JP2004307616A - Composite aluminum pigment and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite aluminum pigment which has excellent dispersibility, high uniformity in particle size, heat resistance, and mechanical strength, and its manufacturing method. <P>SOLUTION: The composite aluminum pigment has an aluminum deposited layer covering the entire surface of a core of a silica fine particle which is synthesized by the sol-gel method and has an average particle diameter of ≤5 μm. The composite aluminum pigment can further have a surface protective layer on the aluminum deposited layer. The manufacturing method comprises (1) introducing silica fine particles having an average particle diameter of ≤5 μm which are synthesized by the sol-gel method into a deposition chamber having a disk-shaped plane base and at least a ring side as the side in contact with the base, (2) agitating the silica fine particles to successively expose the entire surface of each of the silica fine particles under vacuum conditions and feeding an aluminum vapor in this state to form an aluminum deposited layer on the surface of each of the silica fine particles. A surface protective layer can be further formed after formation of the aluminum deposited layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a composite aluminum pigment and a method for producing the same. The composite aluminum pigment of the present invention has a narrow particle size distribution, high particle size uniformity, excellent dispersibility, and can provide a more excellent metal color.
[0002]
[Prior art]
Aluminum pigments have hitherto been widely used for obtaining metallic luster such as metallic feeling, and various techniques relating to aluminum pigments have been proposed.
For example, Japanese Patent Application Laid-Open No. 7-62226 (Patent Document 1) describes a colored aluminum powder that can be used as a colorant for paints and inks. However, the aluminum powder described in this publication is mainly for paints, and the powder used is also scaly, and has a relatively large particle size, so that it tends to settle, and the powder shape is poor in uniformity. When used as a paint, it has the disadvantage of poor gloss, and when used as a pigment for ink jet recording, clogging occurs.
JP-A-2002-121423 (Patent Document 2) describes an aluminum pigment obtained by further treating a resin-coated aluminum pigment with phosphoric acid or a phosphate. However, the technology described in this publication is based on hydrogen gas generated when it is blended in water-based paints and water-based inks, thickening and gelling phenomena when it is blended in UV-curable paints, and a decrease in withstand voltage. The purpose of the present invention is to provide a means for solving the above-mentioned problem. The aluminum powder used is a flake-like aluminum powder obtained by a crushing method, and its average particle size is 5 to 100 μm, so that it tends to settle. In addition, the powder has poor uniformity, so that it has a disadvantage of poor gloss even when used in water-based paints and water-based inks. Further, when used as a pigment for inkjet recording, clogging occurs.
Furthermore, Japanese Patent Application Laid-Open No. 2002-226733 (Patent Document 3) describes an aluminum pigment obtained by coating the surface of a flake-like aluminum powder with a resin, and provides a metallic coating film having excellent adhesion. It is possible to give. However, the aluminum powder described in this publication is also in the form of flakes, the preferred particle size is 5 to 35 μm, and the uniformity of the powder shape is poor. And is unsuitable as an inkjet recording pigment because clogging occurs.
[0003]
On the other hand, an ink jet recording ink containing a dispersion liquid of ultrafine metal particles obtained by an evaporation method in a low vacuum gas is described in, for example, JP-A-2002-121437 (Patent Document 4). According to this publication, ultrafine metal particles having a particle size of 100 nm or less can be obtained, and can be used as a colorant for an ink for inkjet recording. However, although gold, silver, copper, palladium, or tin is specifically described as a usable metal, aluminum is not specifically illustrated. This is presumably because, as described below, the preparation is difficult because of high reactivity with water.
[0004]
Further, JP-A-2002-179960 (Patent Document 5) describes an ink jet recording ink using a pigment prepared by forming a metal film on the surface of a light plastic spherical core material. However, since the core material is a plastic spherical body, heat resistance and mechanical strength are inferior, especially when hollow particles are used as the core material, it is easily deformed, and when formed into a coating film, it is easily affected by scratches and scratches It will be.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-62262 [Patent Document 2]
JP 2002-121423 A [Patent Document 3]
JP 2002-226733 A [Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-121437 [Patent Document 5]
JP 2002-179960 A
[Problems to be solved by the invention]
As described above, although aluminum pigments have been conventionally used for the purpose of obtaining a metallic luster such as a metallic feeling, all of the aluminum powders used are inferior in dispersibility because they have a relatively large particle size. Poor gloss due to poor uniformity of the body shape, and clogging occurred when used as a colorant for ink jet recording inks.
On the other hand, with an aluminum pigment using a plastic spherical core material, although the nonuniformity of the powder shape can be eliminated, the application field is limited due to poor heat resistance and mechanical strength of the aluminum pigment itself, and the coating film is not coated. There was a drawback that it was susceptible to scratches and abrasions.
Therefore, an object of the present invention is to provide an excellent dispersibility due to a small average particle size, a high uniformity of powder shape, and a narrow particle size distribution. Even without clogging, it has excellent heat resistance and mechanical strength, so it can be used in a wide range of fields, and it is possible to form a coating film that is not easily affected by scratches and abrasions. It is an object of the present invention to provide a composite aluminum pigment capable of providing a metallic luster such as, for example, and a method for producing the same.
[0007]
[Means for Solving the Problems]
The above object is achieved by the present invention
This problem can be solved by a composite aluminum pigment which is synthesized by a sol-gel method and has an aluminum vapor-deposited layer covering the entire surface of a silica fine particle core having an average particle diameter of 5 μm or less.
According to a preferred embodiment of the present invention, the apparatus further comprises a surface protective layer covering the entire surface of the aluminum vapor-deposited layer.
According to another preferred embodiment of the present invention, the silica fine particle core is a spherical fine particle.
The present invention also relates to an aqueous dispersion or an aqueous aluminum pigment composition (for example, an ink composition for inkjet recording) containing the composite aluminum pigment as a colorant component.
[0008]
Further, the present invention provides
(1) Silica fine particles synthesized by a sol-gel method and having an average particle diameter of 5 μm or less are charged into a vapor deposition chamber having a bottom surface of a disk-shaped flat surface and a side surface having a ring shape at least in contact with the bottom surface.
(2) In a state where the silica fine particles are stirred under a vacuum condition to expose the entire surface of each silica fine particle in order, aluminum vapor is supplied to the entire surface of the silica fine particles, whereby aluminum The present invention also relates to a method for producing a composite aluminum pigment, which comprises forming a vapor-deposited layer.
According to a preferred embodiment of the method of the present invention, after forming an aluminum deposition layer on the surface of the silica fine particles, a surface protective layer is formed on the aluminum deposition layer.
According to another preferred aspect of the method of the present invention, each of the silica fine particles is formed by rotating the disk-shaped bottom surface of the vapor deposition chamber in the horizontal direction and moving the circumferential portion of the disk-shaped bottom surface vertically up and down. Is supplied to the entire surface of the silica fine particles in a state where the entire surface is exposed in order.
Furthermore, according to another preferred embodiment of the method of the present invention, the disk-shaped bottom surface of the vapor deposition chamber is not rotated in the horizontal direction, but is inclined from the horizontal direction, so that the lowest circumferential portion and the highest circumferential portion are separated from each other. By rotating along the circumference, aluminum vapor is supplied to all the surfaces of the silica fine particles in a state where all the surfaces of the silica fine particles are sequentially exposed.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The silica fine particles used in the present invention have an average particle size of 5 μm or less, and preferably 3 to 5 μm. Preferably, the maximum particle size is 6 μm or less, and the minimum particle size is 1 μm or more. Further, the silica fine particles used in the present invention are preferably spherical fine particles.
[0010]
As used herein, the term "average particle size" refers to a method in which silica fine particles are diluted with an aprotic polar organic solvent (e.g., acetonitrile), and the particle size distribution in the diluted state is measured using a particle size distribution analyzer (e.g., Microtrac UPA-150; Nikkiso Co., Ltd.). (Manufactured by Co., Ltd.) and means a cumulative particle size value of 50%. In addition, the maximum particle size and the minimum particle size mean the maximum value and the minimum value, respectively, as measured by a particle size distribution meter.
[0011]
The silica fine particles used in the present invention can be prepared by a known sol-gel method. The principle of the sol-gel method is that, starting from a solution of an organic or inorganic compound of a metal, the solution is converted into a gel in which fine particles of a metal oxide or a hydroxide are dissolved by hydrolysis and polycondensation of the compound in the solution. Further, the reaction is further advanced to form a gel body, and when the gel body is dried and heated, the gel body grows to finally generate a polycrystalline material.
[0012]
A method for producing silica fine particles by a sol-gel method is described in, for example, C.I. J. Brinker and G.W. W. Scherer, Sol-Gel Science (Academic Press Inc. 1990). When alkoxysilane and water are reacted in the presence of ammonia in an alcohol solvent, the alkoxysilane is hydrolyzed to produce silicic acid. Then, the spherical particles can be obtained as a colloid before gelation.
[0013]
As the alkoxysilane, for example, tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] or tetramethoxysilane [Si (OCH ₃ ) ₄ ] can be used. As the alcohol solvent, for example, methanol, ethanol, Alternatively, isopropyl alcohol or the like can be used. SiO ₂ particles (gel) is produced by the hydrolysis and polycondensation reaction of the alkoxysilane, and the gel body by growing the the progress of the further reaction gel. When this gel body is heated, silica fine particles having a uniform particle size distribution can be obtained. The hydrolysis and polycondensation reaction of the alkoxysilane is preferably performed at about 0 to 80 ° C. The heating of the obtained gel body is preferably performed at about 600 to 1200 ° C.
[0014]
The silica fine particles thus obtained are subsequently charged into a vapor deposition device. The vapor deposition device used in the present invention includes a vapor deposition chamber. The bottom surface of the vapor deposition chamber is a disk-shaped flat surface. The side surface of the vapor deposition chamber is generally cylindrical, and at least a portion connected to the bottom surface has a cylindrical (ie, ring-shaped) side surface. The deposition chamber can be under vacuum conditions and can supply aluminum vapor.
[0015]
In the present invention, the amount of the silica fine particles charged inside the vapor deposition chamber is not particularly limited. That is, as long as the silica fine particles charged into the vapor deposition chamber are stirred, the surfaces of all the fine particles are exposed to the aluminum vapor, and the silica fine particles on which the aluminum vapor is vapor-deposited do not agglomerate with each other. The amount is not limited.
[0016]
In the present invention, in the vapor deposition chamber, aluminum vapor is vapor-deposited on the entire surface of each of the silica fine particles, and an aluminum vapor-deposited layer is formed on the entire surface of the silica fine particles. During this deposition process, it is necessary to carry out the deposition process with stirring so that each silica fine particle does not aggregate with each other and each individual fine particle can form an aluminum deposited layer on the surface. is there.
[0017]
The stirring can be performed, for example, by rotating the disk-shaped bottom surface of the vapor deposition chamber in the horizontal direction, and moving the circumferential portion of the disk-shaped bottom surface up and down in the vertical direction. The aluminum vapor can be supplied to the entire surfaces of the silica fine particles while the entire surfaces of the silica fine particles are sequentially exposed. In this case, the number of rotations of the disc-shaped bottom surface in the horizontal direction can be, for example, 10 to 100 rpm (preferably 40 to 80 rpm), and the inclination angle of the disc-shaped bottom surface in the vertical direction is, for example, ±. It can be 10 ° to ± 50 ° (preferably ± 20 ° to ± 40 °).
[0018]
Further, for example, the stirring does not rotate the disk-shaped bottom surface itself of the vapor deposition chamber in the horizontal direction, but tilts the disk-shaped bottom surface from the horizontal direction, so that the lowest circumferential portion and the highest circumferential portion (the At the opposite side of the diametric direction) and by rotating the same along the circumference, and by this stirring, the entire surface of each silica fine particle is sequentially exposed, and the silica fine particles All surfaces can be supplied with aluminum vapor. In this case, the inclination angle of the disc-shaped bottom surface in the vertical direction may be, for example, ± 10 ° to ± 50 ° (preferably ± 20 ° to ± 40 °), and the lowest circumferential portion and the highest The number of rotations with respect to the circumferential portion (the portions opposite to each other in the diametric direction) can be, for example, 10 to 100 rpm (preferably 40 to 80 rpm).
[0019]
The above-described deposition process is performed under a vacuum condition. For example, after the silica fine particles to be treated are charged into the vapor deposition chamber, the pressure is reduced, and the degree of vacuum is preferably reduced to 5 × 10 ⁻³ Pa or less. Can be implemented. In addition, the above-described deposition treatment is preferably performed under heating, and can be performed, for example, at 50 to 500 ° C.
[0020]
The deposition amount of aluminum deposited on the surface of each of the silica particles to be treated by the above-mentioned vapor deposition treatment is not particularly limited, and can be appropriately determined depending on the purpose of use. The supply amount of the aluminum vapor supplied to the fine particles can also be appropriately determined.
[0021]
In the present invention, it is preferable that after forming an aluminum vapor-deposited layer on the silica fine particle surface, a surface protective layer is formed on the aluminum vapor-deposited layer to impart water resistance. Surface treatment for imparting water resistance is, for example, by a known method, surface treatment with a silane coupling agent, formation of a surface protective layer by hydrolysis of alkoxysilane, or a phosphate compound, or oxalic acid, citric acid, Alternatively, it can be performed by forming a surface protective layer with an organic acid such as malic acid.
The composite aluminum pigment having a water-resistant surface protective layer can be easily used in water-based paints and water-based ink compositions.
[0022]
Using the composite aluminum pigment of the present invention, various ink compositions or coating compositions can be prepared by a known method. The composite aluminum pigment according to the present invention has an average particle size of at most 5 μm or less, and can be used as an ink composition for inkjet recording. In addition, the dispersion stability in the dispersion liquid is excellent because it includes a silica fine particle core having a low specific gravity and aluminum deposited thereon has a low specific gravity. Further, the silica fine particles synthesized by the sol-gel method have a narrow particle size distribution range and a high uniformity of particle size, so that the composite aluminum pigment of the present invention containing those silica fine particles as a core material also has a particle size distribution range. Narrower and more uniform particle size.
[0023]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but these do not limit the scope of the present invention.
<Example 1>
(1) Preparation of silica fine particles 100 mL of a methanol aqueous solution in which 21 g of tetraethoxysilane was dissolved was added dropwise to a 500 mL flask charged with 150 mL of a 9.0% ammonia methanol solution at 5 ° C. over 1.5 hours with stirring. After completion of the dropwise addition, the mixture was allowed to stand at 20 ° C. overnight with stirring. The solvent component was distilled off from the obtained colloidal liquid (250 mL), and the obtained residue was dried at 110 ° C. for 1 hour and calcined at 1100 ° C. for 1 hour to obtain silica fine particles. The obtained silica fine particles had an average particle size of 1.0 μm (dispersed in ion-exchanged water and measured with a microtrack) and had a narrow particle size distribution with a standard deviation of 0.038 in the particle size.
[0024]
(2) Aluminum vapor deposition treatment 1.0 g of the silica fine particles prepared in the preceding paragraph (1) was deposited in a cylindrical vapor deposition chamber (diameter = 115 mm; height = 230 mm; stainless steel) of a vapor deposition apparatus (VE-1010; manufactured by Vacuum Device Inc.). ). The cylindrical deposition chamber was rotated in the horizontal direction at 600 rpm, and vertically moved at an inclination angle of ± 30 ° in the vertical direction. After the degree of vacuum was reduced to 5 × 10 ⁻³ Pa or less, aluminum vapor was supplied by heating the aluminum target. After about 10 hours, the supply of aluminum vapor was stopped, the movement of the cylindrical deposition chamber was stopped, and the inside was replaced with dry N ₂ gas, and then aluminum-deposited silica fine particles were taken out.
[0025]
(3) Surface treatment 0.5 g of the aluminum-deposited silica fine particles obtained in the above item (2) was weighed into a 100 mL flask, 10 mL of ethanol was added thereto, and the mixture was dispersed using an ultrasonic disperser. Subsequently, 10 mL of a 2.5 wt% tetraethoxysilane in tetrahydrofuran solution and 1 mL of an aqueous 0.1 mol / L HCl solution were added, and the mixture was reacted at room temperature for 24 hours with stirring. The product is separated into a pigment and a reaction solution by a centrifugal separation method, and the operations of washing with a sufficient amount of ethanol and centrifugal separation are repeated three times, and then naturally dried to form a water-resistant surface protective layer. A composite aluminum pigment was obtained.
The obtained water-resistant surface protective layer-coated composite aluminum pigment is dispersed in ion-exchanged water using an ultrasonic disperser, and this dispersion is dropped on matte paper (MC matte paper, model number KA450MM, manufactured by Seiko Epson). As a result, a silver glossy coating film was obtained.
[0026]
【The invention's effect】
According to the present invention, a composite aluminum pigment is obtained. This composite aluminum pigment has excellent dispersion stability in a dispersion liquid because the specific gravity of the silica fine particles serving as the core is light, and the aluminum deposited thereon has a low specific gravity. Further, the silica fine particles synthesized by the sol-gel method have a narrow particle size distribution range and a high uniformity of particle size, so that the composite aluminum pigment of the present invention containing those silica fine particles as a core material also has a particle size distribution range. Since it is narrow and the uniformity of particle size is high, excellent metallic luster can be obtained. Furthermore, it has excellent heat resistance and mechanical strength, can be used in a wide range of fields, and can form a coating film having resistance to scratches and abrasions. Further, since the composite aluminum pigment of the present invention has a small average particle size, it is also suitable as a colorant for an ink composition for inkjet recording.

Claims (10)

A composite aluminum pigment which is synthesized by a sol-gel method and has an aluminum vapor-deposited layer covering the entire surface thereof on a silica fine particle core having an average particle diameter of 5 μm or less. The composite aluminum pigment according to claim 1, further comprising a surface protective layer covering the entire surface of the aluminum vapor-deposited layer. The composite aluminum pigment according to claim 1, wherein the silica fine particle core is a spherical fine particle. An aqueous dispersion containing the composite aluminum pigment according to any one of claims 1 to 3 as a colorant component. An aqueous aluminum pigment composition comprising the composite aluminum pigment according to claim 1 as a colorant component. The aqueous aluminum pigment composition according to claim 5, which is an ink composition for inkjet recording. (1) Silica fine particles synthesized by a sol-gel method and having an average particle diameter of 5 μm or less are charged into a deposition chamber having a bottom surface of a disk-shaped flat surface and a side surface having at least a side surface in contact with a ring,
(2) In a state in which the silica fine particles are agitated under a vacuum condition to expose the entire surface of each silica fine particle in order, aluminum vapor is supplied to the entire surface of the silica fine particles, whereby aluminum A method for producing a composite aluminum pigment, comprising forming an evaporation layer. The method for producing a composite aluminum pigment according to claim 7, wherein after forming an aluminum vapor-deposited layer on the surface of the silica fine particles, a surface protective layer is formed on the aluminum vapor-deposited layer. By rotating the disk-shaped bottom surface of the vapor deposition chamber in the horizontal direction, and moving the circumferential portion of the disk-shaped bottom surface up and down in the vertical direction, the entire surface of each silica fine particle is exposed in order, 9. The method according to claim 7, wherein aluminum vapor is supplied to the entire surface of the silica fine particles. By not rotating the disk-shaped bottom surface itself of the vapor deposition chamber in the horizontal direction, inclining it from the horizontal direction, and rotating the lowest circumferential portion and the highest circumferential portion along the circumference, each silica fine particle. 9. The production method according to claim 7, wherein an aluminum vapor is supplied to all surfaces of the silica fine particles in a state where all surfaces of the silica particles are sequentially exposed.