Note: Descriptions are shown in the official language in which they were submitted.
~7~7i5'7
'Cured'Pblvure't~an~s
Technical Field
This invention relates to cured polyurethanes
prepared by curing polyurethane precursors with selected
aromatic diamines.
Background Art
Diamines are especially valuable for curing various
polyurethanes, particularly isocyanate terminated poly-
urethane prepolymers. Aromatic diamine curatives are
particularly valuable for curing aromatic isocyanate-
terminated prepolymers (,to provide polyurethanes having
enhanced age resistance in the presence of moisture and
various liquid hydrocarbon fuels). However, many
aromatic diamines typically react too fast with aromatic
isocyanate-terminated prepolymers and therefore seriously
inhibit their commercial significance. The 4,4'-
methylene bis (2-chloroaniline), sometimes reerred to
as MOCA, a well known diamine, is slower reacting at
' room temperature and should be considered one of the
exceptions to such typical fast reacting aromatic
diamines.
For such MOCA cured aromatic NCO-terminated
prepolymers a catalyst is many times used to shorten
the reaction time and enhance their commercial signifi-
cance especially in the preparation of ure~hane films
in solution systems.
Therefore, it is an,object of this invention to
provide aromatic diamines suitable for curing aromatic
isocyanate-terminated polyurethane prepolymers, methods
of preparing such aromatic diamines and isocyanate-
términated polyurethanes extended with aromatic diamines.
Disclosure And Practice Of Invention
In'accordance with this invention? a cured poly-
urethane is provided which is prepared by reacting (A)
a diamine selected from at least one of the group
,
7~
.2
consisting o~ 3,5-diam~nobenzotrifluoride, and ~is(:2-
aminoph.enyl)sulf~de, with.'(B.~ an isocyanate~ter~inated
prepolymèr prepared ~y the meth.od which co~prises
reacting a poly~socyanate h.a~ing an i.socyanato function-
ality o~ 2 to 3, wit~.a ~olyol com~rised o~ about 80 toabout lO.0 wei.~ht percent polymeric pol~ols selected
from ~olyester polyols, polyether ~olyols and hydroxyl
terminated unsaturated polymerlc polyols, and, correspond-
ingly, about 20 to a~out 0 weight percent monomeric
hydrocarbon d~ols hav~ng 3 to 8 carbon atoms; where the
ratio of ~socyanato graups to hydroxyl ~roups of the
polyol, or polyol mixture, is in the range of about
1~3!1 to about 5/1, and where the ratio of amino groups
of said diamine to excess isocyanato groups of said
hydroxyl groups is in the range of about 0.5/1 to a~out
1. 1~1. '
Rep~e.sentative examples of various monomeric
polyols suitable for use in the preparation of the
polyurethane are ethylene glycol, 1,3-propane diol,
1,4-butane diol, 1,5-pentane diol, 1,6-hexane diol and
decamethylene glycol.
The polyurethane reaction mixtures used in this
invention are typically liquid mixtures with the
addition of a solvent commonly used to prepare poly-
urethanes, if desired, and particularly flexible
polyurethanes, by the well known one-shot prepolym~r or
quasi-prepolymer techniques. The quasi-prepolymer
method differ's from the prepolymer method in that only
a portion of the pol~ol is initially reacted with the
3G polyisocyanate, with the remainde.r then added and
reacted to form the prepQlymer. The prepolymer i5 then
cured ox extended ~ith t~e d'i.a~ine.
The cura.t.i~e., pol~ols and polyisocyanates are
typically reacted ~t te~pe.~atu~es in the range o about
20C, to about 15~C. and pre.f~er~ in t~.e range o~
about 2~C. to about lO~QG.
A sol~ent can ~e u~.-ed ~ith th.e'reaction mixture to
facilitate its use ~n the form of a fluid mixture or
7~'7
solution, although it is generally preferred to use the
reaction mixture with only a minor amount of solvent,
if any. If a solvent is used, it can be added to form
a mixture containing up to about 60 weight percent
solvent based on the total mixture. A preferable
mixture can contain from about 40 to about 95 weight
percent solids. However, a higher or lower concentra-
tion of solids might be used. When the solids concen-
tration is low, the individual applications will tend
to deposit a thin layer of polyurethane polymer and a
large amount of the solvent will have to be removed
during the curing process. A solids concentration of 45
weight percent or higher is generally desired if a
solven~ is used.
Other methods generally known for the preparatiGn
of polyurethane reaction mixtures with or withou~ the
aid of solvents may also be used.
The diamine curative of this invention has a
curative reactivity which allows improved processing
for many commercial applications. Indeed, its typical
curative reactivity with aromatic isocyanate-terminated
polyurethane prepolymers enhances such a polyuréthane's
commercial significance. The curative reactivity is
valuable because it typically provides a shorter reaction
time instead of the rather slow reaction provided by
sterically hindered diamines like 4,4'-methylene-bis-
(2-chloroaniline~, otherwise known as MOCA.
Thus, the diamine curatives of this invention can,
if desired, eliminate the need o a catalyst such as
the well-known tertiary amines, the tin salts of fatty
acids, such as dibutyltin dilaurate and stannous octoate
and accelerators such as ~ercaptobenzothiazole.
Xn the preparation o~ the polyurethanes by this
invention, the polymeric polyols typically comprise at
least one member selected from the group consisting of
polyester polyols, polyether polyols, and hydroxyl-
terminated unsaturated polymeric polyols. The hydroxyl-
terminated unsaturated polymeric polyols typically have
a molecular weight of from about 2000 to about ~000 and
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a hydroxyl functionality o from about 2 to about 3.
The reactive hydrogen-containing material generally
used, other than the hydroxyl-terminated unsaturated
polymeric polyol, has a molecular weight in the range
of from about 500 to about 5000, and usually from about
1000 to about 3000. (I the molecular weight of the
reactive hydrogen-containing material is too low, the
polyurethane will not have suicient elasticity.)
Generally, the polyester polyols are the preferred
10 active hydrogen-containing material where high strength
and solvent resistance are desired.
Representative examples of polyester polyols are
the condensation products of low molecular weight
polyols wlth an organic polycarboxylic acid or anhydride.
15 ~epresentative low molecular weight polyols are glycols
such as ethylene glycol, propylene glycol, butylene
glycol, pentylene glycol, decamethylene glycol, etc.
Representative examples o the organic dicarboxylic
acids that can be used are succinic acid, glutaric
20 acid, adipic acid, phthalic acid, terephthalic acid,
isophthalic acid, suberic acid, sebacic acid, pimelic
acid and azelaic acid. The anhydrides of such acids
can be used in place of the acid. If desired, rom
about 1 to 20 percent by weight of a triol or higher
25 polyfunctional polyol or polyfunctional acid can be
present to produce branching in the polyurethane polymer.
Further examples o polyesters are caprolactone
polyesters. The caprolactone polyesters are substan-
tially linear, hydroxyl-terminated polymers prepared by
30- reactin~ a caprolactone having 6 to 8 carbon atoms,
preferably 6 carbon atoms, with a glycol having 4 to 7
carbon atoms and preferably 4 to 6 carbon atoms.
Various suitable caprolactones include
~ -caprolactone, zeta-caprolactone and eta-capro-
t 35 lactone. Alkyl substituted caprolactones can be used
with alk~l substituents containing 1 to 2 carbon atoms
selected from methyl and ethyl radicals such as methyl
~ -caprolactone. Desirably, the caprolàctone polyester
7 8
has a molecular weight in the range of about 800 to
about 3500, preferably about 1200 to about 3000, with
- corresponding hydroxyl numbers in the range of about
140 to about 32 and about 95 to about 37, respectively.
Polyether polyols useful in preparing the poly-
urethanes of this invention can be prepared by poly-
merizing or copolymerizing alkylen~ oxides, such as
ethylene oxide, propylene oxide, and butylene oxides,
by polymerizing or copolymerizing the low molecular
weight glycols, or by the reaction of one or more such
alkylene oxides with the glycols or with triol, or with
a polycarboxylic acid, such as phthalic acid. The
polyether polyols include polyalkylenearyl ether glycols
or triols, polytetramethylene ether glycols, polyalkylene
ether-thioether glycols or triols and alkyd resins.
Generally the polytetramethylene ether glycols are the
preferred polyether glycols.
It is usually preferred that the hydroxyl-terminated
unsaturated polymeric polyol has a molecular weight of
20 from about 2000 to about 4000 and a corresponding
hydroxyl number of from about 50 to about 25. The
hydroxyl-terminated unsaturated polymeric polyols used
in this invention are unsaturated polymers of the type
prepared by polymerizing unsaturated monomers comprising
25 from about 70 to about 100 percent conjugated dienes
selected from the group consist-ing o 1,3-butadiene and
isoprene and up to abut 30 percent styrene with the aid
of organic peroxy catalysts to provide polymers which
are gen~rally terminated at both ends of their chain
3~ with hydroxyl groups and have a hydroxyl functionality
of from about 2 to about 3 and usually from about 2.1
to about 2,8. The preferred hydroxyl-containing poly-
meric polyols are polybutadiene polyols, polyisoprene
polyols~ butadiene-sty~ene copolymer polyols having
about 70 to 90 percent units derived from butadiene and
about 30 to 10 percent units derived from styrene and
also butadienè-acrylonitrile copolymer polyols.
The organic polyisocyanates used in this invention
having 2 to 3 isocyanato groups particularly include
various organic diisocyanates, dimers and trimers
thereof, and their mixtures as well as polyisocyanates
having 2.3 to 2.7 isocyanato groups. The organic
polyisocyanates can be aromatic, aliphatic or cyclo-
aliphatic or combinations of these types.
Representative examples of such polyisocyanatesinclude the toluene diisocyanates, m-phenylene diiso-
cyanate, 4-chloro-1,3-phenylene diisocyanate, 4,4'-
tetramethylene diisocyanate, 1,6-hexamethylene diiso-
10 ' cyanate, 1,10-decamethylene diisocyanate, 1,4-cyclo-
hexylene diisocyanate, 4,4'-methylene-bis (cyclo-
hexylisocyanate), 3,3'-dimethyl-4,4'-diphenylmethane
diisocyanate and 1,5-tetrahydronaphthalene diisocyanate
and mixtures of such diisocyanates For ~he purposes of
the present invention, the toluene diisocyanates,'
diphenylmethane-4,4'-diisocyanate, 3,3'-dimethyI-4,4'-
bis-phenylene diisocyanate, 4,4'-methylene-bis(cyclo-
hexylisocyanate~ and 3,3'-dimethyl-4,4'-diphenylmethane
diisocyanate are preferred. For convenience, these
diisocyanates are sometimes referred to as TDI, ~DI,
TODI, H12 MDI and DMMDI, respectively.
~ aricus non-reactive solvents known to those
skilled in the polyurethane art can be used for the
preparation of the prepolymer solùtions and polyurethane
reaction mixtures, if a solvent is desi~ed. ~epresenta-
tive ex~mples of the solvents are aromatic solvents
such as benzene, xylene and toluene and ~he liquid
lower ketones such as acetone, methyl ethyl ketone,
methyl isobutyl ketone and diisobutyl ketone. If the
polyurethane reaction ~ixtuxes are to be used to prepare
the cured polyurethanes in confined areas which are
subject to explosive hazardsj nonflammable polyurethane
solvents can be used to form nonflammable polyurethane
reaction mixtures. Mixtures of solvents may also be
used to obt~in sat~sfactory spreading properties and
evaporation rates when the polyuret~ane spray composition
is applied to a polymeric surface.
To enhance the cured polyurethane's hydrolysis
resistance, about 1 to about 15, preferably about 2 to
~74~
about 5, weight percent of an epoxy resin and at least
suEficient to give an excess of epoxide groups relative
to the total excess of amino groups of the diamine
curative over the said isocyanato groups might be used.
Thus, for such a modification an excess of epoxide
groups is required over the amino groups of the curative,
such as at least about 5 to about 50 equivalent percent
excess, based on two epoxy groups per amino (-NH2)
group, to provide a polyurethane composition containing
sufficient free epoxide groups.
Hydrolysis resistance is typically determined by
immersion in distilled wa~er at 158F. A substantial
retention of tensile strength and elongation after 1~
days immersion can be related to a substantial resistance
to hydroly5is. The tensile and elongation are normally
determined at about 25C. by methods typically used by
those skilled in the art.
Preferred resins for this invention are derived
from epichlorohydrin and 2,2'-bis(4-hydroxyphenyl)
propane with an epoxide equivalency of about 150 -to
about 220, preferably about 175 to about 210. Resins
which are pourable liquids at about 25C. are preferred
but others can be used in solution. Typical resins are
those obtainable under the tradenames Epon 828 and Epon
1001 from the Shell Chemical Company.
. The practice of this inven~ion is further illus-
trated by reference to the following examples which are
intended to be representatîve rather than restrictive
of the scope of the invention. Unless otherwise indi-
c~ted, all parts and percentages a~e by weight.
- EXoMP*E I
Cured polyurethanes were prepared by reacting
various diamines of this invention with various iso-
cyanate-terminated polyurethane prepolymers.
The prepolymers were p~epared by reacting an
excess of various diisocyanates with various polymeric
polyether and polyester polyols. The diisocyanates
were selected from 4,4'-diphenyl methane diisocyanate
.' - (MDI) and 3,3'-dimethyl-4,4'-diisocyanato diphenyl
1~478 ~
methane (DMMDI). The various polymeric polyols were
selected from polyethylene adipate with a molecular
weight (mw) of about 1000, polypropylene adipate (mw
2000), and polytetramethylene ether glycol (mw 2000).
5The experiments and physical properties are
summarized in Table 4. The Rv value is the NCO/OH
.ratio of the prepolymer.
The various physical properties were measured by
conventional means. The values for the various poly-
mer.ic polyols are the relative amounts used by weight,
with the total being a normalized 100. The pot life
relates the time from mixing the diamine curative with
the prepolymer until the mixture is very difficult to
pour.
15TABLE 1
.
- PHYSICAL PROPERTIES OF POLYURETHANES
' Ex~eriment A B
Polyethylene adipate 45 --
Polypropylene adipate 55 --
20 Polytetramethylene ether glycol -- 100
MDI Rv 2.0 __
DMMDI Rv . ~~ 1.9
Diamine * **
100% Modulus, psi 270 680
300% Modulus, psi 600 1600
500% Modulus, psi 2600 --
Ultimate Tensile (psi) 4400 4300
Ultimate Elongation (%) 530 570
Crescent Tear (lb/in) 410 280
Compression Set (%) -- 16
30 Shore'A Hardness 75 79
Pot Life, Minutes 1 ~-
* For experiment (A~ the diamine was bis(2~aminophenyl)
'' -sulfide.
: ** For experiment (B), the diamine was 3,5-diaminobenzo-
trifluoride.
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While certain representative embodiments and
details have been shown for the purpose of illustrating
the invention, it will be apparent to those skilled in
this art that various changes and modifications may be
made therein without departing rom the spirit or scope
i of the invention.
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