, organic high elastic fiber, etc. may be bonded to the surface thereof, that is, the surface opposite to the surface supported by the peeling sheet. Two or more types of reinforcing fibers can be used, for example, by aligning several carbon fibers and glass fibers or organic high-modulus fibers in a regular manner and arranging them in one direction, or by aligning carbon fibers in one direction. Aligned fibers and glass fibers or organic high modulus fibers aligned in one direction are cross-laminated, or carbon fibers and glass fibers or organic high modulus fibers are used in combination in the form of a woven cloth. 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, aluminum foil is bonded to the surface opposite to the supporting surface of the prepreg, so the aluminum foil prevents the paper base material from absorbing moisture and slows down its rate. This prevents stretching due to moisture absorption. Also, shrinkage due to dehumidification and thermal shrinkage are very small. Additionally, aluminum foil has a higher modulus of elasticity than kraft paper and the like, and can withstand stress during the manufacturing process of prepreg materials. Therefore, it is possible to prevent sagging, 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: Single gloss bleached kraft paper (basis weight 80g/
^m2 , thickness 85μ) high quality paper (basis weight 80g/ ^m2 , thickness 85μ)
and unbleached kraft paper (basis weight 80g/m ² , thickness
85μ) were used. Use an acrylic adhesive (Cybinol RC-902, manufactured by Saiden Chemical Co., Ltd.) as the adhesive, and apply the adhesive with a roll coater for 3 minutes.
g/m ² (solid content) coated Al foil (thickness 7μ) was laminated on one side of each paper base material and dried. next,
2 g/m ² of polyvinyl alcohol (Denka Poval K-17E, manufactured by Denki Kagaku Kogyo Co., Ltd.) was applied to each of the Al foil surface and the paper surface of the obtained laminated base material and dried. Furthermore, a light release silicone release agent (SRX-357, manufactured by Toray Silicone Co., Ltd.) was applied to the Al foil surface, and a heavy release silicone release agent (SRX-357, manufactured by Toray Silicone Co., Ltd.) was applied to the paper surface.
-370: Manufactured by Torre Silicone) 1 each
g/m ² (solid content) was coated using a roll coater and dried and cured (Samples Nos. 1, 2, and 3). Comparative samples were manufactured in the same manner as above except that aluminum foil was not laminated (Samples Nos. 4, 5, and 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] Carbon fiber "Torega" T-300 manufactured by Toray Industries, Inc. (average single yarn diameter 7μ, number of single yarns 6000) is arranged in a sheet shape parallel to each other in one direction, and carbon fiber manufactured by Yuka Ciel Co., Ltd. Epoxy resin “Epicoat” 1004 and
Boron trifluoride and monoethylamine 10:
The resin solution was dissolved in methyl ethyl ketone at a weight ratio of 10:1 to make the resin component 60% by weight, and then impregnated with a resin solution, which was then placed on two types of release sheets and passed through a hot air drying oven at 150°C to remove methyl ethyl ketone. After evaporation, the carbon fibers were pressed between a pair of hot rolls with a surface temperature of 110°C to spread them out, creating a prepreg material. This prepreg material had a thickness of about 0.12 mm excluding the release sheet, and a carbon fiber content of about 63% by weight. Furthermore, a glass fiber plain weave scrim cloth having a thickness of 0.03 mm and a basis weight of 25 g/m ² was laminated onto the prepreg. The above two types of release sheets are one-sided bleached kraft paper/Al (sample No. 1) and one-sided bleached kraft paper (sample No. 4) in Table 1. In the case of using Al, prepreg is supported on the surface opposite to the surface of the Al foil. 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 the drawing]

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...Paper base material, 2...Aluminum foil, 3...
Adhesive layer, 4, 4'... Undercoat layer, 5, 5'... Release agent coating layer.

Claims (1)

[Scope of Claims] 1. A paper base material, a release agent coating layer formed on one side of the paper base material, an aluminum foil laminated to the other surface of the paper base material, and a release agent coating layer formed on the surface of the paper base material. A double-sided release sheet comprising a coating layer of a release agent. 2. A prepreg material in which a reinforcing fiber prepreg is supported on one surface of a release sheet, the release sheet comprising a paper base material, a coating layer of a release agent formed on one surface of this paper base material, and the other paper base material. A double-sided release sheet having an aluminum foil bonded to one surface and a coating layer of a release agent formed on the surface of the aluminum foil is used, and the prepreg is supported on the surface opposite to the surface to which the aluminum foil is bonded. A prepreg material that is characterized by its properties.