JPH03227609A - Manufacture of hollow manifold made of resin - Google Patents

Abstract

PURPOSE:To extract easily a core by dissolving resin into water after molding, by making use of a molding core which is coated with water-soluble resin. CONSTITUTION:A core material having shape retention is made into a core 1 by coating the same with water-soluble resin and forming resin is molded on the circumference of the core 1 by inserting the core 1 into a mold 3. Then the water-soluble resin is dissolved into water and then the core material is extracted. Although thermoplastic resin or thermosetting resin is contained as the water-soluble resin, the same is concretely a linear polymer having a- COOH group or -CONH2 group or -OH group within a molecule and, for example, polyacrylamide or polyacrylic acid or polyvinyl methyl ether or a copolymer consisting mainly of those is mentioned. With this construction, a hollow manifold made of resin having a complicated form such as one having ramification can be manufactured industrially easily.

Description

[Detailed description of the invention] [Industrial application field] The present invention uses a molding core coated with a water-soluble resin,
The present invention relates to a method for manufacturing a resin hollow manifold, which comprises dissolving the resin in water after molding to make it easier to pull out the core.

More specifically, the present invention relates to a manufacturing method that easily provides a resin hollow manifold having a complex shape.

[Conventional technology]

Conventionally, methods for manufacturing resin hollow manifolds (hereinafter also simply referred to as hollow pipes or manifolds) include extrusion molding,
Alternatively, blow molding is known. However, with these methods, there is a limit to the degree of freedom in the shape of the manifold, and it is particularly difficult to obtain a product having a flange portion. That is, although extrusion molding allows hollow tubes to be manufactured continuously, it is impossible to obtain products that have different shapes, branches, or flanges along the way.

In addition, in the case of blow molding, it is possible to obtain a product with a manifold, but it is difficult to obtain the smoothness of the inner surface of the manifold, and moreover, the viscosity behavior of the resin during melt processing makes it difficult to obtain a usable material. The disadvantage is that it is limited. In addition, it is industrially disadvantageous because a large amount of paris is generated.

Furthermore, it is extremely difficult to obtain a molded product with a flange or a molded product with a thick part or a part for attaching bolts for fixing the product in the middle by blow molding alone. For this reason, composite molding has been proposed in which the hollow tube part is manufactured by blow molding and the flange part is formed by injection molding, but the adhesion between the blow molded part and the injection molded part is insufficient.
Moreover, it is practically difficult to provide a plurality of injection molded parts.

C Problems to be Solved by the Present Invention] On the other hand, the method of obtaining a product by forming a resin around the core using a core by means such as injection molding or compression molding is difficult because the inner surface of the tube is smooth. If there is no non-linear part, it is possible to obtain a resin hollow manifold by forcibly removing the core after processing the pipe. However, if the inner tube is long,
The resistance to pulling out the core is large, and the resin is likely to be deformed when pulled out. Further, if the inner tube part has irregularities, steps, bends, etc., it is practically difficult to pull out the core without destroying the resin.

For this reason, in order to easily pull out the core, there are methods to give the core flexibility (Japanese Patent Application Laid-Open No. 64-63117), a method of using a low melting point alloy for the core, and a method of making the resin that forms the hollow tube. Methods have been proposed to unravel the core at a temperature that does not melt it. However, in the former case, it is difficult to remove the core depending on the degree of bending of the tube, and there are significant restrictions on the shape. In addition, in the latter case, it is necessary to mix rare metals such as bismuth in order to control the melting temperature of the alloy to a temperature at which the resin does not melt, which not only makes the low melting point alloy itself expensive, but also increases the When the alloy is melted, gases harmful to the human body are generated, which poses a risk of causing pollution problems.

Furthermore, since the resin or resin additives are eluted into the low melting point alloy, when the low melting point alloy is recycled and used, work is required to remove the eluted material, which increases energy costs. Furthermore, since the resin is heated when melting the low melting point alloy, it is necessary to select a resin that does not undergo thermal deformation at the melting temperature of the alloy and has little thermal deterioration, which limits the resins that can be used.

Therefore, the reality is that a method for manufacturing hollow manifolds that is industrially easy and has no restrictions on the resin to be used has yet to be found.

[Means to solve the problem]

As a result of intensive research into the manufacturing method of cores, the present inventor coated the periphery of a core material with shape retention with water-soluble resin, used it as a molding core, and coated the periphery with a predetermined shape. After coating with resin, the water-soluble resin is dissolved in water,
It has been discovered that a resin hollow manifold can be easily manufactured by pulling out the core material.

That is, the gist of the present invention is as follows: (1) A core material having shape retention properties is coated with a water-soluble resin to form a core, which is inserted into a mold and a molding resin is molded around the core. A method for producing a hollow manifold made of resin, characterized in that the water-soluble resin is then dissolved in water, and then the core material is pulled out, and (2) a water-soluble resin is used as the shape-retentive core material. is coated by injection molding to form a core, which is inserted into a mold and a thermoplastic resin for molding is injection molded around the cough core.Then, the water-soluble resin is dissolved in water, and then the core is A method for manufacturing hollow resin manifolds, which is characterized by pulling out material.

It is.

[Structure of the invention]

The present invention will be specifically explained below.

The manufacturing method of the present invention has the advantage that hollow manifolds of complex shapes can be manufactured freely.

Therefore, the resin hollow manifold in the present invention is not particularly limited in shape or use, as long as it is a hollow tube having branches, within the scope of the present invention.

There are no particular limitations on the material constituting the resin hollow manifold (molding resin of the present invention), but molding resins commonly used in the present invention include polyamide, polyester, polycarbonate, polyethylene, polypropylene, etc. Examples include thermoplastic resins. Thermosetting resins may also be used.

Furthermore, the water-soluble resin used in the present invention includes thermoplastic resins and thermosetting resins, and specifically, those containing -COOH groups, -〇〇N Hz groups, -OH groups, etc. in the molecule. For example, polyacrylamide, polyacrylic acid, polymethacrylic acid, polyitaconic acid, polyvinyl alcohol, polyethylene oxide,
Examples include polyvinylpyrrolidone, polyvinylmethyl ether, and copolymers mainly composed of these.

More specifically, polyethylene oxide resins with a molecular weight of several hundred thousand to several million (e.g., manufactured by Akiho Kagaku Kogyo ■, trade name Alcox), isoprene resins soluble in alkaline aqueous solution (manufactured by Clarei Soprene Chemical ■, Water-soluble elastomer), ethyl acrylate-acrylic acid copolymer resin (BELLAND A, G, Switzerland, BELLAND
plastic), etc.

EMBODIMENT OF THE INVENTION Hereinafter, the manufacturing method of the resin hollow manifold of this invention is demonstrated step by step using FIGS. 1-3.

(A) Core formation The core material, which is the main material that forms the core, is not particularly limited in material as long as it has enough shape retention to withstand the pressure during resin processing, but examples include metal, ceramic, resin, etc. etc. can be used. Among these, iron or aluminum is preferably used because it is industrially easily obtained, easy to process, and has high rigidity and heat resistance. The core material is formed from a plurality of hollow tubes or rod-shaped objects (hereinafter collectively referred to as core material forming elements) made of such materials, and when the core is removed as described below, it promotes the dissolution of the water-soluble resin. For this reason, a core forming element with minute holes or a part of mesh structure is sometimes used.

Examples of forming the core material according to the present invention are shown in FIGS. 1 and 2.

(Figure 2 is a cross-sectional view (A-A') of the core material shown in Figure 1.
). ) The core material consists of a plurality of core material forming elements and is assembled to match the shape of a predetermined molded product. The branches are simply butted together, or one is inserted into the other, and the structure is such that it can be easily pulled out (.

The core material thus obtained is inserted into a mold, and then, as shown in FIGS. 3 and 4, the core material is coated with a water-soluble resin to form a core. (Figure 4 is a cross-sectional view of Figure 3 (A
-A'). ) The water-soluble resin may cover the entire core material, or may cover only the joints of the plurality of tubes or tubes forming the core material forming elements. If the surface of the core material has uneven parts, sharp steps, bent parts, etc., the core surface can be made smooth by covering those parts with a water-soluble resin.

Further, if it is desired to form irregularities on the surface of the resulting resin hollow manifold, a water-soluble resin can be formed on the surface of the core material so that the core has a shape corresponding to the irregularities.

Although various methods such as injection molding, compression molding, transfer molding, and powder molding can be used to form the coating with the water-soluble resin, it is particularly preferable to select a thermoplastic resin as the water-soluble resin and form the coating by injection molding.

[B] Molding of Hollow Manifold The core thus obtained is set in a mold having a predetermined external shape, as shown in FIG. 5, and a molding resin is molded around it. The shape of the core should be designed so that the length of the tube is slightly longer than the actual length of the hollow manifold so that the core can be fixed by sandwiching the periphery between the molds. .

Molding of molding resin is done by compression molding, transfer molding,
Various resin processing methods well-known to those in the industry can be applied, such as vacuum forming, heat stamping molding, and injection molding, but selecting a thermoplastic resin and performing injection molding makes it easier to obtain a hollow tube with a smooth inner surface. preferable. In this case, in order to prevent the water-soluble resin from melting at the same time when the molding resin to be injection molded is in a molten state, a thermoplastic resin with a melting point not more than 100°C higher than the melting point of the water-soluble resin should be selected. It is desirable to perform injection molding at as low pressure and speed as possible.

(C) Removal of the core After molding, the water-soluble resin is first dissolved using water or steam, but dissolving the water-soluble resin can be done by immersing the product itself in water or leaving it under steam. This is done by passing water or steam inside the core. Depending on the type of water-soluble resin, it is possible to increase the dissolution rate by adjusting the pH. In that case, it is possible to adjust the pH of the water within a range that does not erode the resin that forms the hollow tube. is preferred.

After the water-soluble resin is dissolved, a resin hollow manifold having a predetermined shape is obtained by dividing and pulling out each of the core forming elements.

〔Example〕

The present invention will be specifically explained below with reference to Examples.
The present invention is not limited to this embodiment unless it departs from the gist thereof.

Example Two aluminum pipes (outer diameter 30 φ, inner diameter 22 φ) having a ring-shaped undercut with a depth of 2 mm were used as core forming elements. After assembling the core material as shown in Figures 1 and 2, It was inserted into an injection mold for forming a child. Next, a commercially available polyethylene oxide resin (manufactured by Meisei Kagaku Kogyo ■, trade name: Alcox E30) was used to cover the periphery of the joint of the core material forming element and to form an undercut part.
Injection molding was performed at a resin temperature of 80° C. to form the shape shown in FIGS. 3 and 4. This was inserted into a hollow tube mold as a core for resin molding, and a commercially available high-density polyethylene resin (manufactured by Mitsubishi Kasei ■, product name: Mitsubishi Polyethylene JU-080) was used as the molding resin. A hollow tube with a wall thickness of 4II111 and a flange portion of 5 nm, as shown in FIG. 5, was injection molded at 200°C.

The product thus obtained was left in a water bath with circulating water at 50°C for 3 hours to dissolve the water-soluble resin, and then the aluminum pipe that formed the core material was pulled out. It was easily pulled out, and the desired resin hollow manifold was obtained.

Comparative Example 1 A core forming element that already had a ring-shaped undercut portion with a depth of 2 mm was used, and the same procedure as in Example was performed except that only the joint portion of the core forming element was covered with a water-soluble resin. in this case,
One of the core forming elements without an undercut part could be easily pulled out, but the core forming element with an undercut part did not come out even when a load of 50 kg was applied, and
When the load was increased to 1 kg, the polyethylene resin hollow tube broke.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the joint portion of the core material forming element was not coated with a water-soluble resin, and the outer periphery of the core material was injection molded with high-density polyethylene. In this case, the molding resin flowed inward from the joint of the core forming element and crushed the inside, making it impossible to obtain a hollow tube.

〔Effect of the invention〕

As shown in the examples, according to the manufacturing method of the present invention, it is possible to industrially easily manufacture resin hollow manifolds having complicated shapes such as those having branches.

Further, it is preferable because a manifold pipe with a smooth inner surface can be obtained without causing thermal deformation or thermal deterioration.

[Brief explanation of drawings]

FIG. 1 is an example of a core material of the present invention formed by core material forming elements. FIG. 2 is a sectional view taken along line AA' in FIG. 1. FIG. 3 is an example of the core of the present invention obtained by coating the surface of the core material with a water-soluble resin. B in Figure 3 is depth 2+m
This is the ring-shaped undercut part of a. FIG. 4 is a sectional view taken along line AA' in FIG. 3. In Fig. 4, a is the joint part of the core forming element coated with water-soluble resin, and b
The core material forming element is made of water-soluble resin and has a depth of 2I! 1
This is a ring-shaped undercut part of m. FIG. 5 is a diagram showing an example of a hollow tube molding die into which the resin hollow manifold and core of the present invention are inserted. In the figure, 1 is a core, 2 is a resin hollow manifold, and 3 is a mold for molding a hollow tube.

Claims (2)

[Claims] (1) A core material with shape retention properties is coated with a water-soluble resin to form a core, this is inserted into a mold, a molding resin is molded around the core, and then the water-soluble resin is 1. A method for manufacturing a hollow resin manifold, which comprises melting the resin by melting the core material, and then pulling out the core material. (2) A core material with shape retention properties is coated with a water-soluble resin by injection molding to form a core, which is inserted into a mold and a thermoplastic resin for molding is injected around the core, and then A method for producing a resin hollow manifold, which comprises dissolving the water-soluble resin in water and then pulling out the core material.