A process for pretreating reclaimed cotton fibers to be used in the production of molded bodies from regenerated cellulose characterized by effective metal redaction and adjustment of the degree of polymerization and brightness, including a metal removing stage and an oxidative bleaching stage of the reclaimed cotton fibers or pulp produced thereof. Reclaimed cotton fibers treated according to the described process may be used alone or in blends with conventional dissolving pulp as raw material for the production of molded bodies from regenerated cellulose. The process enables technically smooth, safe, and economically feasible spinning via the Viscose or Lyocell process, therefore, the current invention provides an efficient recycling pathway for cotton waste materials.

A process for pretreating reclaimed cotton fibers to be used in the production of molded bodies from regenerated cellulose characterized by effective metal redaction and adjustment of the degree of polymerization and brightness, including a metal removing stage and an oxidative bleaching stage of the reclaimed cotton fibers or pulp produced thereof. Reclaimed cotton fibers treated according to the described process may be used alone or in blends with conventional dissolving pulp as raw material for the production of molded bodies from regenerated cellulose. The process enables technically smooth, safe, and economically feasible spinning via the Viscose or Lyocell process, therefore, the current invention provides an efficient recycling pathway for cotton waste materials.

A method of producing high yield chemical cellulosic pulp includes: (a) chemically pulping wood chips to separate lignin and liberate cellulosic fibers from the wood chips to generate a cellulosic pulp; (b) washing and screening the pulp of step (a); (c) pre-treating the washed pulp with oxygen; (d) optionally washing the treated pulp of step (c); (e) bleaching the pre-treated pulp in an extended duration oxidative bleaching stage; (f) optionally washing the bleached pulp of step (e); and (g) optionally further oxidatively or reductively bleaching the bleached pulp in a shorter duration bleaching stage, wherein the bleached pulp is produced at a yield of greater than 60% based on the weight of the pulped wood chips (dry basis).

A recycled pulp that is reusable sanitary products is efficiently manufactured by recovering pulp fiber from used sanitary products containing the pulp fiber and a polymer absorbent. The method of the present invention comprises: a step applying a mechanical force to the used sanitary products in an aqueous solution containing a polyvalent metal ion or an acidic aqueous solution with a pH of 2.5 or lower and thus degrading the used sanitary products into the pulp fiber and other materials; a step separating the pulp fiber from the mixture of the pulp fiber and other materials that has been formed in the degradation step; and a step treating the pulp fiber thus separated with an ozone-containing aqueous solution with a pH of 2.5 or lower.

A recycled pulp that is reusable sanitary products is efficiently manufactured by recovering pulp fiber from used sanitary products containing the pulp fiber and a polymer absorbent. The method of the present invention comprises: a step applying a mechanical force to the used sanitary products in an aqueous solution containing a polyvalent metal ion or an acidic aqueous solution with a pH of 2.5 or lower and thus degrading the used sanitary products into the pulp fiber and other materials; a step separating the pulp fiber from the mixture of the pulp fiber and other materials that has been formed in the degradation step; and a step treating the pulp fiber thus separated with an ozone-containing aqueous solution with a pH of 2.5 or lower.

An arrangement and a method for controlling a gas flow separated from a suspension of medium consistency pulp. The pulp is treated in a pulp treatment apparatus including a first pump and a second pump, wherein the second pump is a degassing centrifugal pump provided with a degassing system including a degassing conduit in which a degassing valve is arranged for regulating a pressure difference between an inlet of the second pump and the degassing conduit. The degassing system further includes a pressurized degassing vessel working under overpressure and having an inlet and an outlet, wherein the outlet of the vessel is connected to a pressure control valve for maintaining a desired overpressure in the vessel.

The purpose of the present disclosure is to provide a method for producing pulp fibres for saccharification from the pulp fibres of used sanitary items, said pulp fibres for saccharification having low lignin contents distributed within a narrow range, and enabling the production of pulp fibres for saccharification having superior saccharification properties. The production method according to the present disclosure is characterised by comprising the following: a step for supplying a mixed solution (51) containing pulp fibres and highly-absorbent polymers sourced from used sanitary items to a treatment tank (31) via a mixed-solution supply port (32); a step for supplying an ozone-containing gas (53) to a treatment solution (52) within the treatment tank (31) via an ozone-containing-gas supply port (43); a step for lifting the ozone-containing gas (53) whilst lowering the pulp fibres and highly-absorbent polymers within the treatment tank (31), thereby bringing the ozone-containing gas (53) into contact with the pulp fibres and highly-absorbent polymers, and forming pulp fibres for saccharification from the pulp fibres; and a step for discharging the treatment solution (52) via a treatment-solution discharge port (33). The method is further characterised in that the pulp fibres for saccharification have lignin contents of 0.1% or less.

The purpose of the present invention is to provide a method for producing recycled pulp fibers such that articles using the recycled pulp fibers can easily achieve a uniform whiteness and users are not prone to feel psychological resistance to articles using the recycled pulp fibers. This method is described below. The method is characterized by involving: a step for supplying, from a mixed solution supply port (32) to a treatment tank (31), a mixed solution (51) which contains superabsorbent polymers and pulp fibers derived from multiple types of used sanitary products; a step for supplying an ozone-containing gas (53) from an ozone-containing gas supply port (43) to a treatment solution (52) inside of the treatment tank (31); a step in which, by raising the ozone-containing gas (53) while lowering the superabsorbent polymers and pulp fibers in the treatment tank (31), the ozone-containing gas (53) is brought into contact with the superabsorbent polymers and the pulp fibers, and the pulp fibers are bleached to form recycled pulp fibers; and a step for discharging the treatment solution (52) from a treatment solution discharge port (33), wherein the recycled pulp fibers have a 0-10 ΔYI with respect to a standard white plate.

The present disclosure belongs to the technical field of papermaking, and specifically relates to a short-sequence ECF bleaching process X/Z/D-E.sub.OP-D or X/D/Z-E.sub.OP-D for kraft wood pulp, comprising the following steps: (1) sequential bleaching (X/Z/D or X/D/Z): subjecting an oxygen delignified wood pulp to X/Z/D.sub.1 or X/D.sub.1/Z sequential bleaching to prepare a semi-bleached pulp; (2) reinforced alkaline extraction treatment (E.sub.OP): performing hydrogen peroxide and oxygen enhanced alkaline extraction treatment on the pulp after sequential bleaching to further dissolve the residual lignin in the pulp; (3) supplemental bleaching (D): performing a chlorine dioxide supplemental bleaching on the pulp after the enhanced alkaline extraction treatment to obtain a fully bleached pulp (88% ISO).

The present disclosure belongs to the technical field of papermaking, and specifically relates to a short-sequence ECF bleaching process X/Z/D-E.sub.OP-D or X/D/Z-E.sub.OP-D for kraft wood pulp, comprising the following steps: (1) sequential bleaching (X/Z/D or X/D/Z): subjecting an oxygen delignified wood pulp to X/Z/D.sub.1 or X/D.sub.1/Z sequential bleaching to prepare a semi-bleached pulp; (2) reinforced alkaline extraction treatment (E.sub.OP): performing hydrogen peroxide and oxygen enhanced alkaline extraction treatment on the pulp after sequential bleaching to further dissolve the residual lignin in the pulp; (3) supplemental bleaching (D): performing a chlorine dioxide supplemental bleaching on the pulp after the enhanced alkaline extraction treatment to obtain a fully bleached pulp (88% ISO).