DESC:FIELD
The present disclosure relates to a coating composition and a process for its preparation.
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 indicate otherwise.
Rebar - refers to steel reinforcement bars.
Glass Transition temperature abbreviated as Tg - refers to a temperature at which a polymer structure turns into a viscous liquid.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Concrete and metallic pipes including rebars are commonly used in the construction industry. The pipes are susceptible to corrosion and therefore, in order to extend life of the constructed structure, pipes need to be made corrosion resistant. Various types of coating are well known in the industry for imparting corrosion resistance and Fusion bonded epoxy (FBE) coating is one such type of coating applied on a metallic surface. FBE coating, typically, comprises a resin and a hardener which is in a powder form and remains unreacted individually. The resin powder and the hardener powder are typically melted at a high temperature which changes the powder into a liquid form. The liquid is applied on the metallic surface and turns into a solid coat. The solid coat is cured by a curing agent and the coat is called a fusion bonded epoxy coat.
The resin powder and the hardener powder used for the FBE coating should be highly reactive and should get cured within a few seconds and at the same time be quenched in a similar short time period of a few seconds. Conventionally, in order to achieve the objective of high reactivity, quick curing and quenching, different catalyst like imidazole and hydrazide catalysts, are used in the composition. The catalysts are used in a combination. However, the FBE composition is highly sensitive to the catalyst proportions. A miniscule change in the catalyst proportion results in increased heating and cooling time. Further, the catalysts used in the conventional FBE coating are expensive.
Thus, there is a need to provide a powder coating composition that mitigates the drawbacks mentioned herein above or at least provide an alternate solution.
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 coating composition.
Still another object of the present disclosure is to provide a coating composition with improved mechanical properties.
Yet another object of the present disclosure is to provide a process for the preparation of a coating composition.
Still another object of the present disclosure is to provide a process for the preparation of coating composition that is devoid of a catalyst.
Another object of the present disclosure is to provide a simple and economic process for the preparation of a composition which is economical.
Yet another object of the present disclosure is to provide a powder coating composition.
Still another object of the present disclosure is to provide a powder coating composition that has high mechanical properties.
Another object of the present disclosure is to provide a highly reactive epoxy resin (type 4 epoxy resin) having epoxy equivalent weight in the range of 600 to 1200 is develop through Use of aliphatic alcohol (both linear and branch) with BPA.
Still another object of the present disclosure is to provide a highly reactive epoxy resin (type 4 epoxy resin) having epoxy equivalent weight in the range of 600 to 1200.
Yet another object of the present disclosure is to provide a process for preparing a highly reactive epoxy resin (type 4 epoxy resin) having epoxy equivalent weight in the range of 600 to 1200 by using aliphatic alcohol (both linear and branched) with bisphenol A (BPA).
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 coating composition and a process for its preparation. The coating composition comprises at least one Type 4 epoxy resin, at least one Type 7 epoxy resin and at least one phenolic resin and the weight ratio of the Type 4 epoxy resin to the Type 7 epoxy resin is in the range of 4:1 to 10:1.
In accordance with an embodiment of the present disclosure, Type 4 epoxy resin comprises at least one aromatic diepoxide, at least one diol, at least one polyhydric phenol and at least one monohydric phenol.
In accordance with an embodiment of the present disclosure, the aromatic diepoxide is a glycidal ether of Bisphenol selected from glycidal ether of Bisphenol A, glycidal ether of Bisphenol F and a combination thereof.
In accordance with the present disclosure, the aromatic diepoxide is in the range of 60 wt% to 90wt % with respect to the total weight of the Type-4 epoxy resin.
In accordance with an embodiment of the present disclosure, the diol is a glycol selected from monoethylene glycol, diethylene glycol, neopentyl glycol, trimethylol propane and a combination thereof.
In accordance with the present disclosure, the diol is present in an amount in the range of 0 wt% to 10 wt% with respect to the total amount of type-4 epoxy resin.
In an embodiment of the present disclosure, the polyhydric phenol is selected from resorcinol, hydroquinone, catechol, bisphenol and a combination thereof.
In accordance with the present disclosure, the polyhydric phenol is present in an amount in the range of 5 wt% to 30% with respect to the total amount of the Type-4 epoxy resin.
In an embodiment of the present disclosure, the monohydric phenol is selected from a substituted phenol and an unsubstituted phenol.
In accordance with the present disclosure, the monohydric phenol is present in an amount in the range of 5wt % to 20 wt% with respect to the total amount of the Type- 4 epoxy resin.
In accordance with an embodiment of the present disclosure, the Type 4 epoxy resin is having a melt viscosity of 10 poise to 75 poise at 200oC, a glass transition temperature in the range from 30 oC to 70 oC and a softening point in the range of 65° C to 140° C.
In accordance with the present disclosure, the process of preparation of the coating composition comprises preparing a Type 4 epoxy resin and mixing a pre-determined weight ratio of a Type 4 epoxy resin and a Type 7 epoxy resin obtaining a first resin mixture, wherein the weight ratio of the Type 4 and the Type 7 epoxy resin is in the range of 4:1 to 10:1. In accordance with the present disclosure, a pre-determined amount of a phenolic resin is added to the first resin mixture, obtaining the coating composition. In accordance with the present disclosure, the process is devoid of a catalyst.
In accordance with an embodiment of the present disclosure, the Type 4 epoxy resin is prepared by mixing a pre-determined amount of the aromatic diepoxide, a pre-determined amount of the diol, a pre-determined amount of the polyhydric phenol and a pre-determined amount of the monohydric phenol, obtaining a mixture and allowing the mixture to react at a predetermined temperature for a pre-determined period of time, to obtain the Type-4 epoxy resin.
In an embodiment of the present disclosure, the pre-determined amount of aromatic diepoxide is in the range of 60 wt% to 90wt % with respect to the total weight of the Type-4 epoxy resin.
In an embodiment of the present disclosure, the predetermined amount of the diol is in the range of 0 wt% to 10 wt% with respect to the total amount of the Type-4 epoxy resin.
In an embodiment of the present the present disclosure, the predetermined amount of the polyhydric phenol is in the range of 5 wt% to 30% with respect to the total amount of the Type-4 epoxy resin.
In an embodiment of the present disclosure, the pre-determined amount of the monohydric phenol is in the range of 5wt % to 20 wt% with respect to the total amount of the Type- 4 epoxy resin.
In an embodiment of the present disclosure, the pre-determined temperature is in the range of 120oC to 220oC and the pre-determined time period is in the range of 4 hours to 12 hours.
DETAILED DESCRIPTION
The present disclosure relates to a coating compostion and a process for its preparation.
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 methods, 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 method 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.
Metals and concrete are extensively used in the construction industry. Steel pipes, rebars, connectors, valves and the like, constitute metallic elements therein. Metal is susceptible to corrosion and needs to be protected. Various types of coating are well known in the industry which imparts corrosion resistance. Fusion bonded epoxy (FBE) coating is one such type of coating applied on a metallic surface. FBE coating, typically, comprises a resin and a hardener is in a powder form which remains unreacted individually. The resin powder and the hardener powder are typically melted at a high temperature changing the powder into a liquid form. The liquid is applied on the metallic surface and turns into a solid coat. The solid coat is cured by a curing agent and the coat is called a fusion bonded epoxy coat.
The resin powder and the hardener powder used for the FBE coating should be highly reactive and should get cured within a few seconds and at the same time be quenched in a similar short time period of a few seconds. Conventionally, in order to achieve the objective of high reactivity, quick curing and quenching, different catalyst like imidazole and hydrazide catalysts, are used in the composition. However, the FBE composition is highly sensitive to the catalyst proportions and the combination of the catalysts. A miniscule change in the catalyst proportions results in increased heating and cooling time. Further, the catalysts used in the conventional FBE coating are expensive.
The present disclosure envisages a coating composition and a process for its preparation.
In an aspect of the present disclosure, the present disclosure provides a coating composition comprising at least one Type 4 epoxy resin, at least one Type 7 epoxy resin and a phenolic resin, wherein weight ratio of Type 4 to Type 7 is the range of 4:1 to 10:1.
In another aspect, the present disclosure envisages a highly reactive Type 4 epoxy resin comprising:
• at least one aromatic diepoxide;
• at least one diol;
• at least one polyhydric phenol; and
• at least one monohydric phenol.
In an embodiment of the present dislcosure, the aromatic diepoxide is a glycidal ether of Bisphenol. In an embodiment of the present disclosure, the glycidal ether of Bisphenol may be selected from a glycidal ether of Bisphenol A, glycidal ether of Bisphenol F and a combination thereof.
In accordance with an embodiment of the present disclosure, the aromatic diepoxide is present in an amount in the range of 60 wt% to 90wt % with respect to the total weight of the Type-4 epoxy resin.
In accordance with an embodiment of the present disclosure, the diol is a glycol selected from a monoethylene glycol, diethylene glycol, neopentyl glycol, trimethylol propane and a combination thereof.
In accordance with an embodiment of the present disclosure, the diol is present in an amount in the range of 0 wt% to 10 wt% with respect to the total amount of type-4 epoxy resin.
In accordance with an embodiment of the present disclosure, the polyhydric phenol is selected from resorcinol, hydroquinone, catechol, bisphenol and a combination thereof.
In accordance with an embodiment of the present disclosure, the polyhydric phenol is present in an amount in the range of 5 wt% to 30% with respect to the total amount of the Type-4 epoxy resin. In an exemplary embodiment, the polyhydric phenol is a bisphenol.
In accordance with an embodiment of the present disclosure, the monohydric phenol is selected from a substituted phenols and an unsubstituted phenols. In an exemplary embodiment, monohydric phenol is cresol.
In accordance with an embodiment of the present disclosure, the monohydric phenol is present in an amount in the range of 5wt % to 20 wt% with respect to the total amount of the Type- 4 epoxy resin.
In accordance with an embodiment of the present disclosure, the Type 4 epoxy resin is characterized by having
• epoxy equivalent weight ranging from 500 g/EQ to 1500 g/EQ;
• melt viscosity of 10 poise to 75 poise at 200 °C;
• a glass transition temperature in the range from 30°C to 70°C, more precisely 35°C to 50 °C; and
• a softening point in the range of 65°C to 140° C.

In accordance with the present disclosure, the coating composition is having a gel time in the range of 8 seconds to 14 seconds at 200oC to 240oC.
In another aspect, the present disclosure envisages a process for preparing the Type 4 epoxy resin and mixing a pre-determined weight ratio of the prepared Type 4 epoxy resin and the Type 7 epoxy resin obtaining a first resin mixture, wherein the weight ratio of the Type 4 and the Type 7 epoxy resin is in the range of 4:1 to 10:1. A predetermined amount of a phenolic resin is added to the first resin mixture, obtaining the coating composition. The process is devoid of a catalyst.
In an embodiment of the present disclosure, Type-4 epoxy resin and Type-7 epoxy resins are mixed in ratio of 10:1. Addition of Type 7 epoxy resin to Type 4 epoxy resin allows obtaining a balance of hardness and flexibility. The coating composition may further comprise one or more fillers, pigments, dyes and a flow modifier. In an embodiment of the present disclosure, the coating composition gel time ranges from 8 seconds to 14 seconds at a temperature range of 200 oC to 240 oC. The coating composition of the present disclosure may be in th form of a powder coating composition.
In another aspect, the present disclosure envisages a process for preparation of highly reactive Type 4 epoxy resin and the steps of preparation comprise mixing a pre-determined amount of the aromatic diepoxide, a pre-determined amount of the diol, a pre-determined amount of the polyhydric phenol and a pre-determined amount of the monohydric phenol, obtaining a mixture and allowing the mixture to react at a predetermined temperature for a pre-determined period of time, to obtain the Type-4 epoxy resin.
In an embodiment, aromatic diepoxide is a glycidal ether of bisphenol and is selected from glycidal ether of Bisphenol A, glycidal ether of Bisphenol F and a combination thereof and the w% of aromatic diepoxide is in the range of 60 wt% to 90wt % with respect to the total weight of the Type-4 epoxy resin.
In an embodiment, diol is a glycol selected from monoethylene glycol, diethylene glycol, neopentyl glycol, trimethylol propane and a combination thereof and the wt% in the range of 0 wt% to 10 wt% with respect to the total amount of type-4 epoxy resin.
In an embodiment, polyhydric phenol is selected from resorcinol, hydroquinone, catechol, bisphenol and a combination thereof and the wt% of polyhydric phenol is present in an amount in the range of 5 wt% to 30% with respect to the total amount of the Type-4 epoxy resin.
In an embodiment, the monohydric phenol is selected from a substituted phenol and an unsubstituted phenol and is present in an amount of 5wt % to 20 wt% with respect to the total amount of the Type- 4 epoxy resin.
Type 4 epoxy resin has been designed with monomeric phenolic compound and high reactive diol which in an exemplary embodiment is glycol, giving high Tg of the final epoxy compound. The multi-stage addition of polyhydric phenol, which in an exemplary embodiment is bisphenol, to Bisphenol A diglycidyl ether (DEGBA) system also helps to control molecular weight and viscosity of the Type 4 epoxy resin which in turn helps to get the final product to possess high mechanical properties, proper balance of hardness and flexibility.
In an embodiment of the present disclosure, the predetermined reaction conditions include a temperature in the range of 120 oC to 220 oC, and a pre-determined time period in the range of 4 hours to12 hours.
In an aspect of the present disclosure, the drop wise addition of a polyphenol allows obtaining controlled molecular weight distribution with desired polydispersity index in the obtained Type-4 epoxy resin.
In an aspect of the present disclosure, epoxy weight equivalent of the so obtained type-4 epoxy resin ranges from 600g/eq to 1200 g/eq, more particularly 700 g/eq to 1000 g/eq and having a melt viscosity of the type 4 epoxy resin is in the range of 10 centipoise to 75 centipoise at 200oC having a polydispersity index of the obtained type 4 epoxy resin in the range of 3 to 5 and glass transition temperature (Tg) in the range of 30 oC to 50 oC.
The present disclosure provides corrosion resistant coating which obviates need for using a catalyst for curing. The coating composition can be applied over a blasted panel in 100 to 300 microns DFT. The coating composition withstood salt spray resistance for 800 to 1500 hours as per test method ASTM B117. The coating composition displayed a creepage of 4mm to 10 mm after 28 days of cathodic disbondment test as per test method ASTM A 775/ A775M. The coating composition can be used to coat a surface for corrosion protection and also for decorative finishes (aesthetic purposes).
The foregoing description of the embodiments has been provided for purposes of illustration and 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.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but is not limited to the realization of a coating composition
- that has a very less gel time;
- that is devoid of catalyst;
and
- a simple, efficient and economic process for preparing the coating composition.
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.
,CLAIMS:WE CLAIM
1. A coating composition comprising
• at least one Type 4 epoxy resin;
• at least one Type 7 epoxy resin; and
• at least one phenolic resin,
wherein weight ratio of the Type 4 epoxy resin to the type 7 epoxy resin is in the range of 4:1 to 10:1.
2. The coating composition as claimed in claim 1 wherein the Type 4 epoxy resin comprises
• at least one aromatic diepoxide;
• at least one diol;
• at least one polyhydric phenol; and
• at least one monohydric phenol.
3. The coating composition as claimed in claim 2 wherein the aromatic diepoxide is a glycidal ether of Bisphenol.
4. The coating composition as claimed in claim 3 wherein glycidal ether of Bisphenol is selected from glycidal ether of Bisphenol A, glycidal ether of Bisphenol F and a combination thereof.
5. The coating composition as claimed in claim 2 wherein the aromatic diepoxide is present in an amount in the range of 60 wt% to 90wt % with respect to the total weight of the Type-4 epoxy resin.
6. The coating composition as claimed in claim 2 wherein the diol is a glycol selected from monoethylene glycol, diethylene glycol, neopentyl glycol, trimethylol propane and a combination thereof.
7. The coating composition as claimed in claim 2 wherein the diol is present in an amount in the range of 0 wt% to 10 wt% with respect to the total amount of type-4 epoxy resin.
8. The coating composition as claimed in claim 2 wherein the polyhydric phenol is selected from the group consisting of resorcinol, hydroquinone, catechol, bisphenol and a combination thereof.
9. The coating composition as claimed in claim 2 wherein the polyhydric phenol is present in an amount in the range of 5 wt% to 30% with respect to the total amount of the Type-4 epoxy resin.
10. The coating composition as claimed in claim 2 wherein the monohydric phenol is selected from a substituted phenol and an unsubstituted phenol.
11. The coating composition as claimed in claim 2 wherein the monohydric phenol is present in an amount in the range of 5wt % to 20 wt% with respect to the total amount of the Type- 4 epoxy resin.
12. The coating composition as claimed in claim 1, wherein the Type 4 epoxy resin is having a melt viscosity in the range of 10 poise to 75 poise at 200oC, a glass transition temperature in the range of 30 oC to 70 oC and a softening point in the range of 65° C to 140° C.
13. A process for preparation of a coating composition, said process comprising the following steps of:
• mixing a pre-determined weight ratio of a Type 4 epoxy resin and a Type 7 epoxy resin to obtain a first resin mixture, wherein the weight ratio of said Type 4 to Type 7 epoxy resin is in the range of 4:1 to 10:1; and
• adding a pre-determined amount of a phenolic resin to the first resin mixture, to obtain the coating composition,
wherein the process is devoid of a catalyst.
14. The process as claimed in claim 13 wherein the Type 4 epoxy resin is prepared by reacting a pre-determined amount of an aromatic diepoxide, a pre-determined amount of the diol, a pre-determined amount of the polyhydric phenol and a pre-determined amount of a monohydric phenol, at a predetermined temperature for a pre-determined time period, to obtain the Type-4 epoxy resin.
15. The process as claimed in claim 14 wherein the aromatic diepoxide is a glycidal ether of Bisphenol and is selected from glycidal ether of Bisphenol A, glycidal ether of Bisphenol F and a combination thereof.
16. The process as claimed in claim 14 wherein the diol is a glycol selected from monoethylene glycol, diethylene glycol, neopentyl glycol, trimethylol propane and a combination thereof.
17. The process as claimed in claim 14 wherein the polyhydric phenol is selected from resorcinol, hydroquinone, catechol, bisphenol and a combination thereof.
18. The process as claimed in claim 14, wherein the monohydric phenol is selected from a substituted phenol and an unsubstituted phenol.
19. The process as claimed in claim 14 wherein the pre-determined amount of aromatic diepoxide is in the range of 60 wt% to 90wt % with respect to the total weight of the Type-4 epoxy resin, the predetermined amount of the diol is in the range of 0 wt% to 10 wt% with respect to the total amount of the Type-4 epoxy resin, the predetermined amount of the polyhydric phenol is in the range of 5 wt% to 30% with respect to the total amount of the Type-4 epoxy resin and the pre-determined amount of the monohydric phenol is in the range of 5wt % to 20 wt% with respect to the total amount of the Type- 4 epoxy resin.
20. The process as claimed in claim 14 wherein the pre-determined temperature is in the range of 120oC to 220oC.
21. The process as claimed in claim 14 wherein the pre-determined time period is in the range of 4 hours to 12 hours.

Dated this 16th day of December, 2023

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI