EP2480416A1

EP2480416A1 - Method for producing a digitally printed workpiece

Info

Publication number: EP2480416A1
Application number: EP10757759A
Authority: EP
Inventors: Rene Pankoke
Original assignee: Theodor Hymmen Verwaltungs GmbH
Current assignee: Hymmen GmbH Maschinen und Anlagenbau
Priority date: 2009-09-23
Filing date: 2010-09-21
Publication date: 2012-08-01
Anticipated expiration: 2030-09-21
Also published as: LT2480416T; DE102009044091B4; ES2798274T8; PL2480416T3; WO2011036141A1; EP2480416B1; DE102009044091A1; ES2798274T3

Abstract

The invention relates to a method for producing a digitally printed workpiece (3, 20) that is flat and in the form of a strip or a board, and which comprises an abrasion resistant surface. Said method is characterised by the following steps: A) provision of a digital data set for a decorative image for a digital printing device (1); B) feeding of a printable work piece (3, 20) into the printing device (1); C) digital printing by means of the printing device (1) using at least one solvent-based printing ink (6); D) reduction of solvent content in the workpiece (3, 20) to the level of residual moisture; E) impregnation of the surface of the printed workpiece (3, 20) with a resin mixture (19); and F) curing of said resin mixture (19) by means of a heat press (14, 15).

Description

Method for producing a digitally printed workpiece

The invention relates to a method for producing a digitally printed flat, web-shaped or plate-shaped workpiece, for example a kitchen worktop, a furniture front or a laminate floor part with a decorative and resistant surface.

In order to accelerate the manufacture of such a workpiece and to be able to react flexibly, digital printing methods, e.g. Inkjet jerkverfahren (inkjet) used. However, the difficulty with this ink jet printing method is that the ink jet printheads used are difficult to handle in industrial printing with water-based inks. It often comes to blockages, the ink dries on the nozzles of the inkjet printheads, there are so-called nozzle misfires (Nozzelfehler).

The known use of radiation-curing acrylate-containing printing inks also prevents subsequent impregnation with aqueous melamine resins due to the formation of a barrier layer and is therefore not possible.

It is therefore an object of the present invention to provide a method for producing a digitally printed flat, sheet-like or plate-shaped workpiece with a durable surface, which avoids the disadvantages mentioned above and ensures a digital decor print with high quality.

The object is achieved by a method having the features of claim 1.

Advantageous embodiments of the invention are contained in the subclaims.

In the method according to the invention, a digitally printed flat, web-shaped or plate-shaped workpiece having an abrasion-resistant surface is produced, wherein initially a digital data record for a decorative image is provided, sent from a computer to a digital printing device. This is followed by feeding a printable workpiece to the printing device.

Subsequently, the digital printing of the respective workpiece by means of the printing device is carried out exclusively using solvent-based printing inks. As solvent-based printing inks all printing inks are detected, which do not contain water as the main component. This includes, for example, all organic solvents, such as alcohols, and mixtures of various solvents.

The printing is followed by reducing the solvent content to a defined residual moisture in the workpiece. The evaporation of the solvent can be additionally accelerated by heating the workpiece, for example by a hot air blower. The defined residual moisture describes a maximum content of solvent which remains in the workpiece.

The subsequent impregnation of the printed workpiece with a resin mixture can be done for example by coating, impregnating, wetting or spraying the workpiece with the respective solid or liquid resin mixture, wherein the resin mixture is then cured in a hot press.

The method has the advantage that the use of solvent-containing printing inks in the method according to the invention, the nozzles of the print heads of Druckvorrichtun not be added, which has longer life of the printing device result.

Compared to the use of radiation-curing acrylate-containing printing inks, the use according to the invention of solvent-containing printing inks enables only the further process steps of impregnation by means of aqueous resins.

At the same time, the reduction of the solvent content in the workpiece, for example, when using short-chain monohydric alcohols, significantly faster than water-based inks, whereby drying of the printed workpiece can be done with less energy. Finally, unlike the use of water-based printing inks, the use of solvent-based printing inks in the method according to the invention does not lead to a swelling of the surface in the printing area of the workpiece.

By the method according to the invention, decorative coated workpieces such as e.g. Kitchen worktops, kitchen furniture fronts, other furniture fronts or even laminate flooring and similar workpieces are produced with decorative surfaces of high quality. The reproduction of a wood structure or a stone structure, fantasy decors or other nature-inspired decors can be achieved, the workpieces at the same time also have positive physical properties such as abrasion resistance, scratch resistance, heat resistance.

It is furthermore advantageous if digital printing takes place using at least one solvent-based printing ink with a weight proportion of solvent of 40-99%, preferably 65-92%. Radiation-curing inks can act as a barrier layer after their curing, for example by UV radiation in a subsequent impregnation of such a printed workpiece with a water-based resin solution thus prevent a permanent connection between the printed workpiece with underlying material layers. Due to the high proportion of solvent, the formation of a barrier layer of polymerized acrylates can be particularly advantageously prevented because the solvent distributes the printing dyes on the surface and also transported into the workpiece.

In a preferred method, one or more unprinted, resinous material layers are arranged above and / or below the printed workpiece prior to curing in the heating press, so that the resin flow from these material layers impregnates the non-bonded, printed workpiece during the pressing process. In this case, both material layers and the workpiece, for example, consist of absorbent materials such as paper.

In addition, in this variant of the method can be dispensed with an additional step of impregnating the printed workpiece with the resin mixture. After impregnating the printed workpiece or arranging a material layer impregnated with resin mixture on and / or under the printed workpiece, the workpiece can be applied to one or more layers of material and then be joined together by pressing. Thus, for example, an impregnated and printed decorative paper on a wooden material plate, preferably a chipboard, MDF or HDF board, are applied, whereby a Laminterung a bending resistant substrate.

By drying the workpiece to a residual moisture content of less than 4%, preferably less than 1, 5%, swelling and lifting of the printed surface relative to the unprinted surface is advantageously prevented.

It is advantageous if the solvent-based printing ink contains pigments, since pigments are colourfast and consequently there is no aging and decomposition of the printing inks by UV light. The use of a pigmented printing ink thus ensures a high-quality print image over a long service life.

It is advantageous if after the impregnation of the printed workpiece with the resin mixture, a subsequent predrying of the resin mixture takes place. As a result, a pre-crosslinking of constituents of the resin mixture can be achieved and a reduction of the water content to a residual moisture of less than 10%, preferably less than 4%.

It is also advantageous if a Meiaminharzbasis resin mixture is used, since this material penetrates the workpiece under pressure and in an underlying material layer, such as a fiberboard, penetrate and after hardening of the resin mixture has entered into a non-detachable connection with the material layer. In addition, melamine resin has, after curing, positive physical properties, e.g. Moisture resistance, temperature resistance and scratch resistance.

The curing of the resin mixture takes place, for example, in the case of aminoplasts by crosslinking of polymer strands as a result of a condensation reaction known per se at elevated pressure in the range 20-60 bar, preferably 30-60 bar. 40bar and temperatures of 150-230 ° C, preferably 170-200X using a hot press.

It is advantageous if the curing of the resin mixture is carried out by a continuous double belt press. This press allows both the processing of continuous material and piece material with a high processing speed. It is particularly advantageous if the double belt press further, non-printed, impregnated material layers, especially paper layers are pressed with the printed and impregnated workpiece. Since the supply of Werkstoffiagen can be made as continuous material, the double belt press offers a higher throughput than, for example, a short-cycle press due to their continuous operation. During the pressing process, it is also possible to structure the surface.

It is in the pressing of a layer sequence of one or more unprinted, impregnated material layers, in particular paper layers, a layer of pre-printed and optionally impregnated workpiece and a further material layer, in particular a wood-based panel (13), to a solid, cured unit advantageous if This compression is performed in a pressing operation of a short-cycle press. Thus, several layers can be pressed together.

Embodiments of the invention will be described in more detail below with reference to attached Figures 1-8. They show:

Fig. 1: Schematic representation of three inventive

Process steps B), C) and D)

2: Schematic representation of a method step E) according to the invention

3: Schematic representation of two method steps E) and F) according to the invention

4: Schematic representation of two alternative method steps E) and F) according to the invention Fig. 5: Schematic representation of the sequence of layers of a variant of a workpiece produced by the method according to the invention

Fig. 6: Schematic representation of the layer sequence of another embodiment of a workpiece produced by the inventive method

Fig. 7: Schematic representation of the layer sequence of another embodiment of a workpiece produced by the method according to the invention

Fig. 8: Schematic representation of the layer sequence of another embodiment of a workpiece produced by the method according to the invention

1 schematically shows a feed station 102, with a roll 2 for decorative paper 3 to be printed, a printing station 103 for a decorative paper 3 and a station for reducing the solvent content 104 in the decorative paper 3 by a printing device. The printing in digital printing can take place on decorative paper 3 also directly on a surface of a workpiece, in particular an HDF or DF plate. In this case, the printing device 1 to a printer 4, which has four printheads 5. These release solvent-based printing ink 6 onto the surface of decorative paper 3.

Following the printing of the workpiece, the printing ink is optionally dried with a dryer 7 shown diagrammatically. In the case of highly volatile solvents, the drying process may possibly already take place during printing without the aid of a drier.

After the printing process, the decorative paper 3 can be rolled up for storage, transport and further processing on a roll 8.

The way in which a workpiece is fed depends on the nature of the material. Paper sheets can be clamped and unrolled, while wood-based panels are fed on treadmills of the printing device. The printheads 5 can be arranged stationarily in the printer 4 in order to realize a single-pass printing process. In this case, the print heads can advantageously extend over the entire width of the area to be printed. The individual print heads 5 have, for example, a width of 70 mm and are arranged side by side in a printing module, preferably with the solvent-containing printing inks black, angenta, cyan and yellow. If several printing modules are arranged side by side, it is also possible to print workpieces, for example with a width greater than 1 m. The arrangement of several printing modules stationary next to each other allows a uniform multi-color print image on which no transitions between the individual printing modules can be seen.

Alternatively, the printheads 5 can be arranged in the arrangement on a movable carriage, so that a printing of the workpiece in the multi-pass method can be performed.

The above-described stationary and movable printhead assembly may also be arranged in a multi-row succession to achieve a higher printing speed compared to a single-row arrangement. As an alternative to a printhead arrangement, nozzle bars may also be arranged.

It can also be used instead of four and six or more or less inks in the printing device 1.

Fig. 2 shows a station for impregnating the workpiece 105 with a resin mixture 19, e.g. with an amino resin (melamine resin mixture). In this case, the previously printed decorative paper 3 is unwound from the roll 8, pulled through a resin bath 9 with the liquid resin, squeezed off excess resin by means of a squeegee 10 and then dried by a dryer 11 shown schematically. This dryer 11 is designed such that it allows drying of the resin. For example, the dryer 1 may be designed as a forced air or hot air dryer. After drying of the resin, the workpiece can be wound onto a further roller 12 for storage.

As an alternative to winding on the roll 12 may also be provided a cutting device, not shown, to cut the impregnated and dried paper in sheets.

3 shows a station 07 for arranging two unprinted paper layers 17, which are impregnated with a resin mixture 19, above and / or below a printed wood workpiece 20.

In the station 107 can also apply a printed and impregnated decorative paper 3 above or below a wood-based panel 13 done. In this case, the printed and impregnated decorative paper 3 is unwound above and below the wood-based panel 13 and this merged package is then cured in a double belt press 14.

Subsequently, the curing of the resin mixture and bonding of the individual layers with the respective printed workpiece in the double belt press 14 with two rollers 15 and a feed for the wood-based material plate 13th

In an alternative embodiment, the curing and bonding of the printed decorative paper 3 with the wood-base plate 13 (FIG. 4) takes place in a heated short-cycle press 16.

5 shows an exemplary structure of a product produced by the method according to the invention. On a wood-based panel 13, a decorative paper 3 printed with the solvent-containing printing ink 6, preferably the solvent-containing digital printing ink, is applied. The decorative paper 3 has dyed pigments, which are placed on and in decorative paper 3 during printing 103. Above this resin-impregnated decor paper 3 provided with the color pigments is a further resinated paper, which is provided as overlay paper 17 with a resin mixture 19 by impregnation 105.

In the exemplary embodiment of a product shown in FIG. 6, in addition to the product of FIG. 5, a wear protection layer 21 is applied which has corundum (aluminum oxide (Al ₂ O ₃ )) or another material for increasing the abrasion resistance.

In a further embodiment according to FIG. 7, a further resinated paper can be applied on the underside of the wood-based panel 13 as a counter-pull paper. This can also be formed as printed and impregnated decorative paper 18, as on the top, if the finished end product is to be decorative coated from both sides, optionally also as described above, supplemented by a wear resistant to alumina overlay paper 17.

In an alternative embodiment, the overlay paper 17 may also be omitted or, alternatively, supplemented by two or more papers at the top, optionally also at the bottom.

In a further embodiment variant according to FIG. 8, a resinated paper 17 can be applied to the underside of a printed wood workpiece board 20.

In the method according to the invention, in the printing apparatus 1, in a first method step, a digital data record for a decorative image, for example a wooden structure replica or stone tile reproduction or another near-natural image or even a fantasy decor, is provided. Further, a material to be printed is fed to the printing apparatus 1. A suitable material is, for example, a paper, preferably a non-resinated and uncoated decorative paper, which has a whitening agent, for example titanium dioxide (TiO ₂ ), applied and is absorbent. In an alternative embodiment, this decorative paper can also be provided with a melamine resin impregnation, so that in the dried state 5-40%, particularly preferably 10-20%, of the total weight of the paper are predetermined by the melamine fraction. As a printable workpiece but also plastic materials and any other printable material can be used. This includes, inter alia, a direct printing of a wood-based panel.

Subsequently, in a further method step, the digital printing device is printed on the decorative paper or the workpiece by means of inkjet printheads. The used inkjet jerk heads give off individual small droplets in the same or different droplet sizes. Suitable droplet sizes are between 3 and 100 pl per droplet, more preferably between 5 and 45 pl per droplet size. The droplets are released from a nozzle opening at the bottom of the print heads. The size of the nozzle opening is between 10-1 OOprn, preferably 15-40 pm.

The digital printing ink used is preferably a pigmented ink in which solids (pigments) of a size between 0.01 μm-5 μm, preferably 0.1-3 μm, are used as the dyes. Also possible is a mixture of pigments and liquid dyes. In a preferred embodiment, four inks are used with cyan, magenta, yellow and black pigments.

The ink used contains pigments as colorants, ie solids which have a high to very high color stability. This color stability, according to the known Woll scale, is between 5 and 8, more preferably 6-8. The pigments used have an average particle size of 0.01 to 5 μm, more preferably 0.1 to 3 μm. The proportion of the pigments based on the total weight of the digester printing ink used is 0.4-25%, more preferably 1-10%.

The further main constituent of the digital printing ink used according to the invention is a solvent which is not water, preferably an organic solvent. Here, in a preferred embodiment, an alcohol, particularly preferably ethyl alcohol, is used in a concentration of 40-99%, more preferably 65-92% (weight percent).

Other ingredients of the ink may be dispersants as well as a variety of other additives. These additives affect the desired physical properties of the ink, such as viscosity, temperature stability, durability, pH, electrical conductivity, etc.

reference numeral

1 printing device

2 roll

3 decorative paper

4 printers

5 printheads

6 printing ink

7 dryers

8 roll

9 resin bath

10 nip rolls

11 dryers

12 roll

13 wood-based panel

14 double belt press

15 roll

16 short-cycle press

7 Overi paper

18 decorative paper

19 resin mixture

20 wood-based panel

21 protective layer

102 feeding station

103 printing station

104 drying station

105 impregnation station

Claims

claims

1. A method for producing a digitally printed flat, web-shaped or plate-shaped workpiece (3, 20) with an abrasion-resistant surface, characterized by the following steps:

A) providing a digital record for a decorative image for a digital printing device (1);

B) feeding a printable workpiece (3, 20) to the printing device d);

C) digital printing by means of the printing device (1) using at least one solvent-based printing ink (6);

D) reducing the solvent content to a residual moisture in the workpiece {3, 20);

E) impregnating the printed workpiece (3, 20) with a resin mixture (19); and

F) curing of the resin mixture (19) by means of a heating press (14, 15).

2. The method according to claim 1, characterized in that the digital printing in step C) using at least one solvent-based printing ink (6) with a weight proportion of solvent 40 - 99%, preferably 65 - 92%, takes place.

3. The method according to claim 1 or 2, characterized in that on the workpiece (3, 20) one or more material layers (13) are applied, which are firmly connected to the workpiece (3, 20) during the curing in step F) ,

4. The method according to any one of the preceding claims, characterized in that at least one with a resin mixture (19) impregnated material layer (17) on the workpiece (3, 20) is applied.

5. The method according to any one of the preceding claims, characterized in that the reduction of the solvent content to a residual moisture content in the workpiece (3, 20) of less than 4%, preferably less than 1, 5%

6. The method according to any one of the preceding claims, characterized in that the solvent-based printing ink (6) is a pigmented printing ink.

7. The method according to any one of the preceding claims, characterized in that after the step of reducing the Lösemtttelhänattes to a residual moisture in the workpiece (3, 20) arranging an unprinted with a resin mixture containing material support (17), and then a pressing in a heating press.

8. The method according to any one of the preceding claims, characterized in that for impregnating the printed workpiece (3, 20) or the unprinted material layer (17), a resin mixture (19) is used melanin resin-based.

9. The method according to any one of the preceding claims, characterized in that the curing of the resin mixture (19) by a continuous double belt press (14).

10. The method according to claim 9, characterized in that prior to curing further, non-printed, impregnated material layers (17), in particular paper layers, above and / or below the printed impregnated workpiece (3, 20) or the one or more Material layer (13) are arranged.

11. The method according to any one of the preceding claims, characterized in that takes place during or after curing of the wetting agent-containing resin mixture, a surface treatment for the production of a decorative laminate. - 1.5 -

12. The method according to any one of the preceding claims, characterized in that the curing of the resin mixture (19) by a short-cycle press (15).

13. The method according to claim 12, characterized in that each pressing operation of the short-cycle press (15), the layer sequence of one or more

unprinted, impregnated material layers, in particular paper layers (17), a layer of the pre-printed and optionally impregnated workpiece (3, 20) and another material layer, in particular a wood-based panel (13), are pressed into a solid, cured unit.