| 摘要 |
PROBLEM TO BE SOLVED: To inhibit polymerization occurring in a thin-film evaporator by making a gas containing molecular oxygen mixedly exist in distilled vapor by specifying the amount of the liquid-wetting surface of a wall and by feeding a solution containing a readily polymerizable material, of a low viscosity, to the inlet of a raw material in the course of vaporization of the fed solution in the vaporizing part of the evaporator. SOLUTION: When a solution containing a readily polymerizable material is fed to, by the centrifugal force of a rotor axis 4 for agitation, and is vaporized in the vaporizing part 6 of a thin-film evaporator, distilled vapor includes a gas containing molecular oxygen, the solution to be discharged from a liquid-accepting part 12 or the solution of viscosity lower than that of the solution to be discharged is circulated into a raw material inlet 1, and the amount of wetting liquid per unit length of a vaporizing surface is set at 0.02-2 m3/(m.Hr), and further the feeding amount of gas containing molecular oxygen is 0.01-5% by volume of the amount (in terms of standard state) of vaporized vapor of the readily polymerizable material. The gas containing molecular oxygen is also fed to a mechanical seal 8 of the rotor axis 4. The solution to be discharged or the solution of lower viscosity may be fed to an outlet 10 of the solution to be discharged.
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