Decor paper for laminates

Abstract

Decoration paper for a decorative laminate, which is inkjet printable, comprising a paper substrate comprising at least one opacifying pigment having a refractive index of greater than 2, and on at least one face of the substrate a surface treatment comprising a binder and between 0.5 and 9 g/m.sup.2 of a filler having a specific surface area of between 2 and 100 m2/g and a refractive index of less than or equal to 2.

Claims

1. Decor paper for decorative laminates printable by inkjet, comprising a paper substrate with at least an opacifier pigment of refractive index greater than 2, and on at least one side of the substrate, a surface treatment comprising a binder and between 0.5 and 9 g/m.sup.2 of a filler with specific surface area from 2 to 100 m.sup.2/g and refractive index equal to or less than 2.

2. Paper according to claim 1, with specific surface area of the filler from 2 to 50 m.sup.2/g.

3. Paper according to claim 1 with a resin penetration time on at least the side having received the surface treatment equal to or less than 10 s.

4. Paper according to claim 3, the paper having a resin penetration time on each of its sides equal to or less than 10 s.

5. Paper according to claim 1 wherein the binder represents between 10 and 50% in dry weight of the surface treatment.

6. Paper according to claim 1 wherein the filler represents between 50 and 90% in dry weight of the surface treatment.

7. Paper according to claim 1 wherein the surface treatment is deposited at a rate from 1 to 10 g/m.sup.2 in dry weight per treated side.

8. Paper according to claim 1 wherein the binder is water-soluble.

9. Paper according to claim 1 wherein the binder contains PVOH.

10. Paper according to claim 1 wherein the surface treatment is without silica.

11. Paper according to claim 1 wherein the surface treatment contains silica, in particular in a proportion equal to or less than 50% in mass of the said filler.

12. Paper according to claim 1 wherein the filler contains at least one compound chosen from among clays, calcined clays, kaolins (natural, calcined, delaminated, and other silicates of aluminium, in particular synthetic), talc, diatomaceous earths, aluminium trihydrate, and mixtures of these.

13. Paper according to claim 1 wherein the surface treatment contains a salt of an alkaline earth metal.

14. Paper according to claim 1 wherein the surface treatment contains at least one cationic polymer.

15. Paper according to claim 1 wherein the opacifier pigment contains TiO.sub.2.

16. Paper according to claim 1 wherein the quantity of opacifier pigment in the paper substrate, in particular TiO.sub.2, is equal to or greater than 10% of the total dry weight of the paper in g/m.sup.2.

17. Paper according to claim 1 wherein only one side of the paper substrate has received the surface treatment.

18. Paper according to claim 1 wherein the quantity of filler is between 2 and 4 g/m.sup.2 per treated side.

19. Paper according to claim 1 wherein the filler to binder ratio is greater than 3.1.

20. Printed decor paper, comprising a decor paper according to claim 1 and an inkjet print.

21. Decor paper manufacturing process, comprising the step consisting in applying to at least one side of a paper substrate at least one composition comprising a binder and a filler with specific surface area between 2 and 100 m.sup.2/g and refractive index equal to or less than 2, in a quantity such that between 0.5 and 9 g/m.sup.2 of filler in dry weight is deposited on the paper.

22. Process according to claim 21 wherein the composition is applied by a film transfer system.

23. High, low or continuous pressure laminate, comprising a decor paper comprising a paper substrate with at least an opacifier pigment of refractive index greater than 2, and on at least one side of the substrate, a surface treatment comprising a binder and between 0.5 and 9 g/m.sup.2 of a filler with specific surface area from 2 to 100 m.sup.2/g and refractive index equal to or less than 2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a table of the concentrations and formulations of examples 1 to 15.

(2) FIG. 2 is a chart of the optical density and air permeability of examples 1 to 15.

(3) Filler

(4) In the meaning of the invention, filler is intended to designate particles of a single type of particular material or a mixture of particles of different types of particular material, each with the required properties in terms of specific surface area and refractive index. The filler is preferably composed of a single particular material such as calcined kaolin.

(5) The ink fixing particles of a filler suitable for the invention have a specific surface area from 2 to 100 m.sup.2/g, or better from 2 to 50 m.sup.2/g.

(6) The specific surface area of the particles of a filler suitable for the invention is measured by the BET method according to standard DIN 66132.

(7) The particles of a filler suitable for the invention can have a median diameter D50 in mass from 0.1 to 20 m.

(8) The particles of a filler suitable for the invention can have a shape chosen from among a lamellar shape, a globular shape; a spherical shape or any shape intermediate between the aforementioned shapes.

(9) The particles of a filler according to the invention have a refractive index equal to or less than 2. The particles of a filler suitable for the invention preferably have a refractive index n between 1.3 and 1.8. TiO.sub.2 (rutile and anastase forms) having a refractive index from about 2.5 to 2.8 is therefore excluded from the definition of a filler according to the invention.

(10) The refractive index is measured using a refractometer, the most well known of which being the Abbe model.

(11) Advantageously, the particles of a filler of the invention will be chosen such as to have a refractive index equal to, or substantially close to, the refractive index of the thermosetting resin used to impregnate the decorative paper of the invention.

(12) Thus, between a filler according to the invention and a thermosetting resin, the difference .sub.n between the refractive indices will advantageously be equal to or less than 0.3.

(13) The filler particles according to the invention can be chosen from among mineral particles, organic particles and mixtures of these.

(14) The filler particles will preferably be chosen from among mineral particles.

(15) Mineral filler particles suitable for the invention can be chosen from among clays, calcined clays, kaolins (in particular natural, calcined, delaminated and other aluminium silicates, in particular synthetic), talc, diatomaceous earths, aluminium trihydrate and mixtures of these, each with the required refractive index and specific surface area.

(16) It is to be understood that, when a decorative paper according to the invention contains more than one type of filler particle according to the invention, in particular two, or three, or four distinct types of particle according to the invention, i.e. conforming in terms of specific surface area and refractive index, the quantities of filler given above present in the surface treatment must be taken as referring to the mixture of these particles, and not to each individual type of particle.

(17) According to a preferred method of implementation, a decor paper according to the invention advantageously contains mineral particles and fillers composed of calcined kaolin. Advantageously, these particles are used at a rate varying from 2 4 g/m.sup.2 in dry weight per treated side.

(18) The filler particles, in particular mineral, used in the invention within the surface treatment are preferably neutral in terms of acidity or alkalinity towards thermosetting resins. By neutral in terms of acidity or alkalinity of the filler according to the invention in terms of thermosetting resin we mean the fact that the filler does not behave either as an acid or a base towards thermosetting resins.

(19) Decor Paper

(20) A decor paper according to the invention can have a paper weight from 20 to 200 g/m.sup.2, preferably from 40 to 100 g/m.sup.2 and more preferably from 50 to 80 g/m.sup.2.

(21) The weight of the sheets is determined according to standard ISO 536 after conditioning according to standard ISO 187. The weight is that of the sheet before impregnation by resin.

(22) A decor paper according to the invention can be of any colour; more preferably it is of a light colour.

(23) A decor paper according to the invention has in particular the property of being printable on the side coated with surface treatment, in particular by inkjet printing, while maintaining the thermosetting resin absorption properties identical or very close to those of known decor papers.

(24) The impregnation of a decor paper according to the invention with a resin, in particular thermosetting, is advantageously carried out after a stage of inkjet printing of this paper.

(25) A decor paper according to the invention can have a resin impregnation rate as defined below, equal to or less than 10 seconds, preferably equal to or less than 5 seconds, on the side coated with surface treatment.

(26) The impregnation rate is measured by determining the resin penetration time through the sheet; this time is determined as follows: a 50% by weight solution of resin is prepared by dissolving melamine-for-maldehyde KAURAMIN 773 resin in powder form in distilled water heated to about 45 C. Its viscosity is adjusted by slightly diluting with water so that it is of the order of 55 mPas (cps) around 20 C. on a Brookfield viscosimeter measured at 100 rpmShaft No. 2, the impregnation time of a sheet of paper is then determined as follows: two square samples are cut (1010 cm) per test; to test each side, the side is identified, a watchglass is filled with resin, the square of paper is placed on the surface of the resin with the side to be tested in contact with the resin, and the stopwatch is started at the same time, the time for complete penetration through the paper is recorded, giving the penetration time of the resin.

(27) A decor paper according to the invention can have a Gurley porosity of 5 to 60 seconds, ideally 15 to 40 seconds. The air permeability, or Gurley porosity method, is determined according to standard ISO 5636-5:2013.

(28) A decor paper of the invention can be smoothed or unsmoothed. A decor paper according to the invention can be smoothed by any process known to experts in the field. The paper can be given a smoothing treatment before receiving the surface treatment.

(29) According to one method of implementation, a decor paper according to the invention has on at least one of its sides a Bekk smoothness of 20 to 200 seconds.

(30) The surface treatment can be applied by any known coating technique. Thus, various paper treatments known to experts in the field can thus be used to apply the surface treatment: size press, film press, coating bar, Meyer bar, knife coating, curtain coating, engraved cylinder, spraying, droplet projection (in particular, inkjet type). Preferably, the treatment is carried out by a film transfer system (film press), as indicated above.

(31) The surface treatment binder can be chosen from among water-soluble binders, in particular polymeric binders, such as PVOH, starch, gelatin, casein, CMC, guar. Preferably, the binder is PVOH.

(32) The opacity of the decor paper according to the invention can be relatively high, as required.

(33) A high pressure or low pressure laminate obtained with the decor paper according to the invention can contain one or more layers having a certain opacity.

(34) The opacity of high pressure or low pressure laminates is measured by measuring the luminance Lo of the kraft side of the laminate. The luminance of the laminate at infinity (L) is measured on an opaque white background. The opacity is calculated by the formula: L.sub.0/L*100. The lower the value, the less opaque the paper, or the more transparent.

(35) A high pressure laminate obtained with a decor paper according to the invention preferably has an opacity L.sub.0/L*100 equal to or greater than 70%, or better 80%.

(36) A paper according to the invention can have the advantage of providing opacity, and need not be used with a white or coloured backsheet on which it is superposed.

(37) A decor paper according to the invention can have a design printed on at least one of its sides. This design is advantageously printed by inkjet printing. The design is printed after drying and before impregnation by resin, in particular thermosetting resin.

(38) A decor paper according to the invention can moreover contain the usual components entering into the formulation of decor papers.

(39) Other Components

(40) The paper substrate of a decor paper according to the invention traditionally contains cellulose fibres.

(41) The cellulose fibres can be a mixture of short and long cellulose fibres.

(42) Advantageously, a decor paper according to the invention contains a mixture of cellulose fibres with 60 to 100% of short cellulose fibres in dry weight. The decor paper can be without long fibres.

(43) According to one method of implementation, the short cellulose fibres are eucalyptus fibres.

(44) A decor paper according to the invention can contain synthetic fibres.

(45) The paper substrate of a decor paper according to the invention can contain at least one additional agent chosen from the group consisting of a wet strength agent, a retention agent, decorative particles, mineral or organic particles, a cationic polymer, an absorbent organic polymer.

(46) The substrate of a decor paper according to the invention can contain at least a wet strength agent.

(47) By wet strength agent we mean any agent able to confer tensile strength to the wet paper. Such agents are known to experts in the field. Preferably, such an agent can be a polyamine-epichlorohydrin resin, a polyamide/polyamine-epichlorohydrin resin, a cationic polyacrylate, a modified melamine-formaldehyde resin or a cationic starch.

(48) The proportion of a wet strength agent can be from 0.2 to 2.5% in dry weight with respect to the dry weight of the sheet, and more preferably from 0.4 to 0.8%.

(49) The substrate of a decor paper according to the invention can contain at least a retention agent.

(50) By retention agent we mean any agent able to fix mineral fillers to the fibres. Such agents are known to experts in the field. Preferably, such an agent can be chosen from the group consisting of a system of inorganic microparticles, for example anionic silicas, and a low ionicity polyacrylamide.

(51) By low ionicity with respect to the polyacrylamide suitable for the invention, we mean a polyacrylamide containing few cationic co-monomers of the quaternary ammonium type and/or few acrylate groups of anionic character.

(52) As described previously, during the manufacture of high pressure, low pressure or continuous pressure laminates, the decor paper is generally printed first, then impregnated with a heat-stable thermosetting resin and finally hot pressed on its support at high or low pressure. Alternatively, as described previously, in the case of a process without impregnation (dry process), the printed decor paper is stacked, non-impregnated, between two papers impregnated with thermosetting resin, and the decor paper is impregnated while pressure is exerted on the whole stack. As a result, a decor paper according to the invention can be used with or without thermosetting resin.

(53) In particular, this thermosetting resin can be chosen from among melamine-formaldehyde resins, urea-formaldehyde resins, benzoguanamine-formaldehyde resins, unsaturated polyester resins, dicyandiamide-formaldehyde resins, epoxy resins, polyurethane resins and mixtures of these.

(54) Once the decor paper is impregnated with resin, it is heated, the resin is partially cured (thermoset) so that it is no longer in a tacky state and the sheet can be handled. A decor paper impregnated with partially cured resin is called in the trade decor film or decorative film or melamine film. This melamine film contains a proportion of resin preferably varying from 50 to 55% but it can vary from 30 to 70%.

(55) This step is generally carried out by heating the decor paper at temperatures of about 110 to 140 C. and is controlled such that during the final lamination of the decor film, the resin flows properly in the sheet, by measuring the proportion of volatiles remaining in the decor film. The decor film then contains a certain percentage, of the order of 5 to 8%, of volatile products (resin solvent water, water from chemical condensation of the resin, residual formaldehyde, other residual products, etc.). These volatiles represent the compounds that will be eliminated when the resin is completely cured, during lamination of the decor film.

(56) Once the resin has been cured, after lamination, it will provide strength to the surface of the final laminate (abrasion resistance, dirt resistance, steam resistance and resistance to chemicals such as solvents, acids and bases, etc.).

(57) According to one special case, a decor paper of the invention is impregnated with thermosetting resin, then the resin is partially cured in acid medium, the proportion of volatile compounds being between 5 and 8% of the weight of the sheet.

(58) The invention also relates to a decorated laminated board or profile containing at least a decor paper according to the invention.

(59) A laminate according to the invention can contain, superposed by contact, at least two, preferably at least three and more preferably at least four, decor papers according to the invention.

(60) Production Process

(61) The fibrous base of a decor paper according to the invention containing cellulose fibres can be prepared by any process known to experts in the field.

(62) Thus, a wet fibrous composition of cellulose, or paper pulp is first prepared.

(63) According to one method of implementation, the particles of opacifier pigment are mixed with the fibrous cellulose composition before the latter is deposited on the formation surface.

(64) This mixture can be made, for example, in the paper pulp vat, at the headbox, in the storage vat, at the refiners, or at the mixing pump.

(65) According to one method of implementation, such a mixture can be made in a paper pulp vat.

(66) One process for preparing decor paper of the invention can comprise a step consisting in adding a wet strength agent and/or a retention agent, such as defined above.

(67) Preferably, the wet strength agent is an epichlorhydrin polyamine resin, and the retention agent can be a system of inorganic microparticles, for example anionic silicas or a low ionicity polyacryamide.

(68) One process for preparing a decor paper according to the invention comprises a drying step which can be carried out by any method known to experts in the field, and usually used in the field. Such methods do not therefore need to be described further here.

(69) One process for preparing a decor paper according to the invention comprises an extra step to apply a surface treatment.

(70) This step can in particular be carried out by coating processes such as those listed above, preferably online, but also possible offline.

(71) One paper according to the invention can advantageously be used to prepare a high or low pressure or continuous pressure laminate.

(72) In the case of a high pressure laminate, the components of the base of the laminate are kraft sheets impregnated with thermosetting resin and the decor paper according to the invention impregnated or not with a resin, in particular thermosetting.

(73) In the case of a low pressure laminate, the components of the base of the laminate are the supporting board, such as particle board, and a decor paper of the invention impregnated or not with a resin, in particular thermosetting.

EXAMPLES

(74) A decor paper is first produced on a paper machine, the paper composed in particular of 100% short eucalyptus cellulose fibres, of TiO.sub.2 for a proportion of 35% in the paper substrate, small quantities of pigment providing a shade to aim for a defined colour and various chemical agents, in particular a wet strength agent.

(75) The manufacture of this paper follows the traditional paper process known to experts in the field, namely pulping of the paper, refining, addition of components (TiO.sub.2, coloured pigments, additives), dilution then formation of the sheet, pressing and drying before arriving at the coating station which is always located on the paper machine.

(76) The various formulations described in examples 1 to 15 in the tables corresponding to FIGS. 1 and 2 in the appended drawing are then applied to the paper. In examples 1 to 14, the coating station is a size press, a widely used paper process. In example 15, coating is done manually on one side of the substrate with a grooved rod to simulate coating (Meyer bar, knife coating layer, etc.) or film transfer (film press). The concentrations and formulations are adapted so as to obtain dry deposits with the values given in the table of FIG. 1. In the examples according to the invention given in FIG. 1 (except for example 15), the final paper weight obtained is between 75 et 80 g/m.sup.2 but could be adjusted by changing the paper weight of the substrate. Example 15 has the lowest paper weight, because of the lesser quantity of deposit applied to a single side of the substrate, but this too could be adjusted by changing the paper weight of the substrate.

(77) The results firstly show the pronounced effect of the silica-based formulation (called silica A in the example), which decreases the air permeability of the paper (the higher the Gurley index, the lower the permeability). Thus, even with only 5 g/m.sup.2 from the formula given in example 1, the paper already has a Gurley value of 35 seconds while in example 4 according to the invention, the Gurley value is only 23 seconds for a deposit of 9.4 g/m.sup.2. If the comparison is made between close deposition of 9.5 g/m.sup.2 in example 3 and 9.4 g/m.sup.2 in example 4, the difference is still more marked, with respectively 56 seconds vs 23 seconds.

(78) The recto/verso penetration times of the resin are still more clearly affected: 23/15 seconds in example 1, 49/52 seconds in example 3 compared with 3/2 seconds in example 4.

(79) The advantage of the invention can be seen very clearly in the optical density values since that of the paper in example 4 is 1.61 compared with 1.51 in example 3.

(80) The same conclusions can be drawn for the optical densities of the papers after lamination.

(81) The treatment of the invention thus enables an extremely useful compromise to be found between optical density and resin penetration time, reflecting the impregnability.

(82) The other examples produced by adding a cationic product to formula 1 according to the invention (PolyDADMAC or CaCl.sub.2) show synergy in the optical density without altering the resin penetration time.

(83) The word between is understood as inclusive of limits unless otherwise stated.