FIELD OF THE INVENTION:
The present invention relates to a solvent base heat-seal lacquer composition for sealing polyester to paper.
BACKGROUND OF THE INVENTION:
US2015275032A1 discloses a solvent based low temperature heat seal coating solution which contains an amorphous or semi-crystalline polyester or co-polyester resin, tackifier, anti-blocking agent, and solvent, wherein the heat seal resin provides adhesion to substrates including paper, polyester, polypropylene, polyvinyl chloride, nylon films, metal foils, etc.
US2005249903A1 discloses heat-seal compositions comprising ethylene/vinyl acetate copolymers, tackifying resins and optionally polyolefins (for example, polyethylene and polypropylene). The tackifying resins include coumarone-indene resins, terpene resins, utadiene-styrene resins, hydrocarbon resins such as polybutenes, low molecular weight styrene hard resins, and rosin materials.
US2005159549A1 discloses compositions of ethylene/(meth)acrylate copolymers, polyolefins (e.g., polyethylene and polypropylene), optional tackifier resins and optional fillers for peelable heat seals, wherein the tackifiers include para-coumarone-indene resins, terpene resins, butadiene-styrene resins, polybutadiene resins, hydrocarbon resins, rosins.
JP3497058B2 discloses a thermoplastic polymer composition, which contains a thermoplastic polyurethane (A) and a block copolymer comprising an aromatic vinyl polymer block and conjugated diene polymer block and/or hydrogenation product of the block copolymer (B) in a wt. ratio of A/B of (20/80)-(80/20). The polyurethane is a reaction product of a high-molecular polyol having a number average mol. wt. of 500-10,000, an organic diisocyanate.
JP1917226C discloses a resin composition consisting of a polyester elastomer, a thermoplastic polyurethane elastomer and a specified graft copolymer, wherein 95-30wt% vinyl chloride is grafted onto 5-70wt% ethylene/vinyl acetate copolymer having a vinyl acetate content of 10-50wt% to obtain a graft copolymer (C). lOOpts.wt. polyester elastomer (A) having a m. p. of 80-200 deg.C and a weight ratio

of soft segment to hard segment of 85/15-10/90 is blended with a thermoplastic polyurethane elastomer (B) having a molar ratio of isocyanate group to hydroxyl group of 0.9-1.2.
US2008139734A1 discloses a sealing material composition comprising an alkenyl group-terminated isobutylene-based polymer (A), a thermoplastic resin (B) and a compound (C) containing at least two hydrosilyl groups within the molecule thereof.
CN103952103A discloses a hot-seal adhesive is prepared from the following raw materials by weight: 23-26 parts of a thermoplastic acrylic acid resin, 8-10 parts of a thermoplastic polyurethane resin, 12-14 parts of polyisobutylene, 10-14 parts of ethyl acetate, 42-45 parts of butyl acetate, 2-3 parts of anilino-methyl-triethoxysilane, 3-4 parts of nanometer silica, 2-3 parts of vinyl propionate, 1-2 parts of polyoxyethylene lauryl ether, 1-2 parts of an antioxidant 010, and 4-5 parts of a tackifying auxiliary agent.
CN101914360A discloses a low-temperature hot-seal adhesive, which consists of the following raw materials in percentage by weight: 10 to 30 percent of main resin, 5 to 15 percent of auxiliary resin, 0.2 to 3 percent of plasticizer, 0.2 to 1 percent of surface modifier and 60 to 80 percent of solvent. The main resin is one or two of a polyester resin, a plastic polyurethane resin and a plastic acrylic resin with the molecular size of between 15,000 and 25,000; and the auxiliary resin is one of a vinyl chloride copolymer resin, a plastic polyurethane resin and an epoxy resin with the molecular size of between 10,000 and 20,000.
The solvent base heat-seal lacquer compositions available in the industry show poor adhesion between polyester films and paper.
OBJECTS OF THE INVENTION:
The principal objective of the present invention is to provide a solvent base heat-seal lacquer composition for superior adhesion between a polyester film and a paper-based film or paper-based sheet.
Another objective of the present invention is to provide a solvent base heat-seal lacquer composition that exhibits excellent heat seal strength between a polyester

film and a paper-based film or paper-based sheet even after a longer time period of about six months.
SUMMARY OF THE INVENTION:
The present invention relates to a solvent base heat-seal lacquer composition for sealing polyester to a paper-based film or paper-based sheet.
The solvent base heat-seal lacquer composition comprising about 45 to 65% by weight of a varnish A, about 35 to 55% by weight of a varnish B, and about 0.5 to 1.0% by weight of additives,
wherein the varnish A includes about 15 to 35% by weight of a thermoplastic polyurethane resin (TPU), and about 65 to 85% by weight of an aromatic and/ or aliphatic hydrocarbon solvent,
wherein the varnish B includes about 15 to 35% by weight of a copolymer containing at least vinyl chloride and vinyl acetate monomer units, wherein the vinyl chloride units form at least 70% of the copolymer structure, and about 65 to 85% by weight of an aromatic and/ or aliphatic hydrocarbon solvent.
In another aspect of the invention, a method of preparation of the solvent base heat-seal lacquer composition is also provided.
The method of preparation of the solvent base heat-seal lacquer composition comprising:
a. mixing about 15 to 35% by weight of a thermoplastic polyurethane resin
(TPU), and about 65 to 85% by weight of an aromatic and/ or aliphatic
hydrocarbon solvent to form a varnish A,
b. mixing about 15 to 35% by weight of a copolymer containing at least vinyl
chloride and vinyl acetate monomer units, wherein the vinyl chloride units
form at least 70% of the copolymer structure, and about 65 to 85% by weight
of an aromatic and/ or aliphatic hydrocarbon solvent to form a varnish B,
c. forming a varnish mixture by mixing about 45 to 65% by weight of the varnish
A, and about 35 to 55% by weight of the varnish B; and
d. adding about 0.5 to 1.0% by weight of additives to the varnish mixture.

The fraction of the thermoplastic polyurethane resin (TPU) in the varnish A, and the fraction of the copolymer containing at least vinyl chloride and vinyl acetate monomer units in the varnish B are solid content weight fractions.
The aromatic and/ or aliphatic solvents in the varnish A and varnish B are selected from methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, toluene and mixtures thereof, preferably the solvent in the varnish A and varnish B is methyl ethyl ketone.
DETAILED DESCRIPTION OF THE INVENTION:
The preferred embodiments of the present invention will be described in detail with the following disclosure and examples. The foregoing general description and the following detailed description are provided to illustrate only some embodiments of the present invention and not to limit the scope of the present invention. The invention is capable of other embodiments and can be carried out or practiced in various other ways.
Unless otherwise specified, all the technical and scientific terms used herein have the same meaning as is generally understood by a person skilled in the art pertaining to the present invention. All the patents published patent applications referred to throughout the entire disclosure herein, unless specified otherwise, are incorporated by reference in their entirety.
It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from greater than 0 % by weight to about 25 % by weight should be interpreted to include not only the explicitly recited limits of greater than 0 % by weight to about 25 % by weight, but also to include individual values, such as 0.05 % by weight, 0.9 % by weight, 7 % by weight, 21 % by weight, etc., and sub-ranges, such as from about 1 % by weight to about 24 % by weight, from about 5 % by weight to about 20 % by weight, etc. Furthermore, when "about" is utilized to describe a value, this is meant to encompass minor variations (up to +/-10%) from the stated value.
Reference throughout this specification to "one embodiment," "an embodiment," "one example," or "an example" means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one

embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment," "in an embodiment," "one example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and/or sub-combinations in one or more embodiments or examples. In addition, it should be appreciated that if any figures are provided herewith, they are for explanation purposes to persons ordinarily skilled in the art and that the drawings of them are not necessarily drawn to scale.
In this specification, certain aspects of one embodiment include process steps and/or operations and/or instructions described herein for illustrative purposes in a particular order and/or grouping. However, the particular order and/or grouping shown and discussed herein are illustrative only and not limiting. Those of skill in the art will recognise that other orders and/or grouping of the process steps and/or operations and/or instructions are possible and, in some embodiments, one or more of the process steps and/or operations and/or instructions discussed above can be combined and/or deleted. In addition, portions of one or more of the process steps and/or operations and/or instructions can be re-grouped as portions of one or more other of the process steps and/or operations and/or instructions discussed herein. Consequently, the particular order and/or grouping of the process steps and/or operations and/or instructions discussed herein do not limit the scope of the disclosure.
The present invention relates to a solvent base heat-seal lacquer composition for sealing polyester to a paper-based film or paper-based sheet.
The solvent base heat-seal lacquer composition comprising about 45 to 65% by weight of a varnish A, about 35 to 55% by weight of a varnish B, and about 0.5 to 1.0% by weight of additives,
wherein the varnish A includes about 15 to 35% by weight of a thermoplastic polyurethane resin (TPU), and about 65 to 85% by weight of an aromatic and/ or aliphatic hydrocarbon solvent,
wherein the varnish B includes about 15 to 35% by weight of a copolymer containing at least vinyl chloride and vinyl acetate monomer units, wherein the vinyl chloride

units form at least 70% of the copolymer structure, and about 65 to 85% by weight of an aromatic and/ or aliphatic hydrocarbon solvent.
The fraction of the thermoplastic polyurethane resin (TPU) in the varnish A, and the fraction of the copolymer containing at least vinyl chloride and vinyl acetate monomer units in the varnish B are solid content weight fractions.
The aromatic and/ or aliphatic solvents in the varnish A and varnish B are selected from methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, toluene and mixtures thereof, preferably the solvent in the varnish A and varnish B is methyl ethyl ketone.
In another aspect of the invention, a method of preparation of the solvent base heat-seal lacquer composition is also provided.
The method of preparation of the solvent base heat-seal lacquer composition comprising:
a. mixing about 15 to 35% by weight of a thermoplastic polyurethane resin
(TPU), and about 65 to 85% by weight of an aromatic and/ or aliphatic
hydrocarbon solvent to form a varnish A,
b. mixing about 15 to 35% by weight of a copolymer containing at least vinyl
chloride and vinyl acetate monomer units, wherein the vinyl chloride units
form at least 70% of the copolymer structure, and about 65 to 85% by weight
of an aromatic and/ or aliphatic hydrocarbon solvent to form a varnish B,
c. forming a varnish mixture by mixing about 45 to 65% by weight of the varnish
A, and about 35 to 55% by weight of the varnish B; and
d. adding about 0.5 to 1.0% by weight of additives to the varnish mixture.
The fraction of the thermoplastic polyurethane resin (TPU) in the varnish A, and the fraction of the copolymer containing at least vinyl chloride and vinyl acetate monomer units in the varnish B are solid content weight fractions.
The aromatic and/ or aliphatic solvents in the varnish A and varnish B are selected from methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, toluene and mixtures thereof, preferably the solvent in the varnish A and varnish B is methyl ethyl ketone.
According to another aspect of the present invention an article is made by laminating

a polyester film to a paper-based film or a paper-based sheet with the help of the solvent base heat-seal lacquer composition of the present invention.
The polyester film is preferably polyethylene terephthalate (PET), and the paper-based film or the paper-based sheet is selected from a cardboard, a coated paper, an uncoated paper, or a paperboard.
Thermoplastic polvurethane resin (TPU)
TPU is a block copolymer comprising of alternating sequences of hard and soft segments or domains formed by the reaction of (1) diisocyanates with short-chain diols (so-called chain extenders) and (2) diisocyanates with long-chain diols. By varying the ratio, structure and/or molecular weight of the reaction compounds, an enormous variety of different TPU can be produced.
Gel permeation chromatography (GPC) was used to determine the number average molecular weight (Mn) of thermoplastic polyurethane (TPU). GPC was performed on an Agilent 1100 series instrument (Agilent Technologies Inc, Santa Clara, Calif.) with both a refractive index and UV detector and three phenogel columns (102A, 104A and 105A pore sizes, Torrence, Calif.) kept at 50° C. TPU samples were dissolved at 20 mg/ml in THF containing 0.75 ul/ml benzonitrile internal standard, and 30 uL was injected into the system at a flow rate of 1 mL/min. The Mn was calculated relative to polystyrene standards (Fluka, Buchs, Switzerland) using the GPC software (ChemStation Addon Rev. A.02.02).
The TPU used in the Varnish A of the present invention has a measured number average molecular weight (Mn) of about 100,000 to 200,000 daltons. The preferred TPU used in the Varnish A of the present invention has a number average molecular weight (Mn) of about 120,000 to 180,000 daltons, and more preferably about 130,000 to 150,000 daltons.
Copolymer containing at least vinyl chloride and vinyl acetate monomer units
The copolymer containing at least vinyl chloride and vinyl acetate monomer units used in the Varnish B of the present invention may be a carboxylate-containing terpolymer of vinyl chloride (VC), vinyl acetate (VAc) and a dicarboxylic acid, which has a weight average molecular weight (Mw) (according to Size Exclusion Chromatography (SEC)-Polystyrene standard) of about 50,000 to 100,000 daltons,

more preferably about 60,000. to 90,000 daltons, and most preferably about 60,000 to 80,000 daltons.
The copolymer containing at least vinyl chloride and vinyl acetate monomer units used in the Varnish B of the present invention is selected from several VINNOL® series copolymers produced by Wacker Chemie AG such as VINNOL® H 15/45 M, VINNOL® E 15/45 M, and VINNOL® E 18/38. M. The VINNOL® H 15/45 M is a copolymer of approx. 84 wt.% vinyl chloride (VC), approx. 15 wt.% of vinyl acetate (VAc) and 1 wt.% of dicarbonic acid produced through suspension polymerisation. VINNOL® E 15/45 M is a copolymer of approx. 84 wt.% vinyl chloride (VC), approx. 15 wt.% of vinyl acetate (VAc) and 1 wt.% of dicarbonic acid produced through emulsion polymerisation. VINNOL® E 18/38 is a copolymer of approx. 82 wt.% vinyl chloride (VC) and approx. 18 wt.% of vinyl acetate (VAc) produced through emulsion polymerisation.
Preferably the copolymer containing at least vinyl chloride and vinyl acetate monomer units used in the Varnish B is selected from VINNOL® H 15/45 M or VINNOL® E 15/45 More preferably the copolymer containing at least vinyl chloride and vinyl acetate monomer units used in the Varnish B is VINNOL® H 15/45 M.
Additives:
The additives in the solvent base heat-seal lacquer composition of the present invention may be selected from a levelling agent, a wetting agent, a filler, an adhesion promoter, a defrother (anti-foaming agent), an antistatic agent, a viscosity modifier or a combination thereof, or any other additives may be added to provide a specific functions.
Examples:
The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the invention without being limited to the specific examples given here.
Preparation of Varnish-A
About 65 to 85 kg of methyl ethyl ketone solvent was taken in a drum, and about 15 to 35 kg of thermoplastic polyurethane resin (TPU) was added to the solvent to form Varnish A. The different formulations of Varnish-A prepared are shown in the Examples 1 to 5 in Table 1.

Preparation of Varnish B
About 65 to 85 kg of methyl ethyl ketone solvent was taken in a drum, and about 15 to 35 kg of VINNOL® H 15/45 M was added to the solvent to form Varnish B. The different formulations of the Varnish B prepared are shown in the Examples 6 to 10 in Table 2.
Table 2
Preparation of the solvent base heat-seal lacquer composition Examples 11 to 15
The most preferred embodiments of the invention to prepare the solvent base heat-seal lacquer composition using Varnish A-3 and Varnish B-3 are given in examples 11 to 15 in table 3 depicted as HSL-1 for Heat-seal-lacquer 1, HSL-2 for Heat-seal-lacquer-2, HSL-3 for Heat-seal-lacquer-3, HSL-4 for Heat-seal-lacquer-4, HSL-5 for Heat-seal-lacquer-5.

Preparation of the solvent base heat-seal lacquer composition Examples 16 to 20
The most preferred embodiments of the invention to prepare the solvent base heat-seal lacquer composition using Varnish A-4 and Varnish B-4 are given in examples 16 to 20 in table 4 depicted as HSL-6 for Heat-seal-lacquer 6, HSL-7 for Heat-seal-lacquer-7, HSL-8 for Heat-seal-lacquer-8, HSL9 for Heat-seal-lacquer-9, HSL-10 for Heat-seal-lacquer-10.
Table 4
Laminate article:
A laminate article is formed in the following way.
a. a base layer of a polyethylene terephthalate (PET) film,
b. a layer of solvent base heat-seal lacquer composition applied on the
polyester film; and

c. a paper-board laminated above the solvent base heat-seal lacquer composition.
The article can be expressed as PET/ heat-seal lacquer (HSL)/ paper-board.
Preparation of the PET/ HSL/ paper-board article
The preferred embodiments of the polyester/ heat-seal lacquer (HSL)/ paper-board articles made from HSL of examples 11 to 15 are given in examples 21 to 25 in table 5 depicted as Article-1, Article-2, Article-3, Article-4, and Article-5.
Table 5
Preparation of the PET/ HSL/ paper-board article
The preferred embodiments of the polyester/ heat-seal lacquer (HSL)/ paper-board articles made from HSL of examples 16 to 20 are given in examples 26 to 30 in table 6 depicted as Article-6, Article-7, Article-8, Article-9, and Article-10.
Table 6

Product evaluation of heat-seal lacquer composition:
The solvent base heat-seal lacquer compositions of examples 11 to 15 were evaluated for their performance, and the evaluation results have been provided in the following Table 7.
Table 7
Rating: 1=Poor; 5=Excellent
The solvent base heat-seal lacquer compositions of examples 16 to 20 were evaluated for their performance, and the evaluation results have been provided in the following Table 8.
Table 8
Rating: 1=Poor; 5=Excellent

Product evaluation of the PET/ HSL/ paper-board article:
The PET/ HSL/ paper-board articles (Article 1 to Article 5) of examples 21 to 25 were evaluated for their performance, and the evaluation results have been provided in the following Table 9.
Table 9
* Rating: 1=Poor; 5=Excellent
The PET/ HSL/ paper-board articles (Article 6 to Article 10) of examples 26 to 30 were evaluated for their performance, and the evaluation results have been provided in the following Table 10.
Table 10
* Rating: 1=Poor; 5=Excellent
Advantages:
The solvent base heat-seal lacquer composition of the present invention has the following advantages:

a. exhibits good adhesiveness between polyester film and paper-board.
b. shows good bond strength between polyester film and paper-board even after
a time period of six months.
Applications:
The end use of these polyester and paper-based film / sheet laminates are intended for packaging applications of items such as food, drinks, pharmaceutical and other medical products, other suitable food packaging and non- food packaging applications can be envisaged by a person skilled in the art.
Although the present disclosure is described in terms of certain preferred embodiments and examples, other embodiments and examples will be apparent to those of ordinary skill in the art, given the benefit of this disclosure, including embodiments and examples that do not provide all of the benefits and features set forth herein, which are also within the scope of this disclosure. It is to be understood that other embodiments may be utilized, without departing from the true spirit and scope of the present invention being indicated by the following claims.

We claim:
1. A solvent base heat-seal lacquer composition comprising:
about 45 to 65% by weight of a varnish A, about 35 to 55% by weight of a varnish B, and about 0.5 to 1.0% by weight of at least one additive,
wherein, the varnish A includes about 15 to 35% by weight of a thermoplastic polyurethane resin (TPU), and about 65 to 85% by weight of an aromatic and/ or aliphatic hydrocarbon solvent,
wherein, the varnish B includes about 15 to 35% by weight of a copolymer containing at least vinyl chloride and vinyl acetate monomer units, wherein the vinyl chloride units form at least 70% of the copolymer structure, and about 65 to 85% by weight of an aromatic and/or aliphatic hydrocarbon solvent,
wherein, the fraction of the thermoplastic polyurethane resin (TPU) in the varnish A, and the fraction of the copolymer containing at least vinyl chloride and vinyl acetate monomer units in the varnish B are solid content weight fractions.
2. The solvent base heat-seal lacquer composition according to claim 1, wherein, the TPU in the varnish A has a number average molecular weight (Mn) of about 100,000 to 200,000 daltons, more preferably about 120,000 to 180,000 daltons, and most preferably about 130,000 to 150,000 daltons.
3. The solvent base heat-seal lacquer composition according to claim 1, wherein, the copolymer containing at least vinyl chloride and vinyl acetate monomer units in the varnish B is a terpolymer of vinyl chloride (VC), vinyl acetate (VAc) and a dicarboxylic acid, having a weight average molecular weight (Mw) of about 50,000 to 100,000 daltons, more preferably about 60,000 to 90,000 daltons, and most preferably about 60,000 to 80,000 daltons.
4. The solvent base heat-seal lacquer composition according to claim 1, wherein, the aromatic and/ or aliphatic solvents in the varnish A and varnish B are selected from methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, toluene and mixtures thereof, preferably the solvent in the varnish A and varnish B is methyl ethyl ketone.

5. The solvent base heat-seal lacquer composition according to claim 1, wherein, the additive is selected from at least one of a levelling agent, a wetting agent, a filler, an adhesion promoter, a defrother (anti-foaming agent), an antistatic agent, a viscosity modifier or a combination thereof.
6. A method of preparation of a solvent base heat-seal lacquer composition comprising:
a. mixing about 15 to 35% by weight of a thermoplastic polyurethane resin
(TPU), and about 65 to 85% by weight of an aromatic and/or aliphatic
hydrocarbon solvent to form a varnish A,
b. mixing about 15 to 35% by weight of a copolymer containing at least vinyl
chloride and vinyl acetate monomer units, wherein the vinyl chloride units
form at least 70% of the copolymer structure, and about 65 to 85% by weight
of an aromatic and/ or aliphatic hydrocarbon solvent to form a varnish B,
c. forming a varnish mixture by mixing about 45 to 65% by weight of the varnish
A, and about 35 to 55% by weight of the varnish B; and
d. adding about 0.5 to 1.0% by weight of additives to the varnish mixture,
wherein, the fraction of the thermoplastic polyurethane resin (TPU) in the varnish A, and the fraction of the copolymer containing at least vinyl chloride and vinyl acetate monomer units in the varnish B are solid content weight fractions.
7. The method of preparation of the solvent base heat-seal lacquer composition according to claim 6, wherein, the aromatic and/ or aliphatic solvents in the varnish A and varnish B are selected from methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, toluene and mixtures thereof, preferably the solvent in the varnish A and varnish B is methyl ethyl ketone.
8. The method of preparation of the solvent base heat-seal lacquer composition according to claim 6, wherein, the additive is selected from at least one of a levelling agent, a wetting agent, a filler, an adhesion promoter, a defrother (anti-foaming agent), an antistatic agent, a viscosity modifier or a combination thereof.
9. A laminate article comprising:
a. a base layer of a polyethylene terephthalate (PET) film,
b. a layer of solvent base heat-seal lacquer composition of claim 1 applied on
the PET film; and

c. a layer of paper-based film or a paper-based sheet is laminated above the solvent base heat-seal lacquer composition.
10. The laminate article according to claim 9, wherein the paper-based film or sheet is selected from a cardboard, an uncoated paper, a coated paper or a paperboard.