JPH06344441A - Heat recovering article - Google Patents

Abstract

PURPOSE:To provide a heat recovering article such as heat shrinkable tube which has a high adhesion with both ionomer and PVC, is inexpensive, and is provided with an inner layer material with poor hygroscopicity. CONSTITUTION:A heat recovering article is obtained which comprises an outer layer which is formed of polymer and has a heat recovering property and an inner layer which is formed of a resin composition containing 50-99wt.% of ethylene-alkyl(meth)acrylate-carbon monoxide copolymer and 1-50wt.% modified polyolefin having hydroxyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-recoverable article such as a joint for electric wires and cables and a heat-shrinkable tube used for terminal treatment.

[0002]

2. Description of the Related Art Heat-shrinkable tubes and other heat-recoverable articles are used for various purposes such as joints (connection parts) for electric cables and communication cables, terminal protection treatment for wiring in various devices, and corrosion protection of steel pipes. There is. For example, when a heat shrink tube is put on the connection part of the electric wire cable and heated, the heat shrink tube shrinks along the shape of the joint part,
Because of the close contact, the connection portion can be protected from external damage. When a high degree of adhesion is required for waterproofing or the like, a heat-shrinkable tube with an inner layer material in which an adhesive is applied to the inner surface of the heat-shrinkable tube is used.

Conventionally, as the adhesive used as the inner layer material, ethylene / vinyl acetate copolymer (EVA), ethylene / ethyl acrylate copolymer (EEA), hot melt adhesives based on these, and further polyamide resin Hot melt adhesives such as saturated copolyester resins and saturated copolyester resins are generally used (JP-A-54-84294, JP-A-60-22413). As the adhesive used as the inner layer material, a suitable one is individually selected from these depending on the material of the heat shrinkable tube to which the inner layer material is applied and the substrate to be treated (adherend).

As a method for producing a heat-shrinkable tube, a resin composition made of a polymer material is molded into a tube shape, irradiated with an ionizing radiation such as an electron beam or γ-ray, chemically crosslinked, or water-crosslinked (silane crosslinked). It is general to crosslink by a method such as the above, expand this in a high temperature atmosphere, and cool while keeping its shape. As a method of crosslinking, irradiation with an electron beam having a short crosslinking time and good productivity is most commonly performed.

Adhesive (inner layer material) on the inner surface of the heat-shrinkable tube
As a method of applying the, the method of extruding the heat shrinkable tube and also extruding the inner layer material at the same time (coextrusion method) is the most productive and efficient. In this case, when an electron beam is irradiated to crosslink the outer layer of the two-layer tube obtained by the coextrusion method, the inner layer material is also irradiated with the electron beam, which causes the inner layer material to be crosslinked. Then, since the fluidity at the time of melting is lost and the adhesiveness is lost, the inner layer material should be a material that does not crosslink even when irradiated with an electron beam, or it is necessary to devise so as not to crosslink.

Conventionally, polyamide-based hot melt adhesives have been often used as the inner layer material of the heat-shrinkable tube from the viewpoint of excellent adhesion to various adherends. Particularly, for the purpose of adhering to polyvinyl chloride (PVC), a polyamide hot melt adhesive is suitable as the inner layer material (Japanese Patent Publication No. 56-17218). However, the polyamide resin has a drawback that it is expensive and absorbs moisture, and there is a problem that it easily foams during manufacturing. Further, the saturated copolyester resin has properties similar to those of the polyamide-based hot melt adhesive, so it cannot be said that it is a material which can sufficiently satisfy the problem of foaming.

On the other hand, EVA has low hygroscopicity and is excellent in adhesion to a relatively large number of substances, but has a drawback that it is poor in adhesion to PVC. Further, EVA has a problem that it tends to be cross-linked by electron beam irradiation to lose its melt fluidity, and that addition of an antioxidant cannot sufficiently suppress the decrease in melt fluidity. Therefore, it has been desired to develop an adhesive that has excellent adhesiveness to various adherends, is inexpensive, has low hygroscopicity, and does not crosslink even when irradiated with ionizing radiation. Therefore, the present inventor is inexpensive and has no hygroscopic property,
As an inner layer material that is difficult to be cross-linked by irradiation, an inner layer material that uses an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer as a base resin was previously proposed (Japanese Patent Application No. 4-69655).
issue).

By the way, recently, ionomers have also come to be used as a material for heat-shrinkable tubes. Ionomer is excellent in toughness, low temperature resistance, transparency, oil resistance and the like, and is suitable as a material for heat shrinkable tubes. PV using this ionomer heat shrink tube
In order to waterproofly protect the C-coated electric wire and the like, it is necessary to use, as the inner layer material, a material that can be bonded to both the outer layer ionomer and the adherend PVC. However, the ethylene / alkyl (meth) acrylate / carbon monoxide copolymer is not suitable as an inner layer material for a heat-shrinkable tube made of an ionomer because of poor adhesion to the ionomer. On the other hand, the polyamide-based hot melt adhesive has a problem that it is expensive and has hygroscopicity because it has excellent adhesiveness to both ionomer and PVC, but as an inner layer material for a heat-shrinkable tube made of an ionomer. It is the current situation that I had no choice but to use it.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide good adhesion to both ionomers and PVC, at low cost,
It is intended to provide a heat-recoverable article including a heat-shrinkable tube using an inner layer material having a low hygroscopic property. The inventors of the present invention have conducted extensive studies to overcome the above-mentioned problems of the prior art, and as a result, as an inner layer material, an ethylene alkyl (meth) acrylate is formed on the inner surface of the outer layer having a heat recovery property formed of a polymer material. It was found that the above object can be achieved by using a resin composition containing a carbon monoxide copolymer and a modified polyolefin containing a hydroxyl group, and the present invention has been completed based on this finding.

[0010]

Thus, according to the present invention, a heat-recoverable outer layer formed from a polymeric material and an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer 50-99 wt. % And a modified polyolefin containing a hydroxyl group in an amount of 1 to 50% by weight, and a heat recoverable article comprising an inner layer formed of a resin composition. Hereinafter, the present invention will be described in detail.

The heat-recoverable article of the present invention has two outer layers and an inner layer.
It is composed of layers. The outer layer is a layer having a heat recovery property formed of a polymer material, and the inner layer is an adhesive layer for adhering to an adherend. The outer layer can be formed of the same material as a heat-recoverable article such as a conventionally known heat-shrinkable tube, and the material is not particularly limited, and can be produced from various polymer materials by a known method. . Examples of the polymer material forming the outer layer include ionomer, polyethylene, PVC, EVA, ethylene / ethyl acrylate copolymer (EEA), chlorinated polyethylene, and various thermoplastic elastomers (eg, polyester elastomer). . These polymeric materials may contain various additives such as a cross-linking agent, a cross-linking aid and a filler, if necessary. Among these polymeric materials, ionomers are particularly preferable as a target to which the inner layer material of the present invention is applied.

An ionomer is a resin obtained by neutralizing a carboxylic acid of a copolymer of ethylene and an unsaturated carboxylic acid (such as methacrylic acid) with a metal ion (Na ⁺ , Zn ^2+, etc.), and a metal ion at room temperature. Although it is a cross-linked polymer by bond formation, it has the property of easily breaking and flowing when a shear force acts at high temperature. As the ionomer, those commercially available under the trade names of Himilan (Mitsui DuPont Polychemical), Surlyn (DuPont) and the like can be used.

In the present invention, a resin composition containing an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer and a modified polyolefin containing a hydroxyl group is used as the inner layer material. In addition, in this invention, an alkyl (meth) acrylate shall mean an alkyl acrylate or an alkyl methacrylate. Examples of the ethylene / alkyl (meth) acrylate / carbon monoxide copolymer include ethylene / methyl acrylate / carbon monoxide copolymer, ethylene / ethyl acrylate / carbon monoxide copolymer, ethylene / methyl methacrylate / monoxide. Carbon copolymers and the like can be mentioned. Further, as the modified polyolefin containing a hydroxyl group, E
A saponified product of VA (a product obtained by completely or partially replacing the acetoxy group of EVA with a hydroxyl group) and the like can be mentioned.

The composition of the ethylene / alkyl (meth) acrylate / carbon monoxide copolymer is not particularly limited, but the melt flow index (MI) measured at a temperature of 190 ° C. and a load of 2.16 kg is usually 1 ~ 5
It is desirable to be in the range of 00 g / 10 minutes, preferably 5 to 400 g / 10 minutes. Similarly, a modified polyolefin containing a hydroxyl group also has a temperature of 190 ° C. and a load of 2.16 kg.
It is desirable that the MI measured in 1. is usually in the range of 1 to 500 g / 10 minutes, preferably 5 to 400 g / 10 minutes.
If the MI of the inner layer material is less than 1, the flowability is not sufficient.
Poor adhesion to the substrate to be treated, conversely MI of 500
If it exceeds, the inner layer material will flow out when the tube is expanded by heating.

A resin composition containing an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer and a modified polyolefin containing a hydroxyl group is an ionomer or P
Excellent adhesion to both VC. The reason is that the ethylene / alkyl (meth) acrylate / carbon monoxide copolymer contributes to the adhesion with PVC, while the modified polyolefin containing a hydroxyl group contributes to the adhesion with the ionomer. For example, in the case of saponified EVA, a large number of hydroxyl groups are contained in the molecule, but it is considered that the adhesive force is improved because the hydroxyl groups react with the non-ionized carboxylic acid moiety of the ionomer during heating. .

The blending ratio of each resin component in the resin composition forming the inner layer material is 50 to 99% by weight, preferably 70 to 98% by weight of ethylene / alkyl (meth) acrylate / carbon monoxide copolymer. It is more preferably 80 to 98% by weight, and the modified polyolefin containing a hydroxyl group is 1 to
It is 50% by weight, preferably 2 to 30% by weight, more preferably 2 to 20% by weight. Ethylene alkyl (meta)
When the blending ratio of the acrylate / carbon monoxide copolymer is less than 50% by weight, the adhesion of the substrate to be treated with PVC becomes poor. If the blending ratio of the modified polyolefin containing a hydroxyl group is less than 1% by weight, the effect of improving the adhesiveness with the ionomer is poor, and if it exceeds 50% by weight, the hygroscopicity becomes high and water absorption and foaming easily occur.

When it is required to be able to read markings and the like written on a substrate protected by a heat-recoverable article such as a heat-shrinkable tube, the heat-recoverable article needs to be transparent. The parallel light transmittance of each of the outer layer material and the inner layer material is 5
When it is at least 0%, the transparency of the heat-recoverable article will be good, and the marking or the like on the substrate to be treated can be easily read. If the outer layer has poor abrasion resistance, the surface of the outer layer is easily scratched, and the scratches make it difficult to read the contents written on the substrate. However, if the outer layer material has good wear resistance, such a problem can be prevented. Ionomer is suitable as the outer layer material satisfying both abrasion resistance and transparency. Further, as the inner layer material, from the viewpoint of transparency,
A resin composition containing 80 to 99% by weight of an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer and 1 to 20% by weight of a modified polyolefin containing a hydroxyl group is preferable. When the mixing ratio of the both is within this range, an inner layer having a parallel light transmittance of 50% or more can be formed. When the blending ratio of the modified polyolefin containing a hydroxyl group exceeds 20% by weight, the transparency of the inner layer material is lowered.

When the outer layer of a heat-recoverable article such as a heat-shrinkable tube is crosslinked by irradiation with ionizing radiation, the inner layer material may also be irradiated with ionizing radiation. When the material is cross-linked, the melt fluidity is lost, the MI value becomes less than 1 g / 10 minutes, the burying property in the substrate to be treated is impaired, and the function as the inner layer material is lost. Therefore, in order to prevent cross-linking even when irradiated with ionizing radiation, for example, phenol-based, hindered phenol-based, organic sulfur-based, amine-based, phosphite ester-based, hydroquinone derivative, etc. oxidation prevention Agent
It is effective to add it to the resin composition forming the inner layer material.

If desired, various additives such as flame retardants, colorants and light stabilizers can be added to the resin composition forming the inner layer material. In addition, the resin composition has a third content within the range that does not adversely affect the adhesiveness and hygroscopicity.
As a component, a small amount of another resin such as EVA or EEA may be added.

As a method for producing the heat-recoverable article of the present invention, a method of melt extrusion molding a material forming an outer layer and a material forming an inner layer by a coextrusion method is preferable. Next, crosslinking is performed by irradiating ionizing radiation from the outer layer side. Other than irradiation cross-linking, it may be cross-linked by chemical cross-linking or silane cross-linking. After cross-linking, the molded product is expanded in a high temperature atmosphere and cooled while maintaining its shape, so that heat recoverability can be imparted.

The substrate to be treated with the heat-recoverable article of the present invention is not particularly limited, and its material is, for example, a metal such as copper, iron, aluminum, tin or nickel,
Examples thereof include glass and various polymer materials. Among these, PVC is particularly preferable.

[0022]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The evaluation method of the physical properties is as follows. <Adhesiveness> A heat-shrinkable tube is placed on a PVC insulated electric wire having an outer diameter of 5 mm and heat-shrinked to prepare an adhesiveness test sample. This sample is cut into a semi-cylindrical shape in the longitudinal direction, the tip portion of the heat-shrinkable tube with the inner layer material is peeled from the wire and folded back at 180 degrees, and the tip portion is grasped and peeled from the wire at a pulling speed of 50 mm / min. The peel strength at that time was measured. In the evaluation, 1 kg or more was ◯, and less than 1 kg was X. <Hygroscopicity of inner layer material> 1 g of inner layer material was sampled, and 8
It was dried at 0 ° C. for 8 hours. The dried sample was weighed and then immersed in water at 23 ° C. for 24 hours, and then the water absorption amount was measured to calculate the water absorption rate. When the water absorption rate was less than 1%, it was evaluated as ◯. <Transparency> For the outer layer material and the inner layer material, a sheet having a thickness of 1 mm was prepared, and the parallel light transmittance was measured.

[Example 1] An ionomer (Himilan 1554: Zn ion type: manufactured by Mitsui DuPont Polymeical Co., Ltd.) was used as the outer layer material, and an ethylene / ethyl acrylate / carbon monoxide copolymer (MI = 1 was used as the inner layer material.
00g / 10 minutes) 90 parts by weight, saponified EVA (Dumilan D229: manufactured by Takeda Pharmaceutical Co., Ltd.) 10 parts by weight, and an antioxidant triethylene glycol-bis [3- (3-t-butyl-5-methyl-4). -Hydroxyphenyl) propionate] 5 parts by weight of a resin composition was used to coextrude the outer layer and the inner layer by a melt extrusion method to obtain an outer layer outer diameter of 6 mmφ
(Outer layer inner diameter 5 mmφ), inner layer inner diameter 4 mmφ (inner layer outer diameter 5
A tube with an inner layer material of (mmφ) was produced. This tube was irradiated with an electron beam having an accelerating voltage of 1 MeV for 15 Mrad. Then, the obtained tube was expanded in a constant temperature bath at 150 ° C. so that the inner diameter of the inner layer was 8 mmφ, to prepare a heat-shrinkable tube.

[Example 2] The same procedure as in Example 1 was carried out except that an ionomer (Himilan 1555: Na ion type: manufactured by Du Pont Mitsui Polymer Co., Ltd.) was used as the outer layer material.

[Examples 3 to 5] The same procedure as in Example 1 was repeated except that the resin composition of the inner layer material was changed as shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that only ethylene / ethyl acrylate / carbon monoxide copolymer was used as the resin for the inner layer material.

[Comparative Example 2] The procedure of Example 2 was repeated except that only ethylene / ethyl acrylate / carbon monoxide copolymer was used as the resin for the inner layer material.

[Comparative Examples 3 to 4] The same procedure as in Example 1 was repeated except that the resin composition of the inner layer material was changed as shown in Table 2.

[Comparative Example 5] In the resin composition for the inner layer material, EVA (Evaflex E) was used instead of the saponified EVA.
V220: manufactured by Mitsui DuPont Polychemical Co., Ltd., but in the same manner as in Example 1.

Comparative Example 6 The procedure of Example 1 was repeated except that a polyamide resin (Versalon 1300: manufactured by Nippon General Mills Chemical Co., Ltd.) was used as the resin for the inner layer material. The results are collectively shown in Tables 1 and 2.

[0032]

[Table 1]

[0033]

[Table 2]

(Footnote) <Himilan 1554> Ionomer (Zn ion type), Mitsui DuPont Polychemical <Himilan 1555> Ionomer (Na ion type), Mitsui DuPont Polychemical * 1: Ethylene / ethyl acrylate / carbon monoxide copolymer (MI = 100) * 2: Dumilan D229, Takeda Yakuhin * 3: Triethylene glycol-bis [3- (3-t-
Butyl-5-methyl-4-hydroxyphenyl) propionate] * 4: Evaflex EV220, Mitsui DuPont Polychemical * 5: Versalon 1300, Japan General Mills Chemicals

The heat-shrinkable tubes described in Examples 1 to 5 are
Excellent adhesion and hygroscopicity. However, in Example 4, since the amount of saponified EVA contained in the inner layer material is large,
Since the parallel light transmittance is less than 50%, it is unsuitable for applications requiring transparency. Comparative Examples 1 and 2 are saponified EVs.
This is the case where A was not blended, but no adhesion was obtained regardless of the ion species of the ionomer. Comparative Example 3
Is 0.5% by weight of saponified EVA, but this amount is too small to obtain practical adhesiveness. Comparative Example 4 is a case where the blending ratio of the saponified EVA is 60% by weight, but the water absorption rate exceeds 1%, which is likely to cause foaming. Comparative Example 5
When EVA is used instead of saponified EVA, there is no adhesive effect. Comparative Example 6 is a case where the polyamide resin is used as the inner layer material, but the adhesiveness is good, but there is a problem that the water absorption is very high.

[0036]

INDUSTRIAL APPLICABILITY According to the present invention, a resin composition containing an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer and a modified polyolefin having a hydroxyl group as an inner layer material of a heat recovery article such as a heat shrinkable tube. By using the material, a heat-recoverable article that does not foam at the time of production because it absorbs little moisture and has excellent adhesiveness to both the ionomer of the outer layer material and the PVC of the adherend is provided.

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Claims (3)

[Claims] 1. A heat-recoverable outer layer formed of a polymer material, and 1 to 50 weight% of an ethylene / alkyl (meth) acrylate / carbon monoxide copolymer and a hydroxyl group-containing modified polyolefin. %, And an inner layer formed of a resin composition containing 10% by weight. 2. The heat-recoverable article according to claim 1, wherein the modified polyolefin having a hydroxyl group is a saponified product of an ethylene-vinyl acetate copolymer. 3. The heat-recoverable article according to claim 1, wherein the outer layer is formed of a polymer material containing an ionomer.