SUBSTRATE SHEET FOR DECORATIVE FLOOR OR WALL COVERING

Abstract

Aspects of the present invention relates to a method for producing a substrate sheet for a decorative floor or wall covering (10), a method for producing a decorative floor or wall covering and a decorative floor or wall covering (10). The method for producing a substrate sheet comprises providing a first thermoplastic composition comprising recycled PVC granules (S2), the first thermoplastic composition (S2) having a shade. In addition the method comprises admixing a darkener to the first thermoplastic composition so as to obtain a first thermoplastic composition having a specific shade (S6). A second thermoplastic composition (S4) is also provided. The method further comprises coextruding (S8) the first thermoplastic composition (S2) having a specific shade with the second composition (S4) so as to form a first and a second adjacent coextruded layers. The first coextruded layer is a support layer having the specific shade, the first coextruded layer comprising the first thermoplastic composition (S2). The second coextruded layer is a digitally printable layer, the second coextruded layer comprising the second thermoplastic composition (S4).

Claims

1. A method for producing a substrate sheet for a decorative floor or wall covering, comprising: providing a first thermoplastic composition comprising recycled PVC granules, the first thermoplastic composition having an initial shade; admixing a darkener to the first thermoplastic composition so as to confer to the first thermoplastic composition a specific shade; providing a second thermoplastic composition; coextruding the first thermoplastic composition having the specific shade with the second composition so as to form a first and a second adjacent coextruded layers; wherein the first coextruded layer is a support layer having the specific shade, the first coextruded layer comprising the first thermoplastic composition; and wherein the second coextruded layer is a digitally printable layer, the second coextruded layer comprising the second thermoplastic composition.

2. The method according to claim 1, wherein the step of admixing the darkener comprises: a) adding darkener to the first thermoplastic composition so as to confer to the first thermoplastic composition shade darker than the initial shade; b) comparing the darker shade with the specific shade; and c) based on the comparison, if necessary, repeating steps a) and b) until obtaining the first thermoplastic composition having the specific shade.

3. The method according to claim 1, wherein the step of admixing the darkener to the first thermoplastic composition is implemented as a negative feedback loop so as to obtain the first thermoplastic composition having the specific shade by adding darkener to the first thermoplastic composition.

4. The method according to claim 1, wherein the first thermoplastic composition comprises from 10% to 50% by weight of recycled PVC granules.

5. The method according to claim 1, wherein the first thermoplastic composition comprises from 30% to 70% by weight of one or more fillers.

6. The method according to claim 1, wherein the first thermoplastic composition comprises from 0.01% to 0.1% by weight of darkener.

7. The method according to claim 1, wherein the second coextruded layer has a thickness comprised in the interval from 0.1 mm to 5 mm.

8. The method according to claim 1, wherein the first coextruded layer has a thickness comprised in the interval from 2 mm to 15 mm.

9. A method for producing a decorative floor or wall covering comprising: providing a first thermoplastic composition comprising recycled PVC granules, the first thermoplastic composition having a shade; admixing a darkener to the first thermoplastic composition so as to change the shade of the first thermoplastic composition into a specific target shade; providing a second thermoplastic composition; coextruding the first thermoplastic composition having the specific target shade with the second composition so as to form a first and a second adjacent coextruded layers; wherein the first coextruded layer is a support layer having the specific target shade, the first coextruded layer comprising the first thermoplastic composition; and wherein the second coextruded layer is a digitally printable layer, the second coextruded layer comprising the second thermoplastic composition; and digitally printing a décor on the digitally printable layer.

10. The method according to claim 9, comprising applying a wear layer on the digitally printed décor.

11. The method according to claim 9, comprising applying a polyurethane-based top layer.

12. The method according to claim 9, wherein the décor has a thickness comprised in the interval from 0.05 mm to 1 mm.

13. The method according to claim 9, wherein the décor is translucent.

14. (canceled)

15. A method for producing a decorative floor or wall covering comprising: providing a first thermoplastic composition comprising recycled PVC granules, the first thermoplastic composition having an initial shade; controlledly admixing darkener to the first thermoplastic composition so as to darken the first thermoplastic composition until the first thermoplastic composition has a specific target shade darker than the initial shade; providing a second thermoplastic composition; coextruding the first thermoplastic composition having the specific target shade with the second composition so as to form a first and a second adjacent coextruded layers; wherein the first coextruded layer is a support layer comprising the first thermoplastic composition having the specific target shade; and wherein the second coextruded layer is a digitally printable layer, the second coextruded layer comprising the second thermoplastic composition; and digitally printing a décor on the digitally printable layer.

16. The method according to claim 15, wherein the step of controlledly admixing the darkener comprises monitoring whether the darkened first thermoplastic composition has a shade matching the specific target shade; continuing the controlled admixing of darkener as necessary until matching the specific target shade.

17. The method according to claim 16, wherein the first thermoplastic composition comprises from 15% to 35% by weight of recycled PVC granules.

18. The method according to claim 17, wherein the first thermoplastic composition comprises from 30% to 70% by weight of one or more fillers.

19. The method according to claim 18, wherein the first thermoplastic composition comprises from 0.01% to 0.1% by weight of darkener.

20. The method according to claim 19, wherein the second coextruded layer has a thickness in the interval from 0.1 mm to 5 mm and wherein the first coextruded layer has a thickness in the interval from 2 mm to 15 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] By way of example, preferred, non-limiting embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

[0037] FIG. 1: is flowchart of a method for producing a multilayer decorative floor or wall covering, according to a preferred embodiment of the present invention;

[0038] FIG. 2: is a flowchart of process for obtaining a thermoplastic composition having a specific shade;

[0039] FIG. 3: is a cross-sectional view of a part of a multilayer decorative floor or wall covering according to an embodiment of the present invention; and

[0040] FIG. 4: is a cross-sectional view of a part of a multilayer decorative floor or wall covering according to another embodiment of the present invention.

[0041] The reader's attention is drawn to the fact that the drawings are not to scale. Furthermore, for the sake of clarity, proportions between height, length and/or width may not have been represented correctly.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0042] FIG. 1 illustrates a method for producing a multilayer decorative floor or wall covering according to a preferred embodiment of the present invention. The method comprises providing (S2) a first thermoplastic composition comprising recycled PVC granules and providing a second thermoplastic composition, both of which will be coextruded at a later stage so as to form a first and a second adjacent coextruded layers.

[0043] The first thermoplastic composition also comprises a virgin PVC (e.g. a suspension PVC (S-PVC), micro-suspension PVC, emulsion PVC) and filler. In addition, the first thermoplastic composition may comprise one or more additives such an impact modifiers, processing aids, (oxidized) polyethylene wax (PE wax) and stearic acid. The first thermoplastic composition comprises from 10% to 50% by weight, preferably from 15% to 35% by weight, more preferably from 17% to 32% by weight of recycled PVC granules. The ratio of virgin PVC and recycled PVC is comprised in the interval from 0.5 to 1.5, preferably in the interval from 0.75 to 1.25. The first thermoplastic composition comprises from 30% to 70% by weight, preferably from 35% to 65% by weight, more preferably from 45% to 55% by weight of one or more fillers.

[0044] The PVC granules may originate from different products (e.g. recycled floor or wall coverings, pipes, furnitures, etc). Therefore, the chemical composition and physical properties (e.g. plasticizer content, shade, additive content, etc) of such PVC granules can be accurately controlled only to the extent the mixture of recycled PVC granule is exactly known. In addition, as the first thermoplastic composition is meant to be coextruded, the chemical composition of the PVC granules may vary from batch to batch.

[0045] In the next step (S6), a darkener is added to the first thermoplastic composition so as to obtain a first thermoplastic composition having a specific shade. It follows that, at the end of step S6, the first thermoplastic composition has a specific shade, irrespective of the chemical composition of the PVC granules.

[0046] The first and second thermoplastic compositions are then coextruded (S8) so as to form the first and a second adjacent coextruded layers. The first coextruded layer is a support layer comprising the first thermoplastic composition. The second coextruded layer is a substantially white digitally printable layer. The second coextruded layer comprises the second thermoplastic composition.

[0047] The first coextruded layer has a thickness comprised in the interval from 2 mm to 15 mm, preferably in the interval from 3 mm to 12 mm, more preferably in the interval from 4 mm to 10 mm. The second coextruded layer has a thickness comprised in the interval from 0.1 mm to 5 mm, preferably in the interval from 0.1 mm to 3 mm, more preferably in the interval from 0.1 mm to 1 mm, even more preferably in the interval from 0.1 mm to 0.3 mm. It should be noted that it generally desirable that the thickness of the support layer is greater that the thickness of the digitally printable layer. Indeed, the production costs of digitally printable layers having only virgin PVC and no recycled PVC are usually much higher than the production costs of support layers. For example, the ratio of the thickness of the digitally printable layer and the thickness of the support layer may be comprised in the interval between 0.05 and 0.5, preferably in the interval between 0.1 and 0.4, and more preferably in the interval between 0.15 and 0.3. At the end of step S8, a substrate sheet is produced.

[0048] The method comprises digitally printing (S10) a décor directly on the digitally printable layer of the substrate sheet. The digital printing may be effected by inkjet printing or laser printing or a combination of both. The décor may either be in the form of a layer, preferably a layer having a uniform thickness, or a pattern. The pattern may represent a natural design such as wood or stone. The decorative pattern may also be a fantasy design or a photograph.

[0049] Subsequently, a wear layer may be applied (step S12) on the décor, followed by the application of a polyurethane topcoat (step S14) on the wear layer. One or the other layers may be omitted.

[0050] The wear layer and the polyurethane layer may be applied e.g. by calendering, hot pressing or any other technique known in the art.

[0051] The wear layer and the polyurethane are transparent or translucent, so that the décor is visible when looking at the top of the decorative floor or wall covering.

[0052] It will be appreciated that accurately controlling the shade of the support layer allows for providing decorative floor or wall coverings comprising recycled PVC with decors having no to little differences in shade, even when the recycled PVC originates from different sources. This is especially the case for very thin digitally printable layers. In other words, darkening the support layer allows for providing digitally printable white layers having an improved constancy for digital printing, which, in turn, allows for providing decorative floor or wall coverings having no to little differences in shade from one coextrusion batch to the other.

[0053] With reference to FIG. 2, the process for obtaining a first thermoplastic composition having a specific shade according to an embodiment of the present invention is detailed.

[0054] In step S22, the shade of the first thermoplastic composition (S2) is determined. This step may be carried in various ways. For example, a spectrophotometer maybe used for determining the shade of the first thermoplastic composition. Additionally or alternatively, a calibrated digital camera for taking digital pictures of the composition under controlled lighting may be used. The digital image is then processed for determining the shade of the first thermoplastic composition, in particular the triplet (L*.sub.d, a*.sub.d, b*.sub.d) in CIELAB colour space of the first thermoplastic composition is determined. Preferably, the matching tolerance is set so that the specific shade “s” ((L*.sub.s, a*.sub.s, b*.sub.s) in CIELAB colour space) and the darker shade “d” ((L*.sub.d, a*.sub.d, b*.sub.d) in CIELAB colour space) differ from one another by a value of ΔE of at most 5, preferably by a value of ΔE of at most 3, even more preferably by a value of ΔE of at most 1, wherein ΔE is computed according to

ΔE=√{square root over ((L*.sub.s−L*.sub.d).sup.2+(a*.sub.s−a*.sub.d).sup.2+(b*.sub.s−b*.sub.d).sup.2)}.

[0055] The determined shade of the first thermoplastic composition is then compared to the specific shade (S24) having the triplet (L*.sub.s, a*.sub.s, b*.sub.s) in CIELAB colour space. In this step, it is determined whether the shade of the first thermoplastic composition matches the specific shade within the matching tolerance. Specifically, the distance ΔE between the shade of the first thermoplastic composition and the specific shade is determined according to ΔE=√{square root over ((L*.sub.s−L*.sub.d).sup.2+(a*.sub.s−a*.sub.d).sup.2+(b*.sub.s−b*.sub.d).sup.2)}. The matching tolerance ΔEmax indicates the maximal value of ΔE for determining whether the first thermoplastic composition matches the specific shade within the matching tolerance. The matching tolerance ΔEmax may be equal to 5, preferably equal to 3, even more preferably equal to 1. If the shades match up the matching tolerance (i.e. ΔE≤ΔEmax), the first thermoplastic composition having the specific shade is obtained. If it is not the case (i.e. ΔE>ΔEmax), a controller (S26) instructs an actuator to add darkener to the thermoplastic composition (S28). The thermoplastic composition has now a shade that is darker than before. Steps S22-S26 are repeated until the shade of the thermoplastic composition matches the specific shade within the matching tolerance.

[0056] It should be noted that the process defined in steps S22-S28 may be performed on a sample taken from the first thermoplastic composition. The controller stores the amount of darkener that was necessary for obtaining the first thermoplastic composition having the specific shade. The proportion of darkener to be added to the first thermoplastic composition itself is known.

[0057] The process for obtaining a first thermoplastic composition having a specific shade may also be carried out differently. For example, a plurality of samples may be extracted from the first thermoplastic composition. Each of the samples are provided with a different amount of darkener (for example in an increasing sequence). The shade of each of the samples is then determined by e.g. a spectrophotometer or a calibrated digital camera and compared, as above. The shade of each of the samples may even be determined by visual inspection. The sample having the shade that matches the specific shade within the matching tolerance, or is the closest to the specific shade is selected. In the same way as before, the amount of darkener to be added to the first thermoplastic composition is obtained by simple cross-multiplication. It should be noted that, in the embodiment where the closest sample is selected, the number of samples (and thus shades) should be quite high so that the selected shade is very close to the specific shade. For example, fifty samples with different amounts of darkener may be prepared, so as to obtain fifty shades of grey for comparison.

[0058] Examples of floor or wall covering 10 according to embodiments of the invention are depicted in FIGS. 3 and 4. From bottom to top, the floor or wall covering 10 comprises: a support layer 12, a digitally printable layer 14, a décor, 16, a wear layer 18 and a PU top layer 20. The support layer 12 and a digitally printable layer 14 form the coextruded substrate sheet 22. During installation of the floor or wall covering 10, the bottom surface 24 of the support layer 12 is applied to the floor or wall.

[0059] The embodiment depicted in FIG. 4 differs from the embodiment depicted in FIG. 3 in that the décor is patterned (see e.g. zones 26 that are left untouched by the décor). It should be noted that the zones 26 may be filled by the wear layer, e.g. in the case where the composition for forming the wear layer is applied in a liquid state on the décor, thereby filling the gaps defined by zones 26.

[0060] A possible thermoplastic composition for the support layer is provided in Tab. 1 below.

TABLE-US-00001 TABLE 1 Amount Material (% by weight) Virgin PVC 19-23 Recycled PVC 19-23 Stabilizer   1-2.5 Impact modifier   1-2.5 Processing aid 0.5-2   Filler 45-70 PE wax   0-0.5 Filler Compatibilizer 0.5-2   Stearic acid 0.1-0.2 Darkener 0.01-0.1  Total: 100%

[0061] A possible thermoplastic composition for the digitally printable layer is provided in Tab. 2 below.

TABLE-US-00002 TABLE 2 Amount Material (% by weight) Virgin PVC 22-30 Stabilizer 1-3 Impact modifier   1-2.5 Processing aid 0.5-2   Filler 45-60 PE wax  0-0.5 Filler Compatibilizer 0.5-2   Stearic acid 0.01-0.10 Whitener 1-5 Total: 100%

[0062] The weight percentages in Tab. 1 are given with respect to the thermoplastic composition (for the support layer or the digitally printable layer) as a whole. The virgin PVC is VYNOVA S6760 (Vynova). The stabilizer is Mark CZ 2081 (Galata). The impact modifier is Durastrength 200 from Arkema. The processing aid is LG PA912 from LG. The filler is OMYA BL20 from OMYA. The PE wax is LUWAX Afrom BASF. The filler compatibilizer is Viscowax 443 from Innospec. The stearic acid is stearyna RG from Brenntag. The whitener is Biel tytanowa RFC 5 from Tytanpol (pigment). The darkener is carbon black corax from Orion.

[0063] While specific embodiments have been described herein in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.