JPS5953857B2 - Manufacturing method of composite pipe - Google Patents

Description

[Detailed description of the invention] This invention relates to a method of manufacturing a composite pipe.

2. Description of the Related Art Synthetic resin lined pipes are already known in which a metal pipe and a synthetic resin pipe that can be inserted into the metal pipe are bonded together to form a single body.

Furthermore, methods for manufacturing such lined tubes are already known. Known manufacturing methods include applying an adhesive to the inner surface of a metal tube or the outer surface of a synthetic resin tube, and then enlarging the inner diameter of the synthetic resin tube to bring the resin tube into close contact with the inner surface of the metal tube. One method was to reduce the outer diameter and bring the metal tube into close contact with the outer surface of the resin tube.

This is due to the fact that a non-foaming adhesive was used, and secondly, as long as it is a lined pipe, the metal pipe and resin pipe are placed as close as possible, and there is a large gap between them. This is because, since it is ideal to have no space, it was necessary to enlarge the inner tube or reduce the outer tube in order to reduce the space between the two tubes. On the other hand, a composite pipe is known in which a wide gap is provided between a metal pipe and a synthetic resin pipe, and a synthetic resin foam layer is interposed between the metal pipe and the synthetic resin pipe. For example, Utility Model Application Publication No. 50-35877 and Utility Model Application Publication No. 52-
It is described in the publication No.-118221. To manufacture this composite pipe, after inserting a synthetic resin pipe into a metal pipe,
A method is performed in which a liquid material forming a synthetic resin foam is injected between the two tubes. However, in the method of injecting a liquid, the injection location is limited to one area, so in narrow gaps of 2 mm or less, it is difficult to spread the liquid uniformly over a long distance, and it is difficult to spread the liquid uniformly over a long distance. Unable to foam evenly across the entire area. Therefore, with the conventional injection method, it was not possible to make an integrated lining pipe by bringing the synthetic resin pipe and the metal pipe into close contact with each other with a narrow gap of 2 mm or less. Under the above-mentioned conditions, the inventor has made it easier to create a lining tube in which a metal tube and a resin tube are brought close to each other and integrated without enlarging the inner tube or reducing the outer tube. We investigated whether there was a way to manufacture it. As a result, the inventor added a small amount of a liquid substance that dissolves or swells the resin pipe to the potentially foamable adhesive, and applied this thinly to the inner surface of the metal pipe or the outer surface of the θ synthetic resin pipe, and then When inserting a synthetic resin pipe into a metal pipe and heating the metal pipe in the inserted state to foam and harden the adhesive, the gap between the two pipes should be kept narrow and the pipes should be placed close to each other. It was confirmed that it could be firmly bonded. This invention was completed based on such confirmation. This invention uses a metal tube and a synthetic resin tube that can be inserted into the metal tube, uses a foamable resin containing a liquid substance that dissolves or swells the resin tube as an adhesive, and applies the adhesive to the metal tube. Manufacture of a composite pipe characterized by applying the adhesive to the inner surface of the pipe or the outer surface of the resin pipe, inserting the resin pipe into the metal pipe before foaming the adhesive, heating the metal pipe, and foaming and curing the adhesive. The method is summarized.

The method of this invention uses a large-diameter metal tube and a small-diameter synthetic resin tube that can be inserted into the large-diameter metal tube.

In this case, the diameter of the tube is 50 mm or more, usually 100 to 5 mm.
00mm.

When the synthetic resin tube is inserted into the metal tube, it is preferable that 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 an average value. 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. In the method of this invention, a resin having a potential foaming property and containing a liquid substance that dissolves or swells the resin tube is used as the adhesive.

A liquid substance that dissolves or swells resin pipes has a boiling point of 5.
The temperature is preferably 0°C or higher, and if the resin tube is made of polyvinyl chloride, examples include ketones such as acetone, methyl ethyl ketone, and cyclohexane, esters such as ethyl acetate, and halogenated hydrocarbons such as dichloroethane. It will be done. The amount added is preferably 2 to 10 wt % based on the foamable resin described below. The form of the resin may be liquid or solid at room temperature, but liquid is preferred. The resin may be thermosetting or thermoplastic. Specifically, urethane-based, epoxy-based, and unsaturated polyester-based resins are preferred. These resins undergo a chemical reaction to produce a network-like three-dimensional structure. In order to impart foaming properties to these resins, hydrocarbons such as freon, hexane, heptane, water, etc. are included as foaming agents. The adhesive with latent foaming properties is desirably composed of a mixture of two or more liquids, which immediately becomes foamable when mixed. Examples are isocyanates, polyols,
This is a liquid material for producing urethane resin consisting of a mixture of water and a reaction promoting catalyst. The time it takes for this liquid to harden to produce a solid resin is extremely short, but it is said that this time can be classified into the following four types.

The first time is the mixing time of the raw materials, the second is the time called cream time, the third is the time called rice time, and the fourth time is called set time. Cream time is defined as the time from when the liquid material to produce the resin starts foaming, becomes a cloudy creamy liquid, and just before this liquid starts to visibly expand. Rice time is the time from when a creamy liquid begins to expand until it reaches its maximum expansion. Set time is the time from the end of rice time until the surface of the foam is completely cured. This is true not only for liquid materials for producing urethane fat, but also for all types of resins in which a liquid material hardens into a resin and simultaneously foams. The method of the present invention will be explained below based on the time classified as above.

When the liquid is in the cream time, it is applied to the inner surface of the metal tube or the outer surface of the synthetic resin tube.
Thereafter, the resin tube is immediately inserted into the metal tube, but this insertion is performed at least until the rice time is reached, and the resin tube is placed at a predetermined position within the metal tube. During rice time, the metal tube is heated externally to promote foaming and hardening of the liquid. Resins with latent foaming properties are
When this is heated appropriately and placed under conditions that allow it to foam, it generates bubbles, increases in volume, and hardens.

At this time, if the resin is allowed to foam freely without particularly restricting the space in which it can foam, the resin will produce a large foamed body. However, if the space in which foaming can occur is restricted, the resin will not be able to foam to a large extent. In the method of this invention, the space in which foaming can occur is limited between the metal pipe and the synthetic resin pipe, so the actual foaming ratio will vary depending on the amount of adhesive applied. In the method of this invention, the amount of adhesive applied is adjusted in order to maintain the actual foaming ratio at an appropriate value. In the method of this invention, the amount of adhesive applied is controlled according to the following general principles. When the foaming performance of the adhesive is low, the amount of adhesive applied is increased, and when the foaming performance of the adhesive is high, the amount of adhesive applied is decreased. Even if the amount of adhesive applied is increased, it cannot be made larger than the space volume that can be foamed. Conversely, although the amount of adhesive applied may be reduced, it cannot be so small that it cannot fill the entire space due to free foaming. Thus, it is desirable to apply the adhesive so that its thickness accounts for 10 to 90% of the gap width j between the metal tube and the synthetic resin tube. Further, the coating amount is preferably such that the ratio of the gap width to the coating thickness is less than half of the free expansion ratio of the adhesive. In this way, as a result of foaming the adhesive in the gap between the metal pipe and the synthetic resin pipe, it is desirable that the adhesive actually foams 10 times or less, and it is preferable that the adhesive foams 5 times or less. Especially desirable.

When the adhesive has a short cream time and rice time, apply the adhesive to the inner surface of the metal tube J or the outer surface of the resin tube, and insert the resin tube into the metal tube sequentially from the applied area. In the method of this invention, the metal tube is heated in order to foam and harden the adhesive.

The metal tube, especially the inner surface of the metal tube, is heated to a temperature of 80 to 100°C.
It is desirable to do so in a manner that Further, it is desirable that the time required to reach this temperature be as short as possible, in other words, it is desirable that the temperature be raised as rapidly as possible. There are no particular restrictions on the heating method, and methods such as hot water, steam, hot air, infrared rays, and dielectric heating can be employed. According to the method of this invention, a resin with latent foaming properties is used as an adhesive, this 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 foaming of the adhesive. Therefore, the adhesive can be thinly and evenly distributed between both tubes.

Furthermore, since the adhesive has foaming properties, it foams between the two tubes, hardens, and fixes the two tubes together.

Since the adhesive contains a small amount of a liquid substance that dissolves or swells the resin tube, interfacial peeling between the foam and the resin tube is reduced and both tubes are firmly fixed. For this reason, the adhesive layer can be reduced to zero without reducing the diameter of the metal tube or expanding the diameter of the resin tube.
．． Composite tubes can be produced with layers as thin as 2 mm to 2 mm. Although such a composite tube with a thin adhesive layer could not be produced using the conventional injection method, the present invention has a great advantage in that it has become possible. Next, the details of the method of this invention will be explained with reference to Examples.

The example metal tube has an outer diameter of 76.3 mm, an inner diameter of 67.9 mm,
A steel pipe with a length of 3 m is used as a synthetic resin pipe with an outer diameter of 65.
A hard vinyl chloride pipe with a diameter of 9 mm, an inner diameter of 61.9 mm, and a length of 3 m was used.

As a result, there was a gap of 1.0 mm between the two tubes. A semi-rigid urethane stock solution was used as the adhesive.

This stock solution had the following composition (parts by weight). When this stock solution was allowed to foam freely, it expanded to about 30 times its original size, producing an open-celled foam.

While rotating the resin tube, the stock solution was uniformly applied to the outer surface of the resin tube to a thickness of 0.5 mm, and the tube was advanced and inserted into the metal tube. During insertion, in order to maintain a uniform gap of 1 mm between both tubes, a hard vinyl chloride rod with a diameter of 1 mm and a length of 'SLO mm is placed on the outer surface of the resin tube along the tube axis direction. This was used as a gap retaining material. In this way, after inserting the resin tube, the outer surface of the metal tube was heated to 100℃.
The metal tube was heated by applying hot air.

As a result, the stock solution rapidly foamed and hardened. Two composite pipes were made, and three 3.0 cm long samples were cut from each pipe and an adhesion test was conducted according to the JWWA Kll6-1927 "Hard PVC Lining Steel Pipe" adhesion test section, and the average adhesion strength was 25 kg. /CII
It was l2. When a similar comparative adhesion test was conducted on a composite pipe containing no cyclohexanone in accordance with the above example, the average adhesion strength was 8 kg/Cn]2.

Claims (1)

[Claims] 1. Using a metal pipe and a synthetic resin pipe that can be inserted into the metal pipe, a foaming resin containing a liquid substance that dissolves or swells the resin pipe is used as an adhesive, and the adhesive is applied to the inner surface of the metal pipe. Alternatively, a method for producing a composite pipe, which comprises applying the adhesive to the outer surface of the resin pipe, inserting the resin pipe into the metal pipe before foaming the adhesive, heating the metal pipe, and foaming and curing the adhesive.