FIELD OF THE INVENTION

The present invention is related to water-borne multi-stage polymer, a method for preparing the same, a water-borne multi-stage polymer emulsion comprises the water-borne multi-stage polymer, and the applications thereof. In particular, the present invention is related to multistage polymer emulsions which are suitable for printing ink applications.

BACKGROUND OF THE INVENTION

Water-borne polymer emulsions find applications in many fields, such as coatings, adhesion, etc. When applied in inks, especially in printing inks for food package, it is desirable that the material could have excellent gloss and blocking resistance. Many technical solutions have been proposed to develop emulsion polymers and/or compositions that could have such properties.

US8420709B2 discloses a coating composition comprising at least one photo-initiator and at least one (meth)acryl-polymer having units that are derived from (meth)acryl-monomers that have at least one double bond and 8 to 40 carbon atoms in the alkyl residue. According to the disclosure, the coating composition exhibits high chemical resistance and increased weathering stability and also a high blocking resistance and rapid tack-free and dust-free status. In addition, the coating composition also leads to coatings having a high gloss. However, a special monomer as well as expensive exposure unit is applied to obtain such coating composition.

FR2819515A1 discloses a latex with a high content of dry extract and a low Tg, which, is obtained by emulsion copolymerization of styrene and 2-ethylhexyl acrylate using, as sole emulsifier, styrene/maleic anhydride copolymer(s) in aqueous solution and in partly or completely neutralized or esterified form. The purpose of the invention is to provide a latex with a dry extract content of at least 40 wt%, a glass transition point (Tg) of not above 50 °C and a Brookfield viscosity of not more than 1000 mPa.s at 23 °C. The invention also mentions that such latex may be useful to be used in paints, inks and varnishes, paper, etc. However, there is no information related to properties, such as gloss and blocking resistance.

Therefore, there is still a need for developing a more suitable emulsion system for the application in printing inks, especially printing inks for food packaging, which requires excellent gloss and blocking resistance properties.

SUMMARY

One objective of the present invention is to provide water-borne multi-stage polymer. Another objective of the present invention is to provide water-borne multi-stage polymer emulsions comprises water-borne multi-stage polymer, which, once applied in a printing ink composition, shows excellent gloss and blocking resistance.

The third objective of the present invention is to provide a method for producing the water-borne multi-stage polymers. The water-borne multi-stage polymers are synthesized with monoethylenically unsaturated monomers under the presence of styrene-maleic anhydride copolymer by multi-stage emulsion polymerization.

The fourth objective of the present invention is to provide an application of the water-borne multi-stage polymer emulsions as printing ink, especially a printing ink for food packaging.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise specified, all terms/terminology/nomenclatures used herein have the same meaning as commonly understood by the skilled person in the art to which this invention belongs to.

Expressions “a”, “an” and “the”, when used to define a term, include both the plural and singular forms of the term.

The term “polymer” or “polymers”, as used herein, includes both homopolymer(s), that is, polymers prepared from a single reactive, monomeric compound; and copolymer(s), that is, polymers prepared by reaction of at least two polymer forming reactive, monomeric compounds.

The term “multi-stage emulsion polymer” means a polymer that includes at least a first-stage polymer formed in a first emulsion polymerization process and at least a second-stage polymer which is subsequently polymerized in a second emulsion polymerization process.

The designation (meth)acrylate and similar designations are used herein as an abbreviated notation for “acrylate and/or methacrylate”.

All percentages and ratios denote weight percentages and weight ratios unless otherwise specified.

The present invention relates to water-borne multi-stage polymer emulsions comprises waterborne multi-stage polymer, which shows excellent gloss and blocking resistance. The waterborne multi-stage polymers are synthesized with monoethylenically unsaturated monomers under the presence of styrene-maleic anhydride copolymer.

In one embodiment, the multi-stage polymers according to the present invention have a Fox Tg in the range of 0 to 80 °C. Within the context of the present application, the term Fox Tg refers to a glass transition temperature (Tg) as calculated according to the following Fox equation as disclosed in T.G. Fox, Bulletin of the American Physical Society, Volume 1 , Issue No. 3, page 123 (1956):

1/Tg = W Tgi + W ₂ /Tg ₂ + ••• + W _n /Tg _n wherein

Wi, W ₂ , ... W _n , are the mass fractions of the monomers 1 , 2, . . . n, respectively, and

Tgi , Tg ₂ , ... Tg _n , are the glass transition temperatures of homopolymers of the monomers 1 , 2, . . . n in degrees Kelvin, respectively.

The Tg values for homopolymers of the majority of monomers are known and are listed in, for example, Ullmann's Ecyclopedia of Industrial Chemistry, Vol. 5, Vol. A21 , page 169, VCH Weinheim, 1992. Other sources of glass transition temperatures of homopolymers include, for example, J. Brandrup, E. H. Immergut, Polymer Handbook, 1st Edition, J. Wiley, New York 1966, 2nd Edition, J. Wiley, New York 1975, and 3rd Edition, J. Wiley, New York 1989.

To avoid any doubt, the Fox Tg is calculated without taking the styrene-maleic anhydride copolymer into consideration.

The water-borne multi-stage polymer emulsions comprise one or more multi-stage polymers in an aqueous medium. There is no specific limitation on the monomers that shall be used for producing the water-borne multi-stage polymers. In one preferred embodiment, the resulted polymers have a Fox Tg in the range of 0 to 80 °C, preferably 5 to 70 °C and most preferably 10 to 50 °C. Meanwhile, it’s preferably that the water-borne multi-stage polymer emulsions are synthesized with at least three stages.

The monomers for the first-stage polymer, second-stage polymer and third-stage polymer may each independently be selected from monomers known to be useful for preparing water-borne polymer in the field of printing ink. Species of such monomers may be the same or different, provided that the resulted polymer can have specific Fox Tg as discussed above.

The monomers for the first-stage polymer, second-stage polymer and third-stage polymer may each independently comprise at least one hydrophobic monoethylenically unsaturated monomer (a).

The at least one hydrophobic monoethylenically unsaturated monomer (a) may be selected from the group consisting of (meth)acrylate monomers, (meth)acrylonitrile monomers, styrene monomers, vinyl alkanoate monomers and monoethylenically unsaturated di-and tricarboxylic ester monomers.

Particularly, the (meth)acrylate monomers may be Ci-Ci9-alkyl (meth)acrylates, for example, but not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2- ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate (i.e. lauryl (meth)acrylate), tetradecyl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate and a mixture thereof.

Particularly, the styrene monomers may be unsubstituted styrene or Ci-Ce-alkyl substituted styrenes, for example, but not limited to, styrene, a-methylstyrene, ortho-, meta- and paramethylstyrene, ortho-, meta- and para-ethylstyrene, o,p-dimethylstyrene, o,p-diethylstyrene, ispropylstyrene, o-methyl-p-isopropylstyrene or any mixtures thereof.

Particularly, the vinyl alkanoate monomers may be vinyl esters of C2-Cn-alkanoic acids, for example, but not limited to, vinyl acetate, vinyl propionate, vinyl butanoate, vinyl valerate, vinyl hexanoate, vinyl versatate or a mixture thereof.

In addition, the monoethylenically unsaturated di-and tricarboxylic ester monomers may be full esters of monoethylenically unsaturated di-and tricarboxylic acids, for example, but not limited to, diethyl maleate, dimethyl fumarate, ethyl methyl itaconate, or any mixture thereof.

In a preferred embodiment according to the present invention, one or more Ci-Ci2-alkyl (meth)acrylates, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate, styrene or a mixture thereof is chosen as the at least one hydrophobic monoethylenically unsaturated monomer (a).

It’s possible that one or more hydrophilic monoethylenically unsaturated monomer (b) may be presented for the synthesis of the water-borne multi-stage polymer.

Such hydrophilic monoethylenically unsaturated monomer (b) may be monoethylenically unsaturated monomers containing at least one functional group selected from the group consisting of carboxyl, carboxylic anhydride, sulfonic acid, phosphoric acid, hydroxyl and amide.

Particularly, the hydrophilic monoethylenically unsaturated monomer (b) includes, but is not limited to, monoethylenically unsaturated carboxylic acids, such as (meth)acrylic acid, itaconic acid, fumaric acid, citraconic acid, sorbic acid, cinnamic acid, glutaconic acid and maleic acid; monoethylenically unsaturated carboxylic anhydride, such as itaconic acid anhydride, fumaric acid anhydride, citraconic acid anhydride, sorbic acid anhydride, cinnamic acid anhydride, glutaconic acid anhydride and maleic acid anhydride; monoethylenically unsaturated amides, especially N-alkylolamides, such as (meth)acrylamide, N-methylol (meth)acrylamide, 2- hydroxyethyl (meth)acrylamide; and hydroxyalkyl esters of monoethylenically unsaturated carboxylic acids, such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate.

In a preferred embodiment according to the present invention, acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide or a mixture thereof is preferred as the at least one hydrophilic monoethylenically unsaturated monomer (b)., In the case that both the at least one hydrophobic monoethylenically unsaturated monomer (a) and the at least one hydrophilic monoethylenically unsaturated monomer (b) are presented, the at least one hydrophobic monoethylenically unsaturated monomer (a) may be in an amount of at least 80 % by weight, preferably at least 85 % by weight, more preferably at least 90% by weight, and mostly preferably at least 95 % by weight; while the at least one hydrophilic monoethylenically unsaturated monomer (b) may be in an amount of at least 0.1% by weight and no more than 20 % by weight, preferably no more than 15 % by weight, more preferably no more than 10 % by weight, and mostly preferably no more than 5 % by weight. The abovementioned weight percentage is based on the total weight of (a) and (b).

The monomers for the water-borne multi-stage polymer may further comprise one or more crosslinking monomers (c). The crosslinking monomers can be chosen from di- or polyisocyanates, polyaziridines, polycarbodiimide, polyoxazolines, glyoxals, triols, epoxy molecules, organic silanes, carbamates, diamines and triamines, hydrazides, carbodiimides and multi- ethylenically unsaturated monomers. In the present invention, suitable crosslinking monomers include, but not limited to, glycidyl (meth)acrylate, N-methylol(meth)acrylamide, (isobutoxymethyl)acrylamide, vinyltrialkoxysilanes such as vinyltrimethoxysilane; alkylvinyldialkoxysilanes such as dimethoxymethylvinylsilane;

(meth)acryloxyalkyltrialkoxysilanes such as (meth)acryloxyethyltrimethoxysilane, (3- acryloxypropyl)trimethoxysilane and (3-methacryloxypropyl)trimethoxysilane, allyl methacrylate, diallyl phthalate, 1,4-butylene glycol dimethacrylate, 1,2-ethylene glycol dimethacrylate, 1,6- hexanediol diacrylate, divinyl benzene or any mixture thereof.

The crosslinker can be added in an amount of no more than 10% by weight, preferably no more than 8% by weight, more preferably no more than 5% by weight, based on the total weight of all monomers used for the synthesis of polymers.

The calculated Fox Tg of a polymer can be managed via varying the weight ratio of hard monomers and soft monomers applied for the synthesis of the polymers. In the present invention, a monomer is regarded as a hard monomer if it can result a homopolymer with a calculated Fox Tg of over 10 °C, otherwise, it will be regarded as a soft monomer.

A soft monomer may include, but not limited to, methyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, nonyl acrylate, ethyl acrylate, decyl methacrylate, isodecyl methacrylate, hexyl (meth)acrylate, cyclohexyl acrylate, dodecyl (meth)acrylate, octyl methacrylate, propyl acrylate, ethylene adipate, diethyl fumarate, 1 ,4-butadiene, 1-pentenylene, di-2-ethylhexyl maleate, di-2-ethylhexyl fumarate and mixtures thereof. In a preferred embodiment, alkyl acylates with 4 to 12 carbon atoms in the alkyl group, such as n-butyl acrylate and 2-ethylhexyl acrylate, are used as the soft monomers.

A hard monomer many include, but not limited to, methyl methacrylate t-butyl acrylate, benzyl methacrylate, ethyl methacrylate, acrylamide, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, citraconic acid, sorbic acid, cinnamic acid, glutaconic acid and maleic acid vinyl alcohol, vinyl acetate, vinyl butyrate, vinyl formate, vinyl valerate, vinyl versitate, styrene, Ci-Ce- alkyl substituted styrenes. In a preferred embodiment, acrylic acid, methacrylic acid, methyl (meth)acrylate, styrene, acrylamide, methacrylamide or a mixture thereof is used as the hard monomers.

In one preferred embodiment, the water-borne multi-stage polymer of the present invention have a Fox Tg in the range of 0 to 80 °C, preferably 5 to 70 °C and most preferably 10 to 50 °C.

In one embodiment, the styrene-maleic anhydride (SMA) copolymer used in the present invention may have a weight average molecular weight of between 500 and 15,000, a styrene I maleic anhydride molar ratio of between 1 :6 and 6:1 and an index of acid between 50 and 500 KOH/g. Preferably, the SMA may have a weight average molecular weight of between 1,000 and 10,000, a styrene I maleic anhydride molar ratio of between 1:3 and 3:1 and an index of acid between 100 and 500 KOH/g. More preferably, the SMA may have a weight average molecular weight of between 1 ,500 and 7,500, a styrene I maleic anhydride molar ratio of between 1:3 and 3:1 and an index of acid between 150 and 500 KOH/g. It is used especially in neutralized form in aqueous solution, the neutralizing agent may be an organic base such as an amine, or ammonia, or a mineral base such as sodium hydroxide, potassium hydroxide, etc.

As examples of aqueous solutions of SMA copolymers that may be used in the present invention, mention may be made of aqueous solutions of styrene-maleic anhydride copolymers in hydrolyzed form, neutralized with a sodium salt or with an ammonium salt. More specifically, many of the commercially available SMAs could be used for the purpose of the present invention. Such commercially available SMAs include, but not limited to, products from Cray Valley, such as SMA® 1000, SMA® 2000, SMA® 3000, SMA® 3840, SMA® 4000, SMA® 1000 HNa, SMA® 2000 HNa, SMA® 3000 HNa, SMA® 1000G, SMA® 2000G, SMA® 3000G, etc; products from Polyscope, such as XI RAN® SL series, XI RAN® SG series.

According to a preferably embodiment of the present invention, the SMA (dry weight) may account for 20 wt% to 80 wt%, preferably 30 wt% to 70 wt% and more preferably 35 wt% to 55 wt%, based on the total dry weight of water-borne multi-stage polymer emulsions.

In a preferred embodiment, the first stage polymer may account for 5 wt% to 40 wt%, the second stage polymer may account for 5 wt% to 40 wt%, and the third stage polymer may account for 25 wt% to 90 wt%, based on the total weight of multi-stage polymer (which does not include the SMA). Preferably, the first stage polymer may account for 10 wt% to 30 wt%, the second stage polymer may account for 10 wt% to 30 wt%, and the third stage polymer may account for 30 wt% to 80 wt%, based on the total weight of multi-stage polymer (which does not include the SMA). More preferably, the first stage polymer may account for 15 wt% to 30 wt%, the second stage polymer may account for 15 wt% to 30 wt%, and the third stage polymer may account for 40 wt% to 70 wt%, based on the total weight of multi-stage polymer (which does not include the SMA). In a preferred embodiment, the first stage polymer is synthesized with Ci-Ci2-alkyl (meth)acrylates and styrene, and the weight ratio of Ci-Ci2-alkyl (meth)acrylates over styrene is over 1 (i.e. , styrene accounts for less than 50 wt%, based on the total weight of Ci-Ci2-alkyl (meth)acrylates and styrene).

In a more preferred embodiment, both the first stage polymer and the second stage polymer are synthesized with Ci-Ci2-alkyl (meth)acrylates and styrene. And the weight ratio of Ci-Ci2-alkyl (meth)acrylates over styrene is over 1 for the first stage polymer and the weight ratio of C1-C12- alkyl (meth)acrylates over styrene is less than 1.2 for the second stage polymer.

In another preferred embodiment, the first stage polymer, the second stage polymer and third stage polymer are synthesized with Ci-Ci2-alkyl (meth)acrylates and styrene. And the content of styrene is increasing (i.e. the weight ratio of styrene is lowest in first stage polymer, higher in second stage polymer and highest in the third stage polymer).

In an even more preferred embodiment, the weight ratio of Ci-Ci2-alkyl (meth)acrylates over styrene is over 1 for the first stage polymer, the weight ratio of Ci-Ci2-alkyl (meth)acrylates over styrene is less than 1.2 for the second stage polymer and styrene is the only monomer used in the preparation third stage polymer.

The water-borne multi-stage polymer emulsion according to the present invention may be prepared by a multi-stage polymerization process including polymerization of the first-stage monomers resulting the first-stage polymer, subsequently polymerization of the second-stage monomers resulting the second stage polymer and finally polymerization of the third-stage monomers resulting the third-stage polymers. Multi-stage polymerization techniques well known in the art may be used for preparing the aqueous multi-stage copolymer dispersion according to the present invention, such as the process disclosed in US2728804A, US20170096575A1 , US20170355802A1 , etc.

The emulsion polymerization may be conducted either as a batch operation or in the form of a feed process (i.e., the monomer mixture is fed into the reactor in a staged or gradient procedure). Feed process is a preferred process. In such a process, the monomer mixture of the first-stage polymerization is supplied to the reactor, usually by way of two or more spatially separate feed streams. After the completion of the feeding, the reaction is further carried out for another 10 to 30 min and, optionally, followed by complete or partial neutralization of the mixture. After the completion of the first-stage polymerization, monomer mixture of the second- stage polymerization is supplied to the reactor in the same manner as described above. Then, it is followed by the addition of the third stage polymerization monomers. Upon the completion of the feeding, the polymerization is kept for another 30 to 90 min. Afterwards, the reaction mixture may be subject to oxidants, neutralizing agents, etc.

In a multi-stage polymerization process, most surfactants known to the skilled person in the art may be used. Surfactant to be used according to the present invention may be a non-reactive surfactant, a reactive surfactant or a combination thereof. Surfactants may be formulated together with the monomers and fed into a reaction reactor. Alternatively, the surfactants may be added into the reaction medium first followed by the feeding of monomers. Surfactants may be used in a suitable amount known to the skilled person in the art, for example, in a total amount of 0.1% to 6% by weight, based on the total weight of the monomers.

Surfactants may be non-reactive anionic and/or nonionic surfactants. Suitable non-reactive anionic surfactants, for example, include, but are not limited to, alkyl, aryl or alkylaryl sulfate salts, sulfonate salts or phosphate salts; alkyl sulfonic acids; sulfosuccinate salts; fatty alcohol ether sulfate salts and fatty acids. Suitable non-reactive nonionic surfactants for example include alcohol or phenol ethoxylates such as polyoxyethylene alkylphenyl ether.

Surfactants may also be polymerizable surfactants, also called reactive surfactants, containing at least one ethylenically unsaturated functional group. Suitable polymerizable surfactants for example include, but are not limited to, allyl polyoxyalkylene ether sulfate salts such as sodium salts of allyl polyoxyethylene alkyl ether sulfate, allyl alkyl succinate sulfonate salts, allyl ether hydroxyl propanesulfonate salts such as sodium salts, polyoxyethylene styrenated phenyl ether sulfate salts such as ammonium salts, for example DKS Hitenol® AR 1025 and DKS Hitenol® AR 2020, polyoxyethylene alkylphenyl ether sulfate ammonium salts, polyoxyethylene allyloxy nonylphenoxypropyl ether, and phosphate acrylates such as SI POM ER® PAM 100, phosphate acrylates such as SI POM ER® PAM 200, etc.

The emulsion polymerization may be carried out in the presence of various common initiating systems, including but not limited to a thermal or redox initiator. The initiator is usually used in an amount of no more than 10% by weight, preferably 0.02 to 5% by weight, more preferably 0.1 to 1.5 wt%, based on the total weight of the two stage monomers.

Thermal initiators, such as peroxides, persulfates and azo compounds, are generally used. Peroxides, which may be used include, but are not limited to, inorganic peroxides, such as hydrogen peroxide, or peroxodisulfates, or organic peroxides, such as tert-butyl, p-menthyl or cumyl hydroperoxide, tert-butyl perpivalate, and dialkyl or diaryl peroxides, such as di-tert-butyl or di-cumyl peroxide. Azo compounds which may be used, include, but not limited to, 2,2 - azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile). Among others, sodium persulfate (SPS), potassium persulfate (KPS), ammonium persulfate (APS), 2,2'-azobis(amidinopropyl) dihydrochloride (AIBA, V-50 TM), and 4,4'-azobis(4-cyanovaleric acid) (ACVA , V501) are preferred as the thermal initiator.

A redox initiator usually comprises an oxidizing agent and a reducing agent. Suitable oxidizing agents include the abovementioned peroxides. Suitable reducing agents may be alkali metal sulfites, such as potassium and/or sodium sulfite, or alkali metal hydrogensulfites, such as potassium and/or sodium hydrogensulfite. Preferable redox initiators include an oxidizing agent selected from the group consisting of t-butylhydroperoxide and hydrogen peroxide, and a reducing agent selected from ascorbic acid, sodium formaldehyde sulfoxylate, sodium acetone bisulfite and sodium metabisulfite (sodium disulfite).

The polymerization may be carried out and maintained at a temperature lower than 100 °C throughout the course of the reaction. Preferably, the polymerization is carried out at a temperature between 60 °C and 95 °C. Depending on various polymerization conditions, the polymerization may be carried out for several hours, for example 2 to 8 hours.

An organic base and/or inorganic base may be added into the polymerization system as a neutralizer during the polymerization or after the completion of such process. Suitable neutralizers include, but are not limited to, inorganic bases such as ammonia, sodium/potassium hydroxide, sodium/potassium carbonate or any combination thereof. Organic bases such as dimethyl amine, diethyl amine, triethyl amine, monoethanolamine, triethanolamine, or a mixture thereof can also be used as the neutralizer. Among others, sodium hydroxide, ammonia, dimethylaminoethanol, 2-amino-2-methyl-1-propanol or any mixture thereof is preferable as the neutralizer useful for the polymerization process. Upon the addition of a neutralizer, pH of the final polymer emulsion shall be in the range of 6.0 to 10.0, preferably in the range of 7.0 to 9.5, more preferably in the range of 7.0 to 9.0.

The aqueous multi-stage copolymer dispersion according to the present invention may have a solid content in the range of 10% to 70% by weight, preferably 20% to 60% by weight, more preferably 30 to 60% by weight, and most preferably 40 to 60 % by weight.

The fourth objective of the present invention is to provide an application of the water-borne multi-stage polymer emulsions as printing ink, especially a printing ink for food packaging. For different ink applications, the component concentrations may be adjusted. For example, a gravure ink or a flexographic ink preferably comprises about 8 to 60 wt.% of the water-borne multi-stage polymer emulsions, about 3 to 30 wt.% of the pigment colorant and about 15 to 60 wt.% solvent or water.

The colorant may be organic or inorganic. The most common 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 organic pigments include diarylide yellow AAOT (for example, Pigment Yellow 14 Cl#21095), diarylide yellow AAOA (for example, Pigment Yellow 12 CI#21090), Phthalocyanine Blue (for example, Pigment Blue 15), lithol red (for example, Pigment Red 52:1 C 5860:1 ), 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 CI#74260), phthalocyanine blue (for example, Pigment Blue 15 CI#74160), naphthoic acid red (for example, Pigment Red 48:2 Cl# 15865:2). 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. The colorant is not limited to the foregoing. Thus, the colorant may be any conventional organic or inorganic pigment such as 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.

The printing inks may also contain the usual ink additives to adjust flow, surface tension, and gloss of a printed ink. Such additives typically are polymeric dispersants, surface active agents, waxes, or a combination thereof. These additives may function as leveling agents, wetting agents, fillers, dispersants, defrothers or deaerators, or additional adjuvants may be added to provide a specific function. The lamination printing inks may contain a polymeric dispersant when the colorant 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 (the medium) to form a "base" which is subsequently blended with the remaining components of the ink composition. 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 or an acrylic resin solution. Thus, the ink of this invention may contain 0 to about 12 parts by weight of the polymeric dispersant. Other useful colorants, solvents and adjuvants can be identified by consulting The Printing Ink Manual.

The printing ink preferably comprises 8 to 60% by weight, preferably 15 to 50 % by weight of the water-borne multi-stage polymer emulsions, 3 to 30% by weight, preferably 6 to 30% by weight of pigments, 15 to 60% by weight, preferably 30 to 60% by weight of water and 0.1 to 5% by weight of additives such as surfactants, antifoam agents, and waxes.

The present invention is further demonstrated and exemplified in the Examples, however, without being limited to the embodiments described in the Examples. EXAMPLES

Description of commercially available materials used in the following Examples: SMA® 1000, styrene-maleic anhydride copolymer (Mn -2,000, molar ratio of styrene: maleic anhydride is about 1:1), from Cray Valley

XI RAN® 1000, styrene-maleic anhydride copolymer (Mn -5,000, molar ratio of styrene: maleic anhydride is about 1:1), from Polyscope llniol D-1200, Polypropylene Glycol, from NOF Corporation (hereinafter “PPG”)

EHA: 2-Ethylhexyl acrylate, from Mitsubishi Chemical Corporation

Styrene: from GODO Corporation

All experiments described hereinafter were performed at a temperature of 20 °C unless otherwise specified.

Example 1 (Inventive):

To a 2.5 L glass reactor equipped with a mechanical stirrer, 7.93 g of PPG, 19.6 g of diethylene glycol monoethyl ether, 235.0 g of SMA® 1000 and 249.0 g of deionized water were added. Then, the mixture was neutralized with 136.7 g of 25% aqueous NH3 and 50.0 g of deionized water and stirred for 60 min at 88 °C. The reaction temperature was kept at 88 °C until it was cooled down. After addition of 2.35 g of ammonium persulphate in 28.0 g of deionized water, a mixture containing 24.7 g of styrene and 45.8 g of EHA were added over 30 min and then stirred for another 10 min. Afterwards, a mixture containing 39.4 g of styrene and 19.4 g of EHA were added over 20 min and stirred for another 10 min. Then, 2.4 g of ammonium persulphate and 25.0 g of deionized water were added and stirred for 5 min. Last, 105.8 g of styrene was added over 40 min and stirred for another 90 min. After polymerization at the same temperature, the mixture was cooled down. This emulsion was used for evaluation without further treatment.

The Fox Tg of the obtained polymer is 29 °C. The obtained aqueous polymer emulsion has a pH of 9 and a solid content of 49 wt.%.

Example 2 (Inventive):

To a 2.5 L glass reactor equipped with a mechanical stirrer, 7.93 g of PPG, 19.6 g of diethylene glycol monoethyl ether, 188.0 g of SMA® 1000 and 275.7 g of deionized water were added. Then, the mixture was neutralized with 109.4 g of 25% aqueous NH3 and 50.0 g of deionized water and stirred for 60 min at 88 °C. The reaction temperature was kept at 88 °C until it was cooled down. After addition of 2.8 g of ammonium persulphate in 28.0 g of deionized water, a mixture containing 19.7 g of styrene and 36.7 g of EHA were added over 30 min and then stirred for another 10 min. Afterwards, a mixture containing 47.2 g of styrene and 23.3 g of EHA were added over 20 min and stirred for another 10 min. Then, 2.5 g of ammonium persulphate and 25.0 g of deionized water were added and stirred for 5 min. Last, 155.1 g of styrene was added over 40 min and stirred for another 90 min. After polymerization at the same temperature, the mixture was cooled down. This emulsion was used for evaluation without further treatment.

The Fox Tg of the obtained polymer is 44 °C. The obtained aqueous polymer emulsion has a pH of 9 and a solid content of 49 wt.%.

Example 3 (Inventive):

To a 2.5 L glass reactor equipped with a mechanical stirrer, 7.93 g of PPG, 19.6 g of diethylene glycol monoethyl ether, 164.5 g of XI RAN® 1000 and 288.9 g of deionized water were added. Then, the mixture was neutralized with 95.7 g of 25% aqueous NH3 and 50.0 g of deionized water and stirred for 60 min at 88 °C. The reaction temperature was kept at 88 °C until it was cooled down. After addition of 3.1 g of ammonium persulphate in 28.0 g of deionized water, a mixture containing 6.4 g of styrene and 85.2 g of EHA were added over 30 min and then stirred for another 10 min. Afterwards, a mixture containing 30.6 g of styrene and 30.6 g of EHA were added over 20 min and stirred for another 10 min. Then, 2.8 g of ammonium persulphate and 25.0 g of deionized water were added and stirred for 5 min. Last, 152.8 g of styrene was added over 40 min and stirred for another 90 min. After polymerization at the same temperature, the mixture was cooled down. This emulsion was used for evaluation without further treatment.

The Fox Tg of the obtained polymer is 10 °C. The obtained aqueous polymer emulsion has a pH of 9 and a solid content of 49 wt.%.

Example 4 (Inventive):

To a 2.5 L glass reactor equipped with a mechanical stirrer, 7.93 g of PPG, 19.6 g of diethylene glycol monoethyl ether, 188.0 g of XI RAN® 1000 and 275.7 g of deionized water were added. Then, the mixture was neutralized with 109.4 g of 25% aqueous NH3 and 50.0 g of deionized water and stirred for 60 min at 88 °C. The reaction temperature was kept at 88 °C until it was cooled down. After addition of 2.8 g of ammonium persulphate in 28.0 g of deionized water, a mixture containing 34.6 g of styrene and 64.2 g of EHA were added over 30 min and then stirred for another 10 min. Afterwards, a mixture containing 47.2 g of styrene and 23.3 g of EHA were added over 20 min and stirred for another 10 min. Then, 2.5 g of ammonium persulphate and 25.0 g of deionized water were added and stirred for 5 min. Last, 112.8 g of styrene was added over 40 min and stirred for another 90 min. After polymerization at the same temperature, the mixture was cooled down. This emulsion was used for evaluation without further treatment.

The Fox Tg of the obtained polymer is 23 °C. The obtained aqueous polymer emulsion has a pH of 9 and a solid content of 49 wt.%. Example 5 (Inventive):

To a 2.5 L glass reactor equipped with a mechanical stirrer, 7.93 g of PPG, 19.6 g of diethylene glycol monoethyl ether, 188.0 g of XI RAN® 1000 and 275.7 g of deionized water were added. Then, the mixture was neutralized with 109.4 g of 25% aqueous NH3 and 50.0 g of deionized water and stirred for 60 min at 88 °C. The reaction temperature was kept at 88 °C until it was cooled down. After addition of 2.8 g of ammonium persulphate in 28.0 g of deionized water, a mixture containing 5.9 g of styrene and 78.7 g of EHA were added over 30 min and then stirred for another 10 min. Afterwards, a mixture containing 28.2 g of styrene and 28.2 g of EHA were added over 20 min and stirred for another 10 min. Then, 2.5 g of ammonium persulphate and 25.0 g of deionized water were added and stirred for 5 min. Last, 141.0 g of styrene was added over 40 min and stirred for another 90 min. After polymerization at the same temperature, the mixture was cooled down. This emulsion was used for evaluation without further treatment.

The Fox Tg of the obtained polymer is 10 °C. The obtained aqueous polymer emulsion has a pH of 9 and a solid content of 49 wt.%.

Example 6 (Comparative):

In a 2.5 L glass reactor equipped with a mechanical stirrer, 135.8 g of XI RAN® 1000 and 506.3 g of deionized water were placed. Then, the mixture was neutralized with 78.2 g of 25% aqueous NH3 and 78.2 g of deionized water, and the mixture was heated at 85 °C. The reaction temperature was kept at 85 °C until it was cooled down. After addition of 7.4 g of ammonium persulphate in 82.3 g of deionized water, a mixture containing 267.6 g of styrene and 144.1 g of EHA were added over 120 min and stirred for 120 min at the same temperature. After polymerization, the mixture was cooled down. This emulsion was used for evaluation without further treatment.

The obtained aqueous polymer emulsion has a pH of 8 and a solid content of 43 wt.%.

Paint Preparation and Test Method

These emulsions prepared from Example 1 to Example 6 were printed on the paper by using bar coater No.6, and dried in the oven at 110 °C for 1 min.

Gloss Measurement a) Prepare drawdowns under the above conditions. b) Dry drawdowns for 24 hours at room temperature. c) Measure the gloss 5 times (at an angle of 60°), note the average gloss.

5 = very high gloss 3 = middle level 1 = very low gloss Blocking resistance Measurement a) Prepare drawdowns under the above conditions. b) Dry drawdowns for 24 hours at room temperature. c) Cut drawdown in 4x5 cm and put them face to face, then store for 24 hours at 50 °C and 80% Relative Humidity condition. A load of 500g/cm ² was applied to the test piece. d) Release the pressure after storage and wait till the test piece is cooled till room temperature. e) Tear the drawdowns off each other and rate the damage as follows:

5 = no damage/ full release

3 = damage/ a lot of blocking 1 = not release

The results of gloss measurement and blocking resistance measurement of Example 1 to

Example 6 are listed in the Table 1 as below: Table 1 Gloss measurement and blocking resistance measurement