Aromatic polyamines and their preparation

In a process for producing a reaction product of aniline and formaldehyde which contains a diaminodiphenylmethane mixture together with a mixture of polymethylene polyphenylpolyamines having from two to four methylene groups, the method of obtaining between about 15wt. % and about 95 wt. % of 2,4'-diaminodiphenylmethane in said diaminodiphenylmethane mixture which comprises:

• A. heating an aniline-formaldehyde mixture containing from about one to about ten mols of aniline for each mol of formaldehyde;
• B. in the presence of a solid acidic siliceous catalyst of the group consisting of acid-activated siliceous clays and silica-alumina of silica-magnesia catalysts;
• C. at a reaction temperature within the range of about 80.degree. to 300.degree. C.;
• and
• D. controlling the proportion of 2,4'-diaminodiphenylmethane in the said reaction products by controlling the reaction temperature within said range when the catalyst is an acid-activated siliceous clay and by controlling the starting temperature of the reaction within said range when the catalyst is silica-alumina or silica-magnesia.

In a process for producing a reaction poduct of aniline and formaldehyde which contains a diaminodiphenylmethane mixture together with a mixture of polymethylenepolyphenylpolyamines having from two to four methylene groups, the method of obtaining between about 15 and about 95 wt. % of 2,4'-diaminodiphenylmethane in said diaminodiphenylmethane mixture while avoiding the presence of secondary polyamines therein which comprises the steps of:

• A. reacting about 1 to about 10 mols aniline per mol formaldehyde in the presence of a solid acidic siliceous catalyst of the group consisting of acid-activated siliceous clays and silica-alumina of silica-magnesia catalysts at a first temperature within the range of about 80.degree. to about 150.degree. C. to thereby provide a reaction product comprising diaminodiphenylmethane isomers, secondary amines and higher molecular weight condensation products of aniline and formaldehyde;
• B. heating said mixture at a second temperature within the range of about 175.degree. to about 250.degree. C. for about 1 to about 5 hours to thereby convert said secondary amines to polyaminopolyphenylmethane compounds;
• C. controlling the proportion of 2,4'-diaminodiphenylmethane in said reaction products by controlling thetemperature within the ranges of steps (A) or (B)l when the catalyst is an acid-activated siliceous clay and by controlling the starting temperature within the range of step (A) when the catalyst is silica-alumina or silica-magnesia;
• and
• D. recovering said diaminodiphenylmethane isomers and higher molecular weight condensation products from the reaction mixture.

In a process for producing a reaction product of aniline and formaldehyde which contains a diaminodiphenylmethane mixture together with a mixture of polymethylenepolyphenylpolyamines having from two to four methylene groups, the method of obtaining between about 30 and about 95 wt. % of 2,4'-diaminodiphenylmethane in said diaminodiphenylmethane mixture which comprises:

• A. heating an aniline-formaldehyde mixture containing from about 1 to about 10 mols of free aniline for each mol of formaldehyde;
• B. with an acid-activated siliceous clay catalyst;
• C. at a reaction temperature within the range of about 80.degree. to 250.degree. C.;
• and
• D. controlling the proportion of 2,4'-diaminodiphenylmethane in the said reaction products by controlling the reaction temperature within said range.

In a process for producing a reaction product of aniline and formaldehyde which contains a diaminodiphenylmethane mixture together with a mixture of polymethylenepolyphenylpolyamines having from two to four methylene groups, the method of obtaining between about 15 wt. % and about 50 wt. % of 2,4'-diaminodiphenylmethane in said diaminodiphenylmethane mixture which comprises:

• A. heating an aniline-formaldehyde mixture containing from about 1 to about 10 mols of free aniline for each mol of formaldehyde;
• B. with a silica-alumina or silica-magnesia catalyst;
• C. at a reaction temperature within the range of about 80.degree. to 250.degree. C.;
• and
• D. controlling the proportion of 2,4'-diaminodiphenylmethane in the said reaction products by controlling the starting temperature of the reaction within said range.