WO2002019494A1

WO2002019494A1 - Armature for heat shrinkable sleeve and heat shrinkable sleeve comprising it

Info

Publication number: WO2002019494A1
Application number: PCT/KR2001/001162
Authority: WO
Inventors: Bong-Ik Hwang
Original assignee: Chunma Corporation; Jung, Young-Hyun
Priority date: 2000-08-30
Filing date: 2001-07-06
Publication date: 2002-03-07
Also published as: AU2001269578A1; KR100378880B1; BR0103788A; CN1451197A; KR20020017433A

Abstract

The present invention relates to a reinforcement for a heat shrinkable sleeve and a heat shrinkable sleeve containing the same. The present invention provides a heat shrinkable sleeve and a reinforcement thereof, wherein the polymer of the inner layer having a high melting point remains intact even after heat treatment, and it binds with a fabric firmly, owing to the cross-linking of the polymer of the outer layer having high melting point, a fabric, another inner layer polymer having high melting point and a polymer layer having low melting point, so that the heat shrinkable sleeve becomes more resistant to the inner air pressure and the outside air when the reinforcement is applied to an air injection type heat shrinkable sleeve, and its bursting can be prevented during heat recovery. In addition, the present invention provides a heat shrinkable sleeve and reinformcement thereof, which can significantly shorten the time for heat recovery or heat shrinking by reducing the total thickness of the reinforcement to about one third of the thickness of conventional products.

Description

AMATURE FOR HEAT SHRINKABLE SLEEVE AND HEAT SHRINKABLE SLEEVE

COMPRISING IT

Technical Field The present invention relates to a reinforcement (armature) for a heat shrinkable sleeve and a heat shrinkable sleeve containing the same. More particularly the present invention relates to a reinforcement, which is used to improve the function of a heat shrinkable sleeve for sealing joints of long materials such as communication cable.

Background Art

Generally cables laid underground are coated with various coating materials to prevent permeation of water into their joint. For example, a heat shrinkable sleeve can be wrapped around a joint, fixed with a banding clip and adhered to the joint by being heated with a burner such as a torch lamp and so on.

Such heat shrinkable sleeves are classified into single layered type and composite layered type. Single layered heat shrinkable sleeves are used for small communication cable or a simple connector. The single layered heat shrinkable sleeves are prepared by heating and mixing high density polyethylene (HDPE) , medium density polyethylene (MDPE) , low density polyethylene

(LDPE) , linear low density polyethylene (LLDPE) 'or polypropylene (PP) with carbon black, silicon dioxide and other additives to yield a heat-melting sheet, which is then cross-linked, and drawn. However said single layered heat shrinkable sleeve has a low heat shrinkage rate and cannot seal up completely joints of communication cable from the outside environment . Therefore, for joints of communication cable composed of multiple lines, composite layered heat shrinkable sleeves are used.

Said composite layered heat shrinkable sleeves can be explained with reference to Figure 5 as follows. First, on an outer side or on both sides of a fabric (2) is extruded and coated a mixture of carbon black and a polymer of high melting point (1) (hereinafter referred to as "polymer of high m.p.") with a density of 0.94 to 0.96, which has been previously subjected to heat melting. Said polymer coated on the fabric is subsequently cross-linked to produce a complex composite of heat shrinkable fabric and polymer (hereinafter referred to as "the fabric composite") . Further a metal layer (5) on which a polymer of low melting point (3) (hereinafter referred to as "polymer of low m.p.") in the form of a film or an extruded product is laminated is coated on the inner side, and an adhesive having a low melting point (7) such as polyamide, ethylene vinylacetate

(EVA) and the like is finally coated to complete the product. By using such a composite layered heat shrinkable sleeve, a disturbance of electromagnetic wave from the outside can be blocked, a water resistant effect is remarkably enhanced and the joints of the communication cable can be sealed more efficiently.

With respect to techniques of conventional heat shrinkable sleeves, European Patent No. 112390 discloses a sleeve product having improved preservability and impermeability and British Patent No. 1604379 discloses a sleeve product in which a metal sheet of a thickness of 10 to 25 μm is used. However, these products have drawbacks such as heat shrinkage of the sleeve is inhibited due to the use of a thick metal sheet. Further, neither the heat shrinkable sleeve of European Patent No. 116393, which employs a material for a polymeric matrix nor the heat shrinkable sleeve of British Patent Publication No. 2075991 which uses an adhesive such as polyamide and EVA resin has provided a satisfactory effect in complete sealing joints of communication cable. Korean Patent Publication No. 96-753, which is related to a conventional reinforcement for a heat shrinkable sleeve for sealing joints of communication cable, describes that, while the polymeric substance (1) disposed at the outer side of the fabric (2) should be desirably cross-linked so as to prevent it from being deteriorated or shifted in terms of physical properties particularly when the sleeve is heat-recovered by a torch, the polymer (la) disposed at the inner side should desirably not be cross-linked so as to be flown and combined with an adjacent strengthening layer during a heat recovery process. More specifically, it is clearly described that said uncross-linked polymer (la) applied at the inner side of the fabric (2) can be flown and bond to a strengthening layer (3a, 4.5.8), and therefore enhancing its bonding to the strengthening layer. It is also described that the polymer (1) which is not cross-linked and disposed at the inner side, namely the meltable substance layer between the fabric composite and the strengthening layer should desirably have a thickness of 20 to 30 μm and the reinforced layer may consist a single layered or double layers or more including for instance a "Mylar" (i.e., enriched polyester film) or nylon layer attached to a single side or both sides of the metal layer such as aluminum.

However, said conventional heat shrinkable sleeve has problems as the following. Namely, in a conventional heat shrinkable sleeve, only the outer polymer of the heat shrinkable fabric is cross-linked and the inner materials are laminated after the outer polymer is cross-linked. Subsequently, the fabric composite is adhered to the strengthening layer by being subjected to a corona treatment and heat-melting, in order to strengthen the bonding between them. Accordingly said process, which consists of cross-linking — lamination -- corona treatment, cannot be carried out simply. Thus the process is complicated, and the production efficiency is lowered. Further it has a problem that the inner polymer is often separated from the fabric or the sleeve is burst due to the lack of cross-linkage in the inner polymeric substance . A "Mylar" , i.e., polyester layer (8), is employed to support the aluminum layer and a LLDPE layer (9) is used to prevent the oxidation of the aluminum layer. Since the LLDPE layer (9) has poor adhesiveness with adhesives having a low melting point (which is mostly polyamide) , a film of ethylene acrylic acid (EAA) co-polymer should be coated between them by extrusion. Further an urethane adhesive should be coated between all these layers to adhere the respective layers. Consequently the number of layers of the reinforcement amounts to eight and the total thickness of the product becomes 100 to 105 μm. Still further in respect to reinforcement of conventional heat shrinkable sleeves, a film of polymer of low m.p. (3a) is adhered to a polyester film through a urethane adhesive (4) by dry lamination and it should be aged at 40 to 50 °C for 24 to 48 hours. And then polyester film (8) is adhered to the aluminum layer through a urethane adhesive (4) and it should be aged again at 40 to 50 °C for 24 to 48 hours. Subsequently the co-polymer of LLDPE and EAA is corextruded and adhered to the aluminum layer (5) through a urethane adhesive and it is aged under the same condition as above and then the EAA layer is adhered to the polyamide adhesive layer. Accordingly, the process for production of said reinforcement has problems of being complicated, time consuming, and expensive. Namely it has been a problem that the aging time itself requires 3 to 4 days for producing a reinforcement of the conventional heat shrinkable sleeve.

Disclosure of Invention

The present invention is contrived to solve the aforementioned problems.

An object of the present invention is to provide a heat shrinkable sleeve for sealing junctions of the communication cable and a reinforcement for improving the functions of a sleeve. More particularly, an object of the invention is to provide a heat shrinkable sleeve and a reinforcement thereof, wherein, by cross-linking polymers of outer layer having high m.p., fabric composite, polymers of inner layer having high m.p. , and a polymer layer having low m.p., the inner polymer of high m.p. does not flow during heat-recovery and remains to be bound to the fabric, therefore when it is applied to a heat shrinkable sleeve of air injection type, the sleeve becomes more resistant to the inner air pressure and the outside air, and bursting during heat recovery can be prevented. A further object of the invention is to provide a heat shrinkable sleeve and a reinforcement thereof, wherein, by lowering the total thickness of the reinforcement attached to the heat shrinkable sleeve to one-third of the thickness of conventional products, the time for heat-recovery or contraction can be shortened remarkably.

Brief Description of Drawings Figure 1 is a cross section of a reinforcement for a heat shrinkable sleeve of the present invention,

Figure 2 is a cross section of a heat shrinkable sleeve of the present invention,

Figure 3 is a cross section of a heat shrinkable sleeve when it is applied to communication cable and is subjected to heat contraction,

Figure 4 is a cross section of a conventional reinforcement for a heat shrinkable sleeve,

Figure 5 is a cross section of a conventional heat shrinkable sleeve.

Best Mode for Carrying out the Invention

In accomplishing the above objects, a reinforcement for a heat shrinkable sleeve of the present invention is characterized in that a polymer of low melting point (3) , an oil-based or aqueous emulsion adhesive (4), a metal layer (5) and an emulsion co-polymer primer (6) are laminated successively to improve the function of the sleeve in sealing junctions of communication cable by heat contraction. In the present invention, the polymer of low m.p. (3) means

a thermoplastic polymer having a melting point of below 200^°C and an adhesiveness with a fabric.

Said oil-based or aqueous emulsion adhesive (4) includes all adhesives of emulsion type used for adhering films. Urethane adhesive is preferable. The thickness of the oil-based or aqueous emulsion adhesive (4) is desirably 0.5 to 1 μm.

The metal layer (5) improves the pressure retaining ability and the creep performance of the heat shrinkable sleeve and prevents the permeation of other substances, and is desirable to have a tensile strength of more than 10 MPa at 100 °C . Particularly, aluminum is preferably used.

Said emulsion co-polymer primer (6) includes all primer materials of emulsion type which are used in the field of film coating to combine layers which are not by themselves adhesive to each other. Examples for such primer include a primer which consists principally of ethylene-acrylic acid co-polymer, propylene-acrylic acid co-polymer and butylene-acrylic acid co-polymer being dispersed in water. The emulsion co-polymer primer (6) is desirably coated with a coating of a thickness of 0.5 to lμm.

The heat shrinkable sleeve of the present invention is a heat shrinkable sleeve for adhering to junctions of the communication cable by heat shrinkage, characterized in that the polymer of high melting point (1), fabric (2), the polymer of high m.p. (la), polymer of low m.p. (3), oil-based or aqueous emulsion adhesive

(4), metal (5), emulsion co-polymer primer (6) and low m.p., adhesive (7) are successively laminated in turn.

The polymer of high m.p. (1) of the present invention signifies a polymeric substance having a melting point of over

200°C, for instance ethylene/vinylacetate co-polymer, ethylene/ethyleneacrylate co-polymer, LLDPE, LDPE, MDPE, HDPE, polypropylene, polyester and polyamide can be used.

The fabric (2) of the present invention indicates a fabric shrinkable by heating, and any conventional fabrics used for heat shrinkable sleeves can be employed without restriction. To illustrate, a heat shrinkable fabric woven from glass fiber such as warp and HDPE such as weft may be used.

Said polymer of high m.p. (1), fabric (2), polymer of high m.p. (la) and polymer of low m.p. (3) are desirably to be cross-linked. All conventional methods for polymer cross-linking employed in the pertinent field may be adopted, particularly the radiation cross-linking method is preferred.

The present invention will be explained in the following, particularly with reference to the drawings attached.

Figure 1 is a cross-section of the reinforcement for the heat shrinkable sleeve of the present invention, and Figure 2 is a cross-section showing the heat shrinkable sleeve with the reinforcement shown in Figure 1. As indicated in the figures, the reinforcement for the heat shrinkable sleeve of the present invention is prepared by coating the polymer of low m.p. (3) film with an amount of 1 to 3 g/m² (thickness : 0.5 to 1 μm) of the oil-based or aqueous emulsion adhesive (4) to laminate the metal (5) layer and by coating the other surface of the metal (5) layer with an amount of 1 to 3 g/m² (thickness : 0.5 to 1 μm) of the emulsion co-polymer primer (6) .

In addition, in the reinforcement for the heat shrinkable sleeve of the present invention, the polymer of high m.p. (1) is coated on the outer side of the fabric (2) by melt coating and, then the polymer of high m.p. (la) is coated by melt coating on the inner side of the fabric (2) to produce the fabric composite.

Apart from this, the oil-based or aqueous emulsion adhesive (4) is coated on the surface of the polymer of low m.p. (3) at the amount of 1 to 3 g/m² (thickness: 0.5 to 1 μm) to laminate the metal

(5) layer, on which the emulsion co-polymer primer (6) is coated at the amount of 1 to 3 g/m² (thickness : 0.5 to 1 μm) and the surface thereof is coated with the adhesive (7), to complete the reinforcement. The polymer of low m.p. (3) in the reinforcement for the heat shrinkable sleeve thus prepared is then adhered to the polymer of high m.p. (la) , and the reinforcement is subsequently coated with the adhesive layer (7) to complete the product.

In particular, a conventional heat shrinkable sleeve is disadvantageous in that in order to adhere the polyamide adhesive to the EAA film surface (10), the EAA film surface (10) should

be treated with hot air of 100 to 130^°C by a high frequency corona treatment of 20,000 to 25,000V. However, the heat shrinkable sleeve of the present invention employing the emulsion co-polymer primer (6) coated on the surface of the aluminum layer (5) has excellent adhesiveness without any treatment or modification being applied to the polyamide adhesive (7) and can be used without aging.

Table 1 below shows the result of a test on physical properties of the reinforcement for the heat shrinkable sleeve of the present invention.

Table 1

In the above test for physical properties, five samples were taken to give the mean value of each property, which was obtained to determine the adhesive force between the fabric composite and the reinforcement.

Table 2 shows the result of the test on the contraction time and contraction condition with respect to the entire structural thickness of the reinforcement for said heat shrinkable sleeve, when heated.

Table 2

The data for the above test were obtained by attaching the reinforcement for the heat shrinkable sleeve of the present invention to a heat shrinkable sleeve and subsequently treating it by a torch method conventionally utilized in communication constructions. The changes in the thickness of the reinforcement result from the changes in thickness of the film adhered to the metal layer.

As a result, it is understood that the thicker the reinforcement attached to the heat shrinkable tube is, the longer the processing time it takes, and the appearance becomes irregular after processing.

Table 3 below summarizes the comparison of the heat shrinkable sleeve of the present invention with a conventional heat shrinkable sleeve, wherein the sleeves and their effects clearly distinguished.

Table 3

Adhesion of Adhesion to the surface of Adhesion to a co-extruded film polyamide the aqueous emulsion primer of LLDPE and polymeric EAA or to layer having a thickness of a film of the same prepared by

0.1 to 0.005 μm separate processes, having a

(adhesive force - no thickness of 30~40 μm exfoliation) (adhesive force - 700g/15mm)

Torch work No bursting of the sleeve on Bursting of the sleeve on heating heating

The present invention is not restricted to the above examples, and variations are allowed within the technical scope of the present invention.

Industrial Applicability

As set forth herein above, the reinforcement for the heat shrinkable sleeve of the present invention has an overall thickness of a mere 30% of the thickness of conventional products. Thus, its effect on sealing up the joints of the communication cable by heat contraction is excellent. The adhesive force between the sheet layers is high and exfoliation of the layers does not occur even after torch treatment. Simplification of the process can be accomplished, and the production cost is lowered. Particularly, the time for contraction on processing is remarkably shortened.

Claims

What is claimed is:

1. A reinforcement for a heat shrinkable sleeve for sealing joints of communication cable, characterized in that a polymer of low melting point, an oil-based or aqueous emulsion adhesive, a metal layer and an emulsion co-polymer primer are laminated successively.

2. The reinforcement of claim 1, wherein said oil-based or aqueous emulsion adhesive is coated at a thickness of 0.5 to lμm.

3. The reinforcement of claim 1, wherein said oil-based or aqueous emulsion adhesive is urethane.

4. The reinforcement of claim 1, wherein said emulsion co-polymer primer is coated at a thickness of 0.5 to 1 μm.

5. A reinforcement for a heat shrinkable sleeve, characterized in that a polymer of low melting point, and an oil-based or aqueous emulsion adhesive are laminated, and on the surface of said oil-based or aqueous emulsion adhesive, a metal layer is deposited, and then on the surface of said metal layer, an emulsion co-polymer primer is laminated.

6. The reinforcement of any one of claims 1 to 5, wherein said metal layer comprises aluminum.

7. A heat shrinkable sleeve for sealing joints of communication cable, characterized in that a first polymer of high m.p., a fabric, a second polymer of high m.p., a polymer of low m.p., an oil-based or aqueous emulsion adhesive, a metal layer, an emulsion co-polymer primer and an adhesive of low m.p. are successively laminated.

8. The heat shrinkable sleeve according to claim 7, wherein said first polymer of high m.p., fabric, second polymer of high m.p. and polymer of low m.p. are cross-linked.

9. The heat shrinkable sleeve according to claim 7 or claim 8, wherein said metal layer comprises aluminum.