JPH0335095B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing moldings such as side moldings attached to the side of an automobile body and bumper moldings attached to a bumper. The present invention relates to a method of manufacturing a molding having a molding.

[Prior Art] In recent years, there has been a demand for lighter weight automobiles, and there is also a desire for lighter moldings. A common way to reduce the weight of a molding is to make the inside hollow. However, in the case of soft moldings, it is often difficult to maintain the shape if the molding is hollow. Therefore, a soft molding having a foam inside the molding has been developed.

By the way, in order to manufacture such a molding that has a foam inside, conventionally, a skin resin and a foamed resin are extruded in two colors, the foaming agent is decomposed in the cylinder of an extruder, and then released at the exit of the die. This is done by extrusion foam molding, which involves foaming under pressure, or by injecting foamed resin into a mold and foaming it by heating with high frequency or the like.

[Problem to be solved by the invention] In the conventional extrusion foam molding, the shape retention of the skin cannot be maintained if the foam is highly foamed, so the limit is a foam with a specific gravity of about 0.8 to 1, and weight reduction is not possible. There was a limit to this. Further, the foam is exposed at the ends of the obtained molded body, and in order to treat the ends, only the ends are formed by injection molding or the like. However, in this case, processing of the boundary between the injection molded part and the extrusion molded part is troublesome, takes many man-hours, and has the disadvantage that the appearance is not good. Also, in heat foam molding,
If the foam is made to be highly foamed, the smoothness of the surface will be impaired, so it is only possible to obtain a foam with a specific gravity of around 1, and there is a limit to the weight reduction.

The present invention has been made in view of the above problems, and provides a method for easily manufacturing a molding having a highly foamed material inside.

[Means for Solving the Problems] The method for manufacturing a soft molding of the present invention is to place a heat-softened cylindrical or pair of sheet-like soft resin material in a mold, supply gas to the inside, and apply gas pressure. A first molding step of forming a skin body whose outer surface has a predetermined molded shape and a hollow portion by blow molding to expand a soft resin material; A second step of injecting resin and foaming the foamable resin within the hollow portion to form a resin foam that fills the hollow portion.
It is characterized by consisting of a molding process.

The first molding step is a step of molding a skin body having a predetermined molding shape from a soft resin material. Here, as the soft resin material, soft polyvinyl chloride resin, polyethylene, ionomer-modified polypropylene, etc. can be used.

This first molding step is performed by blow molding. That is, a cylindrical parison or a pair of sheets made of the above-mentioned soft resin is placed in a blow molding die in a thermally softened state. At this time, at least both ends are sandwiched between molds and closed, and a pressurized gas is introduced into the inside thereof. Therefore, the softened soft resin material expands due to the gas pressure and is pressed against the mold surface to form a skin body having a hollow portion. Compressed air is usually used as this gas.

The most distinctive feature of the present invention lies in the following second molding step. In conventional general blow molding, molding is completed only in the first molding step, but if a soft resin material is formed into a hollow shape, it may have poor shape retention and may deform. Therefore, in the present invention, with the skin body placed in a blow mold, foamable resin is injected into the hollow part of the skin body and foamed, thereby filling the hollow part with the resin foam. This reliably prevents the skin from deforming, and the skin is further pressed against the mold surface by the foaming pressure, resulting in a more precise molding.

As the foamable resin to be used, polyurethane resin, polystyrene, polyethylene, polypropylene, etc. can be used. The foaming ratio can be high because the skin is prevented from deforming, for example, the specific gravity is 0.05 to 0.6.
It can be made into a foam. In addition, as a foaming method, conventional methods such as adding a foaming agent such as chlorofluorocarbon, methylene chloride, or butane, or using a reaction product gas such as carbon dioxide produced by the reaction of water and isocyanate may be used. Can be adopted.

Note that it is convenient to inject the foamable resin through the gas injection hole during blow molding.

[Operations and Effects of the Invention] That is, according to the method for manufacturing a soft molding of the present invention, since the skin body is formed by blow molding, the end treatment can be performed at the same time as molding, and the number of man-hours can be significantly reduced. Improves appearance. Then, foam molding is performed in the hollow part without removing the skin from the mold, and the hollow part is filled with resin foam.
A molding with a precise shape is obtained without deformation of the skin body. Furthermore, the first molding step and the second molding step can be performed continuously, resulting in excellent productivity.

In addition, since foam molding is performed in a blow mold, the resin foam can be highly foamed, and an extremely lightweight molding can be manufactured.

Furthermore, since the skin is formed by blow molding,
As shown in the examples, the bright layer, the clip seat, etc. can be easily formed integrally, and from this point of view as well, the number of man-hours can be significantly reduced.

[Example] This will be explained in detail below using examples.

(First molding process) A sheet material made of soft vinyl chloride resin is
After being heated and softened, the entire periphery was sandwiched between molds and welded, and placed in a blow molding mold. Then, pressurized air is introduced between the two sheets of material at a pressure of 6 kg/cm ² and blow molding is performed by pressing the sheet material against the mold surface, so that the outer surface forms the specified mold as shown in Figure 2. A skin body 1 having a shape and having a hollow portion 10 was molded. At this time, pressurized air was introduced from the back side of the molding, and both ends of the molding were formed into a predetermined bag shape.

(Second molding step) Next, with the skin body 1 placed in the blow mold, a foamed resin material made of polyurethane resin to which a foaming agent has been added is injected through the hole into which pressurized air is introduced, and the temperature is raised to approximately 40°C. The foamed resin material was foamed by heating for 5 minutes. After the foamed resin material was foamed and solidified, the mold was opened and the molded product was taken out.

As shown in Fig. 1, the obtained molded product has a resin foam 2 densely filled inside the skin 1, and the specific gravity of the resin foam 2 is 0.3, so that a lightweight molding can be obtained. Ta. The terminal part of the molding was integrally molded with the other parts, giving it an excellent appearance quality.

According to the manufacturing method of this embodiment, it is also possible to mold the skin body 4 having the glitter layer 3 made of aluminum as shown in FIG. 3 in the first molding step.
In this case, the glitter layer 3 can be integrally molded by placing the glitter layer 3 in a blow mold in advance and blow molding the skin body 4 in that state.

Furthermore, as shown in FIG. 4, it is also possible to form a skin 7 of a molding for clipping, which has a clip seat surface 6 in which an insert 5 is embedded. In this case as well, the insert 5 can be easily integrated by blow molding while holding it on the mold surface in advance. Then, by foaming the foamable resin within the skin body 7 in the same manner as described above, a lightweight molding can be easily manufactured.

[Brief explanation of drawings]

1 and 2 are diagrams relating to a manufacturing method according to an embodiment of the present invention, in which FIG. 1 is a partial perspective view showing a partial cross section of the obtained molding, and FIG. 2 is a diagram showing the first molding process. FIG. 3 is a partial perspective view showing a partial cross section of the obtained skin body. FIGS. 3 and 4 are cross-sectional views showing other examples of skin bodies obtained by the manufacturing method of the example. 1, 4, 7... Skin body, 2... Resin foam, 3
... Bright layer, 5 ... Insert, 6 ... Clip seat surface, 10 ... Hollow part.

Claims (1)

[Claims] 1. The outer surface is formed by blow molding, in which a heat-softened cylindrical or pair of sheet-shaped soft resin material is placed in a mold, gas is supplied to the inside, and the soft resin material is expanded by gas pressure. a first molding step of molding a skin body having a predetermined molding shape and a hollow portion, and a foaming resin is injected into the hollow portion with the skin body placed in the mold, and the foaming is performed within the hollow portion. a second molding step of foaming a flexible resin to form a resin foam that fills the hollow portion.