JPH10140031A - Powdery magnetite and its applications - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain powdery magnetite used suitably for magnetic toners for electrophotography and resin dispersion carriers. SOLUTION: This powdery magnetite is coated with 0.1-29wt.% of an aqueous type of resin, preferably an emulsified resin composed of polyvinyl acetate, vinyl acetate-acrylic copolymer, water-soluble colloidal dispersion resin composed essentially of alkyd- or epoxyester-based resin, or water-soluble resin composed essentially of alkyd or acrylic resin, and SiO2 , and has preferably 40sec or shorter bulk density measurement time measured with a powder tester and agitation torque of 0.016kg.cm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner for electrophotography and a resin-dispersed carrier, a granular magnetite particle powder used for a black pigment for a paint, and an application thereof.

[0002]

2. Description of the Related Art There is a demand for particulate magnetite having good dispersibility and fluidity for use in magnetic toners for electrophotography. It is considered that the more easily the pigment is loosened when the pigment and the binder resin are premixed with a Henschel mixer or the like in the toner production process, the better the dispersibility. In general, magnetite synthesized in an aqueous solution is disclosed in JP-A-5-213620.
As described in the above, the liquidity is poor, and at the same time, the workability is poor. In particular, the screw feeder may be stopped due to overload due to poor fluidity during transport by the screw feeder. Granular magnetite which is easily loosened and has good fluidity is desired.

One of the causes of loosening and poor fluidity of granular magnetite is van der
It is possible that the Wales force is large. As a method of reducing this force, a method of coating the particle surface with particles sufficiently smaller than the particle or a method of coating the particle surface with a substance having a small Hamaker constant can be considered.

A method utilizing the former is disclosed in JP-A-5-21.
3620. In this method, a method is disclosed in which a silicon component is contained inside magnetite particles, and a particularly fine silicon component is exposed on the surface of the particles. However, although this method is effective in increasing the electric resistance of the magnetite particles and increasing the charge amount to a negative value, magnetite with improved fluidity has a specific surface area of 15 m ² / g or more, Specific surface area is too large for a magnetite for use, and there is a problem in dispersibility.
In addition, since the silicon component is exposed on the surface of the magnetite particles, there is a problem that the washing cake becomes thixotropy in a water washing step for removing an alkali salt produced as a by-product at the time of magnetite synthesis, and the workability is significantly deteriorated.

As a method utilizing the latter, a method of coating the surface of the granular magnetite with a resin can be considered. Generally, the Hamaker constant of a resin is about half as small as that of iron oxide, and by coating the surface of the granular magnetite with the resin, magnetite particles which are easily loosened and have excellent fluidity can be obtained. In addition to granular magnetite, pigments generally have many surface treatments with organic substances in aqueous solutions for the purpose of improving dispersibility, etc.The methods are roughly classified into surfactant treatment, silane and titanium coupling agent treatment, and resin treatment. Is done.

In the case of magnetite used in magnetic toners for electrophotography and resin-dispersed carriers, the structure of the surfactant is preferably a fatty acid salt, but when used as a toner, fatty acid odor is remarkably generated due to heat during fixing. There is a problem to do. Also, silane and titanium coupling agents are generally expensive and not preferred.

[0007] Resin treatment is broadly divided into two types: in situ polymerization and phase separation. The in situ polymerization method is a method in which a pigment is dispersed in a monomer or a monomer solution, and a polymerization initiator is added to generate a polymer on the surface of the pigment. For electrophotographic materials, there are application examples as a method for producing a toner as disclosed in JP-A-7-248649, and as a method for producing a magnetic carrier as disclosed in JP-A-4-11624. Rather than a surface treatment technique for magnetite particles, the obtained particles are huge as magnetite particles of 1 μm or more. The phase separation method is a method of dispersing a pigment in a polymer solution, lowering the solubility of the polymer, and depositing the polymer on the pigment surface.This method can uniformly apply a small amount of polymer to the pigment surface, Magnetite surface-treated by such a method using an aqueous resin has not yet been obtained.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide magnetite particles which are easy to loosen and have excellent fluidity.

That is, the present invention provides: (1) Granular magnetite particle powder coated with 0.1 to 20% by weight of an aqueous resin. (2) 0.1 to 20 wt% of the coated granular magnetite particles in aqueous resin and SiO _2. (3) The amount of SiO _{2 to be} coated is 0.1
The magnetite according to (2), which is ５5% by weight. (4) The bulk density measurement time in the powder tester is 40 seconds or less, and the stirring torque is 0.016 Kg · m.
A granular magnetite particle powder according to any one of the following (1) to (3). (5) Aqueous resin is vinyl acetate, vinyl acetate-acrylic copolymer,
Vinyl acetate-veova copolymer, vinyl acetate-ethylene copolymer, polyacrylate ester, acrylic-styrene copolymer,
Acrylic, styrene, polyethylene, polyvinyl chloride,
Among the emulsion resins mainly composed of urethane, alkyd-based, epoxy ester-based, colloidal dispersion resins mainly composed of acryl-based and water-soluble resins mainly composed of alkyd-based, acrylic-based and melamine-based The granular magnetite particles according to any one of (1) to (4), wherein the granular magnetite particles are coated with one or more selected ones. (6) An electrophotographic magnetic toner using the magnetite particle powder according to any one of (1) to (5). (7) A resin-dispersed carrier using the magnetite particle powder according to any one of (1) to (5). About.

An advantage of using an aqueous resin is that, since granular magnetite is synthesized in an aqueous solution, a magnetite synthesis plant generally requires processing equipment for a high-concentration organic solvent when processing an oily resin. In the case of using, there is no need for an organic solvent treatment facility, so that it is economical and reduces costs.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The granular magnetite particles of the present invention may be spherical, cubic, octahedral, or polyhedral, and have no particular restriction on the size, and may be contained inside and / or near the surface of the particles. The metal in the case is Si, Al,
Zn, Mn, Cu, Ni, P, Co, Mg, Ca, S
There is no particular limitation on r, Ba, Cr, V, Mo, Ti, Sn and the like.

The aqueous resin of the present invention is an emulsion resin, a colloidal dispersion resin, or a water-soluble resin, preferably vinyl acetate, a vinyl acetate-acrylic copolymer,
Vinyl acetate-veova copolymer, vinyl acetate-ethylene copolymer, polyacrylate ester, acrylic-styrene copolymer,
Acrylic, styrene, polyethylene, polyvinyl chloride,
Each emulsion resin containing urethane as a main component, alkyd-based, epoxy ester-based, each colloidal dispersion resin containing acrylic-based as a main component, and alkyd-based, acrylic, melamine-based water-soluble resins. One or two or more selected from these may be properly used depending on the application and purpose. For example, if kneaded into a styrene acrylic resin for final use, a vinyl-based resin is preferable, and an acryl-styrene-based resin having a still more similar structure is preferable. In order to improve heat resistance, a water-soluble resin which can be treated more uniformly than an emulsion is preferable. The amount coated on the granular magnetite particle powder is 0.1 to 20% by weight, preferably 0.2 to 5% by weight, based on the granular magnetite particle powder. If the amount is less than 0.1% by weight, the ease of loosening and the effect of improving the fluidity are reduced. If the amount is more than 20% by weight, the characteristics of the final product, for example, the environmental characteristics in the case of toner, may be deteriorated.
Not preferred.

The granular magnetite particles of the present invention may be coated with SiO ₂ in addition to the aqueous resin for the purpose of improving the charging properties of magnetite. The coating amount of SiO ₂ is preferably 0.1 to 5% by weight based on the granular magnetite particle powder.

[0014] The granular magnetite particles of the present invention preferably have a bulk density measurement time of 4 hours in a powder tester.
0 seconds or less and the stirring torque is 0.016 kg
・ M or less.

The term "bulk density measurement time in a powder tester" as used herein refers to the time required for measuring the bulk density using a powder tester (manufactured by Hosokawa Micron). The shorter the measurement time, the easier it is to loosen. 4
If the time is 0 second or less, the powder is more easily loosened. Further, the stirring torque is used as a powder fluidity index, using an oil absorption meter (Frontex Co., Ltd.),
100 mL of the powder was placed in a mixing container in accordance with JIS K6221-1982, and the stirring torque at the time of stirring was measured. The smaller the stirring torque, the better the fluidity, and preferably 0.016 kg · m or less. If so, it can be regarded as a powder having good fluidity.

The granular magnetite particle powder of the present invention is prepared by adding at least one or two or more selected from the above aqueous resins to magnetite by adsorbing 0.1 to 20%, filtering, washing and drying. , By grinding.

Further, in order to increase the electrification of the magnetite to a negative value, after the synthesis of the granular magnetite particles, the Si
Fluidity can be improved by treating the same aqueous resin with a slurry coated with O ₂ at 0.1 to 5% by weight. As a treatment method of SiO ₂ , a predetermined amount of Na ₂ SiO ₃ , a silicate such as Na ₂ SiO ₅ is neutralized with a sulfuric acid, hydrochloric acid, an acid such as nitric acid in a magnetite slurry, and SiO ₂ is precipitated on the magnetite surface, What is necessary is just to coat. Usually, particles obtained by coating the surface of the particles with SiO ₂ in this way have a thixotropic filtration cake in the filtration and washing steps, resulting in markedly poor workability. However, after SiO ₂ coating,
When the above-mentioned aqueous resin is added, the particles are aggregated by the adsorption of the resin, the filterability is improved, and the workability is improved. There is no limitation on the magnetite concentration at the time of the aqueous resin treatment, but the concentration is preferably 20 to 600 g / L from the viewpoint of productivity, and more preferably 100 to 400 g / L in consideration of uniformity. The pH when treating the aqueous resin differs depending on the resin used,
In general, the emulsion form is preferably in the neutral region, and the water-soluble form is made weakly acidic to make the resin insoluble and easy to adsorb. The temperature at which the aqueous resin treatment is performed is not particularly limited, and may be performed at a liquid temperature convenient for the process. The magnetite slurry to which the aqueous resin has been added as described above can be filtered, washed, dried and pulverized as usual to obtain a resin-coated magnetite. The obtained magnetite is a powder in which the resin is uniformly treated, is easily loosened, and has good fluidity. As described above, the aqueous resin treatment is economical because no special equipment is required.

Further, the treatment with the aqueous resin of the present invention is not limited to granular magnetite particles, but other particles such as iron oxide, hydrated iron oxide, titanium oxide, aluminum oxide, etc.
Alternatively, the present invention can be applied to fibrous particles such as potassium titanate and sodium titanate.

[0019]

The present invention will be described in detail below with reference to examples. It should be noted that the following examples are shown for illustrative purposes only, and the scope of the invention is not limited by these examples.

Example 1 1.05 g of a spherical magnetite slurry (concentration: 300 g / L) having a specific surface area of 7.5 m ² / g was added to 1 L and mixed well. Thereafter, filtration, washing, drying, and pulverization were performed to obtain a magnetite powder coated with a 0.35% acrylic styrene resin. The bulk density measurement time and the stirring torque were measured. The bulk density measurement time was as short as 40 seconds, the stirring torque was as small as 0.0152 Kg · m, and the powder was easily loosened and had good fluidity.

Example 2 Acrylic styrene emulsion was added to Example 1
The same procedure was performed except that the amount was increased to 20 g. A magnetite powder coated with 1.4% acrylic styrene resin was obtained.
The bulk density measurement time was as short as 32 seconds, the stirring torque was as small as 0.0136 kg · m, and the powder was easily loosened and had good fluidity.

Example 3 In Example 1, 1.5 g of an epoxy ester was used instead of the acrylic styrene emulsion.
The same procedure was carried out except for the addition. A magnetite powder coated with 0.5% epoxy ester was obtained. The bulk density measurement time was as short as 23 seconds, and the stirring torque was 0.01
The powder was as small as 28 kg · m, easily loosened, and had good fluidity.

Example 4 An aliphatic polyester-based polyurethane resin was prepared in the same manner as in Example 1 except that the acrylic polyester emulsion was replaced with an aliphatic polyester-based polyurethane resin.
The same operation was performed except that g was added. A magnetite powder coated with 0.5% urethane resin was obtained. The bulk density measurement time was as short as 30 seconds, and the stirring torque was 0.016.
The powder was as small as 0 Kg · m, easily loosened, and had good fluidity.

Example 5 The procedure of Example 1 was repeated except that 3.0 g of a water-soluble acrylic resin was added instead of the acrylic styrene emulsion. A magnetite powder coated with 1.0% acrylic resin was obtained. The bulk density measurement time was as short as 22 seconds, the stirring torque was as small as 0.0152 Kg · m, and the powder was easily loosened and had good fluidity.

Example 6 The same procedure as in Example 1 was carried out except that 3.0 g of a water-soluble alkyd resin was added in place of the acrylic styrene emulsion. A magnetite powder coated with 1.0% alkyd resin was obtained. The bulk density measurement time was as short as 18 seconds, the stirring torque was as small as 0.0160 kg · m, and the powder was easily loosened and had good fluidity.

Example 7 1 L of a spherical magnetite slurry (concentration: 300 g / L) having a specific surface area of 7.5 m ² / g was adjusted to pH 10 at room temperature.
No. 3 water glass equivalent to 3.0 g as SiO ₂ was added dropwise with stirring. After neutralizing the pH to 7.0 with dilute sulfuric acid, the temperature was raised to 60 ° C. and aged for 1 hour to obtain magnetite coated with 1% of SiO ₂ . Further, 1.5 g of an epoxy ester was added as a resin. Filtration, washing, drying, and pulverization were performed to obtain a magnetite powder in which 1% of SiO ₂ and 0.5% of an epoxy ester were combined. The bulk density measurement time was as short as 21 seconds, and the stirring torque was 0.0136 kg.
-It was a small powder of m and it was easy to loosen and it was a powder with good fluidity.

Comparative Example 1 The same procedure was performed as in Example 1 except that the acrylic styrene resin was not added. Resin is untreated powder. The bulk density measurement time was as long as 64 seconds, the stirring torque was as large as 0.024 kg · m, and the powder was difficult to loosen and had poor fluidity.

Comparative Example 2 The procedure of Example 7 was repeated except that no epoxy ester resin was added. The sample became dispersed as the washing proceeded, making it difficult to filter and wash.

Claims (7)

[Claims] 1. A particulate magnetite particle powder coated with 0.1 to 20% by weight of an aqueous resin. 2. An aqueous resin of 0.1 to 20% by weight and SiO
_2. Granular magnetite particle powder coated with ₂ . 3. The granular magnetite particle powder according to claim _{2, wherein the} amount of SiO _{2 to be} coated is 0.1 to 5% by weight based on the granular magnetite particle powder. 4. The bulk density measurement time of the powder tester is 40 seconds or less, and the stirring torque is 0.01
The granular magnetite particle powder according to any one of claims 1 to 3, wherein the particle size is 6 kg · m or less. 5. An aqueous resin comprising vinyl acetate, a vinyl acetate-acrylic copolymer, a vinyl acetate-veova copolymer, a vinyl acetate-ethylene copolymer, a polyacrylic ester, an acrylic-styrene copolymer, acrylic, Emulsion resins based on styrene, polyethylene, polyvinyl chloride and urethane, colloidal dispersion resins based on alkyd, epoxy ester and acrylic, and alkyd, acrylic and melamine based The granular magnetite particle powder according to any one of claims 1 to 4, wherein the granular magnetite particle powder is coated with one or more selected from water-soluble resins. 6. A magnetic toner for electrophotography using the particulate magnetite particles according to claim 1. 7. A resin-dispersed carrier using the granular magnetite particles according to claim 1.