JP2883441B2 - Method for producing colored pearlescent mica pigment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mica particle surface coated with a special titanium oxide film in which the component ratio of titanium and oxygen changes in the film thickness direction.
The present invention relates to a method for producing a colored pearlescent mica pigment having an interference color.

[Conventional technology]

One of the known pearlescent pigments is a fine flaky mica having a titanium dioxide layer formed on the surface thereof, has a pearly luster and exhibits various interference colors. The manufacturing method is Japanese
Hydrolyzing an aqueous solution of an inorganic acid salt of titanium (e.g., titanyl sulfate) as found in -25644 in the presence of mica;
Generally, a method of precipitating hydrated titanium dioxide on the mica surface and then heating is performed. The mica to be used is often a transparent muscovite mica whose particle diameter has been adjusted to a range of 5 μm to 200 μm using a sieving mill. The generated pearlescent pigment exhibits various interference colors depending on the thickness of the titanium dioxide coating layer on the surface of the mica particles. The interference color changes to red, blue and green in the direction of increasing titanium dioxide layer in the amount of titanium dioxide in the range of 26-40% of the product, in the range of 40-50%, to red, blue and green, and further in the range of 50-60% High order interference colors are obtained. Although these pearlescent mica pigments have pearl luster and various interference colors, the appearance is always close to white,
No vivid appearance color was obtained. Therefore, conventionally, colored pigments such as iron oxide, navy blue, chromium oxide, carbon black, and carbon have been added to pearlescent mica pigments in order to obtain various appearance colors. However, when such a plurality of pigments are mixed and used, the luster and interference colors inherent in the pearlescent mica pigments are impaired, so that the design is inferior.

Therefore, further studies have been made on the improvement of pearlescent mica pigments having better design properties, and the following three typical methods have been reported.

1) Titanium dioxide-coated mica is dispersed in water, a base is added to the dispersion to adjust the pH, and at the same time, an aqueous solution containing an oxidizing agent and an iron (II) salt is gradually added, and the titanium dioxide-coated mica particles are added. A method for producing a blackish colored pearlescent mica pigment which is further coated with a precipitate of iron tetroxide (Fe ₃ O ₄ ) on the surface of
A process for producing a red-colored pearlescent mica pigment heat-treated at a temperature in the range of 0 to 1000 ° C (JP-A-61-19666).

2) Heat treatment of flaky mica coated with titanium dioxide (including hydrate) or composite of titanium dioxide and metal oxide (including hydrate) at a temperature of 600 to 950 ° C in a flow of ammonia NH ₃ To reduce titanium dioxide to titanium monoxide (JP-A-58-164653).

3) Mica particle surface is titanium dioxide and lower titanium oxide,
Alternatively, as a method of producing a colored pigment coated with lower titanium oxide, for example, a commercially available pearlescent mica pigment 500-1
000 ° C, preferably a method of heating and reducing with a mixed gas of a gas having a reducing power such as hydrogen gas and ammonia gas and an inert gas such as argon gas and nitrogen gas at a temperature of 700 to 900 ° C, a commercially available method. Titanium dioxide is mixed with the pearlescent mica pigment, and the mixture is heated and reduced by the above method, or a commercially available pearlescent mica pigment is mixed with metal titanium, and the mixture is placed under a pearl under a 500-1000
C., preferably 700-900 C. Further, an aqueous solution of an inorganic salt of titanium (for example, titanyl sulfate) as shown in JP-B-43-25644 is hydrolyzed in the presence of mica, thereby precipitating hydrated titanium dioxide on the surface of mica particles. 1000
C., preferably a gas having a reducing power such as hydrogen gas and ammonia gas at a temperature of 700 to 900 ° C. and helium gas,
Heat reduction with a mixed gas with an inert gas such as argon gas or nitrogen gas, or precipitation of hydrated titanium dioxide on the surface of mica particles followed by heating to form titanium oxide-coated mica, which is then marketed as the above-mentioned pearl The reduction may be carried out in the same manner as in the production of the glossy mica pigment. Further, the method of reduction is not limited to the method using a reducing gas such as the above-described hydrogen gas or ammonia gas, a method of reducing titanium oxide-coated mica using a reducing flame such as hydrogen, or a method of reducing mica particles. A method of suspending the suspension in a solution of a titanium halide, for example, titanium tetrachloride, and subjecting the suspension to oxidative decomposition in a flame of a mixed gas of air and hydrogen (JP-A-59-21)
2422).

Each of the above methods 1) has a drawback that only red and black types can be obtained, and the method 2) can only produce blue, blue black, black and brown black types. On the other hand, in the method 3), coloring such as blue, green, gold and magenta is possible, but the pearlescent mica pigment coated with titanium dioxide is heat-reduced at a high temperature of 500 to 1000 ° C. in a hydrogen gas atmosphere. Since the thickness of titanium dioxide is very small, if the reduction is performed at a high temperature of 500 to 1000 ° C., the entire titanium dioxide film may be reduced. Control is difficult. Further, at this temperature, the titanium dioxide-coated mica particles are sintered and coagulated and solidified to obtain a monodispersed fine powder pigment, and a special device is required to maintain the powder state.

A method of forming a titanium oxide film by sputtering titanium (under reduced pressure) on the mica particles in an oxygen gas stream is also conceivable. However, the titanium target reacts with oxygen to oxidize the target, and furthermore the oxygen gas The sputter rate is not practical because it is significantly smaller than that of argon gas or helium gas. Also, it is extremely difficult to control the change in the component ratio between titanium and oxygen in the particle size direction.

[Problems to be solved by the invention]

The present inventors have conducted intensive studies to solve the problems of the conventional colored pearlescent mica pigment and the method for producing the same.When the surface of titanium dioxide-coated mica is coated with titanium metal by sputtering under vacuum conditions, A phenomenon in which the titanium dioxide film was reduced to a lower oxide was discovered.
According to this method, there is no need to heat and reduce to 500 to 1000 ° C. in hydrogen gas. In addition, it is possible to produce various kinds of colors such as gold, silver, red, blue and green, and also has an interference color, so that it is possible to produce a colored pearlescent mica pigment having a new design that has never been seen before. Was found.

As a method of further coating titanium metal on the surface of titanium dioxide-coated mica, it is conceivable to apply a known method such as a vacuum evaporation method, an ion plating method, and a CVD method in addition to the sputtering method described above. However, there is still a problem with respect to the structure and operation of the apparatus because the target is powder.

[Means for Solving the Problems / Configuration of the Invention]

The present invention provides a pearlescent mica pigment composed of mica coated with titanium dioxide, which is further coated with metal titanium by a sputtering method, thereby reducing the titanium dioxide film to a lower oxide. Provided is a method for producing a glossy mica pigment.

The present invention also provides a powder decompression heat treatment zone, a fluidized bed sputtering zone, and a fluid mill powder dispersion treatment zone,
The present invention provides a method for producing a colored pearlescent mica pigment, in which a pearlescent mica pigment composed of titanium dioxide-coated mica is circulated between these three zones, and a metal titanium coating treatment is repeatedly performed by sputtering.

The sputtering is performed at a temperature of 200 ° C. or less. If the temperature is higher than 200 ° C., the pearlescent mica pigment will be strongly agglomerated, causing agglomeration and making it difficult to coat titanium uniformly.

The product must have the same color tone of the interference color of the pearlescent mica pigment composed of the raw material titanium dioxide-coated mica and the color of the colored pearlescent pigment according to the present invention, as well as titanium and oxygen in the lower oxide film. Is characterized in that the component ratio changes in the film thickness direction.

As pearlescent mica pigment of titanium dioxide coated mica,
For example, on the surface of mica having a particle size of 5 μm to 200 μm,
An aqueous solution of an inorganic acid salt of titanium (for example, titanyl sulfate) as shown in JP-B-43-25644 is hydrolyzed in the presence of mica, and is prepared by heating after precipitating hydrous titanium dioxide on the surface of the mica. Things can be used. The content of titanium dioxide is in the range of 10 wt% to 60 wt%, and interference colors such as silver, blue, green, red, magenta and gold are given depending on the film thickness.

The coating of titanium dioxide-coated mica on the pearlescent mica pigment by the sputtering method of titanium metal is disclosed in Jpn.
Alternatively, it can be implemented by the technology disclosed in Japanese Patent Application No. 1-74770. These techniques disperse fine powders of metals, ceramics or plastics into primary particles by (a) air jet milling in an inert atmosphere and dispersing them into primary particles. Heat treatment under reduced pressure in an atmosphere. (C) Charge the heat-treated fine powder into a rotating container containing a sputtering source, rotate the container to form a fluidized bed of the fine powder, and flow while rotating the container. A method for coating a fine powder, which comprises coating the fine powder by sputtering, (1) a rotatable and evacuable barrel supported on discrete rotating shafts that are not continuous, and a A sputter source supported on one rotating shaft is provided, the second rotating shaft has a function as a fine powder introduction path and an exhaust path to be coated, and has a vacuum exhaust and an inert gas introduction therein. (2) jet mill means communicating with a fine powder discharge path of a second rotating shaft of the sputtering chamber by a communication path having a valve; (3) the jet mill And (4) a fine powder conduit having a valve, which communicates with the stirring vessel and the first rotating shaft. It is a fine powder coating device.

In the above invention, various metals such as iron,
Copper, silver, gold, tin, platinum, nickel, titanium, cobalt,
Although it has already been disclosed that it is possible to coat chromium, aluminum, zinc, tungsten and their alloys, the present invention uses pearlescent mica pigments, which are titanium dioxide coated mica, as raw material, It is based on a newly discovered phenomenon that titanium dioxide is reduced to a lower oxide film when coated with titanium metal by a sputtering method.

(Specific description of the invention)

Although the method of the present invention can be carried out in a variety of devices, it is advantageous to carry out it continuously using the devices described above.

FIG. 1 is a conceptual view showing a structure of an example of an apparatus used in the method of the present invention and appropriately showing a cross section as viewed from one side.
The figure is a similar view showing the device shown in FIG. 1 in a cross-section taken generally along the line II-II in FIG. 1 when viewed from a direction perpendicular to FIG.

The main part of the apparatus comprises a reduced pressure heat treatment chamber 1, a rotary barrel type sputtering chamber 2, a fluid jet mill 3, and a powder filter 4.

The reduced-pressure heat treatment chamber 1 is a container heated by electric resistance, and includes a main exhaust system 6 and an advanced exhaust system 7
Communicate with The main exhaust system is a mechanical vacuum pump, and the advanced exhaust system is a combination of a cryosorption pump, a turbo molecular pump, a mechanical booster pump, or the like and a cooling trap. The reduced pressure heat treatment chamber 1 is provided with a screw feeder 9 for dropping the fine powder 8 subjected to the reduced pressure heat treatment into a conduit 10 for feeding into the rotary barrel type sputtering chamber 2 and a motor 40 for rotating the screw feeder 9.

As shown in FIG. 2, a barrel-type sputtering chamber (hereinafter, may be simply referred to as a barrel) 2 is a rotating cylindrical body having a structure like a ball mill.
And the exhaust systems 6 and 7 communicating with the same conduit 10. One of the side walls is supported by a horizontal portion, at which the conduit 10 extends downward and then gently bends at right angles, as a rotation axis. A magnetic seal 30 is used as a bearing between the shaft and the side wall of the barrel 2 to maintain airtightness.

From the opposite side wall of this barrel, a similar bearing mechanism 30 '
A shaft functioning as a rotating shaft of the barrel 2 is inserted through the through hole, and a sputtering device 50 is held at the tip of the shaft. The attitude is not vertical but has a tilt determined by the position of the powder bed caused by the rotation of the barrel 2 described below.

The sputter source is operated by a high-frequency current from a power source (not shown) supplied through the center axis of rotation of the barrel.

The sputtering chamber 2 is connected to the reduced pressure heat treatment chamber 1 via a fluid jet mill 3, and its conduits 10 and 11 have valves 12 respectively.
1 and 122 are provided. The conduit 10 curves horizontally as described above and enters the barrel 2 and then curves down again to reach near the bottom of the barrel. In this case, the curvature is not directed vertically downwards, but rather to the location where a fluidized bed of fine powder produced by rotation of the barrel is created.

The other side wall of the sputtering chamber is rotatably supported by another shaft 12, likewise by a magnetic seal 30. The sputtering chamber is controlled while being rotated by the support roll 13, the rotation motor 14, and the pulley 15. In addition, a small-diameter pipe communicating with the fine powder transport conduit 10 and the discharge conduit 11 inside the sputtering chamber 2 and the evacuation system.
19 is made of graphite which is hardly coated by sputtering.

The sputter source 50, for example a bipolar magnetron,
It is supported on an extension of 12 and has a structure in which the distance between the fine powder and the fluidized bed 18 can be adjusted by a height adjusting screw (not shown). Of course, this operation is performed while the operation is stopped, with the side wall of the barrel removed.

The fine powder coated by sputtering depressurizes the decompression heat treatment chamber 1, closes the valve 121 and opens the valve 122 to cut off the communication between the decompression heat treatment chamber 1 and the sputtering chamber 2 and send an inert gas. By feeding the inert gas little by little from the inlet pipe 19, it can be conveyed to the fluid jet mill 3. The fluid jet mill 3 has a structure in which a fine powder carrying an inert gas flow impinges on a propeller 21 rotated at a high speed by a motor 20. Needless to say, a conductor for supplying electricity to the sputtering source is accommodated inside the shaft 12.

The discharge side of the jet mill 3 communicates with a fine powder circulation pipe 23 having a valve 22, and further communicates with the vacuum heat treatment chamber 1. The fine powder circulation pipe 23 communicates with the powder filter 4 from a lower portion of the valve 22 through a branch pipe having a valve 24. This powder filter 4 is a trap connected to an exhaust system 26 via a cylindrical filter 25.

This device is manufactured by San-Ei Riken Co., Ltd. based on the design of some of the present inventors, and has approximately the following dimensions. 300mm in diameter and 150mm in height of the vacuum processing chamber, 500mm in diameter and 300mm in thickness of the rotary barrel type sputtering chamber. The sputtering source used was "1500D" manufactured by Tokyo High Power Co., and the jet mill used was "DA-3" manufactured by Sankyo Electric Industry Co., Ltd.

The color of the colored pearlescent mica pigment is the same system as the color tone of the pearlescent mica pigment composed of titanium dioxide coated mica as the raw material.The smaller the amount of titanium metal sputtering, the brighter the color, and the higher the amount, the darker the color. is there. The amount of sputtering of titanium metal is preferably 1 wt% to 30 wt% based on the pearlescent mica pigment composed of titanium dioxide-coated mica. If less than 1 wt%, there is almost no coloring effect and 30w
If it exceeds t%, the color becomes gray metallic tone which is not chromatic, which is not preferable.

 The invention will now be illustrated by way of examples.

Example 1 50 g of a mica frame (diameter: 10 to 20 μm, thickness: about 0.5 μm) was added to 500 ml of ion-exchanged water, sufficiently stirred, and uniformly dispersed. To the resulting dispersion was added 158.2 ml of a 40% by weight aqueous solution of titanyl sulfate, and the mixture was heated with stirring and boiled for 6 hours. After standing to cool, the mixture was filtered, washed with water, and calcined at 900 ° C. to obtain 90 g of a pearlescent mica pigment having a red interference color whose surface was coated with titanium dioxide. Next, 10 wt% of titanium metal was sputtered using the powder sputtering apparatus shown in FIGS. That is, the above 90g
The mica pigment coated with titanium dioxide was charged into a rotary barrel type sputtering chamber with the side wall removed, and then the pressure reduced heat treatment chamber was depressurized to 2 × 10 ⁻⁵ Torr, and argon gas was gradually fed from an inert gas feed pipe. And dispersed in primary particles using a fluid jet mill, and then collected in a reduced pressure heat treatment chamber. 2x the collected titanium dioxide-coated mica pigment
While reducing the pressure to 10 ^-2 Torr, heat it to 100 ° C with a heater,
Drying and degassing were performed for 30 minutes. Next, the titanium dioxide-coated mica pigment was transferred to a sputtering chamber that had been previously replaced with argon gas. After the transfer, the sputtering chamber was rotated at 5 rpm, and sputtering was performed with a two-pole magnetron under a reduced pressure of 2 × 10 ^-2 Torr (power 0.2 k).
(W × 2, frequency 13.56 MHz) was started. The temperature of the titanium dioxide-coated mica pigment was 200 ° C. or less. About one hour
A 0.2% by weight amount of titanium metal coating was formed. This process was repeated five times, yielding a total of 1.0 wt% titanium metal coating.

After the completion of the coating operation by sputtering, an argon gas flow containing the mica pigment was fed into the powder filter while introducing argon gas into the sputtering chamber through an inert gas feed pipe to obtain a red pearlescent mica pigment.

As a result of observation, the mica surface of the red pearlescent mica pigment obtained in this example had a titanium-oxygen component ratio of about 2,900 ° in the film thickness direction as shown by the Auger analysis result in FIG. It was found that it was covered by a thick titanium low oxide film.

Example 2 50 g of the same mica flakes as used in Example 1 were added to 500 ml of ion-exchanged water, sufficiently stirred, and uniformly dispersed. To the obtained dispersion, 3125.5 ml of a 40% by weight aqueous solution of titanyl sulfate was added, and the mixture was heated with stirring and boiled for 6 hours. After allowing to cool, it was filtered, washed with water, and calcined at 900 ° C. to obtain 100 g of a pearlescent mica pigment having a green interference color, the surface of which was coated with titanium dioxide. Next, 30 wt% of titanium metal was sputtered using the powder sputtering apparatus shown in FIGS. 1 and 2 described above. That is,
100 g of pearlescent mica pigment was charged into a rotary barrel type sputtering chamber, and then the pressure reduced heat treatment chamber was depressurized by 2 × 10 ^-2 Torr. Then, argon gas was gradually fed from an inert gas feed pipe and simultaneously a fluid jet was performed. After being dispersed into the primary particles using a mill, the particles were collected in a vacuum heat treatment chamber. While reducing the collected mica pigment to 2 × 10 ^-2 Torr,
Heating to 0 ° C. was performed for drying and degassing for 30 minutes. Next, the mica pigment was transferred to a sputtering chamber that had been previously replaced with argon gas. After the transfer, sputtering was performed by a two-pole magnetron method under a reduced pressure of 2 × 10 ⁻² Torr while rotating the sputtering chamber at a rotation speed of 5 rpm (power 3.
0kW x 2 units, frequency 13.56MHz). The temperature of the mica pigment was below 200 ° C. Approximately 3% by weight of metallic titanium adhered in one hour. Repeat this process 10 times for a total of 30wt%
An amount of titanium metal coating was applied.

After the completion of the coating operation by sputtering, an argon gas flow containing the mica pigment was fed into the powder filter while introducing argon gas into the sputtering chamber through an inert gas feed pipe to obtain a green pearlescent mica pigment.

Observation of the green pearlescent mica pigment obtained according to this example shows that the surface ratio of the mica particles varies in the component ratio between titanium and oxygen in the film thickness direction as shown by the Auger analysis result in FIG. It was found that it was covered by a 6,600 mm thick titanium oxide film.

[Functions and effects of the invention]

These colored pearlescent mica pigments can be used for exterior building materials, interior building materials, home appliances, automobiles, ships and the like as new coloring pigments for paints and plastics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one side showing the concept of an apparatus for carrying out the method of the present invention, and FIG. 2 is a cross-sectional view taken along a line II-II of FIG. It is a conceptual sectional view.
FIG. 3 and FIG. 4 are graphs showing the results of Auger analysis in the diameter direction of the red and green pearlescent pigments which are the products of the present invention, respectively. 1 and 2, 1... Reduced pressure heat treatment chamber 2... Rotary barrel type sputtering chamber 3... Fluid jet mill 4... Powder filter 5... Filter 6... Main exhaust system 7. ... powder heated under reduced pressure 9 ... screw feeder 10, 11 ... conduit 121, 122 ... valve 13 ... support roll 14, 20 ... motor 15 ... pulley 18 ... fluidized bed of fine powder 19 ... ... inert gas Inlet pipe 21 Propeller 22, 24 Valve 23 Fine powder circulation pipe 25 Cylindrical filter 26 Exhaust system 27 Motor 28 Sputtering source

Continued on the front page (72) Inventor Hiroshi Ito 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Kenji Kuroyagi 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Invention Person Yuji Tanaka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-59-212422 (JP, A) JP-A-2-153068 (JP, A) (JP, U) JP 61-57336 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 14/00-14/58 C09C 1/36

Claims (2)

(57) [Claims] 1. The method of claim 1, wherein the surface of the pearlescent mica pigment composed of mica coated with titanium dioxide is coated with titanium metal by a sputtering method at a temperature of 200 ° C. or less, thereby reducing titanium dioxide to lower titanium oxide. For producing colored pearlescent mica pigments. 2. A powder pressure reduction heat treatment zone, a fluidized bed sputtering zone, and a fluid mill powder dispersion treatment zone are provided, and a pearlescent mica pigment composed of titanium dioxide-coated mica is circulated between these three zones. The method according to claim 1, wherein the metal titanium coating treatment by sputtering is repeatedly performed.