Process and apparatus for making tubing and product so produced

Abstract

Abstract 524,777. Moulding sausage skins &c. SYLVANIA INDUSTRIAL CORPORATION. Feb. 7, 1939, No. 4026. Convention date, Feb. 19, 1938. [Class 87 (ii)] [Also in Group IV] Tubing for use as sausage skins, or for packing other foodstuffs or other articles, is made from non-fibrous coagulable plastic material by a continuous process comprising the steps of shaping the material into the form of a tube, completely coagulating the material, subjecting the tube to stretching by application of internal pressure and subjecting it to a fixing operation while in the stretched state. The tube may be formed by coating a mandrel with a solution or dispersion of the plastic material or by extrusion through an orifice. Longitudinal as well as transverse stretching may be effected. The plastic may be a cellulose ester or ether, e.g., one which is soluble in organic solvents, or alkalies, or water. It may be cellulose acetate, nitrate, or butyrate, or methyl cellulose, benzyl cellulose, a cellulose etber xanthate, cellulose thiourethane, or cellulose xanthofatty acid. It may be a urea-formaldehyde, vinyl, or glycerolphthalic anhydride resin, or rubber, chlorinated rubber, gelatine or casein. Cellulose derivatives may be fixed after stretching by converting them to cellulose hydrate. Soft resins may be fixed by converting them into a hard non-fusible form by heating, radiation, or other means. The major part of the solvents are removed before the stretching. They may be replaced by swelling agents. Stretching may be facilitated by heating the tube. As shown in Fig. 2, tubing which has been produced by extrusion and wet coagulation, and which has passed through a chamber 7 in opposite direction to a current of heated air is passed between pressure rolls 9, flattening rolls 10, rollers 11, and drawing rolls 12. Longitudinal stretching is effected by rolls 12, and transverse stretching by means of liquid 13 within the tubing. The transverse stretch is adjusted by travelling belts 14, and plates 16. The tube 2 may be surrounded by a casing containing steam or vapour, at the place where it contains liquid 13. Gas may be used instead of liquid for effecting the transverse stretch. The expanded tube may be fixed by chilling it, by passing through a cold liquid, if it has been softened by heat. As shown in Fig. 5, the tube 2 passes through chamber 37 where it is rendered more plastic, and then over mandrel 39. The stretched tube is set by means of a liquid which chills or hardens it. As shown in Fig. 6, the tube 2 passes through a softening liquid in bath 49 and between squeeze rolls 50. It is then extended to normal diameter by means of a column 51 of heavy liquid, e.g. mercury. It then passes through vacuum chamber 52 wherein the cylindrical parts 55, 56 are connected by a porous fabric or earthenware tube 57. Pressure of gas within the plastic tube causes it to be pressed against fabric 57 and stretched.

Inventors

No inventors recorded.

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