JPH0242048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention eliminates the need to perform burr treatment on the through-hole portion of the molded product when molding a foamed resin molded product having through-holes by reaction injection molding, and improves the shape of the through-hole. The present invention relates to a molding method for obtaining a strong and beautiful foamed resin molded product with good quality.

The reaction injection molding method is a method to obtain a resin molded product of a desired shape by mixing two or more reactive foam resin materials immediately before injection, injecting the mixture, and then reaction-curing it in a mold. Computer housings, television cabinets, automobile parts, etc. have been obtained by this method. Among these foamed resin molded products, it is particularly necessary to form through holes for loopers, switch parts, cathode ray tube parts, etc. in computer housings and the like. Conventionally, when forming a foamed resin molded product having such a through hole, a mold A as shown in FIGS. 3 and 4 has been used. The mold A shown in FIG.
Female mold B provided with a protrusion C for forming a through hole
and a male mold D that abuts on the female projection,
This male die D is brought into contact with the protrusion C of the female die B to seal the mold A, and the reactive foam resin material is injected into the cavity and foamed. According to this method, the structure of the mold is simple, so the manufacturing cost is low and the manufacturing period is short. However, since the reactive foam resin material has good initial fluidity, the reactive foam resin material gets into the small gap between the contact surface between the protrusion C of the female mold B and the male mold D, and this becomes a burr. The drawback was that the through holes had to be burred after the molding. In addition, the mold A shown in FIG.
A recess E into which the projection C of the female mold B fits is provided in the male mold D, and the mold A is sealed by fitting the upper part of the projection C of the female mold B into the recess E of the male mold D.
After the reactive foam resin material is injected and foamed and the mold is released, the burr that has entered the gap between the recess E of the male mold D and the upper part of the projection C is cut off. This method cuts the burrs that protrude almost perpendicularly from the surface of the molded product, so it is relatively easier to remove burrs than the former method. Since it is necessary to insert the mold into the mold, the manufacturing cost of the mold increases, the manufacturing period becomes longer, and the disadvantage is that after the mold is released, the part corresponding to the upper part of the protrusion must be cut off, which is an additional process. It was hot.

Furthermore, in all of the conventional examples, the high-density foam skin layer, ie, the skin layer, formed on the surface of the edge portion of the through hole is destroyed by the burr treatment, resulting in a problem of deterioration of the surface strength and appearance.

The present invention uses a mold with a special structure, eliminates the need to burr the through holes of the molded product, and
A foamed resin molded product in which the through hole is formed in a good shape and the through hole part is strong and beautiful can be easily obtained by reaction injection molding, and its gist is This method uses a mold consisting of a mold provided with a projection for forming a through hole, and a mold provided with a soft material made of silicone rubber or the like at a position opposite to the projection. Foaming characterized by sealing a mold by pressing the soft material of the other mold against the projections of the mold, and injecting a reactive foam resin material into the cavity of the sealed mold to cause foaming. It is in the molding method of resin molded products.

An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a mold used in the method of the present invention, and FIG. 2 is an enlarged sectional view of a portion of the mold.

In the present invention, a foamed resin molded article having through holes, such as a computer housing, is molded by reaction injection molding, and a mold 1 as shown in FIG. 1 is used during the molding. The molding die 1 is exemplified as a two-part mold consisting of a female die 11 as one die and a male die 12 as the other die. By closing and sealing the female die 11 and the male die 12, a cavity 2 having the same shape as the desired shape of the product to be molded is constructed. One of the molds, the female mold 11, is provided with projections 3 for forming through holes in the molded product. In addition, a soft material 4 is disposed on the other mold, the male mold 12, at a position facing the protrusion 3 of the female mold 11. As the soft material 4, silicone rubber, soft synthetic resin,
Various materials such as rubber can be used. Furthermore, in order to arrange the soft material 4 such as silicone rubber on the male mold 12, a groove may be formed at a position facing the protrusion 3 of the female mold 11, and the soft material 4 may be directly fitted into the groove. death,
The metal plate to which the soft material 4 is attached may be attached to the male mold 12 at a position facing the protrusion 3 using a magnet. The mold 1 is sealed by pressing the soft material 4 of the male mold 12 against the projections 3 of the female mold 11. Then, as shown in FIG. 2, the protrusion 3 of the female mold 11 and the soft material 4 of the male mold 12 come into close contact.
Depending on the degree of pressure contact, the soft material 4 around the upper end portion of the protrusion 3 will swell toward the cavity 2 side.
A predetermined amount of a reactive foamed resin material (not shown) is injected into the cavity 2 of this closed molding mold 1 and foamed. Reactive foam resin materials include rigid, semi-rigid, flexible urethane foam, epoxy foam,
There are various materials such as acrylic foam. When this material is injected and foamed, it fills the cavity 2 and a foamed resin molded product having the shape of the cavity 2 is formed. At this time, the protrusion 3 of the female mold 11 and the male mold 12
The reactive foam resin material does not enter between the soft material 4 and the soft material 4. Thereafter, the male mold 12 is released from the female mold 11, and a foamed resin molded product having the shape of the cavity 2 in which the through hole is formed by the protrusion 3 of the female mold 11 is molded.

As described above, in the present invention, a molding die includes a mold provided with a protrusion for forming a through hole, and a mold provided with a soft material made of silicone rubber or the like at a position facing the protrusion. The molds are sealed by pressing the soft material of the other mold onto the projections of one mold. In this way, the protrusions and the soft material come into close contact and the reactive foamed resin material does not get in between them, so there is no need to burr the through holes after mold release, and it is possible to form the desired shape. Through-holes can be formed accurately. In addition, unlike conventional methods, there is no burr treatment or cutting of the upper part of the protrusion, so the edge of the through hole is completely covered with a skin layer, making that part strong. Moreover, a foamed resin molded product with a beautiful appearance can be obtained. Furthermore, the mold is made of a soft material such as silicone rubber, and has various advantages such as not requiring precision machining and can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a mold used in the method of the present invention, FIG. 2 is an enlarged sectional view of a portion of the mold, and FIGS. FIG. 3 is a cross-sectional view of a mold used in the method. In the figure, 1 is a mold, 2 is a cavity, 3 is a protrusion, 4 is a soft material, 11 is a female mold, and 12 is a male mold.

Claims (1)

[Claims] 1. When molding a foamed resin molded product with a through hole by the reaction injection molding method, a mold is provided with a protrusion for forming the through hole, and a soft material made of silicone rubber or the like is placed opposite the protrusion. A mold is used, and the mold is sealed by pressing the soft material of the other mold onto the protrusion of one mold, and the soft material of the other mold is sealed. A method for molding a foamed resin molded product, characterized by injecting a reactive foamed resin material into a cavity and foaming it.