Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
  • C07C209/68—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton
  • C07C209/78—Preparation of compounds containing amino groups bound to a carbon skeleton from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton from carbonyl compounds, e.g. from formaldehyde, and amines having amino groups bound to carbon atoms of six-membered aromatic rings, with formation of methylene-diarylamines

Definitions

• Polyamines of the diphenylmethane series are formed as condensation products from aniline and formaldehyde on acidic catalysts.
• aniline and formaldehyde react without catalysts to form N-alkyl compounds, which are referred to as precondensates.
• this precondensate rearranges into polyamines of the diphenylmethane series. This creates a mixture of 2,2'-, 2,4'-, 4,4'-diaminodiphenylmethanes and higher condensation products (trinuclear to hexahedral compounds).
• the corresponding polyisocyanates of the diphenylmethane series are obtained, which are valuable starting materials in the production of polyurethane plastics, in particular polyurethane foams.
• polyurethane plastics in particular polyurethane foams.
• the proportion of ortho-permanent isocyanate groups present in them in particular the proportion of 2,2'- and 2,4'-diisocyanatodiphenylmethane, is as shame as possible.
• the aniline / formaldehyde condensation is aimed at polyamine mixtures of the diphenylmethane series which meet these requirements with regard to the isomer distribution.
• hydrochloric acid When using hydrochloric acid as a catalyst, it is possible to adjust the content. keep o-isomers in the condensation mixture low, but the use of hydrochloric acid (or aniline hydrochloride) is associated with the disadvantages of corrosiveness and the need for neutralization or complex removal of the catalyst from the reaction product. In principle, these disadvantages can be overcome through the use of heterogeneous acid catalysts, e.g.
• Ion exchangers can be avoided, but it has so far not been possible to use these catalysts to prepare polyamines of the diphenylmethane series which, for example, contain less than 12% of 2,4'-diaminodiphenylmethane and less than 2% of 2,2 ' - Have diaminodiphenylmethane.
• a polyamine mixture of the diphenylmethane series is obtained on organic acidic ion exchangers, which contains 24-26% by weight of 2,4'- and approximately 2.8% by weight of 2,2'-diaminodiphenylmethane.
• any primary or secondary arylamines to be regarded as substituted anilines can be used as starting materials in the process according to the invention.
• the only prerequisite for the suitability of the amines as starting material in the process according to the invention is that the substituents which may be present are inert under the reaction conditions of the process according to the invention and that the para-position is unsubstituted to an aromatically bound amino group.
• Arylamines suitable as starting materials are accordingly N-methylaniline, N-ethylaniline, o-toluidine, o-chloroaniline, m-chloroaniline, o-anisidine, 2,3-xylidine, 3,5-xylidine, o-cyclohexylaniline, o-benzylaniline, a-naphthylaniline, methylmercaptoaniline or the aniline particularly preferred in the context of the present invention.
• the formaldehyde to be used as a reactant for the arylamine in the process according to the invention is preferably used as an aqueous formalin solution, although in principle gaseous formaldehyde or substances which release formaldehyde under the reaction conditions, such as e.g. Paraformaldehyde or trioxymethylene are suitable.
• the catalysts can be used in various external forms, e.g. in lumpy form, in the form of commercially available pearl granules or in a finely ground state. Activation of the catalyst can optionally be achieved in a manner known per se by acid treatment.
• the molar ratio of arylamine: formaldehyde is generally kept in the range from 3: 11 to 15: 1, preferably 5: 1 to 10: 1.
• the process according to the invention is carried out in such a way that the aqueous formaldehyde solution or the formaldehyde-releasing substance is added to the aromatic amine, care being taken to ensure thorough mixing and removal of the heat of reaction.
• the aromatic amine is expediently used immediately in the excess desired for the further conduct of the reaction and at the same time serves as a solvent for the N-substituted precondensate which forms, under certain circumstances. in any case, the reaction mixture must be saturated with water by the additional addition of water.
• the water-saturated reaction mixture is then reacted further at elevated temperature using the abovementioned catalysts, the process product according to the invention being formed from the precondensate and part of the amine present in excess.
• the process product according to the invention being formed from the precondensate and part of the amine present in excess.
• the process according to the invention is carried out in particular during the catalyzed rearrangement of the N-substituted intermediates according to the invention into the process products according to the invention at elevated temperatures generally in the temperature range from 50 to 150 ° C.
• care must be taken to ensure that pressure and temperature conditions are selected so that the water and condensation water introduced into the reaction mixture are not distilled off to any appreciable extent, so that it is always ensured that the catalyst is present in the water-saturated state. It is essential, therefore, that when working at temperatures above 100 ° C., a pressure preventing the water from distilling off is maintained.
• the formation of the N-substituted precondensates generally in the temperature range from 20 to 50 ° C. and the catalytic rearrangement of these precondensates into the process products according to the invention in the temperature range from 50 to 120 ° C is done.
• the process according to the invention can be carried out continuously in a contact bed, a stirred tank or a stirred tank cascade, or batchwise in the stirred tank. Since it is not necessary to separate and recycle the catalyst in the contact bed, this type of procedure is recommended.
• reaction management in particular to remove the heat of reaction, it can also be advantageous to allow the reaction to take place in several stages connected in series, the heat of reaction formed in each case being able to be removed after the individual stages.
• the reaction mixture is preferably worked up by distillation, although in principle any other suitable separation process can be used.
• the lower boiling excess amine is distilled off overhead and returned to the process, while the polyamine mixture present as a distillation residue is immediately, e.g. can be further processed in known manner to a polyisocyanate mixture by phosgenation.
• reaction solution was separated off and the ion exchanger was reacted again with a new starting solution.
• the reaction solution was saturated with water in each case, which could be recognized by clouding the reaction solution or by forming a separate water phase.
• the reaction solution after dist. Separation of the aniline examined by high pressure liquid chromatography.
• the polyamine mixture contains 0.6% by weight of 2,2'-, 10.8% by weight of 2,4'- and 75.3% by weight of 4,4'-diaminodiphenylmethane, the rest consisted of 3- or 4-core connections.
• Example 1 is repeated, with the only difference that an appropriate amount of a water-moist, macroporous ion exchanger which is crosslinked with 18% by weight of divinylbenzene, based on divinylbenzene-styrene copolymer, was used.
• the polyamine mixture obtained was composed of 0.6% by weight of 2,2'-, 8.0% by weight of 2,4'- and 73.2% by weight of 4,4'-diaminodiphenylmethane and higher-nucleus compounds
• the tests were carried out as in Example 1 for 3000 h without any change in conversion or selectivity.
• Example 1 is repeated, with the only difference that a gel-shaped, water-moist ion exchanger crosslinked with 4% by weight of divinylbenzene, based on divinylbenzene-styrene copolymer, was used.
• the polyamine mixture obtained was composed of 1.1% by weight of 2,2'- 14.6% by weight of 2,4'- and 57.2% by weight of 4,4'-diaminodiphenylmethane. Almost 20% by weight consisted of 3- and higher-core compounds.
• Example 1 is repeated, with the only difference that a gel-like, water-moist ion exchanger crosslinked with 8% by weight of divinylbenzene based on divinylbenzene-styrene copolymer was used.
• Example 2 465 parts by weight Aniline and 43 parts by weight a 35% aqueous formaldehyde solution was first reacted without a catalyst in the apparatus described in Example 1.
• the water of the aqueous formaldehyde solution and the water of condensation formed were removed by distillation to a value below 0.07% by weight.
• 20% by weight of the dry ion exchanger mentioned in Example 1 was added and the solution was reacted at 100 ° C. for 20 hours. After the end of the experiment, the reaction solution was separated off and reacted with new, dry starting solution. After a few experiments, small amounts of the water that might have been introduced were also distilled off, so that the reaction was always water-free.
• the polyamine mixture formed contained 3.4% by weight of 2,2'-, 16.5% by weight of 2,4'- and 54% by weight of 4,4'-diaminodiphenylmethane. The rest consisted of higher core connections.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 1977
  • 1977-08-16 DE DE19772736862 patent/DE2736862A1/de not_active Withdrawn
• 1978
  • 1978-08-04 DE DE7878100591T patent/DE2860072D1/de not_active Expired
  • 1978-08-04 EP EP78100591A patent/EP0000778B1/de not_active Expired
  • 1978-08-11 ES ES472514A patent/ES472514A1/es not_active Expired
  • 1978-08-11 IT IT50728/78A patent/IT1106878B/it active
  • 1978-08-14 JP JP9828478A patent/JPS5432461A/ja active Pending
  • 1978-08-15 BR BR7805250A patent/BR7805250A/pt unknown

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