Patent ID: 8663427

Claim:
A process comprising the following steps: a. providing an at least partially delignified pulp fiber web having a Kappa number of less than about 130; and b. treating the at least partially delignified pulp fiber web with an aqueous endothermic fire retardant solution having a pH of about 10 or less and comprising at least about 10% of one or more endothermic fire retardants based on the solids in the solution; wherein the pulp fiber web treated with the endothermic fire retardant solution has a pH of from about 5 to about 9, wherein the pulp fiber web is treated with a total amount of endothermic fire retardants from at least about 20 lbs to about 250 lbs of endothermic fire retardants per ton of the pulp fiber web, and wherein at least about 5% of the total amount of endothermic fire retardants are added at a point prior to when the pulp fiber web is formed.