JPH07205285A - Heat shrinkable tube and production thereof - Google Patents

Abstract

PURPOSE:To obtain a heat shrinkable tube composed of a fluorine-containing elastomer excellent in toughness, generating no die refuse at the time of extrusion processing and shrinkable at low temp. CONSTITUTION:A heat shrinkable tube is constituted of a composition prepared by adding 0.5 pts.wt. or more of a crosslinking aid to 100 pts.wt. of a resin component consisting of a tetrafluoroethylene/propylene copolymer and a vinylidene fluoride/hexafluoropropylene copolymer and produced by molding the compsn. into a tubular shape and irradiating the tubular molded object with ionizing radiation to crosslink the same and subsequently expanding the diameter of the crosslinked molded object to fix the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable tube, and more specifically to a heat-shrinkable tube made of a fluorine-containing elastomer having excellent toughness and a manufacturing method therefor.

[0002]

2. Description of the Related Art Tetrafluoroethylene-propylene copolymers are heat resistant, oil resistant, chemical resistant, electrically insulating,
Since it is excellent in flexibility and the like, it is optimal as a heat-shrinkable tube material. However, the tetrafluoroethylene-propylene-based copolymer has low mechanical properties such as tensile strength and tear strength as compared with a general fluororesin typified by a tetrafluoroethylene-hexafluoropropylene copolymer. , There was a problem with toughness. Moreover, since the diameter cannot be fixed even if the tube formed by the tetrafluoroethylene-propylene copolymer is cooled after being blown, it is difficult to impart the function of heat shrinkage.

In order to improve these problems, it has been proposed to blend a tetrafluoroethylene-propylene copolymer with a fluorine resin such as an ethylene-tetrafluoroolefin copolymer.

[0004]

Since the above-mentioned fluororesin has a high melting point, it is necessary to raise the compounding or extrusion processing temperature to 200 ° C. or higher. As a result, a chemical reaction occurs with the cross-linking auxiliary material to cause extrusion. There was a problem that dice residue was generated during processing. If the die residue adheres to the outside of the tube, it can be easily removed by a means such as sending compressed air to blow it away, but if it adheres to the inside of the tube, it is difficult to remove it. there were. The die residue that came out of the inside of the tube blocked the inside surface of the tube and caused the tube to burst during the diameter expansion work of the tube.

Further, it is preferable that the tube diameter expansion work is performed at a temperature equal to or higher than the melting point of the pace polymer because the diameter expansion pressure can be lowered and it has been conventionally adopted. However, the contraction temperature is almost the same as the diameter expansion temperature. When the above high melting point fluororesin is blended, the shrinkage temperature is 200 ° C.
Will exceed. The heat shrinkage of the tube is usually caused by heating with a dryer or the like, but there is a problem that the shrinking work becomes very difficult when the shrinkage temperature exceeds 200 ° C. as described above.

The present invention has been made in view of the above-mentioned problems of the prior art, and is excellent in toughness, eliminates the generation of die residue during extrusion, and is heat-shrinkable from a fluorine-containing elastomer that can shrink at low temperature. It aims at providing a sex tube and its manufacturing method.

[0007]

The heat-shrinkable tube provided by the present invention comprises a resin component containing a tetrafluoroethylene-propylene copolymer and a vinylidene fluoride-propylene hexafluoride copolymer. The composition is characterized by comprising 100 parts by weight, and 0.5% by weight or more of a crosslinking aid.

Further, the method for producing a heat-shrinkable tube provided by the present invention comprises molding the composition as described above into a tube shape, crosslinking the tube-shaped molded article by irradiation with ionizing radiation, and then fixing the diameter. It is characterized by doing.

In the present invention, the tetrafluoroethylene-propylene-based copolymer is, in addition to the main components tetrafluoroethylene and propylene, a component copolymerizable therewith, such as ethylene, butene-1, isobutene, Acrylic acid and its alkyl ester, methacrylic acid and its alkyl ester, vinyl fluoride, vinylidene fluoride, hexafluoropropene, chloroethyl vinyl ether, glycidyl vinyl ether, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, etc. good.

The tetrafluoroethylene-propylene-based copolymer has a molar ratio of tetrafluoroethylene / propylene of 95/5 to 30/7 from the viewpoints of heat resistance and moldability.
It is desirable to select from the range of 0, and particularly preferred is 9
It is 0/10 to 45/55. Further, the content of other components added to the main component is preferably selected from the range of 50 mol% or less, particularly 30 mol% or less.

The blending ratio of the tetrafluoroethylene-propylene copolymer and vinylidene fluoride-propylene hexafluoride is not particularly limited, but in the weight ratio of the tetrafluoroethylene-propylene copolymer and vinylidene fluoride-propylene hexafluoride. It is desirable to select from the range of 80 to 30/20 to 70.

In the present invention, a crosslinking aid is added to enhance the crosslinking reactivity. As the crosslinking aid,
Acrylic type compounds, sulfur, organic amines, maleimides, methacrylates, divinyl compounds, polybutadiene and the like can be mentioned, but allyl type compounds represented by triallyl isocyanurate and triallyl cyanurate are particularly preferable. The amount of the crosslinking aid added is 0.5 parts by weight or more based on 100 parts by weight of the resin content. That is, if it is less than 0.5 parts by weight, a sufficient degree of crosslinking cannot be achieved. It is particularly preferably 1 to 20 parts by weight, and the effect of addition of the crosslinking aid is saturated at 20 parts by weight.

In addition to the above components, a filler, a stabilizer,
Pigments such as titanium white, additives such as antioxidants, plasticizers and lubricants may be added. As the filler, silicic acid-based filler such as silicic acid anhydride, talc and clay, MT carbon, F
Examples include EF carbon.

The various components as described above are uniformly kneaded, and then introduced into an extruder to form a tube, which is crosslinked by irradiation with ionizing radiation, and then ethylene-tetrafluoroethylene-fluoroolefin copolymer. A predetermined heat-shrinkable tube is manufactured by expanding the diameter of the polymer by blowing or the like at a temperature equal to or higher than the crystal melting point of the polymer, followed by cooling and fixing.

[0015]

EXAMPLES Table 1 shows Examples 1 to 6 of the present invention and
2 shows Comparative Examples 1 and 2.

[0016]

[Table 1]

The components shown in Examples 1 to 6 in Table 1 are melt-kneaded at 180 ° C. using a kneader. Die: 180 ° C, head 180
℃, Cylinder: 180 ℃, Cylinder 2: Using a 40 mm extruder (L / D = 22) set to 160 ℃, inner diameter 2
A tube having a diameter of 3 mm and an outer diameter of 3 mm was extrusion-molded and irradiated with an electron beam of 5 Mrad to crosslink. Subsequently, while blowing nitrogen gas at 180 ° C. into the tube, the tube was blown to have an outer diameter of 6 mm, and in a state where the diameter was expanded, water-cooling fixation was performed to obtain a heat-shrinkable tube.

The components shown in Comparative Example 1 in Table 1 were used in Example 1 except that the kneading temperature and the extrusion temperature were both 280 ° C.
A heat-shrinkable tube was manufactured by the same method as described above. The components shown in Comparative Example 2 were prepared in the same manner as in Example 1 except that the kneading temperature and the extrusion temperature were both 100 ° C.
A heat shrinkable tube was manufactured.

The results obtained by measuring the extrusion appearance and tensile properties of the heat-shrinkable tubes of the respective examples produced as described above are shown in the lower column of Table 1. As is clear from these results, in each of Examples 1 to 6, no die residue was generated during extrusion, good blowing property was obtained, tensile strength and elongation were sufficiently high, and heat shrink temperature was 150 ° C. I made it low. On the other hand, in Comparative Example 1, a high melting point ethylene-tetrafluoroethylene copolymer was used, but a large amount of die residue was generated during extrusion, the inside of the tube was closed, and the phenomenon that the tube bursts during blowing was observed. It happened a lot. Further, the shrinkage temperature was as high as 260 ° C. In Comparative Example 2, the system does not contain a resin component, but the diameter returns to the original size even if an attempt is made to solidify with water immediately after blowing,
No heat shrink function was obtained.

[0020]

According to the present invention as described above, the toughness is excellent and the generation of die residue during extrusion processing is eliminated,
The intended purpose of providing a heat-shrinkable tube made of a fluorine-containing elastomer capable of shrinking at a low temperature and a method for producing the same is sufficiently achieved, and the practical effect is overwhelming.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C08L 27:12 (72) Inventor Akira Saito 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Hitachi Electric Wire FM Co., Ltd.

Claims (2)

[Claims] 1. A resin component containing a tetrafluoroethylene-propylene copolymer and a vinylidene fluoride-propylene hexafluoride copolymer is 100 parts by weight, and 0.5 parts by weight or more of a crosslinking aid is added. A heat-shrinkable tube comprising a composition comprising: 2. A resin component containing a tetrafluoroethylene-propylene copolymer and a vinylidene fluoride-propylene hexafluoride copolymer is 100 parts by weight, and 0.5 parts by weight or more of a crosslinking aid is added. A method for producing a heat-shrinkable tube, characterized in that the composition comprising the above is molded into a tube, and the tube-shaped molded body is crosslinked by irradiation with ionizing radiation and then expanded and fixed.