LU100436B1 - Rigid floor or wall covering production method - Google Patents

Abstract

A method of producing a floor or wall covering comprises: providing a carrier plate comprising a mineral or polymeric cement and a mineral or organic, preferably fibrous, filler or reinforcement material, provided that at least one of the cement and the filler or reinforcement material comprises a mineral material or mineral material mixture representing at least 25% by weight, of the carrier plate, the carrier plate having a front face and a back face; and applying a radiation-curable polymer formulation on the front face, curing the polymer formulation by exposing the radiation-curable polymer formulation to radiation and thereby producing a wear-resistant layer at least locally on the front face.

Description

DESCRIPTION

RIGID FLOOR OR WALL COVERING PRODUCTION METHOD

Field of the Invention [0001 ] The disclosure relates to the field of finishing work, especially for but not limited to buildings. In particular, the disclosure relates to floor or wall coverings. An aspect of the invention relates to wear resistant surfaces for rigid floor or wall coverings comprising a radiation-curable polymer formulation.

Background of the Invention [0002] Laminate floors are well known. Laminated floors typically have 6-12 mm thick fiberboard core, a sub-millimeter thick upper decorative surface layer and a submillimeter thick balancing layer on the bottom side.

[0003] The surface layer generally consists of two layers of paper, separately applied one on top of the other. The lower of the two layers provides the decoration function and may consist of a melamine formaldehyde (hereinafter: “melamine” for simplicity) impregnated printed paper. The upper of the two layers is the wear layer and may be a melamine impregnated transparent overlay.

[0004] The décor may be applied by any suitable process, e.g., printing (rotogravure, digital printing, etc.) directly on the core layer or on a printing substrate that is laminated on the core layer. The print is then covered with the protective wear layer, which may take the form of an overlay, a plastic foil, a lacquer, etc. So called “Luxury Vinyl Tiles” (LVT floorings) are an example of a layered product. LVT comprises a PVC-based structural layer and a printed decorative PVC foil on the upper side. A transparent vinyl wear layer protects the decorative foil. The protective layer may include a polyurethane coating that provides additional wear and stain resistance.

[0005] Wear layers may also be used if the production of the floor covering involves no printing step. Ceramic tiles are one example.

Summary of the Invention [0006] Aspects of the present invention are particularly suitable for manufacture of floor or wall coverings, which are formed of floor or wall panels comprising a rigid, machinable core, optionally a décor, and a wear-resistant protective layer (“wear layer”) on top. Embodiments may be fibrocement floors and rigid thermoplastic, thermoset or radiation-cured polymeric floors comprising mineral cement material and/or mineral filler or reinforcement material.

[0007] A first aspect of the invention relates to a method of producing a floor or wall covering, comprising: o providing a, preferably (but not necessarily) PVC-free, carrier plate comprising a mineral or polymeric cement and a mineral or organic, preferably fibrous, filler or reinforcement material, provided that at least one of the cement and the filler or reinforcement material comprises a mineral material or mineral material mixture representing at least 25%, preferably at least 35%, more preferably at least 50%, by weight, of the carrier plate, the carrier plate having a front face and a back face; and o applying a radiation-curable polymer formulation on the front face, curing the polymer formulation by exposing the radiation-curable polymer formulation to radiation (e.g. visible light, UV radiation, XUV radiation, electron beam, etc.) and thereby producing a (preferably transparent or at least translucent) wear-resistant layer at least locally on the front face.

[0008] Preferably, the carrier plate qualifies as a rigid carrier plate in the sense that the carrier plate elastically deforms only to a radius of curvature of 50 cm or more, i.e. bending of the carrier plate to a radius of curvature smaller than 50 cm either leads to plastic deformation of the carrier plate or breaking thereof. More rigid carrier plates are not excluded and may be preferred in some embodiments. For instance, the rigidity may be such that the carrier plate elastically deforms only to a radius of curvature of 75 cm or more, or 1 m or more, or 1.5 m or more, or 2 m or more.

[0009] According to an embodiment, the radiation-curable polymer formulation comprises an admixture of solid inorganic particles, which become firmly embedded within the wear-resistant layer during the curing.

[0010] It should be noted that the expression “solid inorganic particles” designates inorganic particles in the solid state. The solid inorganic particles do not undergo a phase change during the curing step and remain distinguishable (i.e. do not form a uniform phase) with the wear resistant layer into which they are incorporated. For the solid inorganic particles, the wear resistant layer forms, after curing, an anchoring matrix. Preferably, the solid inorganic particles comprise ceramic particles, e.g., carbide, nitride and/or oxide particles. It should be noted that the solid inorganic particles may be provided as part of a particle mixture or a powder comprising other particles, e.g. organic particles. The other particles, if any, could participate in the formation of the wear layer and become indistinguishable from it in the final product. Alternatively, the other particles could be embedded in the wear layer substantially in the same way as the inorganic particles and remain distinguishable in the final product. The optional organic particles could comprise (previously) cured thermoset or (previously) radiation-cured particles.

[0011] The solid inorganic particles could include ceramic particles, e.g., carbide, nitride and/or oxide particles. The solid inorganic particles could, e.g., be selected from the group consisting of: AI2O3, S12O, S13N4, SiOxNx, AIN, BN, AINO, MgO, ZnO, SnO2, NiO, ZrO2, Cr2O3, MOO2, RuO2, CoOx, CuOx, VOx, FeOx, MnOx, T1O2, CaF2, BaF2, MgF2, SiC, WC, B4C, ternary and/or complex oxides involving one or more of the elemental species of the mentioned compounds and mixtures thereof. The inorganic particles preferably have a Mohs hardness of at least 3, preferably of at least 4, more preferably of at least 5, still more preferably of at least 6 and most preferably of at least 7.

[0012] According to an embodiment, a décor layer is bonded to the front face of the carrier plate and the radiation-curable polymer formulation is applied on the décor layer. The décor layer could carry a printed decorative pattern. The décor layer could be bonded to the front face of the carrier plate using adhesive, preferably a hotmelt (e.g. a polyurethane-based or epoxy-based hotmelt) or a polyvinyl-acetate-based adhesive. The décor layer could comprise a fused plastisol layer as the printing substrate. Alternatively, the décor layer could comprise a paper printing substrate or a multilayer printing substrate.

[0013] According to an embodiment, the carrier plate comprises a fibrocement plate. As used herein, a “fibrocement plate” is a plate wherein the principal binder (in terms of weight) is a mineral cement or a mineral cement mixture. In a fibrocement plate, the presence of organic cement(s) is not excluded, provided that the mineral cement (mixture) outweighs the organic cement(s). Alternatively, the carrier plate comprises a rigid plastic plate (with a polymeric cement). At least one of the cement and the filler or reinforcement material preferably comprises a mineral material or mineral material mixture representing at least 25%, preferably at least 35%, more preferably at least 50%, by weight, of the carrier plate. Higher contents of mineral materials, e.g. at least 60% by weight, 70% by weight, 75% by weight, 80% by weight or even more, may be possible in specific embodiments.

[0014] The fibrocement plate preferably comprises cementitious binder and organic fibres, e.g. a mixture of polymeric fibres and cellulosic fibres.

[0015] The radiation-curable polymer formulation could be applied directly on the fibrocement plate but a printed intermediate décor layer may be preferred for certain applications.

[0016] Preferably, the thickness of the wear-resistant layer obtained after curing amounts to a value in the range from 1 μm to 200 μm, more preferably in the range from 2 μm to 100 μm, still more preferably in the range from 2 to 50 μm, even more preferably in the range from 3 to 30 μm and most preferably in the range from 5 to 20 μm.

[0017] The cementitious binder is preferably a hydraulic cement, (e.g. Portland cement, blast furnace cement, etc.). Preferably, the hydraulic is a mixture comprising belite (2CaO SiO2), alite (3CaOSiO2), tricalcium aluminate (3CaOAl2O3) and/or brownmillerite (4CaOAl2O3-Fe2O3).

[0018] According to an embodiment, the radiation-curable polymer formulation is a radiation-curable polyurethane formulation that comprises at least one radiation-curable polyurethane acetate (component A), at least one acidic adhesion promoter (component B) and at least one mono- or polyfunctional reactive diluent (component C). The radiation-curable polyurethane formulation may be a (100%) solid formulation, i.e. a formulation containing no water or other (organic) solvent in liquid state.

[0019] The radiation-curable polyurethane acetate (component A) preferably has an average molecular weight comprised in the range from 500 to 25 000 gmol'1, more preferably in the range from 1000 to 20 000 g mol'1, and still more preferably in the range from 1500 to 15 000 g mol'1.

[0020] Radiation-curable polyurethane acrylates (component A) are preferably prepared from hydroxyl-containing monomers and/or polymers and compounds, which, at one and the same time, contain at least one isocyanate-reactive group (e.g., alcohol, amine or thiol) and at least one polymerizable acrylate group, by reaction with polyisocyanates. The radiation-curable polyurethane acetate contains both urethane groups and acrylate groups.

[0021] Suitable hydroxyl containing monomers are preferably chosen from the group consisting of: methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, 1,3-butylene glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1,4-cyclohexanediol, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), diols derived from dimer fatty acids, 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester), glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane and/or castor oil. Neopentyl glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol and/or trimethylolpropane are particularly preferred.

[0022] Suitable hydroxyl-containing polymers preferably include polyesters, polyethers, polyether-esters, polycarbonates, polyether carbonate polyols and polycarbonate polyesters having a functionality of from 1.0 to 3.0, in each case with a weight average molecular weight in the range of from 300 to 4000, preferably 500 to 2500 g mol'1. Hydroxyl functional polyesters and polyether diols are particularly preferred. Polyether diols particular useful are dihydroxy-terminated polyalkylene oxides having 2 to 4 carbon atoms in each alkylene group. Such polyether diols are made by polymerizing ethylene oxide, propylene oxide, or butylene oxide, or mixtures thereof to form block copolymers, with a dihydric initiator. Such initiators are ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,4-butanediol (and the like). A preferred polyether diol is made by polymerizing tetrahydrofuran to a polyether diol having 4 carbon atoms in each alkylene group. Preferably, the polyether diols have molecular weights of 800 to 2000 g mol’1. Especially preferably, the polyether diols have a molecular weight of 800 to 1200 g mol’1.

[0023] Hydroxyl-containing polyesters may be prepared by polycondensation of suitable dicarboxylic acids and diols. Condensation may take place in an inert gas atmosphere at temperatures from 180 to 260°C, preferably 200 to 230°C, in the melt, or in azeotropic mode.

[0024] Carboxylic acids that are preferred for polyester preparation may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic in nature and may, if desired, be substituted by halogen atoms and/or be unsaturated. Examples of carboxylic acids include the following: succinic, adipic, suberic, azelaic, sebacic, phthalic, terephthalic, isophthalic, trimellitic, pyromellitic, tetrahydrophthalic, hexahydrophthalic, hexahydroterephthalic, dichlorophthalic and tetrachlorophthalic, endomethylene tetrahydrophthalic, and glutaric acid, 1,4-cyclohexanedicarboxylic acid, and -where obtainable- their anhydrides or esters. Adipic acid and 1,4-cyclohexanedicarboxylic acid may be found particularly suitable.

[0025] Examples of suitable polyols include monoethylene glycol, 1,2- and 1,3-propylene glycol, 1,4- and 2,3-butylene glycol, di-ß-hydroxyethylbutanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, decanediol, dodecanediol, neopentyl glycol, cyclohexanediol, bis(hydroxymethyl)tricyclo(5.2.1.0(2,6))decane (Dicidol), 1,4-bis(hydroxymethyl)cyclohexane, 2,2-bis-(4-hydroxycyclohexyl)propane, 2,2-bis[4-(ß-hydroxy-ethoxy)phenyl]propane, 2-methylpropane-1,3-diol, 2-methyl-pentane-1,5-diol, 2,2,4(2,4,4)-trimethyl-hexane-1,6-diol, glycerol, trimethylolpropane, trimethylolethane, hexane-1,2,6-triol, butane-1,2,4-triol, tris(ß-hydroxyethyl)isocyanurate, pentaerythritol, mannitol, and sorbitol, and also diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polypropylene glycols, polybutylene glycols, xylylene glycol, and neopentyl glycol hydroxypivalate. Preference is given to monoethylene glycol, neopentyl glycol, Dicidol, cyclohexanedimethanol, trimethylolpropane, and glycerol.

[0026] Polyesters used for obtaining radiation-curable polyurethane acrylates preferably have an OH number of 15 to 750 mg KOH/g. Mixtures of polyesters can be used as well.

[0027] For preparing urethane acrylates, the polyisocyanates used are preferably diisocyanates of (cyclo)aliphatic or aromatic structure. Examples of (cyclo)aliphatic polyisocyanates are: 2-methylpentamethylene 1,5-diisocyanate (MPDI), hexamethylene diisocyanate (HDI), trimethylhexamethylene 1,6-diisocyanate (TMDI), in particular 2,2,4- and the 2,4,4 isomer and technical mixtures of both isomers, 4,4'-methylenebis(cyclohexyl isocyanate) (H12MDI), norbornane diisocyanate (NBDI), and 3,3,5-trimethyl-1-isocyanato-3-isocyanatomethyl-cyclohexane (IPDI). Likewise highly suitable are polyisocyanates, which are obtainable by reacting polyisocyanates with themselves via isocyanate groups, such as isocyanurates, which come about through reaction of three isocyanate groups. The polyisocyanates may likewise contain biuret groups or allophanate groups. IPDI and/or IPDI trimer may be found especially suitable.

[0028] Examples of aromatic polyisocyanates are 1,4-diisocyanatobenzene (BDI), 2,4-diisocyanatotoluene (2,4-TDI), 2,6-diisocyanatotoluene (2,6-TDI), 1,T-methylenebis[4-isocyanatobenzene] (MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 1,5-naphtalene diisocyanate (NDI), tolidine diisocyanate (TODI) and p-phenylene diisocyanate (PPDI). Preference may be given to (cyclo)aliphatic polyurethanes.

[0029] Examples of suitable polymerizable compounds having at least one free OH group and a polymerizable (meth)acrylate group include the esterification products of aliphatic and/or aromatic polyols with (meth)acrylic acid having a residual average hydroxyl functionality of 1. The partial esterification products of (meth)acrylic acid with tri-, tetra-, penta- or hexahydric polyols or mixtures thereof may be preferred. In this context, it is also possible to use reaction products of such polyols with ethylene oxide and/or propylene oxide or mixtures thereof, or reaction products of such polyols with lactones, which add to these polyols in a ring-opening reaction. Examples of suitable lactones are γ-butyrolactone and, in particular, δ-valerolactone and ε-caprolactone. These modified or unmodified polyols are partly esterified with acrylic acid, methacrylic acid or mixtures thereof until the desired residual hydroxyl functionality is reached.

[0030] Particularly preferred are compounds comprising at least two (meth)acryl functions such as glycerol diacrylate, trimethylolpropane diacrylate, glycerol diacrylate, pentaerythritol triacrylate, ditrimethylolpropane triacrylate, dipentaerythritol pentaacrylate and their (poly)ethoxylated and/or (poly)propoxylated equivalents.

[0031] Other suitable compounds are the (meth)acrylic esters with linear and branched polyols in which at least one hydroxy functionality remains free, like hydroxyalkyl(meth)acrylates having 1 to 20 carbon atoms in the alkyl group. Preferred molecules in this category are hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate.

[0032] Hydroxyl functional polyester (meth)acrylates, polyether (meth)acrylates, polyether-ester (meth)acrylates, polycarbonate (meth)acrylates and polyether carbonate (meth)acrylates, comprising at least one hydroxyl functionality, can be used as well.

[0033] To prepare urethane acrylate from OH-containing monomers and/or polymers, polyisocyanates, and the acrylate component, first of all the polyisocyanate is introduced, a suitable catalyst (e.g., DBTL) and a polymerization inhibitor (e.g., IONOL CP, Shell) are added, and the acrylate component, hydroxyethyl acrylate, for example, is added in an NCO.OH ratio of 2.5 to 1:1. Thereafter, the OH-containing monomers and/or polymers, preferably the polyester, is added to the reaction product, in a residual NCO.OH ratio of 0.5 to 0.95:1, and the reaction is completed at 40 to 120°C, so that an NCO content below 0.1% is obtained.

[0034] The acidic adhesion promoter (component B) preferably comprises one or more acid functionalities and one or more (meth)acrylic functionalities. The one or more acid functionalities are preferably selected from the group consisting of -SO3H, -OSO3H, -COOH, -OPO3H2 and -OPO2HO- Optionally, the acidic hydrogen could be substituted by an alkali metal or an ammonium base. The acidic adhesion promoter is preferably the reaction product of one or more acid-functionality-comprising components with one or more functionalized (meth)acrylates. Examples are ethylenically unsaturated polyesters and polyurethanes comprising one or more of -SO3H, -OSO3H, -COOH, -OPO3H2 and -OPO2HO- functionality.

[0035] Polyesters comprising one or more acid functionalities are preferably prepared from one or more polyol components and one or more polybasic acid components, wherein at least one or more diol components and/or one or more dibasic acid components contain one or more of -SO3H, -OSO3H, -COOH, and -OPO3H2 functionality.

[0036] Examples of -SO3H, -OSO3H, -COOH, and -OPO3H2 functionality-comprising polybasic acid or polyol include: 5-sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-sulfophthalic acid, 3-sulfophthalic acid, dialkyl 5-sulfoisophthalate, dialkyl 2-sulfophthalate, alkyl 4-sulfophthalic acid, alkyl 3-sulfophthalic acid, sodium or potassium salt of these compounds, and dimethylolpropionic acid. Optionally, the sodium, potassium or ammonium salt could be used.

[0037] Polyesters comprising one or more phosphate groups in the polyester chain could be prepared from condensation of one or more polyols and one or more polybasic acids in the presence of phosphoric acid.

[0038] Ethylenically unsaturated polyurethane resin having one or more acid functionalities could be synthesized from reaction of a polyisocyanate compound, a polyol component having one or more acid functionalities, e.g. a polyester polyol having one or more acidic functionalities and/or dimethylolpropionic acid, and a compound having a hydroxyl functionality and at least one ethylenically unsaturated double bond, such as, for example, 2-hydroxyethylecrylate.

[0039] Hydroxyl functional polyesters having one or more acid functionalities could be converted into ethylenically unsaturated polyesters having one or more acid functionalities through reaction with (meth)acrylic acid.

[0040] Acid functional polyesters having one or more -SO3H, -OSO3H, -COOH, -OPO3H2 and -OPO2HO- functionality could be converted into ethylenically unsaturated polyesters having one or more acid functionalities through reaction with glycidyl(meth)acrylate or hydroxyethyl(meth)acrylate.

[0041] Other examples of acidic adhesion promoters are: the reaction product of hydroxyethylacrylate and phosphorpentoxide forming 2-acryloylethylphosphate, the reaction product of 2-hydroxyethylacrylate and succinic anhydride, the reaction product of a polyester oligomer comprising hydroxyl and carboxyl functionalities with acrylic acid and the reaction product of a carboxyl functionalized polyester oligomer with hydroxyethyl(meth)acrylate.

[0042] The acidic adhesion promoter (component B) preferably has a molecular weight of less than 10 000 gmol'1, more preferably of less than 7500 gmol-1 and most preferably of less than 5000 g.mol-1.

[0043] Reactive diluents (component C) comprise, for example, the alcohols methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, dihydrodicyclopentadienol, tetra hydrofurfuryl alcohol, 3,3,5-trimethylhexanol, octanol, decanol, dodecanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, 1,3-butylene glycol, 1,4- cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1,4-cyclohexanediol, hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol esterified completely with (meth)acrylic acid, and the ethoxylated and/or propoxylated derivatives of these alcohols esterified completely with (meth)acrylic acid and the technical grade mixtures obtained during (meth)acrylation of the abovementioned compounds.

[0044] Further suitable reactive diluents (component C) are, for example, epoxy (meth)acrylates, polyether (meth)acrylates, polyester (meth)acrylates and polycarbonate (meth)acrylates having a number average molecular weight preferable comprised between 500 and 10000 g mol’1.

[0045] Reactive diluents comprising more than one ethylenically unsaturated group may be found particularly well suited.

[0046] The radiation-curable polymer formulation may comprise any suitable photoinitiator. The usual photoinitiators are the type that generate free radicals when exposed to radiation energy. Suitable photoinitiators include, for example, aromatic ketone compounds, such as benzophenones, alkylbenzophenones, Michler's ketone and anthrone halogenated benzophenones. Further suitable compounds include, for example, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, phenylglyoxylic acid esters, anthraquinone and the derivatives thereof, benzil ketals and hydroxyalkylphenones. Other suitable photoinitiators include 2,2-diethoxyacetophenone; 2- or 3- or 4-bromoacetophenone; 3- or 4-allyl-acetophenone; 2-acetonaphthone; benzaldehyde; benzoin; the alkyl benzoin ethers; benzophenone; benzoquinone; 1-chloroanthraquinone; p-diacetyl-benzene; 9,10-dibromoanthracene 9,10-dichloroanthracene; 4,4-dichlorobenzophenone; thioxanthone; isopropylthioxanthone; methylthioxanthone; alpha,alpha,alpha-trichloro-para-t-butyl acetophenone; 4-methoxybenzophenone; 3-chloro-8-nonylxanthone; 3-iodo-7-methoxyxanthone; carbazole; 4-chloro-4'-benzylbenzophenone; fluoroene; fluoroenone; 1,4-naphthylphenylketone; 1,3-pentanedione; 2,2-di-sec.-butoxy acetophenone; dimethoxyphenyl acetophenone; propiophenone; isopropylthioxanthone; chlorothioxanthone; xanthone; maleimides and their derivatives; and mixtures thereof.

[0047] Several suitable photoinitiators are commercially available from Ciba, for instance, Irgacure® 184 (1-hydroxy-cyclohexyl-phenyl-ketone), Irgacure® 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide), Irgacure® 1850 (a 50/50 mixture of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide and 1-hydroxy-cyclohexyl-phenyl-ketone), Irgacure® 1700 (a 25/75 mixture of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one), Irgacure® 907 (2-methyl-1 [4-(methylthio)phenyl]-2-morpholonopropan-1-one), Darocur® MBF (a phenyl glyoxylic acid methyl ester), Irgacure® 2020 Photoinitiator blend (20% by weight of phenylbis(2,3,6-trimethyl benzoyl)phosphine oxide and 80% by weight of 2-hydroxy-2-methyl-1-phenyl-1-propanone) and Darocur® 4265 (a 50/50 mixture of bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one). There may be other suitable photoinitiators that are not listed.

[0048] Photoactivators can be used in combination with the aforementioned photoinitiators. Photoactivators could e.g. be selected among: methylamine, tributylamine, methyldiethanolamine, 2-aminoethylethanolamine, allylamine, cyclohexylamine, cyclopentadienylamine, diphenylamine, ditolylamine, trixylylamine, tribenzylamine, n-cyclohexylethyleneimine, piperidine, N-methylpiperazine, 2,2-dimethyl-1,3-bis(3-N-morpholinyl)-propionyloxypropane, and mixtures thereof.

[0049] The radiation-curable polymer formulation could comprise additives, such as , e.g., dispersing agents, flowing aids, thickening agents, defoaming agents, deaerating agents, pigments, fillers, flattening agents, matting agents and wetting agents.

[0050] According to an embodiment, the radiation-curable polymer formulation is a radiation-curable polyurethane formulation in the form of an aqueous dispersion. A radiation-curable aqueous polyurethane dispersion for being used in the present invention may be obtained from the reaction of at least one polyisocyanate (component AA), at least one hydrophilic compound containing at least one reactive group capable of reacting with isocyanate groups and at least one group which is capable of rendering the polyurethane dispersible in aqueous medium either directly or after a reaction with a neutralizing agent to provide a salt (component BB), at least one polymerizable ethylenically unsaturated compound containing at least one reactive group capable of reacting with isocyanate groups (component CC) and at least one compound, which differs from component CC, containing at least one reactive group capable of reacting with isocyanate groups (component DD).

[0051] Component AA may comprise organic compound(s) including at least two isocyanate groups. The polyisocyanate (component AA) could comprise not more than three isocyanate groups. The polyisocyanate (component AA) is most preferably a diisocyanate. The polyisocyanate (component AA) could be selected from aliphatic, cycloaliphatic, aromatic and/or heterocyclic polyisocyanates or combinations thereof.

[0052] Examples of aliphatic and cycloaliphatic polyisocyanates are: 1,6-diisocyanatohexane (HDI), 1,T-methylene bis[4-isocyanatocyclohexane] (H12MDI), 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethyl-cyclohexane (isophorone diisocyanate, IPDI). Aliphatic polyisocyanates containing more than two isocyanate groups are for example the derivatives of above mentioned diisocyanates like 1,6-diisocyanatohexane biuret and isocyanurate. Examples of aromatic polyisocyanates are 1,4-diisocyanatobenzene (BDI), 2,4-diisocyanatotoluene (2,4-TDI), 2,6- diisocyanatotoluene (2,6-TDI), 1,T-methylenebis[4-isocyanatobenzene] (MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 1,5-naphtalene diisocyanate (NDI), tolidine diisocyanate (TODI) and p-phenylene diisocyanate (PPDI).

[0053] The hydrophilic compound (component BB) could be a polyol or polyamine comprising a functional group that can exhibit an ionic or non-ionic hydrophilic nature. Preferably it is a polyol or polyamine containing one or more anionic salt groups, such as a carboxylate and sulfonate salt groups or acid groups which may be converted to an anionic salt group, such as carboxylic acid or sulfonic acid groups. Preferred are hydroxycarboxylic acids represented by the general formula (HOxR(COOH)y, wherein R represents a straight or branched hydrocarbon residue having 1 to 12 carbon atoms, and X and y, independently, are integers from 1 to 3. Examples of these hydroxycarboxylic acids include citric acid, malic acid, lactic acid and tartaric acid. The most preferred hydroxycarboxylic acids are the α,α-dimethylolalkanoic acids, wherein x=2 and y=1 in the above general formula, such as for example, 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid.

[0054] Alternatively a polyol containing one or more potentially cationic groups such as amine groups, which may be converted in ammonium salt groups such as for example N-methyldiethanolamine, could be used as component BB.

[0055] The polymerizable ethylenically unsaturated compound (component CC) preferably has one or more reactive groups capable of reacting with isocyanate groups and at least one (meth)acrylated group.

[0056] Component CC could comprise one or more unsaturated functions, such as acrylic or methacrylic groups and essentially one nucleophilic function capable of reacting with isocyanate, such as a hydroxyl group. Preferred are (meth)acryloyl monohydroxy compounds, more particularly poly(meth)acryloyl mono-hydroxy compounds. Other useful compounds include the esterification products of aliphatic and/or aromatic polyols with (meth)acrylic acid having a residual average hydroxyl functionality of (about) 1. The partial esterification products of (meth)acrylic acid with tri-, tetra-, penta-or hexahydric polyols or mixtures thereof are preferred. In this context, it is also possible to use reaction products of such polyols with ethylene oxide and/or propylene oxide or mixtures thereof, or reaction products of such polyols with lactones, which add to these polyols in a ring-opening reaction. Examples of suitable lactones are gammabutyrolactone and, in particular, δ-valerolactone and ε-caprolactone. These modified or unmodified polyols are partly esterified with acrylic acid, methacrylic acid or mixtures thereof until the desired residual hydroxyl functionality is reached.

[0057] Particularly preferred are compounds comprising at least two (meth)acryl functions such as glycerol diacrylate, trimethylolpropane diacrylate, glycerol diacrylate, pentaerythritol triacrylate, ditrimethylolpropane triacrylate, dipentaerythritol pentaacrylate and their (poly)ethoxylated and/or (poly)propoxylated equivalents.

[0058] Other suitable compounds are the (meth)acrylic esters with linear and branched polyols in which at least one hydroxy functionality remains free, like hydroxyalkyl(meth)acrylates having 1 to 20 carbon atoms in the alkyl group. Preferred molecules in this category are hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate.

[0059] Hydroxyl functional polyester (meth)acrylates, polyether (meth)acrylates, polyether-ester (meth)acrylates, polycarbonate (meth)acrylates and polyether carbonate (meth)acrylates, comprising at least one hydroxy functionality, can be used as well.

[0060] Component DD, containing at least one reactive group capable of reacting with isocyanate groups, could comprise monomeric mono- and/or polyols and/or mono- and/or polyamines. Mono-, di- and/or triols could be chosen from the group consisting of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, 1,3-butylene glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1,4-cyclohexanediol, hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), diols derived from dimer fatty acids, 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester), glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane and/or castor oil. Neopentyl glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol and/or trimethylolpropane are preferred.

[0061] Diamines chosen from the group of ethylenediamine, 1,6-hexamethylenediamine, isophoronediamine, 1,3- and 1,4-phenylenediamine, piperazine, 4,4'-diphenylmethanediamine, amino-functional polyethylene oxides, amino-functional polypropylene oxides and hydrazine could be used as component DD. Ethylenediamine may be particularly preferred.

[0062] Component DD could furthermore comprise oligomeric and/or polymeric hydroxy-functional compounds. Such oligomeric and/or polymeric hydroxy-functional compounds could be, for example, polyesters, polyethers, polyether-esters, polycarbonates, polyether carbonate polyols and polycarbonate polyesters having a functionality of from 1.0 to 3.0, in each case with a weight average molecular weight in the range of from 300 to 4000, preferably from 500 to 2500 g mol·1. Hydroxyl functional polyesters may be considered particularly preferred.

[0063] The polymerizable ethylenically unsaturated water dispersible polyurethane could be prepared in a one-step or in a multi-step process.

[0064] In case of a one-step process, components AA to DD may be reacted in the presence of a bismuth or tin catalyst and an inhibitor for preventing the radical reaction of the ethylenically unsaturated groups, preferably under substantially anhydrous conditions and at a temperature between 20°C and 130°C until the reaction between the isocyanate groups and the isocyanate-reactive groups is substantially complete. The isocyanate content can be followed by titration with an amine.

[0065] In case of a multi-step process, the polymerizable ethylenically unsaturated water dispersible polyurethane is preferably obtained by a process comprising a first step comprising the reaction of a stoichiometric excess of compound AA with compound CC, a second step comprising the reaction of the product of the first step with compounds BB and DD and, optionally, a third step wherein the remaining free isocyanate groups provided by compound AA are reacted to give allophanate groups. [0066] The reactants are generally used in proportions corresponding to an equivalent ratio of isocyanate groups provided by compound AA to isocyanate-reactive groups provided by compounds BB, CC and DD of from (about) 0.8:1 to (about) 2:1 [0067] The optional third step preferably takes place at high temperature, usually in the range from 80°C to 130°C.

[0068] In a fourth step, the polyurethane obtained may be dispersed in an aqueous medium by adding the polymer slowly into water or by adding water to the polymer, preferably under high sheer mixing. The dispersion may require the preliminary neutralization of the hydrophilic groups provided by compound BB, such as the carboxylic acid or sulfonic acid groups, into anionic salts. This may be done by adding a neutralizing agent to the polymer or the water.

[0069] Suitable neutralizing agents for potentially anionic groups include ammonia, tertiary amines such as trimethylamine, triethylamine, triisopropylamine, tributylamine, N,N-dimethylcyclohexylamine, Ν,Ν-dimethylaniline, N-methylmorpholine, N-methylpiperazine, N-methylpyrrolidine and N-methylpiperidine and inorganic bases comprising monovalent metal cations, preferably alkali metals such as lithium, sodium and potassium and anions such as hydroxides, hydrides, carbonates and bicarbonates. Alkali metal hydroxides may be regarded particularly preferred.

[0070] Suitable neutralizing agents for potentially cationic groups may include acids chosen from the group of lactic acid, acetic acid, phosphoric acid, hydrochloric acid and/or sulfuric acid.

[0071] The necessary amount of these neutralizing agents can be calculated according to the total amount of acid groups to be neutralized.

[0072] The ethylenically unsaturated polyurethane preferably has a double bond equivalent (number of milli-equivalents of ethylenic double bonds per gram of solid) in the range from 0.05 to 6 meq/g, preferably of from 1 to 3 meq/g.

[0073] Preferably, the weight average molecular weight (Mw) of the ethylenically unsaturated polyurethane is between 1000 and 100 000 g mol·1, preferably between 3000 and 80 000 g mol·1, more preferably between 3000 and 60 000 g mol·1.

[0074] The aqueous dispersion optionally contains reactive diluents containing at least one group which can undergo free radical polymerization. The reactive diluents could be employed to the extent of 0 to 65% by weight of the ethylenically unsaturated polyurethane. Reactive diluents could be added before the dispersion is made or after. Addition before dispersion may be preferred in most cases.

[0075] Reactive diluents are, for example, the alcohols methanol, ethanol, 1 -propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, dihydrodicyclopentadienol, tetrahydrofurfuryl alcohol, 3,3,5-trimethylhexanol, octanol, decanol, dodecanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, 1,3-butylene glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1,4-cyclohexanediol, hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol esterified completely with (meth)acrylic acid, and the ethoxylated and/or propoxylated derivatives of said alcohols esterified completely with (meth)acrylic acid and the technical grade mixtures obtained during (meth)acrylation of the abovementioned compounds.

[0076] Further suitable reactive diluents are for example epoxy (meth)acrylates, polyurethane (meth)acrylates, polyether (meth)acrylates, poly-ester (meth)acrylates and polycarbonate (meth)acrylates having a number average molecular weight preferable comprised between 500 and 10 000 g mol·1.

[0077] The radiation curable aqueous polyurethane dispersion could furthermore comprise additives, such as photoinitiators, curing accelerators, flow agents, wetting agents, antifoaming agents, levelling agents, matting agents, fillers and other customary auxiliaries.

[0078] The photoinitiators could be of the unimolecular (type I) or of the bimolecular type (type II).

[0079] Suitable type-1 photoinitiators are aromatic ketone compounds, such as e.g. benzophenones in combination with tertiary amines, alkylbenzophenones, 4,4'-bis(dimethylamino)benzophenone (Michler's ketone), anthrone and halogenated benzophenones or mixtures of the types mentioned.

[0080] Type-ll photoinitiators could comprise, e.g.: benzoin and its derivatives, benzil ketals, acylphosphine oxides, 2,4,6-trimethyl-benzoyl-diphenylphosphine oxide, bisacylphosphine oxides, phenylglyoxylic acid esters, camphorquinone, alphaaminoalkylphenones, alpha,alpha-dialkoxyacetophenones and alphahydroxyalkylphenones.

[0081] Photoinitiators which can easily be incorporated into aqueous compositions may be preferred. Such products are, for example, Irgacure® 500 (a mixture of benzophenone and (1-hydroxycyclohexyl) phenyl ketone, Ciba, Lampertheim, DE), Irgacure® 819 DW (phenyl-bis-(2,4,6-trimethylbenzoyl)-phosphine oxide, Ciba, Lampertheim, DE), Esacure® KIP EM (oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)-phenyl]-propanone], Lamberti, Aldizzate, Italy). Mixtures of these compounds can also be employed.

[0082] The amount of photoinitiator(s) is preferably comprised in the range from 0.5 to 8% by weight, preferably between 2 and 5 % by weight relative to the ethylenically unsaturated group comprising compounds (polyurethane and optional reactive diluents).

[0083] According to an embodiment, the radiation-curable polymer formulation is a varnish composition that comprises a polyester acrylate resin and a polyester polyol resin, or a polyester resin comprising acrylate and polyol functions, or a polyester acrylate resin with grafted hydroxyl groups, a reactive thinner and at least one photoinitiator. Preferably, the varnish composition is applied on the carrier plate either directly or on any intermediary layer on the front face so as to form a varnish layer having the desired thickness. Preferably the varnish composition is cured over a thickness of 0.1 to 0.3 pm using electromagnetic radiation having a wavelength comprised in the range from 150 to 200 nm, preferably from 170 to 174 nm, to form a partially (superficially) cured varnish layer, and then further curing the varnish composition over the remaining thickness using electromagnetic radiation having a wavelength comprised in the range from 200 to 320 nm (preferably in the range from 220 o 260 nm) or electron-beam curing.

[0084] Preferably, the varnish composition comprises a least one reticulation activator (preferably a polyfunctional acrylate monomer, like for example PETA (pentaerythritol triacrylate) or PETTA (pentaerythritol tetracrylate)), one or more additives to adjust the gloss level of the varnish layer, one or more fillers and/or one or more wetting agents.

[0085] Preferably, the polyester acrylate resin and the polyester polyol resin, or the polyester resin comprising acrylate and polyol functions, or the polyester acrylate resin with grafted hydroxyl groups represent between 40 and 60% by weight of the total weight of the varnish composition. Preferably, the reactive thinner represents between 40 and 60% by weight of the total weight of the varnish composition.

[0086] Preferably, the photoinitiator represents 0.1 and 20% by weight of the total weight of the varnish composition.

[0087] Optionally, the varnish composition could be required to have a viscosity of between 0.2 to 1.0 Pas.

[0088] According to an embodiment, the varnish composition is applied on the carrier plate with a surface density comprised in the range from 1 to 100 g/m2, preferably in the range from 2 to 50 g/m2 and still more preferably in the range from 5 to 20 g/m2.

[0089] The reactive thinner could be an acrylate monomer, mono or polyfunctional, like, for example, isobornyl acrylate, hexanedioldiacrylate, propoxylated glycerol triacrylate (OTA® 480 from Cytec), triacrylate or tetraacrylate like alkoxylated pentaerythritol tetraacrylate (Ebecryl® 40 from Cytec). The reactive thinner preferably represents between 20 and 40% of the total weight of the varnish composition.

[0090] Examples of radiation sources that can be used for electromagnetic radiation generation are medium and high-pressure mercury vapour lamps, lasers, pulsed lamps (flashlights), halogen lamps and excimer emitters.

[0091] Irradiation by medium pressure mercury vapour UV radiators may be preferred The radiation dose could, e.g., be in the range of from 80 to 3000 mJ/cm2.

[0092] Alternatively or additionally, curing could be achieved by bombardment with high-energy electron beams (EB) at for instance 150-300 keV. The presence of photoinitiators in the formation is not necessary for EB curing.

[0093] According to an embodiment of the invention, solid inorganic particles are attached to the carrier plate by the radiation-curable polymer formulation, and the carrier plate is cut into smaller floor or wall covering elements after the curing step by cutting along cutting lines, incorporation of the solid inorganic particles being carried out in such a way that strip-shaped areas running along the cutting lines are spared from the solid inorganic particles.

[0094] An aspect of the invention relates to a floor or wall covering element produced in accordance with a method described.

Brief Description of the Drawings [0095] By way of example, preferred, non-limiting embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1: is a cross-sectional view of a part of a composite carrier plate comprising on its front side a wear layer including solid wear-resistant particles;

Fig. 2: is a cross-sectional view of a another part of the composite carrier plate of Fig. 1.

Detailed Description of Embodiments [0096] In the following description, the to-be-exposed surface of the floor or wall covering is referred to as the “front side”, while the opposite side of the floor or wall covering, facing the wall or the subfloor, is called the “rear side” or “back side”.

[0097] Wear layers of floor or wall coverings comprising wear-resistant particles are known for particular types of substrates.

[0098] Figs. 1 and 2 illustrate a floor or wall covering element 10 (panel, plank, tile, etc.) produced in accordance with an embodiment of the present invention. The floor or wall covering element 10 comprises a structural core 12, a radiation-cured wear layer 14 on the front side, and a backing or balancing layer 16 on the back side.

[0099] The floor or wall covering element 10 comprises mechanical connection profiles 18, 20 along at least two of its edges. The interlocking elements or connectors are of complementary shapes. Fig. 1 shows the first connector 18, which can mechanically engage with the second connector 20, shown in Fig. 2. The shapes of the connectors 18, 20 are preferably such that they effect an interlocking when the connectors are engaged. Preferably, the interlocking occurs both (a) in the direction normal to the front side and (b) in the direction parallel to the front side and normal to the edges that are put together. It should be noted, however, that embodiments of the connectors providing interlocking effect only in one of these directions are not excluded and may even be preferred in certain applications. The connectors shown in Figs. 1 and 2 comprise, respectively, a first locking element in the form of a protruding tongue 22 and a second locking element in the form of a groove 24. The rear part of the groove 24 is delimited by a bracket 26, which is shaped complementarily to the rear side 28 of the tongue 22.

[0100] The connection profiles 18, 20 are mechanically machined into the edges of the structural core 12. The rigidity of the composite carrier plate forming the structural core 12 is, therefore, chosen such that the machining (e.g. cutting, milling) can be effected without difficulty. This may be achieved using a composite carrier plate that comprises a mineral or polymeric cement and a mineral or organic, preferably fibrous, filler or reinforcement material, wherein at least one of the cement and the filler or reinforcement material comprises a mineral material or mineral material mixture representing at least 25%, preferably at least 35%, more preferably at least 50%, by weight, of the carrier plate.

[0101] The composite carrier plate forming the structural core 12 preferably consists of a fibrocement plate comprising mineral (e.g. glass), polymeric and/or cellulosic fibers embedded in a mineral, preferably hydraulic, cement. As used herein, the term “cellulosic fibers” is intended to include lignocellulosic fibers (e.g. sisal fibers, hemp fibers, bamboo fibers, wood pulp, etc.). The fibers may be microfibrillated. Preferably, the fibrocement comprises a mixture of cellulosic fibers of two or more different SR fineness degrees (measured according to ISO 5267-1).

[0102] As an alternative to a fibrocement plate as the structural core layer, a polymer-based core layer charged with at least 25% by weight (with respect to the total weight of the carrier plate), preferably more, of a mineral filler or reinforcement material. Filler or reinforcement material could comprise, e.g., calcium carbonate, limestone, gypsum, ground stones, glass fibers, clay, or the like. The presence of organic filler or reinforcement materials is not excluded. For instance, the composite carrier plate could comprise cellulosic or polymeric fibers (e.g. wood flour or saw dust).

[0103] It should be noted that the expression “solid inorganic particles” designates inorganic particles in the solid state. The solid inorganic particles do not undergo a phase change during the bonding step and remain distinguishable (i.e. do not form a uniform phase) with the anchoring matrix into which they are incorporated. Preferably, the solid inorganic particles comprise ceramic particles, e.g., carbide, nitride and/or oxide particles. It should be noted that the solid inorganic particles may be provided as part of a particle mixture or a powder comprising other particles, e.g. organic particles. The other particles, if any, could participate in the formation of the anchoring matrix and become indistinguishable from it in the final product. Alternatively, the other particles could be embedded in the polymeric anchoring matrix substantially in the same way as the inorganic particles and remain distinguishable in the final product.

[0104] The wear layer could comprise hard inorganic particles incorporated therein. Such particles could, e.g., be AI2O3 particles. Preferably, the solid inorganic particles have a particle size of -40 +635 mesh, more preferably of -45 +400 mesh, yet more preferably of -45 +325 mesh, and most preferably of -60 +270 mesh. As used herein, mesh sizes are indicated as US standard mesh sizes (i.e. the number of openings per linear inch of the sieve). A "+" before the mesh indicates the particles are retained by the sieve, whereas a before the mesh size indicates the particles pass through the sieve. A particle size indicated as -20 +400 mesh thus means that at least 90% (by weight) of the particles pass through the 20 mesh sieve but are retained by the 400 mesh sieve. See e.g. page T848 of the Aldrich 2003-2004 Catalog/Handbook of Fine Chemicals for reference. The following table indicates the correspondence between opening size and US mesh number:

[0105] Embodiments of the invention could use the following particle sizes (other particle sizes not being excluded in alternative embodiments): -40 +45 mesh, -45+50 mesh, -50 +60 mesh, -60+70 mesh, -70+80 mesh, -80+100 mesh, -100+120 mesh, -120+140 mesh, -140+170 mesh, -170+200 mesh, -200 +230 mesh, -230 +270 mesh, -270 +325 mesh, -325 +400 mesh, -60 +325 mesh, -60 +230 mesh, -60 +200 mesh, -80 +270 mesh, -100 +230 mesh, -120 +200 mesh.

Example 1 [0106] A fibrocement plate (hydraulic cement-based, with a mixture of cellulosic and polymeric fibres) having a thickness of 6 mm was covered with the ethylenically unsaturated polyurethane formulation specified in Table 1 hereinafter.

[0107] The coating was applied in an air knife coating process under conditions yielding a coating thickness comprised between 10 and 12 μm.

[0108] In table 1, the UV-curable polyurethane is Desmolux® U 10, an aliphatic urethane acrylate, from Bayer; HDDA is hexandioliacrylate and OTA 480 is a triacrylated reactive diluent based on a glycerol derivative, both from Allnex; Ebecryl™ 770 is a carboxylated polyester acrylate oligomer diluted with 40% of hydroxyethylmethacrylate monomer from Allnex; Esacure KIP 100 F is a mixture of oligo [ 2-hydroxy-2-methyl-1-[ 4-(1-methylvinyl) phenyl] propanone] and 2-hydroxy-2-methyl-1-phenyl propan-1-one from Lamberti; Additol® BP is benzophenone from Allnex; Ebecryl™ is an amine-based photoactivator from Allnex; Disperbyk® 185 is a wetting and dispersing additive from Byk Chemie; Syloid® Rad 2005 is a matting agent from Grace; Deuteron® MK is a matting agent from Deuteron; Orgasol® 2002 DNAT 1 is a spheroidal powder of polyamide 12 used as reinforcing and matting agent (from Arkema); Alodur® F 800 is aluminum oxide from Imerys.

[0109] The coating formulation of table 1 was applied on the fibrocement plate at a temperature of 25°C, by an air-knife coating process.

[0110] The fibrocement plate coated with the uncured ethylenically unsaturated polyurethane formulation subsequently was subjected for 6 seconds to irradiation with ultraviolet light emitted by a 160 W/cm medium pressure mercury vapour UV-bulb (Fusion UV Systems Ltd) with a total UV dose of 1500 mJ/cm2.

Examples 2 and 3 [0111] A fibrocement plate (hydraulic cement-based, comprising a mixture of synthetic fibres and two different grades of cellulosic fibres) having a thickness of 5.5 mm was covered with the aqueous ethylenically unsaturated polyurethane dispersions detailed in Table 2 hereinafter.

[0112] The coating was applied by a smooth roll-coating process under conditions yielding a dry coating thickness comprised between 10 and 12 μm.

[0113] In table 2, the UV-curable polyurethane dispersion (UV-PUD) is Bayhydrol® UV 2720/1 XP from Bayer, characterized by a solid content of 40%; the pH stabilizer is AMP 90™, 2-Amino-2-methyl-1 -propanol, from Dow; the matting agent is a 4/1 mixture of Deuteron® MK from Deuteron and Acematt®TS 100 from Evonik; the antifoaming agent is Neocryl AP 2861 from DSM Coating Resins; the wetting agent is Byk-348 from Byk Chemie; the photoinitiator is Irgacure® 2100 from Ciba Speciality Chemicals in example 2 and Esacure® KIP 100 F from Lamberti in example 3; the reactive diluent used (only) in example 3 for dissolving the photoinitiator in order to have it properly dosed is SR 238 (HexaneDiolDiAcrylate) from Arkema.

[0114] The formulations of examples 2 and 3 were applied on the fibrocement plate at a temperature of 50°C. After evaporation of the water in a convection oven at 100°C, curing was effected by exposure, during 6 seconds, to UV light emitted by a 160 W/cm medium pressure mercury vapor UV-bulb (Fusion UV Systems Ltd) with a total UV dose of 1500 mJ/cm2.

Examples 5, 6, 7 and 8 [0115] A fibrocement plate (hydraulic cement-based, comprising a mixture of synthetic fibres and two different grades of cellulosic fibres) having a thickness of 6 mm was covered with the radiation-curable formulations indicated in Table 3 hereinafter.

[0116] In table 3, the polyester acrylate is Desmolux® XP 2744 from Bayer, the polyester polyol is Desmophen® FW 1652 from Bayer, the polyester acrylate with grafted hydroxyl groups is Desmolux® FW 5094 from Bayer, the reactive thinner is an hexane diol diacrylate (e.g. Sartomer SR 238 from Cray Valley), the curing speed adjuster is an ethoxylated pentaerythritol tetraacrylate (e.g. Miramer4004 from Rahn), the photoinitiator is Irgacure® 184 from Ciba, the wetting agent is silicone (e.g. Byk 307 from Byk), and the matting agent is silica, for example Syloid® RAD 2005 from Grace.

[0117] The varnish composition was applied on the fibrocement plate and was partially cured in a nitrogen atmosphere using a first radiation source having a wavelength comprised between 170 and 174 nm (in these examples a Xenon lamp with an emission at 172 nm was used) Due to limited penetration of this radiation, only the upper layer of the varnish composition was cured, over a thickness of 0.1 to 0.5 μm. The rest of the thickness of the varnish composition still remained liquid. As a consequence, the upper surface of the varnish layer presented a shrinkage pattern

which diffused light and generated a low gloss aspect. The partially cured varnish layer was then cured through the remaining thickness using a second curing device emitting UV radiation having a wavelength between 200 and 320 nm. In the examples, a high pressure mercury vapor lamp was used.

[0118] After curing, the decorative fibrocement plates coated according to examples 1 to 8 showed outstanding wear resistance, examined by a Taber abrasion resistance test with CS-17 abrasive wheels under a load of 1 kg according to JIS K 7204 (good after 15 000 revolutions).

[0119] While specific embodiments have been described herein in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims (20)

1. Un procédé de fabrication d’un revêtement de sol ou de mur, comprenant: la mise à disposition d’une plaque de support, préférablement sans PVC, comprenant une matrice de ciment minéral ou polymérique et un matériau de remplissage ou de renforcement minéral ou organique, préférablement fibreux, à la condition qu’au moins un de la matrice de ciment et du matériau de remplissage ou de renforcement comprenne un matériau minéral ou un mélange de matériaux minéraux représentant au moins 25%, préférablement au moins 35%, plus préférablement au moins 50%, en poids, de la plaque de support, la plaque de support ayant une face avant et une face arrière; l’application d’une formulation polymérique à durcissement par radiation sur ladite face avant, le durcissement de ladite formulation polymérique par exposition de ladite formulation de polyuréthane à durcissement par radiation à une radiation de sorte à produire ainsi une couche anti-usure au moins localement sur ladite face avant.A method of manufacturing a floor or wall covering, comprising: providing a support plate, preferably PVC-free, comprising a matrix of mineral or polymeric cement and mineral filler or reinforcing material or organic, preferably fibrous, provided that at least one of the cement matrix and the filling or reinforcing material comprises a mineral material or a mixture of mineral materials of at least 25%, preferably at least 35%, plus preferably at least 50%, by weight, of the support plate, the support plate having a front face and a back face; applying a radiation-curable polymeric formulation to said front face, curing said polymeric formulation by exposing said radiation-curable polyurethane formulation to radiation so as to thereby provide an anti-wear layer at least locally on said front face. 2. Le procédé tel que revendiqué à la revendication 1, dans lequel ladite formulation de polyuréthane à durcissement par radiation comprend un mélange de particules inorganiques solides, qui deviennent fermement incorporées dans ladite couche anti-usure lors de l’étape de durcissement.The process as claimed in claim 1, wherein said radiation-curable polyurethane formulation comprises a mixture of solid inorganic particles, which become firmly incorporated into said anti-wear layer during the curing step. 3. Le procédé tel que revendiqué à la revendication 2, dans lequel lesdites particules inorganiques solides incluent des particules céramiques, p. ex., carbures, nitrures et/ou particules d’oxydes.The process as claimed in claim 2, wherein said solid inorganic particles include ceramic particles, e.g. eg, carbides, nitrides and / or oxide particles. 4. Le procédé tel que revendiqué à la revendication 2 ou 3, dans lequel lesdites particules inorganiques solides sont sélectionnées dans le groupe consistant en: AI2O3, S12O, S13N4, SiOxNx, AIN, BN, ΑΙΝΟ, MgO, ZnO, SnO2, NiO, ZrO2, Cr2O3, MOO2, RuO2, CoOx, CuOx, VOx, FeOx, MnOx, T1O2, CaF2, BaF2, MgF2, SiC, WC, B4C, des oxydes ternaires et/ou complexes impliquant une ou plusieurs des espèces élémentaires des composés mentionnés, et des mélanges de ceux-ci.4. The process as claimed in claim 2 or 3, wherein said solid inorganic particles are selected from the group consisting of: Al2O3, S12O, S13N4, SiOxNx, AlN, BN, ΑΙΝΟ, MgO, ZnO, SnO2, NiO, ZrO2, Cr2O3, MOO2, RuO2, CoOx, CuOx, VOx, FeOx, MnOx, TiO2, CaF2, BaF2, MgF2, SiC, WC, B4C, ternary oxides and / or complexes involving one or more of the elemental species of the compounds mentioned, and mixtures thereof. 5. Le procédé tel que revendiqué à l’une quelconque des revendications 1 à 4, dans lequel une couche de décoration est liée à la face avant de ladite plaque de support et dans lequel la formulation polymérique à durcissement par radiation est appliquée sur la couche de décoration.The method as claimed in any one of claims 1 to 4, wherein a decorative layer is bonded to the front face of said support plate and wherein the radiation curable polymeric formulation is applied to the layer. of decoration. 6. Le procédé tel que revendiqué à la revendication 5, dans lequel la couche de décoration porte un motif de décoration imprimé.The method as claimed in claim 5, wherein the decorative layer bears a printed decorative pattern. 7. Le procédé tel que revendiqué à la revendication 5 ou 6, dans lequel la couche de décoration est liée à la face avant de ladite plaque de support par un adhésif, préférablement par un adhésif thermofusible (p. ex. un adhésif thermofusible à base de polyuréthane ou à base d’epoxy) ou par un adhésif à base de polyvinylacetate.The method as claimed in claim 5 or 6, wherein the decorative layer is bonded to the front face of said backing plate by an adhesive, preferably a hot melt adhesive (eg a hot melt adhesive based on polyurethane or epoxy) or polyvinyl acetate adhesive. 8. Le procédé tel que revendiqué à la revendication 5, 6 ou 7, dans lequel la couche de décoration comprend une couche de plastisol fusionné comme couche de support d’impression.The method as claimed in claim 5, 6 or 7, wherein the decorative layer comprises a layer of plastisol fused as a printing support layer. 9. Le procédé tel que revendiqué à l’une quelconque des revendications 1 à 8, dans lequel la plaque de support comprend une plaque de fibrociment.The process as claimed in any one of claims 1 to 8, wherein the support plate comprises a fiber cement sheet. 10. Le procédé tel que revendiqué à la revendication 9, dans lequel ladite plaque de fibrociment comprend un liant cimentaire et des fibres organiques, p. ex. un mélange de fibres polymériques et de fibres cellulosiques.The process as claimed in claim 9, wherein said fiber cement sheet comprises a cementitious binder and organic fibers, e.g. ex. a mixture of polymeric fibers and cellulosic fibers. 11. Le procédé tel que revendiqué à la revendication 10, dans lequel ladite formulation polymérique à durcissement par radiation est appliquée directement sur la plaque de fibrociment.The process as claimed in claim 10, wherein said radiation curable polymeric formulation is applied directly to the fiber cement sheet. 12. Le procédé tel que revendiqué à la revendication 10 ou 11, dans lequel ledit liant cimentaire est un ciment hydraulique.The process as claimed in claim 10 or 11, wherein said cementitious binder is a hydraulic cement. 13. Le procédé tel que revendiqué à l’une quelconque des revendications 1 à 12, dans lequel ladite formulation polymérique à durcissement par radiation comprend au moins un acétate de polyuréthane à durcissement par radiation, au moins un promoteur d'adhésion acide et au moins un diluant réactif mono- ou polyfonctionnel.The process as claimed in any one of claims 1 to 12, wherein said radiation curable polymeric formulation comprises at least one radiation curable polyurethane acetate, at least one acidic adhesion promoter and at least one a mono- or polyfunctional reactive diluent. 14. Le procédé tel que revendiqué à l’une quelconque des revendications 1 à 12, dans lequel la formulation polymérique à durcissement par radiation est une formulation de polyuréthane à durcissement par radiation en dispersion aqueuse, obtenue par la réaction de: au moins un polyisocyanate, au moins un composé hydrophile contenant au moins un groupe réactif capable de réagir avec des groupes isocyanates et au moins un groupe qui est capable de rendre le polyuréthane dispersable dans un milieu aqueux soit directement soit après une réaction avec un agent neutralisant pour fournir un sel, au moins un composé éthylèniquement insaturé contenant au moins un groupe réactif capable de réagir avec des groupes isocyanates; et au moins un composé, qui diffère dudit au moins un composé hydrophile, contenant au moins un groupe réactif capable de réagir avec des groupes isocyanates.The process as claimed in any one of claims 1 to 12, wherein the radiation curable polymeric formulation is an aqueous dispersion radiation curable polyurethane formulation obtained by the reaction of: at least one polyisocyanate at least one hydrophilic compound containing at least one reactive group capable of reacting with isocyanate groups and at least one group which is capable of rendering the polyurethane dispersible in an aqueous medium either directly or after a reaction with a neutralizing agent to provide a salt at least one ethylenically unsaturated compound containing at least one reactive group capable of reacting with isocyanate groups; and at least one compound, which differs from said at least one hydrophilic compound, containing at least one reactive group capable of reacting with isocyanate groups. 15. Le procédé tel que revendiqué à l’une quelconque des revendications 1 à 12, dans lequel la formulation polymérique à durcissement par radiation est une composition de vernis qui comprend une résine polyester acrylate et une résine polyester polyol, ou une résine polyester comprenant des fonctions acrylates et polyols, ou une résine polyester acrylate avec des groupes hydroxyles greffés, un diluant réactif et au moins un photo-initiateur.The process as claimed in any one of claims 1 to 12, wherein the radiation curable polymeric formulation is a lacquer composition which comprises a polyester acrylate resin and a polyester polyol resin, or a polyester resin comprising acrylate and polyol functions, or a polyester acrylate resin with grafted hydroxyl groups, a reactive diluent and at least one photoinitiator. 16. Le procédé tel que revendiqué à l’une quelconque des revendications 1 à 15, dans lequel particules inorganiques solides sont attachées à la plaque de support par ladite formulation polymérique à durcissement par radiation, dans lequel ladite plaque de support est coupée en éléments de revêtements sol et de mur plus petits, après l’étape de durcissement, par découpe le long de lignes de découpe et dans lequel l’incorporation des particules inorganiques solides est réalisée de telle façon que les domaines en forme de bande le long desdites lignes de découpe soient épargnées desdites particules inorganiques solides.The process as claimed in any one of claims 1 to 15, wherein solid inorganic particles are attached to the carrier plate by said radiation-curable polymeric formulation, wherein said carrier plate is cut into carrier elements. smaller ground and wall coatings, after the hardening step, by cutting along cutting lines and in which the incorporation of solid inorganic particles is carried out such that the strip-like domains along said lines of cutting are spared said solid inorganic particles. 17. Le procédé conformément aux revendications 4, 7, 10 et 12.17. The process according to claims 4, 7, 10 and 12. 18. Le procédé conformément à la revendication 17 et l’une des revendications 13, 14 et 15.18. The process according to claim 17 and one of claims 13, 14 and 15. 19. Le procédé conformément aux revendications 17 et 16.19. The process according to claims 17 and 16. 20. Un élément de revêtement de sol ou de mur fabriqué conformément à un procédé tel que revendiqué à l’une quelconque des revendications 1 à 19.20. A floor or wall element made in accordance with a method as claimed in any one of claims 1 to 19.