JPH03205128A - Manufacture of vinyl chloride tube - Google Patents

Abstract

PURPOSE:To stabilize the produce quality and upgrade the working efficiency by carrying forced-air cooling for a vinyl chloride tube just after the bonding process. CONSTITUTION:A vinyl chloride tube coated with a bonding agent on its outer surface is inserted into a steel tube and heated by the heating zones 4 - 6 to bond the vinyl chloride tube with the inner surface of the steel tube. Just after the bonding process, forced-air cooling is applied to the vinyl chloride tube by means of a fan 8. As a result, a vinyl chloride lining tube 1 can be cooled to the normal temperature without damaging the bonding force between the steel tube and the vinyl chloride tube.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing PVC-lined pipes. [Prior art] The basic method for lining steel pipes with PVC pipes is to insert a PVC pipe whose outer surface is coated with an adhesive film (50 to 70 μm thick) into the steel pipe, and then heat it to melt the film. At the same time, the PVC pipe is expanded and bonded to the inner surface of the steel pipe. At this time, if air bubbles accumulate between the inner surface of the steel pipe and the outer surface of the PVC pipe, it will become a defective product, so it is necessary to heat the steel pipe from the center toward the ends to expel air from the pipe. Furthermore, if the heating temperature is high, the PVC pipe expands too much, causing the inner surface of the PVC pipe to partially protrude. Therefore, the key points of this method are as follows.

■Heat from the center of the tube to the ends.

■Accurately control heating temperature. FIG. 2 is an explanatory diagram showing the prior art. In FIG. 2, a steel pipe with a PVC pipe 1, which is a material to be heated, is preheated by a preheating zone 2 having a square structure from the center of the pipe toward the ends of the pipe, and the temperature of the pipe reaches 60 to 80°C. After that, through intermediate zone 3, V
In the first heating zone 4 of the mold, the center of the tube is heated to 145°C. During that time, when the pipe temperature reaches 90°C, the adhesive melts, and as the temperature rises further, the PVC pipe becomes limp. 145
If the temperature exceeds ℃, PVC pipe becomes overtensioned. Thereafter, the object to be heated is heated to 145° C. toward the tube end by the C-shaped second silence zone 5, and finally the tube end is softened in the after-heating zone 6 and left to cool in the atmosphere.

[Problems to be solved by the invention] However, the conventional technology has the following problems. That is, as mentioned above, after being heated, the product is allowed to cool in the atmosphere, which requires a considerable amount of time, for example, 12 hours or more, resulting in problems such as lower work efficiency and the need for a horizontal holding yard for work-in-progress products. There is. The purpose of the present invention is to solve the above-mentioned problems and to propose a method for manufacturing PVC-lined pipes that improves work efficiency and provides stable product quality.
``Means for Solving the Problems'' The method of manufacturing a PVC-lined pipe according to the present invention involves inserting a PVC pipe whose outer surface is coated with an adhesive into a steel pipe, heating it, and applying the adhesive to the inner surface of the steel pipe. In the method of manufacturing a PVC lined pipe to which the PVC pipe is bonded, the PVC lined pipe is forcedly air cooled immediately after the bonding step.The cooling rate is preferably 15 to 25°C/min. It is desirable to cool the pipe. If the cooling rate exceeds 25°C/min, thermal contraction in the longitudinal direction of the PVC pipe may occur and the adhesion strength may decrease; if it is below 15°C, the PVC pipe will not be sufficiently cured. This is because it interferes with the subsequent pipe end treatment of the PVC lined pipe (cutting off excess PVC pipe at the pipe end, finishing the pipe end surface, etc.).

[Function] The method for manufacturing a PVC lined pipe in the present invention involves inserting a PVC pipe whose outer surface is coated with an adhesive into a steel pipe, heating it, and bonding the PVC pipe to the inner surface of the steel pipe with the adhesive. In the pipe manufacturing method, the PVC lined pipe is forced to air cool immediately after the bonding process, so the PVC lined pipe can be cooled to room temperature in a short time without damaging the adhesive strength between the steel pipe and the PVC lined pipe. becomes. Below, we will explain the adhesive force between the steel pipe and the PVC-lined pipe when the heated PVC-lined pipe is cooled under various cooling conditions. Use f. The dimensions of the PVC pipe are steel pipe outer diameter 48.6 mm, inner diameter 41.6 mm, PVC pipe outer diameter 39.9 mm, inner diameter 36.9 mm, and length of both 5 mm.
It is m. The adhesive was ethylene vinyl acetate, and the line speed was 1.2 m/min. Table 1 shows the heating and cooling conditions and the adhesive strength of the product. The temperatures in Table 1 are the averages at several points in the axial direction of the bond between the steel pipe and the PVC pipe. Regarding adhesive strength, samples were taken from the end of the tube during heating, at 120+n from the end of the tube, and from the center, and variations were determined. Adhesive strength is measured according to the Japan Water Works Association standard JWWA K11.6, and this test method measures the adhesive strength between a steel pipe and a PVC pipe by extruding a composite PVC pipe. As shown in Table 1, the adhesive strength value in forced air cooling does not deteriorate compared to natural cooling. [Example] Figure 1 is an explanatory diagram showing an example of the present invention. In FIG. 1, a steel pipe 1 with a PVC pipe, which is a material to be heated, is preheated by a preheating zone 2 having a V-shaped structure from the center of the pipe toward the ends of the pipe, and the temperature of the pipe reaches 60 to 80°C. After that, after passing through the intermediate zone 3, in the V-shaped first heating zone 4, the center part of the tube is 145 mm.
It is heated to ℃. During that time, when the tube temperature reaches 90℃,
When the adhesive melts and the temperature rises further, the PVC pipe expands. 1
If the temperature exceeds 45°C, PVC pipe will over-expand. Thereafter, the object to be heated is heated by the second heating zone 5 of the shape 145 toward the tube end.
℃, and finally the tube end is heated in the after-heating zone 6. Thereafter, in the rapid cooling zone 7, the PVC pipe-attached steel pipe 1 is forcedly air-cooled by a fan 8 placed above it to room temperature, and then transported to the next process. The wind speed of the cooling fan in this example is 5-10 m/s
It is. Also, as shown in the diagram, eight cooling fans are arranged in two rows. The cooling rate is 15-25°C/min. As a result of implementing the method of the present invention, it has become possible to conduct heating, cooling, and certain product processes online. [Effects of the Invention] As described above, according to the present invention, in the PVC-lined pipe manufacturing process, the PVC-lined pipe is heated to bond the steel pipe and the PVC pipe, and then forced air-cooled at a predetermined cooling rate. This has the effect of stabilizing product quality and improving work efficiency.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a conventional technique. 1...Steel pipe with PVC pipe, 2...Preheating zone, 3...Intermediate zone, 4...Lth heating zone, 5...Second heating zone, 6...After heating zone, 7.・Rapid cooling zone, 8 ・Fan.

Claims (1)

[Claims] In a method for manufacturing a PVC-lined pipe in which a PVC pipe coated with an adhesive on the outer surface is inserted into a steel pipe and heated, and the PVC pipe is bonded to the inner surface of the steel pipe with the adhesive, the PVC lining is bonded immediately after the bonding step. A method for manufacturing a PVC-lined pipe, characterized by forcing the pipe to cool with air.