Process for the preparation of polyesters containing 1,4-cyclohexanedimethanol

Abstract

Disclosed is a process for the preparation of high molecular weight polyesters by reacting one or more dicarboxylic acids directly with 1,4-cyclohexanedimethanol and, optionally, one or more diols. The process uses an overall diol to dicarboxylic acid molar ratio of about 0.97 to about 1.2 and an incremental addition of either the diacid or diol components. The process provides a shorter total reaction time and, thus, lessens the thermal degradation of polyester which may result in high color and reduced molecular weight.

Description

CROSS-REFERENCE[0001]This application is a divisional application of prior application Ser. No. 11 / 414 / 466, filed Apr. 28, 2006.FIELD OF THE INVENTION[0002]This invention pertains to a process for the preparation of thermoplastic polyesters. More particularly, this invention pertains to a polyester process in which one or more dicarboxylic acids is reacted directly with a diol component comprising 1,4-cyclohexanedimethanol and, optionally, one or more diols, in a low overall diol:dicarboxylic acid ratio.BACKGROUND OF THE INVENTION[0003]Polyesters containing 1,4-cyclohexanedimethanol (abbreviated hereinafter as “CHDM”) as a diol component are often produced using a dialkyl esters such as, for example, dimethylterephthalate (DMT), dimethylisophthalate, and 1,4-dimethylcyclohexane dicarboxylate, as the source of the diacid component. In a typical process, for example, a dialkyl ester is reacted with one or more diols in a transesterification reaction to produce an oligomer. The alkyl a...

AI Technical Summary

Benefits of technology

This process efficiently produces high molecular weight thermoplastic polyesters with excellent clarity, suitable for packaging, textiles, and film applications, while minimizing thermal degradation and process time, and is particularly effective for polyesters with high-boiling diols like CHDM.

Problems solved by technology

Removal of excess diol, however, is difficult when high-boiling diols are used, that is diols having a boiling point greater than about 230° C. such as, for example, CHDM.

Unfortunately, using dicarboxylic acids as a starting material instead of a dialkyl esters in polyester process presents a number of problems, especially when CHDM and other high boiling diols are used as a diol component.

Any excess diol, however, must be removed during the polymerization step, often requiring extended process times at elevated temperatures and low pressures (typically less than 0.7 kPa).

In addition, long reaction times during the polymerization step are often required to build sufficient molecular weight.

Lengthy process times and elevated temperatures, however, frequently can lead to the development of color and the thermal degradation of the polyester.

In polyester compositions that are substantially amorphous, this degradation can lead to a loss of clarity or to the formation of high color in the polyester product.

Solid state polymerization, however, is expensive and requires additional equipment.