GB593768A - Improvements in or relating to the production of cellulose - Google Patents

Abstract

Raw cotton linters are purified by a process comprising treatment with strong caustic alkali at atmospheric temperatures such that substantially no mercerization occurs, subsequent treatment in an alkali, of lower concentration, at an elevated temperature and under superatmospheric pressure, and treatment with an oxidizing bleach. Raw cotton linters are steeped in solutions of caustic soda of 6-15 per cent concentration at a temperature of 5-50 DEG C. for 10 mins. to 4 hours. The steeping liquor is drained off and may be followed by an oxidizing bleach. The cotton linters are then digested in dilute caustic soda at about 400 DEG F. and under the corresponding saturated steam pressure. If desired, digestion may be performed in the presence of turkey red oil, FF wood rosin, sodium abietate, tall oil, disodium-sulphoethylphenyl stearate, or isopropyl naphthalene sodium sulphonate. The bleach treatment may involve the use of alkaline or acid solutions of available chlorine such as free chlorine, hypochlorites, chlorites; peroxides; peroxygen compounds or permanganates and the like. In one example, raw cotton linters steeped in a 9 per cent solution of sodium hydroxide at 25 DEG C. for 45 minutes are separated from the steep liquor, washed, treated with a dilute solution containing available chlorine (such as hypochlorite) for 1- 1/2 hour, washed and then digested in a 2.5 per cent sodium hydroxide solution, containing 0.8 per cent by weight turkey red oil, for 3 hours at about 275 DEG F. and a steam pressure of about 30 lbs. per square inch. The washed linters are then subjected to a multistage bleaching process.