Process for reducing the acidity of organic polymeric isocyanate

Details Process for reducing the acidity of organic polymeric isocyanate Process for reducing the acidity of organic polymeric isocyanate

1974-09-25

1978-10-03

Tayman, Jr., James H.

Distillation: processes, separatory

Filming of distilland for vaporization

260453SP, 203 98, 203 69, B01D 300

Patent

active

041182863

ABSTRACT:
In a process for purifying and reducing the acidity of a polymethylene polyphenylpolyisocyanate mixture wherein the mixture is subjected to a distillation step, such as by passing a flowing stream of a crude polymethylene polyphenylpolyisocyanate mixture through a distillation column which has a reboiler means consisting of a thin film evaporator apparatus mounted therewith for rapidly heating the stream to about 190.degree. C. to about 250.degree. C. whereby the solvent and impurities are taken overhead, and then allowing the distillation residue of polymethylene polyphenylpolyisocyanate to cool, an improvement is disclosed which comprises maintaining the distillation residue of the polymethylene polyphenylpolyisocyanate at a temperature of about 190.degree. C. to about 250.degree. C. for a time period of from about 1 to about 60 minutes and then recirculating continuously a portion of the distillation residue to the distillation column for admixture with the flowing feed stream of crude polymethylene polyphenylpolyisocyanate at a recirculation rate of from about 1:1 to about 3:1 volumes of isocyanate distillation residue per volume of crude isocyanate feed. The acid level of the polymethylene polyphenylpolyisocyanate mixture treated by the improved process of the invention is substantially reduced without adversely affecting the isocyanate equivalent weight, viscosity or other physical and chemical characteristics of the product.

REFERENCES:
patent: 3219678 (1965-11-01), Kober et al.
patent: 3793362 (1974-02-01), Kalakowski et al.
patent: 3853936 (1974-12-01), Van Winkle

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