JPH0217341B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The object of the present invention is to improve the low-temperature properties of a fluoroelastomer heat-shrinkable tube made of a mixture of two or more fluororesins. [Prior Art] Fluorine elastomers are used for gaskets, packing, hoses, etc. due to their excellent heat resistance, oil resistance, and chemical resistance. Due to these characteristics, there is a high demand for it as an electrical insulating material such as heat-shrinkable tubes for protecting terminals. However, conventionally used fluorine elastomers have various drawbacks such as poor electrical insulation properties and poor mechanical strength, and improvements have been desired. In recent years, tetrafluoroethylene-propylene copolymers have been developed as fluoroelastomers with particularly excellent electrical insulation properties. Tetrafluoroethylene-propylene copolymers include, in addition to the main components tetrafluoroethylene and propylene, components that can be copolymerized with these, such as ethylene, isobutylene, acrylic acid and its alkyl esters, methacrylic acid and its alkyl esters. It may also contain an appropriate amount of ester, vinyl fluoride, vinylidene fluoride, hexafluoropropene, chloroethyl vinyl ether, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, or the like. However, when such a copolymer is used as an insulator in heat-shrinkable wire tubes, etc., its mechanical strength is so low that it cannot be used as is. In addition, in order to provide heat-setting properties (inflate the tube and maintain its shape) as a heat-shrinkable tube, it is necessary to add a crystalline polymer, and as a crystalline fluororesin, ethylene-tetrafluoroethylene copolymer , tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, vinylidene fluoride-fluoroolefin copolymer, and the like were studied for blending with the fluorine elastomer. [Problems to be Solved by the Invention] However, although the mechanical strength can be improved by blending with these fluororesins, the low temperature resistance deteriorates, and the -10°C temperature required for ordinary heat-shrinkable insulation tubes is deteriorated. It also failed the low temperature test and was unusable. The present invention was achieved as a result of intensive studies aimed at improving this low-temperature property. [Means for Solving the Problems] The present invention provides 100 parts by weight of a tetrafluoroethylene-propylene copolymer, 10 parts by weight or more and less than 100 parts by weight of a vinylidene fluoride-fluoroolefin copolymer, and a crosslinking accelerator. This is a fluoroelastomer heat-shrinkable tube characterized by using a composition that is blended and crosslinked by electron beam irradiation. The vinylidene fluoride-fluoroolefin copolymer used in the present invention has a fluoroolefin content of 1
~20 mol%. As such fluorofrefine, propylene hexafluoride or ethylene tetrafluoride is preferable from the viewpoint of processability and the like. The reason why the amount of vinylidene fluoride-fluoroolefin copolymer is 10 parts by weight or more per 100 parts by weight of tetrafluoroethylene-propylene copolymer is that if it is less than 10 parts by weight, it cannot be heat-set sufficiently as a heat-shrinkable tube. It is. On the other hand, the reason why the amount of vinylidene fluoride-fluoroolefin copolymer added is less than 100 parts by weight is that if more than 100 parts by weight is added, the effect of improving low temperature properties by electron beam irradiation will not appear, or will actually worsen. It is. The present invention will be explained below using specific examples. [Example] Examples 1 to 4 The resin composition shown in Table 1 was made into a mold with an inner diameter of 4 mm and a wall thickness.
After extruding to a size of 0.5 mm, it was irradiated with a 10 Mrad electron beam using a 2 MeV electron beam accelerator. the tube
After heating 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 6 mm, and after cooling, a heat-shrinkable tube was formed. Heat the heat shrink tube to 180℃
After shrinking in a constant temperature bath for -5 minutes, a low temperature embrittlement test was conducted to measure the lowest temperature at which the tube would not break. The results of the low temperature embrittlement test are shown in Table 1. Comparative Examples 1 to 5 Heat-shrinkable tubes were prepared using the resin compositions shown in Table 1 in the same manner as in the examples, and a low-temperature embrittlement test was conducted. As a result, the tetrafluoroethylene-propylene copolymer alone could not be heat set and could not be made into a heat shrinkable tube. [Effects of the invention] As shown in Table 1, for 100 parts by weight of tetrafluoroethylene-propylene copolymer, vinylidene fluoride-fluoroolefin copolymer alone and tetrafluoroethylene-propylene copolymer, In the resin compositions to which 100 parts by weight or more of the vinylidene fluoride-fluoroolefin copolymer was added, the low-temperature properties either worsened or did not change even when irradiated with an electron beam. On the other hand, in the resin composition of the present invention, both
Improvements in low-temperature properties were seen, and it became possible to use it at -10℃.

【table】

[Table] ** 8 mol% of hexafluorinated propylene as fluoroolefin
＊＊＊ Tetrafluoroethylene 7 mol% as fluoroolefin

Claims (1)

[Scope of Claims] 1. Fluoroolefin is contained in an amount of 1 to 100 parts by weight of the tetrafluoroethylene-propylene copolymer.
Vinylidene fluoride-fluoroolefin containing 20 mol% (1 to 20 mol% fluoroolefin)
1. A fluoroelastomer heat-shrinkable tube comprising a composition containing 10 parts by weight or more but less than 100 parts by weight of a copolymer and a crosslinking accelerator and crosslinked by electron beam irradiation. 2. The fluoroelastomer heat-shrinkable tube according to claim 1, wherein the fluoroolefin in the vinylidene fluoride-fluoroolefin copolymer is propylene hexafluoride or ethylene tetrafluoride.