JPS5949884B2 - 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 metal pipe with a large diameter and a long synthetic resin pipe with a small diameter that can be inserted into the long metal pipe are bonded together.

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 was due to the fact that non-foaming adhesive was used, and secondly, as long as it was a lined pipe,
Ideally, the metal tube and the resin tube should be as close to each other as possible without a large space between them, so in order to reduce the space between the two tubes, it is necessary to expand the inner tube or reduce the outer tube. Depends on what was needed. On the other hand, a composite pipe is known in which a wide gap is provided between a metal tube and a synthetic resin tube, and a foam layer of polyurethane resin is interposed between the gaps.

It is described, for example, in Japanese Utility Model Application Publication No. 50-35877 and Japanese Utility Model Application Publication No. 52-118221. In order to manufacture this composite pipe, a synthetic resin pipe is inserted into a metal pipe, and then a liquid material forming a synthetic resin foam is injected between the two pipes. However, in the method of injecting liquid substances, the injection location is limited to one area, so 2 u
If the gaps are as narrow as below, it will be difficult to uniformly spread the liquid over a long distance, and therefore it will not be possible to foam evenly over the entire area. Therefore, with the conventional injection method, it has not been 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 Vft or less. In addition, when the composite tube obtained by crushing is repeatedly heated and cooled, the synthetic resin tube gradually shrinks along the axial direction, and the unlined portion of the composite tube ends. There was a drawback that caused 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 expanding the inner tube or contracting the outer tube. I searched to see if there was a way to manufacture it.

As a result, the inventor applied a thin layer of a latent foaming adhesive to the inner surface of a metal tube or the outer surface of a synthetic resin tube, and before foaming, inserted the synthetic resin tube into the metal tube, and in the inserted state. By heating the metal tube and foaming the adhesive,
It was confirmed that both tubes could be bonded to each other by reducing the gap between the two tubes. At the same time, the inventor discovered that when the thus obtained lined tube was repeatedly heated and cooled,
In order to prevent the synthetic resin pipe from shrinking at the end of the pipe and peeling off from the metal pipe, it is necessary to use polyurethane resin as an adhesive and to foam the urethane resin production solution while leaving some foaming capacity. confirmed. This invention was made based on such confirmation. 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, and the gap between the metal tube and the synthetic resin tube is reduced to approximately 0.
．． A composition consisting of polyisocyanate, a polyol, a blowing agent, and a curing catalyst is used as an adhesive, and the composition is applied to the inner surface of the metal pipe or the outer surface of the resin pipe, and the coating thickness is adjusted to the gap width. 10 to 90% of
In addition, the ratio of the gap width to the coating thickness is less than half of the free foaming ratio of the composition, and immediately after coating, the resin tube is inserted into the metal tube, the metal tube is heated, and the composition is foamed. The present invention relates to a method of manufacturing a synthetic resin-lined metal pipe, which is characterized by curing.

This invention 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 long metal tube.

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 50v! t or more, usually 100TRJn to 500v
It is ranked B. When a synthetic resin tube is inserted into a metal tube, an extremely small gap exists between the two tubes. The degree of the small gap is about 0.2V11 to 27
It is 7za. The size of this gap is a value expressed as an average value. This gap has 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 this method, a composition comprising a polyisocyanate, a polyol, a blowing agent and a curing catalyst is used as an adhesive. As each of these components, those already known for producing urethane resins can be used. For example, polyisocyanates include tolylene diisocyanate, diphenylmethane-4,4'-
Diisocyanate, hexamethylene diisocyanate, etc. can be used. As the polyol, various types of polyols such as ether type, ester type, and butadiene type can be used, and polyhydric alcohols such as ethylene glycol and glycerin can be used alone or in combination. As the blowing agent, water, Freon, and hydrocarbons can be used. As the curing catalyst, various amine-based or tin-based catalysts can be used. The urethane resin used in the method of this invention may be either soft or hard, but soft urethane resins are preferred.

Soft urethane resins are said to have an 0H value of 300 or less, hard urethane resins have an 0H value of 400 or more, and there are semi-hard urethane resins in between, but semi-hard urethane resins & AOH values in the 300 range It is of value. In the method of this invention, it is desirable to use an OH value of 400 or less. The above-described compositions will foam freely when left in the atmosphere, typically producing open-celled polyurethane foams.

According to the experimental results, the reason why the conventional composite pipe manufactured by the injection method caused shrinkage of the synthetic resin pipe at the pipe end is because the polyurethane foam had many open cells. Therefore, we reduced the number of open cells in the polyurethane foam,
Increasing the number of closed cells prevents the synthetic resin pipe from shrinking at the pipe end. In order to reduce the number of open cells and increase the number of closed cells in a polyurethane foam, when foaming the urethane stock solution, it is necessary to foam rapidly so as to leave sufficient foaming power.

For this purpose, firstly, it is necessary to narrow the average gap between the metal tube and the synthetic resin tube. This means that the width should be about 2u or less, based on the width normally required for a lining pipe. Secondly, it is necessary that the stock solution for producing urethane foam has sufficient foaming performance. Foaming performance is expressed by the volume occupied by free foaming when the stock solution is left in the atmosphere. The free foaming ratio is the value that indicates how many times the original volume the foam becomes when it foams freely. It can be said that the greater the free foaming ratio, the greater the foaming performance. The free expansion ratio is 5 or more, preferably 10 or more. Thirdly, it is necessary to narrow the space in which the urethane stock solution can actually foam. That is, it is actually necessary to suppress the space in which foaming can occur to less than half of the space occupied during free foaming. The ratio of the space actually occupied by the foam divided by the space occupied when it is free foamed is called the packing ratio, and it is necessary to keep the packing ratio to a small value of 1/2 or less. Fourthly, it is desirable that the urethane foam is not expanded too much so that the specific gravity remains at a value of 0.1 or more. In terms of expansion ratio, it is desirable that the expansion ratio is 10 times or less, particularly 5 times or less. Fifth, it is desirable that foaming occur rapidly. For the above-mentioned reasons, in the method of the present invention, the above-mentioned composition is applied to the inner surface of a metal tube or the outer surface of a synthetic resin tube.

When coating, the coating thickness should be 10 to 90 times the width of the gap between both pipes.
%, apply thinly. In addition, this coating thickness is
In view of the foaming performance of the composition, in order to have sufficient foaming capacity when the gap is filled, the coating thickness is adjusted so that the volume of the gap is suppressed to less than half of the volume when it is free foamed. do. Needless to say, this coating thickness is an average value. It is desirable that the coating be uniform both in the tube axis direction and in the circumferential direction. The liquid that forms the polyurethane foam described above has a very short time to cure to form a solid resin, typically foaming within a few minutes.

It is said that the time it takes for this liquid to become a foam 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 is the time called set time. Cream time is the time from when the liquid to produce the resin starts foaming and becomes a cloudy creamy liquid until just before this liquid starts to visibly expand. What is rice time?
It is the time from when the creamy liquid begins to expand until the expansion reaches its maximum value. Set time is the time from the end of rice time until the surface of the foam is completely cured. 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. It is desirable to heat the metal tube so that the inner surface of the metal tube reaches a temperature of 80 to 100°C.

Further, it is desirable that the time required to reach this temperature be as short as possible, or in other words, it is desirable to heat 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. It is desirable that the foamed urethane has a low foaming ratio of 10 or less, particularly 5 or less.

In terms of specific gravity, it is desirable that the specific gravity is 0.1 or more, particularly 0.2 or more. Also, from the nature of the bubbles, 60% are closed cells.
It is desirable that the total number of employees be at least the same. According to this invention method,
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 are used, and the average gap between the metal tube and the synthetic resin tube is made as small as about 0.2vt to 2vt. Therefore, it is possible to obtain a pipe with a small gap width and a large capacity as a lining pipe.

In addition, a polyurethane foam forming liquid is used as an adhesive, and this is applied to the inner surface of the metal pipe or the outer surface of the resin pipe,
The coating thickness is 10 to 90% of the gap width, and immediately after coating,
That is, since the resin tube is inserted into the metal tube before the adhesive is foamed, it is easy to insert the resin tube, and the adhesive can be thinned and evenly distributed between the two tubes, making it easier to manufacture. is easy. In addition, the urethane coating thickness is set to 10 to 90% of the gap width, which is smaller than the gap width, and foaming is performed in a narrow space less than half of the space where free foaming is possible, with foaming capacity remaining, so closed cell foam is formed. The result is a large amount of foam. Furthermore, during foaming, the metal tube is heated to increase the foaming speed, which further increases the proportion of closed cells. The foam thus obtained typically has a closed cell content of 60%.
It accounts for more than Furthermore, since the average gap between the metal tube and the resin tube is set to be as small as about 0.2 u to 2&w, the above-mentioned polyurethane will firmly adhere the resin tube to the metal tube. For this reason, even if a fluid is poured into the lining tube obtained by crushing and heating and cooling are repeated, the resin tube will not shrink or peel, and therefore it can be used as a lining tube for a long time. You can get the best quality possible. The present invention provides significant benefits in this respect. Next, the details of the method of the present invention will be further explained with reference to Examples.

Example A steel pipe with an outer diameter of 76.3 u, an inner diameter of 67.9 m, and a length of 3 m was used as the metal pipe, and the outer diameter of the synthetic resin pipe was 65.9 m.
A hard vinyl chloride pipe with an inner diameter of 61.9 u and a length of 3 m was used.

As a result, there was a gap of 1.07&W between the two tubes. A stock solution for producing semi-rigid urethane resin was used as the adhesive.

This stock solution had the following composition in parts by weight. It expanded to double its size and became a foam with open cells.

While rotating the resin tube, the above stock solution was uniformly applied to the outer surface of the resin tube to a thickness of about 0.5 μ, and the resin tube was advanced and inserted into the metal tube.

When inserting, in order to maintain a uniform gap of 1u between both tubes, a diameter Iu) is placed on the outer surface of the resin tube along the tube axis direction.
A hard vinyl chloride rod having a length of 30 u was brought into contact with the rod and used as a gap retaining material. After stirring and inserting the resin tube, 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 synthetic resin-lined metal tube obtained by stirring, the resin tube and the metal tube were strongly adhered to each other.

Claims (1)

[Claims] 1. Use a long metal tube with a large diameter and a long synthetic resin tube with a small diameter that can be inserted into the long metal tube, and keep the average gap between the metal tube and the synthetic resin tube as small as about 0.2 mm to 2 mm. , a composition consisting of polyisocyanate, polyol, a blowing agent, and a curing catalyst is used as an adhesive, and the composition is applied to the inner surface of a metal tube or the outer surface of a resin tube, and the coating thickness is set to 10 times the width of the gap.
90% and the ratio of the gap width to the coating thickness,
The free foaming ratio of the composition is set to less than half, and immediately after application, the resin tube is inserted into the metal tube, and the metal tube is heated.
A method for producing a synthetic resin-lined metal pipe, the method comprising foaming and curing a composition.