Claims:1. A polyethylene terephthalate copolymer resin suitable for extrusion blow molding operations, said resin is prepared by a polymerization reaction of a first monomer comprising at least one of terephthalic acid and lower dialkyl esters thereof, with a second monomer comprising ethylene glycol, along with, at least one comonomer selected from the group consisting of 2-methyl-1,3-propane diol and isosorbide, and a chain branching agent, in the presence a chain terminating agent, and a nucleating agent,
wherein the ratio of the amounts of said first monomer and said second monomer is in the range of 57:43 wt% to 71:29 wt%, and
wherein said copolymer resin is suitable for extrusion blow molding operations.
2. The polyethylene terephthalate copolymer resin as claimed in claim 1, wherein the amount of said at least one comonomer is in the range of 1 wt% to 5 wt% of the total amount of said first and second monomers, the amount of said chain branching agent is in the range of 0.01 wt% to 0.1 wt% of the total amount of said first and second monomers, the amount of said chain terminating agent is in the range of 0.1 wt% to 5 wt% of the total amount of said first and second monomers, the amount of said nucleating agent is in the range of 0.001 wt% to 0.25 wt% of the total amount of said first and second monomers.
3. The polyethylene terephthalate copolymer resin as claimed in claim 1, wherein said lower dialkyl ester of terephthalic acid is dimethyl terephthalate.
4. The polyethylene terephthalate copolymer resin as claimed in claim 1, wherein said chain branching agent is at least one selected from the group consisting of pentaerythritol (C(CH2OH)4), trimesic acid (C6H3(COOH)3), pyromellitic acid (C6H2(COOH)4), pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, and trimethylol propane (C2H5C(CH2OH)3.
5. The polyethylene terephthalate copolymer resin as claimed in claim 1, wherein said chain terminating agent is stearic acid.
6. The polyethylene terephthalate copolymer resin as claimed in claim 1, wherein said nucleating agent is at least one selected from the group consisting of sodium benzoate, silica, barium sulphate, and talc.
7. A process for preparing a polyethylene terephthalate copolymer resin, suitable for extrusion blow molding operations said process comprising the following steps:
i. reacting a first monomer comprising at least one of terephthalic acid and lower dialkyl esters thereof, with a second monomer comprising ethylene glycol at a temperature in the range of 250° C to 270° C in an inert atmosphere at a pressure in the range of 1 bar to 3 bar, to form an esterified product, wherein the ratio of the amounts of said first monomer and said second monomer is in the range of 57:43 wt% to 71:29 wt%,;
ii. adding a nucleating agent in an amount in the range of 0.001 wt% to 0.25 wt% of the total amount of said first and second monomers, at least one comonomer selected from the group consisting of 2-methyl-1,3-propane diol and isosorbide in an amount in the range of 1 wt% to 5 wt% of the total amount of said first and second monomers, a chain branching agent in an amount in the range of 0.01 wt% to 0.1 wt% of the total amount of said first and second monomers, and a chain terminating agent in an amount in the range of 0.1 wt% to 5 wt% of the total amount of said first and second monomers to the esterified product at a temperature in the range of 250° C to 270° C to obtain a pre-polymeric product;
iii. polymerizing said pre-polymeric product at a temperature in the range of 270° C to 290° C to obtain a polymer of intrinsic viscosity of up to 0.70 dL/g; and
iv. subjecting said polymer to solid state polymerization at a temperature in the range of 205° C to 210° C for a time period in the range of 10 hours to 24 hours to obtain the polyethylene terephthalate copolymer resin having intrinsic viscosity more than 0.70 dL/g and up to 1.1 dL/g.
8. The process as claimed in claim 6, wherein said lower dialkyl ester of terephthalic acid is dimethyl terephthalate.
9. The process as claimed in claim 6, wherein said chain branching agent is at least one selected from the group consisting of pentaerythritol (C(CH2OH)4), trimesic acid (C6H3(COOH)3), pyromellitic acid (C6H2(COOH)4), pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, and trimethylol propane (C2H5C(CH2OH)3.
10. The process as claimed in claim 6, wherein said chain terminating agent is stearic acid.
11. The process as claimed in claim 6, wherein said nucleating agent is at least one selected from the group consisting of sodium benzoate, silica, barium sulphate, and talc.
12. A process for preparing extrusion blow molded articles using the copolymer resin as claimed in claim 1, wherein said polyethylene terephthalate copolymer is subjected to an extrusion blow molding process at a temperature in the range of 220° C to 240° C to obtain said extrusion blow molded articles.

13. Extrusion blow molded articles prepared by the process as claimed in claim 11.
, Description:FIELD
The present disclosure relates to polymers.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
The term “Extrusion blow molding operations” as used herein refers to a process that can create hollow parts from plastic/polymer. In Extrusion Blow Molding (EBM), plastic is melted and extruded into a hollow tube (a parison).
The term "parison" as used herein refers to the molten viscous tubular form made on an extrusion blow molding machine by extruding thermoplastic resins. This parison is let into two halves of a blow mold and shaped to the form of the cavity of mold by blowing compressed air.
The terms “melt strength (MS)” and “melt viscosity” as used herein refers to the ratio T1/T2, wherein T1 is travel time which is the time taken by the material exiting from annual die to travel a certain length (550cm) and T2 equals the time taken to hold the parison at that length. A melt strength value of from about 1.0 to about 2.0 is desirable when the material is to be used in extrusion blow molding applications.
The term "high melt strength" polyesters as used herein refers to polyesters having a ratio of T1 /T2 approaches the ideal value of 1.0.
The term "intrinsic viscosity” as used herein refers to the ratio of a solution’s specific viscosity to the concentration of the solute extrapolated to zero concentration. Intrinsic viscosity reflects the capability of a polymer in solution to enhance the viscosity of the solution.
The term “shear sensitivity” as used herein, refers to a measure of the change in viscosity of PET as a function of shear rate. At zero shear rate or at a shear rate which is sufficiently low such that viscosity is independent of shear rate, viscosities generally in the range of about 105 poise to about 106 poise are considered acceptable for extrusion blow molding applications. To enable the PET to move through an extrusion die at reasonable temperatures and pressures and to allow the extruded parison to hang prior to blowing without deformation under its own weight, the melt viscosity must be shear rate dependent. Shear rates are measured at a temperature in the range of from 265° C to 300° C.
The term “die swell” as used herein, refers to a polymer stream compressed by entrance into a die, and followed by a partial recovery or “swell” back to the former shape and volume of the polymer after exiting the die,
L*, a*, and b* as used herein, refer to the three coordinates of CIELAB which represent the lightness of the color (L* = 0 yields black and L* = 100 indicates diffuse white; specular white may be higher), its position between red/magenta and green (a*, negative values indicate green while positive values indicate magenta) and its position between yellow and blue (b*, negative values indicate blue and positive values indicate yellow).
“Tc” as used herein refers to the crystallization temperature of a polymer.
“Tm” as used herein refers to the melt temperature of a polymer.
“No gel” or “gel-free” as used herein, refer to the absence of gels (cross-links) in the article prepared.

The term “Lower dialkyl esters” as used herein refers to the esters of carbonic acid. The esters of carbonic acid consist of a carbonyl group flanked by two lower alkoxy groups. Particularly, lower dialkyl esters, as used herein, refer to the di-esters of a di-carboxylic acid with C1-C6 alcohols.
The term “Chain branching agent” as used herein refers to the agent that allows the introduction of the necessary amount of chain terminator into the polyester molecule without reducing the molecular weight of the polyester.

The term “Chain terminating agent” as used herein refers to the agent that terminates/stops the formation of reactive intermediates in a chain propagation step in the course of a polymerization.

The term “Nucleating agent” as used herein refers to the agent that is widely used to modify the properties such as rate of crystallization and size of the crystals, of various polymers.

BACKGROUND
Extrusion blow molding (EBM) is a manufacturing process used to make pipes, hoses, drinking straws, curtain tracks, rods, fibre, and bottles using thermoplastics. Most thermoplastics can be used for extrusion. Common thermoplastics used in the extrusion molding processes are Polyethylene (PE), Polypropylene (PP), Polycarbonate (PC), Polystyrene (PS), Acrylics, Polyesters, Polyvinylchloride (PVC), Acrylonitrile Butadiene Styrene (ABS) and the like.
Polyethylene terephthalate (PET) is commonly employed in the plastic packaging industry because of its ease in processing and recycling with the products exhibiting the desired end properties. PET is widely used to produce numerous types of articles such as bottles and other storage containers (which may herein be collectively referred to as simply “containers”). In the bottle industry, bottle-grade PET resin which has a resin intrinsic viscosity (IV) between 0.65 dL/g and 0.87 dL/g is typically, made use of. Manufacturing of bottles using bottle grade PET is typically carried out using Injection stretch blow molding (ISBM). These resins are difficult to be extrusion blow molded due to their relatively low inherent viscosities and high melting points which lead to low melt strength at the processing temperatures.
Linear PET has a relatively low molecular weight and a narrow molecular weight distribution. This combination of characteristics results in a low melt strength polymer having low shear sensitivity which is unsuitable for extrusion blow molding applications. Materials with higher stiffness and/or melt strength are usually preferred for extrusion blow molding since they are easier to form and maintain the desired shape.
EBM-grade PET can be desirable in connection with a number of applications, as it can permit the use of PET to form articles that are commonly formed from HDPE, for example, large plastic containers with handles. For PET to be suitable for EBM processes, a higher molecular weight PET, i.e., one having a higher IV (e.g., about 1.0 dL/g or greater) may be needed. However, such co-polymers are commonly amorphous, or slow-crystallizing, which can present certain conversion and reclamation challenges. While a slow-crystallizing co-polymer may allow for easier processing in EBM environments, the resulting container can, among other things, present recyclability challenges. For instance, when the material has not yet crystallized, and remains amorphous, it may melt at lower temperatures. Further, when amorphous or slow crystallizing resins are added to the PET recycling stream, the resins can cause, inter alia, unwanted sticking, thermal agglomeration, and bridging (or port plugging) issues. Such issues can make PET polymer resins unsuitable for conventional recycling programs and processes.
In the past, attempts have been made to modify various polyesters, some including PET, by the incorporation of a chain branching agent or a chain terminating agent or both. The attempts have been concerned with rendering polyesters suitable for use, e.g., as electrical or thermal insulating materials, coating compositions or fiber and filament-forming materials with increased dye receptivity.
It is known in the art that high melt-strength polyethylene terephthalate polymers are suitable for use in conventional extrusion blow molding containers having high clarity and gloss. However, the processing of such polymers is always difficult as they have high crystallization temperatures.
Therefore, there remains a need for an extrusion blow molding-grade PET compositions or formulations which can be feasibly processed to produce blow molded articles having high clarity and gloss.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a polyester resin having high zero shear rate melt viscosity.
Another object of the present disclosure is to provide a polyester resin having low rate of crystallization with lower crystallinity.
Still another object of the present disclosure is to provide a polyester resin which can be feasibly processed into extrusion blow molded articles at lower temperatures.
Yet another object of the present disclosure is to provide a process for preparing a polyester resin suitable for extrusion blow molding process.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY
In accordance with one aspect of the present disclosure, a polyethylene terephthalate (PET) copolymer resin having high zero shear rate melt viscosity and low degree of crystallinity for use in extrusion blow molding operations is disclosed. The polyethylene terephthalate copolymer resin is prepared by the polymerization reaction of a first monomer comprising at least one of terephthalic acid and lower dialkyl esters thereof, with a second monomer comprising ethylene glycol, along with at least one comonomer selected from the group consisting of 2-methyl-1,3-propane diol and isosorbide, and a chain branching agent, in the presence of a chain terminating agent, and a nucleating agent. Typically, the ratio of the amounts of the first monomer and the second monomer is in the range of 57:43 wt% to 71:29 wt%.
Typically, the amount of the at least one comonomer is in the range of 1wt% to 5wt% with respect to the total amount of the first and second monomers. The amount of the chain branching agent is in the range of 0.01wt% to 0.1wt% with respect to the total amount of the first and second monomers. The amount of the chain terminating agent is in the range of 0.1 wt% to 5 wt% with respect to the total amount of the first and second monomers. The amount of the nucleating agent is in the range of 0.001 wt% to 0.25 wt% with respect to the total amount of the first and second monomers.
Typically, the lower dialkyl ester of terephthalic acid is dimethyl terephthalate.
Typically, the chain branching agent is at least one selected from the group consisting of pentaerythritol (C(CH2OH)4), trimesic acid (C6H3(COOH)3), pyromellitic acid (C6H2(COOH)4), pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, and trimethylol propane (C2H5C(CH2OH)3.
Typically, the chain terminating agent is stearic acid.
Typically, the nucleating agent is at least one selected from the group consisting of sodium benzoate, silica, barium sulphate, and talc.
In accordance with another aspect of the present disclosure, a process for preparing the polyethylene terephthalate copolymer resin is disclosed.
A first monomer comprising at least one of terephthalic acid and its lower dialkyl esters is reacted with a second monomer comprising ethylene glycol at a temperature in the range of 250° C to 270° C in an inert atmosphere at a pressure in the range of 1 bar to 3 bar, to form an esterified product. The ratio of the amount of the first monomer and the second monomer is in the range of 57:43 wt% to 71:29 wt%. The esterified product is then reacted with at least one comonomer selected from the group consisting of 2-methyl-1,3-propane diol, and isosorbide in an amount in the range of 1 wt% to 5 wt% of the total amount of the first and second monomers, and a chain branching agent in an amount in the range of 0.01 wt% to 0.1 wt% of the total amount of the first and second monomers, in the presence of a nucleating agent in an amount in the range of 0.001 wt% to 0.25 wt% of the total amount of the first and second monomers, and a chain terminating agent in an amount in the range of 0.1 wt% to 5 wt% of the total amount of the first and second monomers at a temperature in the range of 250° C to 270° C to obtain a pre-polymeric product.
The pre-polymeric product is then subjected to polymerization at a temperature in the range of 270° C to 290° C to obtain a polymer of intrinsic viscosity of up to 0.70 dL/g. The polymer is then subjected to solid state polymerization at a temperature in the range of 205° C to 210° C for a time period in the range of 10 hours to 24 hours to obtain the polyethylene terephthalate copolymer resin having intrinsic viscosity more than 0.70 dL/g and up to 1.1 dL/g.
Typically, the chain branching agent used in the process of the present disclosure is at least one selected from the group consisting of pentaerythritol (C(CH2OH)4), trimesic acid (C6H3(COOH)3), pyromellitic acid (C6H2(COOH)4), pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, and trimethylol propane (C2H5C(CH2OH)3.
Typically, the chain terminating agent used in the process of the present disclosure is stearic acid.
Typically, the nucleating agent used in the process of the present disclosure is at least one selected from the group consisting of sodium benzoate, silica, barium sulphate, and talc.
In accordance with a further aspect of the present disclosure, a process for preparing extrusion blow molded articles using the polyethylene terephthalate copolymer resin of the present disclosure is also disclosed wherein the polyethylene terephthalate copolymer resin is subjected to an extrusion blow molding process at a temperature in the range of 220° C to 240° C to obtain extrusion blow molded articles.
DETAILED DESCRIPTION
It is known that to perform a successful extrusion blow molding operation with PET, the molten PET must form into a stable parison for a time long enough to permit a mold to enclose the parison. If the molten PET does not possess this sufficient "melt strength" or “melt viscosity”, the parison will tend to elongate or draw under its own weight and either not be blow moldable or result in a blow molded article which has a non-uniform wall thickness, low surface gloss, poorly defined sample shape, and a large number of pit marks. Besides having sufficient melt viscosity or "melt strength", PET to be successfully used in extrusion blow molding applications should also possess sufficient die swell, i.e., the molten PET should expand as it is released from the die. This die swell is important for extrusion blow molding applications since (a) the larger the diameter of the extruded PET, the easier it is for air to be blown into the parison, and (b) the greater the die swell the greater the expansion of the molten PET to fit the particular mold. To enable the PET to move through an extrusion die at reasonable temperatures and pressures and to allow the extruded parison to hang prior to blowing without deformation under its own weight, the melt viscosity must be shear rate dependent.
For a PET polymer to be acceptable for use in extrusion blow molding operations the modified PET should have sufficient shear sensitivity, melt strength and low degree of crystallinity.
In accordance with one aspect of the present disclosure, a polyethylene terephthalate (PET) copolymer resin having high zero shear rate melt viscosity and low degree of crystallinity for use in extrusion blow molding operations is disclosed. The polyethylene terephthalate copolymer resin is prepared by the polymerization reaction of a first monomer comprising at least one of terephthalic acid and lower dialkyl esters thereof, with a second monomer comprising ethylene glycol, along with at least one comonomer selected from the group consisting of 2-methyl-1,3-propane diol and isosorbide, and a chain branching agent, in the presence of a chain terminating agent, and a nucleating agent.
The ratio of the amounts of the first monomer and the second monomer is in the range of 57:43 wt% to 71:29 wt%, the amount of the at least one comonomer is in the range of 1wt% to 5wt% of the total amount of the first and second monomers.
In an embodiment, the lower dialkyl ester of terephthalic acid is dimethyl terephthalate.
The chain branching agent in PET helps to raise the melt viscosity of the polyester resin. The chain branching agents are tri-functional and tetra-functional alcohols, and acids and anhydrides thereof. The amount of the chain branching agent is in the range of 0.01wt% to 0.1wt% of the total amount of the first and second monomers. In accordance with the embodiments of the present disclosure, the chain branching agent is at least one selected from the group consisting of pentaerythritol (C(CH2OH)4), trimesic acid (C6H3(COOH)3), pyromellitic acid (C6H2(COOH)4), pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, and trimethylol propane (C2H5C(CH2OH)3. In a preferred embodiment of the present disclosure, pentaerythritol in an amount in the range of 0.01 wt% to 0.1 wt%, preferably, 0.03 wt% to 0.07 wt% is used as the chain branching agent.
In accordance with the embodiments of the present disclosure, the nucleating agent is at least one selected from the group consisting of sodium benzoate, silica, barium sulphate, and talc. The amount of the nucleating agent is in the range of 0.001 wt% to 0.25 wt% of the total amount of the first and second monomers.
The chain terminating agent used in preparing the polyethylene terephthalate copolymer resin overcomes the gelation of the resin during preparation and further processing of the resin. The amount of the chain terminating agent is in the range of 0.1 wt% to 5 wt% of the total amount of the first and second monomers. In a preferred embodiment of the present disclosure, stearic acid, in an amount in the range of 0.1 wt% to 5 wt%, preferably 0.1 wt% to 1.5 wt% is used as the chain terminating agent.
The comonomer, used along with ethylene glycol, for preparing the polyethylene terephthalate copolymer resin reduces the rate of crystallization and thus, the processing temperature which leads to the improvement in clarity and gloss of the article prepared using the copolymer resin. The comonomer as described in the present disclosure is at least one selected from the group consisting of 2-methyl 1,3 propane diol and isosorbide. The use of comonomer improves the chain entanglement which helps to increase the melt strength and melt viscosity of the copolymer resin.
Addition of nucleating agent in PET enhances the rate of crystallization and improves the mechanical properties of the polymer. Non-limiting examples of the nucleating agent according to the present disclosure are sodium benzoate, silica, barium sulphate, and talc. In a preferred embodiment of the present disclosure, talc is used as the nucleating agent.
In accordance with another aspect of the present disclosure, a process for preparing the polyethylene terephthalate copolymer resin is disclosed.
A first monomer comprising at least one of terephthalic acid and its lower dialkyl esters is reacted with a second monomer comprising ethylene glycol at a temperature in the range of 250° C to 270° C in an inert atmosphere at a pressure in the range of 1 bar to 3 bars, to form an esterified product. The ratio of the amount of the first monomer and the second monomer is in the range of 57:43 wt% to 71:29 wt%. In an embodiment, the reaction is carried out in an esterification reactor. In another embodiment, the inert atmosphere is an atmosphere of nitrogen.
The esterified product is then reacted with at least one comonomer selected from the group consisting of 2-methyl-1,3-propane diol and isosorbide in an amount in the range of 1 wt% to 5 wt% of the total amount of the first and second monomers, and a chain branching agent in an amount in the range of 0.01 wt% to 0.1 wt% of the total amount of the first and second monomers, in the presence of a nucleating agent in an amount in the range of 0.001 wt% to 0.25 wt% of the total amount of the first and second monomers, and a chain terminating agent in an amount in the range of 0.1 wt% to 5 wt% of the total amount of the first and second monomers at a temperature in the range of 250° C to 270° C to obtain a pre-polymeric product.
The pre-polymeric product is then subjected to polymerization at a temperature in the range of 270° C to 290° C to obtain a polymer of intrinsic viscosity of up to 0.70 dL/g. The polymer is then subjected to solid state polymerization at a temperature in the range of 205° C to 210° C for a time period in the range of 10 hours to 24 hours to obtain the polyethylene terephthalate copolymer resin having intrinsic viscosity more than 0.70 dL/g and up to 1.1 dL/g. In an embodiment, the polyethylene terephthalate copolymer resin obtained is cut into at least one form selected from chips, and pellets.
In accordance with a further aspect of the present disclosure, a process for preparing a blow molded article using the polyethylene terephthalate copolymer resin is also disclosed.
Chips of the polyethylene terephthalate copolymer resin obtained are dried and extruded through an extruder having blow molding equipment at temperature in the range of 220° C to 240° C to obtain an extrudates in the form of a parison. In an embodiment, the die of the extruder is an annular die. The parison obtained from the die is then pressed between a vertically split hollow mold and blown with compressed air to form a blow molded article. The polyethylene terephthalate copolymer resin can be used to prepare extrusion blow molded articles such as pipes, hoses, drinking straws, curtain tracks, rods, fibers, and bottles. In accordance with an embodiment of the present disclosure, the blow molded article is a bottle.
Polyethylene terephthalate homopolymer resin is normally processed at a temperature between 280° C and 285° C. The copolymer resin of the present disclosure can be conveniently processed at a temperature in the range of 220° C to 240° C. It has been found that the addition of nucleating agent after the esterification enhances the rate of crystallization and improves the mechanical properties of the copolymer resin of the present disclosure. Conventional processing equipment and processing conditions can be used.
The present disclosure is further described in the light of the following laboratory experiments which are set forth for illustration purpose only, and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale, and the results obtained can be extrapolated to industrial scale.

EXPERIMENTS
Experiment 1
A mixture of 6 kg purified terephthalic acid and 4.5 kg ethylene glycol (MEG) was subjected to esterification in an esterification reactor for 3.5 hours at 260° C under a nitrogen pressure of 2 bar to obtain 7 kg of molten esterified product (polymer) with remaining byproducts like water and excess of MEG.
A mixture of 2.1g antimony trioxide and 0.49g of stannous oxalate in 250 ml ethylene glycol was added to the molten esterified product in the esterification reactor. After an interval of 5 min, 0.35 g (0.005 wt%) of talc, 4.2 g (0.06 wt%) of pentaerythritol in 100 g ethylene glycol and 210 g (3 wt%) of 2- methyl 1-3 propane diol were added to the molten esterified product in the reactor and the mixture was agitated for 5 min followed by the addition of 0.65 g of orthophosphoric acid in 50 ml of ethylene glycol to the reactor with agitation for 5 minutes to obtain a resultant orthophosphoric acid which acts as a thermal stabilizer
0.75 g of cobalt acetate in 100 ml of ethylene glycol and 70 g (1 wt%) stearic acid were added to the resultant in the esterification vessel to obtain a resultant mixture. After an interval of 10 min, the resultant mixture was transferred to a polymerization reactor wherein polymerization was carried out at 285° C, while the pressure was gradually reduced to 1 mmHg over 45 minutes to obtain a polymeric product. The intrinsic viscosity of the polymeric product was found to be 0.63 dL/g using ASTM D4603 test procedure.
Chips of the polymeric product were crystallized at 140° C in an oven, and then subjected to solid state polymerization at 210° C for 22 hours to obtain the polyethylene terephthalate copolymer resin having an intrinsic viscosity of 1 dL/g.
The obtained polyethylene terephthalate copolymer resin was dried at 170° C for 5 hours and extruded using a single screw extruder having an attached blow molding equipment. The extruder screw L/D ratio was 24 and processing temperatures were kept between 220° C and 245° C. The parison obtained from the die was blown using a mould to obtain a 250 ml and a 500 ml bottle.
Table 1 shows the barrel temperature (of various zones) and the die temperatures
Table 1 - Barrel zonal temperatures and die zonal temperatures
Barrel temperature (°C) Die temp (°C)
Z1 Z2 Z3 Z4 DZ1 DZ2
220 240 240 240 235 235
Experiment 2 (Comparative Experiment)
Experiment 1 was repeated but without using the nucleating agent, talc.
Experiment 3
The polyethylene terephthalate copolymer resin was prepared by the process as described in Experiment 1 but by using 5 wt% of isosorbide as the comonomer, instead of propane diol. The polyethylene terephthalate copolymer resin was then extrusion blow moulded into a 250 ml bottle.
Table 2 shows comparative properties of the polyethylene terephthalate copolymer resin obtained in experiments 1-3.
Experiment 4 (Comparative Experiment)
Experiment 1 was repeated but without using the cobalt acetate and orthophosphoric acid. Blue toner 0.14 g and red toner 0.035 g were added into the esterification vessel and agitated for 5 min and then 2.38 g Zinc phosphate was added as a thermal stabilizer.

Experiment 5
Experiment 4 was repeated with 0.7 g Tricalcuim phosphate as thermal stabilizer.

Table 2 – Comparison of the properties of the copolymer resins obtained in Experiments 1, 2, and 3
Experiment 1 Experiment 2 Experiment 3
Composition 6 kg terephthalic acid + 4.5 kg ethylene glycol + 210 g (3 wt%) 2-methyl-1,3-propane diol + 4.2 g (0.06 wt%) pentaerythritol + 70 g (1 wt%) stearic acid 6 kg terephthalic acid + 4.5 kg ethylene glycol + 315 g (3 wt%) 2-methyl-1,3-propane diol + 6.3 g (0.06 wt%) pentaerythritol + 105 g (1 wt%) stearic acid 6 kg terephthalic acid + 4.5 kg ethylene glycol + 525 g (5 wt%) isosorbide + 6.3 g (0.06 wt%) pentaerythritol + 105 g (1 wt%) stearic acid
additive 0.35 g (0.005 wt%) Talc --- 0.525 g (0.005 wt%) Talc
Base chip properties
IV 0.617 0.613 0.603
L* 65.1 61.6 60.1
a* 4.8 2.7 2.1
b* -2.8 3.5 9.6
-COOH value 19 18 18
Solid State Polymerization properties
IV (after 20 hr.) 0.95 0.95 0.92
L* 83.60 82.79 79.17
a* -0.89 -1.714 0.399
b* 0.00 2.99 6.62
Tm 238.15 234.09 242.17
Tc 190.33 167.99 195.9

From Table 2, it can be seen that the Tc is increased by the addition of nucleating agents.
The polyester produced with isosorbide showed higher b* value.
Table 3 shows a comparative result of the melt strength properties of the polyethylene terephthalate copolymer resins obtained in experiments 1, 2, and 3, with HDPE and PET homopolymer.
Table 3 – Comparison of melt strengths

Experiment 1 Experiment 2 Experiment 3 HDPE PET homopolymer
(0.8 IV)
Travel time 550 cm length (sec) 33 33 28 36 8
Parison hold time (sec) 5 4 3 22 2
Total time (sec) 38 37 31 58 10
Observation Good melt strength, no gels, and high clarity, Perfectly blown & Excellent productivity Good melt strength. No gels, clear bottle. Perfectly blown & Excellent productivity Good melt strength. Excellent melt strength Very low melt strength.

The parison exits the annular die and travels a certain length (550 cm) before it reaches the mold. The time taken to travel the length is called the travel time. The time taken to hold the parison at that length is called the hold time. The ratio of the travel time to the hold time is defined as the melt strength. If this ratio is equal to one then, the material exhibits higher melt strength. The melt strength of the copolymer resin of the present disclosure can be considered high based on the travel time which is much higher than that of PET homopolymer resin. The melt strength of this polyethylene terephthalate copolymer resin is adequate to be able to prepare blow molded articles.

Table 4 shows a comparison of the rheological properties of the resins of experiments 1, 2, 3 and HDPE.
Table 4 – Comparison of the rheological properties
Shear rate (1/s) Viscosity (Pa.s) @ 260° C
Experiment 1 Experiment 2 Experiment 3 HDPE 0.3 MFI @ 210° C
100 1409 1214 1168 1190
250 754 844 779 780
500 538 632 511 471
1000 393 452 318 302
2500 248 272 196 140
5000 147 180 124 90
Table 4 shows that the melt viscosity of the polyethylene terephthalate copolymer resin of experiments 1, 2 and 3 at 260° C is higher than or comparable to the melt viscosity of 0.3 MFI HDPE grade (at 210° C).

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a polyethylene terephthalate copolymer resin that:
? has high zero shear rate melt viscosity;
? has a low rate of crystallization and lower crystallinity; and
? can be feasibly processed into extrusion blow molded articles at lower temperatures.

The foregoing description of the specific embodiments so fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
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.
Any discussion of documents, acts, materials, devices, articles or 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.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments 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 changes in the preferred embodiment as well as other embodiments of the disclosure 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.