FIELD OF THE INVENTION:
The present invention relates to a novel gravure ink suitable for mono-reducer ester based solvent system involving a high molecular weight (HMW) polyester polyol (A), a polyvinyl chloride resin (B) and combination of aromatic hydrocarbon free organic solvents (C).
BACKGROUND OF THE INVENTION:
Aromatic hydrocarbon solvent based printing inks pose several environmental hazards as releasing a large amount of volatile organic compounds (VOC) to the atmosphere. In view of safeguarding the environment, the regulations on the printing industries in the recent times has prompted the printing processes to resort to aromatic hydrocarbon free printing inks.
The reducers used in printing inks are hard to recover, and also they release a large amount of volatile organic compounds (VOC) to the atmosphere causing hazard to the environment.
JP2018165373A and JP2018109131A disclose a gravure ink composition that contains a polyurethane resin including a castor oil polyol-derived structure, and a structure derived from a polyester polyol, a polyvinyl chloride copolymer resin, a pigment and an organic solvent.
OBJECTS OF THE INVENTION:
The principal objective of the present invention is to provide an environmentally safe gravure ink suitable for mono-reducer ester based solvent system containing a high molecular weight (HMW) polyester polyol resin (A) and a polyvinyl chloride resin (B) based binder and a combination of aromatic hydrocarbon free organic solvents (C).
Another objective of the present invention is to provide an environmentally safe gravure ink, where the mono-reducer ester based solvent system can be recovered with minimum emission of volatile organic compounds (VOC) to the environment.

Another objective of the present invention is to provide an environmentally safe gravure ink, where the mono-reducer ester based solvent system resolves the issue of cell filling of cylinder during printing process.
Another objective of the present invention is to provide a cost-efficient gravure ink, where the mono-reducer ester based solvent system can be distilled or recovered easily and reused in the printing industries and/or ink manufacturing industries.
Another objective of the present invention is to provide a user-friendly mono-reducer ester based solvent system which reduces the complications of forming a mixture of multiple solvents system for the personnel working in production during printing process, which sometimes leads to errors and consequently change the properties of the printing inks.
SUMMARY OF THE INVENTION:
The present invention relates to a gravure ink suitable for mono-reducer ester based solvent system having a binder comprising a high molecular weight (HMW) polyester polyol resin (A) and a polyvinyl chloride resin (B) in a combination of aromatic hydrocarbon free organic solvents (C). Preferably the polyvinyl chloride resin (B) is a polyvinyl chloride, vinyl acetate and vinyl alcohol ter-polymer.
The gravure ink of the present invention is manufactured in such a way that the total solid content of the binder [HMW polyester polyol resin (A) and the polyvinyl chloride resin (B)] is in the range of 6-40% by weight. Out of the total binder content, HMW polyester polyol resin (A) which is a condensation product of a dibasic acid and a diol is in the range of 3-15 % by weight. The number-average molecular weight of the HMW polyester polyol resin (A) is in the range of 3000 to 12000 daltons, more specifically between 4000 to 6000 daltons. The dibasic acid and the diol is reacted in such a way that the hydroxyl value of the HMW polyester polyol resin (A) remains in the range of 15 to 40 mg KOH/g. The polyvinyl chloride resin (B) is in the range of 3-15 % by weight of the total binder content.
The diol used in the formulation of HMW polyester polyol resin (A) of the present invention may be selected from diethylene glycol (DEG), monoethylene glycol (MEG), methyl propane diol, methyl pentane diol, neopentyl diol, 1,4-butanediol, 1,6 hexane

diol and the like. Preferably, methyl pentane diol and methyl propane diol or a combination of the same has been used.
The dibasic acid used in the formulation of HMW polyester polyol resin (A) of the present invention may include adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, pimelic acid, azelaic acid, suberic acid, glutaric acid, 1,4-cyclohexyl dicarbon Acid, dimer acid, hydrogenated dimer acid, and the like. Of these, adipic acid is particularly preferred.
The polyvinyl chloride resin (B) used in the formulation is a terpolymer of vinyl chloride, vinyl acetate and vinyl alcohol.
The solvents used in the formulation to dissolve the components of inks are aromatic-hydrocarbon-free solvents such as Ethyl acetate, Methyl ethyl ketone, Isopropyl acetate etc.
However, a person skilled in the art pertaining to the present invention may optionally use certain quantity of aromatic or aliphatic solvents.
DETAILED DESCRIPTION OF THE INVENTION:
The preferred embodiments of the present invention will be described in detail with the following disclosure and examples. The foregoing general description and the following detailed description are provided to illustrate only some embodiments of the present invention and not to limit the scope of the present invention. The invention is capable of other embodiments and can be carried out or practiced in various other ways.
Unless otherwise specified, all the technical and scientific terms used herein have the same meaning as is generally understood by a person skilled in the art pertaining to the present invention. All the patents published patent applications referred to throughout the entire disclosure herein, unless specified otherwise, are incorporated by reference in their entirety.
Definitions of terms used in this specification:

The term mono-reducer as used herein refers to a single solvent based diluent, which is added to the gravure ink during printing to reduce the viscosity of the fresh ink to appropriate printing viscosity, and enhance the printability.
A chemical compound that comprises at least two ester (R-CO-OR) linkages in the same linear chain of atoms is known in this disclosure as a "polyester". A chemical compound that includes both multiple ester linkages and multiple -OH functional groups is known in the present disclosure as a "polyester polyol".
Gravure Ink Composition
The present invention relates to a gravure ink suitable for mono-reducer ester based solvent where the ink contains a binder that includes a high molecular weight (HMW) polyester polyol resin (A) and a polyvinyl chloride resin (B) dissolved in aromatic-hydrocarbon-free solvents (C) such as Ethyl acetate, Methyl ethyl ketone, Isopropyl acetate etc. Preferably the polyvinyl chloride resin (B) is a polyvinyl chloride, vinyl acetate and vinyl alcohol ter-polymer.
However, a person skilled in the art pertaining to the present invention may also use certain quantity of aromatic solvents.
The present invention provides an environmentally safe gravure ink suitable for mono-reducer ester based solvent system, where the mono-reducer ester based solvent system resolves the issue of cell filling of cylinder during printing process.
The present invention relates to cost-efficient gravure ink suitable for mono-reducer ester based solvent system, where the mono-reducer ester based solvent system can be distilled easily and reused for the printing inks.
The present invention provides a user-friendly mono-reducer ester based solvent system which reduces the complications of forming a mixture of multiple solvents system for the personnel working in production during printing process, which sometimes lead to errors and consequently change the properties of the printing inks.
The HMW polyester polyol resin (A) is a condensation product of a dibasic acid and a diol. Polyvinyl chloride resin (B) especially polyvinyl chloride, vinyl acetate and vinyl alcohol ter-polymer has very good compatibility with the HMW polyester polyol resin

(A), wherein the gravure ink obtained has excellent printability on flexible substrates such as polyester, BOPP & nylon.
The gravure ink suitable for mono-reducer ester based solvent system of the present invention is manufactured in such a way that the total solid content of the binder [HMW polyester polyol resin (A) and the polyvinyl chloride resin (B)] is in the range of 6-40% by weight. Out of the total binder content, HMW polyester polyol resin (A) which is a condensation product of a dibasic acid and a diol is in the range of 3-15 % by weight. The number-average molecular weight of the HMW polyester polyol resin (A) is in the range of 3000 to 12000 daltons, specifically between 4000 to 6000 daltons. The dibasic acid and the diol is reacted in such a way that the hydroxyl value of the HMW polyester polyol resin (A) remains in the range of 15 to 40 mg KOH/g. The polyvinyl chloride resin (B) is in the range of 3-15 % by weight of the total binder content.
Polyester polyol Composition:
The diol in the HMW polyester polyol resin (A) can be selected from diethylene glycol (DEG), monoethylene glycol (MEG), methyl propane diol, methyl pentane diol, neopentyl diol, 1,4-butanediol, 1,6 hexane diol and the like.
The dibasic acid may include adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, pimelic acid, azelaic acid, suberic acid, glutaric acid, 1,4-cyclohexyl dicarbon Acid, dimer acid, hydrogenated dimer acid, and the like. Of these, adipic acid is particularly preferred.
The number average molecular weight of the HMW polyester polyol resin (A) is 3000 to 12000 daltons, more preferably between 4000 to 6000 daltons.
Method of preparation of polyester polyol
The HMW polyester polyol resin (A) is prepared from the diol and the diacid by the following method.
The calculated amount of diol was introduced into a 1 litter reaction kettle with condenser, stirrer, thermometer, and nitrogen gas inlet tube. Provision to take out

condensation water as by-product through a column has also been provided in the reactor assembly. The required amount of adipic acid was then introduced and the mixture was allowed to react by heating up to 90-100°C. When the internal temperature was between 120 to 130°C, water was distilled out and the temperature of column was gradually increased up to 90-95°C until the distilled out water had slowed down. When the acid value of the reaction mixture was slowed down to 25-30 mg KOH/g, then 0.01% of catalyst was added. The reaction was continued until the acid value dropped down to 2. Then vacuum was applied to keep the desired hydroxyl value as shown in the table 1.
Optionally, the HMW polyester polyol resin (A) can be partially reacted with isocyanates. Examples of isocyanates suitable for use according to this invention include, Isophorone diisocyanate (IPDI), Toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), Tetramethylxylene diisocyanate (TMXDI) in such a way that the hydroxyl values of the hydroxyl terminated polyurethanes remain within the ranges of 20 to 60 mg KOH/g.
The total solid content of the binder [HMW polyester polyol resin (A) and the polyvinyl chloride resin (B)] in the gravure ink are 6.0% to 40.0% by weight, more preferably 10.0% to 40.0% by weight, and most preferably 12.0% to 40% by weight of the total weight of the gravure ink of the present invention.
The solid content of the HMW polyester polyol resin (A) in the total binder content is in the range of 2% to 40% by weight, more preferably 5% to 30% by weight, and most preferably 3% to 15% by weight.
The solid content of the polyvinyl chloride resin (B) especially polyvinyl chloride, vinyl acetate and vinyl alcohol ter-polymer in the total binder content is in the range of 2% to 45% weight, more preferably 2.5% to 25% by weight, and most preferably 3% to 15% by weight.
Colourants
The gravure ink suitable for mono-reducer ester based solvent system of the present invention may include a colourant.

The solid content of the colourant in the gravure ink of the present invention is present in the range of about 3 to 40% by weight of the total weight of the gravure ink.
The colourant may be organic based or inorganic based for example, azo compounds (monoazo, di-azo, p-Naphthol, Naphthol AS salt type azo pigment lakes, benzimidazolone, di-azo condensation, isoindolinone, isoindoline), and polycyclic (phthalocyanine, quinacridone, perylene, perinone, diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine, triarylcarbonium, quinophthalone) pigments, and mixtures of any of the foregoing. In certain embodiments, the organic material is selected from perylenes, quinacridones, phthalocyanines, isoindolines, dioxazines (that is, triphenedioxazines), 1,4-diketopyrrolopyrroles, anthrapyrimidines, anthanthrones, flavanthrones, indanthrones, perinones, pyranthrones, thioindigos, 4,4'-diamino-1,1'-dianthraquinonyl, as well as substituted derivatives thereof, and mixtures thereof.
The most common non-limiting pigments include azo dyes (for example, Solvent Yellow 14, Dispersed Yellow 23, and Metanil Yellow), anthraquinone dyes (for example, Solvent Red 111, Dispersed Violet 1 , Solvent Blue 56, and Solvent Orange 3), xanthene dyes (Solvent Green 4, Acid Red 52, Basic Red 1 , and Solvent Orange 63), azine dyes (for example, Jet Black), and the like.
Major usable non-limiting organic pigments include diarylide yellow AAOT (for example, Pigment Yellow 14 Cl#21095), diarylide yellow AAOA (for example, Pigment Yellow 12 Cl#21090), Phthalocyanine Blue (for example, Pigment Blue 15), lithol red (for example, Pigment Red 52:1 Cl#15860:1 ), toluidine red (for example, Pigment Red 22 Cl#12315), dioxazine violet (for example, Pigment Violet 23 Cl#51319), phthalocyanine green (for example, Pigment Green 7 Cl#74260), phthalocyanine blue (for example, Pigment Blue 15 Cl#74160), naphthoic acid red (for example, Pigment Red 48:2 Cl# 15865:2).
Examples of Inorganic pigments include titanium dioxide (for example, Pigment White 6 Cl#77891), carbon black (for example, Pigment Black 7 Cl#77266), iron oxides (for example, red, yellow, and brown), ferric oxide black (for example, Pigment Black 1 1

Cl#77499), chromium oxide (for example, green), ferric ammonium ferrocyanide (for example, blue), and the like.
Thus, the colourant may be any conventional organic or inorganic pigments without any restriction for example Zinc Sulfide, Pigment White 6, Pigment Yellow 1 , Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 63, Pigment Yellow 65, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 106, Pigment Yellow 1 14, Pigment Yellow 121 , Pigment Yellow 126, Pigment Yellow 127, Pigment Yellow 136, Pigment Yellow 174, Pigment Yellow 176, Pigment Yellow 188, Pigment Orange 5, Pigment Orange 13, Pigment Orange 16, Pigment Orange 34, Pigment Red 2, Pigment Red 9, Pigment Red 14, Pigment Red 17, Pigment Red 22, Pigment Red 23, Pigment Red 37, Pigment Red 38, Pigment Red 41 , Pigment Red 42, Pigment Red 57, Pigment Red 1 12, Pigment Red 122, Pigment Red 170, Pigment Red 210, Pigment Red 238, Pigment Blue 15, Pigment Blue 15:1 , Pigment Blue 15:2, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Green 7, Pigment Green 36, Pigment Violet 19, Pigment Violet 23, Pigment Black 7 and the like.
Additives:
The gravure ink suitable for mono-reducer ester based solvent system of the present invention may also contain the usual ink additives to adjust flow, surface tension, and gloss of printed ink. Such additives typically are polymeric dispersants, surface active agents, waxes, or a combination thereof.
These additives may function as levelling agents, wetting agents, fillers, dispersants, adhesion promoters, defrothers (anti-foaming agent), an antistatic agent, a viscosity modifier or other additives may be added to provide a specific function.
The gravure ink suitable for mono-reducer ester based solvent system may contain a polymeric dispersant when the colourant is a pigment to disperse the pigment during mixing and grinding operations in the solvent. All components of the ink may be blended together and ground to reduce the pigment particles to the desired size distribution, typically 10 microns or less, or alternatively the pigment and the polymeric dispersant can be premixed and ground in the solvent to form a "base"

which is subsequently blended with the remaining components of the gravure ink. The ink components may be mixed in a high speed mixer until a slurry consistency is reached and then passed through a media mill until the pigment is reduced to 10 microns or smaller. The wide versatility of the inks of this invention allows them to be prepared without a polymeric dispersant, but preferably they are made with a polymeric dispersant for grinding in, for example, polyvinyl butyral or blending with, for instance, a nitrocellulose base. Other useful colourants, and additives are also possible known to the persons skilled in the art.
Mono-reducer Ester based solvent
The mono-reducer ester based solvent system in the gravure ink of the present invention is used to reduce the viscosity of fresh ink to appropriate printing viscosity, and enhance the printability.
This mono-reducer ester based solvent system is an esterified product of an aliphatic alcohol and acetic acid, wherein the mono-reducer ester based solvent system is selected from ethyl acetate, n-propyl acetate, n-butyl acetate, preferably ethyl acetate, n-propyl acetate, more preferably ethyl acetate.
During printing, the mono-reducer ester based solvent system is added to the gravure ink of the present invention in the range of about 5% to 70% by weight.
Examples:
The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the invention without being limited to the specific examples given here.
Synthesis Example 1a. 1b. 1c
[Preparation of HMW polyester polyol resin (A)]
As shown in Table 1 below in examples 1a to 1c, the calculated amount of diol was introduced into a 1 litter reaction kettle with condenser, stirrer, thermometer, and nitrogen gas inlet tube. Provision to take out condensation water as by-product through a column has also been provided in the reactor assembly. The required amount of adipic acid was then introduced and the mixture was allowed to react by heating up to 90-100°C. When the internal temperature was between 120 to 130°C,

water was distilled out and the temperature of column was gradually increased up to 90-95°C until the distilled out water had slowed down. When the acid value of the reaction mixture was slowed down to 25-30 mg KOH/g, then 0.01% of catalyst was added. The reaction was continued until the acid value dropped down to 2 mg KOH/g. Then vacuum was applied to keep the desired hydroxyl value.
Table 1
Examples 2a - 2f
Preparation of Ink
The most preferred six embodiments of the invention to prepare the polyol based ink composition using HMW polyester polyol resin (A) of each of the above examples individually and a polyvinyl chloride resin (B) are given in examples 2a to 2c in Table 2 below depicted as lnk-1 to lnk-3; and a mixture of more than one HMW polyester polyol resins (A) and a polyvinyl chloride resin (B) are given in examples 3a to 3c in Table 3 below depicted as lnk-4 to lnk-6.
Table 2

* Other aforementioned pigments or a mixture of pigments can be used to impart the desired colour to the ink composition.
Table 3

* Other aforementioned pigments or a mixture of pigments can be used to impart the desired colour to the ink composition.
Sample test result
The polyurethane ink formulation evaluation results have been provided in the following Table 4.
Table 4
Rating: 1=poor; 5=Excellent
The advantages of the gravure ink of the present invention include at least the following.
a. The gravure ink fully soluble in ester solvents,
b. The mono-reducer solvent component is recoverable with minimum emission of
VOC to the environment.

c. The recovered solvent can be reused in the printing industries and/or ink
manufacturing industries.
d. The mono- reducer solvent system resolves the cell filing issue of cylinder during
printing process.
e. The mono-reducer solvent system also provides a user friendly environment to
the personnel working in production area by reducing the complications of mixing
the multiple solvent system.
While various aspects and embodiments have been disclosed herein, other aspects, embodiments and uses of the invention will be apparent to those skilled in the art. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

We claim:
1. A gravure ink suitable for mono-reducer ester based solvent system comprising a binder, wherein the binder includes a high molecular weight (HMW) polyester polyol resin (A) and a polyvinyl chloride resin (B); and a combination of aromatic hydrocarbon free organic solvents (C), wherein the HMW polyester polyol resin (A) has a number average molecular weight of about 3000 to 12000 daltons.
2. The gravure ink suitable for mono-reducer ester based solvent system according to claim 1, wherein the HMW polyestrer polyol (A) is derived from a diol selected from diethylene glycol (DEG), monoethylene glycol (MEG), methyl propane diol, methyl pentane diol, neopentyl diol, 1,4-butane diol, 1,6 hexane diol, preferably methyl propane diol and methyl pentane diol; and a diacid selected from adipic acid, phthalic acid, isopthalic, terephthalic acid, sebacic acid, preferably adipic acid.
3. The gravure ink suitable for mono-reducer ester based solvent system according to claims 1 or 2, wherein the total solid content of the binder is in the range of 6-40% by weight, wherein the solid content of the HMW polyester polyol resin (A) in the total solid content of the binder is in a range of about 3% to 15% by weight; and the solid content of the polyvinyl chloride resin (B) in the total solid content of the binder is in a range of about 3% to 15% by weight.
4. The gravure ink suitable for mono-reducer ester based solvent system according to claim 1, wherein the polyvinyl chloride resin (B) preferably is a polyvinyl chloride, vinyl acetate and vinyl alcohol ter-polymer.
5. The gravure ink suitable for mono-reducer ester based solvent system according to claim 1, wherein the mono-reducer ester based solvent system is added to the gravure ink during printing in a range of 5% to 70% by weight of the gravure ink.
6. The gravure ink according to claim 1, wherein the number average molecular weight of the HMW polyester polyol resin (A) is preferably about 4000 to 6000 daltons.

7. The gravure ink suitable for mono-reducer ester based solvent system according to claim 1 includes a colourant, wherein the solid content of the colourant in the gravure ink is present in the range of about 3 to 30% by weight of the total weight of the gravure ink.
8. The gravure ink suitable for mono-reducer ester based solvent system according to claim 1 additionally includes at least one additive such as a levelling agent, a wetting agent, a filler, a dispersant, an adhesion promoter, an anti-foaming agent, an antistatic agent, a viscosity modifier.
9. A method of preparation of a gravure ink suitable for mono-reducer ester based solvent system comprising a binder, wherein the binder includes a high molecular weight (HMW) polyester polyol resin (A) and a polyvinyl chloride resin (B); and a combination of aromatic hydrocarbon free organic solvents (C), wherein the HMW polyester polyol resin (A) has a number average molecular weight of about 3000 to 12000 daltons.
10. The method of preparation of a gravure ink suitable for mono-reducer ester based solvent system according to claim 9, wherein the polyvinyl chloride resin (B) preferably is a polyvinyl chloride, vinyl acetate and vinyl alcohol ter-polymer.