Chitosan yarn having a crystal structure corresponding to the anhydrous allomorph and a tensile strength, after immersion in demineralized water for fifteen hours, of at least 150 mpa

Abstract

The invention relates to a method for producing an elongate polysaccharide element, in particular a chitosan thread, comprising an operation of extruding an extrusible solution of said polysaccharide through an extrusion die and an operation of coagulating the extruded solution. The extrusible solution is a hydroalcoholic solution containing an alcohol that does not form an azeotrope with water and which has a boiling point of more than 150° C. at atmospheric pressure. The coagulation operation includes a step of evaporating the water, preferably over the alcohol, producing a gelled extruded elongate element in the form of a mainly alcoholic gel, in particular by subjecting the extruded solution to a hot air flow. At least one operation of eliminating the alcohol contained in said gel makes it possible to obtain the elongate polysaccharide element. The chitosan thread has a crystalline structure corresponding to the anhydrous allomorph and a rupture stress of at least 150 MPa after being immersed in demineralized water for fifteen hours. The apparatus (1) for the wet extrusion of polysaccharide thread () includes an extruder () with at least one extrusion die (), an evaporation enclosure () placed immediately after the output () of the extrusion die () and supplied with a hot air flow, a neutralization unit (), a washing unit (), a drying unit () and a winding unit ().