Compositions for producing matt-gloss inkjet inks and use thereof in inkjet printing processes

Abstract

The invention relates to digitally applicable, UV-curing coating substances, in particular inkjet inks, which produce matt-gloss coatings. Their compositions contain 10 to 40% by weight of one or more difunctional monomers, 20 to 50% by weight of one or more monofunctional monomers, 5 to 35% by weight of one or more organic matting agents, 1 to 30% by weight of one or more acrylate oligomers and / or polyfunctional acrylate monomers, and 2 to 13% by weight of one or more photoinitiators. The invention also relates to coating systems in which the coating materials according to the invention are used to produce a final, matt-gloss topcoat layer or finishing coat, and to methods for producing these systems.

Description

[0001]Mankiewicz Gebr. & Co. Abstract: The invention relates to digitally applicable, UV-curing coating materials, in particular inkjet inks, which produce matte-gloss coatings. Their compositions contain 10 to 40 wt. % of one or more difunctional monomers, 20 to 50 wt. % of one or more monofunctional monomers, 5 to 35 wt. % of one or more organic matting agents, 1 to 30 wt. % of one or more acrylate oligomers and / or polyfunctional acrylate monomers, and 2 to 13 wt. % of one or more photoinitiators. The invention further relates to coating systems in which the coating materials of the invention are used to produce a final, matte-gloss topcoat layer or covering coat, and to processes for producing these systems. 0070172WO 13.09.2023 Mankiewicz Gebr. & Co.1 Compositions for producing matt-gloss inkjet inks and their use in inkjet printing processes. The invention relates to digitally applicable, UV-curing coating materials which produce matt-gloss coatings. It particularly relates to UV-curing inks which can be applied by inkjet printing processes. Furthermore, the invention relates to coating systems in which the coating materials, in particular the inkjet inks, are used to produce a final topcoat layer or covering coat. As a rule, decorative, colored coatings are produced using digital printing processes, especially using inkjet printing processes. The term inkjet printing process is understood below to mean a non-contact, direct, instant printing process without a printing form, which is based on electronic principles.In this process, a suitable coating material is pressed through a microscopically fine nozzle according to the electronic instructions of a computer and then directed onto the substrate to be printed using electrostatic or magnetic fields to create text or images. However, the creation of matte-gloss surfaces has not been possible using digital printing processes to date, as conventional matte varnishes cannot be used in these processes. To achieve a matte-gloss print, the matte varnishes must be applied after inkjet printing in an additional process step using suitable methods, for example, by spray application followed by oven drying. These additional process steps result in increased labor and time expenditure for the printing process. 0070172WO 13.09.2023 Mankiewicz Gebr. & Co.2 It is an object of the present invention to provide improved coating compositions, in particular inkjet inks and coating systems, which produce matt-gloss surfaces and can be produced using conventional inkjet printing processes. This object is achieved by coating compositions according to the main claim and their use for producing matt-gloss coatings and coating systems. Further embodiments are disclosed in the subclaims and the description. The compositions according to the invention contain at least 10 to 40 wt. % of one or more difunctional monomers, 20 to 50 wt. % of one or more monofunctional monomers, 5 to 35 wt. % of one or more organic matting agents, 1 to 30 wt.-% of one or more acrylate oligomers or one or more polyfunctional acrylate monomers or mixtures of one or more acrylate oligomers and one or more polyfunctional acrylate monomers, 2 to 13 wt.% of one or more photoinitiators, the weight proportions being based in each case on the total weight of the composition. In preferred embodiments, the compositions contain 10 to 40 wt.%, preferably 15 to 35 wt.%, of one or more difunctional monomers, 20 to 45 wt.%, preferably 20 to 42 wt.%, of one or more monofunctional monomers, 0070172WO 13.09.2023Mankiewicz Gebr. & Co.3 5 to 25 wt.%, preferably 5 to 20 wt.%, of one or more organic matting agents, 5 to 30 wt.%, preferably 10 to 30 wt.%, of one or more acrylate oligomers or one or more polyfunctional acrylate monomers or mixtures of one or more acrylate oligomers and one or more polyfunctional acrylate monomers, 4 to 11 wt.-%, particularly preferably 6 to 9 wt. %, of one or more photoinitiators, where the weight proportions are in each case based on the total weight of the composition. The term matting agents is understood to mean additives and auxiliaries which reduce the gloss of a coating or produce a matte gloss. They are used to scatter light on the surface of the coating obtained by applying and curing coating materials. Matting agents suitable according to the invention are organic matting agents based on polymer powders with a particle size D90 < 2 µm. This means that 90% of the particles have particle diameters of less than 2 µm. Preference is given to polymer powders with a particle size D90 < 1 µm. This means that 90% of the particles have particle diameters of less than 1 µm. Preference is given to using polymethylurea powders.In a further embodiment, the polymethylurea powders are predispersed in diacrylates. Suitable difunctional monomers according to the invention are 1,6-hexanediol diacrylate, 3-methyl-1,5-pentanediol diacrylate, 1,4-butanediol acrylate, propoxylated neopentyl glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, tetraethylene glycol diacrylate, and mixtures thereof. 1,6-hexanediol diacrylate, 3-methyl-1,5-pentanediol diacrylate, tripropylene glycol diacrylate, and mixtures thereof are preferably used. Monofunctional monomers suitable for the invention are isodecyl acrylate, lauryl acrylate, octyldecyl acrylate, isobornyl acrylate, 4-tert-butylcyclohexyl acrylate, trimethylcyclohexyanol acrylate, trimethylolpropane formal acrylate, and mixtures thereof. Isodecyl acrylate, lauryl acrylate, and mixtures thereof are preferred.Acrylate oligomers suitable for the invention are amine-modified acrylate oligomers, urethane acrylate oligomers, hyperbranched acrylate oligomers, and mixtures thereof. Mixtures of amine-modified acrylate oligomers and urethane acrylate oligomers are preferred. Suitable polyfunctional acrylate monomers are monomers with at least four functional groups. Suitable photoinitiators are methyl benzoyl formate (e.g. available under the trade name Genocure MBF), 2-hydroxy-2-methyl-1-phenylpropane (e.g. available under the trade name Omnirad 1173), 1-hydroxycyclohexyl phenyl ketone (e.g. available under the trade name Omnirad 184), 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one (e.g. available under the trade name Omnirad 127), 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)penoxy)phenyl)-2-methylpropan-1-one (e.g.available under the trade name Esacure KIP 160), difunctional ketosulfones such as 1-(4-[(4-benzoylphenyl)thio]phenyl)-2-methyl-2-[(4-methylphenyl)sulfonyl]-1-propan-1-one (e.g. available under the trade name Esacure 1001M), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g. available under the trade name Omnirad 819), ethyl-(2,4,6-trimethylbenzoyl)phenylphosphinate (e.g. available under the trade name Omnirad TPO-L), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (e.g. available under the trade name Genocure TPO), 2,4-diethylthioxanthone (e.g. available under the trade name Genocure DETX), isopropylthioxanthone (e.g. available under the trade name Genocure ITX), 1-chloro-4-propoxythioxanthone (e.g. available under the trade name Omnirad CPTX), polymeric ethyl (2,4,6-trimethylbenzoyl)phenyl phosphinate (e.g. available under the trade name Omnipol TP) and mixtures thereof.Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropane, 1-hydroxycyclohexylphenyl ketone, and mixtures thereof are preferably used. In a further preferred embodiment, the composition according to the invention contains 0.1 to 1.3 wt. %, preferably 0.3 to 1.0 wt. %, particularly preferably 0.4 to 0.8 wt. %, based in each case on the total weight of the composition, of one or more stabilizers to prevent polymerization during storage.Suitable stabilizers are methoxyphenol, butylhydroxytoluene, 2,6-bis(1,1-dimethylethyl)-4-(phenylenemethylene)-cyclohexa-2,5-dien-1-one, tris(N-hydroxy-N-nitrosophenylaminato-O,O')aluminium and mixtures thereof dissolved in radiation-curable resins or in acrylate acid esters (for example the commercially available products with the trade names Genorad 16, Genorad 22, Genorad 23, Genorad 24, Genorad 26 and Irgastab UV 22). 0070172WO 13.09.2023Mankiewicz Gebr. & Co.6 In a further preferred embodiment, the composition according to the invention contains 0.1 to 1.0 wt. %, preferably 0.2 to 0.8 wt. %, particularly preferably 0.3 to 0.6 wt. %, in each case based on the total weight of the composition, of one or more leveling additives for reducing the surface tension.Suitable flow control additives are organically modified silicones such as silicone polyethers and silicone acrylates (for example, the commercially available products with the trade names Tego Rad 2200 N, Tego Rad 2300, Tego Glide 432, Efka SL 3299, Byk UV 3500, Byk UV 3510, and Byk 377). Furthermore, the compositions according to the invention can contain the customary additives and auxiliaries familiar to the person skilled in the art. The compositions according to the invention produce matt-gloss coatings with gloss levels between 8 and 60 GU at a measurement angle of 60°. Coatings previously produced using inkjet printing processes exhibit gloss levels in the range of 60 to 90 GU at a measurement angle of 60°. The term "gloss" refers to the optical property of a surface to reflect light in a fully or partially specular manner. The degree of gloss is expressed as the quotient of the directly reflected portion and the diffusely reflected portion of a luminous flux falling on a surface.Specular gloss has a diffusely reflected component close to zero, ideally zero. In contrast, matt gloss or dullness has a proportion of specularly reflected light close to zero, ideally zero. The gloss of surface coatings such as varnish and paint layers is usually determined using a reflectometer or glossmeter. For this purpose, directed light is shone onto the sample surface at a defined angle. A detector records the light radiation reflected from the sample surface at the same angle. The results obtained are expressed in gloss units (GU). The angle at which the measurement is taken is selected depending on the material and the expected gloss to maximize the sensitivity of the detector. Measurements are usually taken at angles of 20°, 60°, and 85° to obtain the most accurate values.It has been found that the addition of a matting agent alone does not significantly reduce the gloss of the cured coating surface. Only the inventive combination of matting agents, monomers, oligomers, and photoinitiators results in digitally printable coating materials that form coatings with a matte-gloss surface. Due to the inventive combination of polar particles of the matting agent and nonpolar monomers of the binder, the matting agent particles accumulate in the surface of the applied, wet layer. This accumulation is favored by a low viscosity of the composition. However, it has been shown that an excessively low viscosity of the composition leads to particle separation even before application, which significantly complicates application or printing.In a preferred embodiment, the compositions according to the invention have viscosities in the range from 5 to 15 mPa*s at 45°C and 1000 / s, preferably 5 to 12 mPa*s at 45°C and 1000 / s, particularly preferably 5 to 8 mPa*s at 45°C and 1000 / s. The viscosities were determined using the Rheostress 600 instrument from Haake with the following parameters: measuring geometry plate-cone, temperature 45°C, shear rate 1000 / s. 0070172WO 13.09.2023Mankiewicz Gebr. & Co.8 In a further embodiment, the compositions according to the invention can be used as inks for producing matt-gloss coatings in inkjet printing processes, since they meet the requirements for inkjet inks. In addition to the required viscosity, they contain solid particles that are sufficiently small to pass through the nozzles of the print heads. The inks also exhibit a curing behavior that produces flawless print images in the very fast inkjet printing processes.The inks according to the invention can therefore be readily applied using commercially available inkjet printheads, for example from Konica Minolta. The compositions according to the invention, in particular the inkjet inks according to the invention, can be used for printing substrates such as glass, ceramics, plastics such as ABS-PC (acrylonitrile-butadiene-styrene copolymers in combination with polycarbonate) and polystyrene, wood, paper, and cardboard. They are preferably used for printing glass, furniture, toys, and packaging such as corrugated cardboard packaging. In a particularly preferred embodiment of the present invention, the inkjet inks are used to produce matt-gloss topcoats, in particular as topcoats in coating systems.In the following, the terms "cover coating" or "topcoat" refer to the uppermost layer of a coating system, which protects the underlying layers against mechanical and chemical damage. A further embodiment of the present invention are coating systems which have at least one pattern layer 0070172WO 13.09.2023Mankiewicz Gebr. & Co.9 made from one or more color inks and a topcoat layer made from one or more matte-gloss inks according to the invention. UV-curing color inks suitable for the inkjet printing process are used to produce the pattern layer. The color inks preferably contain pigments, oligomers, photoinitiators, and reactive diluents. In addition, they may contain other additives known and familiar to those skilled in the art.To improve the print image, the coating systems according to the invention can contain an additional ink layer beneath the color ink layer, which is produced from UV-curing inks containing light, preferably white, color pigments. The inks customary in color printing are then applied to this white ink layer. Particular preference is given to the colors cyan, magenta, yellow, and black, which are used in four-color printing (CMYK inks). In a further embodiment, the coating systems according to the invention also have a primer layer. This is produced from one or more primer coating materials, as is known and customary to those skilled in the art. It forms the bottommost layer of the coating system, which is applied first to the substrate. This is followed, if appropriate, by the white ink layer, then the pattern layer, and, as the uppermost layer, the topcoat layer.The invention further relates to a method for producing the coating system according to the invention, which comprises the following steps: 0070172WO 13.09.2023Mankiewicz Gebr. & Co.10 (a) applying one or more color inks by means of an inkjet printing process, (b) gelling the applied color inks by irradiation with UV radiation, (c) applying one or more matte-gloss inks by means of an inkjet printing process, (d) curing the entire layer structure by irradiation with UV radiation. In a further embodiment, the matte-gloss ink or matte-gloss inks applied in step (c) can be gelled by irradiation with UV radiation in a further step (c1) before curing the entire layer structure in step (d). The additional gelling of the matte-gloss ink layer enhances the matte gloss of the resulting surface.In the final step (d), the entire layer structure comprising the gelled pattern layer and the topcoat layer is fully cured by irradiation with radiation or light in the wavelength range between 450 and 180 nm. Medium-pressure mercury lamps with a power of 200 to 500 W / cm² and LED lamps with a power of 10 to 30 W / cm² are preferably used for this purpose, with the preferred radiation dose being in the range between 500 and 2000 mJ / cm². In a further preferred embodiment of the process, steps (a) and (b) are first carried out using white inks and then repeated using colored inks. In this way, a light, preferably white, ink layer is produced, onto which the actual image or pattern is printed. The white underlay 0070172WO 13.09.2023Mankiewicz Gebr. & Co.11 results in a significantly improved print image, especially on colored or dark substrate surfaces.After an ink has been applied to a substrate, it is usually cured by irradiation with UV light or UV radiation to form a coating. To improve adhesion within a coating system containing several consecutive layers, the layers are first only partially cured or gelled to the point where they no longer run. This process step is referred to below as pinning. The terms gelling or pinning refer to the fixing of a coating material by a pre-reaction. The coating material is gelled, i.e. it is pre-cured to the point where it is no longer liquid. It already forms a sufficiently solid coating, which, however, is not yet fully cured. LED lamps that emit radiation with a wavelength of 385 or 395 nm are preferably used as the radiation source for gelling or pinning. The power is between 2 and 5 W.Preferably, irradiation is carried out with a dose in the range of 20 to 100 mJ / cm². In the last step, the entire layer structure is fully cured. During this final curing of all printed and gelled layers, the coatings also crosslink with one another, resulting in very stable layer structures. In a preferred embodiment of the process according to the invention, the process parameters are specified such that a surface structure is formed. The formation of grid structures is particularly preferred. In a further preferred embodiment, the matt-gloss inks are applied with layer thicknesses in the range of 3 to 60 µm. The process according to the invention can be carried out with commercially available inkjet printers in the known and familiar manner to the person skilled in the art. known methods familiar to the person skilled in the art. In a further embodiment, a primer layer is first applied to the substrate surface in order to 0070172WO 13.09.2023Mankiewicz Gebr. & Co.13 Example mono un one e cry a - monomers 35 polymethylurea powder 5 polyfunctional acrylate monomers 12 acrylate oligomers 6 photoinitiators 7 Example 2 Component Share / [wt.%] difunctional acrylate monomers 30 monofunctional acrylate monomers 42 polymethylurea powder 10 polyfunctional acrylate monomers 5 acrylate oligomers 6 photoinitiators 7 Example 3 Component Share / [wt.%] difunctional acrylate monomers 15 monofunctional acrylate monomers 39 polymethylurea powder 15 polyfunctional acrylate monomers 12 acrylate oligomers 12 photoinitiators 7 0070172WO 13.09.2023Mankiewicz Gebr. & Co.14 Example 4 Component Share / [Wt.%] difunctional acrylate monomers 25 monofunctional acrylate monomers 20 polymethylurea powder 20 polyfunctional acrylate monomers 14 acrylate oligomers 14 photoinitiators 7 testing Coating thickness: approx. 15 µm UV radiation sources: IST MBS-5 (270 W / cm) with 600 mJ / cm² Gloss level: A standard gloss meter (BYK Gardener gloss meter from BYK) is used to determine the gloss level. The gloss is measured at an angle of 60°. Visual inspection: The surface of the coating was visually inspected by observing the sample under standard D65 illuminant at an angle of 45°. Good leveling results in a closed surface (result: OK). 0070172WO 13.09.2023

Claims

Mankiewicz Gebr. & Co.15 Thumb-Twist Test: The thumb is pressed against the coated surface of the test specimen and rotated on the surface. A fully cured coating does not feel sticky, and twisting the thumb does not leave any smear marks (result: OK). The results of the tests are shown in Table 1. Table 1 Gloss level visual test Thumb-twist test [GU at 60°] Example 1 19 OK OK Example 2 17 OK OK Example 3 15 OK OK Example 4 14 OK OK 0070172WO 13.09.2023Mankiewicz Gebr. & Co.16 Patent claims 1. Coating material composition containing 10 to 40 wt. % of one or more difunctional monomers, 20 to 50 wt. % of one or more monofunctional monomers, 5 to 35 wt. % of one or more organic matting agents, 1 to 30 wt.-% of one or more acrylate oligomers or one or more polyfunctional acrylate monomers or mixtures of one or more acrylate oligomers and one or more polyfunctional acrylate monomers, 2 to 13 wt.% of one or more photoinitiators, each based on the total weight of the composition.

2. Composition according to claim 1, characterized in that the matting agent(s) are selected from organic matting agents based on polymer powders.

3. Composition according to one of the preceding claims, characterized in that the composition further contains 0.1 to 1.3 wt.% of one or more stabilizers, based on the total weight of the composition.

4. Composition according to claim 3, characterized in that the stabilizer(s) are selected from methoxyphenol, butylhydroxytoluene, 2,6-bis(1,1-dimethylethyl)-4-(phenylenemethylene)-cyclohexa-2,5-diene- 0070172WO 13.09.2023Mankiewicz Gebr. & Co.17 1-one, tris(N-hydroxy-N-nitrosophenylaminato-O,O')aluminum and mixtures thereof.

5. Composition according to one of the preceding claims, characterized in that the composition further contains 0.1 to 1.0 wt. % of one or more leveling additives, based on the total weight of the composition.

6. Composition according to claim 5, characterized in that the leveling additive(s) are selected from organically modified silicones.

7. Use of the composition according to one of claims 1 to 6 as a matt gloss ink for producing matt gloss topcoats in inkjet printing processes.

8. Coating system comprising - at least one pattern layer produced from one or more color inks, - at least one topcoat layer produced from one or more matt gloss inks according to one of claims 1 to 6.

9. Coating system according to claim 8, characterized in that the coating system additionally comprises a primer layer.

10. The coating system according to claim 8 or 9, characterized in that the coating system additionally comprises a layer made of one or more white inks. 0070172WO 13.09.2023.

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