摘要 |
<p>Color lightening of polymeric diphenylmethane diisocyanate (MDI) for use in polyurethane preparation comprises irradiating at 250-2500 nm. Independent claims are included for: (i) The composition of the polymer, which comprises a mixture containing up to 70 wt.% 4,4'-, 2,4'- and 2,2'-isomers of MDI; and (ii) preparation of the polymer, comprising irradiation at 300-450 nm for 2 seconds to 30 minutes and the MDI is dissolved in an organic solvent, preferably monochlorobenzene.</p> |