Low-viscosity silane-terminated resin for sealant and preparation method thereof

A preparation method for a low-viscosity silane-terminated resin for a sealant, comprising the following steps:

• S1, adding 1 part by weight of alcohol initiator and alkali metal to a reaction kettle, raising the temperature to 75˜150° C. after replacing air in the reaction kettle with nitrogen, adding 7.5˜14.5 parts by weight of epoxy alkane, controlling the pressure to be 0.0˜0.4 MPa, curing until the pressure is no longer decreased, cooling, degassing, and refining, to obtain a low-molecular-weight polymer;
• S2, adding 1 part by weight of the low-molecular-weight polymer prepared in the Step S1 and 5-15 ppm of a polymetallic cyanide catalyst by total mass to the reaction kettle, raising the temperature to 120˜130° C. after replacing air in the reaction kettle with nitrogen, dehydrating, then raising the temperature to 130˜140° C., adding 250˜355 parts by weight of the epoxy alkane, controlling the pressure to be 0.0˜0.4 MPa, curing until the pressure is no longer decreased, cooling, degassing, and discharging, to obtain a high-molecular-weight polymer resin;
• and
• S3, adding organic tin catalyst and isocyanate silane to the high-molecular-weight polymer resin prepared in the Step S2 for a reaction, during the reaction, taking a reaction mixture for an infrared characteristic peak test, and ending the reaction when there is no longer an isocyanate infrared characteristic peak in the reaction mixture, to obtain the silane-terminated resin;
• the structural formula of the silane-terminated resin is as follows:
• wherein, ‘A’ is —(CHR1—CH2—O—)x-CHR1—, wherein x≥172;
• R being CnH2n, n=1˜5;
• R1 being a straight chain alkyl CmH2m+1, m≥1, and the mass ratio of R1 as a methyl in the repeated unit being 50˜90%;
• R2 being CH3 or CH2CH3;
• and R3 being OR2 or R2;
• the number average molecular weight of the silane-terminated resin is about 15000-30000.