JPH06102709A - Magnetic particle and its production - Google Patents

Abstract

PURPOSE:To obtain magnetic particles having good affinity to a binder resin, excellent heat resistance and wear resistance and suitable as a carrier by incorporating a magnetic powder and an amino resin powder bonded with high polymer chains on the surface. CONSTITUTION:This magnetic powder contains a magnetic powder and an amino resin powder bonded with high polymer chains on its surface. This magnetic powder is produced by treating the amino resin powder with a treating agent to introduce functional groups into the surface, and then allowing a polymn. initiator having functional groups to be bonded with the functional groups is allowed to react to bond the polymn. initiator to the surface of the amino resin powder. The treating agent has a halogenated acyl group and functional groups same as this halogenated acyl group or different from that in one molecule. A monomer phase containing this amino resin powder, magnetic powder and vinyl monomers is prepared and dispersed as liquid drops in a dispersion medium to effect polymn. The magnetic particles produced by this treating method have a small particle size with a narrow distribution of particle size, excellent heat resistance and wear resistance, and are hard and hardly cracked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier which constitutes a two-component developer together with a chargeable toner in an image forming apparatus utilizing an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like, The present invention relates to magnetic particles used not only as a magnetic toner as a one-component developer but also for magnetic displays and the like, and a method for producing the same by suspension polymerization.

[0002]

2. Description of the Related Art Heretofore, as the magnetic particles, ferrite particles whose surfaces are coated with a resin are generally used. However, when the above ferrite particles are used in an image forming apparatus as a carrier of a two-component developer, for example, it is the current situation that it is not possible to sufficiently meet the recent demand for higher image quality.

In a developing section of an image forming apparatus using a two-component developer composed of a carrier and a toner, the developer is first agitated and mixed to charge the toner, and the toner is attached around the carrier particles, and then the magnet is magnetized. A magnetic brush is formed by magnetically adhering a carrier to the surface of the developing sleeve containing the carrier. Then, when the magnetic brush is brought close to or in contact with the surface of the photoconductor on which the electrostatic latent image is formed, the toner in the magnetic brush electrostatically adheres to the electrostatic latent image, and the electrostatic latent image is formed. The toner image is visualized.

However, when ferrite particles are used as the carrier, due to the weight of the ferrite particles, the magnetic brush greatly expands due to the centrifugal force generated when the developing sleeve rotates, and the surface of the photoconductor is damaged by inertial force. The toner electrostatically adhered to the surface of the photoconductor is scraped off or the adhering position is shifted to deteriorate the quality of the formed image.

Another cause of deterioration in the quality of the formed image is that it is difficult to reduce the particle size because the carrier composed of the above-mentioned ferrite particles is manufactured by sintering ferrite powder, and that the carrier has a perfect spherical shape. There is also the fact that it is not possible to form it and the fluidity is poor. Therefore, in recent years, in order to solve the problems of the carrier made of the ferrite particles and to improve the quality of the formed image, a lightweight carrier in which magnetic powder is dispersed in the particles made of a binder resin, that is, a so-called binder type carrier is used. Research and development on carriers are being actively conducted.

Since this binder type carrier is lighter than the ferrite particles, the magnetic brush does not greatly expand due to centrifugal force, and the inertial force is small, so that the surface of the photoconductor is damaged or the surface of the photoconductor is static. It does not scrape off the toner that has been electro-deposited or shift the attachment position. The binder type carrier can also be produced by melt-kneading a binder resin such as styrene-acrylic resin, magnetic powder such as ferrite powder and other additives, and then pulverizing and classifying. However, such a pulverized type carrier has a problem that the particle size distribution is wide, the particle size is large, and the carrier is not completely spherical.

Therefore, it has been studied to produce the above binder type carrier by utilizing the suspension polymerization method. This method is a radical polymerizable vinyl monomer that is the basis of the binder resin, and a liquid monomer phase containing magnetic powder and other additives is heated while being dispersed in a dispersion medium in a droplet form, It is a method of polymerizing a vinyl monomer. The binder type carrier obtained by such a method has a narrow particle size distribution,
In addition, since it is possible to reduce the particle size and to obtain a particle close to a perfect sphere, it is possible to improve the quality of the formed image as compared with the case where a carrier made of ferrite particles is used.

[0008]

It is preferable to disperse the amino resin powder in the binder type carrier in order to improve the charging property of the magnetic particles. Amino resins are curable resins (amino resins) such as melamine resins, urea resins, guanamine resins and their derivatives, which have a higher hydrophilicity than the vinyl monomer that is the raw material of the binder resin, When the carrier is manufactured by the legal method, the binder-type carrier thus formed can be effectively imparted with the charging property, because the carrier collects in the vicinity of the surface of the droplet of the monomer phase in contact with water as the dispersion medium. Further, since the amino resin powder has high hardness, there is an advantage that the wear resistance of the binder type carrier can be improved.

However, since the amino resin powder has a high hydrophilicity, the binding property with the binder resin is poor, and moreover, as described above, a large amount is present in the vicinity of the surface of the carrier, so that carrier cracking occurs at the interface between the two. There is also a problem that the amino resin powder falls off from the carrier particles. Since the amino resin powder that has fallen off the carrier particles has a high chargeability, if this amino resin powder behaves arbitrarily in the developing section of the image forming apparatus, the charging characteristics and fluidity of the developer will deteriorate, and the toner will be poorly charged. Also, the fragments of the binder resin generated when the carrier is cracked or the carrier particles themselves may contaminate the photosensitive drum and the formed image.

The present invention has been made in view of the above circumstances, and has good dispersibility of amino resin powder, dispersion stability, good affinity with a binder resin, a small particle size and a wide particle size distribution. The object is to provide magnetic particles which are narrow and have excellent heat resistance, abrasion resistance, etc., and which are hard and difficult to break, and which can be suitably used for carriers and the like, and a production method by the polymerization method.

[0011]

Means and Actions for Solving the Problems The magnetic particles of the present invention for solving the above problems are characterized by containing magnetic powder and amino resin powder having a polymer chain bonded to the surface thereof. Further, the method for producing magnetic particles of the present invention comprises treating the surface of an amino resin powder by treating an amino resin powder with a treating agent having an acyl halide group and a functional group which is the same as or different from the acyl halide group in one molecule. Introducing a functional group, reacting a polymerization initiator having a functional group that binds to this functional group, after binding the polymerization initiator to the surface of the amino resin powder, the amino resin powder, and a magnetic powder, It is characterized in that a monomer phase containing a vinyl monomer is polymerized while being dispersed in a dispersion medium in the form of droplets.

In the present invention having the above constitution, when the amino resin powder is treated with a treating agent having an acyl halide group and a functional group which is the same as or different from the acyl halide group, the hydrophilicity of the surface of the amino resin powder is obtained. Since the functional group (hydroxyl group, amino group, aldehyde group, etc.) reacts with the acyl halide group of the treatment agent to make the amino resin powder hydrophobic, the dispersibility and dispersion stability of the amino resin powder in the monomer phase. Is improved. Further, the functional group of the treating agent introduced on the surface of the amino resin powder is bound with a polymerization initiator in the subsequent step and further bound with a polymerizable monomer in the suspension polymerization step to form a graft chain. , Grafting the amino resin powder.

Therefore, according to the present invention, the dispersibility of the amino resin powder, the dispersion stability, and the affinity with the binder resin are improved, so that the magnetic particles produced may be cracked or the amino resin powder may fall off. Is prevented. The grafting reaction proceeds between the amino resin powder having the polymerization initiator introduced on the surface by the two-step treatment and the polymerizable vinyl monomer, and therefore the grafting rate is extremely high.
Further, the treatment agent used for the treatment of the amino resin powder has a polymerization initiator bound to a functional group in a subsequent step even if an excess amount is generated, and further, a monomer is polymerized in a suspension polymerization step to enhance the polymerization. Since it is made into a molecule, it does not exist in the magnetic particles with a low molecular weight. Therefore, the produced magnetic particles are excellent in heat resistance, wear resistance, etc., and are hard and hard to break.

In addition, as described above, since no polymer is generated in the preceding step up to the suspension polymerization step, the viscosity of the monomer phase used for suspension polymerization is low and the viscosity is low in the dispersion medium. It becomes easy to disperse in a drop shape. Therefore, the produced magnetic particles have a small particle size and a narrow particle size distribution,
The particle size will be uniform. The present invention will be described below according to the steps of the manufacturing method.

First, the amino resin powder is treated with the above treating agent to introduce a functional group into the surface of the amino resin powder. As the treating agent used for treating the amino resin powder, various compounds having an acyl halide group and a functional group which is the same as or different from the acyl halide group in one molecule can be used.

Various groups can be considered as the functional group,
Considering that it has no reactivity with an acyl halide group and has a good reactivity with another functional group, the same acyl halide group is preferable as the functional group. Therefore, as the above-mentioned treating agent, a compound having two or more acyl halide groups in one molecule is preferably used. 2 in 1 molecule
As the compound having one or more acyl halide groups,
Examples include halides of divalent acyl compounds such as malonic acid dichloride, succinic acid dichloride, glutaric acid dichloride, adipic acid dichloride, pimelic acid dichloride, suberic acid dichloride, azelaic acid dichloride, sebacic acid dichloride, and phthalic acid dichloride. To be

To treat the amino resin powder with a treating agent having an acyl halide group, a solvent such as chloroform is used.
Both may be reacted in the presence of pyridine. The amount of the treating agent used is not particularly limited, but the amino resin powder 100
The amount is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on parts by weight.

When the amount of the treating agent used is less than the above range, the amino resin powder is not sufficiently hydrophobized and the dispersibility,
In addition to the possibility that the dispersion stability may decrease, because the grafting rate decreases, the affinity with the binder resin deteriorates and cracks and the amino resin powder fall off, or the grafting rate decreases, There is a possibility that heat resistance, abrasion resistance, etc. may deteriorate, and that the magnetic particles may become soft and easily crack.

On the other hand, when the amount of the treating agent used exceeds the above range, the treating agent itself shows a considerable hydrophilic property.
Not only the moisture resistance and chargeability of the magnetic particles are impaired, but a large amount of free processing agent that does not bind to the amino resin powder remains in the particles, so a large amount of polymerization initiator is required to react with this. . In that case, since the molecular weight of the binder resin becomes small, the magnetic particles become soft,
Durability when used as a carrier or magnetic toner may be impaired.

The treating agents may be used alone or in combination of two or more. Examples of the amino resin powder treated with the treating agent include melamine resin, urea resin, guanamine resin and derivatives thereof. The particle size of the amino resin powder is not particularly limited, but is preferably about 0.01 to 5 μm. If the particle size of the amino resin powder is less than the above range, the viscosity of the monomer layer increases, so that the particle size of the suspension of the monomer layer, and hence the particle size of the magnetic particles, cannot be reduced, and the particle size distribution becomes wider, resulting in a particle size distribution. There is a possibility that magnetic particles with uniform distribution may not be obtained. Further, since the surface area of the amino resin powder becomes too large, a large amount of a treating agent and a polymerization initiator that binds to the treating agent are required, which may impair the moisture resistance, chargeability (distribution amount) and durability of the magnetic particles. . Further, if the particle size of the amino resin powder exceeds the above range, the dispersibility and the dispersion stability may be reduced even if the treatment is performed with a treating agent, and the grafting rate is reduced. Affinity deteriorates, causing cracking and dropping of amino resin powder,
Alternatively, there is a possibility that heat resistance, abrasion resistance, etc. may be deteriorated and the magnetic particles may be soft and easily cracked as the grafting ratio decreases.

Next, a polymerization initiator having a functional group capable of binding to the functional group of the treatment agent introduced on the surface of the amino resin powder is added to the above treatment liquid, whereby the functional group introduced on the surface of the amino resin powder is added. And the functional group of the polymerization initiator are bonded,
The polymerization initiator is bonded to the surface of the amino resin powder via the treating agent. As the polymerization initiator, various compounds containing a functional group capable of binding to the functional group of the treating agent in one molecule and a portion of the polymerization initiator can be used.

When the functional group capable of binding to the functional group of the treating agent is an acyl halide group as described above, the functional group on the polymerization initiator side is the above-mentioned acyl halide group and a relatively low temperature of about room temperature. Secondary amines and the like capable of binding under the conditions of are preferred. The secondary amine is preferably a 5-membered ring such as an imidazoline ring, a 6-membered ring such as a pyrimidine ring or a 7-membered ring such as a diazepine ring having two nitrogen atoms in the ring.
Further, as a part of the polymerization initiator, an azo group or the like which does not react with the above secondary amine at room temperature and generates a radical by heating or the like to start the polymerization reaction of the polymerizable vinyl monomer Is preferred.

Specific examples of the above-mentioned polymerization initiator include, for example, 2,2'-azobis [2- (2-imidazoline-2-
Yl) propane], 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane], 2,
2'-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane], 2,2'-azobis [2- (5-hydroxy-3,4,5,6-tetrahydropyrimidine] -2-yl) propane], 2,2'-azobis [2- (4,5,6,7-tetrahydro-1H-
1,3-diazepin-2-yl) propane] and the like.

The amount of the polymerization initiator used is not particularly limited, but it is desirable to set the amount used so that the functional group equivalent of the polymerization initiator is equal to or more than the functional group equivalent of the treating agent.
When the functional group equivalent of the polymerization initiator is less than the functional group equivalent of the treating agent, the treating agent to which the polymerization initiator is not bonded remains on the surface of the amino resin powder, and the amino group is treated by the functional group. The powder exhibits hydrophilicity and may adversely affect the weather resistance, especially the moisture resistance, of the magnetic particles to be produced, and an excessive amount of the treatment agent not bonded to the surface of the amino resin powder,
The polymer may not be polymerized by the polymerization initiator and may remain in the magnetic particles with a low molecular weight, resulting in deterioration of heat resistance, abrasion resistance, etc., or the magnetic particles may be soft and easily cracked.

The polymerization initiator may be used alone, or
Two or more kinds can be used in combination. After the above treatment, in the production method of the present invention, the treated amino resin powder is mixed with magnetic powder, vinyl monomer or the like to prepare a monomer phase for suspension polymerization. Then, the monomer phase is polymerized while being dispersed in a suitable dispersion medium in the form of droplets, whereby the magnetic particles of the present invention are produced.

When the polymerization initiator bound to the surface of the amino resin powder is cut by heat or the like, free radicals are generated in both the portion remaining on the amino resin powder side and the portion separated from the amino resin powder. Therefore, it is not necessary to intentionally add a polymerization initiator to the above-mentioned monomer phase. However, in order to ensure the formation of the binder resin and to control the molecular weight of the formed binder resin, a polymerization initiator may be supplementarily added.

As the magnetic powder, a metal exhibiting ferromagnetism and its
Alloys, various ferrites, or elements that exhibit ferromagnetism
Although it does not contain, it can be made to have ferromagnetism by appropriate heat treatment.
All known magnetic materials such as the alloys shown
Powders of can be used. As a metal that exhibits ferromagnetism
Include iron, cobalt, nickel, etc.
It is also possible to use alloys containing these metals
It Examples of ferrite include ferrosoferric oxide (Fe₃O
_Four), Ferric oxide (γ-Fe₂O₃), Zinc oxide (ZnFe
₂O_Four), Yttrium iron oxide (Y₃Fe_FiveO₁₂), Oxidation
Iron cadmium (CdFe₂O_Four), Iron gadolinium oxide (Gd
₃Fe_FiveO_Four), Iron oxide copper (CuFe₂O_Four), Iron oxide lead (Pb
Fe₁₂O₁₉), Iron oxide neodymium (NdFeO₃), Iron oxide burr
Um (BaFe ₁₂O₁₉), Magnesium iron oxide (MgFe
₂O_Four), Iron manganese oxide (MnFe₂O_Four), Iron oxide orchid
Tan (LaFeO₃) Etc. Also by heat treatment
An alloy exhibiting ferromagnetism is, for example, manganese-copper-acetate.
Manganese and copper, such as luminium and manganese-copper-tin
And Heusler alloys containing These are just
Besides being used alone, two or more kinds can be used in combination.

The particle size of the magnetic powder is not particularly limited, and it is preferably about the same as that used for an ordinary binder type carrier, that is, about 0.01 to 5 μm. If the particle size of the magnetic powder is less than the above range, the saturation magnetization may be lowered, or the viscosity of the monomer phase may increase, so that it is not possible to obtain magnetic particles having a minute and uniform particle size. If the particle size of the magnetic powder exceeds the above range, it may not be possible to obtain magnetic particles having uniform magnetic properties.

The magnetic powder contains a titanate coupling agent, a silane coupling agent, an aluminum coupling agent, etc. in order to improve the dispersibility and dispersion stability in the toner phase and the affinity for the binder resin. It is preferable to treat the surface with a coupling agent to make the surface hydrophobic. Examples of vinyl monomers include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, monoolefin monomers, halogenated monomers. Various conventionally known vinyl monomers such as olefin monomers and polyvinyl monomers can be used.

As the monovinyl aromatic monomer, the following general formula (1):

[0031]

[Chemical 1]

[Wherein R ² represents a hydrogen atom, a lower alkyl group or a halogen atom, and R ³ represents a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group, a vinyl group, a sulfo group, or sodium. Indicates a sulfonate group, a potassium sulfonate group, or a carboxyl group. ), For example, styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o, m, p
-Chlorostyrene, p-ethylstyrene, sodium styrenesulfonate, etc. may be mentioned.

The acrylic monomer has the following general formula:
(2):

[0034]

[Chemical 2]

[In the formula, R ⁴ represents a hydrogen atom or a lower alkyl group, and R ⁵ represents a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, a vinyl ester group or an aminoalkyl group. ) A compound represented by, for example, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, acrylonitrile, methyl methacrylate, Butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, β-hydroxy acrylate, γ-hydroxy acrylate, δ-hydroxy butyl acrylate, β-hydroxy methacrylate, γ-amino propyl acrylate, Examples include γ-N, N-diethylaminoacrylic acid propyl ester, ethylene glycol dimethacrylic acid ester, and tetraethylene glycol dimethacrylic acid ester.

Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate and the like. Examples of vinyl ether-based monomers include vinyl methyl ether, vinyl ethyl ether, vinyl-n-butyl ether, vinyl phenyl ether, vinyl cyclohexel ether and the like.

Examples of the diolefin-based monomer include butadiene, isoprene, chloroprene and the like. Examples of the monoolefin-based monomer include ethylene, propylene, butene-1, pentene-1,4-methylpentene-1 and the like. Examples of the halogenated olefin-based monomer include vinyl chloride and vinylidene chloride.

Further, examples of the polyvinyl monomer include divinylbenzene, diallyl phthalate and tricyanurate. These can be used alone or in combination of two or more. For example, when magnetic particles containing the most common styrene-acrylic binder resin are produced, styrene and an acrylic monomer may be used in combination as the vinyl monomer.

The mixing ratio of the vinyl monomer and the amino resin powder having a polymerization initiator bonded on the surface is such that the amino resin powder is 0.05 to 100 parts by weight based on the total amount of the vinyl monomer.
It is preferably blended in a ratio of 5 parts by weight. If the blending amount of the amino resin powder is less than the above range, the effect of improving the charging characteristics and wear resistance of the magnetic particles may be insufficient, and conversely if the blending amount of the amino resin powder exceeds the above range. In addition, the viscosity of the monomer phase may increase, and it may not be possible to obtain fine magnetic particles having a uniform particle size, and it may be impossible to obtain magnetic particles having a uniform charging characteristic.

The mixing ratio of the magnetic powder varies depending on the use of the magnetic particles, but in the case of a binder type carrier, 100 to 250 parts by weight of the magnetic powder is added to 100 parts by weight of the total amount of vinyl monomer. It is preferable that the amount is 150 to 200 parts by weight. The auxiliary polymerization initiator is preferably one that is insoluble in the dispersion medium and compatible with the vinyl monomer, such as azobisisobutyronitrile or 2,2'-azobis- (2 ，
4-dimethylvaleronitrile), 2,2'-azobis-
(4-methoxy-2,4-dimethylvaleronitrile),
2,2'-azobis- (2-cyclopropylpropionitrile), 2,2'-azobis- (2-methylpropionitrile), 2,2'-azobis- (2-methylbutyronitrile), 1 , 1'-azobis- (cyclohexane-
1-carbonitrile), 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, dimethyl-2,
Azo compounds such as 2'-azobis (2-methylpropionate); cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, benzoyl peroxide, lauroyl peroxide and other peroxides In addition to the above, a conventionally known photopolymerization initiator can be used when the polymerization is carried out by irradiation with ultraviolet rays or visible rays. These are used alone,
Two or more kinds can be used in combination.

The amount of the polymerization initiator used is 10
The amount is 0.001 to 10 parts by weight, preferably 0.01 to 6 parts by weight, based on 0 parts by weight. It is also possible to initiate the polymerization using γ-rays, accelerated electron beams, etc. In this case, it is not necessary to use a polymerization initiator. Further, the polymerization may be initiated by combining ultraviolet rays and various photosensitizers.

If necessary, in addition to the above components,
Various additives, such as a charge control agent, an offset preventing agent (release agent), and a cross-linking agent, may be added. The charge control agent is blended when the magnetic particles are used as a carrier of a two-component developer or a magnetic toner as a one-component developer. Depending on the charging polarity, the charge control agent can be used for positive charge control or negative charge control. There are two types of charge control agents.

As the charge control agent for controlling the positive charge, an organic compound having a basic nitrogen atom such as a basic dye, an aminopyrine, a pyrimidine compound, a polynuclear polyamino compound, an aminosilane, or the like, and each of the above compounds are surface-treated. Examples include fillers. Examples of the charge control agent for controlling the negative charge include oil-soluble dyes such as nigrosine base (CI5045), oil black (CI26150), Bontron S, and Spiron Black; charge control resins such as styrene-styrene sulfonic acid copolymers; Examples thereof include compounds having a carboxy group (for example, metal chelate of alkylsalicylic acid), metal complex dyes, fatty acid metal soaps, resin acid soaps, naphthenic acid metal salts and the like.

The charge control agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the vinyl monomer. The offset preventing agent is for preventing aggregation of magnetic particles, and examples thereof include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. Among them, the weight average molecular weight is 1000-
About 10,000 aliphatic hydrocarbons are preferred. Specifically, one or a combination of two or more of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, a low molecular weight olefin polymer composed of olefin units having 4 or more carbon atoms, silicone oil and the like is suitable.

The anti-offset agent is a vinyl monomer 100.
0.1 to 10 parts by weight, preferably 0.5
Used at a rate of ~ 8 parts by weight. The cross-linking agent cross-links the graft chains of the binder resin or the amino resin powder to improve the mechanical or thermal properties of the magnetic particles, and to further strongly integrate the amino resin powder and the binder resin. And a divinyl compound such as divinylbenzene; diallyl phthalate, diallyl isophthalate, diallyl adipate, diallyl glycolate, diallyl maleate, diallyl sebacate and the like; triallyl phosphate, triallyl aconitate, Triallyl compounds such as triallyl cyanurate, allyl ester of trimellitic acid, allyl ester of pyromellitic acid; 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol diacrylate, diethylene glycol diac Rate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, butylene glycol diacrylate, pentaerythritol diacrylate, 1,4-butanediol diacrylate, and other diacrylate compounds; trimethylolpropane triacrylate, pentaerythritol triacrylate, and other triacrylates Compounds; Dimethacrylate compounds such as 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, butylene glycol dimethacrylate; trimethylolpropane tri Methacrylate, etc. Trimethacrylate compounds; poly (meth) acrylate compounds such as dipentaerythritol hexaacrylate, tetramethylolmethane tetraacrylate, acrylic acid esters of N, N, N ', N'-tetrakis (β-hydroxyethyl) ethylenediamine; allyl acrylate, Allyl-acrylic compounds such as allyl methacrylate; acrylamide compounds such as N, N'-methylenebisacrylamide, N, N'-methylenebismethacrylamide; prepolymers such as polyurethane acrylate, epoxy acrylate, polyether acrylate, polyester acrylate, etc. Can be given.

The crosslinking agent is used in an amount of 0 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the vinyl monomer. When the magnetic particles of the present invention are used as a carrier, the crosslinking agent may be blended in a higher proportion. When the magnetic particles of the present invention are used as a magnetic toner, a colorant may be further added. As the colorant, various conventionally known colorants such as carbon black, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green, and rose bengal are used. Can be used. The colorant is used in an amount of 1 to 15 parts by weight, preferably 5 to 10 parts by weight, based on 100 parts by weight of the vinyl monomer.

The dispersion medium in which the monomer phase composed of each of the above components is dispersed does not dissolve the raw material components such as vinyl monomers and the magnetic particles after polymerization at all, or hardly dissolves them, and is an inert solvent. Is used. Suitable dispersion media include, for example, water or water-based solvents. In order to obtain a good dispersion state, it is preferable to add a suspension stabilizer to the dispersion medium.

As the suspension stabilizer, various conventionally known suspension stabilizers can be used, but the desired particle size of the magnetic particles is
Considering that the carrier has a particle size of 50 to 70 μm or less and the magnetic toner has a particle size of 5 to 10 μm or less, it is necessary to have an excellent suspending and dispersing ability, and in order not to affect the characteristics of the magnetic particles after production. Must be easy to remove from the magnetic particles. Examples of suspension stabilizers preferably used in the present invention which satisfy the above requirements include a combination of a calcium phosphate such as tricalcium phosphate and sodium dodecylbenzenesulfonate.

A monomer phase containing each of the above components is added to the above dispersion medium, and, for example, 10 ² to 10 ⁸ dynes / cm.
When the mixture is stirred with a shearing force of a certain degree, the monomer phase is suspended in the dispersion medium and granulated into a spherical shape. In this state, -30 to 90
When the polymerization is carried out at a temperature of 30 ° C., particularly 30 to 80 ° C. for about 0.1 to 50 hours, the vinyl monomer is polymerized to obtain spherical magnetic particles. At this time, it is preferable to replace the inside of the reaction system with an inert gas in order to suppress the termination reaction of the polymerization due to oxygen. In order to obtain a high-resolution image, the magnetic particles thus obtained have a volume average particle size of 50 to 70 μm or less in the case of a carrier and 5 to 1 in the case of a magnetic toner as described above.
It is preferably 0 μm or less.

According to the above-mentioned production method of the present invention, since each component contained in the monomer phase has a low molecular weight, the monomer phase has a low viscosity and can be easily dispersed in a dispersion medium in a droplet form. is there. Therefore, in the case of carrier, 50 to 70
It is possible to produce magnetic particles having a uniform particle size of less than μm, 5 to 10 μm in the case of a magnetic toner, and having an extremely narrow particle size distribution.

Since the amino resin powder is hydrophobized by the treatment agent and the polymerization initiator, it has excellent dispersibility and dispersion stability when dispersed in the monomer phase.
Since it does not re-aggregate, it is almost uniformly dispersed in the produced magnetic particles, and the magnetic particles have excellent charging characteristics. Further, during the polymerization reaction, the vinyl monomer is polymerized and highly efficiently grafted to the polymerization initiator on the surface of the amino resin powder, so that the polymer grafted on the amino resin powder and the binder resin of the magnetic particles are The amino resin powder and the binder resin are integrated into a state where they are mixed almost uniformly in the magnetic particles. For this reason, there is no risk of cracks occurring at the interface between the two and the amino resin powder falling off from the magnetic particles, and the manufactured magnetic particles have excellent durability.

Moreover, in the above reaction process, a low molecular weight polymer and unreacted components which deteriorate the physical properties of the magnetic particles are hardly formed, so that the magnetic particles are excellent in heat resistance and abrasion resistance and hard. And it becomes difficult to break. As described above, the magnetic particles of the present invention can be used as a carrier that constitutes a two-component developer together with a chargeable toner, and also can be used as a magnetic toner as a one-component developer or in various magnetic displays. Can be used in the field of.

[0053]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Example 1 20 parts by weight of a pulverized powder of benzoguanamine resin (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) (volume-based median diameter of 3.2 μm), 0.2 part by weight of adipic dichloride as a treating agent, and 5 parts by weight of pyridine. Parts were added to 60 parts by weight of chloroform, heated to 55 ° C., stirred for 5 minutes, mixed, and processed.

Next, the above treatment liquid was cooled to 30 ° C., and 0.3 part by weight of 2,2′-azobis [2- (2-imidazolin-2-yl) propane] as a polymerization initiator was added,
After further stirring and mixing for 5 minutes and treating, chloroform was removed by a reduced pressure drying method to recover the treated benzoguanamine resin powder. Next, 20.5 parts by weight of the above benzoguanamine resin powder was mixed with each component shown below to prepare a paste-like monomer phase.

Component parts by weight Magnetic powder: triiron tetraoxide powder (product number BL-100 manufactured by Titanium Industry Co., Ltd.) 100 ferric oxide powder (product number BL-200 manufactured by Titanium Industry Co., Ltd.) 100 titanate coupling agent (Product number KR-TTS manufactured by Ajinomoto Co., Inc.) 0.5-Vinyl monomer: Styrene 70 Butyl methacrylate 20-Crosslinking agent: divinylbenzene 2 Diethylene glycol dimethacrylate 8-Polymerization initiator: 2,2'-azobis- (2 4-dimethylvaleronitrile) 6 Next, after dissolving 40 parts by weight of tricalcium phosphate as a suspension stabilizer and 0.5 part by weight of sodium dodecylbenzenesulfonate in 600 parts by weight of distilled water as a dispersion medium, The above monomer phase was added, and the mixture was stirred using a mixer with modified high viscosity legs of TK Homo Mixer (made by Tokushu Kika Kogyo Co., Ltd.). Suspended and stirred for 12 minutes by the number 7000～8500R.Pm, the monomer phase was liquid droplets.

Next, this suspension was transferred into a separable flask and heated at 80 ° C. under nitrogen atmosphere with stirring at a rotation speed of 250 rpm to carry out a polymerization reaction for 5 hours. Then, the polymer particles were separated by filtration, washed with dilute acid, washed with water and dried to obtain magnetic particles. Example 2 n-butylated melamine resin (product number 2 manufactured by Mitsui Toatsu Chemicals, Inc.
1R) pulverized powder (volume-based median diameter 2.6 μm)
20 parts by weight, 0.25 parts by weight of phthalic acid dichloride as a treating agent, and 5 parts by weight of pyridine were added to 60 parts by weight of chloroform, heated to 50 ° C., stirred for 5 minutes and mixed for treatment. did.

Next, the above treatment liquid was cooled to 25 ° C., and 2,2′-azobis [2- (3,4, as a polymerization initiator was used.
5,6-Tetrahydropyrimidin-2-yl) propane] 0.35 part by weight was added, and the mixture was stirred for 5 minutes, mixed and treated, and then treated with n-butylation by removing chloroform by a vacuum drying method. The melamine resin powder was recovered.

Magnetic particles were obtained in the same manner as in Example 1 except that 20.5 parts by weight of the n-butylated melamine resin powder was used in place of the benzoguanamine resin powder. Comparative Example 1 Magnetic particles were obtained in the same manner as in Example 1 except that the benzoguanamine resin powder was not added.

Comparative Example 2 Benzoguanamine resin powder 20.5 not treated with adipic dichloride as a treating agent and 2,2'-azobis [2- (2-imidazolin-2-yl) propane] as a polymerization initiator Other than using parts by weight,
Magnetic particles were obtained in the same manner as in Example 1.

The following tests were conducted on the above Examples and Comparative Examples to evaluate the characteristics. Average particle size measurement The volume-based median diameter D ₅₀ of the particle size distribution of the magnetic particles produced in each Example and Comparative Example was measured using a laser diffraction particle size measuring device (Model No. LA-700 manufactured by Horiba Ltd.). To obtain the average particle size. Also, 25% residual diameter D ₂₅ and 75
The ratio D ₂₅ / D ₇₅ to the% residual diameter D ₇₅ was determined to evaluate the width of the particle size distribution. The results are shown in Table 1.

[0061]

[Table 1]

From the results shown in Table 1 above, the magnetic particles of Examples 1 and 2 have a D _{50 value} higher than that of the magnetic particles of Comparative Examples 1 and 2.
It was found that the average particle size is small due to the small particle size, and the D ₂₅ / D ₇₅ is small, so that the width of the particle size distribution is narrow and the particle size is uniform. From this fact, it was confirmed that according to the production method of the present invention, the viscosity of the monomer phase can be lowered, and therefore the monomer phase can be easily dispersed in the dispersion medium as fine droplets.

Practical Test Using the magnetic particles produced in each of the Examples and Comparative Examples as a carrier, a toner having an average particle size of 10 μm (for DC2585 manufactured by Mita Industry Co., Ltd.) and a toner concentration of 8% were used. A two-component developer was prepared by blending, and the following measurements were performed to evaluate the characteristics.

Image Density Measurement Each developer was treated with a plain paper copying machine (model No. D) manufactured by Mita Industry Co., Ltd.
C2585) as a starting developer, and using the same toner used as the developer as a replenishing toner, continuous copying of 30,000 black and white originals was performed.
The image density of the first image formed (initial), the 20,000th image, the 24,000th image, and the 30,000th image formed was measured using a reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.). Measured.

Measurement of Fog Density The density of the blank area of the first image (the initial stage), the 20,000th sheet, the 24,000th sheet, and the 30,000th sheet of the above image formed was measured using the reflection densitometer. did. Blow-off charge amount measurement The charge amount of the developer before continuous copying (initial stage) of 30,000 sheets, after copying 20,000 sheets, after copying 24,000 sheets and after copying 30,000 sheets was measured by blow-off charging manufactured by Toshiba Chemical Co. It measured using the quantity measuring device.

The image density measurement results are shown in Table 2, the fog density measurement results are shown in Table 3, and the blow-off charge amount measurement results are shown in Table 4.

[0067]

[Table 2]

[0068]

[Table 3]

[0069]

[Table 4]

From the results of the above tables, the developer containing the magnetic particles of Comparative Example 1 as a carrier does not contain the amino resin powder, so that the blow-off charge amount at the initial stage is low and the fog density is high. In addition, the image density decreased as the number of copies increased, the fog density further increased, and the blow-off charge amount further decreased. Observation of the formed image revealed that the 20,000th image had fogging over the entire surface, and the 24,000th image had fogging over the entire surface, and many white streaks occurred. Therefore, when continuous copying was stopped and the developing section of the copying machine was inspected, it was observed that the carriers were aggregated and clogged in the part of the cutting board of the developing section.

Further, with the developer containing the magnetic particles of Comparative Example 2 as a carrier, the fog density increased from the 24,000th sheet, and fog was observed in the formed image. Then, at the stage of the 30,000th sheet, the fog density remarkably increased, and the image density and blow-off charge amount decreased. Further, when the developer was inspected after the continuous copying of 30,000 sheets, a decrease in fluidity which was considered to be caused by the cracking of the toner and the falling off of the amino resin powder was observed.

On the other hand, in Examples 1 and 2, 3
Even after continuous copying of ten thousand sheets, almost no change was observed in each characteristic, and the formed image was good. From this, it was confirmed that the magnetic particles of Examples 1 and 2 were excellent in durability.

[0073]

As described in detail above, according to the present invention,
The amino resin powder has good dispersibility, dispersion stability, good affinity with the binder resin, a small particle size and a narrow particle size distribution, and is excellent in heat resistance, wear resistance, etc., and is hard and difficult to crack. Binder type magnetic particles are obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location C08F 4/02 MEF 7242-4J C08G 12/40 NCH 8416-4J C09C 1/24 PAN 8218-4J 3 / 10 PCC 8218-4J G03G 9/083 9/087 G03G 9/08 321 384

Claims (2)

[Claims] 1. A magnetic particle comprising magnetic powder and amino resin powder having a polymer chain bonded to the surface thereof. 2. Amino resin powder is treated with a treating agent having an acyl halide group and a functional group which is the same as or different from the acyl halide group in one molecule to introduce the functional group onto the surface thereof. After reacting a polymerization initiator having a functional group that bonds with this functional group to bond the polymerization initiator to the surface of the amino resin powder, the amino resin powder, magnetic powder, and vinyl monomer are combined. A method for producing magnetic particles, which comprises polymerizing while containing a containing monomer phase in a dispersion medium in the form of droplets.