JP2004307617A - 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 a mechanochemical aluminum adhering 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 adhering layer. The manufacturing method comprises treating silica fine particles which are synthesized by the sol-gel method and have an average particle diameter of ≤5 μm and metallic aluminum fine particles by the mechanochemical method to form a mechanochemical-aluminum adhering layer on the entire surface of each of the silica fine particles. A surface protective layer can be further formed on or after forming the aluminum adhering 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
The problem can be solved by a composite aluminum pigment characterized by having a mechanochemical-aluminum fixing layer covering the entire surface of a silica fine particle core synthesized by a sol-gel method and having an average particle diameter of 5 μm or less. it can.
According to a preferred embodiment of the present invention, the device further comprises a surface protective layer covering the entire surface of the mechanochemical-aluminum fixing 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]
Also, the present invention
A silica fine particle synthesized by a sol-gel method and having an average particle diameter of 5 μm or less, and a metal aluminum fine particle are treated by a mechanochemical method to form a mechanochemical-aluminum fixed layer on the entire surface of the silica fine particle. The present invention also relates to a method for producing a composite aluminum pigment.
According to a preferred aspect of the method of the present invention, the mechanochemical method is a wet mechanochemical method carried out in the presence of an organic dispersion medium using a metal aluminum paste containing metal aluminum particles.
According to another preferred embodiment of the method of the present invention, the mechanochemical method is a dry mechanochemical method carried out in the absence of an organic dispersion medium using dry metal aluminum fine particles.
Further, according to another preferred embodiment of the method of the present invention, after forming a mechanochemical-aluminum fixing layer on the surface of the silica fine particles, a surface protective layer is formed on the mechanochemical-aluminum fixing layer.
Further, according to another preferred embodiment of the method of the present invention, the particle diameter ratio (Ds / Da) between the average particle diameter (Ds) of the silica fine particles and the average particle diameter (Da) of the metal aluminum fine particles is 0.5. ~ 7.
[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]
Subsequently, the silica fine particles thus obtained and the metal aluminum fine particles are brought into contact with each other by a mechanochemical method, and metal aluminum is physically fixed on the entire surface of the silica fine particles to form a metal aluminum layer. That is, the surface of the silica fine particles can be coated with an aluminum layer by deforming and fixing the aluminum fine particles on the surface of the silica fine particles using a mechanical external force. Specifically, for example, when using a planetary mill to contact silica fine particles and aluminum fine particles in the presence of zirconia beads, the impact force of the zirconia beads deforms the aluminum fine particles on the surface of the silica fine particles, To form a mechanochemical-aluminum fixing layer.
[0015]
The mechanochemical method described above can be carried out by either a wet method or a dry method. The wet mechanochemical method is performed in the presence of an organic dispersion medium using an organic dispersion medium paste containing metal aluminum particles, and the dry mechanochemical method is performed in the absence of an organic dispersion medium using dry metal aluminum particles. It is carried out in.
[0016]
The organic dispersion medium used in the wet mechanochemical method is not particularly limited as long as it does not react with highly active metal aluminum fine particles, but an aprotic organic solvent, particularly a nonpolar aprotic organic solvent is preferable. Specifically, aromatic hydrocarbons such as benzene, toluene, or cyclohexane, and aliphatic hydrocarbons such as n-hexane or mineral spirit are preferable. Note that, in order to avoid a reaction with the metal aluminum fine particles, it is preferable to remove moisture and impurities in advance.
[0017]
In the mechanochemical method of the present invention, the particle diameter ratio (Ds / Da) of the average particle diameter (Ds) of the silica fine particles and the average particle diameter (Da) of the metal aluminum fine particles in both the wet method and the dry method. However, it is preferably 0.5 to 7, and more preferably 1 to 5. When the particle diameter ratio (Ds / Da) is out of the range of 0.5 to 7, aluminum fine particles which are not compounded remain, or aluminum fine particles having a reduced particle diameter due to being pulverized occur, resulting in gloss. , And storage stability (settling). In order to remove these impurities, it is necessary to carry out a separation / purification step, resulting in a cost burden.
[0018]
In the mechanochemical method of the present invention, the amount of the silica fine particles and the metal aluminum fine particles is preferably 50 to 300 parts by weight with respect to 100 parts by weight of the silica fine particles in any of the wet method and the dry method. It is used in an amount of 100 parts by weight, more preferably 100 to 200 parts by weight. If the amount of the metal aluminum fine particles is less than 50 parts by weight, the surface coating may be insufficient, and if it exceeds 300 parts by weight, uncomplexed free aluminum fine particles may be generated.
[0019]
In the mechanochemical method of the present invention, any of the wet method and the dry method can be performed using a known dispersing machine. Examples of the dispersing machine include a planetary ball mill, a paint shaker, and a rotary ball mill. Or a hybridizer can be used. In the case of a paint shaker or a ball mill, a wet method is preferably performed, and in the case of a hybridizer, a dry method is preferably performed.
[0020]
In the present invention, it is preferable that a mechanochemical-aluminum fixing layer is formed on the surface of the silica fine particles, and then a surface protective layer is formed on the mechanochemical-aluminum fixing 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.
[0021]
The formation of the surface protective layer can be performed simultaneously with the operation of the mechanochemical method in any of the wet method and the dry method. That is, the operation of the mechanochemical method described above can be carried out in the presence of a surface treatment agent, for example, a silane coupler. In this case, the compounding step and the surface treatment step can be carried out simultaneously, It is preferable in terms of cost.
[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, since the mechanochemical-aluminum fixed layer supported on the silica fine particle core having a low specific gravity has a low proportion of the whole, the dispersion stability in the dispersion is excellent. 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 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) Wet mechanochemical treatment In a glove box replaced with argon, 0.5 g of the silica fine particles prepared in the above item (1) and 0.5 g of aluminum paste in toluene (Toyo Aluminum Co., Ltd.) were placed in a polyethylene processing container having a capacity of 80 mL. Flake aluminum; average particle size = 4 μm), 150 g of zirconia beads (diameter = 0.3 mm), and 5 g of anhydrous toluene were weighed and sealed.
Using a planetary ball mill (P-5; manufactured by Fritsch Co.), the treatment was performed three times at 400 rpm for 10 minutes, and then 5 g of anhydrous toluene was added to the treatment container, and the beads and the dispersion were separated. A pigment toluene dispersion having a mechanochemical-aluminum fixed layer was obtained.
[0025]
(3) Surface treatment In a glove box replaced with argon, 5 mL of the toluene dispersion obtained in (2) above is weighed and placed in a 100 mL flask, and subsequently, 10 mL of a 2.5% by weight tetraethoxysilane solution in tetrahydrofuran, and 1 mL of 0.1 mol / L HCl aqueous solution was added, and the reaction was carried out at room temperature for 24 hours. The obtained composite aluminum pigment was taken out with a glove box, separated from the reaction solution by a centrifugal separation method, and then washed and centrifuged three times with a sufficient amount of ethanol, and then air-dried. Thus, a composite aluminum pigment having a water-resistant surface protective layer was obtained.
The obtained composite aluminum pigment was dispersed in ion-exchanged water using an ultrasonic disperser, and this dispersion was dropped on matte paper (MC matte paper, model number KA450MM, manufactured by Seiko Epson) to obtain a silvery gloss. A certain coating film could be obtained.
[0026]
<Example 2>
(1) Preparation of Silica Fine Particles Silica fine particles were obtained in the same manner as in Example 1 (1).
[0027]
(2) Dry mechanochemical treatment In a glove box replaced with argon, 0.5 g of the silica fine particles and 0.5 g of metal aluminum fine particles prepared in (1) above (0670TS; manufactured by Toyo Aluminum Co., Ltd.) were placed in a polyethylene processing container. Aluminum; average particle size = 4 μm) and 150 g of zirconia beads (diameter = 0.3 mm) were weighed and sealed.
The container was mounted on a planetary ball mill (P-5; manufactured by Fritsch Co.), and a cycle of 15 minutes at a revolving speed of 400 rpm and standing for 1 minute was continued for 24 hours. Subsequently, the kneading liquid and the zirconia beads were separated by a stainless steel sieve (sieve = 212 μm) to obtain a composite pigment having a mechanochemical-aluminum fixed layer.
[0028]
(3) Surface treatment The composite pigment obtained in the above item (2) was used as a toluene dispersion, and the composite having a water-resistant surface protective layer was obtained using the toluene dispersion by the same treatment as in Example 1 (3). An aluminum chloride pigment was obtained. The obtained composite aluminum pigment was dispersed in ion-exchanged water using an ultrasonic disperser, and this dispersion was dropped on matte paper (MC matte paper, model number KA450MM, manufactured by Seiko Epson) to obtain a silvery gloss. A certain coating film could be obtained.
[0029]
【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 because the specific gravity of the silica fine particles serving as the core is low and the aluminum fixing layer formed 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 (11)

A composite aluminum pigment synthesized by a sol-gel method, comprising a silica fine particle core having an average particle diameter of 5 μm or less, and having a mechanochemical-aluminum fixing layer covering the entire surface thereof. The composite aluminum pigment according to claim 1, further comprising a surface protective layer covering the entire surface of the mechanochemical-aluminum fixing 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 any one of claims 1 to 4 as a colorant component. The aqueous aluminum pigment composition according to claim 5, which is an ink composition for inkjet recording. A silica fine particle synthesized by a sol-gel method and having an average particle diameter of 5 μm or less, and a metal aluminum fine particle are treated by a mechanochemical method to form a mechanochemical-aluminum fixed layer on the entire surface of the silica fine particle. A method for producing a composite aluminum pigment. The method for producing a composite aluminum pigment according to claim 7, wherein the mechanochemical method is a wet mechanochemical method carried out in the presence of an organic dispersion medium using a metal aluminum paste containing fine metal aluminum particles. The method for producing a composite aluminum pigment according to claim 7, wherein the mechanochemical method is a dry mechanochemical method performed using dry metal aluminum fine particles in the absence of an organic dispersion medium. The composite aluminum pigment according to any one of claims 7 to 9, wherein after forming the mechanochemical-aluminum fixing layer on the surface of the silica fine particles, a surface protective layer is formed on the mechanochemical-aluminum fixing layer. Production method. 11. The particle diameter ratio (Ds / Da) of the average particle diameter (Ds) of the silica fine particles to the average particle diameter (Da) of the metal aluminum fine particles is 0.5 to 7. The method for producing a composite aluminum pigment described in the above item.