| 摘要 |
A method for preparing an aqueous dispersion of organopolysiloxane is provided to obtain a stable and finely divided crosslinked organopolysiloxane that gives a transparent elastomeric film when removing water and to obtain an aqueous dispersion useful for a sealant or coating material. A method for preparing an aqueous dispersion of organopolysiloxane comprises the steps of: (a) reacting an organopolysiloxane containing a group capable of condensation and represented by the formula of R1O(R2SiO)xR1 with a silane represented by the formula of (R3O)3SiCR22-Y or hydrolyzate thereof, in the presence of water and an emulsifier, wherein R is a C1-C18 monovalent hydrocarbyl radical, R1 is H(preferred) or a C1-C8 alkyl, x is and integer of 10-1100(preferably of 20-700, more preferably of 30-500), R2 is H(preferred) or a C1-C4 monovalent alkyl radical, R3 is a C1-C8 alkyl radical, and Y is a radical represented by the formula of -NHR4, -NR42 or the formula (a) (wherein R4 is a C1-C18 monovalent hydrocarbyl radical optionally having N and/or O, and R5 is a C3-C12 divalent hydrocarbyl radical optionally having N and/or O); (b) if necessary, adding an aqueous silica dispersion mixed with the silane during or after reaction (a), preferably after reaction (a); (c) optionally, adding an adhesion enhancer during or after reaction (a), preferably after reaction (a); and (d) optionally adding other materials not participating in reaction (a) during or after reaction (a), preferably after reaction (a), with the proviso that any metal-containing catalyst is not used, and the organopolysiloxane and silane are used in such an amount that the organopolysiloxane forms an elastomeric film non-soluble in toluene when removing water.
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