Precipitated silica used as reinforcing filler for elastomers

Abstract

The invention relates to a novel process for the preparation of precipitated silica which can be used as a reinforcing filler for elastomers. The invention also relates to novel precipitated silicas in the form of powder, granules or, preferably, substantially spherical beads, these silicas being characterized in that they have a BET specific surface of between 185 and 250 m 2 /g, a CTAB specific surface of between 180 and 240 m 2 /g, and a pore distribution such that the pore volume V2 made up of the pores with a diameter of between 175 and 275 Å represents less than 50% of the pore volume V1 made up of the pores with diameters of less than or equal to 400 Å, a pore volume (V d1 ), made up of the pores with a diameter of less than 1 μm, of greater than 1.65 cm 3 /g, a fineness value (F.V.) of between 70 and 100 Å, and a content of fines (τ f ), after deagglomerability with ultrasound, of at least 50%.

1 - 26 . (canceled) 
     
     
         27 . A precipitated silica having:
 a BET specific surface of 185 to 220 m 2 g, a CTAB specific surface of 190 to 240 m 2 g, a pore distribution and pore volumes V1, and V2, such that the pore volume V2 made up of pores with a diameter of 175 to 275 Å represents less than 50% of the pore volume V1 made up of pores with diameters of less than or equal to 400 Å, a pore volume, made up of pores with a diameter of less than 1 μm, of at least 1.70 cm 3 /g, a pore volume V3 made up of pores with a diameter of 100 to 300 Å, of at least 0.82 cm 3 /g, a fineness value of 80 to 100 Å, and a content of fines, after deagglomeration with ultrasound, of at least 50%.   
     
     
         28 . A silica according to  claim 27 , comprising a pore distribution such that the ratio V2/V1 is not more than 0.45. 
     
     
         29 . A silica according to  claim 27 , comprising a median diameter, after deagglomeration with ultrasound, of less than 8.5 μm. 
     
     
         30 . A silica according to  claim 29 , wherein the median diameter, after deagglomeration with ultrasound, of 5 to 7 μm. 
     
     
         31 . A silica according to  claim 27 , comprising an ultrasound deagglomerability factor of greater than 5.5 ml. 
     
     
         32 . A silica according to  claim 31 , wherein the ultrasound deagglomerability factor is greater than 9 ml. 
     
     
         33 . A silica according to  claim 27 , comprising a total pore volume of greater than 3.0 cm 3 /g. 
     
     
         34 . A silica according to  claim 33 , wherein the total pore volume is 3.1 to 3.4 cm 3 /g. 
     
     
         35 . A silica according to  claim 27 , comprising a packed filling density of greater than 0.28. 
     
     
         36 . A silica according to  claim 27 , having an oil absorption value of 230 to 330 ml/100 g. 
     
     
         37 . A silica according to  claim 27 , being in the form of substantially spherical beads with an average size of at least 80 μm. 
     
     
         38 . A silica according to  claim 27 , being in the form of powder with an average size of at least 15 μm. 
     
     
         39 . A silica according to  claim 27 , being in the form of granules at least 1 mm in size. 
     
     
         40 . A reinforcing filler for elastomers, comprising a silica as defined in  claim 27 . 
     
     
         41 . A silica according to  claim 27 , wherein the pore volume of pores with a diameter of less than 1 μm, is 1.70 to 1.80 cm 3 /g. 
     
     
         42 . A silica according to  claim 30 , comprising a pore distribution such that the ratio V2/V1 is not more than 0.45. 
     
     
         43 . A silica according to  claim 30 , comprising an ultrasound deagglomerability factor of greater than 5.5 ml. 
     
     
         44 . A silica according to  claim 30 , comprising a total pore volume (TPV) of greater than 3.0 cm 3 /g. 
     
     
         45 . A silica according to  claim 30 , being in the form of substantially spherical beads with an average size of at least 80 μm. 
     
     
         46 . A silica according to  claim 30 , being in the form of powder with an average size of at least 15 μm. 
     
     
         47 . A silica according to  claim 30 , being in the form of granules at least 1 mm in size. 
     
     
         48 . A reinforcing filler for elastomers, comprising a silica as defined in  claim 30 . 
     
     
         49 . A silica according to  claim 27 , comprising a BET specific surface of 200 to 220 m 2 g and a CTAB specific surface of 190 to 205 m 2 g.