Selective process for the preparation of diphenylmethane diisocy

Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters

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C07C26100

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active

052064123

ABSTRACT:
A selective process for the preparation of diphenylmethane diisocyanate precursors is disclosed. An alkyl phenylcarbamate or an N,N-dialkyl-N'-phenylurea is reacted with a methylene bis(alkyl carbamate) in the presence of an acid catalyst. The use of a staged addition of phenylcarbamate or phenylurea to the methylene bis(carbamate) and the use of a ramped temperature program are the keys to good selectivity to MDI dimer products.

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