The invention discloses a method for preparing a defoaming agent composition, belonging to the technical field of
fine chemical preparation. The invention provides a defoaming agent composition widely used for removing harmful foams in industrial production. The defoaming agent composition comprises the following components: (1) polysiloxane RaSiO(4-a) / 2; (2) a
coupling agent; (3) fine filler particles such as
silicon dioxide and the like; (4) organic
silicon resin; (5) polyether modified polysiloxane MDx(CH3GSiO)yM, wherein M is
chain link R'2SiO1 / 2, D is
chain link R'2SiO2 / 2, G is polyether radical-(CH2)z(EO)g(PO)hR'' and (6) an
alkaline catalyst. The preparation method comprises the following steps: (1) heating the polysiloxane and the
coupling agent together in a stirring
machine, adding the
alkaline catalyst to carry out a
polymerization reaction at the temperature of 40-140 DEG C; (2) after crosslinking the mixture, adding the organic
silicon resin and the polyether modified polysiloxane, carrying out a reaction again for 1-7 h at the temperature of 80-140 DEG C, and then adding the fine filler particles to mix uniformly, carrying out a reaction for 1-6 h at temperature of 90-180 DEG C; (3) after finishing the reaction, keeping the mixture for 0.1-1.5 h at the vacuum degree of -0.01 to -0.08 MPa, and finally, cooling to the
room temperature to obtain white active materials that are defoaming agent compositions.