JP2995250B2 - A method for plasma spraying titanium oxide powder on a substrate and a product having a plasma sprayed coating. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal foil, glass,
Plasma spraying method of titanium oxide powder on a substrate such as cloth, paper, plastic film or brick or concrete by plasma spraying an anatase type titanium oxide film, and thermal spray coating of anatase type titanium oxide having photocatalytic function Belongs to the technical field of products having a plasma sprayed coating formed on the surface.

[0002]

2. Description of the Related Art Methods for sterilizing or controlling microorganisms include heating, freeze sterilization, sterilization by ultraviolet rays, radiation, far-infrared rays, ultrasonic cell destruction, electric sterilization, high magnetic field sterilization, drugs, poisons, and halogens including antibiotics. There are drug administration sterilization by a system surfactant and the like, and it is used while taking various forms in a wide range of fields. However, in any of these methods, a relatively large-scale device is required, and the product is often damaged at the same time as sterilization because of emphasis on immediate effect. In addition, it has been pointed out that, in the case of drug use, persistence and safety should always be considered.

The photocatalytic reaction of titanium oxide (TiO ₂ )
It is known to lead to a wide range of reactions such as redox, isomerization, substitution, condensation, polymerization and the like. In particular, it is considered that decomposition of environmental pollutants, purification of drinking water, sterilization, and the like using this reaction system are based on active oxygen generation. And T
iO ₂ has a rutile type and an anatase type due to a difference in crystal structure. However, the present inventor has found that the rutile type has a very low active oxygen generation yield of about 1/15 to about 1/200 of the anatase type. I discovered that.

In addition, the present inventor has found that a surface developed based on a method for producing a material surface having a high anatase content has a production amount of active oxygen of about 15 to about 200 times that of a material surface having a high rutile content. It was confirmed that the sterilization efficiency and the ability to decompose pollutants (tobacco tar components) were high.

Further, the present inventor has superoxide radical active oxygen by irradiating the long-wavelength ultraviolet light of TiO ₂ in the spraying material ^- preliminary experiments that and hydroxyl radicals (· OH) generated (O ₂₎ Confirmed.

By the way, the bactericidal action based on the strong biological damaging action of active oxygen is already known, and the bactericidal action of the photo-semiconductor sprayed with anatase TiO ₂ during the development of the functional composite material is due to the active oxygen. Is also known. It is already known that the effect of suppressing the growth of green algae is exhibited when a material sprayed with TiO ₂ coexists in an aquarium installed indoors.

[0007] Japanese Patent Publication No. 2-46664 discloses that a powdery fluorescent material made of a celite or wollastonite powder is plasma-sprayed on a surface of a base material made of a metal, a ceramic sintered body or a glass. A method for forming a fluorescent light-emitting film for forming a film having a fluorescent light-emitting function on the surface of a substrate is described. This publication also discloses a plasma spray nozzle (manufactured by Basedate, USA, plasma output 17).
26 KW), the other electrode 2 is fixed in a hollow nozzle body 1 serving as an electrode, a power source 3 is connected to both electrodes, and a plasma is applied to a tip nozzle body 1 of the electrode 2. An ejection hole 5 composed of a small hole of the flame 4 is formed, and a gas introduction hole 6 for injecting an inert gas such as argon (35 l / min) is formed at the rear of the bottom inside the nozzle body 1. Then, a base material (mild steel) 8 is positioned at each of the nozzle plasma spraying positions so as to face the ejection holes 5 and face each other.
(Spray distance 100 mm), the powder fluorescent material is ejected into the plasma flame 4 from the supply port 7 and melts, is sprayed on the surface of the substrate S, and adheres as the fluorescent film 9 having a thickness of 150 to 200 μm. I have.

The photocatalyst of titanium oxide undergoes charge separation when irradiated with light of 400 nm or less, and generates electrons and holes having a strong oxidizing power. Furthermore the hole may react with water vapor or oxygen in the air, the superoxide radical (O ₂ ^-)
It generates active oxygen species such as OH and hydroxyl radical (.OH) and decomposes organic substances adsorbed on the surface. It is expected to be used for environmental purification such as deodorization, antifouling, and sterilization using its strong oxidizing power. Have been.

The oxygen reduction is represented by the following chemical formula (1)
Can be indicated by O ₂ ^{chromatography} (dissolved oxygen) + e ^- → O ₂ ^- (superoxide radical) (1) The disproportionation of superoxide radicals may be represented by the following formula (2). 2O ₂ ⁻ + 2H ⁺ → H ₂ O ₂ (hydrogen peroxide) (2) And the generation of hydroxyl radical can be represented by the following chemical formula (3). H ₂ O ₂ + e ⁻ → OH (hydroxyl radical) + OH ⁻ (3) The generation of the hydroxyl radical can be represented by the following chemical formula (4). _{^{h + (TiO 2) + OH}} - → · OH + TiO 2 (4)

Titanium oxide (TiO ₂ ) is a safe material widely used as a white pigment and an ultraviolet absorbing material in paints and cosmetics, and is also recognized as a food additive. It is also known that the material exhibits an antifouling effect without preparing a special light source, and that this is due to a photochemical reaction (photocatalytic reaction) using sunlight in the shade or ordinary indoor lighting. Have been.

A material having titanium oxide having high photoactivity on its surface shows a very remarkable antifouling effect (self-cleaning effect), and the fact that it absorbs only in the ultraviolet means that it is colorless. It is rather convenient to apply it to various materials.

The system for generating active oxygen can be used for sterilization, for inhibiting the growth of microorganisms and algae, and for repelling small animals. Active oxygen is effective only on the surface because of its short life, and has no persistence and no environmental pollution.

Furthermore, plasma spraying, the metal foil, glass, cloth, paper, plastic film, brick, with a substrate made of a material such as concrete is possible to deposit TiO ₂ as a thin film, the TiO ₂ Since there is no elution after welding, the effect can be said to be semi-permanent.

Active oxygen species is a reaction involving dissolved oxygen. Under anaerobic conditions, active oxygen is generated by the following reaction. In the photocatalytic reaction, TiO ₂ + hν (near ultraviolet light) → h ⁺ TiO ₂ + e ^- hydroxyl radical is generated by h ⁺ (TiO ₂ ) + OH ⁻ → OH + TiO ₂ (4) And the reverse reaction of the photocatalyst is , H ⁺ (TiO ₂ ) + e ⁻ → TiO ₂ (5) And, the hydroxyxyl radical, the most oxidative active oxygen species generated under aerobic conditions, has a 90% production yield by (3). And the production yield according to (4) is 10%. From the above, it is considered that a superoxide radical, a hydroxyl radical, and further h ⁺ (TiO ₂ ) are involved in the oxidation reaction by the TiO ₂ photocatalyst, and a superoxide radical and e ⁻ are involved in the reduction.

The present invention is based on the finding that anatase type titanium oxide has a higher photocatalytic activity per unit area and higher active oxygen sterilization ability than rutile type titanium oxide.

[0016]

SUMMARY OF THE INVENTION The present invention relates to a method for directly plasma-spraying anatase-type titanium oxide powder on a surface of a base material including a high-temperature weak material such as a metal foil or a plastic film without using a binder. It is an object of the present invention to provide a method for plasma spraying a titanium oxide powder on a substrate, in which a sprayed film of anatase type titanium oxide having an oxygen sterilizing ability is formed on the substrate.

Further, the present invention provides a medical treatment for sterilization,
It is intended to provide a product having a sprayed coating of titanium oxide that can be used not only in the food field but also in a wide range of fields such as clothing, fisheries, and industry, which are fields of use depending on the sterilizing ability of active oxygen. .

[0018]

According to the present invention, there is provided a method for plasma spraying a titanium oxide powder onto a substrate, comprising the steps of: (a) producing a plasma flame of a mixed gas comprising at least argon gas and nitrogen gas from a plasma flame outlet of a plasma nozzle body; And an anatase-type titania powder is jetted out of the anatase-type titanium oxide powder outlet provided in the vicinity of the outlet of the plasma flame-jet opening into the plasma flame of the mixed gas, and a photocatalytic function is provided on the surface of the base material. And spray-forming a film of anatase-type titanium oxide having

The method for plasma spraying a titanium oxide powder on a substrate according to the present invention is characterized in that the titanium oxide powder is ejected from a plasma flame ejection hole of a plasma nozzle body at a high speed with a plasma flame of an argon gas or a mixed gas of hydrogen gas and nitrogen gas. The anatase-type titania powder is ejected from the outlet of the anatase-type titanium oxide powder provided in the vicinity of the outlet of the plasma flame ejection hole into the plasma flame of the mixed gas, and the anatase type having a photocatalytic function on the surface of the base material. This is for forming a sprayed titanium oxide film.

According to the method for plasma spraying titanium oxide powder on a substrate according to the present invention, a plasma flame of a mixed gas comprising argon gas and helium gas or hydrogen gas is ejected at a high speed from a plasma flame ejection hole of a plasma nozzle body. Anatase-type titania oxide powder is ejected from the outlet of the anatase-type titanium oxide powder provided in the vicinity of the outlet of the plasma flame ejection hole into the plasma flame of the mixed gas,
In this method, a film of anatase-type titanium oxide having a photocatalytic function is formed by spraying on the surface of a substrate.

The product having the plasma sprayed coating according to the present invention is obtained by heating at least an argon gas or a mixed gas of a helium gas and a nitrogen gas in which anatase type titania powder is heated on the surface of a base material constituting the product by a plasma nozzle body. The sprayed film of anatase type titanium oxide having a photocatalytic function is formed by high-speed injection with a plasma flame.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a method for plasma spraying titanium oxide powder on a substrate and a product having a plasma sprayed coating according to the present invention will be described with reference to the drawings and tables. An apparatus for performing plasma spraying of titanium oxide powder P used for plasma spraying on a base material 8 is configured such that the anode side of a DC power supply 3 is a plasma nozzle body 1
, And the cathode side of the power supply 3 is connected to the negative electrode 2.

The plasma nozzle body 1 is provided with a plasma flame ejection hole 5 composed of a small hole through which the plasma flame 4 passes, and behind the bottom of the nozzle body 1 is a mixed gas composed of argon gas and nitrogen gas. A mixed gas inlet 6 for injecting the gas G is formed.

The titanium oxide powder P is blown into the plasma flame 4 from the outlet 7 of the titanium oxide powder blowing member 10 provided near the outlet of the plasma flame outlet 5 of the plasma nozzle main body 1, and is melted into the base material. 8, a titanium oxide film 9 is formed on the surface of the base material (metal foil, plastic film, etc.) 8.

The relationship between the size of the nozzle of the plasma nozzle main body 1 used in the plasma spraying method according to the present invention, the flow rate of the mixed gas G in the plasma flame outlet 5 and the mixed gas G will be described below. The distance from the tip 11 of the negative electrode 2 of the nozzle body 1 to the end of the ejection hole 5 of the plasma flame 4, that is, the distance between the negative electrode 2 and the outer end of the Cu positive electrode 12, is L.
Where S is the cross-sectional area of the plasma flame ejection hole 5.
/ L, for example, S / L = 9mm ² /12mm=0.75m
The flow velocity of the mixed gas G of the argon gas and the nitrogen gas in the plasma flame outlet 5 when the size is m is 550 m / sec.
c (hereinafter referred to as “high speed”). In addition, the ^{S / L = 9mm 2 / 12mm} = 0.
The flow rate of the mixed gas G of the argon gas and the helium gas in the plasma flame ejection hole 5 at a size of 75 mm is 4
50 m / sec (hereinafter referred to as “quasi-high speed”). In the plasma spraying method according to the present invention, S / L = 28
mm ² /16mm=1.75mm mixed flow rate of at least 35 of the plasma flame ejection holes 5 of the gas G when the size of
It is desirable that the flow velocity is 0 m / sec or more. The flow velocity at which the flow velocity of the plasma flame outlet 5 is 350 m / sec is hereinafter referred to as “normal velocity”.

The heating efficiency of the mixed gas G for heating and melting the sprayed oxide powder is desirably H ₂ >He> N ₂ > Ar with a high heat transfer coefficient (enthalby) at a high temperature. Since the property depends on the density of the substance constituting the mixed gas G, from the magnitude of the density, Ar> N ₂
It is desirable that the mixed gas G be a gas composed of substances in the order of>He> H ₂ . In order to allow a large amount of anatase-type titanium oxide to remain, it is necessary to select conditions that are high-speed and do not overheat the particles. For this purpose, a mixed gas G of Ar and N ₂ is more advantageous than a mixed gas of Ar and He.

Table 1 shows the thermal spray rate, whether the titanium oxide film or the knitted nonwoven fabric of titanium oxide is anatase type or rutile type.
The production ratio of malondialdehyde (MDA) is shown depending on whether or not there is a titanium oxide film. Table 1 shows the results obtained by measuring the amount of hydroxyl radical (.OH), which is active oxygen, for each sample by a known malondialdehyde (MDA) determination method as the MDA generation ratio. According to this, it can be seen that those having the anatase type titanium oxide film 9 sprayed at a high speed show exceptional numerical values.

[Table 1]

[0028]

[Table 2] Table 2 shows the difference in the content (wt%) of the anatase type in the titanium oxide sprayed coating 9 depending on the spraying conditions, the composition of the mixed gas, and the plasma output. The high-speed spraying type argon (Ar) of the sample No. 1 was used. A gas mixture of nitrogen and nitrogen (N ₂ ) having a plasma output of 20 KW (500 A) has the largest content of anatase type of 28.9 wt%, and then the sample (No. 2) of a quasi-high speed spray type of argon (Ar) and helium. (He) mixed gas with a plasma output of 22 KW (70
OA) having an anatase type content of 16.6 wt%
belongs to. When compared with the normal fast spray type of sample No. 3, the spraying speed is higher and the composition of the mixed gas is argon (A
r) and nitrogen (N ₂ ), argon (Ar) and helium (H
e) shows that the content of the anatase type in the titanium oxide sprayed coating 9 is remarkably large.

[0029]

[Table 3] Table 3 shows the change over time in the amount of MDA production (unit: nM) and the viability (%) of E. coli for 30 minutes for each of the three samples obtained by adding the commercially available antibacterial tile and the ceramic tile substrate itself. It is a thing. According to Table 3, the three samples as the plasma sprayed coating 9 applied to the base material 8 obtained by the plasma spraying method of the titanium oxide powder p on the base material 8 according to the present invention, and a commercially available antibacterial tile MDA production (nM) and viability of Escherichia coli (%)
Also, it can be seen that there is a marked difference. That is, the sample N
It can be seen that the sample of No. 1 has remarkably high MDA production and the sterilizing effect on Escherichia coli, and the sample of No. 2 has a large effect in the above aspect.

FIG. 3 shows the relationship between the content of anatase and the amount of MDA produced in the titanium oxide powder used in the method of plasma spraying the titanium oxide powder on the substrate according to the present invention. Then, it can be seen that the sample No. 3 has a larger anatase content, and the larger the anatase content, the larger the MDA generation amount.

FIG. 4 is a graph showing the bactericidal effect of the plasma sprayed coating 9 according to the present invention on Escherichia coli as a function of the light irradiation time and the survival rate of Escherichia coli.
o1, the sample No. 2 has a light irradiation time of 3 against E. coli.
It can be seen that the sterilization effect of E. coli in 0 minutes is remarkably large.

FIG. 5 is a graph showing the bactericidal effect of the plasma sprayed coating 9 according to the present invention on enterobacteria in relation to the light irradiation time and the survival rate of enterobacteria.
o1, the sample No. 2 has a light irradiation time of 3 against S. Enteritidis.
It can be seen that the sterilizing effect of S. Enteritidis in 0 minutes is remarkably large.

FIG. 6 is a graph showing the bactericidal effect of the plasma sprayed coating 9 according to the present invention on Staphylococcus aureus in relation to the light irradiation time and the survival rate of Staphylococcus aureus.
According to the results, it can be seen that the samples No. 1 and No. 2 have a remarkably large sterilizing effect on Staphylococcus aureus during a light irradiation time of 30 minutes.

According to FIG. 7, a commercial antibacterial tile sprayed with rutile-acid-based titanium oxide shows about 60 percent of Staphylococcus aureus and 50 percent of Escherichia coli after 30 minutes of light irradiation against Staphylococcus, Escherichia coli and Enteritidis. As a result, the survival rate of S. enteritidis was as high as about 30%, indicating that the sterilization effect on each of the bacteria was remarkably lower than that obtained by spraying anatase type titanium oxide.

In the embodiment shown in the embodiment of the present invention, the distance L from the tip 11 of the negative electrode 2 of the plasma nozzle body 1 to the plasma flame ejection hole 5 and the cross-sectional area S of the ejection hole 5 are different. When the ratio, that is, L / S is 0.75 mm, the flow rate of the mixed gas G of the argon gas and the nitrogen gas in the ejection hole 5 becomes a high-speed flow, and the titanium oxide powder P to be sprayed is sprayed.
The heating efficiency of the mixed gas G for heating and melting is in the order of H ₂ >He> N ₂ > Ar having a large heat transfer coefficient (enthalby) at a high temperature. Since the acceleration of the sprayed titanium oxide powder P depends on the density of the substance constituting the mixed gas G,
It is desirable to use a mixed gas of gases composed of substances in the order of Ar> N ₂ >He> H _{2 in view} of the density. In order to leave a large amount of the anatase type titanium oxide film 9, it is a high-speed spraying type, and It is necessary to select conditions that will not overheat the particles. This shows that a mixed gas G of an argon (Ar) gas and a nitrogen (N ₂ ) gas is more advantageous than a mixed gas of an argon (Ar) gas and a helium (He) gas. In addition, an anatase type titanium oxide powder P having a titanium oxide film 9 formed on the surface of a base material 8 made of metal or the like opposed to the plasma nozzle main body 1 was subjected to an antibacterial test to sterilize Escherichia coli, Enteritis bacteria and Staphylococcus aureus. , Has a great effect on the reduction.

[0036]

According to the method for plasma spraying titanium oxide powder on a substrate according to the present invention, a so-called low-temperature plasma spraying method is used to coat an anatase type material on a surface of a substrate including a high-temperature weak material such as a metal foil or a plastic film. Titanium oxide powder can be directly sprayed without a binder, and an effect of reliably and easily forming a sprayed coating of anatase-type titanium oxide having an active oxygen sterilizing ability on a substrate surface can be obtained.

The product having a sprayed coating of titanium oxide according to the present invention can be used not only in the medical and food fields for sterilization, but also in clothing, which is a field of application depending on the sterilization ability of active oxygen,
This has the effect that it can be used in a very wide range of fields such as fishing and industry.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a plasma nozzle body used in a method for plasma spraying titanium oxide powder on a substrate according to the present invention.

FIG. 2 is a cross-sectional view showing a method of plasma spraying a titanium oxide powder on a substrate according to the present invention.

FIG. 3 is a graph showing the relationship between the content of anatase and the amount of MDA produced in the titanium oxide powder used in the method for plasma spraying a titanium oxide powder on a substrate according to the present invention.

FIG. 4 is a graph showing the bactericidal effect of the plasma sprayed coating according to the present invention on Escherichia coli in relation to the light irradiation time and the survival rate of Escherichia coli.

FIG. 5 is a graph showing the bactericidal effect of the plasma sprayed coating according to the present invention on S. Enteritidis in relation to the light irradiation time and the survival rate of Escherichia coli.

FIG. 6 is a graph showing the bactericidal effect of the plasma sprayed coating according to the present invention on Staphylococcus aureus in relation to the light irradiation time and the survival rate of Escherichia coli.

FIG. 7 is a graph showing the bactericidal effect of a commercially available antibacterial tile having a conventionally known rutile-type titanium oxide film on Staphylococcus aureus, Escherichia coli, and Enteritidis in relation to the light irradiation time and the survival rate of each bacterium. It is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma nozzle main body 2 Negative electrode 3 Power supply 4 Plasma flame 5 Plasma flame ejection hole 6 Mixed gas introduction port 7 Titanium oxide powder ejection port 8 Substrate 9 Titanium oxide film 10 Titanium oxide powder ejection member 11 Negative electrode tip 12 Cu Positive electrode P Titanium oxide powder G Mixed gas

Claims (4)

(57) [Claims] A plasma flame of at least a mixed gas of argon gas and nitrogen gas is ejected at high speed from a plasma flame ejection hole of a plasma nozzle body, and an anatase type oxidation provided near an outlet of the plasma flame ejection hole. The titanium oxide powder is characterized by spraying anatase-type titania powder into the plasma flame of the mixed gas from the outlet of the titanium powder, and spray-forming a film of anatase-type titanium oxide having a photocatalytic function on the surface of the base material. Plasma spraying method for substrate. 2. An anatase provided in close proximity to an outlet of the plasma flame ejection hole, wherein the plasma flame is ejected at high speed from a plasma flame ejection hole of a plasma nozzle body by a plasma flame of an argon gas or a mixed gas of hydrogen gas and nitrogen gas. Anatase-type titania powder is blown out from the outlet of the type-titanium oxide powder into the plasma flame of the mixed gas, and a film of anatase-type titanium oxide having a photocatalytic function is formed on the surface of the base material by thermal spraying. A method of plasma spraying powder onto a substrate. 3. A plasma flame of a mixed gas comprising argon gas, helium gas or hydrogen gas is ejected at a high speed from a plasma flame ejection hole of a plasma nozzle body, and anatase provided near an outlet of said plasma flame ejection hole. Anatase-type titania powder is blown out from the outlet of the type-titanium oxide powder into the plasma flame of the mixed gas, and a film of anatase-type titanium oxide having a photocatalytic function is formed on the surface of the base material by thermal spraying. A method of plasma spraying powder onto a substrate. 4. Anatase having a photocatalytic function by injecting anatase-type titania powder at high speed with a plasma flame of a mixed gas comprising at least argon gas and nitrogen gas or helium gas onto a surface of a base material constituting a product by a plasma nozzle body. A product having a plasma sprayed coating, wherein a sprayed coating of type titanium oxide is formed.