Cellulose@ sponge production from acetylated cellulose

摘要

Cellulose sponge production includes: (a) swelling cellulose by stirring with an at least 4-fold excess of 15-35 % caustic alkali solution with respect to the dry weight of the cellulose; (b) allowing to submerged cellulose to stand for 1 hour; (c) expressing the caustic alkali until the weight of the press-cake is three times the dry weight of the original cellulose; (d) milling the press-cake to a particle size of less than 3 mm diameter; (e) submerging the comminuted press-cake in a stirred vessel with a 5-fold amount of a liquid acetylating agent for Na-cellulose; (f) stirring the reaction mixture for 1 hour; (g) expressing the liquid phase from the solid mass with simultaneous suction; (h) washing the acetylated cellulose derivative with water; (i) drying the cellulose acetate mass at 100 deg C to form a powder; (j) dissolving the cellulose acetate derivative powder in a dimethylsulphoxide (DMSO) or dimethylacetamide (DMAC) based solvent system at 20-50 deg C to form a 4-12 % solution; (k) adding to the solution (= 100 wt. %) (i) 100-500 wt. % of a salt which is anhydrous at room temperature, water soluble and inert with respect to the cellulose derivative, as pore-former, (ii) 0.5 - 4 wt. % fibres which are insoluble in the solvent, and (iii) up to 5 wt. % colourants; (l) stirring or kneading the mixture at room temperature for 10-30 minutes to give homogeneous distribution of the components; (m) pressing a quantity of the composition into a mould with perforated walls having the desired final shape of the sponge; (n) immersing the mould in a boiling water bath until a coherent sponge body has been formed; (o) removing the mould from the boiling water and demoulding the product; and (p) washing the product with water.