MXPA01002766A - Production of improved polymers via the use of star cores - Google Patents

Abstract

There is provided a process for producing high molecular weight polymer comprising the step of reacting one or more preformed linear polymers with one or more cores (as hereinbefore defined) to form high molecular weight polymers;wherein the preformed linear polymers are at a temperature in the range from the melting point of the preformed linear polymers to 330°C.

Description

PRODUCTION OF IMPROVED POLYMERS VIA THE USE OF STAR NUCLEI FIELD OF THE INVENTION This invention relates to a process for producing high molecular weight polymers. The invention also relates to star cores which can be used in the production of the above polymers. More particularly, the star cores are bifunctional polymer ("I"), trifunctional (Y ") and tetrafunctional (" H ") cores.

BACKGROUND OF THE INVENTION It will be appreciated that while the following specific description relates to polyester polymers and applications thereof to blow-molding and stretching, the invention is not limited in this way. One current practice is to produce a high molecular weight polymer such as a melt of intrinsic viscosity of about 0.6 dl / g and then to extrude and freeze the product to provide granules that are further polymerized by solid state polymerization to provide an intrinsic viscosity of 0.8. ~ * s, ?? * i? t?. & »t. * ¿..- *. - -. > --- ... - - * ^ 7 * if «H_Sai-S ---_ &» ^^ dl / g for blow molding and stretching and 1.0 dl / g for a high tenacity fiber for tire cords. The granules melt and then conform. It is recognized that the production of an appropriate average weight in the molecular weight in the original melt, followed by the immediate use of the molten polymer can avoid the costly intermediate steps currently used with additional processing and has the potential to save time and energy as well as a considerable cost. Similarly, the desire to be able to convert polymers with an average low molecular weight weight into a polymer with a high average molecular weight weight, for example in the production of fibers, has also been recognized as highly advantageous. In order that a polyethylene terephthalate ("PET") polymer can be blow molded and stretched, it must have a relatively high average molecular weight and sufficient intrinsic viscosity. Table 1 presents a table that relates the intrinsic viscosity with the Mw. One of the main difficulties in producing a PET polymer polymer has been the production of a polymer with an average weight of sufficient molecular weight. The average molecular weight (Mw) weight of a polymer chain can be calculated as follows: avMw =? Mi2 / S My where Mi is the molecular weight of the individual polymer TABLE 1 Average weight of molecular weights versus, intrinsic viscosity, dl / g IV-0.6 Mw = 33600 IV = 0.61 Mw = 34400 IV = 0.62 Mw = 35300 IV = 0.63 Mw = 36200 IV = 0.64 Mw = 37000 IV = 0.65 Mw = 37900 IV = 0.66 Mw = 38800 IV = 0.67 Mw = 39700 IV = 0.68 Mw = 40600 IV = 0.69 Mw = 41500 IV = 0.7 Mw = 42400 IV = 0.71 Mw = 43400 IV = 0.72 Mw = 44300 IV = 0.73 Mw = 45200 IV = 0.74 Mw = 46200 IV = 0.75 Mw = 47100 IV = 0. 76 Mw = 48100 IV = 0.77 Mw = 49100 IV = 0.78 Mw = 50000 IV = 0.79 Mw = 51000 IV = 0.8 Mw = 52000 IV = 0.81 Mw = 53000 IV = 0.82 Mw = 54000 IV = 0.83 Mw = 55000 IV = 0.84 Mw = 56000 IV = 0.85 Mw = 57000 IV = 0.86 Mw = 58000 IV = 0.87 Mw = 59100 IV = 0.88 Mw = 60100 IV = 0.89 Mw = 61100 IV = 0.9 Mw = 62200 IV = 0.91 Mw = 63200 IV = 0.92 Mw = 64300 IV = 0.93 Mw = 65400 IV = 0.94 Mw = 66400 IV = 0.95 Mw = 67500 IV = 0.96 Mw = 68600 IV = 0.97 Mw = 69700 IV = 0.98 Mw = 70800 IV = 0.99 Mw = 71900 IV = 1. Mw _ 73000 From a theoretical perspective, in order that a PET polymer be able to be blow molded and stretched must have an intrinsic viscosity in the range of 0.7 to 0.8 d? / G. The viscosity can be determined if the average molecular weight weight of the polymer chain is known since the logarithm of the melt viscosity is related to the square root of the average molecular weight weight of the polymer chain. The equation for the molten viscosity is: log (n) = constant * V "(avMw) where n is viscosity and Mw is the average weight of molecular weight. Thus, the technically important flow characteristics required during blow-molding and stretching (such as injection molding) depend on the average molecular weight weight. Even when sufficient Mw is obtained, another substantial problem in the polymers has been the tendency during polymerization of the polymer to be gelled. During uncontrolled polymerization, the random cross-linking and branching reactions that result present in gelled products due to the highly branched structures. Such polymer structures are not suitable for blow molding and stretching or production -._- _-_._ ___-. «______« > .., ^ t ^ .. ^. ^, ^ M ^. -, t? rflrnÉwriTirt'ff ^) Hir ^ of fibers. It has been recognized that polymers suitable for blow and stretch molding should have a small change in viscosity when the cut is changed and this property is found in linear polymers. In contrast, polymers containing polymers with many randomly separated branches are gel-like and do not have this property. As a result, research has been carried out to develop a process to prepare polymers having controlled degrees of branching and having a central core that binds linear chains and polymers with multifunctional centers or cores to which linear polymers are preferably attached. It is known from the prior art that linear polymers can be altered to what are called star polymers by using small portions of polyfunctional additives which form the "core" of the star polymer and allow the linear polymers to join and therefore increase the average molecular weight weight of the resulting polymer. There is a considerable amount of knowledge that these star polymers allow the properties of a polymer preparation to be anticipated (for example, J. R. Schaefgen &P. J. Flory, J. Am. Chem. Soc. 70, 2709, 1948"Shaefgen"). The process in the prior art uses substances that are thermally unstable, expensive and produce yellow byproducts, and in addition these processes produce products with gel branching. Schaefgen describes initial investigations into the use of star polymers. This research explored the use of polyamines and polybasic acids (such as polyacrylic acid), however no commercially useful products were made. Schaefgen, while describing the theoretical basis of star polymers and correctly anticipating problems, does not provide practical solutions. In addition, Schaefgen does not address the formation of PET polymers which have unique problems because they are ester polymers, and it is difficult to develop appropriate polyfunctional compounds. The use of polyfunctional cores is also described in U.S. Patent Nos. 3,692,744, 3,714,125 and 3,673,139. In U.S. Patent No. 3,673,139, the increased viscosity and rubbery elasticity of polyesters is recognized due to increasing degrees of crosslinking or branching, and which is sought to be resolved by condensing during processing of the polymer, 0.001 to 1 mol % of a compound having not less than three polyester-forming functional groups so as to form slightly branched polyesters or ^^ M ^ ^ ^? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ with an intrinsic viscosity of at least 0.8 dl / g or preferably 0.9 dl / g and a substance which promotes crystallization. The process described is a reaction of the terephthalic acid ester, ethylene glycol 5 and the polyester-forming group. The products of these processes are unsatisfactory insofar as they do not satisfy the necessary characteristics of color and linear viscosity with the low speed of addition described. US Pat. No. 3,692,744 describes the inclusion of a poly-esterification mixture, in addition to a terephthalic acid component and a diol component, of 0.05-3 mole percent of the acid component of a compound containing at least 3, of Preferably 3-4 ester-forming groups (for example, a tricarboxylic or tetracarboxylic acid, a triol or tetrol, or a hydroxycarboxylic acid containing all 3 or more ester-forming groups). Again, the methods described in this technique provides the addition of the polyfunctional compound as an initial material. This patent describes the use of triols and tetraols which are not suitable because the substances are unstable and at temperatures greater than about 290 ° C they are dehydrated to provide a double bond carbon which produces by-products with color. ._. «-_« «---__ _. ... . ^ ... ^ ._, ^ _ ^ ^. , ... "_ ^ ..,. aateatesfeaasai ^ U.S. Patent No. 3,714,125 describes a polyfunctional core or nucleus substantially in the form of "+" which is an aromatic ortho-carbonate. These substances are highly unstable in melts and, for example, they can not be suitable for transparent soft drink bottles. It is also known that the number of carboxylic acid groups or an aromatic ring is increased, the decomposition rate to provide carbon dioxide is increased in proportion to the number of such substituents. Accordingly, when four or more carboxylic acid groups are present then one or more are rapidly lost to generate carbon dioxide. Such substances are difficult to prepare and their production has ceased due to the substances with carcinogenic and too expensive to produce. All the polyfunctional additives or multifunctional cores that have been used in star polymer technology to date suffer from considerable disadvantages. Although the choice of polyfunctional additives that have been used to date have attempted to control random cross-linking or branching during polymerization, the polymers produced continue to suffer from ..._ ^ _-, t ^ MK > > .. "i-, -. ^ A ^^ A ^ k ^ ^^ ^ f ^ r ^ m ^ me unacceptable gel which do not allow the products to be commercially useful for blow molding and stretching. In some cases, the polymers of the prior art also have average molecular weight weights or an intrinsic viscosity, or both, insufficient to be useful, particularly when the stars only have a functional core. In addition, in each of the known processes, commercially unacceptable star polymer products are produced as a result of continuous gelling and colored by-products which render the products unsuitable for use, for example, in bottles for transparent beverages. Therefore, there is a need for a process for producing star polymers which are commercially useful, especially in the production of PET bottles.

BRIEF DESCRIPTION OF THE INVENTION Through this specification and the claims, it will be understood that the word "core" means a compact molecule with more than one reactive group that is relatively stable under the conditions of use. This is because the core does not react with the constituents of the polymer melt. Throughout this specification and in the claims, the word "preformed" is used to indicate that the conformation of long chain linear polymers exists before the use of any star core additive. According to the invention, a process is provided for producing polyester high molecular weight comprising the step of reacting one or more preformed linear polymers with one or more cores (as defined above) to form polyesters of high molecular weight; wherein the preformed linear polymers are at a temperature in the range of the melting point of the linear polymers preformed to 330 ° C. The pressure under which the reaction is carried out is not critical. Preferably, the reaction is carried out under vacuum to maximize the removal of by-products such as ethanediol and acetic acid. Preferably, the preformed linear polymers are at a temperature of at least about 270 ° C. More preferably, the preformed linear polymers are at a temperature of about 280 ° C. Preferably, the reaction occurs for a time period of less than 10 minutes. It is necessary to limit the reaction time to maximize the core reactions with long chain linear polymers and avoid the formation of a balance. The preformed linear polymers can be prepared using any of the methods known to those skilled in the art. Preferably, the cores used to join The polymers are in the form of a mixed anhydride since these nuclei provide particularly rapid routes for the production of high molecular weight polymers. Most preferably, the mixed anhydride is the acetic acid anhydride of isophthalic acid. Preferably, the star cores are selected from the group consisting of star cores of the general forms "H", "Y" or "I" discussed above, trimellitic acid, trimellitic anhydride or mixtures thereof. According to the invention, it is possible to set an objective for the Mw of the finished product and to choose an initial material with an appropriate Mw. The initial material can be a commercially available product. For example, low Mw polymers can be purchased economically and then by using a - «afe- -, - _ • .-» **. < w * _ «w» ^ -. * »- ~« -. «_» __ M > ___- ^ _..- jÉS áá¡k¡toÍMá * s **** - < -? - __ Aflo? ÚSStrál ^ Sl ^ lßÁMarjSdSÉA simple process of this invention, can be converted to a high Mw polymer which may be suitable for, for example, be blown and stretched. Packaging manufacturers can therefore easily obtain a polymer with high Mw and then extrude the polymer to make, for example, bottles for non-alcoholic beverages. The intrinsic viscosity of the initial material can be determined previously by the process used for its formation. Preferably, the preformed linear polymers are polyester polymers. In the preferred forms of the invention, the polyester polymer is preferably selected from the group including PET, polybutylene terephthalate and polyethylene naphthenates. More preferably, the polyester polymer is PET. When the polymer is PET, it can be formed, for example, by reacting terephthalic acid with ethanediol to form a PET polymer having an intrinsic viscosity of between 0.7 dl / g and 0.8 dl / g. It has been further found that by using this process, PET polymers can be formed with an average weight of predetermined defined molecular weight and without a detectable color change. In this way, the resulting average weight of molecular weight can be improved by forming initially the linear polymers of PET and then the polymers are grown in the star core. This allows the amount of star core that is aggregated to be determined with statistical precision. The ability to calculate the required amounts of star core based on the preformed linear polymers allows this process to be commercially valuable. The PET ester polymers produced according to the invention are preferably capable of being blow molded and stretched. For this purpose, it will be understood by persons skilled in the art that this invention allows the solid state polymerization step of, for example, basic polyethylene terephthalate processing to be removed and that the molding by Direct injection of the product is feasible to produce a polymer useful for non-alcoholic beverage bottles and other applications. This invention therefore allows a significant reduction in the production costs of the useful polymer. It will be understood that the invention includes polyester polymers (such as PET ester polymers) when produced by the processes of the invention. It will be further understood that the invention includes a process for producing blow-molded and stretched products that use polyester polymers (such as PET polymer) which are ^ _____ ^ _ ^ ~. . ^ - ^ _-. "> - | Ma || r || , 1 ^ ** ^, * ^ has produced by the methods of this invention and in addition blow molded and stretched products when they are produced by such processes. It has also been found that by using cores of the general form "I", "H" or "Y", polymers can be produced which have an average molecular weight weight within the defined range which allows such polymers to become more commercially useful, for example in blow-molding and drawing or in the fiber production. According to a second aspect of the invention, star cores are provided for use in the preparation of a high molecular weight polymer which is selected from the group consisting of compounds of the general formula "H": R2 is -OH, -O-CO-CH, -OCH, CH, OH * t * m *, á¿ «* ~? é * -. _. ^ ___. t ^ tÉiS? ^ i.s * ^^^ where R is O-CH2CH2-O- compounds of the general formula "Y" fifteen Where R is -OCOCH, or -OCH, CH, OH a »and compounds of the general formula" I " or mixtures thereof. The star nuclei may be in the form of free carboxylic acid or an active form, that is, a mixed anhydride or an ester (for example with ethanediol). The mixed anhydride form of the invention is preferred because to which it has been demonstrated that it is the most efficient star nucleus with superior results which are obtained very quickly. In particular it allows the production of different distributions of different molecular weight with a high average Mw quickly and without problems significant colors. The mixed anhydride is not based on transesterification, which is intrinsically slow, but rather based on the rapid reaction of mixed anhydrides with free terminal hydroxyl groups. Therefore, the examples of the trifunctional "Y" core _ ^^^^^^^^^^^^^^^^^^^^^^ j | ^^^ _ ^ _ jjg ^ g | ^^ g¡ ^ g¡g¿gí include trimellitic anhydride, anhydride trimellitic acetic acid or tris-hydroxyethyl trimellitate. When the "I" core is used, the addition of the core causes a simple bonding of the polymer chains. It has been found that isophthalic acid can form useful derivatives but terephthalic acid does not. The "I" cores provide a rapid linkage of the terminal hydroxyl groups to provide linear polymers with a "fold" due to the substitution of isophthalic acid by terephthalic acid. Preferably, star cores of the "I", "H" and "Y" form of the formulas described above are provided for use in the process to form the polyester polymers (such as polyethylene terephthalate polymers "PET")) which have a general form "I", "H" or "Y" respectively. It has been found that the optimum viscosity of the polymers can be found by the addition of an "H" core during the last stage of polycondensation, because the minimum amount of cross-bar is converted to a single-star polymer by transesterification of the bar cross. It is considered that the transesterification reaction in the polymer production medium connecting the ester bonds of the core H are also attacked possibly resulting in the conversion of the "Y" core form. By .-.... ^ i ^ ..... ^ MA.A .. r ~ ^ * ~ **** ~ ^^ * ~ * ^^ course, this may be a preferred process, if it is predominantly desirable a "Y" star polymer. Obviously, since this is a statistical process, the delay in the addition reduces the conversion rate to the "Y" form if the "H" form is preferred. The star cores of these "I", "H" and "Y" forms have the structure and reactive groups to allow them to be used to produce polyester polymers (particularly, PET polymers) which have improved characteristics. Specifically, the polyester polymers produced are of an average weight of sufficient molecular weight to allow them to be blow molded and stretched and can be produced without creating color by-products. In particular, according to the process of this invention, the linear properties and ease of manufacture of the "PET" polymers "I", "H" and "Y" can be markedly improved by delaying the addition of the core until it has enough polymerization has occurred for the core to subsequently react with linear polymers and provide the required polymer properties. The delayed addition is not essential and the improved polymers can of course be obtained, for example by the early addition of the cores. For example, very high reaction rates can be obtained ^ j -f or -altas using the mixed anhydride forms of the invention. The reaction is promoted by the use, for example, of mixed anhydride cores with the target terminal hydroxyl groups without the undesirable side reactions of released ethanediol and then the attack and breaking of existing long linear chains.

DESCRIPTION OF THE PROCESS FOR THE PRODUCTION OF NUCLEUS STAR The process used to produce the star cores of this invention will now be described in greater detail followed by the examples of their production. The star cores of this invention can be produced in various ways. From the above structures it will be appreciated that the "Y" star cores can be constructed using a trifunctional element and the "H" star cores can be constructed using two trifunctional elements and a short crossbar. The simplest method is to extensively transesterify polyethylene terephthalate ester in a high proportion of bis (hydroxyethyl) terephthalate using excess ethanediol and then rapidly evaporate the excess ethanediol from the mixture. This produces ^^ a ^^^^^^^ aa - ^^ - * ^^^ mainly monomer and dimer. The product is then reacted with trimellitic anhydride to provide esterification of the hydroxyl groups of the short oligomers, to provide a simpler star A core. The product A is reacted with ethanediol to esterify the carboxylic acid groups to produce the star B-core. Alternatively, A can be treated with acetic anhydride to convert the carboxylic acid groups to mixed acid anhydride groups to provide the star core C. Then "C" is reacted with ethanediol to provide a star core D which has fewer three-star cores as a by-product. Alternatively, trimellitic anhydride can be reacted with ethanediol directly to provide only one ethylene crossbar. This is best done in two stages: the first stage with an inert solvent for the ethanediol where the trimellitic anhydride reacts and the solvent is then removed, followed by the second stage; wherein the free carboxylic acid groups are esterified with ethanediol to provide a four-star D-core. i ^^ feg ^^^^^^^^^^? - ^^^^^^ ij Finally, isophthalic acid can be reacted exhaustively with acetic anhydride to produce the nucleus "I", "E", as a mixed acetic anhydride. Those skilled in the art will understand that each of the cores, A, B, C, D and E will have different proportions of star, triestrella and tetraestrella and a different production cost. Each star core will form a core in the reactor in the polycondensation stage where it will react with the linear polymers present to provide a significant proportion of "H" polymers or "Y" polymers (if it has a high proportion of triestrella). In addition, addition of the additive in the polycondensation can be delayed to prevent transesterification of the cross bars to form "Y" polymers. It has also been found that the tetrastar nucleus can be produced by reacting cyclohexanedimethanol "with trimellitic anhydride.The ester bonds produced are more stable than with ethanediol and do not generate yellow by-products in the same degree.

^^^^^^^^^^^^^^^^^^^^^^^ X ^^^^^^^^^ j ^^ EXAMPLES The invention will now be further explained and illustrated with reference to the following non-limiting examples. Examples 1 to 5 relate to the second aspect of the invention. The first three examples are directed to the production of star cores "H", the fourth example is directed to the production of star polymers "Y" and the fifth example to star polymers "I". Examples 6 to 12 relate to the production of high molecular weight polymers from star cores according to the first aspect of the invention.

EXAMPLE 1 192 g of trimellitic anhydride and 72 g of cyclohexanedimethanol are intimately mixed and heated at 140 ° C for 1 hour and then maintained at this temperature for 3 hours. The product is cooled and triturated to provide a core A of tetracarboxylic acid. Then 132 g of product A are mixed with acetic acid anhydride at room temperature for 10 hours to cause dissolution, and then it is heated at 100 ° C for 2 hours and the by-product acetic acid is slowly stirred under vacuum to provide a mixed anhydride core (B): Then "B" is reacted with 5 moles of ethanediol at 160 ° C for 1 hour and then the excess of ethanediol is removed under vacuum to provide the ester core (C).

EXAMPLE 2 192 g of trimellitic anhydride and 35 g of ethanediol are intimately mixed and heated at 140 ° C for 1 hour and then maintained at that temperature for 3 hours. The product is cooled and triturated to provide the tetracarboxylic acid core (Al). Then 132 g of the product (Al) are mixed with acetic anhydride at room temperature for 10 hours to cause dissolution and then heated at 100 ° C for 2 hours and the by-product acetic acid is slowly stirred under vacuum to provide the core. of mixed anhydride (Bl). Then "Bl" is reacted with 5 moles of ethanediol at 160 ° C for 1 hour and then the excess of ethanediol is removed under vacuum to provide the ester (Cl) core.

EXAMPLE 3 192 g of trimellitic anhydride and 72 g of bis (hydroxyethyl) terephthalate are intimately mixed and heated at 140 ° C for one hour and then maintained at that temperature for three hours. The product is cooled and triturated to provide the tetracarboxylic acid core (A2). Then 132 g of the product (A2) are mixed with acetic acid anhydride at room temperature for 10 hours to cause dissolution, and then heated at 100 ° C for two hours and the by-product acetic acid slowly removed under vacuum to provide the mixed anhydride core (B2). Then "B2" is reacted with 5 moles of ethanediol at 160 ° C for one hour and then the excess ethanediol is removed under vacuum to provide the ester core (C2).

EXAMPLE 4 96 g of trimellitic anhydride are mixed with acetic anhydride at room temperature for 10 hours to cause dissolution. Then it is heated at 100 ° C for 2 hours and the acetic acid by-product is slowly stir under vacuum to provide the core of mixed anhydride (B3). Then B3 is reacted with 5 moles of ethanediol at 160 ° C for 1 hour and then the excess of ethanediol is removed under vacuum to provide the ester core (C3). This reaction can be represented by the following equation: where R, is -0-CH, CH, OH ™ ^^^^ j ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 50 grams of isophthalic acid are treated with 250 milliliters of acetic anhydride, 1.25 grams of zinc acetate and 0.25 grams of anhydrous oxalic acid at 80 ° C for 2 hours under a nitrogen atmosphere, allowing slow evaporation of about half of the acetic anhydride. The three extra additions of 0.25 grams of oxalic acid with evaporation of evaporated acetic anhydride, which requires 8 hours in total. Finally, the excess acetic anhydride is removed to provide the bifunctional core (E).

EXAMPLE 6 A batch of molten linear PET polymers is prepared by the master batch technique with 250 ppm of germanium oxide catalyst. The torque of the agitator indicates that the product has reached a viscosity intrinsic 0.57 dl / g and a temperature of 285 ° C. To the melt is added 2 g / kg of core "A" as a fine powder. Immediately the viscosity begins to increase at a speed of 0.072 dl / (g.h). The reaction stops after 45 minutes and the PET polymer product weighs High molecular weight is extruded and granulated.

^^^^^ ^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ A batch of molten linear PET polymers is prepared by the masterbatch technique with 250 ppm of germanium oxide catalyst. The torque of the agitator indicates that the product has an intrinsic viscosity of 0.63 dl / g and a temperature of 285 ° C. To the melt is added 3 g / kg of the "Cl" core as a viscous liquid. Immediately the viscosity begins to increase at a speed of 0.3 dl / (g.h). The reaction is stopped after 30 minutes and the high molecular weight PET product is extruded and granulated. The yellow byproducts only provide an increase of b = 0.7 during the star reaction.

EXAMPLE 8 A compound former extruder is placed as a source of molten linear PET polymers with a retention time of 3 minutes and a product temperature of 307 ° C. The extruded product is conventionally cooled in a water bath and then granulated. A sample without additive is produced and then the core "B" is added to 0.1 mol%, which causes an increase in the melt viscosity corresponding to a four-fold increase - ffiiir ir- •• f i II I - - - '-t1__j-_l -l-r Tflffitrr ^ on average apparent molecular weight and an increase of b = 0.5.

EXAMPLE 9 A compounding extruder is placed as a source of molten linear PET polymers with a retention time of 3 minutes and a product temperature of 307 ° C. The extruded product is cooled in a water bath and then granulate. A sample without additive is produced and then the "B3" core is added to 0.1 mol%, which causes an increase in the melt viscosity corresponding to a three-fold increase in the average apparent molecular weight and an increase of b = 07.

EXAMPLE 10 A compound-forming extruder is placed as a molten linear PET polymer source with a retention time of 4.75 minutes and a product temperature of 307 ° C. The extruded product is conventionally cooled in a water bath and then granulated. A sample without additive is produced and then the core "B" is added to 0.1 25 mol%, which causes an increase in the viscosity of _____ ám __ ^ _- ^. ^^ _- 1AAWa5fc * dbaa ^^ - "J ^ ^^ j¿¡ ^^^^ A ^^ - ^^ .. ^^^ fused that corresponds to an increase of four times in the average weight of apparent molecular weight and an increase of b = 0.5.

EXAMPLE 11 A compound-forming extruder is placed as a molten linear PET polymer source with a retention time of 4.75 minutes and a product temperature of 307 ° C. The extruded product is conventionally cooled in a water bath and then granulated. A sample without additive is produced and then the "E" core is added at 0.1 mol%, which causes an increase in the melt viscosity corresponding to a three-fold increase in the average apparent molecular weight and an increase in b = 0.5 EXAMPLE 12 An extruder is placed as a source of molten linear PET polymers at a temperature of 285 ° C and is pumped into a swept surface evaporator with a surface temperature of 290 ° C and a pressure of 100 Pa, and a time of 4 minute retention The product is cooled and granulated, which provides control. The molten polymer is then introduced back into the reactor and the molten E core is dosed in the evaporator at 0.07 mol%. The action of the blades is used to mix the 5 components and evaporate the acetic acid byproduct. The polymer is retained in the evaporation zone for 4 minutes and then extracted and cooled conventionally in a water bath and then granulated. The comparison of control and treated products with additive shows a increase in the melt viscosity corresponding to an increase of 2.5 times in the average apparent molecular weight and an increase in b = 04. It will be understood by persons skilled in the art that the products made by the process covered by this invention are suitable for blow-molding and stretching. Those skilled in the art will understand that many types of equipment can be used to perform the required operations. It will be further understood by persons skilled in the art that the "H" shape in general will not be symmetric but will follow the distribution of oligomers found in the feed polymer melts in the finishing step. Similarly, the stem and branches of the "Y" shape will not necessarily be of the same length. It will be understood that the use of the symbols "I", "H" and "Y" through this specification | jjjg ^^ ¡|| g ^^^^^^^ l ^^ 8y (ggte g ^ has been designed to include symmetric and fully asymmetric forms of "I", "H" and "Y". "comprises" and its forms of the word "comprising" as used in this description and in the claims do not limit the claimed invention to exclude any variant or additions.Other advantages and modifications of the invention described in the foregoing will be apparent to one skilled in the art and such modifications and adaptations are included in the scope of the invention. _ »Aa« fc * _fc £ »> .. t * ~ jt * .m ** Üí? t ?? r ^^? ^^^^ S ^ É ^^^^^^^^^^^^^^^^^^^ ^ ¡¡¡¡¡¡

Claims (20)

1. A process for producing high molecular weight polyesters, comprising reacting one or more preformed linear polymers, as defined herein, with one or more cores, as defined herein, to form high molecular weight polyesters; wherein the preformed linear polymers are at a temperature in the range from the melting point of the preformed linear polymers to 330 ° C.

2. The process according to claim 1, characterized in that the reaction occurs under vacuum.

3. The process according to any of claims 1 or 2, characterized in that the preformed linear polymers are at a temperature of at least 270 ° C.

4. The process according to claim 3, characterized in that the preformed linear polymers are at a temperature of about 280 ° C. éj ^ eáiá ^^^ ^^

5. The process according to any of claims 1 to 4, characterized in that the reaction occurs for a period of less than 10 minutes.

6. The process according to any of claims 1 to 5, characterized in that the preformed linear polymers are polyester polymers.

7. The process according to claim 6, characterized in that the polyester polymers are polyethylene terephthalate polymers.

8. The process according to any of claims 1 to 7, characterized in that the cores are in the form of a mixed anhydride.

9. The process according to claim 8, characterized in that the mixed anhydride 20 is the isophthalic acid anhydride of acetic acid.

10. A polyethylene terephthalate polymer of high molecular weight when produced using a method according to any of the claims 25 1 to 9.

11. A process for producing polymers, capable of being blow molded and stretched using high molecular weight polymers produced according to the method of any of claims 1 to 9.

12. A star core for use in the preparation of a high molecular weight polymer, characterized in that it is selected from the group consisting of compounds of the general formula "H":

R2 is -OH, -O-CO-CH, -OCH, CH, OH where R is 25 -. 25 -O-CH2CH2-O- ^^^^^^^^ g ^^^^^^^^^^^^^^^^^^^^ compounds of the general formula "Y": wherein R is -OCOCH, or -OCH, CH, OH and compounds of the general formula "I" ,:? í- x ^ ¡.í -jj £ s.,., or mixtures thereof. 13. A star core, according to claim 12, characterized in that it is in the form of a mixed anhydride.

14. A star core, according to any of claims 12 or 13, characterized in that the compound of the general form Y is selected from the group consisting of trimellitic acetic anhydride or trishydroxyethyltrimellitate.

15. A high molecular weight polymer, when produced using cores that are selected from star cores, according to claims 12 to 14, trimellitic acid, trimellitic anhydride or mixtures of 25 the same.

16. The high molecular weight polymer according to claim 15, characterized in that the star nuclei are in the form of mixed anhydrides.

17. The high molecular weight polymer according to claim 15, characterized in that the polymer is a polyester polymer.

18. The high molecular weight polymer according to claim 17, characterized in that the polyester polymer is selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthenates.

19. The high molecular weight polymer according to claim 18, characterized in that the polyester polymer is polyethylene terephthalate.

20. The process according to any of claims 1 to 7, characterized in that the cores are selected from star cores according to any of claims 12 to 14, trimellitic acid, trimellitic anhydride, isophthalic acid 25 or mixtures thereof.