JPH0473699B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a heat-shrinkable molded article. More specifically, the present invention relates to a heat-shrinkable molded article that has good insulating properties, excellent oil resistance, and low-temperature properties and is used for waterproofing, anticorrosion, and other protection of electric wires, cables, and various types of pipes. (Prior Art and Problems) Heat-shrinkable molded bodies, especially heat-shrinkable tubes, are used for the purpose of insulating protection of the assembly of internal wiring and terminal connections, as well as waterproof protection of joints of thick power cables and communication cables, and pipes. It is becoming widely used for the purpose of corrosion prevention and protection of joints of lines and steel pipes. Known materials for such heat-shrinkable molded bodies include olefin resins such as polyethylene, polyvinyl chloride resins, and fluorine rubbers. but,
These conventional materials tend to crack during shrinkage, have low expansion ratios, and, especially in the case of low-temperature shrinkable materials, require processing steps to prevent shrinkage at room temperature, and are soft and easily scratched. The following problems have been pointed out. (Means for Solving the Problems) The present inventors have conducted intensive studies to obtain a material free from the above-mentioned problems as a material for a heat-shrinkable molded article. As a result, the above-mentioned problems have been overcome, and the material itself has appropriate strength, good flexibility even without plasticizer, excellent oil resistance and low-temperature properties, and has high electron beam crosslinking efficiency during manufacturing. We have discovered a heat-shrinkable material that has good properties and can be colored. The present invention is a heat-shrinkable molded article comprising a crystalline epichlorohydrin resin. The crystalline epichlorohydrin resin used in the present invention has the structural formula:

It refers to a crystalline polymer compound having a chloromethyl group represented by the formula and having a polyether bond as its main chain. In particular, the molecular weight is 50,000~
1 million, preferably 100,000 to 500,000, is suitable as a heat-shrinkable material. The epichlorohydrin resin preferably has a crystallinity of 20 to 50%. If the crystallinity is less than 20%, the retention rate of the shape formed by stretching or expanding by heating after cooling is poor and the performance as a heat-shrinkable material is lost, which is not preferable. Moreover, if it exceeds 50%, the obtained heat-shrinkable material will lose its low-temperature properties. A known method can be employed as a method for producing the crystalline epichlorohydrin resin. Especially organic tin
The polymerization method described in US Pat. No. 3,773,694 of the present applicant using a phosphoric acid ester condensate as a polymerization catalyst is preferred because it can be obtained in high yield. That is, in the presence of the above catalyst, epichlorohydrin is polymerized using an aliphatic or aromatic hydrocarbon as a solvent at a polymerization temperature of 10 to 70°C.
A polymerization yield of around 98% can be obtained by polymerizing for 15 hours. The obtained crystalline epichlorohydrin resin has physical properties such as a specific gravity of 1.4, a softening point of 115 to 120°C, a tensile strength of 300 to 420 Kg/cm ² , an elongation of 350 to 480%, and a hardness (Shor D) of 60 to 65. The heat-shrinkable molded article of the present invention may be made of only crystalline epichlorohydrin resin, or may be made by adding a flame retardant such as tetrabromobisphenol A or tris(chlorobromopropyl) phosphate to increase the flame retardant effect. You may also use The method for producing a heat-shrinkable molded product is to mold the material into a predetermined shape, for example, a tube shape using an extruder, crosslink it chemically or by irradiating it with an electron beam, and then bring the molded product to a softening point. Alternatively, it can be obtained by heating above the melting point to stretch or expand, and then cooling and fixing. During crosslinking, it is preferable to add a crosslinking agent such as triallylcyanurate, pentaerythritol, or acrylate monomer to further enhance the crosslinking effect. The degree of stretching or expansion is preferably 1.5 to 3 times, and the heating temperature is selected to be 120 to 180°C. Example Epichlorohydrin resin with a molecular weight of 350,000 and a crystallinity of 40% was extruded into a tube with a wall thickness of 1 mm and an inner diameter of 10 mm using an extruder, and then extruded using a 2 MeV electron beam accelerator.
A 15 Mrad electron beam was irradiated. The obtained crosslinked tube was heated in a heating furnace at 150°C, internal pressure was applied in a die for controlling the outer diameter so that the inner diameter became 20 mm, and after cooling, a heat-shrinkable tube was obtained. The resulting heat-shrinkable tube has excellent heat-setting properties (90℃) and a volume resistivity of 2×10 ⁺¹⁵ Ω・cm
The low temperature embrittlement temperature was -20°C. Also
The weight change rate after immersion in JIS No. 3 oil at 70℃ for 168 hours is +1.2%, and the tensile strength in the tensile test is 500.
It was Kg/ ^cm2 . (Effect of the invention) The heat-shrinkable molded article of the present invention has a heat set property of 70
It is as low as ~100℃ and does not shrink at room temperature.
In addition, the shrinkable protective film obtained thereby has excellent oil resistance and low-temperature properties.

Claims (1)

[Claims] 1. A heat-shrinkable molded article comprising a crystalline epichlorohydrin resin.