Method of preparing low-molecular-weight styrene-acrylate emulsion copolymer

The invention relates to a method of preparing low-molecular-weight styrene-acrylate emulsion copolymer, and the method is designed so as to solve technical problems of fine and harsh reaction conditions, high manufacturing costs, relatively large energy consumption and environment pollution, and poor polymer stability existing in present method. The method uses a semi-continuous emulsion polymerization method, and main design points are that employed chain transferring agent comprises thiols and halogenated hydrocarbons. The method comprises: (1) preparing a seed emulsion, (2) preparing a pre-emulsion, (3) uniformly adding the pre-emulsion into the seed emulsion, and controlling a reaction time and temperature; (4) distilling under a reduced pressure after the polymerization reaction, thereby distilling the halogenated hydrocarbons and volatile components and preparing the low-molecular-weight emulsion copolymer. The method is simple to operate, low in cost and good in effect, reduces mercaptan contents containing offensive odor during a preparation process, thereby the synthesized product being environmental-friendly, non-polluted, and wide in application range, and the method is suitable for being used as the method for the low-molecular-weight emulsion copolymer, or improvement of similar methods.