Elevated temperature and pressure two stage hypochlorite peroxide pulp bleaching process

Claim 1

A TWO STAGE BLEACHING METHOD FOR BLEACHING SEMICHEMICAL AND CHEMICAL PAPER PULP, THE STEPS COMPRISING A FIRST STAGE OF BLEACHING INCLUDING SUBJECTING THE PULP TO THE ACTION OF HYPOCHLORITE HAVING 2% TO 10% AVAILABLE CHOLRINE BASED ON THE WEIGHT OF OVEN DRY PULP WITH THE PULP MIXTURE HAVING A PH IN THE RANGE OF 9 TO 14, BLEACHING THE PULP ABOUT 30 TO 40 MINUTES AT A TEMPERATURE OF ABOUT 100* F. UNTIL A PREPARED SHEET OF THIS PULP PROVIDES A G.E BRIGHTNESS OF ABOUT 44 TO 65, WASHING THE PULP, MIXING THE PULP WITH SECOND STAGE OXYGEN PRODUCING CHEMICALS WHICH PRODUCE ACTIVE OXYGEN IN AMOUNTS OF FROM .04% TO .66% BASED UPON THE DRY WEIGHT OF THE PULP PRESENT, ADJUSTING THE PH TO WITHIN THE RANGE OF 9 TO 14, SUBJECTING THE MIXTURE TO PRESSURES OF ABOUT 10 POUNDS PER SQUARE INCH TO 50 POUNDS PER SQUARE INCH AND TEMPERATURES EQUIVALENT TO THAT OF SATURATED STEAM AT THIS PRESSURE FOR A PERIOD WHICH VARIES INVERSELY WITH THE VARIATIONS IN PRESSURE AND TEMPPERATURE, DISCONTINUING THE BLEACHING ACTION WHILE LEAVING A SLIGHT RESIDUAL OXYGEN PRODUCING CHEMICAL IN THE PULP AND AFTER A TIME INTERGAL OF NOT OVER ABOUT TWENTY MINUTES, FOR A TOTAL BLEACHING TIME OF NOT OVER ABOUT ONE HOUR FOR THE FIRST AND SECOND STAGES OF BLEACHING UNTIL SHEET MATERIAL PREPARED THEREFROM HAS A G.E. BRIGHTNESS READING OF FROM ABOUT 72 TO ABOUT 85.