EP2910708A1

EP2910708A1 - Synthetic floor coverings with colored overlay

Info

Publication number: EP2910708A1
Application number: EP14156614.1A
Authority: EP
Inventors: Bugarcic Branko
Original assignee: Tarkett GDL SA
Current assignee: Tarkett GDL SA
Priority date: 2014-02-25
Filing date: 2014-02-25
Publication date: 2015-08-26

Abstract

The invention concerns a laminate comprising:
- a core; and
- a surface layer comprising a decorative paper or a decorated core layer; and
- a wear layer comprising a first overlay and on top thereof a second wear overlay, characterized in that the first overlay is tinted.

It further concerns a method for the manufacture of such a laminate.

Description

[Technical Field]

The present invention concerns the field of synthetic floor coverings, notably laminates and a method for their manufacture.

[Background Art]

Heterogeneous synthetic floor coverings generally comprise at least two layers such as a substrate or core layer and a surface layer.
The surface layer generally comprises two paper sheets, a printed decorative paper and a transparent overlay paper applied over the decorative paper to protect the decorative paper from abrasion. At times, the décor can also be formed by the aspect or a décor applied onto the core layer. However, in both cases, the laminate floor is characterized in that the decorative and wear properties are obtained with two separate layers.
In order to manufacture floor coverings with a number of different designs, it is thus necessary to hold and manage a stock of as many different decorative papers. More specifically, in the case of the manufacture of laminate with a wood pattern, it is required to hold and manage a stock of decorative paper for each kind of wood reproduced.
The maintenance and management of a large stock of decorative papers is a cost factor both in terms of space and time.

[Technical Problem]

The present invention aims to provide a synthetic surface floor covering, notably laminates, which is less costly. More specifically, it aims to provide such floor covering which may be produced with different patterns using fewer different decorative papers. Further, it aims to provide a process for manufacturing such floor covering.

[Solution to Problem]

According to the most general definition, the above technical problems may be solved according to the invention by providing a floor covering wherein the surface layer comprises a tinted overlay.
Indeed, depending on the tint of the overlay, a decorative paper or decorated core layer will exhibit a distinct visual effect. The use of a tinted overlay thus multiplies the designs available using a single decorative paper. In case of a decorative paper representing a wood pattern, tinted variations of such pattern may include reproductions of different wood species.
Because different designs may be obtained simply by changing the overlay tint, the number of different decorative papers required is reduced. Fewer decorative papers are thus required to be stocked, thus reducing the space and management time needed. The use of a tinted overlay thus allows for substantial savings in the method of manufacture.

[Summary of Invention]

According to a first aspect, the invention is directed to a laminate comprising:

a core; and
- a surface layer comprising a decorative paper or decorated core layer; and
- a wear layer comprising a first overlay and on top thereof a second wear overlay, characterized in that the first overlay is tinted.

Preferably, the first tinted overlay comprises a mineral or organic pigment, preferably formulated in form of an ink.
According to a particular embodiment of the invention, the first and /or second overlays comprise an overlay paper. Such overlay paper may comprise cellulose fibers, and preferably α-cellulose fibers. The overlay paper may further comprise a resin, notably a melamine resin.
The ink is preferably water based. It may be applied onto the overlay paper in particular via printing, in particular digital printing.
The second overlay is preferably untinted.
According to another preferred embodiment of the invention, the first and/or second overlay may also comprise a resin, for example a melamine resin, but no paper(such overlay is also designated "liquid overlay").
Advantageously, so as to reinforce the wear properties, the second overlay further comprises corundum particles.
Preferably, the surface layer comprises a decorative paper with a wooden pattern.
The core of the laminate of the invention is preferably selected from medium density fiberboard (MDF), high density fiberboard (HDF) and particle board.
According a preferred embodiment of the invention, the core is provided with a backing layer.
According to a second aspect, the invention is directed to a process for the manufacture of such a laminate, comprising the steps of:

(i) providing a surface layer comprising a decorative paper or decorated core layer;
(ii) providing a wear layer comprising a first tinted overlay;
(iii) providing on top of the first tinted overlay a second wear overlay; and
(iv) bonding the surface and wear layers to a core using heat and pressure.

Preferably, the decorative paper has a thickness of 0.01 to 1 mm.
Preferably, the first tinted overlay comprises an overlay paper which is printed with an ink. The ink is preferably water based. According to one embodiment of the invention, the ink may be applied onto the overlay paper, in particular by digital printing.
Advantageously, step (iv) is carried out at a temperature of 50 to 300°C, preferably 80 and 250 °C and at a pressure of 10 to 80 kg/cm², preferably 40 to 65 kg/cm².

[Detailed Description]

Within the present invention, the term "paper" designates a thin material produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets.
The overlay papers used within the present invention are selected so as to become transparent once they are bonded to the rest of the laminate, for instance by impregnation with a resin, such as a melamine resin. A tinted overlay comprising a tinted overlay paper, for instance an overlay paper printed with a colored ink, once bonded, thus behaves like a transparent color filter. An untinted overlay comprising an overlay paper, once bonded, will be transparent and untinted and will thus not affect notably the visual aspect of the laminate.
The present invention is directed to a laminate which may be manufactured at a reduced cost.
According to a first aspect, the present invention is directed to a laminate comprising:

The most common core material used in laminate floorings is fibreboard with high density and good stability usually called HDF - High Density Fibreboard. As an alternative, MDF - Medium Density Fibreboard - may also be used as core. Other core materials such as particleboard may further also be used.
The thickness of the core may vary largely. However, so as to produce a floor covering with satisfying properties, it is preferred that the core has thickness of 6 to 15 mm.
So as to balance the weight of the surface and wear layer applied on top of the core, the back side of the core may be provided with a suitable backing layer. Such a suitable backing layer may be for instance a paper having an appropriate weight, for instance between 60 and 220 g/m².
Except when the core layer is decorated, the surface layer of the laminate provides the laminate with an essential part of its visual effect.
The surface layer of the laminate thus generally comprises in particular a decorative paper.
Conventional decorative papers as known in the art may be used for the manufacture of the laminate of the present invention. Printed decorative papers are particularly preferred.
The thickness of the decorative paper may vary largely. However, it is generally preferred that the decorative paper has a thickness of 0.01 to 1 mm, and preferably of 0.05 to 0.5mm.
The surface layer may further comprise other components and/or layers so as to meet particular specifications.
The thickness of the surface layer may vary largely, but is most often lower than the thickness of the core. Generally, the surface layer has a thickness of 0.05 to 2, preferably of 0.1 to 1 mm.
The wear layer of the laminate according to the invention protects the surface layer of the laminate from wear, notably from abrasion.
Therefore, the wear layer preferably comprises or consists of materials that have a high resistance to wear.
As explained above, the wear layers become transparent once they are bonded to the surface layer and the core by impregnation with a resin and the use of heat and pressure.
According to the present invention, the wear layer comprises a first overlay which is tinted and thus provides for colour. The wear layer further comprises a second overlay which reinforces the protection of the decorative paper from abrasion.
The first tinted overlay is thus preferably disposed between the surface layer comprising the decorative paper or decorated core layer and the second overlay.
The first tinted overlay layer may be provided by conventional impregnation using a tinted resin. Such a tinted resin may be obtained by mixing resin with a suitable pigment or ink. The resin applied forms upon hardening a sheet or film.
As an alternative, the first tinted overlay may be provided by a tinted overlay paper. Such a tinted overlay paper may in particular comprise an overlay paper, notably comprising such as α-cellulose fibres on which a suitable pigment or ink is applied, for instance by digital printing.
For ease of application, the pigment is preferably formulated with a binder to form an ink. Different printing inks are available on the market, in particular water based inks and UV curable inks. Water based inks adhere well on polar resins such as melamine. Their use is thus preferred in the cases where the laminate comprises melamine.
The wear layer further comprises a second overlay disposed on top of the first tinted overlay. The second overlay is preferably not tinted. The second overlay may, as explained above for the first overlay, comprise a transparent paper which is impregnated into a resin, or be formed by application of a liquid resin such as a melamine resin which subsequently hardens to form a film. Preferably, the second overlay further comprises hard abrasive particles so as to improve the wear resistance provided. Preferably, the particles are of a hard material such as aluminium oxide (in particular a-Al₂O₃, also called corundum). Preferably, the particles are not coloured. Also, their size is preferably selected so as to interfere as little as possible with the light, and reduce their impact with regard to transparency.
The laminate according to the invention, comprising a wear layer with two distinct overlays, unexpectedly also shows a technical advantage in that it allows deeper embossing on its surface, up to and over 220µm.
The wear layer may further comprise other components and/or layers so as to meet particular specifications.
The thickness of the wear layer may vary largely, but is lower than the thickness of the core. Generally, the surface layer has a thickness of 0.05 to 2, preferably of 0.1 to 1 mm.
While the laminate of the invention may also comprise further other layers, such laminates are more expensive and thus less preferred in the framework of the present invention. Therefore, the laminate of the invention is preferably comprised solely of the above mentioned layers.

[Process of manufacture]

According to a second aspect, the invention is directed to a process for the manufacture of laminate as described above, comprising the steps of:

(i) providing a surface layer comprising a decorative paper or decorated core layer;
(ii) providing a wear layer comprising a first tinted overlay;
(iii) providing on top of the first tinted overly a second wear overlay; and
(iv) bonding the surface and wear layers to a core using heat and pressure.

Advantageously, the laminates of the invention do not require particular equipment or processing parameters.

Step (i) of the process of the invention can be realized conventionally, for instance by providing a conventionally printed and impregnated décor paper, a decorated core layer or by direct printing.
Step (ii) of the process according to the invention may be carried out by any conventional process known in the art, such as by digital printing of an ink onto an overlay paper or by impregnation with a tinted resin.
Step (iii) of the process above can be realized by the same conventional process known in the art mentioned for step (ii) except that the second wear overlay is preferably untinted. Mineral particles such as corundum particles may be included in the resin.

With regard to step (iv) of the process above, a temperature of 50 to 300 °C, preferably 80 to 250 °C is generally appropriate. A heating of the assembled layers for a period comprised between 2 seconds to 10 minutes, preferably 5 to 60 seconds is sufficient in most cases. During this time, a pressure is applied. A pressure of 10 to 80 kg/cm², preferably 40 to 65 kg/cm² is generally appropriate..

[EXAMPLES]

EXAM PLE

Preparation of laminate according to the invention

A decorative laminate is manufactured as follows.
A surface layer consists of a standard decorative paper having a thickness of 0.1 mm made using a gravure printing method and subsequently impregnated with melamine resin.
The decorative paper is subsequently covered by an overlay paper (standard quality AC1) impregnated with melamine resin and digitally printed with a water based ink to form a first overlay.
Then, a second overlay is formed on top of the assembly, by application of an overlay impregnated with melamine resin and comprising corundum particles (quality AC5).
The laminate is manufactured by bonding the assembled wear and surface layers on top of the core (high density fibreboard (HDF) having a thickness of 10mm) by applying pressure and pressing in a press at a temperature comprised between 180 and 220 °C for 10 to 30 seconds under a pressure of 40 to 65 kg/cm².
As a balance, a paper having a paper weight of 140 g/m² is bonded to the back of the core.
The laminate according to the invention shows comparable visual aspect and mechanical properties. It further allows for a deeper embossing.
Using a tinted overlay, laminates of the invention with different designs may be manufactured using the same decorative paper but different tints. Accordingly, such laminates require a fewer number of decorative papers, which allows for a reduction of stock and management. The present invention thus provides for a laminate which may be manufactured with a lower cost.

Claims

A laminate comprising:
- a core; and

- a surface layer comprising a decorative paper or decorated core layer; and

- a wear layer comprising a first overlay and on top thereof a second wear overlay, characterized in that the first overlay is tinted.
The laminate according to claim 1, wherein the first tinted overlay comprises a mineral or organic pigment , preferably formulated in form of an ink.
The laminate according to claim 1 or 2, wherein the first and/or second overlays comprise an overlay paper.
The laminate according to claim 3, wherein the overlay paper comprises α-cellulose fibers.
The laminate according to claim 3 or 4, wherein the overlay paper further comprises a resin.
The laminate according to any of claims 1 to 5, wherein the first and/or second overlay comprises a resin but no overlay paper.
The laminate according to any of claims 1 to 6, wherein the second overlay further comprises corundum particles.
The laminate according to any of claims 1 to 7, wherein the surface layer comprises a decorative paper with a wooden pattern.
The laminate according to any of claims 1 to 8, wherein the core is selected from medium density fiberboard (MDF), high density fiberboard (HDF) and particle board.
The laminate according to any of claims 1 to 9, wherein the core is provided with a backing layer.
A process for the manufacture of laminate according to any of claims 1 to 10, comprising the steps of: (i) providing a surface layer comprising a decorative paper or decorated core layer;
(ii) providing a wear layer comprising a first tinted overlay;

(iii) providing on top of the first tinted overlay a second wear overlay; and

(iv) bonding the surface and wear layers to a core using heat and pressure.
The process according to claim 11, wherein the first tinted overlay comprises an overlay paper which is printed with an ink.
The process according to claim 12, wherein the ink is water based.
The process according to any of claims 12 to 13, wherein the ink is applied onto the overlay paper by digital printing.
Process according to any of claims 11 to 14, wherein step (iv) is carried out at a temperature of 50 to 300 °C, preferably 80 and 250 °C and at a pressure of 10 to 80 kg/cm², preferably 40 to 65 kg/cm².