Process for the preparation of di(amino phenyl)methanes

A process for the preparation of a mixture of di(aminophenyl)methane and oligomeric polymethylene polyphenyl polyamines wherein the diamine content is of the order of 90 percent by weight and wherein the p,p'-isomer content of said diamine is of the order of 85 percent by weight, which process comprises the steps of

• a. reacting aniline and formaldehyde in a proportion within the range of 4 moles to 6 moles of aniline per mole of formaldehyde at a temperature of 10.degree. C. to 55.degree. C. and in the absence of acid catalyst to form a mixture of aminals;
• b. separating the water from said aminals;
• c. contacting said aminals, free from water, with a diatomaceous earth catalyst at a temperature of 20.degree. C. to 55.degree. C. until the reaction mixture contains from about 80 to 100% by weight of the corresponding benzylamines;
• d. thereafter adjusting the temperature of the reaction mixture to 55.degree. C. to 65.degree. C. until from about 75% to 90% by weight of said benzylamines have been converted to methylene polyphenyl polyamines;
• and
• e. thereupon finally raising the temperature of the reaction mixture to 80.degree. C. to 100.degree. C. until conversion to methylene polyphenyl polyamines is complete.

A process for the preparation of a mixture of di(aminophenyl)methane and oligomeric polymethylene polyphenyl polyamines wherein the diamine content is of the order of 90 percent by weight and wherein the p,p'-isomer content of said diamine is of the order of 85 percent by weight, which process comprises the steps of

• a. reacting aniline and formaldehyde in a proportion within the range of 4 moles to 6 moles of aniline per mole of formaldehyde at a temperature of 10.degree. C. to 55.degree. C. and in the absence of acid catalyst to form a mixture of aminals;
• b. separating the water from said aminals;
• c. contacting said aminals, free from water with an attapulgus clay catalyst at a temperature of 20.degree. C. to 55.degree. C. until the reaction mixture contains from about 80 to 100% by weight of the corresponding benzylamines;
• d. thereafter adjusting the temperature of the reaction mixture to 55.degree. C. to 65.degree. C. until from about 75% to 90% by weight of said benzylamines have been converted to methylene polyphenyl polyamines;
• and
• e. thereupon finally raising the temperature of the reaction mixture to 80.degree. C to 100.degree. C. until conversion to methylene polyphenyl polyamines is complete.