JPH07330979A - Silane/olefin copolymer composition and heat-shrinking tube made therefrom - Google Patents

Abstract

PURPOSE:To obtain a water-crosslinkable polyolefin improved in properties such as flexibility, stress cracking resistance, impact resistance and adhesiveness without detriment to extrudability and being quickly crosslinked in the presence of water. CONSTITUTION:This copolymer composition comprises 100 pts.wt. silane/olefin copolymer prepared by copolymerizing ethylene with an ethylenically unsaturated silane compound, 1-24 pts.wt. silanegrafted polyolefin, and 0.001-10 pts.wt. silanol condensation catalyst.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention improves performances such as flexibility, stress cracking resistance, impact resistance, and adhesiveness without impairing the extrusion moldability of silane copolymerized polyolefin, and in the presence of moisture. The present invention relates to a silane copolymerized polyolefin composition capable of being rapidly crosslinked and a heat shrinkable tube comprising the same.

[0002]

2. Description of the Related Art Various molded products of silane-copolymerized polyolefin can be cross-linked in the presence of water after molding, so that molded products and sheets excellent in heat resistance, stress cracking resistance, heat shrinkage properties, etc. Widely used as a covering material for tubes, heat shrinkable tubes and electric wires.

The silane copolymerized polyolefin is mainly produced from ethylene and an ethylenically unsaturated silane compound described in JP-A-55-9611.

As a method for crosslinking a polyolefin,
After the silanol condensation catalyst is mixed with the silane-copolymerized polyolefin, a crosslinking method such as electron beam crosslinking of irradiating the polyolefin with an electron beam and chemical crosslinking with a peroxide may be used in addition to the water crosslinking method of crosslinking in warm water or a high temperature and humidity chamber. Although known, the water-crosslinking method is widely used as a simple crosslinking method because it can be crosslinked by hydrolyzing and condensing a molded article in the presence of water.

As a water-crosslinkable polyolefin, the polyolefin resin described in Japanese Patent Publication No. 48-1711 is heated above the decomposition temperature of the free radical generator in the presence of an unsaturated silane compound and a free radical generator. Silane-grafted polyolefins are known.

Further, in order to improve the heat resistance of the silane-modified polyolefin, it has been proposed in JP-A-55-155045 to blend a large amount of silane-grafted polyolefin with the silane copolymerized polyolefin.

The silane-copolymerized polyolefin has advantages over the silane-grafted polyolefin such as storage stability, long-term molding processing stability, less contamination by foreign substances, and less odor. Taking advantage of its performance,
It is known to blend a polyolefin resin such as an ethylene-based polyolefin in order to improve performances such as flexibility, stress cracking resistance, impact resistance and adhesiveness.

[0008]

However, when a polyolefin resin such as an ethylene-based polyolefin is blended with the above-mentioned silane copolymerized polyolefin of the known example, 8
There is a problem that it takes a long time to crosslink when it is placed in a hot water tank of 0 to 100 ° C. or a high temperature and constant humidity tank and crosslinked. Also,
When a large amount of silane-grafted polyolefin is mixed with the silane-grafted polyolefin or the silane-copolymerized polyolefin, the cross-linking speed is high, but the appearance of the extrusion-molded product is often inferior.

[0009]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above problems in a silane copolymerized polyolefin composition, the present invention has revealed that a silane copolymerized polyolefin obtained by copolymerizing ethylene and an ethylenically unsaturated silane compound. 1
1 to 100 parts by weight of silane-grafted polyolefin
24 parts by weight and silanol condensation catalyst 0.001-10
By using a silane copolymerized polyolefin composition characterized by comprising parts by weight, flexibility, stress cracking resistance, without impairing the extrusion moldability,
The present invention has been accomplished by finding that a water-crosslinked polyolefin that has improved properties such as impact resistance and adhesiveness and that can be rapidly crosslinked in the presence of water can be obtained.

In the present invention, the silane copolymerized polyolefin is a copolymer of ethylene and an ethylenically unsaturated silane compound, and preferable ethylenically unsaturated silane compounds include vinyltrimethoxysilane, vinyltriethoxysilane, Examples thereof include vinylacetoxysilane, γ-methacryloxypropyltrimethoxysilane and γ-methacryloxypropylmethyldimethoxysilane. The copolymerization amount of the ethylenically unsaturated silane compound is usually 0.1
It is preferably from 15 to 15% by weight, particularly from 0.1 to 5% by weight. Further, the copolymerization of ethylene and the ethylenically unsaturated silane compound can be carried out by any method in which the copolymerization of both occurs. For example, pressure 500 to 4000 kg / c
The copolymerization is carried out in a tank or tubular reactor in the presence of a polymerization initiator, a comonomer copolymerizable with ethylene, and a chain transfer agent under conditions of m ² and a temperature of 100 to 400 ° C. Further, as a comonomer copolymerizable with ethylene, vinyl acetate, carboxylic acid vinyl ester, (meth) acrylic acid ester, (meth) acrylic acid, maleic acid, fumaric acid, (meth) acrylonitrile, (meth) Examples thereof include (meth) acrylic acid derivatives such as acrylic acid amide, vinyl methyl ether, vinyl phenyl ether, etc., which are added to the reactor simultaneously or stepwise.

The silane-grafted polyolefin of the present invention is a resin having a relatively high compatibility with the silane copolymerized polyolefin, that is, high density polyethylene, low density polyethylene, ultra low density polyethylene, high molecular weight polyethylene, polypropylene, or ionomer resin. In the presence of an unsaturated silane compound such as vinylmethoxysilane and a free radical generator such as dicumyl peroxide in a polyolefin resin such as ethylene-based copolymer such as ethylene vinyl acetate copolymer and ethylene ethyl acrylate copolymer. It is obtained by heating above the decomposition temperature of the free radical generator. The amount of the silane-grafted polyolefin blended is preferably in the range of 1 to 24 parts by weight with respect to 100 parts by weight of the silane copolymerized polyolefin, and a blending amount exceeding 24 parts by weight impairs the appearance of the extrusion-molded product and is not preferred. If it is less than 1 part by weight, it is difficult to improve the performance of the silane copolymerized polyolefin.

Specific examples of the silane-copolymerized polyolefin compounded with the silane-grafted polyolefin include:
For example, a combination of silane-copolymerized low-density polyethylene and a silane-grafted ethylene-vinyl acetate copolymer is preferable. In this combination, flexibility, stress cracking resistance and impact resistance of the silane copolymerized polyolefin composition are preferable. In particular, the performance such as adhesion is improved.

As the silanol condensation catalyst in the present invention, those which can accelerate dehydration condensation between silanols of silicone can be generally used. For example, tin, zinc, iron,
Examples thereof include carboxylates of metals such as lead and cobalt, organic bases, inorganic acids and organic acids, and specifically, dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate and the like are preferably used. The amount of the silanol condensation catalyst used is the silane copolymerized polyolefin 10
It is 0.001 to 10 parts by weight, preferably 0.001 to 5 parts by weight, based on 0 parts by weight. With a compounding amount exceeding 10 parts by weight, gelation locally progresses in the extruder during extrusion molding. As a result, the appearance of the molded product is significantly deteriorated. Also, 0.001
If the amount is less than the amount by weight, the crosslinking reaction does not proceed sufficiently, which is not preferable.

In the present invention, when the isocyanate compound and / or the epoxy compound is added to the silane-copolymerized polyolefin in the presence of a silanol catalyst, a cocatalyst effect of further accelerating the crosslinking rate can be obtained.

The above-mentioned isocyanate compound preferably has two or more isocyanate groups in the molecule. Specific examples preferably used include 4,4-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, isophorone diisocyanate, 4,4
-Dicyclohexylmethane diisocyanate, m or ρ-tetramethylxylylene isocyanate, lysine ester triisocyanate, 1,8-diisocyanate octane, 2,4-toluene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, carbodiimide modified Examples include carbodiimide-modified and polyol-modified isocyanate compounds such as diphenylmethane diisocyanate and polyol-modified diphenylmethane diisocyanate. Moreover, you may use the said isocyanate compound 1 type or in mixture of 2 or more types. The amount of the isocyanate compound compounded is 0.01 to 10 parts by weight, preferably 0.001 to 5 parts by weight, based on 100 parts by weight of the silane copolymerized polyolefin. The gelation locally progresses in the extruder and the appearance of the molded product is significantly deteriorated. Also, 0.0
If the amount is less than 01 parts by weight, a sufficient effect of promoting crosslinking cannot be obtained, which is not preferable.

Examples of the epoxy compound include glycidyl ether, diglycidyl ether, glycidyl ester,
It is a compound of diglycidyl ester, and specific examples thereof include glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, resorcin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene polyethylene glycol. Diglycidyl ether, propylene polypropylene glycol diglycidyl ether, polytetramethylene glycol ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, phenol polyethylene glycol glycidyl ether, ρ
-Tert-butyl phenyl glycol glycidyl ether, lauryl alcohol polyethylene glycol glycidyl ether, adipic acid diglycidyl ester, O-phthalic acid diglycidyl ester, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol poly Glycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycidyl phthalimide, terephthalic acid diglycidyl ester, bisphenol S diglycidyl ether,
Bisphenol A diglycidyl ether, versatic acid glycidyl ester, dimer acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, saturated fatty acid diglycidyl ester, benzoic acid glycidyl ester, stearic acid glycidyl ester, tertiary butyl phenyl glycidyl ester, etc. To be Further, an epoxy compound substituted with bromine or chlorine such as dibromophenyl glycidyl ether or dibromoneopentyl glycol diglycidyl ether can also be used. Moreover, you may use the said epoxy compound 1 type or in mixture of 2 or more types. The amount of the epoxy compound compounded is 0.01 to 10 parts by weight, preferably 0.001 to 5 parts by weight, based on 100 parts by weight of the silane-modified polyolefin. The gelation locally progresses in the machine and the appearance of the molded product is significantly deteriorated. Further, if the blending amount is less than 0.001 part by weight, a sufficient effect of promoting crosslinking cannot be obtained, which is not preferable.

Further, in the present invention, the polyolefin resin is a resin which is relatively excellent in compatibility with the silane copolymerized polyolefin, such as high density polyethylene, low density polyethylene, ultra low density polyethylene, high molecular weight polyethylene,
Polypropylene or polyolefin resin such as ionomer resin, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and other ethylene-based copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and other ethylene-based copolymer A combination in which a copolymer is blended is preferable, and in this combination, performances such as flexibility, stress cracking resistance, impact resistance and adhesiveness of the silane copolymerized polyolefin composition are particularly improved. The blending amount of the polyolefin resin is 1 to 50
Weight part is preferable, and if it is less than 1 part by weight, the performance of the silane copolymerized polyolefin composition such as flexibility, stress cracking resistance, impact resistance and adhesiveness is not improved. Also,
If the amount exceeds 50 parts by weight, the crosslinking rate is greatly affected, which is not preferable.

Further, within a range not impairing the performance of the present invention, a styrene-isoprene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-butadiene block copolymer, a styrene-butadiene-styrene block copolymer, A styrene elastomer such as styrene-ethylene-butadiene-styrene block copolymer or a thermoplastic elastomer such as natural rubber, butyl rubber, polyester elastomer, amide elastomer or polyurethane elastomer may be added. further,
Known thickeners, fillers, reinforcing agents, flame retardants, coloring agents,
Clarifying agents, plasticizers, UV blockers, antiaging agents, etc. can also be added.

Examples of the method for producing the silane copolymerized polyolefin composition and the water-crosslinked polyolefin of the present invention include a silane copolymerized polyolefin, a silanol condensation catalyst such as silane gufto polyolefin and dibutyltin dilaurate, and optionally an isocyanate compound and / or an isocyanate compound.
Alternatively, a silane-copolymerized polyolefin composition capable of water crosslinking can be obtained by mixing an epoxy compound and introducing the mixture into an extruder whose temperature is controlled at about 130 to 240 ° C to perform extrusion molding. Further, a water-crosslinked polyolefin is obtained by crosslinking the obtained silane-copolymerized polyolefin composition in a hot water tank or a high temperature constant humidity tank at about 80 to 100 ° C.

Water-crosslinked polyolefin is used as a heat-shrinkable tube by heating an industrial material or a tube or tube molded product utilizing excellent heat resistance and stress cracking resistance to a softening temperature or higher to expand the diameter and cool the shape. used. Further, it is also used as a multilayer tube having an adhesive layer or the like as an inner layer and a multilayer heat shrinkable tube. As the resin used in the adhesive layer, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer saponified product, ethylene-vinyl acetate copolymer hydrolyzate, ethylene-ethyl acrylate copolymer, Ethylene-glycidyl methacrylate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methacrylic acid-acrylate copolymer, ethylene-
Butene 1 copolymer, ethylene-propylene copolymer, ionomer resin and other ethylene-based copolymers and ethylene-based copolymers are directly copolymerized or grafted with α, β-unsaturated carboxylic acid components such as maleic anhydride. The ethylene-based copolymer obtained by the above is preferably used, and two or more kinds of ethylene-based copolymers may be used. Nylon 6, Nylon 66, Nylon 12, Nylon 610, Nylon 1 to improve the adhesion performance to metal etc.
Polyamide resin in which two or more components such as 1 are copolymerized, for example, nylon 6 / nylon 66, nylon 6 /
Nylon 66 / Nylon 610, Nylon 6 / Nylon 66 / Nylon 610 / Nylon 12, Nylon 6 / Nylon 66 / Nylon 610 / Nylon 11 and polyether ester amide copolymer, polyamide resin such as dimer acid polyamide resin, etc. You may mix it.

[0021]

The present invention is directed to the silane copolymerized polyolefin,
By forming a silane-copolymerized polyolefin composition characterized by comprising a silane-grafted polyolefin and a silanol condensation catalyst, flexibility, stress cracking resistance, impact resistance, and adhesiveness can be achieved without impairing extrusion moldability. It is possible to obtain a water-crosslinked polyolefin that has improved properties such as the above and can be rapidly crosslinked in the presence of water.

[0022]

EXAMPLES The effects of the present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples,% and parts are based on weight unless otherwise specified.

Evaluation method of extrusion moldability: The surface appearance of a strand-shaped extrusion-molded product of about 3 mmφ discharged from the extruder was visually observed.

Evaluation method of degree of crosslinking (gel fraction): Soxhlet extractor was used to perform extraction for 12 hours at a temperature above the boiling point of xylene, and the proportion of the remaining insoluble component was taken as the degree of crosslinking (gel fraction).

Evaluation method of heat resistance: The extruded product after water-crosslinking was cut into a length of 10 cm and placed in a dryer whose temperature was controlled at 200 ° C. for 5 minutes. By observing the heat shrinkage and deformation in the length direction of the extruded product taken out at room temperature, the shrinkage deformation is relatively small, and the extruded product that has the shape of the extruded product before being put into the dryer is considered good It was judged. In addition, an extrusion-molded product having a significantly large shrinkage deformation was judged to have a large shrinkage deformation.

Example 1 A single-screw extruder with L / D = 20 and a diameter of 20 mmφ, which was temperature-controlled at 190 ° C. (Toyo Seiki Seisakusho “Labo Plastomill” 20)
mmφ extruder), silane copolymerization low density polyethylene (Mitsubishi Yuka Co., Ltd. "Linkron" XF800T) 100
Part, silane-grafted ethylene vinyl acetate copolymer (Mitsubishi Yuka Co., Ltd. "Linkron" VE-800N) 20 parts, 5 parts of a catalyst masterbatch containing about 1 part of dibutyltin dilaurate as a silanol condensation catalyst. Was added, and the obtained strand-shaped silane copolymerized polyolefin composition was dipped in a hot water bath at 80 ° C. for 4 hours and 10 hours to obtain a water-crosslinked polyolefin.

Example 2 To the composition of Example 1 was added 1 part of polymethylene polyphenyl polyisocyanate ("Millionate MR200" manufactured by Nippon Polyurethane Industry Co., Ltd.) as an isocyanate compound, and a water-crosslinked polyolefin was prepared in the same manner as in Example 1. Got

Example 3 1 part of sorbitol polyglycidyl ether ("Denacol" EX611, Nagase Kasei Co., Ltd.) as an epoxy compound was added to the composition of Example 1 to prepare a water-crosslinked polyolefin in the same manner as in Example 1. Obtained.

Example 4 An ethylene vinyl acetate copolymer having a vinyl acetate content of about 10% was added to the composition of Example 1 (“Evatate” manufactured by Sumitomo Chemical Co., Ltd.).
D2021) 5 parts were blended to obtain a water-crosslinked polyolefin in the same manner as in Example 1.

Example 5 A two-layer tube molding machine equipped with two extruders for forming the outside and the inside of a two-layer tube whose temperature was controlled at 190 ° C. was used, and an example of an extruder for forming the outside was used. A silane copolymerized polyolefin composition raw material having the same composition as 1 was charged in the same manner as in Example 1, and the extruder forming the inside had a vinyl acetate content of about 1
0% ethylene vinyl acetate copolymer (Sumitomo Chemical Co., Ltd.)
"Evatate" D2021) is thrown in and the outer diameter is about 6 mm
A two-layer tube molded product having φ, an inner diameter of about 4 mmφ, and a wall thickness of the inner layer material of about 0.2 mm was obtained. The obtained two-layer tube molded product was immersed in a hot water bath at 80 ° C for 4 hours and 10 hours as in Example 1, and the diameter was increased about 1.5 times with a diameter-expanding device adjusted to about 115 ° C. The diameter was expanded to obtain a water-crosslinked polyolefin heat-shrinkable tube having an outer diameter of about 9 mmφ.

Comparative Example 1 Instead of 20 parts of the silane-grafted ethylene vinyl acetate copolymer of the composition of Example 1, 20 parts of ethylene vinyl acetate copolymer (“Evatate” D2021 of Sumitomo Chemical Co., Ltd.) was blended. A water-crosslinked polyolefin was obtained in the same manner as in Example 1.

Comparative Example 2 Silane Copolymerized Low Density Polyethylene 1 of Composition of Example 1
Silane grafted low density polyethylene instead of 00 parts (Sumitomo Bakelite Co., Ltd. "Moldex" S-18
1) was blended and a water-crosslinked polyolefin was obtained in the same manner as in Example 1.

Comparative Example 3 Silane Copolymerized Low Density Polyethylene 1 of Composition of Example 1
Silane grafted low density polyethylene instead of 00 parts (Sumitomo Bakelite Co., Ltd. "Moldex" S-18
1) and the silane-grafted polyolefin 2 of Example 1
20 parts of an ethylene vinyl acetate copolymer (Sumitomo Chemical Co., Ltd. "Evatate" D2021) was blended in place of 0 part to obtain a water-crosslinked polyolefin in the same manner as in Example 1.

Comparative Example 4 Silane Copolymerized Low Density Polyethylene 1 of Composition of Example 1
Silane grafted low density polyethylene instead of 00 parts (Sumitomo Bakelite Co., Ltd. "Moldex" S-18
1) and the silane-grafted polyolefin 2 of Example 1
A water-crosslinked polyolefin was obtained in the same manner as in Example 1 except that 0 part was used as the composition.

Comparative Example 5 Silane-grafted ethylene vinyl acetate copolymer of the composition of Example 1 (Mitsubishi Rika Co., Ltd. "Linkron" VE-800)
A water-crosslinked polyolefin was obtained in the same manner as in Example 1, except that the amount of N) was 40 parts.

Extrusion moldability (surface appearance of molded articles) of the water-crosslinked polyolefin and the water-crosslinked polyolefin heat-shrinkable tubes obtained in Examples 1 to 5 and Comparative Examples 1 to 5 and a hot water tank at 80 ° C. for 4 hours and 10 hours. The gel fraction of the water-crosslinked polyolefin that had been soaked in time was measured to compare the crosslinking rates. Table 1 shows the results obtained by evaluating the heat resistance of the water-crosslinked polyolefin.

[0037]

[Table 1]

From Table 1, in the case of the crosslinked polyolefin, which is a composition of the silane copolymerized polyolefin and the polyolefin of Comparative Example 1, the progress of water crosslinking is slow, so that the heat resistance of the water-crosslinked polyolefin is insufficient and the molded product shrinks greatly. It was transformed. Examples 1, 4 and 5 of the present invention
It is clear that the composition of the silane copolymerized polyolefin and the silane-grafted polyolefin described above has a fast water crosslinking rate and is excellent in the surface appearance of molded articles and heat-shrinkable tubes.

Water-crosslinked polyolefins obtained from the compositions of silane-grafted polyolefins or the compositions containing a large amount of silane-grafted polyolefins instead of the silane-copolymerized polyolefins of Comparative Examples 2 to 5 have a progressive water-crosslinking rate. Although it was quick, the surface of the molded product had irregularities and the external appearance was impaired, and the external appearance was unusable as a product.

As the crosslinking aid of Examples 2 to 3 of the present invention,
It is clear that the water-crosslinked polyolefin obtained from the composition containing the isocyanate compound or the epoxy compound has an excellent surface appearance of the molded article and has a significantly improved water-crosslinking rate.

[0041]

Industrial Applicability The present invention provides a silane copolymerized polyolefin composition in which a small amount of a silane grafted polyolefin and a silanol condensation catalyst are mixed with a silane copolymerized polyolefin obtained by copolymerizing ethylene and an ethylenically unsaturated silane compound. According to the above, since a water-crosslinked polyolefin that can be rapidly crosslinked in the presence of moisture can be obtained without impairing the extrusion moldability, a molded article excellent in flexibility, stress cracking resistance, impact resistance, adhesiveness, etc., Applications are expected to expand as a covering material for sheets, tubes, heat-shrinkable tubes, and electric wires.

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Claims (11)

[Claims] 1. A blend of 1 to 24 parts by weight of a silane-grafted polyolefin and 0.001 to 10 parts by weight of a silanol condensation catalyst to 100 parts by weight of a silane copolymerized polyolefin obtained by copolymerizing ethylene and an ethylenically unsaturated silane compound. A silane-copolymerized polyolefin composition comprising: 2. The silane copolymerization according to claim 1, further comprising 0.01 to 10 parts by weight of an isocyanate compound and / or 0.01 to 10 parts by weight of an epoxy compound based on 100 parts by weight of the silane copolymerized polyolefin. Polyolefin composition. 3. The silane-copolymerized polyolefin composition according to claim 1, which further comprises 1 to 50 parts by weight of a polyolefin resin based on 100 parts by weight of the silane-copolymerized polyolefin. 4. A water-crosslinked polyolefin obtained by water-crosslinking the silane copolymerized polyolefin composition according to any one of claims 1 to 3. 5. A tube comprising the silane copolymerized polyolefin composition according to claim 1 or a water-crosslinked polyolefin. 6. A multilayer tube having at least one layer comprising the silane copolymerized polyolefin composition or the water-crosslinked polyolefin according to any one of claims 1 to 4. 7. A heat-shrinkable tube made of the water-crosslinked polyolefin according to claim 4. 8. A multi-layer heat-shrinkable tube in which at least one layer is a layer formed of the water-crosslinked polyolefin according to claim 4. 9. The multilayer heat-shrinkable tube according to claim 8, further comprising an adhesive layer. 10. The adhesive layer comprises an ethylene-based copolymer and / or
The multilayer heat-shrinkable tube according to claim 9, which is made of an ethylene-based copolymer obtained by copolymerizing or grafting maleic anhydride. 11. The adhesive layer comprises an ethylene-based copolymer and / or
The multilayer heat-shrinkable tube according to claim 9, which is composed of a composition obtained by further mixing a polyamide resin with an ethylene-based copolymer obtained by copolymerizing or grafting maleic anhydride.