JPH079556A - Manufacture of composite tube - Google Patents

Abstract

PURPOSE:To provide a method for stably manufacturing a composite tube of high quality by scarcely causing a deviation, an irregular thickness or an air gap between layers, etc., to occur at foamable resin layers. CONSTITUTION:Resin of two layers are so simultaneously extruded by a two- layer resin extrusion die 10 as to position a solid resin layer 1a at an inner surface side and a foamable resin layer 1b at an outer surface side, the layer 1a of the outer surface side is cooled immediately after the extrusion to foot a resin 2 layer tube 1 in which foaming is suppressed, the tube is inserted into the metal tube to be integrated by foaming the layer 1a by postheating and bringing it into the inner surface of the tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite pipe in which the inner surface of a metal pipe is lined with a resin layer, and more specifically, a foaming resin layer is provided as an intermediate layer for use in, for example, building drainage. A method for producing a suitable composite pipe.

[0002]

2. Description of the Related Art Among composite pipes in which the inner surface of a metal pipe is lined with a resin layer, an inner solid resin layer (non-foamed resin layer)
A composite pipe in which a foamable resin layer such as urethane is interposed as an intermediate layer between the outer and outer metal pipes.
When used as a drainage pipe, for example, there is an advantage that drainage noise is reduced by the sound absorbing effect of the foamed resin layer.

A conventional method for producing a composite pipe having such a foamed resin layer as an intermediate layer is to insert a preformed solid resin pipe into a metal pipe and to form a foamable material such as urethane between the two pipes. A method of adhering the stock solution to the inner surface of the metal tube while foaming and hardening the stock solution by interposing a stock solution of the resin and heating from the outside of the metal tube, or using a two-layer extrusion die, a solid resin layer on the inner surface side,
By simultaneously extruding two layers of resin so that the foamable resin layer is located on the outer surface side, the foamable resin layer on the outer surface side is foamed, and the two-layer resin tube is inserted into the metal tube via an adhesive or the like. Then, a method of adhering both the tubes by expanding the diameter of the resin tube or reducing the diameter of the metal tube is mainly adopted.

[0004]

By the way, in any of the above-mentioned conventional production methods, the foamable resin layer is caused by the flow of the undiluted solution of the foamable resin or the occurrence of unevenness during extrusion to foaming at high temperature. However, there is a problem that unevenness or uneven thickness is generated, or a void or the like is generated between the foamed resin layer and each layer inside and outside thereof.

When the foamed resin layer has an uneven thickness or an uneven thickness, for example, when two composite pipes are connected by a joint, it causes a step in the pipe line and is used as a drain pipe. Will lead to the problem that solids and the like in the drainage will adhere to this step. Further, if a gap is formed between the foamable resin layer and any of the tubes inside and outside thereof, water or the like may enter the foamable resin layer through the tube end to corrode the metal tube, It also causes the metal tube and the resin layer to be separated.

The present invention has been made in view of the above circumstances, and it is possible to stably obtain a high-quality composite pipe without unevenness or uneven thickness in the expandable resin layer or voids between layers. The purpose is to provide a possible manufacturing method.

[0007]

In order to achieve the above object, the method for producing a composite pipe of the present invention uses a two-layer resin extrusion molding die, wherein a solid resin layer is formed on the inner surface side and a foaming property is formed on the outer surface side. Two layers of resin are extruded at the same time so that the resin layer is located, and immediately after the extruding, the resin foam on the outer surface side is cooled to form a resin two-layer pipe in which foaming is suppressed. It is characterized in that the foamable resin layer is foamed by heating and brought into close contact with the inner surface of the metal tube when it is inserted into and integrated with.

[0008]

By rapidly cooling the foamable resin extruded from the two-layer resin extrusion die, a two-layer resin pipe having a foamable resin layer cured in a non-foaming state on the outer peripheral side can be obtained. This 2
When the layer resin pipe is foamed by being post-heated in a state of being inserted in the metal pipe and brought into close contact with the inner surface of the metal pipe, there is no deviation or gap between the metal pipe and the solid resin layer, and stable A composite pipe having a foamed resin layer of uniform thickness as an intermediate layer can be obtained.

[0009]

1 is a cross-sectional view showing an apparatus used for manufacturing a resin double-layer pipe 1 in the steps of the embodiment of the present invention.

The two-layer resin extrusion die 10 has two resin inflow ports 11 and 12, which are connected to a main extruder and a sub-extruder (neither is shown). The resin inlets 11 and 12 are respectively connected to the resin flow passages 13 and 1.
4, the resin flow passages 13 and 14 join together before the cylindrical resin discharge port 15, and the resin from one resin flow inlet 11 is directed to the inner surface side and from the other resin flow inlet 12 The resin can be discharged from the cylindrical resin two-layer pipe 1 such that the resin is located on the outer surface side. In this figure, the two-layer resin extrusion die 10 shows only a portion relating to resin flow for the sake of explanation, and omits other detailed structures.

A refrigerant jetting portion 16 for jetting air or another suitable refrigerant C is disposed in the vicinity of the resin discharge outlet 15 of the two-layer resin extrusion die 10 as described above, and the resin discharge outlet is provided. The outer peripheral surface of the resin double-layer pipe 1 extruded from 15 can be uniformly cooled.

In such a manufacturing apparatus, for the two-layer resin extrusion die 10, the solid resin is supplied from the main extruder through the resin inlet 11 and the resin is injected from the sub extruder 12 through the resin inlet 12.
The foamable resin is extruded in a molten state through the. As a result, the foamable resin layer 1 extends from the resin discharge port 15 to the outer surface side.
a, the resin two-layer tube 1 having the solid resin layer 1b on the inner surface side is extruded, and the foamed resin layer 1a on the outer surface side of the resin two-layer tube 1 is air from the refrigerant ejection portion 16 or another suitable refrigerant. Quenched by C. As a result, foaming of the foamable resin layer 1a is prevented, and the resin two-layer pipe 1 having the unfoamed foamed resin layer 1a outside the solid resin layer 1b is obtained.

Two-layer resin tube 1 obtained as described above
Is then inserted into the metal tube 2, as shown in the radial cross section in FIG. At this time, it is desirable to apply an adhesive to at least one of the outer peripheral surface of the two-layer resin tube 1 and the inner peripheral surface of the metal tube 2.

Then, in this state, the metal tube 2 is heated from the outside to foam the foamable resin layer 1a, and at the same time, the adhesive is melted to activate the adhesive, thereby activating the outer peripheral surface of the foamable resin layer 1a and the metal. After the inner peripheral surfaces of the tube 2 are adhered to each other, the tube is cooled and solidified. As a result, a composite pipe having the solid resin layer 1b as the inner layer, the foamable resin layer 1a in the foamed state as the intermediate layer, and the metal pipe 2 as the outer layer is obtained as shown in the radial cross-sectional view in FIG. Although an adhesive layer is actually interposed between the foamable resin layer 1a and the metal tube 2, the adhesive layer is not shown in FIG.

According to such a manufacturing method, the expandable resin layer 1a is interposed between the solid resin layer 1b and the metal tube 2 in a state where the foamable resin layer 1a is cured in an unfoamed state, and is foamed by post-heating in that state. , Solid resin layer 1b and metal tube 2
In the space regulated between and, unevenness and unevenness of foaming do not occur, and uneven thickness of the foamable resin layer 1a and generation of voids between layers hardly occur.

Here, the resin two-layer pipe 1 is inserted into the metal pipe 2 in a state where the adhesive is applied to any of the foamable resin layers 1
A step of reducing the diameter of the metal tube 2 may be inserted before a is foamed by heating from the outside.

Next, an example in which a composite pipe is actually manufactured by using the manufacturing method of the present invention as described above will be described. <First Example> A baking soda-based (or diazo-based) hard vinyl chloride compound is used as the foamable resin of the intermediate layer, and is guided from the sub-extruder to the resin inlet 12 of the two-layer resin extrusion mold 10 shown in FIG. It was

Hard vinyl chloride is used as the solid resin for the inner layer, and the same two-layer resin extrusion die 10 is used from the main extruder.
To the resin inflow port 11. Then, these resins are melted and merged in the two-layer resin extrusion die 10 and the resin discharge port 15
Immediately after exiting from the above, it was rapidly cooled with air to obtain a resin two-layer tube 1 in which the expandable resin was cured in an unfoamed state.

A steel pipe is used as the metal pipe 2, a thermoplastic hot melt adhesive is applied to the outer surface of the resin two-layer pipe 1 obtained above, and then the metal pipe is inserted into the metal pipe 2 and heated from the outside to form a foam. The resin layer 1a was foamed and the adhesive was melted to activate the adhesive, and then the entire tube was cooled.

<Second Example> The process until the production of the resin two-layer pipe 1 having the foamable resin layer 1a cured in the unfoamed state on the outer surface side and the application of the adhesive to the outer surface is the same as the first example. ,
The diameter of the metal tube 2 is reduced with this inserted into the metal tube 2,
Then, the expandable resin layer 1a was foamed by external heating, and finally the entire tube was cooled in the same manner.

In both the first and second examples described above, neither the uneven thickness of the expandable resin layer 1a nor the voids between the layers were found.

[0022]

As described above, according to the present invention,
In manufacturing a composite pipe having a foamable resin layer as an intermediate layer between a solid resin layer and a metal pipe, first, a two-layer resin extrusion mold is used to form a solid resin layer on the inner side and a foamable resin layer on the outer side. The two layers of resin are extruded at the same time so that the resin is positioned, and immediately after the extruding, the foamable resin on the outer surface side is cooled to form a resin two-layer pipe in a state in which foaming is suppressed. When inserting into a metal tube and integrating,
Since the foamable resin layer is foamed by heating and adheres closely to the inner surface of the metal pipe, uneven thickness of the foamable resin layer and voids between layers do not occur, and a composite pipe with low drainage noise and propagation sound can be stably provided. It has become possible to manufacture with high quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an apparatus used for manufacturing a two-layer resin tube 1 in a process of an embodiment of the present invention.

FIG. 2 is a sectional view showing a part of the process of the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a composite pipe obtained by a process of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resin 2 layer pipe 1a Foaming resin layer 1b Solid resin layer 2 Metal pipe 10 2 layer resin extrusion die 15 Resin discharge port 16 Refrigerant ejection part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 105: 04 B29L 9:00 23:22

Claims (1)

[Claims] 1. A two-layer resin extrusion molding die is used to simultaneously extrude two layers of resin so that a solid resin layer is located on the inner surface side and a foamable resin layer is located on the outer surface side, and immediately after the extrusion, the outer surface is extruded. When the resin two-layer pipe in which the foamed resin on the side is cooled to suppress foaming is formed, and the resin two-layer pipe is inserted and integrated into the metal pipe, the foamable resin layer is foamed by heating and the inside of the metal pipe A method for manufacturing a composite pipe that is in close contact with the surface.