RU2426187C1 - Method of preparing ferromagnetic liquid - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: method of preparing ferromagnetic liquid involves precipitation of finely dispersed magnetite from aqueous solutions of di- and trivalent iron salts with excess divalent iron with an ammonium 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 which contains a fatty acid, washing the stabilised magnetite with distilled water and peptisation while heating in a liquid carier based on synthetic hydrocarbon oil, characterised by that peptisation is carried out in 4-6 hours immediately after washing the stabilised magnetite with distilled water, the surfactant used is oleic acid, the acetic acid is glacial acetic acid and the synthetic hydrocarbon oil is alkarene. ^ EFFECT: high quality of ferromagnetic liquid as an end product, simple method of preparation, low power consumption of the process and high environmental safety of the process. ^ 1 tbl

Description

INTRODUCTION

The invention relates to colloidal chemistry and can be used to obtain high-temperature, with various viscosities, high-vacuum ferromagnetic liquids 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 ferric iron salts with an ammonia solution, washing the precipitate with distilled water to a pH of 10–12, and peptizing a solution of oleic acid in alkene at 115-120 ° C 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] to obtain 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 a ferromagnetic fluid [RF Patent for the invention No. 220584 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 of an aqueous precipitate of magnetite at 90 ° C for 30 minutes;

- simultaneous activation and stabilization of magnetite sediment. For this, a preheated 40% acetic acid solution 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 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 publ. "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. P.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 a ferromagnetic fluid, including the precipitation of highly 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 a t-carrier based on synthetic hydrocarbon oil, which would improve the quality of the target product, simplify the method, reduce the cost of the product, reduce the energy consumption of the process and increase environmental safety.

The problem is solved by a method of producing a ferromagnetic fluid, including the deposition 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 on again synthetic hydrocarbon 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 alkaren as synthetic hydrocarbon oil .

The invention allows to obtain the following advantages:

- improve the quality of the target product, reaching a saturation magnetization of at least 60 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 -40 to 180 ° C;

- maintaining the properties of the obtained product when heated to 180 ° 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 a ferromagnetic 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, at least 95%, GOST 4148-78 "hch";

- iron (III) trichloride 6 - water (FeCl ₃ * 6H 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";

- Alkaren, TU 6-01-26-54-85, TU 6-01-26-54-83.

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 deposit 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 a carrier fluid, alkaren, which is a synthetic hydrocarbon oil, is used.

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. 10 g of alkarne D12 are added and the resulting mixture is peptized at 85 ° C for 6 hours.

Qualitative indicators of the ferromagnetic 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 ferromagnetic fluid obtained according to the claimed invention:

- increase saturation magnetization by 25 ÷ 30%;

- increase in density by 5%;

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

Table. Quantitative indicators of the quality of a ferromagnetic fluid. Examples Options Indicators τ, hour t, ° C Saturation magnetization, kA / m Density, g / cm ³ Effective viscosity in the speed range 180-1350 sec ^-1 (Pa · s), no more Magnetic field stability up to 1 T Stability in the gravitational field up to 6000 g one 6 85 60 1.6104 0.45 + + 2 four 90 62 1.6895 1.1 + + 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 RF Patent for the invention No. 2208584

Claims (1)

A method for producing a ferromagnetic 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 by heating in a carrier fluid based on a synthetic carbohydrate natural oil, characterized in that the 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 alkaren as synthetic hydrocarbon oil .