JP2727276B2 - Carbon black dispersion aid, masterbatch, toner manufacturing method - Google Patents

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 carbon black dispersing aid, a masterbatch and a toner. More particularly, the present invention relates to a carbon black dispersing aid for imparting excellent electrical properties to a toner, and a toner coloring masterbatch and a method for producing a toner using the same.

[0002]

2. Description of the Related Art In an electrophotographic toner, carbon black is used as a coloring material of the toner. Conventionally, a toner binder, carbon black and other additives (charge control agent, release agent, etc.) are premixed in a powder premixer (Henschel mixer, Nauter mixer, etc.) and then melt kneader (biaxial extrusion) ), And carbon black and other additives are dispersed in a toner binder. However, in this kneading and dispersing step, an auxiliary for dispersing carbon black is not particularly used. The kneaded material is roughly pulverized, medium pulverized, finely pulverized, and further classified to obtain an electrophotographic toner.

[0003]

However, according to the prior art, the dispersion of carbon black is insufficient, and a deviation in the carbon black content occurs in each toner particle, so that there is a problem in the electrical characteristics of the toner. That is, the magnitude of the absolute value of the charge amount or the toner of the opposite polarity is generated due to the difference in the surface property of each toner particle, which causes fogging of a copied image or toner scattering in a copying machine. In addition, poor dispersion of carbon black causes a reduction in image density. To improve the dispersion of carbon black, "double kneading" in which the melt-kneaded material is coarsely pulverized and melt-kneaded again has been attempted, but at the same time, the cost is significantly increased, and the performance is deteriorated due to excessive dispersion of other additives ( For example, a reduction in the overall charge amount due to overdispersion of the charge control agent) causes no sufficient effect.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to find a method for producing a toner having a good carbon black dispersion. The present inventors have found that a master batch with an auxiliary agent can be used, and have reached the present invention.

That is, the present invention comprises the following <1> to <4>. <1> N- (1,1-dimethyl-3-oxobutyl)
An auxiliary agent for dispersing carbon black in a toner binder, comprising an acrylamide (a) and a copolymer (A) having a styrene monomer and / or a (meth) acrylic monomer (b) as a constitutional unit. <2> A toner coloring masterbatch comprising the dispersing aid and carbon black (B). <3> the dispersing aid, carbon black (B),
A method for producing a toner, comprising melting and kneading a component comprising a toner binder (C). <4> The masterbatch and the toner binder (C)
A method for producing a toner, comprising melting and kneading components consisting of:

[0006]

In the present invention, styrene and alkylstyrene (α-methylstyrene, o-, m- or p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene) in (b) , Pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, etc.) and their 2
Combinations of more than one species may be mentioned. Of these, styrene, α-methylstyrene and o-, m- or
p-Methylstyrene.

In the present invention, among (b), (meth) acrylic monomers include alkyl (meth) acrylate (alkyl having 1 to 18 carbon atoms) [methyl (meth) acrylate, ethyl (meth) acrylate, n -Or iSO-butyl
(Meth) acrylate, n-octyl (meth) acrylate,
2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc.]; hydroxyl group-containing (meth) acrylate [hydroxylethyl (meth) acrylate, etc.]; amino group-containing
(Meth) acrylate [dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc.]; (meth) acrylonitrile; (meth) acrylic acid, etc., and a combination of two or more of these. Among these, preferred are methyl (meth) acrylate, ethyl
(Meth) acrylate, n- or iSO-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate.

In the present invention, a polymerizable monomer other than (a) and (b) may be used together as a monomer constituting the copolymer (A), if necessary. Other polymerizable monomers include maleic acid monomers [maleic acid derivatives such as maleic acid, maleic anhydride, dialkyl maleate (butyl maleate, maleic acid-2-ethylhexyl ester)]; and nitrile group-containing monomers. (Meth) acrylic compounds (such as acrylonitrile); vinyl esters (such as vinyl acetate and vinyl propionate); aliphatic hydrocarbon-based vinyl monomers (such as butadiene); nitrile compounds (such as acrylonitrile and methacrylonitrile);
Vinyl ether (vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc.); vinyl ketone (vinyl methyl ketone, vinyl hexyl ketone, etc.); N-vinyl compound (N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N- Vinyl halides (eg, vinyl pyrrolidone); vinyl halides (eg, vinyl chloride);
A polyfunctional monomer having at least two polymerizable double bonds (such as divinylbenzene, divinyltoluene, ethylene glycol diacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate); The above combinations may be used. Of these, polyfunctional monomers are copolymers
It is preferably used when the molecular weight of (A) is further increased.

In the present invention, the weight average molecular weight (Mw) of the copolymer (A) is usually 250,000 or less, preferably 100,000 or less. If it exceeds 250,000, it is difficult to obtain a sufficient dispersion of the carbon black, and the electrical properties of the toner are impaired. In the present invention, the copolymer (A) is preferably a copolymer satisfying the following formula. 1 ≦ (Mn) × (W) / (MWa) ≦ 7 A particularly preferable range is the following formula. 1.5 ≦ (Mn) × (W) / (MWa) ≦ 5 [wherein (Mn) is the number average molecular weight of the copolymer (A),
(W) is N- (1,1-dimethyl-) in the copolymer (A).
The weight fraction of (3-oxobutyl) acrylamide (a) unit, and (MWa) represents the molecular weight of (a). ] (Mn) ×
If (W) / (MWa) is less than 1 or more than 7, the dispersion of carbon black is insufficient, and the electrical properties of the toner are impaired.

The number average molecular weight (Mn) and weight average molecular weight (Mw) of the copolymer (A) can be measured by gel permeation chromatography. The conditions for measuring the molecular weight are as follows. Apparatus: HLC-802A manufactured by Toyo Soda Column: 2 TSK gel GMH6 Measurement temperature: 40 ° C. Sample solution: 0.5% by weight THF solution Solution injection amount: 200 μl Detector: Refractive index detector The molecular weight calibration curve is standard. Created using polystyrene.

The copolymer (A) can be obtained by a usual method. Specific examples include a method using a radical polymerization initiator (such as an azo-based polymerization initiator and a peroxide polymerization initiator), and a method using a thermal radical. Also, for molecular weight adjustment,
If necessary, a chain transfer agent may be used. Examples of the radical polymerization initiator include an azo polymerization initiator [2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile, etc.)], a peroxide polymerization initiator (peroxide Benzoyl oxide, lauroyl peroxide, etc.), or two or more of these. The amount used when a radical polymerization initiator is used is usually 0.1 to 10 based on the total weight of (a), (b) and, if necessary, other polymerizable monomers.
%, Preferably 0.3 to 5%. A chain transfer agent can be used for the polymerization, if necessary. Examples of the chain transfer agent include mercaptan compounds (such as n-butyl mercaptan), halogen compounds (such as carbon tetrachloride), and α-methylstyrene dimer. When a chain transfer agent is used, the amount used is usually 5% or less, preferably 1% or less, based on the total weight of (a), (b) and, if necessary, other polymerizable monomers. The auxiliary agent for dispersing carbon black of the present invention is usually the copolymer (A) itself, but if necessary, when used in the masterbatch or toner of the present invention, other additives may be used within a range that does not have a negative effect. May be included.

In the present invention, carbon black (B) having a specific surface area of usually 80 m ² / g or more by BET can be used. Particularly, those having a specific surface area of 130 m ² / g or more are preferable. When the specific surface area is less than 80 m ² / g, the coloring power for the toner is insufficient. Specific examples of carbon black (B) include contact black, furnace black, and oxidized furnace black, and two or more of these may be used in combination. The pH of the carbon black (B) is not particularly limited, but is preferably acidic, particularly pH 4 or less.

In the masterbatch of the present invention, the content of the copolymer (A) (A _wt ) and the content of the carbon black (B) (B _wt ) generally have the following relationship. 0.04 ≦ (A _wt ) × (W) / (B _wt ) ≦ 0.80 A preferable range is the following expression. 0.08 ≦ (A _wt ) × (W) / (B _wt ) ≦ 0.40 [wherein (W) represents N- (1,1-dimethyl-3-oxobutyl) acrylamide in (A) a) Represents the weight fraction of the unit. ]

The method for obtaining the masterbatch of the present invention includes a method of dry-mixing, melt-kneading, and mixing in a solvent the carbon black (B) with the dispersing aid of the present invention comprising the copolymer (A). No. Of these, the method of melt-kneading is preferred. Dry mixing may be performed by any conventional powder mixer such as a Henschel mixer. Melt kneading is performed by a general kneading machine such as a twin-screw extruder, a three-roll mill, or a Labo Plastmill. Of these, a twin screw extruder is preferably used. When performing melt kneading, preliminary mixing is performed in advance using a dry mixer as required. The temperature at the time of melt kneading is usually 130 ° C to 240 ° C, preferably 160 ° C to 220 ° C, particularly preferably 175 ° C.
１９195 ° C. If the temperature is lower than 130 ° C., dispersion of carbon black is insufficient. If the temperature exceeds 240 ° C., the copolymer (A) is thermally degraded and the storage stability of the toner is reduced. As a mixing method using a solvent, the dispersing aid of the present invention comprising (A) and carbon black are mixed with a solvent (xylene, toluene, etc.).
And dispersing the carbon black in a pressure-resistant reaction vessel at 160 to 240 ° C. to distill off the solvent.

The method of the present invention comprises the dispersant of the present invention,
A method for producing a toner by melt-kneading a component comprising carbon black (B) and a toner binder (C), or melt-kneading a component comprising a masterbatch of the present invention and a toner binder (C). is there. The component composed of the toner binder (C) is a compounding component that is usually used in the production of a toner. In addition to the toner binder (C), a release agent, a charge control agent, and the like are used as necessary. In any of these methods, the dispersing aid of the present invention exhibits an effect of improving the dispersion of carbon black in the toner, but the latter method using the masterbatch of the present invention is more effective. In the latter method, the masterbatch of the present invention is used in place of carbon black at the time of preliminary mixing before melt-kneading in the toner production process. The masterbatch of the present invention can be used in combination with carbon black. In the latter method, the amount of the masterbatch used in the present invention is such that the carbon black content in the toner is usually 2 to 2 times.
The amount is 0% by weight, preferably 3 to 10% by weight, particularly preferably 4 to 7% by weight. By using the masterbatch of the present invention, the dispersibility of carbon black is good,
Since high coloring power is obtained, there is an advantage that the amount of carbon black used can be reduced by 20 to 30% as compared with the conventional case.

[0017]

EXAMPLES The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples. Synthesis Example 1 Synthesis of Dispersing Aid of the Present Invention To a reactor equipped with a thermometer, a stirrer, a gas inlet tube, a dropping funnel and a cooling tube, 1,000 parts of xylene was charged. The system was purged with nitrogen and kept under a nitrogen atmosphere thereafter. Heat the mixture with stirring and raise the temperature.
, A solution of 100 parts of N- (1,1-dimethyl-3-oxobutyl) acrylamide, 20 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) and 50 parts of xylene were added dropwise. The mixture was further refluxed for 3 hours to complete the polymerization. The solvent was distilled off to obtain a vinyl polymer having a glass transition point of 87 ° C., a number average molecular weight of 7,300 and a weight average molecular weight of 24,000. This polymer is referred to as a dispersing aid (A-1). (Mn) of dispersing aid (A-1)
The value of × (W) / (MWa) is 4.3.

Example 1 667 parts of a dispersing aid (A-1) and carbon black MA 100
After mixing 333 parts of powder (manufactured by Mitsubishi Kasei: pH 3.5, specific surface area: 134 m ² / g), the mixture was melt-kneaded at a resin temperature of 180 ° C. and a rotation speed of 10 to 170 rpm for 90 minutes using a twin screw extruder. A master batch (E-1) was obtained. (A _wt ) × (W) / (B) of master batch (E-1)
_wt ) is 0.20. Example 2 Carbon black MA100 (manufactured by Mitsubishi Kasei: pH 3.5, specific surface area 134 m ² / g) when preparing the master batch (E-1) of Example 1
Instead of using carbon black # 2350 (manufactured by Mitsubishi Chemical: pH 2.0, specific surface area 260 m ² / g), in the same manner as in Example 1,
A master batch (E-2) of the present invention was obtained. Master Badge
The value of (A _wt ) × (W) / (B _wt ) in (E-2) is 0.20. Example 3 In a pressure-resistant reaction vessel with stirring, 667 parts of a dispersing aid (A-1) and carbon black MA 100 (manufactured by Mitsubishi Chemical: pH 3.5, specific surface area 13)
333 parts of 4 m ² / g) and 3,500 parts of xylene were charged. The reactor was purged with nitrogen, heated to reflux for 5 hours. After removing water from the reflux liquid, the reaction vessel was sealed and subjected to a dispersion treatment at 205 ° C. for 7 hours. After cooling to 180 ° C., xylene was distilled off by a film evaporator to obtain a master batch (E-3) of the present invention. The value of (A _wt ) × (W) / (B _wt ) of the master batch (E-3) is 0.
20. Example 4 Dispersing Aid (A-1) 790 parts, and carbon black MA 100
210 parts (Mitsubishi Chemical: pH 3.5, specific surface area: 134 m ² / g) were mixed with a Henschel mixer at 3,200 RPM for 15 minutes to obtain a master batch (E-4) of the present invention. (A _wt ) × (W) / of master batch (E-4)
The value of (B _wt ) is 0.38.

Comparative Example 1 In preparing the master batch (E-1) of Example 1, the number average molecular weight was changed to 8,200 and the weight average molecular weight was changed to 29,0 instead of the dispersing aid (A-1).
A comparative coloring material (E-5) was obtained in the same manner as in Example 1 except that the styrene homopolymer of Example No. 00 was used.

Synthesis Example 2 Synthesis of toner binder 720 parts of styrene, 190 of 2-ethylhexyl acrylate
A solution of 90 parts of methyl methacrylate and 6.5 parts of divinylbenzene [(solution 1-1)], a solution of 8.5 parts of 2,2'-azobisisobutyronitrile and 250 parts of toluene [(solution 1- 2)] and a solution of 2 parts of 2,2'-azobisisobutyronitrile and 55 parts of toluene [(solution
1-3)] was created. In a reactor equipped with a thermometer, stirrer, gas inlet tube, dropping funnel and cooling tube, toluene 25
0 parts were charged. The system was purged with nitrogen and kept under a nitrogen atmosphere thereafter. The solution was heated and heated while stirring, and while refluxing toluene, (Solution 1-1) and (Solution 1-2) were added dropwise over 4 hours, and the mixture was further refluxed for 2 hours. Thereafter, every one hour (solution 1-3) was added twice to complete the polymerization. Solvent is distilled off and the glass transition point is 61
C., a vinyl polymer having a number average molecular weight of 11,000 and a weight average molecular weight of 300,000 was obtained. This polymer is used as a toner binder
(P-1).

Examples 5 to 8, Comparative Examples 2 to 4 Masterbatches (E-1) to (E-4), comparative coloring materials (E-5),
Carbon black MA100 (Mitsubishi Chemical: pH 3.5, specific surface area 1)
34m ² / g) and carbon black # 2350 (Mitsubishi Chemical: pH
2.0, each having a specific surface area of 260 m ² / g).
1> to <T-7> were prepared. Then, the toner <T
Table 2 shows the results of evaluation of up to 1,500 copies of each of the images using -1> to <T-7> with a commercially available copying machine.

[0022]

【table 1】

Note) Release agent: Low molecular weight polypropylene: Hyscol 550P manufactured by Sanyo Kasei Kogyo Co., Ltd. Charge control agent: Speron Black TRH manufactured by Hodogaya Chemical Industry Co., Ltd.

[0024]

[Table 2]

[0025]

The dispersing aid of the present invention and the masterbatch of the present invention are each used for the production of toner by the method of the present invention, and a toner in which carbon black is uniformly finely dispersed can be obtained. Therefore, excellent electrical properties are imparted to the toner,
There is an effect that a copied image without fogging is obtained, and that the coloring power of the toner is improved and a high image density is obtained.

Claims (8)

(57) [Claims] 1. A copolymer (A) having N- (1,1-dimethyl-3-oxobutyl) acrylamide (a) and a styrene monomer and / or a (meth) acryl monomer (b) as constituent units. An auxiliary agent for dispersing carbon black in a toner binder. 2. The dispersing aid according to claim 1, wherein the copolymer (A) is a copolymer satisfying the following formula. 1 ≦ (Mn) × (W) / (MWa) ≦ 7 [wherein (Mn) is a number average molecular weight of the copolymer (A),
(W) is N- (1,1-dimethyl-) in the copolymer (A).
The weight fraction of (3-oxobutyl) acrylamide (a) unit, and (MWa) represents the molecular weight of (a). ] 3. A toner coloring masterbatch comprising the dispersion aid according to claim 1 or 2 and carbon black (B). 4. The dispersing aid and carbon black (B)
The masterbatch according to claim 3, which is a melt-kneaded product of the components consisting of: 5. The content weight (A _wt ) of the copolymer (A)
_{5. The} masterbatch according to claim 3, wherein the masterbatch has the following relational expression between the content and the content (B _wt ) of the carbon black (B). 0.04 ≦ (A _wt ) × (W) / (B _wt ) ≦ 0.80 wherein (W) is N- (1,1-dimethyl-) in (A).
The weight fraction of (3-oxobutyl) acrylamide (a) unit is shown. ] 6. The masterbatch according to claim 3, wherein the pH of the carbon black (B) is 4 or less. 7. A dispersing aid according to claim 1 or 2,
A method for producing a toner, comprising melting and kneading a component comprising carbon black (B) and a toner binder (C). 8. A method for producing a toner, comprising melting and kneading the master batch according to claim 3 and a component comprising a toner binder (C).