JP2996785B2 - Suspension polymerization monomer composition and method for producing suspension polymerization toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monomer composition for suspension polymerization and a method for producing a suspension polymerization toner.

[0002]

2. Description of the Related Art For example, as a method for producing a toner used in electrophotography, a coloring agent and other additives used as needed are conventionally added to a thermoplastic resin as a binder, and these are melt-kneaded. A so-called pulverization method for manufacturing the toner by pulverizing and classifying the toner is known. In this pulverization method, it is practically difficult to produce a toner having a small particle diameter, for example, having a volume average particle diameter of about 1 to 5 μm, for the purpose of preventing generation of fine powder due to brittle fracture of the resin. In addition, the volume average particle size is about 10 μm.
However, such a toner having a large particle size cannot meet the recent demand for higher image quality, and thus has a problem in that fine line reproducibility is poor.

Under these circumstances, in recent years, a method for producing a toner by a suspension polymerization method has been proposed. For example, Japanese Patent Application Laid-Open No. 1-145664 proposes a technique of using a nigrosine dye to increase the dispersibility of carbon black in a polymerizable monomer when producing a toner by a suspension polymerization method. Also, Japanese Unexamined Patent Publication No.
Japanese Patent No. 17253 proposes a technique of using hydrophobic carbon black in order to enhance the dispersibility of carbon black in a polymerizable monomer when producing a toner by a suspension polymerization method.

[0004]

However, the above-mentioned prior art still has a problem that the dispersibility of carbon black in the polymerizable monomer is poor. More specifically, in the suspension polymerization method, polymerization is carried out by suspending a monomer composition for suspension polymerization containing at least a polymerizable monomer and carbon black in an aqueous medium. In the monomer composition, it is necessary that carbon black is sufficiently dispersed in the polymerizable monomer. That is, when a toner having a small volume average particle diameter of 1 to 5 μm is produced by a suspension polymerization method, the particle diameter of the carbon black is smaller than the particle diameter of the toner when the carbon black is dispersed in the polymerizable monomer. If the suspension is not small, when the suspension is prepared in an aqueous medium, the carbon black is detached from the suspension to form a suspension containing no carbon black, or the carbon black itself is not formed. Are released, resulting in a toner having a low degree of blackening, and there is a problem that an image is fogged due to charging failure due to poor dispersion of carbon black.

Accordingly, a first object of the present invention is to provide a monomer composition for suspension polymerization which contains a polymerizable monomer and carbon black and has sufficiently high dispersibility of carbon black. It is in. A second object of the present invention is to provide a method for reliably producing a suspension-polymerized toner having a high degree of blackening in which carbon black is sufficiently dispersed .

[0006]

In order to achieve the above object, the monomer composition for suspension polymerization of the present invention comprises a carbon black
, Polymerizable monomer and carbon represented by the following formula
It is characterized by containing a black dispersing aid.

[0007]

Embedded image

(In the above formula 2, R is an alkyl group,
Represents an alkoxy group, a substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic group, and n represents an integer of 1 to 6. The method for producing a suspension-polymerized toner of the present invention is characterized in that the monomer composition for suspension polymerization is subjected to suspension polymerization in an aqueous medium.

Hereinafter, the present invention will be described specifically. [ Monomer composition for suspension polymerization ] The monomer composition for suspension polymerization of the present invention is a carbon black.
, A polymerizable monomer and a carbon black represented by the above formula (2).
It contains a dispersing aid for racks. Carbon bra
Specific examples of the dispersing aids for the packs include those listed in Tables 1, 2 and 3 below.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

[Table 4]

[0014]

[Table 5]

[0015] The content of the dispersing aid of the above carbon black
By doing so, in the monomer composition for suspension polymerization, 0.05 to 0.
It can be well dispersed in a state of a small particle size of about 5 μm. Therefore, when the monomer composition for suspension polymerization is suspended in an aqueous medium, carbon black is surely dispersed and contained in suspension droplets having a small particle diameter.

[Suspension Polymerized Toner] A monomer composition for suspension polymerization obtained by dispersing carbon black in a polymerizable monomer in the presence of a carbon black dispersing agent represented by the above formula (2). Is subjected to suspension polymerization in an aqueous medium to obtain a suspension polymerization toner. The volume average particle diameter of the suspension polymerization toner is preferably 1 to 5 μm. According to the toner having such a small particle diameter, it is possible to form an image having high resolution and excellent reproducibility of fine lines. The volume average particle diameter of the suspension polymerization toner is a value measured by a laser diffraction type particle size distribution analyzer “HELOS” (manufactured by SYMPATEC).

Examples of the carbon black include commercially available carbon black, carbon black grafted with a polymerizable monomer, and the like, surface-treated with a surface treating agent such as a silane coupling agent or an aluminum coupling agent. Carbon black or the like can be used. Particularly, carbon black having a pH of 6 to 10, preferably 7 to 9 is preferable. When carbon black having a too low pH is used, radicals are trapped, so that polymerization does not proceed and a problem of gelation occurs.

As the polymerizable monomer, conventionally known ones can be used, and radical polymerizable ones are particularly preferable. One or a combination of two or more can be used so as to satisfy the thermal characteristics and electrostatic characteristics required for the toner. Specifically, a vinyl aromatic monomer,
Acrylic monomers, vinyl ester monomers, vinyl ether monomers, olefin monomers and the like can be suitably used.

Examples of the vinyl aromatic monomer include, for example,
Styrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n- Styrene-based monomers such as octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, 2,4-dimethylstyrene, and 3,4-dichlorostyrene, and derivatives thereof. .

As the acrylic monomer, acrylic acid,
Methacrylic acid, methyl acrylate, ethyl acrylate,
Butyl acrylate, 2-ethylhexyl acrylate,
Cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, methacryl Dimethylaminoethyl acrylate, diethylaminoethyl methacrylate and the like.

Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl benzoate and the like. Examples of the vinyl ether monomer include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl phenyl ether and the like. Examples of the olefin monomer include ethylene, propylene, isobutylene, 1-butene, 1-pentene, and 4-methyl-
Monoolefin monomers such as 1-pentene and diolefin monomers such as butadiene, isoprene and chloroprene are exemplified.

Further, a crosslinking monomer may be added in order to improve the properties of the suspension-polymerized toner particles. As crosslinkable monomers, divinylbenzene, divinylnaphthalene,
Examples thereof include those having two or more unsaturated bonds such as divinyl ether, diethylene glycol methacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and diallyl phthalate.

The toner contains additives such as a fixing property improving agent and a charge control agent as necessary. When these additives are used, they are mixed with the polymerizable monomer. A monomer composition for suspension polymerization is formed, and the monomer composition for suspension polymerization is used by adding it to an aqueous medium.

As the fixing property improver, a conventionally known one can be used. In particular, a polyolefin-based material is preferable, but not limited thereto. Also, 1
Species or a combination of two or more species may be used. Examples of the polyolefin-based fixability improver include low molecular weight polyethylene, low molecular weight polypropylene, acid-modified polyethylene, acid-modified polypropylene, oxidized polyethylene, oxidized polypropylene, such as paraffin wax, etc. And the like. In particular, the dispersibility of carbon black is further improved by adding polypropylene to the monomer composition for suspension polymerization. It is considered that the viscosity of the suspension becomes moderately high and a sufficient shearing force is applied.

Examples of the charge control agent include metal complex dyes, nigrosine dyes, and ammonium compounds.

If necessary, a fluidizing agent or the like may be added from the outside to the suspension polymerization toner obtained as described above. As such a fluidizing agent, silica, titanium oxide, inorganic oxides such as aluminum oxide, inorganic nitride,
Carbides, organic fine particles and the like. These may be used in combination as appropriate.

[Production Method of Suspension-Polymerized Toner] In the production method of the suspension-polymerized toner of the present invention, carbon black is polymerized in the presence of a carbon black dispersing agent represented by the above formula (2). To prepare a monomer composition for suspension polymerization, and the monomer composition for suspension polymerization is subjected to suspension polymerization in an aqueous medium to produce a suspension polymerization toner.
The use ratio of the carbon black dispersing agent represented by Chemical Formula 2 is preferably 0.05 to 1% by weight, and particularly preferably 0.1 to 0.7% by weight, based on the polymerizable monomer. Although there is no particular problem even if this use ratio is large, it is not practical because the effect is saturated. On the other hand, if the use ratio is too small, the particle size of the carbon black increases, and the dispersibility in the polymerizable monomer deteriorates.

In one example of the production example, a polymerizable monomer constituting the binder resin of the toner, carbon black, and other additives used as necessary are dispersed by, for example, a sand mill or the like. A polymerization initiator is added as needed to prepare a dispersion of the monomer composition (oil phase). Next, the dispersion of the oil phase is added to an aqueous phase composed of water, a suspension stabilizer such as tricalcium phosphate, and a surfactant, and the dispersion is added to a dispersion having a concentration of 1 to 5 μm using a disperser such as a homomixer.
m droplets. The preferred ratio of oil phase to aqueous phase is 1:
It is set in the range of 1 to 1:10 so that aggregation of the particles does not occur during polymerization. The suspension is transferred to a kolben equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube, and polymerized in a range of 40 to 100 ° C. under a nitrogen stream.
After completion of the polymerization, the temperature is returned to room temperature, and an acid such as hydrochloric acid is added to add phosphoric acid 3
After dissolving the poorly water-soluble inorganic compound such as calcium, the aqueous phase is removed by filtration or centrifugation, washed with water and dried to obtain the intended suspension polymerization toner.

As the polymerization initiator, for example, 2,2'-
Azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis ( Oil-soluble azobis polymerization initiators such as 2-methylbutyronitrile) and 1,1'-azobis (cyclohexane-1-carbonitrile), benzoyl peroxide, lauroyl peroxide, tert-butylperoxy-2-ethylhexano Eat, acetyl peroxide,
Organic peroxides such as tert-butyl perbenzoate are exemplified. The amount of the polymerization initiator used can be adjusted in accordance with the required molecular weight, but the amount used is 0.1% with respect to the polymerizable monomer.
Is preferably in the range of 10 to 10% by weight, particularly 1.5 to 7% by weight.
Is preferable.

[0030]

(Preparation of monomer composition for suspension polymerization)

Polymerizable monomer Styrene 90 parts Butyl acrylate 10 parts Dispersing aid Exemplified Compound No. 7 0.2 parts Coloring agent Carbon black "Regal 330R" 5 parts (Cabot, pH = 8.0) Fixing property improver polypropylene 5 parts After the above materials are thoroughly mixed and homogenized with a sand grinder, 1.8 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator was added to prepare a monomer composition for suspension polymerization.

[Preparation of Aqueous Medium] (A) Trisodium phosphate dodecahydrate 25.6 parts (Na ₃ PO ₄ .12H ₂ O) Water (H ₂ O) 53.4 parts (B) Calcium chloride ( CaCl ₂ ) 11.2 parts Water (H ₂ O) 102.0 parts (C) Sodium dodecylbenzenesulfonate 0.04 part (C ₁₂ H ₂₅ C ₆ H ₄ SO ₃ Na) Above (A), (B) , (C) were mixed to prepare an aqueous medium containing a poorly water-soluble inorganic compound [Ca ₃ (PO ₄ ) ₂ ]. This poorly water-soluble inorganic compound [Ca ₃ (PO ₄ ) ₂ ]
Is generated by a reaction represented by the following formula. 2Na ₃ PO ₄ + 3CaCl ₂ → Ca ₃ (PO ₄ ) ₂ + 6NaCl

[Preparation of Suspension] The above monomer composition for suspension polymerization was charged into the above aqueous medium, and the mixture was stirred and dispersed at 10,000 rpm for 30 minutes using a homomixer (manufactured by Tokushu Kika). A liquid was prepared. In this suspension, the volume average particle diameter D ₅₀ of the dispersed carbon black was measured using a particle size distribution analyzer “Sejimputa SPT-C” (manufactured by Hosokawa / Akashi Co., Ltd.) and found to be 0.28 μm. Was. The viscosity of the suspension was 135 CP.

[Polymerization reaction] This suspension was stirred at 70 ° C. for 7 hours at 200 to 300 rpm in a nitrogen atmosphere.
The polymerization was carried out over time. Then cool to room temperature,
Hydrochloric acid aqueous solution is added, and the poorly water-soluble inorganic compound [Ca
₃ (PO ₄ ) ₂ ], and then washed with water, filtered,
After drying, a suspension polymerization toner was obtained.

With respect to the obtained suspension polymerization toner, the following items were evaluated. (1) The volume average particle size D ₅₀ above suspension polymerization toner in the toner, laser diffraction particle size distribution measuring apparatus using "SALD-1100" (manufactured by Shimadzu Corporation) to measure the volume average particle diameter D _50.

(2) Degree of blackening The suspension polymerization toner is uniformly adhered to the adhesive label so as to wipe off the excess, and this is "Sakura Densitometer PDA-65" (manufactured by Konica Corporation). Was used to measure the concentration.

(3) Amount of Charge of Toner A suspension polymerization toner and an electrophotographic copying machine “U-Bix500”
The two-component developer is prepared by mixing the “0” carrier with the carrier for a toner concentration of 4% by weight, and the two-component developer is shaken using “YS-LD” (manufactured by Yayoi). A sample was prepared by shaking for 20 minutes, and the charge amount of the toner in this sample was measured using a charge amount measuring device “Blow-off TB-
200 "(manufactured by Toshiba Corporation). The above results are shown in Tables 7 and 8 below.

Examples 2 to 6 Each suspension polymerization toner was produced in the same manner as in Example 1 except that the carbon black and the dispersing aid were changed as shown in Table 6 below. 1 was evaluated in the same manner. The results are shown in Tables 7 and 8.

[0038]

[Table 6]

Example 7 Example 1 was the same as Example 1 except that polypropylene as a fixing property improving agent was not added.
A suspension polymerization toner was manufactured in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Tables 7 and 8 below.

Comparative Example 1 A suspension polymerization toner was produced in the same manner as in Example 1 except that no dispersing aid was used, and evaluated in the same manner as in Example 1. The results are shown in Tables 7 and 8 below.

Comparative Example 2 In Example 1, the dispersing aid was changed to the soluble copper phthalocyanine “Zap”
on Blue 807 ”(manufactured by BASF Corp.), and a suspension polymerization toner was manufactured in the same manner as in Example 1. The results are shown in Tables 7 and 8 below.

[0042]

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Comparative Example 3 In Example 1, a nigrosine dye "Bontron N-04" (a product of Orient Chemical Co., Ltd.), which is a mixture of compounds represented by the following chemical formulas (4), (5), (6) and (7), was used. The same procedure as in Example 1 was carried out to produce a suspension polymerization toner, except that the toner was changed to the same.
The results are shown in Tables 7 and 8 below.

[0044]

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[0045]

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[0046]

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[0047]

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Comparative Example 4 A suspension polymerization toner was prepared in the same manner as in Example 1, except that the dispersing aid was changed to an oil-soluble surfactant "Emulgen 104P" (manufactured by Kao Corporation, polyoxyethylene lauryl ether). It was manufactured and evaluated in the same manner as in Example 1. The results are shown in Tables 7 and 8 below.

[0049]

[Table 7]

[0050]

[Table 8]

As shown in Table 8, according to Examples of the present invention, suspension polymerization having a small volume average particle diameter of 1 to 5 μm, carbon black uniformly dispersed, and excellent blackening degree. A toner is obtained. Further, the charge amount of the suspension polymerization toner is also in an appropriate range. However, in Comparative Examples 1 to 4, the resulting suspension-polymerized toner has a low degree of blackening due to poor dispersibility of carbon black.

[0052]

As described in detail above, according to the monomer composition for suspension polymerization of the present invention, the dispersibility of carbon black is sufficiently high. Suspension polymerization toner of the present invention
According to the production method , carbon black is sufficiently dispersed and a suspension polymerization toner having a high degree of blackening can be reliably produced.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-279264 (JP, A) JP-A-2-89064 (JP, A) JP-A-2-284151 (JP, A) JP-A-3-284 181952 (JP, A) JP-A-3-16853 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 2/00-2/44

Claims (2)

(57) [Claims] 1. A monomer composition for suspension polymerization, comprising a carbon black, a polymerizable monomer and a carbon black dispersing agent represented by the following chemical formula 1. Embedded image (In the above Chemical Formula 1, R represents an alkyl group, an alkoxy group, a substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic group, and n represents an integer of 1 to 6.) Characterized by suspension polymerization in an aqueous medium for suspension polymerization monomer composition according to 2. A method according to claim 1
A method for producing a suspension polymerization toner.