JPH05197209A - Magnetic particle - Google Patents

Abstract

PURPOSE:To provide a magnetic particle which is superior in the strength and electrification property and enables to provide an excellent image, when it is used for a developer, by manufacturing the magnetic particle by a suspension polymerization process from a composition containing a polymerizable monomer, an amino resin and magnetic powder. CONSTITUTION:The magnetic particle is manufactured from a composition containing the polymerized monomer, the amino resin and the magnetic powder by a suspension polymerization process, and the magnetic powder is dispersed into the resin particles. Here the content of the amino resin is preferably 0.05-5 pts.wt. for 100 pts.wt. polymerizable monomer and the content of the magnetic powder is preferably 50-300 pts.wt. for the total 100 pts.wt. of the polymerizable monomer and the amino resin. Since the magnetic particle is obtained by a suspension polymerization of the composition containing the polymerizable monomer and besides the amino resin, the electrification property is excellent and further, the amino resin is present more on the surface side than the central part of the magnetic particle, so the electrification property is imparted efficiently. Thus the exfoliation does not generate and the strength is sufficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic particles, and more particularly, it is used for developing an electrostatic latent image or a magnetic latent image in electrophotography, electrostatic recording, electrostatic printing and the like. Binder type carrier.

[0002]

2. Description of the Related Art Generally, in electrophotography or electrostatic recording, coloring is performed in order to develop an electrostatic latent image formed on a latent image carrier made of a photoconductive photoconductor or a dielectric. A two-component developer composed of fine powder toner and carrier is widely used.

As a carrier used in this two-component developer, a binder type carrier in which magnetic powder is dispersed in resin particles has been proposed in order to reduce the weight, reduce the particle size and improve the fluidity. .. As the binder resin, a styrene polymer or a styrene-acrylic copolymer is generally used.

[0004]

However, since the resin particles using the above-mentioned polymer as a binder resin have insufficient strength, when the magnetic particles are used as a carrier, they are not used in a copying machine. Carrier breaks during use and carrier jumps to the image. In addition, since the charging property is insufficient, when these magnetic particles are used as a carrier,
Toner scattering occurs during image formation.

The present invention is intended to solve the above problems, and an object thereof is to provide magnetic particles excellent in strength and chargeability.

[0006]

The magnetic particles of the present invention are produced by a suspension polymerization method comprising a composition containing a polymerizable monomer, an amino resin and magnetic powder. It is characterized in that they are dispersed, whereby the above-mentioned problems can be achieved.

Next, the invention will be described in detail.

The magnetic particles of the present invention are composed of resin particles and magnetic powder dispersed in the resin particles.

The polymerizable monomer used in the above resin particles is a radical polymerizable monomer, for example, styrenes such as styrene, chlorostyrene, alkylstyrene, vinylstyrene; ethylene, propylene, butylene, Mono-olefins such as isobutylene; vinyl acetate,
Vinyl esters such as propylene vinyl, vinyl benzoate and vinyl butyrate; methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, Α-Methylene aliphatic monocarboxylic acid esters such as dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether;
Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone are preferred. These compounds may be used alone or in combination of two or more.

The resin particles contain at least an amino resin. Examples of the amino resin include melamine resin, guanazine resin, urea resin and the like.

The content of the amino resin is preferably 0.05 to 5 parts by weight with respect to 100 parts by weight of the polymerizable monomer. When the content of the amino resin is less than 0.05 parts by weight, the magnetic particles obtained have insufficient functionality such as charging properties and strength. On the other hand, when the content of the amino resin is more than 5 parts by weight, the viscosity of the monomer composition increases and it becomes difficult to uniformly mix the monomer composition, so that the dispersion of the characteristics of the obtained magnetic particles increases. Magnetic particles cannot be obtained, or the particle size distribution of the obtained magnetic particles becomes broad.

The magnetic powder used in the present invention is a substance that is extremely strongly magnetized in that direction by a magnetic field, for example,
Metals such as iron, cobalt, nickel: Alloys or compounds containing ferromagnetism elements such as ferrite, magnetite, hematite, etc. such as ferrite, magnetite, hematite: Proper heat treatment without containing ferromagnetic elements An alloy exhibiting ferromagnetism, for example, manganese-
Heusler alloys containing manganese such as copper-aluminum or manganese-copper-tin and copper are listed.
These compounds may be used alone or in combination of two or more.

The content of the magnetic powder is 50 based on 100 parts by weight of the total amount of the polymerizable monomer and the amino resin.
˜300 parts by weight is preferred. When the content of the magnetic powder is less than 50 parts by weight, the magnetic attraction of the developing sleeve is weakened,
When magnetic particles are used as a developer carrier, carrier adhesion to the photoconductor and developer spillage from the developing machine are likely to occur. On the other hand, when the content of the magnetic powder exceeds 300 parts by weight, the binding effect of the resin cannot be sufficiently obtained, and the carrier may crack. In addition, the dispersion of the contained powder such as magnetic powder may be deteriorated, and a homogeneous resin may not be obtained.

The particle size of the magnetic powder is 0.01-5.
μm is preferred. If the particle size of the magnetic powder is less than 0.01 μm, the saturation magnetization may be reduced, or the viscosity of the composition may increase, so that a carrier having a uniform particle size may not be obtained.
On the other hand, if the particle size of the magnetic powder exceeds 5 μm, it may not be possible to obtain a homogeneous carrier. In addition, the magnetic powder may drop out of the droplet during suspension granulation.

The magnetic particles of the present invention can be produced by the suspension polymerization method shown below. That is, a composition containing the radically polymerizable monomer, the amino resin, the magnetic powder, and a polymerization initiator is dispersed in an aqueous medium and suspended and granulated. As the amino resin, resin particles that do not undergo a polymerization reaction or a resin having a polymerizable functional group is used.

As the above-mentioned polymerization initiator, radical polymerization initiators such as azo polymerization initiators and peroxide polymerization initiators are used.

The composition contains, in addition to the polymerizable monomer, the amino resin, the magnetic powder, a crosslinking agent, if necessary.
You may contain a coloring agent, a charge control agent, etc.

Examples of the cross-linking agent include divinyl compounds, diallyl compounds, triallyl compounds, diacrylate compounds, triacrylate compounds, dimethacrylate compounds and trimethacrylate compounds.

Examples of the colorant include carbon black, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green, lamp black and rose bengal. Is mentioned. These colorants may be used alone or in combination of two or more.

Examples of the charge control agent include Fett Schwartz HBN having a positive triboelectric charging property described in Japanese Patent Publication No. 41-2427, nigrosine soluble in alcohol, Sudan Chief Schwarz BB, Solvent Black 3, Brilliant. Examples thereof include Spirit Schwartz TN, Szavon Schwarz X, quaternary ammonium compounds, Ceres Schwarz (R) G, which has a negative triboelectric charging property, Chromogen Syubalz ETOO, Azo Oil Black (R), Spin Black and Pontron. These charge control agents may be used alone or in combination of two or more.

When the magnetic particles of the present invention are used as a one-component type developer for electrophotography, it is particularly effective to include the colorant and the charge control agent in the composition.

The above-mentioned granulation method is suspension granulation using stirring with a mixer or the like, and the temperature at this time is arbitrary, but it is preferable that the temperature is constant during granulation.

The aqueous solvent is usually water containing a small amount of suspension stabilizer, and a mixed solvent with alcohols and glycols may be used.

After suspension granulation, polymerization is carried out at the decomposition temperature of the polymerization initiator or higher. When an amino resin having a polymerizable functional group is used, it is preferable that the radical polymerizable monomer is polymerized and then the temperature is further raised to polymerize the amino resin having a polymerizable functional group.

In the above polymerization reaction, if necessary, a suspension stabilizer may be used. For example, an ionic surfactant,
Examples include nonionic surfactants and water-soluble polymers.

The magnetic particles of the present invention are particles containing the above-mentioned amino resin. The content of the magnetic particles is such that amino resin particles which do not undergo a polymerization reaction are dispersed or an amino resin having a polymerizable functional group is polymerized. Is what In the case of the latter magnetic particles, the polymer of the amino resin having the polymerizable functional group forms a crosslinked structure, and the polymer of the radical polymerizable monomer is entangled in the gap.
Since the amino resin has hydrophilicity, when it is produced by the suspension polymerization method, the amino resin moves to the vicinity of the surface of the monomer droplet during suspension granulation. There are many. By polymerizing such monomer droplets, it is possible to obtain magnetic particles in which the content of the amino resin is higher on the surface side than in the central portion.
Amino resins have a positive charge. Therefore, such magnetic particles are preferable because they can effectively impart the charging property. Magnetic particles whose surface is coated with an amino resin may cause separation between the central part and the surface vicinity part,
Magnetic particles in which the composition of the resin particles is continuously changed so that the content of the amino resin is higher on the surface side than in the central portion are more preferable, and peeling does not occur and the strength is sufficient. Become.

In the present invention, since the magnetic particles are produced by the suspension polymerization method, spherical magnetic particles can be obtained.

The magnetic particles of the present invention can be suitably used as a carrier for developing an electrostatic image, a toner, colored particles for an image forming apparatus and the like.

The particle size of the magnetic particles of the present invention is preferably 30 to 150 μm when used as a carrier, and 5 to 10 μm when used as a magnetic toner, and the shape thereof is preferably spherical.

[0030]

The magnetic particles of the present invention are obtained by suspension polymerization of a composition containing an amino resin in addition to a polymerizable monomer, so that the chargeability is good, and the amino resin is the core of the magnetic particles. Since it is more present on the surface side than the part, the charging property is effectively imparted. As described above, when the content of the mino resin is higher on the surface side than in the central portion and is continuous, peeling does not occur and the strength is sufficient. Therefore, for example, when the magnetic particles are used as a carrier, carrier scattering and toner scattering do not occur.

[0031]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples.

Example 1 Styrene 70 parts by weight Butyl methacrylate 20 parts by weight Divinylbenzene 2 parts by weight Diethylene glycol dimethacrylate 8 parts by weight Iron trioxide (BL-100 made by Titanium Industry) 100 parts by weight Iron trioxide (BL-200 titanium) Industrial) 100 parts by weight Titanate coupling agent (KR-TTS manufactured by Ajinomoto) 0.5 parts by weight 2,2′-azobis- (2,4-dimethylvaleronitrile) 6 parts by weight Amino resin powder 20 parts by weight The materials were mixed. Next, 40 parts by weight of tricalcium phosphate and 0.5 parts by weight of sodium dodecylbenzenesulfonate are dispersed in 600 parts by weight of distilled water, and the above mixture is added to this dispersion liquid to enhance the TK homomixer (manufactured by Tokushu Kika Kogyo). A suspension was obtained by stirring for 12 minutes at a rotation speed of 8000 rpm using a mixer with modified viscosity legs. The suspension was transferred to a separable flask, and the polymerization was completed by reacting for 5 hours while stirring at a temperature of 80 ° C. and a rotation speed of 250 rpm under a nitrogen atmosphere. Then, the polymer was filtered, washed with water, and dried to obtain binder type carrier particles having a center particle size of 100 μm.

Example 2 Styrene 70 parts by weight Butyl methacrylate 20 parts by weight Divinylbenzene 2 parts by weight Diethylene glycol dimethacrylate 8 parts by weight Iron trioxide (BL-100 manufactured by Titanium Industry) 100 parts by weight Iron tetraoxide (BL-200 titanium) Industrial) 100 parts by weight Titanate coupling agent (KR-TTS manufactured by Ajinomoto) 0.5 parts by weight 2,2′-azobis- (2,4-dimethylvaleronitrile) 6 parts by weight n-butylated melamine resin (21R Mitsui) Toatsu Chemical Co., Ltd.) 20 parts by weight The above compositions were mixed. Next, 40 parts by weight of tricalcium phosphate and 0.5 parts by weight of sodium dodecylbenzenesulfonate are dispersed in 600 parts by weight of distilled water, and the above mixture is added to this dispersion liquid to enhance the TK homomixer (manufactured by Tokushu Kika Kogyo). A suspension was obtained by stirring for 12 minutes at a rotation speed of 7,000 rpm using a mixer with modified viscosity legs. The suspension was transferred to a separable flask, and the polymerization was completed by reacting for 5 hours while stirring at a temperature of 80 ° C. and a rotation speed of 250 rpm under a nitrogen atmosphere. Then, the polymer is filtered, treated with dilute acid, washed with water,
Heat treatment was performed in an atmosphere of 150 ° C. to cause condensation and desolvation to obtain binder type carrier particles having a center particle size of 100 μm.

Comparative Example 1 Styrene 70 parts by weight Butyl methacrylate 20 parts by weight Divinylbenzene 2 parts by weight Diethylene glycol dimethacrylate 8 parts by weight Iron trioxide (BL-100 manufactured by Titanium Industry) 100 parts by weight Iron trioxide (BL-200 titanium) Industrial) 100 parts by weight Titanate coupling agent (KR-TTS manufactured by Ajinomoto) 0.5 parts by weight 2,2′-azobis- (2,4-dimethylvaleronitrile) 6 parts by weight The above compositions were mixed. Next, 40 parts by weight of tricalcium phosphate and 0.5 parts by weight of sodium dodecylbenzenesulfonate are dispersed in 600 parts by weight of distilled water, and the above mixture is added to this dispersion liquid to enhance the TK homomixer (manufactured by Tokushu Kika Kogyo). A suspension was obtained by stirring for 12 minutes at a rotation speed of 8000 rpm using a mixer with modified viscosity legs. The suspension was transferred to a separable flask, and the polymerization was completed by reacting for 5 hours while stirring at a temperature of 80 ° C. and a rotation speed of 250 rpm under a nitrogen atmosphere. Then, the polymer is filtered, treated with dilute acid, washed with water,
Heat treatment was performed in an atmosphere of 150 ° C. to cause condensation and desolvation to obtain binder type carrier particles having a center particle size of 100 μm.

Comparative Example 2 100 parts by weight of styrene-acrylic resin 100 parts by weight of iron trioxide (BL-100 manufactured by Titanium industry) 100 parts by weight of iron trioxide (100 parts by weight of BL-200 titanium industry) 100 parts by weight of amino resin powder 10 parts by weight or less The composition shown in (1) was mixed, melt-kneaded, and then pulverized and classified to obtain a binder type carrier having a center particle size of 100 μm.

100 parts by weight of the binder type carriers obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were mixed with 6 parts by weight of a toner for DC-2585 (manufactured by Mita Kogyo Co., Ltd.) to prepare a developer, and the charging was started. The characteristics were evaluated. Further, this developer was used and evaluated using a plain paper copying machine DC-2585 (manufactured by Mita Kogyo). The results are shown in Tables 1 and 2.

[0037]

[Table 1]

[0038]

[Table 2]

From Tables 1 and 2, it can be seen that the binder type carriers obtained in Examples 1 and 2 have sufficient strength and excellent chargeability, so that excellent images can be formed.

[0040]

As is clear from the above description, the magnetic particles of the present invention, which contain an amino resin, are excellent in strength and chargeability. Therefore, when the magnetic particles are used in a developer, they are good. Images can be provided.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masaya Shiozaki 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Industrial Co., Ltd. (72) Shinji Kikuta 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Within Kogyo Co., Ltd. (72) Inventor Kazuhisa Edahiro 1-22 Tamatsukuri Chuo-ku, Osaka Mita Kogyo Co., Ltd.

Claims (1)

[Claims] 1. Magnetic particles in which magnetic powder is dispersed in resin particles, which is produced by a suspension polymerization method from a composition containing a polymerizable monomer, an amino resin and magnetic powder.