Polyester resins

An unsaturated polyester resin syrup containing styrene monomer in which styrene volatilization is suppressed using a substituted succinic acid or substituted succinic anhydride.

BACKGROUND OF THE INVENTION 
The present invention relates to unsaturated polyester resin compositions. 
In one of its aspects it relates to processes for making unsaturated 
polyester resin compositions. In still another aspect this invention 
relates to controlling the volatilization of the styrene ingredients 
utilized in unsaturated polyester resin compositions. 
Unsaturated polyester resins are a class of soluble, essentially linear, 
low molecular weight, macromolecules which contain both carboxylic ester 
groups and carbon carbon double bonds as recurring units along the main 
chain. Unsaturated polyesters can be prepared by the condensation of (a) 
ethylenically unsaturated dicarboxylic acids or their anhydrides to impart 
unsaturation, (b) saturated dicarboxylic acids or their anhydrides to 
modify the unsaturated polyesters and (c) dihydric alcohols. 
Unsaturated polyester resin compositions can include monomeric styrene as a 
copolymerizable monomer. A solution of monomeric styrene and unsaturated 
polyester resin is frequently identified as polyester resin syrup. Styrene 
customarily is present in an amount ranging from about 20 to about 50 
weight percent of the syrup. When polyester resin syrup is employed in 
hand layup or spray applications to produce glass fiber reinforced plastic 
products and the like, styrene monomer in the syrup has a the tendency to 
volatilize. Volatilization of the styrene is objectable for several 
reasons: among others (1) the cost of the lost styrene is appreciable, (2) 
the variable loss of styrene from day to day and batch to batch can result 
in non-uniform product performance, and the presence of styrene vapors in 
the atmosphere at the work place constitutes both a health hazard to 
workers and a fire hazard. 
There exists a need, therefore, to provide compositions of polymerizable 
unsaturated polyester resin including monomeric styrene in which the 
volatilization of styrene is successfully suppressed to acceptable levels 
without adversely affecting the characteristics of the resulting products. 
An object of this invention is to provide an unsaturated polyester resin 
that reduces the volatilization of styrene. Another object of this 
invention is to reduce the overall resin costs or to improve physical and 
mechanical properties of the polyester, preferably both. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an inexpensive substitute for the 
saturated dicarboxylic acid component of unsaturated polyester resin has 
been found by utilizing alkyl-, alkenyl- or alkaryl-substituted succinic 
acid or the corresponding anhydride formed from a mixture of maleic 
anhydride and alkyl-, alkenyl- and alkaryl-substituted hydrocarbon. 
Combination of (a) substituted succinic acid or the corresponding 
anhydride such as benzyl succinic acid, methylbenzyl succinic acid, 
dimethyl-benzyl succinic acid and 1-dodecenyl succinic acid or the 
corresponding anhydride with (b) unsaturated carboxylic acid and anhydride 
such as maleic anhydride and tetrahydrophthalic anhydride and (c) glycol 
such as ethylene glycol, diethylene glycol and propylene glycol, provides 
useful unsaturated polyester resin that reduce the volatility of styrene. 
In accordance with this invention, unsaturated polyester resins are 
prepared by contacting under polycondensation conditions (a) at least one 
compound selected from (1) alkyl-, alkenyl- and alkaryl-substituted 
succinic anhydride having from about 7-10 carbon atoms per molecule, and 
(2) alkyl-, alkenyl- and alkaryl-substituted succinic acid, having from 
about 7-10 carbon atoms per molecule, (b) at least one unsaturated 
dicarboxylic acid or the corresponding anhydride having from about 4 to 10 
carbon atoms per molecule and (c) at least one dialcohol having from about 
2 to 10 carbon atoms per molecule. In an embodiment of the invention, a 
second dicarboxylic acid or the corresponding anhydride such as phthalic 
acid or phthalic ahydride is also present during the contacting. 
In another embodiment, a mixture of styrene monomer and unsaturated 
polyester resins as prepared by the process of this invention is provided. 
In a further embodiment of this invention, cured polyesters are provided 
which have been prepared by heating of mixture of styrene monomer and 
unsaturated polyester resins of this invention under conditions to form 
resinous, normally solid, polyesters. 
In a preferred embodiment maleic anhydride and xylene are reacted to form 
methyl benzylsuccinic acid, which is used in the preparation of the 
unsaturated polyester resin. 
DETAILED DESCRIPTION OF THE INVENTION 
Alkyl-, alkenyl- and alkaryl-substituted succinic acids and their 
anhydrides are prepared in good yield by reacting one equivalent of maleic 
anhydride with about 5 to about 20 equivalents of an alkyl-, alkenyl- and 
alkaryl-substituted hydrocarbon. Preferred hydrocarbons can be selected 
from toluene, pseudocumene, dodecene and xylenes. In the most preferred 
embodiment, xylene or 1-dodecene is utilized. The alkyl-, alkenyl- and 
alkaryl-substituted hydrocarbon acts as reactant and solvent. 
A catalytic amount of a peroxide selected from benzoyl peroxide, lauryl 
peroxide, cumene hydroperoxide and di-t-butyl peroxide can also be present 
to initiate the reaction to form the succinic acid. The reaction to 
produce the succinic acid is carried out at a temperature ranging from 
about 100.degree. C. to about 200.degree. C. for a time of about 2 to 
about 16 hours. The succinic acid is then separated from the reaction 
mixture by a process such as extraction with aqueous bases. Acidification 
of the aqueous layer precipitates the product as the diacid. 
In another embodiment of this invention substituted succinic anhydride is 
synthesized. This reaction can be carried out in the same reactor used for 
the subsequent preparation of polyester resin. Succinic anhydride adduct 
is prepared in a reactor using about 5 to about 20 equivalents of 
substituted hydrocarbon for each equivalent of maleic anhydride. 
Di-t-butyl peroxide or any other peroxide catalyst, substituted 
hydrocarbon and maleic anhydride are charged to a reactor. Upon being 
heated to a temperature in the range of about 120.degree.-125.degree. C. 
the stirred solution clouds and oily semi-solids separate. After refluxing 
for 2 to about 16 hours, during which such well known radical scavengers 
such as hydroquinone are present, a distillation of substituted succinic 
anhydride is produced which can be polymerized in the same reaction vessel 
by contact with maleic anhydride and propylene glycol, using standard 
unsaturated polyester synthesis techniques. 
A typical reaction for forming the polyester resin utilizing the 
substituted succinic acid or anydride comprises contacting about 2 to 
about 3 equivalents of unsaturated dicarboxylic acid or anhydride with 
about 0.5 to about 1.5 equivalents of substituted succinic acid or 
anhydride and about 3 to about 4 equivalents of dihydric alcohol. This 
mixture is heated under a nitrogen atmosphere for removal of H.sub.2 O at 
a temperature in the range of 120.degree. C. to about 190.degree. C. for a 
time of about 4 to about 12 hours to yield polyester resin having an acid 
value in the range of about 10 to about 60. 
Unsaturated polyester resin produced as set out above can be combined in a 
syrup composition with styrene monomer which, generally, will result in a 
syrup composition in which the styrene has a reduced tendency to 
volatilize. Generally such a mixture will comprise about 50% to about 20% 
styrene and about 50% to about 80% unsaturated polyester resin. Preferably 
about 40% to about 30% styrene and about 60% to about 70% resin will be 
used. 
The following examples provide details for the specific invention.

EXAMPLE I 
This example illustrates the synthesis of (1) substituted succinic acid and 
(2) substituted succinic anhydride to be used for making polyesters in 
accordance with the process of this invention. 
(1) An aralkyl-substituted succinic acid (labeled Monomer A) was prepared 
by heating 103.2 grams (1.0 mole) of maleic anhydride and 1,000 grams (9.1 
moles) of mixed xylenes (o, m and p-xylenes) in the presence of 10 grams 
of dibutyl peroxide, under reflux conditions (about 
140.degree.-145.degree. C.) for about 6 hours in a round bottom flask. The 
reaction mixture was extracted with 800 mL of an aqueous solution 
containing 100 grams of NaOH. The extract solution was acidified with 
concentrated HCl to a pH of 2-3, and the acidified solution was extracted 
three times with 200 mL aliquots of ethyl acetate. The ethyl acetate 
extract was dried with magnesium sulfate, ethyl acetate was evaporated 
under reduced pressure conditions, and 185.9 of a yellow oil was recovered 
(crude yield: 86% of the theoretical yield). This yellow oil consisted 
substantially of methylbenzyl succinic acid (Monomer A) having the 
following structural formula: 
##STR1## 
(2) An alkenyl-substituted succinic anhydride (labeled Monomer B) was 
prepared by heating 98.1 grams (1.0 mole) of maleic anhydride and 340 
grams (1.35 mole) of 1-dodecene, in the presence of 5.5 grams of 
hydroquinone for about 6 hours at about 200.degree. C. in a sealed, 
stirred 1-liter reactor. The cooled reactor was opened, and the 
yellow-brown solution was distilled under vacuum conditions (at about 5 
torr) so as to produce, at a yield of about 66%), 1-dodecenyl succinic 
anhydride (Monomer B) having the following structural formula: 
##STR2## 
A portion of monomer B may have been hydrolyzed to the corresponding 
diacid. 
EXAMPLE II 
This example illustrates the preparation of two unsaturated polyesters 
utilizing Monomers A and B (described in Example I). 
Polyester A was prepared by mixing 183 grams (0.8 mole) of Monomer A, 242.5 
grams (2.5 moles) of maleic anhydride and 273.6 grams (3.6 moles) of 
propylene glycol, and then heating the mixture for about 2 hours at 
140.degree.-150.degree. C. in a 1 liter glass reactor, under a nitrogen 
atmosphere. Thereafter, the temperature was raised to 
170.degree.-180.degree. C., and the reaction mixture heated for 7.5 hours 
at this temperature, while formed water was removed. Finally, the 
temperature was increased to 180.degree.-205.degree. C., and heating 
continued for 3 more hours so as to attain Polyester A having an acid 
value of 57 (determined in accordance with ASTM procedure D2849). 
0.08 grams of tolylhydroquinone antioxidant was added to the above reaction 
product (to decompose unreacted peroxides) at a temperature of about 
160.degree. C. When the temperature dropped to about 90.degree. C., 225 
grams of styrene was added so as to make 860 grams of a "polyester syrup" 
containing about 68 weight-% of Polyester A. 
A polyester labeled Polyester A' was prepared substantially in accordance 
with procedure for Polyester A, except that the molar ratio of propylene 
glycol to maleic anhydride was about 1.8 (in lieu of 1.4). The reaction 
mixture containing Monomer A was heated for 8 hours at 
150.degree.-160.degree. C. and then for 8 hours at 180.degree.-210.degree. 
C. 960 grams of wet Polyester A' resin (acid value: 31) was recovered. A 
second run yielded 955 grams of Polyester A' having an acid value of 32. 
The two Polyester A' batches were mixed with 986 grams of styrene so as to 
make a polyester syrup containing about 66 weight-% of Polyester A'. 
Polyester B was prepared by charging 5.32 grams (0.02 mole) of Monomer B, 
146.5 grams (1.0 mole) of phthalic anhydride, 97 grams (1.0 mole) of 
maleic anhydride and 167.2 grams of (2.2 moles) of propylene glycol and 
then heating the mixture for 6 hours at 160.degree.-170.degree. C. and for 
14 hours at 180.degree.-200.degree. C. under a nitrogen atmosphere. During 
this heating, the reaction mixture was stirred, and water was continuously 
removed. The reaction product having an acid number of 26 was mixed with 
180 grams of styrene and 0.1 gram of tolylhydroquinone (THQ) so as to form 
515 grams of a polyester syrup containing about 65 weight-% of Polyester 
B. 
A polyester labeled Polyester B' was prepared substantially in accordance 
with the procedure described for Polyester B, using 0.1 mole of Monomer B, 
0.95 mole of maleic anhydride, 0.95 mole of phthalic acid and 2.2 moles of 
propylene glycol. 37 mg of THQ antioxidant and 180 g of styrene were added 
to the reaction product at about 90.degree. C. The polyester syrup 
contained 67 weight-% of Polyester B'. 
Control Polyester C was a commercial polyester produced by Interplastics 
Corporation, Minneapolis, Minn., by polycondensation of about 1 mole of 
maleic anhydride, about 1 mole of phthalic anhydride and about 2.4 moles 
of propylene glycol. A styrene syrup of this resin also contained 65-70 
weight-% Polyester C. 
EXAMPLE III 
This example illustrates the differences in styrene loss of polyester 
syrups (concentrated solutions in styrene as solvent) containing 65-70 
weight-% of Polyesters A, A', B, B' and C. About 55 g of these polyester 
syrups were left 1 day in open containers under a fume hood. Weight losses 
due to styrene evaporation were: 
Polyester A syrup 2.9% 
Polyester A' Syrup 2.9% 
Polyester B Syrup 2.3% 
Polyester B' Syrup 2.8% 
Polyester C Syrup 5.4% 
These data clearly show that the invention polyesters (A, A', B, B') 
exhibited considerably reduced styrene losses from concentrated solution 
versus the commercial control Polyester C. This reduction in styrene 
losses will be beneficial both for cost and environmental reasons. 
EXAMPLE IV 
This example illustrates the mechanical properties of clear castings of 
polyesters described in Example II. 1/8 inch thick castings were made by 
curing polyester syrups (about 65 weight-% solutions of these polyesters 
dissolved in styrene) at room temperature, in the presence of 0.25 
weight-% cobalt naphthenate (added as a 6 weight-% solution; available 
from Al-Dow Chemicals, Inc.,) and 0.5 weight-% of methylethyl ketone 
peroxide (Cadox M-50; Noury Chemical Corporation, Burt, NY) After 5 hours 
at room temperature, the cured resin samples were demolded and post-cured 
at 50.degree. C. for 15-24 hours. The thus cured samples were then cut 
into test bars for mechanical testing. Pertinent mechanical properties are 
listed in Table I. 
TABLE I 
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Polyester 
Polyester 
Polyester 
Polyester 
A (In- A' (In- B (In- C 
Resin.sup.6 vention) vention) vention) 
(Control) 
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Flex Modulus.sup.1, MPa 
2,990 2,460 3,650 4,090 
Flex Strength.sup.1, MPa 
84 72 108 88 
Tensile Strength and 
51 58 44 51 
Break.sup.2, MPa 
Elongation.sup.2, % 
2 .sup. 9.sup.5 
4 1.2 
Izod Impact, 40 39 39 32 
Notched, Joule/m 
Heat Distortion.sup.4, .degree.C. 
-- 58 63 68 
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.sup.1 determined according to ASTM D 790 
.sup.2 determined according to ASTM D 638 
.sup.3 determined according to ASTM D 256 
.sup.4 determined according to ASTM D 648 
.sup.5 result is believed to be too high 
.sup.6 polymer B' was not tested 
Data in Table show that invention polyesters (A, A' and B) and control 
polyester C generally exhibited comparable mechanical properties. Izod 
impact and elongation of invention polyesters were consistently higher 
than those of control Polyester C.