Methods for preparing alkali cellulose and cellulose ether
AssigneeShin-Etsu Chemical Co., Ltd.
InventorMitsuo Narita
Life of this patent
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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.
Claims11
A method for preparing alkali cellulose, comprising:
- a) introducing a pulp onto a moving filtration plane;
- b) a contact filtration step comprising
- bringing the pulp into contact with an alkali metal hydroxide solution on a moving filtration plane for vacuum filtration,
- filtering the alkali metal hydroxide solution through the moving filtration plane by vacuuming a back side of the moving filtration plane to collect a contact product remaining on the moving filtration plane,
- adjusting a height level of the pulp using two or more screw-type or blade-type leveling devices placed along a path of the moving filtration plane, and
- gathering the pulp towards a middle of the moving filtration plane from both sides of the moving filtration plane with the two or more screw-type or blade-type leveling devices;
- c) a draining step comprising draining the collected contact product to obtain a cake,
- wherein bringing the pulp into contact with the alkali metal hydroxide solution comprises spraying the alkali metal hydroxide solution from two or more spray ports placed along the path of the moving filtration plane, wherein adjusting and gathering is performed prior to or after bringing the pulp into contact with the alkali metal hydroxide solution, and
- wherein the screw-type or blade type leveling device adjusts the height level to 100 mm or less.
An apparatus for preparing alkali cellulose, comprising:
- a continuous horizontal vacuum filter type contactor comprising:
- a horizontal filtration plane moving in a horizontal direction for vacuum filtration through the filtration plane by vacuuming a back side of the filtration plane,
- a pulp inlet for introducing pulp onto the moving filtration plane,
- two or more spray ports placed along a path of the filtration plane configured to spray an alkali metal hydroxide solution to the pulp thus introduced,
- two or more screw-type or blade-type leveling devices placed along the path of the filtration plane wherein the two or more screw-type or blade-type leveling devices are configured to adjust a height level of the pulp introduced onto the filtration plane or the pulp brought into contact with the alkali metal hydroxide solution and to gather the pulp introduced onto the filtration plane or the pulp brought into contact with the alkali metal hydroxide solution to a middle from both sides of the filtration plane,
- a vacuum pump enabling vacuum suction of the back side of the moving filtration plane,
- an outlet for collecting a contact product remaining on the filtration plane after bringing the pulp into contact with the alkali metal hydroxide solution on the moving filtration plane for vacuum filtration, and
- a drainer for draining the contact product collected from the outlet to obtain a cake, and
- wherein the screw-type or blade type leveling device adjusts the height level to 100 mm or less.
Dependencies are inferred from the claim text.