JPS633734B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heat-shrinkable composite pipe comprising two or more water-crosslinkable polymer layers.

In the production of heat-shrinkable composite pipes made of different materials, there are inherent factors that make it extremely difficult to manufacture the composite pipes, perform cross-linking to impart heat-shrinkability, and expand the cross-linked composite pipes. However, no effective method has been found for economically industrializing it.

That is, methods for laminating different materials in the manufacture of composite pipes include parallel or tandem extrusion molding, but the equipment required for these methods is enormous in cost. Furthermore, there are technical problems such as deformation of the pipe when the materials are molded at different temperatures.

Crosslinking treatment is carried out to impart great shrinkage, but in this case, crosslinking by electron beam irradiation has limitations on the pipe size, and gamma ray irradiation requires a long time. Chemical crosslinking using a chemical radical generator such as an organic peroxide has problems with processability because the extrusion temperature is limited, and there is also the problem of pipe deformation due to heating during crosslinking. These problems become more difficult as the pipe size increases.

In the expansion treatment of crosslinked composite pipes, a method is generally known in which the pipe is placed in a desired cylindrical molding device, heated, a fluid such as liquid or gas is introduced into the pipe to expand it, and then cooled as it is. However, as shown in FIG. 2, the expansion of the pipe 22 inside the cylinder 21 may start from the end, and in this case, the air 23 in the middle part has no place to escape, and the desired expansion may not be obtained or it may not be inserted. There is a problem in that the pressure of the fluid used can destroy it.

The present invention eliminates the above problems, is extremely economical, eliminates restrictions due to pipe size,
Moreover, it is an object of the present invention to provide a method for manufacturing a heat-shrinkable composite pipe that is capable of uniform expansion.

The method for manufacturing the heat-shrinkable composite pipe of the present invention includes 2
A wrapped body made of a water-crosslinkable polymer of more than 10% is wrapped and laminated around the wrapped body, the layers are integrated by heating, and then crosslinked by contact with moisture or the wrapped body is removed. Either of the above is first performed to obtain a cross-linked composite pipe, the cross-linked composite pipe is housed in a cylindrical molding machine having degassing holes, heated, and a pressurized fluid is introduced into the pipe to expand it. It is characterized by being cooled as it is.

Here, water-crosslinkable polymers include polyolefins, olefin copolymers, olefin-based copolymers, chlorinated polyolefins, and other polymers with the general formula RR'SiY ₂ (R is a monovalent olefinic unsaturated Hydrocarbon group or hydrocarbon ether group, Y
is a hydrolyzable organic group, R' is a monovalent hydrocarbon group containing no aliphatic unsaturated bond, or the same group as R or Y) is grafted in the presence of a radical-generating compound. It refers to what was caused. In the present invention, antioxidants, flame retardants, fillers, colorants, etc. may be added thereto. The water-crosslinkable polymer is crosslinked by being molded into a predetermined shape and then brought into contact with moisture in the presence of a silanol condensation catalyst.

The water-crosslinkable polymer is formed into a tape, sheet, etc. to form a wound body. The thickness, length, shape, etc. of the wound body are not particularly limited, but the thickness is preferably 5 mm or less.

There are no particular restrictions on the shape or size of the deaeration hole provided in the cylindrical molding device, but if it is too large, the material of the wrapped body may protrude from the deaeration hole due to the pressure of the fluid introduced into the pipe. 5 in diameter
mm or less is preferable. Note that the cylindrical molding device may also be formed of a metal mesh.

Hereinafter, specific examples of the present invention will be described.

Water-crosslinkable polyethylene and water-crosslinkable ethylene-propylene copolymer were each molded into sheets with a thickness of 0.3 mm. These two types of sheets are used as a wrapping body, and a water-crosslinkable polyethylene sheet is placed as an inner layer on the circumference of a copper tube with an outer diameter of 40 mm and a length of 1000 mm that has been surface-treated with a fluorine-based polymer. An ethylene-propylene copolymer sheet is used as the outer layer, wrapped and laminated, heated at 150℃ for 5 minutes to fuse and integrate the inner and outer layers, and then immersed in hot water at 80℃ to crosslink. A crosslinked composite pipe was obtained by removing the wrapped body from the pipe. As a result of the crosslinking treatment, the inner polyethylene layer showed a gel fraction of about 70%, and the outer layer ethylene-propylene showed a gel fraction of about 65%, indicating that the crosslinking was complete.

The cross-linked composite pipe is an aluminum cylindrical molding machine with an inner diameter of 80 mm, an outer diameter of 84 mm, and a length of 1500 mm, with one end sealed, a liquid feeding jig attached to the other end, and multiple deaeration holes of 0.3 mm in diameter on the surface. I put it in. FIG. 1 shows this state, where 1 is a cylindrical former, 2 is a demolition hole, and 3 is a crosslinked composite pipe.

The cross-linked composite pipe was placed in a cylindrical molding machine with degassing holes, heated at 180°C for 10 minutes, and expanded by filling the pipe with 0.5 kg/cm ² of nitrogen gas.
It was cooled in water in that state. In addition, in this operation, since there was no trapped air between the molding machine and the pipe, it was possible to produce a uniformly expanded pipe with no constrictions or twists and an extremely good appearance.

When the pipe manufactured in this way was exposed to hot air at 150°C to examine its shrinkage, it was found that the shrinkage was approximately 42°C in the radial direction.
% shrinkage, and the longitudinal shrinkage was less than 5%.

On the other hand, as shown in FIG. 2, when a cylindrical molding machine without a degassing hole was used, air remained between the molding machine and the pipe, resulting in constrictions and portions that did not expand in the expansion pipe.

In the above embodiment, the wrapped body was removed after cross-linking, but it is also possible to remove the wrapped body and then cross-link. Further, although the description has been given using a cylindrical pipe as an example, the present invention is not limited to this, and can also be applied to irregularly shaped products.

As explained above, since the present invention forms a pipe by wrapping it and crosslinks it by contacting it with moisture, it does not require an extrusion molding machine or equipment for crosslinking, and is extremely economical. , can be easily manufactured from large to small sizes. Further, since the expansion operation is performed using a cylindrical molding machine having degassing holes, a uniform product can be manufactured.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the case where the expansion operation is performed using a cylindrical molding machine with a degassing hole, and Figure 2 is an explanatory diagram of the case where the expansion operation is performed using a cylindrical molding machine without a degassing hole. be. 1: Cylindrical molder, 2: Deaeration hole, 3: Pipe.

Claims (1)

[Claims] 1 Wound bodies made of two or more types of water-crosslinkable polymers are wrapped and laminated around the circumference of the wrapped body, the layers are integrated by heating, and then cross-linked by contacting with moisture or the wrapped body is A cross-linked composite pipe is obtained by first performing either of the above steps, followed by heating the cross-linked composite pipe in a cylindrical molding machine with degassing holes, and then introducing a pressurized fluid into the pipe to expand it. A method for manufacturing a heat-shrinkable composite pipe, which is characterized in that the pipe is heated and cooled as it is.