Claims:We Claim:
1. High solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxyl functional monomer and with the hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/ gm.
2. High solid acrylic polyols as claimed in claim 1 involving a copolymerized product of said modified castor oil and monomers including alkyl or aryl acrylates, alkyl methacrylates, styrene, derivative of styrene, vinyl/ ethylenic type monomers and their derivatives and mixtures thereof.
3. High solid acrylic polyols as claimed in anyone of the preceding claims wherein said monomers preferably include vinyl aromatic monomers, unsaturated nitriles, vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, unsaturated anhydrides, unsaturated dicarboxylic acids, acrylic and methacrylic acids, acrylamide, methacrylamide, fluorinated acrylics, silane functional vinyl /acrylics, crosslinking acrylics like diacrylates/methacrylates, functional acrylics with dual reactivity, conjugated dienes and mixtures thereof.
4. High solid acrylic polyols as claimed in anyone of the preceding claims optionally include hydroxy alkyl acrylate /methacrylate, vinyl / ethylenic monomer and low Tg soft monomers including butyl acrylate, 2-ethyl hexyl acrylate, lauryl acrylate.
5. High solid acrylic polyols as claimed in anyone of the preceding claims having high renewable content compatible with cost-effective monomers like styrene and its derivatives.
6. High solid acrylic polyols as claimed in anyone of the preceding claims wherein said carboxylic acid anhydride modified castor oil monomer replaces or reduces the need of carboxylic acrylic monomers of acrylic acid/ methacrylic acid as monomers in said acrylic copolymer to attain desired adhesion and reaction rate when cured with crosslinkers.
7. High solid acrylic polyols as claimed in anyone of the preceding claims having solids content of upto 100%, renewable content of upto 70%, low VOC content of< 110 gm/ Kg, weight average molecular weights within the range of about 1000 to 12000, viscosity upto 200 poise at 25 ?C, acid value in the range of 3 to 15 mg KOH/gm and having a glass transition temperature (Tg) within the range of about -30°C to about 45°C.
8. High solid acrylic polyols as claimed in claim 7 wherein the average molecular weight is preferably in the range of 1500-7500 and wherein the preferred hydroxyl value is in the range of 90 to about 160 mg KOH/ gm.
9. A process for the synthesis of high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin as claimed in claims 1-8 comprising the steps of
(a) providing said modified castor oil monomer;
(b) providing said monomers for addition at controlled rate;
(c) providing free radical initiator addition at controlled rate;
(d) providing chain transfer agent;
(e) copolymerizing said ingredients (a), (b), (c) and (d) in the presence of solvents in a desired temperature range adapted to control the free radical polymerization to obtain hydroxy functional high solid acrylic copolymers/resins having hydroxyl value in the range of 80 to about 200 mg KOH/gm and involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer.
10. A process for the synthesis of high solid acrylic polyols as claimed in anyone of claims 8-9 wherein modified castor oil is provided within the range of about 10-70 weight % and more preferably in the range of about 20-60 weight % based on resin solids; wherein the monomers are provided in the range of 20 to 70 weight %, preferably in the range of 30 to 60 weight %; wherein the free-radical initiator is in the range of about 0.5 to about 10 weight % based on the amount of monomers preferably within the range of about 1 to about 8 weight %; most preferably in the range of about 3.0 to about 7.0 weight % wherein chain transfer agent is provided in the range of 0.1-2 weight% and more preferably in the range of 0.2-0.8 weight %.
11. A process for the synthesis of high solid acrylic polyols as claimed in anyone of claims 8-10 wherein the reaction temperature range is within about 80° C to about 160°C and preferably in the range of about 100° C to about 150° C and wherein the free-radical initiator is gradually added to the other components of the reaction during the course of the polymerization and preferably wherein the addition of the free-radical initiator and the monomer mixture to the reaction mixture is maintained at the same rate.
12.A process for the synthesis of high solid acrylic polyols as claimed in anyone of claims 8-11 wherein the solvents employed do not interfere with free-radical polymerization reaction or do not react with the monomers and include solvents selected from ethers, esters, ketones, aromatic and aliphatic hydrocarbons, glycol ether esters, or mixtures thereof.
13. A process for the synthesis of high solid acrylic polyols as claimed in anyone of claims 8-12 wherein the free radical initiators includes peroxide, hydroperoxide, or azo compound preferably the initiators with a decomposition temperature greater than about 100° C and selected from tert-butyl hydroperoxide, di-tert-butyl peroxide, Ditertiary amyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, dicumyl peroxide and wherein said chain transfer agents are preferably thiol chain transfer agents including Tertiary Doedecylmercaptan, N-doedecylmercaptan.
14. A polyurethane composition comprising a reaction product of
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80to about 200 mg KOH/gm; and
(b) an isocyanate.
15. A polyurethane composition as claimed in claim 14 wherein said isocyanates include polyisocyanate, isocyanate-terminated prepolymer or blocked isocyanates and are selected from toluene diisocyanate, methylene diphenyldiisocyanate, polymeric methylene diphenyldiisocyanate, carbodiimide-modified methylene diphenyldiisocyanate, hydrogenated methylene diphenyldiisocyanate, isophoronediisocyanate, biurates & isocyanurate of hexamethylene di-isocyanate and isophoron di-isocyanate.
16. A polyurethane composition as claimed in claims 14-15 including adhesives, sealants, coatings, and elastomers.
17. A process for the preparation of a polyurethane composition as claimed in claims 14-16 comprising the steps of reacting
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200mg KOH/gm; with
(b) an isocyanate at the desired NCO: OH ratio to obtain a polyurethane composition therefrom.
18. A process for the preparation of a polyurethane composition as claimed in claim 17 wherein preferably said high solid acrylic polyol and isocyanate are reacted in the ratio of 1:1.
19. A process for the preparation of a polyurethane composition as claimed in anyone of claims 17-18 comprising moisture curing in case of excess NCO groups in said polyurethane product.
20. Thermoset polymers comprising a reaction product of
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/gm; and
(b) an amino resin.
21. Thermoset polymers as claimed in claim 20 wherein said amino resins includes melamine formaldehyde resin selected from hexamethoxy methylmelamines, such as Cymel 303 (Cytec Industries), Setamine US 138 (Nuplex Industries) and Maprenal 618 (Ineosmelamines) or like.
22. A process for the synthesis of thermoset polymers as claimed in anyone of the claims 20-21 comprising the steps of reacting
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/gm; with
(b) an amino resin to obtain said thermoset polymers therefrom.
23. A coating composition comprising
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200mg KOH/gm;
(b) Cross linker
(c) pigments.
24. A coating composition as claimed in claim 23 adapted for a dry film thickness ranging from 25-100 microns favoring at least one or more coats i.e. primer, base coat, and top coat.

Dated this the 31st day of May, 2016 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)
, Description:FIELD OF THE INVENTION
The present invention provides high solid acrylic polyols comprising hydroxy functional acrylic copolymers/ resins involving an acrylic backbone having modified castor oil sourced hydroxyl functionalities and a process thereof and more particularly, relates to high solid solvent borne hydroxyl bearing acrylics for use in high build, low VOC clear or pigmented coatings for variety of substrates like wood, metal, plastics and concrete etc. Advantageously, such high solid acrylic resins of the present invention may be employed for ambient temperature curing 2K polyurethane finishes with suitable polyisocyanates, 1K polyurethane finishes with blocked isocyanates or in single component stoving finishes with amino resins like melamine formaldehyde or urea formaldehyde resins as cross-linkers. More advantageously, the present invention provides hydroxy functional high solid acrylic resins wherein hydroxyl functionality is solely or partially sourced from modified castor oil that copolymerizes with alkyl acrylates, alkyl methacrylates, styrene & optionally hydroxyl alkylacrylates/ methacrylates and vinyl /ethylenic being other co-monomers. Considering high renewable content, such high solid acrylic polyols provide sustainable and cost effective solutions to the coating formulators.

BACKGROUND ART
Hydroxy functional high solid acrylic resins have attracted interest of coating formulators across the globe in view of their suitability to design high solid low VOC coatings. These resins typically have molecular weight of 1000 to 12000 and are synthesized by copolymerizing hydroxyl alkyl acrylate or hydroxyl alkyl methacrylates monomers or mixture thereof with other alkyl acrylate/ alkyl methacrylate monomers such as butyl acrylate, butyl methacrylate, methyl methacrylate etc. alongwith styrene, methacrylic acid, initiator and chain transfer agent. Since hydroxy alkyl acrylate/ methacrylate monomers are fairly expensive and obtained from non-renewable petroleum resources, inexpensive ways to introduce hydroxyl functionality into acrylics while achieving desired solid content and coating performance is an area of interest.
In order to meet the basic objective of achieving economy and performance, polymer scientists have used vegetable oil or its derivatives with acrylics and some of such references are being mentioned here.
Use of Castor oil to modify thermosetting acrylic based coating compositions have been reported in US 3454509 to impart flexibility, hardness and low baking schedule to the coating. This prior art relates to the addition of small quantity of castor oil or its derivative into the coating recipe containing thermosetting acrylic co-polymer and cured with hexa methoxy methyl melamine cross-linker. The patent describes the use of castor oil as a reactive flexibilizer (as an additive) where hydroxy group of castor oil does not react with base polymer and is not integral part of polymer backbone instead it separately reacts with cross-linker i.e. melamine formaldehyde towards film formation.
In another patent US 5432221, hydroxy functional acrylic polymers have been reported which are compatible with castor oil. Such acrylic polymers find application in multi curable coating compositions comprising of hydroxy functional acrylic, polyisocyanate and castor oil. Use of castor oil provides flexibility and wetting to the polyurethane coatings prepared thereof but does not impart any hydroxy functionality to the acrylic polymer backbone as such.
US5432221 describes use of acrylate resin based on petroleum based hydroxyl monomers (like Hydroxy Ethyl Acrylate/ methacrylates etc.) which are highly reactive and hence to make it flexible castor oil and polyisocyanates have been used wherein the polyisocyanates react separately with acrylate resin and castor oil.
International patent WO 2010/ 100121A1 discloses the synthesis of hydroxy functional oil polyol acrylic graft copolymers. This was accomplished by heating epoxidized vegetable oil and a hydroxy functional material in the presence of an acid catalyst to prepare hydroxy functional oil poyol and reacting the same with a mixture of ethylenically unsaturated monomer composition in presence of an initiator. The polymers prepared thereof were cured with suitable cross linker to prepare coating compositions for food & beverage packaging containers.
Epoxidized vegetable oil though a renewable material based polymer, it is entirely different in structure compared to castor oil grafted acrylate resin of the present invention. Examples cited in WO2010/100121 A1 utilize various commercial grades of epoxidized vegetable oil like Vikolox, Vikoflex 7170, Vikoflex 7190, Drapex 6.8, Drapex 10.4 etc having low iodine value (between 1-3) indicating almost no unsaturation and therefore leaves little scope of chemical grafting of monomers through unsaturation.
US2005/ 0203246 A1 discloses that ethylenically unsaturated vegetable oils like soya bean oil and Linseed oil have been modified by the addition of an enophile or dienophile having acid, ester or anhydride functionality. The modified vegetable oil is then reacted with functional vinyl monomer to form a vegetable oil derivative. Such derivatives were found useful in forming latexes for coatings.
CN101074313A discloses synthesis of unsaturated polyester resin involving castor oil and maleic anhydride followed by copolymer formation using various monomers. It discloses the synthesis of unsaturated polyester resin where hydroxyl group of castor oil is completely reacted by large quantity of maleic anhydride leaving no free hydroxyl group from castor oil. It discloses the use of polyester resin in polyurethane foam application.
WO2010051346A1 and WO2012131050A1 disclose aqueous copolymeric dispersions prepared in water miscible co-solvent with sufficient carboxylic functionality/ acid value to enable neutralization with suitable amines followed by dilution with water meant exclusively for waterborne coatings.

Co-pending patent application 1803/MUM/2013 dt. 21st May, 2013 (PCT publication no.WO2014188438 A1) discloses synthesis of hydroxyl functional acrylic resin using modified castor oil as one of the reactant. Modified castor oil was used along with other acrylic/ ethylenic monomers for synthesis of hydroxyl functional resin having max 75% solid content, hydroxyl value of 40-90 mg KOH/gm and renewable content upto 50% on resin solids.
While the above cited arts describe the use of castor oil as an additive or other modified oils in hydroxy functional acrylics, there is a long felt need in the art for the provision of having renewable material derived hydroxyl functional acrylic copolymers/resins wherein the renewable material would be a co-reactant for resin synthesis to provide for high solid acrylic polyols with hydroxyl functionality as high as upto 200 (mg KOH /gm) to facilitate high crosslinking density upon curing as desired for high performance low VOC coatings.
OBJECTS OF THE INVENTION
It is thus the primary object of the present invention to provide for high solid acrylic polyols comprising hydroxyl functional acrylic copolymers/resin involving an acrylic backbone with modified castor oil monomer sourced hydroxyl functionalities.
It is another object of the present invention to provide for a process of synthesis of said high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin wherein the hydroxyl functionality would be solely or partially sourced from modified castor oil monomer based renewable material.
It is another object of the present invention to provide for said high solid acrylic polyols with hydroxyl functionality as high as upto 200 (mg KOH /gm) would favour high crosslinking density upon curing as desired for high performance coatings.
It is another object of the present invention to provide for said high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin that would be completely or partially free of low Tg soft monomers like butyl acrylate, 2-ethyl hexyl acrylate, lauryl acrylate and like.
It is yet another object of the present invention to provide for said renewable material derived high solid acrylic polyols comprising hydroxy functional acrylic copolymer/resin with high renewable content and high solid content useful for clear /pigmented low VOC sustainable coatings.
It is still another object of the present invention to provide said high solid acrylic polyols comprising hydroxy functional acrylic copolymer/ resin having high renewable content but still compatible with cost-effective monomers like styrene and its derivatives.
It is another object of the present invention to provide for said high solid acrylic polyols comprising hydroxy functional acrylic copolymer/ resin involving carboxylic acid anhydride modified castor oil monomer that would replace fully or partially the use of small quantity of carboxylic acrylic monomers like acrylic acid / methacrylic acid grafting into the acrylic polyol copolymer to get improved adhesion and reaction rate when cured with suitable crosslinkers.
It is another object of the present invention to provide for said renewable material derived high solid acrylic polyols comprising hydroxy functional acrylic copolymer/resin which are compatible with other specialty monomers like fluorinated acrylics, silane functional vinyl/acrylics, crosslinking acrylics i.e. diacrylates/ methacrylates, functional acrylics with dual reactivity and mixtures thereof to modify or improve end-use properties suchas surface gloss, hardness, chemical resistance, and other properties.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided high solid acrylic polyols comprising hydroxy functional acrylic copolymers/ resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxyl functional and with the hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/ gm. According to another preferred aspect of the present invention there are said high solid acrylic polyols wherein castor oil sourced hydroxyl functionalities comprise modifications of castor oil with reactants selected from unsaturated carboxylic acid / acid anhydride.
According to yet another preferred aspect of the present invention there is provided said high solid acrylic polyols involving a copolymerized product of said modified castor oil and monomers including alkyl or aryl acrylates, alkyl methacrylates, styrene, derivative of styrene, vinyl/ ethylenic type monomers and their derivatives and mixtures thereof.
It was thus significantly found by way of the present invention that though long alkyl chains are present in the castor oil to prohibit other monomers to penetrate and react on its unsaturation point, yet the same could be incorporated in the resin backbone at the levels as high as upto 70 wt. % by selective modification of the castor oil to provide resin with much desired beneficial high hydroxyl functionality into the resin backbonewhich could not have been achieved before through a renewable monomer.
It was thus unexpectedly found by way of the present invention that when the said castor oil was modified by reactants selected from unsaturated acid anhydride or carboxylic functionality in-situ the same favoured copolymer formation with selective combination of other monomers in the presence of suitable chain transfer agents preferably thiol chain transfer agents, whereby said modified castor oil could be incorporated as the co-reactant at the levels of upto 70% weight of resin formulation, to advantageously economize the resin, achieve high hydroxyl functionality and reduce VOC content.
Importantly therefore the hurdle of incorporation of castor oil as the co-reactant at high levels of upto 70% into an acrylic backbone to bring economy to the resin and to enhance the renewable content of the resin, could thus be circumvented by way of the present invention by modification of the castor oil with reactants selected from unsaturated acid anhydride or carboxylic functionality that was found to favour co-polymer formation with selective combinations of specific monomers in the presence of suitable chain transfer agents preferably thiol chain transfer agents such as Tertiary Doedecyl mercaptan, N-doedecylmercaptan or like to achieve the desired low molecular weight and consequently high solid hydroxyl functional acrylic copolymer.
Surprisingly therefore, it was found by way of the present invention that simple castor oil as a hydroxy bearing monomer when incorporated only at the levels of upto 10 weight % without any modification in combination with other monomers only resulted in an acrylic resin that is not useful commercially in the complete absence of any curing properties. The same castor oil when suitably modified with selective quantity of unsaturated acid anhydride or carboxylic functionality in selective combination with different monomers selected from acrylates, methacrylates, ethylenic, styrene derivatives and in the presence of suitable chain transfer agents preferably thiol chain transfer agents helped achieve castor oil incorporation to the levels of upto 70 weight %. This provided for high hydroxyl functionality of the high solid acrylic copolymers/resin as the desired end product enabling high crosslinking density and consequently high performance when cured with suitable cross linker.
In view of the various objects of the invention as stated above, it is thus an important finding that carboxylic acid anhydride modified castor oil as a co-reactant in the presence of suitable chain transfer agents preferably thiol chain transfer agents, serves varied purpose of providing desired hydroxyl functionality, facilitates copolymerization with variety of acrylic and nonacrylic unsaturated monomers, imparts flexibility typical of long fatty chain reducing the need of low Tg acrylic monomers wherein the presence of free carboxylic group facilitates improved adhesion and reaction rate upon curing with suitable crosslinkers.
Thus the process of the present invention in employing special reaction conditions and ingredient combination at special selective levels aids in having modified castor oil as the co-reactant and a source of hydroxy functionality in the said resin with complete elimination or partial reduction of petroleum based hydroxyl functional acrylic monomers such as hydroxyl ethyl acrylate or hydroxyl methyl acrylate etc. As the castor oil being soft monomer, it may provide complete elimination or partial reduction of soft monomers like butyl acrylate, 2-ethyl hexyl acrylate, lauryl acrylate etc. to achieve desired viscosity and glass transition temperature.
Significantly, in the present invention, the castor oil being the major reactive renewable component of acrylic resin wherein chemical grafting has been carried out with different monomers (acrylates, methacrylates, ethylenics) on the unsaturation present in castor oil in the presence of suitable chain transfer agents preferably thiol chain transfer agents resulting in the said resin that has low molecular weight and consequently high solid and the durable compositions attained thereof. The hurdle to reach to the said resin was circumvented by suitably modifying the castor oil in-situ with selective ingredients using the same as a co-reactant for copolymer formation with other select monomers in the presence of suitable chain transfer agents preferably thiol chain transfer agents.
According to another aspect of the present invention there is provided said high solid and high hydroxyl functional acrylic polyols involving a copolymerized product of said modified castor oil and monomers including alkyl or aryl acrylates, alkyl methacrylates, styrene, derivative of styrene, vinyl/ ethylenic type monomers and their derivatives and mixtures thereof. Preferably in said high solid acrylic polyols, said monomers preferably include vinyl aromatic monomers, unsaturated nitriles, vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, unsaturated anhydrides, unsaturated dicarboxylic acids, acrylic and methacrylic acids, acrylamide, methacrylamide, fluorinated acrylics, silane functional vinyl /acrylics, crosslinking acrylics like diacrylates/methacrylates, functional acrylics with dual reactivity, conjugated dienes and mixtures thereof. Preferably, said high solid acrylic polyols optionally includes hydroxy alkyl acrylates/ methacrylate and a vinyl/ ethylenic monomers and low Tg soft monomers including butyl acrylate, 2-ethyl hexyl acrylate, lauryl acrylate.
Preferably, said high solid acrylic polyols having high renewable content is compatible with cost-effective monomers like styrene and its derivatives.
More preferably, in said high solid acrylic polyols said carboxylic acid anhydride modified castor oil monomer replaces or reduces the need of carboxylic acrylic monomers of acrylic acid / methacrylic acid as monomers in said acrylic copolymer to attain desired adhesion and reaction rate when cured with crosslinkers.
According to another aspect of the present invention, suitable chain transfer agent mainly thiols such as Tertiary Doedecyl mercaptan, N-doedecyl mercaptan or like has been incorporated as one of the ingredient out of series of measures to achieve the desired low molecular weight and consequently high solid of the hydroxyl functional Acrylic copolymer.
Advantageously, said high solid acrylic polyols have solids content of upto 100%, renewable content of upto 70%, low VOC content of< 110 gm/ Kg, weight average molecular weights within the range of about 1000 to 12000, viscosity upto 200 poise at 25 ?C, acid value in the range of 3 to 15 mg KOH/gm and having a glass transition temperature (Tg) within the range of about -30°C to about 45°C.
More advantageously, said high solid acrylic polyols preferably have average molecular weight preferably in the range of 1500-7500 and wherein the preferred hydroxyl value is in the range of 90 to about 160 mg KOH/gm.
According to another aspect of the present invention there is provided a process for the synthesis of said high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin comprising the steps of
(a) providing said modified castor oil monomer;
(b) providing said monomers for addition at controlled rate;
(c) providing free radical initiator addition at controlled rate;
(d) providing chain transfer agent
(e) copolymerizing said ingredients (a), (b), (c) and (d) in the presence of very small amount of solvent in a desired temperature range adapted to control the free radical polymerization to obtain hydroxy functional high solid acrylic copolymers/resin having hydroxyl value in the range of 80 to about 200 mg KOH/gm involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer.
According to another preferred aspect of the said process for the synthesis of high solid acrylic polyols, said modified castor oil is used in the levels based on the desired hydroxyl value of the resin.
According to yet another preferred aspect of the said process the synthesis of high solid acrylic polyols wherein modified castor oil is provided within the range of about 10-70 weight % and more preferably in the range of about 20-60 weight % based on resin solids; wherein the monomers are provided in the range of 20-70 weight%, preferably in the range of 30-60 weight %; wherein the free-radical initiator is in the range of about 0.5 to about 10 weight % based on the amount of monomers preferably within the range of about 1 to about 8 weight %; most preferably in the range from about 3.0 to about 7.0 weight %; wherein chain transfer agent in the range of 0.1 to 2.0 weight% and more preferably in the range of 0.2-0.8 weight %.
According to another preferred aspect of the said process the reaction temperature range is within about 80°C to about 160°C and preferably in the range of 100°C to about 150°C and wherein the free-radical initiator is gradually added to the other components of the reaction during the course of the polymerization and preferably wherein the addition of the free-radical initiator and the monomer mixture to the reaction mixture is maintained at the same rate.
According to yet another preferred aspect of the said process the solvents employed do not interfere with free-radical polymerization reaction or do not react with the monomers or with the crosslinkers and include solvents selected from ethers, esters, ketones, aromatic and aliphatic hydrocarbons, glycol ether esters, or mixtures thereof.
According to another preferred aspect of the said process the free radical initiators includes peroxide, hydroperoxide, or azo compound preferably the initiators with a decomposition temperature greater than about 100°C and selected from tert-butyl hydroperoxide, di-tert- butyl peroxide, di-tert-amyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, dicumyl peroxide and wherein the chain transfer agents are preferably thiol chain transfer agents including Tertiary Doedecyl mercaptan, N-doedecyl mercaptan .
According to another aspect of the present invention a polyurethane composition is provided comprising a reaction product of
(a) High solid acrylic polyols comprising hydroxy functional acrylic copolymers/ resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/gm; and
(b) an isocyanate.
According to yet another preferred aspect a polyurethane composition is provided wherein said isocyanates include polyisocyanate, isocyanate-terminated prepolymer or blocked isocyanates and are selected from toluene diisocyanate, methylene diphenyldiisocyanate, polymeric methylene diphenyldiisocyanate, carbodiimide-modified methylene diphenyldiisocyanate, hydrogenated methylene diphenyldiisocyanate, isophoronediisocyanate, biurates & isocyanurate of hexamethylene di-isocyanate and isophoron di-isocyanate.
According to yet another preferred aspect, said polyurethane composition includes adhesives, sealants, coatings, and elastomers.
According to yet another preferred aspect of the present invention there is provided said process for the preparation of a polyurethane composition comprising the steps of reacting (a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/gm;
with (b) an isocyanate at the desired NCO: OH ratio to obtain a polyurethane composition therefrom.
Preferably, a process for the preparation of a polyurethane composition is provided wherein said high solid acrylic polyol and isocyanate are reacted preferably in the ratio of 1: 1.
More preferably, said process comprises moisture curing in case of excess NCO groups in said polyurethane product.
According to another aspect of the present invention there is provided thermoset polymers comprising a reaction product of
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/ resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/gm; and
(b) an amino resin.
Preferably in said thermoset polymers said amino resin includes melamine formaldehyde resin selected from hexamethoxy methyl melamines, such as Cymel 303 (Cytec Industries), Setamine US 138 (Nuplex Industries), Maprenal 618 (IneosMelamines) or like.
According to another aspect of the present invention there is provided said process for the synthesis of thermoset polymers comprising the steps of reacting:
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/ resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/gm; with
(b) an amino resin including urea formaldehyde resin or melamine formaldehyde resin or a combination thereof to obtain said thermoset polymers therefrom.
According to another aspect of the present invention there is provided a coating composition comprising:
(a) high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having carboxylic acid anhydride modified castor oil as hydroxy functional monomer and with hydroxyl value of the acrylic polyols in the range of 80 to about 200 mg KOH/gm;
(b) Crosslinkers
(c) Pigments
Preferably, a coating composition is provided that is adapted for a dry film thickness ranging from 25-100 microns favouring at least one or more i.e. primer, base coat and top coat. The present invention thus relates to the synthesis of hydroxy-functional high solid acrylic copolymers for variety of surface coating applications. All acrylic polyols essentially contain hydroxy functional acrylic monomers which are derived from petroleum based depleting resource. In the present invention a noble approach has been used to introduce hydroxyl functionality in the high solid acrylic backbone using renewable castor Oil. Apart from acrylic monomers, other monomers like styrene, styrene derivatives or vinyl & ethylenic derivatives have also been used to bring economy to the synthesized copolymer based on modified castor oil. Present invention also describes the use of modified castor oil as a renewable substitute to petroleum based soft monomers like butyl acrylates, 2 ethyl hexyl acrylates, lauryl acrylate and the like, in synthesizing high solid acrylic copolymer.
Due to unique chemical structure of castor oil comprising about 90%hydroxyl bearing Ricinoleic acid, it has hydroxyl value of about 160-168 (mg KOH/gm). Its incorporation by modifying it into the acrylic backbone provides series of hydroxy functional high solid acrylic resins depending on the type and concentration of monomers employed. Such high solid acrylic polyols therefore provide economy, renewable component, low VOC and latitude in usefor the coating technologists. These resins of the present invention are uniquely prepared using large amount of renewable materials, and do require a very small amount of solvent during processing to control the free radical polymerization and consequently have VOC content of 100-200 gm/Kg.
Higher hydroxyl functionality of such high solid acrylic copolymers can crosslink with different type of chemical crosslinkers. Prominent of them is reaction of hydroxyl group of the high solid acrylic polyol with -NCO of polyisocyanates to provide 1K / 2K ambient temperature curing polyurethane coatings. Performance and pot life of such polyurethane coatings would largely depend on the type of hydroxy acrylic copolymer and polyisocyanate used. Solvents used in polyurethane coatings are generally aliphatic /aromatic hydrocarbon, acetate ester, glycol ether ester, ketone or VOC exempt solvents like tert-butyl acetate. The solvents used should be ideally free from moisture or OH functionality.
Urea & Melamine formaldehyde resins are other widely used chemical cross linkers for hydroxy acrylates for single component industrial finishes at baking temperature of 100°C - 160°C for 10-40 minutes. Solvents used in such urea formaldehyde/melamine formaldehyde resin crosslinked coatings are aliphatic/aromatic hydrocarbons, alkyl alcohols, glycol ethers and esters etc.
Coating compositions comprising high solid hydroxyl functional acrylic copolymers based on present inventions can be successfully used for primer surfacer, base coat and top coat depending on the binder type, its concentration and quantity/ type of pigments used in suitable solvent medium. Typically such coating compositions may be designed & applied to achieve dry film thickness ranging from 25-100 microns per coat. Suitable application equipment for the application of such coating compositions are brush, roller, air spray, airless spray or electrostatic spray.
DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore the present invention provides for modified castor oil as a hydroxyl bearing monomer which when suitably modified with selective ingredients reacts with different monomers selected from acrylates, methacrylates, ethylenic, styrene derivatives in the presence of suitable chain transfer agents to achieve hydroxy functional high solid acrylic copolymers/resin wherein the acrylic backbone has modified castor oil sourced hydroxyl functionalities.
The present invention also details the synthesis of high solid hydroxyl functional acrylic resins which can be cured with suitable curing agents for use on treated/untreated metal, wood, plastic, concrete and cementitious substrates etc. Preferable areas for use would be finishes for automobiles, appliances, machineries, general /agricultural equipment, furniture, refineries & chemical plants, etc.
Castor oil is a vegetable oil obtained from the castor bean and is a colourless to pale yellow liquid with mild or no odour or taste. It is a triglyceride in which approximately 90 percent of fatty acid chains are ricinoleic acid. Oleic and linoleic acid are the other significant components. Ricinoleic acid, a monounsaturated, 18-carbon fatty acid, is unusual in that it has a hydroxyl functional group on the 12th carbon. This functional group causes ricinoleic acid (and castor oil) to be unusually polar, and also allows chemical derivatization that is not practical with most other vegetable oils. It is the hydroxyl group which makes castor oil and ricinoleic acid valuable as chemical feedstock. Castor oil employed in the present invention has the general structure as given hereunder:

The amount of modified castor oil used in high solid acrylic copolymer of the present invention depends on many factors, but most important of them is the desired hydroxyl value of the copolymer and hence the levels of the modified castor oil that can be incorporated in the resin leads to the desired hydroxyl value of the resin. The other important factor is complete or partial removal of petroleum based soft monomers like butyl acrylate, 2-ethyl hexyl acrylate, lauryl acrylate and the like. Generally, it is preferred to incorporate into the resin an amount of modified castor oil within the range of about 10-70 weight %; a more preferred range is from about 20-60 weight % based on resin solids.
The present invention provides for a process for making hydroxy-functional high solid acrylic resins wherein the process comprises copolymerizing an alkyl or aryl acrylate or methacrylate monomer, modified castor oil generated in-situ, styrenics and optionally hydroxyalkyl acrylate/ methacrylate, ethylenic monomer in presence of a free-radical initiator and chain transfer agent. Examples include, but are not limited to, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, lauryl methacrylate and the like, and mixtures thereof. It is often advantageous to use mixtures of various acrylates and methacrylates to control the resin glass-transition temperature. The acrylate or methacrylate monomers are commonly the major component in the resin. The amount used depends on many factors, particularly the desired end use of the resin.
An ethylenic/ vinyl / specialty monomer is optionally included in the hydroxyl acrylate resins of the invention. The monomers are selected to modify or improve end-use properties such as surface gloss, hardness, chemical resistance, and other properties. Preferred monomers include vinyl aromatic monomers, unsaturated nitriles, vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, unsaturated anhydrides, unsaturated dicarboxylic acids, acrylic and methacrylic acids, acrylamide, methacrylamide, fluorinated acrylics, silane functional vinyl /acrylics, crosslinking acrylics like diacrylates/ methacrylates, functional acrylics with dual reactivity, conjugated dienes and mixtures thereof.
The high solid acrylate resins of the invention have weight average molecular weights within the range of about 1000 to 12000 and more preferably 1500-7500. The acrylate resins have hydroxyl value within the range of about 80 to about 200 mg KOH/gm and acid value in the range of 3 to 15 mg KOH/gm and viscosity upto 200 poise at 25 ?C. A more preferred hydroxyl value range is from about 90 to about 160 mg KOH/gm. The resins preferably have glass transition temperatures (Tg) within the range of about -30°C to about 40°C. Present invention broadly comprises following reaction compositions for synthesizing hydroxy functional high solid acrylic copolymers: Use by weight of about 20-60% castor oil, 30-60% mix of alkyl acrylate/alkyl methacrylate, hydroxylalkyl acrylate/ hydroxyalkyl methacrylate, 0.2-3.0% unsaturated carboxylic acid/ acid anhydride/ acrylic/ methacrylic acid, 0-20% of styrene/ styrene derivative or ethylenic monomer in one or mix of solvents broadly classified as aliphatic/ aromatic hydrocarbon, acetate ester, glycol ether ester, ketone or VOC exempt solvents like tert-butyl acetate etc. About 3.0-7.0 weight % free-radical initiator preferably a peroxide, hydroperoxide, or azo compound and suitable thiol chain transfer agent such as Tertiary doedecyl mercaptan in the range of 0.1-2 weight% and more preferably in the range of 0.2- 0.8 weight %.
The high solid acrylic copolymers formed were characterized for their general properties like molecular weight, glass transition temperature (Tg), hydroxyl value, acid value, viscosity and % solid content. The resins were also cured with suitable polyisocyanates (2K ambient temp curing) and Urea /melamine formaldehyde resin (single component stoving finishes) in clear/ pigmented system and tested for physical, mechanical, chemical & corrosion resistance and weathering properties.
The free-radical initiator is preferably a peroxide, hydroperoxide, or azo compound. Preferred initiators have a decomposition temperature greater than about 100°C. Examples include tert-butyl hydroperoxide, di-tert-butyl peroxide, di-tert-amyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, dicumyl peroxide, and the like.
The amount of free-radical initiator needed varies, but is generally within the range of about 0.5 to about 10 weight % based on the amount of monomers. Preferably, the amount of free-radical initiator used is within the range of about 1 to about 8 weight %; most preferred is the range from about 3.0 to about 7.0 weight %. Generally, it is preferred to add the free-radical initiator to the reactor gradually during the course of the polymerization; it is also desirable to match the addition rate of the free-radical initiator to the addition rate of the acrylate or methacrylate monomer mixture.
The process of the invention can be performed over a broad temperature range. Generally, the reaction temperature will be within the range of about 80°C to about 160°C. A more preferred range is from about 100°C to about 150°C. The process of the present invention is performed in the presence of small amount of reaction solvent. Useful solvents include those that will not interfere with the free-radical polymerization reaction or otherwise react with the monomers. Suitable solvents include, but are not limited to, ethers, esters, ketones, aromatic and aliphatic hydrocarbons, glycol ether esters, and the like, and mixtures thereof.
A polyurethane composition is made by reacting hydroxyl functional high solid acrylic resins of the invention with a polyisocyanate, isocyanate-terminated prepolymer or blocked isocyanates. Suitable polyisocyanates are those well known in the polyurethane industry and include, for example, toluene diisocyanate, methylene diphenyldiisocyanate, polymeric methylene diphenyldiisocyanate, carbodiimide-modified methylene diphenyldiisocyanate, hydrogenated methylene diphenyldiisocyanate, isophoronediisocyanate, biurates & isocyanurate of hexamethylene di-isocyanate, isophoron di-isocyanate and the like. Isocyanate-terminated prepolymers are made in the usual way from a polyisocyanate and a polyether polyol, polyester polyol, or the like. The polyurethane is formulated at desired NCO: OH ratio, but it is preferred to use an NCO: OH ratio close to 1. Generally all of the available NCO groups are reacted with hydroxy groups from the high solid hydroxyacrylate resins and any chain extenders. Alternatively, an excess of NCO group remain in the product, as in moisture-cured polyurethane. Many types of polyurethane products can be made, including, for example, adhesives, sealants, coatings, and elastomers.
The present invention includes thermoset polymers prepared by reacting the high solid hydroxy functional acrylic resins of the invention with suitable amino resin crosslinking agents. For example, melamine-based polymer coatings can be prepared by reacting the hydroxyacrylate resins with melamine resins. Suitable melamine resins include hexamethoxymethylmelamines, such as Cymel 303 (Cytec Industries), Setamine US 138 (Nuplexlndustries) and Maprenal 618 (IneosMelamines) etc.
Examples 1-4 below illustrate synthesis of high solid hydroxyl functional acrylic resins of the present invention. The invention is described hereunder in greater details in relation to the non-limiting examples.
Example 4 below illustrates the preparation of polyurethane based and melamine based coating compositions from high solid hydroxyl functional acrylic resins in accordance with the present invention.
Example 1
A Hydroxy functional high solid 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.
Parts by Weight
Portion I
Commercial Castor Oil 45.0
Portion II
Maleic anhydride 0.8
Methoxy Propyl acetate 5.0
Portion III
Tert-dodecyl Mercaptan 0.2
Portion IV
Methylmethacrylate 35.0
Hydroxyethyl methacrylate 8.0
Ditertiaryamylperoxide 5.8
Portion V
Ditertiaryamylperoxide 0.2
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about (100-160°C). Portion II is charged into the reactor and is maintained at a temperature of about (100-160°C) for 1-2 hour. Portion III is added at a temperature of about 100-160°C. Portion IV is added at a uniform rate over a 3-5 hours period at 100-160°C. After Portion IV is added, the reaction mixture is held at the same temperature for an additional hour. Portion V is added, reaction is allowed to continue for 1-3 hours period. %NVM 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 high solid acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 89% by weight of polymer solids. The polymer has a weight average molecular weight of 2556, and a hydroxyl value of 120 mg of KOH/gm. Acid value is 6.9 mg of KOH/g and Viscosity is 170.40 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). Glass transition temperature (Tg) of the resin is approximately -2.3°C primary and 28.3°C secondary.
The above resin was evaluated in 2K PU clear and cured with Desmodur N 3390 (Ex Bayer) at NCO/OH ratio of 1 using methoxy propyl acetate/ methyl isobutyl ketone mix as thinner. Coating is applied on MS panel using Spray gun at dry film thickness of 35-45 microns. The panel touch dried in 50-60 minutes and hard dried after over night. Scratch hardness of the film using Sheen Scratch hardness tester after 7 days of ageing found to be 1.2-1.3 Kg. Coating passed 100 Xylene rubs and 35 methyl ethyl ketone rubs after 7 days curing.
Example 2
A Hydroxy functional high solid 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.
Parts by Weight
Portion I
Commercial Castor Oil 48.0
Portion II
Maleic anhydride 0.3
MethoxyPropyl acetate 4.0
Portion III
Tert-dodecyl Mercaptan 0.2
Portion IV
Methylmethacrylate
Styrene
Butyl Acrylate 17.0
9.0
3.5
Hydroxyethyl methacrylate 11.0
Ditertiaryamylperoxide 5.8
Portion V
Ditertiaryamylperoxide 0.2
MethoxyPropyl acetate 1.0
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about (100-160°C). Portion II is charged into the reactor and is maintained at a temperature of about (100-160°C) for 1-2 hour. Portion III is added at a temperature of about 100-160°C. Portion IV is added at a uniform rate over a 3-5 hours period at 100-160°C. After Portion IV is added, the reaction mixture is held at the same temperature for an additional hour. Portion V is added, reaction is allowed to continue for 1-3 hours period. %NVM 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 high solid acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 90% by weight of polymer solids. The polymer has a weight average molecular weight of 3196, and a hydroxyl value of 140 mg of KOH/gm. Acid value is 4.82 mg of KOH/g and Viscosity is 101.70 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). Glass transition temperature (Tg) of the resin is approximately -12.5°C primary and 37.3°C secondary.
The above resin was evaluated in 2K PU clear and cured with Desmodur N 3390 (Ex Bayer) at NCO/OH ratio of 1 using methoxy propyl acetate & methyl isobutyl ketone mix as thinner. Coating is applied on MS panel using Spray gun at dry film thickness of 35-45 microns. The panel touch dried in 45-55 minutes and hard dried after over night. Scratch hardness of the film using Sheen Scratch hardness tester after 7 days of ageing found to be 1.2-1.3 Kg. Coating passed 100 Xylene rubs and 40 methyl ethyl ketone rubs after 7 days curing.
Example 3
A Hydroxy functional high solid 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.
Parts by Weight
Portion I
Commercial Castor Oil 45.0
Portion II
Maleic anhydride 0.3
MethoxyPropyl acetate 4.0
Portion III
Tert-dodecyl Mercaptan 0.2
Portion IV
Methylmethacrylate
Styrene
Butyl Acrylate 13.0
7.0
9.5
Hydroxyethyl methacrylate 14.0
Di tertiary amyl peroxide 5.8
Portion V
Di tertiary amyl peroxide 0.2
Methoxy Propyl acetate 1.0
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about (100-160°C). Portion II is charged into the reactor and is maintained at a temperature of about (100-160°C) for 1-2 hour. Portion III is added at a temperature of about 100-160°C. Portion IV is added at a uniform rate over a 3-5 hours period at 100-160 °C. After Portion IV is added, the reaction mixture is held at the same temperature for an additional hour. Portion V is added, reaction is allowed to continue for 1-3 hours period. %NVM 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 high solid acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 90% by weight of polymer solids. The polymer has a weight average molecular weight of 2369, and a hydroxyl value of 150 mg of KOH/gm. Acid value is 3.09 mg of KOH/g and Viscosity is 95.70 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20).Glass transition temperature (Tg) of the resin is approximately -11.3°C primary and 41°C secondary.
The above resin was evaluated in 2K PU clear and cured with Desmodur N 3390 (Ex Bayer) at NCO/OH ratio of 1 using methoxy propyl acetate/ methyl isobutyl ketone mix as thinner. Coating is applied on MS panel using Spray gun at dry film thickness of 35-45 microns. The panel touch dried in 40-50 minutes and hard dried after over night. Scratch hardness of the film using Sheen Scratch hardness tester after 7 days of ageing found to be 1.5-1.6 Kg. Coating passed 100 Xylene rubs and 50 methyl ethyl ketone rubs after 7 days curing.
Example 4
A Hydroxy functional high solid 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.
Parts by Weight
Portion I
Commercial Castor Oil 54.5
Portion II
Maleic anhydride 0.3
MethoxyPropyl acetate 4.0
Portion III
Tert-dodecyl Mercaptan 0.2
Portion IV
Methylmethacrylate
Styrene 13.0
7.0
Hydroxyethyl methacrylate 14.0
Ditertiaryamylperoxide 5.8
Portion V
Ditertiaryamylperoxide 0.2
MethoxyPropyl acetate 1.0
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about (100-160°C). Portion II is charged into the reactor and is maintained at a temperature of about (100-160°C) for 1-2 hour. Portion III is added at a temperature of about 100-160°C. Portion IV is added at a uniform rate over a 3-5 hours period at 100-160°C. After Portion IV is added, the reaction mixture is held at the same temperature for an additional hour. Portion V is added, reaction is allowed to continue for 1-3 hours period. %NVM 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 high solid acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is clear with 89% by weight of polymer solids. The polymer has a weight average molecular weight of 2719, and a hydroxyl value of 160 mg of KOH/gm. Acid value is 4.7 mg of KOH/g and Viscosity is 36.8 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). Glass transition temperature (Tg) of the resin is approximately -11.7°C primary and 37.2°C secondary.
The above resin was evaluated in 2K PU clear and cured with Desmodur N 3390 (Ex Bayer) at NCO/OH ratio of 1 using methoxy propyl acetate/ methyl isobutyl ketone mix as thinner. Coating is applied on MS panel using Spray gun at dry film thickness of 35-45 microns. The panel touch dried in 40-50 minutes and hard dried after over night. Scratch hardness of the film using Sheen Scratch hardness tester after 7 days of ageing found to be 1.3-1.4 Kg. Coating passed 100 Xylene rubs and 50 methyl ethyl ketone rubs after 7 days curing.
The above resin was evaluated in white paint and cured with Desmodur N 3390 (Ex Bayer) at NCO/OH ratio of 1 using methoxy propyl acetate/ methyl isobutyl ketone mix as thinner. Coating is applied on MS panel using Spray gun at dry film thickness of 30-40 microns. The panel touch dried in 40-50 minutes and hard dried after over night. Scratch hardness of the film using Sheen Scratch hardness tester after 7 days ageing found to be 1.1-1.2 Kg. Coating passed 100 Xylene rubs and 50 methyl ethyl ketone rubs after 7 days curing. Initial gloss of the coating was 90-93 at 60º gloss head.The panels exposed to QUV 313 with exposure conditions as condensation 45±1°C/4hrs, UV 50±1°C/4hrs at 0.55±0.01 irradiance level showed 98% gloss retention after 500 hrs and 95% gloss retention after 1000 hrs of exposure.
The above resin was also evaluated in white stoving finish having 18% Titanium dioxide with melamine formaldehyde resin Maprenal 618 (Ineos Melamines) using High solid acrylic resin: Melamine formaldehyde ratio of 70: 30 (on resin solids) with UV absorber and HALS additives. The coating is applied to achieve 30-40 micron dry film thickness on mild steel panel and baked at 150 ?C/30 minutes. Coating showed scratch hardness of 0.9-1.0 Kg, Ericsen cupping of 8.0 and gloss of 83-85 at 60? gloss head. The panels exposed to QUV 313 with exposure conditions as condensation 50 ±1 °C/4hrs, UV 60 ± 1°C/4hrs at 0.55 ± 0.01 irradiance level showed 75% gloss retention after 1000 hrs.
Example 5
A Hydroxy functional high solid 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.
Parts by Weight
Portion I
Commercial Castor Oil 45.0
MethoxyPropyl acetate 5.0
Portion II
Methylmethacrylate 36.0
Hydroxyethyl methacrylate 8.0
Ditertiaryamylperoxide 5.8
Portion III
Ditertiaryamylperoxide 0.2
Total 100.00

Portion I is charged into the reactor and is heated to a temperature of about (100-160°C). Portion II is added at a uniform rate over a 3-5 hours period at 100-160°C. After Portion II is added, the reaction mixture is held at the same temperature for an additional hour. Portion III is added, reaction is allowed to continue for 1-3 hours period. %NVM 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 high solid acrylic polyol resin solution is filtered.
The resulting acrylic polyol resin solution is hazy with 87.9% by weight of polymer solids. The polymer has a weight average molecular weight of 2338, and a hydroxyl value of 120 mg of KOH/gm. Acid value is 1.68 mg of KOH/g and Viscosity is 251.40 Poise on Brookfield Viscometer at 25°C, (Model No DV-I+, Spindle no. 4, RPM 20). No clear transition (very weak transition) observed during measurement of Glass transition temperature (Tg).
Hence it is confirmed by this example that without maleic anhydride modification, copolymer formation is hindered resulting in hazy material with very low acid value of the product (1.68 mg KOH/g). Also without chain transfer agent viscosity of the polymer is very high (251.4 poise against 170.4 poise).
While a range of organic compounds may be used as chain-transfer agents in the production of acrylic polymers including chlorinated hydrocarbons, such as carbon tetrachloride, trichloroethylene, and perchloroethylene; and mercapto organic compounds, such as n-dodecyl mercaptan, isooctylthioglycolate, Tert-dodecyl Mercaptan and 2-mercaptoethanol etc., and while the chlorinated hydrocarbons cause environmental pollution when emitted into the atmosphere during processing, storage, and usage of the polymer, it was importantly found by way of the present invention that thiols acted as efficient chain transfer agents for the monomers used in the present invention resulting in significant decrease in the polymer molecular weight with viscosity levels of upto 200 poise at 25 ?C without adversely affecting the polymerization rate.
It is thus possible by way of the present advancement to provide for improved high solid acrylic polyols comprising hydroxy functional acrylic copolymers/resin involving an acrylic backbone having modified castor oil sourced hydroxyl functionalities and a process thereof wherein the renewable content of castor oil can be incorporated in the said resin to an extent of upto 70%. Advantageously, said high solid acrylic polyols of the present invention may be employed for the synthesis of ambient curing 2K polyurethane finishes with suitable polyisocyanates, 1K polyurethane finishes with blocked isocyanates or in single component stoving finishes with amino resins like melamine formaldehyde or urea formaldehyde resins as cross linkers.
More advantageously, the present invention provides hydroxy functional high solid acrylic resins with hydroxyl functionality solely or partially sourced from acid anhydride modified castor oil monomer in presence of alkyl acrylates, alkyl methacrylates, styrenic monomers & optionally hydroxy alkylacrylates / methacrylates and vinyl/ ethylenic monomers. It brings renewable component as well as economy to the resin and consequently to different compositions and coating formulations prepared thereof. More advantageously, the present invention in providing for hydroxy functional high solid acrylic resins sourced from modified castor oil monomer can completely or partially replace petroleum based soft monomers such as butyl acrylate, 2-ethyl hexyl acrylate, lauryl acrylate and the like. Most advantageously, the present invention provides hydroxy functional high solid acrylic resins having modified castor oil monomer with low VOC content of< 110 gm/ Kg.