Paper making and fiber liberation – Processes and products – Non-fiber additive
Patent
1992-05-08
1995-09-05
Bell, Mark L.
Paper making and fiber liberation
Processes and products
Non-fiber additive
106482, 2523156, 1621683, 162175, 162183, D21H 1769, B01J 1306, C04B 1404
Patent
active
054476046
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to new silica sols, to a process suitable for the production of the sols and to the use of the new sols in the production of paper. More particularly the invention relates to new silica sols which have particles with a high specific surface area and which have a fairly low molar ratio SiO.sub.2 to M.sub.2 O, ie a fairly high excess of alkali. The new sols are particularly suitable for use in the production of paper as additives in combination with cationic polymers.
Silica sols, which term is used herein for silica hydrosols, are aqueous systems with very small silica particles which can be used in several fields of application, among other things dependent on the particle size. At the production of paper silica based sols with anionic particles have gained an increased utilization during the last few years. The silica sols are here used as additives to the stock in combination with cationic polymers, primarily to increase retention and dewatering at papermaking. In the European patent 41056 is for example disclosed the use of colloidal silica sols in combination with cationic starch in the production of paper. It is stated in a general manner that the silica particles have a specific surface area within the range of from 50 to 1000 m.sup.2 /g. It is further generally stated for the sols that they have been stabilized with alkali to a molar ratio of SiO.sub.2 to M.sub.2 O of 10:1 to 300:1, and preferably to a ratio of 15:1 to 100:1. The at production of paper commercially used sols are of the type which have a colloidal particles with a particle size usually from about 4 to about 7 nm, ie a specific surface area of from about 700 to about 300 m.sup.2 /g and above all sols with particles having a specific surface area of about 500 m.sup.2 /g have been used commercially. It has generally been considered that sols with colloidal particles of the above given size have given the best results and they have also been preferred with regard to their stability. The commercial sols have usually had a molar ratio SiO.sub.2 to M.sub.2 O of about 40:1, ie they have been stabilized with smaller amounts of alkali. Attempts have been made, as evident from the mentioned European patent, to prepare silica sols with particles which have a high specific surface area. However, these have not been sufficiently stable to be used on a larger scale.
According to the present invention it has been found that silica sols with particles which have a high specific surface area are stable and that the high specific surface area can be maintained within a high range for sufficiently long times to enable commercial handling through the fact that the sols have a certain molar ratio SiO.sub.2 to M.sub.2 O.
The present invention thus relates to new silica sols which are characteristic in that they contain particles which have a comparatively high specific surface area and in that they have a comparatively low molar ratio SiO.sub.2 to M.sub.2 O (where M stands for alkali metal ion and/or ammonium ion and M preferably means a sodium ion), ie a comparatively high alkali content. It has been found that these sols which contain anionic particles are useful at the production of paper and similar products and that they hereby, in combination with cationic polymers, give very good improvement of retention and dewatering. In addition to silica sols as defined in the appended claims the present invention also relates to a process for the production of silica sols and to the use of the sols, as defined in the appended claims.
As has been mentioned above, the present silica sols are characteristic in that the silica particles have a comparatively high specific surface area and this is within the range of from 700 to 1200 m.sup.2 /g. The given specific surface area has been measured by means of titration with NaOH according to the method described by Sears in Analytical Chemistry 28(1956):12, 1981-1983. The silica sols according to the invention are further characteristic in that they have a comparatively low molar ratio SiO.
REFERENCES:
patent: 3533816 (1970-10-01), Oken
patent: 3655578 (1972-04-01), Yates
patent: 4385961 (1983-05-01), Svending et al.
patent: 4388150 (1983-06-01), Sunden et al.
patent: 4946557 (1990-08-01), Svending
patent: 5098448 (1992-03-01), Puppe et al.
Johansson Hans E.
Larsson Bo V.
Bell Mark L.
Eka Nobel AB
Hertzog Scott
LandOfFree
Silica sols, a process for the production of silica sols and use does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silica sols, a process for the production of silica sols and use, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silica sols, a process for the production of silica sols and use will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-470395