A new method of preparing high-solid-content and low-viscosity poly(methyl methacrylate/n-butyl acrylate/acrylic acid) emulsion with relative low emulsifier concentration and simple technology was investigated．It contains two steps

i. e.(1) prepare mono-dispersed P(MMA/BA/AA) seeded emulsion with solid content at 50％ and large particle size (480～500 nm) by semi-continuous seeded emulsion polymerization；(2) use the seeded emulsion as medium

sodium dodecyl sulfate as emulsifier

sodium bicarbonate as buffer and ammonia persulfate as initiator to prepare target emulsion by semi-continuous emulsion polymerization The preparing period was about 8 h． The total mass ratio of monomers was MMA：BA=40：60．and the amount of AA was 3.0％ of the total mass of monomers．A series of such emulsions were prepared．in which the highest solid content WaS 72％ with a viscosity of 400 mPa·s at a shear rate of 20 s-1 and the coagulum rate was 0.05％．and the emulsifter concentration of which was 2.1％ of the mass of monomers．The stability during polymerization

particle size

rheology properties

gloss properties etc．of the seeded emulsion and the high-solid-content emulsion were also discussed and compared with the conventional emulsion

which Was prepared with almost the same recipe．The results indicated that the obtained emulsions were bimodal in particle size

the large particle diameter was 500～600 nm and that of the small one was about 80nm．which led to its low viscosity．as well as better glossy properties of films．It is concluded that preparing high-solid-content P(MMA/BA/AA) with this method has the following merits

(1) simple technology

(2) short preparing period

(3) low emulsifier concentration

(4) low viscosity and high gloss value．