JPS5930146B2 - Method for manufacturing heat-shrinkable tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heat-shrinkable tube for covering connection parts, terminal parts, etc. of electric wires, cables, pipes, steel pipes, etc.

Conventionally, heat-shrinkable tubes made of polyethylene resin, vinyl chloride resin, ethylene vinyl acetate copolymer, tetrafluoroethylene resin, silicone rubber, ethylene propylene rubber, etc., have been used as heat-shrinkable coatings for various electric wires, cables, pipes, steel pipes, etc. It was used for electrical insulation, waterproofing, and protection of connections and terminals.

When using these heat-shrinkable tubes for connections or terminals, first apply or bond an insulating or waterproof adhesive or adhesive to the surface of the wire or steel pipe connection, and then how to coat heat shrinkable tubing,
Or apply adhesive to the inner surface of the heat-shrinkable tube in advance.
Alternatively, use a shrinkable tube coated with an adhesive dissolved in a solvent, or a sheet of adhesive or adhesive pasted together with a roller, etc., and integrate it with the electric wire or steel pipe during early shrinkage. method was adopted. However, with the former method, adhesive must be applied each time electric wires or steel pipes are connected, which not only takes a lot of time to connect, but also poses problems in terms of insulation and waterproof quality. Ta. For this reason, a double heat-shrinkable tube such as the latter, in which an adhesive is applied to the inner surface of the heat-shrinkable tube, has been desired. However, the conventional method for manufacturing double heat-shrinkable tubes is to dissolve the adhesive with a solvent, apply it to the inner surface of the tube, and dry it, or process the adhesive into a sheet and apply it to the inner surface of the heat-shrinkable tube. Alternatively, the adhesive is melted and applied to a core mold with a diameter slightly smaller than the inner diameter of the heat-shrinkable tube, the heat-shrinkable tube is coated on the outside, the heat-shrinkable tube is heat-shrinked, and after cooling, the core mold is pulled out and the tube and adhesive are bonded together. A method of integrating the two has been considered. However, these methods require a large number of processing steps and have low productivity, making them very expensive.

The present invention provides an inexpensive method for manufacturing a heat-shrinkable tube that requires less processing, has excellent productivity, and has excellent insulation and waterproof properties.

The present invention provides a circular or polygonal ring inscribed inside a heat-shrinkable tube, and while extruding a hot-melt adhesive in a ring shape, the hot-melt adhesive is continuously applied to the inner wall of the heat-shrinkable tube. It is characterized by applying pressure using a circular or polygonal ring.

This will be explained below based on the drawings. FIG. 1 is a schematic diagram of a method for manufacturing a heat-shrinkable tube with a hot-melt adhesive.

A pipe-like throat 2 longer than the length of the heat-shrinkable tube is attached to the tip of a screw extruder 1, and a tube guide link 3, an adhesive expansion die 4, and an adhesive application ring 5 are attached to the head portion of the throat. The shape of the ring may be circular or polygonal. The three devices attached to the head portion may be integrated or separated. However, it is necessary that the inner surface of the heat-shrinkable tube 6 is inscribed in at least several places. As an example, it is preferable that the adhesive applicator ring 5 is shaped like a gear as shown in FIG. Further, when the heat-shrinkable tube has a polygonal shape, it is preferable that the applicator ring also has the same polygonal shape. The hot-melt adhesive 7 supplied to the screw extruder is melt-mixed inside the screw and the pipe-like throat, and then supplied onto the adhesive application ring.

The heat-shrinkable tube 6 is fixed to a tube holder 9 set on a movable frame 8, and lifted until the tip of the die and the lower end of the heat-shrinkable tube coincide. When a match is reached, the supply of adhesive is started, and the heat-shrinkable tube is lowered at a constant speed. At this time, the adhesive on the applicator ring is pressed against the inner surface of the tube and is evenly applied to a thickness similar to the height of the protrusion of the applicator ring like adhesive 7'. The thickness and length of the coating can be freely adjusted depending on the shape of the ring inscribed in the tube, the moving speed of the tube, and the moving distance. Further, the material and shape of the tube guide ring 3 and the adhesive application ring 5 can be arbitrarily selected from the following combinations. If the tube guide ring is made of a hard material such as iron, copper, or aluminum, and the adhesive applicator ring is made of a soft and elastic material such as tetrafluoroethylene resin, fluorine rubber, or silicone rubber, the applicator ring should be made of a hard material such as iron, copper, or aluminum. It is preferable that the tube guide ring has a larger disc or cone shape, and vice versa, the tube guide ring should be a soft and elastic disc or cone, and the applicator ring should have a diameter equal to or larger than the inner diameter of the tube. Preferably, it is gear-shaped with an outer diameter of . Furthermore, if both rings are made of a hard material, it is preferable that only the applicator ring is gear-shaped with an outer diameter equal to or larger than the inner diameter of the tube, and if both rings are made of a soft and elastic material, Both rings are preferably disc-shaped or conical-shaped rings having an outer diameter equal to or larger than the inner diameter of the tube. In this case, the disk or cone may be gear-shaped. As mentioned above, the reason why it is preferable that the outer diameter of the tube guide ring or adhesive applicator ring is equal to or larger than the tube inner diameter is that when the heat-shrinkable tube comes into contact with hot melt adhesive, thermal expansion and extrusion pressure occur. This is because the inner diameter of the tube swells and the gap with the applicator ring becomes too large.Furthermore, if the applicator ring is smaller than the inner diameter of the tube, uneven thickness of the adhesive will occur. The pressed adhesive 7' is cooled by the cold air sent through the cold air adjustment gauge 10 and the air pipe 11, thereby preventing the heat-shrinkable tube from shrinking. At this time, the blower pipe 11 is completely insulated so as not to impede the flow of the hot-melt adhesive. In addition, for tubes with a narrow diameter, cold air may be sent in from the bottom end of the tube. Furthermore, in the method of manufacturing a heat-shrinkable tube with a hot-melt adhesive using this apparatus, pressure coating can be performed by making the pipe-shaped throat, die, ring, etc. horizontal, and moving the heat-shrinkable tube parallel to it.

Polyolefin adhesives, polyamide adhesives, rubber adhesives, etc. can be used as hot melt adhesives, but the raw materials include polyethylene, ethylene-rezovinyl acetate copolymer, ethylene ethyl acrylate copolymer, dimer acid amide, nylon, natural One or more mixtures of high molecular weight materials such as rubber, butyl rubber, isoprene rubber, neoprene rubber, chloroprene rubber, etc., or coumaron resin, phenol resin, terpene resin, allylsulfone resin, rosin tackifier, etc. It is possible to use products that have been further kneaded to improve adhesive strength.

These hot-melt adhesives must be sufficiently softened at the shrinkage start temperature of the heat-shrinkable tube and exhibit good wettability to the adherend. The following will be explained based on examples. Example 1 A polyethylene heat-shrinkable tube with an inner diameter of 50 mmψ, a wall thickness of 2.0 m, a length of 71 L, and a length of 1 m is fixed to a tube holder 9, and a pipe-shaped throat 2 with a length of 1.5 m is attached by a frame 8.
It was set concentrically on the outside of the

A hot melt adhesive 7 containing a 1:L mixture of ethylene ethyl acrylate and ethylene vinyl acetate copolymer was supplied to the extruder 1, kneaded at 130° C. by a screw, and extruded into the throat.

At the tip of the throat, there is an adhesive expansion die and 0.6mu protrusions at 12 locations on the circumference. 50m77! Attach the adhesive applicator ring. When the tip of the applicator ring and the bottom end of the tube coincide, extrude the hot melted adhesive from the die, and at the same time insert a 100cm heat shrinkable chain.
It was lowered at a rate of IrL/min to apply the adhesive to the inner wall of the tube. Adhesive thickness after application is 0.4~
0.5m7! It was L.

Example 2 Inner diameter 100mmψ, wall thickness 2.0m, length 1m
Heat-melt adhesive was extruded into a polyethylene heat-shrinkable tube at 130°C in the same manner as in Example 1, and the end of the throat was
．． Outer diameter 101m with 12 8mm protrusions on the circumference
Attach a mψ adhesive applicator ring and lower the descending speed to 1000.
! The coating was applied to the inner wall of the tube at a rate of n/min.

The thickness of the adhesive after application was 0.6 to 0.7 m1. Example 3 A polyamide-based heat-shrinkable tube (bar salon 1
300: Manufactured by Japan General Mills Chemical Co., Ltd.) extrude hot-melt adhesive at 120°C, attach an adhesive applicator ring with an outer diameter of 153 mmψ with 1.0 mm protrusions at 16 locations on the circumference to the tip of the throat, and lower. The coating was applied by pressing onto the inner wall of the tube at a speed of 50 CTfL/min.

The thickness of the adhesive after application was 0.7 to 0.8 mm. As a result of the above examples, it was found that the adhesive was applied to the inner wall of the heat-shrinkable tube to a uniform thickness, and that no air bubbles were observed between the tube and the adhesive, and that they were integrated.

However, it is smaller than the adhesive applicator ring described in the Examples.
In other words, it has been found that when the adhesive is applied using a disc-shaped ring that is not inscribed on the inner surface of the tube, the thickness of the adhesive varies greatly from about 0 to 3 mm, making it impossible to put it into practical use. In addition, if you simply pour hot melted adhesive onto the inner surface of the heat-shrinkable tube from one end of the tube and squeeze it with a cloth or rubber band, the adhesive will not be applied evenly, and the heat-shrinkable tube will be uneven. It was also found that the product shrank to such an extent that it could not be put to practical use. This was achieved by providing a ring inscribed inside the heat-shrinkable tube, extruding the hot-melt adhesive in a ring shape, and continuously pressing the ring against the inner wall of the heat-shrinkable tube to apply the adhesive. be.

The heat-shrinkable tube obtained in the example was heat-shrinked as an anti-corrosion layer at the cable connection part and integrated with the cable sheath.

As a result of conducting severe performance tests such as hot water immersion tests, heat cycle tests, and bending tests on the corrosion-resistant layer at the connection part, no water was found to have entered the cable, making it an excellent anti-corrosion heat-shrinkable tube. I found out something.

Furthermore, according to the manufacturing method of the present invention, it is possible to automatically apply a hot-melt adhesive, and a heat-shrinkable tube with excellent productivity and low cost can be obtained.

This proves the superiority of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a method for manufacturing a heat-shrinkable tube with a hot-melt adhesive. 1 is a hot melt adhesive extruder, 2 is a pipe-like throat, 3
is a tube guide ring, 4 is an adhesive expansion die, 5 is an adhesive application ring, 6 is a heat-shrinkable tube, 7 is a hot-melt adhesive, 7' is a state in which the adhesive is melted and expanded, 8 is a movable frame, 9 is a tube holder; 10 is a cold air adjustment gauge 11 is a blower pipe. FIG. 2 is a top view of one embodiment of the adhesive applicator ring.

Claims (1)

[Claims] 1. The hot melt adhesive extruded from the head of the pipe-like throat through a pipe-like throat longer than the length of the heat-shrinkable tube provided at the tip of the extruder is applied to the head. The heat-melting adhesive is continuously applied in a circular or polygonal manner onto the inner wall of the heat-shrinkable tube while being expanded into a ring shape by a circular or polygonal ring that is attached and inscribed inside the heat-shrinkable tube. A method for manufacturing a heat-shrinkable tube characterized by applying pressure using a square ring. 2. The method for manufacturing a heat-shrinkable tube according to claim 1, wherein the inscribed circular or polygonal ring is gear-shaped. 3. The method of manufacturing a heat-shrinkable tube according to claim 1, wherein the inscribed circular or polygonal ring is made of a soft and elastic material.