JPS586613B2 - Method for manufacturing double shrink tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing double shrink tubes suitable for protective coverings of cable joints.

Heat-shrinkable tubes, when heated,
It is manufactured by expanding it to a predetermined size using some kind of expansion means, and then cooling and fixing it.

When using such heat-shrinkable tubes as protective covers for cable joints, in order to make them more completely waterproof, it is necessary to prepare an inner layer on the inside of the tubes to prevent the adhesive between the cable sheath and the tubes. It needs to be double shrink tubing.

Moreover, this inner layer also
It goes without saying that something that flows out at temperatures around 0°C would be bad.

It is extremely difficult to make a double shrink tube with the inner layer of the shrink tube made of a material that does not melt at such high temperatures.

This is because the tube shrinks when heated to integrate the tube and the inner layer.

As a result of various studies on how to integrate the tube with the inner layer agent while preventing the tube from shrinking, we found that while rotating the tube at a speed sufficient to generate a centrifugal force that overcomes the shrinkage force of the tube, the inner layer agent and tube It was discovered that by heating the tube, the two can be integrated without shrinking the tube, and the present invention was completed.

Example After crosslinking a polyethylene tube with an inner diameter of 50 mmφ and a thickness of 3 mmφ by irradiating it with a 20 megarad electron beam,
It was mechanically expanded in a heating atmosphere at 0° C. until it became a hexagon with a side length of about 75 mm.

This tube was placed in a metal pipe with an inner diameter of 155 mm, and a pellet of Versamide 125* was placed inside the tube, and the tube was rotated at 4000 rpm.

(*Polyamide resin product name) While rotating in this manner, the tube and inner layer agent were applied to the inside of the metal pipe by heating from the inside with an infrared heater.

After the tube and the inner layer agent were integrated in this manner, the infrared heater was turned off, and the tube was cooled while continuing to rotate, and then the rotation was stopped.

In this way, it was possible to obtain a double shrink tube with an inner layer agent for adhesion to the cable, but since the inner layer agent was supplied in the form of pellets, the thickness of the inner layer agent was uneven in the length direction of the tube.

(A product with approximately uniform thickness in the circumferential direction was obtained.

) Therefore, Versamide 125 was previously formed into a tape shape with a thickness of 2 mm and a width of 70 mm, which was placed into a tube and integrated with the tube in the same manner as described above.

By forming the inner layer agent into a tape shape in advance, a double shrink tube with a uniform inner layer thickness not only in the circumferential direction but also in the longitudinal direction could be obtained.

I mentioned polyethylene as a tube here.

This method can be applied to any tube material that can be used to produce a shrinkable tube, such as PvC or rubber.

It goes without saying that not only the polyamide resins mentioned herein but also ethylene copolymers such as ethylene ethyl acrylate and ethylene vinyl acetate can be used as the inner layer agent.

Claims (1)

[Claims] 1. A shrinkable tube is placed in a pipe having an inner diameter slightly larger than the outer diameter of the shrinkable tube, and a material for an inner layer agent is placed inside the shrinkable tube, and the shrinkage force of the shrinkable tube is absorbed. Rotate these at a rotation speed that generates a centrifugal force, and heat the tube and inner layer agent while rotating.
A method for manufacturing a double shrink tube, which is characterized in that the tube is integrated, cooled while continuing to rotate, and then taken out. 2. The method for manufacturing a double shrink tube according to claim 1, characterized in that the inner layer agent is previously formed into a tape shape and placed in the shrink tube.