Silica-based sols
View Patent ↗The invention relates to a sol containing silica-based particles having an axial ratio of at least about 10 and specific surface area of at least about 600 m2/g. The invention further relates to a sol containing silica-based particles having an axial ratio of at least about 10 and S-value up to about 25. The invention further relates to a sol containing silica-based particles having an axial ratio of at least about 10 and a specific surface area of at least about 400 m2/g, wherein the silica-based particles are surface-modified. The invention further relates to a sol containing silica-based particles having a viscosity of at least 50 cP and silica content of at least about 3% by weight, wherein the silica-based particles have a specific surface area of at least about 400 m2/g. The invention further relates to a process for producing the aqueous silica-based sol according to the invention, a sol containing silica-based particles obtainable by the process, use of the sol containing silica-based particles as a flocculating agent. The invention further relates to a process for producing paper in which the sol containing silica-based particles is used as a drainage and retention aid.
1. A process for producing paper which comprises:
(i) providing an aqueous suspension comprising cellulosic fibers;
(ii) adding to the suspension one or more drainage and retention aids comprising a sol containing silica-based particles having an axial ratio of at least about 10 and specific surface area of at least about 600 m 2 /g; and
(iii) dewatering the obtained suspension to provide a sheet or web of paper.
2. The process of claim 1 , wherein said silica-based particles have a specific surface area in the range of from about 800 to about 1600 m 2 /g.
3. The process of claim 1 , wherein said silica-based particles have a specific surface area of at least about 1000 m 2 /g.
4. The process of claim 1 , wherein said sol is modified with aluminum.
5. The process of claim 1 , wherein said sol has an S-value up to about 35%.
6. The process of claim 1 , wherein said sol has an axial ratio of at least about 11.
7. The process of claim 1 , wherein said one or more drainage and retention aids comprise cationic starch.
8. The process of claim 1 , wherein said one or more drainage and retention aids comprise a cationic synthetic polymer.
9. The process of claim 1 , wherein said one or more drainage and retention aids comprise an anionic polymer.
10. The process of claim 1 , wherein said one or more drainage and retention aids comprise a polyacrylamide.
11. A process for producing paper which comprises
(i) providing an aqueous suspension comprising cellulosic fibers;
(ii) adding to the suspension one or more drainage and retention aids comprising an aqueous sol containing silica-based particles having an axial ratio of at least about 10 and S-value up to about 25%; and
(iii) dewatering the obtained suspension to provide a sheet or web of paper.
12. The process of claim 11 , wherein said sol has an axial ratio is at least about 11.
13. The process of claim 11 , wherein said sol has an axial ratio is at least about 12.
14. The process of claim 1 , wherein said sol has an axial ratio of at least about 13.
15. The process of claim 1 , wherein said sol has an axial ratio of at least about 50.
16. The process of claim 11 , wherein said sol has an S-value in the range of from about 5 to about 20%.
17. The process of claim 11 , wherein said sol is modified with aluminum.
18. The process of claim 11 , wherein said one or more drainage and retention aids comprise cationic starch.
19. The process of claim 11 , wherein said one or more drainage and retention aids comprise a cationic synthetic polymer.
20. The process of claim 11 , wherein said one or more drainage and retention aids comprise a polyacrylamide.
21. A process for producing paper which comprises:
(i) providing an aqueous suspension comprising cellulosic fibers;
(ii) adding to the suspension one or more drainage and retention aids comprising a sol containing silica-based particles having an axial ratio of at least about 10 and specific surface area of at least about 400 m 2 /g; wherein the silica-based particles are surface modified; and
(iii) dewatering the obtained suspension to provide a sheet or web of paper.
22. The process of claim 21 , wherein said silica-based particles are surface modified with aluminum.
23. The process of claim 21 , wherein said sol containing silica-based particles has a mole ratio of Si:Al of from about 1:1 to about 40:1.
24. The process of claim 21 , wherein said one or more drainage and retention aids comprise one or more organic polymers selected from the group consisting of anionic starch, amphoteric starch, cationic starch, anionic acrylamide-based polymer, amphoteric acrylamide-based polymer, cationic acrylamide-based polymer, and mixtures thereof.
25. A process for producing paper which comprises:
(i) providing an aqueous suspension comprising cellulosic fibers;
(ii) adding to the suspension one or more drainage and retention aids comprising a sol containing silica-based particles having a viscosity of at least 50 cP and silica content of at least about 3% by weight, wherein the silica-based particles have a specific surface area of at least about 400 m 2 /g and wherein the sol is diluted to a silica content within the range of from 0.05 to 2% by weight prior to addition to the suspension; and
(iii) dewatering the obtained suspension to provide a sheet or web of paper.
26. The process of claim 25 , wherein said silica-based particles have a specific surface area of at least about 600 m 2 /g.
27. The process of claim 25 , wherein said silica-based particles have a specific surface area of at least about 1000 m 2 /g.
28. The process of claim 25 , wherein said sol containing silica-based particles has a viscosity of at least 75 cP.
29. The process of claim 25 , wherein said sol containing silica-based particles has a silica content of at least about 5% by weight.