JP2627085B2 - Method for producing polymerized toner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a toner used in electrophotography.

[Prior Art] As described in U.S. Pat. No. 2,297,691 and the like, a large number of electrophotographic methods are known. Generally, a photoconductive substance is used on a photoreceptor by using various methods. Forming an electrical latent image on the substrate, and then developing the latent image with toner,
If necessary, the toner image is transferred to a transfer member such as paper and then fixed by heating, pressure, solvent vapor, or the like to obtain a copy.
Various methods have been conventionally proposed as a method of developing using toner or a method of fixing a toner image, and a method suitable for each image forming process is adopted.

Conventionally, toners used for these purposes have generally been prepared by melt-mixing a coloring agent composed of a dye and a pigment in a thermoplastic resin and uniformly dispersing the same, and then producing a toner having a desired particle size by a fine pulverizing device and a classifier. Was.

Although this method can produce a very good toner,
There is a certain limitation, namely the selection range of toner materials. For example, the resin colorant dispersion must be sufficiently brittle and capable of being pulverized in economically feasible manufacturing equipment.
However, when the resin colorant dispersion is made brittle to satisfy these requirements, the particle size range of the particles formed when actually pulverized at a high speed tends to be widened, and in particular, a relatively large proportion of the fine particles The problem of inclusion occurs. Further, such a highly brittle material is more susceptible to pulverization or pulverization when used for development in a copying machine or the like. Further, in this method, it is difficult to completely and uniformly disperse fixed fine particles such as a coloring agent in a resin, and depending on the degree of the dispersion, an increase in fog, a decrease in image density, and a color mixing property / transparency. Attention must be paid to dispersion, as it will cause defects. Further, exposure of the coloring agent to the fractured surface may cause a change in development characteristics.

On the other hand, in order to overcome the problems of the toner caused by these pulverization methods, Japanese Patent Publication Nos. 36-10231, 43-10799 and 51-14.
No. 895 and the like have proposed a method for producing a toner by a suspension polymerization method. In the suspension polymerization method, a polymerizable monomer, a colorant, a polymerization initiator and, if necessary, a crosslinking agent, a charge control agent, and other additives are uniformly dissolved or dispersed to form a monomer composition. This monomer composition is dispersed in a continuous phase containing a dispersion stabilizer, for example, an aqueous phase using a suitable stirrer, and simultaneously undergoes a polymerization reaction to obtain toner particles having a desired particle size.

Since this method does not include a pulverizing step at all, the toner does not need to be brittle and can use a soft material.
Further, there is an advantage that a colorant is not exposed on the surface of the particles and uniform triboelectricity is obtained.

In addition, in the case of the suspension polymerization method, the polar component in the polymerizable monomer system is moved to the vicinity of the surface layer of the particles due to the characteristic that the polymerizable monomer system is subjected to suspension polymerization in an aqueous phase, and the non-polar component (wax) ) Are unevenly distributed inside the particles, and the toner obtained by forming a pseudo capsule structure has excellent blocking resistance. However, with the recent increase in the functions of copiers and the like, further improvement in blocking resistance of toner is required.

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

[Means and Actions for Solving the Problems] The method for producing a polymerized toner of the present invention has been developed to solve the above-mentioned problems, and more specifically, a polymerizable monomer containing at least a wax. A method for producing a polymerized toner obtained by subjecting a system to suspension polymerization in an 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 the wax. This is achieved by raising the temperature above the melting point.

 Hereinafter, the present invention will be described in detail.

The present inventors have conducted intensive studies, and as a result, when performing the suspension polymerization, a part of the polymerizable monomer system was in an emulsified state, generating submicron order fine powder, and the fine powder was obtained by the suspension polymerization. Attention was paid to the fact that blocking resistance was reduced due to the presence on the surface. That is, it is considered that the presence of the fine powder containing the wax on the surface of the polymerized toner lowers the blocking resistance. In order to transfer the wax in the fine powder into the polymerized toner, a polymerizable monomer is used. When the degree of polymerization of the body reaches 70 to 95%, the reaction temperature in the polymerization process is raised to the melting point of the wax or higher, and the molecular motion of the wax is activated. Since the non-polar wax is more distant from the interface with the highly polar aqueous medium, the energy in the system can be more stabilized. Internal migration is possible.

As a result, it has been found that a toner having excellent blocking resistance can be obtained, and the present invention has been achieved.

If the reaction temperature in the polymerization process is increased when the polymerization degree of the polymerizable monomer is less than 70%, the amount of low molecular weight components in the binder resin is increased, and the blocking resistance is significantly reduced. When the reaction temperature is increased to 95% or more, the wax is not sufficiently transferred because the polymerization is considerably advanced and the viscosity is high.

The wax usable in the present invention has a melting point of 55 to 70 ° C.
Are preferably used. For example, as paraffin wax, there are products manufactured by Japan Petroleum and Nippon Seiswax, and as branched paraffin wax, there are microcrystalline wax (manufactured by Japan Wax), microwax (manufactured by Japan Petroleum) and the like.

The amount of the wax added is preferably 1 to 30 parts by weight based on 100 parts by weight of the polymer.

As the polymerization initiator, any suitable polymerization initiator, for example, 2,2'-azobis-2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (Cyclohexane-1-carbonitrile), 2,
2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, other azobisisobutyronitrile (AIBN)
Azo-based or diazo-based polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorylbenzoyl peroxide, and lauroyl peroxide-based polymerization initiators Agents. These polymerization initiators are generally
About 0.5 to 10% of the initiator by weight of the polymerizable monomer is sufficient.

The polymerized toner used in the present invention is obtained by the following method. That is, wax in the polymerizable monomer, a coloring agent,
A monomer which is uniformly dissolved or dispersed by an ultrasonic disperser, a homogenizer or the like after adding other additives such as a polymerization initiator, is mixed with an ordinary stirrer in an aqueous phase containing a suspension stabilizer (that is, a continuous phase). Alternatively, it is dispersed with a homomixer, a homogenizer, or the like. Preferably, the stirring speed and time are adjusted so that the monomer droplets have a desired toner particle size, generally 30 μm or less, and thereafter, stirring is performed so that the state is substantially maintained by the action of the dispersion stabilizer. What is necessary is just to carry out to the extent that sedimentation of particles is prevented. The polymerization is started at a polymerization temperature of 40 ° C or higher, generally at a temperature of 50 to 70 ° C. The polymerization temperature is raised to carry out the polymerization.

After completion of the reaction, the generated toner particles are collected by washing, passing, and dried. In the suspension polymerization method, usually a monomer
It is preferable to use 300 to 3000 parts by weight of water as a dispersion medium with respect to 100 parts by weight.

As the polymerizable monomer applicable to the toner of the present invention,
Styrene, o-methylstyrene, m-methylstyrene,
styrene such as p-methylstyrene, p-methoxystyrene, p-ethylstyrene and derivatives thereof; methyl methacrylate, ethyl methacrylate, propyl methacrylate;
Ester such as n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like Class; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, Acrylic esters such as phenyl acrylate; and vinyl monomers such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

These monomers can be used alone or as a mixture.
Of the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or as a mixture with other monomers as a polymerizable monomer in terms of the developing characteristics and durability of the toner.

It is more preferable to add a polymer or a copolymer having a polar group as an additive during the polymerization of the monomer to polymerize the monomer. In the present invention, a polymerizable monomer system to which a polymer, a copolymer or a cyclized rubber having a polar group is added at the time of polymerization is suspended in an aqueous phase in which the polar polymer and a dispersant having an opposite charge are dispersed. It is preferable to conduct turbidity and polymerize. That is,
The cationic or anionic polymer, copolymer or cyclized rubber contained in the polymerizable monomer system is composed of an inversely charged anionic or cationic dispersant dispersed in an aqueous phase and a toner undergoing polymerization. The particles attract electrostatically on the surface of the particles, and the surface of the particles is covered with a dispersant to prevent and stabilize the coalescence of the particles.At the same time, the polar polymer added during polymerization collects on the surface layer of the toner particles. And the resulting particles form pseudo capsules. A relatively high molecular weight polar polymer, copolymer or cyclized rubber is used to give the toner particles excellent properties of blocking property and development abrasion resistance. By performing polymerization so as to contribute, it is possible to obtain a toner that satisfies conflicting requirements of fixing property and blocking property. The polar polymer (including the polar copolymer) and the reverse charge dispersant which can be used in the present invention are exemplified below.

(I) Examples of the cationic polymer include a polymer of a nitrogen-containing monomer such as dimethylaminoethyl methacrylate and diethylaminoethyl acrylate and a copolymer of styrene, an unsaturated carboxylic acid ester and the like with the nitrogen-containing monomer. .

(Ii) Examples of the anionic polymer 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 polymers of anhydrides and nitro monomers.

(Iii) Aerosil # 200,
There are colloidal silicas such as # 300 and # 380 (manufactured by Nippon Aerosil Co., Ltd.).

(Iv) Examples of the cationic dispersant include fine particles of hydrophilic positively chargeable silica such as aluminum oxide and aminoalkyl-modified colloidal silica. A cyclized rubber may be used instead of the polar polymer.

Such a dispersant is based on 100 parts by weight of the polymerizable monomer.
0.2 to 20 parts by weight is preferred. More preferably, it is 0.3 to 15 parts by weight.

On the other hand, as the charge control substance to be added as needed, generally known substances are 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 and dialkylsalicylic acid, and the like are used.

As the colorant used for the toner, any known colorants can be used, and examples thereof include carbon black, iron black, nigrosine, benzidine yellow, quinacridone, rhodamine B, and phthalocyanine blue.

Further, in order to use the toner as a magnetic toner, a magnetic powder may be contained. As such magnetic powder, a substance which is magnetized when placed in a magnetic field is used, and examples thereof include powders of ferromagnetic metals such as iron, cobalt, and nickel, and compounds such as magnets and ferrites.

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

The fluidity modifier may be mixed (externally added) with the toner particles and used. Colloidal silica as a fluidity modifier,
Examples include fatty acid metal salts and fine powder of Teflon. In addition, fillers such as calcium carbonate and finely powdered silica are used in an amount of 0.
It may be blended in the toner in the range of 5 to 20% by weight.

 The polymerization degree was determined by the following equation.

Before the sample was dried, 1% by weight of the polymerization inhibitor MEHQ was added to the sample. The polymerization degree was determined by two significant figures.

Example Hereinafter, a detailed description will be given based on an example. All parts are by weight and the physical properties 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 to prepare a monomer system.

Separately, add 10 g of aminoalkyl-modified colloidal silica to 1200 ml of ion-exchanged water, add the above monomer composition to a dispersion medium system adjusted to pH 6 with hydrochloric acid, and use a TK homomixer at 8,000 rpm at 60 ° C. under a nitrogen atmosphere. The mixture was stirred for 60 minutes to granulate the monomer composition. The mixture was heated and stirred at 60 ° C with a paddle stirring blade. When it was confirmed that the degree of polymerization exceeded 70%, the polymerization temperature was raised to 80 ° C.
C., and the mixture was heated and stirred to complete the polymerization. As a result of the measurement, the degree of polymerization was 75%.

Thereafter, the reaction product was cooled, sodium hydroxide was added, the dispersant was dissolved, and the mixture was washed, washed with water, and dried to obtain a polymerized toner.

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

next Was added and the mixture was heated to 70 ° C., dissolved or dispersed to prepare a monomer system.

Separately, add the above monomer composition to a dispersion medium obtained by adding 10 g of aminoalkyl-modified colloidal silica to 1200 ml of ion-exchanged water, and use a TK homomixer at 70 ° C. in a nitrogen atmosphere.
The mixture was stirred at 8,000 rpm for 60 minutes to granulate the monomer composition. The mixture was heated and stirred at 70 ° C. with a paddle stirrer, and when it was confirmed that the degree of polymerization exceeded 80%, the polymerization temperature was raised to 80 ° C., and the heating and stirring were continued to complete the polymerization. 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 washed, 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, 10 parts of an initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved while maintaining the temperature at 70 ° C. to prepare a monomer composition.

Separately, 10 parts of Aerosil # 200 (manufactured by Nippon Aerosil) are added to 1200 ml of ion-exchanged water, and 2 parts of NaCO ₃ are further added.
The mixture was heated to 0 ° C and dispersed at 10,000 rpm for 15 minutes using a TK homochimizer. Further, add 2.2 parts of Al ₂ (SO ₄ ) ₃ to 10,000 rpm
For 15 minutes to prepare a dispersion medium. The above monomer composition was added thereto, and the mixture was stirred under a nitrogen atmosphere at 70 ° C. using a TK homomixer at 10,000 rpm for 60 minutes to granulate the monomer composition. Heat and stir at 70 ° C with a paddle stirring blade to reduce the degree of polymerization.
When it was confirmed that it exceeded 85%, 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 90%. Then, the reaction product is cooled,
Add sodium hydroxide, dissolve the dispersant, wash with water,
The polymer toner was obtained by drying.

Comparative Example 1 A polymerization toner was obtained in the same manner as in Example 1 except that the polymerization temperature was not changed in the middle.

Comparative Example 2 A polymerization toner was obtained in the same manner as in Example 2 except that the polymerization temperature was not changed in the middle.

Example 3 A polymerization toner was obtained in the same manner as in Example 3 except that the polymerization temperature was not changed in the middle.

[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.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-167955 (JP, A) JP-A-61-28957 (JP, A) JP-A-58-168055 (JP, A) JP-A-62-16955 157050 (JP, A) JP-A-62-295073 (JP, A) JP-A-59-26740 (JP, A)

Claims (1)

(57) [Claims] A method for producing a polymerized toner obtained by subjecting a polymerizable monomer system containing at least a wax to suspension polymerization in an aqueous phase, wherein the polymerization degree of the polymerizable monomer is from 70 to 70.
A process for producing a polymerized toner, wherein the reaction temperature in the polymerization process is raised to a temperature equal to or higher than the melting point of the wax when the content reaches 95%.