Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Removing and recycling removed material from an ongoing...
Reexamination Certificate
2005-05-03
2005-05-03
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Removing and recycling removed material from an ongoing...
C528S302000, C528S308600, C528S481000, C528S501000, C528S503000, C526S065000, C526S066000, C526S068000
Reexamination Certificate
active
06887953
ABSTRACT:
A process that can be used for direct esterification of a dicarboxylic acid such as terephthalic acid with a glycol such as 1,3-propanediol. The process comprises (1) contacting, at an elevated temperature, optionally in the presence of a preformed oligomer, the acid with the glycol to produce a product mixture comprising (i) a water-glycol vapor mixture, which or a portion of which exits the product mixture at the temperature to form a water-glycol vapor mixture and (ii) a liquid product mixture comprising an oligomer having a degree of polymerization of from about 1.9 to about 3.5 and comprising repeat units derived from the acid; (2) separating the glycol from the water-glycol mixture to produce a recovered glycol; and (3) returning the recovered glycol to the product mixture such that the liquid product mixture comprises an excess free glycol.
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Acquah Samuel A.
E.I. du Pont de Nemours and Company
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