Abstract: Provided is a method for producing low-substituted hydroxypropyl cellulose with less yellowing. More specifically, the method for producing purified low-substituted hydroxypropyl cellulose includes the steps of: reacting alkali cellulose and an etherifying agent to obtain a reaction mixture; dispersing the reaction mixture in water containing a portion of acetic acid necessary for neutralizing the total amount of the reaction mixture to neutralize a portion of the reaction mixture, and then completely neutralizing with the remaining acetic acid to cause precipitation, to obtain a slurry containing crude low-substituted hydroxypropyl cellulose; disintegrating a solid component in the slurry through a cutter pump, the solid component containing the crude low-substituted hydroxypropyl cellulose, and discharging the slurry containing the disintegrated solid component; washing the discharged slurry with water to obtain a cake of purified low-substituted hydroxypropyl cellulose; and drying the cake.

Abstract: Provided is hydroxypropylmethylcellulose having a high thermal gelation temperature and a high thermal gel strength and a method for producing the same and a food comprising the hydroxypropylmethylcellulose. More specifically, provided is hydroxypropylmethylcellulose having an average substitution degree of a methoxy group of 1.0 to 2.0 per glucose unit, an average substitution degree of a hydroxypropoxy group of 0.05 to 0.4 per glucose unit, and a A/B value of 0.305 or greater wherein A represents a substitution degree of a methoxy group directly substituted for a hydroxy group on carbon at position 6 in a glucose unit free from a hydroxypropoxy group-substituted hydroxy group, B represents a substitution degree of a methoxy group per glucose unit, and the A/B represents a value of A divided by B.

Abstract: Provided is a method for preparing cellulose ether which is transparent as dissolved in water and has low water-insoluble content. More specifically, provided are a method for preparing alkali cellulose comprising a contact step of bringing a pulp sheet having a pore volume of 1.0 ml/g or greater, or chips into which the pulp sheet has been converted, into contact with an alkali metal hydroxide solution to obtain an alkali cellulose reaction mixture, and a drain step of draining the alkali cellulose reaction mixture; and a method for preparing water-soluble cellulose ether comprising a step of reacting the alkali cellulose with an etherifying agent.

Abstract: Provided is a method for preparing nonionic water-soluble cellulose ether having low insoluble content and providing a transparent solution. More specifically, provided is a method for preparing nonionic water-soluble cellulose ether comprising at least the steps of: drying a pulp sheet or pulp chips into which the pulp sheet has been converted, bringing the dried pulp sheet or pulp chips into contact with an alkali metal hydroxide solution to obtain alkali cellulose, draining the alkali cellulose, and reacting the drained alkali cellulose with an etherifying agent.

Abstract: A water-soluble cellulose ether is separated from its suspension by passing a suspension of water-soluble cellulose ether particles in water through a filter of perforated metallic or ceramic filter medium under pressure, removing the filter cake of water-soluble cellulose ether from the filter medium, and cleaning the filter medium with steam, compressed air or water under pressure. The invention enables to separate a water-soluble cellulose ether, especially having a high dissolution temperature, avoids the filter from being clogged, and extends the operative time of the filter.

Abstract: There is provided a method for producing alkali cellulose comprising efficiently removing cellulose particles which are introduced by a pulp and have accumulated in a circulating alkali metal hydroxide solution. More specifically, there is provided a method for producing alkali cellulose, comprising at least the steps of bringing a pulp into contact with an alkali metal hydroxide solution to obtain a contact product, draining the contact product by a drainer, reusing an alkali metal hydroxide solution recovered in the step of draining for contact with a pulp, and adjusting an amount of cellulose particles in the recovered alkali metal hydroxide solution to 0.5% by weight or less prior to reusing for contact with the pulp.

Abstract: Provided is a method for producing cellulose ether whose aqueous solution is transparent and contains a smaller amount of water-insoluble portion. The method comprises at least the steps of providing at least two alkali cellulose materials having different compositions, each of the materials having been prepared by bringing a pulp into contact with a solution of alkali metal hydroxide and draining; and mixing the at least two alkali cellulose materials having different compositions, wherein each weight ratio of the alkali metal hydroxide in each of the alkali cellulose materials having different compositions to a solid component in the pulp (alkali metal hydroxide/solid component in pulp) is equal to 0.4 to 2.5 times of a weight ratio of alkali metal hydroxide in the alkali cellulose obtained in the step of mixing to solid components in a sum of pulps used for preparation of the alkali cellulose materials.

Abstract: Provided is a method for efficiently preparing alkali cellulose having a uniform alkali distribution. More specifically, provided are a methods for preparing alkali cellulose comprising a contact filtration step of bringing a pulp into contact with an alkali metal hydroxide solution on a moving filtration plane for vacuum filtration to collect a contact product remaining on the filtration plane, and a draining step of draining the contact product; and a method of preparing cellulose ether by using the alkali cellulose. Also provided is an apparatus for preparing alkali cellulose comprising a continuous horizontal vacuum filter type contactor.

Abstract: A degree of polymerization of cellulose ether is accurately controlled, and quality and a manufacturing process of the cellulose ether are stabilized. There is provided a method for producing depolymerized alkali cellulose having a degree of polymerization controlled, comprising at least a step of depolymerizing, in the presence of an oxygen-containing gas flow, alkali cellulose obtained by bringing a pulp into contact with an alkali solution, while measuring feeding and discharging amounts of oxygen in the oxygen-containing gas flow. There is also provided a method for producing cellulose ether, comprising at least a step of adding an etherifying agent to the depolymerized alkali cellulose having a degree of polymerization controlled.

Abstract: When a combination of pulps having different alkali metal hydroxide solution absorption rates is as a raw material, contact conditions such as a contact temperature and a contact time have to be changed frequently, depending on the absorption rate of pulps currently processed, thereby causing a problem of reduced productivity. For solving the problem, provided is a method for producing alkali cellulose, comprising at least the steps of: bringing two or more types of pulps having different alkali metal hydroxide solution absorption rates into contact with an alkali metal hydroxide solution to obtain a contact product; and draining the contact product, wherein the highest absorption rate is not more than 4.0 times as fast as the lowest absorption rate.

Abstract: Provided is a method for producing low-substituted hydroxypropylcellulose in which depolymerization capable of achieving a target viscosity in a short time is carried out safely after an etherification reaction step. More specifically, provided is a method for producing low-substituted hydroxypropylcellulose having a degree of hydroxypropoxy substitution of from 9.5 to 16.0% by weight, comprising at least a step of reacting alkali cellulose with an etherifying agent and a step of carrying out depolymerization after the reaction.

Abstract: Provided is a method for preparing alkali cellulose having alkali distributed uniformly therein. A uniform alkali distribution in the alkali cellulose makes it possible to prepare cellulose ether which has been substituted uniformly in an etherification reaction step. The resulting cellulose ether does not contain a floating water-insoluble portion which will otherwise appear owing to insufficient substitution. More specifically, provided are a method for preparing alkali cellulose, comprising simultaneously feeding pulp powder and an aqueous alkali solution to a high speed disperser to continuously bring them into contact with each other and a method for preparing cellulose ether, comprising reacting the resulting alkali cellulose with an etherifying agent.

Abstract: Provided is hydroxypropylmethylcellulose having a high thermal gelation temperature and a high thermal gel strength and a method for producing the same and a food comprising the hydroxypropylmethylcellulose. More specifically, provided is hydroxypropylmethylcellulose having an average substitution degree of a methoxy group of 1.0 to 2.0 per glucose unit, an average substitution degree of a hydroxypropoxy group of 0.05 to 0.4 per glucose unit, and a A/B value of 0.305 or greater wherein A represents a substitution degree of a methoxy group directly substituted for a hydroxy group on carbon at position 6 in a glucose unit free from a hydroxypropoxy group-substituted hydroxy group, B represents a substitution degree of a methoxy group per glucose unit, and the A/B represents a value of A divided by B.

Abstract: Provided is a method for preparing cellulose ether which is transparent as dissolved in water and has low water-insoluble content. More specifically, provided are a method for preparing alkali cellulose comprising a contact step of bringing a pulp sheet having a pore volume of 1.0 ml/g or greater, or chips into which the pulp sheet has been converted, into contact with an alkali metal hydroxide solution to obtain an alkali cellulose reaction mixture, and a drain step of draining the alkali cellulose reaction mixture; and a method for preparing water-soluble cellulose ether comprising a step of reacting the alkali cellulose with an etherifying agent.

Abstract: Provided is a method for preparing cellulose ether which is transparent as dissolved in water and has low water-insoluble content. More specifically, provided is a method for preparing alkali cellulose, comprising a contact step of bringing a pulp sheet having a sheet density of 0.60 g/ml or less or being formed from pine, or chips into which the pulp sheet has been converted, into contact with an alkali metal hydroxide solution at 5 to 70° C. for 10 to 600 seconds to obtain an alkali cellulose reaction mixture, and a drain step of draining the reaction mixture, wherein an amount of the alkali metal hydroxide solution to be used for the contact step is selected so that the alkali cellulose obtained by the drain step has a ratio of a weight of alkali metal hydroxide component determined by neutralization titration of the alkali cellulose to a weight of solid component in the pulp {(alkali metal hydroxide component)/(solid component in the pulp)} of 0.3 to 1.5.

Abstract: The invention is a method for efficiently preparing alkali cellulose having a uniform alkali distribution therein. More specifically, the invention is a method for preparing alkali cellulose comprising steps of bringing pulp into continuous contact with an alkali metal hydroxide solution in a bucket conveyor type contactor to generate a contact mixture, and draining the contact mixture; a method for preparing a cellulose ether comprising use of the alkali cellulose thus prepared; and an apparatus for preparing alkali cellulose comprising a bucket conveyor contactor comprising at least one inlet port for introducing pulp and an alkali metal hydroxide solution at one end and at least one outlet port for discharging a contact mixture wherein the pulp and the alkali metal hydroxide solution can be moved from one end to the other end while bringing them into contact with each other to generate the contact mixture; and a drainer for separating a cake from the contact mixture discharged from the outlet port.

Abstract: The invention is an efficient method for preparing alkali cellulose having the low water content and a uniform alkali distribution therein. More specifically, the invention is a method for continuously preparing alkali cellulose comprising steps of bringing pulp into continuous contact with an alkali metal hydroxide solution to generate a contact mixture and then draining the contact mixture by a centrifugal separator. The invention also includes a method for preparing cellulose ether comprising a step of etherifying the alkali cellulose.

Abstract: The invention is a method for efficiently preparing alkali cellulose having a uniform alkali distribution therein. More specifically, the invention is a method for preparing alkali cellulose comprising steps of bringing pulp into continuous contact with an alkali metal hydroxide solution in a rotary feeder type contactor to generate a contact mixture, and draining the contact mixture; and a method for preparing cellulose ether comprising use of the alkali cellulose thus prepared; an apparatus for preparing alkali cellulose, comprising a rotary feeder comprising a cyclic housing comprising an inlet port and an outlet port, a cyclic contact drum being circularly rotatable along the housing in the housing and comprising a plurality of filter cells arranged in a circumferential direction, and a filtrate-discharging tube being disposed in a diameter direction inside of the cyclic contact drum and collecting the filtrate which has passed the filter, and a drainer for draining a cake discharged from the contactor.

Abstract: The invention is a method for efficiently preparing alkali cellulose having a uniform alkali distribution therein. More specifically, pulp and an excess alkali metal hydroxide solution are introduced continuously in a screw conveyor type contactor and brought into contact with each other in the screw conveyor type reactor. By changing at least one factor selected from the group consisting of a rotation speed of the screw conveyor, a screw pitch and a length of immersion zone, a ratio of an alkali to cellulose in the alkali cellulose obtained by draining is controlled. The alkali cellulose thus obtained is etherified into the corresponding cellulose ether.

Abstract: The invention is a method for efficiently preparing alkali cellulose having a uniform alkali distribution therein. More specifically, the invention is a method for preparing alkali cellulose comprising steps of bringing pulp into continuous contact with an alkali metal hydroxide solution in a pipe type contactor to generate a contact mixture and draining the contact mixture; a method for preparing cellulose ether comprising use of the alkali cellulose; and an apparatus for preparing alkali cellulose, comprising a pipe type contactor having at least one inlet port at one end thereof for introducing pulp and an alkali metal hydroxide solution, and an outlet port at the other end for discharging a contact mixture, wherein the pulp and the alkali metal hydroxide solution are moved from one end to the other end while bringing them into contact with each other, and a drainer for separating a cake from the contact mixture discharged from the contactor.