U.S. patent application number 16/884146 was filed with the patent office on 2020-12-17 for method for preparing an amine hydrochloride suspension.
The applicant listed for this patent is Covestro Intellectual Property GmbH & Co. KG. Invention is credited to Frank Gerhartz, Stefan Hirschfeld, Tim Loddenkemper, Michael Merkel.
Application Number | 20200392074 16/884146 |
Document ID | / |
Family ID | 1000004881894 |
Filed Date | 2020-12-17 |
United States Patent
Application |
20200392074 |
Kind Code |
A1 |
Merkel; Michael ; et
al. |
December 17, 2020 |
METHOD FOR PREPARING AN AMINE HYDROCHLORIDE SUSPENSION
Abstract
The invention relates to a method for preparing a suspension of
a hydrochloride of an organic amine, comprising the following steps
of (i) initially charging at least one organic solvent in a
reaction vessel to form a liquid level, (ii) adding hydrogen
chloride, (iii) adding the organic amine, wherein the organic amine
is added below the liquid level present in the reaction vessel and
steps (ii) and (iii) are at least partly carried out
simultaneously. Furthermore, the present invention also relates to
a method wherein the suspension obtained after step (iii) is
reacted in a step (iv) with phosgene to obtain the organic
isocyanate corresponding to the organic amine used, to the
corresponding organic isocyanate and to the use of the organic
isocyanate for producing polyisocyanates.
Inventors: |
Merkel; Michael;
(Dusseldorf, DE) ; Loddenkemper; Tim; (Dormagen,
DE) ; Gerhartz; Frank; (Leverkusen, DE) ;
Hirschfeld; Stefan; (Alpen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Covestro Intellectual Property GmbH & Co. KG |
Leverkusen |
|
DE |
|
|
Family ID: |
1000004881894 |
Appl. No.: |
16/884146 |
Filed: |
May 27, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 263/10 20130101;
C07C 209/74 20130101; C08G 18/758 20130101 |
International
Class: |
C07C 263/10 20060101
C07C263/10; C07C 209/74 20060101 C07C209/74; C08G 18/75 20060101
C08G018/75 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2019 |
EP |
19179482.5 |
Claims
1. A method for preparing a suspension of a hydrochloride of an
organic amine, comprising the following steps: (i) initially
charging at least one organic solvent in a reaction vessel to form
a liquid level, (ii) adding hydrogen chloride, (iii) adding the
organic amine, wherein the organic amine is added below the liquid
level present in the reaction vessel and steps (ii) and (iii) are
at least partly carried out simultaneously.
2. The method according to claim 1, wherein the temperature of the
organic solvent in the reaction vessel prior to step (ii) is
adjusted to -20 to 100.degree. C.
3. The method according to claim 1, wherein step (iii) is carried
out using a dip tube.
4. The method according to claim 1, wherein the at least one
organic solvent is selected from the group consisting of aromatic
hydrocarbons, halogenated aromatic hydrocarbons, particularly
chlorinated aromatic hydrocarbons, esters, ethers, halogenated
hydrocarbons and mixtures thereof.
5. The method according to claim 1, wherein the organic amine is
added as a solution in an inert solvent.
6. The method according to claim 5, wherein the concentration of
the organic amine in the solvent is 5 to 50% by weight, based on
weight of the solution.
7. The method according to claim 1, wherein the substance streams
of hydrogen chloride and organic amine during steps (ii) and (iii)
are in an equivalence ratio to each other of from 1:1 to 10:1.
8. The method according to claim 1, wherein the end concentration
of hydrochloride in the reaction mixture is 5 to 30% by weight.
9. The method according to claim 1, wherein steps (ii) and (iii)
are carried out while stirring with the aid of an aeration stirrer,
paddle stirrer or a dynamic mixer selected from the group
consisting of disperser disks, rotor-stator systems and
combinations thereof.
10. The method according to claim 1, wherein the organic amine is
selected from the group consisting of aromatic amines.
11. The method according to claim 1, wherein the suspension
obtained after step (iii) is reacted in a step (iv) with phosgene
to obtain the organic isocyanate corresponding to the organic amine
used.
12. The organic isocyanate, obtainable by the method according to
claim 11, selected from the group consisting of
1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI),
1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI),
1,3-bis(isocyanatomethyl)benzene (m-XDI), isomers of
bis(isocyanatomethyl)cyclohexane (H6-XDI), isomers of
bis(isocyanatomethyl)norbornane (NBDI),
2,4,4-trimethylhexamethylenediamine,
2,2,4-trimethylhexamethylenediamine and mixtures thereof.
13. In a process for producing polyisocyanates comprising one of
isocyanurate groups, polyisocyanates comprising uretdione groups,
polyisocyanates comprising biuret groups, polyisocyanates
comprising urethane or allophanate groups, polyisocyanates
comprising oxadiazinetrione groups or iminooxadiazinedione groups
and/or uretonimine-modified polyisocyanates, the improvement
comprising including the organic isocyanate according to claim
12.
14. One of polyisocyanates comprising isocyanurate groups,
polyisocyanates comprising uretdione groups, polyisocyanates
comprising biuret groups, polyisocyanates comprising urethane or
allophanate groups, polyisocyanates comprising oxadiazinetrione
groups or iminooxadiazinedione groups and/or uretonimine-modified
polyisocyanates produced by the process according to claim 13.
15. In a process for producing plastics comprising urethane,
thiourethane, isocyanurate, amide and/or urea groups by the
polyisocyanate polyaddition process or for producing light-stable
polyurethane lacquers and coatings, the improvement comprising
including the organic isocyanate according to claim 12.
16. method according to claim 10, wherein the organic amine is
selected from the group consisting of pure isomers or isomeric
mixtures of diaminotoluene, diaminodimethylbenzene,
diaminonaphthalene, diaminobenzene, diaminodiphenylmethane and
mixtures thereof.
17. The method according to claim 10, wherein the organic amine an
aliphatic, cycloaliphatic or araliphatic amine selected from the
group consisting of 1,4-diaminobutane, 1,5-diaminopentane (PDA),
1,6-diaminohexane (HDA), 1,11-diaminoundecane,
1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA),
bis(p-aminocyclohexyl)methane (PACM), 1,5-diamino -2-methylpentane,
2,5-diamino-2,5-dimethylhexane, 1,4-diaminocyclohexane,
2,4-hexahydrotoluylenediamine, 2,6-hexahydrotoluylenediamine
(H6TDA), 1,3-bis(aminomethyl)benzene (m-XDA),
1,4-bis(aminomethyl)benzene (p-XDA), isomers of
bis(aminomethyl)cyclohexane (H6-XDA), tetramethylxylylenediamine
(TMXDA), isomers of bis(aminomethyl)norbornane (NBDA),
neopentanediamine, 2,4,4-trimethylhexamethylenediamine,
2,2,4-trimethylhexamethylenediamine and mixtures thereof
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under the Paris
Convention to EP Serial No. 19179482, filed Jun. 11, 2019, the
entire contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for preparing a
suspension of a hydrochloride of an organic amine, comprising the
following steps of (i) initially charging at least one organic
solvent in a reaction vessel with formation of a liquid level, (ii)
adding hydrogen chloride, (iii) adding the organic amine, wherein
the organic amine is added below the liquid level present in the
reaction vessel and steps (ii) and (iii) are at least partly
carried out simultaneously. Furthermore, the present invention also
relates to a method wherein the suspension obtained after step
(iii) is reacted in a step (iv) with phosgene to obtain the organic
isocyanate corresponding to the organic amine used, to the
corresponding organic isocyanate and to the use of this organic
isocyanate for producing polyisocyanates.
BACKGROUND OF THE INVENTION
[0003] It is known that organic isocyanates can be prepared by
reacting phosgene with the corresponding amines. In particular in
the case of the conversion of aliphatic amines to the corresponding
aliphatic isocyanates, owing to the high reactivity, high contents
of undesired by-products continuously form, for example resinous,
high-boiling compounds or chlorinated compounds, which form by
deamination.
[0004] There has therefore been no lack of attempts to avoid or at
least reduce these problems. For instance, DE 1 593 588 describes
the phosgenation of xylylenediamine, in which hot phosgenation is
operated with an excess of phosgene at 120 to 180.degree. C. and a
pressure of 2 to 5 atu (196 to 490 kPa). Also with this method, at
most ca. 90% of the desired xylylene diioscyanate and
correspondingly 10% and more of undesired by-products are
formed.
[0005] EP 1 908 749 describes a variant of the method in which the
amine in the so-called base phosgenation is not reacted directly
with phosgene. Rather the amine is firstly reacted with hydrogen
chloride to the corresponding amine hydrochloride which is then
phosgenated. It should be noted that using the method according to
the prior art, particularly at amine concentrations above 5% by
weight in the solvent, very highly viscous suspensions are obtained
which have poor flowability and pumping capability and therefore
also poor stirrability. The problem is solved according to the
document mentioned by operating the formation of the hydrochloride
under a pressure which is at least 0.01 MPa above atmospheric
pressure.
[0006] A disadvantage of such a method is operation under positive
pressure which places increased requirements on the apparatus and,
in the case of external leakage, the risk potential increases due
to leaking gaseous hazardous substances.
[0007] DE 69 011 358 also describes a method for preparing xylylene
diisocyanate in which xylylenediamine hydrochloride is reacted with
phosgene in the presence of an ester as reaction solvent. The
xylylenediamine in this case in one embodiment in a first step is
converted to the hydrochloride at a temperature of 30.degree. C. or
less with hydrogen chloride and later phosgenated at 120 to
170.degree.. Owing to the exothermic reaction, strong cooling is
required for this procedure in order to minimize the formation of
carboxamides by aminolysis of the solvent. However, it cannot be
completely prevented. On the other hand, it is recommended not to
lower the temperature below 0.degree. C. such that ultimately only
a narrow process window remains. Furthermore, this method is
limited to the use of esters as reaction solvent wherein the
previously mentioned aminolysis of the solvent occurs as a side
reaction. In a phosgenation commonly preferred chlorinated aromatic
solvents such as chlorobenzene or ortho-dichlorobenene which, owing
to their physical and chemical properties, are particularly
suitable for the preparation of isocyanates by phosgenation of the
corresponding amines, cannot be used in this method.
DETAILED DESCRIPTION OF THE INVENTION
[0008] Proceeding from this prior art, the object of the present
invention was to avoid the known disadvantages of the prior art,
the object of the present invention particularly being to obtain
even at standard pressure or in an unpressurized process and at
temperatures above 30.degree. C., a stirrable and pumpable
suspension comprising the respective hydrochloride of organic
amines. A further object of the invention was the economic,
efficient and simple preparation of aliphatic isocyanates,
preferably aliphatic diisocyanates, by phosgenation of
appropriately prepared amine hydrochlorides which are in
suspension.
[0009] This object was solved according to the invention by the
method for preparing a suspension of a hydrochloride of an organic
amine comprising the following steps: [0010] (i) initially charging
at least one organic solvent in a reaction vessel with formation of
a liquid level, [0011] (ii) adding the organic amine, [0012] (iii)
adding hydrogen chloride, [0013] wherein the organic amine is added
below the liquid level present in the reaction vessel and steps
(ii) and (iii) are at least partly carried out simultaneously.
[0014] The individual steps of the method according to the
invention are described in detail below.
[0015] Step (i) of the method according to the invention comprises
initially charging at least one organic solvent in a reaction
vessel to form a liquid level.
[0016] In the context of the present invention, all organic
solvents that appear suitable to a person skilled in the art for
preparing hydrochlorides of organic amines can generally be
used.
[0017] In accordance with the invention, an aprotic solvent is
preferably used. Particularly preferably, the at least one organic
solvent is selected from the group consisting of aromatic
hydrocarbons, halogenated aromatic hydrocarbons, particularly
chlorinated aromatic hydrocarbons, esters, ethers, halogenated
hydrocarbons and mixtures thereof.
[0018] A particularly preferred aromatic hydrocarbon used in
accordance with the invention is toluene.
[0019] Particularly preferred halogenated hydrocarbons used in
accordance with the invention are selected from the group
consisting of bromobenzene, chlorobenzene, dichlorobenzene, for
example ortho-dichlorobenzene, and mixtures thereof.
[0020] The organic solvents used in accordance with the invention
are very particularly preferably chlorobenzene, dichlorobenzene,
for example ortho-dichlorbenzene, or mixtures thereof.
[0021] The method according to the invention can generally be
carried out in any reactor deemed as suitable to a person skilled
in the art. By means of steps (ii) and (iii), sufficient mixing can
take place. It is evident to a person skilled in the art that the
use of an additional mixing device is not essential but is an
advantageous configuration.
[0022] For example, a stirred vessel is suitable as reactor. A
suitable stirred vessel is described, for example, in DE 19957816
A1. It is preferably a rotationally symmetric stirred vessel with a
vertical main axis. The stirred vessel can have different diameters
along this main axis but is preferably essentially cylindrical. The
base and top can be constructed, for example, with a dish-shaped or
flat end. For temperature control, the stirred vessel can be
provided with heat exchanger pipes, welded-on half-tube profiles, a
double-jacketed and/or a pillow-plate system known to those skilled
in the art or heat exchanger plate system, wherein the heat
exchanger pipes can be configured either internally or
externally.
[0023] Inlet and outlet nozzles can be positioned at any point on
the wall, top and bottom of the stirred vessel. In order to fulfil
the essential feature of the invention that the organic amine is
added below the liquid level present in the reaction vessel, it is
preferred in accordance with the invention that at least one first
feed line for the organic amine or the solution of the organic
amine is configured such that it flows into the reactor in the
lower region. This can be achieved, for example, by means of a
nozzle in the lower region of the reactor which may optionally be
provided with a jet nozzle through which the organic amine or the
solution of the amine can be injected into the reaction mixture. By
means of the addition of the organic amine or the solution of the
amine mentioned above, especially by injection, sufficient mixing
of the suspension can for example already be achieved.
Alternatively or in addition other mixing devices can also be used.
Suitable mixing devices are, for example, stirrers, jet nozzles or
ultrasound mixers. Preference is given to using a stirrer mounted
on a rotating shaft. When using jet nozzles it is conceivable, for
example, to withdraw part of the reaction mixture and feed it again
to the reaction vessel through the jet nozzle or to add the amine
or the amine solution through such a jet nozzle such that there
will automatically be mixing of the reaction mixture.
[0024] In a preferred embodiment is a method for preparing a
suspension of a hydrochloride of an organic amine comprising the
following steps: [0025] (i) initially charging at least one organic
solvent in a reaction vessel to form a liquid level, [0026] (ii)
adding the organic amine, [0027] (iii) adding hydrogen chloride,
[0028] wherein the organic amine is added below the liquid level
present in the reaction vessel and steps (ii) and (iii) are at
least partly carried out simultaneously and the resulting
suspension is intermixed during the amine addition.
[0029] All other embodiments in the description and the patent
claims can be combined with one another as desired and in
particular with the aforementioned embodiment, unless the context
clearly indicates otherwise.
[0030] In a preferred embodiment, the feed line flows into the
reactor via a dip tube such that when carrying out the method
according to the invention, the organic amine or the solution of
the organic amine is passed through the dip tube directly into the
reaction mixture.
[0031] The present invention therefore relates preferably to the
method according to the invention wherein step (iii) is effected
using a dip tube.
[0032] The ratio of the fill height to the diameter of the stirred
vessel in accordance with the invention is preferably from 0.5:1 to
1.5:1. Higher ratios are also possible but generally also require
the use of multi-stage mixing devices, preferably multi-stage
stirring elements. It should be noted that by adding the reactants
in the course of the method, the fill height in the vessel changes.
Particularly preferably, although not mandatory, the process
parameters such as initial fill level, vessel size and metering
amounts are selected such that the ratio of fill height and
diameter of the stirred vessel is always in the range specified
above. If by the addition of the amine the range specified is
breached, it is advantageous to use a multi-stage mixing device,
preferably a multi-stage mixing element, such that the entire
reaction mixture is well-dispersed at all times.
[0033] It is generally advantageous if the fill height of the
solvent initially charged is so high that the mixing device,
preferably the mixing element, is immersed in the liquid such that
from the start good mixing and the highest possible heat transfer
can be provided.
[0034] In accordance with the invention, the hydrogen chloride used
is preferably hydrogen chloride gas. In addition, the reactor is
therefore preferably provided with a second feed line for hydrogen
chloride gas. Various embodiments are available for the gas feed
line. If the hydrogen chloride gas is passed over, i.e. above the
liquid level in the reactor, it is preferable in accordance with
the invention to use a self-aspirating aeration stirrer. More
preferably, the addition takes place via a nozzle in the lower
region of the reactor, i.e. below the liquid level. The addition is
particularly preferably via an inlet pipe which flows into the
reactor below the stirrer, preferably in a gas diffuser, via which
the gas already diffused as much as possible is introduced into the
liquid below the stirrer. Also in this case, particular preference
is given to using a self-aspirating aeration stirrer such that
optimal dispersion of the hydrogen chloride gas introduced results
from the external addition below the stirrer and the diffusion of
the aspirated gas again from the gas space above the liquid. In a
further preferred embodiment of the method according to the
invention, an aeration stirrer with a hollow shaft is used for
introducing the hydrogen chloride gas, wherein preferably
compressed gas is fed to the hollow shaft via the second feed
line.
[0035] Self-aspirating aeration stirrers in accordance with the
invention are understood to mean those stirrers which are driven by
a hollow shaft which have openings in the upper region, i.e. above
the liquid level in the reactor, through which gas is aspirated
from the gas space into the hollow shaft. The aspirated gas is
transported downwards through the hollow cavity and escapes again
through further openings in the stirrer blade elements below the
liquid surface where it is mixed intensively with the liquid.
[0036] For addition of the organic solvent, either the first feed
line can be used or alternatively a further, third, feed line.
Other nozzles can be used for process monitoring, for example by
means of sensors, sight glasses or sampling devices.
[0037] In addition, the reactor used in accordance with the
invention is preferably equipped with a suitable stirrer, for
example an aeration stirrer, paddle stirrer and/or a dynamic mixer
selected from the group consisting of disperser disks, rotor-stator
systems and combinations thereof.
[0038] The present invention therefore preferably relates to the
method according to the invention, wherein steps (ii) and (iii) are
carried out while stirring with the aid of an aeration stirrer, a
paddle stirrer or a dynamic mixer selected from the group
consisting of disperser disks, rotor-stator systems and
combinations thereof.
[0039] The reactor preferably used in accordance with the invention
furthermore also has at least one offgas line. Appropriate suitable
offgas lines are known per se to those skilled in the art.
[0040] The organic solvent which is filled into the reactor in step
(i) according to the invention may in this case already contain
certain concentrations of the organic amine to be reacted. This
concentration is, for example, 5% by weight or less, preferably 3%
by weight or less, particularly preferably 2% by weight or less. If
the organic amine is already present dissolved in the solvent, it
is preferably present in an amount of at least 0.001% by weight.
The organic amine can in accordance with the invention already be
dissolved beforehand in the solvent. Alternatively, the solution is
prepared only in the reaction vessel.
[0041] Particularly preferably however, the at least one organic
solvent, when initially charging in the reactor, is initially free
of organic amine to be reacted except for possible traces that may
occur.
[0042] In the method according to the invention, the temperature of
the organic solvent in the reaction vessel prior to step (ii) is
preferably adjusted to -20 to 100.degree. C., particularly
preferably 20 to 90.degree. C., especially preferably 30 to
90.degree. C.
[0043] Step (ii) of the method according to the invention comprises
the addition of hydrogen chloride.
[0044] Hydrogen chloride (HCl) is known per se to those skilled in
the art and can be added in accordance with the invention as a gas
or in aqueous solution as hydrochloric acid. In accordance with the
invention, hydrogen chloride is preferably added as a gas,
optionally in mixtures with one or more further gases, for example
inert gases such as nitrogen or noble gases, preferably nitrogen.
In the case that hydrogen chloride is added in a mixture with one
or more inert gases, the content of hydrogen chloride in the gas
mixture is preferably 5 to 99% by weight, particularly preferably
50 to 99% by weight, especially preferably 80 to 99% by weight.
[0045] Methods for preparing hydrogen chloride are known per se to
those skilled in the art, for example it can be produced from the
elements in a chlorine detonating gas reaction or is obtained as
by-product in the chlorination of organic compounds.
[0046] Hydrogen chloride is added in gaseous form in accordance
with the invention preferably at a temperature of -20.degree. C. to
100.degree. C., particularly preferably 10.degree. C. to 50.degree.
C.
[0047] In the possible case according to the invention that organic
amine is already in the reaction vessel, it is advantageous to
initially meter in hydrogen chloride in an amount that is
sufficient to fully convert the organic amine initially charged to
the corresponding hydrochloride, before starting metering in
further organic amine according to step (iii).
[0048] It is also possible in accordance with the invention to
begin the metering in of the hydrogen chloride at the same time as
metering in the organic amine (step (iii)). Owing to the higher
risk of agglomerate formation in this embodiment, either the
hydrogen chloride gas can be metered in in accordance with the
invention in higher excess based on the amine, or after addition of
the amine is complete further hydrogen chloride is added until the
total amount of organic amine has been converted to the
hydrochloride. In this case, a higher excess preferably signifies
an equivalence ratio of HCl to amine of from 1.1:1 to 20,
particularly preferably from 1.2:1 to 5:1.
[0049] The hydrogen chloride gas is preferably introduced below the
liquid level in the reactor. The hydrogen chloride gas is
particularly preferably introduced below the mixing device,
preferably the mixing element, especially preferably the addition
being carried out through a gas diffuser below the mixing device,
preferably the mixing element.
[0050] The gas feed device is preferably positioned such that, even
in the case of thrombus formation, the feed always takes place in
the liquid and not in the gas space.
[0051] Step (iii) of the method according to the invention
comprises the addition of the organic amine.
[0052] The organic amines used can in principle be all compounds
having primary amino groups known to those skilled in the art.
However, in accordance with the invention, preference is given to
those compounds having at least 2, particularly preferably 2 or 3
NH.sub.2 groups which may be bonded aliphatically,
cyclopaliphatically, araliphatically or aromatically. In accordance
with the invention, very particular preference is given to those
amines having 2 aliphatically, cycloaliphatically and/or
araliphatically bonded NH.sub.2 groups.
[0053] Suitable aromatic amines are, for example, selected from the
group consisting of pure isomers or isomeric mixtures of
diaminotoluene, diaminodimethylbenzene, diaminonaphthalene,
diaminobenzene, diaminodiphenylmethane and mixtures thereof.
Particularly preferred aromatic amines are selected from the group
consisting of 2,4-diaminotoluene, 2,6-diaminotoluene,
1,5-diaminonaphthalene, p-phenylenediamine and mixtures
thereof.
[0054] Suitable aliphatic, cycloaliphatic or araliphatic amines
are, for example, selected from the group consisting of
1,4-diaminobutane, 1,5-diaminopentane (PDA), 1,6-diaminohexane
(HDA), 1,11-diaminoundecane,
1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA),
bis(p-aminocyclohexyl)methane (PACM), 1,5-diamino-2-methylpentane,
2,5-diamino-2,5-dimethylhexane, 1,4-diaminocyclohexane,
2,4-hexahydrotoluylenediamine, 2,6-hexahydrotoluylenediamine
(H6TDA), 1,3-bis(aminomethyl)benzene (m-XDA),
1,4-bis(aminomethyl)benzene (p-XDA), isomers of
bis(aminomethyl)cyclohexane (H6-XDA), tetramethylxylylenediamine
(TMXDA), isomeren of bis(aminomethyl)norbornane (NBDA),
neopentanediamine, 2,4,4-trimethylhexamethylenediamine,
2,2,4-trimethylhexamethylenediamine and mixtures thereof.
[0055] The present invention therefore preferably relates to the
method according to the invention, wherein the organic amine is
selected from the group consisting of aromatic amines, preferably
selected from the group consisting of pure isomers or isomeric
mixtures of diaminotoluene, diaminodimethylbenzene,
diaminonaphthalene, diaminobenzene, diaminodiphenylmethane and
mixtures thereof, aliphatic, cycloaliphatic or araliphatic amines,
preferably selected from the group consisting of 1,4-diaminobutane,
1,5-diaminopentane (PDA), 1,6-diaminohexane (HDA),
1,11-diaminoundecane,
1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA),
bis(p-aminocyclohexyl)methane (PACM), 1,5-diamino-2-methylpentane,
2,5-diamino-2,5-dimethylhexane, 1,4-diaminocyclohexane,
2,4-hexahydrotoluylenediamine, 2,6-hexahydrotoluylenediamine
(H6TDA), 1,3-bis(aminomethyl)benzene (m-XDA),
1,4-bis(aminomethyl)benzene (p-XDA), isomers of
bis(aminomethyl)cyclohexane (H6-XDA), tetramethylxylylenediamine
(TMXDA), isomers of bis(aminomethyl)norbornane (NBDA),
neopentanediamine, 2,4,4-trimethylhexamethylenediamine,
2,2,4-trimethylhexamethylenediamine and mixtures thereof.
[0056] In accordance with the invention, especially preferred
organic amines are selected from the group consisting of
1,5-diaminopentane (PDA), 1,6-diaminohexane (HDA),
1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA),
1,3-bis(aminomethyl)benzene (m-XDA), isomers of
bis(aminomethyl)cyclohexane (H6-XDA), isomers of
bis(aminomethyl)norbornane (NBDA),
2,4,4-trimethylhexamethylenediamine,
2,2,4-trimethylhexamethylenediamine and mixtures thereof.
[0057] In step (iii) of the method according to the invention, the
organic amine or the mixture comprising more than one organic amine
can be added without solvent or dissolved in at least one solvent.
Suitable solvents are all solvents known per se to those skilled in
the art which are inert to the prevailing reaction conditions. The
at least one organic amine is preferably dissolved in the same
solvent or solvent mixture which is initially charged in the
reactor. Particularly preferred solvents to dissolve the at least
one organic amine are therefore selected from the group consisting
of aromatic hydrocarbons, halogenated aromatic hydrocarbons,
particularly chlorinated aromatic hydrocarbons, esters, ethers and
halogenated hydrocarbons and mixtures thereof. Particularly
preferred aromatic hydrocarbons used in accordance with the
invention are selected from the group consisting of toluene,
bromobenzene, chlorobenzene, dichlorobenzene, for example
ortho-dichlorobenzene, and mixtures thereof. In accordance with the
invention, particular preference is given to using chlorobenzene,
dichlorobenzene or mixtures thereof.
[0058] In accordance with the present method, the organic amine is
preferably used dissolved in at least one solvent, preferably
selected from the group consisting of aromatic hydrocarbons,
halogenated aromatic hydrocarbons, particularly chlorinated
aromatic hydrocarbons, esters, ethers and halogenated hydrocarbons
and mixtures thereof, especially selected from the group consisting
of toluene, bromobenzene, chlorobenzene, dichlorobenzene, for
example ortho-dichlorobenzene, and mixtures thereof.
[0059] The organic amine is preferably added as a solution in an
inert solvent. The concentration of the organic amine in the
solvent is preferably 5 to 50% by weight, particularly preferably
10 to 30% by weight, based in each case on the solution. In this
manner, in accordance with the invention, the formation of
agglomerates due to local superelevated concentrations of the
organic amine can be further minimized.
[0060] A feature essential to the invention is that the organic
amine is added below the liquid level present in the reaction
vessel, wherein the input is preferably effected via a dip tube. In
accordance with the invention, below the liquid level present in
the reaction vessel signifies that preferably the feed is effected
continuously into the reaction mixture in the reaction vessel.
[0061] A further feature essential to the invention is that steps
(ii) and (iii) are at least partly, preferably completely, carried
out simultaneously. In the context of the present invention, at
least partly signifies that the addition is effected simultaneously
preferably to an extent of 40 to 100%, particularly preferably 80
to 99%, particularly preferably 80 to 95%. That means that this
mass fraction of the total amount of the organic amine to be added
is is passed into the reactor while also hydrogen chloride is
passed into the reactor in order to react with the organic amine to
the corresponding hydrochloride. However, it is also possible in
accordance with the invention that organic amine or hydrogen
chloride are partly initially charged and then the simultaneous
addition is carried out.
[0062] The metering in of the organic amine and hydrogen chloride
is carried out in a preferred embodiment of the method according to
the invention such that the hydrogen chloride is added in
stoichiometric excess based on the amino groups of the organic
amine metered in. In this manner, it is prevented that the organic
amine accumulates to undesired high concentrations and a finely
divided suspension is obtained.
[0063] While both reactants are metered in, the substance streams
of hydrogen chloride and organic amine are preferably at an
equivalence ratio to each other of from 1:1 to 10:1, particularly
preferably 1:1 to 3:1, especially preferably 1.05:1 to 1.8:1.
[0064] The total amount of hydrogen chloride metered in is
preferably sufficient to fully convert the organic amine, i.e. to
an extent of more than 99%, preferably more than 99.5% and
particularly preferably more than 99.9% to the hydrochloride.
[0065] The end concentration of hydrochloride in the reaction
mixture is preferably 5 to 30% by weight, particularly preferably 7
to 25% by weight, especially preferably 10 to 20% by weight. The
value for the end concentration of hydrochloride is calculated from
the mass of the organic amine present in the reactor under
consideration of the molecular weight increase due to formation of
the hydrochloride, wherein a complete conversion of all amino
groups to the corresponding ammonium chloride groups is assumed,
based on the total mass of the reactor content. In the preferred
concentration range specified in accordance with the invention, a
particularly advantageous compromise of high efficiency of the
method and good handling of the suspension is available.
[0066] After the preparation of the hydrochloride according to the
invention comprising steps (i), (ii) and (iii), the suspension
obtained after step (iii) is preferably reacted in a step (iv) with
phosgene to obtain the organic isocyanate corresponding to the
organic amine used.
[0067] The present invention therefore preferably relates to the
method according to the invention wherein the suspension obtained
after step (iii) is reacted in a step (iv) with phosgene to obtain
the organic isocyanate corresponding to the organic amine used.
[0068] The suspension of hydrochloride obtained by the method
according to the invention can be subsequently converted to the
corresponding isocyanate by reaction with phosgene. For this
purpose, the suspension can either remain in the reaction vessel or
be transferred to another reaction vessel.
[0069] For the phosgenation step, the same types of reaction
vessels can be used as previously described for the preparation of
the hydrochloride suspension. The suspension is then heated to a
temperature of 120 to 200.degree. C. with introduction of phosgene,
optionally diluted with an inert gas or gas mixture, for example
nitrogen or noble gases. Particularly for less thermally stable
isocyanates, it is preferable that this temperature is 120 to
170.degree. C., particularly preferably 120 to 160.degree. C.
[0070] In accordance with the invention therefore, the phosgenation
is preferably carried out at a temperature of 120 to 170.degree.
C., particularly preferably 130 to 160.degree. C. The phosgenation
can be carried out either at atmospheric pressure or at positive
pressure. The pressure is preferably 1 to 10 bar(a), particularly
preferably 1 to 5 bar(a).
[0071] Phosgene is preferably used in stoichiometric excess for the
phosgenation. Higher excesses act positively on the reaction rate
and therefore the duration of the reaction but naturally impair the
economy of the method. Typically therefore the reaction is carried
out using a phosgene excess of 100 to 500%, preferably 150 to 300%.
Optionally, an inert gas can also be introduced into the reaction
mixture.
[0072] The phosgene is added to the hydrochloride suspension,
preferably by introducing gaseous phosgene. The phosgene is
preferably introduced below the liquid level in the reactor. The
phosgene is particularly preferably introduced below the mixing
device, especially preferably the addition being carried out
through a gas diffuser below the mixing device. Aeration stirrers
with hollow shaft are preferably used as mixing device as already
described above.
[0073] In an alternative embodiment, the phosgene is introduced
into the reactor as a solution in an inert solvent. The same
solvent is preferably used for this purpose in which the suspension
of the hydrochloride is also present.
[0074] In a further alternative embodiment, it is also possible to
initially charge a phosgene solution in a reaction vessel and to
add the hydrochloride suspension prepared according to the
invention to this solution.
[0075] It can be advantageous to flush the feed lines for amine
and/or hydrogen chloride, before and/or after the reaction, with
solvent and/or inert gas, preferably nitrogen.
[0076] After completion of the reaction, i.e. at largely complete
conversion, i.e. preferably 80 to 99%, particularly preferably 90
to 99% of the theoretical value, of the hydrochloride to the
corresponding isocyanate, excess phosgene and hydrogen chloride are
preferably removed from the reaction mixture. For this purpose,
generally an inert gas, preferably nitrogen, is passed through the
reaction mixture. Optionally, phosgene and hydrogen chloride can be
removed or be assisted also by applying a negative pressure. If
needed, filtration can be carried out in order to remove solids
possibly present such as unreacted hydrochloride particles.
[0077] Subsequently, the reaction product is preferably processed
according to methods known from the prior art, i.e. it is
preferably purified in a multi-stage vacuum distillation. In
particular, in this distillative processing, the isocyanate is
freed from solvent, chlorinated by-products and higher-boiling
residues.
[0078] Since solvents are preferably used for preparing isocyanates
which have a lower boiling point than the respective isocyanate,
the distillation preferably comprises solvent removal. In this
distillation step, low-boiling secondary components, particularly
chlorinated low-boiling secondary components, are removed. The
solvent can, optionally after further purification steps, be fed
back again into the process.
[0079] In addition, such a purification process preferably
comprises a purification by distillation to separate the isocyanate
from high-boiling residue. All distillation steps are preferably
carried out under reduced pressure in order to reduce the
temperatures required for distillation and thus the thermal stress
on the product. In particular, this distillation step is carried
out at a pressure of 5 to 50 mbar(a) and a bottom temperature of 90
to 250.degree. C., preferably 120 to 170.degree. C. When necessary,
in order to suppress the formation of uretdiones in the distillate,
the distillate is preferably cooled as rapidly as possible to
temperatures below 90.degree. C., preferably below 80.degree. C.
This can be achieved, for example, by quenching the distillate,
especially by mixing with product already cooled.
[0080] After step (iv) of the method according to the invention,
the organic isocyanate is preferably obtained, in particular
1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI),
1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI),
1,3-bis(isocyanatomethyl)benzene (m-XDI), isomers of
bis(isocyanatomethyl)cyclohexane (H6-XDI), isomers of
bis(isocyanatomethyl)norbornane (NBDI),
2,4,4-trimethylhexamethylenediamine,
2,2,4-trimethylhexamethylenediamine or mixtures thereof, in pure
form, i.e. at a purity of at least 99.5%.
[0081] The present invention also relates to an organic isocyanate
obtainable by the method according to the invention. In particular,
the present invention relates to an organic isocyanate obtainable
by the method according to the invention selected from the group
consisting of 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane
(HDI), 1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane
(IPDI), 1,3-bis(isocyanatomethyl)benzene (m-XDI), isomers of
bis(isocyanatomethyl)cyclohexane (H6-XDI), isomers of
bis(isocyanatomethyl)norbornane (NBDI),
2,4,4-trimethylhexamethylenediamine,
2,2,4-trimethylhexamethylenediamine and mixtures thereof.
[0082] The present invention also relates to the use of the organic
isocyanates according to the invention for producing
polyisocyanates comprising isocyanurate groups, polyisocyanates
comprising uretdione groups, polyisocyanates comprising biuret
groups, polyisocyanates comprising urethane or allophanate groups,
polyisocyanates comprising oxadiazinetrione groups or
iminooxadiazinedione groups and/or uretonimine-modified
polyisocyanates.
[0083] Such polyisocyanates based on organic isocyanates according
to the invention or the organic isocyanate itself can be used, for
example, for producing plastics comprising urethane, thiourethane,
isocyanurate, amide and/or urea groups by the polyisocyanate
polyaddition process. Such polyisocyanate mixtures are particularly
used for producing light-stable polyurethane lacquers and
coatings.
EXAMPLES
Comparative Example 1
[0084] A stirred vessel composed of glass with a heat-controlled
jacket and a length-to-internal diameter ratio of 1.2 was equipped
with a paddle stirrer, where the stirrer paddle diameter to
internal diameter of the reactor was at a ratio of 0.75. The
stirred vessel was charged with 5 g of monochlorobenzene. At the
same time 1 kg of m-xylylenediamine in 4 kg of o-dichlorobenzene
was initially charged in a raw material reservoir. At the same
time, with stirring at atmospheric pressure, hydrogen chloride gas
was passed into the reactor via a gas inlet tube and the amine
solution provided in the raw material reservoir was added, wherein
the amine solution was added from above, i.e. above the liquid
level in the stirred vessel. The metered addition was effected over
2 h at a metered addition rate of 321 g/h for hydrogen chloride and
2.5 kg/h for the amine solution. The amine feed was then terminated
and hydrogen chloride was further fed for 60 min at a metered
addition rate of 150 g/h. The temperature in the stirred vessel
during the entire procedure was maintained at 25.degree. C. by
means of the heat-controlled jacket.
[0085] Thick sticky deposits were evident on the wall of the
stirred vessel, on the stirrer and on the inlet nozzle of the amine
solution. The reaction mixture obtained comprised large solid
agglomerates with diameters >1 mm, which settled out. The
resulting reaction mixture was therefore no longer suitable for
being stirred or pumped.
Example 2 (According to the Invention)
[0086] The stirred vessel according to comparative example 1 was
modified so that now the amine solution was fed directly into the
reaction mixture through a dip tube and therefore below the liquid
level. In addition, after termination of the amine addition,
hydrogen chloride was further fed for 30 minutes at a metered
addition rate of 150 g/h. The experiment of comparative example 1
was repeated under otherwise unmodified conditions. The temperature
in the stirred vessel was maintained at 25.degree. C. by means of
the heat-controlled jacket.
[0087] There were only minor deposits on the wall of the stirred
vessel. The stirrer and the dip tube for feeding were free of
adhesions. The resulting suspension could be stirred and pumped but
still comprised relatively large solid particles but the size of
which was below 1 mm in diameter.
Example 3 (According to the Invention)
[0088] For a further experiment, the stirred vessel was again
modified by replacing the paddle stirrer with an aeration stirrer.
The experiment of example 2 (according to the invention) was
repeated, wherein now the hydrogen chloride was introduced through
the aeration stirrer. In addition, the reactor was preheated to
35.degree. C. by the heat-controlled jacket and was maintained at
this temperature during addition of the reactants. After completion
of the experiment, only small deposits were again observed on the
wall of the stirred vessel, while the stirrer and the dip tube were
free of deposits. The resulting suspension was homogeneous,
finely-divided and could be stirred and pumped.
Example 4 (According to the Invention)
[0089] The experiment of example 3 (according to the invention) was
repeated, wherein contrary to the conditions in example 3, the
reactor was preheated to 80.degree. C. by the heat-controlled
jacket and was maintained at this temperature during the addition
of the reactants. This again resulted in a homogeneous
finely-divided, stirrable and pumpable suspension and also deposits
on the wall of the reactor could be further minimized.
Example 5 (According to the Invention)
[0090] The method was as in example 4 but an isomeric mixture of
2,2,4- and 2,4,4-trimethylhexamethylenediamine was used as amine.
This was placed in the raw material reservoir as a 20% by weight
solution in monochlorobenzene. The temperature was again regulated
to 80.degree. C. and the metered addition rate was 2.5 kg/h for the
amine solution and 275 g/h for hydrogen chloride. After 2 hours,
the metered addition of amine was terminated and hydrogen chloride
was further fed for 30 min at a metered addition rate of 100 g/h. A
homogeneous finely-divided, stirrable and pumpable suspension was
again obtained. Deposits did not occur.
Comparative Example 6
[0091] In deviation from example 5, in comparative example 6 the
reactor was initially charged with 10 kg of a 10% solution of the
isomeric mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine
in monochlorobenzene and temperature-controlled at 25.degree. C.
Then, with vigorous stirring, hydrogen chloride gas was introduced
over 2.5 h at a metered addition rate of 275 g/h. There were heavy
deposits on walls and stirrers and relatively large solid
agglomerates with diameters >1 mm formed, which settled on the
bottom of the vessel.
Example 7 (According to the Invention)
[0092] In the raw material reservoir, 900 g of isomeric mixture of
2,2,4- and 2,4,4-trimethylhexamethylenediamine were initially
charged in 4 kg of monochlorobenzene. In the stirred vessel, a
further 100 g of the amine were initially charged in 5 kg of
monochlorobenzene. The reaction mixture was heated to 60.degree. C.
and while stirring initially 70 g of hydrogen chloride were added
through the aeration stirrer. Only then was the simultaneous
metered addition of the amine solution and further hydrogen
chloride begun. The metered addition rates were 2.45 kg/h for the
amine solution, which was fed in accordance with the invention
through a dip tube below the liquid level and 250 g/h for the
hydrogen chloride. After 2 hours, the addition of amine was
terminated and hydrogen chloride was further metered in for 30 min
at a reduced metered addition rate of 100 g/h. After completion of
the experiment, only small deposits were again observed on the wall
of the stirred vessel, while the stirrer and the dip tube were free
of deposits. The resulting suspension was homogeneous,
finely-divided and could be stirred and pumped.
Example 8 (According to the Invention)
[0093] In a stirred vessel modified as described in example 3, 5000
g of monochlorobenzene were initially charged and the reactor was
preheated to 70.degree. C. by means of the heat-controlled jacket
and maintained at this temperature during addition of the
reactants. A solution of 1000 g of aniline in 4000 g of
monochlorobenzene was added as amine solution from the raw material
reservoir via the dip tube. Hydrogen chloride gas was introduced
through the aeration stirrer. The metered addition rates were 2
kg/h for the amine solution and 500 g/h for hydrogen chloride.
After 2.5 h all the amine had been added and further hydrogen
chloride was introduced for 30 minutes at a metered addition rate
of 100 g/h. A homogeneous finely-divided, stirrable and pumpable
suspension was obtained. Deposits did not occur.
Example 9 (According to the Invention)
[0094] The experiment of example 5 was repeated wherein, instead of
o-dichlorobenzene, in this case monochlorobenzene was initially
charged and the amine solution was added in o-dichlorobenzene.
Other conditions remained unchanged. A homogeneous finely-divided,
stirrable and pumpable suspension was again obtained. Deposits did
not occur.
* * * * *