JPS62132620A - Molded member made of plastic and its manufacture - Google Patents

Abstract

PURPOSE:To enable the molded member to become rigid enough in the surface and contain a cave by one time molding, by a method wherein one-side mold is moved in an extracting direction of the mold while foamed plastics is under uncured state and gasification of a foaming agent is accelerated. CONSTITUTION:Foamed plastics injected into a mold through a molding machine by compounding with a foaming agent is expanded in a molding chamber (d). When one-side movable mold (b) is moved in the direction of an imaginary line, while the foamed plastics is under uncured state in the inside of a thick part 3 and a cave part 2 is being formed by gas of the foaming agent under a stage wherein a skin layer 4, cooled by welding to a mold surface with pressure is being formed, formation of the cave part 2 is accelerated and expanded. When pressure gas is supplied through a supply pipe 6 at a formation stage of the cave 2, the formation is accelerated. With this construction, one time injection molding process is capable of forming the continuous cave 2 within a thick part of an injection molded member 1 by running along about a surface form.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a plastic material in which a foaming agent is put into a plastic material and injection molded in a mold to form a cavity inside the molded product. Concerning shapes and their manufacturing methods.

Conventional technology Conventionally, plastic molded objects with a cavity formed therein have been made into one container, such as a blow-molded container, or an outer container and an inner container separately molded by injection molding. (For example, Japanese Utility Model Application Publication No. 52-157377, Japanese Utility Model Application Publication No. 54-14585)
Publication No. 1).

Problems to be Solved by the Invention The former, which is formed using the blow molding method, has a limitation in terms of use in that it is not suitable for structures that are subject to large loads because the rigidity of the container body is weak. In addition, the latter method, in which two separately molded vessels are combined, has the disadvantage of high costs because separate molds are used for the inner and outer parts, and an operation is required to combine and join the two types of vessels. Therefore, it is required to produce a plastic molded product with sufficient surface rigidity and a continuous cavity within the wall thickness that roughly follows the surface shape through two rounds of molding. was.

Means for Solving the Problems Therefore, the present invention provides an injection molded foamed plastic body having a hollow portion in its thick wall portion that is continuous approximately along the surface shape, and a method for manufacturing the same. As,
By appropriately moving one of the molds in the drawing direction when the thick wall part of the foamed plastic injected into the mold is in an unsolidified state, gasification of the foaming agent contained in the material is promoted. The present invention provides a method for manufacturing a plastic thermoformed body, characterized in that a continuous cavity is formed in the thick portion of the injection molded body, substantially following the surface shape.

Function As described above, in the present invention, a cavity is formed within the wall thickness by injection molding of foamed plastic, so that the surface has sufficient rigidity and a cavity is provided inside by molding twice. A plastic molded article can be obtained, and the above-mentioned conventional drawbacks can be eliminated.

Example Embodiments of the present invention will be described below with reference to the drawings.

In Figure 1, (1) is an injection molded product made of foamed plastic, and (2) is a thick part (3) of the injection molded product (1).
) is formed and continues along the surface shape of the mold, (4) is the foamed plastic injected into the mold, which is brought into pressure contact with the mold, cooled and solidified into a dense hard structure; The skin layer (5) forming the surface layer of the injection molded article (1) is a foamed layer with a coarse structure interposed between the skin layer (4) and the cavity (2).

FIG. 2 schematically shows an example of the manufacturing apparatus for the injection molded article (1) constructed as described above, in which (a) shows a fixed mold connected to a nozzle of an injection molding machine (not shown); (b) is a movable mold that coaxially faces the fixed mold fal and is movable in the direction of the imaginary line in the figure; (cl is another movable mold that forms the outer peripheral surface of the molded body; (6) ) inserts the fixed mold fat into the mold chamber fcl formed by each mold fa) fbl fcl.
This is a pressurized gas supply pipe inserted so as to protrude inward and reach the thick walled part (3) of the foamed plastic molded in the mold chamber fd).

The manufacturing method of the present invention using this manufacturing apparatus will be described below. The foamed plastic mixed with a foaming agent and injected into the mold from the molding machine expands in the mold chamber ((11). At the stage where the skin layer (4) is being formed, which is cooled by pressure contact with the foaming agent, the thick portion (3) is in an unsolidified state and the foaming agent gas is forming the cavity portion (2). Sometimes, when one movable mold fbl is moved in the direction of the phantom arrow, the formation of the primary cavity (2) is promoted and expanded.Furthermore, during the formation stage of this cavity (2), pressurized gas is supplied to the supply pipe. (
6), its formation is further promoted.

Further, the cavity (2) may be filled with a heat storage medium such as potassium chloride or sodium chloride depending on the purpose.

Effects of the Invention According to the present invention configured as described above, a hollow portion that continues along the shape of the surface is formed within the thickness of the injection molded product whose surface is covered with a dense and hard skin layer. Since this is done in one injection molding process, it is possible to produce at a low cost, and also to obtain a plastic molded article using foamed plastic as a raw material, which has great strength and has sufficient cavities.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a partially cutaway perspective view of a molded body, and FIG. 2 is a partially cutaway sectional view of an apparatus used in the manufacturing method of the present invention. 1. Injection molded body, 2. Cavity portion, 3. Thick wall portion, 4.
- Skin layer, 5... Foaming layer, a... Fixed mold, b. C: Movable mold, d: Mold chamber, 6: Supply pipe.

Claims (4)

[Claims] (1) An injection-molded foamed plastic article, which has a hollow portion in its thick wall portion that continues approximately along the surface shape. (2) The plastic molded article according to claim 1, wherein the cavity is filled with a heat storage medium such as potassium chloride or sodium chloride. (3) When the thick part of the foamed plastic injected into the mold is in an unsolidified state, one of the molds is appropriately moved in the drawing direction to promote gasification of the foaming agent contained in the material. A method for producing a plastic molded article, characterized in that a cavity is formed in a thick wall portion of the injection molded article, the cavity continuing substantially along the surface shape. (4) A gas supply pipe that reaches the thick wall of the foamed plastic from the outside is inserted into the mold into which the foamed plastic is injected, and when the mold is moved in the drawing direction, the gas is supplied from the supply pipe. 4. The method of manufacturing a plastic molded article according to claim 3, wherein the formation of the cavity is promoted by the supplied pressurized gas.