DESC:FIELD
The present disclosure relates to a phenalkamine curing agent and a process for its preparation. The present disclosure further relates to a coating composition comprising the phenalkamine curing agent.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Phenalkamines are good epoxy resin hardeners for curing at a room temperature or at a low temperature. In addition, phenalkamines offer good chemical resistance, excellent water resistance, and good compatibility with epoxy resins; and also has a low toxicity and a good flexibility. As a result, they are used in marine applications, industrial maintenance, civil engineering applications and the like.
Generally, phenalkamines are the mixtures of poly(aminoalkylene) substituted phenols prepared from cardanol, polyethylene polyamines and formaldehyde. In general, it is not possible to easily control the molecular weight distribution of these products and hence, they are usually viscous liquids. Moreover, the conventional phenalkamine has a dark color, based on the Gardner scale, of greater than 12. The dark color in the conventional phenalkamine is due to impurities, including cardols (a di-hydroxy alkyl phenol) which lead to rapid polymerization and oxidation reactions, thereby generating precursor color bodies, either during storage or during phenalkamine manufacturing.
Therefore, there is felt a need for a phenalkamine curing agent that mitigates the drawbacks mentioned hereinabove or at least provides a useful alternative.
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 background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a phenalkamine curing agent.
Still another object of the present disclosure is to provide a phenalkamine curing agent that has improved UV stability.
Yet another object of the present disclosure is to provide a phenalkamine curing agent that is useful for preparing coating composition that has low viscosity, high solid and low VOC.
Still another object of the present disclosure is to provide a simple, efficient and economical process for the preparation of a phenalkamine curing agent.
Yet another object of the present disclosure is to provide a coating composition comprising a phenalkamine curing agent.
Still another object of the present disclosure is to provide a coating composition that has low curing temperature, fast drying and improved chemical resistance.
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 phenalkamine curing agent. The curing agent is a product of (i) an intermediate reaction product of an alkyl phenol, at least one amine and an aldehyde; and (ii) an epoxy resin.
The alkyl phenol is cardanol.
The amine is selected from the group consisting of an aliphatic amine, a cycloaliphatic amine and a combination thereof.
The aliphatic amine is selected from the group consisting of diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylenepentamine (TEPA), and polyether amine.
The cycloaliphatic amine is selected from the group consisting of isophoron diamine (IPDA), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) and cyclohexylamine.
The aldehyde is selected from the group consisting of paraformaldehyde, heptanaldehyde, hexanaldehyde, acetaldehyde and propionaldehyde.
The epoxy resin is bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
The curing agent is characterized by having;
• Gardner color in the range of 3 to 6;
• amine value in the range of 200 mg KOH/g to 300 mg KOH/g; and
• viscosity in the range of 300 to 600 cps at 25 °C.
The present disclosure further relates to a process for the preparation of a phenalkamine curing agent.
The process comprising the following steps:
(a) reacting an alkyl phenol, at least one amine and an aldehyde in a predetermined molar ratio at first predetermined conditions to obtain an intermediate reaction product; and
(b) reacting the intermediate reaction product with an epoxy resin in a fluid medium at second predetermined conditions to obtain the phenalkamine curing agent,
wherein the first predetermined conditions and the second predetermined conditions are selected from a temperature, a time period and a ratio.
In an embodiment, the step (a) of the process for the preparation of the phenalkamine curing agent comprises the following sub-steps:
(i) mixing an alkyl phenol and at least one amine in a predetermined molar ratio to obtain a mixture;
(ii) heating the mixture to a first predetermined temperature followed by adding a predetermined amount of an aldehyde over a first predetermined time period to obtain a first reaction mass; and
(iii) maintaining the first reaction mass under stirring at a second predetermined temperature for a second predetermined time period and distilling off water azeotropically to obtain the intermediate reaction product.
In an embodiment, the step (b) of the process for the preparation of the phenalkamine curing agent comprises the following sub-steps:
(i) mixing the intermediate reaction product obtained in step (a) in a fluid medium to obtain a homogeneous slurry;
(ii) heating the homogeneous slurry to a third predetermined temperature to obtain a heated slurry followed by adding an epoxy resin in the fluid medium to the heated slurry over a third predetermined time period to obtain a second reaction mass; and
(iii) maintaining the second reaction mass under stirring at a fourth predetermined temperature for a fourth predetermined time period to obtain the phenalkamine curing agent.
The predetermined molar ratio of the alkyl phenol to the amine to the aldehyde is in the range of 1:2:2 to 1:4:4.
A weight ratio of the epoxy resin to the intermediate reaction product is in the range of 1:5 to 1:15.
The first predetermined temperature is in the range of 60 °C to 80 °C.
The second predetermined temperature is in the range of 70 °C to 100 °C.
The first predetermined time period and the second predetermined time period are independently in the range of 1 hour to 4 hours.
The fluid medium is selected from the group consisting of benzyl alcohol, xylene, butanol, toluene, o-xylene, C9 solvent.
The third predetermined temperature is in the range of 60 °C to 80 °C.
The third predetermined time period is in the range of 50 minutes to 80 minutes.
The fourth predetermined temperature is in the range of 70 °C to 100 °C.
The fourth predetermined time period is in the range of 30 minutes to 120 minutes.
The present disclosure furthermore relates to a coating composition comprising
(i) a phenalkamine curing agent of the present disclosure;
(ii) at least one resin;
(iii) at least one pigment;
(iv) at least one filler;
(v) at least one fluid medium; and
(vi) at least one additive.
The resin is an epoxy resin. The epoxy resin is bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
The pigment is titanium dioxide.
The filler is at least one selected from the group consisting of barium sulfate and silica.
The fluid medium is at least one selected from the group consisting of xylene and butanol
The additive is at least one selected from the group consisting of a thickening agent and a dispersing agent.
The coating composition of the present disclosure is characterized by having
• a specific gravity in the range of 1 g/cm3 to 2 g/cm3;
• a solid content in the range of 50 % to 90 %; and
• a pot life at 25 °C in the range of 200 minutes to 250 minutes.
DETAILED DESCRIPTION
The present disclosure relates to a phenalkamine curing agent and a process for its preparation. The present disclosure further relates to a coating composition comprising the phenalkamine curing agent.
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, known processes or well-known apparatus or 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 are 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.
Phenalkamines are good epoxy resin hardeners for curing at a room temperature or at a low temperature. In addition, phenalkamines offer good chemical resistance, excellent water resistance, and good compatibility with epoxy resins; and also has a low toxicity and a good flexibility. As a result, they are used in marine applications, industrial maintenance, civil engineering applications and the like.
Generally, phenalkamines are the mixtures of poly(aminoalkylene) substituted phenols prepared from cardanol, polyethylene polyamines and formaldehyde. In general, it is not possible to easily control the molecular weight distribution of these products and hence, they are usually viscous liquids. Moreover, the conventional phenalkamine has a dark color, based on the Gardner scale, of greater than 12. The dark color in the conventional phenalkamine is due to impurities, including cardols (a di-hydroxy alkyl phenol) which lead to rapid polymerization and oxidation reactions, thereby generating precursor color bodies, either during storage or during phenalkamine manufacturing.
The present disclosure provides a phenalkamine curing agent and a process for its preparation. The present disclosure further provides a coating composition comprising the phenalkamine curing agent.
In a first aspect, the present disclosure provides a phenalkamine curing agent. The phenalkamine curing agent is a product of:
(i) an intermediate reaction product of an alkyl phenol, at least one amine and an aldehyde; and
(ii) an epoxy resin.
In accordance with an embodiment of the present disclosure, the alkyl phenol is Cardanol (produced from Cashew Nut Shell Liquid).
The amine is selected from the group consisting of an aliphatic amine, a cycloaliphatic amine and a combination thereof.
The aliphatic amine is selected from the group consisting of diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylenepentamine (TEPA), and polyether amine.
The cycloaliphatic amine is selected from the group consisting of isophoron diamine (IPDA), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) and cyclohexylamine.
The aldehyde is selected from the group consisting of paraformaldehyde, heptanaldehyde, hexanaldehyde, acetaldehyde and propionaldehyde.
The epoxy resin is bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
The phenalkamine curing agent of the present disclosure is a reaction product of cardanol (i.e. Distilled Cashew nut shell liquid), polyamine and aldehyde with active hydrogen atom and is based on Mannich reaction. The polyamine functional compound has at least one amine function per molecule. The phenalkamine curing agent of the present disclosure is the condensation product of an alkyl phenol (cardanol), formaldehyde and one or more difunctional amines.
The conventional phenalkamine has disadvantage of color darkening when exposed to sunlight or UV light. The inventors of the present disclosure used cycloaliphatic polyamine to improve the UV stability of the phenalkamine curing agent. The phenalkamine curing agents are especially useful for preparing coating composition that has low viscosity, high solid, and low VOC. The coating composition has improved properties such as low temperature curing, fast drying and improved chemical resistance.
In an embodiment of the present disclosure, the intermediate reaction product is characterized by having;
• Gardner color in the range of 5 to 7;
• amine value in the range of 350 mg KOH/g to 450 mg KOH/g; and
• viscosity in the range of 300 to 500 cps at 25 °C.
In an embodiment of the present disclosure, the phenalkamine curing agent is characterized by having;
• Gardner color in the range of 3 to 6;
• amine value in the range of 200 mg KOH/g to 300 mg KOH/g; and
• viscosity in the range of 300 to 600 cps at 25 °C.
The curing agent of the present disclosure is synthesised in two stages, i.e. the intermediate reaction product is obtained by Mannich reaction while the final product is ontained by an addition reaction. The Gardner colour shows the shade of the product (curing agent) which should be low for coating application, the amine value is required for curing reaction of paint, the low viscosity of the curing agent helps to give goo glossy finish to the final paint.
In a second aspect, the present disclosure provides a process for the preparation of a phenalkamine curing agent.
The process comprises the following steps:
(a) reacting an alkyl phenol, at least one amine and an aldehyde in a predetermined molar ratio at first predetermined conditions to obtain an intermediate reaction product; and
(b) reacting the intermediate reaction product with an epoxy resin in a fluid medium at second predetermined conditions to obtain the phenalkamine curing agent;
wherein the first predetermined conditions and the second predetermined conditions are selected from a temperature, a time period and a ratio.
In an embodiment, the step (a) of the process for the preparation of the phenalkamine curing agent comprises the following sub-steps:
(i) mixing an alkyl phenol with at least one amine in a predetermined molar ratio to obtain a mixture;
(ii) heating the mixture to a first predetermined temperature followed by adding a predetermined amount of an aldehyde over a first predetermined time period to obtain a first reaction mass; and
(iii) maintaining the first reaction mass under stirring at a second predetermined temperature for a second predetermined time period and distilling off water to obtain the intermediate reaction product.
In an embodiment, the step (b) of the process for the preparation of the phenalkamine curing agent comprises the following sub-steps:
(i) mixing the intermediate reaction product obtained in step (a) in a fluid medium to obtain a homogeneous slurry;
(ii) heating the homogeneous slurry to a third predetermined temperature to obtain a heated slurry followed by adding an epoxy resin in the fluid medium to the heated slurry over a third predetermined time period to obtain a second reaction mass; and
(iii) maintaining the second reaction mass under stirring at a fourth predetermined temperature for a fourth predetermined time period to obtain the phenalkamine curing agent.
The process for preparing the phenalkamine curing agent is described in detail herein below.
Step (a): Preparation of an intermediate reaction product
An alkyl phenol is mixed with at least one amine in a predetermined molar ratio to obtain a mixture. The mixture is heated to a first predetermined temperature followed by slowly adding a predetermined amount of an aldehyde over a first predetermined time period to obtain a first reaction mass. Maintaining the first reaction mass at a second predetermined temperature for a second predetermined time period and distilling off water to obtain the intermediate reaction product.
The schematic representation for the preparation of the intermediate reaction product in accordance with an exemplary embodiment of the present disclosure is given below as Scheme 1.

Scheme 1
In accordance with an embodiment of the present disclosure, the alkyl phenol is Cardanol (produced from Cashew Nut Shell Liquid).
The amine is selected from the group consisting of an aliphatic amine, a cycloaliphatic amine and a combination thereof.
The aliphatic amine is selected from the group consisting of diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylenepentamine (TEPA), and polyether amine. In an exemplery embodiment of the present disclosure, the aliphatic amine is diethylene triamine (DETA).
The cycloaliphatic amine is selected from the group consisting of isophoron diamine (IPDA), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) and cyclohexylamine. In an exemplery embodiment of the present disclosure, the cycloaliphatic amine is isophoron diamine (IPDA).
The aldehyde is selected from the group consisting of paraformaldehyde, heptanaldehyde, hexanaldehyde, acetaldehyde and propionaldehyde. In an exemplery embodiment of the present disclosure, the aldehyde is paraformaldehyde.
The predetermined molar ratio of the alkyl phenol to the amine to the aldehyde is in the range of 1:2:2 to 1:4:4. In an exemplery embodiment of the present disclosure, the predetermined molar ratio of the alkyl phenol to the amine to the aldehyde is 1: 2.5:2.5.
The first predetermined temperature is in the range of 60 °C to 80 °C. In an exemplery embodiment of the present disclosure, the first predetermined temperature is 75 °C.
The second predetermined temperature is in the range of 70 °C to 100 °C. In an exemplery embodiment of the present disclosure, the second predetermined temperature is 85 °C.
The first predetermined time period and the second predetermined time period are independently in the range of 1 hour to 4 hours. In an exemplary embodiment of the present disclosure, the first predetermined time period is 2 hours. In an exemplary embodiment of the present disclosure, the second predetermined time period is 2 hours.
Step (b): Preparation of the phenalkamine curing agent
The intermediate reaction product obtained in step (a) is mixed in a fluid medium to obtain a homogeneous slurry. The homogeneous slurry is heated to a third predetermined temperature followed by slowly adding an epoxy resin in the fluid medium over a third predetermined time period to obtain a second reaction mass. The second reaction mass is maintained at a fourth predetermined temperature for a fourth predetermined time period to obtain the phenalkamine curing agent.
The schematic representation for the preparation of the phenalkamine curing agent from the intermediate reaction product in accordance with an exemplary embodiment of the present disclosure is given below as Scheme 2.

Scheme 2
The fluid medium is selected from the group consisting of benzyl alcohol, xylene, butanol, toluene, o-xylene and C9 solvent. In an exemplary embodiment of the present disclosure, the fluid medium is benzyl alcohol.
The epoxy resin is bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
A weight ratio of the epoxy resin to the intermediate reaction product is in the range of 1:5 to 1:15. In an exemplary embodiment of the present disclosure, the weight ratio of the epoxy resin to the intermediate reaction product is 1: 8.12.
The third predetermined temperature is in the range of 60 °C to 80 °C. In an exemplery embodiment of the present disclosure, the third predetermined temperature is 70 °C.
The third predetermined time period is in the range of 50 minutes to 80 minutes. In an exemplary embodiment of the present disclosure, the third predetermined time period is 60 minutes.
The fourth predetermined temperature is in the range of 70 °C to 100 °C. In an exemplery embodiment of the present disclosure, the fourth predetermined temperature is 80 °C.
The fourth predetermined time period is in the range of 30 minutes to 120 minutes. In an exemplary embodiment of the present disclosure, the fourth predetermined time period is 60 minutes.
In a third aspect, the present disclosure provides a coating composition comprising the phenalkamine curing agent.
In an embodiment of the present disclosure, the coating composition comprises:
(i) a phenalkamine curing agent of the present disclosure;
(ii) at least one resin;
(iii) at least one pigment;
(iv) at least one filler;
(v) at least one fluid medium; and
(vi) at least one additive.
The resin is an epoxy resin. The epoxy resin is bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
The pigment is titanium dioxide.
The filler is at least one selected from the group consisting of barium sulfate and silica. In an exemplary embodiment of the present disclosure, the filler is a combination of barium sulfate and silica
The fluid medium is at least one selected from the group consisting of xylene and butanol. In an exemplary embodiment of the present disclosure, the fluid medium is a combination of xylene and butanol.
The additive is at least one selected from the group consisting of a thickening agent and a dispersing agent. In an exemplary embodiment of the present disclosure, the additive is a combination of thickening agent and a dispersing agent.
The coating composition of the present disclosure is characterized by having
• a specific gravity in the range of 1 g/cm3 to 2 g/cm3;
• a solid content in the range of 50 % to 90 %; and
• a pot life at 25 °C in the range of 200 minutes to 250 minutes.
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.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
EXPERIMENT DETAILS:
Experiment 1: Preparation of the phenalkamine curing agent in accordance with the present disclosure
Step (a): Preparation of an intermediate reaction product
In a reactor, 300 g (1 mol) of cardanol, 51.5 g (0.5 mol) of diethylene triamine (DETA), 340 g (2 mol) of isophoron diamine (IPDA) were added to obtain a mixture. The mixture was heated to 75 °C and then 75 g (2.5 mol) paraformaldehyde was added slowly over 2 hours and cooling the reactor to keep the temperature at 70 °C to obtain a first reaction mass. The reaction mass was maintained at 85 °C for 2 hours to complete reaction and after 2 hours, water was distilled off using 650 mmHg of vacuum to obtain the intermediate reaction product.
The intermediate reaction product was obtained with Gardner color = 6, Amine value = 380 mg KOH/g, viscosity at 25°C = 400 cps.
Step (b): Preparation of the phenalkamine curing agent
650 g of the intermediate reaction product obtained in step (a) and 200 g benzyl alcohol was charged in a reactor and mixed well to obtain a homogenous slurry. The homogeneous slurry was heated to 70 °C followed by slowly adding a solution prepared from 80 g epoxy resin (EEW=190) in 80 g benzyl alcohol over 60 minutes to obtain a second reaction mass. After complete addition, the second reaction mass was maintained at 80 °C for 1 hour to obtain the phenalkamine curing agent.
The phenalkamine curing agent was obtained with Gardner color = 4 to 5, Amine value = 240 mg KOH/g, viscosity at 25 °C = 400-500 cps.
Comparative example:
The commercially available curing agent PPA-7041 (Phenalkamine curing agent) was compared with the curing agent of the present disclosure.
It is observed that the viscosity of the commercially available curing agent (phenalkamine curing agent) was found to be in the range of 25000 to 35000 cps which is much higher than the viscosity of the phenalkamine curing agent of the present disclosure.
Experiment 2: Preparation of a coating composition comprising the phenalkamine curing agent obtained in experiment 1.
A coating composition was prepared by mixing the predetermined amounts of all the ingredients in a specific sequence as provided in Table 1.
Table 1: The components of the coating composition in accordance with the present disclosure
Sr. No. Material/components Function Quantity (g)
1. TiO2 RUTILE Pigment 15
2. Barium sulfate (BARYTIES 500) Filler 6
3. SILICA 500# Filler/ extender 4
4. NEWSPER – 657 (dispersing agent) Additive 0.3
5. Epoxy resin (EEW=190) Resin 25
6. Hydrophilic fumed silica (CABOSIL) Thickening agent (additive) 0.56
7. JAYTHIK-P-2 Additive 0.6
8. Xylene Fluid medium 16.65
9. Butanol Fluid medium 4.16
10. Phenalkamine Curing agent Curing agent 15
11. Xylene Fluid medium 2.4
The coating composition comprising the phenalkamine curing agent of the present disclosure is characterized by the following properties as tabulated in Table 2.
Table 2: Properties of the coating composition in accordance with the present disclosure
Specific gravity (g/cm3) 1.26
Solids % 70
Pot life at 25 °C(minutes) 220
The coating composition comprising the phenalkamine curing agent of the present disclosure showed the following performance properties as tabulated in Table 3.
Table 3: Performance properties of the coating composition in accordance with the present disclosure
Drying time
Set-to-touch at 25°C 5 hours
Hard dry at 25°C 20 hours
Adhesion 5B
Gloss at 60 °C 95
Gloss retention after Exterior exposure 3 months 55
From table 3, it is observed that drying time for phenalkamine curing agent is within 24 hours which can help the applicator to reduce maintenance period of coating. Also the gloss retention is 55% after 3 months of exterior exposure and shows good UV resistance.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of
? a phenalkamine curing agent that
• has improved UV stability;
• is useful for achieving/preparing coating composition that has a low viscosity, a high solid, and a low VOC; and
• can be used in the coating composition that has low curing temperature, fast drying and improved chemical resistance;
and
? a process for the preparation of a phenalkamine curing agent that
• is simple, efficient and environment friendly.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
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 disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments 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 phenalkamine curing agent being a product of
(i) an intermediate reaction product of an alkyl phenol, at least one amine and an aldehyde; and
(ii) an epoxy resin.
2. The curing agent as claimed in claim 1, wherein said alkyl phenol is cardanol.
3. The curing agent as claimed in claim 1, wherein said amine is selected from the group consisting of an aliphatic amine, a cycloaliphatic amine and a combination thereof.
4. The curing agent as claimed in claim 3, wherein said aliphatic amine is selected from the group consisting of diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylenepentamine (TEPA), and polyether amine.
5. The curing agent as claimed in claim 3, wherein said cycloaliphatic amine is selected from the group consisting of isophoron diamine (IPDA), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) and cyclohexylamine.
6. The curing agent as claimed in claim 1, wherein said aldehyde is selected from the group consisting of paraformaldehyde, butyraldehyde, heptanaldehyde, hexanaldehyde, acetaldehyde and propionaldehyde.
7. The curing agent as claimed in claim 1, wherein said epoxy resin is bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
8. The curing agent as claimed in claim 1 is characterized by having;
• Gardner color in the range of 3 to 6;
• amine value in the range of 200 mg KOH/g to 300 mg KOH/g; and
• viscosity in the range of 300 to 600 cps at 25 °C.
9. A process for the preparation of a phenalkamine curing agent, said process comprising the following steps:
(a) reacting an alkyl phenol, at least one amine and an aldehyde in a predetermined molar ratio at first predetermined conditions to obtain an intermediate reaction product; and
(b) reacting said intermediate reaction product with an epoxy resin in a fluid medium at second predetermined conditions to obtain said phenalkamine curing agent,
wherein said first predetermined conditions and said second predetermined conditions are selected from a temperature, a time period and a ratio.
10. The process as claimed in claim 9, wherein said step (a) comprises the following sub-steps:
(i) mixing said alkyl phenol and at least one amine in said predetermined molar ratio to obtain a mixture;
(ii) heating said mixture to a first predetermined temperature followed by adding a predetermined amount of said aldehyde over a first predetermined time period to obtain a first reaction mass; and
(iii) maintaining said first reaction mass under stirring at a second predetermined temperature for a second predetermined time period and distilling off water azeotropically to obtain said intermediate reaction product.
11. The process as claimed in claim 9, wherein said step (b) comprises the following sub-steps:
(i) mixing said intermediate reaction product obtained in step (a) in said fluid medium to obtain a homogeneous slurry;
(ii) heating said homogeneous slurry to a third predetermined temperature to obtain a heated slurry followed by adding said epoxy resin in said fluid medium to said heated slurry over a third predetermined time period to obtain a second reaction mass; and
(iii) maintaining said second reaction mass under stirring at a fourth predetermined temperature for a fourth predetermined time period to obtain said phenalkamine curing agent.
12. The process as claimed in claims 9 and 10, wherein said alkyl phenol is produced from Cashew Nut Shell Liquid (CNSL).
13. The process as claimed in claims 9 and 10, wherein said amine is selected from an aliphatic amine, a cycloaliphatic amine and a combination thereof.
14. The process as claimed in claim 13, wherein said aliphatic amine is selected from the group consisting of diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylenepentamine (TEPA), and polyether amine.
15. The process as claimed in claim 13, wherein said cycloaliphatic amine is selected from the group consisting of isophoron diamine (IPDA), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC) and cyclohexylamine.
16. The process as claimed in claims 9 and 10, wherein said aldehyde is selected from the group consisting of paraformaldehyde, heptanaldehyde, hexanaldehyde, acetaldehyde and propionaldehyde.
17. The process as claimed in claims 9 and 10, wherein said predetermined molar ratio of said alkyl phenol to said amine to said aldehyde is in the range of 1:2:2 to 1:4:4.
18. The process as claimed in claim 10, wherein said first predetermined temperature is in the range of 60 °C to 80 °C.
19. The process as claimed in claim 10, wherein said second predetermined temperature is in the range of 70 °C to 100 °C.
20. The process as claimed in claim 10, wherein said first predetermined time period and said second predetermined time period are independently in the range of 1 hour to 4 hours.
21. The process as claimed in claim 11, wherein said fluid medium is selected from the group consisting of benzyl alcohol, xylene, butanol, toluene, o-xylene and C9 solvent.
22. The process as claimed in claims 9 and 11 wherein said epoxy resin is selected from bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
23. The process as claimed in claims 9 and 11, wherein a weight ratio of said epoxy resin to said intermediate reaction product is in the range of 1:5 to 1:15.
24. The process as claimed in claim 11, wherein said third predetermined temperature is in the range of 60 °C to 80 °C.
25. The process as claimed in claim 11, wherein said third predetermined time period is in the range of 50 minutes to 80 minutes.
26. The process as claimed in claim 11, wherein said fourth predetermined temperature is in the range of 70 °C to 100 °C.
27. The process as claimed in claim 11, wherein said fourth predetermined time period is in the range of 30 minutes to 120 minutes.
28. A coating composition comprising
i. a phenalkamine curing agent as claimed in claim 1;
ii. at least one resin;
iii. at least one pigment;
iv. at least one filler;
v. at least one fluid medium; and
vi. at least one additive.
29. The coating composition as claimed in claim 28, wherein said resin is an epoxy resin, wherein said epoxy resin is bisphenol A diglycidyl ether with epoxy equivalent weight (EEW) = 190.
30. The coating composition as claimed in claim 28, wherein said pigment is titanium dioxide.
31. The coating composition as claimed in claim 28, wherein said filler is at least one selected from the group consisting of barium sulfate and silica.
32. The coating composition as claimed in claim 28, wherein said fluid medium is at least one selected from the group consisting of xylene and butanol.
33. The coating composition as claimed in claim 28, wherein said additive is at least one selected from the group consisting of a thickening agent, and a dispersing agent.
34. The coating composition as claimed in claim 28 is characterized by having
• a specific gravity in the range of 1 g/cm3 to 2 g/cm3;
• a solid content in the range of 50 % to 90 %; and
• a pot life at 25 °C in the range of 200 minutes to 250 minutes.
Dated this 17th day of January, 2024

_______________________________
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