CA1177620A - Heat recoverable articles - Google Patents
Heat recoverable articlesInfo
- Publication number
- CA1177620A CA1177620A CA000382616A CA382616A CA1177620A CA 1177620 A CA1177620 A CA 1177620A CA 000382616 A CA000382616 A CA 000382616A CA 382616 A CA382616 A CA 382616A CA 1177620 A CA1177620 A CA 1177620A
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- Prior art keywords
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- recoverable
- heat
- article
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- Prior art date
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
Abstract
A B S T R A C T
HEAT RECOVERABLE ARTICLES
Production of heat-recoverable electrical insulation articles by (a) deforming a body of polymeric material to render it heat recoverable, (b) bonding parts of the body to itself or another substrate to form a heat recoverable article and (c) cross-linking the bond-forming parts of the deformed body and the substrate to each other, together with any additional bonding material which may be present. This provides a highly efficient way of producing durably bonded heat recoverable articles.
HEAT RECOVERABLE ARTICLES
Production of heat-recoverable electrical insulation articles by (a) deforming a body of polymeric material to render it heat recoverable, (b) bonding parts of the body to itself or another substrate to form a heat recoverable article and (c) cross-linking the bond-forming parts of the deformed body and the substrate to each other, together with any additional bonding material which may be present. This provides a highly efficient way of producing durably bonded heat recoverable articles.
Description
l 177620
- 2 - RK121 ~he present invention concerns heat-recoverable polymeric articles, especially hollow articles, the dimensional configuration of which may be made to change by subjecting ~. to heat, and in particular, a process for the manufacture of such articles.
- Hitherto, hollow heat-recoverable articles have generally been produced by forming a polymer into the desired heat : stable configuration, simultaneously or subsequently cross-linking the polymer in its heat stable configuration, heating the article to a temperature above the crystalline melting point or softening point of the cross-linked poly-mer, deforming the article and cooling-the article whilst in the deformed state so.that the deformed configuration is retained. In use, since-the deformed state of the article is heat unstable, application ~f heat will cause the article to revert or tend to revert to its original heat stable -configuration.
When hollow articles are of such configuration that they cannot be produced directly by extrusion, for example electrical boots, udders (a term employed herein in a general sense to cover any hollow heat shrinkable article comprising at least three outlets employed in the termin-ation of electrical cables and also in cable ~breakouts") or end-caps (a hollow tubular article having a smoothly taper-ing sealed end) for electric cables, then hitherto such articles have generally been formed into the desired heat stable configuration on an item-by-item basis by moulding, e.g. by injection, compression or transfer moulding tech-niques.
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`\ 1177~20 Quite apart from the added expense of such techniques, for com-plicated shapes, e.g. udders, distortion may be necessary to remove the articles from the moulding pin or core requiring that the articles be resiliently deformable. Furthermore, in order to render such articles heat-recoverable, such moulded parts have in general hitherto been heated and deformed into a heat unstable configuration on an item-by-item basis.
It is an object of the present invention to provide a process of producing heat-recoverable articles which obviates or reduces the above-mentioned difficulties.
Accordingly, the present invention provides a process for the production of a heat-recoverable article which comprises (a) providing a first body of fusion bondable polymeric material having a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20~ and deforming the body at a temperature below the softening point of the material to produce a heat-recoverable polymeric material having a thickness of at least 0.1 millimetres, (b) forming a bond between one or more parts of the first body and a second body of fusion bondable polymeric material to produce the configuration of at least one seam bonded heat-recoverable article, and (c) cross-linking the bond between the deformed first body and the second body.
Another aspect of the present invention provides a process for the production of a heat-recoverable article which comprises (a) providing a first body of fusion bondable polymeric material having a gel content as measured by test method ANSI/ASTM
D2765-68 of less than 20% and deforming the body at a temperature ., ~, . , , ' below the softening point of the material to render the material heat-recoverable, (b) forming a bond between one or more parts of the first body and a second body of fusion bondable polymeric material to produce the configuration of at least one seam bonded hollow tubular article heat recoverable substantially only in the radial sense, and (c) cross-linking the bond between the deformed first body and the second body.
These two aspects of the invention may be combined with each other, and it is to be understood that references to "seam bonded" articles mean articles wherein two parts are seamed together by bonding in a manner somewhat analogous to sewing, and are specifically intended to exclude laminates and coextrusions in which a major surface of one layer is substantially wholly bonded to a major surface of another layer. Articles having bonds of relatively large surface area are not, however, excluded provided that the article is clearly seamed together, for example as viewed from inside a hollow article which may be externally surrounded by a large bonded area, as in the case of two sheets bonded together to form a plurality of hollow articles with large bond areas between adjacent articles.
The invention also provides a seam-bonded heat-recoverable article comprising a first body of polymeric material which has been deformed at a temperature below the softening point of the material to render the material heat-recoverable, the deformed material having a thickness of at least 0.1 millimetres, one or more parts of the first body having been bonded to a second body of polymeric material with the first and second bodies each having , .
l 17~20 a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20~ and the bond between the first body and the second body being cross-linked.
Finally, the invention provides a seam-bonded hollow tubular heat-recoverable article comprising a first body of polymeric material which has been deformed at a temperature below the softening point of the material to render the material heat-recoverable, one or more parts of the first body having been bonded to a second body of polymeric material with the first and second bodies each having a gel content as measured by test method ANSI/AST~ D2765-68 of less than 20% in such arrangement that the article is heat-recoverable substantially only in the radial sense, the bond between the first body and the second body being cross-linked.
The bonded region is preferably elongate and of narrow width, and may define the outline of the said article. The bonding of the first and second bodies may be achieved via further bonding material in addition to the first and second bodies, which further material is cross-linked with that of the bodies.
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Preferably, the bonding is effected by fusion of the said polymeric material, preferably in direct contact of the first body with the second body.
By tbe expression "fusion bonding" as employed herein is meant a process wherein the material in the parts to be bonded together is caused to flow to form the bond, e.g.
welding by heat, solvent or ultrasonic or radio frequency energy,preferably with the application of pressure, either to form a bridge from the materials of the respective bodies or to fuse the parts with further material which is cross-linked with the material of the said parts by the cross-linking step of the process.
, The bonding (preferably fusion) step may be effected either before or after the deformation step, preferably however after the deformation step. Bonding before deformation _produces the configuration of the article before it is rendered heat recoverable, and care must be taken not to break the bond during the subsequent deformation. It will be understood that references to "hollow" articles include articles in a flat state which can be opened to reveal their hollow interior, and references to "tubular" articles include multi-legged, tapering, or irregular articles of a generally elongate hollow form, and these terms may refer to articles only part of which is hollow or tubular as afore-said. -The process is applicable to both crystalline and non-crystalline polymers, the softening point (by which is meant the crystalline melting point for crystalline polymers) being selected accordingly as the maximum deform-ation temperature.
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I 177~20 By "fusion bondable" polymeric materials and substrates as employed herein is meant not cross-linked, or cross-linked only to the extent - that the material can still be readily bonded to itself or to another polymeric component by fusing. In general, the level of cross-linking in the polymeric material expressed in terms of gel content (ANSI/ASTM D2765-68) is less than 20%, particularly less than 5%. When cross-linking in accordance with the process, preferably gel contents of at least 40%, e.g. at least 50%, particularly at least 65% are attained.
Preferably, the cross-linking cross-links substantially all of the polymeric material in addition to the bond-forming material. Cross-linking is preferably performed after the deforming and bonding steps, but could be effected after the deformation step and during the bonding step. Of particular interest is a process wherein the second body to which part of the first body is bonded is another part of the first body, in which case the first body may be in the form of a tube expanded radially by the deformation step, or may be a web which is expanded longitudinally by the deformation step. Also of interest is a process wherein the second body to which part of the first body is bonded is initially separate from the first body, in which case both the first body and the second body may be in the form of a web and both may be longitudinally expanded by the deformation step.
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1 177~0 In a further preferred process the deforming step locally deforms at least one substantial region of the ~irst body, the second body is locally deformed in at least one substan-tial region at a temperature below the softening point of the material to render it heat recoverable, and the first body is bonded to the second body with their respective deformed regions co-operating with each other to produce hollow said article(s). Vacuum forming of a web of poly-meric material is the preferred method of performing the localised deformation.
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Hollow heat-recoverable articles produced by the process of the invention also form part- of the present invention.
One advantage of the artic~es of the invention is that they are substantially recoverable, e g. to at least 50% of their maximum extent, at a temperature below the softening point of the polymeric material from which they have been pro-duced, e.g. in the range 60C to the crystalline melting point or softening point.
The process is particularly useful in the manufacture of heat-recoverable boots, transitions, udders and end-caps for electrical applications, e.g. electrical cables, the use of such products being extensive and well reported in the literature e.g. Proc. IEE 1970j, 117(7), 1365 - 1372. Such products ~ay, for example, be produced in accordance with the process of the invention by welding together at least two super-imposed flaps of a single folded pre-stretched and flattened polymeric tube. Such materials to be fused together may be disposed in accordance with any of the appropriate jointing techniques, e.g. to provide a lap joint or a butt joint. . The polymeric material may be deformed in any direction which will provide the desired direction of recovery in the final product which, especially in the case of boots, udders and end-caps, is preferably substantially only radially inward shrinkage in relation to the substrate to which they are applied, that is in the substantial absence of shrinkage longitudinally (e.g. less than 10%
longitudinal shrinkage when fully radially recovered) in relation to said substrate. Such shrinkage may be achieved by mono-axial deformation of the polymeric material.
Another embodiment of the invention involves bonding of a single stretched sheet to itself t~o form a circular or spiral wrapped heat recoverable tube.
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The process of the present invention also lends itself to ~the production of such articles having parts thereof of different polymeric composition so that the properties of the article such as flexibility or electrical conductivity can be varied within a single article. For example, one part of an article such as the multiple legs of a cable udder may be produced as a single component by blow mould-ing, e.g. from an extruded tube of one material, to the desired configuration and another part, e.g. the cable side of the udder, produced in tubular form by extrusion of a different material with subse~uent expansion. When blow moulding techniques are employed, it is found that this may provide the necessary degree of deformation to impart heat-recoverability to the final article. The two parts are subsequently bonded together in the desired configuration.
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1 177~20 In such manner, the legs of the udder may, e.g. have semi-conducting electrical characteristics and the cable inlet part ` insulating characteristics.
In the production of heat-recoverable articles in accordance with the invention, it is not always necessary to deform the whole of the polymeric starting material. For example, when employing polymeric material in the form of a web, it is possible locally to deform specific areas of the web, for example by pressing or by vacuum fo~ming at an elevated temperature below the crystalline melting point or softening point of the material with subsequent cooling to maintain the deformed condition of the deformed components so formed. Such deformed components may then be fused to other components, for example to a similar component formed in a separate web, to produce the configuration of the desired product.
Hollow heat recoverable articles produced in accordance with the process of the invention may advantageously be coated internally with an adhesive or other sealant, as described and claimed in Canadian Application 382,617 filed on even date herewith, e.g. an adhesive such as described in U.K. Patent No. 1,116,878.
The application of the sealant may be effected before, during or after the process of the invention by appropriate choice of adhesive or sealant and process conditions. For example, a hot-melt adhesive may be applied to the polymeric material before the fusion step and thereafter the parts to be fused together locally heated and pressed together to locally displace the adhesive in the regions to be fused together.
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.: ; ' ! 1 17 7~20 Alternatively, the sealant may be applied after the bonding step and, where the process involves producing a plurality ; of separable articles, the sealant is preferably applied before separation of the articles.
If self-adhesion of sealant-coated contacting parts is a problem, then such parts may be separated by a non-adherable material such as release paper.
Any fusion bondable polymeric material which can be cross-linked by the cross-linking step(c) and to which the property of ` 10 dimensional recoverability may be imparted such as those disclosed in U.K. Specification No. 990,235 may be used to form the articles.
Polymers which may be used as the polymeric material include polyolefins such as polyethylene and polypropylene, and ethylene copolymers, for example with propylene, butene, hexene, octene, vinyl acetate or other vinyl esters or methyl or ethyl acrylate, polyamides, polyurethanes, polyvinyl chloride, polyvinylidine ` fluoride, or other fluorinated polymers or copolymers, e.g. Tefzel (trade mark - commercially available from Dupont), elastomeric materials such as those disclosed in UK specification No.
1,010,064 and blends such as those disclosed in UK specification Nos. 1,284,082 and 1,294,665, and compositions such as those disclosed in our U.S. Patent No. 4275180. The polymeric materials can be tailored to suit the intended use by the addition of fillers, e.g. semi-conducting fillers or anti-tracking agents, flame retardants, plasticisers, pigments, stabilisers and lubricants, or where necessary, e.g. where the polymeric material is sub-stantially non-crystalline, a hold-out agent such as a thermo-plastic polymer, e.g. polyethylene, may be included in the material.
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, The polymeric material may be cross-linked ~y irradiation, for example, by means of an electron beam or by gamma radiation or it may be chemically cross-linked. Whichever cross-linking process is used, it may be advantageous to incorporate one or more co-curing agents for example poly-unsaturated monomers such as triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetra-methacrylate, allyl methacrylate and vinyl methacrylate.
One method of chemical cross-linking that may be used in the process according to the invention involves grafting an unsaturated hydrolysable silane on the polymer and sub-jecting the article to moisture during a curing stage, for example, as described in UK Patent specification Nos.
1,286,460 and 1,357,549.
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Any of the techniques conventionally employed for fusing together polymeric materials may be employed in the process of the present invention, e.g. radio frequency, ultrasonic or hot bar welding, and pressure may additionally be applied to ensure a satisfactory bond. Furthermore, it is possible to make use of the fusing operation to separate the articles one from another or from surplus polymeric starting mater-ial. For example, it is possible to use a heating/cutting device such as a hot wire cutter or a laser beam, if nec-essary in association with pressure applying means such as a roller. -.
If the seam bonded heat-recoverable article is produced with an undesired protruding external weld, then this may be avoided by turning the article inside-out.
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As hereinbefore described, the process is particularly appropriate in the production of hollow heat-recoverable articles for use in the electrical field, e.g. boots, udders and end-caps. In general, such products are char-acterised by a wall thickness prior to heat-recovery thereof of preferably from 0.1 to 5 mm, especially from 0.5 ~o 3 mm e.g. 1 to 3 mm.
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Specific embodiments of the invention will now be described by way of example with specific reference to Figures 1 to 16 of the accompanying drawings wherein:
Figure 1 is a schematic top view of -an assembly of sep-arable heat-recoverable udders for the termination of an electrical cable, Figure 2 is a diagramatic isometric view of an udder - produced from the assembly shown in Figure 1, Figure 3 is a schematic top view of an assembly of sep-arable heat-recoverable boots employed for sealing an electrical cable at the termination thereof, Figure 4 is a diagramatic isometric view of a boot produced from the assembly of Figure 3, Figure 5 ~ is a schematic top view of an alternative assembly of separable heat-recoverable boots from which the boot of Figure 4 may be produced, . . -1 177~0 Figure 6 is a schematic top view of an assembly of sep-a-able heat-recoverable end-caps employed for sealing the ends of electrical cables, Figure 7 is an isometric view of an end cap produced from the assembly of Figure 6, Figure 8 is a schematic top view of an assembly of sep-arable heat-recoverable 4-legged udders, Figure 9 is an isometric view of a boot produced from the assembly of Figure 8, Figure 10 is an isometric top view of an alternative assembly of separable heat-recoverable 4-legged 1 . udders, . Figure 11 is an isometric view of an udder produced from the ;: . assembly on Figure 10.
Figure 12 is a schematic top view of an assembly of sep-arable heat-recoverable boots, Figure 13 is an isometric view of a boot produced from the assembly of Figure 12.
Figure 1~ is a schematic isometric view of a polymeric web of material that has been locally deformed to produce boots analogous to that shown in Figure 13, .
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1 177~20 Figure 15 is an isometric view of a right angle electrical boot produced in analogous manner to that depicted in Figure 14, .
~ and Figure 16 is an isometric view of a 2-legged udder produced ~` in analogous manner to that depicted in Figure 14.
In the embodiment shown in Figures 1 and 2, a pair of polyethylene sheets 1a and lb which have been expanded longitudinally to 3 times their original length at a tem-perture of 100C and cooled whilst in the expanded con-dition, are superimposed one on the other and welded at positions 2 employing an ùltrasonic we;ding tool to produce welded seams 3. The welded shee~s are then irradiated in an electron beam at a dosage of 15 Mrads causing cross-linking of the polyethylene. After cross-linking the assembly is severed along the weld seams 3 employing a mechanical cutter to produce a plurality of heat-recoverable electrical udders 4 each having two legs 5 defined by the welds 3. The areas depicted by reference numeral 6 are discarded.
Such udders may be employed in the electrical termination of a cable comprising two primary wires by heat recovering the udder about the end of the cable, the primary wires passing through t~he legs of the udder.
In a modification (not shown) of the above embodiment the sheets are internally pré-coated with a sealant or adhesive such as a hot-melt adhesive before the welding stage. The .
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sealant or adhesive selected is one that is relatively insensitive to the subsequent radiation treatment. Furthee-more, the regions of the sheet to be welded together are locally pre-heated and pressed together by suitably located heated rollers engageable with the sheets causing the sealant or adhesive in the region to be welded to flow and be displaced immediately prior to the welding stage. The resulting product is thereafter treated in analogous manner to that described above.
.~ , In ~nalogous manner to that described in relation to the first embodiment the transitions 7 and end-caps 8 shown in Figures 3, 4 and S and Figures 6 and 7 respectively are pcoduced, hereinafter the same reference numerals being employed for analogous parts.
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It may be advantageous to arrange the welds in end caps (and in other articles) to be tearable in order to facilitate removal of the article from a substrate onto which it has been heat-shrunk in use. In such arrangements the open end of the article may be shaped to provide a tab for convenient gripping to tear off the article.
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In the embodiment illustrated in Figures 8, 9,10 and 11, two methods of producing 4-legged udders are depicted employing non-cross-linked polyethylene tubing 9 which has been radially expanded to three times its original diameter at a temperatrure of 100C and cooled in the expanded condition. In the embodiment shown in Figures 8 and 9, the tubing is welded axially thereof to produce welded seams 3 . . .
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which define the four legs of each udder, i.e. in a planar configuration, the tubing thereafter being irradiated with an electron beam as hereinbefore described and thereafter severed transversely thereof along the lines X - X.
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In the embodiment shown in Figures 10 and 11 the tubing is welded axially thereof so as to produce welded seams 3 which define each`udder in a cruciform configuration as shown in Figure 11.
In the embodiment shown in Figures 12 and 13, electrical boo~s are produced from non-cross-linked radially expanded polyethylene tubing (produced as described in the preceding embodiment), the boots being profiled by welding to produce welded seams 3 and severing along the weld seams
- Hitherto, hollow heat-recoverable articles have generally been produced by forming a polymer into the desired heat : stable configuration, simultaneously or subsequently cross-linking the polymer in its heat stable configuration, heating the article to a temperature above the crystalline melting point or softening point of the cross-linked poly-mer, deforming the article and cooling-the article whilst in the deformed state so.that the deformed configuration is retained. In use, since-the deformed state of the article is heat unstable, application ~f heat will cause the article to revert or tend to revert to its original heat stable -configuration.
When hollow articles are of such configuration that they cannot be produced directly by extrusion, for example electrical boots, udders (a term employed herein in a general sense to cover any hollow heat shrinkable article comprising at least three outlets employed in the termin-ation of electrical cables and also in cable ~breakouts") or end-caps (a hollow tubular article having a smoothly taper-ing sealed end) for electric cables, then hitherto such articles have generally been formed into the desired heat stable configuration on an item-by-item basis by moulding, e.g. by injection, compression or transfer moulding tech-niques.
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`\ 1177~20 Quite apart from the added expense of such techniques, for com-plicated shapes, e.g. udders, distortion may be necessary to remove the articles from the moulding pin or core requiring that the articles be resiliently deformable. Furthermore, in order to render such articles heat-recoverable, such moulded parts have in general hitherto been heated and deformed into a heat unstable configuration on an item-by-item basis.
It is an object of the present invention to provide a process of producing heat-recoverable articles which obviates or reduces the above-mentioned difficulties.
Accordingly, the present invention provides a process for the production of a heat-recoverable article which comprises (a) providing a first body of fusion bondable polymeric material having a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20~ and deforming the body at a temperature below the softening point of the material to produce a heat-recoverable polymeric material having a thickness of at least 0.1 millimetres, (b) forming a bond between one or more parts of the first body and a second body of fusion bondable polymeric material to produce the configuration of at least one seam bonded heat-recoverable article, and (c) cross-linking the bond between the deformed first body and the second body.
Another aspect of the present invention provides a process for the production of a heat-recoverable article which comprises (a) providing a first body of fusion bondable polymeric material having a gel content as measured by test method ANSI/ASTM
D2765-68 of less than 20% and deforming the body at a temperature ., ~, . , , ' below the softening point of the material to render the material heat-recoverable, (b) forming a bond between one or more parts of the first body and a second body of fusion bondable polymeric material to produce the configuration of at least one seam bonded hollow tubular article heat recoverable substantially only in the radial sense, and (c) cross-linking the bond between the deformed first body and the second body.
These two aspects of the invention may be combined with each other, and it is to be understood that references to "seam bonded" articles mean articles wherein two parts are seamed together by bonding in a manner somewhat analogous to sewing, and are specifically intended to exclude laminates and coextrusions in which a major surface of one layer is substantially wholly bonded to a major surface of another layer. Articles having bonds of relatively large surface area are not, however, excluded provided that the article is clearly seamed together, for example as viewed from inside a hollow article which may be externally surrounded by a large bonded area, as in the case of two sheets bonded together to form a plurality of hollow articles with large bond areas between adjacent articles.
The invention also provides a seam-bonded heat-recoverable article comprising a first body of polymeric material which has been deformed at a temperature below the softening point of the material to render the material heat-recoverable, the deformed material having a thickness of at least 0.1 millimetres, one or more parts of the first body having been bonded to a second body of polymeric material with the first and second bodies each having , .
l 17~20 a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20~ and the bond between the first body and the second body being cross-linked.
Finally, the invention provides a seam-bonded hollow tubular heat-recoverable article comprising a first body of polymeric material which has been deformed at a temperature below the softening point of the material to render the material heat-recoverable, one or more parts of the first body having been bonded to a second body of polymeric material with the first and second bodies each having a gel content as measured by test method ANSI/AST~ D2765-68 of less than 20% in such arrangement that the article is heat-recoverable substantially only in the radial sense, the bond between the first body and the second body being cross-linked.
The bonded region is preferably elongate and of narrow width, and may define the outline of the said article. The bonding of the first and second bodies may be achieved via further bonding material in addition to the first and second bodies, which further material is cross-linked with that of the bodies.
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Preferably, the bonding is effected by fusion of the said polymeric material, preferably in direct contact of the first body with the second body.
By tbe expression "fusion bonding" as employed herein is meant a process wherein the material in the parts to be bonded together is caused to flow to form the bond, e.g.
welding by heat, solvent or ultrasonic or radio frequency energy,preferably with the application of pressure, either to form a bridge from the materials of the respective bodies or to fuse the parts with further material which is cross-linked with the material of the said parts by the cross-linking step of the process.
, The bonding (preferably fusion) step may be effected either before or after the deformation step, preferably however after the deformation step. Bonding before deformation _produces the configuration of the article before it is rendered heat recoverable, and care must be taken not to break the bond during the subsequent deformation. It will be understood that references to "hollow" articles include articles in a flat state which can be opened to reveal their hollow interior, and references to "tubular" articles include multi-legged, tapering, or irregular articles of a generally elongate hollow form, and these terms may refer to articles only part of which is hollow or tubular as afore-said. -The process is applicable to both crystalline and non-crystalline polymers, the softening point (by which is meant the crystalline melting point for crystalline polymers) being selected accordingly as the maximum deform-ation temperature.
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I 177~20 By "fusion bondable" polymeric materials and substrates as employed herein is meant not cross-linked, or cross-linked only to the extent - that the material can still be readily bonded to itself or to another polymeric component by fusing. In general, the level of cross-linking in the polymeric material expressed in terms of gel content (ANSI/ASTM D2765-68) is less than 20%, particularly less than 5%. When cross-linking in accordance with the process, preferably gel contents of at least 40%, e.g. at least 50%, particularly at least 65% are attained.
Preferably, the cross-linking cross-links substantially all of the polymeric material in addition to the bond-forming material. Cross-linking is preferably performed after the deforming and bonding steps, but could be effected after the deformation step and during the bonding step. Of particular interest is a process wherein the second body to which part of the first body is bonded is another part of the first body, in which case the first body may be in the form of a tube expanded radially by the deformation step, or may be a web which is expanded longitudinally by the deformation step. Also of interest is a process wherein the second body to which part of the first body is bonded is initially separate from the first body, in which case both the first body and the second body may be in the form of a web and both may be longitudinally expanded by the deformation step.
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1 177~0 In a further preferred process the deforming step locally deforms at least one substantial region of the ~irst body, the second body is locally deformed in at least one substan-tial region at a temperature below the softening point of the material to render it heat recoverable, and the first body is bonded to the second body with their respective deformed regions co-operating with each other to produce hollow said article(s). Vacuum forming of a web of poly-meric material is the preferred method of performing the localised deformation.
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Hollow heat-recoverable articles produced by the process of the invention also form part- of the present invention.
One advantage of the artic~es of the invention is that they are substantially recoverable, e g. to at least 50% of their maximum extent, at a temperature below the softening point of the polymeric material from which they have been pro-duced, e.g. in the range 60C to the crystalline melting point or softening point.
The process is particularly useful in the manufacture of heat-recoverable boots, transitions, udders and end-caps for electrical applications, e.g. electrical cables, the use of such products being extensive and well reported in the literature e.g. Proc. IEE 1970j, 117(7), 1365 - 1372. Such products ~ay, for example, be produced in accordance with the process of the invention by welding together at least two super-imposed flaps of a single folded pre-stretched and flattened polymeric tube. Such materials to be fused together may be disposed in accordance with any of the appropriate jointing techniques, e.g. to provide a lap joint or a butt joint. . The polymeric material may be deformed in any direction which will provide the desired direction of recovery in the final product which, especially in the case of boots, udders and end-caps, is preferably substantially only radially inward shrinkage in relation to the substrate to which they are applied, that is in the substantial absence of shrinkage longitudinally (e.g. less than 10%
longitudinal shrinkage when fully radially recovered) in relation to said substrate. Such shrinkage may be achieved by mono-axial deformation of the polymeric material.
Another embodiment of the invention involves bonding of a single stretched sheet to itself t~o form a circular or spiral wrapped heat recoverable tube.
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The process of the present invention also lends itself to ~the production of such articles having parts thereof of different polymeric composition so that the properties of the article such as flexibility or electrical conductivity can be varied within a single article. For example, one part of an article such as the multiple legs of a cable udder may be produced as a single component by blow mould-ing, e.g. from an extruded tube of one material, to the desired configuration and another part, e.g. the cable side of the udder, produced in tubular form by extrusion of a different material with subse~uent expansion. When blow moulding techniques are employed, it is found that this may provide the necessary degree of deformation to impart heat-recoverability to the final article. The two parts are subsequently bonded together in the desired configuration.
,. ' ' .' .
1 177~20 In such manner, the legs of the udder may, e.g. have semi-conducting electrical characteristics and the cable inlet part ` insulating characteristics.
In the production of heat-recoverable articles in accordance with the invention, it is not always necessary to deform the whole of the polymeric starting material. For example, when employing polymeric material in the form of a web, it is possible locally to deform specific areas of the web, for example by pressing or by vacuum fo~ming at an elevated temperature below the crystalline melting point or softening point of the material with subsequent cooling to maintain the deformed condition of the deformed components so formed. Such deformed components may then be fused to other components, for example to a similar component formed in a separate web, to produce the configuration of the desired product.
Hollow heat recoverable articles produced in accordance with the process of the invention may advantageously be coated internally with an adhesive or other sealant, as described and claimed in Canadian Application 382,617 filed on even date herewith, e.g. an adhesive such as described in U.K. Patent No. 1,116,878.
The application of the sealant may be effected before, during or after the process of the invention by appropriate choice of adhesive or sealant and process conditions. For example, a hot-melt adhesive may be applied to the polymeric material before the fusion step and thereafter the parts to be fused together locally heated and pressed together to locally displace the adhesive in the regions to be fused together.
_g_ ~ .
.
.: ; ' ! 1 17 7~20 Alternatively, the sealant may be applied after the bonding step and, where the process involves producing a plurality ; of separable articles, the sealant is preferably applied before separation of the articles.
If self-adhesion of sealant-coated contacting parts is a problem, then such parts may be separated by a non-adherable material such as release paper.
Any fusion bondable polymeric material which can be cross-linked by the cross-linking step(c) and to which the property of ` 10 dimensional recoverability may be imparted such as those disclosed in U.K. Specification No. 990,235 may be used to form the articles.
Polymers which may be used as the polymeric material include polyolefins such as polyethylene and polypropylene, and ethylene copolymers, for example with propylene, butene, hexene, octene, vinyl acetate or other vinyl esters or methyl or ethyl acrylate, polyamides, polyurethanes, polyvinyl chloride, polyvinylidine ` fluoride, or other fluorinated polymers or copolymers, e.g. Tefzel (trade mark - commercially available from Dupont), elastomeric materials such as those disclosed in UK specification No.
1,010,064 and blends such as those disclosed in UK specification Nos. 1,284,082 and 1,294,665, and compositions such as those disclosed in our U.S. Patent No. 4275180. The polymeric materials can be tailored to suit the intended use by the addition of fillers, e.g. semi-conducting fillers or anti-tracking agents, flame retardants, plasticisers, pigments, stabilisers and lubricants, or where necessary, e.g. where the polymeric material is sub-stantially non-crystalline, a hold-out agent such as a thermo-plastic polymer, e.g. polyethylene, may be included in the material.
I 177~20 - 11 - RK121 ~~
, The polymeric material may be cross-linked ~y irradiation, for example, by means of an electron beam or by gamma radiation or it may be chemically cross-linked. Whichever cross-linking process is used, it may be advantageous to incorporate one or more co-curing agents for example poly-unsaturated monomers such as triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetra-methacrylate, allyl methacrylate and vinyl methacrylate.
One method of chemical cross-linking that may be used in the process according to the invention involves grafting an unsaturated hydrolysable silane on the polymer and sub-jecting the article to moisture during a curing stage, for example, as described in UK Patent specification Nos.
1,286,460 and 1,357,549.
"
Any of the techniques conventionally employed for fusing together polymeric materials may be employed in the process of the present invention, e.g. radio frequency, ultrasonic or hot bar welding, and pressure may additionally be applied to ensure a satisfactory bond. Furthermore, it is possible to make use of the fusing operation to separate the articles one from another or from surplus polymeric starting mater-ial. For example, it is possible to use a heating/cutting device such as a hot wire cutter or a laser beam, if nec-essary in association with pressure applying means such as a roller. -.
If the seam bonded heat-recoverable article is produced with an undesired protruding external weld, then this may be avoided by turning the article inside-out.
., ~ .
` l 177~20 - 12 - RK121 - ~
.
As hereinbefore described, the process is particularly appropriate in the production of hollow heat-recoverable articles for use in the electrical field, e.g. boots, udders and end-caps. In general, such products are char-acterised by a wall thickness prior to heat-recovery thereof of preferably from 0.1 to 5 mm, especially from 0.5 ~o 3 mm e.g. 1 to 3 mm.
.
Specific embodiments of the invention will now be described by way of example with specific reference to Figures 1 to 16 of the accompanying drawings wherein:
Figure 1 is a schematic top view of -an assembly of sep-arable heat-recoverable udders for the termination of an electrical cable, Figure 2 is a diagramatic isometric view of an udder - produced from the assembly shown in Figure 1, Figure 3 is a schematic top view of an assembly of sep-arable heat-recoverable boots employed for sealing an electrical cable at the termination thereof, Figure 4 is a diagramatic isometric view of a boot produced from the assembly of Figure 3, Figure 5 ~ is a schematic top view of an alternative assembly of separable heat-recoverable boots from which the boot of Figure 4 may be produced, . . -1 177~0 Figure 6 is a schematic top view of an assembly of sep-a-able heat-recoverable end-caps employed for sealing the ends of electrical cables, Figure 7 is an isometric view of an end cap produced from the assembly of Figure 6, Figure 8 is a schematic top view of an assembly of sep-arable heat-recoverable 4-legged udders, Figure 9 is an isometric view of a boot produced from the assembly of Figure 8, Figure 10 is an isometric top view of an alternative assembly of separable heat-recoverable 4-legged 1 . udders, . Figure 11 is an isometric view of an udder produced from the ;: . assembly on Figure 10.
Figure 12 is a schematic top view of an assembly of sep-arable heat-recoverable boots, Figure 13 is an isometric view of a boot produced from the assembly of Figure 12.
Figure 1~ is a schematic isometric view of a polymeric web of material that has been locally deformed to produce boots analogous to that shown in Figure 13, .
: `
:- `
- .. -' ' '~ - .
1 177~20 Figure 15 is an isometric view of a right angle electrical boot produced in analogous manner to that depicted in Figure 14, .
~ and Figure 16 is an isometric view of a 2-legged udder produced ~` in analogous manner to that depicted in Figure 14.
In the embodiment shown in Figures 1 and 2, a pair of polyethylene sheets 1a and lb which have been expanded longitudinally to 3 times their original length at a tem-perture of 100C and cooled whilst in the expanded con-dition, are superimposed one on the other and welded at positions 2 employing an ùltrasonic we;ding tool to produce welded seams 3. The welded shee~s are then irradiated in an electron beam at a dosage of 15 Mrads causing cross-linking of the polyethylene. After cross-linking the assembly is severed along the weld seams 3 employing a mechanical cutter to produce a plurality of heat-recoverable electrical udders 4 each having two legs 5 defined by the welds 3. The areas depicted by reference numeral 6 are discarded.
Such udders may be employed in the electrical termination of a cable comprising two primary wires by heat recovering the udder about the end of the cable, the primary wires passing through t~he legs of the udder.
In a modification (not shown) of the above embodiment the sheets are internally pré-coated with a sealant or adhesive such as a hot-melt adhesive before the welding stage. The .
l 177620 .
sealant or adhesive selected is one that is relatively insensitive to the subsequent radiation treatment. Furthee-more, the regions of the sheet to be welded together are locally pre-heated and pressed together by suitably located heated rollers engageable with the sheets causing the sealant or adhesive in the region to be welded to flow and be displaced immediately prior to the welding stage. The resulting product is thereafter treated in analogous manner to that described above.
.~ , In ~nalogous manner to that described in relation to the first embodiment the transitions 7 and end-caps 8 shown in Figures 3, 4 and S and Figures 6 and 7 respectively are pcoduced, hereinafter the same reference numerals being employed for analogous parts.
...
It may be advantageous to arrange the welds in end caps (and in other articles) to be tearable in order to facilitate removal of the article from a substrate onto which it has been heat-shrunk in use. In such arrangements the open end of the article may be shaped to provide a tab for convenient gripping to tear off the article.
.
.
In the embodiment illustrated in Figures 8, 9,10 and 11, two methods of producing 4-legged udders are depicted employing non-cross-linked polyethylene tubing 9 which has been radially expanded to three times its original diameter at a temperatrure of 100C and cooled in the expanded condition. In the embodiment shown in Figures 8 and 9, the tubing is welded axially thereof to produce welded seams 3 . . .
,;.. - . , ~
~.
:
which define the four legs of each udder, i.e. in a planar configuration, the tubing thereafter being irradiated with an electron beam as hereinbefore described and thereafter severed transversely thereof along the lines X - X.
, .
In the embodiment shown in Figures 10 and 11 the tubing is welded axially thereof so as to produce welded seams 3 which define each`udder in a cruciform configuration as shown in Figure 11.
In the embodiment shown in Figures 12 and 13, electrical boo~s are produced from non-cross-linked radially expanded polyethylene tubing (produced as described in the preceding embodiment), the boots being profiled by welding to produce welded seams 3 and severing along the weld seams
3 to separate the boots from the superflous regions 6. The profiled tube is then subjected to electron irradiation as hereinbefore described and subsequently severed transversely along lines X - X to produce the individual boots as shown in Figure 13.
In the embodiment shown in Figure 14, an alternative method of producing the boots of Figure 11 is illustrated. In this embodiment a sheet of non-cross-linked non-expanded poly-ethylene 1 is heated to a temperature of 100C and passed over a series of vacuum moulds. After application of vacuum, the sheet is impressed with a plurality of expanded areas ~3 corresponding in shape to one half of the boot to be produced. After cooling, the sheet is removed from the mould and superimposed on a similarly processed sheet of complimentary form such that the half-boots of one sheet are in register with the half-boots of the other. Each com-plimentary and registering pair of half-boots are thereafter welded together and the whole boots so formed are separated from the surrounding area by severing along the welds 3 and also across the ends to produce the transitions in their final form as illustrated in Figure 13. The articles so formed are thereafter irradiated in an electron beam as hereinbefore described.
By employing appropriate vacuum moulds, the electrical boots of Figure 15 and the two legged udders of Figure 16 are produced. It will be seen that this method of forming the article of Figure 15 has the advantage that two axes of recovery can be produced in a single operation.
In each of the preceding embodiments, the wall thickness of the polyethylene after deformation may be 0.1mm, 0.5mm, 1.Omm, 1.5mm, 2.Omm, 2.Smm, 3.Omm, 3.5mm, 4.0mm, 4.5mm and S.Omm with similar results.
In all embodiments of this invention, the fact that the polymeric material is cross-linked after the article has been assembled enables it to be cross-linked by irradiation, thereby reducing the time taken for cross-llnking, obviating the necessity to incorporate peroxide or other chemic~l curing agents in the material, and strengthening the bonded regions. The latter feature is particularly significant when the first and second bodies have been bonded together by fusion and results in strong cross-linked bonded regions.
The fusion bonding is preferably carried out under such pressure and other conditions as will cause a bead of fused material to be exuded along the edge of the bonded seam, thus indicating a high degree of flow of the bond material to enhance the effectiveness of the bonding.
,, ~, :.
,, ~ -' .
:,, l 1 77B20 It will be appreciated that the second body could be substantially non-heat-recoverable ~e.g. less than 10 percent recovery), even semi-rigid, for example in the form of a disc with the first body comprising one or more tubes endwise bonded to perforations in the first body and cross-linkedJ such an arrangement being within the scope of this invention.
:;
- 17a -.
.:~
;' .' ' '
In the embodiment shown in Figure 14, an alternative method of producing the boots of Figure 11 is illustrated. In this embodiment a sheet of non-cross-linked non-expanded poly-ethylene 1 is heated to a temperature of 100C and passed over a series of vacuum moulds. After application of vacuum, the sheet is impressed with a plurality of expanded areas ~3 corresponding in shape to one half of the boot to be produced. After cooling, the sheet is removed from the mould and superimposed on a similarly processed sheet of complimentary form such that the half-boots of one sheet are in register with the half-boots of the other. Each com-plimentary and registering pair of half-boots are thereafter welded together and the whole boots so formed are separated from the surrounding area by severing along the welds 3 and also across the ends to produce the transitions in their final form as illustrated in Figure 13. The articles so formed are thereafter irradiated in an electron beam as hereinbefore described.
By employing appropriate vacuum moulds, the electrical boots of Figure 15 and the two legged udders of Figure 16 are produced. It will be seen that this method of forming the article of Figure 15 has the advantage that two axes of recovery can be produced in a single operation.
In each of the preceding embodiments, the wall thickness of the polyethylene after deformation may be 0.1mm, 0.5mm, 1.Omm, 1.5mm, 2.Omm, 2.Smm, 3.Omm, 3.5mm, 4.0mm, 4.5mm and S.Omm with similar results.
In all embodiments of this invention, the fact that the polymeric material is cross-linked after the article has been assembled enables it to be cross-linked by irradiation, thereby reducing the time taken for cross-llnking, obviating the necessity to incorporate peroxide or other chemic~l curing agents in the material, and strengthening the bonded regions. The latter feature is particularly significant when the first and second bodies have been bonded together by fusion and results in strong cross-linked bonded regions.
The fusion bonding is preferably carried out under such pressure and other conditions as will cause a bead of fused material to be exuded along the edge of the bonded seam, thus indicating a high degree of flow of the bond material to enhance the effectiveness of the bonding.
,, ~, :.
,, ~ -' .
:,, l 1 77B20 It will be appreciated that the second body could be substantially non-heat-recoverable ~e.g. less than 10 percent recovery), even semi-rigid, for example in the form of a disc with the first body comprising one or more tubes endwise bonded to perforations in the first body and cross-linkedJ such an arrangement being within the scope of this invention.
:;
- 17a -.
.:~
;' .' ' '
Claims (40)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the production of a heat-recoverable article which comprises (a) providing a first body of fusion bondable polymeric material having a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20% and deforming the body at a temperature below the softening point of the material to produce a heat-recoverable polymeric material having a thickness of at least 0.1 millimetres, (b) forming a bond between one or more parts of the first body and a second body of fusion bondable polymeric material to produce the configuration of at least one seam bonded heat-recoverable article, and (c) cross-linking the bond between the deformed first body and the second body.
2. A process according to claim 1 wherein the bodies are bonded to produce the configuration of at least one hollow heat-recoverable article.
3. A process according to claim 2 wherein the bodies are bonded to produce at least one tubular article recoverable substantially only in the radial sense.
4. A process for the production of a heat-recoverable article which comprises (a) providing a first body of fusion bondable polymeric material having a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20% and deforming the body at a temperature below the softening point of the material to render the material heat-recoverable, (b) forming a bond between one or more parts of the first body and a second body of fusion bondable polymeric material to produce the configuration of at least one seam bonded hollow tubular article heat recoverable substantially only in the radial sense, and (c) cross-linking the bond between the deformed first body and the second body.
5. A process according to claim 4, wherein the heat-recoverable material is at least 0.1 millimetres thick.
6. A process according to any claim 1 or 4, wherein the bonding is effected by fusion of the said polymeric material.
7. A process according to claim 1 or 4, wherein the bond-forming material includes further material in addition to the first body and the second body and the cross-linking cross-links the said further material with that of the first body and the second body.
8. A process according to claim 1 or 4, wherein the cross-linking cross-links substantially all of the said polymeric material in addition to the bond.
9. A process according to claim l or 4, wherein the cross-linking is effected after the deforming and bonding steps.
10. A process according to claim l or 4, wherein the cross-linking is effected after the deforming step and during the bonding step.
11. A process according to claim 1 or 4, wherein the bonding step is performed after the deforming step.
12. A process according to claim 1 or 4, wherein the fusion bondable polymeric material before the cross-linking step has a gel content as measured by test method ANSI/ASTM
D2765-68 of less than 5%.
D2765-68 of less than 5%.
13. A process according to claim 1 or 4, wherein the second body to which part of the first body is bonded is another part of the first body.
14. A process according to claim 1 or 4, wherein the first body is in the form of a tube and the deforming step expands the tube radially.
15, A process according to claim 1 or 4, wherein the first body is in the form of a web and the deforming step expands the web longitudinally.
16. A process according to claim 1 or 4, wherein the second body to which part of the first body is bonded is initially separate from the first body.
17. A process according to claim 1 or 4, wherein the first body is in the form of a web and the second body is in the form of a web.
_ 21 _ RK121
_ 21 _ RK121
18. A process according to claim 1 or 4, wherein the first and second bodies are both webs and the deforming step expands the first body longitudinally and the second body is similarly expanded.
19. A process according to claim 1 or 4, wherein the deforming step locally deforms at least one region of the first body, the second body is locally deformed in at least one region at a temperature below the softening point of the material to render it heat recoverable, and the first body is bonded to the second body with their respective deformed regions co-operating with each other to produce one or more hollow said article(s).
20. A process according to claim 1 or 4 wherein the deforming of the first body and/or of the second body is effected by vacuum forming of a web of the polymeric material.
21. A process according to claim 1 or 4, wherein the bonding is effected so as to produce the configuration of a plurality of separable said articles.
22. A process according to claim 1 or 4, wherein the polymeric material after deformation has a wall thickness in the range from 0.1 to 5.0 millimetres.
23. A process according to claim 1 or 4, wherein the resulting article is shaped and non-planar.
24. A process according to claim 1 or 4, which is carried out continuously on a continuous first body and/or second body of polymeric material.
25. A process according to claim 1 or 4, which produces a train of interconnected said articles.
26. A process according to claim 1 or 4, wherein the cross-linking is effected by means of ionising radiation.
27. A seam-bonded heat-recoverable article comprising a first body of polymeric material which has been deformed at a temperature below the softening point of the material to render the material heat-recoverable, the deformed material having a thickness of at least 0.1 millimetres, one or more parts of the first body having been bonded to a second body of polymeric material with the first and second bodies each having a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20% and the bond between the first body and the second body being cross-linked.
28. A seam-bonded hollow tubular heat-recoverable article comprising a first body of polymeric material which has been deformed at a temperature below the softening point of the material to render the material heat-recoverable, one or more parts of the first body having been bonded to a second body of polymeric material with the first and second bodies each having a gel content as measured by test method ANSI/ASTM D2765-68 of less than 20% in such arrangement that the article is heat-recoverable substantially only in the radial sense, the bond between the first body and the second body being cross-linked.
29. An article according to claim 27 or 28, wherein the first body and the second body are fusion bonded to each other or to further material which is cross-linked to the material of the first body and the second body.
30. An article according to claim 27 or 28, in which sub-stantially all of the said polymeric material has been cross-linked.
31. An article according to claim 27 or 28, wherein the second body to which part of the first body is bonded is another part of the first body.
32. An article according to claim 27 or 28, wherein the second body to which part of the first body is bonded is discrete from the first body.
33. An article according to claim 27 or 28, wherein the first body and the second body have each been locally deformed in at least one region at a temperature below the softening point of the material to render the material heat-recoverable and are bonded to each other with their respective deformed regions co-operating with each other to provide one or more hollow said articles.
34. An article according to claim 27 or 28, wherein the polymeric material in the deformed state has a thickness within the range from 0.1 to 5.0 millimetres.
35. A process according to claim 1, wherein the second body is substantially non-heat-recoverable.
36. A process according to claim 4, wherein the second body is substantially non-heat-recoverable.
37. An article according to claim 27 or 28 wherein the second body is substantially non-heat-recoverable.
38. An article according to claim 27 or 28, which has been subjected to cross-linking by means of ionising radiation.
39. A train of interconnected articles according to claim 27 or 28.
40. A process according to claim 1 or 4, which includes only steps (b) and (c) which are carried out using a first body which has already been separately deformed in accordance with step (a).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8,024,623 | 1980-07-28 | ||
| GB8024623 | 1980-07-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1177620A true CA1177620A (en) | 1984-11-13 |
Family
ID=10515082
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000382616A Expired CA1177620A (en) | 1980-07-28 | 1981-07-27 | Heat recoverable articles |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5766924A (en) |
| CA (1) | CA1177620A (en) |
| ZA (1) | ZA815056B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58193116A (en) * | 1982-05-06 | 1983-11-10 | Seibu Gas Kk | Anti-corrosive coating method and anti-corrosive covering member |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60220B2 (en) * | 1979-01-29 | 1985-01-07 | 古河電気工業株式会社 | Method for manufacturing heat-shrinkable covering for branch parts |
-
1981
- 1981-07-23 ZA ZA815056A patent/ZA815056B/en unknown
- 1981-07-27 CA CA000382616A patent/CA1177620A/en not_active Expired
- 1981-07-28 JP JP56119036A patent/JPS5766924A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5766924A (en) | 1982-04-23 |
| ZA815056B (en) | 1982-07-28 |
| JPH0318574B2 (en) | 1991-03-12 |
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