| 摘要 |
A colloidal dispersion of a partially polymerized dimethylol urea or dimethylol urea ether is prepared by ageing an aqueous solution of substantially unpolymerized dimethylol urea or ether thereof containing sufficient sulphur dioxide to produce a pH between 0.5 and 3 when measured at a solids content of about 10 per cent until the dispersed particles have polymerized to dimensions within the colloidal range. The products are useful for improving the wet strength of waterlaid mineral fibre or wool products. The ethers of the di-methylol urea may be prepared with alcohols such as methyl or ethyl or glycols such as ethylene, diethylene, triethylene, or corresponding propylene or butylene glycols, or glycol monoethers. The dispersions are anionic, but may be mixed with the cationic dispersions described in Specification 622,905 without coagulation. Such mixed solutions may be added to suspensions of kraft paper fibres, glass, asbestos or wool fibres (see Group VIII) or used to treat woollen cloth. Other fibres may also be present in the suspension. The condensation products may be cured by heat on the fibres. In making felted asbestos fibre products, substances such as starch, wax, rubber, chlorinated waxes, soaps, drying oils, sodium silicate, talc, montan wax, stearin pitch, rosin, bitumens, chlorinated naphthalene or diphenyl, glue, casein, saponin, or metallic particles may be added to the dispersions. Examples describe the preparation of dispersions from aqueous solutions of dimethylol urea allowed to stand for various times in presence of sulphur dioxide. Electrophoresis of such dispersions and their use in making water-laid asbestos sheets is described and the properties of the sheets compared. In example (4) paraffin wax size is used in conjunction with the dimethylol urea dispersions to prepare asbestos sheets. In example (5) starch replaces the wax size. In example (6) the dispersions are used in making sheets of mixed kraft and asbestos fibres. In example (8) the dispersions are used in the manufacture of felted wool fibre products and for treating woollen fibre and cloth.ALSO:A colloidal dispersion of a partially polymerised dimethylol urea or dimethylol urea ether is prepared by ageing an aqueous solution of substantially unpolymerised dimethylol urea or ether thereof containing sufficient sulphur dioxide to produce a pH between 0.5 and 3, when measured at a solids content of about 10 per cent, until the dispersed particles have polymerised to dimensions within the colloidal range. The products are useful for improving the wet strength of waterlaid mineral fibre or wool products. The ethers of the di-methylol urea may be prepared with alcohols such as methyl or ethyl or glycols such as ethylene, diethylene, triethylene, or corresponding propylene or butylene glycols or glycol mono-ethers. The dispersions are anionic but may be mixed with the cationic dispersions described in Specification 622,905, [Group IV (a)], without regulation. Such mixed solutions may be used to treat woollen cloth. |
