MXPA97008932A - Article encogible with ca - Google Patents

Abstract

A fabric (10) with shrinkable HDPE fibers (12) in a wrapping direction lamed to the LDPE film (14) on the outside and coated with adhesive (16) on the inside is wound around a small diameter object, such as a wire splice to withstand the development during heat shrink and thus provide a side entry splice (SES) especially suitable for automotive wire assembly

Description

HEATED ARTICLE DESCRIPTION OF THE INVENTION This invention relates to a heat shrinkable article for wrapping around an object up to 25 millimeters in diameter, said article being especially useful for protecting wire splices from environmental contamination, for example, in automotive preformed cabling. Heat-shrinkable tubes of plastic material have been used for such purposes for many years, but such tubes have the disadvantage that they can be slid over a free end of wire, which is not always convenient in practice. Attempts to wrap thermally shrinkable plastic laminates around small diameter objects, such as wire splices, have been commercially unacceptable in the past due to the difficulty of securing the ends of the sheet around the object to be enclosed. Clamping devices of a well-known type for wrapping cables in enclosures are impractical to a small scale of wire splices, and attempts to secure the sheet through the adhesive tend to fail due to the tendency of the sheet to unwind from the object during shrinkage by heat The present invention provides an ingenious and relatively low-cost route to mitigate these problems.

The invention provides a heat-shrinkable article for wrapping an object up to 25 millimeters in diameter, comprising: (i) a fabric having shrinkable fibers with heat extending in the wrapping direction, (ii) a flexible layer of plastic material laminated interlacing to a main surface of the fabric that faces outwardly from said object during use, and (iii) heat activatable adhesive worn on the other major surface of the fabric that faces inward toward said object during use, the construction of the article being such that the heat recovery of the fabric during use winds the article around said object and towards the surface carrying the adhesive and activates the adhesive. The flexible layer (ii) and the adhesive (iii) can be brought (preferably adhered) directly on the fabric, or on other layers of intervention in direct contact with the fabric. By placing the shrinkable fabric with heat as the inner layer (in use) of a two component laminate with the interlaced plastic material, the present invention has the advantage of the asymmetric shrinkage force generated in the laminate by the heat shrinkable fibers in the the wrapping direction for curling the article during shrinkage in a manner in which it reinforces the wrapping action and thus counteracts the tendency to unwind during heat shrinkage. It has surprisingly been found that an article according to this invention can survive recovery after being initially secured around the object through an overlap joint using a pressure sensitive adhesive, without unacceptable opening, although the overlap can slide up to 50% of its original overlap width during said shrinkage. Preferably, the fabric will have the shrinkable fibers with heat extending substantially only in the wrapping direction. The heat shrinkage ratio of the article (i.e., the ratio of the length in the wrapping direction before heat shrinking to that after completing the heat shrink) is preferably within the range of 1: 10: 1 to 5: 1, most preferably from 1.3: 1 to 3: 1, especially from 1.5: 1 a. twenty-one . The article can be conveniently provided in the form of a strip or roll, for example, any between 1 and 1000 meters in length in the wrapping direction, and it will be understood that said roller or strip can be advantageously fed to the automatic installation equipment. or other equipment suitable for enclosing relatively small items such as wire splices in an online production base. Alternatively, the article according to this invention can be provided in the form of a pre-cut strip or sheet carrying the pressure-sensitive adhesive on at least one of its regions capable of securing the wrapped article around said object during use before use. heat shrink the item.

Various forms of fabric containing heat-shrinkable fibers can be selected to suit the end-use requirements, the heat-shrinkable fibers in a preferred form of this invention being formed of high density polyethylene, preferably entangled by irradiation. Suitable materials for said layer of plastic material laminated to the fabric can also be selected by trial and error, a preferred material being low density polyethylene, preferably entangled by irradiation after lamination to the fabric. The fabric can be irradiated before lamination to the plastic layer, but preferably it is irradiated together with the plastic laminate after the lamination and before coating with the adhesive. Any heat activatable adhesive can be carried on the surface of the fabric that looks away from the laminated plastic material, the preferred adhesives being hot melt or heat curable adhesives, the adhesive being naturally selected to suit the final use of the article. The materials, dimensions and construction of the article are all selected and balanced to suit the final use in question, and for automotive wire splices, for example, they will be selected to make the article shrinkable in less than 30 seconds, preferably in less than 20 seconds. , very preferably 10 to 15 seconds, by the application of hot air or infrared heating, preferably at a temperature of 250 to 270 ° C on the external surface of the article. Examples of adhesives, which may be suitable for the purposes of the present, are described in WO-A-8707755 (RK310), GB-A-2104800- (RK149), EP-A-0157478 (RK232) and the International Application co-pending PCT / GB96 / 00731 (B247), the descriptions of all these are incorporated herein by reference. Methods for forming the fabric, preferably by weaving, by applying the laminate of the plastic material and by applying the adhesive will be well known to those skilled in the art. The article can be made of shrinkable fibers with heat and other fibers as generally described in GB-A-2134334, but preferably with the omission of the second plastic laminate and the metallized Mylar laminate described therein. For example, the fabric may use a flat weave (1 above and 1 below) of interlaced density polyethylene Wrapped Fiber wrap with a diameter of 0.2-0.3 mm at 35.4 ends per centimeter and weft fibers of 3 x 68 g / km or 0.1 mm of PE monofilaments in 3.9 peaks per centimeter. The weft fibers will be separated so as not to interfere to an unacceptable degree with the shrinkage of the wrapping fibers. Alternative fabric designs are indicated in the following table.

Constr uction of the Fabric Preferably, the fabric article includes an adherent polymeric material, preferably a laminate of adherent polymeric film (preferably a polyethylene film), which causes the fabric article to be substantially porous. For example, a low density polyethylene film with a thickness of about 0.2 mm can be laminated through known lamination methods on one side of the woven fabric. After lamination, the film and the fabric are preferably irradiated by customary means (known per se), preferably at a dose of at least 10, preferably at least 12, especially at least 14, megarrads, for improve the temperature performance and the joint joint of the laminated article. Suitable irradiation methods and equipment, for example, electron beams, are well known. Preferably, doses over 20 Mrads are not used, and an added small advantage is gained by doses above 15 Mrads. The fabric article can be made resistant to the transmission of liquids in the plane of the fabric sheet, usually known as making the article "flat hermetic", through methods including those described in EP-A-0324630. The invention also provides a kit of parts comprising an article, as described above, according to the invention and a pressure sensitive adhesive for securing the article wrapped around an object in use prior to heat shrinking of the article. Another aspect of the invention provides a method for enclosing an object comprising wrapping an article in accordance with this invention, as described above, around the object and heat shrinking the article. Said method preferably includes the step of securing the article wrapped around the object, preferably by pressure sensitive adhesive, before heat shrinking the article. As mentioned, the invention is particularly applicable when the enclosed object is an electrical wire splice, especially an automotive wire splice. The average diameter of the enclosed object is preferably less than 20 mm, most preferably within the range of 5 to 15 mm. Articles having lower installation temperature scales can be prepared using linear low density polyethylene fibers instead of currently preferred high density polyethylene heat shrinkable fibers. Higher temperature scales can be obtained using fluoropolymers such as PVDF such as recoverable fibers, possibly in combination with glass fibers, and higher temperature adhesives and laminated materials that can be easily selected by those skilled in the art, for example. example, as described in GB-A-2133740, the description of which is incorporated herein by reference. One embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 schematically shows the structure of an article according to this invention; Figure 2 shows an article according to the present invention wrapped around a wire splice with the heat-shrinkable fibers of the article lying in the wrapping direction; Figures 3A to 3D schematically represent the formation of the fabric (i) with the flexible laminate (ii); Figures 4A and 4B schematically illustrate the application of heat melting and pressure sensitive adhesives to the laminated fabric; Figures 5A through 5E illustrate in more detail the application of adhesives, and the envelope of the heat-shrinkable article and that the adhesive bears around a wire joint; and Figure 6 illustrates schematically the heat shrinkage of the article around the wire joint. As shown in an exploded form in Figure 1, the article according to this invention consists of the fabric 10 having heat shrinkable fibers 12 that lie in the directed envelope, with a layer of the low density polyethylene film. 14 laminated to a main surface of the fabric and a coating of heat fusion adhesive of polyamide 16 on the other main surface. The article 20 in Figure 2 is secured in the configuration wrapped around a splice (not visible) in wires 25 through a pressure sensitive adhesive 20 in an overlap joint. During the heat shrinking of the article, the hot melt adhesive 40 flows and during cooling solidifies to seal the enclosed wire splice against contamination and / or short circuit. Figure 3A indicates a plain weave fabric made of high density polyethylene warp monofilaments 30 with a diameter of 0.25 mm with polyethylene terephthalate weft monofilaments 32 with a diameter of 0.1 mm. This fabric 34 is laminated on one side with an extruded layer having a thickness of 0.25 mm of low density polyethylene, as indicated schematically in Figure 3B, and the resulting laminate article 35 is subjected to 14 Mrads of ionization radiation from of an electron beam 36 in a known manner, as schematically indicated in Figure 3C. The irradiated laminate 38 is then longitudinally grooved in roll 39 with a width of 50 mm and a length of 100 meters, or other dimensions to suit the end-use requirements, as indicated in Figure 3D. Figure 4A schematically indicates the application of a known polyamide 40 heat fusion adhesive strip and a strip of double sided pressure sensitive adhesive tape 41 (PSA) known to the fabric laminate fed from a roller 42 similar to those produced in Figure 3D. Application equipment 43 of any convenient design applies sufficient heat and pressure to adhere the heat fusion adhesive and the PSA to the side of the farthest fabric of the LDPE laminate. The resulting structure is shown in more detail in Figure 4B, where the fabric 45, with the LDPE laminate 46 on a major surface, has the heat-melt adhesive 47 over most of its other major surface, with a strip of free edge of the heat fusion carrying the PSA 48. The thickness of this article coated with recoverable adhesive with full heat is about 0.7 mm. Figure 5A presents an enlarged schematic indication of the hot melt adhesive 50 and the pressure sensitive adhesive 51 being applied to the fabric side of the LDPE / cloth laminate 52, the heat melt 50 terminating adjacent to an end strip of the fabric to which the PSA is applied. Figure 5B shows the laminate 53 carrying the adhesive with a wire splice 54 placed thereon, after which, a suitable section of the laminate 53 is cut, as indicated in Figure 5C, and fed together with the splicing to suit wrapping means indicated by the guide 55 in Figure 5D, which clamp the laminate 53 around the splice 54 through a link connection with the PSA 51, as indicated in Figure 5E. These procedures can be easily automated through those skilled in the art for efficient use in the production of automotive wire. Figure 6 illustrates schematically the wire splice 60, with the fabric laminate 61 carrying the heat shrinkable adhesive wrapped and clamped around it, being fed to a known band heater 62, which shrinks the wrapped article 61 around the 60 wire splice to produce the finished protected wire assembly 63.

Claims (3)

1. CLAIMS 1 .- A heat-shrinkable article for wrapping around an object with a diameter of up to 25 millimeters, comprising: (i) a fabric having shrinkable fibers with heat extending in the wrapping direction, (ii) a flexible layer of laminated plastic material laminated to a main surface of the fabric facing outwardly from said object during use, and (iii) heat activatable adhesive worn on the other main surface of the fabric facing inward toward said object during use, the construction of the article being such that the heat recovery of the fabric during use winds the article around said object and towards the surface carrying the adhesive and activates the adhesive.
2. 2. A heat-shrinkable article according to claim 1, having the shrinkable fibers with heat extending substantially only in the wrapping direction.
3. 3. A heat-shrinkable article according to claim 1 or 2, wherein the ratio of its length in the envelope direction before the heat shrink to that after completing the shrinkage with heat is within the scale of 1. 10: 1 to 5: 1, preferably from 1.3: 1 to 3: 1, most preferably from 1.5: 1 to 2: 1. 4. - A heat-shrinkable article according to any of the preceding claims, wherein the surface of the fabric carrying the heat-activatable adhesive has at least one region, which is free of the adhesive, said region can be attached to the another main surface of the heat-shrinkable article to secure the article wrapped around the object during use, prior to heat shrinking of the article. 5. A heat-shrinkable article according to claim 4, in the form of a strip or sheet carried over the region, which is preferably one of its edge regions, the pressure-sensitive adhesive capable of securing the article wrapped around said object during use, before shrinking with heat of the article. 6. A heat-shrinkable article according to any of the preceding claims, wherein the heat shrinkable fibers are formed of high density polyethylene, preferably entangled by irradiation. 7. A heat-shrinkable article according to any of the preceding claims, wherein said layer of plastic material is formed of low density polyethylene, preferably entangled by irradiation after lamination to the fabric. 8. A heat-shrinkable article according to any of the preceding claims, wherein the fabric has been irradiated prior to lamination of the plastic layer thereto. 9. - A heat shrinkable article according to any of the preceding claims, wherein said adhesive is a hot melt adhesive or a heat curable adhesive. 10. A heat-shrinkable article according to any of the preceding claims, whose materials, dimensions and construction are selected to make it shrinkable in less than 30 seconds, preferably less than 20 seconds, most preferably 10 to 15 seconds, by the application of hot air or infrared heating, preferably at a temperature of 250 to 270 ° C on the external surface of the article. 1 - A piece of equipment comprising an article according to any of the preceding claims and a pressure sensitive adhesive for securing the article wrapped around an object during use, prior to heat shrinking of the article. 12. A method for enclosing an object comprising wrapping an article according to any of claims 1 to 10 around the object and heat shrinking the article. 13. A method according to claim 12, comprising securing an article according to any of claim 4 or 5 around the object through a pressure sensitive adhesive prior to heat shrinking of the article. 14. - A method according to claim 12 or 13, wherein the enclosed object is an electrical wire splice. 15. - A method according to any of claims 12 to 14, wherein the average diameter of said object is less than 20 millimeters, preferably within the range of 5 to 15 millimeters. 16. An article, equipment or method according to any of the preceding claims, wherein the fabric is substantially as written in any of the examples 1 to 4 in the previous table, preferably example 3.