JPH0139330B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a synthetic resin lined pipe, which is a metal pipe whose inner surface is coated with a synthetic resin layer.

Conventionally, the method for producing synthetic resin lined pipes as described above involves applying an adhesive to the outer circumferential surface of a heat-expandable synthetic resin pipe whose diameter expands when heated, and inserting this into a metal pipe. A method has been adopted in which the diameter of the synthetic resin pipe is expanded by heating, and the synthetic resin pipe is brought into close contact with the inner surface of the metal pipe.

However, since solution-type adhesives are usually used in such methods, there are drawbacks such as harmful organic solvents volatilizing and contaminating the working environment, and requiring space for drying. Furthermore, since it is difficult to uniformly apply the adhesive to the outer periphery of the synthetic resin pipe, the thickness of the adhesive layer tends to be uneven.
This method has a major drawback in that the adhesive strength between the synthetic resin pipe and the metal pipe varies, making it difficult to stabilize the quality of the product. Furthermore, in order to eliminate the above-mentioned drawbacks, a method of using a heat-sensitive adhesive that does not contain a solvent has also been considered. However, in order to perform extrusion coating using a so-called cross-head die, which is the usual method of applying heat-sensitive adhesive, the heat-sensitive adhesive is extruded into a cylindrical shape from the annular discharge opening of the cross-head die, and the synthetic resin is inserted through the die and transferred. The outer surface of the pipe is coated, but when the heat-sensitive adhesive extruded from the discharge port is stretched and coated on the synthetic resin pipe as a thin film, the adhesion of the heat-sensitive adhesive to the synthetic resin pipe is weak, and it may not adhere to the metal pipe. The adhesive layer peels off when inserted, making it difficult to insert into the synthetic resin pipe, and even if it can be inserted, the synthetic resin pipe cannot be evenly and strongly bonded to the metal pipe, which is a quality defect. It was hot.

The present invention solves the above-mentioned drawbacks and provides a method for manufacturing a high-quality synthetic resin lined pipe that can strongly bond a synthetic resin pipe to a metal pipe by coating a synthetic resin pipe with a heat-sensitive adhesive with strong adhesive strength. The gist is that heat-expandable synthetic resin pipes are
Guide the resin tube into an extrusion coating mold having an annular discharge port and a pressure chamber having a through hole around the outer circumference of the discharge port that allows the resin tube to be slid and sealed, and extrude the heat-sensitive adhesive into a cylindrical shape from the mold; A synthetic resin lined pipe characterized in that the resin pipe is coated with the cylindrical heat-sensitive adhesive while applying air pressure supplied to a pressurizing chamber, and the adhesive-coated resin pipe is inserted into a metal pipe and heated. It depends on the manufacturing method.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram showing an example of the manufacturing process of an adhesive-coated synthetic resin pipe used in manufacturing the synthetic resin lined pipe of the present invention, and 1 in the figure is a heat-expandable synthetic resin pipe. This synthetic resin pipe 1 has the property that its diameter increases when it is heated and softened, and during molding of the synthetic resin pipe, it is extruded into a cylindrical shape from an extruder, and while it is in a softened state, it is extruded by a forming device. It is produced by a method such as cooling and solidifying while reducing the diameter to a smaller diameter than the original state.

This resin tube 1 is coated with a heat-sensitive adhesive layer 3 using an extrusion coating mold 2 . The mold 2 consists of an inner mold 21, an outer mold 22, and a die lip 23. The inner mold 21 is fitted into the outer mold 22, and the die lip 23 is provided at the tip of the inner mold 22 with an annular discharge port between it and the inner mold 21. 24.

This mold 2 is attached to an extruder (not shown), and melted heat-sensitive adhesive is introduced from an adhesive inlet 25, divided into flows, distributed in the circumferential direction by a manifold 26, and extruded from an annular discharge port 24. It's summery.

The thickness of the adhesive extruded from the annular discharge port 24 is adjusted by adjusting the degree of fitting of the inner mold 21 to the outer mold 22 using adjustment bolts 27, and variations in the thickness in the circumferential direction are This is done by adjusting the mounting position of 23 with an adjustment bolt 28.

The inner mold 21 is provided with a resin tube insertion opening 29, the resin tube 1 is inserted through the insertion opening 29, and the entire surface is coated with the adhesive extruded into a cylindrical shape from the annular discharge opening 24.

In the present invention, the adhesive layer extruded into a cylindrical shape from the annular discharge port 24 is applied to the resin tube 1 while applying air pressure from the outside.

To apply air pressure, a pressurizing chamber 5 having a through hole 51 for the resin pipe 1 is provided around the annular discharge port 24 as shown in FIG. It is designed to supply pressurized gas.

The through hole 51 is made to be the same as or slightly smaller than the outer diameter of the resin tube 1, and is formed of a plate having rubber elasticity.
It is preferable to do this so that there is no gap with the resin pipe 1. If the through hole 51 is provided in multiple stages and has a thin peripheral edge, the resin pipe 1
This is preferable because the resistance during insertion is small and the sealing performance is improved.

The degree of pressurization in the pressurizing chamber 5 is such that the adhesive is melted and extruded from the annular discharge port 24, stretched in accordance with the insertion speed of the resin tube 1, and then coated on the resin tube 1. It is preferable to make it as high as possible. For this purpose, it is best to set the degree of pressure to about 300 to 700 mm of water column and provide a gap between the annular discharge port 24 and the resin pipe 1, although it varies depending on the melt strength and thickness of the molten adhesive. It is preferable to form an enlarged diameter portion at the distal end of the inner mold 21 by enlarging the diameter of the insertion opening 29 as shown in the figure. If the degree of pressure is too high, the extruded adhesive layer may be torn or the inner mold 2 may be damaged before it is coated on the resin tube 1.
This may cause problems such as contacting the inner surface of the surface of the layer 1 and resulting in an uneven covering layer that is broken.

Further, the thickness of the adhesive layer 3 coated on the resin pipe 1 is not particularly limited, but if it is thick, the adhesive strength tends to be uneven, and if it is thin, it becomes difficult to coat it with a uniform thickness. About 100 microns, especially 30~
It is preferably about 60 microns. With such a thickness, the adhesive layer 3 is immediately cooled due to its close contact with the resin tube 1 without any particular need for cooling.

The heat-sensitive adhesive used in the present invention includes, but is not limited to, polyolefin, ethylene-vinyl acetate resin, polyamide, polyester, polyurethane, rubber, etc. Heat-sensitive adhesives can be used.

In the present invention, the adhesive-coated resin tube thus obtained is inserted into a metal layer having an inner diameter slightly larger than the outer diameter of the tube and heated. The process is carried out at a temperature higher than the softening temperature of the synthetic resin forming the resin tube, whereby the resin tube 1 expands in diameter and comes into close contact with the inner surface of the metal tube.
The inner surface of the metal tube and the outer surface of the synthetic resin tube are firmly adhered by the adhesive layer 3, and a synthetic resin lined tube is manufactured.

The method for manufacturing the synthetic resin lined pipe of the present invention is as described above, in which the resin pipe is coated with air pressure applied to the adhesive layer extruded into a cylindrical shape, so that the heat-sensitive adhesive layer is pressed against the surface of the resin pipe. As a result, the bonding strength increases as a result of the bonding being carried out without the presence of air between the two. Therefore, when the adhesive-coated resin tube is inserted into a metal tube, the adhesive layer is prevented from peeling off, and the insertion can be performed easily and efficiently.

In addition, in order for the adhesive layer to firmly adhere to the resin pipe, this adhesive strength is maintained even after the resin pipe is heated and lined with the metal pipe, and the adhesive strength between the metal pipe and the resin pipe that is the lining layer is maintained. This results in a product that is uniform, strong, and of excellent quality.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the manufacturing process of an adhesive-coated synthetic resin pipe used in the method of manufacturing a synthetic resin-lined pipe of the present invention. 1: Heat-expandable synthetic resin pipe, 2: Extrusion coating mold, 21: Inner mold, 22: Outer mold, 23: Die lip, 24: Annular discharge port, 29: Resin pipe insertion port,
4: Pressure blower, 5: Pressure chamber, 51: Through hole.

Claims (1)

[Scope of Claims] 1. An extrusion covering mold for a heat-expandable synthetic resin tube, which has an annular discharge port and a pressurizing chamber having a through hole around the outer periphery of the discharge port through which the resin tube can be slid and sealed. The heat-sensitive adhesive is extruded into a cylindrical shape from the mold, and the resin tube is coated with the cylindrical heat-sensitive adhesive while applying air pressure supplied to the pressure chamber, and the adhesive-coated resin tube is molded into metal. A method for manufacturing a synthetic resin lined pipe, which comprises inserting the pipe into the pipe and heating it. 2. A gap is provided between the annular discharge port and the resin pipe by an enlarged diameter section in which the tip end of the inner mold is enlarged, and the extruded heat-sensitive adhesive layer is stretched in this gap. The manufacturing method according to item 1. 3. The manufacturing method according to claim 1 or 2, wherein the air pressure is 300 to 700 mm water column.