| 摘要 |
A process for the manufacture of olefin polymers by polymerization of alpha -monoolefins by means of a silicic acid xerogel/chromium trioxide catalyst, which is obtained by a method wherein (1) a finely divided silicic acid xerogel is first manufactured by (1.1) employing a silicic acid hydrogel of relatively high solids content, (1.2) extracting at least 60% of the water contained in the hydrogel from the latter by means of a particular organic liquid, (1.3) drying the gel thus obtained until there is no further loss in weight (xerogel formation) and (1.4) reducing the xerogel thus obtained to particles of diameter from 20 to 2,000 mu m, 2. THIS XEROGEL IS THEN CHARGED WITH THE DESIRED AMOUNT OF CHROMIUM FROM A SOLUTION OF CHROMIUM TRIOXIDE OR A SOLUTION OF A CHROMIUM COMPOUND WHICH UNDER THE CONDITIONS OF STAGE (3) IS CONVERTED TO CHROMIUM TRIOXIDE, WITH EVAPORATION OF THE SOLVENT, AND 3. FINALLY THE PRODUCT THUS OBTAINED IS HEATED IN AN ANHYDROUS STREAM OF GAS CONTAINING OXYGEN. The process according to the invention is charaterized in that a catalyst is employed which is manufactured under such conditions that in stage (1) the starting material is a silicic acid hydrogel (1.1) which is substantially spherical, has a particle diameter of from 1 to 8 mm and is obtained by A. introducing a solution of sodium waterglass or potassium waterglass both longitudinally and tangentially into a vortical stream of an aqueous inorganic acid, B. spraying droplets of the resulting silicic acid hydrosol into a gaseous medium, C. allowing the sprayed hydrosol to solidify to a hydrogel in the gaseous medium and D. freeing the resulting substantially spherical hydrogel from salts by washing, without prior aging. The catalyst gives polymers having good processability.
|
