FIELD OF THE INVENTION
[001] The present invention relates to methods for preparing water based heat seal coating compositions for Alu - Alu and Blister packs. In particular, the disclosed methods include methods for preparing water based heat seal coating compositions which are suitable for heat sealing of, coated polyester with coated polyester or uncoated polyester, coated aluminum foil with coated aluminum foil, and coated polyester film with coated aluminum foil, coated polyester film with uncoated aluminum foil and uncoated polyester film with coated aluminum foil.
BACKGROUND OF THE INVENTION
[002] Heat seal coatings (HSC) have been used in food, pharmaceutical, medical, and industrial packaging applications. The sector for food-and-drink packaging and tablet pack aging has for some time now used not only polystyrene (PS) and polyvinyl chloride (PVC), Poly Propylene (PP) but polyethylene terephthalate (PET or polyester) also. Examples of heat seal coatings products include water based ethylene vinyl acetate (EVA)-resin- based heat seal coatings (i.e. Ateva® EVA Polymers, Celanese Corporation), VMCH coating (i.e. VINNOL®H 15/45 M, Wacker Chemie AG, Germany) etc. Aluminum foils are usually sealed with blister by applying coating of VMCH, EVA, polyvinyl acetate, polyethylene, or high seal polyester coatings. However, these systems have been developed specifically for the sealing of blister with lidding materials.
[003] The PVC is primary substrate for blister packs. The use of PVC as forming material has attracted much criticism because its combustion produces hydrochloride emissions and, under unfavorable conditions, highly toxic dioxins which are considered carcinogens. On the other hand, the use of Poly Propylene (PP) has its drawbacks. PP film cannot offer rigid blister and PP is not clear transparent generally. PP is difficult to thermoform and temperatures required for thermoforming PP and for the subsequent cooling process must be controlled precisely. Warping also can occur, in which case the packages must be straightened before cartooning. Other difficulties associated with the use of PP include its thermal instability, higher rigidity than PVC, and susceptibility to post processing shrinkage. In addition, PP is difficult to run on a standard blister packing machine and cannot be processed as fast as PVC. If a company runs PP and needs new equipment, it must go through a precise validation process, performing various tests on PP to satisfy FDA requirements. As a result, PP is virtually nonexistent in rigid pharmaceutical blister packaging in most countries. Polyvinylidene chloride (PVDC)–coated PVC, PVC / chlorotrifluoroethylene (CTFE), Polystyrene (PS) is also incompatible due to one or another reason to be a suitable substitute of PVC. Polyester is another material that may replace PVC to be a universal substrate for blister packs or ALU- ALU packs.
[004] VMCH / EVA coatings have only limited suitability for the sealing of aluminum foils or of aluminum coatings with wide range of polyester based blister films. For example, the poly (meth) acrylate resins Co-polymer, which have proved successful in the sealing of polystyrene or of PVC e.g. DEGALANR P 24, cannot be used because they cannot achieve the seal seam strength. A very often adhesion problem occurs. There is no heat-sealing coating known thereto which has a suitable formulation giving suitability not only for the sealing of aluminum foils with polyester films but also for the sealing of polyester films with other polyester films whether coated or uncoated. Further, VMCH / EVA coatings are very expensive and Solvent based.
[005] In the conventional Cold Form Laminate Alu-Alu blister packaging- there are three layers – Nylon, Aluminum and PVC. Flex film has developed revolutionary Alu-Alu packaging where special polyester film has replaced the conventional Nylon and PVC while retaining Aluminum making it an indigenous product since both PVC and BON have to be imported from other countries. For this unique development, Alu-Alu packaging provides sustainability and cost optimization giving it an edge over conventional Alu-Alu packaging.Since, in this structure of blister pack also sealing layer is of polyester which is to be sealed with lidding material by applying coatings.
[006] Therefore, a lower-cost process for manufacturing water based HSC products while still maintaining or improving quality and HSC performance, is desired. Additionally, the EVA / VMCH resin is likely to be subject to hydrolysis in the batch dispersion process due to longer processing in a strong base environment at high temperature, so a continuous dispersion process with short residence time is highly desired to significantly mitigate EVA hydrolysis.
[007] Further, water based heat seal coating products are typically manufactured by a batch dispersing process, which has relatively high conversion cost due to long cycle time as well as substantial batch-to-batch variations in the produced dispersions. In addition, significant waxes are required as process aids in the batch dispersion process in order to help dispersibility and reduce the melt viscosity of the composition even though the waxes do not contribute to the adhesion properties.
[008] More recently, and with the limitations of batch processes in mind, water based heat seal coatings have been produced by continuous processes in which a single extruder is used to blend, emulsify, and dilute the final dispersion. However, continuous processes have surprisingly encountered scalability issues on large, commercial-scale extruders where the final product is not sufficiently dispersed, i.e., non-uniform dispersion of a narrow particle size distribution, resulting in an unstable dispersion product. This is likely a consequence of the difference in melting temperatures of the raw materials used to produce the dispersions. Accordingly, methods for efficiently and effectively producing a uniform, aqueous dispersion suitable for use in heat seal coating applications, while still maintaining or improving quality and water based heat seal coating performance, is desirable.
[009] Coatings based on polyvinyl chloride or related halide-containing vinyl polymers, like polyvinylidene chloride, possess the above-listed advantageous properties of chemical resistance and corrosion inhibition, and also are economical. Nevertheless, investigators continually seek improved coating compositions for food and beverage containers and closures, and for metal containers in general, that retain the advantageous properties of adhesion, flexibility, chemical resistance, and corrosion inhibition, and that are economical and do not adversely affect the taste or other aesthetic properties of sensitive food and beverages packaged in the container.
[010] The present invention is directed to an improved water based coating composition based on a N Butyl Acrylate homo- and / or copolymer which is useful for coating on Aluminum foil and Polyester film. The coating compositions of the present invention do not require any primer before coating and have excellent adherence properties with Al-Foil to Al-Foil or Polyester offering good seal-ability between wide range of temperatures, Environment friendly as it is water based, and at the same time have outstanding chemical resistance properties. Where presently available VMCH coating doesn’t seal with polyester. The coated pharmaceutical lidding foil coated with the present Invention coating is free of retained solvents.

OBJECT OF THE PRESENT INVENTION
[011] It is an object of the present invention to provide, via development and formulation of suitable polymers, heat-sealing coatings which are suitable for sealing Special polyester foils or polyester coated foils with respect to variety of Alu-Alu or blister material.
[012] It is another object of the present invention is to provide a heat seal coating where polyester is sealed with polyester based lidding material or laminate of polyester with aluminum foil by applying coating on either or both sealing side of the substrates.
[013] It is another object of the present invention is to develop a heat seal binder composition suitable for sealing lidding polyester laminated foils or polyester coated film or polyester coated laminates with respect to PET/polyester based blister materials.
[014] Another object was to achieve sufficiently high strengths of the sealing with conventional sealing cycle used in the heat sealing of plastic foils.
[015] Another object was to develop a heat seal coating binder which is suitable for lidding material of not only for coated aluminum foils but also coated polyester foils or coated polyester film or coated polyester laminate with poly vinyl chloride.
[016] Another object was to achieve high adhesion even at relatively high temperatures of 130° C to 150° C after sealing process, since this can achieve short cycle times for the sealing of the foil for food and drink packages.
[017] Another object of the present invention is to provide a heat seal coating that is water dispersible.
[018] The present invention provides a heat seal coating wherein the heat seal coating comprises co-polymer of N-Butyl acrylate.
[019] It is another object of the present invention to provide water based heat seal coating to be applied on aluminum foil or polyester, coated Aluminum Foil to coated Aluminum Foil, coated Polyester to coated polyester, coated polyester film with coated aluminum foil, coated polyester film with uncoated aluminum foil and uncoated polyester film with coated aluminum foil.
[020] It is another object of the present invention is to provide a coating solution which can seal with polyester whereas presently available VMCH coating doesn’t seal with Polyester.
[021] It is another object of the present invention to provide a coating solution which can be applied by Gravure Coater.
[022] It is another object of the present invention to provide a coating solution which is cost effective in use.
[023] It is another object of the present invention to provide a coating solution for blister packaging system which has higher degree of integrity comparable to conventional systems.
[024] It is another object of the present invention to provide a pharmaceutical lidding foil free of retained solvents.
SUMMARY OF THE PRESENT INVENTION
The present invention is to provide a water based, cost effective and low odor, co-polymer base coating for Aluminum foil and Polyester film, more specifically been developed for heat-seal coatings on push through lidding foil for pharmaceutical blisters. Available HSC based on acrylic or Styrene / Butyl Methacrylate based copolymer are suitable for hard and soft tempered aluminum push through foils in all standard gauges with PVC.
In one aspect, the invention is a formulated water-based composition that is coated onto a web of packaging film or foil, which when dry enables face to face heat sealing at a bonding temperature in range of 130°C to 150°C. The formulated composition contains a heat coating (e.g. 37 to 47% by weight) comprising a (methyl) acrylate homo- and / or copolymer, comprising a methacrylate and / or an acrylate with a glass transition temperature (Tg, ASTM D 3418) between 4° to 6°C and melting point of co-polymer is about 75°C to 85°C.
The composition also contains anti-block additives or other additives or both from 4 % to 8% by weight, consists of ethyl acetate and Silica C812 or PQ 576 or Syloid 7000 or Syloid 244FP, fatty amides, waxes or talc and (e.g.). It is desirable that the composition must include water by 53 to 58 % of weight.
[025] In an exemplary embodiment, the heat seal coating is a combination of standard homo polymer or copolymer of poly acrylate and / or poly methacrylate is any of or combination of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and isobutyl methacrylate or styrene, a-methylstyrene, acrylonitrile, allyl alcohol, butadiene, vinyl chloride, vinyl acetate, vinyl stearate, vinyl methyl Ketone, vinyl isobutyl ether, allyl acetate, allyl chloride, allyl isobutyl ether, allyl methyl ketone, dibutyl phthalate, cis-butenedioic acid Dilauryl ester and dibutyl itaconate. Such a resin provides consistent seal strength for sealing temperatures between 130° C. to 160° C. or above.
[026] Importantly, no primer coating is needed for this heat seal coating to adhere to many of the commonly used substrates.
[027] In another aspect, the coating adheres to blister packaging films or lidding foils made of polyester, amorphous polyester or co-polyester, aluminum foils without requiring a primer be applied to the surface of the film or foil before applying the water based composition to the surface of the blister film or foil and drying the composition to form the heat sealable coating on the surface of the film or foil.
[028] Other features and advantages of the invention may be apparent to those skilled in the art upon reviewing the following drawings and description thereof.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[029] The inventive heat seal coating formulation described herein is water based coating. In the below charts the applied heat seal coating formulation may be described as R-312.
The water based heat seal coating composition can be used with any type of blister packs/forming packs where polyester is the sealing layer with Aluminum foil or laminate foil with polyester. Further the present heat seal coating can be applied with Polyvinyl chloride which can be sealed with coated polyester or coated aluminum foil.
[030] The formulated composition contains a heat seal coating (HSC) comprising a (methyl) acrylate homo- and / or copolymer, comprising a methacrylate and / or an acrylate copolymer (e.g. 37 to 47% by weight) with a glass transition temperature (Tg, ASTM D 3418) between 4°C to 6°C and melting point of co-polymer is about 75°C to 85°C. The composition also contains anti-block additives and other additives from 4% to 8% by weight, consists of ethyl acetate, silica (C812), and NN Dimethylethalonammine etc., further, it is desirable that the composition must include water 53% to 58 % by weight.

[031] The present disclosure of water based coating uses copolymer of N Butyl Acrylate. The initial solution is prepared in the range of below described ratio by using Xylene, Tert Butyl Perbenzoate, N Hydroxyl Methyl Acrylate and copolymer of N Butyl Acrylate.
S. No. Ingredients Parts by Weight (range) %
composition %
Solid
1 Xylene 85-95 12.6-14.6 78-94
2 Tert Butyl Perbenzoate 27-33 4.0-5.0
3 N Hydroxy Methyl Acrylate 240-300 36-44
4 N Butyl Acrylate 240-300 36-44
[032] The final acrylic base polymer has solid content 78% to 94% by weight of total ingredients obtained after condensation at 120°C for 2 hrs. The solid content prepared by above formulation is called as copolymer.
[033] The copolymer prepared according to the disclosed composition, the copolymer of N Butyl Acrylate can be any of or combination of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and isobutyl methacrylate or styrene, a-methylstyrene, acrylonitrile, allyl alcohol, butadiene, vinyl chloride, vinyl acetate, vinyl stearate, vinyl methyl Ketone, vinyl isobutyl ether, allyl acetate, allyl chloride, allyl isobutyl ether, allyl methyl ketone, dibutyl phthalate, cis-butenedioic acid Dilauryl ester and dibutyl itaconate.
[034] In some embodiments, the content of heat seal coating composition comprises copolymer in the range from 37 to 47 percent, or from 39 to 45 percent, or from 40 to 47 percent, or from 38 to 44 percent, by weight.
[035] The HSC composition comprises water, is in the range from 53 to 58 percent by weight in various compositions.
[036] The composition comprises an Anti-block Additives & other additives, is in the range from 4 to 8 percent or from 3 to 8 percent by weight or from 5 to 7 percent by weight. The composition may contain other additives including but not limited to de-foamers, rheology modifiers, organic or inorganic pigments.
[037] Antiblock: To improve the handling of the film, the process ability of the film (winding of the film on / from the roll) on the respective machines (printing and sealing), but in particular to improve the blocking behavior of the film, it is advantageous to further modify the heat-sealable coating. This is best done with the help of suitable anti blocking agents, which can optionally be added to the sealing layer in quantities such that blocking of the film is prevented, and the blocking optimized. The anti-block material modifies the behavioral characteristic of the of the film is improved.
[038] Common Anti blocking agents (also referred to as "particles") are inorganic and / or organic particles such as calcium carbonate, amorphous silica, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, alumina, lithium fluoride, calcium, barium, zinc or manganese salts, dicarboxylic acids, carbon black, titanium dioxide, kaolin or cross-linked polystyrene or cross-linked polymer particles based on acrylic acid derivatives ethyl acetate and Silica C-812 or PQ 576 or Syloid 7000 or Syloid 244FP.
[039] Coating Method: In practice, converters use the product by supplying a roll of packaging film or foil to a printing press such as a gravure or flexographic printing press. Then, the converter uses the printing press to apply the solvent-based, heat seal coating onto one face of the packaging film or foil. The converter then dries the solvent-based heat seal coating to remove the solvent, for example using a conventional in-line drying systems, thereby leaving a dry solid layer of heat seal coating on the packaging film or foil. The converter then rewinds the coated and dried film or foil into roll form for later use on blister packaging machine.
EXAMPLE
[040] The following example demonstrates several aspects of certain preferred embodiment of the present invention and is not to be construed as limitation thereof.
[041] Heat seal coating composition R-312 manufactured using present invention is water based coating with a Tg of 5.55°C and Vicat softening point of 100°C. A coating copolymer is obtained by below composition:
S. No. Ingredients Parts by Weight %
Composition %
Solid
1 Xylene 90 13.6 86.4
2 Tert Butyl Perbenzoate 30 4.6
3 N Hydroxy Methyl Acrylate 270 40.9
4 N Butyl Acrylate 270 40.9
[042] Xylene is used as solvent or as of dispersing agent for its preparation. The solvent xylene is evaporated during the reaction process obtaining. the co-polymer of N Butyl Acrylate and get 86.4 % solid content of copolymer by weight. The copolymer obtained with above composition is comparatively solid. The below mentioned diluters and additives are further added to copolymer to obtain Heat seal composition R-312:
Ingredient Name Approx. Weight (%)
Co-Polymer Solution 37– 47 %
DM Water 53 – 58 %
Anti-block Additives & other additives and NN Dimethylethalonammine ~4 -8 %
[043] The coating solution is applied to polyester film or aluminum foil using Roto Gravure coater. The coating film is dried at 120°C for 1 minute or inline dried on the coating machine. A heat seal coating of about 4 ~ 6 GSM is applied on the polyester film or aluminum foil.
Preparation Method
[044] The initial material is heated in the reaction vessel with the agitation speed 50 rpm and reflux temperature 141°C to 150°C. The Xylene and catalyst (Tert Butyl Perbenzoate) are charged gradually in 2 to 3 hour. to maintain the reaction speed and temperature (solution A) once complete the process of addition solution A, charge the material – n hydroxyl methyl acrylate and n butyl methyl acrylate with some amount of Xylene.
[045] The reaction is held for the 2 to 2.5 hours on 135°C -142°C to complete the polymerization.
[046] The reaction composition was cooled and filtered with 20-micron mesh size filter. The final acrylic polymer has solid content of 70% ~ 90% evaluated at 120°C 2 hour. (Solution B) this polymer final molecular weight around 3,500 to 3,800 as determined by GPC (Gel permeation chromatography) using polystyrene as standard.
[047] The final polymer has acid numbers around 7 to 9. The traces of Xylene may be present in the final polymer, which is in the range of 0 to100 ppm.
[048] The above acrylic polymer is dispersed in aqueous medium.
[049] The Solution is charged in the water bath 3 neck round bottom flask reactor and heated to 78°C ~ 80°C for the 1 hour with the agitation speed 100 ~ 120rpm. This reaction vessel is suitable for the Azeotropic distillation under the atmospheric pressure condition.
[050] The funnel is mounted on the reactor for the addition of neutralizing and stabilized agent for the polymer. The Azeotropic distillation of the acrylic polymer is cooled and filtered with the Nylon mesh 200, the dispersion solids are obtaining 37 - 47% and PH is around 8.1 ~ 9.5 and the Xylene content is 0.01% with the particle size 660 angstrom.
[051] Acrylates might be Acrylonitrile-Styrene-Acrylate (ASA) or N- butyl methacrylate or N butyl methy methacrylate or N hydroxypropyl methacrylate and their composition of all.
Anionic initiator
[052] The electron donors (or initiators) are either electron transfer agents or strong anions. The transfer of an electron from a donor molecule to the vinyl monomer leads to the formation of an anion radical, the so-called carbanion.
[053] Typical electron donors (Lewis bases or nucleophiles) are alkali metals, such as lithium or sodium. Other strong nucleophilic initiators include covalent or ionic metal amides, alkoxides, hydroxides, amines, phosphines, cyanides, and organometallic compounds such as alkyl lithium compounds and Grignard reagents, styrene, dienes, methacrylate, vinyl pyridine, and lactones. Polar monomers, such as vinyl sulfone, vinyl ketone, acrylonitrile (ACN), and cyanoacrylate, undergo anionic polymerization using controlled conditions and low temperatures.
Antiblocks/additive for the coatings
[054] Wax Additive (bio based, micronized wax additive for water based coatings)
1) Silica C812 or PQ 576 or Syloid 7000 used. (fumed with the lower particle size 0.5 micron to 2.5 micron).
In particular, the Antiblock Solution Preparation Method for Heat Seal Coating is given below and it is not limited to this composition and may include other alternatives for the Antiblock preparation for the water based heat sealing coating.
a) Take 500 gm. Ethyl acetate in a Beaker.
b) Slowly start the agitation with medium speed (depending upon the motor rpm).
c) Now take Silica (C-812) 0.004 gm. (approx. 0.8%)
d) Mix this silica slowly along with agitation so that it will mix properly.
e) Now increase the agitation speed for complete dissolution of silica and to reduce the particle size.
f) Allow them to stir the solution for at least 1-2 hr. for proper dissolution.
Finally check visually after that Silica solution is ready for use in formulation.

2) Slip agent / additive - butylene glycol, glycerine, polysorbates, and propylene glycol etc.
Dispersion Methods
[055] Below described dispersion methods is used to prepare the final Heat Seal coating solution:
1) Ultrasonic dispersion - Ultrasonic waves are passed through a liquid medium, a large number of microbubbles form, grow, and collapse in very short times of about a few microseconds. Ultra sonication generates alternating low-pressure and high-pressure waves in liquids, leading to the formation and violent collapse of small bubbles.
2) Mechanical dispersion - It consists of two metallic discs nearly touching each other and rotating in opposite directions at a very high speed. The space between the discs of the mill is so adjusted that coarse suspension is subjected to great shearing force giving rise to particles of colloidal size.
Table 1
S.
No. Co-polymer type Coating type TDS (%) Coated base film (GSM) Test Condition
(150°C/2.1 bar/1 sec) Remark
Heat seal strength(gm/15mm)
Polyester film Alu Foil Coated Polyester film + Coated Alu Foil Coated Polyester film + Uncoated Alu Foil Uncoated Polyester film + Coated Alu Foil
1 Std.
(VMCH coated) Solvent based 25.00 6.0 7.0 750-850 NO SEAL NO SEAL
2 R-310 Water based 34.78 6.1 4.8 472-542 290-314 371-449 Coating Partially Transferred
3 R-311 Solvent based 20.15 6.2 4.7 327-346 247-258 396-398 Coating Partially Transferred
4 R 312 A Water based 40.0 6.0 5.0 779-802 370-414 381-542 OK
5 R-312 B Water based 47.0 5.9 5.0 811-830 414-500 534-558 OK
6 R-313 Water based 50.0 6.0 5.0 645-747 464-575 462-470 Coating Partially Transferred
[056] An aqueous coating composition comprising as wherein the highest heat seal strength of coated polyester film and coated aluminum film is from 779 ~ 830 gram per 15 mm at 150°C, pressure of 2.1 bar and 1 second dwell time in coating R-312 A and R-312 B, Both chemical formulated by same method and only difference being the TDS of R-312 A is approx. 40% and. approx. 47% of R-312 B.

Table-2
S.
No. Co-polymer type Coating type TDS
(%) Coated base film (GSM) Test Condition
(140°C / 2.1 bar / 1 sec) Remark
Heat seal strength (gm./15mm)
Polyester film Alu Foil Coated Polyester film + Coated Alu Foil Coated Polyester film + Uncoated Alu Foil Uncoated Polyester film + Coated Alu Foil
1 Std
(VMCH coated) Solvent based 25.0 6.0 7.0 700-800 NO SEAL NO SEAL
2 R-310 Water based 34.8 6.1 4.8 410-430 270-290 390-410 Coating Partially Transferred
3 R-311 Solvent based 20.2 6.2 4.7 270-300 225-235 330-340 Coating Partially Transferred
4 R 312 A Water based 40.0 6.0 5.0 690-772 350-400 400-450 OK
5 R-312 B Water based 47.0 5.9 5.0 710-800 400-440 440-460 OK
6 R-313 Water based 50.0 6.0 5.0 580-590 340-416 410-430 Coating Partially Transferred

[057] An aqueous coating composition comprising as wherein the highest heat seal strength of coated polyester film and coated aluminum film is from 690 -800 gram per 15 mm at 140°C, pressure of 2.1 bar and 1 second dwell time in Coating R-312 A and R-312 B, both chemical formulated by same method and only difference being the TDS in the solution i.e. approx. 40% in R-312 A and 47% in R-312 B.

Table-3
S.
No. Co-polymer type Coating type TDS (%) Coated base film (GSM) Test Condition
(130°C/2.1 bar/1 sec) Remark
Heat seal strength(gm/15mm)
Polyester film Alu Foil Coated Polyester film + Coated Alu Foil Coated Polyester film + Uncoated Alu Foil Uncoated Polyester film + Coated Alu Foil
1 Std.
(VMCH coated) Solvent based 25.0 6.0 7.0 675-750 NO SEAL NO SEAL
2 R-310 Water based 34.8 6.1 4.8 330-352 260-270 271-349 Coating Partially Transferred
3 R-311 Solvent based 20.2 6.2 4.7 225-235 220-230 396-398 Coating Partially Transferred
4 R 312 A Water based 40.0 6.0 5.0 650-701 340-380 390-442 OK
5 R-312 B Water based 47.0 5.9 5.0 670-730 380-430 430-455 OK
6 R-313 Water based 50.0 6.0 5.0 460-490 320-380 400-418 Coating Partially Transferred
[058] The above data in Table-1, 2 & 3 indicates that after using the Heat seal coating prepared from the above mentioned formulation with polyester or metal foil have good sealing characteristics.
[059] The seal strength is measured by ASTM F-88 using machine Heat sealer and UTM machine.
[060] The heat seal strength of coated polyester film and coated aluminum film is from 779 gram per 25 mm to 830 gram per 15 mm at 150o C, pressure of 2.1 bar and 1 second.
[061] The heat seal strength of coated polyester film and uncoated aluminum film is from 370 grams per 25 mm to 500 grams per 15 mm at 150 o C, pressure of 2.1 bar and 1 second.
[062] The heat seal strength of uncoated polyester film and uncoated aluminum film is from 381 grams per 25 mm to 558 grams per 15 mm at 150 o C, pressure of 2.1 bar and 1 second.

WE CLAIM:

[01] An aqueous coating composition comprising:
a copolymer from 37% by weight to 47% by weight;
a DM water in an amount of from 53% by weight to 58% by weight;
an anionic initiator additive and other additives from 4% by weight to 8% by weight.
[02] An aqueous coating composition as claimed in claim 1 wherein copolymer comprises of
an anionic initiator Tert Butyl Perbenzoate from 4.5 % by weight;
a N Hydroxy Methyl Acrylate 40.9% by weight; and
a N Butyl Acrylate homo- and/or copolymer, by 40.9 percent by weight.
[03] An aqueous coating copolymer as claimed in claim 2, wherein xylene is used as solvent or as of dispersing agent for its preparation.
[04] An aqueous coating copolymer solution as claimed in claim 2, wherein the xylene is dried out to get solid copolymer 86.4 % by weight of total ingredients.
[05] An aqueous coating composition as claimed in claim 2, wherein the homo polymer or copolymer of N Butyl Acrylate is any of or combination of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and isobutyl methacrylate or styrene, a-methylstyrene, acrylonitrile, allyl alcohol, butadiene, vinyl chloride, vinyl acetate, vinyl stearate, vinyl methyl Ketone, vinyl isobutyl ether, allyl acetate, allyl chloride, allyl isobutyl ether, allyl methyl ketone, dibutyl phthalate, cis-butenedioic acid Dilauryl ester and dibutyl itaconate.
[06] An aqueous coating composition as claimed in claim 1, wherein the anionic initiator and other additive can be any of lithium, sodium, metal amides, alkoxides, hydroxides, amines, phosphines, cyanides, alkyl lithium compounds and Grignard reagents, styrene, dienes, methacrylate, vinyl pyridine, lactones. vinyl sulfone, vinyl ketone, acrylonitrile (ACN), and cyanoacrylate.
[07] An aqueous coating composition as claimed in claim 1, wherein the antiblock solution consists of calcium carbonate, amorphous silica, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, alumina, lithium fluoride, calcium -, barium, zinc or manganese salts, dicarboxylic acids, carbon black, titanium dioxide, kaolin or cross-linked polystyrene or cross-linked polymer particles based on acrylic acid, derivatives of ethyl acetate and Silica C812 or PQ 576 or Syloid 7000 or Syloid 244FP OR NN Dimethylethalonammine.
[08] An aqueous coating composition comprising as claimed in claim 1, wherein the heat seal coating anchors to packaging films or foils made of polyester, amorphous polyester or co-polyester, polyvinyl chloride, Aluminum foils without requiring that a primer be applied to the surface of the film or foil before applying the water based composition to the surface of the film or foil and drying the composition to form the heat sealable coating on the surface of the film or foil.
[09] An aqueous coating composition comprising as claimed in claim 1, wherein the heat seal strength of coated polyester film and coated polyester aluminum film is from 779 gram per 15 mm to 830 gram per 15 mm.
[10] An aqueous coating composition comprising as claimed in claim 1, wherein the heat seal strength of coated polyester film and coated aluminum film is from 779 gram per 15 mm to 802 gram per 15 mm at 150 o C, pressure of 2.1 bar and 1 second dwell time.
[11] An aqueous coating composition comprising as claimed in claim 1, wherein the heat seal strength of coated polyester film and uncoated aluminum film is from 370 gram per 15 mm to 500 gram per 15 mm at 150 o C, pressure of 2.1 bar and 1 second dwell time.
[12] An aqueous coating composition comprising as claimed in claim 1, wherein the heat seal strength of uncoated polyester film and uncoated aluminum film is from 381 gram per 15 mm to 558 gram per 15 mm at 150o C, pressure of 2.1 bar and 1 second.
[13] An aqueous coating composition comprising as claimed in claim 1, wherein a coating thickness ranging from 4-6 GSM (gram per square) is required on surface of Aluminum foil or substrate for heat sealing.
[14] An aqueous coating composition comprising as claimed in claim 2, wherein the Glass transition temperatures (Tg) of co-polymer is about 4o C to 6o C.
[15] An aqueous coating composition comprising as claimed in claim 2, wherein melting point of co-polymer is about 75oC to 85oC.