MXPA99005161A - Process for making pen/pet blends and transparent articles therefrom - Google Patents

Abstract

Process for controlling the change of intrinsic viscosity and transesterification during solid stating of a polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) blend, with an effective amount of an alkylene glycol compound. The process enables the production of a copolymer based on predefined initial and final IV's and final transesterification level, by varying the solid-stating time and/or effective amount of alkylene glycol. In one embodiment, a relatively greater amount of post-consumer PET (e.g., 70%) having an IV of on the order of 0.72-0.73, is incorporated in the blend to provide a final IV on the order of 0.80-0.85, and a moderate, controlled level of transesterification;the blend is used to injection mold a sleeve layer of a preform. Inanother embodiment, a substantially transparent neck finish for a preform is made from a PEN/PET blend having an amount of alkylene glycol which enables substantial transesterification, without excessive increase in IV.

Description

PROCESS FOR MAKING MIXTURES OF POLYETHYLENE-NAPHTHALATE / POLYETHYLENE-TERTHTALATE AND TRANSPARENT ARTICLES THEREOF FIELD OF THE INVENTION The present invention relates to a process for making blends of polyethylene naphthalate and polyethylene terephthalate, and more particularly to a method for controlling the change in intrinsic viscosity and the level of transesterification during solid fixation of these blends.

BACKGROUND OF THE INVENTION Polyethylene naphthalate (PEN) has a significantly higher glass transition temperature (Tg) than polyethylene terephthalate (PET), ie approximately 120 ° C compared to 80 ° C, as well as a five-fold improvement in the property of oxygen barrier. PEN in this manner is a desirable polymer for use in thermally resistant beverage containers (ie, hot refillable containers, REf .: 30406 refillable and / or pasteurizable), and for packaging oxygen sensitive products (eg, beer, juice). However, the PEN is more expensive (both in terms of material and processing costs) than the PET, and therefore, the improvement in the properties must be balanced against the increased expense. One method to achieve an item that is lower cost than PEN, but with superior thermal and barrier properties, is to provide a mixture of PEN and PET. However, the mixing of these two polymers frequently results in an opaque material with incompatible phases. Efforts to produce a clear container or film of a PEN / PET mixture have been continued for ten years, but there is still no commercial process in widespread use to produce these articles. A suggested method for making substantially transparent PEN / PET mixtures is a solid fixing process that increases the level of transesterification (copolymerization) of the two polymers. For example, WO 92/02584 (Eastman) declares that transesterification occurs when the polymer crystallized, or mixed with fusion is they maintain a temperature below the melting point and are subjected to a flow of inert gas in order to increase the inherent viscosity and / or remove acetaldehyde. This transesterification is also that which occurs during fusion mixing and molding operations. However, Eastman reports that when the level of transesterification between the two polymers is very high, the crystallinity and physical properties resulting from mixing are reduced to the point where they are undesirable to make oriented containers with good mechanical properties. Eastman teaches the addition of a phosphorus stabilizer to control (reduce) the amount of transesterification that occurs during solid fixation. Thus, Eastman claims to limit the amount of transesterification to an amount not greater than about 20%, based on a theoretical maximum transesterification amount that is equal to 100%, for example, in Table 2, Eastman describes transesterification and inherent viscosity of several PEN / PET mixtures, fixed in solid, where the initial inherent viscosity of the mixture was in the order of 0.55 to 0.65, and the inherent viscosity final was approximately 0.90 to 0.85. in a control example (50-50 of PEN / PET), the inherent, final viscosity was acceptable (0.86) after eight hours, but the percent of transesterification (25.0) was too high (above 20%) . By adding 0.5 to 1.0% of Ultramox 626 (a phosphite stabilizer) in the first two examples, the Eastman process provided a final inherent viscosity of 0.80 to 0.84 after eight hours, and an acceptable percent of transesterification of 17.0 to 19.0 (below 20%). The other three metal stabilizers / deactivators tested in Table 2 failed to provide the inherent, desired, final viscosity and transesterification levels. Although the Eastman process may be suitable for certain starting materials, limited, and desired levels of transesterification, different combinations of intrinsic viscosity, solid fixation time, and transesterification levels can not be expected in general. For example, of potential interest is an elaborate mixture of the precursor homopolymer PEN and the PEN after the consumer (PC- PET). The intrinsic viscosity of PC-PET is much higher than that of virgin fiber PET, so that a mixture of PEN / PC-PET will require a relatively large amount of transesterification per intrinsic unit viscosity increase (compared to a mixture). of PEN / virgin PET). Therefore, among other disadvantages, the prior art does not provide a process that allows a desired level of both intrinsic viscosity and transesterification level. It is possible to produce substantially transparent preforms (for container blow molding) with a PET / PEN mixture, without fixed solidification, but the disadvantages are such that the process is not commercially viable. First, the injection molding temperature of the preform (ie, the barrel temperature) and / or the equilibrium time (ie, the barrel time) must be increased such that the resulting process is not cost efficient. or sufficiently reproducible for a commercial process. For example, in certain cases, the barrel time will increase by a factor of four (ie, an increase over the normal cycle from 45 seconds to 180 seconds); as a result, You probably will not be able to run the processes in a normal injection molding machine. In addition, the increase in temperature in the barrel / temperature increases the levels of acetaldehyde (AA) in the preform to an unacceptably high level, such that AA is likely to be extracted in the food product to produce an off-flavor, particularly with a product such as bottled water. In this way, this has not proven to be the desired solution.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, a process is provided to control both the intrinsic viscosity change (IV) and the transesterification level of a mixture of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) during solid fixation. The method comprises providing PEN having a first intrinsic viscosity (IV), providing PET having a second IV, and reacting the PEN and the PET in the presence of an alkylene glycol compound that is added in sufficient quantity to achieve an IV desired end and the final level of transesterification in the PEN / PET product, copolymerized. In one embodiment, a full length preform sleeve layer is made from a PEN / PET mixture by adding an effective amount of alkylene glycol to increase the Tg by at least about 15 ° C. Other layers of the preform body can be PET. In this mode, a controlled, moderate level of transesterification is provided to allow stress / crystallization orientation in both the mixture and the PET layers to optimize mechanical performance, while maintaining optical clarity (substantial transparency). In another embodiment, the process is used to make preforms of the container having a neck finish with a level of transesterification of at least about 30% or greater. For example, a mixture of 30% PEN and 70% PET percent by weight is formed by adding an effective amount of alkylene glycol to obtain a high, desired level of transesterification, but without increasing the molecular weight (ie, viscosity). intrinsic) too high. This mixture will provide a Tg neck finish portion high and also fuses compatible with adjacent PET layers to maintain clarity and adhesion. Because the neck finish does not elongate, it is not necessary to provide a lower level of transesterification as would be required to allow tension / crystallization orientation. In other embodiments, the method of this invention allows the use of higher molecular weight initial polymers. For example, it may be desirable to use post-consumer PET (PC-PET), which has an initial IV of 0.72-0.73 dL / g., in an amount of about 60-90 weight percent, with the remaining component being PET. A predetermined final IV and transesterification level are achieved by adjusting the solid fixation time and / or amount of alkylene glycol used. The alkylene glycol preferably has up to 6 carbon atoms, more preferably 2 or 3 (propylene or ethylene), and more preferably 2 (ethylene). It can be pre-composed with PET and PEN, or added to the reaction chamber in which PET and PEN are copolymerized. Preferred alkylene glycol amounts include less 0.05 weight percent based on the total weight of PET and PEN, more preferably, 0.1 to 2 weight percent, most preferably 0.1 to 0.5 weight percent. These and other features and advantages of the present invention are described more particularly with respect to the following detailed description and drawings.

BRIEF DESCRIPTION OF THE FIGURES Figures 1-2 are graphs showing the change in melting temperature (MP) and orientation temperature (Tg) for various randomized PEN / PET copolymer compositions; Figure 3 is a cross-sectional view of a preform embodiment of the present invention having a full-length inner body sleeve of the mixture of PEN / PET; Figure 4A is a front elevational view of a refillable, returnable, carbonated beverage container, partially in section, elaborated from the preform of Figure 3, and Figure 4B is a fragmentary, elongated, cross-section of the side wall of the container, taken along line 4B-4B of Figure 4A; Figure 5A is a cross-sectional view of another embodiment of the preform of the present invention having a monolayer neck finish insert and a multilayer body portion, and Figure 5B is a fragmentary, enlarged, cross-sectional view. of the neck / body termination joint of the preform of Figure 5A; Figure 6 is a graph of the intrinsic viscosity versus solid fixation time illustrating the rate of IV increase for various compositions; Figure 7 is a graph of percent transesterification versus solid fixation time illustrating the rate of transesterification for various compositions; Figure 8 is a graph of the initial drop in intrinsic viscosity as a function of the weight percentage of ethylene glycol added to the reaction mixture before solid fixation; Figure 9 is a plot of the intrinsic viscosity gain rate versus the weight percent of ethylene glycol added to the reaction mixture before solid fixation; Y Figure 10 is a graph of the transesterification rate as a function of the weight percentage of ethylene glycol added to the reaction mixture before solid fixation.

DETAILED DESCRIPTION When PET / PEN mixtures are subjected to a solid fixation process, for example, to increase the IV and / or to reduce the generation of acetaldehyde, the amount or level of transesterification is increased, based on a theoretical maximum amount of transesterification ( random copolymerization) of 100%. Transesterification is measured by spectroscopy of nuclear magnetic resonance (NMR), more specifically when determining the reactive area of the NMR curves of the ethylene protons associated with the naphthalene-dicarboxylate-ethylene glycol-terephthalate units, compared to that which would be found for a completely copolymer Randomly prepared with naphthalenedicarboxylic acid, terephthalic acid, and ethylene glycol. The random copolymer would be considered to have 100% transesterification. See WO 92/02584 (Eastman). The PEN / PET mixture can be formed by extrusion composition (preferably with alkylene glycol), agglomeration, crystallization and then solid fixation at a desired transesterification level. Subsequently, it is contemplated that the solid fixed polymer will be extruded or injection molded to form a preform; this step will probably produce a production in the IV and an increase in transesterification. Finally, the preform will expand (eg, blow molded) into a substantially transparent container or other article. There are three significant variables in the solid fixation process, specifically the IV change, solid fixation time, and change of transesterification level. The temperature is also important, but usually adjusts to the highest possible temperature without melting the polymer mixture. 0 in general, for a given application, the initial and final IV are specified, as well as the final level of transesterification. It would be desirable to control the process to achieve these predetermined parameters, by adjusting the solid fixing time and / or by the use of additives. According to the present invention, the amount of alkylene glycol present during the solid fixation process can be used to control both the rate of change of IV and the rate of transesterification. In particular, it has been found that the addition of an increasing amount of alkylene glycol to the mixture before solid fixation results in a copolymer having a high level of transesterification. This surprising result since conventional knowledge indicates that the addition of the alkylene glycol to the reaction mixture will result in a decrease in the level of transesterification of the resulting copolymer.

More particularly, it is desirable to add PEN to a PET polymer in order to increase the thermal performance, i.e., Tg. However, at PEN levels in the order of 20-80 weight percent in a random copolymer (see Figures 1-2), the mixture is substantially amorphous, which means that the material can not be crystallized. In general, a recrystallizable material is required in a blow molded article, elastic because it provides the necessary levels of orientation and barrier properties, and controls the distribution of the material. Also, with PET / PEN blends, there is a problem with the incompatible phases that make the opaque article. In general, too low a transesterification level provides a poorly clear (ie, substantially non-transparent) PEN / PET preform, while too high a transesterification level prevents crystallinity (i.e., stress-induced crystallization and mechanical properties). improved, resulting). In this way, in certain situations there is some intermediate level of desired transesterification in order to obtain both substantial transparency and good mechanical properties The specific level of transesterification required will vary with the relative amounts of the polymers, their IVs, layer thicknesses, and temperature of use, use of copolymers, etc. In other applications, the PEN / PET mixture may have a relatively high level of transesterification. The copolymers of the present invention having a transesterification of more than about 30% demonstrate similar properties to copolymers having a transesterification level of about 100% (ie, relatively random copolymers). Thus, a relatively high level of transesterification as used herein refers to a copolymer having a level of transesterification of more than about 30%, and more preferably more than about 35%. As is known to those skilled in the art, the actual level of transesterification at which a copolymer demonstrates the properties of a truly random copolymer depends on a variety of parameters. Figures 1-2 graphically illustrate the change in melting temperature (MP) and the orientation temperature (Tg) for almost random PET / PEN copolymer compositions as the weight percent of PEN increases from 0 to 100. There are three kinds of PET / PEN compositions: (a) a high concentration of PEN that has in the order of 80-100% of PEN and 0-20% of PET per total weight of the composition, is material hardenable by tension (orientable) and crystallizable; (b) an intermediate concentration of PEN having the order of 20-80% PEN and 80-20% PET, which is a non-crystallizable, amorphous material, which when it is at a relatively high level of transesterification, will not suffer hardening by tension; and (c) a low concentration of PEN having in the order of 1-20 T of PEN of 80-99% of PET, which is a material crystallizable and hardenable by tension. A particular PEN / PET composition can be selected from Figures 1-2 based on the particular application. The PEN and PET polymers useful in the blends of this invention were easily prepared using typical polyester polycondensation reaction conditions known in the art. They can be processed by either a batch process or continuous process at a value of IV wanted. Examples of methods that can be employed to prepare the PET and PEN polymers useful in the present invention are found in U.S. Patent No. 4,617,373. For example, polyethylene naphthalate (PEN) is a polymer produced when dimethyl 2,6-naphthalene bicarboxylate (NDC) is reacted with ethylene glycol. The PEN polymer comprises 2,6-naphthalate repeating units. PEN resin is available having an inherent viscosity of 0.67 dl / g and a molecular weight of about 20, 000 from Eastman Chemical Co. , Kingsport, Tennessee USA. The PEN has a glass transition temperature Tg of about 123 ° C, and a melting temperature MP of about 267 ° C. Either or both of the PET and PEN polymers can optionally be modified with various materials such as dicarboxylic acids, glycols, cyclohexanes, xylenes and bases suitable for the formation of polyester. These modifying materials are typically pre-composed with PET or PEN. Thus, as used in the present PET and PEN it is meant to include these modified polymers.

When dicarboxylic acids are used as the modifying materials, the PEN or PET should include up to 15 mol% and preferably up to 10 mol% of one or more of the dicarboxylic acids (ie, different from the isomer (s) of naphthalenedicarboxylic acid in the case of PEN and different from the isomer (s) of terephthalic acid in the case of PET) containing from 2 to 36 carbon atoms, and / or one or more different glycols (ie, different from ethylene glycol) than contains from 2 to 12 carbon atoms. Modifying dicarboxylic acids, typical for PENs include terephthalic, isophthalic, adipic, glutaric, azelaic, sebasic, fumaric, and stilbenodicarboxylic acids and the like. Typical examples of a modification glycol for PEN include 1,4-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and the like. The PEN polymers are preferably derived from 2,6-naphthalene dicarboxylic acid, but can be derived from 2,6-naphthalene dicarboxylic acid and also optionally contain up to about 25 mol% (preferably up to 15 mol%, more preferably up to 10 mol%) of one or more residues of different isomers of naphthalene dicarboxylic acid such as 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3- , 2,43-, 2,5-, 2,7-, or 2, 8-isomers. Also useful are PEN polymers based primarily on 1,4-, 1,5-, or 2,7,7-naphthalenedicarboxylic acid. Typical glycols used to modify PEN include, but are not limited to ethylene glycols, such as propylene glycol, butyl glycol, pentylene glycol, 1,6-hexanediol, and 2,2-dimethyl-1,1-propanediol. Suitable cyclohexane modifiers for use with PEN are 6-membered, non-aromatic ring compounds that can act as base portions in the condensation reactions. These compounds include, for example, 1,4-cyclohexanediol dimethanol (CAS # 105-08-8, available from Aldrich Chemicals, Milwaukee, WI, USA). Suitable xylenes to modify PEN are benzene-containing compounds which include * less a methyl group attached to the benzene ring and which may have additional alkyl groups attached to the benzene ring. These xylenes include, for for example, toluene, paraxylene, methylethylbenzene, methotropylbenzene and methybutylbenzene. The amide formation, PEN modification bases suitable for use in the present invention include methylene diamine (CAS # 1477-055-0, available from Aldrich Chemicals), hexamethylenediamine (CAS # 124-09-4, available from Aldrich Chemicals), and the like. Modifying dicarboxylic acids typical for PET include isophthalic acid, adipic acid, glutaric acid, azelaic acid, sebasic acid, fumaric acid, stilbenodicarboxylic acid, biphenyldicarboxylic acid, any of the isomers of naphthalenedicarboxylic acid, and the like. Typical modification glycols for PET include alkylene glycols, such as ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and the like. Cyclohexanes, xylenes and amides, mentioned above can also be used to modify PET. The commercially available PET "bottle grade" includes PET homopolymer and PET copolymers suitable for making containers, which are well known in the art. These PET copolymers may include a minor portion, for example, up to about 10% by weight, of monomer units that are compatible with the ethylene terephthalate units. For example, the portion of glycols can be replaced by an aliphatic or alicylic glycol such as cyclohexane-dimethanol (CHDM). The dicarboxylic acid portion can be replaced by an aromatic dicarboxylic acid such as isophthalic acid (IPA). Post-consumer PET (PC-PET) is a type of recycled PET prepared from plastic PET containers and other recyclable products that are returned by consumers for a recycling operation, and now they have been approved by the FDA for use in certain food containers. PC-PET is known to have a certain level of IV (intrinsic viscosity), moisture content, and contaminants. For example, the typical PC-PET (which has a flake size of half an inch maximum), has an average IV of approximately 0.073 dl / g to approximately 0.7 4 dl / g, a moisture content of at least 0.25% and the following levels of contaminants: PVC: < 100 ppm Aluminum: < 50 ppm Olefin Polymers (HDPE, LDPE, PP): < 500 Paper and labels: < 250 ppm colored PET: < 2000 ppm Other contaminants: < 500 ppm.

PC-PET can be used alone or in one or more layers to reduce cost or for other benefits. The amount of PET in the mixture (ie, component (A)) is preferably from about 50 to about 90% by weight, more preferably from about 60 to about 80% by weight. Accordingly, the amount of PEN in the mixture (ie, component (B)) is preferably from about 10 to about 50% by weight and more preferably from about 20 to about 40% by weight. An effective alkylene glycol amount can be made to substantially reduce the increase in intrinsic viscosity (molecular weight) before and / or during solid fixation. The total desired increase (or decrease) of the IV and the increase in transesterification can be selected by varying the amount of weight percent in glycol, depending on the initial and final IV, particular, the transesterification level and the solid fixation time. Typically, the effective amount of alkylene glycol will be at least about 0.05 weight percent, based on the weight of the polymer blend, preferably from about 0.1 to 2%, and most preferably from about 0.1% to 0.5%. Suitable alkylene glycols have from 2 to 6 carbon atoms, ie ethyl C2, propyl C3, butyl C4, pentyl C5, or hexyl C6- Preferred glycols are ethylene glycol (CH2OHCH2OH) and propylene glycol (CH3CHOHCH2OH). Particularly preferred is ethylene glycol, CH2OHCH2OH, a clear, colorless liquid having a specific gravity of 1.1155 (20 ° C) and a boiling point of 197.2 ° C. The solid fixation process that results in the transesterification of the PET / PEN mixtures can be any solid fixation process commonly used in the polyester art to increase IV and / or reduce the acetaldehyde concentration. Basically, the Solid application is a process wherein a polymer is heated until the desired level of IV accumulation is achieved and a means is provided to remove the glycol during heating. However, according to the present invention, the amount of alkylene glycol present is manipulated such that the desired final IV and the level of transesterification are achieved. The amount of heating is between the highest vitreous transition temperature (Tg) of the polymers present and the lowest melting temperature (MP) of the polymers present. Typically, the temperature) during the solid melt is between about 150 ° C and about 250 ° C, more preferably between about 210 ° C and 250 ° C, more preferably between about 215 ° C and about 230 ° C. The amount of IV accumulation for a typical solid fixation process is an increase of at least about 5%, and more preferably at least about 10%. Usually, no more than a 50% increase in the IV is desired, although the highest accumulation is commercially useful for some applications (eg, tire rope).

The time required for solid fixation will vary; at least about 6 hours, and up to about 30 hours, is typical. Preferably, no more than about 24 hours is desired. The flow of nitrogen or vacuum used during the solid fixation process must be strong enough to remove the alkylene glycol from the reaction mixture such that the amount of alkylene glycol present in the reaction mixture results in the desired final IV and the level of transesterification. wanted. There are two sources of this alkylene glycol. The first source is the alkylene glycol which is added to the reaction mixture before the reaction, and the second source is alkylene glycol formed as a by-product of the condensation reaction of terminal, functional groups of the polymer chains. It has been found that by adding a specific amount of liquid alkylene glycol before the solid fixation process, while the alkylene glycol is removed during the reaction, that the IV and the transesterification rates can be controlled.

As is apparently easy for one skilled in the art, all parameters for solid fixation (such as time, temperature and chemical nature of the polymer (s)) are independent and will be varied to suit a particular desired result. The compositions of the present invention are suitable for high temperature packaging applications such as hot fill, returnable and refillable, and pasteurizable beverage and food containers. The particular composition of total desired mixture can be terminated by the barrier and thermal properties necessary for the end use requirements. The intrinsic viscosity (IV) affects the processability of the polyester resin. Polyethylene terephthalate having an intrinsic viscosity of about 0.8 is widely used in the carbonated beverage industry. The resins for various applications may vary from about 0.6 to about 1.2, and more particularly from about 0.65 to about 0.85. 0.6 corresponds to approximately an average molecular weight of viscosity of 59,000 and 1.2 at an average viscosity molecular weight of 12,000. Intrinsic viscosity measurements can be made according to the procedure of ASTM D-2857, by employing 0.0050 ± 0.0002 g / ml of the polymer in a solvent comprising o-chlorophenol (melting point 0 ° C), respectively, 30 ° C. It is the intrinsic viscosity by the following formula: where: Vsoin. It is the viscosity of the solution in any unit. Vsoi It is the viscosity of the solvent in the same units; and C is the concentration in grams of polymer per 100 ml of solution. The IVs of the PEN and PET polymers before solid fixation are typically about 0.5 to about 0.8, and most preferably about 0.6 to about 0.7. The IV of the polymers after solid fixation are typically about 0.5 to about 1.0, and more typically up to 0.7 to about 0.8 The preform and the blown containers should be substantially transparent. A measure of transparency is the percent of haze for light transmitted through the wall (Ht) that is given by the following formula: Ht = [Yd * (Yd + Y,)] X 100 Where Yd is the diffuse light transmitted by the specimen, and Ys is the specular light transmitted by the specimen. The diffuse and reflective light transmission values are measured according to ASTM method D1003, using any normal color difference meter, such as model D25D3P manufactured by Hunterlab, Inc. A substantially transparent container must have a percent of mist (through the wall) of at least about 15%, preferably less than about 10%, and more preferably less than about 5%. A substantially amorphous preform must have a haze percent of no more than about 20%, more preferably no more than about 10%, and most preferably no more than about 5%. The preform can be single-layer or multi-layer and can be made according to well-known injection molding processes, which as described in U.S. Patent No. 4,710,118 issued December 1, 1987 to Krishankurmas, et al. , which is incorporated in this way as a reference in its entirety. The materials, wall thicknesses, preform contours and bottle can all be varied for a specific final product while still incorporating the substance of the invention. The container may be for pressurized or non-pressurized beverages, including beer, juice and milk, or for non-beverage products. The improved thermal resistance provides for this invention makes the hot fill containers particularly well suited. Hot fill containers typically must withstand elevated temperatures in the order of 82-85 ° C (the product's fill temperature) and positive internal pressures in the order of 2-5 psi (fill line pressure) without substantial deformation , that is, a volume change of no more than about ± 1%. Other important factors in the manufacture of hot filled containers are described in U.S. Patent No. 4,863,046 to Collette et al. granted on September 5, 1989, which is incorporated in this way by reference in its entirety. The improved thermal resistance of the PEN / PET blends of the invention is also particularly useful since one or more layers of a refillable carbonated beverage container is capable of withstanding numerous filling cycles while maintaining aesthetic and functional characteristics. An employment procedure to simulate this cycle without crack failure and with a maximum volume change of ± 1.5% as follows. Each container is subjected to a commercial, typical, caustic wash solution prepared with 3.5% sodium hydroxide by weight and tap water. The washing solution is maintained at the desired washing temperature, for example, 60 ° C, 65 ° C, etc. The bottles are immersed uncovered in the wash for 15 minutes to assimilate the time / temperature conditions of a commercial bottle washing system. After the removal of the washing solution, the bottles are rinsed with water from the tap and then refilled with a carbonated aqueous solution at 4.0 to ± 0.2 atmosphere (to simulate the pressure of a carbonated beverage container), they are capped and placed in a conversion oven at 38 ° C at 50% relative humidity for 24 hours. This elevated furnace temperature is selected to simulate prolonged, commercial storage periods at lower ambient temperatures. In the removal of the furnace, the container is emptied and subjected again to the new filling cycle, until the failure. A fault is defined as any crack that is prepared through the wall of the bottle that results in leakage and loss of fusion. The change in volume is determined by comparing the volume of the liquid, the container will maintain the ambient temperature, both before and after each filling cycle. The container can preferably resist at least 10 fill cycles, and more preferably 20 fill cycles at a wash temperature of at least 60 ° C without failure, and with more than about ± 1.5 volume change in total. For use as a refillable bottle, the bottle preferably has a champagne base relatively thick processed according to the prior art filling containers described in Continental PET Technologies, Inc. Patents of US Nos. 4,725,464 and 5,066,528, which are hereby incorporated by reference in their entirety. The dome and bell form a thick base portion that is approximately 3-4 times the thickness of the cylindrical side wall, which has an average crystallinity of no more than about 10%. Radially outwardly of the bell, there is an outer, thinner base portion of about 50-70% of the thickness of the thick base portion and the increase in crystallinity until it is joined to the side wall. The base, outer, thinner wall provides improved impact resistance. The thick dome and bell provides improved resistance to the caustic crack. A preferred planar elongation ratio is 8-12: 1 for a cylindrical wall of a polyester fill beverage bottle of about 0.5 to 2.0 liters / volume, and most preferably about 9-11: 1. The elongation of the ring is preferably 3-3.6: 1 and elongation axial is 2.4-3: 0. This produces a sidewall of the container with a desired resistance to misuse, and a sidewall of preform with the desired visual transparency. The thickness of the side wall and the ratio of elongation selected depends on the directions of the specific bottle, the internal pressure (for example, 2 atm for beer, 4 atm for carbonated drinks) and the processing characteristics of the particular material (as determined for example, by the intrinsic viscosity). The portion of the cylindrical side wall of the vessel that is blown to the greatest extent has the highest average percent of crystallinity, preferably between about 25-35%. The tapered shoulder, which must also expand substantially more than the base, preferably has an average percent crystallinity of 20-30%. In contrast, the substantially thicker and less blown base has a crystallinity of about 0-10% in the dome and bell, which increases in crystallinity from an outer base that moves upward toward the sidewall. The neck finish does not expand and remains substantially amorphous at 0-2% crystallinity. Various levels of crystallinity can be achieved by a combination of expansion (induced by tension) and thermal hardening (thermally induced). Methods for making a full-length and / or partial collar-shaped sleeve, separated according to the examples shown in Figures 3-6 are described in the copending and commonly-owned US patent application, Serial No. 08 / 534,126 filed on September 26, 1995, entitled "PREFORM AND CONTAINER WITH CRYSTALLIZED NECK FINISH AND METHOD OF MAKING THE SAME", by Wayne N. Collette and Suppayan M. Krishnakumar, which in turn is a continuation of part of the application U.S. Patent No. 8 / 499,570 filed July 7, 1995, entitled "APPARATUS AND METHOD FOR MAKING MULTILAYER PREFORMS", by Suppayan M. Krishnakumar and Wayne N. Collette, both of the which are incorporated in this way by reference in their entirety.

Figure 3 shows a preform 30 including an outer layer 22 and an inner sleeve layer 20, of full length, a sleeve having a portion 21 extending over the upper sealing surface of the neck finish. Figures 4A-4B illustrate a filled carbonated beverage container that has been stretched and blow molded from the preform of Figure 3. The multilayer container 40 includes a cross section in the interior and axially expanded layer 41 formed of the inner preform sleeve layer 20, and the axially expanded outer layer 33 (formed of the outer preform layer 22). The container includes an upper neck finish 42 (same as the preform), a dome-shaped shoulder section 44, a cylindrical panel section 45, and a base 48. The base includes a central dome 52, recessed, surrounding a central portion 51, a right ring or bell 54 surrounding the dome, and an outermost base region 56 connecting the bell to the side wall. Figure 4B is an expanded view of the multilayer panel section 45, showing a relatively inner layer 41 thin and the outer layer 43 relatively thick. The PEN / PET mixture can be used either as the inner or outer layers, with the other layer being PET or other compatible polymer. As a cost saving to minimize the use of PEN, the inner layer 41 may be the PEN / PET blend. Figures 5A-5B illustrate another manner of preform. In this case, a monolayer neck finish is made from the PEN / PET mixture, to provide thermal resistance. This is particularly useful in hot refillable containers. A multilayer body portion may include one or more layers of PET, PC / PET, a PET / PEN blend of the present invention, or other compatible polymers. The preform 330 includes a neck finish portion 340 and body portion 350. The neck finish includes an open top end 342 that includes a top seal surface 341, external threads 343, and a bottom flange 344. The body portion 350 includes a tapered, upper portion 351 that will form the shoulder portion of the container, a cylindrical body portion 352, which will form the container stop, and a lower, base forming portion 353. In this example, the body portion includes the outer layer 354, the core layer 356, and the inner layer 358. In the central base portion there is an additional layer 359 that is generally made to rinse the core material nozzle, in preparation for the next injection molding cycle. The following examples illustrate the invention, but are not construed as limiting the invention.

Example 1, PET / PEN . 3 kg of clean, post-consumer PET flake, with an average IV of 0.74 and 16.3 pounds of granules of a PEN homopolymer, with an IV of 0.67, are manually mixed and dried at 150 ° C using a desiccant dryer D -100 of Conair during periods of 8-10 hours at a dew point at -40 ° C or lower. The sedated mixture of 22.7 kg is then composed in a 3.81 cm extruder with a ratio L / D of 36: 1 and a compression ratio of 3: 1. The complete transition zone is a barrier design with a 0.0254 cm gap between the screw and the barrel. The extruder outlet directs to a right nozzle. Then melted strands are pulled through a cooling water bath, then finally cut into granules 0.635 cm long by 0.318 cm long with a final IV of 0.68. The granules are then dried under vacuum with stirring at 120 ° C for 3 hours; then crystallize under vacuum with stirring at 175 ° C for an additional hour before solid fixation at 220 ° C under high vacuum (2 Torr) and stirring for a period of 24 hours in a double planetary mixer of Ross VB-001 , Hauppauge New York. The processing of these materials under these conditions produced a transesterification level of 20%. The level of transesterification (in this and subsequent examples) was determined by NMR spectroscopy carried out by Eastman Chemical, Kingsport, Tenessee USA. 24 hours of solid fixation at an IV rate increase of 0.012 / hr produces granules such as an unacceptably high IV of 0.97. Although the 20% transesterification rate sought in this example was achieved, and the solid state processing time was reasonable, the final IV was too high to be used for the commercial production of bottles molded by sopiado-stretched.

Example 2 PET / PEN with 1% Ultranox 626 The same compounding steps as in Example 1 were carried out, but to the dried 22.7 kg mixture was added 1% (by weight) Ultramox 626 (Eastman phosphine setter), mixed by hand, and then form a compound. The IV of the granules was 0.69. The granules were then dried, crystallized and solids fixed as in Example 1, but the solid fixation time was 36 hours. The transesterification rate was 0.29 / hour, and the final transesterification level was 10.5%. The 36 hours of solid fixation at an IV speed increase of 0.021 / hr, produced granules with an unacceptably high IV of more than 1.1. In this way, not only was the transesterification level below the target, but the IV was also too high to produce bottles. Also, the 36 hours of processing time then excessive and is not generally suitable for a commercial process.

Example 3. PET / PEN with 0.5% ethylene glycol The same compound formation steps, in Example 1, were carried out but at 22.7 kg of dry mix 0.5% (by weight) of liquid ethylene glycol was added, mixed by hand in a bucket, and then formed into compound . After the compound formation, the IV of * the granules were 0.50. The granules were dried, crystallized and solids fixed as in Example 1, but the solid fixation time was 11 hours. The final transesterification level was 20%. The 11 hours of solid fixation at an IV speed increase of 0.0056 / hr produced granules with an IV of 0.55. Although a desired 20% transesterification level was achieved, and the solid fixation time was acceptable, the resulting IV was too low to be used for the commercial production of bottles molded by sopiado-stretched.

Example 4 PET / PEN with 0.13% ethylene glycol The same compounding steps as in Example 1 were carried out but at 22.7 kg of the dry mixture 0.13% (by weight) of liquid ethylene glycol was added. After the compound formation, the IV of the granules was 0.54. The granules were dried, crystallized and solids fixed as in Example 1, but the solid fixation time was 21 hours. The final transesterification level was 20%. The 21 hours of solid fixation pressure at an IV speed increase of 0.010 / hr produced granules with an IV of 0.76. a transesterification level of 20% was achieved, the IV of 0.76 was acceptable, and the solid fixation time was acceptable for the commercial production of molded bottles by sopiado-estirado. This example shows how, by adjusting the amount of ethylene glycol and the solid fixing time, the desired final IV and the desired level of transesterification are provided.

Example 5 Preform with PEN / PET neck finish A preform using a PEN / PET mixture for the neck finish as shown in Figures 5A-5B was produced as follows: 15.9 kg of virgin PET pellets, with an average IV of 0.80, of 6.8 kg of granules of Homopolymer PEN, with an average IV of 0.60, were mixed by hand and dried as in Example 1. In a polyethylene bucket, 0.3% ethylene glycol was added to the mixture by hand. The mixture was formed of a compound as in Example 1. The IV of the granules was 0.59. The granules were dried, crystallized and left solid as in Example 1, but the solid fixation time was 26 hours. The final transesterification level was 35%; the IV speed increase was 0.082 / hr to provide a final IV of 0.80. The state of the material as it comes from the reactor is highly crystalline, which allows normal PET drying and processing methods to be used. However, when this material is subsequently melted (during injection molding to form a preform), does not recrystallize, but rather, remains amorphous. The relatively high Tg of the 92 ° C material allows it to resist hot filling and pasteurization temperatures when incorporated into a preform neck finish. The comparatively high level of transesterification provides a compatible melting material and generally adheres to adjacent layers of PET (ie, resistant to delamination under conditions of normal use). The neck finish of the preform (as in Figure 5A) can be produced in an injection molding machine, removed and placed inside a second injection molding machine where the body portion is overmoulded. Alternatively, both the body and the finish of the preform can be processed by different processing steps within the same injection molding machine. The relatively high level of transesterification at the neck finish of this example is acceptable because it is not required to subject to stress oriented crystallization.

Example 6 Gaseous Ethylene Glycol Reactor Added A theoretical example of a method for introducing ethylene glycol to control the rate of transesterification and the rate of increase of IV is as follows. 15.3 kg of clean, post-consumer PET flake, with an average IV of 0.74 and 16.3 pounds of PEN homopolymer granules, with an IV of 0.6 7, mixed by hand and dried at 150 ° C using a desiccant dryer Conair D-100 for a period of 8-10 hours at a dew point of -40 ° C or lower. The 22.7 kg of dry mix is then formed into a compound of a 3.81 cm extruder with a L / D ratio of 36: 1 and a compression ratio of 3: 1. The complete transition zone is a barrier design with a 0.0254 cm gap between the screw and the barrel. The extruder outlet is directed in a strand forming nozzle; the melted strands are pulled through a water bath for cooling, and finally cut into granules 0.635 cm long by 00.318 cm in diameter with a final IV of 0.68. These granules are then dried under vacuum with stirring at 120 ° C for 3 hours in a reactor at empty, agitated and chamfered 1 cubic foot; then they are crystallized under vacuum with stirring at 175 ° C for an additional hour before raising the temperature to 220 ° C and proceeding under high vacuum (2 Torr) of agitation for a period of 2 hours. The connection from the reactor of the vacuum pump is then closed by trapping the vacuum inside the reactor but stopping the removal of the gases from it. 400 grams of ethylene glycol are slowly added to the reactor maintaining the temperature and stirring for 4 hours. This is approximately twice the amount of ethylene glycol added in the previous examples and it is expected that at least part of the ethylene glycol will diffuse into the granules. Then, the vacuum is restored by removing all remaining gaseous ethylene glycol. The reaction is continued under vacuum for an additional 20 hours. The granules are now expected to have an IV of about 0.80 and a transesterification level of about 20%.

Example 7 PET / PEN with Propylene Glycol As a theoretical example, propylene glycol was replaced by ethylene glycol in the above examples, using the same weight percent (as ethylene glycol). It is expected that some amount of propyl groups will be included in the copolymer structure, and that the use of propylene glycol in place of ethylene glycol (based on the same relative weight percent) will provide a faster increase in IV and a slower rate of transesterification. Figures 6-11 and the following table illustrate the effects of processing caused by the addition of ethylene glycol to the solid fixation process according to the present invention. In the graph of Figure 6, the Y axis is the intrinsic viscosity (IV) as determined according to ASTM D / 2857 (see discussion above). On the X axis, the solid fixation time is displayed in hours, from 0 to 20 hours. The conditions of compound formation and solid fixation were similar to those described in the previous examples 1-5. As a reference (A), see table Subsequently, a composition of 100% by weight of virgin PET 6307, available from Shell Company (Houston, TX), having an initial IV of 0.6400 dL / g was used. After solid fixation for 16 hours, the final IV was 0.9, at an IV speed increase of 0.0163 (dL / g) / hour. As a control sample (B), a composition of 67.4% by weight of PET and 32.6% by weight (PEN 15967 available from Eastman Chemical Company, Kingsport, TN), having an initial IV of 0.6145 dL / g, was used . After 14 hours of solid fixation, the final IV was 0.7641, at an IV speed increase of 0.011 (dL / g) / hour. A first sample (C) according to the invention is the same as the control sample (B), but also includes 0.125% by weight of ethylene glycol. It has an initial IV much lower than 0.5440 due to a fall of the IV during compound preform; after 17 hours of solid fixation, the final IV was 0.7254 at an IV speed increase of 0.011 / hour. A second sample (D) according to the invention is the same as the control sample but also includes 0.5% by weight of ethylene glycol. It has an initial IV of 0.4478; after 16 hours of fixing solid, the final IV was 0.5429 at an IV speed increase of 0.0056 / hour. A third sample (E) according to the invention is the same as the control sample but also includes 2% by weight of ethylene glycol. He had an initial IV of 0.3665; after 15 hours of solid fixation the final IV was 0.3151, at a IV speed decrease of -0.0036 / hour. It is noted that the third sample (E) has a complete negative change (decrease) in IV, ie the polymer chains are broken at a faster rate than when they were combined. As indicated, each of the three samples (C, D, E) according to the invention has a final IV significantly lower than the control sample (B). As an additional distinction, a sample (F) in accordance with WO 92/02584 of Eastman included 67.4% by weight of PET and 32.6% by weight of PEN, and in addition 1% by weight of Ultranox 626 (phosphite stabilizer): m had an initial IV of 0.6338 and a final IV of 0.9845 after 17 hours, for an IV rate of increase of 0.021 / hour. Again, this is a significantly higher IV rate increase than the three samples (C, D, E) of the present invention.

The percent transesterification for the above copolymers B-F was measured as a function of the amount of ethylene glycol for several times of solid fixation (Figure 7). In addition, the initial IV drop, the IV gain rate and the transesterification rate were also measured. These results are summarized in Table I and shown in Figures 6-10.

As is clear from Table I, if ethylene glycol is not added to the reaction mixture, the rate of transesterification is relatively slow. However, when adding an amount With the addition of ethylene glycol to the reaction mixture, the rate of transesterification increases automatically. In particular, by adding 2% by weight of ethylene glycol to the reaction mixture, the rate of transesterification is increased by a factor of more than 5 relative to a reaction mixture to which no ethylene glycol was added before the reaction. In this way, the addition of ethylene glycol to the reaction mixture before the solid fixation allows control of the IV and the transesterification level of the copolymer as well as the solid fixation time. Figure 6 shows that # the intrinsic viscosity of the copolymer decreases as the amount of ethylene glycol added to the reaction mixture increases before the solid fixation. In this way, by adding ethylene glycol, the molecular weight of the copolymer is reduced. It was determined by distracting and measuring samples at one-hour intervals that the IV velocity was generally linear during the solid fixation time. Figure 7 shows that the percent transesterification increases as the amount of ethylene glycol added to the reaction mixture increases before solid fixation.

This is an unexpected result since conventional wisdom indicates that the addition of ethylene glycol should reduce the transesterification level of the copolymer. Figure 8 shows that the drop of the initial IV in the copolymer increases as the weight percent of ethylene glycol added to the reaction mixture increases before the solid fixation. During the initial extrusion process the added ethylene glycol increases the speed at which the molecular weight of the copolymer decreases. Figure 9 shows that the rate of IV gain during solid fixation is reduced as the percentage by weight of ethylene glycol added to the reaction mixture before solid fixation increases. As a result, the added ethylene glycol decreases the rate at which the molecular weight increases. Figure 10 shows that the rate of transesterification increases as the percentage by weight of ethylene glycol added to the reaction mixture increases before the solid fixation. The result is surprising since conventional wisdom dictates that the The presence of this additional ethylene glycol should reduce the transesterification rate of the copolymer. Although several preferred embodiments of this invention have been specifically illustrated and described herein, it is to be understood that variations may be made to the method of the invention without departing from the spirit and scope of the invention as defined in the claims. annexes.

It is noted that in relation to this date, the best method known by the applicant to carry out the present invention is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property:

Claims (36)

1. A method for copolymerizing polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), characterized in that it comprises: providing PEN having a first intrinsic viscosity (IV); provide PET that has a second IV; reacting the PEN and PET in the presence of alkylene glycol having up to 6 carbon atoms to form a copolymerized product of PEN / PET, the alkylene glycol is added in an amount sufficient to achieve a desired final IV and final level of transesterification desired in the copolymerized product of PEN / PET.

2. The method according to claim 1, characterized in that the copolymerized PEN / PET product comprises about 60 to 95 weight percent PET and about 5 to 40 weight percent PEN.

3. The method according to claim 2, characterized in that the PEN / PET copolymerized product comprises about 35 to 85 weight percent PET and about 15 to 35 weight percent PEN.

4. The method according to claim 1, characterized in that the alkylene glycol is selected from the group consisting of propylene glycol and ethylene glycol.

5. The method according to claim 4, characterized in that the alkylene glycol is ethylene glycol.

6. The method according to claims 1 and 4, characterized in that the alkylene glycol is formed with the PEN and the PET before the formation of the copolymerized product of PEN / PET.

7. The method according to claims 1 and 4, characterized in that the alkylene glycol is added to a reaction chamber in which the PEN and the PET are copolymerized to form the copolymerized product.

8. The method according to claims 1 and 4, characterized in that the effective amount of alkylene glycol is at least about 0.05 weight percent based on the total weight of PEN and PET.

9. The method according to claims 1 and 4, characterized in that the effective amount of alkylene glycol is about 0.1 to 2 weight percent based on the total weight of PEN and PET.

10. The method according to claims 1 and 4, characterized in that the effective amount of alkylene glycol is about 0.1 to 0.5 percent by weight based on the total weight of PEN and PET.

11. The method according to claim 1, characterized in that either or both of the PET and PEN is modified with up to about 15 mole percent of one or more different dicarboxylic acids and contains from 2 to 36 carbon atoms, one or more different glycols containing 2 to 12 carbon atoms, or one mixture of one or more different dicarboxylic acids and one or more different glycols.

12. The method according to claims 1 and 4, characterized in that the reaction step is carried out at a temperature of about 175 ° C to 250 ° C for at least 6 hours such that a level of transesterification of the copolymerized product PEN / PET it increases to at least about 5%.

13. The method according to claim 12, characterized in that the reaction step is carried out at a temperature of about 215 ° C to 240 ° C for about 8 to 12 hours such that the level of transesterification of the copolymerized product of PEN / PET it increases to approximately 5 to 25%.

14. The method according to claim 1, characterized in that the reaction step is carried out at a temperature of about 175 ° C to 250 ° C.

15. The method according to claim 1, characterized in that the copolymerized product of PEN / PET is modified by a compound selected from a group consisting of alkylene glycols, alcohols, cyclohexanes, toluenes and mixtures thereof.

16. The method according to claim 1, characterized in that the copolymerized product of PEN / PET is modified by a compound selected from the group consisting of propylene glycol, butylene glycol, cyclohexanedimethanol, toluene and mixtures thereof.

17. The method according to claims 1 to 4, characterized in that the second IV is about 0.70 dL / g to 0.75 dL / g.

18. The method according to claims 1 and 4, characterized in that the PET is post-consumer PET (PC-PET).

19. The method according to claims 1 and 4, characterized in that the amount of alkylene glycol reduces the rate of increase of IV during the reaction step by at least about 10 5.

20. The method according to claims 1 and 4, characterized in that the amount of alkylene glycol causes the final IV to be greater than the second IV.

21. The method according to claims 1 and 4, characterized in that the amount of alkylene glycol is greater than about 2% by weight of the PEN and PET.

22. The method according to claims 1 and 4, characterized in that the amount of alkylene glycol is selected to decrease the time of the reaction step.

23. The method according to claims 1 and 4, characterized in that a phosphite antioxidant entity is present in the reaction step of an amount sufficient to reduce the rate of transesterification during the reaction step.

24. The method according to claims 1 and 4, characterized in that the copolymerized product of PEN / PET has the level of transesterification greater than about 30%.

25. The method according to claims 1 and 4, characterized in that both the amount of alkylene glycol and the time of the reaction step are selected to achieve the final IV and the final level of transesterification.

26. The method according to claims 1 and 4, characterized in that the copolymerized product of PEN / PET is used for the injection molding of a substantially transparent article.

27. The method according to claims 1 and 4, characterized in that the PEN / PET copolymerized product is used for injection molding in a substantially transparent manner.

28. The method according to claims 1 and 4, characterized in that the copolymerized product PEN / PET is used for the injection molding of a substantially transparent portion of a preform.

29. The method according to claims 1 and 4, characterized in that the copolymerized product PEN / PET is used for the injection molding of at least one substantially transparent layer of a preform.

30. The method according to claim 29, characterized in that the preform has a substantially transparent PET layer adjacent to at least one layer.

31. The method according to claim 26, characterized in that the injection molded article is blow molded to form a substantially transparent, expanded article.

32. The method according to claim 31, characterized in that the expanded article is multilayer and includes at least a first PEN / PET product layer and at least a second polyester layer adjacent to the first layer.

33. The method according to claim 26, characterized in that the article is a multilayer article.

34. The method according to claim 33, characterized in that the multilayer article includes at least a first PEN / PET product layer and at least a second polyester layer adjacent to the first layer.

35. The method according to claim 1, characterized in that the first IV is from about 0.75 dL / g to about 0.8 dL / g, the second IV is from about 0.70 dL / g to about 0.75 dL / g, the final IV is at less 5% higher than the second IV and the level of transesterification is greater than about 30%.

36. The method according to claim 1, characterized in that the first IV is about 0.5 dL / g to about 0.8 dL / g, the second IV is about 0.70 dL / g to about 0.75 dL / g, the final IV is at least 5 % greater than the second IV, and the level of transesterification of the copolymerized product of PEN / PET is increased by about 5 to 25%.