Appeal No. 2004-0495 Paper 22
Application No. 09/503,599 Page 2
1. A process for the continuous production of at least one of bis(3-
hydroxypropyl) terephthalate and low molecular weight oligomers of 1,3-
propanediol and terephthalic acid, comprising:
(a) preheating 1,3-propanediol to a temperature of about
150oC to about 200oC;
(b) preheating one or more lower dialkyl esters of
terephthalic acid to a temperature of about 150 oC to about 220oC;
(c) combining the preheated 1,3-propanediol and catalyst with
the preheated terephthalic acid ester to form a mixture having a mole ratio
of 1,3-propanediol to terephthalic acid ester of about 1.2:1 to about 2.3:1
and maintaining the temperature of the mixture at about 150oC to about
220oC;
(d) continuously feeding the preheated 1,3-
propanediol/terephthalic acid ester mixture through at least one inlet to an
ester exchange vessel where the mixture undergoes a continuous
transesterification reaction to form a liquid reaction mixture and gaseous
reaction products;
(e) continuously heating and mixing the liquid reaction mixture,
whereby the temperature of the mixture in a base portion of the ester
exchange vessel is maintained at about 215oC to about 250oC and the
pressure in a base portion of the ester exchange vessel is maintained at
about 800 mm Hg to about 1,000 mm Hg, thereby continuing the
transesterification reaction to form liquid reaction products and gaseous
reaction products;
(f) continuously separating the gaseous reaction products from
the liquid reaction mixture in a separating portion of the ester exchange
vessel which is above the base portion; and
(g) continuously removing a stream of liquid reaction products
from the base portion of the ester exchange vessel, the stream comprising
at least one of bis(3-hydroxypropyl) terephthalate and low molecular
weight oligomers of 1,3 propanediol and terephthalic acid.
16. The process according to claim 1, wherein said at least
one inlet is located below the midpoint of the ester exchange vessel.
According to the specification, the ester exchange vessel is preferably a bubble
cap column wherein the liquid reactants are heated to about 215oC to about 250oC (3:32
- 4:2) and the base of the column is maintained at a pressure of about 800 mm Hg to
about 1,000 mm Hg, while the pressure at the top of the column is at or near
atmospheric pressure (4:26-33). Further according to the specification, a
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