Ink compositions

Abstract

Disclosed is an ink composition comprising: - a methyl ester of a C16-C18 fatty acid; - beta-form copper phthalocyanine having a bulk density of 0.40 kgL-1 or more; - a C14-C18 hydrocarbon; and - a fatty acid amine salt of sulfonated copper phthalocyanine; wherein the weight ratio of the C14-C18 hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.　Methods for producing ink compositions, methods of printing and printed articles are also disclosed

Description

INK COMPOSITIONS

[0001] The present invention relates to ink compositions, methods for producing ink compositions, methods of printing and printed articles.

[0002] Growing interest in sustainability and environmentally-friendly technologies has led to increased demand for plant-based inks. In addition, concerns over the flammability of ink components has led to increased demand for inks with non-flammable components. Changes in particle size and viscosity over time will lead to inks being unsuitable for inkjet printing.

[0003] There is therefore a need for new ink compositions which solve the above problems.

[0004] In one aspect, the present invention provides an ink composition comprising: - a methyl ester of a C16-C18fatty acid; - beta-form copper phthalocyanine having a bulk density of 0.40 kgL-1or more; - a C14-C18hydrocarbon; and - a fatty acid amine salt of sulfonated copper phthalocyanine; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

[0005] In another aspect, the present invention provides a method of manufacturing an ink composition comprising: - providing a methyl ester of a C16-C18fatty acid; - providing beta-form copper phthalocyanine having a bulk density of 0.40 kgL-1or more; - providing a C14-C18hydrocarbon; and - providing a fatty acid amine salt of sulfonated copper phthalocyanine; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

[0006] In a further aspect, the present invention provides a method of printing comprising: - providing an ink composition of the present invention; and - using an inkjet printer to print the ink composition onto a substrate.

[0007] In a still further aspect, the present invention provides a printed article comprising a substrate and an ink composition of the present invention.

[0008] Advantages of the ink composition of the present invention which will be apparent from the following detailed description of the invention, and include good particle size stability and good viscosity stability when using a plant-based carrier fluid and a high flashpoint dispersant

[0009] In one aspect, the present invention provides an ink composition comprising: - a methyl ester of a C16-C18fatty acid; - beta-form copper phthalocyanine having a bulk density of 0.40 kgL-1or more; - a C14-C18hydrocarbon; and - a fatty acid amine salt of sulfonated copper phthalocyanine; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

[0010] The ink composition of the present invention comprises a methyl ester of a C16-C18fatty acid (hereinafter referred to as a first ester). The first ester may act as a carrier fluid in the ink composition.

[0011] As used herein a methyl ester of a C16-C18fatty acid is a fatty acid having 16 to 18 carbon atoms in which the -OH group of the acid moiety is replaced with an -O-CH3group. The first ester may be a single compound or a mixture of compounds. The first ester is derived from a fatty acid or mixture of fatty acids (hereinafter the acid component of the first ester) and methanol. The first ester may be a plant-based material. As used herein, a plant-based material is a material obtainable by processing vegetable matter, e.g., by hydrolysis of vegetable oil such as soy oil. Plant-based materials suitable for the first ester include plant-based oils described for example in CRC Handbook of Chemistry and Physics, edited by Robert C. Weast and Melvin J. Astle, CRC Press, 1979.

[0012] The acid component of the first ester may be branched or unbranched, and may be linear or cyclic. Typically the acid component of the first ester is linear and unbranched. The acid component of the first ester may be saturated or unsaturated. Suitable acid components of the first ester include polyunsaturated acids (examples of which include linoleic acid and linolenic acid), monounsaturated acids (examples of which include oleic acid), saturated acids (examples of which include palmitic acid and stearic acid), and mixtures thereof. In some embodiments the acid component of the first ester is linoleic acid, oleic acid, palmitic acid, linolenic acid. stearic acid, or a mixture thereof.

[0013] In some embodiments, the acid component of the first ester is an unsaturated fatty acid. Preferably the acid component of the first ester is a mono-unsaturated fatty acid. Mono-unsaturated fatty acids may be obtained, for example, by hydrolysis of vegetable oils (e.g. soy oil). Preferred examples of suitable mono-unsaturated fatty acids include C18monounsaturated fatty acids such as oleic acid. C18monounsaturated fatty acids such as oleic acid can be obtained by hydrolysis of soy oil.

[0014] Thus, in preferred embodiments, the methyl ester of a C16-C18fatty acid in the ink composition of the present invention is a methyl ester of a C18monounsaturated fatty acid, such as methyl oleate, for example having the CAS number 67762-38-3.

[0015] Suitable methyl esters of C16-C18fatty acids are available commercially, such as METHYL OLEATE P, available from Mosselman S.A. In some embodiments, the methyl esters of C16-C18fatty acids is METHYL OLEATE P, available from Mosselman S.A.

[0016] The amount of the methyl ester of a C16-C18fatty acid present in the ink composition of the present invention is not particularly limited. The amount of the methyl ester of a C16-C18fatty acid present in the ink composition of the present invention may be around 60 wt％ or more, based on the total weight of the composition, for example 65 wt％ or more, 70 wt％ or more, or 75 wt％ or more, based on the total weight of the composition. The amount of the methyl ester of a C16-C18fatty acid present in the ink composition of the present invention may be around 95 wt％ or less, based on the total weight of the composition, for example 90 wt％ or less, 85 wt％ or less, or 80 wt％ or less, based on the total weight of the composition. The amount of the methyl ester of a C16-C18fatty acid present in the ink composition of the present invention may be from 60 wt％ to 90 wt％, from 65 wt％ to 85 wt％, or from 70 wt％ to 80 wt％, based on the total weight of the composition.

[0017] The ink composition of the present invention comprises beta-form copper phthalocyanine. The beta-form copper phthalocyanine may act as a cyan pigment in the ink composition. Thus, the ink composition of the present invention is typically a cyan ink.

[0018] Copper phthalocyanine, also known as CuPc or phthalocyanine blue, is a blue phthalocyanine pigment having CAS number 147-14-8 and the following chemical structure 1: As can be seen from the structure above, copper phthalocyanine comprises a phthalocyanine macrocyclic ligand having four isoindole units and Cu(II).

[0019] Copper phthalocyanine is generally crystalline, and may exist in different crystalline forms. Crystalline forms include the α, s, γ, η, and χ polymorphs. The copper phthalocyanine in the ink composition of the present invention is in the s crystal form, and is referred to as beta-form copper phthalocyanine. The s crystal form is well known in the art and is described for example by J. M. Robertson, J. Chem. Soc. (1935) 615. The s crystal form of copper phthalocyanine may be characterised by an XRPD (CuKα) spectrum comprising peaks at 7.1±0.2 °2θ, 9.1±0.2 °2θ, 10.6±0.2 °2θ, 28.5±0.2 °2θ, and 31.9±0.2 °2θ. Beta-form copper phthalocyanine pigments are widely available from commercial sources, for example as Heliogen Blue L7101F (15:4) from Sun Chemical Colors & Effects GmbH and as Lionol Blue FG-7400-G (15:4) available from Toyocolor Co., Ltd.

[0020] The beta-form copper phthalocyanine in the ink composition of the present invention has a bulk density of 0.40 kgL-1or more. As used herein, the bulk density of the beta-form copper phthalocyanine is typically as measured according to ASTM D1895-17.

[0021] In the ink composition of the present invention, the beta-form copper phthalocyanine has a bulk density of 0.40 kgL-1or more. Preferably the beta-form copper phthalocyanine has a bulk density of 0.42 kgL-1or more, more preferably 0.44 kgL-1or more, still more preferably 0.46 kgL-1or more, most preferably 0.48 kgL-1or more. The　　beta-form copper phthalocyanine typically has a bulk density of 1.50 kgL-1or less preferably has a bulk density of 1.00 kgL-1or less, more preferably 0.80 kgL-1or less, still more preferably 0.60 kgL-1or less, most preferably 0.50 kgL-1or less. Typically the beta- form copper phthalocyanine has a bulk density of from 0.40 kgL-1to 1.50 kgL-1, preferably from 0.42 kgL-1to 1.00 kgL-1, more preferably from 0.44 kgL-1to 0.80 kgL-1, still more preferably from 0.46 kgL-1to 0.60 kgL-1, most preferably from 0.48 kgL-1to 0.50 kgL-1. When the beta-form copper phthalocyanine has a bulk density of 0.40 kgL-1or more, and particularly has a bulk density in the typical and preferred amounts described above, the ink composition of the present invention exhibits favourable properties such as particle size stability and viscosity stability.

[0022] In some embodiments, the beta-form copper phthalocyanine in the ink composition of the present invention is Lionol Blue FG-7400-G (15:4), available from Toyocolor Co., Ltd.

[0023] The amount of the beta-form copper phthalocyanine present in the ink composition of the present invention is not particularly limited. The amount of the beta-form copper phthalocyanine present in the ink composition of the present invention may be around 2 wt％ or more, based on the total weight of the composition, for example 4 wt％ or more, 6 wt％ or more, or 8 wt％ or more, based on the total weight of the composition. The amount of the beta-form copper phthalocyanine present in the ink composition of the present invention may be around 18 wt％ or less, based on the total weight of the composition, for example 16 wt％ or less, 14 wt％ or less, or 12 wt％ or less, based on the total weight of the composition. The amount of the beta-form copper phthalocyanine present in the ink 　　composition of the present invention may be from 2 wt％ to 18 wt％, from 4 wt％ to 16 wt％, from 6 wt％ to 14 wt％, or from 8 wt％ to 12 wt％, based on the total weight of the composition.

[0024] The ink composition of the present invention comprises a C14-C18hydrocarbon. The C14-C18hydrocarbon may act as a dispersant in the ink composition of the present invention.

[0025] As used herein a C14-C18hydrocarbon is a compound having 14 to 18 carbon atoms, and containing only carbon and hydrogen atoms. The C14-C18hydrocarbon may be branched or unbranched. Branched C14-C18hydrocarbons include C14-C18isoalkanes. Unbranched C14-C18hydrocarbons include C14-C18n-alkanes. The C14-C18hydrocarbon may be saturated or unsaturated. The C14-C18hydrocarbon may be linear or cyclic. Cyclic C14-C18hydrocarbons comprise one or more cyclic moiety and optionally further comprise one or more linear moiety. The one or more cyclic moiety may be aromatic or non- aromatic.

[0026] The C14-C18hydrocarbon preferably has a flashpoint of 93℃ or more, for example 93℃ to 120℃, 93℃ to 110℃, or 93℃ to 100℃. The flashpoint of the C14-C18hydrocarbon can be measured by appropriate techniques known in the art, for example according to ISO 2719:2016.

[0027] The C14-C18hydrocarbon may be a single compound or a mixture of compounds. Preferably, the C14-C18hydrocarbon is a mixture of compounds selected from the group consisting of: - C14-C18n-alkanes; - C14-C18isoalkanes; - non-aromatic cyclic C14-C18hydrocarbons; and - aromatic C14-C18hydrocarbons.

[0028] When the C14-C18hydrocarbon is a mixture of compounds and comprises one or more aromatic C14-C18hydrocarbon, the aromatic C14-C18hydrocarbon is preferably present in an amount of 2 wt％ to 30wt％, based on the total weight of the C14-C18hydrocarbon.

[0029] More preferably the C14-C18hydrocarbon is a mixture of compounds and comprises　　one or more C14-C18n-alkane, one or more C14-C18isoalkane, one or more non-aromatic cyclic C14-C18hydrocarbon, and one or more aromatic C14-C18hydrocarbon. Still more preferably the C14-C18hydrocarbon is a mixture of compounds and comprises one or more C14-C18n-alkane, one or more C14-C18isoalkane, one or more non-aromatic cyclic C14-C18hydrocarbon, and one or more aromatic C14-C18hydrocarbon, wherein the one or more aromatic C14-C18hydrocarbon is present in an amount of 2 wt％ to 30 wt％, based on the total weight of the C14-C18hydrocarbon.

[0030] Suitable C14-C18hydrocarbons are available commercially and include Solsperse 13940 from The Lubrizol Corporation. In some embodiments the C14-C18hydrocarbon in the ink composition of the present invention is Solsperse 13940 from The Lubrizol Corporation.

[0031] The absolute amount of the C14-C18hydrocarbon in the ink composition of the present invention is not particularly limited. The amount of the C14-C18hydrocarbon present in the ink composition of the present invention may be around 4 wt％ or more, based on the total weight of the composition, for example 6 wt％ or more, 8 wt％ or more, or 10 wt％ or more, based on the total weight of the composition. The amount of the C14- C18hydrocarbon present in the ink composition of the present invention may be around 18 wt％ or less, based on the total weight of the composition, for example 16 wt％ or less, 14 wt％ or less, or 12 wt％ or less, based on the total weight of the composition. The amount of the C14-C18hydrocarbon present in the ink composition of the present invention may be from 4 wt％ to 18 wt％, from 6 wt％ to 16 wt％, from 8 wt％ to 14 wt％, or from 10 wt％ to 12 wt％, based on the total weight of the composition.

[0032] The ink composition of the present invention comprises a fatty acid amine salt of sulfonated copper phthalocyanine. The fatty acid amine salt of sulfonated copper phthalocyanine may act as a dispersant synergist in the ink composition of the present invention. The presence of a fatty acid amine salt of sulfonated copper phthalocyanine in the ink composition of the present invention results in favourable properties such as particle size stability and viscosity stability.

[0033] As used herein a fatty acid amine salt of sulfonated copper phthalocyanine comprises a copper phthalocyanine sulfonate anion, and a quaternary ammonium cation.

[0034] The copper phthalocyanine sulfonate anion comprises one or more sulfonate group attached to a carbon atom in an isoindole unit of the phthalocyanine macrocycle. The copper phthalocyanine sulfonate anion may for example have one, two, three or four sulfonate groups. Each sulfonate group may be attached to a carbon atom in an isoindole unit of the phthalocyanine macrocycle. In some embodiments the copper phthalocyanine sulfonate anion has one sulfonate group attached to a carbon atom in an isoindole unit of the phthalocyanine macrocycle.

[0035] The quaternary ammonium cation in the fatty acid amine salt comprises n C8to C22hydrocarbon groups attached to the quaternary nitrogen atom, wherein n is from 1 to 4. In addition to the n C8to C22hydrocarbon groups, the quaternary ammonium cation in the 　　fatty acid amine salt comprises 4-n other groups attached to the quaternary nitrogen atom. The 4-n other groups may, for example, be independently selected from hydrogen and C1to C7alkyl. The quaternary ammonium cation in the fatty acid amine salt may for example comprise: - 1 C8to C22hydrocarbon group attached to the quaternary nitrogen atom, and 3 groups independently selected from hydrogen and C1to C7alkyl attached to the quaternary nitrogen atom; or - 2 C8to C22hydrocarbon groups attached to the quaternary nitrogen atom, and 2 groups independently selected from hydrogen and C1to C7alkyl attached to the quaternary nitrogen atom; or - 3 C8to C22hydrocarbon groups attached to the quaternary nitrogen atom, and 1 group independently selected from hydrogen and C1to C7alkyl attached to the quaternary nitrogen atom; or - 4 C8to C22hydrocarbon groups attached to the quaternary nitrogen atom, and no further groups attached to the quaternary nitrogen atom.

[0036] The n C8to C22hydrocarbon groups in the quaternary ammonium cation in the fatty acid amine salt may be the same or different and may each be, for example, a C14to C22hydrocarbon group, C16to C20hydrocarbon group, or C18hydrocarbon group, such as a C14to C22alkyl group, C16to C20alkyl group, or C18alkyl group. The 4-n other groups in the quaternary ammonium cation in the fatty acid amine salt may be the same or different and may each be, for example a hydrogen atom or a C1to C2alkyl group; such as for example a methyl group. In some embodiments the quaternary ammonium cation comprises 2 C18alkyl groups attached to the quaternary nitrogen atom, and 2 methyl groups attached to the quaternary nitrogen atom.

[0037] In some embodiments, the fatty acid amine salt of sulfonated copper phthalocyanine comprising a copper phthalocyanine sulfonate anion having one, two, three or four sulfonate groups, and a quaternary ammonium cation having, attached to the quaternary nitrogen atom, n C8to C22hydrocarbon groups and 4-n groups selected from hydrogen and C1to C7alkyl, wherein n is from 1 to 4. In some embodiments, the fatty acid amine salt of sulfonated copper phthalocyanine comprises a copper phthalocyanine sulfonate anion having one sulfonate group, and a quaternary ammonium cation having, attached to the quaternary nitrogen atom, 2 C16to C20hydrocarbon groups and 2 groups selected from hydrogen and C1to C2alkyl.

[0038] Suitable fatty acid amine salts of sulfonated copper phthalocyanine are available commercially and include Solsperse 5000S available from The Lubrizol Corporation. In some embodiments, the fatty acid amine salt of sulfonated copper phthalocyanine in the ink composition of the present invention is Solsperse 5000S available from The Lubrizol Corporation.

[0039] The absolute amount of the fatty acid amine salt of sulfonated copper phthalocyanine in the ink composition of the present invention is not particularly limited. The amount of the fatty acid amine salt of sulfonated copper phthalocyanine present in the ink composition of the present invention may be around 0.06 wt％ or more, based on the total weight of the composition, for example 0.09 wt％ or more, 0.12 wt％ or more, or 0.15 wt％ or more, based on the total weight of the composition. The amount of the fatty acid amine salt of sulfonated copper phthalocyanine present in the ink composition of the present invention may be around 0.50 wt％ or less, based on the total weight of the composition, for example 0.45 wt％ or less, 0.40 wt％ or less, or 0.35 wt％ or less, based on the total weight of the composition. The amount of the fatty acid amine salt of sulfonated copper phthalocyanine present in the ink composition of the present invention may be from 0.06 wt％ to 0.50 wt％, from 0.09 wt％ to 0.45 wt％, from 0.12 wt％ to 0.40 wt％, or from 0.15 wt％ to 0.35 wt％, based on the total weight of the composition.

[0040] The presence of a fatty acid amine salt of sulfonated copper phthalocyanine in the ink composition of the present invention, particularly with the composition and in the amounts discussed above, results in favourable properties such as particle size stability and viscosity stability.

[0041] The ink composition of the present invention may further comprise an alkyd resin. As used herein, an alkyd resin comprises an ester (hereinafter referred to as a second ester). The second ester is derived from an acid (hereinafter the acid component of the second ester) and an alcohol (hereinafter the alcohol component of the second ester). The second ester may be a plant-based material as defined elsewhere herein.

[0042] In some embodiments, the acid component of the second ester is an unsaturated fatty acid. Preferably the acid component of the second ester is a di-unsaturated fatty acid. Di-unsaturated fatty acids may be obtained, for example, by hydrolysis of vegetable oils (e.g. soy oil). Examples of suitable di-unsaturated fatty acids include linoleic acid, eicosadienoic acid, docosadienoic acid and linolelaidic acid. Linoleic acid is preferred as the acid component of the second ester. Linoleic acid can be obtained by hydrolysis of soy oil.

[0043] In some embodiments, the alcohol component of the second ester is a polyhydric alcohol. Examples of suitable polyhydric alcohols include glycerol, trimethylolpropane, and pentaerythritol. Pentaerythritol is preferred as the alcohol component of the second ester.

[0044] The second ester may be an ester of a di-unsaturated fatty acid and a polyhydric alcohol, and examples of the second ester include glyceryl esters of linoleic acid (e.g. glyceryl monolinleate, glyceryl dilonleate, glyceryl trilinoleate, or any mixture thereof) , glyceryl esters of eicosadienoic acid (e.g. glyceryl monoeicosadienoate, glyceryl dieicosadienoate, glyceryl trieicosadienoate or any mixture thereof), trimethylolpropyl esters of linoleic acid (e.g. trimethylolpropyl monolinoleate, trimethylolpropyl dilinoleate, trimethylolpropyl trilinoleate or any mixture thereof), trimethylolpropyl esters of eicosadienoic acid (e.g. trimethylolpropyl monoeicosadienoate, trimethylolpropyl dieicosadienoate, trimethylolpropyl trieicosadienoate or any mixture thereof), trimethylolpropyl esters of docosadienoic acid (e.g. trimethylolpropyl monodocosadienoate, trimethylolpropyl didocosadienoate, trimethylolpropyl tridocosadienoate or any mixture thereof), pentaerythrityl esters of linoleic acid (e.g. pentaerythrityl monolinoleate, pentaerythrityl dilinoleate, pentaerythrityl trilinoleate, pentaerythrityl tetralinoleate, or any mixture thereof), pentaerythrityl esters of eicosadienoic acid (e.g. pentaerythrityl monoeicosadienoate, pentaerythrityl dieicosadienoate, pentaerythrityl trieicosadienoate, pentaerythrityl tetraeicosadienoate, or any mixture thereof), and pentaerythrityl esters of docosadienoic acid (e.g. pentaerythrityl monodocosadienoate, pentaerythrityl didocosadienoate, pentaerythrityl tridocosadienoate, pentaerythrityl tetradocosadienoate, or any mixture thereof). Pentaerythrityl esters of tetralinoleic acid are preferred as the second ester. Mixtures comprising pentaerythrityl monolinoleate and pentaerythrityl dilinoleate are particularly preferred.

[0045] The alkyd resin may be a single substance, or a mixture of different substances. The one or more further substances may be other esters (e.g. other esters of unsaturated fatty acids and polyhydric alcohols), or other substances of the types commonly found in alkyd resins.

[0046] In certain embodiments the alkyd resin is Vilkyd 782, available from Vil Resins Ltd.

[0047] In some embodiments, the alkyd resin, if present, is present in an amount of 0.5wt％ or more, based on the total weight of the composition. In preferred embodiments of the ink composition of the present invention the alkyd resin, if present, is present in an amount of 0.5 to 8 wt％, based on the total weight of the composition. In some preferred embodiments, the alkyd resin, if present, is present in amount of 1 to 6 wt％, based on the total weight of the composition. In particularly preferred embodiments, the alkyd resin, if 　　present, is present in an amount of 2 to 4 wt％, based on the total weight of the composition.

[0048] The weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine in the ink composition of the present invention is from 6:1 to 45:1. Preferably, the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 40:1. More preferably, the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6.25:1 to 40:1. When the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1, and particularly from 6:1 to 40:1 or from 6.25:1 to 40:1, the ink composition of the present invention exhibits favourable properties such as particle size stability and viscosity stability.

[0049] In some embodiments, the ink composition comprises - a methyl ester of a C16-C18monounsaturated fatty acid; - beta-form copper phthalocyanine having a bulk density of from 0.42 kgL-1to 1.00 kgL-1; - a C14-C18hydrocarbon which is a mixture of compounds selected from the group consisting of C14-C18n-alkanes, C14-C18isoalkanes, non-aromatic cyclic C14-C18hydrocarbons, and aromatic C14-C18hydrocarbons; - a fatty acid amine salt of sulfonated copper phthalocyanine comprising a copper phthalocyanine sulfonate anion having one, two, three or four sulfonate groups, and a quaternary ammonium cation having, attached to the quaternary nitrogen atom, n C8to C22hydrocarbon groups and 4-n groups selected from hydrogen and C1to C7alkyl, wherein n is from 1 to 4; and - an alkyd resin; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

[0050] In some embodiments, the ink composition comprises - a methyl ester of a C18monounsaturated fatty acid; - beta-form copper phthalocyanine having a bulk density of from 0.46 kgL-1to 0.60 kgL-1; - a C14-C18hydrocarbon which is a mixture of one or more C14-C18n-alkane, one or more C14-C18isoalkane, one or more non-aromatic cyclic C14-C18hydrocarbon, and one or more aromatic C14-C18hydrocarbon; - a fatty acid amine salt of sulfonated copper phthalocyanine comprising a copper phthalocyanine sulfonate anion having one sulfonate groups, and a quaternary ammonium cation having, attached to the quaternary nitrogen atom, 2 C16to C20hydrocarbon groups and 2 groups selected from hydrogen and C1to C2alkyl; and - an alkyd resin comprising an ester of a di-unsaturated fatty acid and a polyhydric alcohol; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

[0051] In some embodiments, the ink composition comprises - 60 wt％ to 90 wt％, based on the total weight of the composition, of a methyl ester of a C16-C18monounsaturated fatty acid; - 2 wt％ to 18 wt％, based on the total weight of the composition, of beta-form copper phthalocyanine having a bulk density of from 0.42 kgL-1to 1.00 kgL-1;4 wt％ to 18 wt％, based on the total weight of the composition, of a C14-C18hydrocarbon which is a mixture of compounds selected from the group consisting of C14-C18n-alkanes, C14-C18isoalkanes, non-aromatic cyclic C14-C18hydrocarbons, and aromatic C14-C18hydrocarbons; - 0.06 wt％ to 0.50 wt％, based on the total weight of the composition, of a fatty acid amine salt of sulfonated copper phthalocyanine comprising a copper phthalocyanine sulfonate anion having one, two, three or four sulfonate groups, and a quaternary ammonium cation having, attached to the quaternary nitrogen atom, n C8to C22hydrocarbon groups and 4-n groups selected from hydrogen and C1to C7alkyl, wherein n is from 1 to 4; and - 1 wt％ to 6 wt％, based on the total weight of the composition, of an alkyd resin; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

[0052] In some embodiments, the ink composition comprises - 70 wt％ to 80 wt％, based on the total weight of the composition, of a methyl ester of a C18monounsaturated fatty acid; - 6 wt％ to 14 wt％, based on the total weight of the composition, of beta-form copper phthalocyanine having a bulk density of from 0.46 kgL-1to 0.60 kgL-1; - 8 wt％ to 14 wt％, based on the total weight of the composition, of a C14-C18hydrocarbon which is a mixture of one or more C14-C18n-alkane, one or more C14-C18isoalkane, one or more non-aromatic cyclic C14-C18hydrocarbon, and one or more aromatic C14-C18hydrocarbon, wherein the one or more aromatic C14-C18hydrocarbon is present in an amount of 2 wt％ to 30wt％, based on the total weight of the C14-C18hydrocarbon; - 0.12 wt％ to 0.40 wt％, based on the total weight of the composition, of a fatty acid amine salt of sulfonated copper phthalocyanine comprising a copper phthalocyanine sulfonate anion having one sulfonate groups, and a quaternary ammonium cation having, attached to the quaternary nitrogen atom, 2 C16to C20hydrocarbon groups and 2 groups selected from hydrogen and C1to C2alkyl; and - 2 wt％ to 4 wt％, based on the total weight of the composition, of an alkyd resin comprising an ester of a di-unsaturated fatty acid and a polyhydric alcohol; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 40:1 (or from 6.25:1 to 40:1).

[0053] The ink compositions of the present invention can be prepared by techniques known in the art, for example by providing the components of the composition. The components of the composition may be milled and / or subjected to ultrasonic dispersion (e.g. in an ultrasonic dispersion bath).

[0054] The ink compositions of the present invention can be used as inkjet inks. For example they can be printed onto a substrate using an inkjet printer according to techniques known in the art. The substrate is not particularly limited and includes, for example, paper, card, and board. A printed article comprising a substrate and an ink composition of the present invention can be obtained by printing the ink onto the substrate, e.g. by inkjet printing.

[0055] The invention is illustrated below by means of the following non-limiting examples. All Examples and Comparative Examples used methyl oleate (METHYL OLEATE P, from Mosselman S.A) as the carrier, a C14-C18hydrocarbon with a flash point of 96℃ (Solsperse 13940 from The Lubrizol Corporation) as the dispersant, and an alkyd resin (Vilkyd 782) as a resin.

[0056] Examples 1 to 4 and Comparative Examples 2 and 3 used a fatty acid amine salt of sulfonated copper phthalocyanine (Solsperse 5000S from The Lubrizol Corporation; Dispersant Synergist 1) as a dispersant synergist. Comparative Example 4 used a VOC free fatty acid-based polymer (ADD-6245 from ADD Additives BV; Dispersant Synergist 2) as a dispersant synergist.

[0057] Examples 1 to 4 and Comparative Examples 1, 2 and 4 used a beta-form copper phthalocyanine having a bulk density of 0.48 kgL-1(Lionol Blue FG-7400G (15:4) from Toyocolor Co., Ltd.; bulk density measured according to ASTM D1895-17; Pigment 1) as the pigment. Comparative Example 3 used a beta-form copper phthalocyanine having a bulk density of 0.33 kgL-1(Heliogen Blue L 7101F (15:4) from Sun Chemical Colors & Effects GmbH; bulk density measured according to ASTM D1895-17; Pigment 2) as the pigment.

[0058] Ink compositions having the components set out in Table 1 were prepared as Examples 1 to 4. Ink compositions having the components set out in Table 2 were prepared as Comparative Examples 1 to 4. The compositions of Examples 1, 2 and 4, and Comparative Examples 1 2 and 3, were prepared by milling components in a MiniZeta laboratory mill. The compositions of Example 3 and Comparative Example 4 were prepared by dispersion in an ultrasonic bath.

[0059] The inks of Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated for stability of particle size and stability of viscosity. The results are set out in Table 3.

[0060] As evidenced in the examples, the combination of dispersant synergist and dispersant according to the present invention produces good particle size stability and viscosity stability when using a plant-based carrier fluid and a high flashpoint dispersant.

[0061] The invention is described above with reference to certain embodiments. However, those embodiments are merely illustrative and a skilled person will appreciate that various modifications are possible, including combinations of features which are described above with reference to separate embodiments, without departing from the scope of the invention as defined in the following claims (with due account being taken of equivalents thereto).

[0062] The present application is based on and claims priority of United Kingdom Priority Application No. GB 2218413.9 filed on December 7, 2022, the entire contents of which are hereby incorporated herein by reference.

Claims

1. An ink composition comprising: - a methyl ester of a C16-C18fatty acid; - beta-form copper phthalocyanine having a bulk density of 0.40 kgL-1or more; - a C14-C18hydrocarbon; and - a fatty acid amine salt of sulfonated copper phthalocyanine; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

2. An ink composition according to claim 1, wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6.25:1 to 40:1.

3. An ink composition according to claim 1 or 2, wherein the methyl ester of a C16-C18fatty acid is present in an amount of 60 wt％ to 90 wt％, based on the total weight of the composition.

4. An ink composition according to any one of claims 1 to 3, wherein the methyl ester of a C16-C18fatty acid is a plant-based material.

5. An ink composition according to any one of claims 1 to 4, wherein the beta-form copper phthalocyanine is present in an amount of 2 wt％ to 18 wt％, based on the total weight of the composition.

6. An ink composition according to any one of claims 1 to 5, wherein the beta-form copper phthalocyanine has a bulk density of from 0.42 kgL-1to 1.00 kgL-1.

7. An ink composition according to any one of claims 1 to 6, wherein the C14-C18hydrocarbon is present in an amount of 4 wt％ to 18 wt％, based on the total weight of the composition.

8. An ink composition according to any one of claims 1 to 7, wherein the C14-C18hydrocarbon is is a mixture of compounds selected from the group consisting of C14-C18n- alkanes, C14-C18isoalkanes, non-aromatic cyclic C14-C18hydrocarbons, and aromatic C14- C18hydrocarbons.

9. An ink composition according to any one of claims 1 to 8, further comprising: - an alkyd resin.

10. An ink composition according to claim 9, wherein the alkyd resin is present in an amount of 1 wt％ to 6 wt％, based on the total weight of the composition.

11. An ink composition according to claim 9, wherein the alkyd resin is present in an amount of 1 wt％ to 6 wt％, based on the total weight of the composition.

12. A method of manufacturing an ink composition comprising: - providing a methyl ester of a C16-C18fatty acid; - providing beta-form copper phthalocyanine having a bulk density of 0.40 kgL-1or more; - providing a C14-C18hydrocarbon; and - providing a fatty acid amine salt of sulfonated copper phthalocyanine; wherein the weight ratio of the C14-C18hydrocarbon to the fatty acid amine salt of sulfonated copper phthalocyanine is from 6:1 to 45:1.

13. A method according to claim 12, wherein the methyl ester of a C16-C18fatty acid; the beta-form copper phthalocyanine; the C14-C18hydrocarbon; and / or the fatty acid amine salt of sulfonated copper phthalocyanine is as defined in any one of claims 2 to 11.

14. A method of printing comprising: - providing an ink composition as defined in any one of claims 1 to 11; and - using an inkjet printer to print the ink composition onto a substrate.

15. A printed article comprising a substrate and an ink composition as defined in any one of claims 1 to 11.

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