Process for imparting flame resistance to cellulosic textile materials and cellulosic materials obtained thereby

A process for rendering a cellulosic textile material flame-resistant comprising;

• impregnating the material with an aqueous solution of a partially polymerized methylolated phosphorus compound, prepared by reacting from about 4.0 to about 9.0 parts by weight of tetrakis(hydroxymethyl)phosphonium sulfate with about 1.0 part by weight of urea, to deposit thereon about 3.0-7.0 weight % phosphorus based on the weight of the untreated textile material;
• partially drying the impregnated textile material;
• impregnating the partially dried textile material with a thickened aqueous solution of ammonium hydroxide containing about 17-29% by weight of ammonia and sufficient water soluble thickening agent to provide a solution viscosity of about 500-10,000 centipoises at 25.degree. C to deposit thereon about 2-6 gram-moles of ammonia per gram-atom of phosphorus present thereon, the temperature of the thickened ammonium hydroxide ranging from about 20.degree. C. to about 60.degree. C;
• rolling the ammonium hydroxide-impregnated textile material;
• storing the rolled material in a suitable sealed container for about 1/2-60 minutes at ambient temperature to allow the formation of an unsoluble polymer within the rolled material from the reaction of said phosphorous compound and ammonium hydroxide impregnated therein;
• recovering and unrolling the stored textile material;
• rinsing the unrolled textile material with water;
• and drying the treated textile material.