JPS602337A - Manufacture of thermally shrinkable tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a heat-shrinkable cheese having a heat-melting adhesive layer on its inner surface.

[Background of the invention]

Heat-shrinkable tubes, which are easy to work with, are widely used for insulating the connections of electric wires and the sunrise parts of motors, etc. In such a treatment, various composite tubes having an adhesive layer on the inner surface have been studied in order to improve the adhesion between the tube and the adherend and provide water-repellent properties.

However, there were problems in that it was difficult to form an adhesive layer on the inner surface and the manufacturing cost was high.

[Summary of the invention]

Therefore, we investigated various ways to efficiently manufacture composite tubes with an adhesive layer on the inner surface.We made the tubes from a specific plastic, that is, a thermoplastic resin or an elastomer that has heat-melting properties, and used low-voltage Chi = using an accelerator
- It was discovered that the desired tube could be obtained by crosslinking only the outside of the tube, and the present invention was completed.

[Detailed description of the invention]

The thermoplastic resin or elastomer having heat-melting properties used in the present invention includes polyethylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, saponified ethylene vinyl acetate copolymer, ionomer resin,
Polybutene-1 resin One or a mixture of two or more of polyamide resins, polyester resins, ethylene propylene elastomers, polyester elastomers, polyurethane elastomers, styrene butadiene elastomers, etc., preferably polyolefins having an ethylene content of 50% by weight or more Good resin. These polyolefin resins can be used to improve adhesiveness and tackiness, such as tackifiers such as L Melf', = Merosin, terpene resin, terpene phenol resin, alkyl phenol resin, and other petroleum resins, polybutene, pro-7 oil, and paraffin wax. A resin mixed with fluidity modifiers such as polyethylene wax, pigments, and anti-aging agents is good. The thermoplastic resin or elastomer is preferably one that does not have tackiness at room temperature and can be molded into a chive shape using an extrusion molding machine.

The thermoplastic resin or elastomer molded into a tube was irradiated with an electron beam from the outer surface of the tube to crosslink the portion from the outer surface of the tube to the inner margin to form the outer layer of the tube.

The electron beam irradiation device used in the present invention has an accelerating voltage of 1
A 50kV to 500kV accelerator is preferred. Accelerating voltage 1
This is because at 50 kV or less, even materials with low density, such as materials with an ethylene content of 50% by weight or more, are only cross-linked on the surface and cannot be processed into heat-shrinkable tubes. If the thickness is about 1 mm, the electron beam will penetrate and cross-link not only the outer layer of the tube but also the inner surface of the tube, and the inner surface will lose its heat-melting properties, making it impossible to form a heat-shrinkable tube with an inner layer agent. This is because there is no

As a method of cross-linking only the portion from the outer surface of the tube to the inner part (outer layer of the tube), it is possible to cross-link only the portion (outer layer of the tube) from the outer surface of the tube to the inner part of the tube. This is done by installing a magnet and irradiating the electron beam so that the beam hits the entire surface of the bent tube uniformly.

FIG. 1 is a schematic side view of the electron beam irradiation device, and FIG. 2 is a plan view schematically showing the magnet shown in FIG. 1 from the top.

Referring to Figures 1 and 2, (1) is the particle emission source, (2
) is the accelerator tube, (3) is the scanning device, (4) is the beam guide unit, (5) is the emission window, (6), (force, (8), (9), 0
0), 0υ, (2), α■ are the magnetic pole faces, 04) is the object to be irradiated, α0 is the notch 0 koji, and 071, α8) are the particle beams.

A and B indicate magnets.

Further, the accelerator does not have to be limited to the scanning type, and a curtain flow type accelerator may also be used.

The thickness of the outer tube layer is approximately determined by the accelerating voltage. When the accelerating voltage is low, the crosslinking occurs only on the outer surface, and when the accelerating voltage is high, the crosslinking can be carried out to a considerable extent inside, and the degree of crosslinking is determined by the amount of electron beam radiation.

In the present invention, the thickness of the outer layer is 1/3 of the outer layer of the tube.
~2/8 had excellent thermal expansion processability, and the degree of crosslinking was preferably 30 to 80% by weight.

The cross-linked tube is heat-shrinkable by heating it above the melting point of the tube, injecting pressurized air into the tube and reducing the pressure on the outer layer of the tube, expanding it to a desired outer diameter, and then cooling and solidifying it. Cheeve is obtained. Since the inner surface of the heat-shrinkable tube is not cross-linked by electron beams, the heat-sealability of the outer layer of the tube is maintained, and the inner layer of the tube acts as an adhesive layer, as shown in Figure 3. It becomes a heat-shrinkable double-walled tube. In FIG. 3, Qe is the outer layer of the tube, and (e) is the inner layer of the tube which is not crosslinked.

According to the present invention, by extrusion molding one layer of cheese using one material, the inner layer of the cheese acts as an adhesive layer, making it easy to produce a heat-shrinkable cheese similar to adhesive-coated heat-shrinkable cheese. Can be molded into

The following description will be made based on examples.

Example 1 A thermoplastic resin was mixed with 60% by weight of low density polyethylene, 30% by weight of ethylene ethyl acrylate copolymer, and 10% by weight of terpene resin and had an outer diameter of 10 mm.

It was extruded into a tube shape with a wall thickness of 1.0 mm and irradiated with 24 Mrad using an electron beam irradiation device with an acceleration voltage of 300 kV. After that, the cheese was heated to 150°C and the inside was pressurized,
A heat-shrinkable tube was obtained by expansion molding to an outer diameter of 20 mm96 by reducing the pressure on the outside.

The gel fraction of the outer layer and inner layer of the obtained cheese was determined using xylene solvent, and the thickness of the tube was examined to see how many millimeters it was crosslinked. The tube was heat-shrinked in an iron vibrator having an outer diameter of 15 mm, and after cooling, a notch with a width of 10 mm was made in the tube to measure its peel strength.

The results are shown in Table 1.

Example 2 A thermoplastic resin made by mixing 70% by weight of ethylene vinyl acetate copolymer (vinyl acetate content: 20% by weight) and 30% by weight of polyamide resin was molded in the same manner as in Example 1 to form a heat-shrinkable tube. After obtaining the performance test.

Example 8 A thermoplastic resin obtained by kneading 20% saponified ethylene vinyl acetate copolymer (acetic acid content 30% by weight), 30% by weight ionomer resin, and 20% ethylene propylene elastomer was molded in the same manner as in Example 1. A heat-shrinkable tube was obtained and its performance was tested.

As can be seen from the results in Table 1, thermoplastic resins with heat-sealing properties made by kneading polyethylene or polyethylene copolymers with tackifiers crosslink only the outer layer of the tube when exposed to a moderate amount of radiation. Expansion processing of the shrinkable tube was easy.

The outer layer had a sufficient gel fraction, and the inner layer had a gel fraction of zero, and its thickness was about 1/2.

Therefore, sufficient adhesion to metal was obtained.

In this way, a heat-shrinkable team with a two-layer structure made from one material
It was confirmed that the ability to easily obtain this material is very economically advantageous, and there are no practical problems. This proves the superiority of the present invention.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a side view schematically showing an electron beam irradiation device, and FIG. 2 is a plan view of a magnet and an irradiated object in the electron beam irradiation device of FIG. FIG. 3 is a cross-sectional view of a heat-shrinkable tube obtained according to the present invention.

Claims (2)

[Claims] (1) An electron beam is irradiated from the outer surface of the tube made of a thermoplastic resin or elastomer with heat-sealing properties using an electron beam irradiation device with an output voltage that does not penetrate the tube wall thickness, and the inner surplus is measured from the tube wall thickness. 1. A method for manufacturing a heat-shrinkable tube, which comprises: crosslinking the tube up to the middle to form a thick tube, then expanding the tube under pressure while heating it above its melting point, and cooling and solidifying the tube. (2) The heat-shrinkable thermoplastic resin or elastomer according to claim (1), wherein the thermoplastic resin or elastomer having heat-fusibility is a polyolefin resin tube having at least 50% by weight or more of co-ethylene content. Method for producing sex cheese.