POLYAMIDE-BASED SYNTHETIC SAUSAGE CASING ABLE TO BE FILLED WITHOUT STRETCHING AND METHOD OF PRODUCTION THEREOF

摘要

The invention relates to single- or multilayer synthetic heat-shrinkable sausage casings that one can fill without preliminary humidification and virtually without stretching and make as a result taut sausages, and also relates to a method of production of such casings. At least one polyamide layer of the casing is made of polyamide resin based on at least one aliphatic (co)polyamide, selected from polyamide-6, polyamide-66 or copolyamide-6/66. The casing, being ready to be filled, has following characteristics: the Young's modulus is not less than 300 MPa in the machine direction and not less than 400 MPa in the transverse direction; on exposure to an air with relative humidity 60% and a temperature of 25°C for 5 days its shrinkage value is no more than 2% both in the machine and transverse directions; on exposure to a water with temperature 40°C for 2 hours its shrinkage value is 3-10% in the machine direction and 4-10% in the transverse direction; on exposure to water with temperature 80°C for 30 minutes its shrinkage value is 8-15% in the machine direction and 9-18% in the transverse direction. The method of production of such sausage comprises extrusion of single- or multilayer extrudate, resulting in tubular film, orientation drawing and thermofixation of the tubular film, and the subsequent additional treatment. The subsequent treatment consists in additional drawing of the oriented thermofixed tubular film, having temperature of 60-140°C, by 3-8% in the machine direction and 4-10% in the transverse direction; subsequent cooling of this tubular film, while it is in the drawn (strained) state, to the temperature that is not higher than glass transition temperature of the polyamide composition of the polyamide layer; and its winding up on a core. Said steps of the process can be performed at the aggregate that is either built in the line for accomplishment of the previous steps of process, or at a separate machine.