Methods for preparing alkali cellulose and cellulose ether
AssigneeShin-Etsu Chemical Co., Ltd.
InventorsMitsuo Narita, Masaki Tabata, Atsushi Yoshida, Hiroshi Umezawa
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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.
Claims15
A method for preparing a cellulose ether, comprising the steps of:
- bringing pulp into continuous contact with 35 to 60% by weight aqueous solution of alkali metal hydroxide to generate a contact mixture consisting essentially of alkali cellulose and unreacted alkali metal hydroxide solution, said pulp is in the form of chips;
- draining the contact mixture using a continuous centrifugal separator to separate a cake comprising the alkali cellulose from an alkali metal hydroxide containing liquid, wherein said centrifugal separator is a continuous centrifugal separator comprising a perforated rotor;
- and
- etherifying the alkali cellulose obtained in the draining step with an etherifying agent to produce cellulose ether,
- wherein the alkali metal hydroxide containing liquid obtained in the draining step is subjected to addition of a new alkali metal hydroxide solution and recycled into said step of bringing pulp into continuous contact in an amount equal to an amount of the alkali metal hydroxide solution contained in the alkali cellulose so as to keep the concentration of the alkali metal hydroxide solution constant in the step of bringing pulp into continuous contact.
A method for preparing a cellulose ether, comprising the steps of:
- bringing pulp into continuous contact with 35 to 60% by weight aqueous solution of alkali metal hydroxide to generate a contact mixture consisting essentially of alkali cellulose and unreacted alkali metal hydroxide solution, said pulp is in the form of chips;
- draining the contact mixture using a continuous centrifugal separator to separate a cake comprising the alkali cellulose from an alkali metal hydroxide containing liquid, wherein said centrifugal separator is a continuous centrifugal separator comprising a perforated rotor and said alkali metal hydroxide containing liquid having an alkali metal hydroxide concentration less than that of the alkali metal hydroxide concentration of the contact mixture;
- and
- etherifying the alkali cellulose obtained in the draining step with an etherifying agent to produce cellulose ether,
- wherein the 35 to 60% by weight alkali metal hydroxide solution is maintained at a constant predetermined concentration by mixing the alkali metal hydroxide containing liquid obtained in the draining step with a new alkali metal hydroxide solution having an alkali metal hydroxide concentration greater than the alkali metal hydroxide concentration of the alkali metal hydroxide containing liquid to form the 35 to 60% by weight alkali metal hydroxide solution used in the step of bringing pulp into continuous contact with the alkali metal hydroxide solution so as to keep the concentration of the 35 to 60% by weight alkali metal hydroxide solution constant in the step of bringing pulp into continuous contact.
A method for preparing a cellulose ether, comprising the steps of:
- bringing pulp into continuous contact with 35 to 60% by weight aqueous solution of alkali metal hydroxide to generate a contact mixture consisting essentially of alkali cellulose and unreacted alkali metal hydroxide solution, said pulp is in the form of chips;
- centrifuging the contact mixture with a continuous centrifugal separator comprising a perforated rotor to separate solid alkali cellulose from an alkali metal hydroxide containing liquid;
- and
- etherifying the alkali cellulose obtained in the centrifuging step with an etherifying agent to produce cellulose ether.
Dependencies are inferred from the claim text.