Resin-Impregnated Fibrous Material in the Form of a Sheet or a Web

Abstract

Disclosed herein are sheets or webs of a resin-impregnated fibrous material, including an impregnating resin, which includes a combination of a) at least one resin component A, which is selected from the group consisting of aminoplast resins and phenoplast resins and mixtures thereof; and b) at least one resin component B, which is an oligomer or polymer having ethylenically unsaturated double bonds, where at least 40 mol % of the ethylenically unsaturated double bonds are selected from the group consisting of allyl groups, acryl groups and methacryl groups. Further disclosed herein is a process for producing a resin-impregnated fibrous material, which includes impregnating a fibrous material in the form of a sheet or a web with a liquid resin composition including a combination of a) the resin component A; and b) the resin component B.

Claims

1. A resin-impregnated fibrous material in the form of a sheet or a web, comprising an impregnating resin which comprises a combination of a) at least one resin component A, which is selected from the group consisting of aminoplast resins and phenoplast resins and combinations thereof; and b) at least one resin component B, which is an oligomer or polymer having ethylenically unsaturated double bonds, wherein at least 40 mol-% of the ethylenically unsaturated double bonds are selected from the group consisting of allyl groups, acryl groups and methacryl groups.

2. The resin-impregnated fibrous material of claim 1, wherein the resin component B comprises at least one oligomer or polymer which is selected from the group consisting of polyurethane (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, polyetherester (meth)acrylates, melamine (meth)acrylates, (meth)acrylate modified polyacrylates and mixtures thereof.

3. The resin-impregnated fibrous material of claim 2, wherein the resin component B comprises at least 50% by weight, based on the total weight of resin solids of component B, of at least one polyurethane (meth)acrylate.

4. The resin-impregnated fibrous material of claim 1, wherein the resin component B has from 0.2 to 8 mol/kg of ethylenically unsaturated double bonds, based on resin solids in the resin component B.

5. The resin-impregnated fibrous material of claim 1, wherein the resin component A comprises at least 30% by weight, based on the total weight of resin solids in component A, of at least one aminoplast resin selected from the group consisting of melamine formaldehyde resins, urea formaldehyde resins, melamine urea formaldehyde resins and combinations thereof.

6. The resin-impregnated fibrous material of claim 1, wherein the relative amounts of components A and B are such that the impregnating resin comprises from 0.01 to 3 mol/kg of ethylenically unsaturated double bonds, based on total weight of resin solids of the impregnating resin.

7. The resin-impregnated fibrous material of claim 1, wherein the weight ratio of resin solids of resin component A to resin solids of resin component B is in the range from 60:40 to 99:1.

8. The resin-impregnated fibrous material of claim 1, wherein the total amount of impregnating resin in the resin impregnated sheet or web of the fibrous material is in the range of range of 10 to 80% by weight, calculated as resin solids and based on the total weight of impregnated sheet or web.

9. The resin-impregnated fibrous material of claim 1, wherein the sheets or webs of the fibrous material is selected from the group consisting of sheets and webs of paper, cardboard and nonwovens.

10. A process for producing a resin-impregnated fibrous material as claimed in claim 1, which comprises impregnating a sheet or a web of a fibrous material with a liquid resin formulation comprising a combination of a) the resin component A; and b) the resin component B.

11. The process of claim 10, wherein the impregnation comprises i. a first step, where the sheet or the web of the fibrous material is impregnated with a first liquid resin formulation which contains the resin component A and which contains less than 1% by weight, based on the total weight of resin solids in the first liquid resin composition, of resin component B, calculated as resin solids of resin component B; ii. and a second step, where the sheet or the web of the fibrous material obtained in the first step is impregnated with a second liquid resin formulation containing both the resin component A and the resin component B.

12. The process of claim 11, wherein the weight ratio of resin component A to component resin component B in the second liquid resin formulation is in the range from 60:40 to 95:5, calculated as resin solids of the respective resin components A and B.

13. A method of using the resin-impregnated fibrous sheet material as defined in claim 1, the method comprising using the resin-impregnated fibrous sheet material for providing a plastic surface to a panel.

14. A process for providing a panel with a plastic surface, which comprises providing a sheet or a web of a resin-impregnated fibrous material as defined in claim 1 on at least one surface of the panel.

15. A panel having a plastic surface, which is obtainable by the process of claim 14.

16. The panel of claim 15, which further comprises a varnish on the plastic surface.

Description

[0102] Preferred methods for impregnating a sheet or a web of a fibrous material will now be described with reference to the figures.

[0103] FIG. 1 is a schematic view of an apparatus for carrying out the impregnation by dipping.

[0104] FIG. 2 is a schematic side view of an apparatus for carrying out the impregnation by rolling application.

[0105] As shown in FIG. 1, an embodiment for carrying out the impregnation comprises a web 1, a resin applicator 19 and a dryer 14 to prepare a resin impregnated web 2. The resin applicator 19 comprises a resin tank 17 with a resin composition of the invention, a pre-wetting roller 18, a spreader rollers (banana roller) 12, dipping rollers 16, metering rollers 15 and smoothening rollers 13. The web 1 is passed through the resin tank 17 by means of the wetting roller 18 and then passed to the spreader rollers 12. Between the wetting roller 18 and the spreader roller 12 there is a rest section 11, also called breathing section, so that the resin composition can penetrate the web 1. After passing the spreader rollers 12, the web is again passed through the resin tank 17. The web is moved to a dryer 14 with a system of dipping rollers 16, metering rollers 15 and smoothening roller 13. The dryer 14 is downstream in the transport direction of the applicator 19 and may be a hot dryer, a circulating-air dryer or a circulating-air, flotation dryer. In the further course the impregnated web can be rewound into rolls with a rewinding station or cut into sheets by means of a rotary cross cutter and deposited on pallets provided.

[0106] As shown in FIG. 2, a further embodiment for carrying out the impregnation comprises a web 1′, a resin applicator, e.g. a so called gravure coater station, 27 and a dryer 25 to prepare an impregnated web 2′. The resin applicator 27 comprises a web aligner roll 26, gravure rolls 23a and 23b, smoothening rollers 24, doctor blades 22a and 22b and resin tanks 21a and 22a each with a resin composition of the invention. A web 1′ is guided by means of the web aligner roll 26 and then along the upstream gravure roll 23a and the downstream gravure roll 23b to the smoothening roller 24 and to the dryer 25. A doctor blade 22a is set with a small spacing against the upstream gravure roll 23a, downstream of the web aligner roll 26, i.e. after the web aligner roll 26 in the direction of transport. A doctor blade 23b is set with a small spacing against the downstream gravure roll 23b, i.e. before the downstream gravure roll 23b in the direction of transport. The gravure rolls 23a and 23b have recesses to receive the resin composition of the invention, provided by the doctor blades 22a and 22b. The doctor blades 22a and 22b are each connected to a resin tank 21a and 22a, respectively, comprising the resin composition of the invention. The dryer 25 may be a hot dryer or a circulating-air dryer. In the further course the impregnated web can be rewound into rolls with a rewinding station or cut into sheets by means of a rotary cross cutter and deposited on pallets provided.

[0107] After impregnation, the impregnated web or sheet is dried to remove volatile components. Drying is typically carried out at elevated temperatures e.g. in the range of 80 to 220° C. Typically drying is achieved by using a vented oven or by IR radiators. Typically drying is carried out until the residual moisture is in the range of 4.5 to 8.0%. The residual moisture, as referred herein, is determined by the gravimetric drying oven method at 160° C. and 5 minutes drying time according to DIN EN ISO 638:2009-01. It is calculated from the difference of the weight of a specimen before drying and the weight after drying and given in % by weight, based on the weight before drying. The drying typically results in a partial crosslinking of the resin component A.

[0108] The resultant impregnated sheets or webs can then be further processed conventionally, in case of webs e.g. wound up to give rolls or cut into sheets.

[0109] According to a preferred group of embodiments, impregnation is carried out in a two step process. In a first step i., the sheet or web of the fibrous material is impregnated with a first liquid resin formulation which contains the resin component A and which contains less than 1% by weight of the resin component B, based on the total weight of the resin composition used in step A and calculated as solids. In the second step ii., the the sheet or the web of the fibrous material obtained in the first step is impregnated with a second liquid resin formulation containing both the resin component A and the resin component B.

[0110] Preferably, the resin composition A contained in the first liquid resin formulation contains an aminoplast resin. This aminoplast resin is preferably selected from UF resins, including wholly or partially etherified UF resins, MUF resins, including wholly or partially etherified MUF resins, and MF resins, including wholly or partially etherified MF resins. In the liquid resin formulation of the first step, the resin component A is preferably present in the form of a pre-condensate, i.e. it is essentially not crosslinked. For example, the degree of crosslinking of the resin component A in the liquid resin formulation is at most 10% or even 0%.

[0111] Besides the resin component A, the first liquid resin formulation may contain one or more of the aforementioned additives typically used in liquid resin formulations for impregnating fibrous materials. Preferably, the first liquid resin formulation is an aqueous resin composition, which besides the resin does not contain more than 10% by weight of organic solvents.

[0112] Frequently, the first liquid resin formulation has a viscosity characterized by flow time determined at 20° C. as described above of not more than 30 s, in particular in the range of 10 to 15 s. The solids content of the liquid resin formulation is typically in the range of to 65% by weight.

[0113] Preferably, step i. is carried out in a manner that the total amount of resin component A in the resin-impregnated fibrous material obtained in step i. does not exceed 90%, in particular 80% and especially 75% of the final resin content and is typically in the range of 20 to 90%, in particular 30 to 80% and especially 40 to 75% of the final resin content, in each case calculated as resin solids. For example, the total amount of resin component A in the resin-impregnated fibrous material obtained in step i. may be in the range of 6.5 to 72% by weight, in particular in the range of 18 to 56% by weight and especially in the range of 30 to 49% by weight, based on the total weight of impregnated sheet or web of the fibrous material, where the resin is calculated as resin solids.

[0114] Step i. is typically carried out by conventional impregnation methods used for impregnating a sheet or web of fibrous material with a liquid resin composition. For example, the sheet or web of fibrous material is impregnated by immersing the sheet or web in the first liquid resin formulation, whereby the first liquid resin formulation penetrates into the pores of the sheet or web of the fibrous material. Any adherent liquid resin formulation may be removed by blades or rollers. A suitable resin applicator for carrying out step i. is shown in FIG. 1. However, any other application method as described above may be applied.

[0115] Before carrying out step ii. the impregnated sheet or web obtained in step i. may be dried as described above. Drying before step i. is typically carried out at temperatures in the range of 80 to 220° C. Typically drying is carried out until the residual moisture is in the range of 7 to 15% as determined by the gravimetric drying oven described above.

[0116] The liquid resin composition used in step ii. may be any liquid resin composition containing both the resin component A and the resin component B and optionally one or more of the aforementioned additives typically used in liquid impregnating resin formulations for impregnating fibrous materials.

[0117] Preferably, the resin composition A contained in the second liquid resin formulation contains an aminoplast resin. This aminoplast resin is preferably selected from UF resins, including wholly or partially etherified UF resins, MUF resins, including wholly or partially etherified MUF resins, and MF resins, including wholly or partially etherified MF resins. In particular, the resin composition A contained in the second liquid resin formulation comprises at least 30% by weight, in particular at least 50% by weight, especially at least 70% or at least 90% by weight, based on the total weight of resin component A in the second liquid resin composition, of at least one aminoplast resin selected from the group consisting of MF resins, including wholly or partially etherified MF resins, and MUF resins, including wholly or partially etherified MUF resins, and mixtures thereof. In the second liquid resin formulation used for the second step, the resin component A is preferably present in the form of a pre-condensate, i.e. it is essentially not crosslinked. For example, the degree of crosslinking of the resin component A in the liquid resin formulation is at most 10% or even 0%.

[0118] Besides the resin component A, the second liquid resin formulation contains the resin component B with preference given to those resins, which are mentioned above as preferred resins, particular preference given to oligomer and/or polymer of groups i) to vi), in particular at least one oligomer and/or polymer of groups i), ii), iii) and iv), and a combination thereof with a low molecular compound, and also to combinations of polyacrylate polymers with low molecular compounds as defined above.

[0119] In the second liquid resin formulation the weight ratio of resin component A to component resin component B is as given above or lower, e.g. in the range of 60:40 to 95:5, in particular in the range of 75:25 to 90:10, based on resin solids of the respective components A and B.

[0120] Preferably, the second liquid resin formulation is an aqueous resin composition, which besides the resin does not contain more than 10% by weight of organic solvents.

[0121] Frequently, the second liquid resin formulation has a viscosity characterized by a flow time, determined at 20° C. according to the method described above of not more than s, in particular in the range of 10 to 20 s. The solids content of the liquid resin formulation is typically in the range of 45 to 65% by weight.

[0122] Preferably, step ii. is carried out in a manner that the total amount of resin components in the resin-impregnated fibrous material obtained in step ii. is that of the final product.

[0123] Typically, the relative amount of impregnating resin applied in the second stage is in the range of 10 to 80%, in particular 20 to 70% and especially 25 to 60% of the final resin content, in each case calculated as resin solids. For example, the amount of impregnating resin applied in the second stage ii may be in the range of 3.5 to 64% by weight, in particular in the range of 12 to 49% by weight and especially in the range of to 39% by weight, based on the total weight of impregnated sheet or web of the fibrous material, where the resin is calculated as resin solids.

[0124] Step ii. is typically carried out by conventional impregnation methods used for impregnating a sheet or web of fibrous material with a liquid resin composition. Preferably, the sheet or web of the fibrous material is impregnated by second liquid resin composition to one or both sides of the impregnated sheet or web obtained in the first step, whereby the second liquid resin formulation penetrates into the outer areas of the sheet or web of fibrous material. Preferably, step ii is carried out by roller coating, anilox coating or reverse coating. A suitable resin applicator for carrying out step i. is shown in FIG. 2. However, any other application method as described above may be applied.

[0125] In particular, the following procedure may be used. In the first step i., a web of the fibrous material is impregnated as outlined in FIG. 1 above to provide a pre-impregnated web, followed by an impregnation as outlined in FIG. 2 above. In this specific embodiment, the resin tank 17 usually comprises a prior art resin composition instead of a resin composition according to the invention. The prior art resin composition usually is an inexpensive aminoplast resin, e.g. urea formaldehyde or phenol formaldehyde resin. After passing the dryer 14, the pre-impregnated web is subjected to a further impregnation as outlined in FIG. 2, i.e. the pre-impregnated web is impregnated with the resin composition according to the invention. To this, the resin composition of the invention is applied by means of gravure rollers 23a and 23b with recesses for receiving the resin composition of the invention provided by the resin tanks 21 a and 22a, respectively. The impregnated web is then passed through dryer 25. In the further course the impregnated web can be rewound into rolls with a rewinding station or cut into sheets by means of a rotary cross cutter and deposited on pallets provided.

[0126] The impregnated sheet or web obtained in step ii. is typically dried as described above such that the residual moisture is in the range of 4.5 to 8.0%, as determined by the gravimetric drying oven method described above.

[0127] The impregnated sheet or web obtained in step ii. can then be further processed conventionally, in case of webs e.g. wound up to give rolls or cut into sheets.

[0128] The resin impregnated sheets or webs of the fibrous material can be used by analogy to known resin impregnated sheets or webs for providing plastic surfaces, in particular duroplastic surfaces, on arbitrary panels or boards, respectively. Therefore, the present invention also relates to a process for providing a panel with a plastic surface, in particular with a duroplastic surface, which comprises providing a sheet or a web of a resin-impregnated fibrous material as disclosed herein on at least one surface of the panel. For example, the plastic surface may be provided by laminating a resin impregnated sheet or web of the present invention to at least one surface of the panel or board, respectively. Alternatively, the resin impregnated sheets or webs of the present invention can be used as outer layers in the production of a laminate.

[0129] Suitable panels include but are not limited to [0130] wood-based panels, such as chipboards, fiberboards, for example, MDF boards (medium density fiberboard), HDF boards (high density fiberboard) or OSB boards (oriented structural board), [0131] boards of wood plastic composites (WPC boards); [0132] stone plastic composite boards (SPC boards); [0133] mineral material panels, also termed solid surface boards or solid surface panels, e.g. panels of the trademarks VARICOR®, CORIAN®, KRION® etc.; [0134] laminates, such as high pressure laminates (HPL) and continuous pressure laminates (CPL).

[0135] For this, a resin impregnated sheet of the present invention is laminated to at least one surface of the panel. For lamination, typically a resin impregnated sheet of the present invention is pressed to at least on surface of the panel at elevated temperature. In the production of CPL, which are typically prepared by laying several resin impregnated paper layers on top of one another and pressing them at elevated temperature, the resin impregnated sheet of the present invention will form the outer layer(s).

[0136] The process for providing a sheet or a web of a resin-impregnated fibrous material as disclosed herein on at least one surface of the panel or board, is typically carried out at elevated temperature and elevated pressure, to achieve a high degree of crosslinking of the resin components, namely of the resin component A and thus a duroplastic surface and a good adhesion of the plastic surface. These conditions are similar to the conditions conventionally used in the production of products having a plastic surface obtained by providing a resin impregnated sheet or web onto the surface of a board or panel. The temperature is typically in the range from 130 to 230° C., in particular 140 to 220° C. The pressure applied is typically in the range of 10 to 100 kg/cm.sup.2. Pressure and heat are typically applied for a duration in the range of 5 s to 100 min. Suitable presses for applying the necessary pressure include but are not limited to short cycle presses (KT presses), multi-stack recooling presses or double belt presses are suitable for this purpose. Temperature, applied pressure and duration, however, may vary in a known manner from the type of the board to be coated and the press used for this purpose. Standard values are given in the following table:

TABLE-US-00001 Temperature Pressure Press [° C.] [kg/cm.sup.2] Duration Standard values for LPL.sup.1) on 170-220 20-30 8-30 s KT presses Standard values for HPL.sup.2) on 140-180 70-90 45-90 min multi-stack recooling presses Standard values for CPL.sup.3) on 170-200 25-70 15-30 m/min double belt presses .sup.1)LPL: Low pressure laminate, i.e. a laminate having an outer plastic layer obtained by laminating a resin impregnated sheet or web to an existing board; .sup.2)HPL: High pressure laminate .sup.3)CPL: continuous pressure laminate

[0137] It is a particular advantage of the present invention that that the plastic surface provided by the resin-impregnated sheet or web of the present invention provides for very good adherence of coatings, irrespective of the kind of varnish formulation, thereby making grinding of the surface and the use of adhesion promoters unnecessary. The panels having a plastic surface formed by a laminated resin-impregnated sheet or web of the present invention provide in particular beneficial adherence of coatings formed from crosslinkable varnish formulations including radiation curable formulations and thermally curable varnishes such as 1K or 2K polyurethane formulations.

[0138] Therefore, the invention also relates to panels having a plastic surface formed by a laminated resin-impregnated sheet or web of the present invention, i.e. panels having a plastic surface, which are obtainable by a the method of laminating resin-impregnated sheet or web of the present invention to the surface of the present invention and also panels having a plastic surface formed by a laminated resin-impregnated sheet or web of the present invention and which further comprise a varnish on the plastic surface.

[0139] Typical varnish formulations, which can be successively applied to the plastic surface of the board obtained from the lamination of the resin-impregnated sheet or web of the present invention to a panel include aqueous and non-aqueous liquid coating formulations, including radiation curable varnish formulations, solventborne and waterborne 2K varnish formulations such as 2K polyurethane coatings, solvent borne and waterborne 1K varnish formulations such a 1K polyurethane coating formulations and waterborne coating formulations containing an aqueous polymer dispersion as a binder. The polymer dispersion may be crosslinkable or non-crosslinkable and is preferably crosslinkable. The varnish formulations can be applied to the plastic surface by any conventional coating techniques for applying coating formulations, in particular liquid coating formulations, onto surfaces, including brushing, spraying doctoring, rolling, casting, curtain coating and the like. The varnish may be cured by high energy radiation, including UV radiation or electron beams, or by heating. In case of physically drying liquid coating formulations, it may be sufficient that the coating formulation is dried at ambient temperature.

EXAMPLES

[0140] If not stated otherwise, all % values are % by weight; all ratios are weight ratios, all parts are weight parts. If not stated otherwise, the water used is deionized water.

Starting Materials

[0141]

TABLE-US-00002 TABLE 1 Components of an aqueous resin composition Resin commercially available melamine-formaldehyde resin, water compo- content of 7.1% by weight, Kauramin ® impregnating resin nent A 738, BASF SE Resin aqueous dispersion of a polyurethane acrylate having a compo- functionality of 3.8 and a solids content of 38%, prepared nent B1 according to example 1 of WO 2014/063920. Estimated density of acrylate groups at least 0.8 mol/kg, based on resin solids. Resin aqueous dispersion of a polyurethane acrylate having a compo- functionality of 3.4 and a solids content of 39%, prepared nent B2 according to example 1 of WO 2015/028397. Estimated density of acrylate groups at least 0.5 mol/kg, based on resin solids. Resin Aqueous 37% by weight polymer latex of a polyacrylate compo- polymer additionally containing 57% by weight, based on the nent B3 polyacrylate, of the triacrylate of ethoxylated trimethylol propane (degree of ethoxylation = 3), prepared according to Example 1 of WO 200399949. Estimated density of acrylate groups at least 1.5 mol/kg, based on resin solids. Hardener blend of methylethanolammonium sulfite and sodium bisulfite Solvent water

Preparation of the Aqueous Resin Formulations I-1 to I-7

[0142] For each example, the components listed in table 1 were intimately mixed in a polyethylene beaker in the relative parts given in table 2. Parts are given as parts by weight. All weights are given telle quelle.

TABLE-US-00003 TABLE 2 Example I-1* I-2 I-3 I-4 I-5 I-6 I-7 Resin 100 100 100 100 100 100 100 component A Hardener 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Water 7.1 7.1 7.1 7.1 7.1 7.1 7.1 Resin — 10 — — 20 — — component B1 Resin — — 10 — — 20 — component B2 Resin — — — 10 — — 20 component B3 *not according to the invention

Preparation of a Resin Impregnated Decorative Paper Sheet: Comparative Example CP1, Examples P2 to P8

[0143] A white decorative paper having a grammage of 75 g/m.sup.2 was impregnated by dip impregnation with the aqueous resin formulations I1*, I2, I3, I4, I5, I6 and I7, respectively. Excess resin was stripped off using a squeegee unit from TGW Robotics GmbH and smooth or spiralized squeegee bars. The thus impregnated papers were dried in a convection oven (e.g. from Fresenberger or Mathis) for 2 min at 180° C., to a moisture content as given in table 3. Table 3 also shows the resin application.

TABLE-US-00004 TABLE 3 Example CP1 P2 P3 P4 P5 P6 P7 Resin composition I-1* I-2 I-3 I-4 I-5 I-6 I-7 moisture content [%] 4.7 4.0 5.2 4.9 4.3 4.9 5.1 resin application [%] 164 167 172 161 156 158 162 *not according to the invention

Application Examples

1. Preparation of Melamine Coated MDF Boards B-1 to B-7

[0144] The respective impregnate of comparative example P1 and inventive examples P2 to P7 was pressed onto a MDF board using a hot press (e.g. from the companies Saspol, Buerkle or Wickert) for 50 seconds at 165° C., the applied pressure being 30 kg/cm.sup.2. Once the press has opened the coated MDF board was removed from the press and allowed to cool at ambient conditions.

TABLE-US-00005 TABLE 4 Application Example B-1* B-2 B-3 B-4 B-5 B-6 B-7 Impregnate CP1 P2 P3 P4 P5 P6 P7 *not according to the invention

2. Preparation of Varnished MDF Boards: Application Examples A1 to A21

[0145] Then the MDF boards B-1 to B-7, respectively, were varnished over with a UV varnish, waterbased varnish and polyurethane varnish, respectively. The following varnishes were used:

a) UV Varnishes

[0146] The compositions of the UV varnishes U1 and U2 are shown in table 5 below:

TABLE-US-00006 TABLE 5 U1 97 parts aromatic epoxy acrylate based on bisphenol A, functionality 2.4 3 parts photoinitiator, 1-hydroxy-cyclohexyl-phenyl-ketone 0.5 parts dispersing agent based on an organic modified polysiloxane U2: 97 parts aromatic epoxy acrylate based on bisphenol A, containing 15% of dipropylene glycol diacrylate, functionality 2.3 3 parts photoinitiator blend of 50% benzophenone and 50% 1-hydroxycyclohexyl-phenyl ketone 0.5 parts dispersing agent based on an organic modified polysiloxane

b) Acrylic Waterbased Varnishes

[0147] The compositions of the acrylic waterbased varnishes W1, W2 and W3 are shown in table 6 below:

TABLE-US-00007 TABLE 6 W1 82 parts acrylic dispersion, solids content: 45%, Brookfield viscosity: ca 70 mPas at 23° C., pH 7.7 at 23° C., acid number: 53 mg KOH/g, MFT of 10° C. 0.4 parts Defoamer: modified polydimethylsiloxane 9.5 parts water 3.0 parts coalescence agent: 2-butoxyethanol 2.0 parts coalescence agent: dicarboxylic acids-diisobutyl ester 2.0 parts slip and leveling agent: aqueous dispersion of metallic soap, 1.0 parts rheology modifier: hydrophobic modified ethoxylated urethane (HEUR) polymer in water/ diethylene gylcol monobutyl ether mixture 0.1 parts aqueous ammonia solution, till pH 8.2 W2 86.2 parts OH-functional acrylic dispersion, solids content: 44%, Brookfield viscosity: 300 mPas at 25° C., pH 8.2, MFT of 48° C. 0.3 parts defoamer: polyethersiloxane copolymer(Tego Foamex 810) 0.8 parts defoamer: Modified polydimethylsiloxane, (Efka 2580) 0.5 parts rheology modifier: hydrophobically modified ethoxylated urethane in water/butyl diglycol, solids content: 40% by weight 0.5 parts wetting additive: Alkoxylated Alcohol, CAS-No 204336-40-3, available from Evonik (Tego Wet 500), wetting additive 3.4 parts butylglycol acetate/butyldiglycol acetate (7:3) 0.3 parts N,N-dimethylethanolamine/water (1:1) 8.0 parts water 21.1 parts modified hexamethylene diisocyanate-isocyanurate, 80% solution in propylene carbonate, viscosity at 23° C., 450-850 mPas (DIN EN ISO 3219), crosslinker, to be added just before use W3 100 parts acrylic dispersion, solids content: 40%, Brookfield viscosity: ca 75 mPas at 23° C., pH 8.0, acid number: 25 mg KOH/g, MFT of less than 5° C.

c) Polyurethane Varnishes

[0148] The polyurethane varnishes P1 and P2, both available from Alfred Clouth Lackfabrik, Offenbach, Germany, are shown in table 7.

TABLE-US-00008 TABLE 7 P1 100 parts Clou Monosiegel ® N Matt, 1K polyurethane varnish P2 100 parts Cloucryl ® 2012 Matt, 2K polyurethane-acrylic varnish,  10 parts Cloucryl ® hardener, Alfred Clouth Lackfabrik, Offenbach, Germany, to be added just before use

Test Method

[0149] The UV varnishes U1 and U2 were applied by means of a spiral doctor blade with a dry film thickness of 10 g/m.sup.2. Directly after application, the UV varnish was cured by means of a UV mercury lamp (output 100 W/cm) at a belt speed of 10 m/min. Thereby the varnished boards of application examples A1 to A12 were obtained.

[0150] The waterbased varnishes W1 to W3 and the polyurethane varnishes P1 and P2 were applied with a 120 μm box doctor blade and dried at 20° C. and a relative humidity of 45% for 24 hours. Thereby the varnished boards of application examples A13 to A17 and A18 to A21, respectively, were obtained.

[0151] After drying, the varnished surfaces obtained in the examples A1 to A21 were was assessed by the cross-cut test in accordance with DIN EN ISO 2409:2019-09. Before the cross-cut test, the boards were conditioned in accordance with the standard DIN EN ISO 2409:2019-09. Assessment was made using the system of ratings stipulated in the standard, with 0 denoting very good adhesion (no flaking at all) and 5 denoting very bad adhesion corresponding to appropriately sheet-like flaking, the rating being abbreviated GT 0 to GT 5. The results are summarized in the following table 8:

TABLE-US-00009 TABLE 8 Example A1* A2 A3 A4 A5 A6 A7* A8 A9 A10 A11 Melamine coated MDF board B1* B3 B4 B5 B6 B7 B1* B2 B3 B5 B6 Varnish U1 U1 U1 U1 U1 U1 U2 U2 U2 U2 U2 Adhesion (after 1 d), GT 5 2 3 0 0 0 5 3 3 0 0 Adhesion (after 7 d), GT — — — — — — — — — — — Adhesion (after 42 d), GT 5 2 3 1 0 2 5 3 2 0 0 Example A12 A13 A14* A15 A16* A17 A18* A19 A20* A21 aqueous resin composition B7 B6 B1* B6 B1* B6 B1* B6 B1* B6 Varnish U2 W1 W2 W2 W3 W3 P1 P1 P2 P2 Adhesion (after 1 d), GT 1 0 1 0 5 4 2 1 2 0 Adhesion (after 7 d), GT — 0 5 0 5 1 3 1 3 0 Adhesion (after 42 d), GT 1 — — — — — — — — — *comparative example