Title of Invention

A METHOD FOR PREPARING A SLEEVE FOR USE IN SEALING THE EXTERIOR OF JUNCTURE OF COMMUNICATION CABLES

Abstract

Conventional sleeves have been found to suffer from a number of drawbacks, such as poor productivity and consequent higher cost. Further, heat shrinkability of the sleeves is modulated with the temperatures in the summer and winter seasons, seriously affecting the communication cable works, which render the sleeves poor in appearance after work because of their uneven surface. The present invention provides a method of preparing said sleeve to overcome the above drawbacks which comprises extruding a mixture of a polymer and an appropriate amount of carbon black to a sheet with a predetermined thickness and ß-crosslinking by radiation of 4-13 megarads to form a polymeric sheet (2) ; elongating the polymer sheet 7-10 folds in the width direction, and bonding said sheet (2) on at least one surface of a texture made of polyester alone or in combination with glass fiber through a polymeric adhesive (3) and subjected to thermal extrusion or-thermal fusion in known manner to give said sheet a high bursting strength.

Full Text

The present invention relates to a method of preparing a sleeve for use in sealing the exterior of juncture of communication cables. This invention also deals with preparation of heat-shrinkable sleeve used to seal the exterior of the juncture of the communication cables Description of the Prior Art When communication cables are joined to each other, a sleeve is usually used to seal up the juncture. For this seal, the heat shrinkability of the sleeve is utilized : when heat is applied, it is shrunk so that it tightly seals the exterior of the joined part. A sleeve in current use is typically composed of two sheets and a synthetic fibre-textured web therebetween. After the sleeve is applied to a join of two communication cables, it is shrunk by heating, so as to tightly cover the exterior of the join. Korean Patent Publication No 90-6685, entitled "Dimensionally restorable product and manufacturing method therefor", discloses a sleeve structure comprising between two sheets a fibre-textured web which is contractionally restored. 1A According to the method, a polymer, such as high density polyethylene or medium density polyethylene, alone or in combination, is melted. The melted polymer is extruded into a fiber with a diameter of 1-3 m/m, which is then subjected to rove slubbing crosslinking, followed by elongation to 5-7 folds, to give a heat shrinkable fibre. The crosslinked heat shrinkable fibres and glass fibres are cross weaved to the web. Since the web itself is contractionally restored by heat, the sleeve comprising the web between two sheets is shrunk to seal a juncture of cables. This product and method is economically unfavorable because the apparatus for rove slubbing crosslinking is very expensive. In addition, because the sheets are contracted together with the textured web, the resulting surface is rugged. Further, it takes a long time for the sleeve to contract, In Korean Pat. Publication No. 93-10051, entitled "Heat-shrinkable sleeve for juncture of cables or pipes", a sleeve comprises a texture made of polyamide, polypropylene or polyester between two heat-shrinkable sheets which are chemically crosslinked and elongated in one direction and whose external surfaces are applied with polymeric adhesives. Upon heating, the sleeve is shrunk by the contractional restoration of the heat-shrinkable sheets. The two types of sleeves mentioned above are, however, 2 poor in productivity. For example, they are both_produced at a yield of 1-5 m/min. Therefore, the poor productivity increases their cost. In addition, the sleeves are not contracted without the transfer of the external heat into the interior acting materials (e.g. the heat-shrinkable web in the patent 90-6685 and the heat-shrinkable sheet in the paten 93-3 0051). Since the wiring works of communication cable are mostly carried out on the outside, the heat shrinkability of the sleeves is modulated with the temperatures in the summer season and the winter season, seriously affecting the communication cable works. Furthermore, the sleeves are poor in appearance after work because of their rugged surface. SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to overcome the above problems encountered in prior arts and to provide a sleeve for the juncture of communication cables, whose surface is maintained smoothly even after wiring work. It is another object of the present invention to provide a method for preparing such a sleeve, by which the productivity of the sleeve can be remarkably improved and therefore, the cost thereof is reduced. 3 " The foregoing objects are achieved by the present invention relating to a method for preparing a sleeve for use in sealing the exterior of the juncture of communication cables, comprising the steps of : extruding a mixture of a polymer and an appropriate amount of carbon black to a sheet with a predetermined thickness and ß-crosslinking the sheet by radiation of 4.13 megarads to form a polymeric sheet; elongating the polymer sheet 7-10 folds in the width direction ; and bonding said sheet on at least one surface of a texture made of polyester alone or in combination with glass fiber through a polymeric adhesive and subjected to thermal extrusion or thermal fusion in known manner to give said sheet a high bursting strength. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS. " 3A The above and other aspects of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which: Fig. 1 is a partial cross sectional view schematically showing a heat-shrinkable sleeve according to an embodiment of the present invention; and Figs. 2 through 5 each are partial cross sectional views showing sleeves for respective uses according to other embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described according to processes. First step A polymer with 3-4 % by weight of carbon black was mixed in an extruder and extruded into a roll 2-3 mm thick which was, then, cross-linked by radiation at 4-13 megarads. Second step The radiation-crosslinked roll was elongated 7-10 folds 4 an the width direction, to gave a polymer sheet. Third step The polymer sheet which was radiation cross linked and elongated was bonded through a polymeric adhesive to one surface of a polyester texture or glass fiber-remforced texture. To this end, the polymer sheet and the polyester texture with the polymeric adhesive therebetween were subjected to thermal extrusion. The resulting complex was improved in bursting strength. Fourth step As in the Third step, the radiation-crosslinked and elongated polymer sheet was bonded through another polymeric adhesive to the other surface of the polyester texture or glass fiber-reinforced texture by the thermal fusion, so as to give a sleeve in which the polyester texture was sandwiched between two upper and lower polymer sheets which play a role of heat-shrinkable layers. Depending on its use, the sleeve of the present invention is produced or may be modified or additionally supplemented. For example, the integrated sheets with the texture of the 5 Fourth step may be joined with an aluminum thin film or further with a heat seal layer, to yield sleeves suitable for the joint of connecting cables. The application of the preferred embodiments of the present invention is best understood with reference to the accompanying drawings, wherein like reference numerals are used for like and corresponding parts, respectively. Fig. 1 is a schematic cross section showing a heat-shrinkable sleeve 1 for use in the junction of communication cables. Two heat-shrinkable sheets 2 each are integrated through a polymeric adhesive 3 onto the opposite side of a cloth 4, the lower sheet 2 being covered with a heat seal layer 6, A sleeve 1 suitable to shield external electronic waves is illustrated in Fig. 2. This sleeve is structured in such a way that two heat-shrinkable sheets 2 are attached through polymeric adhesives 3 on the opposite sides of a cloth 4, respectively, the lower sheet 2 being added sequentially with an aluminum thin film 5 and a heat seal layer 6. Fig. 3 shows a sleeve 1 for use in rupture prevention and shielding electronic waves, which is obtained by integrating a heat-shrinkable sheet 2, a texture 4 and an aluminum thin film 5, in sequence, through the medium of a polymeric adhesive 3 and adhering a heat seal layer on the lowest aluminum thin film 5. 6 Turning now to Figs. 4 and 5, two heat-shrinkable sleeves are shown which are suitable for preventing rupture and for joining cables, respectively. The sheet used in the sleeve for use in the junction of communication cables of the present invention is compared with conventional sleeves used in the above-illustrated prior arts in physical aspects and the results are given as shown in the following table 1. TABLE 1 The Present Invention Korean Pat. Pub.NO.90-6685 Korean Pat. Pub.NO.93/10051 Crosslinking Radiation(ß) Radiation Chemical heat-shrinkable Upper & Lower Layer Medium Layer Medium Layer Elongation Direction Width of Sheet Length of Fibre Width of Sheet Elongation Ratio 700-1,000% 800% 500% The heat-shrinkable sleeve according to the present invention was tested for physical properties. The specimen was obtained from the double-faced heat sheet of Fig. 1. The heat-shrinkable sheet 1 was radiation ß-crosslinked and elongated at a ratio of 800%, Polyester fibres were weaved at a density of weft 46 lines and warp 8 lines per inch to the 7 texture 4 which was of high thermal resistance and did not inhibit the heat contraction. The texture 4 was then interposed between the two heat shrinkable sheets and bonded with each other through the polymeric adhesives 3. Table 2 shows the results of the test. TABLE 2 Test Items 1 units Test Conditions Results Test Standards Bursting Strength (pre-contraction) Compressing speed kg/mm at rupture 100mm/min 700 ASTM JIS Tensile Strength (pre-contraction) Tensile Strength kgf/mm2 100 mm/min MD 1.7 CD 4.0 KSM Interlayer Peeling Strength Peeling Speed kgf/mm2 100 mm/min > 40 KSM Shrrikability % 200°C 1kg load > 80 Crosslinking Degree % Rad.(B) 30sec > 50 Shrinking Time min 200°C 6 As apparent from the above tables, the sleeves prepared according to the present invention are far superior in shrinkability at the same temperature to the conventional products which are contracted by the action of the medium layers. In addition, the surfaces of the sleeves of the present invention are smoothly maintained. Further, the heat-shrinkable sheet can be produced at an amount of 30-50 m per 8 min by the method of the present invention. Therefore, the sleeves comprising the heat-shrinkable sheet are very advantageous in productivity. Consequently, the sleeves according to the present invention are of high performance and economically very favorable. The process of invention has been described in an illustrative manner, and it is to be understood the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. 9 WE CLAIM : 1. A method for preparing a sleeve for use in sealing the exterior of the juncture of communication cables, comprising the steps of : extruding a mixture of a polymer and an appropriate amount of carbon black to a sheet with a predetermined thickness and ß-crosslinking the sheet by radiation of 4.13 megarads to form a polymeric sheet (2) ; elongating the polymer sheet 7-10 folds in the width direction ; and bonding said sheet (2) on at least one surface of a texture made of polyester alone or in combination with glass fiber through a polymeric adhesive (3) and subjected to thermal extrusion or thermal fusion in known manner to give said sheet a high bursting strength. 2. A method as claimed in claim 1, comprising the step of coating a heat seal layer (6) on one sheet (2) when said sheet is bonded on each of the opposite surfaces of said texture or directly coating a heat seal layer (6) on said texture (4) when said sheet is bonded on only one surface of the texture. 3. A method as claimed in claim 1, comprising the steps of bonding an aluminum thin film (5) on one sheet when said sheet is bonded on each of the opposite surfaces of the texture and coating a heat seal layer on said aluminum thin film or directly bonding an aluminum thin film on said texture when said sheet is bonded on only one surface of the texture and coating a heat seal layer on said aluminum thin film (5). 10 4 A method as claimed in any one of Claims 1 to 4, wherein the radiated and ß-crosslinked sheets are elongated so that they are shrunk with heat, allowing said sleeve to be deformed to seal the exterior of the juncture of the communication cables. 5 A method for preparing a sleeve for use in sealing the exterior of the juncture of communication cables, substantially as hereinbefore described particularly with reference to the accompanying drawings DATED THIS 12TH DAY OF NOVEMBER, 1997 11 Conventional sleeves have been found to suffer from a number of drawbacks, such as poor productivity and consequent higher cost. Further, heat shrinkability of the sleeves is modulated with the temperatures in the summer and winter seasons, seriously affecting the communication cable works, which render the sleeves poor in appearance after work because of their uneven surface. The present invention provides a method of preparing said sleeve to overcome the above drawbacks which comprises extruding a mixture of a polymer and an appropriate amount of carbon black to a sheet with a predetermined thickness and ß-crosslinking by radiation of 4-13 megarads to form a polymeric sheet (2) ; elongating the polymer sheet 7-10 folds in the width direction, and bonding said sheet (2) on at least one surface of a texture made of polyester alone or in combination with glass fiber through a polymeric adhesive (3) and subjected to thermal extrusion or-thermal fusion in known manner to give said sheet a high bursting strength.

Documents:

02131-cal-1997-abstract.pdf

02131-cal-1997-claims.pdf

02131-cal-1997-correspondence.pdf

02131-cal-1997-description(complete).pdf

02131-cal-1997-drawings.pdf

02131-cal-1997-form-1.pdf

02131-cal-1997-form-13.pdf

02131-cal-1997-form-2.pdf

02131-cal-1997-form-3.pdf

02131-cal-1997-form-5.pdf

02131-cal-1997-pa.pdf

02131-cal-1997-priority document other.pdf

2131-CAL-1997-CORRESPONDENCE 1.1.pdf

2131-CAL-1997-FORM 27.pdf

2131-CAL-1997-PA.pdf