Abstract: A method and apparatus for the delignification of cellulosic fiber material to minimize the amount of reject material in the final pulp produced. The fiber material is digested, washed, oxygen delignified, and passed through a screening stage to provide a main pulp stream, and a reject stream from the separation stage. The flow and consistency of the separated reject material is determined, the reject material is refined, and sufficient chemical is added to the separated reject material, based upon the flow and consistency thereof, so that subsequent delignification of the reject material may be effected. This may be accomplished either by passing the reject material through a separate oxygen delignification stage and then returning it to the main pulp stream, or adding caustic to it and soaking it in a soak tank for predetermined period of time, and then returning it to the main pulp stream before the oxygen delignification stage therein.

Abstract: A process is provided for the bleaching of cellulose pulp, particularly for the peroxide bleaching of high yield pulp, which comprises forming a suspension of lignocellulosic pulp material; mixing the suspension in a mixing zone with a bleaching agent while adjusting the temperature of the pulp suspension to within the range from about +10.degree. C. to about -10.degree. C. of a temperature within the range from about 40.degree. to about 95.degree. C. at which bleaching is to be carried out; quickly dewatering the pulp suspension to a pulp consistency within the range from about 18 to about 50%, equal to or at most 5% less than the pulp consistency of the pulp suspension charged to the mixing zone; passing the dewatered pulp suspension to the bleaching zone before its temperature can change substantially from the adjusted temperature; carrying out the bleaching with a bleaching agent at the selected bleaching temperature within the range from about 40 to about 95.degree. C.

Abstract: Soft, absorbent, bulky paper web useful in tissue, towel, sanitary, and like products. The web is formed by supplying an aqueous furnish which includes thermomechanically defibrated pulp in admixture with chemically defibrated pulp to a foraminous surface such as a Fourdrinier wire, transferring the moist web to an imprinting fabric, thermally drying the web without mechanical compression to a consistency of from about 30 percent to about 98 percent, imprinting the pattern of the fabric into the thermally predried web, and finally drying the web. The resulting web has relatively high tensile strength at relatively low density. Also, the strength properties of the web are significantly improved if the thermomechanically defibrated pulp is made from wood chips which have been soaked in chemical solutions prior to defibrating and then treated with ozone after defibrating.

Abstract: A lignocellulosic material, such as wood chips, is pretreated with an aqueous solution containing from 0.1 to 10% by weight of a water soluble lower aliphatic amine selected from monoethanolamine, methylamine and dimethylamine, at elevated temperature and pressure in a closed vessel. This pretreated material is then subjected to conventional soda or two-stage soda-oxygen pulping.

Abstract: A process for preparing pulp in a closed system by pre-cooking fibrous raw material in an alkaline aqueous solution of sodium carbonate or a mixture of sodium carbonate and sodium bicarbonate as the only alkaline ingredients at 90.degree.-190.degree. C, defibrating the pre-cooked material, pulping the defibrated material in an alkaline aqueous solution of sodium carbonate or a mixture of sodium carbonate and sodium bicarbonate as the only alkaline ingredients in a pressurized vessel at 90.degree.-170.degree. C in the presence of an oxygen-containing gas, subjecting waste liquor discharged from the pre-cooking and pulping steps to wet combustion to recover an alkaline aqueous substance and recycling the alkaline aqueous substance resulting from combustion to the pre-cooking and/or pulping steps.

Abstract: .[.A process for the delignification of chips of vegetable matter by pretreating the chips to obtain at least 64 percent by weight refined vegetable matter, and delignifying the refine vegetable matter with chlorine dioxide. A pulp produced in high yield by the process which refines easier, dries more readily on a paper machine, exhibits higher on-machine filler retention, and possesses greater strength than conventionally bleached kraft pulp made from the same wood mixture. A paper produced from said pulp which has higher tensile, tear, burst, fold, pick and delamination strengths and greater brightness stability that paper produced from conventionally bleached kraft pulp made from the same wood mixture..]. .Iadd.