JP2004256658A - Method for preparing novel aluminum pigment paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preparing an aluminum pigment paste having a concentration process with productivity, processability, and safety improved without causing damage to the quality or designability that a metallic pigment is expected to present. <P>SOLUTION: The aluminum pigment paste preparing method has a concentration process wherein a slurry comprising a flaky aluminum pigment and an organic solvent is so controlled that the fatty matter dissolved in the solvent accounts for ≤2 wt.% in the ultimate concentrate. In the concentration process, the organic solvent is evaporated under ≤100 Torr vacuum degree at ≤120°C heating temperature until the aluminum content accounts for >50 but ≤95 wt.%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００４０】
【発明の効果】
本発明のアルミニウム顔料ペーストの製造方法を用いれば、メタリック顔料としての品質、意匠性を損なうことなく、生産性、作業性、安全性を向上することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a metallic pigment to be applied to automobiles and home electric appliances, or an aluminum pigment paste used for high-grade metallic ink such as printing.
More specifically, the present invention uses a new aluminum pigment concentration / recovery method instead of the filter press conventionally used for the purpose of concentrating an organic solvent slurry of flake aluminum pigment and recovering an aluminum pigment cake. The present invention relates to a method for producing a pigment paste.
[0002]
[Prior art]
Flake-like aluminum pigments are pigments that have a unique metallic feeling that is not found in other pigments and have excellent hiding power on the substrate, such as high-grade metallic paints for automobile bodies and parts, metallic paints for automobile repair, metallic paints for home appliances, and industrial paints. It is widely used in the field of high-grade metallic paints such as metallic paints, and in the field of high-grade metallic printing inks such as gravure printing, offset printing, and screen printing.
[0003]
The aluminum pigment paste is usually produced through a pulverization / polishing step, a classification (screen) step, a filtration / concentration step, and a mixing step. (For example, see Non-Patent Document 1)
In the grinding / polishing process, using a ball mill or a medium stirring mill, in the presence of an organic solvent and a grinding aid or a lubricant, the raw material granular atomized aluminum powder or aluminum foil piece is formed into a very thin flat flake shape. Wet pulverization and polishing into particles. The flake-like aluminum pigment thus obtained is adjusted in particle size distribution in the next classification (screening) step, and is separated from a large amount of an organic solvent in a filtration / concentration step to be recovered as an aluminum pigment cake. An aluminum pigment paste is obtained by adding an organic solvent and additives to the recovered cake, uniformly stirring and mixing the resultant, and adjusting the concentration of nonvolatile components.
[0004]
Heretofore, cake filtration represented by a filter press has been mainly used as a solid-liquid separation method used in a filtration / concentration step. However, in recent years, the problem of the concentration step using a filter press has become apparent.
The first problem is that productivity is reduced due to reduction in filtration efficiency.
In cake filtration, solids (aluminum pigment particles) that cannot pass through the filter are deposited as filter cake on the filter surface, and the cake acts as a filter medium for subsequent filtration. As the filtration proceeds, the filtration rate decreases. Go on.
[0005]
In recent years, with the increase in the particle size of aluminum pigments, the filtration resistance of the cake has increased. For this reason, the time required for filtration and concentration is significantly increased. Further, in order to further increase the concentration, it is conceivable to use squeezing or the like in combination, but it is expected that productivity and workability will be further reduced. In addition, aluminum pigments have poor detachability from filters due to their flat flake-like shape characteristics, and workability during cake recovery is extremely poor.
[0006]
The poor workability, which is cited as the second problem, is also caused by the structure of the filter press.
In the filter press, the filter and the plate with the groove that becomes the flow path of the filtrate are alternately arranged and tightened between the end plates to form a compartment sandwiched between the filters, and the slurry is pressed into this compartment to perform filtration. Is going. When the cell is filled with the cake, the device is once disassembled, the cake in the cell is collected, the device is assembled again, and the filtration is resumed. In order to recover the cake from the filter press in this way, it is necessary to disassemble the apparatus and perform the recovery operation for each compartment, which takes time and labor. In addition, since the compartment is exposed to the outside air when the device is disassembled, the organic solvent is volatilized from the exposed surface, which becomes a source of odor and pollutes the environment of the work site.
[0007]
As a device for concentrating a slurry by a mechanical separation method, in addition to a filter press, a device for continuously filtering in a closed type (eg, a drum filter or a belt filter (belt press)) or a decanter using a sedimentation method There is a centrifugal separator, but in any case, because of the poor drainage of the aluminum pigment cake, the degree of concentration does not increase until it becomes an aluminum pigment cake, or a huge device is required to recover the cake. .
[0008]
On the other hand, as a method of concentrating the slurry, it is conceivable to use evaporation of the organic solvent by heating. This method can reliably adjust the degree of concentration by controlling the amount of heat to be heated, but when concentrating a low-concentration slurry under excessive heating conditions, it is necessary to collect a large amount of solvent at once. In this respect, the risk is high, and the scale of the apparatus is large. In addition, when heating with stirring and mixing for the purpose of increasing the heat transfer efficiency, if shear stress is applied to the aluminum pigment cake for a long time, the chemical reaction on the surface of the aluminum pigment particles is promoted, and the design as a metallic pigment is improved. There were concerns about adverse effects.
[0009]
[Non-Patent Document 1] The Japan Light Metal Association, Aluminum Paste Committee, "Safety Guide for Handling Aluminum Paste", (Japan), revised edition, Japan Light Metal Association, October 1996, p. 1
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing an aluminum pigment paste having a novel concentration step in which productivity, workability, and safety are improved without impairing the quality and design of a metallic pigment.
[0011]
[Means for Solving the Problems]
The present inventors have conducted repeated studies on the basic physical properties of the flake-like aluminum pigment slurry and the concentration technology using various devices in order to solve the above-mentioned problems.As a result, the heating was performed under reduced pressure, and the slurry was obtained in a specific operating condition range. It has been found that by evaporating the solvent from, the aluminum pigment can be concentrated without deteriorating the quality of the aluminum pigment, and the present invention has been accomplished.
[0012]
That is, the present invention relates to a method for producing an aluminum pigment paste, wherein a flake-form aluminum pigment and a slurry comprising an organic solvent containing a fatty solvent solution are mixed with a fatty solvent solution contained in the obtained final concentrate. The solvent is evaporated under the conditions of a degree of vacuum of 100 Torr or less and a heating temperature of 120 ° C. or less while controlling the proportion to be 2% by weight or less, so that the aluminum content is higher than 50% by weight and 95% by weight or less. A method for producing an aluminum pigment paste, comprising the step of concentrating to an aluminum pigment paste.
The present invention is also a method for producing an aluminum pigment paste, wherein the concentration is performed using a continuous stirring type indirect heating dryer having a paddle having a self-cleaning mechanism.
[0013]
Furthermore, the present invention is a method for producing an aluminum pigment paste, comprising performing continuous and mechanical solid-liquid separation before the concentration step. Furthermore, the present invention measures the concentration of the fatty solvent solution contained in the slurry, and based on the measurement result, performs concentration in the continuous and mechanical solid-liquid separation in the concentration step and / or the preceding step. A method for producing an aluminum pigment paste, comprising controlling the ratio of a fatty solvent solute contained in a final concentrate obtained from the concentration step by determining a degree.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be specifically described.
The slurry composed of the flake aluminum pigment and the organic solvent for concentration is adjusted by adjusting the amount of the organic solvent in the slurry in the pulverization / polishing step and the classification (screening) step, and, if necessary, performing the pretreatment described later. Thus, the aluminum content is adjusted in the range of 60% by weight or less. Flake-like aluminum pigment is usually a ball mill, or a medium stirring mill, obtained by wet-milling and polishing granular atomized aluminum powder or aluminum foil pieces as a raw material, is a very thin flake-like pigment. . As the organic solvent, hydrocarbon solvents such as conventionally used mineral spirits, solvent naphtha, and toluene, and low-viscosity solvents such as alcohols, ethers, ketones, esters, and glycols can be used. Use of mineral spirits is preferred from the viewpoint of versatility and safety.
[0015]
Further, the organic solvent may contain a grinding aid or lubricant, which is a solvent solution of a fatty acid, and a modified product thereof. Examples of the grinding aid include conventionally used higher fatty acids such as oleic acid and stearic acid, higher aliphatic amines such as stearylamine, and higher aliphatic alcohols. The concentration is adjusted by adjusting the amount of the organic solvent so that the content as a fatty solvent solution becomes 4.0% by weight or less. In addition, the content of the aliphatic solvent solution in the organic solvent is preferably 3.0% by weight or less, more preferably 2.5% by weight or less.
When the content of the fatty solvent solution in the organic solvent exceeds 4.0% by weight, the content of the fatty solvent solution in the final concentrate obtained by the method of the present invention is reduced to 2.0% by weight. The following control may be difficult.
[0016]
In the present invention, the aluminum content of the aluminum pigment slurry is higher than 50% by weight and 95% by weight by evaporating the organic solvent in the slurry under the conditions of a degree of vacuum of 100 Torr or less and a heating temperature of 120 ° C. or less. Concentration is performed until the target concentration is in the following range. When the degree of vacuum exceeds 100 Torr, it is necessary to set the heating temperature to 120 ° C. or higher in order to evaporate the solvent. At this temperature, a chemical reaction proceeds on the surface of the aluminum pigment, and the quality of the aluminum pigment, particularly the design, There is a concern that the property may be adversely affected, which is not preferable. From the viewpoint of product quality and productivity, the degree of vacuum and the heating temperature are preferably 50 Torr or less, 110 ° C. or less, more preferably 10 Torr or more and 20 Torr or less, and controlled in the range of 75 ° C. or more and 90 ° C. or less. More preferred. Further, the concentration of the concentrate is preferably such that the aluminum content is 60% by weight or more and 90% by weight or less, and more preferably 75% by weight or more and 85% by weight or less.
[0017]
The apparatus for performing the concentration is not particularly limited as long as it has a function of heating the slurry under reduced pressure, but a dryer or a mixer that performs heating by heat transfer having a function of reducing the pressure in the apparatus is provided. Can be used. In addition, in order to shorten the time when heat or shear stress is applied to the aluminum pigment, and to perform concentration with high productivity, a continuous type having a paddle with a self-cleaning mechanism, which is one of the groove type conduction heat transfer dryers It is preferable to use a stirring type indirect heating dryer.
[0018]
Before the concentration under heating under reduced pressure, it is preferable to increase the concentration of the slurry to be supplied by using continuous and mechanical solid-liquid separation. Mechanical solid-liquid separation is a velocity difference separation in which a solid-liquid separation is performed by giving a velocity difference between a solid and a liquid under a specific field. Examples of a field for separating a solid from a solid-liquid dispersion system include a force field represented by gravity and centrifugal force and an obstacle represented by a filter. By using such a mechanical solid-liquid separation together, the amount of heat applied to the aluminum pigment during the concentration can be reduced. From the viewpoint of improving productivity, it is preferable that mechanical solid-liquid separation be performed continuously. Examples of devices capable of performing such continuous and mechanical solid-liquid separation include a centrifuge, a belt filter, and a drum filter. Preferably, a centrifuge is used. By such pretreatment, the content of the aluminum pigment in the aluminum pigment slurry can be concentrated to 35% by weight or more and 60% by weight or less, more preferably, 40% by weight or more and 50% by weight or less. It is difficult to carry out the above pretreatment at more than 60% by weight, and if it is less than 35% by weight, the amount of evaporation in the subsequent heat-concentration step under reduced pressure is large. It is not preferable because it may be difficult to control the content of the substance to 2.0% by weight or less.
[0019]
The concentration until the aluminum content becomes 15% by weight is preferably performed by cakeless filtration using a membrane prepared to have a pore size smaller than the particle size of the aluminum pigment particles. Cakeless filtration is a filtration method in which particles reaching the cake surface during the filtration operation are swept away to prevent the growth of cake as much as possible, and can be continuously and stably concentrated for a long period of time. An example is cross-flow filtration.
[0020]
In performing the concentration operation, in order to maintain the quality of the aluminum pigment, the ratio of the fatty solvent-soluble material such as a higher fatty acid contained in the final concentrate of the concentrated aluminum pigment slurry is 2% by weight or less. It is important to control so that When a final concentrate having a ratio of a fatty solvent solution exceeding 2% by weight is commercialized and used as a pigment for metallic paint or a pigment for printing ink, the resulting coating film or printed matter has a poor adhesion to a substrate. The quality, including physical properties and design, deteriorates.
[0021]
As a control method, the concentration of the fatty solvent solution contained in the slurry is appropriately measured, and based on the measurement result, the concentration step by heating under reduced pressure and / or the concentration in continuous and mechanical solid-liquid separation. It is preferred to determine the degree. In the heating operation under reduced pressure performed in the condition range of the present invention, since the fatty solvent solutes do not evaporate, they remain in the concentrate. It can be separated uniformly regardless of the difference in boiling points. Taking advantage of this, from the concentration measurement result of the fatty solvent solution contained in the slurry, it was not excluded to make the ratio of the fatty solvent solution contained in the final concentrate 2% by weight or less. By calculating the amount of fatty solvent solutes that must be retained, determining the enrichment in continuous and mechanical solid-liquid separation, and / or determining the enrichment by heating under reduced pressure. Can be controlled.
[0022]
【Example】
The present invention will be described based on examples. In addition, the measuring method of each physical property used in the Example and the Comparative Example is as follows.
[0023]
▲ 1 ▼ mean particle _{size: d 50}
It was measured with a laser micron sizer LMS-24 (manufactured by Seishin Enterprise Co., Ltd.). Mineral spirit was used as a measuring solvent. The aluminum pigment used as a sample was subjected to ultrasonic dispersion for 2 minutes as a pretreatment.
{Circle around (2)} Residues for heating According to the method for measuring residues for heating described in JIS K 5906: 1998, the mixture was heated in an atmosphere at 105 ° C. for 3 hours, and the weight fraction of the residue excluding the evaporated components was measured.
[0024]
{Circle around (3)} Acetone-soluble content Measured according to the acetone-soluble content measurement method described in JIS K 5906: 1998.
{Circle around (4)} The aluminum pigment slurry used as the sample of the concentration of the fatty solvent in the solvent was used as the sample. Filtration is performed using 5C filter paper to separate the aluminum pigment and the solvent. The separated solvent was heated for 3 hours in an atmosphere at 105 ° C. for 3 hours according to the method for measuring the residue on heating of a sample described in JIS K 5906: 1998, and the weight fraction of the residue excluding the evaporation component was measured.
[0025]
{Circle around (5)} Adhesion evaluation (1) Preparation of paint and coating film To 12 g of aluminum pigment paste, 90 g of mixed thinner and 50 g of base clear were added, and the mixture was shaken with a paint shaker for 5 minutes. The mixed thinner is a mixture of toluene, ethyl acetate and butyl cellosolve at a weight ratio of 7: 2: 1. Base clear is a mixture of Acrydic 47-712 (manufactured by Dainippon Ink and Chemicals, Inc.) and Super Beckamine J-820 (manufactured by Dainippon Ink and Chemicals, Inc.) at a weight ratio of 4: 1. It was done.
This base coat paint was applied using an air spray to prepare a coat having a dry coat thickness of 10 to 15 μm. Subsequently, a clear coat was applied on the coating film by a wet-on-wet method and then baked at 140 ° C. for 30 minutes. The dry coating thickness of the clear coat was 25 to 30 μm.
[0026]
(2) Evaluation The coating film obtained in the above (1) was evaluated according to the cross-cut tape method of adhesion evaluation in the test method for resistance of the coating film described in JIS K 5400: 1998.
The evaluation of adhesion was defined as follows.
ご と Each cut is thin and smooth on both sides, and there is no peeling at the intersection of the cut and each square.
○ There is no peeling of each square, and the area of the missing part is within 5% of the total square area.
× The area of the defective portion is 5% or more of the area of the entire square.
[0027]
{Circle around (6)} Coloring power (1) Preparation of paint / coating Acrylic No. was added to 5 g of aluminum pigment paste. 8 g of 2000GL thinner (manufactured by Kansai Paint Co., Ltd.) was added, and the mixture was pre-dispersed. After adding 97 g of 2026GL clear (manufactured by Kansai Paint Co., Ltd.), the mixture was shaken with a paint shaker for 10 minutes to obtain a silver metallic paint. Further, 45 g of the silver metallic paint is coated with Acrylic No. 5 g of 2365GL blue pigment (manufactured by Kansai Paint Co., Ltd.) was added, and the mixture was shaken with a paint shaker for 10 minutes to obtain a blue metallic paint. This blue metallic paint was coated on art paper using a 9 mil applicator, and then dried at room temperature.
[0028]
(2) Colorimetry Using a SM color computer SM-7-CH (manufactured by Suga Test Instruments Co., Ltd.), apply the coating film obtained in (1) to the coating film from the incident angles of -45 and 45 degrees. The incident light was received at an acceptance angle of 0 °, and the L value of the Hunter Lab color system was measured.
(3) Coloring power The coloring power of the blue metallic coating film is defined by the following formula (1).
(Coloring power) = 100 + 10 × (L value difference between sample coating film and reference coating film) (1)
Evaluation of coloring power was defined as follows.
着色 The coloring power is 96 or more and 104 or less.
△ Coloring power is 94 or more and less than 96, or more than 104 and 106 or less.
X The coloring power is less than 94 or greater than 106.
[0029]
[Example 1]
A ball mill having an inner diameter of 1 m and a length of 1 m is filled with a composition comprising 20 kg of atomized aluminum powder (average particle size: 8 μm), 200 kg of mineral spirit, and 2 kg of oleic acid, and glass beads having a diameter of 3 mm (specific gravity of 2.6). ) Using 600 kg, pulverized and polished at 25 rpm for 14 hours.
After the completion of the grinding and polishing, the slurry in the mill was washed out with mineral spirits, passed through a 650 mesh vibrating sieve, and the passed slurry was collected.
The collected aluminum pigment slurry had a total amount of 4000 kg and an aluminum content of 0.5% by weight. In addition, the concentration of the fatty solvent solution in the solvent constituting the slurry was 1.1% by weight.
[0030]
The aluminum pigment slurry is concentrated in a cross-flow filtration system until the aluminum content in the slurry is 10% by weight, and then concentrated using a decanter centrifuge until the aluminum content is 50% by weight. did. A monolithic ceramic ultrafiltration membrane (pore size 0.2 μm) was used for the crossflow filtration system. A concentration operation was performed at a filtration pressure of 0.1 MPa, and backwashing was performed intermittently. Two decanter-type centrifuges were assembled in a cascade, and a centrifugal force was applied in a range of 500 G or more and 1000 G or less to perform a concentration operation.
[0031]
In this manner, the aluminum pigment slurry concentrated to 50% by weight by continuous and mechanical solid-liquid separation is converted into a continuous stirring indirect heating dryer with a self-cleaning function (SCP-100, manufactured by Kurimoto Iron Works, Ltd.). , Until the aluminum content reached 85% by weight to obtain a final concentrate. In this case, the concentration of the fatty solvent in the final concentrate is 1.0% by weight. The heating dryer was operated such that the degree of vacuum in the apparatus was adjusted to 15 Torr, the heating temperature was adjusted to 80 ° C., and the residence time became 10 minutes.
[0032]
The above concentration operation was performed for 2 hours, and the final concentrate was recovered at 11 kg / Hr.
After adding a predetermined amount of solvent naphtha and an additive, the final concentrate was mixed for 15 minutes with a mixing stirrer to obtain an aluminum pigment paste having a heating residue of 74% by weight.
As a result of measuring the physical properties of the pigment paste, the average particle size was 20.0 μm, and the acetone-soluble matter was 0.9% by weight.
As a result of evaluating this pigment paste, the adhesion was evaluated as ◎. In addition, the tinting strength was evaluated as ○ for six months from the time of production, and there was no problem in storage stability with respect to color tone.
[0033]
[Example 2]
An aluminum pigment paste was obtained in the same manner as in Example 1, except that the degree of vacuum in the concentration operation by heating under reduced pressure was adjusted to 40 Torr and the heating temperature was adjusted to 90 ° C.
Table 1 shows the physical properties and evaluation results of this pigment paste.
[0034]
[Example 3]
The same operation as in Example 1 was carried out except that the concentration was carried out with a batch-type vacuum mixing stirrer for 150 minutes instead of the continuous stirring-type indirect heating dryer with a self-cleaning function, and the aluminum pigment paste was used. Obtained.
Table 1 shows the physical properties and evaluation results of this pigment paste.
[0035]
[Example 4]
The same operation as in Example 1 was performed except that the aluminum content of the aluminum pigment slurry to be heated under reduced pressure was set to 40% by weight and the residence time in the heating dryer was set to 14 minutes. did.
Table 1 shows the physical properties of the paste and the evaluation results.
[0036]
[Comparative Example 1]
The aluminum pigment slurry passed through the vibrating sieve was concentrated by a filter press, which is a conventionally used concentrator, until the aluminum content became 85% by weight to obtain a final concentrate. Otherwise, the same operation as in Example 1 was performed.
Table 1 shows the physical properties and evaluation results of the obtained pigment paste.
[0037]
[Comparative Example 2]
The same operation as in Example 1 was carried out except that the degree of vacuum in the concentration operation by heating under reduced pressure was adjusted to 110 Torr, the heating temperature was adjusted to 140 ° C., and the residence time in the apparatus was set to 9 minutes. A paste was obtained.
Table 1 shows the physical properties and evaluation results of this pigment paste.
The evaluation results of the pigment paste were as follows: the coloring power was evaluated as Δ at the time of production and × at three months after production and for half a year, indicating that the storage stability relating to the color tone could not be satisfied.
[0038]
[Comparative Example 3]
The same operation as in Example 1 was carried out except that the aluminum content of the aluminum pigment slurry to be heated under reduced pressure was 30% by weight and the residence time in the heating dryer was 20 minutes, and the aluminum pigment paste was used. Obtained. In this case, the fatty solvent solution in the final concentrate is 2.2% by weight, which is outside the scope of the present invention.
Table 1 shows the physical properties and evaluation results of this pigment paste.
The evaluation of the pigment paste was evaluated as x for the adhesion.
In the embodiment, a case where a cross-flow filtration system and a centrifugal separator are used as a continuous and mechanical solid-liquid separation device has been described. However, the present invention is not limited to this. It is possible to employ a device such as a filter.
[0039]
[Table 1]

[0040]
【The invention's effect】
By using the method for producing an aluminum pigment paste of the present invention, productivity, workability, and safety can be improved without impairing the quality and design of the metallic pigment.

Claims (6)

In the method for producing an aluminum pigment paste, an aluminum pigment slurry composed of a flake-like aluminum pigment and an organic solvent containing a fatty solvent solution is mixed with a final solvent concentrate containing 2% by weight of a fatty solvent solution. %, While evaporating the organic solvent under the conditions of a degree of vacuum of 100 Torr or less and a heating temperature of 120 ° C. or less, thereby concentrating the aluminum content to a range higher than 50% by weight and 95% by weight or less. A method for producing an aluminum pigment paste, comprising the steps of: The method for producing an aluminum pigment paste according to claim 1, wherein the concentration step is performed using a continuous stirring indirect heating dryer having a paddle having a self-cleaning mechanism. The method for producing an aluminum pigment paste according to claim 1, wherein a continuous and mechanical solid-liquid separation is performed before the concentration step. The method for producing an aluminum pigment paste according to claim 3, wherein a centrifuge is used for the solid-liquid separation. 4. The solid-liquid separation according to claim 3, wherein the concentration until the aluminum content becomes 15% by weight is performed by cakeless filtration using a membrane prepared to have a pore diameter smaller than the particle diameter of the aluminum pigment particles. A method for producing an aluminum pigment paste. The concentration of the fatty solvent solution contained in the slurry is measured, and the concentration in the concentration step and / or continuous and mechanical solid-liquid separation is determined based on the measurement result. A method for producing the aluminum pigment paste according to the above.