Method for producing hollow resin particles
Provided is a method for producing hollow resin particles in which a residual amount of a hydrocarbon solvent once held inside particles in a production process is reduced and particle breakage is suppressed. The method for producing hollow resin particles, which include preparing a mixture liquid containing a polymerizable monomer, a hydrocarbon solvent, a polymerization initiator and an aqueous medium, suspending the mixture liquid to prepare a suspension, subjecting the suspension to a polymerization reaction to prepare a precursor composition containing precursor particles having a hollow portion and including the hydrocarbon solvent in the hollow portion, and removing the hydrocarbon solvent from the precursor particles, wherein the polymerizable monomer contains a crosslinkable monomer in an amount of from 40% by mass to 100% by mass, and wherein the removal of the hydrocarbon solvent is performed by a specific method.
1 . A method for producing hollow resin particles, the method comprising:
preparing a mixture liquid containing a polymerizable monomer, a hydrocarbon solvent, a polymerization initiator and an aqueous medium,
suspending the mixture liquid to prepare a suspension in which droplets of a polymerizable monomer composition containing the polymerizable monomer, the hydrocarbon solvent and the polymerization initiator are dispersed in the aqueous medium,
subjecting the suspension to a polymerization reaction to prepare a precursor composition containing precursor particles having a hollow portion and including the hydrocarbon solvent in the hollow portion,
performing solid-liquid separation of the precursor composition to obtain the precursor particles separated from the aqueous medium, and
heat-drying the precursor particles separated from the aqueous medium to remove the hydrocarbon solvent from the precursor particles,
wherein the polymerizable monomer contains a crosslinkable monomer in an amount of from 40% by mass to 100% by mass,
wherein, with respect to a boiling point T 1 (° C.) of the hydrocarbon solvent and a thermal decomposition initiation temperature T 2 (° C.) of the precursor particles, a temperature T 0 (° C.) of the heat-drying for the removal of the hydrocarbon solvent satisfies (T 1 +70)≤T 0 ≤(T 2 −5), and
wherein the removal of the hydrocarbon solvent is performed by heat-drying and stirring simultaneously the precursor particles separated from the aqueous medium in combination with at least one kind of fine particles selected from the group consisting of inorganic fine particles and organic fine particles in a stirring vessel to coat a surface of the precursor particles with the fine particles and remove the hydrocarbon solvent from the precursor particles.
2 . The method for producing the hollow resin particles according to claim 1 , wherein the boiling point T 1 of the hydrocarbon solvent is from 70° C. to 90° C.
3 . The method for producing the hollow resin particles according to claim 1 , wherein a void ratio of the hollow resin particles is from 50% to 95%.
4 . The method for producing the hollow resin particles according to claim 1 , wherein a pressure applied during the heat-drying for the removal of the hydrocarbon solvent is from 0 kPa to 101.3 kPa.
5 . The method for producing the hollow resin particles according to claim 1 , wherein the hydrocarbon solvent is a hydrocarbon solvent having 4 to 7 carbon atoms.
6 . The method for producing the hollow resin particles according to claim 1 , wherein a water content of the precursor particles used in the removal of the hydrocarbon solvent is 50% or less.