JPH01228536A - Production of magnetic fluid - Google Patents

Abstract

PURPOSE:To increase dispersion stability of fine ferrite particles by adding a specified succinimide to a suspension of fine surfactant-adsorbed ferrite particles dispersed in a low boiling hydrocarbon and by treating it at 70 deg.C or higher. CONSTITUTION:N-alkylenepolyamino-alkenylsuccinimide is added to a dispersion of fine surfactant-adsorbed ferrite particles in a low boiling hydrocarbon solvent, a heat treatment is carried out at 70 deg.C or higher and the low boiling hydrocarbon solvent is separated afterward. Next, a base oil which has a vapor pressure of 0.1mmHg or lower at 25 deg.C, N-alkylenepolyamino-alkenylsuccinimide, nonionic surface active agent, etc., are added to the ferrite fine particles coated by N- alkylenepolyamino-alkenylsuccinimide and then a dispersion treatment is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 fine ferrite particles are stably dispersed at a high concentration in a low vapor pressure base oil, thereby improving saturation magnetization.

[Conventional technology]

Ferrite particles are manufactured by pulverization, coprecipitation, vapor deposition, etc., but among these methods, the coprecipitation method is generally used in terms of purity, particle size control, productivity, etc. ing. By the way, since the coprecipitation method is a precipitation reaction from an aqueous solution containing iron ions, the generated magnetic fine particles are obtained in a suspended state in the aqueous solution.

On the other hand, it is desirable that the magnetic particles for magnetic fluid be dispersed one by one without being aggregated. Therefore, in the case of coprecipitated magnetic particles, it is possible to adsorb a surfactant to prevent agglomeration on the particle surface in a dispersion state without going through a drying process that involves the risk of adhesion and aggregation of the particles. Therefore, water-soluble surfactants are used.

In magnetic fluids in which fine magnetic particles are dispersed using water-soluble surfactants, the dispersion base oil is limited to relatively volatile solvents such as kerosene and toluene.
However, when magnetic fluids are used for magnetic fluid seals, magnetic fluid polishing, etc., evaporation of the base oil is considered to be an important problem that impairs the functionality of the magnetic fluid itself.

[Problem to be solved by the invention]

A magnetic fluid is generally made by dispersing fine ferrite particles in a base oil using a dispersant such as a higher fatty acid salt or a sorbitan ester.

However, simply dispersing ferrite fine particles in a low vapor pressure base oil fails to provide high dispersibility, making it extremely impractical.

Even if a fairly good dispersibility is obtained when dispersing in such a low vapor pressure base oil, the low vapor pressure base oil exhibits a kinematic viscosity (at 40°C) below I Cst, whereas ordinary organic solvents and water exhibit Since it has a high kinematic viscosity of about 8 to 50 Cst (40°C), it takes a very long time to form a uniform suspension. Moreover, the ferrite fine particles that should be dispersed do not form a stable suspension, and a large proportion of the ferrite fine particles are often removed during purification by centrifugation, resulting in very poor efficiency. be.

An object of the present invention is to efficiently produce a magnetic fluid in which fine ferrite particles are stably dispersed in a low vapor pressure base oil at a high concentration.

[Means to solve the problem]

The object of the present invention is to add N-
After adding the alkylene polyamine-substituted alkenyl succinimide and heating at a temperature of about 70° C. or higher, the low boiling hydrocarbon solvent is separated.

The separated N-alkylenepolyamine-substituted alkenylsuccinimide-coated ferrite fine particles are treated with a low vapor pressure base oil having a vapor pressure of 0.1 mm or less at 25°C and an N-alkylpolyamine-substituted alkenylsuccinimide, mono- or This is achieved by adding a dispersant, which is a phosphoric acid ester having a di-oxyalkylene substituent or a nonionic surfactant, and carrying out a dispersion treatment.

In the method of the present invention, first, a surfactant is adsorbed.
A low boiling point that allows ferrite fine particles with a particle size of approximately 50 to 300 particles, preferably approximately 70 to 120 particles, to be dispersed relatively easily after sufficiently drying and removing moisture that would be an inhibiting factor during dispersion in oil. Dispersion in a hydrocarbon solvent to form a stable low-boiling hydrocarbon-based suspension therein is accomplished by conventional methods.

The ferrite particles may be manufactured by any method, but the purity is important.

Those produced by coprecipitation are preferably used because they are advantageous in terms of particle size control and, above all, productivity.

Surfactants adsorbed on ferrite particles include:
The following materials that are commonly used when dispersing fine particles in a low-boiling hydrocarbon solvent are used, and higher fatty acid salts or sorbitan esters are preferably used.

Higher fatty acid aerosols such as oleic acid and stearic acid - dialkyl sulfosuccinates such as 〇T polyoxyethylene alkyl esters alcohol sulfate esters such as dodecyl sulfate esters alkylbenzenesulfonic acid phosphates such as oleyl phosphate polyoxyethylene alkylamine glycerin Ester amino alcohol ester As a low-boiling hydrocarbon solvent, an aliphatic, alicyclic or aromatic hydrocarbon solvent having a boiling point of about 60 to 200°C, such as n
At least one of -hexane, n-hebutane, low octane, isooctane, n-decane, cyclohexane, toluene, xylene, mesitylene, ethylbenzene, petroleum ether, petroleum benzine, naphtha, ligroin, etc. is used.

The above-mentioned surfactant-adsorbed ferrite fine particles are dispersed using these low-boiling hydrocarbon solvents and a homogenizer, and if necessary, centrifugation is performed to remove sediments, resulting in a dispersion concentration of approximately 0.01 to 30% by weight. %, preferably about 0.1-2
A suspension of 0% by weight is formed. If the concentration is higher than this, the ferrite particles will gel and will not form a stable suspension.

This low-boiling hydrocarbon-based suspension can be used in the next process by centrifugation, which is a common method of ferrofluid purification to remove particles that are too large or have poor dispersibility. A second surfactant is then added to this stable low-boiling hydrocarbon-based suspension.

This coats the magnetic particles. For this reason, it is desirable that the low-boiling hydrocarbon used to form the suspension be one that dissolves this surfactant, and as the surfactant, detergent-dispersing agents, which are a type of lubricating oil additive, are used. In particular, when heat treatment is performed after coating with this surfactant, an ashless detergent/dispersant is preferable.

As such a second surfactant, one such as a primary surfactant has a surfactant of about 0.
It is used in a ratio of 1 to 10 parts by weight.

(2) Multipolar acrylic acid ester polymer C0OR'
C0OR"NR'.

R': Divalent group such as alkylene group or arylene group The low-boiling hydrocarbon-based suspension to which these second surfactants are added is heat-treated at a temperature of about 70° C. or higher with stirring. The heat treatment is carried out at the reflux temperature of the low-boiling hydrocarbons, it being also possible for the low-boiling hydrocarbons to be distilled off without refluxing. The heat treatment can also be carried out in the coexistence of a low vapor pressure base oil described below, in which case the heat treatment at about 200 to 300 °C under normal pressure, reduced pressure, or an inert gas atmosphere is carried out at about 30 to 300 °C. This is carried out for 60 minutes, and the low-boiling hydrocarbon solvent is also distilled off at the same time.

Thereafter, the residue from which low-boiling hydrocarbons have been distilled off or a mixture of this and low vapor pressure base oil is washed using a mixed solvent such as toluene-acetone, toluene-methanol, n-hexane-acetone, isooctane-acetone, etc. This is generally done to remove excess surfactants, low-boiling hydrocarbons, thermal decomposition products, etc. that increase the viscosity or reduce the dispersion concentration of magnetic fine particles when made into a magnetic fluid. After washing, the magnetic fine particles are dried if necessary.

A low vapor pressure base oil and a third surfactant are added to the magnetic fine particles coated with the second surfactant obtained in this way, and the heat treatment converts them into low vapor pressure base oil. The dispersibility of is in good condition.

As a low vapor pressure base oil, 0.1 mmHg at 25°C
The liquids 5 preferably have a vapor pressure of 0.01n++nHg or less, such as natural oils such as white oil (liquid paraffin), mineral oil, spindle oil, etc., or synthetic oils such as higher alkylbenzenes, higher alkylnaphthalenes, and polybutenes (molecular weight approximately 300). ~2000), dicarboxylic acid diesters (dioctyl azelate, dioctyl adipate, dioctyl sebacate, dibutyl phthalate, dibutyl frate, etc.), polyols (neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, etc.), these polyols and a carboxylic acid having 6 to 10 carbon atoms, polyol polyesters (trimethylolpropane tri-n-heptyl ester, pentaerythritol tetra-n-hexyl ester, pentaerythritol tetra-2-ethylhexyl ester, etc.), phosphoric acid triesters (phosphoric acid tributyl ester) , tri2-ethylhexyl phosphate, tricresyl phosphate, etc.), and further contains so-called lubricating additives such as antioxidants, anti-wear agents, oil-based agents, and detergent-dispersing agents. The dispersion concentration of ferrite particles in the magnetic fluid is approximately 10 to 50% by weight.
It is used in proportions such that

For these low vapor pressure base oils, the following three types are used as the third dispersant, which is generally about 10 to 0 weight2.

(1) N-alkylenepolyamine-substituted alkenylsuccinimide (2) Mono- or di-oxyalkylene group-containing phosphoric acid ester or mixture thereof HRO(CnH2nO)4~. -P=0H n: 2 or 3 (3) Nonionic surfactant ethylene oxide type: polyoxyethylene alkylaryl ether polyoxyethylene alkyl ether polyoxyethylene alkyl ester sorbitan fatty acid ester type: sorbitan higher fatty acid mono(tri)ester Polyoxyethylene sorbitan fatty acid ester system: Glycerin ester system: Glycerin higher fatty acid mono(tri)ester Dispersion treatment with the addition of these is carried out by a conventional method using a homogenizer, ultrasonic waves, vibration mill, etc. Adding small amounts of boiling hydrocarbon solvents is also effective in increasing dispersion efficiency.

After the dispersion treatment, washing with a mixed solvent is performed as necessary, as in the treatment after adding the second surfactant. If a low-boiling hydrocarbon solvent is added during dispersion or washing is performed with a mixed solvent, the resulting magnetic fluid should be heat-treated under reduced pressure in order to control the dispersion concentration of the magnetic fluid and the evaporated components. It is preferable to distill off low-boiling components, so that the dispersibility of the magnetic fluid is not impaired.Furthermore, purification methods such as those described above by centrifugation or standing in a magnetic field gradient may be used as necessary. can be applied.

〔Effect of the invention〕

According to the method of the present invention, first, a surfactant is adsorbed to prevent ferrite fine particles from agglomerating, and then a low-boiling hydrocarbon solvent dispersion suspension is formed, and then the ferrite particles are coated with a second and third specific surfactant. , it is possible to efficiently produce a magnetic fluid in which fine magnetic particles are simply and stably dispersed in a low vapor pressure base oil, which is a necessary condition for various applications such as magnetic fluid seals. Moreover, since the obtained magnetic fluid can disperse magnetic fine particles at a high concentration of about 40 to 50 weight X, its saturation magnetization value can also be increased.

The method of the present invention is suitably applied to coprecipitation ferrite fine particles, and only water-soluble surfactants, which were the biggest weakness of the coprecipitation method, can be used. It is freed from the constraints of being limited to hydrogen solvents and allows the use of low vapor pressure base oils.

〔Example〕

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

Example I FeCQ 2.4H20184g and FeCQ 3
・6Hz 0500g of aqueous solution 1850ml
A 6N Na0II aqueous solution was added dropwise to Q without stirring until the pll reached 11, then the mixture was aged at 80°C for 30 minutes, cooled, and the salt was removed by decantation to obtain a magnetite suspension.

An aqueous solution containing 70 g of sodium oleate was added to this suspension, and an adsorption reaction was carried out at 90°C for 30 minutes.
Then, while stirring, add INH (l) dropwise until the pH becomes 6.
I left it still. Conductive dust in the supernatant liquid is 5.5 x 10-'/Ω
・After decanting with demineralized water until Cl11,
The mixture was passed through the mouth and dried to obtain oleic acid-coated magnetite fine particles.

40 g of the obtained oleic acid-coated magnetite fine particles were added to 250 g of xylene, and stirred (10,000 rpm, 60 minutes) using a homogenizer (New Excel Homogenizer DX model manufactured by Nippon Seiki Co., Ltd.) to obtain a xylene-based suspension. To 100 g of this suspension was added 1.8 g of polybutenyl succinimidote 1-4 ethylene pentamine (polybutenyl group molecular weight approximately 1300), stirred (10000 rpm, 30 minutes), and then heated to 160°C under normal pressure using a rotary evaporator. Xylene was removed while heating, and the remaining magnetite fine particles were washed five times with an acetone-xylene (1:1) mixture and dried.

After adding 4.1 g of tricresyl phosphate and 0.4 g of polybutenyl succinimidotetraethylene pentamine to 2 g of the obtained polybutenyl succinimidotetraethylene pentamine-adsorbed magnetite fine particles, the mixture was subjected to ultrasonic irradiation for 12 hours. Through dispersion treatment, magnetite fine particles are stably dispersed in tricresyl phosphate, and the saturation magnetization (1
A magnetic fluid of 247G (6K Oe) was obtained.

Example 2 40 g of oleic acid-coated magnetite fine particles obtained by the method described in Example 1 and 4 g of polybutenylsuccinimidotetraethylenepentamine were added to 200 g of isooctane, and stirred using a homogenizer (10,000 rpm).
m, 60 molecules IIj) An isooctane-based suspension was obtained. This was transferred to an eggplant-shaped flask equipped with a reflux condenser and heated to 99°C for 30°C under a nitrogen gas bubble stirring atmosphere.
Heated for a minute. Using a rotary evaporator, the isooctane was distilled off by heating to 50° C. under reduced pressure, and the separated magnetite fine particles were washed five times with an acetone-toluene (1:1) mixture and dried.

Alkylnaphthalene (Lion Product Pump Oil-5) in which 2.5 g of polyoxyethylene nonylphenyl ether was dissolved in 25 g of the obtained polybutenyl succinimidotetraethylene pentamine-adsorbing magnetite fine particles
Add 22.5g and stir using a homogenizer (1
0000 rpm for 60 minutes), a dispersion treatment was carried out by ultrasonic irradiation for 12 hours to obtain a magnetic fluid in which fine magnetite particles were stably dispersed in the alkylnaphthalene at a high concentration of 50% by weight and the saturation magnetization was 500G.

Example 3 40 g of oleic acid-coated magnetite fine particles obtained by the method described in Example 1 were added to 250 g of n-octane,
Stir using a homogenizer (10,000 rpm, 60
After centrifugation (10,000 rpm, 30 min),
), and the supernatant was collected to obtain an n-octane-based suspension. This suspension 200g,
16 g of alkylnaphthalene in which 4 g of polybutenyl succinimidotetraethylene pentamine was dissolved was added,
Stir using a homogenizer (10,000 rpm.

60 minutes). Thereafter, the mixture was transferred to an eggplant-shaped flask and heated at 280° C. for 30 minutes under an argon gas bubble stirring atmosphere, during which time n-octane was distilled and recovered. After cooling, the remaining magnetite fine particles were dissolved in acetone-toluene (1:1).
It was washed 5 times with the mixed solution and dried.

16 g of the obtained polybutenylsuccinimidotetraethylenepentamine adsorbed magnetite fine particles and 1.6g of polybutenylsuccinimidotetraethylenepentamine
was added to 14.4 g of alkylnaphthalene and stirred using a homogenizer (10,000 rpm.

(60 minutes) to obtain a magnetic fluid in which fine magnetite particles were stably dispersed in the alkylnaphthalene and the saturation magnetization was 500G.

Examples 4 to 5 10 g of polybutenylsuccinimidotetraethylenepentamine adsorbed magnetite fine particles obtained by the method described in Example 3 and polyoxyethylene phosphate ester (Example 4) or polyoxyethylene sorbitan oleyl ester (Example 4) Example 5) Add 1g to 9g of alkylnaphthalene and stir using a homogenizer (loooorp
m, 60 minutes), and then subjected to dispersion treatment by ultrasonic irradiation for 12 hours, and the fine particles were stably dispersed in the alkylnaphthalene at a height of 1 degree by 50% by weight, and the saturation magnetization was 4 degrees.
A 70G (Example 4) or 320G (Example 5) magnetic fluid was obtained.

Example 6 10 g of polybutenylsuccinimidotetraethylenepentamine-adsorbed magnetite fine particles obtained by the method described in Example 3 and 1 g of polyoxyethylene nonylphenyl ether were added to 9 g of dioctyl sebacate, and stirred using a homogenizer. (10000 rpm, 60 minutes)
After that, dispersion treatment was performed by ultrasonic irradiation for 12 hours,
A magnetic fluid was obtained in which fine particles were stably dispersed in dioctyl sebacate at a high concentration of 50% by weight, and the saturation magnetization was 240G.

Example 7 250 g of oleic acid-coated magnetite fine particles obtained by the method described in Example 1 were added to 750 g of ligroin,
Stir using a homogenizer (10000 rpm, 3
After 0 minutes), centrifugation treatment (5000 rpm, 3
0 minutes) and the supernatant was collected to obtain a ligroin base suspension. This suspension 700g,
Mix 63 g of alkylnaphthalene in which 7 g of polybutenyl succinimidotetraethylene pentamine is dissolved,
After irradiating with ultrasonic waves for 10 minutes, the mixture was heated at 200° C. for 30 minutes under aspirator vacuum using a rotary evaporator to distill off ligroin. The residue is acetone-
It was washed three times with a toluene (1:1) mixture and dried under reduced pressure.

The same weight of 1
A solution of 0% by weight polybutenylsuccinimidotetraethylenepentamine in alkylnaphthalene was mixed, irradiated with ultrasound for 72 hours, and then centrifuged (5000 rpm, 30 minutes) to obtain 50% by weight of fine particles in the alkylnaphthalene.
A magnetic fluid was obtained which was stably dispersed at a high concentration of and had a saturation magnetization of 427G.

Comparative Example 20 g of oleic acid-coated magnetite fine particles obtained by the method described in Example 1 were added to 250 g of isooctane, stirred using a homogenizer (10,000 rpm, 60 minutes), and centrifuged (10,000 rpm, 30 minutes). The supernatant was collected to obtain an isooctane-based suspension. To 250 g of this suspension, add 4 ml of polybutenyl succinimidotetraethylene pentamine.
g and stirred using a homogenizer (10,000 g).
rpm, 60 minutes). An equal amount of acetone was added to this to precipitate the fine particles, which were then mixed with acetone-isooctane (Il
l) After washing with the mixed solution, 1 g of polyoxyethylene nonylphenyl ether and 9 g of alkylnaphthalene were added, and homogenizer treatment 4 (toooo.

rpm for 60 minutes) and ultrasonication (72 hours), but the supernatant liquid turned slightly brown and was hardly dispersed.

Claims (2)

[Claims] 1. After adding N-alkylene polyamine-substituted alkenyl succinimide to a suspension of surfactant-adsorbed ferrite fine particles dispersed in a low-boiling hydrocarbon solvent and heat-treating the suspension at a temperature of about 70°C or higher, the low-boiling hydrocarbon solvent is separated. , a low vapor pressure base oil having a vapor pressure of 0.1 mmHg or less at 25°C and an N-alkylene polyamine substituted alkenyl succinimide, mono- or di-coated ferrite fine particles coated with N-alkylene polyamine-substituted alkenyl succinimide - A magnetic fluid in which fine ferrite particles are stably dispersed in a low vapor pressure base oil, which is characterized by adding a dispersing agent that is a phosphoric acid ester having an oxyalkylene substituent or a nonionic surfactant and performing a dispersion treatment. manufacturing method. 2. N-alkylene polyamine-substituted alkenyl succinimide and a low vapor pressure base oil having a vapor pressure of 0.1 mmHg or less at 25° C. are added to a suspension of surfactant-adsorbed ferrite fine particles dispersed in a low-boiling hydrocarbon solvent. After heat treatment at a temperature of ~300°C, the low-boiling hydrocarbon solvent is separated, and the separated N-alkylenepolyamine-substituted alkenylsuccinimide-coated ferrite fine particles have a low vapor pressure of 0.1 mmHg or less at 25°C. It is characterized by adding a vapor pressure base oil and a dispersant which is an N-alkylene polyamine-substituted alkenyl succinimide, a phosphoric acid ester having a mono- or di-oxyalkylene substituent, or a nonionic surfactant, and performing a dispersion treatment. A method for producing magnetic fluid in which fine ferrite particles are stably dispersed in a low vapor pressure base oil.