1  5,684,180  2  FRACTIONATION  AND  PURIFICATION  OF  AROMATIC POLYAMINE  MIXTURES AND  THE USE THEREOF  BACKGROUND  OF THE  INVENITON  BRIEF  DESCRIPTION  OF THE  DRAWINGS  DESCRIPTION  OF THE  INVENITON  The present invention  provides a process  for the fraction› ation and purification  of aromatic  polyarnine mixtures,  par› ticularly polyamine  mixtures of the  diphenylmethane  series,  which is characterized  in that  Such  disproportionation  effects in two-phase  systems  have also already  been described  for aromatic polyamine  It  is well known that  amines may be separated  in certain  cases by  partial  conversion  to their salts, wherein  use may be  made inter alia  of the different  base strengths. These  are  usually monoamines  with very different  base strengths.  4,4’-Diaminodiphenylmethane  is also attracting  increas› ing interest  as a  raw material  for di-(4- isocyanatocyclohexyl)methane,  the form of  4,4’- diisocyanatodiphenylmethane  hydrogenated  on the nucleus,  wherein the provision  of suitable aromatic  polyamine mix› tures for the  hydrogenation  stage with the highest,  possible  content of  4,4’-diarninodiphenylmethane  with simulta› neously the smallest  possible proportion  of 2,4’- diaminodiphenylmethane  is very  expensive.  The present invention  is a broadly  applicable process,  by  means of which  the object of  fractionating  and purifying  aromatic di- and  polyamine mixtures,  in particular of  the  diphenylmethane  series, may be achieved.  Finally, the process  according to the  invention may be  used to  co-fractionate synthesis-dependent  secondary prod› ucts and  intermediates unwanted  in the end product  and to  deplete them in  one product fraction  and enrich them  accordingly  in another, and optionally  to expel them in  an  individual fraction.  On the other hand,  the process according  to the invention  may be used to obtain  product fractions  conforming with  the  standard or the starting  polyamines from  any, i.e. also from  recovered polyamine  mixtures that differ  from the originally  used polyamines  or  isocyanates  in terms of  contamination  or  non-random,  i.e. selective losses  in the case of individual  components during  recovery from  the originally used  polyamines  or  isocyanates.  Isomer separation  methods or enrichment  methods within  the fraction of  polynuclear homologues,  or of  polyfunctional  amine constituents,  and of isocyanates  of the diphenyl› methane series,  are virtually unknown.  Even in recent times,  the 2,4’ isomer in  the enriched form  has gained increasing  importance  as a  polyurethane  raw  material, but may  be enriched compared  with the 4,4’ isomer  and separated from  the 2,2’ isomer possibly  present only by  an elaborate  distillation procedure.  Initially, a proportion  of the binuclear  compounds  is  usually separated  from the remainder.  The 4,4’› diisocyanatodiphenylmethane  from the binuclear  fraction is  then separated from  the other isomers  in a second  distillation  stage requiring many  separation stages.  Other polyamine  mixtures of varying  composition  are  obtained during  the  fractionation  of aromatic  polyamine  mixtures according  to the  invention. These  derived  polyamine mixtures  may be those that  are obtainable only  at  great expense by  known synthesis  routes. They may  also be  polyamine mixtures  which are more suitable  for a simplified  preparation  of  isocyanates than  the well known  polyamine  mixtures that are  technically easy  to prepare in that  they, for  example, anticipate  in the amine stage  the isomer separa› tions that are difficult  to perform in the  isocyanate stage.  Such mixtures may  also be completely  novel polyamine  mixtures, because  they cannot be prepared  according to the  prior  art,  which lead to completely  new types of isocyanates.  An  example  is the  production  of 4,4’› diisocyanatodiphenylmethane  which is important  for the  preparation  of valuable  polyurethane materials,  the amine  precursor of which  may  be  obtained usually  from aniline and  formaldehyde  only together with  isomers, particularly  the  2,4’ isomers and  more highly functional  polyamines.  Although these  constituents  are the basis for  isocyanates  which are also  sought after, the  separation of the  crude  isocyanates into  the  isocyanates and  isocyanate mixtures  suitable for subsequent  use is not easy.  In  many cases, however,  the resulting  isocyanates and  isocyanate mixtures  are not obtained  in the form and  com› position subsequently  preferably used  in the  isocyanate  stage but have to  be converted  beforehand  to the  appropriate  form for use by  means of sometimes  elaborate working-up  and separation  processes. Suitable  polyamine precursors  which may be converted  in a less elaborate  manner to the  isocyanate use forms  are in many cases  difficult to produce  or  unobtainable  in terms of process  technology,  or economi› cally unattractive.  The above object  could be achieved  by the process  according to the  invention which  achieves a surprisingly  good separating  efficiency during  the  fractionation  of aro› matic polyamine  mixtures, particularly  of the diphenyl› methane series, and  in terms of its effect  thereby far exceeds  the known effects  of the prior art.  FIGS.  1  through 4 are flow  diagrams of various  embodi› ments of the present  invention.  The preparation  of aromatic  polyamines and  polyamine  mixtures, particularly  of the  diphenylmethane  series, is  described in numerous  patent  applications  and patents, as is  the use of these  products. Outstanding  importance  is  attached to the use  of these products  as raw materials  for the  preparation  of  isocyanates, usually  by reaction of  the  polyamine mixtures  with phosgene according  to the gener› ally  conventional  and well known  methods.  The present invention  relates to a process  for the frac› tionation and purification  of aromatic  polyamine mixtures  and to the use thereof.  The object was thus  to provide a process  which allows the  pwposeful production  of aromatic  polyamine mixtures  of a  purer, novel composition  in an economic manner  under mild  conditions.  As a result of the  numerous components  present in such  a mixture, the amino  groups of which  hardly differ at all  in  terms of type (virtually  all of them are arylamino  groups),  the effects are not  particularly great  and  pronounced  to be of  interest for direct  use with simple  means.  mixtures, particularly  of the  diphenylmethane  series  (German Auslegeschriften  2,238,319 and 2,528,694).  a) the  polyamine starting  mixture (A) is distributed  in a  two-phase system  comprising  (i) a  hydrophobic solvent  phase (B) which  is  composed substantially  of hydro› phobic solvent  and  optionally an aromatic  auxiliary  amine that is virtually  insoluble  in  water and under  normal pressure  has a boiling point  at least 20°  C.  below the boiling  point of the lowest  boiling compo-