JPS61202827A - Manufacture of hollow resin molding - Google Patents

Abstract

PURPOSE:To enable to discharge a core mold in a short period of time by contriving molding of a precise hollow product, by a method wherein a core made of resin inside of which is filled with substance such as sand or iron dust is inserted into a mold and the skin is molded on an external circumferential part of the core through injection molding. CONSTITUTION:An open part 3a at one side end of a core material 1 is closed with a plug 4a, a powdery filler 2 such as sand or iron dust is pressed in the inside of the core material 1 through an open part 3b at the other side end so as not to leave a gap behind, the end open part 3b is closed with a plug 4b and a core 5 made of resin is formed. Then the core 5 made of the resin is inserted into a cavity of a mold 6 for skin mold surface and the skin 8 based on injection molding is formed by fixing the core 5 by fitting parts 7a, 7b with the mold. As for the resin for the skin 8, thermoplastic resin such as nylon or polyester is appropriate and it is desirable to make the fusion point of the same is higher than that of the core material 1 and to make quality of the same identical with that of the core material. A hollow molded article is obtained by a method wherein cylindrical end parts 9a, 9b of a product material 9 is cut off along flange parts 10, 11 of the skin and the filler 2 in the inside of the core material 1 is pulled out.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing resin blow molded products such as pipes, joints, containers, etc. It is used for manufacturing hollow shaped products.

(Prior art) As a prior art related to the present invention, Japanese Patent Application Laid-Open No. 58-2129
There is a publication entitled No. 21 "Method for molding plastic hollow molded products," and this method for molding hollow molded products uses a heat-melting substance (for example, paraffin, etc.) and sand.

After forming a core mold with a mixture of a filler such as cement or metal powder, and forming a plastic molded article around the outer periphery of the core mold, the core mold is heated and softened so that the filler inside the plastic molded article is heated and softened. This is a molding method that produces a plastic hollow molded product by removing a certain core mold.

(Problems to be Solved by the Invention) However, in the above molding method, in order to remove the core mold made of a heat-melting substance and a filler, a band heater is provided at the axis of the core mold to melt the core mold, or the core mold is melted. After melting the area around the band heater, hot air or steam is injected into the cavity to melt it.

However, the method described above has the problem that the core mold is melted and removed using a heat source such as heat transfer or hot air, so a heat source is required and melting takes time.

The present invention allows accurate molding of hollow products using a core mold,
To provide a manufacturing method capable of removing a core mold in a short time without requiring a heat source for removing the core mold.

[Structure of the invention]

(Means to solve the problem) The technical measures taken to solve the above technical problem are:
It is as follows. That is, a hollow core material is formed by suction molding or extrusion molding, a cylindrical open part is provided in at least one of the cough core materials, and powder or granular material such as sand or iron powder is placed inside the hollow part. A resin core filled with is inserted into a mold, an outer skin is formed on the outer periphery of the core by injection molding, the resin product and the core are integrated into a product material, and one end of this product material or Powder or granular material is discharged from both ends to produce hollow resin products.

(effect) The technical means are as follows.

After suction molding or extrusion molding, a core material with a complex shape with an undercut can be easily made, and a resin core made by filling the core material with sand, iron powder, etc. without any gaps can be molded. Several hundred ktr/c by injection molding machine
Even if the thermoplastic resin that will become the outer shell is injected under the strong pressure of It is held in a mold, and the outer skin and resin core are melted and solidified to form a product material, and by cutting the ends and easily discharging the filler, a resin blow molded product is manufactured. Since the resin serving as the outer skin does not come into direct contact with the filler, there is no so-called seizure phenomenon caused by powder, and a resin hollow molded product with accurate dimensions can be manufactured.

(Example) Examples of the present invention will be described below.

1 is a core material obtained by blow molding a thermoplastic resin such as nylon, polyester, or polyethylene. A composite agent containing a reinforcing agent and a filler such as glass fiber and talc can also be used in the material. Thickness 1-10
The size of a crane can be molded, but 1 to 3 cranes is particularly good.

In addition to the above-mentioned suction moldability, it is also possible to extrude a similar material into a pipe shape and then bend it, but in this case, the shape is more complicated than with the suction molding method. There are cases where this is not possible.

Next, the open part 3a at one end of the core material 1 is closed with a plug 4a,
Powdered filler 2 such as sand or iron powder is packed into the core material 1 from the open part 3b at the other end so that no gap remains, and the end 3b is closed with a plug 4b to form a resin core 5. do.

Next, the resin core 5 is inserted into the cavity of the outer skin molding die 6, and fixed with the attachment parts 7a and 7b to the die.

During injection molding using a molding machine, resin pressure of approximately several hundred kg/c+d is applied to 7a and 7b, so it is necessary to perform sufficient mold matching to ensure sealing performance. The surfaces of the molds 7a and 7b are made of silicone rubber.

It is effective to use an elastomer such as Teflon.

A thermoplastic resin such as nylon or polyester is suitable as the resin for forming the outer skin 8 by injection molding, and it is a resin with a higher melting point than the core material 1, and it is preferable to use the same material in consideration of the adhesiveness of the core material. is desirable.

The resin for the combination of the core material and the outer skin is nylon-nylon, polyester-polyester, or nylon.
A combination of polyethylene-polyester or nylon is preferred.

Next, the cylindrical ends 9a and 9b of the product material 9 are cut along the flange portions 10.11 of the outer skin, and the filling material 2 inside the core material is extracted using a vibrator or the like, thereby forming the resin blow molding 12. It's something you get.

〔Effect of the invention〕 The present invention has the following unique effects.

1. Although the core material uses fillers such as sand and iron powder, it can be used repeatedly because it is not subject to chemical or thermal changes.

2. There are some products that solidify fillers such as sand and iron and use them directly as core materials (Japanese Patent Application Laid-open No. 83609/1983).
In this method, the filler adheres to the inner surface of the hollow molded product, making sand removal difficult and resulting in roughness of the inner surface. However, in this example, the inner surface of the pre-molded core material is used as is. No problem at all.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the core material of this example, and the second
The figure is a cross-sectional view of the core material filled with powder, Figure 3 is a cross-sectional view of the resin core held in the mold, Figure 4 is an external view of the resin blow molding material, and Figure 4 is a cross-sectional view of the core material filled with powder. FIG. 5 is a perspective view of the resin hollow molded product. DESCRIPTION OF SYMBOLS 1... Core material, 2... Powder, 5... Resin core, 6... Mold, 8... Outer skin, 12... Resin hollow molded product

Claims (1)

[Claims] In a method of manufacturing a hollow molded product by injecting a thermoplastic resin into a mold, a hollow core material is molded by a suction molding method or an extrusion molding method, and inorganic fine particles are added to the hollow interior of the core material. The core is filled into a resin core, the core is inserted into a mold, a thermoplastic resin is injection molded around the outer periphery of the core to form an outer skin, and the outer skin and the resin core are integrated. A method for producing a resin hollow molded article by discharging the inorganic fine particles.