DESC:FIELD OF INVENTION
The present invention provides formulations for pigment dispersion based on copolymers in aqueous media suitable as aqueous pigment dispersing agents comprising select copolymer components preferably based on sodium salt or potassium salt of copolymer of maleic anhydride that not only effectively disperses pigment in aqueous emulsion paints and colorant master batches for water-based interior, exterior architectural paints, and highly pigmented colorants but also provides for anti-syneresis attributes.
BACKGROUND ART
High contents of solvents (polymerization processing solids <50%) are conventionally used in prior art pigment dispersing agents. High contents of crosslinkers such as divinyl benzene which is toxic are reported in prior art and crosslinker at >0.05 moles of maleic anhydride. Further, either solid non-hydrolyzed dispersing agents are reported or liquid dispersing agents using specialty monomers such as non-ionic functional acrylates, glycidyl methacrylate or diacetone acrylamide are reported.
US2378629 describes the polymerization of copolymer of diisobutylene and maleic anhydride without crosslinker in high content of aromatic solvent (polymerization processing solids <50%).
The preparation of polymeric salt from copolymer of maleic anhydride and diisobutylene is described in US 2,725,367 where maleic anhydride, diisobutylene and divinylbenzne (0.3 to 5%). The copolymer is then converted to salt form by neutralisation with bases such as sodium hydroxide, potassium hydroxide, ammonium hydroxide etc. This prior process and product are using high contents of crosslinker to attain desired properties.
GB1511652 describes the reaction of diisobutylene and maleic anhydride without the use of any crosslinker. Water-soluble or water dispersible salt of an acidic polymeric compound is described with average molecular weight from 350 to 35000, and are not restricted to lower molecular weight polymers with Mw<10000.
CN105131162A describes polymerization of diisobutylene and maleic anhydride (MAN) using solvent such as Benzene, Toluene, Xylene, Dioxane and ethyl acetate. Solvent to Maleic weight ratio: 1: (0.8 to 1.1).
The third monomer is a cross-linkable acrylic monomer–N- methylol acrylamide, diacetone acrylamide, HEMA, GMA, Penta erythritol acrylate. MAN (maleic anhydride) to third cross linkable monomer molar ratio is 1: 0.05-0.1. High contents of crosslinkers have been used in this prior art.
WO97/15382 describes a mixture of salts of styrene maleic anhydride and an alpha-olefin maleic anhydride copolymer for inorganic pigment dispersion.
WO2018206195 teaches a copolymer which is obtainable by reacting a mixture, comprising: (A) = 30 - =70 wt% of at least one ethylenically unsaturated monomer with a carboxylic function; (B) = 30 - = 70 wt% of at least one non-ionic ethylenically unsaturated monomer; (C) = 1 - = 40 wt% of at least one monomer of formula I, wherein R1 denotes hydrogen or Me, n is a real number in the range of= 10 - = 80, and R2 denotes branched, unsubstituted C10-15alkyl; (D) = 0 - = 1 wt% of at least one crosslinking reagent; (E) = 0 - = 10 wt% of at least one ethylenically unsaturated monomer which is different from (A), (B), and (C); and (F) = 0 - = 1 wt% of at least one chain transfer agent; and wherein wt% is based on the total weight of the mixture, characterized in that the C10-15 alkyl has a mean degree of branching (iso-index) in the range of = 1.5 - = 3.5. A method for manufacturing the copolymer of the invention by copolymerizing in a liquid medium a monomer mixture is also claimed. This prior invention also relates to the use of the copolymer of the invention in aqueous compositions as a thickener for coating formulations for achieving high thickening efficiency at high shear rates and a Newtonian rheology profile of the formulations. The invention also claims an aqueous composition in the form of a coating formulation, which comprises = 0.01 - = 10 wt%, based on the total weight of the aqueous composition, of at least one copolymer of the invention, and = 15 - = 99.9 wt%, based on the total weight of the aqueous composition, of at least one of the components, selected from the group consisting of pigments, fillers, binders, solvents, defoamers, neutralizing agent, wetting agent, pigment dispersing agents, and water. Includes monomer of ethyleneically unsaturated non-ionic monomer as component B with the copolymer made by emulsion polymerization and not solution polymerization. Preferably, the copolymer of this prior art has an average molecular weight of > 10000 g/mol to < 3000000 g/ mol. High molecular weight copolymers and specialty non-ionic monomers with unsaturation have been used in this prior art.
CN102911321 discloses pesticide suspension dispersing agent is a polymer with comb structure, wherein the main chain of the polymer is bonded via C-C bond, and the side chain of the polymer is linked with polyoxyethylene- or polyoxypropylene-containing side chain and ionizable carboxyl group. The preparation method contains dissolving 20-80 wt% of unsaturated macromonomer A with polyoxyethylene or polyoxypropylene long chain, 17-77 wt% of unsaturated carboxylic acid or its derivative B and 3-51 wt% of other comonomer C containing ethylenic bond in water, adding pH regulator to pH=7, adding crosslinking agent (0.1-5 wt% of total monomer) and surfactant (1-40 wt% of total monomer), heating under stirring in N2 atm. to 40-100°, dropping free radical initiator (0.01-3 wt% of total monomer), performing emulsion polymerization, and vacuumizing for removing unreacted monomer and small mol. polymer to obtain pesticide suspension dispersing agent with mol. weight of 5000-500000. The unsaturated macromonomer with polyoxyethylene or polyoxypropylene long chain is selected from one or more of polyoxyethylene methacrylate, polyoxyethylene acrylate, allyl alc. polyoxyethylene ether, or allyl alc. polyoxyethylene oxypropylene ether. The unsaturated carboxylic acid or its derivative is selected from one or more of methacrylic acid, acrylic acid, maleic anhydride or maleic acid. The comonomer containing ethylenic bond is selected from methacrylate, acrylate, vinyl caprolactam, vinyl pyrrolidone, vinyl aromatic compound, vinyl ether, vinyl ester or diisobutylene. The initiator contains persulfate or water-soluble azoamidine initiator. The surfactant contains sodium dodecyl benzenesulfonate, polyoxyethylene ether phosphate, phenolic resin sulfonate, fatty acid polyoxyethylene ether sulfonate, alkylphenyl polyoxyethylene ether, or fatty alcohol polyoxyethylene ether. Specialty non-ionic monomers with unsaturation have been used in this prior art.
JP2009138115 teaches compositions, useful for electronic materials, contain (A) =1 dispersing agents based on amides or esters of olefin-unsaturated dibasic acid copolymers (amidation or esterification ratio on the dibasic acids 10-60 mol%) and (B) non-aromatic organic solvents with solubility parameter 8.5-22 (cal/cm3)1/2. Thus, a slurry composition containing diisobutylene-maleic anhydride copolymer amide with oleylamine (amidation ratio 50 mol%, Mw 12,000), alumina, and propylene glycol Me ether acetate showed B viscosity 118 mPa-s. This prior art thus involves an amide component formed via oleyl amine modification of maleic anhydride.
CN113980527 teaches latex paint comprises 20-24 parts of base material (waterborne acrylic resin), 30-34 parts of filler (10-15 parts of talc, 10-15 parts of kaolin, and 10-15 parts of calcium carbonate), 16-20 parts of auxiliary agent, 2-6 parts of antibacterial and mildew-proof agent (2-methyl-5-chloro-3-isothiazolone and methylisothiazolinone), and 120-150 parts of water; wherein, auxiliary agent is composed of 3-5 parts of neutralizer (sodium hydroxide and ammonia water), 3-5 parts of dispersant (poly(meth)acrylic acid sodium (ammonium) salt or maleic anhydride-diisobutylene copolymer sodium (ammonium) salt), 3-5 parts of film-forming aids (diethylene glycol Bu ether acetate), 3-5 parts of defoamer (polyoxyethylene polyoxypropylene pentaerythritol ether), and 3-5 parts of thickener (alkali-swellable thickener, associative thickener and cellulose).
CN110483672 discloses supramolecular solid dispersant comprising 50-80% of maleic anhydride monomer, methacrylic acid monomer, styrene monomer, 20-50% of butadiene monomer, diisobutylene monomer and polyisobutylene having a number average mol. weight of 400-1200. This prior art involves use of styrene as a monomer in high amounts together with a butadiene monomer to form a solid dispersant and not a hydrolyzed liquid dispersing agent.
JP2018168285 teaches dispersant composition which contains: (a) an amidated product formed from amines or a salt thereof, the amidated product being a copolymer of an olefin and an unsaturated dibasic acid and having a branched alkyl group having 6-10 carbon atoms; and (b) a mixed organic solvent of (b1) an acetate ester and (b2) a lower alcohol.
JP2015052029 teaches prior dispersants that are copolymers made from a-olefin and unsaturated dibasic acid in water and have been neutralized with a mixture of an amine and an alkali metal hydroxide where the slurry contains carbon materials having sp. surface area of 500-2650 m2/g, e.g., carbon black, and water as medium. Thus, polymerizing diisobutylene with maleic anhydride in the presence of Lutonal A 50 (polyvinyl Et ether) and Perbutyl O (perester) and neutralizing the resulting copolymer with a 25% ammonia aqueous solution and a 32% NaOH aqueous solution yielded a dispersant.
DE19743841 is directed to storage-stable paints comprising polymeric binders, water, pigments, fillers, and, as dispersant, a mixture of diisobutylene-maleic anhydride copolymer 0.05-10, polyphosphate 0.01-0.5, and alkali metal or ammonium polyacrylate 0.05-2 weight% (on total dispersion composition). Thus, a composition of water 317, ethylene-vinyl acetate copolymer binder 85, TiO2 50, CaCO3 540, Calgon N 0.5, Lopon 895 1.5, Lopon PO 2.0, and other additives 5-9 parts showed good storage stability (constant viscosity) and wet rub resistance. Limited to known copolymers as dispersing agents.
EP364328 teaches homogeneous aqueous dispersions of rare earth halides (0.1-0.5 µm) for use as lubricating fluids prepared by mixing dispersing agents 0.1-12, antifoaming agents 0-5, and antigelling agents 0-20% in water (to 100%, including the following addition) followed by adding the particulate rare earth halides 5-80% and mixing. The dispersion is milled and degassed. The rare earth halides are trifluorides, especially of Ce, La, Pr, Nd, and/or Sm. The dispersants are (1) a copolymer of an ethylenically unsaturated carboxylic acid and an a-olefin and/or a vinyl compound; (2) a homopolymer or copolymer of an ethylenically unsaturated carboxylic acid, (3) a copolymer of =1 ethylenically unsaturated carboxylic acid and =1 salt of an ethylenically unsaturated sulfonic acid; or (4) a polymer of an (arylalkyl)phenol alkylene oxide, which is optionally esterified with phosphate or sulfate. Dispersing agents of the invention include Na salt of maleic anhydride-diisobutylene copolymer, triethanolamine salt of polyacrylic acid, K salt of polymethacrylic acid, and triethanolamine salt of the phosphate ester of tri(phenyl-1-ethyl)phenol polyoxyethylene. Hence limited to the of a known copolymer as dispersing agents. The molecular weight of the copolymers mentioned in this prior patent are in a higher range of Mw = 10000 to 200000, and hence this prior art is not limited to copolymers which are lower in molecular weight with Mw<10000.
US2725367 discloses that addition of 0.3-5% divinylbenzene to a mixture of maleic anhydride and diisobutylene before copolymerization greatly improves the sizing effect on paper of the resulting product as measured by the ink-penetration time. In a typical preparation, a mixture of diisobutylene 402, maleic anhydride 294, and C6H6 330 g. was stirred and heated to boiling in a CO2 atm.; 6 g. Bz2O2 (Benzoyl peroxide) was then added followed by 4 hrs. reflux, then 2 g. more Bz2O2 and 1 hr. more reflux. Divinylbenzene (9 g. of a 53% solution in ethylstyrene) was added at reflux and heating continued another hr. The mixture was diluted with an equal weight of C6H6, added to 1lt. boiling water, the C6H6 distilled off, and the terpolymer separated by filtration and oven dried at 88° giving a yield of 550 g. NH4, K, and Na salts were prepared by use of aqueous NaOH and NH4OH. The products are also useful for sizing of textiles and leather. The NH4 salts are preferred. Thus, this prior work discusses that high content of divinyl benzene crosslinker to be incorporated in the copolymer of maleic anhydride and diisobutylene.
In spite of the above known dispersant agents both in solution form and solid form there is a need in the art to explore for copolymers and their formulations involving select copolymers in water base preferably suitable for pigment dispersion that would try to provide a balance of desired attributes of pigment dispersibility for aqueous emulsion paints and anti-syneresis, anti-curdling in colorant masterbatches in the presence of specific ratios of copolymer components optionally with low contents of crosslinkers.
OBJECTS OF THE INVENTION
Thus the basic object of the present invention is to provide for formulations intended for pigment dispersion based on copolymers in aqueous base/media suitable as pigment dispersing agents and involving select copolymers in water base preferably suitable for pigment dispersion for water-based interior, exterior architectural paints, and highly pigmented colorants.
Another object of the present invention is to provide a process for preparing formulations for pigment dispersion in water base in the presence of low solvent content (>50% processing solids) and optionally with low contents of crosslinkers.
Yet another object of the present invention is to provide for said process for preparing pigment dispersing agents/ formulations for pigment dispersion by involving solvents which can be easily recovered and recycled.
Another object of the present invention is to provide for said formulations for pigment dispersion in water base which in addition to effectively dispersing pigment in colorant master batches would also provide for anti-syneresis and anti-curdling attributes so that they remain storage stable.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a pigment dispersion formulation in aqueous base comprising
A) copolymer of a higher olefin of boiling point > 90 ?C including copolymer of maleic anhydride with linear or branched olefin compounds with 5 to 17 carbon atoms preferably Diisobutylene (DIB);
B) copolymer of maleic anhydride with vinyl or acrylate co-monomer;
wherein the vinyl or acrylate comonomer residue is between 0.1 to 3 wt.% in overall formulation and the maleic anhydride residue coming from copolymer (B) is also restricted between 0.1 to 3 wt.% of the overall formulation.
Preferably said pigment dispersion formulation is provided wherein said select copolymer components preferably based on sodium salt of copolymer of maleic anhydride not only effectively disperses pigment in aqueous emulsion paints and colorant master batches for water-based interior, exterior architectural paints, and highly pigmented colorants but also provides for anti-syneresis, anti-curdling attributes in colorant masterbatches.
More preferably said pigment dispersion formulation is provided wherein said formulation comprises 40-70 wt. % processing/ polymerization solids and includes recoverable common organic solvent dissolving both copolymers.
According to another preferred aspect of the present invention there is provided a pigment dispersion formulation wherein copolymer component (A) is optionally cross-linked with upto 2 wt.% crosslinkers by weight on polymer solids or less than 0.03 moles of maleic anhydride and are selected from ethylene glycol dimethacrylate (EGDMA), hexanediol diacrylate (HDDA), divinyl benzene (DVB) and other known multifunctional acrylates, methacrylates and vinyl compounds wherein the amount of crosslinker is restricted to balance improvement in anti-syneresis, anti-curdling tuned to pigment dispersibility for aqueous emulsion paints and colorant master batches.
Preferably in said pigment dispersion formulation wherein ratios of ingredients of copolymer component (A) includes reaction product of Diisobutylene/maleic anhydride at molar ratio = 2/1 to 1/1; Crosslinker/maleic anhydride molar ratio = 0.01/1 to 0.03/1 considering polymerization solids to be in the range of 40 to 70 wt.% in solvent, preferably 50 to 70% by weight;
said copolymer component (B) as a reaction product includes ingredients restricted to upto 3 wt.% vinyl or acrylate monomer wherein vinyl monomer includes vinyl aromatic monomer styrene or vinyl aliphatic monomer including aliphatic ester of vinyl alcohol, and wherein acrylate monomer includes aliphatic ester of acrylic acid, methyl methacrylate, methacrylic acid, acrylic acid and favourably inhibits crystalline precipitate formation and precipitate generation in a colorant premix when the colorant premix consists of glycols, surfactants, demineralized water, defoamers and in-can preservatives.
According to another aspect of the present invention there is provided a facile process for manufacturing pigment dispersion formulation comprising
Blending select ratios of copolymer (A) optionally crosslinked, and, copolymer (B) obtained from solvent based free radical polymerization of monomers;
Hydrolysing said copolymers together by a caustic solution and neutralizing with agents to obtain a neutralized formulation soluble in water;
dispersing 20-30 wt.% solid content of said neutralized blend in water adapted for end use and application as pigment dispersing agent in an aqueous emulsion paint or colorant masterbatch compositions.
Yet another facile process for manufacturing pigment dispersion formulation is provided comprising
providing copolymer component (A) by free-radical polymerization in solvent;
providing copolymer component (B) generated in-situ towards the end of polymerization of component (A), wherein maleic anhydride residue occurring in component (B) is obtained either by adding required quantity at the end of polymerization of component (A) or obtained from unreacted maleic anhydride monomer at the end of polymerization of component (A) during free radical polymerization in solvent medium involving thermal initiators including azo initiators and peroxides.
According to another preferred aspect of the process for manufacturing pigment dispersion formulation wherein said providing copolymer components are based on the sub-steps of
(i) Charging solvent xylene, maleic anhydride and DIB in a reactor and heated to 115-117 ?C followed by adding Tertiary butyl perbenzoate (TBPB) catalyst in 5 equal parts after an interval of 1 hour each and observing the exotherm after addition of each dosage of catalyst by maintaining the temperature at 115-117 ?C;
(ii) Neutralizing by allowing temperature to come down upto 90-92°C to start neutralizing the reaction mixture of step (i) by NaOH addition followed by dilution with water with NaOH addition rate maintained to arrest the temperature rise below 94°C and to retain in range of 90 -92°C, followed by holding the reaction at 90 - 92°C for 1hr;
(iii) distilling azeotropically to remove entrapped xylene by initially keeping the temperature at 95-98°C thereafter continuing the distillation process till complete removal of xylene till material becomes clear followed to which polymer solid levels are adjusted by water cooled to 40 ?C, filtered and discharged to obtain therefrom TBPB catalyzed pigment dispersion formulation with clear clarity, solid levels 40-70 wt. %, viscosity 70-100 cps at 25-40 ?C that can be easily pumped by metering pump, with number average mol. wt. of 1500-1800, weight average mol. wt. of 2000-3000, polydispersity of 1.2-1.5, surface tension of 28-35 mN/m.
Preferably in said facile process for manufacturing pigment dispersion formulation wherein post addition of the catalyst, styrene is added to react the residual maleic anhydride in the reaction mixture to obtain therefrom styrene based pigment dispersion formulation.
According to yet another preferred aspect of the facile process for manufacturing pigment dispersion formulation wherein said providing copolymer components are based on the sub-steps of
(i) Charging Maleic anhydride, Butyl Acetate, Azobisisobutyro nitrile (AIBN) and DIB to the reactor at room temperature, followed by nitrogen charging and heating to 95 ?C and starting stirring at 80 ?C as the reaction mass starts to melt and continuing stirring for 1 Hr followed by adding chaser catalyst in an interval of 30 minutes for about 4 times post which stirring was continued for 1 more hour at 95 ?C followed by cooling the reaction mixture to 70 ?C;
(ii) adding water dropwise to said cooled reaction mixture using metering pump and post completion of water addition temperature for heating was set at 95-97 ?C such that when temperature crosses 85 ?C, solvent and water starts to evaporate for collection in a separator with water and solvents collected separately, during which required quantity of water is compensated to adjust the solid levels followed by cooling to 70 ?C;
(iii) neutralizing the reaction mixture of step (ii) by adding a solution of NaOH in water in dropwise manner using metering pump followed by gradual increase of the temperature to 90 ?C and stirring till all the solid parts gets dissolved in water to get a clear solution that is adjusted for solid levels of 40-70 wt. % by addition of water followed by cooling to 40 ?C, filtration and discharge to obtain therefrom AIBN catalyzed styrene and acrylate free pigment dispersion formulation having viscosity levels of 97 cps.
Preferably in said facile process for manufacturing pigment dispersion formulation wherein said providing copolymer components of sub-step (i) includes charging Maleic anhydride, Butyl Acetate, EGDMA (Ethylene glycol dimethacrylate (EGDMA), AIBN and DIB all at once into a reactor for catalyzing with chaser catalyst to obtain therefrom AIBN catalyzed acrylate based styrene free pigment dispersion formulation at said solid levels having viscosity close to 65 cps.
More preferably in said facile process for manufacturing pigment dispersion formulation wherein said providing copolymer components of sub-step (i) includes charging Maleic anhydride, AIBN and DIB to the reactor at room temperature, nitrogen purging, heating to 95 ?C and starting slow stirring when the temperature reaches 80 ?C as the reaction mass starts to melt and maintaining 95 ?C temperature for 1 Hr, followed by chaser catalyst addition in an interval of 30 minutes and after 3rd chaser catalyst addition was added EGDMA to the reactor and post EGDMA addition reaction mixture was run for 30 minutes and charged with chaser catalyst for the 4th time and continuing stirring for 1 more hour at 95 ?C and thereafter cooling to 70 ?C, followed by steps (ii) and (iii) to obtain therefrom AIBN catalyzed styrene free pigment dispersion formulation having viscosity close to 120 cps.
According to yet another preferred aspect of the process for manufacturing pigment dispersion formulation wherein said copolymers are hydrolyzed with caustic solution at temperatures ranging from 30 ?C to 95 ?C and the strength of the caustic solution used for hydrolysis is from 2.5% solution to 50 % solution, preferably 10 to 25% solution.
Preferably in said facile process for manufacturing pigment dispersion formulation said neutralizing agents includes amines, aminoalcohols, ammonia, alkali metal hydroxides (sodium hydroxide, potassium hydroxide) or mixtures thereof.
More preferably in said facile process for manufacturing pigment dispersion formulation whereby low contents of solvents at =50 wt.% processing solids are involved during polymerization whereby a partial neutralization step is done before solvent removal to enable uniform dispersion of the copolymer into water with simultaneous removal and recovery of solvent for reaction taking place even at temperatures of 85 to 90 ?C free of vacuum and temperatures <85 ?C with vacuum in a stripping/separator setup.
Preferably again in said facile process for manufacturing pigment dispersion formulation wherein solvents with boiling point = 100 ?C involved is selected from polar or non-polar aromatic or aliphatic solvent dissolving both the copolymers, with the aromatic solvents being xylene, ethyl benzene or toluene, and the aliphatic solvents being butyl acetate or methoxy propyl acetate, with other solvents for polymerization including esters, ethers, glycol ethers, ketones, alcohols, and hydrocarbons.
According to yet another preferred aspect of the facile process for manufacturing pigment dispersion formulation wherein the hydrolysed formulation has a pH range from 8 to 11, preferably, between 9 to 11 and more preferably between 9.5 to 10.5 for neutralization.

DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore, the present invention provides for pigment dispersing agents/ formulations for pigment dispersion in aqueous media preferably suitable for dispersing pigments comprising components
A) A copolymer of a higher olefin of boiling point >90 ?C including Diisobutylene with maleic anhydride;
B) A copolymer of maleic anhydride with a vinyl or acrylate co-monomer;
wherein the vinyl or acrylate comonomer residue occurring in the overall composition is between 0.1 to 3% and the maleic anhydride residue coming from component (B) is between 0.1 to 3% of the overall composition and the composition includes a common organic solvent that dissolves both the components.
According to an aspect of the invention component A is preferably and optionally crosslinked with low contents of crosslinkers to provide for the improved attributes of anti-syneresis.
Preferred ratios of the ingredients are as follows: Diisobutylene/ maleic anhydride molar ratio = 2/1 to 1/1; Crosslinker/maleic anhydride molar ratio = 0.01/1 to 0.03/1; Polymerization solids = 40 to 70% in solvent, preferably 50 to 70% by weight, as the processing/polymerization solids does not include water and water is only added in the neutralization stage and not during polymerization.
According to an embodiment of the process of manufacture the composition of copolymers is hydrolysed together by a caustic solution to obtain a final neutralized composition soluble in water.
The organic component from the final hydrolysed composition as above is distilled off from the final water-soluble composition at any time in the beginning or during or at the end of the hydrolysis process.
The vinyl monomer can be a vinyl aromatic monomer or an aliphatic ester of vinyl alcohol. The acrylate monomer can be an aliphatic ester of acrylic acid or methacrylic acid.
The vinyl monomer is preferably styrene, and the acrylic monomer is preferably methyl methacrylate. Styrene is the preferred monomer over methyl methacrylate.
The solvents with boiling point = 100 ?C can be a polar or non-polar aromatic or aliphatic solvent that dissolves both the components. The aromatic solvents can be xylene, ethyl benzene or toluene. The aliphatic solvents can be butyl acetate or methoxy propyl acetate. Other solvents for polymerization include esters, ethers, glycol ethers, ketones, alcohols, and hydrocarbons.
Component B can either be mixed with component A or can be generated in-situ towards the end of polymerization of component A.
The maleic anhydride residue occurring in component B can be obtained either by adding required quantity at the end of polymerization of component A or obtained from the unreacted maleic anhydride monomer at the end of polymerization of component A, whereby the polymerization can be done by free radical polymerization in solvent medium using thermal initiators such as azo initiators and peroxides.
The hydrolysis with caustic solution can be done at any temperature ranging from 30 ?C to 95 ?C and the strength of the caustic solution used for hydrolysis can be from 2.5% solution to 50 % solution, preferably 10 to 25% solution.
Additional neutralizing agents can include amines, aminoalcohols, ammonia, alkali metal hydroxides (sodium hydroxide, potassium hydroxide) and their mixtures.
Component A can be preferably cross-linked as per a preferred aspect during polymerization by mixing any known crosslinker selected from ethylene glycol dimethacrylate (EGDMA), hexanediol diacrylate (HDDA), divinyl benzene (DVB) and other known multifunctional acrylates, methacrylates and vinyl compounds wherein the amount of crosslinker in the composition is not more than 2% by weight on solids.
In both components A and B, a methacrylic acid or acrylic acid monomer can be added optionally during polymerization, which may be also partially replacing the maleic anhydride.
Higher olefin compounds (linear or branched) with 5 to 17 carbon atoms can be used. The higher olefin compound is preferably diisobutylene.
The final hydrolysed composition has a pH range from 8 to 11, preferably, between 9 to 11 and more preferably between 9.5 to 10.5. The final dispersing agent has a solid content of 20 to 30 percent by weight in water, having end use and application as pigment dispersing agent in an aqueous emulsion paint or colorant masterbatch composition.
Aqueous emulsion paint comprises water-based binder such as an emulsion or water reducible polymer with pigments, inorganic fillers, and various functional additives. Functional additives include rheological agents, flow-levelling agents, defoamers, coalescing agents, freeze-thaw stabilizers and anti-microbial agents.
EXAMPLES:
Table 1: Formulations for pigment dispersion
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
Raw Material Wt.% Wt.% Wt.% Wt.% Wt.% Wt.%
Butyl acetate 0 0 0 17.48 20.68 17.48
O-Xylene 22.34 23.78 22.07 0 0 0
Diisobutylene (DIB) 12.65 13.66 12.50 11.89 11.14 11.89
Maleic Anhydride 7.12 6.43 7.03 7.26 7.36 7.26
Tertiary butyl perbenzoate (TBPB) 0.15 0.27 0.15 0 0 0
Azobisisobutyro nitrile (AIBN) 0 0 0 0.45 0.45 0.45
Ethylene glycol dimethacrylate (EGDMA) 0 0 0 0 0.13 0.13
Styrene 0.00 0.00 1.22 0 0 0
NaOH (50% aq. solution) 8.90 8.04 8.79 11.72 12.02 11.72
Water for dilution 48.84 47.82 48.24 51.2 48.22 51.07
Total 100.00 100.00 100.00 100 100 100
Polymer Properties Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
pH 10.1 10.18 10.1 10.7 10.64 10.45
Solids 25 25.08 25 25.2 25.6 25.3
Clarity Clear Clear Clear Clear Clear Clear
Viscosity (cps) 73 45 73 97 63 119
Molecular weight Mn 1636 1762 1636 1588 1517 1547
Mw 2232 2532 2232 2329 2201 2027
Polydispersity 1.36 1.44 1.36 1.47 1.45 1.31
Surface Tension (mN/m) 31.2 30 31.2 31.8 33.4 33.44
Opacity, Whiteness Index and Reducing strength in architectural paint (paint with a PVC of 40 using Titanium dioxide and inorganic fillers such as calcium carbonate) Pass Pass Pass Pass Pass Pass
Compatibility in colorant premix (mixture of propylene glycol, water, and non-ionic surfactant) Shows white precipitate Shows white precipitate No precipitate observed Shows white precipitate Shows white precipitate Shows white precipitate
Stability with colorant at 55 ?C after 30 days Syneresis after hot box Syneresis after hot box Pass Syneresis after hot box Pass Pass

The formulations for the copolymer based dispersing agents are given in Table 1. It can be seen from the below examples that processing in varied manner with different catalysts and different monomer components gives varied copolymer based attributes of the formulation. While the opacity, whiteness index in architectural paints are seen to pass the test, some incompatibility issues could be seen with only certain ingredients such as propylene glycol in colorant premix masterbatches. Example 3 shows good compatibility with colorant premix while examples 3, 5 and 6 shows good colorant stability. The rest attributes of the formulations such as anti-syneresis, anti-curdling attributes in colorant master batches, and its effectiveness in an aqueous media for dispersing pigments is shown in the table above when the formulation has polymer solids in aqueous media and when solvents employed during its preparation are finally stripped off.

Example 1, 2 and 3: Use reactor with stirrer, separator, condenser, and temperature controller. Charge xylene, maleic anhydride and DIB in a reactor and heat to 115-117 ?C. Add TBPB catalyst in 5 equal parts after an interval of 1 hour each. Th exotherm is observed after addition of each dosage of catalyst. The temperature is maintained at 115-117 C. Then allow the temperature to come down upto 90 - 92°C and start neutralising the reaction material by given quantity of NaOH and dilution water. Neutralisation temperature should not rise above 94°C. Adjust the addition rate of NaOH solution, that the temperature of reaction mass remains in range of 90 -92°C. After Neutralisation process hold the reaction on 90 - 92°C for 1hr. Start azeotropic distillation to remove the entrapped xylene. Initially keep the temperature at 95 - 98°C. Continue distillation process till complete removal of xylene. Material becomes clear after complete removal of xylene. After completion of removal of xylene, stop the heating and allow the temperature of material to come to room temperature. Adjust the solids by water. Cool the batch to 40 ?C followed by filtration and discharge. In Table 1, examples 1 and 2 are following the above process. For example, 3, after the addition of the catalyst, styrene is added to react the residual maleic anhydride in the reaction mixture.
Example 4: Use reactor with stirrer, separator, condenser, and temperature controller. Charge Maleic anhydride, Butyl Acetate, AIBN and DIB to the reactor at room temperature. After charging is completed, start Nitrogen purging to the reactor. Start heating to 95 ?C. Start stirring at 80 ?C as the reaction mass starts to melt. After attaining 95 ?C, continue stirring for 1 Hr. After 1hr start chaser catalyst addition in an interval of 30 minutes. After completion of the 4-chaser catalyst addition continue stirring for 1 more hour at 95 ?C. After 1-hour cool reaction mixture to 70 ?C. While attaining 70 ?C, add water dropwise using metering pump. After completion of water addition set temperature to 95- 97 ?C. When the temperature crosses 85 ?C, solvent and water starts to evaporate and it will be collected in the separator. Collect water and solvent separately. During this stage, compensate the required quantity of water to adjust the solids. Then cool the batch to 70 ?C. When temperature reaches to 70 ?C, add solution of NaOH in water to the reactor in dropwise manner using metering pump. After completing the addition gradually increase the temperature to 90 ?C. Keep stirring till all the solid parts gets dissolved in water. After getting a clear solution check the solids and adjust it to 25% by water addition. Cool the batch to 40 ?C followed by filtration and discharge.
Example 5: Use reactor with stirrer, separator, condenser, and temperature controller. Charge Maleic anhydride, Butyl Acetate, EGDMA, AIBN and DIB to reactor at room temperature. After charging is completed, Start Nitrogen purging to the reactor. Start heating to 95 ?C. Start slow stirring at 80 ?C as the reaction mass starts to melt. After attaining 95 ?C keep medium stirring for 1 Hr. After 1hr start chaser addition in an interval of 30 minutes. After completion of the 4-chaser catalyst addition continue stirring for 1 more hour at 95 ?C. After 1-hour cool the reaction mixture to 70 ?C. While attaining 70 ?C, add water dropwise using metering pump. After completion of water addition set temperature to 95- 97 ?C. When the temperature crosses 85 ?C solvent and water started to evaporate and it will be collected in the separator. Collect water and solvent separately. Cool the batch to 70 ?C. When temperature reaches to 70 ?C, add solution of NaOH in water to the reactor in dropwise manner using metering pump. After completing the addition gradually increase the temperature to 90 ?C. Keep stirring till all the solid parts get dissolved in water. After getting a clear solution check the solids and adjust it into 25% by water addition. Cool the batch to 40 ?C followed by filtration and discharge.
Example 6: Use reactor with stirrer, separator, condenser, and temperature controller. Charge Maleic anhydride, AIBN and DIB to the reactor at room temperature. After charging is completed, start Nitrogen purging to the reactor. Start heating to 95 ?C. Start slow stirring at 80 ?C as the reaction mass starts to melt. After attaining 95 ?C keep medium stirring for 1 Hr. After 1hr start chaser addition in an interval of 30 minutes. After third chaser add EGDMA to the reactor. After EGDMA addition run the batch for 30 minutes and charge 4th chaser. After completion of the 4th chaser addition continue stirring for 1 more hour at 95 ?C. After 1-hour cool reaction mixture to 70 ?C. While attaining 70 ?C, add water dropwise using metering pump. After completion of water addition set temperature to 95- 97 ?C. When the temperature crosses 85 ?C solvent and water started to evaporate and it will be collected in the separator. Collect water and solvent separately. Then cool the batch to 70 ?C. When temperature reaches to 70 ?C, add solution of NaOH in water to the reactor in dropwise manner using metering pump. After completing the addition gradually increase the temperature to 90 ?C. Keep stirring till all the solid parts get dissolved in water and it will take almost 4 hours. After getting a clear yellow solution check the solids and adjust it into 25% by water addition. Then cool the batch to 50 to 40 ?C and filter it and discharge.
It has been found that some of the crosslinked compounds of the present invention show improved anti-syneresis property, anti-curdling property in the colorant masterbatches.
It is also found that the stage of addition of the crosslinker can also impact the reducing strength of aqueous emulsion paint.
It is yet another finding of the present invention that the absence of component B generates crystalline precipitate in a colorant premix when the colorant premix consists of glycols, surfactants, demineralized water, defoamers and in-can preservatives. However, also more than 3 wt.% vinyl or acrylate monomer residue coming from component B induces precipitate generation.
A copolymer of maleic anhydride and diisobutylene (DIB) using a facile manufacturing process is thus attained where specific ratios of A and B and optionally low contents of crosslinker is preferably involved during polymerization to improve anti-syneresis property. Low contents of solvent are used during polymerization (=50% processing solids) whereby a partial neutralization step is done before solvent removal to enable uniform dispersion of the copolymer into water with simultaneous removal of ester solvent. Complete recovery of the ester type solvent takes place even at temperatures of 85 to 90 ?C (without vacuum) and temperatures <85 ?C (with vacuum) using a stripping/separator setup.
While literature mentions use of high contents of solvents (<50% processing solids) to prepare the maleic anhydride copolymers followed by neutralization and dispersion into water and with the solvent removed by decanting or distilling out high contents of solvent which is either difficult to remove, or highly flammable (e.g. toluene) or carcinogenic (e.g. benzene), in which backdrop the present invention advantageously involves low content of solvent which can be completely recovered, the low content being (>50% processing solids) which can be recovered completely and recycled for use in next batch. Even the cross-linker is used at low dosage levels being less than 0.03 moles of maleic anhydride.
The key advantages are the following:
The dispersing agent contributes to prevent curdling, syneresis and settling phenomena in highly pigmented systems such as colorants;
A light-colored dispersing agent is produced which is homogenous, free of particulate matter and is clear in appearance.
The dispersing agent contributes to provide desired pigment dispersion in interior and exterior water based architectural paints and colorant masterbatches with required viscosity and reducing strength.
Aspects of the present invention include the following:
Polymer composition in water base preferably suitable for pigment dispersion comprising components
A) A copolymer of a higher olefin of boiling point > 90 deg ?C with maleic anhydride;
B) A copolymer of maleic anhydride with a vinyl or acrylate co-monomer;
wherein the vinyl or acrylate comonomer residue occurring in the overall composition is between 0.1 to 3 wt. % and the maleic anhydride residue coming from component (B) is between 0.1 to 3 wt.% of the overall composition and the composition includes a common organic solvent that dissolves both the components.
Said polymer composition preferably as a water-based pigment dispersing agent comprises:
Reaction product of diisobutylene (DIB) and maleic anhydride (MAN) with DIB to MAN ratio (<2:1) preferably with a low dosage of crosslinker (<0.03 moles of MAN) is obtained of a solution polymerization reaction in low content of solvent with processing solids (>50%) that is neutralized with alkali metal hydroxide and water to enable a water base dispersion of the polymer composition having copolymer with average molecular weight of <10000 g/mol.
Said crosslinker consists of multifunctional acrylates such as diacrylates, triacrylates e.g. hexanediol diacrylate and ethylene glycol diacrylate and polyvinyl compounds such as divinyl benzene, allylic crosslinkers such as allyl methacrylate and said solvent includes esters such as butyl acetate and hydrocarbons such as xylene with the processing solids in the range of 50 to 70 wt.%.
It is thus possible for the present invention to provide for said pigment dispersion formulation in aqueous base preferably suitable as aqueous pigment dispersing agents whereby select maleic anhydride-based pigment dispersing copolymers with efficient pigment dispersibility and anti-syneresis and anti-curdling property could be provided.
,CLAIMS:We Claim:
1. Pigment dispersion formulation in aqueous base comprising
A) copolymer of a higher olefin of boiling point > 90 ?C including copolymer of maleic anhydride with linear or branched olefin compounds with 5 to 17 carbon atoms preferably Diisobutylene (DIB);
B) copolymer of maleic anhydride with vinyl or acrylate co-monomer;
wherein the vinyl or acrylate comonomer residue is between 0.1 to 3 wt.% in overall formulation and the maleic anhydride residue coming from copolymer (B) is also restricted between 0.1 to 3 wt.% of the overall formulation.

2. The pigment dispersion formulation as claimed in claim 1 wherein said select copolymer components preferably based on sodium salt of copolymer of maleic anhydride not only effectively disperses pigment in aqueous emulsion paints and colorant master batches for water-based interior, exterior architectural paints, and highly pigmented colorants but also provides for anti-syneresis, anti-curdling attributes in colorant masterbatches.
3. The pigment dispersion formulation as claimed in claims 1 or 2 wherein said formulation comprises 40-70 wt. % processing/ polymerization solids and includes recoverable common organic solvent dissolving both copolymers.
4. The pigment dispersion formulation as claimed in claims 1-3 wherein copolymer component (A) is optionally cross-linked with upto 2 wt.% crosslinkers by weight on polymer solids or less than 0.03 moles of maleic anhydride and are selected from ethylene glycol dimethacrylate (EGDMA), hexanediol diacrylate (HDDA), divinyl benzene (DVB) and other known multifunctional acrylates, methacrylates and vinyl compounds wherein the amount of crosslinker is restricted to balance improvement in anti-syneresis, anti-curdling tuned to pigment dispersibility for aqueous emulsion paints and colorant master batches.
5. The pigment dispersion formulation as claimed in claims 1-4 wherein ratios of ingredients of copolymer component (A) includes reaction product of Diisobutylene/maleic anhydride at molar ratio = 2/1 to 1/1; Crosslinker/maleic anhydride molar ratio = 0.01/1 to 0.03/1 considering polymerization solids to be in the range of 40 to 70 wt.% in solvent, preferably 50 to 70% by weight;
said copolymer component (B) as a reaction product includes ingredients restricted to upto 3 wt.% vinyl or acrylate monomer wherein vinyl monomer includes vinyl aromatic monomer styrene or vinyl aliphatic monomer including aliphatic ester of vinyl alcohol, and wherein acrylate monomer includes aliphatic ester of acrylic acid, methyl methacrylate, methacrylic acid, acrylic acid and favourably inhibits crystalline precipitate formation and precipitate generation in a colorant premix when the colorant premix consists of glycols, surfactants, demineralized water, defoamers and in-can preservatives.
6. A facile process for manufacturing pigment dispersion formulation as claimed in claims 1-5 comprising
Blending select ratios of copolymer (A) optionally crosslinked, and, copolymer (B) obtained from solvent based free radical polymerization of monomers;
Hydrolysing said copolymers together by a caustic solution and neutralizing with agents to obtain a neutralized formulation soluble in water;
dispersing 20-30 wt.% solid content of said neutralized blend in water adapted for end use and application as pigment dispersing agent in an aqueous emulsion paint or colorant masterbatch compositions.
7. A facile process for manufacturing pigment dispersion formulation as claimed in claims 1-5 comprising
providing copolymer component (A) by free-radical polymerization in solvent;
providing copolymer component (B) generated in-situ towards the end of polymerization of component (A), wherein maleic anhydride residue occurring in component (B) is obtained either by adding required quantity at the end of polymerization of component (A) or obtained from unreacted maleic anhydride monomer at the end of polymerization of component (A) during free radical polymerization in solvent medium involving thermal initiators including azo initiators and peroxides.
8. The facile process for manufacturing pigment dispersion formulation as claimed in claims 7 wherein said providing copolymer components are based on the sub-steps of
(i) Charging solvent xylene, maleic anhydride and DIB in a reactor and heated to 115-117 ?C followed by adding Tertiary butyl perbenzoate (TBPB) catalyst in 5 equal parts after an interval of 1 hour each and observing the exotherm after addition of each dosage of catalyst by maintaining the temperature at 115-117 ?C;
(ii) Neutralizing by allowing temperature to come down upto 90-92°C to start neutralizing the reaction mixture of step (i) by NaOH addition followed by dilution with water with NaOH addition rate maintained to arrest the temperature rise below 94°C and to retain in range of 90 -92°C, followed by holding the reaction at 90 - 92°C for 1hr;
(iii) distilling azeotropically to remove entrapped xylene by initially keeping the temperature at 95-98°C thereafter continuing the distillation process till complete removal of xylene till material becomes clear followed to which polymer solid levels are adjusted by water cooled to 40 ?C, filtered and discharged to obtain therefrom TBPB catalyzed pigment dispersion formulation with clear clarity, solid levels 40-70 wt. %, viscosity 70-100 cps at 25-40 ?C that can be easily pumped by metering pump, with number average mol. wt. of 1500-1800, weight average mol. wt. of 2000-3000, polydispersity of 1.2-1.5, surface tension of 28-35 mN/m.
9. The facile process for manufacturing pigment dispersion formulation as claimed in claim 8 wherein post addition of the catalyst, styrene is added to react the residual maleic anhydride in the reaction mixture to obtain therefrom styrene based pigment dispersion formulation.
10. The facile process for manufacturing pigment dispersion formulation as claimed in claims 7 wherein said providing copolymer components are based on the sub-steps of
(i) Charging Maleic anhydride, Butyl Acetate, Azobisisobutyro nitrile (AIBN) and DIB to the reactor at room temperature, followed by nitrogen charging and heating to 95 ?C and starting stirring at 80 ?C as the reaction mass starts to melt and continuing stirring for 1 Hr followed by adding chaser catalyst in an interval of 30 minutes for about 4 times post which stirring was continued for 1 more hour at 95 ?C followed by cooling the reaction mixture to 70 ?C;
(ii) adding water dropwise to said cooled reaction mixture using metering pump and post completion of water addition temperature for heating was set at 95-97 ?C such that when temperature crosses 85 ?C, solvent and water starts to evaporate for collection in a separator with water and solvents collected separately, during which required quantity of water is compensated to adjust the solid levels followed by cooling to 70 ?C;
(iii) neutralizing the reaction mixture of step (ii) by adding a solution of NaOH in water in dropwise manner using metering pump followed by gradual increase of the temperature to 90 ?C and stirring till all the solid parts gets dissolved in water to get a clear solution that is adjusted for solid levels of 40-70 wt. % by addition of water followed by cooling to 40 ?C, filtration and discharge to obtain therefrom AIBN catalyzed styrene and acrylate free pigment dispersion formulation having viscosity levels of 97 cps.
11. The facile process for manufacturing pigment dispersion formulation as claimed in claims 10 wherein said providing copolymer components of sub-step (i) includes charging Maleic anhydride, Butyl Acetate, EGDMA (Ethylene glycol dimethacrylate (EGDMA), AIBN and DIB all at once into a reactor for catalyzing with chaser catalyst to obtain therefrom AIBN catalyzed acrylate based styrene free pigment dispersion formulation at said solid levels having viscosity close to 65 cps.
12. The facile process for manufacturing pigment dispersion formulation as claimed in claims 10 wherein said providing copolymer components of sub-step (i) includes charging Maleic anhydride, AIBN and DIB to the reactor at room temperature, nitrogen purging, heating to 95 ?C and starting slow stirring when the temperature reaches 80 ?C as the reaction mass starts to melt and maintaining 95 ?C temperature for 1 Hr, followed by chaser catalyst addition in an interval of 30 minutes and after 3rd chaser catalyst addition was added EGDMA to the reactor and post EGDMA addition reaction mixture was run for 30 minutes and charged with chaser catalyst for the 4th time and continuing stirring for 1 more hour at 95 ?C and thereafter cooling to 70 ?C, followed by steps (ii) and (iii) to obtain therefrom AIBN catalyzed styrene free pigment dispersion formulation having viscosity close to 120 cps.
13. The facile process for manufacturing pigment dispersion formulation as claimed in claims 6-12 wherein said copolymers are hydrolyzed with caustic solution at temperatures ranging from 30 ?C to 95 ?C and the strength of the caustic solution used for hydrolysis is from 2.5% solution to 50 % solution, preferably 10 to 25% solution.
14. The facile process for manufacturing pigment dispersion formulation as claimed in claims 6-13 wherein said neutralizing agents includes amines, aminoalcohols, ammonia, alkali metal hydroxides (sodium hydroxide, potassium hydroxide) or mixtures thereof.
15. The facile process for manufacturing pigment dispersion formulation as claimed in claims 6-14 whereby low contents of solvents at =50 wt.% processing solids are involved during polymerization whereby a partial neutralization step is done before solvent removal to enable uniform dispersion of the copolymer into water with simultaneous removal and recovery of solvent for reaction taking place even at temperatures of 85 to 90 ?C free of vacuum and temperatures <85 ?C with vacuum in a stripping/separator setup.
16. The facile process for manufacturing pigment dispersion formulation as claimed in claims 6-15 wherein solvents with boiling point = 100 ?C involved is selected from polar or non-polar aromatic or aliphatic solvent dissolving both the copolymers, with the aromatic solvents being xylene, ethyl benzene or toluene, and the aliphatic solvents being butyl acetate or methoxy propyl acetate, with other solvents for polymerization including esters, ethers, glycol ethers, ketones, alcohols, and hydrocarbons.
17. The facile process for manufacturing pigment dispersion formulation as claimed in claims 6-16 wherein the hydrolysed formulation has a pH range from 8 to 11, preferably, between 9 to 11 and more preferably between 9.5 to 10.5 for neutralization.

Dated this the 30th day of November, 2023 Anjan Sen
Of Anjan Sen and Associates
Applicants Agent & Advocate
IN/PA-199