Abstract: In a method for producing hydrophilic polymer particles, a dispersion in which an aqueous-phase component including hydrophilic monomers and a polymerization initiator is dispersed in an oil-phase component including a hydrophobic solvent is prepared. Thereafter, the hydrophilic monomers are polymerized in the aqueous phase by supplying oxygen to a reaction vessel and, while oxygen is being supplied, heating the dispersion having a reduced dissolved oxygen concentration in the reaction vessel so that the temperature of the dispersion is increases. The time from the start of reduction of the dissolved oxygen concentration of the dispersion to the start of the heating is 0.1 hour or more and 3.5 hours or less. The amount of oxygen supplied to the reaction vessel is greater than or equal to 0.02 volume %/h and less than or equal to 0.9 volume %/h with respect to the volume of the dispersion under standard conditions.

Abstract: In a method for producing hydrophilic polymer particles, a dispersion in which an aqueous-phase component including hydrophilic monomers and a polymerization initiator is dispersed in an oil-phase component including a hydrophobic solvent is prepared. Thereafter, the hydrophilic monomers are polymerized in the aqueous phase by supplying oxygen to a reaction vessel and, while oxygen is being supplied, heating the dispersion having a reduced dissolved oxygen concentration in the reaction vessel so that the temperature of the dispersion is increases. The time from the start of reduction of the dissolved oxygen concentration of the dispersion to the start of the heating is 0.1 hour or more and 3.5 hours or less. The amount of oxygen supplied to the reaction vessel is greater than or equal to 0.02 volume %/h and less than or equal to 0.9 volume %/h with respect to the volume of the dispersion under standard conditions.