JPH02206694A - Production ultrafine particles of magnetite easily dispersible in water - Google Patents

Abstract

PURPOSE:To obtain the title magnetite of high saturation magnetization and dispersion stabilized for a long period of time by adding a basic aqueous solution to the organic layer resulting from extraction of a solution in which a sol of hydrated iron oxide is coagulated with an organic solvent, then adding a secondary surfactant to transfer the sol into the aqueous phase. CONSTITUTION:A basic aqueous solution is added to an aqueous solution containing a soluble ferrous salt and a soluble ferric salt to adjust the pH to 1 to 4.5 to form a sol of hydrated iron oxide which is clear and positive and has particle size of less than 300 A on the average, then the sol is aged and stabilized at higher than room temperature. Then, the resultant dispersion is combined with a primary surfactant to coagulate a sol, which is combined with an organic dispersant whereby the sol is transferred into and dispersed in the organic phase. Then, the dispersion is washed with water to remove salts. The solution is separated to collect the organic phase. The organic phase is mixed with water, heated over 50 deg.C and combined with a basic aqueous solution under stirring to adjust the pH to over 9, mixed with the secondary surfactant to transfer the ultrafine particles of magnetite into and disperse in the aqueous phase. Then, the organic dispersant is removed to give the objective magnetite.

Description

DETAILED DESCRIPTION OF THE INVENTION (&) Industrial Application Field The present invention relates to a method for producing water-dispersible ultrafine particle magnetite that is extremely easily dispersed in water.

(b) Prior Art Water-dispersible ultrafine particle magnetite is attracting attention as a safe pigment for cosmetics as well as water-based magnetic fluids, printing inks and pigments.

Conventional methods for producing water-dispersible ultrafine particle magnetite include the following.

That is, (1) to produce water-dispersible ultrafine particle magnetite, ultrafine particle magnetite is obtained all at once by adding a basic aqueous solution to a mixed solution of soluble ferrous salt and soluble ferric salt and rubbing with alkaline 1; To this aqueous suspension of ultrafine particle magnetite, a surfactant containing an unsaturated fatty acid or its salt as a main component is added in an amount necessary to complete at least a monomolecular adsorption layer on the ultrafine particle magnetite in the suspension. After adsorbing more than a molecular layer of the surfactant on the surface of the ultrafine magnetite particles in the suspension, an acid is further added to form an acidic aqueous solution with a pH of 7 or less to aggregate the suspended solids. After washing with water or other polar solvents, an anionic or nonionic surfactant is added to the water to form a suspension (JP-A-51-44580). Public bulletin).

■In producing water-dispersible ultrafine particle magnetite, a basic aqueous solution is added to a mixed solution of soluble ferrous salt and soluble ferric salt to make it alkaline and ultrafine particle magnetite is obtained all at once. The ultrafine magnetite particles are surrounded by a monomolecular adsorption layer of a first surfactant mainly composed of unsaturated fatty acids or their salts, and further covered with an anionic or nonionic second surfactant. coating with a surfactant to obtain a water-dispersed magnetic fluid, and then adding an acid to the water-dispersed magnetic fluid to lower the pH value to a predetermined value depending on the type of the second surfactant. The ultrafine particle magnetite is agglomerated, the agglomerated liquid is separated into solid and liquid by filtration, and a base is added to the separated filter cake until a predetermined po value is reached depending on the type of the second surfactant. This method involves adding an aqueous solution and redispersing it (JP-A-52-103760).

(e) Problems to be Solved by the Invention However, in the method (2) above, an aqueous solution containing ferrous salts and ferric salts is made alkaline to form ultrafine magnetite particles all at once, and then this solution is mixed with unsaturated Fatty acid salts are added to coat ultrafine magnetite particles with a monomolecular film of unsaturated fatty acid salts, but with this method, the particle size of the colloidal particles varies widely, resulting in poor dispersibility (sedimentation, aggregation, concentration changes, etc.). There are quality issues due to segregation, etc.

In addition, method (■) above has the same problems as (■) above, and
1111 i11 adjustment is required, filtration is necessary and troublesome, and the obtained water-dispersed magnetic fluid is alkaline and unstable, so it is easily deteriorated, and as a result,
Its uses are extremely limited, and there are problems in that it is particularly irritating to the skin and cannot be used in cosmetics at all.

In view of the above problems, the present invention uses ultrafine particle magnetite with uniform particle size as a dispersoid, has extremely good dispersibility, does not cause sedimentation, agglomeration, concentration change, segregation, etc., does not require filtration, and has saturation magnetization. The object of the present invention is to obtain water-readily dispersible ultrafine particle magnetite which has a high viscosity and can be suitably used as a pigment in various applications.

(d)? :Means for solving one problem The inventors:
As a result of repeated consideration to solve the above problems, the following findings were obtained.

That is, a basic aqueous solution is added to a solution containing a soluble ferrous salt and a soluble ferric salt to form ultrafine magnetite particles all at once, and then unsaturated fatty acid salts are added to the surface of the ultrafine magnetite to form ultrafine particles. It has been found that when magnetite is coated with a monomolecular film of unsaturated fatty acids, the particle size of the ultrafine magnetite particles is large (variation), and as a result, water easily dispersible ffi fine particle magnetite of stable quality cannot be obtained.

Therefore, in producing water-readily dispersible ultrafine particle magnetite using Hi fine particle magnetite as a dispersoid, a basic aqueous solution is added in two stages, and in the first stage, pl
After suppressing + and preparing a transparent positive hydrated iron oxide sol with an average particle size of 300 Å or less in an acidic region, when this is aged, surprisingly, the particle size of the sol becomes uniform, Next, add a basic aqueous solution to this (second step) p
It has been found that by setting II to 9 or more, ultrafine particle magnetite with uniform particle size and excellent dispersibility can be obtained.

Furthermore, with this method, filtration is not required, and the final substance is neutral, so it is stable and non-irritating to the skin (it has also been found that it can be used satisfactorily in cosmetics, etc.).

The present invention has been completed based on the above findings.

First, the book Mili! A method for producing water-ready dispersible ultrafine particle magnetite according to Item 1 will be explained.

In the present invention, by adding a basic aqueous solution to an aqueous solution containing a soluble ferrous salt and a soluble ferric salt to adjust the pH to 1 to 4.5, a transparent and positive hydrated iron oxide with an average particle size of 300 Å or less is produced. Step (A) of adjusting the sol of

The soluble ferrous salt used in the present invention is not particularly limited as long as it is soluble in water or hot water. Specifically, ferrous chloride, ferrous bromide, etc. Examples include iron, ferrous iodide, ferrous perchloride, ferrous sulfate, ferrous nitrate, ferrous vinegar Fll, ferrous ammonium sulfate, and the like.

Further, the soluble ferric salt used in the present invention is not particularly limited as long as it is soluble in water or hot water, and specifically, for example, ferric salt 7. , ferric chloride, ferric perchlorate, ferric bromide, ferric sulfate, ferric nitrate, ferric thiocyanate, ferric oxalate, ferric ammonium sulfate, ferric potassium sulfate Examples include iron.

The concentrations of the soluble ferrous salt aqueous solution and the soluble ferric salt aqueous solution are both 0.1 to 5 pupils 01/1! It is preferable to set it as the range of 5 soo1/N, and it is not preferable because there is a possibility that turbidity will occur or the particle size distribution will be expanded. On the other hand, if it is less than 0 or 1 aro1/1, the concentration will be too thin, resulting in a lack of mass productivity and being extremely uneconomical, which is not preferable.

Moreover, the above-mentioned soluble ferrous salt (a) and soluble ferric salt (b)
There is no particular limitation on the molar ratio of (a) to 1 to b) of 0.7 to 1.3 when used as a black pigment.
It is preferable to set it within the range of (2); outside this range, it is not desirable because stable ultrafine particle magnetite cannot be obtained (and the degree of saturation magnetization and black color is low).

Examples of the basic aqueous solution include aqueous solutions of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, carbonate aqueous solutions such as sodium carbonate and potassium carbonate, hydrogen carbonate, potassium hydrogen carbonate, and carbonic acid. Examples include aqueous solutions of hydrogen carbonates such as ammonium hydrogen, aqueous ammonia, and the like.

In addition, the concentration of the basic aqueous solution is 0.5 to 5 o
1/l is preferable; if it exceeds 5 mol/12, the concentration is too high and it becomes difficult to adjust H31;
On the other hand, if it is less than 5 mol/1, the concentration becomes too thin and the amount of liquid increases, which is not preferable because the reactor becomes larger and the handling becomes worse.

When preparing a sol of hydrated iron oxide by reacting an aqueous solution containing the above-mentioned soluble ferrous salt and soluble ferric salt with a basic aqueous solution, it is necessary to carry out the reaction in the pH range of 1 to 4.5, that is, in the acidic region. I) If it is less than 81, the pH becomes too high and it is difficult to completely obtain a sol of hydrated iron oxide.On the other hand, if the pH exceeds 4.5, ultrafine particle magnetite is generated all at once, and it is difficult to obtain a sol of hydrated iron oxide at a time when the pH is more than 4.5. Also, it becomes difficult to make the particle size uniform, which is undesirable from the viewpoint of dispersibility and quality stability.

In the present invention, a step (13) of aging and stabilizing the hydrated iron oxide sol obtained in the above step (A) at room temperature or higher is carried out.

The particle size and shape of the hydrated iron oxide sol obtained in this step (B) '11' become the size and shape of the ultrafine particle magnetite as they are, and therefore, in producing the ultrafine particle 31f in this step (A). The aging temperature and aging time are important.

The temperature for this ripening may be room temperature or higher, but specifically, it is preferably in the range of 20 to 450'C. If this temperature is lower than 20°C, the ripening time becomes long, resulting in a lack of mass productivity or aging. If the temperature exceeds 450°C, the apparatus becomes complicated, which is preferable (Ii).

In this case, an autoclave may be used when the aging temperature exceeds 100°C.

In addition, the helding time varies depending on the temperature, but from the viewpoint of productivity and economy, it is set to be in the range of 1 to 24 hours.
;A'l is preferable.

By aging in this way, the particle size becomes almost 100%.
A sol of hydrated iron oxide in the range of ~150 is obtained.

In the present invention, the step (C) of adding a primary surfactant to the dispersion obtained in step (B) and coagulating the hydrated iron oxide sol is carried out.

Examples of the secondary surfactant include sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium caproate, sodium caprylate, sodium ricylate, sodium laurate, and sodium oleate.
・Rium, sodium alkylnaphthalene sulfonate,
Alternatively, anionic surfactants of phosphate ester salt type, for example, anionic surfactants such as higher alcohol phosphoric acid monoester nonsodium salts, higher alcohol phosphoric acid diester sodium salts, oleic acid, linoleic acid, phosphoric acid, −
Fatty acids such as rulic acid, riluic acid, lauric acid, palmitic acid, myristic acid, stearic acid, salts of low polymerization degree polycarboxylic acids, such as low polymerization degree sodium polyacrylate, low polymerization degree polybutyl acrylate, low polymerization degree Polymethacrylic acid sorg, further casein or its alkali metal salt,
Amino acids or derivatives thereof, ami7carboxylic acid or alkali metal salts thereof, hydroxycarbon M La or alkali metal salts thereof, sulfonated polystyrene represented by the following formula (% formula %), sodium dioctyl sulfosuccinate, polyoxyethylene oleyl ether Among these, higher unsaturated fatty acids or their alkali metal salts, sodium furkylsulfosuccinates such as sodium dioctylsulfosuccinate, and polyoxyalkylene oleyl ethers such as polyoxyethylene oleyl ether are used. In this step (C), which is preferred, the concentration and amount of the primary surfactant aqueous solution to be added vary depending on the type of primary surfactant used, and are appropriately determined.

The concentration of the aqueous solution of the above-mentioned surfactant is 0.05
It is desirable that the concentration be in the range of 1 m to 1 m o 1/1; if this concentration is less than 0.05 mo 1/1, the concentration is too thin (too much and lacks mass productivity).

! If it exceeds /1, the concentration will become too high and there is a risk of adding an excessive amount of primary surfactant 1, which is not preferable because it requires considerable care in handling.

In addition, when adding the aqueous solution of the above-mentioned surfactant to aggregate the hydrated iron oxide sol, the temperature is from room temperature to 250°C.
It is desirable that the range be within the range of .

In the present invention, organic content is added to a solution in which the hydrated iron oxide sol obtained in step (C) is aggregated. A step (D) of adding a medium to transfer and disperse the sol in the organic layer, washing it with water, and desalting is carried out.

The organic dispersion medium used here is not particularly limited as long as it is insoluble in water (for example, n-hexane, n-dodecane, toluene, ethyl ether, xylene, pentaerythritol). Hingo esters such as caproic acid esters, kerosene, ligroin,
MEK, ethyl acetate, tetrahydro7ran, 2-
Examples include pyrrolidone, alkylnaphthalene, turbine oil, fatty acids, vegetable oils and fats.

In addition, in this step (D), the method of washing and desalting the 8IIMI sol does not require any special technique, and it is sufficient to repeat washing and separation and removal using water or hot water. .

In the present invention, the solution obtained in step (D) above is separated, the organic layer is collected, water is added thereto, and the temperature is increased to 50°C.
Heat at above °C and add basic aqueous solution while stirring to adjust pH.
9 or more to obtain ultrafine magnetite (IE).

Examples of the basic aqueous solution used here include those similar to those mentioned above.

Then, by adding this basic aqueous solution to make the pH 9 or more, i! 1 fine particle magnetite is produced.

The particle size of this ultrafine magnetite is almost 100 to 1
50, and ultrafine particle magnetite with good dispersibility, high saturation magnetization, and stable quality can be obtained.

In the present invention, the solution obtained in step (E) above is washed with water, the aqueous layer is removed, and then step (F) of newly adding water is carried out.

Washing with water in step (F) does not require any special technique or equipment (it can be performed in the same manner as in step (D) above).

In the present invention, the final step (G ), to be carried out.

The secondary surfactant used here is not limited to any anionic surfactant or nonionic surfactant.

The above-mentioned anionic surfactant is not particularly limited (specifically, for example, fatty acid soap, alkali metal salt or ethanolamine salt of alkyl sulfate or furkyl ether sulfate, alkylbenzenesulfonic acid or its alkali metal salt) , noalkylsulfosuccinic acid or its alkali gold R salt, alkyl alfusinate, polycarboxylic acid or its alkali metal salt, and the like.

The nonionic surfactants mentioned above are not particularly limited, and include ether type, alkyl 72/-'' type ester type, sorbitan ester ether type, oxyethylene block polymer, oxypropylene block polymer, polyglycerin fatty acid ester. etc.

Washing with water in this step (F) may be performed in the same manner as in the above step (D).

In addition, as a method for removing the organic dispersion medium, methods such as liquid separation and distillation of the organic layer may be employed.

In this way, easily water-dispersible ultrafine particle magnetite can be obtained, but in this case, water, which is a dispersion medium, may be distilled under reduced pressure to concentrate it to a desired concentration.

Water easily dispersible ultrafine particle magnetite is obtained through the above steps (A) to (G), and the m whole particle magnetite thus obtained has uniform particle size and good dispersibility.
Its production does not require filtration, resulting in good productivity.Moreover, it has high saturation magnetization, is neutral, ensures long-term stability in quality, and can also be used in cosmetics.

Next, the method for producing water-readily dispersible ultrafine particle magnetite according to claim 2 will be described in detail.

In other words, this water-easily dispersible Nihao particle magnetite! 1! !
The method is to add a basic aqueous solution to an aqueous solution containing a soluble ferrous salt and a soluble ferric salt to obtain a transparent positive hydrated iron oxide with an average particle size of 300 Å or less. Step (A) of adjusting the sol, step (B) of aging and stabilizing the sol of hydrated iron oxide obtained in the above step (A) at room temperature or higher, and stabilizing the dispersion obtained in the above step (B). After adding the agent,
- Next, add a surfactant to make a sol of hydrated iron oxide! step (C), adding a dispersion medium to a solution in which the hydrated iron oxide sol obtained in the above step (C) is aggregated, and transferring the sol to an organic layer;
Step (D) of dispersing, washing with water, and desalting; separating the solution obtained in the above step (D);
A step (E) of collecting N, adding water to it, heating it at a temperature of 50°C or higher, and adding a basic aqueous solution while stirring to make the pH 9 or higher to produce ultrafine particle magnetite, the above step (E) After washing the solution obtained in step (F) with water and removing the aqueous layer, adding new water (F), adding a secondary surfactant to the solution obtained in step (F) above to form "C Ultrafine Particles 7 Gnetite". The method for producing water-readily dispersible ultrafine particle magnetite comprises a step (G) of transferring and dispersing the organic dispersion medium into an aqueous layer, and then removing the organic dispersion medium. The manufacturing method is characterized in that a stabilizer is added before adding the surfactant in step (C), and therefore, step (A) and step (B)
Furthermore, since the steps (D-G) are the same as those in claim 1 of the present application, their explanation will be omitted to avoid duplication.

The above-mentioned stabilizer may be either an organic compound or an inorganic compound as long as it is a cationized compound at the neutralization isoelectric point (pif) of ferrous and ferric ions, and is not particularly limited. do not have. This stabilizer is electrostatically bonded to the surface of the negatively charged ultrafine particle magnetite, thereby stabilizing the H1 particle magnetite.

The stabilizers include soluble aluminum salts, soluble zinc salts, soluble orthosulfates, soluble orthosilicates, 7-sfulvic acid, erythrobic acid, gallic acid, amino acids,
Legucton M (amylguctone M), tin, antimony,
Examples include soluble salts such as titanium, norconium, and niobium, amines such as dehydroacetic acid and 7-enyl β·-su7-tylamine, phosphorus compounds such as dithiophosphoric acid, and alkyl amide/carboxylic acids.

In this way, a magnetic fluid with excellent stability in addition to the various properties of the easily dispersible water-dispersible ultrafine particle 7 gnetite of claim 1 of the present application can be obtained.

(e> Effect) The present invention has the above structure, and when adding a basic aqueous solution to an aqueous solution containing a soluble ferrous salt and a soluble ferric salt, when ultrafine particle magnetite is formed all at once, ultrafine particle magnetite Since the particle size of 3i119L varies widely, the basic aqueous solution is added in two stages.In the first stage, the pH is suppressed and the average particle size is 30% in the acidic region.
After preparing a transparent and positive hydrated iron oxide sol with a size of 0 Å or less, it is aged to equalize the particle size of the hydrated iron oxide sol, and then a basic aqueous solution is added thereto (second Step) Ultrafine particle magnetite is obtained by raising the pH to 9 or higher, and the ultrafine particle magnetite thus obtained has a uniform particle size, has good stagnation and dispersibility, and is free from sedimentation, aggregation, and concentration changes. In addition, it does not cause segregation, has high saturation magnetization, and has the effect of obtaining water-readily dispersible m-fine particle magnetite of excellent quality.

In the method for producing easily water-dispersible ultrafine particle magnetite of the present invention, a surfactant is added to a dispersion of hydrated iron oxide sol to solidify the sol. ! By adding a stabilizer before adding this surfactant, long-term stability can be improved in addition to the above-mentioned effect.

(f) Examples Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Ferrous sulfate 1°2 [IIo1/1 aqueous solution 1! , ferric sulfate 1 and Omo 1/1 aqueous solution 11 were mixed and stirred, and while maintaining the liquid temperature at 30°C, 2.5 m
A transparent and positive hydrated iron oxide sol with an average particle size of 300A or less is prepared by dropping o1/1' sodium carbonate until the pif becomes 2.8 (Step A).

After aging and stabilizing this sol at 30°C for 3 hours (Step B
), 500 ml of 0.25 o1/1 sodium oleate (-- surfactant) was added to coagulate the hydrated iron oxide organosol (Step C), and then n- Hexane (organic dispersion medium) 300I111 is added to transfer and disperse the hydrated iron oxide Ol 7 sol in the PIi layer, which is washed with water and desalted (Step D).

After that, this solution was divided into 1 L, the organic layer was collected, 200 + a1 of water was added to it in a new tank, and a condenser was attached.
Transfer to a flask and heat with stirring at a temperature of 75℃ for 2 hours.
Ultrafine particle magnetite is generated by gradually adding 0 wt % sodium hydroxide solution = 100 mN to give ptllo, 5 (Step E).

After this reaction is completed, this solution is washed and the aqueous layer is removed, then 300+*p of fresh water is added (Step F), and then a secondary surfactant is added to disperse and transfer the ultrafine magnetite into the aqueous layer. A certain sodium laurate 30% by weight fi3
0+a/ was added with stirring. Once the ultrafine magnetite particles have migrated to the water layer, remove the n-hexane layer,
The aqueous layer was concentrated under reduced pressure to obtain 320 g of water-based water-based easily dispersible ultrafine particle magnetite (Step G).

The average particle size of this ultrafine particle magnetite was 130, and it was recognized that the particle sizes were uniform.

Furthermore, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured and found to be 380G.

Example 2 In Example 1, the aqueous layer of the solution obtained in step (A-E) was removed and washed, and after removing the aqueous layer, 30Cj of fresh water was added.
tsl was added (Step F), and then 50 mN of a 30% aqueous solution of sodium dodecylbenzenesulfonate, which is a secondary surfactant, was added with stirring in order to disperse and transfer the ultrafine magnetite particles to the water layer. Once the ultrafine particle magnetite had migrated to the water layer, the n-hexane layer was removed, the aqueous layer was concentrated under reduced pressure, and 320 g of water-based water-based easily dispersible 'Mihui particle magnetite was obtained (Step G). .

The average particle size of this ultrafine particle magnetite is 125 particles, and it is not recognized that the particle sizes are uniform.

Further, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured and found to be 320G.

Example 3 Ferrous chloride 1゜2 tool/(l aqueous solution 11 and ferric chloride 2 vaol/1 aqueous solution 11 were mixed and stirred, and while maintaining the liquid temperature at 20°C, 2.5 moN was added to the mixed solution.
A transparent and positive hydrated iron oxide sol with an average particle size of 300 Å or less is prepared by dropping sodium hydroxide of 100 mL to pl+2.2 (Step A).

After aging and stabilizing this sol at room temperature for 24 hours (Step B)
To this dispersion, 550 ml of 0.25 mo (1/N ricinoleic acid) ram (sub-surfactant) was added to coagulate the hydrated iron oxide organosol (Step C).
), then add 300I of toluene (a dispersion medium) to this.
oN is added, the hydrated iron oxide organosol is transferred and dispersed in the well, and this is washed with water and desalted (Step D).

After that, this solution was separated, the organic layer was collected, and 200+ aN of water was added to it, transferred to a 21 flask equipped with a condenser, and heated and stirred at a temperature of 90°C to produce 20% hydroxyl. An aqueous sodium solution of 400++N was gradually added to generate ultrafine magnetite particles (Step E).

To this solution, 300 uiN of water was newly added, and 35 nN of sodium dioctyl sulfosuccinate, which is a secondary surfactant, was gradually added to this while stirring in a 30 weight 1% aqueous solution, and the ultrafine magnetite was added to the water layer. After dispersion, 11-hexane was separated and removed, and the aqueous layer was concentrated under reduced pressure to obtain 310 g of water-based ultrafine particle magnetite.

The average particle size of the ultrafine magnetite particles was 125, and it was found that the particle sizes were uniform.

Further, the saturation magnetization of this magnetic fluid was measured and found to be 360G.

Example 4 Mix and stir ferrous sulfate 1, 2 mob/1 aqueous solution 11 and ferric sulfate 1, Omol/1 aqueous solution 11,
While keeping the liquid temperature at 25℃, add 2.5% to this mixed solution.
- Xa the transparent positive hydrated iron oxide sol with an average particle size of 300 Å or less by dropping sodium carbonate in an amount of 1/r until the pH becomes 3.0 (Step A).

After aging and stabilizing this sol at 30°C for 3 hours (Step B)
To this dispersion, 500 mN of sodium oleate (a surfactant) of 0.25 vroll/1 was added to aggregate the hydrated iron oxide sol/sol (step C), and then n- Add 300 mN of hexane (organic dispersion medium) to transfer and disperse the hydrated iron oxide olff/sol in the organic layer, which is then washed with water and desalted (Step D).

After that, this solution was separated into layers, the organic layer was collected, 200 ml of water was added to it, and it was transferred to a 31-7 flask equipped with a condenser, and while stirring at a temperature of 75°C, 20 ml of water was collected.
% sodium hydroxide? (By gradually adding 350 ml of I to obtain ptllo and O, H1 grain magnetite is generated (Step E).

To this solution, newly added 300IIl& of water, and while stirring sodium nooctylsulfosuccinate as a secondary surfactant, 30w/1% solution of 35IIe was gradually added, and the ultrafine magnetite was mixed with water/ 1 and dispersed, n-hexane was separated and removed, and the aqueous layer was concentrated under reduced pressure to obtain 310 g of water-based, water-based, easily disintegrable, fine particle magnetite.

The saturation magnetization of this water easily dispersible ultrafine particle magnetite is 32
It was 0G.

The average particle size of this Him fine particle magnetite was 125, and it was recognized that the particle sizes were uniform.

Example 5 Ferrous sulfate 1, 2 mol/1 aqueous solution 1 and ferric sulfate 1, 0 mol/1 aqueous solution 11 were mixed and stirred, and while maintaining the temperature of the liquid at 40°C, 2.
A transparent, positive iron oxide hydrated sol with an average particle size of 300 Å or less is prepared by dropping 5 yaol/1 sodium hydroxide until pI+2.3.

After aging and stabilizing this sol at a temperature of 70°C for 1 hour,
．． 25wol sodium oleate (surfactant) 500+
++i! After adding hydrated iron oxide or ff/sol,
1) Add rum aqueous solution (heat and stir at a temperature of 80 to 90°C, and add 20 wt. 1% hydroxide).

5) After generating ffi fine particle magnetite, remove the aqueous layer, add 300 mj' of new water after washing, and stir 30 m1 of 30 wt 1% solution of sodium laurate as a secondary surfactant to disperse and transfer to the aqueous layer. I added while doing so. Once the ultrafine magnetite particles have migrated to the aqueous layer and been dispersed, the n-hexane layer is removed, the aqueous layer is concentrated under reduced pressure, and 32
0 g of water-based water-based easily dispersible ultrafine particle magnetite was obtained.

The average particle size of this ultrafine magnetite particle was 1258, and it was found that the particle sizes were uniform.

Further, the saturation magnetization of this water easily dispersible m-fine particle magnetite was measured and found to be 320G.

Example 6 Ferrous ammonium sulfate (Mohr salt) (FeSO, (
NH<)zS O4' 6 HzO)1, 3+ao
N//aqueous solution 11 and diferric sulfur ammonium (iron alum) (FeNH+(SO2)z・12 H2O)2.
OmoN, /'t! Water easily dispersible m fine particle magnetite) 330 in the same manner as in Example 1 except that aqueous solution 11 was used.
1? I got it.

The average particle size of this ultrafine particle magnetite was 125 particles, and it was recognized that the particle sizes were uniform.

In addition, the saturation magnetization of this water easily dispersible ultrafine particle magnetite was measured to be 380 G.6 Example 7 The n-hexane ultrafine particle magnetite M prepared in Example 1 (Step A-1) was newly added with water. Add 300 mN and gradually oxidize the ultrafine particle magnetite while adding a 10% hydrogen peroxide aqueous solution at a temperature of 50 ° C. At the same time, add 32 g of polyoxyethylene oleyl ether.
In addition, a water-based water-based easily dispersible ultrafine particle magnetite whose surface was oxidized to γ-Fe20 was obtained.

The average particle size of this m-fine particle magnetite is 125, and it is not recognized that the particle sizes are uniform.

Further, the saturation magnetization of this water easily dispersible ultrafine particle magnetite was measured and found to be 280G.

Example 8 In step C of Example 1, before adding the secondary surfactant (sodium olinate), 0 as a stabilizer was added.
, 2 mol/1 aluminum chloride aqueous solution 500ml
Water-readily dispersible ultrafine particle magnetite 3408 was obtained in the same manner as in Example 1 except that aluminum ion charges were added to the surface of the hydrated iron oxide sol.

The average particle size of the ultrafine magnetite particles was 125, and it was found that the particle sizes were uniform.

Further, the saturation magnetization of this water easily decomposable superimage particle magnetite was measured and was found to be 320G.

Example 9 In step C of Example 2, 0.0% was added as a stabilizer before adding the secondary surfactant (sodium oleate).
211Io(1/(!Aluminum chloride aqueous solution 500
Water-ready dispersible ultrafine particle magnetite 3158 was obtained in the same manner as in Example 2, except that - was added to impart an aluminum ion charge to the surface of the hydrated iron oxide sol.

The average particle size of this ultrafine particle magnetite was 130, and it was recognized that the particle sizes were uniform.

Further, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured and found to be 320G.

Example 10 In step C of Example 3, before adding the secondary surfactant (sodium lysylate), 0 as a stabilizer was added.
．． 211Io1/1 aluminum chloride water solution 9500ml
300 g of easily dispersible water-dispersible ultrafine particle magnetite was obtained in the same manner as in Example 3, except that aluminum ion charges were imparted to the surface of the hydrated iron oxide sol.

The average particle size of this ultrafine particle magnetite was 130, and it was recognized that the particle sizes were uniform.

Furthermore, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured and found to be 350G.

Example 11 In step C of Example 4, 0.0% as a stabilizer was added before adding the secondary surfactant (sodium oleate).
310 g of water-readily dispersible ultrafine particle magnetite was obtained in the same manner as in Example 4, except that 2 mol/1 aqueous solution of aluminum chloride + 1 was added to impart an aluminum ion charge to the surface of the hydrated iron oxide sol.

The average particle size of this ultrafine particle magnetite was 130, and it was recognized that the particle sizes were uniform.

Furthermore, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured and found to be 350G.

Example 12 In step C of Example 6, before adding the secondary surfactant (sodium oleate), 0 as a stabilizer was added.
, 25o (1/l aluminum chloride aqueous solution 5001f
338 g of easily water-dispersible ultrafine particle magnetite was obtained in the same manner as in Example 6, except that IN was added to impart an aluminum ion charge to the surface of the hydrated iron oxide sol.

The average particle size of this ultrafine particle magnetite was 120, and it was recognized that the particle sizes were uniform.

Further, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured and found to be 320G.

Comparative Example 1 Put 1 mol/(l ferrous sulfate and 1 uol/N ferric sulfate aqueous solution) into a reaction tank, and mix them while adding 6N NaOH aqueous solution until H becomes 7.3. dripped. After that, the colloidal particles were mixed for about 20 minutes to prepare an ultrafine particle magnetite colloidal solution, and then 640 mj' of 10% sodium oleate solution was added and mixed for 30 minutes, thereby forming the colloidal particles into a monolayer of sodium oleate. Cover.

Add kerosene 550a, a non-aqueous growth solvent, to this solution.
When +N is poured, a blackish brown organic layer is formed.

After the reaction was completed, the aqueous layer was removed, and after washing, water 30011 was newly added, and 30% by weight solution of sodium laurate 3011 as a secondary activator was added with stirring to disperse and transfer to the aqueous layer. Once the ultrafine magnetite particles have migrated to the aqueous layer, the n-hexane layer is removed, the aqueous layer is concentrated under reduced pressure,
320 g of water-based, easily dispersible, ultrafine particle magnetite was obtained.

The ultrafine magnetite particles ranged from extremely small particle sizes to aggregates, and it was observed that there was a large variation in particle size.

Furthermore, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured to be 145G.

Comparative Example 2 In a 5a flask, 40 gs of water and 1600 gs of toluene
8. Sodium hydroxide 14.0g (0,349moff
Add 96g of oleic acid sequentially and stir the mixture.
(0.349 mol) was added and stirred for 30 minutes while keeping the liquid temperature at 75-80°C, resulting in an emulsion containing sodium oleate. Next, the liquid temperature was lowered to 35° C., and 534.3 g (3.8 mol) of 28% aqueous ammonia was added and mixed with stirring to obtain a uniform emulsion.

Ichiriki, 278g of ferrous sulfate heptahydrate (1so01), 508g of ferric sulfate hexahydrate (1mol12), 1125g of water
A mixed aqueous solution of was dropped into the above Emaruno 9 to perform generation and adsorption treatment of ultrafine magnetite colloid.

It took 2.5 hours to drop this iron salt aqueous solution, and at the end of the nine drops, the reaction solution turned into a black dispersion, so the temperature of the solution was raised to 75-80°C, and stirred at this temperature for 30 minutes. Aged. After this, it was transferred to a 51 separatory funnel and poured. The toluene layer in which ultrafine magnetite colloids were dispersed was collected.

This toluene layer was again transferred to flask No. 51 and subjected to azeotropic dehydration.

After the reaction was completed, the aqueous layer was removed, and after washing, 300 ml of fresh water was added, and 30% sodium laurate solution 30I61 as a secondary activator was added with stirring to disperse and transfer to the aqueous layer. If magnetite has finished migrating to the aqueous layer, II-
The hexane layer was removed, the aqueous layer was concentrated under reduced pressure, and 320 g
A water-based water-based easily dispersible ultrafine particle magnetite was obtained.

The ultrafine magnetite particles ranged from extremely small particle sizes to aggregates, and it was observed that there was a large variation in particle size.

Furthermore, the saturation magnetization of this water-easily dispersible ultrafine particle magnetite was measured and found to be 280G.

The fractional properties and stability of each of the above Examples and Comparative Examples were investigated using the methods described below.

Dispersibility: 0.1 μm to 1.0 μm. Immediately after production and after leaving at room temperature using a membrane filter of 1.0 μm. 12
20m+aHg'c under reduced pressure to check the dispersibility after several months.
A filtration test was performed.

The sample used for filtration was prepared as an aqueous dispersion with a magnetite content of 20% by weight.

The results are shown in Table 1.

(Margin below) Table 1 ◎: No aggregates remain on the non-plan filter.

○: A slight amount of aggregate is observed on the Menplan filter.

Δ: Aggregates clearly remain on the /amplan filter.

×: Aggregates remain on the upper surface of the membrane filter.

Stability: Judgment was made based on both the decrease in saturation magnetization after one month of exposure at a temperature of 60°C and the change in color when left at a temperature of 60°C.

The results are shown in Table 2 and below.

Regarding the dispersibility in Table 2, each example had a pore size of 0.
It was observed that even a membrane filter with a diameter of 1 μm was passed through smoothly and completely, and no precipitates were deposited on the membrane filter.

On the other hand, in each of the comparative examples, even noodles with a pore diameter of 1 μm were found to be deposited on the membrane filter as they were. Therefore, each comparative example was centrifuged (5
000G), only this dispersion was collected and subjected to the same test as above, and it passed through a membrane filter with a pore size of 0.65μ.

However, in this case, the yield of ultrafine particle magnetite is 50
~70% by weight.

As for stability, slight color change was observed in the larons of Examples 1 to 7 from around the 10th point, and in the cases of Examples 8 to 12, the color change was observed at 3.
No change was observed for 0 days, but 2 for each comparative example.
Color change was observed within a few days.

This difference is considered to be due to the degree of variation in particle size.

From the above results, compared to those of each comparative example, those of each example have uniform particle sizes, are stable, can be suitably used as a black pigment for various purposes, and have good dispersibility. It is recognized that the saturation magnetization is high.

In particular, it is recognized that the magnetic fluids using stabilizers (Examples 8 to 12) have excellent stability during the planting period.

Further, in each of the Examples, no sedimentation, aggregation, concentration change, or segregation occurred in the obtained state, but in each Comparative Example, sedimentation, aggregation, etc. were observed in the obtained state.

(8) Effects of the Invention Since the present invention is configured as described above, it produces the effects described below.

The method for producing easily water-dispersible ultrafine particle magnetite according to claim 1 has the above-mentioned structure, and a basic aqueous solution is added to an aqueous solution containing a soluble ferrous salt and a soluble ferric salt to form ultrafine particle magnetite. In order to equalize the particle size of the ultrafine magnetite particles, a basic aqueous solution was added in two stages.In the first stage, pl+ was suppressed and the average particle size of the ultrafine magnetite particles was 300 Å or less. After preparing a transparent and positive hydrated iron oxide sol, it is aged to make the particle size of the hydrated iron oxide sol uniform, and then a basic aqueous solution is further added thereto to produce <m two steps) p If 9
By doing the above, ultrafine particle magnetite is obtained, and the ultrafine particle magnetite thus obtained has a uniform particle size, has good dispersibility, and does not cause sedimentation, agglomeration, concentration change, segregation, etc. Moreover, it has the effect of producing a magnetic fluid with high saturation magnetization and excellent quality.

In particular, in the present invention, the ultrafine particle magnetite has extremely good dispersibility, does not cause sedimentation, agglomeration, concentration changes, or segregation, does not require filtration, has high saturation magnetization, and is suitable for various uses as a pigment. It has a usable effect.

In the method for producing easily water-dispersible ultrafine particle magnetite according to claim 2, when adding a primary surfactant to a dispersion of hydrated iron oxide sol and coagulating this sol, Aji to which this secondary surfactant is added is added. By adding stability six times in advance, the ultrafine I magnetite has a uniform particle size, has good dispersibility, does not cause sedimentation, agglomeration, concentration changes, segregation, etc., and has high saturation magnetization and high quality. Moreover, it does not require filtration, has a high saturation magnetization, can be suitably used as a pigment for various purposes, and has the effect of being stable during the -frI period and the plateau period.

Claims (2)

[Claims] (1) A transparent and positive hydrated iron oxide sol with an average particle size of 300 Å or less is produced by adding a basic aqueous solution to an aqueous solution containing a soluble ferrous salt and a soluble ferric salt to adjust the pH to 1 to 4.5. (A), a step (B) of aging and stabilizing the sol of hydrated iron oxide obtained in the above step (A) at room temperature or higher, and a step (B) of aging and stabilizing the hydrated iron oxide sol obtained in the above step (A); Step (C) of adding an activator to agglomerate the sol of hydrated iron oxide; adding an organic dispersion medium to the solution in which the sol of hydrated iron oxide obtained in step (C) is agglomerated; move to layer,
Step (D) of dispersing, washing and desalting with water, separating the solution obtained in the above step (D), collecting the organic layer, adding water to this and heating at a temperature of 50 ° C. or higher, Step (E) of making ultrafine particle magnetite by adding a basic aqueous solution to pH 9 or higher while stirring, washing the solution obtained in the above step (E) with water, removing the aqueous layer, and then adding new water. Step (F): After adding a secondary surfactant to the solution obtained in the above step (F) and transferring and dispersing the ultrafine particle magnetite to the water layer,
A method for producing easily water-dispersible ultrafine particle magnetite, comprising a step (G) of removing an organic dispersion medium. (2) A transparent and positive hydrated iron oxide sol with an average particle size of 300 Å or less is obtained by adding a basic aqueous solution to an aqueous solution containing a soluble ferrous salt and a soluble ferric salt to adjust the pH to 1 to 4.5. (A), a step (B) of aging and stabilizing the hydrated iron oxide sol obtained in the above step (A) at room temperature or above, and adding a stabilizer to the dispersion obtained in the above step (B). After adding
Step (C) of adding a primary surfactant to aggregate the sol of hydrated iron oxide; Adding an organic dispersion medium to the solution of the sol of hydrated iron oxide obtained in the above step (C); is transferred to the organic layer,
Step (D) of dispersing, washing and desalting with water, separating the solution obtained in the above step (D), collecting the organic layer, adding water to this and heating at a temperature of 50 ° C. or higher, Step (E) of producing ultrafine particle magnetite by adding a basic aqueous solution to pH 9 or higher with stirring; washing the solution obtained in the above step (E) with water, removing the aqueous layer, and adding new water; Adding step (F), after adding a secondary surfactant to the solution obtained in the above step (F) and transferring and dispersing the ultrafine particle magnetite to the water layer,
A method for producing easily water-dispersible ultrafine particle magnetite, comprising a step (G) of removing an organic dispersion medium.