Note: Descriptions are shown in the official language in which they were submitted.
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UNSATURATED POLYESTERS PREPARED
FROM A DICARBOXYLIC ACID AND
DIBROMONEOPENTYL GLYCOL
Unsaturated polyester resins are convention-
ally prepared by reacting dibasic acids; i.e., phthalic
anhydride, maleic anhydride, etc., and difunctional alco-
hols; i.e., ethylene glycol, propylene glycol, etc., in
stainless steel reactors at temperatures between 170C-
-200C. Corrosion of stainless steel is slow enough in
thèse systems that it does not have an adverse effect on
either reactor life or resin color.
Synthesis of unsaturated polyester resins such
as those described in U.S. Patent 3,507,933, i.e., fire
retardant resins prepared from phthalic anhydride, maleic
ànhydride, and dibromoneopentyl glycol, results in corro-
sion problems when carried out in stainless steel reactors,
and this in turn :Leads to color problems.
The use of sulfuric acid and sulfonic acids as
catalysts for polyesterification reactions using saturated
dibasic acids are known in the prior art, e.g., P. J. Flory
disclosed the use of p-toluene sulfonic acid (p-TSA) as a
catalyst for the reaction of adipic acid and ethylene gly-
col in 1939. Later attempts to use strong acid catalysts
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in the preparation of unsaturated polyester resins ha~e
been less than suceessful. Weakly acidic or basic cata- --
lysts are usually required for reactions in~olving ali-
phatic diols in order to prevent dehydration to ether or
olefin. It has also been pointed out that acid catalysts
such as sulfuric acid or p-TSA, while increasing the rate
of bo-th esterification and isomerization, usually cause
color formation and other detrimental side reactions.
Some of these adverse reactions caused by the
presence of sulfuric, or sulfonic acids, include premature
gelation of the styrenated and unstyrenated resins and the
loss of glycol from the cook due to the formation of vola-
tile ethers. It has been shown that as little as 50 ppm
of sulfuric acid will catalyze the formation of ethers
from aliphatic diols at polyester reaction temperatures.
The present invention is a process for prepar-
ing unsaturated polyesters by reacting an unsaturated
dicarboxylic acid with a polyol composed at least in part
with dibromoneopentyl glycol wherein the catalyst employed
is an aryl sulfonic acid and followi~g completion of the
reaction there is added a su~`ficient amount of an acid
#CaVenger to neutralize s~id sulfonic acid.
An unsaturated polyest2r is a condensation
polymer produced by condensing approximately equimolar
proportions of at least one dicarboxylic acid, ~t least
a portion of which contains ethylenic unsaturation, with
at le2st one pGlyol, which for purposes of this inven-
tion, must be made up at least in part of di~romoneopen-
tyl glycol. Examples of such unsaturated acids include
maleic, fumaric and itaconic acids. Th~ ~emainder, if
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any, of the dicarboxyllc acids are usually either satu-
rated nonTal aliphatics, such as adipic acid, succinic
acid, or aromatic diacids, such as phthalic acid or iso-
phthalic acid. The tPrm dicarboxylic acid, as used herein,
S is intended to e~brace the anhydride as well.
The unsaturated acid provides the unsaturation
needed for curing the resin. Therefore, the actual ratio
of unsaturated acid to saturated acid will be dictated by
the deg,ee of cross-linking desired in the cured product.
That degree of cross-linking may be predetermined by sim-
ple preliminary experiments as is standard in the poly-
ester art.
The polyol to be used is dibromoneopentyl gly-
col. Other no~halogenated glycols may ~e used in small
amounts without affecting the inventive concept. However,
when using aryl sulfonic acids as the esterification cata-
lysts, those nonhalogenated glycols form ethers and other
undesirable by-products.~ The preserlt invention appears
to be singularly well adapted or use with dibromoneopen-
tyl glycol which must form the substantial majority ofthe polyol.
The acid scaveng~r to be use~ in the process
is any compound that will neutralize -t~ acid catalyst
through formation of a salt, ester, amine salt or by
other means. Typical of such scavengers are the oxirane
compounds, such as epichlorohydrin, the diglycidyl ether
of a polyol as, for example, a diglycidyl ether of an
aliphatic glycol having an epoxy equivalent weight of
175-205, and other epoxy compounds; oxetane compoun~s
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such as bis-2,2-(dibromonethyl)oxetane; amines such as
diethanolamine or triethanolamine; soluble salts of weak
acids such as sodium acetate or hypophosphorous acid.
The esterification catalyst is an aryl sul-
fonic acid. Typical of those acids are benzene sulfonicacid and p-toluene sulfonic acid. The amount of catalyst
can vary between about 0.OS and 3 percent by weight of
the reactants. Preferably, the amount is between 0.1 and
0.4 weight percent.
The polyester is made in generally conventional
manner except as otherwise described herein. The acid and
dibromoneopentyl glycol are introduced into a suitable
esterification reaction vessel equipped with means for
removing water of esterification suitably as it is ormed
in the reaction. T~e reactants are blanketed with an
inert atmospher~, preferably nitrogen gas, then agitated
and heated to effect the reaction for a desired period
of time. The reaction temperature can range from about
100C to 200C, preferably from 135C to 155C. The exact
reaction time will depend on the resin ormulation, the
amount of catalyst, the reaction temperature and pressure
and the inert gas sparge rate.
The degree of reaction is conveniently deter-
mined by measuring the acid number or by measuring the
amount of water liberated in the reaction. The reaction
is discontinued when the product has a desired acid num-
ber, e.g., an acid number of 40 or below. After the
reaction has been carried to the desired degree of com-
pletion, the acid scavenger is added.
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The resin is then recovered and blended with
an ethyleni~all~- unsaturated monomer copolymerizable with
the unsaturated polyester polymers to form a blend wherein
the weight ratio of polyester to monomer is in the range
5 from about 4:1 to about 1;2. Such ethylenically unsatu-
rated monomers are well-known and include styrene, chloro-
styrene, vinyl toluene, divinylbenzene, dicyclopentadiene
alkenoate, acrylic and methacrylic acid, diallyl phthalate,
or mixtures thereof.
These polyester blends with unsaturated mono-
mers should contain about 20 to about 60 percent by weight
and preferably 30 to 50 perc~nt by weight of the monomers
based on the weight of the polyester. A'small amount of
an inhibitor such as tertiary butyl catechol or hydroqui-
none may be added to this mixture.
The final blend is a cross-linkable polyester
composition which is useful to make laminates, castings
or coatings.
Laminates can be made by mixing into the cross-
-linkable composition, free radical-forming catalysts in
known amounts and ad~ing this mixture to a suitable fibrous
reinforcement such as carbon fibers, fibrous glass or lnor-
ganic fibers.
Examples of these catalysts are benzoyl per-
~5 oxide, tertiary butyl peroxide and methylethyl ketoneperoxide. It is frequently of value to add accelerators
such as cobalt naphthenate or dimethyl aniline.
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The polyester resin is roll~d, sprayed or
impregnated into the fibrous reinforcement s~ch as
fibrous glass and cured in a manner well-known in the
art. When fibrous glass is used, it can be in any form
such as chopped strands, filaments, gl~ss ribbon~, glass
yarns or reinforcing mats.
The follo~ing exa~ples illustrate the inven-
tion.
Example 1
The laboratory cooks were carried out in a
2-liter resin flask, equipped with a mechanical stirrer,
a stainless steel N2 sparge tube, a stainless steel
thermowell, and a steam heated (100C) partial condenser,
followed by a trap, followed by a water cooled condenser.
The reaction heat source was two 275 watt infrared lamps
and the whole resin flask was kept in a hot air oven.
The resin flask was charged with 800 ~rams
(3.05 moles) of commèrcial dibromoneopentyl glycol, 170
grams (1.73 moles) of maleic anhydride, 110 grams (0.74
mole) of phthalic a~hydride and 80 yrams ~4.44 moles)
of water.
The reactor was sparged with N2 (1190 cc/min)
to remove air from the system prior to ~he start of the
reaction and to aid in the removal of water after the
reaction was started. [For comparative purposes, the
cook time is considered to be that part of the cycle
from the time the reaction temperature reached 125C
until the reaction was terminated.
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The temperature controller was set at 135C
and the reaction started. The reaction reached 125C
in about 45 minutes and 135C in 55 minutes. The reac-
tion temperature was maintained at 135C until the acid
number reached 29. ~The normal end acid number is 30+2.)
The cook time was 22 hours.
The crude alkyl was poured into a polytetra-
fluoroethylene coated pan and allowed to cool.
Samples were made up for testing by dissolv-
ing 75 grams of alkyd in 25 grams of styrene, contain-
ing 0.02 gram of toluhydroquinone. The styrenated resin
had the following properties: ~
Gardner Color 8.7
SPI Gel Time 5.1 min.
SPI Peak Time 6.9 min.
SPI Peak Exotherm 188C
.~
To a sample of this resin was added 1 weight percent epi-
chlorohydrin to bleach the color. The bleached sample had
the following properties:
Gardner Color 3.9
SPI Gel Time 6.1 min.
SPI Peak Time 8.1 min.
SPI Peak Exotherm 213C
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Example 2
The above procedure W2S repeated except that
2.1 grams (0.011 mole) of p-TSA was added to the
reactor along with the charge. The reaction reguired
5.0 hours to reach an acid nu.~er OI 30. Samples of
styrenated resin were-made up as in Example 1 and the
following results were o~tained:
Without With
EPichlorohvdrin Epichlorohydrin
10 Gardner Color 2.4 2.4
SPI Gell Time 1.6 min........... 6.6 min.
SPI Cure Time 2.7 min. 8.8 min.
SPI Peak Exotherm 133C 209C
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