Claims:We Claim:

1. Hydroxy functional acrylic copolymer based tint pastes comprising acrylic copolymer having castor oil grafted acrylic backbone and includes vinyl co-monomers together with hydroxyl functional monomers involving a select combination of 8-18 wt.% castor oil and 10-20 wt.% hydroxy functional acrylic monomers, said acrylic copolymer having hydroxyl value in the range of 75-125 (mg KOH/ gm) sourced from said hydroxyl functional monomers is solvent borne.

2. Hydroxy functional acrylic copolymer based tint pastes as claimed in claim 1 wherein said vinyl co-monomers comprises isobutyl methacrylate (IBMA) as at least one vinyl co-monomerin the levels of at least 9 wt.% for incorporation of castor oil at levels of 9-14 wt. % in said acrylic copolymer having said hydroxyl value range sourced from combination of castor oil and hydroxy functional acrylic monomers present in select non-polar: polar solvent thereby favouring desired compatibility as tint pastes with resins including epoxy resins, acrylated alkyds, alkyds and castor oil modified styrene based acrylics, amino resins, polyesters, polyamides and polyisocyanate.

3. Hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1 or 2 wherein said castor oil grafted acrylic backbone is free of select vinyl co-monomer of isobutyl methacrylate (IBMA) and has saidhydroxyl value in the range of 75-125 (mg KOH/gm)being solvent borne is present in select non-polar: polar solvent of Xylene: Butyl acetate::2.5:1 to about 2:1adapted as tint pastes being compatible with moderatevariety of resins.

4. Hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1-3 wherein said castor oil grafted acrylic backbone having said hydroxyl value in the range of 75-125 (mg KOH /gm) preferably has hydroxyl value sourced from castor oil in the range of 25-35 (mg KOH/ gm) and that sourced of hydroxy functional acrylic monomers preferably in the range of 50-90 (mg KOH /gm).

5. Hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1-4 having castor oil grafted acrylic backbone of co-monomers including castor oil at 8-18wt. %, MMA at 12-22 wt. %, BA at 14-30 wt.%, IBMA at 7-20 wt.%, HEMA at 10-20 wt.% and MAA at about 1 wt.%in select non-polar: polar solvent of Xylene: Butyl acetate:: 2.5:1 to about 2:1.

6. Hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1-5 including co-monomers preferably castor oil at 12-14 wt.%, MMA at 14-16 wt. %, BA at 14-16 wt.%, IBMA at 9-11 wt.%, HEMA at 9-14 wt.% and MAA at 1 wt.%, wherein said hydroxyl functional monomers other than castor oil includes one or more hydroxy methyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate.

7. Hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1-6 that are exclusively solvent borne free from hydroxyl containing solvents including water, isopropanol;and free of nitrogen containing basic acrylic as co-monomer and yet compatible with resin including epoxy amine adduct, aliphatic isocyanate, amino resins.

8. Hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1-7 is free of styrene co-monomer and compatible with variety of resin and crosslinker chemistriesresulting in universal tint paste with improved compatibility with variety of resin, resin systems and other coating ingredients including pigments, dispersing agent and solvents used in solvent borne coating compositions.

9. Hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1-8 compatible with binders of different resin chemistries including epoxy, modified epoxy, polyamides / adducts, polyamines / adducts, acrylics, polyisocyanates, polyesters, short oil alkyds and acrylated alkyds, amino resins, silicone modified resins and ketonic resin; being compatible with variety of coating resins, varied organic and inorganic pigments and mixtures thereof, solvents and additives facilitating single binder system for tint pastes thereby meeting the requirement of 1K as well as 2K Paints based on said binder chemistries and across varied pigment types required for creating number of shades.

10. A process for the preparation of hydroxy functional acrylic copolymer based tint pastes as claimed in claims 1-9 comprising the steps of
Providing vinyl co-monomers together with hydroxyl functional monomers involving select combination of 8-18 wt.% castor oil and 10-20 wt.% hydroxy functional acrylic monomers in select solventand polymerizing to obtain said hydroxy functional acrylic copolymer adapted as tint pastes having hydroxyl value in the range of 75-125 (mg KOH/ gm) sourced from said hydroxyl functional monomers.

11. A process for the preparation of hydroxy functional acrylic copolymer based tint pastes as claimed in claim 10
Optionally, involving isobutyl Methacrylate (IBMA) as vinyl co-monomersin the levels of at least 9 wt.% for incorporation of castor oil at levels of 9-14 wt. % in said acrylic copolymer after polymerization and achieving said hydroxyl value range 75-125 (mg KOH /gm) in select non-polar: polar solvent of said hydroxy functional acrylic copolymer as tint pastes favouring desired compatibility with varied resins including epoxy resins, acrylated alkyds, alkyds and castor oil modified styrene based acrylics, amino resins, polyesters, polyamides and polyisocyanate.

12. A process for the preparation of hydroxy functional acrylic copolymer based tint pastes as claimed in claim 10-11 comprising
(i) Providing said castor oil at 8-18wt. % in non-polar: polar solvent preferably in the ratio range of Xylene: Butyl acetate:: 2.5:1 to about 2:1 and heated to a temperature of about 120-140°C that is maintained for about 5 minutes;
(ii) adding a mixture of co-monomers including Methyl methacrylate (MMA) at 12-22 wt. %, Butyl Acrylate (BA) at 14-30 wt.%, optionally Isobutyl Methacrylate (IBMA) at 7-20 wt.%, Hydroxyethyl methacrylate (HEMA) at 10-20 wt.% and Methacrylic acid (MAA) at about 1 wt.% to the mixture of step (i) at uniform rate over a 3-5 hours at the temperature of 135-145°C followed by holding the reaction mixture for about 1 hour;
(iii) adding free radical initiator preferably Tertiary butyl per benzoate to the mixture of step (ii) and allowing the reaction to continue for 1-3 hours to achieve monomer conversion of 99.0% or higher and to obtain said solvent borne hydroxy functional acrylic copolymer therefrom.

13. A process for the preparation of hydroxy functional acrylic copolymer based tint pastes as claimed in claim 10-12
wherein said step (ii) preferably includes co-monomers of castor oil at 12-14 wt.%, Methyl methacrylate (MMA) at 14-16 wt. %, Butyl Acrylate (BA) at 14-16 wt.%, Isobutyl Methacrylate (IBMA) at 9-11 wt.%, Hydroxyethyl methacrylate (HEMA) at 9-14 wt.% and Methacrylic acid (MAA) at 1 wt.% to attain said desired solvent borne hydroxy functional acrylic copolymer therefrom favouring desired compatibility with varied resins including epoxy resins, acrylated alkyds, alkyds and castor oil modified styrene based acrylics, amino resins , polyesters, polyamides and polyisocyanate.

14. A process for the preparation of hydroxy functional acrylic copolymer based tint pastes as claimed in claim 10-13 wherein said hydroxyl functional monomers other than castor oil includes one or more hydroxy methyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate.

Dated this the 20th day of June, 2019 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)
IN/PA-199
, Description:FIELD OF INVENTION

The present invention provides for a universal tinting paste/ system comprising select acrylic copolymer having castor oil grafted acrylic backbone that provides for excellent compatibility across paints with different functionalities and is also compatible with different binder systemsand other coating ingredients including pigments, dispersing agent and solvents employed in solvent borne coating compositions.

BACKGROUND ART

Tinting systems are required for operational efficiency and such that it is universally accepted across paints. It is also required that such tinting systems would be compatible to solvent borne coating systems and variety of cross-linkers.
Reference is drawn to several prior arts as below:

US20090064897A1 & CA2639509 A1 on universal tint bases and coating systems employing such tint bases discloses about combining dual functional polymer and pigments to make tint bases wherein dual functional polymer comprises a plurality of hydroxy functional groups and a plurality of acetoacetyl functional groups. The dual functional polymer comprises a backbone selected from the group consisting of polyester and Poly (meth) acrylates and is not purely an acrylic co-polymer and hence is based on dual functionality having plurality of OH functional and aceto acetyl functional groups.

EP 2754704 A1 teaches about a paste resin A which is a mixture of at least two acrylic copolymer resins (A1 + A2) wherein A1 has at least one basic acrylic comonomer and A2 has at least one acidic acrylic comonomer and a method of use thereof for formulating both waterborne and solvent borne tinted paints with a wide variety of pigments. The acrylic copolymers A1 has isopropanol as major solvent and acrylic copolymer A2 has Isopropanol and water as solvent medium. The two have been mixed at elevated temp and diluted with water in presence of acetic acid.Thus this prior art is about use of mixture of at least two acrylic copolymer resins (A1 + A2) wherein A1 has at least one basic acrylic comonomer and A2 has at least one acidic acrylic comonomer dissolved in water miscible co-solvent i.e. IPA.

PCT application no : FI96000450 discloses about colorants (colorant pastes) used for the tinting of paint products. The colorants contain pigment component comprising of one or more organic and/or inorganic pigments and possibly extender pigments, diluent component comprising of one or more organic solvents other than aliphatic alcohols or aromatic hydrocarbons and binder component consists of a ketone aldehyde, ketone and/or aldehyde resin soluble in aliphatic hydrocarbons and 0-30% of the total weight of the binder consists of other binders commonly used in colorants, for example acrylic, alkyd or polyester resin, and one or more additives suitable for use in colorants. This prior art employs mix of polymers having ketone aldehyde resin as essential component.

WO 2014/107445 A1 teaches that pigments can be added to silicone resin obtained from a Functional silicone resin intermediate which are end capped with an alcohol to form a tint paste that has high solid content and preferably 100 % solid and thus is substantially free of solvents. This universal tint paste can be used in a wide variety of solvent borne and high solid coatings and also discloses the use of silicone functional resin end capped with alcohol and thus has a different polymer backbone.

EP 2110410 A1 discloses about a paste resin AB which is a mixture of a water soluble alkyd resin B and a basic acrylic copolymer resin A comprising of atleast one amino group containing vinyl type monomer. Hence this prior art is based on mixture of water soluble alkyd and basic acrylic resin containing amino group.

WO2017/029290 A1 discloses about aqueous, low VOC/SVOC universal pigment preparations comprising a pigment component, water soluble, non ionic surface active additive comprising a copolymer formed from a vinyl monomer and an ethylenically unsaturated monomer selected from the group consisting of mocarboxylic ester, dicarboxylic esters, monocarboxamides and dicarboxamides, the vinyl monomer and /or ethlenically unsaturated monomer containing an -N group with pigment affinity, a phosphoric, a phosphoric ester and optionally customary additives. The aqueous pigment preparation are suitable for the coloring of inks, paints for metering at point of sale or in plant tinting systems. This prior art is based on monocarboxamides and dicarboxamides modified water borne acrylic copolymers essentially having pigment affinic -N group .

WO2017208252 teaches high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resins are provided having hydroxyl functionality sourced solely or partially through renewable and modified castor oil wherein the copolymers had upto 100% solids and high hydroxyl values ranging from 80-200 (mg KOH /gm). Said high solid acrylic polyols involving modified castor oil as monomers and essentially styrene as a monomer, favored complete or partial replacement of soft monomers like Bu acrylate, 2-Et hexyl acrylate, lauryl acrylate and the like in said high solid acrylic polyol synthesis. The renewable content of these resins can be as high as 70% on resin solids thereby providing economical and sustainable polymer for high performance coatings. The synthesized high solid acrylic polyols find application in high solid and high build coatings having low Volatile Org. Component (VOC) content for decorative and industrial use. Said high solid acrylic polyols have been synthesized by co-reacting acid anhydride modified castor oil as sole/major hydroxyl functional monomer with variety of acrylic monomers, styrene or its derivatives and optionally hydroxyalkyl acrylates/ methacrylates and ethylenic monomer through free radical polymerization in presence of initiator(s).

CN103421156 teaches UV-curing resin is prepared by (1) polymerizing polyhydric alcohol selected from one or two of propylene glycol, neopentyl glycol, glycerol, 2-butyl-2-ethyl-1,3-propanediol, trimethylolpropane, pentaerythritol and di(trimethylolpropane), polybasic acid selected from one or more of phthalic acid, isophthalic acid, terephthalic acid and adipic acid, and fatty acid selected from one or two of eleostearic acid, oleic acid, linoleic acid, soya oil acid, linolenic acid, ricinoleic acid and dehydrated castor oil acid in toluene at 160-240°C till the acid value is <15 mg-KOH/g, cooling to 40°C to obtain alkyd resin, (2) reacting ester compd. (hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate or hydroxypropyl methacrylate) with isophorone diisocyanate in the presence of polymn. inhibitor and catalyst at 60-100°C till the hydroxyl group content is <0.3 wt%, and cooling to 40°C to obtain urethane acrylate, and (3) reacting the alkyd resin with the urethane acrylate at 60-100°C for 2-3h. Hence first preparing alkyd resin (Oil modified polyester) and urethane acrylate followed by reacting the two enabled UV curable Resin composition of this prior art.

CN101481451 teaches isocyanato terminated urethane prepolymer, neutralizing and emulsifying to give a water-thinned polyurethane emulsion, and emulsion polymerizing to form a latent-curable poly(urethane acrylate) hybrid emulsion and is not based any acrylic copolymer synthesis.

WO 2009127668 is based on a paste resin comprising mixture of watersoluble alkyd and basic acrylic resin containing amino group and is not pure Hydroxy functional Acrylic Copolymer.

WO 2014108450 teaches prior paste resin A which is a mixture of at least two acrylic copolymer resins A, wherein the acrylic copolymer resin A1 comprises at least one basic acrylic comonomer, and the acrylic copolymer resin A2 comprises at least one acidic acrylic comonomer. The acrylic copolymers A1 has isopropanol as major solvent and acrylic copolymer A2 has Isopropanol and water as solvent medium. The two have been mixed at elevated temperature and diluted with water in presence of acetic acid.

In the backdrop of the above state of the art there can be said to be noexistence of acrylic copolymer grafted with renewable hydroxy functional monomer for use in tinting systems that provides compatibility across the solvent borne resin chemistries /their crosslinkers and compatible with range of organic/ inorganic pigments, solvents, dispersing agents and other additives employable in variety of coating systems, and hence there is a need in the art, to provide for acrylic copolymers based tinting systems with excellent wetting and dispersing characteristics for use in tint pastes that would be compatible not only with resins but also with the solvents used in the resin and paint making process and would also show good wetting and dispersing characteristics with organic pigments, inorganic pigments and extenders.

OBJECTS OF THE INVENTION

It is thus the primary object of the present invention to provide for a universal tinting system/paste based on select acrylic copolymer having castor oil grafted acrylic backbone that would show excellent compatibility across paints with different functionalities and would also be compatible with different binder systems.

It is another object of the present invention to provide for said common tinting system based on select acrylic copolymer that would avoid the use of tinting systems having binder of similar chemical construction as that used in base paint, and hence would eliminate the need of using multiple tinting system based on different binder/ binder chemistries.
It is yet another object of the present invention to provide for said common tinting system that would on one hand include high levels of castor oil and at the same time would achieve compatibility not only with resins but also with the solvents used in the resin and paint making process.

It is still another object of the present invention to provide for said select acrylic copolymer based common tinting system that would have good wetting and dispersing characteristics with organic Pigments, inorganic pigments and extenders attributableto their hydroxyl functionality flowing fromrenewable castor oil and hydroxy methyl acrylate with optimized combination of acrylic monomers taken in select ratios.

It is another object of the present invention to provide for tint paste compatible with variety of paints including variety of resin/ crosslinker chemistries including polyisocyanates, minus hydroxyl containing solvents like water, isopropanol as well as nitrogen containing basic acrylic comonomer which are considered to beforbidden in the interest of overall paint performance.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided hydroxy functional acrylic copolymer based tint pastes comprising acrylic copolymer having castor oil grafted acrylic backbone and includes vinyl co-monomers together with hydroxyl functional monomers involving a select combination of 8-18 wt.% castor oil and 10-20 wt.% hydroxy functional acrylic monomers, said acrylic copolymer having hydroxyl value in the range of 75-125 (mg KOH/ gm) sourced from said hydroxyl functional monomers is solvent borne.

Generally a single resin does not have compatibility with binder/binder system of different chemical construction restricting its use in being incompatible with variety of paints of different chemical nature/ functional end use. Surprisingly, the developed resin based tint pastes of the present invention eliminates the need of multiple tinting systems to be used for paints based on different binder chemistries. It has provided substantial advantage in respect of operational efficiency over existing tinting system in view of its universal acceptability across paints. Other benefits include reduced raw material cost and reduced dependency on petroleum based monomer due to incorporation of castor oil as hydroxy functional monomer, that could be incorporated in higher wt. % range.

No background knowledge exists that a single acrylic copolymer advantageously having castor oil co-monomer favours tinting systems/pastes which can be used for 1 K as well as 2K solvent borne coating systems which coating systems comprises of variety of crosslinkers right from metallic driers in 1K systems to ambient curing polyisocyanates for 2K Polyurethanes, polyamines/polyamides /adduct for 2 K epoxy systems and amino resins in 1 K stoving finishes.
The paints made from the acrylic copolymers based tint pastes of the present invention showed satisfactory performance and compatibility with varied resin systems vis-à-vis the tinting systems having binder of similar chemical construction as that employed in base paint. The present invention thus eliminated the need of using multiple tinting system based on different binder / binder chemistries.

Thus the acrylic copolymer based tint pastes of the present invention having high content of castor oil based hydroxy functional monomer together with other hydroxyl functional acrylate monomers involves striking a balance between said castor oil and hydroxyl functional acrylate monomers in combination with vinyl monomers including IBMA and certain other acrylic monomers, their ratios exclusively in solvent borne medium preferably including select solvents, becomes surprisingly compatible with satisfactory performance with variety of resins.

The acrylic copolymer preferably the hydroxy functional acrylic copolymer based tint paste of the present invention involving acrylic co-monomers especially the incorporation of isobutyl methacrylate together with castor oil when taken in selective levels provides enough/balance of hydroxylic and carboxylic functionality into the resin backbone such as to impart excellent compatibility with varied resins, even in the absence of styrene.

Solvent system of acrylic copolymer of the present invention is crucial to the extent that binder/ binder system of the respective paints with whom compatibility is checked requires to also be soluble in the solvents employed in the acrylic copolymer of the present invention to finally provide compatibility with broad range of polymer chemistries/ binders.

According to a preferred aspect of the present invention there is provided said hydroxy functional acrylic copolymer based tint pastes wherein said vinyl co-monomers comprises isobutyl methacrylate (IBMA) as at least one vinyl co-monomerin the levels of at least 9 wt.% for incorporation of castor oil at levels of 9-14 wt. % in said acrylic copolymer having said hydroxyl value range sourced from combination of castor oil and hydroxy functional acrylic monomers present in select non-polar: polar solvent thereby favouring desired compatibility as tint pastes with resins including epoxy resins, acrylated alkyds, alkyds and castor oil modified styrene based acrylics, amino resins, polyesters, polyamides and polyisocyanate.

Accordingly with regard to another preferred aspect said hydroxy functional acrylic copolymer based tint pastes is provided wherein said castor oil grafted acrylic backbone is free of select vinyl co-monomer of isobutyl methacrylate (IBMA) and has saidhydroxyl value in the range of 75-125 (mg KOH/gm)being solvent borne is present in select non-polar: polar solvent of Xylene: Butyl acetate::2.5:1 to about 2:1adapted as tint pastes being compatible with moderatevariety of resins.

Preferably said hydroxy functional acrylic copolymer based tint pastes is provided wherein said castor oil grafted acrylic backbone having said hydroxyl value in the range of 75-125 (mg KOH /gm) preferably has hydroxyl value sourced from castor oil in the range of 25-35 (mg KOH/ gm) and that sourced of hydroxy functional acrylic monomers preferably in the range of 50-90 (mg KOH /gm).

Accordingly with regard to yet another preferred aspect said hydroxy functional acrylic copolymer based tint pastes is provided having castor oil grafted acrylic backbone of co-monomers including castor oil at 8-18wt. %, MMA at 12-22 wt. %, BA at 14-30 wt.%, IBMA at 7-20 wt.%, HEMA at 10-20 wt.% and MAA at about 1 wt.%in select non-polar: polar solvent of Xylene: Butyl acetate:: 2.5:1 to about 2:1.

Preferably said hydroxy functional acrylic copolymer based tint pastes is provided including co-monomers preferably castor oil at 12-14 wt.%, MMA at 14-16 wt. %, BA at 14-16 wt.%, IBMA at 9-11 wt.%, HEMA at 9-14 wt.% and MAA at 1 wt.%, wherein said hydroxyl functional monomers other than castor oil includes one or more hydroxy methyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate.

More preferably, said hydroxy functional acrylic copolymer based tint pastes is provided that are exclusively solvent borne free from hydroxyl containing solvents including water, isopropanol;and free of nitrogen containing basic acrylic as co-monomer and yet compatible with resin including epoxy amine adduct, aliphatic isocyanate, amino resins.

According to a preferred aspect of the present invention there is provided said hydroxy functional acrylic copolymer based tint pastes that is free of styrene co-monomer and compatible with variety of resin and crosslinker chemistriesresulting in universal tint paste with improved compatibility with variety of resin, resin systems and other coating ingredients including pigments, dispersing agent and solvents used in solvent borne coating compositions.

Preferably said hydroxy functional acrylic copolymer based tint pastes is provided that is compatible with binders of different resin chemistries including epoxy, modified epoxy, polyamides / adducts, polyamines / adducts, acrylics, polyisocyanates, polyesters, short oil alkyds and acrylated alkyds, amino resins, silicone modified resins and ketonic resin; being compatible with variety of coating resins, varied organic and inorganic pigments and mixtures thereof, solvents and additives facilitating single binder system for tint pastes thereby meeting the requirement of 1K as well as 2K Paints based on said binder chemistries and across varied pigment types required for creating number of shades.

According to another aspect of the present invention there is provided a process for the manufacture/ preparation of hydroxy functional acrylic copolymer based tint pastes is provided comprising the steps of
Providing vinyl co-monomers together with hydroxyl functional monomers involving select combination of 8-18 wt.% castor oil and 10-20 wt.% hydroxy functional acrylic monomers in select solventand polymerizing to obtain said hydroxy functional acrylic copolymer adapted as tint pastes having hydroxyl value in the range of 75-125 (mg KOH/ gm) sourced from said hydroxyl functional monomers.

Preferably in said process for the preparation of hydroxy functional acrylic copolymer based tint pastes there is optionally, involving isobutyl Methacrylate (IBMA) as vinyl co-monomers in the levels of at least 9 wt.% for incorporation of castor oil at levels of 9-14 wt. % in said acrylic copolymer after polymerization and achieving said hydroxyl value range 75-125 (mg KOH /gm) in select non-polar: polar solvent of said hydroxy functional acrylic copolymer as tint pastes favouring desired compatibility with varied resins including epoxy resins, acrylated alkyds, alkyds and castor oil modified styrene based acrylics, amino resins, polyesters, polyamides and polyisocyanate.

More preferably, said process for the preparation of hydroxy functional acrylic copolymer based tint pastes comprises
(i) Providing said castor oil at 8-18wt. % in non-polar: polar solvent preferably in the ratio range of Xylene: Butyl acetate:: 2.5:1 to about 2:1 and heated to a temperature of about 120-140°C that is maintained for about 5 minutes;
(ii) adding a mixture of co-monomers including Methyl methacrylate (MMA) at 12-22 wt. %, Butyl Acrylate (BA) at 14-30 wt.%, optionally Isobutyl Methacrylate (IBMA) at 7-20 wt.%, Hydroxyethyl methacrylate (HEMA) at 10-20 wt.% and Methacrylic acid (MAA) at about 1 wt.% to the mixture of step (i) at uniform rate over a 3-5 hours at the temperature of 135-145°C followed by holding the reaction mixture for about 1 hour;
(iii) adding free radical initiator preferably Tertiary butyl per benzoate to the mixture of step (ii) and allowing the reaction to continue for 1-3 hours to achieve monomer conversion of 99.0% or higher and to obtain said solvent borne hydroxy functional acrylic copolymer therefrom.

According to yet another preferred aspect of the process for the preparation of hydroxy functional acrylic copolymer based tint pastes
said step (ii) preferably includes co-monomers of castor oil at 12-14 wt.%, Methyl methacrylate (MMA) at 14-16 wt. %, Butyl Acrylate (BA) at 14-16 wt.%, Isobutyl Methacrylate (IBMA) at 9-11 wt.%, Hydroxyethyl methacrylate (HEMA) at 9-14 wt.% and Methacrylic acid (MAA) at 1 wt.% to attain said desired solvent borne hydroxy functional acrylic copolymer therefrom favouring desired compatibility with varied resins including epoxy resins, acrylated alkyds, alkyds and castor oil modified styrene based acrylics, amino resins , polyesters, polyamides and polyisocyanate.

Preferably in said process for the preparation of hydroxy functional acrylic copolymer based tint pastes as provided said hydroxyl functional monomers other than castor oil includes one or more hydroxy methyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate.

DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore, the present invention provides for acrylic copolymer based tint paste comprising hydroxy functional acrylic copolymers including a combination of vinyl monomers and renewable hydroxy functional monomer grafted into the acrylic backbone, and a process of manufacture thereof. Such select acrylic copolymers is specially and ideally suitable for universal tinting system providing excellent compatibility with variety of resin, resin systems and other coating ingredients including pigments, dispersing agent and solvents used in solvent borne coating compositions.
The said acrylic copolymers are unique having hydroxyl value of 75-125 (mg KOH/ gm) attainable from combination of renewable castor oil and hydroxy functional acrylic monomer such as hydroxy ethyl methacrylate. The selectacrylic monomers and their ratios especially with regard to the incorporation of isobutyl methacrylate (IBMA) and castor oil while creating enough hydroxylic and carboxylic functionality into the resin backbone surprisingly provided excellent compatibility with binders of different resin chemistries such as epoxy, modified epoxy, polyamides / adducts, polyamines/ adducts, acrylics, polyisocyanates, polyesters, short oil alkyds and acrylated alkyds, amino resins, silicone modified resins and ketonic resin.
Apart from compatibility with variety of coating resins, the designed acrylic copolymer also provides excellent compatibility with host of organic and inorganic pigments, solvents and additives enabling this as single binder for preparing tint pastes meeting the requirement of 1 K as well as 2K Paints based on aforesaid binder chemistries and across the pigment range required for creating number of shades.

Examples:
Example 1
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.

Ingredients Parts by Weight
Portion I
Castor Oil 9.80
Xylene 17.49
Butyl acetate 8.00
Portion II
Methyl methacrylate 19.00
Butyl Acrylate 20.28
Isobutyl Methacrylate(IBMA) 7.70
Hydroxyethyl methacrylate 12.58
Methacrylic acid 0.73
Tertiary butylper benzoate 4.32
Portion III
Tertiary butylper benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about 120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solids and viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 71% solids. The polymer has hydroxyl value of 99 mgKOH/gm, Acid value 6.9 mg of KOH/g and Viscosity of22.6 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showedincompatibility with epoxy resin (Epoxy equivalent weight 400-550) and short oil alkyd resin having hydroxyl value of 60-70 (mg KOH /gm).

Example 2
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 00.00
Xylene 22.98
Butyl acetate 10.00
Portion II
Methyl methacrylate 21.50
Butyl Acrylate 23
Isobutyl Methacrylate 0.00
Hydroxyethyl methacrylate 18.00
Methacrylic acid 0.70
Tertiary butyl per benzoate 3.72
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solidsand viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 65.6% solids. The polymer has hydroxyl value of 118 mg KOH/gm, Acid value 7 mg of KOH/g and Viscosity 46 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showed incompatibility with castor oil modified acrylic resin, short oil alkyd, acrylated alkyd and epoxy resin having Epoxy Equivalent weight 400-550.

Example 3
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.

Ingredients Parts by Weight
Portion I
Castor Oil 12.00
Xylene 23.85
Butyl acetate 10.00
Portion II
Methyl methacrylate 15.00
Butyl Acrylate 16.00
Isobutyl Methacrylate(IBMA) 5.00
Hydroxyethyl methacrylate 14.00
Methacrylic acid 0.70
Tertiary butyl per benzoate 3.35
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00
Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solidsand viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 66.5% solids. The polymer hashydroxyl value of 121 mg KOH/gm, Acid value 7.2 mg of KOH/g and Viscosity of 9.7 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showed incompatibility with castor Oil modified acrylic resin having hydroxyl value of 60-70.

Example 4
A Hydroxy functional acrylic copolymer is synthesized by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 12.50
Xylene 20.97
Butyl acetate 9.00
Portion II
Methyl methacrylate 16.25
Butyl Acrylate 15.89
Isobutyl Methacrylate(IBMA) 9.78
Hydroxyethyl methacrylate 10.72
Methacrylic acid 0.73
Tertiary butyl per benzoate 4.06
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solids and viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 68.5% solids. The polymer has hydroxyl value of 98 mg of KOH/gm, Acid value 8.5 mg of KOH/g and Viscosity of 4.8 Poise on Brookfield Viscometer at 25°C (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showedgood compatibility with variety of polymers i.e. alkyd, polyester resin, amino resins, epoxy resin, acrylic polyols, polyamide resin and polyisocyanates.

Example 5
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.

Ingredients Parts by Weight
Portion I
Castor Oil 12.50
Xylene 20.97
Butyl acetate 9.00
Portion II
Methyl methacrylate 18.88
Butyl Acrylate 18.52
Isobutyl Methacrylate(IBMA) 4.51
Hydroxyethyl methacrylate 10.72
Methacrylic acid 0.70
Tertiary butyl per benzoate 4.1
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solidsand viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 68.66% solids. The polymer has hydroxyl value of 98 mg of KOH/gm, Acid value 6.5 mg of KOH/g and Viscosity of11.8 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20).The above resin incompatibility with short oil alkyd resin and epoxy resin (Epoxy Equivalent weight 400-550).

Example 6
A Hydroxy functional acrylic copolymer is synthesized by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 12.50
Xylene 20.97
Butyl acetate 9.00
Portion II
Methyl methacrylate 17.21
Butyl Acrylate 17.84
Isobutyl Methacrylate(IBMA) 9.15
Hydroxyethyl methacrylate 8.44
Methacrylic acid 0.73
Tertiary butyl per benzoate 4.06
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solidsand viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 67.5% solids. The polymer has hydroxyl value of 85 mg of KOH/gm, Acid value is 5.4 mg of KOH/g and Viscosity of 9.7 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showed incompatibility with epoxy resin (Epoxy Equivalent Weight 400-450).

Example 7
A Hydroxy functional acrylic copolymer is synthesized by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 12.90
Xylene 18.40
Butyl acetate 8.33
Portion II
Methyl methacrylate 14.14
Butyl Acrylate 15.75
Isobutyl Methacrylate(IBMA) 9.38
Hydroxyethyl methacrylate 16.08
Methacrylic acid 0.75
Tertiary butyl per benzoate 4.17
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solidsand viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 71.35% solids. The polymer has hydroxyl value of 121 mg of KOH/gm, Acid value of 4.5 mg of KOH/g and Viscosity of 38.6 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showed incompatibility with acrylated alkyd resin only.

Example 8
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 0.00
Xylene 22.83
Butyl acetate 10.00
Portion II
Methyl methacrylate 20.00
Butyl Acrylate 24.60
Isobutyl Methacrylate (IBMA) 0.00
Hydroxyethyl methacrylate 18.00
Methacrylic acid 0.60
Tertiary butyl per benzoate 3.87
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solidsand viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 66.7% solids. The polymer has hydroxyl value of 116 mg KOH/gm, Acid value of6.1 mg of KOH/g and Viscosity of 54 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20).The above resin showed incompatibility with castor oil modified acrylic resin.

Example 9
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 0.00
Xylene 20.00
Butyl acetate 9.00
Portion II
Methyl methacrylate 20.29
Butyl Acrylate 22.20
Isobutyl Methacrylate(IBMA) 7.15
Hydroxyethyl methacrylate 15.50
Methacrylic acid 0.73
Tertiary butyl per benzoate 5.03
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solids and viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The prepared acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 70.01% solids. The polymer has hydroxyl value of 95 mg of KOH/gm, Acid value 7.2 mg of KOH/g and Viscosity of54 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showed incompatibility with castor modified acrylic resin and short oil alkyd.

Example 10
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 12.50
Xylene 20.97
Butyl acetate 9.00
Portion II
Methyl methacrylate 15.57
Butyl Acrylate 15.20
Isobutyl Methacrylate(IBMA) 9.15
Hydroxyethyl methacrylate 12.72
Methacrylic acid 0.73
Tertiary butyl per benzoate 4.06
Portion III
Tertiary butyl per benzoate 0.10
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about 120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solidsand viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The resulting acrylic polyol is clear with 70.22% solids and hydroxyl value of 108 mg KOH/gm, Acid value 10.7 mgKOH/g and Viscosity of 24.6 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20).
The above resin showed compatibility with variety of polymers i.e. alkyd, polyester resin, urea formaldehyde resin, melamine formaldehyde resin, epoxy resins, acrylic polyols, polyamide resin and polyisocyanates.

Example 11
A Hydroxy functional acrylic copolymer is prepared by charging the following ingredients into a polymerization reactor equipped with a heating mantle, thermocouple, dropping funnel, metering pump and a reflux condenser.
Ingredients Parts by Weight
Portion I
Castor Oil 18.00
Xylene 32.45
Butyl acetate 0.00
Portion II
Methyl methacrylate 0.00
Styrene 28.00
Butyl Acrylate 9.00
Isobutyl Methacrylate(IBMA) 0.00
Hydroxyethyl methacrylate 9.70
Methacrylic acid 1.00
Tertiary butyl per benzoate 1.80
Portion III
Tertiary butyl per benzoate 0.05
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about120-140°C and is maintained for 5 minutes. Portion II is added at a uniform rate over a 3-5 hours period at the temperature of 135-145°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added and the reaction is allowed to continue for 1-3 hours period. Solids and viscosity of the resin are monitored to ensure monomer conversion. The reaction is carried out until monomer conversion is 99.0% or higher. The resulting acrylic polyol is clear with 65.08% solids and hydroxyl value of 110mg KOH/gm, Acid value 11.46 mgKOH/g and Viscosity of 21.0 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). The above resin showed incompatibility with epoxy resins.

Table 1:Acrylic Copolymers Compatibility with variety of Resins and cross-linkers
Resin used for Combability Example
1 Example 2 Example 3 Example
4 Example 5 Example
6 Example
7 Example 8 Example
9 Example
10 Example
11
Acrylated alkyd Hazy Hazy Hazy Clear Clear Clear Hazy Hazy Hazy Clear Clear
Short Oil Alkyd Hazy Hazy Hazy Clear Hazy Clear Clear Hazy Hazy Clear Clear
Styrene Acrylic Resin - OH Value 50-70 Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Styrene FreeAcrylic -OH Value 110-130 Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Castor oil modified Acrylic OH value 60-80 Clear Hazy Hazy Clear Clear Clear Clear Hazy Hazy Clear Clear
Acrylic Resin
OH Value 30-50 Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Epoxy Resin- EEW 400-550 Hazy Hazy Clear Clear Hazy Clear Clear Clear Clear Clear Hazy
Epoxy Resin- EEW 185 -200 Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Hazy
Epoxy Amine adduct Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Aliphatic Polyisocyanate Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Melamine Formaldehyde Resin Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Saturated Polyester Resin Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear Clear
Hydroxyl Value (mg KOH/gm) 99 118 121 98 98 85 121 116 95 108 110
Conclusions Castor oil coupled with IBMA content <9% showed incompatibility with alkyds

Castor Oil free design ( Example 2)showed incompatibility with Acrylated Alkyd , Short oil alkyd, castor modified acrylic and Epoxy Resin Increase in IBMA provides compatibility with variety of resins while decrease in IBMA<9% leads to incompatibility with Short Oil alkyd and Epoxy resin. Hydroxyls from Castor &HEMA with> 9% IBMA showed good compatibility High OH value > 125 showed incompatibility with not only Acrylated alkyd but also other resins In the absence of castor oil, incompatibility is seen in alkyds and castor modified acrylic as observed in example 2 as well. Higher OH but<125 from Castor& HEMA with IBMA > 9% provided good compatibility Styrene acrylic with no IBMA and no Butyl acetate showedincompatibility with Epoxies

As evident from the compatibility chart, acrylic copolymerbased tint pastes of the present invention are essentially obtained by ensuring the presence of select and sufficient hydroxyl functionality coming from castor oil as well as hydroxy ethyl methacrylate while maintaining specific monomer combination and their ratios. Preferred hydroxyl value of such acrylic copolymer is in the range of75-125(mg KOH /gm) sourced from castor Oil and one of the hydroxy functional acrylic monomer. It was significantly found that that acrylic copolymers of the present invention with specific hydroxy functionality alonedid not help in compatibility with certain resins like epoxy resins, acrylated alkyds, alkyds and castor oil modified styrene based acrylics. This necessitated the need for modification of acrylic polyol of the present invention and it was surprisingly found that by incorporating isobutyl methacrylate (IBMA) as one of the co-monomer, the compatibility performance could be much enhanced. It was also observed that castor oil modified acrylic copolymers having 9-14% castor oil content are compatible if the acrylic copolymer of the present invention is free from IBMA. However, to attain compatibility with alkyds and acrylic copolymers having higher castor oil content, the acrylic of the present invention essentially need to have >9% IBMA content. Acrylic copolymers based tint pastes of the present invention with specific monomer type/ ratios as stated above providedexcellent compatibility with variety of resins and resin cross-linkers. Interestingly, the designed acrylic copolymers provided excellent wetting and dispersing characteristics used in tint pastes.
The role of select polar and non polar solvent combination such as Xylene: Butyl acetate::2.5:1 to about 2:1 was also found to be crucial to the synthesized acrylic copolymer of the present invention as it helped in achieving compatibility not only with varied types of resins but also with the solvents used in the resin and paint making process. The working ratios beyond the levels did not produce the required workability and compatibility.

Interestingly, it was found by the present technical advancement that hydroxy functional acrylic copolymer of the present invention showed good wetting and dispersing characteristics with organic pigments, inorganic pigments and mixtures thereof and extenders attributed to the hydroxyl functionality provided by renewable castor oil and hydroxy methyl acrylate involving select combination with other acrylic monomers taken at select levels.

Acrylic polyols of the present invention should have hydroxyl value range of 75-125 (mg KOH /gm) sourced from combination of castor oil and hydroxy functional acrylic monomers wherein hydroxyl value sourced from castor oil component should be preferably in the range of 25-35mg KOH / gm and that of obtained from hydroxy functional acrylic monomers like hydroxy methyl acrylate, hydroxy ethyl acrylate , hydroxy propyl methacrylate or similar should be preferably in the range of 50-90 mg KOH/ gmwith min 9% IBMA contentto ensure good compatibility with variety of polymers and crosslinkers commonly used in surface coatings as highlighted in the Table 1.

It was thus a significant finding of the present invention that castor oil modified acrylic copolymers having 9-14% castor oil content with lower levels of IBMA or even when free of IBMA while are compatible with moderate number of resins, however, to attain improved compatibility with wide variety of resins such as alkyds and acrylic copolymers having higher castor oil contents, the hydroxy functional acrylic of the present invention essentially needs to have>9% IBMA content. Such improvementof compatibility could be thus attained even without styrene.
Acrylic polyols (Hydroxy functional acrylic copolymer) of the present invention having hydroxyl value range of 75-125 ( mg KOH /gm) are thus sourced of a combination of castor oil and hydroxy functional acrylic monomers wherein hydroxyl value sourced from castor oil component is preferably in the range of 25-35 mg KOH/ gm and that obtained from hydroxy functional acrylic monomers includingone or more hydroxy methyl acrylate, hydroxy ethyl acrylate, hydroxy propyl methacrylate being preferably in the range of 50-90 mg KOH/ gm,said acrylic polyols having min 9 wt.% IBMA content.

The role of select polar and non polar solvent combination such as Xylene: Butyl acetate:: 2.5:1 to about 2:1 was also found to be crucial to the synthesized acrylic copolymer of the present invention as it helped in achieving compatibility not only with varied types of resins but also with the solvents used in the resin and paint making processas certain polymer like epoxy resin, and pure acrylics of high hydroxyl value are not compatible with xylene alone.
Ratio beyond and below this affects the compatibility of said hydroxy functional acrylic copolymer based tint pastes with various types of resin and crosslinkers.