Chemistry Reference
In-Depth Information
A polyester is being manufactured in Japan from a methyl ester of
p
-2-hydroxyethoxybenzoic acid
by transesterification:
O
O
O
n
HO
OH
O
O
n
The product is used as a fiber.
During the last 8 or 10 years, there has been a considerable effort to introduce a new potentially
high volume polyester, poly(trimethylene terephthalate) [
24
], into the market. The polyester is sold
under a commercial trade name as “Corterra” and as a fiber by the trade name “Sorona.”
Polyesters based on 2,6-disubstituted naphthalene have gained commercial importance in recent
years due to their higher tensile strength, higher modulus, and good mechanical properties. These
polyesters offer an additional advantage over poly(ethylene terephthalate) and poly(butylene tere-
phthalate) by having higher first and second transition temperatures. Polyesters based on naphthalene
are typically prepared by either solution polymerization or by ester interchange in the melt.
O
n
RO
+
OR
n
HO
OH
x
O
O
+
n
ROH
O
x
O
n
where
x ¼
2,4
7.2.1.3 Copolyesters
Mixed dicarboxylic acids are usually used to formcopolyesters. For instance, terephthalic and isophthalic
acids are reacted together with 1,4-dimethylol cyclohexane to form copolyester. The product is amor-
phous and transparent. Another copolyester is manufactured from terephthalic, isophthalic, and an
aliphatic dicarboxylic acid like adipic with either 1,4 butanediol or 1,6-hexanediol. The aliphatic
dicarboxylic acid is used inminor quantities.Many such copolyesters are used as high-strength adhesives.
In addition, there are thermoplastic polyester elastomers. These are produced by equilibrium melt
transesterification of dimethyl terephthalate, 1,4-butanediol, and a poly(tetramethylene ether) glycol
(molecular weight about 1,000). Because equilibrium conditions exist in the melt, the products are
random copolymers:
O
O
2n
OH
x
+
+
n
HO
OH
n
HO
O
4
O
O
O
O
O
O
