GB822587A - Processes for the preparation of solutions of amylose, and for the production of films, sheets, fibres and the like therefrom and articles thereof - Google Patents

Abstract

Amylose solutions are prepared wherein before, during or after the preparation of the amylose-water system an aldehyde or the trimer of formaldehyde is added thereto. Aldehydes specified are formaldehyde, acetaldehyde, acrolein, glyoxal and furfural. The aldehyde may be added to the amylose-water system at a temperature above the gelation temperature of the system, particularly when solutions of concentration exceeding 25% by weight of amylose are prepared. Films, sheets and other articles obtained from such amylose solutions are clear and transparent but are generally water-soluble. They may be rendered water-insoluble and water-resistant by heating, e.g. for 2 hours at 130-150 DEG C., or by bringing them into contact with gaseous ammonia. If an acid substance such as hydrochloric acid, oxalic acid or ammonium chloride is incorporated before, during or after the preparation of the amylose solution bringing the pH below 7, it is possible to obtain from these solutions films which are insoluble in water. If glyoxal is used as the aldehyde when preparing the amylose solution, films which are water-insoluble without an after-treatment may be obtained. In preparing the solutions, it is preferred to add a reducing agent such as sodium sulphite to combat discoloration. The solutions containing above 25% by weight of amylose may be used to produce amylose films by methods other than casting, such as, for example, by spreading, or by extruding in a coagulation bath; even spinning of fibres and dry spinning becomes possible.