Readily dispersible precipitated silica

- Nov 30, 2018-

1,Precipitated silica, characterized by the  following physico-chemical parameters:BET surface  area 120-300 m2/g CTAB surface area 100-300 m2/g BET/CTAB ratio 0.8-1.3 Sears index (consumption  of 6-25 ml 0.1 N NaOH) DBP index 150-300 g/100  g wk  coefficient <3.4 Particle size of the  degraded <1.0 μm particlesParticle size of the non- 1.0-100  μm. degradable  particles

2. A process for the preparation  of precipitated silica having the  following physico-chemical parameters:BET surface  area 120-300 m2/g CTAB surface area 100-300 m2/g BET/CTAB ratio 0.8-1.3 Sears index (consumption  of 6-25 ml 0.1 N NaOH) DBP index 150-300 g/100  g wk  coefficient <3.4 Particle size of the  degraded <1.0 μm ParticlesParticle size of the non- 1.0-100  μm Degradable  particles
comprising: reacting an alkali metal silicate with one or  more mineral acids at temperatures of 60°-95° C. at a pH of 7.0-11.0 with  continuous stirring, continuing the reacting step up to a solids  concentration of 40 g-110 g, adjusting the pH to a value between 3 and  5, filtering off the precipitated silica, and washing, drying,  optionally grinding and optionally granulating the precipitatedsilica


3. The process according to  claim 2, comprising at least  one condition selected from the group consisting of the solids concentration is  less than 80 g/l, the temperature is less than 80° C., the precipitation time is  less than 76 minutes the precipitation is interrupted and a dilute or  concentrated mineral acid is employed. 


4. The process according to  claims 2 or 3, wherein the following conditions are  maintained for the preparation of a precipitated silicahaving a BET surface area of  120 to 140 m2/g and a wk coefficient  of less than 3.4: Solids concentration: 68 to 85 g/l Temperature: 74° to 82° C. pH: 8 to 9, and said process comprises: adding water-glass and sulfuric acid over a  period of 15 to 25 minutes, interrupting the adding step for 30 to 90  minutes, and adding water-glass and sulfuric acid over a period of 50 to 70  minutes,where total precipitation time is 130 to 140 minutes. 


5. The process  according to claims 2 or 3,  wherein the following conditions are maintained for the preparation of  a precipitated silicahaving a BET surface area of  140 to 160 m2/g and a WK coefficient  of less than 3.4: Solids concentration: 40 to 60 g/l Temperature: 88° to 96° C. pH: 7 to 9, and said process comprises: adding water-glass and sulfuric acid over a  period of 38 to 50 minutes. 


6. The process according to  claims 2 or 3, wherein the following conditions are  maintained for the preparation of a precipitated silicahaving a BET surface area of  160 to 180 m2/g and a wk coefficient  of less than 3.4: Solids concentration: 68 to 84 g/l Temperature: 59° to 65° C. pH: 8 to 9, wherein said process  comprises: adding water-glass and sulfuric acid over a  period of 150 to 170 minutes. 


7. The process according to  claims 2 or 3, wherein the following conditions are  maintained for the preparation of a precipitated silicahaving a BET surface area of  180 to 200 m2/g and a wk coefficient  of less than 3.4: Solids concentration: 74 to 94 g/l Temperature: 75° to 83° C. pH: 8 to 10, wherein said process  comprises: adding water-glass and sulfuric acid over a  period of 60 to 70 minutes. 


8. The process according to  claims 2 or 3, wherein the following conditions are  maintained for the preparation of a precipitated silicahaving a BET surface area of  200 to 300 m2/g and a wk coefficient  of less than 3.4: Solids concentration: 70 to 110 g/l Temperature: 60° to 76° C. pH: 8 to 10, wherein said process  comprises: adding water-glass and sulfuric acid over a  period of 60 to 86 minutes. 


9. The process according to  claims 2 or 3, comprising: employing at least one member selected from  the group consisting of chamber filter presses, membrane filter presses, belt  filters, rotary filters, and automatic membrane filter presses. 


10. The process according to  claims 2 or 3, comprising: employing a dryer selected from the group  consisting of a flow dryer, rack dryer, flash dryer and spin-flash dryer. 


11. The process according to  claims 2 or 3, comprising: drying liquefied filter cakes in a spray dryer  with at least one member selected from the group consisting of an atomizer, a  two-component nozzle, a one-component nozzle and an integrated fluidized  bed. 


12. The process according to  claims 2 or 3, comprising: granulating the precipitated silica with a roller  compactor. 


13. Precipitated silicas  according to claim 1,  comprising: in which the symbols denote Z: —SCN, —SH, —Cl, NH(if q=1) or —Sx—(if  q=2), R and R1: an alkyl group having 1 to 4 carbon  atoms, the phenyl radical, wherein all the radicals R and Rcan each have the same or a  different meaning, R: a C1-C4-alkyl, C1-C4-alkoxy group, N: 0; 1 or 2, Alk: a divalent straight-chain or branched  hydrocarbon radical having 1 to 6 carbon atoms, m: 0 or 1, Ar: an arylene radical having 6 to 12 C atoms,  preferable 6 C atoms, P: 0 or 1, with the proviso that p and n do  not simultaneously denote 0 X: a number from 2 to 8, alkyl: a monovalent straight-chain or branched  unsaturated hydrocarbon radical having 1 to 20 carbon atoms, preferably 2 to 8  carbon atoms, alkenyl: a monovalent straight-chain or  branched unsaturated hydrocarbon radical having 2 to 20 carbon atoms, preferably  2 to 8 carbon atoms. 


14. The process for the preparation of the  silicas according to claim 13, comprising: modifying the precipitated silicas  with organosilanes in mixtures of 0.5 to 50 parts, based on 100 parts  of precipitated silica, carrying out the reaction  between precipitated silica and organosilane  during preparation of the mixture or externally by spraying on and subsequent  heat treatment of the mixture, or by mixing the silane and  the silica suspension with  subsequent drying and heat treatment.


 15. Vulcanizable rubber mixtures and  vulcanizates which comprise, as a filler, the precipitated silica according to  claim 1.