JPH10279314A - Nonmagnetic black pigment powder, nonmagnetic black paint using the nonmagnetic black pigment powder, and black rubber / resin composition using the nonmagnetic black pigment powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-magnetic black pigment powder which is excellent in blackness and heat resistance and more excellent in dispersibility and, when colored with the non-magnetic black pigment powder, has an acid resistance. Black paint and black rubber with excellent aging resistance
A resin composition is provided. SOLUTION: The Mn content of nonmagnetic black granular particles having a hematite structure containing iron as a main component and containing Mn and having an average diameter of 0.1 to 10 μm is 5 to 40% by weight based on the nonmagnetic black powder. A nonmagnetic black powder having a powder pH value of 5.5 or more, a soluble sodium salt content of 500 ppm or less in terms of Na, and a soluble sulfate content of 200 ppm or less in terms of SO _4. It is a nonmagnetic black pigment powder, which is a powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention provides a non-magnetic black pigment powder which is excellent in blackness and heat resistance and more excellent in dispersibility, and when colored by the non-magnetic black pigment powder, An object of the present invention is to provide a black coating film having excellent acid resistance and a black rubber / resin composition having excellent aging resistance.

[0002]

2. Description of the Related Art Typical black pigments include:
Magnetite particle powder, carbon black, fluorinated graphite and the like are known. These black pigments are widely used as paints by mixing and dispersing in vehicles, and as colorants for rubber and resins by kneading and dispersing in rubber and resins.

In recent years, from the viewpoint of safety and hygiene, improvement of work efficiency and improvement of various characteristics in the energy-saving era, it is safe and harmless, and it is excellent in blackness and heat resistance, as well as in dispersibility. Due to its excellent properties, a black pigment powder having excellent workability and various properties is strongly required.

[0004] Conventionally used black pigments such as magnetite particle powder, carbon black and fluorinated graphite are:
When formed into a coating film, the L ^* value is 10 to 25, and the a ^* value is -2.5.
It shows values of -2.5 to 2.5 in terms of -2.5 and b ^* value, and is excellent in blackness.

[0005] Next, regarding the heat resistance of the pigment, it is required to be excellent in heat resistance since it is exposed to a high temperature in the molding process of rubber and resin.

Further, in baking, in which a coating film is dried at a high temperature, a pigment which does not discolor even at a high temperature of 100 to 400 ° C., which varies depending on the coating resin, is required.

In order to improve the workability, it is important that the pigment is a nonmagnetic powder having an appropriate size and excellent in dispersibility so that it can be handled easily.

[0008] The good dispersibility of the pigment means that the color tone becomes clear and the basic characteristics of the pigment, such as tinting strength and hiding power, are improved, as well as the gloss and sharpness of the coating film are improved. These improve the properties of the coating film such as the acid resistance and aging resistance of the coating film, and therefore, there is a strong demand for improvement in the dispersibility of the pigment.

Furthermore, in recent years, the natural environment and living environment have deteriorated due to the problem of acid rain, and in particular, the improvement of the acid resistance and aging resistance of the film-forming products and rubber and resin compositions used outdoors has been increasing. Highly required.

Heretofore, hematite particle powders containing Mn as a safe, harmless and non-magnetic black pigment have been known (JP-B-43-17288, JP-B-47-30085). Japanese Patent Publication No. 54-37004
JP-A-49-124127, JP-A-49-127127
-149200, JP-A-8-143316, etc.).

[0011]

Non-magnetic black pigments, which are excellent in blackness and heat resistance and more excellent in dispersibility, are currently most demanded. Has not yet been obtained.

That is, although the known magnetite particle powder is safe and harmless, it starts to change into maghemite at a temperature of 150 ° C. or higher, and thus changes color from black to brown and has a problem in heat resistance. . In addition, since the particles have magnetism, reagglomeration occurs between the particles, making dispersion difficult, resulting in poor workability. And when the coating film was formed using the magnetite particle powder, the acid resistance of the coating film was hardly good.

[0013] The above-mentioned known carbon blacks are not sufficiently heat-resistant, are ultrafine particles of about 0.01 to 0.1 µm, and are bulky powders, so that they are difficult to handle and have poor workability. Things. In addition, safety such as carcinogenicity,
Problems related to hygiene have also been pointed out.

The above-mentioned known fluorinated graphite is hard to say that it is safe, and since the hue changes greatly at about 500 ° C., it is not enough to have sufficient heat resistance and dispersibility.

The above-mentioned known hematite particle powder containing Mn is safe and harmless, but has a hue of reddish brown or blackish brown and insufficient blackness. In addition, the dispersibility is hardly sufficient. When a coating film or a rubber / resin composition was formed using the particle powder, acid resistance and aging resistance were hardly good.

Therefore, the present invention is safe, harmless,
It has excellent blackness and heat resistance, and it is possible to obtain a non-magnetic black pigment that is more excellent in dispersibility, and a non-magnetic black paint excellent in acid resistance and aging resistance using the non-magnetic black pigment. A technical problem is to obtain an excellent black rubber / resin composition.

[0017]

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

That is, according to the present invention, an average diameter of 0.1 to 1 having a hematite structure mainly containing iron containing Mn.
The Mn content of non-magnetic black granular particles of 0 μm or less is 5 to 70% by weight based on the non-magnetic black pigment powder, the powder pH value is 5.5 or more, and the content of soluble sodium salt is Non-magnetic black pigment powder characterized in that the amount is 500 ppm or less in terms of Na and the content of soluble sulfate is 200 ppm or less in terms of SO ₄ , and if necessary, the particle surface is made of aluminum. A non-magnetic black powder comprising the non-magnetic black granular particles coated with at least one of a hydroxide, an oxide of aluminum, a hydroxide of silicon, and an oxide of silicon; It is a pigment powder.

Further, the present invention is a non-magnetic black paint characterized in that any one of the above-mentioned non-magnetic black pigment powders is blended in a paint constituting base material.

Further, the present invention is a non-magnetic black rubber / resin composition characterized in that any one of the above-mentioned non-magnetic black pigment powders is blended in a rubber / resin composition constituent base material.

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

First, the nonmagnetic black pigment powder according to the present invention will be described.

The non-magnetic black powder according to the present invention was confirmed to be non-magnetic because of a hematite structure as a result of X-ray diffraction, as shown in Examples below.

The nonmagnetic black powder according to the present invention is composed of granular particles, and the average size of the particles is 0.1 to 10 μm.
If it is less than 0.1 μm, it is difficult to disperse the particles because they are fine particles. If it exceeds 10 μm, the particle size is too large, so that it is difficult to obtain a smooth surface when forming a coating film or a resin composition.

The geometric standard deviation (σg) of the particle diameter of the nonmagnetic black powder according to the present invention is 2.0 or less, preferably 1.7 or less, more preferably 1.5 or less. When σg exceeds 2.0, the proportion of the coarse particles increases, so that it becomes difficult to obtain smoothness of the surface when forming a coating film or a resin composition. Considering industrial properties such as productivity, σ
The lower limit of g is 1.01.

The nonmagnetic black powder according to the present invention has a Mn content of 5 to 40% by weight based on the nonmagnetic black pigment powder.
If it is less than 5% by weight, it is difficult to obtain the required blackness.
If it exceeds 40% by weight, the desired blackness can be obtained, but the blackness is saturated and there is no point in containing more than necessary. Preferably it is 9 to 35% by weight, more preferably 10 to 20% by weight.

The non-magnetic black powder according to the present invention has a powder pH of 5.5 or more. If the powder pH value is less than 5.5, many acidic impurities remain between the particles, so that cross-linking occurs and dispersibility is hindered. In consideration of dispersibility, the powder pH value is preferably 6.5 or more, and more preferably 8.0 or more. The upper limit is a powder pH value of 12 or less, preferably a powder pH value of 11 or less, and more preferably a powder pH value of 10 or less.

The non-magnetic black powder according to the present invention has a soluble sodium salt content of 500 ppm or less in terms of Na. If it exceeds 500 ppm, impurities including sodium salt are crosslinked between particles, and dispersibility is impaired. In consideration of the dispersibility of the black pigment powder in the vehicle, it is preferably 450 ppm or less, more preferably 4 ppm or less.
It is at most 00 ppm, even more preferably at most 300 ppm. In consideration of industrial properties such as productivity, the lower limit is about 0.01 ppm.

The non-magnetic black powder according to the present invention has a soluble sulfate content of 200 ppm or less in terms of SO ₄ . 2
If it exceeds 00 ppm, impurities including sulfates are crosslinked between particles, and dispersibility is impaired. Considering the dispersibility of the black pigment powder in the vehicle,
ppm or less, more preferably 150 ppm or less.
Considering the industrial properties such as productivity, the lower limit is 0.01
It is about ppm.

The nonmagnetic black powder according to the present invention has an L ^* value of 10 to 25, an a ^* value of -2.5 to 2.5 and a b ^* Value is -2.5 to 2.5
Therefore, it is not inferior to known black pigments. In consideration of the hue, the L ^* value is preferably from 10 to 24, and more preferably from 15 to 23. a ^* value is -2.5 ~
2.0 is preferred, and -2.0 to 1.0 is more preferred.
The b ^* value is preferably from -2.5 to 2.0, and from -2.5 to 1.
0 is more preferred.

The heat resistance of the nonmagnetic black powder according to the present invention is 0.
２．５2.5. If it exceeds 2.5, discoloration and the like become remarkable when resin coloring or the like is performed using black pigment powder, which is not preferable.

When a non-magnetic black paint according to the present invention is formed into a coating film, the L ^* value is 15 to 25 and the a ^* value is -2.5 to 2.5, as shown in Examples described later. Since the b ^* value is -2.5 to 2.5, it is comparable to the case where a known black pigment powder is used. The glossiness is 80% or more, and the acid resistance is ΔG value of 8.0.
Hereinafter, the ΔL ^* value is 1.0 or less. In consideration of the hue, the L ^* value is preferably 17 to 24, more preferably 20 to 23. a ^* value is preferably −2.5 to 2.0,
2.0 to 1.0 is more preferable. b ^* value is -2.5 ~
2.0 is preferred, and -2.0 to 1.0 is more preferred.
The gloss is preferably 83% or more, more preferably 85% or more. The acid resistance is preferably such that the ΔG value is 7.0 or less, and 6.0 or less.
The following is more preferred. The ΔL ^* value is preferably 0.8 or less, more preferably 0.6 or less.

The non-magnetic black rubber / resin composition according to the present invention has an L ^* value of 15 to 25 and an a ^* value of -2.5 to 2.5, as will be shown in Examples described later. And the b ^* value is-
Since it is 2.5 to 2.5, it is comparable to the case where a known black pigment powder is used. The result of visual observation of dispersibility was in the range of 4 to 5. The aging resistance is such that the proportion of discolored portions when heated at 190 ° C. for 90 minutes is 15% or less. Considering hue, L ^* value is 1
7-24 are preferable and 20-24 are more preferable. a ^*
The value is preferably -2.5 to 2.0, more preferably -2.0 to 1.0. The b ^* value is preferably -2.5 to 2.0,
-2.0 to 1.0 is more preferable. The aging resistance is preferably 10% or less, more preferably 5% or less.

Next, a method for producing the nonmagnetic black powder according to the present invention will be described.

The black pigment powder according to the present invention has an average particle size having a hematite structure containing iron as a main component and containing Mn obtained by the following production method described in the above-mentioned JP-A-4-144924. After wet-pulverizing a slurry containing octahedral particles or spherical particles having a particle size of 0.05 to 5.0 μm, the pH value of the slurry is adjusted to 13 or more, and the slurry is heated at a temperature of 80 ° C. or more. Separately, it can be obtained by washing with water and drying.

Octahedral particles having a hematite structure containing iron as a main component and containing Mn and having an average particle size of 0.05 to 5.0 μm are prepared by using an aqueous ferrous salt solution and an aqueous ferrous salt solution. The suspension containing the ferrous hydroxide colloid obtained by reacting 1.01 to 1.3 equivalents of an aqueous alkali hydroxide solution with respect to Fe ²⁺ is heated to a temperature range of 45 to 100 ° C. A suspension containing magnetite particles is formed by oxidizing the ferrous hydroxide colloid by a magnetite generation reaction in which an oxygen-containing gas is aerated while generating magnetite particles, and the suspension containing the magnetite particles contains Mn or Mn and Fe ²⁺ are added in the form of an aqueous solution, and the total F
Then, the suspension is heated and oxidized under the same conditions as the magnetite formation reaction, so that the surface of the magnetite particles is treated with hydroxide of Mn or Mn and Fe. The magnetite particles coated with a hydroxide and then coated with the hydroxide of Mn or the hydroxide of Mn and Fe are separated by filtration, washed with water, dried, and then heated in a temperature range of 750 to 1000 ° C. Obtained by firing.

Spherical particles having a hematite structure containing iron as a main component and containing Mn and having an average particle diameter of 0.1 to 10 μm are formed by using an aqueous ferrous salt solution and Fe ^{2+ in the} aqueous ferrous salt solution.
The suspension containing the ferrous hydroxide colloid obtained by reacting 0.80 to 0.99 equivalents of an aqueous alkali hydroxide solution with respect to the oxygen-containing suspension is heated to a temperature range of 45 to 100 ° C. A suspension containing magnetite particles is generated by oxidizing the ferrous hydroxide colloid by a reaction to generate magnetite particles through which gas is passed to generate magnetite particles, and the suspension containing the magnetite particles is added to the suspension containing the magnetite particles. After adding an aqueous solution of an Mn compound of 8 to 150 atomic% with respect to Fe and an aqueous solution of an alkali hydroxide exceeding 1.00 equivalent with respect to the Mn compound and the remaining Fe ²⁺ , the same reaction as in the magnetite formation reaction was performed. By heating and oxidizing under the conditions, the surface of the magnetite particles is changed to hydroxide or Mn of Mn.
And a hydroxide of Fe, and then the Mn
The magnetite particles coated with a hydroxide or a hydroxide of Mn and Fe are filtered, washed with water, dried,
It is obtained by heating and baking in a temperature range of 1000 ° C.

The conditions for producing octahedral particles and spherical particles having a hematite structure containing iron as a main component and containing Mn will be described.

As the aqueous ferrous salt solution, ferrous sulfate, ferrous chloride and the like can be used.

As the aqueous solution of the Mn compound, manganese sulfate, manganese chloride or the like can be used. In order to uniformly coat the surface of the magnetite particles, it is preferable to add the aqueous solution.

As the aqueous alkali hydroxide solution, sodium hydroxide, potassium hydroxide and the like can be used.

As a method for producing octahedral magnetite particles from which the non-magnetic black pigment powder of octahedral particles is obtained, for example, the technical means disclosed in Japanese Patent Publication No. 44-668 is used. Can be used.

The amount of the aqueous alkali hydroxide solution is 1.01 to 1.3 equivalents to Fe ²⁺ in the aqueous ferrous salt solution.
When the amount is less than 1.01 equivalent, it is difficult to control the alkali addition ratio, and in some cases, the equivalent ratio may be less than 1.0, and it is also difficult to control the particle size and the like. When the amount exceeds 1.3 equivalents, acicular goethite particles are mixed.

The reaction temperature is in the range of 45 to 100 ° C. If the reaction temperature is lower than 45 ° C., needle-like goethite particles may be present. Magnetite particles are produced but are not economical.

The amount of Mn that coats the surface of the octahedral magnetite particles with Mn hydroxide or Mn and Fe hydroxide is 8 to 15 with respect to the total Fe in the suspension.
0 atomic%. When Mn is less than 8 atomic%, a nonmagnetic pigment powder is obtained, but a desired blackness is hardly obtained. If it exceeds 150 atomic%, the desired blackness can be obtained, but the blackness is saturated and there is no point in containing more than necessary. Preferably 10 to 100 atomic%,
More preferably, it is in the range of 15 to 50 atomic%.

[0046] Further, if necessary, to add Fe ²⁺ together with Mn is in order to facilitate coating the Mn on the particle surfaces of magnetite particles, the amount of Fe ²⁺ to be added, in suspension Less than 25 atomic% based on the total Fe, 2
When it exceeds 5 atomic%, a nonmagnetic black pigment powder can be obtained, but the blackness is slightly inferior.

The Fe ²⁺ compound to be added is desirably the same as the ferrous salt aqueous solution used for forming the magnetite particles. In the coating treatment, an alkali hydroxide aqueous solution is further added. May be. The conditions such as the processing temperature for coating may be the same as the conditions for forming the magnetite particles.

As a method for producing spherical magnetite particles from which the nonmagnetic black pigment powder of the spherical particles is obtained, for example, the technical means disclosed in Japanese Patent Publication No. 51208/1987 can be used. .

The amount of the aqueous alkali hydroxide solution is 0.80 to 0.99 equivalent to Fe ²⁺ in the aqueous ferrous salt solution. If it is less than 0.80 equivalent or more than 0.99 equivalent, it is difficult to produce spherical magnetite particles.

The reaction temperature is in the range of 45 to 100 ° C. If the reaction temperature is lower than 45 ° C., needle-like goethite particles may be present. Generates but is not economical.

The amount of Mn added to the spherical magnetite particles is also 8 to 150 atomic% based on the total Fe in the suspension.
It is. Preferably it is 10 to 100 atomic%, and more preferably it is in the range of 15 to 50 atomic%. The reason is the same as in the case of the octahedral magnetite particles.

The amount of the alkali hydroxide added to coat Mn and the hydroxide of Fe is more than 1.00 equivalent to the added Mn compound and the remaining Fe ²⁺ . If the amount is less than 1.00 equivalent, since Mn and Fe ²⁺ do not precipitate in total, it is impossible to coat uniformly. When it exceeds 1.00 equivalent, it is preferably 1.01 to 1.3 equivalent in consideration of economy.

The aqueous alkali hydroxide solution to be added is desirably the same as the aqueous alkali hydroxide solution used for producing the magnetite particles, and the conditions such as the treatment temperature for coating are determined by the conditions for producing the magnetite particles. May be the same as

The reaction can be oxidized by passing an oxygen-containing gas (eg, air) through the reaction suspension, and is preferably performed in a reactor equipped with a stirring function.

Magnetite particles coated with a hydroxide of Mn or a hydroxide of Mn and Fe are then 750-10
By heating in a temperature range of 00 ° C., granular particles having a hematite structure mainly containing iron containing Mn are obtained. 7
When the temperature is lower than 50 ° C., the degree of blackness is insufficient. When the temperature exceeds 1000 ° C., the particles become too large and the coloring power cannot be obtained.

The heating and firing are performed in the atmosphere. The heating and firing in the air is for oxidizing the magnetite to transform it into a hematite structure.

Incidentally, Si, Al, P, B, Cu, Zn, C
Metal compounds such as r, Co, Sn, Cd, V, and Mo may be added before or during the reaction in the above-mentioned production methods.
The surface of the magnetite particles coated with the hydroxides of n and Fe may be coated with the above-mentioned metal compound to form and maintain the particle shape.

The granular particles having a hematite structure containing iron as a main component and containing Mn are then coarsely pulverized by a dry method to loosen the coarse particles, then slurried, and then wet-pulverized. Loose coarse grains. The wet pulverization may be performed using a ball mill, a sand grinder, a Dyno mill, a colloid mill, or the like so that coarse particles of at least 44 μm or more are eliminated. The degree of the wet pulverization is 10% or less, preferably 5% or less, and more preferably 0% of coarse particles having a size of 44 μm or more. If coarse particles having a size of 44 μm or more remain in excess of 10%, it is difficult to obtain a treatment effect in an aqueous alkaline solution in the next step.

A slurry containing granular particles having a hematite structure containing iron as a main component and containing Mn from which coarse particles have been removed is adjusted to a pH of 13 or more by adding an aqueous alkali solution such as sodium hydroxide to the slurry. After adjusting to 80 ℃
Heat treatment is performed at the above temperature.

The concentration of the alkaline suspension having a pH value of 13 or more and containing granular particles having a hematite structure containing Mn as a main component of iron is preferably 50 to 250 g / l.

When the pH value in an alkaline suspension containing granular particles having a hematite structure containing iron as a main component and containing Mn is less than 13, the soluble sodium salt present inside the particles and on the surface of the particles may be used. Insufficient washing out of soluble sulfates and the like. The upper limit is a pH value of about 14. Considering the effect of washing out soluble sodium salts, soluble sulfates and the like, and the washing effect for removing alkali such as sodium adhering to the particle surface during the treatment with the alkaline aqueous solution, the pH value is 13.1 to 13 .8 is preferred.

The heating temperature of the alkaline aqueous solution having a pH value of 13 or more containing the particulate particles having a hematite structure containing Mn as a main component is preferably 80 ° C. or more, more preferably 90 ° C. or more. If the temperature is lower than 80 ° C., the washing out of soluble sodium salts and soluble sulfates present inside the particles and on the surface of the particles becomes insufficient. The upper limit of the heating temperature is preferably 103 ° C, more preferably 1 ° C.
00 ° C. If the temperature exceeds 103 ° C., an autoclave or the like is required, and the liquid to be treated boils under normal pressure, which is not industrially advantageous.

The particles heat-treated in an alkaline aqueous solution are as follows:
By a conventional method, filtration and washing with water are performed to remove soluble sodium salts and soluble sulfates washed out from the inside of the particles and from the particle surface, and alkalis such as sodium attached to the particle surface during the treatment with the aqueous alkali solution, and then drying. .

Examples of the water washing method include a method generally used in industry such as a method of washing by decantation, a method of washing by a dilution method using a filter thickener, and a method of washing by passing water through a filter press. Just use it.

It should be noted that if the soluble sodium salt or soluble sulfate contained in the inside of the granular particles having a hematite structure containing Mn as a main component is washed out with water, the subsequent steps Even if a soluble sodium salt or a soluble sulfate adheres to the particle surface of the particle in a step, for example, a coating treatment step to be described later, it can be easily removed by washing with water.

The granular particles heat-treated in an alkaline aqueous solution may be heat-treated in an alkaline aqueous solution if necessary.
It may be filtered by a conventional method, washed with water, and then coated with at least one of aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide.

The coating treatment is performed by adding an aluminum compound to a water suspension obtained by dispersing a cake, slurry, and dry powder of granular particles heat-treated in an alkaline aqueous solution in an aqueous solution.
By adding a silicon compound or both compounds and mixing and stirring, or, if necessary, by adjusting the pH value, on the particle surface of the granular particles, aluminum hydroxide, aluminum oxide, silicon A hydroxide and a silicon oxide may be applied, followed by filtration, washing, drying and pulverization. If necessary, a deaeration / consolidation treatment may be performed.

Aluminum compounds added in the coating treatment include aluminum acetate, aluminum sulfate,
Aluminum salts such as aluminum chloride and aluminum nitrate, alkali aluminates such as sodium aluminate, alumina sol and the like can be used.

The addition amount of the aluminum compound is 0.01 to 50.00% by weight in terms of Al based on the granular particles heat-treated in an aqueous alkaline solution. If it is less than 0.01% by weight, the dispersion in the vehicle is insufficient, and if it exceeds 50.00% by weight, the coating effect is saturated, so that there is no point in adding more than necessary.

As the silicon compound to be added in the coating treatment, No. 3 water glass, sodium orthosilicate, sodium metasilicate, colloidal silica and the like can be used.

The amount of the silicon compound added is 0.01 to 50.00% by weight in terms of SiO _{2 based} on the granular particles heat-treated in an aqueous alkali solution. If it is less than 0.01% by weight, the dispersion in the vehicle is insufficient, and if it exceeds 50.00% by weight, the coating effect is saturated, so that there is no point in adding more than necessary.

When the aluminum compound and the silicon compound are used in combination, the total amount of the converted amount of Al and the converted amount of SiO ₂ is 0.01 to 50.00% with respect to the granular particles heat-treated in an alkaline aqueous solution. % By weight is preferred.

Next, the paint according to the present invention will be described.

The compounding ratio of the nonmagnetic black pigment powder in the paint according to the present invention can be used in the range of 0.1 to 200 parts by weight with respect to 100 parts by weight of the base material constituting the paint. If so, preferably 0.1 to 1
00 parts by weight, more preferably 0.1 to 50 parts by weight.

In the present invention, a resin, a solvent, and, if necessary, an extender, a drying accelerator, a surfactant, a curing accelerator, an auxiliary agent, and the like are blended as the paint constituting base material.

As the resin, an acrylic resin, an alkyd resin, a polyester resin, a polyurethane resin, an epoxy resin, a phenol resin, a melamine resin, an amino resin and the like which are usually used for solvent-based paints can be used. For water-based paints, commonly used water-soluble alkyd resins, water-soluble melamine resins, water-soluble acrylic resins,
A water-soluble urethane emulsion resin can be used.

As the solvent, toluene, xylene, butyl acetate, methyl acetate, methyl isobutyl ketone, butyl cellosolve, ethyl cellosolve, butyl alcohol, aliphatic hydrocarbon, etc., which are generally used for solvent-based paints, can be used.

For water-based paints, butyl cellosolve, butyl alcohol and the like which are usually used in addition to water can be used.

As defoaming agents, Nopco 8034 (trade name), SN deformer 477 (trade name), SN deformer 5013 (trade name), SN deformer 247
(Trade name), SN Deformer 382 (Trade name) (all manufactured by San Nopco Co., Ltd.), Anti-Home 0
Commercial products such as No. 8 (trade name) and Emulgen 903 (trade name) (both manufactured by Kao Corporation) can be used.

Next, the rubber / resin composition according to the present invention and a method for producing the same will be described.

The compounding ratio of the nonmagnetic black pigment powder in the rubber / resin composition according to the present invention can be used in the range of 0.01 to 200 parts by weight per 100 parts by weight of the constituent base material. In consideration of handling of the resin composition, the amount is preferably 0.05 to 100 parts by weight, more preferably 0.1 to 50 parts by weight.

As the constituent base material in the rubber or resin composition according to the present invention, together with a nonmagnetic black pigment powder and rubber or a known thermoplastic resin, if necessary, a lubricant, a plasticizer,
Additives such as antioxidants, ultraviolet absorbers, and various stabilizers are added.

The amount of the additive may be 50% by weight or less based on the total amount of the nonmagnetic black pigment powder and the rubber or thermoplastic resin. When the content of the additive exceeds 50% by weight, the moldability decreases.

The rubber or resin composition according to the present invention is obtained by thoroughly mixing the rubber or resin raw material and the nonmagnetic black pigment powder in advance and then applying a strong shearing action under heating using a kneader or an extruder. After the aggregate of the black pigment powder is broken and the black pigment powder is uniformly dispersed in the rubber or the resin, the black pigment powder is molded into a shape suitable for the purpose and used.

[0085]

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

The average particle size of the black pigment was about 350 particles as shown in a photograph (× 80000) obtained by magnifying an electron micrograph (× 20000) four times in the vertical and horizontal directions.
The diameter in the fixed direction was measured for each piece, and the average value was shown.

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

The specific surface area was indicated by a value measured by the BET method.

The amounts of Mn, Al and Si present inside the particles and on the surface of the black pigment powder were measured using a fluorescent X-ray analyzer 3063 (manufactured by Rigaku Corporation).
The measurement was performed according to SK0119 “General rules for X-ray fluorescence analysis”.

The powder pH value was determined by weighing 5 g of a sample in a 300 ml Erlenmeyer flask, adding 100 ml of boiled pure water, heating and maintaining the boiled state for about 5 minutes, then stoppering and allowing to cool to room temperature. After that, open the stopper, add pure water equivalent to the weight loss, stopper again, shake for 1 minute, leave for 5 minutes,
The pH of the obtained supernatant was measured according to JIS Z 8802-7, and the obtained value was defined as a powder pH value.

The content of the soluble sodium salt and the content of the soluble sulfate were determined by using the above-prepared supernatant prepared for the measurement of the powder pH value. The solution was filtered using 5C filter paper, and N
a ⁺ and SO ₄ ^2- were measured using an inductively coupled plasma emission spectrometer (manufactured by Seiko Instruments Inc.).

The hue of the black pigment powder was obtained by kneading 0.5 g of a sample and 0.7 cc of castor oil with a Hoover-type muller to form a paste, and adding 4.5 g of clear lacquer to the paste.
, Kneaded and made into a paint, and 6 mi
A coated piece (coating thickness: about 30 μm) was prepared using an applicator (1), and the coating piece was subjected to JIS using a multi-source spectrophotometer MSC-IS-2D (manufactured by Suga Test Instruments Co., Ltd.). The color index L ^* value, a ^* value, and b ^* value were indicated by measured values according to Z8729.

Similarly, regarding the hue of the paint using the black pigment powder, the hue of the coating film using the paint having the composition described below, and the hue of the resin composition, the hue of the resin plate having the composition described later were determined using the multi-light source. Spectrophotometer MSC-IS-2D
Using JIS Z8729 (manufactured by Suga Test Instruments Co., Ltd.)
Color index L ^* value, a ^* value, b ^*
The values are shown as measured values.

The a ^* value indicates reddish color, and a larger value means stronger reddish color. The b ^* value represents yellowness, and a larger value means a stronger yellowness. The L ^* value represents lightness.

The heat resistance of the black pigment powder was measured by placing 10 g of a sample in a porcelain crucible, performing a heat treatment at 500 ° C. for 3 hours using an electric furnace, and after cooling, measuring the hue of the sample powder. And the change in hue after the heat treatment was measured, and was represented by ΔE ^* expressed by the following equation based on the colorimetric value before the heat treatment. The smaller the ΔE ^* , the smaller the change in hue and the better the heat resistance. ΔE ^* = ｛(ΔL ^* ) ² + (Δa ^* ) ² + (Δ
b ^* ) ² ｝ ^1/2 where ΔL ^* : difference in L ^* value between samples to be compared Δa ^* : difference in a ^* value between samples to be compared Δb ^* : difference in b ^* value between samples to be compared

The remaining amount of the sieve after the wet pulverization is determined by separately obtaining the slurry concentration after the wet pulverization, and passing a slurry corresponding to 100 g of the solid content of the black pigment powder through a 325 mesh (44 μm mesh) sieve. And the amount of solids remaining in the sieve was determined.

The dispersibility in the paint vehicle was examined by the glossiness of the coated surface of a coating film produced in the same manner as in the embodiment of the invention described later.

The gloss was measured using a gloss meter UGV-5D.
(Suga Test Machine Co., Ltd.) was used to measure and determine the gloss at 20 °. The higher the gloss value, the better the dispersibility.

The paint viscosity was measured at 25 ° C. using a E-type viscometer (cone plate viscometer) EMD-R (manufactured by Tokyo Keiki Co., Ltd.) at a shear rate of 25 ° C. D = 1.92 sec ^-1 .

The dispersibility in the resin composition was evaluated by visual evaluation of the number of undispersed aggregated particles on the surface of the obtained resin composition, and evaluated on a scale of 1 to 5. 5 indicates that the dispersion state is the best. 5: No undispersed substance is observed. 4: 1 to 4 particles are observed per 1 cm ² . 3: 5 to 9 particles are observed per 1 cm ² . 2: 10 to 49 cells are found per 1 cm ² . 50 or more are observed per 1 cm ² .

The acid resistance is determined by coating a coating material using the black pigment powder obtained in Examples described later with a cold-rolled steel plate (0.8 mm × 70 mm).
mm × 150mm: 150μ in JIS G-3141)
A sample having a coating film produced by coating and drying with a thickness of m is prepared, and the gloss and the hue are measured. Next, 100
A 5 wt% sulfuric acid aqueous solution is put into a 0 cc beaker, and the sample is hung with a thread and immersed to a depth of about 120 mm.
For 24 hours.

Next, the sample is taken out of the aqueous sulfuric acid solution, gently washed with running water, and the water is shaken off. Then, the gloss and the hue of the central portion of the sample are measured. The change in gloss (ΔG value) and the change in hue (ΔL) before and after immersion in a sulfuric acid aqueous solution.
^* Value: Difference in L ^* value between samples) was measured, and the acid resistance was evaluated based on the magnitude of the difference. The smaller the ΔG value and the ΔL ^* value, the better the acid resistance.

The aging resistance can be measured by using a colored resin plate (15 mm × length) kneaded with black pigment powder obtained in Examples described later.
(15 mm wide × 1 mm thick) when heated at 190 ° C., a value obtained by measuring an area S of a portion where the resin is degraded due to discoloration and an area S ₀ (15 m) of the surface of the colored resin plate before heating.
m × 15 mm = 2.25 cm ² ) with a ratio S / S ₀ of 5%
It was determined by quantification in increments. That is, (S / S ₀ )
When × 100 is 0%, it indicates that there is no deterioration, and (S
When / S ₀ ) × 100 is 100%, it indicates that the resin is completely degraded.

<Production of magnetite particles> The concentration was 1.4.
300 l of 0 mol / l ferrous sulfate aqueous solution was previously prepared in a reactor equipped with a stirrer in 210 l of water and 15.7.
An aqueous ferrous salt solution containing ferrous hydroxide was produced at a pH of 13 or more and a temperature of 85 ° C. in addition to 60 L of a 5N aqueous sodium hydroxide solution.

The aqueous ferrous salt solution containing ferrous hydroxide was air-flowed at a temperature of 90 ° C. at a rate of 250 l / min for 90 minutes to produce magnetite particles.

Next, the magnetite particles 32.4 k
g of an aqueous suspension containing 570 g, 100 l of an aqueous ferrous sulfate solution having a concentration of 1.4 mol / l and 100 l of a manganese sulfate aqueous solution containing 1.4 mol / l (Mn content corresponds to 20 atomic% with respect to Fe and Mn). ) And 50 l of a 11.2 N aqueous sodium hydroxide solution (corresponding to the amount that neutralizes the added Mn amount and the added Fe ²⁺ amount). Air was passed through for 180 minutes to produce magnetite particles covering the Mn and Fe hydroxides. The produced particles were separated by filtration, washed with water, dried and pulverized by a conventional method to obtain a black powder.

Subsequently, the obtained black powder was passed through a continuous electric furnace having a furnace tube made of ceramic, and was placed in air at 900 ° C.
A black powder was obtained with an average residence time of 60 minutes.

The obtained black powder had an average particle size of 0.30 μm as shown in the electron microscope (× 20000) of FIG.
m, granular particles having a geometric standard deviation value of 1.39 for the particle diameter, and a BET specific surface area of 3.8 m ² / g. As a result of X-ray fluorescence analysis, the Mn content was 13.8% by weight,
Powder pH value is 7.4, soluble sodium salt content is N
712 ppm in terms of a, and soluble sulfate content is SO ₄
The conversion is 856 ppm, and the hue is L ^* value of 2
2.10, a ^* value was 0.21, and b ^* value was -1.31.

As a result of X-ray diffraction, a hematite peak was observed. As for magnetism, the magnetization value when an external magnetic field of 10 kOe was applied was 0.31 emu / g, which was almost the same as that of hematite.

Further, a heat resistance test was performed on 10 g of the above black powder, and the hue of the black powder after the heat treatment had an L ^* value of 2
2.08, the a ^* value was 0.16, the b ^* value was -1.26, and the heat resistance ΔE was 0.07, indicating that the heat resistance was excellent.

<Alkali Heat Treatment of Black Pigment Powder> Next, 20 kg of this black powder was brought into contact with 150 l of pure water using a stirrer, and further homogenized with a homomic line mill (manufactured by Tokushu Kika Kogyo Co., Ltd.). The slurry was passed to obtain a slurry of a black powder.

Subsequently, the obtained black slurry was transferred to a horizontal SG.
Using M (Mighty Mill: Inoue Seisakusho Co., Ltd.), five passes were performed at a shaft rotation speed of 2000 rpm.
The sieve residue of the black powder in the obtained slurry at 325 mesh (mesh size: 44 μm) was 0%.

The concentration of the obtained black powder slurry was adjusted to 10
0 g / l and 150 l of the slurry were collected. While stirring the slurry, a 6N aqueous sodium hydroxide solution was added to adjust the pH value of the slurry to 13.1. continue,
The slurry was heated with stirring to a temperature of 95 ° C. and maintained at that temperature for 3 hours.

Next, this slurry was washed with water by a decantation method to obtain a slurry having a pH value of 10.5. For the sake of accuracy, the slurry concentration was confirmed at this point to be 99 g / l. Take 50 l of this slurry,
The resultant was separated by filtration and dried to obtain a black powder (A).

The obtained black powder had an average particle diameter of 0.30 μm as shown in an electron microscope (× 20000) in FIG.
m, granular particles having a geometric standard deviation value of 1.39 for the particle diameter, and a BET specific surface area value of 4.1 m ² / g. As a result of X-ray fluorescence analysis, the Mn content was 13.7% by weight,
Powder pH value is 8.6, soluble sodium salt content is N
The content of soluble sulfate was 32 ppm in terms of SO ₄ , and the heat resistance ΔE was 0.07 in terms of a. Further, the hue has an L ^* value of 22.12 and an a ^* value of 0.1.
9. The b ^* value was −1.26.

As a result of X-ray diffraction, a hematite peak was observed. As for magnetism, the magnetization value when an external magnetic field of 10 kOe was applied was 0.36 emu / g, which was almost the same as that of hematite.

<Coating of Black Pigment Powder> The remaining 100 l of the slurry was heated to 60 ° C., and a 1.0 mol / l sodium aluminate aqueous solution 36
67 ml (1.0% by weight in terms of Al based on black pigment powder)
Corresponds to. ) Was added and the mixture was kept for 30 minutes, and then the pH value was adjusted to 8.0 with acetic acid. After maintaining in this state for 30 minutes, 685.1 g of an aqueous solution of No. 3 water glass (corresponding to 2.0% by weight in terms of SiO _{2 based on} black pigment powder)
Was added and kept for 30 minutes, and then the pH value was adjusted to 7.5 using acetic acid. Subsequently, the powder is filtered, washed with water, dried and pulverized to obtain a black powder (B) consisting of black particles whose surfaces are coated with aluminum hydroxide and silicon oxide.
I got

As a result of electron microscopic photograph observation, the obtained black powder was granular particles having an average particle diameter of 0.30 μm, a geometric standard deviation of the particle diameter of 1.39, and a BET specific surface area of 11.2 m. ² / g. As a result of X-ray fluorescence analysis, M
The n content was 13.5% by weight, the Al content was 0.97% by weight, the SiO ₂ content was 1.93% by weight,
The value was 8.1, the content of soluble sodium salt was 123 ppm in terms of Na, and the content of soluble sulfate was 7 in terms of SO _4.
The heat resistance was 8 ppm, and ΔE was 0.1. In addition, the hue is L ^* value of 22.31, a ^* value of 0.37, b ^*
The value was -1.31. As a result of X-ray diffraction, a peak indicating a hematite structure was observed.

<Production of paint using black pigment powder>
Using 10 g of each of the black pigment powders (A) and (B) in a 0 ml glass bottle, the coating composition was blended in the following ratio, and mixed and dispersed with 90 g of 3 mmφ glass beads for 90 minutes using a paint shaker to prepare a mill base.

The obtained coating composition was as follows. Black pigment powder (A) or (B) 12.2 parts by weight Amino alkyd resin 19.5 parts by weight (Amilac No. 1026: manufactured by Kansai Paint Co., Ltd.) Thinner 7.3 parts by weight

Using the above-mentioned mill base, the paint composition was blended in the following proportions and mixed and dispersed for further 15 minutes with a paint shaker to contain paint (A) containing black pigment powder (A) and black pigment powder (B). Paint (B) was obtained.

The coating composition obtained was as follows. Mill base 39.0 parts by weight Amino alkyd resin 61.0 parts by weight (Amirac No. 1026: manufactured by Kansai Paint Co., Ltd.)

Next, the obtained paint was applied to a cold-rolled steel plate (0.
8 mm x 70 mm x 150 mm: JIS G-314
1) was coated and dried with a thickness of 150 μm.

The coating film produced using the paint (A) had a gloss of 96% and a hue of L ^* value of 22.81, a ^* value of 0.41, and b ^* value of -1.49. The gloss change ΔG value based on the acid resistance test of the coating film was 3.8%, and the lightness change Δ
The L ^* value was 0.31.

The coating film produced using the coating material (B) had a glossiness of 105% and a hue of L ^* value of 22.76, a ^* value of 0.37 and b ^* value of -1.51. The gloss change ΔG value based on the acid resistance test of the coating film is 2.1% and the lightness change Δ
The L ^* value was 0.10.

<Production of resin composition containing black pigment powder>
Using each of the black pigment powders (A) and (B), 1.5 g of the black pigment powder and the polyvinyl chloride resin powder 103E
48.5 g of P8D (manufactured by Nippon Zeon Co., Ltd.) was weighed, placed in a 100 cc polybeaker, and mixed well with a spatula to obtain a mixed powder.

To the obtained mixed powder, 0.5 g of calcium stearate was added and mixed, the clearance of a hot roll heated to 160 ° C. was set to 0.2 mm, and the mixed powder was kneaded little by little into the roll. After the kneading was continued until the resin composition was integrated, the resin composition was peeled off from the roll and used as a colored resin plate raw material.

Next, the above resin composition was sandwiched between stainless steel plates whose surfaces were polished, placed in a hot press heated to 180 ° C., and pressed under a pressure of 1 ton / cm ² to form a colored resin having a thickness of 1 mm. Plates (A) and (B) were obtained.

The dispersion state of the obtained colored resin plate (A) was 5. 1.5cm colored resin plate (A)
The three test pieces cut into corners were put into a gear oven heated to 190 ° C., taken out one by one every 30 minutes, and the state of resin deterioration was examined. The degree of deterioration after 30 minutes (S / S)
₀ × 100) is 0%, the degree of resin deterioration after 60 minutes is 5%,
The degree of resin deterioration after 90 minutes was 5%.

The dispersion state of the obtained colored resin plate (B) was 5. 1.5cm colored resin plate (B)
The three test pieces cut into corners were placed in a gear oven heated to 190 ° C., taken out one by one every 60 minutes, and the state of resin deterioration was examined. The degree of deterioration after 30 minutes (S / S)
₀ × 100) is 0%, the degree of resin deterioration after 60 minutes is 0%,
The degree of resin deterioration after 90 minutes was 0%.

[0131]

First, the most important point in the present invention is that the Mn content of nonmagnetic black granular particles having an average diameter of 0.1 to 10 μm and having a hematite structure containing iron as a main component and containing Mn is Fe. 5 to 70% by weight, the powder pH value is 5.5 or more, the content of soluble sodium salt is 500 ppm or less in terms of Na, and the content of soluble sulfate is in terms of SO ₄ . This is the fact that the nonmagnetic black granular particles having a concentration of 200 ppm or less have excellent blackness and heat resistance, and are more excellent in dispersibility.

Regarding the reason why the blackness is excellent, the present inventors have found that when Mn is unevenly contained inside the particles or hematite particles which are contained only in the surface layer, the blackness is excellent. And 750 of magnetite particles coated with Mn hydroxide or Mn and Fe hydroxide.
By heating and baking in a temperature range of ~ 1000 ° C, magnetite is oxidized to change into a hematite structure, and when the coated Mn hydroxide diffuses from the particle surface into the particle, the blackness is excellent. Therefore, it is considered that the location of Mn in the hematite structure has an influence.

The reason why the heat resistance is excellent is that the present inventors believe that particles having a hematite structure containing iron as a main component and containing Mn are produced at a high temperature of 750 ° C. or higher. thinking.

Regarding better dispersibility, the inventor of the present invention concluded that solid crosslinkage was reduced by the fact that soluble sodium salts and soluble sulfates derived from the raw materials causing solid crosslinkage could be removed by alkali treatment. It is thought that the dispersibility was improved because it was disentangled and the coagulation was released.

An important point of the present invention is that a paint or a rubber / resin composition obtained by using the particles having a hematite structure containing iron as a main component and containing Mn according to the present invention is black. It is the fact that, in addition to being excellent in degree and heat resistance, in the case of a paint, acid resistance is excellent, and in the case of a rubber / resin composition, aging resistance is excellent.

It is not yet clear why the acid resistance of the paint and the aging resistance of the rubber / resin composition are excellent.
The present inventor believes that components that inhibit acid resistance in the black powder after the heat treatment, for example, soluble sodium salts and soluble sulfates derived from the raw materials could be removed by the alkali treatment.

[0137]

Next, examples and comparative examples will be described.

<Production of Black Pigment Powder> Examples 1 to 6 Starting materials 1 to 4 were produced in the same manner as in the embodiment of the present invention.

Table 1 shows the properties of the obtained starting materials 1 to 4.

Using the starting materials 1 to 4, a black pigment powder having a hematite structure containing iron as a main component and containing Mn was produced in the same manner as in the embodiment of the present invention.

Table 2 shows the main conditions and various characteristics at this time.

[0142]

[Table 1]

[0143]

[Table 2]

Examples 7 to 12 Various kinds of black powder having a hematite structure containing Mn as a main component and having a hematite structure, the presence or absence of wet pulverization, and the pH value, temperature, and time in the heat treatment in an alkaline aqueous solution were varied. Other than the above, a black pigment powder treated with an aqueous alkali solution was obtained in the same manner as in the embodiment of the present invention.

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

[0146]

[Table 3]

Examples 13 to 18 The surface of the particles was changed in the same manner as in the embodiment of the present invention except that the black pigment powders of Examples 7 to 12 were used and the type and amount of the surface coating were variously changed. A black pigment powder consisting of black particles covered with the coating was obtained.

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

[0149]

[Table 4]

Comparative Examples 1 to 10 Comparative Examples 1 to 10 each being a black pigment powder having a hematite structure containing iron as a main component and containing Mn before alkali treatment.
3. Comparative Examples 4 to 7 which are known black pigment powders and Comparative Examples 8 to 10 which are black pigment powders having a hematite structure mainly containing iron containing Mn after alkali treatment were prepared.

Tables 5 and 6 show the properties of these black pigment powders.

The Mn solid solution iron oxide pigment powder of Comparative Example 7 was produced according to the production method described in Japanese Patent Application Laid-Open No. 8-143316.

[0153]

[Table 5]

[0154]

[Table 6]

<Manufacture of Paint> Examples 19 to 30 and Comparative Examples 11 to 20 A paint was manufactured in the same manner as in the embodiment of the present invention except that the type of the black pigment powder was variously changed. Was formed.

Table 7 shows the main production conditions and coating film properties at this time.
And Table 8 below.

[0157]

[Table 7]

[0158]

[Table 8]

<Production of Resin Composition> Examples 31 to 42 and Comparative Examples 21 to 30 Resin compositions were obtained in the same manner as in the above embodiment of the present invention, except that the type of black pigment powder was variously changed. Was.

Tables 9 and 10 show the main production conditions and various characteristics at this time.

[0161]

[Table 9]

[0162]

[Table 10]

[0163]

The non-magnetic black pigment powder according to the present invention has excellent blackness and heat resistance, and is more excellent in dispersibility. It is suitable as a filler.

The paint according to the present invention can provide a coating film having excellent blackness and excellent acid resistance due to the use of the non-magnetic black pigment powder having the above-mentioned various properties. .

The rubber / resin composition according to the present invention has excellent blackness and excellent aging resistance due to the use of the nonmagnetic black pigment powder having the above-mentioned various properties. A resin composition can be obtained.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (× 20000) showing a particle structure of a black pigment powder having a hematite structure containing iron as a main component and containing Mn before alkali treatment obtained in an embodiment of the present invention. is there.

FIG. 2 is an electron microscope showing a particle structure of a black pigment powder obtained by an embodiment of the present invention and subjected to a heat treatment with an alkaline aqueous solution having a hematite structure containing iron as a main component and having a main component of Mn before the alkali treatment. It is a photograph (x20000).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09C 1/24 C09C 1/24 C09D 7/12 C09D 7/12 Z

Claims (4)

[Claims] An Mn content of nonmagnetic black granular particles having an average diameter of 0.1 to 10 μm or less and having a hematite structure containing iron as a main component containing Mn is 5 to 5% with respect to the nonmagnetic black pigment powder. 40% by weight and a powder pH value of 5.
A non-magnetic black powder having a content of soluble sodium salt of 500 ppm or less in terms of Na and a soluble sulfate content of 200 ppm or less in terms of SO ₄ , which is not less than 5; Pigment powder. 2. The main component is iron containing Mn whose particle surface is coated with at least one of aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. The Mn content of nonmagnetic black particulate particles having a hematite structure and having an average diameter of 0.1 to 10 μm is 5 to 40% by weight based on the nonmagnetic black pigment powder, and the powder pH value is 5.5 or more. Te, and, following 500ppm in a content of Na in terms of soluble sodium salt, a non-magnetic black pigment powder, wherein the content of soluble sulfate salt is a non-magnetic black powder is 200ppm or less in terms _of SO _4. 3. A non-magnetic black paint, wherein the non-magnetic black pigment powder according to claim 1 or 2 is blended in a paint constituting base material. 4. A non-magnetic black rubber / resin composition comprising the non-magnetic black pigment powder according to claim 1 or 2 incorporated into a rubber / resin composition constituent base material.