JPH0654734B2 - Magnetic fluid manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing magnetic fluid.

Prior art and its problems As a magnetic fluid, it has already been treated with a surface active agent of fine particles of an oxide magnetic material (magnetite, Fe ₃ O ₄ ) and dispersed in oil, water, etc. in a colloidal state. Things are known and are actually put to practical use in various fields.

For example, application to various seals such as a rotary shaft seal is generally known.

In these applications, practically low solvent volatility,
Thermal stability and lubricity are often required.

As a solvent satisfying such requirements, it is known that a fatty acid ester or diester type, a polyphenyl oil type, etc. are suitable, and in the oxide magnetic fluid, magnetic fluids using these solvents have already been prepared. ing.

However, the use of metal fine particles having high saturation magnetization of dispersed fine particles itself has not been successful.

If it is possible to produce a magnetic fluid with a high concentration of metal fine particles using the above-mentioned solvent using metal fine particles, a magnetic fluid with high saturation magnetization and excellent thermal stability can be obtained. It is expected that the range will be expanded.

II Object of the invention The object of the present invention is to disperse cobalt metal fine particles in a low-volatile solvent to obtain a practical method for producing a magnetic fluid that has a significantly higher saturation magnetization than conventional magnetic fluids. Especially.

Such an object is achieved by the present invention described below.

That is, the first invention is to manufacture a magnetic fluid containing cobalt metal fine particles, a nonionic or oil-soluble anionic surfactant, and a low-volatile solvent, in which a cobalt carbonyl compound is added to polyglycerin or sorbitan. It is a method for producing a magnetic fluid, which is obtained by thermally decomposing in the presence of a fatty acid ester to obtain the cobalt metal particles.

A second invention is to manufacture a magnetic fluid containing fine metal particles of cobalt, a nonionic or oil-soluble anionic surfactant, a low volatility solvent, and a low boiling point solvent. Is a method for producing a magnetic fluid, in which the cobalt metal fine particles are obtained by thermally decomposing the above in the presence of a fatty acid ester of polyglycerin or sorbitan.

And 3rd invention WHEREIN: When manufacturing the magnetic fluid containing the metal fine particle of cobalt, a surfactant, and a solvent, first, the carbonyl compound of cobalt, the fatty acid ester of polyglycerin or sorbitan, and a low boiling point solvent A solution containing and is thermally decomposed, cobalt metal fine particles, a polyglycerin or sorbitan fatty acid ester, to prepare a dispersion containing a low boiling point solvent, and then a part of the low boiling point solvent in the dispersion or It is a method for producing a magnetic fluid, in which the whole is solvent-substituted with a low-volatile solvent in which a nonionic or oil-soluble anionic surfactant is dissolved.

III Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

In the magnetic fluid using the cobalt metal fine particles of the present invention,
First, since it is indispensable to disperse the ferromagnetic fine particles in the liquid, it is necessary to make the particle size to overcome its magnetic cohesive force.

In the present invention, cobalt metal fine particles having a particle size of 70 to 120 Å are used.

Since the magnetic fluid is required to have low volatility, thermal stability, lubricity, etc. of the solvent for practical use, a low volatility solvent is used.

As the low-volatile solvent, for example, a boiling point of 150 mm at 1 mmHg
The above is better.

When one or more kinds of diester solvents and fatty acid saturated hydrocarbon solvents are used as the solvent, the dispersibility is improved.

As the diester solvent, dicarboxylic acid diester,
In particular, one or more diesters of aliphatic saturated dicarboxylic acids having 6 to 10 carbon atoms are preferable, which are represented by the following formula [I]
Indicated by.

[I]

ROOC (CH ₂ ) _n COOR In the above formula [I], n = 4 to 8, and as the aliphatic saturated dicarboxylic acid, adipic acid of n = 4, azelaic acid of n = 7, sebacic acid of n = 8 and the like. Is preferred.

Further, R is an aliphatic saturated hydrocarbon residue, and is preferably an octyl group having 3 to 10 carbon atoms, particularly a 2-ethylhexyl group having 8 carbon atoms.

That is, the following diester solvents are preferable.

i) Dioctyl adipate ii) Dioctyl azelate iii) Dioctyl sebacate And a mixed solvent thereof may be used.

These diester solvents are used for metal fine particles in an amount of 5
0 to 300% by weight is contained.

Instead of or in addition to the diester solvent, one or more aliphatic saturated hydrocarbon solvents can be used as a medium.

In this case, those having 19 to 30 carbon atoms are preferable.

Preferred compounds are listed below.

i) pristane _{[(CH 3) 2 CH (CH} 3) 3 CH (CH 3) (CH 3) 3 CH (CH 3) (CH 2) 3 CH (CH 3) 2 ] ii) squalane [(CH _{3) 2} CH (CH ₂ ) ₃ CH (CH ₃ ) (CH ₂ ) ₃ CH (CH ₃ ) CH ₂ CH ₂ ] ₂ iii) α-olefin oligomer (N is 1 to 4, particularly 1 or 2, R is 2-1 to 2 carbon atoms
2, especially about 6 alkyl groups, for example, Syncelane30 manufactured by Nikko Chemicals Co., Ltd. One or more of these aliphatic saturated hydrocarbon solvents are diester-based solvents that are added to metal fine particles as needed. The total amount is 50 to 300% by weight.

Further, the magnetic fluid of the present invention has the above-mentioned low volatility (high boiling point).
In addition to the solvent, one or more low boiling point solvents may be used in combination.

The low boiling point solvent preferably has a boiling point of about 100 to 160 ° C., and a hydrocarbon medium is particularly preferable.

In this case, the hydrocarbon used as the medium has 7 carbon atoms.
To 22 are preferred, and paraffin or olefins such as kerosene and aromatics such as triene and xylene are preferred.

The hydrocarbon-based medium is contained in an amount of 0 to 5% by weight or more based on the metal fine particles.

On the other hand, in order to prevent aggregation due to van der Waals' attractive force, oxide magnetic particles are chemically coated with a polar molecule surfactant to prevent aggregation due to repulsion between the particles.

However, no coating agent of this type has been found in the case of metallic magnetic fluids.

In the present invention, a nonionic or oil-soluble anionic surfactant is used.

As the nonionic surfactant to be used, polyglycerin fatty acid ester or polyethylene glycol alkyl ether is preferable, and they are represented by the following [III] and [IV].

[III] Polyglycerin fatty acid ester In the above formula [III], R is an unsaturated fatty acid-based acyl group or hydrogen. Also, n is a positive number. When R is an acyl group, a plurality of R may be different in some cases, but they are usually the same.

In the fatty acid ester of polyglycerin, the degree of polymerization of polyglycerin is 2 to 10, that is, n = 0 to 8, and more preferably n = 4 to 8.

Below, the specific example of the surfactant used is given.

1) decaglyceryl point pen Tao rate 2) deca glyceryl hept-oleate 3) decaglyceryl Gao rate 4) hexaglyceryl point pen Tao rate 5) tetra glyceryl point pen Tao rate 6) diglyceryl dioleate (IV) polyethylene glycol alkyl ether R-O- (CH ₂ —CH ₂ O) _n H In the above formula [IV], R is an unsaturated alkyl group.

Moreover, n = 1 to 3 is preferable. Usually, what is commercially available is a mixture of substances having different degrees of polymerization.

Specific examples of the surfactant used below will be given.

1) Dioxyethylene oleyl ether 2) Neugen ET69 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyethylene glycol oleyl ether; 2.3 moles of ethylene glycol mixed with oleyl alcohol) 3) Neugen ET89 (Daiichi Kogyo Seiyaku Co., Ltd.) Polyethylene glycol oleyl ether; 3.8 mol of ethylene glycol mixed with oleyl alcohol) As the oil-soluble anionic surfactant, sulfosuccinic acid ester is suitable, and this is represented by the following formula [V].

In the above formula [V], R is an aliphatic saturated hydrocarbon group, and preferably an octyl group having 8 carbon atoms such as a 2-ethylhexyl group.

Y is an alkali metal such as Na or K or hydrogen.

The surfactants contained are one kind or two or more kinds, and the total amount thereof is about 5 to 20% by weight based on the metal fine particles.

If it is less than 5% by weight, there is no effect, and if it exceeds 20% by weight
It becomes a paste and does not disperse.

Two or more kinds of these surfactants can be used.

In order to produce such a magnetic fluid, first, metal carbonyl is added to a low boiling point solvent in which a surfactant is dissolved, especially the above-mentioned hydrocarbon medium, and the mixed solution is heated to thermally decompose the metal carbonyl. To do.

Co ₂ (CO) ₈ may be used as the metal carbonyl.

Further, the thermal decomposition temperature is 140 to 160 ° C., and the thermal decomposition time is 2
Approximately 4 hours. The temperature and time may be appropriately changed depending on the cobalt concentration.

In such a case, a surfactant coexists during the thermal decomposition. As a surfactant to be used, Japanese Patent Application No. 59-159
The fatty acid ester of polyglycerin or sorbitan described in JP-A No. 630 (JP-A-61-36907) is preferable. Now, this surfactant is referred to as a second surfactant, and the above-mentioned nonionic or oil-soluble cationic surfactant is referred to as a first surfactant. When a fatty acid ester of polyglycerin is used as the second surfactant, the first and second surfactants may be the same.

The fatty acid ester of polyglycerin described in the above publication has the same meaning as that represented by the above formula [III].

The fatty acid ester of polyglycerol of the formula [III] is
It is preferably a partial ester of a fatty acid. In this case, the esterification rate is about 25 to 85%.

Further, the fatty acid ester of sorbitan described in the above publication,
Examples thereof include fatty acid monos such as 1,5-sorbitan and 1,4-sorbitan, and sesquis (a mixture of mono and di) or diesters.

Among these, 1,5-sorbitan or 1,4-sorbitan fatty acid mono- or sesquiesters represented by the following formulas [VI] and [VII] are preferable.

In the above formula [VI] or [VII], R is a saturated or unsaturated fatty acid-based acyl group.

These fatty acid esters have 10 to 18 carbon atoms,
Particularly preferred are 18 fatty acids, that is, esters of stearic acid, isostearic acid or oleic acid.

Specific examples of the surfactant described in the above publication will be given below.

1) Polyglycerin fatty acid ester I) Decaglyceryl pentaoleate II) Decaglyceryl pentastearate III) Decaglyceryl pentaisostearate IV) Decaglyceryl heptasterearate V) Decaglyceryl heptaisostearate VI) Decaglyceryl heptaolate VII) Decaglyceryl decaisostearate VIII) Decaglyceryl decastearate IX) Decaglyceryl decaurate X) Diglyceryl monooleate XI) Diglyceryl dioleate XII) Tetraglyceryl tristearate XIII) Tetraglyceryl tetrastearate XIV) Tetraglyceryl penta Olate XV) Hexaglyceryl tristearate XVI) Hexaglyceryl pentastearate XVII) Hexaglyceryl pentastearate 2) Sorbitan unsaturated fatty acid ester I ) 1,5-sorbitan monooleate II) 1,4-sorbitan monooleate III) 1,4-sorbitan monostearate IV) 1,4-sorbitan monoisostearate V) 1,4-sorbitan sesquioleate VI) 1 , 4-Sorbitan sesquiisostearate and the amount ratio of the low boiling point solvent to Co is 50 to 250
%, And the ratio of the surfactant to Co is 25 to 60% by weight.

By such an operation, a dispersion of cobalt fine particles dispersed by the second surfactant is produced using the low boiling point solvent as a medium.

Then, a part or all of the low boiling point solvent in this dispersion is replaced with a low volatility solvent in which the nonionic or oil-soluble anionic surfactant (first surfactant) is dissolved.

The amounts of the nonionic or oil-soluble anionic surfactant and the low volatile solvent used are as described above.

When replacing the solvent, first, cobalt fine particles are usually agglomerated from the dispersion using the low boiling point solvent.

Upon aggregation, the solvent may be distilled off, but usually,
About half the amount of acetone or the like may be added to the solvent having a polarity different from that of the dispersion medium, for example, a hydrocarbon medium such as kerosene or xylene.

In addition to these, dioxane and the like can also be used.

Then, usually, the solvent is almost completely removed, and the solvent can be added to a low-volatile solvent in which a nonionic or oil-soluble anionic surfactant is dissolved and redispersed by, for example, an ultrasonic cleaner.

That is, in the final dispersion, the low boiling point solvent and the initially added second surfactant are not usually contained, but they may be contained in these final dispersions. The content thereof is preferably 5% by weight or less of the low boiling point solvent and 2% by weight or less of the surfactant added in the initial stage, based on the metal fine particles.

Such a magnetic fluid needs to be stored in a predetermined container. Then, it is preferable to replace the inside of the container with an inert gas such as argon or nitrogen.

IV Specific Actions and Effects of the Invention The magnetic fluid obtained by the present invention is C having high saturation magnetization.
o Since fine metal particles can be dispersed in a low-volatile solvent by using a nonionic or oil-soluble anionic surfactant as a surfactant, they have excellent dispersibility and have a much higher saturation magnetization than conventional magnetic fluids. I have.

In addition, since the medium uses a low-volatile solvent, low volatility of the solvent, thermal stability, good lubricity, etc. are effectively exhibited,
It is extremely advantageous in practical use.

Then, as described above, by solvent replacement that is easy to manufacture,
Such an effect is realized.

V Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown to explain the present invention in more detail.

Example 1 12 g of decaglyceryl heptaolate was added to kerosene medium 30.
The solution dissolved in g was placed in a three-necked flask equipped with a condenser, a thermometer, and a stirrer. To this, 120 g of octacarbonyldicobalt Co ₂ (CO) ₈ was added.

This mixed solution was gradually heated with a mantle heater while stirring, and cobalt carbonyl was thermally decomposed while refluxing. At this time, CO produced by decomposition from the upper part of the cooler
Occurs. The evolution of CO was confirmed by passing it through a PdCl ₂ solution (acetone: water = !: 1).

That is, the orange PdCl ₂ solution turns black by the introduction of CO.

After the generation of CO was completed, stirring was continued for about 30 minutes and then cooled. This produced a black solution. This black solution was centrifuged at 6000 rpm for 1 hour.

However, at this time, there was almost no separation / sedimentation.

Acetone was added to the Co magnetic fluid produced as described above to aggregate the Co fine particles.

After removing the solvent, 10% of the previously prepared surfactant decaglyceryl heptaolate was dissolved.
A low-volatile solvent as shown in (3) was added and redispersed with an ultrasonic cleaner.

This dispersion was subjected to centrifugation (16000 rpm) for about 20 minutes to confirm that it was dispersed, and then the dispersion was placed on a rotary evaporator (oil bath 160 ° C.).

Here, the presolvent was reliably distilled off after 30 minutes. After cooling, it was centrifuged again and it was confirmed that they were dispersed.

By changing the amount of the high boiling point solvent, good dispersibility was obtained even when the concentration of the magnetic fluid was changed variously.

An example of magnetic properties after dispersion is shown in Table 1 (here, specific gravity is used as a parameter instead of concentration).

Example 2 In Example 1, xylene was used in place of the kerosene medium.

The subsequent operations are the same as in Example 1.

However, Syncelane 30 was used as the low-volatile solvent.

The specific gravity of the solution was 1.3421 and the saturation magnetization was 1250G.

Example 3 As the surfactant for redispersion in Example 1, dioxyethylene oleyl ether was used instead of decaglyceryl heptaoleate.

However, Syncelane 30 was used as the low-volatile solvent.

The specific gravity of the solution was 1.3985, and the saturation magnetization was 1362G.

Example 4 As the surfactant for redispersion in Example 1, sulfosuccinic acid (2-ethylhexyl) was used instead of decaglycerheptaoleate. However, a low volatile solvent as shown in Table 2 was used.

From the above, the effect of the present invention is clear.

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Claims (16)

[Claims] 1. A method for producing a magnetic fluid containing fine metal particles of cobalt, a nonionic or oil-soluble anionic surfactant, and a low-volatile solvent, wherein a cobalt carbonyl compound is used as a fatty acid ester of polyglycerin or sorbitan. A method for producing a magnetic fluid, which is obtained by thermally decomposing in the presence of: to obtain the cobalt metal fine particles. 2. The average particle size of the metal fine particles is 70 to 120Å
The method for producing a magnetic fluid according to claim 1, wherein 3. The low-volatile solvent has a boiling point of 15 at 1 mm / Hg.
The method for producing a magnetic fluid according to claim 1 or 2, wherein the temperature is 0 ° C or higher. 4. The low-volatile solvent is an ester solvent and / or
Alternatively, the method for producing a magnetic fluid according to any one of claims 1 to 3, which is a hydrocarbon solvent. 5. The method for producing a magnetic fluid according to claim 4, wherein the ester solvent is a diester of an aliphatic saturated dicarboxylic acid. 6. The aliphatic saturated dicarboxylic acid has 6 carbon atoms.
10. The method for producing a magnetic fluid according to claim 5, which is 10 to 10. 7. The method for producing a magnetic fluid according to claim 4, wherein the hydrocarbon solvent is an aliphatic saturated hydrocarbon having 19 to 30 carbon atoms. 8. The low-volatile solvent is 50 to 50 with respect to the metal fine particles.
The method for producing a magnetic fluid according to any one of claims 1 to 7, which contains 300% by weight. 9. The method for producing a magnetic fluid according to claim 1, wherein the oil-soluble anionic surfactant is a sulfosuccinate ester. 10. The method for producing a magnetic fluid according to any one of claims 1 to 8, wherein the nonionic surfactant is a polyglycerin fatty acid ester or a polyethylene glycol alkyl ether. 11. The method for producing a magnetic fluid according to any one of claims 1 to 9, wherein the nonionic or oil-soluble anionic surfactant is contained in an amount of 5 to 20% by weight based on the metal fine particles. . 12. A cobalt carbonyl compound is added to polyglycerin in the production of a magnetic fluid containing metal fine particles of cobalt, a nonionic or oil-soluble anionic surfactant, a low-volatile solvent and a low-boiling solvent. Alternatively, a method for producing a magnetic fluid, in which the metal fine particles of cobalt are obtained by thermally decomposing in the presence of a fatty acid ester of sorbitan. 13. The method for producing a magnetic fluid according to claim 12, wherein the low boiling point solvent has a boiling point of 100 to 160 ° C. 14. The low boiling point solvent is a hydrocarbon solvent having 7 to 22 carbon atoms, and the low boiling point solvent is claim 12 or 13.
A method of manufacturing a magnetic fluid according to the item. 15. The method according to claim 12, wherein the low boiling point solvent is contained in an amount of 5% by weight or more based on the metal fine particles.
A method for producing a magnetic fluid according to any one of items. 16. When producing a magnetic fluid containing cobalt metal fine particles, a surfactant and a medium, first, a cobalt carbonyl compound, a polyglycerin or sorbitan fatty acid ester, and a low boiling point solvent are included. The solution is pyrolyzed, metal fine particles of cobalt, polyglycerin or fatty acid ester of sorbitan, to prepare a dispersion containing a low boiling point solvent, then, part or all of the low boiling point solvent in this dispersion, A method for producing a magnetic fluid, in which a solvent is replaced with a low-volatile solvent in which a nonionic or oil-soluble anionic surfactant is dissolved.