| 摘要 |
Latex is thickened to any desired degree without coagulation by the addition thereto of a colloidal sulphide, and a fixed alkali, preferably zinc sulphide and sodium hydroxide. Auxiliary thickeners and stabilizers such as soap, glue, may also be added. The colloidal sulphide is preferably formed in situ in the latex. According to an example, to 286 parts of normal latex (35 per cent solids) is added 10 parts of a 10 per cent sodium oleate solution, 6 parts of sodium polysulphide solution, and a paste consisting of 0,25 glue, 5 water, 5 zinc oxide and 6 sodium polysulphide solution. To this mix is added 2,15 parts of a 25 per cent solution of sodium hydroxide. The sodium polysulphide solution consists of 100 parts Na2S.9H2O, 50 parts sulphur, and 46 parts water. If the films obtained from this latex are to be vulcanized, additional sulphur is added. The viscosity depends upon the amount of alkali added, and may be reduced at any time by the addition of a weak acid, such as boric. Ammonium or potassium polysulphides, or a solution of sulphur in sodium hydroxide may replace the sodium polysulphide.
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