| 摘要 |
SILICAS IN THE FORM OF POWDER AND SUBSTANTIALLY SPHERICAL BEADS OR GRANULES ARE CHARACTERIZED BY A CTAB SPECIFIC SURFACE OF 140 AND 240 M2/G A HIGH ULTRASONIC DISAGGREGATION FACTOR, AN AVERAGE DIAMETER, WHICH IS SMALL AFTER ULTRASONIC DISAGGREGATION, AND OPTIONALLY, A POROUS DISTRIBUTION, THE POROUS VOLUME FORMED BY THE PORES WITH A DIAMETER OF 175 TO 275 A BEING LESS THAN 50OF THE POROUS VOLUME FORMED BY THE PORES WITH DIAMETERS OF 400 A OR LESS. THE SILICAS MAY BE USED AS REINFORCING FILLERS FOR ELASTOMERS. THE INVENTION ALSO CONCERNS A METHOD FOR PREPARING PRECIPITATED SILICA OF THE TYPE COMPRISING THE REACTION OF AN ALKALINE METAL SILICATE M WITH AN ACIDIFYING AGENT, RESULTING IN A SUSPENSION OF PRECIPITATED SILICA, AND THE SEPARATION AND DRYING OF SAID SUSPENSION, WHEREIN PRECIPITATION IS PERFORMED AS FOLLOWS: (I) AN INITIAL SEED IS FORMED COMPRISING A PORTION OF THE TOTAL QUANTITY OF ALKALINE METAL SILICATE M IN THE REACTION, THE SILICATE CONCENTRATION (EXPRESSED AS SIO2) IN SAID SEED BEING LESS THAN 20 G/L; (II) AN ACIDIFYING AGENT IS ADDED TO THE INITIAL SEED UNTIL AT LEAST 5OF THE QUANTITY OF M2O IN THE INITIAL SEED IS NEUTRALIZED; (III) THE ACIDIFYING AGENT AND THE REMAINING QUANTITY OF ALKALINE METAL SILICATE M ARE ADDED SIMULTANEOUSLY SO THAT THE RATIO OF THE QUANTITY OF ADDED SILICATE (EXPRESSED AS SIO2) TO THE QUANTITY OF SILICA IN THE INITIAL SEED (EXPRESSED AS SIO2) IS GREATER THAN 4 AND AT MOST 100.
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