WO1998053017A1

WO1998053017A1 - Stabilized bronze (copper/zinc) printing ink powder

Info

Publication number: WO1998053017A1
Application number: PCT/US1998/015259
Authority: WO
Inventors: Paul Michael Swan
Original assignee: Eastman Chemical Company
Priority date: 1998-07-21
Filing date: 1998-07-21
Publication date: 1998-11-26

Abstract

The present invention provides a stabilized aqueous bronze printing ink formulation comprising (a) a bronze printing ink powder; (b) an aqueous additive formulation. The aqueous additive formulation comprises: i) an emulsifiable wax; ii) a surfactant in the range of from 0.025 to 60 parts by weight of per part of the emulsifiable wax; iii) a base having a pH in the range of 7 to about 12, present in the range of from 0.0005 to 2 parts by weight of the emulsifiable wax; iv) at least one additive in the range of from 0.05 to 160 parts by weight of the emulsifiable wax; and v) at least enough water to render the resulting combination fluid.

Description

STABILIZED BRONZE (COPPER/ZINC) PRINTING INK POWDER

BACKGROUND OF THE INVENTION This invention relates to stabilized aqueous dispersions of bronze printing ink powder. The present invention further relates to stabilized bronze printing ink formulations employing the stabilized bronze printing ink powder, which reduced color change, good viscosity stability and reduced tendency to settle out into a hard layer on storage. Bronze printing ink powders are used to produce inks in organic solvents with gold effect. However, in aqueous ink systems, such powders have several drawbacks including color change, gas evolution and unstable viscosity. The bronze pigment manufacturers have responded to such problems by producing powders which have tended to be relatively expensive and, further, do not offer a complete solution to the stability problems for aqueous ink systems.

An article by D.J. Quick titled "Advancing Technology of Metallic Pigments," published in the Polymer Paint and Colour Journal (PPCJ), Argus Business Media, Redhill, England, (1997), p. S9-S10, describes gold bronze pigments as copper-zinc alloys having limited stability in aqueous systems.

Therefore, a need exists for stabilized aqueous dispersions of bronze printing ink powder exhibiting reduced color change, good viscosity stability and reduced tendency to settle on storage. There is also a need for stabilized aqueous printing ink formulations containing bronze printing ink powder. "Bronze" in the context of the present application is used to denote a copper/zinc alloy. SUMMARY OF THE INVENTION

It is an object of the present invention to provide stabilized aqueous dispersions of bronze printing ink powder, which exhibit superior stability, reduced color change, good viscosity stability and reduced tendency to settle on storage. Such a dispersion can provide a master batch vehicle for waterborne ink formulations containing bronze printing ink powder.

It is another object of the present invention to provide stabilized aqueous printing ink formulations containing bronze printing ink powder which exhibits superior stability, reduced color change, good viscosity stability and reduced tendency to settle on storage.

These and other objects of the present invention have been achieved by providing: (a) a bronze printing ink powder dispersed in (b) an aqueous additive formulation. The aqueous additive formulation comprises components (i) to (v) as discussed below.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides stabilized aqueous dispersions of bronze printing ink powder comprising (a) bronze printing ink powder, and

(b) an aqueous additive formulation comprising components (i) to (v). Although any bronze printing ink powder may be used in accordance with the present invention, a preferred bronze printing ink powder is SUPEROTO 300 bronze powder, manufactured by Wolstenholme International.

A preferred aqueous additive formulation in accordance with the present invention, is one described in U.S. Patents 5,443910 and 5,358,560, incorporated herein by reference. The aqueous additive formulation may be in the form of an aqueous additive system or in the form of a solid additive system dispersible in an aqueous medium. The formulation is comprised of: i) an emulsifiable wax; ii) a surfactant in the range of from about 0.025 to about 60 parts by weight per part of the emulsifiable wax; iii) a base having a pH in the range of from 7 to about 12, present in the range of from about 0.0005 to about 2 parts by weight of the emulsifiable wax; iv) optionally, an additive present in an amount up to 160 parts by weight of the emulsifiable wax; and v) at least enough water to render the resulting combination fluid; i.e. having a preferred viscosity of between about 200 to about 500 cps

(centipoise).

The emulsifiable wax employed as component (i) in the practice of the present invention may include any wax that can be readily emulsified using methods known in the art. Suitable emulsifiable waxes include polyolefin waxes such as oxidized polyolefin waxes or modified polyolefin waxes. Preferred oxidized polyolefin waxes include waxes having a density in the range of about 0.92 to 0.96 g/cm³, melt viscosities in the range of about 50-4,000 cps at 125°C and an acid number in the range of about 12 to 55. Exemplary waxes include an oxidized polyethylene wax having a density of 0.939 g/cm³, a melt viscosity of 250 cps at 125°C, and an acid number of 16; an oxidized polyethylene wax having a density of 0.942 g/cm³, a melt viscosity of 900 cps at 125°C, and an acid number of 15; an oxidized polyethylene wax having a density of 0.955 g/cm³, a melt viscosity of 250 cps at 125°C, and an acid number of 16; and a maleated polypropylene wax having a density of 0.934 g/cm³, a melt viscosity of 400 cps at 190°C, and an acid number of 47. A preferred emulsifiable wax is Epolene E14 wax, available from Eastman Chemical Company.

Suitable surfactants or emulsifiers as component (ii) include commercially available anionic, cationic and nonionic surfactants such as those described in "McCutcheon's Emulsifiers and Detergents, Published by MC Publishing Company, Glen Rack, NJ (1993), incorporated herein by reference. Especially preferred surfactants and emulsifiers include TERGITOL 15-S-15 surfactant, an ethoxylated linear alcohol having a hydrophilic-lipophiiic balance of 15.4 (as determined according to Griffin, W. G. Office. Dig. Federation Paint Varnish Prod. Blubs 28, 446 (1956)); and anti-foam agents such as SWS-211antifoam (a mixture of food grade emulsifiers, 10% by wt. silicone compounds, and water). Suitable emulsifiers may also contain potassium hydroxide, sodium tetraborate, sodium carbonate, sodium bicarbonate, calcium carbonate or magnesium carbonate, morpholine, 2-amino-2-methylpropanol, tall oil fatty acid, ethylene glycol and ethoxylated stearyl alcohol (commercially available as Industrol A99), and the like.

Suitable bases for use as component (iii) include alkali metal salts of weak acids such as sodium tetraborate, sodium carbonate, sodium bicarbonate; alkali earth salts of weak acids such as calcium carbonate, calcium stearate, magnesium carbonate and the like.

The additives employed in the practice of the present invention as component (iv) may be selected from antioxidants, e.g., tetrakis[methylene 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)-propionate]methane, octadecyl 3-(3',5'-di-t-butyl-4-hydroxy-phenyl)propionate, 1 ,3,5-trimethyl-2,4,6-tris- (3,5-di-tert-butyl)-4-(hydroxybenzene, bis(2,4-di-t-butyl-phenyl) penta- erythritol diphosphite, tris(mono nonyl-phenyl) phosphite, 4,4'-butylidene- bis(5-methyl-2-t-butyl)phenol, tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, tris-nonylphenyl phosphite, distearyl pentaerythritol diphosphite, tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylylene-diphosphonite; tris-(2,3-di-t-butylphenyl) phosphite, butylated hydroxy toluene, dicetyl thiodipropionate, dimyristyl thiodipropionate, poly(1 ,4-cyclohexylene dimethylene-3,3'-thiodipropionate (partially terminated with stearyl alcohol), and the like; coupling agents, e.g., silanes; titanates, chromium complexes, low molecular weight polyolefins (with carboxylic moieties), high molecular weight polyolefins and acrylates (with carboxylic moieties), chlorinated paraffins, and the like; antistatic agents, e.g., glycerol monostearates, ethoxylated amines, polyethylene glycol, quaternary ammonium compounds (salts), and the like; nucleating agents, e.g., sodium benzoate, diphenyl phosphinic acid (including magnesium, sodium, calcium, aluminum salts), phenyl phosphinic acid (including salts), phenyl phosphorous acid (including salts), and the like; metal deactivators, e.g., oxalyl bis(benzylidene hydrazide), 2,2'-oxamido bis-( ethyl 3-(3,5-di-t-butyl- 4-hydroxyphenyl) propionate, and the like; lubricants/slip agents/anti- blocking agents, e.g., diatomaceous silica (earth), talc, clay, metallic stearates, alkyl bis-stearamids, glycerol monostearates, polyethylene glycol, erucamid, oleamid, and the like; UV inhibitors, e.g., 2-hydroxy- 4-octoxybenzophenone, 2-hydroxy-4-isooctoxybenzophenone, 4-hydroxy- 4-n-dodecyloxybenzo-phenone, 2-(3-di-t-butyl-2-hydroxy-5-methylphenyl- 5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tamylphenyl) benzotriazole, p-t-butylphenyl salicyllate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxy- benzoate, nickel bis-ortho-ethyl(3,5-dit-butyl-4-hydroxybenzyl) phosphonate, 2,2',6,6'-tetramethyl-4-piperidinyl sebacate, and the like; flame retardants, e.g., decabromodiphenyl oxide, dodecachlorodimethane dibenzocyclooctane, ethylene bis-dibromo norbomane dicarboximide, ethylene bis-tetrabromophthalimide, antimony trioxide, and the like; biocides, e.g., methyl paraben, ethyl paraben, propyl paraben, halogenated alkyl organic compounds, transition metal carbamate salts, and the like; as well as mixtures of any two or more of the above mentioned classes of compounds, or mixtures of two or more compounds from within a given class of compound.

The aqueous additive formulation may be prepared by first agitating a combination of component (i), an emulsifiable wax, in the range of about 5 to 35 wt.%; component (ii), a surfactant, in the range of about 0.5 to 6 wt.%; component (iii), a base, in the range of about 0.2 to 1.0 wt.%; and component (v), water, as the remainding wt. %; in a pressure vessel at a temperature sufficient to melt all solids and at a pressure sufficient to prevent boiling of the vessel contents for a period of time in the range of about 0.1 up to 6 hours. Once all the solids have been melted and the mixture thoroughly combined, the vessel contents are rapidly cooled to room temperature.

The resulting emulsion (50-70 wt.%) is then mixed with component (iv), additive(s) to be incorporated into the aqueous additive formulation (30- 50 wt.%). Optionally, additional water (0-35 wt.%) may be added to achieve a preferred viscosity of between about 200 to about 500 cps. An optional antifoam agent (0-1 wt.%) may also be added. This mixture is then charged to a ball mill, sand mill, hammer mill, or the like and subjected to milling for a time in the range of about 2 up to 24 hours. The resulting aqueous additive formulation is then ready for dispersion of the bronze printing ink powder into the additive formulation.

The aqueous additive formulation is preferably present at a level calculated to contain from 0.2 to 5 wt.% of the base based on the weight of the bronze printing ink powder.

Prior to addition of the bronze printing ink powder, the masterbatch aqueous additive formulation prepared as described above, may optionally be further diluted with additional quantities of water. Such dilution may be carried out, for example, to improve the ease of incorporating the aqueous additive formulation with the bronze printing ink powder, and to make it easier to vary the quantity of an additive applied to the bronze printing ink powder.

The preferred solids content of the stabilized aqueous bronze printing ink formulation is preferably between 10 and 30 wt. %. The term "solids content" is used to denote the remainder weight % after substantially all volatile materials have been removed in a forced draft oven at about 150 °C for about 20 minutes. Further, the present invention provides stabilized aqueous bronze paste formulations. The stabilized aqueous paste formulations comprise the same components as described above for the stabilized aqueous bronze printing ink formulations except that the formulation is further dried such that the solids content of the bronze paste is in the range of 40 to 60 wt. %.

An additional preferred composition is a stabilized bronze printing ink powder, wherein the formulation is further dried such that substantially all the water has been removed from the stabilized aqueous bronze printing ink formulation and the remaining bronze powder has a solids content of about 100 wt.%.

The invention also provides methods of incorporating a wide range of additives with the bronze printing ink powder. One method of incorporating additives comprises contacting the bronze printing ink powder with an emulsion or suspension containing an additive formulation, as disclosed above, and subsequently drying the bronze printing ink powder to leave the additive solids adhered to the bronze printing ink powder.

The present invention also provides aqueous ink formulations comprising a stabilized aqueous dispersion of bronze printing ink powder and a polyester. Aqueous emulsions or dispersions sometimes contain potassium hydroxide or sodium hydroxide, and other additives such as processing aids, stabilizers or other functional additives for printing inks, as component (iv). These types of compounds may cause the formation of color complexes when certain additives are present. For example, n-octa- decyl S-^'^'-di-tert-butyM'-hydroxypheny propionate, a hindered phenolic primary antioxidant, forms a color complex which imparts undesirable color to the bronze printing ink powder dispersed in such emulsions.

However, it has been found that when such aqueous emulsions contain component (iii) of the present invention, or a similar base component in the pH range of between about 7 and about 12, color complex formation is not observed. Emulsions or dispersions containing a base, such as sodium tetraborate, may also contain additives such as stabilizers, for example, n-octadecyl 3-(3',5'-ditert-butyl-4'-hydroxyphenyl) propionate, without imparting color to the bronze printing ink powder to which the aqueous emulsions or dispersions containing the additives are applied. The addition level of sodium tetraborate or a similar weak base to the aqueous emulsions or dispersions may vary from about 0.2 to about

1.05 percent by weight.

The polyester in accordance with the present invention is formed by the reaction of the following components:

Component (1 ): at least one difunctional aromatic, saturated aliphatic or saturated alicyclic dicarboxylic acid.

The dicarboxylic acid component of the polyester may be selected from aliphatic dicarboxylic acid, alicyclic dicarboxylic acid, aromatic dicarboxylic acid, or mixtures of two or more of these acids. Examples of such dicarboxylic acids, include succinic, glutaric, adipic, azelaic, sebacic,

1 ,4-cyclohexanedicarboxylic, phthalic, terephthalic and isophthalic acid.

Terephthalic acid and isophthalic acid are preferred as the carboxylic acid component of the polyester. It should be understood that use of the corresponding acid anhydrides, esters, and acid chlorides of these acids is included in the term

"dicarboxylic acid."

Component (2): from about 4 to about 25 mol %, based on a total of all acid and hydroxyl equivalents being equal to 200 mol %, of at least one difunctional sulfomonomer containing at least one metal sulfonate group attached to aromatic nucleus wherein the functional group is hydroxy or carboxyl.

The difunctional sulfomonomer component of the polyester may advantageously be a dicarboxylic acid or an ester thereof containing a metal sulfonate group, a glycol containing a metal sulfonate group or a hydroxy acid containing a metal sulfonate group. The metal ion of the sulfonate salt may be Na⁺, Li⁺, K⁺ and the like. When a monovalent alkali metal ion is used, the resulting polyesters are less readily dissipated by cold water and more readily dissipated by hot water. When a divalent or a trivaient metal ion is used the resulting polyester is not ordinarily easily dissipated by cold water but is more readily dissipated in hot water. It is possible to prepare the polyester using, for example, a sodium sulfonate, by ion-exchange replacement of this ion with a different ion, and thus alter the characteristics of the polymer. The difunctional monomer component may also be referred to as the difunctional sulfomonomer and is further described herein below.

Advantageous difunctional sulfomonomer components are those where the sulfonate salt group is attached to an aromatic acid nucleus such as benzene, naphthalene, diphenyl, oxyphenyl, sulfonyldiphenyl or methylenediphenyl nucleus. Preferred results are obtained through the use of sulfophthalic acid, sulfoterephthalic acid, sulfoisophthalic acid, 4-sulfo- naphthalene-2,7-dicarboxylic acid, and their esters.

Particularly superior results are achieved when the difunctional sulfomonomer component is 5-sodiosulfoisophthalic acid or its esters, and the glycol is a mixture of ethylene glycol or 1 ,4-cyclohexanedimethanol with diethylene glycol.

Component (3): at least one difunctional reactant selected from a glycol or a mixture of a glycol and a diamine having two -NRH groups. Preferably, the glycol of component (3) above contains a small amount of poly(ethylene glycol) to aid in water dispersibility. When poly(ethylene glycol) is used, the content of the sulfomonomer can be lower, which aids in flexibility of formulating the polyester.

The water dispersibility of the polyester is related to the weight % of poly(ethylene glycol) and mol % of sulfomonomer. Therefore, if the content of either is relatively low, the other should be relatively high to maintain adequate dispersibility. The poly(ethylene glycol) need not be present in the initial reaction charge, because poly( ethylene glycol) may form in situ from decomposition products and be incorporated into the polyester chain. It is well known, for example, that diethylene glycol is formed in situ in such reactions.

In the preferred form of the present invention, the polyester contains repeating units of a poly(ethylene glycol) of the formula H-(OCH -CH₂)_n-OH wherein "n" is an integer of 2 to 500. The value of "n" is preferably from between about 2 to about 20. The values of "n" and the mole percent of poly(ethylene glycol) in the polyester, if used, are adjusted such that the mole percent of poly(ethylene glycol) within the stated range is inversely proportional to the quantity of "n" within the stated ranges. Thus, when the mole percent is high, the value of "n" is low. On the other hand, if the mole percent is low, the value of "n" is high. It is apparent, therefore, that the weight percent (product of mole percent and molecular weight) of the poly( ethylene glycol) is an important consideration because the water dissipatability of the copolyester decreases as the weight percent poly( ethylene glycol) in the copolyester decreases. For example, if the weight of poly( ethylene glycol) is too low, the water dissipatability of the copolyester may be inadequate. Furthermore, the weight percent of poly(ethylene glycol) is preferably adjusted such that it is inversely proportional to the mole percent of the difunctional sulfomonomer because the water dissipatability of the copolyester is a function of both the mole percent sulfomonomer and the weight percent polyethylene glycol. Examples of suitable poly(ethylene glycols) include relatively high molecular weight poly( ethylene glycols), some of which are available commercially under the designation "CARBOWAX", a product of Union Carbide. Diethylene glycol is also especially suitable. Other useful glycols for preparing copolyester may consist of aliphatic, alicyclic and aralkyl glycols. Examples of these glycols include ethylene glycol, propylene glycol, 1 ,3-propanediol, 2,4-dimethyl-2-ethy- Ihexane 1 ,3-diol, 2,2-dimethyl-1 ,3-propanediol, 2-ethyl-2-butyl-1 ,3-propane- diol, 2-ethyl-2-isobutyl-1 ,3-propanediol, 1 ,3-butanediol, 1 ,4-butanediol,

1 ,5-pentanediol, 1 ,6-hexanediol, 2,2,4-trimethyl-1 ,6, hexanediol, thiodi- ethanol, 1 ,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, 2,2,4,4,-tetramethyl-1 ,3-cyclobutanediol, and p-xylylenediol. Component (4): optionally, at least one difunctional reactant selected from a hydroxycarboxylic acid having one -CR₂-OH; an aminocarboxylic acid having one -NRH group; an aminoalcohol having one -CR₂-OH group and one -NRH; or mixtures thereof, wherein each R is an H atom or an alkyl group of 1 to 4 carbon atoms. The polyester comprises repeat units from about 5 to about 40% by weight of a linear water- dissipatable polymer having car bonyloxy linking groups in the linear molecular structure wherein up to 80% of the linking groups may be carbonylamido linking groups. The linear polymer should have an inherent viscosity of at least about 0.1 , measured in a 60/40 parts by weight solution of phenol/tetrachloroethane at 25°C and at a concentration of about 0.25 g of polymer in 100 ml of the solvent, the polymer containing substantially equimolar proportions of acid equivalents (100 mol %) to hydroxy and amino equivalents (100 mol %).

The polyester in accordance with the present invention is present in an amount from 45 to 55 wt. % based on the weight of the bronze printing ink powder.

It is preferred that the polyester in accordance with the present invention has repeat units from isophthalic acid, sodiosulfoisophthalic acid, diethylene glycol, and another glycol selected from at least one of ethylene glycol and 1 ,4-cyclohexanedimethanol. Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limited unless otherwise specified.

EXAMPLES Example 1

A commercial bronze printing ink powder was first blended in a 1 :1 ratio with de-ionized water, in the presence of about 2 wt.% isopropyl alcohol based on the bronze printing ink powder weight, to aid pigment wetting, prior to the addition of the aqueous additive formulation. The bronze printing ink powder was then dispersed in the aqueous additive formulation described in Table 1 , and enough water was removed to form a stabilized bronze printing ink paste. The emulsifiable wax, component (i), was prepared as an emulsion, prior to use in the additive formulation, using the following ingredients:

Table I: Aqueous Additive Formulation

The aqueous additive formulation was added to the bronze printing ink powder at a level calculated to employ 10,000 ppm (1 wt%) of calcium stearate based on the weight of the bronze printing ink powder.

The treated bronze printing ink paste was stored in a glass jar at room temperature and compared at regular intervals against the following bronze printing ink paste formulations: 1. Bronze printing ink powder plus water with no additives;

2. Bronze printing ink powder plus water plus 10,000 ppm (1 wt%), based on bronze printing ink powder, of wax employed from the aqueous additive formulation;

3. Bronze printing ink powder plus water plus 10,000 ppm (1 wt%), based on bronze printing ink powder, of calcium stearate employed as a powder that is not in the form of an aqueous additive formulation. After a period of four weeks, the bronze paste containing calcium stearate from the aqueous additive formulation was visibly brighter than the other mixtures when applied to a substrate.

Example 2

A water based ink was formed by admixing 27.3 g of bronze printing ink powder of Example 1 with 45.4 g of aqueous medium containing 13.62% by weight of a polyester formed from repeat units of isophthalic acid, sodiosulfoisophthalic acid, diethylene glycol and ethylene glycol. It was found that the resulting ink had superior stability to a similar formulation without the aqueous additive formulation, reduced color change, good viscosity stability and reduced tendency to settle out into a hard layer on storage.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Claims

CLAIMSWhat is claimed is:

1. An stabilized aqueous bronze printing ink formulation, comprising:

(a) a bronze printing ink powder; and (b) an aqueous additive formulation; wherein said aqueous additive formulation comprises: i) an emulsifiable wax, ii) a surfactant in the range of from 0.025 to 60 parts by weight of per part of the emulsifiable wax; iii) a base having a pH in the range of about 7 to about 12, present in the range of from 0.0005 to 2 parts by weight of the emulsifiable wax; iv) at least one additive present in the range of from 0.05 to 160 parts by weight of the emulsifiable wax, said additive selected from the group consisting of antioxidants, coupling agents, antistatic agents, nucleating agents, metal deactivators, lubricants/slip agents/antiblocking agents, UV inhibitors, flame retardants, biocides and mixtures there of; and v) at least enough water to render the resulting emulsion fluid; wherein said formulation has a viscosity in the range of 200 to 500 cps.

2. The stabilized aqueous bronze composition of claim 1 , wherein said base is selected from the group consisting of sodium tetraborate, sodium carbonate, sodium bicarbonate, calcium carbonate, calcium stearate and magnesium carbonate.

3. An aqueous ink formulation, comprising:

(a) a bronze printing ink powder;

(b) an aqueous additive formulation; and

(c) an aqueous polyester dispersion wherein said aqueous additive formulation comprises: i) an emulsifiable wax; ii) a surfactant in the range of from 0.025 to 60 parts by weight of per part of the emulsifiable wax; iii) a base having a pH in the range of 7 to about 12, present in the range of from 0.0005 to 2 parts by weight of the emulsifiable wax; iv) at least one processing aid, stabilizer or other functional additives present in the range of from 0.05 to 160 parts by weight of the emulsifiable wax; and v) at least enough water to render the resulting combination fluid; wherein said formulation has a viscosity in the range of 200 to 500 cps.

4. The water based ink formulation of claim 3, wherein said polyester is formed by a reaction of components comprising: 1 ) at least one difunctional aromatic, saturated aliphatic or saturated alicyclic dicarboxylic acid; 2) at least one difunctional sulfomonomer containing at least one metal sulfonate group attached to aromatic nucleus wherein the functional group is hydroxy or carboxyl; and 3) at least one difunctional reactant selected from a glycol or a mixture of a glycol and a diamine having two - NRH groups.

5. The water based ink formulation of claim 3, wherein said base is selected from the group consisting of sodium tetraborate, sodium carbonate, sodium bicarbonate, calcium carbonate, calcium stearate and magnesium carbonate.

6. A stabilized aqueous bronze paste formulation, comprising:

(a) a bronze printing ink powder; and

(b) an aqueous additive formulation; wherein said aqueous additive formulation comprises: i) an emulsifiable wax, ii) a surfactant in the range of from 0.025 to 60 parts by weight of per part of the emulsifiable wax; iii) a base having a pH in the range of about 7 to about 12, present in the range of from 0.0005 to 2 parts by weight of the emulsifiable wax; iv) at least one additive in the range of from 0.05 to 160 parts by weight of the emulsifiable wax, said additive selected from the group consisting of antioxidants, coupling agents, antistatic agents, nucleating agents, metal deactivators, lubricants/slip agents/antiblocking agents, UV inhibitors, flame retardants, biocides and mixtures there of; and v) at least enough water to render the resulting formulation fluid; wherein said formulation is further dried to a solids content of about 40 to about 60 wt. % to render a stabilized bronze printing ink paste.

7. A stabilized bronze printing ink powder, comprising: (a) a bronze printing ink powder; and

(b) an aqueous additive formulation; wherein said aqueous additive formulation comprises: i) an emulsifiable wax, ii) a surfactant in the range of from 0.025 to 60 parts by weight of per part of the emulsifiable wax; iii) a base having a pH in the range of about 7 to about 12, present in the range of from 0.0005 to 2 parts by weight of the emulsifiable wax; iv) at least one additive in the range of from 0.05 to 160 parts by weight of the emulsifiable wax, said additive selected from the group consisting of antioxidants, coupling agents, antistatic agents, nucleating agents, metal deactivators, lubricants/slip agents/antiblocking agents, UV inhibitors, flame retardants, biocides and mixtures there of; and v) at least enough water to render the resulting formulation fluid; wherein said formulation is further dried to remove substantially all of the water and the remaining formulation has a solids content of 100% of the bronze printing ink powder.