GB2338435A - Composite sheeting, floor covering comprising said sheeting, and corresponding manufacturing processes - Google Patents

Abstract

The invention relates to a process for manufacturing composite plastic sheeting, and comprises the following phases: the formation of a first particular layer, for example a wearing surface, by dusting (9) a special resin onto the surface of a mobile support (7); and the formation of at least a second particular layer (11, 12) on top of the first particular layer, thereby forming a preform of a multilayered composite structure. Pressure and heat are applied to the preform to fuse the particles. The invention is characterized by the fact that the heat and pressure application phase consists in continuously pressing the preform flat at a temperature of approximately 150 ‹C to approximately 200 ‹C and a pressure of approximately 0.5 to approximately 20 bar, so that the preform is transformed into a multilayered composite sheet with no substantial creep from one layer into the other.

Description

COMPOSITE SHEET, FLOOR COVERING WHICH COMPRISES THIS SHEET, AND

CORRESPONDING PRODUCTION METHODS The present invention relates to a method for obtaining a composite sheet with a base made of thermoplastic material, and a multi-layer composite sheet which has improved resistance to delamination.

In the present application, the expressions used in the description and the claims have the following significance:

"PVC" also means polymers, the K values of which are preferably between 45 and 110, for example homopolymers. with K values of between.55 and 110, copolymers of vinyl chloride and vinyl acetochloride, or grafted copolymers with a K value of between 45 and 100. The term "PVC" can also be applied to PVC waste or compositions with a PVC or PVC copolymer base. PVCs in emulsion and/or in microsuspension can also be used, with or without anti-clumping treatment. It will be appreciated that these various homopolymer or copolymer PVCs can also be used in a mixture; "dry blend" or "dry bl ' end mixture" means a mixture of PVC and plasticiser(s), in which the plasticiser(s) has or have been absorbed by the PVC grain, such that a product in powder form is retained, with a size grading which is generally between 80 gm and 250 gm.

In general, composite sheets based on at least one layer of plastics material, for example polyvinyl chloride (PVC), as previously defined, are known. Composite sheets of this type habitually comprise on their surface at least one non-foamed wear layer made of plastics material substantially with a PVC base, beneath which there is disposed at least one layer made of plastics material, which is optionally foamed, with a base layer in the form of a non-woven sheeting, made of glass fibres for example, which is optionally embedded in a plastics material, and 2 acts as a reinforcement for the composite structure as a whole.

This reinforcement imparts a given levelness and dimensional stability to the composite structure or sheet, such as to prevent shrinkage during conditioning and use. In addition, a reinforcement layer has always been considered necessary for composite sheets which are designed to be used as floor-covering tiles, for example, since this effectively prevented or decreased the aforementioned shrinkage of the sheet caused by the internal stresses of the composite structure. This need to incorporate a reinforcement in composite sheets of this type was disadvantageous, since it complicated the is production process and increased the production cost substantially. This problem became all the greater when the aim was to obtain a composite sheet designed for a floor covering which had not only good mechanical characteristics, but also improved acoustic performance, since in general the known composite sheets did not damp impact noise sufficiently.

There therefore existed a problem of simplification of the structure of a composite sheet of this type, such that the latter does not have any reinforcement, whilst maintaining mechanical performance equivalent to a sheet which is provided with a reinforcement of this type, and at the same time improving the acoustic performance of the sheet, in the fields of application of composite sheets of this type, and in particular floor coverings.

The object was thus to obtain the above-described performance levels, whilst simplifying the method for obtaining composite sheets of this type.

It is known from document EP-A-0 747 241 to produce floor coverings by depositing separate particulate layers.

1 3 The problem which is solved by this document consists of obtaining particular decorative motifs, which can be modified as required. The method consists of depositing a first particulate layer of resin, for example PVC, on a mobile support. This layer then undergoes at least one mechanical deformation, for example by means of an embossing roller, for the purpose of distributing the particles according to a specific decorative motif. A second particulate layer of resin is then deposited on the first layer, these particles accumulating in particular in the depressions created in the first layer by the mechanical deformation. Heat is then applied, optionally with pressure, to the particulate preform obtained from the preceding steps, in order to form a sintered multi-layer composite structure. This composite structure is unfinished, i.e. it is not suitable for use as a floor covering, since the particles of the second layer are fused with those of the first layer only intermittently and incompletely. It is therefore necessary to carry out an additional step of final fusion between two heated rollers, in order to fuse all the resins.

Consequently, an object of the present invention is a method for production of a composite plastic sheet comprising steps which consist of: forming a first particulate layer, for example a wear layer, by dusting a particulate resin onto the surface of a mobile support; forming at least one second particulate layer an the first particulate layer, in order to form a preform with a multi-layer composite structure; and applying pressure and heat to the preform in order to fuse the particles. The method is more particularly characterised in that the step of application of pressure and heat consists of pressing the preform flat continuously, at a temperature of between approximately 1500C and approximately 2500C, and at a pressure of 1 il- 4 approximately 0.5 bar to approximately 20 bars, such that the preform is transformed into a multi-layer composite sheet, without substantial creepage of one layer into the other.

The present applicant has discovered that, unexpectedly, it is possible to obtain a finished multilayer composite sheet which is ready to use, and has the required, previously described performance levels, by modifying the method described in this document, in the manner previously described. In addition, it has been found that, contrary to expectations, the two layers of particles do not substantially fuse into one another, i. e. there is no creepage, or substantial penetration of one layer into the other.

Advantageously, the second layer substantially has a PVC waste base.

Additionally, a decorative layer can preferably be formed, based on a mixture of coloured granules, or a film which is printed onto the first layer, before the second layer is formed.

According to a preferred embodiment of the method according to the invention, the method comprises the additional step which consists of laminating continuously a resilient underlayer made of foamed plastics material, continuously onto the second layer.

In this case, the resilient underlayer can be formed by depositing an adhesive layer consisting of an adhesive heat-fusible film or powder onto the second layer, heating until the adhesive fuses, and laminating a regenerated polyurethane foam onto the median layer, at a temperature of between approximately 1000C and 1800C, and at a pressure of between approximately 0.2 bar and approximately 2 bars.

A further object of the present invention is a method for production of a floor covering, which consists of producing a composite plastics sheet according to the method previously described, the method comprising additional steps consisting of embossing and sanding the surface of the first layer, after the second layer has been pressed, and before the underlayer is laminated, cutting the composite sheet into a required format, after lamination has taken place, stabilising the composite sheet in at least one stabilisation tunnel, and conditioning the composite sheet which has previously been cut into tiles.

Another object of the present invention is a multilayer composite plastics sheet, comprising at least one continuous first layer, for example a wear layer, comprising a thermoplastic resin, for example a polyvinyl chloride (PVC), and at least one second layer, for example a median layer, which also comprises a thermoplastic resin. The composite sheet is more particularly characterised in that before being pressed with application of heat, it is a preform which comprises at least two separate layers of particles, and after being pressed with application of heat, it is a finished multi-layer composite sheet, without substantial creepage from one layer into the other layer.

A further object of the present invention is a floor covering, in particular in the form of tiles, comprising a composite sheet according to the preceding definition.

The composite sheet according to the present invention is dimensionally stable and flat, i.e. from a mechanical point of view it acts substantially like a composite sheet of a known type which comprises a reinforcement, which for example consists of glass fibres which are embedded in a layer of plastics material, and has good acoustic behaviour. In addition, it has been found that it is virtually impossible to delaminate the various layers of 6 the sheet according to the invention, which is not the case for the composite sheets according to the prior art.

Advantageously, the first layer, which for example is 5 a wear layer, has a thickness of between approximately 0.10 mm and approximately 0.70 mm, and preferably has a thickness which is selected from amongst 0.25 mm, 0. 50 mm and 0.65 mm.

According to a preferred embodiment, the composite sheet comprises a decorative layer between the first layer and the second layer. According to a preferred variant of this embodiment, the decorative layer is obtained by pressing coloured plastics granules, and optionally adding an additional relief layer based on flakes, chips, and/or filaments. According to another preferred variant of this embodiment, the decorative layer consists of a printed film.

Advantageously, the composite sheet comprises a resilient underlayer, which has a discontinuous alveolar structure, the thickness of which is cross-linked, and which comprises at least -one plastics material.

Preferably, the sheet comprises an adhesive layer between the second layer [sic], and more preferentially, the adhesive layer is selected from amongst the group which consists of a heat-fusible film, a double layer of copolyamide and ethylene vinyl acetate (EVA), a double layer of copolyester, a heat-fusible powder of the polyurethane or polyester type, a hot melt layer of the polyurethane type, an "emulsion" glue of the polyurethane type, and a "solvent" glue of the polyurethane type. Advantageously, the adhesive layer is selected in order to prevent migration of the plasticisers of the second layer towards the resilient underlayer, and thus to prevent dimensional developments such as curvature during ageing.

1 ( 11 7 Preferably, the second layer is substantially based on polyvinyl chloride (PVC) waste, and can have a deposited thickness which is preferably between approximately'0.20 mm and approximately 2 mm.

- Advantageously, the resilient underlayer substantially consists of cross- linked regenerated polyurethane foam. More preferentially, the resilient underlayer consists of a homogeneous mixture of: flakes of selected, cross-linked polyurethane foam; bonding prepolymer with a polyurethane base; regenerated rubber powder; optionally granules of cork; and other additives, such as pigments and waterproofing 15 agents.

According to another preferred embodiment of the invention, the resilient underlayer consists of an opencell foam which is rendered waterproof.

Another object of the present invention is a composite plastics sheet, comprising a continuous wear layer which is optionally decorated, comprising a thermoplastic resin, for example a polyvinyl chloride (PVC), the sheet also comprising a resilient underlayer'which has a discontinuous alveolar structure, the thickness of which is cross-linked, comprising at least one plastics material. The composite sheet is more particularly characterised in that the sheet also comprises a median layer which is bonded on one side by being pressed to the wear layer, and on the other side by being glued to the resilient underlayer, the said median layer comprising a thermoplastic resin, for example a polyvinyl chloride, in practice all without any reinforcement integrated in all or part of the structure of the said composite plastics sheet.

1 1 i Y 8 Another object of the present invention is a floor covering, in particular in the form of tiles, comprising a composite sheet according to the preceding definition.

A further object of the present invention is a method for production of a composite plastics sheet, according to the definition previously given. This method is characterised in that initially, the wear layer is formed, for example by coating the surface of a mobile support with a plastisol, then gelling the latter, then the median layer is added onto and assembled directly or indirectly with the wear layer by being pressed, and the resilient underlayer is added onto and glued to the median layer, by means of which the plastics sheet is formed in reverse order, starting with the wear layer which acts as a substrate.

The composite sheet according to the present invention is dimensionally stable and flat, i.e. it behaves from a mechanical point of view substantially like a composite sheet of the known type which comprises a reinforcement, for example which is made of glass fibres embedded in a layer of plastics material, and has good acoustic performance. It has also been found that if the sheet is constructed starting from the median layer, i.e. according to the prior conventional construction art, there is deformation of this median layer during pressing, and levelness can no longer be ensured.

Advantageously, the wear layer has a thickness of between approximately 0.25 mm and approximately 0.70 mm, and preferably has a thickness selected from amongst 0.25 mm, 0.50 mm and 0.65 mm.

According to a preferred embodiment, the wear layer comprises a decorative layer between the wear layer and the median layer. According to a preferred variant of this embodiment, the decorative layer is obtained by fusing and 9 pressing coloured plastics granules, and optionally adding an additional relief layer based on flakes, chips, and/or filaments. According to another preferred variant of this embodiment, the decorative layer consists of a printed 5 film.

Advantageously, the composite sheet comprises an adhesive layer between the median layer and the resilient underlayer. Preferably, the adhesive layer is selected from amongst the group which consists of a heat-fusible film, a double layer of copolyamide and ethylene vinyl acetate (EVA), a double layer of copolyester, a heat-fusible powder of the polyurethane or polyester type, a hot melt layer of the polyurethane type, an "emulsion" glue of the polyurethane type, and a,solvent" glue of the polyurethane type.

Preferably, the median layer is substantially based on polyvinyl chloride (PVC) waste, and can have a deposited thickness which is preferably between approximately 0.40 mm and approximately 1.50 mm.

Advantageously, the resilient underlayer substantially consists of crosslinked regenerated polyurethane foam.

More preferably, the resilient underlayer consists of a homogeneous mixture of: flakes of selected, cross-linked polyurethane foam; bonding prepolymer with a polyurethane base; rubber powder; 30 optionally granules of cork; and other additives, such as pigments, waterproofing agents and dyes.

According to another preferred embodiment of the invention, the resilient underlayer consists of an opencell foam.

1. I According to a preferred embodiment of the method according to the present invention, the latter comprises at least the steps which consist of: forming continuously in reverse order on transport means at least one non-foamed wear layer which substantially has a PVC base; forming on the wear layer a median layer which substantially has a PVC waste base, by continuous flat pressing with the wear layer; and - laminating a resilient underlayer made of foamed plastics material continuously onto the median layer.

Advantageously, the wear layer is formed by coating an over-plasticised plastisol/ substantially with a polyvinyl Chloride base, onto a conveyor belt.

Preferably, the median layer based on plastics material waste is formed by dusting onto the wear layer particles of waste substantially with a PVC base, the particles then being pressed flat at a temperature of between approximately 1500C and approximately 2000C, and at a pressure of approximately 5 to approximately 20 bars.

According to a variant embodiment of the aforementioned preferred method of execution, the median layer based on PVC waste is formed by extruding particles of waste, substantially with a PVC base, through a flat die, at approximately 1850C.

Advantageously, the resilient underlayer is formed by depositing an adhesive layer consisting of an adhesive heat-fusible film or powder, onto the median layer, heating until the adhesive fuses, and laminating a regenerated polyurethane foam onto the median layer, at a temperature of between approximately 1300C and 1800C, and at a pressure of between approximately 2 bars and approximately 5 bars.

A decorative layer, based on a mixture of coloured granules or a printed film, can optionally be formed by fusion and pressing on the wear layer, before the median layer is formed.

According to a preferred variant of the method previously defined, in order to produce a floor covering from a composite plastics sheet according to the invention, additional steps are carried out, consisting of embossing or sanding the surface of the wear layer, sanding the surface of the median layer after the latter has been pressed and before the underlayer has been laminated, cutting the composite sheet into a required format, after lamination has taken place, stabilising the composite sheet in at least one stabilisation tunnel, and conditioning the composite sheet which has previously been cut into tiles.

The present invention is now described in greater detail with reference to the examples of a preferred embodiment of the invention, and with reference to the figures, in which:

figure 1 is a perspective, partially cutout view of a preferred embodiment of a composite sheet according to the present invention, without a reinforcement; - figure 2 is a schematic view in cross section of a production line for a composite sheet according to the present invention; figure 3 is a schematic view in cross section of a particulate, multilayer composite preform, before being pressed; figure 4 is a schematic view in cross section of a multi-layer composite sheet according to the invention, after being pressed; figure 5 is a schematic view in cross section of the continuation of the production line in figure 2, according to a preferred embodiment of a floor covering according to the invention; and k_ 1.

12 figures 6 and 7 show a schematic view in cross section of another production line for a composite sheet according to the present invention.

Figure 1 shows a partially cutout perspective view of a preferred embodiment of a multi-layer composite plastics sheet 1 according to the present invention, as it would be used for example for a floor covering, in particular in the form of a tile. From top to bottom, and for the requirements of the description of the invention, the sheet 1 comprises a first layer, known as the wear layer 2, a decorative layer 5, a second layer, known as the "median layer" 3, an adhesive layer 6, and a resilient underlayer 4, although the decorative layer 5, the adhesive layer 6, and the resilient underlayer are not compulsory for production of a suitable floor covering. The production of this sheet is now described with reference advantageously to figures 2 to 5, which illustrate schematically a preferred embodiment of the method for obtaining a composite plastics sheet, which is designed for use as a floor covering in the form of tiles.

The wear layer 2 is produced by depositing granules, for example dry blends, onto a conveyor belt 7. The conveyor belt consists of a material on which the adhesion of the layers formed is low or zero at the end of the pressing step, which allows the plastics sheet formed to be removed easily from the conveyor belt. Amongst the conveyor belts which can be suitable for transport of the sheet, reference can be made in particular to belts which are in the form of a metal strip, or belts which are made of Teflon@ or silicon.

According to the invention, the particles which constitute the first layer are preferably a dry blend with a base consisting of a PVC in suspension, the particles having a size grading of between 150 gm and 25Ogm, whereas 1 13 normal PVC suspensions have a size grading of approximately 130 gm.

The dry blend of the first layer can be obtained firstly by introducing the PVC in suspension into a hightank rapid mixer, which may or may not be provided with a heating envelope, together with plasticisers, stabilisers, lubricants and other additives necessary, and optionally conventional pigments, and then by raising the temperature to approximately 1200C by means of the high speed of the rotor (approximately 3000 rpm), then emptying all of the mixture, at this temperature, into a low-tank mixer with a cooling envelope. This makes it possible in particular to obtain small, plasticised dry round balls, which are optionally coloured. After suitable filtering, in order to eliminate the large and fine particles, there is obtained an optionally coloured mixture of grains, which are very regular and flow perfectly.

The granules can be deposited by means of any suitable depositing system 9, and in particular by means of a card distributor, a turbine sprinkler which may or may not be electrostatic, or by means of electrostatic spray pistols.

It is important to note that this layer is the first to be formed in the method according to the present invention, which means that the composite sheet 1 is constructed in reverse order, contrary to the habitual practice for production of composite sheets of this type, in particular when production of floor coverings is involved. This first layer, or "wear layer" 2, can also consist of a highly plasticised PVC plastisol, but without addition of any diluting agent, which permits additional easy de-bubbling. It can be coated onto the belt, then advantageously reinforced with PVC by additional electrostatic spraying (not shown) of a PVC in a very fine suspension (particles of approximately 35 gm to 45 gm), then pre-gelled by passage onto heating means, for example infrared lamps, at 14 approximately 1850C. This makes it possible to obtain a wear layer which is advantageously rigid, and in particular is well-suited for a floor covering in the form of tiles. This type of addition to the basic plastisol is commonly 5 known as PVC extender.

Advantageously, when the composite sheet 1 is designed for an application such as a floor covering, for example, the first layer can have a thickness of between approximately 0.10 mm and approximately 0.70 mm, and preferably has a thickness selected from amongst 0.25 mm, 0.50 mm and 0. 65 mm. After the granules have been deposited, the wear layer 2 can optionally be pre-gelled by passage beneath heating means, for example infrared lamps 10 at approximately 1850C.

The wear layer 2 can optionally be decorated, for example by providing a decorative layer 5, which will be applied or formed between the wear layer and the second layer, or the "median layer". In this case, the decorative layer can consist of a decorative film, or can be a coloured dry blend mixture, as previously defined, with pigments additionally incorporated. If a coloured dry blend is used in order to form the decorative layer, the latter is advantageously distributed by means of a distributor drum 11, such as to obtain a continuous mat of grains of different colours, and advantageously with a basis weight which is at least equivalent to 200 9/M2, based on grains which are 500 gm in diameter. In fact, below a basis weight of this type, it is found that the second layer 3 may be conveyed into the gaps created by the lack of coloured grains, which can disrupt the required decorative effect, when the second layer 3 consists ofregenerated materials such as PVC waste.

It has been found that the best results can be obtained by selecting size gradings which are quite similar 1.

is between the first and the second layer, i.e. between the wear layer and the median layer, but it has also been found that it is possible to obtain composite sheets according to the method, which are altogether suitable for use as a floor covering, by using granules, the median of the size grading of a layer of which, for example the second layer or "median layer", does not exceed 6 times the median of the size grading of the other layer, for example the first layer or "wear layer".

It has also been found that the fusibility of the particles can be important in order to obtain the best results. This fusibility is determined according to the following experimental method. A layer of particles of thermoplastic resin, for example dry blend, is deposited on a metal plate which is heated to 1900C. The time is then measured which is necessary for fusion (evaluated by means of the aggregation around a spatula), of all of the particles. The quality of the fused layer obtained in the composite sheet is all the better, the faster the fusibility, as previously described. In particular, particles which have fusibility of less than a few seconds, and more preferentially less than 15 seconds, make it possible to obtain composite sheets which have better performance levels.

The wear layer 2 and the median layer 3, and the decorative layer 5, if it is present, are then hot- and flat-pressed, during the pressing step which will be described in greater detail hereinafter. By this means, the decorative layer 5 obtained resembles very closely the decoration of a false plain printed sheet, whilst avoiding any printing and thus the need to provide a system of cylinders for printing and transfer of printed sheets. Preferably, the decorative layer 5 has a thickness after being pressed of approximately 0.10 mm. In addition, it has been found that use of a conventional coloured dry blend, -1.

16 consisting of a conventional PVC suspension with a size grading of approximately 130 gm, in order to form the decorative layer 5 in the manner previously described, does not provide this required decorative appearance, since the resulting decoration has no tones.

variants of colour and motifs can be introduced into the decorative layer 5, by adding chips with a selected size grading or form, for example which are opaque, transparent, coloured, multi-coloured, printed, or pearls, coloured wood and/or threads. If additives of this type are used, it is preferable to use particles with a small thickness, i.e. of approximately 0.08 mm to 0. 10 mm, in order to avoid deformations in the wear layer 2, and to distribute them on the latter before the dry blend mixture is distributed.

Preferably, the median layer 3 is substantially based on polyvinyl chloride (PVC) waste. PVC waste means for example production waste, either from edges, or from the assembly of the wear layer/median layer, but also from the assembly of the wear layer/median layer/resilient underlayer. Unexpectedly, the low percentage of polyurethane foam does not affect the recycling, since the presence of plasticised PVC in the mixture which constitutes the median layer permits satisfactory hot bonding under pressure. This PVC waste can also be obtained from crushed waste of floor coverings which have already been produced, and have been manufactured by means of coating or calendering, or for example from PVC bottles. The waste can optionally be modified by adding plasticisers, or fillers such as chalk etc. The thickness of the median layer deposited is preferably between approximately 0.40 mm and approximately 2 mm.

According to the embodiment illustrated in figure 2, the median layer is obtained by micronising a mixture of 1 17 waste as previously described,until a size grading of between approximately 300 gm and approximately 1200 gm is obtained, and preferably between 500 gm and 700 gm, which provides a heterogeneous mixture. This mixture is then distributed after distribution of the decorative layer, by a distribution means 12, such as already described for the wear layer and the decorative layer, in the form of a mat of particles, onto the decorative layer. The multi-layer composite preform thus formed is shown schematically in 10 cross section in figure 3. It can be seen that the particulate layers are separate, without substantial mixing of the various particles through the layers.

Then, the preform or the assembly of the layers, i.e.

the wear layer, optionally the decorative layer, and the median layer, are transferred into a flattening press 13a,13b. Flattening presses are commercially available, for example from the companies KVAERNER, HELD, HYMEN or SCHOTT ET MEISSNER, VILLARS, MEYER. In the case of the company KVAERNER, or HELD, or HYMEN, the press is provided with a double conveyor belt, and makes it possible to obtain a temperature of 2100C, with a maximum pressure of 80 bars. The press made by the companies SCHOTT ET MEISSNER, or VILLARS, or MEYER, is in fact a laminator, which is provided with a double conveyor belt made of silicon-coated or teflon-coated fabric, with a lower conveyor belt which is offset upstream, and permits transport of the granules, and which makes it possible to obtain a maximum operating temperature of 2500C, and a pressure of between 0.1 bar and 3 bars. According to the invention, the flattening press 13a,13b functions continuously, in a temperature range of between approximately 1500C and approximately 2000C, and at pressures of between approximately 0.5 bar and approximately 20 bars, according to a preferred embodiment.

The step of pressing flat consists of passing the assembly of the wear/decorative/median layers into a first hot area 18 13a approximately 4 m long, at a temperature of approximately 1800C, and at a pressure of approximately 8 bars. In this hat area 13a, the plastics materials of the wear, decorative 5 and median 3 layers fuse and are pressed together. The assembly then passes into a colder area 13b, which also has a length of approximately 4 m, and again a pressure of approximately 8 bars, but a temperature of approximately 700C. In practice, the press can be of the type which is commonly used in the industry for production of agglomerates or melamine resins, or such as previously described. The sheet thus pressed, comprising the wear, decorative and median layers, is discharged from the press at a temperature of between approximately SOOC and approximately 700C, which makes it possible to transfer the product at a low temperature, and thus to avoid retention of internal stresses, which would be detrimental for application of the finished composite sheet as a floor covering in the form of tiles.

At the end of this pressing step, a multi-layer composite sheet is obtained, in which there is virtually no interpenetration of the different layers, i.e. in which there is virtually no creepage. A structure of this type is shown schematically in figure 4.

In addition, it has been found that although the layers are geometrically independent from one another, the multi-layer composite sheet is virtually non-delaminable, and is suitable in its existing condition for use as a floor covering, in particular in the form of rolls. In fact, the applicant has carried out delamination tests, in accordance with standard NF EN 431, according to which a sample of the sheet is soaked in an acetone bath for 15 minutes, in order to stimulate delamination between the layers. The delamination force is then measured on a dynamometer. A value greater than 0.8 daN/em is considered to be excellent in terms of resistance to delamination. The 1.

19 composite sheets obtained according to the method of the present invention all have resistanee to delamination greater than 2 daN/cm, such that a layer is ruptured before the delamination can be measured.

The following step, which is optional for production of a composite sheet according to the invention, depends on the surface effect required. This step is desirable when the sheet is designed for use as a floor covering in the form of tiles. It consists of embossing and sanding the surface of the wear layer 2, and sanding the surface of the median layer 3, after it has been pressed, and before the underlayer 4 is laminated. For this purpose, the assembly obtained from the pressing step is heated, for example by passing it onto a hot drum (not shown), or beneath infrared lamps (not shown), at approximately 1100C. The free surface of the wear layer 2, i.e. the surface which will be exposed to the passages, is then subjected to embossing 14 at approximately 1100C, by means of an engraved embosser, for example, then to cooling 15 to ambient temperature, and calibration of the thickness by sanding 16, which makes it possible to impart greater regularity to the assembly produced.

After the step of pressing, and optionally embossing and sanding, the assembly can be glued to a resilient underlayer 4, the thickness of which can vary between approximately 1.5 mm and 3 mm, and is preferably 2 mm. This resilient underlayer 4 preferably consists substantially of cross-linked regenerated polyurethane foam, and in particular of polyurethane polyether foam waste, agglomerated by a polyurethane binding agent. In addition, and preferably, this resilient underlayer can also contain another cellular material, for example cork or a polyurethane polyester foam, fillers, and a waterproofing agent, such as an acrylic copolymer which contains fluorine (for example FC 3540 sold by the company MINNESOTA MINING r. 1, AND MANUFACTURING CO.), Foraperle 351 sold by the company ELF ATOCHEM, or a polyethylene wax (for example Hoechst Wax E, Ceridust 9502 sold by the company HOECHST, or AC 400 sold by the company Allied Signal).

In addition, the resilient underlayer 4 can consist of an open-cell foam. The constitution of the resilient underlayer in the form of open cells provides improved performance in terms of damping of impact noise, and unexpectedly, this improvement is not obtained to the detriment of residual indentation. In fact, polyurethane foam with a three-dimensional network (cross-linked), which can be used for the resilient underlayer, is very favourable to return after deformation. This makes it possible to avoid the major disadvantage of creepage which is encountered with plasticised PVC foams, or cork-based layers with a plasticised PVC-based matrix. In addition, another advantage of cellularisation opened by remelting the resilient underlayer, is that it makes it possible to obtain bonding more easily at the moment of adhesion, when the composite sheet is used for example as a floor-covering tile. The density of the resilient underlayer is between approximately 200 and 350 kg/ml, and more advantageously between 220 and 300 kg/m3.

With reference to the acoustic behaviour of the sheet according to the present invention, with an underlayer thickness of the type previously described, of between approximately 1.5 mm and approximately 3.0 mm, and with a density of 300 kg /M3, the applicant has obtained:

acoustic attenuation of between 14.4 dB(A) and 19.9 dB(A); static residual indentation after 150 minutes, of between approximately 0. 15 mm and approximately 0.26 mm; and static residual indentation after 24 hours, of between approximately 0.11 mm and approximately 0.18 mm.

1 - 1 1 21 with an underlayer thickness of 2.5 mm, and with a density of 220 kg/m', the applicant has also obtained:

acoustic attenuation of 21 dB(A); - static residual indentation after 150 minutes of 0.30 mm; and - static residual indentation after 24 hours of 0.22 mm.

Preferably, the resilient underlayer is assembled to, and on, the pressed assembly obtained from the preceding steps, by continuous lamination with an adhesive layer 6. This adhesive layer can be in the form of a film, or it can be deposited in cold liquid form (solvent glue) or hot liquid form (hot melt), or as a powder. The choice of the adhesive depends on the components of the layers to be assembled. It has been found for example that with a median layer which is made of PVC/polyurethane foam waste, the best results can be obtained by using as an adhesive copolyamides or copolyesters, for example a film known as TC 203, which is sold by the company Prochimir, or a powder known as UNEX 4103 sold by the company UNEX DAKOTA.

The resilient polyurethane underlayer 4 can be assembled with the median layer 3 as follows, and as illustrated in figure 5. The glue or adhesive layer 6 is applied or deposited on the median layer 3, which is supported by transport means, such as a conveyor belt. The quantity of glue deposited varies according to the nature and form of the latter, but is generally approximately 20 g to 60 g for a powder, and 30 g to 100 g for a film. The assembly is advanced as far as a continuous lamination unit 17, the adhesive layer 6 having been previously heated to approximately 1300C by heating means 18, for example infrared lamps, which are disposed at the intake of the lamination unit. The resilient underlayer 4 is unwound from above without tension, and is passed together with the assembly previously obtained, and which supports the adhesive layer, into the continuous lamination unit. The 22 adhesion of the underlayer is obtained by means of hot reactivation and progressive hot flat pressing. The lamination unit comprises two areas, a first hot area 17a, and a second area 17b which is colder than the first area, and resembles the pressing unit previously described. The hot area 17a has a length of approximately 4 m, but has a temperature difference between the upper part and the lower part of this area, i.e. the temperature above the conveyor belt is approximately 1800C, whereas that below the conveyor belt is approximately 1300C. The pressure which is is applied for the purpose of gluing is between approximately 0.2 bar and approximately 2 bars. The second, colder area, has a length of approximately 2 m, and functions at a temperature of approximately 420C. It is also possible to re-position the various layers when they are admitted into the lamination unit, as during the pressing step, which is not possible if a reinforcement is present. After passage through the lamination unit, the composite sheet obtained according to the invention is flat.

In order to be suitable for use as a floor covering in the form of tiles, the assembled composite sheet can then be cut 19 into a required format, stabilised, preferably flat without tension, for example, in a first stabilisation tunnel 20, which functions at approximately 1150C, and in a second stabilisation tunnel 21, which functions at 200C and then 100C at the output of the tunnel, and is finally conditioned in a conditioning unit 22. During the stabilisation, the conveyor belt is preferably a teflon- coated belt, in order to permit relaxation of stresses which may have formed in the sheet.

Thus, the finished composite sheet has excellent dimensional stability, and for example for floor covering tiles 2 m long has shrinkage of approximately only 0.05% both in length and width, according to NF EN 434. This sheet also has a very regular thickness, with a difference 1 j 23 of thickness of the resilient underlayer of approximately only 0.10 mm. Preferably, the total thickness of the completely assembled composite sheet is between approximately 2.5 mm and 4.5 mm, and the sheet can preferably have a surface area weight of between approximately 2000 9/m2 and approximately 3400 9/m2.

The following examples are intended to illustrate the preceding description. In these examples, two formulations have been used in order to create the first and second layers, i.e. DRYBLEND A and WASTE B, the compositions of which are given hereinafter:

DRYBLEND A Parts by weight PVC S K-Wert 70 100 Octyl Benzyl Phthalate 32 Stabiliser BaZn 2 Ca epoxystearate 3 PVC E K-Wert 64 2 Polyethylene wax 0.5 WASTE B Parts by weight PVC S K-Wert 64 80 PVC acetochloride (15%) 20 Dioctylphthalate 30 Ca stearate 1.5 Pb sulfate 2.5 Petroleum wax 3 CaC03 120 Stearin 0.4 Black chips BK30 2 24 Example 1

A composite sheet is produced as follows:

a layer of 320 g/m2 of DRYBLEND A particles with a size grading of 150 pm is deposited on a continuously moving metal plate; a second layer, consisting of 1350 9/m2 of particles of WASTE B, with a size grading of 300 pm, is then deposited on this first layer; - the preform is pressed at 15 bars at 1800C for 1 minute, the pressure is maintained at 15 bars for 1 additional minute, and the assembly is cooled, in order to reach a temperature of 700C.

is After these steps, a multi-layer composite sheet with a thickness of 1.12 mm is obtained, the resistance to delamination of which, measured according to standard NF EN 431, is greater than 2.7 daN/cm, and for which the rupture of the wear layer takes place before the delamination can be measured.

Example 2

A composite sheet is produced as follows:

320 9/M2 of DRYBLEND A particles with a size grading of 150 pm is deposited on a continuously moving metal plate; a second layer, consisting of 1350 9/m2 of particles of WASTE B, with a size grading of 300 pm, is then deposited on this first layer; - the preform is pressed at 80 bars at 1800C for 1 minute, the pressure is maintained at 80 bars for 1 additional minute, and the assembly is cooled, in order to reach a temperature of 700C.

After these steps, a multi-layer composite sheet with a thickness of 1.12 mm is obtained, the resistance to delamination of which, measured according to standard NF EN 431, is greater than 2.5 daN/cm, and for which the rupture of the wear layer takes place before the delamination can be measured.

Example 3

A composite sheet is produced as follows:

320 9/M2 of DRYBLEND A particles with a size grading of 150 pm is deposited on a continuously moving metal plate; a decorative film 0.09 mm thick is unwound; a second layer, consisting of 1350 g/m2 of particles of WASTE B, with a size grading of 300 pm, is then deposited on this first layer; - the preform is pressed at 15 bars at 1800C for 1 minute, the pressure is maintained at 15 bars for 1 additional minute, and the assembly is cooled, in order to reach a temperature of 700C.

After these steps, a multi-layer composite sheet with a thickness of 1.21 mm is obtained, the resistance to delamination of the various layers of which, measured according to standard NF EN 431, is greater than 2.4 daN/cm, and for which the rupture of the wear layer takes place before the delamination can be measured. when the sheet is cut vertically, it can be seen that the decorative film is not deformed and separates regularly, without significant interpenetration, the two layers obtained from particles.

Example 4 (comparative) A composite sheet is produced as follows:

320 9/M2 of DRYBLEND A particles with a size grading of 150 pm is deposited on a continuously moving metal plate; 26 a decorative film 0.09 mm thick is unwound; a second layer, consisting of 1350 g/m2 of particles of WASTE B, with a size grading of 1250 gm, is then deposited on this first layer; - the preform is pressed at 15 bars at 1800C for 1 minute, the pressure is maintained at 15 bars for 1 additional minute, and the assembly is cooled, in order to reach a temperature of 700C.

After these steps, a multi-layer composite sheet with a thickness of 1.21 mm is obtained, the resistance to delamination of the various layers of which, measured according to standard NF EN 431, is greater than 2 daN/cm. when the sheet is cut vertically, it can be seen that the decorative film is deformed by the presence of excessively large particles in the layer of waste, with deterioration of the appearance and geometry of the decoration.

In accordance with figures 6 and 7, another method is described hereinafter for obtaining a composite plastics sheet, which is designed for use as a floor covering in the form of tiles.

The wear layer 2 can be produced for example by calendering, by extrusion, by depositing of dry blend granules (dry blends means a mixture of PVC and plasticiser(s) in which the plasticiser(s) has or have been absorbed by the PVC grain, such that a product in powder form is maintained), or by coating a plastisol onto a conveyor belt 7, which in particular is in the form of a metal belt. The coating can be carried out in particular by means of cylinders, a preferred arrangement of which is the device with a reverse-roll coater, spray pistols, and a scraper 9, the latter being shown in figure 2. It is important to note that this layer is the first to be formed in the method according to the present invention, which means that the composite sheet 1 is constructed in reverse 27 order, contrary to the habitual practice for production of composite sheets of this type, in particular when the production of floor coverings is involved. This wear layer 2 is substantially based on polyvinyl chloride, which is preferably highly plasticised, and thus very fluid, but without addition of diluting agent, which permits easy debubbling and simplifies the production process as a whole. The wear layer 2 can be reinforced with PVC by electrostatic spraying (not shown) of a PVC in a very fine suspension (particles of approximately 35 pm to 45 pm), which makes it possible to obtain a wear layer which is advantageously rigid, and in particular is well-suited for a floor covering in the form of tiles. This type of addition to the basic plastisol is commonly known as PVC extender. Advantageously, when the composite sheet 1 is designed for application as a floor covering, for example, the wear layer 2 can have a thickness of between approximately 0.25 mm and approximately 0.70 mm, and preferably has a thickness selected from amongst 0.25 mm, 0.50 mm and 0.65 mm. After being coated, the wear layer 2 can optionally be pre-gelled by passage beneath heating means, for example infrared lamps 10 at approximately 1850C.

The wear layer 2 can optionally be decorated, for example by providing a decorative layer 5, which will be formed between the wear layer and the median layer. In this case, the decorative layer can consist of a mixture known as a coloured dry blend, which uses a PVC in suspension, with a size grading of between 300 pm and 700 pm, and preferably approximately 500 pm, whereas normal PVC suspensions have a size grading of approximately 130 pm.

The dry blend mixture can firstly be introduced into a high-tank rapid mixer, provided with a heating envelope (approximately 120OC), together with plasticisers, pigments and conventional stabilisers, and then introduced into a low-tank mixer with a cooling envelope. This makes it 1 1 R.. fl 28 possible to obtain small, plasticised, coloured, round balls. After suitable filtering, in order to eliminate the large and fine particles, there is obtained a coloured mixture of grains, which are very regular and flow perfectly.

These balls can then be distributed on the wear layer 2, which is already deposited on the conveyor belt 7 upstream. The dry blend mixture is preferably distributed, for example, by means of a distributor drum 11, such as to obtain a continuous mat of grains of different colours, and advantageously with a basis weight which is at least - equivalent to 200 9/M2, based on grains which are 500 pm in diameter. In fact, below a basis weight of this type, it is found that the median layer 3 may be conveyed into the gaps created by the lack of coloured grains, which can disrupt the required decorative effect, when the median layer 3 consists of regenerated materials such as PVC waste.

The.decorative layer 5, if it is present, is then hot pressed flat, between the wear layer 2 and the median layer 3, during a pressing step which will be described in greater detail hereinafter. By this means, the decorative layer 5 obtained resembles very closely a false plain printed sheet, whilst avoiding any printing, and thus the need to provide a sys tem of cylinders for printing and transfer of printed sheets. Preferably, the decorative layer 5 has a thickness after being pressed of approximately 0.15 mm, and is engaged in the mass of the wear layer 2. In addition, it has been found that use of a conventional pigmented dry blend, consisting of a conventional PVC suspension with a size grading of approximately 130 pm, in order to form the decorative layer 5 in the manner previously described, does not provide this required decorative appearance, since the resulting decoration has no tones.

1 29 According to the present invention, the median layer 3 is bonded on one side by being pressed in a press 13a,13b, to the wear layer 2, and on the other side by being glued to the resilient underlayer 4, the said median layer 3 comprising a thermoplastic resin, for example a polyvinyl chloride. Preferably, this median layer 3 is substantially based on polyvinyl chloride (PVC) waste. PVC waste means for example production waste, either from edges, or from the assembly of the wear layer/median layer, but also from the assembly of the wear layer/median layer/resilient underlayer. Unexpectedly, the low percentage of polyurethane foam does not affect the recycling, since the presence of plasticised PVC in the mixture which constitutes the median layer permits satisfactory hot bonding under pressure. This PVC waste can also be obtained from crushed waste of floor coverings which have already been produced, and have been manufactured by means of coating or calendering, or for example from PVC bottles. The waste can optionally be modified by adding plasticisers, or fillers such as chalk etc. It is possible to form the median layer 3 in two preferred manners, which will be described hereinafter. The thickness of the median layer deposited is preferably between approximately 0.40 mm and approximately 1.50 mm.

According to a first variant, which is illustrated in figures 6 and 7, the median layer 3 is obtained by extrusion, at approximately 1850C, for example by means of a flat die extruder 12, of a mixture of waste obtained from edges, off-cuts, and polyurethane foam waste, into a plasticised PVC mixture with non-thermoplastic cross-linked polyurethane foam. In addition, the extrusion has the advantage that the mixture can be controlled easily, in particular concerning the addition of additives, for example chalk, and also makes it possible to produce a film with a thickness which is quite regular, and which will be integrated perfectly in the press 13a,13b, without 1 disturbing the mixture of the decorative layer 5. This step of the method can also be automated in terms of the supply, the thickness of the film produced, and the flow rate which is necessary for the press 13a,13b.

According to a second variant, the median layer is obtained by micronising a mixture of waste as previously described, until a size grading of approximately 1200 gm is obtained, which provides a heterogeneous mixture. This mixture is then distributed after distribution of the decorative layer, in the form of a mat of particles, onto the decorative layer. Then, the assembly of the layers, i.e. the wear layer, optionally the decorative layer, and the median layer, are transferred into a flattening press 13a,13b.

The flattening press 13a,13b functions continuously, in a temperature range of between approximately 1500C and approximately 2001C, and at pressures of between approximately 5 bars and approximately 20 bars. The step of pressing flat consists of passing the assembly of the wear/decorative/median layers into a first hat area 13a approximately 4 m long, at a temperature of approximately 1800C, and at a pressure of approximately 8 bars. In this hot area 13a, the plastics materials of the decorative 5 and median 3 layers fuse and are pressed together with the wear layer 2. It is also possible in this area to realign the various layers relative to one another, which is not the case if a reinforcement is present. The assembly then passes into a colder area 13b, which also has a length of approximately 4 m, and again at a pressure of approximately 8 bars, but at a temperature of approximately 700C. In practice, the press can be of the type which is commonly used in the industry for production of agglomerates. The sheet thus pressed, comprising the wear, decorative and median layers, is discharged from the press at a temperature of between approximately 500C and approximately 1 1 31 700C, which makes it possible to avoid retention of internal stresses, which would be detrimental for application of the finished composite sheet as a floor covering in the form of tiles.

After the step of pressing, and optionally embossing and sanding, the assembly is glued to a resilient underlayer 4, the thickness of which can vary between approximately 1.5 mm and 3 mm, and is preferably 2 mm. This resilient underlayer 4 preferably consists substantially of cross-linked regenerated polyurethane foam, and in particular of polyurethane polyether foam waste, agglomerated by a polyurethane binding agent. In addition, and preferably, this resilient underlayer can also contain another cellular material, for example cork or a polyurethane polyester foam, fillers, and a waterproofing agent, such as an acrylic copolymer which contains fluorine (for example FC 251 sold by the company Minnesota mining and Manufacturing Co.), or a polyethylene wax (for example Hoechst Wax E, sold by the company Hoechst).

In addition, the resilient underlayer 4 can consist of an open-cell foam. The constitution of the resilient underlayer in the form of open cells provides improved performance in terms of damping of impact noise, and unexpectedly, this improvement is not obtained to the detriment of residual indentation. In fact, polyurethane foam with a three-dimensional network (cross-linked) which can be used for the resilient underlayer is very favourable to return after deformation. This makes it possible to avoid the major disadvantage of creepage which is encountered with plasticised PVC foams, or cork-based layers with a plasticised PVC-based matrix. In addition, another advantage of cellularisation opened by remelting the resilient underlayer is that it makes it possible to obtain bonding more easily at the moment of adhesion, when the composite sheet is used for example as a floor-covering 1 32 tile. The density of the resilient underlayer is between approximately 200 and 350 kg/m, and more advantageously between 250 and 310 kg/m3.

With reference to the acoustic behaviour of the sheet according to the present invention, with an underlayer thickness of the type previously described, of between approximately 1.5 mm and approximately 3.0 mm, and with a density of 305 kg/m3, the applicant has obtained:

- acoustic attenuation of between 14.4 dB(A) and 19.9 dB(A); - static residual indentation after 150 minutes, of between approximately 0.15 mm and approximately 0.26 mm; and is - static residual indentation after 24 hours, of between approximately 0.11 mm and approximately 0.18 mm.

with an underlayer thickness of 2.8 mm, and with a density of 255 kg/m3, the applicant has also obtained:

acoustic attenuation of-21 dB(A); static residual indentation after 150 minutes of 0.35 mm; and static residual indentation after 24 hours of 0.23 mm.

The resilient polyurethane underlayer 4 can be assembled with the median layer 3 as follows. The glue or adhesive layer 6 is applied or deposited on the median layer 3, which is supported by transport means, such as a conveyor belt. The quantity of glue deposited varies according to the nature and form of the latter, but is generally approximately 20 9 to 60 9 for a powder, and 50 g to 100 g for a film. The assembly is advanced as far as a continuous lamination unit 17, the adhesive layer 6 having been previously heated to approximately 1300C by heating means 18, for example infrared lamps, which are disposed at the intake of the lamination unit. The resilient underlayer 4 is unwound from above without tension, and ispassed with 1 33 the assembly previously obtained, and which supports the adhesive layer, into the continuous lamination unit. The adhesion of the underlayer is obtained by means of hot reactivation and progressive hot flat pressing. The lamination unit comprises two areas, a first hot area 17a, and a second area 17b which is colder than the first area, and resembles the pressing unit previously described. The hot area 17a has a length of approximately 4 m, but has a temperature difference between the upper part and the lower part of this area, i.e. the temperature above the conveyor belt is approximately 1800C, whereas that below the conveyor belt is approximately 1300C. The pressure which is applied for the purpose of gluing is between approximately 2 bars and approximately 5 bars. The second, colder area, has a length of approximately 2 m, and functions at a temperature of approximately 420C. It is also possible to re-position the various layers when they are admitted into the lamination unit, as during the pressing step, which is not possible if a reinforcement is present. After passage through the lamination unit, the composite sheet obtained according to the invention is flat.

In order to be suitable for use as a floor covering in the form of tiles, the assembled composite sheet can then be cut 19 into a required format, stabilised, preferably flat without tension, for example, in a first stabilisation tunnel 20, which functions at approximately 1150C, and in a second stabilisation tunnel 21, which functions at 200C and then 100C at the output of the tunnel, and is finally conditioned in a conditioning unit 22. During the stabilisation, the conveyor belt is preferably a tefloncoated belt, in order to permit relaxation of stresses which may have formed in the sheet.

Thus, the finished composite sheet has excellent dimensional stability, and for example for floor covering tiles 2 m long has shrinkage of approximately only 0.05% 1 1 34 both in length and width. This sheet also has a very regular thickness, with a difference of thickness of the resilient underlayer of approximately only 0.10 mm. Preferably, the total thickness of the completely assembled composite sheet is between approximately 2.5 mm and 4.5 mm, and can preferably have a surface area weight of between approximately 2400 9/M2 and approximately 3400 9/M2.

1 -1.

Claims (21)

1 - Method for production of a composite plastics sheet, comprising the steps consisting of: forming a first particulate layer, for example a wear layer, by dusting a particulate resin onto the surface of a mobile support; forming at least one second particulate layer on the first particulate layer, in order to form a preform with a multi-layer composite structure; and applying pressure and heat to the preform in order to fuse the particles, characterised in that the step of application of pressure and heat consists of pressing the preform flat continuously, at a temperature of between approximately 1500C and approximately 2o0OC, and at a pressure of approximately 0.5 bar to approximately 20 bars, such that the preform is transformed into a multi- layer composite sheet, without substantial creepage of one layer into the other.

is 2'. Method for production of a composite sheet (1) according to claim 1, characterised in that the method comprises the additional step which consists of laminating a resilient underlayer (4) made of foamed plastics material, continuously onto the second layer.

3. Method according to claim 1, characterised in that the second layer (3) is substantially based on PVC waste.

4. Method according to claim 1, characterised in that a resilient underlayer (4) is formed by depositing an adhesive layer (6) consisting of an adhesive heat-fusible film or powder onto the second layer (3), heating until the adhesive (6) fuses, and laminating a regenerated polyurethane foam (4) onto the median layer (3), at a temperature of between approximately 1000C and 1800C, and 1 L 36 at a pressure of between approximately 0.2 bar and approximately 2 bars.

5. Method according to claim 1, characterised in that a decorative layer (5) is additionally formed, based on a mixture of coloured granules, or a film which is printed onto the first layer (2), before the second layer (3) is formed.

6. Method for production of a floor covering, consisting of producing a composite plastics sheet according to any one of claims 1 to 5, characterised in that the method. comprises additional steps consisting of embossing (14) and sanding (16) the surface of the first layer (2), after the second layer (3) has been pressed, and before the underlayer (4) is laminated, cutting (19) the composite sheet (1) into a required format, after lamination has taken place, stabilising the composite sheet (1) in at least one stabilisation tunnel (20,21), and conditioning (22) the composite sheet (1) which has previously been cut into tiles.

7. Multi-layer composite plastics sheet (1), comprising at least one continuous first layer (2), for example a wear layer, comprising a thermoplastic resin, for example a polyvinyl chloride (PVC), and at least one second layer (3), for example a median layer, which also comprises a thermoplastic resin, characterised in that before being pressed with application of heat, it is a preform which comprises at least two separate layers of particles, and after being pressed with application of heat, it is a finished multi-layer composite sheet (1), without substantial creepage from one layer (2) into the other layer (3).

8. Composite plastics sheet (1) according to claim 7, characterised in that the first layer (2) has a thickness 1 37 of between approximately 0.10 mm and approximately 0.70 mm, and preferably has a thickness which is selected from amongst 0.25 mm, 0.50 mm and 0.65 mm.

9. Composite plastics sheet (1) according to claim 7, characterised in that it comprises a decorative layer (5) between the first layer (2) and the second layer (3).

10. Composite plastics sheet (1) according to claim 9, characterised in that the decorative layer (5) is obtained by pressing coloured plastics granules, and optionally adding an additional relief layer based on flakes, chips, and/or filaments.

11. Composite plastics sheet (1) according to claim 9, characterised in that the decorative layer (5) consists of a printed film.

12. Composite plastics sheet according to claim 7, characterised in that it additionally comprises a resilient underlayer (4), which has a discontinuous alveolar structure, the thickness of which is cross-linked, and which comprises at least one plastics material.

13. Composite plastics sheet (1) according to claim 7, characterised in that it comprises an adhesive layer (6) between the second layer (3) and a resilient underlayer (4).

14. Composite plastics sheet (1) according to claim 13, characterised in that the adhesive layer (6) is selected from amongst the group which consists of a heat-fusible film, a double layer of copolyamide and ethylene vinyl acetate (EVA), a copolyester, a heat-fusible powder of the polyurethane or polyester type, a hot melt layer of the polyurethane type, an "emulsion" glue of the polyurethane type, and a "solvent" glue of the polyurethane type.

1 1 38

15. Composite plastics sheet (1) according to claim 14, characterised in that the adhesive layer (6) is selected in order to prevent migration of the plasticisers of the second layer (3) towards the resilient underlayer (4).

16. Composite sheet according to claim 7, characterised in that the second layer (3) is substantially based on polyvinyl chloride (PVC) waste.

17. Composite sheet according to claim 7, characterised in that the thickness of the second layer deposited is preferably between approximately 0.40 mm and approximately 2 mm.

18. Composite sheet according to claim 12, characterised in that the resilient underlayer (4) substantially consists of cross-linked regenerated polyurethane foam.

19. Composite sheet according to claim 12, characterised in that the resilient underlayer (4) consists of a homogeneous mixture of: flakes of selected, cross-linked polyurethane foam; a bonding prepolymer with a polyurethane base; a regenerated rubber powder; optionally granules of cork; and other additives, such as pigments and waterproofing agents.

20. Composite sheet according to claim 7, characterised in that the resilient underlayer (4) consists of an open-cell foam which is rendered waterproof.

21. Floor covering, in particular in the form of tiles, comprising a composite sheet according to any one of claims 7 to 20.