Preparation process and purification process of dimeric cyclic e

Details Preparation process and purification process of dimeric cyclic e Preparation process and purification process of dimeric cyclic e

1997-01-23

1998-11-03

Acquah, Samuel A.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Treating polymer containing material or treating a solid...

528481, 528487, 528491, 528494, 528495, 528501, 528502, 528503, 524706, 524755, 524765, 524758, 549274, C08F 600, C08J 300

Patent

active

058309918

ABSTRACT:
The invention provides an economical and efficient process for preparing a dimeric cyclic ester of an .alpha.-hydroxycarboxylic acid by depolymerizing a corresponding .alpha.-hydroxycarboxylic acid oligomer, which comprises the steps of (1) heating a mixture containing the .alpha.-hydroxycarboxylic acid oligomer and at least one high-boiling polar organic solvent having a boiling point within a range of 230.degree.-450.degree. C. to a temperature, at which the depolymerization of the oligomer takes place, under atmospheric pressure or reduced pressure, (2) dissolving the oligomer in the solvent until a residual rate of a melt phase of the oligomer reaches 0.5 or lower, (3) further continuing the heating at the temperature, at which the depolymerization of the oligomer takes place, to depolymerize the oligomer, (4) distilling out the dimeric cyclic ester formed together with the high-boiling polar organic solvent, and (5) recovering the dimeric cyclic ester from the distillate. The invention also provides a process for purifying a crude dimeric cyclic ester of an .alpha.-hydroxycarboxylic acid.

REFERENCES:
patent: 2668162 (1954-02-01), Lowe
patent: 4727163 (1988-02-01), Bellis
patent: 4835293 (1989-05-01), Bhatia
patent: 5326887 (1994-07-01), Di Cosimo et al.
patent: 5342969 (1994-08-01), Ford et al.

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