JP2504745B2 - Method of manufacturing toner for electrophotography - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electrophotographic toner, and more specifically, to a method for producing a toner for a fixing resin, in which a colorant is contained and a particle diameter is increased during a polymerization process of the fixing resin. Relates to a method for producing electrophotographic toner in a range suitable for toner at once. The present invention relates to a method for producing an electrophotographic toner which is excellent not only in fluidity but also in electrophotographic characteristics, particularly in an offset prevention effect.

(Prior Art and Technical Problem of the Invention) In the field of electrophotography, a 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 crushing the kneaded composition, and classifying the crushed material to bring it into a predetermined particle size range. However, the yield of the toner obtained by this pulverization / classification is extremely 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.

Heretofore, many proposals have been made for directly manufacturing a toner in a step of polymerizing a resin for the 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. However, in this suspension polymerization method, the particle size of the final toner is determined by the state of suspension of the monomer composition in water, and the particle size distribution is determined by adding the monomer composition to water or stirring. Depending on the situation, it is very broad and it is difficult to obtain a single particle size. In addition, this suspension polymerization method generally produces only coarse particles of about several tens of μm to several mm, and it is difficult to obtain particles having a particle size of 1 to 30 μm, which are useful as toners for developers. Of course, it is possible to make the particle size of the produced toner finer by increasing the blending amount of the dispersant, but in this case, since the dispersant is contained in the toner, it tends to be sensitive to humidity. Deterioration of electrophotographic characteristics is likely to occur. In order to prevent this, a special post-treatment operation is required, and the number of steps is large and impractical.

Further, a so-called emulsion polymerization method is known as a method for producing polymer particles having a relatively uniform particle size. The particles obtained by this polymerization method are fine particles having a particle size of 1 μm or less, or After the polymerization, it is difficult to directly obtain the colored resin for the toner in the polymerization step because a step of removing the emulsifier and the like is required.

Further, when the radical polymerizable monomer and the offset preventing agent are individually added to the reaction system and stirred, the dispersed state of the offset preventing agent is not uniform in the generated particles and is not incorporated in the generated particles. In addition, since it has a larger particle size than the generated particles, it cannot have a sufficient offset preventing effect as toner particles.

(Object of the Invention) Therefore, an object of the present invention is to provide a method in which the above-mentioned various drawbacks of the conventional production of the electrophotographic toner are eliminated.

Another object of the present invention is to produce a colored resin, which has a particle size constitution suitable for use as a toner and which does not substantially contain an inhibitor for the electrophotographic properties of the toner, directly in the resin polymerization step. A method of manufacturing a photographic toner is provided.

Still another object of the present invention is to produce a toner in which the particle size of the colored resin is stably controlled in the range of 1 to 30 μm suitable for the toner during the polymerization process and the particle size distribution is uniformly maintained. There is a way to provide.

Still another object of the present invention is a method for producing an electrophotographic toner capable of effectively preventing a so-called offset phenomenon in which a fixed toner adheres to a heating roller and, as a result, the toner adhered to the roller is transferred onto the next recording paper. To provide.

Still another object of the present invention is to provide a method for obtaining toner particles having the above characteristics by a relatively simple means.

(Structure of the Invention) According to the present invention, in a method for producing an electrophotographic toner comprising a composition of a fixing resin and a colorant dispersed in the resin, an offset inhibitor is previously added to a radical-polymerizable monomer. The radical-polymerizable monomer and the colorant are dissolved or dispersed in the reaction medium by dissolving or dispersing, and the radical-polymerizable monomer and the reaction medium are dissolved in the reaction medium. The produced polymer is selected so as not to be dissolved in the reaction medium, and the polymerization system is polymerized in the presence of a radical initiator to give an average particle size of 1 to 30 μm composed of a composition of a resin and a colorant. Provided is a method for producing a toner for electrophotography, which comprises obtaining substantially spherical particles.

 The present invention is described in detail below.

(Preferred Embodiment of the Invention) Principle and Effect In the present invention, the radically polymerizable monomer and the colorant are dissolved or dispersed in the reaction medium (solvent) and the polymerization is carried out in the presence of the radical initiator. It is an important feature that the radical-polymerizable monomer and the reaction medium are such that the monomer is dissolved in the reaction medium, but the polymer produced is not dissolved in the reaction medium. Under the combination conditions, the particle size is larger than the resin particles obtained by the usual emulsion polymerization, and the particle size is finer than the resin particles obtained by the usual suspension polymerization. It is based on the finding that the colored resin in 1 can be obtained.

Generally, the polymerization which proceeds in a solution is called a solution polymerization, but in the method of the present invention, the polymer produced is dissolved in a solvent, that is, a reaction Distinguished in that it does not dissolve in the medium.

In the present invention, the reason why the above-mentioned polymerization method produces colored particles having a particle size range within the above-mentioned specific range and having a relatively sharp particle size distribution is not restricted to this, but is as follows. It is considered to be a thing. That is, in the polymerization system of the present invention, polymerization is initiated in the reaction medium at the initial stage of assembly, and the growing polymer chains are united with the colorant particles having a large specific surface area dispersed in the polymerization system. Mid-polymerization,
That is, after the polymer particles are formed, the polymerization is initiated or the chain growth occurs inside the polymer particles under the condition that the interface between the polymer particles or the monomer is easily taken into the generated polymer particles. Thus, it is believed that the polymerized form has both emulsion polymerization and suspension polymerization. For this reason, it is considered that the colored polymer particles produced have a particle size in the toner suitable range between the resin particles obtained by the emulsion polymerization method and the resin particles obtained by the suspension polymerization method. Further, when the diameter of the polymer particles in the polymerization system is r, the generation rate of the polymer particles is considered to be inversely proportional to the surface area 4πr ² . On the other hand, the volume (4/3) π of polymer particles increases in proportion to the r ³ polymerization time. Therefore, in the case of fine polymer particles, the rate of increase in particle size is large, and in the case of large polymer particles, the speed is small, and as a result, particles having a relatively sharp particle size distribution and uniform particle size can be obtained. Further, there is an advantage that the colored polymer particles, which grow with the progress of the polymerization, are maintained in a substantially perfect spherical shape due to the interfacial tension between the colored polymer particles and the reaction medium.

Another feature of the present invention is to dissolve or disperse the offset inhibitor in the radical-polymerizable monomer prior to the polymerization. By preliminarily dissolving or dispersing the offset inhibitor in the monomer, the offset inhibitor in the polymerization reaction system is dissolved or combined with the produced polymer particles while being dispersed in the form of fine particles, and the resulting colored polymer particles are obtained. Since the offset preventive agent is uniformly present as fine particles, the toner has excellent electrophotographic properties.

Thus, the colored particles obtained by the present invention do not require a classification operation or the like, have little loss of raw materials, and are extremely excellent in productivity, and also have fluidity as a powder, blocking resistance,
It has excellent anti-offset properties, and further, by controlling the amount of the dispersant and activator used, it has the remarkable advantage that there is substantially no impeding factor for the electrophotographic characteristics of the toner.

Still another feature of the present invention is that a part of the required monomer is polymerized in the presence of a radical initiator, and the remaining monomer is dividedly added multiple times in the polymerization step, or the polymerization step is performed. The point is to add it continuously. That is, it is considered that the concentration of the growing polymer radical is constant when the polymerization process is in a steady state, but when the concentration of the monomer in the reaction system decreases, an additional amount of the monomer is sequentially or continuously added. Addition to the colored polymer particles allows the colored polymer particles to grow further while maintaining the steady state. Of course, at this time, due to the above-mentioned effects, the particle size distribution of the growing polymer particles becomes sharper, and the particle size becomes uniform.

Some types of colorants, such as carbon black, have the drawback that the growing polymer radicals are trapped on the surface of the colorant particles, the growth of polymer chains is stopped, and very fine particles are mixed in the final product. May occur. In order to prevent this, the radical initiator addition is also dividedly added multiple times during the polymerization process, or is continuously added during the polymerization process so that the growth of the polymer chain is stopped on the surface of the colorant particles. Polymerization may be restarted. This preferred embodiment of the invention has the advantage that substantially all of the colorant particles can be combined with the resulting polymer, eliminating the need for post-treatments such as sorting or classification.

In this latter embodiment, it is advisable to add an additional amount of radical initiator to an additional amount of monomer and add this mixture either sequentially or continuously.

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, an acrylic monomer, a vinyl ester monomer, a vinyl ether monomer, a diolefin monomer, and a monoolefin monomer. The body etc.

The monovinyl aromatic monomer has the formula 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 may be used alone or in combination of two or more, and the above-mentioned other monomers are as follows. Are listed respectively.

formula 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.

formula 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.

formula, In the formula, each of R ₇ , R ₈ and R ₉ is a hydrogen atom, a lower alkyl group or a halogen atom, and diolefins, especially butadiene, isoprene, chloroprene and the like.

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

In the present invention, it is particularly desirable that the radical-polymerizable monomer is such that the produced polymer is well dissolved in the monomer itself in order to make the particle size of the colorant resin particles uniform. As such a monomer, a monovinyl aromatic monomer, particularly styrenes, or an acrylic monomer,
Further combinations of these may be mentioned.

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 PRILIANT ORANGE RK, Benzidine orange G, INDUSTREN PRILIANT 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 ), iron yttrium oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), iron oxide copper (CuFe ₂ O ₄ ), iron oxide Lead (PbFe ₁₂ O ₁₉ ), iron neodymium oxide (NdFeO ₃ ), iron oxide barium (BaFe ₁₂ O ₁₉ ),
Magnesium iron oxide (MgFe ₂ O ₄ ), manganese iron oxide (MnF
e ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni), etc. are known.
Also in the present invention, any of the known fine powders of magnetic materials can be used.

As the anti-offset agent, polyolefin having a molecular weight of 1000 to 3000, various waxes, silicone oil and the like are used. Examples of the polyolefin include polyethylene and polypropylene, which may be used alone or in combination.

In the present invention, an additive component other than the above-mentioned additives, which is preferably contained in the toner, 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) or spirone black, a metal salt of naphthenic acid, a fatty metal soap. , Resin acid soap and the like can be blended.

Polymerization Method According to the present invention, an organic solvent is used as a reaction medium which dissolves the above-mentioned monomer but does not dissolve the produced polymer. Further, it is desirable that this organic solvent is a readily volatile one in order to prevent the adverse effect of the residual solvent in the toner. The specific solvent name should be determined by the type of monomer and its polymer, but generally speaking, suitable organic solvents include alcohols, cellosolves, ketones or hydrocarbons. In addition, these may be used together or as other organic solvents compatible with each other, or as a mixed solvent with water or the like, but are not limited thereto. Alcohols include lower alcohols such as methanol, ethanol and propanol, and cellosolves include methyl cellosolve,
Acetone, methyl ethyl ketone, methyl butyl ketone and the like are used as ketones such as ethyl cellosolve, and n-hexane, n-heptane, cyclohexane and the like can be mentioned as hydrocarbons.

Examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide and di-t.
-Butyl peroxide, benzoyl peroxide, lauroyl peroxide, and other peroxides that are soluble in the mixture of the monomer and the medium are used. In addition to these, combinations of ionizing radiation such as γ-rays and accelerated electron beams and ultraviolet rays with various photosensitizers are also used.

The amount of the monomer charged is preferably such that the amount of the monomer in the reaction medium is 1 to 50% by weight, particularly 5 to 30% by weight, based on the reaction medium. The colorant may be added in an amount contained in the toner resin, and is generally 1 to 30 per monomer charge amount.
%, Especially in the range 3 to 20% by weight is suitable. When a magnetic material is used as a pigment, generally 5 to 300% by weight, particularly 10 to 250% by weight, based on the charged amount of the monomer, is suitable.

The amount of the initiator such as an azo compound or peroxide to be added may be a so-called catalyst proper amount, and it is generally preferable to use it in an amount of 0.1 to 10% by weight based on the charged monomers. The polymerization temperature and time may be those known in the art, and generally, polymerization at a temperature of 40 to 100 ° C. for 1 to 50 hours is sufficient. The reaction system may be stirred gently so that a homogeneous reaction occurs as a whole, and in order to prevent inhibition of polymerization by oxygen, the reaction system is replaced with an inert gas such as nitrogen to carry out polymerization. May be.

The monomer may be charged into the medium either continuously or intermittently.
In the case of intermittent charging, the additional amount of the monomer is preferably 0.5 times or more the amount of the initial charged monomer, and it is desirable to divide and add at least twice. In this case, the type of the added monomer may be the same as the first charged monomer,
Also, different types may be used. It should be understood that in the latter case the formation of block copolymers is also possible. It is desirable that the average addition rate of the monomers be a rate substantially corresponding to the polymerization rate of the monomers.

Further, the additional amount of the polymerization initiator is preferably 0.1 to 10 times by weight, particularly 0.5 to 5 times by weight the initial amount of the polymerization initiator added, and the additional amount of the polymerization initiator is the additional amount of the monomer. It is also possible to add it to the polymerization system by dissolving it therein.

Since the polymerized product after the reaction is obtained in the form of granules having the above-mentioned particle size range, the produced particles are filtered, washed with the above solvent if necessary, and dried to obtain colored particles for toner.

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

Further, in the production of the toner, a dispersion stabilizer can be used if necessary. Examples of such a dispersion stabilizer include polymers soluble in a medium such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, polyacrylic acid, polyacrylamide, polyethylene oxide, poly (hydroxystearic acid-g-methyl methacrylate-eu. -Methacrylic acid) copolymer, nonionic or ionic surfactant, etc. are appropriately used.

 The invention is illustrated by the following example.

Example 1 To 80 g of styrene and 20 g of n-butyl methacrylate, 1.5 g of low molecular weight polyethylene as an offset inhibitor was added and dissolved by heating. This was added to 800 ml of ethanol in which 8 g of polyacrylic acid was dissolved, and carbon black (Printex L:
(Degussa) 5 g and azobisisobutyronitrile 1 g are added, and 150 r.p.
Polymerization was completed by reacting at 80 ° C. for 15 hours while stirring at m. When the polymer was observed with an optical microscope, it was approximately 10μ.
m spherical black particles. The polymer was filtered through a 100 mesh to remove some agglomerates, and then the polymer was separated by sedimentation, washed with ethanol three times and dried to obtain 95 g of a toner. The particle size distribution of this toner was sharp as shown in Table 1 as a result of measurement by a Coulter counter, and its average particle size was 10.4 μm.
When this toner was put into a mitaDC-211 copying machine and a copying test was carried out, a clear image was obtained and the offset phenomenon did not occur.

Example 2 8 g of polyacrylic acid was dissolved in 800 ml of ethanol, and 5 g of carbon black (Plintex L: manufactured by Degussa) and 1 g of azobisisobutyronitrile were added thereto. In a separate container, 80 g of styrene and 20 g of n-butyl methacrylate were added, and 1.5 g of low molecular weight polyethylene as an offset preventive was added thereto and dissolved by heating. 26.5 g of this polyethylene-dissolved monomer was added to the reaction system, and the temperature was raised to 80 ° C. while stirring at 150 rpm in a separable flask under a nitrogen stream, and after 2 hours, 4 hours and 6 hours. After that, 25 g of the remaining monomer was additionally added and reacted for 15 hours to complete the polymerization. When the polymer was observed with an optical microscope, it was about 10 μm.
It was spherical black particles. The polymer was filtered through 100 mesh to remove some aggregates, and then the polymer was separated by sedimentation,
Further, it was washed with ethanol three times and dried to obtain 103 g of toner. The particle size distribution of this toner was very sharp as shown in Table 1 as a result measured by a Coulter counter.

When this toner was put into a mitaDC-211 copying machine and a copying test was carried out, an extremely clear image was obtained and the offset phenomenon did not occur.

Comparative Example 1 First, 8 g of polyacrylic acid was dissolved in 800 ml of ethanol,
To this, 80 g of styrene, 20 g of n-butyl methacrylate, 5 g of carbon black (Printex L: Degussa), 1 g of azobisisobutyronitrile, and 1.5 g of low molecular weight polyenylene as an anti-offset agent were added afterwards. 80 with stirring in a separable flask under a nitrogen stream at 150 rpm.
Polymerization was carried out by reacting at 15 ° C for 15 hours. When the polymer was observed with an optical microscope, it was spherical black particles of about 10 μm. The polymer was filtered through 100 mesh to remove some agglomerates, and then the polymer was separated by sedimentation, washed with ethanol three times, and dried to obtain 90 g of toner. The particle size distribution of this toner was as sharp as in Example 1. When this toner was put into a mitaDC-211 copying machine and a copying test was performed, a clear image was initially obtained, but an offset phenomenon occurred as the number of copied sheets was increased.

Claims (7)

(57) [Claims] 1. A method for producing an electrophotographic toner comprising a composition of a fixing resin and a colorant dispersed in the resin, wherein an offset inhibitor is previously dissolved or dispersed in a radical polymerizable monomer, The radical-polymerizable monomer and the colorant are dissolved or dispersed in the reaction medium, where the radical-polymerizable monomer and the reaction medium are dissolved in the reaction medium, but the produced polymer is reacted. It should be selected so that it does not dissolve in the medium, and this polymerization system is polymerized in the presence of a radical initiator to obtain substantially spherical particles composed of a composition of a resin and a colorant and having an average particle size of 1 to 30 μm. A method for producing an electrophotographic toner, comprising: 2. A part of the radical-polymerizable monomer is polymerized in the presence of a radical initiator, and the remaining monomer is dividedly added over a plurality of times during the polymerization step, or during the polymerization step. The method according to claim 1, wherein the method is continuously added. 3. The method according to claim 1, wherein the radical-polymerizable monomer is such that the polymer produced is well soluble in the monomer itself. 4. The radical-polymerizable monomer is a monomer mainly containing styrene, and the reaction medium is alcohols.
The method according to claim 1, which is a medium mainly composed of cellosolves or ketones. 5. The method according to claim 1, wherein the radically polymerizable monomer is a styrene-based monomer, and the reaction medium is a hydrocarbon-based medium. 6. The offset preventing agent is a polyolefin,
Claim 1 which is silicone oil and various waxes.
Method described in section. 7. The method according to claim 6, wherein the polyolefin is polyethylene and / or polypropylene having a molecular weight of 1000 to 3000.