WO1994021721A1

WO1994021721A1 - Floor coverings

Info

Publication number: WO1994021721A1
Application number: PCT/GB1994/000587
Authority: WO
Inventors: Gary John Wilson; Ivor Charles Harwood
Original assignee: Amtico Co Ltd
Current assignee: Amtico Co Ltd
Priority date: 1993-03-25
Filing date: 1994-03-22
Publication date: 1994-09-29
Anticipated expiration: 1995-09-25
Also published as: GB9306187D0; JPH08512097A; EP0690888A1

Abstract

Resilient floor coverings are disclosed whose wear layer consists of a plasticised acrylic polymer composition which contains essentially no chlorine or bromine. The composition may contain 25 to 65 parts by weight plasticiser per 100 parts acrylic polymer. The composition may additionally contain up to 15 parts by weight of a thermoplastic polymer having urethane groups in its backbone per 100 parts acrylic polymer. The floor coverings of the invention have improved wet slip properties, clarity, and resistance to UV light compared with known vinyl floor coverings, and have excellent cigarette burn resistance.

Description

FLOOR COVERINGS

Background of the Invention

1. Field of the Invention

This invention relates to resilient floor coverings, particularly in sheet or tile form.

2. Description of the Related Art

Floor coverings are described in an article entitled "Flooring Materials" in Encyclopaedia of Polymer Science and Engineering, Volume 7 (Wiley-Interscience, 1987), at page 233. They are also described in an article entitled "Floor Coverings" inUllmann's Encyclopaedia of Industrial Chemistry, VCH Publishers, Volume All (1988), at page 263.

Vinyl sheet and vinyl tile resilient floor coverings are well-known and have enjoyed considerable commercial success. They are based on homopolymers or copolymers of vinyl chloride, for example vinyl chloride/vinyl acetate copolymers. The homopolymers and the copolymers are both commonly referred to as PVC resins or PVC polymers. Compositions which comprise PVC resin are commonly referred to as PVC compositions or simply as PVC. PVC Technology, ed. W.V. Titow, Elsevier Applied Science Publishers, 4th Edition (1984) , describes the manufacture, properties and uses of PVC, and of the nature and properties of materials such as plasticisers used in PVC compositions. The amounts of the various components in a PVC composition are commonly expressed either as percentages by weight on the whole composition or as parts per hundred by weight of PVC resin (phr) . PVC compositions which contain no or little plasticiser (for example up to about 2% by weight) are relatively rigid and brittle, and are commonly referred to as rigid PVC, unplasticised PVC, or UPVC. PVC compositions which contain relatively large amounts of plasticiser (for example around 10-40% by weight, or correspondingly around 10- 50 phr) are more flexible and have a lower modulus than UPVC, and are commonly referred to as flexible PVC, plasticised PVC, or PPVC. Rigid PVC and flexible PVC are materials which have significantly different properties, technology and end-uses. Environmental objections have been raised against the manufacture and use of PVC polymers and other polymers which contain chlorine. There is a desire to replace such polymers by polymers which contain lower amounts of or preferably no chlorine.

Vinyl sheet and vinyl tile floor coverings are based on flexible PVC. Vinyl sheet and vinyl tile floor coverings are usually composite materials constructed from a number of layers or films, in which each layer is specially formulated for a particular duty. The uppermost layer, which is commonly called the wear layer, is formulated for good resistance to abrasion and wear. In one common form of construction, the wear layer is transparent, so that the colouring or patterning of lower layers can be seen through it, and it may then be referred to as a clear wear layer.

GB-A-1517428 describes internally plasticised vinyl chloride copolymers which can be used in the manufacture of vinyl flooring without additional plasticiser. The copolymer is made by addition polymerisation of 45-80 parts vinyl chloride, 15-54 parts C2-C10 alkyl acrylate and 1-15 parts C8- C22 dialkyl maleate or fumarate, all parts being by weight.

EP-A-342562 describes the use of polyacrylate plastisols for the continuous coating of PVC floor coverings, particularly textured floor coverings. The plastisol contains a mixture of an emulsion polymer and a suspension polymer in the ratio 90-30:10-70 together with 50 to 200 phr plasticiser. Use of such plastisols is said to provide a coating with a 'dry' surface and to prevent destruction of the PVC foam backing by mobile plasticiser.

US-A-4110296 describes flame retardant compositions comprising an acrylic terpolymer and a fire retardant additive which can be used as top coatings for floor tiles. The terpolymer is made by addition polymerisation of 20-60 parts C1-C16 alkyl acrylate or methacrylate, 10-40 parts acrylonitrile or a derivative thereof and 20-70 parts halogenated olefinic monomer, for example vinylidene chloride or pentachloroethyl methacrylate, all parts being by weight. The fire retardant additive is usually a plasticiser for the terpolymer, for example a triorgano phosphate.

The manufacture, properties and uses of acrylic and methacrylic ester polymers are described in an article entitled "Acrylic and Methacrylic Ester Polymers" in Encyclopaedia of Polymer Science and Engineering, Volume 1 (Wiley-Interscience, 1985) , at page 234. Such polymers may be referred to generally as acrylic ester polymers or acrylate ester polymers.

Various polymeric substances have been added to rigid PVC compositions as processing aids or as impact modifiers which improve the toughness of such compositions, as described in Plastics Additives Handbook, edd. R. Gachter and H. Mύller, 3rd Edition (Hanser Publishers, 1990), Chapters 7 and 8. Known polymeric processing aids and impact modifiers include acrylic ester polymers (commonly called acrylic modifiers and also known as acrylate ester polymers) such as copolymers of methyl methacrylate with ethyl or butyl acrylate, which also impart good resistance to light and weathering to the rigid PVC composition.

Summary of the Invention

The present invention provides a resilient floor covering wherein the wear layer of the floor covering consists of a flexible composition which comprises an acrylic ester polymer and a plasticiser, characterised in that the floor covering contains essentially no chlorine or bromine. The flexible composition may be referred to as a plasticised acrylic ester composition.

The acrylic ester polymer is a thermoplastic polymer, and generally has a glass transition temperature (Tg) of at least 50°C, often at least 80°C. The acrylic ester polymer is an addition polymer of one or more olefinic monomers including at least 50 per cent by weight of at least one alkyl acrylate or methacrylate, where the alkyl group is preferably a C1-C16 alkyl group. Preferred monomer mixtures may include 75 or 90 per cent by weight of or consist essentially only of such alkyl acrylates and methacrylates. One preferred example of a monomer is methyl methacrylate which serves to provide a polymer of high Tg, although in general poly(methyl methacrylate) is too hard a polymer to be used satisfactorily in the floor coverings of the invention. Examples of other preferred monomers include ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, which serve to provide a polymer of lower Tg and of greater softness and flexibility. The polymer generally includes at least two, preferably two or three, such alkyl acrylates or methacrylates. Preferred polymers are copolymers of methyl methacrylate with one or more alkyl acrylates having a C2-C16 alkyl group. The acrylic ester polymer may include minor proportions of other olefinic monomers, for example styrene and acrylonitrile. The use of chlorine- or bromine-containing monomers such as vinyl chloride and vinylidene chloride is generally not preferred and preferably the acrylic ester polymer contains essentially no chlorine or bromine. Blends of more than one acrylic ester polymer may be used.

The flexible composition generally contains 25 to 65 parts plasticiser per hundred parts acrylic ester polymer (25 to 65 phr) , preferably 35 to 55 phr, more preferably 40 to 50 phr, further preferably about 45 phr. Compositions containing too little plasticiser have generally been found to exhibit unsatisfactory scratch resistance. Compositions containing too much plasticiser have generally been found to be too soft and to have properties approaching those of plastisols.

One class of plasticiser suitable for use in the flexible composition consists of those materials known from

PVC technology as monomeric plasticisers or simple ester plasticisers. These materials are organic esters with high boiling points, and in most cases they have molecular weights in the range 300 to 500. Examples of simple ester plasticisers suitable for use in the invention include phthalic diesters, phosphoric esters, esters of dibasic aliphatic acids, and trimellitic esters. The esterifying groups in such esters may be the same or different. Mixtures of more than one type of simple ester plasticiser may be used. Examples of phthalic diesters include esters of phthalic acid with C4 to C12 alcohols, for example dioctyl phthalate (DOP) , diisooctyl phthalate (DIOP) , diisononyl phthalate (DINP) , diisodecyl phthalate (DIDP) , diisoundecyl phthalate (DIUP) , butyl benzyl phthalate (BBP) and octyl benzyl phthalate (OBP) . Examples of phosphoric esters include octyl diphenyl phosphate, isodecyl diphenyl phosphate, tritolyl phosphate

(TTP) , triphenyl phosphate (TPP) and 2-ethylhexyl diphenyl phosphate. Phosphoric esters provide burn and char resistant properties in the floor coverings of the invention. Examples of esters of dibasic aliphatic acids include dioctyl adipate, diisodecyl adipate, dioctyl azelate and dioctyl sebacate. An example of a trimellitic ester is trioctyl trimellitate. A mixture of more than one type of plasticiser may be used. A mixture of OBP with another phthalic ester or with a phosphoric ester or both may be preferred. Preferred mixtures of plasticisers generally contain at least 35 per cent by weight of a phosphoric ester, preferably at least 40 per cent, more preferably about 50 per cent. Mixtures containing less than about 35 per cent phosphoric ester generally do not significantly improve the burn and char resistance of the flexible composition. Flexible compositions in which the plasticiser is a mixture containing more than about 60 per cent phosphoric ester may be too soft and have unsatisfactory scratch resistance.

Another class of plasticiser suitable for use in the flexible composition consists of those known from PVC technology as polymeric plasticisers, for example aliphatic polyesters and polyphthalates. Polyphthalate plasticisers have generally been found to be more compatible with the acrylic ester polymer than aliphatic polyester plasticisers. Mixtures of monomeric and polymeric plasticisers may be used.

The flexible composition preferably additionally contains up to 15 phr of a thermoplastic polymer having urethane groups in its backbone, more preferably 5 to 15 phr, further preferably about 10 phr. This polymer is preferably a polyurethane. The polyurethane may be based on an aliphatic or aromatic polyisocyanate. It is preferably based on an aliphatic polyiso yanate, because such polyurethanes are known to have good resistance to yellowing on prolonged exposure to sunlight. The polyurethane is generally based on a high molecular weight polyol, for example a polyester or polyether polyol. It is preferably based on a polyester polyol, because such polyurethanes are known to have good resistance to sunlight and to oxidation. The presence of such a polyurethane in the flexible composition at such levels has been found to give improved abrasion resistance, scratch resistance and indentation recovery to the floor coverings of the invention.' Improved abrasion resistance may not be obtained if higher levels of polyurethane are used. The polyurethane is preferably one which is solid at room temperature and which is available in the form of a powder for ease in use. The polyurethane may be used in pure form or in the form of a powder dusted with a suitable blocking agent. An example of a suitable polyurethane is supplied by Bayer AG under the Trade Mark "Baymod PU" .

The flexible composition preferably additionally contains up to 2 phr of a processing lubricant, more preferably 1 to 2 phr. The lubricant is preferably chosen to be one which segregates to the surface of the composition during processing, which does not plate out on the surface of the composition, and which does not reduce the clarity of the composition. Examples of suitable lubricants include long chain fatty acids, for example stearic acid, fatty esters, for example glycerol monooleate, and polyethylene waxes, for example those supplied by Hoechst AG under the Trade Mark "Ewax" . Long chain fatty acids are generally not preferred when the flexible composition comprises a thermoplastic polymer having urethane groups in its backbone.

The acrylic ester polymer, the plasticiser and the flexible composition should contain essentially no chlorine or bromine, by which is meant that none of them should contain more than about 2 percent by weight total chlorine and bromine in combination.

The floor coverings of the invention resist scratching in a similar manner to known vinyl floor coverings. The floor coverings of the invention generally possess better resistance to scuffing and dry antislip properties than known vinyl floor coverings. For example, they may exhibit a dry slip resistance in the SATRA test of 0.8 or more. The floor coverings of the invention preferably exhibit a wet slip resistance in the SATRA test of 0.3 or more. The floor coverings of the invention generally resist crease-whitening at least as well as known vinyl floor coverings. The floor coverings of the invention generally exhibit better clarity and better resistance to ultraviolet light than known vinyl floor coverings. The ease of cleaning of the floor coverings of the invention is similar to that of known vinyl floor coverings. The stain resistance of the floor coverings of the invention is similar to that of known vinyl floor coverings. The floor coverings of the invention generally have excellent cigarette burn resistance, often surprisingly better than that of known vinyl floor coverings.

Known resilient floor coverings in the form of composite vinyl tiles commonly have Shore D hardness in the range 55 to 60, often about 58. The floor coverings of the invention generally have Shore D hardness in the range 35 to 55, preferably 40 to 50. Floor coverings with lower Shore D hardness have generally been found to have unsatisfactory scratch resistance, and floor coverings with higher Shore D hardness have generally been found to have unsatisfactorily low slip resistance. It is remarkable that floor coverings which are very soft compared with known floor coverings should exhibit a desirable combination of properties. The hardness of a single film of a plasticised acrylic ester composition is generally lower than that of a composite tile containing the film as wear layer. Such a single film may for example have Shore D hardness in the range 25 to 40.

The flexible composition may additionally contain a crosslinking agent, for example a polyfunctional olefinic monomer. The polyfunctional olefinic monomer may be an ester containing two or preferably three or four acrylic or methacrylic groups, for example tetraethyleneglycol di (meth) acrylate, acryloxypivaloyl acryloxypivalate, trimethylolpropane tri (meth)acrylate and pentaerythritol tetra(meth) acrylate. Other examples of polyfunctional olefinic monomers include divinyl benzenes and allylic compounds containing two or preferably three or four allylic groups, for example triallyl cyanurate and triallyl isocyanurate. The composition may contain about 10 to 30 phr, preferably about 20 phr, of the crosslinking agent. The crosslinking agent can be polymerised in the extruded film, for example by heating or by electron-beam treatment, to provide improved toughness and scratch and abrasion resistance in the floor coverings of the invention. The polymerised crosslinking agent tends to plasticise the flexible composition, and accordingly when such a crosslinking agent is used the preferred plasticiser content of the composition is reduced. The plasticiser content is preferably reduced by about 1 phr for each 2 phr crosslinking agent used.

The flexible composition is a uniform blend of acrylic ester polymer and plasticiser with the optional materials such as polyurethane, lubricant and crosslinking agent.

The floor coverings of the invention may additionally contain particles of a relatively hard material exposed at the surface of the we r layer to provide a surface with high wear and slip resistance. The size of the particles may be in the range 100 to 500 micron. If the floor covering has a clear wear layer, the particles are preferably clear particles, and further preferably have the same or similar refractive index as the flexible composition. The refractive indices of the particles and the composition may differ by 0.02 or less, preferably 0.01 or less. The particles are preferably of a plastics material, for example an unplasticised acrylic polymer. The particles preferably have a flow temperature of 140°C or above, more preferably 160°C or above. The particles preferably have Rockwell M hardness of 85 or greater, more preferably 90 or greater, further preferably 95 or greater. The wear layer may contain about 2 to 25 per cent, preferably about 5 to 10 per cent, by weight of the particles. Examples of suitable plastics particles are those sold by Rohm & Haas Co. under the Trade Mark Oroglas VM100 (which is specified as having Rockwell M hardness 89 and flow temperature 140°C) and especially Oroglas V825 (which is specified as having Rockwell M hardness 97 and flow temperature 163°C) .

Floor coverings according to the invention can be prepared using conventional equipment for the manufacture of vinyl sheet and vinyl tile floor coverings.

A typical procedure for the manufacture of film suitable for the manufacture of floor coverings according to the invention is as follows. Acrylic ester polymer powder and plasticiser are blended in a Z-blade mixer. Other components, for example the optional polyurethane, optional lubricant and optional hard particles as well as pigments, processing aids, antioxidants and stabilisers, may be blended into the mixture at the same time. In general, no pigment is added if it is desired to produce a film suitable for use as a clear wear layer. The powdery blend is then charged into an intensive mixer, for example a Banbury mixer, and worked to produce a hot melt, for exaiαple at a temperature of 130-180°C. The melt is further worked by being fluxed on a two-roll mill heated to a similar temperature. It is then extruded between rollers to form a film having a controlled thickness, for example in the range 0.2-1.0 mm, which is cooled and collected on a reel.

The floor coverings of the invention are preferably composite materials made by laminating two or more films together. The wear layer of the floor covering may consist of one, two or three films of the flexible composition. The wear layer may be a clear wear layer, and this may be preferred. The film or films other than the film or films which make up the wear layer may be made from plasticised acrylic ester polymer compositions or from other materials known in the manufacture of resilient floor coverings. If the laminate contains a thin film, for example a patterned printed layer inside the laminate, such a film may be made from a conventional unplasticised acrylic ester polymer. The layer on the side of the floor covering opposite to the wear layer is known as the backing layer. Alternative materials for the backing layer in the floor coverings of the invention include known materials such as nitrile rubbers and highly-filled ethylene copolymers, for example ethylene/vinyl acetate (EVA) copolymers. The backing layer may be coated in known manner with a plastisol containing a blowing agent which provides a foam structure when heated, so that the floor coverings of the invention may be foam cushion sheets or tiles. The floor coverings of the invention contain essentially no chlorine or bromine, that is to say they contain less than about 2 percent by weight total chlorine and bromine.

A typical procedure for the manufacture of laminated floor coverings according to the invention is as follows. Two or more films are fed between heated nip rollers, for example maintained at a temperature around 175°C, in order to fuse the films together. One or more sets of nip rollers may be used. The films may all be fed between the first set of nip rollers or one or more of the films may be introduced between later sets of nip rollers. The resulting film laminate may then be bonded to a backing fabric by passage of the laminate and the fabric between a further set of heated nip rollers. The backing fabric may be coated with a plastisol containing a blowing agent to provide a foam layer. Alternatively, the lower face of the film laminate may be embossed to provide a roughened surface, for example by contact with a fabric carrier or a drum. The wear layer may be patterned by passage over a heated drum whose surface is the negative of the desired pattern to provide a wear layer with an embossed surface. The resulting floor covering is then cooled and is typically cut into strips or squares ready for use. A typical film laminate might consist of one or two clear wear layers, a patterned printed layer, a white or other pig ented layer (known as a face ply) to provide visual depth to the pattern and a black layer (a backing layer) to ensure opacity.

A preferred floor covering according to the invention is a laminate of films having the following construction in sequential order:

(1) Clear wear layer 500-750 micron (20-30 mil) thick consisting of acrylic ester polymer, plasticiser, polyurethane and lubricant;

(2) Clear wear layer as (l) ;

(3) Patterned printed layer 50-125 micron (2-5 mil) thick consisting of acrylic ester polymer;

(4) Face ply 250-500 micron (10-20 mil) thick consisting of acrylic ester polymer, plasticiser, lubricant and pigment, for example a white pigment such as titanium dioxide; and

(5) Backing layer 750-1000 micron (30-40 mil) thick, embossed on the underside with the pattern of a fabric carrier belt, consisting of acrylic ester polymer, plasticiser, lubricant and pigment, for example a black pigment such as carbon black. Description of the Preferred Embodiments

The invention is illustrated by the following Examples,

(in which all p?rts and proportions are by weight unless otherwise specified) and the accompanying drawing, the sole Figure of which is a schematic section through a laminated floor tile:

Example 1

Compositions were prepared having the following constituents:

100 parts Paraloid K125 (acrylic ester polymer) varying Santiciser 141 (2-ethyl exyl diphenyl phosphate) varying DINP

10 parts Baymod PU (aliphatic polyester polyurethane)

1 part Loxiol G71S (Complex ester lubricant)

Paraloid is a Trade Mark of Rohm & Haas Co. Santiciser is a Trade Mark of Monsanto Co. Baymod is a Trade Mark of Bayer AG. Loxiol is a Trade Mark of Henkel KGaA. Santiciser 141 and DINP are together referred to as plasticiser. The amounts of Santiciser 141 and DINP were generally in the range 60:40 to 50:50 by weight.

Each composition was blended on laboratory scale in a Banbury mixer to a temperature of 90°C, fluxed on a two-roll mill at 110-130°C for 5 minutes, and then extruded between calender rolls at 110-130°C to form a film 500 micron (22 mil) thick suitable for use as a clear wear layer in a resilient floor tile. In larger scale trials, the composition was blended to a final temperature of 130°C, fluxed at 180°C, and extruded at 175°C.

A conventional vinyl film having the following composition was used as control: 100 parts PVC resin

26 parts DIOP

5.7 parts epoxidised soya bean oil

2.5 parts heat stabiliser

The following experimental results were obtained on single films:

Plasticiser Shore D Abrasion Coin Indentation phr Hardness Resistance Scratch micron g/1000 rev

30 45-47 0.13-0.16 poor <25

35 39-51 0.11-0.18 average 25

40 30-42 0.11-0.26 good <50

45 22-40 0.21-0.33 good >75

Control 58 0.17 average 25 Abrasion resistance was assessed by recording the loss in weight of a disc 100 mm in diameter in a Taber abrasion tester mounted between two rotating abrasive wheels each with 1 kg loading. Coin scratch was assessed subjectively. Indentation was assessed according to B.S. 3261 by applying a 36 kg load through a stiletto heel 4.5 mm in diameter for 10 min and measuring the depth of the residual identation 60 min after removing the heel. Original indentation results were rounded to the nearest mil, and are therefore quoted to the nearest 25 micron.

Example 2

A composition was prepared to the following recipe :

100 parts Paraloid K125 (acrylic ester polymer)

22 .5 parts Santiciser 141 (2 -ethylhexyl diphenyl phosphate)

17 .5 parts DINP

10 parts Baymod PU (aliphatic polyester polyurethane)

1 part Loxiol G71S (complex ester lubricant)

The composition was blended on laboratory scale in a Banbury mixer to a temperature of 90 °C, fluxed on a two-roll mill at 110-130 °C for 5 minutes , and then extruded between calender rolls at 110-130°C to form a film 500 micron (22 mil) thick suitable for use as a clear wear layer in a resilient floor tile.

Composite floor tiles were made which were laminates of the following sequence of films:

(1) Clear wear layer as above;

(2) Clear wear layer as above;

(3) Patterned printed acrylic film 50, 75 or 125 micron (2, 3 or 5 mil) thick; (4) Face ply film of the same composition as the wear layer, pigmented with titanium dioxide or other suitable pigment, 380 micron (15 mil) thick; and

(5) Backing film of the same composition as the wear layer but with the omission of Baymod PU, pigmented with carbon black, 810 micron (32 mil) thick.

The accompanying drawing illustrates such a tile, in section, the layers being numbered as detailed above.

These tiles were essentially free of halogen, in particular chlorine. The tiles exhibited Shore D hardness 45, indentation 50 micron, abrasion 0.14 g/1000 rev and were rated good in the coin scratch test.

The floor tiles were assessed for stain resistance in comparison with conventional vinyl tiles. Results were identical in every case. Lipstick, orange crayon, boot polish and tomato ketchup left no detectable stain. Curry powder left a pronounced stain.

Example 3

Compositions were prepared containing the following constituents: 100 parts Paraloid K125 (acrylic ester polymer)

20 parts Santiciser 141 (2 - ethylhexyl diphenyl phosphate ¹

20 parts DINP varying Baymod PU ( aliphat ic polyester polyurethane )

1 part Loxiol G71S ( complex ester lubricant )

The compositions were blended and extruded to produce f ilms in the same manner as in Example 1 . These films had the properties shown in the following Table :

Baymod PU Abrasion Resistance Indentation Slip phr g/1000 rev micron Resistance

0 0.21 50 0.82

5 0.16 50 0.84

10 0.12 25 0.90

15 0.19 25 0.85

Slip resistance was assessed by the SATRA method under dry conditions using a 4S rubber (RAPRA specification) heel as described in M.P. Wilson, "Development of SATRA Slip Test and Tread Pattern Design Guidelines", Slips, Stumbles, and Falls: Pedestrian Footwear and Surfaces, ASTM STP 1103, B.E. Gray, Ed. , American Society for Testing and Materials, Philadelphia, 1990, pp. 113-123. Each sample was tested five times, and the results quoted are the average of tests three to five. A conventional vinyl film as described in Example 1 gave a result of 0.80 in this test.

Example 4

Four compositions A-D were prepared to the following formulations:

100 100 100 100 Paraloid K125 45 22.5 0 0 DINP

0 22.5 45 0 Santiciser 141 0 0 0 45 Triphenyl phosphate

1 1 1 1 Loxiol G71S

These compositions were blended and extruded to produce films approximately 1.3 mm thick in the same manner as Example 1. The same conventional vinyl film as Example 1 was used for comparison (reference PVC) .

Cigarette burn resistance was assessed (1) by stubbing out a lit cigarette on the film, and (2) by allowing a lit cigarette laid on the film to smoulder until it burnt out. The following observations were made:

Reference S ub -out Smoulder

PVC Large area of black char. Severe charring. Depth of degradation very pronounced.

Similar area of charring to Black charred central area PVC, but discoloration less of damage with surrounding severe. Reasonable result. orange region, Depth of penetration less than for PVC.

Smaller area of degradation Similar to A, though and less charring than A. charring possibly more Good result. severe. Very similar to B. Good Similar to A. result .

Only a small area of Area of damage similar to A, degradation and little but predominantly orange in charring. Very good result. colour with only a very small amount of black char.

It will be noted that sample A gave a better result than the conventional vinyl tile even though (1) it did not contain any phosphoric ester plasticiser and (2) PVC is an inherently burn-resistant material as a consequence of its chlorine content, in contrast to the acrylic ester polymer. It will also be noted that samples B and C gave similar results, even though sample C contained twice as much phosphoric ester plasticiser as sample B.

Claims

1. A resilient floor covering wherein the wear layer of the floor covering consists of a flexible composition which comprises an acrylic ester polymer and a plasticiser, wherein the floor covering contains essentially no chlorine or bromine.

2. A floor covering according to claim 1, wherein the flexible composition contains 25 to 65 parts by weight plasticiser per 100 parts acrylic ester polymer.

3. A floor covering according to claim 1, wherein the plasticiser is a simple ester plasticiser.

4. A floor covering according to claim 3, wherein the plasticiser contains at least 35 per cent by weight of a phosphoric ester.

5. A floor covering according to claim 1, wherein the flexible composition additionally comprises 5 to 15 parts by weight of a thermoplastic polyurethane per 100 parts acrylic ester polymer.

6. A floor covering according to claim 1, wherein it has Shore D hardness in the range 35 to 55.

7. A floor covering according to claim 1, wherein the flexible composition additionally comprises 10 to 30 parts by weight of a crosslinking agent per 100 parts acrylic ester polymer.

8. A floor covering according to claim 7, wherein the crosslinking agent is a polyfunctional acrylic monomer.

9. A floor covering according to claim 1, wherein it contains particles of a relatively hard material compared with the flexible composition, the particles being 100 to 500 micron in size and exposed at the surface of the wear layer.

10. A floor covering according to claim 9, wherein the particles consist of an unplasticised acrylic polymer.

11. A floor covering according to claim 1, wherein the wear layer is a clear wear layer.

12. A floor covering which is a laminate of films in the following sequential order:

(1) Clear wear layer 500 to 750 micron thick consisting of acrylic ester polymer, plasticiser, thermoplastic polyurethane and lubricant;

(2) Clear wear layer as (1) ;

(3) Patterned printed layer 50 to 125 micron thick consisting of acrylic ester polymer,- (4) Face ply 250 to 500 micron thick consisting of acrylic ester polymer, plasticiser, lubricant and pigmen ; and (5) Backing layer 750 to 1000 micron thick, embossed on the underside with the pattern of a fabric carrier belt, consisting of acrylic ester polymer, plasticiser, lubricant and pigment.