FIELD
The present disclosure relates to a process for preparing epoxy ester resin. Particularly, the present disclosure relates to a green process for preparing radiation curable epoxy ester resin.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.
Epoxy equivalent value: The term "epoxy equivalent value", refers to one number of the reactive epoxy group present in a number of gms of the epoxy resin. For instance, if the epoxy equivalent value of an epoxy resin is 314, it means that one reactive epoxy group is present in 314 gms of the epoxy resin.
Acid value: The term "Acid value" is defined as the mass of KOH in milligrams that is required to neutralize one gram of chemical substance and is an indicator of the mass of free acid present in the chemical substance.
BACKGROUND
The background information hereinbelow relates to the present disclosure but is not necessarily prior art.
Epoxy ester resins are known in the prior art for their use in cable coatings, paints, and adhesives. Typically, the preparation of epoxy ester resin is a two-stage process. The first stage is a condensation product of epichlorohydrin, bisphenol A and sodium hydroxide, giving epoxy resin and a large amount of salt. The condensation product has high viscosity and therefore, separation of salt is very challenging. Conventionally, epoxy ester resin is rendered free of salt, with several water washings, generating a lot of wastewater. Typically, wastewater

contains 50,000-95000 ppm TDS and 50000-60000 ppm COD, which, therefore, requires large capital investment for wastewater treatment plants.
The second stage is an esterification process of epoxy resin produced in the first stage, producing epoxy ester resin. The second stage is also very challenging as along with the esterification process, as the free radical generation takes place simultaneously, resulting in the formation of undesirable epoxy ester resin which is unstable, has a dark color and bad odor.
Epoxy ester resin manufacturing becomes very difficult at a high loading of fatty acid and when low free acid is required for the specific application. However, the high loading of fatty acid is a prime requirement for increasing PI value (photo-initiation value) of epoxy ester resin. Another issue with epoxy ester resin manufacturing is the stability of the finished product as it undergoes self-crosslinking slowly at ambient storage conditions. In coating formulations, epoxy ester resin becomes more reactive in contact with the additives and undergoes cross-linking, which results in the shortening pot life of the coating. During the manufacturing of epoxy ester resin, even though stoichiometry of epoxy-carbonyl is perfect, the reaction approaches gel formation due to parallel free radical reactions along with esterification. After a certain level of epoxy-carbonyl conversion, a parallel free radical pathway dominates the esterification pathway which results in undesirable output like dark color, very high viscosity and high acidity, etc. The only use of phenolic antioxidants fails in controlling the color of the product as free radicals have a number of sites available in epoxy resin phenyl rings for the attack. At the same time heat supplied to the material drives the free radical pathway reaction greater than esterification. This parallel free radical pathway is centered at the vinyl group in the epoxy ester resin. Therefore, the choice of proper vinyl polymerization inhibitors becomes a crucial point in designing the formulation of epoxy ester resin. Typical vinyl polymerization inhibitors are quinones and their derivatives.

Thus, there is a need for developing a process for the preparation of epoxy ester resin which mitigates the drawbacks mentioned hereinabove.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the preparation of the epoxy ester resin that is salt-free.
Yet another object of the present disclosure is to provide a process for the preparation of the epoxy ester resin, which is radiation curable.
Still another object of the present disclosure is to provide the epoxy ester resin having excellent storage stability, transparency and no inherent odor.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a process for preparing epoxy ester resin. The process comprises, first, synthesizing a salt-free and a color free epoxy resin; and esterifying the salt-free and the color free epoxy resin by using a fatty acid in the presence of at least one catalyst, at least one antioxidant and at least one free-radical inhibitor at a predetermined temperature for a predetermined time period in an inert atmosphere to obtain a product mixture comprising the epoxy ester resin. The acid value of the product mixture is less than 1.5 mgKOH/gm.

The present disclosure further relates to a process for preparing the salt-free and the color free epoxy resin by reacting epichlorohydrin with bisphenol A in a fluid medium in the presence of at least one antioxidant followed by slowly adding 50% solution of a base for a time period in the range of 18 hours to 20 hours, in an inert atmosphere, at a temperature in the range of 80°C to 130°C to obtain a reaction mixture. Water is removed from the reaction mixture azeotropically to obtain a mixture of epoxy resin and salt. The salt is separated from the mixture by adding methyl isobutyl ketone and filtering it by using a centrifuge filter to obtain a product mixture comprising epoxy resin having traces of salt, methyl isobutyl ketone and the fluid medium. The product mixture is contacted with an adsorbent to obtain a salt-free epoxy resin having traces of methyl isobutyl ketone and the fluid medium. The methyl isobutyl ketone and the fluid medium are distilled off under vacuum at a temperature in the range of 80 °C to 130 °C to obtain the salt-free and the color free epoxy resin.
The present disclosure provides an epoxy ester resin which is radiation curable, stable, color and odor-free.
DETAILED DESCRIPTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a," "an," and "the" may be intended to include the plural forms as well,

unless the context clearly suggests otherwise. The terms "comprises," "comprising," "including," and "having," are open-ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third, etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
The process of preparation of epoxy ester resin is typically a two-stage process. First, an epoxy resin is prepared by the condensation of epichlorohydrin and bisphenol A by using a base. A large amount of salt is co-produced during the process of condensation. Epoxy resins are highly viscous and therefore, removal of salt is very challenging. Conventionally salt is removed by washing the condensation product with water. Several water washings result in the generation of a large amount of wastewater. The wastewater contains high TDS of around 50000-95000 ppm and COD of around 50000-60000 ppm. Treatment of generated wastewater requires the installation of a water treatment plant which adds to the CAPEX and OPEX of the process of epoxy resin preparation.
In the second stage, epoxy resin is converted into epoxy ester resin using a fatty acid during the esterification process. This stage is also very challenging due to the generation of free radicals during the process of esterification resulting in the formation of unstable epoxy ester resin which has a dark color and bad odor.

The present disclosure provides a process for the preparation of epoxy ester resin which solves the problem mentioned hereinabove and also provides epoxy ester resin which is radiation curable, stable and color and odor-free.
In an aspect, the present disclosure provides a process for the preparation of epoxy ester resin. The epoxy ester resin is prepared by esterifying a salt-free and the color free epoxy resin by using a fatty acid in the presence of at least one catalyst, at least one antioxidant and at least one free-radical inhibitor at a predetermined temperature for a predetermined time period in an inert atmosphere to obtain a product mixture comprising the epoxy ester resin. The acid value of said product mixture is less than 1.5 mgKOH/gm.
The process is described in detail as given below.
First, a salt-free and a color free epoxy resin are synthesized.
The salt-free and the color free epoxy ester resin is synthesized by reacting epichlorohydrin with bisphenol A in a fluid medium in the presence of at least one antioxidant followed by slowly adding 50% aqueous solution of a base for a time period in the range of 18 hours to 20 hours, in an inert atmosphere, at a temperature in the range of 80°C to 130°C to obtain a reaction mixture. Water is removed from the reaction mixture, azeotropically, to obtain a mixture of epoxy resin and salt.
In an embodiment, water recovered from azeotropic distillation has TDS around 700-800ppm and COD around 300- 250 ppm which easily treatable and reusable.
The fluid medium is selected from toluene, xylene, and cyclohexene. In an exemplary embodiment, the fluid medium is toluene.
The base is selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide. In an exemplary embodiment, the base is sodium hydroxide.

The salt is separated from the mixture by adding methyl isobutyl ketone (MTBK) and filtering it by using a centrifuge filter to obtain a product mixture comprising epoxy resin having traces of salt, methyl isobutyl ketone and the fluid medium. Further, the product mixture is contacted with an adsorbent to obtain a salt-free epoxy resin having traces of methyl isobutyl ketone and the fluid medium.
The adsorbent is selected from molecular sieves and anion exchange resins. In accordance with the present disclosure, the absorbent is selected from Hyflo filtration media, diatomaceous earth, anion exchange resin such as DIAION SA10, DOWEX MARATHON™ 4200 CI, and Amberlite IRA-CL.
In an embodiment, the salt is separated from the mixture by diluting the reaction mixture with 30% - 40% methyl isobutyl ketone. The use of methyl isobutyl ketone cut down the viscosity of the resin thin enough to render the salt settles down to the bottom of the reactor. In an embodiment, the settled salt is drained out of the reactor from the bottom wall and the suspended salt particles filtered using a centrifuge filter to obtain the salt-free epoxy resin. The so obtained epoxy resin solution contains 0.5 to 0.2% chloride ions which may alter the properties of the finished good.
This resin solution with chloride concentration around 0.5 to 0.2% is treated with the absorbents like molecular sieves, anion exchange resins to remove chloride ion. The treatment of the product mixture with the adsorbent is in the range of 15 min to 45 minutes, preferably 30 minutes. In an embodiment, the treatment of the product mixture with the adsorbant is done for 30 min that found perfect to capture all chloride from the resin. After 30 minutes contacting/treating with absorbent, the resin solution is then filtered through the 100 micron size centrifuge bag filter or press filter.
Further, methyl isobutyl ketone and the fluid medium are distilled off at a temperature in the range of 80 °C to 130 °C under vacuum to obtain the salt-free and the color free epoxy resin. The recovered fluid medium & MTBK is reused for thinning the next batch.

The molar ratio of the epichlorohydrin to the base solution is in the range of 1:1 to 8:1. In an embodiment, the molar ratio of the epichlorohydrin to the sodium hydroxide solution is in the range of 1:1 to 1:8.
The pore size of the filter bag used in centrifuge filter is in the range of 80 microns to 120 microns, typically the pore size is 100 microns. The anti-oxidant is pentaerythritol tetrakis [3-(3,5 di-tert butyl - 4 - hydroxyphenyl) propionate].
The so obtained salt-free and the color free epoxy resin is esterified by using a fatty in the presence of at least one catalyst, at least one antioxidant and at least one free-radical inhibitor at a predetermined temperature for a predetermined time period in an inert atmosphere to obtain a product mixture comprising the epoxy ester resin. The acid value of the product mixture is less than 1.5 mgKOH/gm.
The catalyst is at least one selected from the group consisting of dimethylaniline, triphenylphosphine, trimethylamine, zinc oxalate, and zinc acetate.
In an exemplary embodiment, the catalyst is zinc oxalate. In another exemplary embodiment, the catalyst is zinc acetate. In yet another exemplary embodiment, the catalyst is N, N-dimethyl aniline. In yet another exemplary embodiment, the catalyst is triphenylphosphine.
The inventors found that zinc oxalate and zinc acetate (organozinc salt) found to be a comparatively better catalyst in the process of the present disclosure. The reaction conversion is found to be in the range of 95-98% when zinc oxalate is used as a catalyst and the reaction conversion is found to be in the range of 90-95% when zinc acetate is used as a catalyst.
Other benefits of zinc oxalate/zinc acetate catalyst over other catalyst are that the so obtained product is low viscosity and color free.
The amine catalysts drive both reactions pathways such as free radical at vinyl group and esterification at the carboxylic site of the acrylic acid. These complex sideway reactions turn the material in high viscosity pickup even at 60-70%) conversion and thus gelling of the polymer is observed in such cases. On the other

hand, zinc oxalate/zinc acetate expedites esterification, selectively, by capturing vinyl-free radicals.
In accordance with the present disclosure, the fatty acid is unsaturated fatty acid. The unsaturated fatty acid is selected from the group consisting of acrylic acid, soy fatty acid, dehydrated castor fatty acid, anacardic acid, recinoleic acid, oleic acid, linolenic acid, methacrylic acid and the like. In an exemplary embodiment the fatty acid is acrylic acid. The unsaturated fatty acid has a higher PI values, due to which a faster curing of epoxy ester resin is observed. Therefore, the epoxy ester resin of the present disclosure is radiation curable as well as used in air drying application.
Further, the longer addition time of the acrylic acid (about 8 hrs) in the reaction mixture allows adding up a single molecule in the polymer chain, due to which a low molecular weight epoxy acrylate is formed which has low processing viscosity. The longer addition time of acrylic acid in acrylation of epoxy is the safest way for preparing epoxy acrylate resin which also controls sideways free radical linking of acrylic acids. Hence there is less availability of another acrylic acid to react with vinyl radicals of acrylic acid in the chain and hence there are fewer chances of gelling or crosslinking of material during manufacturing.
The anti-oxidant is pentaerythritol tetrakis [3-(3,5 di-tert butyl - 4 -hydroxyphenyl) propionate].
The free radical inhibitor is at least one selected from the group consisting of monomethyl ether of hydroquinone, hydroquinone, triphenyl phosphite, and butylated hydroxyl toluene. In an exemplary embodiment, the free radical inhibitor is monomethyl ether of hydroquinone. In another exemplary embodiment, the free radical inhibitor is hydroquinone. In accordance with the present disclosure, the ratio of the monomethyl ether of hydroquinone to the acrylic acid is in the range of 0.1 wt% to lwt%, and the ratio of the hydroquinone to the acrylic acid is in the range of 0.05wt% to 0.2wt%.

The predetermined temperature is in the range of 70 °C to 100 °C. In an exemplary embodiment, the predetermined temperature is in the range of 80 °C to 90 °C.
The predetermined time period is in the range of 10 hours to 40 hours. In an exemplary embodiment, the predetermined time period is in the range of 20 hours to 30 hours.
The present disclosure provides the epoxy resin having an epoxy equivalent value in the range of 300-314.
In an exemplary embodiment, the temperature during the esterification reaction is maintained at 80°C and acrylic acid is added over a period of 8 hours. The temperature is further raised to 90°C and maintained for a period of 15 to 30 hours until the acid value of the reaction mixture falls to <1.5 mgKOH/gm. In an embodiment of the present disclosure, the temperature of 90°C is maintained for a time period of 24 hours and the acid value of the reaction mixture is <1.5 mgKOH/gm. The so obtained epoxy ester resin is stable, color and odor-free.
In accordance with the embodiments of the present disclosure, the epoxy ester resin obtained by reacting epoxy resin and acrylic acid are radiation curable (UV, LED, Electron beam) or energy curable or ultrasound curable.
In an exemplary embodiment, the so obtained epoxide ester resin is diluted with reactive diluents like Trimethylolpropane triacrylate (TMPTA) or Hexanediol diacrylate (HDDA). The thinned material is printed on coated paper substrate cards and passed through the UV drier under a 270 nm wavelength lamp. The applied coating dries very fast within a few microseconds and in a single pass. The coating becomes completely tack free after UV drying. The dried coating shows excellent resistance properties such as thumb rub and solvent rub resistance. In accordance with the present disclosure, the degree of cure of the so obtained epoxy ester resin is tested with the standard procedure ASTM D4752.

The present disclosure provides a technical advancement in terms of providing a process for resin preparation wherein no wastewater is generated and therefore, no wastewater treatment is required. The epoxy ester resin prepared by the process is radiation-curable or energy curable and therefore, cures in a very short period of time. Unlike the typical epoxy ester resin which is thermally cured and takes a long time for curing besides being uneconomical. The epoxy ester resin prepared by the process of the present disclosure is stable and color free and odor-free.
In the present disclosure, the thermodynamic-kinetic control is balanced by inhibiting the free radical generation and at the same time driving esterification in the single acid-epoxy chain. At the primary level, autoxidation in the reaction mixture is inhibited by the use of Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) antioxidant along with nitrogen purging. In the second approach, already generated free radicals (vinyl radicals) are captured with the mono-methyl ether of hydroquinone. Due to this, the requirement of low processing viscosity and the stable finish product is achieved by the process of the present disclosure.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment but are interchangeable. Such variations are not to be regarded as a departure from the present disclosure and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purposes only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to an industrial scale.

EXPERIMENTAL DETAILS
Experiment 1. Preparation of epoxy resin:
In a three-necked glass reactor equipped with stirrer, azeotropic distillation trap & nitrogen purging facility, 228.29 gm of Epichlorohydrin (ECH), 228.29 of bisphenol-A (BPA) (mol ratio ECH/ BPA 2.468 A), O.lgm Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and 58 ml of toluene were charged. After charging the ingredients, agitation was started, nitrogen gas was blown in the reactor at a flow rate of 10 liters /hour and the material was heated up to 80°C and kept on hold at 80°C for 30 minutes till the reaction mixture became clear. Heating was discontinued and a solution of 109 ml of 50% NaOH solution was added to the reaction mixture for a period of 20hrs, with a gradual increment in temperature from 80-130°C. While adding the NaOH solution, water was removed azeotropically through the Dean & Stark trap. After 20 hours, the material sample showed a 340 epoxy value and a Refractive index of 1.16.
Thereafter, the mixture was cooled down to 60°C to obtain a cooled mixture. 300gms of methyl isobutyl ketone was added in the cooled mixture for separating the salt. Then this mixture was allowed to settle down for 10 minutes and then filtered through a 100-micron size centrifuge filter to obtain a resin solution. The composition of this resin solution is epoxy resin, methyl isobutyl ketone, toluene, and traces of chloride ions. This resin solution made completely chloride-free with anion exchange resin DOWEX MARATHON™ 4200 CI by adding, mixing and contacting for 30min, followed by separation to separate DOWEX MARATHON™ 4200 CI beds. The chloride content of the filtered epoxy resin observed in the range of 0.005-0.001ppm (ASTM D1726). The filtered resin contained methyl isobutyl ketone and toluene which was then distilled out to make it solvent-free.
The so obtained epoxy resin shows 300-314 epoxy values and a 43°C melting point.

Table 1: Effect of the ratio of NaOH/ECH on epoxy equivalent weight
Table 1, shows the effect of the mole ratio of NaOH / ECH on the stability of the film. The mole ratio of NaOH / ECH of 1.1/1, provides an epoxy resin of epoxy equivalent weight of 314 and the corresponding number of methyl ethyl ketone (MEK) rubs until the failure or break-through of the film occurs (ASTM D4752). 12-14 number of MEK rubs shows that the epoxy ester resin is quite stable.
Experiment 2: Process for the preparation of epoxy ester in accordance with the present disclosure
Experiment 2a: Process for the preparation of epoxy ester using monomethyl
ether of hydroquinone (MEHQ), as a free radical inhibitor
A reactor equipped with a stirrer, a nitrogen purger, and a reflux condenser was charged with 300 gms. of epoxy resin prepared in experiment 1.
1 gm of zinc oxalate, 0.5gms of monomethyl ether of hydroquinone (MEHQ), 0.1 gm of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) were added in the reactor containing epoxy resin to obtain a mixture. The mixture was heated up to 80°C and the temperature was held for 30 minutes. Holding temperature 30 minutes activates resin for esterification. 100 gms of acrylic acid were added drop by drop for 8 hours at 80°C under continuous stirring to add up a single molecule in a chain at a time. After completion of the addition of the

acrylic acid, the temperature was raised to the 90 °C and the heating of the reaction mixture was continued till the acid value of reaction mixture reached below 1.5 mg KOH / g to obtain the product epoxy ester resin. The resin is smell-free when the acid value of the reaction mixture is less than 1.5 mgKOH /g acid. The total time period for heating at elevated temperature was 24 hrs.
Experiment 2b-2e: Process for the preparation of epoxy ester using
monomethyl ether of hydroquinone (MEHQ), as a free radical inhibitor
The experiments were conducted in the same manner as in experiment 2a by varying the ratios of monomethyl ether of hydroquinone (MEHQ) to acrylic acid. The results are provided in Table 2.
Table 2: Effect of MEHQ/ acrylic acid ratio on acid value
Monomethyl ether of hydroquinone (MEHQ)
Table 2 shows the effect of the ratio of MEHQ / acrylic acid, reaction time cycle, process temperature on the acid value of the reaction mixture at the end of the reaction time cycle. It is inferred from the table that a ratio of MEHQ/ acrylic acid of 0.2%, gives reaction mixture with very low acid values, and therefore the product is smell free.
Table 3: MEHQ sublimation and stability of the epoxy ester

Table 3 shows that in experiment no 2a and 2e reactions carried out in 80-110°C range. And due to high-temperature processing at 110°C even though the dose of MEHQ is very high around 0.1%, it gets sublimes and ultimately reaction gels. With this study, it is found that processing temperature is a crucial point in manufacturing epoxy acrylates.
Experiment 2f-2i: Process for the preparation of epoxy ester using
Hydroquinone as a free radical inhibitor:
The experiment was conducted in the same manner as the experiment 2 by varying the ratios of hydroquinone as a free radical inhibitor to acrylic acid. The results are provided in Table 4.
Table 4: Effect of HQ/ acrylic acid ratio on acid value
^Hydroquinone (HQ):
Table 3 shows the effect of the ratio of hydroquinone / acrylic acid, reaction time cycle, process temperature on the acid value of the reaction mixture at the end of the reaction time cycle. It is inferred from the table that when HQ/acrylic acid is

0.1353% and even though reaction time is increased to 30 hrs and the temperature is elevated from 81-124°C, the acid value of the reaction mixture is still 24.
Conventionally, the epoxy ester resin had an odor due to the high percentage of free monomer present in it. The high acid values in experiment 2f-I in table 4 is an indicator of the typical acrylic acid odor in the epoxy ester. Comparatively MEHQ allow consuming all acid in a reaction mixture hence very negligible amount of free acid remains in the final product.
Experiment 3: Analysis of Epoxy ester resin:
In accordance with the present disclosure, a strong oxidizing agent is used for checking to cure surface coated with epoxy ester resin. In an embodiment of the present disclosure, 1% KMnC^ is used as an oxidizing agent for evaluating the curing of the epoxy ester film. If the film is completely cured, there is no stain and in case of optimum curing of film, the film is slightly stained after 5 minutes of exposure to KMn04. Table 5 shows that in all the cases, the minimal stain was observed, indicating good curing and stability of the obtained epoxy ester resin.
Table 5 : solvent rub resistance
*TMPTAOTA - Trimethylolpropane ethoxy triacrylate *TMPTA - Trimethylolpropane triacrylate

*GTA - Glycerol triacrylate *TPGDA - Tripropylene glycol diacrylate *PETA -Pentaerythritol triacrylate *HDDA—Hexanediol diacrylate
It is inferred that, when diluent PETA is added to so obtained epoxy ester resin, no stain was observed and therefore, is highly resistant and stable. In all other embodiments, the minimal stain was observed.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to a process for the preparation of epoxy ester resin. The technical advancements are enumerated hereunder:
- the process is economical as a generation of wastewater with high TDS and
high COD is avoided.
the green process for removing chloride from epoxy resin
- Epichlorohydrin free and chloride free resin to control lay defeated, pinholes
in radiation-curable resin
epoxy ester produced by the process is radiation-curable and therefore, takes a
few seconds for curing.
Stable epoxy ester produced by this method is odor-free which helps to
maintain the good air quality in the manufacturing area.
color free resin allows to quick photoinitiation of all ingredients in the coating
and ultimately fast curing.
an epoxy resin obtained by the process of the present disclosure having a
lower level of free residual monomers
- to avoid MEHQ sublimation with longer storage life.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a

stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions, and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

WE CLAIM:
1. A process for preparing epoxy ester resin, said process comprising the
following steps:
a) synthesizing a salt-free and a color free epoxy resin; and
b) esterifying said salt-free and said color free epoxy resin by using a fatty acid in the presence of at least one catalyst, at least one antioxidant and at least one free-radical inhibitor at a predetermined temperature for a predetermined time period in an inert atmosphere to obtain a product mixture comprising said epoxy ester resin,
wherein the acid value of said product mixture is less than 1.5 mgKOH/gm.
2. The process as claimed in claim 1, wherein said salt-free and said color
free epoxy resin is prepared by the following steps:
(i) reacting epichlorohydrin with bisphenol A in a fluid medium in the presence of at least one antioxidant followed by slowly adding 50% aqueous solution of a base for a time period in the range of 18 hours to 20 hours, in an inert atmosphere, at a temperature in the range of 80°C to 130°C to obtain a reaction mixture;
(ii) removing water azeotropically from said reaction mixture to obtain a mixture of epoxy resin and salt;
(iii) separating said salt from said mixture by adding methyl isobutyl ketone and filtering by using a centrifuge filter to obtain a product mixture comprising epoxy resin having traces of salt, methyl isobutyl ketone and toluene;
(iv) contacting said product mixture with an adsorbent to obtain a salt-free epoxy resin having traces of methyl isobutyl ketone and said fluid medium; and

(v) distilling said traces of methyl isobutyl ketone and toluene at a temperature in the range of 80 °C to 130 °C to obtain said salt-free and said color free epoxy resin.
3. The process as claimed in claim 1, wherein said catalyst is one selected from the group consisting of dimethylaniline, triphenylphosphine, trimethylamine, zinc oxalate, and zinc acetate.
4. The process as claimed in claim 1, wherein said fatty acid is selected from acrylic acid, soy fatty acid, dehydrated castor fatty acid, anacardic acid, recinoleic acid, oleic acid, linolenic acid, and methacrylic acid.
5. The process as claimed in claim 1, wherein said fatty acid is added in a dropwise manner at a temperature in the range of 80-90 °C.
6. The process as claimed in claim 1, wherein said anti-oxidant is pentaerythritol tetrakis [3-(3,5 di-tert butyl - 4 - hydroxyphenyl) propionate].
7. The process as claimed in claim 1, wherein said free radical inhibitor is at least one selected from the group consisting of monomethyl ether of hydroquinone, hydroquinone, triphenyl phosphite, and butylated hydroxyl toluene.
8. The process as claimed in claim 1, wherein said free radical inhibitor is selected from monomethyl ether of hydroquinone and hydroquinone.
9. The process as claimed in claims 1 and 8, wherein the ratio of said monomethyl ether of hydroquinone to said acrylic acid is in the range of 0.1 wt% to lwt%, and wherein the ratio of said hydroquinone to said acrylic acid is in the range of 0.05wt% to 0.2wt%.
10. The process as claimed in claim 1, wherein said predetermined temperature is in the range of 70 °C to 100 °C.
11. The process as claimed in claim 1, wherein said predetermined time period is in the range of 10 hours to 40 hours.
12. The process as claimed in claim 2, wherein the molar ratio of said epichlorohydrin to said base solution is in the range of 1:1 to 8:1.

13. The process as claimed in claim 2, wherein said fluid medium is selected from toluene, xylene, and cyclohexene.
14. The process as claimed in claim 2, wherein said base is selected from sodium hydroxide, potassium hydroxide and calcium hydroxide.
15. The process as claimed in claim 2, wherein said absorbent is selected from molecular sieves and anion exchange resins.
16. The process as claimed in claim 2, wherein the pore size of said centrifuge filter is in the range of 80 microns to 120 microns.