JPH0945516A - Magnetic particle powder, its manufacture and water-base magnetic paint using said magnetic particle powder as well as magnetic recording sheet using the water-base magnetic paint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method in which a magnetic particle powder whose dispersibility into water-base paint is excellent can be obtained industrially. SOLUTION: A magnetic particle powder ic composed of magnetic particles in which a polysiloxane modified by one or more kinds selected from a polyether, a polyester and an aralkyl are applied to the surface of the particles. The magnetic particle powder can be obtained in such a way that the magnetic particles and the polysiloxane which is modified by one or more kinds selected from polyeter, polyester and aralkyl are mixed at a temperature of 80 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic particle powder used in a magnetic paint for forming a magnetic layer of a magnetic recording sheet and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the use of magnetic recording sheets has been expanding in various fields for the purpose of labor saving of office work and work and improvement of efficiency. That is, it is a magnetic ticket for railways, a magnetic commuter pass ticket, a highway pass ticket, a credit card, an ID (identification) card, a telephone card, an orange card, and the like.

In these magnetic recording sheets, a stripe-shaped magnetic layer is provided on one surface of a non-magnetic support such as plastic such as polyvinyl chloride or paper, which is coated with a magnetic paint in which magnetic particle powder is dispersed in a vehicle. In general, one side of the support is a magnetic layer and the other side has a structure in which an image such as a picture or a character is printed.

Magnetic paints include solvent-based magnetic paints containing an organic solvent as a main solvent and water-based magnetic paints containing water as a main solvent, depending on the type of solvent.
Water-based magnetic paints are regarded as promising from the viewpoints of safety, hygiene, and environment because they save resources and energy, and have a low risk of fire.

However, since the dispersion mechanism of the magnetic particle powder in the water-based magnetic paint is different from that of the conventional solvent-based magnetic paint, the magnetic particle powder is sufficiently dispersed in the vehicle by the same dispersion technique as the solvent-based magnetic paint. Cannot be dispersed. That is, in the case of water-based magnetic paint, water-based resin (color spreader)
The water-based resin is a solvent-based resin (color-developing agent).
Exists in a dissolved state with a spread, while it exists mainly in a particle state such as emulsion-polymerized particles or colloidal particles, first of all, by what means the magnetic particle powder is dispersed in the vehicle, and how much Is required, that is, the easy dispersibility and dispersion uniformity of the pigment become a problem, and then the re-aggregation is likely due to the interaction between the dispersed magnetic particles and the water-based resin particles. Dispersion stability becomes a problem. In particular, when the particles to be dispersed in the water-based coating material have magnetism, magnetic agglomeration occurs, so that these problems of dispersibility are particularly serious.

If the dispersibility of the magnetic particle powder in the water-based magnetic paint is insufficient, it causes deterioration of the smoothness of the surface of the magnetic coating film and deterioration of magnetic characteristics such as squareness ratio, and as a result, the magnetic recording sheet. Output fluctuations, dropouts, etc.

Therefore, it is strongly required to improve the dispersibility of the magnetic particle powder in the water-based magnetic paint to obtain the magnetic particle powder having excellent dispersibility, dispersion uniformity and dispersion stability.

Conventionally, in order to improve the dispersibility of the magnetic particle powder in the vehicle, the particle surface of the magnetic particle powder has been coated with various inorganic compounds or organic compounds,
For example, a method of depositing organopolysiloxane on the particle surface of magnetic particle powder (Japanese Patent Publication No. 58-13099).
Japanese Examined Patent Publication No. 5-4129, Japanese Patent Laid-Open No. 63-113082.
JP, JP-A-63-165461, JP-A-63
-168346, JP-A-1-182368, JP-A-2-212561, JP-A-3-163
No. 172, etc.), a method of depositing an organosilicon compound on the particle surface of magnetic particle powder (JP-A-50-44498, JP-A-51-40903, JP-A-62-87).
No. 237, etc.) and a method of depositing a silane coupling agent on the particle surface of magnetic particle powder (JP-A-49-5960).
No. 8, JP 51-134899, and JP 5
2-44794, JP-A-54-7310,
JP-A-54-110999 and JP-A-60-240
769, JP-A-4-18930, JP-A-5
-239446 gazette) etc. are tried.

Further, Japanese Unexamined Patent Publication (Kokai) No. 62-187772 discloses that polyester-modified polysiloxane is used by adding it to a coating material because it has an action of lowering tackiness and improving lubricity. ing.

[0010]

It is currently most demanded to improve the dispersibility in an aqueous magnetic coating composition to obtain a magnetic particle powder having excellent dispersibility, dispersion uniformity and dispersion stability. However, such magnetic particle powder has not been obtained yet.

That is, magnetic particle powders having the above-mentioned known organopolysiloxane, organosilicon compound, silane coupling agent, etc. deposited on the surface of the particles are easily dispersed in a vehicle as shown in Comparative Examples below. It is difficult to say that all of the properties, dispersion uniformity, and dispersion stability are sufficient.

Also, when the polyester-modified polysiloxane disclosed in the above-mentioned Japanese Patent Laid-Open No. 62-187772 is added to the paint, the dispersibility of the magnetic particle powder in the vehicle is also similarly shown in the comparative example. Is insufficient in easy dispersibility, dispersion uniformity, and dispersion stability.

Therefore, it is a technical object of the present invention to obtain a magnetic particle powder having improved dispersibility in a water-based magnetic coating material and excellent in dispersibility, dispersion uniformity and dispersion stability.

[0014]

The above technical problems can be achieved by the present invention as described below.

That is, according to the present invention, magnetoplumbite type ferrite particles or magnetic oxidization in which polysiloxane modified with one kind or two kinds or more selected from polyether, polyester and aralkyl are coated on the surface of particles. Magnetic particle powder consisting of iron particles, if necessary, the surface of the particles is coated with squaric acid, and further the surface of the deposited squaric acid is one or more selected from polyether, polyester or aralkyl. Magnetoplumbite-type ferrite particles coated with polysiloxane that has been modified by the above method, or magnetic particle powder consisting of magnetic iron oxide particles, magnetoplumbite-type ferrite particles or magnetic iron oxide particles, and if necessary, the magnetoplumbite-type Water suspension containing ferrite particles or magnetic iron oxide particles and squaric acid After mixing the liquids, the mixture is filtered and dried to obtain square plume-type magnetoplumbite-type ferrite particles or magnetic iron oxide particles, and one or more selected from polyether, polyester and aralkyl. A method for producing magnetic particle powder, which comprises mixing polysiloxane modified by the method at a temperature of 80 ° C. or higher, an aqueous magnetic coating material and a non-magnetic support obtained by mixing the magnetic particle powder in a water-based coating material. In a magnetic recording sheet having a magnetic layer provided on at least a part of a body, the magnetic layer is formed by applying the aqueous magnetic coating material and drying, and the surface roughness of the magnetic layer is 0. The magnetic recording sheet has a squareness ratio of 35 μm or less and a squareness ratio of 0.87 or more.

The structure of the present invention will be described in detail below.

First, the magnetic particle powder according to the present invention will be described.

The magnetic particle powder according to the present invention is a magnetoplumbite type ferrite particle powder or magnetic iron oxide particle powder.

Examples of the magnetoplumbite type ferrite particle powder include barium ferrite particle powder, strontium ferrite particle powder, barium-strontium ferrite particle powder and these ferrite particle powders.
It contains various elements such as Co, Ti, Zn, Sn, Al, and Ni that are added to control the magnetic characteristics.
The particle shape may be any shape such as a plate shape or an amorphous shape. Plate-like particles are preferable in consideration of the orientation in the paint.

The particle size of the magnetoplumbite type ferrite particle powder is preferably 0.01 to 10.0 μm,
More preferably, it is 0.1 to 1.0 μm. The BET specific surface area value is preferably 1.0 to 15 m ² / g, more preferably 2.0 to 10 m ² / g. The plate ratio (plate surface diameter: thickness) is preferably 1.5: 1 to 20: 1, and more preferably 3: 1 to 10: 1. Coercive force Hc is 100-60
00 Oe is preferable, and more preferably 200 to 5000
Oe. The saturation magnetization σs is preferably 50 to 65 emu / g, and more preferably 55 to 65 emu / g.

When the particle size is less than 0.01 μm, the particles are extremely fine and magnetically aggregate easily,
Dispersibility in the vehicle tends to be difficult. When the particle size exceeds 10.0 μm, the surface of the magnetic layer to be obtained becomes poor in smoothness and is liable to be disadvantageous for magnetic recording due to the spacing loss.

If the BET specific surface area is less than 1.0 m ² / g, the particles become coarse and the smoothness of the magnetic layer surface is poor, which is likely to be disadvantageous for magnetic recording. When the BET specific surface area value exceeds 15 m ² / g, the particles are extremely fine or the particles are porous, and it becomes difficult to obtain good dispersion.

When the plate ratio is less than 1.5: 1, the orientation of the magnetic particle powder in the magnetic field tends to be insufficient.
When the plate ratio exceeds 20: 1, the magnetic particle powders are easily oriented in the magnetic field, but stacking occurs between the particles and particle aggregates are easily generated, and noise is easily generated. .

When the coercive force Hc is less than 100 Oe,
Since the coercive force is extremely low, it tends to be affected by an external magnetic field, and the recorded information is likely to be insufficiently protected. If the coercive force Hc exceeds 6000 Oe, an extremely strong magnetic field is required for erasing written information, which necessitates enlargement of the device and is industrially and economically unfavorable.

As the magnetic iron oxide particle powder, magnetite ( FeO _x · Fe ₂ O ₃ ) particle powder, maghemite particle powder, those obtained by doping these particles with Co, or those obtained by coating or modifying the particle surface with a Co compound are used. Further, those containing or adhering elements such as Al, Si, Zn, P, Sn, etc., which are usually used for improving magnetic properties to these, etc. Shape,
It may have any shape such as a spindle shape or a plate shape.

In the case of granular particles, the particle size of the magnetic iron oxide particles is preferably 0.01 to 10.0 μm in average particle diameter, and more preferably 0.1 to 1.0 μm in consideration of dispersibility. In the case of acicular particles or spindle-shaped particles, the major axis diameter is 0.1 to 20 μm and the axial ratio (major axis diameter: minor axis diameter) is 2: 1.
Particles having a major axis diameter of 0.1 to 1.0 μm and an axial ratio (major axis diameter: minor axis diameter) of 3: 1 to 10: 1 are preferable in view of dispersibility and orientation. Is more preferable. Further, in the case of plate-like particles, the average particle size (plate surface diameter) is 0.01 to 2
Particles having a thickness of 0.0 μm and a thickness of 0.005 to 2.0 μm are preferable. Considering dispersibility and orientation, an average particle diameter (plate surface diameter) of 0.1 to 10.0 μm and a thickness of 0.01 to 1. 0 μm
Are more preferable.

The coercive force Hc of the magnetic iron oxide particles is preferably 100 to 500 Oe in the case of magnetite particles.
More preferably 250 to 400 Oe, in the case of maghemite particles, 210 to 400 Oe is preferable, and more preferably 250 to 380 Oe, Co is doped, or Co is used.
In the case of magnetite particles or maghemite particles in which the surface of the particles is coated or modified with a compound, 300 to 1500 Oe is preferable, and 400 to 900 Oe is more preferable.

The saturation magnetization σs of the magnetic particle powder is preferably 75 to 90 emu / g in the case of magnetite particles, more preferably 78 to 90 emu / g, and 70 to 85 emu / g in the case of maghemite particles, and more preferably 75 to 85 emu / g, 70 to 90 emu / g in the case of magnetite particles or maghemite particles which are Co-doped or whose particle surface is adhered or modified with a Co compound.
g is preferable, and more preferably 75 to 90 emu / g.

The modified polysiloxane deposited on the surface of the magnetic particles according to the present invention includes a polyether modified polysiloxane represented by Chemical formula 1, a polyester modified polysiloxane represented by Chemical formula 2, and an aralkyl modified polysiloxane represented by Chemical formula 3. One or more selected from polysiloxanes (referred to as a specific modified polysiloxane).

The molecular weight of the polyether modified polysiloxane is in the range of 350 to 500,000, preferably 1
000 to 100,000, more preferably 2
It is in the range of 000 to 50,000.

The polyester-modified polysiloxane has a molecular weight in the range of 400 to 500,000, preferably 1.
000 to 100,000, more preferably 2
It is in the range of 000 to 50,000.

The molecular weight of the aralkyl-modified polysiloxane is in the range of 350 to 500,000, preferably 1.
000 to 100,000, more preferably 2
It is in the range of 000 to 50,000.

[0033]

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[0034]

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[0035]

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The amount of the specific modified polysiloxane deposited is preferably 0.01 to 10% by weight based on the magnetic particles in terms of C.
When the amount is less than 0.01% by weight, it becomes difficult to obtain the magnetic particle powder excellent in dispersibility which is the object of the present invention. 1
Even if it exceeds 0% by weight, the magnetic particle powder excellent in dispersibility which is the object of the present invention can be obtained, but the effect is in a saturated state and it is meaningless to add more than necessary.

The dispersibility of the magnetic particle powder according to the present invention, in which the specific modified polysiloxane is adhered on the surface of the particle, is used in a solvent-based paint, has a squareness ratio of 0.87 or more, preferably 0.88 or more. Ra of the coating film is 0.37 μm or less, preferably 0.35 μm or less, RMS is 0.44 μm or less,
It is preferably 0.42 μm or less, and the change rate of Ra showing dispersion stability when the coating is diluted is 8.9% or less, preferably 8.5.
% Or less.

When the magnetic particle powder according to the present invention, in which the specific modified polysiloxane is adhered to the surface of the particle, is used in the water-based paint, the dispersibility is such that the squareness ratio is 0.86 or more, preferably 0.88 or more, Ra of the coating film is 0.35 μm or less, preferably 0.30 μm or less, RMS is 0.41 μm or less, preferably 0.36 μm or less, and the rate of change of Ra upon dilution of the paint showing dispersion stability is 15% or less, preferably Is 10% or less, and the Ra value after storage showing the storage stability is 0.45μ
m or less, preferably 0.35 μm or less.

The amount of squaric acid deposited on the magnetic particle powder according to the present invention is 0.01 to 10% by weight based on C based on the magnetic particles.
Is preferred. If the amount is less than 0.01% by weight, it becomes difficult to obtain the magnetic particle powder having the better dispersibility, which is the object of the present invention. Even if the amount exceeds 10% by weight, the magnetic particle powder having a more excellent dispersibility, which is the object of the present invention, can be obtained, but the effect is in a saturated state and it is meaningless to add more than necessary.

The ratio of the amount of the specific modified polysiloxane deposited on the magnetic particle powder according to the present invention to the amount of squaric acid deposited is:
It is preferably 1: 1000 to 1000: 1. It is more preferably 1: 100 to 100: 1.

Dispersion in the case where a magnetic particle powder according to the present invention in which squaric acid is adhered to the surface of a particle and further the specific modified polysiloxane is adhered to the surface of the adhered square acid is used in a solvent-based paint. As for the property, the squareness ratio is 0.88 or more, preferably 0.89 or more, Ra of the coating film is 0.35 μm or less, preferably 0.33 μm or less, RMS is 0.43 μm or less, preferably 0.42 μm or less, Ra Change rate of 8.
It is 0% or less, preferably 7.5% or less.

The dispersibility of a magnetic particle powder according to the present invention, in which squaric acid is adhered to the surface of a particle, and further the specific modified polysiloxane is adhered to the surface of the adhered square acid, is used in an aqueous paint. Has a squareness ratio of 0.86 or more, preferably. 088 or more, Ra of the coating film is 0.35 μm or less, preferably 0.30 μm or less, RMS is 0.40 μm or less,
It is preferably 0.35 μm or less, and the rate of change of Ra upon dispersion of the coating showing dispersion stability is 12.0% or less, preferably 1
The Ra value after storage of the coating composition, which is 0.0% or less and has storage stability, is 0.40 μm or less, preferably 0.30 μm or less.

The mixing ratio of the magnetic particle powder to the coating material in the present invention is 10 to 90 relative to 100 parts by weight of the coating material base material.
It can be used in the range of parts by weight, and considering the handling of the paint, preferably 20 to 60 parts by weight,
It is preferably 30 to 50 parts by weight.

A resin, a solvent, and if necessary, an extender pigment, a drying accelerator, a surfactant, a curing accelerator, an auxiliary agent, an antifoaming agent, etc. are mixed in the coating material base material according to the present invention.

The blending ratio of the resin and the solvent in the coating material in the present invention is 50 to 5,000 with respect to 100 parts by weight of the resin.
Part by weight is preferred, and more preferably 100 to 2000 parts by weight. If the amount is less than 50 parts by weight, the viscosity of the vehicle becomes too high and it becomes difficult to uniformly mix and disperse. 5000
If the amount is more than parts by weight, the amount of the solvent composition in the coating material becomes too large, and the dispersion share to the particles is not applied during mixing and dispersion, which is not preferable.

As the resin, vinyl chloride / vinyl acetate copolymer resin, vinyl chloride resin, vinyl acetate resin, nitrocellulose, polyvinyl butyral resin, acrylic resin, alkyd resin, polyester resin, polyurethane, which are usually used for solvent type paints, are used. Resins, epoxy resins, phenol resins, melamine resins, amino resins and the like can be used. For the water-based paint, a water-soluble alkyd resin, a water-soluble melamine resin, a water-soluble acrylic emulsion resin, a water-soluble urethane emulsion resin and the like which are commonly used can be used.

As the solvent, use may be made of toluene, xylene, butyl acetate, methyl acetate, methyl isobutyl ketone, butyl cellosolve, ethyl cellosolve, butyl alcohol, methyl ethyl ketone, cyclohexanone, and aliphatic hydrocarbon which are commonly used for solvent-based paints. You can

For water-based paints, butyl cellosolve, butyl alcohol and the like which are commonly used can be used.

As the defoaming agent, Nopco 8034 (trade name), SN deformer 477 (trade name), SN deformer 5013 (trade name), SN deformer 247.
(Brand name), SN Deformer 382 (Brand name) (all above are manufactured by San Nopco Ltd.), Anti Home 08
Commercial products such as (trade name) and Emulgen 903 (trade name) (all of which are manufactured by Kao Corporation) can be used.

The magnetic recording sheet according to the present invention is one in which a magnetic layer is provided on at least a part of a non-magnetic support, and if necessary, a concealing layer for protecting the color of the magnetic layer and a protective layer. Layers and the like are provided.

The non-magnetic support is a plastic such as vinyl chloride or polyester, a composite paper obtained by compounding paper and plastics (paper / polyester / paper, polyester / paper / polyester), high-quality paper, or the like. is there.

For bank cards, credit cards, cash cards, POS cards, key cards, etc.,
Polyvinyl chloride is used for sealless commuter passes, program cards, telephone cards, etc., and highway coupons, postal savings ledgers, composite paper for seal commuter passes, expressway pass tickets, process control cards, buses Paper is commonly used for common coupon tickets, some POS cards, railroad tickets, and horse voting tickets.

The thickness of the non-magnetic support is preferably 100 to 1000 μm in the case of vinyl chloride, more preferably 500 to 900 μm, and 10 to 50 in the case of polyester.
0 μm is preferable, and more preferably 100 to 300 μm.
m, in the case of composite paper, 50 to 500 μm is preferable, more preferably 100 to 300 μm, and in the case of high-quality paper, 50 to 500 μm.
1000 μm is preferable, and more preferably 100-80
0 μm.

The magnetic layer is provided on a part of one surface of the non-magnetic support, the entire surface of one surface, a part of the one surface and the entire surface of the other surface, and the entire surfaces of both surfaces, and the thickness thereof is preferably 0.5 to 20.0 μm. , And more preferably 1.0 to 10.0 μm.

Next, a method for producing the magnetic particle powder according to the present invention as described above will be described.

The shape, particle size, BET specific surface area value, coercive force Hc and saturation magnetization σ of the magnetoplumbite type ferrite particle powder used as the particles to be treated in the present invention.
s is almost the same as those characteristics of the magnetic particles after the above-mentioned specific modified polysiloxane is adhered.

It is essential that the modified polysiloxane in the present invention is modified by one or more selected from polyether, polyester and aralkyl. Polydimethylsiloxane, methylphenylpolysiloxane, known in the above, Depending on the organopolysiloxane such as methylhydrogenpolysiloxane, dimethylpolysiloxycyclolide, alkoxypolysiloxane, amino group-end modified polysiloxane, or silane coupling agent, as shown in Comparative Examples below, the dispersibility of the present invention can be improved. It is impossible to obtain a magnetic particle powder having excellent properties.

As the specific modified polysiloxane in the present invention, a commercially available product may be used. As the polyether-modified polysiloxane, BYK-320, BYK-32
5, BYK-080 (trade name) (Big Chemie Co., Ltd.)
Manufactured by BYK-310 (trade name) (by BIC Chemie Co., Ltd.).
Manufactured), and as the aralkyl modified polysiloxane,
There is BYK-322 (trade name) (manufactured by BYK Chemie Co., Ltd.), all of which are in a solution state, and may be used by adding them to the magnetic particle powder as they are.

The addition amount of the specific modified polysiloxane is preferably 0.05 to 20.0% with respect to the magnetic particle powder.
If it is less than 0.05%, it becomes difficult to obtain the magnetic particle powder having excellent dispersibility, which is the object of the present invention. 20.
Even if it exceeds 0%, the magnetic particle powder excellent in dispersibility, which is the object of the present invention, can be obtained, but the effect is in a saturated state and it is meaningless to add more than necessary.

The mixing of the magnetic particles and the specific modified polysiloxane in the present invention is carried out at a temperature of 80 ° C. or higher. 80
When the temperature is lower than 0 ° C, the viscosity of the modified polysiloxane is so high that it becomes difficult to uniformly deposit the magnetic particles on the particle surfaces, and the magnetic particle powder aimed at by the present invention cannot be obtained.

When the magnetic particles are mixed with the modified polysiloxane, it is preferably heated in advance at 80 ° C. or higher to reduce the water content, and particularly adjusted to 0.2% by weight or less. If the magnetic particles have a large amount of water, the water that is liquid-crosslinked between the particles strengthens the agglomeration of the particles, making it difficult to uniformly apply the particles to each other.

As a device for mixing, a high speed agitate mixer which is usually used in mixing the magnetic particle powder and the surface treatment agent, specifically, a Henschel mixer, a speed mixer, a ball cutter, a power mixer, a hybrid is used. A mixer or the like may be used, and a Henschel mixer is preferably used in consideration of uniform deposition of the specific modified polysiloxane.

It is essential that the stirring time be sufficient to mix the magnetic particles and the specific modified polysiloxane in the high speed agitator mixer, and at least 5 minutes or more, preferably 1 minute.
0 minutes or more.

The squaric acid in the present invention is commercially available 3,4-dihydroxy-3-cyclobutene-1,2-
Zion (manufactured by Tokyo Chemical Industry Co., Ltd.) can be used.

Squaric acid is in a powder state and can be used by directly adding it to water to be coated, or by dissolving it in water in advance to obtain a solution concentration of 0.1 to 50 g / l, preferably 0. Although it may be used in an amount of 0.5 to 10 g / l, the latter method is preferable.

The process for depositing squaric acid in the present invention is as follows.
After mixing an aqueous suspension containing magnetic particles and squaric acid,
It may be filtered and dried.

The magnetic particles and the squaric acid may be added to the water either first or simultaneously.

The amount of squaric acid added is 0.01 to 30.0%, preferably 0.02 to 25.0%, based on the magnetic particles.
%. If it is less than 0.01%, it becomes difficult to obtain the magnetic particle powder having a better dispersibility than the object of the present invention. Even when the content exceeds 30.0%, magnetic particle powder having an excellent dispersibility, which is the object of the present invention, can be obtained, but the effect is in a saturated state and it is meaningless to add more than necessary.

It is essential that the mixing time of the aqueous suspension is such that the magnetic particles and the squaric acid are sufficiently mixed and stirred, and it is at least 5 minutes, preferably 10 minutes or more.

For the production of a magnetic recording sheet, a direct coating method in which a magnetic coating is directly coated on a non-magnetic support and then dried,
There are a tape application method in which a separately manufactured magnetic tape is applied onto a non-magnetic support, and a magnetic layer transfer method in which a transfer type magnetic tape is adhered onto a non-magnetic support and the base is peeled off.

[0071]

The most important point in the present invention is that the magnetic particles coated with the specific modified polysiloxane on the surface of the particles exhibit excellent dispersibility not only in the solvent-based paint but also in the water-based paint.

The present inventor believes that the magnetic particles coated with the specific modified polysiloxane according to the present invention exhibit excellent dispersibility, particularly in an aqueous paint.

In the solvent-based paint, the resin is spread and adsorbed on the surface of the magnetic particles, and when the adsorbed resin brings the magnetic particles close to each other, a large exchange repulsive force is exerted, so-called steric hindrance occurs, and the magnetic particles They prevent them from approaching each other and the magnetic particles are stably present in the paint.

However, in the water-based paint, as described above, the resin does not spread and exists in a particle state, so that the steric hindrance effect seen in the magnetic powder in the solvent-based paint is difficult to be exerted. Becomes difficult to disperse.

It is generally known that the larger the absolute value of the zeta potential of the suspended particles in the paint, the better the dispersibility of the suspended particles due to electrostatic repulsion. When the zeta potential of the magnetic particles coated with the specific modified polysiloxane is measured in a water-based paint, as shown in the examples below, about -40 to -80 mV, and particularly -45 to -80 mV and the same. Since the absolute value is high, the surface of the particles in the water-based paint is likely to be negatively charged, and the electric repulsion between the particles is large. Moreover, since the molecular chains of polyether, polyester, aralkyl, etc. are spread and adsorbed on the particle surface, the synergistic effect of the large electric repulsion and steric hindrance effect makes it easy to loosen the aggregation, and the primary particles It becomes possible to disperse even to a state close to, and as a result, excellent dispersibility and dispersion uniformity are obtained.

After the particles are once dispersed in a state close to the primary particles, the electrical repulsion can maintain the dispersed state for a long time, resulting in excellent dispersion stability.

[0077]

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

The average particle diameter of the particles in the following Examples and Comparative Examples is shown by the average value of the numerical values measured from electron micrographs, and the specific surface area of the particles is shown by the value measured by the BET method. The thickness and plate ratio of the plate particles are BE
Specific surface area value measured by T method and the above average diameter (plate surface diameter)
It is shown by the numerical value obtained from.

The shape of the particles was observed with a transmission electron microscope and a scanning electron microscope.

The amount of the modified polysiloxane and squaric acid deposited was determined by "Horiba Metal Carbon / Sulfur Analyzer EMIA-220".
0 ”(manufactured by Horiba, Ltd.) was used to show the amount of carbon measured.

The smoothness of the surface of the magnetic coating film is obtained by coating the base film made of paper with the coating composition obtained by mixing the below-mentioned predetermined components in a predetermined ratio and dispersing the mill base, magnetic field orientation, and drying. Surface smoothness of the surface profile measuring device Surfcom 57
The center line average roughness (Ra) and the mean square roughness (RMS) measured using 5A (manufactured by Tokyo Seiki Co., Ltd.) are shown.

The dispersibility of the magnetic particle powder is shown by the easy dispersibility, the dispersion stability, the storage stability, the smoothness of the coating film surface and the orientation of the particles in the magnetic layer.

The easy dispersibility was shown by comparing various characteristics of the magnetic layer prepared by using two kinds of magnetic coating materials prepared by changing the dispersion time of the mill base. The smaller the difference, the better the dispersibility.

Dispersion stability is determined by mixing the following predetermined components in a predetermined ratio, and in the case of a solvent-based paint, the mill base (2) is mixed and dispersed for 120 minutes, and the solvent-based paint is mixed with a solvent (MEK / Toluene / cyclohexanone = 5/3/2)
40% of the diluted paint, in the case of water-based paint, the diluted paint obtained by adding 40% of water to the water-based paint when the mill base is mixed and dispersed for 60 minutes is applied to the base film at a thickness of 50 μm, The surface roughness Ra of the magnetic layer produced by drying was measured, and shown as the percentage increase with respect to the surface roughness Ra of the magnetic layer similarly produced by using the coating material before dilution. The smaller the value, the better the dispersion stability.

The degree of smoothness of the final magnetic coating film means the degree of uniform dispersion of the magnetic particle powder. The smaller the values of Ra and RMS, the better the surface smoothness of the coating film, and the better the uniform dispersibility of the magnetic particles in the vehicle.

The storage stability of the water-based paint was determined by blending the following predetermined components in a predetermined ratio and dispersing the mill base for 60 minutes, and leaving the paint for 1 day. The surface roughness Ra of the coating film produced by applying and drying the thickness was shown by the measured value. The smaller the value, the better the storage stability.

The orientation is determined by blending the following predetermined components in a predetermined ratio and dispersing the mill base to obtain a coating, applying the coating on the substrate, magnetic field orientation, and the squareness ratio (RS) of the dried coating. The measured values are shown. The higher the squareness ratio, the better the orientation and the preferred direction for the magnetic recording sheet.

The value of the zeta potential of the magnetic particles in the water-based paint is more than 0.5% with respect to 100 g of pure water by adding 0.5 g of the paint obtained by blending the below-mentioned predetermined composition in a predetermined ratio and dispersing the mill base. A zeta potentiometer MODEL-501 (PEN-KEM) was used by using a suspension obtained by dispersing with a sonic disperser C-10 (manufactured by Ultrasonic Industrial Co., Ltd.) for 1 minute.
It was shown by the value measured by the company.

<Production of Magnetic Particle Powder> Examples 1-12, Comparative Examples 1-14;

Example 1 Average particle size 0.65 μm, BET specific surface area value 4.6 m ² /
g, coercive force Hc2753Oe, saturation magnetization σs55.6e
3.0 kg of granular barium ferrite particles having a mu / g, a pH value of 9.5 and a water content of 0.17 wt% were preheated to 85 ° C.
The mixture was charged into a Henschel mixer (10 l) heated to 1, and operated and mixed at a rotation speed of 1200 rpm for 10 minutes to adjust the water content of barium ferrite particles to 0.06 wt%.

Maintaining the Henschel mixer at a temperature of 85 ° C., polyether modified polysiloxane BYK-0
80 (trade name) (manufactured by BYK Chemie Co., Ltd.) 30 g (100% active ingredient) (1.0 for barium ferrite particles)
Corresponds to% by weight. ) At a rate of 3.0 g / min.
The mixture was added over a period of 20 minutes, followed by mixing for 20 minutes to deposit the polyether-modified polysiloxane on the surface of the barium ferrite particles.

Then, the mixture was cooled to room temperature while mixing with a Henschel mixer to obtain barium ferrite particles having polyether modified polysiloxane deposited on the surface of the particles.

The obtained barium ferrite particle powder is
The deposited amount of the polyether modified polysiloxane was 0.52% by weight in terms of C.

Examples 2 to 6 and Comparative Examples 6 to 14 Type and amount of magnetic particle powder and heat treatment temperature, presence and amount of squaric acid addition, presence and type of modified polysiloxane,
Magnetic particle powders were obtained in the same manner as in Example 1 except that the amount and the temperature at the time of mixing were variously changed.

Various conditions at this time are shown in Tables 1 and 2.

Comparative Examples 1 to 5 Untreated magnetic particle powders were prepared for comparison. Table 2 shows various characteristics of these magnetic particle powders.

[0097]

[Table 1]

[0098]

[Table 2]

Example 7 Squaric acid 3,4-dihydroxy-3-cyclobutene-
35 g of 1,2-dione (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was previously added to 5 l of pure water, and water was added to the squaric acid solution to make 35 l, which was well stirred with a stirrer. The concentration of squaric acid at this time was 1.0 g / l.

An average particle size of 0.65 was added to the square acid solution.
μm, BET specific surface area value 4.6 m ² / g, coercive force Hc2
753 Oe, saturation magnetization σs 55.6 emu / g, pH value 9.5, 3.5 kg of granular barium ferrite particles having a water content of 0.17 wt% were gradually added, and 30 were added with a homomixer.
After mixing and stirring for a minute, filtration, drying and pulverization were carried out to apply squaric acid to the particle surface of the barium ferrite particles.

The obtained barium ferrite particle powder is
The amount of deposited square acid was 0.40% by weight in terms of C.

3.0 kg of barium ferrite particle powder having the surface of particles coated with squaric acid was put into a Henschel mixer (10 l) preheated to 85 ° C., and the mixture was operated and mixed at a rotation speed of 1200 rpm for 10 minutes. The water content was removed to make the water value of the barium ferrite particles 0.03% by weight.

While maintaining the temperature of the Henschel mixer at 85 ° C., polyether modified polysiloxane BYK-
080 (trade name) (manufactured by BYK Chemie Co., Ltd.) 60 g (100% active ingredient) was added at an addition rate of 3.0 g / min over 20 minutes, followed by mixing for 20 minutes, and the particle surface of the barium ferrite particles was added. Was coated with polyether modified polysiloxane.

Then, the mixture was cooled to room temperature while mixing with a Henschel mixer to obtain barium ferrite particles in which the polyether modified polysiloxane was adhered to the square acid surface.

The obtained barium ferrite particle powder is
Polyether-modified polysiloxane deposited amount is 1.
It was 05%.

Examples 8 to 12 Treated in the same manner as in Example 7 except that the type, amount and heat treatment of the magnetic particle powder, the temperature, the type and amount of the modified polysiloxane treatment, and the mixing temperature were variously changed. A magnetic particle powder was obtained.

Table 1 shows various conditions and various characteristics at this time.

<Production of Solvent-Based Paint> Examples 13 to 24, Comparative Examples 15 to 28;

Example 13 18 g of the treated magnetic particle powder obtained in Example 1 was used in a 140 ml mayonnaise container, and the following coating composition was blended in the following proportions and mixed with 100 g of 1.5 mmφ glass beads for 15 minutes on a paint shaker. Dispersion was performed to obtain a mill base (1).

<Composition of Millbase (1)> Treated Magnetic Particle Powder Obtained in Example 3 37.5 parts by weight Lecithin solution (2.5 wt% cyclohexanone solution) 7.5 parts by weight

Next, using the obtained mill base (1),
The following coating composition was blended in the following proportions and further mixed and dispersed by a paint shaker to obtain a mill base (2). At this time, two types of mill bases (2) were prepared, with the mixing and dispersing time of 60 minutes and 120 minutes.

<Composition of Millbase (2)> Millbase (1) 45.0 parts by weight Vinyl chloride vinyl acetate copolymer resin solution 12.5 parts by weight (VAGF Union Carbide Co., 30 wt% cyclohexanone solution) Methyl ethyl ketone 16.3 parts by weight Department

Further, using the obtained mill base (2), the following coating compositions were blended in the following proportions and mixed and dispersed for 30 minutes with a paint shaker to obtain a solvent-based coating.

<Composition of Solvent-Based Paint> Millbase (2) 73.8 parts by weight Polyurethane resin solution 12.5 parts by weight (Nipporan 2301 Nippon Polyurethane Industry Co., Ltd., methyl ethyl ketone / toluene = 1/1 30 wt% solution) Methyl ethyl ketone 3.4 parts by weight Cyclohexanone 10.3 parts by weight

The obtained solvent-based coating material was filtered through a stainless steel mesh having an opening of 44 μm, coated on a PET base film with a thickness of 50 μm, oriented with an orientation magnetic field of 2800 G, and dried to obtain a coating film. Various properties of the obtained coating film are shown in Tables 3 and 4.

For comparison, the same procedure as in Example 13 was carried out except that the polyether-modified polysiloxane BYK-080 was added to the paint of the solvent-based paint without depositing it on the surface of the barium ferrite particles. The coating film produced by using this coating material is a coating material produced by applying the coating material (corresponding to the method described in JP-A-62-187772).
In the case of a coating film prepared by using a mill base (2) having a dispersion time of 120 minutes, coercive force Hc is 2703 Oe, Rs is 0.85, Ra is 0.47 μm, and RMS is 0.56 μm.
The rate of change of Ra upon dilution was 11.4%.

Examples 14 to 24, Comparative Examples 15 to 28 Example 1 except that the type of magnetic particle powder was variously changed.
A solvent-based paint was produced in the same manner as in 3.

Tables 3 and 4 show various properties of the obtained solvent-based paint.

[0119]

[Table 3]

[0120]

[Table 4]

<Production of Water-based Paint> Examples 25-36, Comparative Examples 29-42;

Example 25 Using 20.0 g of the barium ferrite particle powder obtained in Example 1 in a 140 ml glass container, the coating composition was blended in the following proportions and mixed and dispersed with 100 g of 1.5 mmφ glass beads in a paint shaker. , A mill base was produced. At this time, two types of mill bases were prepared, where the mixing and dispersing time was 30 minutes and the mixing and dispersing time was 60 minutes.

<Composition of Millbase> Barium ferrite particle powder obtained in Example 1 44.4 parts by weight Dispersant 0.5 parts by weight (trade name: Poise-521 (40% aqueous solution): manufactured by Kao Corporation) Defoamer 0.3 parts by weight (Brand name: Nopco 8034: manufactured by San Nopco Ltd.) Ion-exchanged water 18.4 parts by weight Butyl cellosolve 7.9 parts by weight

Using the above mill base, the coating composition was blended in the following proportions and further mixed and dispersed for 15 minutes on a paint shaker to obtain an aqueous coating.

<Composition of water-based paint> Millbase 71.5 parts by weight Water-soluble acrylic emulsion (35 wt%) 28.5 parts by weight (Brand name: SW-135: Sanyo Kasei Co., Ltd.)

The obtained water-based paint was filtered through a stainless mesh having an opening of 44 μm, applied on a paper base film with a thickness of 50 μm, oriented with a 3200 G orientation magnetic field, and dried to obtain a coating film. Table 5 shows various properties of the obtained coating film.

For comparison, the same procedure as in Example 25 was carried out except that the polyether-modified polysiloxane BYK-080 was added to the coating material during the production of the water-based coating material without adhering to the surface of the barium ferrite particles. A paint was produced (corresponding to the method described in JP-A-62-187772). A coating film produced by using this coating material is a coating film produced by using a mill base having a dispersion time of 60 minutes. , Coercive force Hc is 2710 Oe, Rs is 0.83, R
a is 0.42 μm, RMS is 0.50 μm, the rate of change of Ra upon dilution is 18.6%, and the Ra upon storage is 0.
56 μm, zeta potential of particles in paint is -21.6 mV
Met.

Examples 26 to 36, Comparative Examples 29 to 42 Example 2 except that the type of magnetic particle powder was variously changed.
A water-based paint obtained in the same manner as in No. 5 was produced.

Table 5 and Table 6 show various properties of the obtained water-based paint.
Shown in

[0130]

[Table 5]

[0131]

[Table 6]

[0132]

INDUSTRIAL APPLICABILITY The magnetic particle powder according to the present invention is a magnetic particle powder having excellent dispersibility and orientation in paints, especially in water-based paints, as shown in the above-mentioned Examples, and therefore magnetic recording sheet. Suitable as magnetic particle powder for use.

The water-based coating material produced by using the magnetic particle powder according to the present invention has good dispersibility and orientation of the magnetic particle powder, and since it is water-based, it is well compatible with paper. It is particularly preferable when it is used for a magnetic recording sheet using paper as the sheet.

Continued Front Page (72) Inventor Hiroko Morii 4-1-2 Funairi Minami, Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Industry Co., Ltd. Creative Center

Claims (6)

[Claims] 1. Magnetoplumbite-type ferrite particles or magnetic iron oxide particles, the surface of which is coated with a polysiloxane modified with one or more selected from polyether, polyester and aralkyl. Magnetic particle powder. 2. The surface of the particles is coated with squaric acid, and the surface of the deposited square acid is polyether,
Magnetic particle powder consisting of magnetoplumbite type ferrite particles or magnetic iron oxide particles coated with a polysiloxane modified with one or more selected from polyester or aralkyl. 3. Magnetoplumbite-type ferrite particles or magnetic iron oxide particles are mixed with a polysiloxane modified by one or more selected from polyether, polyester and aralkyl at a temperature of 80 ° C. or higher. 2. The method for producing magnetic particle powder according to claim 1, wherein the modified polysiloxane is deposited on the surface of the magnetoplumbite ferrite particles or magnetic iron oxide particles. 4. A magnetoplumbite ferrite particle or magnetic iron oxide particle is mixed with an aqueous suspension containing squaric acid, and then filtered and dried to obtain the magnetoplumbite ferrite particle or magnetic iron oxide particle. Squaric acid is adhered to the particle surface, and then modified by magnetoplumbite type ferrite particles or magnetic iron oxide particles to which the square acid is adhered and one or more kinds selected from polyether, polyester and aralkyl. A polysiloxane which has been modified by one or more selected from polyether, polyester or aralkyl, and is mixed on the surface of the deposited square acid by mixing the polysiloxane with a polysiloxane having a temperature of 80 ° C. or higher. The method for producing the magnetic particle powder according to claim 2, wherein 5. A water-based magnetic coating material, wherein the magnetic particle powder according to claim 1 or 2 is blended in a water-based coating material. 6. A magnetic recording sheet comprising a magnetic layer provided on at least a part of a non-magnetic support, wherein the magnetic layer is formed by applying the aqueous magnetic coating composition according to claim 5 and drying. The magnetic recording sheet is characterized in that the magnetic layer has a surface roughness of 0.35 μm or less and a squareness ratio of 0.87 or more.