GB2105612A - Surface covering material and process for its manufacture - Google Patents

Abstract

The dimensional stability of a surface covering material is improved by incorporating in a support layer fibres of length 100 mu m to 250 mu m, the fibres preferably being glass. The material may be one comprising a thermoplastic layer reinforced by the fibres having a foamed plastic layer on one surface.

Description

SPECIFICATION Surface covering material and process for its manufacture This invention relates to a surface covering material, and to a process for its manufacture, especially a covering material comprising a foamed thermoplastic composition. More especially, it relates to such a material suitable as a floor covering, in any form, for example as sheet material or in tile form, and especially such a material carrying a decorative pattern, with or without a surface texture, e.g.

embossing.

There has been a continuous effort over many years in the industry to improve the dimensional stability of surface covering materials so that once cut to a desired size at the time of being laid they neither shrink nor expand, or do so to an insignificant extent, nor curl at edges. Such dimensional stability can often be obtained only at the expense of flexibility. Lack of flexibility makes laying difficult, especially in awkward corners. It also necessitates greater care in ensuring planarity of the surface to be covered, since for example irregularities in heights of floor boards will cause cracking when a stiff covering material laid over them is walked on.

Foamed thermoplastic surface covering materials have been provided with a variety of backing or support layers, which may be provided, on what in a floor covering material is the underside, with a further layer, which may or may not be a foamed layer. As support layers that have been used or proposed in the past, there may be mentioned woven and non-woven fabrics, felt, asbestos, asphalt, and glass fibre mats. These materials may be impregnated or coated with resin. A commonly used support layer is wet laid asbestos felt, formed by draining water from a slurry of asbestos fibres and binder in water. Asbestos is known, however, to constitute a health hazard, and numerous attempts to replace it with other materials have been made.Where glass fibre has been proposed, as for example in British Patent Specification No. 1,532,621, it has been used in the form of a mat, especially a nonwoven mat of fibre bonded with a resin binder.

The present invention is based on the observation that a thermoplastic layer may be used as a support layer in a surface covering material if fibres having lengths in a particular range are dispersed therein.

The present invention accordingly provides a surface covering material comprising a thermoplastic support layer having fibres dispersed therein, the fibres having lengths within the range of from 100 Mm to 250 ,um, the support layer carrying a foamed plastic layer on a first surface thereof.

The invention also provides a method of improving the dimensional stability of a surface covering material, which comprises dispersing fibres of length within the range of from 100 ym to 250 ym at least in the material that forms a support layer thereof. The fibres are advantageously glass fibres, although other fibres, especially polymeric fibres, for example polypropylene or polyester fibres, may also be used.

The use in the present invention of a support layer having such fibres dispersed therein, in practice as uniformly as possible, is in contrast to those prior art proposals in which, for example, a preformed bonded fibre mat is employed.

The fibre-reinforced layer may be foamed or, preferably, unfoamed. More than one layer in a surface covering material may be reinforced.

The various layers may contain any suitable ingredients in the formulations which may, apart from their fibre content, be any desired formulation, many of which are conventional. For example, the formulation for a foamable layer may contain a thermoplastic resin, usually of polyvinyl chloride, or a vinyl chloride copolymer, of paste grade, and also if desired a similar resin of extender grade, plasticizer', blowing agent and, if desired, the usual additives, e.g., activator, pigment, filler and stabilizer. The formulation for a support layer would be similar apart from the omission of the blowing agent and any activator for the blowing agent. Formulations may be prepared and applied in any suitable manner, many of which are conventionally available.Convenient mixing arrangements are in a low shear, low speed mixer, fibres being added at the same time as resins. Application, e.g., by reverse roll coater, is also conventional. The proportion of fibre, based on the total weight of the layer composition, will vary depending on the nature of the layer. For an unfoamed support layer, it is desirably at least 10%, and advantageously at least 12%. A preferred range is from 14% to 20%. For a foamed support layer the proportions may be within the range of from 5 to 10%, advantageously about 6.5%.

Lower levels of fibre reinforcement may be used if other layers are being reinforced, e.g. up to 5%, advantageously about 3% for a clear wear layer, all percentages being based on the total weight of the composition.

The fibres are, as indicated above, advantageously glass fibres. For glass fibres, lengths are advantageously in the range of 1 50 ym to 200 ym, especially about 190 ym. Such lengths may be conveniently achieved by milling, or chopping. Mixtures of fibres of two or more different lengths may be used.

Fibre diameters are advantageously in the range 8 Mm to 20 ym, preferably 10 ym to 1 5 ym, for example 12 ym.

As will be indicated in more detail in Example 1 below, especially with reference to Formulation 2, a milled glass fibre having the properties given under the designation ECL 9 is a preferred material. A second preferred material, which is available under the designation EMF 1691, has a nominal fibre length of 1 50 ,um, and a nominal fibre diameter of 12 ,um. It is silane-treated fibre.

In one preferred embodiment, the present invention provides a surface covering material comprising an unfoamed thermoplastic support layer having reinforcing fibres dispersed therein, the support layers carrying a foamed thermoplastic layer at least on a first surface thereof and also if desired on a second surface thereof, the foamed layer on the first surface, if desired, carrying an advantageously clear layer. If desired the wear layer and either or both of the foamed layers also have reinforcing fibres dispersed therein. The surface of the foamed layer carrying the wear layer may be printed with a decorative pattern. The thermoplastic copolymer.

One form of material constructed in accordance with the invention, and a process for its manufacture, will now be described, by way of example only with reference to the accompanying drawing, the sole figure of which is a cross section through a surface covering material.

Referring now to the drawing, there is shown a laminate on a temporary carrier 1. In contact with one surface of the carrier 1 is a foamed polyvinyl chloride layer 2. Above this is an unfoamed polyvinyl chloride support layer 3 having glass fibres 4 dispersed therein. Above the layer 3 is a further foamed polyvinyl chloride layer 5 having a printed design 6 in its upper surface. Finally, on the printed surface of the layer is a clear wear layer 7.

The layers are applied in the form of plastisols foamable where required, in the order listed, the first layer 2 being applied to one surface of the carrier 1 and the remaining layers to the free surface of the preceding layer, by reverse roll coating or knife over roll coating, each layer being gelled before application of the next layer, the layer 5 being gelled before printing. Finally, the whole structure was heated sufficiently to fuse the wear layer and expand the foamable layers, and the release carrier stripped off.

Suitable thicknesses, in mm, for the various layers of the preferred embodiment are as follows: Range Preferred Layer 2 0.5 to 3.0 1.00 Layer3 0.1 to 0.6 0.30 Layer 5 0.5 to 1.5 0.65 Layer7 0.1 to 0.35 0.25 As indicated above, any of the layers 2, 5 and 7 may also be reinforced by dispersed fibres.

The following examples illustrate the invention: EXAMPLE 1 EXAMPLE 1 The following plastisol formulation was prepared: FORMULATION 1 Parts by Weight Paste dispersion grade PVC resin 50 (Quirvil 268) Paste dispersion grade PVC resin 30 (Vestolit B7021) Extender grade PVC resin (Lucovyl PB8015) 20 Dioctyl phthalate (plasticizer) 27.5 Buryl Benzylphthalate/dodecyl benzene 26.2 mixture (plasticizer) Octyl epoxy tallate (Lankroflex ED-6) 1.5 (plasticizer) Zinc neodecanoate activator 0.8 Barium neodecanoate activator 0.3 Blowing agent ABFA coated grade 1.4 (Ficel 23/3) Titanium dioxide pigment 4.0 Mineral spirit solvent 1.2 Barium sulphate (SP Barytes) 52.8 Silica Filler (Aerosil 200V) 1.4 The formulation was prepared as follows:: A portion of the plasticizers, together with the activators, resins and blowing agents were charged into a slow speed, low shear ribbon mixer and blended with the titanium dioxide pigment until a homogeneous mix was obtained. The barium sulphate filler was then added and the mix agitated for a periodof fifteen minutes before the remaining plasticizer was included. Mixing then took place until a homogeneous paste was achieved.

This material was then coated onto a release paper, or a release coated carrier felt, using either a reverse roll coater or a knife over roll coater and gelled by heating to 1 40CC. To the free surface of this gelled layer was applied the following composition: FORMULATION 2 Parts by Weight Paste dispersion grade PVC resin 40 (Vinnol E79-CS) Paste dispersion grade PVC resin 40 (Lucovyl PB1702) Extender grade PVC resin (Lucovyl PB8015) 20 Dioctyl phthalate 14.7 Di isodecyl adipate (plasticizer) 1 5.2 2,2,4-trimethyl 1,3-pentadiol di-isobutyrate 13.9 (Texanol isobutyrate) (Eastman Kodak TXIB) (plasticizer) Octyl epoxy tallate (Lancroflex ED-6) 3 Barium/Zinc stabilizer (Ciba-Geigy BZ505) 2 Calcium Carbonate (Steetley 310) 20 Titanium dioxide pigment 4 Mineral spirits solvent 1.2 Milled Glass Fibre ECL9 30 ECL9 fibre is produced by hammer milling continuous filament glass fibres. The fibre length is nominally 1 90 jim, the fibre diameter nominally 12 jim and the bulk modulus 295 kg/m3, measured by BS 2972:1975 Section 3 (13-3b). Mixing and preparation of this formulation was carried out in the following manner: A portion of the plasticizers together with all the resins, pigments, milled glass fibre and stabilizers were charged into a low speed, low shear mixer and blended to a paste. The calcium carbonate filler was then added and mixing took place until a homogeneous blend was obtained. The remaining plasticizer was added and mixing continued until a homogeneous paste was achieved.

This fibre reinforced plastisol was applied to the upper surface of the previously gelled sheet using a reverse roll coater or a knife over roll coater and gelled at 1 400C to give a film thickness of approximately 0.35 mm. To the upper (free) surface of this second gelled layer was applied a coating of the following compositions: FORMULATION 3 Parts by Weight Dispersion grade PVC resin 69.1 Extender grade PVC resin 30.9 Dioctyl phthalate 28.6 Butylbenzylphthalate/dodecyl benzene mixture 26.1 Octyl epoxy tallate 1.5 Blowing agent ABFA coated grade 2.7 Zinc neodecanoate activator 1.8 Barium neodecanoate activator 0.6 Titanium dioxide pigment 4.0 Calcium Carbonate 25.0 This plastisol was prepared in a low speed, low shear ribbon mixer in a similar manner to Formulations 1 and 2 and mixed until a homogeneous paste resulted.

This plastisol coating was applied to the free surface of the previously applied layer using a reverse roll or knife over roll coater and gelled at 1 400C to give a fused thickness of approximately 0.22 mm.

The resultant triple layer of gelled sheet carried on a release paper substrate was printed with a suitable design before the final clear PVC wear layer was applied and fused.

This clear PVC plastisol was composed of the following formulation: FORMULATION 4 Parts by Weight Dispersion grade PVC resin 80 Extender grade PVC resin 20 Dioctyl phthalate 19 Butyl benzylphthalate/dodecyl benzene mixture 1 7 Octyl epoxy tallate Texanol isobutyrate 17 Barium-Zinc stabilizer compound 4 Triethylene Glycol 2 Mixing of this plastisol was carried out in a similar manner to that used on Formulations 1, 2 and 3, i.e., using a low speed, low shear ribbon mixer and proceeding until the desired dispersion was achieved.

The wear layer was applied using either a reverse roll or knife coater to the printed surface of the previously gelled coating. The complete structure was then heated at 1 950C for a period of two minutes to Xuse the clear-coat plastisol and expand the foam gell layers. The resulting structure, on discarding of the!release paper, is suitable for use as a PVC cushioned floor covering.

The product is designed to function as a floor covering utilizing loose fibre reinforcement as a relacement for the usual felt, glass fibre mat or rockwool substrates, currently employed in such materials. The dimensions of the foam layers may of course vary in order to provide a range of finished pry ducts suitable for end use as domestic and contract floor-coverings, retaining the characteristics and qualities normally associated with such material.

Tests conducted on structures produced in the manner described in Example 1 revealed that the product performed to a standard very close to that of a solid substrate control structure. The use of reinforcing fibre in a thermoplastic matrix in place of solid carrier achieves full flexibility and good dimensional stability.

Tests conducted on material produced in the same manner as described in Example 1, but without reinforcing fibre, exhibited poor dimensional stability characteristics when tested.

EXAMPLE 2 The method described in Example 1 was repeated using twenty five parts by weight of reinforcing milled glass fibre ECL9, instead of thirty parts and tests conducted on the resultant material. These tests revealed that the product performed with slightly less dimensional stability than that exhibited by Example 1. The conclusion drawn therefrom was that a level of fibre reinforcement equal to thirty parts by weight per hundred parts of polymer was preferable when using milled glass fibre of 1 90 jim length.

EXAMPLE 3 Example 1 was repeated using ten parts by weight of reinforcing glass fibre and the resultant product tested in the prescribed manner. These tests revealed that the material performed slightly better than an un-reinforced structure tested at the same time.

EXAMPLE 4 Example 1 was repeated, up to the application of the printed design on the upper surface of the gelled sheet (Formulation 3), and then the following plastisol wear layer was applied.

FORMULATION 5 Parts by Weight Paste dispersion grade PVC resin 80 Extender grade PVC resin 20 Dioctyl phthalate 19 Butyl benzylphthalate/dodecyl benzene mixture 1 7 Octyl epoxy tallate 3 Texanol isobutyrate 17 Barium/Zinc activator compound 4 Triethylene Glycol 2 Milled glass fibre ECL9 5 This plastisol formulation was prepared as follows: A portion of the plasticizers and all the resin, reinforcing fibres and stabilizers were charged into a slow speed, low shear mixer and blended into a paste. The remaining plasticizer and liquids were then added and mixing continued until the required dispersion was achieved.

This resultant reinforced layer was then applied to the printed surface using a reverse roll coater or knife over roll coater and the whole structure heated at 1 950C for a period of two minutes to fuse the wear layer and expand the gelled foam layers. The release paper carrier was then removed and the resultant structure was subjected to tests.

The object of this experiment was to determine the effect upon the clear PVC wear layer of the addition of milled glass fibre reinforcement.

EXAMPLE 5 FORMULATION 6 Parts by Weight Paste dispersion grade PVC resin 80 Extender grade PVC resin 20 Dioctyl phthalate 27.5 Butyl benzylphthalate/dodecyl benzene mixture 26.2 Octyl epoxy tallate 1.5 Zinc neodecanoate activator 0.8 Barium neodecanoate activator 0.3 Blowing agent ABFA coated grade 1.4 Titanium dioxide pigment 4.0 Mineral spirits solvent 1.2 Barium sulphate 52.8 Silica 1.4 Milled glass fibre 190 jim length 1 5 This formulation was prepared in the following manner, using a low speed, low shear ribbon mixer: A portion of the plasticizer was charged into the mixer together with all the resins, pigments, activators and reinforcing fibres and mixing took place until a homogeneous blend was achieved. The barium sulphate was then added and mixing continued until this was adequately dispersed in the blend.

The remaining plasticizer was then added and mixing continued until a homgeneous paste resulted.

This plastisol was then used to prepare structures identical to those detailed in Example 1 , with Formulation 6 replacing Formulation 1.

The overall dimensions of the product used for test purposes in all Examples (1 to 5) are given above; however, adjustment may be made to any individual layer, or to all layers, in order to impart the desired performance characteristics to the finished material designed for use as a cushioned floor covering.

Claims (8)

1. A method of improving the dimensional stability of a surface covering material, which comprises dispersing fibres of length within the range of from 100 jim to 250 jim in at least the material that forms a support layer thereof.

2. A surface covering material comprising a thermoplastic support layer having fibres of length within the range of from 100 jim to 250 jim dispersed therein, the support layer carrying a foamed thermoplastic layer on a first surface thereof.

3. A material as claimed in claim 2, wherein the layer on the surface of the foamed layer remote from the carrier layer has a decorative pattern thereon.

4. A material as claimed in claim 2 or claim 3, wherein the foamed thermoplastic layer carries a clear wear layer on the surface remote from the carrier layer.

5. A material as claimed in any one of claims 2 to 4, wherein a second surface of the carrier layer carries a foamed thermoplastic layer.

6. A material as claimed in any one of claims 2 to 5, wherein the fibres are glass fibres.

7. A material as claimed in claim 2, substantially as described in any one of the Examples herein.

8. A process for the manufacture of a surface covering material, which comprises forming a dispersion of fibres of length within the range of from 100 jim to 250 Mm in the material that forms a support layer thereof.