Note: Descriptions are shown in the official language in which they were submitted.
Mo-2119
~1- PU-109
2,2,q,4-TETR~ALKYL-1,3-CYCLOBUTANEDIOL
~ODIFIED DIPHENYLMETHANE DIISOCYANATE
BAC~GROUND OF THE INVENTIOM
This invention relates to organic diisocyanates and
mixtures of organic diisocyanates based on 2,2'-, 2,4'-
and/or 4,4'-diphenylmethane diisocyanates which are liquid
at room temperature. The invention also relates to a process
for preparing these diisocyanates.
Diisocyanates which are liquid at room temperature
10 have numerous advantages over solid diisocyanates because they
are easier to mix and work with. Diisocyanates, however, which
are liquid at room temperature, are as a rule physiologically
harmful because of their high vapor pressure and Call only be
handled if certain precautions are taken. For this reason,
15 various attempts have been made to start with diisocyanates
that are solid at room temperature and convert these into
the liquid form by certain measures. However, one usually
obtains isocyanates with lligh functionality, i.e., tri-
or polyisocyanates or higher molecular weight diisocyanates
20 or a combination of these~
The most important diisocyanates which are solid at
room temperature and which are readily available on a
large commercial scale are 4,4'-diphenylmethane diisocyanate
and the 2,4'-isomer thereof which melt at 39C and 34.5C,
25 respectively. Attempts have been made also to liquefy the
4,4'-diphenylmethane diisocyanate isomer. Thus, for
example, according to U.S. Patent 3,152,162, 4,4'-diphenyl-
methane diisocyanate is heated at temperatures above 150C
to affect a partial carbodiimization of the isocyanate.
30 The isocyanate groups still present partly react with the
resulting carbodiimide groups to form uretone imine. The
resultant liquid products are not diisocyanates but are
polyisocyanates. This manifests itself in the reaction
of the products with bifunctional low molecular weight or
35 higher molecular weight hydroxyl compounds, the reaction
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leading not to soluble linear ~roducts but to insoluble
cross-linked products.
It is known from U.S. Patent 3,644,457 to react
4,4'- and/or 2,4'-diphenylmethane diisocyanate with a
branched aliphatic dihydroxy compound which yields a
product which is liquid at room temperature.
It is therefore an object of this invention to
provide improved liquid organic diisocyanates which are
liquid at room temperature. ~nother object of this invention
is to provide a mixture or diphenylmethane diisocyanates
which i's liquid at room temperature. A further object of
this invention is to provide organic diisocyanates which
remain liquid even on prolonged storage at low temperatures.
Still another object of this invention is to provide an
improved process for preparing liquid organic diisocyanates.
DESCRIPTION OF THE INV~NTION
The instant invention is directed to a process for
preparing a liquid modified diphenylmethane diisocyanate
comprising reacting a 2,2,4,4-tetraalkylcyclobutanediol
and preferably, 2,2,4,4-tetramethylcyclobutanediol, with
diphenylmethane diisocyanate at a temperature between about
40 to 120C, preferably between 40 to 100C, more preferably
be~ween 45 to 80C, and most preferably between 50 to 60C
in such a ratio as to produce a product having a weight
percent NCO value in the range of 20 to 30%, and preferably
in the range of 21 to 27%. In general, the weight ratio of
diphenylmethane diisocyanate to diol will be from 15:1 to 5:1
and is preferably from 10:1 to 6:1. The liquid modified
diphenylmethane diisocyanate may also be prepared as a concen-
trate (that is, with a lower percent NCO) and diluted with
additional diphenylmethane diisocyanate to adjust the ,
percent NCO to the desired value.
The instant invention is a'lso directed to d'iisocyanatecompounds which are both stable and liquid at room temperature,
prepared by reacting a diphenylmethane diisocyanate with
a 2,2,4,4-tetraalkylcyclobutanediol at a temperature of
from about 40C to about 120C in such a ratio as to afford
A''~o-A!il 9
PU-109
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a product having a weight percent NCO value in the range
of 20 to 30%. As used herein, the term "diphenylmethane
diisocyanate" is defined as 2,2'-diphenylmethane diisocyanate,
2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane
diisocyanate and mixtures thereof.
Most short chain diols, such as 1,4- and 1,3-butane-
diol, ethylene glycol, and the like when reacted with
diphenylmethane diisocyanate result in solids at room
temperature. In contrast, the instant li~uid modified
10 diphenylmethane diisocyanate remains a liquid at 25C.
The process of the instant invention may also be used to
increase the hard block concentration via the prepolymer
of the RIM formulation instead of increasing the butanediol
concentration in the polyol side which leads to mixing
15 problems. Heat sag values are specially improved when the
instant prepolymers are used. ;
The liquid diisocyanates which can be prepared
according to the invention, preferably from 4,4'- and/cr
2,4'-diphenylmethane diisocyanate, have a very low viscosity
20 and can therefore be processed very easily. For example,
they can be cast or metered through pumps. Additionally,
they have a very low vapor pressure and are therefore less
physiologically harmful.
The process may be carried out by introducing the
25 2,2,4,4-tetraalkylcyclobutanediol into the diisocyanate at
temperatures of about 40 to about 120C with stirring. The
isocyanate content of the products of the process amounts
to about 20% by weight NCO to about 30~ by weight NCO,
and preferably 21 to 27%.
2,2,4,4-tetraalkylcyclobutanediols wherein each alkyl
group, which may be the same or different, contains from
1 to 7 carbon atoms are preferably used. The presently
preferred compound is 2,2-,4,4-tetramethylcyclobutanediol.
It is also possible to blend the tetraalkylcyclo-
35 butanediol of the present invention with other hydroxy
functional materials. If the hydroxyl functional material
Mo-2119
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to be blended is of the type which forms liquid products i
with diphenylmethane diisocyana-te ~such as those described
in U.S. Patents 3,644,457; 4,115,429 and 4,118,411), as
little as 10% by weight (based on the weight of the tetra-
alkylcyclobutanediol and other hydroxy functional materials)of the tetraalkylcyclobutanediol can be used. Where the
hydroxy func-tional material does not normally form a li~uid
product with diphenylmethane diisocyanate, the tetraalkyl-
cyclobutanediol should constitute at least 50% by weight
10 of the mixture of the tetraalkylcyclobutanediol with other
hydroxy functional materials. It is generally preferred,
however, to use the tetraalkylcyclobutane alone.
The products of the process can be used for all sorts
of different polyaddition reactions in the lacquer and
15 plastics industry. For example, they may be used in the
production of polyurethane foams or polyurethane elastomers
which are in turn useful for the preparaiion of cushions
or cast gear wheels, respectively. The invention is further
illustrated by the following Example.
EXAMPLE
E~AMPLE 1
About 850 g of 4,4'-diphenylmethane diisocyanate
(97% 4,4'-MDI and 3% 2,4'-MDI) are melted and mixed a~
about 58 to 73C with about 85.9 g of 2,2,4,4-tetramethyl-
25 cyclobutanediol with stirring for about 3 hours. The
resulting product hadan NCO value of 25%. The viscosity
was 367 cPs at 25C.
Although the invention has been described in
considerable detail in the foregoing, it is to be understood
30 that such detail is solely for the purpose of illustration
and that many variations can be made by those skilled in
the art without departing from the spirit and scope of
the invention except as set forth in the claims.
Mo-2119
PU-109
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