Patent Application
20230279613
The present invention relates to a resin-impregnated fibrous material in the form of a sheet or a web, comprising an impregnating resin selected from the group consisting of aminoplast resins and phenoplast resins and combinations thereof. The present invention also relates to a process for producing the resin-impregnated fibrous material and to the use thereof from providing a resin surface to a panel.
A long known method of manufacturing panels with a plastic surface involves laminating a resin-impregnated paper or a sheet or web of a similar resin-impregnated fibrous material onto at least one of the surfaces of the panel. Typically, these fibrous materials are impregnated with amino resins, such as melamine formaldehyde resins (MF resins), urea formaldehyde resins (UF resins) and melamine-urea formaldehyde resins (MUF resins), phenoplast resins or combinations thereof. To laminate, the sheet or web is pressed onto at least one of the surfaces of the panel in a suitable press, such as a short cycle press, (Kurztaktpresse) at elevated temperature. Under the laminating conditions, the resin contained in the sheet or web undergoes a polycondensation within the fibre structure of the web or sheet yielding a highly cross-linked and durable plastic coating layer. Typical examples of such sheets or webs of resin-impregnated fibrous materials are decorative papers, also termed décor papers, and overlay papers, but also counteracting layer impregnants. While decorative papers, also termed “décor papers” and overlay papers provide visible plastic surfaces to the panel, counteracting layer impregnants are applied to a non-visible backside of a panel and serve to compensate for the pulling forces exerted by the décor paper and/or the overlay paper.
While the mechanical durability of the visible plastic surfaces obtained from the laminated décor paper or overlay paper is satisfactory, they often exhibit unsatisfactory UV resistance or weathering resistance. In particular, color changes of the plastic surface may occur over time due to UV radiation from the sunlight. To achieve sufficient color stability and improve weathering resistance and thus life-time of the panels, it may become necessary to provide a coating to the plastic surface of the panel. A coating may also be desired for aesthetic reasons.
EP 122396 describes a decorative laminate comprising a core of at least one fibrous sheet, namely craft paper, which is impregnated with a blend of a phenol/formaldehyde resin and a cross-linkable acrylic copolymer and optionally a melamine/formaldehyde resin. The cross-linkable acrylic resins are prepared by radically polymerizing ethylenically unsaturated monomers, such as ethyl acrylate and methyl methacrylate and a third monomer which contains reactive polar group, thereby resulting in a polymer containing said reactive polar groups in the polymer chain which are susceptible to self-crosslinking or by reacting with a crosslinking agent such as a melamine resin.
WO 2009/077561 describes a resin impregnated compressible décor paper which can be printed by ink-jet and which has a residual moister of at least 3.5% and a flow of greater than 0.4% after drying. The impregnated compressible décor paper is prepared by core-impregnation of the paper with a conventional impregnating resin, pre-drying the core-impregnated paper in a manner that the impregnating resin is not fully cured and subsequently coating the ink receiving layer on the surface of the pre-dried impregnated décor paper.
When applying a coating formulation onto the plastic surface of a board, the resulting coating shows poor adhesion to the plastic surface. The low adherence will typically cause instability of the coating and poor resistance to damage from mechanical impact. The problem is particularly serious with UV-curing coatings and polyurethane coatings, which show very poor adhesion to plastic surfaces obtained from laminated resin-impregnated fibrous materials.
While it is principally possible to overcome this problem by providing specifically formulated coating compositions, their good adhesion to plastic surfaces is only achieved for a specific plastic surface and typically cannot be transferred to qualities of plastic surfaces of different manufacturers. The reason seems to be the very good resistance of the highly cross-linked plastic surface, which neither allows swelling nor covalent bonding of subsequent layers.
The use of one- and two-component adhesion primers or the grinding of the plastic surface have been suggested as more general ways to overcome the above adhesion problem. However, both the application of adhesion primers and the grinding of the plastic surface represents an additional, cost-intensive processing step for the producer of coated panels.
WO 2015/106771 describes a layered building board having a layer of a melamine-impregnated paper laminated to a core layer and an acrylic coating layer, where between and the acrylic coating layer and adhesion layer is arranged comprising a polyurethane and an acrylate component. The polyurethane is obtained from the reaction of an isocyanate and a hydroxyl containing acrylate. The process is tedious and the components of the adhesion layer are expensive.
WO 2010/000781 describes a resin combination for impregnating a paper web which comprises a resin combination of an urea formaldehyde resin, a melamine formaldehyde resin and an unsaturated polyester obtained by polycondensation of a maleic acid anhydride and a mono- or polyalkyleneglycol. The impregnated web is used for providing a counteracting layer on the backside of a panel in the production of laminate floors.
It is an object of the present invention to provide means for improving the adhesion of coatings on plastic surfaces obtained from laminated resin-impregnated webs or sheets, which make roughening of the surface and the use of adhesion promoters unnecessary.
It was surprisingly found that resin-impregnated sheets or webs of fibrous materials, such as décor paper or overlay paper, according to the present invention solve the above problems. The resin-impregnated sheets or webs of fibrous materials the present invention contain an impregnating resin which comprises a resin component B having ethylenically unsaturated double bonds in the form of allyl, acryl or methacryl groups in combination with a conventional impregnating resin, i.e. a resin which is selected from the group consisting of aminoplast resins and phenoplast resins, hereinafter resin component A. The presence of said ethylenically unsaturated double bonds in the impregnating resin in combination with the reactive sites of the conventional aminoplast or phenoplast resin in the impregnating resin results in plastic surfaces providing a better adherence of coatings, in particular of UV-curing coatings and polyurethane coatings, but also of water-borne coatings containing latex binders.
Therefore, a first aspect of the present invention relates to sheets or webs of a resin-impregnated fibrous material which has been impregnated with an impregnating resin comprising a combination of
As the impregnating resin remains in the sheets or webs of the resin-impregnated fibrous material, a first aspect of the present invention relates to sheets or webs of a resin-impregnated fibrous material which contains an impregnating resin comprising the at least one component A and the at least one component B as defined herein.
In a second aspect, the invention also relates to a process for producing a resin-impregnated fibrous material as claimed in any one of the preceding claims, which comprises impregnating a fibrous material in the form sheet or a web with a liquid resin composition comprising a combination of
In a third aspect, the invention relates to the use of a web or a sheet of the resin-impregnated fibrous material as defined herein for providing a plastic surface, in particular a duroplastic surface, to a panel.
The present invention is associated with the benefit that the plastic surfaces obtained from the sheets or webs of the resin-impregnated material of the present invention provide for very good adherence of coatings, irrespective of the kind of coating formulation, thereby making grinding of the surface and the use of adhesion promoters unnecessary.
Here and in the following, the term acryl relates to a group of the formula (I), the term “methacryl” relates to a radical of the formula (II) and the term “allyl” relates to a radical of the formula (III). In formulae (I), (II) and (III), the #indicates the point of attachment to the remainder of the resin molecule.
In the resin of component B, the allyl groups, the acryl group and likewise the methacryl group may be bound to the resin by a single bond or via a heteroatom or heteroatom group, e.g. by an oxygen atom or an NH group. In case, the allyl group and likewise the acryl group and methacryl group are bound to the resin via an oxygen atom, they are present in the form of an acryloxy group of the formula (Ia), methacryloxy group of the formula (IIa) and allyloxy group of the formula (IIIa), respectively. In case, the allyl group and likewise the acryl group and methacryl group are bound to the resin via an NH group, they are present in the form of an acrylamido group of the formula (Ib), methacrylamido group of the formula (IIb) and allylamino group of the formula (IIIb), respectively.
In formulae (Ia), (IIa) and (IIIa), the #indicates the point of attachment to the remainder of the resin molecule.
Here and in the following, the term “(meth)acryl” refers to both acryl and methacryl. Here and in the following, the term “(meth)acryloxy” refers to both acryloxy and methacryloxy. Likewise, the term “(meth)acrylate” refers to both acrylate and methacrylate.
Here and in the following the term resin solids refers to the total amount of resin matter of the respective components A and B including polymers, oligomers and there combination with monomers present in the respective components A and B.
In the context of the present invention the term “resin-impregnated fibrous material in the form of a sheet or web” refers to a sheet or web made of fibrous material, which has been impregnated with the impregnating resin of the present invention. Here and in the following, the terms “resin-impregnated fibrous material in the form of a sheet or web”, “resin impregnated sheet or web of fibrous material” and “resin-impregnated sheet or web” have the same meaning and are used synonymously.
Preferably, at least 40 mol-%, in particular at least 60 mol-%, especially at least 80 mol-% or at least 90 mol-% or 100 mol-% of the ethylenically unsaturated double bonds in the resin component B are selected from the group consisting of acryl groups (I) and methacryl groups (II), in particular from the group consisting of acryloxy groups (Ia) and methacryloxy groups (IIa). More preferably, at least at least 40 mol-%, in particular at least 60 mol-%, especially at least 80 mol-% or at least 90 mol-% or 100 mol-% of the ethylenically unsaturated double bonds in the resin component B are acryl groups (I), especially acryloxy groups (Ia).
It is preferable that the resin molecules of the resin B have on average more than one ethylenically unsaturated double bond per resin molecule. The average number of ethylenically unsaturated double bounds per resin molecule is also referred to as the average functionality of the resin. Preferably, the resin molecules of the resin B have an average a functionality in the range of 1.2 to 20, in particular in the range of 1.5 to 10. Mixtures of different resins B with different functionalities having an average functionality in the range of 1.2 to 20, in particular in the range of 1.5 to 10, are also suitable. Preferably, the resin molecules of the resin B have an average functionality in the range of 1.2 to 20, in particular in the range of 1.5 to 10, where at least 40 mol-%, in particular at least 60 mol-%, especially at least 80 mol-% or at least 90 mol-% or 100 mol-% of the ethylenically unsaturated double bonds in the resin component B are acryl groups (I), especially acryloxy groups (Ia).
Principally any resin material which has ethylenically unsaturated double bonds as defined herein is suitable as resin component B. The resin component B may be an oligomer or polymer having ethylenically unsaturated double bonds as defined herein. The resin component B may also be a combination of one or more low molecular weight compounds having ethylenically unsaturated double bonds as defined herein and an oligomer or polymer having ethylenically unsaturated double bonds as defined herein. The resin component B may also be a combination of one or more low molecular weight compounds having ethylenically unsaturated double bonds as defined herein and an oligomer or polymer having essentially no ethylenically unsaturated double bonds, provided that the resin component on average provides the desired amount and type of ethylenically unsaturated double bonds.
The term “ethylenically unsaturated double bonds as defined herein” means that at least 40 mol-%, in particular at least 60 mol-%, especially at least 80 mol-% or at least 90 mol-% or 100 mol-% of the ethylenically unsaturated double bonds are selected from the group consisting of allyl groups, acryl groups and methacryl groups, in particular from the group consisting of acryloxy groups (Ia) and methacryloxy groups (IIa), with particular preference given to acryloxy groups.
Preferably, the resin component B comprises at least oligomer and/or polymer having ethylenically unsaturated double bonds as defined herein, in particular as a main component, i.e. in an amount of at least 50% by weight, in particular at least 55% by weight, e.g. in an amount of 50 to 100% by weight or 55 to 95% by weight, based on the total weight of organic resin matter, i.e. solid resins, in resin component B. If the resin component B comprises one or more low molecular weight compounds having ethylenically unsaturated double bonds or oligomers having ethylenically unsaturated double bonds, the total amount thereof will usually not exceed 50% by weight and is typically in the range of 5 to 50% by weight or 5 to 45% by weight, based on solid resins in resin component B. In particular, the resin component B comprises a least one oligomer and/or polymer having ethylenically unsaturated double bonds as defined herein, in particular in an amount of 50 to 95% by weight or 55 to 95% by weight, based on the total weight of organic resin matter, and one or more low molecular weight compounds having ethylenically unsaturated double bonds as defined herein, where the total amount of low molecular compounds having ethylenically double bonds is in particular in the range of 5 to 50% by weight or 5 to 45% by weight, based on solid resins in resin component B.
A low molecular compound is understood as a compound having a defined structure and a molar mass of not more than 500 g/mol, frequently not more than 400 g/mol. In contrast thereto, the term “oligomer” as well as the term “polymer” relate to compounds and compound mixtures which have a molar mass (number average) of at least 500 g/mol. The transitions between the terms “oligomer” and “polymer” are quite smooth and the terms cannot be clearly distinguished from each other. The term “oligomer” typically relates to compounds and compound mixtures which have a molar mass (number average) e.g. in the range of 400 to 1500 g/mol, and in particular in the range of 500 to 1000 g/mol. The term “polymer” typically relates to compounds and compound mixtures which have a molar mass (number average) of at least 1000 g/mol, frequently at least 1500 g/mol, e.g. in the range of 1000 to 1000000 g/mol, and in particular in the range of 1500 to 500000 g/mol. The molecular weights of the oligomers and polymers given herein relate to the number average weight, as e.g. determined by gel permeation chromatography, e.g. using tetrahydrofurane as an eluent and polystyrenes of defined molecular weight as standards.
Preferably, the resin component B has from 0.2 to 8.0 mol/kg, in particular from 0.3 to 6.0 mol/kg, based on the solid resin in component B, of ethylenically unsaturated double bonds as defined herein, wherein preferably at least 40 mol-%, in particular at least 60 mol-%, especially at least 80 mol-% or at least 90 mol-% or 100 mol-% of the ethylenically unsaturated double bonds are selected from the group consisting of acryloxy groups (Ia) and methacryloxy groups (IIa), and wherein especially at least 40 mol-%, in particular at least 60-mol-%, especially at least 80 mol-% or at least 90 mol-% or 100 mol-% of the ethylenically unsaturated double bonds are acryloxy groups (Ia).
For reasons of processability, the resins of resin component B are preferably emulsifiable or dispersible in water. In this case, at least a portion of the resins of resin component B bear one or more polar functional groups, which render the resins hydrophilic and thus further emulsification or dispersability in water. Such groups are polyethyleneoxide groups, typically having a number average molecular weight of 200 to 2000 and anionic or acidic groups, such as carboxyl groups, phosphate groups, phosphonate groups, sulfonate groups and sulfonate groups, which are preferably present in their anionic, hence, neutralized form. Preferably, the resin component B is an aqueous emulsion or dispersion of the resin constituents of resin component B.
Preferably, the resin component B comprises at least one oligomer and/or polymer which is selected from the following groups i) to vi) and combinations thereof:
The oligomers and polymers having ethylenically unsaturated double bonds, in particular those of groups i) to vi) are well known to a skilled person, e.g. from P. Glöckner et al. “Radiation Curing for Coatings and Printing Inks” Vincentz Network 2008, and the references cited herein, as well as from EP 574775, EP 694531 A2, DE 19525489 A1, DE 19810793 A1, DE 19933012 A1, DE 19957604 A1, EP 1591502 A1, WO 02/034808, WO 03/022552, WO 2011/015540, WO 2014/063920, WO 2015/028397 and WO 2017/029280. They are also commercially available, e.g. from BASF SE as Laromer® grades PE 22 aqua, PE 55 aqua, UA 8949 aqua, UA 8983 aqua, UA 9005 aqua, UA 9060 aqua, UA 9064 aqua, UA 9059 aqua, UA 9095 aqua and UA 9122 aqua.
Amongst the oligomers and polymers of groups i) to vi) preference is given to oligomers and polymers of groups i), ii), iii) and iv), and combinations thereof, especially to oligomers and polymers of group i) and combinations thereof with one or more further oligomers or polymers selected from groups ii), iii) and iv).
Preferably, the resin component B comprising at least one 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), or a combination thereof with a low molecular compound, is an aqueous emulsion or dispersion of the resin constituents of resin component B, i.e. an aqueous emulsion of at least one oligomer and/or polymer of groups i) to vi), in particular of at least one oligomer and/or polymer of groups i), ii), iii) and iv), or of a combination thereof with a low molecular compound.
Preferably, the resin component B comprises at least one oligomer and/or polymer selected from the groups i) to vi), in particular from groups i) to iv) and mixtures thereof and especially an oligomer and/or polymer of group i) as a main component, i.e. in an amount of at least 50% by weight, in particular at least 55% by weight, e.g. in an amount of 50 to 100% by weight or 55 to 95% by weight, based on the total weight of organic resin matter, i.e. resin solids, in resin component B. Preference is also given to resin component B which comprise at least one oligomer and/or polymer selected from the groups i) to vi), in particular from groups i) to iv) and mixtures thereof and especially an oligomer and/or polymer of group i) as a main component, e.g. in an amount of 50 to 95% by weight or 55 to 95% by weight, based on the total weight of resin solids of resin component B, and 5 to 50% by weight or 5 to 45% by weight, based on resins solids in resin component B, of at least one low molecular compounds having ethylenically double bonds as defined herein.
Suitable low molecular compounds having ethylenically unsaturated double bonds as defined herein, are the allyl ethers of polyhydric alcohols and the (meth)acrylates of polyhydric alcohols. In this context, the polyhydric alcohols have typically from 2 to 6 hydroxyl groups. Preferred polyhydric alcohols include in particular aliphatic polyols having from 2 to 6 hydroxyl groups and 2 to 10 carbon atoms and cycloaliphatic polyols having from 2 to 6 hydroxyl groups and 6 to 10 carbon atoms, as well as alkoxylated derivatives thereof, in particular ethoxylated and/or propoxylated derivatives thereof, wherein the degree of alkoxylation, i.e. the number average of alkylene oxide repeating units therein is 1 to 10. Examples of these polyhydric alcohols include ethylene glycol, butane diol, neopentyl glycol, hexane diol, octane diol, diethylene glycol, triethylene glycol, trimethylol propane (=2-ethyl-2-hydroxymethyl-1,3-propanediol), trimethylol butane (=2-propyl-2-hydroxymethyl-1,3-propanediol), bis(trimethylol propane) (=2,2′-oxybis(methylene)bis(2-ethyl-1,3-propanediol)), pentaerythritol (=2,2-bishydroxymethyl-1,3-propanediol), dipentaerythritol (=2,2′-[oxybis(methylene)]-bis[hydroxymethyl)]-1,3-propandiol), ethoxylated and/or propoxylated trimethylolpropane, ethoxylated and/or propoxylated bis-trimethylolpropane, ethoxylated and/or propoxylated glycerol, ethoxylated and/or propoxylated pentaerythritol, ethoxylated and/or propoxylated dipentaerythritol, 1,4-cyclohexanediol and 1,4-bis(hydroxymethylethyl)cyclohexanediol. Particular preference is given to the acrylates and methacrylates of aliphatic polyols having from 2 to 6 hydroxyl groups and 2 to 10 carbon atoms and cycloaliphatic polyols having from 2 to 6 hydroxyl groups and 6 to 10 carbon atoms, and also to the acrylates and methacrylates of the alkoxylated derivatives of aliphatic polyols having from 2 to 6 hydroxyl groups and 2 to 10 carbon atoms and cycloaliphatic polyols having from 2 to 6 hydroxyl groups and 6 to 10 carbon atoms, in particular ethoxylated and/or propoxylated derivatives thereof, wherein the degree of alkoxylation, i.e. the number average of alkylene oxide repeating units therein is 1 to 10. Particular preference is given to the acrylates and methacrylates of the aforementioned polyhydric alcohols having 2 to 6 acrylate groups or 2 to 6 methacrylate groups.
Particular examples of suitable low molecular compounds having ethylenically unsaturated double bonds as defined herein include but are not limited to butanediol diacrylate, butanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, octane diol diacrylate, octane diol dimethacrylate, ethylene glycol diacrylate, ethylene glycol diamethcrylate, diethylene glycol diacrylate, diethylene glycol diamethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolbutane diacrylate, trimethylolbutane triacrylate, trimethylolbutane dimethacrylate, trimethylolbutane trimethacrylate, trimethylolpentane triacrylate, trimethylolpentane trimethacrylate, bis(trimethylolpropane)triacrylate, bis(trimethylolpropane)trimethacrylate, bis(trimethylolpropane)tetraacrylate, bis(trimethylolpropane)tetramethacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol tetraacrylate, dipentaerythritol triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, dipentaerythritol tetramethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexamethacrylate, etc. Also suitable low molecular compounds are the esters of alkoxylated polyols having on average 1 to 10 alkyleneoxide groups in particular the esters of ethoxylated and/or propoxylated polyols with acrylic acid or methacrylic acid, examples being the di(meth)acrylates of ethoxylated and/or propoxylated trimethylolpropane, the tri(meth)acrylates of ethoxylated and/or propoxylated trimethylolpropane, the di(meth)acrylates of ethoxylated and/or propoxylated glycerol, the tri(meth)acrylates of ethoxylated and/or propoxylated glycerol, the di(meth)acrylates of ethoxylated and/or propoxylated pentaerythritol, the tri(meth)acrylates of ethoxylated and/or propoxylated pentaerythritol, the tetra(meth)acrylates of ethoxylated and/or propoxylated pentaerythritol, the di(meth)acrylates of ethoxylated and/or propoxylated bis-(trimethylolpropane), the tri(meth)acrylates of ethoxylated and/or propoxylated bis-(trimethylolpropane), the tetra(meth)acrylates of ethoxylated and/or propoxylated bis-(trimethylolpropane), the tri(meth)acrylates of ethoxylated and/or propoxylated dipentaerythritol, the tetra(meth)acrylates of ethoxylated and/or propoxylated dipentaerythritol, the penta(meth)acrylates of ethoxylated and/or propoxylated dipentaerythritol, the hexa(meth)acrylates of ethoxylated and/or propoxylated di pentaerythritol. Additionally suitable are the esters of alicyclic diols, such as 1,4-cyclohexanediol di(meth)acrylate and 1,4-bis(hydroxymethylethyl)cyclohexanediol di(meth)acrylate.
Preference is also given to resin components B which comprise at least one polymer having essentially no ethylenically unsaturated double bond and at least one oligomer or low molecular compound having ethylenically unsaturated double bonds as defined herein, in particular with one or more low molecular compounds having 2 to 6 ethylenically unsaturated double bonds as defined herein. Preferably, the polymer having essentially no ethylenically unsaturated double bond is a polyacrylate polymer, i.e. a homo or copolymer having a polymer backbone of polymerized units of C1-C6 alkyl (meth)acrylates and optionally one or more co-monomers selected from the group consisting of (meth)acrylic acid, hydroxyl-C2-C4 alkyl (meth)acrylates, glycidyl(meth)acrylates and crosslinking monomers. Preferably, these resin compositions comprise the at least one polyacrylate polymer in combination with at least one low molecular compound, which is selected from acrylates and methacrylates of aliphatic polyols having from 2 to 6 hydroxyl groups and 2 to 10 carbon atoms and cycloaliphatic polyols having from 2 to 6 hydroxyl groups and 6 to 10 carbon atoms, and also to the acrylates and methacrylates of the alkoxylated derivatives of aliphatic polyols having from 2 to 6 hydroxyl groups and 2 to 10 carbon atoms and cycloaliphatic polyols having from 2 to 6 hydroxyl groups and 6 to 10 carbon atoms, in particular ethoxylated and/or propoxylated derivatives thereof, wherein the degree of alkoxylation is 1 to 10. In these resin compositions, the amount of polymer having essentially no ethylenically unsaturated double bonds is typically in the range of 50 to 95% by weight or 55 to 95% by weight, based on the total weight of resin solids of resin component B, while the amount of low molecular compounds having ethylenically double bonds as defined herein is in the range of 5 to 50% by weight or 5 to 45% by weight, based on resins solids of resin component B.
Preferably, these resin components B, which comprise at least one polymer having essentially no ethylenically unsaturated double bond and at least one oligomer or low molecular compound having ethylenically unsaturated double bonds as defined herein, in particular at least one low molecular compound having 2 to 6 ethylenically unsaturated double bonds as defined herein, is an aqueous emulsion or dispersion of the resin constituents of resin component B, i.e. an aqueous emulsion or dispersion of at least one polymer having essentially no ethylenically unsaturated double bond and at least one oligomer or low molecular compound having ethylenically unsaturated double bonds as defined herein. These aqueous emulsions or dispersions are known, e.g. from EP 232016, EP 486278, U.S. Pat. No. 4,107,013, EP 624610, EP 736573 and EP 1511817.
Particular preference is given to resin components B which comprise at least one polyurethane (meth)acrylate, in particular at least one polyurethane acrylate, and mixtures thereof with one or more low molecular weight compounds having ethylenically unsaturated double bonds as defined herein, in particular with one or more low molecular compounds having 2 to 6 ethylenically unsaturated double bonds as defined herein. In particular, the resin components B comprises at least one polyurethane (meth)acrylate in an amount of at least 50% by weight, in particular at least 55% by weight, based on the resin solids of component B. In particular, the resin components B comprise at least one polyurethane (meth)acrylate in an amount of from 50 to 95% by weight or from 55 to 95% by weight, based on the total weight of resin solids of resin component B, and at least one low molecular compound having ethylenically double bonds as defined herein in an amount of 5 to 50% by weight or 5 to 45% by weight, based on resins solids in resin component B. In this type of component B, the low molecular compound is as defined herein and in particular selected from the group consisting of acrylates and methacrylates of aliphatic polyols having from 2 to 6 hydroxyl groups and 2 to 10 carbon atoms and cycloaliphatic polyols having from 2 to 6 hydroxyl groups and 6 to 10 carbon atoms, and also from the acrylates and methacrylates of the alkoxylated derivatives of aliphatic polyols having from 2 to 6 hydroxyl groups and 2 to 10 carbon atoms and cycloaliphatic polyols having from 2 to 6 hydroxyl groups and 6 to 10 carbon atoms, in particular ethoxylated and/or propoxylated derivatives thereof, wherein the degree of alkoxylation is 1 to 10.
Polyurethane (meth)acrylates are polymers which contain urethane groups and which bear ethylenically unsaturated double bonds in the form of groups of the formulae (Ia) or (IIa), in particular in the form of acrylate groups (Ia). In particular, polyurethane (meth)acrylates have an average number of from 1.2 to 20, in particular from 1.5 to 10, acrylate or methacrylate groups per molecule. Preferably, the polyurethane (meth)acrylates are selected from water-emulsifiable polyurethane (meth)acrylates. Frequently, polyurethane (meth)acrylates, in particular water-emulsifiable polyurethane (meth)acrylates, have from 0.2 to 8.0 mol/kg, in particular from 0.3 to 6.0 mol/kg, based on the solid resin polyurethane (meth)acrylate. Typically, polyurethane (meth)acrylates, in particular water-emulsifiable polyurethane (meth)acrylates have a number average molar mass of at least 1000 g/mol, frequently at least 1500 g/mol, e.g. in the range of 1000 to 1000000 g/mol, and in particular in the range of 1500 to 500000 g/mol.
Polyurethane (meth)acrylates, in particular water-emulsifiable polyurethane (meth)acrylates are known from, for example, EP 694531 A2, DE 19525489 A1, DE 19810793 A1, DE 19933012 A1, DE 19957604 A1, EP 1591502 A1, WO 02/034808, WO 03/022552, WO 2011/015540, WO 2014/063920, WO 2015/028397 and WO 2017/029280. They are also commercially available, e.g. from BASF as Laromer® grades UA 8949 aqua, UA 8983 aqua, UA 9005 aqua, UA 9060 aqua, UA 9064 aqua, UA 9059 aqua, UA 9095 aqua and UA 9122 aqua.
Polyurethane (meth)acrylates are typically obtainable via polyaddition of one or more OH containing compounds. Typically, polyurethane (meth)acrylates are obtainable via polyaddition of the following compounds:
Compounds a. include e.g. aromatic, aliphatic and cycloaliphatic diisocyanates, i.e. low molecular compounds having 2 isocyanate groups per molecule, and oligomers thereof having on average more than 2 isocyanate groups per molecule. In particular, the compounds a. comprise a combination of at least one diisocyanate and at least on oligomer of a diisocyanate.
Examples of aromatic diisocyanates are toluene diisocyanate, xylylene diisocyanate, and methylenediphenylisocyanate.
Examples of aliphatic diisocyanates are in particular those having 4 to 20 C atoms such as tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, hexamethylene diisocyanate (1,6-diisocyanatohexane), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, trimethylhexane diisocyanate, and tetramethylhexane diisocyanate.
Examples of cycloaliphatic diisocyanates are 1,4-, 1,3- or 1,2-diisocyanatocyclohexane, 4,4′- or 2,4′-di(isocyanatocyclohexyl)methane, 1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexane (isophorone diisocyanate), 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or 2,4-, or 2,6-diisocyanato-1-methylcyclohexane, and also 3 (or 4), 8 (or 9)-bis(isocyanatomethyl)-tricyclo[5.2.1.02,6]decane isomer mixtures.
Oligomers of diisocyanates are e.g. isocyanurates, biureths and allophanates of the aforementioned aromatic, aliphatic or cycloaliphatic diisocyanate. They typically have a number-average molecular weight in the range of 400 to 1800 daltons, more particularly in the range of 500 to 1600 daltons. The degree of oligomerization is typically in the range of 2.5 to 8, more particularly in the range of 3 to 6. The average isocyanate functionality of the oligomers is preferably in the range of 2.5 to 6, and more particularly in the range of 2.8 to 4.5, and especially in the range of 2.8 to 4.0. An average isocyanate functionality is understood to be the average number of isocyanate groups in the oligomer (number average). Preferred oligomers A1a are those having an isocyanate equivalent weight in the range of 180 to 500 g/mol NCO, more particularly in the range of 200 to 400 g/mol NCO.
Compounds b. include e.g. but are not limited to hydroxy-C2-C8 alkyl esters of acrylic acid, hydroxy-C2-C8 alkyl esters of methacrylic acid, hydroxy-C2-C8 alkylamides of acrylic acid, hydroxy-C2-C8 alkylamides of methacrylic acid, diesters of C3-C8 alkanetriols with acrylic acid, diesters of C3-C8 alkanetriols with methacrylic acid, diesters and triesters of C4-C8 alkanetetraols with acrylic acid, diesters and triesters of C4-C8 alkanetetraols with methacrylic acid. Particular examples are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, trimethylolpropane diacrylate, pentaerythritol diacrylate and pentaerythritol triacrylate.
Compounds c. include but are not limited to acyclic aliphatic diols having 2 to 8 C atoms, as for example ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,2-ethanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethylpropane-1,3-diol, 2-methyl-2-ethylpropane-1,3-diol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, or diethylene glycol and cycloaliphatic diols such as 1,2-, and 1,3-cyclopentanediols, 1,2-, 1,3-, and 1,4-cyclohexanediol, 1,1-, 1,2-, 1,3- and 1,4-bis-(hydroxymethyl)cyclohexanes, 1,1-, 1,2-, 1,3- and 1,4-bis(hydroxyethyl)cyclohexanes, bis(4-hydroxycyclohexane)methane, and bis(4-hydroxycyclohexane)isopropylidene.
Compounds d. include but are not limited to polyesterols, polyetherols, and polycarbonate polyols. Compounds d. preferably have a number-average molecular weight in the range of 350 to 10000 g/mol, more particularly in the range of 400 to 8000 g/mol, especially in the range of 450 to 5000 g/mol, as e.g. determined by gel permeation chromatography, e.g. using tetrahydrofurane as an eluent and polystyrenes of defined molecular weight as standards. Preferably, compounds c are selected from aliphatic polyester polyols and aliphatic/aromatic polyesterols. Preferred polyesterols are those based on aromatic, aliphatic and/or cycloaliphatic dicarboxylic acids with aliphatic diols. Preferred polyester polyols have OH numbers, determined according to DIN 53240-2:2007-11, in the range of 5 to 220, more particularly in the range of 10 to 200 mg KOH/g. The acid number is preferably below 20 mg KOH/g, more particularly below 10 mg KOH/g. Amongst the aliphatic polyester polyols, particular preference is given to aliphatic polyester polyols constructed from at least one C3-C12 alkanedicarboxylic acid, such as adipic acid, sebacid acid or brassylic acid, and at least one C3-C10 alkanediol, such as ethandiol, propanediol, butandiol, neopentylglycol or hexandiol. Amongst the aliphatic/aromatic polyester polyols, particular preference is given to polyester polyols constructed from a combination of at least one aromatic dicarbonxylic acid, such as terephthalic acid or isophthalic acid, at least one C3-C12 alkanedicarboxylic acid, such as adipic acid, sebacid acid or brassylic acid, and at least one C3-C10 alkanediol, such as ethandiol, propanediol, butandiol, neopentylglycol or hexandiol. For example, the polyesterol may be constructed from adipic acid and neopentyl glycol and which in particular has an OH number in the range of 20 to 200 mg KOH/g.
Compounds e. include but are not limited to compounds of the formula
(F′)n—R—I′
Preference is given to compounds e. selected from aliphatic mono- and dihydroxycarboxylic acids, more particularly from those having 3 to 10 C atoms and their salts. Examples of such aliphatic mono- and dihydroxycarboxylic acids are glycolic acid, lactic acid, 2,3-dihydroxypropanic acid, 2,2-dimethylolpropionoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolpentanoic acid, with preference being given to 2,2-dimethylolpropionic acid and dimethylolbutyric acid. Preference is also given to the salts of 2-[(2-aminoethyl)amino]ethanesulfonic acid, e.g. the sodium salt.
Compounds f. include but are not limited to poly-C2-C3 alkylene oxide compounds having an average OH functionality in the range of 0.9 to 1.2. This refers to polyethylene glycol ethers, polypropylene glycol ethers, and polyethylene glycol-co-propylene glycol ethers which have on average 0.9 to 1.2 and more particularly 1 hydroxyl group in the molecule.
In addition to the resin component B, the impregnating resin comprises at least on resin component A, which is selected from aminoplast resins and phenoplast resins and mixtures thereof.
Aminoplast resins are polycondensation products of one or more amino compounds and one or more aldehydes. Useful amino compounds in this respect are primary amines having at least two primary amino groups, in particular 2 or 3 primary amino groups. These amines are preferably characterized in that each of their primary amino groups is attached to a carbon atom, which is linked via a double bond to an oxygen atom, sulfur atom or nitrogen atom. Preferred examples of such amines are urea, thiourea, melamine, cyanoguanamine (=dicyandiamide), acetoguanamine and benzoguanamine. Useful aldehydes in this respect are C1-C10-alkanals, especially C1-C4-alkanals, such as formaldehyde, acetaldehyde, propanal or n-butanal, and C2-C10-alkandials, especially C2-C6-alkandials, such as glyoxal or glutaraldehyde. Preferred aldehydes are formaldehyde, glyoxal and glutaraldehyde, in particular formaldehyde. The aminoplast polymer may be partially or wholly etherfied by alkanols, in particular C1-C4-alkanols such as methanol, ethanol, n-propanol or n-butanol.
Examples of aminoplast resins include, but are not limited to melamine-formaldehyde resins (=MF resins), including wholly or partially etherified MF resins, urea-formaldehyde resins (=UF resins), thiourea-formaldehyde resins (=TUF resins), melamine-urea-formaldehyde resins (=MUF resins), including wholly or partially etherified MUF resins, melamine-thiourea-formaldehyde resins (=MTUF resins), including partially etherified MTUF resins, urea-glutaraldehyde resins, benzoguanamine-formaldehyde resins, dicyandiamide-formaldehyde resins and urea-glyoxal resins, i.e. from polymers that are obtained by polycondensation of melamine, urea, thiourea, melamine/(thio)urea mixtures, benzoguanamine or dicyandiamide with formaldehyde, by polycondensation of urea with glutaraldehyde, or by polycondensation of urea with glyoxal.
Phenoplast resins are polycondensation products of one or more phenolic compounds such as phenol, resorcin, hydroxytoluene or hydroxyxylene, and one or more aldehydes, in particular C1-C10-alkanals, more particularly C1-C4-alkanals, especially formaldehyde. Examples of phenoplast resins include but are not limited to novolaks and resoles.
Preferably, the resin composition A comprises at least one aminoplast resin, in particular in an amount of at least 30% by weight, in particular at least 50% by weight, especially at least 70% by based, based on the total weight of resin solids in component A. Especially, the resin composition A consists of at least one aminoplast resin.
Preferably, the resin composition A comprises at least 30% by weight, in particular at least 50% by weight, especially at least 70% by based, based on the total weight of resin solids in component A, of an aminoplast resin, which is selected from the group consisting of MF resins, including wholly or partially etherified MF resins, MUF resins, including wholly or partially etherified MUF resins, and UF resins. In particular, the resin composition A comprises at least 30% by weight of a MF resin, and especially a wholly or partially etherified MF resin.
In the resin-impregnated sheet or web of the fibrous material, the resin component A is typically still reactive, i.e. it is not fully crosslinked and thus can be further crosslinked to a duroplastic polymer, when the resin-impregnated sheet or web is laminated to a surface to provide a plastic surface of a panel.
The relative amount of the resin composition A to the resin composition B is preferably chosen such that the impregnating resin comprises from 0.01 to 3 mol/kg, in particular form 0.1 to 2.5 mol/kg and especially from 0.2 to 2.0 mol/kg, based on total weight of resin solids of the impregnating resin, of ethylenically unsaturated double bonds as defined herein, in particular of (meth)acryl groups of the formulae (I) and/or (II), more preferably of (meth)acrylate groups of the formulae (Ia) and/or (IIa) and especially of acrylate groups. Typically, the weight ratio of resin solids of component A to resin solids component B is in the range of 60:40 to 99:1, in particular in the range of 70:3 to 98:2 and especially in the range of 80:20 to 95:5.
Typically the resin composition A and the resin composition B are essentially the sole resin components of the impregnating resin. However, the impregnating resin may contain one or more resins different from the resins of resin components A and B. The amount of such resins will generally not exceed 10% by weight, based on the total resin solids of the impregnating resin.
The impregnating resin may comprise one or more additives typically used in impregnating resins for impregnating fibrous materials. These additives include but are not limited to hardeners, e.g. acids which effect hardening of the resin component A, wetting agent such as mixtures of tensides, e.g. the commercial products DeuroWET MA 30 or ALTON WLF-15, release agents, in particular parting-active ester compounds, such as phosphate esters, e.g. the commercial products DeuroLEASE PHO or ALTON R 1014, anti-dusting agents such as salts of phosphate esters ALTON ES 711, anti-blocking agents, such as polymers and polymer blends, including silicones, fluoropolymers, or waxes, typically in the form of dispersions, e.g. the commercial products ALTON AT 839 or DeuroSLIDE PG. Examples of suitable hardeners include but are not limited to weak acids, e.g. carboxylic acids, such as maleic acid, and ammonium salts, such as ammonium sulfite, ethanolamine hydrochlorid, N-methylethanolammonium sulfite, N,N-dimethylethanolammonium sulfite, the morpholine salt of toluene sulfonic acid, and combinations of N-methylethanolamine/SO2 and ethanolamine/N-methylethanolamine/SO2.
The fibrous material to be impregnated, i.e. the non-impregnated sheet or web of fibrous material, may be fibrous material in the form of a sheet or a web which is commonly used for the production of resin impregnated sheets or webs for providing plastic surfaces. Prior to impregnation, the sheet or web of the fibrous material may have a grammage in the range of 15 to 300 g/m2, in particular in the range of 15 to 250 g/m2. Here and in the following, the grammage refers to weight per area as defined and determined according to DIN EN ISO 536:2020-05.
For example the non-impregnated fibrous material may be a sheet or web of paper or cardboard, which preferably has a grammage in the range of 15 to 300 g/m2, in particular in the range of 15 to 250 g/m2, including
For example the non-impregnated sheet or web of the fibrous material may also be a sheet or web of a textile material or a non-woven, e.g. a textile or non woven based on natural fibres such as cotton fibre, flax fibre, sisal fibre, hemp fibre or mixtures thereof, including mixtures with synthetic fibres, such as glass fibre, synthetic fibre and carbon fibre, nonwovens based on synthetic fibres, nonwovens based on glass fibre and mixtures thereof with plastic fibres. Suitable textiles and non wovens may have a grammage in the range of 30 to 300 g/m2 prior to impregnation.
The total amount of impregnating resin in the resin-impregnated fibrous material will of course be dependent from the grammage of the non-impregnated sheet or web of the fibrous material. For example, the total amount of impregnating resin in the resin-impregnated fibrous material may be in the range of 10 to 80% by weight, based on the total weight of impregnated sheet or web and is preferably in the range of 30 to 70% by weight, in particular in the range of 45 to 65% by weight of the impregnated sheet or web of the fibrous material, where the resin is calculated as resin solids. The grammage of the resin-impregnated sheet or web of fibrous material is typically in the range of 20 to 800 g/m2, in particular in the range of 30 to 700 g/m2, depending on the grammage of the sheet or web used for impregnation. In case of a resin impregnated paper having a grammage in the range of 40 to 150 g/m2, the total amount of resin is in particular in the range of 30 to 100 g/m2, in particular in the range of 40 to 90 g/m2.
The resin-impregnated fibrous material can be produced by analogy to well known techniques of impregnating sheets or webs of fibrous materials with impregnating resins. For this, the sheet or a web of the fibrous material is impregnated with a liquid resin formulation comprising the resin component A and the resin component B.
In the liquid resin formulation, 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% as determined by the procedure described in US 2010/282407. Typically the pre-condensate is an monomer, an oligomer having on average (number average) from 2 to 20 repeating units or a polymer having on average (number average) from 21 to 500 repeating units or a mixture thereof. The degree of oligomerization/polymerization can be determined by gel permeation chromatography as described in the art, e.g. by Jeong et al., J. Korean Wood Sci. Technol. 2016, 44(6): 913-922.
The liquid resin formulation contains the resin components A and B, preferably in the above relative amounts. In addition, the liquid resin formulation contains a solvent, which is capable of dissolving or emulsifying the resin components A and B. Suitable solvents include but are not limited to water, C1-C4 alkanols and mixtures thereof. Preferably, the liquid resin formulation is an aqueous resin composition, which besides the resin does not contain more than 10% by weight of organic solvents. In addition to the resin components A and B, the liquid resin formulation may contain one or more additives typically used in liquid resin formulations for impregnating fibrous materials. These additives include but are not limited to the aforementioned hardeners, release agents, anti-dusting agents and blocking agents.
Typically, the liquid resin formulation has a viscosity that allows the resin to penetrate into the fibrous material to be impregnated while providing good handling and uniform application of the liquid resin formulation. Frequently, the liquid resin formulation has a viscosity in terms of flow time, determined according to DIN EN ISO 2431:2018-08 at 20° C. with 4 mm nozzle of not more than 35 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 30 to 60% by weight as determined e.g. by DIN EN 827:2006-03.
The impregnation can principally achieved by any method of impregnating a sheet or web of a fibrous material. Typically, the liquid resin formulation to at least one of the surfaces of the sheet or the web of the fibrous material. The sheet or the web of the fibrous material may be a non-impregnated sheet or web or it may be a pre-impregnated material that still has capacity to absorb further liquid impregnating resin composition.
The application of the liquid resin formulation can be achieved by any conventional techniques for impregnation of a porous sheet or web substrate with a liquid resin formulation. For example, the liquid resin formulation containing the resin components A and B can be applied as a liquid coating onto one or both surfaces of the sheet or web, by conventional coating techniques such as slot nozzle coating, squeegee coating, spray coating, roller coating, anilox coating, reverse coating, cascade or curtain casting, by means of a gluing press or by immersing the sheet or web in the liquid resin formulation or by combinations or the aforementioned impregnation techniques.
Preferred methods for impregnating a sheet or a web of a fibrous material will now be described with reference to the figures.
As shown in
As shown in
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.
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.
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.
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%.
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.
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.
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.
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
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.
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.
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%.
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.
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.
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.
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.
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.
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.
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
In particular, the following procedure may be used. In the first step i., a web of the fibrous material is impregnated as outlined in
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.
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.
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.
Suitable panels include but are not limited to
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).
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/cm2. 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:
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;
2)HPL: High pressure laminate
3)CPL: continuous pressure laminate
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.
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.
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.
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.
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.
A white decorative paper having a grammage of 75 g/m2 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.
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/cm2. Once the press has opened the coated MDF board was removed from the press and allowed to cool at ambient conditions.
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:
The compositions of the UV varnishes U1 and U2 are shown in table 5 below:
The compositions of the acrylic waterbased varnishes W1, W2 and W3 are shown in table 6 below:
The polyurethane varnishes P1 and P2, both available from Alfred Clouth Lackfabrik, Offenbach, Germany, are shown in table 7.
The UV varnishes U1 and U2 were applied by means of a spiral doctor blade with a dry film thickness of 10 g/m2. 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.
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.
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:
| Number | Date | Country | Kind |
|---|---|---|---|
| 20185316.5 | Jul 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/069023 | 7/8/2021 | WO |
