Preparation of cellulose sponge cloth free from sulphur compounds

摘要

Preparation of a cellulose sponge cloth involves (1) swelling pulp in a stirred vessel by covering it with at least a 4-fold excess of 15-35% aqueous alkali hydroxide solution with respect to the weight of dry pulp; (2) allowing it to stand for 1 hour; (3) pressing to remove the alkali until the weight of the cake is 3 times that of the dry pulp, then milling to a particle diameter < 3 mm; (4) covering the crushed cake with 5 times the amount of liquid acylating agent with respect to sodium cellulose; (5) stirring for 60 minutes; (6) removing the liquid by pressing and suction; (7) washing the resultant mass of cellulose derivative with water; (8) drying to a powder at 100 deg C; (9) making the powder into a 4-12 wt.% solution in a solvent system based on dimethyl sulphoxide (DMSO) or dimethylacetamide (DMA) at 20-50 deg C; (10) treating the solution (100 wt.%) with (a) 10-500 wt.% water-soluble salt, which is anhydrous at room temperature and inert towards the cellulose derivative, as pore former, (b) 0.5-4 wt.% fibres insoluble in the solvent and (c) /} 5 wt.% dye and foam former; (11) stirring or kneading the mixture at room temperature for 10-30 minutes, until all components are homogeneously distributed; (12) casting or spreading the mixture, in the thickness required for the sponge cloth, on a conveyor belt with the required 3-dimensional surface structure and passing the belt through a boiling water bath until a cohesive sponge web forms; (13) separating the product from the belt; (14) washing it with water; and (15) drying at 100 deg C. Also claimed is the sponge cloth made in this way.