JPS6218341B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) 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.

(Prior Art and Problems) Conventionally, the method for producing synthetic resin lined pipes as described above involves applying an adhesive to the outer peripheral surface of a heat-expandable synthetic resin pipe whose diameter expands when heated. A method has been adopted in which the diameter of the synthetic resin tube is expanded by inserting it into a metal tube and heating it, thereby bringing the synthetic resin tube into close contact with the inner surface of the metal tube.
For example, there is an invention described in Japanese Patent Application Laid-Open No. 51-20288 (hereinafter referred to as the first conventional example).

However, in such a first conventional example,
Since solution-type adhesives are usually used, there are drawbacks such as harmful organic solvents evaporating and contaminating the work environment, and the need for space for drying. A major disadvantage is that the thickness of the adhesive layer tends to be uneven because it is difficult to apply it uniformly to the outer periphery, which causes variations in the adhesive strength between the synthetic resin pipe and the metal pipe, making it difficult to stabilize the quality of the product. It had 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, when applying heat-sensitive adhesives, the common method is to melt the adhesive at high temperatures and turn it into a low-viscosity liquid. This makes it difficult to coat, and the film thickness becomes uneven, which tends to cause variations in quality.

Furthermore, in order to make the plastic coating layer easier to peel off and remove, it is known from the invention described in Japanese Patent Application Laid-Open No. 141663/1983 (hereinafter referred to as the second conventional example) that the coating layer is immediately cooled during extrusion coating of the plastic. ing. However, during normal extrusion coating, a temperature difference of 100° C. or more exists even if the object to be coated is not particularly cooled. Therefore, in the case of the second conventional example, the extrusion coating is limited to a multilayer structure. In addition, in this second conventional example, since the entire object to be coated is cooled, the object coated thereon is likely to be peeled off as a whole, and water and liquid materials are likely to enter between the two, which poses a problem.

(Means for Solving the Problems) The present invention aims to improve the quality of synthetic resin-lined pipes, and as a result of various studies on the uniform application of adhesive in the manufacture of such pipes, a crosshead having an annular discharge port was developed. A heat-sensitive adhesive is extruded from a die into a cylindrical shape and coated on a heat-expandable synthetic resin tube. At this time, the extruded adhesive cylindrical material is intermittently cooled, and the thus obtained adhesive-coated tube is coated with a predetermined shape. This method was developed based on the discovery that good results could be obtained by cutting the tube into lengths, inserting it into a metal tube, and heating it. The heat-sensitive adhesive film is introduced into a crosshead die having an annular discharge port, and extruded from the crosshead die into a cylindrical shape. The entire outer circumferential surface of the resin pipe is coated to form an adhesive-clad tube, and then the adhesive-clad tube is attached to the length of the metal tube to be lined so that the cooled portions of the adhesive coating layer become both ends of the tube. A synthetic resin characterized by cutting the adhesive cladding tube into slightly longer lengths, inserting the cut adhesive cladding tube into a metal tube, and heating the adhesive cladding tube while peeling off the adhesive coating layer at both ends. The invention consists in a method of manufacturing a lining pipe.

(Example) This will be explained below with reference to the drawings.

FIG. 1 is for explaining the manufacturing process of the adhesive-clad tube used for manufacturing the synthetic resin lined tube according to the present invention, and the reference numeral 1 in the figure is an extruder, from which the synthetic resin tube 2 is shown. is pushed out and advanced forward by the pulling device 6. The extruded synthetic resin pipe 2 is guided to a forming device 3 and a cooling solidification device 4, where the inner diameter or outer diameter is regulated to a predetermined size, and is cooled by a refrigerant such as water and solidified. and the shape is fixed. In the present invention, at this point, the synthetic resin tube 2 is imparted with heat-expandable property and becomes a heat-expandable synthetic resin tube 5, which increases in diameter by being heated and softened. In addition, in order to impart thermal expansion properties to the synthetic resin pipe, tension was applied to the extruded synthetic resin pipe, which had not been cooled and was still in a softened state, while being reduced in diameter to a smaller diameter than the extruded state using a forming device. Conventionally used methods, such as rapid cooling and solidification in the same state, may be employed. In addition, the forming device 3 for regulating the diameter of the synthetic resin pipe 2 includes a forming plate for regulating the outer diameter dimension by passing the pipe through this, and a forming device 3 for regulating the outer diameter dimension by passing the pipe through this, and a forming device 3 for regulating the outer diameter dimension by reducing the pressure on the inner circumferential surface of the pipe, etc. An inner diameter forming device may be used to regulate the inner diameter of the tube in a similar manner.

Next, the heat-expandable synthetic resin tube 5 thus obtained, which has been cooled to approximately room temperature, is introduced into a crosshead die 8 having an annular discharge port connected to an adhesive extruder 7. 8 and is extruded from the crosshead die 8 to cover the entire outer peripheral surface of the synthetic resin tube 5 to form an adhesive coated tube 11.

Further, the reference numeral 9 in the figure is a cooling device, and the cooling device 9 operates intermittently, and during its operation, a film-like adhesive is extruded by blowing cold air or the like and coated on the surface of the synthetic resin pipe. Cool immediately.

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.

Further, reference numeral 13 in the figure indicates a portion of the adhesive coating layer that is formed at intervals in the adhesive coating tube 11 and is cooled during coating with the adhesive. Since the agent layer was cooled, it was not sufficiently bonded to the synthetic resin pipe 5, resulting in poor adhesion.

The adhesive cladding tube 11 manufactured in this way is cut into a predetermined length by a cutting device 12 such as a circular saw, but the cutting is performed so that the adhesive coating layer portion 13, that is, the defective adhesive portion is formed by cutting. The lining is done so that the lining is at both ends of the pipe, and the length of the pipe is slightly longer than the length of the metal pipe to be lined. In this way, an adhesive cladding tube 14 having defective adhesion portions at both ends is obtained.

In addition, in the present invention, it is preferable that the length of the adhesive-clad tube 14 excluding the defective adhesion portions at both ends is equal to the length of the metal tube to be lined. When coating the adhesive tube, it is preferable to adjust the period of intermittent cooling of the adhesive tube depending on the length of the metal tube to be lined.

Next, the adhesive cladding tube 14 prepared as above
is inserted into a metal tube and heated, but this heating is performed after the adhesive coating layer on both ends of the adhesive coating tube 14 has been peeled off. Since the portions are poorly bonded as described above, this can be easily done before or after insertion into the metal tube. Further, the above heating is usually performed by attaching attachments for blowing heated air or steam to both ends of the adhesive cladding tube 14 inserted into the metal tube, and blowing heated air or steam into the tube.
If adhesive is present in the attachment mounting part, it will be difficult to remove the attachment after heating, so it is necessary to remove the adhesive from this part.However, in the present invention, as described above, the adhesive is removed. The adhesive at both ends of the agent-coated tube 14 can be easily removed.

Due to the heating, the diameter of the adhesive clad tube inserted into the metal tube expands, and the inner surface of the metal tube and the outer surface of the synthetic resin tube are firmly bonded with uniform adhesive strength by the heat-sensitive adhesive layer of uniform thickness. A lined pipe of excellent quality can be obtained.

Note that the portion of the synthetic resin tube that protrudes from the metal tube may be cut off as appropriate.

(Effects of the Invention) Since the method for manufacturing a synthetic resin lined pipe of the present invention is as described above, it is possible to coat the inner surface of the metal pipe with a heat-sensitive adhesive layer on the outer peripheral surface of the synthetic resin pipe with a uniform thickness. It is easy to install, and there is no uneven adhesion between the inner surface of the metal tube and the coating layer.
To easily produce products with stable quality without worrying about environmental pollution caused by organic solvents or the like. Furthermore, the adhesive layer on both ends of the synthetic resin pipe, which is required when the synthetic resin pipe is heated and expanded, can be easily removed. Not taken.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing an example of the manufacturing process of an adhesive-clad tube used in the method for manufacturing a synthetic resin-lined tube of the present invention. 1... Extruder, 2... Extruded synthetic resin pipe,
3...forming device, 4...cooling solidification device,
5... Heat-expandable synthetic resin pipe, 6... Taking-off device,
7...Adhesive extruder, 8...Crosshead die, 9...Cooling device, 10...Extruded film-like adhesive cylinder, 11...Adhesive cladding tube, 12
... Cutting device, 13 ... Adhesive coated portion cooled during coating, 14 ... Adhesive coated tube having adhesion defects at both ends.

Claims (1)

[Claims] 1. A heat-expandable synthetic resin tube extruded and molded by an extruder is guided to a crosshead die having an annular discharge port, and a film-shaped heat-sensitive adhesive is extruded from the crosshead die into a cylindrical shape. The entire outer peripheral surface of the heat-expandable synthetic resin tube is coated with the adhesive cylindrical object while being cooled intermittently to form an adhesive-coated tube, and then the adhesive-coated tube is coated with the cooled portion of the adhesive coating layer. Cut the metal tube so that it is both ends of the tube and is slightly longer than the length of the metal tube to be lined, insert the cut adhesive clad tube into the metal tube, and remove the adhesive at both ends of the adhesive clad tube. A method for producing a synthetic resin lined pipe, which comprises heating the pipe with the coating layer peeled off.