A high efficiency bleaching method for cellulosic pulp includes: (a) providing a charge of aqueous cellulosic pulp to a bleaching vessel at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5; and (b) bleaching the aqueous cellulosic pulp in the bleaching vessel while maintaining a bleaching temperature of from 110° F. (43° C.) to 135° F. (57° C.) and a pH of the charge from 9.5 to 12.5 for an extended bleaching retention time. The bleaching method is advantageously used to bleach low brightness recycle pulp, and/or as part of a multistage process with bleaching stages of lesser duration, and/or as a high peroxy efficiency, low dose bleaching process or in connection with concurrently storing and bleaching pulp.

This disclosure relates to methods of making novel dissolving wood pulps by processes comprising acid prehydrolysis, pulping, and a multi-stage bleaching process comprising oxidation with a catalyst and peroxide under acidic conditions, as well as to products made therefrom having a combination of medium-purity, low viscosity, and improved reactivity, filterability, and/or clogging that can be used as a substitute for traditional high-purity dissolving pulps in a wide variety of applications.

A high efficiency bleaching method for cellulosic pulp includes: (a) providing a charge of aqueous cellulosic pulp to a bleaching vessel at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5; and (b) bleaching the aqueous cellulosic pulp in the bleaching vessel while maintaining a bleaching temperature of from 110° F. (43° C.) to 135° F. (57° C.) and a pH of the charge from 9.5 to 12.5 for an extended bleaching retention time. The bleaching method is advantageously used to bleach low brightness recycle pulp, and/or as part of a multistage process with bleaching stages of lesser duration, and/or as a high peroxy efficiency, low dose bleaching process or in connection with concurrently storing and bleaching pulp.

A feedstock includes feedstock paper and non-paper material. The feedstock paper includes lignin and cellulose. A method includes cooking the feedstock in cooking liquor to dissolve at least a portion of the lignin from the feedstock paper and to at least partially dissolve the non-paper material in the cooking liquor, thereby yielding a cooked pulp. The method further includes washing the cooked pulp to yield washed pulp and spent cooking liquor, regenerating the spent cooking liquor to yield regenerated cooking liquor, and bleaching the washed pulp.

This disclosure relates to methods of making novel dissolving wood pulps by processes comprising acid prehydrolysis, pulping, and a multi-stage bleaching process comprising oxidation with a catalyst and peroxide under acidic conditions, as well as to products made therefrom having a combination of medium-purity, low viscosity, and improved reactivity, filterability, and/or clogging that can be used as a substitute for traditional high-purity dissolving pulps in a wide variety of applications.

The invention relates to method for producing viscosity controlled cellulosic material having a viscosity value in a range between 150 ml/g and 500 ml/g in a continuous process, the method comprising the following steps: i) forming a cellulose-water mixture (15) comprising water and chemically treated wood-based cellulosic material, the cellulose-water mixture (15) having a dry matter content between 3% and 20%, ii) treating the formed cellulose-water mixture (15) in a plasticization step (100) at a temperature between 130° C. and 200° C., and a pressure between 3 bars and 15 bars, at least 5 minutes and 120 minutes at the most, while mixing the cellulose-water mixture (15), and feeding hot water and/or water steam to the cellulose-water mixture, thereby obtaining a treated mixture (18), and iii) depressurizing the treated mixture (18) in a depressurizing step (105) in a controlled manner, thereby obtaining the viscosity controlled cellulosic material (20). This invention further relates to a viscosity controlled cellulosic material and a system for producing viscosity controlled cellulosic material.

This disclosure relates to methods of making novel dissolving wood pulps by processes comprising acid prehydrolysis, pulping, and a multi-stage bleaching process comprising oxidation with a catalyst and peroxide under acidic conditions, as well as to products made therefrom having a combination of medium-purity, low viscosity, and improved reactivity, filterability, and/or clogging that can be used as a substitute for traditional high-purity dissolving pulps in a wide variety of applications.

A high efficiency bleaching method for cellulosic pulp includes: (a) providing a charge of aqueous cellulosic pulp to a bleaching vessel at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5; and (b) bleaching the aqueous cellulosic pulp in the bleaching vessel while maintaining a bleaching temperature of from 110° F. (43° C.) to 135° F. (57° C.) and a pH of the charge from 9.5 to 12.5 for an extended bleaching retention time. The bleaching method is advantageously used to bleach low brightness recycle pulp, and/or as part of a multistage process with bleaching stages of lesser duration, and/or as a high peroxy efficiency, low dose bleaching process or in connection with concurrently storing and bleaching pulp.

A high efficiency bleaching method for cellulosic pulp includes: (a) providing a charge of aqueous cellulosic pulp to a bleaching vessel at a consistency of from 10% to 30% along with a peroxy bleaching agent and an alkaline agent effective to adjust pH of the charge to 9.5 to 12.5; and (b) bleaching the aqueous cellulosic pulp in the bleaching vessel while maintaining a bleaching temperature of from 110 F. (43 C.) to 135 F. (57 C.) and a pH of the charge from 9.5 to 12.5 for an extended bleaching retention time. The bleaching method is advantageously used to bleach low brightness recycle pulp, and/or as part of a multistage process with bleaching stages of lesser duration, and/or as a high peroxy efficiency, low dose bleaching process or in connection with concurrently storing and bleaching pulp.

The present invention is directed to a method for scouring and increasing the brightness of non-wood fibers. The method comprises forming a mixture of non-wood fibers, exposing the mixture to a scouring liquor and a scouring agent comprising oxygen gas to form a scouring mixture, and scouring the scouring mixture by radially circulating the scouring liquor throughout the scouring mixture to provide scoured fibers.