JPS608392B2 - Tube inner surface coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly provides a tube for restoring the function of an existing buried pipe in soil or the like.

Cast iron pipes, steel pipes, asbestos pipes, etc. are used for water pipes and gas pipes, but as they age, rust and deposits form on the inner surface of the pipes, resulting in a decrease in flow rate and deterioration of the pipes. According to
Water leakage and gas leakage from connections and defective parts has become a major problem.

In order to repair this problem, digging up the underground pipe and adding protection from the outside or replacing it is not only expensive but also has the problem of blocking traffic, making it extremely difficult to implement. There is sex. Therefore, there is a need for a method of cleaning the inner surface of the buried pipe and applying some kind of coating to it while the pipe remains buried, and several methods have been proposed and implemented. These can be roughly divided into two types: those in which short (several lengths) of plastic tubes are inserted while being welded on-site, and those in which paint is applied to the inner surface of the tubes by some method. The former method requires considerable effort, and the latter method has a problem in that it is difficult to completely cover the defective portion. Therefore, the button was continuously inserted and extracted into one unit of long plastic pipe.
It would be very convenient to have something that could form a coating that tightly adhered to the inner surface of the tube. As a result of various studies, the present invention has resulted in a method that can meet the above requirements. It is very difficult to insert a plastic tube with a length of, for example, 100 mm into a buried tube when the outer diameter of the plastic tube is approximately equal to the inner diameter of the buried tube. Due to the frictional force between the plastic pipe and the wall of the buried pipe, the tension during insertion and retraction becomes large, and even if the traction force can be increased and retraction is possible, there is a problem that the plastic pipe may be damaged. On the other hand, if the diameter of the inserted plastic tube is smaller than the inner diameter of the buried tube, it is difficult to bring the plastic tube into close contact with the inner wall of the buried tube, resulting in a gap. In this case, if there is a defect in the buried pipe, if rainwater or the like enters from the outside, it will run in the length direction of the pipe, which is not preferable. Therefore, a process of filling this gap by some means is required, which cannot be said to be an effective method. The key is to have a long plastic pipe that has an outer diameter equal to or slightly smaller than the inner diameter of the buried pipe, that can be easily inserted into the buried pipe, and that can be brought into close contact with the wall of the buried pipe. If obtained, it will serve the intended purpose.

In the conventional method of inserting and connecting plastic pipes, thick-walled plastic pipes are used, such as a 5-thick wall for a 10-wall pipe and a 9-thick wall for a 30-wall pipe.

This is to withstand the tensile force during insertion, the injection pressure of cement milk used to fill the gap, etc.
If the plastic pipe could be brought into close contact with the inner wall of the buried pipe, even if internal pressure is applied like a water pipe, the inserted plastic pipe would not be directly exposed to pressure, so there would be no problem when inserting the pipe. In other words, the thickness may be small.Also, in the case of gas pipes, the internal pressure is small, so as long as the inner surface can be tightly coated, the thickness is not a problem.Polyethylene to polypropylene, ethylene-virulyl acetate copolymer, ethylene - Pipes made of polyolefin resins such as ethyl acrylate copolymer have high strength at room temperature, but when the temperature rises to near their melting point, their strength drops significantly and they can easily deform. Furthermore, even at room temperature, it is possible to deform the plastic pipe with a small thickness relatively easily.The present invention focuses on the above fact, and the present invention has been developed to We have devised a material that can be easily inserted into buried pipes by deforming the cross section of plastic pipes with the same outer diameter to a smaller size by heating and cooling them, or by folding them at room temperature and binding them with plastic tape. It is.

For example, Fig. 1A shows a plastic pipe with a normal circular cross section, but if the pipe is thin, it can be crushed to have a flat cross section as shown in the opening in Fig. 1. However, as it is, the long diameter will be larger than the original pipe diameter, making it difficult to insert it into the buried pipe, but if it is further folded in half as shown in Figure 2 A, the pipe will be about the same diameter as the original pipe. It becomes smaller during the season. If this shape is maintained, it can be easily inserted into a buried pipe. The method of holding it is by using the thermoplasticity of the plastic pipe, and
Heat the circular pipe shown in Figure A and shape it into the shape shown in Figure 2 A.
Possible methods include a cooling method or a method of physically forming the shape as shown in FIG. 2A without heating and then wrapping and fixing a plastic tape thereon. After a thermoformed plastic pipe is inserted into a buried pipe, it can be restored to its circular shape by raising the temperature of the plastic pipe to its melting point and applying internal pressure at the same time. In addition, if you use the second method and reduce the thickness of the plastic tape at the opening in Figure 2, the pipe will return to its circular shape by inserting the bound plastic pipe into the buried pipe and applying internal pressure to the pipe. As,
Tension is applied to the plastic tape and it is finally cut, no longer constrained by the tape and a pipe with a circular cross section is obtained. The plastic tape used in the present invention is desirably one that is heated after cutting and becomes integrated with an adhesive to bond the tube and the inner wall of the pipe, but especially in the case of a tape with a narrow tape width, the adhesive Even if they are not integrated, the effects of the present invention can be achieved as long as the adhesion between the tube and the inner wall of the tube is not impaired. The reason we specifically chose tape to bind plastic pipes is that it needs to be thin and narrow in order to reduce its mechanical strength to a certain extent so that it can be cut.
This is because binding with a string-like elongated body increases the thickness and increases the diameter in the outer radial direction, which also becomes an obstacle when being pulled in. Next, in order to firmly adhere the plastic pipe to the inner wall of the buried pipe, it is desirable to use an adhesive, and the second
As shown in Figure ', it is necessary to provide an adhesive layer on the top surface of the plastic pipe.

Examples of adhesives include pine resin, asphalt, polyamide resins, polyolefin resins with wax and tackifier added, and other materials that melt at high temperatures and re-form into a storm shape when cooled to function as adhesives. That is, a hot-melt adhesive is preferred, but a thermosetting adhesive may also be used. Coating with these adhesives may be done by applying a melt or solution of the adhesive to the plastic pipe, or when extrusion molding the plastic pipe, double extrusion using two extruders may be used to coat the adhesive layer. may be provided. In the case of a thermosetting type, the adhesive layer provided on the plastic pipe does not take hold for a long time, so it is necessary to apply the adhesive layer immediately before the pipe is inserted into the buried pipe. In the case of a plastic pipe molded into the shape shown in Figure 2 A, adhesive may be applied to the plastic pipe before the pipe is inserted, or adhesive may be applied to the inner surface of the buried pipe before the pipe is inserted. . In the case of the opening in Figure 2, it is relatively difficult to apply adhesive on the plastic pipe, so the adhesive is applied to the inner surface of the buried pipe in advance, but it is preferable to apply the adhesive at the same time as the plastic pipe is inserted. In addition, as shown in Figure 2 C, if parts of the adhesive layer are glued together at the 3' part, it is possible to maintain the shape of the plastic pipe without heating, and it can be inserted into the buried pipe. After that, if the plastic pipes are heated, the adhesive force between them will be reduced, so by applying pressure inside the plastic pipes, the adhesive at the 3' portion will come off and it will be possible to restore the circular shape.

Also, the plastic tape on the plastic pipe is the third
As shown in the figure, it is preferable to wrap the plastic pipe at appropriate intervals because it can be easily cut by the internal pressure of the plastic pipe after insertion.

As shown in Fig. 2, the adhesive layer 3 is provided on the plastic pipe 1, and the plastic tape 2 is further wrapped around it. This is advantageous because it does not interfere with the adhesion of the pipes. In addition, when plastic pipes are made of polyolefin resin, for example, it is preferable that they be cross-linked in advance, and if a cross-linked pipe is used, the
There is no risk of melting during heating, and if the cross-sectional shape is changed by heating after crosslinking to facilitate insertion,
Since it can easily return to its original shape by reheating, it is more advantageous in terms of work than non-crosslinked products. If it is not necessary to bond the entire surface of the plastic pipe and the buried pipe, as shown in FIG. 4, an adhesive layer may be provided only on the surface of the pipe that cannot be covered by the plastic tape 2 made of adhesive. As described above, the material constructed by the method of the present invention can be easily inserted into an existing buried pipe whose inner surface has been cleaned, and after being inserted, it is heated by an appropriate means and pressure is applied inside. By applying it, it becomes circular in cross-section and adheres tightly to the inner surface of the buried pipe, forming a coating, so it is possible to quickly and easily restore the functionality of the existing buried pipe, and prevent water leakage and gas leakage from the existing buried pipe. It has the advantage of effectively preventing the intrusion of bad water, the generation of red water, etc.

[Brief explanation of the drawing]

FIG. 1A is a cross-sectional view of an ordinary plastic pipe, the mouth of which has been deformed into a flattened shape. Fig. 2 is a cross-sectional view showing an embodiment of the present invention, and Fig. 2 shows a pipe that has been deformed into a flat shape and is further folded in two.
This indicates that the cross-sectional shape has become smaller. The mouth is a cross-sectional view with plastic tape wrapped around it, and Figure 3 shows the mouth.
A sketch of it was shown. Figure 2C is a cross-section of a deformed plastic pipe provided with an adhesive layer, and Figure 2C is a cross-section of a plastic tape wrapped around it. Fourth
The figure shows a cross section of a plastic tape wrapped around a deformed plastic pipe partially coated with adhesive. 1...Plastic pipe, 2...Plastic tape, 3...Adhesive layer. O diagram (A) Bar diagram (〇) Force 2 diagram

【stomach) Figure 2 （〇） Figure 2 Deha) Soup 2 figure [D] force 3 diagram force 4 figure

Claims (1)

[Claims] 1 A plastic pipe whose cross section has been changed in shape to reduce its outer diameter, wrapped with plastic tape, is inserted into the pipe, and then internal pressure is applied to the plastic pipe to expand the plastic pipe to the cross section before the shape change. A method for coating an inner surface of a tube, characterized in that the inner surface of the tube is covered with the plastic pipe by breaking the plastic tape.