Silica by precipitation at constant alkali number, and its use
View Patent ↗Precipitated silica or silicates, obtainable by acid precipitation of aqueous silicate solutions while maintaining a constant alkali number of at least 1.
1. A silica having the following physicochemical characteristics:
BET surface area
from 50 to 700 m 2 /g;
DBP absorption
from 100 to 450 g/100 g;
Choline chloride
from 150 to 400 g/100 g (75% ab-
absorption
sorption by weight aqueous solution);
CTAB surface area
from 50 to 350 m 2 /g;
DPB/choline chloride absorption
less than 1.07; and
Sears number
greater than 25 ml/5 g.
2. The silica of claim 1 , having a modified Sears number of from at least 25 to 45.
3. The silica of claim 1 , having a BET surface area of 180-210 m 2 /g, a DBP adsorption of 280-450 g/100 g, and a CTAB surface area of 130-200 m 2 /g.
4. A process for preparing precipitated silica, comprising:
simultaneously metering into an aqueous silicate solution more aqueous silicate solution and a Lewis and/or Brønsted acid over a precipitation period of 40 to 65 minutes followed by reacidifying the mixture to a pH of 7-3.0 to provide an acidified mixture having a solid content of the suspension of from 79.3 to 104 g/l,
optionally filtering the acidified mixture to obtain a filtered precipitated silica,
optionally drying the filtered precipitated silica,
wherein the metered addition of the aqueous silicate solution and the Lewis and/or Brønsted acid is carried out while maintaining a constant alkali number in the mixture of at least 15, and
wherein said silica has the following physicochemical characteristics:
BET surface area
from 50 to 700 m 2 /g;
DBP absorption
from 100 to 450 g/100 g;
Choline chloride
from 150 to 400 g/100 g (75% ab-
absorption
sorption by weight aqueous solution);
CTAB surface area
from 50 to 350 m 2 /g;
DPB/choline chloride absorption
less than 1.07; and
Sears number
greater than 25 ml/5 g.
5. The process of claim 4 , wherein the alkali number is of from 25 to 50.
6. The process of claim 4 , further comprising the addition of an electrolyte prior to or during the simultaneous addition of aqueous silicate solution and Lewis and/or Brønsted acid.
7. A method comprising contacting the precipitated silica of claim 1 with a feed additive, a chemical intermediate, or a laundry detergent component.
8. A method comprising contacting the precipitated silica of claim 1 with formic acid, propionic acid, lactic acid, phosphoric acid, choline chloride solution, a plant extract, a melamine resin, a coatings additive, a fragrance, or a detergent.
9. An elastomer, plastic, battery separator, toothpaste, catalyst support or flocculation assistant comprising the precipitated silica of claim 1 .
10. A process for preparing precipitated silica, comprising:
simultaneously metering into a vessel an aqueous silicate solution and a Lewis and/or Brønsted acid over a precipitation period of 40 to 65 minutes followed by reacidifying the mixture to a pH of 7-3.0 to provide an acidified mixture having a solid content of the suspension of from 79.3 to 104 g/l,
optionally filtering the acidified mixture to obtain a filtered precipitated silica,
optionally drying the filtered precipitated silica,
wherein the metered addition of the aqueous silicate solution and the Lewis and/or Brønsted acid is carried out while maintaining a constant alkali number in the mixture of at least 15, and
wherein said silica has the following physicochemical characteristics:
BET surface area
from 50 to 700 m 2 /g;
DBP absorption
from 100 to 450 g/100 g;
Choline chloride
from 150 to 400 g/100 g (75% ab-
absorption
sorption by weight aqueous solution);
CTAB surface area
from 50 to 350 m 2 /g;
DPB/choline chloride absorption
less than 1.07; and
Sears number
greater than 25 ml/5 g.
11. The process of claim 10 , wherein the alkali number is of from 25 to 50.
12. The process of claim 10 , further comprising the addition of an electrolyte prior to or during the simultaneous addition of aqueous silicate solution and Lewis and/or Brønsted acid.
13. The process of claim 4 , wherein said filtering of said acidified mixture is performed.
14. The process of claim 13 , wherein said drying of said filtered precipitated silica is performed.
15. The process of claim 10 , wherein said filtering of said acidified mixture is performed.
16. The process of claim 15 , wherein said drying of said filtered precipitated silica is performed.
17. The precipitated silica of claim 1 , having a modified Sears number greater than 28 ml/5 g.
18. The precipitated silica of claim 1 , having a modified Sears number greater than 28 ml/5 g.
19. The precipitated silica of claim 1 , having a modified Sears number greater than 28 ml/5 g.