Laminate and method for producing same

Abstract

A laminate for application onto a support material having a resin-impregnated decorative layer and at least one resin-impregnated core layer. The decorative layer and the at least one core layer are adapted for being pressed together under high pressure and heat. A technical problem of improving a laminate for application onto the support material is solved in that the decorative layer and the at least one core layer can be compressed by a short-cycle press and have a width of more than 1800 mm. A method for producing the laminate is also provided.

Claims

1. A laminate for application on a support material, the laminate comprising: a resin-impregnated decorative layer; and at least one resin-impregnated core layer, wherein the decorative layer and the at least one core layer are adapted to be pressed together under high pressure and heat by a multi piston short-cycle press, wherein a thickness of a stack of the decorative layer and the at least one core layer after pressing is less than 2 mm, wherein the decorative layer and the at least one core layer has a width of more than 1,800 mm, wherein a top surface of a bottom layer is arranged directly on one of the at least one core layers opposite to the decorative layer, and a bottom surface of the bottom layer is provided with an embossed structure configured to be pressed on the support material, wherein the embossed structure comprises a grinding groove, and wherein when a drop of tap water at room temperature having a maximum diameter of 15 mm is provided on the embossed structure, the drop of tap water forms a contact angle greater than 40 with the bottom layer having the embossed structure.

2. The laminate according to claim 1, wherein the decorative layer and the at least one core layer have a length equal to or less than 5,600 mm.

3. The laminate according to claim 1, wherein the thickness of the stack of the decorative layer and the at least one core layer after the pressing is less than 1.5 mm.

4. The laminate according to claim 1, wherein the depth of the embossed structure has a mean roughness of less than 20 m.

5. The laminate according to claim 1, wherein the grinding groove comprises parallel running grooves.

6. The laminate according to claim 5, wherein the bottom layer is impregnated with a resin, which corresponds in its tensile behaviour to the resin that is used for the impregnation of the decorative paper.

7. The laminate according to claim 1, wherein the bottom layer is a decorative, counteracting paper having corresponding properties to those of the decorative paper.

8. A method for producing a laminate, the method comprising: arranging a resin-impregnated decorative layer and at least one resin-impregnated core layer in layers on top of one another; and pressing the decorative layer and the at least one core layer together under high pressure and heat by a single-level multi piston short-cycle press, wherein a thickness of a stack of the decorative layer and the at least one core layer after pressing is less than 2 mm, wherein the decorative layer and the at least one core layer have a width of more than 1,800 mm, wherein a top surface of a bottom layer is arranged directly on one of the at least one core layers opposite to the decorative layer, and a bottom surface of the bottom layer is provided with an embossed structure configured to be pressed on the support material, wherein the embossed structure comprises a grinding groove, and wherein when a drop of tap water at room temperature having a maximum diameter of 15 mm is provided on the embossed structure, the drop of tap water forms a contact angle greater than 40 with the bottom layer having the embossed surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in more detail hereinafter with the aid of exemplary embodiments, and with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a structure of a first laminate before the pressing,

(3) FIG. 2 shows a structure of a first laminate before the pressing,

(4) FIG. 3 shows a finished laminate before the pressing onto a support plate,

(5) FIG. 4 is a schematic representation of a cycle press with a press plate according to the invention,

(6) FIG. 5 is a simplified diagram to explain the term contact angle,

(7) FIG. 6 is a schematic representation of a water drop on the surface of an embossed laminate in a diagonal plan view,

(8) FIG. 7 is a schematic representation of a water drop on the surface of an embossed laminate in a side view to measure the contact angle,

(9) FIG. 8 is a schematic representation of a water drop on a ground surface of a laminate (prior art) in a diagonal plan view, and

(10) FIG. 9 is a schematic representation of a water drop on a ground surface of a laminate (prior art) in a side view to measure the contact angle.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIG. 1 shows a layer structure of a laminate 2 for application on a support material, in particular on a support plate, before the pressing. The laminate 2 has a resin-impregnated decorative paper 4 as decorative layer and three resin-impregnated kraft papers 6, 8 and 10 as core layers. The decorative paper 4 and the core papers 6, 8 and 10 are suitable to be pressed together under high pressure and heat. The desired laminate 2 is thereby produced. The decorative paper 4 has on its surface an optical pattern as decoration. Instead of the printed decorative paper 4 a monochrome decorative paper can also be used.

(12) According to the invention the decorative layer 4 and the at least one core layer 6, 8, 10 can be pressed by means of a short-cycle press 40, which is described in more detail hereinafter, and the decorative layer 4 and the at least one core layer 6, 8, 10 have a width of more than 1,800 mm, in particular more than 2,000 mm. Furthermore the decorative layer 4 and the at least one core layer 6, 8, 10 have a length of for example 5,600 mm. Finally, the thickness of the stack of the decorative layer 4 and the at least one core layer 6, 8, 10 after the pressing is less than 2 mm, preferably less than 1.5 mm.

(13) In addition the kraft paper 10 arranged opposite to the decorative paper 4 is provided with an embossed structure during the pressing, which corresponds substantially to a structure produced by grinding. The embossed structure imparts to the surface of the layer 10 an enlarged surface, so that the bonding to a support plate is improved.

(14) FIG. 2 shows a second exemplary embodiment of a layer structure of a laminate 2 according to the invention, here with a bottom layer 12 formed as counteracting layer. In this case the counteracting layer 12 being the bottom layer is provided with the embossed structure during the pressing. In order to further minimise a warping of a laminate constructed in this way, the counteracting layer or the counteracting paper are impregnated with a resin that has a similar tensile behaviour as the resin used for the impregnation of the decorative paper. Preferably the same resin, in particular melamine resin, is used.

(15) FIG. 3 shows a laminate 2 produced according to the invention in a stack with a support plate 14 of wooden material, for example a MDF plate (medium density fibreboard plate) or a HDF plate (high density fibreboard plate) and a counteracting layer 16 arranged underneath the support plate 14. This stack is then processed further in a press under the application of pressure and temperature to form a laminated wood material panel.

(16) The impregnated structure of the lowermost layer 10 or 12 corresponds in depth and/or geometry to a structure produced by grinding. In this connection identical geometries and/or identical topographies, i.e. a true copy of a structure produced by mechanical grinding, are not important. The fact is the effect achieved according to the invention on the surface is obtained if the same mechanical dimensions are maintained. These dimensions are in fact decisive for the good bonding properties.

(17) Therefore for example the depth of the embossed structure with a mean roughness of less than 20 m, in particular less than 10 m, which is also produced in a typical grinding process, is chosen. At the same time or alternatively the geometry of the embossed structure corresponds to a grinding groove structure, in particular of parallel running grooves.

(18) An example of a structure according to the invention is illustrated hereinafter in the form of a table, in which the structure has been characterised with conventional parameters. The measurement was carried out with an area-based method for 3D surface measurement according to EN ISO Standard 25178. In particular the focus variation as area-based measurement method was employed in this case.

(19) TABLE-US-00001 Name Value [] Description Ra 1.25 m Mean roughness of the profile Rq 8.45 m Root mean square of the roughness of the profile Rt 43.9 m Overall height of the roughness profile Rz 28.8 m Averaged height of the roughness profile Rmax 34.0 m Maximum height of the roughness profile within an individual measuring section Rp 21.2 m Height of the largest profile peak of the roughness profile Rv 22.7 m Depth of the largest profile valley of the roughness profile Rc 25.6 m Mean height of the profile irregularities of the roughness profile Rsm 364 m Mean interspacing of the profile irregularities of the roughness profile

(20) FIG. 4 now shows a press 40 for producing laminates, which operates according to the HPL short-cycle method. In the left-hand region of FIG. 4 a stacking device 42 is illustrated, in which the several layers 4 to 10 of the laminate 2 to be formed are stacked on top of one another according to the exemplary embodiment of FIG. 2. These layers are cut to size, i.e. sheets predetermined in regard to their length and width.

(21) The stacked layers 4 to 10 are conveyed by means of a linear transporter to the pressing station 44 shown on the right-hand side and are arranged between a lower pressing plate 46 and an upper pressing plate 48. By means of a plurality of pressure cylinders 50 the upper pressing plate 48 is lowered so that the stacked layers 4 to 10 are pressed together under high pressure. Since the pressing plates 46 and 48 are also preheated, in addition to the pressure a high temperature is also applied. After a predetermined period the pressing station 44 is opened and the finished laminate is removed.

(22) The special feature of the short-cycle press 40 is the fact that the individual pressure cylinders can be controlled separately. Thus, an exact control of the distance between the two pressing plates 46 and 48 is possible, so that also thin stacks of layers of the laminate to be produced having a thickness of less than 2 mm can be pressed.

(23) FIG. 5 shows a simplified diagram to illustrate the term contact angle. A drop of a liquid that is surrounded by a gaseous phase, preferably air, is located on the surface of the solid. Owing to the surface tension of the liquid on the one hand and the surface tension of the surface of the solid on the other hand, the illustrated drop shape is formed. At the three-phase point, i.e. where the solid phase, the liquid phase and the gaseous phase are present next to one another, the surface of the drop shape forms an angle with the surface of the solid, which is termed the contact angle. Since the surface tension of the liquid plays a role in the formation of the drop shape, the area of the surface that is covered by the liquid on the surface of the solid is also important for determining the contact angle. Therefore the liquid is usually applied in such a way that it does not exceed a predetermined area. For example, when using water an area of more than 15 mm diameter should not be exceeded.

(24) FIG. 6 shows a schematic representation of a water drop 100 on the surface of an embossed laminate 2 in a diagonal plan view. The water drop 100 is sharply definable in terms of its contour, the surrounding sections of the surface are not wetted, and the material lying underneath the laminate 2 has not absorbed any moisture, which can be recognised by the uniform coloration of the surface.

(25) FIG. 7 shows a schematic representation of a water drop 100 on the surface of an embossed laminate 2 in a side view in order to determine the contact angle.

(26) To determine the contact angle the drop shape analysis (DSA) method can be used for example. The drop shape analysis is an image analysis method used to determine the contact angle from a side view or from the shadow image of a drop located on the surface. For this, a drop is placed on a solid surface (sessile drop). An image of the drop is taken with a camera.

(27) For a rough analysis, which is generally sufficient, the angle between the liquid surface and the surface of the laminate can be directly measured in the image using a ruler. In the present case the contact angle was measured in this way in FIG. 7 using a ruler and found to be 50.

(28) For a more accurate analysis the image can be processed by a drop shape analysis software. By means of a grey level analysis of the image a contour recognition performed initially. In the second step a geometrical model describing the drop shape is fitted by a mathematical method to the shape. The contact angle is then found from the angle between the determined drop shape function and the sample surface, whose projection in the drop image is termed base line.

(29) FIG. 8 shows a schematic representation of a water drop 100 on a ground surface of a laminate 102 in a diagonal plan view, i.e. on a sample as it is known from the prior art.

(30) In contrast to FIG. 6 the sessile drop 100 can no longer be sharply defined and the drop 100 has a flatter shape than that shown in FIG. 6. In addition the regions 104 of the surface surrounding the drop 100 have become wet, which means that some of the water of the drop 100 has been absorbed by the laminate 102. The wetness is demonstrated by the dark discoloration compared to the significantly lighter outer surroundings of the surface.

(31) FIG. 9 shows a schematic representation of a water drop on a ground surface of a laminate 102 in a side view in order to determine the contact angle. As already follows from FIG. 8, the drop 100 has a flatter shape and the contact angle was measured in the photograph with a ruler and found to be 10.

(32) For the illustrated experiments according to FIGS. 6 to 9 tap water was used having the following physical and chemical properties: water temperature 20 C. (room temperature) pH 7.5 electrical conductivity at 25 C.: 709 S/cm carbonate hardness: 11.0 dH total hardness: 13.4 dH with an alkaline earth total of 2.4 mmol/l nitrate NO3: 12 mg/l nitrite NO2: <0.02 mg/l phosphate (total): PO.sub.4.sup.3: 1.2 mg/l silicia SiO.sub.2: 8.8 mg/l fluoride F: 0.13 mg/l chloride Cl: 74 mg/l sulphate SO.sub.4.sup.2: 59 mg/l hydrogen carbonate HCO.sub.3: 213 mg/l mg/l sodium Na.sup.+: 35 mg/l magnesium Mg.sup.2+: 11 mg/l calcium Ca.sup.2+: 79 mg/l potassium K.sup.+: 4 mg/l

(33) The drop size was chosen so that the drop occupied an area with a diameter of ca. 10 to 15 mm, in the ground laminates according to FIGS. 8 and 9 to start with before the drop began to disintegrate.