JPH02273758A - Production of polymerized toner - Google Patents

Abstract

PURPOSE:To obtain the toner having excellent blocking resistance by subjecting a polymerizable monomer system contg. wax to a suspension polymn. in a water phase and increasing the reaction temp. to the m. p. of the wax or above when the rate of polymn. of the polymerizable monomer attains 70 to 90%. CONSTITUTION:The polymerizable monomer system contg. at least the wax is subjected to the suspension polymn. in the water phase and the reaction temp. in the polymn. process is increased up to the m. p. of the wax or above when the rate of polymn. of the polymerizable monomer attains 70 to 90% to activate the molecular motion of the wax. The wax which is nonpolar can more stabilize the intra-system energy as the wax parts from the boundary with the aq. medium of large polarity and, therefore, the molecular motion is activated, by which the wax is migrated from the fine powder side to the inside of the polymerized toner contg. the nonpolar component at a higher ratio. The toner having the excellent blocking resistance is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing toner used in electrophotography.

[Prior Art] Many electrophotographic methods are known, as described in U.S. Pat. An electrical latent image is formed on the photoreceptor, and then the latent image is developed using toner, and if necessary, the toner image is transferred to a transfer member such as paper, and then heated, pressured, solvent vapor, etc. It is fixed and a copy is obtained. Furthermore, various methods have been proposed as methods for developing with toner or methods for fixing toner images, and methods suitable for each image forming process are adopted.

Conventionally, toners used for these purposes are generally produced by melt-mixing coloring agents such as dyes and pigments in thermoplastic resin, uniformly dispersing the mixture, and then using a pulverizer and classifier to produce toner having the desired particle size. Tegita.

Although this method of manufacture can produce quite good toners, it does have certain limitations, namely the range of choices of materials for the toner. For example, the resin colorant dispersion must be sufficiently brittle to be comminuted in economically viable manufacturing equipment. However, if the resin colorant dispersion is made brittle in order to meet these requirements, the particle size range of the particles formed when actually pulverized at high speed tends to be wide, and in particular, a relatively large proportion of fine particles are likely to become brittle. The problem of inclusion arises. Furthermore, such a highly brittle material is more likely to be pulverized or powdered when used in a developing device such as a copying machine. In addition, with this method, it is difficult to completely and uniformly disperse solid particles such as colorants into the resin, and depending on the degree of dispersion, there may be an increase in fog, a decrease in image density, or a problem with color mixing and transparency. Therefore, attention must be paid to dispersion. Furthermore, exposure of the colorant to the fracture surface may cause variations in development characteristics.

On the other hand, in order to overcome the problems of toner produced by these pulverization methods, methods for producing toner using a suspension polymerization method have been proposed in Japanese Patent Publication No. 36-10231, Japanese Patent Publication No. 43-10799, Japanese Patent Publication No. 51-14895, etc. . In the suspension polymerization method, a monomer composition is prepared by uniformly dissolving or dispersing a polymerizable monomer, a colorant, a polymerization initiator, and if necessary, a crosslinking agent, a charge control agent, and other additives. This monomer composition is dispersed in a continuous phase containing a dispersion stabilizer, such as an aqueous phase, using a suitable stirrer, and a polymerization reaction is simultaneously carried out to obtain toner particles having a desired particle size.

Since this method does not involve any pulverization process, the toner does not need to be brittle and soft materials can be used, and the colorant is not exposed to the particle surface, resulting in uniform triboelectric charging properties. It has the advantage of having

In addition, in the case of suspension polymerization, since the polymerizable monomer system is suspended in an aqueous phase, the polar components in the polymerizable monomer system are transferred to the vicinity of the surface layer of the particles, and the non-polar components (wax etc)
is unevenly distributed inside the particles and forms a pseudo-capsule structure, so the toner obtained has excellent blocking resistance. However, as copiers have become more sophisticated in recent years,
There is a demand for further improvement in blocking resistance of toners.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing a toner that satisfies the above requirements and has excellent blocking resistance.

[Means and effects for solving the problem] The method for producing a polymerized toner of the present invention was developed to solve the above-mentioned problems. A method for producing a polymerized toner obtained by suspension polymerization in a systematic aqueous phase, wherein when the degree of polymerization of the polymerizable monomer reaches 70 to 95%, the reaction temperature in the polymerization process is adjusted to This is achieved by raising the temperature above the melting point of

The present invention will be described in detail below.

As a result of extensive studies, the present inventors found that during suspension polymerization, some of the polymerizable monomer systems become emulsified, producing submicron-order fine powder, and this fine powder becomes the polymerized toner obtained by suspension polymerization. We focused on the fact that its presence on the surface reduces blocking resistance. That is, it is considered that the presence of fine powder containing wax on the surface of the polymerized toner reduces the blocking resistance, and the wax in the fine powder should be transferred into the interior of the polymerized toner. When the degree of polymerization of the polymer reaches 70 to 95%, the reaction temperature during the polymerization process is raised above the melting point of the wax to activate the molecular movement of the wax. By moving further away from the interface with the medium, the energy within the system can be further stabilized, and by activating molecular movement, it becomes possible to migrate from the fine powder side to the inside of the polymerized toner, where there are more nonpolar components.

As a result, it has been discovered that a toner with excellent blocking resistance can be obtained, leading to the present invention.

When the degree of polymerization of the polymerizable monomer is less than 70%, if the reaction temperature during the polymerization process is increased, the amount of low molecular weight components in the binder resin increases, resulting in a significant decrease in blocking resistance.

If the reaction temperature is increased to 95% or higher, polymerization has progressed considerably and the viscosity has increased, so that the wax cannot be transferred sufficiently.

The wax that can be used in the present invention has a melting point of 55 to 70
Paraffinic hydrocarbons in the range of °C are preferably used. For example, paraffin waxes include products manufactured by Nippon Oil Co., Ltd. and Nippon Seiro Co., Ltd., and branched paraffin waxes include microcrystalline wax (manufactured by Hiki Seiro Co., Ltd.) and micro wax (manufactured by Nippon Seiro Co., Ltd.).

Further, the amount of wax added is preferably 1 to 30 parts by weight per 100 parts by weight of the polymer.

As the polymerization initiator, any suitable polymerization initiator such as 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1' -azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2
, 4-dimethylvaleronitrile, and other azo or diazo polymerization initiators such as azobisisobutyronitrile (^IBN); benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate, cumene hydroperoxide, 2. Examples include peroxide-based polymerization initiators such as 4-dichlorylbenzoyl peroxide and lauroyl peroxide. Generally, about 0.5 to 10% of the polymerization initiator based on the weight of the polymerizable monomer is sufficient.

The polymerized toner used in the present invention can be obtained by the following method. That is, a monomer system containing a suspension stabilizer is obtained by adding wax, a colorant, a polymerization initiator, and other additives to a polymerizable monomer and uniformly dissolving or dispersing them using an ultrasonic disperser, homogenizer, etc. into the aqueous phase (ie, continuous phase) using a conventional stirrer, homomixer, homogenizer, etc. Preferably, the stirring speed and time are adjusted so that the monomer droplets have the desired toner particle size, generally 30 μm or less, and thereafter stirring is carried out so that this state is approximately maintained by the action of the dispersion stabilizer. It is sufficient to carry out the treatment to the extent that sedimentation of particles is prevented.

The polymerization temperature was set at 40°C or higher, numerically 50 to 70°C, and the polymerization was started until the degree of polymerization of the polymerizable monomer was 70°C.
When it reaches ~95%, the polymerization temperature is raised above the melting point of the wax to carry out polymerization.

After the reaction is completed, the generated toner particles are collected by washing, filtration, and dried. In the suspension polymerization method, usually monomer 1
It is preferable to use 300 to 3000 parts by weight of water as a dispersion medium per 00 parts by weight.

Polymerizable monomers that can be applied to the toner of the present invention include:
Styrene, 0-methylstyrene, I-methylstyrene,
Styrene and its derivatives such as p-methylstyrene, p-methoxystyrene, p-ethylstyrene; methyl methacrylate, ethyl methacrylate, propyl methacrylate,
°n-butyl methacrylate, isobutyl methacrylate,
Methacrylic acid esters such as n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, dietylaminoethyl methacrylate; methyl acrylate, acrylic acid Acrylic acid esters such as ethyl, n-butyl acrylate, isobutyl acrylate, propyl acrylate, 0-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate. Classes include vinyl monomers such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

These monomers can be used alone or in combination. Among the above-mentioned materials, styrene or a styrene conductor can be used alone or mixed with other materials to obtain polymerizable 11.
It is preferable to use the toner as an ffi form in terms of the development characteristics and durability of the toner.

Moreover, it is more preferable to add a polymer or copolymer having a polar group as an additive during polymerization of the monomer. In the present invention, a polymerizable monomer system to which a polymer, copolymer, or cyclized rubber having a polar group is added during polymerization is added to an aqueous phase in which a dispersant having a charge opposite to that of the polar polymer is dispersed. It is preferable to suspend and polymerize in. That is, the cationic or anionic polymer, copolymer or cyclized rubber contained in the polymerizable monomer system is undergoing polymerization with the oppositely charged anionic or cationic dispersant dispersed in the aqueous phase. Electrostatically attracts each other on the surface of the particles that become the toner, and the dispersant covers the particle surface to prevent the particles from coalescing and stabilize them, and the polar polymer added during polymerization gathers on the surface of the particles that become the toner. Therefore, it takes on a kind of shell-like shape, and the resulting particles become pseudo-capsules. A relatively high molecular weight polar polymer, copolymer or cyclized rubber is used to give toner particles excellent blocking properties and development abrasion resistance, while a relatively low molecular weight internally improves fixing properties. By carrying out polymerization in such a manner as to contribute to the toner, it is possible to obtain a toner that satisfies the contradictory requirements of fixing properties and blocking properties. Examples of polar polymers (including polar copolymers) and retrograde dispersants that can be used in the present invention are shown below.

(1) Examples of cationic polymers include polymers of nitrogen-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl acrylate, or copolymers of nitrogen-containing monomers with styrene, unsaturated carboxylic acid esters, etc. .

(ii) Anionic polymers include nitrile monomers such as acrylonitrile, halogen-containing monomers such as vinyl chloride, unsaturated carboxylic acids such as acrylic acid, unsaturated dibasic acids, and unsaturated dibasic acids. There are anhydride and nitro monomer polymers.

(iii) As the anionic dispersant, Aerosil #
200. #300. There are colloidal silicas such as #380 (manufactured by Nippon Aerosil Co., Ltd.).

(tv) Examples of the cationic dispersant include aluminum oxide, hydrophilic positively charged silica fine powder such as aminoalkyl-modified colloidal silica, and the like. Cyclized rubber may be used instead of the polar polymer.

Such a dispersant is preferably used in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the polymerizable monomer. More preferably 0.
It is 3 to 15 parts by weight.

On the other hand, as the charge control substance added as necessary, generally known substances can be used. For example, nigrosine, azine dyes containing an alkyl group having 2 to 16 carbon atoms, metal complex salts of monoazo dyes, metal complex salts of salicylic acid, dialkyl salicylic acid, etc. are used.

All known colorants can be used for the toner, such as carbon black, iron black, nigrosine, benzidine yellow, quinacridone, rhodamine B,
Examples include phthalocyanine blue.

In addition, in order to use the toner as a magnetic toner, it may contain magnetic powder. As such magnetic powder, a substance that is magnetized when placed in a magnetic field is used, such as iron, cobalt, nickel, etc. There are powders of ferromagnetic metals such as ferromagnetic metals, and compounds such as magnetite and ferrite.

In particular, when carbon black or magnetic powder is used, it is more preferable to perform a hydrophobic treatment.

Further, a fluidity modifier may be mixed (externally added) with toner particles and used. Examples of the fluidity modifier include colloidal silica, fatty acid metal salts, and fine Teflon powder. In addition, fillers such as calcium carbonate and finely powdered silica are added for the purpose of increasing the volume.
It may be blended into the toner in a range of 5 to 20% by weight.

The degree of polymerization was determined from the formula below.

Note that 1% by weight of a polymerization inhibitor MEHQ was added to the sample before drying the sample. Also, the degree of polymerization is 2 significant figures
I asked for it in digits.

[Example] Hereinafter, a detailed explanation will be given based on an example. Note that all parts are parts by weight, and the physical property values of the obtained toner are summarized in Table 1.

Example 1 The above formulation was heated to 60° C., dissolved or dispersed in a container, and the monomer system was adjusted.

Separately, a log of aminoalkyl-modified colloidal silica was added to ion-exchanged water 120 (lnj), and the above monomer composition was added to a dispersion medium system adjusted to pH 6 with hydrochloric acid, and the mixture was heated at 60°C under a nitrogen atmosphere using a TK homomixer. 8.000rpm
The mixture was stirred for 60 minutes to granulate the monomer composition. The mixture was heated and stirred at 60° C. using a paddle stirring blade, and when it was confirmed that the degree of polymerization exceeded 70%, the polymerization temperature was raised to 80° C., and heating and stirring were continued to complete the polymerization. As a result of the measurement, the degree of polymerization was 75.
%Met.

After that, the reaction product was cooled and sodium hydroxide was added.
A polymerized toner was obtained by dissolving the dispersant, filtering, washing with water, and drying.

Example 2 The above formulation was dispersed for 15 minutes using an ultrasonic disperser (RUS-300, manufactured by Nippon Seiki Seisakusho Co., Ltd., frequency: 20 kHz, output: 30 W) heated to 70° C. to perform hydrophobization treatment of carbon black.

Next, the monomer system was adjusted by adding and heating to 70°C, and dissolving or dispersing.

Separately, the above monomer composition was added to a dispersion medium system in which 10 g of aminoalkyl-modified colloidal silica was added to 1200 m4 of ion-exchanged water, and the mixture was stirred for 60 minutes at 8.00 Orpm using a TK homomixer at 70°C under a nitrogen atmosphere. , the monomer composition was granulated. The mixture was heated and stirred at 70° C. using a paddle stirring blade, and when it was confirmed that the degree of polymerization exceeded 80%, the polymerization temperature was raised to 80° C., and the polymerization was completed by continuing heating and stirring.

As a result of the measurement, the degree of polymerization was 85%. Thereafter, the reaction product was cooled, sodium hydroxide was added to dissolve the dispersant, and the mixture was filtered, washed with water, and dried to obtain a polymerized toner.

Example 3 The components of the above formulation were heated to 70° C. in a container, and dissolved and dispersed using an ultrasonic disperser (10 kHz, 200 W) to obtain a monomer mixture. Further, while maintaining the temperature at 70°C, 10 parts of initiator V-601 (manufactured by Wako Tsumugi Pharmaceutical Co., Ltd.) was added and dissolved to prepare a monomer composition.

Separately, add Aerosil #20 to 1200ml of ion-exchanged water.
0 (manufactured by Nippon Aerosil) and 10 parts of NaCO3.
Add 2 parts of , warm to 70°C, and mix using a TK homomixer for 10. Dispersion was performed for 15 minutes at OOOrpm. Furthermore, add 2.2 parts of Ai'z(SO4)s and 10. OOO
The dispersion medium was adjusted by dispersing at rpm for 15 minutes. The above monomer composition was added to this, and TK was carried out at 70°C under nitrogen atmosphere.
10. using a type homomixer. The monomer composition was granulated by stirring at OOO rpm for 60 minutes. 7 with paddle stirring blades
The mixture was heated and stirred at 0°C, and when it was confirmed that the degree of polymerization exceeded 85%, the polymerization temperature was raised to 80°C, and the polymerization was completed by heating and stirring. As a result of the measurement, the degree of polymerization was 90%. Thereafter, the reaction product was cooled, sodium hydroxide was added to dissolve the dispersant, and the mixture was filtered, washed with water, and dried to obtain a polymerized toner.

Comparative Example 1 A polymerized toner was obtained in the same manner as in Example 1 except that the polymerization temperature was not changed during the course of the polymerization.

Comparative Example 2 A polymerized toner was obtained in the same manner as in Example 2 except that the polymerization temperature was not changed during the course of the polymerization.

Example 3 A polymerized toner was obtained in the same manner as in Example 3 except that the polymerization temperature was not changed during the course of the polymerization.

Table 1 = Physical properties of polymerized toner *3: When the toner was left in a constant temperature bath at 50° C. for 3 days or 1 week, it was rated O if it did not block, and it was rated × if it blocked.

[Effects of the Invention] As is clear from the above description, the polymerized toner produced by the production method of the present invention has extremely excellent blocking resistance.

Claims (1)

[Claims] (1) A method for producing a polymerized toner obtained by suspension polymerizing a polymerizable monomer system containing at least wax in an aqueous phase, the polymerizable monomer having a degree of polymerization of 70 to 95.
%, the reaction temperature in the polymerization process is raised above the melting point of the wax.