CA2117928A1 - Process for preparing trans-trans-4,4'-diamino-dicylcohexy lmethane - Google Patents

Process for preparing trans-trans-4,4'-diamino-dicylcohexy lmethane

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Publication number
CA2117928A1
CA2117928A1 CA002117928A CA2117928A CA2117928A1 CA 2117928 A1 CA2117928 A1 CA 2117928A1 CA 002117928 A CA002117928 A CA 002117928A CA 2117928 A CA2117928 A CA 2117928A CA 2117928 A1 CA2117928 A1 CA 2117928A1
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Prior art keywords
trans
diimine
diaminodicyclohexylmethane
solution
separating
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CA002117928A
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French (fr)
Inventor
Hartmut Nefzger
Claus-Dieter Eisenbach
Christian Steinlein
Karl Fischer
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Bayer AG
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Individual
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C211/00—Compounds containing amino groups bound to a carbon skeleton
    • C07C211/33—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of rings other than six-membered aromatic rings
    • C07C211/34—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of rings other than six-membered aromatic rings of a saturated carbon skeleton
    • C07C211/36—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of rings other than six-membered aromatic rings of a saturated carbon skeleton containing at least two amino groups bound to the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
    • C07C209/82—Purification; Separation; Stabilisation; Use of additives
    • C07C209/86—Separation
    • C07C209/88—Separation of optical isomers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
    • C08G18/75—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic
    • C08G18/758—Polyisocyanates or polyisothiocyanates cyclic cycloaliphatic containing two or more cycloaliphatic rings
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
    • C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
    • C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
    • C08G69/265—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids from at least two different diamines or at least two different dicarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/44—Polyester-amides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
    • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1003—Preparatory processes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2601/00—Systems containing only non-condensed rings
    • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
    • C07C2601/14—The ring being saturated

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

A PROCESS FOR THE PREPARATION OF
TRANS,TRANS-4,4'-DIAMINO-DICYCLOHEXYLMETHANE
ABSTRACT OF THE DISCLOSURE
The present invention relates to a new and easier process for the preparation of 4,4'-diaminodicyclohexylmethane having a high content of the trans,trans-isomer. This process comprises 1) condensing an isomeric mixture of 4,4'-diamino-dicyclohexylmethane with carbonyl compounds in the presence of a non-polar organic solvent which forms an azeotrope with water, which is heated to remove the reaction water and form the corresponding diimine, 2) isomerizing the solution of diimine by adding at least one base, and at least one polyether and/or c) a crown ether, to the diimine solution and allowing these to act on the diimine for at least 3 hours at room temperature or at an elevated temperature, 3) separating the trans,trans-4,4'-diaminodicyclohexylmethane diimine which crystallizes out of the solution, and 4) hydrolyzing it in a known manner to yield trans,trans-4,4'-diaminodicyclohexylmethane.
It is also possible to add seed crystals of the corresponding trans,trans-4,4'-diaminodicyclohexylmethane diimine to the isomerized solution of diimine, or simultaneously while separating the diimine which crystallizes out of the solution.
Other variations of the process are also disclosed.

Description

, ;.~ h ~1 .'17 ~ ~ 8 Mo-4113 LeA 29,953 A PROCESS FOR PREPARING
TRANS-TRANS-4 4'-DIAMINO-ûICYCLOHEXYLMETHANE
BACKGRQl)ND ~ETHE INVENTION
Segmented polyurethanes containing 4,4'-diisoGyanatodiphenyl-methane (MDI) as the diisocyanate compon~nt are industrially important PU elastomers. MDI is obtained on an industrial scale by r~acting 4,4'-diaminodiphenylmethane (MDA), the so-oalled phenyl base, with 5 phosgene. Structurally similar and also useful as a diisocyanate, 4,4'-diisocyanatodicyclohexylmethane (HMDI) is accessible on an industrial scale by hydrogenation of the phenyl base, to give 4,4'-diaminodi,-.yolo-hexylmethane (HMDA), and subsequent reaction with phosgene.
Hydrogenation of the phenyl base leads to a mixture of the three 10 possi~le configurational isomers (trans,trans; cis,trans and cis,cis). The resulting HMDA isomer composition depends on the catalyst used and the reaction conditions (pressure, temperah~re, etc.). IVlodern processes produce a cis,cis fraction of less than 10%, the yield of trans,trans isomer which can be achieYed is about 50%.
The mat~rial properties of polyureth~nes based on HMDI are strongly dependent on the isomeric ratio. High trans,trans fractions 9enefally produce better mat~rial properti~s, such as e.g. higher working ;
temperatures and better resistance to solv~nts. The elastomers are ~enerally characterized by their high optical transparency. They are 20 stable to light and hydrolysis and ~ossess ~ood physical and mechanical prop~rties.
Tests on the HMDI/1 ,4-butanediol/polyoxytetramethylene system using different proportions of trans,trans isomers ~20~o, 40%, 60%, 80/~
and 100% of trans,trans fraction) have shown that the solvent resistance 2~ :

Le A 29 953 - Foreign Countries : ~

n, ~
~ ,~ .; I .~

of the elastomers improves greatly with increasing trans,trans fractions.
The mechanicai and thermal prop~rties of polyurethane elastomers which are prepared with isomerically pure trans,trans-HMDI as the diisocyanate are far superior to those of multi-block copolymers prepared using HMDi isomer mixtures. The elastomers prepared using isomerically pUTe HMDI
exhibit a hard s~gment having a 70~C higher melting point (200oc instead of 130C) as eompared with polymers which contain 20 %
trans,trans-HMDI, and thus, have a essentially extended eiastomer plateau. In addition, the improved phase separation leads to a larger module in the elastic plateau r~gion.
Predominantly isomerically pure trans,trans-HMDI is obtained on a large scale by fra~ional crystallization of the diisocyanate isomers.
However, this produces large amounts of cis,trans-HMDI/cis,cis-HMDI
isomer rnixture, which cannot be used for synthesizing high-quality elastomers. This process is uneconomic due to the large amount of "waste". From an economic point of view, a process for preparing trans,trans-HMDi with hardly any by-products would be more adv~ntageous.
A process which permits preparation of the trans,trans isomer as qu~ntitatively as possible ~and therefore without the produ~ion of ~ :
economically and industrialiy less useful cis,trans and cis,cis isomers, ~ ~ :
which is inevitable when using pure separation methods) at the diamino stage, by isomerization of a given isomeric mixture, would be economically desirable. In this way, both trans,trans-HMDA would be available for use as a co-called chain len9thener and also the corresponding diisocyanate HMDI, readily accessible by means of phosgenation, would be available in any amount for the synthesis of ~:
polyurethane plastics. In addition, it would also be possible, by admixing or by interrupting the isomerization process, to freely adjust, Mo-4113 `` I~J'~L.. 3~792~

independently of each other, all trans,trans contents from the given starting value, produced e.g. by hydrogenation or by other enri&hment or depletion processes, right up to 100%, both on the chain-lerlgthening side (HMDA) and also on the diisocyanate side (HMDI).
Separation of the three isomers of 4,4'-diaminodiGyclohexyl-methane is barely possible using physical methods since there are no significant differences in melting or boiling points, nor sufficient differences in the solubilities of the isomers. Here, it is more appropriate to pr~pare derivatives which crystallize cleanly and then fractionally crystallize these compounds. The separation of diamino mixtur~s into pure isomers via diformyl and diacetyl derivatives is known on a laboratory scal~.
Another known method comprises initially converting the HMDA
isomeric mixture in toluene with two equivalents of benzaldehyde to give the corresponding 4,4'-di-(benzylidenamino)-dicyclohexylmethane The whole isomeric mixture is then isomerized to give the the~modynamically most stable trans,trans-diamine by base catalysis in dimethoxyethane as solvent. Hydrolysis of the Schifl's base produc~s isomeri~lly pure trans,trans-HMDA.
Aza-allyl carbanions are postulated as reaction intermediates during isomerization.
Using 10% strength (w/v~ potassium tert.butylate solution in ~,2-dimethoxyethane ~DME) more than 90% of the trans,trans product is produced by stirring at room temperature. The reaction time up to a,oproximate establishment of equilibrium in this system is about 60 hours. Model studies with different imines, based on cyclohexanone and benzylamine derivatives show that the formation of 4,4'-diiminodicyclo hexylmethane by-products during this type of isomerization is largely Mo-4113 7 .`~ 2 ~

avoided, this being confirmed by analytical product characterization (nuclear resonance and infra-red spectroscopy~.
The choice of solvent and the substrate concentration (50%
strength (w/v) solution) are important for suc~essful reaction. The trans, 5 trans-diimine is insoluble in 7ME at the ooncentration used and it precipitates out during the course of reaction. A corresponding shi7t in the equilibrium concentration leads to high rates of isomerization. The use of other bases (NaOMe, NaOEt, NaH or LiOH) or other carbonyi functions (salicylaldehyde, p-nitroben~aldehyde, acetone or isatin), leads to lowsr 10 rates of isomerization.
Following completion of isomerization, pure trans,trans~,4'-di-(benzyliden-amino~-dicyclohexylmethane can be obtained by precipitating in water and washing the precipitate with e.g. methanol. Hydrolysis of trans,trans4,4'-di-(benzylidenamino)-dicyclohexylmethane takes placa 15 quantitatively with ~.g. 2 N-hydrochloric acid at temperatures of 50 to 60C. The benzaldehyde formed at the sarne time can be completely separated and recovered without any problems.
The disadvantage of this known method of isornerization is the change in solvent. The toluene used as solvent during preparation of the 20 diirnine must be removed completely and then the whole residue remaining aft0r evaporation has to be dissolved in DME. It would be `
technically and eoonomically adYantag~ous if synthesis of th~ diimine ~-and isomeri~ation could be performed in the same solvent.
Surprisingly, it has now be~n found that it is possible, in a mors 25 efficient manner, to prepare the Sohiff s base of an isomeric mixture of HMDA without changing the solvent and to isomeriz0 almost completely to give the trans,trans isomer.

Mo-4113 ' .'.'. .' ' i ' ' .' . ' ' ;' ' ` ' . ' ` ' '. ` ' ' ` ' : : ., ~ . . ` . .'. . `.' ' ! ':

- 21~7.92~

DESCRIPTION OF THE INVEN ï ION
The present invention provid~s a process for preparing 4,4'-diamino-dicyclohexylmethane with a high content of the trans,trans isomer. This process comprises the steps of 5 1 ) condensing a) an isomeric mixture of 4,4'-diamino-dicyclohexylmethane with b) carbonyl compounds of the general formula R1-CO-R2, wherein:
1û R' represents hydrogen or an alkyl or aryl group, and R2 represents an alkyl or aryl yroup, in a non-poiar organic solvent which forms an azeotrope with water which ~ .
is heated at an temperature no greater than the boiling point of the azeotrope to remove the resulting reaction water and form a solution of the corresponding diimine, r 2) isomerizing said solution of diimine by the addition of c) at least one base and d) at least one compound selected from the group oonsisting f:
il at least one polyether corresponding to the general formula:
R-~ocH2cH2ln-oR
wher~in:
n > 1 and R represents hydrogen or an alkyl group, and ii) a crown ether at room temperature or at an elevated temperature for a period of at least 3 hours, wherein said elevated temperature is no greater Mo-41 1 3 h i~ 7~2~
:, than the boiling point of the components c) or d) or the solvents from steps 1) or 2), 3) separating the tranis,trans-4,4-diamino-dicyclohexylmethane diimine which crystallizes out of said solution, and 5 4) hydrolyzing said trans,trans-4,4 diaminodicyclohexylmethane diimine from step 3) in a known manner to yield trans,trans-4,4'-diaminodicyclohexylmethane.
In accordance with the above embodiment of the present invention, it is possible to add seed crystals of the corresponding trans,trans-diimine compound. The iiie seed crystals may be added to i~
the isomerized solution of diimine from step 2) above, or ii3 simultaneouslywhile separating the trans,trans-4,4'-diamino ~ :
dicyclohexylmethane diimine which crystallizes out of the solution in step :
3). :~
In another embodirnent of the invention, the process comprises the st~ps of 1 ) oonderlsing a) an isomeriomixture of 4,4'-diamino-dicyclohexylmethana with b~ carbonyl compounds having the general formula:
R' CC) R2 wherein:
R' represents hydrogen or an alkyl or aryi group, and R2 represents an alkyl or aryl group, in a non-polar organic solvent which forms an azeotrope with water which is heated at a temperature no greater than the boiling point of the azeotrope to rernove the resulting Mo-4i 13 ,j"j;~, ",, "",",,,,"","",;,, ,,,,,~ , ", ",,, ,, " , ,;, ,, ,~ ,". :::, ::.:,:~'::':;i;~i ~ ' ': ' ' ' ' ' ' "' ' 7 1 ~ 2 ~
,, .

reaction water and form a solution of the corresponding diimine, 2) cooling the solution of ths corresponding diimine while adding seed c~stals of the corresponding trans,trans-diimine compound continuously during the cooling phase, ~:
3) separating the trans,trans-4,4'-diaminodicyclohexylmethane:~
diiminewhich crystallizes out of said solution, 4) isomerizing the remaining solution of diimine from whioh the trans,trans-diimine compound was separated out, by the ~ ~
1D addition of ~ :
c) at least one base and d) at least one component selected from the group -~
consisting of:
i) at least one polyether corresponding to the ~ :
generalformula:
R~[OCH2CH2]n~oR
wherein:
n > 1 and P~ represents hydro~en or an alkyl group, ~:
and ii) a crown ether at room temperature, or at an elevated temperature ~or a period of at least 3 hours, wherein the elevated temperature is no greater than the boiling point of components ~) or d) or the solvents from steps 1) or 4), 5) separating the trans,trans-4,4'-diaminodicyclohexylmethane diimine which crystaliizes out of the solution, and Mo-41 1 3 ~ ~",~`.,.~".,.. ,., i, i ii h ~ ~ 7 ~ 2 ~
,. .
6) hydrolyzing the trans,trans-4,4'-diaminodicyclohexylmethane diimine from step 3) in a known manner to yield trans,trans-4 ,4~-diaminodicyclohexylmethane In this embodiment, it is also possible to add seed crystals of the trsns,trans-4,4'-cliamino-dicyclohexyl-methane diimine to the isomeriz~d solution of diimine from step 4~ or simultaneously while separating the diimine compound which crystallizes out of the solution in step 5).
According to the invention, it is preferred that an aldehyde is used -3, as a carbonyl compound, and toluene andlor benzene is used as an 10 organic non-polar solvent, and that some of the or~anic non-polar solven~
is removed after completion of condensation reacUon 1). It is also preferred that a molar excess of carbonyl compound of at least 1.95:1 be used with respect to 4,4'-diaminodicyclohexylmethane. The starting material preferably is an isomeric mixture of 4,4'-diaminodicyclohexyl-15 methane having a trans,trans-isomer content of 0 to 90% by wt.
The present invention also relates to the use of the trans,trans-4,4'-diaminodicyclohexylmetharle obtainablel by the processes described hereinabove as a starting component for the preparation of plastics, and preferably for the preparation of polyurethanes, polyamides or polyimides, 20 and as a co-condensation component for ths preparation of polyester-amides.
The present invention aiso provides for the use of the trans,trans-4,4' diaminodicyclohexylrnethane obtainable by the processes described hereinabove as a starting material for the preparation of trans,trans~,4'-2~ diisocyana~odicyciohexylmethane.
The diimine is prepared by condensing the diamine (4,4'-diamino-dicyclohexylmethane, isomeric mixture) with a carbonyl compound in an organic non-polar solvent which forms an azeotrope with water since th~
resulting reaction water can be readily azeotropically removed, and thus, Mo-4113 .79;?~

quantitative yields of the diimine are produced. Suitable carbonyl compounds include, for example, cyclopentanone, acetone, banzalde-hyde, p-nitrobenzaldehyde. Some suitable examples of organic non-polar solvents for use in the present invention include chlorobenzene, 5 cyclohsxane, 1,2-dichloroethane, benzene, toluene, and 1,4-dioxan.
Toluene is a particularly preferred solvent for the process of the invention.
Surprisingly, it was found that by the addition of seed crys~als during cooling of the diimine solution, trans,trans-diimine directly 10 crystallizes ou~ of the reaction mixture in ~n isomeri~lly pure form and can be easily separated. The cis,trans- and cis,ds-isnmers remain în solution, together with a small residual of the trans,trans-isomer. This is of particular advantage because only the mother liquor has to be isomerized by the process according to the inYention in the subsequent 15 isornerization step.
The mother liquor (e.g. as a solution in toluene~ is then isomerized in a second reaction step by adding a base which is sufficiently strong and which dissolves adequately (e.g. in toluene), in the presence o~ a polyether of the yeneral formula mentioned and/or of a crown ether.
20 Suitable bases are alkaline- and alkalinl earth alcoholates which include, for example~ potassium tert-butylate, potassium 2-phenyl~ropanolate, potassium 2,2-dimethyl-3-ethyl pentanolate, etc.. .. -Potassium tert-butylate is the most pre~erred base. According to the invention, reliable systems for the solvent toluene include, for example, potassium tert.butylate and dimethoxyethane, and potassium tert.butylate 25 and 18-crvwn-6. Examples of polyethers and crown ethers which ~n be suitable for the present invention include compounds such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glyeol dimethyl ether, tetraethylenP glycol dimethyl ether, polyethylene glycol dimethyl ~ther, 1,4,7,10-Mo-4113 tetraoxycycloclodecane, 1,4,7,10,13-pentaoxycyclopentadecane, and 1 ,4,7,10,13,16-hexaoxycyclooctadecane.
Surprisingly, it was found that on using the base systems according to the invention, isomerization rates of up to more than 95%
are achieved within 10 to 12 days, even at room temperature, wherein preferably seed crystals olF the tr~ns,trans-diimine are added.
By means of this new process, on~ is now able to perform the diimine isomerization in the same solvent as diimine synthesis.
Therefore, it is also possible to perform the two reaction steps one after the other without having to isolate the condensation product (diimine), as was required by the previous processes, this being associated with changing the solvent.
The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.
EXAMPLES
Workin~ Examples Exam~le 1:
PreParation of 4,4'-di-(benzYlidenamino~-dis~yclohex~ethane:
120.1 ~ (0.57 mol) of 4,4'-diaminodicyclohexylmethane and 121.2 9 (1.14 mol) of bellzaldehyde were dissolved in toluene. This solution was boiled on a water separator until the oondensed toluene remained olear and no more water separated out (time about 2 hours). Then 100 ml of toluene was distilled off. The solution was allowed ~o cool slowly and seed crystals of the pure trans,trans compound were added continuously during the cooling phase (from 100C to 40C, every 10C~.
After 12 hours, most of the trans,trans compound had crystallized out in the form of colorless needles. The crystals were filtered off, and washed Mo-41 1 3 2 g wi~h 290 ml of cold hexane (71.3 9, 0.18 mol, yield 32%, melting point:
1 48-1 50~C).
Exam~le 2:
Isomerization in toluene as solvent:
30 ml of the filtrate from the diimine synthesis (ca. 50% by wt.
strength diimins solution in toluene) set forth in Exarnple 1 were stirred together with 9% by wt. of potassium tert.butylate and 15% by vol. of dimathoxyethane (DME) at 25C and with the addition of seed crystals of the trans,trans-diimine.
~0 ~ ml samples ~N~re withdrawn, diiuted with 10 ml of toluene and washed twice with 15 ml of water. The solvent was removecl at 50C
under a high vacuum, and the isomeric ratio in the evaporation residue was determined using lH-NMR spectroscopy.
Table ~
Determinatioll of the isometric ratio in the evaporation residue from Example ~ using 'H-NMR spectroscopy.
Sample time (h) trans-configuration (%) Comment 0 56.2 Motherliquor from Example 1 2 ~4 64.9 3 144 83.4 4 576 91.3 ExamP!e 3:
Isomer zatlon in toluene as solvent:
30 ml of the filtrate from the diimine synthesis (ca. 50% by wt.
strength diimin~ solution in toluene~ se~ forth in Example 1 were stirred together with 10% by wt. of potassium tert.butylate, 1% by wt. of 18-crown-6 at 25~C and with the addition of seed crystals of the trans,trans Mo-4113 I'J ~ 2 ~
~.~
....,~, diimine. 5 ml samples were removed, diluted with 10 ml of toluene and washed twice with 15 ml of water. The solvent was removed at 50C
under a high vacuum, and the isomeric ratio in the evaporation residue was determined using 'H-NMR spectroscopy.
Table 2 Determination of the isomeric ratio in the evaporation residue from Example 3 using 'H-NMR spectroscopy Sample time (h) trans-configuration (%~ Comment 0 56.2 Mother liquor from Example 1 2 72 76.~
3 144 95.6 ExamPle 4 (comparison example):
30 ml of the filtrate from diimine synthesis (ca. 50% by wt. strength 15 diimine solution in toluene) set forth in Example 1 were stirred together with 10% by wt. of potassium tert.butylate at 25C and with the addition of seed crystais of the trans,trans-diimine. ~ ml samples were withdrawn, diluted with 10 ml of toluene and washed twice with 15 ml o~ watet. The solvent was removed at 50~C under high valcuum, and the isomeric ratio 20 in the evaporation residue was determined using 1H-NMR spectrosoopy.
Table 3 Deîermination of the isomeric ratio in th~ eYaporation residue from Exampie 4 using 1H-NMR spectroscopy Sampie time (h3 trans-configuration (%3 Comment 0 56.2 Mother liquor from Example 1 2 24 56.3 3 144 57.3 Mo-4113 V`~

Example 5 (comparison example):
Isomerization in toluene as solvent:
30 ml of the filtrate from diimine synthesis (ca. 50% by wt. strength diimine solution in toluene) set forth in Example 1 were stirred together 5 with 3% by wt. of benzyltriethylammonium bromide, 50% by vol. of 10 N
aqu~ous NaOH at 25C and with the addition of seed crystals of the trans,trans-diimine. 10 ml sampies were withdrawn (5 ml ~ach from the organic and the aqueous phase), diluted with 10 ml of tolu~ne and washed twice with 15 ml of water. The solvent was removed at 5ûC
10 under high vacuum, and the isomerio ratio in the evaporation residue was determined using 1H-NMR spectroscopy.
Table 4 Determination of the isomeric ratio in the evaporation residue from Example 5 using 1H-NMR spectroscopy:
15 Sample time (h) trans-configuration (%~ Comment 0 56.2 Mother liquor from Example 1 2 24 56.8 3 144 57.2 ~le 6 ~comparison example):
Isomeri~ation of the diimine in dimethoxyethane (in accordance with the ~rocess described in J. Or~. Chem. 4319~978~ p. 1825~:
The mother liquor from Example 1 was evaporated and dried under high vacuum (143.9 9, 0.37 mol, yellow/red oil).
127.0 g (0.33 mol) of the evaporated rnother liquor were stirred together with 25.0 9 (0.22 mol) of potassium tert.buty!ate and 250 rnl of dimethoxyethane at room temperature, under argon, for 60 hours, wherein seed crystals of the trans,trans compound were added after 1 hour. Trans,trans-4,4'-di-(benzylidenamino)-dicyclohsxylmethane Mo-41 1 3 2~ t7~,~8 precipitated out during the course of isomerization. The suspension was poured into 1200 rnl of ice water and the precipitate was filtered off. After washing the precipitate with a total of 1,000 ml of water, it was taken up in 300 ml of methanol. The methanol suspension was stirred for 30 minutes, then filtered a~ain and the residue was dried.
Example 7:
Hydrolysis of the trans,trans-4,4'-di-(benzyliden-aminoLd~clohexvlmethane frorn Examples 2 and 3:
60.7 9 (0.16 moi~ of diimine were stirred with 600 m. (1.2 mol) of 2 N-hydrochloric acid overni~ht at an oil-bath temperature of 60QC, wherein benzaldehyde was separated out and the white suspension becam transparent. After cooling, the benzaldehyde was removed by extraction with 4 x 60 ml of dichloromethane. The 3queous phase was then made alkaline with 65 g ~1.6 mol) of NaOH in 200 ml of water, and the precipitated diamin~ was ~xtracted with 100 ml of dichloromethane, four times. The combined organic phases were washed with 100 ml of water, two times, and dried over Na2SO4. After concenlrating by evaporation, 3û.9 9 (0.15 mol, yield: 94%) of trans,trans-4,4'~diaminodicyclohexyl-rnethane remain as white crystals, which ~an be used without further purification.
ExamPle 8:
Isomerization reactions in which potassium tert.-butylate was used as a base and oligoethy!ene glycol dimethyl ethers or dimethoxyethane were added:
25 ml of the filtrate from the synthesis of the diimine (an approxirnately 50/~ by weight solution of the diimins in toluene) set forth in Example 1 were stirred with 2.5 g of potassium tert.-butylate and 2.5 g of oligoethylene glycol dimethyl ether (or 5 ml of dimethoxyethane) under Mo-41 13 ~ h~ L .~l 7 3 2 ~

an argon atmosphere at the temperature indicated in Table 4 and seed crystals of the trans,trans-diimine were adcled.
1 ml samples were extracted after 3 and 18 hours, diluted with 10 ml o~ toluene and washed twice, each time with 15 ml of water. The 5 solvent was removed under a high vacuum at i50C and the ratio of isomers was d0termined with the aid of 'H-NMR spectroscopy.
Table 4 Determination of the ratio of isomers in the evaporation residue of Ex-ample 8 with th~ ~id of 'H-NMR spectroscopy:
10 a) base: potassium tert.-butylate solvent: tetraethylene glycol dimethyl ether temperature: 25C
sample time (h) trans-configuration (%) note 1 0 49 rnother liquorfrom Example 1 2 3 7~

b) base: potassium tert.-butylate 2Q solvent: tetraethyl9ne gl~col dimethyl ether temperature: 75C
sample time (h) trans-configuration (%~ note o ~9 mother liquorfrom Example 1 Mo-4113 ~ .

i ~ ; . r ' : ; ' . ~ ; ~: , . ~', ; , ~ . , ;

~ 2~ ~7~23 c) base: potassium tert.-butylate solvent: polyethylene glycol dimethyl ether, l~in = 1000g/mol temperature: 25C
5 sample time (h) trans-configuration (%) note 0 49 mother liquorfrom Example 1 d) base: potassium tert.-butylate solvent: dimethoxyethane temperature: 75C
sample time (h) trans-configuration t%3 not2 15 1 0 49 mother liquorfrom Example 1 ExamPle ~:
Isomerization reactions in which potassiurn 2-phenylpropanolate and potassium 2,2-dimethyl-3-ethylpentanolate were used as the base and tetraethylene glycol dimethyl ether was added.
25 ml of the filtrate from the synthesis of the diimine (an approximately 50% by weighlt ~oluUon of the diimine in toluene) set ~orih 25 in Example 1 were stirred with 2.5 9 of potassium 2-ptlenylpropanolate and 1.1 9 of potassium 2,2-dimethyl-3-ethylpentanolate in 10 ml of toluene and 2.5 g of tetraethylene ~Iycol dimethyl ether under an ar~on atmosphere at the temperature indicated in Table 5 and seed crystals of the trans,trans-diimine were added.
The sampleswere furthertreated by the process as described hereinabove in Example 8. ;

Mo-4113 ~-. .

Table 5 Determination of the ratio of isomers in the evaporation residue of Example 9 with the aid of 1H-NMR spectroscopy:
a) base: potassium 2-phenylpropanoiate solvent: tetraethylene glycol dimethyl ether temperature: 25C
sample time (h) trans-configuration (%) note 0 49 mother liquorfrom Example 1 b) base: potassium 2,2-dimethyl-3-ethyl pentanolate solvent: tetraethylene glycol dimethyl ether temperature: 75C
sample time (h) trans-conf~uration (%) note ___ 0 49 mother liquor from Example 1 3 7~ 60 Although the invention has been desc:ribed in detail in the foregoing for the purpose of illustration, it i~ to be understood that SU~7 detail is solely for that purpose and that variations can be mad~ therein 25 by those skilled in the art without departing from the spirit and seope of the inYention except as it may be limited by the olaims.

': ~

Mo-4113

Claims (12)

1. A process for the preparation of 4,4'-diaminodicyclohexyl-methane containing a high trans,trans-isomer content, comprising the steps of 1) condensing a) an isomeric mixture of 4,4'-diamino-dicyclohexylmethane with b) carbonyl compounds having the general formula:

wherein:
R1 represents hydrogen or an alkyl or aryl group, and R2 represents an alkyl or aryl group, in a non-polar organic solvent which forms an azeotrope with water which is heated at a temperature no greater than the boiling point of the azeotrope to remove the resulting reaction water and form a solution of the corresponding diimine,
2) isomerizing said solution of diimine by the addition of c) at least one base and d) at least one component selected from the group consisting of:
i) at least one polyether corresponding to the general formula:
R-[OCH2CH2]n-OR
wherein:
n ? 1 and R represents hydrogen or an alkyl group, and ii) a crown ether at room temperature, or at an elevated temperature for a period of at least 3 hours, wherein said elevated temperature is no greater than the boiling point of components c) or d) or the solvents from steps 1) or 2),
3) separating the trans,trans-4,4'-diaminodicyclohexylmethane diimine which crystallizes out of said solution, and
4) hydrolyzing said trans,trans-4,4'-diaminodicyclohexyl-methane diimine from step 3) in a known manner to yield trans,trans-4,4'-diaminodicyclohexylmethane.
2. The process of Claim 1, wherein seed crystals of the corresponding trans,trans-diimine compound are added i) to said isomerized solution of diimine from step 2, or ii) simultaneously while separating said trans,trans-4,4'-diaminodicyclohexylmethane diimine which crystallizes out of said solution in step 3).
3. A process for the preparation of 4,4'-diaminodicyclohexyl-methane containing a high trans,trans-isomer content, comprising the steps of 1) condensing a) an isomeric mixture of 4,4'-diamino-dicyclohexylmethane with b) carbonyl compounds having the general formula:

wherein:
R' represents hydrogen or an alkyl or aryl group, and R2 represents an alkyl or aryl group, in a non-polar organic solvent which forms an azeotrope with water which is heated at a temperature no greater than the boiling point of the azeotrope to remove the resulting reaction water and form a solution of the corresponding diimine, 2) cooling said solution of corresponding diimine while adding seed crystals of said corresponding trans,trans-diimine compound continuously during the cooling phase, 3) separating the trans,trans-4,4'-diaminodicyclohexylmethane diimine which crystallizes out of said solution, 4) isomerizing the remaining solution of diimine from which the trans,trans-diimine compound was separated out, by the addition of c) at least one base and d) at least one component selected from the group consisting of:
i) at least one polyether corresponding to the general formula:
R-[OCH2CH2]n-OR
wherein:
n?1 and R represents hydrogen or an alkyl group, and ii) a crown ether at room temperature, or at an elevated temperature for a period of at least 3 hours, wherein said elevated temperature is no greater than the boiling point of components c) or d) or the solvents from steps 1) or 4),
5) separating the trans,trans-4,4'-diaminodicyclohexylmethane diimine which crystallizes out of said solution, and
6) hydrolyzing said trans,trans-4,4'-diaminodicyclohexyl-methane diimine from step 3) in a known manner to yield trans,trans-4,4'-diaminodicyclohexylmethane.
4. The process of Claim 3 wherein seed crystals of the corresponding trans,trans-diimine compound are added to said isomerized solution of diimine from step 4, or simultaneously while separating said trans,trans-4,4'-diaminodicyclohexylmethane diimine which crystallizes out of said solution in step 5).
5. The process of Claim 1, wherein said carbonyl compound is an aldehyde, said non-polar organic solvent is selected from the group consisting of toluene, benzene, and mixtures thereof, and some of said non-polar organic solvent is removed after completion of the condensation in step 1).
6. The process of Claim 1, wherein the molar ratio aid carbonyl compound to said 4,4'-diaminodicyclohexylmethane is at least 1.95:1.
7. The process of Claim 1, wherein said isomeric mixture of 4,4'-diaminodicyclohexylmethane contains a trans,trans-isomer content of from 0 to 90% by weight.
8. In a process for the preparation of trans,trans-4,4'-diisocyanatodicyclohexylmethane by the phosgenation of trans,trans-4,4'-diaminodicyclohexylmethane, the improvement wherein said trans,trans-4,4'-diaminodicyclohexylmethane is prepared by the process of Claim 1.
9. The process of Claim 3, wherein said carbonyl compound is an aldehyde, said non-polar organic solvent is selected from the group consisting of toluene, benzene, and mixtures thereof, and some of said non-polar organic solvent is removed after completion of the condensation in step 1).
10. The process of Claim 3, wherein the molar ratio said carbonyl compound to said 4,4'-diaminodicyclohexylmethane is at least 1.95: 1 .
11. The process of Claim 3, wherein said isomeric mixture of 4,4'-diaminodicyclohexylmethane contains a trans,trans-isomer content of from 0 to 90% by weight.
12. In a process for the preparation of trans,trans-4,4'-diisocyanatodicyclohexylmethane by the phosgenation of trans,trans-4,4'-diaminodicyclohexylmethane, the improvement wherein said trans,trans-4,4'-diaminodicyclohexylmethane is prepared by the process of Claim 3.
CA002117928A 1993-10-13 1994-10-12 Process for preparing trans-trans-4,4'-diamino-dicylcohexy lmethane Abandoned CA2117928A1 (en)

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