Description:FIELD
The present disclosure relates to a curable paint composition and a process for its preparation. Particularly, the present disclosure relates to a curable stoving paint composition.
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.
Stoving paint refers to a paint composition blended with high-quality resins, selective additives, and highly durable pigments which impart exceptional colour retention, high gloss, smooth finish, hardness, and solvent resistance to a substrate.
Effective metal temperature (EMT) refers to the temperature and the time at which the paint is cured at the baking schedule on application over a substrate.
Persoz hardness refers to a pendulum test used to evaluate the elasticity of the film prepared by using the composition by measuring the damping time of an oscillating pendulum.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Stoving paints are highly durable and easy-to-use paint compositions that are specifically used to provide exceptional colour retention, high gloss, smooth finish, hardness, solvent resistance, and the like.
The stoving paints found their use in industrial applications such as home appliances, electrical fittings, steel furniture, commercial equipment, medical equipment, automobile, decorative coating for exterior purposes, and the like. Particularly, these compositions are used on refrigerators, water filters, kitchen appliances, washing machines, drum linings, and the like. In the automobile industry, the stoving paints are selected based on colour retention on exterior exposure, corrosion resistance, gasoline resistance, and scratch resistance to the substrates.
Stoving paints impart good flexibility, abrasion resistance, colour retention, improved adhesion, good finish, gloss, very high resistance to water/ detergents, /mild acids/mild alkalis/chemicals, resistance to alcohol, do not react with vegetable oil and grease, excellent finish on steel and aluminium, excellent weather resistance and hardness, and UV stability.
The conventional stoving paint composition contains resins such as a mixture of polyester resin, acrylic resin, melamine formaldehyde resin, and the like, that can be cured at a baking schedule of 140°C/20 minutes effective metal temperature (EMT). The acid value of the resins is well enough to internally catalyze the reaction with a cross-linker at 140ºC. These stoving paint compositions are generally applied by electrostatic spray painting for which the electrical resistance of the paint composition needs to be in the range of 200-600 KOhm for the safe application of coatings with optimized transfer efficiency. The conventional paint compositions are not suitable for ultra-low bake conditions, when applied at low bake conditions as it does not cure properly and doesn’t provide the desired hardness.
Further, applying the stoving paints at an EMT schedule of 140°C/20 minutes requires a high amount of energy. Such a problem can be overcome by the excess addition of acid catalyst to reduce the EMT schedule, however, increasing the addition of acid catalyst drastically reduces electrical resistance from 400 KOhm to as low as 50 KOhm, which is not suitable for electrostatic spray painting. Moreover, the addition of excess acid catalyst also deteriorates the storage stability of paints.
Therefore, there is felt a need to provide a curable paint composition that mitigates the aforestated drawbacks or at least provide an alternative solution.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.
An object of the present disclosure is to provide a curable paint composition.
Another object of the present disclosure is to provide a stoving paint composition.
Still another object of the present disclosure is to provide a curable stoving paint composition that has low EMT (effective metal temperature).
Yet another object of the present disclosure is to provide a process for the preparation of the curable paint composition.
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 curable paint composition and the process for its preparation. In an aspect, the curable paint composition comprising a) at least one polyester resin in an amount in the range of 20 mass% to 35 mass% with respect to the total mass of the composition b) at least one acrylic resin in an amount in the range of 5 mass% to 15 mass% with respect to the total mass of the composition; c) at least one melamine formaldehyde resin in an amount in the range of 15 mass% to 25 mass% with respect to the total mass of the composition; d) at least one anti-settling additive in an amount in the range of 4 mass% to 8 mass% with respect to the total mass of the composition; e) at least one acid blocked catalyst in an amount in the range of 0.1 mass% to 2 mass% with respect to the total mass of the composition; f) at least one white pigment in an amount in the range of 15 mass% to 25 mass% with respect to the total mass of the composition; g) at least one anti-sagging additive in an amount in the range of 2 mass% to 5 mass% with respect to the total mass of the composition; h) at least one solvent in an amount in the range of 5 mass% to 15 mass% with respect to the total mass of the composition; and i) at least one additive in an amount in the range of 0.5 mass% to 10 mass% with respect to the total mass of the composition.
In another aspect, the process for the preparation of a curable paint composition comprises mixing a first portion of a polyester resin, a wetting agent, a first portion of solvent, and blending at a speed in the range of 800 rpm to 1000 rpm for a first predetermined time period to obtain a resin mixture. The resin mixture is blended with a white pigment at a speed in the range of 1000 rpm to 2500 rpm for a second predetermined time period to obtain a slurry. The slurry is grinded at a predetermined temperature for a third predetermined time period to obtain a dispersion. A second portion of the polyester resin and a second portion of the solvent are blended with the dispersion at a speed in the range of 2000 rpm to 3000 rpm for a fourth predetermined time period to obtain a resultant dispersion. A third portion of the polyester resin, an acrylic resin, a melamine formaldehyde resin, an acid blocked catalyst, an anti-settling additive, an anti-sagging additive, a flow additive, an anti-popping agent, an UV additive, a black pigment, and a third portion of the solvent, are blended sequentially with the resultant dispersion at a speed in the range of 800 rpm to 1000 rpm for a fifth predetermined time period to obtain the curable paint composition.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a graph depicting the effect of an acid catalyst on the electric resistivity of the curable paint composition of the present disclosure; and
Figure 2 illustrates a graph depicting the effect of an acid catalyst and melamine formaldehyde resin on the Persoz hardness of the present disclosure;
DETAILED DESCRIPTION
The present disclosure relates to a curable paint composition and a process for its preparation. Particularly, the present disclosure relates to a stoving paint composition.
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
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.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
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 conventional stoving paint composition contains resins such as a mixture of polyester resin, acrylic resin, melamine formaldehyde resin, and the like, that can be cured at a baking schedule of 140°C/20 minutes effective metal temperature (EMT). The acid value of the resins is well enough to internally catalyze the reaction with a cross-linker at 140ºC. These stoving paint compositions are generally applied by electrostatic spray painting for which the electrical resistance of the paint composition needs to be in the range of 200-600 KOhm for the safe application of coatings with optimized transfer efficiency. The conventional paint compositions are not suitable for ultra-low bake conditions when applied at low bake conditions as it does not cure properly and doesn’t provide the desired hardness.
Further, applying the stoving paints at an EMT schedule of 140°C/20 minutes requires a high amount of energy. Such a problem can be overcome by the excess addition of acid catalyst to reduce the EMT schedule, however, increasing the addition of acid catalyst drastically reduces electrical resistance from 400 KOhm to as low as 50 KOhm, which is not suitable for electrostatic spray painting. Moreover, the addition of excess acid catalysts also deteriorates the storage stability of paints.
The present disclosure provides a curable paint composition, which reduces the EMT schedule, which is safe for application by electrostatic spray painting, and has excellent storage stability of the paint.
In an aspect of the present disclosure, there is provided a curable paint composition.
The curable paint composition comprises a) at least one polyester resin in an amount in the range of 20 mass% to 35 mass% with respect to the total mass of the composition b) at least one acrylic resin in an amount in the range of 5 mass% to 15 mass% with respect to the total mass of the composition; c) at least one melamine formaldehyde resin in an amount in the range of 15 mass% to 25 mass% with respect to the total mass of the composition; d) at least one anti-settling additive in an amount in the range of 4 mass% to 8 mass% with respect to the total mass of the composition; e) at least one acid blocked catalyst in an amount in the range of 0.1 mass% to 2 mass% with respect to the total mass of the composition; f) at least one white pigment in an amount in the range of 15 mass% to 25 mass% with respect to the total mass of the composition; g) at least one anti-sagging additive in an amount in the range of 2 mass% to 5 mass% with respect to the total mass of the composition; h) at least one solvent in an amount in the range of 5 mass% to 15 mass% with respect to the total mass of the composition and i) at least one additive in an amount in the range of 0.5 mass% to 10 mass% with respect to the total mass of the composition.
In an embodiment of the present disclosure, the polyester resin is characterized by having a solid content in the range of 64% to 66%, an acid value in the range of 4 to 17 mg KOH/gm, and a hydroxyl value in the range of 70 to 80.
In an embodiment of the present disclosure, the polyester resin is characterized by having a solid content of 65 ±1 %, an acid value in the range of 4 to 7 mg KOH/gm, and a hydroxyl value in the range of 100 to 120 (65% PE 384). The polyester resin 65% PE 384 is of low viscosity and provides better wetting and dispersion.
In another embodiment of the present disclosure, the polyester resin is characterized by having a solid content of 65 ± 1 %, an acid value in the range of 4 to 8.5mg KOH/gm, and a hydroxyl value in the range of 70 to 80 (65% PE 214). The polyester resin 65% PE 214 is a base resin that provides flexibility and chemical resistance.
In still another embodiment of the present disclosure, the polyester resin is characterized by having a solid content of 65 ± 1 %, an acid value of 9.5 to 16.6 mg KOH/gm, and a hydroxyl value of 70 to 80 (SETAL 186 XX-65).
In an exemplary embodiment of the present disclosure, the polyester resin is 65% PE 384. In another exemplary embodiment of the present disclosure, the polyester resin is 65% PE 214.
In an embodiment of the present disclosure, the acrylic resin is characterized by having a solid content in the range of 68% to 71% and an acid value in the range of 8.5 to 15 mg KOH/gm.
In an embodiment of the present disclosure, the acrylic resin is characterized by having a solid content of 68 ± 1 % and an acid value in the range of 13 to 15 mg KOH/gm (70% HS ACR 12).
In another embodiment of the present disclosure, the acrylic resin is characterized by having a solid content of 68 ± 1 % and an acid value in the range of 12 to 14 mg KOH/gm (70% HS ACR 13).
In still another embodiment of the present disclosure, the acrylic resin (polyol) is characterized by having a solid content of 69% to 71% and an acid value of 8.9 to 12.1 mg KOH/gm (SETALUX 1753 SS-70).
In an exemplary embodiment of the present disclosure, the acrylic resin is 70% HS ACR 12 and 70% HS ACR 13.
In an embodiment of the present disclosure, the acrylic resins 70% HS ACR 12 and 70% HS ACR 13 imparts hardness to the film after baking the curable paint composition on a metal susbrate.
In an embodiment of the present disclosure, the melamine formaldehyde resin is at least one selected from the group consisting of methylated and isobutylated melamine formaldehyde resin (65% MF 25), n-butylated high imino melamine crosslinker in butanol (70% MF 132, Setamine US-132), methylated high imino melamine crosslinker in iso-butanol (90% MF 327, Cymel 325, Cymel 327), methylated/n-butylated high imino melamine resin in n-butanol (Cymel 250), methylated/iso-butylated melamine formaldehyde resin in iso-butanol (Maprenal MF 927), n-butylated melamine formaldehyde resin in butanol (Maprenal VMF 3611), and butylated melamine-formaldehyde cross-linking agent in butanol (Cymel 1158). In an exemplary embodiment of the present disclosure, the melamine formaldehyde resin is 65% MF 25, 70% MF 132, cymel 325, and cymel 327.
The melamine formaldehyde resin 65% MF 25 is characterized by having a solid content of 68 ± 1%, an acid value of < 0.15 mg KOH/gm, and a xylene tolerance in the range of 1400% to 2000%. The melamine formaldehyde resin 70% MF 132 is characterized by having a solid content of 69% to 73%, an acid value of < 0.15 mg KOH/gm, and an MTO (Mineral Turpentine Oil) tolerance in the range of 275 to 475%. The melamine formaldehyde resin 90% MF 327 is characterized by having a solid content of 90 ± 2%, and a free formaldehyde content of < 0.8%.
In an embodiment of the present disclosure, the melamine formaldehyde resin 65% MF MS25 provides gloss, weathering, and chemical resistance to the curable paint composition. The melamine formaldehyde resin 70% MF 132 and 90% MF 327 provides hardness and solvent resistance.
In an embodiment of the present disclosure, the anti-settling additive is at least one selected from the group consisting of 50% modified polyurea resin, saturated polyester resin modified with sag control agent (SCA) (SETAL 90173 SS-50), an alkylol ammonium salt of a copolymer with acidic groups (BYK 180), an organic derivative of a hectorite clay (Bentone -27), an organic derivative of a hectorite clay (Bentone 38); and an adduct of benzylamine and polyisocyanate compounds (50% BT -10). In an exemplary embodiment of the present disclosure, the anti-settling additive is 50% modified polyurea resin.
Anti-settling additives refer to compounds used to delay the drying and solidification of a curable paint composition during storage or after application on a metal substrate.
In an embodiment of the present disclosure, the acid-blocked catalyst is at least one selected from the group consisting of DDBSA (dodecyl benzene sulfonic acid) type, amine blocked dodecylbenzenesulfonic acid (Nacure 5528), amino blocked acidic catalyst (Cycat 6395), amine neutralized p-toluenesulfonic acid (p-TSA) (Nacure 2500), amine blocked para-toluene sulfonic acid catalyst (Cycat 4045), amine-neutralized dodecylbenzene sulfonic acid (Cycat 6030) and partially amine counterbalanced para-toluenesulfonic acid (p-TSA) (Nacure 2558). In an exemplary embodiment of the present disclosure, the acid-blocked catalyst is Nacure 5528 and Cycat 6030.
The Cycat 6030 is amine-neutralized dodecylbenzene sulfonic acid in isopropanol having an acid value of 54 to 62 mg KOH/gm and solid content of 40%.
In an embodiment of the present disclosure, the acid-blocked catalyst catalyzes the reaction between polyester resin, acrylic resin, and melamine formaldehyde resin to form a complex film when the curable paint composition with a thinner applied on a metal substrate and baked at a baking schedule i.e. an effective metal temperature (EMT) in the range of 120°C/10 minutes to 120°C/20 minutes.
In an embodiment of the present disclosure, the white pigment is at least one selected from the group consisting of titanium dioxide (Tioxide TR 92 by Huntsman), rutile titanium dioxide pigment (TiO2 content 93%, CR 826), rutile titanium dioxide pigment (TiO2 content 95%, CR 828), chloride-process rutile titanium dioxide pigment (Tiona 596), rutile titanium dioxide pigment (BLR 601), rutile crystal structured white pigment (JR 701). In an exemplary embodiment, the titanium dioxide is CR 826.
In an embodiment of the present disclosure, titanium dioxide provides colour and opacity.
In an embodiment of the present disclosure, the anti-sagging additive is at least one selected from the group consisting of non-aqueous acrylic dispersion (45% NAD acrylic resin), saturated polyester resin with sag control agent (SCA) (SETAL 90173 SS-50), acrylic non-aqueous dispersion resin (PARALOID NAD-10V), and hydroxy functional microgel containing acrylic copolymers (SETALUX 1850 SA-50).
In an embodiment of the present disclosure, the 45% NAD acrylic resin is non-aqueous dispersion of acrylic characterized by having a solid content of 48 ±2%, and an acid value of 5 to 8 mg KOH/gm.
In an exemplary embodiment of the present disclosure, the anti-sagging additive is 45% NAD acrylic resin.
Anti-sagging additives refer to a class of compounds used to prevent the weakening of the coating due to gravity.
In an embodiment of the present disclosure, the solvent is at least one selected from the group consisting of n-butanol, diethylene glycol monobutyl ether (butyl carbitol), butyl acetate, mixed xylene, aromatic solvent C9, aromatic solvent C10 (solvesso 150), butyl acetate, butanol, methanol, ethanol/iso-propanol (60/40%) mixture (mosstanol 120), ester solvents, glycol ether, and aromatic hydrocarbons. In an exemplary embodiment of the present disclosure, the solvent is a combination of butyl carbitol, aromatic solvent C9, aromatic solvent C10, methanol, mosstanol 120, mixed xylene, and butyl acetate.
In an embodiment of the present disclosure, n-butanol provides stability, the ester solvents is a fast solvent and glycol ether is a slow solvent, the combination provides the desired properties to the curable paint composition.
In an embodiment of the present disclosure, the additive is at least one selected from the group consisting of a wetting agent, a black pigment, an anti-popping agent, a flow additive, and an UV additive.
In an embodiment of the present disclosure, wherein additive in a composition comprises a. wetting agent in an amount in the range of 1 mass% to 6 mass% with respect to the total mass of the composition; b. black pigment in an amount in the range of 0.1 mass% to 3 mass% with respect to the total mass of the composition; c. anti-popping agent in an amount in the range of 0.1 mass% to 4 mass% with respect to the total mass of the composition; d. flow additive in an amount in the range of 0.02 mass% to 10 mass% with respect to the total mass of the composition; and e. UV additive in an amount in the range of 0.1 mass% to 6 mass% with respect to the total mass of the composition.
In an embodiment of the present disclosure, the wetting agent is at least one selected from the group consisting of alkylolammonium salt of a copolymer with acidic groups (DISPER BYK 180), solution of a high molecular weight block copolymers (DISPER BYK 160, BYK 162, and BYK 163), and solution of modified polyurethane with pigment affinic groups (BYK 2025 and Efka 4047). In an exemplary embodiment of the present disclosure, the wetting agent is DISPER BYK 180.
In an embodiment of the present disclosure, the wetting agents also work as dispersing agent.
In an embodiment of the present disclosure, the black pigment is at least one selected from the group consisting of charcoal, carbon black, UV pigment carbon black (MA 100), and carbon black (BP 1300). In an exemplary embodiment of the present disclosure, the black pigment is MA 100.
In an embodiment of the present disclosure, the flow additive is at least one selected from the group consisting of acrylic resin 005 (acrylic resin having a solid content of 50%), silicon solution, silicone-free non-ionic surface-active acrylic polymer (Disparlon L 1984), acrylic polymer with silicone (Diparlon LHP 96), acrylic flow modifier without silicone (Modaflow 9200). In an exemplary embodiment of the present disclosure, the flow additive is acrylic resin 005 and silicon solution.
Flow additives refer to compounds used to ease powder flow by physically lubricating inter particulate movement and by disrupting the cohesive bonds between particles within the powder.
In an embodiment of the present disclosure, the anti-popping agent is at least one selected from the group consisting of 50% polyacrylate solution (BYK 390) and 52% polyacrylate solution (BYK 392). In an exemplary embodiment of the present disclosure, the anti-popping agent is a polyacrylate solution (BYK 390).
Anti-popping agent refers to compounds used to control popping during baking.
In an embodiment of the present disclosure, the UV additive is at least one selected from the group consisting of UV absorber; Hindered amine light stabilizers (HALS); a mixture of Bis (1, 2, 2, 6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1, 2, 2, 6, 6-pentamethyl-4-piperidyl sebacate (Tinuvin 292); mixture of a) 50% ß-[3-(2-H-Benzotriazole-2-yl)-4-hydorxy-5-tert-butylphenyl]-propionic acid-poly(ethylene glycol) 300-ester, b) 38% Bis{ß-[3-(2-H-Benzotriazole-2-yl)-4-hydroxy5tert.butylphenyl]-propionic acid}-poly(ethylene glycol) 300 –ester, and c) 12% polyethylene glycol (Tinuvin 1130); and mixture of bis (1, 2, 2, 6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1, 2, 2, 6, 6- pentamethyl-4-piperidyl sebacate (Tinuvin 292). In an exemplary embodiment of the present disclosure, the UV additive is Tinuvin 1130 and Tinuvin 292.
In an embodiment of the present disclosure, the mass ratio of the polyester resin to the acrylic resin to the melamine formaldehyde resin is in the range of 2.5:1:2 to 4:1:3. In an exemplary embodiment of the present disclosure, the mass ratio of the polyester resin to the acrylic resin to the melamine formaldehyde is 3.2:1:2.2.
In an embodiment of the present disclosure, the mass ratio of the melamine formaldehyde resin to the acid blocked catalyst is in the range of 1:0.02 to 1:0.04. In an exemplary embodiment of the present disclosure, the mass ratio of the melamine formaldehyde to the acid blocked catalyst is 1:0.023.
In another aspect of the present disclosure, there is provided a process for the preparation of the curable paint composition. Particularly, the present disclosure provides a process for the preparation of stoving paint composition.
The process is described in detail.
In a first step, a first portion of polyester resin, and a wetting agent are mixed with a first portion of a solvent and then blended at a speed in the range of 800 rpm to 1000 rpm for a first predetermined time period to obtain a resin mixture.
In an embodiment of the present disclosure, the polyester resin is characterized by having a solid content in the range of 64% to 66%, an acid value in the range of 4 to 17 mg KOH/gm, and a hydroxyl value in the range of 70 to 80.
In an embodiment of the present disclosure, the first portion of polyester resin is in the range of 15% to 20% with respect to the total mass of the polyester resin. In an exemplary embodiment, the first portion of the polyester resin is 17.2%.
In an embodiment of the present disclosure, the wetting agent is at least one selected from the group consisting of alkylolammonium salt of a copolymer with acidic groups (DISPER BYK 180, solution of a high molecular weight block copolymers (DISPER BYK 160, BYK 162, and BYK 163), and solution of modified polyurethane with pigment affinic groups (BYK 2025 and Efka 4047). In an exemplary embodiment of the present disclosure, the wetting agent is DISPER BYK 180.
In an embodiment of the present disclosure, the solvent is at least one selected from the group consisting of n-butanol, diethylene glycol monobutyl ether (butyl carbitol), butyl acetate, mixed xylene, solvesso 150, butyl acetate, butanol, methanol, an ester solvent, glycol ether, and aromatic hydrocarbons. In an exemplary embodiment of the present disclosure, the solvent is butyl carbitol.
In an embodiment of the present disclosure, the first portion of the solvent is in the range of 20% to 45% with respect to the total mass of the solvent. In an exemplary embodiment of the present disclosure, the first portion of the solvent is 25.5% with respect to the total mass of the solvent.
In an embodiment of the present disclosure, the first predetermined time period is in the range of 5 minutes to 20 minutes. In an exemplary embodiment, the first predetermined time period is 10 minutes.
In a second step, a white pigment is blended with a resin mixture at a speed in the range of 1000 rpm to 2500 rpm for a second predetermined time period to obtain a slurry.
In an embodiment of the present disclosure, the white pigment is at least one selected from the group consisting of titanium dioxide (Tioxide TR 92 by Huntsman), rutile titanium dioxide pigment (TiO2 content 93%, CR 826), rutile titanium dioxide pigment (TiO2 content 95%, CR 828), chloride-process rutile titanium dioxide pigment (Tiona 596), rutile titanium dioxide pigment (BLR 601), rutile crystal structured white pigment. In an exemplary embodiment of the present disclosure, the white pigment is titanium dioxide.
In an embodiment of the present disclosure, the second predetermined time period is in the range of 2 minutes to 10 minutes. In an exemplary embodiment, the second predetermined time period is 5 minutes.
In a third step, the slurry is grinded at a predetermined temperature for a third predetermined time period to obtain a dispersion.
In an embodiment of the present disclosure, the predetermined temperature is in the range of 20°C to 50°C. In an exemplary embodiment of the present disclosure, the predetermined temperature is 30°C to 40°C.
In an embodiment of the present disclosure, the third predetermined time period is in the range of 30 minutes to 60 minutes. In an exemplary embodiment of the present disclosure, the third predetermined time period is 45 minutes.
In an embodiment of the present disclosure, the grinding is performed by using zirconium beads at a rotor speed in the range of 2000 rpm to 3000 rpm. In an exemplary embodiment, the rotor speed is 2500 rpm.
In an embodiment of the present disclosure, the dispersion has a particle size in the range of 5 microns to 15 microns. In an exemplary embodiment of the present disclosure, the particle size of the dispersion is in the range of 7 to 10 microns.
In a fourth step, the second portion of the polyester resin and a second portion of the solvent is blended with dispersion at a speed in the range of 2000 rpm to 3000 rpm for a fourth predetermined time period to obtain a resultant dispersion.
In an embodiment of the present disclosure, the second portion of the polyester resin is in the range of 15% to 25% with respect to the total mass of polyester resin. In an exemplary embodiment, the second portion of the polyester resin is 20.3%.
In an embodiment of the present disclosure, the second portion of the solvent is in the range of 7% to 10% with respect to the total mass of the solvent. In an exemplary embodiment of the present disclosure, the second portion of the solvent is 8.1% with respect to the total mass of the solvent.
In an embodiment of the present disclosure, the fourth predetermined time period is in the range of 5 minutes to 20 minutes. In an exemplary embodiment of the present disclosure, the fourth predetermined time period is 10 minutes.
In a final step, the third portion of the polyester resin, an acrylic resin, a melamine formaldehyde resin, an acid blocked catalyst, an anti-settling additive, an anti-sagging additive, a flow additive, an anti-popping agent, an UV additive, a black pigment, and the third portion of the solvent are blended sequentially with the resultant dispersion at a speed in the range of 800 rpm to 1200 rpm for a fifth predetermined time period to obtain the curable paint composition.
In an embodiment of the present disclosure, the solid acrylic resin is characterized by having a solid content in the range of 68% to 71 % and an acid value in the range of 8.5 mg KOH/gm to 15 mg KOH/gm.
In an embodiment of the present disclosure, the melamine formaldehyde resin is at least one selected from the group consisting of methylated and isobutylated melamine formaldehyde resin (65% MF25), n-butylated high imino melamine crosslinker in butanol (70% MF 132), methylated high imino melamine crosslinker in iso-butanol (90% MF 327), methylated/n-butylated high imino melamine resin in n-butanol (Cymel 250), methylated/iso-butylated melamine formaldehyde resin in iso-butanol (Maprenal MF 927), n-butylated melamine formaldehyde resin in butanol (Maprenal VMF 3611), and butylated melamine-formaldehyde cross-linking agent in butanol (Cymel 1158).
In an embodiment of the present disclosure, the anti-settling additive is at least one selected from the group consisting of 50% modified polyurea resin, saturated polyester resin modified with sag control agent (SCA) (SETAL 90173 SS-50), alkylol ammonium salt of a copolymer with acidic groups (BYK 180), organic derivative of a hectorite clay (Bentone-27), an organic derivative of a hectorite clay (Bentone 38) and an adduct of benzylamine and polyisocyanate compounds (50 % BT -10).
In an embodiment of the present disclosure, the black pigment is at least one selected from the group consisting of charcoal, carbon black, UV pigment carbon black (MA 100), and carbon black (BP 1300). In an exemplary embodiment of the present disclosure, the black pigment is Carbon Black BP 1300.
In an embodiment of the present disclosure, the flow additive is at least one selected from the group consisting of acrylic resin 005 (acrylic resin having a solid content of 50%), silicon solution, silicone-free non-ionic surface-active acrylic polymer (Disparlon L 1984), acrylic polymer with silicone (Disparlon LHP 96), acrylic flow modifier without silicone (Modaflow 9200). In an exemplary embodiment of the present disclosure, the flow additive is acrylic resin 005 and silicon solution.
In an embodiment of the present disclosure, the anti-sagging additive is at least one selected from the group consisting of non-aqueous acrylic dispersion (45% NAD acrylic resin), saturated polyester resin with sag control agent (SCA) (SETAL 90173 SS-50), acrylic non-aqueous dispersion resin (PARALOID NAD-10V), and hydroxy functional microgel containing acrylic copolymers (SETALUX 1850 SA-50).
In an embodiment of the present disclosure, the anti-popping agent is at least one selected from the group consisting of polyacrylate solution (BYK 390). In an exemplary embodiment of the present disclosure, the anti-popping agent is a polyacrylate solution (BYK 390).
In an embodiment of the present disclosure, the UV additive is at least one selected from the group consisting of UV absorber, Hindered amine light stabilizers (HALS), a mixture of Bis (1, 2, 2, 6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1, 2, 2, 6, 6-pentamethyl-4-piperidyl sebacate (Tinuvin 292); mixture of a) 50% ß-[3-(2-H-Benzotriazole-2-yl)-4-hydorxy-5-tert.butylphenyl]-propionic acid-poly(ethylene glycol) 300-ester, b) 38% Bis{ß-[3-(2-H-Benzotriazole-2-yl)-4-hydroxy5tert.butylphenyl]-propionic acid}-poly(ethylene glycol) 300 –ester, and c) 12% polyethylene glycol (Tinuvin 1130); and a mixture of bis (1, 2, 2, 6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1, 2, 2, 6, 6- pentamethyl-4-piperidyl sebacate (Tinuvin 292). In an exemplary embodiment of the present disclosure, the UV additive is Tinuvin 1130 and Tinuvin 292.
In an embodiment of the present disclosure, the acid-blocked catalyst is at least one selected from the group consisting of DDBSA (dodecyl benzene sulfonic acid) type, amine blocked dodecylbenzenesulfonic acid (Nacure 5528), amino blocked acidic catalyst (Cycat 6395), amine neutralized p-toluenesulfonic acid (p-TSA) (Nacure 2500), amine blocked para-toluene sulfonic acid catalyst (Cycat 4045), amine-neutralized dodecylbenzene sulfonic acid (Cycat 6030) and partially amine counterbalanced para-toluenesulfonic acid (p-TSA) (Nacure 2558). In an exemplary embodiment of the present disclosure, the acid-blocked catalyst is DDBSA (Dodecyl Benzene Sulfonic Acid) type. In an exemplary embodiment of the present disclosure, the acid-blocked catalyst is Cycat 6030.
In an embodiment of the present disclosure, the third portion of the polyester resin is in the range of 50% to 70% with respect to the total mass of the polyester resin. In an exemplary embodiment of the present disclosure, the third portion of polyester resin is 62.6% with respect to the total mass of polyester resin.
In an embodiment of the present disclosure, the third portion of the solvent is in the range of 45% to 75% with respect to the total mass of the solvent. In an exemplary embodiment of the present disclosure, the third portion of the solvent is 66.4% with respect to the total mass of the solvent.
In an embodiment of the present disclosure, the fifth predetermined time period is in the range of 15 minutes to 60 minutes. In an exemplary embodiment of the present disclosure, the fourth predetermined time period is 30 minutes.
In an embodiment of the present disclosure, the acid catalyst is diluted with the solvent before blending with the resultant dispersion.
In an embodiment of the present disclosure, the curable paint composition is kept overnight for 12 hours to 14 hours for maturation.
In an embodiment of the present disclosure, the curable paint composition of the present disclosure, when applied on a substrate as a topcoat, can be cured at an effective metal temperature (EMT) in the range of 120°C/10 minutes to 120°C/20 minutes. In an exemplary embodiment of the present disclosure, the curable paint composition after application on a metal substrate is cured at a temperature of 120°C/10 mins EMT.
In another aspect of the present disclosure, there is provided a method for coating a metal substrate with the curable paint composition,
The method is described in detail.
In a first step, a predetermined amount of the curable paint composition of the present disclosure is mixed with a predetermined amount of a thinner to obtain a mixture.
In an embodiment of the present disclosure, the thinner is a mixture of a polar solvent and a spray thinner.
In an embodiment of the present disclosure, the polar solvent is at least one selected from the group consisting of isobutanol and butanol.
In an embodiment of the present disclosure, the spray thinner is a mixture of C10 aromatic fluid, isobutanol, and ethylene glycol monobutyl ether.
In an embodiment of the present disclosure, the mass ratio of the curable paint composition to the thinner is in the range of 10:1 to 10:3.
In the final step, the mixture is coated on a metal substrate at a temperature in the range of 25°C to 30°C and relative humidity in the range of 65 to 70, followed by baking at an effective metal temperature (EMT) in the range of 120°C/10 minutes to 120°C/20 minutes to obtain the coated metal substrate.
In an embodiment of the present disclosure, the mixture is coated on a metal substrate to obtain a dry film thickness (DFT) of 35 ±5 micron on the coated metal substrate.
The present disclosure provides the curable paint composition, which on the application on a metal substrate after baking at an EMT, provides enhanced flexibility, enhanced abrasion resistance, improved colour retention/adhesion/finish/gloss, increased scratch resistance, and resistance to water/ detergents/chemicals. The curable paint composition also helps in reducing energy requirements. The curable paint composition of the present disclosure can be used on any pre-treated metallic substrate as a stoving topcoat. The pre-treated metallic substrate refers to a metallic substrate coated using Cathodic Electro Deposition (CED). In an exemplary embodiment of the present disclosure, the metallic substrate is tri-cationic phosphating coated using CED.
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 described in light of the following experiments which are set forth for illustration purpose 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 industrial scale.
EXPERIMENTAL DETAILS
EXAMPLE 1: Process for the preparation of the curable paint composition in accordance with the present disclosure
4.87 gm of polyester resin (65% PE FT 384), 1.2 gm of DISPER BYK 180, 1.33 gm of butyl carbitol, and 1.24 gm of solvent C9 were blended at a speed of 1000 rpm for 10 minutes to obtain a resin mixture. To the resin mixture, 20.3 gm of titanium dioxide (CR 826) was added and blended at a speed of 1000 rpm for 5 minutes to obtain a slurry. Maintaining the temperature at 30°C to 40°C, the slurry was grinded using zirconium oxide beads at a speed of 2500 rpm for 45 min to obtain a dispersion having a particle size of 7 to 10 microns.
The so obtained dispersion was blended with 5.74 gm of polyester resin (65% PE 214) and 0.81 gm of solvent C10 at a speed of 2500 rpm for 10 minutes to obtain a resultant dispersion. The resultant dispersion was blended with 17 gm of polyester resin (65% PE 214), 5.37 gm of acrylic resin (70% HS ACR 12), 3.57 gm of acrylic resin (70% HS ACR 13), 10.23 gm of methylated and isobutylated melamine formaldehyde resin (65% MF 25), 6.81 gm of n-butylated high imino melamine crosslinker in butanol (Setamine US-132), 2.61 gm of methylated high imino melamine crosslinker in iso-butanol (Cymel 327), 0.45 gm of amine-neutralized dodecylbenzene sulfonic acid (Cycat 6030), 5.78 gm of an adduct of benzylamine and polyisocyante compound, 3.71 gm of 45% NAD acrylic resin, 0.2 gm of silicon solution, 0.1 gm of acrylic resin 005, 0.2 gm of BYK 390, 0.4 gm of TINUVIN 292, 0.2 gm of TINUVIN-1130, 0.5 gm of MA 100, 1 gm of methanol, 1 gm of mosstanol (60% ethanol and 40% iso-propanol), 0.45 gm of mixed xylene, 2.63 gm of butyl acetate in a sequential manner (one after the other) at a speed of 1000 rpm for 30 minutes to obtain the curable paint composition.
EXAMPLE 2: Electric resistivity of the curable paint composition
The electric resistivity of the paint composition of Example 1 (DOE 7) and the paint compositions having various concentrations of acid catalysts, polyester resins, acrylic resins, melamine resins, and solvents were also prepared in a similar manner as given in Example 1. The details of the compositions are provided in Table 1. The electric resistivity of the paint compositions was determined according to ASTM D 5628. The results are illustrated in Figure 1.
EXAMPLE 3: Persoz hardness of the curable paint composition
The Persoz hardness of the paint composition of Example 1 and the paint compositions having various concentrations of an acid catalyst, polyester resins, acrylic resins, melamine resins, and solvents were also prepared in a similar manner as given in Example 1. The details of the compositions are provided in Table 1 below. The Persoz hardness of the curable paint compositions was determined according to ASTM D 4366 and ISO 1522. The results are illustrated in Figure 2.
It was evident from the graph that the curable paint composition having catalyst -1 (N5528) with a dosage of 2% by mass, ER reduces to 50-150 KOhm and a Persoz hardness in the range of 180 to 182. The Persoz hardness in the range of 220 to 250 is desired for the optimum performance of the curable paint composition. Hence, the curable paint composition with catalyst 1 failed to provide the desired Persoz hardness.
With Catalyst -1 (N5528) dosage of 2.0% by mass, ER reduces to 50-150 KOhm but despite using a higher dosage of 2.0%, Persoz hardness was only 180-182 as against a minimum requirement of 220 to 250 Persoz.
The curable paint compositions comprising catalyst-2 (CYCAT 6030), were able to achieve the ER of 200 to 280 KOhms while obtaining a Persoz hardness in the range of 220 to 280. The Persoz hardness in the range of 220 to 250 is desired by automotive manufacturers for optimum performance.
The amount of catalyst and the choice of the resins (polyester resins, acrylic resins, and melamine resins) are critical features for obtaining the desired properties.
The details of the composition with varying amounts of catalysts are provided below in Table-1.

Table – 1: Composition details with varying amounts of catalysts
CATALYST 1 CATALYST 2
Code DOE 1 DOE 2 DOE 3 DOE 4 DOE 5 DOE 6 DOE 7 DOE 8
PERSOZ HARDNESS (Target > 200 oscillation) 182 181 254 249 237 280 238 191
ELECTRICAL RESISTIVITY (Target > 300 Kohm) 55 150 78 220 292 285 318 447
Sr. No Description Quantity (%)
1 65% FT 384 4.87 4.87 4.87 4.87 4.87 4.87 4.87 4.87
2 BUTYL CARBITOL 1.33 1.33 1.33 1.33 1.33 1.33 1.33 1.33
3 DIST. C IX SOLVENT 1.24 1.24 1.24 1.24 1.24 1.24 1.24 1.24
4 DISPER BYK 180 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20
5 TITANIUM DIOXIDE CR 826 20.30 20.30 20.30 20.30 20.30 20.30 20.30 20.30
6 POLYESTER RESIN 65% FU214 5.74 5.74 5.74 5.74 5.74 5.74 5.74 5.74
7 DIST. C IX SOLVENT 0.81 0.81 0.81 0.81 0.81 0.81 0.81 0.81
8 65 % FT 384 0.73 0.73 0.73 0.73
9 POLYESTER RESIN 65% FU214 14.46 14.46 14.46 14.46 17 17.00 17.00 17.00
10 TSA RESIN HIGH SOLID 4.69 4.69 4.69 4.69 5.35 5.35 5.35 5.35
11 TSA RESIN HIGH SOLID 3.04 3.04 3.04 3.04 3.57 3.57 3.57 3.57
12 M.F.RESIN MS-25 12.34 12.34 12.34 12.34 10.23 10.23 10.23 10.23
13 SETAMINE US-132 BB-71 11.80 11.80 11.80 8.26 6.81 6.81 6.81 6.81
14 CYMEL 327 3.14 2.61 2.61 2.61
15 CYMEL 325 2.92
16 CAT 1 - NACURE 5528 2.00 2.00
17 CAT 2 - CYCAT 6030 1.25 0.63 0.5 0.5 0.45 0.3
18 50% BT-10 Y430 FT ADDITIVE 5.78 5.78 5.78 5.78 5.78 5.78 5.78 5.78
19 45% NZ-011 NAD ACRYLIC RESIN 3.71 3.71 3.71 3.71 3.71 3.71 3.71 3.71
20 SILICONE#10% BYK 300 SOLN. 0.20 0.20 0.2 0.2 0.2 0.2 0.2 0.2
21 ACRYLIC RESIN 005 0.10 0.10 0.1 0.1 0.1 0.1 0.1 0.1
22 BYK 390 0.20 0.20 0.2 0.2 0.2 0.2 0.2 0.2
23 TINUVIN 292 / E 93 0.40 0.40 0.4 0.4 0.4 0.4 0.4 0.4
24 TINUVIN-1130 0.20 0.20 0.2 0.2 0.2 0.2 0.2 0.2
25 DIST. C IX SOLVENT 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60
26 NA MA 100 BLACK STN -2300846 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49
27 Polar solvent - METHANOL 1.00 1.00 1.00 1.00 1.00 1.00 1.00
28 Polar Solvent- MOSTANOL -120 1.00 1.00 1.00 1.00 1.00 1.00 1.00
29 MIXED XYLENE 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45
30 Butyl acetate 1.05 1.05 1.80 2.82 2.58 2.27 2.63 2.78
Total 100.00 98.00 100.00 100.00 100.00 100.00 100.00 100.00

EXAMPLE 4: Accelerated storage stability of the curable paint composition
The stability of the curable paint composition of Example 1 and the stability of the stoving paint composition (DOE4, Table 1) was subjected to accelerated stability testing at 60°C for 240 hrs. The physicochemical properties before and after the stability testing are provided below in Table 2.
Table-2
Accelerated stability testing
Sample Parameter Fresh Sample Incubator Sample
Existing composition (DOE4)
(140ºC/20 mins EMT) Hegman Gauge <10 micron <10 micron
Viscosity (FCB4- sec) 60 78
Thinner Intake (% wt) 15 19
Application Viscosity
(FCB4- sec) 25 25
Dry Film Thickness (DFT) 32-35 µ 33-36 µ
Persoz Hardness 249 205
Gloss (20°) 86-89 85-87
Gloss (60°) 95-97 93-94
Example 1
(DOE 7)
(120ºC/10 mins EMT) Hegman Gauge 10 micron 10 micron
Viscosity (FCB4- sec) 60 79
Thinner Intake (% wt) 18 21
Application Viscosity
(FCB4- sec) 25 25
Dry Film Thickness (DFT) 32-36 µ 31-34 µ
Persoz Hardness 238 208
Gloss (20°) 89-91 85-86
Gloss (60°) 95-97 95-97

It is evident from the above data, that the physical properties of the curable paint composition of the present disclosure do not change even after accelerated stability conditions (60°C for 240 hrs). Moreover, the gloss which is an important parameter for the curable paint compositions doesn’t alter the curable paint composition of the present disclosure i.e. Example 1 when compared with the existing curable paint composition. Thus the curable paint composition of the present disclosure is stable.
It is observed that the curable paint composition of the present disclosure even after incubation retains the properties of the curable paint composition.
EXAMPLE 5: Electrostatic values of the curable paint composition
100 ml of the curable paint composition of Example 1 was mixed with 20 ml of Spray thinner for stoving paint (20 isobutanol & 80% solvent C9 or C10) to obtain a thinned curable paint. The electrostatic values of the curable paint composition of Example 1 and the thinned curable paint were determined according to ASTM D 4366. The electrostatic (Electrical Resistance) values are provided below in Table 3.
Table-3
Wt % ER (k?)
As such Paint (excluding catalyst) 100 1062
Catalyst 2
(Cycat 6030) 0.45 462
Polar thinner
(Isobutanol & Butanol) 2 % 230
Spray Thinner
(Solvesso150/Isobutanol/ Butyl Cellosolve : 80/10/10) 18% 318

It is evident from the above table that the electrical resistivity of the curable paint composition of Example 1 (excluding acid blocked catalyst) has an ER of 1062 KOhm. The curable paint composition when mixed with an acid-blocked catalyst (0.45%) reduces the ER to 462 KOhm. Thus the addition of an appropriate amount of acid-blocked catalyst was critical to achieve the desired electrical resistivity. Further, the amount of thinner was critical to make the curable paint composition with the desired properties.
The curable paint composition was mixed with the polar thinner and the spray thinner to obtain a thinned curable paint that has an ER of 318 KOhm, which indicates that the curable paint composition even after thinning provides desired hardness and stability to the paint composition.
EXAMPLE 6: Baking of the curable paint composition on a metal substrate
100 ml of curable paint composition of the present disclosure was mixed with 2 ml of polar solvent (Isobutanol & Butanol) and 18 ml of Spray thinner for curable paint (10% isobutanol, 10% ethylene glycol monobutyl ether & 80% C10 aromatic fluid) to obtain a thinned curable paint composition. The thinned curable paint composition is applied on a metal substrate (dry film thickness (DFT) of 35±5 micron on the metal substrate) at 25°C±2 and relative humidity of 65 to 70, followed by baking at an effective metal temperature (EMT) of 120°C/10 minutes. The process of baking at an EMT of 120°C/10 minutes forms a film on the metal substrate.
TECHNICAL ADVANCES AND ECONOMIC SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a curable paint composition, which
• is curable at a low baking schedule of 120°C/10 min (EMT);
• reduces the curable time;
• suitable for robotic-electrostatic spray painting;
• has a good shelf-life; and
• improved energy saving;
and
a process for the preparation of the curable paint composition is simple and environment friendly.
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 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 curable paint composition comprising:
a. at least one polyester resin in an amount in the range of 20 mass% to 35 mass% with respect to the total mass of the composition;
b. at least one acrylic resin in an amount in the range of 5 mass% to 15 mass% with respect to the total mass of the composition;
c. at least one melamine formaldehyde resin in an amount in the range of 15 mass% to 25 mass% with respect to the total mass of the composition;
d. at least one anti-settling additive in an amount in the range of 4 mass% to 8 mass% with respect to the total mass of the composition;
e. at least one acid blocked catalyst in an amount in the range of 0.1 mass% to 2 mass% with respect to the total mass of the composition;
f. at least one white pigment in an amount in the range of 15 mass% to 25 mass% with respect to the total mass of the composition;
g. at least one anti-sagging additive in an amount in the range of 2 mass% to 5 mass% with respect to the total mass of the composition;
h. at least one solvent in an amount in the range of 5 mass% to 15 mass% with respect to the total mass of the composition; and
i. at least one additive in an amount in the range of 0.5 mass% to 10 mass% with respect to the total mass of the composition.

2. The composition as claimed in claim 1, wherein said polyester resin is characterized by having a solid content in the range of 64% to 66%, an acid value in the range of 4 to 17 mg KOH/gm, and a hydroxyl value in the range of 70 to 80.
3. The composition as claimed in claim 1, wherein said acrylic resin is characterized by having a solid content in the range of 68% to 71% and acid value in the range of 8.5 to 15 mg KOH/gm.
4. The composition as claimed in claim 1, wherein said melamine formaldehyde resin is at least one selected from the group consisting of methylated and isobutylated melamine formaldehyde resin, n-butylated high imino melamine crosslinker in butanol, methylated high imino melamine crosslinker in iso-butanol, methylated/n-butylated high imino melamine resin in n-butanol, methylated/iso-butylated melamine formaldehyde resin in iso-butanol, and n-butylated melamine formaldehyde resin in butanol.
5. The composition as claimed in claim 1, wherein said anti-settling additive is at least one selected from the group consisting of 50% modified polyurea resin, alkylol ammonium salt of a copolymer with acidic groups, organic derivative of a hectorite clay and adduct of benzylamine and polyisocyante compounds.
6. The composition as claimed in claim 1, wherein said acid-blocked catalyst is at least one selected from the group consisting of dodecyl benzene sulfonic acid (DDBSA), para toluene sulphonic acid (PTSA), dinonyl napthalenesulphonic acid (DNNSA), amine blocked dodecylbenzenesulfonic acid, amine-neutralized dodecylbenzene sulfonic acid, amino blocked acidic catalyst, amine neutralized p-toluenesulfonic acid (PTSA), amine blocked para-toluene sulfonic acid catalyst, and partially amine counterbalanced para-toluenesulfonic acid (PTSA).
7. The composition as claimed in claim 1, wherein said white pigment is titanium dioxide.
8. The composition as claimed in claim 1, wherein said anti-sagging additive is at least one selected from the group consisting of non-aqueous acrylic dispersion, saturated polyester resin with sag control agent (SCA), acrylic non-aqueous dispersion resin, and hydroxy functional microgel containing acrylic copolymers.
9. The composition as claimed in claim 1, wherein said solvent is at least one selected from the group consisting of n-butanol, diethylene glycol monobutyl ether, butyl acetate, mixed xylene, aromatic solvent C9, aromatic solvent C10, butyl acetate, methanol, ethanol/iso-propanol (60/40%) mixture, ester solvents, glycol ether, and aromatic hydrocarbons.
10. The composition as claimed in claim 1, wherein said additive is at least one selected from the group consisting of wetting agent, black pigment, anti-popping agent, flow additive, and UV additive.
11. The composition as claimed in claim 10, wherein said composition comprising
a. wetting agent in an amount in the range of 1 mass% to 6 mass% with respect to the total mass of the composition;
b. black pigment in an amount in the range of 0.1 mass% to 3 mass% with respect to the total mass of the composition;
c. anti-popping agent in an amount in the range of 0.1 mass% to 4 mass% with respect to the total mass of the composition;
d. flow additive in an amount in the range of 0.02 mass% to 10 mass% with respect to the total mass of the composition; and
e. UV additive in an amount in the range of 0.1 mass% to 6 mass% with respect to the total mass of the composition.
12. The composition as claimed in claim 10, wherein said wetting agent is at least one selected from the group consisting of alkylolammonium salt of a block copolymer with acidic groups, solution of modified polyurethane, solution of a high molecular weight block copolymers, solution of modified polyurethane with pigment affinic groups.
13. The composition as claimed in claim 10, wherein said black pigment is at least one selected from the group consisting of charcoal, and carbon black.
14. The composition as claimed in claim 10, wherein said flow additive is at least one selected from the group consisting of acrylic resin, silicon solution, silicone-free non-ionic surface-active acrylic polymer, acrylic polymer with silicone, and acrylic flow modifier without silicone.
15. The composition as claimed in claim 10, wherein said anti-popping agent is polyacrylate solution.
16. The composition as claimed in claim 10, wherein said UV additive is at least one selected from the group consisting of UV absorber; hindered amine light stabilizers (HALS); mixture of bis (1, 2, 2, 6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1, 2, 2, 6, 6-pentamethyl-4-piperidyl sebacate; mixture of a) 50% ß-[3-(2-H-Benzotriazole-2-yl)-4-hydorxy-5-tert.butylphenyl]-propionic acid-poly(ethylene glycol) 300-ester, b) 38% Bis{ß-[3-(2-H-Benzotriazole-2-yl)-4-hydroxy5tert.butylphenyl]-propionic acid}-poly(ethylene glycol) 300 –ester, and c) 12% polyethylene glycol; and mixture of bis (1, 2, 2, 6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1, 2, 2, 6, 6- pentamethyl-4-piperidyl sebacate.
17. The composition as claimed in claim 1, wherein a mass ratio of said polyester resin to said acrylic resin to said melamine formaldehyde resin is in the range of 2.5:1:2 to 4:1:3.
18. The composition as claimed in claim 1, wherein a mass ratio of said melamine formaldehyde resin to said acid blocked catalyst is in the range of 1:0.02 to 1:0.0.04.
19. The composition as claimed in claim 1, wherein said curable paint composition has an effective metal temperature (EMT) in the range of 120°C/10 minutes to 120°C/20 minutes.
20. A process for the preparation of a curable paint composition, said process comprising the following steps
a. mixing a first portion of a polyester resin, a wetting agent, a first portion of solvent and blending at a speed in the range of 800 rpm to 1000 rpm for a first predetermined time period to obtain a resin mixture;
b. adding a white pigment to said resin mixture and blending at a speed in the range of 1000 rpm to 2500 rpm for a second predetermined time period to obtain a slurry;
c. grinding said slurry at a predetermined temperature for a third predetermined time period to obtain a dispersion;
d. adding a second portion of said polyester resin and a second portion of solvent to said dispersion and blending at a speed in the range of 2000 rpm to 3000 rpm for a fourth predetermined time period to obtain a resultant dispersion; and
e. sequentially adding a third portion of said polyester resin, acrylic resin, melamine formaldehyde resin, acid blocked catalyst, anti-settling additive, anti-sagging additive, flow additive, anti-popping agent, UV additive, black pigment, and third portion of solvent to said resultant dispersion at a speed in the range of 800 rpm to 1200 rpm for a fifth predetermined time period to obtain said curable paint composition.
21. The process as claimed in claim 20, wherein said first predetermined time period is in the range of 5 minutes to 20 minutes.
22. The process as claimed in claim 20, wherein said second predetermined time period is in the range of 2 minutes to 10 minutes.
23. The process as claimed in claim 20, wherein said grinding is performed by using zirconium beads at a rotor speed is in the range of 2000 rpm to 3000 rpm.
24. The process as claimed in claim 20, wherein said dispersion obtained in step c) has a particle size in the range of 5 microns to 15 microns.
25. The process as claimed in claim 20, wherein said third predetermined time period is in the range of 30 minutes to 60 minutes.
26. The process as claimed in claim 20, wherein said predetermined temperature is in the range of 20°C to 50°C.
27. The process as claimed in claim 20, wherein said fourth predetermined time period is in the range of 5 minutes to 20 minutes.
28. The process as claimed in claim 20, wherein said fifth predetermined time period is in the range of 15 minutes to 60 minutes.
29. The process as claimed in claim 20, wherein said first portion of said polyester resin is in the range of 15% to 20% with respect to the total mass of polyester resin, said second portion of said polyester resin is in the range of 15% to 25% with respect to the total mass of polyester resin and said third portion of said polyester resin is in the range of 50% to 70% with respect to the total mass of polyester resin.
30. The process as claimed in claim 20, wherein said first portion of said solvent is in the range of 20% to 45% with respect to the total mass of the solvent, said second portion of said solvent is in the range of 7% to 10% with respect to the total mass of the solvent, and said third portion of said solvent is in the range of 45% to 75% with respect to the total mass of the solvent.
31. A method for coating a metal substrate, said method comprises the following steps;
a. mixing curable paint composition as claimed in claim 1 with a predetermined amount of a thinner to obtain a mixture; and
b. coating said mixture on a metal substrate at a temperature in the range of 25°C to 30°C and at a relative humidity in the range of 65 to 70, followed by baking at an effective metal temperature (EMT) in the range of 120°C/10 minutes to 120°C/20 minutes to obtain coated metal substrate.
32. The method as claimed in claim 31, wherein said thinner is a mixture of polar solvent and spray thinner.
33. The method as claimed in claim 32, wherein said polar solvent is at least one selected from the group consisting of isobutanol and butanol.
34. The method as claimed in claim 32, wherein said spray thinner is a mixture of C10 aromatic fluid, isobutanol, and ethylene glycol monobutyl ether.
35. The method as claimed in claim 31, wherein the mass ratio of said curable paint composition to said thinner is in the range of 10:1 to 10:3.
Dated this 30th day of May, 2023

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