Isocyanate modified cellulose products and method for their manufacture
AssigneeWeyerhaeuser Company
InventorsFrank R. Hunter, James F. L. Lincoln, David W. Park
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Abstract
A method is disclosed for producing a polyureacellulose composite material from substantially delignified cellulosic material and an isocyanate resin. The isocyanate resin comprises a polyisocyanate, preferably PMDI, and a miscible organic solvent, preferably one such as propylene carbonate having a high boiling point and low flammability and toxicity. The composite surprisingly exhibits values of physical parameters that are at least as good as, and sometimes far superior to, corresponding parameters of similar composites made using neat (undiluted) polyisocyanate. Single- and multiple-ply composites can be made, employing only a single curing step.
Claims28
A method for making a polyurea-cellulose composite which comprises:
- impregnating a substantially delignified cellulosic material with an isocyanate resin comprising at least one polyisocyanate compound and a miscible organic solvent therefor, where the solvent comprises up to about 20% w/w of the polyisocyanate and the isocyanate resin constitutes about 8% to about 20% w/w of the cellulosic material so as to form a polyisocyanate-impregnated cellulosic material;
- and
- curing the polyisocyanate-impregnated cellulosic material at a temperature within a range of about 105.degree. to about 245.degree. C. for a time not exceeding about 5 minutes and at a pressure within a range of about 130 to about 1200 psig.
A method for making a laminated polyurea-cellulose composite material comprising the steps:
- individually impregnating each of plural sheets of substantially delignified cellulosic material with an isocyanate resin comprising at least one polyisocyanate compound, a miscible organic solvent therefor, and a catalyst, wherein the solvent comprises up to about 20% w/w of the polyisocyanate and the resin constitutes about 8 to about 20% w/w of the cellulosic material so as to form plural polyisocyanate-impregnated cellulosic lamina;
- plying at least two of the polyisocyanate-impregnated cellulosic lamina together so as to form a laminar stack of said polyisocyanate-impregnated cellulose lamina;
- and
- curing the stack of plied lamina at a temperature in a range of about 105.degree. C. to about 245.degree. C. for a time not exceeding about 5 minutes and at a pressure within a range of about 130 to about 1200 psig.
A method for making a polyurea-cellulose composite, comprising the steps:
- impregnating a substantially delignified cellulosic material with a resin comprising an isocyanate compound and propylene carbonate, wherein the propylene carbonate is present in the resin at a concentration of up to about 20% w/w relative to the polyisocyanate and the resin constitutes about 8% to about 20% w/w of the cellulosic material, so as to form a polyisocyanate-impregnated cellulosic material;
- and
- curing the polyisocyanate-impregnated cellulosic material at a temperature within a range of about 105.degree. C. to about 245.degree. C. for a time not exceeding about 5 minutes and at a pressure within a range of about 130 to about 1200 psig.
Dependencies are inferred from the claim text.