JP2915874B2 - Paint composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition containing a colored aluminum powder pigment and mainly used for coatings for automobiles and home appliances. hydrolyzed relates to coating compositions containing coloring aluminum powder pigment obtained by coating on the aluminum powder surface. [0002] Conventionally, as a method of obtaining a colored metallic coating film, a method of using a metal powder and a colored organic and / or inorganic pigment as a pigment component in a coating material is known. To add more pigment,
In addition to the complicated process, there is a problem that the tint changes due to a delicate difference in the mixing ratio of each. [0003] As a method of solving the above problems,
Pigments having both metallic luster and tinting strength have been devised. One is a method using a metal pigment, a method of using a colored metal pigment, or a method of coloring the metal pigment itself as desired, and the other is different from the metal luster itself, In this method, a pigment having a pearly luster is used. [0004] For example, as a method of obtaining a gold-colored metallic coating film, a small piece of brass may be used as a pigment. However, the material brass is expensive and harmful to the human body, so its application range is narrow, and in addition, there is a problem that discoloration and gloss deterioration are remarkable depending on the environment. On the other hand, as a method for coloring the surface of a highly safe and inexpensive metal to a desired color, there is a method of treating the surface of an aluminum powder with a coloring material (Japanese Patent Publication No. Sho 5 (1988)).
3-4004 and JP-A-60-50176, 60-7
2969). [0005] That is, in Japanese Patent Application Laid-Open No. 53-4004, after the aluminum powder is subjected to boehmite treatment as required, the aluminum powder is immersed in a weak alkaline solution containing a metal salt and an organic compound having chelating ability, whereby the surface of the aluminum powder is chelated. A method of forming and obtaining a colored metallic aluminum powder is disclosed. However, this method has a problem that the aluminum powder reacts with the alkali during the alkali treatment to cause gelation or hydrogen gas generation. Further, Japanese Patent Application Laid-Open Nos. 60-50176 and 60-7
No. 2969 discloses a method of obtaining a golden aluminum powder by treating a surface of aluminum powder with chromic anhydride, dichromic acid, and fluoride to adsorb hexavalent or trivalent chromium on the surface. The use of the compound as a treating agent poses environmental and economical problems such as safety during treatment and the need to take measures against pollution of the waste liquid. Further, pigments having a pearly luster, which is different from the metallic luster, have been devised. This is a thin piece of a high-refractive-index substance or a thin film of a high-refractive-index substance formed on a colorless and transparent inorganic substrate, and both are colored pigments utilizing the interference color of the thin film. As these pearly luster pigments, for example, guanine crystals extracted from scales of herring are famous, but they have a problem that they are expensive because natural substances can take only a small amount. As an alternative to this, crystal fragments of basic carbonate and bismuth trichloride have been developed, but are not widely used at present due to their toxicity. For example, Japanese Patent Publication No. 35-5367 discloses a method of imparting pearl luster by coating a transparent flaky substance with titanium dioxide formed from titanium alcoholate. A method of coating a mica substance with titanium dioxide generated from titanium tetrachloride. In Japanese Patent Publication No. 43-25644, pigments giving interference colors are obtained by forming metal oxides such as titanium dioxide, zirconium dioxide, iron oxide and chromium oxide on non-opaque mica pieces. However, as described above, all of these pearlescent pigments exhibit an interference color by forming a high refractive index layer on a colorless and transparent substrate, and have a low concealing rate, and It is strongly affected by the underlayer during film formation. Therefore, the number of undercoating steps is increased (JP-A-59-160571,
59-215857) or a complicated process such as mixing with a pigment having a high hiding power such as aluminum powder for use. Further, since a natural product such as mica is used as the substrate, it is difficult to adjust the particle size distribution and shape of the substrate to desired conditions, and it is difficult to arbitrarily adjust various design properties resulting from these conditions. DISCLOSURE OF THE INVENTION The present invention relates to a colored aluminum pigment obtained by relatively easily producing an aluminum powder pigment excellent in safety, rich in color tone and excellent in workability having a large hiding power. An object of the present invention is to provide a coating composition containing: Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a single pigment has both a metallic feeling and a desired color, and is safe, concealable, and processed. A novel colored aluminum pigment having excellent properties and a method for producing the same have been solved. That is, the constitution of the present invention is a coating composition containing a colored aluminum powder pigment obtained by hydrolyzing a substance represented by the following general formula and coating the aluminum powder surface with the product . The general formula: ## STR4 ## However, M: metal atom O: oxygen atom R: alkyl group n: an integer of 1 to 40 or less, the present invention will be described in more detail. The hydrolysis reaction in the present invention is carried out by gradually adding a metal alcoholate and water in an amount capable of hydrolyzing the same in a state where aluminum powder is suspended in a solvent. Precipitates on the particle surface. For example, when n = 1 in the general formula, a reaction of M (OR) ₄ + 2H ₂ O → MO ₂ + 4ROH occurs, and a metal oxide and a compound having a partially remaining alkyl group are formed on the aluminum surface by hydrolysis. It is considered something. The method of adding the metal alcoholate and water may be a batch addition method or a method in which the metal alcoholate and water are divided into multiple stages little by little. Each addition order may be such that the metal alcoholate is first dissolved or suspended in the solvent and water is added, or the water is first dissolved or suspended in the solvent and then the metal alcoholate is added. Alternatively, they may be added alternately little by little. However, in general, when the reaction is carried out gently, the generation of suspended particles tends to be reduced. Therefore, it is desirable to add the solution little by little as necessary in a state where the concentration is reduced with a solvent. Here, it is considered that the hydrolyzate of metal alcoholate and aluminum are bonded via a hydroxyl group existing on the surface. However, when the bonding force is weak and a large number of suspended particles are generated, a carboxyl group is used as an anchor site. A compound having a group capable of forming a hydrogen bond or an ionic bond at both ends with a hydrolyzate of a metal alcoholate such as an amino group or an aluminum group and aluminum (for example, a dicarboxylic acid or the like) may be added. It is considered that the principle that the aluminum powder is colored by the coating of the hydrolyzate is that a high refractive index thin film is formed on the surface of the aluminum powder, interference of the thin film occurs, and an interference color is exhibited. Incidentally, JP-B described above as prior art 35- 5367, 39-2885,43-25644
The difference from the invention of the present invention is that the prior art uses a non-opaque substance for the substrate and transmits the complementary color of the reflected light as transmitted light. Because aluminum powder is used, the metallic pigment has a hiding property. The aluminum powder used in the present invention comprises:
Although not particularly limited, the surface is preferably smooth and scaly in view of utilizing the interference of the parallel thin film. The metal alcoholate has the following general formula: Wherein M is a metal atom, O is an oxygen atom, R is an alkyl group, and n is a compound satisfying an integer of 1 to 40, and the amount of addition is 1 mg or more in terms of metal per 1 m ² of surface area of the aluminum powder. 360mg
The following is desirable. If less than 1 mg, the color is weak, 360 m
If it exceeds g, the interference color becomes weak and the number of suspended particles increases, which is not preferable. Further, metal atoms include titanium, zirconium, silicon, tantalum, aluminum, calcium, sodium, potassium, boron, lanthanum, zinc, and the like.
Zirconium is particularly preferred. As the alkyl group, methyl, ethyl, propyl, butyl, octyl, stearyl and the like can be used, and those having from ethyl group to about octyl group are particularly preferable. This is because the higher the molecular weight of the alkyl group, the gentler the hydrolysis, while if the molecular weight is too high, the alkyl group becomes waxy and the solvent that can be uniformly dispersed is limited. In particular, when the reaction rapidly occurs with a monomer (n = 1 in the general formula) and a large amount of suspended particles are generated, a dimer (n = 2), a trimer (n = 3), a tetramer It is desirable to use a condensate such as a monomer (n = 4). However, if the number of n is too large, the viscosity of the metal alcoholate itself increases, making it difficult to dissolve in the solvent. These metal alcoholates may be used alone or in combination of two or more. In order to slow the hydrolysis rate, it is also desirable to dilute the metal alcoholate with a solvent and add it at a low concentration. The metal alcoholate used in the present invention includes, for example, tetraethyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-sec-butyl titanate, tetra-tert-butyl titanate, tetra-2-ethylhexyl titanate, Examples include tetraethyl zirconate, tetraisopropyl zirconate, tetra-n-butyl zirconate, tetra-sec-butyl zirconate, tetra-tert-butyl zirconate, tetra-2-ethylhexyl zirconate, and condensates thereof. The solvent generally used in the present invention is preferably a solvent which dissolves a metal alcoholate such as alcohols, mineral spirits, solvent naphtha, benzene, toluene, xylene, petroleum benzine, etc., but reacts in suspension. Therefore, it is not particularly limited. These may be used alone or as a mixture of two or more. Further, alcohol is by-produced by the addition of water in the hydrolysis reaction of the metal alcoholate, so that alcohol can be used as a polymerization rate regulator. In the step of hydrolyzing the metal alcoholate in the present invention, water is added in an amount required for hydrolysis. When water is added later, it is desirable to dilute with a solvent before use. On the other hand, when the addition amount is small, the reaction takes too much time or the metal alcoholate tends to condense linearly, so that three-dimensional crosslinking does not occur on the surface of the aluminum powder, and it is difficult to form a uniform film. On the other hand, if there is too much water, gelation is likely to occur, agglomeration of the aluminum powder occurs, and it may react with the aluminum powder and generate hydrogen gas, and the amount added is several times the number of moles of the metal alcoholate. It is desirable that However, when alcohol is used as the solvent, the alcohol acts as an inhibitor of the reaction, and the reaction is slowed down. ,
All you have to do is remove the water. In this case, if a catalyst such as hydrogen chloride is used, it is not necessary to use a large amount of water. Hydrolysis occurs at a reaction temperature of room temperature, but if the reaction is too rapid, cooling is desirable. Further, by heating the coated aluminum powder at 200 ° C. or higher and below the ignition point of the aluminum powder, a colored aluminum powder having a strong color can be obtained. Note that it is desirable to replace oxygen with an inert gas because of the possibility of ignition during heating. According to the above-mentioned production method, a colored aluminum powder which is excellent in safety and easy to produce can be obtained. Hereinafter, the present invention will be specifically described with reference to production examples and examples. Production Example 1 After washing an aluminum paste (our product) having a specific surface area of 2.4 m ^{2 /} g (BET method) with petroleum benzene / acetone,
After suction filtration and drying at 50 ° C. for 2 hours, 50 g was taken, suspended in 500 ml of n-butanol, and 12.75 g of tetra-n-butyl titanate was added while maintaining the state. Then, while stirring, 6.75 g of water was added to n-
The solution diluted in 120 g of butanol was added in small portions. Then water was added in small portions until the butanol became saturated. After washing the slurry with butanol, the slurry was filtered through a glass filter and taken out. This powder had a golden color. When this powder was further taken and heated at 250 ° C. for 15 minutes, an aluminum powder having a stronger golden color was obtained. Observation of an electron microscope image (hereinafter abbreviated as SEM image) of this powder showed that the surface of the aluminum powder was covered with a granular coating. Production Examples 2 to 12 Table 1 shows the coloring states of Production Example 1 and those obtained by changing the treating agent, treatment amount and heating conditions. All conditions other than those in the table were processed under the same conditions as in Production Example 1. Comparative Production Example 1 When the aluminum powder before washing, which was washed and dried in Production Example 1, was heated at 250 ° C. for 15 minutes, there was no color change, and no particles in the surface layer were observed in the surface SEM image. Comparative Production Examples 2 to 6 Table 1 shows the coloring states of Production Example 1 and those obtained by changing the treatment amount and the heating conditions. Example 1 A coating composition was prepared using the aluminum pigment and the coating resin obtained in Production Example 1, and the obtained coating composition had a golden color. [Table 1] [0034] As has been described in the foregoing, without color-rich, discoloration according to the present invention, and the coating composition hiding power contains good colored aluminum powder pigment workability large Can be provided.

Claims (1)

(57) [Claims] A coating composition comprising a colored aluminum powder pigment obtained by hydrolyzing a substance represented by the following general formula and coating the aluminum powder surface with the product. General formula Here, M: metal atom O: oxygen atom R: alkyl group n: an integer of 1 to 40 After hydrolyzing the substance represented by the above general formula, and coating the surface of the aluminum powder with the product,
A coating composition comprising the colored aluminum powder pigment according to claim 1, which is heated at a temperature of not less than ℃ and lower than the ignition point of the aluminum powder. 3. The compound represented by the general formula is 1 mg or more and 360 mg as a metal component per 1 m ² of the surface area of the aluminum powder.
A coating composition containing the colored aluminum powder pigment according to claim 1 or 2 which is present below. 4. A coating composition comprising the colored aluminum powder pigment according to any one of claims (1) to (3), wherein the metal atom of the general formula is titanium or zirconium.