AU2001237497B2 - Method for producing a plastic floor covering - Google Patents

Abstract

The invention concerns a method for producing a floor covering which consists in: in a first operational phase, classically producing a base structure (1b) with plasiticized PVC, by pressing, calendering, extrusion or coating, optionally reinforced with a textile core and associated with an additional backing (1a); then in a second operational phase, producing a surface covering consisting of a double-layer complex comprising a thermoplastic layer coated with a thermosetting polymer film. The invention is characterised in that said double-layer complex is formed, either continuously and in line with the production of the base structure, or on a transfer support enabling complexing in a subsequent phase by: depositing on the upper surface of the base complex, or on a transfer support, a transparent or coloured layer (2) of PVC plastisol which is pre-gelled by heat treatment; continuously coating the pre-gelled plastisol layer (2) with thermosetting powder (7) and heat treatment transforming the powder into a continuous liquid film (9); passing the resulting complex in a warm air furnace (11), bringing about gelling and crosslinking of the two constituents (2, 9) of the surface layer.

Description

CERTIFICATE OF VERIFICATION Bruno VUILLERMOZ Cabinet LAURENT CHARRAS Rue Louis Chirpaz BP 32 F- 69131 ECULLY CEDEX France state that to the best of my knowledge the attached document is a true and correct translation of publication of International PCT application no PCT/FR 01/00557 Dates this 2 day of July 2002 Signature of Translator.

WO 01/64996 PCT/FR01/00557 METHOD FOR PRODUCING A PLASTIC FLOOR COVERING Technical field The present invention relates to a method for producing a plastic floor covering, making it possible to obtain not only very good surface properties, but also not to impair the characteristics of the base structure constituting said covering.

Prior art It was proposed a very long time ago to produce flexible floor coverings made of plastic.

In general, such floor coverings consist of a thermoplastic base structure, especially made of plasticized PVC, obtained by pressing or calendering.

This base structure may be optionally strengthened by a textile structure embedded in the mass of the material.

Moreover, to improve the comfort or to impart specific characteristics on the covering pertaining to its use, this base structure may be combined with a backing, for example a foam backing.

In addition, the visible face is covered with a top layer giving the assembly specific properties such as UV resistance and resistance to crushing, scratching, wear, abrasion, scuffing and cigarette burns.

It is desirable for such coverings to be resistant to specific stains which may be produced at the place of use, for example in hospitals (alcoholic iodine Stains, alcoholic eosin stains, etc.).

Finally, it is also desirable to prevent the emission of volatile organic compounds, which can be achieved by a barrier effect of the upper surface layer.

2 To produce the surface layer of such floor coverings, it was envisioned a very long time, as is apparent in particular from FR 2 341 021, to use a composition either based on a thermoplastic PVC, optionally filled or a thermoset, in particular crosslinked polyurethane.

However, the method described in that document is complex to implement.

Very many proposals have also been made for producing surface layers made of different synthetic polymers, as is apparent from US 4 337 296, EP 794 281 and GB 2 285 012.

In all these proposals, the problem that arises is that of being able to achieve good adhesion between the thermoset surface layer and the thermoplastic base structure, and of not impairing the characteristics of this base structure.

An improved method has now been found, and it is this which forms the subject matter of the present invention, which allows all of these problems to be solved.

Summary of the invention In general, the method according to the invention for producing a floor covering consists: in a first operating phase, in conventionally producing a base structure made of plasticized PVC, by pressing, calendering, extrusion or coating, said base structure being optionally strengthened by a textile reinforcement and/or combined with an additional backing; then 0 in a second operating phase, in producing a surface coating consisting of a two-layer complex comprising a thermoplastic layer coated with a film 3 based on a thermoset polymer.

In the method according to the invention, the two-layer complex constituting the surface coating is formed, either continuously and in line with the production of the base structure, or on a transfer support allowing a complexing operation to be carried out during a subsequent phase by: depositing, on the upper face of the base complex or on a transfer support, a layer of transparent or colored PVC plastisol, which is pregelled by heat treatment; continuously covering the pregelled plastisol layer with a layer of thermosetting powder, followed by a heat treatment which converts said powder into a continuous liquid film; and passing the complex thus formed through a hotair oven, resulting in the gelling and the final crosslinking of the two constituents of the surface layer, the assembly then optionally being embossed and reeled up.

To implement this method, the PVC-based thermoplastic layer of the surface complex is obtained from a PVC plastisol composition (PVC resin, plasticizer and conventional stabilizers and rheology-controlling additives), this surface layer being colored or transparent and having a thickness of between 0.1 and 2 mm and preferably 0.2 to 0.8 mm. This plastisol may also be produced from an acrylic resin in a plasticizer.

The plastisol is then pregelled by heat treatment at a temperature of between 120 0 C and 130 0 C for thirty to sixty seconds by passing it through a hot-air or infrared oven.

The external layer associated with this PVC-based layer is itself produced from a thermosetting powder 4 composition exhibiting rapid crosslinking (setting) characteristics, setting in between one minute and at most seven minutes at 2100C.

The formulation of this powder is such that it allows adhesion to the plasticized polymer (PVC) without impairing the pliancy, the hardener also not attacking the PVC.

Such a powder may be obtained from a composition comprising: a hydroxylated polyester resin, a carboxylated polyester resin, a polyurethane resin, a polyester/epoxy hybrid resin, etc.; a crosslinking agent of the glycidyl ester type, a crosslinking agent of the hydroxyalkylamide type or a crosslinking agent of the blocked or dimerized isocyanate type.

The thermosetting powder is preferably deposited by electrostatic powder coating in an amount ranging from to 200 g/m 2 This powder is converted into a liquid film by a heat treatment carried out by combining the action of an infrared radiation rail followed by passage through a hot-air tunnel.

Such a process allows a very uniform and continuous film to be formed, which is explained by the fact that the infrared radiation causes the powder to rapidly melt and the action of the hot air smooths out the film.

This heat treatment depends on the nature of the thermosetting powder, the infrared radiation raising the latter to a temperature of between 110°C and 2000C over a time of between one and thirty seconds, whereas the hot-air treatment is carried out at a temperature 5 which may vary from 80 to 120 0 C for a time of thirty seconds to one minute.

After treatment, the surface film of thermosetting polymer, preferably based on a copolyester, has a thickness of between 15 and 150 tm and preferably between 30 and 80 gm.

Brief description of the drawings The invention and the advantages that it affords will, however, be more clearly understood from the description which follows, this being illustrated by the appended drawings in which: figure 1 is a schematic view of a line for producing a floor covering according to the invention; and figure 2 is a schematic perspective view illustrating the overall structure of such a floor covering.

Manner of realizing the invention In the rest of the description, the invention will be described in the case of the production of a floor covering continuously with the production of the base structure of the floor covering, it being understood that this surface layer could be produced during a separate phase on a transfer support in order to be combined with the base layer during formation of the latter.

Referring to the appended figures, a PVC base structure is conventionally produced, in a first operating phase, by pressing, calendering, extrusion or coating.

Such a base structure may be strengthened by a layer of textile material and may include, on its reverse side, a backing such as a foam backing (la) According to the invention, the surface coating of the 6 base complex thus formed is produced by depositing, on the upper face of this support a uniform layer of a plastisol based on a thermoplastic, particularly PVC, but this plastisol may also be an acrylic plastisol.

This plastisol coating is produced conventionally by making the support pass over a roll associated with a doctor blade The plastisol layer has a thickness of between 0.2 and 0.8 mm.

The assembly is subjected to a continuous pregelling heat treatment which heats the material to a temperature of between 120 and 130°C for 30 to seconds by passing it through a hot-air or infrared oven Next, a thermosetting powder composition is deposited on this pregelled, and therefore cured, plastisol layer This coating is produced by electrostatic powder coating by means of a powder-coating system which may be a hopper associated with an electrostatic charging assembly or an electrostatic spray-gun system suitable for flat powder coating. This coating is deposited in an amount ranging from 20 to 200 g/m 2 preferably between 40 and 100 g/m 2 The powder is then converted into a continuous liquid film by a heat treatment This heat treatment combines both the action of an infrared rail, causing the powder to melt, and then of passage through a hotair tunnel, causing the film formed to be smoothed out.

Depending on the nature of the powder, the infrared radiation heats the latter to a temperature of between 7 110C and 2000C, for a time of one to thirty seconds, while the product passes through the hot air, heated to a temperature of between 80 and 120'C, for a time of thirty seconds to one minute.

The thickness of the film is between 15 4m and 150 ptm, preferably between 30 and 80 pm.

The complex thus formed then undergoes a heat treatment inside a hot-air oven causing the gelling and final crosslinking of the two constituents 9) of the surface layer.

The temperature inside the oven is controlled between 200'C and 210"C, the treatment time being between one and seven. minutes.

The complex thus formed is then taken up, for example in the form of a reel.

Figure 2 shows, schematically, in cross section the overall structure of such a floor covering, which therefore comprises a base support covered with a two-layer transparent structure consisting, on the one hand, of a thermoplastic layer preferably made of plasticized PVC, associated with a film based on a thermoset, particularly polyester.

As may be seen in this figure, in such a complex the various layers are intimately bonded to one another without, however, interpenetration of the constituents from one of the layers into the adjacent layer, thereby allowing all the properties of each of the layers to be preserved..

Example The surface coating of a base structure produced beforehand, comprising a foam backing (la) associated on the reverse side with a sheet (Ib) of PVC optionally 8 strengthened by a textile structure, is produced by means of a plant as described above.

Such a support has a thickness of 15 mm.

Deposited on the surface of this support by means of the doctor blade is a 625 g/m 2 layer of a plastisol having a viscosity of 10 Pa.s (10 000 cPs) at a shear rate of 100 s 1 using the Rheomat equipment, having the following composition: polyvinyl chloride (100 parts) 40 phr of a dioctyl phthalate (DOP)-type plasticizer 2 phr of a stabilizer of the sulfur-containing butyltin type diluent.

A layer having a thickness of 0.5 mm is thus formed on the surface of the support The assembly then undergoes a heat treatment by passing it beneath an infrared rail which heats the material to a temperature of 110 0 C, causing this layer to be pregelled and therefore cured.

Downstream of the infrared rail is deposited, in an amount of 60 g/m 2 a thermosetting powder consisting of a copolyester-based composition comprising: resin of the hydroxylated polyester type hardener of the dimerized isocyanate type.

The complex then undergoes a second heat treatment (8) which combines the action of an infrared rail, heating the material to 120°C for ten seconds, and then of a treatment in a hot-air tunnel heated to 95'C for a time of forty seconds, allowing a film having a thickness of around 50 pm to be obtained.

The coating thus formed then passes through a hot-air 9 oven (11) heated to a temperature of 200°C, the treatment time being 3 minutes.

What is obtained on leaving the plant is a floor covering as illustrated in figure 2, having a total thickness of 2 mm.

Such a floor covering has very good surface properties, especially as regards resistance to crushing, scratching, abrasion, wear and UV.

Moreover, it is very resistant to stains.

Claims (4)

1. A method for producing a floor covering which consists- in a first operating phase, in conventionally producing a base structure (Ib) made of plasticized PVC, by pressing, calendering, extrusion or coating, said base structure being optionally strengthened by a textile reinforcement and combined with an additional backing then in a second operating phase, in producing a surface coating consisting of a two-layer complex comprising a thermoplastic layer coated with a film based on a thermoset polymer, characterized in that said two-layer complex is formed, either continuously and in line with the production of the base structure, or on a transfer support allowing a complexing operation to be carried out during a subsequent phase by: depositing, on the upper face of the base complex or on a transfer support, a layer of transparent or colored PVC plastisol, which is pregelled by heat treatment; continuously covering the pregelled plastisol layer with a layer of thermosetting powder followed by a heat treatment which converts said powder into a continuous liquid film and passing the complex thus formed through a hot- air oven resulting in the gelling and the final crosslinking of the two constituents 9) of the surface layer.

2. The method as claimed in claim 1, characterized in that the heat treatment which converts the powder into a continuous liquid film is carried out by the combination of the action of an infrared rail, causing said powder to melt, and then of a treatment in 11 a hot-air oven, which smooths out the film formed.

3. The method as claimed in one of claims 1 and 2, characterized in that: the thickness of the plastisol layer is between 0.2 and 0.8 mm; the thermosetting powder being deposited by electrostatic powder coating in an amount ranging from to 200 g/m 2 the continuous liquid film formed after the heat treatment has a thickness of between 15 pm and 150 pm and preferably between 30 and 80 plm.

4. The method as claimed in one of claims 1 to 3, characterized in that: the first heat treatment for pregelling is carried out at a temperature of between 120 and 130°C for 30 to 60 seconds by passage through a hot-air or infrared oven the second heat treatment forming the film is produced by the action of an infrared rail heating the powder to a temperature of between 110 and 200°C for one to thirty seconds, the hot-air treatment being carried out at a temperature between 80 and 120°C for a time of thirty seconds to one minute; and the final treatment, for gelling and crosslinking the complex, is carried out inside a hot- air oven (11) heated to a temperature of 200°C, the treatment time being 3 minutes.