JPH083662B2 - Method of manufacturing toner for electrophotography - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electrophotographic toner having an excellent combination of fixability and offset resistance, and more specifically to an emulsion polymerization method and a suspension method. It relates to a method for producing the above toner by a specific combination with a turbid polymerization method.

(Prior Art) In the field of electrophotography, toner is used for the purpose of visualizing an electrostatic image. The toner particles are composed of a composition in which a colorant and, if necessary, another compounding agent such as a charge control agent are mixed in a resin medium in a certain particle size range, for example, a particle size range of 1 to 30 μm. As the resin medium, a resin having a desired electroscopic property and binding property, for example, a styrene resin or the like is used, and as the colorant, carbon black or another organic or inorganic color pigment is used. To be done.

The most typical method for producing an electrophotographic toner comprises a step of melt-kneading the above-mentioned resin medium and a colorant, cooling and pulverizing the kneaded composition, and classifying the pulverized material to make it uniform within a certain particle size range. However, the yield of the toner obtained by this pulverization / classification is low, and a large amount of equipment is required for these operations, which makes the manufacturing cost of the toner extremely high. In addition, since the shape of the obtained particles is irregular, the flowability of the toner is generally low, and blocking is likely to occur.

Conventionally, many proposals such as emulsion polymerization and suspension polymerization have been accepted for directly producing a toner in a step of polymerizing a resin for a toner. A typical example thereof is a water-insoluble monomer in which a soluble polymerization initiator is dissolved, and an additive such as a colorant is further added, and the composition is mixed with a suitable dispersant such as a water-soluble polymer. The colored polymer particles are produced by suspending the mixture in an aqueous solution containing an inorganic powder, a surfactant and the like by high-speed shearing stirring and polymerizing the suspension.

Many proposals have already been made to improve the fixability and anti-offset property of toner particles obtained by the suspension polymerization method. For example, a method of decreasing the molecular weight by a chain transfer agent, a method of partially crosslinking, a polyolefin wax, etc. There is known a method of mixing in, a method of suspending polymer resin particles produced by suspension polymerization and a monomer, and conducting polymerization.

(Problems to be Solved by the Invention) However, in the suspension polymerization method, if the molecular weight is too low, the fixing property is improved but the offset is likely to occur. Then, it is effective in improving the offset resistance. However, the suitable amount range of the polyfunctional monomer is narrow, and the adjustment is difficult. If the amount is too small, the offset resistance cannot be obtained, and if the amount is too large, the fixability is inferior. In the case, the compatibility between the polyolefin wax and the vinyl-based monomer (polymer) is poor and good dispersion cannot be obtained, so that the sufficient offset resistance effect cannot be obtained. In addition, the electrophotographic characteristics may be adversely affected.

In that case, the molecular weight of the resin obtained by the suspension polymerization in the first stage is still lower than that obtained by the emulsion polymerization method, and the offset resistance is not yet sufficiently satisfactory, and the polymerized polymer resin is filtered and washed. In addition to the complicated steps of removing the dispersant with a monomer, drying it, and then mixing it with the monomer to carry out suspension polymerization, if the washing is inadequate, the hygroscopic property of the dispersant may cause However, there is a drawback that the charging characteristic becomes unstable.

Therefore, the object of the present invention is that the composition of the high molecular weight resin that contributes to the offset resistance and the low molecular weight resin that contributes to the fixability is uniform and constant for each toner particle, and as a result, the stable fixability is always obtained. Another object of the present invention is to provide a method for producing an electrophotographic toner that can obtain offset resistance.

(Means for Solving the Problems) According to the present invention, a high-molecular-weight resin particle obtained by emulsion polymerization of a radical-polymerizable monomer having a property that a produced polymer is dissolved in the monomer is Dissolving the colorant in a fixed amount ratio in the monomer and dispersing the colorant to produce a solution having a uniform composition,
A method for producing an electrophotographic toner excellent in fixing property and offset resistance, which comprises suspending this solution in water and polymerizing a monomer in the suspended particles in the presence of a radical initiator, Provided.

(Function) In the present invention, a radical-polymerizable monomer having a characteristic that the produced polymer is dissolved in the monomer is first used. By emulsion-polymerizing this radical-polymerizable monomer, a blended resin component having a high molecular weight sufficient to impart sufficient offset resistance to the toner can be obtained.

An important feature of the present invention is to dissolve the high-molecular-weight resin particles obtained by this emulsion polymerization in the above-mentioned monomer at a constant ratio to obtain a solution having a uniform composition. Generally, the particle size of resin particles obtained by emulsion polymerization is on the order of 0.01 to 1 μm, and the particle size of electrophotographic toner is 1 to 30 μm.
The particle size is very small as compared with the range of m. Therefore, when the monomers are polymerized by using individual particles as a seed by emulsion polymerization and the growth is performed to the toner particle size, the content ratio of the emulsion-polymerized resin, that is, the high-molecular-weight resin becomes small, resulting in sufficient resistance. The offset property cannot be obtained. Needless to say, such a drawback will be solved if one suspension particle contains emulsion polymerization particles in an amount or number commensurate with a predetermined blending ratio. The composition ratio of the emulsion-polymerized particles and the monomer contained varies depending on the suspended particles, so that the combined characteristics of the fixability and the offset resistance vary depending on the toner particles. In the present invention, the emulsion-polymerized resin particles are dissolved in the monomer to homogenize the whole, whereby the composition of the suspended particles becomes constant for each particle, and excellent combination characteristics are obtained.

Raw Material In the present invention, the monomer used is a radically polymerizable monomer, and the resulting polymer has the fixability and the electric detection property required for the toner, and the monomer has ethylenic unsaturation. One kind or a combination of two or more kinds is used under the above-mentioned restrictions. Suitable examples of such a monomer include a monovinyl aromatic monomer or an acrylic monomer, a vinyl ester monomer, a vinyl ether monomer, a diolefin monomer and a monoolefin monomer. It is a combination with monomers and the like.

As the monovinyl aromatic monomer, In the formula, R ₁ is hydrogen base paper, 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, monovinyl. 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. And other examples of the above-mentioned other monomers include the following.

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.

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

formula 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.

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

A preferred monomer composition comprises 30 to 100% by weight of styrene, especially 50 to 90% by weight, and 0 to 70% by weight of acrylic monomer, especially 10 to 50% by weight.

As the colorant, various pigments and dyes (hereinafter simply referred to as color pigments) for coloring the toner are used.

 Suitable examples of color pigments are:

Black pigment carbon black, acetylene black, lamp black, aniline black.

Yellow pigment Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline Yellow rake, permanent yellow NCG, tartrazine rake.

Orange pigment Red lead yellow molybdenum, molybdenum orange, permanent orange GTR, pyrazolo orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK.

Red pigment red iron oxide, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake,
Rhodamine Rake B, Alizarin Rake, Brilliant Carmine 3B.

Purple pigment Manganese purple, fast violet B, methyl violet lake.

Blue pigment Navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, fast sky blue, indanthrene blue B
C.

Green pigments Chrome green, chromium oxide, pigment green B, malachite green lake, fanal yellow green G.

White pigment Zinc white, titanium oxide, antimony white, zinc sulfide.

Extender barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white.

Conventional magnetic material pigments include, for example, ferric tetroxide (Fe ₃ O
₄ ), ferric oxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe
₂ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium iron oxide (CdFe ₂ O ₄ ), gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ),
Iron oxide copper oxide (CuFe ₂ O ₃ ), iron oxide lead oxide (PbFe ₁₂ O ₁₉ ), iron oxide nickel (NiFe ₂ O), iron oxide neodymium (NdFeO ₃ ), iron oxide barium (BaFe ₁₂ O ₁₉ ), iron oxide magnesium (MgF
e ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), iron oxide lanthanum (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni), etc. are known. In the present invention, any of these known fine powders of magnetic materials can be used.

In the present invention, an additive component which is desirable to be contained in the toner in addition to the above-described colorant may be blended in the polymerization system prior to the polymerization.

For example, for use as a two-component pigment, a charge control agent known per se, for example, an oil-soluble dye such as nigrosine base (CI5045) oil black (CI26150) and spirone black, a metal salt of naphthenic acid, and a fatty metal soap. , A resin acid soap and the like can be blended, and a release agent such as low molecular weight polyethylene, low molecular weight polypropylene, various waxes, and silicone oil can be contained in order to add an offset preventing effect to the toner.

Emulsion Polymerized Resin Particles The emulsion polymerized resin particles used in the present invention are produced by subjecting the above-mentioned monomers to emulsion polymerization known per se. This resin particle is generally 0.01 to 1 μ
It has a particle size of m, especially 0.1 to 0.7 μm, and a weight average molecular weight (w) of 200,000 or more, particularly 300,000 to 2,000,000.

Resin particles obtained by ordinary emulsion polymerization have a surface-active agent layer used as an emulsifier on the surface thereof. The resin particles can be used as they are in the present invention, but it is preferable from the viewpoint of the electrical characteristics of the toner that the surface active agent is removed by means such as washing and extraction to be used in the present invention.

A particularly preferable emulsion-polymerized resin for the purpose of the present invention is resin particles obtained by so-called emulsifier-free emulsion polymerization. Emulsifier-free emulsion polymerization is a unit amount dispersed or dissolved in an aqueous phase by using a water-soluble radical polymerization catalyst such as persulfate or redox system without adding an emulsifier to a polymerization system containing water and a monomer. This is a method in which polymerization is carried out using the body as a nucleus, and the emulsion-polymerized resin particles obtained by this method are particularly excellent in purity and electrical characteristics.

Preparation of Resin Solution The emulsion-polymerized resin particles and the above-mentioned monomer are mixed in a fixed amount ratio and heated as desired to prepare a solution in which the whole is homogenized. The mixing ratio of the polymer resin particles and the monomer varies depending on the required properties, but is 5:95 to 50:50, especially
It is advisable to mix them in a weight ratio of 10:90 to 30:70. If the blending ratio of the emulsion-polymerized particles is less than the above range, the offset resistance tends to be poor, while if it is large, the heat fixing property tends to be poor.

Into this resin solution, a compounding agent used for the developing toner, for example, a colorant, a charge control agent, a release agent, etc. is dispersed at the same time. The colorant is based on the total amount of resin and monomer,
1 to 30% by weight, particularly 3 to 10% by weight, preferably 0 to 10% by weight, especially 1 to 5% by weight of the charge control agent, 0 to 10% by weight of the release agent, In particular, it is preferable to add it in an amount of 1 to 5% by weight.

Suspension Polymerization Method In the method of the present invention, the above-mentioned solution is suspended in water.
In order to stabilize the suspension in water, an organic or inorganic dispersant is generally used.

Examples of the organic dispersant include gelatin, starch, water-soluble starch derivatives, water-soluble cellulose derivatives such as carboxymethyl cellulose and ETHOCEL, polyvinyl alcohol, water-soluble acrylic resins, water-soluble polymers such as vinyl ether-maleic acid copolymers, and anions. Examples include nonionic, cationic, and amphoteric surfactants.

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

These inorganic or organic dispersants may be used alone or in combination with 2.
Combinations of more than one species can also be used. In the case of the present invention, it is generally not necessary, but if desired, in addition to the above dispersant, NaC for the purpose of adjusting the medium specific gravity, surface tension, viscosity, etc.
It is also possible to use water-soluble salts such as l, KCl, Na ₂ SO ₄ .

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

The ratio of monomer to water can vary considerably,
Generally, it is preferable to use a weight ratio of 1:99 to 50:50, particularly 5:95 to 30:70. Although the amount of the dispersant used varies depending on the type, the water-soluble polymer dispersant is preferably used in an amount of 0.1 to 10% by weight, especially 1 to 5% by weight, and the inorganic dispersant is used in an amount of 1 to 1% per monomer. It is preferably used in an amount of from 100 to 100% by weight, especially from 2 to 50% by weight. If a surfactant is used, it should not be used in such an amount that the suspended particles are of 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 initiator is preferably added to the resin monomer solution and supplied to the polymerization system.

Prior to the polymerization, the inside of the reaction vessel may be replaced with an inert gas such as nitrogen, and oxygen or the like dissolved in the polymerization system may be purged with nitrogen or the like. In order to stabilize the suspended state, stirring may be performed or ultrasonic waves may be applied.

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 kind of the monomer, but the time for completing the polymerization is selected from the range of 2 to 20 hours. Is good.

According to the present invention, by carrying out the polymerization under the above-mentioned conditions, the particle size of the produced polymer particles, that is, the toner particles is from 1 to 30.
It is easy to control in the range of 5 μm, especially 5 to 20 μm, and the produced particles are spherical close to a true sphere, and the particle size distribution is extremely sharp, and the standard deviation is generally 3
Within.

The produced particles are separated from the reaction medium, and if necessary, a purification operation such as washing is performed, and dried to obtain a toner product.

If necessary, the colored particles for toner are sprinkled with carbon black, hydrophobic silica or the like to obtain the final toner.

The toner particles obtained by the method of the present invention are GP of FIG.
As shown in the C molecular weight distribution curve, it has a molecular weight distribution having two peaks on the high molecular weight side and the low molecular weight side. Generally speaking, the weight average molecular weight is more than 200,000, especially 300,000.
To 2000000 resins and 100000 or less, especially 3000 to 30000
The resin ratio of 5:95 to
The range is 50:50.

(Advantageous Effects of the Invention) According to the present invention, the composition of the high molecular weight resin that contributes to the offset resistance and the low molecular weight resin that contributes to the fixability is uniform and constant for each toner particle, and as a result, It has become possible to provide an electrophotographic toner that can obtain stable fixing properties and offset resistance.

(Example) The present invention will be described more specifically by the following example.

Example 1 7 parts by weight of styrene and 3 parts by weight of n-butyl methacrylate were placed in a four-necked flask together with 90 parts by weight of water in which 0.1 parts by weight of potassium persulfate was dissolved, and the mixture was stirred at 70 ° C. under a nitrogen stream at 100 rpm. Polymerized for 5 hours. The molecular weight of the obtained polymer was Mw = 650,000. The emulsion was centrifuged and the supernatant was discarded. 32 parts by weight of styrene, 8 parts by weight of n-butyl methacrylate, 3 parts by weight of carbon black (Printex L; made by Degussa), charge control agent (Spiron Black TR
H; Hodogaya Chemical Co., Ltd.) 1 part by weight, AIBN (Wako Pure Chemical Industries, Ltd.) 2
Parts by weight, octyl thioglycolate (manufactured by Wako Pure Chemical Industries) 0.
After adding 5 parts by weight and thoroughly stirring and dispersing, 200 parts by weight of a 2% polyvinyl alcohol aqueous solution was added, and the suspension was stirred using a TK homomixer (made by Tokushu Kika Kogyo Co., Ltd.) at 5000 rpm for 10 minutes. Got Place this suspension in a weight flask
Polymerize at 70 ℃ for 8 hours, filter, wash, dry, classify,
A toner having an average particle size of 11 μm was obtained.

When this toner was put into a copying machine DC-1001 manufactured by Mita Kogyo Co., Ltd. and a copying test was conducted, a clear image without fog was obtained and an offset phenomenon did not occur.

Comparative Example 1 Styrene 39 parts by weight, n-butyl methacrylate 11 parts by weight, carbon black 3 parts by weight, charge control agent TRH 1 part by weight, AIBN 2 parts by weight and octyl thioglycolate 0.5 parts by weight were thoroughly stirred and dispersed, and then 2%. Add 200 parts by weight of the polyvinyl alcohol aqueous solution of
Stirred at 0 rpm for 10 minutes. This was put in a polymerization flask and the same operation as in Example 1 was carried out to obtain a toner having an average particle size of 11 μm.

When this toner was put into a copying machine DC-1001 manufactured by Mita Kogyo Co., Ltd. and a copying test was conducted, an image without fog was obtained, but fixing offset occurred.

Comparative Example 2 7 parts by weight of styrene, 3 parts by weight of n-butyl methacrylate, and 0.2 parts by weight of AIBN were suspended in 40 parts by weight of water in which 1 part by weight of tricalcium phosphate and 0.01 part by weight of sodium dodecylbenzenesulfonate were dispersed. Polymerization was carried out at 70 ° C. for 5 hours, filtration, washing with diluted hydrochloric acid and drying. The molecular weight of this polymer was Mw = 180,000. Further, when dissolved in tetrahydrofuran, a small amount of insoluble matter, which is considered to be residual tricalcium phosphate, was precipitated.

To 10 parts by weight of this polymer, 32 parts by weight of styrene, 8 parts by weight of n-butyl methacrylate, 3 parts by weight of carbon black,
1 part by weight of the charge control agent TRH, 2 parts by weight of AIBN and 0.5 part by weight of octyl thioglycolate were added, and a toner having an average particle size of 11 μm was obtained by the same operation as in Example 1.

When this toner was placed in a copying machine DC-1001 manufactured by Mita Kogyo Co., Ltd. and a copying test was conducted, a slightly offset image was formed and fixing offset was also generated.

[Brief description of drawings]

FIG. 1 is a GPC molecular weight distribution curve of the toner obtained by the method of the present invention.

Claims (6)

[Claims] 1. A high-molecular-weight resin particle obtained by emulsion-polymerizing a radical-polymerizable monomer having a property that the resulting polymer is soluble in the monomer is dissolved in the monomer at a constant ratio. Further, a colorant is dispersed to produce a solution having a uniform composition, the solution is suspended in water, and the monomer in the suspended particles is polymerized in the presence of a radical initiator. A method for producing an electrophotographic toner having excellent offset resistance. 2. The method according to claim 1, wherein the radically polymerizable monomer is a styrene monomer or a combination of a styrene monomer and an acrylic monomer. 3. The method according to claim 1, wherein the high molecular weight resin particles obtained by emulsion polymerization are obtained by emulsion-free emulsion polymerization. 4. The method according to claim 1, wherein the high molecular weight resin particles have a particle diameter of 0.01 to 1 μm and a weight average molecular weight of 200,000 or more. 5. The high molecular weight resin particles and the monomer are mixed at 5:95 to 5: 5.
The method of claim 1 wherein the weight ratios of 0:50 are mixed to form a solution. 6. The method according to claim 1, wherein the polymerization of the suspended particles is carried out to obtain toner particles of 1 to 30 μm.