JPH02130902A - Black magnetic fluid - Google Patents

Abstract

PURPOSE:To maintain a fluid in a low-viscosity state while the fluid brings out black color by dispersing a specific magnetic metal oxide and black coloring agent into a solvent. CONSTITUTION:When a magnetic metal oxide of the chemical composition expressed by Formula I and a black coloring agent are dispersed into a solvent, an excellent black magnetic fluid which can maintain a low viscosity while the fluid brings out black color and seldom causes the nozzle of a printer to get clogged is obtained. The A, B, and C of the formula are respectively set to 0.3<=A<=1.0, 0.8<=C<=2.0, and A+B=1.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to black magnetic fluid.

[Conventional technology]

A magnetic fluid is made by stably dispersing very fine ferromagnetic particles with a diameter of about 1 Onm in a solvent such as an organic solvent or water, and the particles are dispersed in a gravity field, a normal centrifugal field, or a magnetic field. Because no agglomeration or sedimentation occurs, it behaves like a ferromagnetic liquid.

Regarding the production of such ferromagnetic materials, for example, Japanese Patent Publication No. 53-17118 describes a method for producing an oil-based magnetic fluid, and Japanese Patent Publication No. 54-40069 describes a method for producing a water-based magnetic fluid. Each is listed.

In the former production method, a basic salt of an unsaturated fatty acid such as oleic acid is added to an aqueous suspension of a wet-synthesized magnetic metal oxide such as magnetite, and the unsaturated fatty acid carboxylic acid is added to the fine particles of the magnetic metal oxide. An oil-based magnetic fluid is produced by adsorbing and aggregating ions and dispersing the agglomerates in oil.

In the latter production method, the aggregates obtained in the same manner as in the former production method are placed in water, and an anionic surfactant having 9 or more carbon atoms in the hydrocarbon chain is added to create a water-based magnetic material. Manufacture fluids.

The magnetic fluid produced in this way has already been used for rotary shaft seals, specific gravity differential selection, various dampers, acceleration sensors, tilt sensors, etc., and its application fields are expanding more and more.

As the field of application is expanding, for example, applications to magnetic ink for printers are beginning to be considered.

[Problem to be solved by the invention]

In conventional black magnetic ink, the magnetic fluid itself was intended to produce a black color, so the concentration of the magnetic material was extremely high, and the high concentration resulted in extremely high viscosity. Furthermore, since the amount of solvent is small, it is susceptible to drying and the nozzle is easily clogged.

[Means for solving the above problems]

The invention according to claim 1 for solving the above problem is based on a first-order composition formula % formula % () [wherein A, B, and C in the formula satisfy the following relationship.

0.3≦A≦1.0, 0.8≦C≦2.0, A+B
This is a black magnetic fluid characterized by being made by dispersing a magnetic metal oxide represented by the following formula in a solvent.

The invention according to claim 2 has a first-order composition formula (% formula %) [wherein A, B, and C in the formula satisfy the following relationship.

0.3≦A≦1.0, 0.8≦C≦2.0, A
This is a black magnetic fluid characterized by being made by dispersing a magnetic metal oxide represented by +B=13 and a black colorant in a solvent.

This invention will be explained in detail below.

The black magnetic fluid of this invention is.

Composition formula (N!10)A (zllo)8 (Fe203
)C [However, A, B, and C in the formula satisfy the following relationship.

0.3≦A≦t, o, o, a≦C≦2.0, A
It is made by dispersing particles of a magnetic metal oxide represented by +B-11 in a solvent.

The particle size of the magnetic metal oxide is not particularly limited as long as the magnetic metal oxide is dispersed in a solvent and becomes a colloid, and is usually 1 to 20 nm.

Examples of the solvent include paraffinic hydrocarbons such as hexane, pentane, octane, and dodecane, benzene, isobutyne polymers, oligomers of polyα-olefins, alkylnaphthalenes, polybutenes, esters, ethers, and saturated or unsaturated aliphatic An acid with relatively low polarity.

and water.

Which of these solvents is preferred depends on the intended use of the magnetic fluid; for example, kerosene and water may be suitable solvents.

The concentration of the magnetic metal oxide in the solvent is appropriately set depending on the use of the magnetic fluid, and is usually in the range of 5 to 85% by weight.

If the concentration is less than 5% by weight, the obtained black magnetic fluid may not exhibit magnetism, and if it exceeds 85% by weight, the viscosity of the obtained black magnetic fluid increases and it becomes gel-like. , and its liquidity may decrease.

Further, the black magnetic fluid of the present invention can also be dispersed in the solvent after the particles of the magnetic metal oxide are coated with a surfactant.

The surface-active substance adsorbs to the magnetic metal oxide particles and forms a monomolecular film of the surface-active substance on the surface of the particles, thereby causing the magnetic metal oxide particles to aggregate or precipitate in the solvent. It has an action or function of maintaining a uniform and stable dispersion state without any problems.

Examples of the surface-active substance include oleic acid, linoleic acid, linuric acid, dodecylbenzenesulfonic acid, and dodecylsulfuric acid.

The black magnetic fluid of the present invention becomes more preferable when a black colorant is dispersed in the solvent together with the magnetic metal oxide.

The black colorant can be combined with the original black of the magnetic metal oxide to form a black magnetic fluid that exhibits a more vivid black color.

Examples of the black colorant include oil-based dyes such as oil black, and water-based dyes such as serious black.

These colorants may be used alone.

Further, a plurality of types of colorants may be used in combination.

In addition, in consideration of heat resistance and light fastness, the oil-based dyes include Oil Black BW, Oil Black BY, Oil Black BS, Oil Black ES, and Oil Black T-.
Preferred are metal complex dyes such as 505, Oil Black MF, and Oil Black HBB.

When the aqueous dye is used in an aqueous colored magnetic fluid, direct dyes such as Serious Black VE, Serious Black L, and Fast Black, which are stable at pH 7 or higher, are preferred.

The amount of the black colorant used is usually preferably 10 parts by weight or less based on the magnetic metal oxide.

Next, a method for producing a black magnetic fluid according to the present invention will be explained.

The above compositional formula (MnO)*(ZnO)e(Fez03)
c [However, A, B, and C in formula 1 satisfy the following relationship.

0.3≦A≦i, o, o, s≦C≦2.0, A+
A magnetic metal oxide represented by B=l] can be produced as follows.

First, salts of manganese, zinc, and ferric iron, such as sulfates, nitrates, and chlorides, are weighed out so that the metal composition ratio of the salts corresponds to the composition of each metal in the above composition formula. , dissolve each of the metal salts in water.

The mixing ratio of the total amount of metal salt and water at this time is (water: metal salt)
is 0.2 to 4 mol per liter of water, preferably 1.0 to 3.0 mol per liter of water.

Next, an alkali such as hydric soda is added to this mixed solution to adjust the pH to 7 to 13, preferably 1G-12i,
:m! ! do.

When the pH of the mixed solution is adjusted to the above value, a mixture of the metal hydroxide and water is obtained.

Next, this mixture is subjected to hydrothermal synthesis.

The heating temperature for the hydrothermal synthesis is 60 to 120°C, preferably 80 to 100°C.

It should be noted that if the heating temperature is less than 80°C, the reaction may not occur and an oxide may not be formed, and if it exceeds 120°C, the particle size may become large and it may not be possible to form a magnetic fluid.

The time for the hydrothermal synthesis is usually 20 minutes, although it depends on the scale.
minutes to 10 hours, preferably 30 minutes to 5 hours. If the reaction time is less than 20 minutes, the reaction may not occur and oxides may not be formed, and if it exceeds 10 hours, the particle size will increase and the magnetic fluid It may become impossible to realize the

The magnetic metal oxide can be obtained by cooling the mixture thus obtained and then removing water.

In this invention, if desired, a surfactant substance can be adsorbed onto the particles of the magnetic metal oxide obtained.

In the adsorption method, first, the magnetic metal oxide, water, and a surfactant substance are mixed.

Incidentally, after the mixing, heating may be performed as desired.

The heating temperature is usually 80° C. or higher, and the heating time is 20 minutes or longer.

By this mixing, a monomolecular layer or a bimolecular layer of the surfactant is formed on the surface of the magnetic metal oxide particles.

Next, the pH of the obtained mixture is usually adjusted to about 5 to 7 to remove the surfactant constituting the outer layer of the bimolecular layer of surfactant from the bimolecular layer.

As a result of its removal, the dispersed molecules momentarily aggregate and precipitate.

A lipophilic inorganic fine powder can be obtained by filtering the thus obtained precipitate and then drying it.

By mixing this lipophilic inorganic fine powder and a non-polar or weakly polar solvent, or by mixing this lipophilic inorganic fine powder, a solvent, and the black colorant,
It is possible to obtain a colored black magnetic fluid in which lipophilic inorganic fine powder is dispersed in a solvent.

On the other hand, by mixing the lipophilic inorganic fine powder with water and other 7-ionic, cationic, or nonionic surfactant whose hydrocarbon chain has 10 or more carbon atoms, or by mixing the lipophilic inorganic fine powder with water, By mixing inorganic fine powder, water, and other 7-ionic, cationic, or non-ionic surfactants whose hydrocarbon chain has 10 or more carbon atoms, coloring and water-friendly inorganic A magnetic fluid in which fine powder is dispersed can be obtained.

The black magnetic fluid obtained in this way has low viscosity and
It is a clear black magnetic fluid.

〔Example〕

(Example 1) Production of magnetic metal oxide A magnetic metal oxide was produced by hydrothermal synthesis as follows.

That is, 0.7 mol of special grade reagent manganese sulfate tetrahydrate,
0.3 mol of zinc sulfate heptahydrate and hydrated ferric sulfate [Fe
11.0% of 2(SO4)s·lH2O was dissolved in 1 liter of distilled water.

Aqueous sodium hydroxide solution was added to the obtained aqueous solution until the pH thereof became 11±1 to form a gel.

The obtained gelled product was loaded into a stainless steel autoclave and kept at 120° C. for 40 minutes to perform hydrothermal synthesis.

After the reaction, the autoclave was cooled and the contents were taken out from the autoclave to obtain a magnetic metal oxide as a slurry suspension.

The slurry-like suspension of the magnetic metal oxide has a concentration of 10
The resulting suspension was prepared into a suspension that was 200% by weight.
g and 100 jr/i of sodium oleate aqueous solution 15
Mix with 0 mJl and heat to 90°C.

The adsorption reaction was carried out for 30 minutes while maintaining the temperature.

The suspension was then flocculated by adding IN hydrochloric acid to bring the pH of the suspension to 5-7, the electrolyte and excess sodium oleate were removed by repeated decantation, and the suspension was poured onto filter paper. A dehydrated cake was obtained by filtration, and this dehydrated cake was further air-dried.

Next, the air-dried dehydrated cake was added to 50 g of benzene, and the temperature was raised while stirring. When the liquid temperature reached 60°C, heating and stirring were stopped, and a dispersion of magnetic metal oxides dispersed in benzene was prepared. I got it.

This dispersion was loaded into a centrifuge and centrifuged at 8,000 G for 30 minutes to remove a small amount of sediment, yielding 85 g of benzene-based magnetic fluid. The concentration of magnetic metal oxide in this magnetic fluid was 23% by weight.

CIK standard color system (JI) of this benzene-based fluid stock solution
S 28722) are shown in Table 2.

Sample 1 is a mixture of the benzene-based magnetic fluid stock solution Ice, 0.05 g of dye oil black (manufactured by Orient Chemical Industries), and benzene Ice, and the CIK of this 1 is
The standard color system (JIS 28722) is shown in Table 1.

Sample 2 was a mixture of 1 cc of the benzene-based magnetic fluid stock solution, 0.2 g of dye oil black (manufactured by Orient Chemical Industry Co., Ltd.), and 4 cc of benzene.
I! The standard color system (JIS Z8722) is shown in Table 1.

Sample 3 was a mixture of 1 cc of the benzene-based magnetic fluid stock solution, 0.4 g of dye oil black (manufactured by Orient Chemical Industry Co., Ltd.), and 8 cc of benzene.
) CIE@Semi-color system (JIS Z8722) I Shown in Table 1.

(Example 2) Using the same magnetic metal oxide as in Example 1, a magnetic fluid was manufactured as shown below.

The air-dried dehydrated cake of Example 1, 2 g of sodium dodecylbenzenesulfonate, and 50 g of water were mixed with stirring to obtain a uniform dispersion.

This dispersion was centrifuged in the same manner as above to obtain 88 g of water-based magnetic fluid.

The concentration of magnetic metal oxide in this magnetic fluid was 22% by weight.

Sample 4 was a mixture of the water-based magnetic fluid stock solution ice, 0.05 g of dye Serious Black L (manufactured by Bayer AG), and 1 cc of water, and the CIE standard brown color (IS Z8722) of sample 4 is shown in Table 1.

Sample 5 was a mixture of the water-based magnetic fluid stock solution ice, 0.2 g of Dye Serious Black L (manufactured by Bayer AG), and 4 cc of water. Standard color system (J
IS Z8722) is shown in Table 1.

Sample 6 was a mixture of 1 cc of the water-based magnetic fluid stock solution, Dye Serious Black L (manufactured by Bayer, 30.4 g, and 8 cc of water).
S Z8722) is shown in Table 1.

Sample 7 is a mixture of the water-based magnetic fluid stock solution ice, 0.03 g of dye Serious Black vE (manufactured by Bayer AG), and water ice.The CI of sample 7! Standard color system (
JIS Z8722) is shown in Table 1.

Sample 8 was a mixture of 1 cc of the water-based magnetic fluid stock solution, 0.1 g of dye Serious Black VE (manufactured by Bayer AG), and 4 cc of water. .

Sample 9 is a mixture of 3 cc of pre-water distribution base magnetic fluid stock solution, 0.2 g of dye Serious Black VE (manufactured by Bayer) and 8 cc of water, and the GIE standard color system (
JIS 28722) is shown in Table 1.

Table 1 [Effects of the Invention] According to the present invention, it is possible to maintain a low viscosity while developing a clear black color, so even if it is used as a magnetic ink for an inkjet printer, for example, it will not cause clogging of printer nozzles. Further, by further dispersing a black colorant, it is possible to provide a black magnetic fluid that has advantages such as being able to develop a clearer black color while maintaining a low viscosity.

Claims (1)

[Claims] (1) The following compositional formula (MnO)_A(ZnO)_B(Fe_2O_3)_C
[However, A, B, and c in the formula satisfy the following relationship. 0.3≦A≦1.0, 0.8≦C≦2.0, A+B=1
] A black magnetic fluid characterized by being formed by dispersing a magnetic metal oxide represented by the following in a solvent. (2) The following compositional formula (MnO)_A(ZnO)_B(Fe_2O_3)_C
[However, A, B, and C in the formula satisfy the following relationship. 0.3≦A≦1.0, 0.8≦C≦2.0, A+B=1
] A black magnetic fluid characterized by being formed by dispersing a magnetic metal oxide represented by the following formula and a black colorant in a solvent.