DESC:Field of Invention

The present disclosure relates to an alkyd resin having a high bio-renewable content, and a process for preparing said alkyd resin.

Background

Alkyd resins are widely used in the coatings and paints industry and have become indispensable raw materials to produce industrial and household finishes. Generally, these alkyd resins are obtained from condensation reaction of fatty acids or vegetable oils, polyols such as glycerol and polyacids such as phthalic anhydride. Currently, most of these alkyd resins use phthalic based diacids, such as, phthalic anhydride, isophthalic acid and terephthalic acid. These phthalic based diacids are of petrochemical origin. Given the environmental concerns associated with the use of petroleum based raw materials, there has been a need and expectation to use bio-renewable substitutes of phthalic based diacids.

US9321883 B2 discloses an alkyd emulsion containing isosorbide as one of the bio-sourced polyol components along with another polyol and polyacids.

US9902870B2 discloses itaconate alkyd resins emulsion which are prepared from bio sourced raw materials. An itaconate acid or its derivative (Diels-alder adduct with fatty acid/ rosin) along with other diacids, i.e., sebacic acid, and polyols, are used as monomer to prepare an alkyd resin which can be further emulsified.

US10131741B2 relates to the synthesis of an alkyd resin, which is prepared from at least one fatty acid, a bio-renewable polyol, a part of bio-sourced polyol derived from isosorbide, bio-renewable succinic acid/anhydride, and rosin.

WO2019050786A1 discloses alkyd resins comprising up to 50% lactide and a fatty acid or a fatty acid precursor. The lactide is a mixture of meso-lactide with one or both of L- and D-lactides.

WO2013128132A1 discloses alkyd resin obtained by polycondensation of a mixture comprising at least one unsaturated fatty acid and/or one unsaturated fatty acid ester comprising at least one alcohol function, a polyol, a polyacid, and polymerized abietic acid.

US10066053B2 discloses alkyd resin compositions comprising an imide compound, an alcohol, fatty acids or vegetable oils and an optional mono/and/or polyfunctional compound capable of esterification.

Although various alkyd resins are known, there has been a constant requirement to achieve environment-friendly alkyd resins with improved corrosion resistance performance and mechanical properties such as flexibility, adhesion, scratch resistance, impact resistance, and salt spray resistance.

Summary

An alkyd resin is disclosed. Said alkyd resin comprises a reaction product of a polyacid derivative, the polyacid derivative comprising a reaction product of an epoxide and a Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof; one or more polyols; and one or more fatty acids.

A process for preparing the aforesaid alkyd resin is also disclosed. Said process comprises the steps of reacting 1-7 wt.% solids of an epoxide with 35-55 wt.% solids of a Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof to obtain a polyacid derivative; and reacting 36-62 wt.% solids of the polyacid derivative with 25-45 wt.% solids of one or more fatty acids and 12-22 wt. % solids of one or more polyols, to obtain the alkyd resin.
Detailed Description

Reference will now be made in detail to embodiments of the present disclosure. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner, simply because it is being utilized in conjunction with a detailed description of certain specific embodiments of the invention. Furthermore, embodiments of the invention may include several features, no single one of which is solely responsible for its desirable attributes, or which is essential to practicing the inventions herein described.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

The terms “a,” “an,”, and “the” are used to refer to “one or more” (i.e., to at least one) of the grammatical object of the article.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion and are not intended to be construed as “consists of only”, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method.

Likewise, the terms “having” and “including”, and their grammatical variants are intended to be non-limiting, such that recitations of said items in a list are not to the exclusion of other items that can be substituted or added to the listed items.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.

The term “bio-renewable content” refers to substances with a renewable carbon content. The degree of bio-renewable content depends on the number of carbons in the monomers which are derived from biological, recycled, renewable, or otherwise sustainable materials. The bio-renewable content is measured by calculating the percentage of bio-based carbon content in a product compared to the total sum of bio-based and petroleum-based (carbon) content in that same product. Alternatively, the bio-renewable content can be calculated using ASTM D6866 test method.

In one aspect, an alkyd resin is described. The disclosed alkyd resin comprises a reaction product of:
- a polyacid derivative, the polyacid derivative comprising a reaction product of an epoxide and a Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof;
- one or more polyols; and
- one or more fatty acids.

In another aspect, a process for preparing the disclosed alkyd resin is described. Said process comprises the steps of:

(a) reacting 1-7 wt.% solids of an epoxide with 35-55 wt.% solids of a Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof, to obtain a polyacid derivative; and

(b) reacting 36-62 wt.% solids of the polyacid derivative with 25-45 wt.% solids of one or more fatty acids and 12-22 wt. % solids of one or more polyols to obtain the alkyd resin.

In the disclosed process, Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof comprising an excess of carboxylic functionality is partially reacted with epoxy group of the epoxide to obtain the polyacid derivative. The obtained polyacid derivative is further reacted with one or more polyols and one or more fatty acids to obtain the alkyd resin having a high bio-renewable content therein.

In an embodiment, the Diels-Alder adduct of rosin with the unsaturated dicarboxylic acid/ anhydride thereof is prepared by reacting rosin with the unsaturated dicarboxylic acid/anhydride to undergo Diels-Alder reaction at 175-225°C for a time-period ranging between 1- 3 hours. In some embodiments, the reaction is carried out at 180-200°C for 2 hours. In this reaction, abietic acid, the unsaturated cyclic mono acid present in rosin undergoes isomerization to form levopimaric acid, which reacts with the unsaturated dicarboxylic acid/anhydride thereof to form said Diels-Alder adduct.

In an embodiment, the unsaturated dicarboxylic acid/anhydride thereof is selected from the group consisting of maleic anhydride, itaconic acid, glutaconic acid, and citraconic acid. In some embodiments, the unsaturated dicarboxylic acid is itaconic acid. An exemplary reaction scheme for the preparation of the Diels-Alder adduct of rosin and itaconic acid is presented below:

In some embodiments, the unsaturated anhydride is maleic anhydride. An exemplary reaction scheme for the preparation of the Diels-Alder adduct of rosin and maleic anhydride is presented below:

In an embodiment, in the next step, the obtained Diels-Alder adduct of rosin and the unsaturated dicarboxylic acid/anhydride thereof is cooled at a temperature in a range of 160-180°C. In some embodiments, the obtained Diels-Alder adduct of rosin and the unsaturated dicarboxylic acid/anhydride thereof is cooled to 175-180°C.

In the next step, the Diels-Alder adduct of rosin and the unsaturated dicarboxylic acid/ anhydride thereof is reacted with the epoxide at an elevated temperature to obtain a reaction mixture containing the polyacid derivative. In an embodiment, the reaction of the Diels-Alder adduct of rosin and the unsaturated dicarboxylic acid/anhydride thereof, and the epoxide is carried out at a reaction temperature in the range of 160-200°C for a time-period in the range of 30-90 minutes. In some embodiments, the reaction is carried out at 180°C for 30-60 minutes.
In an embodiment, the epoxide is selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, epoxy novolac, mono glycidyl ether of cardanol (or cardyl glycidyl ether) and polyglycidyl ether of cardanol. In some embodiments, the epoxide is cardyl glycidyl ether.

Cardyl glycidyl ether is a cardanol based epoxide. Cardyl glycidyl ether being a bio-derived functional material increases the bio-renewable content in the backbone of alkyd resin. Hence, alkyd resins having 42-93% bio-renewable content can be obtained. In some embodiments, the epoxide is diglycidyl ether of bisphenol A having an Epoxide Equivalent Weight (EEW) in the range of 400-650 gm /equivalent. In some embodiments, the epoxide comprises a mixture of cardyl glycidyl ether and diglycidyl ether of bisphenol A.

In the next step, the reaction mixture containing the polyacid derivative is maintained at a temperature in a range of 160-200°C for a time period in a range of 30-90 minutes. In some embodiments, the reaction mixture is maintained at 180 °C for 30-60 minutes.

Further, the obtained polyacid derivative is reacted with the one or more fatty acids and the one or more polyols at an elevated temperature to obtain a reaction mass. In an embodiment, the reaction of the polyacid derivative with the one or more fatty acids and the one or more polyols is carried out at the elevated temperature in a range of 210-250°C for a time-period ranging between 7-12 hours. In some embodiments, the reaction is carried out at 240°C for 10 hours.

The one or more fatty acids used in the disclosed alkyd resin are any fatty acids that comprise unsaturated fatty acid moieties. In an embodiment, the one or more fatty acid is selected from the group consisting of soya bean oil fatty acid, linseed oil fatty acid, sunflower fatty acid, safflower fatty acid, tall oil fatty acid, and dehydrated castor oil fatty acid. In some embodiments, the fatty acid is soya bean oil fatty acid. In an embodiment, the fatty acid has an iodine value in the range of 120-180 gm I2 /100gm. In some embodiments, the fatty acid has the iodine value of 120-140 gm I2 /100gm. In an embodiment, the fatty acid has an acid value (mg KOH/gm) in the range of 185-205.

The one or more polyols used in the disclosed alkyd resin comprises of two or more hydroxyl groups per molecule. In an embodiment, the polyols include glycerol, pentaerythritol, sorbitol, trimethyl pentanediol and isosorbide. In some embodiments, the polyols are glycerol and bio based pentaerythritol (Voxtar M 100) which enable increased bio-renewable content of the disclosed alkyd resins.

In an embodiment, the reaction of the polyacid derivative with the one or more fatty acids and the one or more polyols is carried out in the presence of an esterification catalyst and a reflux solvent to obtain the alkyd resin.

The esterification catalyst includes any suitable esterification catalyst for the synthesis of alkyd resins now known or developed in the future. In an embodiment, the esterification catalyst is an organometallic catalyst selected from the group consisting of dibutyl tin oxide, lithium hydroxide, calcium oxide, zirconium octoate, calcium octoate and zinc oxide. In some embodiments, the esterification catalyst is dibutyl tin oxide. In an embodiment, the esterification catalyst is added in an amount ranging between 0.02-0.1 wt. % of the reaction mass. In an embodiment, the reflux solvent is mixed xylene. In an embodiment, the reflux solvent is added in an amount in a range of 1-4 wt.% of the reaction mass. In some embodiments, the reflux solvent is added in the amount in the range of 1-2 wt.% of the reaction mass.

In an embodiment, the obtained alkyd resin is maintained at a temperature between 210-250°C for a time-period ranging between 7-12 hours till an acid value (mg KOH/gm) of 15-25 and dilution viscosity on Gardner scale @ 25°C of W-Z1 at 50% solid in Mineral Turpentine Oil (MTO) or alpha pinene is achieved. Once the desired acid value and viscosity is achieved, the alkyd resin is cooled to a temperature in the range of 160-190°C. In some embodiments, the cooling is done to the temperature of 180°C. After cooling, the obtained alkyd resin is diluted in the solvent. Any known aliphatic or aromatic hydrocarbon solvents can be used. In an embodiment, the solvent includes but is not limited to xylene, MTO, aliphatic solvent C9, petroleum-based hydrocarbons solvent, and gum pine spirits like mix of alpha pinene and beta pinene. In some embodiments, the solvent is MTO. In some embodiments, the solvent is alpha pinene. Alpha pinene being a bio-based solvent allows substituting traditional petroleum-based solvent to further increase the overall bio-renewable content of the alkyd resin.

In an embodiment, the obtained alkyd resin has an acid value (mg KOH/gm) in a range of 16-25. In an embodiment, the obtained alkyd resin has a color on Gardener scale in a range of 11-18. In some embodiments, the obtained alkyd resin has the color on Gardener scale of 11-14. In an embodiment, the obtained alkyd resin has a % non-volatile matter (NVM) 120°C/1 hour in a range of 45-55. In some embodiments, the obtained alkyd resin has the % non-volatile matter (NVM) 120°C/1 hour in the range of 48-52.

In an embodiment, the disclosed alkyd resin has the bio-renewable content of at least 42-93%. In some embodiments, the disclosed alkyd resin has the bio-renewable content of 85-93%.

The present disclosure also relates to a coating composition. Said coating composition comprises 15-30 wt. % of the disclosed alkyd resin, and 30-50 wt. % of one or more additives.

The one or more additives that may be added are the components generally known to be useful for the preparation, storage, application, and curing of coating compositions. In an embodiment, one or more additives is selected from the group consisting of anticorrosive pigments, inorganic fillers, organic pigments, inorganic pigments, rheology modifiers, dispersing agents, and metallic driers.
In an embodiment, the anticorrosive pigment includes but is not limited to zinc oxide, calcium phosphate, strontium phosphosilicates, modified aluminium triphosphate, zinc molybdate, zinc phosphomolybdate, aluminium zinc phosphate, micaceous iron oxide, zinc phosphate, and strontium chromate. In some embodiments, the anticorrosive pigment is zinc phosphate.

Fillers are added in finely divided form in the coating composition. They are added in the coating composition to bring down the cost of the coating composition and to thicken the coating composition. Any known inorganic filler now known or developed in the future can be used. In an embodiment, the inorganic filler includes but is not limited to mica, steatite, dolomite, silica, and barytes. In some embodiments, the inorganic filler is steatite. The amount of the inorganic filler used in the coating composition depends on the characteristics of the filler such as their oil absorption, shape, size, and the properties desired in the coating composition.

The metallic driers used in the coating compositions react with the unsaturation present in the fatty acid and accelerate the conversion of the coating into a cross-linked dry film through auto-oxidative polymerization. In an embodiment, the metallic driers include, but are not limited to, calcium octoate, manganese octoate, and zirconium octoate.

The following examples illustrate certain embodiments and aspects of the present invention and are not to be construed as limiting the scope thereof. All parts and percentages are on a weight basis unless otherwise stated.

Examples

Materials used: Soyabean oil fatty acid was purchased from Fairchem Organics Ltd., Gujrat. Mono pentaerythritol (98%) based on petroleum feed stock was sourced from Kanoria Chem & Ind Ltd., Maharashtra. Mono pentaerythritol (Voxtar M100) based on 100% biobased feed stock was sourced from Perstorp Speciality Chemicals. Cardyl glycidyl ether was obtained from Paladin Paints & Chemicals Pvt. Ltd., Maharashtra, India. Mineral Turpentine Oil was sourced from Bharat Petroleum Corporation Limited and Alpha pinene obtained from Himalaya Terpenes Pvt. Ltd., Mumbai.

Comparative Example 1: Preparation of alkyd resin without using epoxide

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 1a below:

Table 1a: Reactants used for the preparation of the alkyd resin
S. No. Reactants Parts by weight
1. Indonesian rosin 19.09
2. Maleic anhydride 5.32
3. Soya Oil Fatty Acid (SOFA) 18.29
4. Glycerine 8.92
5. Mixed xylene 1.61
6. Dibutyl tin oxide 0.02
7. Mineral turpentine oil 46.75
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine and dibutyl tin oxide were added to the flask to obtain a reaction mass. This reaction mass was heated to 245-255°C and maintained till acid value of <25 mg KOH/g and viscosity at 50% in MTO on Gardner scale X-Y is achieved. This was followed by cooling to <180 °C and dilution with MTO to 50% solids of alkyd resin. The resin obtained has renewable content of 46.20 wt.%.

Product Characterization: Table 1b provides characteristics of the alkyd resin obtained above.
Table 1b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 12-13
2. Acid Value (mg KOH /gm) 19.63
3. % NVM @ 120°C/1 hour 51.16

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 11.

Observation: Though all the initial physical and mechanical properties of the primer paint were found to be satisfactory, after 15 days of accelerated storage stability at 55°C, gelation in the paint was observed.

Comparative Example 2: Preparation of alkyd resin without using epoxide

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 2a below:

Table 2a: Reactants used for the preparation of the alkyd resin
S. No. Reactants Parts by weight
1. Indonesian rosin 18.62
2. Maleic anhydride 5.01
3. Soya Oil Fatty Acid (SOFA) 18.88
4. Glycerine 6.49
5. Mono pentaerythritol (Voxtar M100, 100% bio based) 2.61
6. Mixed xylene 1.58
7. Dibutyl tin oxide 0.02
8. Mineral turpentine oil 46.79
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol, and dibutyl tin oxide were added to the flask to obtain a reaction mass. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in MTO on Gardner scale X-Y is achieved. This was followed by cooling to <180 °C and dilution with MTO to 50% solids of alkyd resin. The resin has renewable content of 46.60 wt.%.

Product Characterization: Table 2b provides characteristics of the alkyd resin obtained above.
Table 2b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 11-12
2. Acid Value (mg KOH /gm) 20.28
3. % NVM @ 120°C/1 hour 51.23

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 11.

Observation: After 30 days of accelerated storage stability at 55°C, gelation in the paint was observed.

Comparative Example 3: Preparation of alkyd resin without using epoxide

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 3a below:
Table 3a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 17.37
2. Itaconic acid 6.37
3. Soya Oil Fatty Acid (SOFA) 18.14
4. Mono pentaerythritol (Voxtar M100, 100% bio based) 9.19
5. Mixed xylene 1.57
6. Dibutyl tin oxide 0.02
7. Mineral turpentine oil 47.34
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, itaconic acid and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and itaconic acid. Thereafter, the obtained Diels-Alder adduct of rosin and itaconic acid was cooled to 180°C. The reaction kettle was arranged for azeotropic distillation and SOFA, mono pentaerythritol and dibutyl tin oxide were added to the flask to obtain a reaction mass. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in MTO on Gardner scale Z-Z1 is achieved. This was followed by cooling to <180 °C and dilution with MTO to 50% solids of alkyd resin. The resin obtained has renewable content of 51.07 wt%.

Product Characterization: Table 3b provides characteristics of the alkyd resin obtained above.

Table 3b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 17-18
2. Acid Value (mg KOH /gm) 20.95
3. % NVM @ 120°C/1 hour 49.56

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 11.

Example 1: Preparation of alkyd resin in accordance with an embodiment of the present disclosure

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 4a below:

Table 4a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 18.85
2. Maleic anhydride 5.15
3. Cardyl glycidyl ether 1.61
4. Soya Oil Fatty Acid 17.08
5. Glycerine 7.62
6. Mono Pentaerythritol (Voxtar M100, 100% bio based) 1.23
7. Mixed xylene 1.62
8. Dibutyl tin oxide 0.02
9. Mineral turpentine oil 46.82
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C and cardyl glycidyl ether was added to form a reaction mixture. The reaction mixture was maintained for 30 minutes. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol and dibutyl tin oxide were added to the flask. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in MTO on Gardner scale X-Y is achieved. This was followed by cooling to <180 °C and dilution with MTO to 50% solids of alkyd resin. The resin obtained has renewable content of 46.39 wt.%.

Product Characterization: Table 4b provides characteristics of the alkyd resin obtained above.
Table 4b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 13-14
2. Acid Value (mg KOH /gm) 22.29
3. % NVM @ 120°C/1 hour 50.5

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The resulting primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 11.

Example 2: Preparation of alkyd resin in accordance with an embodiment of the present disclosure

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 5a below:

Table 5a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 18.99
2. Maleic anhydride 4.36
3. Cardyl glycidyl ether 1.65
4. Di glycidyl ether of Bisphenol-A (Epoxy equivalent weight: 450-550 gm /equivalent) 75% in xylene 0.37
5. Soya Oil Fatty Acid 16.57
6. Glycerine 5.11
7. Mono pentaerythritol (Petroleum based, 98%) 4.4
8. Mixed xylene 1.79
9. Dibutyl tin oxide 0.02
10. Mineral turpentine oil 46.74
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C and cardyl glycidyl ether and diglycidyl ether of bisphenol A were added to form a reaction mixture. The reaction mixture was maintained for 30 minutes. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol and dibutyl tin oxide were added to the flask. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in MTO on Gardner scale W-X was achieved. This was followed by cooling to <180 °C and dilution with MTO to 50% solids of the alkyd resin. The resin has renewable content of 42.32 wt.%.

Product Characterization: Table 5b provides characteristics of the alkyd resin obtained above.

Table 5b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 13-14
2. Acid Value (mg KOH /gm) 16.29
3. % NVM @ 120°C/1 hour 50.85
Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The resulting primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 12A.

Observation: Excellent adhesion of paint film over metal panels was observed after the incorporation of cardyl glycidyl ether and diglycidyl ether of bisphenol-A. Further, the presence of a long alkyl chain at the meta position of cardyl glycidyl ether imparts hydrophobicity to paint film. Due to the incorporation of an epoxy functional group into the alkyd backbone, the water permeability of the paint film decreased significantly, improving its barrier property for corrosion resistance. The salt spray resistance of the coating film passed 600 hrs.

Example 3: Preparation of alkyd resin in accordance with an embodiment with an embodiment of the present disclosure

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 6a below:

Table 6a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 18.99
2. Maleic anhydride 4.36
3. Cardyl glycidyl ether 1.65
4. Di glycidyl ether of Bisphenol-A (Epoxy equivalent weight: 450-550 gm /equivalent ) 75% in xylene 0.37
5. Soya Oil Fatty Acid 16.57
6. Glycerine 5.11
7. Mono pentaerythritol (Petroleum based, 98%) 4.4
8. Mixed xylene 1.79
9. Dibutyl tin oxide 0.02
10. Alpha pinene 46.74
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C and cardyl glycidyl ether and diglycidyl ether of bisphenol A were added to form a reaction mixture. The reaction mixture was maintained for 30 minutes. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol and dibutyl tin oxide were added to the flask. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in alpha pinene on Gardner scale Y-Z was achieved. This was followed by cooling to <180 °C and dilution with alpha pinene to 50% solids of the alkyd resin. The resin obtained has renewable content of 89.06 wt%.

Product Characterization: Table 6b provides characteristics of the alkyd resin obtained above.
Table 6b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 13-14
2. Acid Value (mg KOH /gm) 17.34
3. % NVM @ 120°C/1 hour 50.35

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 12A.

Observation: Excellent adhesion of paint film over metal panel was observed after incorporation of cardyl glycidyl ether and diglycidyl ether of bisphenol-A. The salt spray resistance of the coating film passed till 600 hours and the tack free drying time of primer paint film increased to 8 hours when thinned with solvent alpha pinene.

Example 4: Preparation of alkyd resin in accordance with an embodiment of the present disclosure.

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 7a below:

Table 7a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 19.32
2. Maleic anhydride 4.44
3. Cardyl glycidyl ether 1.68
4. Di glycidyl ether of Bisphenol-A (Epoxy equivalent weight: 450-550 gm /equivalent) 75% in xylene 0.37
5. Soya Oil Fatty Acid 15.97
6. Glycerine 5.2
7. Mono pentaerythritol (Voxtar M100,100% bio based) 4.48
8. Mixed xylene 1.81
9. Dibutyl tin oxide 0.02
10. Alpha pinene 46.71
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C and cardyl glycidyl ether and diglycidyl ether of bisphenol A were added to form a reaction mixture. The reaction mixture was maintained for 30 minutes. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol and dibutyl tin oxide were added to the flask. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in alpha pinene on Gardner scale Z-Z1 was achieved. This was followed by cooling to <180 °C and dilution with alpha pinene to 50% solids of the alkyd resin. The resin obtained has renewable content of 92.96 wt%.

Product Characterization: Table 7b provides characteristics of the alkyd resin obtained above.

Table 7b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 13-14
2. Acid Value (mg KOH /gm) 20.35
3. % NVM @ 120°C/1 hour 50.11

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 12A.

Observation: The salt spray resistance of the coating film passed till 650 hours and the tack free drying time of primer paint film increased to 8 hours when thinned with solvent alpha pinene.

Example 5: Preparation of alkyd resin in accordance with an embodiment of the present disclosure

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 8a below:

Table 8a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 18.5
2. Maleic anhydride 5.05
3. Cardyl glycidyl ether 1.6
4. Soya Oil Fatty Acid 16.7
5. Glycerine 7.5
6. Mono pentaerythritol (Voxtar M100,100% bio based) 1.2
7. Mixed xylene 2.08
8. Dibutyl tin oxide 0.02
9. Mineral turpentine oil 47.35
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C and cardyl glycidyl ether was added to form a reaction mixture. The reaction mixture was maintained for 30 minutes. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol and dibutyl tin oxide were added to the flask. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in MTO on Gardner scale W-X was achieved. This was followed by cooling to <180 °C and dilution with mineral turpentine oil to 50% solids of the alkyd resin. The resin obtained has renewable content of 45.50 wt.%.

Product Characterization: Table 8b provides characteristics of the alkyd resin obtained above.
Table 8b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 13-14
2. Acid Value (mg KOH /gm) 22.29
3. % NVM @ 120°C/1 hour 50.23

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 12B.

Example 6: Preparation of alkyd resin in accordance with an embodiment of the present disclosure

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 9a below:

Table 9a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 18.99
2. Maleic anhydride 4.36
3. Cardyl glycidyl ether 1.65
4. Di glycidyl ether of Bisphenol-A (Epoxy equivalent weight: 450-550 gm /equivalent) 75% in xylene 0.37
5. Soya Oil Fatty Acid 16.57
6. Glycerine 5.11
7. Mono pentaerythritol (Voxtar M100,100% bio based) 4.4
8. Mixed xylene 1.79
9. Dibutyl tin oxide 0.02
10. Mineral turpentine oil 46.74
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C and cardyl glycidyl ether and diglycidyl ether of bisphenol A were added to form a reaction mixture. The reaction mixture was maintained for 30 minutes. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol and dibutyl tin oxide were added to the flask. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in MTO on Gardner scale W-X was achieved. This was followed by cooling to <180 °C and dilution with mineral turpentine oil to 50% solids of the alkyd resin. The resin obtained has renewable content of 46.72 wt.%.

Product Characterization: Table 9b provides characteristics of the alkyd resin obtained above.

Table 9b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 13-14
2. Acid Value (mg KOH /gm) 17.34
3. % NVM @ 120°C/1 hour 50.86

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 12B.

Observation: Tack free drying time of primer paint film was 3 hours when thinned with solvent MTO.

Example 7: Preparation of alkyd resin in accordance with an embodiment of the present disclosure.

Materials: The reactants used for the preparation of the alkyd resin along with their respective weight percentages are listed in Table 10a below:

Table 10a: Reactants used for the preparation of the alkyd resin
S.No. Reactants Parts by weight
1. Indonesian rosin 19.32
2. Maleic anhydride 4.44
3. Cardyl glycidyl ether 1.68
4. Di glycidyl ether of Bisphenol-A (Epoxy equivalent weight: 450-550 gm /equivalent) 75% in xylene 0.37
5. Soya Oil Fatty Acid 15.97
6. Glycerine 5.2
7. Mono pentaerythritol (Voxtar M100,100% bio based) 4.48
8. Mixed xylene 1.81
9. Dibutyl tin oxide 0.02
10. Mineral turpentine oil 46.71
Total 100

Processing: In a four- necked reactor flask equipped with a temperature controller, heating mantle, nitrogen sparger, overhead stirrer and Dean Stark assembly, Indonesian rosin, maleic anhydride and mixed xylene were charged and heated to 180-200°C for 2 hours to form Diels-Alder adduct of rosin and maleic anhydride. Thereafter, the obtained Diels-Alder adduct of rosin and maleic anhydride was cooled to 180°C and cardyl glycidyl ether and diglycidyl ether of bisphenol A were added to form a reaction mixture. The reaction mixture was maintained for 30 minutes. The reaction kettle was arranged for azeotropic distillation and SOFA, glycerine, mono pentaerythritol and dibutyl tin oxide were added to the flask. This reaction mass was heated to 245-255°C and maintained till acid value of < 25 mg KOH/g and viscosity at 50% in mineral turpentine oil on Gardner scale X-Y was achieved. This was followed by cooling to <180°C and dilution with MTO to 50% solids of the alkyd resin. The resin obtained has renewable content of 46.25 wt.%.

Product Characterization: Table 10b provides characteristics of the alkyd resin obtained above.

Table 10b: Characteristics of the alkyd resin
S. No. Parameter Characteristic
1. Color on Gardner scale 13-14
2. Acid Value (mg KOH /gm) 20.35
3. % NVM @ 120°C/1 hour 50.62

Preparation of anti-corrosive primer coating compositions: The alkyd resin thus obtained along with synthetic yellow oxide, zinc phosphate, marble powder 10-micron, steatite 500 mesh, zinc octoate, soya lecithin, soya oil monoglyceride, octoates of zirconium, cobalt, calcium and manganese, glycidyloxy propyl trimethoxy silane, methyl ethyl ketone oxime, bentonite and mineral turpentine oil were used to prepare the primer coating composition.

The obtained primer coating composition was applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70 micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats. After seven days of curing, these test panels were evaluated for various performance properties like flexibility, adhesion, scratch hardness, impact resistance and salt spray resistance. The test results are summarized in Table 12B.

Example 8: Preparation of the primer coating compositions.

Primer coating compositions were prepared using the alkyd resins of comparative examples 1-3 and examples 1-7. These coating compositions were tested for drying time, physical, mechanical, weathering and corrosion resistance.

Tests Conducted:

The flexibility of the coating compositions was tested by conducting a Mandrel bend test as per ASTM D522.

Scratch hardness of the coating was tested using Sheen make automatic scratch tester Ref. No. 705 with 1mm 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 × 15.9± 0.08 mm diameter × 908±1 gm load).

The salt spray resistance of the coating composition tested according to ASTM B117. To assess corrosion resistance, the appearance of corrosion product was evaluated periodically.

Results: Tables 11, 12A and 12B provide the test results of the primer coating film obtained using the coating compositions prepared above, applied on sanded mild steel panel (1.6 × 70 × 150 mm) by spraying application and left to stand at room temperature. A 50–70-micron dry film thickness of coating was obtained in 2 coats with maturation time of 16-24 hours between the 2 coats.

Table 11: Test results of the primer coating film

Property Comparative Example 1 Comparative Example 2 Comparative Example 3
DFT (microns) 55-60 50-60 50-60
Surface dry time in minutes (ASTM D 5895) 40 min 40 min 40 min
Tack free time in hours (ASTM D 5895) 2.5 hrs. 2.5 hrs. 7 hrs.
Hard dry time in hours (ASTM D 5895) 24 hrs. 24 hrs. 24 hrs.
Scratch hardness after 48 hours (gm) (ISO 1518) 800 gm 900 gm 1000 gm
Flexibility ¼ inch mandrel (ASTM D 522) Pass Pass Pass
Impact resistance (1 Kg front & reverse) (ISO 6272) Pass Pass Pass
Adhesion (ASTM D 3359) 2B 2B 2B
Salt spray test (hr.) (ASTM B117) 350 350 400

Table 12A: Test results of the primer coating film
Property Example 1 Example 2 Example 3 Example 4
DFT (microns) 60-70 60-70 60-70 60-70
Surface dry time in minutes (ASTM D 5895) 30 min 30 min 40 min 40 min
Tack free time in hours (ASTM D 5895) 2 hrs. 2 hrs. 8 hrs. 8 hrs.
Hard dry time in hours (ASTM D 5895) 24 hrs. 24 hrs. 24 hrs. 24 hrs.
Scratch hardness after 48 hours (gm) (ISO 1518) 700 gm 1100 gm 1100 gm 1100 gm
Flexibility ¼ inch mandrel (ASTM D 522) Pass Pass Pass Pass
Impact resistance (1 Kg front & reverse) (ISO 6272) Pass Pass Pass Pass
Adhesion (ASTM D 3359) 3B 5B 5B 5B
Salt spray test (hrs.) (ASTM B117) 500 600 600 650

Table 12B: Test results of the primer coating film
Property Example 5 Example 6 Example 7
DFT (microns) 60-70 60-70 60-70
Surface dry time in minutes (ASTM D 5895) 25 min 30 min 30 min
Tack free time in hours (ASTM D 5895) 2 hrs 3 hrs 3 hrs
Hard dry time in hours (ASTM D 5895) 24 hrs 24 hrs 24 hrs
Scratch hardness after 48 hours (gm) (ISO 1518) 900 gm 1100 gm 1100 gm
Flexibility ¼ inch mandrel (ASTM D 522) Pass Pass Pass
Impact resistance (1 Kg front & reverse) (ISO 6272) Pass Pass Pass
Adhesion (ASTM D 3359) 3B 5B 5B
Salt spray test (hrs.) (ASTM B117) 400 600 650

Observation: The coating compositions comprising the inventive alkyd resins (comprising a polyacid derivative comprising a reaction product of an epoxide and a Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof) exhibited improved corrosion resistance, salt spray resistance and adhesion as compared to the coating compositions based on alkyd resins comprising diacids comprising Diels Alder adduct of rosin and maleic anhydride.

Industrial Applicability

The disclosed process incorporates bio-renewable raw materials in the alkyd backbone, thereby increasing the bio-renewable content in the resultant alkyd resin. In some embodiments, the disclosed alkyd resin has the bio-renewable content greater than 85%. The disclosed alkyd resin thus eliminates the requirement of commonly used phthalic based dicarboxylic acids and provides an environment friendly alkyd resin.

The disclosed alkyd resin also possesses superior corrosion resistance due to the use of rosin adducts and the grafting of epoxy functionalities. Thus, the disclosed alkyd resin, when used in coating applications, exhibits improved corrosion resistance and performance properties. For instance, as illustrated in tables 11, 12A and 12B, the coating compositions based on disclosed alkyd resins, when applied to a sanded mild steel panels at a dry film thickness of 50-70 microns in two coats with an interval of 16 hours between the coats, provides a corrosion resistance performance of 600 hours or more without any sign of under-film corrosion as per the salt spray test (ASTM B117). Also, the disclosed coating composition passes the flexibility test conducted by a Mandrel bend test (as per ASTM D 522), and impact resistance tested 1 Kg front and reverse (as per ISO 6172).

Thus, the disclosed alkyd resin not only has an increased bio-renewable content, but also exhibits improved processing as well as performance properties especially corrosion resistance and adhesion than those obtained for alkyd resins based on phthalic acid, and other bio-based alkyd resins known in the art.

The disclosed alkyd resin is air-drying. The disclosed alkyd resin can be used with 100% biobased solvent as well as commonly used MTO, white spirit, xylene, naphtha solvent obtained from petroleum crude for broader end use.
,CLAIMS:1. An alkyd resin comprising a reaction product of:
- a polyacid derivative, the polyacid derivative comprising a reaction product of an epoxide and a Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof;
- one or more polyols; and
- one or more fatty acids.
2. The alkyd resin as claimed in claim 1, wherein the unsaturated dicarboxylic acid/ anhydride thereof is selected from the group consisting of maleic anhydride, itaconic acid, glutaconic acid and citraconic acid.
3. The alkyd resin as claimed in claim 1, wherein the epoxide is selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, epoxy novolac, mono glycidyl ether of cardanol and polyglycidyl ether of cardanol.
4. The alkyd resin as claimed in claim 1, wherein the one or more polyols is a bio-based polyol.
5. The alkyd resin as claimed in claim 1, wherein the fatty acid has an iodine value in the range of 120-180 gm iodine/100gm, the fatty acid being selected from the group consisting of soya bean oil fatty acid, linseed oil fatty acid, sunflower fatty acid, safflower fatty acid, tall oil fatty acid, and dehydrated castor oil fatty acid.
6. The alkyd resin as claimed in claim 1, characterized by having an acid value in the range of 16-23 mg KOH/gm, color on Gardener scale of 11-18, and % non-volatile matter @ 120°C/1 hour in the range of 45-55.
7. A process for preparing an alkyd resin, said process comprising the steps of:
(a) reacting 1-7 wt.% solids of an epoxide with 35-55 wt.% solids of a Diels-Alder adduct of rosin and an unsaturated dicarboxylic acid/ anhydride thereof, to obtain a polyacid derivative; and
(b) reacting 36-62 wt.% solids of the polyacid derivative with 25-45 wt.% solids of one or more fatty acids and 12-22 wt. % solids of one or more polyols to obtain the alkyd resin.
8. The process as claimed in claim 7, wherein the unsaturated dicarboxylic acid/anhydride thereof is selected from the group consisting of maleic anhydride, itaconic acid, glutaconic acid and citraconic acid.
9. The process as claimed in claim 7, wherein the epoxide is selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, epoxy novolac, mono glycidyl ether of cardanol and polyglycidyl ether of cardanol.
10. The process as claimed in claim 7, wherein the one or more polyols is a bio-based polyol.
11. The process as claimed in claim 7, wherein the fatty acid has an iodine value in a range of 120-180 gm iodine/100gm, the fatty acid being selected from the group consisting of soya bean oil fatty acid, linseed oil fatty acid, sunflower fatty acid, safflower fatty acid, tall oil fatty acid, and dehydrated castor oil fatty acid.
12. The process as claimed in claim 7, wherein the reaction of the Diels-Alder adduct of rosin and the unsaturated dicarboxylic acid/ anhydride thereof, with the epoxide in step (a) is carried out at a reaction temperature in the range of 160-200°C for a time-period in the range of 30-90 minutes.
13. The process as claimed in claim 7, wherein the reaction of the polyacid derivative with the one or more fatty acids and the one or more polyols in step (b) is carried out at an elevated temperature in the range of 210-250°C for a time-period in the range of 7-12 hours.
14. The process as claimed in claim 7, wherein the reaction of the polyacid derivative with the one or more fatty acids and the one or more polyols is carried out in the presence of 0.02-0.1 wt.% of an esterification catalyst.
15. The process as claimed in claim 14, wherein the esterification catalyst is an organometallic catalyst selected from the group consisting of dibutyl tin oxide, lithium hydroxide, calcium oxide, zirconium octoate, calcium octoate and zinc oxide.
16. The process as claimed in claim 7, wherein the obtained alkyd resin is maintained at a temperature ranging between 210-250°C for a time-period ranging between 7-12 hours till an acid number of 15-25 mg KOH/gm and dilution viscosity on Gardner scale @ 25°C of W-Z1 at 50% solid in Mineral Turpentine Oil (MTO) or Alpha Pinene, is achieved.
17. A coating composition comprising:
- 15-30 wt.% of the alkyd resin as claimed in claim 1; and
- 30-50 wt.% of one or more additives.
18. The coating composition as claimed in claim 17, wherein the one or more additives is selected from the group consisting of anticorrosive pigments, inorganic fillers, organic pigments, inorganic pigments, rheology modifiers, dispersing agents, and metallic driers.