CN1954012A - Methods of making titanium-catalyzed polyethylene terephthalate resins - Google Patents

Abstract

The present invention relates to a process for the manufacture of titanium catalyzed polyethylene terephthalate resins with reduced comonomer substitution, as well as preforms, bottles or films made from these resins.

Description

Process for the manufacture of titanium-catalyzed polyethylene terephthalate resins

Cross Reference to Commonly Assigned Applications

This application is a continuation-in-part of commonly assigned patent applications: U.S. Patent Application Serial No. 10/850,269, "Process for Making Titanium-Catalyzed Polyester Resins," filed May 20, 2004; and filed May 21, 2004 US Patent Application Serial No. 10/850,918, "Slow Crystallizing Polyester Resins." Each of these pending applications is hereby incorporated by reference in its entirety. U.S. Patent Application Serial Nos. 10/850,269 and 10/850,918 claim earliest priority to U.S. Provisional Patent Application Serial No. 60/472,309, "Titanium-Catalyzed Polyester Resins, Preforms, and Bottles," filed May 21, 2003, This provisional patent application is also incorporated by reference in its entirety.

This application further claims the benefit of the following commonly assigned provisional patent applications: US Provisional Patent Application Serial No. 60/559,983, "Titanium-Catalyzed Polyester Resins, Preforms, and Bottles," filed April 6, 2004; and US Provisional Patent Application Serial No. 60/573,024, "Slow Crystallizing Polyester Resins and Polyester Preforms with Improved Reheat Properties," filed on March 20. This application incorporates these provisional applications by reference in their entirety.

This application further incorporates by reference the following commonly assigned patent and patent application in its entirety: Serial No. 09/738,150, "Post-polymerization Injection Process in Continuous Polyethylene Terephthalate Production," filed December 15, 2000, Now US Patent No. 6,599,596; Serial No. 09/932,150, filed August 17, 2001, "Post-Polymerization Extrusion Injection Process in the Production of Polyethylene Terephthalate," now US Patent No. 6,569,991; 2001 Serial No. 10/017,612, "Post-Polymerization Injection Process in the Production of Condensation Polymers," filed December 14, now US Patent No. 6,573,359; Serial No. 10/017,400, filed December 14, 2001, "In Post-polymerization extrusion injection method," now US Patent No. 6,590,069; Serial No. 10/628,077, filed July 25, 2003, "Method for Delayed Incorporation of Additives into Polyethylene Terephthalate" ; Ser. No. 09/738,619, filed Dec. 15, 2000, "Polyester Bottle Resin Having Reduced Friction Properties and Method for Making The Same," now US Patent No. 6,500,890 and Ser. No. 10/176,737, filed June 21, 2002 , "Polymer resins with friction-reducing properties", now US Patent No. 6,727,306.

Background of the invention

Because of its strength, heat resistance and chemical resistance, polyester containers, films and fibers are an integral part of many consumer products manufactured around the world. In this regard, the most commercially valuable polyester for use in polyester containers, films and fibers is polyethylene terephthalate polyester.

Polyester resins, especially polyethylene terephthalate and its copolyesters, are also widely used in the production of rigid packaging, such as 2 liter soft drink containers. Polyester packaging produced by stretch blow molding possesses outstanding strength and crack resistance, as well as excellent gas barrier and sensory properties. As a result, this lightweight plastic has largely replaced glass in the packaging of many consumer goods such as carbonated soft drinks, juices and peanut butter.

In a common method of making bottle resins, a modified polyethylene terephthalate resin is polymerized in the melt phase to an intrinsic viscosity of about 0.6 deciliters per gram (dl/g), after which it is further polymerized in the solid phase Intrinsic viscosity for better bottle forming. Thereafter, the polyethylene terephthalate can be injection molded into preforms, which in turn can be blow molded into bottles.

Unfortunately, at normal production speeds, most polyester resins cannot be efficiently formed into preforms and bottles suitable for hot fill applications. Most high clarity polyester bottles do not possess the necessary dimensional stability for hot filling products at temperatures of about 180 to 205°F, especially about 195 to 205°F. In particular, conventional polyester bottles exhibit unacceptable shrinkage and haze at such high temperatures.

Accordingly, there is a need for polyethylene terephthalate suitable for making high clarity, hot-fill bottles that can be filled with product at temperatures of about 180 to 205[deg.]F.

Contents of the invention

Accordingly, it is an object of the present invention to provide efficient methods of forming titanium catalyzed polyethylene terephthalate resins, preforms, bottles and films.

Another object of the present invention is to provide a high clarity polyester bottle which maintains acceptable dimensional stability after hot filling with the product at a temperature of about 195[deg.]F to 205[deg.]F.

It is a further object of the present invention to provide high clarity preforms which can be efficiently formed into hot-fill polyester bottles.

Yet another object of the present invention is to provide polyethylene terephthalate that can be efficiently formed into high clarity, hot fill polyester preforms and bottles.

Yet another object of the present invention is to provide polyethylene terephthalate which can be efficiently formed into high clarity polyester bottles suitable for carbonated soft drinks.

Yet another object of the present invention is to provide polyethylene terephthalates useful in the preparation of fibres, yarns and fabrics.

The above and other objects and advantages of the present invention and the manner of realizing the present invention are further clarified in the following detailed description and accompanying drawings.

Description of drawings

Figures 1-2 illustrate the differentials performed on a titanium-catalyzed polyethylene terephthalate resin having an intrinsic viscosity of 0.78 dl/g and modified with 1.6 mol% diethylene glycol and 1.5 mol% isophthalic acid Scanning calorimetry thermal analysis.

Figures 3-4 illustrate the differentials performed on an antimony-catalyzed polyethylene terephthalate resin having an intrinsic viscosity of 0.78 dl/g and modified with 1.6 mol% diethylene glycol and 1.5 mol% isophthalic acid Scanning calorimetry thermal analysis.

Figures 5-6 illustrate the differentials performed on a titanium-catalyzed polyethylene terephthalate resin having an intrinsic viscosity of 0.78 dl/g and modified with 1.6 mol% diethylene glycol and 2.4 mol% isophthalic acid. Scanning calorimetry thermal analysis.

Figures 7-8 illustrate the differentials performed on an antimony-catalyzed polyethylene terephthalate resin having an intrinsic viscosity of 0.78 dl/g and modified with 1.6 mol% diethylene glycol and 2.4 mol% isophthalic acid Scanning calorimetry thermal analysis.

Figure 9 illustrates a graph of haze versus preform thickness measured for step parisons of titanium-catalyzed and antimony-catalyzed polyethylene terephthalate resins.

Figure 10 illustrates the theoretical loss of intrinsic viscosity for polyethylene terephthalate having an intrinsic viscosity of 0.63 dl/g as a function of concentration of reactive carrier at various molecular weights.

Figure 11 illustrates the theoretical loss of intrinsic viscosity for polyethylene terephthalate having an intrinsic viscosity of 0.45 dl/g as a function of concentration of reactive carrier at various molecular weights.

Figures 12-13 illustrate the absorption (cm ^-1 ) of a representative polyethylene terephthalate by no enhancement of heating rate additive.

Detailed description

The present invention is a slow crystallization polyethylene terephthalate resin. The inventive polyethylene terephthalate resins disclosed herein have significantly higher heating crystallization exothermic peak temperatures (T _CH ) than those of common antimony-catalyzed polyethylene terephthalate resins. This elevated heating crystallization exotherm delays the onset of crystallization. Accordingly, the polyethylene terephthalate resins of the present invention are particularly useful for making hot-fill bottles with outstanding clarity and shrinkage properties.

In one aspect, the present invention has a heating crystallization exothermic peak temperature (T _CH ) in excess of about 140° C., an absorbance (A) of at least about 0.18 cm ⁻¹ at a wavelength of 1100 nm or 1280 nm, and as described in CIE L* Polyethylene terephthalate resins with L* values over about 70 classified in the a*b* color space.

In another aspect, the invention is a polyethylene terephthalate resin comprising at least two parts per million (ppm) - preferably, less than 50 ppm - elemental titanium and a comonomer substitution of less than about 6 mole percent. The titanium catalyzed polyethylene terephthalate resins are especially useful for containers, films and packaging, but also for fibers, yarns and fabrics.

In yet another aspect, the present invention is a polyethylene terephthalate preform useful in a reinforced heat-set bottle. The polyethylene terephthalate preform has a heating crystallization exothermic peak temperature (T _CH ) in excess of about 140° C., an absorbance (A) of at least about 0.18 cm ⁻¹ at a wavelength of 1100 nm or 1280 nm, And polyethylene terephthalate resins having an L* value in excess of about 70 as classified in the CIE L*a*b* color space.

In yet another aspect, the present invention is a polyester preform capable of being formed into a high clarity bottle with excellent low shrinkage properties. The preform includes less than about 6 mole percent comonomer substitution and has an intrinsic viscosity of less than about 0.86 dl/g. In a related aspect, the invention is a high clarity, hot-fill bottle formed from a preform.

In yet another aspect, the present invention is a polyester preform capable of being formed into a high clarity bottle having excellent thermal expansion properties. The preform includes less than about 6 mole percent comonomer substitution and has an intrinsic viscosity of about 0.78 to 0.86 dl/g. In a related aspect, the invention is a high clarity, carbonated soft drink bottle formed from the preform. Carbonated soft drink bottles can withstand an internal pressure of approximately 60 psig.

In yet another aspect, the present invention is a titanium-based catalyst system that promotes the melt phase polymerization of polyethylene terephthalate resins.

In yet another aspect, the present invention is a Group I and Group II metal catalyst system that promotes solid state polymerization (SSP) of polyethylene terephthalate resins. The SSP catalyst system preferably includes alkali metals (ie, Group I metals), alkaline earth metals (ie, Group II metals), or both.

In yet another aspect, the present invention includes methods of making such polyester resins, preforms and bottles, in this regard generally comprising allowing a terephthalic acid component and a diol component (i.e., terephthalic acid moiety and diol moiety) in the presence of a titanium catalyst to form a polyethylene terephthalate precursor, which is then polymerized via melt phase polycondensation to form polyethylene terephthalate of the desired molecular weight Polymers of glycol esters. During polycondensation, usually enhanced by catalysts, ethylene glycol is removed continuously to produce favorable reaction kinetics.

It is clear to those of ordinary skill in the art that most commercial polyethylene terephthalate polymers are in fact modified polyethylene terephthalate polyesters. In fact, the polyethylene terephthalate resins described herein are preferably modified polyethylene terephthalate polyesters. In this regard, the modifiers in the terephthalic acid component and the diol component are generally randomly substituted in the resulting polyester composition.

As mentioned above, titanium catalyzed polyethylene terephthalate resins have low comonomer substitution. Polyethylene terephthalate typically includes less than about 6 mole percent comonomer substitution. Polyethylene terephthalate typically includes less than 5 mole percent comonomer substitution or greater than 2 mole percent comonomer substitution, or both.

While higher comonomer substitution disrupts crystallization, thereby improving clarity, heat setting is enhanced at lower comonomer substitution. Thus, for resins used to make hot-fill bottles, polyethylene terephthalate preferably includes about 3 to 4 mole percent comonomer substitution. For example, in one such embodiment, modified polyethylene terephthalate is composed of approximately 1:1 molar ratio of (1) 2.4 mole percent isophthalic acid to the remainder of the diacid of terephthalic acid component, and (2) a diol component consisting of 1.6 mol% of diethylene glycol and the remainder of ethylene glycol.

The term "diol component" as used herein refers primarily to ethylene glycol, although other glycols (eg, diethylene glycol) may also be used.

The term "terephthalic acid component" broadly refers to diacids and diesters that can be used in the preparation of polyethylene terephthalate. In particular, the terephthalic acid component mainly comprises terephthalic acid or dimethyl terephthalate, but can also comprise diacid and diester comonomers. In other words, "terephthalic acid component" is "diacid component" or "diester component".

The term "diacid component" refers more specifically to a diacid (eg, terephthalic acid) that can be used to prepare polyethylene terephthalate via direct esterification. However, the term "diacid component" is intended to include relatively small amounts of diester comonomers (e.g., primarily terephthalic acid and one or more diacid modifiers, but optionally also some diester modifier ).

Similarly, the term "diester component" refers more specifically to a diester (such as dimethyl terephthalate) that can be used to prepare polyethylene terephthalate via transesterification. However, the term "diester component" is intended to include relatively small amounts of diacid comonomers (e.g., primarily dimethyl terephthalate and one or more diester modifiers, but optionally also with some diacid Modifier).

Also, as used herein, the term "comonomer" is intended to include monomeric modifiers and oligomeric modifiers (eg, polyethylene glycol).

The diol component may include diols other than ethylene glycol (e.g., diethylene glycol, polyethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol , neopentyl glycol, and isosorbide), or in addition to terephthalic acid or its dialkyl esters (i.e., dimethyl terephthalate), the terephthalic acid component can include modifiers such as Isophthalic acid or its dialkyl ester (i.e., dimethyl isophthalate) 2,6-naphthalene dicarboxylic acid or its dialkyl ester (i.e., dimethyl 2,6-naphthalene dicarboxylate) , adipic acid or its dialkyl ester (i.e., dimethyl adipate), succinic acid, its dialkyl ester (i.e., dimethyl succinate), or its anhydride (i.e., succinic anhydride ), or one or more functionalized derivatives of terephthalic acid.

For the polyethylene terephthalate bottle resin according to the present invention, isophthalic acid and diethylene glycol are preferred modifiers. Those of ordinary skill in the art know that, as a modifier, cyclohexanedimethanol effectively suppresses polymer crystallinity, but has poor oxygen permeability.

For the polyethylene terephthalate fiber resins according to the invention, no comonomer substitution is necessary, but where used diethylene glycol or polyethylene glycol is preferably included.

It should be understood that when the terephthalic acid component is predominantly terephthalic acid (i.e., the diacid component), the diacid comonomer should be used, whereas when the terephthalic acid component is predominantly terephthalic acid In the case of dimethyl esters (ie, the diester component), a diester comonomer should be used.

Those of ordinary skill in the art will further understand that in order to obtain the polyester composition of the present invention, a molar excess of the diol component reacts with the terephthalic acid component (i.e., the diol component reacts in excess of the stoichiometric ratio amount exists).

In the reaction of the diacid component and the diol component via direct esterification, the molar ratio of the diacid component to the diol component is generally about 1.0:1.0 to 1.0:1.6. Alternatively, in the reaction of the diester component and the diol component via transesterification, the molar ratio of the diester component to the diol component is generally greater than about 1.0:2.0.

The diol component generally forms the majority of the ends of the polymer chains and is therefore present in somewhat higher amounts in the resulting polyester composition. This is what is called the phrases "a terephthalic acid component and a diol component in a molar ratio of about 1:1", "a diacid component and a diol component in a molar ratio of about 1:1", and "about a 1:1 molar ratio". 1 molar ratio of diester component and diol component", each of which may be used to describe the polyester composition of the present invention.

The titanium catalyzed polyethylene terephthalate resin preferably consists of a diacid component and a diol component in a molar ratio of about 1:1. The diacid component includes at least 94 mole percent terephthalic acid (eg, terephthalic acid and isophthalic acid) and the diol component includes at least 94 mole percent ethylene glycol (eg, ethylene glycol and diethylene glycol).

The titanium catalyzed polyethylene terephthalate resins according to the present invention generally have an intrinsic viscosity of less than about 0.86 dl/g. However, those of ordinary skill in the art will appreciate that polyester resins tend to lose intrinsic viscosity (eg, about 0.02-0.06 dl/g intrinsic viscosity loss from chip to preform) during injection molding operations.

For polyester preforms capable of forming high clarity, hot-fill bottles according to the present invention, polyethylene terephthalate generally has an intrinsic viscosity of less than about 0.86 dl/g, such as about 0.72 to 0.84 dl/g intrinsic viscosity. More typically, polyethylene terephthalate has an intrinsic viscosity greater than about 0.68 dl/g or less than about 0.80 dl/g, or both (i.e., about 0.68 dl/g to 0.80 dl/g) . The polyethylene terephthalate preferably has an intrinsic viscosity above about 0.72 dl/g or below 0.78 dl/g, or both (ie, about 0.72 dl/g to 0.78 dl/g). Most preferably, the polyethylene terephthalate also has an intrinsic viscosity in excess of about 0.75 dl/g (ie, about 0.75 dl/g to 0.78 dl/g). For preforms used to make hot-fill bottles, heat-setting properties are reduced at high intrinsic viscosity levels, while mechanical properties (e.g., stress cracking, dart impact, and creep) are reduced at low intrinsic viscosity levels (e.g., low Decrease at 0.6dl/g).

For polyester preforms capable of forming high clarity, carbonated soft drink bottles according to the present invention, polyethylene terephthalate generally has properties greater than about 0.72 dl/g or less than about 0.84 dl/g Viscosity, or both (ie, about 0.72 dl/g to 0.84 dl/g). The polyethylene terephthalate preferably has an intrinsic viscosity in excess of about 0.78 dl/g, most preferably, an intrinsic viscosity of about 0.80 to 0.84 dl/g.

For the polyester fibers according to the present invention, polyethylene terephthalate generally has an intrinsic viscosity of about 0.50dl/g to 0.70dl/g, preferably about 0.60dl/g to 0.65dl/g (e.g. , 0.62dl/g). The polyethylene terephthalate resins generally only polymerize in the melt phase (ie, fiber resins generally do not undergo solid state polymerization).

The term "intrinsic viscosity" as used herein is the ratio of the specific viscosity of a polymer solution of known concentration to the concentration of solute, extrapolated to zero concentration. Intrinsic viscosity, widely considered a standard measure of polymer properties, is directly proportional to average polymer molecular weight. See, for example, Dictionary of Fiber and Textile Technology, Hoechst Celanese Corporation (1990); Tortora & Merkel, Fairchild's Dictionary of Textiles (7th Edition, 1996).

One of ordinary skill in the art can measure and determine intrinsic viscosity without undue experimentation. For the intrinsic viscosity values stated herein, the intrinsic viscosity was determined by dissolving the copolyester in o-chlorophenol (OCP), measuring the relative viscosity of the solution with a Schott Autoviscometer (AVS Schott and AVS500 Viscosystem), and then calculating the intrinsic viscosity from the relative viscosity. See, for example, Dictionary of Fiber and Textile Technology ("Intrinsic Viscosity").

Specifically, 0.6 g of sample (+/- 0.005 g) of dry polymer sample was dissolved in about 50 ml (61.0-63.5 g) of o-chlorophenol at a temperature of about 105°C. Fiber and yarn samples are typically cut into small pieces and the chipped samples are ground. After cooling to room temperature, the solution is added to the viscometer at a controlled constant temperature (eg, about 20 to 25° C.) and the relative viscosity is measured. Intrinsic viscosity was calculated from relative viscosity as described above.

As noted above, titanium catalyzed polyethylene terephthalate resins generally include about 2 ppm to 50 ppm elemental titanium. Preferably, the resin includes less than 25 ppm elemental titanium (eg, about 2 to 20 ppm). More preferably, the resin includes at least about 5 ppm elemental titanium or less than about 15 ppm elemental titanium, or both (ie, about 5 to 15 ppm, such as about 10 ppm). Titanium catalysts are usually titanates such as titanium bis(acetylacetonate)diisopropoxide or tetrabutyl titanate.

Those of ordinary skill in the art know that germanium is an excellent catalyst for polyethylene terephthalate. However, germanium is prohibitively expensive, so it is not popular in the production of industrial polyester.

Thus, the resin reduces cost by incorporating less than about 20 ppm elemental germanium, typically less than about 15 ppm elemental germanium, and more typically less than about 10 ppm elemental germanium. Preferably, the titanium catalyzed polyethylene terephthalate resin includes less than 5 ppm elemental germanium and more preferably less than about 2 ppm elemental germanium. In many cases, titanium-catalyzed polyethylene terephthalate resins are substantially free of elemental germanium. In other instances, however, the titanium-catalyzed polyethylene terephthalate resin includes at least about 2 ppm elemental germanium.

Those of ordinary skill in the art will further appreciate that titanium catalyzed polyester resins have a lower rate of crystallization compared to common antimony catalyzed polyester resins. The titanium catalyzed polyethylene terephthalate resins of the present invention have lower crystallinity than otherwise identical antimony catalyzed polyethylene terephthalate resins. Without being bound by a particular theory, it is believed that titanium is a poor nucleating agent compared to antimony. Thus, the titanium-catalyzed polyethylene terephthalate resins of the present invention have a lower crystallization rate than antimony-catalyzed polyesters. As will be appreciated by those of ordinary skill in the art, this allows the preforms according to the invention to be blow molded into high clarity bottles.

Accordingly, the resins of the present invention include less than about 100 ppm elemental antimony, typically less than about 75 ppm elemental antimony, more typically less than about 50 ppm elemental antimony. Preferably, the titanium catalyzed polyethylene terephthalate resin includes less than 25 ppm elemental antimony, more preferably less than about 10 ppm elemental antimony. In many cases, titanium-catalyzed polyethylene terephthalate resins are substantially free of elemental antimony. Antimony-free polyethylene terephthalate resins may be desirable because antimony is considered a heavy metal. In other instances, however, the titanium catalyzed polyethylene terephthalate resin includes at least about 10 ppm elemental antimony.

Figures 1-8 depict differential scanning calorimetry (DSC) thermal analyzes of titanium-catalyzed and antimony-catalyzed polyester resins with intrinsic viscosities of approximately 0.78 dl/g. Figures 1-4 compare titanium-catalyzed and antimony-catalyzed polyethylene terephthalate resins with about 3 mol% comonomer substitution. Figures 5-8 compare titanium-catalyzed and antimony-catalyzed polyethylene terephthalate resins with about 4 mol% comonomer substitution.

Differential scanning calorimetry is performed by (1) maintaining a modified polyethylene terephthalate sample at 30°C for 1 minute; (2) heating the sample from 30°C to 280°C at a rate of 10°C/min ; (3) keeping the sample at 280°C for 2 minutes; and (4) cooling the sample from 280°C to 30°C at a rate of 10°C/min. Figures 1, 3, 5 and 7 correspond to heating of an amorphous polymer, while Figures 2, 4, 6 and 8 correspond to cooling of the same polymer starting from the melt phase.

Figures 1-2 show that at approximately 3% comonomer substitution (i.e., 1.6 mol% diethylene glycol and 1.5 mol% isophthalic acid substitution), titanium-catalyzed polyethylene terephthalate The ester has a heating crystallization exothermic peak temperature (T _CH ) of 144.2°C, a crystallization melting peak temperature ( _TM ) of 253.2°C, and a cooling crystallization exothermic peak temperature (T _CC ) of 186.8°C.

Figures 3-4 show that at approximately 3% comonomer substitution (i.e., 1.6 mol% diethylene glycol and 1.5 mol% isophthalic acid substitution), antimony-catalyzed polyethylene terephthalate The ester has a heating crystallization exothermic peak temperature (T _CH ) of 130.6°C, a crystallization melting peak temperature ( _TM ) of 251.5°C, and a cooling crystallization exothermic peak temperature (T _CC ) of 191.0°C.

Figures 5-6 show that at approximately 4% comonomer substitution (i.e., 1.6 mol% diethylene glycol and 2.4 mol% isophthalic acid substitution), titanium-catalyzed polyethylene terephthalate The ester has a heating crystallization exothermic peak temperature (T _CH ) of 146.3°C, a crystallization melting peak temperature ( _TM ) of 250.0°C, and a cooling crystallization exothermic peak temperature (T _CC ) of 181.3°C.

Figures 7-8 show that at approximately 4% comonomer substitution (i.e., 1.6 mol% diethylene glycol and 2.4 mol% isophthalic acid substitution), antimony-catalyzed polyethylene terephthalate The ester has a heating crystallization exothermic peak temperature (T _CH ) of 131.5°C, a crystallization melting peak temperature ( _TM ) of 250.9°C, and a cooling crystallization exothermic peak temperature (T _CC ) of 187.8°C.

As illustrated in Figures 1-8, the titanium-catalyzed polyethylene terephthalate resins of the present invention have significantly higher heating crystallization exothermic peaks compared to antimony-catalyzed polyethylene terephthalate resins temperature (T _CH ). Those of ordinary skill in the art will appreciate that this higher heated crystallization exotherm temperature is particularly desirable in blow molding operations because it delays the onset of crystallization, thereby facilitating the formation of high clarity bottles.

Thus, at a heating rate of 10°C/min as determined by differential scanning calorimetry, the polyethylene terephthalate resin has a temperature of more than about 140°C and preferably more than about 142°C (eg, 143°C to 153°C). The heating crystallization exothermic peak temperature (T _CH ). In fact, polyethylene terephthalate resins can have a crystallization exothermic peak temperature (T _CH ) > 155°C. Those of ordinary skill in the art will recognize that the heating crystallization exothermic peak temperature (T _CH ) is measured for non-crystalline polyethylene terephthalate resins.

The polyethylene terephthalate resin also has a crystalline melting peak temperature (T _M ) of at least about 240°C, usually at least about 245°C, more usually at least about 250°C. Those of ordinary skill in the art understand that the melting point is largely dependent on the comonomer content.

Furthermore, the polyethylene terephthalate resin has a cooling crystallization exotherm peak below about 190°C and typically below about 185°C at a cooling rate of 10°C/minute as determined by differential scanning calorimetry temperature (T _CC ). In some cases, the polyethylene terephthalate resin has a cooling crystallization exotherm peak temperature (T _CC ) of less than about 180°C.

The titanium catalyzed polyethylene terephthalate resins of the present invention have higher clarity than otherwise identical antimony catalyzed polyethylene terephthalate resins. In this regard, FIG. 9 depicts the ratio of an intrinsic viscosity of approximately 0.78 dl/g and 3 mol % comonomer substitution (i.e., 1.6 mol % diethylene glycol and 1.5 mol % isophthalic acid substitution) or 4 mol % comonomer Turbidity measured on step parisons of titanium-catalyzed and antimony-catalyzed polyethylene terephthalate resins with body substitution (i.e., 1.6 mol% diethylene glycol and 2.4 mol% isophthalic acid substitution). The relationship between the degree percentage and the thickness of the preform. Figure 9 illustrates that at a given comonomer substitution rate, the titanium-catalyzed polyethylene terephthalate resin has significantly lower haze than the corresponding antimony-catalyzed polyethylene terephthalate resin. Those of ordinary skill in the art will know that, generally, higher comonomer substitution disrupts polymer crystallinity, thereby reducing preform and bottle haze.

The polyethylene terephthalates of the present invention generally have a haze of less than about 20% - preferably less than about 15% haze, as measured on stepped preforms, at thicknesses greater than about 6 mm, And at thicknesses above about 4 mm, the haze is below about 5%. Also, the polyethylene terephthalate preferably has less than about 10% haze (e.g., Less than about 10% haze at a thickness of 4.5-6.0 mm). In certain formulations, the polyethylene terephthalate has less than about 20% haze at a thickness of 5.5-6.5 mm, as measured on the stepped preform. As depicted in Figure 9, polyethylene terephthalate can have a haze of less than about 50% at thicknesses in excess of about 7 mm.

Those of ordinary skill in the art understand that polyethylene terephthalate preforms and bottles must have excellent color (ie, not too yellowish). In this regard, too high levels of titanium catalyst can yellow the polyethylene terephthalate resin.

Color difference is usually classified according to the L*a*b* color space of the Commission Internationale 1’Eclairage (CIE). The three components of the system consist of L*, which describes lightness on a scale of 0-100 (ie, 0 is black and 100 is white), and a*, which describes the red-green axis (ie, positive values are red and negative values are green ), and the composition of b* (ie, positive values are yellow and negative values are blue) describing the yellow-blue axis. For characterizing polyester resins, L* and b* are of particular interest.

In this regard, it is best to measure the color of the polyester in the solid phase after polymerization. After solid-state polymerization, the polyethylene terephthalate resins of the present invention have a poly(ethylene terephthalate) resin of more than about 70, preferably more than about 75 (e.g., 77), most preferably more than about 70, as classified in the CIE L*a*b* color space. An L* value (ie, lightness) of 80. In addition, the polyethylene terephthalate resin preferably has a b* color value of less than about 2, more preferably less than about 0, as classified by the CIE L*a*b* color space. Most preferably, the polyethylene terephthalate resin has a b* color value of about -3 to 2 as classified with the CIEL*a*b* color space.

Those of ordinary skill in the art will appreciate that while it is possible to measure the color of polyester preforms and polyester bottles, it is often more convenient to measure polyester pellets or polyester slabs. (The term "pellet" as given herein generally refers to chips, pellets, etc.).

Those of ordinary skill in the art will appreciate that polyethylene terephthalate resins are typically formed into pellets before undergoing crystallization and solid state polymerization. Thus, the polyethylene terephthalate resins of the present invention are crystalline pellets after solid state polymerization but before polymer processing (eg, injection molding); it is best to measure color in this state. In this regard and unless otherwise stated (e.g., as for non-crystalline plates), the CIE L*a*b* color space values reported herein for the polyethylene terephthalate resins of the invention relate to crystalline Polyethylene terephthalate pellets.

The crystalline polyethylene terephthalate was determined using a HunterLab LabScan XE spectrophotometer (illuminant/observer: D65/10°; 45°/0° geometry; total reflection diffuser NBS78; standard color protocol LX16697) CIEL*a*b* color space values for ester pellets. Those of ordinary skill in the art will appreciate that crystalline polyester pellets are translucent and so are typically measured by reflection using a clear sample cup. In this regard, test procedures (eg, standards and calibrations) suitable for measuring the color properties of crystalline polyesters in various morphologies (eg, pellets) are readily available and understood by those of ordinary skill in the art. See http://www.hunterlab.com/measurementmethods.

As described herein, the polyethylene terephthalate resins of the present invention can be injection molded into preforms which in turn can be blow molded into bottles. However, measuring the color of preforms and bottles can be tricky. Therefore, it is best to form the preforms and bottles into panels for comparative color measurements. In this regard, polyethylene terephthalate preforms and bottles according to the invention were ground, melted at 280°C, and injected into a cold mold to form standard 3mm amorphous polyester test panels. The CIE L*a*b* color space values reported herein for the polyethylene terephthalate preforms and bottles of the present invention refer to measurements made on such standard test panels.

When forming these standard test panels from polyester preforms or polyester bottles, the polyester constituents may have an unfavorable thermal history. Those of ordinary skill in the art will appreciate that this may degrade the polyester composition somewhat. In this regard, it has been noted that injection molded preforms from pellets of crystalline polyethylene terephthalate according to the invention (thereafter to form standard test panels) may introduce some yellowing (i.e., b* color value slightly elevated).

Accordingly, the polyethylene terephthalate preforms and bottles of the present invention preferably have a color as classified in the CIE L*a*b* color space of less than about 4, more preferably less than about 2 (e.g., less than about 0) The b* color value of . The polyethylene terephthalate preforms and bottles very preferably have a b* color value of about -3 to 3 as classified in the CIE L*a*b* color space.

However, like the crystalline polyethylene terephthalate pellets described above, the polyethylene terephthalate preforms and bottles of the present invention have more than An L* value of about 70, preferably greater than about 75 (eg 77), most preferably greater than about 80 (eg 83 or higher).

As noted, these CIE L*a*b* color space values refer to measurements from standard amorphous polyester test panels.

3 mm, amorphous polyethylene terephthalate was measured using a HunterLab LabScan XE spectrophotometer (illuminant/observer: D65/10°; 45°/0° geometry; diffuse 8° standard; clear port) CIE L*a*b* color space values for glycol ester test panels. It will be understood by those of ordinary skill in the art that amorphous polyester panels are substantially transparent and so are measured by light transmission. In this regard, test procedures (eg, standards and calibrations) suitable for measuring the color properties of non-crystalline polyesters in various morphologies are readily available and understood by those of ordinary skill in the art. See http://www.hunterlab.com/measurementmethods.

According to the invention, such colors have been obtained by adding about 10 to 50 ppm elemental cobalt, preferably about 15 to 40 ppm elemental cobalt, very preferably 20 to 30 ppm elemental cobalt. In the absence of cobalt, the polyethylene terephthalate resins of the present invention tend to appear yellowish. The polyethylene terephthalate resin of the present invention has excellent color without including a colorant (other than a cobalt catalyst). (It will be understood by those of ordinary skill in the art that cobalt not only provides catalytic activity, but also imparts a blue color to the polyethylene terephthalate resin).

If the polyethylene terephthalate resin is intended for use in packaging (eg polyester preforms and bottles), it preferably includes a heating rate additive. In this regard, the heating rate additive is present in the resin in an amount sufficient to improve the reheat profile of the resin. As will be understood by those of ordinary skill in the art, heating rate additives assist the preform in absorbing energy during preform reheating. In reheating a preform, the inside of the preform should be at least as hot as the outside of the preform because the inside experiences more stretching during blow molding.

The use of slow crystallizing polyethylene terephthalate resins in the manufacture of heat set bottles is counterintuitive to those of ordinary skill in the art. For example, US Patent No. 6,699,546 (Tseng) teaches the introduction of nucleating agents to accelerate the rate of resin crystallization for obtaining improved heat set bottles.

As previously explained, slow crystallizing polyethylene terephthalate resins have significantly higher heating crystallization exothermic peak temperatures (T _CH ) compared to those of antimony-catalyzed polyethylene terephthalate resins. . The purpose of the heat-setting process is to maximize bottle crystallinity and stress relaxation while maintaining clarity. It appears that slower crystalline resins have lower heat-setting capabilities. Therefore, there appears to be no practical benefit in introducing heating rate additives to achieve higher preform temperatures - and thus increase the crystallinity of slower crystalline resins. In such cases, one of ordinary skill in the art would not expect to obtain improved bottle properties (eg, clarity and shrinkage).

For example, bottle preforms prepared from slow crystallizing polyethylene terephthalate resins (eg, the titanium-catalyzed polyester resins disclosed herein) further comprising a heating rate additive are contemplated. As mentioned above, titanium slows down the initiation of thermal crystallization of the preform compared to antimony when the preform is heated. However, the heating rate additive causes the preform to absorb more energy and thus reach significantly higher temperatures before crystallization starts. Thus, good preform clarity is maintained even at elevated preform temperatures.

Surprisingly, the inventors have discovered that introducing sufficient heating rate additives to modify slow crystallizing polyester resins to improve the reheat properties of the resins actually improves blow molding performance and bottle performance, such as shrinkage. Elevated preform temperatures in the blow molding and heat setting processes increase bottle crystallization and stress relaxation while producing bottles with better clarity than antimony catalyzed polyethylene terephthalate resins.

In one embodiment, the heating rate additive is a carbon-based heating rate additive. Carbon-based heating rate additives are typically present in polyethylene terephthalate resins in amounts below about 25 ppm. More preferably, the carbon-based heating rate additive is present in the polyethylene terephthalate resin in an amount of about 4 to 16 ppm (eg, 8-12 ppm), most preferably in an amount of about 6 to 10 ppm. Suitable carbon-based additives include carbon black, activated carbon and graphite. For example, satisfactory carbon black heating rate additives are disclosed in US Patent No. 4,408,004 (Pengilly), which is incorporated herein by reference in its entirety.

In another embodiment, the heating rate additive is a metal-containing heating rate additive. The metal-containing heating rate additive is generally present in the polyethylene terephthalate resin in an amount of about 10-300 ppm, more typically in an amount greater than about 75 ppm (eg, about 150 to 250 ppm). Suitable metal-containing heating rate additives include metals, metal oxides, minerals (eg, copper chromite spinel), and dyes. For example, US Patent No. 6,503,586 (Wu), which is hereby incorporated by reference in its entirety, discloses satisfactory inorganic black pigments and particles.

Preferred metal-containing heating rate additives are tungsten-based additives, such as tungsten metal or tungsten carbide. In this regard, the tungsten-containing heating rate additive powder preferably has an average particle size of about 0.7 to 5.0 microns, more preferably about 0.9 to 2.0 microns.

Particle size is typically determined by light scattering based techniques, as will be appreciated by those skilled in the art. Particle size and particle size distribution are often characterized according to ASTM B330-2 ("Standard Test Method for Fisher Number of Metal Powders and Related Compounds).

Other preferred metal-containing heating rate additives are molybdenum-based additives, especially molybdenum sulfide ( _MoS2 ). In this regard, molybdenum sulfide has outstanding heat absorbing properties, so it can be introduced in slightly lower amounts (eg, 5-100 ppm) than other metal-containing heating rate additives.

The most preferred heating rate additives are natural and synthetic spinels. The spinel is preferably included in the polyethylene terephthalate resin in an amount of about 10 to 100 ppm (eg, about 15 to 25 ppm). Particularly prominent spinel pigments are copper chromite black spinel and chromite nickel black spinel.

These spinels are disclosed in commonly assigned US Patent Application Serial No. 09/247,355, "Thermoplastic Polymers Having Improved Infrared Reheat Properties," filed February 10, 1999, and divisions thereof; In US Patent Application Serial No. 09/973,499 published January 31, 2002 as US Patent Publication 2002/0011694A1; US Patent Application Serial No. 09/973,520 published March 7, 2002 as US Patent Publication 2002-0027314A1; and US Patent Application Serial No. 09/973,436, published March 21, 2002 as US Patent Publication 2002-0033560A1. Each of these patent applications and patent publications is incorporated by reference in its entirety.

For a particular bottle production rate, the heating rate of a polyethylene terephthalate preform can be described by surface temperature measurements at fixed locations on the preform.

In the manufacture of polyethylene terephthalate bottles, polyethylene terephthalate bottle preforms are reheated by passing the preforms through the reheat oven of a blow molding machine. The reheat furnace consisted of a set of quartz lamps (3,000 and 2,500 watt lamps) that primarily emitted radiation in the infrared range. The ability of the preform to absorb this radiation and convert it into heat, thereby bringing the preform to the orientation temperature for blow molding, is important for optimal bottle performance and efficient production. Important bottle properties for bottle use characteristics are material distribution, orientation and sidewall crystallinity.

The preform reheat temperature is important to control these properties. The preform reheat temperature is generally in the range of 30-50°C above the glass transition temperature ( _Tg ) of polyethylene terephthalate, depending on the type of bottle to be manufactured. The reheat temperature depends on the application (eg, hot fill beverage bottles or carbonated soft drink bottles). In high speed polyethylene terephthalate blow molding machines, such as those manufactured by Sidel, Inc. (Le Havre, France), the rate at which the preform can be reheated to the orientation temperature is important for optimal bottle use characteristics of. This is especially true for heat set bottles intended to be filled with hot liquids in excess of 185°F. In the manufacture of heat-set bottles, this preform is heated rapidly to the highest possible temperature. This maximizes crystallization during blow molding and avoids thermal crystallization of the preform. Those of ordinary skill in the art will appreciate that such thermal crystallization may result in unacceptable turbidity due to spherical crystallization.

In view of the importance of preform reheating, the following method has been employed to evaluate the reheat characteristics of polyethylene terephthalate preforms. As a first thing to do, this test method analyzes polyethylene terephthalate preforms (or resins) by forming test parisons from one or more polyethylene terephthalate resin formulations. ) reheating characteristics. Experimental parisons are actually tested, not industrial preforms:

First, test resins were molded into 5.25 inch test parisons having a weight of 47 grams, an overall diameter of 1.125 inches, and a neck finish of 0.75 inches. To form the test parisons, polyethylene terephthalate resin was dried in a dryer at 350°F for 4 hours. The dry resin was introduced into a 4 oz Newbury injection molding machine. The resin was kneaded and melted to provide a molten resin having a temperature of 500-520°F. The molten resin was then injected into a preform mold designed for a 2L carbonated soft drink bottle. The total cycle time is 60 seconds, including injection, filling and cooling times. The mold was continuously cooled to 45°F. These injection molding conditions resulted in clear test parisons that were predominantly amorphous (ie, less than about 4% crystallinity).

The reheat performance of 5.25 inch test parisons was tested with a Sidel SBO1 laboratory blow molding machine. The machine has a reheating furnace with a set of up to 10 independently regulated quartz lamps, an infrared camera for measuring the surface temperature of the preform, a robot for transfer from the furnace to the blow mold, a blow mold, The plastic mold extends to the bottle manipulator at the machine outlet.

In this test method, a SBO1 laboratory blow molding machine continuously produces polyethylene terephthalate bottles at a rate of 1,000 bottles/hour using 8 quartz lamps. The oven has a power control that can be adjusted as a percentage of the total oven power output. Also, each lamp can be adjusted as a percentage of independent lamp power output.

To determine the reheat characteristics of 5.25 inch preforms, the machine was set at a bottle production rate of 1,000 bottles/hour. A standard resin is selected to produce the test parison. Then, the reheat characteristics of the test parisons were determined. Using the reheat feature, commercially acceptable bottles were produced at 80% of the total power output. Thereafter, the percentage of total power was varied between 65 and 90%, and the surface temperature was repeatedly measured at a fixed location on the test parison.

The reheat performance of the 5.25 inch test parisons was measured unchanged at 1.4 inches below the support ring of the necklace. At this location (ie, 1.4 inches below the support ring), the test parison had a wall thickness of 0.157 inches.

Example 1

Two liter polyethylene terephthalate bottle test preforms were produced from a standard resin (ie, Wellman's PermaClear(R) HP806 polyester resin). The test preform required eight reheat zones for making straight walled two liter bottles. The reheat characteristics of the PermaClear(R) HP806 test parison at 80% total oven power percentage are shown in Table 1:

Table 1

Heating zone Power output (%) 1 74 2 60 3 55 4 55 5 55 6 68 7 86 8 74

After establishing this reheat profile, two samples were prepared from antimony-catalyzed polyethylene terephthalate resins with less than about 6 mol% comonomer replacement. One sample included approximately 11 ppm of a carbon-based heating rate additive (Resin A) and the other sample, the control, included no heating rate additive (Resin B). Resins A and B were otherwise identical except for the presence of the reheat rate additive. The reheat performance (ie, via surface temperature) of Resin A and Resin B was then measured (in 5% increments) at 65-90% of the total oven power output:

Table 2

Total oven power output (%) Resin A (surface temperature ℃) Resin B (surface temperature ℃) 65 87.3 81.0 70 92.0 85.0 75 95.8 87.5 80 100.5 92.0 85 107.0 97.3 90 113.0 101.0

Table 2 illustrates that improved preform reheat characteristics were obtained as a result of the introduction of the heating rate additive.

Therefore, in order to improve preform reheat characteristics, the polyethylene terephthalate resin of the present invention preferably includes a concentration sufficient to obtain the reheat surface temperature of the above-mentioned 5.25 inch test parison (at a neck wall thickness of 0.157 inches). Measured at 1.4 inches below the decorated support ring) is at least about 4°C higher than the corresponding reheat temperature obtained from an otherwise identical 5.25 inch test parison (i.e., without the reheat rate additive), where the reheat rate additive Blow molding in a Sidel SBO1 laboratory operating at a production rate of 1,000 bottles/hour with 8 lamps at heated surface temperatures of 65%, 70%, 75%, 80%, 85% and 90% of total power On-board measurement. More preferably, the difference in temperature between the reheated surfaces is at least about 7°C, most preferably at least about 10°C.

In another embodiment, the polyethylene terephthalate of the present invention preferably includes a concentration sufficient to achieve the average reheat surface temperature of the above-mentioned 5.25 inch test parison (at the support ring of the neckpiece with a wall thickness of 0.157 inches). Measured at 1.4 inches below) is at least about 5°C, preferably about 10°C, higher than the average reheat surface temperature obtainable from an otherwise identical 5.25 inch test parison (i.e., without the reheat rate additive), Wherein the reheat surface temperature is determined on a Sidel SBO1 laboratory blow molding machine operating at a production rate of 1,000 bottles/hour and employing 8 lamps at a total power level between 65% and 90%.

Alternatively, the intrinsic heating rate of a polyester resin can be described by its characteristic energy absorption. In this regard, electromagnetic radiation exists in several spectra. For example, electromagnetic radiation can be measured in the ultraviolet, visible, near-infrared, and far-infrared ranges. The visible spectrum is between approximately 430nm and 690nm. The spectrum is bounded by ultraviolet radiation and far infrared radiation, respectively. Near infrared radiation (NIR) is of particular interest for the reheat profile of polyesters.

More specifically, the intrinsic heating rate of polyester resins can be characterized by their electromagnetic radiation absorptivity. The rate of absorption is described by Beer's law, which is expressed in Equation 1:

Equation 1 A＝ε·1·c

in

A is the electromagnetic radiation absorptivity of the sample,

ε is the proportionality constant of the sample (i.e., the "molar absorptivity"),

l is the path length of the sample through which the electromagnetic radiation must travel, and

c is the concentration of the sample (usually measured in mol/L).

However, for polyester resins, Equation 1 can be simplified. For certain polyester resins, molar absorptivity and sample concentration are negligible. Also, there is a linear relationship between absorbance and path length (ie, sample thickness). Therefore, for a polymer resin, the absorbance (A) can be calculated from the transmittance (T) as follows:

Equation 2 A=log(100)-log(%T)

As expressed in Equation 3, Equation 2 is further simplified:

Equation 3 A=2-log(%T)

Simply put, transmittance is the ratio of the intensity of electromagnetic radiation transmitted through a polymeric resin to the intensity of electromagnetic radiation entering the polymeric resin. Absorption (calculated from the relationship expressed in Equation 3) as reported here describes the electromagnetic radiation that non-crystalline polyethylene terephthalate resin fails to transmit.

As previously stated, the polyethylene terephthalate resins of the present invention generally have an absorbance (A) of at least about 0.18 cm ^-1 at a wavelength of 1100 nm or at a wavelength of 1280 nm. Moreover, the polyethylene terephthalate resin of the present invention generally has an absorptance (A) of at least about 0.20 cm ^-1 at a wavelength of 1100 nm or at a wavelength of 1280 nm, preferably at a wavelength of 1100 nm or at a wavelength of 1280 nm. Typically have an absorbance (A) of at least about 0.24 cm ⁻¹ at a wavelength, more preferably at a wavelength of 1100 nm or generally have an absorbance (A) of at least about 0.28 cm ⁻¹ at a wavelength of 1280 nm.

Those of ordinary skill in the art will understand that, as used herein, transitional conjunctions (ie, "or") include coordinating conjunctions (ie, "and"). Also, for purposes of this disclosure, absorbance is reported for non-crystalline polyesters.

In its most preferred embodiment, the polyethylene terephthalate resin has an absorbance (A) of at least about 0.25 cm ⁻¹ at a wavelength of 1100 nm or at a wavelength of 1280 nm, preferably at a wavelength of 1100 nm Or having an absorbance (A) of at least about 0.30 cm ⁻¹ at a wavelength of 1280 nm. In certain embodiments, the polyethylene terephthalate resin has an absorbance (A) of at least about 0.30 cm ⁻¹ at a wavelength of 1100 nm or at a wavelength of 1280 nm, and in particular embodiments, at 1100 nm having an absorbance (A) of at least about 0.40 cm ⁻¹ at a wavelength of 1280 nm or at a wavelength of 1280 nm. These polyethylene terephthalate resins can be obtained by incorporating about 10-100 ppm of copper chromite black spinel.

In this respect, heating rates for amorphous, unreinforced polyethylene terephthalate resin (PET) and otherwise identical but with 22 ppm copper chromite black spinel in the visible and NIR spectral ranges Additive-reinforced polyethylene terephthalate resin (PET/spinel) was used to determine the absorbance. Table 3 reports the absorbance of these polyester resins at 550nm, 700nm, 1100nm and 1280nm:

table 3

Absorption rate(cm ^-1 ) 550nm 700nm 1100nm 1280nm PET 0.209 0.170 0.145 0.144 PET/Spinel 0.399 0.374 0.314 0.314

The wavelengths reported in Table 3 are meaningful. In particular, 550nm is near the midpoint of the visible spectrum and 700nm is near the upper end of the visible spectrum. Also, as depicted in Figures 12-13, the absorbance of unenhanced PET is nearly flat (i.e., the slope is about 0) at 1100 nm and 1280 nm, thereby facilitating achievable spectra at these wavelengths in the NIR spectral range. Repeated measurements.

To enhance color, it is preferred that the heating rate additive promotes the absorption of more NIR radiation and less visible radiation. This can be described by the absorption ratio as defined herein. Briefly, for polyester resins, the absorptance ratio is simply the antilog of the absorbance at the first wavelength divided by the antilog of the absorbance at the second wavelength. This is expressed in Equation 4:

Equation 4 Absorption ratio = (antilog A ₁ )/(antilog A ₂ )

in

A ₁ is the absorbance at the first wavelength, and

_A2 is the absorbance at the second wavelength.

For absorbance, the first wavelength is typically in the NIR spectrum (eg, 1280nm) and the second wavelength is typically in the visible spectrum (eg, 550nm). Table 4 shows that polyethylene terephthalate reinforced with 22 ppm copper chromite spinel has similar absorption selectivity to unreinforced polyethylene terephthalate, but significantly higher Absorbance (eg, absorbance above 0.30 cm ⁻¹ at 1100 nm and 1280 nm).

Table 4

Absorption ratio 1100:550 1280:550 1100:700 1280:700 PET 0.864 0.862 0.945 0.943 PET/Spinel 0.822 0.822 0.871 0.871

The polyethylene terephthalate resins of the present invention preferably have a 1100:550 absorption ratio of at least about 70%, or at least about 70% of a 1280:550 absorption ratio. More preferably, the polyethylene terephthalate resins of the present invention have a 1100:550 absorption ratio of at least about 75%, or at least about 75% of a 1280:550 absorption ratio. In certain embodiments, the polyethylene terephthalate resins of the present invention preferably have a 1100:550 absorption ratio of at least about 80%, or at least about 80% of a 1280:550 absorption ratio.

Similarly, the polyethylene terephthalate resins of the present invention preferably have a 1100:700 absorption ratio of at least about 85%, or at least about 85% of a 1280:700 absorption ratio. In certain embodiments, the polyethylene terephthalate resins of the present invention preferably have an absorption ratio of at least about 90% (i.e., 95% or higher) of 1100:700, or at least about 90% (i.e., 95% or higher). Higher) 1280:700 absorption ratio.

For this disclosure, a Foss Series 6500 Transport Analyzer was used to determine the absorbance of three millimeter (3 mm) amorphous polyester panels. This instrument is typical of those capable of measuring transmittance in the visible and NIR spectrum, since instrument coefficients (eg, lamp, detector, vibration, and air filtration) can affect absorbance measurements. The use of appropriate standards and calibrations is, of course, within the purview of one of ordinary skill in the art.

To control for assay variability, the absorbance data had to be normalized at an incident wavelength of 2132 nm such that the corresponding absorbance was 0.473 mm ⁻¹ (ie, 4.73 cm ⁻¹ ). At this wavelength, the additive has a modest effect on the absorbance of amorphous polyethylene terephthalate.

The inventors have also considered the effect of sample reflectance, but have determined that it can be ignored in determining the absorbance of polyester resins. In short, reflectivity is the radiation scattered from the surface of a solid, liquid or gas. As expressed in Equation 5, the reflected electromagnetic energy is expressed in terms of absorbed and transmitted energy:

Equation 5 I _O =I _A +I _T +I _R

in

I _O is the incident energy,

I _A is the absorbed energy,

I _Y is the transmitted energy, and

I _R is the reflected energy.

Absorptivity is derived from transmittance, as described earlier. See Equation 3. The reflectance is generally not measured, so the inventors have considered whether ignoring the reflectance in the measurement of the absorptivity introduces a large error.

In this regard, polyester panels with polished surfaces appear to have higher reflectivity than polyester panels with "matte" or other non-reflective finishes. Increasing reflectance appears to decrease transmittance if reflectance is not considered. According to Equation 3, this will have the effect of spuriously increasing the calculated absorption rate.

Therefore, batches of the polyester sheet should have a consistent finish (ie, semi-gloss) in order to reduce absolute reflectance and control reflectance variability. It is believed that by controlling the physical properties of the polyester sheet in this manner, reflectance can be neglected in evaluating absorptance and absorptance ratio.

Those of ordinary skill in the art know that there are two general methods for forming polyethylene terephthalate. These methods are well known to those skilled in the art.

One method employs direct esterification using terephthalic acid and excess ethylene glycol. In this technique, the above step of reacting the terephthalic acid component and the diol component involves reacting terephthalic acid and ethylene glycol in a heated esterification reaction to form a mixture of terephthalic acid and ethylene glycol. Monomers and oligomers, and water by-products. In order for the esterification reaction to proceed substantially to completion, water, if formed, must be continuously removed. The monomers and oligomers are then catalytically polymerized via polycondensation to form polyethylene terephthalate polyester. As mentioned above, ethylene glycol is continuously removed during polycondensation, resulting in favorable reaction kinetics.

Other methods involve two-step transesterification and polymerization using dimethyl terephthalate and excess ethylene glycol. In this technology, the above-mentioned step of reacting the terephthalic acid component and the diol component comprises allowing dimethyl terephthalate and ethylene glycol to react in a heated, catalyzed transesterification reaction (i.e., transesterification), Bis(2-hydroxyethyl) terephthalate monomer is formed, as well as methanol as a by-product.

In order for the transesterification reaction to proceed substantially to completion, methanol must be continuously removed as it is formed. The bis(2-hydroxyethyl) terephthalate monomer product is then catalytically polymerized via polycondensation to form polyethylene terephthalate polymer. The resulting polyethylene terephthalate polymer is essentially identical to the polyethylene terephthalate polymer obtained from direct esterification with terephthalic acid, with some minor chemical differences (e.g., terminal differences).

Polyethylene terephthalate can be produced in a batch process in which the product of the transesterification or esterification reaction is formed in one vessel and then transferred to a second vessel for polymerization. Generally, the second vessel is agitated and the polymerization is continued until the power applied to the agitator reaches a level indicating that the polyester melt has achieved the desired intrinsic viscosity and thus the desired molecular weight. However, it is more practical industrially to carry out the esterification or transesterification reaction followed by the polymerization reaction as a continuous process. Continuous production of polyethylene terephthalate results in higher throughput and is therefore more typical in large-scale production facilities.

In the present invention, direct esterification is preferred over the old fashioned two-step transesterification which is uneconomical and often results in polyethylene terephthalate with an undesirable color.

In this regard, and as described above, the direct esterification technique reacts terephthalic acid and ethylene glycol with no more than 6 mole percent diacid and diol modifiers to form low molecular weight monomers, oligomers and water. In particular, titanium and cobalt catalysts are preferably added during the esterification process, as this has been found to improve the color of the resulting polyethylene terephthalate resin. The polyethylene terephthalate resin may optionally include other catalysts, such as aluminum-based catalysts, manganese-based catalysts, or zinc-based catalysts.

More specifically, the titanium catalyst is incorporated in an amount sufficient that the final polyethylene terephthalate resin contains from about 2 to 50 ppm elemental titanium. Likewise, the cobalt catalyst is incorporated in an amount sufficient that the final polyethylene terephthalate resin includes about 10 to 50 ppm elemental cobalt. In order to prevent process failures (eg, clogged pipes), it is recommended to introduce the titanium and cobalt catalysts into the esterification vessel using different delivery devices.

The introduction of titanium or cobalt catalysts increases the rate of esterification and polycondensation, thus increasing the production of polyethylene terephthalate resin. However, these catalysts ultimately degrade the grade of polyethylene terephthalate. For example, degradation can include polymer discoloration (eg, yellowing), acetaldehyde formation, or molecular weight reduction. To reduce these undesirable effects, stabilizing compounds can be used to sequester ("cool") the catalyst. The most commonly used stabilizers contain phosphorus, usually in the form of phosphates and phosphites.

Accordingly, the resins of the present invention generally include a phosphorus stabilizer. In this regard, the phosphorus stabilizer is preferably incorporated into the polyethylene terephthalate polymer such that, on an elemental (eg, about 5 to 15 ppm), more preferably less than about 10 ppm (ie, about 2 to 10 ppm), is present in the resulting resin. The phosphorus stabilizer may be introduced into the melt phase at any time after esterification, but preferably the phosphorus stabilizer is added to the melt after polycondensation is substantially complete.

Although adding phosphorus stabilizers to polymer melts in batch reactors is a relatively simple process, many problems arise if the stabilizers are added in the continuous production of polyethylene terephthalate. For example, although early addition of a stabilizer prevents discoloration and degradation of polyester, it also causes a reduction in throughput (ie, a reduction in the rate of polycondensation reaction). Also, the addition of phosphorus stabilizers, which are usually soluble in glycol, further slows down the polymerization process. Thus, adding stabilizers early in the polymerization process requires an undesirable choice between polymer throughput and thermal stability. "Thermal stability" as used herein refers to a low rate of acetaldehyde production, little discoloration, and retention of molecular weight after subsequent heat treatment or other processing.

Late addition of phosphorus stabilizer may provide insufficient opportunity for complete blending of the stabilizer with the polymer. Therefore, phosphorus stabilizers may not prevent polyester degradation and discoloration. Additionally, adding phosphorus stabilizers during polymer processing is often inconvenient and does not provide economies of scale.

US Patent No. 5,376,702, entitled "Method and Apparatus for Direct and Continuous Modification of Polymer Melts," discloses dividing a polymer melt stream into an unmodified stream and a branch stream receiving additives. In particular, side streams introduce a portion of the branch stream to the extruder where the additives are introduced. However, this technique is complex and costly, requiring screw extruders and melt piping to handle the additives. Thus, such formulations are inconvenient and even impractical at low total additive concentrations (eg, less than 1 wt%).

Some of the problems associated with late addition of stabilizers are addressed in US Patent No. 5,898,058, entitled "Postpolymerization Stabilization of Highly Active Catalysts in Continuous Polyethylene Terephthalate Production"; Method for stabilizing highly active polymerization catalysts in the production of ethylene terephthalate. This patent, which is commonly assigned with this application, is hereby incorporated by reference in its entirety.

In particular, US Patent No. 5,898,058 discloses the addition of stabilizers, preferably containing phosphorus, at the end of or after polymerization and prior to polymer processing. This deactivates the polymerization catalyst and increases the throughput of the polyester without adversely affecting the thermal stability of the polyethylene terephthalate polyester. While a significant improvement over conventional techniques, US Patent No. 5,898,058 teaches adding stabilizers without a carrier. As a result, adding the solids to the polymer necessitates the costly use of extruders.

The aforementioned US Application Serial No. 09/738,150 (now US Patent No. 6,599,596), entitled "Post-Polymerization Injection Process in Continuous Polyethylene Terephthalate Production," discloses the use of Process for producing high quality polyethylene terephthalate polyester improved by stabilizer addition technology.

More specifically, US Application No. 09/738,150 discloses the post-incorporation of additives into the process of making polyethylene terephthalate. These additives are introduced during the polycondensation of the polyethylene terephthalate polymer, preferably afterwards. In particular, the method employs a reactive carrier, which not only serves as a delivery vehicle for one or more additives, but also reacts with polyethylene terephthalate to incorporate in the polyethylene terephthalate resin the carrier. Also, US Application Serial No. 09/738,150 discloses that this can be accomplished with a simplified additive delivery system that does not require the use of an extruder. (US Application Serial No. 09/932,150 entitled "Post-Polymerization Extruder Injection Process in the Production of Polyethylene Terephthalate", now US Patent No. 6,569,991, is a continuation-in-part of US Application Serial No. 09/738,150 , discloses a method of introducing additives at the end of the extruder during the process of preparing polyethylene terephthalate.)

The phosphorus stabilizers disclosed herein can be incorporated into polyethylene terephthalate polymers directly, as a concentrate in polyethylene terephthalate, or as a concentrate in a liquid carrier. The preferred time of addition in the polyethylene terephthalate polymerization process is after polycondensation is complete (ie, mixing with the molten polymer stream after the final polymerization vessel).

The phosphorus stabilizer is preferably incorporated into the polyethylene terephthalate polymer via a reactive carrier rather than via an inert carrier or completely unsupported. The reactive support, preferably having a molecular weight above about 200 g/mol and below about 10,000 g/mol, can be introduced during the polycondensation, or more preferably, after the polycondensation is complete. In either aspect, the reactive carrier should be incorporated into the polyethylene terephthalate polymer in such an amount that the properties of the bulk polymer are not significantly affected.

In general, the reactive carrier should not exceed about 1% by weight of the polyethylene terephthalate resin. Preferably, the reactive carrier is incorporated into the polyethylene terephthalate polymer in an amount such that its concentration in the polymer resin is less than about 1,000 ppm (ie, 0.1 wt %). Reducing the reactive carrier to an amount such that its concentration in the polymer resin is below 500 ppm (ie, 0.05 wt %) will further reduce potential adverse effects on bulk polymer properties.

Most preferably, the reactive carrier has a melting point that ensures that it is a liquid or slurry at near ambient temperature. Near ambient temperature not only simplifies device operation (eg, extruders, heaters, and piping), but also minimizes degradation of inert particulate additives. As used herein, "near ambient temperature" includes temperatures of about 20 to 60°C.

In general, reactive supports with carboxyl, hydroxyl or amine functional groups are advantageous. It is preferred that the polyols, especially polyester polyols and polyether polyols, have a molecular weight high enough that the polyol does not significantly reduce the intrinsic viscosity of the polyethylene terephthalate polymer and that the pumping of the polyol is facilitated the viscosity. Polyethylene glycol is the preferred polyol. Other exemplary polyols include functionalized polyethers such as polypropylene glycol prepared from propylene oxide, random and block copolymers of ethylene oxide and propylene oxide, and polytetramethylene obtained from the polymerization of tetrahydrofuran. diol.

Additionally, the reactive support may include dimerized or trimerized acids and anhydrides. In another embodiment, the reactive support may have internal functional groups (eg, esters, amides, and anhydrides) that are reactive with polyethylene terephthalate polymers in addition to or instead of terminal functional groups. In yet another embodiment, the reactive carrier may include non-functionalized esters, amides, or anhydrides that are capable of reacting into the polyethylene terephthalate polymer during solid-state polymerization without rendering the polyethylene terephthalate polymer Ethylene glycol diformate polymers suffer from loss of intrinsic viscosity during the injection molding process.

In view of the foregoing, a preferred method of preparing the titanium-catalyzed polyethylene terephthalate resins of the present invention involves allowing a diacid component comprising at least 94 mole percent terephthalic acid and a diacid component comprising at least The diol component of 94 mol% ethylene glycol was reacted. The diacid and diol modifiers should be included such that the resulting polyethylene terephthalate polymer has a comonomer substitution of less than about 6 mol%. For example, the diacid component preferably comprises about 1.6 to 2.4 mole percent isophthalic acid with the balance terephthalic acid, and the diol component comprises 1.6 mole percent diethylene glycol and the balance ethylene glycol.

The esterification reaction is catalyzed by titanium and cobalt to form monomers and oligomers of terephthalic acid and diacid modifiers with ethylene glycol and diol modifiers, and water. As water is formed, it is continuously removed to allow the esterification reaction to proceed substantially to completion. The titanium catalyst and the cobalt catalyst are simultaneously in amounts sufficient to cause the polyethylene terephthalate resin to contain about 2 to 50 ppm (e.g., 5-15 ppm) of elemental titanium and about 10 to 50 ppm of elemental cobalt (e.g., 20-30 ppm). introduce.

The monomers and oligomers are then polymerized via melt phase polycondensation into polyethylene terephthalate polymer. The phosphorus stabilizer is then incorporated into the polyethylene terephthalate polymer, preferably using a reactive carrier. As noted above, the reactive carrier promotes homogeneous blending within the polymer melt. Phosphorus stabilizers are generally incorporated into polyethylene terephthalate polymers such that phosphorus is present in the resulting resin in an amount of about 2 to 60 ppm, preferably less than about 10 or 15 ppm on an elemental basis. Thereafter, the polyethylene terephthalate polymer is formed into pellets and then polymerized in the solid state to an intrinsic viscosity below 0.86 dl/g (eg, 0.75-0.78 dl/g).

Preferably, the reactive carrier is a polyol (e.g., polyethylene glycol) with a molecular weight such that the polyol is pumpable at near ambient temperatures (e.g., below 60° C.) and such that polyethylene terephthalate The bulk properties of the alcohol ester polymer are incorporated into the polyethylene terephthalate polymer in an amount such that the bulk properties of the alcohol ester polymer are not significantly affected (eg, an amount such that its concentration in the polymer is less than about 1 weight percent). The polyethylene terephthalate polymer is then formed into chips (or into pellets via a polymer cutter) prior to solid state polymerization. Importantly, the polyol-reactive carrier binds the polyethylene terephthalate polymer so that it cannot be extracted during subsequent processing operations (eg, forming polyester preforms or beverage containers).

Other additives can be introduced into the polyethylene terephthalate resin of the invention via a reactive carrier. Such additives include preform heating rate enhancers, friction reducing additives, UV absorbers, inert particulate additives (such as clay or silica), colorants, antioxidants, branching agents, oxygen barriers, carbon dioxide barriers, oxygen scavengers agent, flame retardant, crystallization control agent, acetaldehyde reducer, impact modifier, catalyst deactivator, melt strength enhancer, antistatic agent, lubricant, chain extender, nucleating agent, solvent, filler and plasticizer.

Post-addition is especially desirable when the additive is volatile or prone to thermal degradation. Common additive injections prior to polycondensation, such as in the esterification stage of polyester synthesis, or early during the polycondensation stage subject the additive to high temperature (above 260° C.) and reduced pressure (below 10 Torr) conditions for several hours. As a result, additives with significant vapor pressure under these conditions will be lost from the process. Advantageously, the late addition via the reactive carrier significantly reduces the time the additive is exposed to high polycondensation temperatures.

As will be understood by those of ordinary skill in the art, a macromolecule is considered to be a polymer having an intrinsic viscosity of about 0.45 dl/g. This roughly translates to a molecular weight of at least about 13,000 g/mol. In contrast, reactive supports according to the invention have a molecular weight of more than about 200 g/mol and less than about 10,000 g/mol. The molecular weight of the reactive carrier is generally below 6,000 g/mol, preferably below 4,000 g/mol, more preferably about 300 to 2,000 g/mol, most preferably about 400 to 1,000 g/mol. Molecular weight as used herein is a number average molecular weight, not a weight average molecular weight.

Figures 10 and 11 illustrate the theoretical loss of intrinsic viscosity as a function of reactive carrier concentration at several molecular weights. Figure 10 depicts the effect of a reactive carrier on polyethylene terephthalate having an intrinsic viscosity of 0.63 dl/g. Similarly, Figure 11 depicts the effect of a reactive carrier on polyethylene terephthalate having an intrinsic viscosity of 0.45 dl/g. Note that reactive carriers with high molecular weight have less detrimental effect on the intrinsic viscosity of the polymer resin at any concentration.

In a typical exemplary process, a continuous feed is entered into a direct esterification reaction vessel which is operated at a temperature of about 240 to 290° C. and a pressure of about 5 to 85 psia for about 1 to 5 hours. The esterification, preferably catalyzed with titanium and cobalt catalysts, forms low molecular weight monomers, oligomers and water. Water is removed as the reaction proceeds to drive a favorable reaction equilibrium.

Thereafter, low molecular weight monomers and oligomers are polymerized via polycondensation to form polyethylene terephthalate polyester. The polycondensation stage typically employs a train of two or more vessels and operates at a temperature of about 250 to 305°C for about 1 to 4 hours. The polycondensation reaction usually starts in a first vessel called the low polymerizer. The oligomer operates at a pressure range of approximately 0 to 70 Torr. Polycondensation of monomers and oligomers to form polyethylene terephthalate and ethylene glycol.

Ethylene glycol is removed from the polymer melt with an applied vacuum to drive the reaction to completion. In this regard, the polymer melt is typically agitated to facilitate the separation of ethylene glycol from the polymer melt and to facilitate passage of the highly viscous polymer melt through the polymerization vessel.

When the polymer melt is fed to a continuous vessel, the molecular weight and thus the intrinsic viscosity of the polymer melt increases. The temperature of each vessel is generally increased and the pressure decreased to provide higher polymerization in each successive vessel.

The final vessel, commonly referred to as a "high polymerizer", operates at a pressure of about 0 to 40 Torr. Like the oligomerizer, each polymerization vessel is connected to a vacuum system with a condenser, and each is usually agitated to facilitate the removal of ethylene glycol. The residence time in the polymerization vessel and the feed rate of the ethylene glycol and terephthalic acid fed continuous process are determined in part by the target molecular weight of the polyethylene terephthalate polyester. Because the molecular weight can be easily determined from the intrinsic viscosity of the polymer melt, the intrinsic viscosity of the polymer melt is generally used to determine the polymerization conditions, such as temperature, pressure, feed rate of reactants, and in the polymerization vessel. the residence time.

Note that in addition to the formation of the polyethylene terephthalate polymer, side reactions occur which form undesirable by-products. For example, the esterification of ethylene glycol forms diethylene glycol, which is incorporated into the polymer chain. As known to those skilled in the art, diethylene glycol lowers the softening point of the polymer. Also, cyclic oligomers (for example, trimers and tetramers of terephthalic acid and ethylene glycol) may be present in small amounts. Continuous removal of ethylene glycol as it is formed in the polycondensation reaction generally reduces the formation of these by-products.

After the polymer melt exits the polycondensation stage, usually from the polymerizer, the phosphorus stabilizer is introduced via the reactive carrier. Thereafter, the polymer melt is usually filtered and extruded. After extrusion, the polyethylene terephthalate is quenched, preferably by spraying with water, to solidify it. Cut the cured polyethylene terephthalate polyester into chips or pellets for storage and handling. The polyester pellets preferably have an average mass of about 15-20 mg. As used herein, the term "pellet" is used to refer generally to chips, pellets, and the like.

While the preceding discussion assumes a continuous production process, it should be understood that the invention is not so limited. The teachings disclosed herein can be applied to semi-continuous processes, and even batch processes.

As is known to those skilled in the art, pellets formed from polyethylene terephthalate polymers can be crystallized followed by solid state polymerization to increase the molecular weight of the polyethylene terephthalate resin. Compared to antimony, for example, titanium is significantly less active as an SSP catalyst. Therefore, in order to facilitate the solid state polymerization of polyethylene terephthalate resins, a complementary SSP catalyst is introduced into the polymer melt prior to solid state polymerization, preferably during polycondensation.

Preferred SSP catalysts include Group I and Group II metals. Acetates of Group I and II metals (eg, calcium acetate, lithium acetate, manganese acetate, potassium acetate, or sodium acetate) or terephthalates can increase the rate of solid state polymerization. The SSP catalyst is generally incorporated in an amount sufficient that the polyethylene terephthalate resin includes about 10 to 70 ppm of elemental metal.

Following solid state polymerization, the polyester chips are then remelted and reextruded to form bottle preforms, which can thereafter be formed into polyester containers (eg, beverage bottles). Bottles formed from the resins and preforms described herein preferably have a sidewall haze of less than about 15%, more preferably less than about 10%.

Typically, hot-fill bottles according to the present invention exhibit an average circumferential dimensional change of less than about 3% when filled at 195°F and less than about 5% when filled at 205°F, which The average circumferential dimensional change is measured from the shoulder to the base of the bottle. Moreover, such hot-fill bottles according to the present invention exhibit a maximum circumferential dimension change from shoulder to base of the bottle of less than about 5% - preferably less than 4% - when the bottle is filled at 195°F. (This shrinkage performance was determined using 24-hour aged bottles.)

As will be understood by those of ordinary skill in the art, polyethylene terephthalate is typically converted into containers via a two-step process. First, an amorphous bottle preform (eg, less than about 4% crystallinity and typically about 4 to 7 mm thickness) is produced from the bottle resin by melting the resin in an extruder and injection molding the molten polyester into a preform. The outer surface area of such preforms is generally at least an order of magnitude smaller than the outer surface area of the final container. The preform is reheated to the orientation temperature, which is typically 30°C above the glass transition temperature ( _Tg ).

The reheated preform is then put into a bottle blow mold and shaped into a heated bottle by stretching and expanding with high-pressure air. The blow mold is maintained at a temperature of about 115 to 200°C, typically about 120 to 160°C. Those of ordinary skill in the art will recognize that the introduction of compressed air into the heated preform affects the formation of the heated bottle. Thus, in a variant, the cooling of the heated bottle is facilitated by the turbulent release of compressed air from the bottle by balayage techniques. It is believed that preforms according to the invention can be blow molded into low shrinkage bottles using sub-atmospheric pressures for compressed air.

For the high clarity, hot fill polyester bottle of the present invention, after the reheat step, the preform is blow molded into a low shrink bottle in a cycle time of less than about 6 seconds (i.e., at normal production rates) .

Those of ordinary skill in the art will understand that any defects in the preform are generally transferred to the bottle. Therefore, the quality of the bottle resin used to form the injection molded preform is critical to obtaining an industrially acceptable bottle. Injection molded preforms and stretch blow molded bottles are discussed in US Patent No. 6,309,718 entitled "Large Polyester Containers and Methods of Making Same," which patent is hereby incorporated by reference in its entirety.

Those of ordinary skill in the art will further appreciate that branching agents can be incorporated in small amounts (eg, less than about 2,000 ppm) to increase the rate of polymerization and improve the bottle manufacturing process. Chain branching agents can be introduced, for example, during esterification or melt phase polymerization. Typically, less than 0.1 mole percent branching agent is included in the polyethylene terephthalate resins of the present invention.

The term "branching agent" as used herein refers to a multifunctional monomer that promotes the formation of side branches along the main polymer chain that link monomer molecules. See Odian, Principles of Polymerization, pp. 18-20 (second edition 1981). The chain branching agent is preferably selected from trifunctional, tetrafunctional, pentafunctional and hexafunctional alcohols or acids copolymerizable with polyethylene terephthalate. As will be understood by those skilled in the art, trifunctional branching agents have one reactive site available for branching, tetrafunctional branching agents have two reactive sites available for branching, pentafunctional Branching agents have three reactive sites available for branching, while hexafunctional branching agents have four reactive sites available for branching.

Acceptable chain branching agents include, but are not limited to, pyromellitic acid (C ₆ H ₃ (COOH) 3 ), pyromellitic acid (C ₆ H ₂ (COOH) ₄ ), pyromellitic dianhydride, metamellitic acid Trimellitic acid, trimellitic anhydride, trimethylolpropane (C ₂ H ₅ C(CH ₂ OH) ₃ ), ditrimethylolpropane (C ₂ H ₅ C(CH ₂ OH) ₂ C ₂ H ₄ OC(CH ₂ OH) ₂ C ₂ H ₅ ), dipentaerythritol (CH ₂ OHC(CH ₂ OH) ₂ C ₂ H ₄ OC(CH ₂ OH) ₂ CH ₂ OH), pentaerythritol (C(CH ₂ H) ₄ ), ethyl Oxylated glycerol, ethoxylated pentaerythritol (3EO/4OH and 15EO/4OH) from Aldrich Chemicals), ethoxylated trimethylolpropane (2.5EO/OH and 20EO/3OH from Aldrich Chemicals), and Lutrol HF-1 (ethoxylated glycerol ex BASF).

Preferred aromatic chain branching agents - aromatic rings appear to inhibit stress nucleation - include trimellitic acid (TMLA), trimellitic anhydride (TMA), pyromellitic acid (PMLA) pyromellitic dianhydride (PMDA ), benzophenone tetracarboxylic acid, benzophenone tetracarboxylic dianhydride, naphthalene tetracarboxylic acid, and naphthalene tetracarboxylic dianhydride, and their derivatives:

(Trimellitic acid-TMLA)

(Trimellitic Anhydride-TMA)

(pyrimellitic acid-PMLA)

(Pyrimellitic dianhydride-PMDA)

(Benzophenone-3,3',4,4'-tetracarboxylic dianhydride)

(1,4,5,8-naphthalene tetracarboxylic dianhydride)

This application fully incorporates by reference the following commonly assigned patents, each of which discusses stoichiometric molar ratios relative to reactive end groups (i.e., "molar equivalent branches"): entitled "Polyethylene Glycol Modified Polyesters US Patent No. 6,623,853 entitled "Nonwoven Fabric Formed from Polyethylene Glycol-Modified Polyester Fibers and Method of Preparation"; US Patent No. 6,582,817 entitled "Polyethylene Glycol Alcohol-modified polyester fiber" US Patent No. 6,509,091; US Patent No. 6,454,982 entitled "Method for preparing polyethylene glycol-modified polyester filament"; US Patent No. 6,399,705 entitled "Process for Polyester Filament of Polyethylene Glycol-modified Polyester Fibers"; US Patent No. 6,322,886 entitled "Nonwoven Fabrics Formed from Polyethylene Glycol-Modified Polyester Fibers and Process for Making the Same"; and US Patent No. 6,303,739, entitled "Polyethylene Glycol Modified Polyester Filament and Process for its Preparation." US Patent No. 6,303,739.

Typical embodiments of the present invention have been disclosed in the specification and drawings. Certain terms are used in a generic and descriptive sense only and not for limitation. The scope of the invention is given in the following claims.

Claims (47)

1. The manufacture method of the titanium-catalyzed polyethylene terephthalate resin, comprising: In the esterification reaction, a diacid component comprising at least 94 mol % terephthalic acid and a diol component comprising at least 94 mol % ethylene glycol are reacted to form terephthalic acid and the diacid modifier with ethylene glycol and monomers and oligomers of diol modifiers, and water; introducing a titanium catalyst and a cobalt catalyst during the esterification reaction in an amount sufficient for the polyethylene terephthalate resin to include about 2 to 50 ppm elemental titanium and about 10 to 50 ppm elemental cobalt; removing the water formed during the esterification reaction so that the esterification reaction can be substantially completed; Monomers and oligomers are polymerized via melt phase polycondensation to a polyethylene terephthalate polymer, wherein the polyethylene terephthalate polymer has a comonomer substitution of less than about 6 mole percent ;and The polyethylene terephthalate polymer was solid state polymerized. 2. The method according to claim 1, wherein the step of introducing a titanium catalyst and a cobalt catalyst comprises making the polyethylene terephthalate resin sufficient to include about 2 to 20 ppm of elemental titanium and about 15 to 40 ppm of elemental cobalt Quantities of titanium catalyst and cobalt catalyst were introduced. 3. The method according to claim 1, wherein the step of polymerizing the monomers and oligomers via melt phase polycondensation comprises polymerizing the monomers and oligomers into polyparaphenylene having a comonomer substitution of less than about 2 and 5 mole % Ethylene glycol dicarboxylate polymer. 4. The method according to claim 1, wherein the step of solid state polymerizing the polyethylene terephthalate polymer comprises solid state polymerizing the polyethylene terephthalate polymer to a concentration of less than about 0.86 dl/g intrinsic viscosity. 5. The method according to claim 1, wherein the step of solid state polymerizing the polyethylene terephthalate polymer comprises solid state polymerizing the polyethylene terephthalate polymer to a concentration greater than about 0.68 dl/g intrinsic viscosity. 6. The method according to claim 1, further comprising the step of introducing a phosphorus stabilizer. 7. The method according to claim 6, wherein the step of introducing a phosphorus stabilizer comprises: after completing the esterification reaction and before starting solid-state polymerization, so that the polyethylene terephthalate resin is sufficient to include about 2 to An amount of 60 ppm elemental phosphorus was introduced into the phosphorus stabilizer. 8. The method according to claim 6, wherein the step of introducing a phosphorus stabilizer comprises introducing a reactive carrier having a molecular weight of about 200 g/mol to 10,000 g/mol into the polyethylene terephthalate polymer, the The reactive carrier is the delivery vehicle for the phosphorus stabilizer. 9. The method according to claim 8, wherein the step of introducing the reactive carrier into the polyethylene terephthalate polymer comprises injecting the reactive carrier as a liquid or slurry at a temperature close to ambient temperature. 10. The method according to claim 8, wherein the step of introducing the reactive carrier into the polyethylene terephthalate polymer comprises satisfying the requirements of the reactive carrier in the polyethylene terephthalate polymer. The reactive carrier is introduced at a concentration of less than about 1 wt%. 11. The method according to claim 10, wherein the reactive support has a molecular weight of about 300 to 2,000 g/mol. 12. The method according to claim 8, wherein the step of introducing the reactive carrier into the polyethylene terephthalate polymer comprises satisfying the requirements of the reactive carrier in the polyethylene terephthalate polymer. The reactive carrier is introduced at a concentration of less than about 1,000 ppm. 13. The method according to claim 8, wherein the reactive support has a molecular weight of less than about 4,000 g/mol. 14. The method according to claim 8, wherein the reactive support has a molecular weight of about 400 to 1,000 g/mol. 15. The method according to claim 1, further comprising the step of introducing a heating rate additive in an amount sufficient to improve the reheat performance of the polyethylene terephthalate resin. 16. The method of claim 15, wherein the step of introducing a heating rate additive comprises introducing a carbon-based heating rate additive in an amount of less than about 25 ppm. 17. The method of claim 16, wherein the step of introducing a carbon-based heating rate additive comprises introducing a carbon-based heating rate additive selected from the group consisting of carbon black, activated carbon, and graphite, and combinations thereof, in an amount of about 4 to 16 ppm. 18. The method of claim 15, wherein the step of introducing a heating rate additive comprises introducing a metal-containing heating rate additive in an amount of about 10 ppm to 300 ppm. 19. The method of claim 18, wherein the step of introducing a metal-containing heating rate additive comprises introducing spinel in an amount of about 10 ppm to 100 ppm. 20. The method of claim 1, further comprising the step of introducing an SSP catalyst that increases the rate of solid state polymerization. 21. The method according to claim 20, wherein the step of introducing the SSP catalyst comprises introducing the SSP catalyst during melt phase polycondensation. 22. The method according to claim 20, wherein the SSP catalyst comprises an alkali or alkaline earth metal. 23. The method of claim 1, further comprising the step of forming the polyethylene terephthalate polymer into pellets prior to initiating solid state polymerization. 24. The method of claim 1, further comprising the steps of forming the polyethylene terephthalate polymer into a bottle preform and thereafter forming the bottle preform into a bottle. 25. The method according to claim 1, further comprising the step of forming the polyethylene terephthalate polymer into a film. 26. The method according to claim 1, wherein the step of introducing a titanium catalyst and a cobalt catalyst comprises simultaneously introducing a titanium catalyst and a cobalt catalyst during the esterification reaction. 27. The method according to any one of claims 2-25, wherein the step of introducing a titanium catalyst and a cobalt catalyst comprises simultaneously introducing a titanium catalyst and a cobalt catalyst during the esterification reaction. 28. The method of any one of claims 1-26, wherein the step of introducing a titanium catalyst comprises introducing the titanium catalyst in an amount sufficient to include about 5 to 15 ppm elemental titanium in the polyethylene terephthalate resin. 29. The method of any one of claims 1-26, wherein the step of introducing a cobalt catalyst comprises introducing the cobalt catalyst in an amount sufficient to include about 20 to 30 ppm elemental cobalt to the polyethylene terephthalate resin. 30. The method according to any one of claims 1-26, wherein the step of polymerizing monomers and oligomers via melt phase polycondensation comprises polymerizing the monomers and oligomers to have less than about 3 and 4 mole % comonomer replacement rate polyethylene terephthalate polymer. 31. The method according to any one of claims 1-26, wherein the step of solid state polymerizing the polyethylene terephthalate polymer comprises solid state polymerizing the polyethylene terephthalate polymer to about 0.72 to an intrinsic viscosity of 0.84dl/g. 32. The method according to any one of claims 1-26, wherein the step of solid state polymerizing the polyethylene terephthalate polymer comprises solid state polymerizing the polyethylene terephthalate polymer to less than about Intrinsic viscosity of 0.80dl/g. 33. The method of any one of claims 6-14, wherein the step of introducing a phosphorus stabilizer includes introducing a phosphorus stabilizer in an amount sufficient to include less than about 40 ppm elemental phosphorus in the polyethylene terephthalate resin. 34. The method of any one of claims 6-14, wherein the step of introducing a phosphorus stabilizer includes introducing a phosphorus stabilizer in an amount sufficient to include less than about 15 ppm elemental phosphorus in the polyethylene terephthalate resin. 35. The method according to any one of claims 8-14, wherein the reactive carrier comprises a polyol having a molecular weight sufficiently high that the polyol does not significantly degrade the polyethylene terephthalate The intrinsic viscosity of the polymer. 36. The method according to any one of claims 1-26, further comprising the step of forming the polyethylene terephthalate polymer into a preform. 37. The method of claim 36, further comprising the step of forming the preform into a container. 38. A polyethylene terephthalate resin manufactured according to the method of any one of claims 1-26. 39. The polyethylene terephthalate resin produced according to the method of any one of claims 1-26, wherein the polyethylene terephthalate resin comprises less than 100 ppm elemental antimony and less than about 20 ppm element germanium. 40. The polyethylene terephthalate resin produced according to the method of any one of claims 1-26, wherein the polyethylene terephthalate resin comprises less than 50 ppm elemental antimony. 41. The polyethylene terephthalate resin produced according to the method of any one of claims 1-26, wherein the polyethylene terephthalate resin comprises less than 25 ppm elemental antimony and less than about 5 ppm element germanium. 42. A polyethylene terephthalate resin manufactured according to the method of any one of claims 1-26, wherein the polyethylene terephthalate resin has a color space as in CIE L*a*b* L* values greater than about 75 for the medium classification. 43. A polyethylene terephthalate resin manufactured according to the method of any one of claims 1-26, wherein the polyethylene terephthalate resin has a color space as in CIE L*a*b* b* color values below 2 for the medium category. 44. A polyethylene terephthalate resin manufactured according to the method of any one of claims 1-26, wherein the polyethylene terephthalate resin has a color space as in CIE L*a*b* L* values greater than about 80 for the medium classification. 45. A polyethylene terephthalate preform manufactured according to the method of any one of claims 1-26. 46. A polyethylene terephthalate container manufactured according to the method of any one of claims 1-26. 47. A polyethylene terephthalate film manufactured according to the method of any one of claims 1-26.

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