FR2761295A1 - COMPOSITE SHEET, FLOOR COVERING COMPRISING SAME, AND METHODS OF MAKING SAME - 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 DEG C to approximately 200 DEG 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

 The present invention relates to a composite sheet without reinforcement, for example a polyvinyl chloride (PVC) floor covering, and to a method for obtaining it. In particular, the present invention relates to a composite sheet which does not require reinforcement in the form of a layer of reinforcing fibers to improve its dimensional stability.

In the present application, by the expression "PVC" is meant both polymers whose K values are preferably between 45 and 110, for example homopolymers with K values between 55 and 110, vinyl chloride copolymers and vinyl acetochloride, or graft copolymers with a K value between 45 and 100. The term "PVC" can also apply to PVC waste or compositions based on PVC or PVC copolymers. PVC emulsion and / or microsuspension can also be used with or without anti-caking treatment. It goes without saying that these different
PVC homopolymers or copolymers can also be used as a mixture.

 In general, composite sheets based on at least one layer of plastic, for example polyvinyl chloride (PVC) as defined above, are known. Such composite sheets usually comprise on the surface at least one non-foamed wear layer of plastic material essentially based on PVC, beneath which one or more at least one layer of plastic material, optionally foamed, with a base layer under form of a non-woven sheet, of glass fibers for example, possibly embedded in a plastic material, and which serves as a reinforcement for the entire composite structure.

 This frame gives a certain flatness and dimensional stability to the composite structure or sheet, so as to prevent shrinkage during its packaging and use. Furthermore, a reinforcing layer has always been considered necessary for composite sheets intended to find application as floor covering tiles, for example, because it effectively prevented or reduced the shrinkages of the sheet mentioned above, caused by internal stresses. of the composite structure.

This need to incorporate a reinforcement in such composite sheets was disadvantageous, because it complicated the manufacturing process and significantly increased the cost of production. This problem became all the more important when it was a question of obtaining a composite sheet intended for a floor covering presenting not only good mechanical characteristics, but also an improved acoustic behavior, because generally known composite sheets n '' did not dampen enough impact noise.

 There was therefore a problem, on the one hand, in simplifying the structure of such a composite sheet so that it has practically no reinforcement, while maintaining the equivalent mechanical performance of a sheet provided with '' such a reinforcement, and at the same time, by improving the acoustic behavior of the sheet, in the fields of application of such composite sheets, in particular floor coverings, and on the other hand in the simplification of a manufacturing process for such composite sheets, avoiding the incorporation of relatively expensive reinforcing layers.

 Consequently, an object of the present invention is a composite plastic sheet, comprising a wear layer, possibly decorated, continuous, comprising a thermoplastic resin, for example a polyvinyl chloride (PVC), the sheet also comprising a resilient undercoat having a discontinuous cellular structure, crosslinked in its thickness, comprising at least one plastic. The composite sheet is more particularly characterized in that the sheet further comprises a middle layer bonded on one side by pressing to the wear layer, and on the other side by bonding with the resilient under layer, said middle layer comprising a thermoplastic resin, for example a polyvinyl chloride, all without practically any reinforcement integrated into all or part of the structure of said composite plastic sheet.

 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.

 Yet another object of the present invention is a method of manufacturing a composite plastic sheet, according to the definition given above. This process is characterized in that at the outset the wear layer is formed, for example by coating the surface of a mobile support with a plastisol, then gelling of the latter, then it is attached to and assembled directly or indirectly with the layer the middle layer of wear, by pressing, and the resilient underlayer is attached to and bonded with the middle layer, whereby said plastic sheet is formed upside down, from the wear layer serving as a substrate.

 The composite sheet according to the present invention is dimensionally stable, and planar, that is to say that it behaves from a mechanical point of view essentially like a composite sheet of known type comprising a reinforcement, for example of glass embedded in a layer of plastic, and has good acoustic behavior. I1 was also found that if the sheet was constructed from the middle layer, that is to say according to the usual prior technique of construction, there was a deformation of this middle layer during pressing, and the flatness does not could no longer be insured.

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

 In a preferred embodiment, the wear layer comprises a decorative layer between the wear layer and the middle layer. According to a preferred variant of this embodiment, the decorative layer is obtained by melting and pressing of colored plastic 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 layer of adhesive between the middle layer and the resilient sublayer. Preferably, the adhesive layer is chosen from the group consisting of a hot-melt film, a bilayer of copolyamide and ethylene vinyl acetate (EVA), a bilayer of copolyester, a hot-melt powder of the polyurethane or polyester type, a "hot melt" layer. "of the polyurethane type, an" emulsion "adhesive of the polyurethane type, and a" solvent "adhesive of the polyurethane type.

 Preferably, the middle layer is essentially based on polyvinyl chloride (PVC) waste and may have a deposited thickness preferably between approximately 0.40 mm to approximately 1.50 mm.

Advantageously, the resilient underlay consists essentially of crosslinked regenerated polyurethane foam. More preferably, the resilient underlay consists of a homogeneous mixture
- selected and crosslinked polyurethane foam flakes
- a polyurethane-based bonding prepolymer
- rubber powder
- possibly cork granules
- and other adjuvants, such as pigments, water repellents, and dyes.

 According to another preferred embodiment of the invention, the resilient underlay consists of open cell foam.

In a preferred embodiment of the method according to the present invention, it comprises at least the steps consisting in:
- continuously forming upside down at least one non-foaming wear layer essentially based on PVC on means of transport;
- forming a middle layer essentially based on PVC waste on the wear layer by continuous flat pressing with the wear layer;
- and continuously laminate a resilient foam plastic underlay on the middle layer.

 Advantageously, the wear layer is formed by coating an overplasticized plastisol essentially based on polyvinyl chloride on a conveyor belt.

 Preferably, the middle layer based on plastic waste is formed by sprinkling waste particles essentially PVC-based on the wear layer, these then being pressed flat at a temperature of between about 1500C and approximately 2000C, and at a pressure of approximately 5 to approximately 20 bars.

In an alternative embodiment of the preceding preferred embodiment, the middle layer based on waste in
PVC is formed by extruding, through a flat die at around 1850C, waste particles essentially based on PVC.

 Advantageously, the resilient sub-layer is formed by depositing an adhesive layer consisting of a film or an adhesive hot-melt powder on the middle layer, by heating until the adhesive melts, and by laminating a foam in polyurethane regenerated on the middle layer at a temperature between about 1300C and 1800C and at a pressure between about 2 to about 5 bars.

 It is optionally possible to form, by fusion and pressing, a decorative layer on the wear layer before forming the middle layer, based on a mixture of colored granules or a printed film.

 In a preferred modification of the process defined above, to manufacture a floor covering from a composite plastic sheet according to the invention, the additional steps are carried out consisting of graining or sanding the surface of the wear layer, sanding the surface of the middle layer after pressing the latter and before laminating the sublayer, cutting the composite sheet after laminating in a desired format, stabilizing the composite sheet in at least one stabilization tunnel, and conditioning the sheet composite previously cut into tiles.

The present invention will now be described in more detail with reference to the examples of a preferred embodiment of the invention and with respect to
Figures, in which
- Figure 1 shows a partially cutaway perspective view of a preferred embodiment of a composite sheet without reinforcement according to the present invention;
- Figure 2 shows a schematic sectional view of a manufacturing line for a composite sheet according to the present invention.

 Figure 1 shows a partially cutaway perspective view of a composite plastic sheet 1 according to the present invention, as it would be used for example as a floor covering, in particular in the form of a slab. From top to bottom, the sheet 1 comprises a wear layer 2, a decorative layer 5, a middle layer 3, an adhesive layer 6, and a resilient sublayer 4. The manufacture of this sheet will now be described with reference usefully in Figure 2, which schematically illustrates a preferred embodiment of the process for obtaining a composite plastic sheet, for use as a floor covering in the form of slabs.

 The wear layer 2 can be manufactured, for example by calendering, by extrusion, by deposition of dry blends granules (dry blends is understood to mean a mixture of PVC and plasticizer (s) in which the plasticizer (s) have been absorbed by the PVC grain in such a way that a pulverulent product is preserved) or also by coating with a plastisol on a conveyor belt 7, in particular in the form of a metallic strip.

The coating can be done in particular by means of cylinders, a preferred arrangement of which is the reverse roller coater device, spray guns, a doctor blade 9, the latter being shown in FIG. 2. It is important to note that this layer is the first to be formed in the process according to the present invention, which means that the composite sheet 1 is constructed upside down, contrary to the usual practice of manufacturing composite sheets of this type, in particular when it comes to the manufacture of floor coverings. This wear layer 2 is essentially based on polyvinyl chloride, preferably very plasticized, therefore very fluid, but without the addition of diluent, which allows easy boiling and simplifies the entire manufacturing process. The wear layer 2 can be reinforced in PVC by electrostatic spraying (not shown) of a PVC in very fine suspension (particles of approximately 35 μm to 45 m), which makes it possible to obtain a wear layer advantageously. rigid, in particular well suited to a floor covering in the form of tiles. This type of addition to the basic plastisol is commonly called "PVC Extender". Advantageously, when the composite sheet 1 is intended for an application as a floor covering, for example, the wear layer 2 may have a thickness of between approximately 0.25 mm to approximately 0.70 mm, and preferably present a thickness chosen from 0.25 mm, 0.50 mm and 0.65 mm. After coating, the wear layer 2 can be pre-gelified by passing under heating means, for example infrared lamps 10 at around 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 middle layer. In this case, the decorative layer may consist of a mixture called "dry blend" colored, which uses a suspended PVC with a particle size between 300 ssm and 700 pm, and preferably of the order of 500 pm, while the normal suspensions of
PVC have a particle size of the order of 130 pm. The dry blend can first be introduced into a fast mixer with a high tank provided with a heating jacket (around 1200C), with the usual plasticizers, pigments and stabilizers, and then introduced into a mixer with a low tank with a jacket. cooling. This makes it possible to obtain small round, plasticized and colored beads. After appropriate sieving to remove large particles and fines, a mixture of very regular and perfectly flowing colored grains is available.

 These balls can then be distributed on the wear layer 2 already deposited on the conveyor belt 7 upstream. Preferably, the “dry blend” mixture is distributed, for example using a distributor drum 11, so as to obtain a continuous mattress of grains of different colors, and advantageously in a grammage at least equal to 200 g / m2 based on grains at 500 µm in diameter. Indeed, below such a grammage, it can be seen that the middle layer 3 can appear in the voids created by the lack of colored grains, which can disturb the desired decoration when the middle layer 3 is made of regenerated materials. , such as PVC waste.

 The decorative layer 5, if present, is then hot pressed and flat between the wear layer 2 and the middle layer 3, during a pressing step which will be described in more detail below. In this way, the decorative layer 5 obtained resembles a decoration very close to a false plain printed sheet, while avoiding printing, and therefore the need to provide a system of printing cylinders and sheet transfer printed. Preferably, the decorative layer 5 has a thickness after pressing of the order of about 0.15 mm and is taken from the mass of the wear layer 2. Furthermore, it has been observed that the use of a usual pigmented "dry blend" consisting of a usual PVC suspension with a particle size of approximately 130 μm, to form the decorative layer 5 in the manner described above, does not give this desired decorative appearance, because the decoration which results is without nuances.

 Variants of color and patterns can be introduced into the decorative layer 5 by adding chips of particle size or chosen shape, for example opaque, transparent, colored, multicolored, printed, or pearlescent, colored wood, and / or sons. If such additions are used, it is preferable to use particles of small thickness, that is to say of the order of 0.08 mm to 0.10 mm, in order to avoid deformations in the layer. wear 2, and distribute them on the latter upstream of the distribution of the "dry blend".

According to the present invention, the middle layer 3 is bonded on one side by pressing in a press 13a, 13b to the wear layer 2, and on the other side by bonding with the resilient underlay 4, said layer median 3 comprising a thermoplastic resin, for example a polyvinyl chloride. Preferably, this middle layer 3 is essentially based on polyvinyl chloride (PVC) waste. By waste in
PVC is understood to mean, for example, line scrap, either from selvedges or from the wear layer / middle layer assembly, but also from the wear layer / middle layer / resilient underlayment assembly. Surprisingly, the low percentage of polyurethane foam does not disturb recycling, because the presence of plasticized PVC in the mixture constituting the middle layer allows sufficient bonding when hot under pressure. This PVC waste can also come from crushed waste from floor coverings already produced, manufactured by coating or calendering, or for example also from PVC bottles. The waste can optionally be modified by adding plasticizers, fillers, for example chalk, etc. It is possible to form the middle layer 3 in two preferred ways, which will be described below. The thickness of the deposited middle layer is preferably between approximately 0.40 mm to approximately 1.50 mm.

 In a first variant, and that which is illustrated in FIG. 2, the middle layer 3 is obtained by extrusion, at around 185 "C, for example with an extruder 12 in a flat die, of a mixture of waste from selvedges, cutting grids, polyurethane foam waste, in a mixture of plasticized PVC with non-thermoplastic crosslinked polyurethane foam. Furthermore, the extrusion has the advantage that the mixture can be easily controlled, in particular as regards the addition of adjuvants, for example chalk, and also makes it possible to produce a film of fairly regular thickness which will integrate perfectly into the press 13a, 13b without disturbing the mixing of the decorative layer 5. This step of the process can also be automated in terms of feeds, the thickness of the film produced and the flow required for the press 13a, 13b.

 In a second variant, the middle layer is obtained by micronizing a mixture of waste as described above up to a particle size of approximately 1200 m, which gives a heterogeneous mixture. This mixture is then distributed downstream of the distribution of the decorative layer, in the form of a mattress of particles, on the decorative layer. Then, all of the layers, that is to say the wear layer, the optional decorative layer, and the middle layer pass through a flat press 13a, 13b.

 The flat press 13a, 13b operates continuously, in a temperature range between about 1500C to about 2000C, and at pressures between about 5 bar to about 20 bar. The flat pressing step consists in passing all of the wear / decorative / middle layers in a first hot zone 13a of approximately 4 meters long, at a temperature of approximately 1800C, and at a pressure of about 8 bar. In this hot zone 13a, the plastics of the decorative layers 5 and middle 3 merge and are pressed together with the wear layer 2. It is also possible in this zone to realign the different layers with respect to each other, which is not the case if an armature is present. The assembly then passes into a cooler zone 13b, also about 4 meters in length, and still under pressure of around 8 bar, but at a temperature of around 700C. In practice, the press can be of the type commonly used in the particle board industry. The sheet thus pressed comprising the wear layers, decorative and middle, leaves the press at a temperature between about 50 C and about 700C, which avoids the storage of internal stresses which would be troublesome for an application of the composite sheet finished as a floor covering in the form of tiles.

 The next step, which is optional for the production of a composite sheet according to the invention, depends on the desired surface effect. This step is desired when it is intended for use as a floor covering in the form of tiles. It consists of graining and sanding the surface of the wear layer 2 and sanding the surface of the middle layer 3 after pressing and before laminating the undercoat 4. To do this, the whole assembly is heated with pressing step, for example by passing it over a hot drum (not shown), or under infrared lamps (not shown), at around 1100C. The free surface of the wear layer 2, that is to say the surface which will be exposed to the passages, is then subjected to a graining 14 at about 1100C, by means of an embossed grainer, for example, then a cooling 15 to room temperature, and calibrating the thickness by sanding 16, which makes it possible to give greater regularity to the assembly produced.

After the pressing step, and possibly of graining and sanding, the assembly is bonded to a resilient underlay 4, the thickness of which can vary between approximately 1.5 mm and 3 mm, and preferably is 2 mm. This resilient sublayer 4 is preferably essentially constituted of crosslinked regenerated polyurethane foam, and in particular waste polyurethane polyether foam agglomerated by a polyurethane binder. Furthermore, and preferably, this resilient underlayment can additionally contain another cellular material, for example cork or a polyurethane polyester foam, fillers, as well as a water-repellent agent, such as an acrylic copolymer. fluorinated (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).

 Furthermore, the resilient underlayer 4 may consist of an open cell foam. The constitution of the resilient underlay in the form of open cells gives a better behavior to the damping of impact noises, and surprisingly, this improvement is not done to the detriment of the residual punching. Indeed, the polyurethane foam with a three-dimensional network (crosslinked) capable of being used for the resilient underlay is very favorable to the return after deformation. This avoids the major drawback of creep that is observed with plasticized PVC foams or cork-based layers with a matrix based on plasticized PVC.

Furthermore, another advantage of open cellularization by recasting the resilient underlay is that it makes it easier to hang when bonding when using the composite sheet, for example as a slab of flooring.

The density of the resilient sub-layer is between approximately 200 and 350 kg / m3 and more advantageously between 250 and 310 kg / m3.

With regard to the acoustic behavior of the sheet according to the present invention, the applicant has obtained, with a thickness of underlay of the type described above of between approximately 1.5 mm and approximately 3.0 mm, and of density of 305 kg / m3
- an acoustic loss between 14.4 dB (A) and 19.9 dB (A);
- a static residual punching after 150 minutes between approximately 0.15 mm and approximately 0.26 mm
- a static residual punching after 24 hours ranging between approximately 0.11 mm to approximately 0.18 mm.

The depositor also obtained with an undercoat thickness of 2.8 mm and a density of 255 kg / m3
- an acoustic reduction of 21 dB (A);
- a static residual punch after 150 minutes of 0.35 mm
- a static residual punching after 24 hours of 0.23 mm.

 Preferably, the resilient sublayer is assembled to and on the pressed assembly of the preceding steps by continuous lamination with an adhesive layer 6. This adhesive layer can be in the form of a film or be deposited in liquid or powder form. The choice of adhesive depends on the components of the layers to be assembled. It has been found, for example, that with a middle layer of PVC waste / polyurethane foam, the best results could be obtained by using copolyamides or copolyesters as an adhesive, for example a film called TC 203 / CX7 sold by the company. Prochimir, or a powder called UNEX 4103 sold by the company UNEX DAKOTA.

 The assembly of the resilient underlay 4 in polyurethane with the middle layer 3 can be done as follows. The glue or adhesive layer 6 is applied or deposited on the middle layer 3, which is supported by means of transport, such as a conveyor belt. The quantity of adhesive deposited varies according to the nature and the form thereof, but is generally of the order of 20 g to 60 g for a powder, and from 50 g to 100 g for a film. The assembly is advanced to a continuous laminating station 17, the adhesive layer 6 having been previously heated to around 1300C by heating means 18, for example infrared lamps, arranged at the entrance to the laminating station. The resilient sublayer 4 is unwound from above without tension, and is passed with the assembly previously obtained and carrying the adhesive layer, in the continuous laminating station. The adhesion of the sublayer is obtained by hot reactivation and hot pressing and progressive flat. The laminating station has two zones, a first hot zone 17a, and a second zone 17b cooler than the first zone, and resembles the pressing station described above. The hot zone 17a has a length of approximately 4 meters, but has a temperature difference between the upper part and the lower part of this zone, namely the temperature above the conveyor belt is approximately 1800C, while that in - below the conveyor belt is around 1300C. The pressure applied for bonding is between approximately 2 bar to approximately 5 bar. The second cooler zone has a length of around 2 meters and operates at a temperature of around 420C. It is also possible to reposition the different layers when they enter the laminating station, as during the pressing step, which is not possible if an armature is present. After passing through the laminating station, 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 desired format, stabilized, preferably flat without tension, for example, in a first stabilization tunnel 20, operating at around 115 "C, and a second stabilization tunnel 21 operating at 200C and then 100C at the exit of the tunnel, and finally conditioned in a conditioning station 22. During stabilization, the conveyor belt is preferably a teflon belt, in order to allow the relaxation of stresses which may have formed in the sheet.

 Thus, the finished composite sheet has excellent dimensional stability, exhibiting for example, for floor covering tiles 2 meters long, a shrinkage of only 0.05% in both long and wide directions. This sheet also has a very regular thickness, with a difference in thickness of the resilient sub-layer of the order of only 0.10 mm. Preferably, the total thickness of the fully assembled composite sheet is between approximately 2.5 mm and 4.5 mm, and may have a preferential surface mass of between approximately 2400 g / m2 and approximately 3400 g / m2.

Claims (21)

 1 / composite plastic sheet (1), comprising a wear layer (2), possibly decorated, continuous, comprising a thermoplastic resin, for example a polyvinyl chloride (PVC), the sheet also comprising a resilient underlay (4 ) having a discontinuous honeycomb structure, crosslinked in its thickness, comprising at least one plastic, characterized in that the sheet further comprises a middle layer (3) bonded on one side by pressing to the wear layer (2) , and on the other side by bonding with the resilient undercoat (4), said middle layer (3) comprising a thermoplastic resin, for example polyvinyl chloride, all without practically any reinforcement integrated into all or part of the structure of said composite plastic sheet.  2 / composite plastic sheet (1) according to claim 1, characterized in that the wear layer (2) has a thickness between about 0.25 mm to about 0.70 mm, and preferably has a thickness chosen from 0.25 mm, 0.50 mm and 0.65 mm.  3 / composite plastic sheet (1) according to claim 1, characterized in that the wear layer (2) has a decorative layer (5) between the wear layer (2) and the middle layer (3).  4 / plastic composite sheet (1) according to claim 3, characterized in that the decorative layer (5) is obtained by melting and pressing of colored plastic granules, and optionally adding an additional relief layer based on flakes, chips , and / or filaments.  5 / composite plastic sheet (1) according to claim 3, characterized in that the decorative layer (5) consists of a printed film.  6 / composite plastic sheet (1) according to claim 1, characterized in that it comprises an adhesive layer (6) between the middle layer (3) and the resilient underlayer (4).  7 / composite plastic sheet (1) according to claim 6, characterized in that the adhesive layer is chosen from the group consisting of a hot-melt film, a bilayer of copolyamide and ethylene vinyl acetate (EVA), a bilayer of copolyester, a hot-melt powder of the polyurethane or polyester type, a "hot melt" layer of the polyurethane type, an "emulsion" adhesive of the polyurethane type, and a "solvent" adhesive of the polyurethane type.  8 / composite sheet according to claim 1, characterized in that the middle layer (3) is essentially based on polyvinyl chloride (PVC) waste.  9 / composite sheet according to claim 1, characterized in that the thickness of the middle layer deposited is preferably between about 0.40 mm to about 1.50 mm.  10 / composite sheet according to claim 1, characterized in that the resilient underlayer (4) consists essentially of crosslinked regenerated polyurethane foam.  11 / composite sheet according to claim 1, characterized in that the resilient underlay (4) consists of a homogeneous mixture  - selected and crosslinked polyurethane foam flakes  - a polyurethane-based bonding prepolymer  - rubber powder  - possibly cork granules  - and other adjuvants, such as pigments, water repellents, and dyes.  12 / composite sheet according to claim 1, characterized in that the resilient underlay (4) consists of an open cell foam.  13 / Floor covering, in particular in the form of tiles, comprising a composite sheet according to any one of the preceding claims.  14 / A method of manufacturing a composite plastic sheet (1) according to any one of claims 1 to 12, characterized in that at the outset the wear layer (2) is formed, for example by coating the surface of a mobile support (7) with a plastisol, then gelation of the latter, then we attach on and assemble directly or indirectly with the wear layer (2) the middle layer (3), by pressing, and we report on and glue the resilient underlayer (4) with the middle layer (3), whereby said plastic sheet (1) is formed upside down, from the wear layer (2) serving as a substrate.  15 / A method for manufacturing a composite sheet (1) according to claim 14, characterized in that the method comprises at least the steps consisting in:  - continuously forming upside down at least one non-foaming wear layer (2) essentially based on PVC on means of transport (7)  - forming a middle layer (3) essentially based on PVC waste on the wear layer (2) by continuous flat pressing (13a, 13b) with the wear layer  - And continuously laminate a resilient underlayer (4) of foamed plastic on the middle layer.  16 / A method according to claim 14, characterized in that the wear layer (2) is formed by coating an overplasticized plastisol essentially based on polyvinyl chloride on a conveyor belt (7).  17 / A method according to claim 14, characterized in that the middle layer (3) essentially based on PVC waste is formed by sprinkling waste particles essentially PVC-based, on the wear layer (2), those -this then being pressed flat at a temperature between about 1500C and about 2000C, and at a pressure of about 5 to about 20 bar.  18 / A method according to claim 14, characterized in that the middle layer (3) is formed by extruding, through a flat die at about 1850C, waste particles essentially PVC-based.  19 / A method according to claim 14, characterized in that the resilient sub-layer (4) is formed by depositing an adhesive layer (6) consisting of a film or an adhesive hot-melt powder on the middle layer (3 ), by heating until the adhesive (6) melts, and by laminating a regenerated polyurethane foam (4) on the middle layer (3) at a temperature between approximately 1300C and 1800C and at a pressure between approximately 2 to about 5 bars.  20 / A method according to claim 14, characterized in that, in addition, forming, by fusion and pressing, a decorative layer (5) on the wear layer (2) before forming the middle layer (3), based on a mixture of colored granules or a printed film.  21 / A method of manufacturing a floor covering consisting of manufacturing a composite plastic sheet according to any one of claims 14 to 20, characterized in that the method comprises additional steps consisting of graining (14) and sanding (16 ) the surface of the wear layer (2) after pressing the middle layer (3) and before laminating the undercoat (4), cutting (19) the composite sheet (1) after laminating in a desired format, stabilizing the composite sheet (1) in at least one stabilization tunnel (20,21), and conditioning (22) the composite sheet (1) previously cut into slabs.