JPS6120724A - Thermally restorable article - Google Patents

Abstract

PURPOSE:To manufacture radiation crosslinking fluororubber shrinkable tube excellent in heat deterioration resistance by adding monomer having a specified functional group and zinc or lead compound to fluorine-containing thermoplastic elastomer. CONSTITUTION:Fluorine-containing thermoplastic elastomer is prepared by adding 3 parts of trimethyl propane trimethacrylate of multifunctional monomer having two or more unsaturated bonding functional group in a molecule and 5 parts of PbO as lead compound to 100 parts of block copolymer composed mainly of vinylidene fluoride and propane hexafluoride as fluorine-containing thermoplastic elastomer. A tube is formed of mixed compound to execute crosslinking treatment by electronic radiation. This tube is heated and expanded at 250 deg.C, and cooled to obtain fluoro-rubber thermally shrinkable tube.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a heat-recoverable article made of a fluororubber composition particularly having excellent flame retardancy and heat aging resistance.

[Background of the invention]

Molded products such as tubes and caps are used to insulate and protect exposed conductor parts such as terminals and wiring connections of audio equipment such as TVs, VTs, and R's, communication equipment, heating equipment, or electrical equipment such as copying machines. It is also widely used as a cover for resistors and capacitors.

Conventionally, materials for tubes, caps, etc. have been polyvinyl chloride resin, polyolefin, polyester resin (
Polyethylene terephthalate (12), silicone resin, nylon resin, etc. are used. Further, in order to improve the flame retardancy and heat aging resistance of these materials, flame retardants, anti-aging agents, etc. are added. In recent years, the characteristics required for these materials have become stricter, and higher flame retardance and higher continuous operating temperatures have been required.

In addition to this, improvements in flexibility, oil resistance, and chemical resistance are also required. When flexibility is required to improve individual properties, rubbers such as ethylene propylene rubber (EPR, EPDM, etc.) and silicone rubber are used. Nitrile rubber, hydrin rubber, etc. are used to improve oil resistance. However, in either case, there are advantages and disadvantages, and fluorine-based materials are optimal as materials that satisfy all requirements. Therefore, under the above severe conditions, the fluororesin polytetrafluoroethylene (PTFE)
, tetrafluoroethylene and 67-fluoropropylene copolymer (F
EP), tetrafluoroethylene and ethylene copolymer (E
Materials used include fluororesins such as TFE), polyvinylidene fluoride (PVDF), and fluororubbers typified by copolymers of vinylidene fluoride and propylene hexafluoride. Among these materials, fluororesins, which have good extrusion moldability and good processability, are hard and inflexible. Further, in the case of flexible fluororubber, there are drawbacks such as poor moldability and the need for vulcanization. Furthermore, vulcanization of hollow articles such as tubes has the disadvantage that deformation occurs due to heating. In order to solve these drawbacks, vinylidene fluoride and propene hexafluoride ((vinylidene fluoride and propene hexafluoride) are block copolymerized with other olefins, so that they have a melting point similar to that of resin when heated, and become fluid when heated. A thermoplastic elastomer has been developed that has good extrusion processability and flexibility similar to that of rubber without being vulcanized. As described in Japanese Patent Application Laid-Open No. 58-3495, vinylidene fluoride and propene hexafluoride are block copolymerized to create soft segments with elasticity and fluidity that melts when heated. By having the image part of the hard segment in the elastomer,
It is described that such thermoplastic elastomers are produced. By using such a thermoplastic nidistomer, it has become possible to manufacture rubber molded products with good processability.

However, since this thermoplastic elastomer also flows and deforms at temperatures above its melting point, it was necessary to vulcanize it. It does not flow even when heated through vulcanization, and since it is thermoplastic, it can be heated to a molten state and then strained and then cooled in that state to create a heat-shrinkable tube that returns to its original shape when heated. However, as a vulcanization method, 1. When a method of adding a vulcanizing agent and heating and vulcanizing is adopted, hollow molded products such as tubes may be deformed during heating, so radiation irradiation vulcanization such as electron beam irradiation is advantageous. However, simply performing radiation irradiation does not progress vulcanization, resulting in a decrease in physical properties, resulting in stickiness, and no improvement in heat deformability. The reason for this is thought to be that in general, fluorine-based resins are not only crosslinked but also cut due to radiation, and even if the irradiation dose is increased, the degree of crosslinking does not progress as much as in normal polyolefins. Therefore, conventionally, polyfunctional monomers having two or more unsaturated bond functional groups in the molecule have been added to promote vulcanization. This improved heat deformability and also eliminated stickiness.

However, it has been found that when the above fluoroelastomer composition is left at high temperatures for a long period of time, it deteriorates and its strength decreases.

[Summary of the invention]

The present invention relates to the improvement of heat-recoverable articles using the above-mentioned fluororubber (nidistomer) composition, and involves block copolymerizing vinylidene fluoride and 67-fluorinated propene or these with other unsaturated olefins to form elastomeric polymer chain segments and A polyfunctional monomer having two or more unsaturated bond functional groups in the molecule is added to a heptad-containing thermoplastic elastomer consisting of di-stomer polymer chain segments,
Furthermore, it is an object of the present invention to provide a heat-recoverable article using a fluororubber compounded composition with excellent heat deterioration resistance due to the addition of a zinc compound or a lead compound.

[Detailed description of the invention]

In the present invention, by adding a fluorine-containing thermoplastic elastomer, it is possible to obtain a radiation-crosslinked fluororubber shrink tube with excellent heat deterioration resistance.

Fluorine-containing thermoplastic elastomer differs from ordinary fluororubber in that it is made of a block copolymer of vinylidene fluoride, propene hexafluoride, or these and other unsaturated olefins, and has a rubber-like soft segment and a hard segment that melts when heated. It has a two-phase structure and becomes fluid when heated.

In the present invention, polyfunctional monomers include tri-allylic cyanurate (TAC), lylyl isocyanurate)
(TAIC), 1.3 butylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane triacrylate, trimethylol triacrylate, tetramethylolmethane tetraacrylate. It is a difunctional or trifunctional monomer.

Zinc oxide (ZnO) is a zinc compound or lead compound.
), zinc chloride, -lead oxide (pbo), basic lead sulfate, lead hydroxide, lead tetraoxide (PbsO+), etc. can be used.

The effects of the present invention are not impaired even if pigments, lubricants, etc. that are added or blended with ordinary rubbers, resins, etc. are added or blended.

Furthermore, based on the principle of this patent, it is not limited to shrinkable tubes, but can also be used in other shapes that support deformation by heating and then recover their original shape by heating while maintaining the deformation (for example, tapes, sheets, caps, boot shapes, etc.). ) can be used for heat recovery molded products.

〔Example〕

Examples and comparative examples of the present invention will be described below. 1st
Table 2 shows compositions used in Examples and Comparative Examples of the present invention.

The fluorine-containing thermoplastic elastomer is Daiel Elastomer T530 manufactured by Daikin Industries, which is a block copolymer mainly composed of vinylidene fluoride and propene hexafluoride.
(trade name) was used, and the formulations described in Examples 1-8 were added to this elastomer. A tube with an inner diameter of 2M and a wall thickness of 0.5 mm was prepared from the resulting blended composition, and crosslinked by electron beam irradiation. The tube was heated to 250"C and then cooled while expanding to create a fluororubber heat-shrinkable tube. The tube was then left in air at 250°C for 7 days and then subjected to a tensile test. As a result, the elongation and
We were able to obtain a fluororubber heat-shrinkable tube with good tensile strength and good heat deterioration resistance, with almost no deterioration compared to the original.

As a comparative example, a similar test was conducted on a sample to which no lead or zinc compound was added. The results are from Comparative Example 1 to
It can be seen that when the sample after being left in air at 250°C for 7 days is not added as shown in No. 3, the heat deterioration resistance is poor.

No significant effect is expected when the amount of addition is 0.1 part, and the effect decreases when 20 parts or more is added. From these results, the optimum addition amount is considered to be 0.5 parts to 10 parts.

Table 2 Comparative Example TMPT: ) Abbreviation for Limethylolpropane trimethacrylate

Claims (4)

[Claims] (1) A fluorine-containing thermoplastic elastomer that is a block copolymer of vinylidene fluoride and hexafluoropropene or these and other ethylenically unsaturated monomers, which is composed of an elastomeric polymer chain segment and a non-elastomeric polymer chain segment. A heat-recoverable article comprising a fluororubber composition containing a polyfunctional monomer having two or more unsaturated bond functional groups in the molecule and a zinc compound or a lead compound. (2) The polyfunctional monomer is triallyl isocyanurate, triallyl cyanurate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane triacrylate,
The heat recovery article according to claim (1), which is one or more monomers selected from the group of trimethylolethane triacrylate and tetramethylolmethane tetraacrylate. (3) The heat recovery article according to claim (1), wherein the content of the zinc compound or lead compound is 0.5 to 10 parts by weight based on 100 parts by weight of the fluorine-containing thermoplastic elastomer. (4) A heat-recoverable article according to claim (1) or (3), in which a fluororubber composition is crosslinked by radiation.