Polyesters from trans-4,4'-stilbenedicarboxylic acid and 1,6-hexanediol

Disclosed are polyesters containing repeating units from trans-4,4'-stilbenedicarboxylic acid and 1,6-hexanediol, the polyesters having an I.V. of at least 1.20, a tensile strength of at least 20,000 psi in 1/16-in. thick injection-molded bars, and a melt viscosity of 3000 poise or less at 265.degree. C. and a shear rate of about 107 sec.sup.-1.

TECHNICAL FIELD 
This invention relates to polyesters of trans-4,4'-stilbenedicarboxylic 
acid and 1,6-hexanediol, which are especially useful as films, fibers, and 
molding plastics. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 2,657,195 broadly discloses polyesters of various 
stilbenedicarboxylic acid isomers with glycols, aminoalcohols, and 
diamines. Various glycols are disclosed containing 2 to 16 carbon atoms. 
U.S. Pat. No. 3,496,839 relates to low molecular weight homopolymers of 
4,4'-stilbenedicarboxylic acid and aliphatic glycols useful in 
radiation-cured crosslinked polyester coatings. 1,6-Hexanediol is 
disclosed in Column 2, lines 20 to 44, in a general listing of the glycols 
useful in these coatings. Neither U.S. Pat. No. 2,657,195 nor U.S. Pat. 
No. 3,496,839 distinguishes one stilbenedicarboxylic acid isomer from 
another, i.e., 4,4'- from 3,3'- or cis- from trans-, etc. 
Our own U.S. Pat. No. 4,420,607, U.S. Pat. No. 4,459,402, U.S. Pat. No. 
4,468,510 and U.S. Pat. No. 4,526,822 all disclose polyesters based on 
trans-4,4'-stilbenedicarboxylic acid using various glycols which include 
1,6-hexanediol. 
Other patents which dislcose trans-4,4'-stilbenedicarboxylic acid are 
Japanese Kokai No. 72348/74, and U.S. Pat. Nos. 2,657,194, 3,190,174, 
3,247,043, 3,842,040, 3,842,041, and 4,073,777. Polyesters of 
trans-4,4'-stilbenedicarboxylic acid and neopentyl glycol, 
1,5-pentanediol, 1,6-hexanediol, and 1,10-decanediol are disclosed by 
Meurisse, et al., in the British Polymer Journal, Vol. 13, 1981, page 57 
(Table 1). Jackson and Morris disclose homopolyesters from 
trans-4,4'-stilbenedicarboxylic acid and various aliphatic glycols in the 
Journal of Applied Polymer Science, Applied Polymer Symposia, 41, 307-326 
(1985). Our copending applications entitled, "Polyesters of 
trans-4,4'-Stilbenedicarboxylic Acid, 1,6-Hexanediol, and 
1,4-Cyclohexanedimethanol" "Polyesters of trans-4,4'-Stilbenedicarboxylic 
Acid, 1,4-Butanediol and 1,6-Hexanediol", and "Polyesters of 
trans-4,4'-Stilbenedicarboxylic Acid, Ethylene Glycol and 1,6-Hexanediol" 
also are of interest. 
Japanese Kokai No. 72348/74 referred to on page 1 discloses that 
4,4'-stilbenedicarboxylic acid polyesters having I.V.s of 0.2 to 2.0 could 
be used to make blends with poly(butylene terephthalate), but only I.V.s 
of less than 0.9 were exemplified. Therefore, there is no suggestion of 
the unexpected properties of the present invention. 
Insofar as we are aware, the art does not disclose unexpected properties of 
polyesters of trans-4,4-stilbenedicarboxylic acid and 1,6-hexanediol 
having inherent viscosities (I.V.) above 0.9. We have surprisingly found 
that such polyesters having I.V.s of at least 1.20 have exceptionally low 
melt viscosities at these high molecular weights and unexpectedly high 
tensile strengths when injection molded. The low melt viscosities at high 
I.V. (hence, high molecular weight) are very desirable from a 
processability standpoint.

DISCLOSURE OF THE INVENTION 
According to the present invention, the polyester comprises repeating units 
from at least 80 mol % trans-4,4'-stilbenedicarboxylic acid and repeating 
units from at least 80 mol % 1,6-hexanediol, the total mol % of acid 
components and glycol components each being 100 mol %, and the polyester 
having an inherent viscosity of 1.20 or more. 
The polyesters of this invention are prepared from 
trans-4,4'-stilbenedicarboxylic acid and/or its esters, and 
1,6-hexanediol. Examples of such useful esters are the dimethyl, diethyl, 
dibutyl, and diphenyl esters, etc., or any combination of these esters. 
The polyesters may also be prepared from glycol esters or 
half-ester/half-acid derivatives of trans-4,4'-stilbenedicarboxylic acid. 
The acid portion of the polyesters may contain minor amounts of other 
aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 
1,5-, 1,4-, 2,6-, or 2,7-naphthalenedicarboxylic acid, 
4,4'-diphenyldicarboxylic acid, and the like. The dicarboxylic acid 
portion of the polymer may also contain minor amounts of aliphatic or 
cycloaliphatic dicarboxylic acids such as malonic, succinic, glutaric, 
adipic, pimelic, suberic, azelaic, sebacic, cis- or 
trans-1,4-cyclohexanedicarboxylic, or dodecanedicarboxylic acid. These 
polyesters may contain up to about 20 mol % of these other dicarboxylic 
acids such that the sum of the dicarboxylic acid components is equal to 
100 mol %. Essentially 100% trans-4,4'-stilbenedicarboxylic is preferred 
as the acid component. 
The glycol portion of these polymers may contain minor amounts (not 
exceeding about 20 mol %) of other glycols such that the sum of the glycol 
components is equal to 100 mol %. Examples of useful glycols are ethylene 
glycol, 1,4-butanediol, 1,2-propanediol, 1,3-propanediol, 
2,2-dimethyl-1,3-propanediol, trans- or 
cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,5-pentanediol, 1,3- or 
1,4-cyclohexanedimethanol, or p-xylenediol. 
The polyesters may be prepared using conventional techniques well known to 
those skilled in the art. For example, the references cited herein contain 
such techniques, and are incorporated herein by reference. 
The polyesters of this invention may contain antioxidants, conventional 
flame retardants such as phosphorus or halogen compounds, fillers such as 
talc or mica, or reinforcing agents such as glass fiber or carbon fiber. 
The following example illustrates the preparation of the polyester 
consisting of 100 mol % trans-4,4'-stilbenedicarboxylic acid units and 100 
mol % 1,6-hexanediol units. A mixture of 177.6 g (0.60 mol) dimethyl 
trans-4,4'-stilbenedicarboxylate, 92.0 (0.78 mol) 1,6-hexanediol, and 0.13 
g titanium tetraisopropoxide is placed in a 1-liter flask equipped with a 
metal stirrer, an inlet for nitrogen, and a short distillation column. The 
contents of the flask are heated under nitrogen with stirring at 
240.degree. C. for 1 hr. The temperature is raised to 260.degree. C. for 
30 min and a vacuum of 0.5 mm is gradually applied over the next 5 min. 
Full vacuum is maintained for about 15 to 20 min and then the reaction is 
stopped. A high melt viscosity, white, crystalline polymer is obtained 
with an I.V. of 1.0. Polymer is solid-state polymerized by heating polymer 
ground to pass a 3-mm screen at 110.degree. C. for 1 hr, 180.degree. C. 
for 1/2 hr, and then at 235.degree. C. for 4 hr to give polymer having an 
I.V. of 1.73. The polyesters are ground, dried at 100.degree. C., and 
injection molded on a 1-oz Watson-Stillman molding machine at 260.degree. 
to 300.degree. C. The other polymers in the tables are prepared in a 
similar manner. 
The polyesters of the present invention have inherent viscosities 
.gtoreq.1.20, tensile strengths of &gt;20,000 psi in 1/16-in. thick 
injection-molded bars, and melt viscosities .ltoreq.3,000 poise at 
265.degree. C. and a shear rate of about 107 sec.sup.-1 or higher. Table 1 
illustrates the effect of raising the I.V. on the melt viscosity of 
poly(1,6-hexamethylene trans-4,4'-stilbenedicarboxylate) at 265.degree. C. 
and a number of shear rates. The data shows that the usual increase in 
melt viscosity with increasing I.V. up to about 1.23 is observed. As the 
I.V. increases further to 1.36 and to 1.78, the melt viscosity decreases. 
In addition to this unobvious decrease in melt viscosity with increasing 
I.V., tensile strength also increases (Table 2). The teaching of our own 
disclosure of poly(1,6-hexamethylene trans-4,4'-stilbene-dicarboxylate) 
molding plastics properties in J. Appl. Polym. Sci., 41, 307 (1985) is 
that as the molding temperature is raised to a temperature at which the 
polymer is not liquid crystalline (290.degree. C.) we expect a decrease in 
tensile strength (18,000 psi down to 12,800 psi). Table 3 shows that 
poly(1,6-hexamethylene trans-4,4'-stilbenedicarboxylate) at 2.5 I.V. not 
only has higher tensile strength at 265.degree. C. than the prior art, but 
higher tensile strength when molded at 300.degree. C. than when molded at 
265.degree. C. 
TABLE 1 
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The Effect of I.V. on the Melt Viscosity of 
Poly(1,6-Hexamethylene trans-4,4'-Stilbenedicarboxylate) 
Melt Viscosity at 265.degree. C., Poise 
@ Inherent Viscosity 
Shear Rate, Sec.sup.-1 
0.68 1.05 1.23 1.36 1.78 2.5.sup.a 
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32 376 3100 8680 7410 6940 3123 
107 225 1940 2950 2730 2970 1687 
320 178 667 1110 1050 1000 831 
1067 117 268 507 366 310 468 
3200 69 112 178 162 122 257 
10668 39 54 73 79 56 139 
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.sup.a Some insoluble matter was filtered from the solvent prior to 
inherent viscosity determination. 
TABLE 2 
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Molding Plastic Properties of 
Poly(1,6 Hexamethylene trans-4,4'-Stilbene- 
dicarboxylate) Molded at 265.degree. C. 
I.V. Before Molded Bar 
Molding I.V. Tensile Strength, psi 
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0.98 0.94.sup. .sup. 18000.sup.a 
1.40 1.21.sup.b 20900 
1.90 1.73.sup.b 25200 
2.50 1.87.sup.b 33600 
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.sup.a See Journal of Applied Polymer Science, 41, 307 (1985). 
.sup.b Some insoluble matter was filtered from the solvent prior to 
determining the inherent viscosity. 
TABLE 3 
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Effect of Molding Temperature and I.V. on the Molding 
Plastic Properties of Poly(1,6-Hexamethylene 
trans-4,4'-Stilbenedicarboxylate) 
Molding Molding Tensile Strength, 
I.V. Temperature, .degree.C. 
psi 
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0.98.sup. 260 18000 
290 12800 
2.50.sup.a 265 33600 
285 37500 
300 37800 
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.sup.a Some insoluble matter was filtered from the solvent prior to 
determining the inherent viscosity. 
The melt viscosities of the polyesters of this invention are determined at 
265.degree. C. on an Instron Model 3211 Melt Rheometer having a barrel 
diameter of 0.375-in., a capillary diameter of 0.50-in., and a capillary 
length of 2.50 inches following the procedure of ASTM D3835. The 
polyesters are dried at 100.degree. C. for 24 hr overnight in a vacuum 
oven prior to making the melt viscosity determination. 
The inherent viscosities are determined in 25/35/40 
phenol/tetrachloroethane/p-chlorophenol at 25.degree. C. at a 
concentration of 0.1 g/100 mL. The tensile strength is determined on 
injection-molded 1/16-in. D1822 Type L tensile bars according to the 
procedure of ASTM D638. 
While the invention has been described in detail with particular reference 
to preferred embodiments thereof, it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.