JPH06262636A - Injection molding method - Google Patents

Abstract

PURPOSE:To form a branched pipelike article by injection molding without using a mold having complicated structure by a method wherein molten resin and gas are poured from a mold portion corresponding to the end of one branched pipe in the molding of the multiply-branched pipelike article. CONSTITUTION:Resin and gas are poured from the positions of mold corresponding to the end of a multiply-branched pipelike molded article. The amount of molten resin to be poured by injection is one, which does not completely fill a cavity, but is enough to fill the cavity when pressurized gas is poured in the cavity. The pressurized gas is poured through the gas gate 2 of the mold cavity. The molten resin is forcibly spread to the terminal of the flow passage, resulting in forming continuously hollow part. After releasing, the terminal parts 3 of the branched pipe are cut, resulting in obtaining a continuous hollow pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection molding a hollow pipe-shaped molded product having a plurality of branches. The above molded product is
For example, it can be widely used as a connector for branching a fluid used for passing a fluid for heat radiation or heating.

[0002]

2. Description of the Related Art In the conventional injection molding, when a pipe-shaped molded article is injection-molded, a method of inserting an insert piece into a mold or molding by incorporating a core is known, but it is complicated. In order to form such a hollow portion, the mold structure becomes complicated and there is a practical limit. In addition, by using molten metal or water-soluble resin, the shape of the hollow part is made in advance and inserted into the mold at the time of molding, and after molding, the molten metal inside is melted or the water-soluble resin is melted to make it hollow. Although there are methods of forming a structure, these methods have a problem in that the number of manufacturing steps is increased, such that it is necessary to form a shape that becomes a hollow portion in advance.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to inject a molten resin and a gas from a mold portion corresponding to one end of one of the branched pipes in the molding of a pipe-shaped molded product having a plurality of branches. And does not require complicated mold structure,
An object of the present invention is to provide an injection molding method for a branched pipe-shaped molded product.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors found that each end of a pipe part branched into a plurality is extended from the product shape, and any one of By providing a resin injection portion and a gas injection port in the extension portion, injecting a molten resin into the cavity after gas injection in an amount sufficient to form the molded article, and by injecting a pressurized gas during the injection process, The present invention has been completed by discovering that a pipe-shaped molded product having a continuously branched interior can be molded.

That is, the present invention is an injection molding method for a branched pipe-shaped molded article, wherein a pressurized gas is applied from a pipe-shaped end portion during injection and injection of a molten resin into a branched pipe mold cavity. The present invention relates to an injection molding method for a pipe-shaped molded article, which is characterized in that a pipe-shaped product having a shape branched into a plurality of pieces is manufactured by pouring.

In the present invention, as the resin forming the hollow pipe portion, not only a general thermoplastic resin such as a general thermoplastic resin, ie, polyolefin, polystyrene, ABS resin, AS resin, methacrylic resin, fluorine-containing resin, etc. Polyamide, saturated polyester, polycarbonate
So-called engineering plastics such as those exemplified by bonnet, polyacrylate, polyacetal, polysulfone and modified polyrenylene ether can be used.

A preferred molding method of the method of the present invention will be described below. As the mold to be used, one having a structure in which resin and gas can be injected from the part corresponding to the end of the pipe-shaped molded product that is branched into a plurality of parts is used. A resin having the smallest outer diameter is preferable, but injection positions of the resin and gas are not particularly limited. In addition, the end of each pipe section is 10m longer than the size required by the product in order to cut and form a continuous pipe.
It is desirable to design the product so that m or more is long.

A thermoplastic resin melted in the cylinder of the injection molding machine is weighed in a predetermined amount using the mold as described above, and then injected into the cavity. However, the amount of this molten resin is an amount that is insufficient to completely fill the mold cavity and is sufficient to fill the cavity when the pressurized gas body is injected.

The molten thermoplastic resin is entirely injected and injected into the cavity, and a pressurized gas is supplied to the mold cavity through a gas nozzle provided in the mold before the injection is completed. Via injection into the product cavity. As the pressurized gas, it is usually preferable to use nitrogen gas. The molten thermoplastic resin flows along the flow path of the cavity provided in the mold while being pushed and spread by the pressurized gas. The molten resin is pushed to the end of the flow path by the pressurized gas body to form a continuous hollow portion inside the product. In the cooling step, the pressure is kept by the pressurized gas in the hollow portion, and after the molten resin is cooled and solidified,
The product is taken out by opening the mold with the pressure in the hollow part at atmospheric pressure. Next, the end portion of the branched pipe portion is cut by machining to obtain a continuous hollow pipe-shaped product.
By the above injection molding method, it is possible to mold a T-shaped, cruciform, star-shaped or other shaped product.

EXAMPLES The present invention will be described below based on examples.

Example 1 Each end of an object having a T-shaped cylinder having an outer diameter of 15 mmφ and a length of 100 mm is extended by 15 mm from the center of a cylinder having an outer diameter of 20 mmφ and a length of 200 mm. 1
Using a cavity-shaped mold provided with a resin gate and a gas gate at the end portion of 5 mmφ, a polycarbonate resin (trade name: UPILON S30 manufactured by Mitsubishi Gas Chemical Co., Inc.)
00) was injected to fill 60% of the cavity volume. The temperature of the molten resin in the cylinder during injection is 29
The injection pressure was 0 MPa and the injection pressure was 75 MPa. Before the completion of injection of the molten resin, nitrogen gas was injected under pressure from a gas gate located at the same end as the resin gate. The molten resin was extruded with nitrogen gas, filled up to the end of a 20 mmφ cylindrical portion inside the cavity, and then cooled with the nitrogen gas pressure kept at 3.5 MPa. After the nitrogen gas pressure in the hollow part of the molded product was reduced to atmospheric pressure and the mold was released, the molded product shown in FIG. 1 was taken out.
Each end of the molded product was cut into 15 mm to obtain a T-shaped product having a continuous hollow portion.

Example 2 Each end portion of a shape in which a cylinder having an outer diameter of 20 mm and a length of 150 mm is attached in a cross shape is extended by 15 mm from the center of a cylinder having an outer diameter of 15 mm and a length of 150 mm, and an outer diameter of 15 mmφ.
Using a cavity-shaped mold in which a resin gate and a gas gate are provided at the end portion of the cylinder, polycarbonate resin (trade name: UPILON S300, manufactured by Mitsubishi Gas Chemical Co., Inc.)
0) was injected to fill 60% of the cavity volume. The temperature of the molten resin in the cylinder during injection is 290
C., the injection pressure was 75 MPa. Before the completion of injection of the molten resin, nitrogen gas was injected under pressure from a gas gate located at the same end as the resin gate. The molten resin was extruded by nitrogen gas, filled up to the end of a 20 mmφ cylindrical portion inside the cavity, and then cooled with the nitrogen gas pressure kept at 4 MPa. The nitrogen gas pressure in the hollow part of the molded product was lowered to atmospheric pressure, and after releasing the mold, the molded product shown in FIG. 2 was taken out. Each end of the molded product was cut into 15 mm to obtain a cross-shaped product having a continuous hollow portion.

Example 3 Each end of a star-shaped cylinder having an outer diameter of 15 mmφ and a length of 100 mm is extended by 15 mm, and a resin gate and a gas gate are provided at one end. Using the provided cavity-shaped mold, a polycarbonate resin (trade name: UPILON S3000, manufactured by Mitsubishi Gas Chemical Co., Inc.) was injected to fill 70% of the cavity volume. The temperature of the molten resin in the cylinder at the time of injection was 290 ° C, and the injection pressure was 75 MPa. Before the end of injection of molten resin,
Nitrogen gas was pressed in from a gas gate located at the same end as the gate. The molten resin is extruded by nitrogen gas, and after filling up to the end of each 15 mmφ cylindrical portion inside the cavity,
The resin was cooled while the nitrogen gas pressure was kept at 4 MPa. The nitrogen gas pressure in the hollow part of the molded product was lowered to atmospheric pressure, and after releasing the mold, the molded product shown in FIG. 3 was taken out. Each end of the molded product was cut into 15 mm to obtain a star-shaped product having a continuous hollow portion.

[0013]

According to the present invention, a structural part having a shape which has conventionally required a molten core method or a die having a complicated structure,
Since it can be molded by injection molding with a normal mold structure, a large amount of the same product can be obtained in a short time and the productivity is improved.

[Brief description of drawings]

FIG. 1 is a plan view of a T-shaped product molded in Example 1.

2 is a plan view of a cross-shaped product formed in Example 2. FIG.

3 is a plan view of a star product molded in Example 3. FIG.

[Explanation of symbols]

 1: Resin gate position 2: Gas gate position 3: Cut point

Claims (4)

[Claims] 1. A method for injection molding a branched pipe-shaped molded article, comprising: injecting a pressurized gas from a pipe-shaped end portion during injection and injection of a molten resin into a mold cavity for a branched pipe. An injection molding method for a pipe-shaped molded product, which comprises molding a pipe-shaped product having a shape branched into a plurality of parts. 2. The injection molding method according to claim 1, wherein the branched pipe-shaped product is T-shaped. 3. The injection molding method according to claim 1, wherein the branched pipe-shaped product has a cross shape. 4. The injection molding method according to claim 1, wherein the branched pipe-shaped product is a star-shaped product.