FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule13)
1. TITLE OF THE INVENTION : An improved process for the production of
slow crystallizing polyester resin for large container application
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 : A18 Garden Estate, Off D P Road, Aundh, Pune -411007,
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 : Ayodhya, Srinivasacharya Ramacharya
(b)Nationality : Indian
(c) Address : Flat No: 7, Phoenix Co-op Housing Society, Plot No. 23,
Sector 9A, Vashi, Navi Mumbai - 400 703,
Maharashtra, India
(a)Name : Jain, Ashwin Kumar
(b)Nationality : Indian
(c) Address : C-6/2/1/1, CIDCO Colony, Sector - 18, New Panvel,
New Mumbai-400706
Maharashtra, India

(a)Name : Rane Sachin Narayan
(b)Nationality : Indian
(c) Address : Shree Ashapura Residency,
FlatNo.107.PlotNo.A5/1
Sector 7 Khanda Colony
New Panvel(W) 410206
Maharashtra, India
(a)Name
(b)Nationality : (c) Address
Limaye Chetan Vijay
Indian
Flat No.3, Pratik Pooja
Co-op Hsg. Soc. Amar Chowk Makhmalabad Naka
Panchawati Nashik- 422003
Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:
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FIELD OF THE INVENTION:
This invention relates to improved process for the production of high molecular weight polyester resin comprising neopentyl glycol or 2-methyl -1,3-propanediol suitable for thick walled container applications with slow rate of crystallization.
Particularly, the invention relates to improved process for the production of low molecular weight crystalline prepolymer having IV of about 0.1 dl/g to about 0.4 dl/g comprising neopentyl glycol or 2-methyl -1,3-propanediol, which is used as a precursor for solid-state polymerization to increase the molecular weight up to 1dl/g.
This invention relates to high molecular weight polyester resin with reduced melting point and slow rate of crystallization produced by the above process.
This invention relates to use of high molecular weight polyester resin for the production of large thick walled transparent polyester containers.
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 chip of prepolymer polyester is amorphous in nature. Base prepolymer 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.
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Using SSP process, depending on the application, different IV resin can be produced. Conventional polyester .polymerization processes are disclosed in US 3,405,098; US 3,544,525; US 4,245,253; US 4,238,593; and US 5,408,035.
Another polymerization process, which is different than conventional polymerization process, is disclosed in US 5,510,454; US 5,532,333; US 5,540,868; US 5,714,262; US 5,830,982; and US 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 is 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. In this polymerization process, the residence time in the solid-state polymerizer reactor is 24 to 32 hours. Due to such longer residence time, the crystal perfection increases resulting in the higher melting temperature of the resin. This results in higher injection moulding temperatures. Higher processing temperature would result in higher energy consumption and hence higher cost of production. Also^acetaldehyde content in the finished product such as preform and bottle would be on the higher side.
None of the processes reported in the prior art US 5,510,454, US 5,532,333, US 5,540,868, US 5,714,262, US 5,830,982, and US 6,451,966 disclose the polyester resin having neopentyl glycol as a co-monomer for reducing the crystal perfection for lower melting point.
Polyester resins are widely used as film for industrial uses and for food packaging. Polyester resins are also used in biaxially stretched bottles for packaging liquid foods and for producing large containers having volume more than five liters. Polyethylene terephthalate has excellent hygienic properties, impact resistance, heat resistance, transparency, gas barrier properties, chemical resistance, weatherability, etc. Polyethylene terephthalate (PET) resins are well known for the production of transparent containers, which are widely
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used in packaged water applications. The volume of such containers is usually in the range of about 0.25 liter to about 2 liter and the wall thickness is from about 0.2 mm to about 5 mm. These containers are produced by a stretch blow molding process in which injection moulded preforms having thickness of about 2 mm to about 10 mm are biaxially stretched to make a container of suitable shape. The clarity of preforms and bottles is essential for obtaining better market potential. If the rate of crystallization is very high, it imparts crystallinity in the preform thus making the preform hazy. If such crystalline preforms are blown to produce the bottles, the bottle will also loose the clarity and thus giving haze and further reducing the mechanical properties. In order to obtain fully amorphous preforms, the rate of crystallization of polyester must be very low. Hence, very low rate of crystallization of PET is an essential requirement for production of large thick walled transparent containers having volume from about 5 liters to about 30 liters. This is because; the thickness of the injection moulded preforms for such big containers is in the range from about 2 mm to about 10 mm and the resulting bottle thickness in the range from about 0.2 mm to 5 mm. Due to the higher thickness of preforms, in order to avoid crystallization, the cooling time for bringing the preform below the glass transition temperature increases. In order to avoid crystallization in the preform during cooling process, PET needs to be modified to exhibit very low crystallization rate.
In the prior art, PET was modified to minimize crystallization rate during parison molding and blow molding, by adding a small quantity of isophthalic acid (IPA) together with terephthalic acid as dicarboxylic acid component of PET, or cyclohexanedimethanol (CHDM) or neopentyl glycol together with ethylene glycol as glycol component of PET, thus producing copolymeric PET having a slow crystallizing rate by conventional copolymerization (Lecture abstracts of the 11th Colloquium on Structure and Physical Properties of High Polymers, held by the Japanese High Polymer Society, Kanto Branch, on June 16, 1981, "Recent Progress in Modification of Polymers" p.3.). These co-monomers are preferably added at the stage of polymerization
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Polymerization process disclosed in US 5,510,454; US 5,532,333; US 5,540,868; US 5,714,262; US 5,830,982; and US 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 the 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. Prepolymer quality can be judged by its onset of melting temperature, crystallinity, dust generation capability and particle shape and size distribution. These properties are associated with the crystallization behavior of prepolymer. Using this process, prepolymer having any additive or co-monomer that reduces the rate of crystallization, is extremely difficult since above mentioned properties deteriorate if rate of crystallization is lower.
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 uniformity in the crystalline morphology developed in the prepolymer during the particle former process. If the crystalline morphology of low IV prepolymer is non-uniform, it causes uneven solid-state polymerization reaction rate, lump formation, and high dust generation during the SSP process. 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 process.
OBJECTS OF THE INVENTION :
An object of the invention is to provide improved process for the continuous production of low molecular weight crystalline polyester prepolymer having IV of 0.1 dl/g to 0.4 dl/g comprising the co-monomer, neopentyl glycol or 2-methyl -1,3-propanediol along with conventional monomers.
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Another object of the invention is to provide the process for the continuous production of high molecular weight crystalline polyester resin having IV of about 0.5 dl/g to about 1 dl/g from the low molecular weight crystalline prepolymer having IV of 0.1 dl/g to 0.4 dl/g comprising, the co-monomer neopentyl glycol or 2-methyl -1,3-propanediol along with conventional monomers.
Yet another object of the present invention is to provide low molecular weight crystalline polyethylene terephthalate (PET) prepolymer having IV of 0.1 dl/g to 0.4 dl/g comprising co-monomer neopentyl glycol or 2-methyl -1,3-propanediol possessing lower rate of crystallization.
Yet another object of the present invention is to provide high molecular weight polyethylene terephthalate (PET) and similar terephthalate polyesters having IV of about 0.5 dl/g to about 1 dl/g comprising co-monomer neopentyl glycol or 2-methyl -1,3-propanediol possessing lower rate of crystallization and having lower melting point.
Yet another object of the present invention is to provide use of high molecular weight polyethylene terephthalate (PET) and similar terephthalate polyesters having IV of about 0.5 dl/g to about 1 dl/g comprising co-monomer neopentyl glycol or 2-methyl -1,3-propanediol for the production of thick walled container applications.
DETAILED DESCRIPTION OF THE INVENTION:
According to the invention there is provided an improved process for the continuous production of slow crystallizing high molecular weight polyester resin having IV of about 0.5 dl/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, comprising a neopentyl glycol or 2-methyl-1,3-propandiol.
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According to the present invention, there is provided an improved process for the production of uniform hemispherical polyester resin prepolymer comprising at least one dicarboxylic acid or mono- or di-ester of dicarboxylic acid, at least one polyol (The term "polyol" means alcohol having atleast two or more hydroxyl group) and neopentyl glycol or 2-methyl-1,3-propanediol. The IV of the prepolymer is in the range of about 0.1 dl/g to about 0.4 dl/g. The base polyester chips produced with this process are crystalline in nature. These crystalline prepolymer chips further used as a precursor for solid-state polymerization for increasing the IV.
According to the invention there is provide an improved process for the continuous production of slow crystallizing polyester resin suitable for the production of preforms, containers and films, particularly beverage containers, 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 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 to
290°G;
c. removing excess or unreacted polyol or water produced from the step
(b);
d. polymerizing the esterified mixture at temperature in the range at
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 neopentyl glycol or 2-methyl-1,3-propandiol at any stage during
melt polymerization steps of (a), (b), (c) or (d) but before the particle
former process;
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f. producing a crystalline and a hemispherical shape prepolymer by using
particle former process at temperature in the range of 110 to 160°C
and; and
g. polymerizing crystalline and hemispherical prepolymer by solid- state
polymerization at temperature 200°C - 240°C to produce high
molecular weight polyester resin with slow crystallizing property
suitable for the production of preforms, beverage containers and films.
Preferably, neopentyl glycol or 2-methyl-1,3-propanediol is added in the range of 0.01% to 10% by weight of polyester. More preferably, neopentyl glycol or 2-methyl-1,3-propanediol is added in the range of about 0.5% to about 5% by weight of polyester. Neopentyl glycol or 2-methyl-1,3-propanediol is added in the esterification reactor, oligomer line or column reactor particularly in the oligomer line but before the particle former process to produce polyester with slow crystallization resin. Neopentyl glycol or 2-methyl-1,3-propanediol is added to the resin at any stage of melt polymerization intended for reducing the rate of crystallization required for the production of thick walled preforms and large containers with accepted clarity.
Here weight % means the weight of the co-monomer with respect to the polyester.
The 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 using particle former process which is disclosed in US 5510454 and incorporated herein as a reference in its entirety.
Solid state polymerization process for the production of high molecular weight PET from the low molecular weight crystalline prepolymer is disclosed in US
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5,510,454; US 5,532,333; US 5,540,868; US 5,714,262; US 5,830,982; and US 6,451,966, which is incorporated herein as a refrence in its entirety. However, none of these patents disclose the composition for the production of polyester resin having neopentyl glycol for reducing its rate of crystallization.
The term "polyester" used herein is intended to include polymer and copolymer of polyethylene terephthalate (PET) or any other polyester.
Anhydrides such as pyromellitic dianhydride or trimellitic anhydride is also be used instead of dicarboxylic acid for producing slow crystallizing resin. Preferably, high molecular weight polyester resin comprises any suitable additives for the improvement of any performance of polyester article. Preferably, high molecular weight polyester resin also comprises slip additive for the improvement of slip performance of polyester article.
US 4,415,727 discloses polyester resin comprising 2-methyl -1,3-propanediol produced by the conventional polymerization process for the production of thick-walled clear polyester bottles. While none of the process reported in the US 5510454, US 5532333, US 5540868, US 5714262,. US 5830982, and US 6451966 dislcosed polyester resin comprising 2-methyl -1,3-propanediol for slow crystallizing resin for large container applications.
According to the invention there is provided slow crystallizing low molecular weight crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 and having uniform hemispherical shape, uniform particle size, uniform crystallinity prepared by the above mentioned process.
According to the invention there is provided slow crystallizing low molecular weight crystalline hemispherical 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
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thereof or diesters thereof and at least one polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane diol and neopentyl glycol or 2-methyl-1,3-propanediol in the range of 0.01% to 10% by weight of polyester. The base prepolymer polyester chips produced with this process are crystalline in nature. These crystalline prepolymer chips further used as a precursor for solid-state polymerization for increasing the IV.
According to the invention there is provided slow crystallizing low molecular weight crystalline hemispherical polyethylene terephthalate (PET) prepolymer having IV of 0.1 dl/g to 0.4 dl/g comprising co-monomer neopentyl glycol or 2-methyl -1,3-propanediol possessing lower rate of crystallization.
According to the invention there is provided slow crystallizing high molecular weight polyester resin with an IV from about 0.5dl/g to about 1 dl/g having reduced melting point prepared by the above mentioned process.
According to the invention there is provided slow crystallizing high molecular weight polyester resin having IV 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, 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 and at least one polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane diol and neopentyl glycol or 2-methyl-1,3-propanediol in the range of 0.01% to 10% by weight of polyester.
According to the invention there is provided slow crystallizing high molecular weight I polyethylene terephthalate (PET) having IV about 0.5 dl/g to about 1 dl/g produced from low molecular weight crystalline prepolymer
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having IV of about 0.1 dl/g to about 0.4 dl/g, comprising among other things, CO-monomer neopentyl glycol or 2-methyl -1,3-propanediol in the range of 0.01 % to 10% by weight of polyester.
Preferably, slow crystallizing high molecular weight polyester resin also comprises any suitable additives for the improvement of any performance of polyester article. Preferably, slow crystallizing high molecular weight polyester resin also comprises slip additive for the improvement of slip performance of polyester article.
According to the present invention, there is provided slow crystallizing high molecular weight polyester resin prepared by the above process which is used for the production of thick walled preforms or large containers or films with accepted clarity.
The present invention uses co-monomer, neopentyl glycol or 2-methyl-1,3-propanediol with branched structure, pendent groups or branching agents, which reduce the crystallizability and the packing efficiency of the chains and thus reduce the crystal perfection. Melting point will therefore be on the lower side.
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.
Example 1
PET prepolymer of 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 1% wt neopentyl glycol was added in the oligomer line. The
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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 thermal stabilizer. 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 160CC and then collected for carrying out solid-state polymerization. They were used as precursor for solid-state polymerization.
Example 2 Comparative
PET prepolymer of 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. 2wt % Isophthalic acid and 1.5 wt % diethylene glycol (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. 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 obtained was used as precursor for solid-state polymerization. This prepolymer was considered as "Control".
Example 3:
Solid state polymerization
Crystalline prepolymer having IV of 0.245 dl/g obtained in the example 1 to 2, 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
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temperature 236°C with residence time of at least for 13 minutes. The material was further passed through crystallizer maintained at 224°C and passed through a reactor of stage 1 maintaining temperature at 232°C and gas to solid ratio 0.6 with atleast two hours residence time. The material was further passed through a reactor of stage 2 maintaining temperature at 221 °C and gas to solid ratio 0.5 for atleast 23 hours residence time.
The properties of hemispherical shaped low molecular crystalline prepolymer of PET with and without neopentyl glycol prepared according to Examples 1 and 2 are given in the table 1.
TABLE 1 : Properties of hemispherical shaped low molecular crystalline prepolymer of PET with and without neopentyl glycol

Prepolymer IV (dl / g) Neopentyl glycol(wt%) Carboxylendgroups(meq / kg) Tmpeak(°C) Delta Hm (Jig)
Prepolymer ofPET(preparedaccording toExample 2) 0.245 0 141 256.0 48.0
Prepolymer ofPET(preparedaccording toExample 1) 0.255 1 123 254.1 48.4
Wherein Tm peak is the peak melting temperature and Delta Hm is the heat of fusion obtained using differential thermal calorimetry (DSC).
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Results of table 1 indicated the similar melting temperatures and crystallinity in the prepolymer with and without neopentyl glycol. This is extremely important for trouble free run of SSP process.
Melting properties of high molecular weight resin with and without neopentyl glycol are given in the table 2.
Table 2 : Melting properties of high IV resin with and without neopentyl glycol

Resin Neopetyl glycol (wt%) IV (dl/g) Melting temperatures (°C)
Tm onset Tm peak Tm end DHm(J/g)
PET (prepared according to Examples 2 and 3) 0 0.821 262.7 269.8 274.2 71.8
PET (prepared according to Examples 1 and 3) 1 0.870 256.0 263.7 269.7 65.4
Melting temperatures are obtained using DSC. Heating rate was 10°C/min.
In spite of higher IV of resin, addition of neopentyl glycol was found to reduce melting point to a larger extent.
The crystallization properties of high molecular weight resin with and without neopentyl glycol are given in the table 3.
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TABLE 3 : crystallization properties of high IV resin with and without
neopentyl glycol

Resin Neopentyl glycol (wt%) IV (dl/g) Tc onset °C (DSC) Spherulite sizeat180°C(microns)
PET(preparedaccording toExamples 2and 3) 0 0.821 223.0 21.6
PET(preparedaccording toExamples 1and 3) 1 0.870 Not observed 14.5
Wherein Tc onset is the onset of crystallization obtained by differential scanning calorimetry (DSC) during cooling from the melt state and the spherulite size obtained using hot-stage optical microscopy at 180°C during cooling scan from the molten state.
Table 3 indicated that polyester containing neopentyl glycol did not crystallize as seen from the Tc onset temperature data obtained from DSC.
Optical microscopy was used to study the morphology development in the PET resin with and without neopentyl glycol. Spherulite size obtained with neopentyl glycol (prepared according to Examples 1 and 3) was much lower than that of Control indicating slower rate of crystallization.
Preforms having sidewall thickness of 9 mm was produced using each of the high IV polyester resin obtained in a comparative example 3 was moulded in a
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injection moulding machine. Preforms were blow moulded in a 20L containers using blow-moulding machine. Table 4 indicates the injection and stretch blow moulding performance of the PET resin with or without neopentyl glycol (PET control).
Table 4 : injection and stretch blow moulding performance of PET resin
with and without neopentyl glycol

Resin Neopentyl glycol (wt%) Moulding temp (°C) Container color properties % Haze -Container
L* b*
PET-Control(preparedaccording toExamples 2and 3) — 270 - 280 — — —
PET(preparedaccording toExamples 1and 3) 1 270 - 280 95.2 1.5 0.7
As given in the table 4, clear performs could not be obtained from PET control resin (Without neopentyl glycol). Preforms made with control resin were opaque thus not subjected to blow moulding process. Better clarity of performs as well as containers were observed with PET resin containing neopentyl glycol.
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claim
1. Improved process for the continuous production of slow crystallizing
polyester resin suitable for the production of preforms, containers and
films, particularly beverage containers,
the process comprising:
h. 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 polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane diol;
i. esterifying the mixture of step (a) at temperature in the range of 250 to 290°C;
j. removing excess or unreacted polyol or water produced from the step
(b); k. polymerizing the esterified mixture at temperature in the range at
260°C - 300°C to obtain low molecular weight polyester prepolymer
having IV of about 0.1 to about 0.4 dl/g; I. adding neopentyl glycol or 2-methyl-1,3-propandiol at any stage during
melt polymerization steps of (a), (b), (c) or (d) but before the particle
former process; m. producing a crystalline and a hemispherical shape prepolymer by using
particle former process at temperature in the range of 110 to 160°C
and; and n. polymerizing crystalline and hemispherical prepolymer by solid- state
polymerization at temperature 200°C - 240°C to produce high
molecular weight polyester resin with slow crystallizing property
suitable for the production of preforms, beverage containers and films.
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2. Process as cliamed in claim 1, wherein neopentyl glycol or 2-methyl-1,3-propanediol is added in the range of 0.01% to 10% by weight of polyester.
3. Slow crystallizing low molecular weight crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 and uniform hemispherical shape, uniform particle size, uniform crystallinity prepared by the process as cliamed in claim 1.
4. Slow crystallizing prepolymer as cliamed in claim 3, wherein 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 and at least one polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane diol and neopentyl glycol or 2-methyl-1,3-propanediol in the range of 0.01% to 10% by weight of polyester.
5. Slow crystallizing high molecular weight polyester resin with an IV from about 0.5dl/g to about 1 dl/g having reduced melting point prepared by the process as claimed in claim 1.
6. Slow crystallizing high molecular weight polyester resin as cliamed in claim 5, wherein the resin having IV 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, 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 and at least one polyol selected from monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylenes glycol or 1,4-cyclohexane diol and
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neopentyl glycol or 2-methyl-1,3-propanediol in the range of 0.01 % to 10% by weight of polyester.
7. Use of slow crystallizing high molecular weight polyester resin as cliamed in claim 5 prepared by the process as cliamed in claim 1, for the production of thick walled preforms or large containers or films with accepted clarity.

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Improved process for the continuous production of slow crystallizing polyester resin suitable for the production of preforms, containers and films, particularly beverage containers comprising addition of neopentyl glycol or 2-methyl-1,3-propandiol at any stage during melt polymerization steps but before the particle former process. Slow crystallizing low molecular weight crystalline hemispherical prepolymer having IV of about 0.1 dl/g to about 0.4 and uniform hemispherical shape, uniform particle size, uniform crystallinity prepared by the above process and is used as precursor to prepare high molecular weight resin. Slow crystallizing high molecular weight polyester resin with an IV from about 0.5dl/g to about 1 dl/g having reduced melting point prepared by the above process and is used for the production of thick walled preforms or large containers or films with accepted clarity