ISOCYANATE COMPOSITIONS AND CELLULOSE PRODUCTS IMPREGNATED WITH THE COMPOSITIONS
The invention is directed to a composition of matter useful as a paper impregnant, to the method of its use, and to the products produced by the method. Poly (diphenylmethane diisocyanate) or PMDI has been used in the past as a paper impregnant with or without propylene carbonate as a diluent. These...
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Zusammenfassung: | The invention is directed to a composition of matter useful as a paper impregnant, to the method of its use, and to the products produced by the method. Poly (diphenylmethane diisocyanate) or PMDI has been used in the past as a paper impregnant with or without propylene carbonate as a diluent. These products have generally required pressing under high pressures and at elevated temperatures. It has now been found that triacetin and/or triethyl citrate in usages up to about 20% of PM DI give superior performance in impregnated products. The modified PMDI will cure at essentially ambient conditions in times as short as 1-2 days to insoluble polyureas with low residual amounts of isocyanates and reaction byproducts such as 4,4'- diaminodiphenylmethane. The treated papers can be used in applications of which skins for sandwich panels and high strength corrugated board would be exemplary. |
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