Polyester modification method

Abstract

The subject invention provides a means for modifying existing polyester polymers to optimize characteristics for solid state polymerization and for utilization in a wide array of specific applications. For instance, the modification technique of this invention may be used to adjust the melting point, crystallization temperature (either from the solid or on cooling from the melt), glass transition temperature, natural stretch ratio, barrier properties, melt strength, and / or solid state polymerization characteristic of the polyester. Application of the instant invention could result in a polymer with substantially different physical properties, potentially allowing modification of commodity resins for use in heretofore high cost, specialty applications. A further advantage of the invention is that recycled polymer may be modified to broaden its potential uses into more demanding higher performance applications.

Description

[0001]This is a continuation-in-part of U.S. patent application Ser. No. 16 / 277,550, filed on Feb. 15, 2019, which claims priority to U.S. Provisional Patent Application Ser. No. 62 / 702,118, filed on Jul. 23, 2018. The teachings of U.S. patent application Ser. No. 16 / 277,550 and U.S. Provisional Patent Application Ser. No. 62 / 702,118 are incorporated herein by reference in their entirety.FIELD OF THE INVENTION[0002]This invention relates to the modification of a polyester polymer after the completion of melt polymerization. The polymers to be modified by this invention typically have an intrinsic viscosity (IV) of at least about 0.4 dL / g or a number average molecular weight (Mn) of at least about 10,000 daltons or a degree of polymerization (DP) of at least about 50. This modification may be undertaken to affect the physical properties of the final polymer including but not limited to the melting point, crystallization temperature either from the solid or on cooling from the melt, g...

AI Technical Summary

Benefits of technology

[0015]The subject invention provides a means for modifying existing polyester polymers to optimize characteristics for solid state polymerization and for utilization in a wide array of specific applications. For instance, the modification technique of this invention may be used to adjust the melting point, crystallization temperature (either from the solid or on cooling from the melt), glass transition temperature, natural stretch ratio, barrier properties, melt strength, and / or solid state polymerization characteristic of the polyester. Application of the instant invention could result in a polymer with substantially different physical properties, potentially allowing its use in heretofore high cost, specialty applications. A further advantage of the invention is that recycled polymer may be modified to broaden its potential uses into more demanding, higher performance applications.

[0016]The present invention more specifically discloses a method for modifying a polyester polymer, comprising reacting (a) the polyester polymer (b) a first compound which has at least two reactive groups which are selected from the group consisting of hydroxyl groups, primary amine groups, or secondary amine groups and (c) a second compound which has at least two reactive groups capable of reacting with the reactive groups of the first compound to produce a modified polyester polymer, wherein said method is conducted in the melt phase, and wherein the polyester polymer has an intrinsic viscosity of at least about 0.40 dL / g as measured at 25° C. in a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane.

[0017]The subject invention further reveals a method for modifying a polyester polymer comprising reacting the polyester polymer with a hydroxy substituted carboxylic acid to produce a modified polyester polymer, wherein said method is conducted in the melt phase, and wherein the polyester polymer has an intrinsic viscosity of at least about 0.40 dL / g as measured at 25° C. in a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane.

[0018]The present invention also discloses a method for modifying a polyester polymer comprising reacting the polyester polymer with a hydroxy substituted carboxylic acid to produce a modified polyester polymer, wherein said method is conducted in the melt phase, wherein the polyester polymer is modified with less than 5 mole percent of the hydroxyl substituted carboxylic acid based upon the total number of repeat units in the polyester polymer, and wherein the modified polyester polymer has an intrinsic viscosity of at least about 0.30 dL / g as measured at 25° C. in a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane. The hydroxy substituted carboxylic acid can be a member selected from the group consisting of glycolic acid and lactic acid and the polyester polymer can be polyethylene terephthalate. The polyester polymer can be modified with less than 4 mole percent, 3 mole percent, 2 mole percent, 1 mole percent, 0.5 mole percent, 0.2 mole percent, 0.1 mole percent, or even 0.05 mole percent of the hydroxyl substituted carboxylic acid, based upon the total number of repeat units in the polyester polymer. In one embodiment of this invention the hydroxyl substituted carboxylic acid is added to the polyester polymer as it is being extruded. The modified polyester polymer will typically have an intrinsic viscosity of at least 0.35 dL / g, 0.40 dL / g, 0.45 dL / g, or 0.50 dL / g as measured at 25° C. in a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane. In the practice of this invention the polyester polymer is not added sequentially or in stages.

[0019]The subject invention further reveals a method for modifying a polyester polymer, comprising reacting (a) the polyester polymer having an intrinsic viscosity of at least 0.40 dL / g as measured at 25° C. in a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane, (b) a first compound which has at least two reactive groups which are selected from the group consisting of hydroxyl groups, primary amine groups, or secondary amine groups and (c) a second compound which has at least two reactive groups capable of reacting with the reactive groups of the first compound to produce a modified polyester polymer, wherein said method is conducted in the melt phase, wherein the modified polyester polymer is modified with less than 5 mole percent of the first compound based upon the total number of repeat units in the polyester polymer, wherein the modified polyester polymer is modified with less than 5 mole percent of the second compound based upon the total number of repeat units in the polyester polymer, and wherein the modified polyester polymer has an intrinsic viscosity of at least 0.30 dL / g as measured at 25° C. in a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane. In this process the first compound and the second compound are added to the polyester polymer as it is being extruded and the polyester polymer is not added sequentially or in stages. The modified polyester polymer typically modified with less than 5 mole percent, 4 mole percent, 3 mole percent, 2 mole percent, 1 mole percent, 0.5 mole percent, 0.2 mole percent, 0.1 mole percent, or 0.05 mole percent of the first compound, based upon the total number of repeat units in the polyester polymer, and the modified polyester polymer is modified with less than 5 mole percent, 4 mole percent, 3 mole percent, 2 mole percent, 1 mole percent, 0.5 mole percent, 0.2 mole percent, 0.1 mole percent, or 0.05 mole percent of the second compound based upon the total number of repeat units in the polyester polymer. The polyester polymer is frequently polyethylene terephthalate.

Problems solved by technology

While all the aliphatic acid based polyester resins have poor hydrolytic stability relative to PET, they have found significant uses.

These polymerization lines typically produce 50 to 100 thousand pounds of polymer per hour resulting in significant losses during resin transitions as the polymer produced during the change can at best be recycled to recover the raw material value.

This has resulted in the manufacturing process becoming less flexible with it being increasingly more problematic and impractical to change the composition of the polyester to meet particular desired physical characteristics.

In other words, current large scale manufacturing techniques are less suitable for making specialty polyesters having desired physical characteristics which are needed or desirable for use in various applications.

For instance, specialty polymers which are modified with additional monomers to attain desired characteristics cannot be made efficiently in such large scale operations and are typically made in small scale operations at substantially higher cost.

In practice, it is difficult to carry out melt polymerization for a sufficient length of time to build the molecular weight desired for the final product because it becomes progressively more difficult to remove by-products from the molten resin and the power requirements to mix it become increasingly high.

Also, side reactions leading to degradation of the polymer begin to become significant.

However, in doing so the polymer chain of the polyester is cleaved and consequently the molecular weight of the polyester is reduced and its associated physical properties also changed (frequently in an undesirable manner).

The generation of two alcohol end groups on cleavage of a polyester chain by a glycol or polyol is deleterious to the ability to rebuild chain length or molecular weight for several reasons.

A second effect of polyester chain cleavage by a glycol or polyol on rebuilding molecular weight is that by-product removal becomes more difficult.

This is particularly true in cases where the polyester having the needed characteristics is simply not available or is too costly.

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