JPH06295102A - Electrophotographic magnetic carrier and its production - Google Patents

Abstract

PURPOSE:To obtain the carrier having a complex cross-linked structure, in which ferromagnetic fine grains are sufficiently dispersed in a resin by a coupling agent and a polar group such as a sulfonic group and a carboxyl group and firmly adhered to the resin, with the service life of a developer prolonged since the carrier surface is curved and hardly damaging a photosensitive body. CONSTITUTION:This electrophotographic carrier consists of a ferromagnetic fine grain and a resin. The resin is a polyurethane polyurea contg. one or >=2 kinds of polar groups selected from a group consisting of a sulfonic group, a sulfonate group, a carboxyl group and a carboxylate group and having a complex cross-linked structure consisting of a urethane coupling and a urea coupling. An electrophotographic magnetic carrier with the average grain diameter controlled to 10-300mum and having a curved surface is produced in this way.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a so-called two-component developer used for developing an electrostatic latent image or a magnetic latent image in the technical fields of electrophotography, electrostatic recording, electrostatic printing and the like. The present invention relates to a magnetic carrier for electrophotography, and more specifically to a magnetic substance dispersion type carrier composed of ferromagnetic fine particles and a resin, and a method for producing the same.

[0002]

2. Description of the Related Art In electrophotography, a photoconductive substance such as selenium, an organic semiconductor, or amorphous silicon is used as a photoconductor, an electrostatic latent image is formed by various means, and a magnetic brush is formed on the electrostatic latent image. A method in which toner is made to adhere by using a developing method or the like to make it visible is generally adopted.

In this developing process, a carrier is applied in order to impart a proper amount of positive or negative static electricity to the toner, form a magnetic brush on the developing sleeve containing a magnet, and convey the toner to the surface of the photoreceptor. The magnetic carrier particles referred to are used.

Conventionally, iron powder carriers have been used as carriers.
Ferrite carriers, magnetic substance-dispersed carriers (carriers in which magnetic fine particles are dispersed in resin and made into particles by means such as pulverization) have been developed and put into practical use.

However, although iron powder carriers are flake-shaped, sponge-shaped, and spherical in shape, their true specific gravity is as large as 7 to 8 and bulk specific gravity is as large as 3 to 4, so that they are large for stirring the developer. Since the driving force is required and the impact force applied to the toner and the photoconductor during stirring is large, so-called spent toner is generated, the chargeability of the carrier itself is deteriorated, and the photoconductor is easily damaged.

The ferrite carrier has a spherical shape, a true specific gravity of 4.5 to 5.5, and a bulk specific gravity of 2 to 3, which alleviates the above problems of the iron powder carrier. High-speed copying machines and high-speed laser printers tend to require high-speed stirring and high-speed development, and it is still insufficient to meet this demand.

The magnetic substance-dispersed carrier is, for example, Japanese Patent Publication No.
As described in Japanese Patent Application Laid-Open No. 9-24416, it is manufactured by melt-mixing magnetic fine powder and an insulating resin and then cooling and pulverizing. The bulk specific gravity is reduced from 1 to 2, but naturally. As a result, the shape becomes indefinite, the fluidity when the developer is stirred is poor, and it is still insufficient for high-speed development.
Further, this type of carrier has a drawback that when the amount of the magnetic fine powder is increased to increase the magnetic force, hard magnetic fine particles are easily exposed on the surface of the carrier particles, which easily damages the photoreceptor.

As a means for solving the drawbacks of these conventional carriers, the inventors of the present invention have developed a novel magnetic material composed of composite crosslinked particles in which a magnetic material having an urethane bond inside and an urea bond outside is encapsulated. Although a dispersion type carrier has been proposed (Japanese Patent Application No. 4-259760), sufficient performance has not yet been obtained in terms of carrier durability, scratch resistance of the photoreceptor and the like.

[0009]

The prior art carriers suffer from the drawbacks mentioned above. The present invention solves these drawbacks and provides a carrier which can cope with higher speed development.

More specifically, the problem to be solved by the present invention is to provide a carrier having a low bulk density, a curved surface, a good fluidity, and a low driving force for stirring a developer. That is.

Another object of the present invention is to provide a carrier which is less likely to be spent because the impact on the toner is small when the developer is agitated, and the life of the developer can be extended. Furthermore, it is another object of the present invention to provide a carrier that is less likely to damage the photoconductor by producing the photoconductor by a method that has a small impact on the photoconductor and that does not expose the hard magnetic fine particles to the surface of the carrier particle.

[0012]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems, the present inventors have made a dispersion of ferromagnetic fine particles and a resin raw material,
The present invention has been achieved as a result of earnest research on a method for manufacturing a carrier that improves wetting and makes a magnetic material and a resin adhere firmly to each other.

That is, the first invention is an electrophotographic carrier comprising fine ferromagnetic particles and a resin, wherein the resin is selected from the group consisting of a sulfonic acid group, a sulfonic acid group, a carboxylic acid group and a carboxylic acid group. A magnetic carrier for electrophotography, which is a polyurethane polyurea containing one or more polar groups and having a complex cross-linked structure composed of a urethane bond and a urea bond.

The second invention is an electrophotographic carrier comprising fine ferromagnetic particles and a resin, wherein the resin contains a silane coupling agent and / or a titanium coupling agent,
A magnetic carrier for electrophotography, which is a polyurethane polyurea having a composite crosslinked structure composed of urethane bonds and urea bonds.

A third invention is a polyol having ferromagnetic particles and one or more polar groups selected from the group consisting of sulfonic acid groups, sulfonic acid groups, carboxylic acid groups and carboxylic acid groups. A method for producing a magnetic carrier for electrophotography, which comprises suspending and dispersing a mixture of a polyol containing ## STR3 ## as a main component and a polyisocyanate in an aqueous phase containing polyamine, and then reacting the suspension with the polyamine.
That is, a step (A) of preparing a dispersion organic phase containing a mixture of ferromagnetic fine particles, a polyol and a polyisocyanate and, if necessary, an organic solvent, suspending and dispersing the above organic phase in water containing polyamine, In the step (B) of carrying out a urethane reaction inside the turbid particles and a urea reaction at the interface, by packing the carrier in an ion exchange resin column, 50% of the alkali metal cations of the polar groups present on the carrier surface can be obtained.
% Or more ion-exchange with 1 or 2 or more cations selected from the group consisting of hydrogen ions, divalent or higher valent metal cations, and organic cations (C), dehydration drying step (D) And a method for producing a magnetic carrier for electrophotography.

Ferromagnetic materials used in the present invention include gamma iron oxide, magnetite, and metals other than iron (Mn, C).
(O, Ni, Zn, Mg, Cu, etc.) containing one or more of spinel type ferrite, magnetoplumbite type such as barium ferrite, garnet type ferrites, chromium oxide, and having an oxide film on the surface Fine particles of iron or alloy may be mentioned.

The shape of the ferromagnetic fine particles may be any of granular, spherical and acicular. The carrier of the present invention can obtain a desired saturation magnetization by appropriately selecting the type and content of the ferromagnetic fine particle powder. For example,
When trying to obtain a magnetization of 40 to 70 emu / g, ferrites may be used, and further 70 to 100 emu / g
In order to obtain the magnetization of g, magnetite or Z
Spinel ferrite containing n may be used. Further, in order to obtain high magnetization of 100 emu / g or more, fine particles of iron or alloy having an oxide film on the surface may be used. Considering the chemical stability of ferromagnetic particles,
It is preferable to use a ferromagnetic fine particle powder such as magnetite or ferrite.

The content of the ferromagnetic fine particle powder is 50 to 99.
Weight% is suitable, but more preferably 60 to 95 weight%. If the content is less than 50% by weight, the magnetic attraction force of the carrier particles is too weak, depending on the type of the ferromagnetic material, the particle size of the carrier particles and the strength of the magnet in the sleeve, but part of the carrier particles The phenomenon that the toner adheres to the photoconductor together with the toner, the so-called carrier pulling phenomenon easily occurs. If it is more than 99% by weight, in other words, if the content of the binder resin is too small, the mechanical strength of the carrier particles becomes insufficient and the carrier particles become brittle and easily broken.

As the polyol which is a raw material of the polyurethane polyurea used in the present invention, any compound can be used as long as it is a compound containing at least two active hydrogens and having a molecular weight in the range of 62 to 100,000.

Specifically, for example, polyester polyol, polyether polyol, polyether ester polyol, polyester amide polyol, acrylic polyol, polyurethane polyol, polycarbonate polyol, epoxy polyol, epoxy modified polyol, polyhydroxyalkane, oil modified polyol, castor oil. , Silicone polyols or mixtures thereof.

Examples of polyester polyols include reaction products of polyhydric alcohols and polybasic acids. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, hexanediol, nonanediol, dodecanediol, methylpentanediol, trimethylpropanediol or dimethylisopropylpropanediol, hydroxystearyl alcohol, oleyl alcohol dimer, Cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc. Methylolpropane, glycerin,
Examples include pentaerythritol, sorbitol, castor oil, and the like. Examples of polybasic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, cyclohexanedicarboxylic acid, trimellitic acid. , These anhydrides, etc. can be mentioned.

A polyester polyol obtained by ring-opening polymerization of a lactone such as caprolactone, methylcaprolactone, valerolactone or methylvalerolactone with glycol or the like can also be used.

Examples of polyether polyols include ethylene oxide, propylene oxide, butylene oxide, tetrohydrofuran, styrene oxide,
Examples thereof include those obtained by polymerizing an epoxide compound such as epichlorohydrin, phenylglycidyl ether, and allylglycidyl ether in the presence of a catalyst. That is, it can be produced by adding these epoxide compounds individually or as a mixture of two or more kinds, or alternately by adding them to the active hydrogen-containing initiator.

Examples of the active hydrogen-containing initiator include water,
Examples include polyols, amino alcohols and polyamines.
Examples of the polyether ester polyol include those obtained by subjecting the above polyether to a polybasic acid as a raw material and subjecting it to a polyesterification reaction, and also obtained by a ring-opening copolymerization reaction of an epoxide compound and an acid anhydride. A compound having both polyether and polyester segments in one molecule can be mentioned.

An example of the polyesteramide polyol is obtained by using a polyamine compound together in the above polyesterification reaction. The acrylic polyol generally refers to a hydroxyl group-containing polymer. This acrylic polyol can be synthesized by copolymerizing a monomer having one or more hydroxyl groups in one molecule with another monomer copolymerizable therewith. Examples of the monomer having a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, trimethylolpropane acrylic acid monoester, methacrylic acid derivatives corresponding to these, polyhydroxyalkyl malate and fumarate. . Examples of the copolymerizable monomer include acrylic acid, its methyl, ethyl, propyl, butyl and 2-
Ethylhexyl ester, methacrylic acid, maleic acid,
Fumaric acid, itaconic acid, and their corresponding esters, as well as vinyl monomers such as styrene, α-methylstyrene, vinyl acetate, acrylonitrile and methacrylonitrile.

As the polyurethane polyol, for example, a reaction product of the above-mentioned polyol and polyisocyanate having a hydroxyl group at the terminal can be mentioned. Further, a product obtained by replacing a part of the polyol with the above-mentioned polyamine compound and reacting it can also be used as the polyurethane polyol.

Examples of the epoxy polyol include a condensation type epoxy resin obtained by reacting a polyphenol compound or a hydrogenated product thereof with epichlorohydrin, and in addition to this, for example, a fatty acid and an epoxy resin are obtained. Also included are epoxy ester resins obtained and modified epoxy resins obtained by reacting with alkanolamines.

Examples of polyhydroxyalkanes include saponified products of vinyl acetate homopolymers or copolymers with other copolymerizable monomers having an ethylene bond, or polybutadiene polyols.

Further, not only the above-mentioned polyol compounds having a relatively high molecular weight, but also low molecular weight polyols having a molecular weight in the range of 62 to 400 can be used alone or in combination. These low molecular weight polyols include ethylene glycol, propylene glycol,
Butylene recall, neopentyl glycol, hexanediol, nonanediol, dodecanediol, methylpentanediol, trimethylpentanediol, hydroxystearyl alcohol, oleyl alcohol dimer, cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, poly In addition to diols such as oxypropylene glycol, polyoxybutylene glycol, hydrogenated bisphenol A, ethylene oxide adduct of bisphenol A and propylene oxide adduct of bisphenol A, trimethylolpropane, glycerin, pentaerythritol, sorbitol and the like can be mentioned. .

As the polyol used in the present invention, one or more polar groups selected from a sulfonic acid group, a sulfonic acid group, a carboxylic acid group and a carboxylic acid group in the molecule of the polyol as described above. That is, the polyol introduced with is used as a main component. It is preferable to use together a polyol having no polar group introduced therein with a polyol having a polar group introduced therein.

When a polar group (a sulfonic acid group, a sulfonic acid group, a carboxylic acid group, a carboxylic acid group) is introduced, the wetting of the ferromagnetic fine particles and the resin raw material is significantly improved, and the effect of lowering the viscosity of the dispersion organic phase is obtained. There is. Therefore, there is an advantage that the necessary amount of the organic solvent used can be reduced.

Further, a remarkable effect as the introduction of the polar group is the effect of strongly adhering the magnetic material and the urethane urea resin to be formed to the same level as or more than the effect of using the silane coupling agent described later. Is there.

The total amount of the sulfonic acid group, the sulfonic acid group, the carboxylic acid group and the carboxylic acid group introduced is preferably 0.001 to 1 mmol / g, more preferably 0.01 to 0.3, based on the total resin content. It is mmol / g.

When the amount introduced is less than this range, the effect of lowering the viscosity of the organic phase, the effect of reducing the amount of the organic solvent, and the effect of firmly adhering the magnetic material and the urethane urea resin produced are lost. On the other hand, if the amount introduced is larger than this, the carrier becomes too hydrophilic, which adversely affects the charging property. In particular, in a high humidity environment, the amount of charge is reduced.

Examples of the method of introducing a sulfonic acid group or a sulfonic acid group include, for example, 2-sulfosodium-1,4-butanediol, 1-sulfosodium-
1,4-butanediol, 3-sulfosodium-
2,5-dimethyl-3-hexene-2,5-diol,
2,5-Disulfopotassium-3,4-hexanediol, 3-sulfopotassium-1,5-pentanediol, taurine, N, N-bis (2-hydroxyethyl)
Such as taurine or sulfobetaines, the monomers of _{various, HOROOCCH 2 CH (SO 3 M} ) COOR'OH [R, R ' is _{C n H 2n (n = 2~8} ), or - (CH ₂ C
_{H 2 O) m - (CH} 2 CHCH 3 O) l - (m, l = 0~2
0), M is an alkali metal], and a sulfonic acid alkali metal base-containing glycol is used as a short-chain diol, or is used as a raw material glycol for a new polyester polyol, or as an initiator of a polyether diol or a polycaprolactone diol. It is possible to introduce a sulfonic acid group or a sulfonic acid group into the polyol, polyether diol, or polycaprolactone diol.

As another introduction method, as an acid component of polyester polyol, 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoisophthalic acid, 2-potassium sulfoisophthalic acid, sodium sulfite is used. It is possible to introduce a sulfonate group and a sulfonate group into the polyester polyol by using phosuccinic acid or the like.

As the method for introducing the carboxylic acid group or the carboxylic acid group, for example, dimethylolpropionic acid or an alkali metal salt thereof is used as a short chain diol as it is, or the same as the introduction of the sulfonic acid group or the sulfonic acid group. In the form of polyester polyol, polyether diol, polycaprolactone diol with a carboxylic acid group,
It is possible to introduce a carboxylate group.

As the polyisocyanate used in the present invention, any of those known per se can be used, but of these, only representative ones will be exemplified. As aliphatic isocyanate, hexamethylene diisocyanate, 2,4-diisocyanate-1-methylcyclohexane, diisocyanate cyclobutane, tetramethylene diisocyanate, o-, m- or p-xylylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate , Dimethyldicyclohexylmethane diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, dodecane diisocyanate, tetramethyl xylene diisocyanate or isophorone diisocyanate Cyanate, and the like. or,
As the aromatic isocyanates, only typical ones are listed. Tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3-methyldiphenylmethane-4, 4'-diisocyanate, m- or p-phenylene diisocyanate, chlorophenylene-2,4-diisocyanate, naphthalene-1,5
-Diisocyanate, diphenyl-4,4'-diisocyanate, 3,3'-dimethyldiphenyl-1,3,5
-Triisopropylbenzene-2,4-diisocyanate Carbodiimide-modified diphenylmethane diisocyanate, polyphenyl polymethylene isocyanate, diphenyl ether diisocyanate and the like.

As another polyisocyanate, for example, a polyurethane polyisocyanate obtained by reacting an excess isocyanate compound with a polyhydroxy compound represented by various dihydric alcohols, trihydric alcohols or polyhydric alcohols having a valence of 4 or more is obtained. Method, obtained by polymerizing various diisocyanates or polyisocyanates as listed above, a method for obtaining a polyisocyanate containing an isocyanurate ring, or a method for obtaining a polyisocyanate containing an allophanate bond, further, The isocyanate prepolymer obtained by a method of obtaining a polyisocyanate containing a buret bond reacted with water or a method of reacting with carbon dioxide may be used alone or in combination.

The number average molecular weight of the polyisocyanate is 2 because the magnetic carrier is excellent in toughness.
The range of 00 to 10,000 is preferable. Further 300
The range of ~ 7,000 is more than 500-5,000
Is most appropriate.

In the present invention, as the polyamines to be preferably added to water and used, there are known and commonly used diamines, polyamines, or a mixture thereof, but among them, only typical ones are mentioned. 1,2-ethylenediamine, bis (3-aminopropyl) amine, hydrazine, hydrazine-2-
Ethanol, bis (2-methylaminoethyl) methylamine, 1,4-diaminocyclohexane, 3-amino-
1-methylaminopropane, N-hydroxyethylethylenediamine, N-methyl-bis (3-aminopropyl) amine, tetraethylenediamine, hexamethylenediamine, bis (N, N'-aminoethyl) -1,2-
Ethylenediamine, 1-aminoethyl-1,2-ethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, isophoronediamine, xylylenediamine, hydrogenated xylylenediamine,
Hydrogenated 4,4'-diaminodiphenylmethane and other aliphatic amines, phenylenediamine, toluylenediamine,
There are aromatic amines such as 2,4,6-triaminotoluene, 1,3,6-triaminonaphthalene, and 4,4′-diaminodiphenylmethane. Further, there are various derivatives of the above-mentioned polyamines such as epoxy compounds, adducts with acrylic compounds, and amidation condensates with organic carboxylic acids.

As the diamine compound having a sulfonic acid group, there are diaminotoluenesulfonic acid metal salt, naphthylenediamine sulfonic acid metal salt and the like, and these may be used.

The silane coupling agent used in the present invention means an organic silicon monomer having two or more different reactive groups in the molecule. One of the two reactive groups is a reactive group that chemically bonds with an inorganic substance (methoxy group, ethoxy group, cellosolve group, etc.), and the other reactive group chemically reacts with an organic synthetic resin (vinyl group, epoxy group). Group, methacryl group, amino group, mercapto group, etc.).

The use of the silane coupling agent improves the wettability of the ferromagnetic fine particles with the resin raw material, and has the effect of firmly bonding the magnetic material and the urethane urea resin produced.

Commercially available silane coupling agents usable in the present invention include vinyltrichlorosilane, vinyltris (βmethoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, γmethacryloxypropyltrimethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N- β
(Aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-
Phenyl-γ-aminopropyltrimethoxysilane, γ
-Mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane and the like can be mentioned. More preferably, it has an epoxy group, an amino group, or a mercapto group as a reactive group that chemically bonds to the organic synthetic resin, but the silane coupling agent of the present invention is not limited to these.

The silane coupling agent may be added directly to the mixture of the ferromagnetic fine particles, the polyol and the polyisocyanate, or the surface of the ferromagnetic fine particles may be treated with the silane coupling agent in advance. May be. The amount of the silane coupling agent used is 0.01 for the ferromagnetic fine particles.
.About.3% by weight, more preferably 0.1 to 1% by weight. Amount of silane coupling agent is 0.01% by weight
If it is less than the above range, the effect of improving wetting will not be obtained, and if it exceeds 3% by weight, no further effect of improving the wetting will be recognized and the cost will increase, which is not preferable.

In the present invention, a titanium coupling agent may be used instead of the silane coupling agent. It is also possible to use a silane coupling agent and a titanium coupling agent in combination.

In the present invention, an organic solvent is added to lower the viscosity of the organic phase and facilitate suspension particle formation.
Suitable organic solvents are aromatic or aliphatic hydrocarbons, esters, ethers, or ketones, among which benzene, toluene, xylene, cyclohexane, methylcyclohexane, diphenyl ether, mineral spirits, etc. are suitable. There is.

The silane coupling agent may be previously dissolved in these organic solvents and added to the ferromagnetic fine particles.
Since it is necessary to remove the organic solvent after completion of the urethane reaction and the urea reaction, it is preferable to use as little amount as possible.

With respect to the amount of polyamine, the amount of polyamine is 0.1 to 1.0 equivalent, more preferably 0.3 to 0.1, per equivalent of excess isocyanate group to OH group of the polyol contained in the organic phase. It is better to add 8 equivalents.

The magnetic carrier of the present invention can be obtained by carrying out a urea reaction at the interface of carrier particles and a urethanization reaction inside the particles. When the organic phase is suspended and dispersed in the aqueous phase, polyvinyl alcohol, hydroxyalkyl cellulose, carboxyalkyl cellulose, gum arabic, polyacrylic acid, polyacrylamide, polyvinylpyrrolidone or ethylene anhydride is used in order to stabilize the suspension dispersion. One or two or more of various suspension stabilizers such as maleic acid copolymers are added to the aqueous phase in an amount of 0.01 to 20% by weight, preferably 0.02 to 20% by weight. It is better to use within the range.

In the case of polyvinyl alcohol, the saponification degree is 7
0 to 90 mol% is preferable. Further, the aqueous phase may contain various known and commonly used nonionic, anionic or cationic surfactants. The amount of surfactant is 0.001-1% by weight, preferably 0.0
Used in an amount of 02 to 1% by weight.

In the present invention, inside the particles,
Although it causes a urethanization reaction, as is well known,
The urethanization reaction between the hydroxyl group and the isocyanate group tends to have a smaller reaction rate than the ureation reaction with the amino group, particularly when the isocyanate group is based on an aliphatic group. As is well known, the reactivity between water and an isocyanate group is extremely small compared to the reactivity with a hydroxyl group, and the permeation effect of the outer wall formed by the addition of polyamines allows the permeation of water into the inside of particles. The object of the present invention of carrying out the urethanization reaction in the particles by raising the reaction temperature and taking time from a negligible place is of course achieved.

In this case, dibutyltin oxide, cobalt naphthenate, zinc naphthenate, stannous chloride, stannic chloride, and tetrachloride are used for the purpose of accelerating the reaction between the isocyanate group and the hydroxyl group in the particle very effectively. -N-
Butyltin, tri-n-butyltin acetate, n-butyltin trichloride, trimethyltin hydroxide,
One or more of various organometallic catalysts such as dimethyltin dichloride, dibutyltin acetate, dibutyltin dilaurate, tin octenoate or potassium oleate can be added. The amount of this organometallic catalyst is
5 to 10,000 ppm, preferably 1 with respect to the organic phase
It is desirable to add it within the range of 0 to 5,000 ppm. By adding the organometallic catalyst, in an extremely short time,
A strong magnetic carrier can be formed. That is, these organometallic catalysts can very effectively promote the reaction between the isocyanate group and the hydroxyl group.

The catalyst is added in advance in the organic phase prior to the dispersion in water, or the step of dispersing the organic phase in water and the step of adding polyamines. It is appropriate to do it in the middle. The addition of the catalyst after adding the polyamines makes it difficult for the catalyst to be taken into the inside of the particle due to the state where the outer wall of the particle is being formed, and as a result, the urethanization reaction accelerating property inside the particle tends to decrease. It is not preferable because

In the present invention, the resin raw materials constituting the organic phase, the compounding ratio, the introduced amount of the polar group (sulfonic acid group, sulfonate group, carboxylic acid group, carboxylate group) in the resin, the added amount of the solvent, The particle size can be freely designed by appropriately selecting the types of suspension stabilizers and / or surfactants used in the dispersion step and their amounts, or various conditions such as stirring speed and reaction temperature in the dispersion step. Can be adjusted.

The average particle size of the magnetic carrier of the present invention is designed according to the particle size of the toner used, the development gap (distance between the photosensitive member and the development sleeve) and the required resolution. It is usually in the range of about 10 to 300 μm (μm), and more preferably in the range of 15 to 150 μm.

For the particle size, a 50% volume average particle size is measured using a laser diffraction particle size analyzer PRO-7000S manufactured by Seishin Enterprise Co., Ltd. The magnetic carrier of the present invention is generally manufactured as follows. In the step (A) of adjusting the organic phase, first, the ferromagnetic fine particles, the polyol and a small amount of the organic solvent are mixed. At this time, if necessary, a kneading / dispersing device such as a kneader, an attritor, a ball mill, a sand mill, a roll mill or an ultrasonic homogenizer may be used. Next, polyisocyanate is added and mixed quickly to obtain an organic phase. An organometallic catalyst may be added at this stage.

If necessary, various additives that are active or inactive with respect to isocyanate groups, charge control agents, carbon black, lubricants, and various synthetic resins such as xylene resin and ketone resin may also be used. Alternatively, they may be appropriately added to the organic phase and used. The step (B) of suspending and dispersing the above organic phase in an aqueous phase can be performed by a homomixer, a homodisper, an ultrasonic homogenizer, or the like. In making the particles spherical, in many cases, after the dispersion step is completed,
It is more preferable to stir the dispersion mildly using a propeller stirrer or the like. Before the addition of the polyamines, the above-mentioned organometallic catalyst for urethanization reaction, such as dibutyltin dilaurate, is added to the suspension dispersion in a mildly stirred state.

Polyamines are added to the dispersion, and the polyamines are preferably added by diluting with water or an organic solvent so that the active ingredient is 5 to 70%.

Then, after several tens of minutes to several hours, the reaction temperature is raised to 40 to 95 ° C., preferably 50 to 90 ° C., and the temperature is maintained for 1 hour to several hours to terminate the reaction. To do.

The organic solvent added at the same time when adjusting the organic phase or when adding the polyamine is distilled off at the same time during the above reaction time, but if it still remains, it is completely removed under reduced pressure after completion of the reaction. Distill off. (C) When an alkali metal sulfonate or an alkali metal carboxylic acid is present on the surface of the carrier particles, 50% or more, preferably 90%, of the alkali metal cation is used.
The above is preferably ion-exchanged with one or more kinds of cations selected from hydrogen ions, divalent or higher valent metal cations, and organic cations.

In this step, the column for the ion exchange resin is filled with the carrier particles of the present invention, and the ion exchange can be easily carried out by the same method as the ion exchange resin. Two
Examples of metal cations having a valence of more than 3 are Mg, Ca, B
a, Zn, Al, Sn, Fe, Co, Ni, Mn, Cu
Examples of the metal cations such as and organic cations include ammonium salts such as trimethylbenzylammonium. (D) The polyurethane polyurea crosslinked particles containing the ferromagnetic fine particles thus obtained are thoroughly washed with water and then subjected to a spray drying method, a centrifugal drying method, a filtration drying method, a freeze drying method or a fluidized bed drying method. It is dried, crushed and classified if necessary.

It is also possible to control the charging property, conductivity and fluidity by further modifying the surface with various coating agents. The above method discloses a production method in which water is used as a main component of the suspension dispersion, but a general organic solvent or a mixed solvent of an organic solvent and water is used as the suspension dispersion medium. It is also possible to use.

[0065]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, all parts and% are based on weight unless otherwise specified.

First, each raw material used will be outlined. (1): Polyisocyanate "Bernock DN-980S" (manufactured by Dainippon Ink and Chemicals, Inc., isocyanurate ring-containing polyisocyanate obtained using hexamethylene diisocyanate; isocyanate group content = 21.0%); Hereinafter, this is referred to as PI-1.

"Bernock DN-750" [a 75% ethyl acetate solution of toluene diisocyanate / adduct type polyisocyanate, manufactured by Dainippon Ink and Chemicals, Inc .; solid content conversion isocyanate group content = 17.3
%]; Hereinafter, this is referred to as PI-2.

"Bernock 9-409" (polymer of diphenylmethane diisocyanate manufactured by Dainippon Ink and Chemicals, Inc .; isocyanate group content 31.
0%; hereinafter referred to as PI-3.

"Bernock DN901S" (manufactured by Dainippon Ink and Chemicals, Inc., isocyanurate ring-containing polyisocyanate obtained using hexamethylene diisocyanate; isocyanate group content = 23.5)
%]; Hereinafter, this is referred to as PI-4. (2): Polyol Polycaprolactone polyester triol having a hydroxyl value of 168.5, obtained by polycondensation reaction of trimethylolpropane and ε-caprolactone; hereinafter referred to as PO-1.

Polypropylene glycol having a hydroxyl value of 160.3; hereinafter referred to as PO-2. (3): Polyamine compound Ethylenediamine; hereinafter abbreviated as EDA.

Isophoronediamine; hereinafter abbreviated as IPDA. Synthesis Example 1 5 parts of 148 parts of sodium sulfoisophthalic acid, 114.4 parts of neopentyl glycol and 0.08 part of zinc acetate were added.
The mixture is placed in a 00 ml four-necked flask and transesterified at 190 ° C. for 6 hours to obtain an intermediate (A). Next, 16.3 parts of this intermediate (A), neopentyl glycol 13
Charge 9.4 parts, 153.3 parts of adipic acid, and 0.1 parts of dibutyltin oxide into a 500 ml four-necked flask,
The temperature was raised to 220 ° C. over a period of time, and the esterification reaction was further performed at 220 ° C. for 6 hours to give an acid value of 5.0 and a hydroxyl value of 132.
A polyester polyol (B) containing 6 sodium sulfonate groups was obtained.

Example 1 Magnetite MAT-305 (manufactured by Toda Kogyo KK) 100
, Shin-Etsu Chemical silane coupling agent KBM803 (γ
-Mercaptopropyltrimethoxysilane) 0.5 part,
After 200 parts of acetone was mixed and stirred in a 500 ml beaker, acetone was distilled off to obtain a silane coupling agent-treated magnetite (C).

In a 1,000 ml flask, "Fuji HE
An aqueous phase was prepared by dissolving 19 parts of "CAL-15F" (hydroxyethyl cellulose manufactured by Fuji Chemical Co., Ltd.) in 356 parts of water.

In a separate container, 18.1 parts of PI-1 and P
11.4 parts of O-1, 70.5 parts of the magnetite (C) treated with the above silane coupling agent, and 20 parts of toluene were mixed to form an organic phase.

At 20 ° C., using a homomixer,
While stirring the aqueous phase at 7,000 to 7,500 rpm, an organic phase prepared in advance was charged therein and stirred for 1 minute to obtain a suspension dispersion liquid.

Then, this suspension dispersion was transferred to another flask, 0.1 part of dibutyltin dilaurate (DBTDL) was added while stirring at 200 rpm by a paddler type stirring blade, and after 2 minutes, further, 1.4 parts of a 50% aqueous solution of EDA was charged.

After being kept at room temperature (about 25 ° C.) for 2 hours,
The temperature was raised to 50 ° C. and the reaction was continued for 1 hour and further at 80 ° C. for 2 hours. After the completion of the reaction, the target magnetic carrier was obtained by washing with water, filtering, drying and crushing.

The average particle diameter of this product was 24 μm. 90 parts of this magnetic carrier and 10 parts of non-magnetic toner are mixed to make a developer, and a development tester (commercial copying machine EP
430) was modified and the development test was performed,
A high quality image with high resolution and good solid part uniformity was obtained.

After a continuous operation test corresponding to copying 70,000 sheets, the surface of the photoreceptor was observed and found to be good with few scratches. In addition, the carrier side was good, with almost no damage or deterioration.

As a result of observing the surface of this carrier with a scanning electron microscope, it was found that the magnetic substance and the resin were well adhered. Comparative Example 1 Styrene acrylic resin 2 having a weight average molecular weight of 30,000 2
9.5 parts and 70.5 parts of magnetite MT305 were melt-kneaded using a pressure kneader and pulverized with a jet mill,
By classification, a magnetic carrier having an average particle diameter of 25 μm was obtained. The same test as in Example 1 was conducted using 90 parts of this magnetic carrier and 10 parts of non-magnetic toner as a developer.
In the development test, almost the same image was obtained, but when the surface of the photoconductor was observed after the continuous operation test equivalent to copying 70,000 sheets, the damage was remarkable and it appeared in the image.

Example 2 A target magnetic carrier was obtained in the same manner as in Example 1 except that the formulation was changed as described below.

That is, as the water phase, "P
VA-205 "(partially saponified polyvinyl alcohol manufactured by Kuraray Co., Ltd.), 9 parts," PVA-217 "(same as above)
10 parts and 356 parts of water were used, while the organic phases were 26.7 parts of PI-2 and 7.-1 of PO-1, respectively.
6 parts, polyester polyol (B) described in Synthesis Example 1
2 part, magnetite is untreated magnetite MAT3
70.4 parts of 05 and 10 parts of toluene were used, 0.18 parts of DBTDL was further used as the urethanization catalyst, and 2.5 parts of a 25% aqueous solution of EDA was used as the polyamine. The reaction product was filtered with a filter paper, washed with water, packed in a column, flowed with a 5% ferric chloride aqueous solution for ion exchange, and sufficiently washed with water to obtain a magnetic carrier.
The average particle diameter of this product was 28 μm.

90 parts of the magnetic carrier and 10 parts of the non-magnetic toner were mixed as a developer, and a development test was conducted with a development tester (a commercial copying machine EP430 was modified). High image quality with good part uniformity was obtained. After the continuous operation test corresponding to copying 70,000 sheets, the surface of the photoreceptor was observed and found to be good with few scratches. In addition, the carrier side was good, with almost no damage or deterioration.

Example 3 A target magnetic carrier was obtained in the same manner as in Example 1 except that the formulation was changed as described below.

That is, as the water phase, "P
9 parts of "VA-205", 10 parts of "PVA-217" and 273 parts of water were used, while the organic phase was 15.0 parts of PI-3 and 12.8 parts of PO-2, respectively. 0.6 parts of dimethylolpropionic acid and 15 parts of toluene
71 parts of the silane coupling agent-treated magnetite (C) described in Example 1 are used as the magnetite.
Further, 6 parts of DBTDL as a urethane catalyst
0.18 parts of
Fully crosslinked polymer particles were obtained by using 7.8 parts of a 30% aqueous solution of DA.

The average particle size of this product was 24 μm. 90 parts of this magnetic carrier and 10 parts of non-magnetic toner are mixed to make a developer, and a development tester (commercial copying machine EP
430) was modified and the development test was performed,
A high quality image with high resolution and good solid part uniformity was obtained. After the continuous operation test corresponding to copying 70,000 sheets, the surface of the photoreceptor was observed and found to be good with few scratches. Further, the carrier side was good, with almost no breakage or deterioration observed.

Example 4 The target magnetic carrier was obtained in the same manner as in Example 1 except that the formulation was changed as described below.

That is, as the water phase, "P
0.15 parts of VA-420 "and 340 parts of water were used, while the organic phase was 19.
9 parts, 1 part of PO-1, 1.9 parts of the polyester polyol (B) described in Synthesis Example 1 and 28 parts of toluene were used, and the magnetite was the silane coupling agent-treated magnetite described in Example 1. (C) 71.6
And 0.003 part of DBTDL as the urethanization catalyst, and E as the polyamine.
3.2 parts of a 25% aqueous solution of DA were used. The rotation speed of the homomixer was 4500 to 5000 rpm.

The average particle diameter of this product was 40 μm. A photograph of this magnetic carrier taken by a scanning electron microscope is shown in FIG. 90 parts of this magnetic carrier and 10 parts of non-magnetic toner were mixed as a developer, and a development test was conducted with a development tester (a commercial copying machine EP430 was modified). A good high image quality was obtained. After the continuous operation test corresponding to copying 70,000 sheets, the surface of the photoconductor was observed and found to be good with few scratches. Further, the carrier side was good, with almost no breakage or deterioration observed.

[0090]

The electrophotographic carrier of the present invention has a crosslinked structure in which the inner portion is a urethane bond and the outer wall is a urea bond,
Due to the effect of the coupling agent, the sulfone group, and the carboxyl group, the encapsulated ferromagnetic fine particles are well dispersed and firmly adhered in the resin, and because the carrier surface has a curved shape, This has the effect that the developer has a long life and is less likely to damage the photoreceptor.

[Brief description of drawings]

 (Photo as substitute for drawing) Shape and structure of carrier particles

FIG. 1 is a scanning electron micrograph of a magnetic carrier of Example 4.

Claims (8)

[Claims] 1. An electrophotographic carrier comprising fine ferromagnetic particles and a resin, wherein the resin is one or two selected from the group consisting of a sulfonic acid group, a sulfonic acid group, a carboxylic acid group and a carboxylic acid group. A magnetic carrier for electrophotography, which is a polyurethane polyurea containing at least one kind of polar group and having a composite crosslinked structure composed of a urethane bond and a urea bond. 2. An electrophotographic carrier comprising fine ferromagnetic particles and a resin, wherein the resin contains a silane coupling agent and / or a titanium coupling agent and has a composite crosslinked structure composed of a urethane bond and a urea bond. A magnetic carrier for electrophotography, which is a polyurethane polyurea. 3. The magnetic carrier for electrophotography according to claim 1, wherein the carrier surface has a curved shape. 4. The magnetic carrier for electrophotography according to claim 1, wherein the average particle size of the carrier is 10 to 300 μm. 5. A main component is a ferromagnetic fine particle and a polyol having one or more polar groups selected from the group consisting of a sulfonic acid group, a sulfonic acid group, a carboxylic acid group, and a carboxylic acid group. A method for producing a magnetic carrier for electrophotography, which comprises suspending and dispersing a mixture of a polyol and a polyisocyanate to be dispersed in an aqueous phase containing polyamine and then reacting the suspension with the polyamine. 6. The method for producing a magnetic carrier for electrophotography according to claim 5, wherein a silane coupling agent and / or a titanium coupling agent is added to the mixture of polyol and polyisocyanate. 7. The method for producing an electrophotographic carrier according to claim 5, wherein the surface of the ferromagnetic fine particles is previously treated with a silane coupling agent and / or a titanium coupling agent. 8. After completion of the reaction, 50% or more of the alkali metal cations of polar groups present on the surface of the carrier are selected from the group consisting of hydrogen ion, divalent or higher valent metal cation, and organic cation, or 2 or more. The method for producing a magnetic carrier for electrophotography according to any one of claims 5 to 7, wherein ion exchange is performed with at least one kind of cation.