GB2300593A

GB2300593A - Carpet underlay

Info

Publication number: GB2300593A
Application number: GB9509673A
Authority: GB
Inventors: Travis Moore
Original assignee: Gates
Current assignee: Gates
Priority date: 1995-05-12
Filing date: 1995-05-12
Publication date: 1996-11-13
Anticipated expiration: 2015-05-12
Also published as: GB2300593B; GB9509673D0

Abstract

A carpet underlay comprises a sheet of resiliently deformable polymeric material (3) having an upper backing layer, e.g. of crepe paper (9) and a grid or mesh (12) of substantially non-stretch, preferably textile material incorporated therein, preferably on its lower face. A release layer (5) may be provided on the lower face of the underlay. The grid prevents stretching of the polymeric material (2 or 3), and means that stitching does not need to be incorporated in the crepe paper. The polymeric material can be formed from rubber crumb incorporated in a binder, sponge rubber, latex foam, or polyurethane foam, and is preferably flat, but could be corrugated, ribbed, grooved, or dimpled.

Description

CARPET VNDERLAY This invention relates to carpet underlay. The invention is particularly concerned with carpet underlay primarily for contract use which incorporates a resilient layer of sponge rubber material, or latex foam and/or reconstituted crumb rubber, located between a backing, which is located on the upper face of the resilient layer, and preferably a release layer on the underside of the resilient layer, known as a facing.

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, especially since the resilient layer is often ribbed, convoluted or corrugated.

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 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 is slow and the yarn is costly when compared to the crepe paper part of the material.

The release layer or facing is usually formed of a very light non-woven, usually spun-bonded polyester textile of the order of 20gms per sq.metre weight. The function of this facing textile layer is to ensure release from the substrate floor when at the end of the installation's working life, the carpet/underlay is peeled up from the adhesive used to maintain its position on the floor. It achieves this, although usually sacrificially disintegrating. The release layer is provided to prevent break up of the sponge rubber. This is a possibility which must be avoided, since if rubber adheres to the floor, its removal is a costly and time-consuming task. Traces of polyester fibre remaining on the floor present no difficulties, since new adhesive can be applied directly over it.

Although the use of spun-bonded polyester on the underside, and stitched creped paper on the upper side, is now established through several years of use, there are some disadvantages. One is in the manufacturing process for the underlay. Since the polyester release layer is very light (dictated by economics), when it is applied to the resilient rubber layer in the production process, elaborate precautions must be taken to avoid creasing, and even with these, high scrap rates may be experienced. Another disadvantage is that on occasions the spun bond polyester fails to disintegrate properly and provide acceptable release at the end of the installation's use, so that some rubber still adheres, requiring remedial work. A further disadvantage is the high cost of the upper backing layer of stitched crepe paper.

These disadvantages are overcome in the present invention in which, according to the broadest aspect, 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 incorporating therein, e.g. on its lower facem a grid or mesh of textile material, which is preferably nonstretchable.

Preferably, the textile material is formed of lightweight glass fibres, having a similar cross-section to the fibres of the known spun-bonded polyester textile fibres of the release layer. However, the glass fibres are very much stronger, and thus perform not only the task of acting as a release layer, but also, being of a non-stretch character, 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 glass fibres.

In some embodiments, it is preferred that the known spun-bonded polyester fibre release layer be provided as well as the grid or mesh. This assists in release from adherence to a floor, whereas the grid also ensures that traces of the resiliently deformable polymeric layer are not left on the floor.

The polymeric material may be formed from sponge rubber, rubber crumb or granules, recycled from rubber tyres or other sources, supported in a resin, latex, polyurethane, or other binder material, or a polyurethane, either in the form of a slab slit from virgin slab stock, or in reconstituted form (e.g. reconstituted chips bound with a binder, e.g. of polyurethane) or of similar construction, but is preferably sponge rubber or latex foam. Normally, both surfaces of the polymeric material would be substantially flat, although it is envisaged at least one may be corrugated or convoluted, ribbed or grooved.

In the case of sponge rubber, a sheet of uncured unblown rubber compound is callendered, and is then laid upon a support surface, or upon a facing layer on said surface, prior to it being passed through a heating device, e.g. an oven. A backing, e.g. of crepe paper, is applied to the top surface, either on entry into the oven, or part way down the oven. In the oven, the solid (but viscoelastic) compound is blown and cured to form the finished sponge product. This is then removed from the oven and wound up.

If the sponge material is to be convoluted or corrugated, it is preferably passed through the heating device on a chain mat. Blowing occurs in the oven in a generally known manner.

Instead of supporting the viscoelastic unblown, uncured rubber compound on a chain mat, it is envisaged that the mat could be replaced by the grid or mesh, and this could then be used to support and transport the material through the heating device (e.g. oven). For this purpose, the grid or mesh could be in a long (indeterminate) length, and be advanced through the heating device with the aid of a stentor, which would grip the edges of the grid or mesh, and hold it taut. The viscoelastic polymeric material would flow into the apertures in the grid or mesh, prior to curing, and thus leave a pattern on the surface of the final cured, blown sponge rubber. The backing could be applied to the other surface, as described above.

By altering the weave of the grid or mesh, so the pattern on the underside of the final sponge rubber underlay could be selected. It is envisaged that a different density of warp could be provided in the grid or mesh at the centre of the grid or mesh from that at the longitudinal edges.

Preferably, the edges should be stronger than the central region, to assist in transporting the product through the heating device. It is envisaged that dense edge regions could act as selvedges, for gripping by the stentor, and which would not be covered with the unblown, uncured polymeric compound, and which could subsequently be trimmed off and recycled.

In the case of latex foam, a liquid material (latex), which is whipped up to generate gas bubbles and then spread on the backing, e.g. crepe paper, is then fed into an oven generally in known manner. 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 grid or mesh is applied to the latex material either as it moves into the oven, or after it has moved partly through the oven, and is partially cured.

The mesh or grid can be applied to the polymeric material on its own, or with the release layer. While it is possible to apply these two layers separately, it is preferred to laminate the two webs together beforehand.

This can be done either during manufacture of the grid or mesh, immediately following the gluing together of the wefts and webs, or in a subsequent combining operation, using adhesive. By combining the grid or mesh with the known release layer, the latter becomes easier to handle.

The creped paper on its own (i.e. 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. However, by incorporating the grid or mesh in the manufacturing process, stretching is substantially reduced.

Several alternative embodiments of underlay according to the present invention are now described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view, with parts broken away, of a flat sponge rubber underlay according to a first embodiment of the invention; FIGURE 2 is a section through the underlay shown in Figure 1; and FIGURE 3 is a section through a flat underlay formed of rubber crumb bonded with latex according to a second 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 comprises a flat sheet of sponge rubber 3 having a plain lower surface 5, and a backing 9 in the form of crepe paper attached to its upper surface. On the underside of the flat resilient layer 3 is a facing 15 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 15; when the underlay is pulled up, part of the facing 15 will remain adhered to the floor, and part to the underside of the flat sheet 2 or 3, and very little, if any, of the rubber sheet 2 or 3 will remain adhered to the floor.

Between the facing 15 and the resilient sheet layer 2 or 3, a grid or mesh 12 of textile material is provided.

(This could be provided instead of the facing or release layer 15). This grid 12 is woven from non-stretch fibres, such as glass fibre, and the grid pattern is such that the rectangular (they could have other shapes) apertures are of 2-10mm square. The grid is much stronger than the spunbonded facing 15, and it ensures that only very small quantities of the resilient sheet 2 or 3 can be left on a floor when the underlay has to be removed for replacement.

Furthermore, because of its non-stretch properties, when it has been bonded to the resilient sheet 2 or 3, it prevents stretching, and this in turn means that the crepe paper 9 need not have stitching in it to stop or resist stretching.

This results in a considerable cost saving. However, the crepe paper is required to provide bulk, puncture resistance, and a pleasant appearance.

The underlay shown in Figures 1 and 2 is manufactured by taking a pre-laminated sheet of grid or mesh 12 and facing 15, and laying the facing on a chain or other type of endless support. A calendered sheet of uncured rubber incorporating a blowing agent therein is then laid onto the laminate 12, 15, and shortly prior to the rubber/laminate being fed into an oven, the crepe paper 9 is applied to the top surface. On passing through the oven, the various layers adhere to each other, and the rubber is converted into sponge rubber and cured.

Instead of being formed with a sponge rubber layer 3, the underlay could incorporate a latex foam layer. This would be manufactured by laying a sheet of crepe paper on an endless support, then metering a whipped up latex foam onto the paper layer, and subsequently passing the product through an oven. The grid or mesh layer 12 would be applied on entry of the product into the oven, or while the product is in the oven.

In the alternative embodiment shown in Figure 3, the underlay comprises a resiliently deformable (resilient) polymeric material layer 2 made up of ground-up rubber crumb or particles 6 bonded together with latex, resin, polyurethane, or other binder (not shown).

It will be understood that many variations from the embodiments described with reference to the drawings are possible. Both the crepe paper and the release layer and grid can be of any appropriate weight and the degree of creping 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. 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 glass and resins from natural sources.

It is also envisaged that the polymeric material could be polyurethane, in sheet form cut from virgin slab stock, or reconstituted.

In the illustrated embodiments, the resilient polymeric material layers 2 and 3 are substantially flat, although the upper faces thereof are shown as having "flowed" into the corrugations of the crepe paper 9.

Whether or not this occurs depends on the state of the polymeric material when it is laid on the paper (or vice versa). Obviously, latex foam laid onto crepe paper 9 will flow into the corrugations. However, if the paper 9 is laid onto the callendered rubber 3 after it is partially cured in the oven, only the tips of the corrugations will adhere to the rubber. However, if the paper 9 is applied to the rubber when the rubber is completely uncured, outside the oven, the product will cook as shown in Figures 1 and 2.

It is envisaged that instead of the polymeric material layer 2 or 3 being substantially flat, it could be convoluted, ribbed or otherwise contoured. This could be achieved using a known process although it is envisaged that it would be difficult to achieve in view of the presence of the web or mesh 12. However, if the facing layer 15 (of spun bonded polyester) was omitted, the lower face of the underlay could be given a dimpled effect by allowing the polymeric material partially to flow through the mesh 12, and designing the endless support means, e.g. chain, for feeding the product into the oven, accordingly.

Instead of using a chain to support the polymeric material, the mesh itself could be used for this purpose.

This could be achieved through the oven using a stentor, and, by selecting various different mesh or grid constructions, different contours or patterns could be formed on the underside of the underlay, as described earlier herein. Basically, the grid or mesh would end up within the underlay, as a result of the uncured polymeric material which eventually forms the sponge rubber flowing partially through the apertures in the grid or mesh.

It is also envisaged that the grid or mesh 12, instead of being on the underface of the polymeric layer, or within it, could be located between the crepe paper backing 9 and the polymeric layer. This would then allow the bottom face of the polymeric layer to be ribbed, corrugated, convoluted or otherwise formed with a particular pattern.

Claims

CLAIMS:

1. 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, and incorporating therein a grid or mesh of generally non-stretchable material.

2. A carpet underlay according to claim 1, wherein the grid or mesh is on the lower face of the polymeric material.

3. A carpet underlay according to claim 1 or 2, wherein the grid or mesh is formed of a textile material.

4. A carpet underlay according to claim 3, wherein the textile material is formed of lightweight glass fibres.

5. A carpet underlay according to any one of claims 14, wherein a spun-bonded polyester fibre release layer is provided on the lower face thereof.

6. A carpet underlay according to any one of claims 15, wherein the polymeric material is sponge rubber.

7. A carpet underlay according to any one of claims 15, wherein the polymeric material is formed from ground rubber crumb or granules, supported in a resin, latex, polyurethane, or other binder material.

8. A carpet underlay according to any one of claims 15, wherein the polymeric material is a polyurethane foam material.

9. A carpet underlay according to claim 8, wherein the polyurethane foam material is formed from a slab slit from virgin stock.

10. A carpet underlay according to claim 8, wherein the polyurethane foam material is formed from reconstituted chips bound with a binder.

11. A carpet underlay according to any one of claims 15, wherein the polymeric material is latex foam.

12. A carpet underlay according to any one of the preceding claims, wherein a face thereof is corrugated, convoluted, ribbed, grooved, dimpled or formed with another pattern.

13. A carpet underlay substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.