JPS5953856B2 - Manufacturing method of synthetic resin lined metal pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a synthetic resin-lined metal tube.

2. Description of the Related Art Synthetic resin lined pipes are already known in which a long synthetic resin pipe of a small diameter is inserted into a long metal pipe of a large diameter and the two are bonded together with an adhesive to form a single body.

Furthermore, methods for manufacturing such lined pipes are already known. The following various methods were used to manufacture the above-mentioned Reininder tube.

The first method is to apply adhesive to the inner surface of the metal tube or the outer surface of the synthetic resin tube, and then expand the inner diameter of the synthetic resin tube.
This method brings the resin tube into close contact with the inner surface of the metal tube. The second method is to apply an adhesive to the inner surface of the metal tube or the outer surface of the synthetic resin tube, and then reduce the outer diameter of the metal tube to bring the metal tube into close contact with the outer surface of the resin tube. The third method is
This is a method in which a synthetic resin pipe is inserted into a metal pipe, and then a stock solution for producing urethane resin is injected into the gap between the two pipes, and the stock solution is foamed and hardened to form a unit. Among these methods, the first method and the second method require large-scale equipment because it is necessary to expand the inner diameter of the synthetic resin pipe or reduce the outer diameter of the metal pipe, respectively. It has the disadvantage of being "required" and "complicated to operate".

In the third method, it is not easy to inject the stock solution evenly into the gap between both pipes, and the gap between the synthetic resin pipe and the metal pipe is inevitably large, and the lining pipe must be of good quality. It has the disadvantage that it cannot be obtained. Therefore, it was necessary to devise a method for manufacturing lined pipes of high quality more easily. In response to the above-mentioned needs, this inventor has
First, we proposed a method for manufacturing lined pipes.

The manufacturing method uses a long metal tube with a large diameter and a long synthetic resin tube with a small diameter that can be inserted into the tube, and the difference between the inner diameter of the metal tube and the outer diameter of the resin tube is made small. , apply a foaming adhesive to the inner surface of the metal tube or the outer surface of the resin tube, insert the resin tube into the metal tube immediately after application, allow the adhesive to foam and harden, and join both tubes together. 5. However, in order to carry out this method, it is necessary to insert the resin tube into the metal tube immediately after applying the foam adhesive and to securely hold the resin tube in the center position within the metal tube. Special ingenuity was required. This invention was created in response to such a need. The inventors came up with the idea of using a resin separator to hold the resin tube in a central position within the metal tube.

The resin separator is made of a material softer than the resin from which the resin tube is made and is formed into a rod shape. In this invention, a plurality of these resin separators are attached to the outer surface of the resin pipe at axially symmetrical positions, and the separators are brought into contact with the inner surface of the metal tube, so that the resin pipe is positioned at the center of the metal pipe. The main point is to maintain it. At this time, the longitudinal direction of this resin separator is oriented toward the tube axis direction of the resin pipe, and the tip of the separator is tapered, so that the height of the separator is adjusted to the gap between the metal pipe and the resin pipe. It is intended to be 1 to 1.5 times the width. This invention uses a large-diameter long metal tube, a small-diameter long synthetic resin tube that can be inserted into the long metal tube, and a plurality of resin separators, and the resin separator is made of a material softer than the resin tube. The separator is attached to the outer surface of the resin pipe so that the longitudinal direction of the separator faces the tube axis direction, the tip of the separator is tapered, and the height of the separator is adjusted to the gap between the two pipes. Width 1 to 1.5
Apply a latent foaming adhesive to the outer surface of the resin tube or the inner surface of the metal tube, and then insert the resin tube into the metal tube, with the separator holding the resin tube inside the metal tube. The present invention relates to a method for manufacturing a synthetic resin-lined metal pipe, which is characterized by foaming and curing an adhesive.

The method of this invention will be explained below with reference to the drawings.

FIG. 1 is a cutaway perspective view schematically showing an embodiment of the method of the present invention. 2 and 3 are partially cutaway perspective views of a resin separator used in the method of the present invention. In FIG. 1, 1 is a steel pipe, 2 is a hard vinyl chloride pipe, 3 is a resin separator, 4 is an adhesive jetting nozzle, and 5 is a column that supports the nozzle 4. and 6 is a coating layer of a latent foamable adhesive.
In FIG. 1, four separators 3 are attached at equal intervals on the outer surface of the resin tube 2, with their longitudinal directions facing the tube axis direction of the resin tube 2.

The separator 3 is made of soft vinyl chloride resin, has a chevron-shaped cross section, and has a tapered tip. The height h of the separator 3 is
Assuming that the content of the metal tube 1 is 2R and the outer diameter of the resin tube 2 is 2r, the metal tube 1 is approximately 1.1 times the gap width (R-r).
A spouting nozzle 4 is inserted into the interior of the metal tube 1, and a latent foaming adhesive 6 is spouted from there.
form a layer. Immediately after that, the resin tube 2 is inserted into the metal tube 1. When inserted, the tip of the separator 3 collides with the inner surface of the metal tube 1, but since the separator 3 is made of a flexible material, it deforms appropriately and is not inserted into the metal tube 1 by forcefully inserting it. It is firmly fixed. Since the separators 3 are all molded in the same shape, the resin tube 2 is thereby fixed at the center position within the metal tube 1. Next, details of this invention method will be explained step by step.

In this invention, a large-diameter long metal tube and a small-diameter long synthetic resin tube that can be inserted into the large-diameter long metal tube are used. Here, a long tube refers to a tube with a length of 1 m or more, usually several meters to several meters in length. In this case, the diameter of the tube is 50 mm or more, usually about 100 to 500 mm. When a synthetic resin tube is inserted into a metal tube, an extremely small gap exists between the two tubes. The extent of the small gap is approximately 0.2 mm to 2 mm. The size of this gap is a value expressed as an average value. As already mentioned, this gap is a value expressed by R-r, where the average value of the inner diameter of the metal tube is 2R and the average value of the outer diameter of the resin tube is 2r. The inventive method uses a foamable latent adhesive.

This adhesive may be solid or liquid at room temperature, but liquid is preferred. If it is in solid form, it is applied by dissolving it in a solvent or dispersing it in a non-solvent. As the adhesive, it is preferable to use a resin that undergoes a chemical reaction after application to form network-like molecules, particularly a urethane-based, epoxy-based, or polyester-based resin-forming composition. In order to impart foamability to the adhesive, hydrocarbons such as freon, hexane, heptane, or water, etc. are added as a foaming agent to the adhesive. In the method of this invention, a potentially foamable adhesive is applied to the inner surface of a metal tube or the outer surface of a synthetic resin tube.

When applying, the coating is applied thinly so that the coating thickness is 10 to 90% of the average width of the gap between the two tubes. In addition, regarding this coating thickness, in view of the foaming performance of the adhesive, in order to maintain sufficient foaming capacity even when the adhesive fills the gap, the volume of the gap should be the same as when free foaming occurs. Adjust the coating thickness so that it is less than half the volume. It is desirable that the coating be uniform both in the tube axis direction and in the circumferential direction. In this invention method, a resin separator is used.

The separator is made of a material that is softer than the plastic tube. For example, when the synthetic resin pipe is made of hard vinyl chloride resin, the separator is made of soft vinyl chloride resin. Also,
When the synthetic resin pipe is made of low-pressure polyethylene, the separator is made of high-pressure polyethylene, a copolymer of ethylene and vinyl acetate, or chlorinated polyethylene. The above-mentioned separator can be molded separately from the resin tube and later adhered or fused onto the resin tube.

In addition, this separator is used when extruding resin pipes.
It is also possible to simultaneously extrude from a separate extruder to produce a tapered separator of a predetermined height and immediately fuse it onto the resin tube, thereby molding it integrally with the resin tube from the beginning. The isolate is
It is fixed onto the outer surface of the resin tube with its longitudinal direction facing the tube axis direction of the resin tube. The positions where the separators are fixed are preferably radially, that is, at equal intervals and axially symmetrical, with the tube axis of the resin tube as the center. The isolate is
Although it is possible to provide this by penetrating the outer surface of the resin pipe from end to end, it is also possible to cut it in the middle and provide it intermittently. Preferably, the separator has a constant cross-section.

Its shape is required to be tapered at the tip. In its cross-sectional shape, when the bottom surface is the surface in close contact with the resin tube, the height perpendicular to the bottom surface must be within a certain range with respect to the gap between the metal tube and the resin tube. The above-mentioned shape will be specifically explained as follows.

The cross-sectional shape of the separator 3 may be triangular as shown in FIG. 2, or semi-elliptic as shown in FIG. The length b of the base is usually 0.5 to 5 times the height h, but preferably 0.5 to 3 times the height h. Further, it is desirable that the length b of the base is 0.5 mm or more.
The length of the height h should be selected based on the inner diameter error of the metal tube and the outer diameter error of the resin tube so as to absorb the error. When a resin pipe is inserted into a metal pipe, and the average width of the gap formed between the two pipes is C, the height h is desirably 1.0 to 1.5 times C. After applying the foam adhesive, insert the resin tube into the metal tube.

At this time, since the separator is present, the resin tube is supported by the separator and positioned at the center within the metal tube. In this state, the adhesive foams and hardens. The metal tube is heated externally to promote foaming and curing. It is desirable that the heating be carried out so that the inner surface of the metal tube reaches a temperature of 80 to 100°C. Further, it is desirable that the heating be performed as quickly as possible. There are no particular restrictions on the heating method, and various methods such as hot water, steam, hot air, infrared rays, and dielectric heating can be employed. According to the method of this invention, a separator is attached to the outer surface of the resin tube, and the separator is made of a soft material and is tapered, so that the tip of the separator
Easily deformed or cut.

Moreover, the height of the separator is limited by the distance between the metal pipe and the resin pipe.
It is slightly longer than the average width of the gap. Therefore, when inserting a resin pipe into a metal pipe, it is possible to forcefully deform the separator and push it in. After being pushed in, the separator stretches and holds the resin pipe at the center position inside the metal pipe. It turns out. this child. This is true even if adhesive is present. In this way, the resin tube is fixed at the center of the metal tube. According to the method of this invention, a latent foamable adhesive is applied to the inner surface of a metal tube or the outer surface of a resin tube, and the resin tube is inserted into the metal tube before the adhesive foams. , the adhesive can be thinly and evenly distributed between both tubes. If the applied thickness of the adhesive is made smaller than the gap width and the adhesive is foamed in a space that is less than half of the volume that will expand due to free foaming, the adhesive will fill the gap well and create closed cells. It becomes a multifoamed body with a lot of . For this reason, a high-quality lining pipe with a small gap width can be obtained. Furthermore, in the method of the present invention, if the separator is made to penetrate through the resin pipe from one end to the other, and after the adhesive 7 is applied, the separator is positioned laterally with respect to the tube axis of the resin pipe, The separator will prevent the adhesive from dripping under its own weight.

Therefore, the separator also serves for even distribution of adhesive. Next, the details of the method of the present invention will be further explained with reference to Examples.

Example metal tube: outer diameter 110 mm, inner diameter 106 mm, length 5
．． Using a 5m steel pipe, the outer diameter is 104mm as a synthetic resin pipe.
1. A hard vinyl chloride pipe with an inner diameter of 100 mm and a length of 5.5 m was used.

As a result, when the synthetic resin tube was inserted into the metal tube, there was a gap of 1.0 mm between the two tubes.
A stock solution for producing semi-rigid urethane resin was used as the adhesive with potential foaming properties.

This stock solution had the following composition in parts by weight:
When this stock solution was allowed to foam freely, it foamed to about 30 times its original size and became an open-celled foam.

As the separator, one made of soft vinyl chloride and having an isosceles triangular cross-sectional shape as shown in FIG. 2 was used.

The separator has an h of 1.1 mm. b was 2.0 mm. Four of these separators were attached at equal intervals on the outer surface of the resin tube. When attaching it, it was attached with adhesive. While rotating the resin tube, apply the above stock solution onto the outer surface of the resin tube to a thickness of approximately 0.
．． While applying the solution uniformly to 5 mm, it was advanced and inserted into the metal tube.

Insertion was easy and the resin tube was held in the center of the metal tube. After insertion, hot air at 100° C. was applied to the outer surface of the metal tube to heat the metal tube. As a result, the stock solution rapidly foamed and hardened. In the thus obtained synthetic resin-lined metal tube, the resin tube was located at the center of the metal tube, there was almost no eccentricity, and the resin tube and the metal tube were strongly bonded to each other.

Furthermore, even though heated water and cooling water were repeatedly flowed into this tube, the synthetic resin tube did not shrink much, and the adhesive layer hardly absorbed any water.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view schematically showing an embodiment of the method of the present invention.

Claims (1)

[Claims] 1. Using a long metal tube with a large diameter, a long synthetic resin tube with a small diameter that can be inserted into the long metal tube, and a plurality of resin separators, the resin separators are made of a material softer than the resin tubes. , the separator is attached to the outer surface of the resin pipe so that the longitudinal direction of the separator faces the tube axis direction, the tip of the separator is tapered, and the height of the separator is set to 1 to 1 of the gap width between both tubes. Apply a latent foaming adhesive to the outer surface of the resin tube or the inner surface of the metal tube, and then insert the resin tube into the metal tube so that the separator comes into contact with the inner surface of the metal tube and the resin A method for manufacturing a synthetic resin-lined metal tube, which comprises holding the tube, foaming an adhesive, and curing the adhesive.