Silica-based sols
View Patent ↗An aqueous sol containing silica-based particles which has an S-value within the range of from 10 to 45%, a viscosity within the range of from 5 to 40 cP, and a molar ratio of SiO 2 to M 2 O, where M is alkali metal or ammonium, within the range of from 10:1 to 40:1, or a silica content of at least 10% by weight. The invention further relates to a process for the production of silica-based particles comprising the steps of: (a) acidifying an aqueous silicate solution to a pH of from 1 to 4 to form an acid sol; (b) alkalising the acid sol at an SiO 2 content within the range of from 4.5 to 8% by weight to; (c) allowing particle growth of the alkalised sol for at least 10 minutes, or heat-treating the alkalised sol at a temperature of a least 30° C.; and then (d) alkalising the obtained sol to a pH of at least 10.0. The invention further relates to silica-based particles obtainable by the process, the use of the silica-based particles as drainage and retention aids in the production of paper as well as a process for the production of paper from an aqueous suspension containing cellulosic fibers, and optional filler, in which silica-based particles and at least one charged organic polymer are added to the cellulosic suspension.
1. An aqueous sol containing silica-based particles, which sol has:
(i) an S-value within the range of from 10 to 45%;
(ii) a viscosity within the range of from 5 to 40 cP; and
(iii) a molar ratio of SiO 2 to M 2 O, where M is alkali metal or ammonium, within the range of from 10:1 to 40:1; and
(iv) the silica-based particles have a specific surface area within the range of from 550 to 725 m 2 /g.
2. The aqueous sol according to claim 1 , wherein the S-value is within the range of from 20 to 40%.
3. The aqueous sol according to claim 1 , wherein the sol has a molar ratio of SiO 2 to M 2 O, where M is alkali metal or ammonium, within the range of from 15:1 to 30:1.
4. The aqueous sol according to claim 1 , wherein the sol has pH of at least 10.6.
5. The aqueous sol according to claim 1 , wherein the sol has a viscosity within the range of from 7 to 25 cP.
6. The aqueous sol according to claim 1 , wherein the sol has a molar ratio of Al 2 O 3 to SiO 2 within the range of from 1:4 to 1:1500.
7. The aqueous sol according to claim 1 , wherein the sol has a molar ratio of B, where B is boron, to SiO 2 within the range of from 1:4 to 1:1500.
8. The aqueous sol according to claim 1 , wherein the sol has a molar ratio of Al to B, where B is boron, within the range of from 100:1 to 1:100.
9. An aqueous sol containing silica-based particles, which sol has:
(i) an S-value within the range of from 10 to 45%;
(ii) a viscosity within the range of from 5 to 40 cP; and
(iii) a silica content of at least 10% by weight; and
(iv) the silica-based particles have a specific surface area within the range of from 550 to 725 m 2 /g.
10. The aqueous sol according to claim 9 , wherein the S-value is within the range of from 20 to 40%.
11. The aqueous sol according to claim 9 , wherein the sol has a pH of at least 10.6.
12. The aqueous sol according to claim 9 , wherein the sol has a silica content within the range of from 12 to 20% by weight.
13. The aqueous sol according to claim 9 , wherein the sol has a viscosity within the range of from 7 to 25 cP.
14. The aqueous sol according to claim 9 , wherein the sol has a molar ratio of SiO 2 to M 2 O, where M is alkali metal or ammonium, within the range of from 10:1 to 40:1.
15. An aqueous sol containing silica-based particles, which sol has:
(i) an S-value within the range of from 10 to 45%;
(ii) a viscosity within the range of from 7 to 25 cP;
(iii) a silica content of at least 10% by weight;
(iv) a molar ratio of SiO 2 to M 2 O, where M is alkali metal or ammonium, within the range of from 10:1 to 40:1; and
(v) a pH of at least 10.6.
16. The aqueous sol according to claim 15 , wherein the silica-based particles have a specific surface area of at least 300 m 2 /g up to 1050 m 2 /g.
17. The aqueous sot according to claim 15 , wherein the silica-based particles have a specific surface area within the range of from 775 to 1050 m 2 /g.
18. The aqueous sol according to claim 15 , wherein the silica-based particles have a specific surface area within the range of from 550 to 725 m 2 /g.
19. An aqueous sol containing silica-based particles, which sol has:
(i) an S-value within the range of from 10 to 45%;
(ii) a viscosity within the range of from 5 to 40 cP;
(iii) a silica content of at least 10% by weight;
(iv) a molar ratio of SiO 2 to M 2 O, where M being alkali metal or ammonium, within the range of from 10:1 to 40:1; and
(v) the sol is modified by an aluminium-containing compound, a boron-containing compound or a mixture thereof.
20. The aqueous sol according to claim 19 , wherein the silica-based particles have a specific surface area of at least 300 m 2 /g up to 1050 m 2 /g.