JPS5922654B2 - Method for manufacturing lined long tubes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a long tube whose inner surface is lined with a polyethylene resin.

Traditionally, steel pipes have been lined with polyethylene to protect their inner surfaces, etc. In this case, non-crosslinked polyethylene would have problems in terms of wear resistance and other physical properties, so crosslinked polyethylene was used as the lining material. Polyethylene is used. Polyethylene cross-linked using a cross-linking agent such as organic peroxide or irradiation with ionizing radiation is used to line steel pipes, etc., but when lining long pipes, a certain length of polyethylene is used. It is necessary to fuse polyethylene pipes together to make a long length. In this case, if the pipes are cross-linked, the strength of the fused part may not be sufficient, and the fused part may break when heated or expanded, or it may not be possible to use it for a long time. During this process, creep deterioration occurred and damage occurred at the fused portion. It is also possible to prepare a long piece of cross-linked polyethylene pipe without performing fusion bonding after cross-linking and draw it into the long pipe to line it, but in this case, the long pipe is It is difficult to transport the lining in a straight line to the finishing location, so it has to be rolled up into a loop shape, and even when it is rewound, it is curved and has a long shape. Not only is it difficult to pull the long pipe into the pipe because of the large amount of friction involved in drawing it into the pipe, but the long pipe that has been drawn in is easily damaged by friction with the long pipe, which poses a quality problem.

The present invention was developed as a result of various researches aimed at resolving the drawbacks of the conventional methods as described above. As a result, it is possible to achieve good results by using a pipe made from a specific type of crosslinkable polyethylene resin and crosslinked to a specific range of degree of crosslinking. This was done after discovering that results could be obtained, and the gist of this is that it is made of a silane-modified polyethylene resin composition that has the property of crosslinking when heated in the presence of moisture, and is crosslinked to a degree of crosslinking of 5 to 30%. Using a plurality of pipes, the ends of the pipes are fused and joined to each other to have approximately the same length as the long pipe to be lined, and the long pipes are folded. The present invention relates to a method for manufacturing a lined long tube, which is characterized by drawing the long tube into the long tube and heating and pressurizing the inside of the long tube with steam to bring the surface of the long pipe into close contact with the inside of the long tube.

The silane-modified polyethylene resin composition used in the present invention has the property of crosslinking when heated in the presence of moisture, and contains a silane-modified polyethylene resin and a silanol condensation catalyst as main components. .

The above-mentioned silane-modified polyethylene resin is composed of an ethylene resin such as polyethylene, an ethylene copolymer containing ethylene as the main monomer component, or a chlorinated polyethylene, and a general formula RR'SiY2 (where R is a silicon-carbon bond). represents a monovalent olefinic unsaturated group bonded to silicon by
represents a hydrolysable group selected from acyloxy and oxime groups, and RI is 1 without aliphatic unsaturation.
represents a valent hydrogen-transferring group, the above-mentioned R group or Y group. ) in the presence of a compound that generates free radicals to bond the silane to an ethylene resin. Examples of the silane include vinyltriethoxysilane, pinyltrimethoxysilane, pinylmethyldiethoxysilane, vinylphenyldimethoxysilane, and the like.

Further, as the silanol condensation catalyst contained in the silane-modified polyethylene resin composition used in the present invention, metal carboxylates such as dibutyltin dilaurate, stannous acetate, stannous octate, and zinc octate are suitable, but other metal carboxylates are suitable. Any known silanol condensation catalyst may be used.

Then, the silane-modified polyethylene resin composition is molded into a pipe, and this pipe has a degree of crosslinking of 5 to 3091).
However, various conventional forming methods may be employed to form the pipe, and crosslinking may be achieved by heating the pipe in the presence of moisture, such as in hot water. It is done by immersion.

However, the degree of crosslinking of the pipe used in the present invention is 5 to 30.
%, but if the degree of crosslinking is too low, there is a risk that when the pipe is folded, the inner surfaces will adhere to each other and the pipe will not restore its shape even if the inside is pressurized. This is because if is too high, the joint strength will decrease when the ends of the pipes are joined together.

In order to maintain the degree of crosslinking within the above range, the amount of silane used and the amount of silanol condensation added must be adjusted so that the degree of crosslinking falls within the above range when crosslinking is completed, or the degree of crosslinking must be within the above range. Heating conditions in the presence of moisture may be selected so as to fall within the above range. A more preferable range of the degree of crosslinking in the present invention is 10 to 25%. In addition, the degree of crosslinking in the present invention refers to the total insoluble content of the sample obtained by immersing the sample in hot xylene at 110°C for 43 hours, separating the insoluble content, vacuum drying it at 80°C for 6 hours or more, and determining its weight. % by weight.

In the present invention, the cross-linked pipe prepared as described above has a standard length of preferably 5 to 50 mm for convenient transportation.
Although it is cut into a length of 10 m, the ends are fused and joined to each other so that the long pipe to be lined has approximately the same length as the long pipe to be lined.

For this fusion bonding, an appropriate fusion method such as a butt fusion method may be used. Next, the long pipe obtained above is folded so that it can be easily passed through the long pipe. The folding shape is not particularly limited, but it is preferable to fold it so that the cross section becomes concave. In addition, in order to fold a long pipe, the long pipe is introduced into a hot air heating furnace and softened appropriately, and then passed through a ring or mold to fold it into the desired shape. A method in which the shape is stabilized by cooling is preferred. The long pipe folded in this way is inserted into the long pipe to be lined. In addition, in the present invention,
The fusion joining of the pipes, the folding of the long pipe and the drawing of the folded pipe into the long pipe may be carried out continuously and in parallel, or any of the above steps may be carried out independently and separately. Good too. Then, when water vapor is introduced into the long pipe drawn into the long pipe and the inside of the pipe is heated and pressurized, the long pipe returns to its original shape and expands further if necessary. It sticks to the inside. To introduce steam in this way, install a steam inlet at one end of the drawn-in long pipe and a condensed water outlet at the other end via flanges. <9/C! Il is more preferably 1.5 to 3
It is preferable to introduce steam of 1<g/Cd. Then, after heating and pressurizing for a certain period of time, compressed air is fed into the tube and the tube is cooled under pressure, thereby perfecting the adhesion of the polyethylene layer to the long tube. However, it is preferable that the outer diameter of the pipe used in the present invention is approximately the same as or slightly larger than the inner diameter of the long pipe to be lined.

The present invention is a method for manufacturing a lined long tube having the above-mentioned structure, and is made of a silane-modified polyethylene resin composition that has the property of crosslinking when heated in the presence of moisture, and has a high degree of crosslinking. Since long pipes with 5 to 30% cross-linked pipes are fusion-bonded, the strength of the fusion-bonded parts is excellent, and fusion bonding is possible during heating and pressurization for lining and long-term use. It is better to avoid damage starting from the fused portion due to breakage or creep deterioration.

Furthermore, even if a long pipe is folded, it can be restored to its original shape by heating and pressurizing the contacting surfaces without adhering to each other. The method used is to draw the pipe into the long pipe that is to be lined and then heat and pressurize it.This allows the pipe to be drawn into the long pipe in a straight state, and the surface of the long pipe is This makes it possible to line long pipes without damaging them due to friction. As described above, the present invention is an excellent method for manufacturing lined long pipes. According to the present invention, it is possible to line long pipes with a length of about 500 m, and for example, it is possible to line long pipes that are buried underground. When supply pipes or water supply pipes become obsolete, they can be easily repaired with inner lining.

Next, what about the embodiments of the present invention? I will clarify.

Note that in the following, parts mean parts by weight. Example 1 100 parts of medium-density polyethylene (melt index 0.2, density 0.94), 1 part vinyltriethoxysilane, and 0.05 part dicumyl peroxide were mixed in a sieve machine, and each composition was homogenized. The mixture dispersed in
Pellet A was obtained by extruding the mixture into pellets at a temperature of 200° C. using an extruder.

On the other hand, 100 parts of the same medium density polyethylene and 10 parts of dibutyltin dilaurate as above were mixed in the same manner and extruded to obtain pellets B. Next, add pellets A and B to 100
parts: 5 parts [7] to form a mixture, and this mixture was heated at 200°C using an extruder with a diameter of 65 mm for 18k.
It was formed into a pipe with an outer diameter of 80 mm and a wall thickness of 4 mm at an extrusion rate of g/Hr, and cut into a regular length of 5 m.

When the degree of crosslinking of the molded pipe was measured using a method using hot xylene, the degree of crosslinking was zero, confirming that the polyethylene was not crosslinked.

Next, the pipe obtained above was immersed in hot water at 95° C. for 10 hours to carry out hot water treatment to advance the crosslinking reaction. The degree of crosslinking after hot water treatment was measured and found to be 1801). This cross-linked polyethylene pipe is fused and joined by the butt fusion method [
2. Butt fusion conditions are heating temperature 260℃, heating time 6
After crimping and cooling for 60 seconds, the welding jig was removed. Next, while the pipe was drawn into a hot air heating tank at a temperature of 160°C and heated, the inner diameter 6 heated to a temperature of 150°C was heated.
0! ! It was passed through the mold ring of TIL, and while being pulled off at one end by a pulling machine, it was folded and deformed so that the cross section had a concave shape, and after passing through the mold ring, it was cooled with water. A pipe that is folded and deformed in a connected manner is made as described above, and the total length is 45 m.
The pipe was then drawn into an SGP8OA steel pipe having flanges at both ends, so that both ends of the pipe protruded slightly from the ends of the steel pipe. Both ends of the protruding pipe were heated to return the flanges to the steel pipe flanges, and a steam supply flange was attached to one end, and a condensed water discharge flange was attached to the other end.

Next, steam of 3k9/Cti was fed through the steam supply hole for 1 hour to heat it.

Thereafter, the steam supply was stopped, and cooling was performed while feeding compressed air of 3k9/Crii from the steam supply hole with a compressor. After 6 hours, feeding the compressed air was stopped, and when the inside was observed, it was confirmed that the crosslinked polyethylene had an outer diameter of 80 mm and a wall thickness of 4 mm, and was in close contact with the inner surface of the steel pipe.

Example 2 Using a polyethylene pipe with a degree of crosslinking of 18% prepared in accordance with Example 1, the ends of the pipe were heated together at a heating temperature of 260°C, a heating time of 35 seconds, and a pressurizing time of 30 seconds. Heat bonded using the butt fusion method,
JISK so that the joint is in the center of the joined pipes.
A No. 2 tampel based on -6301 was cut out and prepared, and the tensile strength and elongation were measured using a tensile test at 20°C and 100°C.

The results obtained are shown in Table 1.

For comparison, the same polyethylene as used in Example 1 was used in the same extruder as in Example 1 under the same conditions to produce an outer diameter of 80g1 and a wall thickness of 4J! It was molded into a 1-inch pipe.

The pipe was then irradiated with ionizing radiation and the degree of crosslinking was 18%.
It was cross-linked so that The ends of the cross-linked pipes were joined together by the tube fusion method under the same conditions as above, and a test piece was prepared in the same manner and a tensile test was conducted. The results obtained are shown in Table 1.

Claims (1)

[Claims] 1. Using a plurality of pipes made of a silane-modified polyethylene resin composition that has the property of crosslinking when heated in the presence of moisture and crosslinked to a degree of crosslinking of 5 to 30%, The ends of the pipe are fusion-bonded to each other so as to have approximately the same length as the long pipe to be lined to form a long pipe, and the long pipe is folded and drawn into the long pipe,
A method for manufacturing a lined long pipe, which comprises heating and pressurizing the inside of the long pipe with steam to bring the surface of the long pipe into close contact with the inner surface of the long pipe. 2. The manufacturing method according to claim 1, wherein the length of the pipe before being fusion-bonded is 5 to 10 m. 3. The manufacturing method according to claim 1, wherein the degree of crosslinking of the pipe is 10 to 25%.