Note: Descriptions are shown in the official language in which they were submitted.
~.~2Q'7~
Mo-2325
LeA 20,830
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DIP~lINES AND A PROCESS
FOR THEI~ ~RE~AR~ION
BACKGROUND OF THE INVENTION
_
This invention relates to alkyl-substituted phenyl-
ene diamines in the form of homologous or isomeric mix-
tures and a process for their preparation. These dia-
mines are useful as chain lengthening agents in the pro-
duction of polyurethanes.
Aromatic diamines are a known class of compounds.
The simplest representatives of this class of compounds
(i.e. the isomeric phenylene and tolylene diamines) are
crystalline substances at room temperature. Because of
this crystallinity, they have not been usRd to any signi-
ficant extent as chain lengthening agents for the produc-
tion of polyurethanes.
The preparation o~ long-chain dinitroalkylbenzenes
is described in US Patent 2,934,571. According to US
Patent 2,986,576, such compounds may be converted into
the corresponding diamines. The alkylbenzenes used as
starting material in the examples of US Patent 2,934,571
are largely compounds characterized by a branch-chained
oligopropylene side chain. In US 2,934,571, however, a
special process for nitrat;ng these hydrocarbons is
taught since conventional processes o nitration appear
to have failed to nitrate the exemplified hydrocarbons
to the corresponding dinitroalkylbenzenes. In spite of
the elaborate process described in US Patent 2,934,571
~in which sulfuric acid containing sulfur trioxide is
used) it has been found that the end products contain
troublesome residues of mononitro compounds. Further
reaction of this disclosed nitration product to produce
diamines inevitably leads to diamines containing an
,
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undesirable amount of monoamines. Such a mixture of these
~diamines is not very useful as a chain lengthening agent
in the production of polyurethanes. Consequently, the
products of the above-described process have not been used
5 on a commercial scale by those in the art of polyurethane
chemistry.
SUMMARY OF TEE rNVENTION
It is an object of the present invention to provide
simple aromatic diamines, i.e. diamines having a single
10 aromatic nucleus and two aromatically bound primary amino
groups.
It is also an object of the present invention to
provide simple aromatic diamines which are liquid at room
temperature and show no tendency to crystallize at room
15 temperature.
It is another object o the present invention to
provide simple aromatic diamines which arè liquid at room
temperature and which are substantially free o undesir-
able monoamines.
It is a further object of the present invention
to provide simple aromatic diamines which are liquid at
room temp~rature and which may be used as reactants in
the production of polyisocyanate addition products.
It is yet another object of the present invention
25 to provide a simple process for the production of simple
aromatic diamines which are liquid at room t~mper~ture.
These and other objects which will be apparent to
those skilled in the art are accomplished by nitrating
and hydrogenating a hydrocarbon ~aving a boiling range of
30 270-330C which hydrocarbon corresponds to the formula
R
~`
.
Mo-2325
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in which R represents a saturated, straight-chained ali-
phatic hydrocarbon group having 8-15 carbon atoms.
The thus-produced diamine is a mixture of homologues and
isomers of diamines corresponding-to the formula
R
H2N ~ NH2
in which R is as defined above.
DETAILED DESCRIPTION OF TH~ INVENTION
The present invention relates to diamines correspond-
ing to the formula:
R
H2N ~ ~ NH2
15 in which R denotes a saturated, straight-chained, alipha-
tic hydrocarbon group having 8 to 15 carbon atoms.
These diamines are mixtures of homologues and isomers of
the diamines corresponding to this formula. Such diamines
are obtained by dinitration, ollowed by hydrogenation of
20 the nitro groups, of hydrocarbons corresponding to the
formula:
R
in which R is as defined above. These hydrocarbons have
a boiling range according to ASTM D 86 of 10-50C within
the temperature range of from 270 C to ioo~c at 1013 mbar.
This invention also pr.ovides a process for the
preparation of such diarnines in which a mixture of homo-
Mo-2325.
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logues and isomers of the above-described hydrocarbons is
converted by nitration in known manner into dinitro com-
pounds corresponding to the formula:
R
02N~} N02
10 and these dinitro compounds are subsequently hydrogenated
to orm the corresponding diamines in known manner.
The diamines thus-produced are particularly useful
as chain lengthening agents for the production of poly-
urethanes by the isocyanate polyaddition process.
The starting materials used in the process of the
present invention are mixtures of alkylbenzenes corre-
sponding to the formula:
in which R represents a saturated, straight-chained ali-
phatic hydrocarbon group having 8-15 (preferably
10-13) carbon atoms.
25 These alkylbenzenes are in the form of a mixture of homo-
logues and isomers, which have a boiling range (according
to ASTM D 86) of 10-50 C, preferably 20-30 C within the
Semperature range of from 270 C to 330 C at 1013 mbar.
It is preferred that the alkylenebenzene mixture be
such that at least 30 volume percent boils at a tempera-
~ure below the middle of the boiling range and at least
30 volume percent boils at a temperature above the middle
of the boiling range.
Mo-2325
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The preparation of such alkylbenzene mixtures may
be carried out by techniques known to those skilled in
the art. ~ne such procedure is alkylation of benzene
with appropriate commercial linear olefin mixtures.
5 Suitable linear olefin mixtures include commercial oligo-
ethylene mixtures,other linear oligoolefins and commercial
linear alkyl chloride mixtures such as those described,
for example, in Kirk-Othmer, Encyclopedia of Chemical
Technology, third edition, Vol. 2, (1978), pages 50 to 61.
In the process of the present invention, conversion
o the alkylbenzenes into the corresponding dinitro
compounds may be carried out by known nitration techniques.
In one such method, 2 to 3 mol of concentrated nitric
acid are added for each mol of alkylbenæene with the
15 temperature being maintained at 10-30C. The nitric acid
used may be in the form o a mixture with concentrated
sul~uric acid (nitrating acid). 95~ of all the nitro
groups in the alkyl-substituted dinitrobenz~nes obtained
by this proces.s are determined by nuclear resonance
20 measurements (NMR)~ to be in the meta-position with
respect to each other. About 10 to 30 wt ~ of the dini-
trated alkylbenzenes should be l-alkyl-2,6-dinitrobenzenes
and about 70 to 90 wt % should be 1-alkyl-2,4-dinitro-
benzenes. This distribution of isomers is not, however,
25 essential to the invention. It would he equally possihle,
for example, to carry out the next stage of the process of the
present invention with dinitrated a~.kylbenzenes in which
the above-mentioned isomers are present in different quan-
titative proportions. For example, the .nitrobenzene could
30 be a 1-alkyl-2,4-dinitrobenzene fr~e from the 2,6-isomer.
Such a dinitrobenzene may be obtained, for example, by a
two-stage nitration of an alkylbenzene in which the 1-
alkyl-4-nitrobenzene obtained as an intermediate stage is
Mo-2325
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first separated from the nitration product an~ the~ di-
nitrated before hydrogenation i~ be~un.
Use of the alkyl benzene mixtures required in the
present invention as starting material yields dinitroalkyl-
5 benzene mixtures in which virtually no troublesome mono-
nitro constituents are present. The absence of such mono-
nitro constituents may be confirmed by determination of the
nitro group content and by thin layer chromatographic
investigations of the products of nitration. These
10 dinitroalkyl benzene mixtures are particularly suitable
for direct conversion to the diamines of the present
invention since they require no elaborate methods of
purification ~e.g. removal of mononitro compounds by
distillation under speciic conditions). Such purifica-
15 tion procedures are generally undesirable because aromaticnitro compounds readily decompose in the presence of heat.
The ne~t stage o the process of th~ present inven-
tion is hydrogenation of the nitro groups to the corre-
sponding primary amino groups. This hydrogenation may be
20 carried out by techniques known to those in the
art. In one such method,~aney nickel is used as a hydro-
genation catalyst, and the reaction is carried out at a
temperature of, ~or example, 20 to 60C and at a hydrogen
pressure of, for example, 20 to 40 bar.
In the thus-produced diamines o the present inven-
tion, the amino groups are in the same position as that
previously occupied by the nitro groups and the R group
is the same as that described ~or the R group in the alkyl-
benzenes used as starting materials.
The diamines of the present invention are liquid at
room temperature, show no tendency to crystallize and
contain no undesirable monofunctional amine constituents.
The compounds according to the invention are therefore
valuable chain lengthening agents for the production of
Mo-2325
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polyurethanes by the isocyanate polyaddition process.
When the diamines of the present invention are used
as chain lengthening agents, they are generally reacted
with isocyanate prepolymers in known manner at an NCO/NH2
5 equivalent ratio of from 0.7:1 to 1.3:1, preferably from
n . g 1 to 1.1:1. The isocyanate prepolymers used are
known reaction products of the diisocyanates used in poly-
urethane chemistry and subequivalent quantities of poly-
hydroxyl compounds. The polyhydroxyl compounds which may
10 be used include polyhydroxypolyesters or polyhydro~y-
polyethers having molecular weights o~ from 300 to 10,000,
preferably from 1000 to 4000, and a hydro~yl functionality
~or average hydroxyl functionality when mixtures of poly-
hydroxyl compounds are used) of from 2 to ~, preferably
15 from 2 to 3. The diamines of the present invention may
also be used in a one shot process for the production of
polyurethanes by adding them to a polyhydroxyl compound or
a mixture o polyhydroxyl compounds (of the type described
above~ and then reacting this mi~ture with known poly-
20 isocyanates at an equivalent ratio of isocyanate groupsto isocyanate-reactive groups rnaintained within the range
of about 0.8:1 to 1.2:1, preferably 1:1. Such a one-
shot process may be carried out with the diamines of the
present invention because the polyureas obtained also
25 have no tende~cy to crystallize so that such a one-shot
process is not accompanied by the unwanted separation of
polyureas. The diamines of the present invention may
also be used as chain lengthening agents in such processes
where any of a variety of known auxiliary agents and addi-
30 tives are used. For example, polyurethane-polyurea foams
may be produced with the aid of known blowing agents.
The Examples which follow serve to illustrate the
present invention. Percentages given are percentages by
weight unless otherwise indicated. Ready-made TLC plates
Mo-2325
:~L2~3'7~
(silica gel 60F-254.of Merck AG) were used for the thin
layer chromatographic investigations.
EXAMPLES
Example 1
A homologous mixture of linear alkylbenzenes in
which the alkyl chains had a length of 10 to 13 C~.atoms,
with an average length of about 12 C-atoms, was used in
this Example. The temperature at which the homologous
mixture boiled (according to ASTM D 86) at 1013 mbar was
10 in the temperature ranqe of about 233-313C. About 50
volume percent had distilled over betw~en 283 and 296 C. The product
obtained was a reaction product of benzene with a mixture
of linear C10-Cl3 olefins.
la) Nitration of the alkyl benzene mixture:
A mixture of 1136 ml of 98% nitric acid and 1584 ml
o~ 96~ sul~uric acid was introduced dropwise with
cooling into 1.97 kg o the above-described alkyl-
benzene mixture at a rate such that the reaction
temperature was maintained at 10 to 15C. After
addition of the acids, the r~:action mixture was
stirred for 3 hours at 25 to 30C. The organic
phase was subsequently pourecl onto 10 kg of ice,
washed with sodium bicarbonate solution until it
was neutral and washed again with water. The srgan-
ic phase was separated and substantially freed from
any residue of water by centrifuying. The liquid
dinitroalkyl benzene mixture obtained was used in
the next reaction stage without further purifica-
tion.
Yield: 2.7 kg; N02 content:- 27.5% (theoretical:
27.4~). No residues of mononitro compounds could
be detected by thin layer chromatographic investi-
gations (diluent 90 parts by weight petroleum ether/
lO.parts by weight ether).
Mo-2325
3'~L~
lb) Hydrogenation of the dinitroalkyl benzene mixture:
672 g of the dinitro compound prepared in la) were
dissolved in 1700 ml of ethanol in a stirrer auto-
clave. 70 g of Raney nickel were added. Stirrin~
was continued at 40C and 20 to 40 bar of hydrogen
pressure until absorption of hydrogen had been
completed. The pressure was then released, the
reaction mixture was filt~red to remove the catalyst,
and the ethanol was distilled off. 550 g of a crude
amine mixture were obtained. The crude amine mix-
ture had a nitrogen content of 10.06% (theoretical:
10.1~). 200 g of the crude amine mixture were
distilled at reduced pressure. 167 g of diamine
mixture (83.5% yield) were obtained as a fraction
boiling at 185 to 20~C/2.1 mbar.
Anal~ is (%):
C H N
Found: 78~6 11.5 10.0
Theoretical: 78.3 11.6 10.1
20 (based on C18H32N2)
Example 2 (Comparison Examp~.e)
2a) Nitration of dodecylbenzene:
Dinitrododecylbenzene was prepared according to
Example V of US Patent 2,934,571. The crude
product had an NO2 content of only 18.6 wt %. The
product obtained after distillation had an NO2
content of 20.0 wt %. Thin layer chromatographic
investi~ation indicated the presence of considerable'
amounts of mononitro compounds, which may be de-
duced from the a~oresaid low NO2 content.
2b) Hydrogenation o~ the'product of nitration:
The nitro compound produced in 2a) was converted in-
to the corresponding amino compound by hydrogenation
according to Example V of US Patent No. 2,986,576.
Mo-2325
73~
--10--
Analysis (%):
C H N
Found: 8104 12.1 7.0
Theoretical: 78.3 11.5 10.1
5 (based on Cl~H32N2)
Example 3
2000 g of a linear polypropylene glycol ether (molec-
ular weight 2000, OH number: 56) and 336 g of 1,6-diiso-
cyanato-hexane were heated together to about 90C and
10 maintained at this temperature until an isocyanate content
of about 3.35% was obtained. 500 g o this isocyanate
prepolymer were briefly degasified at about 55C and
mixed within 30 seconds with 53 g of the diamine mixture
of Example lb). After a casting time of 4,to 5 minutes,
15 the sample in the mold (heated to 100C) was removed after
about 1.5 hours. A flexible elastomer having an elasti-
city of about 28~ (Shore A 40) was obtained after 24 hours'
tempering at 110C.
Example 4 (Comparison E~ample)
500 g of the isocyanate prepc>lymer described in
Example 3 and 53 g o the amine mixture rom Example 2
were combined in the manner described in Example 3. The
product obtained was merely a liquid having a viscosity of
15,Q00 mPa.s/20C.
Mo-2325
