Polyisocyanate binder having low toluene diisocyanate content
AssigneeBASF Wyandotte Corporation
InventorThirumurti Narayan
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Abstract
Urethane-modified polyisocyanates prepared from toluene diisocyanate are desirable for economic, processing, and product property reasons. Such products should be low in viscosity to allow spray application and low in free TDI content to avoid undue physiological hazard. By use of prescribed reaction condition and reactant ratios, a suitable product can be prepared from hydroxyl-terminated polyoxyalkylene compounds, toluene diisocyanate, and diphenylmethane diisocyanate.
Claims5
A polyisocyanate composition having a free monomeric toluene diisocyanate content of less than one percent by weight prepared by first reacting (a) a hydroxyl-terminated polyoxyalkylene compound having an equivalent weight of from about 800 to about 1200 with (b) toluene diisocyanate at an NCO to OH equivalent ratio of from about 1.1 to about 1.5 to obtain an intermediate product having an NCO content of about 2.1 to about 2.6 percent by weight and thereafter reacting the intermediate product with (c) about 3.0 to about 5.0 equivalents of diphenylmethane diisocyanate per equivalent of (a) for an additional 0.5 hour to 2.0 hours at from 75.degree. C. to 85.degree. C.
Dependencies are inferred from the claim text.