Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)

As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003

As amended by the Patents (Amendment) Rules, 2016

COMPLETE SPECIFICATION
(See section 10 and rule 13)

TITLE OF THE INVENTION
QUICK DRYING FOOD GRADE COATING AND A PROCESS OF PREPARING THE SAME

APPLICANT
Hindalco Industries Limited, having the address: One Unity Centre (Formerly called as One International Center), Tower 4, 21st Floor, Senapati Bapat Marg, Prabhadevi, Mumbai – 400 013, Maharashtra, India

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
[001] The present invention relates to a coating composition for food or beverage container, more particularly to a quick dry food grade gold colour coating composition for aluminum or tin container. The present invention also relates to a process of preparing the coating composition and method of coating the same.

BACKGROUND OF THE INVENTION
[002] Aluminum has various applications due to its light weight, soft and malleable nature. Aluminum being infinitely recyclable material is important material of construction for various application. Aluminum is non-toxic, has a high thermal conductivity, has excellent corrosion resistance, and can be easily cast, machined, and formed. It is also non-magnetic and non-sparking. It is the second most malleable metal and the sixth most ductile. Aluminum finds its application in a huge variety of products including cans, foils, kitchen utensils, window frames, beer kegs, gas cylinders, and aero-plane parts, automotive parts etc. It is often used as an alloy because aluminum itself is not particularly strong. Alloys with copper, manganese, magnesium, and silicon are lightweight but strong.
[003] Further, aluminum is commonly used as a semi-rigid material for food container applications due to its advantageous properties. It is lightweight, durable, and resistant to corrosion, making it suitable for packaging various food products.
[004] Aluminum containers provide a barrier against oxygen, moisture, and light, helping to preserve the quality and freshness of the food. Additionally, aluminum is a good conductor of heat, allowing for efficient cooking or reheating of food in these containers.
[005] Hence, aluminum coated sheets are often used for semi-rigid food container applications. The coating provides additional protection against corrosion and enhances the container's durability. It also helps to maintain the integrity of the food by providing a barrier against external factors such as oxygen and moisture. The aluminum coated sheet is lightweight and provides good thermal conductivity, enabling efficient heat distribution during cooking or reheating. Overall, the use of aluminum coated sheets enhances the performance and longevity of semi-rigid food containers.
[006] In spite of the usefulness of the aluminum coated sheets, the manufacture of coatings suitable for use in aluminum semirigid containers or coated aluminum sheets for semi rigid containers have several shortcomings.
[007] Regular coatings available in the market do not provide adequate adhesion, elongation, required quick dry time & surface finish and inertness to food items (food grade coatings).
[008] Owing to the foregoing problems, various coating compositions have been formulated which address the issues of regular coating known in the art. Particularly, these compositions address the issues regarding the adequate adhesion, elongation, required quick dry time & surface finish and inertness to food items (food grade coatings). The composition provides a quick dry food grade coating for application on aluminum or use on aluminum sheets for semi rigid container application.

SUMMARY OF THE INVENTION
[009] One aspect of the present invention provides a coating composition comprising an epoxy resin, at least two phenolic resins: Phenolic resin -I and Phenolic resin -II, a crosslinker, an adhesion promotor, a catalyst, a levelling or a wetting agent, and a mixture of at least two solvents: Solvent – A and Solvent – B, wherein at least one phenolic resin Phenolic resin -II is selected from curable unplasticized phenolic resin.
[010] Another aspect of the present invention relates to a process for preparing the coating composition for metal sheet or container.
[011] Another aspect of the present invention relates to a method of coating metal sheet with the coating composition of the present invention.
[012] Another aspect of the present invention relates to the use of the coating composition for metal sheets or container, preferably of aluminum or tin for semi rigid container.

BRIEF DESCRIPTION OF THE DRAWINGS
[010] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 demonstrates the surface finish of 1.5 GSM Coating
Figure 2 demonstrates the surface finish of 2.0 GSM Coating
Figure 3 demonstrates the result of Crosshatch Adhesion Test
Figure 4 demonstrates the results of Impact Test Adhesion
Figure 5 demonstrates the results of coating elongation with Ericson cup and Cupping Method

DETAILED DESCRIPTION OF THE INVENTION
[013] The present invention discloses a coating composition comprising an epoxy resin, at least two phenolic resins: Phenolic resin -I and Phenolic resin -II, a crosslinker, an adhesion promotor, a catalyst, a levelling or a wetting agent, and a mixture of at least two solvents: Solvent – A and Solvent – B, wherein at least one phenolic resin Phenolic resin -II is selected from curable unplasticized phenolic resin.
[014] As used herein, the term “composition” refers to those formulations which function are prepared as mixture, amalgam or blend for coating a metal surface. The composition includes a homogenous or heterogeneous solution and similar formulations known to a person skilled in the art.
[015] In a preferred embodiment, the Phenolic resin -I are selected from the group consisting of, but not limited to, Phenodur-899, PHENODUR PR 827, PHENODUR PR 897, PHENODUR PR 898 or combination thereof.
[016] In a preferred embodiment, the Phenolic resin -I are selected from the group consisting of, but not limited to, Phenodur-307 or Phenodur-308 or combination thereof.
[017] In another preferred embodiment, the Phenolic resin -I and Phenolic resin -II are preferably incorporated in 1 to 4 % wt/wt of the coating composition.
[018] As used herein, the term “epoxy resin” refers to polyepoxide polymer which are a class of reactive prepolymers and polymers containing epoxide groups. Epoxy resins are cross-linked with a wide range of co-reactants (crosslinkers) to get desired properties.
[019] In a preferred embodiment, the epoxy resins have Epoxy equivalent between 1750 to 2100 g/eq.
[020] In another preferred embodiment, the epoxy resin are selected from the group consisting of, but not limited to, Type -7, Type-8, Type-9, Type-10, Epotec YD 907, Epotec YD017, Epotec YD017S, Epotec YD 019, Epotec YD 019S, Epotec YD 909, Epotec YD 010S, D.E.R. 667E, D.E.R. 668-20, D.E.R. 669-20, D.E.R. 669E, Lapox P-5 (ARP-17) , Lapox P-6 (ARP-19), preferably polyepoxide polymer having molecular weight 1750- 2100 of type 7 including Epotec YD 907, Epotec YD017, Epotec YD017S, D.E.R. 667E, Lapox P-5 (ARP-17) or combination thereof.
[021] In another preferred embodiment, the epoxy resin are selected from the group consisting of, but not limited to, Epotec YD 907, Epotec YD017, Epotec YD017S, Epotec YD 019, Epotec YD 019S, Epotec YD 909, Epotec YD 010S, D.E.R. 667E, D.E.R. 668-20, D.E.R. 669-20, D.E.R. 669E, Lapox P-5 (ARP-17) , Lapox P-6 (ARP-19) or combination thereof.
[022] In another preferred embodiment, the epoxy resin are preferably incorporated in 10 to 20 %wt/wt of the coating composition.
[023] As used herein, the term “crosslinker” acts as a co-reactant of the Epoxy resins to get desired properties.
[024] In a preferred embodiment, the crosslinkers are selected from amine based crosslinkers preferably selected from methylated melamine or a methylated high imino melamine.
[025] In another preferred embodiment, the amine based crosslinkers methylated melamine are selected from the group consisting of, but not limited to, CYMEL 301, CYMEL 303 LF, CYMEL 304, ETERMINO 9603-80, ETERMINO 9610-100, DooriChem MM-803, DooriChem MM-803 LF, DooriChem MM- DooriChem 850/MM812, DooriChem MM-825, DooriChem MM-8257, DooriChem MM-823, DooriChem MX-40, DooriChem MX-41, DooriChem MX-1141 or combination thereof.
[026] In another preferred embodiment, the methylated high imino melamine are selected from the group consisting of, but not limited to, CYMEL 325, CYMEL 323, CYMEL 327, DooriChem MM-825, DooriChem MM-8257 DooriChem MM-823 or combination thereof.
[027] In another preferred embodiment, the methylated high imino melamine are selected from the group consisting of, but not limited to, CYMEL 301, CYMEL 303 LF, CYMEL 304, ETERMINO 9603-80, ETERMINO 9610-100, DooriChem MM-803, DooriChem MM-803 LF, DooriChem MM- DooriChem 850/MM812, DooriChem MM-825, DooriChem MM-8257, DooriChem MM-823, DooriChem MX-40, DooriChem MX-41, DooriChem MX-1141, Cymel 325 or combination thereof.
[028] In another preferred embodiment, the crosslinkers are preferably incorporated in 2.45 to 3.5 %wt/wt of the coating composition.
[029] As used herein, the term “Adhesion promoter” refer to an anchoring agent for cured/ dried film with metal sheet or container which results in excellent adhesion properties in severe conditions.
[030] In a preferred embodiment, the adhesion promoter is selected from fatty acid modified epoxy resin ester and solution of polyester alkyl ammonium salt or combination thereof.
[031] In another preferred embodiment, the fatty acid modified epoxy resin ester are selected from the group consisting of, but not limited to, RESYDROL AX 250w/75EP, Lapox ARES-101, Lapox ARES-102, FTC DEE-100 or combination thereof.
[032] In another preferred embodiment, the fatty acid modified epoxy resin ester are selected from RESYDROL AX 250w/75EP.
[033] In another preferred embodiment, the adhesion promoters are preferably incorporated in 2 to 2.5 % wt/wt of the coating composition.
[034] As used herein the wetting cum levelling agent is selected from a group consisting of, but not limited to, polyether modified polysiloxan such as BYK® -348, Borchi® Gol LA 2, Additol 6503N.
[035] In another preferred embodiment, the wetting cum levelling agent is Additol 6503N.
[036] In another preferred embodiment, the wetting cum levelling agent is preferably incorporated in 0.2 to 0.5 %wt/wt of the coating composition.
[037] As used herein the “Catalyst” refers to phosphoric acid derivate such as CYCAT® XK 406 N or p-Toluenesulfonic acid.
[038] In another preferred embodiment, the catalyst is preferably incorporated in 0.45 to 1.0 % wt/wt of the coating composition.
[039] In an embodiment of the present invention the coating composition comprises a mixture of two solvents designated as Solvent-A and Solvent-B.
[040] In a preferred embodiment the Solvent-A is preferably selected from dimethylbenzene.
[041] In another preferred embodiment, the Solvent A is preferably incorporated in 10 to 15 % wt/wt of the coating composition.
[042] In a preferred embodiment the Solvent-B is preferably selected from 2-Butoxyethanol.
[043] In another preferred embodiment, the Solvent B is preferably incorporated in 50 to 55 % wt/wt of the coating composition.
[044] In another aspect, the present invention discloses a process for preparing the coating composition. The process comprising the following steps:
a) Mixing the polyepoxide polymer (Epoxy resin) with at least two solvents selected from Solvent-A and Solvent-B;
b) Stirring at High Speed to dissolve the polyepoxide polymer in solvent;
c) Stirring continuously until polymer is completely dissolved;
d) Adding at least one phenolic resin-I, at least one phenolic resin-II, at least one crosslinker, at least one adhesion promoter, at least one catalyst, at least one levelling cum wetting agent and at least two solvents selected from Solvent-A and Solvent-B;
e) Mixing and transferring the batch to bid mill and mixing in Bid Mill followed by discharging the batch.

[045] In a preferred embodiment, the process comprising the following steps:
a) Mixing of 10 to 20 % wt/wt of at least one polyepoxide polymer (Epoxy resin) with 5 to 10 wt. % of at least Solvent-A and 5 to 10 % wt/wt of at least Solvent-B.
b) Stirring at High Speed to dissolve the polyepoxide polymer in solvent.
c) Stirring continuously until polymer is completely dissolved.
d) Adding 1 to 4 % wt/wt of at least one phenolic resin-I and mixing for 10 min.
e) Adding 1 to 4 % wt/wt of at least one phenolic resin-II and mixing for 10 min.
f) Adding 2.45 to 3.5 % wt/wt of at least another crosslinker and mixing for 10 min.
g) Adding 2.0 to 2.5 % wt/wt of at least one adhesion promotor and mixing for 10 min.
h) Adding 0.45 to 1.0 % wt/wt of at least one catalyst for cross linking reaction and mix for 10 min.
i) Adding 0.2 to 0.5 wt. % of at least one levelling cum wetting agent.
j) Adding 5 to 10 % wt/wt of at least Solvent-A and 45 to 50 % wt/wt of at least Solvent-B and mixing for 10 min;
k) Transferring the batch to bid mill and mixing in Bid Mill for 2 Hrs then discharging the batch.
[046] In another aspect, the present invention discloses a method of coating metal sheet or container with the coating composition of the present invention. Typically, the method of coating comprises the following steps:
a) degreasing of metal sheet with water and drying to remove the residual oil and smut on sheet;
b) coating the metal sheet with coating composition of the present invention using three roller applicator mechanism of appropriate thickness;
c) drying the coated metal sheet in oven for less than 30 sec;
d) cooling the coated metal sheet to room temperature with chilled rolls to get final dried film coating on the metal sheet.
[047] In a preferred embodiment, the the metal sheet or container is selected from aluminum or tin.
[048] In a preferred embodiment, the final dried film coating has a thickness of 1.5 to 2.5 GSM.
[049] In a preferred embodiment, the drying in oven is between 250 to 300 oC, preferably between 255 to 285 oC.
[050] As used herein the degreasing and drying of metal sheet is preferably done in 4% sulfuric acid solution at 45 oC. Metal sheet is then preferably rinsed with demineralized water, and preferably dried in air drying oven from 125 to150 oC.
[051] As used herein “three roller applicator” refers to three roll semi reverse and three roll full reverse applicators.
[052] As used herein “chilled rolls” refer to hollow rolls through which refringent is passed. Chilled rolls act as heat exchanger and reduce the coated metal sheet temperature to ambient conditions before coiling.
[053] Advantageously, the coating composition of the present invention exhibits the adequate adhesion, elongation, demonstrates the required quick drying time and provides the desired surface finish and inertness. Accordingly, the coating compositions are particularly useful for preparing a quick dry food grade coating for application on a metal sheet or container, preferably an aluminum sheets for semi rigid container applications. The coating composition provides the required inertness to food items.
EXAMPLE
[054] The following examples are illustrative of the invention but not limitative of the scope thereof.
[055] Materials and Methods
[056] Materials: Epotec YD 907, Phenodur-899, Phenodur-308, Cymel 325, RESYDROL AX 250w/75EP, p-Toluenesulfonic acid, Additol 6503N, Dimethylbenzene and 2-Butoxyethanol.
[057] Method: Mixing of 10 to 20 % wt/wt of Epotec YD 907 with 5 to 10 % wt/wt of Dimethylbenzene and 5 to 10 % wt/wt of 2-Butoxyethanol. Stirring at High Speed to dissolve the polyepoxide polymer in solvent and stirring continuously until polymer is completely dissolved. Adding 1 to 4 % wt/wt of phenolic resin-I Phenodur-899 and mixing for 10 min. Add 1 to 4 wt. % of phenolic resin-II Phenodur-308 and mixing for 10 min. Adding 2.45 to 3.5 % wt/wt of Cymel 325 and mixing for 10 min. Adding 2.0 to 2.5 % wt/wt of adhesion promotor RESYDROL AX 250w/75EP and mixing for 10 min. Adding 0.45 to 1.0 % wt/wt of p-Toluenesulfonic acid for cross linking reaction and mixing for 10 min. Adding 0.2 to 0.5 wt. % of levelling cum wetting agent Additol 6503N. Adding 5 to 10 % wt/wt of Dimethylbenzene and 45 to 50 % wt/wt of 2-Butoxyethanol and mixing for 10 min. Transfer the batch to bid mill and mix in Bid Mill for 2 Hrs then discharge the batch. The composition of the examples is provided in Table 1 and Table 2 as follows:
Table 1
Sr. No. Material Details Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6
1 Epotec YD 907 19.62 19.29 19.29 19.32 19.27 10.20
2 Phenodur-899 1.64 1.61 1.61 1.61 1.61 3.60
3 Phenodur-308 1.62 3.22 3.22 3.22 3.21 1.02
4 Cymel 325 3.10 3.05 3.05 3.05 3.04 2.48
5 RESYDROL AX 250w/75EP 2.37 2.33 2.33 2.33 2.33 2.01
6 p-Toluenesulfonic acid 0.84 0.83 0.83 0.83 0.83 0.49
7 Additol 6503N 0.31 0.32 0.32 0.32 0.32 0.20
8 Dimethylbenzene 13.97 13.74 13.74 13.60 13.72 20.00
9 2-Butoxyethanol 56.54 55.62 55.62 55.70 55.68 60.00

Table 2
Sr. No. Material Details Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11
1 Epotec YD 907 19.62 19.29 19.29 21.66 20.20
2 Phenodur-899 3.25 0.00 3.85 1.60 1.52
3 Phenodur-308 0.00 4.83 4.02 3.20 3.20
4 Cymel 325 3.10 3.05 0.00 3.02 3.01
5 RESYDROL AX 250w/75EP 2.37 2.33 2.33 0.00 2.25
6 p-Toluenesulfonic acid 0.84 0.83 0.83 0.85 0.00
7 Additol 6503N 0.31 0.32 0.32 0.30 0.32
8 Dimethylbenzene 13.97 13.74 13.74 13.70 13.72
9 2-Butoxyethanol 56.54 55.62 55.62 55.67 55.78

[058] The coating properties of the composition prepared above demonstrate adequate adhesion, elongation, demonstrates the required quick drying time and provides the desired surface finish and inertness as shown in Table 3.
Table 3

Sr. No. Test Specification Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11
1 Appearance Visual Clear gold uniform coating Clear gold uniform coating Clear gold uniform coating Clear gold uniform coating Clear gold uniform coating Clear gold uniform coating Clear uniform coating. Non yellow Clear pale yellow uniform coating Clear pale yellow uniform coating Clear pale yellow uniform coating Clear pale yellow uniform coating
2 MEK Rub ASTM D4152 >100 >100 >100 >100 >100 >100 >100 <25 <50 >100 <25
3 Bend Test ASTM D522 Pass Pass Pass Pass Pass Pass Pass Pass Pass Fail Pass
4 Cross Hatch test ASTM D3359 Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
5 Coating surface strains in Erichsen cupping tests DIN EN ISO 20482 Pass Pass Pass Pass Pass Pass Pass Fail Fail Fail Fail
6 Impact Test Pass Pass Pass Pass Pass Pass Pass Fail Fail Fail Fail
7 Accelerated CuSO4 Corrosion Pass Pass Pass Pass Pass Pass Pass Fail Fail Fail Fail
8 Migration test BS EN 1186 P(3) 2002
BS EN 1186 P(14) 2002
BS EN 1186 (P13 Method B) 2002 Pass Pass Pass Pass Pass Pass Pass Fail Fail Fail Fail
9 Autoclave test 121 oC, 15psi, 45min Pass Pass Pass Pass Pass Pass Pass Fail Fail Fail Fail

[059] Figures 1 to 5 provide appearance details on surface finish, MEK rub, Bend test, crosshatch adhesion and impact test on coating adhesion. Erichsen cupping provide inputs for coating elongation and migration testing, accelerated copper corrosion and auto clave test provide input on inertness of coating.
[060] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims. , Claims:We Claim

1. A coating composition comprising:
- an epoxy resin,
- at least two phenolic resins selected from Phenolic resin -I and Phenolic resin-II wherein the Phenolic resin-II is selected from curable unplasticized phenolic resin,
- a crosslinker,
- an adhesion promotor,
- a catalyst,
- a levelling or a wetting agent, and
- a mixture of at least two solvents selected from Solvent – A and Solvent – B.
2. The coating composition as claimed in claim 1, wherein the composition comprises:
a) Epoxy resin : 10 - 20 parts
b) Phenolic resin -I : 1-4 parts
c) Phenolic resin -II : 1-4 parts
d) Cross linker : 2.45 – 3.5 parts
e) Adhesion promotor : 2.0 – 2.5 parts
f) Catalyst : 0.45 - 1.0 parts
g) Levelling/Wetting Agent : 0.2 - 0.5 parts
h) Solvent - A : 10 - 20 parts
i) Solvent - B : 50 - 60 parts.
3. The coating composition as claimed in claim 1, wherein the epoxy resin is polyepoxide polymer having Epoxy equivalent between 1750-2100 g/eq.
4. The coating composition as claimed in claim 1, wherein the phenolic resin-I is selected from heat curable phenolic or polyester resin or combination thereof.
5. The coating composition as claimed in claim 1, wherein the phenolic resin-II is selected from curable unplasticized phenolic resin.
6. The coating composition as claimed in claim 1, wherein the cross-linker is an amine based crosslinker.
7. The coating composition as claimed in claim 6, wherein the amine based crosslinker is methylated melamine or a methylated high imino melamine or combination thereof.
8. The coating composition as claimed in claim 1, wherein the adhesion promoter is fatty acid modified epoxy resin ester or polyester alkyl ammonium salt or combination thereof.
9. The coating composition as claimed in claim 1, wherein the catalyst is selected from phosphoric acid derivative.
10. The coating composition as claimed in claim 1, wherein the wetting or levelling agent is selected from polyether modified polysiloxan.
11. The coating composition as claimed in claim 1, wherein the solvent A and solvent B is selected from dimethylbenzene and 2-Butoxyethanol respectively.
12. A process for preparing the coating composition as claimed in claims 1 to 11, comprising the following steps:
a) Mixing the polyepoxide polymer (Epoxy resin) with at least two solvents selected from Solvent-A and Solvent-B;
b) Stirring at High Speed to dissolve the polyepoxide polymer in solvent;
c) Stirring continuously until polymer is completely dissolved;
d) Adding at least one phenolic resin-I, at least one phenolic resin-II, at least one crosslinker, at least one adhesion promoter, at least one catalyst, at least one levelling cum wetting agent and at least two solvents selected from Solvent-A and Solvent-B;
e) Mixing and transferring the batch to bid mill and mixing in Bid Mill followed by discharging the batch.

13. A method of coating metal sheet, comprising the following steps:
a) degreasing of metal sheet with water and drying to remove the residual oil and smut on sheet;
b) coating the metal sheet with coating composition as claimed in claims 1 to 11 using three roller applicator mechanism of appropriate thickness;
c) drying the coated metal sheet in oven for less than 30 sec;
d) cooling the coated metal sheet to room temperature with chilled rolls to get final dried film coating on the metal sheet.
14. The method as claimed in claim 12, wherein the metal sheet is selected from aluminum or tin.
15. The method as claimed in claim 12, wherein the final dried film coating has a thickness of 1.5 to 2.5 GSM.
16. The method as claimed in claim 12, wherein the drying in oven is between 255 to 285 oC.
17. Use of the coating composition for coating food grade metal sheets or container, preferably of aluminum or tin for semi rigid container.

Dated 18th of January 2024
Hindalco Industries Limited
By their Agent & Attorney

(Nisha Austine)
of Khaitan & Co
Reg No IN/PA-1390