JPH04281464A - Production of electrostatic charge image developing toner - Google Patents

Abstract

PURPOSE:To obtain the fine particles for the toner having good dispersibility and uniform grain size by controlling the the concn. of a polymerizable monomer and the ratio of tricalcium phosphate to the monomer in a reaction system of a suspension polymn. method. CONSTITUTION:The ratio M/W of the content weight M of the monomer to the weight W of an aq. medium is specified to 0.2 to 1.2 and the ratio CP/W of the weight CP of the tricalcium phosphate to the content weight M of the monomer is specified to 0.2 to 0.3. The toner particles having 0.5 to 10mum volume average are subjected to a suspension polymn. and further to an acid treatment. Namely, the hardly water-soluble tricalcium phosphate and an anionic surfactant are used as a dispersion stabilizer in the aq. medium of a suspension polymerization reactant. The monomer compsn. consisting of the polymerizable monomer, coloring agents and other toner characteristic imparting agents added at need is suspension polymerized in this aq. medium. The monomer compsn. is polymerized in this state and the polymer particles are subjected to a dilute acid treatment, by which the dispersant incorporated into the polymer particles is made soluble in water and is removed.

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 toner for developing electrostatic images formed in electrophotography, electrostatic printing, electrostatic recording, and the like.

0002

[Prior Art] A conventional method for producing a toner for developing electrostatic images involves dispersing a colorant and a charge control agent, which is contained in toner particles and adjusts the charging characteristics of the toner, into a binder polymer by melt-kneading. A common method is to mechanically crush the resulting lumpy toner material and classify it into particles having a particle size range (usually 1 to 50 μm) required for the toner by a classification operation.

However, in this method, the coloring agent, which is an essential component of the toner, is incorporated into the binder polymer, which is already a polymer, by melt-kneading, so the miscibility of the two is generally poor and it is not sufficient. In addition to being difficult to disperse and contain uniformly, the type and amount of colorants, etc. and the type of binder polymer are restricted from the viewpoint of compatibility, and pulverization and classification processes are essential, making particles spherical. It is often required and has low yields.

[0004] From this point of view, as a toner manufacturing method, there is a method in which a monomer composition containing a coloring agent etc. in a monomer that is polymerized to form a binder polymer is polymerized by a suspension polymerization method. . In this method, since the coloring agent is contained in the monomer, a polymer with high miscibility between the two and the coloring agent being uniformly dispersed can be obtained, and since the polymer is formed as spherical particles, it can be crushed. The process and classification process can be made unnecessary.

In order to directly produce polymer particles having a required particle size as a toner by a dispersion polymerization method such as a suspension polymerization method, it is necessary for the monomer composition to have the required particle size in a dispersion medium. It is necessary that the particles be stably dispersed in the form of fine particles, and that these particles do not coalesce into large-diameter particles during polymerization. In particular, in the dot exposure format used in recent laser printing, it is necessary that the toner be fine particles and have a uniform particle size.

In the monomer suspension polymerization method, water or an aqueous medium mainly composed of water is used as the dispersion medium, but in order to obtain a stable dispersion state of the monomer composition, dispersion is usually The agent is contained in the dispersion medium. This dispersant is generally known to be a water-soluble protective colloid, a surfactant, or a fine powder of a poorly water-soluble inorganic substance, such as gelatin, starch, polyvinyl alcohol, carboxymethyl cellulose, anionic and other surfactants, and barium sulfate. , poorly water-soluble salts such as calcium sulfate, barium carbonate, calcium carbonate, and magnesium carbonate, inorganic polymer substances such as talc, clay, silicic acid, and diatomaceous earth, and fine powders of metal oxides such as aluminum oxide and titanium oxide. (Unexamined Japanese Patent Publication No. 56-1
No. 30762, No. 61-22354, JP-A-2-14
No. 8046).

[0007] The dispersant present in the dispersion medium prevents the particles from coalescing with each other by adsorbing or adhering to the surface of the particles of the dispersed monomer composition. It is difficult to remove the dispersant contained in the combined particles, and the hydrophilic nature of the dispersant makes the toner hygroscopic, causing problems such as blocking during storage, so post-treatment such as acid treatment is required. will be removed.

[0008]

[Object of the Invention] In view of the above-mentioned circumstances, the present invention is a method for producing toner particles having good dispersibility, fine particles, and uniform particle size by applying the suspension polymerization method without sacrificing its advantages. Another object of the present invention is to provide a method for producing a high-quality toner with high resolution.

[0009]

[Structure of the Invention] The object of the present invention is to carry out suspension polymerization of a monomer composition containing at least a polymerizable monomer and a coloring agent in an aqueous medium containing tricalcium phosphate and an anionic surfactant. In the polymerization reaction system, the ratio M/W of the content weight (M) of the monomer to the weight (W) of the aqueous medium is 0.
2 to 1.2, the above M of the weight of tricalcium phosphate (CP)
The ratio CP/M to 0.02 to 0.3, suspension polymerization of toner particles having a volume average diameter of 0.5 to 10 μm,
This is achieved by a method for producing a toner for developing an electrostatic image, which is further characterized by acid treatment.

In the embodiment of the present invention, the weight ratio CP/M of tricalcium phosphate Ca3 (PO4)2 and the monomer is 0.01 or less in the prior art, but as a result of investigation, it is 0.02 in the present invention. The range of 0.3 to 0.3, more preferably 0.02 to 0.2. Also, the weight ratio M/W of monomer and aqueous medium
was limited to 0.34 or less in the prior art, but in the present invention, it is possible to select an efficient range of 0.2 to 1.2, and more preferably 0.5 to 1.0. be.

Furthermore, the volume average diameter of the toner is guaranteed to be 0.5 to 10 μm, which is practically useful for forming dot images, and 1 to 5 μm.
It is possible to adjust it within the range of m.

In the present invention, poorly water-soluble tricalcium phosphate Ca3(po4)2 is added to the aqueous medium of the suspension polymerization reaction system.
and an anionic surfactant as a dispersion stabilizer,
A monomer composition consisting of a polymerizable monomer, a colorant, and other toner characteristic imparting agents added as necessary is dispersed and suspended in this aqueous medium, and in this state, the monomer composition is The dispersant contained in the polymer particles is made solubilized in water by polymerizing the particles and treating the polymer particles with dilute acid, and then the dispersant is removed by washing with water, thereby developing an electrostatic image. Manufactures toner for

The dispersant used in the present invention is a poorly water-soluble salt tricalcium phosphate (tertiary calcium phosphate) Ca3 (
PO4)2 is used.

Specific examples of the anionic surfactant used with the above tricalcium phosphate include sodium dodecylbenzenesulfonate, sodium tetradecylsulfate, sodium pentadecylsulfate, sodium octylsulfate, sodium allyl-alkyl-polyethersulfonate, Sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate, 3,3'-disulfone diphenyl urea-4
,4'-diazo-bis-amino-8-naphthol-6-
Sodium sulfonate, ortho-carboxybenzene
Examples include azo-dimethylaniline, sodium 2,2',5,5'-tetramethyl-triphenylmethane-4,4'-diazo-bis-β-naphthol-disulfonate, and others.

[0015] The amount of the anionic surfactant is within the range of 0.001 to 0.01 wt% based on the aqueous medium.

[0016] In order to disperse and suspend the monomer composition in an aqueous medium, it is necessary to stir the system, and this may be carried out using a homomixer, homogenizer, etc., and the rotational speed thereof is usually 1000 to 1000. Although it is 12000 rpm,
Once the monomer composition has been divided into the required particle size, this state is maintained substantially by the action of the dispersant, so stirring may be carried out to the extent that sedimentation of the particles is prevented. The polymerization temperature is usually 55 to 120°C, but polymerization is more uniform at lower temperatures.

Examples of the polymerizable monomer that can be used in the present invention include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, and 2,4-methylstyrene. Dimethylstyrene, p-butylstyrene, p-t-butylstyrene, p-hexylstyrene, p-octylstyrene, p-
Preferred examples include styrene monomers such as nonylstyrene, p-decylstyrene, p-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene. . In addition, ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; Methyl acrylate, ethyl acrylate, and butyl acrylate , isobutyl acrylate, propyl acrylate, octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methacrylate Methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, α-methylene aliphatic monocarboxylic acid esters such as phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; vinyl methyl ether,
Vinyl ethers such as vinyl ethyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; N-vinylpyrrole, N-vinylcarbazole,
N- such as N-vinylindole and N-vinylpyrrolidone
Vinyl compounds; examples include vinylnaphthalenes and others. These monomers can be used alone or in combination, or can be polymerized to form a copolymer.

As the coloring agent used in the present invention, any suitable pigment or dye can be used, such as carbon black, nigrosine dye (C.I. No.
50415B), Aniline Blue (C.I.No.50
405), Calco Oil Blue (C.I.No.Azo
ec Blue 3), Chrome Yellow (C.I.N.
o. 14090), Ultramarine Blue (C.I.N.
o. 77103), DuPont Oil Red (C.I.N.
o. 26105), Orient Oil Red #330 (
C. I. No. 60505), Quinoline Yellow (C.
I. No. 47005), methylene blue chloride (
C. I. No. 52015) Phthalocyanine Blue (
C. I. No. 74160), malachite green oxalate (C.I. No. 42000), lamp black (C.I. No. 77266), rose bengal (C.
．． I. No. 45435), oil black, azo oil black, and others can be used alone or in combination. These colorants may be contained in the toner as a final product in a proportion of about 3 to 20 wt%. In addition, when containing magnetic powder described below,
This magnetic powder can be used as a coloring agent.

In the present invention, as the polymerization initiator for the polymerization of the above-mentioned monomers, a conventional polymerization initiator can be used within a conventional temperature range. Specific examples include benzoyl peroxide, lauryl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), orthochlorobenzoyl peroxide, orthomethoxy Mention may be made of benzoyl peroxide and others. As the polymerization method, a method under normal pressure or under high pressure may be arbitrarily adopted.

The magnetic powder used in the case of the black and white one-component magnetic toner is a substance that is strongly magnetized in the direction of a magnetic field, preferably black in color, chemically stable, and has a particle size is preferably a fine powder of 1 μm or less, and from these points of view, magnetite (triiron tetroxide) is most preferable. Typical magnetic or magnetizable materials include metals such as cobalt, iron, and nickel; aluminum, cobalt, copper, iron, magnesium, nickel, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, and manganese. , alloys of metals such as selenium, titanium, tungsten, vanadium and mixtures thereof;
Metal compounds including metal oxides such as aluminum oxide, iron oxide, copper oxide, nickel oxide, zinc oxide, titanium oxide, and magnesium oxide; nitrides such as vanadium nitride, chromium nitride; such as tungsten carbide and silica carbide carbides; ferrites and mixtures thereof can be used. These magnetic powders preferably have an average particle size of about 0.01 to 1 μm. The proportion contained in the toner is approximately 5% based on the unit weight of the polymer component.
It is desirable that the amount is 0 to 300% by weight, preferably 50 to 200% by weight. Particularly preferably, 90% of the polymer component
~150% by weight.

In addition to the above polymerizable monomers and colorants,
The polymer composition of the present invention may contain other toner property imparting agents, such as a crosslinking agent that improves the physical properties of the polymer, a reactive prepolymer, a release agent for preventing offset in heated roller fixing, a low molecular weight polyolefin, In addition, a charge control agent and others may be contained as necessary. As described above, since the present invention uses a poorly water-soluble salt as a dispersant, even if these dispersants are contained in the polymer particles, they are mainly contained in the surface layer portion of the particles, and the dispersant is a diluted inorganic acid. Since it is easily decomposed by treatment with a solution and becomes soluble in water, the dispersant can be easily removed from the polymer particles by performing such treatment and further washing with water.

As a result, it is possible to obtain a toner that does not contain a dispersant even though the suspension polymerization method is used, and it is possible to fully exhibit the characteristics of the toner characteristic imparting agent contained in the monomer composition in the toner. Accordingly, it is possible to produce a toner for developing electrostatic images having uniform particle diameters and a volume average diameter of 1 to 5 μm and excellent characteristics. Of course, there are advantages of the suspension polymerization method, namely, the number of steps is small and only one step is required, the required toner characteristic imparting agent can be easily and suitably incorporated into the toner particles, and spherical particles can be obtained directly. Therefore, the advantages such as high yield are not impaired at all.

[0023]

[Examples] Examples of the present invention will be described below, but the present invention is not limited thereto.

Examples 1 to 5 and Comparative Examples (1) and (2) The suspension polymerization conditions M/W, CP/M, the toner particle diameter d50 and particle diameter variation coefficient Cv to be produced are as shown in Table 1. Toner particles of Examples and Comparative Examples were prepared by shaking, and their performance was evaluated.

The procedure for preparing toner particles is as follows.

[0026] Also, CP/W (wt%) and toner particle diameter d5
The relationship of 0 is shown in Figure 1. Japanese Patent Publication No. 61-22354
No. 2-148046 is also shown.

(Preparation of toner particles) Monomer composition styrene
90 (parts by weight) butyl methacrylate
10 Carbon black
5 Polypropylene
5. Thoroughly mix and homogenize the above mixture with a sand grinder to obtain V-65; 2,2'
-azobis(2,4-dimethylvaleronitrile) 1.8
Add parts by weight.

Aqueous medium (A) Na3PO4.12H2O
25.6 (parts by weight)
water
53.4 〃 (
B) CaCl2
11.2 〃
water
102 (C)
C12H25 C6H4SO3Na
0.04 The above three materials were mixed to prepare an aqueous medium containing poorly water-soluble Ca3(PO4)2. The reaction for producing Ca3(PO4)2 is as follows.

2Na3PO4 +3CaCl2→Ca3
(PO4) Preparation of 2+6 NaCl suspension After determining M/W and CP/M, the monomer composition was added to an aqueous medium, and a homomixer (manufactured by Tokushu Kika) was used to
A suspension was prepared by stirring and dispersing at 0 rpm for 30 minutes.

Suspension polymerization at 70° C. in a nitrogen atmosphere with stirring at 200 rpm.
, polymerization was carried out for 5 hours.

The polymer particles were added to an acid-treated aqueous hydrochloric acid solution (pH 2) and Ca3(
PO4)2 was dissolved and removed, followed by washing with water, filtration, and drying to obtain toner particles with d50 and Cv, respectively.

Note that d50 is the volume average particle diameter, and Cv is the value obtained by dividing the standard deviation by D50.

(Evaluation) A developer was prepared using the sample toner particles, and image output was evaluated using a laser printer. Regarding resolution, 21μm line (1200dpi
) Chart reproducibility was evaluated based on the criteria in Table 2.

[0034]

[Table 1]

[0035]

Effects of the Invention By adjusting M/W and CP/M, a fine particle toner with small variation in particle size can be obtained, and resolution can be improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between CP/M and d50.

Claims (1)

[Claims] 1. In a polymerization reaction system in which a monomer composition containing at least a polymerizable monomer and a coloring agent is suspension-polymerized in an aqueous medium containing tricalcium phosphate and an anionic surfactant, The ratio M/W of the content weight (M) of the polymer to the weight (W) of the aqueous medium is 0.2 to 1.2, and the ratio CP/M of the weight (CP) of tricalcium phosphate to the above M is 0.
．． 02~0.3, volume average diameter is 0.5~10μ
1. A method for producing a toner for developing an electrostatic image, which comprises suspending and polymerizing toner particles of m and further acid-treating the toner particles.