Production method of toner for developing electrostatic image
A production method of a toner includes a suspension process in which a polymerizable monomer composition is dispersed in an aqueous dispersion medium; and a polymerization process in which suspension polymerization is performed with the suspension in the presence of a polymerization initiator to obtain colored resin particles. In the suspension process an inhibitor of small diameter microparticle production is contained in the aqueous dispersion medium. A minimum reaction activation energy E min of the inhibitor of small diameter microparticle production is 7 kcal/mol or less and an octanol-water partition coefficient log P is 2 or less. The minimum reaction activation energy E min is a minimum value of a reaction activation energy “E” which is required when a phenylpropane radical represented by the following Formula 1 acts on the inhibitor of small diameter microparticle production:
1. A production method of a toner for developing an electrostatic image comprising steps of:
providing a polymerizable monomer composition comprising at least a polymerizable monomer and a colorant;
dispersing the polymerizable monomer composition in an aqueous dispersion medium comprising a dispersion stabilizer to obtain a suspension having droplets of the polymerizable monomer composition dispersed;
adding an inhibitor of small diameter microparticle production from 0.01 to 1 part by weight in the aqueous dispersion medium with respect to the polymerizable monomer of 100 parts by weight after forming droplets of the polymerizable monomer composition, wherein the inhibitor of small diameter microparticle production is provided separately from the polymerizable monomer composition;
performing a suspension polymerization with the aqueous dispersion medium in the presence of a polymerization initiator to obtain colored resin particles;
wherein a minimum reaction activation energy E min of the inhibitor of small diameter microparticle production is 7 kcal/mol or less and an octanol/water partition coefficient logP is 2 or less; and
wherein the minimum reaction activation energy E min is a minimum value of a reaction activation energy “E” which is required when a phenylpropane radical represented by the following Formula 1 acts on the inhibitor of small diameter microparticle production so as to withdraw a hydrogen of a phenolic hydroxyl group present in a molecular structure of the inhibitor of small diameter microparticle production followed by production of a radical:
2. The production method of a toner for developing an electrostatic image according to claim 1 , wherein the inhibitor of small diameter microparticle production has a structure represented by the following Formula 2, 3 or 4:
wherein “R” denotes OX, SO 3 X, CO 2 X or CH═CHCO 2 X; and “X” denotes hydrogen or metal.
3. The production method of a toner for developing an electrostatic image according to claim 2 , wherein the inhibitor of small diameter microparticle production having the structure represented by the Formula 2, 3 or 4 is oxidized so as to be lead to a quinone derivative having the structure represented by the following Formula 5, 6 or 7 and an octanol-water partition coefficient “logP” of 0.6 or less:
4. The production method of a toner for developing an electrostatic image according to claim 1 , wherein pH of the aqueous dispersion medium is from 8 to 11.
5. The production method of a toner for developing an electrostatic image according to claim 1 , wherein the polymerization initiator is organic peroxide.
6. The production method of a toner for developing an electrostatic image according to claim 5 , wherein the organic peroxide is a peroxyester compound.
7. The production method of a toner for developing an electrostatic image according to claim 6 , wherein the peroxyester compound is t-butylperoxy-2-ethylbutanoate.
8. The production method of a toner for developing an electrostatic image according to claim 1 , wherein an average number of small diameter microparticles per colored resin particle is 200 or less.
9. The production method of a toner for developing an electrostatic image according to claim 1 , wherein the toner for developing an electrostatic image is a toner having positively charging ability.
10. The production method of a toner for developing an electrostatic image according to claim 1 , wherein the inhibitor of small diameter microparticle production has a structure represented by the following Formula 2, 3 or 4:
wherein “R” denotes OX or SO 3 X; and “X” denotes hydrogen or metal.
11. The production method of a toner for developing an electrostatic image according to claim 1 , wherein the inhibitor of small diameter microparticle production is added to the polymerizable monomer composition after forming droplets of the polymerizable monomer composition, and before starting the suspension polymerization.