GB2299781A

GB2299781A - Carpet underlay and backing therefor

Info

Publication number: GB2299781A
Application number: GB9513716A
Authority: GB
Inventors: Travis Moore
Original assignee: Gates
Current assignee: Gates
Priority date: 1995-03-29
Filing date: 1995-07-05
Publication date: 1996-10-16
Also published as: GB9513716D0

Abstract

A backing for a rubber or resilient polymeric carpet underlay comprises a layer of crepe paper or the like (9) laminated to a layer of non-stretch material (13). The non-stretch material may be of mesh or grid-like construction or may be flat paper. The backing (7) is normally attached to the underlay which may be formed from ground rubber crumbs (6) supported in a binder material, or of sponge rubber (4), or latex foam (12) or a polyurethane foam and may be convoluted or ribbed. A release layer (14) such as non-woven polyester textile may be located on the side of the underlay opposite the backing (7) and it is preferred that the crepe paper (9) is uppermost.

Description

CARPET UNDERLAY AND BACKING THEREFOR This invention relates to carpet underlay, primarily of the type which incorporates a layer of resiliently deformable polymeric material, such as sponge rubber, latex foam, polyurethane, crumb rubber or the like, and to a backing for the underlay.

Carpet underlays commonly consist of a sponge rubber layer, which is most often in a convoluted or corrugated form, together with a "backing" adhered to the upper side of the sponge rubber layer. The purpose of the backing is to act as a tensile member, giving reinforcement with respect to break strength, puncture resistance, lack of elongation under load and related properties. Without this tensile layer, the carpet underlay would be difficult, or impossible, to handle.

Materials commonly used as backing include woven jute (hessian), non-woven textiles formed from glass, polyester or polypropylene fibres and stitched crepe craft paper. Of these backing materials, the latter, often known as TEXTRON (Registered Trade Mark), is the most common, particularly for high quality products.

TEXTRON stitched craft paper backing has been in production for about 20 years. Whilst details of its specification have changed in minor respects over that period, its basic construction has remained, in principle, unaltered. The TEXTRON material consists of a crepe paper (which is corrugated by a wet or a dry process) into which a plurality of spaced rows of yarns (preferably of polyester) have been stitched to provide a plurality of warps. The warps cross the corrugations and prevent the backing stretching in this direction, whereas the wefts run parallel to or are inclined at one or more angles to the corrugations, and prevent stretching in that direction. The TEXTRON material has an attractive and textile-like appearance, is pleasant to handle, has sufficient bulk, and has an adequate level of physical properties such as tear, break and elongation resistance.However, it is relatively expensive since the polyester stitching cost is high, the stitching process slow and the yarn costly when compared to the crepe paper part of the material.

This disadvantage is overcome in the present invention in which, according to the broadest aspect, we provide a backing for sponge rubber or like carpet underlay comprising a layer of crepe paper laminated to a layer of essentially non-stretch material, preferably a grid or mesh of textile material. The textile material may be formed of lightweight glass fibres, or polyester fibres, or a mixture of the two fibres. Alternatively, the layer of non-stretch material could be a flat paper.

Preferably, the two layers are laminated using an adhesive of the PVA type (polyvinyl alcohol, modified with minor ingredients, and in emulsion form with water).

If the grid or mesh layer is formed of lightweight glass fibres, these provide substantial break and tear strength, but they are brittle, and cannot resist elongation fatigue, to which carpet underlay is subjected. There are advantages, therefore, in incorporating at least some polyester yarns in the grid or mesh layer, as these are resilient. Also, the polyester fibres are easier to handle than glass fibres, especially when the fibres are very light. It is preferred that the grid or mesh layer would have glass fibres across its width, and polyester fibres along its length. A particular grid or mesh like layer which is particularly suitable is a non-woven product known as CRENETTE (Registered Trade Mark).This has a plurality of transverse weft threads, and extending at right angles thereto, a plurality of longitudinally extending warp threads which are normally located, alternately, above and below the weft threads to form the mesh. Normally, the "warp" and "weft" threads are attached to each other by passing the mesh over an adhesive applicator roller, and then passing the adhesive coated mesh between the nips of a plurality of pairs of heated pressure rollers to dry the adhesive.

If the non-stretch material is flat paper, it may contain about 80%, or more, of recycled pulp, whereas the creped paper may contain between about 20% and 50% of recycled pulp, the remainder being virgin pulp.

Also according to the present invention, we provide a carpet underlay comprising a sheet of resiliently deformable polymeric material having on its upper surface a backing as described above. The polymeric material, e.g.

rubber, may be formed from ground rubber crumbs or granules, recycled from rubber tyres or other sources, supported in a resin, latex or other binder material, or a polyurethane foam material, either in the form of a slab slit from virgin stock, or in reconstituted form (reconstituted chips bound with a binder, e.g. of polyurethane) or of similar construction, but is preferably sponge rubber or latex foam.

This may be corrugated or convoluted, or ribbed or grooved.

Also according to the present invention, we provide a carpet underlay comprising a sheet of resiliently deformable polymeric material such as rubber having on its upper face a backing which may be formed of crepe paper or the like, and laminated thereto on its lower face a grid or mesh of at least substantially non-stretchable textile material.

Preferably, the textile material is formed of lightweight glass fibres, typically of the order of 340 d'Tex continuous filament yarn. Since these are very much stronger than the polyester fibres used in a TEXTRON stitching process, they make it unnecessary for the stitching to be provided in the crepe paper backing, thus considerably reducing the price of this backing layer. It is envisaged that the glass fibres could be PVC coated, or that polyester fibres could be used instead of but preferably in combination with glass fibres.

For forming the sponge rubber, a sheet of uncured unblown rubber compound is calendered and the unblown rubber compound then has the backing adhered to its upper surface, prior to or while being passed through a heating device, e.g. an oven, and to the solid compound being blown to form it into a sponge, followed by curing. If the sponge material is to be convoluted or corrugated, it is passed through the heating device on a chain mat.

When the polymeric material is latex foam, the foam material is spread on the backing and is normally flat. If a ribbed, grooved or wavy surface is desired, the foam material is spread flat on the backing with a contoured comb-like knife, which may be moved to and fro to give a wave-like form to the grooves or waves.

The carpet underlay may have a facing or release layer, e.g. of spun-bonded polyester fibre, on the side thereof opposite the backing to give release properties when used in fully adhered installation systems.

Creped paper on its own without stitching is of low cost and is acceptable to the consumer, but apart from puncture resistance, does not have adequate physical properties. In particular, its resistance to elongation is very poor and the amount by which it stretches when subject to load during underlay manufacture and in fitting is unacceptable. The mesh or grid-like layer, on the other hand, is inexpensive and has the necessary physical properties, but is not puncture resistant, but is unacceptable to the consumer on its own because it has very poor handling properties, low bulk, and is of poor appearance. However, in the present invention, which provides a backing formed of creped paper and the mesh or grid layer laminated together, all of the required criteria are met simultaneously.

Several alternative embodiments of underlay according to the present invention are now described, by way of example only, with reference to the accompanying partly schematic drawings, in which: FIGURE 1 is a section through a flat sponge rubber underlay according to a first embodiment of the invention; FIGURE 2 is a section through a convoluted sponge rubber underlay according to a second embodiment of the invention; FIGURE 3 is a section through a flat rubber crumb underlay according to a third embodiment of the invention; and FIGURE 4 is a partly broken away, sectional perspective view through a foam rubber underlay according to a fourth embodiment of the invention.

Referring to the drawings, like components in the various views are identified by the same reference numerals.

In the embodiment of Figure 1, the underlay 1 is made from a sheet of flat sponge rubber 3 having a serrated or otherwise patterned lower surface 5, and a backing 7 in the form of a laminate attached to its upper surface. The laminate 7 comprises an upper layer of crepe paper 9 attached with adhesive, shown schematically at 11 (e.g. a PVA adhesive) to an interwoven grid or mesh-like layer, shown schematically at 13. The laminate 7 may be adhered directly to the rubber prior to curing, using the rubber itself as the adhesive.

In the embodiment shown in Figure 2, the flat sponge rubber is replaced by a sheet of convoluted sponge rubber 4.

This receives its convolutions by being passed through a curing oven on a chain mat. The layer 13 is secured to the tips of the convolutions with an adhesive (not shown) which could be the rubber material itself.

In the alternative embodiment shown in Figure 3, the underlay lb is comprised of a flat sheet 2 made up of ground-up rubber crumbs or particles 6 bonded together with latex, on the upper surface of which is a backing made up of a laminate 7; the laminate is again formed of a grid-like layer 13 adhered with adhesive 11 to a crepe paper 9, the laminate being secured in known manner to the crumb rubber sheet. On the underside of the crumb rubber sheet 2 is a facing 14 of spun bonded polyester.This is a known material, and allows the underlay easily to be released when it is adhered to a floor, e.g. of concrete or wood, by the application of adhesive to the underside of the facing 14; when the underlay is pulled up, part of the facing 14 will remain adhered to the floor, and part to the underside of the flat sheet 2, and very little, if any, of the sheet 2 will remain adhered to the floor. The facing 14 is usually formed of a very light non-woven polyester textile of the order of 20 grams per square metre weight.

In the fourth embodiment of the invention shown in Figure 4, the upper part of the underlay is formed of a crepe paper 9 laminated with adhesive 11 to a grid-like layer 13, and adhered to a foam rubber sheet 10 in known manner. The sheet 10 may have a plain or a ribbed or otherwise patterned underface 12. In this embodiment, the manufacturing direction is indicated by the arrow A, and the transversely extending wefts are shown at 15 and the warps are shown at 17 and 19. As is apparent, every other warp 17 is arranged below all the wefts 15 and the other (alternate) warps 19 are all arranged above the wefts. The peaks and valleys forming the corrugations in the crepe paper extend transversely of the underlay, i.e. parallel to the wefts and normal to the manufacturing direction A.

In all the embodiments, the mesh or grid-like layer 13 is essentially non-stretchable (the grid could be replaced with another sheet or web of essentially, i.e. at least substantially, non-stretch material) and this essentially prevents the crepe paper 9 from stretching, i.e.

stretching to any appreciable extent is prevented. In this respect, it is preferred that not more than 5% and preferably no more than about 2 or 3% stretching should occur at 1 kilonewton/metre force. This therefore gives stability to the whole underlay. The crepe paper 9, on the other hand, provides bulk, has a pleasant appearance, and is puncture resistant.

Obviously, the grid 13 can only be adhered to the crepe paper 9 where the fibres of the grid touch the peaks of the corrugations of the crepe paper with the adhesive.

There are advantages therefore in having a small mesh or grid size to increase the number of points of adherence.

However, because the grid is full of apertures, the polymeric material layer will also assist in adhering the grid to the crepe paper, since the polymeric material will tend to flow through the apertures and adhere directly to the crepe paper. Obviously, if these are too small, this will not occur. Preferably the grid comprises individual strands in the cross machine direction of between 4 and 0.3 per cm, and in the machine direction of between 2 and 0.3 per cm. Continuous filament glass of 340 d'Tex is a preferred weight for the strands but considerable variation will be apparent to those skilled in the art according to the number of strands in the machine and cross machine direction, and according to the strength properties required in a particular product.

It is envisaged that the mesh layer 9 and the crepe paper 13 could be inverted with respect to each other, but it is preferred that the crepe paper 9 be uppermost, since this has greater consumer appeal, and provides the necessary strength and resistance to damage, and allows the rubber to lock the mesh in place.

The release layer or facing 14 shown in Figure 3 is only a preferred feature. It may also be provided in the embodiments of Figures 1, 2 and 4.

One slight disadvantage with commercially available crepe paper is that, in use, it tends to rustle, due to the corrugations rubbing together. This "rustling" can be reduced by adding a softener to the paper, either at the pulp or at the wet creping stage. This could be a sugar derivative, or a starch or a plasticiser, such as PVA. This will also improve the adhesion of the mesh layer 13 (and of the rubber material) to the crepe paper. Alternatively, or additionally, the crepe paper could be coated on at least one side with an appropriate polymeric material, e.g. a plastic film could be laminated to the paper either before or after creping, or the finished crepe paper could be skimmed with a latex foam to fill the corrugations. This would give a leather like texture, stop rustling, and improve adhesion for the grid-like layer and rubber (polymeric) material.

Moreover, with respect to cost, the two components for making the laminate 7 are available at appropriate weights for substantially less than the cost of stitched crepe paper sold as TEXTRON.

Furthermore, since the crepe paper can be laminated with the mesh during its manufacture, there is negligible manufacturing cost above that of the mesh.

Instead of forming the grid 13 with uniformly distributed yarns extending both lengthwise and across the grid, it is desirable in certain circumstances to concentrate the yarns extending longitudinally of the grid or mesh to edge regions and spaced apart central regions.

A concentration of yarns at the edges stops transverse and hence longitudinal tearing and the concentrations of yarns generally ensure that the grid or mesh provides sufficient strength to the underlay to ensure that the underlay remains intact during the manufacturing process. In a preferred construction, two wide bands of longitudinally extending yarns are provided in the longitudinal edge region of the mesh during its manufacture and two slightly less wide bands in the central region approximately one-third and two-thirds of the way across the width of the material.

Normally the crepe paper would be combined with the grid using a PVA adhesive, with the corrugations in the crepe paper extending transversely across the length of the grid; hence it is important that the longitudinally extending yarns in the grid do not appreciably stretch so as at least substantially to prevent stretching of the crepe paper. In a preferred construction, the longitudinally extending yarns in the grid are formed of polyester and are relatively closely spaced, whereas the yarns extending across the grid (i.e. transversely during manufacture) are formed of glass fibre. It is relatively easy to provide large numbers of yarns extending lengthwise of the grid during the manufacturing process, but far more difficult and hence expensive to provide large numbers of transversely extending yarns; hence, stronger glass fibre yarns are preferred as the transversely extending yarns which, due to their strength, can be relatively more widely spaced than the longitudinally extending yarns. If the backing produced by the thus formed grid or mesh reinforced crepe paper is to be used with a corrugated foam or waffle style foam underlay, then it is important to have a large number of yarns extending lengthwise of the grid or mesh material to support the waffles or corrugations.

Two examples of carpet underlay according to the present invention are now described below in greater detail: Example 1 A flat sponge rubber carpet underlay was manufactured which had a finished product weight of 2.7 kg per sq.metre and an overall thickness of 6mm. The backing for the underlay was made with wet creped paper containing 25% recycled material with a finished crepe weight of 110 grms per sq.metre and a starting base weight of 59 grms per sq.metre. Crepe paper was then adhered to the CRENETTE mesh during its manufacture (using a PVA adhesive).The CRENETTE mesh consisted of 340 d'Tex continuous filament glass fibres electrical grid (9 microns) with 28 turns per metre Z twist, in which 2 bands were provided down each edge of the CRENETTE mesh l0cms wide where there were 3 threads per cm width and where there were another 2 bands each Scms wide approximately one-third and two-thirds respectively across the width of the mesh. These central region bands also had a thread density of 3 threads per cm width, with the remaining part having a thread density of 0.8 threads per cm width extending lengthwise in the manufacturing direction of the mesh. In the transverse direction identical glass fibre threads having a thread density of .8 threads per cm (in the lengthwise direction) were used.

During manufacture of the underlay the backing provided excellent resistance to tear and breakage and also resisted manufacturing stresses.

The finished product had excellent handling and consumer appeal and when tested on three different accelerated wear machines performed very satisfactorily.

One test was the "castor chair" test (DIN 54324: 1988) and for 5000 cycles and using 7 gauge stitched TEXTRON with a total weight of 112 grms per metre as a control. The two samples were adhered to a wooden base and no damage showed on either the control sample or on the sample made in accordance with the invention.

The second accelerated wear test was the "TRE-TRADw test (draft European Standard PREN 1963) and after 10,000 cycles against the same control the samples behaved comparatively and there was no damage to either.

In the third accelerated wear test (the HEXAPOD test: British Standard 6659), each sample would normally be subjected to 12,000 cycles, which is equivalent to 4 years of wear on a domestic carpet. In our test the two samples were subjected to 24,000 cycles and the sample made in accordance with the invention performed slightly better than the control sample. Whereas the sample according to the invention appeared to be unaffected by the tests, the control sample had a wrinkled surface and there were signs of perforations in the paper component of the TEXTRON material in the locality of the stitching.

Example 2.

A sponge rubber corrugated or waffle underlay was made having an overall finished weight of 2.4 kg per sq.metre and an overall thickness of 8mm. The backing used was dry creped paper with a base weight of approximately 70 grms per sq.metre creped up to 83 grms per sq.metre and to which was applied an all-polyester CRENETTE which had a yarn of 167 d'Tex in the machine direction and a yarn of 140 d'Tex across the manufacturing machine direction. The threads were arranged at a density of 3 threads per cm running in the machine direction and 0.8 threads per cm running across the machine direction and this CRENETTE material was adhered to the creped paper using a PVA adhesive. The backing material was combined with the waffle underlay in a traditional manufacturing process without any difficulty and gave excellent handling and consumer appeal.

The sample underlay according to the invention was subject to the "castor chair" test with the sample being attached to a wooden support just around its periphery with staples approximately every Scms. A control sample attached to a wooden support in the same manner was 3.3 gauge TEXTRON (3.3 gauge refers to the frequency of stitching down the length) which had a finished weight of 90 grms per sq.metre.

The underlay according to the invention performed rather better than the control sample backed with TEXTRON on a 5000 cycle test in that the TEXTRON backed sample showed some signs of breakage in the paper component around the stitching, whereas there were no such signs in the sample made according to the invention.

It will be understood that many variations from the embodiments described with reference to the drawings are possible. Both the crepe paper and the mesh layer or nonstretch flat paper can be of any appropriate weight and the degree of creping of the crepe paper can be varied, and the finish and other characteristics can be varied. Virgin pulp, recycled pulp or modified conventional paper formulations containing, for example, polypropylene fibres to enhance tensile and tear strength, can be used for the crepe paper and the grid or mesh layer can be of various different constructions and materials. One good alternative to a CRENETTE mesh is a LINOWEAVE fabric, which is similar to CRENETTE mesh but the wefts are woven into the warps.

The crepe paper can be replaced by other paper types similarly treated to texturise, "bulk-up" and improve puncture resistance, e.g. by embossing, punching, grooving, etc., and the term "crepe" paper should be interpreted accordingly. Furthermore, a wide variety of adhesives will be acceptable. These include starch-based products widely used within the paper industry, thermoplastic types, and a variety of resins from natural sources. It is also envisaged that the grid or mesh layer could be replaced by other types of flat sheet or web-like material. Of course, in the embodiments described with reference to the drawings, the various resiliently deformable polymeric materials could be interchanged. It is also envisaged that a sheet of heat sensitive adhesive could be used to laminate the crepe paper to the mesh (and also to the polymeric material), or that the fibres of the mesh could be bi-component fibres, with the central portion providing reinforcement and an outer sheath being a low melting point binder or adhesive material. These alternatives may, however, be too expensive. It is even envisaged that the mesh material might be laminated to the crepe paper "on the bias", i.e.

with neither warp nor weft threads extending truly transversely or longitudinally, or in a "sinuous" manner.

This again may be too expensive.

Claims

CLAIMS:

1. A backing for sponge rubber or like carpet underlay comprising a layer of crepe paper laminated to a layer of essentially non-stretch material.

2. A backing according to claim 1, wherein the two layers are laminated using an adhesive of the PVA type.

3. A backing according to claim 1 or 2, wherein the nonstretch material is in the form of a grid or mesh.

4. A backing according to claim 3, wherein the grid or mesh contains glass fibres.

5. A backing according to claim 3 or 4, wherein the grid or mesh contains polyester fibres.

6. A backing according to any one of claims 3-5, wherein the yarns per cm in one direction are between 2 and 0.3 and the yarns per cm in the other direction normal to the one direction are between 4 and 0.3.

7. A backing according to any one of the preceding claims, wherein the creped paper contains between 20% and 50% of recycled pulp, the remainder being virgin pulp.

8. A backing according to claim 1, and substantially as hereinbefore described.

9. A carpet underlay comprising a web of rubber or resilient polymeric material having on its upper surface a backing as claimed in any one of claims 1-8.

10. A carpet underlay according to claim 9, wherein the rubber material is formed from ground rubber crumbs or granules, recycled from rubber tyres or other sources, supported in a resin binder material.

11. A carpet underlay according to claim 9, wherein the rubber material is sponge rubber.

12. A carpet underlay according to claim 9, wherein the rubber material is latex foam.

13. A carpet underlay according to claim 9, in which the resilient polymeric material is a polyurethane foam.

14. A carpet underlay according to claim 11, 12 or 13, wherein the sponge rubber, latex foam or polyurethane foam is corrugated or convoluted.

15. A carpet underlay according to claim 11, 12 or 13, wherein the rubber or polyurethane foam material is ribbed or grooved.

16. A carpet underlay according to claim 14, wherein, when the rubber material is sponge rubber, the unblown rubber compound has the backing adhered to its upper surface, prior to or while being passed through a heating device, e.g. an oven, and to the solid compound being blown to form it into a sponge, followed by curing.

17. A carpet underlay according to claim 16, wherein the sponge material is passed through the heating device on a chain mat so that it becomes convoluted or corrugated.

18. A carpet underlay according to claim 14, wherein, if the rubber material is latex foam, the foam material is spread on the backing and when a ribbed, grooved or wavy surface is desired, the foam material is spread flat on the backing with a contoured comb-like knife, which may be moved to and fro to give a wave-like form to the grooves or waves.

19. A carpet underlay according to any one of claims 918, wherein a facing on the side thereof opposite the backing is provided to give release properties.

20. A carpet underlay comprising a sheet of resiliently deformable polymeric material having on its upper face a backing formed of crepe paper or the like, to which is adhered a grid or mesh of essentially non-stretchable material.

21. A carpet underlay according to claim 20, wherein the grid or mesh is formed of a textile material.

22. A carpet underlay according to claim 21, wherein glass fibres are contained in the textile material.

23. A carpet underlay according to claim 20 or 21, wherein polyester fibres are contained in the textile material.

24. A carpet underlay substantially as hereinbefore described with reference to figure 1 or Figure 2 or Figure 3 or Figure 4 of the accompanying drawings.