Method of preparing high-concentration colloidal silica

A method of producing a colloidal silica, comprising:

• preparing a first basic aqueous solution (B1) by dissolving a basic catalyst represented by [Chemical Formula 1], [Chemical Formula 2], or [Chemical Formula 3] below in distilled water;
• preparing a second basic aqueous solution (B2) by dissolving a basic catalyst represented by [Chemical Formula 1], [Chemical Formula 2], or [Chemical Formula 3] below in distilled water;
• preparing reactants by providing the first basic aqueous solution (B1) into a reactor and then providing to the reactor simultaneously an alkoxysilane and the second basic aqueous solution (B2) to two different portions of the reactor, wherein the alkoxysilane comprises tetramethyl orthosilicate (TMOS) or tetraethyl orthosilicate (TEOS);
• preparing a first colloidal silica (CS1) by performing hydrolysis/condensation of the reactants;
• and
• preparing a product comprising a second colloidal silica (CS2) by simultaneously adding the second basic aqueous solution (B2) and the alkoxysilane dropwise to the first colloidal silica (CS1):
• R1R2N—(CH2)n—X [Chemical Formula 1]
• wherein R1 and R2 are same as or different from each other and each represent hydrogen, a C1-C5 linear hydrocarbon group, or a branched hydrocarbon, n represents an integer of 2 to 10, and X represents OH or NHR3, in which R3 represents at least one selected from the group consisting of hydrogen, a C1-C3 hydrocarbon group, CH2CH2OH, and combinations thereof;
• R4R5R6N[(CH2)n—Y]+OH− [Chemical Formula 2]
• wherein R4, R5, and R6 are same as or different from each other and each represent a C1-C5 linear hydrocarbon group or a C3-C5 branched hydrocarbon group, Y represents hydrogen or OH, and n represents an integer of 1 to 5;
• and
• M(OH)m [Chemical Formula 3]
• wherein M represents an alkali metal or alkaline earth metal, and m represents 1 or 2.