METHOD FOR MANUFACTURING INKJET PRINTABLE PAPER OR FOIL FOR USE AS A DECOR PAPER OR FOIL

Abstract

An inkjet receiver coating may be used in a method for manufacturing a paper or a thermoplastic foil that is printable with an inkjet printer. The paper or the foil may be used as a decor paper or a decor foil, respectively, in a laminate panel. The paper or the foil may be coated on at least one side with the inkjet receiver coating. The inkjet receiver coating may include at least pigment and binder, and an ink reactive compound.

Claims

1. An inkjet receiver coating for use in a method for manufacturing a paper or a thermoplastic foil that is printable with an inkjet printer, wherein the paper or the foil is for use as a decor paper or a decor foil, respectively, in a laminate panel, wherein the paper or the foil is coated on at least one side with the inkjet receiver coating, the inkjet receiver coating comprising: at least pigment and binder; and an ink reactive compound.

2. The inkjet receiver coating according to claim 1, wherein the ink reactive compound comprises a polyionic polymer.

3. The inkjet receiver coating according to claim 1, wherein the ink reactive compound comprises a substance altering the pH of the inkjet receiver coating.

4. The inkjet receiver coating according to claim 3, wherein the substance is chosen from the list consisting of formic acid, tartaric acid, acetic acid, hydrochloric acid, citric acid, phosphoric acid, sulfuric acid, AlCl.sub.3, and boronic acid.

5. The inkjet receiver coating according to claim 1, wherein the ink reactive compound comprises a metal salt.

6. The inkjet receiver coating according to claim 5, wherein the metal salt is chosen from the list consisting of CaCl.sub.2, MgCl.sub.2, CaBr, MgBr.sub.2, CMA (calcium magnesium acetate), NH.sub.4CI, Calcium Acetate, ZrCl.sub.4, and magnesium acetate.

7. The inkjet receiver coating according to claim 1, wherein the ink reactive compound comprises a flocculating agent.

8. The inkjet receiver coating according to claim 7, wherein said flocculating agent is chosen from the list consisting of sodiumaluminate, a double sulphate salt, polyaluminumchloride, polyacrylate, dicyandiamide, and polyacrylamide.

9. The inkjet receiver coating according to claim 1, wherein the inkjet receiver coating has a pigment to binder ratio between 0.1/1 and 25/1.

10. The inkjet receiver coating according to claim 1, wherein the pigments have a particle surface area between 100 and 16000 m.sup.2 surface of pigment/m.sup.2 surface of paper or foil.

11. The inkjet receiver coating according to claim 1, wherein the pigments have an average particle size of 100 nm to 20 μm.

12. The inkjet receiver coating according to claim 11, wherein the pigments have a particle size between 1-12 μm.

13. The inkjet receiver coating according to claim 1, wherein the pigments are porous inorganic pigments.

14. The inkjet receiver coating according to claim 1, wherein the pigments comprises precipitated silica, amorphous silica, and/or fumed silica.

15. The inkjet receiver coating according to claim 1, wherein the inkjet receiver coating is applied in a first layer of a first composition and, subsequently, a second layer of a second composition; and wherein the first and the second compositions include the binder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0118] 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:

[0119] FIG. 1 schematically shows an embodiment of a paper layer that has been provided with an inkjet receiving coating in accordance with a preferred embodiment of the method of the first aspect of the invention;

[0120] FIGS. 2 and 3 on a larger scale provide a view on the area F3 illustrated in FIG. 1, wherein, in the case of FIG. 2, only a first layer of a dual layer inkjet receiver coating has been applied to the paper layer;

[0121] FIG. 4 shows some steps in a method in accordance with the third aspect of the invention;

[0122] FIG. 5 shows in perspective a panel obtained by means of the method of FIG. 4;

[0123] FIG. 6 shows a view according to the line VI-VI indicated on FIG. 5;

[0124] FIG. 7 shows a piece of equipment for use amongst others in the first aspect of the invention;

[0125] FIG. 8 schematically shows a top view on a printer operated in single-pass mode; and

[0126] FIG. 9 contains a plot of obtained color densities with the treated papers of the invention in comparison to papers not pertaining to the invention.

DESCRIPTION OF NON-LIMITING EMBODIMENTS

[0127] FIG. 1 schematically illustrates a treated paper layer 1 that is printable with an inkjet printer. The printable paper layer 1 comprises a paper sheet 2 provided with an inkjet receiver coating 3, that comprises a first layer 4 with a first composition and a second layer 5 with a second composition. The paper sheet 2 is, in this case, a base printing paper having a weight of about 70 grams per square meter and with a mean air resistance as expressed by Gurley value of below 30 seconds.

[0128] It is generally noted that the dimensions of the represented paper sheet 2 and the layers 4-5 is, in the figures, drawn out of scale in order to better illustrate the invention.

[0129] FIGS. 2 and 3 show that the inkjet receiver coating 3 comprises pigments 6 and binder 7. The composition of the first layer 4, as well as the composition of the second layer 5 both comprise binder. The inkjet receiver coating 3, more particularly at least the second layer 5 thereof, further comprises an ink reactive compound, more particularly a flocculating agent, such in accordance with the first aspect of the invention. It is clear however that the figures are also illustrative for many aspects of the present invention in the cases where a ink reactive compound, more specifically an ink destabilizing agent, other than a flocculating agent has been applied, such as for example a cationic metal salt.

[0130] FIG. 2 illustrates a halfproduct 8 wherein only the first layer 4 has been applied to the paper sheet 2. The binder 7 is partially absorbed into the paper sheet 2, and such in an non-uniform manner. At the surface 9 loose and/or badly bound pigments 6 are present. Such pigments 6 give rise to dust release upon further processing of such halfproduct 8. The obtained surface 9 of the first layer 4 also suffers from unevenness.

[0131] FIG. 3 shows the paper layer 1 wherein also the second layer 5 has been applied on top of the first layer 4. FIG. 3 shows that the second layer 5 evens out the surface 9, leading to a more uniform surface 10 of the second layer and of the paper layer 1. The composition of the second layer 5 has in this case a lower pigment to binder ratio than the composition of the first layer 4, and in addition comprises the ink reactive compound. It is clear that it is not excluded that the first layer 4 may also comprise an ink reactive compound, either the same or different as the ink reactive compound of the second layer 5 and possibly in different concentrations.

[0132] It is noted that FIG. 3 is an example of a paper layer, wherein at the surface of the treated paper layer less than 10 weight percent of the total pigment 6 is unbound or free and wherein the surface 10 of the second layer is essentially, and in this case completely, formed by binder 7.

[0133] FIG. 4 illustrates a method for manufacturing laminate panels 11 of the type shown in FIGS. 5 and 6. The method forms an illustration of the third independent aspect of the invention as described in the introduction of the present patent application. The obtained decorative panels 11 at least comprise a substrate 12 and a top layer 13. The top layer 13 comprises a paper layer 1, manufactured in accordance with the first aspect, and provided with a printed pattern or a digitally printed ink layer 14 representing a wood pattern, as is the case here. The method of the example embodiment comprises at least the step S1 of providing said paper layer 1 having the inkjet receiving layer and the printed pattern with thermosetting resin 15. Hereto the paper layer 1 is taken from a roll 16 and transported to a first impregnation station 17 where said paper layer is immersed in a bath 18 of said resin 15, more particularly a mixture of water and resin 15. The paper layer 1 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 paper layer 1 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 paper layer 1.

[0134] In the example several doctor blades 21 are available for partially removing resin at the surface of the resin provided paper layer 1.

[0135] In a second step S2 the resin provided paper layer 1 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.

[0136] FIG. 4 also illustrates that the continuous paper layer 2 is cut to sheets 23 and stacked.

[0137] FIG. 4 further illustrates that in a subsequent step S3 the obtained sheets 23 or the paper layer 1 is taken up in a stack to be pressed in a short daylight press 24 between upper and lower press plates 25-26. Said stack comprises from bottom to top a counter layer 27, a plate shaped substrate 12, the abovementioned paper layer 1 and a protective layer 28, wherein the counter layer 27 and the protective layer 28 both comprise a paper sheet 2 and resin 15. The stack is then pressed and the press treatment results in a mutual connection between the constituent layers 1-12-27-28, including the substrate 12, of the stack, as well as in a hardening or curing of the available resin 15. More particularly here a polycondensation reaction of the melamineformaldehyde resin 15 takes place, having water as a by-product.

[0138] 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.

[0139] FIGS. 5 and 6 illustrate that the obtained decorative panel or laminate panel 11 can have the shape of a rectangular and oblong laminate floor panel, with a pair of long sides 30 and a pair of short sides 31 and having an HDF or MDF substrate 12. In this case the panel 11 is at long at least the long sides 30 with coupling means 32 allowing to lock the respective sides 30 together with the sides of a similar panel both in a direction R1 perpendicular to the plane of the coupled panels, as in a direction R2 perpendicular to the coupled sides and in the plane of the coupled panels. As illustrated in FIG. 6 such coupling means or coupling parts can basically have the shape of a tongue 33 and a groove 34, provided with additional cooperating locking means 35 allowing for said locking in the direction R2.

[0140] FIG. 7 shows that, in accordance with a preferred embodiment, at least one of the first layer 4 and the second layer 5 of the inkjet receiver coating 3, may be obtained by coating in one of said two partial steps a liquid substance 36 to the paper sheet 2. In this case, the application of the first layer is illustrated. A device 37 comprising reverse metering rollers 38 is applied. Such device 37 may initially apply an excess of the liquid substance 36, which is squeezed off to the desired weight by means of the rollers 38, which also may provide for a smooth coating surface. Preferably, the obtained halfproduct 8 is then dried, e.g. by means of a hot air oven, to reach a residual humidity level of preferably below 10%, or of about 7%. The obtained treated paper is then further treated by applying the second layer 5 of the inkjet receiver coating 3. Such is here not illustrated, but this may be executed in a fairly similar way. It is clear that as an alternative to the device 37, other application techniques may be used, such as application by one or more gravure rollers, possibly also running in reverse.

[0141] FIG. 8 illustrates that the paper layer 1 having the inkjet receiver coating of the first aspect of the invention may be printed by means of an inkjet printer 39, which, in this example comprises several rows 40 of print heads that extend over the area of the paper layer 1 to be printed. The printer 39, in this example, relates to a printer of the single pass type, wherein the provision of the printed pattern involves a relative motion of said inkjet printer 39, more particularly the rows 40, and said paper layer 1 during printing in a printing direction D. In this case, the rows 40 and the print heads are at standstill, while the paper layer 1 moves during ejection of inks onto the paper layer 1, more precisely onto the inkjet receiver coating 3 applied to the paper sheet. The paper layer 1 gets printed during a single continuous movement of the paper layer 1 relative the printer 39 or the rows 40 of print heads. The obtained printed pattern 14 comprises, in the example, a wood motif having wood nerves 41 extending generally in the printing direction D. Preferably a drying station 42 is provided downstream of the printer 39. After drying the inks, the printed paper layer is preferably rolled up and used in the method illustrated in FIG. 4 as the roll 16.

[0142] With the intention of further illustrating the invention, here below, without any limitative character, some more exemplary embodiments are listed, with reference to FIG. 9.

Example C

[0143] 6 kg of commercially available amorphous silica (Syloid ED5) was dispersed in 41 kg of water and heated to a temperature of 80° C. To this mixture 2.7 kg of a silane (Dynasilan), acting as a particle surface modifying agent or coupling agent, was added and let stir with for 30 minutes. Then 2.3 kg of glyoxal 40% (BASF), as a crosslinking agent, was mixed and let stir for another 30 minutes. Then 0.5 kg of boronic acid, also functioning as crosslinking agent, was added and let stir for 10 minutes.

[0144] Separately 2.5 kg of polyvinylalcohol (mowiol 20/98 Kuraray) was dissolved in 26.4 kg of water at 90° C. and left stirring until this was completely dissolved (2 hours).

[0145] Hereafter the silica dispersion was added to the mowiol solution and stirred thoroughly. To this mixture 0.04 kg of leveling agent, 0.04 kg of antifoam and 0.03 kg of fungicide was added and stirred for another 5 minutes before the coating was bottled and cooled down. The obtained coating composition is free from any ink reactive compound or ink destabilizing agent. In particular the availability of the boronic acid is not in an amount capable of lowering the pH of the ink receiver composition to pH 3 or below.

[0146] The pigment to binder ratio was 2.4/1 and the solids content was 13.5% by weight.

[0147] The coating was brought to the correct viscosity for coating with a reverse gravure roller (30 seconds din cup 4 at 23° C.) by adding water. The solids content went to 10% by weight.

[0148] On a blank paper (Technocel MPK 3723) 20 g/m.sup.2 of the coating was applied by means of a reverse gravure roller and dried.

Example D

[0149] 6 kg of commercially available amorphous silica (Syloid ED5) was dispersed in 41 kg of water and heated to a temperature of 80° C. To this mixture 2.7 kg of a silane (Dynasilan), acting as a particle surface modifying agent or coupling agent, was added and let stir with for 30 minutes. Then 2.3 kg of glyoxal 40% (BASF), acting as a crosslinking agent, was mixed and let stir for another 30 minutes. Then 0.5 kg of boronic acid, also acting as a crosslinking agent, was added and let stir for 10 minutes. After this 5 kg of a 40% aqueous solution of polyDADMAC (polyquat40U05 by Katpol) was added and let stir for another 10 minutes. The polyDADMAC is a polyionic polymer that functions as an ink destabilizing agent in accordance with the invention.

[0150] Separately 2.5 kg of mowiol 20/98 (Kuraray) was dissolved in 26.4 kg of water at 90° C. and left stirring until this was completely dissolved (2 hours).

[0151] Hereafter the silica dispersion was added to the mowiol solution and stirred thoroughly. To this mixture 0.04 kg of leveling agent, 0.04 kg of antifoam and 0.03 kg of fungicide was added and stirred for another 5 minutes before the coating was bottled and cooled down.

[0152] The pigment to binder ratio was 2.4/1 and the solids content was 18.5% by weight.

[0153] The coating was brought to the correct viscosity for coating with a reverse gravure roller (30 seconds din cup 4 at 23° C.) by adding water. The solid content went to 15% by weight.

[0154] On a blank paper (Technocel MPK 3723) 20 g/m.sup.2 of the coating was applied by means of a reverse gravure roller and dried.

Example E

[0155] Two coating compositions were made.

[0156] First coating composition:

[0157] 13.4 kg of commercially available amorphous silica (Syloid ED5) was dispersed in 41 kg of water and heated to a temperature of 80° C. To this mixture 6 kg of a silane (Dynasilan) was added and let stir with for 30 minutes. Then 5.2 kg of glyoxal 40% (BASF) was mixed and let stir for another 30 minutes. Then 0.5 kg of boronic acid was added and let stir for 10 minutes. After this 5 kg of polyquat40U05 (by Katpol) was added and let stir for another 10 minutes.

[0158] Separately 2.5 kg of mowiol 20/98 (Kuraray) was dissolved in 26.4 kg of water at 90° C. and left stirring until this was completely dissolved (2 hours).

[0159] Hereafter the silica dispersion was added to the mowiol solution and stirred thoroughly. To this mixture 0.04 kg of leveling agent, 0.04 kg of antifoam and 0.03 kg of fungicide was added and stirred for another 5 minutes before the coating was bottled and cooled down.

[0160] The pigment to binder ratio was 5.5/1 and the solids content was 26% by weight.

[0161] Second Coating Composition:

[0162] 46 kg of the first coating composition was mixed with 54 kg of an 8% mixture of mowiol 20/98 in water.

[0163] The pigment to binder ratio of the second coating composition was 0.95/1 and the solids content was 17% by weight.

[0164] Both coating compositions were brought to the correct viscosity for application by means of reverse gravure rollers (30 seconds din cup 4 at 23° C.) by adding water. The solids content of the first coating composition was 20% by weight and the second coating composition had 11% by weight solids content.

[0165] On a blank paper (Technocel MPK 3723) the inkjet receiver coating was applied in two partial steps, wherein respectively a first layer with 12 g/m.sup.2 of the first coating composition was applied by a reverse gravure roller and then dried, and, subsequently, a second layer was applied there upon with 12 g/m.sup.2 of the second coating composition, also by means of a reverse gravure roller and then dried.

[0166] Print Proofing:

[0167] A premetered application method was used to apply ink on the treated papers of examples C to E, as well as on untreated base paper (Technocel MPK 3723), labelled as paper A, and a commercially available inkjet quality paper, labelled as paper B. The high absorption of the papers excluded Mayer bar coating. For this reason, the K printing proofer by RK printcoat instruments was used with the 100 lines/inch printing plate and a water based red digital printing ink.

[0168] The prints where then analysed by a Byk Spectro guide to measure the L, a and b value. Then the CD (color density) value was calculated by multiplying a with b and dividing this by L. All papers A to E were then ranked according to CD value, this is depicted in FIG. 9. The abscissa contains the different tested papers, where A is the untreated base paper, B is the commercially available inkjet quality paper and C to E correspond to the treated papers of examples C to E. The ordinate gives the CD values obtained with each of the papers. A higher CD value means a better optical density and means a better image quality. This simplified color density (CD) value allows to quickly assess and rank the coatings.

[0169] From FIG. 9 it can be seen that the use of ink destabilizing agents in an inkjet receiver coating has a significant effect on the obtained color density. In the preferred embodiment where the inkjet receiver coating is applied in two steps with different coating compositions a notably high color density was reached.

[0170] The present invention is in no way limited to the above described embodiments, but such methods, paper layers, thermoplastic foils and vitrimeric foils may be realized according to several variants without leaving the scope of the invention.