FIELD OF THE INVENTION:
The present invention relates to a polyurethane based printing ink for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic application.
BACKGROUND OF THE INVENTION:
Printing with nitrocellulose (NC) based inks or polyurethane (PU) based inks via central impression (CI) flexographic printing technique for PE/PP extrusion lamination is quite difficult due to poor extrusion lamination bond strength, adhesion, blocking resistance, printability. Also, smearing of printing inks from the printed laminate articles is a problem.
JP2018131548A discloses a water-based flexo ink that can be used for CI flexographic printing, which contains a pigment, water, a urethane resin having a graft chain, and wax, the urethane resin having an acid value of 25-100 mgKOH/g.
WO2019069736A1 discloses a boilable retort pouch that is surface printed using an electron beam-curable water-based flexo ink for surface printing (that can be used for CI flexographic printing) on the outside of the pouch container, with almost 0% VOC in the ink, wherein the ink contains a water-based resin (X), an ethylenic double bond-bearing electron beam-curable compound (Y), a pigment, and water, where the mass ratio between the solids fraction of the water-based resin (X) and the solids fraction of the ethylenic double bond-bearing electron beam-curable compound (Y) is within the range of (X)/(Y) = 5/100 to 400/100.
JP6065036B2 discloses a printing ink laminate obtained by depositing an ink coating layer (that can be used for CI flexographic printing) formed of a first printing ink comprising an acrylic resin or a polyurethane resin (B), and an organic pigment and/or carbon black, an ink coating layer formed of a second printing ink comprising a polyurethane resin or an acryl-urethane resin, and a white pigment, and an ink coating layer formed of a third printing ink comprising an acrylic resin, successively on a plastic film, wherein the acrylic resin has an acid value of 40 to 180 mgKOH/g.
JP5935464B2 discloses an aqueous ink composition that can be used for CI flexographic printing, which contains a fine aqueous resin particle dispersion obtained by emulsion-polymerizing an ethylenically unsaturated monomer in the presence of an olefin copolymer (excluding acrylic copolymers) and an acrylic copolymer in an aqueous solvent.

OBJECTS OF THE INVENTION:
The principal objective of the present invention is to provide a polyurethane based printing ink for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination bond strength for central impression (CI) flexographic application, irrespective of the lamination is carried out with either solvent base or solvent-free lamination adhesives.
A further objective of the present invention is to provide a printed article using the provided ink compositions that exhibit excellent printability, adhesion, blocking resistance properties on various substrates including biaxially oriented polypropylene (BOPP), chemical coated polyethylene terephthalate (CC PET), corona treated polyethylene terephthalate (CT PET) films.
Yet another objective of the present invention is to provide a printed article using the provided ink compositions that exhibit excellent smearing resistance properties on various substrates including biaxially oriented polypropylene (BOPP), CC PET, CT PET films.
SUMMARY OF THE INVENTION:
The present invention provides a polyurethane based printing ink for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination bond strength for central impression (CI) flexographic application.
The polyurethane is derived from the combination of two different polyols (polyol A and polyol B) reacted with a diisocyanate in presence of amine chain extenders.
The ink composition of the present invention consists of a polyurethane based binder, a varnish, at least one aromatic hydrocarbon free organic solvent, a colourant, and at least one additive.
The polyurethane based binder is present in an amount of from about 20% to 40% by weight of the total ink composition, a varnish is present in an amount of from about 5% to 15% by weight of the total ink composition, a solvent is present in an amount of from about 15% to 50% by weight of the total ink composition; and the colourant is present in an amount of from about 6% up to 30% by weight of the total ink composition, and additives are present in an amount of from about 3% to 7% by weight of the total ink composition, and demineralized water in an amount of from about 3% to 10% by weight of the total ink composition is present in an wherein the

polyurethane based binder may be a single polyurethane, or a mixture of two or more different polyurethanes.
The solvents used in the formulation to dissolve the components of inks are aromatic-hydrocarbon-free solvents such as Ethyl acetate, n-propyl acetate, methoxy propyl acetate, methoxy propyl alcohol, Isopropyl acetate, Isopropanol, Ethanol.
However, a person skilled in the art pertaining to the present invention may optionally use certain quantity of aromatic hydrocarbon, ketonic or aliphatic solvents.
Printed articles using the provided ink compositions exhibit excellent lamination bond strength irrespective of the lamination is carried out with either solvent base or solvent-free lamination adhesives, excellent printability, adhesion, smearing and blocking resistance properties on various substrates including biaxially oriented polypropylene (BOPP), chemical coated polyethylene terephthalate (CC PET), corona treated polyethylene terephthalate (CT PET) films.
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.
It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from greater than 0 % by weight to about 25 % by weight should be interpreted to include not only the explicitly recited limits of greater than 0 % by weight to about 25 % by weight, but also to include individual values, such as 0.05 % by weight, 0.9 % by weight, 7 % by weight, 21 % by weight, etc., and sub-ranges, such as from about 1 % by weight to

about 24 % by weight, from about 5 % by weight to about 20 % by weight, etc. Furthermore, when "about" is utilized to describe a value, this is meant to encompass minor variations (up to +/-10%) from the stated value.
Reference throughout this specification to "one embodiment," "an embodiment," "one example," or "an example" means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment," "in an embodiment," "one example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and/or sub-combinations in one or more embodiments or examples. In addition, it should be appreciated that if any figures are provided herewith, they are for explanation purposes to persons ordinarily skilled in the art and that the drawings of them are not necessarily drawn to scale.
In this specification, certain aspects of one embodiment include process steps and/or operations and/or instructions described herein for illustrative purposes in a particular order and/or grouping. However, the particular order and/or grouping shown and discussed herein are illustrative only and not limiting. Those of skill in the art will recognise that other orders and/or grouping of the process steps and/or operations and/or instructions are possible and, in some embodiments, one or more of the process steps and/or operations and/or instructions discussed above can be combined and/or deleted. In addition, portions of one or more of the process steps and/or operations and/or instructions can be re-grouped as portions of one or more other of the process steps and/or operations and/or instructions discussed herein. Consequently, the particular order and/or grouping of the process steps and/or operations and/or instructions discussed herein do not limit the scope of the disclosure.
Definitions of terms used in this specification:
The term "polyurethane", "PIT, "urethane polymer", as used herein refers to a thermoplastic polymer which can be made crosslinkable (or thermosettable) and which is produced by the reaction of a polyisocyanate (i.e., an organic compound containing at least two isocyanate (-N=C=0) groups per molecule) and a polyol. The polymeric reaction product contains repeating urethane linkages (or carbamate ester linkages) of the structure:

When such linkages are present in a polymer, it is classified as polyurethane herein. Polyisocyanates also react with amines (that is, compounds which contain at least one primary or secondary amino
group per molecule (where Ri is typically an alkyl, aryl, or like hydrocarbonaceous radical) in a similar fashion to produce a polymeric reaction product that contains urea linkages:
Polymers containing both urethane and urea linkages are known as polyurethane ureas and such polyurethane polymers can be used as starting polymers in the practice of this invention.
Either the starting polyisocyanate or the starting polyol can itself have an internal polymeric structure. Examples of suitable structures include polyethers, polyesters, polyalkyls, polydimethylsiloxanes, and the like. Commonly used isocyanates in polyurethane synthesis include Isophorone diisocyanate (IPDI), toluene dissocyanate (TDI) and methylene bis (p-phenyl isocyanate) or 4,4'-dimethylmethane diisocyanate (MDI) although many other isocyanates are available. Commonly used polyols include polyester and polyethers. A polyurethane polymer can contain various functional (i.e., reactive) groups, such as one or more groups selected from the class consisting of isocyanato, hydroxyl and amino (particularly primary or secondary amino). Such functional groups are characteristically associated with polyurethane polymers. However, in addition to, or apart from, such functional groups, a polyurethane polymer can also contain other functional groups such as carboxyl groups, sulfonic acid groups, and the like, as those skilled in the art will appreciate.
A chemical compound with two or more hydroxyl (-OH) groups is known as a "polyol" in this disclosure. A polyol with exactly two -OH groups is a "diol". Similarly a polyol with just three -OH groups is a "triol".

Polyurethane
The method of preparation and formulation of the polyurethane used in the polyurethane based printing ink for polypropylene (PP) or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic application of the present invention has been mentioned in published India Patent Application Number IN201911031513 "Hybrid polyurethane based Ink for improved PP/PE extrusion lamination" filed by Yansefu Inks And Coatings Private Limited. This method of preparation and formulation of the polyurethane has been provided in its entirety here for the present invention.
The polyurethane based printing ink for improved polypropylene (PP)/ Polyethylene (PE) extrusion lamination for central impression (CI) flexographic application, wherein the polyurethane is derived from the combination of two different polyols (polyol A and polyol B) reacted with a diisocyanate in the presence of amine chain extenders, and an aromatic hydrocarbon free solvent.
The Polyol A used to prepare the polyurethane composition of the present invention is selected from polyether polyols such as polypropylene glycol and Polytetrahydrofuran (PolyTHF) having molecular weight 2000 Daltons procured from Dow Chemicals and BASF respectively.
The polyurethane of the present invention comprising polyol units (Polyol A and polyol B) and diisocyanate units is manufactured in such a way that the total polyol content is in the range of 15-30%. Out of this polyol content, polyol A and Polyol B are each in the range of 5-15% of the total polyurethane composition. The formulation has been adopted in such a way that the NCO/OH ratio is in between 1.8 to 2.0. A tin-free catalyst is used within the range of 0.01 to 0.03%. Amines are added in such a way that the viscosity of the polyurethane does not increase beyond 5 poise at 25°C (using Brookfield viscometer). The solvent is aromatic or aliphatic or a combination thereof. The solvent is preferably aromatic hydrocarbon free. The preferred polyol B is the reaction products of adipic acid and the diols such as methyl pentane diol (MPD), methyl propane diol, neo pentyl glycol (NPG), hexane diol (HD), butane diol (BD), 1,2 propane diol (1,2-PDO), mono-ethylene glycol (MEG), diethylene glycol (DEG) etc. The preferred diols are methyl pentane diol (MPD), neo pentyl glycol (NPG) and methyl propane diol.
The most preferable diol is methyl pentane diol (MPD).

Chain extenders such as amines and/or short-chain diols may be used in the polyurethane synthesis. Amine chain extenders are more preferable.
The amines used as chain extender may be Isophorone diamine (IPDA), aminoethyl ethanol amine, Ethylene diamine, Monoethanolamine, Diethylamine, Diethanol amine, Trimethyl hexamethylene diamine, diethylene triamine or a combination thereof. Preferably amines used are Isophorone diamine (IPDA), aminoethyl ethanol amine & trimethyl hexamethylene diamine. The weight percentage of amine used is 0 to 5%.
The short chain diols are selected from methyl propane diol, methyl pentane diol, neo pentyl glycol, hexane diol, 1,2 propane diol, mono-ethylene glycol, diethylene glycol, butane diol etc.
The isocyanate used in the polyurethane formulation of the present invention may be selected from aromatic, cycloaliphatic and/ or aliphatic isocyanates. Preferably, a cycloaliphatic isocyanate such as Isophorone diisocyanate (IPDI) is used.
Method of preparation of Polvol B
The Polyol B is prepared from the diol and the dibasic by the following method.
The calculated amount of diol was introduced into a 1 litter reaction kettle with condenser, stirrer, thermometer, and Heating plate. Provision to take out condensation water as by-product 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. When the internal temperature was between 140 to 180 degree Centigrade, water was distilled out and the temperature was gradually increased to 200-230 degree centigrade until the distilled out water had slowed down. When the acid value of the reaction mixture was slowed down to 10-15, then 0.01% of catalyst (n-Butyl Titanate) 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.
Method of preparation of Polyurethane
The calculated amount of polyol A and polyol B was introduced in 1 litter reaction kettle with condenser, stirrer, thermometer, and nitrogen gas inlet tube at ambient temperature. Stir the reaction mixture for 20 minutes, the required amount of isocyanate has been added to the reactor. Continue the stirring till the temperature of

the raised up to 60°C, add 0.01-0.03% of catalyst and observe exotherm (Exotherm temperature should not exceed 70°C. After completion of exotherm, the reactor temperature was kept up to 80°C for 1-1.5 hours until the desired isocyanate content has been achieved. Cool down the reaction mixture to 50°C and the prepolymer has diluted using about 17% N- Propyl acetate. When, the temperature has decreased below 40°C, the prepolymer has been further diluted with 20% IPA and RO water. The required quantity of amines was mixed with remaining 30% of isopropanol and 4% N- Propyl acetate added to the reactor.
Formulation of the ink
The ink composition of the present invention comprises the aforementioned polyurethane ink binder in, a colourant (colouring agent) such as a pigment, organic solvents, and additives.
The polyurethane contained in the ink composition is in the range of 20-40% by weight, more preferably 25-35% by weight and most preferably about 30% by weight.
Varnish
A solvent based varnish is used for the ink composition of the present invention.
The solvent based varnish composition includes about 15 to 25% by weight of a Poly vinyl butyrate (PVB) resin dissolved in about 65 to 85% an aromatic and/ or aliphatic hydrocarbon solvent or a mixture of aromatic and/ or aliphatic hydrocarbon solvents, and about 5 to 15% by weight of demineralized water. The aromatic and/ or aliphatic hydrocarbon solvent used in the varnish is preferably ethanol.
The weight average molecular weight (Mw) of the PVB resin is 30,000 to 100,000 daltons, more preferably 35,000 to 75,000 daltons, and most preferably 40,000 to 50,000 daltons.
In the ink compositions of the present invention, the total amount of varnish is between about from 5% to 15% by weight of the total ink composition.
Solvents
The non-limiting organic solvents are selected from aliphatic alcohols, organic acid esters, glycol ethers, aliphatic ketones, aliphatic hydrocarbons or cycloaliphatic hydrocarbons.

Suitable aliphatic alcohols include but are not limited to ethanol, Isopropanol, normal-propanol, isobutanol and 1-Methoxy,2-Propanol or mixtures thereof.
Suitable organic acid esters include but are not limited to methyl acetate, ethyl acetate, propyl acetate, butyl acetate and mixtures thereof.
Suitable glycol ethers include but are not limited to diethylene glycol mono-n-butyl ether (DEGMBE), propylene glycol n-butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, dipropylene glycol methyl ether, dipropylene glycol n-butyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol n-propyl ether acetate, dipropylene glycol n-propyl ether, ethylene glycol n-butyl ether (or ethylene glycol monobutyl ether (EGMBE)), diethylene glycol n-butyl ether, triethylene glycol butyl ether, diethylene glycol methyl ether, tripropylene glycol monomethyl ether (TPGME), tripropylene glycol n-butyl ether (TPGBE), and triethylene glycol methyl ether.
Suitable aliphatic ketones include but are not limited to methyl ethyl ketone, methyl isobutyl ketone.
Suitable aliphatic hydrocarbons include but are not limited to pentane, hexane, heptane, octane, nonane, decane, isopentane, isohexanes, isopentanes, isooctanes, 2,2-dimethylbutane, and mixtures thereof.
Suitable cycloaliphatic hydrocarbons include but are not limited to cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane and mixtures thereof.
Mixtures of any of the above solvents may also be used.
In the ink compositions of the present invention, the total amount of solvent is between about from 15% to 50% by weight of the total ink composition.
Preferably the organic solvents are aromatic hydrocarbon free solvents. However, a person skilled in the art pertaining to the present invention may also use certain quantity of aromatic, ketonic solvents or a combination thereof. If used, suitable aromatic hydrocarbons include but are not limited to toluene.
Colourants
The ink composition of the present invention includes a colourant.

The solid content of the colourant in the ink composition of the present invention is present in the range of about 6% to 30% by weight of the total weight of the ink composition.
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 ink composition 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. The additives are present in an amount of from about 3% to 7% by weight of the total ink composition
These additives may function as levelling agents, wetting agents, fillers, dispersants, metal chelate type adhesion promoters, defrothers (anti-foaming agent), an antistatic agent, a viscosity modifier or other additives may be added to provide a specific function.
The ink composition 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.
[Preparation of Polyol B]
The most preferred three polyol B comprising of a dibasic acid and diol are depicted below as Polyol B (a), Polyol B (b), and Polyol B (c) given in table 1.
Table 1
[Preparation of Polyurethane]
The most preferred polyurethanes comprising of a polyol A and polyol B are depicted below in table 2 as Polyurethane 1, Polyurethane 2, and Polyurethane 3 using the Polyol B (a), Polyol B (b), Polyol B (c) of table 1.
Table 2

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.
Preparation of the Ink composition
The most preferred six embodiments of the invention to prepare the polyurethane based ink composition using aforementioned polyurethanes are given in examples 1 to 3 in table 3 depicted as lnk-1 to lnk-3; and a mixture of more than one polyurethane are given in examples 4 to 6 in table 4 depicted as lnk-4 to lnk-6.
Table 3

Table 4
* Other aforementioned pigments or a mixture of pigments can be used to impart the desired colour to the ink composition.
Example 7. Printed article
A printed article, where a treated substrate having a first surface and a second
surface; and on one of first or second surface, a layer comprising a polyurethane
based printing ink composition of the present invention is coated,
wherein the polyurethane based printing ink composition layer has a thickness of
about 0.1 to 3 GSM thick when dried,
wherein, the treated substrate is a flexible plastic film,
wherein, a polyolefin film is extrusion laminated on top of the ink composition layer.
The polyolefin film that is extrusion laminated is selected from a polypropylene film, a
polyethylene film, a polypropylene copolymer film, a polyethylene copolymer film or a
biaxially oriented polypropylene (BOPP) film.
The flexible plastic film is selected from biaxially oriented polypropylene (BOPP), chemical coated polyethylene terephthalate (CC PET), corona treated polyethylene terephthalate (CT PET) films.

Sample test result
The ink composition evaluation results have been provided in the following Table 5.
Table 5
Rating: 1=Poor; 5=Excellent
Advantages:
The ink compositions of the present invention exhibit excellent printing adhesion to substrate, drying, resolubility, printability, smearing and blocking resistance properties on various substrates including biaxially oriented polypropylene (BOPP), chemical coated polyethylene terephthalate (CC PET), corona treated polyethylene terephthalate (CT PET) films.
Although the present disclosure is described in terms of certain preferred embodiments and examples, other embodiments and examples will be apparent to those of ordinary skill in the art, given the benefit of this disclosure, including embodiments and examples that do not provide all of the benefits and features set forth herein, which are also within the scope of this disclosure. It is to be understood that other embodiments may be utilized, without departing from the true spirit and scope of the present invention being indicated by the following claims.

We claim:
1. A polyurethane based printing ink composition for improved polypropylene (PP)
or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic
printing application comprising:
about 20% to 40% by weight a polyurethane based binder derived from
combination of two different polyols (polyol A and polyol B) reacted with a
diisocyanate in presence of amine chain extenders,
about 5% to 15% by weight of a varnish,
about 15% to 50% by weight of an aromatic hydrocarbon free organic solvent,
about 6% to 30% by weight of at least one colourant,
about 3% to 7% by weight of at least one additive; and
about 3% to 10% by weight of demineralized water.
2. The polyurethane based printing ink composition for improved polypropylene
(PP) or Polyethylene (PE) extrusion lamination for central impression (CI)
flexographic printing application according to claim 1, wherein the varnish
includes about 15 to 25% by weight of a Poly vinyl butyrate (PVB) resin, about 65
to 85% of an aromatic and/ or aliphatic hydrocarbon solvent or a mixture of
aromatic and/ or aliphatic hydrocarbon solvents; and about 5 to 15% by weight of
demineralized water.
3. The polyurethane based printing ink composition for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic printing application according to claim 2, wherein the weight average molecular weight (Mw) of the Poly vinyl butyrate (PVB) resin in the varnish composition is 30,000 to 100,000 daltons, more preferably 35,000 to 75,000 daltons, and most preferably 40,000 to 50,000 daltons.
4. The polyurethane based printing ink composition for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic printing application according to claim 1, wherein the aromatic hydrocarbon free organic solvent is selected from aliphatic hydrocarbons,

cycloaliphatic hydrocarbons, substituted aliphatic or cycloaliphatic hydrocarbons, aliphatic alkyl acetates, aliphatic alcohols, and combinations thereof.
5. The polyurethane based printing ink composition for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic printing application according to claim 1, wherein the aromatic hydrocarbon free organic solvent is selected from ethyl acetate, n-propyl acetate, methoxy propyl acetate, methoxy propyl alcohol, Isopropyl acetate, Isopropanol, cyclohexane, butyl acetate, butanol, ethanol, and combinations thereof.
6. The polyurethane based printing ink composition for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic printing application according to claim 1, wherein the colourant is selected from an organic pigment, an inorganic pigment, a dye and combinations thereof.

7. The polyurethane based printing ink composition for improved polypropylene (PP) or Polyethylene (PE) extrusion lamination for central impression (CI) flexographic printing application 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.
8. A printed article, comprising: a treated substrate having a first surface and a second surface; and on at least one of the first surface or the second surface, a layer comprising a polyurethane based printing ink composition of claim 1 is coated,
wherein the polyurethane based printing ink composition layer has a thickness of
about 0.1 to 3 GSM thick when dried,
wherein, the treated substrate is a flexible plastic film,
wherein, a polyolefin film is extrusion laminated on top of the ink composition
layer.

9. The printed article according to claim 9, wherein the polyolefin film is selected from a polypropylene film, a polyethylene film, a polypropylene copolymer film, a polyethylene copolymer film or an biaxially oriented polypropylene (BOPP) film.
10. The printed article according to claim 9, wherein the flexible plastic film is selected from a biaxially oriented polypropylene (BOPP), a chemical coated polyethylene terephthalate (CC PET), and a corona treated polyethylene terephthalate (CT PET) films.