Purification of aqueous reaction or washing medium containing cellulose ethers
AssigneeThe Dow Chemical Company
InventorsYvonne M. Goerlach-Doht, Hans P. Schneider, Juergen Hermanns, Ulf H. Haagensen
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Abstract
In a process for purifying an aqueous liquid reaction and/or washing medium containing i) hot water-insoluble cellulose ethers and ii) hot water-soluble cellulose ethers and/or macromolecular cellulose ether by-products, in a purification step a) the aqueous medium has a temperature above the gel point of the hot water-insoluble cellulose ether and gelled cellulose ether is separated from the aqueous medium by means of a solid-bowl centrifuge or a plate separator and in a purification step b) the remaining aqueous liquor is treated by ultrafiltration at a concentration ratio of at least 40.
Claims20
A process for purifying an aqueous reaction after removal of crude cellulose ether and/or washing medium containing i) a hot water-insoluble cellulose ether and ii) a hot water-soluble cellulose ether and/or macromolecular cellulose ether by-product, the process consisting of:
- a purification step a) wherein the aqueous medium is heated to or kept at a temperature above the gel point of the hot water-insoluble cellulose ether and gelled cellulose ether is separated from the aqueous medium by means of a solid-bowl centrifuge or a disk separator to leave an aqueous liquor, and
- a purification step b) wherein the aqueous liquor is treated by ultrafiltration at a concentration ratio of at least 40.
A process for purifying an aqueous reaction after removal of crude cellulose ether and/or washing medium containing i) a hot water-insoluble cellulose ether and ii) a hot water-soluble cellulose ether and/or macromolecular cellulose ether by-product, the process consisting of:
- a purification step a) wherein the aqueous medium is heated to or kept at a temperature above the gel point of the hot water-insoluble cellulose ether and gelled cellulose ether is separated from the aqueous medium by means of a solid-bowl centrifuge or a disk separator to leave an aqueous liquor, and
- a purification step b) wherein the aqueous liquor is treated by ultrafiltration a concentration ratio of at least 40 and the ultrafiltration is conducted by means of a polysulfone membrane.
A process for purifying an aqueous reaction after removal of crude cellulose ether and/or washing medium containing i) from 0.05 % to 1.5 % of hot water-insoluble cellulose ether and ii) from 0.01% to 2 % of hot water-soluble cellulose ether and/or macromolecular cellulose ether by-product, by the total weight of the aqueous composition, the process consisting of:
- a purification step a) wherein the aqueous medium is heated to or kept at a temperature above the gel point of the hot water-insoluble cellulose ether and gelled cellulose ether is separated from the aqueous medium by means of a solid-bowl centrifuge or a disk separator to leave an aqueous liquor, and
- a purification step b) wherein the aqueous liquor is treated by ultrafiltration at a concentration ratio of at least 40 and the ultrafiltration is conducted by means of a polysulfone membrane.
Dependencies are inferred from the claim text.