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The Use Of REAXIS® Catalysts In The Production Of An Unsaturated Polyester Resin A conversion of maleic anhydride as well as of phthalic anhydride with 1.2-propylene glycol was tested for a model formulation. Formulation Raw Material Maleic anhydride Weight (g) mol 49.0 0.5 Phthalic anhydride 148.12 1.0 1.2-propylene glycol 148.4 1.95 Catalyst 0.1% Remarks 30 mol-% OH surplus As a % of formulation Procedure The new materials are filled into a 500 ml four-necked flask equipped with distillation bridge, nitrogen inlet, thermometer and a temperature control unit. Under a constant flow of nitrogen, the mixture is heated and stirred. At 80 – 85 °C the catalyst is added. The reaction temperature is continuously increased up to 240 °C, ensuring continuous distillation of reaction water. The reaction is stopped after 5 hours. Results The REAXIS® products esterify the secondary hydroxyl groups which are difficult to esterify. Thus per the given conditions, an acid value of < 20 is reached after 5 hours. The use of p-toluenesulfonic acid made the conversion more difficult and the final products darker. Catalyst Reaction temperature °C Final acid value mg KOH/l g Iodine color number 180 – 238 187.1 4 180 – 235 13.2 2 0.1 % REAXIS C248 180 – 240 14.2 2 0.1 % REAXIS® C256 180 – 240 15.3 2 0.1 % p-toluenesulfonic acid 187 – 235 113.1 7 0.2 % REAXIS® C129 ® 09/99