Title of Invention

A PROCESS FOR THE PREPARATION OF FAST REHEAT (FRH) BOTTLE GRADE POLYETHYLENETEREPHTHALATE (PET) RESIN

Abstract

The present invention provides a process for the preparation of Fast Reheat (FRH) bottle grade polyethylene terephthalate (PET) resin by dispersing micron-sized carbon black in monoethylene glycol in the presence of dispersing agents and adding nano-sized particles of ferric oxide and metallic antimony to obtain a mixed carbon slurry followed by the preparation of a polymer slurry of pure terepthalic acid, mono ethylene glycol, isopthalic acid in the presence of a polymerisation catalyst and color toners, said carbon slurry and polymer slurry are added to obtain an addition mixture, which is followed by esterification and polymerisation in the presence of heat stabilizing additives to obtain Fast Reheat (PET) Resin.

Full Text

Technical Field The present invention relates to a process for producing Bottle Grade Fast Reheat (FRH) Polyethyleneterephthalate (PET) resin by the esterification of Pure Terepthalic Acid (PTA), Pure Isopthalic Acid (IPA) and Monoethylene Glycol (MEG) in the presence of a mixture of finely dispersed Carbon Black, nano sized metallic Antimony and Ferric Oxide and the resultant polymer melt is stabilized in the presence of phosphorous based heat stabilizers and with the addition of toners for controlling the colour. Background and prior art During the process of Stretch Blow Molding (SBM) of PET preforms to bottles (in a two-stage process) the reduction in consumption of energy in heating the preforms prior to blowing plays a very important role in the productivity of PET bottles. With the fast cycle blow molding machines, it is critical to have short residence times and shorter equilibration times for the heat-up of Preforms before the actual blowing. The temperature differential between the outer and inner walls of the perform needs to be minimum for ensuring proper blown bottle characteristics. US 2641592, 3028366, 3732182, 3795639 3842043, 3907754, 3962189, 3,965,071, 4010145 and 4082724 all deal with processes for preparing linear polyesters utilizing variety of catalysts comprising Germanium, Antimony, Titanium, Manganese, Cobalt etc. and variety of phosphorous containing compounds as heat stabilizers. However, none of these patents deal with either special additives or the role of catalysts in the heat absorption characteristics of the polymer., US 5484837, 5106905,4879335,4379871,4208318,4116924, 4001171, 3,905,937 & 3007891 and JP 49-87792 deal with carbon black addition to PET to produce a black master batch concentrate for colouring polyesters and not related to their reheat characteristics. U.S. Statutory Invention Registration H2018 H discloses a process wherein fast heat up additives controls the blow temperatures of multilayered preform or container of PET/PEN. Additives like carbon black, graphite, diamond dust and various colorants were tried to bring the two polymeric layers to the respective blow temperatures at almost the same time. In this published work, though the additives are functioning as heating aids, their main purpose is to bring the different layers in a multilayer preform to the same blowing temperature. US 4408004 discloses the use of carbon black (particle size 10-500 nm) in PET in a range less than 10 ppm for producing high clarity, low haze polyester with improved heat up rates. To improve the clarity, phosphates have been used as heat stabilizers along with Cobalt based compounds as bluing agents. In US 6022920 the additives used are black iron oxides Fe304 in the sizes between 0.1 and 10 microns. US6503586 relates to a polyester composition containing inorganic black particles which are copper chromite spinels as I.R. absorbing materials having average particle size of 0.9 and 1.2 micron. These pigments were added at a level of 10-50 ppm to get colourless bottles whose brightness and yellowness is measured. Reheat additives at this high level is likely to cause colour and haze problem in the bottles US 6022920 discloses a process for making PET with improved reheat rates by adding about 5 to 50 ppm black iron oxide particles. In this process the iron particles are added at higher levels viz., 50 ppm to get about 15% less reheat time affecting the L* value and colour of the bottle. US 6197851 presents an invention relating to PET polymer containing one of a series of organic/metallo organic I.R. heat absorbing compounds which includes phthalocyanines, substituted indanthrones and anthrquinones etc. Invariably in such processes controlling the color and haze is difficult. US 5419936 and 5529744 describe a process of using reducing agents for incorporating metal particles like Antimony in the polyester for reducing the reheat time. If the reduction is not controlled, there is a possibility of the total Sb203 getting reduced to Sb, which can result in more graying and haziness in the sheet and bottle apart from reducing the catalytic activity. The combined teachings of the US 6022920, 5419936 and 5529744 disclose methods of obtaining enhanced heating rates. US 6022920 makes use of 5 to 50 ppm of black iron oxide particles as additives and US 5419936 & 5529744 deals with in-situ reduction of Sb203 to metallic particles like antimony by using reducing agents. U.S. Patent Application Publication 2003/0018115 deals with reheat aid additives like FeP, Fe2P, FesP, FeSi or the blends of these, which improve the heat-up rates without substantially affecting the colour of the product. Objects of the invention The main object of the present invention is to provide a process for producing Bottle Grade Fast Reheat (FRH) Polyethyleneterephthalate (PET) resin by the esterification of Pure Terepthalic Acid (PTA), Pure Isopthalic Acid (PA) and Monoethylene Glycol (MEG) in the presence of a mixture of finely dispersed Carbon Black, nano sized metallic Antimony and Ferric Oxide. An object of the present invention is to provide a process to make use of the extended surface area provided by nano sized particles of Ferric Oxide and metallic Antimony to increase the efficiency of heat-up rates. Another object of the present invention is to provide a process to pioduce FRH Resin with carbon levels in the range of 2-7 ppm. Yet another object of the present invention is to provide a process to stabilize the polymer melt in the presence of selective phosphorous based heat stabilizers and with the addition of toners for controlling the colour. It is also an object of the present invention to provide a process for achieving a reduced time frame in the heating of the preforms as obtained by using the process steps of the invention, prior to blowing. Yet another object of the present invention is to provide a process to obtain PET polymer with the increased rate of heat absorption without affecting the clarity and haze characteristics. Summary of the invention The present invention provides a process for the preparation of Fast Reheat (FRH) bottle grade polyethylene terephthalate (PET) resin by dispersing micron-sized carbon black in monoethylene glycol in the presence of dispersing agents and adding nano-sized particles of ferric oxide and metallic antimony to obtain a mixed carbon slurry followed by the preparation of a polymer slurry of pure terepthalic acid, mono ethylene glycol, isopthalic acid in the presence of a polymerisation catalyst and color toners, said carbon slurry and polymer slurry are added to obtain an addition mixture, which is followed by esterification and polymerisation in the presence of heat stabilizing additives to obtain Fast Reheat (PET) Resin. According to this invention there is provided a process for the preparation of Fast Reheat (FRH) polyethylene terephthalate (PET) resin, said process comprising the steps of: i. dispersing micron-sized (in the range of 0.3 to 3 micron) carbon black (in the range of 2.-7 ppm) in monoethylene glycol in the presence of dispersing agents (in the range of 0.2 to 2.5 wt.%) and adding nano-sized particles of ferric oxide and metalhc antimony (in the range of 2.5 to 3.5 ppm) to obtain a mixed carbon slurry, ii. preparing a raw material slurry of pure terepthalic acid, mono ethylene glycol isopthalic acid (in the range of 1.5 to 3.0%)in the presence of a polymerisation catalyst (in the range of 200 to 300 ppm of SbjOs) and red and blue color toners (in the range of 1.1 to 2.5 ppm), iii. adding the carbon slurry to said raw material slurry to obtain an addition mixture, iv. esterifying the addition mixture in an esterification reactor under controlled degree of polymerisation (Degree of Polymerization in the range of 5 to 10) to obtain a pre-polymer, v. retaining a portion of said pre-polymer as pre-polymer heel in said reactor for subsequent batch reactions, vi. polymerising the pre-polymer with an enhanced degree of polymerization (Degree of Polymerization in the range of 100 to 110), under reduced pressure (0.1 to 0.5 mbar abs.) and temperature (260 to 285°C initially and 292 to 298°C towards the end) to obtain a polymer melt, vii. stabilizing said polymer melt by adding at least a heat a stabilizing additive (combination of OPA and TEPA in the ratio of 1:2 at a concentration of 220 ppm so that the phosphorous content in the polymer is 30 ppm), viii. and extruding and converting the polymer melt to form amorphous pellets xmder nitrogen pressure and performing soUd-state polymerization (SSP) to obtain fast reheat polyethylene terepthalate (PET) resin. Brief description of the accompanying drawing Figure 1 describes Schematic Process Flow Diagram of the present invention Description of the Invention The present invention provides a process for producing Fast Reheat (FRH) PET resin by finely dispersing Carbon Black, nano sized particles of Ferric Oxide and metallic Antimony in the presence of a selective combination of phosphorous based heat stabilizers and toners. The embodiments of the present invention are disclosed by initially describing the process steps for the preparation of mixed carbon slurry of desired concentration and thereafter the process steps for the preparation of raw material slurry followed by addition of carbon slurry to the raw material slurry. Finally, the present invention discloses process steps relating to esterification and polymerisation to obtain a bottle grade FRH PET resin. Preparation of mixed Carbon Slurry In order to prepare mixed carbon slurry, USFDA approved special Carbon Printex F alpha by Degussa with very fine particle size in the range of 0.3-5 microns, preferably 1-3 miprons is used and whereas the Carbon Black content is in the range of 2-7 ppm, preferably 2.2-4.8 ppm is suspended in Monoethylene Glycol (MEG) with concentration of l-20wt %, preferably 3-15% and more preferably 4-10%, in the presence of dispersants Polyvinyl Pyrrolidone (PVP), which is sourced from BASF as Kollidon K 17 and polyacrylate (EFKA 4560 - EFKA Additives, The Netherlands,). The polyacrylate polymer carries basic moieties of tertiary amino functions of aromatic or non-aromatic character attached to a modified polyacrylate polymer. The concentration of PVP is in the range of 0.3-2.0%, preferably 0.4-1.5% and polyacrylate in the range of 0.2- 2.5 %, To this suspension nano sized Ferric Oxide and metalhc Antimony having a particle size in the range of 20-30 nm and in the quantities of 0.5-10 ppm, preferably in the range of 2.5-3.5 ppm are added as slurry in MEG. The dispersion of nano sized ferric oxide, nano sized metalhc antimony in the slurry is unique because of their extensive surface area and their effectivenessin heat absorption. This combination is well mixed in a preparation vessel and then circulated through a special bead mill. In the present invention a special agitator bead mill catering to high energy, high flow, multiple pass operations is adopted. This recirculation bead mill passage helps to achieve very narrow submicron particle size distributions of the ingredients. The slurry is mixed in the mill for about 4-12 hours for breaking the agglomerates of carbon black, if any, formed during the preparation process and to obtain slurry with carbon black of desired particle size. This concentration is diluted with Monoethylene glycol (MEG) to the desired end concentration between 0.5-5.0 percent to obtain mixed carbon slurry and said carbon slurry is stored in service tank under agitation. Preparation of Raw Material slurry A slurry of Pure Terephthahc Acid (PTA) and Mono Ethylene Glycol (MEG) in the ratio of about 70:30 wt% is prepared in a paste preparation vessel along with the required concentration Pure Isopthalic Acid (IPA), which is around 0.5-4%, preferably 1-3.5% and more preferably 1.5-3% over the said polymer concentration. The polymerisation catalyst SbjOa in the concentration of 100-400 ppm, preferably 150-350 ppm and more preferably 200-300 ppm is added to the paste preparation vessel along with Cobalt Acetate in the range of 40 to 100 ppm, preferably 45-90 ppm and more preferably in the range of 50-70 ppm as a color toner along with additional red and/or blue toners in the range of 0.2 to 3 ppm, preferably 1-3 ppm and more preferably 1.1-2.5 ppm. In the present invention. Antimony trioxide (Sb203) acts a polymerisation catalyst. The Carbon slurry from the service tank carrying the carbon particles and nano particles of Ferric Oxide and metallic Antimony are added in the paste to give the carbon concentration in the final polymer to the tune of around 0.5 to 4.0 ppm and nano sized particles of Ferric Oxide and metallic Antimony in the range of 0.1 to 4 ppm in the final polymer. Depending on the production schedule, at times, the additives viz. Carbon Black, Nano sized Ferric Oxide and metallic Antimony are added in tiie esterifier instead of in the PTA/ff A/MEG paste. It is understood here that PA is not used whenever the resultant product is a homopolyester as for certain applications the homopolyester resin without the added PA is used. Reaction Process Initially the esterifier reactor is empty and having a temperature in the range of 240-270°C. The reactor is also maintained under an inert Nitrogen atmosphere. The reactor pressure is maintained in the range of 0.5-3.0 Kg/cm2(g). To this reactor, a supply of PTA/ MEG/IPA paste is commenced. Subsequent to the supply of the required quantity of the paste, further supply of the paste is stopped, hi the esterification reactor the PTA/IPA gets converted to a pre-polymer or an ohgomer - bishydroxyethyl terephthalate (BHET). Thus the complete mass gets converted to the BHET viz. prepolymer/oligomer under a degree of polymerization (DP) to the tune of 5-10. The present invention also envisages a HEEL PROCESS for speeding up the esterification process for ensuring very low levels of byproduct formation. This is critical for ensuring that the product formed gives consistent clarity (lack of haze) and colour values in the bottles made there from. In the HEEL PROCESS, after the conversion of first batch PTA/ff A, a portion of BHET remains in the esterifier reactor to act as PREPOLYMER HEEL. This helps to hasten all the above-mentioned unit process in the subsequent batches. After achieving the desired end temperature of 255-275 °C and the conversion of about 98.5 % of the batch processing, the pre-polymer is filtered through a 20 micron filter and transferred to a pre-polyreactor under nitrogen pressure in the case of three reactor systems or directly to the autoclave in the case of two reactor systems. The pre-polyreactor is equipped with an agitator, internal heating coil and external limpet coil. The pre-polymer is processed by gradually reducing the pressure to 5-15 mbar (abs) and increasing the temperature to about 260-285 °C. After an increase in Degree of Polymerisation (DP) the melt is transferred after filtration to the Polymerization reactor, which is equipped with a special agitator, condenser and a fine vacuum system. The polymerization takes place in the presence catalyst viz. Antimony Trioxide. Here the polymer melt with a low starting DP is raised to its required final high DP of 100-110 by reducmg the pressure to as low as 0.1-0.5 mbar (abs) and the temperature to about 292-298°C. The polymer melt is stabilized with a combination of heat stabilizers selected from Phosphorous Acid/Orthophosphoric Acid (OPA)/Triethylphosphonoacetate (TEPA), or a combination thereof The concentration of the heat stabilizers is in the range of 100-500 ppm, preferably 200-300 ppm and more preferably 50-250 ppm. In the present invention a combination of TEPA and OP A is used in the ratio of 1:2. The polymer melt is then extruded under nitrogen pressure and converted into pellets. This amorphous copolyester FRH RESIN is further sohd state polymerized to an Intrinsic Viscosity (IV) of 0.80-0.86 to obtain FRH bottle grade resin. This solid state polymerized resin is used for injection molding preforms which are subsequently blown into bottles by stretch blow molding. The properties of the poljaner resin as obtained by using the process steps of the present invention are as shown below. FRH AMORPHOUS COPOLYESTER IV COOH end groups DEG Melting Point L(CIE) b(CIE) 0.600 ±0.04dl/g 30 ± 5 meq/ kg 1.0±0.1% 246 ± 2 °C 65 ±2 -5.5 + 1.0 FRH SSP RESIN COPOLYESTER IV COOH end groups DEG Melting Point L*(CIE) 'b' (CIE) 0.800 ± 0.02 dVg l.O±0.1% 246±2°C Min.74 MaxO L & h values are standard values as provided by Commission de Veclairage of France (CIE) The polymer obtained in the present invention is also checked for its increased reheat characteristics by a laboratory gadget by ascertaining the time taken to reach 110 °C and compared with the control resin, i.e. similar resin but without any reheat additives. It is observed that by adopting the process steps of the present invention a reduction in the range of 15-18% in reheating of the polymer is observed. The laboratory device is an iu house fabricated setup where a known quantity of resin is heated by heaters to a specific temperature which is monitored by thermal sensors and the time taken is noted. Tliis is further confirmed by measuring the time taken for the preforms to attain the temperature of 110°C. The resultant power saving ui the preform heating is between 15 and 20% depending on the size of the preform and also resulted in the increase :n productivity in PET bottles (~ 10 %) in the injection stretch blow molding machine. Therefore, by adopting a combination of additives along with nano sized Ferric Oxide and metallic Antimony improves the heat-up rates without affecting the clarity and haze in the bottles. This also gives about 10% higher productivity while blowing bottles. Specifications of Raw Materials and Additives used in the present invention: Pure Terephthalic Acid (PTA) Acid Number (mg KOH/g) Moisture (% Wt.) Ash (% Wt.) h-on (ppm) Color (CIE Lab- b*) Bulk Density (g/cc) Foreign Particles Average Particle size (micron) 675 ±2 0.5 maximum 0.0015 maximum 1.0 maximum + 0.5 maximum 1.10 ±0.05 Nil 110 + 20 Mono Ethylene Glycol Moisture (% Wt.) Acidity (% Wt.) (as Acetic Acid) Specific Gravity at 20° C Chlorides (as CI) ppm Iron (as Fe +++) ppm Residue (% Wt.) Color (HU) Appearance Miscibility with water DEC (% Wt.) 0.5 maximum 0.01 maximum 1.115 ±0.001 5 maximum 0.15 maximum 0.0015 maximum 10 maximum Colorless clear hquid No external contamination 100% 0.1 maximum Distillation range (°C): 1st drop 5 ml 95 ml Dry point Ultraviolet Transmittance (%) at: 350 nm 275 nm 250 nm 220 nm 190 minimum 196 maximum 199 maximum 200 maximum 98 minimum 95 minimum 90 minimum 70 minimum Pure Isophthalic Acid (IPA) Acid Number (mg KOH/g) Moisture (% Wt.) Ash (% Wt.) Iron (ppm) Color (CIE Lab- b*) Bulk Density (g/cc) Foreign Particles Average Particle size (micron) 675 ±2 0.5 maximum 0.0015 maximum 1.0 maximum + 0.5 maximum 1.1010.05 Nil 110 + 20 Dispersing Agents KollidonK17(PVP) EFKA 4560 0.3-2.0% 0.2-2.5% Antimony Trioxide Purity (% as Sb203) Moisture (% Wt.) Iron (ppm) Chlorides (ppm) Purity (%,) 1. As Cobalt 99.0 minimum 0.5 maximum 30 maximum Violet Red or Rose, Crystals / Powder 22 minimum from Degussa or similar Food grade approved carbon blacks. Blue Toner Appearance (visual inspection) Labeled as POLYSYNTHRIN Red Toner Appearance (visual inspection) BLUE RBL from Clariant India Ltd or similar Food grade approved special Blue Toner Labeled as POLYSYNTHRIN RED GFP from Clariant hidia Ltd or similar Food grade approved special Red Toner Nano Ferric Oxide 20 - 30 nm powder from Nanostractured & Amorphous Materials, Inc.USA Nano Antimony 20 nm powder from Reade Advanced Materials, USA A comparative account of the product characteristics of the present invention in the form of 'b' values (to indicate the colour of the product) with known resins is provided in the following Table I. TABLE: I * Comparing preform colours has limitations due to the wall thickness variations for different sizes of bottles. A comparative statement of increase in heat-up rates or the reduction in power requirement of the resin of the present invention vis-a-vis prior art resins is as provided in Table - II. TABLE: II The invention is further explained in the form of following Examples. However, these examples should not be construed as limiting the scope of the invention. Example-1 The carbon black slurry is prepared using FDA approved Printex V Carbon by Degussa with a particle size averaging 1-3 microns. It is thoroughly dispersed in Monoethylene Glycol (MEG) of 10 % by using an equal mixture of Kollidon K 17 Polyvinyl PyrroHdone (PVP) and EFKA 4560 as a dispersing agent at 0.5 % level each. To this slurry 6 ppm of Nano sized Ferric Oxide and Nano sized metallic antimony with a particle size of 20 nm are added. This combination slurry is well mixed in the preparation vessel and then circulated through the bead mill for eight hours for breaking any agglomerates and to yield finely dispersed slurry wherein the final particles are not greater than 2 microns. This slurry is then further diluted to a concentration of 3 % and stored in the service tank and kept under continuous agitation. A raw material slurry of PTA/MEG in the ratio of 70:30 wt % along with 2.5 % of IP A, i.e.7 kg of PTA and 3 kg of MEG along with 0.25 kg of IPA is prepared in the presence of Antimony trioxide (SbaOs) (250 ppm) as a polymerisation catalyst along with cobalt acetate (60 ppm) red and blue color toners (1.5 ppm). The carbon slurry from the service tank is added to this such that the final polymer contains 2.5 ppm, 3.0 ppm and 3.0 ppm of the composite carbon black, ferric oxide and antimony. The mixture is transferred to the esterifier and the process of esterification, prepolymerization and polymerization are carried out as described earlier. The polymer is stabilized with a combination heat stabiHzer comprising a combination of OPA and TEPA in the ratio of 1:2 and at a concentration of 220 ppm so that the phosphorous content in the polymer is 30 ppm. The final amorphous polymer is sohd state polymerized to an I.V. of 0.80. The general reaction times of the process steps of the present invention are as follows: (a) Esterification process is about 115-145 minutes (b) Prepolymerization is about 30 minutes (if apphcable) and Polymerization is about 125-155 minutes. The results of the SSP Polymer as obtained by using the above-stated process condition are tabulated m Table m by varying the concentrations of Carbon Black It follows from the trials that shorter reheat values in combination with good L* values are obtained at carbon black composite in the concentration of 2.5 ppm. TABLE: IH Example-2 Example -1 is repeated several times by keeping the carbon black composite ppm at 2.5. The results are summarized in Table -IV for the SSP resin. Good consistency in the properties of the polymer are observed. TABLE: IV A comparative statement of Fast Reheat Additives used conventionally and the present invention is provided in Table V TABLE V Advantages 1. In the present invention a combination of additives, for reheat performance improvement results in power saving and increased productivity in PET bottle manufacture. 2. Nano sized Ferric Oxide and Nano sized metallic Antimony are used as heating aids in the present invention. 3. In the present invention, combination additives proportions are such that it does not affect the clarity and haze of the bottles. We claim: 1. A process for the preparation of Fast Reheat (FRH) polyethylene terephthalate (PET) resin, said process comprising the steps of: dispersing micron-sized (in the range of 0.3 to 3 micron) carbon black (in the range of 2.-7 ppm) in monoethylene glycol in the presence of dispersing agents (in the range of 0.2 to 2.5 wt.%) and adding nano-sized particles of ferric oxide and metallic antimony (in the range of 2.5 to 3.5 ppm) to obtain a mixed carbon slurry, preparing a raw material slurry of pure terepthalic acid, mono ethylene glycol isopthalic acid (in the range of 1.5 to 3.0%)in the presence of a polymerisation catalyst (in the range of 200 to 300 ppm of Sb2O3) and red and blue color toners (in the range of 1.1 to 2.5 ppm), adding the carbon slurry to said raw material slurry to obtain an addition mixture, esterifying the addition mixture in an esterification reactor under controlled degree of polymerisation (Degree of Polymerization in the range of 5 to 10) to obtain a pre- polymer, retaining a portion of said pre-polymer as pre-polymer heel in said reactor for subsequent batch reactions, polymerising the pre-polymer with an enhanced degree of polymerization (Degree of Polymerization in the range of 100 to 110), under reduced pressure (0.1 to 0.5 mbar abs.) and temperature (260 to 285°C initially and 292 to 298°C towards the end) to obtain a polymer melt, stabilizing said polymer melt by adding at least a heat a stabilizing additive (combination of OPA and TEPA in the ratio of 1:2 at a concentration of 220 ppm so that the phosphorous content in the polymer is 30 ppm), and extruding and converting the polymer melt to form amorphous pellets under nitrogen pressure and performing solid-state polymerization (SSP) to obtain fast reheat polyethylene terepthalate (PET) resin. 2. The process as claimed in claim 1, wherein the particle size of carbon black is in the range of 1 to 3 microns. 3. The process as claimed in claim 1, wherein the quantity of carbon black is in the range of 2.2-4.8 ppm. 4. The process as claimed in claim 1, wherein the dispersing agents are selected from polyvinylpyrrolidone (PVP) in the range of 0.3-2.0 wt %, preferably 0.4-1.5 wt % and polyacrylate in the range of 0.2-2.5 wt%. 5. The process as claimed in claim 1, wherein particle size of ferric oxide and metallic antimony is in the range 20-30 nanometers. 6. The process as claimed in claim 1, wherein the quantities of ferric oxide and metallic antimony is in the range of 2.5-3.5 ppm. 7. The process as claimed in claim 1, wherein the pure terepthahc acid (PTA) and mono ethylene glycol (MEG) is in the ratio of 70:30. 8. The process as claimed in claim 1, wherein the quantity of pure isopthalic acid (IPA) is in the range of 1.5-3%. 9. The process as claimed in claim 1, wherein the polymerisation catalyst is antimony trioxide in the range of 200-300ppm. 10. The process as claimed in claim 1, wherein the colour toner is cobalt acetate in the range of 50-70 ppm. 11. The process as claimed in claim 1, wherein the colour toner is red and/or blue toners in the range of 1.1-2.5 ppm. 12. The process as claimed in claim 1, wherein the pre-polymer is bishydroxyethyl terephthalate (BHET). 13. The process as claimed in claim 1, wherein the heat stabilizing additive is selected from a group consisting of phosphorous acid, orthophosphoric acid (OPA) or triethylphosphonoacetate (TEPA) and a combination thereof, preferably a combination of OPA and TEPA.

Documents:

0972-che-2003 abstract-duplicate.pdf

0972-che-2003 abstract.pdf

0972-che-2003 claims-duplicate.pdf

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