JPS6032853A - Pigment and its preparation - Google Patents

Abstract

PURPOSE:To obtain novel black - grayish white pigment having improved safety, stability to oxidation, and miscibility, consisting of aggregate of particles of integrated Al metal part and alumina part, by oxidizing electrochemically Al foil having specific thickness and grinding it. CONSTITUTION:Al foil having 1-1,000mu, preferably 5-500mu thickness, for example, is electrochemically oxidized using an aqueous solution of an inorganic acid such as sulfuric acid, etc. as an electrolyte at 1-300V voltage at 1-200 mA/cm<2> current density at 0-60 deg.C bath temperature. It is then ground (preferably 0.2-20mu average particle diameter), to give the desired pigment consisting of aggregate of particles of integrated Al metal part and alumina part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel pigments, more particularly alumina pigments which have a black to grayish-white color tone due to the partial content of aluminum metal, and a method for producing the same.

Currently, commonly used black pigments are carbon black and black iron oxide.

Further, as a special material, there is titanium black obtained by treating gold RT direct and TiO2 under a reducing atmosphere.

Carbon black has a long history as a black pigment, is cheap, stable, and has poor coloring power, but there is a risk of carcinogenic substances such as 3,4-pentsupyrene and benzanthracene, which are present in trace amounts. has recently been pointed out.

Black iron oxide does not have the carcinogenicity problem seen with carbon black, but it lacks coloring power and has a high specific gravity (and is magnetic, so miscibility with vehicles is a problem). The drawback was that it was easy to use.

Titanium black is a recently developed pigment that has excellent miscibility with vehicles and does not pose the dangers found in carbon black, so it is used for high-end applications such as cosmetics, but its oxidative stability is not necessarily high. It wasn't satisfying.

As a result of intensive studies to improve the technical problems associated with spot color pigments, the present inventors found that a powder that integrates aluminum and alumina has excellent safety and high oxidation stability ( It was discovered that it is a black to grayish-white pigment with excellent miscibility [7] The present invention was completed.

That is, the present invention provides a pigment comprising an aggregate of particles in which an aluminum metal part and an alumina part are integrated.

Since the pigment of the present invention is made up of aluminum and alumina, it also has good miscibility with other vehicles.

The method for producing the pigment of the present invention is not particularly limited, but includes a method of partially oxidizing aluminum, for example, an aluminum plate or foil, by an electrochemical method or a thermal method, and then pulverizing it. It is desirable that the raw material aluminum used at this time be of high purity, but it is also possible to use aluminum of low purity. However, it is preferable that elements that pose a safety problem, such as arsenic, lead, chromium, and cadmium, be as free from contamination as possible.
pm or less, and lead is preferably 20 ppm or less.

In addition, various shapes and sizes of aluminum can be used, such as plates and foils, but considering the operability of the oxidation process, the ease of crushing in the subsequent process, and the uniformity of the color tone of the produced pigment, aluminum can be used in various shapes and sizes. , a foil with a thickness of 1 to 1000 μm is good, and a foil with a thickness of 5 to 500 μm is particularly optimal.

As a method for oxidizing aluminum, an electrochemical method is preferable. Aluminum oxidized by an electrochemical method does not fracture vertically to the membrane surface because the alumina layer formed has a porous structure (it is easy to crush, and even after crushing, alumina and aluminum are separated). It does not separate (it is a very homogeneous powder, making it a good pigment).

Electrochemical oxidation is performed by placing aluminum and a suitable counter electrode in an electrolytic solution, and applying a voltage of usually 1 to 300 V or 1 to 200 V.
It is preferable to carry out at a current density of mA/eJ and a bath temperature of 0 to 60°C. The electrolytic solution may be either an aqueous solution or a non-aqueous solution, and preferable examples include (1) inorganic acids such as sulfuric acid, phosphoric acid, and boric acid; (2) aqueous sodium aliphatic carboxylic acids such as oxalic acid and malonic acid. Alkaline aqueous solutions such as
(5) Examples include mixed solutions of (1) to (3), among which (1) is the most preferred. In addition, the electrolytic voltage or current is
In addition to direct current, modified waves such as alternating current, AC/DC superimposed waves, rectangular waves, and three-phase incomplete waves can also be used, but from an industrial perspective, it is preferable to use direct current, alternating current, and AC/DC superimposed waveforms. can be any conductive material (aluminum, various metals, carbon compounds, etc. can be used).

Aluminum that partially becomes alumina due to oxidation (hereinafter referred to as
The aluminum content in the aluminum-containing alumina (referred to as aluminum-containing alumina) is 50% by weight (
The following are preferred. Incidentally, in the electrochemical oxidation method, the aluminum content can be arbitrarily controlled by the amount of current applied.

The aluminum-containing alumina is ground using a ball mill, sand mill, mortar, bolt mill, air jet mill, or the like. After pulverization, if necessary, it can be passed through an appropriate sieve to adjust the particle size distribution to a desired level. Considering its suitability as a pigment, the average particle size of the powder is 0.1 to 50 μm.
Those with a diameter of 0.2 to 20 μm are particularly preferred.

Since the aluminum-containing alumina powder obtained in this way becomes blackish in proportion to its aluminum content, the brightness of the pigment obtained can be controlled by the aluminum content. This aluminum content is
As mentioned above, it can be precisely controlled by
The lightness control line of the pigment in the present invention can be performed very precisely. In addition, there is no possibility of color separation or color unevenness that tends to occur when adjusting the brightness by mixing two types of powder.

In addition, in order to adjust the color tone of pigments based on their properties, alumina was colored with dyes in patent application No. 58-86935.
It is possible to use methods such as: That is, in the method of electrochemically oxidizing aluminum foil to form a porous alumina film, which is then crushed, colored, and fixed, or colored, crushed, and fixed to form a pigment, the progress of oxidation is controlled to form a porous alumina film. By arbitrarily adjusting the amount, it is possible to obtain a pigment with a darkened, imitative color tone. Furthermore,
The pigment of this application not only exhibits a dark color, but also has electrical conductivity, and can be used in various paints, cosmetics, paints, etc. as a material with features such as safety, stability, and color separation prevention. It can be expected to have a wide range of uses.

Next, the present invention will be explained with reference to Examples.

Example 1 Aluminum foil (purity 99.99%) with a film thickness of 0 μm and a film surface of 7 α x 8 sub-layers was electrolyzed with a 15% aqueous sulfur solution for 4 hours.
Electrolyzed for 0 minutes. At this time, the bath temperature was maintained at 25° C., the electrolytic voltage was 23 V, and the current density was 30 mA/cJ. Aluminum was used for both electrode plates. Eventually, the anode becomes an enemy,
The alumina foil was used as a sample for subsequent experiments.

The partially oxidized aluminum foil obtained as described above was washed with running water and delivered! The material was washed away, air-dried, and then ground in a mortar. The powder was sufficiently ground until the entire amount passed through a 200-mesh sieve, and the Lab value was determined using an SM color computer ysH-3 (xga test machine). , Take a portion of the partially oxidized alumina foil before crushing in a mortar, hold it in a 4N sulfuric acid aqueous solution at 40°C for 55 minutes, and after confirming that only the alumina layer has dissolved, take it out, wash it, and dry it. The content of metal aluminum was measured.

Exactly the same operation and electrolysis time was 50 minutes and 60 minutes.

The test was carried out for 70 minutes, 73 minutes, and 77 minutes, and the amount of aluminum remaining in the obtained film and the Lab value of the pulverized material were measured.

The results are shown in Table-1.

The following is a complete white table-1 Example 2 Among the aluminum-containing alumina powder obtained in Example 1, the aluminum content was 3123.6% and 0.55%.
% were selected and colored with Red No. 104-1, Yellow No. 4 and Blue No. 1. For coloring, first prepare a 3% dye aqueous solution, and add 0% of the aluminum-containing alumina powder.
．． 22) at 10° C. for 10 minutes, filtered and washed with water.

This wet cake was immersed in hot water for 10 minutes, then filtered, washed, and dried. Red, yellow and blue pigments were obtained by such operations.

IJ a b values were calculated for the six types of pigments obtained.

The results are shown in Table 2. Table-2 1 no, 151ζ self

Claims (1)

[Claims] 1. A pigment consisting of an aggregate of particles in which an aluminum metal part and an alumina part are integrated. 1.2. The pigment according to claim 1, in which the aluminum metal part is 50 cents or less. 3. The pigment in which the alumina part is alumina obtained by electrochemically oxidizing aluminum. The pigment according to item 1 or 2. 4. The aluminum metal part and the alumina part are integrated into one body, characterized by electrochemically oxidizing aluminum foil having a thickness of 1 to 1000 microns and then pulverizing it. A method for producing a pigment consisting of an aggregate of particles. & A method for producing a pigment according to claim 4, characterized in that 50% by weight or more of the aluminum foil is electrochemically oxidized.