JPH11348145A - Manufacturing method of synthetic resin tube - Google Patents

Abstract

(57) Abstract: An outer peripheral surface of a synthetic resin pipe in which a foamed synthetic resin layer is concentrically laminated on a non-foamed synthetic resin layer is smoothed. When a synthetic resin tube in which a molten synthetic resin is concentrically laminated on a molten non-foam synthetic resin is extruded from a mold, an inner peripheral surface is cooled by a cooling jacket. Later, the outer peripheral surface of the foamed synthetic resin layer is heated by the heating device 24. Next, the synthetic resin tube 10 passes through the inside of the forming tube 27, and after the outer peripheral surface of the foamed synthetic resin layer is formed into a predetermined shape,
It is cooled by the cooling tank 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a synthetic resin tube suitably used as a lining layer on the inner peripheral surface of a metal tube. Relates to a method of manufacturing a synthetic resin tube laminated concentrically.

[0002]

2. Description of the Related Art In recent years, composite pipes in which a synthetic resin layer is lined on the inner peripheral surface of a metal pipe have been used as a water supply pipe, a hot water supply pipe, a drain pipe, and the like. In such a composite pipe, a synthetic resin layer lined on the inner peripheral surface of the metal pipe is
A two-layer structure of a foamed synthetic resin layer on the outer peripheral side and a non-foamed synthetic resin layer on the inner peripheral side, which is in contact with the inner peripheral surface of the metal tube, is also used. As described above, in the composite pipe in which the foamed synthetic resin layer is provided between the metal pipe and the non-foamed synthetic resin layer, even when cold water and hot water are repeatedly passed, the foamed synthetic resin layer is made of metal. It is not easily peeled off from the inner surface of the pipe, and
Since the inner peripheral surface of the non-foamed synthetic resin layer on the inner peripheral side is smooth, there is an advantage that occurrence of running water noise is reduced.

A composite pipe in which a synthetic resin layer lined on the inner peripheral surface of a metal pipe has a two-layer structure usually has a two-layer structure in which a foamed synthetic resin layer is concentrically laminated on a non-foamed synthetic resin layer on the inner peripheral side. It is manufactured by using a synthetic resin tube. The two-layer synthetic resin tube is inserted into the metal tube and heated. As a result, the two-layered synthetic resin tube expands, adheres to the inner peripheral surface of the metal tube, and a composite tube in which the inner peripheral surface of the metal tube is lined with the two-layered synthetic resin layer is manufactured.

In the case of manufacturing a synthetic resin tube having a two-layer structure, a molten foamed synthetic resin and a non-foamed synthetic resin extruded from each extruder are introduced into one mold, and the molten resin is extruded from the mold. A synthetic resin tube in which a foamed synthetic resin layer is concentrically laminated on a non-foamed synthetic resin layer is extruded. The double-layered synthetic resin tube extruded from the mold is 100-150 ° C from the inner peripheral surface so that it is in a semi-cured state.
It is cooled to a predetermined temperature. As described above, before the synthetic resin pipe is forcibly cooled from a molten state to a semi-cured state before being reduced to a predetermined outer diameter, the synthetic resin pipe is reduced in diameter to a predetermined outer diameter. When the synthetic resin tube is cooled to room temperature and then heated again to a temperature at which it has been cooled so as to be in a semi-cured state, the synthetic resin tube is expanded to a shape in a semi-cured state.

[0005] Thereafter, the synthetic resin pipe is formed into a predetermined outer diameter while passing through the inside of the forming tube, and is cooled by cooling water in a cooling water tank. As a result, a synthetic resin tube having a two-layer structure having a predetermined outer diameter and having heat expandability is obtained.

When the obtained synthetic resin tube is inserted into a metal tube and heated to a temperature which has been cooled so as to be in the above-mentioned semi-cured state, the synthetic resin tube has an outer shape at the time when the semi-cured state is reached. Until it expands and comes into close contact with the inner peripheral surface of the metal tube.

[0007]

In such a method of manufacturing a synthetic resin tube, the molten foamed synthetic resin extruded into the mold is not foamed inside the mold in a high pressure state, but is in a high pressure state. Foaming is started by being extruded from the inside of the mold into the atmosphere. First, the two-layered synthetic resin tube extruded from the mold is cooled from the inner peripheral surface by the inner peripheral surface cooling step. During this time, the outer peripheral surface is opened without being regulated. Therefore, the foamed synthetic resin layer on the outer peripheral side is freely foamed. as a result,
The outer peripheral surface of the foamed synthetic resin layer is in a state in which some irregularities are formed by the start of foaming. After that, the synthetic resin pipe is introduced into the forming tube in a semi-cured state, and the outer peripheral surface is regulated, so that the outer peripheral surface is formed into a state in which the outer peripheral surface is smoothed. Become.

However, since the outer peripheral surface of the foamed synthetic resin layer of the synthetic resin tube introduced into the forming tube is uneven, even if the outer peripheral surface is regulated by the forming tube, it is completely smoothed. And a skin layer may not be obtained. As described above, when the outer peripheral surface of the foamed synthetic resin layer is lined on the inner peripheral surface of the metal tube without being smoothed, an air pocket is formed at an interface between the metal tube and the foamed synthetic resin layer, and the synthetic resin with respect to the metal tube is formed. There is a possibility that the adhesive strength of the pipe is reduced and the synthetic resin pipe is peeled off from the inner peripheral surface of the metal pipe.

The present invention has been made to solve such a problem, and an object of the present invention is to reliably manufacture a synthetic resin pipe in which the outer peripheral surface of a foamed synthetic resin layer laminated on a non-foamed synthetic resin layer is smoothed. It is an object of the present invention to provide a method for manufacturing a synthetic resin tube that can be used.

[0010]

A method for manufacturing a synthetic resin tube according to the present invention comprises the steps of: concentrically laminating a non-foamed synthetic resin in a molten state and a foamed synthetic resin with the non-foamed synthetic resin as an inner peripheral side; After cooling the foamed synthetic resin layer from the inner peripheral surface of the laminated non-foamed synthetic resin layer to a semi-cured state,
The method includes a step of heating the outer peripheral surface of the foamed synthetic resin layer to be in a molten state, and a step of regulating the outer peripheral surface of the heated foamed synthetic resin layer to form a predetermined outer peripheral surface and cooling the same. It is characterized by the following.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of a synthetic resin pipe manufactured by the method for manufacturing a synthetic resin pipe of the present invention.
The synthetic resin tube 10 has a foamed synthetic resin layer 11 concentrically laminated on a cylindrical non-foamed synthetic resin layer 12 over the entire circumference. The non-foamed synthetic resin layer 12 arranged on the inner peripheral side is made of, for example, 2 mm
The foamed synthetic resin layer 11 located on the outer peripheral side is made of a foamed hard resin obtained by adding a foaming agent (ADCA) to the same hard vinyl chloride resin as the non-foamed synthetic resin layer 12 and foaming. The thickness is made 1 mm by vinyl chloride resin. The outer diameter of the foamed synthetic resin layer 11 on the outer peripheral side is, for example, 105 mm.

Such a synthetic resin pipe 10 is expanded, for example, by being inserted into a steel pipe having an outer diameter of 114 mm and a thickness of 2.8 mm and heated to be integrally lined with the inner peripheral surface of the steel pipe. And a composite tube.

As the non-foamed synthetic resin layer 12 located on the inner peripheral side, a thermoplastic resin such as a soft vinyl chloride resin, polyethylene, cross-linked polyethylene, polypropylene, or polystyrene is usually used in addition to such a hard vinyl chloride resin. used. Considering the adhesiveness to the non-foamed synthetic resin layer 12 on the inner peripheral side, a foaming agent is added to the same kind of synthetic resin as the non-foamed synthetic resin layer 12 to form the foamed synthetic resin layer 11 located on the outer peripheral side. Those that have been made are preferred.

FIG. 2 is a schematic view showing an example of an apparatus used for carrying out the method of manufacturing the synthetic resin tube 10. As shown in FIG. In this apparatus, a mold 23 is used for laminating the non-foamed synthetic resin layer 11 and the foamed synthetic resin layer 12 in a molten state concentrically with each other. A molten non-foamed synthetic resin extruded by the first extruder 21 and a molten foamed synthetic resin extruded by the second extruder 22 are introduced into the mold 23, respectively. Inside, the non-foamed synthetic resin is concentrically laminated such that the foamed synthetic resin is on the inner peripheral side and the foamed synthetic resin is on the outer peripheral side. From the mold 23, the synthetic resin tubes 10 in which the foamed synthetic resin layer 11 is laminated concentrically on the non-foamed synthetic resin layer 12 are sequentially extruded.

The synthetic resin tube 10 extruded from the mold 23
Is taken off by a take-off device 29 so as to sequentially pass around a cooling jacket 24 attached to a mold 23, inside a heating device 26, inside a forming tube 27, and inside a cooling tank 28.

The mold 23 has a cooling jacket 24 for cooling the inner peripheral surface of the synthetic resin tube 10 extruded from the mold 23.
Is attached. The synthetic resin tube 10 extruded from the mold 23 passes so as to surround the cooling jacket 24. In the cooling jacket 24, a coolant whose temperature has been adjusted by the temperature controller 25 is passed through the inside of the mold 23. Cooled from. Mold 2
For example, the synthetic resin tube 10 extruded from 3 has a melting temperature of about 200 ° C., which is the melting temperature of the non-foamed synthetic resin and the foamed synthetic resin. Cool down to ~ 150 ° C.

The synthetic resin tube 10 has a size of 100 to 150
In a temperature range of about ° C., the shape is memorized and the heat expansion property is imparted. Therefore, when the synthetic resin tube 10 is cooled to room temperature and then heated to about 100 to 150 ° C., the shape at that temperature is restored.

The synthetic resin tube 10 whose inner peripheral surface is cooled by the cooling jacket 24 is heated by a hot air blower type heating device 2.
6, after the outer peripheral surface of the foamed synthetic resin layer 11 located on the outer peripheral side is heated, the foamed synthetic resin layer 11 is inserted into the forming tube 27 arranged in the cooling bath 28 to be formed to a predetermined outer diameter. I have. The foamed synthetic resin layer 11 of the synthetic resin tube 10 starts foaming at the same time as being extruded from the mold 23, and the heating device 26 heats the outer peripheral surface of the foamed synthetic resin layer 11 in the semi-cured state where foaming has started. By doing so, it is in a molten state.

The heating device 26 is not limited to a hot air blower system, but may employ a heating system using near infrared rays, a flame or the like. The heating temperature of the heating device 26 depends on the foamed synthetic resin layer 1.
The temperature is set to about 180 to 220 ° C. so that the outer peripheral surface of the first element is melted. When the foamed synthetic resin layer 11 is excessively heated, the foamed synthetic resin layer 11 may be melted to the inside, and the foaming ratio may be reduced, or the remaining foaming agent may react and foam unevenly. In the case of the foamed synthetic resin layer 11 in which a foaming agent (ADCA) is added to a hard vinyl chloride resin, the heating temperature is 180 ° C.

The foaming synthetic resin layer 11 is heated by the heating device 26.
The synthetic resin pipe 10 whose outer peripheral surface is in a molten state is inserted into a forming tube 27 arranged in a cooling bath 28, and while passing through the forming tube 27, the outer peripheral surface is regulated. It is formed to a predetermined outer diameter.

At this time, since the outer peripheral surface of the foamed synthetic resin layer 11 located on the outer peripheral side of the synthetic resin tube 10 is heated by the heating device 26 and is in a molten state, the outer peripheral surface is regulated by the forming tube 27. As a result, the skin layer is smoothed to have no irregularities, thereby forming a skin layer.

The synthetic resin pipe 10 having a predetermined outer diameter and an outer peripheral surface serving as a skin layer is
The cooling water in the cooling tank 28 is cooled to room temperature.
Then, the synthetic resin tube 10 cooled to the room temperature is taken up by the take-up machine 29, and is sequentially cut into a predetermined length by the cutting machine 31 arranged downstream of the take-up machine 29.

The synthetic resin tube 10 thus obtained
Is inserted into a steel pipe and heated to, for example, a temperature of 130 ° C. Thereby, the synthetic resin pipe 10 expands, and the foam synthetic resin tank 11 on the outer peripheral side is integrally adhered to the inner peripheral surface of the steel pipe.

[0025]

According to the method for manufacturing a synthetic resin tube of the present invention, the foamed synthetic resin layer concentrically laminated on the non-foamed synthetic resin layer starts foaming and is cooled to a semi-cured state. At this point, after being heated and brought into a molten state, the outer peripheral surface is regulated and molded into a predetermined shape, so that a synthetic resin tube in which the outer peripheral surface of the foamed synthetic resin layer is reliably smoothed is obtained. Therefore, when this synthetic resin tube is used for lining the inner peripheral surface of the metal tube, it is securely adhered to the inner peripheral surface of the metal tube.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a synthetic resin tube manufactured by the method for manufacturing a synthetic resin tube of the present invention.

FIG. 2 is a schematic view showing an example of an apparatus used for carrying out the method for manufacturing a synthetic resin pipe of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Synthetic resin pipe 11 Foam synthetic resin layer 12 Non-foam synthetic resin layer 21 Extruder 22 Extruder 23 Die 24 Cooling jacket 25 Temperature controller 26 Heating device 27 Forming tube 28 Cooling tank 29 Take-off machine 31 Cutting machine

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 105: 04 B29L 9:00 23:00

Claims (1)

[Claims] 1. A step of laminating a non-foamed synthetic resin in a molten state and a foamed synthetic resin concentrically with the non-foamed synthetic resin as the inner peripheral side, and foaming the foamed resin from the inner peripheral surface of the laminated non-foamed synthetic resin layer. After cooling the synthetic resin layer to a semi-cured state, heating the outer peripheral surface of the foamed synthetic resin layer to be in a molten state, and regulating the outer peripheral surface of the heated foamed synthetic resin layer to a predetermined level. A step of cooling the molded product into an outer peripheral surface shape and cooling the molded product.