Note: Descriptions are shown in the official language in which they were submitted.
2~7t79
TITLE
Sulfur~Modified Polytetramethylene Ether
Glycols, A Method for Preparing Them,
and Polyurethanes Prepared Therefrom
S DESCRIPTION
Technical Field
This invention relates to polytetramethylene
ether glycol (PTMEG), which has been modified so that it
contains sulfur-containing moieties in its polymer
chain. It is more particularly directed to such a
PTMEG modified to contain dehydrated ~,~'-dihydroxyalkyl
sulfide (HAS) moieties in its chain.
The invention also relates to a method of
making the modified PTMEG's, to their use as stabili-
zers against the degradation the polyether chain, andto polyurethanes made with them.
Background and Summary of the Invention
Polyurethanes have been known and used for
many years, and the basic general chemistry for their
~ 20 preparation, the reaction of a polyol, a polyisocyanate
and a chain extender, is fully documented.
A polyol frequently used for this purpose is
PTMEG, which is well known to be degraded by exposure
to oxygen, light and heat. It has been the general
practice to guard against this degradation by blending
with the PTMEG an external stabilizer such as a
phenolic, an amine or a sulfur compound.
It has now been found, according to the in-
vention, that the stabilization can be more effectively
and efficiently achieved if the PTMEG is modified so
that it contains in its chain 1-25%, by weight, pref-
erably 3-15%, even more preferably 4-10%, of moieties
represented by the structure
CH 1197
R R
O-CH-CH2-S-CH2-CH-
~ where R is hydrogen, an alkyl radi-
cal of 1-3 carbon atoms or phenyl,
and the oxygen atom is linked to
a hydrogen atom or a carbon atom;
the modified PTMEG having an oxygen/sulfur atom ratio
of 3/1 or greater~
It has been found, according to the inven-
tion, that the scabilization against degradation can
also be achieved if unmodified PTMEG to be used is
physically blended with about 0.4-20%, by weight, of
the modified PTMEG.
In addition, the method for preparing the
modified PTMEG of the invention can be used to in-
crease the molecular weight of PTMEG by coupling
polymer chain segments with HAS moieties.
It has also been found that PTMEG modified
- according to the invention shows significantly better
resistance to acid-catalyzed depolymerization and to
oxidative degradation at high temperatures than unmodi-
fied PTMEG.
Detailed Description of the Invention
The modified PTMEG of the invention is made
by catalytically reacting a PTMEG with an HAS.
The PTMEG used can be any of those commer-
cially available, or can be prepared by any of the
well-known methods of catalytically polymerizing tetra-
hydrofuran. Preferably, the PTMEG has a number average
molecular weight of 500-6000, more preferably 650-3000.
Number average molecular weight is determined
by first determining the hydroxyl number of the sample
by titrating it with acetic anhydride according to
~;~Z~77~
ASTM-D-1638 and then converting this number to number
average molecular weight according to the formula
g hydroxyl number
where n is the hydroxyl functionality
of the sample
The HAS used is represented by the structure
R R
HO-CH-CH2-S-CH2-CH-OH
where R is hydrogen, an alkyl radi-
cal of 1-3 carbon atoms, or phenyl.
The HAS preferred for use is ~ dihydroxy-
ethyl sulfide.
Any such HAS not available in the marketplace
can be made by the well-known reaction of hydrogen sul-
fide and an alkylene oxide.
The preparative reaction is conducted in a
mixture of PTMEG and HAS. The relative amounts of
HAS and P~MEG used are dictated by the weight of HAS
moieties desired in the product. These amounts can be
easily calculated using the principles of stoichiometry.
In general, one uses 0.5-6 moles of HAS for each mole
of PTMEG, preferably 1-2 moles.
The catalyst used can be any heterogeneous
or homogeneous acid catalyst stronger than H3PO~. The
catalyst is preferably an alkyl- or aryl sulfonic acid,
even more preferably one of the strongly acidic catio-
nic ion-exchange resins bearing -SO3H groups, insolu-
ble in the reaction medium. '1Insoluble" means that
the amount of resin which dissolves in the medium under
reaction conditions will give the modified PTMEG prod-
uct an acid number of no greater than 0.05 mg of KOH
:~22~79
per gram. The nature of the "backbone" of the resin
is unimportant. The most common of the commercially
available resins o~ this type have backbones which are
of the polystyrene type, but resins having other back-
bones can be used.
Preferred among the polystyrene type resins,
and prefexred for this use according to the invention,
is one sold by the Rohm & Haas Company of Philadelphia,
PA as Amberlyst* XN-1010. This macroreticular resin
has a cation exchange capacity of 3.1 milliequivalents
per gram, a surface area of 450 square meters per gram,
a porosit~ of 41%l and a mean pore diameter of 0.005
micron.
The catalyst is used at a concentration of
0.1-10%, by weight of the PTMEG, preferably 2-5%.
The preparation is begun by placing the re-
actants and catalyst in a vessel and bringing the re-
sulting mixture to a temperature of 130-170C, prefer-
ably about 150~C, and holding it at that temperature,
with stirring, until the HAS has been consu~ed, as
shown by periodic sampling and analysis by gas
chromatography.
The water formed by the reaction can be re-
moved from the reaction mass by vacuum distillation or
by sweeping the reaction zone with an inert gas e-g-
nitrogen. Preferably, the water is removed as a
water/hydrocarbon azeotrope, even more preferably as
a water/toluene azeotrope. The hydrocarbon can then
be separated from the azeotrope by condensation in a
suitable trap and can be recycled to the reaction mass.
When this procedure is used, the temperature of the
reaction mass can easily be held within the desired
range by adjusting the concentration of toluene.
When the PTMEG-HAS reaction i5 finished,
heating is stopped, the catalyst is filtered off (if a
* denotes trade mark
7~
heterogeneous catalyst is used) and the remaining mate-
rial is stripped of residual volatiles. The resulting
product is a viscous liquid having a number average
molecular weigh-t of 500-10,000, preferably 800-500~,
and an oxygen/sulfur atom ratio of 3/1 or greater,
preferably 5-60/1. Molecular weight can be varied
by simply allo~ing the reaction to proceed until the
desired molecular weight is reached.
The blends of unmodified PTMEG and PTMEG
modified according to the invention can be made by
simply mixing them in amounts which will give a mixture
containing 0.4-20%, by weight, of the modified PTMEG.
A polyurethane can be prepared from a modi-
~ied PTMEG of the invention, or from a modified-unmodi-
fied blend, by reacting it with an organic polyisocyan-
ate and an aliphatic polyol or polyamine chain extender,
as is well known in the art.
The polyisocyanates used in preparing the
polyurethanes can be any of the aliphatic or aromatic
polyisocyanates ordinarily used to pxepare polyure-
thanes. "Polyisocyanate" means any compound bearing
two or more -NCO radicals. Illustrative are
2,4-toluene diisocyanate
2,6-toluene diisocyanate
hexamethylene-1,6-diisocyanate
tetramethylene-1,4-diisocyanate
cyclohexane-1,4-diisocyanate
naphthalene-1,5-diisocyanate
diphenylmethane-4,4'-diisocyanate
xylylene diisocyanate
hexahydro xylylene diisocyanate
dicyclohexylmethane-4,4'-diisocyanate
1,4-benzene diisocyanate
3,3'-dimethoxy-4,4'-diphenyl diisocyanate
~Z~77~
m-phenylene diisocyanate
isophorone diisocyanate
polymethylene polyphenyl isocyanate
4,4'-biphenylene diisocyanate
4-isocyanatocyclohexyl-4'-isocyanatophenyl
methane
p-isocyanatomethyl phenyl isocyanate.
Mixtures of isocyanates can also be used.
The isocyanates preferred for use because of
the desirable properties they confer on the polyure-
thane products are diphenylmethane-4,4'-diisocyanate
and the toluene diisocyanates.
The chain extenders used in preparing the
polyurethanes can be any of the aliphatic polyols, or
any oE the aliphatic or aromatic polyamines ordinarily
used to prepare polyurethanes.
Illustrative of the aliphatic polyols which
can be used as chain extenders are
1,4-butanediol
ethylene glycol
.,
1,6-hexanediol
glycerine
trimethylolpropane
pentaerythritol
1,4-cyclohexane dimethanol
phenyl diethanolamine
Diols like hydroquinone bis(~-hydroxyethyl)ether, tetra-
chlorohydroquinone-1,4-bis(~-hydroxyethyl)ether and
tetrachlorohydroquinone-1,4-bis(~-hydroxyethyl)sulfide,
even though they contain aromatic rings, are considered
to be aliphatic polyols Eor purposes of the invention.
Aliphatic diols of 2-10 carbon atoms are
pre-Eerred. Especially preEerred is 1,4-butanediol.
Mixtures of diols can also be used.
:~L2Z~779
Illustrati~e of the polyamines which can be
used as chain extenders are
p,p'-methylene dianiline
and complexes thereo~ wi~h alkali
metal chlorides, bromides, iodides,
nitrites and nitrates.
4,4'-methylene bis~2-chloroaniline)
dichlorobenzidine
piperazine
2-methylpiperazine
oxydianiline
hydrazine
- ethylenediamine
hexamethylenediamine
xylylenediamine
bis(p-aminocyclohexyl)methane
dimethyl ester of 4,4'-methylenedianthranilic
acid
p-phenylenediamine
m-phenylenediamine
4,4'-methylene bis(2-methoxyaniline)
4,4'-methylene bis(N-methylaniline)
2,4-toluenediamine
2,~-toluenediamine
benzidine
3,4'-dimethylbenzidine
3,3'-dimethoxybenzidine
l dianisidine
; 1,3-propanediol bis(p-aminobenzoate)
isophorone diamine
1,2-bis(2'-aminophenylthio)ethane.
The amines preferred for use are 4,4'-
methylene bis(2-chloroaniline), 1,3-propanediol
7~79
bis(p-aminobenzoate) and p,p'-methylenedianiline and
complexes thereof with alkali metal chlorides, bromides,
iodides, nitrites and nitrates. Mixtures of amines can
also be used.
The polyurethanes can be prepared in two
steps, the ~irst of which is conducted under nitrogen
at ambient pressure to prevent oxidation of the re-
actants and pro~uct, and to prevent exposure of the
reaction mass to atmospheric moisture. In the first
step, the modified PTMEG starting material is dried
by heating it at a temperature of 80-100C under vacuum,
and is then held at 60-125C, preferably about 70-90C,
while a stoichiometric excess, preferably twofold to
tenfold, of organic polyisocyanate is added, with
stirring. The actual amount of isocyanate used depends
on the molecular weight of the modified PTMEG used,
as is well known in the art. The reaction mass is
held for about 1-4 hours at 60-125C, with stirring,
and the free isocyanate content of the mass is then
determined by titrating it with di-n-butylamine, as
described in Analytic Chemistry of the Polyurethanes,
Volume XVI, Part III, D. J. David and H. B. Staley,
Wiley-Interscience, 1969, pages 357-359.
In the second step, an amount of polyamine
or polyol chain extender calculated to gi~e an
isocyanate/hydroxyl or amine mole ratio of about 0.9-
1.1 to 1 in the reaction mass, preferably 1-1.05/1, is
degassed at about 30-120C and 1330-5330 Pa (10-50 mm
Hg) pressure and quickly added to the reaction mass.
- 30 A conventional curing catalyst can be added
at this point if desired. Illustrative of catalysts
which can be used are dibutyltin dilaurate and stannous
octoate. The catalyst can be added to the reaction
mass to give a concentration of about 0.001-0.1%, by
weight, preferably about 0.01%.
r;~7~3
The reaction mass is held with stirring at
60 130C until it is homogeneous, which normally takes
1-5 minutes. The mass is then poured into molds, pref-
erably preheated to 100-120C, and then cured at about
100-120C at a pressure of 1700-2500 kPa for from 5
minutes to several hours. The casting is then cooled,
removed from the mold, aged for about one week at
ambient temperature, and is then ready for use.
The polyurethanes can also be made by reac-
tion-injection and liquid-injection molding techniques,
whereby the starting materials are simultaneously in-
jected and mixed in a mold, preferably together with a
conventional polyurethane catalyst,and then subjected
to pressures ranging from ambient to several million
pascals and temperatures ranging from ambient to lS0C.
Use of a foaming agent e.g. a fluorocarbon or water
is optional.
BEST MODE
In the following example, all parts are by
weight.
The following were added to a reaction vessel
fitted with a reflux condenser and a Dean Stark trap:
PTMEG (Mn 1000) 100 parts
~ dihydroxyethyl
sulfide 12.2 parts
Toluene 50 parts
Amberlyst XN-101~ 4 parts
The resulting mixture was heated to and held at reflux
temperature for four hours, with stirring, while water
30 was continuously removed from the reaction zone as the
water/toluene azeotrope.
The reaction mixture was then filtered to
remove the Amberlyst and the volatiles removed at a
pressure of about 667 Pa (5 mm of Hg) and a temperature
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of about 150C to give 98 parts of a viscous liquid
product containing 5.9% of -O-CH2-CH2-S-CH2-CH2-
moieties, with a number average molecular weight of
2080 and an oxygen/sulfur atom ratio of 24/1. This
polymer slowly crystallized at about 20C.
