US 5,330,567 AGranted

Process and arrangement for preparing a solution of cellulose

AssigneeLenzing Aktiengesellschaft

InventorsStefan Zikeli, Bernd Wolschner, Dieter Eichinger, Raimund Jurkovic, Heinrich Firgo

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Abstract

There is disclosed a process for preparing solutions of cellulose in aqueous tertiary amine oxides from a suspension of cellulose in an aqueous solution of the tertiary amine oxide by supplying heat at a reduced pressure. The suspension is transported over a heating surface, spread in layers or coats, until a homogenous solution of the cellulose has formed, which has a viscosity of between 50 and 15,000 Pas.s. Feeding of the suspension and drawing-off of the homogenous solution are carried out continuously. The solutions are prepared in an indirectly heated evacuatable vessel provided with a stirring device. The vessel is designed as a cylindrical container including a centrically mounted stirring shaft having agitators joined thereto, the radial distance of the agitators from the internal wall of the container being 20 mm at the most. There are provided an intake for the cellulose suspension in the upper part of the container and an outlet for the homogenous cellulose solution in its lower end.

Claims9

Dependent claims

A method of preparing a solution of cellulose in aqueous tertiary amine oxide from a suspension of cellulose in an aqueous tertiary amine oxide solution using an apparatus comprising a vertically oriented indirectly heated and evacuatable vessel having a cylindrical internal wall, an inlet means in the upper part of the vessel, an elongated rotatable shaft mounted centrally of the vessel, a spreading means fixed to the shaft adjacent the inlet means, an agitator means fixed to the shaft below the spreading means, and an outlet means at the lower part of the vessel, said method comprising the steps of:

heating the internal wall of said vessel to a temperature of between 50.degree. and 150.degree. C.;
continuously supplying a suspension of cellulose in an aqueous solution of a tertiary amine oxide to the inlet means;
spreading the suspension on said heated internal wall with said spreading means as it is supplied to the inlet means to form a coat or layer on said internal wall;
continuously rotating said shaft to cause said agitator means to move said layer or coat downwardly along said heated inner wall while intensively mixing said suspension;
subjecting the interior of said vessel to a pressure of 0.5 mbar to 1000 mbar to promote evaporation of water from said layer or coat of cellulose suspension as it moves downwardly along said internal wall to concentrate said aqueous tertiary amine oxide solution until said cellulose dissolves;
and
continuously discharging the resultant cellulose solution from said outlet means.

4 more elements

Dependencies are inferred from the claim text.