POLYESTERS OF 1,2-BIS (HYDROXYPHENYL) ETHANES AND AROMATIC DICARBOXYLIC ACIDS

POLYESTERS DE 1,2-BIS (HYDROXYPHENYL) ETHANES ET D'ACIDES DICARBOXYLIQUES AROMATIQUES

English Abstract

ABSTRACT
Polyester condensates of aromatic dicarboxylic acids and
diphenols containing 1,2-bis(hydroxyphenyl)ethane in which the
hydroxyl is in the 3 or 4 position.
The component acids are selected from the group consisting
of isophthalic acid, terephthalic acid, 3,3'- , 3,4'- and 4,4'-
bibenzoic acids, 1,3-, 1,4- , 1,5- , 1,6-, 1,7- , 1,8- , 2,6- , and 2,7-
naphthalenedicarboxylic acids and acids represented by the formula:
<IMG>
wherein the carboxyl groups are in the 3- or 4- positions, and X is
O, S, SO2, C-O, CH2, CH2CH2, CH(CH3) or C(CH3)2.
The diphenol comprises 1,2-bis(hydroxyphenyl)ethane and
optionally a diphenol selected from the group consisting of resor-
cinol, hydroquinone, 3,3'-, 3,4'- and 4,4'-diphenols, 1,3-, 1,4-,
1,5-, 1,6-, 1,7-, 1,8-, 2,6- and 2,7-dihydroxynaphthalenes and
diphenols represented by the formula:
<IMG>
wherein the hydroxyl groups are in the 3- or 4- positions and Y is
O, S, SO2, C-O, CH2, CH(CH3), C(CH3)2 or (CH2)3.
The aromatic polyesters have superior fire safety perfor-
mance and are used for film, fiber and molding applications.
Rapidly crystallizable polyesters may be obtained with superior sol-
vent resistance and stress cracking resistance.
-2-

Claims

The embodiments of the invention in which an exclu-
sive property or privilege is claimed are defined as follows:
1. A linear polyester comprising the condensation
product of a diphenol and an aromatic dicarboxylic acid,
wherein the diphenol comprises a 1,2-bis(hydroxyphenyl) ethane
in which the hydroxyl groups are in the 3- or 4-positions
and wherein the melt viscosity of the polyester at 350°C.
determined at a shear rate of 100 sec.-1 with a capillary
rheometer, is less than about 105 poise.
2. The linear polyester of claim 1 wherein the
aromatic dicarboxylic acid comprises at least one acid
selected from the group consisting of isphthalic acid,
terephthalic acid, 5-alkyl-isophthalic acid wherein the
alkyl radical contains from 1 to 6 carbon atoms, 3,3'-,
3,4'- and 4,4'-bibenzoic acids, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-,
1,8-, 2,6- and 2,7-naphthalene-dicarboxylic acids, and acids
represented by the formula:
<IMG>
wherein the carboxyl groups are in the 3- or 4-positions, X
is O, S, SO2, C=O, CH2, CH2CH2, CH(CH3) or C(CH3)2, R is H
or a C1 to C6 alkyl radical, R groups ortho to a carboxyl
are small enough to permit esterification, R substituents
ortho to X are limited to one ring and n = 0 to 2.

3. The linear polyester of Claim l wherein the aromatic
dicarboxylic acid comprises at least one acid selected from the
group consisting of isophthalic acid, 5-t-butyl-isophthalic acid,
terephthalic acid, bis(4-carboxyphenyl)ether, bis(4-carboxyphenyl)
sulfide, bis(4-carboxyphenyl)sulfone, bis(4-carboxyphenyl)methane,
1,2-bis(4-carboxyphenyl)ethane, and 2,2-bis(4-carboxyphenyl)
propane.
4. The linear polyester of Claim 1 wherein the diphenol
comprises the 1,2-bis(hydroxyphenyl)ethane and at least one
diphenol selected from the group consisting of resorcinol, hydro-
quinone, 3,3'-, 3,4'- and 4,4'-diphenols, 1,3-, 1,4-, 1,5-, 1,6-,
1,7-, 1,8-, 2,6- and 2,7-dihydroxynaphthalenes, and diphenols
represented by the formula:
<IMG>
wherein the hydroxyl groups are in the 3- or 4- positions, Y is O,
S, SO2, C=O, CH2, CH(CH3), C(CH3)2 or (CH2)3, R' is H or a C1 to
C6 alkyl radical, R' substituents ortho to Y are limited to one
ring, R' substituents ortho to hydroxyl are small enough to permit
esterification and m = 0 to 4.
-46-

5. The linear polyester of Claim 4 wherein the
diphenol comprises the 1,2-bis(hydroxyphenyl)ethane and at
least one diphenol selected from the group consisting of
bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane,
bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide and
bis(4-hydroxyphenyl)sulfone.
6. A linear polyester as defined in Claim 1, and
comprising the condensation product of a diphenol and an
aromatic dicarboxylic acid, wherein the diphenol contains at
least about 60 mol percent of a 1,2-bis(hydroxyphenyl)ethane
in which the hydroxyl groups are in the 3- or 4-positions and
wherein the melt vicosity of the polyester at 350°C. deter-
mined at a shear rate of 100 sec.-1 with a capillary
rheometer, is less than about 105 poise.
-47-

7. The linear polyester of Claim 6 wherein the aromatic
dicarboxylic acid comprises at least one acid selected from the
group consisting of isophthalic acid, terephthalic acid, 5-alkyl-
isophthalic acid wherein the alkyl radical contains from 1 to 6
carbon atoms, 3,3'-, 3,4'- and 4,4'-bibenzoic acids, 1,3-, 1,4-,
1,5-, 1,6-, 1,7-, 1,8-, 2,6- and 2,7-naphthalene dicarboxylic
acids, and acids represented by the formula:
<IMG>
wherein the carboxyl groups are in the 3- or 4- positions, X is O,
S, SO2, C=O, CH2, CH2CH2, CH(CH3) or C(CH3)2, R is H or a C1 to C6
alkyl radical, R groups ortho to a carboxyl are small enough to
permit esterification, R substituents ortho to X are limited to
one ring and n = 0 to 2.
8. The linear polyester of Claim 6 wherein the aromatic
dicarboxylic acid comprises at least one acid selected from the
group consisting of isophthalic acid, 5-t-butyl-isophthalic acid,
terephthalic acid, bis(4-carboxyphenyl)ether, bis(4-carboxyphenyl)
sulfide, bis(4-carboxyphenyl)sulfone, bis(4-carboxyphenyl)methane,
and 2,2-bis(4-carboxyphenyl)propane.
-48-

9. The linear polyester of Claim 6 wherein the diphenol
comprises the 1,2-bis(hydroxyphenyl)ethane and at least one
diphenol selected from the group consisting of resorcinol, hydro-
quinone, 3,3'-, 3,4'- and 4,4'-diphenols, 1,3-, 1,4-, 1,5-, 1,6-,
1,7-, 1,8-, 2,6- and 2,7-dihydroxynaphthalenes, and diphenols
represented by the formula:
<IMG>
wherein the hydroxyl groups are in the 3- or 4- positions, Y is O,
S, SO2, C=O, CH2, CH(CH3), C(CH3)2 or (CH2)3, R' is H or a C1 to
C6 alkyl radical, R' substituents ortho to Y are limited to one
ring, R' substituents ortho to hydroxyl are small enough to permit
esterification, and m = 0 to 4.
10. The linear polyester of Claim 6 wherein the diphenol
comprises the 1,2-bis(hydroxyphenyl)ethane and at least one
diphenol selected from the group consisting of bis(4-hydroxyphenyl)
methane, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)ether,
bis(4-hydroxyphenyl)sulfide and bis(4-hydroxyphenyl)sulfone.
11. The linear polyester of Claim 6 wherein the Tg is
greater than about 100°C.
-49-

12. The linear polyester of Claim 6 wherein the
inherent viscosity at 30°C. determined at a concentration of
0.5 grams polyester per 100 ml. solution in solvent mixture
of 60 parts by weight of phenol and 40 parts by weight of
sym-tetrachloroethane, is at least about 0.3.
13. The linear polyester of Claim 6 wherein the flame
resistance rating of a sheet of polyester of 0.08 cm. thickness
is at least V-I when measured by the Underwriter's Laboratory
"Test for Flammability of Plastic Materials - UL-94, September
17, 1973" based on the ratings effective February 1, 1974.
14. A polyester comprising the condensation product
of a diphenol and an aromatic dicarboxylic acid wherein the
diphenol contains at least about 75 mol percent of a 1,2-bis-
(hydroxyphenyl)ethane in which the hydroxyl groups are in the
3- or 4-positions and the remainder comprises at least one
diphenol selected from the group consisting of bis(4-
hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane,
bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide, and
bis(4-hydroxyphenyl)sulfone; wherein the aromatic dicarboxylic
acid comprises at least one acid selected from the group
consisting of isophthalic acid, 5-t-butylisophthalic acid,
terephthalic acid, bis(4-carboxyphenyl)ether, bis(4-carboxy-
phenyl)sulfide, bis(4-carboxyphenyl)sulfone, bis(4-carboxy-
phenyl)methane, 1,2-bis(4-carboxyphenyl)ethane and 2,2-bis-
(4-carboxyphenyl)propane; wherein the melt viscosity of the
polyester at 350°C. determined at a shear rate of 100 sec. -1
with a capillary rheometer is less than about 105 poise;
wherein the Tg of the polyester is greater than about 100°C.;
wherein the inherent viscosity of the polyester at 30°C.,
determined at a concentration of 0.5 gram polyester per 100
ml. solution, in a solvent mixture of 60 parts by weight of
phenol and 40 parts by weight of sym-tetrachloroethane, is

at least about 0.5; and wherein the flame resistance rating
of a sheet of polyester of 0.08 cm. thickness is at least
V-I when measured by the Underwriter's Laboratory "Test for
Flammability of Plastic Materials - UL-94, September 17, 1973"
based on the ratings effective February 1, 1974.
15. A linear polyester as defined in claim 1 and
comprising the condensation product of a diphenol and at
least one aromatic dicarboxylic acid selected from the group
consisting of isophthalic acid and t-butyl-isophthalic acid;
wherein the diphenol comprises at least about 60 mol percent
1,2-bis(4-hydroxyphenyl)ethane and the remainder comprises
at least one diphenol selected from the group consisting of
1,2-bis(4-hydroxyphenyl)ethane, 1,2-bis(3-hydroxyphenyl)ethane,
bis(4-hydroxyphenyl)methane and 2,2-bis(4-hydroxyphenyl)propane;
wherein the melt viscosity of the polyester at 350°C. deter-
mined with a capillary rheometer at a shear rate of 100 sec.-1
is less than about 105 poise; wherein the Tg of the polyester
is greater than about 100°C. and wherein the inherent
viscosity of the polyester at 30°C. determined at a concentra-
tion of 0.5 gram polyester per 100 ml. solution, in a solvent
mixture of 60 parts by weight of phenol and 40 parts by
weight of sym-tetrachloroethane, is at least about 0.5.
16. A method for improving the fire safety perfor-
mance of a linear polyester condensate of an aromatic dicar-
boxylic acid and a diphenol which comprises substituting for
at least 60 mole percent of the diphenol, a 1,2-bis(hydroxy-
phenyl)ethane in which the hydroxyl groups are in the 3- or
4-positions.
51

17. The method of Claim 16 wherein the aromatic dicar-
boxylic acid is selected from the group consisting of isophthalic
acid, terephthalic acid, 5-alkyl-isophthalic acid wherein the
alkyl radical contains from 1 to 6 carbon atoms, 3,3'-, 3,4'- and
4,4'-bibenzoic acid, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,6- and
2,7-naphthalene dicarboxylic acids, and acids represented by the
formula:
<IMG>
wherein the carboxyl groups are in the 3- or 4-positions, X is 0,
S, SO2, C=O, CH2, CH2CH2, CH(CH3) or C(CH3)2, R is H or a C1 to C6
alkyl radical, R groups ortho to a carboxyl are small enough to
permit esterification, R substituents ortho to X are limited to
one ring and n = 0 to 2; and the diphenol is selected from the
group consisting of resorcinol, hydroquinone, 3,3'-, 3,4'- and
4,4'-diphenols, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,5-, 2,6- and 2,7-
dihydroxynaphthalenes, and diphenols represented by the formula:
<IMG>
wherein the hydroxyl groups are in the 3- or 4- positions, Y is 0,
S, SO2, C=O, CH2, CH(CH3), C(CH3)2 or (CH2)3, R' is H or a C1 to C6
alkyl radical, R' substituents ortho to Y are limited to one ring,
R' substituents ortho to hydroxyl are small enough to permit
esterification, and m = 0 to 4.
52

18. The method of claim 16 wherein the aromatic
dicarboxylic acid is selected from the group consisting of
isophthalic acid, 5-t-butylisophthalic acid, terephthalic acid,
bis(4-carboxyphenyl)ether, bis(4-carboxyphenyl)sulfide, bis(4-
carboxyphenyl)sulfone, bis(4-carboxyphenyl)methane, 1,2-bis(4-
carboxyphenyl)ethane, and 2,2-bis(4-carboxyphenyl)propane;
and the diphenol is selected from the group consisting of
bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane,
bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide and
bis(4-hydroxyphenyl)sulfone.
19. A method as defined in claim 16 for improving
the fire safety performance of a linear polyester condensate
of 2,2-bis(4-hydroxyphenyl)propane and an aromatic dicarboxylic
acid selected from the group consisting of isophthalic acid,
5-t-butylisophthalic acid, terephthalic acid, bis(4-carboxy-
phenyl)ether, bis(4-carboxyphenyl)sulfide, bis(4-carboxyphenyl)
sulfone, bis(4-carboxyphenyl)methane, 1,2-bis(4-carboxyphenyl)
ethane, and 2,2-bis(4-carboxyphenyl)propane; which comprises
substituting for 60 mole percent of the 2,2-bis(4-hydroxyphenyl)
propane, a 1,2-bis(hydroxyphenyl)ethane in which the hydroxyl
groups are in the 3- or 4-positions.
20. The method of claim 19 wherein the 1,2-bis
(hydroxyphenyl)ethane is 1,2-bis(4-hydroxyphenyl)ethane.
21. A method as defined in claim 16 for improving
the fire safety performance of a linear polyester condensate
of 2,2-bis(4-hydroxyphenyl)propane and an aromatic dicarboxylic
acid selected from the group consisting of isophthalic acid,
5-t-butyl-isophthalic acid and terephthalic acid which comprises
substituting at least 60 mol percent of the 2,2-bis(4-hydroxy-
phenyl)propane with 1,2-bis(4-hydroxyphenyl)ethane.
53

22. The linear polyester of claim 1 comprising the
condensation product of a diphenol and an aromatic dicarboxylic
acid wherein the diphenol comprises a 1,2-bis(hydroxyphenyl)
ethane in which the hydroxyl groups are in the 3- or 4-
positions and wherein the polyester is readily crystallized
and has a melting point less than about 350°C.
23. The linear polyester of claim 22 wherein the
aromatic dicarboxylic acid comprises at least one acid selected
from the group consisting of isophthalic acid, terephthalic
acid, 3,3'-, 3,4'- and 4,4'-bibenzoic acids, 1,3-, 1,4-, 1,5-,
1,6-, 1,7-, 1,8-, 2,6- and 2,7-naphthalenedicarboxylic acids
and acids represented by the formula:
<IMG>
wherein the carboxyl groups are in the 3- or 4-positions, and
X is 0, S, SO2, C=O, CH2 or CH2CH2.
54

24. The linear polyester of claim 22 wherein the
aromatic dicarboxylic acid comprises at least one acid
selected from the group consisting of isophthalic acid,
terephthalic acid, bis(4-carboxyphenyl)ether, bis(4-carboxy-
phenyl)sulfide, bis(4-carboxyphenyl)sulfone, bis(4-carboxy-
phenyl)methane and 1,2-bis(4-carboxyphenyl)ethane.
25. The linear polyester of claim 22 having a
melting point less than about 350°C. and comprising the
condensation product of a diphenol and an aromatic dicarboxylic
acid wherein the diphenol contains at least 75 mol percent of
1,2-bis(4-hydroxyphenyl)ethane.

26. The linear polyester of claim 25 wherein the aromatic
dicarboxylic acid comprises at least one acid selected from the
group consisting of isophthalic acid, terephthalic acid, 3,3'-, 3,4'
and 4,4'-bibenzoic acids, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,6-
and 2,7-naphthalenedicarboxylic acids and acids represented by the
formula:
<IMG>
wherein the carboxyl groups are in the 3- or 4- positions, and
X is O, S, SO2, C=O, CH2 or CH2CH2; and wherein the diphenol com-
prises about 75 to 100 mol percent 1,2-bis(4-hydroxyphenyl)ethane
and about 25 to 0 mol percent of at least one diphenol selected
from the group consisting of resorcinol, hydroquinone, 3,3'-, 3,4'-
and 4,4'-diphenols, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,6- and
2,7-dihydroxynaphthalenes, 1-(3-hydroxyphenyl)-2-(4-hydroxyphenyl)
ethane, 1,2-bis(3-hydroxyphenyl)ethane and diphenols represented by
the formula:
<IMG>
wherein the hydroxyl groups are in the 3- or 4- positions and Y is
O, S, SO2, C=O, CH2 or (CH2)3.
56

27. The linear polyester of Claim 25 wherein the aroma-
tic dicarboxylic acid comprises at least one acid selected from the
group consisting of isophthalic acid, terephthalic acid, bis(4-car-
boxyphenyl)ether, bis(4-carboxyphenyl)sulfide, bis(4-carboxyphenyl)
sulfone, bis(4-carboxyphenyl)methane and 1,2-bis(4-carboxyphenyl)
ethane and wherein the diphenol comprises about 75 to 100 mol percent
1,2-bis(4-hydroxyphenyl)ethane and about 25 to 0 mol percent of at
least one diphenol selected from the group consisting of bis(4-
hydroxyphenyl)methane,-2,2-bis(4-hydroxyphenyl)propane, bis(4-
hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide and bis(4-hydroxy-
phenyl)sulfone.
28. The linear polyester of claim 25 wherein the Tg is
greater than about 100°C.
29. The linear polyester of claim 25 wherein the inherent
viscosity at 30°C. determined at a concentration of 0.5 gram poly-
ester per 100 ml. solution in a solvent mixture of 60 parts by
weight of phenol and 40 parts by weight of sym-tetrachloroethane,
is at least about 0.3.
30. The linear polyester of claim 25 wherein the
crystallization rate is greater than about 0.2 min-1.
57

31. A readily crystallized linear polyester of
melting point less than about 350°C. as defined in claim 22,
and comprising the condensation product of at least one
aromatic dicarboxylic acid selected from the group consisting
of isophthalic acid, terephthalic acid, bis(4-carboxyphenyl)
ether, bis(4-carboxyphenyl)sulfide, bis(4-carboxyphenyl)
sulfone, bis(4-carboxyphenyl)methane and 1,2-bis(4-carboxy-
phenyl)ethane and a diphenol comprising a 1,2-bis(4-hydroxy-
phenyl)ethane and a diphenol selected from the group consisting
of 1,2-bis(3-hydroxyphenyl)ethane, 1-(3-hydroxyphenyl)-2-
(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl)methane, bis(4-
hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide and bis(4-
hydroxyphenyl)sulfone; wherein the diphenol comprises at
least about 75 mol percent 1,2-bis(4-hydroxyphenyl)ethane;
wherein the Tg of the polyester is greater than about 100°C.;
wherein the inherent viscosity of the polyester at 30°C.
determined at a concentration of 0.5 gram polyester per 100
ml. solution in a solvent mixture of 60 parts by weight of
phenol and 40 parts by weight of sym-tetrachloroethane, is
at least about 0.5; and wherein the crystallization rate
of the polyester is greater than about 0.2 min-1.
32. A readily crystallized linear polyester of
melting point less than about 350°C. as defined in claim 22,
and comprising the condensation product of at least one
aromatic dicarboxylic acid selected from the group consisting
of isophthalic acid, terephthalic acid, bis(4-carboxyphenyl)
ether, bis(4-carboxyphenyl)sulfide, bis(4-carboxyphenyl)
sulfone, bis(4-carboxyphenyl)methane and 1,2-bis(4-carboxy-
58

phenyl)ethane and a diphenol comprising a 1,2-bis(4-hydroxy-
phenyl)ethane and a diphenol selected from the group consisting
of 1,2-bis(3-hydroxyphenyl)ethane, 1-(3-hydroxyphenyl)-2-
(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl)methane, bis(4-
hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide and bis(4-
hydroxyphenyl)sulfone; wherein the diphenol comprises at
least about 90 mol percent 1,2-bis(4-hydroxyphenyl)ethane;
wherein the Tg of the polyester is greater than about 100°C.;
wherein the inherent viscosity of the polyester at 30°C.
determined at a concentration of 0.5 gram polyester per 100
ml. solution in a solvent mixture of 60 parts by weight of
phenol and 40 parts by weight of sym-tetrachloroethane, is
at least about 0.5; and wherein the crystallization rate
of the polyester is greater than about 0.2 min-1.
59

33. A readily crystallized linear polyester of an
aromatic dicarboxylic acid and a diphenol as defined in
claim 22, and wherein the aromatic dicarboxylic acid com-
prises at least about 67 mol percent of isophthalic acid and
wherein the diphenol comprises at least about 90 mol percent
1,2-bis (4-hydroxyphenyl)ethane; wherein the Tg of the
polyester is greater than about 100°C., wherein the inherent
viscosity at 30°C determined at a concentration of 0.5
gram polyester per 100 ml. solution in a solvent mixture of
60 parts by weight of phenol and 40 parts by weight of
sym-tetrachloroethane, is at least about 0.3; and wherein
the crystallization rate of the polyester is greater than
about 0.2 min-1.
34. The linear polyester of claim 33, wherein
the inherent viscosity is at least about 0.5.
35. A polyester containing recurring units re-
presented by the formula:
<IMG>

Description

719~
C-08-0345
POLYESTERS OF 1,2-BIStHYDROXYPHENYL)ETHANES
AND ARO~TIC DICARBOXYLIC ACIDS
This invention relates to a novel class of tractable linear
aromatic polyesters of improved fire safety performance as well as
to molding powders and shaped articles produced therefrom and is more
particularly concerned with amorphous and crystalline polyesters
comprising recurring units derived from 1,2-bis(hydroxyphenyl)ethanes
and molding powders and shaped articles derived therefrom.
Many polyesters have been suggested for use as molding
resins and engineering thermoplastics since the earliest practical
development of such polymers by Whinfield and Dickson. Although
several of such polyesters and copolyesters have found commercial
success as film and fiber products, few have been successful as
molding resins and engineering thermoplastics. Two of the more
successful, polyethylene terephthalate and polytetramethylene tere-
phthalate prepared from aliphatlc diols and ~erephthalic acid, suffer
from certain deficiencies as engineering thermoplastics. They are
both quite flammable and have rather low glass transition tempera-
tures which limit their usefulness to relatively low temperatures.
U.S. Patent 3,160,602 discloses a process of forming poly-
esters by reaction of diphenol and aromatic carboxyl dihalide in
solvent at temperatures of 270C. or higher. The preferred polyesters
are deTived from hydroquinone and isophthalic acid and resorcinol and
terephthalic acid and cocondensates where part of the hydroquinone or
resorcinol is replaced by another dihydric phenol and part of the iso-
phthalic or terephthalic acid has been replaced with another
dicarboxylic acid.
--3--

~` 1077192
The patent suggests that the process might be used for the
reaction of aromatic carboxyl dihalides and an extremely broad
class of dihydric phenols of the general formula:
: r(Y 1 r (R)p 1 r (Y m
HO t A ~ l E ~ l A ~ OH
However, the instability of alkylene bridged diphenols at
such high reaction temperatures in the presence of hydrogen
halide would prevent the formation of polyesters of adequate
molecular weight and acceptable color and indeed degradation
of such polyesters under severe reaction conditions is recog-
nized in selgian Patent 766,806 by the common assignee.
Drewitt and Lincoln, U.S. Patent 2,595,343, teach a moresatisfactory method of preparing polyesters from diphenols,
by reacting the diacetates of the diphenols with dicarboxylic
acids.
Polyesters prepared from diphenols and aromatic dicar-
boxylic acids are in general usefulat higher temperatures
because of their higher softening temperatures. However,
unless they comprise flame retardants which yield toxic off-
gases containing nitrogen, sulfur, phosphorus or halogen,
they also are fairly flammable, particularly when they are
in the form of thin sheets or filaments. Such polyesters
~ include the polyesters of bisphenol A (2,2'-bis(4-hydroxy-
; phenyl)propane) and of 1,1-bis(4-hydroxyphenyl)ethane. More-
over, many polyesters such as the polyesters of hydroquinone,
4,4'-dihydroxy-diphenyl, bis(4-hydroxyphenyl)methane and the
like have extremely high softening points often above 400C.
and are therefore thermally unstable in the melt, and
impractical for conventional processing since they are in-
tractable at conventional processing temperatures.

771~32
C-08-0345
French Patent 2,006,477 discloses new 1,4-dicarboxy-
1,4-dialkylcyclohexanes and polymers prepared therefrom. Among
the polymers, is a flammable polyester prepared from 1,2-bis
(4-hydroxyphenyl)ethane and the alicyclic acid 1,4-dimethylcyclo-
hexane 1,4-dicarboxylic acid. Kolesnikov et al disclose polycar-
bonates and mixed polycarbonates of 1,2-bis(4-hydroxyphenyl)ethane
(Polymer Science A, USSR 9~764-773 (1967), but do not associate
flame retarding properties with them.
A need, therefore, exists in the art for an engineering
thermoplastic polyester which is flame retardant without addition
of toxic flame retardant elements such as halogen and phosphorus
and which has a relatively high glass transition temperature to
allow it to be useful at temperatures above 100C.
In a review of methylene bridged diphenol polyesters in
Industrial and Engineering Chemistry (Vol. 51-1959 p. 147) Andre
Conix, reported twenty-nine diphenol polyesters. Only two (bisphenol
A terephthalate and bisphenol A/benzophenone-4, 4-dicarboxylic acid)
were found to be crystalline while a third, amorphous (bisphenol A
isophthalate) could be obtained from solution in a semi-crystalline
state by a solution casting technique. The author recognized that
the influence of chemical structure on physical behavior such as
crystallinity is rather complicated and not easily predictable.
Conix, in U.S. Patent 3,448,077 teaches that polyesters
obtained from aromatic dicarboxylic acids and diphenols are amorphous
but may be crystallized by heat treatment.
A need therefore exists for a polyester engineering thermo-
plastic which is relatively high melting to provide high temperature
strength but not so high as to be intractable or degrade on melting

1077192
C-08-0345
and which is amorphous or is rapidly crystallized so that it can be
molded on conventional molding equipment at rapid molding cycles.
A further need exists for a polyester engineering thermo-
plastic which contains a high degree of crystallinity for solvent
and chemical resistance and for dimensional stability of molded or
shaped articles
A further need exists for a rapidly crystallizing,
crystalline polyester engineering thermoplastic which has improved
fire safety performance without addition of toxic flame retardant
elements such as nitrogen, sulfur, phosphorus or halogen.
A group of aromatic diphenol derived polyesters and
copolyesters has now been discovered which possess a combination of
strength, processability, high temperature performance and improved
fire safety performance. This combination is achieved in polyesters
comprising recurring units derived from 1,2-bis(hydroxyphenyl)ethane,
in which the hydroxy groups are in the 3- or 4- positions. The
aromatic polyesters are preferably prepared by reacting the aromatic
dicarboxylic acids with the diacetate of a 1,2-bis(hydroxyphenyl)
ethane or mixtures thereof, under conditions which allow acidolysis
of the diacetate and removal of acetic acid. The component acids
and diphenol or diphenol mixture are selected so that the melt vis-
cosity of the polyester at 350C. determined at a shear rate of 100
sec.~l with a capillary rheometer is less than about 105 poise and
preferably so that the glass transition temperature is greater than
about 100C. For adequate strength, the inherent viscosity of the
polyester is preferably at least about 0.3 determined at 30C. at a
concentration of 0.5 gram polyester per 100 ml. solution, in a mixed
solvent containing 60 parts by weight of phenol and 40 parts by
weight of sym-tetrachloroethane
.

1077192
The component acids preferably comprise at least
one acid selected from the group consisting of isophthalic
acid, terephthalic acid, 5-alkyl-isophthalic acid wherein
the alkyl radical contains from 1 to 6 carbon atoms, 3,3'-,
3,4'- and 4,4'- bibenzoic acids, 1,3-, 1,4-, 1,5-, 1,6-,
1,7-, 1,8-, 2,6- and 2,7-naphthalene dicarboxylic acids,
and acids represented by the formula:
n ~COOH
wherein the carboxyl groups are in the 3- or 4-position, X
is 0, S, S2' C=O, CH2~ CH2CH2, CH(CH3) or C(CH3)2; R is H
or a Cl to C6 alkyl radical, R groups ortho to a carboxyl
are small enough to permit esterification, R substituents
ortho to X are limited to one ring, and n = 0 to 2.
The diphenol comprises 1,2-bis(hydroxyphenyl)ethane
and optionally a diphenol preferably selected from the group
consisting of resorcinol, hydroquinone, 3,3'-, 3,4'- and
4,4'-diphenols, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,6- and
2,7- dihydroxynaphthalenes, and diphenols represented by the
formula
R' R'
:10 , ~Y~
HO OH -
wherein the hydroxyl groups are in the 3- or 4-positions, Y is
O, S, SO2, C=O, CH2, CH(CH3) CtCH3)2, or (CH2)3, R' is H or a
Cl to C6 alkyl radical, R' substituents ortho to Y are limited
to one ring, R' substituents ortho to hydroxyl are small
enough to permit esterification, and m = 0 to 4.
--7--
. . : . .

107~g2
C-08-0345
A preferred group of aromatic diphenol derived polyesters
and copolyesters has also been discovered which possess a combination
of strength, processability, high temperature performance, improved
fire safety performance, crystalli~ity, a rapid rate of crystalliza-
tion, and solvent resistance, and which impart dimensional stabilityto molded or shaped articles manufactured therefrom. This combina-
tian is achieved with polyester condensates of aromatic dicarboxylic
acids and 1,2-bis(hydroxyphenyl)ethane in which the hydroxyl is in
the 3 or 4 position or admixtures thereof. The component acids and
diphenols are selected so that the melting point of the polyester is
less than about 350C. and preferably so that the glass transition
temperature is greater than about 100C.
The component acids of the more preferred, rapidly crys- ~:~
tallizing polyesters comprise at least one acid selected from the
lS .group consisting of isophthalic acid, terephthalic acid, 3,3'-, 3,4'- ~
and 4,4'-bibenzoic acids, 1,3-, 1,4-, l,S-, 1,6-, 1,7-, 1,8-, 2,6- :
and 3,7- naphthalenedicarboxylic acids and acids represented by the
formula: .
~X~
HOOC COOH
wherein the carboxyl groups are in the 3- or 4- positions, and X is
O, S, SO2, C=O, CH2 or CH2CH2. The diphenol comprises 1,2-bis
(hydroxyphenyl)ethane and optionally at least one diphenol selected .
from the group consisting of resorcinol, hydroquinone, 3,3'-, 3,4'-
and 4,4'-diphenols, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,6- and 2,7-
dihydroxynaphthalenes and diphenols represented by the formula:
, . , , ~
~ .

C-08-0345 ~771~3Z
~y~ _
HO OH
wherein the hydroxyl groups are in the 3- or 4- positions
and Y is O, S, SO2, C=O, CH2, or (CH~)3.
The polyesters may be comminuted to form molding powders
and are readily molded or extruded into useful articles with desirable
properties particularly improved fire safety performance.
A feature of the present invention is the discovery that
the aromatic polyesters of 1,2-bis(hydroxyphenyl)ethane have
superior fire safety performance compared with other aromatic poly-
esters in the prior art. Thus, the polyisophthalate of 1,2-bis
t4-hydroxyphenyl)ethane is superior to the polyisophthalate of
2,2-bis(4-hydroxyphenyl)propane (BPA) in flame resistance and degree
of smoke generation on burning. It is therefore a feature of the
present invention to provide sufficient 1,2-bis(hydroxyphenyl)
ethane units in the aromatic polyester to obtain improved fire
safety performance, the selection of dicarboxylic acids and diphenols
being made so that the melt viscosity of the polyester at 350C.
determined at a shear rate of 100 sec. 1 with a capillary rheometer
is less than about 105 poise and so that the glass transition
temperature is preferably greater than about 100C.
It is another feature of the invention that the crys-
talline aromatic polyesters of 1,2-bisthydroxyphenyl)ethane crys-
tallize rapidly so that they can be molded on conventional molding
equipment in rapid molding cycles and provids solvent resistance
and dimensional stability to molded or shaped articles manufactured
~ .
g

1~77~2
C-08-0345
therefrom. It is therefore a feature of a preferred embodiment
of the present invention to select a combination of aromatic
dicarboxylic acid and diphenol containing sufficient 1,2-bis
(hydroxyphenyl)ethane to obtain a polyester having improved fire
S safety performance and crystallinity, the selection of the dicar-
boxylic acid diphenol combination being made so that the melting
point of the polyester is below about 350C. and the melt viscosity
at 350C. determined at a shear rate of 100 sec.~l with a capillary
rheometer is less than 105 poise to enable ready processing without
degradation and so that the glass transition temperature is pre-
ferably above about 100C. to provide a high service temperature.
The polyesters of the present in~ention can be produced
by any convenient method such as by melt condensation or solvent
condensation of mixtures of aromatic dicarbo~ylic acids and
diphenol diesters selected to provide the desired fire safety per-
formance and processability. They can be produced by melt or
solution polymerization of selected mixtures of phenol esters of
aromatic dicarboxylic acids and diphenols and by interfacial poly-
merization of salts of diphenols and aromatic dicarboxylic aciddihalides. Thus, while the combination is foTmally a condensate
of diacid and diphenol, in practice the reactants are diacids and
diphenol esters, or phenyl esters of diacids and diphenols, or salts
of diphenols and diacid halides. The preferred method of prepara-
tion is the melt condensation of mixtures of aromatic dicarboxylicacids and diphenol diesters.
A suitable process for the product~n of the polyesters
comprises reacting a mixture of a 1-7 carbon aliphatic monocar-
boxylic acid diester of the diphenols with a* least one aromatic
-10- .
. - ' ' . '
' :' ' ' " ' : -
, .

771~92C-08-0345
dicarboxylic acid in the melt phase and optionally in the presence
of any of the catalysts which are conventionally used in such acidolyses
such as alkali metal hydroxides, phosphates, carbonates or alkanoates,
titanium dioxide, orthotitanates, and OTganOtin compounds. In
general, the alkali metal salts are the preferred catalysts. The
catalyst may be used in amounts varying from Q 5 to 5.0 mol percent
of the reactants. Preferably however, the amount of catalyst used
is from 1.0 to 2.5 mol percent and more frequently is about 2 mol
percent of the reactants. The reaction is carried out under an inert
: 10 atmosphere substantially free of oxygen and under such conditions of
temperature and pressure that the 1-7 carbon aliphatic monocarboxy-
lic acid produced during the reaction is separated from the reaction
mixture by distillation. The diphenol diesters useful in this melt
condensation process include any of those of the relatively low-
boiling monocarboxylic 1-7 carbon atom acids~ such as acetic, pro-
pionic, butyric, pentanoic, hexanoic or heptanoic acids, or mixtures
thereof, the most preferred being acetic acid.
In more detail the preferred polycondensation process con- -
veniently comprises contacting a mixture of the 1-7 carbon atom
aliphatic carboxylic acid esters of the diphenols with the aromatic
dicarboxylic acid mixture such that the reactants are in substan-
tially stoichiometric proportions up to 10 molar percent excess of
the diester or the diacid, and in the presence of the catalyst.
The reaction temperature is usually from 240C. to 350C. and the
pressure is atmospheric or lower. Commonly the reaction is con-
ducted under an inert atmosphere and in the initial phase at atmos-
pheric pressure and subsequently at a higher temperature and at
lower pressure or at a series of lower pressures until essentially
-11 -

107719~
all of the 1-7 carbon atom aliphatic carboxylic acid has been
removed by distillation and the polyester product has achieved
a high molecular weight. For adequate strength in the poly-
ester, the molecular weight of the polyester is preferably
sufficient to provide an inherent viscosity of at least about
0.3, preferably at least about 0.5, determined at 30C. at a
concentration of Q.5 gram per 100 ml. solution in a mixed
solvent containing 60 parts by weight phenol and 40 parts by
weight sym-tetrachloroethane.
1,2-bis(hydroxyphenyl)ethane can exist in several
isomeric forms, depending on the position of the hydroxyl
groups, such as the 4,4'- 3,4'-, and 3,3'-isomers. For the
purposes of this invention mixtures or blends of the 4,4'-
isomers containing up to 25 percent or more of the 3,4'-
and 3,3'-isomers can provide very useful polyester composi-
tions within the scope of the invention. However, it is pre-
ferred to limit the amount of 3,4'- and 3,3'-isomers to about
10 mol percent, and the substantially pure 4,4'-isomer is
frequently used.
While essentially any suitable aromatic dicarboxylic
acid and admixtures thereof can be used in the practice of the
invention, the preferred aromatic dicarboxylic acids comprise
at least one acid selected from the group consisting of iso-
phthalic acid, terephthalic acid, 5-alkyl-isophthalic acid
wherein the alkyl radical contains from 1 to 6 carbon atoms,
3,3'-, 3,4'- and 4,4'-bibenzoic acids, 1,3-, 1,4-, 1,5-,
1,6-, 1,7-, 1,8-, 2,6- and 2,7-naphthalene dicarboxylic acids,
and acids represented by the formula:
~ ~
HO C OOH
-12-
:
. - : .

1077192
C-08-0345
wherein the carboxyl groups are in the 3- or 4- positions, X is 0,
S, S02, C=0, CH2, C~2CH2, CH~CH3) or C(CH3)2, R is H or a Cl to C6
alkyl radical, R groups ortho to a carboxyl are small enough to
permit esterification, R substituents ortho to X are limited to one
ring and n = 0 to 2. A suitable aromatic dicarboxylic acid and
admixture thereof is defined as an acid or mixture of acids which
can be combined with 1,2-bis(hydroxyphenyl)ethane or 1,2-bis
(hydroxyphenylethane in admixture with suitable diphenols to pro-
vide a polyester with the desired melt viscosity property and glass
transition temperature as defined herein. The more preferred acids
include isophthalic acid, terephthalic acid, S-t-butylisophthalic
acid, bis(4-carboxyphenyl)ether, bis(4-carboxyphenyl)sulfide,
bis(4-carboxyphenyl)sulfone, bis(4-carboxyphenyl)methane, 1,2-bis
(4-carboxyphenyl)ethane, and 2,2-bis(4-carboxyphenyl)propane since
these acids and combinations of acids can be readily combined with
diphenol combinations to provide polyesters w;th the desired melt
viscosity property and glass transition temperature (Tg). Particu-
larly preferred aromatic dicarboxylic acids are isophthalic and
5-t-butylisophthalic acids and combinations thercof. Mixtures of
one or more of the diacids with minor quantities, generally less
than about 25 mol percent, of C2 to C20 aliphatic diacids can also
be used. The quantities of aliphatic diacids in general are
selected so that they do not cause a significant loss in Tg of the
resulting polyesters. Preferably the quantity is limited to a
loss in Tg of not more than 10C. The acid OT admixture of acids
is combined with 1,2-bis(4-hydroxyphenyl)ethane or with 1,2-bis
(4-hydroxyphenyl)ethane in admixture with essentially any other
suitable diphenol or mixture of diphenols to provide the aromatic

10771.9X
polyesters of the present invention with the desired melt vis-
cosity property and glass transition temperature. The pre-
ferred diphenols comprise at least one diphenol selected from
the group consisting of resorcinol, hydroquinone, 3,3'-,
3,4'- and 4,4'-diphenols, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-,
2,6- and 2,7-dihydroxynaphthalenes, and diphenols represented
by the formula: Rlm m
wherein the hydroxyl groups are in the 3- or 4-positions, Y is
~ ' 2' CH(~H3)~ C(CH3)2 or (CH2~3, R' is H or a
Cl to C6 alkyl radical, R' substituents ortho to Y are limited
to one ring, R' substituents ortho to hydroxyl are small
enough to permit esterification, and m = 0 to 4. The pre-
ferred diphenols include bis(4-hydroxyphenyl)methane, 2,2-bis-
15 (4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)ether, bis(4- -
hydro ~ henyl)sulfide and bis(4-hydroxyphenyl)sulfone`and
readily provide polyesters with the desired melt viscosity
and glass transition temperature.
The glass transition temperature of the polyester is
determined by differential scanning calorimetry with the
Perkin-Elmer Model DSC-lB*. The instrument is calibrated
with respect to the differential temperature and average
temperature as suggested in the Perkin-Elmer Instruction Manual.
The sample size is in the range of 5 to 25 milligrams and the
nitrogen flow is set at about 0.05 SCFH (1.42 liters per hour).
The instrument is programmed to heat at the rate of 20C.
per minute. The mid-point of the T discontinuity of the
thermogram is taken as the glass transition temperature.
* Trademark -14-

~` C-08-~345 1077~92
The fire safety performance of a polymer is manifested
in several ways including the flame resistance or resistance to
ignition and propagation of flame, the degree of smoke generation
on combustion and the evolution of toxic gases on combustion. A
polymer of improved fire safety performance is one which is diffi-
cult to ignite, does not readily propagate a flame, generates
little smoke on combustion and evolves little of the more noxious
gases containing nitrogen, sulfur, phosphorus or halogen which are
very frequently a product of combustion of conventional fla~e
retardant materials. Flame resistance is conveniently determined
by the Underwriter's Laboratory "Test for Flammability of Plastic
Materials - UL-94, September 17, 1973" using the ratings which
became effective February 1, 1974. Test samples conforming to
specified dimensional limits are ignited, after which the igniting
flame is removed and the time required for both the flame and any
subsequent glowing to extinguish themselves îs measured. The
samples are classified in order of decreasing flammability as V-II,
V-I or V-O, depending upon the burning and/or glowing time and
whether or not the molten drippings from the sample will ignite
cotton fibers placed below the sample. A rating of V-II indicates
only that the solid polymer is self-extinguishing within an average
time of 25 seconds, based on five trials, following removal of the
igniting flame. The molten material which drips from the flaming
sample may ignite untreated cotton fibers placed 12 inches (30 cm.)
below the test sample. Samples which qualify as V-l are self-
extinguishing within an average time of 25 seconds following removal
of the igniting flame and do not drip flaming molten material that
ignites cotton placed 30 cm. below the test sample. Any localized
-15-

10~71~;~
C-08-0345
glowing must cease within 60 seconds after the second removal of
the test flame, not ~ravel up the ho:Lding clamp and be incapable
of igniting surgical cotton. If the other V-I requirements are
met, the flame is extinguished within an average of 5 seconds
following ignition, no flaming particles are present, and glowing
ceases within 30 seconds after the second removal of the test
flame, the samples are rated V-O. The appropriate Underwriter's
Laboratory publications should be consulted for a more complete
description of the rating system employed for the UL-94 test pro-
cedure. However, these numerical flame spread ratings are notintended to reflect hazards presented by such materials under
actual fire conditions. Test samples are 15 cm. x 1.3 cm. and of
three thicknesses approximately 0.32 cm., 0.16 cm. and 0.08 cm.
and are held in a verticle position during test. The minimum sample
thickness for a V-O or a V-l rating is determined in the test.
Other tests used for rating the fire-resistance of polymers
include the oxygen index test determined in accordance with ASTM
D-2863-70 and a variable flux test in which a sample of 0.16 cm.
thickness is subjected to an ignition source of varying heat flux
for varying times and the time for extinction of the flame is noted.
Smoke generation is determined by the maximum specific optical den-
sity method described in ASTM Special Technical Publication 422 (1969)
by D. ~ross, J. J. Loftus, and F. A. Robertson, by means of the
Aminco NBS Smoke Chamber, with samples of 0.08 cm. thickness. Sur-
prisingly, the polyisophthalate of 1,2-bis(4-hydroxyphenyl)ethane,
without any conventional flame retarding additives gives a flamma-
bility rating of V-O in a test with a sample of thickness 0.08 cm.
or less. In contrast, glass filled polytl,4-butylene terephthalate)
-16-

C-08-0345 1 O 7 7 1 g 2
does not meet the V-II rating at a thickness of 0.30 cm. and the
polyisophthalate of 2)2-bis~4-hydroxyphenyl)propane does not meet
the ~-II rating at a thickness of 0.19 or less. In general, polymers
exhibit higher ratings at greater thicknesses. Combinations of
1,2-bis(4-hydroxyphenyl)ethane and 2,2 bis(4-hydroxyphenyl)propane
are intermediate between the extremes for the homopolymers. In
addition to superior flame resistance, 1,2-(hydroxyphenyl)ethanes
can yield aromatic polyesters which generate less smoke on combustion
and no toxic off-gases containing nitrogen, sulphur, phosphorus or
halogen. Thus, the aromatic polyesters of 1,2-bis(hydroxyphenyl)
ethanes possess unexpectedly superior fire safety performance without
the addition of conventional flame retardants and the introduction
of 1,2-bis(hydroxyphenyl)ethane into a polyester condensate of an
aromatic dicarboxylic acid and a diphenol improves the fire safety
performance of the polyester condensate in one or more aspects.
While minor amounts of 1,2-bis~hydroxyphenyl~ethane in the polyester
condensate can give improvement in fire safety performance, it is
preferred that at least 60 mol percent and e~en more preferably at
least 75 mol percent of the recurring units of the polyester should
be derived from 1,2-bis~hydroxyp}lenyl)ethane so that a more signifi-
cant improvement in fire safety performance can be achieved.
In addition to providing improved fire safety performance,
the combination of aromatic dicarboxylic acids and diphenol com-
prising 1,2-bis(hydroxyphenyl)ethane can be selected to influence the
morphology of the polyester condensate and to provide polymers which
are amorphous or crystalline, and tractable or intractable. The term
amorphous is used in the conventional sense to mean that the polymer
hss a relatively low degree of molecular order, and is generally iso-
tropic and optically transparent. In contrast, the term crystalline
-17-

~07'71~3~
C-08-0345
indicates that the polymer has a relatively high degree of molecular
order and exhibits a sharp peak corresponding to a crystallization
exotherm when a 10 mg. sample of melt in a nitrogen atmosphere is
cooled at a rate of 20C. per minute on a Perkin-Elmer differential
scanning calimorimeter Model DSC-lB. Many of the polyester combina-
tions may actually be crystallizable but difficult to crystallize,
and can be maintained in a metastable amorphous state at tempera-
tures in the range of ambient up to their glass transition tempera-
ture and even higher. The polymers are considered to be tractable
if they soften or melt and flow at temperatures of 350C. or less.
The criterion for tractability or processability is the melt
viscosity determined on a capillary rheometer at a shear rate of
100 sec. . For adequate processability, the polyester combination
of aromatic dicarboxylic acid or admixtur~ thereof and 1,2-bis
(hydroxyphenyl)ethane or admixtures thereof should be selected to
provide a melt viscosity of less than about 105 poise at 350C. and
preferably to provide a melt viscosity in the range of about 102 to
105 poise in the temperature range of 200 to 320C. The combination
is also preferably selected to provide a glass transition tempera-
ture above about 100C. and more preferably above about 140C. to
provide a high service temperature for the polyester.
The novel 1,2-bisthydroxyphenyl)ethane polyesters and
copolyesters of the present invention are useful in many forms and
can be shaped in many ways to produce useful objects. They can be
cast into films of high strength either from the melt or from solu-
tion in suitable solvents such as mixtures of phenol and tetrachloro-
ethane. Those which can be oriented under stress can be melt spun
and drawn into fibers of good strength. They are very useful as
molding resins for the production of molded articles. The novel
-18-

C-08-0345 ~0771~2
polyesters are comminuted into powders or extruded and pelletized
and the powders or pellets can be molded by extrusion into bar or
rod form. They may be injection molded into any desired shape by
conventional molding equipment and machines.
An injection molding procedure found suitable for the novel
1,2-bis(hydroxyphenyl)ethane polyesters involves the use of a screw
fed injection molding machine wherein the stock is maintained at a
suitable temperature to provide a melt viscosity suitable for mold-
ing and the mold is maintained at a temperature in the range of
about 10 to 30C. below the glass transition temperature and pre-
ferably about 20C. below the glass transition temperature. Any
other convenient injection molding and extrusion equipment and pro-
cedures can likewise be employed with the 1,2-bis~hydroxyphenyl)
ethane polyesters and copolyesters described above.
For use as molding resins the novel polyesters can be
blended with or can contain any of the commonly employed additives
generally used ~ith molding resins including waxes, lubricants,
dyes, pigments, flame retardants, luster modifying agents and the
like. Many such additives are known in the molding resin art.
- 20 Their use in conjunction with the 1,2-bis~hydroxyphenyl)ethane poly-
ester molding resins can provide advantageous results. For example,
heat stabilizers can minimize degradation at higher temperatures and
permit processing of the polyesters for longeT periods at such
temperatures.
In molding applications, the polyesters are preferably
amorphous or rapidly crystallized so that they can be molded on con-
ventional molding equipment in rapid molding cycles. Therefore, in
preferred embodiments of the invention the bist4-hydroxyphenyl)ethane
and mixtures thereof and the aromatic dicarboxylic acid and mixtures
-19- .

07~ 32
C-0~-0345
thereof are selected to obtain the desired amorphous or rapidly
- crystallizing characteristics.
In the preferred embodiment of rapidly crystallizing poly-
esters, the polyesters of the present invention are prepared from
any suitable aromatic dicarboxylic acid or mixture of acids which
will yield upon condensation with 1,2-bis(hydroxyphenyl)ethane or
diphenol mixtures containing 1,2-bis~hydroxyphenyl)ethane a rapidly
crystallizing polyester which melts at a temperature less than about
350C. The preferred acid comprises at least one acid selected from
the group consisting of isophthalic acid, terephthalic acid, 3,3'-,
3,4'-, and 4,4'-bibenzoic acids, 1,3-, 1,4-, l,S-~ 196-, 1,7-, 1,8-,
2,6-, and 2,7- naphthalene dicarboxylic acids and acids represented
by the formula:
~X- <~
: HOOC COOH
wherein the carboxyl groups are in the 3- or 4- positions, and X is
O, S, SO2, C=O, CH2 or CH2CH2. The prcferred acids include isoph-
thalic acid, terephthalic acid, bis(4-carboxylphenyl)ether, bis(4-
carboxyphenyl)sulfide, bis(4-carboxyphenyl)sulfone, bis(4-carboxy-
phenyl)methane, 1,2-bis(4-carboxyphenyl)ethane, and 2,2-bis(4-car-
boxyphenyl)propane since these acids and combinations of acids canbe readily combined with diphenol combinations to provide polyesters
with the desired melting point, glass-transition temperature (Tg) and
crystallization rate. A particularly preferred aromatic dicarboxylic
acid is isophthalic acid and combinations theTeof. Mixtures of one
or more of these diacids can also be used with minor quantities,
generally less than about 25 mol percent of C2 to C20 aliphatic
. -20-

07719~
C-08-0345
diacids and more preferably less than about 10 mol percent of C7 to
C12 aliphatic diacids. The quantities of aliphatic diacids in
general are selected to provide improved processability without
significant loss in Tg and melting point of the resulting polyesters.
Preferably the quantity is limited to a loss in Tg of not more than
10C.
In the preferred embodiment of rapidly crystallizing
polyesters, the polyesters are prepared from the aforementioned
dicarboxylic acids and 1,2-bis(hydroxyphenyl)ethane optionally
admixed with any suitable diphenol to provide a polyester which
melts at a temperature of less than about 350C. and crystallizes
rapidly when it is cooled. The preferred optional diphenol com-
prises at least one diphenol selected from the group consisting of
resorcinol, hydroquinone, 3,3'-, 3,4'- and 4,4'-diphenols-, 1,3-,
151,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,6- and 2,7-dihydroxynaphthalenes
and diphenols represented by the formula:
~Y ~\ '
HO OH
wherein the hydroxyl groups are in the 3- or 4- positions and Y is
O, S, SO2, C=O, CH2 or C~CH3)2. The preferred diphenols include
bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane,
bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide and
bis(4-hydroxyphenyl)sulfone.
The more preferred rapidly crystallizing combinations of
sromatic dicarboxylic acids and diphenols contain isophthalic acid
as the major molar component of the acid moiety. In addition, in
the preferred combinations, at least 75 mol percent of the diphenol
-21-
, ~ .
. .
' ' ', , . : ' : ~

1077~2
C-08-0345
moiety is 1,2-bis~4-hydroxyphenyl)ethane and more preferably at
least 90 mol percent and even more preferably 95 to lO0 mol percent.
The preferences are based on the availability and cost of the acid
and desirable glass transition and melting points of the resulting
polyesters. Consequently, one of the more preferred combinations
is obtained from isophthalic acid and 1,2-bis(4-hydroxyphenylethane
without additional components. However, when mixtures of other
aromatic diacids with isophthalic acid are used, up to 33 mol per-
cent of such other diacid has little effect on the crystallization
rate, although some alteration in the glass transition and melting
point occurs. Similarly, when mixtures of 1,2-bis(4-hydroxyphenyl)
ethane and other diphenols are combined with isophthalic acid, up
to 10 mol percent of such other diphenol has little effect on the
crystallization rate, although some alteration in glass transition
and melting point occurs.
Since molding cycles are preferably rapid, it is desirable
that a crystalline polyester crystallize in the short period during
which the polymer is cooling in the mold. Thus a molding material
for uses where high temperature dimensional stability is important,
needs to have a rapid rate of crystallization. Rate of crystalliza-
tion can be determined by means of differential scanning calorimetry
and rates determined by this technique are used throughout this
specification when a crystallization rate is given and are e~pressed
as the inverse of the time required for one half of the crystalliza-
tion exotherm observed when a sample is cooled at a rate of 20C.
` per minute. The apparatus used in determining the crystallization
rate is a DSC-lB Thermal Analyzer ~made by Perkin-Elmer Corporation,
Norwalk, Connecticut) and the method of using this apparatus is des-
cribed in "Instructions, Differential Scanning Calorimeter" by
Perkin-Elmer, Norwalk, Nov. 1966, pp. 7-9.
z~ ~
: " ' ' - : :

C-08-0345 ~0~71~Z
In the determination of the crystallization rate, the
following procedure is used:
The instrument and recorder are turned on and set at the
stand-by position and allowed to warm up for about a half hour.
The instrument is then fully calibrated with respect to the differ-
ential temperature and average temperature as suggested in the
Perkin-Elmer Instruction Manual. About 5 to 10 milligrams of the
polymer sample is crimped in a non-hermetic pan and lid with the
encapsulating tool, making sure that the bottom remains flat. An
empty non-hermetic pan and lid are crimped in the same manner. The
sample and the reference are placed in the right and left sensors
of the DSC-lB. The sample cover is placed in position and the
nitrogen flow is adjusted to about 0.05 SCFH (1.42 liters per hour).
The range of the DSC-lB is set to 4 mcal per second, the scan rate
to 10C. per minute and the chart speed of the recorder to 2.54 cm.
per minute. The "zero" of the instrument is adjusted so that the
recorder pen is at a convenient position on the chart. The recorder
is turned to "on" position and the baseline is recorded at room tem-
perature. The green indicator light on the instrument is on indicat-
ing temperature control and the baseline recorded will be horizontal
when thermal equilibrium is reached between sample and instrument.
The program toggle switch is then placed in the increase position
and the sample is scanned upwards to about 10 above the endothermic
melting peak at the set rate of 10C. per minute. The toggle switch
is placed at the neutral position and let stay for two minutes. While
the sample is held isothermal for two minutes, the scan rate dial is
reset to 20C. per minute and the recorder speed to 5.08 cm. per
minute. The program toggle switch is placed in decrease position
-23-

~0771~;~
" ~
C-08-0345
and the sample is cooled at the set rate of 20C. per minute. The
green indicator light of the instrument shows the temperature is in
control. Exothermic crystallization peak (or peaks) should be seen
on the recorder thermogram if crystallization occurs within the time
interval of the scan. The scan is continued beyond the peak so that
the baseline is re-established and the thermogram is complete. A
typical exothermic crystallization peak is set forth in Figure 1.
The baseline of the thermogram is interpolated on either
side of the crystallization peak (or peaks). The baseline may show
curvature due to the instrument. In that case, an appropriate French
curve has to be used for interpolation. The point [S] at which the
baseline first deviates to form the peak is determined and also the
point [E] at which the peak (or final peak) finishes to rejoin the
baseline. The former indicates the start, while the latter the end
of the crystallization process. Perpendiculars are dropped from
point [S] and point [E] to cut the temperature axis of the thermogram
at TS and TE respectively. The total area [A] under the peak (or
peaks) confined by [S] and [E] is measured with a planimeter. Area
[A] is proportional to the heat of crystaliization of the sample.
- 20 The total time required for crystallization is given by:
TS -TE Ts -TE
min. = min.
cooling rate 20
The peak (or peaks) whose total area [A] has been measured, is sliced
into several segments by dropping perpendiculars from different points
[Bi] on the peak ~or peaks) to cut the interpolated baseline at [Ci]
and the temperature axis of the thermogram at 4 intervals [TCi etc.]
The area [A'] of each segment [SBiCi, SB2C2] is measured with a plani-
meter and the corresponding time of crystallization is calculated:
-24-

1077192
C-08-0345
T -T Ts-Tc
l min.= l min. etc.
cooling rate 20
The area of each segment is divided by the total area of the peak
(or peaks) [A] and the results are expressed in percentages. The
percent of crystallization peak area is plotted against crystalli-
zation time. The half time or the time at which [A'] is 50 percentof [A] is established from the graph. The rate of crystallization
of the sample is the reciprocal of this "half time", e.g., if the
half time is 5 minutes, the reciprocal is 0.2 min 1.
The "rate of crystallization" or "crystallization rate"
as used throughout this specification and claims is therefore under-
stood to be that rate determined as set forth above on a DSC-lB
Thermal Analyzer using a cooling rate of 20C. per minute unless a
different cooling rate is specified. A rate of crystallization of
about 0.2 minutes 1 or greater as determined by this method is
satisfactory in injection molding of polymers because the cooling
rate in the molding operation is generally much faster than the
cooling rate used in the determination of rate of crystallization.
However, a crystallization rate of about 0.5 minutes or greater
is more preferable and for rapid molding cycles a crystallization
rate of about one minute or greater is even more preferred.
In addition to selection of a combination of aromatic
dicarboxylic acids and diphenols containing sufficient 1,2-bis
(hydroxyphenyl)ethane to provide a rapidly crystallizing polyester
and a melting point of less than about 350C., the combination is
preferably selected to provide a glass transition temperature of
more than about 100C. and preferably at least about 140C. so that
the polyester will display adequate resistance to stress both short
-25-
: ' ' '' '

107'71~2
C-08-0345 ~ - '
and long term and dimensional stability at temperatures above about
100C, and preferably at temperatures above 140C. While the melt-
ing point should be less than about 350C., it is preferably in the
range of about 200 to 320C. to provide the opportunity of creating
S filled polyesters with good strength at temperatures of 200C. and
higher. More preferably the melting point should be in the range of
about 250 to 300DC. for high temperature strength without excessive
thermal degradation in the melt.
The gla,ss transition temperature and melting point of the
polyester are determined by differential scanning calorimetry with
the Perkin-Elmer Model DSC-lB. The instrument is calibrated, the
sample and reference are prepared and the nitrogen flow rate is set
in the same ~ashion as described for the determination of rate of
crystallization. The instrument is programmed to heat at the rate
of 20C. per minute. The midpoint of the first discontinuity of the
thermogram is taken as the glass transition temperature (Tg). The
thermogram may show an exotherm of crystallization and at some 150C.
above the glass transition temperature, an endotherm of fusion is
observed, The principal peak of the endotherm is taken as the
melting point (Tm)~
In addition to improved fire safety performance crystalline
1,2-bisthydroxyphenyl)ethane polyesters of the present invention are
outstanding in several particulars. For example the rate of crystall-
ization of the most preferred poly(l,2-bis(hydroxyphenyl)ethane
isophthalates can be faster than that of nylon 6, (polyepsiloncapro-
lactam) and polytetramethylene terephthalate.
-26-

107719Z
C-08-0345
The polyesters and copolyesters, in which the 1,2-bis
(hydroxyphenyl)ethane is in the range of about 90 to`about 100 mol
percent of the diphenol moiety, possess melting points, usually in
the range of 250-320C. and a high glass transition temperature or
Tg in the range of about 110 to 180C. These properties confer high
heat distortion temperature and creep resistance on the various
shapes molded from these polyesters. The polyesters also possess
high temperature stability as evidenced by thermogravimetric
analysis which demonstrates that no appreciable weight loss occurs
until temperatures exceed 450C.
The crystalline polyesters of the invention have been
found to possess excellent resistance to chemical attack. They
demonstrate negligible weight loss after prolonged exposure to non-
polar and medium polarity solvents such as hexane, trichloroethane,
acetone and methylethyl ketone. They resist-attack by acids, bases
and water. Likewise, they do not demonstrate environmental stress
cracking when exposed as molded samples to these solvents. The
moisture absorption of the 1,2-bis(hydroxyphenyl)ethane is generally
low, for example the moisture absorption of poly(l,2-bis(4-hydroxy-
phenyl)ethane isophthalate) is from about 0.2 to 0.3 weight percenteven for low molecular weight samples.
This invention is further illustrated but is not intended
to be limited by the following examples in which ratios of monomers
are mol ratios and all other parts and percentages are by weight,
unless otherwise specified.
The Examples illustrate the preparation and unexpected
properties of the 1,2-bis(hydroxyphenyl)ethane polyesters of this
invention. All inherent viscosities are determined at 30C. at a
-27-
'

-" ~07719~
C-08-0345
concentration of 0.5 g. per 100 ml. in a mixed solvent system of
phenol and sym-tetrachloroethane containing 60 parts by weight of
phenol. The morphology and fire safety performance of the polymers
is determined by the methods described above.
The stress cracking properties of the polyesters are
measured according to a specially devised test procedure in which
a sample strip of dimensions 6 mm x 24 mm is cut from a 0.8 mm
thick film of the polymer. This strip is doubled over and the ends
are stapled together so that the center portion is under mild stress.
This doubled and stapled strip is weighed and immersed in the test
solvent and the state of the sample is observed immediately and
every 24 hours therafter up to 3 days. The amount of solvent
absorbed is determined by weighing the samples at intervals of 1
day, 4 days and 16 days. In extreme cases the sample has no stress
cracking resistance and breaks immediately. Such tests are reported
as "fail". In less extreme cases failure occurs after a number of
days and this is indicated as such in Table 3. In less severe cases
crazing is observed but no further change occurs. Such test results
are reported as "crazed". Some samples, however, show neither
failure nor crazing after the test has been concluded and such are
marked as "pass". These are invariably the crystalline polyesters
of the present invention.
XAMPLE 1
PREPARATION OF POLY(1,2-BIS~4-HYDROXYPHENYL)ET~ANE ISOPHTHALATE
A charge consisting of 8.2 parts of isophthalic acid and
14.8 parts of 1,2-bis(4-acetoxyphenyl)ethane is placed in a reaction
vessel equipped with a stirrer, condenser and receiver. The vessel
is evacuated and purged with nitrogen three ti~es. A nitrogen blanket
-28-

- C-08-0345
~ 077192
is maintained in the reactor while it is heated to 250C. for about
three hours during which period approximately 3.5 to 4.0 parts of
acetic acid distills. Thereupon the vessel is evacuated to a
pressure of about 125 mm. and heating at 275C. is continued for
one half hour during which perioa an additional 1 to 1.5 parts of
acetic acid distills. The vacuum is then increased to reduce the
pressure to about 0.1 ~o 0.2 mm. and the temperature is raised to
290C. for an additional hour. At this point the reaction mixture
becomes so viscous that further stirring is difficult. Heating is
stopped, the reaction mixture is again blanketed with nitrogen and
allowed to cool. The resultant polymer is light yellow in color,
crystalline and demonstrates an inherent viscosity of 0.57 in the
phenol-tetrachloroethane solvent.
EXAMPLE 2
PREPARATION OF POLY~1,2-BIS(4-HYDROXYPHENYL)ETHANE
ISOPHTHALATE
A similar reaction is carried out under the same condi-
tions and with the reactants and equipment described in Example 1
except that after the initial three hour period the temperature is
raised to 275C. and the pressure is reduced to 125 mm. for 30
minutes. Thereafter, the temperature is raised to 290C. during
the final period at high vacuum of 0.1 to 0,2 mm. The resultant
polymer demonstrates an inherent viscosity of 0.83 and is crystalline
and a clear light yellow in color.
-29-
,

77192
C-08-0345
EXAMPLES 3 to 16
Examples 3 to 16 are carried out by reacting mixtures of
diphenol diacetates and isophthalic acid by the method of Example
1, with adjustment in the temperature and heating cycle appropriate
for the rheology and morphology of the particular polyester. The
compositions and physical property data are set forth in Table 1.
. Polyesters of bist4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)
propane and 1,3-bis(4-hydroxyphenyl)propane are set forth for pur-
poses of comparison. Melt viscosities are determined at 316C. with
a Sieglaff-McKelvey*Rheometer at a shear rate of 100 sec 1, using a
capillary with a length to diameter ratio of 25 to 1.
:
* Trademark
-30-
'

107719Z
C-08-0345
TABLE 1
COMPOSITION AND PHYSICAL PROPERTIES OF POLYISOPHTHALATES
Dip enol ~Melt viscosity,
Composition Inherent Tract- ~g poise,
5 ExampleMol Ratio Viscositxability C.100 sec~l,316C.
3 BHPE 0.96 T 140
4 BHPE 0.94 T -1.8 x 104
BHPE 0.62 T -1.8 x 103
6 BHPE 0.5 T
7 BHPE/BPA 0.94 T 1.15 x 104
90 10
8 BHPE/BPA 1.00 T 1552.3 x 104
75 25
9 BHPE/BPA 0.50 T 9.5 x 102
50 50
BHPE/BPA - - T 1704.5 x 104
25 75
11 BPA 0.60 T 180
12 BPA 0.62 T 1.85 x 104
13 BPA 0.98 T -6.2 x 104
14 BPA 0.70 T 180
BHPM - I - -
16 BHPP 0.84 T 110
BHPE - 1,2-bist4-hydroxyphenyl)ethane
BPA - 2,2-bis(4-hydroxyphenyl)propane (bisphenol A)
BHPM - bis(4-hydroxyphenyl)methane
BHPP - 1,3-bis(4-hydroxyphenyl)propane
T - tractable
I - intractable
-31-
~, .

` ~077~9Z
C-08^0345
EXAMPLES 17 to 23
A series of polyesters is prepared by the method of
Example 2 with adjustment in the reaction temperature and heat-
ing cycle appropriate for the rheology and morphology of the
particular polyester.
In a comparison of the polyesters, the flame resistance
is rated by the Limiting Oxygen Index. In Table 2 values for
the Limiting Oxygen Index are set forth and compared to those
LOI values for such other polyesters as polyethylene terephthalate,
BPA isophthalate and BPA oxydibenzoate, a polycarbonate and a
polysulfone. The Limiting Oxygen Index values are determined both
on 62.5 mil (1.56 mm~ slabs and on 8 mil (0.2 mm.~ films reinforced
with a glass scrim weighing 14 grams per square meter. The data
demonstrate the superior flame resistance of the BHPE polyesters
compared with several other polyesters and engineering
thermoplastics.
-32-

C-08- 0345 ~1~77192
~d h
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-33-
.

- ~07719Z
C-08-0345
UL-94 TEST ~:
In Table 3 data obtained with the UL-94 test are set
forth and show the superior flame resistance of polyesters of
1,2-bisthydroxyphenyl)ethane particularly in thin sections
S tExamples 3, 6, 7, 8 and 24) in comparison with polyester of
1,3-bis(4-hydroxyphenyl)propane (Example 16) and polyesters con-
taining a substantial proportion of bisphenol A (Examples 9, 10,
11 and 14).
. -34-

- 1077192
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`--` 1077~9z
EXAMPLES 25 to 29
A series of polyester combinations of 1,2-bis(4-
hydroxyphenyl)ethane and admixtures of isophthalac and 5-t-
butyl-isophthalic acids are prepared by the procedure of Ex-
ample 2 and evaluated in the UL-94 test. The data show that
a V-O rating is obtained with polyester samples of approxi-
mately 0.08 cm thickness.
TABLE_4
COPOLYMERS OF 1,2-BIS(4-HYDROXYPHENYL)ETHANE,
ISOPHTHALIC ACID AND
T-BUTYL-ISOPHTHALIC ACID
UL-94 RATING
INHERENT S~mple Thick-
EXAMPLE ISOPHTHALIC 5-t-BUTYL ISOPHTHALIC VISCOSITY ness 0.079 cm.
mol ratlo
0.86 V-O
26 80 20 0.77 V-O
27 75 25 1.02 V-O
28 75 25 0.82
EXAMPLES 29 to 41
Additional polyester examples are prepared in the
manner set forth in Example 2 with adjustment in reaction
temperature and heating cycle appropriate for the rheology
and morphology of the particular polyester. In Example
31, 0.5 percent by weight of the titanium dioxide catalyst
is used. In Examples 32-35, the diacid charge includes the
indicated mol percentages of other diacids in admixture with
isophthalic acid, including terephthalic acid, 2,6-naphthalene
dicarboxylic acid and bis(4-carboxyphenyl)ether, (oxydibenzoic
acid). In Example 38, the polyisophthalate of a mixture of
90 mol percent 1,2-bis(4-hydroxyphenyl)ethane and 10 mol
percent bis(4-hydroxyphenyl)sulfide is prepared. The inherent
-36-

-- 107719Z
C-08-0345
viscosities, physical appearance, glass transition temperatures
and melting points are set out in Table 5. The data show that
polyester combinations containing high levels of 1,2-bis(hydroxy-
phenyl) ethane and acids such as isophthalic acid are opaque and
exhibit crystalline melting points below 300C. (Examples 29 -
38, 10, 25, 26) while in contrast, polyester combinations con-
taining substantial amounts of other diphenols (~xamples 9, 10,
15, 16, 39-41) and polyester combinations containing substantial
amounts of substituted acids such as S-t-butyl-isophthalic acid
(Examples 27, 28) are amorphous or intractable.
-37-

; C-08-0345
077i9;2
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-38-

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--39--
.

--` 1077192
C-08-0345
RATE OF CRYSTALLIZATION OF POLYESTERS OF
.
1,2-BIS(HYDROXYPHENYL)ETHANE
The rate of crystallization of a series of polyesters
of 1,2-bis(hydroxyphenyl)ethane is determined by the method des-
cribed herein using a Perkin-Elmer Differential Scanning Calori-
meter Model DSC-lB. The data are presented in Table 6 and show
that crystallization rates superior to those of polytetramethy-
lene terephthalate and nylon 6 can be achieved and that minor
amounts of a diphenol such as bis(4-hydraxyphenyl)sulfide in
admixture with 1,2-bist4-hydroxyphenyl)ethane does not appreciably
affect the crystallization rate of polyesters prepared therefrom.
-40-

C-08-0345 1077~9Z o
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-41 -

:~Q77~92
" ~
C-08-0345
SOLVENT RESISTANCE AND STRESS CRACKING RESISTANCE
. .
A comparison of solvent resistance and stTess crack-
ing resistance of crystalline polyisophthalates of
1,2-bis~4-hydroxyphenyl)ethane and amorphous polyisophthalates
of 2,2-bis(4-hydroxyphenyl)propane is made in Tables 7 and 8.
- -42-

1077~9~
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-43 -

1~7192
- C-08-0345
TABLE 8
STRESS-CRACKING RESISTANCE OF POLYtISOPHTHALATES)
STRESS CRACKING
EXAMPLE HEXANE TOLUENE MEK TCE
17 Pass Pass Pass Fail
Pass Pass Pass Fail
36 Pass Pass Pass Failed/
2 days
37 Pass Pass Pass Fail
42 Crazed Fail Fail Fail
From the figures given above in Tables 7 and 8, it
. will be apparent that the crystalline polyesters of the
1,2-bis(4-hydroxyphenyl)ethane are much better adapted than
similar amorphous thermoplastic polyesters such as poly[2,2-
bis~4-hydroxyphenyl)propane isophthalate] to perform satis-
factorily under conditions in which they are exposed to
organic sol~ents.
-44-