# US 2006/0154004 A1 · Cake of easily dispersible precipated silica and process for producing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2006/0154004 A1 - Document ID: US20060154004A1 - Status: Published application - Kind: A1 - Application number: 10/520,466 - Filed: 2003-07-04 - Published: 2006-07-13 - Earliest claimed: 2002-07-10 - Assignees: Tokuyama Corporation - Inventors: Hirokatsu Hayashi; Kenji Fukunaga; Kentaro Fukuda - Web page: https://patentgrep.com/patent/US20060154004A1 ## CPC - C01B 33/143: of aqueous solutions of silicates - B41M 5/5218: {characterised by inorganic additives, e.g. pigments, clays} - B41M 5/5245: {characterised by the use of polymers containing cationic or anionic groups, e.g. mordants} - C01P 2004/50: Agglomerated particles - C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer - C01P 2004/80: Particles consisting of a mixture of two or more inorganic phases - C01P 2006/12: Surface area - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - B41M: PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING, (correction of typographical errors B41J; processes for applying transfer pictures or the like B44C1/16; fluid media for correction of typographical errors by coating C09D10/00; printing textiles D06P) - C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS ## Abstract A silica cake formed of easily dispersible precipitated silica having small primary particle size is provided, from which highly transparent silica dispersion can be effectively obtained. This silica cake is characterized by being a cake of precipitated silica having BET specific surface area of at least 220 m2/g, and when it is dispersed in ion-exchange water to provide an aqueous dispersion of the silica of 5% by weight in concentration and further diluted to reduce the silica concentration to 1.5% by weight, the dispersion having a light-scattering index (n-value) of at least 2. This silica cake can be obtained by simultaneously adding an alkali silicate and a mineral acid to a reaction liquid whose pH is being maintained at a fixed value within a range of 7.5-11.5 and whose temperature is being maintained at not lower than 90° C., whereby forming precipitated silica through their reaction, and separating said precipitated silica from the reaction liquid in wet state. ## Claims ### Claim 1 An easily dispersible cake of precipitated silica which is characterized by having BET specific surface area of at least 220 m2/g and when it is dispersed in ion-exchange water to provide an aqueous dispersion of the silica of 5% by weight in concentration and further diluted to reduce the silica concentration of 1.5% by weight, the dispersion having a light-scattering index (n-value) of at least 2. ### Claim 2 (depends on 1) An easily dispersible cake of precipitated silica according to claim 1, having a water content within a range of 83-93% by weight. ### Claim 3 A process for producing an easily dispersible cake of precipitated silica, characterized by using as an initial reaction liquid one selected from aqueous alkali silicate solution, alkaline aqueous solution of which pH is adjusted with a basic substance, and water; said process comprising simultaneously adding an alkali silicate and a mineral acid to a reaction liquid of which pH is being maintained at a fixed value within a range of 7.5-11.5 and of which temperature is being maintained at not lower than 90° C., whereby forming precipitated silica through their reaction; and separating said precipitated silica from said reaction liquid in wet state. ### Claim 4 (depends on 3) A process for producing an easily dispersible cake of precipitated silica according to claim 3, in which the concentration of the silica solid in the reaction mixture at the ending time of the reaction is not higher than 50 g/L. ### Claim 5 (depends on 1) A dispersion of precipitated silica which is characterized by being a dispersion of an easily dispersible cake of precipitated silica as described in claim 1 in a polar solvent, the average particle size of the precipitated silica particles present in the dispersion being not greater than 300 nm and the ratio of aggregated particles having a particle size equaling to or more than 500 nm being not higher than 5% by volume. ### Claim 6 (depends on 5) A dispersion of precipitated silica according to claim 5, in which further a cationic polymer is dispersed. ### Claim 7 (depends on 5) A process for preparing the dispersion of precipitated silica of claim 5, in which a silica slurry formed by dispersing a cake of precipitated silica in a polar solvent is subjected to a fine pulverization treatment with a high pressure homogenizer, wherein the cake of precipitated silica is characterized by having BET specific surface area of at least 220 m2/2 and when it is dispersed in ion-exchange water to provide an aqueous dispersion of the silica of 5% by weight in concentration and further diluted to reduce the silica concentration to 1.5% by weight, the dispersion having a light-scattering index (n-value) of at least 2. ### Claim 8 (depends on 6) A process for preparing a dispersion of precipitated silica according to claim 6, in which a liquid premixture formed by dispersing a cake of precipitated silica and cationic polymer in a polar solvent is subjected to a fine pulverization treatment with a high pressure homogenizer, wherein the cake of precipitated silica is characterized by having BET specific surface area of at least 220 m2/g and when it is dispersed in ion-exchange water to provide an aqueous dispersion of the silica of 5% by weight in concentration and further diluted to reduce the silica concentration to 1.5% by weight, the dispersion having a light-scattering index (n-value) of at least 2. ### Claim 9 (depends on 1) A coating liquid for ink-jet recording sheet which is characterized by being obtained by dispersing the easily dispersible cake of precipitate silica of claim 1 and a binder in a polar solvent, and the percent transmission of the coating liquid as measured after diluting the same to the silica concentration of 1.5% by weight being at least 20%. ### Claim 10 (depends on 9) A coating liquid for ink-jet recording sheet according to claim 9, which further comprises a cationic polymer. ### Claim 11 (depends on 9) A process for making a coating liquid for ink-jet recording sheet of claim 9, which is characterized by dispersing a cake of precipitated silica and a binder in a polar solvent, wherein the cake of precipitated silica is characterized by having BET specific surface area of at least 220 m2/g and when it is dispersed in ion-exchange water to provide an aqueous dispersion of the silica of 5% by weight in concentration and further diluted to reduce the silica concentration to 1.5% by weight, the dispersion having a light-scattering index (n-value) of at least 2. ### Claim 12 (depends on 10) A process for making a coating liquid for ink-jet recording sheet of claim 10, which is characterized by dispersing a cake of precipitated silica, cationic polymer and binder in a polar solvent, wherein the cake of precipitated silica is characterized by having BET specific surface area of at least 220 m2/g and when it is dispersed in ion-exchange water to provide an aqueous dispersion of the silica of 5% by weight in concentration and further diluted to reduce the silica concentration to 1.5% by weight, the dispersion having a light-scattering index (n-value) of at least 2.