Use of non-volatile and low water sensitive counterions in latices

Abstract

The present invention relates to a latex particle comprising at least one positively charged counter ion on the surface thereof, the use of the latex particle in a coating and / or a printing ink, a coating comprising the latex particle, a printing ink comprising the article, the use of specific positively charged ions in a coating and / or in printing, and a printing method wherein these specific ions are used.

Description

[0001] Use of non-volatile and low water sensitive counterions in latices

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a latex particle comprising at least one positively charged counter ion on the surface thereof, the use of the latex particle in a coating and / or a printing ink, a coating comprising the latex particle, a printing ink comprising the article, the use of specific positively charged ions in a coating and / or in printing, and a printing method wherein these specific ions are used.

[0004] BACKGROUND ART

[0005] In printing with latex prints, polar groups on the surface of the latex particles do not disappear during the film-formation process. In the resulting prints, they always remain a source of unwanted water sensitivity. They may facilitate co-solvent entrapment, which is bad for robustness, or attract water into the film when exposed to a high humidity environment. The type of counter-ion on the surface plays an important role. Polyester latices obtained by phase inversion emulsification processes and having counter-ions like Na+, K+or Li+are known and are amongst others described in US 9,964,880 B1, US 2016 / 0326338 A1, US 9,798,255 B1, and US 2015 / 0025174 A1.

[0006] The coating and paint industry solves this problem by using a volatile counter ion.

[0007] Ammonium becomes ammonia and evaporates during film-formation, which contributes to the water resistance of the film. However, the use of volatile components like ammonia is not compatible with many processes, e.g. a printing process. An alternative approach is to temper water sensitivity by adding a wax to the ink formulation, but the use of wax can come with unwanted side effects like unwanted surfactant interactions or limited formulation freedom / creaming.

[0008] Therefore, there is a need for providing improved latex particles and improved methods of countering polar groups on the surface thereof.

[0009] SUMMARY OF THE INVENTION

[0010] The inventors found specific counterions particularly useful in latices but in printing and coating processes generally, which are not volatile, like ammonia, but also not as water sensitive as the currently used ones, primarily potassium. The lattices particularly also show improved robustness, particularly in printing processes.

[0011] In a first aspect, the present invention relates to a latex particle, comprising at least one positively charged counter ion on the surface thereof, wherein the counter ion is selected from the group consisting of

[0012] carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and

[0013] aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof.

[0014] A second aspect of the invention relates to the use of the latex particle in a coating and / or a printing ink.

[0015] Furthermore disclosed is in a third aspect a printing ink comprising the latex particle, and in a fourth aspect a coating comprising the latex particle.

[0016] A fourth aspect of the invention is directed to the use of a ion selected from the group consisting of

[0017] carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and

[0018] aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof in a coating and / or in printing, particularly in a primer liquid and / or a printing ink. In a fifth aspect, the invention relates to a printing method, comprising: applying a primer liquid on at least one surface of a recording medium; and printing an image with at least one printing ink comprising at least one latex on the surface of the recording medium on which the primer has been applied; wherein the primer liquid and / or the at least one latex comprises an ion selected from the group consisting of

[0019] carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and

[0020] aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof.

[0021] A sixth aspect relates to a dispersion comprising one or more the present latex particles.

[0022] Further aspects and embodiments of the invention are disclosed in the dependent claims and can be taken from the following description, figures and examples, without being limited thereto.

[0023] Where appropriate, the above-mentioned configurations and developments can be combined implementations can be combined with each other as desired, as far as this is reasonable. Further possible configurations, developments and implementations of the invention also include combinations, which are not explicitly mentioned, of features of the invention which have been described previously or are described in the following with reference to the embodiments. In particular, in this case, a person skilled in the art will also add individual aspects as improvements or supplements to the basic form of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will become more fully understood from the detailed description given herein below and accompanying schematical drawings which are given by way of illustration only and are not limitative of the invention, and wherein:

[0025] Fig. 1 shows schematically a method in accordance with an embodiment of the invention.

[0026] Fig. 2 shows results obtained in the present Examples.

[0027] DESCRIPTION OF EMBODIMENTS

[0028] Detailed embodiments of the present invention are disclosed hereinafter; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually and appropriately detailed structure. In particular, features presented and described in separate dependent claims may be applied in combination and any combination of such claims are herewith disclosed.

[0029] Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and / or having, as used herein, are defined as comprising (i.e., open language).

[0030] In the present specification, amounts of a substance are usually given as weight percent (wt%, % w / w), unless noted otherwise or clear from the context.

[0031] Carbohydrates are biomolecules consisting of carbon (C), hydrogen (H) and oxygen (O) atoms. As used herein, the terms "comprises", "comprising", “contains”, “containing”, "includes", "including", "has", "having" or any other variation thereof, are intended to cover a nonexclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0032] According to a first aspect, the present invention relates to a latex particle, comprising at least one positively charged counter ion on the surface thereof, wherein the counter ion is selected from the group consisting of

[0033] carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and

[0034] aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof.

[0035] While the production of the latex particle is not particularly restricted, a latex particle of the invention can e.g. be produced by ion exchange or by phase inversion emulsification process, e.g. by dissolving the latex resin in an organic water miscible solvent like THF in its acidic state, which is commercially available, add an amine to neutralize the COOH groups, and add water while mixing.

[0036] Particularly, the latex particle of the invention can be used in a dispersion, e.g. an aqueous dispersion. Thus, disclosed is also a dispersion comprising one or more the present latex particles. In the dispersion, a solvent is not particularly restricted, and one solvent like water can be used, or a mixture of solvents which are not particularly restricted. The latex particle itself is not particularly restricted regarding its material and / or size. According to certain embodiments, the resin of the latex particle is based on a synthetic resin chosen from the group consisting of polyester resins, polyurethane resins, polyepoxy resins, polyamide resins, polyether resins, poly(meth)acrylic resins, acrylsilicone resins, fluorine-based resins, polyolefin resins, polystyrene-based resins, polybutadiene-based resins, polyvinyl acetate-based resins, polyvinyl alcohol-based resins, polyvinyl ester-based resins, polyvinyl chloride-based resins, polyacrylic acid based resins, unsaturated carboxylic acid-based resins, and copolymers such as styrene- acrylate copolymer resins, styrene-butadiene copolymer resins. The water-dispersible resin may be used in the form of a homopolymer, a copolymer or a composite resin, and all of water-dispersible resins having a monophase structure or core-shell structure and those prepared by power-feed emulsion polymerization may be used. Particularly, the latex particle has at least one negative charged group on the surface thereof, which is not particularly restricted and can e.g. be a carbonyl group, a sulfonic group, a sulfate group, a phosphate group, etc., which can be expressed as a functional acid value. The acid value (AV) is not particularly restricted and can be suitably set. The molecular weight and glass transition temperature of the latex particle are not restricted. Particularly, the latex particle contains a polyester or is composed of a polyester, wherein the polyester is not particularly restricted. Particularly, latex is a polyester latex. Suitable polyesters are e.g. disclosed in US9964880, LIS2016326338, US9798255, LIS2015025174, and EP 1555295 A1, to which reference is made with regard to polyesters. Particularly the latex has polar groups, particularly on a surface thereof.

[0037] The latex particle may comprise the resin in the form of a homopolymer, a copolymer or a composite resin, and e.g. all of water-dispersible resins having a monophase structure or core-shell structure and those prepared by power-feed emulsion polymerization may be used.

[0038] The latex particle comprises at least one positively charged counter ion on the surface thereof, but of course can comprise more than one positively charged counter ion on the surface thereof. The counter ion is selected from the group consisting of carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof. The at least one positively charged counter ion on the surface of the latex particle presumably interacts with the latex particle predominantly due to electrostatic interactions, and other forces probably can be neglected or are not present.

[0039] The carbohydrates with 3 to 6 carbon atoms are not particularly restricted and thus include sugars, particularly monosaccharides, sugar alcohols, uronic acids, deoxy sugars, etc. Also the aromatic alcohols are not particularly restricted. According to certain, preferred, embodiments, the carbohydrates with 3 to 6 carbon atoms, particularly monosaccharides, and / or aromatic alcohols are mono-substituted, i.e. only have one functional group as a substituent. However, it is not excluded that more than one substituent is present, and these may be the same or different.

[0040] The at least one functional group is chosen from a bound ammonium group (-NHa+) bound to the monosaccharide and / or the aromatic alcohol; a bound alkylammonium group (-(NH2RD, wherein R is an alkyl group with 1 to 4 carbon atoms, i.e. methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, preferably 1 to 2 carbon atoms, i.e. methyl, ethyl, and particularly preferably methyl, i.e. a methylammonium group; and a bound acyl ammonium group with 2 to 5 carbon atoms(-(NH2(CO)R)+), wherein R is an alkyl group with 1 to 4 carbon atoms, i.e. methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, preferably 1 to 2 carbon atoms, i.e. methyl, ethyl, and particularly preferably methyl, i.e. an acetylammonium group, as well as mixtures thereof.

[0041] According to certain embodiments, the counter ion is selected from monosaccharides with at least one ammonium group; monosaccharides with at least one alkylammonium group with 1 to 4 carbon atoms in the alkylammonium group, preferably 1 or 2 carbon atoms in the alkylammonium group; monosaccharides with at least one acyl ammonium group with 2 to 5 carbon atoms in the alkylammonium group, preferably 2 to 3 carbon atoms in the alkylammonium group, further preferably at least one acetyl ammonium group; phenols with at least one ammonium group; phenols with at least one alkylammonium group with 1 to 4 carbon atoms in the alkylammonium group, preferably 1 or 2 carbon atoms in the alkylammonium group; phenols with at least one acyl ammonium group with 2 to 5 carbon atoms in the alkylammonium group, preferably 2 to 3 carbon atoms in the alkylammonium group, further preferably at least one acetyl ammonium group; and mixtures thereof. Preferred are monosaccharides, particularly hexoses, with at least one ammonium group; monosaccharides, particularly hexoses, with at least one alkylammonium group with 1 to 4 carbon atoms in the alkylammonium group, preferably 1 or 2 carbon atoms in the alkylammonium group; and / or monosaccharides, particularly hexoses, with at least one acyl ammonium group with 2 to 5 carbon atoms in the alkylammonium group, preferably 2 to 3 carbon atoms in the alkylammonium group, further preferably at least one acetyl ammonium group

[0042] According to certain embodiments, the counter ion is selected from an N-methyl glucosammonium group, a glucosammonium group, an N-acetyl glucosammonium group, an N-methyl galactosammonium group, a galactosammonium group, an N-acetyl galactosammonium group, a fructosammonium group, a mannosammonium group, and mixtures thereof. Particularly preferably are an N-methyl glucosammonium group, a glucosammonium group, and / or an N-acetyl glucosammonium group, and particularly preferable is N-methyl glucosammonium as counter ion on the latex. Methyl glucamine as basis for the N-methyl glucosammonium particularly is excellent in price and nonvolatility as well as regarding low water sensitivity and high robustness, is biobased, non-toxic, food-safe, and degradable. Other suitable substances like very hydrophilic amines like aminoglycerol (also known as 3-amino-1,2-propanediol) are similarly suitable but are rather toxic, so that also from this point the use of the hexose-based counter ions, particularly N-methyl glucosammonium, is preferred.

[0043] The inventors found that having these counter ions on the surface of the latex particle can reduce the water uptake of the ink and thus a swelling of e.g. a substrate like a paper or cardboard in printing, a wall cover that is being coated, etc.

[0044] Further disclosed is the use of a latex particle of the invention in a coating and / or a printing ink. The inventors found that the latex particles are particularly useful in applications where swelling due to water over time can be reduced, while at the same time they are particularly easy to handle and mix and to apply, in contrast to volatile compounds usually used for reducing swelling. Inks and coatings are further described below. A further aspect of the invention relates to a printing ink, comprising the present latex particle, and / or a suspension comprising one or more of the latex particles.

[0045] The ink composition is not particularly limited and can be water-based, e.g. comprise a water-dispersible resin, a water-dispersible colorant, water, a cosolvent, a surfactant and optionally other additives. Preferably, the ink is water-based. In the ink, the amount of each component is not particularly limited as long as a printing ink is obtained. The ink comprises at least the latex particle, as described above, and optionally one or more pigments and / or colorants.

[0046] Water-Dispersible Colorant

[0047] A water-dispersible colorant may be a pigment or a mixture of pigments, a dye or a mixture of dyes or a mixture comprising pigments and dyes, as long as the colorant is water-dispersible. The pigment is not particularly limited and may be suitably selected in accordance with the intended use.

[0048] Examples of the pigment usable include those commonly known without any limitation, and either a water-dispersible pigment or an oil-dispersible pigment is usable. For example, an organic pigment such as an insoluble pigment or a lake pigment, as well as an inorganic pigment such as carbon black, is preferably usable.

[0049] Examples of the insoluble pigments are not particularly limited, but preferred are an azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, or diketopyrrolopyrrole dye.

[0050] For example, inorganic pigments and organic pigments for black and color inks are exemplified. These pigments may be used alone or in combination. As the inorganic pigments, it is possible to use carbon blacks produced by a known method such as a contact method, furnace method and thermal method, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red and chrome yellow.

[0051] As the organic pigments, it is possible to use azo pigments (including azo lake, insoluble azo pigments, condensed pigments, chelate azo pigments and the like), polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perynone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments), dye chelates (e.g., basic dye type chelates, and acidic dye type chelates), nitro pigments, nitroso pigments, aniline black. Among these, particularly, pigments having high affinity with water are preferably used.

[0052] Specific pigments which are preferably usable are listed below.

[0053] Examples of pigments for magenta or red include: C.l. Pigment Red 1 , C.l. Pigment Red 2, C.l. Pigment Red 3, C.l. Pigment Red 5, C.l. Pigment Red 6, C.l. Pigment Red 7, C.l. Pigment Red 15, C.l. Pigment Red 16, C.l. Pigment Red 17, C.l. Pigment Red 22, C.l. Pigment Red 23, C.l. Pigment Red 31, C.l. Pigment Red 38, C.l. Pigment Red 48:1, C.l. Pigment Red 48:2 (Permanent Red 2B(Ca)), C.l. Pigment Red 48:3, C.l. Pigment Red 48:4, C.l. Pigment Red 49:1, C.l. Pigment Red 52:2; C.l. Pigment Red 53:1, C.l. Pigment Red 57:1 (Brilliant Carmine 6B), C.l. Pigment Red 60:1, C.l. Pigment Red 63:1, C.l. Pigment Red 64:1, C.l. Pigment Red 81. C.l. Pigment Red 83, C.l. Pigment Red 88, C.l. Pigment Red 101 (colcothar), C.l. Pigment Red 104, C.l. Pigment Red 106, C.l. Pigment Red 108 (Cadmium Red), C.l. Pigment Red 112, C.l. Pigment Red 114, C.l. Pigment Red 122 (Quinacridone Magenta), C.l. Pigment Red 123, C.l. Pigment Red 139, C.l. Pigment Red 44, C.l. Pigment Red 146, C.l. Pigment Red 149, C.l. Pigment Red 166, C.l. Pigment Red 168, C.l. Pigment Red 170, C.l. Pigment Red 172, C.l. Pigment Red 177, C.l. Pigment Red 178, C.l. Pigment Red 179, C.l. Pigment Red 185, C.l. Pigment Red 190, C.l. Pigment Red 193, C.l. Pigment Red 209, C.l. Pigment Red 219 and C.l. Pigment Red 222, C.l. Pigment Violet 1 (Rhodamine Lake), C.l. Pigment Violet 3, C.l. Pigment Violet 5:1, C.l. Pigment Violet 16, C.l. Pigment Violet 19, C.l. Pigment Violet 23 and C.l. Pigment Violet 38.

[0054] Examples of pigments for orange or yellow include: C.l. Pigment Yellow 1, C.l. Pigment Yellow 3, C.l. Pigment Yellow 12, C.l. Pigment Yellow 13, C.l. Pigment Yellow 14, C.l. Pigment Yellow 15, C.l. Pigment Yellow 15:3, C.l. Pigment Yellow 17, C.l. Pigment Yellow 24, C.l. Pigment Yellow 34, C.l. Pigment Yellow 35, C.l. Pigment Yellow 37, C.l. Pigment Yellow 42 (yellow iron oxides), C.l. Pigment Yellow 53, C.l. Pigment Yellow 55, C.l. Pigment Yellow 74, C.l. Pigment Yellow 81, C.l. Pigment Yellow 83, C.l. Pigment Yellow 93, C.l. Pigment Yellow 94, C.l. Pigment Yellow 95, C.l. Pigment Yellow 97, C.l. Pigment Yellow 98, C.l. Pigment Yellow 100, C.l. Pigment Yellow 101, C.l. Pigment Yellow 104, C.l. Pigment Yellow 408, C.l. Pigment Yellow 109, C.l. Pigment Yellow 110, C.l. Pigment Yellow 117, C.l. Pigment Yellow 120, C.l. Pigment Yellow 128, C.l.

[0055] Pigment Yellow 138, C.l. Pigment Yellow 150, C.l. Pigment Yellow 151, C.l. Pigment Yellow 153 and C.l. Pigment Yellow 183; C.l. Pigment Orange 5, C.l. Pigment Orange 13, C.l. Pigment Orange 16, C.l. Pigment Orange 17, C.l. Pigment Orange 31, C.l. Pigment Orange 34, C.l. Pigment Orange 36, C.l. Pigment Orange 43, and C.l. Pigment Orange 51.

[0056] Examples of pigments for green or cyan include: C.l. Pigment Blue 1 , C.l. Pigment Blue 2, C.l. Pigment Blue 15, C.l. Pigment Blue 15:1, C.l. Pigment Blue 15:2, C.l. Pigment Blue 15:3 (Phthalocyanine Blue), C.l. Pigment Blue 16, C.l. Pigment Blue 17:1, C.l. Pigment Blue 56, C.l. Pigment Blue 60, C.l. Pigment Blue 63, C.l. Pigment Green 1, C.l. Pigment Green 4, C.l. Pigment Green 7, C.l. Pigment Green 8, C.l. Pigment Green 10, C.l. Pigment Green 17, C.l. Pigment Green 18 and C.l. Pigment Green 36.

[0057] In addition to the above pigments, when red, green, blue or intermediate colors are required, it is preferable that the following pigments are employed individually or in combination thereof. Examples of employable pigments include: C.l. Pigment Red 209, 224, 177, and 194, C.l. Pigment Orange 43, C.l. Vat Violet 3, C.l. Pigment Violet 19, 23, and 37, C.l. Pigment Green 36, and 7, C.l. Pigment Blue 15:6.

[0058] Further, examples of pigments for black include: C.l. Pigment Black 1, C.l. Pigment Black 6, C.l. Pigment Black 7 and C.l. Pigment Black 11. Specific examples of pigments for black color ink usable in the present invention include carbon blacks (e.g., furnace black, lamp black, acetylene black, and channel black); (C.l. Pigment Black 7) or metalbased pigments (e.g., copper, iron (C.l. Pigment Black 11), and titanium oxide; and organic pigments (e.g., aniline black (C.l. Pigment Black 1).

[0059] Solvent

[0060] Water is cited as an environmentally friendly and hence desirable solvent.

[0061] Cosolvent

[0062] As a cosolvent of the ink, e.g. for the purposes of improving the ejection property of the ink or adjusting the ink physical properties, the ink preferably contains a water soluble organic solvent in addition to water. There is no restriction in particular in the type of the water soluble organic solvent. Also, more than one cosolvent can be used in the ink used in the present invention.

[0063] Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, ammonium compounds, sulfur-containing compounds, propylene carbonate, and ethylene carbonate.

[0064] Examples of the solvent include: glycerin (also termed glycerol), propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols preferably having a molecular weight of between 200 gram / mol and 1000 gram / mol (e.g. PEG 200, PEG 400, PEG 600, PEG 800, PEG 1000), glycerol ethoxylate, petaerythritol ethoxylate, polyethylene glycol (di)methylethers preferably having a molecular weight of between 200 gram / mol and 1000 gram / mol, tri-methylol-propane, diglycerol (diglycerin), trimethylglycine (betaine), N-methylmorpholine N-oxide, decaglyserol, 1,4-butanediol, 1,3-butanediol, 1,2,6-hexanetriol, 2-pyrrolidinone, dimethylimidazolidinone, ethylene glycol mono-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-propyl ether, diethylene glycol mono-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-propyl ether, triethylene glycol mono-butyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, propylene glycol mono-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, diethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, tri propylene glycol dibutyl ether, 3-methyl 2,4-pentanediol, diethylene-glycol-monoethyl ether acetate, 1,2-hexanediol, 1,2-pentanediol and 1,2-butanediol. Surfactants

[0065] It is preferable that the ink contains at least one surfactant in order to improve an ink ejection property and / or the wettability of the surface of a recording medium, and the image density and color saturation of the image formed and reducing white spots therein. Using surfactants, the surface tension, i.e. the dynamic surface tension as well as the static surface tension, can be adjusted.

[0066] Examples of surfactants are not specifically limited. The following can be cited.

[0067] Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants, in particular betaine surfactants, and silicone surfactants.

[0068] Examples of a cationic surfactant include: aliphatic amine salts, aliphatic quarternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts.

[0069] Examples of an anionic surfactant include: polyoxyethylene alkylether acetic acid salts, dodecylbenzene sulfonic acid salts, lauric acid salts, and salts of polyoxyethylene alkylether sulfate, an aliphatic acid soap, an N-acyl-N-methyl glycin salt, an N-acyl-N-methyl-p-alanine salt, an N-acylglutamate, an acylated peptide, an alkylsulfonic acid salt, an alkylbezenesulfonic acid salt, an alkylnaphthalenesulfonic acid salt, a dialkylsulfo succinate (e.g. sodium dioctyl sulfosuccinate (DSS); alternative names: docusate sodium, Aerosol OT and AOT), alkylsulfo acetate, a-olefin sulfonate, N-acyl-methyl taurine, a sulfonated oil, a higher alcohol sulfate salt, a secondary higher alcohol sulfate salt, an alkyl ether sulfate, a secondary higher alcohol ethoxysulfate, a polyoxyethylene alkylphenyl ether sulfate, a monoglysulfate, an aliphatic acid alkylolamido sulfate salt, an alkyl ether phosphate salt and an alkyl phosphate salt.

[0070] Examples of an amphoteric surfactant include: a carboxybetaine type, a sulfobetaine type, an aminocarboxylate salt and an imidazolium betaine.

[0071] Examples of a nonionic surfactant include: polyoxyethylene alkylether, polyoxypropylene polyoxyethylene alkylether, a polyoxyethylene secondary alcohol ether, a polyoxyethylene alkylphenyl ether, a polyoxyethylene sterol ether, a polyoxyethylenelanolin derivative polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkylester, a polyoxyethyleneglycerine aliphatic acid ester, a polyoxyethylene castor oil, a hydrogenated castor oil, a polyoxyethylene sorbitol aliphatic acid ester, a polyethylene glycols aliphatic acid ester, an aliphatic acid monoglyceride, a polyglycerine aliphatic acid ester, a sorbitan aliphatic acid ester, polyoxyethylene sorbitan aliphatic ester, a propylene glycol aliphatic acid ester, a cane sugar aliphatic acid ester, an aliphatic acid alkanol amide, polyoxyethylene alkylamide, a polyoxyethylene aliphatic acid amide, a polyoxyethylene alkylamine, an alkylamine oxide, an acetyleneglycol, an ethoxylated acetylene glycol, acetylene alcohol.

[0072] Examples of the silicone surfactant include side-chain-modified polydimethylsiloxane, both-ends-modified polydimethylsiloxane, one-end-modified polydimethylsiloxane, and side-chain / both-ends-modified polydimethylsiloxane. Polyether-modified silicone surfactants having, as a modified group, a polyoxyethylene group or a polyoxyethylene polyoxypropylene group are particularly preferable because they exhibit excellent physical properties as water-based surfactants. The silicone surfactant may be suitably synthesized or commercial products may be used. Commercial products are readily available from BYK Chemie GmbH, Shin-Etsu Chemical Co., Ltd., TORAY Dow Corning Silicone Co., Ltd., Nihon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., or the like.

[0073] The polyether-modified silicone surfactant is not particularly limited and may be suitably selected in accordance with the intended use. As the polyether-modified silicone surfactant, commercial products may be used. Examples of the commercial products include KF-618, KF-642 and KF-643 (produced by Shin-Etsu Chemical Co., Ltd.);

[0074] EMALEX-SS-5602 and SS- 1906EX (produced by Nihon Emulsion Co., Ltd.); FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163 and FZ-2164 (produced by TORAY Dow Corning Silicone Co., Ltd.); and BYK-33, BYK 331, BYK 341, BYK 348, BYK 349, BYK 3455, BYK-387 (produced by BYK Chemie GmbH); Tegowet 240, Tegowet 245, Tegowet 250, Tegowet 260 (produced by Evonik); Silwet L-77 (produced by Sabie).

[0075] All surfactants mentioned in this section may be used solely, or they may be used in combination.

[0076] Additives

[0077] The ink composition may optionally further contain additives like biocides or a penetrant, which is a compound that promotes absorption of the ink composition in the print medium, and the additives are not particularly limited and comprise those usually used in inks.

[0078] Additionally disclosed is a coating, comprising the latex particle of the invention.

[0079] The other components of the coating are not particularly restricted, and those usually found in coatings may be used, e.g. a solvent and optionally a cosolvent, as above, and one or more components chosen from one or more binders that are not particularly restricted, one or more fillers that are not particularly restricted, one or more surfactants, e.g. as above, and optionally additives like biocides, etc. An exemplary coating is a protective floor coating, but also any other coatings in contact with water are possible.

[0080] In addition, disclosed is the use of an ion selected from the group consisting of carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and

[0081] aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof

[0082] in a coating and / or in printing, particularly in a primer liquid and / or a printing ink.

[0083] The ions herein are the counter ions as described with regard to the first aspect of the invention, to which reference is made to in this regard. The coating and printing ink can e.g. be as described as above. In addition, a primer liquid is not particularly restricted and can be e.g. as described hereinafter. If used in a primer liquid, the ion can particularly migrate to latex particles in a printing ink and thus also achieve the reduced swelling after the printing is finished.

[0084] If the ion is used as described within the invention, e.g. as counter ion, a (further) counter ion for the ion is not particularly restricted. Preferably, the counter ion should not produce an insoluble or poorly soluble salt. From a viewpoint of corrosion, halides and other reactive anions are less preferred, and colorful anions are less preferred as well. Furthermore disclosed is a printing method, comprising:

[0085] applying a primer liquid on at least one surface of a recording medium; and printing an image with at least one printing ink comprising at least one latex on the surface of the recording medium on which the primer has been applied;

[0086] wherein the primer liquid and / or the at least one latex comprises an ion selected from the group consisting of

[0087] carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and

[0088] aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof.

[0089] The ion is therein as the counter ion of the first aspect, respectively the ion described above for the use in a coating and / or in printing, to which aspects reference is made herewith.

[0090] Primer application

[0091] In the present printing method, applying a primer on at least one surface of a recording medium is not particularly restricted.

[0092] To improve the spreading and pinning (i.e. fixation of pigments and / or water-dispersed polymer particles) of the ink on the recording medium, in particular on slow absorbing media, such as machine coated media, the recording medium is pre-treated, i.e. treated prior to printing an image on the medium, with the primer. The pre-treatment step comprises the application of the primer and may further comprise one or more of the following:

[0093] preheating of the receiving medium to enhance spreading of the used ink on the receiving medium and / or to enhance absorption of the used ink into the receiving medium;

[0094] corona or plasma treatment. Primer pre-treatment

[0095] As an application way of the primer, any conventionally known methods can be used. Specific examples of an application way include: a roller coating, an ink-jet application, a curtain coating and a spray coating. There is no specific restriction in the number of times with which the primer is applied. It may be applied at one time, or it may be applied in two times or more. Application in two times or more may be preferable, since cockling of the coated printing paper can be prevented and the film formed by the primer will produce a uniform dry surface having no wrinkle by applying in 2 steps or more.

[0096] Especially a roller coating method can be used because this coating method does not need to take into consideration ejection properties and it can apply the primer homogeneously to a recording medium. In addition, the amount of the applied primer with a roller or with other means to a recording medium can be suitably adjusted by controlling: the physical properties of the primer; and the contact pressure of a roller in a roller coater to the recording medium and the rotational speed of a roller in a roller coater which is used for a coater of the primer. As an application area of the primer, it may be possible to apply only to the printed portion, or to the entire surface of both the printed portion and the non-printed portion. However, when the primer is applied only to the printed portion, unevenness may occur between the application area and a nonapplication area caused by swelling of cellulose contained in the coated printing paper with water in the primer followed by drying. Then, from the viewpoint of drying uniformly, it is preferable to apply the primer to the entire surface of a recording medium, and roller coating can be preferably used as a coating method to the whole surface. The primer may be an aqueous primer, as described further below.

[0097] Corona or plasma treatment

[0098] Corona or plasma treatment may be used as a pre-treatment step by exposing a sheet of a recording medium to corona discharge or plasma treatment. In particular when used on media like polyethylene (PE) films, polypropylene (PP) films, polyetyleneterephtalate (PET) films and machine coated media, the adhesion and spreading of the ink can be improved by increasing the surface energy of the media. With machine coated media, the absorption of water can be promoted which may induce faster fixation of the image and less puddling on the receiving medium. Surface properties of the receiving medium may be tuned by using different gases or gas mixtures as medium in the corona or plasma treatment. Examples are air, oxygen, nitrogen, carbondioxide, methane, fluorine gas, argon, neon and mixtures thereof. Corona treatment in air is most preferred.

[0099] According to certain embodiments, the primer is essentially dried on the recording medium before the image is printed. An essential drying can be achieved if less than 5 wt.% of the solvents, e.g. water and / or cosolvents, of the primer remain on the recording medium after drying and prior to printing the printing image, e.g. less than 2 wt.% or less than 1 wt.% of the solvents. According to certain embodiments, the primer is dried on the recording medium before the (first) ink for printing the printing image is applied. The drying can be carried out in any way and is not particularly limited. For example, drying can be achieved by heaters and / or radiators, e.g. IR radiators, applied in a printing apparatus at and / or after an application unit for the primer.

[0100] Recording / Receiving media

[0101] Suitable recording media for use in a printing process using an ink or set of inks (e.g. Cyan, Magenta, Yellow and blacK, CMYK; OVG; etc.) according to the present invention are not particularly limited to any type. The receiving medium may be suitably selected depending on the intended application.

[0102] Suitable receiving media may range from strongly water absorbing media such as plain paper to non-water-absorbing media such as plastic sheets (for example PE, PP, PVC and PET films). To optimize print guality, inkjet coated media are known, which media comprise a highly water absorbing coating.

[0103] Further exemplified are Machine Coated (MC) media (also known as offset coated media) and glossy (coated) media. MC media are designed for use in conventional printing processes, for example offset printing and show good absorption characteristics with respect to solvents used in inks used in such printing processes, which are usually organic solvents. MC and glossy media show inferior absorption behavior with respect to water (worse than plain paper, better than plastic sheets), and hence agueous inks.

[0104] Machine coated or offset coated media comprise a base layer and a coating layer.

[0105] The base layer may be a sheet of paper mainly made of wood fibers or a non-woven fabric material comprising wood fibers combined with synthetic fibers. The base layer may be made of wood pulp or recycled paper pulp and may be bleached.

[0106] As an internal filler for the base, a conventional white pigment may be used. For example, the following substances may be used as a white pigment: an inorganic pigment such as precipitated calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, lithophone, zeolite, magnesium carbonate, or magnesium hydrate; and an organic pigment such as styrene plastic pigment, acrylic plastic pigment, polyethylene, microcapsule, urea resin, or melamine resin. These may be used alone or in combination.

[0107] As an internal sizing agent used when producing the base, a neutral rosin size used for neutral papermaking, alkenyl succinic anhydride (ASA), alkyl ketene dimer (AKD), or a petroleum resin size may be used. Especially, a neutral rosin size and alkenyl succinic anhydride are preferable. Alkyl ketene dimer has a high sizing effect and therefore provides an enough sizing effect with a small amount. However, since alkyl ketene dimer reduces the friction coefficient of the surface of recording paper (medium), recording paper made using alkyl ketene dimer may cause a slip when being conveyed in an inkjet recording apparatus.

[0108] The thickness of the base is not particularly limited and may be suitably selected in accordance with the intended use. It is, however, preferably 50 .m to 300 .m. The basis weight of the base is preferably 45 g / m2to 290 g / m2.

[0109] The coating layer may comprise a (white) pigment, a binder and may further contain a surfactant and other components as required.

[0110] An inorganic pigment or a combination of an inorganic pigment and an organic pigment can be used as the pigment.

[0111] Examples of the inorganic pigment include kaolin, talc, calcium bicarbonate, light calcium carbonate, calcium sulfite, amorphous silica, titanium white, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide and chlorite. Among these, kaolin is particularly preferable due to its superior glossability. The addition amount of the kaolin is preferably 50 parts by mass or more with respect to 100 parts of the binder in the coating layer. When the amount of kaolin is less than 50 parts by mass, adequate effects are unable to be obtained with respect to glossiness.

[0112] Examples of the organic pigment include (aqueous) dispersions of, for example, styrene-acrylic copolymer particles, styrene-butadiene copolymer particles, polystyrene particles or polyethylene particles. These organic pigments may be used in combination. The addition amount of the organic pigment is preferably 2 parts by mass to 20 parts by mass with respect to 100 parts by mass of the total amount of the pigment in the coating layer. Since the organic pigment has superior glossability and the specific gravity thereof is small in comparison with inorganic pigment, it allows the obtaining of a coating layer having high bulk, high gloss and satisfactory surface coatability.

[0113] An aqueous resin may be used for the binder. At least one of a water-soluble resin and / or a water-dispersible resin may be used for the aqueous resin.

[0114] There are no particular limitations on the water-soluble resin, the water-soluble resin can be suitably selected according to the intended use. Examples thereof include polyvinyl alcohol and polyvinyl alcohol modification products such as anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol or acetal-modified polyvinyl alcohol; polyurethane; polyvinyl pyrrolidone and polyvinyl pyrrolidone modification products such as copolymers of polyvinyl pyrrolidone and vinyl acetate, copolymers of vinyl pyrrolidone and dimethylaminoethyl methacrylate, copolymers of quaternized vinyl pyrrolidone and dimethylaminoethyl methacrylate or copolymers of vinyl pyrrolidone and methacrylamide propyl trimethyl ammonium chloride; celluloses such as carboxymethyl cellulose, hydroxyethyl cellulose or hydroxypropyl cellulose; cellulose modification products such as cationized hydroxyethyl cellulose; synthetic resins such as polyester, polyacrylic acid (ester), melamine resin or modification products thereof or copolymers of polyester and polyurethane; and poly(meth)acrylic acid, poly(meth)acrylamide, oxidized starch, phosphoric acid-esterified starch, self-modifying starch, cationized starch, various types of modified starch, polyethylene oxide, sodium polyacrylate and sodium arginate. These water-soluble resins may be used alone or in combination.

[0115] There are no particular limitations on the water-dispersible resin, a water-dispersible resin can be suitably selected in accordance with the intended use, and examples thereof include polyvinyl acetate, ethylene-vinyl acetate copolymers, polystyrene, styrene-(meth)acrylic acid ester copolymers, (meth)acrylic acid ester copolymers, vinyl acetate-(meth)acrylic acid (ester) copolymers, styrene-butadiene copolymers, ethylenepropylene copolymers, polyvinyl ether and silicone-acrylic copolymers. In addition, a crosslinking agent such as methylolated melamine, methylolated urea, methylolated hydroxypropylene urea or isocyanate may also be contained, and the water-dispersible resin may self-crosslink with a copolymer containing a unit such as N-methylolacrylamide. A plurality of these aqueous resins can also be used simultaneously.

[0116] The addition amount of the aqueous resin is preferably 2 parts by mass to 100 parts by mass and more preferably 3 parts by mass to 50 parts by mass with respect to 100 parts by mass of the pigment. The amount of the aqueous resin is determined so that the liquid absorption properties of the recording media are within a desired range.

[0117] Primer (also called pre-treatment liquid)

[0118] The primer is not particularly restricted. The primer is particularly an aqueous primer, i.e. contains water, usually contains at least one salt, and may further contain at least one organic acid, e.g. dissolved in the water, one or more cosolvents, one or more surfactants, etc.

[0119] The at least one salt comprised in the primer is not particularly restricted. Furthermore, it is also not excluded that more than one salt is contained. However, according to certain embodiments only one salt is contained in the primer. In the primer, the at least one salt, particularly multivalent cationic salt is present to destabilize color pigments (normally having a negative charge at the pH of usual inks) during the printing process, thus leading to good printing properties. The at least one multivalent cationic salt is not particularly limited, and those usually used in primers for ink-jet printing can usually be applied. For example, useful cationic salts include water-soluble salts of magnesium, calcium, strontium, barium aluminum, copper, iron, nickel and zinc, particularly magnesium and calcium, particularly magnesium. According to certain embodiments, the primer comprises at least one multivalent cationic salt, particularly of magnesium, like magnesium sulfate, e.g. as heptahydrate. According to certain embodiments, the at least one salt is a magnesium salt. Examples of organic acids that can be used in the primer include acetic acid, malonic acid, arginic acid, citric acid, amino acids like glycine and glutamic acid, succinic acid, tartaric acid, oxalic acid, fumaric acid, phthalic acid, maleic acid, and malic acid.

[0120] As stated above, the primer can further comprise at least one cosolvent and / or at least one surfactant, e.g. for facilitating jetting. These are not particularly limited and can comprise those that are normally used in primers. Particularly, the co-solvent is compatible and miscible with water. Further, the surfactant is preferably water-soluble. According to certain embodiments, the co-solvent and / or surfactant can comprise those that are usually used in ink-jet printing inks, like the ones described below with regard to the ink used in the present printing method. An exemplary useful co-solvent comprises for example glycerol or other solvents that can help provide sufficient viscosity and / or surface tension to the primer so that it can spread evenly on the recording medium. Additionally, the one or more surfactant(s) can further help adjust the viscosity and / or surface tension of the primer.

[0121] Additionally, also further components can be comprised in the primer, e.g. additives that are usually used in pre-treatment, respectively priming, liquids in ink-jet printing, for example pH regulators to prevent corrosion of the printing equipment, amine additive, biocides, etc.

[0122] It is not excluded in the present invention that the primer is separated into two or more different portions.

[0123] Printing step

[0124] The step of printing an image with at least one ink on the surface of the recording medium on which the primer has been applied is also not particularly restricted. As stated above, it is preferred that the recording medium on which the primer is applied is dried before the at least one ink is applied. While only an image with one ink may be applied, an image with at least two inks, e.g. two, three, four, five, six and / or seven inks can be printed on the recording medium.

[0125] Image formation may be performed in such a manner that, employing an inkjet printer loaded with inkjet inks, ink droplets are ejected from inkjet heads based on the digital signals onto a recording medium. Although both single pass inkjet printing and multi pass (i.e. scanning) inkjet printing may be used for image formation, single pass inkjet printing is preferably used since it is effective to perform high-speed printing. Single pass inkjet printing is an inkjet recording method with which ink droplets are deposited onto the receiving medium to form all pixels of the image by a single passage of a recording medium underneath an inkjet marking module. In image formation by ejecting an ink, an inkjet head (i.e. printhead) employed may be either an on-demand type or a continuous type inkjet head.

[0126] Optionally, the image formation may be carried out while the recording medium is temperature controlled. For this purpose, a temperature control device may be arranged to control the temperature of the surface of a transportation mechanism (e.g. belt or drum). The temperature control device may be used to control the surface temperature of the recording medium, for example in the range of 30°C to 60°C. The temperature control device may comprise heaters, such as radiation heaters, and a cooling means, for example a cold blast, in order to control the surface temperature of the receiving medium within said range.

[0127] Drying and fixing

[0128] After an image has been formed on the receiving medium, the prints usually have to be dried and the image has to be fixed onto the receiving medium. Drying comprises generally the evaporation of solvents, in particular those solvents that have poor absorption characteristics with respect to the selected recording medium.

[0129] A drying and fixing unit for this purpose may comprise a heater, for example a radiation heater. After an image has been formed, the print is heated such that solvents present in the printed image, to a large extent water, evaporate. The speed of evaporation and hence drying may be enhanced by increasing the air refresh rate in the drying and fixing. Simultaneously, film formation of the ink occurs, because the prints are heated to a temperature above the minimum film formation temperature (MFT).

[0130] Application of varnish

[0131] A varnish may be applied on the printed image, and the step is not particularly restricted. It can be jetted onto the recording medium with the printed image, but can also be jetted onto the whole recording medium so that an even gloss can be obtained. If primer is only applied to regions that are printed on, it is also possible to only apply the varnish on the printed areas. The means for applying, e.g. rod coating, roller coating, jetting, etc., are not particularly restricted.

[0132] Varnish

[0133] In the present ink-jet printing method, the varnish is not restricted, and any varnish for increasing gloss and / or robustness may be used, particularly for increasing gloss.

[0134] The varnish particularly forms a transparent layer on the printed recording medium. As varnish, an aqueous solution comprising components capable of forming a transparent protective layer over a recording medium (e.g. a water-dispersible resin, a surfactant, water, and additives as required) is preferably used. The varnish thus is preferably water-based, and preferably contains a latex emulsion / water-dispersible resin emulsion, an alkali soluble polymer, or a combination of both. Preferably, these carry carboxylic acid groups. The water-dispersible resin comprised in the varnish preferably has a glass transition temperature (Tg) of -30°C or higher, and more preferably in the range of -20°C to 100°C. The minimum film forming temperature (MFT) of the water-dispersible resin is preferably 50°C or lower, and more preferably 35°C or lower. The water-dispersible resin may be radiation curable to improve the glossiness and fixability of the image. The water-dispersible resin and / or alkali soluble polymer can react with residual primer salt components, particularly when they carry acid groups, particularly carboxylic acid groups, which can lead to destabilizing these particles or creating a gel of the soluble polymer part, leading to roughness differences and / or reduced film-forming properties, causing gloss level reduction. Using the neutralizing liquid, reaction of salt components of the primer with varnish components can be reduced or even prevented. This provides an improved freedom of choice of a varnish composition.

[0135] As the water-dispersible resin, for example, an acrylic resin, a styrene-acrylic resin, a urethane resin, an acryl-silicone resin, a fluorine resin and the like may be used. The water-dispersible resin can be suitably selected from the same materials as that used for the inkjet ink. The amount of the water-dispersible resin contained, as a solid content, in the protective layer is preferably 1 wt.% to 50 wt.%. The surfactant comprised in the post-treatment liquid is not particularly limited and may be suitably selected from those used in the inkjet ink. Examples of the other components of the post-treatment liquid include antifungal agents, antifoaming agents, and pH adjustors. Further steps

[0136] Further steps can be carried out in the present ink-jet printing method.

[0137] For example, a drying step may be carried out after varnish application. While drying steps may be implemented between each application step (primer - ink - varnish), wet-in-wet processes are also covered in the present method, e.g. no drying takes place between primer and ink application and / or between ink and varnish application.

[0138] According to certain embodiments, a drying step is carried out at least before application of the varnish.

[0139] An exemplary ink-jet printing method of the invention is schematically shown in Fig. 1.

[0140] Following a step 1 of applying a primer liquid on at least one surface of a recording medium a step 2 of printing an image with at least one printing ink comprising at least one latex on the surface of the recording medium on which the primer has been applied is carried out.

[0141] The above embodiments can be combined arbitrarily, if appropriate. Further possible embodiments and implementations of the invention comprise also combinations of features not explicitly mentioned in the foregoing or in the following with regard to the Examples of the invention. Particularly, a person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0142] EXAMPLES

[0143] The present invention will now be described in detail with reference to several examples thereof. However, these examples are illustrative and do not limit the scope of the invention.

[0144] Example 1 : Latex particle

[0145] Material properties of latices with N-methyl glucosamine have been analysed and compared to the same latex particles bearing different types of counterions (Li+, Na+, K+, Cs+). For this purpose, the latex particles were prepared using ion exchange.

[0146] Alternatively, the counter ion can also be already included in the preparation process of the latex particle. As reference, also the polymer particles in their acidic form without organic counterion were used, titled PE 23.5. The particles were placed as dispersion (~20mL) in an aluminium cup and left to evaporate. The dried latex were subsequently placed in a vacuum oven at 130°C overnight. Vacuum is applied to ensure that a dense airbubble free dry polymeric chuck of material remains after the oven treatment. A small piece (0.3 g) of material was submersed in a vessel with demi water. The closed container was stored and at intervals the grain of polymer was taken from the vessel, left to dry at ambient conditions for ten minutes (during which non-absorbed water adhering to the surface evaporates), after which the mass of the swollen grain was determined. The weight increase is expressed in grams of absorbed water per gram of polymeric material initially taken for the test. After the weight measurement the polymeric grain of material is placed back in the vessel and closed until the next measurement is performed. The results are shown in Figure 2. Large differences are found in the water absorption capacity of the materials. In case of N-methyl glucosammonium counter ions the water absorption is almost as low as it would have been in case of a volatile counterion, i.e. with PE 23.5. However, the acidic form of the latex particle is not usable for printing as is, as it is not stable enough.

[0147] Example 2: Ink and printing

[0148] An ink was prepared with the latex particles of Example 1 with the glucosammonium counterions as polymer dispersion in water. The recipe is given in Table 1.

[0149] Table 1: Composition of ink

[0150] Component Amount (wt.%)

[0151] water 64.97

[0152] glycerol 15

[0153] Additive 0.03

[0154] Surfactant 1

[0155] Polymer dispersion 17

[0156] Pigment 2

[0157]

[0158] On a sheet of paper (Ensocoat 1CS 300 gsm) a primer, the ink, and a varnish were applied, in this order, after an initial plasma treatment. Between each step a drying took place. The primer is an aqueous primer as commonly used and does not influence the printing and the ink. As varnish, a commercially available varnish was used. After printing, the image showed good image quality, high print robustness and good jettability.

[0159] Example 3: Alternative printing process

[0160] Example 3 was carried out like Example 2, except that the polymer dispersion was prepared using PE 23.5 latex particles, and glucosamine or glucosammonium ions (via a salt) were added to the primer liquid. Printing was carried out on the wet primer liquid. The ions could migrate to the latex particles in the ink, so that similar results were obtained as in Example 2. The ion-exchange reaction took place in situ on the print to generate enhanced water fastness without needing to adapt the ink regarding jettability.

[0161] Although the present invention has been described in the above by way of embodiments, it is not limited thereto, but rather can be modified in a wide range of ways. In particular, the invention can be changed or modified in various ways without deviating from the core of the invention.

Claims

CLAIMS1. A latex particle, comprising at least one positively charged counter ion on the surface thereof, wherein the counter ion is selected from the group consisting of carbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; andaromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof.

2. The latex particle of claim 1, wherein the counter ion is selected from monosaccharides with at least one ammonium group; monosaccharides with at least one alkylammonium group with 1 to 4 carbon atoms in the alkylammonium group, preferably 1 or 2 carbon atoms in the alkylammonium group; monosaccharides with at least one acyl ammonium group with 2 to 5 carbon atoms in the alkylammonium group, preferably 2 to 3 carbon atoms in the alkylammonium group, further preferably at least one acetyl ammonium group; phenols with at least one ammonium group; phenols with at least one alkylammonium group with 1 to 4 carbon atoms in the alkylammonium group, preferably 1 or 2 carbon atoms in the alkylammonium group; phenols with at least one acyl ammonium group with 2 to 5 carbon atoms in the alkylammonium group, preferably 2 to 3 carbon atoms in the alkylammonium group, further preferably at least one acetyl ammonium group; and mixtures thereof.

3. The latex particle of claim 1 or 2, wherein the counter ion is selected from an N- methyl glucosammonium group, a glucosammonium group, an N-acetyl glucosammonium group, an N-methyl galactosammonium group, a galactosammonium group, an N-acetyl galactosammonium group, a fructosammonium group, a mannosammonium group, and mixtures thereof.

4. The latex particle of any one of claims 1 to 3, wherein the resin of the latex particle is based on a synthetic resin chosen from the group consisting of polyester resins,polyurethane resins, polyepoxy resins, polyamide resins, polyether resins, poly(meth)acrylic resins, acrylsilicone resins, fluorine-based resins, polyolefin resins, polystyrene-based resins, polybutadiene-based resins, polyvinyl acetate- based resins, polyvinyl alcohol-based resins, polyvinyl ester-based resins, polyvinyl chloride-based resins, polyacrylic acid based resins, unsaturated carboxylic acidbased resins and copolymers such as styrene- acrylate copolymer resins, styrenebutadiene copolymer resins.

5. The latex particle of any one of claims 1 to 4, wherein the latex is a polyester latex.

6. Use of a latex particle of any one of claims 1 to 5 in a coating and / or a printing ink.

7. A printing ink, comprising the latex particle of any one of claims 1 to 5.

8. A coating, comprising the latex particle of any one of claims 1 to 5.

9. Use of an ion selected from the group consisting ofcarbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof in a coating and / or in printing, particularly in a primer liquid and / or a printing ink.

10. A printing method, comprising:applying a primer liquid on at least one surface of a recording medium; and printing an image with at least one printing ink comprising at least one latex on the surface of the recording medium on which the primer has been applied; wherein the primer liquid and / or the at least one latex comprises an ion selected from the group consisting ofcarbohydrates with 3 to 6 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof; and aromatic alcohols with 6 to 10 carbon atoms that are substituted at least by one functional group chosen from an ammonium group; an alkylammonium group with 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms; an acyl ammonium group with 2 to 5 carbon atoms, preferably 2 to 3 carbon atoms; and mixtures thereof.

11. A dispersion comprising one or more latex particles of any one of claims 1 to 5.

Images