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METHOD FOR PRODUCING MIXTURES CONSISTING OF DIPHENYLMETHANE DIISOCYANATES AND POLYPHENYLENE-POLYMETHYLENE-POLYISOCYANATES CONTAINING A REDUCED AMOUNT OF CHLORINATED SECONDARY PRODUCTS AND WITH A REDUCED IODINE COLOR INDEX

  • US 6,576,788 B1
  • Filed: 10/13/2000
  • Issued: 06/10/2003
  • Est. Priority Date: 04/21/1998
  • Status: Expired due to Term
First Claim
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1. A process for preparing mixtures comprising diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having a reduced content of chlorinated by-products and a reduced iodine color number, said process comprising reacting diphenylmethanediamines and polyphenylpolymethylenepolyamines (PMDA) with phosgene in the presence of at least one inert organic solvent in a two-stage reaction comprising first and second phosgenation stages, wherein the mass ratios of said phosgene to hydrogen chloride in a residence time apparatus of the second phosgenation stage are at the same time 10-30:

  • 1 in the liquid phase and 1-10;

    1 in the gas phase.

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