JPH047974B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reaction injection molding method.
More specifically, a method of molding a reactive liquid resin molding material using a mold made of fine particles, such as sand, mixed with or coated with a binder. It is related to.

[Conventional technology and its problems]

Along with the development of industry, many synthetic resins have been developed, and the molding methods for them are extremely diverse, but most of them are molded by injection molding using a mold.

Recently, molding methods such as reaction injection molding (hereinafter sometimes referred to as the RIM method) have come to be used for molding large parts such as automobile bumpers.

As the RIM method, urethane-based material and polyamide-based material molding methods are generally known, but these two-component reaction molding methods require less pressure on the mold and therefore less cost for the mold, but they require a larger mold. When molding something, the cost required for a mold is a large burden, and there are limits to the size of the mold that can be created due to limitations in processing machines and the like.

Therefore, a method of adding a binder to fine particles such as sand and molding it using a mold obtained can be considered, but since the viscosity of molding materials for reaction injection molding is extremely low, the molding resin The material penetrates between the sand grains and cannot be used as a mold.

[Purpose of the invention]

The present invention provides a method for molding a reactive liquid resin molding material using a mold manufactured using fine particles mixed with or coated with a binder without using a mold.

[Structure of the invention]

The present invention involves manufacturing a mold using fine particles mixed with or coated with a binder, and then injecting a reactive liquid resin molding material into the mold with a synthetic resin film tightly adhered to the cavity surface of the mold. This is a method for molding a reactive liquid resin molding material, which is characterized by subjecting it to reaction solidification.

The present inventor discovered that since two-component reaction injection molding methods such as the RIM method require less pressure on the mold, the conventional method involves coating sand with a small amount of resin and then molding it into a certain mold. shell mold method to produce
It was discovered that a reactive liquid resin molding material could be injection molded by using a mold manufactured by a self-hardening resin sand casting method, etc., with a synthetic resin film adhered to the cavity surface of the mold. It has arrived.

The mold used in the present invention is made by adding a binder to fine particles of sand or the like, uniformly mixing and coating the mixture, forming it into a block shape, curing it, and grinding it with a grinder or the like to form a mold of a predetermined shape. In this case, if the cutting is performed by a grinder having an NC-controlled feeding device or by a robot, a mold having a predetermined shape can be obtained without manual intervention through program control.

Further, as in the case of casting, a mold having a predetermined shape can also be obtained using a wooden mold or the like.

If the mold thus manufactured is used as is as a mold for reaction injection molding, the resin liquid will penetrate between the sand grains, so in the present invention, a synthetic resin film is preferably softened by heating on the cavity surface. Although EVA is used, any synthetic resin film that can be used may be polyethylene vinyl synthetic resin-covered film, etc., as long as it has a large elongation when heated. sell.

Next, the present invention will be explained based on the drawings.

As shown in Fig. 1, a mold 1 made by carving a block made of microwave coated sand in which fine grains of sand or the like are coated with a binder is placed in a frame 2 equipped with a nozzle 5, and the cavity of the mold is The synthetic resin film 3 is stretched over 8 surfaces, heated with a burner 4 or the like to an appropriate temperature, for example, 80°C to 90°C (in the case of EVA), and then evacuated from the nozzle 5 with a vacuum pump. As shown in Figure 2, the film 3 is brought into close contact with the cavity surface. Next, as shown in FIG. 3, the upper mold 1' manufactured in the same manner is set on the lower mold 1, and after tightening with bolts 6, etc., the upper mold 1 is placed while continuing to exhaust air from the nozzles 5 and 5'. A two-component reaction type resin molding material is injected into the cavity 8 from the injection port 7 provided at 1, and is reacted and solidified.

As the two-component reaction type resin molding material used, urethane-based materials and polyamide-based materials are used.

Depending on the type of resin molding material or film used, the molded product may adhere to the film 3 and cannot be peeled off. Therefore, the film may be coated with a release agent in advance, or a film laminated with films with good release properties may be used. It is necessary to spray a release agent after using the film or after bringing the film into close contact with the cavity. As the mold release agent, commercially available ones such as silicone-based ones can be used.

In the above explanation, a method was explained in which the synthetic resin film was softened by heating and then brought into close contact with the cavity surface. However, depending on the thickness of the film, it is also possible to bring it into close contact without heating, and If an adhesive is applied to the contact surface with the cavity, the film can be pressed onto the cavity surface by pressing the film from above instead of by vacuum evacuation.

In the case of the present invention, by controlling the thickness of the film, the unevenness of the particles is hidden by the film, and a beautiful surface can be obtained, and it is also possible to manufacture large structures such as large-capacity tanks and large-diameter pipes. This also makes it easier to insert reinforcing materials such as steel materials.

Furthermore, for those that require a core, a core with a synthetic resin film adhered to the surface can be used.

[Brief explanation of drawings]

1, 2, and 3 are drawings for explaining the method of the present invention. 1,1'...Mold made of fine particles and binder, 2...Frame,
3...Synthetic resin film, 4...Burner, 5,5'
...Nozzle, 8...Cavity.

Claims (1)

[Claims] 1. After manufacturing a mold using fine particles mixed with or coated with a binder, a reactive liquid resin is molded into the mold with a synthetic resin film tightly adhered to the cavity surface of the mold. A method for molding a reactive liquid resin molding material, characterized by injecting a material and causing it to react and solidify. 2. Claim 1, which uses a mold manufactured using fine particles mixed with or coated with a binder and a synthetic resin film adhered by suction from the opposite side of the cavity surface with a vacuum pump. A method for molding the reactive liquid resin molding material described above. 3. A method for molding a reactive liquid resin molding material according to claim 1 or 2, which uses a mold in which a synthetic resin film is heated and softened and then brought into close contact with the cavity surface. 4. The reactive liquid according to claim 1, 2, or 3, which uses a mold in which a mold release agent is coated on a synthetic resin film surface that is closely adhered to the cavity surface of the mold. Molding method for resin molding materials.