JPS6211207A - Metallic magnetic fluid - Google Patents

Abstract

PURPOSE:To obtain a metallic magnetic fluid having excellent stability and durability by dispersing ferromagnetic metallic particles into a dispersion medium liquid under a colloidal state by using a dispersant of succinic acid polyamine or benzil polyamine. CONSTITUTION:A Langmuir membrane consisting of a surface active agent of dibenzil polyamine (DPA) is lined onto a dispersion medium liquid of alkyl naphthalene, Co is vacuum-deposited on the membrane, thus acquiring colloid composed of C fine particles coated with DPA, alkyl naphthalene and excess DPA. Colloid is diluted with lower hydrocarbon such as benzene, and secondary particles, the particle size of Co therein increases through heat treatment, are precipitated. The secondary particles are dried, thus obtaining semi-solid cake. Toluene and DPA are added to the cake, and a magnetic fluid employing toluene as a dispersion medium liquid is obtained through ultrasonic treatment. Succinic acid polyamine can also be used in place of DPA.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a metal magnetic fluid. More specifically, by using a specific dispersant, it is possible to provide a metal magnetic fluid that is extremely stable and has excellent durability.

Magnetic fluids are already being used or are being considered for use in fields such as liquid magnets, vacuum rotary shaft seals, inkjet printers, and specific gravity separation. In addition to these fields, applications in a wide range of fields such as radio wave absorbers, thermal energy conversion working materials, and magneto-optical elements can be considered.

Conventional metal magnetic fluids are made by colloidally forming ferromagnetic metal particles in a dispersion medium such as mineral oil or water using a dispersant.
Its production method includes (licobalt carbonyl (Cow)
(Co ) s ) thermal decomposition method and (2) active liquid surface deposition method are known.

In the above method, an acrylonitrile-styrene copolymer was used as a dispersant.However, this dispersant is easily polymerized by ultraviolet light, so it cannot be used in the active interfacial deposition method.Active liquid level In the vapor deposition method, the present inventor has previously proposed that the following dispersant can be used.

(1) Sulfate ester fJ[, (2) Sulfonic acid ester salts, (3) Carboxylic acid ester salts, (4) Phosphate ester salts, (+1) Amine salts, (6) Amino acid type surfactant, (7) betaine type surfactant, (8) polyethylene oxide type nonionic surfactant, (9) polyhydric alcohol type nonionic surfactant, (14 amides and imides, α9 metal phenates, (b) polar group However, the stability and durability of metal magnetic fluids are affected by the dispersant used, and it has been found that the selection of the dispersant is important in order to have excellent stability and durability. Ta.

OBJECTS OF THE INVENTION An object of the present invention is to specify a dispersant and provide a metal magnetic fluid with excellent stability and durability.

Structure of the Invention In order to achieve the above object, the present inventor conducted tests using various dispersants and an active interface deposition method.

The active interface deposition method consists of a vacuum deposition process ω and a heat treatment aggregation/redispersion process shown in FIG.

First, a dispersant film (2) is formed on the dispersion medium (2), and a ferromagnetic metal is vacuum evaporated onto the film to generate ferromagnetic metal fine particles (2). As a result, the ferromagnetic metal fine particles (2) are covered with the dispersant (2) and dispersed in the dispersion medium (2). (cL engineering) When this colloidal dispersion liquid (■) is heated under an inert gas atmosphere, a secondary particle precipitate (■) is generated, and this precipitate is separated to form a cake (■), which is dispersed in a dispersion medium liquid (■). redisperse using an agent.

(Step b) As a result of testing using various dispersants using this method, it was found that the dispersants were sulfuric acid ester salts, sulfonic acid ester salts, and carboxylic acid ester salts.

In both cases, during heat treatment aggregation and redispersion, the dispersion effect is weak, the particles aggregate, and it is difficult to control the particle size of the ferromagnetic metal fine particles. Phosphate ester salts, amine salts, amino acid type surfactants, betaine type surfactants, polyethylene oxide type nonionic surfactants, polyhydric alcohol type nonionic surfactants, metal phenates, and polymethacrylates with polar groups. In both cases, the dispersion effect is weak during heat treatment agglomeration and redispersion, and the particles agglomerate.

In addition to the above-mentioned drawbacks, polyethylene oxide type nonionic surfactants also have drawbacks such as decomposition or polymerization due to radiant heat during vacuum deposition.

On the other hand, polyamines, especially (1) general formula (however,
R is a polybutenyl group or an alkyl group, and n is 2 or more) Polybutenyl succinic acid polyamine (2) Dibenzyl represented by the general formula (R and n are the same as above) When using polyamines.

There are no drawbacks that occur when using the various dispersants mentioned above,
It has been found that a stable and durable metallic magnetic fluid with excellent functions and effects as described below can be obtained.

When the dispersant is used, 1) ferromagnetic metal vapor has good adhesion during vacuum deposition, so a highly concentrated magnetic fluid can be obtained.

2) This dispersant is heat resistant, hardly polymerized or decomposed by light or ultraviolet rays emitted from the evaporation source, and can withstand evaporation for a long time.

3) By heat-treating the vapor deposition product, its particle size can be controlled. Therefore, it is possible to control the magnetism of the metal magnetic fluid.

4) Since the molecules of this dispersant are strongly adsorbed on the surface of the ferromagnetic metal fine particles, a metal magnetic fluid with excellent oxidation resistance can be obtained.

5) It has an excellent dispersing effect and is difficult to aggregate and can be made stable.

6) Since it is oxidation resistant and has good dispersibility, metal magnetic fluids made of iron, cobalt, nickel, and alloys or compounds thereof can be made.

Excellent effects such as these can be achieved.

The present invention was completed based on this knowledge.

The gist of the present invention resides in a metal magnetic fluid characterized in that fine ferromagnetic metal particles are colloidally dispersed in a dispersion medium using a dispersant of succinic acid polyamine or benzyl polyamine.

Water and mineral oil are used as the dispersion medium.

Next, the manufacturing method and the effects of the weeds will be shown in Examples.

Example 1 On a dispersion medium of alkylnaphthalene (C+aHsyM), dibenzylpolyamine (molecular weight of R in the above general formula = 1
A Singmuir film consisting of a surfactant of 000, n = 4) is applied, and metallic cobalt is vacuum-deposited on top of it to form a cobalt film (cobal).
61 particles were generated. A colloid consisting of fine cobalt particles covered with dibenzyl polyamine, alkylnaphthalene, and excess dibenzyl polyamine was obtained.

This colloid was diluted with a lower hydrocarbon such as benzene, transferred to another container under a viscous strainer, and heated under an argon atmosphere for 27 hours.
Heated at 0°C for 40 minutes. As a result of this heat treatment, the cobalt particles increased in particle size, formed secondary particles, and precipitated. This precipitate was dried in an inert gas to obtain a semi-solid cake. This cake is 10PK for 1. So, toluene 5
cc and 1.5 f of dibenzyl polyamine (same as above) were added, and redispersion treatment was performed using ultrasonic waves. As a result, a cobalt magnetic fluid using citoluene as a dispersion medium was obtained.

The magnitude of saturation magnetization of this magnetic fluid was about 300 Gauss at room temperature.

Example 2 Practical Example 1.0 Example 1. In the same manner as above, a cobalt magnetic fluid was prepared using toluene as the dispersion medium.

The magnitude of saturation magnetization of this magnetic fluid was about 400 Gauss at room temperature.

Effects of the Invention The metal magnetic fluid of the present invention is extremely stable and has excellent durability compared to conventional fluids.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the process of manufacturing a metal magnetic fluid by the surface active deposition method, FIG. 1(a) is a diagram of the vacuum deposition process, and FIG. 1(b) is a diagram of the heat treatment aggregation and redispersion process. Dispersion medium liquid 2: Dispersant film 3: Ferromagnetic metal fine particles 4: Ferromagnetic metal fine particles 5: Dispersant 6; Colloidal dispersion liquid 7: Precipitation of secondary particles 8: Cake 9: Dispersion medium liquid Patent applicant Science Ryu Kawa, Director, Metal Materials Technology Research Institute, Technology Agency −

Claims (1)

[Claims] A metal magnetic fluid characterized in that ferromagnetic metal fine particles are colloidally dispersed in a dispersion medium using a dispersant of succinic acid polyamine or benzyl polyamine.