METHOD FOR PRODUCING POLYMER FROM MONOMER WITH ETHYLENICALLY UNSATURATED DOUBLE BOND

PROBLEM TO BE SOLVED: To provide a method for producing a polymer by polymerizing a monomer with ethylenically unsaturated double bond wherein discolored foreign matter contaminating the obtained polymer product is reduced by improving preventive effect for polymer scale build-up. SOLUTION: The polymerization reactor used for polymerizing a monomer has a coating comprising a first layer and a second layer formed on the inner wall thereof for preventing polymer scale from building up. The first layer is formed by coating a first coating liquid containing a condensate (A) of an aldehyde compound and an aromatic hydroxy-based compound using steam as a carrier, and the second layer is formed by coating a second coating liquid containing at least one scale inhibiting aid (B) selected from the group consisting of a water soluble polymer, an inorganic colloid, an inorganic salt and an acid using steam as a carrier. And further, the first layer and the second layer are formed by spray coating of each coating liquid using a two-fluid atomizer.