Description:FIELD OF THE INVENTION
The present invention provides for cardanol modified urethane alkyds and coating formulations thereof having excellent solubility in user friendly Mineral Turpentine Oil (MTO) comprising of aliphatic hydrocarbon as the major component. More particularly, single component coating formulations based on such alkyds are provided capable of quick drying characteristics at ambient temperature with exceptional coating performance in respect of gloss, mechanical properties, corrosion resistance and weathering.

BACKGROUND ART

Rusting of steel continues to have major economic impact on the global GDP and therefore prevention of Corrosion of mild steel holds the prime place for the common man and engineers considering its large consumption by the ever-increasing global population. In order to prevent such colossal losses, efforts are on from major coating manufacturers to create efficient and environmentally compliant methods to prevent corrosion of steel.

Alkyds and coatings obtained thereof continue to be the preferred choice in view of their ease of use and economy. Presently major consumption of alkyds is in the enamels and primers, but such conventional alkyd-based paints offer limited anti-corrosive performance. To improve the coating performance, composite system of primers and topcoats have been used. However, application of primer and topcoat involve material cost, application cost and time.

Designing Polymers for corrosion resistant coatings has been an area of keen interest for the scientists across the globe. Although there are number of polymers available in epoxy and polyurethane chemistry, most of the coatings based on these technologies are in 2 pack with limited pot life and employ strong oxygenated solvents. High cost and hazardous nature of the curing agents is another impediment towards the usage of 2K epoxy and PU coatings especially for non-industrial / domestic use. Cleaning of the application equipment and use of hazardous solvents having obnoxious odor also makes it difficult for the users.
Reference is invited to CN 104829849 that teaches alkyd phase inversion emulsion that is composed of soya oil acid 20-30, pentaerythritol 15-25, phthalic anhydride 30-40, reflux solvent 3-5, deionized water 40-50, compound emulsifiers A and B 3-5, oil-based drier (cobalt iso-octoate, etc.) 0.5-1.0, potassium hydroxide 0.5-1.0, and C9 solvent 3-5 parts, wherein the compound emulsifier A is obtained by esterification reaction of polyethylene glycol with reaction product of cardanol and maleic anhydride; and the compound emulsifier B is anionic emulsifier (sodium dodecyl benzene sulfonate). This emulsion coating is composed of the alkyd phase inversion emulsion 60-70, pigment and filler 10-20, rheology agent 2020 0.5-1.0, defoamer A-10 0.05-0.1, rheology agent 8W 1-1.5, and deionized water 10-25 parts wherein such alkyd phase inversion emulsion has extremely low VOC value; and the alkyd phase inversion emulsion coating has good chemical resistance, water resistance and salt mist resistance. This prior art teaches about synthesis of a water borne phase inversion alkyd emulsion comprising of soya oil alkyd in combination with oil-based driers, potassium hydroxide and deionized water. Emulsification of said alkyd is facilitated through cardanol modified ester emulsifier A obtained through esterification reaction of polyethylene glycol with a reaction product of Cardanol and maleic anhydride in combination with anionic emulsifier B (sodium dodecyl benzene sulfonate). This prior art does not teach about any solvent borne cardanol modified urethane alkyd wherein cardanol is incorporated into the alkyd backbone having sufficient hydroxyl groups which are partially reacted with aliphatic/ cycloaliphatic/ aromatic polyisocyanates and diluted in aliphatic and aromatic hydrocarbon solvents i.e mineral turpentine oil and xylene.
EVALUATION OF CARDANOL ACETATE AS A REACTIVE DILUENT FOR ALKYD COATINGS Njuku, F.W* , Mwangi, P.M1 andThiong’o, G. T1 Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62,000-00200, Nairobi, Kenya, International Journal of Advanced Research (2014), Volume 2, Issue 3, 928-941, is directed to alkyd resins that are viscous, tacky that are difficult to handle. Most often, these handling problems are overcome by dissolving the resins in organic solvents, which evaporate into the atmosphere as volatile organic compounds (VOC’s), giving rise to regulations (in many parts of the world as a way to reduce the environmental impacts). Cashew nut shells are normally burned to provide heat during processing of the nut. This practice ends up in production of dark thick smoke with particulate matter which pollutes the environment profoundly. This is mainly due to the presence of cashew nut shell liquid residue in the shells. Cashew nut shell liquid (CNSL) is not currently utilized in Kenya and the objective of this work was to develop reactive diluents from chemically modified CNSL products and evaluate their compatibility and suitability in alkyd coatings. Cardanol was isolated from decarboxylated CNSL using a combination of physical and chemical methods. The cardanol acetate was synthesized by treating cardanol with acetic anhydride and was also characterized by FT-IR and it showed the presence of the C=O stretch functional group characteristic of the ester and the absence of the OH group that was present in cardanol. Cardanol acetate and neat cardanol were tested as reactive diluents for alkyd resins in coating formulations. Cardanol acetate showed good properties, including low viscosity and good drying performance. Furthermore, a shortening of the drying time of about 25-35 % compared to conventional commercial products. Teaches about synthesis of cardanol acetate and its use as reactive diluent. The resultant Cardanol acetate is blended at 5-25% with long oil alkyds and is claimed to achieve reduction in volatile organic compounds by around 39% with similar or better drying performance, and hence is not directed to in-situ synthesis of cardanol modified urethane alkyd.
Making alkyd greener: Modified cardanol as bio-based reactive diluents for alkyd coating Haoran Wang, Cheng Zhang, Weixiu Zeng, Qixin Zhou, Progress in Organic Coatings, Volume 135, October 2019, Pages 281-290; is directed to bio-based coatings with lower volatile organic compound (VOC) emissions, wherein methacrylated cardanol (MACO) and triethoxysilane-functionalized cardanol (TSCO) were investigated as bio-based reactive diluents for formulating alkyd coatings as a substitute for volatile solvents. The viscosity of the representative alkyd resin was significantly reduced through the use of cardanol-based reactive diluents (over 84% diluent efficiency at 30 wt% loading). Both MACO and TSCO were able to participate in the crosslinked network of the alkyd coating as confirmed by the gel content and cross-link density of the cured coating films. Moreover, the cross-link density of the alkyd coating was significantly improved by using TSCO as the reactive diluent, leading to a significant enhancement in mechanical strength and solvent resistance of the alkyd coating, facilitating adoption of cardanol as a renewable building block in the coating industry in order to produce greener alkyd coatings
Anticorrosive properties of the epoxy–cardanol resin based paints L.K. Aggarwal *, P.C. Thapliyal, S.R. Karade Central Building Research Institute, Roorkee 247667, India, Progress in Organic Coatings, Volume 59, Issue 1, 2 April 2007, Pages 76-80 teaches an epoxy–cardanol resin that was developed using epichlorohydrin, bisphenol-A and cardanol, wherein it was found that epoxy–cardanol resin exhibits better properties as compared to epoxy resin in terms of increase in tensile strength, elongation, bond with steel and lowering of water vapour transmission of the film. Anticorrosive properties of epoxy–cardanol resin based paints are superior to that of the paints formulated with the unmodified epoxy resin. Micaceous iron oxide based paints in epoxy–cardanol resin showed the best performance followed by zinc phosphate based paints. It is concluded that the developed resin is a better binder media for the formulation of paints.

Polyfunctional compounds from cardanol 63 V. Madhusudban* and B. G. K. Murthy Indian Institute of Chemical Technology, Hyderabad-500 007 in Progress in Organic Coatings,Volume 20, Issue 1, 16 March 1992, Pages 63-71 discloses that chemical modification of the alkyl side-chain of cardanol can lead to the formation of polyfunctional compounds. Cardanol was reacted using maleic anhydride as a dienophile under various experimental conditions with products being obtained in up to 70% yield which were subsequently used for preparing water-soluble binders and modified alkyd resins.
Use of cardanol-based acrylate as reactive diluent in UV-curable castor oil based polyurethane acrylate resins Yun Hua, Qianqian Shanga, Jijun Tange, Cuina Wangf, Fei Zhangg , Puyou Jiaa, Guodong Fenga, Qiong Wuf, Chengguo Liua, Lihong Hu , Wen Leif, Yonghong Zhoua, Industrial Crops and products, 117 (2018) (295-302) discloses a biobased diluent, cardanyl acrylate (CA), synthesized from cardanol and used to modify a castor oil-based polyfunctional polyurethane acrylate (PUA) resin. The cardanol-based diluent showed good potential in the development of UV-curable coatings.
Cardanol: a Promising Building Block for Biobased Polymers and Additives; Kunal Wazarkar and Anagha Sabnis Department of Polymer and Surface Engineering, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga (E), Mumbai - 400019, India under Current Opinion in Green and Sustainable Chemistry, Volume 14, December 2018, Pages 26-32 is directed to renewable resource materials, whereby cashew nut shell liquid (CNSL) is considered as an important starting material due to its unique structural features, abundant availability and low cost. A large number of chemicals and products have been developed starting from CNSL by taking advantage of the three reactive sites, namely, phenolic hydroxyl, aromatic ring and unsaturation (s) in the alkenyl side chain that may lead to promising cardanol-based products that could have potential interest in industry, such as epoxy and acrylic monomers, plasticizers and surfactants.
Cardanol-Based Polyurethane Coatings via Click Chemistry: An Eco-friendly Approach, Journal of Renewable Materials, Vol.6, No.5, 2018, pp.517-528, is directed to polyurethane coatings from cardanol modified using thiolene chemistry, wherein unsaturated long alkyl chain of cardanol was successfully utilized via thiol-ene click reaction to synthesize polyol. For this purpose, cardanol and thioglycerol was reacted in the presence of Irgacure 184 (photoinitiator) and 1, 8-Diazabicyclo[5.4.0]undec-7-ene (catalyst) and exposed to UV light for 12 h at 80 °C. It was observed that cardanol-based PU coatings exhibited excellent mechanical, chemical and thermal and anticorrosive properties as compared to that of commercial acrylic-PU coatings.
Synthesis and Characterization of Cardanol based Aqueous 2K Polyurethane Coatings Dinesh Balgudea, Dr.Anagha Sabnisa, Dr. Swapan K. Ghosh a Department of Polymer and Surface Engineering, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga (E), Mumbai-400019, Maharashtra, India. European Polymer Journal, Volume 85, December 2016, Pages 620-634 teaches aqueous 2K-Polyurethane coatings that were developed by reacting water based polyols with water based polyisocynates in a stoichiometric amount for number of end applications such as coatings, adhesives, paints etc. These water based polyols are mainly derived from petroleum based raw materials. Due to growing environmental and health related concerns on the use of petroleum based feed stocks; the exploration of renewable resources can be the only obvious option in view of which one of the derivatives of cardanol, as a potential renewable resource to develop water based polyols for aqueous 2K-Polyurethane coatings was employed.
AIR-DRYING URETHANE-MODIFIED EPOXIDIZED ALKYD FOR ANTICORROSIVE COATINGS, Anand Shivarkar et al. in 2129/MUM/2015 is directed to urethane-modified epoxidized alkyd resin as copolymer hybrid having cardanol and/or hydroxy ether derivative of cardanol incorporated alkyd polymer backbone and the related process of its synthesis. Advantageously, apart from incorporation of cardanol and/or hydroxy ether derivative of cardanol into the alkyd polymer backbone of the said resin, the same could be modified with epoxy resin followed by polyisocyanate that attains solubility in white spirit i.e. mineral turpentine oil (MTO) despite incorporating MTO insoluble epoxy resin into the polymer backbone. The process of manufacture is further selective favouring such incorporation in a manner to impart the desired MTO solubility.
IN202021009573 teaches cardanol polyol modified alkyds preferably air-drying alkyds involving cardanol polyol grafted onto alkyd backbone by partly substituting commonly used polyols including Pentaerythritol, trimethylol propane, glycerin and similar polyols is provided. Said cardanol polyol grafted alkyd being reaction product of cardanol mono glycidyl ether and amino alcohols including diethanol amine.
IN201921037075 teaches a polyester resin containing Rosin (60 to 80% by wt. on polymer solids), Maleic anhydride (5 to 15% by wt. on polymer solids), tri and terta functional polyols such as trimethylolpropane, pentaerythritol (10 to 20% by wt. on polymer solids) is provided having acid value of 60 to 105 mg KOH/g and a hydroxyl value of 0 to 40 mg KOH/g. The no. av. mol. wt. is 500 to 1500 and the polydispersity index is >10. The glass transition temperature of the polyester is 60 to 1000 ?C as measured by DSC and is compatible with alcohols, ketones, glycol ethers, esters, ethers, aromatics Fig. 1b.
CN109438656 discloses cardanol-base polyurethane acrylic resin, a method for preparing the same and application of the cardanol-base polyurethane acrylic resin. The method includes weighing isocyanate, catalysts, polymerization inhibitors and hydroxyl acrylate under the conditions of organic solvents and nitrogen filling protection and carrying out reaction at the temperature of 20-100°C to obtain isocyanate semi-terminated intermediates; carrying out reaction on cardanol and the isocyanate semi-terminated intermediates until the isocyanate content is lower than 0.5%, and removing the solvents by means of rotary evaporation to obtain cardanol-base polyurethane acrylate (CNPUA) which is a final product.
CN101081890A is directed to a process of preparing cashew nut oil modified phenolic resin. The process includes the following steps: preparing the resin A; mixing the resin A 100 weight portions, formaldehyde solution 80-280 weight portions and alkaline catalyst 0.1-5 weight portions; reaction at 70-100 deg.C for 1-5 hr; vacuum distilling in a vacuum distilling kettle at temperature of 40-80 deg.C and vacuum degree of -0.03 MPa to -0.1 MPa to dewater to water content of 0.5-20 %, cooling to room temperature, and adding solvent while stirring to regulate the solid resin content to 30-70 % and viscosity at 25 deg.C to 40-400 cp to obtain the cashew nut oil modified phenolic resin. The cashew nut oil modified phenolic resin has high heat resistance, flame resistance and high toughness, and may be applied as the base material for copper clad panel.
CN103102478B discloses a cashew nut shell oil alkyd resin and a preparation method thereof. The preparation method of the alkyd resin comprises the following steps of: preparing cashew nut shell oil polyether polyol from cashew nut shell oil, subsequently adding polyatomic acid and/or anhydride, an aromatic hydrocarbon solvent and an acid esterification catalyst, carrying out esterification reaction and cooling down so as to obtain the cashew nut shell oil alkyd resin. Compared with the conventional alkyd resin, the alkyd resin disclosed by the invention can be rapidly cured in the presence of a few quantity of heavy metal catalysts, and under the action of a drier, the film-drying and curing time of 40 mum of the alkyd resin disclosed by the invention at 25 DEG C is 23-26 hours.

CN101143917A relates to a production method of cashew nut oil modified phenolic resin. Phenol and cashew nut oil are sufficiently mixed under the acidic or alkaline environment, wherein, the main ingredient of the cashew nut oil is the polyhydric phenol of C8-C27, the weight of the cashew nut oil accounts for twenty to thirty percent (weight percentage) of the total weight of the cashew nut oil and the phenol, and the acidic environment is obtained by using catalyst, the addition amount of which is one to three percent (one to two percent for the alkaline environment); the mixture is mixed with formaldehyde, temperature is raised, reaction lasts until the synthesis of the phenolic resin is finished, and wherein, the molar ratio of the formaldehyde is 1:0.72 to 0.78 (1:1.2 to 1.4 for the alkaline environment. the catalyst must be ammonia). The thermoplastic phenolic resin prepared by the invention is characterized in low free phenol and high molecular weight.
CN103102457B teaches styrene modified cashew nut shell oil alkyd resin and a preparation method thereof. The preparation method of alkyd resin comprises the following steps of: preparing cashew nut shell oil polyether polyol from cashew nut shell oil; adding polybasic acid and/or acid anhydride and an aromatic hydrocarbon solvent for an esterification reaction; and adding styrene and a radical initiator for a polymerization reaction to obtain the final product. Apart from excellent mechanical performance and adhesion, the alkyd resin disclosed herein can be cured very quickly in the presence of a little heavy metal dryer in comparison with traditional alkyd resin, and effectively reduces environmental pollution caused by a great quantity of heavy metal dryer in the traditional alkyd resin; and the dosage of the matching dryer is only 5-20% of the required amount of the traditional alkyd resin. Under the effect of the dryer, the curing time of 40(mu)m dry film of alkyd resin at 25 DEG C reaches 10-18 hours.
CN103755935A discloses a cardanol-based alkyd resin preparation method, which comprises the following steps of adding cardanol into a reaction container, adding an organic solvent for dissolution, adding a metal hydroxide aqueous solution into the reaction container, performing stirring and heating for refluxing, adding fatty acid chloride into the reaction container, performing heating for refluxing, performing vacuum evaporation to remove the organic solvent, adjusting the pH to be 1.5 to 3, adding ethyl acetate for demixing, washing an organic phase by using distilled water, drying the organic phase by using anhydrous sodium sulfate, performing filtration, washing a filter cake by using ethyl acetate, mixing the organic phase, and performing evaporation to remove the solvent to obtain pasty solid; adding the pasty solid and glycerin into a reaction container, heating dimethylbenzene for esterification, separating water by using a water separator, reducing the temperature, adding phthalic anhydride in batches, performing heating for refluxing until the viscosity and the acid value meet requirements, adding dimethylbenzene for dilution, and discharging to obtain alkyd resin that has high performance of heat resistance, hardness and the like.
Therefore, there has been a constant requirement to achieve similar high corrosion resistance performance of cardanol modified alkyds coupled with gloss, mechanical properties, and weathering from 1K ambient temperature curing coatings that would be MTO thinnable which would provide solution to the aforesaid issues to thereby provide for exceptional drying, gloss, mechanical properties, and corrosion resistance performance especially for direct to metal applications, and would preferably enable direct to metal (DTM) enamel for decorative applications with good anti-corrosive properties i.e. > 600 hrs salt spray resistance as per ASTM B117 @ DFT of 55-65 micron.

OBJECTS OF THE INVENTION
It is thus the primary object of the present invention to provide for cardanol modified urethane alkyd resin and coating formulations thereof that is MTO thinnable and coatings prepared thereof involving cardanol modified alkyd preferably thermally polymerized with excess hydroxyl having hydroxyl value in the range of 70–130 mg KOH/g that is further reactable with isocyanates to give the desired mechanical and drying characteristics together with MTO thinnability.
It is another object of the present invention to provide for said cardanol modified urethane alkyd resins as single component coating formulations that shows high corrosion resistance at minimum film thickness.
It is yet another object of the present invention to provide for said single component coating formulations based on such alkyds providing quick drying characteristics at ambient temperature with exceptional coating performance in respect of gloss, mechanical properties, corrosion resistance and weathering.
It is another object of the present invention to provide for said single component coating formulations based on such alkyds that are suitable as clear/ pigmented direct to metal (DTM) anti-corrosive coatings for air drying finishes in combination with metallic driers.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided cardanol modified urethane alkyd and coating formulations thereof comprising a reaction product of
(i) di-isocyanate; and
(ii) cardanol modified base alkyd having hydroxyl value in the range of 70–130 mg KOH/ g that is a reaction product of cardanol, fatty acids having 50-140 gm I2/100 g iodine value, carboxylic acid/ carboxylic anhydride, mono carboxylic acid and polyols.

Preferably in said cardanol modified urethane alkyd and coating formulations thereof provided includes cardanol modified urethane alkyd resins with viscosity on Gardner scale @25°C in the levels of X-Z3 and average molecular weight (Mw) in the levels of 90000–275000.

According to another preferred aspect of the present invention there is provided cardanol modified urethane alkyd and coating formulations thereof adapted for a single component, air-drying, MTO thinnable wherein said cardanol modified base alkyd is a condensation reaction product of
3-15 wt.% cardanol,
24-35 wt.% fatty acids having 50-140 gm I2/100g iodine value,
5-12 wt.% polyols, and
10-15 wt.% dicarboxylic acid/anhydride;
0-5 wt.% monocarboxylic acid dilutable with mineral turpentine oil and Xylene in the ratio of 95:5 and 90:10 at 55% alkyd solid to favour the desired viscosity on Gardner scale @25°C in the levels of D-H and process ability of the base alkyd resin.

Advantageously, in said cardanol modified urethane alkyd and coating formulations thereof said cardanol modified urethane alkyd is a reaction product of alkyd, and, 3-10% aromatic/ aliphatic di-isocyanate on polymer solids, providing for a stable resin that is stable when subjected to accelerated stability test at 55°C for 15 days and is adapted for coating formulations that passes tests of flexibility, impact resistance, scratch hardness, 1 mm crosscut adhesion and resistance to salt spray.

According to yet another preferred aspect of the present invention there is provided cardanol modified urethane alkyd and coating formulations thereof wherein said cardanol modified urethane alkyd as a reaction product of cardanol modified base alkyd having fatty acids of 50-140 gm I2/100g iodine value, and, aliphatic di-isocyanate preferably cycloliphatic di-isocyanate favours corrosion resistance performance of minimum 600 hours in 2 coats at DFT (dry film thickness) of 55-65 microns in ?2 coats wherein time interval between coats to be tack free is 8-10 hours and free of any signs of under film corrosion as per ASTM B117 salt spray test in hours.

Preferably in said cardanol modified urethane alkyd and coating formulations thereof is provided wherein said polyols includes at least one polyol selected from pentaerythritol, glycerine, sorbitol; wherein said carboxylic acid/ carboxylic anhydride includes pthalic anhydride, isophthalic acid; said monocarboxylic acid includes benzoic acid, tertiary butyl benzoic acid, rosin; and said di-isocyanate includes aromatic/ aliphatic di-isocyanates selected from Toluene diisocyanate, Isophorone diisocyanate, Methylene diphenyl diisocyanate.

Preferably said cardanol modified urethane alkyd and coating formulations thereof is provided that is suitable as anti-corrosive coating formulations and involves 0.5 to 6 wt.% of anti-corrosive pigments wherein for balance of gloss and anti-corrosive attributes pigment content is 0.5-3 wt.%; said coating formulation incorporating additives including dispersing agent, metallic driers, flow-levelling additives, rheology modifiers, antioxidants, anti-skinning and anti-settling agents.

According to another aspect of the present invention there is provided a process for the synthesis of cardanol modified urethane alkyd and coating formulations thereof comprising the steps of reacting
(a) providing di-isocyanate; and

(b) providing cardanol modified base alkyd having hydroxyl value in the range of 70–130 mg KOH/g by reacting cardanol, fatty acids having 50-140 gm I2/100g iodine value, carboxylic acid/ carboxylic anhydride, mono carboxylic acid and polyols;

(c) reacting said (i) and (ii) to obtain therefrom said cardanol modified urethane alkyd and coating formulations thereof.

According to yet another preferred aspect of the process for the synthesis of said cardanol modified urethane alkyd and coating formulations thereof
wherein said step (b) of providing cardanol modified base alkyd is enabled by reacting 3-15 wt.% cardanol, 24-35 wt.% fatty acids having iodine value in the range of 50-140 gm I2/100g, 5-12 wt.% polyols, and 10-15 wt.% dicarboxylic acid/anhydride, 0-5 wt.% monocarboxylic acid at a temperature of about 160-170°C for 1 hour and thereafter increasing the reaction temperature from 170 to 235°C in 4-5 hours until an acid number of < 5mg KOH/g and hydroxyl value in the range of 70–130 mg KOH/ g is achieved, followed to which the reaction mixture is cooled down to 120°C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil (MTO): Mixed Xylene in the ratio range of 95:5 to 90:10 to provide for processable viscosity of cardanol modified base alkyd resin on Gardener scale@ 25 °C of D-H.

Preferably in said process for the synthesis of cardanol modified urethane alkyd and coating formulations thereof said step (c) involves processing said cardanol modified base alkyd at temperatures of 70-75 °C adding diisocyanate in 10-15 mins and further flushing with MTO while maintaining a temperature of 95-105 °C that was allowed to react until constant viscosity on Gardner scale @25°C of X-Z3 and average molecular weight (Mw) in the levels of 90000–275000 is achieved upon cooling and diluting with solvents including isobutanol, xylene, MTO.

The present invention thus offers a unique approach for the synthesis of MTO thinnable cardanol modified urethane alkyd resin and coatings prepared thereof based on involving select levels of fatty acid having iodine value in the range of 50-140 gm Iodine /100gm, cardanol, polyols and anhydride favouring said thermally polymerized cardanol modified alkyd with excess hydroxyl having hydroxyl value in the range of 70–130 mg KOH/g that is further reactable with isocyanates to give the desired mechanical and drying characteristics together with MTO thinnability. A process of preparation is also provided based on spanning a reaction temperature range of 170-250 ?C that first allows the reaction between fatty acid having iodine value in the range of 50-140 gm Iodine/100gm, cardanol, polyols and anhydride to achieve cardanol modified alkyd with said excess hydroxyl value and further the unsaturation present in long alkyl chain of cardanol at meta position also undergoes thermal polymerization simultaneously at such higher temperature to yield said thermally polymerized cardanol modified alkyd that is reactable with isocyanates providing cardanol modified urethane alkyd resin that is advantageously MTO thinnable and further advantageously provides exceptional drying, gloss, mechanical properties, and corrosion resistance performance especially for direct to metal applications.

DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore, the present invention fulfills this long-standing need of the consumers in offering a unique construction of cardanol modified urethane alkyds and coating formulations thereof having excellent solubility in user friendly Mineral Turpentine Oil (MTO) comprising of aliphatic hydrocarbon as the major component. Single component coating formulations based on such alkyds provide quick drying characteristics at ambient temperature with exceptional coating performance in respect of gloss, mechanical properties, corrosion resistance and weathering. Coatings based on the present invention are suitable for clear/ pigmented direct to metal (DTM) anti-corrosive coatings for air drying finishes in combination with metallic driers.
Presently epoxy, polyurethane, organic/ inorganic zinc-rich coatings etc. are being offered for anticorrosive coatings as 2K systems which are expensive, have limited pot life and contain hazardous solvents. Conventional Urethane alkyds offer limited corrosion resistance and require high film thickness of 90-100 micron in 3 or more coats.
The co-pending patent application 2129/MUM/2015 by Anand Shivarkar et al., employed epoxidation of cardanol derivative based alkyd followed by urethane modification, whereas the present invention did not require any epoxidation to reach to the desired attributes.
The present invention is free from any epoxy modification and enables involvement of Cardanol and Fatty acid of lower Iodine value range of 50-140 gm Iodine /100gm and is directed to in-situ synthesis of cardanol modified urethane alkyd wherein first cardanol modified alkyd with excess hydroxyl is prepared by reacting its phenolic hydroxyl group with carboxylic anhydride at elevated temperature of 200-250 ?C. Apart from the said grafting, the unsaturation present in long alkyl chain of cardanol at meta position also undergoes thermal polymerization simultaneously. The resultant cardanol modified alkyd is further reacted with suitable polyisocyanates at select concentration to obtain cardanol modified urethane alkyds of the present invention suitable for coating formulations.

EXAMPLES:
EXAMPLE 1
Cardanol modified urethane alkyd resin is prepared in two steps 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.

Ingredients Parts by Weight (PBW)
Sr No. (Part A) Cardanol modified base alkyd
1 Fatty acid of iodine value 120-139 29.37
2 Phthalic anhydride 12.13
3 Pentaerythritol nitration grade 7.46
4 Refined Glycerine 3.71
5 Cardanol 5.83
6 Mixed Xylene 2.37
7 Mineral Turpentine Oil 39.13
Total 100.00

Sr.
No. (Part B) Cardanol modified urethane alkyd ( CMUA 1)

1 Cardanol modified Base
Alkyd (Part A) 93.00

2 Methylene diphenyl diisocyanate 4.20
3 Mixed Xylene (I) 1.0
4 Iso Butanol 0.20
5 Mixed Xylene (II) 1.60
Total 100.00

Cardanol Modified base alkyd (Part A) : Ingredients from serial no. 1-6 are charged into the reactor and is heated to temperature of about 160-170°C for 1 hour and thereafter reaction temperature is increased from 170 to 235°C in 4-5 hours until an acid number dropped < 5mg KOH/g. The reaction mixture is cooled down to 120°C and diluted to 60% non-volatile matter (NVM) with Mineral Turpentine Oil (MTO) providing viscosity at 25 °C on Gardener scale = N-O and the hydroxy value of 97 mg KOH/g when tested by conventional testing procedures.

Cardanol Modified Urethane alkyd (Part B) : Base alkyd synthesized in Part A is charged into the reactor and heated to the temperature of about 70-75°C. Methylene diphenyl diisocyanate is slowly added into reaction mixture under stirring over the period of 5-10 minutes. After complete addition of Methylene diphenyl diisocyanate, the addition vessel is flushed with Mixed Xylene (I). Temperature is increased to 105°C. Reaction is continued till constant viscosity is obtained. Then reaction is cooled to 80 °C. Iso-butanol and Mixed Xylene (II) is added into reaction mixture and mixed for 10-15 minutes. Physical properties of Cardanol modified urethane alkyd resin are: Viscosity on Gardner scale @ 25°C= Z2 and % NVM-120°C/1 hour = 60. Average molecular weight (Mw) obtained was 32378.
The viscosity of the Cardanol modified base alkyd being very low it was optionally thinned at 60% in Mineral Turpentine alone, instead of 55% in Mineral Turpentine: Mixed Xylene as also revealed in the below examples. Also, Cardanol modified urethane alkyd was prepared at 60% solid instead of 55% as reported in all other examples. The same resin when thinned to 55% solid, viscosity obtained was U-V on Gardener scale @ 25 deg C.

EXAMPLE 2
Cardanol modified urethane alkyd resin is prepared in two steps 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.

Ingredients Parts by Weight (PBW)
Sr No. (Part A) Cardanol modified base alkyd
1 Fatty acid of iodine value 120-139 25.66
2 Phthalic anhydride 13.56
3 Pentaerythritol nitration grade 7.37
4 Refined Glycerine 4.12
5 Cardanol 5.48
6 Mixed Xylene 4.46
7 Mineral Turpentine Oil 39.35
Total 100

Sr.
No. (Part B) Cardanol modified urethane alkyd ( CMUA 2)
1 Cardanol modified Based Alkyd (Part A) 94.00
2 Toluene diisocyanate 3.30
3 Mixed Xylene (I) 1.00
4 Iso Butanol 0.25
5 Mixed Xylene (II) 1.45
Total 100

Cardanol Modified base alkyd (Part A) : Ingredients from serial no. 1-6 are charged into reactor and is heated to temperature of about 160-170°C for 1 hour and thereafter reaction temperature is increased from 170 to 235°C in 4-5 hours until an acid number of < 5mg KOH/g is achieved. The reaction mixture is cooled down to 120°C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil : Mixed Xylene (95:5) providing viscosity on Gardener scale at 25 °C = E-F and the hydroxy value of 105 mg KOH/g.

Cardanol Modified Urethane alkyd (Part B) : Base alkyd synthesized in Part A is charged into the reactor and heated to the temperature of about 70-75°C. Toluene diisocyanate is slowly added into the reaction mixture under stirring over the period of 5-10 minutes. After complete addition of Toluene diisocyanate, the addition vessel is flushed with Mixed Xylene (I). Temperature is increased to 105°C. Reaction is continued till constant viscosity is obtained. Then reaction is cooled to 80 °C. Iso-butanol and Mixed Xylene (II) is added into reaction mixture and mixed for 10-15 minutes. Physical properties of the resin are: Viscosity on Gardner scale @25°C = Z- Z1 and % NVM-120°C/1 hour = 55. Average molecular weight (Mw) obtained was 182287.

EXAMPLE 3
Cardanol modified urethane alkyd resin is prepared in two steps 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.

Ingredients Parts by Weight
(PBW)
Sr No. (Part A) Cardanol modified base alkyd
1 Fatty acid of iodine value 120-139 25.66
2 Phthalic anhydride 13.56
3 Pentaerythritol nitration grade 7.37
4 Refined Glycerine 4.12
5 Cardanol 5.48
6 Mixed Xylene 4.46
7 Mineral Turpentine Oil 39.35
Total 100

Sr No. (Part B) Cardanol modified urethane alkyd ( CMUA 3)

1 Cardanol modified Based Alkyd (Part A) 91.99
2 Isophorone diisocyanate 3.83
3 Mixed Xylene 1.00
4 Iso Butanol 0.25
5 Mineral Turpentine Oil 2.93
Total 100

Cardanol Modified base alkyd (Part A) : Ingredients from serial no. 1-6 are charged into reactor and is heated to temperature of about 160-170 °C for 1 hour and thereafter reaction temperature is increased from 170 to 235 °C in 4-5 hours until an acid number of < 5mg KOH/g is achieved . The reaction mixture is cooled down to 120 °C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil: Mixed Xylene (95:5) achieving viscosity on Gardener scale at 25 °C = E-F and the hydroxy value of 105 mg KOH/g.

Cardanol Modified Urethane alkyd (Part B) : Base alkyd synthesized in Part A is charged into reactor and heated to the temperature of about 70-75 °C. Isophorone diisocyanate is slowly added into reaction mixture under stirring over the period of 5-10 minutes. After addition of Isophorone diisocyanate, addition vessel is flushed with xylene and the reaction temperature is increased to 105°C. Reaction is continued till constant viscosity is obtained. Then reaction is cooled to 80 °C. Iso-butanol and Mineral Turpentine Oil is added into reaction mixture and mixed for 10-15 minutes. Physical properties are: - Viscosity on Gardner scale @25°C = Y and % NVM-120°C/1 hour = 55. Average molecular weight (Mw) obtained was 151242.

EXAMPLE 4
Cardanol modified urethane alkyd resin is prepared in two steps 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.
Ingredients Parts by Weight
(PBW)
Sr No. (Part A) Cardanol modified base alkyd
1 Fatty Acid of Iodine Value 99-108 25.46
2 Phthalic anhydride 12.50
3 Pentaerythritol nitration grade 9.39
4 Refined Glycerine 1.86
5 Cardanol 5.09
6 Mixed Xylene 6.21
7 Mineral Turpentine Oil 39.49
Total 100

Sr No. (Part B) Cardanol modified urethane alkyd
( CMUA 4)

1 Cardanol modified Based Alkyd (Part A) 93.4
2 Isophorone diisocyanate 3.63
3 Mixed Xylene (I) 1.00
4 Iso Butanol 0.25
5 Mixed Xylene (II) 1.72
Total 100

Cardanol Modified base alkyd (Part A) : Ingredients from serial no. 1-6 are charged into reactor and is heated to temperature of about 160-170 °C for 1 hour and thereafter reaction temperature is increased from 170 to 235 °C in 4-5 hours until an acid number of < 5mg KOH/g is achieved . The reaction mixture is cooled down to 120°C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil: Mixed Xylene (95:5) achieving viscosity on Gardener scale at 25 °C = E-F and the hydroxy value of 108 mg KOH/g.

Cardanol Modified Urethane alkyd (Part B) : Base alkyd synthesized in Part A is charged into reactor and heated to the temperature of about 70-75 °C. Isophorone diisocyanate is slowly added into reaction mixture under stirring over the period of 5-10 minutes. After complete addition of Isophorone diisocyanate, the reaction mixture is flushed with Mixed Xylene (I). Temperature is increased to 105°C. Reaction is continued till constant viscosity is obtained. Then reaction is cooled to 80 °C. Iso-butanol and Mixed Xylene (II) is added into reaction mixture and mixed for 10-15 minutes. Physical properties are: Viscosity on Gardner scale @25 deg C = Z1 and % NVM-120°C/1 hour = 55. Average molecular weight (Mw) obtained was 149520.

EXAMPLE 5
Cardanol modified urethane alkyd resin is prepared in two steps 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.

Ingredients Parts by Weight
(PBW)
Sr No. (Part A) Cardanol modified base alkyd
1 Fatty Acid of Iodine Value 99-108 25.46
2 Phthalic anhydride 12.50
3 Pentaerythritol nitration grade 9.39
4 Refined Glycerine 1.86
5 Cardanol 5.09
6 Mix-Xylene 6.21
7 Mineral Turpentine Oil 39.49
Total 100

Sr No. (Part B) Cardanol modified urethane alkyd
( CMUA 5)

1 Cardanol modified Based Alkyd (Part A) 94.00
2 Toluene diisocyanate 3.50
3 Mixed Xylene (I) 1.00
4 Iso Butanol 0.25
5 Mixed Xylene (II) 1.25
Total 100

Cardanol Modified base alkyd (Part A) : Ingredients from serial no. 1-6 are charged into the reactor and is heated to temperature of about 160-170°C for 1 hour and thereafter reaction temperature is increased from 170 to 235 °C in 4-5 hours until an acid number of < 5mg KOH/g is achieved. The reaction mixture is cooled down to 120°C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil: Mixed Xylene (95:5) providing viscosity on Gardener scale at 25 °C = E-F and the hydroxy value of 108 mg KOH/g.

Cardanol Modified Urethane alkyd (Part B) : Base alkyd synthesized in Part A is charged into the reactor and heated to the temperature of about 70-75°C. Toluene diisocyanate is slowly added into reaction mixture under stirring over the period of 5-10 minutes. After complete addition of Toluene diisocyanate, the addition vessel is flushed with Mixed Xylene (I). Temperature is increased to 105°C. Reaction is continued till constant viscosity is obtained. Then reaction is cooled to 80 °C. Iso-butanol and Mixed Xylene (II) is added into reaction mixture and mixed for 10-15 minutes. Physical properties are: Viscosity on Gardner scale @25°C= Z2-Z3, and % NVM-120°C/1 hour = 55. Average molecular weight (Mw) obtained was 402327.

EXAMPLE 6
Cardanol modified urethane alkyd resin is prepared in two steps 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.

Ingredients Parts by Weight
(PBW)
Sr No. (Part A) Cardanol modified base alkyd
1 Fatty Acid of Iodine Value 50-62 26.49
2 Phthalic anhydride 13.01
3 Pentaerythritol nitration grade 9.77
4 Refined Glycerine 1.94
5 Cardanol 5.29
6 Mixed Xylene 6.46
7 Mineral Turpentine Oil 37.04
Total 100

Sr No. (Part B) Cardanol modified urethane alkyd
( CMUA 6)

1 Cardanol modified Based Alkyd (Part A) 93.40
2 Isophorone diisocyanate 4.33
3 Mixed Xylene (I) 1.00
4 Iso Butanol 0.50
5 Mixed Xylene (II) 0.77
Total 100

Cardanol Modified base alkyd (Part A) : Ingredients from serial no. 1-6 are charged into the reactor and is heated to temperature of about 160-170°C for 1 hour and thereafter reaction temperature is increased from 170 to 235 °C in 4-5 hours until an acid number of < 5mg KOH/g is achived. The reaction mixture is cooled down to 120 °C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil: Mixed Xylene (95:5) providing viscosity on Gardener scale @ 25 °C= F-G F and the hydroxy value of 108 mg KOH/g.

Cardanol Modified Urethane alkyd (Part B) : Base alkyd synthesized in Part A is charged into reactor and heated to the temperature of about 70-75 °C. Isophorone diisocyanate is slowly added into reaction mixture under stirring over the period of 5-10 minutes. After complete addition of Isophorone diisocyanate, the addition vessel is flushed with Mixed Xylene (I). Temperature is increased to 105°C. Reaction is continued till constant viscosity is obtained. Then reaction is cooled to 80 °C. Iso-butanol and Mixed Xylene (II) is added into reaction mixture and mixed for 10-15 minutes. Physical properties are : Viscosity on Gardner scale @25 deg C= Z2 and % NVM-120°C/1 hour = 55. Average molecular weight (Mw) obtained was 219902.
EXAMPLE 7
Cardanol modified urethane alkyd resin is prepared in two steps 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.

Ingredients Parts by Weight
(PBW)
Sr No. (Part A) Cardanol modified base alkyd
1 Fatty Acid of Iodine Value 50-62 26.49
2 Phthalic anhydride 13.01
3 Pentaerythritol nitration grade 9.77
4 Refined Glycerine 1.94
5 Cardanol 5.29
6 Mixed Xylene 6.46
7 Mineral Turpentine Oil 37.04
Total 100

Sr No. (Part B) Cardanol modified urethane alkyd
( CMUA 7)

1 Cardanol modified Based Alkyd (Part A) 94.00
2 Toluene diisocyanate 3.90
3 Mixed Xylene (I) 1.00
4 Iso Butanol 0.50
5 Mixed Xylene (II) 0.60
Total 100

Cardanol Modified base alkyd (Part A) : Ingredients from serial no. 1-6 are charged into the reactor and is heated to temperature of about 160-170 °C for 1 hour and thereafter reaction temperature is increased from 170 to 235 °C in 4-5 hours until an acid number of < 5mg KOH/g is achieved. The reaction mixture is cooled down to 120 °C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil: Mixed Xylene (95:5) providing viscosity on Gardener scale @ 25 °C = F-G F and the hydroxy value of 108 mg KOH/g.

Cardanol Modified Urethane alkyd (Part B) : Base alkyd synthesized in Part A is charged into the reactor and is heated to the temperature of 70-75°C. Toluene diisocyanate is slowly added into reaction mixture under stirring over the period of 5-10 minutes. After complete addition of Toluene diisocyanate, the addition vessel is flushed with Mixed Xylene (I). Temperature is increased to 105°C. Reaction is continued till constant viscosity is obtained. Then reaction is cooled to 80 °C. Iso-butanol and Mixed Xylene (II) is added into reaction mixture and mixed for 10-15 minutes. Physical properties are: Viscosity on Gardner scale @25 deg C= Z5 and % NVM-120°C/1 hour = 55. Average molecular weight (Mw) obtained was 355296.

The formulation and process of Cardanol modified urethane alkyd resins from examples 1, 2, 3, 4 and 6 provided a stable resin when subjected to accelerated stability test at 55°C for 15 days.

Source of some key Raw Materials employed in the present invention:

Fatty acid of iodine value 120-139 supplied by Cargil India Pvt. Ltd., Fatty acid of iodine value 99-108 supplied by A.P. Refinery Pvt. Ltd., India, Fatty acid of iodine value 50-62 supplied by Bunge India Pvt. Ltd., Phthalic anhydride supplied by Thirumalai Chemicals Ltd., India, Pentaerythritol nitration grade supplied by Asian Paints Ltd., India, Refined Glycerine supplied by Godrej Industries Ltd., India, Cardanol supplied by Adarsh Industrial Chemicals, India, Mixed Xylene supplied by Reliance Industries Ltd., India, Mineral Turpentine Oil supplied by Indian Oil Corporation Ltd, India, Methylene diphenyl diisocyanate supplied by Covestro AG, Germany, Toluene diisocyanate supplied by Gujarat Narmada Valley Fertilizers and Chemicals Ltd., India, Isophorone diisocyanate supplied by Evonik Industries AG, Germany, Isobutanol supplied by Bharat Petroleum Corporation Ltd, India.

Cardanol modified urethane alkyd in Anticorrosive Coating Compositions:
Cardanol modified urethane alkyd resins obtained from above examples were characterized for physical, air drying, mechanical properties and accelerated stability at 55°C in clear varnish. Example 1 showed inferior drying and hardness owing to low molecular weight product having lower viscosity at lower solid levels.
Examples 5 and 7 showed viscosity pick up in accelerated stability test as both these resins have high viscosity and molecular weight. Therefore, these examples were excluded while designing pigmented anticorrosive coating compositions.
The coating compositions were prepared using Cardanol modified urethane alkyd Examples 2, 3, 4 and 6. Coating compositions involved preparation of white Paint at a Pigment Volume Concentration (PVC) of 14-20% using Titanium dioxide, Zinc phosphate, dispersing agent, metallic driers, and flow-levelling additives. The resulting coating compositions were tested for drying, physical, mechanical and corrosion resistance properties and test results are summarized in the following table:

Coating Composition test results:
Coating compositions based on Cardanol modified urethane alkyd (CMUA) CMUA 2 CMUA 3 CMUA 4 CMUA 6
Dry Film Thickness (DFT ) in microns 55 – 65 55 - 65 55 - 65 55 – 65
Surface dry time in minutes (IS 101) 120 120 120 150
Tack free time in hours (IS 101) 8 8 8 9
Hard dry time in hours (IS 101) 18 18 18 18
Scratch hardness after 48 hours (gm) (IS 101) 1100 1200 1100 1000
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
Salt spray test (hours) (ASTM-B117) at DFT 55-65 microns in two coats (no under film corrosion) Passes 500 Passes 650 Passes 650 Passes 450
Gloss @ 20° Gloss Head 80-85 80-85 80-82 70-74

During the experimentation, it has been observed that chemically grafted cardanol through phenolic hydroxyl group coupled with thermally polymerized long alkyl chain at elevated temperature provides exceptional coating properties in respect of drying, hardness and corrosion resistance unlike the physical blend of cardanol or its modified products.
Developed cardanol modified urethane alkyd-based coating compositions are single component, air-drying, MTO thinnable and can be directly applied on metal providing high gloss, mechanical props and ASTM B 117 corrosion resistance of > 600 hrs in ?2 coats at DFT of 55-65 microns.
Cardanol modified urethane alkyd and coating compositions thereof is thus provided comprising a reaction product of cardanol with fatty acids, carboxylic acid/ carboxylic anhydride, mono carboxylic acid and conventional polyols. The alkyd thus obtained is reacted with suitable polyisocyanate.
Cardanol modified base alkyd and its further urethanisation is achieved by way of the following process with the alkyd Intermediate prepared by condensation reaction of Cardanol 3-15 wt.%, 24-35 wt.% fatty acids having 50-140 gm I2/100g iodine value, 5-12 wt.% polyols preferably pentaerythritol/ glycerine/ sorbitol, 10-15 wt.% dicarboxylic acid/anhydride preferably Phthalic anhydride, and 0–5 wt.% monocarboxylic acid by heating in the temperature range of 170 °C to 235 °C and processed to obtain an acid number of < 5 mg KOH/g. The alkyd thus formed is diluted in mineral turpentine oil and Xylene in the ratio of 95:5 and 90:10 at 55% solid depending on viscosity of the base alkyd resin. Further modification of alkyd resin was carried out with various di-isocyanates at 3-10% on polymer solid. During the process base alkyd was charged into the reactor and heated up to 70-75 °C. Once the temperature was reached; addition of isocyanate was carried out in 10-15 mins and further flushing was carried out with MTO. Temperature was maintained at 95- 105 °C and allowed to Process till constant viscosity is obtained on Gardner scale.

DTM enamel Composition:
Coating compositions were prepared using cardanol modified urethane alkyd in combination with coating ingredients such as anti-corrosive pigments, fillers, driers and solvents to make as "one-pack" direct to Metal (DTM) enamel for ready to use application.
Testing of DTM enamel based on Cardanol-polyol modified alkyd:
Enamel paint was applied on mild steel panel and allowed to cure at ambient temperature for 7 days. Cured paint film showed good gloss (>80 @20° gloss head), hardness 1.0-1.5 Kg @ 55-65 micron DFT and good water and corrosion resistance (passed minimum 600 hrs salt spray test in ASTM B117) when applied directly on Mild steel substrate.
According to further aspect of the present invention a test metal panel (cold rolled mild steel) coated with a composition as per the current invention were subjected to various tests after 7 days of application to evaluate the coated film in respect of flexibility, impact resistance, scratch hardness, 1 mm crosscut adhesion and resistance to salt spray. The flexibility of the coatings was tested by conducting a Mandrel bend test (ASTM D 522). Scratch hardness of the coating was tested using Sheen make automatic scratch tester Ref. No. 705 with 1 mm tungsten carbide tip. The 1 mm cross-cut adhesion test was carried out according to ASTM D 3359. Impact Resistance of coating was tested using Falling-Ball Method (65+0.2 cm height x 15.9+ 0.08 mm diameter x 908+1 gm load).
The salt spray resistance of the coating was tested according to ASTM B117. The appearance of corrosion product was evaluated periodically, and test duration depended on the corrosion resistance of the coating; the more corrosion resistant coating, longer the period in testing without showing signs of corrosion.
It is thus possible by way of the present advancement to provide for a Cardanol modified urethane alkyd suitable for ready to use single component air drying Topcoat / self-priming glossy enamel for mild steel substrates for low to high corrosion zones as validated through accelerated corrosion resistance performance through ASTM B 117 salt fog test. Apart from excellent corrosion resistance, the said binder provided good gloss and mechanical properties like hardness, flexibility, impact and adhesion when used in a paint recipe involving Organic / inorganic pigment, anticorrosive pigments, metallic driers, and other additives known in the art.
Advantageously, the said Cardanol modified urethane alkyd provided significantly superior corrosion resistance over conventionally available alkyds or known modified alkyds. Such Cardanol modified urethane alkyds find application in preparing anti-corrosive coating compositions for protecting and maintaining the mild steel, corroded steel, and other metallic substrates across the decorative and industrial segments. However, such coatings would also find application on other substrates including wood, glass and cementitious etc.
Coating compositions obtained from the present invention provide corrosion resistance to metallic objects/ structures used in decorative as well as industrial segments. In a special finding of the present invention, the suitably designed pigmented coating compositions when applied on mild steel substrate at dry film thickness (DFT) of 55-65 microns in 2 or more coats with interval of 8-10 hours between coats provided corrosion resistance performance of minimum 600 hours or more without any sign of under film corrosion as per ASTM B117 salt spray test.
Suitable anti-corrosive pigments of the present invention include zinc phosphate, zinc oxide, calcium phosphate, strontium phosphosilicates, aluminium triphosphate, zinc molybdate, zinc phosphor molybdate, aluminium zinc phosphate, micaceous iron oxide, lead silico chromate, strontium chromate etc. and may form the part of coating composition in an amount of about 0.5 to 6 % of the coating composition based on the total weight of the coating composition. Preferably, the anti-corrosive pigment content used was 0.5-3% based on the total weight of the coating composition. The higher quantities of anticorrosive pigments would improve corrosion resistance performance but significantly reduces the gloss. A preferred anti-corrosive pigment employed in the present coating composition is micronized zinc phosphate.
In one of the embodiments of present invention metallic driers were employed to accelerate the conversion of coating into cross linked dry film through auto oxidative polymerization. Driers are primarily metal soaps of organic acids. Some of the preferred drier combinations employed in context with the present invention are selected from the group comprising: 1) Cobalt Octoate: Acts as a "Surface Drier". It is primarily an oxidation catalyst and an optimum quantity need to be used to avoid surface wrinkling.
2) Borchi Oxy coat: It is a highly active Iron complex and recommended as an alternative to Cobalt based driers. However, in the present invention it has been used synergistically with cobalt to optimize cost and performance.
3) Calcium Octoate: It has both oxidizing and polymerizing properties and produce hard films.
4) Zirconium Octoate: Acts as an active cross-linking agent and improves hardness of dried film as well as its adhesions.
However, the present invention is not limited to the aforesaid preferred metal salts and would also include all metal salts and their combination available under different trade names which could be used synergistically in the optimized ratio to achieve desired coating performance.
In the paint compositions of the present invention may include additives such as rheology modifiers, dispersing agent, antioxidants, anti-skinning and anti-settling agent each in adequate amount. A preferred solvent is MTO. The proportion of solvent may vary according to the desired consistency of the paint composition.
The present invention provides coating compositions which are meant for Topcoat/self-priming enamel/under coat/ primer for various ferrous, non-ferrous, and chemical treated substrates such as degreased, iron/zinc phosphated etc. and may be easily applied by conventional application systems such as brushing, roller, spraying, sprinkling, flow coating, dipping, and the like. The DFT of the coating is preferably 55-65 microns in 2 or more coats wherein time interval between coats is 8-10 hours.
It is thus possible by way of the present advancement to provide for a Cardanol modified urethane alkyd suitable for ready to use single component air drying Topcoat / self-priming glossy enamel for mild steel substrates for low to high corrosion zones as validated through accelerated corrosion resistance performance through ASTM B 117 salt fog test. Apart from excellent corrosion resistance, the said binder provided good gloss and mechanical properties like hardness, flexibility, impact and adhesion when used in a paint recipe involving Organic / inorganic pigment, anticorrosive pigments, metallic driers, and other additives known in the art.
, Claims:We Claim:

1. Cardanol modified urethane alkyd and coating formulations thereof comprising a reaction product of

(i) di-isocyanate; and
(ii) cardanol modified base alkyd having hydroxyl value in the range of 70–130 mg KOH/ g that is a reaction product of cardanol, fatty acids having 50-140 gm I2/100 g iodine value, carboxylic acid/ carboxylic anhydride, mono carboxylic acid and polyols.

2. The cardanol modified urethane alkyd and coating formulations thereof as claimed in claim 1 including cardanol modified urethane alkyd resins with viscosity on Gardner scale @25°C in the levels of X-Z3 and average molecular weight (Mw) in the levels of 90000–275000.

3. The cardanol modified urethane alkyd and coating formulations thereof as claimed in claims 1 or 2 adapted for a single component, air-drying, MTO thinnable wherein said cardanol modified base alkyd is a condensation reaction product of
3-15 wt.% cardanol,
24-35 wt.% fatty acids having 50-140 gm I2/100g iodine value,
5-12 wt.% polyols, and
10-15 wt.% dicarboxylic acid/anhydride;
0-5 wt.% monocarboxylic acid dilutable with mineral turpentine oil and Xylene in the ratio of 95:5 and 90:10 at 55% alkyd solid to favour the desired viscosity on Gardner scale @25°C in the levels of D-H and process ability of the base alkyd resin.

4. The cardanol modified urethane alkyd and coating formulations thereof as claimed in claims 1-3 wherein said cardanol modified urethane alkyd is a reaction product of alkyd, and, 3-10% aromatic/ aliphatic di-isocyanate on polymer solids, providing for a stable resin that is stable when subjected to accelerated stability test at 55°C for 15 days and is adapted for coating formulations that passes tests of flexibility, impact resistance, scratch hardness, 1 mm crosscut adhesion and resistance to salt spray.

5. The cardanol modified urethane alkyd and coating formulations thereof as claimed in claims 1-4 wherein said cardanol modified urethane alkyd as a reaction product of cardanol modified base alkyd having fatty acids of 50-140 gm I2/100g iodine value, and, aliphatic di-isocyanate preferably cycloliphatic di-isocyanate favours corrosion resistance performance of minimum 600 hours in 2 coats at DFT (dry film thickness) of 55-65 microns in ?2 coats wherein time interval between coats to be tack free is 8-10 hours and free of any signs of under film corrosion as per ASTM B117 salt spray test in hours.

6. The cardanol modified urethane alkyd and coating formulations thereof as claimed in claims 1-5 wherein said polyols includes at least one polyol selected from pentaerythritol, glycerine, sorbitol; wherein said carboxylic acid/ carboxylic anhydride includes pthalic anhydride, isophthalic acid; said monocarboxylic acid includes benzoic acid, tertiary butyl benzoic acid, rosin; and said di-isocyanate includes aromatic/ aliphatic di-isocyanates selected from Toluene diisocyanate, Isophorone diisocyanate, Methylene diphenyl diisocyanate.

7. The cardanol modified urethane alkyd and coating formulations thereof as claimed in claims 1-6 suitable as anti-corrosive coating formulations and involves 0.5 to 6 wt.% of anti-corrosive pigments wherein for balance of gloss and anti-corrosive attributes pigment content is 0.5-3 wt.%; said coating formulation incorporating additives including dispersing agent, metallic driers, flow-levelling additives, rheology modifiers, antioxidants, anti-skinning and anti-settling agents.

8. A process for the synthesis of cardanol modified urethane alkyd and coating formulations thereof as claimed in claims 1-7 comprising the steps of reacting
(a) providing di-isocyanate; and

(b) providing cardanol modified base alkyd having hydroxyl value in the range of 70–130 mg KOH/g by reacting cardanol, fatty acids having 50-140 gm I2/100g iodine value, carboxylic acid/ carboxylic anhydride, mono carboxylic acid and polyols;

(c) reacting said (i) and (ii) to obtain therefrom said cardanol modified urethane alkyd and coating formulations thereof.

9. The process for the synthesis of cardanol modified urethane alkyd and coating formulations thereof as claimed in claim 8
wherein said step (b) of providing cardanol modified base alkyd is enabled by reacting 3-15 wt.% cardanol, 24-35 wt.% fatty acids having iodine value in the range of 50-140 gm I2/100g, 5-12 wt.% polyols, and 10-15 wt.% dicarboxylic acid/anhydride, 0-5 wt.% monocarboxylic acid at a temperature of about 160-170°C for 1 hour and thereafter increasing the reaction temperature from 170 to 235°C in 4-5 hours until an acid number of < 5mg KOH/g and hydroxyl value in the range of 70–130 mg KOH/ g is achieved, followed to which the reaction mixture is cooled down to 120°C and diluted to 55% non-volatile matter (NVM) with Mineral Turpentine Oil (MTO): Mixed Xylene in the ratio range of 95:5 to 90:10 to provide for processable viscosity of cardanol modified base alkyd resin on Gardener scale@ 25 °C of D-H.

10. The process for the synthesis of cardanol modified urethane alkyd and coating formulations thereof as claimed in claims 8 or 9
wherein said step (c) involves processing said cardanol modified base alkyd at temperatures of 70-75 °C adding diisocyanate in 10-15 mins and further flushing with MTO while maintaining a temperature of 95-105 °C that was allowed to react until constant viscosity on Gardner scale @25°C of X-Z3 and average molecular weight (Mw) in the levels of 90000–275000 is achieved upon cooling and diluting with solvents including isobutanol, xylene, MTO.

Dated this the 6th day of June, 2022 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)
IN/PA-199