Abstract: Silica sols which have a large alkali excess, i.e. a low molar ratio SiO.sub.2 to M.sub.2 O, and which contain silica particles with a high specific surface area. The silica sols can be prepared through acidification of a water glass solution and subsequent alkalization of the acid sol to the molar ratio in question. The sols are particularly suitable for use as additives, in combination with cationic polymers, in papermaking.

Abstract: Silica sols having a high content of microgel and aluminum modified particles with high specific surface area. The sols can be prepared by a process comprising acidification of a water glass solution, alkalization at a certain dry substance content, particle growth and aluminum modification. The sols are particularly suitable for use as additives, in combination with cationic polymers, in papermaking.

Abstract: In the production of paper or pulp sheets from a paper stock, a binder is added which comprises cationic and anionic components to improve the paper characteristics and the stock characteristics, such that increased retention and a more readily dewatered stock are obtained.The anionic component consists of colloidal anionic particles having at least one surface layer of aluminum silicate or aluminum-modified silicic acid, such that the surface groups of the particles contain silicium and aluminum atoms in a ratio of from 9.5:0.5 to 7.5:2.5.The cationic component consists of cationic carbohydrate having a degree of substitution of 0.01-1.0.