Patent Description:
Laminate flooring is a popular alternative to parquet flooring or hardwood flooring due to its affordability and relatively easy installation. There are generally two methods for producing laminate boards used for laminate flooring: the High Pressure Laminate (HPL) process and the Direct Pressure Laminate (DPL) process.

The HPL process comprises impregnating kraft paper(s), decorating paper, and an overlay paper with a thermosetting resin, usually phenolic resin or melamine resin. The papers are then pressed while heated. The pressure used may typically be between <NUM> to <NUM>/cm<NUM> and the temperature used may typically be between <NUM> to <NUM>. The duration of the pressing depends on the temperature but may typically be for <NUM> to <NUM> minutes, with a cooling down period of between <NUM> to <NUM> minutes. After approximately a day, the pressed papers are glued to a substrate, usually a High Density Fibreboard (HDF) or a Medium Density Fibreboard (MDF). The resulting laminate board is then stored for around <NUM> days before it is further processed, for example by profiling. The HPL process results in high-quality, durable laminate boards with a high product lifetime. However, due to the multi-step approach, the HPL process is laborious and time consuming. From raw material to finished product, the process usually takes <NUM> to <NUM> days.

The DPL process is a simpler process than the HPL process, wherein thermosetting resin impregnated overlay paper and decorative paper is pressed directly on the substrate, such as HDF or MDF. The pressing is performed at high temperature and for less than a minute. The DPL process is less time consuming and laborious than the HPL process and therefore results in a more low-cost final product. However, due to the fewer layers in the laminate board, the DPL laminate boards are less durable and more prone to scratches and dents.

<CIT> relates to a back-grooved laminate wood flooring in which a wood veneer of high pressure resin impregnation laminate (WPL) is laminated on a base selected from a vinyl chloride (PVC) resin layer, on oriented strand board (OSB), a high-density fiberboard (HDF) and a waterproof plywood.

<CIT> relates to a pigmented aqueous inkjet ink set for manufacturing decorative panels includes a cyan aqueous inkjet ink containing a copper phthalocyanine pigment; a red aqueous inkjet ink containing a red pigment selected from the group consisting of C. Pigment Red <NUM>, C. Pigment Red <NUM>, C. Pigment Red <NUM> and mixed crystals thereof; a yellow aqueous inkjet ink containing a pigment C. I Pigment Yellow <NUM> or a mixed crystal thereof; and a black aqueous inkjet ink containing a carbon black pigment, wherein the aqueous inkjet inks contain a surfactant.

In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:.

The following numbering will be adhered to in the figures:
<NUM> - kraft paper; <NUM> - interim sheet; <NUM> - adhesive sheet; <NUM> - decorative sheet; <NUM> - overlay sheet; <NUM> - substrate board; <NUM> - balancing sheet; <NUM> - groove paper; <NUM> - sub stack; <NUM> - stack; <NUM> - laminate board; <NUM> - first pressing step; <NUM> - cutting/grinding step; <NUM> - second pressing step.

Any positional indications refer to the position shown in the figures. In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons, some elements may in some of the figures be without reference numerals. A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

When describing the invention, the terms used are to be construed in accordance with the following definitions, unless the context dictates otherwise.

By way of example, "a resin" means one resin or more than one resin.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements, or method steps.

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g., <NUM> to <NUM> can include <NUM>, <NUM>, <NUM>, <NUM> when referring to, for example, a number of elements, and can also include <NUM>, <NUM>, <NUM> and <NUM>, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g., from <NUM> to <NUM> includes both <NUM> and <NUM>).

Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art.

The terms described above, and others used in the specification are well understood to those skilled in the art.

Preferred statements (features) and embodiments, resins, articles, methods, and uses of this invention are set herein below. Each statement and embodiment of the invention so defined may be combined with any other statement and/or embodiment unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features or statements indicated as being preferred or advantageous.

The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

In a first aspect not according to the claimed invention, the disclosure relates to a method for producing an interim sheet. The method comprises the steps of:.

In the pressing step, the first and second thermosetting resins are heated to a point where they become liquid. By the term "liquid" it is meant that the thermosetting resins are flowable enough to at least partially flow into the alternative sheet material from the sheet material in which they are originally impregnated. That is to say, the first thermosetting resin is in a liquid phase according to the present disclosure when at least part of the first thermosetting resin is flowable enough that it may flow into the second sheet material. The second thermosetting resin is in a liquid phase according to the present disclosure when at least part of the second thermosetting resin is flowable enough that it may flow into the first sheet material.

The advantage of the method according to the first aspect is that the first and second thermosetting resin are not completely cured after the pressing of the sheet material. That is, at least a part of the first and second thermosetting resins may flow again when heated. If the interim sheet is pressed together with other sheets in a stack at a suitable temperature and for a suitable period of time, the first and second thermosetting resin may flow, at least partially, into the adjacent sheets such that the sheets in the stack may adhere as the stack is pressed.

In a second aspect not according to the claimed invention, the disclosure relates to an interim sheet obtained by the method according to the first aspect of the invention. (Preferred) embodiments of the first aspect are also (preferred) embodiments of the second aspect and vice versa.

The invention, as defined in a third aspect, relates to a method for producing a laminate board. The method comprises the step of producing an interim sheet according to the first aspect. The method further comprises the steps of:.

Therefore, the method according to the third aspect comprises the steps of.

In some preferred embodiments, the stack in step c) comprises at least one of the following sheets:.

Such methods provide an easy way to build thickness early on and then decide the design in a later step.

In some preferred embodiments, the stack in step c) comprises a decorative sheet impregnated with a third thermosetting resin. In some preferred embodiments, the stack in step c) comprises a decorative sheet not impregnated with a thermosetting resin and an overlay sheet impregnated with a fourth thermosetting resin, the overlay sheet preferably being positioned as an outermost layer adjacent the decorative sheet in the stack. n some preferred embodiments, the stack in step c) comprises a decorative sheet impregnated with a third thermosetting resin and an overlay sheet impregnated with a fourth thermosetting resin, the overlay sheet preferably being positioned above the decorative sheet in the stack.

(Preferred) embodiments of the first aspect are also (preferred) embodiments of the third aspect and vice versa.

The method according to the third aspect of the invention may have several advantages. Firstly, the interim sheet is not completely cured after the pressing. By the term "not completely cured" it is meant that at least part of the first and second thermosetting resins may flow again upon heating after cooling down after step b). The first and second thermosetting resin may, upon heating and at least partially, flow into the adjacent sheets in the stack such that the sheets in the stack may adhere together upon being pressed together in step d).

Due to the second pressing of the interim sheet with the substrate board, the method according to the invention may be faster. Pressing the stack together takes typically between <NUM> and <NUM> seconds. Typically, glue is not required during the process. If glue is used, the process may provide a reduction in the amount of glue required. In some examples there may be no glue used in the process. Where the use of glue is eliminated, there is no need to wait until the glue has dried. Where the use of glue is reduced, the time required to wait until the glue has dried to start further processing steps with the final laminate board is reduced. The further processing steps may be for example profiling of the final laminate board. After the final pressing step, the laminate board only needs to cool down, typically to a temperature of between <NUM> to <NUM>. The cooling can be done in a cooler system before further processing. The whole process typically takes up to <NUM> days, or preferably <NUM> to <NUM> days until a final laminate board is complete and can be packed.

Secondly, by pressing the first and second sheet materials together in a first step, without the decorative sheet and the overlay sheet, the pressing capacity increases. Normally when stacks of kraft papers, a decorative sheet, and an overlay sheet are pressed together, press plates, typically made of a metal, are placed between the stacks to create texture on the surface of the final laminate board. When only pressing the first and second sheet materials together, there is no need to create a texture on the surface, and therefore no need of press plates at this stage. A thin release sheet may be placed between each of the sub stacks in the press so that the interim sheets can easily be separated after pressing. The release sheets take up less space than the press plates, and thus a higher number of sub stacks can be pressed at the same time. The term "pressing capacity" refers to the number of units of sub stacks that can be pressed at the same time in one press. The term stack or sub stack is used herein to mean an assembly of sheets positioned on top of each other.

Moreover, the planning step, which decides the final visual appearance of the laminate boards, is postponed to after the interim sheet is formed. This is at a later stage compared to a procedure where the kraft papers, the decorative sheet, and the overlay sheet are pressed together in a single step. The texture of the final laminate board may also be decided in the last pressing step, by pressing the decorative sheet or the overlay sheet with a press plate. The method according to the invention may therefore be more flexible. By using this flexible method, the customer may have his/her desired design faster. Less storage space is needed, and the laminate board may arrive to the customer in a short period of time.

The method according to the third aspect of the invention may be a more efficient process, while still resulting in durable laminate boards with a high quality. The interim sheet gives the final laminate boards a thickness that leads to a strong laminate board that is less prone to scratches and dents.

Furthermore, the method according to the invention may lead to less tension in the final laminate board. If different type of sheets impregnated with different thermosetting resins are pressed together, tensions may occur in the interim sheet or laminate board due to a difference in the thermosetting resins' ability to retain the water. By pressing for example two kraft papers together, which have been impregnated with the same thermosetting resin, there may be less tension in the interim sheet causing less bending of the laminate board.

Furthermore, the two-step pressing process may result in less tension and bending of the final laminate board than a process with one pressing step and one gluing step, due to water being released in two pressing steps rather than one. During the first pressing step, the fibres in the interim sheet may stabilise with the liquid, so that a lot of the movement of the fibres in the interim sheet will have been completed before the second pressing step. Furthermore, the two pressing steps may lead to less moisture in the laminate board. Less moisture in a laminate board will decrease movement in the laminate board when it is exposed to low humidity, for example during the winter.

In some preferred embodiments, the method according to the third aspect preferably also comprises the step of digitally printing a motif on the interim sheet, preferably prior to the step of forming a stack.

The method as described above may have many advantages. Firstly, the interim sheet is not completely cured after the pressing. The first and second thermosetting resins may therefore flow again upon heating. The first and second thermosetting resin may, upon heating and at least partially, flow into the adjacent sheets in the stack such that the sheets in the stack may adhere together upon being pressed together in step d).

Secondly, the second pressing of the interim sheet with the substrate board, the method according to the invention may be faster, as explained above.

Furthermore, the method according to the third aspect of the invention has an increased pressing capacity for the first pressing step.

The method according to the third aspect corresponding to the invention may be a more efficient process, while still resulting in custom decorated durable laminate boards with a high quality. The interim sheet gives the final laminate boards a thickness that leads to a strong laminate board that is not prone to scratches and dents.

Furthermore, the method according to the third aspect corresponding to the invention may lead to less tension in the final laminate board, as explained for the third aspect of the invention. By pressing for example two kraft papers together, which have been impregnated with the same thermosetting resin, there may be less tension in the interim sheet and thus less bending of the interim sheet. This may facilitate printing the decorative motif on the interim sheet.

The method according to the third aspect corresponding to the invention may allow for custom made laminate boards. The decorative motif can be chosen by the customer and digitally printed directly on the interim sheet. The method according to the third aspect of the invention is efficient, and the customer may have his/her custom designed laminate boards faster.

In a fourth aspect not according to the claimed invention, the disclosure relates to a laminate board obtained by the method according to the third aspect of the invention. (Preferred) embodiments of the third aspect are also (preferred) embodiments of the fourth aspect and vice versa.

The term "substrate board" refers to a board suitable for forming a laminate board for use on a floor or on a wall. The substrate board may for example be an HDF, an MDF or a plywood board.

The term "decorative sheet" refers to a cellulose paper with a decorative design such as wood imitation, or any other designs.

The term "overlay sheet" refers to a cellulose paper, which may improve durability of the final laminate board and reduce the risk of abrasion of the final laminate board. The overlay sheet may be at least partially translucent and/or at least partially transparent. The overlay sheet may preferably comprise corundum.

The term "balancing sheet" refers to a layer, impregnated with a thermosetting resin, positioned adjacent to a substrate board, on the opposite side as the sheets making up the decorative side of the final laminate board. The composition of the balancing sheet depends on the layers on the opposite side of the substrate board. The balancing sheet may for example comprise one or more groove papers or an interim laminate.

The term "adhesive sheet" refers to a cellulose paper capable to take up a thermosetting resin. Alternative words for adhesive sheet may be impregnation paper or suction paper. The purpose of the adhesive sheet is to increase the adhesion between the substrate board and the interim laminate. The adhesive sheet is preferably impregnated with a thermosetting resin comprising melamine.

The terms "stack" and "sub stack" are used herein to mean an assembly of sheets positioned on top of each other.

The term "thermosetting resin" refers to a soft solid or a viscous liquid of polymer that hardens upon heating. Heating the thermosetting resin results in cross-linking of the polymer chains in the thermosetting resin, which results in curing of the thermosetting resin.

By the term "liquid" it is meant that the first thermosetting resins are flowable enough to at least partially flow into the alternative sheet material from the sheet material in which they are originally impregnated. That is to say, the first thermosetting resin is in a liquid phase according to the present disclosure when at least part of the first thermosetting resin is flowable enough that it may flow into the second sheet material. The second thermosetting resin is in a liquid phase according to the present disclosure when at least part of the second thermosetting resin is flowable enough that it may flow into the first sheet material.

By the term "not completely cured" it is meant that at least a part of the first and second thermosetting resins may flow again after the first pressing step, upon heating. If the interim sheet is pressed together with other sheets in a stack at a suitable temperature and for a suitable period of time, the first and second thermosetting resin may flow, at least partially, into the adjacent sheets such that the stack may adhere together upon being pressed together. As used herein, the term "tension" refers to the interim sheet's or the laminate board's tendency to bend when exposed to changes in temperature and/or humidity.

In some embodiments, the step of providing at least a first sheet material impregnated with a first thermosetting resin comprises the steps of:.

The first impregnatable sheet material may be a kraft paper. The first impregnatable sheet material may be a groove paper.

In some embodiments, the step of providing a second sheet material impregnated with a second thermosetting resin comprises the steps of:.

The second impregnatable sheet material may be a kraft paper. The second impregnatable sheet material may be a groove paper.

In some preferred embodiments, in step b) the temperature is between <NUM> and <NUM>, preferably between <NUM> and <NUM>, preferably around <NUM>. These temperatures have been found to provide optimal results. A temperature that is too low will not laminate the product well enough (may cause delamination) and may cause gas bubbles. A temperature that is too high will overcure the product and cause delamination in the last step.

In some preferred embodiments, in step b) the pressing may be performed for between <NUM> and <NUM> minutes, preferably between <NUM> to <NUM> minutes, preferably around <NUM> minutes. These times have been found to provide optimal results. A pressing time that is too short will not laminate the product well enough (may cause delamination). A pressing time that is too long will overcure the product and cause delamination in the last step.

In some preferred embodiments, in step b) the first sufficient pressure may be between <NUM> and <NUM>/cm<NUM>, preferably between <NUM> and <NUM>/cm<NUM>, preferably around <NUM>/cm<NUM>. These pressures have been found to provide optimal results. Using a pressure outside these ranges may cause cracking or delamination.

One of the first sheet and the second sheet may be a white sheet for improving the aesthetic appearance of the final, digitally printed, laminate board. In other examples another colour may be chosen.

In some embodiments, the first sheet material comprises paper. The first sheet material may be a kraft paper. The first sheet material may be a groove paper.

In some embodiments, the first sheet material comprises paper. The second sheet material may be a kraft paper. The second sheet material may be a groove paper. These materials are environmentally friendly and cheap to use. The present invention also includes the use of other materials for the first and/or second sheet. Using other materials may change the setup in both temperature and press time, but still within the preferred ranges as described herein.

The term "first sheet material" preferably refers to a kraft paper or a groove paper. The term "second sheet material" preferably refers to a kraft paper, or a groove paper.

The term "kraft paper" refers to a high strength paper produced by sulphate pulp. The kraft paper may be bleached or unbleached. The paper weight of the kraft paper may preferably be between <NUM> to <NUM>/m<NUM>. The kraft paper may be a recycled kraft paper. The term "groove paper" refers to a cellulose paper capable to take up a thermosetting resin. Alternative words for groove paper may be impregnation paper or suction paper.

The method according to the first aspect, not according to the claimed invention, may for example be used to press two kraft papers together. The resulting interim sheet may then be used to form a stack of sheets together with for example a substrate board, a decorative sheet, and an overlay sheet. The stack may be pressed together to form a laminate board.

When pressing together two kraft papers, which have been impregnated with the same thermosetting resin, the resulting interim sheet may have less tension. That is, the interim sheet may not be prone to bending. Due to the resulting flat structure of the interim sheet, the interim sheet may more easily be used for printing than if the interim sheet was bent after the pressing step. This may lead to a better quality of the decoration of a final laminate product. The first thermosetting resin may comprise phenol. The first thermosetting resin may comprise melamine. The first thermosetting resin may comprise phenol and melamine. The second thermosetting resin may comprise phenol. The second thermosetting resin may comprise melamine. The second thermosetting resin may comprise phenol and melamine. The first and/or second thermosetting resin may comprise any other suitable thermosetting resin.

The third thermosetting resin may comprise phenol. The third thermosetting resin may comprise melamine. The third thermosetting resin may comprise phenol and melamine. The fourth thermosetting resin may comprise phenol. The fourth thermosetting resin may comprise melamine. The fourth thermosetting resin may comprise phenol and melamine. The first and/or the second and/or the third and/or the fourth thermosetting resin each comprises any other suitable thermosetting resin.

Preferably, the first sheet material is a kraft paper and the second sheet material is a kraft paper. Preferably, the first and second sheet material are impregnated with a phenolic thermosetting resin. Preferably, the decorative sheet and the overlay sheet are impregnated with a thermosetting resin comprising melamine. It is advantageous to impregnate the decorative sheet and overlay sheet with a thermosetting resin that does not comprise phenol due to miscolouring of the sheets upon curing if the phenolic thermosetting resin.

If both the overlay sheet and the interim sheet are impregnated with a thermosetting resin comprising melamine, for example a mixture of <NUM>% melamine and <NUM>% phenol, then decorative sheet, which is positioned between the two impregnated sheets, does not have to be impregnated with a thermosetting resin before step d). During step d) the thermosetting resins from the overlay sheet and the interim sheet may at least partially flow into each side of the decorative sheet so that the three sheets may adhere together upon curing of the two thermosetting resins. The advantage of not impregnating the decorative sheet before pressing the stack together is that it saves time and reduces the use of thermosetting resins.

In some embodiments, the decorative sheet is impregnated with a third thermosetting resin. In some embodiments, the decorative sheet not impregnated with a thermosetting resin and the overlay sheet is impregnated with a fourth thermosetting resin, preferably the overlay sheet is positioned as an outermost layer adjacent the decorative sheet in the stack.

In some embodiments, the decorative sheet is impregnated with a third thermosetting resin and the overlay sheet is impregnated with a fourth thermosetting resin, preferably the overlay sheet is positioned above the decorative sheet in the stack.

In some preferred embodiments, the method may further comprise the step of digitally printing a motif on the interim sheet.

In some preferred embodiments, the interim sheet is in direct contact with the substrate board in the stack formed in step c).

In step c) the stack may further comprise an overlay sheet positioned as an outermost layer adjacent the interim sheet, wherein the overlay sheet is impregnated with a third thermosetting resin. The overlay sheet may be a cellulose paper, which may be added to the stack to improve durability and to reduces the risk of abrasion of the final laminate board.

In some preferred embodiments, in step c) the stack further comprises an adhesive sheet positioned between the substrate board and the interim sheet, wherein the adhesive sheet is impregnated with a fifth thermosetting resin. If the first or second thermosetting resin does not comprise melamine, it is advantageous to add an adhesive sheet impregnated with melamine between the substrate board and the interim sheet to increase the adhesion between the layers in the stack. The pressing step of d) is typically less than a minute, and melamine has a high reactivity and will cure during this step.

The fifth thermosetting resin may comprise melamine. The fifth thermosetting resin may comprise phenol and melamine. The fifth thermosetting resin may comprise any other suitable thermosetting resin.

In some preferred embodiments, in step c) the stack further comprises a balancing sheet, impregnated with a sixth thermosetting resin. The balancing sheet may reduce tension in the laminate board and may reduce the risk of the laminate board to shrink or bend.

The sixth thermosetting resin may comprise melamine. The sixth thermosetting resin may comprise phenol and melamine. The sixth thermosetting resin may comprise any other suitable thermosetting resin.

In some preferred embodiments, step d) comprises heating an uppermost side of the stack with a first temperature and a lowermost side of the stack with a second temperature different from the first temperature. The lowermost side of the stack may be the side formed by the substrate board or the balancing sheet, and the uppermost side may be the side formed by the decorative sheet or the overlay sheet. The temperature may be higher on the lowermost side than the uppermost side during pressing. The difference in temperature may reduce tension in the laminate board and may reduce the risk of the laminate board to shrink or bend. The pressing temperature is preferably between <NUM> to <NUM>. Different temperatures are preferably used on the top of the stack and the bottom of the stack, for about <NUM> on the lower side and <NUM> on the upper side. The inventors have found that these provide optimal temperatures to avoid delamination, debonding, and/or cracking of the final laminate. Working outside the preferred temperature ranges also increases the odds of uneven dimensional stability.

In step d) the pressing may be for between <NUM> to <NUM> seconds, preferably between <NUM> to <NUM> seconds, preferably between <NUM> to <NUM> seconds, preferably around <NUM> seconds. The inventors have found that these provide optimal pressing times to avoid delamination, debonding, and/or cracking of the final laminate. Lower pressing times may make more volume and increase production, but the risk is debonding. Longer pressing times on the other hand will decrease production and could cause too much pressure on the substrate (HDF) making it too thin. The present ranges provide a correct balance between output and quality. Working outside the preferred time ranges also increases the odds of uneven dimensional stability.

In step d) the second sufficient pressure may be between <NUM> and <NUM>/cm<NUM>, preferably between <NUM> and <NUM>/cm<NUM>, preferably around <NUM>/cm<NUM>. The inventors have found that these provide optimal pressures to avoid delamination, and/or cracking of the laminate.

In step d) the stack may be pressed with a press plate on the uppermost side of the stack. The press plate forms structures on the surface of the laminate board allowing for laminate boards to be customised to the preference of the consumer. The structures may improve the visual appearance of the laminate on the decorative side of the laminate board.

The following examples serve to merely illustrate the invention and should not be construed as limiting its scope in any way. While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes and modifications without departing from the scope of the invention.

<FIG> shows a method for producing a laminate board <NUM>, according to an embodiment of the invention. A first and a second sheet material, here shown as two kraft papers <NUM> have each been impregnated with a thermosetting resin comprising phenol, and are stacked on top of each other, forming a sub stack <NUM>. The first pressing step <NUM> comprises a step of pressing the sub stack <NUM> together. The pressure is around <NUM>/cm<NUM>, and the temperature in the press is between <NUM> to <NUM>. The sub stack <NUM> is pressed for <NUM> to <NUM> minutes. Several sub stacks <NUM> may be pressed at the same time, with release sheets between the sub stacks <NUM>.

The first pressing step <NUM> results in an interim sheet <NUM>, which is not completely cured. The interim sheet <NUM> may therefore adhere to other sheets in a stack when the stack is pressed in a subsequent pressing step.

After the interim sheet <NUM> has cooled down sufficiently, to for example room temperature or between <NUM> and <NUM>, preferably around <NUM> either inside or outside the press, or in a cooler system, the interim sheet <NUM> is cut to a desired size and grinded in step <NUM>. The grinding may improve adhesion of the layers in the subsequent assembly step and allow better penetration of the thermosetting resin and melamine into the laminate.

A stack <NUM> is then assembled. Four layers may be stacked on top of a substrate board <NUM>, for example a HDF board, in the following order: the interim sheet <NUM>, a decorative sheet <NUM> and an overlay sheet <NUM>. An adhesive sheet <NUM> may be optionally incorporated in the stack <NUM>. The decorative sheet <NUM> and the overlay sheet <NUM> may be impregnated with a thermosetting resin comprising melamine. In embodiments including the optional adhesive sheet <NUM>, the decorative sheet <NUM>, and the overlay sheet <NUM> may be impregnated with a thermosetting resin comprising melamine. A balancing sheet <NUM>, impregnated with a thermosetting resin comprising melamine, is positioned underneath the substrate board <NUM> to reduce tension in the final laminate board <NUM>.

The second pressing step <NUM> comprises pressing the stack <NUM> together. The stack <NUM> may be pressed with a pressure of at least <NUM>/cm<NUM>, preferably between <NUM> and <NUM>/cm2, or between <NUM> and <NUM>/cm<NUM>, or most preferably <NUM>/cm<NUM> for between <NUM> and <NUM> seconds, or between <NUM> and <NUM> seconds, or between <NUM> and <NUM> seconds, or preferably around <NUM> seconds. The pressing temperature is between <NUM> to <NUM>. Different temperatures are used on the top of the stack <NUM> and the bottom of the stack <NUM>, for example between <NUM> and <NUM> on the bottom of the stack <NUM> and between <NUM> and <NUM> at the top of the stack. Using different temperatures at the bottom and top of the stack may reduce tension in the resulting laminate board <NUM>. There are more fibres and melamine on the top of the stack <NUM>, which requires more heat to cure. A higher temperature on the top of the stack <NUM> may therefore be beneficial to form a flat laminate board.

The second pressing step <NUM> results in a laminate board <NUM>. After sufficient cooling of the laminate board <NUM> to for example room temperature or between <NUM> and <NUM>, the laminate board <NUM> may be further processed.

An alternative exemplary method is shown in <FIG>. In this example, the sub stack <NUM>-<NUM> is formed by a first sheet material, in this case a kraft paper <NUM>, impregnated with a thermosetting resin comprising phenol, and a second sheet material, in this case a groove paper <NUM> impregnated with a thermosetting resin comprising melamine. In <FIG>, the groove paper <NUM> is positioned over the kraft paper <NUM>, but it could equally be positioned under the kraft paper <NUM>.

The sub stack <NUM>-<NUM> is then pressed using the first pressing step <NUM> as explained above. The first pressing step <NUM> results in an interim sheet <NUM>-<NUM>, which is cut and grinded in step <NUM>. A stack <NUM>-<NUM> is then assembled. Three layers are stacked on top of a substrate board <NUM>, for example a HDF board, in the following order: the interim sheet <NUM>-<NUM>, a decorative sheet <NUM> and an overlay sheet <NUM>. Since the interim sheet <NUM>-<NUM> was not completely cured in the first pressing step <NUM> and the groove paper <NUM> comprises melamine, the adhesive sheet <NUM> is left out. The overlay sheet <NUM> is impregnated with a thermosetting resin comprising melamine. The decorative sheet <NUM> is positioned between two melamine impregnated sheets, the interim sheet <NUM>-<NUM> and the overlay sheet <NUM>, so the decorative sheet <NUM> may not be impregnated with a thermosetting resin. A balancing sheet <NUM>, impregnated with a thermosetting resin comprising melamine or phenolic resin or a combination thereof, is positioned underneath the substrate board <NUM> to reduce tension in the final laminate board <NUM>.

The stack <NUM>-<NUM> is then pressed in the second pressing step <NUM>, as explained above. This results in a laminate board <NUM>, which can be further processed after sufficient cooling.

An alternative exemplary method is shown in <FIG>. In this example, the sub stack <NUM>-<NUM> is formed by a first sheet material, in this example a kraft paper <NUM>, impregnated with a thermosetting resin comprising phenol, and a second and third sheet material, in this example two groove papers <NUM> impregnated with a thermosetting resin comprising melamine. The two groove papers <NUM> are positioned on either side of the kraft paper <NUM>.

The sub stack <NUM>-<NUM> is then pressed using the first pressing step <NUM> as explained above. The first pressing step <NUM> results in an interim sheet <NUM>-<NUM>, which is cut and grinded in step <NUM>. A stack <NUM>-<NUM> is then assembled. Three layers are stacked on top of a substrate board <NUM>, in the following order: an adhesive sheet <NUM>, the interim sheet <NUM>-<NUM> and a decorative sheet <NUM>.

The adhesive sheet <NUM> and the decorative sheet <NUM> are impregnated with a thermosetting resin comprising melamine. Since the interim sheet <NUM>-<NUM> was not completely cured in the first pressing step <NUM> and the groove papers <NUM> comprise melamine, the adhesive sheet <NUM> is left out. A balancing sheet <NUM>, impregnated with a thermosetting resin comprising melamine or phenolic resin or a combination thereof, is positioned underneath the substrate board <NUM> to reduce tension in the final laminate board <NUM>.

The parameters for the two pressing steps <NUM> and <NUM> may vary from the examples above. The pressing time, temperature and pressure are dependent on each other, so for example if the temperature in a pressing step is increased, the time may be decreased, etc. A higher pressure in a pressing step may also lead to less pressing time required for sufficient adhesion between the sheets in a sub stack or a stack. Other factors such as number and type of layers in the sub stack <NUM>, <NUM>-<NUM>, <NUM>-<NUM> and the stack <NUM>, <NUM>-<NUM>, <NUM>-<NUM> may also influence the pressing parameters. For example, in the second pressing step <NUM> the pressure may be up to <NUM>/cm<NUM> depending on pressing time, temperature and the number and types of layers in the stack. The type of thermosetting resin may also influence the pressing parameters of the pressing steps <NUM> and <NUM>, such as the temperature and time. A phenolic thermosetting resin needs typically more time to react than a melamine thermosetting resin.

A laminate board was produced by the following procedure:.

Four tests were performed to compare the produced exemplary laminate board with conventional DPL and HPL boards. The moisture content in the laminate boards was measured using the European standard EN322. A drop test, a wear test and a scratch test were performed following the European standard EN13329.

The results from the test can be seen in Table <NUM> below.

As can be seen from the results, the exemplary laminate board performed similarly as the HPL board on the moisture test and the drop test. The drop test revealed a higher durability of the HPL board and the exemplary laminate board.

Furthermore the exemplary laminate board performed better in the wear test than the DPL board, showing a higher wear resistance of the exemplary laminate board compared to the DPL board. The higher wear resistance may be due to the interim sheet underneath the decorative sheet and the overlay sheet, and the high heat and the short pressing time during the second pressing step. The presence of the interim sheet may prevent the corundom in the overlay sheet from penetrating far into the underlaying sheets during the second pressing step. The corundum may therefore stay closer to the top surface of the laminate board resulting in a better wear resistance.

The scratch test also shows a better result for the exemplary laminate board compared to both the DPL board and the HPL board. The exemplary board may therefore be more durable than both conventional laminate boards.

It should be noted that the above-mentioned examples illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments as long as not departing from the scope of the appended claims. Use of the verb "comprise", and its conjugations does not exclude the presence of elements or steps other than those stated in a claim.

Claim 1:
A method for producing a laminate board (<NUM>), comprising the step of producing an interim sheet (<NUM>), the method comprising the steps of:
a) providing at least a first sheet material impregnated with a first thermosetting resin, and a second sheet material impregnated with a second thermosetting resin;
b) pressing the first and second sheet materials together, at a temperature of between <NUM> and <NUM>, for between <NUM> and <NUM> minutes, such that the first and second thermosetting resins become liquid, and pressing with a first sufficient pressure such that the first and second sheet materials fuse to form an interim sheet without fully curing the first and second thermosetting resins such that the first and second thermosetting resins can flow again when heated;
c) forming a stack (<NUM>) comprising the following layers:
- a substrate board (<NUM>); and,
- the interim sheet (<NUM>) of step b); and,
d) pressing the stack together, at a temperature of between <NUM> and <NUM>, for between <NUM> and <NUM> seconds, such that the first and second thermosetting resins flow again, and pressing with a second sufficient pressure such that the layers bond together to form a laminate board (<NUM>).