JPH0940983A - Alcohol-based magnetic fluid and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an alcohol-based magnetic fluid which can be applied as an alcohol fuel capable of being held by a magnetic field and as an alcohol component capable of being held by a magnetic field in a heat pipe and permitting heat exchange to be regulated by a magnetic field, and to provide a process for preparing the same. SOLUTION: This alcohol-based magnetic fluid comprises an alcohol, a surfactant, a liquid crystalline compd. which is liq. at a predetermined temp., and a magnetic metal oxide and/or a magnetic metal particle. The process for preparing the alcohol-based magnetic fluid comprises the steps of: adding an alkali agent to a dispersion contg. a magnetic metal oxide and/or magnetic metal particle, and a surfactant to prepare an alkaline dispersion; adjusting the alkaline dispersion to a pH value of not more than 2; drying the alkaline dispersion; and mixing the dried dispersion, a liq. crystalline compd. and an alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alcohol-based magnetic fluid and a method for producing the same, more specifically, it has excellent dispersibility, fluidity and durability, and can be suitably used in a wide temperature range from room temperature. The present invention relates to an alcohol-based magnetic fluid that can be produced and a method for producing the same.

[0002]

2. Description of the Related Art A magnetic fluid is made by dispersing very fine particles of a ferromagnetic material having a particle size of about 10 nm in a solvent such as an organic solvent or water in a stable state. Magnetic fluid behaves like a liquid having ferromagnetism because particles do not aggregate and settle in a gravitational field, a normal centrifugal field, or a magnetic field. This property is unique to other materials. For example, the sealing effect obtained by placing a magnetic fluid in the magnetic flux concentration part and the magnetic buoyancy acting on a non-magnetic substance in a magnetic fluid placed under a magnetic field gradient are used. It has been proposed to try new applications such as specific gravity selection, storage materials using magnetism, magnetic ink for printers, waste oil treatment, various devices, etc., and is widely expected to have applicability.

Regarding the method for producing such a ferromagnetic material, for example, Japanese Patent Publication No. 53-17118 discloses that "a fine powder of ferromagnetic oxide by a wet method is used, and its aqueous suspension contains a basic unsaturated fatty acid. The salt is added to the fine powder in the suspension in an amount necessary to complete at least the monomolecular adsorption layer of the fatty acid ion so that the fatty acid ion is adsorbed on the surface of the fine powder in the suspension by one molecule or more. , Then add acid to pH 7
The method for producing a magnetic fluid is characterized in that the suspension is agglomerated into an acidic aqueous solution of ~ 5, and the agglomerate is filtered, washed, dehydrated and dispersed in oils. This manufacturing method is understood to be a method of manufacturing an oil-based magnetic fluid.

Japanese Examined Patent Publication No. 54-40069 has disclosed that "basic salt of oleic acid or basic salt of linoleic acid is added to an aqueous suspension of fine powder of ferromagnetic oxide by a wet method. An amount of oleate ion or linoleate ion was added to the fine powder in an amount necessary to complete the adsorption layer of at least a single molecule, and more than one molecule of oleate ion or linoleate ion was adsorbed on the surface of the fine powder in the suspension. After that, the liquid is adjusted to be an acidic solution having a pH of less than PH7 and then filtered to obtain powder particles. The powder particles are washed with water or another polar solvent and then placed in water to find out the carbon number of the hydrocarbon chain. No. 9 or more anionic or nonionic surfactant is added to form a suspension, and a method for producing a magnetic fluid using water as a dispersion medium ”is described. This manufacturing method is understood to be a water-based magnetic fluid manufacturing method.

Japanese Unexamined Patent Publication (Kokai) No. 4-108898 discloses "A dispersion medium containing silicon oil as a main component, ferromagnetic fine particles, and a magnetic fluid composition obtained by dispersing the ferromagnetic fine particles in the dispersion medium. A coupling agent having a functional group that reacts with a functional group on the surface of the ferromagnetic fine particles and directly chemically bonds to the surface of the ferromagnetic fine particles via a reaction product at this time; The magnetic fluid composition is characterized in that the ferromagnetic fine particles are dispersed in the dispersion medium through a reactive silicone oil having a functional group that directly chemically bonds with the functional group.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an alcohol-based magnetic fluid having excellent dispersibility and fluidity. An object of the present invention is to provide an alcohol-based magnetic fluid having a high vapor pressure and a low boiling point, which is excellent in dispersibility and fluidity. Another object of the present invention is to provide a simple method for producing such an excellent alcohol-based magnetic fluid. Further, an object of the present invention is to provide an alcohol-based magnetic fluid capable of controlling heat exchange in a magnetic field (the magnetic field has substantially the same meaning as the magnetic field; see RIKEN), and a magnetic field retained therein To provide a manufacturing method.

[0007]

The invention according to claim 1 for solving the above-mentioned problems is an alcohol, a surfactant, a liquid crystal compound which is liquid at a predetermined temperature, a magnetic metal oxide and / or a magnetic metal. The alcohol-based magnetic fluid according to claim 2, characterized in that an alkaline agent is added to a suspension in which magnetic metal oxide and / or magnetic metal particles are dispersed. An alkaline suspension is thus obtained, a surfactant is added to this alkaline suspension, the pH of the resulting suspension is adjusted to 2 or less, and the resulting acidic suspension is dried to obtain A method for producing an alcohol-based magnetic fluid, which comprises mixing a dried product, a liquid crystal compound that is liquid at a predetermined temperature, and alcohol.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

<Alcohol-based magnetic fluid> The alcohol-based magnetic fluid of the present invention comprises alcohol, a surfactant, a liquid crystal compound which is a liquid at a predetermined temperature, a magnetic metal oxide and /
Alternatively, it contains magnetic metal particles.

-Alcohol-Alcohols that can be used in the present invention include monohydric alcohols and polyhydric alcohols.
Among these, monohydric alcohols are preferable.

The monohydric alcohols include methanol, ethanol, n-propanol, 2-propanol, n-butanol, n-butanol, 2-methylpropanol, 2-butanol, 2-methyl-2-propanol, n-butanol. Pentanol, 3-methylbutanol, 2-
Methyl-1-butanol, 2-methyl-2-butanol, 2,2-dimethylbutanol, n-hexanol,
Examples thereof include n-octanol, 2-octanol, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, and n-octadecanol. Among these, lower alcohols are preferable, and lower alcohols having 1 to 5 carbon atoms are more preferable. 1 to 5 carbon atoms, preferably 1 to 5 carbon atoms
By employing a lower alcohol of 3, alcohol-based ferrofluids with high vapor pressure and low boiling point are obtained.

The polyhydric alcohols include 1,2-
Ethanediol, 1,2-propanediol, 1,3-
Propanediol, 1,4-butanediol, 2,3-
Examples thereof include dimethyl-butanediol and 1,2,3-propanetriol. Among these, preferred are diols having 2 to 5 carbon atoms, and more preferred are diols having 2 to 4 carbon atoms and having hydroxyl groups bonded to both ends.

-Surfactant- As the surfactant that can be used in the present invention,
For example, anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants can be mentioned.

Typical examples of the anionic surfactant include organic acid salts such as carboxylic acid salts and sulfonic acid salts, sulfuric acid ester salts, and phosphoric acid ester salts.

Examples of the carboxylates include sodium laurate, potassium laurate, sodium myristate, sodium palmitate, sodium stearate, sodium oleate, potassium oleate, ether carboxylates and the like. Among these, polyoxyethylene alkyl ether acetate is preferable.

The sulfonates include higher alkyl sulfonates, α-olefin sulfonates, higher fatty acid ester sulfonates, dialkyl sulfosuccinates, higher fatty acid amide sulfonates, and alkyl allyl sulfonates. Examples thereof include alkylbenzene sulfonate, alkylnaphthalene sulfonate, and formalin condensate of alkylallyl sulfonate. Among these, dialkyl sulfosuccinate is preferable.

Examples of the above-mentioned sulfuric acid ester salt include higher alcohol sulfuric acid ester salt (alkyl sulfuric acid ester salt), secondary higher alcohol sulfuric acid ester salt, alkyl ether sulfuric acid ester salt, alkyl allyl ether sulfuric acid ester, higher fatty acid ester sulfuric acid ester salt, Examples thereof include sulfuric acid ester salts of higher fatty acid alkylolamide, sulfated oil and the like. Of these, alkyl ether sulfate ester salts are preferable.

Examples of the phosphoric acid ester salt include sodium didecyl phosphate, sodium polyoxyethylene lauryl ether phosphate, sodium polyoxyethylene cetyl ether phosphate, sodium polyoxyethylene oleyl ether phosphate, and polyoxyethylene alkylphenyl ether phosphate. Examples thereof include sodium. Among these, sodium polyoxyethylene oleyl ether phosphate is preferable.

Typical examples of the cationic surfactant include amine salts and quaternary ammonium salts. Among these, the quaternary ammonium salt is preferable.

Examples of the amine salt include alkylamine salts, polyamines, aminoalcohol fatty acid derivatives and the like. Among these, amino alcohol fatty acid derivatives are preferable.

As the quaternary ammonium salt, an alkyl quaternary ammonium salt, a cyclic quaternary ammonium salt, a quaternary ammonium salt having a hydroxyl group, a quaternary ammonium salt having an ether bond, a quaternary ammonium salt having an amide bond, etc. Is mentioned. Of these, preferred are quaternary ammonium salts having an ether bond.

Examples of the amphoteric surfactant include N-lauryl β-alanine, N-stearyl β-alanine, N,
N, N-trimethylaminopropionic acid, N-hydroxyethyl N, N-dimethylaminopropionic acid, N-
Methyl N, N-dihydroxyethylaminopropionic acid, N, N, N-trihydroxyethylaminopropionic acid, N-lauryl N, N-dimethylaminopropionic acid, N-myristyl N, N-dimethylaminopropionic acid, N- Palmitic N, N-dimethylaminopropionic acid, N-stearyl N, N-dimethylaminopropionic acid, N-hexyl N, N-dimethylaminoacetic acid, N-octyl N, N-dimethylaminoacetic acid, N- Decyl N, N-dimethylaminoacetic acid, N-
Undecyl N, N-dimethylaminoacetic acid, N-lauryl N, N-dimethylaminoacetic acid, N-myristyl N,
Examples thereof include N-dimethylaminoacetic acid, N-palmityl N, N-dimethylaminoacetic acid, N-stearyl N, N-dimethylaminoacetic acid, 1-pyridinium betaine and 1-α-picolinium betaine.

Examples of the nonionic surfactants include ether type nonionic surfactants, ether ester type nonionic surfactants, ester type nonionic surfactants, block polymer type nonionic surfactants, and nitrogen-containing nonionic surfactants. An ionic surfactant is mentioned as a typical example.

As the ether type nonionic surfactant, a single chain length polyoxyethylene ether type ether type nonionic surfactant; polyoxyethylene fatty alcohol ether, polyoxyethylene alkyl allyl ether, polyoxyethylene lanolin Examples thereof include polyoxyethylene alkyl or alkyl allyl ethers such as alcohols; ethylene oxide derivatives of alkylphenol formalin condensates. Among these, polyoxyethylene alkyl allyl ether is preferable. Among the polyoxyethylene alkyl allyl ethers, polyoxyethylene alkylphenyl ethers and the like are preferable.

The ether ester type nonionic surfactant is a polyoxyethylene sorbitan fatty acid ester,
Examples thereof include polyoxyethylene ethers containing an ester bond such as polyoxyethylene glyceryl monofatty acid ester, polyoxyethylene propylene glycol fatty acid ester, and polyoxyethylene sorbitol fatty acid ester; natural oils and fats, and polyoxyethylene derivatives of waxes. Among these, polyoxyethylene ether containing an ester bond such as polyoxyethylene sorbitol fatty acid ester is preferable.

Examples of the ester type nonionic surfactant include polyoxyethylene fatty acid ester and polyhydric alcohol ester.

Examples of the block polymer type nonionic surfactants include pluronic type nonionic surfactants, tetronic type nonionic surfactants, block polymers containing an alkyl group and the like.

Examples of the nitrogen-containing nonionic surfactant include polyoxyethylene fatty acid amide, alkylolamide, and polyoxyalkylamine.

Of these, anionic surfactants and cationic surfactants are preferable. Furthermore,
As the surfactant combined with the particles of the magnetic metal oxide, an anionic surfactant, particularly a carboxylate is preferable, and as the surfactant combined with the magnetic metal, an amine salt is preferable.

From another point of view, anionic surfactants are preferable among the above-mentioned various surfactants, and among them, organic acid salts, alkyl lactates, N-acyl amino acid salts, alkyl ether carboxylic acids. An anionic surfactant having a carboxyl group at the terminal of polyethylene oxide, which is a salt and is ether-bonded with an alkyl group, is particularly preferable. The alkyl group in the anionic surfactant having a carboxyl group at the terminal of polyethylene oxide ether-bonded with this alkyl group has 5 to 5 carbon atoms.
It is 30, preferably 10 to 24, and the number of repeating units of ethylene oxide in polyethylene oxide is 1 to 30, preferably 2 to 10.

These preferred anionic surfactants are:
Generally, it is supplied as a sodium salt or its aqueous solution.

Generally speaking, it is preferable that the above-mentioned various surfactants have sufficient solubility in the liquid crystal compound. From this point of view, when the liquid crystal compound is a cyanobiphenyl compound, a sodium salt of polyethylene tridecyl ether acetic acid, which exhibits high solubility, is preferable.

-Liquid Crystal- Examples of liquid crystal compounds usable in the present invention include nematic liquid crystal compounds, smectic liquid crystal compounds, and cholesteric liquid crystal compounds. Among these, a nematic liquid crystal compound or a smectic liquid crystal compound is preferable.

As the nematic liquid crystal compound and the smectic liquid crystal compound, azomethine compounds, azo compounds, azooxy compounds, ester compounds, stilbene compounds, biphenyl compounds, terphenyl compounds, trans-cyclohexane compounds, pyrimidine compounds. A compound etc. are mentioned.

As the azomethine compound, N-
(4-ethoxybenzylidene) -4-n-hexylaniline, N- (4-butoxybenzylidene) -4-n-octyl-2-methylaniline, N- (4-proxybenzylidene) -4-n-octylaniline, N- (4-n
-Heptylbenzylidene) -4-cyanoaniline, N-
(4-n-octylbenzylidene) -4-cyanoaniline, N- (4-cyanobenzylidene) -4-ethylaniline, N- (4-methoxybenzylidene) -4-butanoyloxyaniline, N- (4-butane) Noyloxybenzylidene) -4-methoxyaniline, N- (4-methoxybenzylidene) -4- (3-methylpentanoyloxy) aniline, N- (4-n-hexyloxybenzylidene) -4- (5-methylhexa) Noyloxy) aniline, N- (4-n-butylbenzylidene) -4-β-cyanoethylaniline and the like.

Examples of the azo compound include n-butyl-
4- (4'-n-butylphenylazo) -phenyl carbonate, 4-ethoxy-4'-n-pentanoyloxyazobenzene, 4-n-pentyl-4'-methoxyazobenzene and the like can be mentioned.

The above-mentioned azooxy compounds include 4-n
-Hexyl-4'-butoxyazobenzene, 4-ethoxy-4'-n-hexanoyloxyazobenzene, 4-
Examples include n-pentyl-4′-n-pentanoyloxyazobenzene and 4-n-heptanoyloxy-4′-cyanoazobenzene.

The ester compounds include 4-n-
Butylbenzoic acid-4'-n-hexyloxylphenyl, 4-n-hexyloxybenzoic acid-4'-n-heptoxylphenyl, 4- (4'-n-pentyloxybenzoyloxy) benzaldehyde, 4-n -Hexylcarbonate-4'-n-pentoxyphenylbenzoate, 4- (4-n-butoxybenzoyloxy) benzoic acid-4'-n-hexyloxylphenyl, 4- (4
-N-Methoxybenzoyloxy) benzoic acid-4'-n
-Propylphenyl, 4- (4-n-methoxybenzoyloxy) benzoic acid-4 '-(4-butylphenoxycarbonyl) phenyl, 4-n-heptylbenzoic acid-4'
-Cyanophenyl, 4- (4-n-pentylphenyl)
Benzoic acid-4'-n-pentylphenyl, 4- (4-n
-Pentylphenyl) benzoic acid-4'-n-cyanophenyl, 4-n-hexylbenzoic acid-4'-isocyanophenyl, 4-n-octyloxy-3-cyanobenzoic acid-4'-n-pentylphenyl , 4- (4-n-octyl-3-cyanobenzoyloxy) benzoic acid-4'-n
-Pentylphenyl, 4- (4-n-pentylbenzoyloxy) benzoic acid-4'-n-pentylphenyl, 4
-(4-n-pentylbenzoyloxy) -3-chlorobenzoic acid-4'-n-pentylphenyl and the like can be mentioned.

The stilbene compound is 4,
4'-diethoxy-trans-stilbene, 4-ethoxy-4'-n-butyl-α-methyl-trans-stilbene, 4-ethoxy-2-methyl-4'-n-butyl-
Trans-stilbene, 4-ethoxy-4'-n-butyl-α-chloro-trans-stilbene, 4-ethoxy-4'-n-butyl-β-chloro-trans-stilbene, 4-ethoxy-4'-n -Octyl-β-chloro-
Trans-stilbene, 4-ethoxy-4 ′-(2-methylhexyl) -β-chloro-trans-stilbene and the like can be mentioned.

The biphenyl compound is 4-n
-Heptoxy-4'-nitrobiphenyl, 4-n-hexyl-4'-cyanobiphenyl, 4-n-octyl-
4'-cyanobiphenyl, 4-n-hexyloxy-
4'-cyanobiphenyl, 4-n-pentanoyloxy-4'-cyanobiphenyl, 4-n-heptyloxy-
4'-n-propylcarbonylbiphenyl, 4-decyl-4'-hexanoylbiphenyl, 4-hexyloxy-4'-hexanoylbiphenyl and the like can be mentioned.

As the terphenyl compound, 4-
n-propyl-4 "-cyano-p-terphenyl, 4-
n-octyl-4 ″ -cyano-p-terphenyl and the like can be mentioned.

Examples of the trans-cyclohexane compound include 4- (trans-4-pentylcyclohexyl) benzonitrile, trans, trans-4'-n-
Propyldicyclohexyl-4-carboxylic acid, trans, trans-4'-propyldicyclohexyl-4-
Carbonitrile, trans-4- (4 "-n-pentylcyclohexyl-4'-cyanobiphenyl, trans-
1,4-bis- (4-n-propoxycarbonyl) cyclohexane, trans-1,4-bis- (4-n-nonyloxycarbonyl) cyclohexane and the like can be mentioned.

Examples of the pyrimidine compound include 5-n
-Hexyl-2- (4-hexyloxyphenyl) pyrimidine, 5-n-heptyl-2- (4-cyanophenyl) pyrimidine, 5-n-cyano-2- (4-n-pentyloxyphenyl) pyrimidine, 5 -Cyanophenyl-2-pentylphenyl-pyrimidine, 5- (4-n-
Butylphenyl) -2- (4-cyanophenyl) pyrimidine, 5-cyanophenyl-2-butylphenyl-pyrimidine, 5-n-propyl-2-4'-cyano-4-biphenyl) pyrimidine, 5-cyano-2 -(4'-n-
Propyl-4-biphenyl) pyrimidine and the like.

As the cholesteric liquid crystal compound,
Cholesterol derivatives and chiral mesogenic substances are mentioned.

Examples of the cholesterol derivative include cholesteryl bromide, cholesteryl-n-hexyl ether, cholesteryl-n-heptanoate, cholesteryl-n-heptyl carbonate, cholesteryl-n-heptylmercaptocarbonate, cholesteryl benzoate, cholesteryl-w-phenylheptano. And cholesteryl erucate, 4-dodecyloxy-1-naphthylidene-cholesteryl-p-aminobenzoate, and the like.

As the above-mentioned chiral mesogen substance,
N- (4-ethoxybenzylidene) -4- (2-methylbutyl) aniline, 4-ethoxy-4 '-(2-methylbutyl) azobenzene, 4-ethoxy-4'-(2-methylbutyl) azooxybenzene, 4- (2-methylbutyl) benzoic acid-4'-n-hexyloxyphenyl,
4-n-heptoxy-4 ′-(2-methylbutyloxycarbonyl) biphenyl, 4- [4- (2-methylbutyl) benzoyloxy] benzoate-4′-n-pentylphenyl, 4- [4- ( 2-Methylbutyl) benzoyloxy] benzoic acid-4'-n-cyanophenyl, 4
-[4- (2-Methylbutyl) benzoyloxy] benzoic acid-4'-n-nitrophenyl, 4- [4- (3-
Methylpentyl) benzoyloxy] benzoic acid-4 '
-N-methylphenyl, 4- (2-methylbutyl)-
4'-cyanobiphenyl, 4- (3-methylpentyl)
-4'-cyanobiphenyl, 4- [4- (2-methylbutyl) phenyl] benzoic acid-4'-n-butylphenyl, 4- [4- (2-methylbutyl) phenyl] benzoic acid-4'-n- Cyanophenyl, trans-4- (2-
Methylbutyl) cyclohexylcarboxylic acid-4'-cyanobiphenyl, 4-n-hexyloxybenzoic acid-4 '
-(2-methylbutoxycarbonyl) phenyl, 4-
(4-methylbutyl) -4 ″ -cyano-p-terphenyl and the like can be mentioned.

As described above, the liquid crystal compounds usable in the present invention are preferably biphenyl compounds and cyclohexane compounds, and more preferably cyclohexane compounds.

-Magnetic Metal Oxide and / or Magnetic Metal Particle-The magnetic metal oxide particle in the present invention is represented by the following composition formula.

(MnO) _X (ZnO) _Y (Fe ₂ O ₃ ) _Z [In the formula, X, Y and Z satisfy the following relationship.

0.2≤X≤1.0, 0.9≤Z≤1.1, X + Y
= 1] The composition of these ferrites is determined according to the properties required for the alcohol-based magnetic fluid. For example, when high magnetization is required, Fe ferrite and Mn ferrite are preferable, and when utilizing the change in magnetization with temperature, Mn-Zn ferrite is preferable.

As the magnetic metal, in-liquid reduction method, vacuum deposition method, spark erosion method, thermal decomposition method, plasma CV
Examples include iron, nickel, cobalt or alloys thereof obtained by the D method and the like.

Magnetic metal oxide and magnetic metal particles are
The particle size is usually preferably 1 to 20 nm.

-Composition of alcohol-based magnetic fluid-The content ratio of each component in the alcohol-based magnetic fluid in the present invention is 40 to 90% by weight of alcohol, preferably 50 to 80% by weight, and 2 to 60% by weight of surfactant. %, Preferably 5 to 20% by weight, 2 to 60% by weight, preferably 10 to 40% by weight of a liquid crystal compound which is liquid at a predetermined temperature, for example, room temperature, and a magnetic metal oxide and /
Alternatively, the content of the magnetic metal particles is 0.01 to 60% by weight, preferably 5 to 60% by weight, particularly preferably 8 to 40% by weight, and the total content of each component is 100% by weight. An appropriate content ratio is adopted within the range.
When the alcohol, the surfactant, the liquid crystal compound and the particles of the magnetic metal oxide and / or the magnetic metal are within the above range, the object of the present invention can be further achieved, and specifically, The final product, the alcohol-based magnetic fluid, has excellent dispersibility, fluidity and durability, and can be suitably used in a wide temperature range from room temperature.

The alcohol-based magnetic fluid of the present invention is within the range that does not impair the object of the present invention, in order to further enhance the characteristics of the alcohol-based magnetic fluid of the present invention, or the original properties of the alcohol-based magnetic fluid of the present invention. In addition to the characteristics, various kinds of additives can be added to impart new characteristics.

Examples of the additive include various powders, various polymers and the like, which are appropriately selected according to the use of the alcohol-based magnetic fluid.

-Production Method of Alcohol-based Magnetic Fluid- The alcohol-based magnetic fluid can be suitably produced by the production method of the present invention.

In the method of the present invention, an aqueous suspension of magnetic metal oxide and / or magnetic metal particles is first prepared. The metal oxide particles can be obtained by employing a hydrothermal synthesis method using a salt of the same metal as the metal in the magnetic metal oxide particles, or a coprecipitation method. Preferred is the coprecipitation method. In the method of the present invention, the magnetic metal oxide and / or magnetic metal particles are contained in an amount of 0.01 to 60% by weight,
It is preferably contained in a proportion of 5 to 60% by weight.

What is important in the present invention is to adjust the aqueous suspension to be alkaline. The aqueous suspension can be easily made alkaline by adding an alkaline agent such as caustic soda to the aqueous suspension. The alkaline agent is not limited to caustic soda, and is not particularly limited as long as it is a compound that can make the aqueous suspension alkaline. The pH of the aqueous suspension prepared to be alkaline is preferably 11 to 12.

In the method of the present invention, a surfactant is added to the obtained alkaline suspension. The amount of the surfactant added is usually 2 to 60% by weight, preferably 5 to 20% by weight, based on the magnetic metal oxide and / or magnetic metal of the dried product. The surfactant may be added to the alkaline suspension by diluting it with a solvent such as water, or the surfactant may be directly added to the alkaline suspension without using a solvent. Is also good.

Then, the obtained surfactant-containing alkaline suspension is dried to obtain an apparently viscous dried product.

In the present invention, the dried product, the liquid crystal compound and the alcohol are mixed.

The amount of the liquid crystal compound added is usually 5 to 100% by weight, preferably 10 to 50% by weight, based on the magnetic metal oxide and / or magnetic metal in the dried product. The amount of alcohol added is usually 50 to 500% by weight, preferably 10% by weight, based on the magnetic metal oxide and / or magnetic metal in the dried product.
It is 0 to 300% by weight.

It is preferable to wash the dried product with alcohol before mixing the dried product, the liquid crystal compound which is liquid at a predetermined temperature, and the alcohol. Examples of alcohols used for washing include methanol, ethanol, propanol, butanol and the like. Among them, methanol and ethanol are preferable. When mixing the dried product and the liquid crystal compound, when the liquid crystal compound is liquid at room temperature, the dried product and the liquid crystal compound can be mixed at room temperature, but in the case of a liquid crystal compound which is not liquid at room temperature, The liquid crystal compound that has been made liquid at a predetermined temperature by heating or the like is mixed with the dried material.

After vapor mixing, the content of each component in the alcohol-based magnetic fluid is adjusted by evaporating, evaporating, decanting, or the like, if necessary, so that each component has the content ratio described above. Good to do.

-Applications of Alcohol-Based Magnetic Fluid- The alcohol-based magnetic fluid according to the present invention has a large temperature dependence of magnetization at normal temperature, a high thermal conductivity and a high temperature sensitivity. Since it has such excellent characteristics,
The alcohol-based magnetic fluid according to the present invention is suitably used for controlling a fluid in a heat pipe, a heat exchange medium, or the like by a magnetic field.

[0065]

Example A magnetic metal oxide was produced by the coprecipitation method. That is, 0.1 mol of ferrous sulfate [FeSO ₄ ] and 0.2 mol of ferric sulfate [Fe ₂ (SO ₄ ) ₃ ] are added to distilled water 1
Dissolved in liters. A caustic soda aqueous solution was added to the obtained aqueous solution until the pH was about 11, and the aqueous solution was gelated.

Polyoxyethylene nonyl phenyl ether (manufactured by Nikko Chemicals Co., Ltd .; ECT)
20 g of D-6NEX) was added.

The gelled product was dried by heating it at 60 ° C. in a vacuum drier to obtain a magnetic metal oxide (hereinafter simply referred to as magnetite).

2.0 g of the magnetite was sampled and placed in a glass tube bottle.

10 ml of ethanol was added to the glass tube bottle. After adding ethanol, the glass tube bottle was sonicated using an ultrasonic cleaner. After applying ultrasonic waves, the glass tube bottle was placed on a permanent magnet to precipitate magnetite. The magnetization of the permanent magnet at this time was measured by a Gauss meter and was found to be about 3,0
00 Gauss.

When magnetite was precipitated as described above, ethanol remained as a supernatant, and this ethanol was removed by evaporation and drying.

The above-mentioned washing with ethanol was performed twice.

After washing, a cyanobiphenyl liquid crystal compound (C ₅ H ₁₁ -C ₆ H ₄ -C _{6) was} added to the solution in the glass tube bottle.
H ₄ —CN) 3 g was added and the mixture was heated and stirred using a sand bath to completely remove ethanol.

After removing ethanol, a liquid crystal magnetic fluid could be obtained. 0.1 liter of ethanol was added to this liquid crystal magnetic fluid.

Thus, an ethanol-based magnetic fluid could be obtained.

FIG. 1 is a graph showing the change in magnetization of the ethanol-based magnetic fluid obtained by the same procedure as described above except that the concentration of magnetite was changed. In FIG. 1, □ indicates an ethanol-based magnetic fluid having a magnetite concentration of 13% by weight, and Δ indicates a magnetite concentration of 1%.
1% by weight represents an ethanol-based magnetic fluid, and ∘ represents an ethanol-based magnetic fluid having a magnetite concentration of 9% by weight.

As a characteristic of this ethanol-based magnetic fluid, in order to investigate the sedimentation characteristic by the magnetic field, the stability with the passage of time, and the retention characteristic with the passage of time, the container for accommodating the ethanol-based magnetic fluid was sealed to 3,000. Place this container directly below the Gaussian permanent magnet and
When left for a day, the precipitate generated in the container was several% or less based on the weight of the magnetic metal oxide, and this ethanol-based magnetic fluid was stably held. Similarly, an alcohol-based magnetic fluid can be obtained by adding 0.1 liter of methanol, ethanol, propanol, or a mixture thereof to the liquid crystal magnetic fluid.

[0077]

According to the present invention, an alcohol-based magnetic fluid having excellent dispersibility and fluidity can be provided. The present invention can provide an alcohol-based magnetic fluid having a high vapor pressure and a low boiling point, which is excellent in dispersibility and fluidity. The present invention can thus provide a simple method for producing an excellent alcohol-based magnetic fluid. Further, according to the present invention, it is possible to provide an alcohol-based magnetic fluid which can control heat exchange in a magnetic field and can be held in the magnetic field, and a method for producing the same.

Furthermore, according to the present invention, when methanol, ethanol, propanol, or a mixture thereof is used, an alcohol-based magnetic fluid having a high vapor pressure and a low boiling point can be provided.

According to the present invention, it is possible to provide an alcohol-based magnetic fluid in which heat exchange can be controlled by a magnetic field and which can be retained as alcohol fuel in the magnetic field.

According to the present invention, it is possible to provide a simple method for producing an alcohol-based magnetic fluid.

[Brief description of drawings]

FIG. 1 is a graph showing a change in magnetization of an alcohol-based magnetic fluid according to an embodiment of the present invention.

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Claims (2)

[Claims] 1. An alcohol-based magnetic fluid containing alcohol, a surfactant, a liquid crystal compound which is liquid at a predetermined temperature, and magnetic metal oxide and / or magnetic metal particles. 2. An alkaline suspension is obtained by adding an alkaline agent to a suspension in which magnetic metal oxide and / or magnetic metal particles are dispersed, and a surfactant is added to the alkaline suspension. The pH of the suspension obtained thereafter is 2
A method for producing an alcohol-based magnetic fluid, which comprises preparing the following acidic suspension, drying the obtained acidic suspension, and mixing the obtained dried product, a liquid crystal compound that is liquid at a predetermined temperature, and an alcohol.