GB2362116A

GB2362116A - Foam-coated web

Info

Publication number: GB2362116A
Application number: GB0011386A
Authority: GB
Inventors: Dany Felix Maria Michiels; Lieven Vangheluwe; Kris Ledegen
Original assignee: Milliken Europe NV
Current assignee: Milliken Europe NV
Priority date: 2000-05-12
Filing date: 2000-05-12
Publication date: 2001-11-14
Also published as: WO2001085863A1; GB0011386D0; AU7403501A

Abstract

A flexible web comprises a substrate of fabric material having an open fabric construction and a layer of polymer foam applied over at least one side of the substrate. The open substrate may be substantially closed by the foam layer. The substrate may be a woven, non-woven, laid, knitted or multi-axial fabric. The polymer foam may be acrylic, nitrile, PU, SBR, EVA, PVAC, neoprene or EAA. The flexible web may have a coating of adhesive on an outer surface. The web has particular application as a mechanical and / or sound dampening product and may be in the form of an adhesive tape such as a cable wrap or harness tape.

Description

Foam-Coated Web

Field of the Invention

The present invention relates to a flexible web, and more particularly to a flexible web having a coating layer of polymer foam.

The flexible web of the invention has particular application as a vibration dampening product for at least partially insulating one or more component from mechanical and/or sound vibrations. Such a vibration dampening product may be in the form of an adhesive tape, such as a cable wrap or harness tape, and it will be convenient to hereinafter describe the invention in relation to this exemplary application. It should be appreciated, however, that the invention is not limited to vibration dampening applications, but that other tape and sheeting applications are also possible.

Furthermore, for the purposes of this specification it will also be appreciated that the term "web" is intended as a generic reference to a relatively thin planar element, such as a sheet or strip; such webs typically having a thickness of not more than about 2mm.

Background of the Invention

Foam-coated flexible webs for use in adhesive tapes, such as cable wrap or harness tape, are already known. It is ever sought, however, to provide improvements in this field namely, superior tape properties and/or simpler and more costeffective production techniques. The present invention is concerned with such improvements.

-2 Summary of the Invention

According to one aspect, the present invention provides a flexible web having a coating layer of polymer foam, characterized in that the flexible web includes a substrate of fabric material having an open fabric construction, the layer of polymer foam having been applied over at least one side of said open fabric substrate. Preferably, the open substrate construction is substantially closed by the layer of polymer foam.

In a preferred form of the invention, an outer surface of the flexible web is provided with adhesive properties for adherence to a range of materials. Furthermore, the web is preferably formed as an elongate strip. Accordingly, the flexible web of the invention preferably takes the form of an adhesive tape, such as cable wrap or harness tape, having sound and vibration absorption properties.

The primary function of the substrate is to provide the foam layer with a degree of robustness and dimensional stability. By employing a fabric substrate having an open fabric construction (i.e. a relatively lowdensity construction exhibiting a plurality of apertures there-through between the fibres or f ilaments of the fabric), the substrate is able to be formed relatively light-weight with low material requirements, and therefore lower cost. The open substrate construction is also advantageously able to be made readily tearable by hand in at least a transverse direction. Desirably also, the foam substantially closes the open substrate construction (i.e. covers or seals the apertures through the fabric substrate) so that there is substantially no "strike-through" of adhesive when an adhesive compound is subsequently applied to the web to provide the adhesive properties.

The open fabric substrate may be selected from the group consisting of woven fabrics, non-woven fabrics, laid fabrics, multi-axial fabrics, and knitted fabrics (including weft and warp knitted fabrics). In one particular embodiment, the substrate is a weft inserted-warp knitted (WIWK) fabric. The fibres or yarns used in the fabric substrate may be spun yarns, monofil, multifil and/or tape yarns and may comprise any one or more of a wide variety of natural, synthetic or anorganic material including, but not limited to, cotton, wool, nylon, rayon, aramid, polyamide, polyethylene, polyester, PEN, PBO and PEEK. As an alternative, the present invention also contemplates that the substrate may be formed from glass and/or carbon fibres or cord.

In a particularly preferred embodiment of the invention, the polymer foam layer is inherently heat resistant and flame retardant. Heat resistance and flame retardance are two important characteristics for products such as harness tape or cable wrap. Typically, such products are used in electromechanical systems that produce mechanical and/or sound vibrations as they operate. For safety reasons in such electromechanical applications, it is usually required that such tapes exhibit heat resistance and/or flame retardance (FR). By rendering these characteristics as inherent properties of the foam layer, the invention provides a superior product having a simpler production technique. That ist no additional treatment or production step is required to achieve the heat resistance and/or fire-resistant properties of the tape.

"Heat resistance" is generally understood as the ability to resist changes in the physical properties of the foam despite increase in temperature, possibly to extreme levels. "Flame retardancy" (FR) refers to a tendency not to burn, or a resistance to burning. The heat resistance and flame retardancy of the foam layer are preferably designed to satisfy industry norms (e.g. SSFMV302). In this regard, halogen compounds may be incorporated in the foam composition, or alternatively, halogen-free FR compounds such as silicates, polyphosphates, amonium polyphosphates and derivatives. Furthermore, other additives to the foam composition such as antimony and phophorous oxide compounds (e.g. antimony trioxide and antimony pentoxide), melamines, and/or aluminium. hydrates (eg trihydrate) can be included f or the desired FR properties - Heat resistance can be provided through PU dispersion.

Accordingly, as an inherently FR and heat resistant foam is applied to the open fabric substrate in the flexible web (e.g. tape) of the invention, the fabric substrate itself may thereby also be treated for heat resistance and flame retardance. of course, the fabric substrate could be pre-treated for any one of its desired properties before application of the foam. For example, fluorocarbon could be applied to the substrate by prespraying or pre- dipping, instead of during the foam coating process.

The polymer foam layer in the invention may be formed as either a chemical foam or a mechanical foam, as is known in the art. In the case of the chemical foam, blowing agents such carbonates may be used. In the case of a mechanical foam, appropriate additives, such as amonium derivatives or amonium laurylsulfate, may be used to create the foam mechanically. The foam layer may be applied to or deposited on the substrate in a dipping or spraying operation. Preferably, a mechanical foam is aerated and pumped as a liquid dispersion and deposited across the surface of a moving open fabric substrate. A doctor blade is employed to spread or distribute the foam mixture evenly over the surface of the substrate. Once coated, the substrate passes through a stenter in which the water in the foam dispersion is evaporated and in which the other foam constituents polymerize in a condensation reaction. The foam- coated web then typically passes between a pair of calender rollers, between which the foam layer is compressed or densified, thereby forming the final foam structure.

According to another aspect, therefore, the present invention also provides a method of manufacturing a flexible web, comprising the steps of:

- providing a substrate sheet of fabric material having an open fabric construction; and -5 applying a layer polymer foam over a surface of said open fabric substrate, including the steps of:

distributing said foam in liquid form substantially uniformly over said surface, and drying or curing said foam to form said foam layer.

Preferably, the step of applying the layer of polymer foam substantially closes the open construction of the substrate.

In a preferred form of the invention the polymer foam composition may include acrylics, nitriles, polyurethane (PU), styrene- butadiene rubber latex (SBR), EVA, PVAC, neoprene and/or EAA in combination with blends thereof and/or copolymers. Additives to the composition may enhance other properties of the product - for example colour, anti-oxidants, anti-ozonants, oil and water repellancy etc. The foam composition may also include fillers, in addition to the desired FR ingredients already described.

In a preferred form of the invention the composition of the foam layer is such that, when the invention is embodied as an adhesive tape, the foam layer also has intrinsically good release properties enabling the tape strip to be easily unwound from a spool or reel. such intrinsic release properties of the foam further simplify manufacture as a special release coating, such as a lacquer, need not be applied. This invention does contemplate embodiments, however, in which an additional lacquer release coating may be applied.

In a preferred form of the invention the adhesive tape is also oil repellent and/or hydrophobic (i.e. water repellent). Such properties may be obtained with fluorocarbons (6 %) and with silicone-based products. Again, such properties are preferably inherent properties of the foam itself. Alternatively, the adhesive tape may include an additional layer or coating.

Similar considerations are also true in respect of the adhesive tape having anti-microbial properties.

In a preferred form of the invention the polymer foam layer may have flocking applied as an outer layer. That is, "flocking", or discontinuous textile fibres, may be applied (typically before drying or curing) to the polymer foam composition already coating the substrate. This provides the tape with an additional level of "cushioning", thereby enhancing its vibration dampening and sound absorption properties. Flocking may also increase the durability of the tape product.

As will be appreciated by persons skilled in the art, adhesive properties of the flexible web of the invention may preferably be provided by a coating of adhesive over an outer surface of the web. For example, a coating of adhesive may be applied (e.g. by spraying or other conventional coating techniques) to one side of the coated substrate. In the event that the open fabric substrate has been coated with foam on one side thereof (e.g. by doctor blade spreading over the fabric surface at that side) then the adhesive is typically applied to the opposite side of the already foam-coated substrate. Because the foam layer preferably closes the open construction of the fabric substrate, there is no strike-through of glue or adhesive as it is applied. The adhesive is preferably a pressure-sensitive adhesive (PSA) as is known in the art. In an alternative embodiment the open fabric substrate may have a layer of foam provided on both sides thereof where, for example, the foam layer is applied to the substrate in a dipping operation.

For assistance in arriving at an understanding of the present invention, an example is hereafter described by way of illustration. That example may be read with reference to the preceding description, but is in no way intended to limit the generality of the preceding description.

In a particularly preferred example, the present invention provides an adhesive tape for use as a cable wrap or harness tape. The tape is naturally formed as an elongate strip of flexible web which is typically provided wound on a reel or spool. As is usual with substantially planar web elements, the tape exhibits two main surfaces, one of which has adhesive properties and the other of which presents a layer of polymer foam.

The elongate web of the tape includes a substrate of fabric material having an open construction. The open fabric substrate is desirably a knitted fabric and most preferably a weft inserted-warp knitted (WIWK) fabric from polyester, although any of a variety of yarn materials may be used. The weft inserted-warp knitted construction of the substrate is desirably designed to be torn by hand in the transverse (i.e. weft) direction. Ready tearability is a highly desirably property for facilitating the actual use of such tapes. The foam layer will also naturally be tearable. The yarns or fibres of the open fabric substrate can be pre-coloured, or may be dyed to the desired colour upon application of the foam layer.

The foam composition itself is preferably pigmented to the desired tape colour (e.g. black) and has a composition which inherently provides a variety of highly desirable properties. In this particular example the foam layer is formed from a mixture of SBR, acrylate and polyurethane, and includes halogen additives which provide fire retardant (FR) and heat resistant properties. Fluorocarbon and silicone additives also provide both oil and water repellancy. Additional additives may also enhance tape ageing and anti-microbial properties.

In manufacturing such a tape according to the invention, the flexible web is typically manufactured in sheet form and later slit into strips of the desired width. The foam is preferably formed as a mechanical foam according to conventional techniques. The aerated foam composition is pumped as a liquid dispersion and distributed over one side of a sheet of the open fabric substrate material (described above) which travels along a manufacturing process path. The sheet substrate passes beneath a doctor blade which uniformly spreads and distributes the liquid foam composition over the surface of the substrate. This doctor blade ensures the evenness of the foam layer while also determining the thickness of the layer. Application of the liquid foam composition, which itself has one or more of a variety of desirable properties, serves to treat the fibres, filaments and/or yarns of the fabric substrate to also provide the substrate with those same properties. For example, the black-coloured foam composition dyes the tape substrate to that same colour and also imparts the desired heat resistance and flame retardance properties.

The substrate then passes through a stenter in which the liquid foam dispersion is dried or cured by evaporating the water therefrom and polymerizing the other constituents in a condensation reaction. After drying/curing in the stenter, the foam-coated substrate typically passes through a calendering operation in which the foam layer is compressed and densified. The foam layer so produced is resiliently deformable and adapted to dampen mechanical and/or sound vibrations. That foam layer furthermore substantially closes the open construction of the fabric substrate, thereby making it more suitable for application of an adhesive substance.

The foam coated substrate sheet is provided with adhesive properties over the surface thereof opposite to the surface carrying the layer of foam. The adhesive properties are provided by application of an adhesive substance or glue such as a pressure-sensitive adhesive (PSA). This is applied as a coating, for example, by spraying. No strike-through of the adhesive occurs by virtue of the now closed construction of the foam coated substrate. After application of the adhesive coating, the sheet is slit into elongate strips which are then wound onto reels or spools to form the final vibration dampening tape product of the invention. The thickness of the tape web is preferably in the range of about 0.4 to 1 mm.

In a variation of the embodiment described, a covering of discontinuous textile fibres or "flocking" may also be added to the foam composition before it is dried or cured to enhance vibration/sound absorption as well as to improve the wear characteristics of the tape.

In its application as a cable wrap or harness tape, the adhesive tape of the invention provides good sound absorption/sound dampening properties. In addition, the properties of the foam are such that it provides good release from its wound condition on the spool or reel. That is, the tacky pressure-sensitive adhesive on one side of the tape web readily releases from its adhesive contact with the polymer foam layer of an adjacent tape web element on the reel. A special lacquer "release" layer is therefore not required.

889843 - IW

Claims

1. A flexible web having a coating layer of polymer foam, characterized in that the flexible web includes a substrate of fabric material having an open fabric construction, the layer of polymer foam having been applied over at least one side of said open fabric substrate.

2. A flexible web as claimed in claim 1, wherein the open substrate construction is substantially closed by the foam layer.

3. A flexible web as claimed in claim 1 or claim 2, wherein the open fabric substrate is selected from the group consisting of woven fabrics, non-woven fabrics, laid fabrics, knitted fabrics and multi-axial fabrics.

4. A flexible web as claimed in claim 3, wherein the fabric substrate has a weft inserted-warp knitted (WIWK) construction.

5. A flexible web as claimed in any one of the preceding claims, wherein the polymer foam layer includes one or more of: an acrylic, a nitrile, polyurethane (PU), styrene-butadiene rubber latex (SBR), EVA, PVAC, neoprene and EAA latecies.

6. A flexible web as claimed in any one of the preceding claims, wherein said polymer foam is inherently heat resistant and flame retardant.

7. A flexible web as claimed in claim 6, wherein the polymer foam composition includes one or more of: a halogen compound, antimony oxide compounds, melamines, -it - aluminium. trihydrate, silicates, amonium polyphosphate and derivatives, to provide the inherent flame retardancy.

8. A flexible web as claimed in claim 7, wherein the polymer foam composition includes one or more fluorocarbon and/or silicone-based product.

9. A flexible web as claimed in any one of the preceding claims, wherein an outer surface of said web is provided with adhesive properties for adherence to a range of materials.

10. A flexible web as claimed in claim 9, wherein the adhesive properties are provided by a coating of an adhesive substance applied over said outer surface of the flexible web.

11. A flexible web as claimed in claim 10, wherein the adhesive substance is a pressure-sensitive adhesive (PSA).

12. A vibration dampening product including a flexible web as claimed in any one of the preceding claims.

13. An adhesive tape comprising a flexible web as claimed in any one of claims 9 to 11, wherein the flexible web is formed as an elongate strip.

14. A method of manufacturing a flexible web, comprising the steps of:

- providing a substrate sheet of fabric material having an open f abric construction; and applying a layer polymer foam over a surface of said open fabric substrate, including the steps of:

-/I--

15. A method as claimed in claim 14, wherein the step of applying the layer of polmer foam substantially closes the open construction of the substrate.

16. A method as claimed in claim 14 or claim 15, wherein the step of applying the layer of polymer foam over said surface of the fabric substrate also treats the fibres, filaments and/or yarns of the substrate to provide one or more desired physical properties selected from the group consisting of: flame retardance, heat resistance, colour, oil repellancy, water repellancy, anti-oxidization, anti-ozonization and antimicrobial properties.

17. A method as claimed in any one of claims 14 to 16, wherein the step of distributing the foam over said surface includes spreading the foam in liquid form with a doctor blade

18. A method as claimed in any one of claims 14 to 17, wherein the step of applying the layer of polymer foam further includes:

calendering the coated substrate after the drying or curing step to compress the foam layer.

19. A method as claimed in any one of claims 14 to 18 further including the step of coating a surface of the substrate sheet opposite that surface to which the foam layer has already been applied with an adhesive substance.

20. A method as claimed in any one of claims 14 to 19 further including the steps of:

slitting the foam-coated substrate sheet into a plurality of elongate strips; and - winding said strips onto individual spools or reels.

889843