colloidal silicas, process for producing a colloidal silica, use of colloidal silica, and process for producing paper and cardboard

摘要

Colloidal Silicas, Process for Producing a Colloidal Silica, Use of Colloidal Silica, and Process for Making Paper and Cardboard The present invention relates to a colloidal silica having a ph above 10, molar ratio of sio2: m2o, in which m is alkali metal, from about 6: 1 to about 16: 1, soluble silica concentration above about 3000 mg of sodium2 / l, and s value from about 18 to about 40%. The invention further relates to a process for producing a colloidal silica comprising acidifying an aqueous metal silicate solution to a pH from 1 to 4 to form an acid colloid, alkalinizing the acid colloid by adding the silicate solution. aqueous alkali metal to obtain an intermediate colloid and stop the addition of aqueous alkali metal silicate solution when the intermediate colloid has reached a ph from about 5 to about 8, agitation of the intermediate colloid for a period of time from approximately 10 to about 6000 seconds without the addition of aqueous alkali metal silicate solution, alkalization of the intermediate colloid by the addition of aqueous alkali metal silicate solution to obtain a colloidal silica having a ph above about 10 and molar ratio of sio2: m2o, where m is alkali metal, from about 6: 1 to about 16: 1, and optional addition of an aluminum compound to the acid colloid, intermediate colloid or colloidal silica. The invention also relates to a colloidal silica obtainable by the process of the invention. The invention relates to the use of colloidal silica as a flocculating agent, in water purification and in the production of paper and cardboard. The invention further relates to a papermaking process comprising: (i) providing an aqueous suspension comprising cellulosic fibers; (ii) adding to the suspension one or more drainage and retention aids comprising colloidal silica; and (iii) dehydrating the suspension obtained to provide a sheet or mesh of paper or cardboard. 1/2