Method for inkjet printing with the aid of a primer in combination with a water-based inkjet ink

Abstract

The present invention relates to an inkjet printing method by means of a combination of a primer and an aqueous inkjet ink, which makes it possible to obtain a very resistant and good-looking printed result. The primer has a non-ionic binding agent (in particular with polyurethane units) and a fixing agent, wherein these two components are used in a specific amount ratio to each other. The aqueous inkjet ink relates to an aqueous inkjet ink whose binding agent comprises acrylic ester units, methacrylic ester units and / or polyurethane units as structural units. This combination of primer and aqueous inkjet ink is highly compatible with each other and can advantageously be employed in a common inkjet printing method.

Description

Technical Field

[0001] This invention relates to an inkjet printing method, wherein at least one primer and at least one water-based inkjet ink are used. Background Technology

[0002] Water-based inkjet inks are known to be used in the printing industry. Inkjet printing methods, often referred to as inkjet printing, involve one or more inkjet printheads releasing water-based inkjet ink onto a substrate in a controlled manner through multiple printing nozzles. To achieve better inkjet ink adhesion and obtain a better printed image on the substrate (such as paper, cardboard, or film), it is generally known to apply a primer / base coat to the substrate beforehand. The application of the primer can be performed within the inkjet printer itself. Commonly, the primer is first partially dried after application, a process known as "pinning." Water-based inkjet ink is then printed onto the partially cured primer, and the substrate is finally dried using infrared and / or hot air methods, resulting in the finished printed product.

[0003] US 2011 / 0143040 A1 describes water-based inkjet inks and an inkjet printing method, wherein the inkjet ink comprises a polyurethane polymer with an acid value greater than 20 mg KOH / g.

[0004] EP 1 486 541 A1 describes water-based inkjet inks and fixative liquids (fixers), wherein the inkjet inks may include polyurethanes with higher acid values.

[0005] The combination of primer and water-based inkjet inks described in the prior art has drawbacks. For example, in some cases, it is impossible to obtain an abrasion-resistant or waterproof film on the substrate. Furthermore, inkjet inks may run on the primer (intercolor bleeding). Another problem may be that the ink film cracks and deteriorates during heat drying.

[0006] The demand for a combination of primer and water-based inkjet inks remains, where these two components are highly compatible and avoid the aforementioned printing drawbacks. Both the primer and water-based inkjet inks should be applicable and dryable using conventional inkjet printers. They should be able to print ink films resistant to mechanical loads (such as abrasion). Furthermore, the ink film should be waterproof and not run over the primer used (with little or no intercolor bleeding). In addition, the printed inkjet ink film should not crack during heat drying, but should produce a flawless appearance. Summary of the Invention

[0007] The inventors have now discovered that certain combinations of primers and water-based inkjet inks can meet the aforementioned requirements, be compatible with conventional inkjet printers, and produce durable and aesthetically pleasing prints. This primer contains a nonionic binder (particularly polyurethane units) and a fixative, wherein these two components are used in specific quantitative ratios to each other. The water-based inkjet inks include acrylate units, methacrylate units, and / or polyurethane units as structural units. When used in common inkjet printing methods, these combinations of primers and water-based inkjet inks precisely coordinate with each other to produce the desired advantageous results.

[0008] Accordingly, the present invention relates to an inkjet printing method, in which:

[0009] i) Provide printing materials

[0010] ii) Applying at least one primer to the substrate, wherein the at least one primer comprises the following components:

[0011] a) at least one fixative selected from metal salts.

[0012] b) At least one binder, said binder being selected from nonionic polymers.

[0013] Wherein, the ratio of component a) to component b) is in the range of 1:35 to 1:600, wherein component a) is counted per kilogram molar of fixative with reference to the total weight of the at least one primer, and component b) is counted as a weight percentage with reference to the at least one primer.

[0014] iii) Dry at least partially the at least one primer on the printing substrate.

[0015] iv) Printing at least one water-based inkjet ink onto the at least one primer using an inkjet printing method, wherein the at least one water-based inkjet ink comprises the following components:

[0016] A) At least one pigment.

[0017] B) At least one moisturizer,

[0018] C) at least one binder selected from polymers having structural units selected from acrylate units, methacrylate units, and polyurethane units, and

[0019] D) Water,

[0020] and

[0021] v) Dry the water-based inkjet ink that has been printed onto the primer.

[0022] As the printing substrate in step i), all types of printing substrates that can be processed in an inkjet printer are preferred, especially paper, paperboard, and plastic film. Non-absorbent printing substrates are particularly preferred, as they are particularly advantageous for printing with primers and water-based inkjet inks.

[0023] In step ii), the at least one primer is applied to the printing substrate, which can be done according to methods known in principle, preferably in the same inkjet printer in which the water-based inkjet ink is subsequently printed, i.e., "inline". The application in step ii) is preferably performed through one or more nozzles.

[0024] In step iii), the printing material is at least partially dried, which can be done according to methods known in principle, preferably by irradiating the printing material with infrared light and / or heating the printing material with hot air. In step v), the printed water-based inkjet ink is dried, which can also be done according to methods known in principle, preferably by irradiating the printing material with infrared light and / or heating the printing material with hot air.

[0025] In step iv), the at least one water-based inkjet ink is printed onto the at least one primer, which is performed by means of inkjet printing. The inkjet printing is carried out in an inkjet printer, wherein, in principle, any inkjet printer suitable for printing with water-based inkjet inks can be used. Such inkjet printers typically include one or more inkjet printheads having multiple printing nozzles. The inkjet printheads are typically connected to an ink supply system.

[0026] According to the present invention, the ratio of component a) to component b) is in the range of 1:35 to 1:600, wherein component a) is counted per kilogram mole of fixative with reference to the total weight of the at least one primer, and component b) is counted as a weight percentage with reference to the at least one primer. Thus, on the one hand, the at least one fixative, as component a) in its amount of substance (mol), is referenced to the total weight of the at least one primer. On the other hand, the weight share of the at least one binder, as component b) in its weight percentage, is referenced to the total weight of the at least one primer. Therefore, these two ratios are proportional to each other in the range of 1:35 to 1:600. In a preferred embodiment, the ratio of component a) to component b) is in the range of 1:50 to 1:150, wherein component a) is counted per kilogram mole of fixative with reference to the total weight of the at least one primer, and component b) is counted as a weight percentage with reference to the at least one primer.

[0027] For example, if the amount of fixative a) in each kilogram of primer is 0.1 mol, then the amount of binder b) is 3.5 to 60% by weight of the primer, or preferably 5.0 to 15% by weight of the primer.

[0028] According to the invention, the at least one binder b) is selected from nonionic polymers. Nonionic polymers should be understood as polymers with no or only a small number of ionic groups (e.g., sulfonate groups or carboxyl groups). The degree of ionicity of the binder can be expressed as an acid value. In a preferred embodiment, the at least one binder b) has an acid value of less than 20 mg KOH / g, particularly preferably less than 10 mg KOH / g, and especially preferably less than 5 mg KOH / g. The acid value indicates the amount of potassium hydroxide (in milligrams) required to neutralize 1 g of the corresponding binder. For example, DIN ISO 2114 describes how to determine the acid value.

[0029] In another preferred embodiment, the at least one binder b) is selected from polymers having structural units selected from polyurethane units. Preferably, it involves one or more polyurethanes (polyurethanes). These polyurethanes can exist in the form of homopolymers or copolymers.

[0030] Polyurethanes are known in principle to those skilled in the art and are obtained by polycondensation of one or more polyisocyanates (typically diisocyanates) with one or more polyols (typically diols). Examples of polyisocyanates are aromatic, araliphatic, aliphatic, or cycloaliphatic diisocyanates such as dimethylene diisocyanate, tetramethylene diisocyanate, 1,12-diisocyanatododecane, hexamethylene diisocyanate, 2,3,3-trimethylhexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 4,4'-dicyclohexyl diisocyanate, 1,4-phenylene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, 1,5-naphthalene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, or 4,4'-diphenyldimethylmethane diisocyanate. Examples of polyols are alkanediols such as ethylene glycol, polyethylene glycol, propylene glycol, tetramethyl ethylene glycol, polytetramethyl ethylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, or 2-methyl-1,8-octanediol.

[0031] If the at least one binder b) is used in the form of a homopolymer, it essentially contains only polyurethane units as linking units in the polymer chain. If it is a copolymer, other linking units besides polyurethane units are present in the polymer chain, preferably ester, ether, or carbonate groups. These preferred copolymers are polymers in which polyurethane units and ester, ether, or carbonate units coexist in the polymer chain, existing alternately or randomly in block form as block copolymers.

[0032] The average molecular weight (Mw) of the at least one binder b) is preferably in the range of 200 g / mol to 70,000 g / mol, particularly preferably in the range of 500 g / mol to 60,000 g / mol, and very particularly preferably in the range of 1,000 g / mol to 40,000 g / mol.

[0033] According to an embodiment of the present invention, the at least one fixative a) is selected from metal salts. In another preferred embodiment, the at least one fixative a) is selected from calcium salts and magnesium salts, preferably selected from calcium chloride, magnesium chloride, calcium nitrate, calcium formate, and magnesium acetate.

[0034] The at least one primer may include other common components, particularly water, defoamers, bactericides, and the like.

[0035] In principle, all pigments that can be used in water-based inkjet inks (such as titanium dioxide) are suitable as pigment A for the at least one water-based inkjet ink.

[0036] In another preferred embodiment, the at least one humectant B) is selected from monohydric alcohols and polyhydric alcohols. In a particularly preferred embodiment, the at least one humectant B) is selected from: ethylene glycol, diethylene glycol, diethylene glycol monoethyl ether, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-hydroxymethyl-2-methyl-1,3-propanediol, 3-methoxy-3-methyl-1-butanol, sorbitol, and sucrose.

[0037] In another preferred embodiment, the at least one binder C) included in the water-based inkjet ink is in the form of one or more polymer dispersions. Such polymer dispersions are commercially available, for example, under brand names. Or Takelac.

[0038] The at least one binder C) is selected from polymers having structural units, which are selected from acrylate units, methacrylate units, and polyurethane units, preferably polyurethane units. They can be homopolymers or copolymers. Such polymers can be obtained, for example, by free radical polymerization or copolymerization of acrylic monomers, methacrylate monomers, and condensation of diols with diisocyanates.

[0039] The average molecular weight (Mw) of the at least one binder C is preferably in the range of 200 g / mol to 70,000 g / mol, particularly preferably in the range of 500 g / mol to 60,000 g / mol, and very particularly preferably in the range of 1,000 g / mol to 40,000 g / mol.

[0040] According to embodiments of the present invention, the amount of structural units (i.e., acrylate units, methacrylate units, and polyurethane units) of the polymer used as binder C is preferably at least 20 mol-%, particularly preferably at least 50 mol-%, and especially preferably at least 70 mol-%.

[0041] In another preferred embodiment, the at least one primer includes the at least one fixative a), wherein the at least one fixative a) is present in an amount of 0.01 mol to 0.30 mol of fixative per kilogram of the total weight of the at least one primer, preferably in an amount of 0.05 mol to 0.20 mol of fixative per kilogram of the total weight of the at least one primer.

[0042] In another preferred embodiment, the at least one primer includes the at least one binder b), wherein the at least one binder b) is present in an amount of 5 to 40 percent by weight of the entire at least one primer, preferably in an amount of 10 to 30 percent by weight of the entire at least one primer.

[0043] In another preferred embodiment, the at least one water-based inkjet ink comprises the at least one pigment A), wherein the at least one pigment A is present in an amount of 0.5 to 20% by weight of the entire at least one water-based inkjet ink, preferably in an amount of 1 to 10% by weight of the entire at least one water-based inkjet ink, and particularly preferably in an amount of 3 to 7% by weight of the entire at least one water-based inkjet ink.

[0044] In another preferred embodiment, the at least one aqueous inkjet ink includes the at least one humectant B), wherein the at least one humectant B) is present in an amount of 2 to 40% by weight of the entire at least one aqueous inkjet ink, preferably in an amount of 5 to 30% by weight of the entire at least one aqueous inkjet ink, and particularly preferably in an amount of 10 to 20% by weight of the entire at least one aqueous inkjet ink.

[0045] In another preferred embodiment, the at least one water-based inkjet ink includes the at least one binder C), wherein the at least one binder C) is present in an amount of 1 to 30% by weight of the entire at least one water-based inkjet ink, preferably in an amount of 2 to 20% by weight of the entire at least one water-based inkjet ink, and particularly preferably in an amount of 4 to 10% by weight of the entire at least one water-based inkjet ink.

[0046] In another preferred embodiment, the at least one water-based inkjet ink includes water (D), wherein water (D) is present in an amount of 10 to 90% by weight of the entire at least one water-based inkjet ink, preferably in an amount of 20 to 80% by weight of the entire at least one water-based inkjet ink.

[0047] The at least one water-based inkjet ink may contain other common components, such as defoamers, bactericides, humectants, wetting agents, corrosion inhibitors, buffers, viscosity additives, etc. Detailed Implementation

[0048] Example 1

[0049] Primer 1:

[0050] 88.9% by weight water

[0051] 10.0% by weight of polyurethane-based binder (referring only to the polymer portion of the dispersion) R-9340)

[0052] 1.0% by weight of fixative (calcium chloride)

[0053] 0.1% by weight of fungicide (Proxel GXL)

[0054] Ink 1:

[0055] 74.0% by weight of water

[0056] 15.0% by weight of humectant (ethylene glycol)

[0057] 5.4% by weight of polyurethane-based binder (Takelac WS 5100)

[0058] 4.5% by weight of pigment (polyelectrolyte-stabilized inorganic pigment)

[0059] 1.0% by weight of wetting agent ( 465)

[0060] 0.1% by weight of fungicide (Proxel GXL)

[0061] Using an automatic coating machine The primer 1 is applied to the plastic film at a thickness of 9 μm using a doctor blade and then dried. Ink 1 is then printed onto the coated plastic film using a desktop inkjet printer or a SAMBA inkjet printhead and dried.

[0062] result:

[0063] Color bleeding, based on optical / visual assessment: Good

[0064] Water resistance, based on wiping with a damp cellulose cotton ball and subsequent optical / visual assessment: Good

[0065] Abrasion resistance, based on rubbing with nitrile gloves and subsequent optical / visual evaluation: Good

[0066] The ink drying performance minimizes film breakage; based on optical / visual evaluation: Good.

[0067] Example 2

[0068] Primer 2:

[0069] 78.9% by weight water

[0070] 20.0% by weight of polyurethane-based binder (referring only to the polymer portion of the dispersion, Takelac XW UM3)

[0071] 1.0% by weight of fixative (magnesium chloride hexahydrate)

[0072] 0.1% by weight of fungicide (Proxel GXL)

[0073] Ink 2:

[0074] 74.0% by weight of water

[0075] 15.0% by weight of humectant (ethylene glycol)

[0076] 5.4% by weight of polyurethane-based binder ( D-2101)

[0077] 4.5% by weight of pigment (polyelectrolyte-stabilized inorganic pigment)

[0078] 1.0% by weight of wetting agent ( 465)

[0079] 0.1% by weight of fungicide (Proxel GXL)

[0080] The primer 2 is applied to the plastic film at a thickness of 9 μm using an automatic coater and doctor blade and then dried. Ink 2 is then printed onto the coated plastic film using a desktop inkjet printer or a SAMBA inkjet printhead and dried.

[0081] result:

[0082] Color bleeding, based on optical / visual assessment: Good

[0083] Water resistance, based on wiping with a damp cellulose cotton ball and subsequent optical / visual assessment: Good

[0084] Abrasion resistance, based on rubbing with nitrile gloves and subsequent optical / visual evaluation: Good

[0085] The ink drying performance minimizes film breakage; based on optical / visual evaluation: Good.

[0086] Comparative Example 1

[0087] Base coat V1:

[0088] 88.9% by weight water

[0089] 10.0% by weight of polyvinyl alcohol-based binder (referring only to the polymer portion of the dispersion) 4-98)

[0090] 1.0% by weight of fixative (calcium chloride)

[0091] 0.1% by weight of fungicide (Proxel GXL)

[0092] Ink V1:

[0093] 74.0% by weight of water

[0094] 15.0% by weight of humectant (ethylene glycol)

[0095] 5.4% by weight of polyurethane-based binder (Takelac WS 5100)

[0096] 4.5% by weight of pigment (polyelectrolyte-stabilized inorganic pigment)

[0097] 1.0% by weight of wetting agent ( 465)

[0098] 0.1% by weight of fungicide (Proxel GXL)

[0099] The primer V1 was applied to the plastic film at a thickness of 9 μm using an automatic coater and doctor blade and then dried. Ink V1 was then printed onto the coated plastic film using a desktop inkjet printer or a SAMBA inkjet printhead and dried.

[0100] result:

[0101] Color bleeding, based on optical / visual assessment: Good

[0102] Water resistance, based on wiping with a damp cellulose cotton ball and subsequent optical / visual assessment: Poor

[0103] Abrasion resistance, based on rubbing with nitrile gloves and subsequent optical / visual evaluation: Good

[0104] The ink drying performance minimizes film breakage; based on optical / visual evaluation: poor.

Claims

1. A method for inkjet printing, wherein in the method: i) Provide printing materials, ii) Applying at least one primer to the printing substrate, wherein, The at least one primer comprises the following components: a) at least one fixative selected from metal salts. b) At least one binder, said binder being selected from nonionic polymers. Wherein, the ratio of component a) to component b) is in the range of 1:35 to 1:600, wherein component a) is counted per kilogram molar of fixative with reference to the total weight of the at least one primer, and component b) is counted as a weight percentage with reference to the at least one primer. iii) At least partially dry the at least one primer on the printing substrate. iv) Printing at least one water-based inkjet ink onto the at least one base coating by means of inkjet printing, wherein the at least one water-based inkjet ink comprises the following components: A) At least one pigment, B) At least one moisturizer, C) at least one binder selected from polymers having structural units selected from acrylate units, methacrylate units, and polyurethane units, and D) Water, and v) Dry the water-based inkjet ink that has been printed onto the substrate.

2. The method according to claim 1, in, The ratio of component a) to component b) is in the range of 1:50 to 1:150, wherein component a) is counted per kilogram molar of fixative with reference to the total weight of the at least one primer, and component b) is counted as a weight percentage with reference to the at least one primer.

3. The method according to claim 1 or 2, in, Component b) At least one binder has an acid value of less than 20 mg KOH / g, as per the whole component b) 4. The method according to claim 1 or 2, in, Component b) At least one binder is selected from polymers having structural units, said structural units being selected from polyurethane units.

5. The method according to claim 1 or 2, in, Component a) At least one fixative is selected from calcium salts and magnesium salts.

6. The method according to claim 1 or 2, in, Component a) At least one fixative is selected from calcium chloride, magnesium chloride, calcium nitrate, calcium formate, and magnesium acetate.

7. The method according to any one of claims 1 or 2, in, Component B) At least one humectant is selected from monohydric alcohols and polyhydric alcohols.

8. The method according to claim 7, in, Component B) At least one humectant is selected from: ethylene glycol, diethylene glycol, diethylene glycol monoethyl ether, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-hydroxymethyl-2-methyl-1,3-propanediol, 3-methoxy-3-methyl-1-butanol, sorbitol and sucrose.

9. The method according to claim 1 or 2, in, The water-based inkjet ink includes component C) in the form of one or more polymer dispersions and at least one binder.

10. The method according to claim 1 or 2, in, Component C) At least one binder is selected from polymers having structural units, said structural units being selected from polyurethane units.

11. The method according to claim 1 or 2, in, The at least one primer includes component a) at least one fixative, wherein component a) at least one fixative has an amount of 0.01 mol to 0.30 mol of fixative per kilogram of the total weight of the at least one primer.

12. The method according to claim 1 or 2, in, The at least one primer includes component b) at least one binder, wherein component b) at least one binder is present in an amount of 5 to 40 weight percent of the entire at least one primer.

13. The method according to claim 1 or 2, in, The at least one water-based inkjet ink includes component A) at least one pigment, wherein component A) at least one pigment has an amount of 0.5 to 20% by weight relative to the whole at least one water-based inkjet ink.

14. The method according to claim 1 or 2, in, The at least one water-based inkjet ink includes component B) at least one humectant, wherein component B) at least one humectant is present in an amount of 2 to 40 percent by weight relative to the whole at least one water-based inkjet ink.

15. The method according to claim 1 or 2, in, The at least one water-based inkjet ink includes component C) at least one binder, wherein component C) at least one binder has an amount of 1 to 30 percent by weight relative to the whole at least one water-based inkjet ink.

16. The method according to claim 1 or 2, in, The at least one water-based inkjet ink includes component D) water, wherein component D) water has an amount of 10 to 90 percent by weight relative to the whole at least one water-based inkjet ink.

17. The method according to claim 1 or 2, in, In steps iii) and v), the printing material is dried by irradiating it with infrared radiation and / or by heating it with hot air.