DESC:FIELD OF INVENTION
The present invention relates to the synthesis of Hydroxy functional acrylic copolymers and coating formulations thereof with said acrylic copolymers including cinnamic acid ester macromonomers and wherein hydroxy functionality of said acrylic copolymers are preferably solely imparted by said cinnamic acid macromonomers, which are the reaction product of Cinnamic acid with stoichiometric molar excess of polyols including Trimethylol propane, Propylene Glycol, 2-Methyl-1,3-propanediol (MP diol glycol), diethylene glycol, neopentyl glycol thereby forming cinnamic acid macromonomers/esters with free hydroxyl groups. In the present invention such hydroxy functional cinnamic acid ester based macromonomers have been involved as one of the monomer along with selectively other acrylic, vinylic monomers including styrene, methyl methacrylate, butyl acrylate and the like in presence of suitable initiators like tertiary butyl perbenzoate, di-tert butyl peroxide, di-tert amyl peroxide and the like and suitable solvent medium like methoxy propyl acetate, butyl acetate, xylene to enable said hydroxy functional acrylic copolymers. This invention eliminates the need of hydroxy functional acrylic monomers such as hydroxy ethyl methacrylate, hydroxy ethyl acrylate and the like and provides exceptional film properties like drying, gloss, chemical resistance, and mechanical/ weathering performance in combination with suitable cross-linkers. Since cinnamic acid ester macromolecules have residual free carboxylic functionality, it eliminates the need of methacrylic acid as employed in standard acrylic copolymers to improve adhesion and catalytic effect in presence of crosslinkers.

In the present invention, acrylic copolymers have been designed at hydroxyl value of 50-150 (mg KOH/ gm) with hydroxyl functionality sourced solely from hydroxy functional cinnamic acid esters. The selection of acrylic monomers and their ratios with the incorporation of hydroxy functional cinnamic acid esterbased macromonomers provided required hydroxyl and carboxylic functionality to the resin.

Such Cinnamic acid ester macromonomer based hydroxy functional acrylic copolymers have been designed for high performance 2K polyurethane coating systems with polyisocyanate crosslinkers. The designed hydroxy functional acrylic copolymers also find use in single component stoving finishes with amino resins crosslinkers such as urea formaldehyde and melamine formaldehyde resins.

BACKGROUND ART
2K PU systems in decorative or industrial coatings make up an important part of coating industry for their superior mechanical, chemical and highly durable properties. Such coatings are designed with acrylic copolymer as binder, which have hydroxyl functionality to react with isocyanate. Typical acrylic copolymer with hydroxyl functionality for coatings is based on acrylic monomers like hydroxyl ethyl methacrylate etc.
Typical acrylic copolymers are based on hydroxy functional acrylic monomers like hydroxyl ethyl methacrylate, hydroxy ethyl acrylate and the like. Alternatives to such conventional monomers are a long felt requirement in the art.
On this reference is drawn to thermo-setting compositions of styrene and cinnamic acid ester of epoxide resin (US2846410A) teaches a thermosettable composition comprising an admixture of an ester of an acid selected from the group consisting of cinnamic acid and mixtures of cinnamic acid and at least one long chain fatty acid containing from 12 to 26 carbon atoms in the chain, and a polyglycidyl polymer resin having a 1,2-epoxide equivalent weight of from about 225 to 4,000; and a vinyl monomer selected from the group consisting of styrene, nuclear alkyl substituted styrene and nuclear halogen-substituted styrene, the amount of said vinyl monomer being from about 5% to about 95% of the combined weight of said monomer and said ester.
Fumaric acid diisopropyl-cinnamic acid ester-bismaleimide copolymer resin and production method thereof (JP2014205814A) discloses a diisopropyl fumarate-cinnamate-bismaleimide copolymer comprising a diisopropyl fumarate residue unit, a cinnamic acid ester residue unit having an alkyl group having 1 to 6 carbon atoms, and a bismaleimide residue unit resin. 50 to 98.5 mol% of diisopropyl fumarate residue units, 1 to 49.5 mol% of cinnamic acid ester residue units having an alkyl group having 1 to 6 carbon atoms, and 0.01 to 0.001 of bismaleimide residue units. The di-isopropyl fumarate-cinnamate-bismaleimide copolymer resin according to claim 1, comprising 5 mol%. The number average molecular weight in terms of standard polystyrene is 60,000 to 500,000, The di-isopropyl fumarate-cinnamate-bismaleimide copolymer resin according to claim 1 or 2. The cinnamate ester residue unit is selected from the group consisting of a methyl cinnamate residue unit, an ethyl cinnamate residue unit, and an isopropyl cinnamate residue unit. 4. The diisopropyl fumarate-cinnamate-bismaleimide copolymer resin according to any one of 3 above. The total amount of di-isopropyl fumarate is 50 to 98.5 mol%, 1 to 49.5 mol% of cinnamic acid ester having an alkyl group having 1 to 6 carbon atoms, and 0.01 to 0.5 mol% of bismaleimide. The diisopropyl fumarate according to any one of claims 1 to 4, wherein the radical polymerization reaction is carried out in the presence of 0.001 to 2 mol% of a radical polymerization initiator with a monomer content of 100 mol%. A method for producing a cinnamic ester-bismaleimide copolymer resin.
New acrylic resin with cinnamyl and fluorene group and its photosensitive resin composition (KR20130123352A) is deals with an acrylate compound with cinnamyl and fluorene groups and a photosensitive resin composition including the same, more specifically, to an acrylate compound with high-refractive properties and improves heat resistance and chemical resistance of a film or a sheet. The present invention provides a new acrylate compound which reduces deformation by heat when exposed to heat and light for a long time of period.
Thermosetting ethylenically Unsaturated Ester Resin Compositions (GB1197810) is directed to a thermosetting resin composition comprises a blend of: (A) at least 30% by wt. of an ethylenically unsaturated resin prepared by first reacting an ethylenically unsaturated monocarboxylic acid, e.g. (meth)acrylic acid or cinnamic acid, with a polyepoxide, e.g. a diglycidyl ether of bisphenol A or an epoxy novolac resin. A dicarboxylic acid anhydride is then reacted with the secondary hydroxyl groups to provide pendant half-ester groups; from 0À8 to 1À2 equivalents of epoxide are used per equivalent of monocarboxylic acid and from 0À1 to 1À2 moles of dicarboxylic acid anhydride, e.g. of maleic or phthalic acid per equivalent epoxide. (B) Up to 70% by weight of a polymerizable monomer containing a >C=CH2 group, e.g. a vinyl aromatic monomer such as styrene, a hydroxyalkyl ester of (meth)acrylic acid or of crotonic acid, alkyl esters of these acids or acrylic or methacrylic acid. Rapidly thickening compositions may be obtained by mixing: (A) a thermosetting composition as set out above; (B) an oxide or hydroxide of a metal of Group II of the Periodic Table, e.g. MgO, in an amount sufficient to provide at least 0À75 equivalents per -COOH equivalent; and (C) a catalytic amount of water, i.e. at least 0À25 equivalents per -COOH equivalent. Water may be provided as water of adsorption by adding clay or other inert fillers. Reinforcing fillers, e.g. glass fibres, may also be present. The composition may contain a catalyst for free radical polymerization, e.g. an organic peroxide.
Reference is also invited to an adduct of cinnamic acid and glycerin, ultraviolet absorbent and external preparation for skin (US5426210A) that relates to an adduct of cinnamic acid and glycerin, an ultraviolet absorbent and an external preparation for skin and more particularly, a cinnamic acid derivative having ultraviolet absorbancy, and an ultraviolet absorbent and an external preparation for skin using the same.
Styrenic copolymer resin (JP2021123637) teaches to provide a styrenic resin having excellent heat resistance and an excellent appearance. SOLUTION: A styrenic copolymer resin is a copolymer comprising a styrenic monomer unit and a cinnamic acid-based monomer unit, with its weight average molecular weight of 50000 or more.
A kind of anti-aging antirust paint and preparation method thereof (CN107384127A) is also taught that relates to application field prepared by antirust paint, more particularly to a kind of anti-aging metallic anti-rust paint. Metal erosion can be brought about great losses, antirust paint traditional at present, and due to not meeting environmental protection concept containing a large amount of organic solvents, secondly such rust inhibitor paint coatings are chronically exposed under air and sunlight, are increased over time, the increase of self-deterioration situation. A kind of anti-aging antirust paint provided by the invention, stirred first by low-temperature magnetic and cinnamic acid, Tea Polyphenols and expansible graphite are prepared into the expansible graphite with age resister slow-release function, be then added in aqueous, environmental protective epoxy resin. Tea Polyphenols has excellent radical-scavenging ability, and cinnamic acid has ultraviolet shielded effect in itself, and Tea Polyphenols and cinnamic acid can solve the shortcomings that coating is oxidizable with synergistic, while the paint is obtained good anti-microbial property. The special interlayer structure of expanded graphite makes it have slow releasing function so that catechin and cinnamic acid can stabilize permanent be present in this coating.
Unique acrylic resins with aromatic side chains by homo-polymerization of cinnamic monomers https://doi.org/10.1038/s42004-019-0215-3 is also known directed to cinnamic monomers, which are useful chemicals, contain a,ß-unsaturated carbonyl groups with an aromatic ring at the ß-position. Homopolymers synthesized by addition polymerization of these compounds are expected to be innovative bio-based polymer materials, as they have both polystyrene and polyacrylate structures. However, polymerization of these compounds by many methods is challenging, including by radical methods, owing to steric hindrance of the substituents and delocalization of electrons throughout the molecule via unsaturated p-bonding. Herein homopolymers of these compounds with molecular weights (Mn) of ~18,100?g?mol-1 and controlled polymer backbones are reported to be synthesized by the group-transfer polymerization technique using organic acid catalysts. Additionally, these homopolymers are shown to have high heat resistance comparable to that of engineering plastics. Overall, these findings may open up possibilities for the convenient homo-polymerization of cinnamic monomers to produce high-performance polymer materials.
Study of green epoxy resins derived from renewable cinnamic acid and dipentene: synthesis, curing and properties https://doi.org/10.1039/C3RA47927G teaches an epoxy based on cinnamic acid (Cin-epoxy) and an anhydride curing agent based on dipentene were prepared. Both products are liquids of low viscosity at room temperature. For the synthesis of the epoxy, cinnamic acid was first converted to a diacid by reacting with maleic anhydride via Friedel–Crafts reaction, followed by allylation of the carboxylic groups and subsequent epoxidation of the allyl double bonds. The curing agent was the Diels–Alder adduct of dipentene and maleic anhydride (DPMA). The chemical structures of Cin-epoxy and DPMA were confirmed by 1H NMR, 13C NMR, FT-IR and ESI-MS. Non-isothermal curing of Cin-epoxy was studied using differential scanning calorimetry (DSC). In addition to DPMA, two commercial anhydrides were also used to cure Cin-epoxy and the curing reactivity and properties of cured resins were compared. Thermal mechanical properties and thermal stability of the cured epoxy resins were studied using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. Results showed that Cin-epoxy was slightly more reactive than the bisphenol A type epoxy DER 332 and displayed good dynamic mechanical properties and thermal stability.
Cinnamic acid derivatives as promising building blocks for advanced polymers: synthesis, properties and applications https://doi.org/10.1039/C9PY00121B
discloses cinnamic acid (CA) and its hydroxy-derivatives that are aromatic building blocks whose structural peculiarities (unsaturation, hydroxylic and/or carboxylic groups) have driven them to a prominent position in polymer science. Indeed, CA hydroxy-derivatives (hydroxycinnamic acids, HCAs) have been extensively used in the preparation of polyesters, but there are also reports about their use in the synthesis of polyamides and poly(anhydride esters), among many other uses. It is worth mentioning that these polymers have a wide spectrum of applications, ranging from industrial (e.g. (super) engineered plastics) to biomedical domains (e.g. drug delivery systems, shape-memory materials). Despite the well-known importance of CA-based polymers and the extensive activity around their synthesis and development, to the best of our knowledge, there are no reviews devoted solely to this theme. Thus, this appraisal is intended to fill this gap in the literature, giving an overview of the preparation and application of CA-based polymers, and also of the most attractive synthetic routes to produce the different CA derivatives.
Production of epoxidized cardanol–based vinyl ester resins with cinnamic acid for eco-friendly coating materials https://doi.org/10.1007/s42247-022-00396-6 in relation to environmental concerns about coating material have led manufacturers towards considering bio-based alternatives to conventional petroleum–derived epoxy resins. Considering these concerns with rise in prices and high depletion of petroleum resources, a viable alternative polymer resin has been synthesized from characteristic cashew nut shell liquid (CNSL). In this study, cardanol, a major component of cashew nut shell liquid, was used to synthesize cardanol-based vinyl ester resole (CBVER) and cardanol-based vinyl ester novolac (CBVEN) resins. The vinyl ester resins synthesized were characterized using international standard methods. The molecular weight of the resins was determined to be 1069 and 1001 g/mol for CBVER and CBVEN, respectively, using gas chromatographic mass spectroscopy (GCMS). Fourier transform infrared (FTIR) and thermogravimetric (TGA) analysis were used to identify the functional groups and analyze the material weight changes with stability relative to temperature. FTIR results revealed functional groups typical of thermosetting resin. The results of the mechanical and thermal properties of the resins showed improved performance and material’s thermal stability (up to a temperature of 280 °C), respectively. The chemical resistance properties of the cardanol-based vinyl ester resins showed improved performance when subjected to solvent, alkalis, and acids, an indication of anti-corrosive properties. The better performances of cardanol-based vinyl ester resins obtained from this study is justifiable and suggest applicability in coatings, for both anticorrosion and interior/exterior decorations.
Miscible blends of styrene–cinnamic acid copolymers with poly (ethyl methacrylate) https://doi.org/10.1002/pi.746 is directed to differential scanning calorimetry and inverse gas chromatography have been used to investigate the miscibility behaviour of blends of poly (ethyl methacrylate) (PEMA) with styrene–cinnamic acid statistical copolymers PSCA5, PSCA8, PSCA23 having compositions of, respectively, 5, 8 and 23?mol% of cinnamic acid. Several probes with different chemical nature and polarity have been used to determine the polymer–solute and polymer–polymer interaction parameters. DSC and CPGI measurements indicate that poly(ethyl methacrylate) is miscible with each poly[(styrene)-co-(cinnamic acid)] copolymer as established from the observation of a single composition-dependent glass transition temperature. This deduction is corroborated by the IGC data; comparison of the experimental retention volume of the blend with the algebraic average retention volumes of the pure components, together with negative values of the apparent polymer–polymer interaction parameter, establish the miscibility of the studied systems. Furthermore, the polymer–polymer interaction parameters are found to show marked probe dependence; this is discussed in terms of the ?? effect. As indicated by the variation of the glass transition temperature with blend composition, the application of the Kwei and the Schneider approaches to the calorimetric results suggests the occurrence of strong specific interactions within the blends; the strength of these intermolecular interactions increases with the cinnamic acid content in the PSCA copolymer.
In spite of the above known conventional knowledge flowing from the state of the art as above, it is a long felt need in the art to explore for alternate raw materials alternate to conventional hydroxyl monomers that would provide for hydroxyl functionality to acrylic copolymer such that need of hydroxy functional acrylic monomers including hydroxy ethyl methacrylate, hydroxy ethyl acrylate could be completely eliminated while providing similar kind of gloss and mechanical properties and so that a design latitude towards creating a large number of acrylic copolymers with varying functionality is made possible.

OBJECTS OF THE INVENTION
The basic object of the present invention is to provide for hydroxy functional acrylic copolymers and coating formulations thereof wherein hydroxyl functionality would be solely imparted by cinnamic acid ester based macromonomers which when reacted with vinyl monomers would provide said hydroxy functional acrylic copolymers that would in turn enable similar gloss and mechanical properties even when free of conventional hydroxy functional acrylic monomers.

It is another object of the present invention to provide for said hydroxy functional acrylic copolymers and coating formulations thereof that would eliminate the need of hydroxy functional acrylic monomers such as hydroxy ethyl methacrylate, hydroxy ethyl acrylate and the like and would yet provide for exceptional film properties like drying, gloss, chemical resistance, and mechanical/ weathering performance in combination with suitable cross-linkers.
It is yet another object of the present invention to provide for said hydroxy functional acrylic copolymers comprising cinnamic acid ester based macromonomer with free hydroxyl groups that is a reaction product of cinnamic acid with range of polyols to provide for design latitude towards creating large number of acrylic copolymers with varying functionality.
It is another object of the present invention to provide for said hydroxy functional acrylic copolymers that would also eliminate the need of methacrylic acid involved in standard acrylic copolymers to improve adhesion as well as to catalyze reaction with crosslinkers, as free carboxylic functionality of cinnamic acid ester macromonomer would provide for desired similar effect.
It is yet another object of the present invention to provide for said acrylic copolymers that would be able to be cured at temperatures including ambient temperature with variety of aliphatic and aromatic polyisocyanate crosslinkers as a two-component polyurethane system.
It is yet another object of the present invention to provide for said acrylic copolymers which when provided as a clear/pigmented coating would show high gloss and good mechanical properties including scratch hardness and excellent cross-cut adhesion.
It is another object of the present invention to provide for said hydroxy functional acrylic copolymer that would find end use and application as single component stoving finishes with amino resins crosslinkers like urea formaldehyde resin and melamine formaldehyde resins.
Summary of the invention
Thus according to the basic aspect of the present invention there is provided hydroxy functional acrylic copolymers comprising reaction product of cinnamic acid ester based macromonomers (A), and, selectively acrylic, vinylic monomers enabling said hydroxy functional acrylic copolymers (B) having hydroxyl value of 50-150 (mg KOH/ gm) that is adapted for curing with crosslinkers favouring single or two component coating formulations.
According to a preferred aspect of the present invention there is provided said hydroxy functional acrylic copolymers wherein said hydroxyl functionality of said hydroxy functional acrylic copolymers are solely sourced from said cinnamic acid ester macromonomers having hydroxyl value of 200-600 mg KOH/gm and acid functionality in the range of 1-5 mg KOH/gm even when free of methacrylic acid monomer adapted to enhance adhesion of coating formulations upon curing including ambient temperature curing in temperature range of -5-50?C.
Preferably said hydroxy functional acrylic copolymers are provided wherein said reaction product of said cinnamic acid ester based macromonomers and acrylic/ vinylic monomers enabling said hydroxy functional acrylic copolymers have 50-75 % non-volatile matter, and, comprises cinnamic acid ester macromonomer at 10-20% wt., vinyl monomers including styrene (10-20 wt.%), butyl acrylate (10-20 wt.%), methyl methacrylate (5-15 wt.%) favouring said hydroxyl value of 50-150 (mg KOH/ gm) and acid value of 1-5 mg KOH/gm.
According to another preferred aspect of the present invention there is provided said hydroxy functional acrylic copolymers wherein said cinnamic acid ester based macromonomers comprise cinnamic acid and polyol/s including Trimethylol propane, Propylene Glycol, 2-Methyl-1,3-propanediol (MP diol glycol), diethylene glycol, neopentyl glycol in 1:1 molar ratio enabling said cinnamic acid ester based macromonomer having sparkling clarity and hydroxyl value 200-600 mg KOH/gm adapted for reactivity selectively with said vinyl, acrylic monomers to result in said hydroxy functional acrylic copolymers (B) with desired hydroxyl value of 50-150 (mg KOH/ gm).
Preferably said Hydroxy functional acrylic copolymers are provided that are adapted to provide curable coating formulations including:
ambient temperature curable two component clear coating formulations in presence of aliphatic, cycloaliphatic and aromatic polyisocyanate crosslinkers which when applied on substrates including mild steel panel showed high gloss, gloss retention and good mechanical properties including scratch hardness, flexibility, impact resistance and excellent cross-cut adhesion after 48 h of air drying; and
single component stoving finishes/formulation with amino resins crosslinkers including urea formaldehyde resin and melamine formaldehyde resins also showing similar gloss and mechanical properties.
According to another aspect of the present invention there is provided a process of manufacturing of said hydroxy functional acrylic copolymers comprising the steps of
(i) providing cinnamic acid ester based macromonomers (A); and
(ii) reacting said cinnamic acid ester based macromonomers selectively with vinylic, acrylic monomers including styrene, Methyl methacrylate, butyl acrylate to achieve therefrom Hydroxy functional acrylic copolymers (B) having said hydroxyl value of 50-150 (mg KOH/gm) adapted for curing with crosslinkers favouring single or two component coating formulations.

Preferably in said process of manufacturing hydroxy functional acrylic copolymers wherein said step (i) comprises reacting cinnamic acid, polyol/s including Trimethylol propane, Propylene Glycol, 2-Methyl-1,3-propanediol (MP diol glycol), diethylene glycol, neopentyl glycol in 1:1 molar ratio under inert gas sparging and in the presence of catalyst including Dibutyl Tin Oxide at 160-170°C for 1 h followed by increasing the reaction temperature to 170 to 210oC in 4-5 h and carrying out the reaction until final acid value of the reaction mass reaches to 1-5 mg KOH/gm followed by mixing solvents including Xylene as azeotropic solvent in the aforesaid esterification reaction and obtaining therefrom cinnamic acid ester based macromonomers at 80-90% non-volatile matter having hydroxyl value 200-600 mg KOH/gm.
According to another preferred aspect of the process of manufacturing said hydroxy functional acrylic copolymers wherein said step (ii) comprises reacting cinnamic acid ester macromonomer (10-20% wt) obtained from step (i) above with vinyl/acrylic monomers including 10-20 wt.% styrene, 5-15 wt.% methyl methacrylate, 10-20 wt. % butyl acrylate along with initiator from a separate vessel through peristaltic pump in 3-4 h duration in presence of solvents while maintaining reaction temperature of 110-145°C, followed by digesting at same said temperature for 1-3 h for complete monomer conversion to achieve Hydroxy functional acrylic copolymers at 50-75 % non-volatile matter having said hydroxyl value of 50-150 (mg KOH/ gm).
Preferably in said process of manufacturing hydroxy functional acrylic copolymers wherein said complete monomer conversion in step (ii) is monitored by constancy of viscosity measurements of the reaction mass at 25°C on Gardner scale and results out of completely converted non-volatile content wherein said viscosity varying with solid content is in the range of U-Z2 at 25°C on Gardner scale for solids content of 50-60% and Z4-Z7 at 25°C on Gardner scale for solids content of 65-70% respectively.
More preferably in said process of manufacturing hydroxy functional acrylic copolymers wherein said solvents of reaction include aliphatic/aromatic hydrocarbons, ketones, esters, glycol ether esters or mixtures thereof free of active hydrogen.
According to another aspect of the present invention there is provided coating formulations as curable coating formulations comprising of
(I) said hydroxy functional acrylic copolymers; and
(II) (a) polyisocyanate crosslinkers selected from aliphatic, cycloaliphatic and aromatic isocyanates at hydroxyl (OH) functional acrylic copolymers and polyisocyanate (NCO) equivalent of OH:NCO in the range of 1.00:0.50 to 1.00:1.10 adapted for ambient temperature curable two component clear coating formulations;
(II) (b) amino resin crosslinkers together with said hydroxyl (OH) functional acrylic copolymers taken in the range of 75-90% on solids and said amino resin selected from urea formaldehyde resin, melamine formaldehyde taken in the range of 10-25% on solids adapted for single component coating/stoving formulations suitable for baking at elevated temperature of 100-140°C for 15-45 minutes;
which when applied on substrates including mild steel panel showed high gloss and good mechanical properties including scratch hardness of (>1.5 kg) and excellent cross-cut adhesion after 48 h of curing.
Advantageously, said coating formulations as curable coating formulations are provided wherein said ambient temperature curable two component clear coating formulations passes flexibility and impact resistance test, shows resistance of coating to scratch hardness when tests were conducted after 48 h and 7 days, also displaying cross cut adhesion at 5B levels and gloss of 90-100 @ 60° Gloss Head with more than 80% retention of gloss after 1000 hrs UV exposure; and
wherein said amino resin crosslinker based single component coating/stoving formulations also passes flexibility, impact resistance, scratch hardness, also displaying cross cut adhesion at 5B levels and higher gloss levels of 95-100 @ 60° Gloss Head.
Detailed description of the invention
As discussed hereinbefore, the present invention provides for hydroxy functional acrylic copolymers and coating formulations thereof comprising reaction product of cinnamic acid ester based macromonomers and acrylic/vinylic monomers wherein hydroxyl functionality of said acrylic copolymers are solely governed by said cinnamic acid ester macromonomers, which in turn is a reaction product of cinnamic acid with various polyols including Trimethylol propane, Propylene Glycol, 2-Methyl-1,3-propanediol (MP diol glycol), diethylene glycol, neopentyl glycol. Such cinnamic acid ester based macromonomer with free hydroxyl groups in turn generate hydroxy functional acrylic copolymers, based on reaction with selectively acrylic, vinylic monomers, which hydroxy functional acrylic copolymers enable similar gloss and mechanical properties even when free of conventional hydroxy functional acrylic monomers.
The approach of the present invention, in one of its aspects is to provide for said hydroxy functional acrylic copolymers and coating formulations thereof wherein hydroxyl functionality is solely obtained of cinnamic acid ester based macromonomer that is a reaction product of Cinnamic acid with varied polyols including Trimethylol propane, diethylene glycol, neopentyl glycol and the like thereby forming cinnamic acid ester with free hydroxyl groups as a macromonomer, adapted for further reactivity with selectively acrylic, vinyl monomers to attain said hydroxy functional acrylic copolymers.
In an aspect of the present invention such hydroxy functional cinnamic acid ester based macromonomer has been involved as one of the monomer alongwith selectively other vinylic, acrylic monomers including styrene, Methyl methacrylate, butyl acrylate in presence of suitable initiators like tertiary butyl perbenzoate, di-tert butyl peroxide, di-tert amyl peroxide etc. in suitable solvent medium including methoxy propyl acetate, butyl acetate, xylene, therefore directed to completely eliminate the need of hydroxy functional acrylic monomers like hydroxy ethyl methacrylate, hydroxy ethyl acrylate and the like while providing similar kind of gloss and mechanical properties.
Also importantly, since cinnamic acid ester based macromonomers have certain free carboxylic functionality, which is the reason why it also eliminates the need of involving methacrylic acid to attain said hydroxy functional acrylic copolymers, which methacrylic acid are otherwise used in standard acrylic copolymers to improve adhesion as well as to catalyze reaction with polyisocyanate as well as amino resin crosslinkers.
The said acrylic copolymers are uniquely designed with hydroxyl value of 50-150 (mg KOH/ gm) obtained from hydroxy functional cinnamic acid esters. The selection of acrylic monomers and their ratios with incorporation of hydroxy functional cinnamic acid ester provided required hydroxylic and carboxylic functionality to the resin into the resin backbone.
In the present invention, cinnamic acid ester based macromonomer is synthesized with polyol in 1:1 molar ratio in presence of catalyst and solvent to form macromonomer (hydroxyl value: 200-600 mg KOH/gm). Macromonomer is further grafted with other selective vinyl, acrylic monomers in presence of suitable initiator and solvent medium to get hydroxy functional acrylic copolymer solution.
In the present invention, the hydroxy functional acrylic copolymer is designed at 50-75 % non-volatile matter with hydroxyl value of preferably 80-125 (mg KOH/ gm). Said hydroxy functional acrylic copolymers thus obtained are cured with variety of aliphatic and aromatic polyisocyanate crosslinkers in a two-component polyurethane system.
The ambient temperature curing clear coating obtained from aforesaid system were applied on mild steel panel. The panels showed high gloss and good mechanical properties i.e. Scratch hardness of (>1.5 kg) and excellent cross-cut adhesion after 48 h of air drying.
Such hydroxy functional acrylic copolymers have been designed to make them ideally suitable for high performance 2K polyurethane coating systems with polyisocyanate crosslinkers. The designed hydroxy functional acrylic copolymers also finds use in single component stoving finishes with amino resins crosslinkers like urea formaldehyde resin and melamine formaldehyde resins.
Thus, the present invention provides an alternative route to synthesize hydroxy functional acrylic copolymers involving cinnamic acid ester based macromonomers. The macromonomers of cinnamic acid based on a range of polyols provides design latitude to create number of hydroxy functional acrylic copolymers with varying molecular structure and hydroxyl value.
The synthesis of cinnamic acid ester macromonomer and its incorporation into acrylic copolymer resin involves two steps:
Step 1 involves synthesis of cinnamic acid ester based macromonomer via condensation reaction between cinnamic acid and one or mixture of polyols. Reactants are charged into a four-necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and dean Stark assembly and is heated to temperature of about 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210oC in 4-5 h. The reaction between cinnamic acid and polyol is carried out till the final acid value of the reaction mass reaches to 1-5 mg KOH/gm. Mix Xylene is used as azeotropic solvent in the aforesaid esterification reaction. The percent nonvolatile matter of the Cinnamic acid ester macromonomer ranges from 80-90%.
Step 2 involves synthesis of hydroxy functional acrylic copolymer wherein the above synthesized cinnamic acid ester macromonomer is incorporated. The purpose of incorporating macromonomer is to provide hydroxyl functionality to the acrylic copolymers. Such hydroxy functional acrylic copolymers with free hydroxyl functionalities are further reacted with either suitable polyisocyanates to form polyurethane coatings or stoving finishes with suitable amino resin crosslinkers. Polyurethane coatings obtained from the hydroxy functional acrylic copolymer of the present invention provide exceptional mechanical and chemical resistance properties coupled with weathering and gloss retention.
The conventional process of incorporating hydroxy functionality includes use of monomers like hydroxyl ethyl methacrylate, hydroxy ethyl acrylate, hydroxy propyl methacrylate and the like, whereby the current invention offers alternative to these conventional monomers with scope to use wide range of hydroxy functional cinnamic acid ester based macromonomers. In the present invention, synthesis of hydroxy functional acrylic copolymers are carried out via free radical addition polymerization in presence of peroxide initiators through vinylic double bond present in hydroxy functional cinnamic acid ester and vinylic/acrylic monomers like styrene, methyl methacrylate, butyl acrylate etc.
The process involves selecting monomer combinations at varying concentrations such as styrene (10-20%), butyl acrylate (10-20%), methyl methacrylate (5-15%) etc with hydroxy functional cinnamic acid ester based macromonomer to produce range of acrylic copolymers at varying hydroxyl values.
During the processing of acrylic copolymers of the present invention, 50-60% cinnamic acid ester macromonomer was mixed with solvent in a four necked reaction flask/kettle and heated to achieve temperature of 110-145°C. The monomer mixture selectively acrylic, vinylic monomer mixture was prepared in a separate vessel along with initiator and added to the reaction kettle through peristaltic pump in 3-4 h duration while maintaining reaction temperature of 110-145°C and further digested at same temperature for 1-3 h for complete monomer conversion. During the acrylic copolymer synthesis, reaction was monitored by testing viscosity of the reaction mass at 25°C on Gardner scale and conversion of monomer through nonvolatile content. The reaction is carried out till constant viscosity and complete nonvolatile conversion of monomers is achieved.
While processing acrylic copolymers at higher nonvolatile content of > 60% using above reaction sequence i.e. taking cinnamic acid ester macromonomer with solvent in reaction vessel, it was surprisingly observed that it provided very high molecular weight copolymers and few of the experiments led to gelation. Therefore, in order to achieve copolymer at higher solids with low viscosity, an alternative processing method was designed wherein the cinnamic acid ester macromonomer was mixed with other monomers and initiator rather than taking it in to the rection vessel with the solvent. Such monomer mixture was then charged slowly in 3-4 h in the reaction vessel having preheated solvent at batch temperature of 110-145°C. It was found that the above processing sequence provided complete monomer conversion as determined through nonvolatile content and a stable viscosity.
The final hydroxy functional acrylic copolymers synthesized has hydroxy value ranging from 50-150 mg KOH/gm and is cured with various polyisocyanates to form two component polyurethane coatings. Preferred solvents to achieve desired consistency of the coating compositions are xylene, butyl acetate, methoxy propyl acetate or their combinations for two component polyurethane coating compositions.
Also, the solvents selected must be free from active hydrogen compounds like alcohols, phenols, amines which are reactive with polyisocyanate as being the crosslinker in 2K coating systems. Therefore, solvents to maintain the desired consistency of hydroxy functional acrylic polymers are selected from any of the aliphatic/aromatic hydrocarbons, ketones, esters, glycol ether esters or mixtures thereof, which also does not react with polyisocyanate crosslinkers in 2K coating systems/ formulations.
The said hydroxy functional acrylic copolymers of the present invention also provided single component stoving coating compositions with amino resins as crosslinkers. Single pack stoving coating compositions formulated with amino resin crosslinkers may contain alcoholic solvents like n-butanol, iso butanol, isopropanol and the like as well unlike in polyurethane coatings.
Such Coating compositions are suitable for application by conventional application systems such as brushing, roller, spraying, flow, dipping, and the like. Cold rolled mild steel (CRMS) test panels were spray coated with the coating compositions prepared using acrylic copolymers of the present invention with suitable crosslinker and were allowed to cure for 7 days in respect of 2K polyurethane coating systems and 24 h in case of single pack stoving coating compositions. The panels were subjected to tests like flexibility, adhesion, impact resistance, scratch hardness, and accelerated weathering resistance. The flexibility of the coatings is tested by conducting a Mandrel bend test (ASTM D522). The scratch hardness of the coating is tested using Sheen make automatic scratch tester Ref. No. 705 with 1mm tungsten carbide tip. The 1 mm cross-cut adhesion test is carried out according to ASTM D 3359. Impact Resistance of coating are tested using Falling-Ball Method (65±0.2 cm height × 15.9± 0.08 mm diameter × 908±1 gm load). The gloss and gloss retention of the coatings is tested by exposing the panels under QUV-B for at least 1000 h and is tested according to ASTM G 53. The gloss values of the exposed films are monitored periodically.
The following examples illustrate certain embodiments and aspects of the present invention as best methods and the scope of the present invention is workable in the whole range unless otherwise specified and hence the working examples should not be construed to limit the scope of the present invention. All parts and percentages are by weight basis unless otherwise stated.

EXAMPLE 1
Cinnamic acid ester based hydroxyl functional macromonomer is prepared by charging the following constituents into a four-necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.
Formulation:
Ingredients Parts by Weight
SN (A) Cinnamic acid ester
1 Cinnamic Acid 48.30
2 Refined Glycerine 30.02
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 2.05
5 Mix Xylene (II) 19.61
Total 100

(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate 3.92
2 Mix Xylene 38.34
3 Cinnamic acid ester (A) 13.70
4 Methyl Methacrylate monomer 7.20
5 Styrene monomer 22.00
6 Butyl acrylate monomer 13.90
7 Tertiary butyl per benzoate 0.94

Total 100

Process:
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and heated to temperature of 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210°C in 4-5 h until an acid number of less than 5 mg KOH/gm is obtained. The reaction mixture is cooled down to 120°C and diluted to 80% non-volatile matter (NVM) with Mix Xylene. Acid Value = 3.11 mg KOH/gm, %NVM @ 120°C/60 mins = 80.22. Hydroxyl value = 505 mg KOH/gm

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate, Mix Xylene and Cinnamic Acid ester (Part A) are charged into reactor and heated to the temperature of about 138-140 °C. Reactants 4-7 are mixed in a monomer vessel and charged into reactor via peristaltic pump in a period of 1-2 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. The batch led to gelation due to high molecular weight build up.
EXAMPLE 2
Cinnamic acid-based hydroxyl functional macromonomer is prepared by charging the following constituents into a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.
Formulation:
Ingredients Parts by Weight
SN (A) Cinnamic acid ester
1 Cinnamic Acid 45.10
2 Tri Methylol Propane 40.84
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 4.52
5 Mix Xylene (II) 9.52
Total 100

(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate 43.60
2 Cinnamic Acid ester 13.95
3 Methyl Methacrylate monomer 10.49
4 Styrene monomer 15.31
5 Butyl acrylate monomer 15.55
6 Tertiary butyl per benzoate 1.10

Total 100

Process :
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and is heated to temperature of 160-170 °C for 1 h and thereafter reaction temperature is increased from 170 to 210 oC in 4-5 h until an acid number less than 5 mg KOH/gm is obtained. The reaction mixture is cooled down to 120°C and diluted to 90% non-volatile matter (NVM) with Mix Xylene. Acid Value = 2.33 mg KOH/gm, %NVM @ 120°C/60 mins = 91.38. Hydroxyl value = 431 mg KOH/gm

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate Cinnamic Acid Based Macromonomer (Part A) and is charged into reactor and heated to the temperature of about 138-140 °C. Reactants 3-6 are mixed in a monomer vessel and charged into reactor via peristaltic pump in duration of 1-2 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. Physical properties of cinnamic acid based acrylic copolymer resin (part B) are: Gardner viscosity @25 deg C W-X, Acid Value = 1.92 mg KOH/gm, Color on Gardener scale = 1-2 & %NVM-150°C/30 mins = 54.91, Hydroxyl Value= 90 mg KOH/gm.

EXAMPLE 3
Cinnamic acid-based hydroxyl functional macromonomer is prepared by charging the following constituents into a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.
Formulation:

Ingredients Parts by Weight
SN (A) Cinnamic acid ester
1 Cinnamic Acid 45.10
2 Tri Methylol Propane 40.84
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 4.52
5 Mix Xylene (II) 9.52
Total 100

(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate
43.05
2 Cinnamic Acid ester (Part A) 12.35
3 Methyl Methacrylate monomer 10.54
4 Styrene monomer 17.525
5 Butyl acrylate monomer 15.435
6 Tertiary butyl per benzoate 1.1

Total 100

Process:
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and are heated to temperature of 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210oC in 4-5 h until an acid number less than 5 mg KOH/gm is obtained. The reaction mixture is cooled down to 120 °C and diluted to 90% non-volatile matter (NVM) with Mix Xylene. Acid Value = 2.33 mg KOH/gm, %NVM @ 120°C/60 mins = 91.38. Hydroxyl value = 431 mg KOH/gm

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate Cinnamic Acid Based Macromonomer (Part A) are charged into reactor and heated to the temperature of about 138-140°C. Reactants 3-6 are mixed in a monomer vessel and charged into reactor via peristaltic pump in duration of 3-4 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. Physical properties of cinnamic acid based acrylic copolymer resin (part B) are: Gardner viscosity @25°C = W+, Acid Value = 1.77 mg KOH/gm, Color on Gardener scale = 1-2 & %NVM @ 150°C/30 mins = 54.23, Hydroxyl Value= 80 mg KOH/gm

EXAMPLE 4
Cinnamic acid-based hydroxyl functional macromonomer is prepared by charging the following constituents into a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.
Formulation:
Ingredients Parts by Weight
SN (A)Cinnamic acid ester
1 Cinnamic Acid 45.10
2 Tri Methylol Propane 40.84
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 4.52
5 Mix Xylene (II) 9.52
Total 100

(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate 41.71
2 Cinnamic Acid ester (Part A) 15.25
3 Methyl Methacrylate monomer 10.54
4 Styrene monomer 16.55
5 Butyl acrylate monomer 14.85
6 Tertiary butyl per benzoate 1.1

Total 100

Process:
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and heated to a temperature of 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210oC in 4-5 h until an acid number of less than 5mg KOH/gm is obtained. The reaction mixture is cooled down to 120°C and diluted to 90% non-volatile matter (NVM) with Mix Xylene. Acid Value = 2.33 mg KOH/gm, %NVM @ 120°C/60 mins = 91.38. Hydroxyl value = 431 mg KOH/gm

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate Cinnamic Acid Based Macromonomer (Part A) is charged into reactor and heated to the temperature of about 138-140°C. Reactants 3-6 are mixed in a monomer vessel and charged into the reactor via peristaltic pump in a period of 3-4 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. Physical properties of cinnamic acid based acrylic copolymer resin (part B) are: Gardner viscosity @25°C = Z+, Acid Value = 1.61 mg KOH/gm, Color on Gardener scale = 1-2 & %NVM @ 150°C/30 mins = 54.88, Hydroxyl Value= 100 mg KOH/gm

EXAMPLE 5
Cinnamic acid-based hydroxyl functional macromonomer is prepared by charging the following constituents into a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.

Formulation:
Ingredients Parts by Weight
SN (A)Cinnamic acid ester
1 Cinnamic Acid 45.10
2 Tri Methylol Propane 40.84
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 4.52
5 Mix Xylene (II) 9.52
Total 100


(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate 39.00
2 Cinnamic Acid ester (Part A) 14.9
3 Methyl Methacrylate monomer 11.30
4 Styrene monomer 17.10
5 Butyl acrylate monomer 16.60
6 Tertiary butyl per benzoate 1.10

Total 100

Process :
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and is heated to temperature of 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210 oC in 4-5 h until an acid number less than 5 mg KOH/gm is obtained. The reaction mixture is cooled down to 120 °C and diluted to 90% non-volatile matter (NVM) with Mix Xylene. Acid Value = 2.33 mg KOH/gm, %NVM-120°C/60 mins = 91.38. Hydroxyl value = 431 mg KOH/gm

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate Cinnamic Acid Based Macromonomer (Part A) is charged into reactor and heated to the temperature of about 138-140 °C. Reactants 3-6 are mixed in a monomer vessel and charged into reactor via peristaltic pump in duration of 3-4 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. Physical properties of cinnamic acid based acrylic copolymer resin (part B) are:- Gardner viscosity @25 deg C= Y-Z, Acid Value = 2.78 mg KOH/gm, Color on Gardener scale = 0-1 & %NVM @150°C/30 mins = 59.76, Hydroxyl Value= 90 mg KOH/gm

EXAMPLE 6
Cinnamic acid-based hydroxyl functional macromonomer is prepared by charging the following constituents into a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.
Formulation :
Ingredients Parts by Weight
SN (A)Cinnamic acid ester
1 Cinnamic Acid 45.10
2 Tri Methylol Propane 40.84
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 4.52
5 Mix Xylene (II) 9.52
Total 100

(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate 28.45
2 Cinnamic Acid ester (Part A) 14.75
3 Methyl Methacrylate monomer 13.10
4 Styrene monomer 19.80
5 Butyl acrylate monomer 19.80
6 Tertiary butyl per benzoate 4.10

Total 100

Process:
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and is heated to temperature of 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210oC in 4-5 h until an acid number less than 5 mg KOH/g is obtained. The reaction mixture is cooled down to 120°C and diluted to 90% non-volatile matter (NVM) with Mix Xylene. Acid Value = 2.33 mg KOH/gm, %NVM @120°C/60 mins = 91.38. Hydroxyl value = 431 mg KOH/gm

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate is charged into the reactor and heated to the temperature of about 138-140°C. Reactants 2-6 are mixed in a monomer vessel and charged into the reactor via peristaltic pump in a period of 3-4 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. Physical properties of cinnamic acid based acrylic copolymer resin (part B) are:- Gardner viscosity @25 deg C = Z6+, Acid Value = 3.21 mg KOH/g, Color on Gardener = 0-1 & %NVM @150°C/30 mins = 69.67, Hydroxyl Value= 80 mg KOH/gm.
EXAMPLE 7
Cinnamic acid-based hydroxyl functional macromonomer is prepared by charging the following constituents into a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.
Formulation :
Ingredients Parts by Weight
SN (A)Cinnamic acid ester
1 Cinnamic Acid 53.45
2 MP Diol Glycol 32.50
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 4.50
5 Mix Xylene (II) 9.53
Total 100

(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate 27.8
2 Cinnamic Acid ester (Part A) 20
3 Methyl Methacrylate monomer 11.90
4 Methacrylic acid 0.30
5 Styrene monomer 17.85
6 Butyl acrylate monomer 17.85
7 Tertiary butyl per benzoate 4.3

Total 100
Process :
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and heated to temperature of 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210oC in 4-5 h until an acid number less than 5 mg KOH/gm is obtained. The reaction mixture is cooled down to 120°C and diluted to 90% non-volatile matter (NVM) with Mix Xylene. Acid Value = 1.02 mg KOH/gm, %NVM @ 120°C/60 mins = 89.11. Hydroxyl value = 225 mg KOH/gm

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate is charged into the reactor and heated to the temperature of about 138-140 °C. Reactants 2-7 are mixed in a monomer vessel and charged into reactor via peristaltic pump for a duration of 3-4 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. Physical properties of cinnamic acid based acrylic copolymer resin (part B) are : Gardner viscosity @25°C = Z6, Acid Value = 2.89 mg KOH/gm, Color on Gardener scale = 0-1 & %NVM-@ 150°C/30 mins = 69.60, Hydroxyl Value= 70 mg KOH/gm

EXAMPLE 8
Cinnamic acid-based hydroxyl functional macromonomer is prepared by charging the following constituents into a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly.
Formulation:
Ingredients Parts by Weight
SN (A) Cinnamic acid ester
1 Cinnamic Acid 56.79
2 Propylene Glycol 29.64
3 Dibutyl Tin Oxide 0.02
4 Mix Xylene (I) 4.50
5 Mix Xylene (II) 9.05
Total 100

(B) Acrylic Copolymer
1 Propylene glycol methyl ether acetate 28.00
2 Cinnamic Acid ester (Part A) 18.75
3 Methyl Methacrylate monomer 10.80
4 Methacrylic acid 0.30
5 Styrene monomer 19.50
6 Butyl acrylate monomer 18.25
7 Tertiary butyl per benzoate 4.4

Total 100

Process:
Part A: Cinnamic Acid Ester
Reactants 1-4 are charged into the reactor and heated to temperature of 160-170°C for 1 h and thereafter reaction temperature is increased from 170 to 210oC in 4-5 h until an acid number less than 5 mg KOH/gm is obtained. The reaction mixture is cooled down to 120°C and diluted to 90% non-volatile matter (NVM) with Mix Xylene. Acid Value = 4.01 mg KOH/gm, %NVM @120°C/60 mins = 88.85. Hydroxyl value = 260 mg KOH/gm.

Part B: Acrylic Copolymer
Propylene glycol methyl ether acetate is charged into the reactor and heated to the temperature of about 138-140°C. Reactants 2-7 are mixed in a monomer vessel and charged into reactor via peristaltic pump for a duration of 3-4 h. Reaction is continued till constant viscosity and complete nonvolatile matter conversion is obtained. Physical properties of cinnamic acid based acrylic copolymer resin (part B) are: Gardner viscosity @25°C = Z6, Acid Value = 3.76 mg KOH/g, Color on Gardener scale = 0-1 & %NVM @150°C/30 mins = 69.81, Hydroxyl Value= 65 mg KOH/gm.

Table for Component A: cinnamic acid ester based macromonomers
Serial No Physical parameters Examples 2 to 6 Example 7 Example 8
Example 1

1 Color 1-2 7-8 11-10 12-13
2 Clarity Haze Clear Clear Clear
3 Acid value (mg KOH/gm) 3.11 2.33 1.02 3.21
4 % NVM (120 Deg C/ 60 mins) 80.22 91.38 89.11 89.01
5 Hydroxyl Value (mg KOH/gm) 505 431 225 263

Table for resulting Component B: Final Hydroxyl Functional Acrylic Copolymers
Serial No Physical parameters Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8
1 Color Not applicable, as gel formation takes place 1-2 1-2 1-2 0-1 0-1 1-2 3-4
2 Clarity Clear Clear Clear Clear Clear Clear Clear
3 Acid value (mg KOH/gm) 1.92 1.77 1.61 2.78 3.21 2.89 3.76
4 % NVM (150 Deg C/ 30 mins) 54.91 54.23 54.88 59.76 69.67 69.6 69.81
5 Gardner viscosity @ 25?C W-X W+ Z+ Y-Z Z6+ Z6 Z6-Z7
6 Hydroxyl Value (mg KOH /gm) 90 80 100 90 80 70 65

Polyurethane coating compositions:
Two pack polyurethane coating compositions comprise of Acrylic Copolymer from examples 2-8, Hexamethylene di-isocyanate (HDI) trimer as crosslinker and suitable solvents. The coating compositions are shown in Table 1. The acrylic copolymers were cured with HDI trimer while keeping hydroxyl (OH) and Isocyanate (NCO) equivalents of 1:1. The coating compositions were applied on sanded mild steel panels (1.6 × 70 × 150 mm) by spray application and left to stand at ambient temperature (min 10°C, max 35°C) and humidity (60-70%). A 45–50-micron dry film thickness (DFT) of coating is obtained in 1 coat. Then after seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and QUV resistance. Test results of the coatings are shown in Tables 2a, 2b and 2c.
Table 1: Two Pack Polyurethane coating compositions
Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8

OH:NCO Equivalent 1:1 1:1 1:1 1:1 1:1 1:1 1:1
PBW PBW PBW PBW PBW PBW PBW
Acrylic copolymer 67.15 68.11 66.22 66.39 66.05 67.22 67.86
HDI Trimer 12.69 11.44 13.9 14.24 14.12 12.61 11.70
Mix Xylene: Butyl Acetate (60:40) 20.16 20.45 19.88 19.37 19.83 20.17 20.44
Total 100 100 100 100 100 100 100

Table 2a: Test Results of Two Pack Polyurethane coating composition
Coating compositions with resin from Example 2 Example 3 Example 4
DFT (microns) 50-60 50-60 50-60
Surface dry time in minutes (IS 101) 45 45 30
Tack free time in hours (IS 101) 3 2 3.5
Hard dry time in hours (IS 101) 8-10 8-10 8-10
Scratch hardness after 48 hours (gm) (IS 101) 1000 1600 1600
Scratch hardness after 7 days (gm) (IS 101) 1100 1800 1800
Flexibility ¼ inch mandrel (ASTM D 522) Passes Passes Passes
Impact resistance (1 Kg front & reverse) ISO 6172 Passes Passes Passes
Cross cut adhesion (ASTM D 3359) 5B 5B 5B
Gloss @ 60° Gloss Head 94-95 90-91 92-93

Table 2b: Test Results of Two Pack Polyurethane coating composition
Coating compositions with resin from Example 5 Example 6 Example 7 Example 8

DFT (microns) 45-50 45-50 45-50 45-50
Surface dry time in minutes (IS 101) 30 40 40 30
Tack free time in hours (IS 101) 3.5 3.5 4 4
Hard dry time in hours (IS 101) 8 8 8 8
Scratch hardness after 48 hours (gm) (IS 101) 1100 1400 1100 1400
Scratch hardness after 7 days (gm) (IS 101) 1100 1700 1600 1800
Flexibility ¼ inch mandrel (ASTM D 522) Passes Passes Passes Passes
Impact resistance (1 Kg front & reverse) ISO 6172 Passes Passes Passes Passes
Cross cut adhesion (ASTM D 3359) 5B 5B 5B 5B
Gloss @ 60° Gloss Head 95-96 94-95 98-99 96-97

Table 2c: % Gloss Retention, QUV B 313 Exposure
Example Gloss (0 hours) Gloss (1000 hours) %Gloss Retention after 1000 hours
5 95 80 84
6 94 85 90
7 99 86 86
8 98 80 81

Single component stoving coating composition with melamine formaldehyde resin:
The coating composition is shown in table 3. The acrylic copolymer and melamine formaldehyde resin ratio is adjusted to 75:25 on solid basis. The coating composition is applied on sanded mild steel panel (1.6 × 70 × 150 mm) by brush and baked at 120 deg C for 30 mins. A 25–35-micron dry film thickness of coating is obtained in 1 coat. These test panels were subjected to various performance properties like flexibility, adhesion, scratch hardness, impact resistance and gloss. Test results of coatings are shown in Table 3a.
Table 3 : Acrylic Copolymer-Melamine Formaldehyde resin coating Composition
Example 4 Example 5 Example 6
PBW PBW PBW
Acrylic Copolymer 67.1 55.0 41.2
Melamine Formaldehyde 21.0 18.7 16.0
Mix Xylene 8.3 18.4 29.9
Iso-Butanol 3.6 7.9 12.9
Total 100 100 100

Table 3a: Test Results of Acrylic Copolymer Cross linked with Melamine Formaldehyde
Coating compositions with resin from Example 4 Example 5 Example 6
DFT (microns) 35-45 35-45 35-45
Scratch hardness (gm) (IS 101) 1200 1400 1500
Flexibility ¼ inch mandrel (ASTM D 522) Passes Passes Passes
Impact resistance (1 Kg front & reverse) ISO 6172 Fails Passes Passes
Cross cut adhesion (ASTM D 3359) 4B 5B 5B
Gloss @ 60° Gloss Head 98-99 97-98 99-100

Advantageously, it is thus possible by way of the present invention to provide for said hydroxy functional acrylic copolymers and coating formulations thereof wherein hydroxyl functionality is solely obtained of cinnamic acid based macromonomer and thus not only eliminates the requirement of conventional hydroxy functional monomers to achieve similar kind of gloss and mechanical properties, but is also able to eliminate the need of methacrylic acid as otherwise used in standard acrylic copolymers to not only improve adhesion but also ably catalyzing reaction with polyisocyanate as well as amino resin crosslinkers to lead to effective 2K polyurethane coating systems and single component stoving finishes therefrom.
,CLAIMS:We Claim:
1. Hydroxy functional acrylic copolymers comprising reaction product of cinnamic acid ester based macromonomers (A), and, selectively acrylic, vinylic monomers enabling said hydroxy functional acrylic copolymers (B) having hydroxyl value of 50-150 (mg KOH/ gm) that is adapted for curing with crosslinkers favouring single or two component coating formulations.
2. The Hydroxy functional acrylic copolymers as claimed in claim 1 wherein said hydroxyl functionality of said hydroxy functional acrylic copolymers are solely sourced from said cinnamic acid ester macromonomers having hydroxyl value of 200-600 mg KOH/gm and acid functionality in the range of 1-5 mg KOH/gm even when free of methacrylic acid monomer adapted to enhance adhesion of coating formulations upon curing including ambient temperature curing in temperature range of -5-50?C.
3. The Hydroxy functional acrylic copolymers as claimed in claims 1 and 2 wherein said reaction product of said cinnamic acid ester based macromonomers and acrylic/ vinylic monomers enabling said hydroxy functional acrylic copolymers have 50-75 % non-volatile matter, and, comprises cinnamic acid ester macromonomer at 10-20% wt., vinyl monomers including styrene (10-20 wt.%), butyl acrylate (10-20 wt.%), methyl methacrylate (5-15 wt.%) favouring said hydroxyl value of 50-150 (mg KOH/ gm) and acid value of 1-5 mg KOH/gm.

4. The Hydroxy functional acrylic copolymers as claimed in claims 1-3 wherein said cinnamic acid ester based macromonomers comprise cinnamic acid and polyol/s including Trimethylol propane, Propylene Glycol, 2-Methyl-1,3-propanediol (MP diol glycol), diethylene glycol, neopentyl glycol in 1:1 molar ratio enabling said cinnamic acid ester based macromonomer having sparkling clarity and hydroxyl value 200-600 mg KOH/gm adapted for reactivity selectively with said vinyl, acrylic monomers to result in said hydroxy functional acrylic copolymers (B) with desired hydroxyl value of 50-150 (mg KOH/ gm).
5. The Hydroxy functional acrylic copolymers as claimed in claims 1-4 that are adapted to provide curable coating formulations including:
ambient temperature curable two component clear coating formulations in presence of aliphatic, cycloaliphatic and aromatic polyisocyanate crosslinkers which when applied on substrates including mild steel panel showed high gloss, gloss retention and good mechanical properties including scratch hardness, flexibility, impact resistance and excellent cross-cut adhesion after 48 h of air drying; and
single component stoving finishes/formulation with amino resins crosslinkers including urea formaldehyde resin and melamine formaldehyde resins also showing similar gloss and mechanical properties.
6. A process of manufacturing Hydroxy functional acrylic copolymers comprising the steps of
(i) providing cinnamic acid ester based macromonomers (A); and
(ii) reacting said cinnamic acid ester based macromonomers selectively with vinylic, acrylic monomers including styrene, Methyl methacrylate, butyl acrylate to achieve therefrom Hydroxy functional acrylic copolymers (B) having said hydroxyl value of 50-150 (mg KOH/gm) adapted for curing with crosslinkers favouring single or two component coating formulations.
7. The process of manufacturing Hydroxy functional acrylic copolymers as claimed in claim 6 wherein said step (i) comprises reacting cinnamic acid, polyol/s including Trimethylol propane, Propylene Glycol, 2-Methyl-1,3-propanediol (MP diol glycol), diethylene glycol, neopentyl glycol in 1:1 molar ratio under inert gas sparging and in the presence of catalyst including Dibutyl Tin Oxide at 160-170°C for 1 h followed by increasing the reaction temperature to 170 to 210oC in 4-5 h and carrying out the reaction until final acid value of the reaction mass reaches to 1-5 mg KOH/gm followed by mixing solvents including Xylene as azeotropic solvent in the aforesaid esterification reaction and obtaining therefrom cinnamic acid ester based macromonomers at 80-90% non-volatile matter having hydroxyl value 200-600 mg KOH/gm.
8. The process of manufacturing Hydroxy functional acrylic copolymers as claimed in claim 6 or 7 wherein said step (ii) comprises reacting cinnamic acid ester macromonomer (10-20% wt) obtained from step (i) above with vinyl/acrylic monomers including 10-20 wt.% styrene, 5-15 wt.% methyl methacrylate, 10-20 wt. % butyl acrylate along with initiator from a separate vessel through peristaltic pump in 3-4 h duration in presence of solvents while maintaining reaction temperature of 110-145°C, followed by digesting at same said temperature for 1-3 h for complete monomer conversion to achieve Hydroxy functional acrylic copolymers at 50-75 % non-volatile matter having said hydroxyl value of 50-150 (mg KOH/ gm).
9. The process of manufacturing Hydroxy functional acrylic copolymers as claimed in claim 6-8 wherein said complete monomer conversion in step (ii) is monitored by constancy of viscosity measurements of the reaction mass at 25°C on Gardner scale and results out of completely converted non-volatile content wherein said viscosity varying with solid content is in the range of U-Z2 at 25°C on Gardner scale for solids content of 50-60% and Z4-Z7 at 25°C on Gardner scale for solids content of 65-70% respectively.
10. The process of manufacturing Hydroxy functional acrylic copolymers as claimed in claims 6-9 wherein said solvents of reaction include aliphatic/aromatic hydrocarbons, ketones, esters, glycol ether esters or mixtures thereof free of active hydrogen.
11. Coating formulations as curable coating formulations comprising of
(I) hydroxy functional acrylic copolymers as claimed in claims 1-5; and
(II) (a) polyisocyanate crosslinkers selected from aliphatic, cycloaliphatic and aromatic isocyanates at hydroxyl (OH) functional acrylic copolymers and polyisocyanate (NCO) equivalent of OH:NCO in the range of 1.00:0.50 to 1.00:1.10 adapted for ambient temperature curable two component clear coating formulations;
(II) (b) amino resin crosslinkers together with said hydroxyl (OH) functional acrylic copolymers taken in the range of 75-90% on solids and said amino resin selected from urea formaldehyde resin, melamine formaldehyde taken in the range of 10-25% on solids adapted for single component coating/stoving formulations suitable for baking at elevated temperature of 100-140°C for 15-45 minutes;
which when applied on substrates including mild steel panel showed high gloss and good mechanical properties including scratch hardness of (>1.5 kg) and excellent cross-cut adhesion after 48 h of curing.
12. The coating formulations as curable coating formulations wherein said ambient temperature curable two component clear coating formulations passes flexibility and impact resistance test, shows resistance of coating to scratch hardness when tests were conducted after 48 h and 7 days, also displaying cross cut adhesion at 5B levels and gloss of 90-100 @ 60° Gloss Head with more than 80% retention of gloss after 1000 hrs UV exposure; and
wherein said amino resin crosslinker based single component coating/stoving formulations also passes flexibility, impact resistance, scratch hardness, also displaying cross cut adhesion at 5B levels and higher gloss levels of 95-100 @ 60° Gloss Head.

Dated this the 2nd day of January, 2024 Anjan Sen
Applicants Agent and Advocate
IN/PA-199