JPH1059724A - Lepidocrocite particle powder and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lepidocrocite particle excellent in dispersibility, coloring property and covering property by allowing a ferrous sulfate aq. solution to react with an alkali hydroxide aq. solution in the presence of a specific compound to prepare a suspension containing a hydroxide of iron and blowing an oxygen-containing gas into the suspension. SOLUTION: The suspension containing the hydroxide of iron and having pH 7-9 is prepared by mixing the ferrous sulfate aq. solution, the alkali hydroxide aq. solution with 0.1-5.0mol% phosphorus compound, citric acid compound or their mixture at 25-55 deg.C. A lepidocrocite particle is obtained next by blowing the oxygen containing gas into the suspension at 25-55 deg.C while adjusting to pH 7-9 to oxidize the hydroxide of iron. The lepidocrocite particle exhibits a rectangular parallelepiped having 0.045-0.5μm minor axis diameter, 0.05-1.0μm major axis diameter and 0.001-0.3μm thickness and the geometric standard deviation of the major axis diameter is <=1.7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lepidocrocite particle powder having a rectangular parallelepiped shape, in which individual particles are dispersed, and a method for producing the same.

[0002] The main use of the lepidocrocite particles according to the present invention is as a coloring pigment for paints, resin moldings, printing inks, road asphalt, cosmetics and the like.

[0003]

2. Description of the Related Art In recent years, orange pigments are widely used as color pigments in the production of paints, resins, printing inks, road asphalts, cosmetics, etc. by being dispersed in vehicles and resins. Since orange is a color that indicates traffic rules and cautions, its use as a coloring pigment for road asphalt and road marking paint (traffic paint) is expanding. Here, the orange color means that the a ^* value is 15 to 50 and the b ^* value is 2 in the “L ^* a ^* b ^* color system”.
The hue is 0 to 55.

Conventionally, orange pigments include organic pigments such as Sudan I, permanent orange and lithol fast orange, as well as red-mouthed graphite (PbCrO ₄ · PbO) and chromium vermilion (PbCrO ₄ · PbMoO ₄ · PbS).
Inorganic pigments such as O ₄ ) have been put to practical use and widely used.

However, organic pigments are generally expensive, while inorganic pigments are toxic because they contain heavy metals such as lead and chromium. Therefore, inexpensive and nontoxic orange pigments are strongly demanded. .

By the way, iron oxide particles such as iron oxide particles and ferric hydroxide particles are stable against oxidation by oxygen in the air, and are harmless and have excellent environmental stability. Since it has various hues and has various hues, it has been widely used as a coloring pigment for paints, resin moldings, printing inks, road asphalt, cosmetics, and the like.

[0007] Among various inexpensive and non-toxic iron oxide particles, those used as orange pigments include yellow goethite (α-FeOOH) particles and red hematite (α-Fe ₂ O ₃ ) particles. And powdered lepidocrocite (γ-FeOOH) particles.

In the production of paints and the like using these pigments, there is a strong demand for improvements in the properties of the particle powder from the viewpoints of improving work efficiency and improving physical properties of coating films in the energy-saving era.

That is, there is a strong demand not only for good dispersibility of the pigment in the vehicle or resin but also for improvement in coloring power and hiding power.

Heretofore, a method for producing lepidocrocite particles has been to prepare a suspension of ferrous hydroxide containing pH 7.0 to 9.0 obtained by reacting a ferrous salt solution with an alkaline solution. A method of producing lepidocrocite particles by passing an oxygen-containing gas at a temperature of 15 ° C. or lower (Japanese Patent Publication No. 336734/1988), a method comprising reacting an aqueous ferrous sulfate solution with an alkaline aqueous solution to obtain water. A suspension having a pH of 5.5 to 7.0 containing ferrous oxide was heated to a temperature of 5 to 15 ° C.
For producing lepidocrocite particles by passing an oxygen-containing gas at the following temperature (JP-A-55-332).
3 publication), a pH containing ferrous hydroxide obtained by reacting an aqueous ferrous sulfate solution with an aqueous sodium hydroxide solution.
A method for producing lepidocrocite particles by passing an oxygen-containing gas through a suspension of less than 5.5 at a temperature of about 45 ° C. in the presence of disodium hydrogen phosphate (JP-A-62-108738, etc.) An oxygen-containing gas is passed through a suspension containing ferrous hydroxide obtained by reacting an aqueous ferrous sulfate solution and an aqueous alkali hydroxide solution at a pH of about 10 or higher in the presence of a water-soluble phosphorus compound or an arsenic compound. To produce lepidocrocite seed crystals,
There is a method of producing lepidocrocite particles by growing a seed crystal of lepidocrocite in a temperature range of 0 ° C. (Japanese Patent Publication No. 43-2214, etc.).

[0011]

It is presently most demanded to obtain an inexpensive and non-toxic orange pigment which is excellent in dispersibility, coloring power and hiding power, and is economical. However, it is hard to say that the above-mentioned known orange pigments composed of iron oxide particles sufficiently satisfy these requirements.

That is, yellow goethite (α-FeOOH)
Since the mixed powder of the particle powder and the red hematite (α-Fe ₂ O ₃ ) particle powder is a mixture of different types of particle powder, the dispersibility in a vehicle or a resin is sufficient when manufacturing a paint or the like. In addition, after dispersion, there is a drawback that color separation is apt to occur in a paint or the like.

[0013] Since lepidocrocite particles are easily formed by forming aggregates of needle-like particles due to the production reaction, the dispersibility in a vehicle or a resin is not sufficient. The coloring power and hiding power are not sufficient due to the particle morphology.

This fact will be described below.

In general, lepidocrocite particles may be prepared by using an aqueous ferrous chloride solution or an aqueous ferrous sulfate solution as an iron raw material. When an aqueous ferrous chloride solution is used as the iron raw material, the reaction vessel and the like are corroded, and this is not industrial.

When an aqueous ferrous sulfate solution is used as the iron raw material, corrosion of the reaction vessel and the like does not occur, but the particle morphology of the produced lepidocrocite particles does not depend on any of the above-mentioned known methods. Acicular particles. And
Particles other than lepidocrocite particles are likely to be mixed due to the generation reaction.

That is, when the reaction pH is in the acidic range, acicular goethite particles are present in addition to lepidocrocite particles.
When the pH of the reaction product is in the alkaline region, particulate magnetite particles are present in addition to the lepidocrocyte particles.

When the pH of the reaction solution is as low as less than pH 7, a precipitate containing the alkali metal and SO ₄ simultaneously formed when the lepidocrocite particles are formed, ie, RFe ₃ (SO ₄ ) ₂ (OH) ₆ (R = K
⁺ , Na ⁺ , and NH ⁺ ), which are inevitably contained inside the particles and between the particles,
The hardly soluble iron-sulfur-containing salt is difficult to remove by washing with water, and remains in a state where the particles are cross-linked, so that aggregated particles are easily generated.

When the reaction for forming lepidocrocite particles is 15 ° C. or lower, it is necessary to cool the system.
Not industrial, economical.

In the case of the above-mentioned known method, the presence of a water-soluble phosphorus compound or an arsenic compound at the time of nucleation allows the reaction at a high temperature of 55 to 100 ° C. at the time of nucleation, and The morphology of the nucleus is changed from non-equiaxed to equiaxed to obtain equiaxed crystals, that is, granular lepidocrocite particles.

In the case of this method, since the shape of the obtained lepidocrocite particles is granular, the coloring power and the hiding power are poor.

In the nucleus crystal formation reaction, the lepidocrocite particles are acicular in shape, as shown in the comparative examples described later, and granular magnetite particles are present in addition to the acicular lepidocrosite particles.

Accordingly, an object of the present invention is to industrially and economically obtain lepidocrocite particles having excellent dispersibility and coloring and hiding properties.

[0024]

The above technical object can be achieved by the present invention as described below.

That is, according to the present invention, the short axis diameter is 0.045 to 0.045.
0.5 μm, the major axis diameter is 0.05 to 1.0 μm,
It is composed of cuboid lepidocrocite particles having a thickness of 0.001 to 0.3 μm, and has a geometric standard deviation of the major axis diameter of 1.70 or less, and if necessary, 1.40 or less. It is a lepidocrocite particle powder.

Further, the present invention relates to an aqueous ferrous sulfate solution, an aqueous alkali hydroxide solution and 0.1 to 5.0 mol% based on Fe.
By mixing a phosphorus compound or a citrate compound or both compounds in a temperature range of 25 to 55 ° C., a suspension containing iron hydroxide and having a pH value of 7 to 9 is produced, The suspension is added to the suspension, if necessary, in the presence of nuclei at a pH of from 7 to 9 at 25 to 55 ° C.
A method for producing each of the above lepidocrocite particles, which comprises oxidizing the hydroxide of iron by passing an oxygen-containing gas in the temperature range described above.

The structure of the present invention will be described in more detail as follows.

First, the lepidocrocite particles according to the present invention will be described.

The lepidocrocite particles according to the present invention have a rectangular parallelepiped shape. Here, the rectangular parallelepiped shape is not only a rectangular parallelepiped that is a hexahedron consisting of only rectangles, but also the ridges and sides of the rectangular parallelepiped are not necessarily straight lines, and are particles having some irregularities or slightly rounded particles. Well,
Particles having a ratio of major axis diameter to minor axis diameter of about 1.1: 1 to 5: 1. If the particles are not cuboid, excellent coloring power and hiding power cannot be obtained. In consideration of coloring power and hiding power, the ratio is preferably about 1.2: 1 to 4.8: 1.

The minor axis diameter is 0.045 to 0.5 μm.
When it is less than 0.045 μm, dispersibility is impaired due to an increase in intermolecular force due to finer particles. Further, the particles become acicular, and excellent coloring power and hiding power cannot be obtained. 0.5
If it exceeds μm, the dispersibility in the vehicle or the resin is good, but the coated surface or the resin composition having a smooth surface cannot be obtained due to coarsening of the particles. A preferred short axis diameter is 0.045.
０．３0.3 μm, more preferably 0.045-0.2 μm
It is.

The major axis diameter is 0.05 to 1.0 μm.
If it is less than 0.05 μm, dispersibility is impaired due to an increase in intermolecular force due to finer particles. If it exceeds 1.0 μm, the particles become acicular, and excellent coloring power and hiding power cannot be obtained. Further, due to the coarsening of the particles, a smooth coated surface or a resin composition cannot be obtained. The preferred major axis diameter is 0.05 to 0.7 μm, more preferably 0.05 to 0.7 μm.
0.5 μm.

The thickness is 0.001 to 0.3 μm.
When it is less than 0.001 μm, dispersibility is impaired due to an increase in intermolecular force due to finer particles. Further, since the thickness becomes thin, excellent coloring power and hiding power cannot be obtained.
When it exceeds 0.30 μm, the particles are coarsened.
A coated surface having a smooth surface or a resin composition cannot be obtained. The preferred thickness is 0.001 to 0.2 μm, more preferably 0.001 to 0.1 μm.

The lepidocrocite particles according to the present invention have an SO ₄ content of 1000 ppm or less, preferably 500 ppm or less.
ppm or less, more preferably 200 ppm or less,
No cross-linking is seen between the particles and the individual particles are fragmented. The lower limit of the SO ₄ content of the obtained lepidocrocite particles is about 0.01 ppm.

The lepidocrocite particles obtained in the absence of the nucleus according to the present invention have a geometric standard deviation of the major axis diameter of 1.70 or less. The geometric standard deviation value is an index indicating the degree of particle size distribution of the particles, and a smaller value means that the particle size distribution of the particles is better. When it exceeds 1.70, the coloring power and the hiding power become insufficient. In consideration of coloring power and hiding power, it is preferably 1.60 or less. The lower limit of the obtained lepidocrocite particles is about 1.05.

The lepidocrocite particles obtained in the presence of the nucleus according to the present invention have a geometric standard deviation of the major axis of 1.40 or less. If it exceeds 1.40, it cannot be said that the particle size distribution is more improved. In consideration of coloring power and hiding power, it is preferably 1.38 or less, more preferably 1.35 or less. The lower limit of the obtained lepidocrocite particles is about 1.01.

The minor axis diameter is 0.045 to 0.5 μm, the major axis diameter is 0.05 to 1.0 μm, and the thickness is 0.001 to
The hue of the lepidocrocite particles according to the present invention, which is composed of cuboidal lepidocrocite particles of 0.3 μm, has an a ^* value of 15.0 to 50.0, and b
^* Value is 20.0-55.0, L ^* value is 20.0-
70.0.

If the value of a ^* exceeds 50.0, the redness becomes strong, which is not preferable. If it is less than 15.0, redness is insufficient, which is not preferable.

If the value of b ^* exceeds 55.0, the yellow color becomes strong, which is not preferable. If it is less than 20.0, the yellowness required for orange color development is insufficient, which is not preferable.

When the L ^* value exceeds 70.0, the color of the pigment becomes too bright, which is not preferable. If it is less than 20.0, it is not preferable because it becomes dark and dull.

The difference between the geometric standard deviation values is determined by the a ^* value or b
^* It does not affect the hue such as the value, but as is well known, there is a slight difference in the smear, and the smear tends to be smaller as the geometric standard deviation value is smaller.

The solvent-based paint obtained by using the lepidocrocite particles according to the present invention has a coloring power of 4 to 5, a hiding power of 25 or less, preferably 23 or less, and a preferred lower limit of 10. . The glossiness on the coating surface of the coated piece is 75
Or more, preferably 78 or more, and the preferred upper limit is 1
40.

The aqueous paint obtained by using the lepidocrocite particle powder according to the present invention has a coloring power of 4 to 5, a hiding power of 29 or less, preferably 27 or less, and a preferred lower limit of 15. . The glossiness of the coated piece on the coating surface is 71.
Or more, preferably 75 or more, and a preferable upper limit is 1
30.

The resin composition obtained using the lepidocrocite particle powder according to the present invention has a dispersion state of 4 to 5.

Next, a method for producing the lepidocrocite particles according to the present invention as described above will be described.

The aqueous ferrous salt solution in the present invention is an aqueous ferrous sulfate solution.

As the aqueous alkali hydroxide solution in the present invention, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution and the like can be used.

Examples of the phosphorus compound in the present invention include phosphates such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphate and tetraphosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate and trisodium phosphate. Sodium salts, ammonium salts such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium sodium hydrogen phosphate, and potassium salts such as tripotassium phosphate, potassium dihydrogen phosphate and dipotassium hydrogen phosphate. be able to.

The citric acid compound in the present invention includes:
As well as citric acid, ammonium salts such as ammonium citrate and ammonium hydrogen citrate, potassium salts such as potassium citrate and potassium hydrogen citrate, sodium salts such as sodium citrate and sodium hydrogen citrate,
A lithium salt such as lithium citrate can be used.

In the present invention, the ferrous sulfate aqueous solution, the alkali hydroxide aqueous solution, the phosphorus compound or the citric acid compound, or both of these compounds may be added in any order at the same time. Is obtained.

Considering that only the lepidocrocite particle powder is produced without producing other particles other than lepidocrocite particles, an aqueous ferrous sulfate solution and an aqueous alkali hydroxide solution and a phosphorus compound or a citric acid compound or It is preferable to mix the two compounds as uniformly as possible.

For this purpose, it is preferred that the phosphorus compound or the citric acid compound or both compounds are previously mixed with an aqueous ferrous sulfate solution, and then the mixed solution is added to an aqueous alkali hydroxide solution. More preferably, after the mixed solution is aged in advance, it may be added to an aqueous alkali hydroxide solution.

The aging time of the mixed solution is preferably 10 minutes or more, more preferably 30 minutes or more. The upper limit of the aging time is not particularly limited, but is about 120 minutes industrially.

The above-mentioned mixed solution to be added to the aqueous alkali hydroxide solution may be added at a time, but in consideration of uniform mixing of the aqueous solution, a small amount may be added continuously or intermittently over 10 to 120 minutes. Preferably, in particular, 50 to
It is more preferable to add over about 70 minutes.

The mixing ratio of the aqueous ferrous sulfate solution and the aqueous alkali hydroxide solution is determined by the reaction of the aqueous solution of ferrous sulfate and the aqueous alkali hydroxide solution with the suspension containing iron hydroxide.
What is necessary is just a ratio which makes H value the range of 7-9. When the pH value of the suspension is less than 7, acicular goethite particles are present in addition to the lepidocrocite particles. If the pH value of the suspension exceeds 9, particulate magnetite particles will be present in addition to the lepidocrocite particles.

The mixing ratio of the phosphorus compound or the citric acid compound or both compounds is 0.1 to 5 mol with respect to Fe.
1%. If the amount is less than 0.1 mol%, it is difficult to generate only lepidocrocite particles, and particulate magnetite particles are mixed. If it exceeds 5 mol%, lepidocrocite particles can be obtained, but the effect of addition is saturated, and there is no point in adding more than necessary.

The addition of the phosphorus compound or the citric acid compound or both compounds needs to be performed before the oxygen-containing gas is passed through the suspension, and an aqueous ferrous sulfate solution, an aqueous alkali hydroxide solution, and an iron-containing precipitate are added. Can be added to any liquid of the suspension containing the substance.

Considering that only the lepidocrocite particle powder is produced without producing other particles other than lepidocrocite particles, it is preferable to add it to the aqueous ferrous sulfate solution as described above.

The temperature at the time of mixing the raw materials is 25 to 55 ° C.
It is. When the temperature is lower than 25 ° C., a long time is required for a reaction for forming lepidocrocite, which is not industrial or economic. 55
When the temperature exceeds ℃, particulate magnetite particles other than lepidocrocite particles are mixed.

It is important that the pH value at the time of mixing the raw materials is adjusted to be in the range of 7 to 9. When the pH value is out of the range, it is difficult to produce only the lepidocrocite particle powder. If the pH value is less than 7, a large amount of the sulfur-containing iron salt is contained in the lepidocrocite particles.

The oxidation of the suspension containing iron hydroxide in the present invention is performed by passing an oxygen-containing gas (for example, air) through the liquid. The amount of aeration is preferably 0.5 to 100 l per minute per 10 l of the reaction mother liquor.

The oxidation reaction temperature in the present invention is from 25 to 5
5 ° C. When the temperature is lower than 25 ° C., a long time is required for the oxidation reaction, which is not industrial and economical. When the temperature exceeds 55 ° C., it is difficult to generate only lepidocrocite particles, and granular magnetite particles and the like are mixed in addition to lepidocrocite particles.

In the oxidation reaction of the present invention, the pH value gradually decreases with the progress of the oxidation reaction.
It is important to adjust to a range of ~ 9. When the pH value is less than 7, it is difficult to generate only lepidocrocite particles, and acicular goethite particles are mixed. When the pH value exceeds 9, it becomes difficult to generate only lepidocrocite particles, and particulate magnetite particles are mixed.

The oxidation reaction time from the start of the oxidation reaction to the end of the reaction in the present invention is 24 hours or less, particularly 12 hours or less. Therefore, the yield of lepidocrocite particles per unit time (yield per unit capacity / unit time) is as large as 4.3 to 15.6 kg / m ³ · hr, which is industrially and economically advantageous.

When the reaction for forming lepidocrocite particles is completed and the oxidation reaction no longer proceeds, the pH value does not change.
The point at which the addition of the NaOH solution for adjusting H became unnecessary became the end point of the oxidation reaction.

In the reaction for producing the lepidocrocite particles according to the present invention as described above, a lepidocrocyte nucleus may be present if necessary.
It is possible to produce lepidocrocite particle powder having a geometric standard deviation of the major axis diameter of 1.40 or less, in other words, more excellent particle size distribution.

The nucleus crystals are prepared from iron hydroxides such as ferrous hydroxide colloids, ferric hydroxide colloids and green rust obtained by well-known production methods, iron oxides such as hematite, magnetite and maghemite. Any of iron hydrates such as goethite, lepidocrocite and akaganite may be used.These nuclei are produced using the same reaction tower as the reaction tower for producing lepidocrocite particles according to the present invention. Or a different reaction tower.
Taking into account the particle size distribution of the major axis diameter of the lepidocrocyte particle powder, which is the target substance, particles having a small number of agglomerated particles and being individually dispersed are preferred.

A preferred method for producing a nucleus crystal is 0.1 to 5.0 parts by weight of an aqueous ferrous sulfate solution, an aqueous alkali hydroxide solution and Fe.
a method of obtaining an iron hydroxide by mixing a mol% of a phosphorus compound or a citric acid compound or both compounds at a temperature of 25 to 55 ° C. and a pH of 7 to 9, or a suspension containing the iron hydroxide In addition, there is a method of further obtaining air by injecting air to obtain lepidocrocite nuclei.

The abundance of nuclei is 0.001 to 0.001 Fe.
0.5 mol / l is preferred. If the amount is less than 0.001 mol / l, the number of nuclei is too small, so that the particle growth becomes uneven and it becomes difficult to produce lepidocrocite particles having an excellent particle size distribution. If it exceeds 0.5 mol / l, the number of nuclei increases, and the growth of particles becomes insufficient.

[0069]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention is as follows.

The major axis diameter and the minor axis diameter of the particles were about 3 particles shown in a photograph (× 120,000) obtained by magnifying an electron micrograph (× 30000) four times in the vertical and horizontal directions, respectively.
The major axis diameter and the minor axis diameter were measured for 50 pieces, respectively, and the average value was shown.

The particle thickness was determined by extracting only the inverted particles from the particles shown in the photograph prepared in the same manner as above, measuring the thickness of about 100 particles, and calculating the average value. Indicated.

The geometric standard deviation (σg) of the major axis diameter of the particles was shown by the value obtained by the following method. That is, the value obtained by measuring the major axis diameter of the particles shown in the enlarged photograph is calculated from the measured major axis diameter and the actual number of the major axis diameter of the particles, and the horizontal axis is plotted on a lognormal probability paper according to a statistical method. , And the vertical axis plots the percentage of the cumulative number of particles belonging to each of the predetermined major axis diameter sections (under the integrated screen). The graph shows that the number of particles is 50% and 84.1.
The value of the major axis diameter corresponding to each of 3% is read, and the geometric standard deviation value (σg) = the major axis diameter at 84.13% below the integrated screen / the major axis diameter at 50% below the integrated screen (geometric mean diameter). It is shown by the calculated value. The smaller the geometric standard deviation value, the better the particle size distribution of the major axis diameter of the particles.

The content of SO ₄ was determined by weighing 5 g of a sample in a 300 ml Erlenmeyer flask, adding 100 ml of pure water,
The mixture was heated to a boiling state by heating for a minute to dissolve the hardly soluble iron-sulfur-containing salt present on the particle surface. The resulting supernatant was 5
Filtration was performed using C filter paper, and SO ₄ ^2- in the filtrate was measured using an induction plasma emission spectrophotometer (manufactured by Seiko Instruments Inc.).

The hue of the powder was determined by kneading 0.5 g of lepidocrocite particle powder and 0.7 cc of castor oil with a Hoover-type muller to form a paste, adding 4.5 g of clear lacquer to the paste, kneading and forming a paint. A coated piece (coating thickness: about 30 μm) was formed on a cast-coated paper using a 6 mil applicator, and a multi-light source spectrophotometer MSC-1S-2D (Suga Test Instruments Co., Ltd.) was prepared for the coated piece. And the colorimetric index L ^* value, a ^* value, and b ^* value were measured and measured according to JIS Z 8729.

The a ^* value indicates reddish color. A larger value means a stronger reddish color. The b ^* value indicates yellowness, and a larger value means stronger yellowness. Therefore, the orange color is a
^* Value and b ^* value. The L ^* value indicates lightness.

The dispersibility in the paint vehicle was examined by measuring the glossiness of the coated surface of the coated piece produced in the same manner as in the embodiment of the present invention described later.

The gloss was measured using a gloss meter UGV-5D.
The gloss was measured at 60 ° on the coated surface using (manufactured by Shimadzu Corporation). The higher the gloss value, the better the dispersibility.

The dispersibility in the resin composition is determined by visual observation of the number of undispersed aggregated particles on the surface of the obtained resin composition, and is determined in five stages (50 or more per 1 cm ³ ).
2: 1 cm less than 50 per ^3, 3: 1 cm less than ten per ^3, 4: less than five per 1 cm ^3, 4: 1
(no undispersed material per cm ³ ). 5 indicates that the dispersion state is the best.

The hiding power was determined according to JIS for the obtained paint.
K 5.11-1991 “Pigment Test Method”, “8.2”
It was determined by the cryptometer method described in the section "Hiding power". The hiding power is indicated by a value of a scale when the boundary line is hidden and cannot be seen, and the larger the value of the scale, the lower the hiding power.

The coloring power of the paint was determined by comparing the obtained paint with a standard white paint (TiO ₂ : a standard paint using TCR73 manufactured by Tochem Products) prepared under the same conditions as in the embodiment of the present invention described later. Are visually checked for the degree of coloring of the colored paint obtained by mixing at a ratio of 1:10. : Considerably colored, 5: markedly colored). 5 indicates that the coloring power is the largest.

<Production of Lepidocrocite Particle Powder> First, the following solution A was prepared in advance and placed in a 35 ° C. chamber.

Solution A: A 1.834 mol / l ferrous sulfate aqueous solution 1 was added to a disodium hydrogen phosphate solution in which 8.66 g of disodium hydrogen phosphate was dissolved in 300 ml of water.
663 ml were added and mixed, and water was further added to make a volume of 270 ml.
0 ml mixed solution.

Next, a reaction for forming lepidocrocite particles is performed.

After heating 2000 ml of water charged in a bubble column (reactor) having an effective volume of 5 l to 40 ° C.,
Stir with air at a rate of 1 / min, then
The pH value was adjusted to 8 by adding 0.1 N NaOH solution. Immediately after the completion of the adjustment of the pH value, the solution A previously aged at 35 ° C. for 30 minutes was introduced into the bubble column.
The introduction was started at a rate of 5 ml / min, and the introduction was continued for 60 minutes. During the charging of the solution A, the temperature in the bubble column was raised to 40 ° C.
And from the NaOH tank to 4.
The pH value of the reaction slurry was constantly adjusted to about 8 by intermittently adding a 5N NaOH aqueous solution. Even after the addition of the solution A was completed, the temperature was maintained at 40 ° C. and the pH value was maintained at 8 while continuously aerating and stirring air. 4.5 after the start of the reaction
After hours an orange precipitate was obtained.

The obtained orange precipitate was filtered by a conventional method, washed with water, and dried at 80 ° C. for 24 hours to obtain a dried product. The yield was 12.04 kg / m ³ · h. This dried product was lepidocrocite particle powder as shown in the X-ray diffraction diagram of FIG. In FIG. 1, peak A is lepidocrocite (γ-FeOOH). This lepidocrocite particle powder is a particle having a rectangular parallelepiped shape as shown in an electron micrograph (× 30000) of FIG.
7 μm, major axis diameter 0.12 μm, thickness 0.017 μm
And the major axis diameter: the minor axis diameter was 2.1: 1. The geometric standard deviation value of the major axis diameter was σg = 1.38, and the particle size distribution was excellent. In addition, soluble SO ₄ is 52 pp
m.

<Manufacture of Solvent-Based Coating> In a 140 ml glass container, 10 g of the above-mentioned lipid crocite particles, an amino alkyd resin and a thinner were blended in the following composition ratio, and the mixture was added together with 90 g of 3 mmφ glass beads.
The mixture was mixed and dispersed by a paint shaker for 90 minutes to prepare a mill base.

Lipid crocite particle powder 12.2 parts by weight Amino alkyd resin 19.5 parts by weight (Amirac No. 1026 manufactured by Kansai Paint Co., Ltd.) Thinner 7.3 parts by weight

Into a 140 ml glass container, a mixture obtained by mixing the obtained mill base and amino alkyd resin in the following composition ratio was charged, and further added with a paint shaker for 15 minutes.
The mixture was mixed and dispersed for minutes to obtain a solvent-based paint.

Mill base 39.0 parts by weight Amino alkyd resin 61.0 parts by weight (Amirac No. 1026 manufactured by Kansai Paint Co., Ltd.)

The coloring power measured using the obtained paint was 5, and the hiding power was 18.

The obtained paint was applied to a standard test plate (length 150 mm × width 70 mm × thickness 0.8 mm, JIS G 3141, cold-rolled steel sheet,
(Japan Test Panel Osaka Co., Ltd.), air-dried for 30 minutes, and baked at 120 ° C. for 30 minutes.

The gloss of the coated surface of the coated piece was 89%. The hue is orange and the a ^* value is 23.
3. The b ^* value was 37.0. Also, when the L ^* value is 51.
It was 4.

<Production of water-based paint> In a 140 ml glass container, 7.62 g of the above-mentioned lipid crocite particles, a water-soluble alkyd resin, an antifoaming agent, and water were blended in the following composition ratio to form a 3 mmφ glass powder. Put together with 90g of glass beads, mix and disperse for 90 minutes with a paint shaker,
A mill base was prepared.

Lipid crocite particle powder 12.4 parts by weight Water-soluble alkyd resin 9.0 parts by weight (S-118, manufactured by Dainippon Ink and Chemicals, Inc.) Antifoaming agent 0.1 part by weight (Nopco 8034 San Nopco Co., Ltd.) Water 4.8 parts by weight Butyl cellosolve 4.1 parts by weight

Into a 140 ml glass container, a mixture prepared by mixing the obtained mill base, a water-soluble alkyd resin, an antifoaming agent and water in the following composition ratio was added, and the mixture was further mixed and dispersed with a paint shaker for 15 minutes. Paint was obtained.

Mill base 30.4 parts by weight Water-soluble alkyd resin 46.2 parts by weight (S-118 manufactured by Dainippon Ink and Chemicals, Inc.) Water-soluble melamine resin 12.6 parts by weight (S-695 Dainippon Ink and Chemicals, Inc.) Defoamer 0.1 parts by weight (Nopco 8034 San Nopco Co., Ltd.) Water 9.1 parts by weight Butyl cellosolve 1.6 parts by weight

The coloring power measured using the obtained paint was 5, and the hiding power was 21.

Using the obtained coating material, a coated piece was obtained in the same manner as in the above-mentioned solvent-based coating material.

The glossiness of the coated surface of the coated piece was 83%. The hue is orange and the a ^* value is 23.
1. The b ^* value was 35.2. The L ^* value is 48.
It was 6.

<Production of Resin Composition> 1.5 g of the above-mentioned lepidocrocyte particle powder and polyvinyl chloride resin powder (103
EP8D, manufactured by Nippon Zeon Co., Ltd.)
The mixture was put into a 0 cc polybeaker and mixed well with a spatula to obtain a mixed powder of lepidocrocite particles and a polyvinyl chloride resin.

0.5 g of calcium stearate was added to the mixed powder, and the mixture was further kneaded little by little using a hot roll heated to 160 ° C. (clearance was set to 0.2 mm). The mixture was kneaded until the mixture became uniform to obtain a resin composition.

After peeling the resin composition from the roll,
Surface polished stainless steel plate (200mm x 200m
m, an interval of 1 mm), and then placed in a hot press heated to 180 ° C. and pressed under a pressure of 1 ton / cm ² to obtain a colored resin plate having a thickness of 1 mm.

The resulting colored resin plate had a dispersion state of 5 as determined by visual inspection. The hue was orange, and the a ^* value was 25.5 and the b ^* value was 31.6. Further, the L ^* value was 46.8.

[0104]

First, the most important point in the present invention is that the ferrous sulfate aqueous solution, the alkali hydroxide aqueous solution and the Fe are 0.1% to 0.1%.
By mixing a phosphorus compound or a citric acid compound or both compounds in a temperature range of 25 to 55 ° C. in a temperature range of 25 to 55 ° C., a suspension containing a hydroxide of iron and having a pH value of 7 to 9 is obtained. When the oxygen-containing gas is formed and then the suspension is aerated with an oxygen-containing gas in a temperature range of 25 to 55 ° C. while adjusting the pH value to a range of 7 to 9, the minor axis diameter is 0.045 to 0. 0.5 μm, major axis diameter 0.05-1.0 μ
m, a lepidocrocite particle powder having a rectangular parallelepiped shape having a thickness of 0.001 to 0.3 μm, and individual particles falling apart, and a pH value of 7 to 9 are obtained. This is a fact that only lepidocrocyte particles can be stably obtained in a temperature range of 25 to 55 ° C. without heterogeneous particles other than lepidocrocite particles.

Regarding the reason that individual lepidocrocite particles are scattered, the present inventor concluded that, as shown in the examples below, the particles were formed in a substantially neutral region having a pH value of 7 to 9 and thus, agglomeration was observed. It is considered that the amount of the hardly soluble iron-sulfur-containing salt that causes the odor is small.

The pH value is in the range of 7 to 9, and
Regarding the reason why lepidocrocite particles can be stably produced in a temperature range of 5 to 55 ° C, the present inventor has found that a phosphorus compound or a citric acid compound or both of these compounds exist in a comparative example described later. Otherwise, since heterogeneous particles other than lepidocrocite particles will be mixed, the presence of a phosphorus compound or a citrate compound or both compounds will lead to an expansion of a region where only lepidocrocite particles are stably generated. We think that it is affecting.

[0107]

Next, examples and comparative examples will be described.

<Production of Particle Powder> Examples 1 to 3 and Comparative Examples 1 to 7 Types, concentrations and amounts of ferrous salt aqueous solutions, types and amounts of phosphate compounds and citrate compounds, types and concentrations of alkaline aqueous solutions A reaction product was obtained in the same manner as in the embodiment of the present invention, except that the method of mixing the raw materials, the pH value and the temperature during mixing and during the reaction were variously changed.

The particles obtained in Examples 1 to 3, Comparative Example 4 and Comparative Example 6 were all confirmed by X-ray diffraction to consist only of lepidocrocite particles.

The reaction products obtained in Comparative Examples 1, 3 and 5 were analyzed by X-ray diffraction. As a result, it was confirmed that magnetite (Fe ₃ O ₄ ) was present in addition to lepidocrocite.

FIG. 3 shows an X-ray diffraction pattern of the reaction product obtained in Comparative Example 2, and FIG. 4 shows an electron micrograph (× 30000). In FIG. 3, peak A is lepidocrocite, peak B
Is goethite (α-FeOOH), and it was recognized that goethite particle powder was present in addition to lepidocrocite particles. In addition, as shown in FIG. 4, cuboid particles and needle particles were mixed.

FIG. 5 shows an X-ray diffraction pattern of the reaction product obtained in Comparative Example 7, and FIG. 6 shows an electron micrograph (× 30000). In FIG. 5, peak A is lepidocrocite, peak C
Is magnetite, and it was recognized that magnetite particle powder was present in addition to lepidocrocite particle powder. Further, as shown in FIG. 4, cuboid particles and granular particles were mixed.

The main manufacturing conditions at this time are shown in Table 1, and various characteristics are shown in Table 2.

[0114]

[Table 1]

[0115]

[Table 2]

<Manufacture of Solvent-Based Coatings> Use Examples 1 to 3 and Comparative Use Examples 1 to 7 Solvent-based coatings were obtained in the same manner as in the embodiment of the invention except that the types of the particle powders were variously changed. .

Table 3 shows the main manufacturing conditions and various characteristics at this time.

[0118]

[Table 3]

<Production of water-based paint> Use examples 4 to 6 and comparative use examples 8 to 14 Water-based paints were obtained in the same manner as in the embodiment of the invention except that the types of the particle powders were variously changed.

Table 4 shows the main production conditions and various characteristics at this time.

[0121]

[Table 4]

<Production of Resin Molded Product> Use Examples 7 to 9 and Comparative Use Examples 15 to 21 Resin molded products were obtained in the same manner as in the embodiment of the invention except that the types of the particle powders were variously changed. .

Table 5 shows the main production conditions and various characteristics at this time.

[0124]

[Table 5]

<Production of Reaction Product> Example 4 First, the following B solution and C solution were prepared in advance,
Placed in separate chambers at 35 ° C.

Solution B: A 1.834 mol / l ferrous sulfate aqueous solution 1 was added to a disodium hydrogen phosphate solution obtained by dissolving 5.68 g of disodium hydrogen phosphate in 300 ml of water.
091 ml was added and mixed.
0 ml mixed solution.

Solution C: 1.834 mol / l ferrous sulfate aqueous solution 572 was added to disodium hydrogen phosphate prepared by dissolving 2.98 g of disodium hydrogen phosphate in 150 ml of water.
ml, add water, add water and add 1000ml
Mixed solution.

Next, a reaction for forming lepidocrocite particles is carried out in the presence of a nucleus crystal.

After heating 2000 ml of water charged in a bubble column (reactor) having an effective volume of 5 l to 35 ° C.,
The solution C previously aged at 35 ° C. for 30 minutes was added to the bubble column while aerating and stirring air at a rate of 1 / min, followed by aeration and agitation for 5 minutes.

Next, a separately prepared NaOH aqueous solution at 35 ° C. (91 ml of an 18.4N NaOH aqueous solution was diluted with water to 500 ml, and 0.1 ml of Fe contained in the C solution was added.
An aqueous solution corresponding to 8 equivalents was obtained. ) Was added little by little to the bubble column, and after the addition was completed, stirring was carried out by passing air at a rate of 10 l / min for another 5 minutes to carry out a nucleation reaction.

Subsequently, the temperature was raised to 40 ° C. while stirring by passing air at a rate of 10 l / min.
The pH was adjusted to 8 by adding a little 4.5N NaOH solution. Immediately after completing the pH adjustment, 30 ° C at 35 ° C.
25 ml of the above B solution at 35 ° C. aged for 25 minutes in a bubble column.
The charging was started at a rate of / min, and the charging was continued for 60 minutes. During the charging of the B solution, while controlling the temperature in the bubble column to 40 ° C., intermittently adding a 4.5N NaOH aqueous solution from the NaOH tank to adjust the pH of the reaction slurry.
The value was constantly adjusted to about 8. After the introduction of the B solution, the temperature is kept at 40 ° C. and p
The H value was maintained at 8. 8.3 hours after the start of the reaction, an orange precipitate was obtained.

The obtained orange precipitate was filtered by a conventional method, washed with water, and dried at 80 ° C. for 24 hours to obtain a dried product. The yield was 6.53 kg / m ³ · h. This dried product is
As a result of X-ray diffraction, only lepidocrocite particles were found. This lepidocrocite particle powder is a particle having a rectangular parallelepiped shape as a result of observation with an electron microscope, and has a short axis diameter of 0.045 μm, a long axis diameter of 0.090 μm, and a thickness of 0.1 μm.
017 μm, and the ratio of major axis diameter to minor axis diameter was 2.0: 1. The geometric standard deviation value of the major axis diameter was σg = 1.32, and the particle size distribution was more excellent. Also,. Soluble SO ₄ was 90 ppm.

Examples 5 to 7 and Comparative Example 8 The concentration and amount of an aqueous ferrous salt solution, the type and amount of a phosphate compound or a citrate compound, the type and concentration of an alkaline aqueous solution,
A reaction product was obtained in the same manner as in Example 4, except that the method of mixing the raw materials, the type and amount of the nucleus, and the pH value and the temperature during mixing and during the reaction were variously changed.

The particles obtained in Examples 5 to 7 and Comparative Example 8 were all confirmed by X-ray diffraction to consist only of lepidocrocite particles.

FIG. 7 shows an X-ray diffraction pattern of the reaction product obtained in Example 6, and FIG. 8 shows an electron micrograph (× 30000). In FIG. 7, the peak A is lepidocrocite, and it was confirmed that the peak A was composed of only lepidocrocite particles.

The main manufacturing conditions at this time are shown in Table 6, and various characteristics are shown in Table 7.

[0137]

[Table 6]

[0138]

[Table 7]

<Production of Solvent-Based Paint> Use Examples 9 to 12 and Comparative Use Example 22 A solvent-based paint was obtained in the same manner as in Use Example 1, except that the type of the particle powder was variously changed.

Table 8 shows the characteristics at this time.

[0141]

[Table 8]

<Production of water-based paint> Use Examples 13 to 16, Comparative Use Example 23 A water-based paint was obtained in the same manner as in Use Example 4, except that the type of the particle powder was variously changed.

Table 9 shows the characteristics at this time.

[0144]

[Table 9]

<Production of Resin Molded Article> Use Examples 17 to 20, Comparative Use Example 24 A resin molded article was obtained in the same manner as in Use Example 7, except that the type of the particle powder was variously changed.

Table 10 shows the characteristics at this time.

[0147]

[Table 10]

[0148]

The lepidocrocite particle powder according to the present invention has a rectangular parallelepiped shape, and the individual particles are dispersed due to the low amount of the hardly soluble iron sulfate salt, so that the dispersibility is excellent. In addition, it has excellent coloring power and hiding power due to its shape, and thus is suitable as an orange coloring pigment.

According to the method for producing lepidocrocite particles according to the present invention, since the reaction is carried out in a temperature range of 25 to 55 ° C. without causing corrosion in a reaction tower or the like and requiring no cooling, A large amount of heat energy is not required, and the desired lepidocrocite particle powder can be obtained industrially and economically advantageously.

Further, since the yield is large, it is industrial and economical.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of a lepidocrocite particle powder having a rectangular parallelepiped shape obtained in an embodiment of the present invention.

FIG. 2 is an electron micrograph (× 30000) showing the particle structure of a cuboid-shaped lepidocrocite particle powder obtained in the embodiment of the present invention.

FIG. 3 is an X-ray diffraction diagram of a reaction product obtained in Comparative Example 2.

FIG. 4 is an electron micrograph (× 30000) showing the particle structure of the reaction product obtained in Comparative Example 2.

FIG. 5 is an X-ray diffraction diagram of the reaction product obtained in Comparative Example 7.

FIG. 6 is an electron micrograph (× 30000) showing the particle structure of the reaction product obtained in Comparative Example 7.

FIG. 7 is an X-ray diffraction diagram of a lepidocrocite particle powder having a rectangular parallelepiped shape obtained in Example 6.

FIG. 8 is an electron micrograph (× 30000) showing the particle structure of a lepidocrocite particle powder having a rectangular parallelepiped shape obtained in Example 6.

Claims (4)

[Claims] 1. A short axis diameter of 0.045 to 0.5 μm, a long axis diameter of 0.05 to 1.0 μm, and a thickness of 0.001
It is made of lepidocrocite particles having a rectangular parallelepiped shape of about 0.3 μm, and the geometric standard deviation of the major axis diameter is 1.70.
Lepidocrocite particle powder characterized by the following. 2. A minor axis diameter of 0.045 to 0.5 μm, a major axis diameter of 0.05 to 1.0 μm and a thickness of 0.001
It is made of lepidocrocite particles having a rectangular parallelepiped shape of about 0.3 μm, and the geometric standard deviation of the major axis diameter is 1.40.
Lepidocrocite particle powder characterized by the following. 3. An aqueous ferrous sulfate solution, an aqueous alkali hydroxide solution and 0.1 to 5.0 mol% of phosphorus compound or citric acid compound or both compounds with respect to Fe at a temperature of 25 to
By mixing in a temperature range of 55 ° C., a suspension having a pH value of 7 to 9 containing iron hydroxide is formed, and then the suspension is adjusted to a pH value of 7 to 9. The method for producing lepidocrocite particles according to claim 1, wherein an oxygen-containing gas is passed in a temperature range of 25 to 55C while oxidizing the hydroxide of iron. 4. An aqueous ferrous sulfate solution, an aqueous alkali hydroxide solution and 0.1 to 5.0 mol% of a phosphorus compound or a citric acid compound or both compounds with respect to Fe at a temperature of 25 to
Mixing in a temperature range of 55 ° C. produces a suspension with a pH value of 7 to 9 containing iron hydroxide, which is then added to the suspension with a pH value of 7 in the presence of nuclei. 3. The method of claim 2, wherein the iron hydroxide is oxidized by passing an oxygen-containing gas in a temperature range of 25 to 55 [deg.] C. while adjusting to a range of from 9 to 9. Law.