Mandrel structure for use in manufacture of cellulose food casing

A method of diametrically sizing a tubular extrusion composed of a thermoplastic cellulose solution comprising:

• a) forming a seamless cellulose tube by downwardly extruding a tube of thermoplastic solution composed of non derivatized cellulose, a tertiary amine oxide and water through an air gap and into a non solvent bath;
• b) during the course of extruding, causing the extrusion to pass over and about a vertically oriented mandrel having a sizing portion generally in the shape of a hollow cylinder that has a diameter larger than the extruded tube, the mandrel having a lower end disposed below the level of the bath and a smooth outer surface provided with a plurality of openings to the interior of the hollow cylinder;
• c) passing gas bubbles evolving from the extruded tube at the interface between the extruded tube and sizing portion through the openings and into the hollow interior;
• and
• d) removing the gas from the hollow interior upwardly through the mandrel.