JP3321964B2 - Manufacturing method of magnetic fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a magnetic fluid. More specifically, the present invention relates to a method for producing a magnetic fluid in which ferrite fine particles are stably dispersed at a high concentration in a low-vapor-pressure base oil to thereby improve saturation magnetization.

[0002]

2. Description of the Related Art The applicant of the present invention has previously proposed an aqueous suspension of ferrite fine particles in order to efficiently produce a magnetic fluid in which ferrite fine particles are stably dispersed in a low vapor pressure base oil at a high concentration. N-polyalkylene polyamine-substituted alkenyl succinimide is added as a solution of a hydrocarbon solvent having a higher boiling point than water, and the N-polyalkylene polyamine-substituted alkenyl succinimide is adsorbed on the ferrite fine particles. The N-polyalkylene polyamine-substituted alkenyl succinimide-adsorbed ferrite fine particles collected by adding a flocculating solvent to the residual hydrocarbon solution are treated with a low vapor pressure base oil having a vapor pressure of 0.1 mmHg or less at 25 ° C. A method for producing a magnetic fluid by dispersing it in a medium has been proposed (JP-A-4-221809).

Although the proposed method has been satisfactory in terms of lower viscosity, longer life and improved performance of the magnetic fluid than the conventional method, there is still room for improvement in yield and saturation magnetization. Was done.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the yield of a magnetic fluid obtained in the above proposed method and to further improve the saturation magnetization value.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
To an aqueous suspension of ferrite fine particles, N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide is added as a solution of a hydrocarbon solvent having a higher boiling point than water, and N-polyalkylene polyamine-substituted alkenyl succinimide halogenide is added. After adsorbing the hydrochloride to the ferrite fine particles, the water is almost completely removed, and the N-polyalkylenepolyamine-substituted alkenylsuccinimide hydrohalide is recovered by adding a flocculating solvent to the residual hydrocarbon solution. 0.1m at 25 ° C
This is achieved by producing a magnetic fluid dispersed in a low vapor pressure base oil having a vapor pressure of mHg or less.

As the ferrite fine particles, those produced by a coprecipitation method, which is advantageous in terms of purity, particle size control and, above all, productivity, are used in the form of an aqueous suspension as it is. That is, the formation of the aqueous suspension by the coprecipitation method is performed through a series of steps of dropping of an aqueous NaOH solution to the aqueous solution of the iron salt mixture, aging, cooling and decanting of the salt, where the particle size is about 50 to 50. 30
0 °, preferably about 70-120 ° ferrites for about 0.1-5
A suspension dispersed at a concentration of 0% by weight, preferably about 1 to 30% by weight, is obtained.

As the N-polyalkylene polyamine-substituted alkenyl succinimide, the following compounds are used. R: a hydrocarbon group having 12 to 24 carbon atoms, a polybutenyl group having a molecular weight of about 300 to 2000, R ': an alkylene group having 1 to 6 carbon atoms, which can be the same or different when two or more R's are repeated n: 1 to 5 m: 0 to 4

[0008] These N-polyalkylene polyamine-substituted alkenyl succinimides are used as hydrohalides, generally as hydrochlorides, hydrobromides and the like. The formation of the hydrohalide is carried out promptly by dissolving the N-polyalkylenepolyamine-substituted alkenyl succinimide in hydrochloric acid, hydrobromic acid or the like.

The N-polyalkylenepolyamine-substituted alkenyl succinimide hydrohalides are prepared as a solution of a hydrocarbon solvent having a boiling point higher than that of water, preferably about 150 ° C. or higher, and which does not azeotrope with water. Is added to an aqueous suspension of ferrite fine particles.

As such a hydrocarbon solvent, for example, n-decane, n-dodecane, 1-decene, n-hexadecane, mesitylene, diethylbenzene, tetralin, decalin, dodecylbenzene, toluene, xylene and the like are used as a single solvent or a mixed solvent. Can be When a solvent that does not azeotrope with water is used among these solvents, it can also be used in combination with toluene, xylene, or the like, which azeotropes with water.

[0011] These hydrocarbon solutions are generally used in a volume ratio of about 0.01 to 100, preferably about 1 to 100, with respect to the aqueous suspension. The mixing of the two is performed using a homogenizer or the like under stirring conditions such that an emulsion is formed. By stirring under such stirring conditions, the N-polyalkylenepolyamine-substituted alkenyl succinimide hydrohalide is adsorbed on the ferrite fine particles at the interface of the emulsion. About 40 ~
It is desirable to carry out stirring treatment at a temperature of 90 ° C., and such treatment is carried out for about 30 to 60 minutes.

After the N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide is adsorbed on the ferrite fine particles, water is almost completely removed. The removal of water is preferably carried out by heating the system in which an emulsion has been formed under heating and stirring conditions to a temperature higher than the boiling point of water, generally about 110 ° C. or higher, and distilling off. At this time, when toluene, xylene, or the like is used in combination, these are distilled off azeotropically with water, which serves to increase the rate of water distillation.

With almost complete removal of water, the color of the solution changes, for example, from dark brown to dark brown. At such a point, acetone, methyl ethyl ketone, methanol, ethanol, etc., which are compatible with the hydrocarbon solvent used in the solution of the residue, are added, which results in N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide. It acts as an aggregating solvent for the adsorbed ferrite fine particles and agglomerates such fine particles. At that time, leave it on a magnet etc.
Collect the sedimented fine particles. Or about 500-100
When centrifugation at 0 G is performed, fine particles with poor dispersion easily settle and can be removed.

The collected fine particles are washed with a mixed solvent of toluene-acetone, toluene-methanol, n-hexane-acetone, isooctane-acetone and the like, generally in an equal amount. By such washing, excess N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide which increases the viscosity when prepared into a magnetic fluid or causes a decrease in the dispersion concentration of ferrite fine particles is removed. I do. After washing, the ferrite fine particles are dried if necessary.

The ferrite fine particles coated with the N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide thus obtained are dispersed by adding a low vapor pressure base oil thereto. However, its dispersibility in a low vapor pressure base oil is in a good state.

As a low vapor pressure base oil, 0.1 m at 25 ° C.
Liquid having a vapor pressure of mHg or less, preferably 0.01 mmHg or less, such as natural oils such as white oil (liquid paraffin), mineral oil, spindle oil and the like, or synthetic oils such as higher alkylbenzene, higher alkylnaphthalene, and polybutene (molecular weight of about 300 Lubricating oils containing so-called lubricating additives such as antioxidants, antiwear agents, oil agents, detergent dispersants, etc., when the dispersion concentration of ferrite fine particles in the finally obtained magnetic fluid is about It is used in such a ratio that it becomes 10 to 50% by weight.

The dispersion treatment with the addition of the low-vapor-pressure base oil is carried out by using at least one of a homogenizer, an ultrasonic wave, a vibration mill and the like as in a conventional method. After the dispersion treatment, purification is performed by centrifugation or standing in a magnetic field gradient.
Dispersion treatment can be performed without passing through a drying step after the adsorption treatment and washing.In this case, from the viewpoint of controlling the dispersion concentration of the magnetic fluid and the evaporation component, the obtained magnetic fluid is subjected to a heat treatment under reduced pressure, It is preferable to distill low boiling components.

[0018]

According to the method of the present invention, a hydrocarbon solution of N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide is added to an aqueous suspension of ferrites, and an emulsion is formed under stirring conditions.
Polyalkylene polyamine-substituted alkenyl succinimide hydrohalide is adsorbed on ferrite fine particles, and then treated under specific conditions to recover the fine particles. A magnetic fluid in which magnetic fine particles are dispersed in a low vapor pressure base oil stably and easily at a high concentration of about 40 to 50% by weight can be produced in good yield. In addition, the saturation magnetization of the obtained magnetic fluid is increased.

[0019]

Next, the present invention will be described with reference to examples.

EXAMPLE A 6N NaOH aqueous solution was added dropwise to 1850 ml of an aqueous solution in which 184 g of FeCl ₂ .4H ₂ O and 500 g of FeCl ₃ .6H ₂ O were dissolved until the pH reached 11, and then at 80 ° C. for 30 minutes. After aging and cooling, the salt was removed by decantation to obtain a magnetite suspension (magnetite concentration 30% by weight).

In 15 ml of the suspension, a tetralin solution of 0.1 molar polybutenyl succinimide tetraethylene pentamine hydrochloride (prepared by dissolving polybutenyl succinimide tetraethylene pentamine in an equimolar amount of hydrochloric acid) 100 ml was added, and the mixture was stirred at 800 rpm using a 50 mm diameter propeller in a 300 ml round bottom separable flask at 60 ° C. for 60 minutes to form an emulsion.

Thereafter, the oil bath was kept at 130 ° C., and water was distilled off with stirring. When the color of the solution changed from dark brown to black brown, water was almost completely removed, and it was determined that the solution had only tetralin.

When 200 ml of acetone is added thereto, the dispersed fine particles are aggregated.
After sedimentation of the fine particles, tetralin was removed by decantation.

The residual magnetite fine particles were washed five times with a mixed solvent of toluene and acetone (1: 1) and dried.

To 3.0 g of the obtained polybutenylsuccinimide tetraethylenepentamine hydrochloride-coated magnetite,
After adding 5.0 g of alkylnaphthalene, the mixture was stirred (10000 rpm, 60 minutes) using a homogenizer (Excel Auto Homogenizer DX, manufactured by Nippon Seiki Seisaku-sho, Ltd.), and further subjected to ultrasonic dispersion treatment for 12 hours, followed by centrifugation (5000 G, 30 The magnetic fluid having a saturation magnetization (16 K Oe) of 400 G was obtained. The yield was 1.1 times that of the following comparative example.

COMPARATIVE EXAMPLE In Example, when polybutenylsuccinimidetetraethylenepentamine hydrochloride was used instead of polybutenylsuccinimidetetraethylenepentamine hydrochloride, the saturation magnetization (16 K Oe ) Was 370G.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI C10M 125: 10 C10M 125: 10 133: 16 133: 16 133: 56) 133: 56) (C10M 161/00 (C10M 161/00 125: 10) 125: 10 149: 02 149: 02 149: 22) 149: 22) C10N 10:16 C10N 10:16 20:00 20:00 A 40:14 40:14 70:00 70:00 (56) References JP-A-5-67514 (JP, A) JP-A-4-221809 (JP, A) JP-A-4-122793 (JP, A) JP-A-5-239488 (JP, A) JP-A-4-221808 ( JP, A) JP-A-5-41316 (JP, A) JP-A-5-198420 (JP, A) JP-A-5-267041 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) H01F 1/44 H01F 1/34 C10M 125/10 C10M 133/16 C10M 133/56 C10M 141/06 C10M 149/02 C10M 149/22 C10M 161/00 C10M 177/00 C10N 10:16 C10N 20: 00 C10N 40:14 C10N 70:00

Claims (3)

(57) [Claims] 1. An N-polyalkylenepolyamine-substituted alkenyl-substituted alkenyl succinimide hydrohalide is added to an aqueous suspension of ferrite fine particles as a solution of a hydrocarbon solvent having a higher boiling point than water. After adsorbing the succinimide hydrohalide to the ferrite fine particles, water was almost completely removed, and the residual hydrocarbon solution was recovered by adding an aggregating solvent.
N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide adsorbed ferrite particles
A method for producing a magnetic fluid, comprising dispersing in a low vapor pressure base oil having a vapor pressure of 0.1 mmHg or less at a temperature of 0 ° C. 2. An N-polyalkylene polyamine-substituted alkenyl succinimide hydrohalide is added to an aqueous suspension of ferrite fine particles as a solution of a hydrocarbon solvent having a boiling point higher than that of water to form an emulsion under stirring conditions. The method for producing a magnetic fluid according to claim 1, wherein the N-polyalkylenepolyamine-substituted alkenylsuccinimide hydrohalide is caused to adsorb and react with the ferrite fine particles. 3. The method for producing a magnetic fluid according to claim 2, wherein an emulsion is formed under heating and stirring conditions, and water is distilled off from the adsorption reaction system.