Method of manufacturing a laminated panel and a floor panel

Abstract

 A method of manufacturing a laminated panel which comprises at least a core (1) and a decoration sheet (4) attached to each other by means of an adhesive (2), comprises the steps of supplying the core (1) and the decoration sheet (4), applying the adhesive (2) to the core (1) and/or the decoration sheet (4) such that in any case the content of the adhesive (2) applied to the decoration sheet (4) is below a saturation level thereof, and laying the core (1) and the decoration sheet (4) onto each other and pressing them together.

Description

[0001] The invention relates to a method of manufacturing a laminated panel which comprises at least a core and a decoration sheet attached to each other by means of an adhesive, wherein the core and the decoration sheet are supplied, laid onto each other and pressed together.

[0002] Such a method is known in the art. Since it is desired to obtain laminated panels, in particular floor panels, having a surface texture which corresponds with a decoration pattern of the decoration sheet (embossment in register), the decoration sheet should be positioned correctly with respect to the embossed press plate. This appears to be difficult in practice, because there is a certain degree of variation in the decoration sheets as supplied before pressing.

[0003] The object of the invention is to provide a method of manufacturing a laminated panel wherein the deviation of the positions of the decoration pattern of the decoration sheet and that of the embossed press plate is minimized.

[0004] This object is accomplished by the method according to the invention which comprises the step of applying the adhesive to the core and/or the decoration sheet such that in any case the content of the adhesive applied to the decoration sheet is below a saturation level thereof.

[0005] Due to these feature the decoration sheet remains more stable during the manufacturing process than in case of the traditional method in which the content of adhesive in the decoration sheet is higher.

[0006] In traditional methods the adhesive is often a resin which is impregnated in the paper of the decoration sheet by submerging the sheet in the resin such that it is saturated with resin. This means that the resin has fully penetrated the paper; if, for example, the resin is applied to one side of the paper, the paper is saturated when the resin comes out of the paper at the opposite side of the paper. After drying, the resin-impregnated sheet size may be different with respect to the decoration sheet before it was impregnated. The sheet may expand due to the resin, whereas the expansion may be non-uniform over the entire sheet. Ambient conditions such as humidity may also influence the extent of deformation of the decoration sheet. Additionally, the decoration sheet which is treated in an impregnation process may be deformed due to drawing it through an impregnation device. Therefore, deformation of the decoration sheet is reduced or even eliminated in the method according to the invention.

[0007] In a preferred embodiment the adhesive is applied to the core only, before laying the core and the decoration sheet onto each other. In this case the decoration sheet is free of the adhesive. As a consequence, at least a part of the adhesive applied to the core penetrates the decoration sheet during pressing. In this case the decoration sheet, including the decoration pattern, cannot be influenced by the adhesive before the sheet contacts the core, and if the adhesive is dry before pressing and becomes liquid during pressing, the decoration sheet can even not be influenced by the adhesive before pressing. This improves the reproducibility of the positioning of the decoration sheet with respect to the (embossed) press plate further.

[0008] In case of applying the adhesive to the core a surface treatment of the core may be performed before applying the adhesive thereto such that penetration of the adhesive into the core is controlled. Such a surface treatment may comprise a treatment to increase the density of the core at the core surface, for example by means of a coating of a certain resin type, resulting in minimized penetration of the adhesive into the core.

[0009] Alternatively, the adhesive may be applied to one side of the decoration sheet which side is facing to the core when the decoration sheet and the core are laid onto each other. In this case the decoration layer comprise the adhesive and may be thus influenced, but the content of the adhesive is below the saturation level of the decoration sheet, which means that the influence is less than in traditional cases.

[0010] A protective layer comprising a protective layer sheet and an anti-wear material may be supplied, and a second adhesive may be applied to the protective layer and/or the decoration sheet such that in any case the content of the second adhesive applied to the decoration sheet is below a saturation level thereof, and the protective layer and the decoration sheet are laid onto each other prior to pressing such that the decoration sheet is disposed between the core and the protective layer. Due to these features the second adhesive may penetrate the decoration sheet such that the content of the second adhesive in the decoration sheet before pressing may be relatively low or even zero. The second adhesive may be identical to the adhesive as mentioned hereinbefore. It is even conceivable to oversaturate the protective layer without applying the second adhesive to the decoration sheet.

[0011] The decoration sheet and/or the protective layer sheet may be paper-based. This material allows printing of a pattern thereon and may have a good absorption capacity of the adhesive and/or the second adhesive.

[0012] The adhesive and/or the second adhesive may be a resin which can be impregnated in the decoration sheet and/or the protective layer sheet. The advantage of a resin is that it may be dried before pressing and can be melted during pressing under increased temperature. This means that the decoration sheet may be free of resin up to the pressing process.

[0013] The paper weight of the decoration sheet may be higher than 90 g/m2, but higher than 80 g/m2 is also conceivable. This reduces the risk of damage of the paper during the manufacturing process. In practice the paper may be lifted by vacuum nozzles, which may deform and damage the paper easily if the paper is relatively light. Furthermore, heavier paper can be cut more easily. It is possible to cut the paper by means of a laser beam.

[0014] It is noted that the temperature may be increased during pressing in the method as described hereinbefore. Furthermore, a surface texture may be applied on the panel during pressing, preferably in register with a pattern present on the decoration sheet.

[0015] The invention is also related to a method of manufacturing a laminated panel which comprises at least a core, a decoration sheet and a protective layer sheet attached to each other by means of an adhesive, wherein the method comprises the steps of:

• supplying the core, the decoration sheet and the protective layer sheet,
• applying the adhesive to the protective layer sheet and/or the decoration sheet and/or the core such that in any case the content of the adhesive applied to the decoration sheet is below a saturation level thereof, and
• laying the core, the decoration sheet and the protective layer sheet onto each other and pressing them together. In this case it is possible, for example, that only the protective layer sheet is saturated or oversaturated with resin and that during pressing at raised temperature the resin is transferred to the decoration sheet and the core.

[0016] The invention is also related to a method of manufacturing a laminated panel which comprises at least a core and a decoration sheet including a pattern, wherein the method comprises the steps of:

• supplying the core and the decoration sheet,
• pressing the decoration sheet on the core, wherein during pressing a first part of the decoration sheet is embossed in register with the pattern of the decoration sheet and a second part of the decoration sheet is pressed on the core without embossing in register with the pattern of the decoration sheet.

[0017] Manufacturing a laminated panel according to this method results in a laminated panel having a first portion of which a surface is embossed in register with the pattern of the decoration sheet, i.e. comprising a three dimensional relief corresponding to the pattern, and a second portion of which a surface is not embossed in register with the pattern. An practice, after performing the method the panel can be cut into smaller pieces such that pieces cut out of the first portion have a surface which is embossed in register and pieces cut out of the second portion have a surface which is not embossed in register. The advantage of this method is that the entire surface of a press plate can be used to press the decoration sheet on the core, whereas only within the first part of the decoration sheet the alignment of the press plate and the decoration sheet before pressing them together requires special attention. Thus, a deviation between the position of the pattern of the decoration sheet and a relief pattern of the press plate before pressing is allowed at the second part of the decoration sheet, and accurate positioning of the decoration sheet with respect to the press plate is less relevant in that region.

[0018] In practice, the first part may be a central portion of the decoration sheet, and the second part may extend between the central portion and a side edge of the decoration sheet. Specifically, it the decoration sheet is made of paper supplied by a paper band and impregnated by a resin to be able to attach it to the core during pressing, the central portion tends to expand less than the paper at the outer edges of the band, whereas there may also be a difference between expansion in length and width of the decoration sheet. Therefore, the central portion of the decoration sheet is preferred for applying embossing in register rather than the other portions which are more sensitive to expansion due to impregnation.

[0019] In a particular embodiment the second part is pressed on the core without embossment or without embossment in register. This means that the second portion of a laminated panel thus manufactured may comprise a smooth surface or a surface having a relief pattern but which is not in register with the decoration layer pattern.

[0020] The invention is also related to a press plate for pressing a decoration sheet on a core so as to form a laminated panel, wherein the press plate comprises an embossed surface portion and a smooth surface portion. The press plate, which may be in the form of a press roller, may comprise parallel regions representing wood planks, for example, wherein a first number of these regions have an embossed surface and a second number of these regions have a smooth surface. When manufacturing laminated panels by using this press plate, at least two kind of planks can be made in one pressing operation: planks having a decoration side including an upper surface which is embossed in register with the decoration pattern of a decoration sheet thereof and planks having a decoration side including an upper surface which is not embossed in register with the decoration pattern. Of course, the individual planks have to be cut off the laminated panel.

[0021] The invention is also related to a floor panel which is manufactured according to the method as described hereinbefore.

[0022] The invention will be explained in more detail hereinafter with reference to the drawings, which schematically show embodiments of the invention.

[0023] Fig. 1 is an illustrative view of an example of the method of manufacturing a laminated panel according to the invention, showing different steps in the method.

[0024] Fig. 2 is an illustrative view of the flow direction of adhesive during one step of the method of Fig. 1.

[0025] Fig. 3 is an illustrative side view of an impregnation process.

[0026] Fig. 4 is a perspective view of a printing cylinder.

[0027] Fig. 5 is a top view of a laminated panel which is manufactured by means of an embodiment of the method according to the invention.

[0028] Fig. 6 is a similar view as Fig. 5, but showing an alternative laminated panel.

[0029] Traditionally, a laminated panel, more particularly a laminated floor panel, is manufactured by preparing different layers, applying adhesive to the layers, laying them onto each other and pressing them together, often supported by a raised temperature in case of a hot melting adhesive.

[0030] Fig. 1 illustrates different steps of an embodiment of the method according to the invention. Fig. 1a shows a core 1, which may be a wood-based panel such as pressurized wood fibres like HDF, but numerous alternative materials are conceivable. An upper surface of the core 1 is provided with an adhesive, for example a resin 2. This can be performed by a roller coater 3, for example, but an alternative means for applying the adhesive or resin 2 to the core 1 is conceivable. Fig. 1b shows the core 1. including the resin 2 coated thereon. In certain cases, depending on the material properties of the resin 2 and the core 1, a surface treatment may be applied to the core 1 before applying the resin 2 thereto so as to control the penetration of the resin into the core 1.

[0031] Fig. 1c shows a manufacturing step in which a balancing layer 3 is positioned with respect to a lower surface of the core 1, which lower surface extends opposite to the upper surface of the core 1. Furthermore, Fig. 1c shows a decoration sheet 4, positioned above the upper surface of the core 1. The decoration sheet 4 is provided with a decoration pattern, for example a wood pattern, stone pattern, or the like. In this case the decoration sheet 4 is a paper sheet and free from resin. In an alternative embodiment the decoration sheet may comprise a certain content of resin 2, for example at the side which is facing to the core 2, but in any case the content of the resin 2 applied to the decoration sheet 4 must be below a saturation level thereof. A saturation level is achieved when the sheet is entirely submerged in a resin for a certain period of time, depending on material properties of the sheet and the resin. In case of applying a relatively small content of resin to the decoration sheet 4 it is advantageous to use a relatively heavy paper type so as to increase stability of the decoration sheet 4.

[0032] Fig. 1d shows a protective layer 5 positioned above the decoration sheet 4 such that the decoration sheet 4 extends between the core 1 and the protective layer 5. The protective layer comprises an anti-wear material and a protective layer sheet, which may be a paper-based sheet. In this case anti-wear material, for example corundum particles, is integrated in the protective layer sheet, and the protective layer sheet is impregnated by a resin as a second adhesive 2', thus forming the protective layer 5. In an alternative embodiment the anti-wear material may be added to the resin 2'. Although in this case the adhesive applied to the core 1 is the same resin 2 as the second adhesive 2' applied to the protective layer sheet, it is also possible that the adhesive 2 and the second adhesive 2' have different compositions, but they are preferably compatible.

[0033] The core 1 including the balancing layer 3, the decoration sheet 4 and the protective layer 5 are laid onto each other and pressed together between press plates 6, which is shown in Fig. 1e. Depending on the properties of the resin 2 on the core 1 and the resin 2 in the protective layer 5 the temperature of the press plates 6 can be increased such that the resin, which was solid before starting pressing, starts to melt and penetrates the decoration sheet 4. This process is illustrated in Fig. 2. The transfer of resin 2' from the protective layer 5 and the transfer of resin 2 from the core 1 to the decoration sheet 4 is indicated by arrows.

[0034] The method according to the invention provides the opportunity to use a decoration sheet 4 containing less resin 2, 2' than in traditional methods or being even free from resin 2, 2', which leads to less or no deformation/expansion of the decoration sheet 4 prior to the pressing process. As a consequence, a possible shift of the pattern of the decoration sheet 4 with respect to a corresponding texture on one of the press plates 6 for embossing in register is minimized.

[0035] Fig. 3 illustrate a process of manufacturing pieces of decoration sheets 4, which are impregnated on one side instead of submerging the whole decoration sheet 4 in a resin 2. In Fig. 3 the decoration sheet 4 in the form of a paper band is supplied from a roll from the left and impreg-nated at its lower surface with a resin 2 by means of a cylinder 7. Of course, alternative impregnation means are conceivable. The sheet 4 including the resin 2 is dried at a dryer 8 and cut in appropriate pieces by a cutter 9. Fig. 3 shows that two rollers are disposed between the dryers 10 for controlling the resin distribution on the decoration sheet 4.

[0036] Fig. 4 shows a printing cylinder 11 for printing a pattern on the decoration sheet 4. This is normally performed before a decoration sheet 4 is provided with a resin 2. The printing cylinder 11 prints two different types of patterns on the decoration sheet 4: an embossing in register type pattern at a first part 14 of the decoration sheet 4 and a non embossing in register type pattern at a second part 15. The first part 14 extends between two second parts 15 as seen in longitudinal direction of the printing cylinder 11. The first part 14 is a central portion of the decoration sheet 4 as seen in longitudinal direction thereof, and the second part is formed by two portions of the decoration sheet 4 each extending at both sides of the central portion between the central portion and a side edge 16 of the decoration sheet 4.

[0037] Fig. 5 shows an upper side of a laminated panel manufactured by using a decoration sheet 4 as printed by the printing cylinder of Fig. 4. The decoration sheet 4 is divided in parallel regions representing wood planks, but imitation of alternative products is also conceivable. Each of the wood planks has a wood pattern which may vary from wood plank to wood plank. The wood planks within the first part 14 or central portion of the decoration sheet 4 are provided with an embossed surface which is embossed in register with the wood pattern of the decoration sheet 4 by means of an embossed portion of a press plate. The wood planks within the second part 15 may be embossed, as well, but are not embossed in register with the decoration pattern of the decoration sheet 4. This means that only at the central portion the press plate and the decoration sheet 4 must be positioned accurately with respect to each other before pressing the decoration sheet 4 on the core 1. When the decoration sheet 4 is made of an impregnated paper the decoration sheet 4 may be deformed due to expansion as described hereinbefore. In practice, the paper deformation due to impregnation is typically the smallest in the central portion of the decoration sheet 4. In the second part 15 of the decoration sheet 4 the paper deformation may be larger, but in this case this part is not embossed in register such that positioning of the press plate with respect to the decoration sheet 4 before pressing is less relevant.

[0038] After the pressing process the laminated panel may be cut in pieces, in the case of Fig. 5 along the edges of the imitated wood planks. As a result, at least two types of imitated wood planks will be produced: planks having a surface which is embossed in register and planks having a surface which is not embossed in register.

[0039] Fig. 6 shows an alternative pattern of the decoration sheet 4. The first part 14 has a pattern which is preferably embossed in register such that in longitudinal, lateral and diagonal directions of the pattern the embossment corresponds with the pattern at the first part 14 of the decoration sheet 4. The pattern of the first part 14 has a mosaic structure, but may have alternative shapes, of course.

[0040] From the foregoing, it will be clear that the invention provides a method of manufacturing a laminated panel wherein the deviation of the positions of the pattern of the decoration sheet and the corresponding pattern of the surface texture of the panel is minimized.

[0041] The invention is not limited to the embodiments illustrated in the figures, which can be varied in several ways within the scope of the invention. It is, for example, possible that the press plates are substituted by press roller. Furthermore, the protective layer as a separate layer could be omitted; in that case anti-wear material may be added to an adhesive applied to the decoration sheet or added to the decoration sheet itself.

Claims

1. A method of manufacturing a laminated panel which comprises at least a core (1) and a decoration sheet (4) attached to each other by means of an adhesive (2), wherein the method comprises the steps of:

- supplying the core (1) and the decoration sheet (4),

- applying the adhesive (2) to the core (1) and/or the decoration sheet (4) such that in any case the content of the adhesive (2) applied to the decoration sheet (4) is below a saturation level thereof, and

- laying the core (1) and the decoration sheet (4) onto each other and pressing them together.

2. A method according to claim 1, wherein the adhesive (2) is applied to the core (1) only, before laying the core (1) and the decoration sheet (4) onto each other.

3. A method according to claim 1 or 2, wherein the adhesive (2) is applied to the core (1), and a surface treatment of the core (1) is performed before applying the adhesive (2) thereto such that penetration of the adhesive (2) into the core (1) is controlled.

4. A method according to claim 1, wherein the adhesive (2) is applied only to the side of the decoration sheet (4) which is facing the core (1) when the decoration sheet (4) and the core (1) are laid onto each other.

5. A method according to one of the preceding claims, wherein a protective layer (5) comprising a protective layer sheet and an anti-wear material is supplied, and a second adhesive (2') is applied to the protective layer and/or the decoration sheet (4) such that in any case the content of the second adhesive (2') applied to the decoration sheet (4) is below a saturation level thereof, and the protective layer (5) and the decoration sheet (4) are laid onto each other prior to pressing such that the decoration sheet (4) is disposed between the core (1) and the protective layer (5).

6. A method according to one of the preceding claims, wherein the decoration sheet (4) is paper-based.

7. A method according to claim 5 or claim 5 and 6, wherein the protective layer sheet is paper-based.

8. A method according to one of the preceding claims, wherein the adhesive (2) is a resin which can be impregnated in the decoration sheet (4).

9. A method according to one of the claims 5-7 and claim 5, wherein the second adhesive (2') is a resin which can be impregnated in the protective layer sheet.

10. A method of manufacturing a laminated panel which comprises at least a core (1), a decoration sheet (4) and a protective layer sheet attached to each other by means of an adhesive (2), wherein the method comprises the steps of:

- supplying the core (1), the decoration sheet (4) and the protective layer sheet,

- applying the adhesive (2) to the protective layer sheet and/or the decoration sheet (4) and/or the core (1) such that in any case the content of the adhesive (2) applied to the decoration sheet (4) is below a saturation level thereof, and

- laying the core (1), the decoration sheet (4) and the protective layer sheet onto each other and pressing them together.

11. A method of manufacturing a laminated panel which comprises at least a core (1) and a decoration sheet (4) including a pattern, wherein the method comprises the steps of:

- supplying the core (1) and the decoration sheet (4),

- pressing the decoration sheet (4) on the core (1), wherein during pressing a first part (14) of the decoration sheet (4) is embossed in register with the pattern of the decoration sheet (4) and a second part (15) of the decoration sheet (4) is pressed on the core (1) without embossing in register with the pattern of the decoration sheet (4).

12. A method according to claim 11, wherein the first part (14) is a central portion of the decoration sheet (4), and the second part (15) extends between the central portion and a side edge (16) of the decoration sheet (4).

13. A method according to claim 11 or 12, wherein the second part (15) is pressed on the core (1) without embossment.

14. A floor panel which is manufactured according to one of the preceding claims.

15. A press plate (11) for pressing a decoration sheet (4) on a core (1) so as to form a laminated panel, wherein the press plate (11) comprises an embossed surface portion and a smooth surface portion.

Drawing