FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section TO and rule!3)
1. TITLE OF THE INVENTION: An improved process for the production of higher molecular weight polyester resin from the low molecular weight crystalline
prepolymer.
2 APPLICANT
(a) NAME : Reliance Industries Limited
(b) NATIONALITY: Indian company incorporated under the Companies Act
1956
(c) ADDRESS : Reliance Technology Center, B-4 MIDC Industrial Area,
Patalganga- 410220, Dist- Raigad, Maharashtra, India. 3. INVENTORS
(a) Name : Nadkarni Vikas Madhusudan
(b) Nationality: Indian
(c) Address : Al8 Garden Estate, Off D P Road, Aundh, Pune -411007,
Maharashtra, India.
(a) Name Dr.Ayodhya Srinavasacharya Ramacharya
(b) Nationality Indian
c) Address Flat No. 7 , Phoenix Co-operative Housing Society,
PlotNo.23,Sector 9A , Vashi, Navi Mumbai 400 703 Maharashtra, India
(a) Name : Wadekar, Shreeram Ashok
(b)Nationality : Indian
(c) Address : 204, Mohandeep Co-op Housing Society Ltd., Almeida Road,
Chandanwadi, Panchpakhadi, Thane (West) - 400 601, Maharashtra, India

(a)Name
(b)Nationality (c) Address

Dubey, Raj an
Indian
201, Ambe Bhawan CHS, Plot No. 65, Sector 12, Vashi, Navi Mumbai - 400 703, Maharashtra, India

(a) Name Jadimath Shivamurthy Padadayya
(b) Nationality Indian
c) Address Madhihal,Shirstedhar galli,Dharwad-580006
Karaataka,India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be
performed:

FIELD OF THE INVENTION:
This invention relates to an improved process for the continuous production of high molecular weight polyester resin having intrinsic viscosity (IV) upto 1 dl/g produced from low molecular weight crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g comprising nucleating agent for improving crystalline morphology, low dust generation, low oligomer volatilization in solid state polymerization process and improved properties of articles made thereof.
This invention also relates to improved process for continuous production of high molecular weight polyester resin that can be used for fiber, film or packaged container applications with acceptable clarity and hot fill performance.
This invention also relates to low molecular weight crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g comprising nucleating agent prepared by the above improved process for improving crystalline morphology, low dust generation, lower oligomer volatilization in solid state polymerization process and improved properties of articles made thereof.
This invention also relates to high molecular weight polyester resin having IV upto 1 dl/g produced from low molecular weight crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g comprising nucleating agent prepared by the above improved process for improving crystalline morphology, low dust generation, lower oligomer volatilization in solid state polymerization process and improved properties of articles made thereof.
This invention also relates to use of above mentioned high molecular weight polyester resin for preparing articles with improved properties like acceptable clarity and hot fill performance.
2

BACKGROUND OF THE INVENTION:
PET resins are well known for making films, fibers and packaged container applications. Generally, two major and distinct process steps are involved in the production of high molecular weight polyesters. These two steps include melt polymerization and solid-state polymerization (SSP).
In the conventional polymerization process for producing polyester having high intrinsic viscosity (IV), base prepolymer of IV of about 0.4 dl/g to about 0.65 dl/g is produced by melt polymerization process. These base chips are cylindrical or spherical in shape. Base polyester is amorphous in nature. Base polyester resin is then subjected to solid-state polymerization after crystallizing it in a crystallizer so as to avoid sintering or lump formation in the SSP reactor. Using SSP process, depending on the application, different IV resin can be produced. Conventional polyester polymerization processes are disclosed in US 3,405,098, 3,544,525, 4,245,253, 4,238,593, and 5,408,035.
Another polymerization process, which is different than conventional polymerization process, is disclosed in US 5,510,454, 5,532,333, 5,540,868, 5,714,262, 5,830,982, and 6,451,966 which are incorporated herein as reference in their entirety. In this polymerization process, a crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g is formed using particle former process. This prepolymer can then be used as a precursor for solid-state polymerization process to increase the IV from about 0.5 dl/g to about 1 dl/g.
However, in order to have a consistent solid-state polymerization (SSP) process, quality of low IV prepolymer has to be good. Here the term "quality" means the rate and uniformity in the crystalline morphology developed in the prepolymer during the particle former process that influence particle former shape and uniformity. If the crystalline morphology of low IV prepolymer is non-uniform, it causes uneven solid-state polymerization reaction rate and thereby variation in
3

IV, higher oligomer volatilization, and high dust generation during the SSP process, which increases the downtime of the plant since oligomers and dust deposits on the nitrogen circulation lines, filters and heaters thereby reducing their life and uneven quality of the finished product.
During the particle former process, the temperature of the prepolymer transfer line that goes from melt polymerization reactor exit to particle former is very critical in order to get the better shape and uniformity of the prepolymer. If the temperature is too low, due to the increase in the melt viscosity, melt flow becomes uneven in the particle former shell. This results in the large size variation of prepolymer causing variation in solid state polymerization since diffusion length changes with particle size. In addition, since prepolymer transfer line temperature is too low, melt freezes quickly at the exit of particle former shell causing chocking of the shell. As a result, down time of the melt polymerization reactor increases. Thus higher temperature in the prepolymer transfer line is preferred.
If transfer line temperature is too high, melt viscosity decreases causing flattening of the prepolymer on the particle former. Flatter shape results in the sharp edges that tend to give rise to higher dust at the exit of particle former and also during conveying of the prepolymer to the solid-state polymerization reactor.
It is also necessary to improve the melting temperatures of low IV prepolymer. Higher onset of melting allows solid-state polymerization process at higher temperature thus resulting in a faster IV build up. If, onset of melting of the prepolymer is low, then higher process temperature causes lump formation due to the partial or complete melting of the prepolymer, which leads to the increase in the frequency of shutdown of the plant.
Another limitation of the process is that it is difficult to produce PET resin having higher co-monomer content such as Isophthalic acid (IPA), Neopentyl glycol
4

(NPG) or Diethylene glycol (DEG). This is due to the fact that IPA, DEG or NPG reduce the rate of crystallization and reduce the melting points of the resin. In order to increase the level of crystallinity and melting point of prepolymer containing higher amount of such co-monomers which have a tendency to reduce rate of crystallization, the particle former belt speed need to be reduced, which causes the reduction in the throughput of the low molecular weight prepolymer.
In Good Manufacturing process, low IV prepolymer has to be well crystallized on the particle former to avoid lump and dust formation during solid-state polymerization under optimum process conditions.
Use of nucleating agent to increase the rate of crystallization of the polyester resin is well known in the art by using conventional polymerization process as described in EP 31,201, EP 21,648, EP 25,573, US 3,761,450, GB 2,015,014, US 3,516,957, US 4,212,791, US 4,425,470, etc.
As we have stated in the above mentioned relevant prior art, none of these patents disclose the use for nucleating agent in particle former process to give improved crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g, which is further used as a precursor for solid state polymerization process to increase the IV from about 0.5 dl/g to about 1 dl/g.
In the conventional process, faster crystallizable hot fill resin is produced by reducing the co-monomer content like IPA or DEG. By reducing the co-monomer content, melting temperature of the resin at the exit of SSP process increases. This requires higher injection moulding temperature resulting in increased energy consumption during perform production. Preforms also become hazy due to the increase in the crystal size.
5

Hot filling is the process in which the foodstuff is filled in the container at higher temperature. Hot fill performance of containers can be increased by heat setting the container after blowing. Heat setting increases the crystallinity level in the container and thus improves the dimensional stability at higher temperature of filling.
OBJECTS OF THE INVENTION:
An object of the invention is to provide an improved process for the continuous production of low molecular weight crystalline polyester prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g comprising, among other things, a nucleating agent selected from organo-metallic compounds such as sodium benzoate or sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica having particle size from about 0.001 micron to 10 micron or any other suitable nucleating agent for improving properties.
Another object of the invention is to provide an improved process for the continuous production of low molecular weight crystalline polyester prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g using nucleating agent having uniform crystalline morphology.
Another object of the invention is to provide improved process for the continuous production of low molecular weight crystalline polyester prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g using nucleating agent having improved shape and uniform size at higher prepolymer transfer line temperature, thereby reducing attrition rate and dust generation in the subsequent SSP process.
Yet another object of the invention is to provide an improved process for the continuous production low molecular weight hemispherical crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g using nucleating agent with
6

increased onset of melting during the particle former operation, thereby significantly reducing tendency of lump formation in SSP and even preventing lump formation under optimum process.
Yet another object of the invention to provide an improved process for the continuous production of low molecular weight hemispherical crystalline prepolymer of IV from about 0.1 dl/g to about 0.4 dl/g having higher co-monomer content such as IPA, NPG or DEG, etc. without reducing throughput on particle former using nucleating agent.
Yet another object of the invention to provide an improved process for the continuous production of low molecular weight hemispherical crystalline prepolymer of IV from about 0.1 dl/g to about 0.4 dl/g where the process is economical and eco-friendly.
Yet another object of the invention is to provide an improved process for the continuous production of high molecular weight polyester resins of IV of 0.5 dl/g to 1 dl/g from the low molecular weight crystalline polyester prepolymer of IV of about 0.1 to about 0.4 dl/g comprising, among other things, polyethylene terephthalate (PET) and similar terephthalate polyesters and a nucleating agent.
Yet another object of the invention is to provide an improved process for the continuous production of high molecular weight polyester resins having IV of about 0.5 dl/g to about.1 dl/g from the low molecular weight crystalline polyester prepolymer having IV of about 0.1 to about 0.4 dl/g comprising, among other things, polyethylene terephthalate (PET) and similar terephthalate polyesters and a nucleating agent for reducing the oligomer volatilization during solid state polymerization process.
Yet another object of the invention is to provide an improved process for the continuous production of high molecular weight polyester resin of IV of 0.5 dl/g to
7

1 dl/g from the low molecular weight crystalline polyester prepolymer having IV of about 0.1 to about 0.4 dl/g comprising, among other things, polyethylene terephthalate (PET) and similar terephthalate polyester and a nucleating agent for reducing the variation in IV during solid state polymerization process.
Yet another object of the invention is to provide an improved process for the continuous production of high molecular weight polyester resins having IV of about 0.5 dl/g to about 1 dl/g from the low molecular weight crystalline polyester prepolymer having IV of about 0.1 to about 0.4 dl/g comprising, among other things, polyethylene terephthalate (PET) and similar terephthalate polyesters and a nucleating agent for improving hot filling performance of the container made thereof.
Yet another object of the invention is to provide an improved process for the continuous production of high molecular weight polyester resins of IV of 0.5 dl/g to 1 dl/g from the low molecular weight crystalline polyester prepolymer of IV of about 0.1 to about 0.4 dl/g where the process is economical and eco-friendly.
Yet another object of the invention is to provide low molecular weight crystalline polyester prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g comprising, among other things, a nucleating agent selected from organo-metallic compounds such as sodium benzoate or sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica having particle size from about 0.001 micron to 10 micron or any other suitable nucleating agent for improving properties.
Yet another object of the invention is to provide low molecular weight crystalline polyester prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g using nucleating agent having uniform crystalline morphology.
8

Yet another object of the invention is to provide low molecular weight crystalline polyester prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g using nucleating agent having improved shape and uniform size at higher prepolymer transfer line temperature, thereby reducing attrition rate and dust generation in the subsequent SSP process.
Yet another object of the invention is to provide low molecular weight hemispherical crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g using nucleating agent with increased onset of melting during the particle former operation, thereby significantly reducing tendency of lump formation in SSP and even preventing lump formation under optimum process.
Yet another object of the invention is to provide low molecular weight hemispherical crystalline prepolymer of IV from about 0.1 dl/g to about 0.4 dl/g having higher co-monomer content such as IPA, NPG or DEG, etc. without reducing throughput on particle former using nucleating agent.
Yet another object of the invention is to provide low molecular weight hemispherical crystalline prepolymer of IV from about 0.1 dl/g to about 0.4 dl/g where the product is cost-effective.
Yet another object of the invention is to provide the high molecular weight polyester resins having IV of about 0.5 dl/g to about 1 dl/g produced from the low molecular weight crystalline polyester prepolymer having IV of about 0.1 to about 0.4 dl/g comprising, among other things, polyethylene terephthalate (PET) and similar terephthalate polyesters and a nucleating agent for reducing the oligomer volatilization during solid state polymerization process.
Yet another object of the invention is to provide the high molecular weight polyester resins of IV of 0.5 dl/g to 1 dl/g from the low molecular weight crystalline polyester prepolymer of IV of about 0.1 to about 0.4 dl/g comprising,
9

among other things, polyethylene terephthalate (PET) and similar terephthalate polyesters and a nucleating agent, sodium benzoate.
Yet another object of the invention is to provide the high molecular weight polyester resins having IV of about 0.5 dl/g to about 1 dl/g produced from the low molecular weight crystalline polyester prepolymer having IV of about 0.1 to about 0.4 dl/g comprising, among other things, polyethylene terephthalate (PET) and similar terephthalate polyesters and a nucleating agent for improving hot filling performance of the container made thereof.
Yet another object of the invention is to provide the high molecular weight polyester resins having IV of about 0.5 dl/g to about 1 dl/g where the product is cost-effective.
Yet another object of the invention is to provide use of high molecular weight polyester resins having IV of about 0.5 dl/g to about 1 dl/g and low molecular weight crystalline polyester prepolymer having IV of about 0.1 to about 0.4 dl/g for the production of article like preforms, beverage containers, sheets and films with improved properties like acceptable clarity and / or hot fill performance.
DETAILED DESCRIPTION OF THE INVENTION :
According to the present invention there is provided an improved process for the continuous production of high molecular weight polyester resin having IV of about 0.5 dl/g to about 1 dl/g produced from low molecular weight crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g by adding nucleating agent at any stage during the melt polymerization, but before a particle former process.
10.

The term "polyester" as used herein means polyethylene terephthalate (PET), which intends to cover polymer and a copolymers of polyethylene terephthalate.
The basic process comprising particle former process and solid-state polymerization is disclosed in US 5,510,454 (herein after referred as '454 patent), US 5,532,333, US 5,540,868, US 5,714,262, US 5,830,982, and US 6,451,966. However, none of these patents disclose the composition for the production of polyester resin having sodium benzoate or sodium acetate or any other nucleating agent for improving the rate of crystallization, uniform crystalline morphology, lower dust and reduced lump formation. Particle former process is disclosed specifically in the '454 patent.
The term "wt %" used herein refers to weight percentages based on the total weight of the polyester composition in its final form with all ingredients added.
According to the present invention there is provided an improved process for the continuous production of high molecular weight polyester resin having IV of about 0.5 dl/g to about 1 dl/g produced from faster crystallizing low molecular weight crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g; the process comprising
a. adding among other things, at least one dicarboxylic acid selected
from terephthalic acid, isophthalic acid, naphthalene dicarboxylic
acid or 4,4'-biphenyl dicarboxylic acid or monoesters thereof or
diesters thereof and at least one glycol or polyol selected from
monoethylene glycol, diethylene glycol, triethylene glycol,
propylene glycol, dipropylene glycol, butylenes glycol or 1,4-
cyclohexane diol;
b. esterifying the mixture of step (a) at temperature in the range of
250°C to 290°C;
c. removing excess of unreacted glycol or water produced in step b;
11

d. polymerizing the esterified mixture at temperature in the range of
260°C - 300°C to obtain low molecular weight polyester prepolymer
having IV of about 0.1 to about 0.4 dl/g;
e. adding nucleating agent at any steps during the melt polymerization
steps of a, b, c or d but before particle former process;
f. producing crystalline hemispherical prepolymer of polyesters by a
particle former process at temperature in the range of 110 to 160°C
and
g. polymerizing prepolymer by solid state polymerization with or
without nucleating agent to obtain high molecular weight polyester
resin having IV of about 0.5 dl/g to about 1 dl/g with faster
crystallization rate.
Preferably, the nucleating agent is selected from organo-metallic compounds such as sodium benzoate or sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica. Preferably, inorganic compounds have particle size from about 0.001 to 10 micron is used as nucleating agent. Preferably, inorganic compounds have particle size from about 0.002 to 0.5 micron is used as nucleating agent. The nucleating agent can be selected from any other suitable nucleating agent. Preferably, the nucleating agent is added in the range of about 0.001 wt % to 5 wt %; more preferably about 0.01wt % to about 0.35wt % by weight of polyester. The nucleating agent is added as a powder or as slurry prepared by mixing it in ethylene glycol at any stage of melt polymerization such as slurry mixing tank, oligomer line and column reactor particularly in the oligomer line, but before the particle former process.
The term "polyol" here intended to include any suitable di- or poly-hydroxy alcohol known to those skilled in the art.
The dicarboxylic acid may be replaced by a polyfunctional acid anhydride selected from phthalic anhydride, trimellitic anhydride or similar substances.
12

According to the present invention there is provided prepolymer having IV of about 0.1 to about 0.4 dl/g and uniform hemispherical shape, uniform particle size, uniform crystallinity, faster crystallization rate, higher onset of melting, or low dust, etc.
According to the invention there is provided prepolymer comprising among other things, at least one dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid or 4,4'-biphenyl dicarboxylic acid or monoesters thereof or diesters thereof; at least one glycol or polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane diol and a nucleating agent, selected from organometallic compounds such as sodium benzoate or sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica in the range of about 0.001 wt % to 5-wt % by weight of polyester.
The base polyester chips produced by particle formed process are crystalline in nature. These crystalline prepolymer chips can then be used as a precursor for solid-state polymerization for increasing the IV.
The above-mentioned process for production of high molecular weight polyester resin also comprises addition of any suitable additives during the solid state polymerization for the improvement of any performance of polyester article.
According to the invention there is provided high molecular weight polyester resin having IV from about 0.5dl/g to about 1 dl/g prepared from low molecular weight crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g and faster crystallization rate.
13

According to the invention there is provided high molecular weight polyester resin with an IV from about 0.5dl/g to about 1 dl/g comprising among other things, at least one dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid or 4,4'-biphenyl dicarboxylic acid or monoesters thereof or diesters thereof; at least one glycol or polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane diol and a nucleating agent, selected from organometallic compounds such as sodium benzoate or sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica in the range of about 0.001 wt % to 5-wt % by weight of polyester.
The high molecular weight polyester resin also comprises any suitable additives for the improvement of any performance of polyester article.
According to the invention there is provided use of high molecular weight polyester resin with the faster crystallization rate for the production of polyester articles such as fibers preforms, beverage containers and films with acceptable clarity and / or hot fill performance.
The present invention further discloses a process for producing a polyester resin from the prepolymer suitable for the production of preforms, containers, sheets and films, particularly beverage containers.
According to the invention there is provided high molecular weight polyester resin containing nucleating agent for the improvement of rate of crystallization, particularly polyester resin with an IV from about 0.5dl/g to about 1 dl/g from low molecular weight crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g using particle former process.
14

Low molecular PET having IV of about 0.1 dl/g to about 0.4 dl/g was prepared by the procedure disclosed in '454 patent.
The process of invention uses nucleating agent at any step during the melt polymerization steps of a, b, c or d but before particle former process. The prepolymer obtained had faster crystallization rate and prepolymer retains a better shape and uniformity on the particle former belt even at higher temperature. Increase in rate of crystallization avoids lump formation as well as reduces dust formation during solid-state polymerization under optimum process conditions and reducing the shutdown frequency of the plant. Thus the present process overcomes the problem associated with the prior art by increasing the rate of crystallization of prepolymer using nucleating agents. Thus the process is cost effective and eco-friendly. Addition of nucleating agent in the resin increases the rate of crystallization thus uniformly imparting more crystallinity in the container sidewalk This improves the dimensional stability of the container at higher temperature than that of the container without nucleating agent. Further, the present invention has a benefit of adding nucleating agent in hot fill performance of containers, more preferably blow moulded containers made from PET resin. The resin of the invention can be processed at lower injection moulding temperature and thereby causing no increase in the energy consumption. Crystal size also remains on the lower side due to the nucleating agent thus improving the clarity of the finished product like preform and bottle. Thus the high molecular weight polyester resin as well as prepolymer of the invention are cost-effective and eco-friendly as there is no dust generation or lump formation.
Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.
15

Example 1
PET prepolymer having IV of 0.245 dl/g was prepared by melt-phase polymerization process disclosed in '454 patent. Purified terephthalic acid and monoethylene glycol (MEG) were charged in 1:2 ratio in reactor. 2 wt % Isophthalic acid and 1.5 wt % diethylene glycol (DEG) were added in the reactor. Esterification reaction was carried out at 280°C. About 200 ppm Sodium benzoate was added in the oligomer. The oligomer obtained was further polymerized at 290°C to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160°C and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hour.
Example 2
PET prepolymer having IV of 0.245 dl/g was prepared by melt-phase polymerization process disclosed in '454 patent. Purified terephthalic acid and monoethylene glycol (MEG) were charged in 1:2 ratio in reactor. 2 wt % Isophthalic acid and 1.5 wt % diethylene glycol (DEG) were added in the reactor. Esterification reaction was carried out at 280°C. About 300 ppm Sodium benzoate was added in the oligomer. The oligomer obtained was further polymerized at 290°C to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving
16

steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160°C and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hour.
Example 3
PET prepolymer having IV of 0.245 dl/g was prepared by melt-phase polymerization process disclosed in '454 patent. Purified terephthalic acid and monoethylene glycol (MEG) were charged in 1:2 ratio in reactor. 2 wt % Isophthalic acid and 1.5 wt % diethylene glycol (DEG) were added in the reactor. Esterification reaction was carried out at 280°C. About 500 ppm Sodium benzoate was added in the oligomer. The oligomer obtained was further polymerized at 290CC to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160°C and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hour.
Example 4
PET prepolymer having IV of 0.245 dl/g was prepared by melt-phase polymerization process disclosed in '454 patent. Purified terephthalic acid and monoethylene glycol (MEG) were charged in 1:2 ratio in reactor. 2.6 wt % Isophthalic acid and 1.5 wt % diethylene glycol (DEG) were added in the reactor. Esterification reaction was carried out at 280°C. About 500 ppm Sodium benzoate was added in the oligomer. The oligomer obtained was further
17

polymerized at 290°C to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160°C and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hour.
Example 5
PET prepolymer of IV of 0.245 dl/g was prepared by melt-phase polymerization process. Purified terephthalic acid and MEG were charged in 1:2 ratio in reactor. 3wt % Isophthalic acid and 1.5 wt % DEG were added in the reactor. Esterification reaction was carried out at 280°C. About 500 ppm Sodium benzoate was added in the oligomer. The oligomer obtained was further polymerized at 290°C to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160°C and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hour.
Example 6
PET prepolymer having IV of 0.245 dl/g was prepared by melt-phase polymerization process. Purified terephthalic acid and monoethylene glycol
18

(MEG) were charged in 1:2 ratio in reactor. 2 wt % Isophthalic acid and 1.5 wt % diethylene glycol (DEG) were added in the reactor. Esterification reaction was carried out at 280°C. About 75 ppm barium sulfate was added in the oligomer. The oligomer obtained was further polymerized at 290°C to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160oC and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hour.
Example 7
PET prepolymer having IV of 0.245 dl/g was prepared by melt-phase polymerization process. Purified terephthalic acid and monoethylene glycol (MEG) were charged in 1:2 ratio in reactor. 2 wt % Isophthalic acid and 1.5 wt % diethylene glycol (DEG) were added in the reactor. Esterification reaction was carried out at 280°C. About 3 ppm carbon was added in the oligomer. The oligomer obtained was further polymerized at 290°C to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160°C and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hour.
19

Example 8 Comparative
PET prepolymer having IV of 0.245 dl/g was prepared by melt-phase polymerization process. Purified terephthalic acid and MEG were charged in 1:2 ratio in reactor. 2 wt % Isophthalic acid and 1.5 wt % DEG were added in the reactor. Esterification reaction was carried out at 280°C. The oligomer obtained was further polymerized at 290°C to raise the IV up to 0.245 dl/g. About 290ppm of antimony was added as a catalyst and 10 ppm P was added as a thermal stabilizer. A static mixer was put after every injection nozzle for adding any suitable additive, co monomer for better dispersion. The low IV prepolymer melt was then passed through the 1.5 mm diameter orifice to form droplets on a continuous moving steel belt of particle former. These droplets were then crystallized on the particle former maintained at a temperature between 110 to 160°C and then collected for carrying out solid-state polymerization. The prepolymer throughput was 72 kg/ hr. This prepolymer was considered as "Control".
Example 9
Solid state polymerization
Crystalline prepolymer having IV of 0.245 dl/g obtained in the examples 1 to 8, was solid-state polymerized under inert atmosphere to raise the IV up to 1 dl/g. During SSP process, the material was passed through fluid bed heater at a temperature 236°C at least for 5 minutes residence time. The material was further passed through crystallizer while maintaining the temperature at 224°C and subsequently passed through a reactor of stage 1 while maintaining the temperature at 232°C and gas / solid ratio 0.6 for atleast two hours residence time. The material was further passed through a reactor of stage 2 while maintaining the temperature at 221 °C for atleast 23 hours residence time and gas to solid ratio 0.5.
20

The properties of hemispherical shaped low molecular crystalline PET prepolymer having with and without nucleating agent prepared according to example 1,6,7 and 8 are given in the table 1.
TABLE 1: properties of hemispherical shaped low molecular crystalline PET
prepolymer

Resin Nucleating agent Concentration (ppm) I PA (wt%) Tm onset (°C) DHm(J/g) Dust content (wt %)
PET prepolymer(preparedaccording toExample 8) — — 2 223.1 51.7 0.55
PET prepolymer(preparedaccording toExample 1) Sodium benzoate 200 2 231.3 47.6 0.03
PET prepolymer(preparedaccording toExample 6) Barium sulfate 75 2 232.4 54.3 0.12
PET prepolymer(preparedaccording toExample 7) Carbon black 3 CM 231.3 45.5 0.01
Tm onset was measured using differential thermal calorimetry. Heating rate was 10°C/min,
21

Dust generation was studied using SPEX Mixer Mill -Model 8000M. Around 16g prepolymer was charged in the mill. Experiment was carried out for 30 minutes and dust generated during this period was collected and weighted.
Table 1 results indicate that the Tm onset temperature was increased and dust content were substantially reduced by adding the nucleating agents, during the melt polymerization, but before the particle former process during the production of the polyester prepolymer.
According to the present invention, the higher Tm onset of prepolymer makes it possible to carry out the SSP process at higher temperature thereby improving the solid-state polymerization rate. Higher onset of melting also reduces the sintering propensity in the SSP process.
According to the present invention, lower dust content in the prepolymer reduces the dust content in the final resin thus making it customer compliant.
Figure I illustrates the effect of nucleating agents on particle formation of PET prepolymer. H / D ratio (2) was plotted against the prepolymer weight (1) in milligrams where H is height of the chips in millimeter and D is diameter of the chips in millimeter as shown in the figure II. Total numbers of 20 prepolymer chips were analyzed. It is clear from the figure 1 that the improved H / D ratio was obtained for PET prepolymer chips with nucleating agents like sodium benzoate 200 ppm (3), barium sulfate (75 ppm) (4) and carbon black 3 ppm (5) than control sample (6) indicating improved particle formation.
The effect of nucleating agent on dust generation at higher prepolymer transfer line temperature was studied by using PET prepolymer prepared according to Examples 2 and 8. The results for the same are tabulated in Table 2. Nucleating agent reduces the dust generation even at higher prepolymer transfer line temperature.
22

TABLE 2: Effect of nucleating agent on dust generation

Resin Prepolymertransfer linetemperature(°C) Sodiumbenzoate(ppm) IPA (wt%) Dust content (wt %)
PET prepolymer(prepared according toExample 8) 290 0 2 0.80
PET prepolymer(prepared according toExample 2) 290 300 2 0.59
The effect of nucleating agent on oligomer volatilization was studied by using PET prepolymer prepared according to Example 2 and 8. The results of oligomer volatilization are tabulated in Table 3.
TABLE 3 : effect of nucleating agent on oligomer volatilization

Resin Prepolymer IV (dl/g) Sodium benzoate (ppm) % Oligomer volatilization
PET prepolymer(prepared accordingto example 8) 0.26 0 0.038
PET prepolymer(prepared accordingto Example 2) 0.26 300 0.029
Oligomer volatilization experiment was carried out in a fixed bed glass reactor at 230°C for 2 hrs under nitrogen. Prepolymer quantity was 50g. The byproduct
23

liberated were collected in a collection pot and weighed. As seen from table 3, addition of nucleating agent decreases the oligomer volatilization.
The properties of hemispherical shaped low molecular crystalline PET prepolymer having 2, 2.6 and 3 % of IPA content with 500 ppm sodium benzoate prepared according to Examples 3, 4 and 5 respectively and 2 % of IPA content without nucleating agent prepared according to Example 8 are given in the table 4.
Table 4: properties of hemispherical shaped low molecular crystalline PET, prepolymer

Resin Sodium'benzoate(ppm) IPA (wt%) Throughput Kg/hr Tmonset(°C) DHm(J/g)
PET prepolymer(prepared according toExample 8) 0 2 72 223.1 51.7
PET prepolymer(prepared according toExample 3) 500 2 72 231.3 47.6
PET prepolymer(prepared according toExample 4) 500 2.6 72 233.1 46.5
PET prepolymer(prepared according toExample 5) 500 3 72 232.6 43.2
Table 4 indicates that in-spite of higher IPA loading; Tm onset of the polyester prepolymer remained on the higher side due to the addition of nucleating agent. Thus, prepolymer with high IPA content can successfully be produced without compromising the throughput with the current process by adding nucleating
24

agent. Melting characteristics of high I PA prepolymer are improved due to the addition of nucleating agent.
Properties of PET resin, which is used for producing injection moulded preforms and subsequent blow moulded bottles, are given in the table 5.
Table 5 : Properties of PET resin

Resin Sodiumbenzoate(ppm) IV (dl/g) COOH (meq /kg) AA (ppm) IPA(wt%) DEG(wt %)
PET resin -control(preparedaccording toexample 8and 9) 0 0.772 28 0.23 2 1.5
PET resin with sodiumbenzoate(prepared according toExample 1 and 9) 200 0.779 25 0.18 2 . 1.5

Properties of injection-moulded preform produced from resin with and without sodium benzoate are given in the table 6.
Table 6: Injection moulding details

Resin Nucleating agent Concentration (ppm) Preform weight (g)
Control(prepared according to example8 and 9) — 48
PET resin(prepared according to example1 and 9) Sodium benzoate 200 48
PET resin(prepared according to example6 and 9) Barium sulfate 75 48
PET resin(prepared according to example7 and 9) Carbon black 3 48
Performs with nucleating agents have acceptable clarity.
Bottles were also produced using SIDEL SB01 single cavity blow moulding machine. Bottles prepared from perform with nucleating agents have acceptable clarity. Hot fill performance of bottles after heat set process was also improved with the addition of nucleating agent.
26

We claim
1. An improved process for the continuous production of high molecular
weight polyester resin having IV of about 0.5 dl/g to about 1 dl/g produced
from faster crystallizing low molecular weight crystalline prepolymer
having IV of about 0.1 dl/g to about 0.4 dl/g;
the process comprising
a. adding among other things, at least one dicarboxylic acid selected
from terephthalic acid, isophthalic acid, naphthalene dicarboxylic
acid or 4,4'-biphenyl dicarboxylic acid or monoesters thereof or
diesters thereof and at least one glycol or polyol selected from
monoethylene glycol, diethylene glycol, triethylene glycol,
propylene glycol, dipropylene glycol, butylenes glycol or 1,4-
cyclohexane diol;
b. esterifying the mixture of step (a) at temperature in the range of
250°C to 290°C;
c. removing excess of unreacted glycol or water produced in step b;
d. polymerizing the esterified mixture at temperature in the range of
260°C - 300°C to obtain low molecular weight polyester prepolymer
having IV of about 0.1 to about 0.4 dl/g;
e. adding nucleating agent at any steps during the melt polymerization
steps of a, b, c or d but before particle former process;
f. producing crystalline hemispherical prepolymer of polyesters by a
particle former process at temperature in the range of 110 to 160°C
and
g. polymerizing prepolymer by solid state polymerization with or
without nucleating agent to obtain high molecular weight polyester
resin having IV of about 0.5 dl/g to about 1 dl/g with faster
crystallization rate.
2. An improved process as cliamed in claim 1, wherein the nucleating agent
is selected from organo-metallic compounds such as sodium benzoate or
27

sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica.
3. An improved process as claimed in claim 2, wherein the inorganic compounds have particle size from about 0.001 micron to 10 micron.
4. An improved process as cliamed in claim 1, wherein the nucleating agent is added in the range of about 0.001 wt % to 5 wt %.
5. Prepolymer having IV of about 0.1 to about 0.4 dl/g and uniform hemispherical shape, uniform particle size, uniform crystallinity, faster crystallization rate, higher onset of melting or low dust prepared by the process as cliamed in claim 1.
6. Prepolymer as cliamed in claim 5, wherein the prepolymer comprises among other things, at least one dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid or 4,4'-biphenyl dicarboxylic acid or monoesters thereof or diesters thereof; at least one glycol or polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1 ,'4-cyclohexane diol and a nucleating agent selected from organometallic compounds such as sodium benzoate or sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica in the range of about 0.001 wt % to 5-wt % by weight of polyester.
7. High molecular weight polyester resin having IV from about 0.5dl/g to about 1 dl/g and faster crystallization rate prepared by the process as claimed in claim 1.
8. High molecular weight polyester resin as cliamed in claim 7, wherein high molecular weight polyester comprising among other things, at least one dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid or 4,4'-biphenyl dicarboxylic acid or monoesters thereof or diesters thereof; at least one glycol or polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane
28

diol and a nucleating agent selected from organometallic compounds such as sodium benzoate or sodium acetate or organic compounds such as carbon black or inorganic compounds such as barium sulfate or silica in the range of about 0.001 wt % to 5-wt % by weight of polyester. 9. High molecular weight polyester resin as cliamed in claim 7, wherein resin with the faster crystallization rate is used for the production of polyester articles such as fibers preforms, beverage containers and films with acceptable clarity and hot fill performance.

29

ABSTRACT
An improved process for the continuous production of high molecular weight polyester resin having IV of about 0.5 dl/g to about 1 dl/g produced from faster crystallizing low molecular weight crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g comprising esterifying at least one dicarboxylic acid with at least one glycol or polyol heating the mixture of step (a) at temperature in the range of 250°C to 290°C; polymerizing the esterified mixture at temperature in the range of 260°C - 300°C to obtain low molecular weight polyester prepolymer having IV of about 0.1 to about 0.4 dl/g; adding nucleating agent at any steps during the melt polymerization steps but before particle former process; producing crystalline hemispherical prepolymer of polyesters by a particle former process at 110 to 160°C temperature and polymerizing prepolymer by solid state polymerization to obtain high molecular weight polyester resin having IV of about 0.5 dl/g to about 1 dl/g with faster crystallization rate. Prepolymer having IV of about 0.1 to about 0.4 dl/g and uniform hemispherical shape, uniform particle size, uniform crystallinity, faster crystallization rate, higher onset of melting or low dust prepared by the above process. High molecular weight polyester resin having IV from about 0.5dl/g to about 1 dl/g and faster crystallization rate prepared by the above process. The resin with the faster crystallization rate is used for the production of polyester articles such as fibers preforms, beverage containers and films with acceptable clarity and hot fill performance.
31