JPH04247932A - Inner mold for molding frp pipe and method of molding frp pipe using the inner mold - Google Patents

Abstract

PURPOSE:To enable an inner mold to be employed repeatedly by the use of a hollow body made of rubber as an inner mold for molding an FRP pipe. CONSTITUTION:First, core molds 11, 12 are inserted into the hollow part of an inner mold 10 from both ends thereof. Next, the barrel part 10a of the inner mold is coated with uncured thermosetting resin so as to form a coated layer 13. After the resin entered in each spiral groove 10c becomes a semi-cured state, for example, a resin impregnated body consisting of roving impregnated with thermosetting resin is wound therearound for forming a wound layer 14 which is cured at an ordinary temperature or by heating. In the next place, the core molds 11, 12 are extracted from the hollow part of the inner mold 10, and thereafter the inner part of the hollow part is decompressed. As a result, the outer surface of the inner mold being in close contact with the molding inner surface is separated. Furthermore, by giving a twist to the end of the inner mold 10, it is decreased in diameter, and then by opening one end of the inner mold 10 and extracting from the other end, the inner mold is easily demolded from the mold.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an inner mold used for molding a fiber-reinforced thermosetting resin pipe (hereinafter referred to as an FRP pipe) in which glass fibers are impregnated with a thermosetting resin, and an inner mold using the same. The present invention relates to a method for forming FRP pipes.

0002

[Prior art] As one of the molding techniques for FRP pipes, glass fiber impregnated with thermosetting resin is wound around a core mold or inner mold, and after being heated and hardened, the molded product and the core mold are There is a method to separate (release or demold) the In this type of molding method, it is necessary to be able to perform the mold release process easily even if the resin shrinks during curing, and especially when molding a molded product with an undercut part such as a tube with an inner helical protrusion. It is required that the molded product be easily demolded.

[0003] In order to deal with such problems, there is a conventional method for releasing a core mold, for example, as described in Japanese Patent Publication No. 45-6957. This method uses a core mold made of thermoplastic resin pipe. After molding, both ends of the core mold are sealed and heated to soften them, and then the air inside the core mold is sucked to deform the molded product. The core mold is released from the mold.

[0004] In addition, Japanese Patent Publication No. 57-7889 and Japanese Patent Publication No. 57-7890 are proposed to facilitate the mold release process, especially when molding a molded product having an undercut portion or a relatively complicated shape. Publication or Japanese Patent Application Publication No. 2-958
There is a technique described in Publication No. 35. Among these, the one described in Japanese Patent Publication No. 57-7889 uses an inner mold formed by forming an outer shell mold with a low-melting point substance around a core mold, and after the core mold is pulled out after molding, the outer shell mold is formed. The outer shell mold is removed from the molded product by heating it from the inside to soften or melt it, and the one disclosed in Japanese Patent Publication No. 57-7890 uses a brittle substance instead of the low melting point substance mentioned above. After molding, the outer shell mold is crushed to remove it from the molded product.

On the other hand, the method described in Japanese Patent Application Laid-Open No. 2-95835 uses an inner mold made of a closed hollow body made of synthetic resin with a degassing nozzle provided at one end of a hemispherical shape, and after molding, the inner mold is The inner mold is buckled by suctioning the air, and the buckled inner mold is pulled out from the molded product and removed from the mold.

[0006]

[Problems to be Solved by the Invention] However, the methods described in the above-mentioned publications do not allow any damage after the mold, such as the inner mold remaining in the molded product, is deformed or collapsed to remove the mold. Since the mold cannot be used again as a mold, it is extremely uneconomical. That is, since the core mold made of thermoplastic resin described in Japanese Patent Publication No. 45-6957 is heated and softened, degassed, and deformed during demolding,
It is disposable and uneconomical.

Furthermore, the outer shell mold described in Japanese Patent Publication No. 57-7889 changes its shape by being heated and softened or melted during demolding, so it can only be used once. Furthermore, the outer shell mold described in Japanese Patent Publication No. 57-7890 is also crushed during demolding, making it impossible to reuse it. Therefore, both shell types are disposable and uneconomical.

[0008] Furthermore, the inner mold described in JP-A-2-95835 is made of a sealed hollow body of thermoplastic synthetic resin, and is buckled by degassing after molding, so it is disposable as in the above case. , it is uneconomical. The present invention addresses the above-mentioned problems in the prior art, and realizes an inner mold that can be used repeatedly as an inner mold used for molding FRP pipes, and uses this inner mold to form a helical shape on the inner surface. An object of the present invention is to provide a method for molding an FRP pipe having protrusions.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention is characterized by the following configuration. That is,
The invention according to claim 1 of the present application is an inner mold used for molding an FRP pipe, which is composed of a rubber hollow body having a predetermined elasticity, and the inner mold part of the molded product is formed in the body of the hollow body. In addition, a groove extending in a helical shape is provided on the outer circumferential surface of the body.

[0010] Furthermore, the invention according to claim 2 of the present application is a method for molding an FRP pipe using the inner mold according to claim 1, comprising:
A coating layer is formed by coating the body of the inner mold with an uncured thermosetting resin made by kneading glass fiber so that the surface is flush. After the thermosetting resin in the groove becomes semi-hardened, a resin-impregnated body made by impregnating roving, glass cloth, net, or nonwoven fabric with the thermosetting resin is wound around the surface of the coating layer. After forming a wound layer and curing these layers at room temperature or by heating to form a molded product, the pressure inside the hollow part of the inner mold is reduced to separate the outer peripheral surface of the inner mold and the inner peripheral surface of the molded product, After that,
The inner mold is twisted from both ends and then pulled out from the molded product to remove the mold.

[0011] The rubber constituting the inner mold is usually styrene-butadiene rubber, ethylene propylene rubber, etc., but from the viewpoint of ease of releasing the inner mold from the molded product, it is suitable for molding FRP pipes. It is preferable to use fluorine-based or silicone-based rubber, which is difficult to stick to commonly used unsaturated polyester resins. Furthermore, depending on the type of polyester resin, the mold releasability may be further improved if a mold release agent such as silicone oil or polytetrafluoroethylene powder is applied to the body of the inner mold in advance.

0012

[Operation] According to the above structure, since the groove extending in a helical manner is provided on the outer peripheral surface of the body of the inner mold in which the inner mold part of the molded product is formed, the protrusion corresponding to the groove is formed on the molded product. formed on the inner surface of Therefore, a molded product, that is, an FRP pipe, having spiral-shaped protrusions on the inner surface is obtained.

[0013] Furthermore, since the inner mold is constituted by a hollow rubber body having a predetermined elasticity, after molding, the pressure inside the hollow part of the inner mold is reduced to separate the outer circumferential surface of the inner mold and the inner circumferential surface of the molded product. Then, by twisting both ends of the inner mold and pulling it out from the molded product, it can be easily demolded. and,
After being demolded in this way, by releasing the torsional force on the inner mold, the inner mold easily returns to its original shape due to its elasticity, so it can be used again to mold an FRP pipe.

[0014]

[Examples] Examples of the present invention will be described below. This embodiment relates to the case of molding an FRP pipe 1 as shown in FIGS. 1 and 2. First, this FRP pipe 1 will be explained. As shown in the figure, this FRP pipe 1 has a plurality of protrusions 1b...1b extending in a spiral shape on its inner surface 1a.
is formed. These protrusions 1b...1b have an inverted V-shaped cross section in the illustrated example, and the number of protrusions is eight.

Next, the inner mold according to this embodiment used for molding this FRP pipe 1 will be explained. As shown in FIG. 3, the inner mold 10 is composed of a hollow body made of rubber (silicone rubber in this example) having a predetermined elasticity, and is used to hold the inner mold portion of the molded product (FRP pipe). Body part 10 to be formed
a, and pre-stocks 10b, 10b are provided at both ends. A plurality of grooves (hereinafter referred to as helical grooves) 10c...10c extending in a spiral shape and having a V-shaped cross section are provided on the outer peripheral surface of the body portion 10a, and these helical grooves 10c...10c By this, spiral-shaped protrusions 1b...1b in the FRP pipe 1 are formed.

Next, a molding method according to this embodiment using the inner mold 10 will be explained. First, as shown in FIG. 4, the core molds 11 and 12 are inserted into the hollow part 10d of the inner mold 10 from both ends. The core molds 11 and 12 in this case are used to assist the bending rigidity of the rubber inner mold 10 and to ensure the axial linearity of the FRP pipe 1 with an inner helical projection. It is not necessary if the rigidity is high. In addition, when the double-core molds 11 and 12 are connected at the center of the inner mold 10 as shown in the figure, the connecting part has a concave-convex fitting part 11a having a taper as shown in the figure, for example, 12a is preferably provided.

Next, as shown in FIG. 5, an uncured unsaturated polyester resin (thermosetting resin) kneaded with glass fiber is placed on the outer surface of the body 10a of the inner mold 10 so that its surface is flush with the outer surface of the body 10a. Press with a spatula so that the helical grooves 10c...10c are filled by hand-rolling. As a result, a coating layer 13 made of glass fiber-containing polyester resin is formed on the outer surface of the body portion 10a.

In this case, the glass fiber has a thickness of several tens of mm.
Short fibers up to 100% can be used. If it exceeds 50 mm, the fibers cannot be mixed uniformly into the resin. Preferably 10
~30mm. This glass fiber is mixed with uncured unsaturated polyester resin in a proportion of 2 to 5% by weight. If it is too low, it will shrink during heat curing and cause cracks. Moreover, if the number is increased, it becomes difficult to enter the helical grooves 10c...10c, and the helical protrusions 1b...1b with a uniform cross section cannot be obtained. These short fibers adjust the viscosity of the thermosetting resin and prevent it from dripping when applied to the inner mold 10.

Next, after the resin that has entered each of the helical grooves 10c becomes semi-hardened, a resin-impregnated body made by impregnating a roving with a thermosetting resin is wound to form a wound layer 14.
This is cured at room temperature or by heating. As a result, an FRP pipe as a molded product is formed on the outer surface side of the inner mold body 10a. Here, it is also possible to use glass cloth, net, nonwoven fabric, etc. in place of the above-mentioned roving.

Furthermore, the reason why the above-mentioned winding operation of the resin-impregnated body is performed after the resin in the helical grooves 10c...10c is in a semi-hardened state is that the resin-impregnated body is wound before the resin becomes a semi-hardened state. When turned, the thermosetting resin that has entered the helical grooves 10c...10c is absorbed into the impregnated body and the molded article FR
This is because the spiral protrusions 1b...1b in the P pipe 1 tend to have an incomplete shape, that is, a moth-eaten protrusion without resin.

Furthermore, the work of forming a semi-hardened thermosetting resin layer on the outer surface of the inner mold body 10a is performed by fixing the inner mold 10 and applying the layer to the upper side (1/4 part of the entire circumference). A process of applying an uncured thermosetting resin layer to form a coating layer 13, and then rotating the inner mold 10 by 1/4 turn with this layer semi-cured to further form a coating layer 13. This is done by repeating. Finally, an FRP layer, that is, a wound layer 1 is placed on the thermosetting resin layer formed all around the inner mold 10.
4 and finish it into a molded product.

Next, as shown in FIG. 6, after the core molds 11 and 12 are removed from the hollow part 10d of the inner mold 10, one end of the core molds is connected to a vacuum pump 17 with plugs 15 and 16 attached to both ends of the inner mold. to reduce the pressure inside the hollow part 10d. When the pressure inside the hollow portion 10d is reduced in this manner, the internal pressure becomes lower than the external pressure, and the inner mold 10, which is a hollow rubber body, elastically contracts and deforms in accordance with the differential pressure. As a result, the outer surface of the inner mold, which was in close contact with the inner surface of the molded product, is sufficiently peeled off from the inner surface of the molded product.

Furthermore, after the inner mold 10 and the molded product are separated at their interface in this way, both ends of the inner mold 10 are twisted in opposite directions, or one side is twisted, as shown in FIG. Secure it and twist the other end. At this time, the rubber inner mold 10 becomes small in diameter, as if it had been wrung out from a rag, so the inner mold 10 is in that state.
The inner mold 10 can be easily removed from the molded product by opening one end of the inner mold 10 and pulling it out from the other end as shown by the arrow in the figure. As a result, the FR is completely separated from the inner mold 10.
P tube 1 is obtained.

[0024] According to the above configuration, the inner mold 10
is constituted by a rubber hollow body having a predetermined elasticity, and spiral grooves 10c...10c are formed on the outer surface of the body 10a.
is provided, so by using this inner mold 10, F having spiral protrusions 1b...1b on the inner surface can be formed.
RP pipe 1 can be molded, and FRP can be formed after molding.
The operation of removing the inner mold 10 from the tube 1 can be easily performed by twisting the inner mold.

The rubber inner mold 10 also has helical grooves 10c...10 formed on the outer surface of the body at the time of manufacture.
Not only can the forming process of c be easier than when the groove is made of other materials, but also the groove has a complex cross-sectional shape, such as a keyhole shape, which requires forcible extraction by deforming the inner mold. It can also be applied to After demolding, by releasing the torsional force on the inner mold 10, the inner mold 10 easily returns to its original shape due to its elasticity. Therefore, using the inner mold 10 that has returned to its original shape, F
RP tubes can be molded.

In this example, the coating layer 13 was formed on the outer surface of the body by rotating the inner mold 10 about 1/4 of the entire circumference, but in other examples, the coating layer 13 could be formed while rotating the inner mold. Apply an uncured thermosetting resin layer from one end to the other,
Thereafter, it is possible to cure the resin layer to a semi-cured state by irradiating it with an ultraviolet lamp, and subsequently form a wound layer on the outer surface of the semi-cured resin layer.

In the FRP pipe 1 shown in the figure, the protrusions 1b...1b provided in a spiral shape have an inverted V-shaped cross section. Even if the cross section is semi-circular or the cross section is keyhole-shaped, it can be molded with the same structure as above, and the number of protrusions is not limited to eight as shown in the example. Furthermore, not only continuous helical shapes as shown in the figure, but also non-continuous shapes can be molded by the method of the present invention. In that case, it goes without saying that the shape and number of spiral grooves or protrusions to be provided on the outer circumferential surface of the body of the inner mold correspond to the shape and number of spiral grooves, etc. of the FRP pipe to be molded.

[0028]

As described above, according to the present invention, since a rubber hollow body is used as the inner mold for FRP pipe molding, FRP
After the tube is formed, the inner mold automatically returns to its pre-molding shape, so that it can be used repeatedly, and the materials and costs required for manufacturing the inner mold can be reduced accordingly.

In addition, in the rubber inner mold of the present invention, the outer surface of the body can be processed to relatively easily form a helical groove on the surface, and moreover, it is possible to form a helical groove on the outer surface of the body relatively easily, and it is also possible to form a complicated keyhole shape that requires forced punching. There is an advantage that even a helical groove having a cross-sectional shape can be formed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an FRP pipe with an inner helical projection manufactured according to an embodiment of the present invention.

FIG. 2 is a partial vertical sectional view of the FRP pipe.

FIG. 3 is a partially omitted perspective view illustrating the inner mold for forming an FRP pipe according to an embodiment of the present invention.

FIG. 4 is a partial vertical sectional view showing a state in which a core mold is inserted into the inner mold.

FIG. 5 is a partial longitudinal cross-sectional view showing a state in which a coating layer and a wound layer are formed by hand-laying up an uncured thermosetting resin in the inner mold.

FIG. 6 is a partial vertical sectional view showing a state in which the pressure inside the hollow part of the inner mold is reduced.

FIG. 7 is a partially cutaway perspective view showing a state in which the inner mold is removed from the FRP pipe after forming the pipe.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Molded product (FRP pipe), 1b... Helical projection on the inner surface of the molded product, 10... Inner mold, 10a... Body part,
10d...Hollow part, 10c...Spiral groove, 13...
- Coating layer, 14... winding layer.

Claims (2)

[Claims] Claim 1: An inner mold used for molding FRP pipes, which is composed of a hollow rubber body having a predetermined elasticity, in which the inner mold part of the molded product is formed in the body, and An inner mold for forming an FRP pipe, characterized in that a groove extending in a spiral shape is provided on the outer peripheral surface of the body. [Claim 2] FRP using the inner mold according to Claim 1
A method of forming a tube, in which a coating layer is formed by coating the body of the inner mold with an uncured thermosetting resin made by kneading glass fiber so that the surface is flush. After the thermosetting resin in the helical groove in the body becomes semi-hardened, a resin-impregnated body made by impregnating roving, glass cloth, net, or nonwoven fabric with the thermosetting resin is applied. A wound layer is formed by winding it around the surface of the coating layer, and after these layers are cured at room temperature or by heating to form a molded product, the hollow part of the inner mold is depressurized and the outer peripheral surface of the inner mold and the molded product are formed. An FRP pipe using an inner mold for molding an FRP pipe, which is characterized in that the inner peripheral surface of the product is peeled off, and then the inner mold is twisted from both ends and then pulled out from the molded product to remove the mold. Molding method.