JPH02258324A - Heat-shrinkable tube - Google Patents

Abstract

PURPOSE:To manufacture a heat-shrinkable tube of optional thickness without using a large device by using jointly a fluorine graft copolymer and at least one kind of specified fluorine containing copolymers. CONSTITUTION:A mixture of at least one kind selected out of fluorine-containing copolymers composed of a tetrafloroethylene - propylene copolymer, a vinylidene fluoride - hexafloropropylene copolymer and a vinylidene fluoride - hexafloropropylene - tetrefloroethylene terpolymer, and a fluorine graft copolymer is used as a constituting material. Sufficient kneading can be carried out without reacting or generating any foams when a crosslinking agent is mixed in said arrangement. Thus, crosslinking can be carried out without depending on the electron radiation crosslinking process, and a heat-shrinkable tube of desired thickness can be manufactured without any limit of thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-shrinkable tube, and more particularly to a heat-shrinkable tube using a fluorine-based graft copolymer.

[Conventional technology]

Conventionally, heat-shrinkable tubes using fluororesin are already known, and it is also known that these heat-shrinkable tubes have excellent heat resistance and chemical resistance. After creating a tube, it is cross-linked, then heated and expanded, and then cooled. As for the crosslinking method in this case, since the processing temperature is high in the case of fluororesin, chemical crosslinking using an organic peroxide crosslinking agent such as peroxide involves mixing the organic peroxide crosslinking agent with the fluororesin.
In the process of mixing I, an early crosslinking reaction starts and bubbles are generated, making tube extrusion extremely difficult. For this reason, electron beam irradiation has conventionally been used exclusively as a crosslinking method.

With this electron beam crosslinking, the thickness of the tube that can be crosslinked is limited by the capacity of the electron beam, and it is only possible to manufacture tubes with a thickness commensurate with the capacity of the electron beam.For example, in order to obtain a large capacity of electron beam, This method requires a large-scale equipment for shielding, which poses a serious problem in industrial implementation.

[Problem to be solved by the invention]

The problem to be solved by the present invention is to develop a means for manufacturing heat-shrinkable tubes by conventional chemical crosslinking. This makes it possible to manufacture products freely without having to do anything.

[Means for solving problems]

This problem was solved by using a heat-shrinkable tube made of tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer. This problem can be solved by using a mixture of at least one selected from fluorine-containing copolymers and a fluorine-based graft copolymer.

[Function and structure of the invention]

In the present invention, a specific organic copolymer resin called a fluorine-based graft copolymer is used, and at least one of the above-mentioned specific fluorine-containing copolymers is further used in combination with a chemical crosslinking agent such as peroxide. The above fluorine-based graft copolymer and the above other fluorine-containing copolymer are sufficiently kneaded without reacting or attracting any bubbles when mixing the crosslinking agent. You can. Therefore, crosslinking can be carried out without relying on the electron beam irradiation crosslinking method, and a heat-shrinkable tube with a desired thickness can be obtained without any thickness restrictions.

As the fluorine-based graft copolymer used in the present invention, a copolymer obtained by graft copolymerizing a fluororesin with a fluororubber is used.

Conventionally known fluororubbers are widely used, and representative examples include vinylidene fluoride-hexafluoropropylene copolymer rubber and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer rubber. etc. can be exemplified. Here, fluororubber refers to a material whose glass transition temperature is below room temperature, and is clearly distinguished from the fluororesin described below.

In addition, in the present invention, any conventionally known fluororesin can be used as the fluororesin to be graft copolymerized with fluororubber, such as vinylidene fluoride, tetrafluoroethylene-ethylene copolymer resin, and tetrafluoroethylene-ethylene copolymer resin. Hexafluoropropane copolymer resin, tetrafluoroethylene-perfluorovinyl ether co-IF
Typical examples include coalescent m fat and the like.

When obtaining the above fluorine-based graft copolymer,
The ratio of fluororubber and fluororesin is 60 to 80% by weight of the former and 40 to 20% by weight of the latter, preferably 6% of the former.
The latter is about 0 to 70% by weight, and the latter about 40 to 30% by weight, and if the amount of fluororesin exceeds the above range, the improvement in flexibility will be insufficient.

Both of these are graft copolymerized, but the graft copolymerization method at this time is not particularly limited and may be carried out by a conventional method. A fluororesin is graft copolymerized at the position.

In the present invention, the tetrafluoroethylene-propylene copolymer to be mixed with the fluorine-based graft copolymer is about 45 moles of propylene per 55 moles of tetrafluoroethylene, and the Mooney viscosity is
) is preferably about 30 to 150.

The vinylidene fluoride-hexafluoropropylene polymer contains iodine in the molecule and has a Mooney viscosity ML,
It is preferable to have a temperature of about 50 to 75 at 100°C.

As vinylidene fluoride-hexafluoropropylenetetrafluoroethylene terpolymer, Mooney viscosity ML
l+4 (100 DEG C.) is preferably about 50 to 75. As these fluorine-containing copolymers, those which can be crosslinked with an organic peroxide crosslinking agent are preferably used.

In the present invention, the blending ratio of the above-mentioned fluorine-containing copolymer to the fluorine-containing graft copolymer is 85/15 to 30/70 in terms of weight ratio of the former/latter, preferably 8 G/20.
~50150. In this case, if the latter is less than 15, the processing temperature cannot be lowered to a temperature at which the crosslinking agent can be mixed, and if the latter is more than 70, the shrinkability of the resulting heat-shrinkable tube will be reduced. descend.

In the present invention, it is not possible to prevent other conventional additives from being added as necessary. In this case, the additives include:
Examples include fillers, colorants, antioxidants, processing aids, acid acceptors, and the like. In addition, for the purpose of increasing the shrinkability of the tube, a shape memory improver can be blended within a range that does not impair heat resistance, and examples thereof include silicone resin, polyethylene, etc.

In the present invention, crosslinking of the tube is generally carried out by chemical crosslinking means, usually using an organic peroxide crosslinking agent, preferably in combination with a common crosslinking aid such as triallyl isocyanurate. .

As the organic peroxide crosslinking agent in this case, any of those conventionally known for chemical crosslinking of polyethylene and the like can be used, but dicumyl peroxide, dicumyl peroxide,
．． 5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexine 3, etc. whose 1-minute half-life temperature is 160°C or higher Polyfunctional compounds such as triallyl cyanurate and triallyl isocyanate are preferred as crosslinking agents.

When producing the heat-shrinkable tube of the present invention, it is preferable to first prepare at least one or more of a fluorine-based graft copolymer and a fluorine-containing copolymer, and further add other agents as necessary. Thoroughly knead with two rolls at 170-180°C, then increase the temperature of the two rolls to 110-180°C.
The temperature is lowered to 130°C, and then the crosslinking agent, crosslinking aid, and other compounding agents are kneaded. The molding machine is usually an extrusion molding machine (temperature 120
~140°C) and extrusion molded into a tube according to a conventional method. After that, crosslinking is carried out for 30 to 60 minutes in a 5 to 7 pupil/- smoked canister. After completion of crosslinking, it is expanded to a predetermined size by appropriate means such as heating, and then cooled.

In the present invention, when obtaining a thin tube, only a crosslinking aid may be added and crosslinked by electron beam irradiation.

〔Example〕

The present invention will be explained below with reference to Examples.

Examples 1 to 3 Using the predetermined components shown in Table 1, first, component A and component B were sufficiently kneaded with two rolls at 170 to 180° C. to prepare a polymer blend.

This polymer blend was then thoroughly kneaded with the other ingredients using two rolls at the processing temperatures shown in Table 1.

Using an extruder whose temperature was preliminarily adjusted to 140° C. and 130° C., a tube with a wall thickness of 4 fi was extruded using a mandrel with an outer diameter of 10 m as a core material.

Next, heat crosslinking was carried out for 60 minutes using a 5 kg/- steam crosslinking pot. Thereafter, the tube was heated in a heating furnace at 180° C., and then expanded by applying internal pressure in a die for controlling the outer diameter so that the inner diameter became 15 m. It was cooled in that state to obtain a heat-shrinkable tube.

Comparative Examples 1 and 2 The same treatment as in Example 1 was carried out using the predetermined components shown in Table 1. However, in Comparative Example 1, mixing was attempted at a temperature of 180°C, but the composition could not be prepared due to scorch generation. Also, comparative example 2
has poor shape memory.

[Margin below]

Table 1 Ru.

Component A: "Cepural Soft G150J (manufactured by Central Glass Co., Ltd.) TFBP-P copolymer: Tetrafluoroethylene-propylene copolymer "Flurus 150EJ (manufactured by Asahi Glass Co., Ltd.) VdF-HEP-TFE terpolymer; to vinylidene fluoride Xafluorobrobylene-tetrafluoroeethylene terpolymer "DAIEL 902J (manufactured by Daikin Industries, Ltd.) Cross-linking agent: 1.3 bis-(t-butyl-peroxy-isopropyl)benzene Cross-linking aid: triallylisocyanate chain Bubble contractility was measured by the following method.

Heat shrinkability: The tube was placed in a constant temperature oven at 180° C. to 190° C. for 5 to 10 minutes to check heat shrinkability. The mark Q indicates sufficient heat shrinkability.

Also, ×1 means that scorch occurred during kneading. What the tube couldn't do, ×1 indicates that it cannot be expanded.

(that's all)

Claims (3)

[Claims] (1) Selected from fluorine-containing copolymers consisting of tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer A heat-shrinkable tube characterized in that it is formed by chemically crosslinking a mixture of at least one kind and a fluorine-based graft copolymer. (2) The mixing ratio of the fluorine-based graft copolymer and the fluorine-containing copolymer (former:latter) is 85:15 to 30:7.
The heat-shrinkable tube according to claim 1, which has a weight ratio of 0 (weight ratio). (3) The heat-shrinkable tube according to claim 1 or 2, wherein the fluorine-based graft copolymer is a graft copolymer of fluororubber and fluororesin.