JPS6249843B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fiber-reinforced plastics (hereinafter simply referred to as
Regarding a new manufacturing method for molded products (called FRP). More specifically, it has a gel coat layer and a core material.
The present invention relates to a method for manufacturing FRP molded products by the resin injecting method (hereinafter simply referred to as the R/I method).

FRP is a strong structural material that is usually molded from a combination of hardening resin, catalyst, various additives, and reinforcing fibers, and is relatively lightweight and can be molded into a wide variety of molded products. It is used in a wide range of fields, from automobiles and ships to bathtubs, septic tanks, and even flat plates and corrugated plates, especially those with relatively simple shapes.

The main methods of FRP molding are the contact pressure molding methods represented by the hand lay-up method, spray-up method, and R/I method.
Although it is suitable for manufacturing FRP molded products, it not only has low work efficiency and a long molding cycle, but also has a problem in that the flat surface of the molded product is not smooth due to the large shrinkage that occurs when the curable resin hardens. The reinforcing fibers stand out on the surface and cause a poor appearance.

On the other hand, press forming methods such as the mated die method, SMC method, and BMC method have better work efficiency and higher productivity than contact pressure forming methods such as the hand lay-up method and spray-up method. Compared to the method, equipment costs are higher and there are limits to the size of the product that can be molded, as well as the disadvantage that reinforcing fibers stand out on the surface of the molded product due to shrinkage of the curable resin during curing.

Among such FRP molded products, R/
The I method has higher productivity than other contact pressure molding methods, and is characterized by a relatively good appearance on both sides of the molded product, and can be said to be a molding method suitable for medium-sized mass production.

The R/I method generally uses a pair of male and female molds made of FRP, etc., a reinforcing fiber preform such as glass fiber is placed in the mold in advance, the mold is closed, and the unsaturated material is poured through injection holes placed at appropriate positions. This is a method of press-filling a curable resin such as polyester resin, plugging the injection hole, and curing and molding at a low temperature (for example, room temperature to about 50°C).The basic molding process is as follows:
(1) Mold cleaning and mold release treatment (gel coat layer formation may also be performed), (2) preform filling (including core material filling), (3) mold closing, (4) clamping,
It consists of (5) injection of curable resin, (6) curing, (7) mold opening, (8) demolding, and (9) post-processing (burring, after-curing, etc.).

However, the R/I method is currently only applied to molded products with a relatively simple shape, and has not been applied to molded products with a complex shape and relatively large size that require rigidity. Nothing happened.

However, the present inventor has studied the possibility of making various body parts of automobiles, which have complicated shapes and are relatively large, such as those having a loading platform at the rear of the vehicle body and a rear body that covers this loading platform, and made these by using FRP. An attempt was made to mold the material using the R/I method.

That is, FIG. 1 is a perspective view of the body of the automobile, and 1 is a steel body main body, for example, a left side panel 2, a right side panel 3, a rear roof 4, a back door 5, a front roof 6, a sunroof 7. Attempts were made to make each component such as FRP. Note that 8 and 9 are window openings.

Hereinafter, the left side panel 2 will be explained using FRP as an example. Figure 2 is a perspective view of the FRP left side panel 2 viewed from the front, Figure 3 is a perspective view of the FRP left side panel 2 viewed from the back, and Figure 4 is the X-X of Figures 2 and 3.
The line enlarged sectional view, FIG. 5, is an enlarged view of the circle A section in FIG. In the drawings, 11 is an FRP layer, and 12 is a preform of reinforcing fibers such as glass fibers. Reference numeral 13 denotes a gel coat layer provided on the outside of the FRP layer 11 in the portion that appears on the surface of the left side panel 2. Reference numeral 14 denotes a core material disposed in a region where strength and rigidity are required.

However, it has been found that the following problems occur when FRP molded articles having the gel coat layer and core material as described above are manufactured by the R/I method.

That is, in the region where the core material 14 is inserted, the core material 14 is sandwiched with the FRP layer 11 as shown in FIG.
FRP layers 11a and 11b together form one FRP layer 1
1c, the FRP part where the core material 14 is present
Even if an attempt is made to obtain a molded product in which the layer 11a and the portion of the FRP layer 11c where the core material 14 is not present form the same plane, a step S will occur on the surface of the FRP layer after hardening. The reason for this is that in the case of molding by the R/I method, the gel coat layer 13 is formed on the lower mold, and then the reinforcing fiber preform 12a, the core material 14, and the reinforcing fiber preform 12b are sequentially set on the gel coat layer 13, and then the lower mold and the upper mold are set. The FRP layer 11a has one preform layer, while the FRP layer 11c has two preform layers, so the FRP layer 11c is FRP.
This is because it is set thicker than layer 11a. That is, as shown in FIG. 6, the curing shrinkage of the FRP layer 11a and the FRP layer 11c occurs around the center surfaces 15a and 15c of those layers, respectively, but the FRP layer 11c is thicker than the FRP layer 11a,
The center plane 15a and the center plane 15c of their curing shrinkage
This is because they are misaligned. The size of the step S is based on the center plane 15c using the formula: S (mm) = X/100 x (Tc-Ta)/2 (where, and Tc are the thickness (mm) of the FRP layer 11a and the thickness (mm) of the FRP layer 11c before curing and shrinkage, respectively.

In order to reduce this step S, the FRP layer 11
The difference between the thickness Ta of a and the thickness Tc of the FRP layer 11c should be set as small as possible, preferably Ta=Tc, but in this case, as shown in FIG.
Sink marks 16 tend to occur on the surface of the molded product at a portion where the FRP layers 11a and 11b combine to form the FRP layer 11c.

This is because at the part where the two FRP layers meet, a rich part of the resin is inevitably created where the reinforcing fiber preforms 12a and 12b are not present, but since there is no reinforcing fiber in that part, it is not reinforced with the reinforcing fiber. This is because the cured portion shrinks by as much as 5 to 10%, whereas the cured portion shrinks by only 2 to 3%. A molded product with sink marks 16 on its surface cannot be used as a vehicle body panel or the like where appearance is important. Furthermore, if a resin-rich portion occurs, there will be a large difference in curing shrinkage rate from the portion reinforced with reinforcing fibers as described above, so internal cracks will occur and the strength of that portion will decrease.

In order to prevent the occurrence of the step S or the sink mark 16, the inventors believe that FRP layers 11a and 11b above and below the core material are used as core materials, as shown in FIG.
The fin portion 14 is placed at the part where the FRP layer 11c is formed.
It was discovered that it was sufficient to use a core material 14 having a shape, and an application was filed earlier (see Japanese Patent Application No. 159761/1983). However, when using the core material 14 having such a fin portion 14a, since the fin portion 14a protrudes in the direction of the FRP layer 11c, the FRP layer 11
Even if the thickness Ta of a is brought close to the thickness Tc of the FRP layer 11c, there is no risk of sink marks occurring, and therefore the FRP
The thickness Ta of the layer 11a can be made as close as possible to the thickness of the FRP layer 11c, and the difference in level can be made as small as possible. However, it is difficult to manufacture a core material with fins through post-processing, and it is necessary to manufacture it by creating a special mold and molding it into a predetermined shape, which reduces the manufacturing cost of the core material. There is a problem with the rise. Also, when using a core material with fins, in order to make the level difference invisible to the naked eye, the thickness Ta of the FRP layer 11a and the thickness Ta of the FRP layer 11c must be adjusted.
It is necessary to set the thickness Tc of 1>Ta/Tc>2/3, but it is difficult to position the core material so as to satisfy this condition.

The next problem is that when there are parts with complex shapes such as corners on the surface of the molded product, as shown in Figure 9 (corresponding to the enlarged view of circle B in Figure 4), gel coating on those parts Cracks are likely to occur in the layer, impairing the appearance quality.
Since the reinforcing fiber preom 12a is made by binding short glass fibers with a length of about 50 mm with a binder, it is difficult to obtain a shape that matches the corner part with a small radius of curvature, and the mold When setting the preome, as mentioned above, the precision is not good, so it deviates from the proper position, and a rich resin part 17 is created at the corner.
Since the curing shrinkage rate of the gel coat layer 17 is larger than that of the portion where the reinforcing fibers are present, internal cracks occur in the portion 17, and along with the occurrence of the internal cracks, cracks occur in the gel coat layer 13 in that portion.

Furthermore, in the R/I method, in which a reinforcing fiber preform 12a, a core material 14, and a reinforcing fiber preform 12b are set in this order on top of the gel coat layer 13, and a curable resin is injected and cured, it is generally difficult to position the core material 14. This means that it is easy to shift vertically and horizontally from a predetermined position. If the core material 14 deviates from a predetermined position, a rich portion of the resin is likely to occur, causing internal cracks and reducing mechanical strength. In addition, when the core material 14 is made of polyurethane foam, gases such as carbon dioxide gas come out from the cells due to heating and concentrate at the boundary with the FRP layer, but due to the shift of the core material 14, the thickness of the FRP layer 11a becomes smaller. In this case, the FRP layer 11a cannot withstand the pressure of the gas and separates from the core material 14, which appears as blisters on the surface of the molded product, resulting in a problem that the appearance quality is impaired.

However, the present inventor has conducted extensive research to solve the various problems mentioned above when manufacturing complex-shaped FRP molded products with a gel coat layer and a core material using the R/I method. We succeeded in developing a new R/I method.

That is, when manufacturing an FRP molded product having a gel coat layer and a core material by R/I, the present invention forms a gel coat layer on one side of the mold, and a mixture of a curable resin and reinforcing fiber is formed on the gel coat layer. This invention relates to a method for manufacturing an FRP molded product, which is characterized by forming a layer of FRP, then setting a core material, then setting a reinforcing fiber layer, and then closing the mold and injecting a curable resin and curing it.

Next, an example in which the method of the present invention is applied to molding the above-mentioned left side panel 2 will be described with reference to the drawings.

FIG. 10 is a sectional view showing a state in which the left side panel 2 is molded, and 21a and 21b are a lower mold and an upper mold, respectively, of a mold for forming an FRP layer or the like for the R/I method.

In the present invention, first, a curable resin for gel coat is spray coated on the lower mold 21a and dried to form the gel coat layer 22.

Next, a mixture of a curable resin and reinforcing fibers is applied onto the gel coat layer 22 by a hand lay-up method or a spray-up method to form a layer 23 of the mixture, and a core material 24 is placed and set thereon. , precuring the layer 23 of the mixture. Next, after setting the reinforcing fiber preform 25, the upper mold 21b is closed and a curable resin is injected and hardened. Thereafter, the mold is opened and demolded to obtain a molded product as shown in FIG. 11. In FIG. 11, 25 is an FRP layer formed by injecting a curable resin.

In the present invention, a preform is set on a gel coat layer as shown in FIGS. 5 to 7 described above, a core material is set thereon, a preform is further set thereon, and then a curable resin is injected. Unlike the method of curing at once, the layer 23 of the mixture of curable resin and reinforcing fibers formed on the gel coat layer 22 is first pre-cured and then cured together with the FRP layer 26 having the preform 25. and FRP layer 2
Since the mixture layer 23 cures independently from the molded article 6, and the thickness change due to curing shrinkage of the mixture layer 23 is almost constant in all parts, there is no possibility that steps or sink marks will occur on the surface of the molded product. Therefore, there is no particular need to use a core material having fins as the core material 24, and a core material formed by cutting can be used. As mentioned above, the core material with fins needs to be molded using a special mold, making it expensive. Furthermore, when using a molded product, a skin layer on the surface is required to improve adhesion to the FRP layer. Sanding to remove the unreacted components and after-cure to completely harden unreacted components are required, but cutting-processed core materials are inexpensive and do not require sanding or after-cure.

Furthermore, in the present invention, since the mixture layer 23 formed on the gel coat layer 22 is an FRP layer made of a uniform mixture of curable resin and reinforcing fibers, resin-rich portions occur at the corner portions as shown in FIG. Therefore, the occurrence of cracks in the gel coat layer at that location is also prevented.

Furthermore, in the present invention, since the core material 24 is set by placing it on the mixture layer 23, positioning is easy, and after the core material 24 is set, the mixture layer 23 is pre-cured. By doing this, the core material 24 is fixed, so there is no risk of the core material 24 shifting during injection and curing of the curable resin, and the occurrence of resin-rich parts due to misalignment of the core material and the occurrence of internal cracks due to this. Also, the gap between the gel coat layer 22 and the core material 24 is prevented.
Since it is easy to ensure the thickness of the FRP layer [mixture layer 23], the occurrence of blisters on the surface of the molded product can be easily prevented.

As described above, when the present invention is used, FRPs that have a complex shape and require good initial and aging quality.
This is extremely advantageous because molded products can be produced inexpensively and reliably.

In the present invention, the gel coat layer 22, the FRP layer 26, etc. used in the conventional R/I method are used, and the curable resin used for forming the FRP layer 26 includes, for example, unsaturated polyester resin, epoxy resin, urethane resin, etc. Examples include polyester resin, epoxy-acrylate resin, diallyl phthalate resin, and unsaturated polyester resin is particularly preferred. Examples of unsaturated polyesters in unsaturated polyester resins include those obtained by condensation polymerization of polyhydric alcohol components such as ethylene glycol and propylene glycol with polybasic acid components such as maleic anhydride, fumaric acid anhydride, and mixtures of these and phthalic acid. Examples of the crosslinking monomer include styrene, and examples of the curing agent include methyl ethyl ketone peroxide, benzoyl peroxide, cyclohexanone peroxide, and cumene hydroperoxide. Other accelerators such as cobalt naphthenate, manganese naphthenate, vanadium octoate, and copper naphthenate may be used as appropriate.

Reinforcing fibers used for the preform 25 include glass fiber, carbon fiber, asbestos, ceramic fiber,
Examples include inorganic fibers such as metal fibers, organic fibers such as animal and plant fibers, and synthetic fibers, with glass fibers being particularly preferred. These reinforcing fibers may be used in forms other than preforms, such as various mats and various cloths.

As the curable resin used to form the gel coat layer 22, for example, an unsaturated polyester resin is used, and the unsaturated polyester includes a polyhydric alcohol component such as ethylene glycol and propylene glycol, maleic anhydride, fumaric acid, and isophthalic acid. Examples include polycondensation products with polybasic acid components such as mixtures with polybasic acids, and the same crosslinking monomers, curing agents, etc. as in the unsaturated polyester resin for the FRP layer 26 are used. The thickness of the gel coat layer 22 is preferably about 0.3 to 0.6 mm, and a molded product with a beautiful appearance can be obtained.

As the curable resin used for the mixture layer 23, the same resin as that for the FRP layer 26 is used. The same reinforcing fibers as those for the preform 25 are also used. The thickness of the mixture layer 23 is also related to the thickness of the FRP layer 26, but it is preferably 1 mm or more in order to sufficiently prevent appearance defects such as steps, sink marks, and blisters, and to ensure mechanical strength. is preferred.

A resin foam is usually used as the core material 24,
Examples of the resin foam include polyurethane foam and acrylic resin foam.

In the above, the method of the present invention has been described as an example in which the method of the present invention is applied to molding the left side panel 2 of an automobile having a cargo bed at the rear of the vehicle body and a rear body that covers this cargo bed. Similarly, it can be applied to the molding of parts such as the light side panel 3, rear roof 4, back door 5, front roof 6, and sunroof 7, as well as various other automobile parts, daily life items such as bathtubs, boats, etc. It can also be applied to the molding of leisure goods.

Next, the method of the present invention will be explained with reference to Examples and Comparative Examples.

Example A left side panel 2 having the shape shown in FIGS. 2 and 3 was manufactured.

Glass fibers (fiber diameter 10μ, fiber major axis 50mm) were molded into a preform mold using unsaturated polyester resin (100 parts of unsaturated polyester obtained from ethylene glycol, maleic anhydride, and phthalic anhydride (parts by weight, the same applies hereinafter), and 30 parts of styrene. , 1 part of methyl ethyl ketone peroxide) to prepare a glass fiber preform 25.

The lower mold 21a made of FRP is made of unsaturated polyester resin (unsaturated polyester obtained from ethylene glycol, maleic anhydride and isophthalic acid).
100 parts of styrene, 30 parts of styrene, 1 part of methyl ethyl ketone peroxide, and 0.5 parts of cobalt naphthenate) was spray coated to form a gel coat layer 22 having a thickness of 0.3 mm.

On the resulting gel coat layer 22, an unsaturated polyester resin with a glass fiber content of 30% by weight was applied by a hand lay-up method to a thickness of 1 mm after curing, and then a hard polyurethane foam was cut. After the prepared core material 24 was placed, the mixture layer 23 was precured at 50° C. for 20 minutes.

Next, the preform 25 is set, the lower mold 21a and the upper mold 21b are closed, and unsaturated polyester resin (the same as that used for making the preform) is injected through the injection hole at an injection pressure of 6 kg/cm ² .
After 3 minutes, the mold was released and after-cured at 70°C for 3 hours to obtain an FRP left side panel 2.

No sink marks, steps, or cracks were observed in the obtained product.

Comparative Example A preform (produced in the same manner as preform 25), core material 24, and preform 25 were set in this order on the gel coat layer 22, and a curable resin was injected and cured, but in the same manner as in the example. The left side panel 2 was produced.
In the obtained product, steps were observed on the surface of the core material 24 portion, and cracks were observed on the gel coat layer 22 at the corner portions.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the body of an automobile that has a cargo bed at the rear of the vehicle body and a rear body that covers this cargo bed, and Figures 2 and 3 show the FRP left side panel viewed from the front and back, respectively. Figure 4 is an enlarged cross-sectional view along the line X--X of Figures 2 and 3, and Figure 5 is a partial cross-sectional view showing a state in which a step has occurred on the surface of an FRP molded product (circle A in Figure 4). Fig. 6 is an explanatory diagram explaining the cause of the difference in level, Fig. 7 is a partial cross-sectional view showing a sink mark on the surface of an FRP molded product, and Fig. 8 is a diagram of the core material. Figure 9 is a partial cross-sectional view of an FRP molded product using a molded product with fins, and Figure 9 is a partial cross-sectional view showing a resin-rich portion in the FRP layer (corresponding to an enlarged view of circle B in Figure 4). ), Fig. 10 is a partial sectional view showing the state in which an FRP molded product is molded by the method of the present invention, and Fig. 11 is a partial cross-sectional view showing the state in which an FRP molded product is formed by the method of the present invention.
FIG. 2 is a partial cross-sectional view showing an FRP molded product. (Main symbols in the drawing), 21a: Lower mold, 21b:
Upper mold, 22: gel coat layer, 23: mixture layer, 2
4: Core material, 25: Preform, 26: FRP
layer.

Claims (1)

[Claims] 1. When producing a fiber-reinforced plastic molded product having a gel coat layer and a core material by the resin injection method, a gel coat layer is formed on one side of the mold, and a curable resin and reinforcing fibers are formed on the gel coat layer. A layer of the mixture is formed, then a core material is set, a reinforcing fiber layer is set, then the mold is closed and a curable resin is injected.
A method for manufacturing fiber-reinforced plastic molded products, which is characterized by hardening.