Paper making and fiber liberation – Processes and products – Non-fiber additive
Patent
1995-02-03
1997-02-18
Chin, Peter
Paper making and fiber liberation
Processes and products
Non-fiber additive
1621812, 1621816, 162183, D21H 2110
Patent
active
056038054
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to new silica sols, to a process suitable for preparation 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 of a certain specific surface area and which have a comparatively high amount of so called microgel. The new sols are particularly suitable for use as additives in combination with polymers in the production of paper.
Silica sols, which term is used herein for silica hydrosols, are aqueous systems with very small silica particles which find use in a variety of fields, among other things dependent on the particle size. In the production of paper silica based sols with very small, colloidal, anionic silica particles have found an increasing utilization during the last few years. Silica sols are hereby used as additives to the stock in combination with cationic or amphoteric polymers, mainly for improving retention and dewatering in the production of paper. In the European patent 41056 the use of colloidal silica sols in combination with cationic starch is for example disclosed. In the PCT applications WO 86/00100 and WO 86/05826 combinations of silica sols, with particles where at least the surface groups contain aluminium, and cationic natural polymers and cationic polyacrylamides, respectively, are disclosed. The silica particles are generally stated to have a specific surface area within the range of from 50 to 1000 m.sup.2 /g. The sols which are used commercially in paper production are of the type which have discrete colloidal particles with a particle size usually of 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 particles of the above mentioned size give the best results and they have also been preferred with regard to stability. Quite generally it has been an aim that the silica sols should be as monodisperse as possible, ie that the particles of the sols should be discrete and non-aggregated and have as narrow particle size distribution as possible. At the preparation of sols it has thus been sought to avoid aggregation, ie formation of microgel. According to the PCT application WO 91/07350 silica sols with a certain degree of microgel formation have been developed. These sols are based on particles with a very high specific Surface area and have been found especially useful in combination with polymers in the production of paper. The sols are based on particles with very high specific surface area, from 750 to 1000 m.sup.2 /g, preferably from 800 to 950 m.sup.2 /g, and the particles are surface modified with aluminium for stabilization of the high surface area.
According to the present invention it has been found that sols of silica based particles, ie particles based on SiO.sub.2, which have a specific surface area within the range 300 to 700 m.sup.2 /g and which contain comparatively high amount of microgel give very good effect as concerns retention and dewatering in papermaking. It has especially been found that sols with particles of the given specific surface area and content of microgel according to the invention give substantially improved effect when they are used in combination with cationic acrylamide based polymers in comparison with previously used silica based sols with specific surface area in the same range which substantially contain discrete particles. The content of microgel, or aggregate, can be controlled during the production of the sols.
The present invention thus relates to new silica sols, as further defined in claims, and also relates to a process for the production of the sols and to the use of the sols.
The new sols are characteristic in that they have a high content of microgel, ie a low S-value, and in that the sol particles have a specific surface area within the range from 300 to 700 m.sup.2 /g. The given specific surfa
REFERENCES:
patent: 2727008 (1955-12-01), Iler
patent: 2892797 (1959-06-01), Alexander et al.
patent: 2974108 (1961-03-01), Alexander
patent: 3533816 (1970-10-01), Oken
patent: 3922393 (1975-11-01), Wallace
patent: 3947376 (1976-03-01), Albrecht
patent: 3956171 (1976-05-01), Moore et al.
patent: 4272409 (1981-06-01), Bergna
patent: 4385961 (1983-05-01), Svending et al.
patent: 4798653 (1989-01-01), Rushmere
patent: 4927498 (1990-05-01), Rushmere
patent: 4964954 (1990-10-01), Johansson
patent: 5066420 (1991-11-01), Chevallier
patent: 5100581 (1992-03-01), Watanabe et al.
patent: 5236623 (1993-08-01), Chevallier
patent: 5368833 (1994-11-01), Johansson et al.
patent: 5447604 (1995-09-01), Johansson et al.
patent: 5470435 (1995-11-01), Rushmere et al.
Andersson Kjell
Larsson Bo
Lindgren Erik
Chin Peter
Eka Nobel AB
Mancini Ralph J.
Morris Louis A.
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