FIELD OF THE INVENTION

The present invention discloses a water soluble co-polyester resin. Particularly the present invention discloses a water soluble co-polyester coating composition, comprising the water soluble co-polyester resin. Further, the present invention discloses a method of producing a water-soluble co-polyester resin. Particularly, the present invention relates to a method of producing a water-soluble co-polyester resin from reclaimed polyester. The present invention further relates to a water-soluble co-polyester coating with improved printability and metal adhesion properties.

BACKGROUND OF THE INVENTION

Polymers such as polyurethanes, co-polyesters, acrylics, and the like are known to be commonly used as binders for in-line as well as off-line coating. These polymers are chosen based on different fields of application. Specifically, polyurethane coating films can be used for direct heat sealing; the coating film of silicone oil can be used for release films and label films; the acrylic acid and co-polyester coating film is mainly applied to the fields of ink printing, electronic packaging and the like.

In recent years, water-based co-polyesters are being preferred over solvent-based co-polyesters as coating materials since they are environment-friendly. Moreover, the content of organic solvent in traditional solvent-based coating liquid is generally above 50%, and the content of organic solvent in aqueous coating liquid can be controlled below 10%. Thus, the emission of Volatile Organic Compounds (VOC) in the production and use processes is greatly reduced. Further, the coating has great advantages compared with polyurethane and polyacrylic acid materials. The water-based co-polyester coating also has the advantages of high glossiness, high fullness, strong adhesive force, and the like.

Water soluble co-polyester resins are generally amorphous polymers of relatively low molecular weight synthesized by polyesterification from polybasic acids and polyhydric alcohols. Several patents also disclose synthesis of water soluble co-polyester resins from recycled/ waste/ post-consumer polyester. Patent literature US5858551A discloses the synthesis of water-soluble polyester resins from recycled PET. Patent literature US4977191A describes a water-soluble or water-soluble polyester resin composition, comprising a reaction product of waste terephthalate polymer, glycol and polyol. However, it is still desired to produce water soluble co-polyester resins with improved surface properties such as ink adhesion and/or adhesive adhesion and/ or metal adhesion on the polyester film.

Keeping in mind, the present inventors have provided a method of producing a water-soluble co-polyester resin from reclaimed polyester. The water-soluble co-polyester coating having the said water-soluble co-polyester resin exhibits improved printability and metal adhesion properties. The present invention aims to solve the problems of environmental protection, cost reduction, VOC emission reduction and the like in the film coating industry.

SUMMARY OF THE INVENTION

The present invention discloses a water soluble co-polyester resin comprising a reaction product of reclaimed polyester, at least one diol, at least one diacid at least and or at least one triacid and/or tetraacid. The present invention discloses a water soluble co-polyester coating composition, comprising the water soluble co-polyester resin. The present invention also discloses a method of producing a water-soluble co-polyester resin. More particularly the present invention discloses to a method of producing a water-soluble co-polyester resin with reclaimed polyester. The method comprises steps of reacting a reclaimed polyester with glycol to produce a depolymerized polyester and then reacting the depolymerized polyester with a diacid and a diol to produce a polymerized product. The polymerized product is reacted with a tri-carboxylic acid or a tetracarboxylic acid to produce a water-soluble co-polyester resin.

The present invention also discloses a water-soluble co-polyester coating having the water- soluble co-polyester resin. The coated films provide improved printability and metal adhesion properties.

DETAILED DESCRIPTION OF THE INVENTION

While the disclosure is susceptible to various modifications and alternative forms, specific aspects thereof have been shown by way of examples and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention.

The biaxially oriented polyester (BOPET) film is an oriented polyester film produced by stretching the polyester in a machine direction followed by stretching in the transverse direction. The production of the polyester film begins when the melt of polyester from the extruder and die falls on the chill roller, to quench the melt and form an amorphous polyester, which is then oriented in a machined direction and then in the transverse direction to produce the biaxial oriented polyester film which is well known in the art. The biaxially oriented polyester so produced can be transparent or opaque or translucent. The biaxially oriented polyester so produced has excellent mechanical and thermal properties and is used for various applications like flexible packaging, industrial applications, etc.

BOPET film when used in flexible packaging can be used as it is or can be treated to improve their surface properties, for increasing the adhesion of ink and/or adhesive and / or metal on the surface. The BOPET film can be treated by corona or by coating. The treatment by corona or coating is applied either by in-line method or offline method. During the inline process the treatment is applied before the transverse orientation and during the production of the polyester film, while offline coating is done after the production of the film by offline coating method. During inline coating a very small quantity of coating is applied which leads to a very layer of coating deposition on the film. Generally inline coating method is preferred over offline coating method.

One aspect of the present invention discloses a water soluble co-polyester resin comprising a reaction product of: a. reclaimed polyester; b. at least one diacids and diols; and c. at least one triacid or tetraacid, wherein the weight % of reclaimed polyester is in the range of 5-50%, diol is in the range of 10-45%, and diacid is in the range of 10-60% and tricarboxylic acid and/or tetra carboxylic acid is in the range of 1 to 10%.

An embodiment of the present invention discloses a water soluble co-polyester resin, wherein reclaimed polyester is post consumable recycled polyester. Another embodiment of the present invention discloses a water soluble co-polyester resin, wherein diacid is selected from aromatic diacid, an aliphatic diacid and/or their esters.

Yet another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the aromatic diacid is selected from terephthalic acid, isophthalic acid and naphthalene dicarboxylic acid and/or their esters.

Another embodiment of the present invention discloses a water soluble co-polyester resin, wherein aliphatic diacid is selected from adipic acid, succinic acid, azelaic acid and sebacic acid and/or their esters.

Still another embodiment of the present invention discloses a water soluble copolyester resin, wherein the diol is aliphatic diol selected from ethylene glycol, diethylene glycol, propylene diol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol or combination thereof.

One another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the tri carboxylic acid or a tetra carboxylic acid is selected from citric acid, trimellitic acid, pyromellitic acid, naphthalene tetra carboxylic acid and/or their anhydrides.

Yet embodiment of the present invention discloses a water soluble co-polyester resin, wherein the mole ratio of total diol to total diacid is between 0.8 to 2.5, preferably 0.9 to 2.1, more preferably between 1.0 to 2.0 and the mole ratio of tri or tetra carboxylic acid to total acid is 0.075 to 0.125.

Still another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the Intrinsic Viscosity of resin is less than 1.2 dL/g and the acid value of resin is from 100 to 2000 mg equivalent of KOH per gram of sample.

Yet another embodiment of the present invention discloses a water soluble co-polyester resin, as and when used in compositions such as retort coating composition, printing composition or metallization of polyester film.

Another aspect of the present invention discloses a water soluble co-polyester resin comprising a reaction product of: a. reclaimed polyester; b.at least one diacids and diols; c.at least one triacid or tetraacid; and d. optionally a crosslinker, wherein the weight % of reclaimed polyester is in the range of 5-50%, the diol is in the range of 10-45%, diacid is in the range of 10-60% and tricarboxylic acid and/or tetra carboxylic acid is in the range of 1 to 10 % and/or crosslinker is in the range of 0 to 30%. An embodiment of the present invention discloses a water soluble co-polyester resin, wherein reclaimed polyester is post consumable recycled polyester.

Another embodiment of the present invention discloses a water soluble co-polyester resin, wherein diacid is selected from aromatic diacid, an aliphatic diacid and/or their esters.

Yet another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the aromatic diacid is selected from terephthalic acid, isophthalic acid, and naphthalene dicarboxylic acid and/or their esters.

Another embodiment of the present invention discloses a water soluble co-polyester resin, wherein aliphatic diacid is selected from adipic acid, succinic acid, azelaic acid and sebacic acid and/or their esters.

Still another embodiment of the present invention discloses a water soluble copolyester resin, wherein the diol is aliphatic diol selected from ethylene glycol, diethylene glycol, propylene diol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol or combination thereof.

One another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the tri carboxylic acid or a tetra carboxylic acid is selected from citric acid, trimellitic acid, pyromellitic acid, naphthalene tetra carboxylic acid and/or their anhydrides.

Yet embodiment of the present invention discloses a water soluble co-polyester resin, wherein the mole ratio of total diol to total diacid is between 0.8 to 2.5, preferably 0.9 to 2.1, more preferably between 1.0 to 2.0 and the mole ratio of tri or tetra carboxylic acid to total acid is 0.075 to 0.125.

Still another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the intrinsic Viscosity of resin is less than 1.2 dL/g and the acid value of resin is from 100 to 2000 mg equivalent of KOH per gram of sample.

Yet another embodiment of the present invention discloses a water soluble co-polyester resin, as and when used in compositions such as retort coating composition, printing composition or metallization of polyester film. Another aspect of the present invention discloses a water soluble co-polyester resin comprising a reaction product of: a. at least one diacid or diols; and b. at least one triacid or tetra acids, wherein weight % of diol is in the range of 20-50 %, and diacid is in the range of 50-90% and weight % of tricarboxylic acid and/or tetra carboxylic acid is in the range of 1 to 10 %.An embodiment of the present invention discloses a water soluble co-polyester resin, wherein reclaimed polyester is post consumable recycled polyester.

Another embodiment of the present invention discloses a water soluble co-polyester resin, wherein diacid is selected from an aromatic diacid and aliphatic diacid and/or their esters.

Yet another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the aromatic diacid is selected from terephthalic acid, isophthalic acid and naphthalene dicarboxylic acid and/or their esters.

Another embodiment of the present invention discloses a water soluble co-polyester resin, wherein aliphatic diacid is selected from adipic acid, succinic acid, azelaic acid and sebacic acid and/or their esters.

Still another embodiment of the present invention discloses a water soluble copolyester resin, wherein the diol is aliphatic diol selected from ethylene glycol, diethylene glycol, propylene diol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol or combination thereof.

One another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the tri carboxylic acid or a tetra carboxylic acid is selected from citric acid, trimellitic acid, pyromellitic acid, naphthalene tetra carboxylic acid and/or their anhydrides.

Yet embodiment of the present invention discloses a water soluble co-polyester resin, wherein the mole ratio of total diol to total diacid is between 0.8 to 2.5, preferably 0.9 to 2.1, more preferably between 1.0 to 2.0 and the mole ratio of tri or tetra carboxylic acid to total acid is 0.075 to 0.125.

Still another embodiment of the present invention discloses a water soluble co-polyester resin, wherein the intrinsic Viscosity of resin is less than 1.2 dL/g and the acid value of resin is from 100 to 2000 mg equivalent of KOH per gram of sample. Yet another embodiment of the present invention discloses a water soluble co-polyester resin, as and when used in compositions such as retort coating composition, printing composition or metallization of polyester film.

The present invention discloses the water soluble co-polyester resin which is produced by using reclaimed polyester, where other diacids and diols are added to the reclaimed polyester at high temperature to undergo depolymerization of reclaimed polyester.

Another aspect of the present invention discloses a method of producing a water soluble co- polyester resin, comprising steps:

(i) reacting a reclaimed polyester with a minimum of one diol at a temperature between 210 °C to 290°C for 1-3 hours to produce a depolymerized polyester,

(ii) reacting the depolymerized polyester with a minimum of one diacid and a minimum of one diol at a temperature between 225 °C to 300 °C for 2 to 3 hours to produce a polymerized product, characterized in that, the polymerized product is reacted with a minimum of one tri carboxylic acid or a minimum of one tetracarboxylic acid for 45 min to 2 hours to obtain a water soluble co-polyester resin.

One embodiment of the present invention discloses that the reclaimed polyester is post consumable recycled polyester. The reclaimed polyester refers to polyester objects like food containers, bottles, objects, films, fibers, etc., that have been disposed of after their initial use. Such objects are considered waste after their use and can be submitted for recycling. The use of reclaimed polyesters is an environmentally friendly option that helps to reduce landfills.

Another embodiment of the present invention discloses the diacid which is selected from an aromatic diacid and aliphatic diacid and/or their esters.

Yet another embodiment of the present invention discloses the aromatic diacids which are selected from but not limited to terephthalic acid, isophthalic acid, and naphthalene dicarboxylic acid and/or their esters.

One embodiment of the present invention discloses that the aliphatic acids are selected from but not limited to adipic acid, succinic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, oxalic acid, malonic acid etc. and/or their esters. Another embodiment of the present invention discloses that the diols can be aliphatic diols. The aliphatic diols can be selected from but not limited to ethylene glycol, diethylene glycol, propylene diol, butanediol, pentanediol, hexanediol, cyclohexane dimethanol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc or combination thereof.

Yet another embodiment of the present invention discloses that the tri carboxylic acid or a tetra carboxylic acid is selected from but not limited to citric acid, trimellitic acid, pyromellitic acid, naphthalene tetra carboxylic acid and/or their anhydrides.

One embodiment of the present invention discloses that the catalyst can be aluminum acetylacetonate and different types of titanium-based catalysts.

Another embodiment of the present invention discloses a catalyst for depolymerization is magnesium acetate in presence of polyphosphoric acid.

Yet another embodiment of the present invention discloses that the mole ratio of total diol to total diacid is between 0.8 to 2.5, preferably 0.9 to 2.1, more preferably between 1.0 to 2.0.

One embodiment of the present invention discloses that the mole ratio of tri or tetra carboxylic acid to total acid is 0.075 to 0.125.

Another embodiment of the present invention discloses that the catalyst for polymerization is antimony trioxide in presence of polyphosphoric acid.

The present invention further discloses a water soluble co-polyester resin, comprising a reaction product of 20-50% by weight of reclaimed polyester, 10-40% by weight of at least one diol, 5- 25% by weight of at least one diacid, tricarboxylic acid and/or tetra carboxylic acid.

The present invention further discloses a water soluble copolyester resin obtainable by the method of the present invention.

The present invention further discloses a water soluble copolyester coating composition, comprising the water soluble copolyester resin of the present invention and a crosslinker.

The water soluble copolyester resin can also be produced by using an acid and glycol combination instead of reclaimed polyester. The acid can be selected from but not limited to selected from terephthalic acid and/or isophthalic acid. The glycol can be selected from but not limited to ethylene glycol, neopentyl glycol or cyclohexane methanediol. The acid and glycol can be added to a mixture of terephthalic acid and ethylene glycol, or a mixture of isophthalic acid and ethylene glycol, or a mixture of terephthalic acid, isophthalic acid or ethylene glycol, or a mixture of terephthalic acid, neopentyl glycol and ethylene glycol, or a mixture of terephthalic acid, isophthalic acid, neopentyl glycol and ethylene glycol.

The acid can also be selected from other aliphatic or aromatic acids. The other aliphatic acids are derived from acids produced containing C2 to C15. More preciously, the aliphatic diacid contains carbon atoms from C2 to CIO. The aliphatic acids can be selected from but not limited to oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, maleic acid, fumaric acid, glutacoinic acid, etc. The other aromatic diacids can be selected from but are not limited to terephthalic acid, isophthalic acid, and 2,6 naphthalene dicarboxylic acid.

Other glycols can be selected from aliphatic glycols derived from C3 to C13, more preferably C3 to CIO glycols. The glycols can be selected from but not limited to propylene glycol, butanediols, pantanediol, hexanediol, heptanediol, octanediol, nonalediol, decanediol, neopentyl glycol, cyclohexanemethandiol etc.

The present invention discloses a mixture of aliphatic and aromatic dicarboxylic acid. The aliphatic dicarboxylic acids used are generally from 0.5 wt% to 50 wt%. More preferably the aliphatic dicarboxylic acid used is 1.0 wt% to 40 wt%, and most preferably the aliphatic dicarboxylic acid used is 1.0 wt% to 30wt%. The aliphatic dicarboxylic acid can be used alone or in combination thereof. The aromatic dicarboxylic acid used is 50 wt% to 99.5 wt%, more preferably between 60wt% to 99 wt% and most preferably between 70wt% to 99wt%. The aromatic dicarboxylic acid can be used alone or in combination thereof.

The present invention discloses the use of aliphatic glycols alone or as a mixture thereof. The aliphatic glycol used is ethylene glycol and /or a mixture of ethylene glycol with other aliphatic glycols. The ethylene glycol used in the present invention is preferable upto 60wt% more preferably upto 55wt% and more preferably upto 50wt%. The other aliphatic diols used are a combinations of various diols upto 50wt% more preferably upto 45wt% and most preferably upto 40wt%.

For the preparation of water soluble copolyester resin, the mixture of diacid and glycols is added to the reaction chamber such that the mole ratio of diol to diacid be between 1.0 to 2.0, more preferably between 1.0 to 1.8 and most preferably between 1.0 to 1.5. The ratio of diol to diacid during the polymerization reaction should be taken considering all components added in the reaction. The components can be diacids or diols present in reclaimed polyester or other diacids or other diols as mentioned in the invention.

The catalyst can be selected from but not limited to antimony or cobalt or zinc or tin or magnesium or manganese or calcium or titanium or aluminum. Either of these catalysts can be used alone or in combination thereof. The catalyst used is most preferably below 1500 ppm or more preferably below 1200ppm. The most common catalyst used is antimony trioxide. Other catalysts that are preferred are aluminum acetylacetonate and different types of titanium-based catalysts commonly available under the trade name of or etc. The common type of tyzor catalyst that is used in the production of copolyester are Tyzor Activate 422, 420, 428 or Tyzor TE, Tyzor TnBT, etc. Stabilizers used for producing water soluble copolyester resin can be orthophosphoric acid or polyphosphoric acid or Tris(nonyl phenyl) phosphite (TNPP) or others as known in the art.

The diacids and diols as mentioned above are allowed to react in presence of a catalyst and stabilizer to produce a copolyester. During this polymerization process, water is liberated out. This polymer so produced is not suitable for water dispersion and will not disperse in water.

The produced polymer is allowed to react with tri carboxylic acids or tetracarboxylic acids to prepare water soluble copolyester resin. The tricarboxylic acids can be selected from but not limited to citric acid or trimellatic acid or their anhydrides, while tetra carboxylic acids can be selected from but not limited to pyromellitic acid or naphthalene tetra carboxylic acid or their anhydrides. The tri or tetra carboxylic acids can be used alone or in combination thereof.

The intrinsic viscosity of water soluble copolyester resin after the addition of tri or tetra carboxylic acids remains below 1.20 dL/g and more preferably below 1.0 dL/g. The acid value of the said water-soluble copolyester resin is above 100 mg equivalent of KOH per gram of sample or most probably above 150 mg equivalent of KOH per gram of sample. It has been found that the higher the acid value of the polymer, it will dissolve easily in water. It has been found that if the acid value is 2000 mg equivalent of KOH per gram of sample, then the resin does not remain in solid form and will become tacky.

Synthesis of water soluble copolyester resin:

1) Depolymerisation of reclaimed copolyester

The depolymerization process involves the use of reclaimed polyester along with different glycols to produce depolymerized content. The reclaimed polyester used is post consumable recyclable polyester which is mixed with other diols. The preferred diols used are aliphatic diols. Out of these the most preferred diols used during the depolymerisation process are ethylene glycol and other aliphatic glycols. Other aliphatic glycols that can be used are 1,4 butanediol, 1,5 pentanediol, 1,6 hexanediol, neopentyl glycol and/or cyclohexanemethandiol. The mole ratio of total diol to total diacid is between 1.0 to 2.0, more preferably between 1.0 to 1.5. the catalyst used for depolymerization is magnesium acetate in presence of polyphosphoric acid. The magnesium acetate used is below 1000 ppm, more preferably below 600ppm. Polyphosphoric acid used is below lOOOppm, more preferably below 700ppm. The depolymerization reaction is carried out at a temperature between 210 °C to 290 °C. The depolymerization reaction is carried out for 1-3 hours.

2) Polymerisation of depolymerized polymer

The product obtained from depolymerization is then subjected to polycondensation after the addition of diacids and diols. The diacids added are aromatic diacids and/or aliphatic diacids. The aromatic diacids used are terephthalic acid and/or isophthalic acid. The aliphatic diacids used are adipic acid, succinic acid, azelaic acid and/or sebacic acid. The mole ratio of total diol to total diacid be kept between 1.0 to 2.0, preferably between 1.0 to 1.5. The catalyst used for polymerization is antimony trioxide in presence of polyphosphoric acid. The antimony trioxide used is below 1000 ppm, preferably below 600 ppm. Polyphosphoric acid used is below 1000 ppm, preferably below 700 ppm. The polymerization reaction is carried out at a temperature between 225 °C to 300 °C. This reaction is carried out for 2 to 3 hrs.

3) Final polymer preparation

To this polymerization product, tri carboxylic acids or tetracarboxylic acids are added and allowed to react for 45 min to 2 hours. The tricarboxylic acids or tetracarboxylic acids can be added such that the mole ratio between diol to diacid be between 0.8 to 1.8, preferably between 0.9 to 1.4. The preferred component is trimellitic acid or trimellitic anhydride. The tricarboxylic acid or tetracarboxylic acid can be added such that the total mole of tri or tetracarboxylic acid is between 0.075 to 0.125 mole to total mole of acid in the water soluble copolyester.

The produced water soluble copolyester resin can be used to coat polyester film via the inline method and for printing and retort coating. The water soluble copolyester resin can also be used for the metallization of the polyester film wherein the metalized film has OTR and WVTR below 1.0. EXAMPLES

The applicant would like to mention that the examples and comparative studies are mentioned to show only those specific details that are pertinent to understanding the aspects of the present invention so as not to obscure the invention with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

The following examples are given to illustrate the present invention and should not be construed to limit the scope of the present invention.

1) The water soluble copolyester resin is prepared such that 18 kgs of reclaimed polyester, 9.1 kg of purified terephthalic acid (PT A), 6.2 kg of isophthalic acid (IPA), 1.8 kg of sebacic Acid, 4.5 kg of hexanediol, 2.5 kgs of neopentyl glycol (NPG) and 1.3 kg of trimellitic acid is used.

2) The water soluble copolyester resin is prepared such that 18 kgs of reclaimed polyester, 9.1 kg of PTA, 6.2 kg of IPA, 1.8 kg of sebacic Acid, 3.01 kg of butanediol, 2.5 kgs of NPG and 1.3 kg of trimellitic acid is used.

3) The water soluble copolyester resin is prepared such that 18 kgs of reclaimed polyester, 9.1 kg of PTA, 6.2 kg of IPA, 1.7 kg of Azelaic acid, 4.5 kg of hexanediol,

2.5 kgs of NPG and 1.3 kg of trimellitic acid is used.

4) The water soluble copolyester resin is prepared such that 18 kgs of reclaimed polyester, 9.1 kg of PTA, 6.2 kg of IPA, 1.7 kg of azelaic acid, 3.01kg of butanediol,

2.5 kgs of NPG and 1.3 kg of trimellitic acid is used.

5) The water soluble copolyester resin is prepared such that 18 kgs of reclaimed polyester, 7.1 kg of PTA, 8.2 kg of IPA, 1.7 kg of azelaic acid, 3.01 kg of butanediol,

3.5 kgs of cyclohexanedimethanol (CHDM) and 1.3 kg of trimellitic acid is used.

6) The water soluble copolyester resin is prepared such that 12 kgs of reclaimed polyester, 7.1 kg of PTA, 8.2 kg of IPA, 1.7 kg of azelaic acid, 3.01 kg of butanediol,

3.5 kgs of CHDM and 1.3 kg of trimellitic acid is used.

7) The water soluble copolyester resin is prepared such that 18 kgs of reclaimed polyester, 7.1 kg of PTA, 8.2 kg of IPA, 1.7 kg of azelaic acid, 3.01 kg of butanediol,

3.5 kgs of CHDM and 1.8 kg of trimellitic acid is used.

8) The water soluble copolyester resin is prepared such that 25.7 kgs of PTA and 12.4 kg of ethylene glycol, 6.2 kg of IPA, 1.8 kg of sebacic Acid, 6.5 kg of hexanediol,

2.5 kgs of NPG and 1.3 kg of trimellitic acid is used. 9) The water soluble copolyester resin is prepared such that 25.7 kgs of PTA and 12.4 kg of ethylene glycol, 6.2 kg of IPA, 1.7 kg of azelaic acid, 4.9 kg of butanediol,

2.5 kgs of NPG and 1.3 kg of trimellitic acid is used.

10) The water soluble copolyester resin is prepared such that 25.7 kgs of PTA and 12.4 kg of ethylene glycol, 6.2 kg of IPA, 1.7 kg of azelaic acid, 4.9 kg of butanediol,

2.5 kgs of NPG and 1.75 kg of trimellitic acid is used.

11) The water soluble copolyester resin is prepared such that 18 kgs of reclaimed polyester, 7.1 kg of PTA, 8.2 kg of IPA, 1.7 kg of azelaic acid, 4.9 kg of butanediol,

3.5 kgs of CHDM and 1.95 kg of trimellitic acid is used.

12) The water soluble copolyester resin is prepared such that 12 kgs of reclaimed polyester, 7.1 kg of PTA, 8.2 kg of IPA, 1.7 kg of azelaic acid, 4.9 kg of butanediol,

3.5 kgs of CHDM and 1.8 kg of trimellitic acid is used.

Tests performed:

1) Intrinsic viscosity (I.V): Approx. 0.15 gms of the polymer sample in a 100ml Erlenmeyer flask is allowed to reflux till dissolution in 30ml of phenol and tetrachloroethane solvent mixture. Using a ubeholde viscometer, which is maintained at 25 °C using water batch, the efflux time of solution and solvent is noted to measure I.V.

I.V is calculated using the below calculation

_/{(R.V.-l)* 1.48+1} -1

I.V. = -

1.48 * WT. OF POLYMER (0 .2500 )

R.V. = T2/T1

Where T1 = Efflux time of solvent

T2 = Efflux time of solution

2) End group analysis: Approx. 1.5 gms of the polymer sample in a 100 ml Erlenmeyer flask is added containing 30ml of phenol : chloroform mixture (40:60 wt%) and refluxed till dissolution is complete. After cooling, 0.3 ml of tertabromophenol blue indicator is added and allowed to titrate with 0.02NKOH solution till color changes from yellow to blue through the green.

The end group is calculated as

N * 1000 (V soln. - V blank) COOH GROUPS = - mili. eq. /kg.

Wt. of sample

Where N = Normality of KOH solution.

V soln. = ml of KOH soln, consumed for the sample.

V blank = ml of KOH soln, consumed for blank.

Results

Preparation of coating solution: The coating solution before inline coating over polyester film is prepared by dissolving the water soluble copolyester resin in water and further mixing it with melamine formaldehyde cross linkers like cymel 327 or 303.

The water soluble copolyester resin is dissolved in water at a temperature of 90 °C for 2 hours. Co-solvent-like isopropyl alcohol can also be added. The isopropyl alcohol amount is such that it should not be greater than 6 wt% in the final coating solution.

The final coating solution is prepared such that the total solid content in the final solution be approx. 10wt% and for each 1 kg of water soluble copolyester resin approx. 0.15 kg of cymel 327 is added. The water soluble copolyester resin coating so obtained is allowed to coat inline over the polyester film. The coating GSM targeted is approx. 40 nm. The coated film is then tested for printability and also allowed for aluminum metallization.

The coated film is printed using vinyl ink and checked for tape test using 3M 610 tape. The printable sample is also put to retort autoclave at 121 °C, for 30 min and checked for ink adhesion using 3M 610 tape.

The inline coated film is subjected to metallization for an optical density of 2.5 and checked for metal bond adhesion as per the amical method and barrier test using a mocon OTR tester.

The results of printability and metallization are mentioned below

The above examples clearly state that desired water soluble copolyester resin can be prepared using diacids and diols in various proportions along with multifunctional acid groups. The water soluble copolyester resin prepared from the method of the present invention exhibits improved printability and metal adhesion properties.

The advantages of the disclosed invention are thus attained in an economical, practical, and facile manner. While examples have been shown and described, it is to be understood that various further modifications and additional configurations will be apparent to those skilled in the art.