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

Abstract

A method is provided for manufacturing a paper or a thermoplastic foil printable with an inkjet printer for use as a decor paper or a decor foil in a laminate panel. The method may involve providing a paper layer or a thermoplastic foil. At least one side of the paper layer or the thermoplastic foil may be coated with an inkjet receiver coating that includes at least a pigment. The pigment may include aluminum silicates or combinations thereof

Claims

1. A method for manufacturing paper or thermoplastic foil printable with an inkjet printer for use as a decor paper or a decor foil in a laminate panel, the method comprising: providing a paper layer or a thermoplastic foil; coating at least one side of the paper layer or the thermoplastic foil with an inkjet receiver coating that includes at least a pigment; wherein the pigment includes aluminum silicates or combinations thereof.

2. The method of claim 1, wherein the aluminum silicates comprises talc, clays, calcined clays and/or kaolin.

3. The method of claim 1, wherein the inkjet receiver coating is a composition that comprises a binder that represents less than 10% based on dry weight of the composition; or wherein the composition is binder free.

4. The method according to claim 1, wherein the aluminum silicates represents more than 50% based on the whole pigment weight.

5. The method according to claim 1, wherein the pigment has particles of a size in between 0.2 and 10 .Math.m.

6. The method according to claim 1, wherein the pigment has particles of a BET surface area of more than 30 m.sup.2/g.

7. The method according to claim 1, wherein the pigment represents between 30 and 85% based on dry weight of a composition of the inkjet receiver coating.

8. The method according to claim 1, wherein the inkjet receiver coating comprises a binder; and wherein a pigment to binder ratio is higher than 20/1.

9. The method according to claim 1, wherein the inkjet receiver coating comprises a dispersant.

10. The method according to claim 9, wherein a pigment/dispersant ratio is between 10/1 and 100/1.

11. The method according to claim 1, wherein the inkjet receiver coating comprises a flocculant.

12. The method according to claim 11, wherein the flocculant is a metal salt.

13. The method according to claim 11, wherein the flocculant content is between 20% and 60% based on dry weight of the inkjet receiver coating.

14. An inkjet paper comprising: an inkjet receiver coating including an inorganic pigment; wherein the inorganic pigment includes aluminum silicates or a combination thereof.

15. The inkjet paper according to claim 14, comprising a Gurley value between 10 and 60 seconds.

16. The inkjet paper according to claim 14, wherein the inkjet receiver coating is provided with a dry weight of between 0.2 and 5 g/sqm.

17. An inkjet receiver coating composition for printing paper or thermoplastic foil, comprising: an inorganic pigment; wherein the inorganic pigment includes aluminum silicates or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] 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:

[0080] 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;

[0081] FIG. 2 on a larger scale provide a view on the area F2 illustrated in FIG. 1;

[0082] FIG. 3 shows some steps in a method in accordance with the fourth aspect of the invention;

[0083] FIG. 4 shows in perspective a panel obtained by means of the method of FIG. 3;

[0084] FIG. 5 shows a view according to the line V-V indicated on FIG. 4;

[0085] FIG. 6 shows a piece of equipment for use amongst others in the first aspect of the invention;

[0086] FIG. 7 schematically shows a side view of a printer operated in single-pass mode on a central cylinder;

[0087] FIG. 8 shows a table for ranking samples according to DIN EN ISO 2409.

DESCRIPTION OF NON-LIMITING EMBODIMENTS

[0088] 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. 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 between 10 and 30 seconds.

[0089] 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.

[0090] FIG. 2 shows that the inkjet receiver coating 3 comprises pigments 4. In the preferred embodiment the pigment substantially consists of kaolinic clay. The inkjet receiver coating 3, further comprises an ink reactive compound, more particularly a flocculating agent and/or a dispersant, 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.

[0091] In the illustrated example, the inkjet receiver coating 3 is free from any binder and any crosslinker. In other embodiments, the inkjet receiver coating 3 can comprise a binder in an amount below 5, more preferably below 1 % of the dry weight of the coating.

[0092] FIG. 3 illustrates some steps of a method for manufacturing laminate panels 11 of the type shown in FIG. 4. The method forms an illustration of the fourth 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.

[0093] In the example several doctor blades 21 are available for partially removing resin at the surface of the resin provided paper layer 1.

[0094] 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.

[0095] FIG. 3 also illustrates that the continuous paper layer 2 is cut to sheets 23 and stacked.

[0096] FIG. 3 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 melamine formaldehyde resin 15 takes place, having water as a by-product.

[0097] 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.

[0098] FIG. 4 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. 5 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.

[0099] FIG. 6 shows that, in accordance with a preferred embodiment, the inkjet receiver coating 3, may be obtained by coating a liquid substance 36 to the paper sheet 2. 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 half product 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%. 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, or with a size press or a film press, preferably in line with the paper machine. Wherein with paper machine is meant the line for the production of the paper. For example said device 37 can be a film press that applies the inkjet receiver coating between two drying steps on the machine paper.

[0100] FIG. 7 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 a central cylinder 40 upon which the paper layer 1 is partially wound and several printing units 41, each comprising one or more print heads, disposed radially around the central cylinder 40 and over the area of the paper layer 1 to be printed. For example, the central cylinder 40 of the inkjet printer 39 comprises a radius between 800 and 950 mm, for example around 880 mm, and comprises a web angle above 270°, for example above 300°, preferably 320°. 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 printing unit 41, and said paper layer 1 during printing in a printing direction D. In this case, the printing unit 41 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.

[0101] With the intention of further illustrating the invention, here below, without any limitative character, some more exemplary embodiments are listed.

Example A

[0102] 33 kg of commercially available kaolin (Imerys argirec B24 was dispersed in 55 kg of water. Then 10 kg of pure Calcium Chloride flakes acting as flocculant, was added and let stir for 10 minutes.

[0103] Separately 0.3 kg of polyvinylalcohol (mowiol 20/98 Kuraray) was dissolved in 1.7 kg of water at 90° C. and left stirring until this was completely dissolved (2 hours).

[0104] Hereafter the kaolin dispersion was added to the mowiol solution at room temperature and stirred thoroughly. Then the coating was bottled

[0105] The pigment to binder ratio was 100/1 and the solids content was 43.3% by weight.

[0106] The coating shows the correct viscosity for coating with a reverse gravure roller (15-17 s DinCup4).

[0107] The blank paper (Kohler white décor paper) selected for the test has a weight of 72 g/m.sup.2 and a starting Gurley value of 13 seconds.

[0108] On the blank paper 5 g/m.sup.2 of the coating was applied by means of a reverse gravure roller and dried to a dried solid content of 2.2 g/sqm. Coated paper showed a Gurley value of 16 s.

Example B

[0109] 44 kg of commercially available kaolin (Imerys argirec B24) was dispersed in a mixture of 41.5 kg of water and 2.5 kg of a 40% aqueous solution of polyDADMAC (polyquat40U05 by Katpol). The polyDADMAC is a polyionic polymer that functions as a dispersion agent. Then 10 kg of pure CaCl.sub.2 flakes, acting as flocculant, was added and let stir for 10 minutes.

[0110] Separately 0.5 kg of mowiol 20/98 (Kuraray) was dissolved in 1.5 kg of water at 90° C. and left stirring until this was completely dissolved (2 hours).

[0111] Hereafter the kaolin dispersion was added to the mowiol solution at room temperature and stirred thoroughly. Then the coating was bottled.

[0112] The pigment to binder ratio was 88/1 and the solids content was 54.9 % by weight.

[0113] The coating owns the correct viscosity for coating with a reverse gravure roller (15-17 s DinCup4).

[0114] The blank paper (Kohlerwhite décor paper) selected for the test has a weight of 72 g/m.sup.2 and a starting Gurley value of 13 seconds.

[0115] On a blank paper (Kohler white décor paper) 5 g/m.sup.2 of the coating was applied by means of a reverse gravure roller and dried to a dried solid content of 2.8 g/sqm. Coated paper showed a Gurley value of 16 s.

Example C

[0116] 5 kg of commercially available kaolin ((Imerys argirec B24) was dispersed in 82.3 kg of water. After this 0.7 kg of a 40% aqueous solution of polyDADMAC (polyquat40U05 by Katpol) was added and let stir for 10 minutes. Then 12 kg of pure CaCl.sub.2 flakes, acting as flocculant, was added and let stir for another 10 minutes.

[0117] This coating composition has been prepared without the addition of any binder.

[0118] The solids content was 17.3 % by weight.

[0119] The coating already has a low viscosity (10 s DinCup4) suitable for reverse gravure coating.

[0120] The blank paper (Kohler white décor paper) selected for the test has a weight of 72 g/m.sup.2 and a starting Gurley value of 13 s.

[0121] On a blank paper, 5 g/m.sup.2 of the coating was applied by means of a reverse gravure roller and dried to a dried solid content of 0.87 g/m.sup.2. Coated paper showed a Gurley value of 15 s.

Print Proofing

[0122] A premetered application method was used to apply ink on the treated papers of examples A to C, as well as on untreated base paper (Kohler white décor paper), labelled as paper D, and a commercially available inkjet quality paper, labelled as paper E.

[0123] Gurley value and dust release were measured on coated samples. The Gurley value reported below as result of the test, represent the time to pass for 100 cubic centimeters of air to pass the paper. Dust release was measured with an internal test by rubbing the coating and by ranking the behavior of the paper from 1, corresponding to no dust release after rubbing, to 5 corresponding to the all coating becoming loose.

[0124] A K printing proofer by RK printcoat instruments was used with the 100 lines/cm printing plate and a water based red digital printing ink.

[0125] The prints were then analyzed by a X-rite Exact spectrophotometer by measuring the L, a, b and OD (Optical Density) value. A higher OD value means a better optical density and means a better image quality. In the present case has been measured optical density of Magenta OD(M).

[0126] To measureresin penetration time and lamination all the samples were impregnated with the same resin by immersion in a bath of melamine-formaldehyde resin and dried at 140° C. for 73 seconds. The impregnated samples were laminated onto an HDF board with overlay in a press applying a pressure of 60 kg/cm.sup.2 at a temperature of 195° C. for 22 seconds. Adhesion after pressing has been measured with the cross-cut test according to DIN EN ISO 2409 that involves making a grid of cross cuts on the surface of the laminate, evaluating the edges of said cuts, the presence of flakes and the detachment of lattice square. Afterwards, an adhesion test is carried out with a defined adhesive tape. The tape is pressed onto the lattice with force before being pulled off at an even speed (between 0.5-1 sec). The surface is rated according to the table illustrated in FIG. 8 from 0 to 5 where 0 means that the cut edges are smooth and free of flakes and that there is no detachment of lattice squares, and 5 means that the coating and surface finish flakes in wide strips and/or that some square of the grids are completely flaked, and that more than the 65% of the crosscut area is affected.

[0127] The tests results are collected in table 1 below.

TABLE-US-00001 Sample Paper weight (g/m.sup.2) Gurley (s) Dust release (1-5) Optical Density (Magen ta) Resin penetration time (s) Adhesion after pressing (0-5) D 72 13 1 0.60 < 3 0 E 80 30 2 1.05 6-10 4 A 74 16 1 1.05 < 3 0 B 74 16 1 1.05 < 3 0 C 73 15 1 1.05 < 3 0

[0128] From table 1 it can be seen that the samples A, B and C show no dust release as an uncoated paper D thereby improving the dust release performance compared to commercially available coated inkjet paper E. At the same time the samples from A to C show the same printing performance of the commercially available inkjet paper E based on optical density of magenta. Moreover the samples from A to C show a very tiny increase of Gurley of the uncoated paper D that provides for a better and faster impregnation of the resin, which contributes to a better adhesion of the impregnated printed paper on the panel after lamination.

[0129] 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.