Patent ID: 7632424

Claim:
A method for inhibiting the discoloration of methylenebisaniline compounds, characterized by adding a phosphine represented by the following general formula: (wherein R 3 is an optionally substituted aryl group or an optionally substituted alkyl group; p is 0, 1 or 2 and q is 1, 2 or 3, with the provisos that the sum of p and q is 3 and that when q is 2 or 3, R 3 may be the same or different from each other) to a compound represented by the following general formula: (wherein R 1 and R 2 are each independently a halogen atom or a C1-C6 alkyl group; a and b are each independently an integer of 0 to 4; m and n are each independently an integer of 1 to 5, with the provisos that the sum of a and m and the sum of b and n are each 5 or less and that when a is 2 or more, R 1 may be the same or different from each other and, when b is 2 or more, R 2 may be the same or different from each other).