JPH08112864A - Manufacture of cfrp molded item - Google Patents

Abstract

PURPOSE: To provide the manufacture of a molded item with an enhanced appearance having no pinholes by a low pressure heating method. CONSTITUTION: An open or autoclave molding method is such that a prepreg consisting of a carbon fiber and a thermosetting resin is laminated on the mold surface to then be subjected to a heat-hardening process under the vacuum bag, wherein a gel-coated resin not causing modification or deformation at a molding temperature is placed on the mold surface, after that, prepreg is laminated to subsequently be hardened through heat-compression.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a prepreg made of carbon fiber and a thermosetting resin, which is laminated on a mold surface and heated or cured under a vacuum bag by an oven or autoclave molding method.
The present invention relates to improvement of a method for producing an RP (carbon fiber reinforced resin) molded product.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a CFRP molded article, an oven or an autoclave molding method, in which a prepreg made of carbon fiber and a thermosetting resin is laminated on a mold surface and heat-cured under a vacuum bag, has become mainstream. There is. However, in most cases, CFRP molded products obtained by these molding methods are
Pinholes are formed on the surface of the molded product due to small air pockets. This pinhole requires a great deal of correction time when painting to obtain a good appearance, which is a factor of cost increase. The gel coat method can be considered as a method of avoiding the problem of such pinholes, but even if it is treated with a normal gel coat, the air inside will be raised and the appearance will be deteriorated, or the surface will collapse due to the accumulation of air inside. Therefore, it takes a lot of time to finish the surface, and the adhesion between the gel coat and the substrate becomes poor, so that it cannot be put to practical use.

[0003]

The present invention provides a method for avoiding these problems by using a special gel coat resin and capable of producing a pinhole-free dense CFRP molded product.

[0004]

The present invention relates to an oven or autoclave molding method in which a prepreg made of carbon fiber and a thermosetting resin is laminated on a mold surface and heat-cured under a vacuum bag. The above problem is solved by a method for manufacturing a CFRP molded product, which comprises arranging a gel coat resin that does not cause deformation, laminating a prepreg, and heating and pressurizing the prepreg.

The carbon fiber used in the present invention is a carbon fiber having high strength and high elasticity such as PAN type and pitch type.
It is used in the form of being subjected to normal forming processing such as woven fabrics and unidirectionally aligned sheets. Prepreg is an uncured, tack-free resin-impregnated intermediate product obtained by impregnating these woven fabrics and unidirectionally aligned sheets with thermosetting resins such as epoxy, vinyl ester and phenol by the solution impregnation method, film impregnation method, etc. Indicate the material. When such prepregs are laminated along the mold and heated under pressure, a molded product matching the mold shape is obtained.

As a method of pressurizing and heating, there is a method of using a press molding machine, but in the case of a large-sized complex molded product using CFRP, the mold and the laminated molded product are sealed with an airtight film and the gas inside is exhausted. , Vacuum bag / oven molding in which atmospheric pressure is applied by applying a so-called vacuum bag to heat in a heating oven, or the mold and molding material system in which the vacuum bag is performed are not simply pressurized at atmospheric pressure, but in an autoclave. An autoclave molding method in which a pressurized gas is used to heat and pressurize is advantageous. However, in these molding methods, the pressure applied per unit area is several tens of kg / mm ^2.
It is difficult, if not impossible, to pressurize above, and it is necessary to perform molding at a relatively low temperature and low pressure in a short time for molding in which productivity and cost are problems. However, when laminating and molding a normal prepreg under such conditions,
The reality is that air bubbles remain on the surface and the resulting molded product has many pinholes.

According to the present invention, in order to obtain a pinhole-free molded product by such low-temperature low-pressure molding, not only a good surface layer having a reaction adhesiveness with a base material laminated prepreg but also a quality change upon heating and pressurization is formed. A specific gel coat resin that does not deform is used. As such a gel coat resin, for example, a two-component mixed epoxy resin or a vinyl ester resin having a heat resistance of 80 ° C. or higher (Tg of 80 ° C. or higher) can be used, but it is necessary to carefully select the product type. A pigment or dye may be mixed in the gel coat resin to be used as a colored gel coat.

These gel coat resins are applied to a mold surface treated with a release agent by a spraying method or a brush coating method to form a film having a certain hardness, and then a base material prepreg is laminated, and a vacuum is applied. After bag processing, the product is heated and pressure-cured in an oven or an autoclave to obtain a molded product. In this case, the heating temperature is determined by the type of prepreg resin, but usually 70 to 130 ° C. is adopted, and the pressurizing pressure is preferably 1 to 4 atm.

[0009]

The present invention will be described in more detail with reference to the following examples. (Example 1) After performing mold release treatment on a mold surface having a curved surface shape, a two-liquid mixed curing type epoxy resin gel coat resin having a Tg of 90 ° C was applied by a spraying method to eliminate tackiness at room temperature. By the way, 80 ° C. cured prepreg of 24 ton type carbon fiber 3K plain weave manufactured by Mitsubishi Rayon Co., Ltd. was laminated. Then, a vacuum bag was carried out by a conventional method, and heat and pressure molding was carried out in an oven at 80 ° C. for 3 hours to remove the mold. As a result, a good molded product having a dense molding surface and no pinhole was obtained. When an automobile spoiler was molded by this method, a spoiler material without pinholes was obtained. Furthermore, when the surface was lightly polished and a clear coating was applied, it became a spoiler product with good depth and good appearance.

(Comparative Example 1) A molded article was formed in the same manner as in Example 1 except that the gel coat resin was not applied, and a pinhole having a diameter of 0.1 to 1 mm was formed on the surface of the obtained molded article. Was seen in large numbers. The surface of this molded product was lightly polished and subjected to clear coating, but the pinhole portion could not be concealed, and the appearance acceptable as a product could not be obtained unless the putty correction coating was repeated.

Example 2 A vinyl ester black gel coat resin having a Tg of 120 ° C. was applied to the same mold as that used in Example 1 and cured to such an extent that it would not be deformed by pressing with a finger. , 120 ° C. prepreg of 30 ton type carbon fiber 3K fabric manufactured by Mitsubishi Rayon Co., Ltd. was laminated. Vacuum bag according to the usual method and 120 ° C in an autoclave.
When a heat and pressure molding was carried out at 4 atm for 2 hours and the mold was removed, a molded product having a good appearance with no pinhole and producing black light was obtained. With respect to this surface, it was possible to obtain a good coated surface with one clear coating.

(Comparative Example 2) A molded article was formed in the same manner as in Example 2 except that the gel coat resin was not applied. The surface of the obtained molded article had a diameter of 0.05 to 0.2 mm. There were some pinholes. This pinhole could not be hidden even by painting, and it was necessary to repeat putty modification and painting in order to obtain a good-looking painted surface.

[0013]

EFFECTS OF THE INVENTION According to the present invention, a molded product having a good appearance surface free of pinholes can be obtained by the low pressure heat molding method, so that a good appearance is required for automobile parts, hulls and other large molded products. CFRP molded products can be used for various purposes.

Claims (1)

[Claims] 1. In an oven or an autoclave molding method in which a prepreg made of carbon fiber and a thermosetting resin is laminated on a mold surface and heat-cured under a vacuum bag, a gel coat resin that does not deteriorate and deform at the molding temperature is arranged on the mold surface. After that, a prepreg is laminated, and heating and pressurization curing is performed, and a method for manufacturing a CFRP molded product, comprising: