DESC:FIELD OF INVENTION
The present invention relates to opaque film forming acrylic polymer blend emulsion having blend of two incompatible emulsions with different glass transition temperature and ultra-white paint formulation thereof comprising said opaque film forming acrylic blend emulsion that shows inherent opaque white film forming attributes even when present in combination with regular cost-effective styrene-acrylic emulsion taken at select levels, and optionally even when free of any pigment during emulsion/binder synthesis, which upon drying aids in improvisation of whiteness enabling superior whiteness, brightness, contrast ratio and total solar reflectance of paint formulation comprising the emulsion.
The opacity of said opaque film forming acrylic polymer blend emulsion having said blend of two incompatible emulsions with different glass transition temperatures, could be further improved by involving compatible extender emulsions with anchoring functionality that enhances the hiding efficiency of pigments including TiO2 leading to added superior whiteness, brightness allowing the possibility of reducing TiO2 dosage levels in paint formulations attained thereof to reach to similar levels of whiteness vis-à-vis that achieved of opaque film forming acrylic polymer blend emulsion taken together with regular styrene-acrylic emulsion and pigments including higher levels of TiO2.

BACKGROUND ART
The opaque polymer pigment or filler is a non-film forming in nature. They form powder upon emulsion drying. Available solution for film forming opaque polymer is multistep complex synthesis process. Four-layer core/shell latex particle formation is involved and hence process found to be cumbersome.
In order to develop brightest paint research groups proposed the use of high doses of white pigments and extenders like Titanium dioxide, Zinc sulfide, barium sulfate, calcium carbonate, clay, opacifying agent etc. However, the use of excessive pigment and extender might negatively affect durability of the final paint specifically for exterior applications. An ultra-white solvent-based paint incorporating barium sulfate (BaSO4) particles that is up to 98.1% reflective, developed by engineers at Purdue University talking about a very high concentration of barium sulfate and different particle sizes of barium sulfate in the paint. However, such use of high loading of pigment or extenders require solvent, which comes under VOC or negatively impact film durability. On this reference is drawn to the following prior arts:
WO2013033181/ US20170267857A1 is dedicated to a process of preparing a water-based emulsion includes adding a first monomer feed to a reaction vessel in the presence of a first initiator and water to form an acid-functional polymer; neutralizing the acid-functional polymer to form a particulate polymer; and adding a second monomer feed to the reaction vessel in the presence of a second initiator to form an agglomerated polymer; where the process is a one-pot process. The first monomer feed includes a (meth)acrylate monomer, a (meth)acrylic acid monomer, and a styrenic monomer; the second monomer feed includes a hydrophobic monomer; the water-based emulsion includes the agglomerated polymer; the agglomerated polymer includes the particulate polymer; and the agglomerated polymer having an aggregated drupelet morphology. The agglomerated polymers may be used in high opacity emulsions.

US 4,908,391/ US4,898,894 discloses enhanced hiding power for opacifiers in paints, inks, and other coatings is provided by employing the opacifiers, such as TiO2, ZnO, talc, CaCO3, and the like, adhered to or embedded in the surface of thermoplastic microspheres. The composite opacifier-microsphere material is readily formed with a preselected specific gravity, so that there is little tendency for the material to separate. In addition, the composite behaves in the coating as a opacifier-air interface, having a very high difference in refractive indices, and exceptional hiding power. The high volume to weight ratio of the composite affords very attractive economic advantages, effectively reducing the weight proportion of opacifiers required in the formulations, and other related advantages.
J. Appl. Polym. Sci. 2015, 132, 42541 is directed to hollow latexes with both opaque and self film-forming properties, the four-layer core/shell latex particles—sequentially consisting of a high carboxyl-containing soft core, a transition layer, a rigid supporting layer, and an outermost film-forming layer—are first designed and prepared by emulsion polymerization, and then treated with alkali to fabricate self film-forming hollow latexes. On the basis of the previous research on the three-layer core/shell latex, influences of the composition and thickness of the film-forming layer on the properties and morphologies of the four-layer core/shell and the final hollow latexes are investigated. Results show that under optimized conditions with butyl acrylate/styrene (BA/St) mass ratio of 2/1, divinyl benzene (DVB) content of 1 wt %, and core/film-forming layer mass ratio of 1/6 in the film-forming layer preparation, the final hollow latex particles exhibit best morphology considering both light scattering efficiency and film-forming capability at room temperature.
EP0634463A2 discloses a brighter white opacified paint, which contains a conventional film-forming polymer together with a conventional optical brightener and particles anatase titanium dioxide and/or zinc sulphide as the white opacifier. Unlike the rutile form of titanium dioxide, the anatase form or zinc sulphide enables the optical brightener to function usefully in the presence of the white opacifier especially when the amount of optical brightener present is not more than 10 micromoles/g of the non-volatiles content of the paint. Preferably the particles are encapsulated in polymer or attached to a discontinuous polymer barrier comprising particles of organic polymer in order to space them apart and improve opacity. A small amount of fluorescence is also obtainable from chloride-produced rutile.
EP0229466A2 is directed to opaque binder system containing a core-shell polymer and polymeric binder. The system is prepared and blended in-situ and demonstrates improvement in contrast ratio and scrub properties over corresponding compositions wherein the core-shell polymer is separately produced and subsequently blended with a binder polymer.
ACS Appl. Mater. Interfaces 2021, 13, 21733-21739 demonstrates in this work that remarkable full-daytime sub-ambient cooling performance with both BaSO4 nanoparticle films and BaSO4 nanocomposite paints. BaSO4 has a high electron band gap for low solar absorptance and phonon resonance at 9 µm for high sky window emissivity.
Melber et.al demonstrated, employing the opacifiers, such as TiO2, ZnO, talc, CaCO3, and the like, embedded in the surface of thermoplastic microspheres provide enhanced hiding power. Available solution for white film forming emulsion is multistep complex synthesis process that may involve bulk of organic solvents attracting VOC hurdles or negatively impact film durability.
Hence there is a need in the art to provide for emulsion polymer blend and coating/paint formulations thereof by avoiding core-shell approach that would form opaque films due to inherent opacity of the emulsion polymer blend even when present together with regular styrene-acrylic emulsion optionally free of pigment or filler during polymerization, thereby obliging to VOC requirements of paint formulations also without negatively impacting on film durability. There is also a need in the art for compatible extender emulsions which when present together with said opaque film forming emulsion polymer blend and regular styrene-acrylic emulsion would be capable of providing enhanced opacity by improving the hiding efficiency of TiO2 pigment to thereby allow involvement of lower dosage of TiO2 pigments to reach to same whiteness/opacity levels.
OBJECTS OF THE INVENTION
It is thus the primary object of the present invention to provide for opaque film forming acrylic polymer blend emulsions as stable emulsions and ultra-white coating/paint formulations thereof which blend emulsions would result in opaque film forming binders even when present together with regular styrene-acrylic emulsions to provide for inherent opacity free of the involvement of fillers or opacity imparting pigments.
It is another object of the present invention to provide for said opaque film forming acrylic polymer blend emulsion based paint formulation that would be compatible with extender emulsions to further enhance the hiding efficiency of opacity imparting pigments in said formulation to thereby result in ultra-white coating/paint formulations even when fortified with low levels of fillers, opacity imparting pigments to achieve excellent whiteness, brightness, and high total solar reflectance through the involvement of such opaque film forming emulsion polymers/binders.
It is still another object of the present invention to provide for said polymer blend emulsions and ultra-white coating/paint formulations thereof that would be VOC compliant in involving reduced whitening pigments and extenders and hence reduced organic solvents.
It is another object of the present invention to provide for said polymer blend emulsions and ultra-white coating/paint formulations thereof that would enable durable coating films and in involving incompatible acrylic polymers in the blend emulsions in relation to the Tg ranges would also be stabilized in the emulsion.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided an emulsion polymer blend based binder emulsion formulation and ultra-white paint/coating formulations thereof comprising
(a) emulsion polymers with high glass transition temperature in the range of 80 ?C to 100?C that is functionalized with select functional groups including acid, hydroxyl;
(b) emulsion polymers with very low glass transition temperature in the range of -20?C to - 60?C and functionalized with select functional groups including acid, hydroxyl, amide;
wherein said emulsion polymers (a) and (b) is in the ratio range of from 70:30 to 30:70 providing for stable binder emulsion formulation.
Preferably said emulsion polymer blend based binder emulsion formulation is provided having incompatible glass transition temperature driven agglomerated particles of said emulsion (a) and emulsion (b) and yet harmonized to be stable in said binder emulsion for a period upto 6 months having agglomerated polymer particle size of from about 200 nm-3000 nm, and is whiteness/ opacity imparting when free of whiteness imparting pigments, and, is also whiteness/opacity imparting to conventional styrene-acrylic emulsion while maintaining stability.
More preferably said emulsion polymer blend based binder emulsion formulation is provided wherein said ultra-white paint/coating formulations comprising the binder formulation is rendered ultra-white with whiteness of the paint increasing manifold upon involving reduced low dosage of pigments and extenders of 2-8 wt.% reduced by 20-45% said pigment/ extenders including titanium dioxide, barium sulphate, calcium carbonate, white clay, marble powder, coarse whiting and combinations thereof, also efficiently dispersing in presence of said binder emulsion formulation; and
wherein said ultra-white paint/coating formulations comprises 30-100% of binder emulsion formulation giving the desired whiteness and opacity upon forming films.
Advantageously the emulsion polymer blend based binder formulation is provided that improves hiding, aids whiteness, brightness, contrast ratio and solar refractive index of water based low to high PVC paints even when free of whiteness pigments including TiO2 and with lower doses of TiO2 when present in combination with conventional styrene-acrylic emulsion, and thereby with PVC of 30-70 preferably 35-50%, whiteness of the paint is = 94, brightness is = 95 and total solar reflectance is = 93.
According to a preferred aspect of the present invention there is provided said emulsion polymer blend based binder emulsion formulation wherein said emulsion polymers (a) and (b) are copolymers of monomers including methyl methacrylate, methyl acrylate, butyl acrylate, ethyl hexyl acrylate, hydroxy ethyl methacrylate, methacrylic acid, acrylic acid, styrene, vinyl acetate and mixtures thereof;
said emulsion polymer (a) being a copolymer of monomers including Methyl methacrylate monomer at the levels of about 30 wt.%, butyl acrylate of about 3 wt.%, hydroxyl functional monomer about 1.5 wt.% respectively;
said emulsion polymer (b) being a copolymer of monomers including Methyl methacrylate monomer about 6 wt.%, 2-Ethyl hexyl acrylate monomer of about 21 wt.%, Butyl acrylate monomer about 21 wt. %, hydroxyl functional monomer about 0.5 wt.%; and
optionally, includes 0.1-0.7 wt% crosslinkers.

More preferably said emulsion polymer blend based binder emulsion formulation is provided wherein said binder formulation having binder solid content of about 40 to 55% weight and includes
emulsion polymers (a) in levels of 40 to 60 wt.%;
emulsion polymer (b) in the levels of 30 to 50 wt.%;
optionally, crosslinkers in the levels of 0.5 to 2 wt.%.

According to a preferred aspect of the present invention there is provided said emulsion polymer blend based binder emulsion formulation wherein opacity/whiteness is improved by involving compatible extender emulsions with anchoring functionality including Nano barium sulphate, RB opashine, nano Calcium carbonate, Britex 95, Omya cab that enhances the hiding efficiency of TiO2 pigments.

Preferably said emulsion polymer blend based binder emulsion formulation is provided including surfactants Disodium ethoxylated alcohol [C10-C12] half ester of sulfosuccinic acid and alkyldiphenyloxide disulfonate surfactant rendering stability to the binder emulsion.

According to another aspect of the present invention there is provided a process for preparing the emulsion polymer blend based binder emulsion formulation comprising the steps of
preparing Low Tg emulsion polymer (b);
preparing High Tg emulsion polymer (a) and in-situ blending said (b) with (a) in the ratio range of from 70:30 to 30:70 and obtaining said stable binder emulsion formulation therefrom.

Preferably in said process for preparing the emulsion polymer blend based binder emulsion formulation wherein said step of preparing said high and low Tg emulsion polymers involve the sub-stages of
charging surfactant and de-mineralized water in a reactor as reactor charge that was heated to 80°C;
providing de-mineralized water, surfactant & initiator and mixed separately into which said monomers are added to form a milky-white pre-emulsion that was added in select amounts of 3-7 % to said reactor charge at said 80 ± 2° C as a seed followed by addition of buffer & initiator solution into the reactor charge;
adding remaining pre-emulsion drop wise for ˜240 minutes by maintaining temperature in the range of 80 ± 2° C;
carrying out digestion with addition of chaser catalysts in reactor for next 60 minutes just after the pre-emulsion addition completion, followed by cooling, neutralizing with ammonia, filtering and obtaining said stable binder emulsion formulation therefrom.

BRIEF DESCRIPTION OF FIGURES
Figure 1 (a) & (b): illustrates SEM image & photographic image of white film forming emulsion respectively, when free of TiO2.
DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore, the present invention provides for simple but effective solution to whiteness of a coating formulation by achieving opaque film forming emulsion polymer blend/ binder and ultra-white paint/coating formulations thereof with excellent whiteness, brightness, and high total solar reflectance through involving said opaque film forming opaque emulsion binder together with regular cost-effective styrene-acrylic emulsion at select levels and optionally even when free of opacity imparting pigments.
The opacity of said opaque film forming acrylic polymer blend emulsion having blend of two incompatible emulsions with different glass transition temperatures, could be further improved by involving compatible extender emulsions with anchoring functionality that enhances the hiding efficiency of pigments including TiO2 leading to added superior whiteness, brightness allowing the possibility of reducing TiO2 dosage levels in paint formulations attained thereof to reach to the same level of whiteness vis-à-vis that achieved of opaque film forming acrylic polymer blend emulsion taken together with regular styrene-acrylic emulsion and pigments including higher levels of TiO2.

The emulsion of the present invention comprises in-situ blending of very high glass transition temperature emulsion with very low glass transition temperature emulsion in appropriate proportion, along with appropriate functional groups on either of the two polymer backbones, and optionally with appropriate cross-linkers, to render an opaque film forming emulsion with agglomerated particles that impart whiteness to emulsion film on drying, free of any pigment. This opaque film forming property of binder aids in improvement in whiteness, brightness, and high total solar reflectance of paint system when put in combination with select levels of regular styrene-acrylic emulsion and even when free of opacity imparting pigments.
Approaches like incorporating inorganic materials (titanium dioxide, silicon dioxide, etc.) within the polymer or incorporation of air domains (hollow spheres) within the polymer particle to have different refractive indexes within the coating materials is well documented. Melber et. al demonstrated, employing the opacifiers, such as TiO2, ZnO, talc, CaCO3, and the like, embedded in the surface of thermoplastic microspheres provide enhanced hiding power. Available solution for white film forming emulsion is multistep complex synthesis process.
However, on the other hand the present invention could surprisingly achieve an opaque film forming emulsion even if free of any pigment or filler during polymerization, whose opacity could be further enhanced with involvement of opacifiers taken at much lower dosage levels based on the involvement of compatible extender emulsion having anchoring functionality vis-à-vis the opacity attained based on the inclusion of higher levels of opacifiers minus the extender emulsion.
This present invention significantly utilizes incompatibility of emulsion possessing different glass transition temperature for inherent opacity along with film formation property, yet such opacity causing incompatibility is harmonized to deliver a stable emulsion that remains stable when synergistically combined with select levels of regular styrene-acrylic emulsion.
Thus a simple but effective film forming opaque emulsion polymer and a way to develop the same having whiteness and brightness equivalent to conventional opaque emulsion available in market could be provided by the present invention without losing film integrity of the emulsion on drying.
Intensive studies were conducted and it was found that whiteness of a paint formulation bearing the opaque emulsion polymer of the present invention along with conventional styrene-acrylic or acrylic emulsion taken at select levels/ ratio can be increased multiple fold through incorporation of lower dosage levels of pigment, and compatible extender emulsion in proper ratio having anchoring functionality. It was also found for the first time that whiteness of a paint can be increased multiple fold by involving film forming opaque emulsion with acrylic emulsion having excellent TiO2 dispersing efficiency in a particular ratio even with lower dosage of TiO2.
It was also found for the first time that an opaque emulsion of the present invention can improve hiding, whiteness, brightness, contrast ratio and solar refractive index of a water based low to high PVC paints without and with lower doses of TiO2 and when present in combination with regular styrene-acrylic emulsion.
According to an aspect of the present invention thus there is provided an opaque film forming acrylic polymer blend emulsion and ultra-white paint/coating formulation thereof said blend emulsion comprising conventional acrylic/ styrene- acrylic emulsion and/ or acrylic emulsion in a particular ratio with or without TiO2 to further enhance the hiding efficiency further when taken with suitable pigment and extender emulsion combination to get the superior whiteness, brightness and total solar reflectance suitable for application at ambient to low temperature for interior and exterior surfaces, said opaque film forming emulsion blend as a stable blend was developed through selective in-situ blending of acrylic polymer emulsion of high and low Tg polymers.
According to another preferred aspect an acrylic polymer blend emulsion and coating formulation thereof are provided wherein the high Tg emulsion comprises a methacrylate, acrylate or styrenic monomer with Tg more than 80 ?C and the low Tg emulsion comprises a methacrylate, acrylate or styrenic monomer with Tg is less than 0 ?C.
According to yet another preferred aspect of the present invention there is provided monomers for the polymer blend emulsion selected from the group consisting of: methyl methacrylate, methyl acrylate, butyl acrylate, ethyl hexyl acrylate, hydroxy ethyl methacrylate, methacrylic acid, acrylic acid, styrene, vinyl acetate and mixtures thereof.

Under separate Tabular embodiments below are illustrated the preferred emulsion polymers (a) & (b) by mentioning the wt.% of monomers involved together with their resulting Tg, together with any optional crosslinker involvement.
Table 1: Typical recipe of low Tg acrylic copolymer emulsion having Tg in the range of -20?C to -60 0?C.
Raw Material
PBW
(parts by wt.)
Reactor Charge
Deionized water 21.20
Anionic surfactant (variants including alkyldiphenyloxide disulfonate surfactant, AW-64-5500 DOWFAX 2A1 SOL) 0.2
Non-ionic surfactant (variants including Alcohol ethoxylate ATPOL-5731/70N) 0.1
Buffer 0.2
Potassium persulfate Initiator 0.12
Pre-emulsion (select amounts of 3-7 % as seed)
Deionized water 24
Surfactant 1.02
Methyl methacrylate monomer 6
2-Ethyl hexyl acrylate 20.5
Butyl acrylate monomer 20.5
Hydroxyl functional monomer (variants including Hydroxyethylmethacrylate Monomer) 0.5
Potassium persulfate 0.06
Digestion Catalyst
Oxidizing Agent (Hydrogen Peroxide) 0.04
Reducing Agent (Sodium Formaldehyde Sulphoxlate) 0.04
Deionized water 2
Additives
Defoamer 0.02
Liq. Ammonia 0.5
Deionized water 3

Table 2: Typical recipe of High Tg acrylic copolymer emulsion having Tg in the range of 80?C to 100?C and its process of preparation.

Raw Material PBW (parts by wt.)
Reactor Charge
Deionized water 14.20
Anionic surfactant (variants including: alkyldiphenyloxide disulfonate surfactant, AW-64-5500 DOWFAX 2A1 SOL) 0.2
Non-ionic surfactant (variants including: Alcohol ethoxylate ATPOL-5731/70N) 0.1
Buffer 0.2
Potassium persulfate Initiator 0.12
Pre-emulsion (select amounts of 3-7 % as seed)
Deionized water 14
Surfactant 1.02
Methyl methacrylate monomer 30
Butyl acrylate monomer 3
Hydroxy Functional monomer (variants including Hydroxyethylmethacrylate Monomer) 1.5
Potassium persulfate 0.06
Digestion Catalyst
Oxidizing Agent (Hydrogen Peroxide) 0.04
Reducing Agent (Sodium Formaldehyde Sulphoxlate) 0.04
Deionized water 2
Additives
Defoamer 0.02
Neutralizer (variants including Liq. Ammonia) 0.5
Low Tg Emulsion of Table 1 32
Deionized water 1

Emulsion polymerization
Two types of emulsions were prepared for the present invention using semi-continuous, seeded emulsion polymerization technique via pre-emulsion addition.
(i) Preferably Low Tg emulsion having glass transition temperature in the range of -40 to -45 °C,
(ii) Preferably high Tg emulsion having glass transition temperature in the range of 90 to 94°C.
General process followed for carrying out emulsion polymerization is as per the following and based on the involvement of raw materials under Tables 1 and 2 above. Surfactant and de-mineralized water was charged into a reactor and the assembly was heated to 80°C. In a separate flask, de-mineralized water, surfactant & initiator were mixed properly. Monomers were then added one by one in it & mixed well to form milky-white pre-emulsion. A known percentage of pre-emulsion was added to the reactor at 80 ± 2° C as a seed followed by addition of buffer & initiator solution into the reactor charge. Then remaining pre emulsion was added drop wise for 240 minutes maintaining the temperature in the range of 80 ± 2° C. Digestion was carried out with addition of chaser catalysts in reactor for next 60 minutes just after the pre-emulsion addition completion. After cooling, reaction product was neutralized using ammonia. Then, the reaction product was filtered through nylon cloth and used for further study.
Typical paint recipe
Experimental latexes were then used as main binder or co-binder system in water based high durable exterior paint. The preparation of emulsion paint was carried out using flat bottom metal vessel, equipped with stainless steel stirrer. General paint preparation was carried out by following steps starting from Dissolution and dispersion of thickening agent in water at alkaline condition, then addition of wetting agent, loading and grinding of pigment-extender, completion with addition of coalescing agent, binder-opacifier and biocides. Final paint samples were used for different general analyses and characterization. A typical paint preparation recipe is shown in Table 3 below:

Table 3: Typical recipe of Paint preparation
Raw Material PBW (parts by wt.)
Deionized water 29.26
Defoamer 0.44
Rheology modifier 0.35
Buffer solution 0.2
Dispersing Agent and emulsifier 2.0
Pigment+ extender 33.75
Coalescence agent 2.0
Present Blend Emulsion of said High Tg and low Tg polymers taken specifically in range of 70:30 to 30:70 30
Additives 2.20

Preferably said opaque film forming acrylic polymer blend emulsion is provided wherein said High Tg and low Tg polymers in the blend emulsion range from 70:30 to 30:70 to give the desired stability as tested below.
According to yet another preferred embodiment of the present invention there is provided said opaque film forming acrylic polymer blend emulsion selectively involving agglomerated polymer particle has an average particle size of from about 200 nm to about 3000 nm and in having incompatible glass transition temperature driven agglomerated particles of said emulsion (a) and emulsion (b) are also harmonized to be stable in said binder emulsion for a period upto 6 months when taken in select ratios.

Freeze & Thaw Stability
Latex filled metal containers were kept for freezing at temperature of -5°C for 17 hours. It was then thawed at 30°C for next 7 hours. 4 more cycles were repeated for the same samples. For each cycle, before keeping them for freezing, some physical parameters were checked like consistency, bits formation, phase separation.
Accelerated storage stability
Accelerated stability test was performed according to ASTM-D 1849-80 test method
Mechanical Stability Test
100 g of emulsion sample was taken in metal container and it was fixed to dispermat. The sample was subjected to high speed stirring for 10 minutes. The sample was diluted by adding 100 g of water and sample was filtered through nylon cloth, with respect to emulsion mass taken for study, coagulum collected in nylon cloth is in the range of 0.3-0.8%.
Based on the tests conducted above, the binder emulsion formulation was found to be stable upto 6 months that was consistent and free of any phase separation meeting the stability requirements as above.
Said opaque film forming acrylic polymer blend emulsion comprising binder has a solids content of about 40 to 55% weight
According to another preferred embodiment of the present invention there is provided paint/ coating formulation where 30-100% of the total emulsion is replaced by opaque film forming emulsion of the present invention.
Preferably for further enhancement of whiteness of the present emulsion, reduced total weight % of pigment and extender may range from 20-45, said pigment/ extender including combinations of titanium dioxide, barium sulphate, calcium carbonate, white clay, marble powder, coarse whiting etc.
Preferably said paint formulation comprises a paint having PVC of from 30-70, and wherein the whiteness of the paint is more than 94, brightness is more than 95 and total solar reflectance is more than 93.
It is thus possible for the present advancement to provide for opaque film forming emulsion polymer blend/ binder and ultra-white paint/coating formulations thereof with excellent whiteness, brightness, and high total solar reflectance through involving said significant opaque film forming emulsion binder as achieved together with regular styrene-acrylic emulsion allowing brightly decorating a surface found on both interior and exterior surface of buildings, free of opacity imparting pigments or by involving reduced dosage levels of pigments and extenders having anchoring functionality over what is conventionally involved thereby complying to VOC norms and regulations in requiring reduced levels of organic solvent.
,CLAIMS:We Claim:

1. Emulsion polymer blend based binder emulsion formulation and ultra-white paint/coating formulations thereof comprising
(a) emulsion polymers with high glass transition temperature in the range of 80 ?C to 100?C that is functionalized with select functional groups including acid, hydroxyl;
(b) emulsion polymers with very low glass transition temperature in the range of -20?C to - 60?C and functionalized with select functional groups including acid, hydroxyl, amide;
wherein said emulsion polymers (a) and (b) is in the ratio range of from 70:30 to 30:70 providing for stable binder emulsion formulation.
2. The emulsion polymer blend based binder emulsion formulation as claimed in claim 1 having incompatible glass transition temperature driven agglomerated particles of said emulsion (a) and emulsion (b) and yet harmonized to be stable in said binder emulsion for a period upto 6 months having agglomerated polymer particle size of from about 200 nm-3000 nm, and is whiteness/ opacity imparting when free of whiteness imparting pigments, and, is also whiteness/opacity imparting to conventional styrene-acrylic emulsion while maintaining stability.
3. The emulsion polymer blend based binder emulsion formulation as claimed in claims 1 or 2 wherein said ultra-white paint/coating formulations comprising the binder formulation is rendered ultra-white with whiteness of the paint increasing manifold upon involving reduced low dosage of pigments and extenders of 2-8 wt.% reduced by 20-45% said pigment/ extenders including titanium dioxide, barium sulphate, calcium carbonate, white clay, marble powder, coarse whiting and combinations thereof, also efficiently dispersing in presence of said binder emulsion formulation; and
wherein said ultra-white paint/coating formulations comprises 30-100% of binder emulsion formulation giving the desired whiteness and opacity upon forming films.
4. The emulsion polymer blend based binder formulation as claimed in claims 1-3 improves hiding, aids whiteness, brightness, contrast ratio and solar refractive index of water based low to high PVC paints even when free of whiteness pigments including TiO2 and with lower doses of TiO2 when present in combination with conventional styrene-acrylic emulsion, and thereby with PVC of 30-70 preferably 35-50%, whiteness of the paint is = 94, brightness is = 95 and total solar reflectance is = 93.
5. The emulsion polymer blend based binder emulsion formulation as claimed in claims 1-4 wherein said emulsion polymers (a) and (b) are copolymers of monomers including methyl methacrylate, methyl acrylate, butyl acrylate, ethyl hexyl acrylate, hydroxy ethyl methacrylate, methacrylic acid, acrylic acid, styrene, vinyl acetate and mixtures thereof;
said emulsion polymer (a) being a copolymer of monomers including Methyl methacrylate monomer at the levels of about 30 wt.%, butyl acrylate of about 3 wt.%, hydroxyl functional monomer about 1.5 wt.% respectively;
said emulsion polymer (b) being a copolymer of monomers including Methyl methacrylate monomer about 6 wt.%, 2-Ethyl hexyl acrylate monomer of about 21 wt.%, Butyl acrylate monomer about 21 wt. %, hydroxyl functional monomer about 0.5 wt.%; and
optionally, includes 0.1-0.7 wt% crosslinkers.
6. The emulsion polymer blend based binder emulsion formulation as claimed in claims 1-5 wherein said binder formulation having binder solid content of about 40 to 55% weight includes
emulsion polymers (a) in levels of 40 to 60 wt.%;
emulsion polymer (b) in the levels of 30 to 50 wt.%;
optionally, crosslinkers in the levels of 0.5 to 2 wt.%.

7. The emulsion polymer blend based binder emulsion formulation as claimed in claims 1-6 wherein opacity/whiteness is improved by involving compatible extender emulsions with anchoring functionality including Nano barium sulphate, RB opashine, nano Calcium carbonate, Britex 95, Omya cab that enhances the hiding efficiency of TiO2 pigments.

8. The emulsion polymer blend based binder emulsion formulation as claimed in claims 1-7 including Disodium ethoxylated alcohol [C10-C12] half ester of sulfosuccinic acid and alkyldiphenyloxide disulfonate surfactant rendering stability to the binder emulsion.

9. The process for preparing the emulsion polymer blend based binder emulsion formulation as claimed in claims 1-8 comprising the steps of
preparing Low Tg emulsion polymer (b);
preparing High Tg emulsion polymer (a) and in-situ blending said (b) with (a) in the ratio range of from 70:30 to 30:70 and obtaining said stable binder emulsion formulation therefrom.

10. The process for preparing the emulsion polymer blend based binder emulsion formulation as claimed in claim 9 wherein said step of preparing said high and low Tg emulsion polymers involve the sub-stages of
charging surfactant and de-mineralized water in a reactor as reactor charge that was heated to 80°C;
providing de-mineralized water, surfactant & initiator and mixed separately into which said monomers are added to form a milky-white pre-emulsion that was added in select amounts of 3-7 % to said reactor charge at said 80 ± 2° C as a seed followed by addition of buffer & initiator solution into the reactor charge;
adding remaining pre-emulsion drop wise for ˜240 minutes by maintaining temperature in the range of 80 ± 2° C;
carrying out digestion with addition of chaser catalysts in reactor for next 60 minutes just after the pre-emulsion addition completion, followed by cooling, neutralizing with ammonia, filtering and obtaining said stable binder emulsion formulation therefrom.

Dated this the 5th day of March, 2024 Anjan Sen
(Applicants Agent)
IN/PA-199