In the production process, the main control temperature, air flow, agitation, pressure and acid value.
1 Temperature control mainly has the following temperature control: the temperature of the center of the reactor; the temperature of the reactor wall; the oil temperature in the jacket; the steam temperature at the top of the fractionation column, often referred to as the "head temperature"; Inlet and outlet water temperature; temperature of the material in the center of the dilution tank; medium temperature in the jacket of the dilution tank.
The temperature at the center of the reactor is the temperature of the reactants, but the temperature of the material near the wall of the kettle is directly affected by the temperature of the medium in the jacket, and the temperature is different from the central portion. Under good agitation, the difference is not large; when the agitation is poor, there is a significant temperature difference, the temperature at which the resin is polymerized is not uniform, and even a partial gel may be generated. The oil temperature in the jacket should not be too high, otherwise the reactants will heat up too quickly, and the walls of the kettle may produce coking crusts.
The control of the vapor temperature at the top of the fractionation column, the "distillation head temperature", is also important. In the polyesterification reaction, the temperature is controlled at about 100 ° C. Because of the large amount of alcohol in the reactant, the alcohol can form an azeotrope with water, and at a lower temperature, the alcohol is distilled off, so that the alcohol is lost. Less than synthetic requirements. For ordinary resins, the ratio of phthalic anhydride, maleic anhydride to alcohol is 1:1:2:2, and the alcohol loss is less. For high content of maleic anhydride or fumaric acid polyester, such as phthalic anhydride and maleic anhydride, the ratio is 1:3:4:4. If the temperature at the top of the fractionation column exceeds 105 °C, it will cause serious loss of alcohol.
The temperature of the above points can be recorded and monitored by a multi-point temperature recorder, and can also be controlled by a computer.