Process for the production of polyisocyanates of the...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant

Reexamination Certificate

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C528S266000, C560S347000, C560S338000, C560S359000, C564S330000, C564S331000, C564S333000

Reexamination Certificate

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07041776

ABSTRACT:
The invention relates to a method of producing polyisocyanates of the diphenylmethane series including the steps ofa) reacting aniline and formaldehyde in the presence of HCl to provide a product mixture containing polyamines of the diphenylmethane series, HCl, aniline and water;b) removing excess aniline and water by distillation to provide a product mixture comprising polyamines of the diphenylmethane series, HCl, no more than 10 wt. % aniline based on the polyamines, and no more than 5 wt. % water based on the polyamines; andc) phosgenating the product mixture in (b).

REFERENCES:
patent: 4597909 (1986-07-01), Keggenhoff et al.
patent: 5310769 (1994-05-01), Konig et al.
patent: 24 04 775 (1975-08-01), None
patent: 1 203 546 (1970-08-01), None
patent: 01/74755 (2001-10-01), None
Chem. Soc. Rev. 3(2), 209 (month unavailable) 1974, pp. 209-230, H. J. Twitchett, “Chemistry of the Production of Organic Isocyanates”.
Kirk-Othmer Encycl. Chem. Technol., 3rded. New York, 2, (month unavailable) 1978, pp. 338-348, William M. Moore, “Methylenedianiline”.

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