RU2462420C1 - Method of producing magnetic liquid - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry. The method of producing magnetic liquid involves precipitation of finely dispersed magnetite from aqueous solutions of iron (II) and iron (III) salts in excess of iron (II) with ammonia solution, washing the precipitate with distilled water, simultaneous activation and stabilisation of the magnetite while heating with a mixture of acetic acid and a surfactant containing a fatty acid, washing the stabilised magnetite with distilled water and peptisation while heating in a carrier liquid based on vacuum oil. Peptisation is carried out for 4-6 hours immediately after washing the stabilised magnetite with distilled water. The surfactant used is oleic acid, the acetic acid used is glacial acetic acid and the vacuum oil used is mineral hydrocarbon oil.

EFFECT: invention improves the quality of the end product, simplifies the method, reduces power consumption and improves environmental safety of the process.

1 ex, 1 tbl

Description

INTRODUCTION

The invention relates to colloidal chemistry and can be used to obtain high-temperature, with various viscosities, stable against oxidation, high-vacuum magnetic fluids with high magnetization.

BACKGROUND

The known method [RF patent for the invention No. 2024085 C1, application 5047739/02, 01/01/1992] for producing a ferromagnetic fluid. It is carried out by precipitation of finely dispersed magnetite from solutions of ferrous and trivalent iron salts with an ammonia solution, washing the precipitate with distilled water to a pH of 10 ÷ 12, peptization with a solution of oleic acid in alkene at 115-120 ° С under vacuum.

However, the magnetic fluid obtained by this method has a low saturation magnetization - up to 22.5 kA / m.

The known method [RF patent for the invention No. 2113027 C1, application 96119620/25, 09/30/1996] for the production of magnetic fluid. It is carried out by precipitation of ferrous and ferric iron salts from aqueous solutions with an aqueous solution of ammonia, washing colloidal magnetite with distilled water, activating an aqueous precipitate of magnetite when heated to 27 ÷ 97 ° C for 30 minutes with 70-80% acetic acid, stabilizing oleic acid acid when heated to 27 ÷ 97 ° C, washing stabilized magnetite with distilled water until complete removal of oleic acid, peptization of stabilized magnetite in a carrier liquid kerosene.

However, the magnetic fluid obtained by this method is volatile; upon evaporation of the solvent, it changes viscosity and density, does not have a sufficient range of operating temperatures, and therefore cannot be widely used in instrumentation.

Closest to the proposed invention is a method for producing magnetic fluid [RF patent for the invention No. 2208584 C2, application 2001111184/12, 04/23/2001]. The method is carried out by sequentially carrying out the following operations:

- precipitation of fine magnetite from aqueous solutions of salts of ferrous and ferrous iron with an excess of ferrous iron with an ammonia solution;

- repeated washing of the precipitate with distilled water;

- thermostating an aqueous precipitate of magnetite at 90 ° C for 30 minutes;

- simultaneous activation and stabilization of magnetite sediment. For this, a preheated 40% solution of acetic acid and a preheated combined surfactant are added to a magnetite precipitate heated to 90 ° C and aged for 30 minutes. Fatty acids and their anhydrides are used as a combined surfactant;

- repeated washing of stabilized magnetite with hot distilled water;

- repeated (until complete removal of the surfactant) washing of stabilized magnetite with organic solvents preheated to 50-70 ° C, first with hexane, then with ethyl alcohol;

- peptization by treatment of stabilized magnetite in a carrier fluid. As the carrier fluid, polyethylsiloxane liquid and / or synthetic hydrocarbon oil of a C ₅ -C ₂₀ olefin polymer are used.

However, the method has the following disadvantages:

- low quality of the target product, characterized by the saturation magnetization is not higher than 45 kA / m This disadvantage is associated with the fact that, as is known [V. Fertman. Magnetic fluids: Ref. allowance. - Mn .: Higher school. 1988. S. 33. Chemical Encyclopedia in 5 volumes. M .: Scientific. ed. "Great Russian Encyclopedia." 1992.V.5. P.86. Chemistry of elements: in 2 volumes / Greenwood N., Ernshaw A. per. from English - M .: BINOM. Knowledge laboratory. 2008. S.410.], When unstabilized magnetite is heated above 40-50 ° C, it oxidizes to hematite, as a result of which the amount of the magnetic phase in the target product is noticeably reduced [Arefiev IM Magnetocaloric effect and heat capacity of highly dispersed magnets. Dis. for a job. student step. Candidate Chem. sciences. Ivanovo 2009];

- sufficient process complexity due to:

• the need for preliminary preparation of surfactants;

• the need for preliminary preparation of solvents;

- the high cost of the drugs used:

• fatty acid anhydrides;

• organic solvents;

- high energy consumption due to the need for several operations with heating to 50-90 ° C with a total duration of at least 11 hours;

- negative impact on the environment due to washing operations with organic solvents at elevated temperatures.

SUMMARY OF THE INVENTION

The inventive task was to find a method for producing magnetic fluid, including the precipitation of finely dispersed magnetite from aqueous solutions of ferrous and ferrous salts with an excess of ferrous iron with an ammonia solution, washing the precipitate with distilled water, simultaneous activation and stabilization of magnetite when heated with a mixture of acetic acid and a surfactant including fatty acid, washing stabilized magnetite with distilled water and peptization when heated in a liquid Itel on the basis of vacuum oil, which would allow to increase the quality of the desired product, to simplify the process, reduce the cost of the product, reduce the energy intensity of the process and improve environmental safety.

The problem is solved by a method of producing a magnetic fluid, including the precipitation of finely dispersed magnetite from aqueous solutions of ferrous and ferrous salts with an excess of ferrous iron with an ammonia solution, washing the precipitate with distilled water, simultaneous activation and stabilization of magnetite when heated with a mixture of acetic acid and a surfactant, including fatty acid, washing stabilized magnetite with distilled water and peptization when heated in a carrier fluid based on vacuum oil, in which peptization is carried out for 4-6 hours immediately after washing the stabilized magnetite with distilled water, oleic acid is used as a surfactant, glacial acetic acid is used as acetic acid, and mineral hydrocarbon oil is used as vacuum oil ( VM).

The invention allows to obtain the following advantages:

- improve the quality of the target product, reaching a saturation magnetization of at least 50 kA / m;

- to simplify the method by eliminating the preliminary preparation of surfactants and solvents;

- reduce the cost of the target product by replacing expensive fatty acid anhydrides with oleic acid and eliminating organic solvents;

- significantly reduce energy consumption by eliminating several operations with preheating for a long time;

- increase the environmental safety of the process by eliminating the use of organic solvents at elevated temperatures.

In addition, the invention allows to obtain the following advantages:

- expand the range of operating temperatures from -20 to 210 ° C;

- maintaining the properties of the obtained product when heated to 210 ° C for 1 hour;

- stability in a gravitational field of 6000 g;

- stability in a magnetic field up to 1 T;

- the ability to obtain magnetic fluid of various viscosities at the request of the customer;

- thermo-oxidative stability;

- aggregative stability.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

For the implementation of the invention using the following substances:

- aqueous ammonia (NH ₄ OH), mass fraction of ammonia not less than 25%, GOST 3760-79;

- iron (II) sulfate 7 - water (FeSO ₄ · 7H ₂ O), the mass fraction of iron (II) sulfate 7 - water is not less than 95%, GOST 4148-78 "hch";

- iron (III) trichloride 6 - water (FeCl ₃ · 6Н ₂ O), the mass fraction of iron (III) trichloride 6 - water is not less than 95%, GOST 4147-74 "hch";

- distilled water, GOST 6709-72;

- glacial acetic acid, GOST 61-75 rev. 1-3 "hh";

- oleic acid, TU 6-09-5290-86 "hch";

- vacuum oil VM-6, TU 38.401-58-3-90.

The proposed method is implemented by sequentially carrying out the following operations:

- precipitation of fine magnetite from aqueous solutions of salts of ferrous and ferrous iron with an excess of ferrous iron with an ammonia solution;

- repeated washing of the precipitate with distilled water;

- simultaneous activation and stabilization of magnetite. For this, glacial acetic acid and a surfactant are added to the unheated precipitate of magnetite. A fatty acid, namely oleic acid, is used as a surfactant. The resulting mixture was heated to 90 ° C and incubated for 1 hour. Since the heating of the magnetite precipitate is carried out in the presence of a surfactant, therefore, magnetite does not oxidize;

- repeated washing of stabilized magnetite with hot distilled water;

- peptization in a carrier fluid. As the carrier fluid, a vacuum oil is used, which is a mineral hydrocarbon oil.

Example 1. Prepare solutions: 45 g of FeSO ₄ · 7H ₂ O in 600 ml of distilled water; 81 g of FeCl ₃ · 6H ₂ O in 600 ml of distilled water; 345 ml of 25% ammonium hydroxide in 300 ml of distilled water.

In a beaker containing 600 ml of ammonia solution, 600 ml of sulfate and iron chloride solutions are simultaneously poured with vigorous stirring at a temperature of 25 ° C. The precipitate of magnetite formed is repeatedly (5–10 times) washed with distilled water to a pH of washings of 6–7. Then the water-magnetite suspension is placed in a thermostat at 90 ° C, at the same time 100 ml of glacial acetic acid and 15 g of oleic acid are added to it with vigorous stirring and the mass is held for 1 hour. Next, the mother liquor is drained and the stabilized magnetite is washed with distilled water until the excess oleic acid is completely removed. Add 10 g of vacuum oil BM-6 and the resulting mixture is peptized at 85 ° C for 6 hours.

Qualitative indicators of the magnetic fluid obtained with various parameters of the method of the invention are shown in the table.

Quantitative indicators of the quality of the liquid obtained according to the invention were determined:

- saturation magnetization by a known method [Perminov S.M. Development of a method, device and method for measuring the magnetization of nanodispersed magnetic fluid. Bulletin of ISEU. 2009. Issue 3. C.1-4];

- density according to GOST 18995.1-73;

- viscosity on the Reotest-2.1 viscometer.

These tables clearly show the high quality of the magnetic fluid obtained according to the claimed invention:

- increase in saturation magnetization by 25-30%;

- decrease in density by 2%;

- the ability to vary the viscosity in a wider range.

Table Quantitative indicators of the quality of magnetic fluid Examples Options Indicators τ, hour τ, ° C Saturation magnetization, kA / m Density, g / cm ³ Effective viscosity in the speed range 180-1350 sec ^-1 (in Pa · s), no more Magnetic field stability up to 1 T Stability in the gravitational field up to 6000 g one 6 85 60 1.5758 3.8 + + 2 four 90 58 1.5532 3.3 + + 3 - prototype ^∗ 8 90 45 1.6 0.35 there is no data there is no data ^∗ ) the indicators of example 3 are taken from table 3 of the patent of the Russian Federation for invention No. 2208584

Claims (1)

A method for producing a magnetic fluid, including the precipitation of finely divided magnetite from aqueous solutions of ferrous and ferrous salts with an excess of ferrous iron with an ammonia solution, washing the precipitate with distilled water, simultaneous activation and stabilization of magnetite when heated with a mixture of acetic acid and a surfactant, including fatty acid, washing stabilized magnetite with distilled water and peptization when heated in a carrier fluid based on vacuum oil, characterized Since peptization is carried out for 4-6 hours immediately after washing the stabilized magnetite with distilled water, oleic acid is used as a surfactant, glacial acetic acid is used as acetic acid, and mineral hydrocarbon oil is used as vacuum oil (VM )