DESC:
FIELD OF INVENTION
The present invention relates to an eco-friendly coating composition for paper based packaging material. Particularly, it provides environment friendly packaging solutions with a unique coating composition.

BACKGROUND OF INVENTION
There is an unprecedented demand for packaging solutions with improved sustainability and environmental credentials. Many consumers packaged goods (CPG) companies have announced the launch of a new version of paper-based or other sustainable bio-based polymers packaging by 2025–2030 on account of sweeping reforms and change in policies and regulations in US, Europe and Asia.
Various desired attributes of petroleum-based materials (polyethylene, polyvinyl chloride, polypropylene, polystyrene, waxes and/or fluorine-based derivatives) such as strength, rigidity, flexibility in case of laminates, high barrier towards water, water vapour, oxygen, oil and grease, lightweight, durability and most importantly its low cost are widely known. Therefore, these materials have been extensively used along with paper for constructing various packaging materials to serve the needs of many industries. However, from an environmental perspective, their continued use is not sustainable and these materials are known to cause enormous damage to our ecosystems.
CN108410024A relates to preparation of nano-cellulose/oxidized starch biomembrane as a biodegradable film for food packaging material.
WO2020238404A1 relates to plastic-free biomass-based oil-proof and antibacterial food packaging paper, comprising: preparation of pulp, preparation of dry paper, sizing, coating, and a drying process. 100 parts of the coating liquid comprises 0.3-0.5 part of chitosan, 0.3-0.6 part of oxidized nanocellulose, and 2.5-30 parts of oxidized starch.
JP6459956B2 relates to an oil-resistant paper having an undercoat coating layer and an overcoat coating layer on at least one side of a paper substrate, wherein the undercoat coating layer is at least one of oxidized starch, fatty acid sizing agent and alkyl ketene dimer and the top coat layer contains at least one of oxidized starch and a styrene-butadiene copolymer.
CN105461971B relates to nano-cellulose base oxidized starch compound bio latex and its preparation and application.
CN108383944B relates to a preparation method of cationic starch/nano-cellulose base water-resistant reinforced composite emulsion.
Though various bio-based polymers are being extensively studied to arrive at packaging solutions with desired performance, some of the issues that put restrictions in performance of these materials include low flexibility, hydrophilicity, crystallization behavior, brittleness or melt instabilities, sealability, and water vapor permeability.
There remains an all-time high need for paper based, environment friendly packaging solutions made up of environment friendly materials such that the coated paper substrate based packaging materials exhibits superior performance when measured in terms of at least one of the parameters that include moisture barrier, oil and grease resistance, phthalate resistance and heat-sealability along with desired mechanical properties. The present inventors have surprisingly developed an effective coating composition which ameliorates the aforesaid shortcomings of the prior art.

OBJECTS OF THE INVENTION
It is an object of the present invention to provide an effective coating composition for paper based packaging material that overcomes the drawbacks of prior art.
It is another object of the present invention to provide a coated paper substrate based packaging material which exhibits superior performance that includes moisture barrier, oil and grease resistance, phthalate resistance, heat-sealability and mechanical property.
It is another object of the present invention to provide a coated paper substrate having various applications such as fragrant material packaging, food packaging, electronic goods packaging, packaging for pharmaceutical products, packaging for clothing, packaging for medical device, and the like.
It is another object of the present invention to provide a method for preparing a coated paper substrate based packaging material.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings wherein:
Figure 1: XRD patterns of Nano-cellulose used in coating composition of present invention.
Figure 2: FTIR spectra of Nano-cellulose used in coating composition of present invention.
Figure 3: Graph showing Viscosity at Constant shear (100rpm) and constant temperature (25°C).
Figure 4: Schematic drawing of a Paper construct with surface sizing at the top surface (a) and bottom surface (a’) of the bleached chemical pulp (b).
Figure 5: A: Coated paper according to present invention with Phthalate drop shows no spotting, B: Uncoated paper with Phthalate drop spot clearly visible.
Figure 6: Graph showing porosity of paper before and after coating.

SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a coating composition comprising
(i) 15-25 % by weight oxidised starch;
(ii) 7.5-10% by weight nano-cellulose;
(iii) 2.5-5% by weight at least one cross-linker; and
(iv) 44% to 68% by weight at least one solvent.
According to another aspect of the present invention there is provided a coated substrate formed by coating with the composition of the present invention, said coated substrate having resistance to oil and/or grease penetration, moisture barrier, oxygen barrier, phthalate resistance, repulpable, compostable, plastic free and biodegradable.
According to a further aspect of the present invention there is provided a process for preparing the composition coating composition of the present invention, said process comprising the steps :
(i) boiling water to its boiling temperature and adding starch to it under stirring;
(ii) dissolving starch completely and cooling to room temperature;
(iii) adding plasticizer and mixing;
(iv) separately mixing nano-cellulose and solvent and then adding the mixture to the starch solution of step (iii) while stirring;
(v) adding defoamer and biocide and stirring;
(vi) adding crosslinker and again mixing to obtain the composition of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.
Accordingly, those skilled in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the scope of the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.
It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, steps or components but does not preclude the presence or addition of one or more other features, steps, components or groups thereof.
The term "paper" as used herein refers to a paper-based substrate of an amalgamation of fibers that can include, at least in part, vegetable, wood, and/or synthetic fibers. As appreciated, other components can be included in the paper-based substrate. The paper-based substrate as used herein, differ in their thickness, stiffness, strength, and/or weight, but are intended to be modified by the embodiments of the coating compositions and methods provided herein to form the coated paper based substrate of the present invention.
The term "coating composition" as used herein refers to liquid solutions, as well as colloidal dispersions, suspensions, emulsions, and latexes.
The term “OGR” as used herein means Oil grease resistance.
The term “barrier coating,” as used herein means a material applied to a surface (or surfaces) of a paper substrate that blocks or hinders contact of unwanted elements with one or more of the applied surfaces, thus stopping or preventing contact of said unwanted elements, such as, oil or grease, with the applied surface(s) of said substrate.
The term “compostable,” as used herein means those solid products are biodegradable into the soil.
The present invention relates to an eco-friendly coating for paper based packaging material.
It has been surprisingly found by the inventors of the present invention that a combination of modified starch (especially oxidized starch), nano-cellulose and selected cross-linker helps in achieving the desired properties of moisture barrier, oil and grease resistance, phthalate resistance, heat-sealability and mechanical property.
Without wishing to be bound by any theory, it is believed that the modified starch in the coating composition imparts excellent oil resistance when applied to the paper base material. Nano-cellulose improves the oxygen barrier properties and enhances the tear resistance of coated paper. Nature of the Nano-cellulose is thermally resistance. Cross-linker bonds with starch and helps in closing the pores of the paper, thus increasing the barrier. It links with starch functional groups in-between paper substrate and bring down the air permeability of the paper by blocking the pores. With the use of a cross-linker, OGR value of the paper is improved by up to 25%.
The present invention provides a coating composition for a paper substrate comprising:
a. modified starch;
b. Nano-cellulose;
c. At least one cross-linker; and
d. At least one solvent.
In an embodiment, the modified starch is present in an amount ranging from 15 to 25 wt.%.
In an embodiment, the modified starch derived from either potato, corn or rice, oxidized by hypochlorite was procured. Modified starch within the meaning of present invention does not include cationic starch. In a preferred embodiment the modified starch is an oxidized starch.
In an embodiment, the nano-cellulose is present in an amount ranging from 7.5 to 10 wt.%.
In an embodiment, the nano-cellulose has a length ranging from 0.2 to 0.6µm and diameter ranging from 10 to 15 nm. Nano cellulose used herein can be from any sources and processed by art known processes to obtain the said dimensions.
In an embodiment, the cross-linker is present in an amount ranging from 2.5 to 5 wt.%.
In an embodiment, the cross-linker including but not limited to copolymer of epichlorohydrin and alkylamine or Ammonium zirconium carbonate (AZC) or Potassium zirconium carbonate (KZC) or Sodium trimetaphosphate (STMP) or Sodium tripolyphosphates (STPP) or combination of thereof. In an embodiment, the alkylamine is selected from alkylamine groups containing carbon atoms ranging from 1 to 20 carbon atoms and 0 to 2 carbon to carbon double bonds.
In an embodiment, the solvent is selected from water, alcohol including but not limited to ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol or combinations thereof. The solvent may be present in an amount 44% to 68% by weight.
In an embodiment, viscosity of the coating composition varies in the range from 500 - 2000 cP and pH of the coating composition varies in the range from 7-12.
In a preferred embodiment the composition in accordance with the present invention has the following composition.
Table 1
Ingredients Quantity (wt.%)
Oxidised starch 15-25
Water 34-53
Nano-cellulose 7.5-10
Plasticizer 5-10
Alcohol 10-15
Defoamer 0.1-0.5
Biocide 0.2-1
Cross linker 2.5-5

The coating compositions of the present invention comprise a variety of additives including but not limited to humectants, defoamer, biocide, fillers, dispersants, extenders, surfactants, pH adjusters, rheology modifiers, or combinations thereof. The types and amounts of such additives will be apparent to those skilled in the art. Those skilled in the art will also appreciate that due to normal differences in application equipment, application conditions, substrates and quality requirements at different end user sites, adjustments will usually be made in the types and amounts of such additives to tailor a coating composition to a particular end user.
Non limiting examples of humectants include propylene glycol, hexylene glycol, and butylene glycol, alpha hydroxy acids such as lactic acid, glyceryl triacetate, lithium chloride, polymeric polyols such as polydextrose, sodium hexametaphosphate, sugar alcohols (sugar polyols) such as glycerol, sorbitol, xylitol, maltitol, urea, and castor oil.
Non limiting examples of defoamer include silicone defoamer, PEG defoamers, mineral oil-based defoamers, vegetable oil-based defoamers, ethylene oxide/propylene oxide (EO/PO) block copolymer defoamers, alkyl polyglucoside (APG) defoamers.
Non limiting examples of biocide include alcohols, organic acids and their esters, aldehydes, amines, quarternary ammonium compounds (QACs), halogen compounds, ionic silver and nanosilver, oxidizing agents, isothiazolones, phenols and biguanides.
Non limiting examples of fillers include lactose, cellulose, microcrystalline cellulose, calcium carbonate, starch, aluminum, alumina, aluminum silicate, aluminum trioxide, barium sulfate, calcium carbonate, calcium sulfate, carbon black, copper, glass fiber, graphite iron, kaolin clay, lead, mica, phenolic or glass microspheres, silica sand, silicon carbide, silver, titanium dioxide, zinc oxide, zirconium silicate.
Non limiting examples of dispersants include sodium citrate, ammonium polyacrylate, sodium tartrate, sodium polyacrylate, sodium succinate, sodium polysulfonate, glyceryl trioleate, poly(ethylene imine).
Non limiting examples of extenders include aluminium silicate, magnesium silicate (talc), silica, calcium carbonate (synthetic and natural) and barium sulfate.
Non limiting examples of surfactants include anionic surfactants such as 2-acrylamido-2-methylpropane sulfonic acid, alkylbenzene sulfonate, ammonium lauryl sulfate, ammonium perfluorononanoate, chlorosulfolipid, disodium cocoamphodiacetate docusate, magnesium laureth sulfate, perfluorobutanesulfonic acid, perfluorodecanoic acid, perfluorohexanesulfonic acid, perfluorononanoic acid, perfluorooctanesulfonic acid, perfluorooctanoic acid, perfluoropropanesulfonic acid, phospholipid, potassium lauryl sulfate, sodium dodecyl sulfate, sodium laurate, sodium laureth sulfate, sodium lauroyl sarcosinate, sodium myreth sulfate, sodium nonanoyloxybenzenesulfonate, sodium pareth sulfate, sodium stearate, sodium sulfosuccinate esters, sodium tallowate, sodium tetradecyl sulfate; cationic surfactants: behentrimonium chloride, benzalkonium chloride, benzethonium chloride, benzododecinium bromide, carbethopendecinium bromide, cetalkonium chloride, cetrimide, cetrimonium bromide, cetrimonium chloride, cetylpyridinium chloride, didecyldimethylammonium chloride, dimethyldioctadecylammonium bromide, dimethyldioctadecylammonium chloride, dioleoyl-3-trimethylammonium propane, domiphen bromide, ethyl lauroyl arginate, lauryl methyl gluceth-10 hydroxypropyl dimonium chloride, octenidine dihydrochloride, olaflur N-Oleyl-1,3-propanediamine, stearalkonium chloride, tetramethylammonium hydroxide, thonzonium bromide; non-ionic surfactants such as alkyl polyglycoside, cetostearyl alcohol, cetyl alcohol, cocamide DEA, cocamide MEA, decyl glucoside, decyl polyglucose, glycerol monostearate, IGEPAL CA-630, isoceteth-20, lauryl glucoside, maltoside, monolaurin, mycosubtilin, narrow-range ethoxylate, nonidet P-40, nonoxynol-9, nonoxynols NP-40, octaethylene glycol monododecyl ether, N-Octyl ß-D-thioglucopyranoside,
octyl glucoside, oleyl alcohol, pentaethylene glycol monododecyl ether, polidocanol, Poloxamer, Poloxamer 407, polyethoxylated tallow amine, polyethylene glycol cetyl ether, polyglycerol polyricinoleate, polysorbate, polysorbate 20, polysorbate 80, sorbitan, sorbitan monolaurate, sorbitan monostearate, sorbitan tristearate, stearyl alcohol, surfactin, Triton X-100, Tween 80. Non limiting examples of pH adjusters include acetic acid, acetic acid, citric acid, citric acid, fumaric acid, hydrochloric acid, hydrochloric acid, lactic acid, malic acid, nitric acid, phosphoric acid, phospohoric acid, propionic acid, sodium phosphate monobasic, sulfuric acid, NF tartaric acid, ammonia solution, ammonium carbonate, diethanolamine, monoethanolamine potassium hydroxide, sodium bicarbonate, sodium borate, sodium carbonate, sodium hydroxide, sodium phosphate dibasic, trolamine.
Non limiting examples of rheology modifiers include natural raw materials (cellulose, xanthum gum), synthetic (polyacrylates), clays, silicas, specialty (modified) clays.
The present invention also relates to an article which comprises the above-described composition applied to a paper substrate. The article has resistance to oil and/or grease penetration, moisture barrier, oxygen barrier, phthalate resistance, repulpable, compostable, plastic free and biodegradable and has the desired mechanical property.
In an embodiment, there is provided a heat-sealable coated paper substrate having thickness ranging from 30 -75 gsm, oil grease resistance measured as 3M Kit value in the range from 8-16, tear strength ranging from 50 - 70 g/gsm.
Typically, the coated paper substrate is heat-sealable at a temperature ranging from 120-160 °C, time duration ranging from 0.2-1 second.
In an embodiment, the coated paper substrate of the present invention is repulpable and compostable. In an embodiment, the coated paper substrate is plastic free and biodegradable. In an embodiment, the coated paper substrate comprises at least 80 wt.% bio-derived materials.
In an embodiment, the article is an Agarbatti/incense stick pouch, bags/cartons/pouch/wrapping films for holding fragrant materials, bags/cartons/pouch/wrapping films for food storage, paperboard, paper sheets, heat-sealed bags/pouch/container/cartons, shopping bag, a container for holding beverages such as tea/coffee/aerated drinks/juices/alcohol, laminates, an outer casing or screen for electronic goods, packaging for pharmaceutical products, packaging for clothing, packaging for medical device, and the like. Specific examples of food packaging uses include fast food wrappers, food bags, snack bags, grocery bags, cups, trays, cartons, boxes, bottles, crates, food packaging films, blister pack wrappers, microwavable popcorn bags, release papers, pet food containers, beverage containers, OGR papers and the like.
According to another aspect of the present invention there is provided a process for preparing the composition of the present invention, said process comprising the steps :
(i) boiling water to its boiling temperature and adding starch to it under stirring;
(ii) dissolving starch completely and cooling to room temperature;
(iii) adding plasticizer and mixing;
(iv) separately mixing nano-cellulose and solvent and then adding the mixture to the starch solution of step (iii) while stirring;
(v) adding other additives, defoamer and biocide and stirring;
(vi) adding crosslinker and again mixing to obtain the composition of the present invention.
It is to be noted that a person skilled in the art can easily derive the reactions depending upon the manufacturing set-up used.
The present invention also provides a method of coating the paper substrate with the coating composition comprising the steps of:
(i). providing a paper substrate; and
(ii). applying the coating composition on one surface or both surface or on all surfaces or in between layers of the paper substrate through a layer by layer coating or in single layer coating method of coating compositions.
The paper substrate may be coated with the composition by any suitable method, for example employing any one of gravure, flexo, semiflexo, curtain coating, rod and bar coater, meter coater and like coating technologies or combinations of technologies.

Advantages of the present invention:
• Coated paper substrate exhibits superior performance when measured in terms of at least one of the parameters that include moisture barrier, gas barrier, oil and grease resistance, phthalate resistance and heat-sealability.
• Coated paper substrate is repulpable and compostable.
• Coated paper substrate is plastic free and biodegradable.
• Exhibits a high tear strength and tensile strength.
• Useful as packaging materials in various applications.

EXAMPLES:
The following examples are meant to illustrate the present invention. The examples are presented to exemplify the invention and are not to be considered as limiting the scope of the invention.

EXAMPLE -1:
Preparation of coating formulation according to an embodiment of present invention

I] Raw materials:
Starch used is modified starch other than cationic starch. Modified starch used in the invention has film forming properties. It is essential to improve coating color rheology on the one hand, and final paper quality enhancing optical properties like brightness, gloss or opacity, sheet smoothness and most importantly printability and print image quality. It also improves coating binding, tensile strength of the films and provides sealing. The formation of starch films mainly depends on the retrogradation characteristics of starch. After starch granules are gelatinized, the hydroxyl groups between the starches are combined through intermolecular hydrogen bonds to form a starch film.
Modified starch is used at a wt.% of 15-25 in water, which forms a free-flowing clear solution.
Oxidised starch was procured from Bangkok.
Nano-cellulose - Properties and Characterization:
Nano-cellulose was manufactured in-house with 2% consistency of hardwood pulp in water.
Nano-cellulose characterization:
Table 2
Parameter Specification
Degree SR >95
Source of fibres Hard wood pulp
Consistency 2%
Fibre size >200 mesh

*Degree SR (Schopper-Riegler) - The Schopper-Riegler test provides an idea of the degree of refining that is related to the drainage rate of a dilute pulp suspension.
Pulp was procured from Chile and is processed into nanocellulose. Nano-cellulose manufactured in-house was tested for its properties.
XRD Analysis
Wide-angle X-ray diffraction (WAXD) patterns of the oven dried and freeze dried Nano-cellulose was performed on a Bruker D8 Advance with rotation of 15 RPM. Wide angle X-ray diffractometer with Cu Ka radiation (?= 0.154 nm) at 40 kV and 40 mA. X-ray diffraction data were collected from 2? =5? to 40? at a scanning rate of 0.5 sec/steps at room temperature.
The mechanical and thermal properties of cellulose were dependent on the crystalline characteristics. The cellulose XRD diffraction patterns were recorded at 2? = 14.8°, 16.6°, 20.5°, 22.9°,31.15°and 33.9° which are characteristic peaks for the cellulose corresponding to the lattice planes 110, 102,200,221 and 023. The intensity ratio of peaks is as in Figure 1. There are several polymorphs of crystalline cellulose (Ia, Iß, II, III, IV). Cellulose Ia (triclinic structure) and Iß (monoclinic structure) are the crystalline celluloses produced naturally by living organisms. Cellulose Iß is the main crystalline component of the Nano-cellulose.

FTIR analysis
The FTIR spectrum of the isolated cellulose displayed characteristic absorption patterns corresponding to the specific functional groups of ß-cellulose (Figure. 2) and was also in good agreement with the reported cellulose (Table-3 below).
Table 3
Wave number (cm-1) Band Origin
3400-3330 OH stretching of alcohols, phenols, and acids
2970-2820 C-H stretching in methyl and methylene groups
1750-1720 C=O stretching in unconjugated ketons, carbonyls, aldehydes and ester groups
1605-1598 Aromatic ring stretching in lignin
1515-1506 Aromatic ring stretching in lignin; C=C stretching of the aromatic ring in lignin
1470-1460 C-H deformation (asymmetric)
1430-1420 Aromatic skeletal vibration with C-H deformation
1370-1365 CH2 bending in cellulose and hemicellulose
1330-1320 Syringyl ring breathing
1240-1229 Syringyl ring and C-O stretch in lignin and xylan
1157-1156 C-O-C vibration in cellulose and hemicellulose
1035-1029 C-H and C-O deformations
897 C-H deformation of cellulose and hemicellulose

Cross-linker:
Cross linker used here is a copolymer of epichlorohydrin and alkylamine. Alkylamine is defined as a material having alkyl group containing carbon atoms ranging from 1 to 20 carbon atoms and 0 to 2 carbon to carbon double bonds.
Plasticizers:
Additionally, a plasticizer may be added to the formulation to improve the machinability of the formulation. The plasticizer is an optional ingredient and may, if required, be added at a concentration known to a person skilled in the art. Glycerol, Propylene glycol and other well-known ingredients act as a humectant. This helps in maintaining the flexibility of the paper.

II] Coating formulation according to an embodiment of present invention
Table 4
Ingredients Quantity (wt.%)
Modified starch 15-25
Water 34-53
Nano-cellulose 7.5-10
Plasticizer 5-10
Alcohol 10-15
Defoamer 0.1-0.5
Biocide 0.2-1
Cross linker 2.5-5

Nanocellulose, starch and cross linker may be added at predetermined ratios to arrive at a working formulation.
Process for preparing the coating formulation:
The above coating formulation is prepared as per the following process steps:
Water was heated in a beaker to its boiling temperature. Under stirring, starch was added in portions. Once starch was completely dissolved, the solution was allowed to cool down to RT. Plasticizer was added and mixed. Parallelly, Nanocellulose and Solvent and mixed in a separate container and added to the starch solution while stirring. Other additives, defoamer and biocide was added and stirred for another 30 minutes. Crosslinker was added and again mixed for 15mins. The formulation was then coated on paper with a bar coated.

Table -5: Working coating formulation 1
S.no Name of component wt%
1 DM water 50
2 Oxidised Starch 20
3 Glycerol 8
4 Nanocellulose 10
5 IPA 11.7
6 Silicone emulsion (Defoamer) 0.1
7 Quarternary ammonium compound (Biocide) 0.2
6 Copolymer of Epichlorohydrin and Alkylamine - Crosslinker 5

Few other working examples according to present invention:

Working formulation 2:
Table 6
Sr. No Name of component Wt.%
1 DM water 50
2 Modified Starch 20
3 Poly ethylene glycol-200 10
4 Nanocellulose 10
5 IPA 9.7
6 Defoamer 0.1
7 Biocide 0.2
6 Copolymer of Epichlorohydrin and Alkylamine 5

Working formulation 3:
Table 7
Sr. No Name of component Wt.%
1 DM water 50
2 Modified Starch 20
3 Poly ethylene glycol-200 10
4 Nanocellulose 10
5 Ethanol 9.7
6 Defoamer 0.1
7 Biocide 0.2
6 Copolymer of Epichlorohydrin and Alkylamine 3

III] Characterization of coating formulation:
Viscosity of the above formulation was measured by B4 cup and was found to be 35-40 sec. On addition of cross linker (3-5 wt%) viscosity was increased to 85-100 sec with B4 cup.
Rheological Measurements:
Rheology is the study of how materials deform and flow as a result of an external force. The rheological measurements were performed using a rotational rheometer (MCR 102 Anton Paar Physica) with parallel plate glass geometry of 43 mm in diameter. Viscosity was measured at constant shear of 100rpm and constant temperature of 25°C over a period of 120s. Viscosity was found to be <300 cP without the addition of cross linker and the viscosity rose to 1000 cP on addition of cross linker (Figure 3).

EXAMPLE 2:
Paper substrate coated with the formulation of present invention:
I] Coating of the Paper Substrate:
Paper is typically constructed of bleached pulp with surface sizing for lowering water absorption and coating oil grease resistance. Figure 4 illustrates a paper construct with surface sizing at the top surface (a) and bottom surface (a’) of the bleached chemical pulp (b).
Paper substrate used were Wrapwell, HSMT. Papers were coated with the formulation of present invention.
II] Characterization of the coated paper substrate:
The coated paper substrate was tested for its various properties like coat weight (GSM), Heat sealability, OGR and Cobb.
A] Cobb test:
Cobb test determines the amount of water absorbed into the surface by a sized paper sample in a set period of time, usually 60 or 180 seconds (Cobb60 or Cobb180). Water absorbency is quoted in g/m2.
B] OGR validation
Oil grease resistance (OGR) of the paper was measured by preparing Kit. A drop of the Kit solution of each Kit rating starting from 1-16 was dropped and allowed for 15sec without disturbing. After 15sec, the solution was wiped off with a tissue paper and observed for any oil stains. If no stain observed then the kit value has passed, if not, same test was repeated with lower kit value.

C] Heat Sealability:
Sealability was tested at 160°C for 0.5s under 4kg pressure. Fibre tear observed at heat-sealed area on pulling apart was considered as good sealing.
Results:

Table-8
Formulation coated with various paper analysis data
S.no Paper substrate GSM Coating Formulations No of coatings Coating GSM Seal strength Kgf -25 mm OGR COBB (g/m2)
160 °C
Wrapwell paper
1 Paper A (40 GSM) Un coated paper NA NA NA 6 22.71
2 Present invention 1 C 3.2 0.37 FT* 10 21.89
3 2 C 6.2 0.47 FT 12 21.56
HSMT paper
1 Paper B (58GSM) Un coated paper NA NA NA 0 24.5
2 Present invention 1C 3.3 0.38 FT 6 22.1
3 2C 6.2 0.51 FT 8 21.95

* Fibre tear
It is observed from the aforesaid Table-8 that:
? Oil grease resistance of the coated papers is higher than that of the uncoated paper.
? Fibre tear (FT) is observed at heat-sealed area for the coated papers but not for the uncoated papers; thus, the coated papers show the property of heat-sealability.
? Cobb values of coated papers is lower than that of the uncoated papers; thus, the water absorbency is reduced for the coated papers.

D] Phthalate resistance
Phthalate resistance was observed by simply placing a drop of phthalate (carrier of fragrance for Agarbatti) and observed for any absorption or penetration of the solvent in to the paper. Further samples were packed with the coated paper and exposed to accelerated aging conditions and tested for the phthalate spots on the paper from outside.
Figure 5 illustrates that A: Coated paper according to present invention with Phthalate drop shows no spotting, B: Uncoated paper with Phthalate drop spot clearly visible.

E] Gas barrier validation:
Gas barrier was validated in terms of air permeability tested with PPM Express; Unit: Coresta (CU); Values expressed as: ml/min/cm2. It was observed that more than 90% of pores on paper was closed after coating with the formulation (Figure 6). Drastic decrease in air permeability was observed after coating.

F] Compostability and repulpability:
Raw materials used in the coating formulation of the present invention are all known to be biodegradable and compostable. As only 5-6 GSM of the formulation is coated on the paper and the formulation being water soluble, the paper is repulpable.

G] Accelerated stability study:
Accelerated aging study was conducted for Agarbatti packed in the coated paper according to present invention at 75% RH & 40°C temperature for 3 months. Samples were taken out and tested for Agarbatti sensory after 15 days, 1 month, 2 month and 3 month. Sensory study includes testing for neat note, profile and strength before burn and post burn (up to 3 hr).

Table 9: Sensory evaluation scores from 15th day to 90th day. Evaluation was conducted for every 15th day in conditioning chamber.
Plastic Free (Agarbatti samples) - Stability Report - 15th Day
Sample details Average of Neat Average of Inburn Average of Post burn Average of Likability Average of Performance Average of Overall
Plastic packaging 4.9 4.7 4.3 4.6 4.6 4.6
Coated Paper 4.4 4.3 3.6 3.9 4.2 4.1

Plastic Free (Agarbatti samples) - Stability Report - 30th Day
Sample details Average of Neat Average of Inburn Average of Post burn Average of Likability Average of Performance Average of Overall
Plastic packaging 5.0 4.8 4.5 4.8 4.7 4.8
Coated Paper 4.0 4.4 4.2 4.2 4.1 4.2

Plastic Free (Agarbatti samples) - Stability Report - 45th Day
Sample details Average of Neat Average of Inburn Average of Post burn Average of Likability Average of Performance Average of Overall
Plastic packaging 4.9 4.5 4.5 4.6 4.7 4.6
Coated Paper 4.2 4.3 4.3 4.0 4.4 4.2

Plastic Free (Agarbatti samples) - Stability Report - 60th Day
Sample details Average of Neat Average of Inburn Average of Post burn Average of Likability Average of Performance Average of Overall
Plastic packaging 5.0 4.3 4.4 4.6 4.5 4.5
Coated Paper 4.8 4.5 4.5 4.6 4.6 4.6

Plastic Free (Agarbatti samples) - Stability Report - 75th Day
Sample details Average of Neat Average of Inburn Average of Post burn Average of Likability Average of Performance Average of Overall
Plastic packaging 5.0 4.6 4.5 4.7 4.7 4.7
Coated Paper 4.2 3.9 3.4 3.8 3.9 3.9

Plastic Free (Agarbatti samples) - Stability Report - 90th Day
Sample details Average of Neat Average of Inburn Average of Post burn Average of Likability Average of Performance Average of Overall
Plastic packaging 4.3 4.4 4.3 4.4 4.3 4.3
Coated Paper 3.6 3.8 4.0 3.7 3.9 3.8
Conclusion:
Basis 3 months accelerated stability study, the drop in profile and performance in sample ITC coated paper is marginal and hence acceptable.

*TS – Top side, BS – Bottom side
**MD – Machine Direction CD – Cross Direction

EXAMPLE 3:
Comparative/ Non-working examples:
Non-working formulation 1:
Table-10
Sr. No Name of component Wt.%
1 DM water 50
2 Oxidised Starch 20
3 Poly ethylene glycol-200 10
4 Nanocellulose 10
5 Ethyl alcohol 9.7
6 Defoamer 0.1
7 Biocide 0.2
6 Polyfunctional aziridine cross linker 5

Non-working formulation 2:
Table-11
Sr. No Name of component Wt.%
1 DM water 50
2 Oxidised Starch 20
3 Propylene Glycol 10
4 Nanocellulose 10
5 IPA 9.7
6 Defoamer 0.1
7 Biocide 0.2
6 Polyfunctional aziridine cross linker 5

Polyfunctional aziridine was tested as a cross linker in examples of Table 10 and Table 11 above. It was observed that the reaction between starch and aziridine cross linker with substrate gave poor results. Coated paper desired OGR properties was reduced using this cross linker as shown in below Table 12.

Table 12
Crosslinker in formulation OGR 3M kit value
Polyfunctional aziridine crosslinker 4 fail
Epichlorohydrin and alkylamine crosslinker 16 pass

Non-working formulation 3:
Table 13
Sr. No Name of component Wt.%
1 DM water 68
2 Cationic Starch 2
3 Glycerol 8
4 Nanocellulose 10
5 IPA 11.7
6 Defoamer 0.1
7 Biocide 0.2
6 Co-polymer of epichlorohydrin- Polyamine – Crosslinker 5
It was observed that Cationic starch formed a very thick lumpy solution at just 2wt%. The bonding of cationic starch with cross-linker was poorer and hence did not contribute towards barrier improvement.

Non-working formulation 4:
Table 14
Sr. No Name of component Wt.%
1 DM water 50
2 Oxidised Starch 20
3 Poly ethylene glycol-200 10
4 Nanocellulose 15
5 IPA 9.7
6 Defoamer 0.1
7 Biocide 0.2
6 Copolymer of Epichlorohydrin and Alkylamine 10

Above example with increased concentration of nanocellulose and crosslinker resulted in increased viscosity and difficulty in processing during coating. On coating, sealing of coated paper was poor. It was observed that nano-cellulose when used more than 10wt.% of the formulation, coated paper heat sealable characteristic is decreased.
Nanocellulose made from cellulose does not have the inherent property of sealing and inhibits sealing property of starch when used at higher concentration. Same was observed as low sealing and peeling off without fibre tear at higher concentration of Nanocellulose above 10% in formulation.
Non-working formulation 5:
Table 15
Sr. No Name of component Wt.%
1 DM water 50
2 Modified Starch 20
3 Propylene Glycol 10
4 Nanocellulose 5
5 IPA 9.7
6 Defoamer 0.1
7 Biocide 0.2
6 Copolymer of Epichlorohydrin and Alkylamine 2.5
Above example with reduced concentration of nanocellulose showed higher air permeability of 5-6 CU for coated paper.

Non-working formulation 6:
Unmodified/native starch as control
Unmodified/native starch when used as control over modified starch resulted in difficulty in higher concentration due to increased viscosity. The use of modified i.e. oxidised starch in present invention helps in providing better barrier and strength to coated paper. The composition used here is Working coating formulation 1 and amount of the starch (native and oxidised) is same as that used in Working coating formulation 1.

Table 16
Parameters Formulation with Native Starch (Control) Present Formulation with Oxidised starch
Viscosity - cP 3000-7000 500-2000

Formulations of oxidized starch-nanocellulose / oxidized starch-crosslinker.
Studies on Tensile strength, tear factor and air permeability was conducted with working formulation 1 and two other formulations having composition exact same as working formulation 1 except that one was without crosslinker and the other without nanocellulose. The results of the studies are shown in Table 17.
Table 17
Sl.no Properties Present formulation
Oxidised starch-nanocellulose-crosslinker (Working coating formulation 1) Oxidised Starch -Nanocellulose Oxidised Starch - Crosslinker
1 Tensile strength - kg/15mm MD: 27.5 - 28.84 MD: 30.1 - 32 MD: 16 – 18.5
2 Tear Factor - gm/gsm MD - 57
CD – 59 MD - 48
CD - 50 MD - 30
CD - 33
3 Air permeability 1.9 Coresta Units 5 Coresta Units 12 Coresta Units

From the aforesaid Table-17, it is observed that the tear strength and air permeability of the present coating composition comprising oxidised starch, nanocellulose and crosslinker is significantly superior as compared to the formulations comprising oxidized starch-nanocellulose or oxidized starch-crosslinker.
The present invention is a synergistic composition of modified starch, Nanocellulose and Crosslinker which helps in providing the resistance to oil, grease and phthalates with good mechanical property and heat sealing of paper. In the absence of Nanocellulose, mechanical property and barrier is compromised. In the absence of crosslinker, air permeability of coated paper will be higher. In the absence of oxidised starch, film forming capacity of formulation is lost, also barrier and mechanical properties of coated papers is highly compromised.
It is to be understood that the present invention is susceptible to modifications, changes and adaptations by those skilled in the art. Such modifications, changes, adaptations are intended to be within the scope of the present invention.
,CLAIMS:1. A coating composition comprising
(i) 15-25 % by weight oxidised starch;
(v) 7.5-10% by weight nano-cellulose;
(vi) 2.5-5% by weight at least one cross-linker; and
(vii) 44% to 68% by weight at least one solvent.

2. The coating composition as claimed in claim 1, wherein said nano-cellulose has a length ranging from 0.2 to 0.6µm and diameter ranging from 10 to 15 nm.

3. The coating composition as claimed in any of the preceding claims, wherein said cross-linker is copolymer of epichlorohydrin and alkylamine or Ammonium zirconium carbonate (AZC) or Potassium zirconium carbonate (KZC) or Sodium trimetaphosphate (STMP) or Sodium tripolyphosphates (STPP) or combination of thereof.

4. The coating composition as claimed in any of the preceding claims, wherein said composition further comprises humectants, defoamer, biocide, fillers, dispersants, extenders, surfactants, pH adjusters, rheology modifiers, or combinations thereof.

5. The coating composition as claimed in any of the preceding claims, wherein said solvent is selected from water, alcohol including but not limited to ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol or combinations thereof.

6. The coating composition as claimed in any of the preceding claims, wherein said composition is applied on a paper substrate.

7. A coated substrate formed by coating a substrate with the composition as claimed in any of the preceding claims said coated substrate having resistance to oil and/or grease penetration, moisture barrier, oxygen barrier, phthalate resistance, repulpable, compostable, plastic free and biodegradable.

8. The coated substrate as claimed in claim 7, wherein said substrate in paper.

9. The coated substrate as claimed in claim 7, wherein said substrate is used in articles selected from agarbatti/incense stick pouch, bags/cartons/pouch/wrapping films for holding fragrant materials, bags/cartons/pouch/wrapping films for food storage, paperboard, paper sheets, heat-sealed bags/pouch/container/cartons, shopping bag, a container for holding beverages such as tea/coffee/aerated drinks/juices/alcohol, laminates, an outer casing or screen for electronic goods, packaging for pharmaceutical products, packaging for clothing, packaging for medical device, food packaging including fast food wrappers, food bags, snack bags, grocery bags, cups, trays, cartons, boxes, bottles, crates, food packaging films, blister pack wrappers, microwavable popcorn bags, release papers, pet food containers, beverage containers, and OGR papers.

10. A process for preparing the composition coating composition as claimed in any of the preceding claims 1 to 6, said process comprising the steps :
(i) boiling water to its boiling temperature and adding starch to it under stirring;
(ii) dissolving starch completely and cooling to room temperature;
(iii) adding plasticizer and mixing;
(iv) separately mixing nano-cellulose and solvent and then adding the mixture to the starch solution of step (iii) while stirring;
(v) adding defoamer and biocide and stirring;
(vi) adding crosslinker and again mixing to obtain the composition of the present invention.