JP2002088274A - Silica-coated aluminum pigment and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum pigment which solves the conventional problems of aluminum pigments such as the generation of a hydrogen gas when incorporated into a water base coating material and a water base ink, the thickening/gelling phenomenon when incorporated into an energy ray-curable coating material, and the lowering in withstand voltage properties. SOLUTION: The silica-coated aluminum pigment has 1-15 mass%, based on aluminum, formed silica film in terms of silicon and, at the same time, 0.01-4 mass%, based on aluminum, phosphorus compound in terms of phosphorus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aluminum pigment produced by a method such as a ball mill pulverization method and a vapor deposition method. More specifically, when blended in a water-based paint or water-based ink, it has excellent storage stability without gas generation, or when blended in an energy ray-curable paint or ink, the paint does not gel, The present invention relates to an aluminum pigment having excellent storage stability. In addition, the present invention relates to an aluminum pigment which satisfies voltage resistance without impairing the metallic feeling when incorporated into a metallic paint for forming a coating film requiring voltage resistance.

[0002]

2. Description of the Related Art Many techniques have been disclosed for aluminum pigments incorporated in water-based paints. For example, Japanese Patent Application Laid-Open No. 07-70468 discloses a processing method characterized by forming a phosphoric acid-based film on a molybdic acid film. Japanese Patent Application Laid-Open No. Hei 10-130545 discloses a method of processing an aluminum pigment with inorganic phosphoric acid, an inorganic phosphate, a phosphate compound, or the like. Japanese Patent No. 2915874 discloses a method of forming a coating and coloring by using a metal alkoxide. Japanese Patent Application Laid-Open No. 62-81460 discloses a method of coating a resin on an aluminum surface. However,
With these methods, it is difficult to obtain aluminum pigments that are excellent in storage stability in water-based paints, storage stability in energy ray-curable paints, etc., and withstand voltage of coating films. is there.

[0003]

The aluminum pigment has the property of reacting with water contained therein to generate hydrogen gas and dissolve when formulated into a water-based paint or water-based ink.
In particular, the tendency is remarkable in aqueous paints and inks having a high pH value.

[0004] Further, when the aluminum pigment is blended into an energy ray-curable paint or ink by ultraviolet rays or the like,
Paints and inks may thicken or gel. The reaction mechanism of this problem has not been elucidated, but it appears that the aluminum metal surface is involved in some way.

Further, when a withstand voltage is required in a painted portion such as an electric product, a paint containing a conventional aluminum pigment satisfies the withstand voltage required for the conductivity of aluminum. There is also a problem that is not done.

[0006] An object of the present invention is to provide an aluminum pigment which solves all of the above problems.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventor has found that a silica film is formed on the surface of an aluminum pigment, and that a P compound is contained in the silica film. It has been found that the above-mentioned problem can be solved by containing the compound, and the present invention has been accomplished. That is, the present invention relates to a silica-coated aluminum pigment represented by the following [1] to [17] and a method for producing the same.

[1] The raw material aluminum pigment is (1) Si
A process for producing a silica-coated aluminum pigment, which comprises contacting a reaction solution containing a compound containing, (2) water, (3) a hydrophilic organic solvent, and (4) phosphoric acid and / or phosphate as essential components. [2] The raw material aluminum pigment is (1) a Si-containing compound,
A silica-coated aluminum, which is brought into contact with a reaction solution containing (2) water, (3) a hydrophilic organic solvent, (4) phosphoric acid and / or phosphate, and (5) a hydrolysis catalyst as essential components. Pigment manufacturing method. [3] S is selected so that the Si element content in the silica coating is 1 to 15% by mass with respect to the aluminum in the aluminum pigment.
The method for producing a silica-coated aluminum pigment according to the above [1] or [2], wherein the i-containing compound is blended. [4] The phosphoric acid and / or phosphate is blended such that the P element in the silica coating is 0.01 to 4% by mass with respect to the aluminum in the aluminum pigment.
The method for producing a silica-coated aluminum pigment according to any one of [3]. [5] The method for producing a silica-coated aluminum pigment according to any one of the above [1] to [4], wherein the Si-containing compound is a silicon alkoxide. [6] silicon alkoxide is tetraethoxysilane,
The method for producing a silica-coated aluminum pigment according to the above [5], which is at least one selected from tetramethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. [7] The method for producing a silica-coated aluminum pigment according to any one of the above [2] to [6], wherein the hydrolysis catalyst is at least one selected from ammonia and ethylenediamine. [8] A method for producing a silica-coated aluminum pigment, comprising forming a silica coating on the surface of an aluminum pigment with a Si-containing compound, and further containing a P compound. [9] A silica coating is formed on the aluminum pigment surface,
A silica-coated aluminum pigment further comprising a phosphorus compound. [10] A raw aluminum pigment is brought into contact with a reaction solution containing (1) a Si-containing compound, (2) water, (3) a hydrophilic organic solvent, and (4) phosphoric acid and / or phosphate as essential components. The resulting silica-coated aluminum pigment. [11] The raw material aluminum pigment is composed of (1) a Si-containing compound, (2) water, (3) a hydrophilic organic solvent, (4) phosphoric acid and / or phosphate, and (5) a hydrolysis catalyst as essential components. A silica-coated aluminum pigment obtained by contact with a reaction solution. [12] The silica-coated aluminum pigment according to any one of the above [9] to [11], wherein the amount of Si element in the silica coating is 1 to 15% by mass with respect to aluminum in the aluminum pigment. [13] The silica-coated aluminum pigment according to any one of [9] to [12], wherein an amount of a phosphorus element in the aluminum pigment is 0.01 to 4% by mass based on aluminum in the aluminum pigment. [14] A paint containing the silica-coated aluminum pigment according to any one of [9] to [13]. [15] An ink composition containing the silica-coated aluminum pigment according to any one of [9] to [13]. [16] A coated article to which the paint according to [14] is applied. [17] A printed material using the ink composition according to [15].

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically, but the present invention is not limited thereto.

The outline of an example of the method for producing the silica-coated aluminum pigment of the present invention will be described. First, the raw material aluminum pigment is dispersed in a hydrophilic organic solvent, and a Si-containing compound (preferably silicon alkoxide) for forming a silica film is added. Next, water and, if necessary, a catalyst are added to carry out a silica formation reaction by hydrolysis of silicon alkoxides, thereby depositing a silica coating on the surface of the aluminum pigment. A phosphorus compound can be contained in the silica coating by adding a phosphoric acid or phosphate aqueous solution during this reaction. The silica-coated aluminum pigment after the reaction can be converted into a pigment or a pigment paste through filtration, solvent washing, drying operation, and the like.

The raw material aluminum pigment used in the present invention is:
It is manufactured by a ball mill pulverization method or a vapor deposition method. The shape and size are not particularly limited, but when used as a metallic paint, it is in the form of flakes and has an average particle diameter (D50: cumulative weight 50% particle diameter) of 5 μm to 1 μm.
00 μm, thickness 1 μm or less, aspect ratio (particle diameter /
(Thickness) is preferably 20 or more.

When the aluminum pigment is made into a dry powder,
Due to the danger of dust explosion and the difficulty of handling, they are usually pastes containing solvents. In the present invention, the aluminum pigment may be used as it is, or may be used after washing to remove the solvent. When using an aluminum paste containing a hydrophobic organic solvent such as mineral spirit, it is preferable to wash with an hydrophilic solvent. Alternatively, a nonionic or anionic surfactant may be added to facilitate emulsification and dispersion in water.

The hydrophilic organic solvent in which the raw material aluminum pigment is dispersed is not particularly limited as long as it has an affinity for water. Preferred examples include glycols and alcohols, and one or more of these are used. be able to. Examples of the glycols include propylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, diethylene glycol monobutyl ether, and the like. In addition, examples of alcohols include ethanol, isopropyl alcohol, and butanol. Among these, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, and diethylene glycol monobutyl ether are particularly preferable in view of the dispersibility of the aluminum pigment.

The silicon-containing compound used for forming the silica coating is preferably a silicon alkoxide. As the silicon alkoxide, those represented by the general formula Si- (OR) ₄ (R is an alkyl group or the like) or those in which part of an alkoxy group is changed to an alkyl group can be used. The silicon alkoxide may be a monomer or an oligomer. Further, a mixture thereof may be used.

Preferred examples of the silicon alkoxide include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like. Among them, tetraethoxysilane having an appropriate hydrolysis rate is particularly preferred. Used.

The amount of the silicon alkoxide used cannot be specified unconditionally because it varies depending on the type of the aluminum pigment used. 3 to 12% by mass, more preferably 4-1
It is desirable to set the usage amount to be 0% by mass.

When the amount of silicon alkoxide used is small, a dense silica layer film is not formed on the surface of the aluminum pigment, and when the amount of silicon alkoxide is too large, silica is excessively adhered to the surface of the aluminum pigment. However, the metallic luster of the aluminum pigment may be impaired, which is not preferred. Further, when a coating of 15 mass% or more in terms of Si atoms is formed on aluminum, the metallic luster (metallic feeling) of the aluminum pigment is obtained.
Is unfavorably damaged.

By adding water or a catalyst to a dispersion containing the raw material aluminum pigment and the silicon alkoxide, the silicon alkoxide can be hydrolyzed to deposit a silica coating on the surface of the aluminum pigment. The hydrolysis rate is adjusted by the molar ratio and the concentration of the water used with the silicon alkoxide, and the molar ratio and the concentration of the catalyst (such as an alkali) added as needed with the silicon alkoxide. The silicon alkoxide is hydrolyzed to form a silanol-OH group, which undergoes a condensation reaction with the -OH group on the surface of the aluminum pigment, and a self-dehydration polymerization reaction of the silicon alkoxide forms a Si-O-Si bond. It is considered that a silica coating is formed on the surface.

As the catalyst, an alkali such as ammonia or an acid such as hydrochloric acid can be used, but ammonia is particularly preferable in view of the hydrolysis rate of silicon alkoxide.

In the above hydrolysis / polymerization reaction,
By adding an aqueous solution of phosphoric acid or phosphate,
Phosphorus can be contained in the formed silica coating. Phosphates include dihydrogen monohydrogen phosphate,
Monoammonium dihydrogen phosphate, aluminum monophosphate and the like can be used. The amount of phosphoric acid or phosphate used cannot be unequivocally specified because it differs depending on the type of aluminum pigment used. % Is more preferred. 25 for the weight of Si used
% By mass or less is preferred. When phosphorus becomes more than 4% by mass,
The silica coating becomes less dense, making it difficult to achieve the object of the present invention. If the content is less than 0.01, the effect of the phosphorus compound may not be exhibited.

The reaction temperature of the hydrolysis / polymerization reaction is 15 ° C.
The reaction time at 35 ° C. and the reaction time is preferably 0.5 to 10 hours.

By adding phosphorus to the silica coating by the above-mentioned method, it was confirmed that the silica coating was made denser and the effect of reducing the decrease in the metallic appearance of the aluminum pigment was reduced.

Observation of the aluminum pigment obtained by the above method with a high-resolution scanning electron microscope reveals that fine particles of silica of 0.01 μm or less adhere to the entire surface of the aluminum pigment to form a film. confirmed. Although it is difficult to measure the thickness of the coating accurately,
To 30 nm.

The silica-coated aluminum pigment of the present invention can be used by blending it into a known and commonly used paint or ink composition. These paints and ink compositions may be oily or aqueous (emulsion, water-soluble). Further, not only a one-component type but also a mixture of two or more types may be used, or a type involving a reaction may be used.

The paint and ink composition containing the silica-coated aluminum pigment of the present invention can contain other pigments and dyes according to the hue of the target paint and ink composition. However, the pigment is desirably used within a range that does not impair the metallic feeling of the silica-coated aluminum pigment of the present invention.

The solvent used for the paint and ink composition containing the silica-coated aluminum pigment of the present invention includes various solvents (including water) that are lipophilic, hydrophilic, and water-soluble depending on the type of the paint and the ink composition. Can be used. Further, the solvent may be a mixture of a plurality of types or a non-solvent according to its function (thinner, retarder, leveling agent, etc.).

As the binder, various natural or synthetic polymers, monomers, oligomers, prepolymers and the like can be used. In the case of a reactive paint or ink composition, a catalyst, an initiator, a crosslinking agent, a curing agent and the like can be contained.

The paint and ink composition containing the silica-coated aluminum pigment of the present invention can contain various additives as required. Examples include surfactants, stabilizers, preservatives, plasticizers, desiccants, pigment wetting agents, pigment dispersants, anticorrosives, flow regulators, fungicides, and ultraviolet absorbers.

[0029]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 Showa Aluminum Powder Co., Ltd. Aluminum Paste Sap FM4010 (aluminum content 6)
76 g) was placed in a glass beaker, dispersed in 200 g of propylene glycol monomethyl ether, and 14.9 g of tetraethoxysilane was added. 2 with stirring
21 g of 9% aqueous ammonia was added, and 378 g of water in which 0.5 g of diammonium hydrogen phosphate was dissolved was further added. After stirring at 25 ° C. for 5 hours, the mixture was filtered, and the filter cake was washed with propylene glycol monomethyl ether to obtain a propylene glycol monomethyl ether paste containing 50% by mass of aluminum.

(Example 2) Aluminum paste Sap 2173 manufactured by Showa Aluminum Powder Co., Ltd.
%) Was dispersed in 200 g of dipropylene glycol monomethyl ether, and tetraethoxysilane 1
8.6 g were added. Under stirring, 29% aqueous ammonia 21
g, and then ammonium dihydrogen phosphate 2.1 g
378 g of water in which 4 g was dissolved were added. After stirring was continued for 3 hours, the mixture was filtered, and the filter cake was washed with propylene glycol monomethyl ether to obtain a paste of propylene glycol monomethyl ether containing 50% by mass of aluminum.

Example 3 A paste was obtained in the same manner as in Example 1 except that the amount of diammonium hydrogen phosphate was changed to 10.6 g.

Example 4 The amount of tetraethoxysilane was 7
A paste was obtained in the same manner as in Example 1 except that the amount was changed to 0 g.

Example 5 A paste was obtained in the same manner as in Example 1 except that the amount of tetraethoxysilane was changed to 1.86 g.

Comparative Example 1 A paste was obtained in the same manner as in Example 1 except that water containing no diammonium monohydrogen phosphate was added.

Comparative Example 2 A paste was obtained in the same manner as in Example 2 except that water containing no monoammonium hydrogen phosphate was added.

(Comparative Example 3) 0 g of tetraethoxysilane
(No addition), except that the same treatment as in Comparative Example 2 was performed.
A paste was obtained.

(Examples 6 to 10, Comparative Examples 4 to 6) Using the aluminum pigment pastes produced in Examples 1 to 5 and Comparative Examples 1 to 3, metallic paints were produced as follows. 5.8 g of aluminum pigment paste and 5.8 g of ethyl acetate are mixed and pre-dispersed, and then 37.5 g of Planet SV manufactured by Origin Electric Co., Ltd. 70.0 g of Planet Thinner # 175 manufactured by Origin Electric Co. are added and stirred for 5 minutes.

Evaluation method of aluminum pigment The aluminum pigments obtained in Examples and Comparative Examples were evaluated by the following methods.

(1) Measurement of Si and P contents The aluminum paste was dried, dissolved in aqua regia, diluted with distilled water, and measured by ICP with a calibration curve drawn with an aqueous solution of known Si and P concentrations. The deposition rate was calculated from the concentrations of Si and P. About 90% of the charged amount is deposited on both Si and P.

(2) Hydrogen gas generation test 3 g of aluminum paste and 3 g of distilled water were added into a test tube, and an acrylic emulsion paint (E-Mitsubishi Chemical Co., Ltd.) was added.
208), 14 g was added, and the mixture was stirred well to prepare an aqueous paint. This was placed in a constant temperature water bath at 50 ° C., and the cumulative amount of hydrogen gas generated for two weeks was measured.

(3) Gelation test 12 g of aluminum paste was placed in a brown glass bottle.
Furthermore, 48 g of a urethane acrylate UV curable ink (Lake Cure LP4700, manufactured by Jujo Chemical) was added, and after sufficient stirring, the mixture was placed in a constant temperature oven at 50 ° C., and the state of gelation after one month was examined.

(4) Coating of paint containing aluminum pigment The paints prepared in Examples 3 and 4 and Comparative Examples 5 to 10 were applied to plastic plates. That is, an automatic coating machine reciprocator made by Kansai Paint, spray gun WA-10 made by Iwata.
Spray coating was performed on the ABS resin plate so as to have a dry film thickness of 15 μm.
After drying for 0 minutes, a test coated plate was obtained.

(5) Withstand voltage test The aluminum pigment-containing paint applied to the ABS plate by the method of (4) was applied to a withstand voltage measuring device (TW-516, manufactured by Tama Denso).
With a breaking current of 0.5 mA and an electrode spacing of 10 mm, 1
A voltage was applied for 20 seconds at kV intervals, and the maximum voltage at which the circuit was not interrupted by dielectric breakdown was defined as the withstand voltage.

(6) Gloss (metallic feeling) The appearance of the coating film coated on the ABS plate was visually observed.

Table 1 shows the results of the above evaluation tests.

[0047]

[Table 1]

[0048]

EFFECT OF THE INVENTION The silica-coated aluminum pigment obtained in the present invention has excellent storage stability when blended in a water-based paint or an energy ray-curable paint, and has a high withstand voltage and gloss (metallic feeling) of the paint film. It provides an aluminum pigment that does not deteriorate.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4J037 AA24 CA18 CA21 CA22 CA24 CB16 CB23 DD19 DD23 EE03 EE14 EE43 FF11 FF23 FF25 4J038 EA011 HA066 HA416 HA446 KA08 KA15 MA08 MA10 NA01 NA17 NA26 PA17 4J039 BA06 BA19 BA21 BA06 EA33 EA44

Claims (17)

[Claims] 1. A raw material aluminum pigment is brought into contact with a reaction solution containing (1) a Si-containing compound, (2) water, (3) a hydrophilic organic solvent and (4) phosphoric acid and / or phosphate as essential components. A method for producing a silica-coated aluminum pigment, comprising: 2. The raw material aluminum pigment must contain (1) a Si-containing compound, (2) water, (3) a hydrophilic organic solvent, (4) phosphoric acid and / or phosphate, and (5) a hydrolysis catalyst. A method for producing a silica-coated aluminum pigment, which is brought into contact with a reaction solution as a component. 3. The production of a silica-coated aluminum pigment according to claim 1, wherein the Si-containing compound is blended so that the amount of Si element in the silica coating is 1 to 15% by mass with respect to the aluminum in the aluminum pigment. Method. 4. The phosphoric acid and / or phosphate is blended so that the P element in the silica coating is 0.01 to 4% by mass with respect to the aluminum in the aluminum pigment.
4. The method for producing a silica-coated aluminum pigment according to any one of items 1 to 3. 5. The method for producing a silica-coated aluminum pigment according to claim 1, wherein the Si-containing compound is a silicon alkoxide. 6. The method for producing a silica-coated aluminum pigment according to claim 5, wherein the silicon alkoxide is at least one selected from tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane and tetrabutoxysilane. 7. The process for producing a silica-coated aluminum pigment according to claim 2, wherein the hydrolysis catalyst is at least one selected from ammonia and ethylenediamine. 8. A method for producing a silica-coated aluminum pigment, comprising forming a silica coating on the surface of an aluminum pigment with a Si-containing compound and further containing a P compound. 9. A silica-coated aluminum pigment, wherein a silica coating is formed on the surface of the aluminum pigment and further contains a phosphorus compound. 10. A raw material aluminum pigment comprising: (1) a Si-containing compound, (2) water, (3) a hydrophilic organic solvent and (4)
A silica-coated aluminum pigment obtained by contacting a reaction solution containing phosphoric acid and / or phosphate as an essential component. 11. The raw material aluminum pigment must contain (1) a Si-containing compound, (2) water, (3) a hydrophilic organic solvent, (4) phosphoric acid and / or phosphate, and (5) a hydrolysis catalyst. A silica-coated aluminum pigment obtained by contact with a reaction solution as a component. 12. The silica-coated aluminum pigment according to claim 9, wherein the amount of Si element in the silica coating is 1 to 15% by mass based on the aluminum in the aluminum pigment. 13. The silica-coated aluminum pigment according to claim 9, wherein the phosphorus element content in the aluminum pigment is 0.01 to 4% by mass based on the aluminum in the aluminum pigment. 14. A paint containing the silica-coated aluminum pigment according to claim 9. 15. An ink composition containing the silica-coated aluminum pigment according to any one of claims 9 to 13. 16. A coated article to which the paint according to claim 14 is applied. 17. A printed material using the ink composition according to claim 15.