JPH086306A - Elecrophotographic magnetic carrier and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the blocking of grains during the process by providing a coating material, which is constituted of polyurethane and a conductivity imparting material, specifies the electrical resistance value, is stiff, and has high conductivity, and depositing polyurethane on the surfaces of the core material grains in a reaction in the electrophotographic magnetic carrier coated with the coating material on the core material grains. CONSTITUTION:In this electrophotographic magnetic carrier coated with a coating material on core material grains, the coating material is constituted of polyurethane and a conductivity imparting material. The coating material constituted of polyurethane and the conductivity imparting material is applied on the core material grains obtained when polyol and polyisocyanate are reacted in an organic solvent under the existence of the core material and the conductivity imparting material. Any conductivity imparting material may be used so far as the electrical resistance value of the carrier of 10<5>OMEGA.cm or below is obtained, the specific resistance of itself is preferably set to 10<2>OMEGA.cm or below, and its grain size is preferably set to 3mum or below in a powdery shape.

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. And a manufacturing method thereof. In particular, it relates to a conductive carrier having an electric resistance value of 10 to 10 ⁵ ohm cm and a method for manufacturing 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.
A ferrite carrier or a magnetic substance dispersion type carrier (a carrier in which magnetic substance fine particles are dispersed in a resin as described in JP-B-59-24416 and made into particles by means such as pulverization) is developed and put into practical use. In addition, in Japanese Patent Application Laid-Open No. 5-197211 filed by the applicant,
A novel magnetic substance-dispersed carrier has been proposed, in which the inner core is mainly composed of urethane bonds and the outer shell is mainly composed of urea bonds, and composite crosslinked particles containing a magnetic substance are contained.

Regarding iron powder carriers and ferrite carriers, the surface thereof is (meth) acrylic resin, vinyl chloride resin, fluorinated olefin resin, fluorinated (meth), with the main purpose of controlling the triboelectric chargeability to toner. A so-called resin-coated carrier coated with an acrylate copolymer or the like is known, and for example, JP-A-51-11763.
No. 8, JP-A-53-97435, JP-A-57-186.
759, JP-A-61-180162, JP-A-61-11-1.
20169, JP 61-120170, JP 6
2-286062, JP 62-295074, JP 62-80669, JP 63-58361,
JP-A-63-226663, JP-A-2-168273
JP-A-2-168274, JP-A-2-21786
No. 9, JP-A-2-280171, Japanese Patent Publication No. 2-5378.
It is described in Japanese Patent Publication No. 2 and the like.

The above-mentioned carrier is generally electrically semi-conductive, and 10 ⁶ to 10 ^{11 in} order to have a function as a counter electrode for the photoconductor and a function for imparting triboelectric charge to the toner. It is set to the electrical resistance value of ohm-centimeter.

[0007]

However, a developing system in which the function as a counter electrode is particularly emphasized, or a developing system having a function of injecting charges from the developing sleeve side to the photoconductor side (Electrophotographic Society, Vol. 31, Vol. 31). Electrically conductive carriers such as those used in the "optical back surface recording method" described in No. 4, pages 542 to 548, are required to have an electric resistance value of 10 ⁵ ohm cm or less.

An object of the present invention is to provide a tough conductive carrier having an electric resistance value of 10 ⁵ ohm cm or less, more preferably 10 ³ ohm cm or less.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted diligent research in order to solve the above problems, and as a result of studying a conductive carrier coating of polyurethane, as a result, polyol and polyisocyanate which are raw materials of polyurethane A novel conductive material obtained by forming a composite film of the conductivity-imparting material and polyurethane on the surface of the core material, which is obtained by stirring, mixing, and raising the temperature in the presence of a solvent, a core material, and a conductivity-imparting substance to cause a reaction. The present invention has been completed by finding that a sexual carrier satisfies the above problems.

That is, as a first invention, a magnetic carrier for electrophotography in which a core material particle is coated with a coating material,
The present invention provides a magnetic carrier for electrophotography, characterized in that the coating material comprises polyurethane and a conductivity-imparting substance.

In a second aspect of the invention, the core particles are characterized by reacting a polyol and a polyisocyanate in an organic solvent in the presence of a core material and a conductivity-imparting substance. The present invention provides a method for producing a magnetic carrier for electrophotography, which is coated with a coating material.

The raw materials used in the present invention, that is, the conductivity-imparting substance, polyisocyanate, polyol, solvent and core material will be described in this order. The conductivity-imparting substance used in the present invention may be any substance as long as the electric resistance value of the finally obtained carrier is 10 ⁵ ohm cm or less, but one having a specific resistance of 10 ² ohm cm or less is preferable. It is preferable to use a powdery powder having a particle diameter of 3 μm or less because it is required to be uniformly dispersed and adhered to the surface of the core material. Specific examples of the conductivity imparting substance include, for example, so-called conductive carbon black such as acetylene black and Ketjen black, metal powder such as silver, copper, nickel and zinc, zinc oxide, tin oxide, indium oxide, titanium oxide and the like. Examples thereof include metal oxide particles. These can be used alone or in combination of two or more. Conductive carbon black is particularly preferable because of its small medium particle size, chemical stability, and low cost.

As the polyisocyanate used as the raw material of polyurethane in the coating material of the present invention, any of those known per se can be used, but among them, only typical ones are exemplified. First, as the aliphatic isocyanate, hexamethylene diisocyanate, 2,4-diisocyanate-1-methylcyclohexane, diisocyanate cyclobutane,
Examples thereof include 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. To be Further, as the aromatic isocyanate, 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 diphenylmetadiisocyanate, polyphenylpolymethyleneisocyanate or diphenyletherdiisocyanate.

As another polyisocyanate, for example, a method of 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, to obtain a polyurethane polyisocyanate, , A method for obtaining a polyisocyanate containing an isocyanurate ring by polymerizing various diisocyanates or polyisocyanates as listed above, or a method for obtaining a polyisocyanate containing an allophanate bond, and further reacting with water. Examples thereof include isocyanate prepolymers obtained by a method of obtaining a polyisocyanate containing a buret bond and a method of reacting with carbon dioxide, and these can be used alone or in combination.

In order that the resin as the coating material has excellent toughness, the number average molecular weight of the polyisocyanate is in the range of 200 to 10,000, preferably 300 to 7,000. The inside is more preferable, and the range of 500 to 5,000 is more preferable.

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

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,
In addition to diols such as ethylene oxide adduct of bisphenol A and propylene oxide adduct of bisphenol A, trimethylolpropane, glycerin, pentaerythritol, sorbitol, castor oil and the like are particularly representative. 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.

As the polyester polyol, it is also possible to use a polyester polyol obtained by ring-opening polymerization of a lactone such as caprolactone, methylcaprolactone, valerolactone or methylvalerolactone with glycol or the like.

Examples of polyether polyols include ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, 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, and these epoxide compounds may be used alone or in a mixture thereof. Further, it is also possible to use a compound obtained by alternately adding these epoxide compounds to an active hydrogen-containing initiator. Examples of the active hydrogen-containing initiator include water, polyol, amino alcohol, polyamine and the like.

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, as well as a ring-opening copolymerization reaction of an epoxide compound and an acid anhydride. A compound having both a polyether segment and a polyester segment in the molecule obtained by can be mentioned.

Examples of the polyester amide polyol include those obtained by using a polyamine compound together in the polyesterification reaction. The acrylic polyol is generally referred to as a hydroxyl group-containing polymer, but can be synthesized by copolymerizing a monomer having one or more hydroxyl groups in one molecule with another monomer copolymerizable with the monomer.

As the monomer having a hydroxyl group, for example, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, trimethylolpropane acrylic acid monoester, corresponding methacrylic acid derivatives thereof, polyhydroxyalkylmalate and fumarate, etc. Examples of monomers copolymerizable therewith include acrylic acid, its methyl, ethyl,
Propyl, butyl, 2-ethylhexyl ester, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and their corresponding esters, as well as styrene, α-
Examples thereof include vinyl monomers such as methylstyrene, vinyl acetate, acrylonitrile, 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 epoxy polyols include condensation type epoxy resins obtained by reacting a polyphenol compound or its hydrogenated product with epichlorohydrin, epoxy ester resins obtained by reacting a fatty acid with an epoxy resin, and alkanolamines. A modified epoxy resin obtained by reacting with

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

Further, as the polyol, a polyol compound having a relatively high molecular weight has hitherto been mentioned.
A low molecular weight polyol having a molecular weight in the range of 400 may be used alone or in combination with a high molecular weight polyol.

Examples of 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, polyoxypropylene glycol, polyoxybutylene glycol, hydrogenated bisphenol A, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc. Besides, trimethylolpropane, glycerin, pentaeryth Examples thereof include litol and sorbitol.

A polyol having at least one polar group selected from a sulfonic acid group, a sulfonic acid group, a carboxylic acid group, and a carboxylic acid group in the molecule of the above-mentioned polyol is used in combination with the above-mentioned polyol. Is also good.

Examples of the method for introducing a sulfonic acid group and 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
- sulfonium potassium-1,5-pentanediol, such taurine, N, N-bis (2-hydroxyethyl) 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 CH 2 O)} m -
_{(CH 2 CHCH 3 O) l} - (m, l = 0~20), or M is used sulfonic acid alkali metal salt group-containing glycol represented by an alkali metal as the short chain diol, raw material glycols new polyester polyols, Alternatively, it can be introduced into a polyester polyol, a polyether diol, or a polycaprolactone diol by using a polyether diol or a polycaprolactone diol as an initiator.

As another method of introducing a sulfonic acid group and a sulfonic acid group, 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoisophthalic acid, and 2-sodium sulfoisophthalic acid are used as the acid component of the polyester polyol. -Using potassium sulfoisophthalic acid, sodium sulfosuccinic acid or the like, it is possible to introduce a sulfonic acid group or a sulfonate group into the polyester polyol.

The carboxylic acid group and the carboxylic acid group can be introduced by using, for example, dimethylolpropionic acid or an alkali metal salt thereof as a short-chain diol as it is, or by introducing the same form as the sulfonic acid group and the sulfonic acid group. It is possible to introduce a carboxylic acid group or a carboxylic acid group into the polyester polyol, polyether diol, or polycaprolactone diol.

The solvent used for conducting the conductive coating of the present invention is appropriately selected from low boiling point organic solvents capable of dissolving polyisocyanate and polyol and dispersing core material particles and a conductivity-imparting substance. Can be used. Examples of the low boiling point organic solvent include ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate, hydrocarbon solvents such as toluene, xylene and cyclohexane, halogenated hydrocarbon solvents such as dichloromethane and chloroform. Is mentioned.

As the core particles used in the present invention, any of iron powder particles, ferrite particles and magnetite particles having an average particle diameter of 10 to 200 microns which have been conventionally used, can be used, and are hardly dissolved in the above solvent. Is preferred. Further, so-called resin dispersion type magnetic core particles in which magnetic powder particles are dispersed in a binder resin can also be used. Examples of such core material particles include resins having a crosslinked structure inside, such as hardened phenol resin-dispersed magnetic core material particles as described in JP-A-2-220068. However, resin-dispersed core material particles of cross-linked polyurethane are particularly preferable, and in this case, a suitable conductive carrier can be provided.

The polyurethane resin-dispersed magnetic core material particles can be manufactured as described in JP-A-5-197211. That is, after a mixture of ferromagnetic fine particles, a polyol and a polyisocyanate is suspended and dispersed in an aqueous phase containing a polyamine, the polyol is reacted with the isocyanate, and the polyisocyanate is reacted with the polyamine. Thus, it is possible to obtain polyurethane-based dispersion-type magnetic core particles having a composite crosslinked structure formed by crosslinking with a urethane bond and a urea bond.

The ferromagnetic fine particles forming the core particles include gamma iron oxide, magnetite, and one or more kinds of metals other than iron (Mn, Co, Ni, Zn, Mg, Cu, etc.). Spinel-type ferrite, magnetoplumbite-type ferrites such as barium ferrite, garnet-type ferrites, chromium oxide, and iron or alloy fine particle powder having an oxide film on the surface can be used.

The shape of the ferromagnetic fine particles may be granular, spherical or acicular. By properly selecting the type and content of the ferromagnetic fine particle powder, carrier particles having a desired saturation magnetization can be obtained. For example 40
To obtain a magnetization of 70 to 70 emu / g, ferrites may be used. To obtain a magnetization of 70 to 100 emu / g, spinel ferrite containing magnetite or Zn may be used. . 1 more
In order to obtain a high magnetization of 00 emu / g or more, fine particles of iron or alloy having an oxide film on the surface may be used. For example, a magnetic material having a ratio of metallic iron and acid value iron of 25:75 to 85:15 as described in JP-B-4-56983 can be used.

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 too small, it depends on the type of ferromagnetic material, the particle size of the carrier particles and the strength of the magnet in the sleeve, but the magnetic attractive force of the carrier particles is too weak and part of the carrier particles together with the toner. The phenomenon of sticking to the photoconductor, the so-called carrier pulling phenomenon, easily occurs.

When the content of the ferromagnetic fine particle powder is too large, in other words, when the binder resin content is too small,
The mechanical strength of the carrier particles is insufficient and they become brittle and easily broken. When the resin-dispersed core material particles of the present invention are produced, it is preferable to use a silane coupling agent in order to disperse the ferromagnetic fine particles well in the resin.

The silane coupling agent is an organosilicon monomer having two or more different reactive groups in the molecule.
One of the 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.).

Examples of commercially available silane coupling agents are 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, all of which can be used in the present invention. Of these, those having an epoxy group, an amino group, or a mercapto group as a reactive group that chemically bonds to the organic synthetic resin are preferable.

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 adhering the magnetic material and the urethane urea resin produced.

The silane coupling agent may be added directly to the organic phase of the present invention, or the surface of the ferromagnetic fine particles may be treated with the silane coupling agent in advance. The amount of the silane coupling agent used is preferably 0.01 to 3% by weight of the ferromagnetic fine particles, more preferably 0.1.
It is recommended to use ~ 1% by weight.

If the amount of the silane coupling agent is less than 0.01% by weight, the effect of improving the wetting is not recognized and the amount is 3% by weight.
If the amount is larger than that, no further improvement in wetting is recognized and the cost increases, which is not preferable.

A titanium coupling agent can 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.

When the core material particles of the present invention are produced, an organic solvent is added and used in order to lower the viscosity of the organic phase and facilitate suspension particle formation. As the organic solvent, aromatic hydrocarbons, aliphatic hydrocarbons, esters, ethers, or ketone solvents, and halogen solvents are suitable.
Examples thereof include benzene, toluene, xylene, cyclohexane, methylcyclohexane, diphenyl ether, mineral spirits, ethyl acetate, butyl acetate and dichloromethane. The coupling agent may be previously dissolved in these 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. When producing the resin-dispersed core material particles of the present invention, as the polyamines that are preferably added to and used in water, known conventional diamines, polyamines, or a mixture thereof may be mentioned. However, to list only representative ones, 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, Screw (N, N '
-Aminoethyl) -1,2-ethylenediamine, 1-aminoethyl-1,2-ethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, isophoronediamine, xylylenediamine, hydrogenated xylylenediamine, hydrogenated 4, Aliphatic amines such as 4'-diaminodiphenylmethane, phenylenediamine, toluylenediamine, 2,4,6-triaminotoluene, 1,3,6-triaminonaphthalene, aromatic such as 4,4'-diaminodiphenylmethane There are amines. 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 sulfonate group, a metal salt of diaminotoluene sulfonate, a metal salt of naphthylene diamine sulfonate, or the like can be used.

With respect to the amount of polyamine, it is preferable to add 0.1 to 1.0 equivalent of polyamine per equivalent of excess isocyanate groups with respect to the OH groups of the polyol contained in the organic phase, and more preferably. 0.3-0.8
It is better to add the equivalent amount. The core material particles of the present invention can be obtained by performing a urea reaction at the particle interface and a urethanization reaction inside the particles.

When the organic phase is suspended and dispersed in the aqueous phase in the production of the core material particles, a suspension stabilizer can be used in order to stabilize the suspension and dispersion. Examples of the suspension stabilizer include polyvinyl alcohol, hydroxyalkyl cellulose, carboxyalkyl cellulose, gum arabic, polyacrylic acid, polyacrylamide, polyvinylpyrrolidone, ethylene-maleic anhydride copolymer, and the like. One of these may be used. Alternatively, two or more kinds can be used. The amount of the suspension stabilizer used is preferably 0.01 to 20% by weight in the aqueous phase, and more preferably 0.02 to 20% by weight.
It is suitable to use within the range. In the case of polyvinyl alcohol, the saponification degree is preferably 70 to 90 mol%.
Further, this aqueous phase may further contain a surfactant. Examples of the surfactant in this case include known and commonly used nonionic, anionic or cationic surfactants. The amount of the surfactant used is 0.
001 to 1% by weight is preferable, and 0.002 to 1% by weight is more preferable.

In the production of the resin-dispersed core material particles of the present invention, a urethanization reaction is carried out inside the particles. As is well known, the urethanization reaction between a hydroxyl group and an isocyanate group does not occur. In particular, when the isocyanate group is based on an aliphatic group, the reaction rate tends to be small as compared with the ureation reaction with an amino group. As is well known, the reactivity between water and an isocyanate group is extremely small as compared with the reactivity with a hydroxyl group, and due to the isolation effect by the outer wall formed by the addition of polyamines,
Since the permeation of water into the particles can be ignored, the purpose of carrying out the urethanization reaction in the particles is achieved by increasing the reaction temperature and taking time. In this case, an organometallic catalyst can be added for the purpose of accelerating the reaction between the isocyanate group and the hydroxyl group in the particles very effectively.

Examples of the organic metal catalyst include dibutyltin oxide, cobalt naphthenate, zinc naphthenate, stannous chloride, stannic chloride, tetra-n-butyltin and tri-.
Examples thereof include n-butyltin acetate, n-butyltin trichloride, trimethyltin hydroxide, dimethyltin dichloride, dibutyltin acetate, dibutyltin dilaurate, tin octenoate or potassium oleate. These 1 type (s) or 2 or more types can be used. The organic metal catalyst is 5 to the organic phase.
It is preferably added in the range of 10,000 ppm, more preferably in the range of 10 to 5,000 ppm. With this organometallic catalyst, a tough magnetic carrier can be formed in an extremely short time. That is, these organometallic catalysts can very effectively promote the reaction between the isocyanate group and the hydroxyl group. The catalyst may be added in advance in the organic phase prior to the dispersion in water, or may be performed between the step of dispersing the organic phase in water and the step of adding the polyamines. Is appropriate. Addition of the catalyst after adding the polyamines, because of the state that the outer wall of the particle is being formed, it becomes difficult for the catalyst to be taken into the inside of the particle, and the urethanization reaction accelerating property inside the particle tends to decrease. From some point, it is not preferable.

The average particle size of the core particles in the present invention is
It is designed according to the particle size of the toner used, the development gap (distance between the photoreceptor and the development sleeve) and the required resolution, but it is usually in the range of 10 to 300 microns (μm), more preferably 15 Is in the range of up to 150 μm.

The average particle diameter of the core particles is determined by the resin raw materials constituting the organic phase, the compounding ratio, the introduced amount of polar groups (sulfonic acid group, sulfonate group, carboxylic acid group, carboxylate group) in the resin, solvent. Can be freely designed by appropriately selecting the addition amount, the types of suspension stabilizers and / or surfactants in the dispersion step and the amounts used, or the stirring speed and reaction temperature in the dispersion step. Can be adjusted.

The particle size of the toner and carrier is the laser diffraction particle size analyzer PRO-700 manufactured by Seishin Enterprise Co., Ltd.
The 50% volume average particle diameter can be measured by using 0S.

The core particles in the present invention are specifically
Outline It is manufactured as follows. (A) Step of adjusting organic phase First, ferromagnetic fine particles, a polyol and a small amount of an 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 to this kneading dispersion and mixed quickly to obtain an organic phase. An organometallic catalyst may be added at this stage.

If necessary, various additives which 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. (B) Step of suspending and dispersing the organic phase in the aqueous phase To suspend and disperse the organic phase obtained in the above step (A) in the aqueous phase, a homomixer, a homodisper, an ultrasonic homogenizer or the like is used. It can be carried out. In order to make the particles spherical, it is more preferable to mildly stir the dispersion system using a propeller stirrer or the like after the above-mentioned dispersion step. 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 40 to 95 ° C., preferably 50 to 90.
The temperature is raised to 0 ° C., and the temperature is maintained for 1 hour to several hours to terminate the reaction.

The organic solvent added at the same time when the organic phase is prepared or when the polyamine is added 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 the reaction. Distill off. (C) Washing / dehydration / drying step The polyurethane polyurea crosslinked particles containing the ferromagnetic fine particles obtained in the above step (B) are thoroughly washed with water and dehydrated /
After being dried, the process proceeds to the next step of coating the polyurethane resin containing the conductivity-imparting substance.

The core particles according to the present invention can be coated with a coating resin by a solution coating method or an emulsion coating method using a spray dry method, or a direct surface polymerization method. . In the case of the solution coat method, the solvent exemplified as the above-mentioned polymerization solvent can be used. Further, in this case, the concentration or viscosity of the solution can be set arbitrarily.

The thickness of the coating material layer on the surface of the core material is usually 0.01 to 30 μm, preferably 0.05 to 30 μm in a dry state.
It is 10 μm. If the coating material layer is too thick, it may be easily peeled off from the core material.

The magnetic carrier for electrophotography of the present invention can be used not only as a developer but also as a conductive magnet brush material which replaces a conventional corona charger or a conductive roll in a charging portion, a transfer portion, and a discharging portion. Is.

[0063]

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 and intermediate used in the present invention will be outlined. (1): Polyisocyanate "Bernock DN-980S" [isocyanurate ring-containing polyisocyanate obtained by using hexamethylene diisocyanate manufactured by Dainippon Ink and Chemicals, Inc .;
Isocyanate group content = 21.0%];
I-1.

"Bernock DN-750" [toluene diisocyanate manufactured by Dainippon Ink and Chemicals, Inc.]
75% ethyl acetate solution of adduct type polyisocyanate; isocyanate group content in terms of solid 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, this is referred to as PI-3.

"Bernock DN901S" [isocyanurate ring-containing polyisocyanate obtained by using hexamethylene diisocyanate manufactured by Dainippon Ink and Chemicals, Inc .; 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.

Isophorone diamine; hereinafter abbreviated as IPDA. Production Example 1 (Production of Core Particle a) Magnetite MAT-305 [manufactured by Toda Kogyo Co., Ltd.] 10
0 part, silane coupling agent KBM803 (γ-mercaptopropyltrimethoxysilane manufactured by Shin-Etsu Chemical) 0.5
Parts and 200 parts of acetone were mixed and stirred in a 500 ml beaker, and then acetone was distilled off to obtain a silane coupling agent-treated magnetite (hereinafter abbreviated as SM).

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 another container, 18.1 parts of PI-1 and P
11.4 parts of O-1 was mixed with 70.5 parts of the above SM and 20 parts of toluene to obtain an organic phase. At 20 ° C., using a homomixer, 7000-7500 rpm
While stirring the aqueous phase with, the organic phase prepared in advance was charged therein and stirred for 1 minute to obtain a suspension dispersion.

Then, this suspension dispersion was transferred to another flask, and dibutyltin dilaurate (hereinafter referred to as DBTDL) was stirred while stirring at 200 rpm with a paddler type stirring blade.
Abbreviated as 0.1), and after 2 minutes, 5 more parts of EDA
1.4 parts of 0% aqueous solution were charged.

After being kept at room temperature (about 25 ° C.) for 2 hours, the temperature was raised to 50 ° C. for 1 hour, and the reaction was continued at 80 ° C. for 2 hours. After completion of the reaction, washing with water, filtration, drying and crushing were carried out to obtain the intended carrier core material particles.

The 50% volume average particle diameter of the core material particles is 2
It was 4 μm. Production Example 2 (Production of Core Material Particle b) The intended core material carrier particles were obtained in the same manner as in Production Example 1 except that the formulation was changed as described below. That is,
As the water phase, 9 parts of "PVA-205",
10 parts of "PVA-217" and 273 parts of water were used, while the organic phases were 15.
0 parts, 12.8 parts of PO-2, 0.6 parts of dimethylolpropionic acid and 15 parts of toluene were used, and as magnetite, 71.6 parts of SM described in Production Example 1 was used.
Further, as the urethane-forming catalyst, 0.1 of DBTDL is used.
Crosslinked core material particles were obtained by using 8 parts and, as the polyamine, 7.8 parts of a 30% aqueous solution of IPDA. The 50% volume average particle diameter was 24 μm.

Production Example 3 (Production of core material particles c) In a 1000 ml flask, 50 parts by weight of phenol,
37% Formalin 6.5 parts by weight, 400 parts by weight of spherical magnetite with an average particle size of 0.24 microns, 4.5 parts by weight of hexamethylenetetramine, 1 part by weight of calcium fluoride, 50 parts by weight of water over 40 minutes while stirring To raise the temperature,
The core particles were obtained by reacting and curing at 85 ° C. for 3 hours. Fifty
The% volume average particle diameter was 104 μm.

Example 1 1.3 parts by weight of polyol PO-1, 1.00 parts by weight of conductive carbon black (# 3950 manufactured by Mitsubishi Kasei) and 190 parts by weight of acetone were charged in a flask and carbon was well dispersed by an ultrasonic homogenizer. After that, 8.61 parts by weight of polyisocyanate PI-4 was used as DBTD as a reaction catalyst.
0.15 parts by weight of 0.1 wt% acetone solution of L was added, and 10 parts of the core material particle a obtained in Production Example 1 was stirred.
0 parts by weight was added, the temperature was raised to 50 ° C., stirring was continued for 20 minutes, and then acetone was distilled off as it was, to deposit a coating layer of conductive carbon black and polyurethane on the surface of the core material particles by reaction. The coating process could be completed without blocking the carrier until almost 100% of the acetone had been distilled off. After heating at 100 ° C. for 4 hours to terminate the reaction, the mixture was classified, and the 50% volume average particle diameter was 29%.
A carrier of μm was obtained. This carrier is called C-1.

The carrier was filled in a measuring cell, and a voltage of 2 V was applied to 10 mm of the carrier-filled layer to measure the electric resistance, which was 1.2 × 10 ² ohm-cm.

To evaluate the toughness (impact resistance, abrasion resistance, adhesion to the core material) of the carrier coating layer, 100 g of the above coated carrier was placed in a cap polyethylene container having a capacity of 100 cc, and a pot mill rotary mount ( After stirring for 24 hours at a rotation speed of 100 rpm on a grind master (manufactured by Bio-Gallery), the mixture is transferred to a polyethylene container with a cap of 100 cc and put on a pot mill rotary stand (Grind Master-manufactured by Bio-Gallery). , 100
After stirring at a rotation speed of rpm for 24 hours, the state of the coating layer was observed by an electron microscope and evaluated. The state of the coating layer of the carrier C-1 did not change at all, and the toughness evaluation result was good.

In order to evaluate the charging performance of the carrier, 84 parts by weight of a styrene / n-butyl methacrylate copolymer resin as a binder resin, 10 parts by weight of carbon black (BPL manufactured by Cabot Co.), a charge control agent (Orient Chem. 2 parts by weight of Bontron N04 manufactured by Mitsui Chemical Co., Ltd. and 4 parts by weight of polyethylene wax (400P manufactured by Mitsui Petrochemical Co., Ltd.) were mixed, kneaded, ground and classified to produce a positively chargeable black toner having an average particle size of 10 μm. Hereinafter, the positively chargeable black toner is referred to as T-1.
Further, as a color toner, 95 parts by weight of polyester made of terephthalic acid / bisphenol A ethylene oxide 2 mol adduct as a binder resin and 5 parts by weight of Pigment Yellow 17 as a pigment were blended, kneaded, pulverized and classified to obtain an average. A negatively-charged yellow toner having a particle size of 8 μm was manufactured. Hereinafter, the negatively chargeable yellow toner is referred to as T-2. 8 parts by weight of these toners and 100 parts by weight of the above-mentioned coated carrier were placed in a polyethylene container with a cap having a capacity of 100 cc and mixed by stirring for 1 hour at a rotation speed of 100 rpm on a pot mill rotating rack to prepare a black developer D. -11 and yellow developer D-12 were prepared. The toner charge amount of the developer was measured with a blow-off powder charge amount measuring device (manufactured by Toshiba Chemical Co.). As a result of measurement with developer D-11, toner T-1
Is +13 microcoulombs / gram, toner T-2 is-
The charge amount was 15 microcoulombs / gram, and it was confirmed that the carrier C-1 had a charge imparting ability required as a carrier.

Comparative Example 1 Instead of 1.3 parts by weight of the polyol P-1 of Example 1 and 8.61 parts by weight of polyisocyanate PI-4, styrene having a glass transition point Tg of 80 ° C. soluble in acetone was used. In the same manner as in Example 1 except that 9.91 parts by weight of n-butyl methacrylate copolymer resin was used, a 50% volume average particle diameter coated with a styrene-n-butyl methacrylate copolymer resin containing conductive carbon black was obtained. A carrier RC-1 of 30 μm was obtained. However, DBTDL used as the reaction catalyst in Example 1 is not used.

In the coating work, it was found that the carrier was blocked by the method of distilling off acetone while stirring the same slurry liquid as in Example 1. Therefore, a flow coater (Spiro coater manufactured by Okada Seiko Co., Ltd.) was used. Coating was carried out by adjusting the coating amount to the same amount as in Example 1 by spraying the coating material liquid on the core material particles flowing at 50 ° C. The obtained carrier is called RC-1.

The electric resistance of this RC-1 was measured and found to be 5.1 × 10 ⁶ ohm cm. Comparative Example 2 Styrene / n-butyl methacrylate containing conductive carbon black was prepared in substantially the same manner except that the amount of the styrene / n-butyl methacrylate copolymer resin used in Comparative Example 1 was reduced from 9.91 parts by weight to 0.5 parts by weight. A carrier coated with a copolymer resin and having a 50% volume average particle diameter of 29 μm was obtained. This carrier is called RC-2. When the electric resistance of RC-2 was measured, it was 3.3 × 10 ⁴ ohm cm, but on the other hand, the toughness evaluation result was poor.

Example 2 Example 1 except that the core particle b shown in Production Example 2 is used.
Similarly to the above, a carrier having a 50% volume average particle diameter of 30 μm was obtained. This carrier is called C-2. When the electric resistance of C-2 was measured, it was 3.6 × 10 ² ohmcm. The toughness evaluation results similar to those in Example 1 were also good.
Similarly, when the charge amount was measured, toner T-1 was +13.
Microcoulombs / gram, toner T-2 shows a charge amount of -15 microcoulombs / gram, and carrier C-2
Was confirmed to have the necessary charge imparting ability as a carrier.

Example 3 Example 1 except that the core particle c shown in Production Example 3 was used.
Similarly to the above, a carrier having a 50% volume average particle diameter of 110 μm was obtained. Hereinafter this carrier is referred to as C-3. When the electric resistance was measured, it was 4.8 × 10 ³ ohm cm. The toughness evaluation results similar to those in Example 1 were also good.
When the charge amount was similarly measured with 4 parts by weight of the toner and 100 parts by weight of this coated carrier, the toner T-1 was +11.
Microcoulomb / gram, toner T-2 shows a charge amount of -10 microcoulomb / gram, and carrier C-3
Was confirmed to have the necessary charge imparting ability as a carrier.

Example 4 100 parts by weight of ferrite core particles having an average particle size of 68 μm were used as core material particles, 0.3 parts by weight of polyol PO-1 and conductive carbon black (# 395 manufactured by Mitsubishi Kasei Co., Ltd.) were used.
0) 1.85 parts by weight and 190 parts by weight of acetone were used and the 50% volume average particle size was 69 μm in the same manner as in Example 1.
m carrier was obtained. This carrier is called C-4. When the electric resistance was measured, it was 8.3 × 10 ³ ohm cm. When the toughness was evaluated in the same manner as in Example 1, it was slightly inferior to the carrier C-1 in Example 1, but the result was almost good. When the charge amount was measured in the same manner as in Example 1, the toner T-1 showed a charge amount of +10 microcoulombs / gram, the toner T-2 showed a charge amount of -11 microcoulombs / gram, and the carrier C-4 was required as a carrier. It was confirmed to have a charge imparting ability.

[0086]

EFFECT OF THE INVENTION The carrier of the present invention is tough and 10 to 10 because the conductive polyurethane coating is formed by reacting and precipitating the polyol, the polyisocyanate and the conductivity-imparting substance on the surface of the core material particles. ^{It has} a low electrical resistance of ⁵ ohm centimeters (high conductivity). Moreover, since the reaction form is such that polyurethane is deposited on the surface of the core material particles,
It has an effect that particles are less likely to be blocked during the process.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location 361

Claims (11)

[Claims] 1. A magnetic carrier for electrophotography, comprising a core material coated with a coating material, wherein the coating material comprises polyurethane and a conductivity-imparting substance. 2. The carrier according to claim 1, wherein the carrier has an electric resistance value of 10 ⁵ ohm cm or less. 3. The carrier according to claim 1, wherein the conductivity-imparting substance is conductive carbon black. 4. The core material is obtained by subjecting a mixture of magnetic particles, a polyol and a polyisocyanate to suspension polymerization in an aqueous medium containing a polyamine. The carrier according to the item. 5. The carrier according to claim 4, wherein the magnetic particles are magnetic particles treated with a silane coupling agent. 6. The carrier according to claim 1, wherein the content of the conductivity-imparting substance is 0.1 to 10 parts by weight with respect to 100 parts by weight of the core material. 7. A core material characterized by reacting a polyol and a polyisocyanate in an organic solvent in the presence of a core material and a conductivity-imparting substance is coated with a coating material comprising polyurethane and a conductivity-imparting substance. And a method for producing a magnetic carrier for electrophotography. 8. The carrier according to claim 7, wherein the carrier has an electric resistance value of 10 ⁵ ohm cm or less. 9. The method according to claim 7, wherein the conductivity-imparting substance is conductive carbon black. 10. The manufacturing method according to claim 7, wherein the ratio of the conductivity-imparting substance is 0.1 to 10 parts by weight with respect to 100 parts by weight of the core material. 11. The method according to claim 7, wherein the core material is obtained by suspension polymerization of a mixture of magnetic particles, polyol and polyisocyanate in an aqueous medium. Method.