JPH09174569A - Manufacture of injection molded hollow plastic product with complex inside shape and water-soluble core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold a hollow product with a complex shape integrally by plastic injection molding by setting a water-soluble core filled with a shape holding core body which is melted or disintegrated simultaneously in a water-soluble hollow outer shell body in a molding mold. SOLUTION: When a hollow resin product with a complex inside shape is manufactured with the use of a water-soluble core 2, after the core 2 being set in a molding mold 1 leaving a cavity with a prescribed shape, a plastic molding material is injected into the cavity to mold a molding in which the core 2 is included and integrated in the mold 1. Next, when the mold 1 is opened to demold a molding and put into a water tank in which the water temperature is adjusted at a prescribed value or higher, the water-soluble outer shell body 3 of the core 2 included in the molding is melted and removed. Associated with the melting of the shell body 3, a shape holding core body 4 which has been in the shell body is released from a fixed state into pieces to be discharged easily from the inside of the molding. As a result, a hollow product the inside of which has prescribed dimensions can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic injection machine having a complicated shape, which enables a hollow product having a complicated shape such as a curved pipe, various valves, a faucet, and the like to be produced efficiently and at low cost by using plastic. The present invention relates to a method for producing a molded hollow product and a water-soluble core used for the method.

[0002]

2. Description of the Related Art Conventionally, hollow products having complicated shapes such as curved pipes such as various valves and valves and faucets have been manufactured by injection molding using a plastic material because they have an inverse tapered portion. Although it has relied on castings as something that cannot be molded, recently, instead of castings, molding of plastics is under consideration for the purpose of weight reduction and cost reduction.

However, in the plastic injection molding method, if there is a reverse taper portion or the like, it cannot be integrally molded due to a draft angle or the like. It requires a large number of molds and requires a large number of production steps, and has a problem that the strength of the bonded portion is inferior because it is not integrally molded, and further increases the production cost. There was a problem.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems in the prior art and to make hollow products having complicated shapes such as various valves, valves and faucets into plastic. High quality plastic hollow products can be produced efficiently and lightly with a small number of processes by performing integral molding by the injection molding method.Furthermore, the number of molds is small and the production cost is significantly reduced. An object of the present invention is to provide a method for producing a plastic injection molded hollow product having a complicated shape and a water-soluble core used therefor.

[0005]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, is to melt a water-soluble outer shell into a hollow water-soluble outer shell mainly made of water-soluble plastic by water. A double structure water-soluble core filled with a shape-retaining core that is melted or disintegrated when set is set in a mold for injection molding, and is formed between the mold and the water-soluble core. After injection molding a plastic molding material into the cavity, the plastic molded body in which the water-soluble core is integrated is released from the mold, and after the mold is released, the water-soluble outer shell is melted by washing with water and the shape-retaining core is melted or A method for producing a plastic injection-molded hollow product with a complex internal shape, characterized by disintegrating and removing the water-soluble core from the inside of the plastic molded body, and a hollow water-soluble plastic mainly composed of water-soluble plastic Inside the outer shell A water-soluble intermediate used in the manufacture of a plastic injection-molded hollow product having a complicated internal shape, characterized by being filled with a shape-retaining core that is melted or disintegrated when the water-soluble outer shell is melted by water. It consists of children.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the figure, reference numeral 1 denotes a mold for injection molding of a plastic valve comprising a pair of split dies, and reference numeral 2 denotes a water-soluble core formed in a predetermined shape in advance. The water-soluble core 2 is set in the mold 1 to form a cavity having a predetermined shape in the mold, and after the plastic material is injection-molded in the cavity, the molded body after the mold is finally removed. A hollow water-soluble outer shell mainly made of a water-soluble plastic such as thermoplastic polyvinyl alcohol (for example, trade name “Ekomaty AX” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), which is removed by washing with water. The body 3 is filled with a rigid shape-retaining core 4 that is melted or collapsed when the water-soluble outer shell 3 is melted by water. The shape-retaining core 4 is made of a powdery, granular, or small lump of ceramic, plastic, metal, or wood as a filler 4a and solidified with a water-soluble glue 4b to obtain a water-soluble material. It has a double structure having rigidity inside the outer shell 3.

The water-soluble outer shell 3 mainly composed of the above-mentioned water-soluble plastic is preferably dissolved in water after molding and is inexpensive and easy to process. Therefore, polyvinyl alcohol is used alone. In addition, a mixture of one or more of powders of ceramic, plastic, metal, and wood in polyvinyl alcohol is used. On the other hand, the shape-retaining core 4 always keeps the water-soluble outer shell 3 from the inside. Although it is reinforced and retains sufficient rigidity to withstand the injection pressure, it is preferable that the water-soluble outer shell 3 has a property of melting or collapsing when it is melted by water and can be provided at low cost. Powdery or granular or small lumps of ceramic, plastic,
A material obtained by solidifying one or more of metal and wood as a filler 4a with a water-soluble paste 4b is generally used.

When manufacturing a hollow resin product having a complicated inside using such a water-soluble core 2, first, the water-soluble core 2 is placed in a mold 1 in a predetermined shape. After setting, leaving a cavity for molding the valve, a plastic molding material is injection-molded in the cavity according to a conventional method to form a molded body in which the water-soluble core 2 is integrated and integrated in a mold. Next, the mold 1 is opened to remove the molded body in which the water-soluble core 2 is integrated and integrated, and the molded body 1 is placed in a water tank 10 having a water temperature of 25 ° C. or higher. First, the water-soluble outer shell 3 made of a water-soluble plastic is melted and removed from the water-soluble core 2 integrated and integrated into the core. Then, as the water-soluble outer shell 3 is melted, the shape-retaining core 4 inside the water-soluble outer shell 3 dissolves the water-soluble paste 4b, and the fixation state of the filler 4a is released. Become
The molded product 1 is easily discharged from the complicated hollow interior. As a result, a hollow product having a high-quality and complicated shape with the inside of the predetermined size is easily formed by the plastic injection molding method.

[0009]

As is apparent from the above description, according to the method of the present invention, a high-quality hollow resin product having a complicated internal shape is integrally molded by an injection molding method, thereby reducing the number of steps in the process. Can be mass-produced, and the production cost can be significantly reduced because the number of molds is reduced, and the water-soluble core according to the present invention enables the above-described production method to be appropriately carried out. In addition, the hollow water-soluble outer shell made mainly of water-soluble plastic is used because it can be thin enough to have the function of holding the shape-retaining core and the function of forming the inner surface of the molded body into a smooth surface. In addition to the small amount of resin, which has the effect of saving resources, the shape-retaining core is low-cost because it is sufficient to obtain inexpensive materials such as ceramics, plastics, metals, wood and other powdery or granular materials or small lumps. Can be provided by There is a throat various advantages. Therefore, the present invention greatly contributes to industrial development as a method for producing a plastic injection-molded hollow product having a complicated shape and a water-soluble core used for the method, which has eliminated the conventional problems.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing one example of the method of the present invention in a state where a water-soluble core is set in a molding die and a plastic material is injection-molded.

FIG. 2 is a process explanatory view of one example of the method of the present invention in a state where a molded body is washed with water in a water tank and a water-soluble core is melted and removed.

FIG. 3 is an enlarged sectional view of a main part showing an example of a water-soluble core of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Water-soluble core 3 Water-soluble outer shell 4 Shape-retaining core 4a Filler 4b Water-soluble paste

Claims (4)

[Claims] 1. A double structure in which a hollow water-soluble outer shell mainly composed of a water-soluble plastic is filled with a shape-retaining core that is melted or disintegrated when the water-soluble outer shell is melted by water. The water-soluble core of the structure is set in the mold for injection molding, the plastic molding material is injection-molded in the cavity formed between the mold and the water-soluble core, and then the water-soluble core is integrated. After removing the molded plastic body from the mold, the water-soluble outer shell is melted by washing with water and the shape-retaining core is melted or collapsed to remove the water-soluble core from the inside of the plastic molded body. A method of manufacturing a plastic injection-molded hollow product having a complicated internal shape. 2. A hollow water-soluble outer shell (3) containing a water-soluble plastic as a main material, wherein the water-soluble outer shell (3) is melted or disintegrated when it is melted by water. Shaped core
A water-soluble core for use in the production of a plastic injection-molded hollow product having a complicated internal shape, which is filled with (4). 3. The interior according to claim 2, wherein the water-soluble outer shell (3) is made of polyvinyl alcohol or a mixture of polyvinyl alcohol and one or more of ceramic, plastic, metal and wood powders. A water-soluble core used for manufacturing hollow plastic injection molded products with complex shapes. 4. A water-soluble paste material (4b), wherein the shape-retaining core (4) is made of one or more of powder, granule or small lump ceramic, plastic, metal and wood as a filler (4a).
The water-soluble core used for producing a plastic injection-molded hollow product having a complicated inside shape according to claim 2 or 3, which is solidified by the above method.