JPS5925202A - Manufacture of acicular magnetic ferrous oxide for magnetic recording material - Google Patents

Abstract

PURPOSE:To form magnetic ferrous oxide into fine grains as well as to imporove their needle-like property by a method wherein an alpha-FeOOH nucleus formation is performed under the presence of phosphorous acid or phosphite, and a dehydration by heating is conducted as possible in an inert gas atmosphere containing no oxygen. CONSTITUTION:A ferrous salt aqueous solution containing ferrous sulfate is partially neutralized using alcali, and the Fe component contained in said solution is partially formed into alpha-FeOOH crystal by peforming an oxidation treatment. At this time, the Fe density of a ferrous sulfate solution is ordinarily established at 30g/l-100g/l. On the stage of nucleus formation, the ordinary range of reaction temperature is 30-55 deg.C. pH is maintained between 3 and 8 in general. The solution, with which nucleus forming reaction has been finished, is oxidized and crystal nucleus is grown while alcali is added under the presence of phosphorous acid or phosphite. Then, the obtained dehydrate is formed into magnetic ferrous oxide with oxidation degree 1.33<=X<=1.50, by reducing it using hydrogen or by performing an additional oxidization process.

Description

[Detailed Description of the Invention] In recent years, the density and quality of magnetic recording has been increased more than once a month.
Ferromagnetic iron oxide for magnetic recording uO, °1 has smaller grains:
The present invention satisfies these requirements and has a small particle size distribution with good magnetism (axial ratio), no branching, and a small particle size distribution. The production method for obtaining acicular magnetic iron oxide with a low content of SO;
2=)u,c,tWQI+,'r[J:Z J:-)
record W, increase the number of t and h children in the body -U', 2 and 8I"J ratio" 4 is measured.
- Naha N) 7.4 - D A Ennni 1 Link Soliiety (, J O former 111IIC) [A11dl ()
UHi++et+rin8Soci(11,y)〜'o
1.2 F+1+! J i+-ri! l(l!I '7
2) To measure whether the signal-to-noise ratio by adult cows on tree fj1 is equal to or less than 1 (++g+::+・: Transaction on 2 Gnetei Nx (l
E +1: 1 'I'ransact,
i+o+ on M 111qnC! 1. icr+
), Vol.

17N(,), G1+: (fl 32・-31) 3
/l (+!] 81) ] and >A1 and HA. However, with the introduction of fine net 7L,
//σ) Problems, for example (1) Decrease of 艮 艮艮 1 koyoruri 1
The shape (axial ratio) of fl(, l-', (wa heat treatment -1-) is low heat resistance, ■ growth is high and bad (
・Koto L:, l nil! i';I;7. %V +74
．． +) (7) pl 14K No1 Mr. Do, (4,)
Xl:/, -1', '! However, in order to increase the yield, (if the member ratio is increased, branching and new cedars will occur) (and so on), it will be necessary to increase the yield. , I? It's twisted.

The present inventor, M., is working on making a small kit, r.
In order to obtain a product with good tetramorphism and a small tit degree distribution, we carried out the test 1], and found that the addition of phosphate monomers during the formation of the nuclear product resulted in If we have sufficiently improved the problems such as a decrease in the axial ratio, a broadening of the degree distribution due to the generation of new cells, the occurrence of branching, and the inability to obtain a sufficient growth rate, we will proceed with further inspection 8J. However, phosphorous acid, which has not been used in the past, is completely different from the phosphoric acid compounds conventionally used for nucleic crystal growth, and has an L-product effect, and the addition of phosphoric acid compounds since IIT has been difficult to achieve. Effects that do not exist, such as signs t,'1. In order to increase R, it suppresses the decline in button-likeness (axial ratio), suppresses branching and nucleation, improves heat resistance, and improves growth (yield by increasing ff). We discovered that the addition of 411 phosphoric acid during the growth of nuclei resulted in 'l, +J
1ri↓1Sho5”/-7580!J is proposed.

Regarding the relationship between 507-content and crystallinity, the incorporation of moss, magnetic iron oxide particles, and SO;- deteriorates the surface condition of the coating film of magnetic recording bodies using it, and as a result, the high frequency Insufficient frequency characteristics (Tokuko Sho 40 Tsukasa 17: (3)
, SOE, the magnetic layer tends to wear out when the magnetic recording body comes into contact with a magnetic head or a guide ball.
Furthermore, when reproducing the recorded information on a magnetic recording medium, the phenomenon of unreadable signals or dropouts may occur (Special Publication No. 4Σ+-27+18), and nail-shaped hydrous oxidation No.
S('), - contained in iron particles is heat dehydration,
Reduction and oxidation heat death J! 1! In the overculm, the ferric oxide particles are removed from the magnet tie (
! During the reduction process in the water tank, compared to air, the reduction process is more severe than in air, and the deformation of the shape and the sintering between the upper and lower shaft elements are affected. It is known that -+5-22 tl (1"7)
There is ζ.

In Precedence 11 described in 1-1, the following method is described for controlling button-shaped iron oxide particles. Hello, the Special Public Service No. 40-I J 73 Rte is,
ff-Fe2(-) 5 or 1 soil Q -Fpo OII in air at 61.1 (1'C or higher) for 1 hour or more [By performing two heat treatments, 507- is dissipated as SO7 and SO7 How to use it, special public interest public 1977-: (7GB +,
In l, α-t' e O(,) I l was heated at 31.10"C dino, 10(i +1 +1 °C) in an empty 5-11, and the water-soluble component S:04 was removed by water washing. death,
The method of reduction is described in 1.
80 I containing a-1” eooll with ferric sulfate)
J? , through which the ′U ambient air at heating ν1 temperature is at least 2
3 (Reducing property in 1'C: ?j', J in IJII air: Sea urchin heated, :31) (+' is more than 140 n
°c）；ノ、'F
In 8-2°7118, by washing magnetite or γ-I'e, 0.
Although a method for removing one is described, the conventional technique is not without problems. For example, heat death of (Dα-Fe0011H in air 1:lj
In order to sufficiently vaporize and dissipate SO in tier-1, G (10'C or higher, especially 7 fl
(During the long process at a temperature close to 1'C, sintering of the grains occurs, causing loss of sword-like properties, resulting in S O
, even though it was an adult cow, it contained: 1. -T coating'441 ft, 11. '? There is a possibility that the variance of +71 will worsen. (Water washing, etc., can be improved as steps 11: filtration, drying, etc. are added in excess to remove SONY, which is disadvantageous industrially.) .

The inventors have discovered that the main raw material is inexpensive L1 cost ゛i, 8-
After neutralizing a portion of the ferrous sulfate solution 't>f using ferrous sulfate, it is oxidized to obtain a CI -FeO(') II nuclear product of 111. Next, the method of growing these nuclei in an acidic region (acidic method) is carried out by using a method of growing the nuclei crystals in an acidic region (acidic method).
6 As a result, as mentioned earlier, the river -
By making the non-acid or its salt (7-FeO01 present at the time of crystallization), the desired a-1・'eOOIt could be reduced to 9!, but the heating of this a-F'eOOII If the atmosphere under 111L water is made into an inert atmosphere that does not contain oxygen as much as possible, the temperature will rise lower than that in air.1.
1: l) 804 α with low content in iτL time
-1・゛(・,01 can be made into 1: without sword-like character, and even after heat treatment of reduction and oxidation, the shape is 1:
< Magnetism-1 with a holding and low 807-content! li
In 1974, he discovered that iron oxide could be dissolved into iron oxide, and completed the present invention.

Dear Sir, the present invention relates to ferrous J, I containing ferrous sulfate.
Jl water〆Fr r+).

Partially neutralize and oxidize to grow a-Fe0011 nucleus crystals, -1, then neutralize J(k) with an alkali and oxidize one to grow the nucleus crystals, 111 was obtained. 1 state Q -l import 0 (,') heating II) B1. Water and then reduce
a is further oxidized so that the oxidation degree X is 1.33≦X≦1.5
A method for producing button-shaped magnetic iron oxide ('F e OX ), which has a magnetic iron oxide ('F e OX ) of 0. d heating +11
1. Water is not completely depleted of oxygen for 4 hours. 4. It is characterized by the fact that it is carried out in the active force calculation method. There is C.

The alkalis to be used include hydroxide-nortrium, potassium hydroxide, acid 1, carbonate calcilano 1,
, carbonic acid 1:1, ammonia, etc., and 21゛ foil-wise, hydroxide 1:1 sodium hydroxide 1, potassium hydroxide 11 is preferable. Phosphorous acid or its 1 compound, For example, phosphorous acid or these one alkali gold J'j (J,
Examples include All, ammonium salts, etc., and any substance that can be used as a phosphite ion can be used.

As the oxidizing agent, air, oxygen, oxidizing agent 11, etc. can be used, but air potassium I is suitable.

In the method of the present invention, first, an aqueous ferrous salt solution containing ferrous sulfate is partially neutralized with an alkali and then oxidized to remove -Ells of Fe in the solution from Q -FeOOll nucleus crystals 1::i- Le. Conotodo, -General 1: +, J (F of ferrous acid solution (!
The concentration of N is 3t) U/ρ to 100 p/θ, and the amount of alkali added is 5 to 258/θ for 1:'e ions in the mother liquor.
θ, preferably 10 to 15R10, is 1) set to 4 as required. If the concentration of the generated nucleus crystals is lower than the range -1-, the production efficiency will decrease, resulting in an industrial (economical)
It becomes unsuitable for practical use and also produces an unfavorable burr-like shape of a-F' (! This results in a decrease in the sharpness of the γ-FetOi, which in turn leads to a deterioration in the magnetic properties of γ-FetOi induced from the koh.

In the nucleation stage of , -, the reaction temperature is jII: 30-5
5°C, preferably: 35.-5o' (2. If this temperature is too low than the above range, the reaction time will be shortened, the shape will not be as sharp, and the temperature will be less than 41 degrees square. It becomes suitable as a nucleus crystal for obtaining a small ladle r-, and it becomes easier to generate granular magnetite 1. 1+ Hli Normal: It can be maintained between to and o.

, -, jq to generate y1 product, γ-F" (! ('
) Contamination of Ol l 'c lj +l Soiro L also neutralizing it or V'? J, it is better to keep f1% or less. Also, in the second case, oxidation suddenly becomes 11) force, IS', 1. *; +, 1 bar [; - (already not specified, but usually 1 () to 10 () minutes, "艷 1 da + or 10.- [; () minutes C.

At this stage of nucleation, by using birophosphoric acid, birophosphoric acid or its salts such as alkali metal salts, ammonium salts, etc., this single reaction 1.6i quality can be achieved.
1st row Ehari S ・-'7 fl゛C and t'
l+-r hoishi. , - addition 171 is; -1°C normally produced a -1'e (-10114A product precipitate at P conversion S1., m (1, t)!; -0.8% by weight, preferably 0.1~0.5%
11 (difficult) - If the blade is too strong, the 4-shaped #: t-r- of the nucleus crystals will become slightly tight.

1!1 J. Natsuru. Nucleus crystal is 13 tons; 'I゛ ratio surface is 50
・≦J f) About 11+'/B, 2, 4, 2, 4, 2, 2, 4, 2, 2, 4.

The liquid after the 1-year-old nuclear crystal reaction described in 116 is O-t'c
00 II nuclear crystals are suspended in an iron sulfate solution (1), and then oxidized with a base of phosphorous acid or its salts while adding an alkali to form four crystals (with a desired value). ff-1”1
1!0011 to 1i).

At this stage of nucleation,! 11-Phosphoric acid or its salt may be mixed with the alkali and added, or may be added separately, and the amount of this phosphorous acid or its salt added depends on the amount of a
-FeO011 total amount group Bi total amount -Bi 11: O at 3u
, t) 3 = 1, ! ') m, Ji%, preferably 0.05.-0.5%. This amount of P
If the amount is too small than the above range, it may be difficult to obtain the desired effect, and if it is too large, the amount of non-magnetic substances in the magnetic P1 iron oxide induced by this may be increased and the saturation magnetization (σS) may be decreased. do. The anti-J7G temperature is usually 35~Of)'C, preferably 5()~7tl'C. If the temperature is too low than the above range, the reaction time will be long and it is not economical, while if it is too crystalline, granular magnetite may be mixed in and the tetramorphism (axial ratio) may be lowered. pl+ is normally kept between 3 and 6. It is better to adjust the growth rate of the nucleus crystals to about 5.-15 g/Q/hour in order to obtain a product with a slight degree of lameness, a small outer distribution width, and a small number of branches. stomach. In addition, the concentration of the mother liquor, the generation of nucleus crystals, and the Fit
(section til ! 'l
By cutting the Q-F'e00f ROM product to the weight of the nucleus, the member l'f ratio is 1.5 to 4.5, village, i
4 Nurture so that L < It 2...3. If this magnification is lower than the range specified in 2.2, the particles will not be large enough, and 9. '/4-shaped α-1・゛(・0011 is 1
On the other hand, if the grain size is too crystalline, the particle size distribution becomes wider and the particles become more branched. In this above, the specific surface area of 131E i' of α-FeO011 which is /l+M is, for example, /I! ] = 71) +11”, / g
It is preferable to do so.

1- Q −F(・0 (,
) From the liquid emitted in 1-1 of II, through normal filtration, water washing, drying and crushing, a-1, "eO (1 powder per month becomes 1 (1
Chill.

α-1・"eO○tl powder heating Jllt water temperature is in an inert force atmosphere containing as little oxygen as possible; LI
I regular 300・~8 (10'C, f (main mechanism 500~
700''C. Examples of the inert gas include nitrogen and argon, but nitrogen is usually used.

It is desirable that the amount of rv1 element mixed into the inert gas atmosphere be as small as possible, and its 5″1 volume is (7-F+・('
) 111 (phosphoric acid or its salt is not substantially oxidized) is 1.

Then, this +11L hydrate was added to 300·~r)L) IJ
'(: Reduced with hydrogen or hydrogen containing water vapor at a temperature of 1 to 9 degrees, or even 1 to 20 (1~・L (1
(Magnetic oxidation f'X (FeOx) which is oxidized with oxygen or air at a temperature of 1'C and has an oxidation degree x of 1.33≦X≦1, 5 (l) can be used.

The magnetic iron oxide leaked by the method of the present invention is of fine particles, has a sharp particle size distribution, has little branching, and has a
It has an axial ratio of J5 and has good magnetic properties. In addition, magnetic iron oxides derived from magnetic iron oxides (1 and 2) and magnetic tapes made from these also have good magnetic properties. The SO4 content is also 0.2i%J
Since the amount of SO in magnetic iron oxide is extremely small (19% of magnetic iron oxide), the surface condition of the coating film of the magnetic recording medium using iron oxide deteriorates, and the high frequency characteristics are also mixed. ing.

(7-Ft・00i1 When phosphorous acid or its salt is present during the formation of the nuclei, 1!l is α-1""e OOl
Why is it that when dehydrating heat-dehydrated α-F”e20* in an inert atmosphere, 5ol of α-F”e20*
- Although the content decreases, no clear reason has been found for this. ■Sulfurous acid or its salts have a weak reducing effect in an inert atmosphere, and SO1 salt decomposes to produce 803 is reduced to SO3, ■SO7 is SO3
More than that! It is assumed that the reason is that it is easy to dissipate from children.

Below, the present invention will be understood with reference to Examples and Comparative Examples.

Examples and Comparative Examples (1) Nucleic crystal generation nozzle reaction (A) Air blowing fixture and stirring fixture
! : Add 1.25 mol 10 of t' e S (') to 20 ρ of an aqueous solution to 4!3'C, ? jll,
While maintaining this temperature with Al1, 2.14Q of Na011 aqueous solution (concentrated Pal', !') mol/'0) was added under stirring (precipitate IMQ Fe, I 5R/ρ), and in this... l +10 = (i 0ρ/hour rate C air was blown into the reactor for 35 minutes, then (7-FcO(',)l
1 liter item! lI, +3 E What is the specific surface area of this nucleus according to the 'l' method? 2+r+9/H.

(2) Nucleic crystal formation reaction ([3) Insert the blowing tube and I!&!4'l'' vessel!
, put 200 ml of 1.25 mol 10 FeS O + aqueous solution into two reactors, heat it to 1'C, and while keeping this temperature at M( (,)011
Add ★・J to the positive star and set it as P -C (birophosphoric acid and f corresponding to 1 or 2%) N a O [-1 aqueous solution (concentration 5 mol/ρ
)2.14ρ(stir l・° plus (sink) beat 1・゛(shi1
5R/θ), into this i l) 0, ~6ri l! 6-(a
-1・゛eo011 nucleus crystal was obtained.The specific surface area of this nucleus crystal according to the B E i' method was found to be 76 m''/g. (3) Member reaction of the nucleus crystal formation reaction completed The remaining solution was heated to 60°C and maintained, and the Na01-1 aqueous solution was added to the predetermined amount of 411 phosphoric acid or a phosphoric acid compound or not, and while blowing air at about 60 () 07:00. (concentration 5 mol/ρ
) was gradually added so that 1)) 1 of the reaction solution remained at 3.5 to 5.51, and the reaction was allowed to occur until the nucleus crystals grew to a predetermined ratio (weight-to-weight ratio).

(4) Heat treatment of a-FeOOIl (C)” 2 (:
)) The reaction solution containing α-F eo Otl was filtered, washed with water, and then dehydrated (6013'CX in nitrogen gas).
2, 0 hours), reduction (in hydrogen containing water vapor, 400
°CX1. ! 'i hours) and reoxidation (in air, 280'
CX for 1.0 hours) to obtain (.gamma.-1-(., 03).

(5) Heat treatment of Q-FeOOII (D) (E) Dehydration (in nitrogen gas, instead of 600° (1 x 2.0 hours) (
1)) Dehydration (in air, +300'CX 2. (1 hour)) (E) Dehydration (in air, 7 (,10"CX2.0 hours)
γ-FeiO3 was obtained in the same manner as in (4) except that.

(6) Heat treatment of α-F eOOH (F) Dehydration (in nitrogen gas, G 00'CX 2 , (1 hour) instead of 1 till.

Water (in nitrogen gas, G 5 +3'CX 1.0 hours)
(T now, write everything except 2 in - (Jl of l and 4i1S
l: shite)'-1-'! ! ,0. uf! +・/−0−1, each γ−1; ゛(・, in OJ), r'
++ Using my own Ichikawa stand, a blend was prepared and mixed in a ball mill to produce -virtual magnetic coating 11.

(1) γ-)・'e, o, powder 1 (seal) 1 inch claw (2) Enter J7. lecithin
1,6 〃(3) 711 surfactant
4 L/(4) Acetic acid vinyl chloride joint resin Ml, 5 tt (5) Dioctyl 7 Talley 14 (6) Methyl ethyl ketone 84 (7)
Toluene 533 Next, each magnetic coating material was applied to a polyester film by a conventional method, oriented and dried to produce a magnetic recording medium having a magnetic coating film about 7 μm thick. , for these magnetic recording bodies, the coercive force (11c), saturation magnetic ratio (Ilm), squareness ratio (13r/tul1l),
Orientation (011), anti-11t<1111! /+! The magnetic distribution (SFl)) and the glossiness of the coating film were measured, and the results shown in Tables 1 and 2 were obtained.

(Total>I'S(') 4J minutes 1i: Hydrochloric acid dissolution test*1 \ Barium sulfate precipitation method 1: Car lO6 analysis S; Regulation: 31 minutes Leave (ko,
16 N, II and O f Danger”: ,
JISl<! '141Nlβ(l+, eye J(experimental method 1
)11.

As is clear from the results in section 1-, 4. of the present invention 1f. The shape is 1'' (well maintained, SO1 included), the (I
X, Kukatsumagnetic ('+4 i41 film face/T1 modification tc4
2 magnetic records, 1 ball, l', + r/ 13 + n
, ()1<, 511) As shown in the figure, it can be seen that the particles are highly dispersible and are fine particles.

Claims (1)

[Claims] A ferrous salt aqueous solution containing ferrous sulfate is added to an ITB filter,
The solution is oxidized to generate α-F (!(',) Oil nucleus crystals, and then the solution is neutralized with an alkali and oxidized to grow the nucleus crystals, resulting in J"J button-shaped a-FL! d('')II is heated and dehydrated, and then reduced or further acidified to give an oxidation degree of X.
Magnetic iron oxide (FcOx) where 33≦X≦1.50
), the growth of the nuclei is carried out in the presence of [11-phosphoric acid or its salt, and!
1. A process for producing shaped magnetic iron oxide for magnetic recording materials, which is characterized by dehydration using an inert gas containing as little oxygen as possible.