| 摘要 |
<p>A composition for rendering fabrics water-repellent comprises a mixture of 20-70 per cent by weight of a methylpolysiloxane containing between 2 and 2.1 CH3 radicals per Si atom and with a viscosity of 1000 to 100,000 centistokes at 25 DEG C., and 80-30 per cent of a methylhydrogenpolysiloxane containing between 1.0 and 1.5 CH3 radicals and between 0.75 and 1.25 hydrogen atoms bonded to silicon per Si atom, there being a total of 2 to 2.25 CH3 radicals and H atoms per Si atom in the methylhydrogen polysiloxane. The mixtures may be subsequently polymerized with evolution of hydrogen by heating at 100 DEG to 475 DEG F. for 5 seconds to 1 hour. Catalysts which may be added to the mixture include sodium bicarbonate, sodium aluminate and iron, cobalt, manganese, lead and zinc salts of carboxylic acids such as acetates, octoates and naphthenates. The composition may be diluted with a hydrocarbon, chlorohydrocarbon, ether or alcohol, e.g. benzene, dioxane or ethanol, or emulsified with water and an emulsifying agent decomposable by heat, e.g. trimethylbenzylammonium chloride and hexadecyldimethylbenzylammonium chloride, the above solvents being used, if desired to thin the emulsions. An organic acid, e.g. acetic acid may be added to inhibit liberation of hydrogen. The liquid dimethylpolysiloxane, end blocked with trimethylsiloxy units, may be made by heating a mixture of decamethyltetrasiloxane, octamethylcyclotetrasiloxane and potassium hydroxide to 160 DEG C., cooling to 100 DEG C. and adding dry ice, with subsequent filtration and distillation under reduced pressure. The other polysiloxane may be made by adding aqueous isopropanol to a benzene solution of CH3.H.Si Cl3, and (CH3)3SiCl, subsequent vacuum distillation yielding a trimethylsiloxy end-blocked methylhydrogenpolysiloxane. Examples are given of various mixtures for rendering fabrics water-repellent. Specification 640,067 is referred to.</p> |
