ES2993351T3 - Method for refining a construction plate - Google Patents

Abstract

The invention relates to a method for finishing a building board (1) made of a wood material, in particular MDF, HDF or a wood-plastic material mixture with an upper side (2) and a lower side, wherein at least on the upper side a relief consisting of at least one strip-shaped depression (5, 6) with a depth running in the longitudinal and/or transverse direction is embossed. According to the invention, to produce the relief, the building board is heated to a temperature of 80 to 100 °C and the depression is then embossed with a depth of at least 0.5 mm by means of at least one calendering roller heated to a temperature of 100 to 150 °C, the calendering roller having structural elements corresponding to the desired relief. (Automatic translation with Google Translate, not legally binding)

Description

DESCRIPTION

Finishing procedure of a construction panel made available

The invention relates to a method for finishing a construction panel made, in particular, of MDF, HDF or a wood/plastics-based material mixture with an upper side and a lower side, by embossing, at least on the upper side, a relief consisting of at least one strip-shaped depression with a depth extending in a longitudinal direction.

Such a process is known, for example, from WO 2017/164806 A1. This process is used for finishing a floor panel by pressing a bevelled edge into the side edges starting from the top side.

The construction panels known from EP 1820640 B1 are divided into individual panels after finishing and are used, for example, as floor or wall and ceiling panels and are usually provided with a wood, stone or fantasy decor with a superimposed three-dimensional surface. The divided panels have connecting elements (tongue and groove) and are usually equipped with locking elements for locking adjacent panels horizontally and vertically (so-called click panels). The overlapping of decor and three-dimensional surface creates a realistic visual and tactile impression of the imitation material.

In particular, it is known that floor panels are coated at least on the upper side and have a structure adapted to the decor. Such a structure is called embossed register. The decor can take the form of a paper layer laminated to the carrier panel or a colour layer printed directly onto the carrier panel. The decor is also provided with a wear-resistant layer. For this purpose, abrasion-resistant paper layers, so-called overlays, or abrasion-resistant lacquer or resin layers are used after curing. The embossed register is available as a three-dimensional surface structure and is stamped onto the surface of the panel using a corresponding three-dimensional press plate. In this case, the thermal components of the coating, which can be activated by pressure, melt, flow and fill the three-dimensional embossed structure during curing. The structure generally has a height of up to 500 pm. The number and depth of structures are limited by the available amount of activatable components, the gross density of the substrate and the pressing force.

In laminate flooring, the edges where adjacent panels meet are problematic. Depending on the incidence of light, even the smallest height differences can cause visually disturbing shadows that negatively affect the overall impression of a floor. Due to the wood core, the panels are also sensitive to moisture. Any liquid spilled on the floor must be cleaned as quickly as possible to prevent it from penetrating the joint between the butt edges. If water penetrates, the wood fibres in the panel core can swell and cause irreversible damage, as the swelling pressure of the wood destroys the structure and/or the adhesive partially hydrolyses. For this reason, it is important to pay particular attention to the edges of future butt joints during panel manufacturing. Adjacent panels must be able to lie firmly against each other, the installed panel floor must have a visually uniform appearance and precautions must be taken to ensure that any spilled liquid cannot immediately penetrate the joints.

EP 3059020 A1 discloses a process for manufacturing a wood-based panel provided with a decorative layer, which provides for treating at least a section of its surface with steam containing water, sanding the moistened surface and then providing it with at least one decorative layer.

US 4,579,767 A describes a hard fibreboard in which a tile pattern simulated by depressions running longitudinally and transversely has been embossed and which is coated in such a way as to imitate tiles. A plurality of individual tiles are represented on a hard fibreboard. Several hardboards can be placed adjacently.

From WO 2016/180643 A1 it is known to produce panels with depressions provided in the edge areas of the usable surface by stamping at least two grooves running parallel to each other with a core formed between them in a large-format wood-based panel and dividing the stamped panel into smaller individual panels by a saw cut through the core. In the described process, the impregnating agents (decoration and coating) are subjected to extreme mechanical stress, as they are extremely deformed or stretched during structuring. This is unfavourable for brittle materials and can lead to cracks and damage to the surfaces. Microcracks in the surface may remain unnoticed for a long time, but moisture can penetrate through them to the core of the panel and destroy it.

DE 10 2006 052 555 B3 describes a method for producing a panel with a structured surface, in which a support panel provided is provided with an elastic coating, the support panel is cut into strips and a surface structure is stamped into the coated surface of the strips. Finally, the strips are profiled and divided into panels.

EP 2905 135 A2 describes a method for producing a panel in which groove-shaped depressions are stamped into the upper side of a support panel using a calender roll. For this purpose, the roll has circumferential elevations on its barrel. Alternatively or additionally, the roll may have at least one elevation parallel to the axis of rotation on its barrel.

Document DE 197 18770 A1 discloses a method and installation for producing structured wood-based panels. In order to maintain the adhesion and strength properties of the panels, the cold wood-based panels are sprayed with water on one or both surfaces and then passed through a heated vapour deposition section. Structuring on one or both sides follows.

Based on this problem, the process described above must be improved accordingly, so that the embossing of the depression is simplified and the embossed relief is clearly contoured. However, the main manufacturing steps must remain as unchanged as possible so that existing systems can continue to be used. In addition, costs must not be increased or the production process slowed down.

In order to avoid the disadvantages mentioned, it is provided according to a general method according to the invention that the building board is heated to a temperature of 80 to 100 °C to produce the relief and then that the at least one depression is stamped to a depth of at least 0.5 mm by means of at least one calender roller heated to a temperature of 100 to a maximum of 150 °C, the calender roller having structural elements corresponding to the desired relief. The structural elements preferably run in a circumferential direction and are formed by a ring placed on the cylindrical barrel of the calender roller.

If at least one further depression running in the transverse direction, preferably at an angle of 90° transversely to the at least one depression running in the longitudinal direction, is embossed, individual panels can be subsequently cut from the supplied large-format construction board which have recessed edges on both the longitudinal and transverse sides.

The stamped depressions cause the top side to be recessed at the side edges. The joint edges of adjacent panels are therefore lower than the top side. In this case, the height shift cannot cause visually noticeable shadows because all butt joints are recessed. A firm connection between adjacent panels can be achieved by appropriate edge profiling, which effectively prevents liquid from penetrating into the butt joint too quickly.

The depressions running in the longitudinal and transverse directions can be created using several calender rolls. Preferably, the depressions running in the longitudinal and transverse directions are stamped with a single calender roll.

In order for the depressions to be visually visible, they must have a minimum depth of 0.5 mm. The material must not be damaged or destroyed when the relief is stamped. To achieve this, the building board and the calender roller are heated. The building board can be heated with steam. Depending on the material from which the building board is made, a so-called "spring effect" may occur, which causes a change in the contour of the stamped depression. The displaced material springs back elastically. In order to achieve the required structuring depth, however, the structuring height of the calender roller in the circumferential direction is 20 to 40 % greater than the depth of the depression to be stamped. The height can preferably be set 25 to 35 %, in particular 30 %, greater than the depth of the depressions to be stamped in the longitudinal direction.

Since linear pressure is applied in a calender press, the height of the structural element must be even greater for transverse structuring if the depressions are stamped in the longitudinal and transverse directions with the same calender roll. It is 40 to 60%, preferably 45 to 55%, in particular 50% higher than the depression to be stamped in the transverse direction.

If a fibreboard, in particular an MDF or HDF board, is used as a building board, its gross density profile (density profile across the cross section of the board) is intended to be reduced compared to a conventional gross density profile such as that known from EP 3023261 B1. When pressing the fibre cake to obtain a building board of the desired thickness, the highest gross density is obtained in the area of the top and bottom sides of the board. The heat input during pressing causes a pressing skin to form on the top and bottom sides, also known as a "rot layer".

The preferred construction board is HDF boards with a pressed skin on the top. This pressed skin can have a thickness of 0.3 to 0.5 mm.

The gross density of the building panel in the surface layer that is to form the upper side is preferably between 800 and 950 kg/m3.

A building board made from a mixture of wood and plastic can also be used. Regardless of the material used for the building board, it is advantageous if it has a filler content of up to 70% in relation to the total weight. Calcium carbonate or substances with similar properties are suitable as fillers.

To improve the stamping result, a tempering agent can be applied to the upper side of the building board before stamping. This tempering agent is preferably an aqueous melamine resin and is in particular preferably made deformable by means of an elasticizing agent. Suitable elasticizing agents are acrylates, polyols, caprolactam, etc. The tempering agent is dried after application.

It is also possible to apply an elastic primer to the top side of the build panel before stamping. This can be white to create a surface that is easy to print on. At least the depression can be printed with a single-colour or multi-colour decoration using a digital printer. Preferably, the entire top side is printed with a decoration. Instead of using a white colour for the primer, any other colour can be used if necessary. It is important that the primer resists plastic deformation during subsequent stamping.

The first stamping stage is carried out using at least one calender roller. This has the advantage that the stamping stage can be integrated into the production line. Stamping can immediately follow the pressing of the wood-based panel in a continuous press, in which the previously spread fibre cake is pressed into a panel of the desired thickness. This optimises production.

After the construction, which consists of at least one primer, one decoration and, if necessary, one abrasion-resistant layer, has been completed, the building board is laminated in a short-cycle press at high pressure and at a high temperature relative to the environment and, in a second stamping stage, a stamping is carried out again in the at least one strip-shaped depression in order to achieve the configuration of the side walls, preferably without changing the position of the base wall in the depth. During the coating process, the side walls configured in the first stamping stage are "rounded" so that the second stamping stage transforms these roundings again into a flat and straight surface.

In order to be able to align the building panel during the following processing steps, markings may be printed on the base walls of the at least one depression, which may consist of lines, circles, dots, crosses or other graphic symbols. Lines are preferred. These markings may be used to align the building panel for the second stamping stage and further subsequent processing steps using a camera system.

Repeated embossing in the depression in the second stamping stage is preferably carried out on a short-cycle press, where strip-shaped elevations are applied to the press plate.

In the first and/or second stamping stage, a structure can be stamped on the upper side which runs at least partially synchronously with the decoration, which is known in the industry as "relief registration".

Once the large-format panel has been finished, it is separated along the stamped depressions and thus divided into individual panels. The saw cuts are preferably made centrally in the depressions running in the longitudinal and transverse directions, and the individual panels are then profiled at their side edges so that several panels can be joined together without glue.

A calender roll for embossing at least one strip-shaped depression at least on the upper side of a building panel made of a wood-based material, in particular MDF or HDF, or a mixture of wood-based material and plastic, consists essentially of a cylindrical body arranged around an axis of rotation and at least one structural element extending in the circumferential direction, which is essentially complementary (congruent) to the depression to be embossed and has a height that projects radially beyond the outer surface of the cylindrical body.

The height of the structural element is 20 to 40%, preferably 25 to 35%, particularly preferably 30% greater than the depth of the depression to be stamped.

In order to be able to stamp depressions in the building board in the longitudinal and transverse directions with a single calender roller, a structural element is provided in the cylinder body which runs in the axial direction (transverse direction), is designed essentially in a complementary (congruent) manner to the depression to be stamped in the transverse direction of the board and has a height which projects radially beyond the outer surface of the cylinder body.

The height of the structural element or elements running in the axial direction (transverse direction) is 40 to 60%, preferably 45 to 55%, in particular 50% greater than the depth of the depression to be stamped in the transverse direction.

Preferably, the structural elements are configured in a linear form and run relative to each other at an angle of 90°.

The structural elements may have any cross section. Preferably, they are configured with a U, V, W, Y or similar cross section.

It is preferably provided that a plurality of structural elements are arranged parallel to one another at least in the circumferential direction. The structural elements can also be distributed among several calender rollers.

The temperature of the calender roll can be raised or lowered relative to ambient temperature. In this way, the calender roll can be heated or cooled. In the method according to the invention, however, the calender roll is heated to a temperature of 100 to 150 °C.

An exemplary embodiment of the invention will be described in more detail below with the aid of a drawing. They show:

Figure 1 - a partial perspective view of a large-format construction panel;

Figure 2 - a top view of the construction panel according to Figure 1;

Figure 3 - a schematic partial view before the second stamping stage;

Figure 4 - an enlarged partial view during the second stamping stage;

Figure 5 - a schematic partial view during the first stamping stage;

Figure 6 - a schematic view of the construction panel located on the short cycle press;

Figure 7 - another schematic partial view during a first stamping stage;

Figure 8 - a schematic partial view during a first stamping stage in which depressions are stamped both in the longitudinal direction and in the transverse direction;

Figure 9 - a gross density profile of an MDF board.

The starting point is a large-format MDF or HDF board with a length of 2,800 or 1,860 mm, a width of 2,070 mm and a thickness of 6 to 14 mm, which is divided into smaller boards (panels) after finishing. The gross density is lower than that of a standard HDF panel. For the configuration of a weak surface layer that can be plastically deformed, the peaks of the surface layer were reduced by at least 40 kg/m3 compared to the standard. Good results have been achieved with a reduction of up to 60 kg/m3. The gross density lies in the range of 850 to 950 kg/m3. An example of the gross density profile of an MDF panel is shown in Figure 9.

In order to be able to emboss the depressions 5, 6 on the upper side 2 of the building board 1, the board is first heated to a temperature of 80 to 100 °C using steam. Then, 10 to 50 g/m3, preferably 30 g/m3 of aqueous melamine resin is applied as a tempering agent. This can be a standard impregnating resin with a solids content of 50 to 65% by weight, preferably 60% by weight. In addition to water, other additives such as hardeners, humectants and the like can be present in the solution. The liquid melamine resin can be made deformable by means of elasticizing agents. Acrylates, polyols, caprolactam, etc. can be used as elasticizing agents. Alternatively, UF resin or mixtures of UF resin and melamine can be used as a tempering agent. This is a postforming resin or a standard impregnation resin which is adjusted to make it more elastic by adding elasticizing agents (e.g. 1,4-butanediol, caprolactam, polyglycol, etc.). The subsequent addition of the elasticizing agent should be carried out in a magnitude of 3 to 7% by weight.

The pretreated building board 1 is passed under one or more consecutively arranged calender rolls 20 heated to a temperature of 100 - 150 °C, with stamping rings arranged parallel to each other thereon and serving as first structural elements 205, and a rib running in the axial direction Q, serving as a second structural element 206. In this respect, in a first stamping stage, 2 depressions 5, 6 with a depth Tu of at least 0.5 mm are stamped on the upper side through the at least two structural elements 205 in the longitudinal direction L and through the second structural element 206 in the transverse direction Q. The transverse direction Q in relation to the building board 1 is identical to the axial direction Q in relation to the calender roll 20. The linear pressure of the structural elements 205 is here up to 300 N/mm and the surface temperature can be, under certain circumstances, up to 220 °C. In this first stamping stage, the tempering agent is at least partially implemented on the upper side 2, i.e. it is at least partially hardened and thus the gross density is increased. The depressions 5, 6 can be formed in stages, for example by using several calender rolls 20 with different stamping rings as structural elements 205 and stamping, for example, first 0.3 mm and then a further depth of at least 0.5 mm. Between the structural elements 205, 206, a structure can be embossed in the sleeve 22 of the calender roll 20 which is then stamped on the upper side 3 next to the depressions 5, 6 in the first stamping stage. In order for the building panel 1 to be able to exhibit so-called "spring-back" during stamping, the height of the structural elements 205, 206 must be greater than the depth of the relief to be stamped.

Before the first stamping stage, the upper side 2 is primed with a white base colour which is also elastically adjusted. The base colour can be applied in one or more layers. After stamping, a decoration 3 is printed on the primer 11 by digital printing, the coloured dots of the digital printer being reproduced not only on the flat upper side 2 but also on the side walls 5.1, 5.2 and the base wall 5.3 of the strip-shaped depressions 5, 6, so that the depressions 5, 6 are completely decorated. The decoration 3 can be monochrome or multicoloured and is applied so that it is at least partially synchronised with the previously stamped structure. Markings 7 are printed on the base wall 5.3 at the same time as the decoration 3. The markings 7 can be circles 7.1, crosses 7.2, lines 7.3 and stripes 7.4 or other geometric figures. These marks 7 can be used to align the construction panel 2 for subsequent processing steps using a camera system.

After the decoration has been printed, which does not necessarily have to be digital but can also be carried out using an analogue process, a support 8 is applied to the underside 9 of the construction panel 1 and a covering paper 4 is applied to the decoration 3. Instead of a covering paper 4, a liquid coating can also be applied by means of a roller into which corundum is mixed or sprinkled. The support 8 can also be applied in liquid form.

This structure is then fed into a short-cycle press 30, the upper press plate 31 of which is provided with bar-shaped elevations 32. The building panel 1 is aligned using the marks 7 and a chamber system so that the elevations 32 are again immersed in the stamped depressions 5, 6 during the subsequent pressing of the structure and the side walls 5.1, 5.2 of the depressions 5, 6, which were rounded during the cladding of the upper side 2, are again stamped to establish parallel and flat side walls 5.1, 5.2 in a second stamping stage without changing in this respect the depth Tu of the depressions 5, 6 or the position of the base walls 5.3.

As shown in Figure 4, the elevations 32 in the transition zone of the side walls 5.1, 5.2 to the base wall 5.3 are configured with a greater magnitude than the width of the depressions 5, 6 in order to safely configure the lower edges of the depressions 5, 6.

The pressing time in the second stamping stage is between 10 and 30 seconds, preferably between 12 and 15 seconds, during which the resins are melted and bonded to the build plate 1. Due to the temperature of the press plates 31, 33, a surface temperature of 120° to 180 °C is reached on the press part during the pressing process. The pressure changes from a pressure increase phase to a holding phase and a pressure reduction phase. The stamping depth Tu is carried out in the sense of a path control.

The at least one calender roller 20 is integrated into the printing installation or is located directly before it. For a useful design, at least two depressions 5, 6 in the longitudinal direction L and two in the transverse direction Q must be stamped in the first stamping stage, so that the side edges of the divided panels are all recessed.

5 schematically shows the calender roll 20, which stamps depressions 5 running in the longitudinal direction L into the building board 1. This calender roll 20 is driven so that it rotates about an axis of rotation A. A plurality of spaced apart rings, which serve as structural elements 205 and project in the radial direction R by a height Hu relative to the surface of the roll 22, are laid on its barrel 22 or milled out of solid material. This height Hu is 20 to 40 % greater than the depth Tu of the depression 5 to be stamped. The calender roll 20 can be tempered. The temperature can be increased or decreased relative to ambient temperature.

The embossing of the depressions 6 in the transverse direction Q can be carried out with a separate calender roll 20, as shown in Figure 7, or with a calender roll 20 which has both the structural elements 205 and at least one rib extending in the axial or transverse direction Q as a structural element 206. This linear structural element 206 runs at an angle as of 90° to the structural elements 205. The height Ha of the structural elements 206 running in the axial direction Q is 40 to 60 % greater than the depth T<l> of the depressions 6 to be embossed in the transverse direction, due to the application of a linear pressure in a calender press. Preferably, the height Ha is 45 to 55 %, and in particular 50 %, greater than the depth Tl.

At least one plate length must be reproduced on the perimeter of the calender roll 20, where "plate length" is understood to mean the length of the plates represented on a panel. The "plate length" and the panel length may or may not coincide. By varying the diameter of the calender roll 20 or by using multiple lengths on the calender roll, different plate lengths can be achieved.

Structural elements 205, 206 are shown with a rectangular cross section. However, they can also have a U, V, W, Y or similar cross section.

List of references

1 Construction Panel

2 Upper side

3 Decoration

4 Abrasion resistant layer/overlay

5 Depression

5.1 Side wall

5.2 Side wall

5.3 Base wall

6 Depression

7 Mark

7.1 Circle

7.2 Cross

7.3 Line

7.4 Raya

8 Support

9 Bottom side

20 Calender roller

21 Cylinder body

22 Shirt

30 Short cycle press

31 Upper press plate

32 Barbell Lift

33 Press bottom plate

205 Structural element

206 Structural element

to Angle

as Angle

A axis of rotation

Hu Height

H<a>Height

L Longitudinal direction

Q Axial directionQ Transverse direction

R Radial direction

T<u>Depth

Claims (10)

1. A method for finishing a building board (1) made of a wood-based material, in particular MDF, HDF or a wood-plastics material mixture, with an upper side (2) and a lower side (9), wherein at least on the upper side (2) a relief is embossed, which is composed of at least one strip-shaped depression (5) with a depth (T) extending in a longitudinal direction (L) and/or in a transverse direction (Q), the depression (5) being embossed to a depth (T) of at least 0.5 mm by means of at least one calender roller (20), the calender roller (20) having structural elements (205, 206) corresponding to the desired relief, characterized in that the building board (1) is heated to a temperature of 80 to 100 ° C to produce the relief and the depression (5) is subsequently embossed therein, the at least one calender roller being heated to a temperature of 100 to 100 ° C. maximum of 150°C. 2. Method according to claim 1, characterized in that at least another second depression (6) is stamped which extends at an angle (a) preferably of 90° transversely to the first depressions (5). 3. Method according to one of the preceding claims, characterized in that the height Hu of the structural element (205) of the calender roller (20) in the circumferential direction is 20 to 40%, preferably 25 to 35%, in particular 30% greater than the depth Tl of the depression (5) to be stamped in the longitudinal direction (L). 4. Method according to claim 3, characterized in that the height Ha of the structural element (205) in the axial direction (A) of the calender roller (20) is 40 to 60%, preferably 45 to 55%, in particular 50% greater than the depth T<l>of the depression (6) to be stamped in the transverse direction (Q). 5. Method according to one of the preceding claims, characterized in that, before embossing, a tempering agent is applied to the upper side (2), which is preferably an aqueous melamine resin, which in particular is preferably set in a deformable manner by means of an elasticizing agent, and the deformability is additionally adjusted by heating the upper side (2) before embossing, the heating taking place before embossing by means of steam. 6. Method according to one of the preceding claims, characterized in that the upper side (2) and at least the depressions (5) are printed in the longitudinal direction (L) by means of a digital printer (15) with a monochrome or multicolour decoration (16). 7. Method according to one of the preceding claims, characterized in that the building panel (1) is laminated at high pressure and high temperature in a short-cycle press (30) after completion of the structure and is stamped into the strip-shaped depressions (5, 6) in a second stamping stage to achieve the exact configuration of the side walls (5.1, 5.2). 8. Method according to claim 7, if dependent on claim 6, characterized in that in one of the stamping steps a structure is embossed on the upper side (2) which runs at least partially synchronously with the decoration (3). 9. Method according to one of the preceding claims, characterized in that the construction panel (1) is divided into individual panels which can be separated in and along the depressions (5, 6). 10. Method according to one of the preceding claims, characterized in that the calender roller (20) has at least a plurality of structural elements (205) arranged parallel to one another at least in the circumferential direction.