: Poly (vinyl alcohol) is one of the well- known surface active agent in the polymerization of vinyl chloride. The aim of our work is to synthesize Polyvinyl alcohol as a dispersing agent for pvc suspension polymerization. In this study, the granular poly(vinyl acetate) has been prepared from emulsion poly(vinyl acetate). Final powder was alcoholized in methanol to produce poly (vinyl alcohol). In this work, the effective parameters (catalyst to polymer weight ratio, reaction time, reaction temperature) influencing the degree of hydrolysis were investigated by using design experiment through response surface methodology and 15 experiments. Since response surface methodology should cover a wide range of degree of hydrolysis, 7 independent tests were done to evaluate the effect of these factors on the degree of hydrolysis and eventually the range of factors were determined in order to design experiments. According to experimental results, the degree of hydrolysis of PVA increased by increasing every studied factor and the most effective factors on the degree of hydrolysis based on importance were ordered as: 1.catalyst to polymer weight ratio, 2.reaction time, and 3.reaction temperature.For preparing desired poly (vinyl chloride), high and low degree of hydrolysis of poly (vinyl alcohol) have to be used. The former makes drops stable in polymerization media and the latter results in porosity on particles of produced poly (vinyl chloride). Using response surface methodology, the optimized conditions to reach degree of hydrolysis 78.2 and degree of hydrolysis 41.2 were achieved catalyst to polymer weight ratio of 0.01, reaction time of 12.79 min, and reaction temperature of 40 ?C and catalyst to polymer weight ratio of 0.003, reaction time of 6.05 min, and reaction temperature of 46?C, respectively. Besides, regarding to the fact that temperature has the least and catalyst has the most influence on degree of hydrolysis, for more repeatability, 12 tests were done in 59.5 ?C, catalyst to polymer weight ratio of 0.003, and various reaction time .Using curve fitting in MATLAB software 2010, optimized conditions to reach degree of hydrolysis 78.2 and degree of hydrolysis 41.2 were reaction time of 15.31 and 3.2 min, respectively. Keywords: Poly(vinyl acetate), Poly(vinyl alcohol), Poly(vinyl chloride), Response surface methodology ,degree of hydrolysis, optimization
