JPS62115052A - Flame-retardant, transparent and heat-shrinkable tube - Google Patents

Abstract

PURPOSE:To obtain a heat-shrinkable tube having flame retardance and transparency, by blending a chlorinated polyethylene having a specified crystallinity with fine particles of antimony trioxide, irradiating the mixture with an ionizing radiation to carry out a crosslinking reaction and a diameter enlargement. CONSTITUTION:A heat-shrinkable tube which is composed of a compsn. obtd. by blending 100pts.wt. chlorinated polyethylene having a crystallinity of 5-15% with 1-20pts.wt. fine antimony trioxide particles having an average particle size of 0.5mu or below is irradiated with an ionizing radiation to be crosslinked and, have an enlarged diameter. When the crystallinity is less than 5%, the shape of the tube subjected to the diameter enlargement can not be retained, while when the crystallinity exceeds 15%, the transparency of the tube is deteriorated. Antimony trioxide must have an average particle size of 0.5mu or below. Then conventional powder having an average particle size of 1-2mu is added, the transparency is deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-shrinkable tube that has both flame retardancy and transparency.

[Prior Art] In recent years, resin products used in various fields are required to be flame retardant for safety reasons.

This also applies to heat shrink tubing, especially
There is a strong demand for flame retardancy when used in the connections and terminals of electric wires and cables.

Polyethylene or ethylene-based copolymers are
Due to its excellent mechanical and electrical properties, it is often used in heat-shrinkable tubes.

[Problems to be solved by the invention] However, these materials are inherently flammable, and adding a flame retardant to make them flame retardant impairs transparency, causing internal damage during and after the tube coating. There is a problem in that it is no longer possible to check visually.

The present invention has been made based on the above, and an object of the present invention is to provide a heat-shrinkable tube having both flame retardancy and transparency.

[Means for Solving the Problems] The heat-shrinkable tube of the present invention has an average particle size of 0.5% based on 100 parts by weight of chlorinated polyethylene with a crystal content of 5 to 15%.
It consists of a resin composition containing 1 to 20 parts by weight of fine particles of antimony trioxide of 5 μm or less, and is characterized by being crosslinked and diameter-expanded by irradiation with ionizing radiation.

Chlorinated polyethylene is a flame-retardant and transparent resin. As a result of intensive studies on the application of this to heat-shrinkable tubes, the inventor found that a crystal content range of 5 to 15% is suitable for achieving the object of the present invention.

That is, if the amount of crystals is less than 5%, the shape of the expanded tube cannot be maintained, and if it exceeds 15%, the transparency of the tube will be impaired.

The antimony dioxide used in the present invention has an average particle size of 0.571 m or less. Antimony dioxide, which is commonly used, has an average particle size of 1 to 2 μm, and when added to chlorinated polyethylene, transparency is impaired.

Antimony trioxide is added to further improve the flame retardancy of chlorinated polyethylene, and its amount needs to be in the range of 1 to 20 parts by weight per 100 parts by weight of chlorinated polyethylene. If it is less than 20 parts by weight, there will be little effect of improving flame retardancy, and if it exceeds 20 parts by weight, transparency will be impaired.

In the present invention, in addition to the above-mentioned components, lubricants, flame retardants, fillers, etc. that do not impair transparency may be added as necessary.

The resin composition thus obtained is formed into a tube shape using an extruder or the like, crosslinked by irradiation with ionizing radiation such as an electron beam, and then expanded under heating at a temperature equal to or higher than the softening temperature of the resin.

When performing irradiation crosslinking, ? In order to enable crosslinking at a low radiation dose and to prevent deterioration of the resin and antioxidant due to ``rrLU radiation,'' the polyfunctional monomer is
It may be added within a range of 0.0%.

Examples of polyfunctional monomers include acrylates (diethylene glycol diacrylate, etc.), dimethacrylates (
dipropylene glycol dimethacrylate, dipropylene glycol dimethacrylate, etc.), triacrylates (trimethylolethane triacrylate, trimethy a-rubucopane triacrylate, etc.), trimethacrylates (trimethylolethane trimethacrylate, trimethylol propane trimethacrylate, etc.), triallyl cyanurate, triallyl isocyanurate, diallyl maleate, etc.

[Example] A resin composition containing various components as shown in Table 1,
It was extruded into a tube shape with an inner diameter of 9 mmφ, a wall thickness of 1 mmφ, and an outer diameter of 11 mmφ, and was crosslinked by irradiating it with an electron beam of 15 Mrad using a 1.5 MeV t-beam accelerator. Next, it was heated to 180° C. and expanded with pressurized air to have an inner diameter of 21 mmφ (thickness of 0.4 mm), and then cooled to produce a heat-shrinkable tube.

The evaluation results for the heat-shrinkable tubes obtained in the six cases are as shown in the lower column of Table 1.

The flame retardance was evaluated based on the all-tubing method specified by UL224.

Transparency was evaluated visually after the heat-shrinkable tube was left at room temperature for 120 days after production.

The inner diameter retention rate was determined by comparing the inner diameter immediately after expansion with the inner diameter after standing at 80'C for 1 hour.

[Effects of the Invention] As explained above, according to the present invention, a heat-shrinkable tube having both flame retardancy and transparency can be realized.

Claims (1)

[Claims] (1) Consisting of a resin composition containing 1 to 20 parts by weight of particulate antimony trioxide with an average particle size of 0.5 μm or less based on 100 parts by weight of chlorinated polyethylene with a crystal content of 5 to 15%, A flame-retardant transparent heat-shrinkable tube characterized by being cross-linked and diameter-expanded by irradiation with ionizing radiation.