JPH0847977A - Production of fiber reinforced plastic using soft gel coat - Google Patents

Abstract

PURPOSE:To prevent premature mold release and to make the crack of a gel coat layer hard to generate without extending a molding cycle or increasing the cost of a product in the molding of fiber reinforced plastic. CONSTITUTION:A gel coat using a soft resin with the tensile modulus of elasticity of 250kg/mm<2> or less such as an unsaturated polyester resin, an urethane resin or an epoxy resin as a base resin is applied to the surface of a mold and an FRP layer is laminated on the gel coat layer to perform molding. Or, the gel coat is applied to the surface of the mold and the aforementioned gel coat is applied to the gel coat layer and the FRP layer is further laminated thereon to perform molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fiber reinforced plastic using a soft gel coat in the molding of a fiber reinforced plastic composed of unsaturated polyester and a reinforcing material.

[0002]

2. Description of the Related Art A fiber reinforced plastic (FRP) is usually a gel coat composed of an unsaturated polyester resin or vinyl ester resin, a pigment and a thickener for the purpose of improving the appearance and protecting the FRP from ultraviolet rays and water. Is applied to the outermost layer. In order to manufacture an FRP molded product with a gel coat, first, a gel coat having a thickness of about 0.5 mm is applied to a mold treated with a release agent and cured. Next, the reinforcing fibers that are the constituent members of the FRP are placed on the gel coat and impregnated with the molding resin containing the curing agent. After the resin is sufficiently cured, the molded product is taken out of the mold to obtain a gel-coated FRP molded product.

In the above method, when the molded product is taken out from the molding die, the gel coat is usually in close contact with the molding die, but the molded product is taken out when the exothermic temperature of the molding resin is high or when the molding resin is thickly laminated at one time. Sometimes the product has come off the mold surface. There are two types of the mold release phenomenon, namely, a case where the molding resin is sufficiently cured and then separated from the mold surface, and a case where the resin is separated from the mold surface while the resin is not sufficiently cured.

When the resin is sufficiently cured and then separated from the mold surface, there is no problem in the appearance of the product. However, when the resin is separated from the mold surface while the resin is not sufficiently cured, the appearance of the product is not observed. Becomes significantly worse. The phenomenon that the product is released from the mold before the resin is sufficiently cured is generally called early mold release. When this early mold release occurs, the gel coat is released from the restraint by the mold surface, and as a result of the shrinkage of the molding resin in that state, the smoothness of the surface of the gel coat decreases and at the same time, the dent occurs. Such a molding defect is generally called "sink". When a sink mark occurs in the product, the gel coat surface is generally sanded to make it smooth, and then the gel coat is sprayed and finally buffed. If the dents do not disappear even after sanding, the polyester putty may be filled, or fibers impregnated with a molding resin may be attached to the surface to improve the smoothness.

[0005]

If the molded product is released from the mold early and the sink mark occurs as described above, it takes a lot of trouble to correct the product. Further, the repaired portion tends to be deteriorated by ultraviolet rays or chemicals earlier than the non-repaired portion, and in this sense, the early release is a big problem in manufacturing the FRP product with the gel coat.

At present, in order to prevent early release in the hand lay-up molding method, the number of fibers to be laminated at one time is reduced, or the heat of curing of the resin is lowered,
Although measures have been taken to prevent the resin from shrinking at the same time, all of these methods have the problem of lengthening the molding time. In the case of heat-closed molding such as RTM molding, a low-shrinking agent is blended with the molding resin to prevent early mold release, but the low-shrinking agent is expensive, which significantly increases the cost of the product. There is a problem of becoming.

Further, since the gel coat layer does not contain the reinforcing fibers used in the FRP layer, the gel coat layer is apt to be cracked when stress, especially tensile stress is applied.
At present, as a method for preventing such cracks, the FRP is made difficult to bend by increasing the thickness of the laminated layer, but this method has the drawback of increasing the weight of the molded product and increasing the cost. .

The present invention has been made in order to solve the above-mentioned conventional drawbacks, prevents early mold release, and does not cause an increase in molding cycle and product cost, and also prevents the gel coat layer from forming. It is an object of the present invention to provide a method for producing a fiber-reinforced plastic using a soft gel coat, in which cracks are less likely to occur.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a gel coat is formed on a mold surface using a soft resin such as an unsaturated polyester resin having a tensile elastic modulus of 250 kg / mm ² or less, a urethane resin and an epoxy resin as a base resin. The mold is formed by coating and then stacking the FRP layer on top.

Further, a gel coat is applied to the mold surface, and a gel coat using a soft resin such as unsaturated polyester resin having a tensile elastic modulus of 250 kg / mm ² or less, urethane resin or epoxy resin as a base resin is applied thereon. Alternatively, the FRP layer may be further laminated thereon to perform molding.

[0011]

In the above structure, a gel coat using a predetermined soft resin as a base resin is applied to the mold surface, and FR is applied on the mold coat.
Molding is performed by stacking P layers, which can prevent early mold release and accompanying sink marks in the production of a gel-coated fiber-reinforced plastic, and prevent the gel coat from cracking. It is possible to improve the sex.

Further, when a usual gel coat is applied to the mold surface and a backup gel coat using a soft resin as a base resin is applied thereon, the above-described effects of preventing sink marks and improving crack resistance are achieved. As well as
Since the surface of the soft resin is covered with a usual gel coat layer, there is an advantage that weakness in weather resistance and wear resistance is eliminated.

Of the components of the FRP, only the molding resin shrinks during molding. The volumetric shrinkage of the unsaturated polyester resin most commonly used for FRP molding is about 8
%. Since early mold release does not occur in the process of applying and curing the gel coat, it is considered that the cause of the early mold release is shrinkage of the molding resin. In addition, the mold is treated with a release agent for the purpose of preventing the gel coat from sticking to the mold. However, when the adhesion force of the gel coat FRP to the mold is measured by making a test piece, it is flat. In the Wise adhesion test, it was found to have an adhesion of about 6.5 kg / cm ² . This means that even if the mold is treated with a release agent, the gel coat and the mold are strongly adhered to each other.

The resin shrinks with the progress of curing and pulls the gel coat layer. Then, when this force exceeds the adhesive force between the gel coat and the mold, early mold release occurs. Therefore, it is considered that if the gel coat is flexible enough to alleviate the tensile force associated with molding shrinkage, the gel coat will not be peeled off from the molding die and premature mold release can be prevented.

To impart flexibility to the gel coat, a soft resin may be used as the base resin for the gel coat. At present, a soft unsaturated polyester resin is generally used as a core material for a bowling ball or a lining laminated resin. However, this soft resin is inferior in weather resistance, abrasion resistance and water resistance to general gel coat resins. For products in which these characteristics do not matter, a soft gel coat based on 100% soft resin can be used. The use of a soft resin not only prevents early release, but also has the advantage of significantly improving the crack resistance of the gel coat. When water resistance is required for the gel coat, a resin having excellent water resistance such as a vinyl ester resin or a bisphenol resin may be blended with the soft resin.

In hand lay-up molding,
In order to facilitate defoaming work, it is preferable to apply a white gel coat and then continuously apply a black gel coat to a thickness of about 0.1 mm. This black gel coat is generally called a backup gel coat. Also, soft resins have the drawback of being inferior in weather resistance and wear resistance,
The surface (the side that contacts the mold surface) uses a normal gel coat,
If a soft resin is laminated thereon as a backup gel coat, the weaknesses in weather resistance and abrasion resistance, which are the performance defects of the soft resin, can be eliminated. Further, when the gel coat is required to have water resistance, the above resin having excellent water resistance may be blended.

[0017]

Example # 6510 (trade name) manufactured by Nippon Yupica Co., Ltd. was used as a general gel coat resin, and FR-200T (trade name) manufactured by Dainippon Ink Co., Ltd. was used as the soft resin. An example of such a case is shown below. The measurement results of the physical properties of the resin are as shown in Table 1.

[0018]

[Table 1]

Example 1 A soft resin was used as the base resin for the gel coat, and a comparative test of early mold release was conducted by the following method.

(Gel coat) Resin # 651 for gel coat
A white gel coat based on 0 and FR200T was prepared and the ratio of the former to the latter was 1: 0, 3: 1, 1: 1.
And 4 gel coats set to 0: 1 were used.

(Molding Mold) An L-shaped unsaturated polyester resin gel-coated FRP molding mold having a bottom surface 11 and an upright surface 12 as shown in FIG. 1 was prepared, and a carbana-based mold release agent was formed on the surface thereof. Applied. The size of the molded body 1 is such that the bottom surface 11 has a width B of 380 mm, a length L of 350 mm, and an upright surface 1.
The height H of 2 was 350 mm.

(Application of gel coat) After adding 0.5% of 6% cobalt naphthenate and 1.0% of a curing agent of methyl ethyl ketone peroxide to the gel coat, spray coating to a mold with a thickness of about 0.5 mm. did. The applied gel coat was left to cure overnight at room temperature.

(Lamination) In this lamination, first, the forming die 1 is subjected to the primary lamination 3 up to the height of 100 mm below the entire bottom surface 11 and the elevation surface 12, and the elevation surface 12 is subjected to the primary lamination 4 on the entire surface thereof.
Therefore, as shown in FIG. 2, the primary lamination 4 was performed by wrapping the primary lamination 3 on the lower portion of the elevation 12 by 100 mm. After the heat generation of the primary laminates 3 and 4 is completed, the bottom surface 1
The secondary lamination 5 including the lap portion was performed on the primary lamination 3 of 1. The primary laminates 3 and 4 and the secondary laminate 5 each had 600 g / m ² of chopped strand mat and 580
^Two roving cloths of g / m ² were alternately used for a total of four sheets, which were impregnated with an unsaturated polyester resin for boats, defoamed, and left at room temperature.

(Releasing) After the above-mentioned lamination and defoaming, the mixture was left overnight at room temperature to cure and then released. For the molded product, the occurrence of sink marks was visually observed to evaluate the early release area.

For the four kinds of materials shown in Table 2, laminated products were manufactured by the above-mentioned method and the occurrence of sink marks was investigated.

As a result, when FR200T, which is a soft resin, is contained in an amount of 50% or more, early release does not occur at all, and even when it is 25%, the area ratio of early release is only 3%. %, Which is significantly improved as compared with 26% when the soft resin is not used (only # 6510).

[0027]

[Table 2]

Example 2 A normal resin was used for the gel coat, a soft resin was used as the base resin for the backup gel coat, and a comparative test of early mold release was conducted by the following method.

(Gel coat) Resin # 651 for gel coat
White gel coat with 0 as base resin and FR20
A black gel coat based on 0T was prepared, and four types of gel coats were used in which the ratio of the former to the latter was set to 1: 0, 3: 1, 1: 1 and 0: 1.

(Application of gel coat) After adding 0.5% of 6% cobalt naphthenate and 1.0% of methyl ethyl ketone peroxide-based curing agent to the gel coat and the backup gel coat, respectively, 6510 (white) was added to the above-mentioned molding die. It was applied to a thickness of 4 mm and the backup gel coat was applied to a thickness of 0.1 mm before it was cured. The laminated gel coat was left to cure overnight at room temperature.

(Lamination) FIG. 2 under the same conditions as in Example 1 above.
The primary laminations 3 and 4 and the secondary lamination 5 were laminated as shown in FIG.

As shown in Table 3, for the four types of materials,
A laminated product as shown in FIG. 2 was manufactured and the occurrence of sink marks was investigated.

[0033]

[Table 3]

As a result, when FR200T, which is a soft resin, is contained in an amount of 50% or more, early mold release does not occur at all, and compared with 20% when no soft resin is used (only # 6510). It turned out that it was greatly improved.

[0035]

As described above, according to the present invention, a mold coat is formed by applying a gel coat using a predetermined soft resin as a base resin on the mold surface and laminating an FRP layer thereon. Thus, in the production of the gel-coated fiber-reinforced plastic, it is possible to prevent early mold release and the accompanying sink marks, and it is possible to improve the crack resistance of the gel coat.

When a normal gel coat is applied to the mold surface and a backup gel coat using a soft resin as a base resin is applied thereon, the above-described effects of preventing sink marks and improving crack resistance are achieved. As well as
Since the surface of the soft resin is covered with a usual gel coat layer, there is an advantage that weakness in weather resistance and wear resistance is eliminated.

[Brief description of drawings]

FIG. 1 is a perspective view of a molding die for carrying out the present invention.

FIG. 2 is a cross-sectional view of a state in which the molding die of FIG. 1 is laminated.

[Explanation of symbols]

 1 Mold 3, 4 Primary stacking 5 Secondary stacking

Claims (2)

[Claims] 1. A gel coat using a soft resin composed of unsaturated polyester resin, urethane resin, epoxy resin or the like having a tensile elastic modulus of 250 kg / mm ² or less as a base resin is applied to the mold surface, and the FRP layer is applied thereon. A method for producing a fiber-reinforced plastic using a soft gel coat, which comprises molding by laminating. 2. A gel coat, which is obtained by applying a gel coat to a mold surface, and using as the base resin a soft resin such as an unsaturated polyester resin having a tensile elastic modulus of 250 kg / mm ² or less, a urethane resin, and an epoxy resin. A method for producing a fiber reinforced plastic using a soft gel coat, which comprises performing coating by coating and further laminating an FRP layer thereon.