Purification of cellulose ether reaction product
AssigneeThe Dow Chemical Company
InventorMaurice L. Zweigle
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Abstract
In the preparation of organosoluble cellulose ethers, the content of alkali metal (hydroxides and the salts thereof) in the resulting cellulose ether is reduced by forming a solution of the cellulose ether and an organic solvent, converting the alkali metal hydroxide therein to an alkali metal salt and heating the resulting solution at conditions sufficient to (1) increase the size of the alkali metal salt particles and (2) remove any water therefrom. Filtering the resulting mixture and drying the filtrate yields a cellulose ether containing a very small percentage of alkali metal salt, e.g., often less than about 500 ppm.
Claims17
A method for reducing the content of alkali metal, in salt or hydroxide form, in an organosoluble cellulose ether, said method comprising
- a. preparing a solution of the cellulose ether, which cellulose ether contains alkali metal, and an organic solvent;
- b. converting the alkali metal hydroxide present in the solution to an alkali metal salt;
- c. heating the resulting solution at conditions such that (1) any water present in the solution is removed therefrom and (2) the alkali metal salt particles grow;
- and
- d. separating the cellulose ether from the enlarged salt particles.
An improved method for preparing a cellulose ether wherein an alkali cellulose is contacted with an etherifying agent at conditions sufficient to form a cellulose ether and the cellulose ether is then recovered from the remainder of the reaction medium, the improvement in said method comprising:
- a. forming a solution of the cellulose ether, which cellulose ether contains alkali metal in salt or hydroxide form, and an organic solvent at some time prior to recovering the cellulose ether from the remainder of the reaction medium;
- b. converting the alkali metal hydroxide in the solution to an alkali metal salt by contacting the alkali metal hydroxide with an acid;
- c. heating the resulting solution at conditions such that the water is removed therefrom and the particles of the alkali metal salt grow;
- and
- d. separating the enlarged salt particles from the remainder of the solution.
Dependencies are inferred from the claim text.