Methods for preparing alkali cellulose and water-soluble cellulose ether

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. Also provided is a method for preparing water-soluble cellulose ether, comprising a step of reacting the resulting alkali cellulose with an etherifying agent.

1 . 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 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.   
   
   
       2 . A method for preparing alkali cellulose, comprising:
 a contact step of bringing a pulp sheet obtained by using pine as a raw material 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 a solid component in the pulp {(alkali metal hydroxide component)/(solid component in the pulp)} of 0.3 to 1.5.   
   
   
       3 . The method for preparing alkali cellulose according to  claim 1 , wherein the pulp sheet has a dichloromethane extract content of 0.10% by weight or less. 
   
   
       4 . A method for preparing water-soluble cellulose ether, comprising a step of reacting alkali cellulose prepared by the method according to  claim 1  with an etherifying agent. 
   
   
       5 . The method for preparing water-soluble cellulose ether according to  claim 4 , wherein 50% by weight or less of the alkali cellulose to be reacted with the etherifying agent has been within 60 minutes after the pulp is brought into contact with the alkali metal hydroxide solution. 
   
   
       6 . The method for preparing water-soluble cellulose ether according to  claim 4 , wherein the alkali cellulose to be reacted with the etherifying agent is in form of chips and is reacted with the etherifying agent after or while being ground. 
   
   
       7 . The method for preparing alkali cellulose according to  claim 2 , wherein the pulp sheet has a dichloromethane extract content of 0.10% by weight or less. 
   
   
       8 . A method for preparing water-soluble cellulose ether, comprising a step of reacting alkali cellulose prepared by the method according to  claim 2  with an etherifying agent. 
   
   
       9 . The method for preparing water-soluble cellulose ether according to  claim 8 , wherein 50% by weight or less of the alkali cellulose to be reacted with the etherifying agent has been within 60 minutes after the pulp is brought into contact with the alkali metal hydroxide solution. 
   
   
       10 . The method for preparing water-soluble cellulose ether according to  claim 9 , wherein the alkali cellulose to be reacted with the etherifying agent is in form of chips and is reacted with the etherifying agent after or while being ground.