METHOD FOR OBTAINING SUPERABSORBENT POLYMERS VIA ALKALINE HYDROLYSIS WITH PRESSURIZED WATER VAPOUR, USING POLYACRYLONITRILE AND ACRYLIC FIBRES AND FABRICS

摘要

The present invention describes a method for producing superabsorbent polymers from polyacrylonitrile (PAN) that is virgin or recycled from acrylic fibre manufacturing waste and discarded fabrics. In order to produce the superabsorbent polymer, the PAN must be subjected to alkaline hydrolysis with pressurized water vapour in an autoclave. In conditions with a water vapour pressure of up to 5 kgf/cm2 and a PAN:OH- molar ratio of 1:0.5 to 0.95, the formation of cross-links of the polymer chain occurs simultaneously with the hydrolysis, and a cross-linked poly(acrylic acid-co-acrylamide) salt is obtained. The hydrolysis process also differs in that it does not use any type of mechanical agitation, graphitizing agents with starch or cross-linking agents, and does not make it necessary to precipitate the superabsorbent polymer obtained from the reaction medium with solvents or through pH adjustment with acids. In the conditions described in the invention, the polymer obtained with recycled PAN leaves the autoclave already having a moisture content of 20% to 35% and a swelling capacity of >150g H2O/g, for use in agricultural applications as a water retainer or soil conditioner, and in other applications. The invention is therefore relevant in the field of the environment and sustainability as it helps to solve three technical problems: recycling polymers, reducing water consumption for irrigation, and producing food.