JP2001117272A - Method of producing toner by polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing an electrophotographic toner excellent in the safeness for the environment with <70 ppm residual polymerizable monomers. SOLUTION: The amount of the residual polymerizable monomers in the electrophotographic toner is decreased by subjecting a dispersion liquid of polymerized particles obtained after suspension polymerization to the treatment by reduced pressure stripping under a specified stirring condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner for use in electrophotographic development, and more particularly, to a method for producing an electrophotographic toner which is low in residual polymerizable monomers and excellent in environmental safety. About.

[0002]

2. Description of the Related Art Generally, a toner for electrophotography comprises a pulverized toner obtained by kneading, pulverizing, and classifying a binder resin with a colorant, a charge controlling agent, a release agent, and the like, a polymerizable monomer, and a colorant. And polymerized toners obtained as fine particles obtained by polymerizing a mixture of a charge control agent, a release agent, and the like by a method such as suspension polymerization, emulsion polymerization, or dispersion polymerization. In any method, it is difficult to completely react the polymerizable monomer in the polymerization step, and a small amount of the unreacted polymerizable monomer remains in the toner. When the toner having the polymerizable monomer remaining therein is used in an electrostatic image forming apparatus, the residual polymerizable monomer volatilizes from the toner due to heating during image fixing, thereby deteriorating the working environment and generating an unpleasant odor. generate. In addition, electrophotographic toner having a large amount of residual polymerizable monomer is likely to cause blocking during storage,
There are problems such as easy offset during image fixing and easy filming on the members of the electrostatic image developing device.

In the case of the pulverized toner, the residual polymerizable monomer is removed at the stage of producing the binder resin, so that the toner is not affected by a coloring agent, a charge controlling agent, a release agent, and the like. The reduction of the reactive monomer is relatively easy. On the other hand, in the polymerization method toner, the residual polymerizable monomer must be removed from the resin containing the colorant, the charge control agent, the release agent, and the like, but the polymerizable monomer is easily adsorbed by these components. It is more difficult to reduce the residual polymerizable monomer than in the case where only the binder resin is used. In particular, in recent years, there has been an increasing demand for a polymerization method toner that can be fixed at a low temperature (low-temperature fixing toner). In such a low-temperature fixing toner, it is extremely difficult to reduce the residual polymerizable monomer while preventing aggregation. Have difficulty.

Polymerization General steps after the polymerization reaction of the toner include a washing step, a dehydration step and a drying step. In order to reduce volatile substances such as residual polymerizable monomers in the polymerization method toner, a process of removing volatile substances in a process after such a polymerization reaction has been often studied. In particular,
(1) Blowing saturated steam into the dispersion of the polymerization toner in the dispersion before the dehydration step (JP-A-5-100485)
(2) A method of performing vacuum drying while injecting gas into the polymerization toner before the drying step after the dehydration step (Japanese Patent Laid-Open No.
0-207122), and (3) a method of subjecting a polymerization toner after the drying step to heat treatment under reduced pressure (JP-A-7-92736).
No. 1). Of these, volatile matter removal before the dehydration step is preferred because of its high efficiency.

[0005] In the step of removing volatile substances before the dehydration step, foaming at the gas-liquid interface of the dispersion, accompanying reduction in the removal ability and aggregation of particles, adversely affect toner quality often become a problem. . As a countermeasure, the generation of bubbles during the treatment is suppressed by performing a stripping treatment while spraying an aqueous medium on the liquid surface, or performing a stripping treatment by adding an antifoaming agent. However, the former tends to increase the energy cost required for removal of the aqueous medium due to an increase in the amount of the aqueous medium during stripping, and the latter causes the defoamer remaining in the product to change the surface characteristics of the toner particles,
In some cases, physical properties such as charge reduction and resistance decrease were adversely affected.

As described above, various methods for reducing the residual polymerizable monomer by post-polymerization treatment have been studied for polymerization toners, but while maintaining the toner performance,
It is difficult to meet the recent demand for environmental safety of less than 100 ppm of residual polymerizable monomer, and no method has been found for reducing the amount of residual polymerizable monomer that is particularly suitable for industrial production of low-temperature fixing toner. Was.

[0007]

Based on such prior art, the present inventors have conducted intensive studies to suppress foaming and toner aggregation in the step of removing volatile substances such as residual polymerizable monomers. Instead of stirring in a state where the stirring blade is completely buried under the dispersion liquid surface of the polymer particles after the suspension polymerization, stirring is performed using a stirring blade at least partially protruding from the liquid surface of the dispersion liquid. By doing so, it has been found that it is easy to remove volatile substances such as an aqueous medium, residual polymerizable monomers and organic solvents without generating bubbles during the processing, and the present invention has been completed. .

[0008]

According to the present invention, a polymerizable monomer composition comprising at least a colorant and a polymerizable monomer is subjected to suspension polymerization in an aqueous medium to disperse polymer particles. A step of obtaining a liquid, and a step of removing volatile substances in the polymer particles while stirring the dispersion, wherein a part of the stirring blade used for the stirring protrudes from the surface of the dispersion during stirring. A process for producing a polymerization toner is provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Method for Producing Polymerization Toner <Suspension Polymerization> In the present invention, a known method may be employed for suspension polymerization. For example, a mixture containing additives such as a polymerizable monomer, a colorant, a macromonomer, a molecular weight modifier, a charge controlling agent, and a release agent is charged into an aqueous dispersion medium, and stirred to granulate droplet particles. And, if necessary, in the presence of a polymerization initiator,
Stirring, heating and polymerization may be used. The aqueous dispersion medium may contain a dispersion stabilizer. The dispersion of the polymer particles thus obtained is a dispersion of the polymer particles used in the stripping treatment (hereinafter, may be simply referred to as a polymer dispersion). In the production of the toner, thereafter, a dehydration and drying step is performed to remove the dispersion medium.

In the polymerization, the polymerization of the polymerizable monomer may be performed in one stage or may be performed in two stages. For example, when polymerizing in two stages, (1) a monomer that polymerizes in the first stage (polymerizable monomer for core) and a monomer that polymerizes in the second stage (polymerizable monomer for shell) (2) a method in which a low Tg core is formed in the first polymerization and a high Tg layer (shell) is formed in the second polymerization,
After polymerizing the monomer in the first stage to form particles, core-shell type polymer particles are produced by a method of adding an arbitrary polymer component and adsorbing or fixing the polymer component to the particles. A so-called capsule toner having a good balance between low-temperature fixability and high-temperature storage property can also be obtained.

The main component of the polymerizable monomer used in the present invention is a monovinyl monomer. This polymerizable monomer is subjected to suspension polymerization to become a binder resin component in the polymer particles. Specific examples of the monovinyl monomer include styrene monomers such as styrene, 4-methylstyrene and α-methylstyrene; unsaturated carboxylic acid monomers such as acrylic acid and methacrylic acid; methyl acrylate and acrylic Ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methacrylic acid 2
-Unsaturated carboxylic acid ester monomers such as ethylhexyl and dimethylaminoethyl methacrylate; derivatives of unsaturated carboxylic acids such as acrylonitrile, methacrylonitrile, acrylamide and methacrylamide; ethylenically unsaturated monomers such as ethylene, propylene and butylene Olefins; vinyl halide monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride;

Vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketone monomers such as vinyl methyl ketone and methyl isopropenyl ketone;
Monovinyl monomers such as nitrogen-containing vinyl monomers such as vinyl pyridine, 4-vinyl pyridine and N-vinyl pyrrolidone. These monovinyl monomers may be used alone, or a plurality of monomers may be used in combination. Of these monovinyl monomers, styrene monomers, unsaturated carboxylic acid monomers, unsaturated carboxylic acid esters, unsaturated carboxylic acid derivatives and the like are preferable,
Particularly, a styrene monomer and an ethylenically unsaturated carboxylic acid ester are preferably used.

When an arbitrary crosslinkable monomer is used together with these monovinyl monomers, the fixing property, particularly the offset property, is improved. Examples of the crosslinkable monomer include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; polyfunctional ethylenically unsaturated carboxylic esters such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and ethylene glycol diacrylate; N, N-divinylaniline, divinyl ether; a compound having three or more vinyl groups; and the like. These crosslinkable monomers can be used alone or in combination of two or more. In the present invention, the crosslinkable monomer is usually added to 100 parts by weight of the monovinyl monomer.
It is desirable to use 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight.

The colorant is not particularly limited as long as it is one commonly used in toner. Examples of the black colorant include carbon black, nigrosine-based dyes and pigments; magnetic particles such as cobalt, nickel, iron tetroxide, iron manganese oxide, iron zinc oxide, and nickel iron oxide;
When carbon black is used, the primary particles have a particle size of 20
When the thickness is up to 40 nm, good image quality can be obtained.
It is also preferable because the safety of the toner to the environment is enhanced. For the color toner, a yellow colorant, a magenta colorant, a cyan colorant and the like are usually used. Compounds such as azo pigments and condensed polycyclic pigments are used as the yellow colorant. Specifically, C.I. I. Pigment Yellow 3, 1
2, 13, 14, 15, 17, 62, 65, 73, 8
3, 90, 93, 97, 120, 138, 155, 18
0 and 181 and the like.

As the magenta colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I.
I. Pigment Red 48, 57, 58, 60, 63,
64, 68, 81, 83, 87, 88, 89, 90, 1
12, 114, 122, 123, 144, 146, 14
9, 163, 170, 184, 185, 187, 20
2, 206, 207, 209, 251, C.I. I. Pigment Violet 19 and the like.

As the cyan coloring agent, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds and the like can be used. Specifically, C.I. I. Pigment Blue 2, 3,
6, 15, 15: 1, 15: 2, 15: 3, 15: 4,
16, 17 and 60. These colorants are usually added to 100 parts by weight of the monovinyl monomer.
It is used in a proportion of 0.1 to 50 parts by weight, preferably 1 to 20 parts by weight.

In the present invention, the macromonomer can be contained in the polymerizable monomer composition together with the monovinyl-based monomer. The macromonomer has a vinyl polymerizable functional group (acryloyl group, methacryloyl group, etc.) at the terminal of the molecular chain, and has a number average molecular weight of usually 1,000.
0-30,000 oligomers or polymers.
The amount of the macromonomer is usually 0.1 to 100 parts by weight of the total amount of the above-mentioned monovinyl monomer and crosslinkable monomer.
The amount is from 0.01 to 10 parts by weight, preferably from 0.03 to 5 parts by weight, more preferably from 0.05 to 1 part by weight. Within this range, a good balance between storability and fixability can be obtained.

Examples of the molecular weight regulator include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan and n-octyl mercaptan; and halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide. . These molecular weight regulators can be added to the reaction system before the start of the polymerization or during the polymerization. The molecular weight modifier is based on 100 parts by weight of the polymerizable monomer.
0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight is used.

Examples of the charge control agent include Bontron N01 (manufactured by Orient Chemical Co., Ltd.) and Nigrosine Base EX
(Orient Chemical Co., Ltd.), Spiro Black TRH (Hodogaya Chemical Co., Ltd.), T-77 (Hodogaya Chemical Co., Ltd.), Bontron S-34 (Orient Chemical Co., Ltd.), Bontron E
-81 (manufactured by Orient Chemical Co.), Bontron E-84
(Orient Chemical), Bontron E-89 (Orient Chemical), Bontron F-21 (Orient Chemical), COPY CHRGE NX VP434 (Hoechst Industries), COPY CHRGE
NEG VP2036 (Hoechst Industries), TNS-4-1 (Hodogaya Chemical), TNS-
4-2 (manufactured by Hodogaya Chemical Co., Ltd.), LR-147 (manufactured by Nippon Carlit Co., Ltd.), etc., and JP-A-11-15192.
JP-A-3-175456, JP-A-3-25-2
Quaternary ammonium (salt) described in 43954
Charge controlling agents such as sulfonic acid (salt) group-containing copolymers described in JP-A-3-243954, JP-A-1-217664, JP-A-3-15858 and the like. Control resin). The charge control resin is preferable in that a toner having stable chargeability can be obtained even in high-speed continuous printing.

The polymerization initiator used in the present invention includes persulfates such as potassium persulfate and ammonium persulfate;
4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis-2-methyl-N-1,1′-bis (hydroxymethyl ) -2-Hydroxyethylpropioamide, 2,
2′-azobis (2,4-dimethylvaleronitrile),
Azo compounds such as 2,2'-azobisisobutyronitrile and 1,1'-azobis (1-cyclohexanecarbonitrile); methylethyl peroxide, di-t-butyl peroxide, acetyl peroxide, dicumylper Oxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl perbutyl neodecanoate, t-hexyl peroxy 2-ethylhexanoate, t-butyl peroxy Pivalate, t-hexylperoxypivalate, di-isopropylperoxydicarbonate, di-t-butylperoxyisophthalate, 1,1 ′,
Peroxides such as 3,3′-tetramethylbutylperoxy-2-ethylhexanoate and t-butylperoxyisobutyrate can be exemplified.

Further, there may be mentioned a redox initiator obtained by combining these polymerization initiators and a reducing agent. Of these, it is preferable to select an oil-soluble polymerization initiator soluble in the polymerizable monomer used, and it is also possible to use a water-soluble polymerization initiator together with the oil-soluble polymerization initiator as necessary. it can. The polymerization initiator is used in an amount of 0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the polymerizable monomer. The polymerization initiator can be added in advance to the polymerizable monomer composition, but in some cases, can be added to the dispersion of polymer particles after the completion of the granulation step.

The releasing agent used as required in the present invention includes low molecular weight polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene;
Low-molecular-weight terminal-modified polypropylene whose molecular terminals are substituted with epoxy groups and block polymers of these and low-molecular-weight polyethylene, low-molecular-weight polyethylene with oxidized molecular terminals, low-molecular-weight polyethylene whose molecular terminals are substituted with epoxy groups, and block polymers of these with low-molecular-weight polypropylene Terminal-modified polyolefin waxes; natural waxes such as candelilla, carnauba, rice, wood wax, jojoba, etc .; paraffin, microcrystalline,
Petrolactam and other petroleum waxes and modified waxes; mineral waxes such as montan, ceresin and ozokerite; synthetic waxes such as Fischer-Tropsch wax; pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, pentaerythritol tetralaurate And polyfunctional ester compounds such as dipentaerythritol esters such as pentaerythritol ester, dipentaerythritol hexamyristate, dipentaerythritol hexapalmitate, and dipentaerythritol hexalaurate. These are used alone or in combination of two or more.

Of these, synthetic waxes, end-modified polyolefin waxes, petroleum waxes, and polyfunctional ester compounds are preferred. Among the polyfunctional ester compounds, pentaerythritol esters having an endothermic peak temperature in the range of 30 to 200 ° C., preferably 50 to 180 ° C., preferably 60 to 160 ° C. in a DSC curve measured by a differential scanning calorimeter. And the endothermic peak temperature is 5
A polyester compound such as dipentaerythritol ester in the range of 0 to 80 ° C. is used for fixing as a toner.
It is particularly preferable in terms of the releasability balance. In particular, the molecular weight is 1000 or more, and 25 parts per 100 parts by weight of styrene.
Dipentaerythritol ester having an acid value of 10 mg / KOH or less dissolved at 5 ° C. or more at 5 ° C. shows a remarkable effect on lowering the fixing temperature. The endothermic peak temperature is ASTM D34
18-82. The release agent is used in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the polymerizable monomer.
It is preferable to use parts by weight (more preferably 1 to 15 parts by weight).

The dispersion stabilizer used in the present invention includes:
Sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide; aluminum hydroxide, magnesium hydroxide and water Metal hydroxides such as ferric oxide; water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; anionic surfactants, nonionic surfactants, and amphoteric surfactants.
Among these, dispersion stabilizers containing metal compounds, especially colloids of poorly water-soluble metal hydroxides, are preferred because they can narrow the particle size distribution of polymer particles and improve the sharpness of images. is there. In particular, when the crosslinkable monomer is not copolymerized, the dispersant containing the colloid of the poorly water-soluble metal hydroxide can improve the dispersion stability of the polymer particles during the volatile substance removal treatment and the fixing property of the toner. And to improve the storage stability.

The dispersant containing the colloid of a poorly water-soluble metal hydroxide is not limited by the method of preparation, but the poorly water-soluble dispersant obtained by adjusting the pH of the aqueous solution of the water-soluble polyvalent metal compound to 7 or more. It is preferable to use a metal hydroxide colloid, particularly a colloid of a poorly water-soluble metal hydroxide formed by a reaction of a water-soluble polyvalent metal compound with an alkali metal hydroxide in an aqueous phase.

The colloid of the poorly water-soluble metal compound used in the present invention has a number particle size distribution D50 (50% cumulative value of the number particle size distribution) of 0.5 μm or less and a D90 (9% of the number particle size distribution).
(0% cumulative value) is preferably 1 μm or less. When the particle size of the colloid is large, the stability of polymerization is lost, and the storage stability of the toner is reduced.

The dispersion stabilizer is usually used in an amount of 0.1 to 20 parts by weight, preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the polymerizable monomer.
Used in a proportion of 3 to 10 parts by weight. If this ratio is small, it is difficult to obtain sufficient polymerization stability and dispersion stability during stripping under reduced pressure, and aggregates are easily formed. Conversely, if this ratio is large, the toner particle size becomes too fine, which is not preferable.

<Volatile substance removal treatment> The dispersion of the polymer particles obtained after the suspension polymerization by the above method is stirred,
Volatile substances such as an aqueous dispersion medium, residual polymerizable monomers, and organic solvents in polymer particles are reduced. When removing volatile substances, any method such as a method of heating under reduced pressure, a bubbling method of blowing nitrogen or water vapor, a stripping method, or a flushing method may be adopted, but from the viewpoint of good efficiency of removing volatile substances. The vacuum stripping method is preferred. According to such a method, since the dispersion medium is distilled off under reduced pressure together with the residual polymerizable monomer, it is possible to remove the polymerizable monomer from the polymer particles with high efficiency. In addition, since the colloid (dispersant) used in the suspension polymerization is present in the dispersion and the polymer particles are protected by the dispersant, the treatment is performed under a temperature condition equal to or higher than the Tg of the binder resin. Can also prevent aggregation of the polymer particles.

The treatment by the vacuum stripping method (hereinafter, referred to as
In the case of the pressure-reduced stripping process, it is usually carried out in a reduced-pressure evaporation tank. Further, in the pressure-reduced stripping process, the volatile substance is converted into a gas, so that the gas is usually discharged from the evaporation tank to the outside. When the volatile substance becomes a gas, bubbles tend to be generated at the gas-liquid interface of the polymer particle dispersion in the evaporation tank, but the stirring blade at least partially protrudes from the liquid surface of the polymerizable particle dispersion. By performing the stripping process while stirring with, the foam at the gas-liquid interface is continuously given the bubble breaking effect by the mechanical impact, and the process is stable and the process which does not adversely affect the toner quality is possible. Becomes The stirring blade in the evaporating tank in the present invention may be in a state where at least a part thereof protrudes above the liquid surface of the polymer dispersion liquid during the volatile substance removal treatment,
The shape is not limited.

The position of the liquid surface in the stirring state is changed by an external factor such as a stirring speed, but it is sufficient that a part of the stirring blade protrudes from the liquid surface in the stirring state. It is preferable that the stirring blades always protrude throughout the stirring, but the stirring blades are continuous from the liquid surface for 50% or more of the whole stirring time, preferably 70% or more, more preferably 90% or more. Alternatively, if it protrudes intermittently, generation of bubbles can be suppressed. In the present invention, the stirring blade needs to be in a state where at least a part thereof protrudes from the surface of the dispersion liquid during stirring. When there are a plurality of blades, it is only necessary that one or more blades be designed to protrude from the liquid surface. Here, the “projecting part” may be any point such as the tip, the center, or the center depending on the shape of the stirring blade. The size of the protruding portion is not particularly limited, and it is sufficient that at least a part of the side w of the blade in contact with the liquid surface L and another side w ′ forming a pair with this side protrude from the liquid surface L. . That is, if d is a positive number among the lengths (d and d '; both 0 or positive numbers) of the portions protruding from the liquid level L, d' is 0 (w 'is completely at the liquid level). Below). When there are a plurality of blades, all the blades may project from the liquid surface, or only some of the blades may project from the liquid surface. Preferably, the average value of d and d '(if there are a plurality of blades, the average value of all blades) is 3% or more, preferably 10%, with respect to the body diameter (diameter) of the evaporation tank.
%, More preferably 15% or more (see FIG. 3).

Examples of the stirring blade used in the present invention include a wide paddle blade, a wide inclined paddle blade, a bull margin blade and its modified blade, a full zone type blade, a wall wetter blade, and the like. As a shape capable of coping with a change in the liquid amount during the stripping process while uniformly mixing, a bulge margin blade, a full zone type blade, a wall wetter blade, and a deformed blade thereof are preferable. In addition, a multi-stage blade is used to achieve both uniform mixing and foaming effect on the liquid surface, and a wing shape like an inclined paddle blade that emphasizes uniform mixing on the middle (lower) side of the liquid, and a foaming effect on the liquid surface (upper). A wing shape such as a bull-margin wing emphasizing the wing shape can also be used.

The end of the stripping treatment is defined assuming that the volume of the polymer particles before the start of the stripping treatment is 100%.
The volume of the dispersion medium after the treatment is 50 to 250%, preferably 7%.
It is the point in time when it becomes 5 to 225%, and it is usually 0.5 to 50 hours, preferably 1 to 30 hours, more preferably 3 to 20 hours from the start of the treatment. In the vacuum stripping treatment, the polymer dispersion in the system is simultaneously concentrated by evaporating and recovering the dispersion medium, the aqueous medium and other volatile substances.

By heating the polymer dispersion at the time of stripping, the volatilization and recovery efficiency of volatile substances can be increased. For heating the polymer dispersion, use an evaporation tank provided with a heating medium circulation jacket, use an evaporation tank provided with a heat exchanger inside, use an evaporation tank connected with an external heat exchanger, and evaporate. It can also be performed by blowing heated gas into the tank. Among these heating methods, a method using an evaporation tank provided with a heating medium circulation jacket is preferable.

The temperature (° C.) of the polymer dispersion is defined by the dispersion temperature Ts (° C.) and the glass transition temperature Tg of the polymer particles.
(° C.) Tg ≦ Ts <100 ° C., preferably Tg
≦ Ts ≦ 90 ° C., more preferably Tg + 5 ° C. ≦ Ts ≦ 8
It is desirable to keep the temperature substantially constant at 5 ° C. When Ts is lower than Tg, evaporation is reduced, and the movement of the residual polymerizable monomer in the polymer particles is extremely slow, so that the removal rate of the residual polymerizable monomer is significantly reduced. From this viewpoint, it is desirable that Ts be set to be 5 ° C. or higher than Tg.
On the other hand, when Ts is higher than 100 ° C., the dispersion stability of the polymer particles is reduced by heat, and the aggregates, scale adhesion to the tank can wall and the stirrer increase during the treatment. When the binder resin produced by the polymerization of the polymerizable monomer has two or more Tg, the lowest Tg is used as a reference. Here, Tg is a value measured by a differential scanning calorimeter (DSC).

The pressure in the evaporation tank is determined by the relationship between the processing temperature and the vapor pressure of the dispersion medium (usually water). In the present invention, the pressure is preferably adjusted appropriately. The pressure is usually 50 to 500 torr, preferably 150 to 400 torr.
The range of rr is preferable in that aggregation of the toner, adhesion of scale to the container wall, and foaming can be efficiently prevented. When a heating device such as a heat exchanger is used at a pressure that is too high, the dispersion of the polymer particles is heated to a considerably high temperature. And may increase aggregates and scale adhesion to vessel walls during processing. Also, if the pressure is too low, the pressure becomes lower than the vapor pressure of the dispersion medium at the processing temperature, so that the gas-liquid equilibrium shifts to the gas side at once, and the dispersion medium and other volatile substances from the inside of the polymer dispersion in the evaporation tank. Boiling of the volatile substance may start, and it may be difficult to suppress bubbles.

Further, in the present invention, the renewal of the interface between the polymer particles in the dispersion and the dispersion medium is promoted to promote the evaporation of the residual polymerizable monomer, so that the temperature and pressure balance of the system are not destabilized. In the range, the pressure-reduced stripping treatment can be performed while blowing gas into the liquid phase in the evaporation tank. The gas to be blown is not particularly limited, and examples thereof include steam, dry air, nitrogen, argon, helium, and carbon dioxide. Of these, nonflammable gases are preferred. When the gas is blown, the temperature of the gas is preferably lower than 100 ° C. in order to prevent aggregation of the polymer particles.

In the present invention, after the volatile substance removing treatment, ordinary dehydration, washing and drying treatments are carried out to obtain dry particles (toner) of a polymer. The residual polymerizable monomer in the obtained particles is less than 70 ppm, preferably 60 ppm or less.

(2) Polymerized toner The polymerized toner of the present invention has a residual polymerizable monomer content of 70 pp.
m, preferably 60 ppm or less, and a fluidity of 55% or more, preferably 60% or more, is a substantially spherical toner, and can be obtained by the method described above. Further, the substantially spherical toner of the present invention has a volume average particle diameter (dv) of 3 to 15 μm, preferably 5 to 10 μm, and a ratio (dv / d) of the volume average particle diameter to the number average particle diameter (dn). dn) is 1
１1.4, preferably 1１〜1.3, and the value (Sc / Sr) obtained by dividing the area (Sc) of a circle whose diameter is the absolute maximum length of the particle by the substantial projected area (Sr) of the particle is 1 And the product (A × dn × D) of the BET specific surface area (A) [m ² / g], the number average particle diameter (dn) [μm] and the true specific gravity (D) is 5 It is preferably in the range of 10 to 10. Particularly preferred polymerization toners have a melt viscosity at 120 ° C. of 100,000 poise or less, preferably 0.1 to 100,000 poise, and more preferably 10,000 to 80,000 poise. The viscosity may be measured using a flow tester. According to the toner having such a melt viscosity, high image quality can be realized even by high-speed printing.

Further, it is desirable to limit the amount of residual metal (ion) in the polymerization toner. In particular, if metals (ions) such as magnesium and calcium remain in the toner, they may absorb moisture under high humidity conditions, which may lower the fluidity of the toner or adversely affect image quality. Magnesium and calcium remaining in such toner (hereinafter, referred to as
A toner having a low content of (residual metal) in a toner can provide high print density and good image quality without fogging with a high-speed machine capable of printing 10 sheets or more per minute even under conditions of high temperature and high humidity. . The amount of residual metal is preferably 170
ppm or less, more preferably 150 ppm or less, particularly preferably 120 ppm or less. In order to reduce the residual metal, for example, in the dehydration stage of the toner manufacturing process described above,
Dehydration, washing, and drying may be performed using a washing dehydrator such as a continuous belt filter or a siphon peeler centrifuge. The ratio (dv / dn) of the volume average particle diameter to the number average particle diameter (dn) can be adjusted by classifying the dried particles or devising a droplet granulation step. Here, the values of the amount of the residual polymerizable monomer, the fluidity, the particle size, the amount of the residual metal, and the like are values measured by the method described in Examples described later.

A capsule toner having a layer structure composed of a core material and a shell material having a higher glass transition point than the core material covering the core material is preferable from the viewpoint of storage stability.
Further, the polymerized toner of the present invention is subjected to an external addition treatment, and an additive (hereinafter, referred to as an external additive) is adhered to and embedded in the surface of the toner particles, whereby the chargeability, fluidity and storage stability of the particles are obtained. Etc. can be adjusted.

Examples of the external additive include inorganic particles, organic acid salt particles, and organic resin particles. As inorganic particles, silicon dioxide, aluminum oxide, titanium oxide, zinc oxide,
Examples include tin oxide, barium titanate, and strontium titanate, and examples of the organic acid salt particles include zinc stearate and calcium stearate. As the organic resin particles, methacrylate polymer particles,
Acrylic acid ester polymer particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, core-shell type particles in which the core is a methacrylic acid ester copolymer and the shell is formed of a styrene polymer, etc. No. Among these, inorganic oxide particles,
Particularly, silicon dioxide particles are preferable.

The surfaces of these particles can be subjected to a hydrophobic treatment, and hydrophobically treated silicon dioxide particles are particularly preferred. The amount of the external additive is not particularly limited, but is usually 0.1 to 6 parts by weight based on 100 parts by weight of the toner. Two or more kinds of external additives may be used in combination. When an external additive is used in combination, a method of combining inorganic particles having different average particle diameters or a combination of inorganic particles and organic resin particles is preferable. In order for the external additive to adhere to the polymer particles, the external additive and the toner particles are usually charged into a mixer such as a Henschel mixer and stirred.

[0043]

EXAMPLES The production method of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. Parts and percentages are by weight unless otherwise specified.

The evaluation method performed in this example is as follows. (Endothermic peak temperature) Measured according to ASTM D3418-82. The DSC curve was measured with the peak top of the curve obtained when the temperature was raised at a temperature rate of 10 ° C./min as an endothermic peak. The differential scanning calorimeter used was “SSC5200” manufactured by Seiko Instruments Inc.

(Particle Size) The volume average particle size (dv) and the particle size distribution of the polymer particles (toner particles), that is, the ratio (dv / dp) of the volume average particle size to the average particle size (dp) are determined by using a multisizer ( (Manufactured by Coulter Inc.). The measurement by this multisizer was performed as follows: aperture diameter: 100 μm, medium: Isoton II, concentration 10%, number of particles measured: 100
The test was performed under the conditions of 000 pieces.

(Amount of Residual Polymerizable Monomer) The residual polymerizable monomer was measured by gas chromatography under the following conditions by the following method. (Column: TC-WAX, 0.25 mm × 30 m) Column temperature: 80 ° C. Injection temperature: 200 ° C. FID detection side temperature: 200 ° C.

After the dehydration treatment, 0.7 g of wet polymer particles before drying and 0.7 g of dried toner are precisely weighed to 1 mg unit.
After adding methanol and dispersing with ultrasonic waves, the volume was adjusted to 10 ml with methanol, and the mixture was allowed to stand at room temperature for 24 hours to extract.
Next, after insoluble matter was precipitated by centrifugation, 2 μl of the supernatant was injected into a gas chromatograph to confirm the residual polymerizable monomer. The standard sample for quantification was a methanol solution of each monomer. The amount of residual polymerizable monomer in the polymer particles after dehydration and before drying was calculated as a ratio to the pure solids in the wet sample. The pure solids were weighed to the nearest 1 mg at the same time as the wet polymer particles were sampled for the sample preparation work, and this was heated at about 200 ° C. for 30 minutes with an infrared lamp. The weight of the solid content obtained was precisely weighed, and the ratio of the pure solid content was calculated from the weight difference before and after drying, and this ratio was multiplied by the weight of the wet polymer particles used for measuring the amount of the residual polymerizable monomer. I asked. On the other hand, the amount of residual polymerizable monomer in the polymer particles after drying is calculated as a ratio to the weight of polymer particles obtained by drying the polymer particles after dehydration at 45 ° C. for 10 hours with a dryer. did.

(Fluidity) The openings are 150 μm and 75, respectively.
Three types of sieves of μm and 45 μm are stacked in this order from the top, and 4 g of the developer to be measured is precisely weighed and placed on the uppermost sieve. Next, the three types of sieves thus stacked were vibrated for 15 seconds using a powder measuring machine (manufactured by Hosokawa Micron Co., Ltd .; trade name “Powder Tester”) under the condition of a vibration intensity scale 4 and then placed on each sieve. The weight of the remaining developer is measured. Each measured value is put into the following formula, and a fluidity value is calculated. The measurement was performed three times per sample, and the average value was determined. Calculation formula: a = [(weight of developer remaining on 150 μm sieve (g)) /
4 g] × 100 b = [(weight of developer remaining on 75 μm sieve (g)) / 4
g] × 100 × 0.6 c = [(weight of developer remaining on 45 μm sieve (g)) / 4
g] × 100 × 0.2 Flowability (%) = 100− (a + b + c)

(Amount of residual metal) Magnesium ions derived from the metal compound used as the dispersion stabilizer were quantitatively analyzed using an inductively coupled plasma emission spectrometer (ICP) (manufactured by Seiko Instruments Inc.).

(Melt Viscosity) The melt viscosity at 120 ° C. was measured using a flow tester (CFT-500C, manufactured by Shimadzu Corporation) under the following measurement conditions. Starting temperature:
35 ° C., heating rate: 3 ° C./min, preheating time: 5 minutes, cylinder pressure: 10.0 Kg · f / cm ² , die diameter:
0.5 mm, die length 1.0 mm, shear stress: 2.4
51 × 10 ⁵ Pa, sample input amount: 1.0 to 1.3 g

(Evaluation of image quality) Environment dependency (H / H, L / L) Commercially available non-magnetic one-component developing type printer (12-sheet machine)
Using a remodeled printer that was modified so that the fixing temperature can be adjusted, 35 ° C x 80 RH% (H / H) environment and 1
Continuous printing is performed from the beginning in each environment of 0 ° C. × 20 RH% (L / L) environment, the printing density is 1.3 or more with a reflection densitometer (manufactured by Macbeth), and a whiteness meter (manufactured by Nippon Denshoku) The number of continuous prints that can maintain image quality of 15% or less of fog in the non-image area on the photoreceptor measured in the step (1) was examined. Whiteness B after printing,
Assuming that the whiteness before printing is A, fog (%) = ((A−
The fog value calculated by the formula of B) / A) × 100 was used.

(Evaluation of Odor) In the image quality evaluation described above,
The sensory evaluation of the odor of the monomer near the printing paper exit was performed by five healthy persons. 5 people do not feel the odor of the monomer (O), 1-2
A person felt the odor of the monomer (△), and three or more people felt the odor of the monomer (×).

Example 1 80.5 parts of styrene and n
-Polymerizable monomer for core comprising 19.5 parts of butyl acrylate (Tg of copolymer obtained by copolymerizing these monomers = 55 ° C.), polymethacrylic acid ester macromonomer (Toa Gosei Chemical Co., Ltd.) Made by Kogyosha, trade name "AA6", T
g = 94 ° C.) 0.3 part, divinylbenzene 0.5 part, t
-1.2 parts of dodecyl mercaptan, 7 parts of carbon black (Mitsubishi Chemical Corporation, trade name "# 25B"), charge control agent (Hodogaya Chemical Co., trade name "Spiron Black TR"
H "), 1 part, release agent (Fischer-Tropsch wax, manufactured by Sasol, trade name" Paraflint Spray ")
30 ", endothermic peak temperature: 100 ° C), 2 parts of which were wet-pulverized using a media type wet pulverizer to obtain a core polymerizable monomer composition A.

On the other hand, in an aqueous solution obtained by dissolving 10.2 parts of magnesium chloride (water-soluble polyvalent metal salt) in 250 parts of ion-exchanged water, 6.2 parts of sodium hydroxide (alkali metal hydroxide) in 50 parts of ion-exchanged water. An aqueous solution in which was dissolved was gradually added under stirring to prepare a magnesium hydroxide colloid (poorly water-soluble metal hydroxide colloid) dispersion liquid A. The particle size distribution of the formed colloid was measured with a SALD particle size distribution analyzer (manufactured by Shimadzu Corporation).
(50% cumulative value of number particle size distribution) is 0.35 μm, and D
90 (90% cumulative value of the number particle size distribution) was 0.62 μm.

On the other hand, methyl methacrylate (Tg = 10
(5 ° C.) 2 parts of water and 65 parts of water were finely dispersed by an ultrasonic emulsifier to obtain an aqueous dispersion A of a polymerizable monomer for shell. The droplet size of the polymerizable monomer for the shell is D90 of 1.6 μm.
Met.

The polymerizable monomer composition for core A is added to the magnesium hydroxide colloidal dispersion A obtained above, and the mixture is stirred until the droplets are stabilized.
-Butyl peroxy-isobutyrate (manufactured by NOF Corporation,
After adding 6 parts of trade name “Perbutyl IB”, 15,000 using Ebara Milder (trade name, manufactured by Ebara Corporation)
The mixture was subjected to high shear stirring at a rotation speed of rpm for 30 minutes to granulate droplets of the monomer mixture. The aqueous dispersion of the granulated monomer mixture was put into a reactor equipped with a stirring blade, and a polymerization reaction was started at 85 ° C., and after the polymerization conversion reached almost 100%, A water-soluble initiator (manufactured by Wako Pure Chemical Industries, trade name “VA-086” = 2,
0.3 parts of 2'-azobis (2-methyl-N- (2-hydroxyethyl) -propionamide) was dissolved and placed in the reactor. After the polymerization was continued for 4 hours, the reaction was stopped to obtain an aqueous dispersion of polymer particles.

A deformable bull margin wing (FIG. 1,
2), the aqueous dispersion of the polymer obtained as described above was charged into an evaporation tank equipped with a stirrer equipped with inclined paddle blades as lower blades, and the pressure in the evaporation tank was reduced to 290 torr. Thereafter, the dispersion was heated to 75 ° C. while stirring. While maintaining these conditions, vacuum stripping was performed, and after 5 hours, the vacuum was released and the dispersion was cooled to 25 ° C. The liquid volume decreased due to evaporation during the stripping under reduced pressure. However, during the treatment, a part of the upper stage blade was constantly agitated in a state of protruding from the liquid surface, and no bubbles were generated on the liquid surface. In addition, no increase in the amount of aggregates in the polymer dispersion after vacuum stripping and no adhesion of scale to the inside of the evaporation tank or the stirrer were observed.

The aqueous dispersion of core-shell type polymer particles obtained above was washed with sulfuric acid while stirring (25%).
C. for 10 minutes) to bring the pH of the system to 4.5 or less. This aqueous dispersion was filtered, dehydrated and washed using a continuous belt filter (trade name “Eagle Filter” manufactured by Sumitomo Heavy Industries, Ltd.), and the solid content was separated by filtration. Thereafter, drying was performed at 45 ° C. for 10 hours using a dryer to obtain core-shell type polymer particles. The amount of residual polymerizable monomer in the polymer particles before and after drying with a dryer was measured.

To 100 parts of the polymer particles obtained above, 0.8 part of hydrophobically treated silica having an average particle diameter of 14 nm (trade name “RX200” manufactured by Degussa Co., Ltd.) was added and mixed using a Henschel mixer. Thus, an electrophotographic toner was obtained. The obtained toner was evaluated. Table 1 shows the measurement results and the evaluation results.

Example 2 An electrophotographic toner was obtained in the same manner as in Example 1 except that the time for the reduced pressure stripping treatment was changed to 10 hours. No bubbles were generated during the stripping under reduced pressure, the amount of aggregates in the polymer dispersion after the stripping under reduced pressure was increased, and no scale was attached to the inside of the evaporation tank or the stirrer. Table 1 shows the measurement results and the evaluation results. Example 3 A core polymerizable monomer composed of 77 parts of styrene and 23 parts of n-butyl acrylate (Tg of a copolymer obtained by copolymerizing these monomers = 48 ° C.),
Carbon black (Mitsubishi Chemical Corporation, trade name "# 25")
7 parts, 2-acrylamido-2-methylpropanesulfonic acid-containing copolymer (Mw = 21,000, styrene ratio 87%, n-butyl acrylate ratio 10%, 2-acrylamido-2-methylpropanesulfonic acid ratio 3% )
One part, 0.3 part of divinylbenzene, and 0.5 part of a polymethacrylic acid ester macromonomer (trade name “AA6”, manufactured by Toa Gosei Chemical Industry Co., Ltd., Tg = 94 ° C.) were stirred and mixed with an ordinary stirring device. Thereafter, the mixture was uniformly dispersed by a media type disperser. To the above dispersion, 10 parts of pentaerythritol = tetramyristate was added, mixed and dissolved to obtain a core polymerizable monomer composition B.

The preparation of the magnesium hydroxide colloid B is as follows:
Except that the amount of magnesium chloride was changed to 9.5 parts and the amount of sodium hydroxide was changed to 5.8 parts, the particle size distribution was measured in the same manner as in Example 1.
The particle size is D50 (50% cumulative value of the number particle size distribution) of 0.
At 36 μm, D90 (90% cumulative value of the number particle size distribution) was 0.80 μm. On the other hand, methyl methacrylate 2
And 30 parts of water were finely dispersed by an ultrasonic emulsifier to obtain an aqueous dispersion B of a shell-polymerizable monomer. The particle size of the droplets of the polymerizable monomer for shell was measured using a SALD particle size distribution measuring device (manufactured by Shimadzu Corporation) particle size measuring device.
0 was 1.6 μm. The core polymerizable monomer composition B was added to the magnesium hydroxide colloid dispersion B obtained above, and the shell polymerizable monomer was used as an aqueous dispersion of the shell polymerizable monomer. To the aqueous dispersion B of
An aqueous dispersion of a polymer was obtained in the same manner as in Example 1, except that a water-soluble initiator obtained by dissolving 0.3 part of ammonium persulfate in 65 parts of distilled water was used.

The obtained aqueous dispersion was subjected to a reduced pressure stripping treatment in the same manner as in Example 1. Core-shell type polymer particles were obtained in the same manner as in Example 1 except that the pH of the system at the time of acid washing was set to 4 or less, and drying was carried out overnight. Core-shell type polymer particles 1 obtained above
To 00 parts, 0.6 part of hydrophobized colloidal silica (trade name “RX200”, manufactured by Nippon Aerosil Co., Ltd.) was added and mixed using a Henschel mixer to prepare an electrophotographic toner. No bubbles were generated during the stripping under reduced pressure, the amount of aggregates in the polymer dispersion after the stripping under reduced pressure was increased, and no scale was attached to the inside of the evaporation tank or the stirrer. Table 1 shows the measurement results and the evaluation results.

Example 4 An electrophotographic toner was obtained in the same manner as in Example 3, except that the time for the reduced pressure stripping treatment was changed to 10 hours. No bubbles were generated during the stripping under reduced pressure, the amount of aggregates in the polymer dispersion after the stripping under reduced pressure was increased, and no scale was attached to the inside of the evaporation tank or the stirrer. Table 1 shows the measurement results and the evaluation results.

Comparative Example 1 A suspension polymerization toner for electrophotography was obtained in the same manner as in Example 1 except that the vacuum stripping treatment was not performed. The glass transition temperature of the obtained toner was 55 ° C., the volume average particle diameter was 7.2 μm, and the particle diameter distribution was narrow, but the residual styrene amount was 360 ppm, the residual n-butyl acrylate amount was 102 ppm, and the residual methyl methacrylate amount was 56 ppm. And the odor evaluation was x. Table 1 shows the results. [Comparative Example 2] A suspension polymerization toner for electrophotography was obtained in the same manner as in Example 3 except that the vacuum stripping treatment was not performed. The volume average particle diameter of the obtained toner is 7.1 μm.
The particle size distribution was narrow, the residual styrene content was 205 ppm, the residual n-butyl acrylate content was 78 ppm, the residual methyl methacrylate content was 42 ppm, and the odor evaluation was Δ. Table 1 shows the results. [Comparative Example 3] The same reduced pressure stripping treatment as in Example 1 was attempted with the stirring blades of the mixing tank equipped with a stirrer being inclined paddle blades in both the upper and lower stages, with both blades constantly immersed in the liquid during the treatment. In addition, the foaming on the liquid surface was so severe that the desired reduced pressure stripping treatment was impossible. As a result, the toner was aggregated and no image was formed.

[0065]

[Table 1]

From the above results, the polymerizable monomer can be efficiently removed by stripping under reduced pressure under specific stirring conditions, and a polymerized toner excellent in fluidity without particle aggregation can be obtained. It was confirmed.

[0067]

By using the electrophotographic toner of the present invention, continuous high-speed printing can be realized with little influence on the environment such as odor.

[Brief description of the drawings]

FIG. 1 is a view for explaining a shape of a deformable bull margin stirring blade viewed from the right side.

FIG. 2 is a diagram illustrating a shape of a deformable bull margin stirring blade viewed from the left side.

FIG. 3 is a diagram illustrating measurement of a length of a portion of a blade protruding from a liquid surface.

[Explanation of symbols]

 w: the side of the wing in contact with the liquid surface w ': the other side forming a pair with w L: the liquid surface

Claims (1)

[Claims] 1. A step of suspension-polymerizing a polymerizable monomer composition comprising at least a colorant and a polymerizable monomer in an aqueous medium to obtain a dispersion of polymer particles, and stirring the dispersion. Removing a volatile substance in the polymer particles while stirring, wherein a part of the stirring blade used for the stirring protrudes from the surface of the dispersion liquid being stirred. .