Patent Application
20240368395
This application claims priority under 35 USC § 119 (a)-(d) from EP patent application Ser. No. 21152949.0, which was filed on Jan. 22, 2021, the entire content of which is incorporated herein by reference.
The present invention relates to a thermosetting resin composition of the kind used for manufacturing panels having a decorative surface, or so-called decorative panels. The invention also relates to a method for manufacturing paper printable with inkjet for use as a decor paper in such panels and to the paper obtainable with such method. According to a variant the obtained decor paper may be used in a laminated assembly other than a panel, such as in so-called CPL (compact laminate) or HPL (high pressure laminate).
More particularly the invention is related to a method for manufacturing laminate panels, wherein said panels at least comprise a substrate material and a provided thereon top layer with a printed decor. The method could be used for manufacturing panels, the top layer of which is formed from thermosetting resin and one or more paper layers, wherein said paper layers comprise a decor paper having a printed pattern. The panels of the invention may relate to furniture panels, ceiling panels, flooring panels or similar, wherein these panels preferably comprise a wood based substrate, such as an MDF or HDF substrate (Medium or High Density Fiberboard) or a substrate material consisting of or essentially made of wood particleboard. Alternatively the panels can comprise a polymeric based substrate, preferably thermoplastic based substrate, such as PVC (Polyvinyl chloride), PP (Polypropylene), LVT (Luxury Vinyl Tile), SPC (Solid Polymer Composite) or WPC (Wood polymer composite) based substrate. The invention can further relate to mineral-based board of cement-based board, like for example, fiber cement based board or magnesium oxide based board.
Traditionally, the decor or pattern of such panels is printed on paper by means of offset or rotogravure printing. The obtained paper is taken up as a decorative paper in a so-called laminate panel. For manufacturing the panels the DPL process can be practiced. According to the DPL process (Direct Pressure Laminate) the already printed paper or decorative paper is provided with melamine resin to form a decorative layer. Afterwards a stack is formed comprising at least a plate shaped substrate, said decorative layer and possibly a protective layer on top of said decorative layer, wherein said protective layer or overlay is based on resin and/or paper as well. Said stack is pressed and the press treatment results in a mutual connection or adherence of the decorative paper, the substrate and the protective layer, as well as in a hardening of the resin present in the stack. As a result of the pressing operation a decorative panel is obtained having a melamine surface, which can be highly wear resistant. At the bottom side of the plate shaped substrate a counter layer or balancing layer can be applied, or as an alternative a decorative layer might be attached to the bottom side as well, especially in the case of laminate panels for furniture. Such a counter layer or balancing layer or any other layer at the bottom side of the laminate panel restricts or prevents possible bending of the decorative panel, and is applied in the same press treatment, for example by the provision of a resin carrying paper layer as the lowermost layer of the stack, at the side of the stack opposite said decorative layer. For examples of a DPL process reference is made to EP 1 290 290, from which it is further known to provide a relief in said melamine surface during the same press treatment or pressing operation, namely by bringing said melamine surface in contact with a structured press element, for example a structured press plate. In case of HPL or CPL the decorative paper and optionally the wear layer is pressed on kraft paper.
The printing of paper by means of an analog printing process, such as by rotogravure or offset printing, at affordable prices inevitably leads to large minimal order quantities of a particular decorative paper or foil and restricts the attainable flexibility. A change of decor or pattern necessitates a standstill of the printing equipment of about 8 hours. This standstill time is needed for exchange of the printing rollers, the cleaning of the printing equipment and for adjusting the colors of the new decor or pattern to be printed.
Instead of analog printing techniques, digital printing techniques, especially inkjet printing techniques, are becoming increasingly popular for the creation of decors or patterns, be it on paper, on foil or directly on a plate-shaped substrate possibly with the intermediary of preparatory layers. Such digital techniques can enhance the flexibility in the printing of decors significantly. Reference is amongst others made to the EP 1 872 959, WO 2011/124503, EP 1 857 511, EP 2 431 190, EP 2 293 946, WO 2014/084787, WO 2015/140682 and the WO 2015/118451, where such techniques are disclosed.
EP 1 044 822, EP 1 749 676 and EP 2 274 485 disclose the use of an inkjet receiver coating to enhance the printing quality on a raw decor paper. Such inkjet receiver coating comprises pigments, especially silica, and a crosslinked polymer such as polyvinyl alcohol (PVA).
During private research, the inventor has also encountered problems with subsequent impregnation and lamination of printed paper. In particular, the inventor has encountered problems with water resistance of the décor paper during lamination under heat in presence of a polycondensation curing resin like melamine. Water resistance for laminate panel is defined by norm EN 438 and is measured according to two different tests:
The inventor has noticed that decor paper provided with inkjet receiver layer are more prone to fail this tests since boiling water and water vapor seem to affect the interaction between the inkjet receiver layer and the ink and the interphase between the décor paper and the overlay.
The present invention aims in the first place at an alternative method for manufacturing panels having a decorative surface or paper, for use in such panels, and seeks, in accordance with several of its preferred embodiments, to solve one or more of the problems arising in the state of the art.
Therefore the present invention, in accordance with its first independent aspect, relates to a method for manufacturing laminate panels, wherein said panels at least comprise a substrate material and a provided thereon top layer, wherein the top layer comprises at least a décor paper, that comprises the steps of:
According to a first measure the thermosetting resin composition can comprise one or more modifiers wherein said the total content of said modifiers is below 10%, preferably below 7%, more preferably below 5%, even more preferably below 3% by weight of the resin. The inventor has found that by reducing the quantity of modifiers in the resin receipt water resistance of the panel is highly increased and the performance of the panel to both the vapor and boiling water test are improved.
Modifiers are substances that are added to the resin receipt in order to modify the plasticity of the thermosetting resin itself. Said modifiers can be grouped in external modifiers and internal modifiers. External modifiers are substances that don't react chemically with the resin, but that create physical irregularities in the microstructure of the resin thereby modifying its plasticity. Examples of external modifiers can be: poly-alcohols, polyglycols, glycerin, polyvinyl alcohol, phenoxyethanol, phenyl glycol, saccharides, polymers, dimethyl formamides. Examples of poly-alcohols can be: butanol, butanediol, propanol, sorbitol. Examples of poly glycols can be: tri-ethylene glycol, diethylene glycol, ethylene glycol. Examples of polymers can be: acrylic resins, polyesters, epoxy resins. Internal modifiers are substances that interact with the resin thereby inhibiting or limiting the crosslinking reaction of the resin itself thereby modifying its plasticity. Examples of internal modifiers can be: Caprolactam, guanamines, toluenesulphonamide, dicyandiamide, urea. Examples of guanamines can be benzo-guanamines or aceto-guanamines.
According to a second measure the thermosetting resin composition can comprise one or more external modifiers in an amount below 5%, more preferably below 3%, even more preferably below 1% by weight of the resin. In a preferred embodiment, the resin can be free from external modifiers. For example, the resin can comprise only internal modifiers. Preferably, the resin can comprise at least internal modifiers in an amount below 7%, preferably below 5%, even more preferably below 3% by weight of the resin. Preferably, the resin can comprise at least internal modifiers in an amount above 2%, preferably 3%, for example above 5% by weight of the resin. In fact, inventors have found that relevant quantity of external modifiers can negatively affect the water resistance of the laminate panel, whereas the presence of internal modifiers have a more limited impact on the water resistance. Therefore, by increasing the quantity of internal modifiers while reducing the quantity of external modifiers it is therefore possible to improve the water resistance of the panel without affecting the flexibility of the thermosetting resin of the top layer.
Preferably said thermosetting resin can comprise at least, or be constituted by, melamine-based resin, such melamine-based resin is a resin that polycondensates while exposed to heat in a pressing operation. The polycondensation reaction creates water as a by-product. It is particularly with these kinds of thermosetting resins, namely those creating water as a by-product, that the present invention is of interest. In the preferred embodiment the thermosetting resin can comprise at least melamine formaldehyde resin, preferably with a formaldehyde to melamine ratio of 1.4 to 2.
According to a third measure the thermosetting resin composition can comprise at least etherified melamine resin. The thermosetting resin can also comprise a mixture of at least melamine formaldehyde resin and etherified melamine resin, preferably in a ratio variable between 10:90 and 90:10, preferably between 30:70 and 70:30, for example 50:50. Other examples of such thermosetting resins leading to a similar polycondensation reaction include ureum-formaldehyde based resins and phenol-formaldehyde based resins. It is not excluded that other resins like water-based polyurethane dispersions or water-based acrylic dispersions are being used or mixed combination thereof. The inventor have noticed that etherified resin shows a better water resistance behavior than melamine formaldehyde resin although the second one shows a higher elasticity, thus a mixture of the two resins can provide for a top layer with sufficient water enhanced water resistance and elasticity.
It is also possible that the top layer comprises multiple layers for example a decorative layer comprising the décor paper and a wear layer above said top layer. Said wear layer can comprise said thermosetting resin, preferably an overlay paper impregnated with said thermosetting resin. According to an embodiment of the invention it is possible that the thermosetting resin impregnating the décor paper is different for the thermosetting resin impregnating the overlay paper. For example, one between the wear layer and the decorative layer can comprise a thermosetting resin comprising at least melamine formaldehyde resin, wherein the other can comprise a thermosetting resin comprising at least etherified melamine resin. In any case it is not excluded that the wear layer and the decorative layer comprise the same thermosetting resin.
The wear layer can comprise wear resistant particles, preferably aluminum dioxide.
Preferably the décor paper can be impregnated with a quantity of thermosetting resin equaling 40 to 250% dry weight of resin as compared to weight of the paper.
Preferably the décor paper can be provided with such an amount of thermosetting resin, that at least the paper core is satisfied with the resin. Such satisfaction can be reached when an amount of resin is provided that corresponds to at least 1.5 or at least 2 times the paper weight. It should be clear that the resin, which is provided on the paper layer, is not necessarily only available in the core of the paper, but may form surface layers on both flat sides of the paper. The inkjet receiver coating may then be present on the surface of the paper with the intermediary of such a surface layer of thermosetting resin. According to a special embodiment, the paper layer is firstly impregnated through or satisfied, and, afterwards, at least at the side thereof to be printed, resin is partially removed and possibly said inkjet receiver coating is provided.
Preferably, the obtained resin provided paper layer, i.e. after provision of the thermosetting resin, has a relative humidity lower than 15%, and still better of 10% by weight or lower.
Preferably the step of providing said paper layer with thermosetting resin involves applying a mixture of water and the resin on said paper layer. The application of said mixture might involve immersion of the paper layer in a bath of said mixture and/or spraying, jetting or otherwise coating said mixture on said paper. Preferably the resin is provided in a dosed manner, for example by using one or more squeezing rollers and/or doctor blades to set the amount of resin added to the paper layer.
Preferably, the method of the first aspect of the invention further comprises the step of applying a counter layer or balancing layer at the surface of the substrate opposite the printed paper layer. The case of a paper-based decor layer, the counter layer or balancing layer preferably comprises a paper layer and thermosetting resin, preferably the same resin as the top layer.
Preferably the mutual adherence of the substrate, the possible counter layer and the possible transparent or translucent layer is obtained in one and the same press treatment. According to the most preferred embodiment of the fourth aspect, these steps are taken up in a DPL process. According to alternative embodiments these steps are taken up in a CPL or in a HPL process.
The substrate can be a wood-based board or panel, preferably a such as to a particle board or an MDF or HDF board. Preferably, the method of the first aspect of the invention is a floor panel manufacturing method and comprises the step of providing said substrate with coupling elements for mechanical coupling to another floor panel. Said step of providing the substrate with coupling element is preferably performed after said pressing under heat step. It is noted that said substrate can also be in form of large board that, after said pressing under heat step, are cut into multiple laminate panel.
As is clear from the above, the method of the first aspect of the invention preferably comprises the step of hot pressing the printed and resin provided paper layer, at least to cure the resin of the obtained resin provided decor paper. Preferably the method of the invention forms part of a DPL process as above described, wherein the printed resin provided paper layer of the invention is taken up in the stack to be pressed as the decorative layer. It is of course not excluded that the method of the invention would form part of a CPL (Compact Laminate) or an HPL (High Pressure Laminate) process in which the decorative layer is hot pressed at least with a plurality of resin impregnated core paper layers, e.g. of so called Kraft paper, forming a substrate underneath the decorative layer, and wherein the obtained pressed and cured laminate layer, or laminate board is, in the case of an HPL, glued to a further substrate, such as to a particle board or an MDF or HDF board.
In the preferred embodiment the décor paper comprises a paper layer, an ink receiver coating on at least one side and a digitally printed patter, preferably an inkjet printed pattern. In the preferred embodiment, the paper comprises a dry amount of ink receiver coating that is below 7 g/m2, more preferably equal or lower than 5 g/m2. Preferably, said paper is provided with 0.2 to 7 g/m2, and preferably between 0.5 and 5 g/m2, dry weight of said ink receiver coating. In fact, inventor has found that by limiting the amount of ink receiver coating on top of the paper layer it may be possible to improve the waterproof performances of the impregnated décor paper and of the laminate panel. The above mentioned amount of ink receiver coating further allow to obtain good printing performances while improving the waterproof performances.
Preferably, the décor paper is provided with thermosetting resin after being printed by inkjet printing. For this reason, preferably the paper is only provided with an inkjet receiver coating at one side thereof, namely at the side provided to be printed upon. The other, opposite, side, is preferably untreated, such that this opposite side shows the original porosity of the paper layer from which it is started. The resin may then be provided substantially from the bottom side into the papers core. To allow sufficient impregnation of the paper having the inkjet receiving coating, the speed of the impregnation channel may be turned down, the resin may be made less viscous, the impregnation may be pressurized and/or the resin may be heated, e.g. to between 30 and 50° C.
The base paper of the décor paper preferably has a base paper weight, i.e. without ink receiving coating, higher than 20 grams per square meter, wherein, in the case of floor panels, of 50 to 100 grams per square meter, e.g. between 60 and 80 grams per square meter. Preferably, the paper layer comprising the ink receiver coating shows a resin penetration time lower than 3 sec.
Preferably, the paper layer is opaque and/or contains titanium oxide as a whitening agent. Alternatively, the paper layer may be a colored, pigmented and/or dyed base paper. The use of a colored and/or dyed base layer enables further the dry weight of deposited ink for attaining a particular pattern or color. In the case of paper, preferably the dye or pigment is added to the pulp before the paper sheet is formed. According to an alternative the ink receiver coating on said paper layer to be printed is colored or pigmented with colored pigments. In accordance with the general disclosure, however, the pigments contained in the ink receiver coating are preferably colorless or white.
Preferably the ink receiver coating comprises at least a pigment or a hygroscopic compound. Preferably, said paper is provided with 0.2 to 10 g/m2, and preferably between 0.5 and 5 g/m2, dry coating weight of a hygroscopic compound or pigment in said ink receiver coating. Preferably said pigment has a BET surface area between 10 and 1600 m2/g, and preferably between 15 and 500 m2/g.
According to the most preferred embodiment, for the pigment of said ink receiver coating at least or mainly silica particles are used. Preferably the silica particles are silane treated. Silane treatment of the pigments, in general, enhances dust release properties of the attained inkjet receiver coating and the thus treated paper or thermoplastic foil. The silane treatment may relate to a treatment with a coupling agent such as amino-organo-silanes, hydroxysilanes, dipodal silanes and/or other silanes. Preferably, the coupling agent is chosen such that the risk of yellowing upon aging of the attained inkjet receiver coating is low. Preferably, the coupling agent forms 0.1 to 5% of the total wet weight of the inkjet receiver coating.
According to variants, for the pigment of said ink receiver coating at least or mainly particles are used chosen from the list consisting of calcium carbonate, silica, alumina, aluminosilicates, ordered mesoporous materials, modified silica, organosilica, modified organosilica, organoalumina, modified alumina, aluminates, modified aluminates, organoaluminates, modified organoaluminates, zeolites, metal organic frameworks and porous polar polymers.
Preferably, said paper is provided with 0.2 to 7 g/m2, and preferably between 0.5 and 5 g/m2, dry coating weight of a binder in said ink receiver coating. According to the most preferred embodiment, for the binder in said ink receiver coating at least or mainly polyvinyl alcohols are used.
According to variants, the ink receiver coating includes, as a binder, a polymer selected from the group consisting of hydroxyethyl cellulose; hydroxypropyl cellulose; hydroxyethylmethyl cellulose; hydroxypropyl methyl cellulose; hydroxybutylmethyl cellulose; methyl cellulose; sodium carboxymethyl cellulose; sodium carboxymethylhydroxethyl cellulose; water soluble ethylhydroxyethyl cellulose; cellulose sulfate; vinylalcohol copolymers; polyvinyl acetate; polyvinyl acetal; polyvinyl pyrrolidone; polyacrylamide; acrylamide/acrylic acid copolymer; polystyrene, styrene copolymers; acrylic or methacrylic polymers; styrene/acrylic copolymers; ethylene-vinylacetate copolymer; vinyl-methyl ether/maleic acid copolymer; poly (2-acrylamido-2-methyl propane sulfonic acid); poly (diethylene triamine-co-adipic acid); polyvinyl pyridine; polyvinyl imidazole; polyethylene imine epichlorohydrin modified; polyethylene imine ethoxylated; ether bond-containing polymers such as polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG) and polyvinyl ether (PVE); polyurethane; melamine resins; gelatin; carrageenan; dextran; gum arabic; casein; pectin; albumin; chitins; chitosans; starch; collagen derivatives; collodion and agar-agar. The most preferred variants for the binder are polyvinyl acetates, ethylvinylacetates, block copolymers based on polyvinylacetate, block copolymers based on polyvinylalcohol, acrylates, latexes, polyvinyl derivaties, VCVAC derivatives, polyurethanes based on polyols and isocyanates, polyurethanes based on polycarbamates and polyaldehydes, e.g. both as a watery dispersion/emulsion or a watery or solvent solution.
As stated above preferred binders for the ink receiving layer include polyvinyl alcohol (PVA), but according to variants a vinylalcohol copolymer or modified polyvinyl alcohol may be applied. The modified polyvinyl alcohol may be a cationic type polyvinyl alcohol, such as the cationic polyvinyl alcohol grades from Kuraray, such as POVAL C506, POVAL C118 from Nippon Goshei.
Preferably, said ink receiver coating has, globally seen, a pigment to binder ratio between 0/1 or 0.01/1 and 25/1, preferably between 0/1 or 0.01/1 and 20/1. It is not excluded that the ink receiver coating is non uniform and shows layerwise or areawise differences in composition, in which case the above values are average values for the totality of the inkjet receiver coating.
The ink receiver coating can further comprise a crosslinking agent. Preferably, the ink receiver coating can preferably comprise a content of crosslinking agent below 5% based on dry weight of the composition. The crosslinking agent can be preferably selected from the group comprising: aldehydes, polyaldehydes, dialdehydes, alcohols, boronic acid, borax, polyalcohols, carbamates, polycarbamates, carbonic acids, glyoxal based agent, zirconium-based agents, titanates and polycarbonic acids.
The ink receiver coating can further comprise a dispersant. A dispersant is an oligomer or polymer which stabilize the liquid dispersions of pigment contained in the ink against flocculation. The dispersant can comprise polycarboxylates, polyphosphates, a polyionic polymer, preferably polyDADMAC (Polydiallyldimethylammonium chloride) polyamine or alumina salts.
Preferably, the ink receiver coating is provided with less than 10%, more preferably less than 5% based on dry coating weight of dispersant, for example between 5 and 0%. Preferably, said ink receiver coating has, globally seen, a pigment to dispersant ratio between 10/1 and 100/1, more preferably it has a pigment to dispersant and binder ratio between 10/1 and 100/1.
The ink receiver coating can also comprise a flocculant, preferably a metal salt, preferably a cationic metal salt. Preferably said metal salt is chosen from the list consisting of CaCl2, MgCl2, CaBr2, MgBr2, CMA (Calcium Magnesium Acetate), NH4Cl, Calcium Acetate, ZrCl4, calcium nitrate and Magnesium Acetate. The positive ion of the dissolved metal salt will tend to neutralize the electrosteric stabilization function of the pigment contained in the ink thereby improving its absorption. The most preferred cationic metal salts are CaCl2, MgCl2, CMA, Calcium Acetate, calcium nitrate and Magnesium Acetate, as the inventors have obtained the best results with these ink reactive compounds. Said flocculant can also be chosen from the list consisting of sodiumaluminate, a double sulphate salt such as alum, polyaluminumchloride, polyacrylate, dicyandiamide (e.g. Floquat DI5 from SNF) and polyacrylamide. The flocculating agent pulls the ink pigments out of the ink dispersion. Thereby the pigments are prevented from penetration to far down into the ink receiver coating. Mainly the vehicle of the ink, e.g. the water in the case of waterbased inks, is absorbed deeper down into the ink receiver coating.
Preferably, ink receiver coating is provided with 20 to 60%, based on dry coating weight of flocculating agent, in particular of metal salt.
The ink receiver coating may also comprise one or more of the following agents:
According to the most preferred embodiment said inkjet receiver coating is present on the décor paper in the form of a unique layer having the inkjet receiving coating composition. Anyway, it is not excluded that said inkjet receiver coating is in the form of two layers, wherein respectively a first layer with a first composition and a second layer with a second composition wherein said first and second composition may be either the same or different compositions.
Preferably, in the method of the invention, the décor paper can be printed using water-based inks or UV curing inks or hydro-UV inks, in particular comprising pigmented inks. In the first place the décor paper used in the method of the first aspect are printed upon using inkjet printing equipment. However, the inventors have also found waterproof performances using analog printed paper.
Preferably the printed pattern applied to the paper layer of the invention, covers the majority, and preferably 50 percent or more of the surface of said paper layer. Preferably, the printed pattern on the décor paper comprises an amount of pigment below 9 g/m2. The inventor has found that limiting the weight of deposited provides for an increased waterproof performance of the impregnated décor paper because of the limited presence on the paper of hygroscopic substances in the ink and in particular in the pigment of the ink
It is to be noted that the fact that the top layer can comprise the thermosetting resin with a composition according to the first independent aspect can form a solution that is independent from the fact that said thermosetting resin is impregnating the décor paper or not. Thereto, with the same aim of the first independent aspect, the invention according to its second independent aspect relates to a method for manufacturing laminate panels, wherein said panels at least comprise a substrate material and a provided thereon top layer, wherein the top layer comprises at least a thermosetting resin, that comprises the steps of:
Preferably, the method of said second aspect can comprise the steps of:
In the preferred embodiment both said décor paper and said overlay paper are impregnated with the same thermosetting resin. In a different embodiment the décor paper and the overlay paper can be impregnated respectively with a first and a second thermosetting resin wherein only one between the first and the second thermosetting resin has a composition according to the second or first independent aspect, or wherein the first and second thermosetting resin are both according to the second or first independent aspect but comprise feature according to different measure. Just for sake of example the first thermosetting resin can have a composition according to the first measure and the second thermosetting resin can have a composition according to the third measure.
It is also to be noted that the invention, according to its third independent relates to a laminate panel comprising a substrate material and a top layer comprising a thermosetting resin, wherein the thermosetting resin comprises a composition that shows one or more of the features illustrated in the above mentioned three measures. It is to be noted that the panel of the third independent aspect can comprise one or more of the features described above in relation to the first and second independent aspects.
It is clear that the present invention also relates a thermosetting resin composition for laminate panel having the features described in relation to the first independent aspect. Thereto, according its fourth independent aspect the invention relates to a thermosetting resin composition comprising a melamine based, with the characteristic that said composition shows one or more of the features illustrated in the above mentioned three measures. The composition of the fourth independent aspect can comprise one or more of the features described in relation to the first independent aspect.
It is to be noted that the fact the décor paper, or the printable paper for forming the décor paper, comprises an inkjet receiver coating in an amount below 7 g/sqm dry weight, more preferably equal or below 5 g/sqm dry weight forms an inventive concept independently from the fact it is used in a panel or in a method according to the first, second and third independent aspect as well as from the fact that it is impregnated with a thermosetting resin having a composition according to the fourth independent aspect. Thereto with the same aim of maximizing the waterproof performance of the décor paper and of the laminate panel comprising the décor paper, the invention, according to its fifth independent aspect relates to a printable paper for décor paper for laminate panel comprising a paper layer and a an ink receiver coating on at least one of the surface of the paper layer, with the characteristic that the ink receiver coating is present in an amount below 7 g/sqm dry weight, more preferably equal or below 5 g/sqm dry weight. Similarly, the invention relates to a décor paper for laminate panel comprising a paper layer wherein said paper layer is provided on one of its surfaces with an ink receiver coating and a printed pattern, with the characteristic that the ink receiver coating is present in an amount below 7 g/sqm dry weight. The printable paper and/or the décor paper of the fifth independent aspect can comprise one or more of the features described in relation to the first independent aspect.
With the same aim of the fifth independent aspect the invention, according to its sixth independent aspect relates to a method for manufacturing a laminate panel that comprises the steps of
Preferably for printing the paper layer or foil of the invention, a digital inkjet printer is applied that allows to jet ink droplets with a volume of less than 50 picoliters. The inventors have found that working with droplets having a volume of 15 picoliters or less, for example of 10 picoliters, brings considerable advantages regarding the limitation of dry weight of deposited inks. Preferably a digital inkjet printer is applied that allows to work with ink droplets of several volumes in one and the same print, or with so-called halftone or gray scale. The possibility of half tone or gray scale printing enables further limitation of the dry weight of deposited ink while maintaining an excellent print definition. Preferably a digital inkjet printer is applied that allows to attain a definition of at least 200 dpi, or even better at least 300 dpi (dots per inch). Preferably said digital inkjet printer is of the single pass type, wherein the paper layer or foil is provided with said printed pattern in a single continuous relative movement of the paper layer with respect to the printer or print heads. It is not excluded that other digital inkjet printers are used to put the invention into practice, such as so-called multi-pass or plotter type printers. It is clear that, according to the most preferred embodiment of the present invention, the paper layer, while printing, is still flexible and that the paper layer is only attached or put on the substrate after printing. According to a variant the paper layer is already attached or loosely laid on the plate shaped substrate while printing. The possible attachment with the substrate can be reached by means of urea based, phenol based, melamine based, polyurethane based glues and similar adhesives. Such attachment can be attained by means of a pressing treatment, whether or not a heated press treatment.
It is also to be noted that, with the same aim of the fifth independent aspect, the invention, according to its seventh independent aspect relates to a method for manufacturing a printable paper or a décor paper with an amount of inkjet receiver coating below 7 g/sqm dry weight, more preferably equal or below 5 g/sqm dry weight. Therefore, the invention relates to a method for manufacturing a printable paper comprising the steps of providing a paper layer and providing at least a surface of said paper layer with an amount of inkjet receiver coating below 7 g/sqm dry weight, more preferably equal or below 5 g/sqm dry weight. The invention further relates to a method for manufacturing a décor paper comprising the steps of providing a paper layer; providing at least a surface of said paper layer with an amount of inkjet receiver coating below 7 g/sqm dry weight, more preferably equal or below 5 g/sqm dry weight, printing a pattern on top of said ink receiver coating, preferably by inkjet printing. Wherein said printing said can comprise one or more of the features described in relation to the first independent aspect. It is to be noted that the ink receiver coating can be provided in line with the printer for printing said pattern. Alternatively, the paper layer can be provided with already the ink receiver coating on top.
Preferably, said ink receiver coating is a liquid substance which is deposited on said paper layer, and which is preferably forcibly dried e.g. in a hot air oven or by means of infrared or near infrared light or by means of microwave drying. Preferably the liquid substance is a water-based suspension of at least said binder, and possibly said pigments. Preferably the liquid substance composition has a dry matter content of 4 to 65 percent by weight of the liquid substance.
The deposition of said liquid substance of the ink receiver coating can be obtained in any way, possibly by means of printing, e.g. inkjet printing, but preferably by means of coating techniques, such as roller coating, e.g. by means of one or more gravure rollers, spraying, metering rollers, bead coating, scattering, slot die coating. With the latter techniques, preferably a coating is obtained that covers at least 80% of the surface of the paper layer or foil. Inline measurement systems may be desirable to steer and control the weight of the inkjet receiver coating. Such technique brings down the risk of obtaining uncoated areas of the paper, which could lead to local flaws in the printed pattern. A preferred equipment for application of the liquid substance is a rotogravure or anilox coating device.
The deposition of the liquid substance for the ink receiving coating may be performed in a rotogravure coating line or, alternatively, on the printing equipment, immediately before the printing operation. This last case solves any possible issues with limited shelf life of the inkjet receiver coating. Preferably the deposition of the liquid substance is performed while the paper or foil is still in an “endless” shape, namely taken from the roll without cutting. Such techniques allow for a more uniform application of the inkjet receiver coating. In the case the coating is wholly or partially done on the printing equipment, the printing equipment is preferably a roll-to-roll or a roll-to-sheet printer, comprising a coating device upstream of the print heads, for example a gravure coater and/or additional printing heads suitable for printing the liquid substance for the respective sublayer of the inkjet receiver coating. Such additional printing heads, for example an additional row of printing heads, may have nozzles with a larger diameter than those used for the actual printing of the pattern. A resolution of 1 to 100, or even 1 to 25 dots per inch may suffice for these nozzles.
It is also possible that the inkjet receiver coating may be applied directly in line with the paper machine with a size press or even more preferable a film press.
Said liquid substance for said ink receiver coating preferably shows a viscosity of 10 to 75 seconds Din cup 4 at 20° C. Such property allows for a straightforward application of the liquid substance to the surface of the paper layer or foil. In experiments, a solid content of about 12% and viscosity of about 20-seconds yielded a sufficiently uniform coating on a previously untreated paper layer, e.g. when applied by means of a roller coater.
With the intention of better showing the characteristics according to the invention, in the following, as an example without limitative character, an embodiment is described, with reference to the accompanying drawings, wherein:
The printable paper 1 comprises an amount of inkjet receiver coating 3 that is equal or lower than 5 g/m2 dry weight.
It is generally noted that the dimensions of the represented paper sheet 2 and the inkjet receiver coating 3 is, in the figures, drawn out of scale in order to better illustrate the invention.
The thermosetting resin 15 has a composition showing one or more of the following features:
In the example the thermosetting resin composition comprises melamine formaldehyde. Said thermosetting resin composition further comprises a total amount of modifier of 4%, wherein said modifiers comprise internal modifiers in an amount of 4% of the resin is free from external modifiers.
Hereto the décor paper 14 is taken from a roll 16 and transported to a first impregnation station 17 where said décor paper 14 is immersed in a bath 18 of said thermosetting resin 15, more particularly a mixture of water and thermosetting resin composition 15. The décor paper 14 is then allowed to rest while in this case being transported upwards. The resting allows for the resin 15 to penetrate the paper core. The décor paper 14 then comes into a second impregnation station 19 where the paper layer 1 is, in this case, again immersed in a bath 18 of resin 15, more particularly a mixture of water and resin 15. A set of squeezing rollers 20 allows to dose the amount of resin 15 applied to the décor paper 14.
In the example several doctor blades 21 are available for partially removing resin at the surface of the resin provided décor paper 14.
In a second step S2 the resin provided décor paper 14 is dried and its residual humidity level is brought to below 10%. In the example hot air ovens 22 are used, but alternatively other heating equipment can be used, such as microwave or infrared drying equipment.
The upper press plate 25 is a structured press plates that provides a relief in the melamine surface of the panel 1 during the same press treatment of the step S3, by bringing the structured surface 29 of the upper press plate 25 into contact with the melamine of the protective layer 28.
The finished pressed product made with the impregnated décor paper has been subjected to the waterproof tests according to norm EN 438 and passed both the test, boiling water test and vapor test, with a passing rate of 5 that means that there are no visible changes on the décor paper after the test.
The present invention is in no way limited to the above described embodiments, but such methods, paper layers, panel may be realized according to several variants without leaving the scope of the invention.
Further, as is clear from the content of the description, the present invention relates to one or more of the items as listed below, numbered from 1 to 49:
| Number | Date | Country | Kind |
|---|---|---|---|
| 21152949.0 | Jan 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/050348 | 1/17/2022 | WO |
