JP2588886B2 - Method for producing toner for developing electrostatic images - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a toner for developing an electrostatic image, and more particularly, to a toner excellent in fluidity, blackness and coloring power, and the toner. In a process of polymerizing a fixing resin with high yield.

(Prior Art) As a toner for visualizing (developing) an electrostatic charge image by electrophotography or the like, a fixing resin medium such as a styrene resin and a carbon black dispersed in the resin medium are used. What has granulated composition with the coloring agent of the above is widely used.

The most typical production method of this toner comprises a step of melt-kneading the above-described resin medium and a colorant, cooling and pulverizing the kneaded composition, classifying the pulverized product, and adjusting it to a certain particle size range. However, carbon black tends to have a chain structure even in a resin, and it is difficult to uniformly atomize and disperse the carbon black in the resin.

To solve this drawback, Japanese Patent Application Laid-Open No. 60-93452 discloses that carbon black treated with an aluminum-based coupling agent is uniformly dispersed in a binder resin by melt-kneading, and then pulverized and classified. Is described.

(Problems to be Solved by the Invention) However, the yield of the toner obtained by this pulverization / classification is low, and a large amount of equipment is required for these operations, so that the production cost of the toner is extremely high. And In addition, since the shape of the obtained particles is irregular, there is also a disadvantage that the fluidity of the toner is generally low and blocking is easily generated.

Further, depending on the melt-kneading with the fixing resin, it is still difficult to completely atomize and disperse even if the surface treatment of carbon black is performed.

If the dispersion of the carbon black in the fixing resin medium is not uniform, the blackness and coloring power are inferior, and the image density is lowered. In addition, the effect of carbon black treatment by the coupling agent depends not only on the type and amount of the coupling agent used, but also on the chemical and physical properties of the surface of the carbon black itself, and also at the time of fixing. The conventional means have not been able to provide satisfactory results because they are affected by the mixing operation with the resin for application.

(Means for Solving the Problems) The present inventors have selected carbon black having a relatively small specific surface area and a pH value of 3.0 or less as carbon black for toner; this specific carbon black and radical Suspending a polymerizable composition containing a polymerizable monomer in an aqueous medium to perform polymerization into spherical particles; and adding an aluminum coupling agent to the polymerizable composition, for fixing. It has been found that it is important for obtaining spherical toner particles in which carbon black is uniformly dispersed in a resin medium.

According to the present invention, the radical polymerizable monomer, specific surface area
A composition containing carbon black and an aluminum coupling agent having a pH of 3.0 or less and an aluminum coupling agent of 300 m ² / g or less is suspended in an aqueous medium, and the suspended particles are polymerized in the presence of a radical initiator. And a method for producing a toner for developing an electrostatic charge image, comprising obtaining spherical particles consisting of carbon black dispersed in the resin.

The toner obtained by such a method has the following formula: In the formula, r ₁ represents the major axis of the toner particles, and r _s represents the minor axis of the toner particles. The spherical particles have a roundness (D) of 0.90 or more defined by:

(Operation) In the present invention, carbon black for toner has a relatively small specific surface area, that is, a specific surface area (BET) of 300 m ^2.
The first feature is to use those having a pH value of 3.0 or less at / g or less. The pH value of carbon black refers to the pH of an aqueous suspension of carbon black, and carbon black having a low pH value may have carbon, hydrogen and a considerable amount of oxygen (generally, 2 to 10%) depending on the production method and treatment method. To 12% by weight). It is recognized that this oxygen exists as a polar group on the surface of the carbon black particles, but the presence of these polar groups cooperates with the aluminum coupling agent to cause the carbon black particles to be included in the fixing resin monomer. In this manner.

It is also important that this carbon black has a specific surface area of 300 m ² / g or less.If the specific surface area exceeds this range, even if it is used in combination with an aluminum coupling agent, the carbon It becomes difficult to uniformly disperse the particles into fine particles, and the conversion rate of the monomer to the polymer and the polymerization rate tend to decrease. This seems to be related to the fact that the larger the specific surface area, the larger the surface activity and the tendency of the particles to aggregate, and the effect of the aluminum coupling agent is not sufficiently exerted.

Channel-type carbon black suitable for the purpose of the present invention can be obtained as Special Black 4, Special Black 5, MA-100 or the like, but is not limited to these.

In the present invention, a composition containing the above-mentioned channel-type carbon black, a fixing resin monomer and an aluminum coupling agent is suspended in an aqueous medium, and the suspended particles are polymerized in the presence of a radical initiator. Is the second feature.

That is, by employing this means, not only the advantage that spherical particles of the resin-carbon black composition having a particle size suitable for the toner are produced at once in the polymerization step of the fixing resin, but also the carbon black particles are obtained. Is very finely dispersed in the resin. Further, according to the present invention, the aluminum coupling agent,
The operation of surface treating individual carbon black particles is unnecessary, and uniform fine dispersion can be achieved by a simple operation of simply adding an aluminum coupling agent to a monomer.

Generally, when carbon black is added to a fixing resin monomer, the polymerization rate tends to decrease, and the conversion to a polymer tends to decrease. This is considered to be because quinoidal oxygen is present on the carbon black surface and exhibits a polymerization inhibiting action. According to the present invention, a carbon black having a relatively small specific surface area is used as the carbon black, and furthermore, by including an aluminum coupling agent in the polymerization composition, the polymerization rate and the conversion to the polymer are also at a high level. Can be maintained.

As coupling agents other than aluminum-based ones, many silane-based and titanium-based coupling agents are known and widely used in various fields. However, according to the study of the present inventors, if a silane coupling agent or a titanium coupling agent is used for this purpose, almost no effect is obtained, and the above-mentioned various actions are not achieved by the aluminum coupling agent. Is unique to
A suitable example of an aluminum-based coupling agent is, but is not limited to, acetoalkoxyaluminum diisopropylate.

In the present invention, the channel type carbon black is
Preferably, it is used in an amount of 1 to 20% by weight, especially 2 to 10% by weight, per monomer, whereas the aluminum coupling agent is present in an amount of 0.1 to 30% by weight, especially 10
It is preferably used in an amount of from 30 to 30% by weight.

In the present invention, the monomer used is a radical polymerizable one, and the resulting polymer has a fixing property and an electric detection property required for a toner, and a monomer having ethylenic unsaturation is used. One or more combinations may be used subject to the limitations set forth above. Suitable examples of such a monomer include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, and monoolefin monomers. Body.

As the monovinyl aromatic monomer, In the formula, R ₁ is a hydrogen atom, a lower alkyl group or a halogen atom, and R ₂ is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group, a vinyl group or a carboxyl group. Aromatic hydrocarbons such as styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene,
o-, m-, p-chlorostyrene, p-ethylstyrene, sodium styrenesulfonate, and divinylbenzene alone or in combination of two or more. Examples of other monomers described above include the following. Respectively.

In the formula, R ₃ is a hydrogen atom or a lower alkyl group, R ₄ is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group,
A vinyl ester group or an aminoalkyl group, an acrylic monomer such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate , Methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate, butyl δ-hydroxyacrylate, ethyl β-hydroxymethacrylate, propyl γ-aminoacrylate , Γ-NN / diethylaminoacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and the like.

Wherein R ₅ is a hydrogen atom or a lower alkyl group, such as vinyl esters such as vinyl formate, vinyl acetate and vinyl propionate.

Wherein R ₆ is a monovalent hydrocarbon group having up to 12 carbon atoms, such as vinyl methyl ether, vinyl ethyl ether, vinyl-n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like.

Wherein each of R ₇ , R ₈ and R ₉ is a hydrogen atom, a lower alkyl group or a halogen atom, such as butadiene, isoprene and chloroprene.

Wherein each of R ₁₀ and R ₁₁ is a hydrogen atom or a lower alkyl group, such as ethylene, propylene, isobutylene, butene-1, butene-1, pentene-1, 4-methylpentene-1 and the like.

In the present invention, an additive component which is desirably contained in the toner in addition to the above-described essential components can be blended in the polymerization system prior to the polymerization.

For example, for use as a two-component pigment, known charge control agents, for example, nigrosine base (C15045),
Oil-soluble dyes such as oil black (C126150) and spiron black, metal salts of naphthenic acid, fatty metal soaps, resin acid soaps, etc. can be compounded. Molecular weight polyethylene,
A release agent such as low molecular weight polypropylene, various waxes, and silicone oil can be contained.

In the method of the present invention, the above-mentioned raw materials are suspended in water.
In order to stabilize the suspension in water, an organic or inorganic dispersant is generally used.

Examples of organic dispersants include gelatin, starch, water-soluble starch derivatives, water-soluble cellulose derivatives such as carboxymethylcellulose and ethocel, polyvinyl alcohol, water-soluble acrylic resins, water-soluble polymers such as vinyl ether / maleic acid copolymers, and anions. And nonionic, cationic and amphoteric surfactants.

Examples of the inorganic dispersant include hardly soluble inorganic fine particles, for example, various clays such as calcium carbonate, magnesium carbonate, magnesium phosphate, barium sulfate, silica, alumina, talc and bennonite, and diatomaceous earth.

These inorganic or organic dispersants can be used alone or
Combinations of more than one species can also be used. In the case of the present invention, although not generally necessary, if desired, the specific gravity of the medium,
For the purpose of adjusting surface tension, viscosity, etc., in addition to the above dispersants,
Water-soluble salts such as NaCl, KCl, and Na ₂ SO ₄ can be used.

Examples of the polymerization initiator include those soluble in monomers such as azo compounds such as azobisisobutyronitrile and peroxides such as cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, and lauroyl peroxide. used.

The ratio of monomer to water can vary considerably, but
Generally, it is preferable to use a weight ratio of 1:99 to 50:50, particularly 5:95 to 30:70. The amount of the dispersant used varies depending on the type, but the water-soluble polymer dispersant is 0.1 to 10% by weight per water,
In particular, it is preferably used in an amount of 0.5 to 5% by weight, and the inorganic dispersant is preferably used in an amount of 0.01 to 10% by weight, particularly 0.1 to 5% by weight per monomer. If a surfactant is used, it must not be used in such an amount that the suspended particles become emulsion size. The radical polymerization initiator is 0.1 per monomer.
It is preferably used in an amount of 1 to 10% by weight, especially 0.5 to 5% by weight.

The polymerization temperature is generally in the range of 40 to 100 ° C., particularly 50 to 90 ° C., and the polymerization time varies depending on the type of the monomer. Is good.

According to the present invention, true spherical particles having a roundness (D) defined by the above formula in the range of 0.9 or more, particularly 0.95 or more are obtained. Further, according to the present invention, by performing the polymerization under the above conditions, it is easy to control the particle size of the produced polymer particles, that is, the toner particles, to a range of 1 to 30 μm, particularly 5 to 20 μm, and Its particle size distribution is very sharp and its standard deviation is generally less than 3. The produced particles are separated from the reaction medium, and if necessary, subjected to a purification operation such as washing, and dried to obtain a toner product.

If necessary, carbon black, hydrophobic silica, or the like is applied to the toner coloring particles to form a final toner.

(Effects of the Invention) According to the present invention, carbon black is completely and uniformly atomized and dispersed in a fixing resin medium, so that the blackness and coloring degree of the toner are increased and a high-density image is formed. Can be. Further, since the toner has a true spherical shape and contains no residual monomer, the toner has excellent fluidity and has almost no blocking tendency during development.

In addition, spherical polymer particles having a predetermined particle size can be obtained at once in the polymerization step of the fixing resin, which has the advantage of high yield and high productivity.

Examples of the present invention are shown below, but the present invention is not limited thereto.

Example-1 Carbon black: MA-100 (specific surface area 134 m ² / g, pH value
3.0) 5 parts by weight of [Mitsubishi Kasei Kogyo] is added to 20 parts by weight of toluene in which 1 part by weight of aluminum coupling agent AL-M (acetoalkoxyaluminum diisopropylate) [Ajinomoto Co., Ltd.] is dissolved. After drying under reduced pressure, carbon black treated with an aluminum coupling agent was obtained. And this AL-M treated carbon black 5
70 parts by weight of styrene and 30 parts by weight of n-butyl methacrylate were added to parts by weight, and the mixture was stirred with a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at 3000 rpm for 5 minutes to obtain a carbon black dispersion. I got When the obtained carbon black dispersion was observed with an optical microscope (× 600), no aggregate of carbon black was observed, and the dispersibility was good.

2 parts by weight of a charge control agent Bontron S-34 (manufactured by Orient Chemical Co., Ltd.), 2 parts by weight of a release agent Biscol 550P (manufactured by Sanyo Chemical Co., Ltd.), and 2,2 'polymerization initiator 5 parts by weight of -azobis- (2-4 dimethylvaleronitrile) was added and sufficiently dispersed. Next, the above dispersion was added to a 2% by weight aqueous solution of polyvinyl alcohol, and stirred at 6000 rpm for 10 minutes using a TK homomixer to obtain oil droplets. These oil droplets were extremely stable, and as a result of observation with an optical microscope, a property imparting agent such as carbon black was uniformly dispersed in the oil droplets. Then, usually with a stirrer
The polymerization reaction was completed at 70 ° C. for 5 hours under a nitrogen stream at a stirring speed of 60 rpm.

After the completion of the polymerization reaction, dehydration and washing were repeated and dried to obtain a toner of the present invention having an average particle diameter of 12 μm.

Using the toner obtained as described above, an image was formed on an electrophotographic copying machine DC-1001 (manufactured by Mita Kogyo Co., Ltd.). As a result, an image having little fog and high blackness was obtained. Was. When this was measured with a reflection densitometer, good results were obtained with a fog density of 0.003 and a black solid image density of 1.4.

Example-2 Carbon black: Special black 5 (specific surface area)
134 m ² / g, pH value 2.7) [manufactured by Degussa Co., Ltd.]
As a result of the treatment with the aluminum coupling agent AL-M and the formation of oil droplets, the dispersibility of carbon black in the oil droplets was good. The obtained oil droplets were synthesized into a toner in the same manner as in Example 1 to obtain a toner of the present invention having an average particle diameter of 12 μm. When an image was formed with DC-1001 using this toner, the fog density was 0.003 and the image density was
Good images with a 1.4 were obtained.

Comparative Example-1 Carbon black FW200 (specific surface area 460 m ² / g, pH value 2.
5) Using 5 parts of [Degussa Co., Ltd.] and treating with aluminum coupling agent AL-M in the same manner as in Example 1 to form oil droplets, the oil droplets contained 1 to Agglomerates of carbon black of about 2 μm were observed. This suspension was toner-synthesized by the same method as in Example 1, and the average particle diameter was 12%.
μm of the toner of the present invention was obtained. DC-
When an image was formed at 1001, fogging occurred at a fog density of 0.007 and an image density of 1.1, and a low image density was obtained.

Comparative Example-2 Carbon black: PRINTEX L (specific surface area 150 m
² / g, pH 8.5) [Examples] using 5 parts [manufactured by Degussa].
1 was treated with the aluminum coupling agent AL-M in the same manner as in Example 1 to form an oil droplet.
About m aggregates of carbon black were observed. This suspension was subjected to toner synthesis in the same manner as in Example 1 to obtain a toner having an average particle diameter of 12 μm. DC-10 using this toner
When an image was formed at 01, a sufficient image density of 0.012 and 0.9 was not obtained.

Comparative Example-3 Not treated with an aluminum coupling agent,
Carbon black: MA-100 (specific surface area 134 m ² / g, pH value 3.
0) Example using 5 parts of [Mitsubishi Chemical Industry Co., Ltd.]
As a result of forming oil droplets in the same manner as in 1, the oil droplets contained 5
Aggregates of carbon black of about 10 μm were observed. This suspension was toner-synthesized in the same manner as in Example 1, and
A toner having an average particle size of 13 μm was obtained. DC using this toner
When an image was formed at -1001, the fog density was 0.02 and the image density was 0.75.

Comparative Example-4 Not treated with an aluminum coupling agent,
Carbon black: Special black 5 (specific surface area 13
Using 5 parts of 4 m ² / g, pH value 2.7) [manufactured by Degussa], oil droplets were formed in the same manner as in Example 1, and as a result, carbon black of about 5 to 10 μm was contained in the oil droplets. Aggregates were observed. This suspension was subjected to toner synthesis in the same manner as in Example 1 to obtain a toner having an average particle size of 14 μm. When an image was formed with DC-1001 using this toner, the fog density was 0.0
2. The image density was 0.78.

Comparative Example-5 No treatment was performed with an aluminum coupling agent.
Carbon black: FW200 (specific surface area 460m ² / g, pH value 2.5)
Using 5 parts of [Degussa], oil droplets were formed in the same manner as in Example 1, and as a result, aggregates of carbon black of about 2 to 10 μm were found in the oil droplets. This suspension was toner-synthesized in the same manner as in Example 1, and the average particle size was 14 μm.
m was obtained. When an image was formed with DC-1001 using this toner, the fog density was 0.02 and the image density was 0.69.

Comparative Example-6 Carbon black not treated with an aluminum coupling agent: PRINTEX L (specific surface area 150 m ² /
g, pH 8.5) [Example 1] using 5 parts of [Degussa].
As a result of forming oil droplets in the same manner as in
Aggregates of about 10 μm of carbon black were observed. This suspension was toner-synthesized by the same method as in Example 1, and DC
When an image was formed at -1001, the fog density was 0.03 and the image density was 0.72.

Table 1 summarizes the results of Examples 1 and 2 and Comparative Examples 1 to 6 described above.
It was shown to.

In each of the above-described embodiments, the classified toner particles are sieved using a square opening mesh having a predetermined size, and the sieved toner is again passed through the same square opening sieve. By repeating this several times, a toner having high roundness was obtained.

As the toner of the comparative example, the toner after ordinary classification was used as it was.

The values of the roundness (D) are shown below. Toner roundness (D) Example 1 0.93 Example 2 0.92 Comparative example 1 0.88 Comparative example 2 0.87 Comparative example 3 0.88 Comparative example 4 0.86 Comparative example 5 0.87 Comparative example 6 0.86 After observing with a microscope, the major axis and the minor axis were measured and calculated by the diameter method.

Continuation of the front page (56) References JP-A-59-50452 (JP, A) JP-A-59-211050 (JP, A) JP-A-61-22353 (JP, A) JP-A-53-33151 (JP, A) JP-A-57-181553 (JP, A) JP-A-59-64854 (JP, A) JP-A-60-45260 (JP, A) JP-A-60-117252 (JP, A) 60-117253 (JP, A) JP-A-60-117254 (JP, A) JP-A-60-117255 (JP, A) JP-A-60-138563 (JP, A)

Claims (1)

(57) [Claims] 1. A radical polymerizable monomer having a specific surface area of 300 m ² /
g and a pH value of 3.0 or less, a composition containing carbon black and an aluminum coupling agent are suspended in an aqueous medium, and the suspended particles are polymerized in the presence of a radical initiator. A method for producing a toner for developing an electrostatic image, comprising obtaining spherical particles composed of carbon black dispersed therein.