Low melt copolyetherester, process for preparing, and implementation thereof

Abstract

The present invention discloses a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% diethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400 to polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170⁰C.

Description

LOW MELT COPOLYETHERESTER, PROCESS FOR PREPARING, AND IMPLEMENTATION THEREOFFIELD OF THE INVENTION:

[0001] The present invention relates to the field of a low melt copolyetherester. In particular, the present invention relates to a low melt copolyetherester based on terephthalic acid, aliphatic diols, combination of antioxidants, and polybutylene terephthalate. The melting point of the low melt copolyetherester is between 80 to 240 C.BACKGROUND OF THE INVENTION:

[0002] Hot-melt adhesives, are materials which are applied to a substrate when molten and cooled to harden the adhesive layer, and are widely used for industrial applications.

[0003] If adhesive formulations are to be applied at temperatures below 150 °C, they may be prepared using low molecular weight components or by incorporating a high wax content. Such formulations achieve low application viscosity but results in loss of adhesive properties.

[0004] Hot melt adhesives for elastic attachment application generally contain 20-35% polymer. Such polymer content results in high viscosity, and thus the typical application temperature is 160 °C or greater. To reduce the energy demands and glue burn-through (hot adhesive partially or completely melts the polymeric substrate) as well as the occupational risks associated with applying hot melt adhesives, there is a need to provide adhesives that are suitable for hot melt applications at lower temperatures.

[0005] Reference is made to US8013107B2 which relates to a method of producing polyalkylene terephthalate, which comprises introducing a prepolymer of polyalkylene terephthalate that is in a molten state comprising 70 mol % or more of ethylene terephthalate. The product is used for moulding sheets and fibres etc

[0006] Another reference is made to JP4771204B2 which relates to a polyester resin composition for providing an environment-friendly moulded product that is softened by lowering the rigidity at room temperature and has a high surface hardness.

[0007] Yet another reference is made to US 6663961 B2 which relates to a process for preparing polyester polymers using a composite catalyst comprises the steps of 1) esterifying naphthalene dicarboxylic acid or a dicarboxylic acids containing NDCA or ester derivatives thereof, with ethylene glycol or glycols containing ethylene glycol or derivatives thereof to produce esterified compounds or its low molecular weight polymers; and then 2) continuously polycondensing the obtained esterification product to produce polyester polymers.

[0008] Further reference is made to US8987372 which discloses low application temperature hot melt adhesives which exhibit desirable thermomechanical and viscoelastic properties. It uses at least one styrenic block copolymer i.e. a styrene content greater than 40 wt. % based on the total weight of the copolymer to achieve adhesive properties.

[0009] Another reference is made to US8129464 which discloses a low application temperature hot melt adhesive by utilizing a high softening point mid-block tackifier with SIS copolymer i.e. 10% to about 40% by weight of an elastomeric block copolymer, preferably styrene-isoprene-styrene (SIS) or styrene-butadiene-styrene (SBS).

[0010] Yet another reference is made to US7019060 which discloses ethylene vinyl acetate copolymers (EVA) having vinyl acetate for achieving good adhesive properties at comparatively lower temperature.

[0011] Accordingly, there exists a dire need in the art to provide low application temperature hot melt adhesives which is easy to process and use.SUMMARY OF INVENTION:

[0012] An object of the present invention is to provide a low melt copolyetherester based on terephthalic acid, aliphatic diols, and combination of antioxidants.

[0013] Another object of the present invention is to provide a low melt copolyetherester wherein the aliphatic diol content is at least 0 to 100 mol % of monoethylene glycol, 0 to 100 mol% diethylene glycol and optionally an additional glycol is added. The content of diols is based upon the overall quantity / proportion of acid.

[0014] Yet another object of the present invention is to provide a low melt copolyetherester wherein 100 mol % of the diol quantity and 25 to 50 weight % polybutylene terephthalate is used based upon overall quantity / proportion of acid.

[0015] Further object of the present invention is to provide a low melt copolyetherester having the melting point between 80 to 240°C.

[0016] Still further object of the present invention is to provide a low melt copolyetherester in the form of chips / pellets, as and when used as an adhesive in textile, flexible packaging, and carpet industry.

[0017] Yet another object of the present invention is to provide a process for preparing the low melt copolyetherester.DETAILED DESCRIPTION OF THE INVENTION:

[0018] Definition of terms

[0019] For convenience, before further description of the present invention, certain terms employed in the specification, examples and appended claims are collected here. These definitions should be read in light of the remainder of the disclosure and understood as by a person of skill in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art.

[0020] The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0021] Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.

[0022] The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.

[0023] Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, 5 to 40 moles % should be interpreted to include not only the explicitly recited limits of 5 to 40 moles %, but also to include sub-ranges, such as 10 moles % to 30 moles %, 7 moles % to 25 moles %, and so forth, as well as individual amounts, including fractional amounts, within the specified ranges, such as 15.5 moles %, 29.1 moles %, and 12.9 moles %, for example.

[0024] The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

[0025] As discussed in the background section of the present invention, the hot melt adhesives for elastic attachment application generally contain 20-35% polymer. Such polymer content results in high viscosity, and thus the typical application temperature is 160 °C or greater. To reduce the energy demands and glue burn-through (hot adhesive partially or completely melts the polymeric substrate) as well as the occupational risks associated with applying hot melt adhesives, there is a need to provide adhesives that are suitable for hot melt applications at lower temperatures.

[0026] To address the problems associated with the art, the present invention provides a low melt copolyetherester having the melting point between 80 to 240°C. With such an increased melting point, the low melt copolyetherester exhibits a higher impact strength because of the higher brittleness level. Further, the low melt copolyetherester with increased Tg value helps in minimizing the ageing effect of the low melt copolyetherester that exists in the art. Moreover, the incorporation of antioxidants in the low melt copolyetherester helps in increasing the heat stability of the polymer, thereby, increasing the bonding strength. Further, the cooling time crystallization of the low melt copolyetherester of the present invention is also increased by 60to 70°C in comparison to low melt copolyetherester known in the art. This positively influences the productivity down the line.

[0027] Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

[0028] While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

[0029] Abbreviations Used in the Invention

[0030] A low melt copolyetherester based on terephthalic acid, aliphatic diols, and combination of antioxidants is developed wherein the molar proportion of terephthalic acid is at least 80 to 100 moles % based on the overall acid quantity, the aliphatic diol content at least 0 to 100 moles % of monoethylene glycol, 0 to 100 moles% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C. Other additives for preparation of low melt copolyetherester are selected from the class of stabilizers, pigments, optical brighteners.

[0031] Additives, Stabilizers or optical brighteners can be selected from but are not limited to, antimony trioxide, cobalt acetate, phosphoric acid, thermal conductivity improvers (for PET) such as zinc oxide, titanium dioxide (available as Altris 500 from Huntsman). Ultraviolet light stabilizers such as resorcinol mono benzoates, phenyl salicylate and 2-hydroxybenzophenones; Hindered amine light stabilizers (HALS) such as benzotriazole, benzophenone, oxalanilide, cerium dioxide and the like.

[0032] Pigments may be selected from carbon blacks, phthalocyanines, quinacridones, nickel azo compounds, mono azo colouring agents, anthraquinones and perylenes and the like.

[0033] The antioxidants include but are not limited to irganox 1010 (Pentaerythritol Tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate), irganox 1076 (Octadecyl-3-(3,5-di-tertiary butyl-4-hydroxyphenyl)-propionate), irgafos 126 (Bis-(2, 4-di-t-butylphenol) Pentaerythritol diphosphite) and irgafos 168 (Tris(2,4-ditert-butylphenyl) phosphite.

[0034] A diol is a chemical compound containing two hydroxyl groups (-OH groups). An aliphatic diol is also called a glycol. Terms diol or aliphatic diol are used interchangeably in the present invention.

[0035] The low melt copolyetherester chopped through underwater melt granulator or underwater strand granulator is produced in the form of chips / pellets having melting point of80 to 240°C, preferably 120 to 150°C can be used as an adhesive in textile flexible packaging and carpet industry.

[0036] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C.

[0037] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 20 to 40 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C. In another embodiment of the present invention, the polybutylene terephthalate has a weight percentage in the range between 23 to 26 weight%.

[0038] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 50 mol% diethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate,wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C.

[0039] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 50 to 60 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C.

[0040] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C, and wherein the antioxidants are selected from the group consisting of Pentaerythritol Tetrakis (3-(3,5-di-tert-butyl-4- hydroxyphenyl) propionate), Octadecyl-3-(3,5-di-tertiary butyl-4-hydroxyphenyl)- propionate), Bis-(2, 4-di-t-butylphenol) Pentaerythritol diphosphate, and Tris(2,4-ditert- butylphenyl) phosphite. In another embodiment of the present invention, the antioxidants are selected from the group consisting of Pentaerythritol Tetrakis (3-(3,5-di-tert-butyl-4- hydroxyphenyl) propionate) and Octadecyl-3-(3,5-di-tertiary butyl-4-hydroxyphenyl)- propionate).

[0041] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C, and wherein the low melt copolyetherester further comprises at least one additive selected from the group consisting of antimony trioxide, cobalt acetate, phosphoric acid, zinc oxide, and titanium dioxide.

[0042] In an embodiment of the present invention, there is provided a low melt copolyetherester as described herein, wherein the low melt copolyetherester have a melting point in the range between 120 to 150°C.

[0043] In an embodiment of the present invention, there is provided a low melt copolyetherester as described herein, wherein the low melt copolyetherester have a glass transition temperature below 60° C.

[0044] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 5000 to 7000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C.

[0045] In an embodiment of the present invention, there is provided a low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants,wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C, and wherein the antioxidants are selected from the group consisting of Pentaerythritol Tetrakis (3-(3,5-di-tert-butyl-4- hydroxyphenyl) propionate), Octadecyl-3-(3,5-di-tertiary butyl-4-hydroxyphenyl)- propionate), Bis-(2, 4-di-t-butylphenol) Pentaerythritol diphosphate, and Tris(2,4-ditert- butylphenyl) phosphite.

[0046] In an embodiment of the present invention, there is provided a low melt copolyetherester as described herein, wherein the low melt copolyetherester have a melting viscosity, measured according to ISO / DIN 1133 at 240° C of range between 100 poise to 1000 poise. In another embodiment of the present invention, the low melt copolyetherester have a melting viscosity, measured according to ISO / DIN 1133 at 240° C of range between 120 poise to 900 poise, or 200 poise to 800 poise, or 400 to 500 poise.

[0047] In an embodiment of the present invention, there is provided a low melt copolyetherester as described herein, wherein the low melt copolyetherester have a melt flow index, measured according to ASTM D 1238 at 160° C, less than 400 gm / 10 min.

[0048] In an embodiment of the present invention, there is provided a low melt copolyetherester as described herein, wherein the low melt copolyetherester have an impact strength, measured according to ASTM D 1709 of not less than 500 gm.

[0049] In an embodiment of the present invention, there is provided a process for preparing the low melt copolyetherester as described herein, said process comprising the steps of: (a) adding aliphatic diols, terephthalic acid, combination of antioxidants, additives to a volume reactor equipped with a mechanical stirrer, following by heating to obtain a mixture, wherein the additive is selected from the group consisting of antimony trioxide, cobalt acetate, zinc oxide, titanium dioxide; (b) subjecting the mixture of step (a) to esterification carried out at atemperature in the range of 240 - 260 °C, and pressure up to 3.0 bars for a time period in the range of 2-3 hours to obtain an esterified mixture; (c) adding an additive selected from phosphoric acid to the esterified mixture of step (b) upon completion of 90 % esterification to obtain a second mixture; (d) transferring the second mixture to poly condensation reactor to obtain a polycondensed mixture; and (e) charging an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 to the polycondensed mixture of step (d), followed by adding polybutylene terephthalate and agitating the polycondensed mixture for 40 minutes to obtain a processed mixture; (f) subjecting the processed mixture of step (e) to poly condensation reaction carried out at temperature between 220 and 270 °C under reduced pressure of less than 0.2 torr to obtain a molten polymer; and (g) cooling the molten polymer of step (f) to obtain the low melt copolyetherester.

[0050] In an embodiment of the present invention, there is provided a process as described herein, wherein the copolyetherester is prepared in form of chips / pellets and used as hot melt adhesive in textile industry.

[0051] In an embodiment of the present invention, there is provided a process as described herein, wherein the copolyetherester is chopped through underwater melt granulator or underwater strand granulator.

[0052] Quality Parameters

[0053] Intrinsic Viscosity

[0054] Intrinsic viscosity (I.V.) is a measure of the molecular mass of the polymer and is measured by dilute solution using an Ubbelohde viscometer. All intrinsic viscosities are measured in a 60:40 mixture of phenol and s-tetrachloroethane with 0.5 % concentration. The flow time of solvent and solution are checked under I.V. water bath maintained at temperature bout 25 °C. The I.V., q, was obtained from the measurement of relative viscosity, qr, for a single polymer concentration by using the Billmeyer equation:

[0055] IV = [q] = 0.25[(RV-l) + 3 In RV] / c

[0056] Wherein q is the intrinsic viscosity, RV is the relative viscosity; and c is the concentration of the polymeric solution (in g / dL). The relative viscosity (RV) is obtained fromthe ratio between the flow times of the solution (t) and the flow time of the pure solvent mixture (to).

[0057] RV = nrel = Flow time of solution (t) / Flow time of solvant (tO)

[0058] I . V. must be controlled so that process ability and end properties of a polymer remain in the desired range. Class 'A' certified burette being used for IV measurement for more accuracy.

[0059] COOH end groups:

[0060] The Polymer was dissolved in a mixture of phenol and chloroform (50: 50 w / v ) under reflux conditions. After cooling to room temperature, the COOH end groups were determined using titration against 0.025 N Benzyl alcoholic KOH solution with bromophenol blue as an indicator. Run a blank simultaneously along with sample and the final end point is at the color change from blue from yellow. COOH groups are calculated based on the below calculation and the results are expressed in meq of COOH / kg. In the equation, TR is the volume of benzyl alcoholic KOH consumed for the sample, N is the normality of benzyl alcoholic KOH, and the blank is the volume of benzyl alcoholic KOH consumed for sample solution.[(TR- Blank) x N x 1000] = COOH end groups (meq / kg)

[0061] DSC analysis

[0062] The Differential Scanning Calorimeter (DSC) is a thermal analyser which can accurately and quickly determine the thermal behaviour of Polymers such as glass transition temperatures (Tg), crystallization exothermic peak temperatures (Tch), peak endotherm temperatures (Tm), heats of crystallization (AH) and heats of fusion for all materials. A Perkin- Elmer model Jade DSC was used to monitor thermal properties of all polymer samples at heating and cooling rates of 10 °C per minute. A nitrogen purge was utilized to prevent oxidation degradation.

[0063] Crystallinity by DSC and DGC:

[0064] The Differential Scanning Calorimeter (DSC) and Density Gradient Column (DGC) are used to calculate the crystallinity of polymer samples.

[0065] By DSC, the crystallinity is calculated by heat of fusion ((AH) of Tml (Heat 1 cycle) with specific heat of polymer. By DGC (Density Gradient Column), the crystallinity is calculated with the help of known standard balls floating at the Lloyds densitometer.

[0066] Melt viscosity and Melt flow index (MFI):

[0067] Melt viscosity and melt flow index both are tested using Rotational Thermofisher Scientific Rheometer (Modular Advanced Rheometer system) & Tinius Olsen plastometer (MP 600). Granules are dried at 110°C for 2 hours, Barrel temp 240°C, Load 2.16 kg

[0068] Impact Strength:

[0069] Impact Strength of Film samples is tested by Dart Impact Tester.

[0070] Resin is dried at 100°C for 2 hrs. This dried resin powdered by using high speed grinder. Film is made by compression moulding using Collin Press. Then kept in a desiccator for 1 hr.

[0071] Dart Impact of film samples is checked by a known dart weight by free fall method on centre of film.Examples

[0072] The following examples are given for the purpose of illustrating various embodiments of the invention and are not meant to limit the present invention in any fashion. The present examples, along with the methods described herein are presently representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Changes therein and other uses which are encompassed within the spirit of the invention as defined by the scope of the claims will occur to those skilled in the art.

[0073] Example 1:

[0074] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 27.1 kg of diethylene glycol, 36.6 kg of terephthalic acid, 21.04gm of antimony tri oxide (220 ppm as antimony) and 18.58 g ofcobalt acetate (55 ppm as cobalt). Esterification was carried out at temperature of 240 - 260°C under pressure up to 3.0 bars for 2-3 hours. After completion of 90% esterification, the reactor was depressurized and phosphoric acid added. The BEET was transferred into poly condensation reactor. PBT chips were added and the reaction mixture is hold for 60 min for melting. Poly condensation reaction was carried out at temperature of 220-270°C under pressure of less than 0.2 Torr. After sufficient melt viscosity is achieved, polymerization was stopped. The molten polymer was cooled in the cold water and then chopped to form pellets. The intrinsic viscosity of the amorphous polymer is 0.635 dl / g and throughput of product from reactor is more than 98.5% (yield).

[0075] The intrinsic viscosity (IV), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured using DSC and the results are summarized in Table 1.

[0076] Example 2:

[0077] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 12.4 kg of ethylene glycol, 16 wt % DEG, 37.5 kg of terephthalic acid, 4.0 kg isoterephthalic acid, 21 ,04gm of antimony trioxide (220 ppm as antimony) and 18.58g of cobalt acetate (55 ppm as cobalt). Esterification was carried out at temperature of 240 - 260 °C under pressure up to 3.0 bars for 2-3 h. After completion of 90 % esterification, the reactor was depressurized and phosphoric acid was added. The BEET was transferred into polycondensation reactor. PBT chips were added and the reaction mixture was hold for 60 min for melting. Polycondensation reaction was carried out at temperatures of 220-270 °C under pressure of less than 0.2 torr. After sufficient melt viscosity is achieved, polymerization was stopped. The molten polymer was cooled in the cold water and then chopped to form pellets through underwater melt granulator. The intrinsic viscosity of the amorphous polymer is 0.435 dl / g and throughput of product from reactor is more than 98.1% (yield).

[0078] The intrinsic viscosity (I. V.), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured using DSC and the results are summarized in Table 1.

[0079] Example 3:

[0080] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 9.4 kg of ethylene glycol, 16 wt.% DEG, 30.6 kg of terephthalic acid, 4.0 kg isoterephthalic acid, 21.04gm of antimony trioxide (220 ppm as antimony) and 18.58 g of cobalt acetate (55 ppm as cobalt). Esterification was carried out at temperature of 240- 260 °C under pressure up to 3.0 bars for 2-3 h. After completion of 90 % esterification, the reactor was depressurized and phosphoric acid added. The BEET was transferred into polycondensation reactor. PEG 1500 filtered solution was added and after 10 min mixing PEG 1500, PBT chips were added and the reaction mixture was kept on hold for 60 min for melting. Polycondensation reaction was carried out at temperature of 220-270 °C under pressure of less than 0.2 torr. After sufficient melt viscosity is achieved, polymerization was stopped. The molten polymer was cooled in the cold water and then chopped to form pellets. The intrinsic viscosity of the amorphous polymer is 0.562 dl / g and throughput of product from reactor is more than 98.4% (yield).

[0081] The intrinsic viscosity (I.V.), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured using DSC and the results are summarized in Table 1.

[0082] Examples 4 to 6

[0083] As outlined in Table 1, different polymer / polyesters were synthesized by using a procedure similar to that of Example 1. Raw material quantities in Table 1 are in wt%, with respect to the polymer. The remaining quantity is terephthalic acid. The melting temperature (Tm), crystallization temperature (Tch), and Tg of the co-polyester were measured using DSC, and the results are summarized in Table 1, below.

[0084] Example 7:

[0085] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 8.9 kg of ethylene glycol, 13 wt. % DEG, 31.5 kg of terephthalic acid, 21.04 g of antimony tri oxide (220 ppm as antimony) and240- 260 °C under pressure up to 3.0 bars for 2-3 h. After completion of 90 % esterification, the reactor was depressurized and phosphoric acid was added. The BHET was transferred to poly condensation reactor. PEG 1500 filtered solution was charged and mixed for 10 min. The PBT charged to reaction mixture and held 60 min to ensure complete melting. The poly condensation reaction was carried out at temperature between 220 and 270 °C under pressure of less than 0.2 torr. After achieving sufficient melt viscosity polymerization, the process came to an end. Batch temperature was then cooled between 270 and 190 °C to facilitate palletization either by underwater strands cutter or by underwater melt granulator. The intrinsic viscosity of the amorphous polymer is 0.527 dl / g and the yield from reactor is more than 98.5%.

[0086] The intrinsic viscosity (I.V.), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured using DSC and the results are summarized in Table 1.

[0087] Example 8:

[0088] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 32.7 kg of post-consumer recycled flakes, 5.3 kg of MEG (for glycolysis of post-consumer recycled flakes), 12.8 kg diethylene glycol, 6.76 g of cobalt acetate (20 ppm as cobalt). Glycolysis was carried out at a temperature of 240-250 °C under pressure at a range of 2-3 bar for 1-2 h. the reactor was depressurized and H3PO4 added in 10 min. Then BHET was transferred into poly condensation reactor. PEG 1500 filtered solution was added and after 10 min mixing PEG 1500, PBT chips were added. A polycondensation reaction was carried out at temperature 240- 270 °C under pressure of less than 0.2 torr. When sufficient melt viscosity was achieved, the polymerization was stopped, and the polymer was emptied from reactor through die at the bottom. The molten polymer that came out from the die as strand was cooled with cold water and then chopped to form pellets through underwater melt granulator. The intrinsic viscosity of the amorphous polymer is 0.464 dl / g and throughput of product from reactor is about 98% (yield).

[0089] The intrinsic viscosity (I.V.), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured using DSC and the results are summarized in Table 1.

[0090] Example 9:

[0091] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 20.7 kg of ethylene glycol, 47.7 kg of terephthalic acid, 24.86 gm of antimony trioxide (260 ppm as antimony), 16.89 g of cobalt acetate (50 ppm as cobalt), 7000ppm Irganox 1010 (antioxidant) and 5000 ppm Irganox 1076 (antioxidant). Esterification was carried out at temperature of 240 - 260 °C under pressure up to 3.0 bars for 2-3 h. After completion of 90 % esterification, the reactor was then depressurized and phosphoric acid added. The BEET was transferred to poly condensation reactor. PEG 1500 filtered solution was charged and mixed for 10 min before inducting PBT, which was then held for 60 min to ensure complete melting. Poly condensation reaction was carried out at temperature between 220 and 270 °C under reduced pressure of less than 0.2 torr. After achieving sufficient melt viscosity, polymerization was stopped. The molten polymer was cooled in and then chopped to form pellets. The intrinsic viscosity of the amorphous polymer is 0.578 dl / g and the yield from reactor is more than 98.5%.

[0092] The intrinsic viscosity (I.V.), melt viscosity, impact strength is measured appropriately in appropriate instruments. The melting, the glass transition temperatures of the polymer is measured using DSC and the results are summarized in Table 1.

[0093] Example 10:

[0094] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 19.5 kg of ethylene glycol, 45 kg of terephthalic acid, 24.86 gm of antimony trioxide (260 ppm as antimony), 16.89 g of cobalt acetate (50 ppm as cobalt), 7000ppm Irganox 1010 (antioxidant) and 5000 ppm Irganox 1076 (antioxidant). Esterification was carried out at temperature of 240 - 260 °C under pressure up to 3.0 bars for 2-3 h. After completion of 90 % esterification, the reactor was depressurized and phosphoric acid added. The BEET was then transferred to poly condensation reactor. PEG 1500 filtered solution was charged and mixed for 10 min. PBT was then charged to the mixture and agitated for 40 min in the reaction. Poly condensation reaction was carried out at temperature between 220 and 270 °C under reduced pressure of less than 0.2 torr. After achieving sufficient melt viscosity, polymerization was stopped. The molten polymer was then cooled and then chopped to form pellets. The intrinsic viscosity of the amorphous polymer is0.556 dl / g and the yield from reactor is more than 98.5%.

[0095] The intrinsic viscosity (IV), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured, and the results are summarized in Table 1.

[0096] Example 11:

[0097] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxing column, a nitrogen inlet and a heat source were added with 3.9 kg of ethylene glycol, 28.3 kg of terephthalic acid, 6.4 kg iso terephthalic acid, 26.68 gm of antimony trioxide (300 ppm as antimony), 13.51 g of cobalt acetate (40 ppm as cobalt), and 1000 ppm Irganox 1076. Esterification was carried out at temperature of 240 - 260 °C under pressure up to 3.0 bars for 2-3 h. After completion of 90 % esterification, the reactor was depressurized and phosphoric acid added. The BHET was transferred to poly condensation reactor. PBT chips were charged to reaction mix and held for 60 min for melting. Poly condensation reaction was carried out at temperature between 220 and 270 °C under reduced pressure of less than 0.2 torr. After achieving sufficient melt viscosity, polymerization was stopped. The molten polymer was then cooled and then chopped to form pellets. The intrinsic viscosity of the amorphous polymer is 0.788 dl / g and the yield from reactor is more than 98.5%.

[0098] The intrinsic viscosity (I. V.), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured and the results are summarized in Table 1.

[0099] Examples 12 to 13. As outlined in Table 1, different polymer / polyesters were synthesized by using a procedure similar to that of Example 11. Raw material quantities in Table- 1 are in wt.%, with respect to the polymer. The melting temperature (Tm), crystallization temperature (Tch), and Tg of the co-polyester were measured using DSC, and the results are summarized in Table 1.

[0100] Example 14:

[0101] To a 0.2 M3volume reactor equipped with a mechanical stirrer, a packed refluxingcolumn, a nitrogen inlet and a heat source were added with 18 kg of ethylene glycol, 36.5 kg of terephthalic acid, 5.0 kg iso terephthalic acid, 24.9 gm of antimony trioxide (280 ppm as antimony) and 18.57 g of cobalt acetate (55 ppm as cobalt). Esterification was carried out at temperature of 240260 °C under pressure up to 3.0 bars for 2-3 h. After completion of 90% 5 esterification, the reactor was depressurized and phosphoric acid was added. The BHET was then transferred to poly condensation reactor. PBT chips were charged and the reaction mixture was held for 60 min for melting. Poly condensation reaction was carried out at temperature between 220 and 270 °C under reduced pressure of less than 0.2 torr. After sufficient melt viscosity was achieved, polymerization was stopped. The molten polymer was cooled in the 10 cold water and then chopped to form pellets. The intrinsic viscosity of the amorphous polymer is 0.698 dl / g and throughput of product from reactor is more than 98.3% (yield).

[0102] The intrinsic viscosity (I.V.), melt viscosity, impact strength by making 300p film and also the melting, the glass transition temperatures of the polymer is measured and the results15 are summarized in Table 1.Table No. 1: Formulations for making various low melt co- polyesters and analysis same

[0103] Solid State depolymerization: The molecular weight of the polymer was significantly decreased by depolymerizing the polymer in a tumble dryer with by heating the contents between 60 and 90 °C over a period of 7 h to get the polymer crystallized, After5 crystallization, DM water was sprayed to the system and the reaction mix was maintained under inert atmosphere between 0.5 and 4.0 bar g and further the mass temperature was maintained between 115 and 125 °C for 15-20 h. SSP was then terminated after achieving the final intrinsic viscosity, and then the vacuum was applied to remove moisture and after completing the drying process, and was then subsequently passed on to a pelletron system for dedusting, 10 sieved finally before the pellets were packed in the form of either spherical or rectangular pellet.This process effects solid state depolymerization and allows molecular weight to be significantly decreased. The intrinsic viscosity (I V.) of the polymer is about 0.386 dl / g.

[0104] The melting, crystallization and the glass transition temperatures of the co-polymers were measured using DSC and the results are summarized in Table 2.5

[0105] Table No. 2 : Solid state polymerization: Comparison Analysis results of random low melt co-polyetherester

[0106] Referring to Tables 1 and 2, it can be inferred that the low melt copolyetherester of 10 Examples 9 and 10 have an excellent bonding strength as compared to that of examples 1 to 8.Further, the low melt copolyetherester of the present invention have higher impact strength as compared to that of example 1 to 3, and 6, as no tackiness issue was observed with the low melt copolyetherester of Examples 9 and 10 during coating. Moreover, it was also observed that the low melt copolyetherester of Examples 9 and 10 have higher temperature coefficientof capacitance (TCC), therefore, no extra cooling is required during coating as compared to that of examples 1 to 8 and 11 to 14. While the copolyetherester of examples 4, 11 to 14 have higher adhesion bonding strength and impact strength but the said copolyetherester fail due to higher viscosity, hence, the flow was very poor and were not able to coat uniform.

[0107] Therefore, it can be inferred from the above results that the low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants of the present invention (as in the case of Examples 9 and 10) exhibits excellent process ability due to higher TCC and no tackiness issue was faced during coating and no extra cooling was required during coating.

Claims

We Claim:

1. A low melt copolyetherester comprising terephthalic acid, aliphatic diols, and combination of antioxidants, wherein the molar proportion of terephthalic acid is at least 80 to 100 mol % based on the overall acid quantity, the diol content at least 0 to 100 mol % of monoethylene glycol, optionally 0 to 100 mol% di ethylene glycol and optionally an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 and mixture thereof to make up 100 mol % of the diol quantity and 10 to 50 weight % polybutylene terephthalate, wherein the antioxidant has a concentration in the range of 4000 to 8000 ppm, and wherein the low melt copolyetherester have a melting point in the range between 80° to 240°C and cooling crystallization temperature in the range between 60 to 170°C.

2. The low melt copolyetherester as claimed in claim 1, wherein polybutylene terephthalate has a weight percentage in the range between 20 to 45 weight%.

3. The low melt copolyetherester as claimed in claim 1, wherein di ethylene glycol has a weight percentage in the range between 0 to 50 mol%.

4. The low melt copolyetherester as claimed in claim 1, wherein monoethylene glycol has a weight percentage in the range between 50 to 60 mol%.

5. The low melt copolyetherester as claimed in claim 1, wherein the antioxidants are selected from the group consisting of Pentaerythritol Tetrakis (3-(3,5-di-tert-butyl-4- hydroxyphenyl) propionate), Octadecyl-3-(3,5-di-tertiary butyl-4-hydroxyphenyl)- propionate), Bis-(2, 4-di-t-butylphenol) Pentaerythritol diphosphate, and Tris(2,4- ditert-butylphenyl) phosphite.

6. The low melt copolyetherester as claimed in claim 1, wherein the low melt copolyetherester further comprises at least one additive selected from the group consisting of antimony trioxide, cobalt acetate, phosphoric acid, zinc oxide, and titanium dioxide.

7. The low melt copolyetherester as claimed in claim 1, wherein the low melt copolyetherester have a melting point in the range between 120 to 150°C.

8. The low melt copolyetherester as claimed in claim 1, wherein the low melt copolyetherester have a glass transition temperature below 60° C.

9. The low melt copolyetherester as claimed in claim 1, wherein the low melt copolyetherester have a melting viscosity, measured according to ISO / DIN 1133 at 240° C of range between 100 poise to 1000 poise.

10. The low melt copolyetherester as claimed in claim 1, wherein the low melt copolyetherester have a melt flow index, measured according to ASTM D 1238 at 160° C, less than 400 gm / 10 min.

11. The low melt copolyetherester as claimed in claim 1, wherein the low melt copolyetherester have an impact strength, measured according to ASTM D 1709 of not less than 500 gm.

12. A process for preparing the low melt copolyetherester as claimed in any one of the claims 1 to 11, said process comprising the steps of:(a) adding aliphatic diols, terephthalic acid, combination of antioxidants, additives to a volume reactor, following by heating to obtain a mixture, wherein the additive is selected from the group consisting of antimony trioxide, cobalt acetate, zinc oxide, and titanium dioxide;(b) subjecting the mixture of step (a) to esterification carried out at a temperature in the range of 240 - 260 °C, and pressure up to 3.0 bars for a time period in the range of 2-3 hours to obtain an esterified mixture;(c) adding an additive selected from phosphoric acid to the esterified mixture of step (b) upon completion of 90 % esterification to obtain a second mixture;(d) transferring the second mixture of step (c) to poly condensation reactor to obtain a polycondensed mixture;(e) charging an additional glycol selected from the group consisting of polyethylene glycol 400, polyethylene glycol 1500 to the polycondensed mixture of step (d), followed by adding polybutylene terephthalate and agitating the polycondensed mixture for 40 minutes to obtain a processed mixture;(f) subjecting the processed mixture of step (e) to poly condensation reaction carried out at temperature between 220 and 270 °C under reduced pressure of less than 0.2 torr to obtain a molten polymer; and(g) cooling the molten polymer of step (f) to obtain the low melt copolyetherester.

13. The process as claimed in claim 12, wherein the copolyetherester is prepared in form of chips / pellets and used as hot melt adhesive in textile industry.

14. The process as claimed in claim 12, wherein the copolyetherester is chopped through underwater melt granulator or underwater strand granulator.

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