JPH02273759A - Production of polymerized toner - Google Patents

Abstract

PURPOSE:To obtain the toner having excellent blocking resistance by subjecting a polymerizable monomer system to a suspension polymn. in an aq. medium phase, adjusting the concn. of styrene to 0.01 to 0.05wt.% when the rate of polymn. of the polymerizable monomer attains >=80%, then adding a water soluble inorg. salt and oil soluble polymn. initiator to the monomer and executing the polymn. again. CONSTITUTION:The polymerizable monomer system is subjected to the suspension polymn. in the aq. medium phase and the concn. of the styrene in the aq. medium system is adjusted to 0.01 to 0.05wt.% when the rate of polymn. of the polymerizable monomer attains >=80%. The styrene is precipitated by adding the water soluble inorg. salt into the aq. medium and further, the oil soluble polymn. initiator is added to the polymer and the polymn. is executed again. The precipitated styrene gathers to the periphery on the surface of the suspended particles and the polymn. reaction is initiated by the added oil soluble polymn. initiator and, therefore, the styrene skeleton content in the binder in the surface layer part of the formed toner particles is higher than in the toner particle. The blocking resistance is improved in this way.

Description

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

[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 with toner, and if necessary, the toner image is transferred to a transfer member such as paper, and then heat, pressure, or solvent vapor is applied. etc. to obtain a copy. Furthermore, as a method for developing using toner or a method for fixing a toner image, various methods have been proposed in the past, and methods suitable for each image forming process have been adopted.

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

Although this manufacturing method can produce fairly good toners, it does have certain limitations, namely the range of choices of materials for the toner. It must be able to be pulverized. 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,
Care must be taken in dispersion, as this may cause increased fogging, decreased image density, and poor color mixing and transparency. 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, we have developed
No. 99 and No. 51-14895, etc., propose a toner production method using a suspension polymerization method. 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.) are unevenly distributed inside the particles and form a pseudo-capsule structure, so the toner obtained has excellent blocking resistance.

However, as copying machines have become more sophisticated in recent years, there has been a demand for toners with further improved blocking resistance.

[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 problems] The polymerized toner of the present invention was developed to solve the above-mentioned problems. A polymerized toner obtained by turbid polymerization, when the degree of polymerization of the polymerizable monomer in the polymerization process reaches 80% or more, the styrene concentration in the aqueous medium is reduced to 0. O1
This is achieved by adjusting the amount of melon to 0.05%, adding a water-soluble inorganic salt and an oil-soluble polymerization initiator to the aqueous medium, and polymerizing again.

The present invention will be described in detail below.

As a result of extensive studies, the present inventors have found that by increasing the content of styrene skeleton in the binder in the surface layer compared to the inside of the toner particles, the mechanical strength increases, and as a result, the blocking resistance of the toner increases. We focused on improving the

That is, the degree of polymerization of the polymerizable monomer in the polymerization process is 80%.
When the styrene concentration in the aqueous medium is reduced to 0.0
The amount is adjusted to 1 to 0.05% by weight, and styrene is precipitated by adding a water-soluble inorganic salt to the aqueous medium. The precipitated styrene gathers around the surface of the suspended particles and starts a polymerization reaction by the added oil-soluble polymerization initiator, so the styrene skeleton content in the binder on the surface layer of the toner particles is different from that inside the toner particles. The present invention was achieved based on the knowledge that

When the degree of polymerization of the polymerizable monomer during the polymerization process is less than 80%, the molecular weight of the binder resin is small and the molecular movement is active, so the precipitated styrene easily enters the inside of the suspended particles, and the binder in the surface layer is The styrene skeleton content is not high enough.

In addition, if the styrene concentration in the aqueous medium is 0.05% by weight or more, submicron-order fine powder is likely to be generated, and if it is 0.01% by weight or less, the styrene skeleton content in the binder in the surface layer will decrease. is not high enough, which is not desirable.

As the oil-soluble polymerization initiator to be added to the aqueous medium, any suitable polymerization initiator may be used, such as 2.2'azobis-(
2,4-dimethylvaleronitrile), 2'-azobisisobutyronitrile, 1. , l'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, and other azo-based or diazo-based compounds such as azobisisobutyronitrile (AIBN). System 1 polymerization initiators can be mentioned. The amount of these oil-soluble polymerization initiators is 1. OX
10-'~1. ．． o Xl0-2% by weight is preferred;
1. If OX is less than 10-3% by weight, the polymerization reaction of the precipitated styrene will not be carried out sufficiently, and if it is more than 1.0 x 1O-2% by weight, low molecular weight polystyrene will be produced and the expected effect will not be obtained.

As the water-soluble inorganic salt, any known water-soluble inorganic salt can be used, but sodium chloride is preferred from the viewpoint of cost and removal of the water-soluble inorganic salt in the post-treatment stage. The amount added is 1.0×to-' to 1.0×to-' to the aqueous medium. Ox 1
0-''% by weight is preferred, and if it is less than 1.OX 10-3% by weight, sufficient styrene precipitation will not occur and the expected effect will not be observed.

Also! , OX exceeding 10"" weight % is not suitable because the burden of removing the water-soluble inorganic salt increases.

The polymerized toner used in the present invention can be obtained by the following method. That is, a monomer system in which wax, colorant, polymerization initiator, and other additives are added to a polymerizable monomer and uniformly dissolved or dispersed using an ultrasonic disperser, homogenizer, etc., and a dispersion stabilizer is added. Aqueous medium (i.e. continuous phase)
The mixture is dispersed 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 almost 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. Polymerization temperature is 40
Polymerization is carried out at a temperature of 50 to 90° C. or higher.

When the degree of polymerization of the polymerizable monomer reaches 80% or more,
The styrene concentration in the aqueous medium is 0. O1~0.05% by weight
A water-soluble inorganic salt and an oil-soluble polymerization initiator are added to the aqueous phase.

After the reaction is complete, the generated toner particles are washed, collected by 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, diethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, Acrylic acid esters such as n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; Vinyl monomers include acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

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

Further, 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 suspended in an aqueous medium in which a dispersant having an opposite charge to the polar polymer is dispersed. It is preferable to make the mixture cloudy and polymerize it. 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 medium. Electrostatically attracts each other on the surface of the particles that become the toner, and the dispersant covers the particle surface, preventing the particles from coalescing and stabilizing them. At the same time, the polar polymer added during polymerization collects on the surface layer of the particles that become the toner. , it takes on a kind of shell-like form, 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 internal material improves fixing properties. By performing polymerization to contribute to
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 oppositely charged dispersants that can be used in the present invention are shown below.

(i) Examples of the cationic polymer include polymers of nitrogen-containing monomers such as dimethylamine ethyl methacrylate and diethylaminoethyl acrylate, or copolymers of styrene, unsaturated carboxylic acid esters, etc., and the nitrogen-containing monomers. .

(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 1
There are 120G, #3QQ, #38Q (manufactured by Nippon Aerosil Co., Ltd.), etc. (7)) Roidal silica.

(1v) As the cationic dispersant, aluminum oxide,
Examples include wood-philic positively chargeable silica fine powder such as aminoalkyl-modified colloidal silica. 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,
3 to 153i parts.

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

Further, a hydrocarbon compound may be added to the toner for the purpose of improving the release property during hot roll fixing.

The hydrocarbon compound that can be used in the present invention has a melting point of 55 to
Paraffin wax at 70°C is preferably used.

Examples of the polymerization initiator include the aforementioned azo or diazo polymerization initiators; benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate, kiemene hydroperoxide, 2,4-dichlorylbenzoyl peroxide, lauroyl peroxide. Examples include peroxide-based polymerization initiators such as. These polymerization initiators are generally about 0.0% by weight of the polymerizable monomer.
5-10% initiator is sufficient.

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 an amount of 5 to 20 percent.

The colorant used in the toner is preferably added to the suspension polymerized particle system, and all known colorants can be used, such as carbon black, iron black, nigrosine, benzidine yellow, quinacridone, rhodamine B, and phthalocyanine blue. be.

Further, in order to use the toner as a magnetic toner, magnetic powder may be included. As such magnetic powder, a substance that is magnetized when placed in a magnetic field is used, and includes powders of ferromagnetic metals such as iron, cobalt, and nickel, and compounds such as magnetite and ferrite. In particular, when using carbon black or magnetic powder, it is more preferable to perform a hydrophobic treatment.

The degree of polymerization was determined from the formula below.

In addition, before drying the sample, 1ffi amount % of polymerization inhibitor ME)IQ was added to the sample. Further, the degree of polymerization was determined using two significant figures.

[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 70°C in a container, dissolved or dispersed, and the monomer system was adjusted.

Separately, 10g of aminoalkyl-modified colloidal silica was added to 1200n+j of ion-exchanged water, and the above monomer composition was immersed in a dispersion medium system adjusted to pH 6 with hydrochloric acid, and heated to 70°C under a nitrogen atmosphere using a homomixer. 8.000rp
The monomer composition was granulated by stirring at m for 60 minutes. Thereafter, during the zero polymerization, which was carried out while maintaining the temperature at 70° C. and stirring with a paddle stirring blade, sampling was performed, and the degree of polymerization was appropriately measured by the measurement method described above, and changes in the degree of polymerization were followed. Six hours after the start of polymerization, when it was confirmed that the degree of polymerization exceeded 80%, the styrene concentration in the dispersion medium was adjusted to 0.04% by weight, and 5 g of sodium chloride and initiator V- 65 (manufactured by Wako Tsumugi Pharmaceutical Co., Ltd.) was added. Further stirring was continued using a paddle stirring blade to complete the polymerization.

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.

Example 2 150 parts of styrene was heated to 70°C using an ultrasonic disperser (RUS-300, manufactured by Nippon Seiki Seiki Co., Ltd., frequency 20kHz, output 30W)
) for 15 minutes, and the carbon black was hydrophobized.

Next, the monomer composition was added and stirred for 60 minutes at 8,000 rpm using a homomixer under a nitrogen atmosphere at 70°C to granulate the monomer composition. Thereafter, the temperature was maintained at 70°C and stirred with a paddle stirring blade, and it was confirmed that the degree of polymerization exceeded 85%.When 7 hours had passed after the start of polymerization, the styrene concentration in the dispersion medium system was reduced to 0.05% by weight. Sodium chloride 5g and initiator V-65 (Wako Tsumugi Co., Ltd.) 5g
g was added. Further stirring was continued using a paddle stirring blade to complete the polymerization. As a result of the measurement, the degree of polymerization was 92%. After that, the reaction product was cooled, sodium hydroxide was added to dissolve the dispersant, and the mixture was filtered.

A polymerized toner was obtained by washing with water and drying.

Example 3 was added, heated to 70°C, and dissolved or dispersed to adjust the monomer system.

Separately, in a dispersion medium system in which 10 g of aminoalkyl-modified colloidal silica was added to 1200 mJ of ion-exchanged water, the ingredients of the above single formulation were heated to 70°C in a container, and the mixture was heated to 70°C using an ultrasonic disperser (1
(0kHz, 200W) to form a monomer mixture. Initiator V-6 was further maintained at 70°C.
01 (Wako Tsumugi! 11) was added and dissolved to prepare a monomer composition.

Separately, add Aerosil #200 to 1200 mJ of ion exchange water.
(manufactured by Nippon Aerosil), further added 2 parts of sodium carbonate, heated to 70°C, and heated to 70°C using a homomixer M type (manufactured by Tokushu Kika Kogyo). Dispersion was performed for 15 minutes at OOOrpm.

Furthermore, add 2.2 parts of ^jz (504) s, and make 10
,000 rpm for 15 minutes to prepare a dispersion medium.

The above monomer composition was immersed in this, and the mixture was heated at 60°C under a nitrogen atmosphere.
At T, the monomer composition was granulated by stirring at 10,000 rpm for 60 minutes using a homomixer. then 60
℃ and stirred with a paddle stirring blade to confirm that the degree of polymerization exceeded 80%.After 6 hours had passed from the start of polymerization, the styrene concentration in the dispersion medium system was adjusted to 0.03% by weight. Then, 5 g of sodium chloride and 4 g of initiator v-65 (manufactured by Wako Tsumugi Pharmaceutical Co., Ltd.) were added. Further stirring was continued using a paddle stirring blade to complete the polymerization. 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 styrene concentration in the aqueous medium was not adjusted, and no inorganic salt and no polymerization initiator were added.

Comparative example 2 Adjustment of styrene concentration in the aqueous medium, inorganic salt.

A polymerized toner was obtained in the same manner as in Example 2 except that no polymerization initiator was added.

Comparative Example 3 A polymerized toner was obtained in the same manner as in Example 3, except that the styrene concentration in the aqueous medium was not adjusted and the inorganic salt and polymerization initiator were not added.

Table 1: Physical properties of polymerized toner As is clear from the above, the polymerized toner of the present invention has extremely excellent blocking resistance, and since the polymerization initiator added is oil-soluble, it has excellent environmental stability under high humidity conditions. is also excellent.

Claims (1)

[Claims] A polymerized toner obtained by suspension polymerizing a polymerizable monomer system in an aqueous medium, when the degree of polymerization of the polymerizable monomer in the polymerization process reaches 80% or more, styrene in the aqueous medium Adjust the concentration to 0.01 to 0.05% by weight,
A method for producing a polymerized toner, which comprises adding a water-soluble inorganic salt and an oil-soluble polymerization initiator to the aqueous medium and polymerizing again.