Coated fabrics

Abstract

The fabric comprises a polyester base layer laminated to the first surface of a cellulosic auxiliary layer. The second surface of the cellulosic layer is coated with a phosphorous based flame retardan

Description

FIELD

[01] This invention relates to coated fabrics, such as upholstery fabrics, having the desired properties, for example enhanced flame retardancy. The invention also relates to methods of making the same. BACKGROUND

[02] Coated fabrics have very wide application, especially in the field of upholstery and bedding. For example, such fabrics are used to make mattress tickings and covers, curtains, clothing and upholstery for use in household and office environments, institutional use such as hospitals, nursing homes, doctors’ surgeries, prisons etc and in marine, automotive, aircraft and other transport applications.

[03] For many applications it is essential that the coated fabrics are flame retardant. Flame retardancy is usually achieved by application of a suitable coating. Traditionally a fabric is coated with a chemical coating composition.

[04] The applied coating composition is absorbed into the fabric, filling the interstices between yarns. As a result, it may substantially alter the fabric properties; for example its stiffness, drape, stretch and handle. Thus, a fabric which was highly elastic before application of the coating composition may become stiff after application, and may not fit to shape so easily. The surface of the fabric may feel rough or hard and so its comfort may be diminished.

[05] Furthermore, such coating compositions can be expensive and potentially harmful to the environment. Known coated fabrics cannot be recycled and therefore pose a further environmental issue.

[06] Accordingly, there is a need for a fabric which is coated with a coating composition to provide desirable characteristics, such as flame retardancy, but without loss of other desirable properties of the fabric. There is also a need for a coated fabric which is less harmful to the environment and cheaper to make compared to known fabrics. SUMMARY

[07] According to a first aspect of the present invention there is provided coated fabric comprising: a polyester base layer; and a cellulosic auxiliary layer having a first and second surface; wherein the cellulosic auxiliary layer is laminated on to the polyester base layer via the first surface; and wherein the second surface of the cellulosic auxiliary layer is at least partially coated with a coating, the coating being derived from a coating composition; and wherein the coating composition comprises a phosphorous based flame retardant.

[08] According to a second aspect of the present invention there is provided a method of forming a coated fabric comprising the steps of: a) providing a polyester base layer and a cellulosic auxiliary layer, the cellulosic auxiliary layer having a first and second surface; b) laminating the polyester base layer with the cellulosic auxiliary layer via the first surface; c) applying a coating composition to at least a portion of the second surface of the cellulosic auxiliary layer, wherein the coating composition comprises a phosphorous based flame retardant; and d) curing the coating composition to form a cured coating.

[09] Advantageously, the combination of the polyester base layer and cellulosic auxiliary layer may provide a char barrier upon exposure to a flame which acts as a barrier to inhibit gaseous products from diffusing to the flame and shield the fabric surface, and / or upholstery fillings, from heat and air, therefore improving the flame retardancy of the fabric. Furthermore, this also means that the amount of coating composition required to provide a flame retardant fabric, which meets flammability regulations, can be reduced. The reduced amount of coating composition required may also provide the advantage of significantly reducing the costs associated with forming the coated fabric and reducing the environmental impact. DETAILED DESCRIPTION

[10] By “laminated” as used herein, is meant the technique / process of manufacturing a material in multiple layers, such as two or more individual layers. Therefore, in the present application, the cellulosic auxiliary layer being laminated to the polyester base layer means that the polyester base layer and the cellulosic auxiliary layer are two separate layers.

[11] The “first surface” and “second surface” as used herein, refers to opposite sides of the cellulosic auxiliary layer (as opposed to different areas of the same side). For example, the “first surface” is the surface of the cellulosic auxiliary layer in contact with the polyester base layer. Whereas the “second surface” refers to the exposed face of the cellulosic auxiliary layer which is not in contact with the polyester base layer.

[12] The term “cellulosic” as used herein refers to a layer comprising cellulose or a derivative of cellulose. The cellulosic auxiliary layer may comprise viscose and / or cotton fibres. Preferably, the cellulosic auxiliary layer comprises viscose.

[13] Preferably, the coating composition is one which provides the fabric with flame retardant properties. The coating composition may be water-based or solvent-based. The coating composition may be in the form of a paste or a foam.

[14] The coating composition may comprise a further flame retardant. Suitably, the coating composition may comprise a further water-based flame retardant. Suitable flame retardants include PVC and PVC derivatives, antimony oxides, aluminium oxides, aluminium hydrates, zinc borates, halogen donors, phosphorous containing additives and melamines intumescent. Preferably, the coating composition may only comprise a phosphorous based flame retardant.

[15] The phosphorous based flame retardant may be present in the coating composition in an amount from 10 to 90 wt.% based on the total solid weight of the coating composition. Typically, phosphorous based flame retardant is present in the coating composition in an amount from 15 to 85 wt.%, more typically from 20 to 80 wt.%, most typically from 30 to 70 wt.% based on the total solid weight of the coating composition.

[16] The phosphorous based flame retardant may be present in the coating composition in an amount of at least 10 wt.% based on the total solid weight of the coating composition, typically at least 15 wt.%, more typically at least 20 wt.%, most typically at least 30 wt.% based on the total solid weight of the coating composition.

[17] The phosphorous based flame retardant may be present in the coating composition in an amount up to 90 wt.% based on the total solid weight of the coating composition, typically up to 85 wt.%, more typically up to 80 wt.%, most typically up to 70 wt.% based on the total solid weight of the coating composition.

[18] The coating composition may be cured by any conventional technique. Suitably, the coating composition may be cured by chemical and / or heat curing. Preferably, the coating composition is cured using heat.

[19] The cellulosic auxiliary layer may be laminated to the polyester base layer by any conventional technique. These include the use of a fusible melt interlayer between the first surface of the cellulosic auxiliary layer and the polyester base layer, an adhesive technique that may be used with or without heating and / or flame lamination.

[20] Preferably, the cellulosic auxiliary layer may be laminated to the polyester base layer by an adhesive. Typically, the adhesive is a thermally activated adhesive. The adhesive may be selected from polypropylene, polyethylene, polyamide, polyester, polyurethane, polyacrylate or a combination thereof. Preferably, the adhesive is polyethylene vinyl acetate.

[21] The adhesive may be applied by any conventional technique. Typically, the adhesive is applied as a powder scatter coat, dot, web, film, spray, rotary gravure and / or rotary screen. Typically, from 2.5 to 60 g / m2 of adhesive is applied to bond the cellulosic auxiliary layer and the polyester base layer. Typically, from 5 to 50 g / m2, more typically from 10 to 45 g / m2 of adhesive is applied. The adhesive may be applied to the first surface of the cellulosic auxiliary layer and / or to the polyester base layer prior to lamination thereof.

[22] The polyester base layer suitably comprises a (co)polyester polymer. The polyester base layer may comprise a blend of one or more (co)polyesters and a further polymer. The polyester base layer may comprise a copolyester and a further polymer. The further polymer may be selected from nylon, elastane, cotton, viscose, wool, or a combination thereof. The polyester base layer suitably comprises a polyester homopolymer.

[23] A “homopolymer” as used herein, refers to a polymer made from only one type of repeating monomer unit. For example, a polyester comprising only repeating units of ester. A “copolymer” as used herein, refers to a polymer made from more than one type of repeating monomer unit. For example, a polyesteramide comprising repeating monomer units of ester and amide.

[24] The polyester base layer and the cellulosic auxiliary layer used in the invention may be of any form including, but not limited to, warp or weft knitted, woven, non-woven stitch bonded, non-woven chemical linked or non-woven melded.

[25] The coating composition may be applied to the second surface of the auxiliary layer by any method for coating one side of a sheet material; for example, the dip coating and doctorknife technique, applied to one side of the fabric; or the doctor-knife on roller or doctor-knife over air method. Screen printing techniques may also be used. Such techniques are familiar to the person skilled in the art and need not be further described.

[26] As defined herein, the coating composition may be in the form of a foam. The coating composition may be in the form of a crush foam coating system or a collapsed foam system. When a crush foam coating system is used, the coating composition is typically mechanically mixed with air into a foam of varying densities but can be a ratio of one part liquid to four parts air. This foam is applied to the fabric using a positive gap system and then dried. The dried foam is then passed through a crush roller or calender roller to consolidate the coating. Preferably, the coating composition may be in the form of a collapsed foam.

[27] Advantageously, because the coating composition is applied to the second surface of the cellulosic auxiliary layer and not directly to the polyester base layer, it does not become dispersed within the fibres or filaments of the polyester fabric. As a result, a coated fabric in accordance with the present invention has improved flexibility compared to a laminated fabric produced by the traditional method(s) described above.

[28] Flock material may be disposed on at least a portion of the coating to, for example, improve handle and allow the use of softer, more flexible coatings.

[29] Preferably, the coated fabric of the invention retains multidirectional stretch, with the result that products made from such fabrics are easy to manufacture and, for example, which require fewer folds and darts to conform to the shape of the item being covered.

[30] The coated fabrics of the invention may have good breathability. The coated fabric may retain at least 20% of the permeability to air of the polyester base layer. The permeability is measured with respect to the Moisture Vapour Permeability test of BS3546, Part 4, 1991, Appendix C.

[31] The cellulosic auxiliary layer may be coated with up to 120 g / m2 of coating composition, preferably up to 80 g / m2, more preferably up to 60 g / m2, most preferably up to 50 g / m2, such as 40 g / m2 of coating composition. Advantageously, low amounts of coating composition may be used whilst still achieving the required flame retardancy of the coated fabric. Lower amounts of coating composition means less flame retardant compound may be used, such as phosphorus based compounds, and therefore a reduced cost and environmental impact.

[32] The coating composition may be applied to the second surface of the cellulosic auxiliary layer, which has already been laminated to a polyester base layer.

[33] Preferably, the cellulosic auxiliary layer is configured to be able to be delaminated from the polyester base layer. For example, the cellulosic auxiliary layer may be delaminated from the polyester base layer upon exposure to heat. Therefore, the cellulosic auxiliary layer and the coating composition can be removed from the polyester base layer easily, allowing for the polyester base layer to be recycled after use.

[34] The coated fabrics of the invention may provide a high level of comfort for uses in close proximity to the human body; for example, as mattress covers and tickings, bedding and upholstery.

[35] The invention will now be further described with reference to the following non-limiting example. EXAMPLES Example 1

[36] A 100% polyester flat woven fabric was laminated to a 40 g / m2 spun bonded viscose using 15 g / m2 of ethylene vinyl acetate copolymer (EVA) applied as a powder scatter coat. The laminate produced was then coated on the auxiliary layer with 50 g / m2 of a red phosphorus containing compound. Comparative Example 2

[37] A 100% polyester flat woven fabric was coated with 120 g / m2 of a brominated compound. Table 1 - Test Results Example Coating Deposited on Fabric (g / m2) BS 5852 Test Time To Self-Extinguish (s) Observations Example 1 50 1 12 No flame. Fabric melted and chard but left no hole 2 11 No flame. Fabric melted and chard but left no hole 3 13 No flame. Fabric melted and chard but left no hole Comparative Example 2 120 1 10 Black and grey smoke, hole formed in fabric 2 9 Black and grey smoke, hole formed in fabric 3 11 Black and grey smoke, hole formed in fabric

[38] The test results of Table 1 show that a coated fabric according to the invention, in which a polyester layer is laminated with a cellulosic layer and the cellulosic layer is then coated with a coating composition comprising a phosphorus-based compound, requires significantly less coating to obtain improved flame retardancy results, compared to coated fabrics with a conventional brominated coating. The coated fabric of the present invention requires vastly reduced chemical application and has recycling properties which have clear environmental and cost saving advantages, compared to conventional coated fabrics.

[39] Testing was carried out using test method BS 5852. The sample was soaked in accordance with clause 4 of BS 5651:1978, followed by line dry. The sample was conditioned for at least 72 hrs in ambient conditions, then for at least 16 hrs in an atmosphere of 20±5°C and 50±20%RH prior to testing.

[40] The sample was tested in an atmosphere within 15 to 30°C and within 20 to 70 % RH. The sample was tested over VP45Y non-combustion modified foam, density of 20-23 g / m3. The ignition source was a butane flame.

[41] The fabric met the following required standards:

[42] Flame retardancy: section 4 of BS5852 1990 - Assessment of ignitability Source 5 -Tested to IMO Resolution A652 (16);

[43] Breathability: Moisture Vapour Permeability BS3546 Part 4 1991 Appendix C;

[44] Abrasion resistance: Severe Contract B5690 1991 as modified by annex F BS2543 1995;

[45] Seam Slippage Meets requirements of BS2543 1995 13 02 25

Claims

1. A coated fabric comprising: a polyester base layer; and a cellulosic auxiliary layer having a first and second surface; wherein the cellulosic auxiliary layer is laminated on to the polyester base layer via the first surface;wherein the second surface of the cellulosic auxiliary layer is at least partially coated with a coating, the coating being derived from a coating composition; and wherein the coating composition comprises a phosphorous based flame retardant.

2. A coated fabric according to claim 1, wherein the cellulosic auxiliary layer comprises viscose and / or cotton fibres.

3. A coated fabric according to claim 1 or 2, wherein the phosphorous based flame retardant is present in the coating composition in an amount of between 10 to 90 wt.% based on the total solid weight of the coating composition.

4. A coated fabric as claimed in any preceding claim, wherein the cellulosic auxiliary layer is laminated to the polyester base layer by an adhesive.

5. A coated fabric as claimed in claim 4, wherein the adhesive is a thermally activated adhesive.

6. A coated fabric according to claim 5, wherein the adhesive is selected from polypropylene, polyethylene, polyamide, polyester, polyurethane, polyacrylate or a combination thereof.

7. A coated fabric according to claim 6, wherein the adhesive is polyethylene vinyl acetate.

8. A coated fabric according to any preceding claim, wherein the polyester base layer comprises a blend of polyester and a further polymer.

9. A coated fabric according to any preceding claim, wherein the coated fabric retains at least 20% of the permeability to air of the polyester base layer.

10. A coated fabric according to any preceding claim, wherein the auxiliary layer is coated with up to 120 g / m2 of coating composition.

11. A coated fabric according to any preceding claim, wherein the coated fabric is a flame retardant upholstery fabric.

12. A coated fabric according to any preceding claim, wherein the cellulosic auxiliary layer is configured to be able to be delaminated from the polyester base layer upon exposure to heat.13 02 2513. A method of forming a coated fabric comprising the steps of:a) providing a polyester base layer and a cellulosic auxiliary layer, the cellulosic auxiliary layer having a first and second surface;b) laminating the polyester base layer with the cellulosic auxiliary layer via the first surface;c) applying a coating composition to at least a portion of the second surface of the cellulosic auxiliary layer, wherein the coating composition comprises a phosphorous based flame retardant; andd) curing the coating composition to form a cured coating.

14. A method according to claim 13, wherein up to 120 g / m2 of coating composition is applied in step c).

15. A method according to claim 13 or 14, wherein the phosphorous based flame retardant is present in the coating composition in an amount of between 10 to 90 wt.% based on the total solid weight of the coating composition.

16. A method according to any of claims 13 to 15, wherein the polyester base layer is laminated with the cellulosic auxiliary layer using an adhesive.

17. A method according to claim 16, wherein the adhesive is applied as a powder scatter coat, dot, web, film, spray, rotary gravure and / or rotary screen.

18. A method according to claim 16 or 17, wherein between 2.5 and 60 g / m2 of adhesive is applied.

19. A method according to any of claims 16 to 18, wherein the adhesive is applied to the first surface of the cellulosic auxiliary layer and / or to the polyester base layer prior to lamination thereof.

20. A method according to any of claims 13 to 19, wherein the coated fabric is a flame retardant upholstery fabric.