JPH07272533A - Manufacture of titanium covered conductive powder - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing such conductive powder at low cost that is free of sedimentation and separation during coating because of its small specific gravity as well as superior conductivity, has superiority in corrosion resistance such as, saltwater resistance, acid rain resistance, corrosive gas resistance, etc., and shows little change in conductivity with the passing of time. CONSTITUTION:Powdered particles 1 are composed of nonmagnetic metal oxides having small water content rate such as alumina, oxide zinc, oxide titanium, oxide titanium covered mica, and mica. The surfaces of the powered particles 1 of 0.1-100mum in average grain size is covered with titanium 4 of 3-20mass% by sputtering method.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a titanium-coated conductive powder used for an antistatic paint, an antistatic film, an antistatic resin and an antistatic fiber (hereinafter collectively referred to as "antistatic composition"). It relates to a method of manufacturing.

[0002]

2. Description of the Related Art An antistatic composition prepared by mixing a conductive powder with a resin binder or a solvent is known. Generally, as a conductive powder mixed in such an antistatic composition,
Metal powders such as Ag, Cu, Al and Ni are used. In the conventional antistatic composition, these metal powders are mixed in at least approximately the same weight as the resin content. However, Ag is expensive. Further, Cu and Al are unstable because they are easily oxidized and their conductivity changes with time. Further, Ni has a drawback that it has a poor dispersibility in a resin or a paint and has a large specific gravity, so that it easily precipitates and separates in a resin binder or a solvent.

In order to overcome the above drawbacks,
Electroless Ag-plated mica, which is a conductive powder obtained by coating mica or glass with Ag or Au (JP-A-64-8767).
No. 4), Au sputter-coated glass powder (JP-A-56-13).
No. 0469) and the like are known. In addition, electroless Ni-P plated mica, which is a conductive powder obtained by coating metal on mica or glass by an electroless plating method (JP-A-63-
54316), electroless Ag, Cu or Ni-P plated glass beads (JP-A-63-317541), reduction-plated copper powder of Au and Ag with hydrazine (JP-A-56).
-150101) and the like are known. These conductive powders have a low specific resistance of 10 ^-4 to 10 ^-5 Ω · cm and are excellent in conductivity. Also, they have a smaller specific gravity than metal powders, so they do not easily settle or separate in paints. Moreover, flake-shaped mica and glass beads have the advantage that they have better dispersibility than metal powder.

On the other hand, a conductive powder obtained by coating a titanium oxide powder with a conductive oxide is also known. Examples thereof include SnO ₂ -coated titanium oxide (JP-A-4-154621), RuO ₂ -coated titanium oxide (JP-A-58-225503), and ZnO-coated titanium oxide (JP-A-57-6762). These conductive powders have an average particle size of 1.0 μm.
It is fine as shown below, and since the color tone of the powder is white or transparent, it is easy to be colored in various color tones, so that it is preferably used in antistatic compositions such as fibers and carpets.

[0005]

However, in any case, A
When u or Ag is plated, there arises a problem that the manufacturing cost is high. Further, the conductive powder obtained by coating a metal on mica or glass by an electroless plating method has a large specific gravity because the coating amount of the metal is as large as 40 to 60 mass%. Furthermore, C
A film formed of u, Ni-P or the like does not necessarily have excellent corrosion resistance and is not practical.

On the other hand, the conductive powder obtained by coating titanium oxide with a conductive oxide has a considerably high specific resistance and is considerably inferior in conductivity as compared with the conductive powder plated with metal.
Since it is a granular fine powder, there is a problem that good conductivity cannot be obtained unless the amount of the fine powder is mixed into the resin binder or the solvent.

The present invention is excellent in conductivity, has a small specific gravity and does not cause sedimentation / separation in paints, and has excellent corrosion resistance such as salt water resistance, acid rain resistance, and corrosion gas resistance. Moreover, it is an object of the present invention to obtain a method capable of producing a conductive powder at a low cost, which has a small change in conductivity over time.

[0008]

According to the present invention, alumina, zinc oxide, titanium oxide, titanium oxide-coated mica, mica, etc. are made of a non-magnetic metal oxide having a low water content and an average particle size. There is provided a method for producing a titanium-coated conductive powder, wherein the surface of powder particles having a particle size of 0.1 to 100 μm is coated with 3 to 20 mass% of titanium by a sputtering method.

The structure of the manufacturing method of the present invention will be described in detail below.

(Type of Metal Oxide) As the metal oxide used in the present invention, those having a low water content and being non-magnetic are suitable. For example, alumina, zinc oxide, titanium oxide, mica coated with titanium oxide, mica, and the like have a low water content and are non-magnetic, and therefore are preferably used as the metal oxide in the present invention. As alumina, for example, α-alumina is suitable.

However, metal oxides having a high water content, such as Ca (OH) ₂ , γ-alumina and silica, cause dehydration phenomenon when a high vacuum is applied to coat titanium on the surface of powder particles by sputtering. It cannot be used because it occurs. Also, magnetic metal oxides such as iron oxide MIO
(Mica-like iron oxide) cannot be used because it is adsorbed by the magnet attached to the sputtering system.

(Average Particle Diameter of Powder Particles) The average particle diameter of the powder particles made of a metal oxide is in the range of 0.1 to 100 μm, preferably 1 to 20 μm. Average particle size is 0.1
When a powder having a particle size of less than μm is used, the coating amount of titanium must be considerably increased in order to improve conductivity. On the other hand, the average particle size of the powder particles is 100 μm
When a powder exceeding the above range is used, there arises such a problem that the dispersed state of the conductive powder is likely to be non-uniform when an antistatic composition such as a paint or a film is produced.

The shape of the powder particles made of metal oxide is not particularly limited, and any of spherical, granular, flake, and whisker shapes can be used. Mica powder, Al ₂ O ₃ whiskers and the like are metal oxides which are particularly preferably used in the present invention.

(Titanium coating method) In the production method of the present invention, titanium is coated on the surface of the above-mentioned powder particles of the metal oxide by the sputtering method. Titanium coating by the sputtering method is, for example,
It can be carried out by a known method disclosed in Japanese Patent Application No. 14360 or Japanese Patent Application No. 1-74770. That is, powder of metal oxide is subjected to air flow jet mill treatment in an inert atmosphere to disperse into primary particles, and fine powder obtained by the dispersion treatment is subjected to reduced pressure heat treatment in an inert atmosphere, The heat-treated fine powder is charged into a rotary container containing titanium as a sputtering source, and the container is rotated to form a fluidized bed of fine powder. ・ Titanium is sputtered on the fluidized fine powder while the container is rotated. To coat.

(Amount of Titanium Coated) The amount of titanium coated on the surface of the powder particles is 3 to 3 with respect to the titanium-coated conductive powder.
The range is 20 mass%, preferably 5 to 15 mass%. When the coating amount of titanium is less than 3 mass%, the titanium-coated conductive powder has extremely poor conductivity.
On the other hand, when the amount of titanium coating exceeds 20 mass%, the specific gravity of the titanium-coated conductive powder increases, but the manufacturing cost also increases, although the conductivity is excellent.

In the present invention, the coating amount of titanium is 3 to 2
It can be considered that the reason why it can be extremely reduced to 0 mass% is that titanium is coated by the sputtering method. In FIG. 1, 1 indicates powder particles of metal oxide. Here, the Ni-P is formed by the electroless plating method.
First, when the coating amount is as low as 3 to 20 mass%, the Ni-P coating 2 only adheres to the surface of the powder particles 1 in an island shape, and excellent conductivity cannot be obtained. Then, by further plating, each of the Ni-P coatings 2 gradually grows, and eventually the coating amount becomes 40 to 6
Only when it reaches 0 mass%, the entire surface of the powder particle 1 is covered with the continuous film 3. Thus, when Ni-P is coated by the electroless plating method, it is possible to obtain the conductive powder having good conductivity only by forming the coating 3 of 40 to 60 mass% on the surface of the powder particle 1. It will be possible. In order to completely cover the entire surface of the powder particle 1 with the Ni-P plated film 3, it is generally considered that Ni-P having a film thickness of 200 angstroms or more is necessary. 20 on all surfaces
To cover a film with a thickness of 0 Å or more,
Very large amounts of Ni-P are required. In addition, the specific gravity of Ni-P, which is a film, is larger than that of oxide, which is a powder particle, and when the mica or glass is coated with Ni-P by an electroless plating method, the conductivity obtained is The characteristic powder becomes extremely heavy and has the drawback that it tends to settle and separate in a resin binder or solvent.

However, when titanium is coated by the sputtering method, when the titanium coating 4 having a relatively small coating amount of 20 mass% or less is attached to the surface of the powder particle 1 in an island shape, the titanium coating 4 is used to form the powder particle 1. Surface is partially reduced. For example, powder particle 1 is Al ₂ O
_{If 3} , the reaction represented by 2Ti + Al ₂ O ₃ → Ti ₂ O ₃ + 2Al occurs on the surface of the powder particle 1, so that the lower oxide of titanium composed of Ti ₂ O ₃ is formed on the surface of the powder particle 1. And a metal part 5 of reduced Al is formed. Similarly, if the powder particles 1 are ZnO, the reaction represented by Ti + ZnO → TiO + Zn occurs on the surface of the powder particles 1, and the powder of the powder particles 1 is reduced with the lower oxide of titanium composed of TiO 2. Zn
A metal part 5 of is formed. Further, when the powder particles 1 are mica, the mica is also XY ₂ to ₃ (Si, Al) ₄ O.
_Since it is composed of a group of layered aluminosilicates having a composition represented by the chemical formula of ₁₀ (OH, F) ₂ , it is reduced by titanium, and the lower oxide of titanium and the reduced metal portion 5 are formed on the surface of the powder particles 1. It is formed.

Therefore, alumina, zinc oxide, mica, etc. are electrically insulators themselves, and are 10 at room temperature.
^It has an extremely large resistivity of ¹² Ω · cm or more, but when titanium is coated on the surface of powder particles made of these metal oxides by the sputtering method, the metals such as Al and Zn are reduced by titanium. At the stage where the coating amount of titanium is relatively small, 20 mass% or less,
It is considered that a continuous layer of a metal such as Al or Zn and titanium or a lower oxide of titanium is formed on the surface of the powder particles. The low-order oxides of titanium, such as TiO and Ti ₂ O ₃ , have a specific resistance of 10 ⁻³ Ω · cm level at room temperature and are a kind of conductor compared to alumina, zinc oxide, mica, etc. Since it can be handled, the continuous layer of metal such as Al and Zn thus formed and titanium and titanium oxide has excellent conductivity, and the titanium coating amount is 20 mass% or less, which is relatively small. Therefore, it is possible to obtain a conductive powder having good conductivity.

The above action is not limited to the case where the entire powder particle is a metal oxide, and the metal such as aluminum or zinc is in a state where only the surface is oxidized and the inside is not oxidized. The same is true for powders.
When titanium is coated on the whole powder particles with metal oxide by the sputtering method, only the continuous layer of metal such as Al and Zn and titanium and lower oxides of titanium formed on the surface of the powder particles is electrically charged. However, when titanium is coated on the metal powder such as aluminum or zinc, which is in a state of metal that is oxidized only in the vicinity of the surface and not oxidized inside, by the sputtering method, not only the surface but powder particles Since electricity can flow inside the powder, it is possible to obtain a powder having a specific resistance of 10 ⁻⁶ Ω · cm and excellent conductivity.

Thus, according to the method of the present invention, the titanium-coated conductive powder obtained by coating the powder particles of the metal oxide with titanium by the sputtering method has metal titanium, a low-order oxide of titanium and a metal on the surface thereof. Since a film composed mainly of the reduced products of Cu is formed,
It shows much better corrosion resistance than the conductive powder plated with -P or the like.

Regarding the specific gravity, the following can be said. For example, when mica with a specific gravity of 2.8 is coated with 50 mass% of Ni-P with a specific gravity of about 8.9 by electroless plating, the specific gravity of the conductive powder obtained is about 5.9. However, when mica having the same specific gravity of 2.8 is coated with titanium in an amount of 10 mass% by the sputtering method, the specific gravity of the conductive powder obtained is about 3.0. Therefore, according to the present invention, it is possible to manufacture an extremely light conductive powder having a specific gravity close to that of mica.

When powder particles made of titanium oxide-coated mica are used, as shown in Japanese Patent Laid-Open No. 173955/1992, titanium is coated by a sputtering method to obtain silver, blue, green. It is known that a powder that develops copper color, red color, magenta color, and gold color can be produced, and that this powder exhibits excellent performance as a coloring pigment. These powders also have a high conductivity of 10 ⁰ ~10 ^-1 Ω · cm, as a coloring conductive powder, practical value is particularly high.

[0023]

The present invention will be described in more detail based on the following examples. First, the structure of the sputtering apparatus will be described with reference to FIGS.

The sputtering chamber 10 has a diameter of 500 mm,
It has a cylindrical shape with a height of 300 mm. On the front and rear side surfaces of the sputtering chamber 10, the sputtering chamber 10
Rotating shafts 11 that are separate from each other while being positioned on the cylindrical axis of
And the rotary shaft 12 is fitted. The sputtering chamber 10 has a magnetic seal 13 for the rotary shaft 11 and the rotary shaft 12,
It is rotatably supported via 14. The lower part of the sputtering chamber 10 is supported by a driving roll 15 and a driven roll 16, and the power of a motor 17 is transmitted to the driving roll 15 by a belt 18 so that the sputtering chamber 10
Is driven to rotate.

At the tip of the rotary shaft 11, two sputtering sources 20, 20 are provided inside the sputtering chamber 10.
Are installed facing each other. Each of these sputtering sources 20 and 20 is provided so as to be slightly inclined from the vertical direction so as to be directed to the fluidized bed of the powder 21 generated by the rotation of the sputtering chamber 10. Sputtering source 2
Reference numerals 0 and 20 are, for example, a configuration in which a two-pole magnetron is attached to the rotating shaft 11, and the distance between the powder 21 and the fluidized bed can be adjusted by adjusting the attachment screw. Although not shown, electric wires for supplying a high-frequency current to the sputtering sources 20, 20 are embedded inside the rotary shaft 11.

The rotating shaft 12 also serves as an introduction pipe 22 for introducing the powder 21 into the sputtering chamber 10. Introductory pipe 2
The second tip 23 is curved downward inside the sputtering chamber 10 and opens near the bottom of the sputtering chamber 10. The tip portion 23 is also the sputtering chamber 10
To direct to the fluidized bed of powder 21 caused by the rotation of
It is provided with a slight inclination from the vertical direction.

An exhaust air supply pipe 25 is provided inside the introduction pipe 22. To the exhaust air supply pipe 25, exhaust pipes 28 and 29 are connected via valves 26 and 27, and an inert gas supply pipe 31 is connected via a valve 30. Exhaust pipe 28,
Reference numeral 29 is connected to a main exhaust system including a mechanical vacuum pump and an advanced exhaust system including a combination of a cryosorption pump, a turbo molecular pump, a mechanical booster pump, and a cooling trap. In addition, sputtering room 1
Introduction pipe 22 and exhaust pipe 2 exposed to the atmosphere inside 0
Each of 5 is composed of a graphite pipe which is hard to be coated with metal by sputtering.

A reduced pressure heat treatment chamber 35 is arranged upstream of the introduction pipe 22 via a valve 34. In the reduced pressure heat treatment chamber 35, the metal oxide powder 21 subjected to the reduced pressure heat treatment is introduced into the sputtering chamber 10 through the introduction pipe 22. The reduced pressure heat treatment chamber 35 of the embodiment has a diameter of 30.
It has a cylindrical shape with a height of 0 mm and a height of 150 mm, and its bottom surface 36 is formed in a funnel shape. At the center of the bottom surface 36, the motor 3
The screw feeder 38 driven by the operation of 7 is installed. A heater 40 is installed on the wall surface of the body of the reduced pressure heat treatment chamber 35. Further, a main exhaust pipe 42 and an advanced exhaust pipe 43 are connected to the ceiling surface of the reduced pressure heat treatment chamber 35 via a filter 41. Similarly, the main exhaust pipe 42 and the advanced exhaust pipe 43 also have a main exhaust system consisting of a mechanical vacuum pump and an advanced exhaust system consisting of a combination of a cryosorption pump, a turbo molecular pump, a mechanical booster pump, etc. and a cooling trap. Communicated.

A branch pipe 45 is connected in the middle of the introduction pipe 22, and the sputtering chamber 10 and the fluid jet mill 46 are communicated with each other via a valve 47. The fluid jet mill 46 is a propeller 50 driven by a motor 48 to rotate at high speed.
Equipped with.

The fluid jet mill 46 and the above-described reduced pressure heat treatment chamber 35 are connected by a circulation pipe 52 via a valve 51. A discharge pipe 53 is connected to the circulation pipe 52 on the upstream side of the valve 51 via a valve 55. The discharge pipe 53 communicates with a trap 56 that collects the powder 21. The trap 56 includes a cylindrical filter 57 for collecting the powder 21 and an exhaust pipe 58.

In the sputtering apparatus configured as described above, powder 21 composed of alumina, zinc oxide, titanium oxide, titanium oxide-coated mica, and mica, respectively.
First, 500 g of the above is charged into the sputtering chamber 10, and the reduced pressure heat treatment chamber 35 and the sputtering chamber 10 are introduced into the introducing pipe 22.
2 × 1 in the reduced pressure heat treatment chamber 35 with no communication
It was reduced to 0 ^-5 Torr. Then, the argon gas was gradually supplied to the sputtering chamber 10 through the exhaust gas pipe 25, and the powder 21 was conveyed to the fluid jet mill 46.

In the fluid jet mill 46, the powder 21 carried by the argon gas flow is made to collide with the rotating propeller 50 to disperse the powder 21 into primary particles, and then the powder 21 is passed through a circulation pipe 52 to form a reduced pressure heat treatment chamber. Collected at 35. While reducing the pressure to 2 × 10 ⁻³ Torr in the reduced pressure heat treatment chamber 35, the heater 40 was heated to 200 ° C., and the drying treatment and the degassing treatment were performed for 30 minutes.

Next, the powder 21 was introduced through the introduction tube 22 into the sputtering chamber 10 which had been previously replaced with an argon gas atmosphere. Then, while rotating the sputtering chamber 10 at a rotation speed of 5 rpm, the pressure inside the sputtering chamber 10 was reduced to 2 × 10 ⁻³ Torr, the power was 3 kw, and the frequency was 13.56 M.
Sputtering was performed by a magnetron system under the condition of Hz, and the powder 21 was coated with titanium. By this operation, about 0.1 mass% of titanium could be coated in 1 hour.

After that, the sputtering was stopped and the dispersion treatment in the fluid jet mill 46 and the reduced pressure heating treatment chamber 3 were performed.
Then, the powder 21 was introduced into the sputtering chamber 10 again, and titanium was coated again by the sputtering operation for 1 hour. This process was repeated several times to produce conductive powder coated with titanium in an amount of 1.0 to 30.0 mass% in total.

As described above, the conductive powder is manufactured by using the sputtering method, and finally, the argon gas is gradually supplied to the sputtering chamber 10 through the exhaust gas pipe 25,
Alumina, zinc oxide, titanium oxide, mica coated with titanium oxide, and conductive powder obtained by coating mica with titanium were collected in the trap 56.

Each of the conductive powders obtained was molded under a pressure of 200 kg / cm ² to produce a powder compact having a diameter of 25 mm and a thickness of 10 mm, and the direct current resistivity was measured. Table 1 shows the measurement results, the type of powder used in the production of each conductive powder, the powder manufacturer, the powder average particle size, and the titanium coating amount. Alumina is an alumina powder manufactured by Showa Denko KK (AL-45-
1) was used. Table 1 also shows the DC specific resistance of each powder not coated with titanium as a comparative example.

[0037]

[Table 1]

From the results shown in Table 1, the specific resistance of the conductive powder of the example produced by the method of the present invention, in which the amount of titanium coated is 3 to 20 mass%, is 7 × 10 ^{1 to} 5 × 10 ⁻² Ω · cm
Thus, it can be seen that the conductive powders of the examples have excellent conductivity.

Next, each of the conductive powders of Examples 1 to 20 and the powders of Comparative Examples 1 to 15 shown in Table 1 was used 10 times.
0 g each, acrylic paint base (Kansai Paint No.
2026 (containing 40 mass% resin) 250 g in a stainless steel container of 800 ml capacity,
Dispersion was carried out for 1 hour with a stirring blade rotating at 0 rpm. Each acrylic paint was applied to a transparent acrylic plate having a thickness of 1.0 mm using a doctor blade so that the dry coating film thickness was about 25 μm, and dried at room temperature. Table 2 shows the surface electric resistance of each coated plate thus obtained.

[0040]

[Table 2]

From the results shown in Table 2, it can be seen that the paint containing the conductive powder of the present invention has excellent conductivity. In addition, the conductive powders of the examples do not cause sedimentation and separation in paints, etc., and are resistant to salt water, acid rain, and
It was also excellent in corrosion resistance such as corrosion gas resistance.

[0042]

EFFECTS OF THE INVENTION According to the manufacturing method of the present invention, even though it is excellent in conductivity, it has a small specific gravity, so that it does not settle in a paint or the like.
Conductive powder that does not cause separation, has excellent corrosion resistance such as salt water resistance, acid rain resistance, and corrosion gas resistance, and has little change in conductivity over time can be manufactured at low cost. The conductive powder produced by the method of the present invention can be widely used for antistatic compositions such as coating materials and fibers for exterior building materials, interior building materials, home appliances, automobiles, ships and the like.

[Brief description of drawings]

FIG. 1 is a sectional view of a conductive powder according to a conventional method and a method of the present invention.

FIG. 2 is a front view of a sputtering device.

FIG. 3 is a cross-sectional arrow view of FIG. 2A-A.

[Explanation of symbols]

 1 Powder Particles 2, 3 Ni-P Film 4 Titanium Film 5 Low-Order Oxide of Titanium and Reduced Metal Part

Claims (1)

[Claims] 1. Alumina, zinc oxide, titanium oxide, titanium oxide-coated mica, mica, etc., which are made of non-magnetic metal oxides with a low water content and have an average particle size of 0.1 to 1
3 by sputtering method on the surface of powder particles of 00 μm
A method for producing a titanium-coated conductive powder, which comprises coating titanium in an amount of -20 mass%.