CN1729143A - Electroconductive zinc oxide powder and method for production thereof, and electroconductive composition - Google Patents

Abstract

This invention relates to a novel conductive zinc oxide powder and an efficient method for manufacturing the same. The conductive zinc oxide powder is characterized by having, relative to the mass of zinc oxide, 0.01 to 10% by mass of at least one element selected from the group consisting of Group IIIB, Group IVB, and Fe; an average primary particle size calculated by specific surface area of less than or equal to 0.03 micrometers; a bulk density of less than or equal to 0.20 g/mL; and a volume resistivity of less than or equal to ^10¹⁰ Ω·cm. By incorporating it as a conductivity-imparting material into rubber or resin, a material with excellent dispersibility and low resistivity can be formed.

Description

Conductive zinc oxide powder, method for producing the same, and conductive composition

technical field

The present invention relates to a conductive zinc oxide powder having excellent dispersibility to substrates such as rubber or resin, and a method for producing the same, and more specifically, to exhibiting a Conductive zinc oxide powder capable of forming a material having excellent dispersibility and low resistance value, a method for producing the same, and a conductive composition imparted with conductivity by blending the conductive zinc oxide powder.

Background technique

Conductive zinc oxide is widely used as an additive for imparting electrical conductivity to paints, rubbers, and resins. Among them, in the field of coatings, generally speaking, if the viscosity of the coating is high, the finishing workability will be reduced, so in order not to increase the viscosity of the coating, powders with relatively large particle diameters are often used. In this regard, in the field of rubber and resin, the viscosity of the compound is not as problematic as that of the paint, so the conductive zinc oxide powder with a relatively small particle size is used.

However, several methods have been proposed as a method for producing conductive zinc oxide powder. For example, Japanese Patent Application Laid-Open No. 1-126228 discloses a method of stirring oxidation in an aqueous dispersion system in the presence of inorganic fine powder. The three components of zinc, water-soluble or water-dispersible aluminum compound, and ammonium carbonate are filtered and dehydrated, and then heated in a non-oxidizing environment at a temperature of 600 ° C or less to produce an average particle size of 0.1 Conductive zinc oxide fine powder with excellent transparency on the micron scale.

However, although the conventional conductive zinc oxide powder obtained by the above-mentioned method can be said to have a small particle size, the limit of the average primary particle size is on the order of 0.1 micron. Even if it is uniformly dispersed in a base material such as a resin, the zinc oxide particles cannot be in close contact with each other in the blended composition, so it is difficult to obtain sufficient conductivity by adding conductive zinc oxide powder alone.

It can be considered that if the particle size of the conductive zinc oxide fine powder can be changed from the current particle size to an ultrafine particle shape that is one order of magnitude smaller or more than one order of magnitude smaller, by uniformly dispersing it in a base such as rubber and resin In the material, the contact points between the particles can be increased, and as a result, a rubber composition or a resin composition with a low resistance value can be obtained.

As another example of such particulate conductive zinc oxide, Japanese Patent Application Laid-Open No. 10-236822 discloses a method in which a mixture of zinc carboxylate and alcohol is heated and matured to produce a zinc oxide precursor, and then the The precursor is mixed with a metal hydroxide or a compound capable of forming a metal hydroxide by reacting with water, and then fired by eliminating the alcohol. Furthermore, it is described that zinc oxide fine powder having an average particle diameter of about 0.001 to 1 micron can be obtained by this method.

In addition, JP-A-7-69631 discloses a method of adding a hexamethylenetetramine solution or a urea solution to a mixed solution of a zinc salt and an aluminum salt, and performing hydrolysis at a pH of 5.5 to 7.5, thereby Generate a flake-shaped alkaline zinc-based coprecipitate, and then add a water-soluble compound of at least one element selected from the group consisting of antimony, indium, tin, zirconium, and titanium to the flake-shaped coprecipitate, the compound The surface of the above-mentioned flaky zinc coprecipitate is coated, and then fired. The zinc oxide obtained by the method has an average thickness of 0.1-2 microns, an average particle diameter of 1-100 microns, and an electrical resistance of less than or equal to 1×10 ³ Ω·cm.

Furthermore, although the application is different, it is considered to be one of the production methods of conductive particulate zinc oxide. In Japanese Patent Application Laid-Open No. 11-279525, a doped conductive zinc oxide powder is disclosed, wherein (a ) The zinc oxide powder contains at least one element selected from group IIIB elements and group IVB elements, (b) the directional arithmetic average particle size in the electron microscope projection image is 3 to 100 nanometers, (c) the above-mentioned group IIIB elements and IVB The total content of group elements is 1-15 mol%.

However, according to the results of studies by the present inventors, when the zinc oxide powder produced by the above-mentioned conventional method is dispersed in a base material such as rubber or resin, although the properties of the base material can be maintained, the decrease in resistance value is insufficient. As long as neither the properties of the base material nor the resistance value is sufficient, it cannot be said that the purpose of adding the conductive zinc oxide powder is fully achieved.

The present invention has been made focusing on such a situation, and its object is to provide a conductive zinc oxide powder which is blended into rubber or resin and a method for producing the same having excellent dispersibility and conductivity-imparting properties. In the base material, the characteristics of the base material will not be reduced, and the composition of the resistance value can be greatly reduced, and the modified conductive zinc oxide powder formed by applying the characteristics of the conductive zinc oxide powder to rubber or resin is also provided. sex composition.

Contents of the invention

The conductive zinc oxide powder of the present invention capable of solving the above-mentioned problems is characterized in that 0.01 to 10% by mass of elements selected from group IIIB elements, group IVB elements, and Fe are solid-dissolved in the conductive zinc oxide powder relative to the mass of zinc oxide. At least one element in the composed group has an average primary particle size calculated from the specific surface area of 0.03 microns or less, a bulk density of 0.20 g/ml or less, and a volume resistivity of 10 ¹⁰ Ω·cm or less.

In addition, since the manufacturing method of the present invention is regarded as an effective manufacturing method of conductive zinc oxide powder having the above-mentioned characteristics, the method has the following features, which are implemented sequentially:

(1) make alkaline carbonate react in the aqueous slurry of zinc oxide and obtain the step of alkaline zinc carbonate;

(II) the step of heating and slaking the basic zinc carbonate;

(III) mixing a water-soluble salt of at least one element selected from the group consisting of IIIB group elements, IVB group elements and Fe into the obtained aging solution and performing re-aging;

(IV) a step of dehydrating and drying the cured product;

(V) a step of firing the dried product obtained;

(VI) A step of pulverizing the dehydrated burnt product.

When implementing this manufacturing method, the concentration of the aqueous slurry of zinc oxide used in the above (I) step should be less than or equal to 10% by mass, and, in the above (V) step, if an oxidizing atmosphere or reducing The method of firing the above-mentioned dried product at 300-600°C under the atmosphere can more reliably obtain the conductive zinc oxide powder satisfying the above-mentioned characteristics specified in the present invention, that is, the average primary particle size is less than or equal to 0.03 μm, and the bulk density is less than or equal to 0.20g/ml, and the volume resistivity is less than or equal to 10 ¹⁰ Ω·cm, so this method is preferred.

The above-mentioned conductive zinc oxide powder according to the present invention can produce excellent electrical conductivity by being blended into various base materials represented by rubber or resin, especially when rubber or resin is selected as the base material, 100 parts by mass of these base materials When 10 to 300 parts by mass of this conductive zinc oxide powder is uniformly dispersed in a crystalline body, it exhibits excellent conductivity with a volume resistivity of 10 ³ to 10 ¹¹ Ω·cm, and therefore it is recommended as a preferable utilization mode of the present invention. .

Description of drawings

Fig. 1 is the accompanying drawing of the electroconductive zinc oxide powder that obtains in the embodiment and replaces electron micrograph;

Fig. 2 is an electron micrograph in place of a drawing of a conventional conductive zinc oxide powder obtained in a comparative example.

Detailed ways

In order to clarify the problems found in the prior art as described above, the inventors of the present invention, in particular, when the conductive zinc oxide powder produced by the conventional method is dispersed in a base material such as rubber or resin, the resistance value is not sufficiently lowered, and the electrical conductivity is not fully exhibited. The reasons for the effect of adding zinc oxide powder have been studied from various angles.

Therefore, it is considered that no matter how small the numerical particle size calculated from the specific surface area of the conductive zinc oxide powder and the microscope projected image is, since the primary particles of these conductive zinc oxide particles are fine, they will almost always aggregate secondary. It cannot be finely dispersed down to 0.1 μm or less, which is a major obstacle in imparting conductivity to substrates such as rubber or resin.

That is, it can be considered that the specific surface area (BET) particle diameter calculated from the specific surface area and the particle diameter obtained from the projected image of the electron microscope are as seen for the conductive zinc oxide fine powder produced by the conventional method as described above. The apparent primary particle size is small, but these primary particles are firmly secondary aggregated, so when dispersed in a substrate such as rubber or resin, they are not dispersed in the expected degree of particulate form.

Therefore, it was clarified that the primary particle size was sufficiently small, but the properties were not effectively exhibited when blended into rubber, resin, etc., and further research was conducted on what kind of aggregation form conductive zinc oxide powder forms. As a result, it was confirmed that in the conventional conductive zinc oxide powder, as shown in FIG. Agglomeration by point contact, that is, the primary particles adhere to each other into a flat shape and are tightly integrated into one body.

In this way, when the primary particles exist in the form of secondary aggregates closely integrated into one body, even though the primary particles are miniaturized, most of them can only be dispersed as secondary aggregates when they are blended into the substrate, and it is difficult to A uniformly dispersed state in the presence of primary particles is obtained. Therefore, it is considered that if the produced ultrafine primary particles do not aggregate into one body with strong cohesive force, but form a secondary aggregate in a state of loose point contact with each other, when blended into a base material such as rubber or resin, the two Whether or not the secondary aggregates are simply dissociated so that ultrafine primary particles can be finely and uniformly dispersed in the substrate. The inventors conducted research along this line of thought.

As a result, it was found that, as will be described in detail later, if the production conditions of this conductive zinc oxide powder are controlled, the bulk density can be very small due to the volume swelling caused by the point contact of the fine primary particles with each other loosely. , a new conductive zinc oxide powder that has very excellent dispersibility to rubber or resin, and can form a composition with a very small volume resistivity at the same time, the above is conceived in the present invention.

Therefore, as will be described in detail later, the present invention is an invention of a practically effective production method, and the conductive zinc oxide powder produced by this method has peculiar characteristics that conventional conductive zinc oxide powders do not have, especially the volume. It is an extremely useful new substance in industry because of its very low density, good dispersibility, and the ability to remarkably reduce the volume resistivity of substrates such as rubber or resin.

Hereinafter, the peculiar physical properties of the conductive zinc oxide powder of the present invention will be mainly described, and at the same time, its manufacturing method will be described in detail.

The conductive zinc oxide powder of the present invention is an ultrafine particle powder with an average primary particle diameter of less than or equal to 0.03 micron calculated by specific surface area. Here, the average primary particle diameter calculated from the specific surface area is a value calculated by measuring the specific surface area by a specific surface area measurement method (BET method) based on a common method, and substituting the obtained value into the following formula (1).

d=1.06/S...(1)

[In the formula, d represents the average primary particle size (unit: micron), and S represents the specific surface area (unit: m ² /g) obtained by the BET method]

The conductive zinc oxide powder of the present invention contains at least one element selected from the group consisting of Group IIIB elements, Group IVB elements, and Fe in a solid solution state in zinc oxide crystals. Zinc atoms in zinc oxide exist as divalent positive ions, but when the above-mentioned selected elements are solid-dissolved in zinc oxide, they become trivalent positive ions. Therefore, these selective elements release one more electron than zinc, and this electron is directly responsible for imparting conductivity to zinc oxide.

Aluminum, gallium, indium, etc. are mentioned as a group IIIB element added in order to impart electrical conductivity; Germanium, tin, etc. are mentioned as a group IVB element. In the present invention, these elements are selected from a group of elements including Fe. These elements may be used alone or in combination of two or more of them as necessary.

Among the above-mentioned elements, the elements of the IIIB group and the IVB group are well-known elements as doping elements for imparting conductivity to zinc oxide, and the present inventors have confirmed that Fe is also effective as these doping elements. Elements that impart electrical conductivity. That is, it was confirmed that Fe, especially trivalent Fe, can maintain a trivalent state even if it is fired in a reducing atmosphere for obtaining conductive zinc oxide powder with low volume resistivity, and can effectively play the role of a doping element. Conductivity can be imparted by solid-dissolving an appropriate amount in zinc oxide.

The preferable content range of the said element is 0.01-10 mass % in terms of metal with respect to the mass of zinc oxide. By the way, if it is less than 0.01% by mass, satisfactory conductivity cannot be imparted to the zinc oxide powder due to insufficient doping, and even if the obtained conductive zinc oxide powder is blended into a base material such as rubber, it is difficult to obtain Desired low resistivity. In addition, if the content exceeds 10% by mass, the volume resistivity of the conductive zinc oxide powder will decrease, but the primary particles will tend to be coarsened, and the conductivity will be imparted when uniformly dispersed in a base material such as rubber. The effect tends to decrease, and there is a possibility of adversely affecting the physical properties of the substrate itself. Therefore, the content of the above-mentioned additional element in terms of metal is more preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass based on the mass of zinc oxide.

In the conductive zinc oxide powder of the present invention, as described above, by adding an appropriate amount of a specific element to zinc oxide, the element is solid-dissolved in the zinc oxide crystal, and as a result, the volume resistivity is reduced to 10 ¹⁰ Ω·cm or less , more preferably, the volume resistivity is equal to or less than 10 ⁸ Ω·cm, more preferably equal to or less than 10 ⁶ Ω·cm. A case where the volume resistivity exceeds 10 ¹⁰ Ω·cm cannot ensure the desired standard conductivity imparting effect in the present invention, and thus is excluded.

Here, the so-called volume resistivity means that 10 g of the test powder is added to a cylinder with an inner diameter of 25 mm processed from polytetrafluoroethylene resin and pressurized at 10 MPa. The measuring device "CDM-2000 type measuring device" measured the value obtained by measuring the volume resistivity of this pressurized powder.

Furthermore, the greatest feature of the conductive zinc oxide powder according to the present invention is that the bulk density is very small compared with the conventional conductive zinc oxide powder, and has a value of 0.20 g/ml or less. This bulk density is a value measured by the method specified in JIS K 5101, and this value has a minimum value of 0.20 g/ml or less when considering the true density (5.6) of zinc oxide. 3.6% (=0.20 g/ml÷5.6 g/ml×100), extremely small. That is, when the zinc oxide powder of the present invention is observed at the micron level, the fine particles occupy the space in a very loose state, and it can be said that the primary particles gather in the space in a very loosely attached state.

In this way, in order to form a state where the fine primary particles are assembled in an extremely loosely attached state, the primary particles must be assembled in a state of point contact with each other. As a result, a very easily dispersed aggregate of the primary particles is formed, and a product containing a secondary aggregate The body of the powder is very bulky. Such an aggregated state can be observed, for example, in the drawing of FIG. 1 mentioned in Examples described later in place of a microscope photograph. In order to exert the characteristics of the present invention more effectively, the more preferred bulk density is less than or equal to 0.17 g/ml.

In the zinc oxide powder of the present invention, since the bulk density formed by gathering the primary particles in a state of extremely loose point contact with each other as described above is small, when blended into rubber or resin, etc., coarse particles and finer secondary particles All are easily dissociated in the base material, and most of them are considered to be finely dispersed in the form of primary particles, showing excellent dispersibility. As an evaluation method of this dispersibility, for example, the method shown below can be used.

1) Accurately weigh 4.7 grams of conductive zinc oxide powder and 4 grams of xylene as a sample and add to 80 grams of epoxy resin (manufactured by Japan Epoxy Resin Corporation, trade name "1001X75"), using a homogenizer ( Nippon Seiki Seisakusho Co., Ltd., trade name "E-S homogenizer AM-7 type") was dispersed at 10,000 rpm for 10 minutes to obtain a dispersion liquid of conductive zinc oxide powder.

2) Add 48 g of an epoxy resin curing agent (manufactured by Japan Epoxy Resin Co., Ltd., trade name "S002") to the dispersion liquid obtained in the above 1), and stir with a propeller mixer for 1 minute to mix.

3) The above-obtained dispersion was coated on a PET film with a thickness of 100 μm by a feeder set at a thickness of 250 μm.

4) Dry for one day after coating, and then measure the thickness of the coating film with a micrometer. The thickness of the coating film (approximately 150 micrometers) is cut out at a uniform and approximately constant portion, and the portion where the incident light is incident on the integrating sphere in the spectrophotometer (manufactured by Shimadzu Corporation, trade name "UV-260") is pasted for adhesion test slices to measure the transmittance.

Among the transmittances measured as described above, if the visible light transmittance is high and the ultraviolet light transmittance is low, it can be judged that the zinc oxide particles are finely dispersed. By the way, as clearly described in the examples and comparative examples described later, the transmittance of the conductive zinc oxide powder related to the present invention has a visible light transmittance of 10% or more and an ultraviolet light transmittance of 10%. Contrary to this, the visible light transmittance of the conventional conductive zinc oxide powder is less than 10%, and the ultraviolet light transmittance exceeds 2%. It can also be known that the conductive zinc oxide powder of the present invention has exceptionally superior of dispersion.

In the present invention, as a method for obtaining a conductive zinc oxide powder having a bulky volume and excellent dispersibility as described above, for example, the method described below can be recommended.

The method implements the following steps in sequence:

(1) make alkaline carbonate react in the aqueous slurry of zinc oxide and obtain the step of alkaline zinc carbonate;

(II) the step of heating and slaking the basic zinc carbonate;

(III) mixing a water-soluble salt of at least one element selected from the group consisting of IIIB group elements, IVB group elements and Fe into the obtained aging solution and performing re-aging;

(IV) a step of dehydrating and drying the cured product;

(V) a step of firing the dried product obtained;

(VI) A step of pulverizing the dehydrated burnt product.

That is, at first adding basic carbonate (or the compound that can generate carbon dioxide and alkali by decomposition) (hereinafter collectively referred to as basic carbonate) to the aqueous slurry containing zinc oxide as raw material to generate basic zinc carbonate (hereinafter This step is sometimes referred to as the basic zinc carbonate generation step).

Zinc oxide used as a raw material can be in any form as long as it is called zinc oxide. For example, a) the French method in which zinc is melted, evaporated, and oxidized in the gas phase; b) zinc ore is calcined and reduced. The American method of oxidation; c) any one of the wet method (thermal decomposition method) such as adding soda ash to the zinc salt solution to precipitate basic zinc carbonate, drying and firing. However, in order to obtain a high-purity conductive zinc oxide powder, it is preferable to use as high-purity zinc oxide as possible.

The water used when suspending the raw zinc oxide to form an aqueous slurry is not particularly limited, and tap water, ion-exchanged water, or distilled water from which impurities have been removed can be appropriately selected according to the purity required for the zinc oxide powder product.

Special attention must be paid to the above-mentioned basic zinc carbonate generation step to make the slurry concentration of the raw material zinc oxide low, preferably 0.1-10 mass%, more preferably 0.5-8 mass%, most preferably 1-5 mass%.

By the way, if the concentration of the slurry exceeds 10% by mass, alkaline zinc carbonate with a large particle size will be generated, or a planar agglomerate strongly agglomerated by the primary particles will be easily generated, and the conductivity obtained by subsequent doping treatment It is also difficult for zinc oxide powder to satisfy the desired physical properties of the present invention. On the other hand, if the slurry concentration is too low, the amount of moisture to be removed in a drying step or the like is too large, thereby reducing productivity and energy efficiency, and is not practical.

The types of alkaline carbonates are not particularly limited, and are generally sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, etc. These substances can be used alone or in combination of two or more as needed . In addition, since carbon dioxide and a base are generated by reacting urea with ammonium nitrate or the like, it can also be used as an equivalent of a basic carbonate.

If the water temperature when dissolving the above-mentioned basic carbonate is too high, the basic carbonate will be thermally decomposed to generate carbon dioxide before reacting with the zinc oxide slurry, so the water temperature can be controlled at preferably less than or equal to 30°C, more preferably less than or equal to 20°C. The concentration of the alkaline carbonate solution is not particularly limited, and a sufficient amount of alkaline carbonate can be completely dissolved in moderate water, preferably water with a saturation solubility or above during the formation of the alkaline zinc carbonate described below. And use.

There is no particular limitation on the device used in the basic zinc carbonate generation step, for example, a stirred tank type reaction device is preferred, and the stirred tank type reaction device has a stirring device, a heating device, a cooling device, etc., so that the zinc oxide particles can not be settled It is made to float reliably to maintain a slurry state, and has a function that the reaction with the zinc oxide particles can be efficiently performed by introducing an alkaline carbonate thereinto.

The generation of basic zinc carbonate can actually be carried out by various methods, and the reaction mode is not particularly limited. As a preferred mode, for example, first adding zinc oxide slurry to the reaction tank, and then continuously supplying basic carbonic acid to it Salt solution to generate a semi-continuous method (semi-batch type) of alkaline zinc carbonate slurry; continuously supply zinc oxide slurry and alkaline carbonate solution to the reaction tank simultaneously to generate alkaline zinc carbonate slurry, and continuously from the reaction tank The continuous method of taking out the generated alkaline zinc carbonate slurry in the tank, etc.

Under the situation of continuous method, the reaction tank that uses can be 1 tank, because the productive rate that uses 2 or more than 2 tanks connected in series can improve the productive rate of basic zinc carbonate, so preferably use. In addition, it is of course also effective to perform continuous production industrially using an in-line stirrer designed to ensure a sufficient residence time when the reaction proceeds.

In the present invention, the reaction of zinc oxide particles and basic carbonate to generate basic zinc carbonate (hereinafter sometimes referred to as basic zinc carbonate generating reaction) is considered to proceed as follows. That is, zinc oxide itself is hardly soluble in water, but a small amount of zinc oxide (for example, about 0.5% by mass at 180° C.) dissolves in a saturated state in the boundary film near the particle surface, and is soluble in alkaline carbonates with high water solubility. Into it, and diffuse to the vicinity of the particle surface, in the boundary membrane of the solid-liquid interface, for example, in the case of ammonium bicarbonate, the liquid phase reaction is carried out by the following formula (2).

…(2)

The generated basic zinc carbonate is a salt hardly soluble in water, and it is considered that there is substantially no supersaturated solubility, and it is immediately precipitated as fine particles.

The reaction temperature for producing basic zinc carbonate is not particularly limited, but may be preferably 10-80°C, more preferably 20-70°C. This is because, for the reaction itself represented by above-mentioned formula (2), temperature is high and then can carry out at a high speed, but can produce carbon dioxide gas when reaction temperature is too high, thereby can reduce the productive rate of basic zinc carbonate. Therefore, in order to increase the reaction rate while preventing the generation of carbon dioxide gas due to decomposition, it is preferable to carry out the reaction in the above-mentioned temperature range.

The reaction time (in the case of a continuous method, the average residence time in the reaction vessel) varies depending on the reaction temperature and the concentration of the basic carbonate introduced, etc., so it cannot be generalized, but it is usually 10 minutes to 10 hours, preferably 30 minutes ~ About 5 hours. In order to obtain a suitable temperature, the reaction equipment used is preferably equipped with a heating device, a heat preservation device, a temperature control device, and the like.

In the present invention, in the slurry containing basic zinc carbonate obtained in the above-mentioned basic zinc carbonate production step, 0.01 to 10 mass % of elements selected from group IIIB, IVB and A compound of at least one element of the group consisting of a group element and Fe is added as an additive for imparting electrical conductivity. If it is less than 0.01% by mass, the conductivity of the finally obtained conductive zinc oxide powder will be insufficient, and a satisfactory conductivity-imparting effect cannot be obtained even if it is blended into rubber, resin, or the like. In addition, when it exceeds 10% by mass, the amount added is too much. Although the volume resistivity of the obtained conductive zinc oxide powder is low, the particle size of the powder is large, and the bulk density is also large, so that the dispersion of rubber or resin, etc. The performance is low, and the desired characteristics of the present invention cannot be brought into full play.

Compounds of the above-mentioned elements added for doping are preferably used in the form of oxides, hydroxides, and soluble salts. When oxides and hydroxides are used, in order to uniformly disperse them in the alkaline zinc carbonate slurry, fine powders having an average particle diameter of preferably 1 micron or less, more preferably 0.1 micron or less can be added. When adding soluble salts, it can be added in a solution of any concentration. Since the slurry containing basic zinc carbonate is alkaline, the added soluble salts will immediately form fine hydroxides after contacting the slurry, thereby It is more uniformly mixed with basic zinc carbonate, so it is preferable.

The subsequent dehydration step can be performed without limitation using the usual slurry dehydration methods, such as centrifugal dehydrators, filter presses, belt filters, suction filters, screw presses, belt presses, spray dryers and other solid-liquid separation methods.

In addition, the firing after drying can be carried out in either an oxidizing atmosphere or a non-oxidizing atmosphere, and can be carried out in a reducing atmosphere if it is desired to further reduce the volume resistivity of the conductive zinc oxide. As the furnace for firing, any firing furnace can be used as long as it can be heated to a necessary temperature, can set the firing temperature arbitrarily, and can be controlled with sufficient precision. Firing can be carried out under either oxidizing atmosphere or non-oxidizing atmosphere, preferably at a temperature of 300°C or higher (more preferably 350°C or higher), 600°C or lower (more preferably ≤ 500°C, more preferably 450°C or less). If the firing temperature is too high, the zinc oxide generated by the decomposition of basic zinc carbonate will undergo grain growth during the firing process, and the primary particle size will grow to be greater than or equal to 0.03 microns. At the same time, the density of secondary particles or aggregates above Melting also proceeds, and the bulk density exceeds 0.20 g/ml, thereby lacking dispersibility when added to rubber or resin or the like. In addition, when the firing temperature is lower than 300°C, fine zinc oxide can be obtained by thermal decomposition of basic zinc carbonate, but the above-mentioned elements that impart conductivity are difficult to dissolve in zinc oxide, and the conductive zinc oxide powder The volume resistivity will exceed 10 ¹⁰ Ω·cm.

The conductive zinc oxide obtained by firing at a relatively low temperature as described above is then pulverized by any method, and the particle size is adjusted as necessary to form conductive zinc oxide powder having a desired bulk density.

The conductive zinc oxide powder of the present invention thus obtained is not only fine in the primary particles themselves as explained in detail above, but also has an extremely small volume density of the secondary aggregates formed by loosely aggregating the primary particles in a state of point contact with each other. , so it has superior dispersibility compared with conventional secondary aggregates, and can be easily microdispersed on various substrates such as rubber or resin. As a result, the contact frequency of the conductive zinc oxide powders in the substrate is high, and an excellent effect of imparting conductivity to the substrate, that is, an effect of reducing the volume resistivity can be exhibited.

Therefore, if such characteristics can be exhibited, it can be widely and effectively used as a conductive or antistatic material by blending it with various rubbers or resins, fiber materials, paints, etc. as exemplified below.

[conductive or antistatic rubber material]

Various conductive rollers for electronic imaging, conveyor belts, roller materials, conductive gloves, conductive work shoes, shoe soles for clean rooms, pressure sensor materials, etc.

[conductive or antistatic resin]

Floor and wall tile materials and various antifouling panel materials, various window materials, transparent conductive plates and film materials, integrated circuits and load commutation inverters (IC·LCI) for factories, houses, public buildings, etc. Packaging materials for electronic components, containers and casings, materials for various molded products such as semiconductor casings, brackets, and jigs, materials for various antistatic devices and daily appliances, and various instrument windows such as cathode ray tube (CRT) windows Materials, image storage materials, electrode forming materials, charge control materials, antistatic materials, color toner materials for electronic photography, color toner materials, toner carrier materials, electromagnetic wave baffle materials, conductive pipe materials, pressure sensor materials, etc.

[Conductive or antistatic coatings, coating materials, primers]

Conductive coating materials, primers for electrostatic finishing, conductive paints, clear paints, etc.

[Conductive or antistatic film, sheet]

Antistatic and dustproof film materials such as packaging films and antistatic films, conductive laminated paper, conductive laminated sheets, tablecloths, antireflection films, touch panels, pressure sensor materials, capacitors, thin film composite circuit materials, liquid crystals, ELs, and ECDs・ Various panel materials such as PDP (Plasma Display), transparent films and sheets for blocking infrared rays or ultraviolet rays, etc.

[conductive or antistatic fiber]

Cleaning room clothes, hats, gloves, work clothes, wall coverings, curtains, curtains, mats, carpet materials, antistatic underwear and outerwear, dust-proof brushes, surgical clothes and other antistatic fiber products.

[conductivity or antistatic glass]

Conductive or antistatic glass materials, cathode ray tube materials, solar cell panel materials, dye-sensitized electrode materials, etc.

[Conductive Cosmetic Materials]

Additives for anti-infrared creams, foundations, whitening creams, wipes, lipsticks, blushes, eyeshadows, sunscreens, powders, and lotions.

[other]

Electrostatic storage paper, electrostatic storage replication substrate, electrothermal storage paper, discharge destruction storage paper, electronic camera paper, electronic camera replication substrate, desulfurization material, surface heating element, electromagnetic shielding material, thermally conductive rubber and resin, etc.

In the above-mentioned applications, rubber and resin (including paint materials) are used as base materials, and when 10 to 300 parts by mass of the conductive zinc oxide powder of the present invention is blended with respect to 100 parts by mass of the base material, volume resistivity display can be obtained. Produce low-value low-resistance rubbers and resins on the order of 1000 to 10 ¹¹ Ω·cm.

Examples of preferred base rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and 1,2-polybutadiene rubber (1,2-BR). , chloroprene rubber (CR), styrene-butadiene rubber (SBR), butyl rubber (IIR), nitrile rubber (acrylonitrile-butadiene rubber) (NBR), hydrogenated nitrile rubber (HNBR), Ethylene-propylene rubber (EPM, EPR, EPDM, EPT), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO), ethylene-vinyl acetate rubber (EVA), silicone rubber (Q ), methyl silicone rubber (MQ), methyl vinyl silicone rubber (VMQ), phenyl-methyl silicone rubber (PMQ), polysulfide rubber (T), polyurethane rubber (U), polyether polyurethane rubber ( EU), polyester urethane rubber (AU), fluororubber (FKM), etc. These rubbers can be used alone, or two or more of them can be used in combination as needed to form a mixed rubber.

As mentioned above, the preferable compounding quantity of the said electroconductive zinc oxide powder with respect to the said rubber is the range of 10-300 mass parts with respect to 100 mass parts of base rubbers. If it is less than 10 parts by mass, the conductive path will not be fully connected, so that the volume resistivity of the modified rubber exceeds 10 ¹¹ Ω·cm level; It is saturated at the level of 10 ³ Ω·cm and will not be further reduced, thus causing waste economically.

In addition, there is no particular limitation on the additives that can be blended into the base rubber simultaneously with the above-mentioned conductive zinc oxide powder, and generally used rubber compounding agents can be used as well. Examples of substances that can be blended into the base rubber include, without limitation, vulcanizing agents (curing agents), vulcanization accelerators, vulcanization accelerators, anti-aging agents (antioxidants), fillers (strengthening agents, Extender), colorant, lubricant, UV absorber, light stabilizer, antibacterial agent, flame retardant, etc.

Examples of vulcanizing agents include conventionally known sulfur, inorganic sulfides, organic sulfides, organic peroxides, metal oxides, and the like. In particular, the use of sulfur and sulfides is preferable since volume resistivity can be more effectively reduced. The preferable compounding quantity of the said sulfur and a sulfide is about 0.1-5 mass % with respect to 100 mass parts of base rubbers.

The base rubber, the above-mentioned conductive zinc oxide powder, and other additives can be kneaded using a closed kneader, kneader, mixer, roller kneader, etc. based on the usual method, and other organic kneaders can be blended as needed. substances or inorganic conductive materials.

As the molding process of rubber products, the kneaded product mixed with conductive zinc oxide powder can be processed into arbitrary shapes such as sheet, ribbon, and cylinder based on common methods. When processing into sheet (especially flake), press processing and rolling sheet processing are preferred; when processing into flat plate or sheet, tube (single layer or multi-layer), round rod (roller), and then complex special-shaped cross-sectional shape , Extrusion molding, injection molding, compression molding, etc. can be used. In addition, vulcanization is usually performed after molding as described above or in the final step of molding. For vulcanization, an elastic rubber product can be obtained by heating and crosslinking a molded body obtained by press processing, extrusion processing, etc. as described above in the presence of a vulcanizing agent such as sulfur.

Any vulcanizer may be used as long as it has the function of holding and heating the blended rubber molding as described above. The vulcanization tank is a representative vulcanization device, and after placing the mixed rubber molded body in it, it can be heated by any method such as steam heating, hot air heating, infrared heating, electric heating, microwave heating, etc. A heat press machine may also be used to heat the molded body while pressing it. Furthermore, when the molded article is in the form of a sheet or a belt, it is preferable to recommend a method of heating and vulcanizing while continuously moving the sheet or belt.

The vulcanization temperature also varies depending on the type of base rubber, vulcanizing agent, vulcanization accelerator, etc., but is usually carried out at 120 to 200°C. Regarding the vulcanization time, the test piece of the rubber molded body is used as the object in advance, and the tensile stress and torque at a given temperature are continuously measured through preliminary experiments to form a graph, and each setting can be made based on the results. The standard Preferably it is 2 to 60 minutes, more usually 5 to 60 minutes.

The volume resistivity of the obtained conductive rubber molded article is also specified in JIS K6911, and can be measured using, for example, products such as Mitsubishi Oil Chemicals' trade name "HIRESTA-IP (100V)" according to this method.

In addition, the type of base resin is not particularly limited, and for example, epoxy resins, acrylic resins, polyamide resins, polyurethane resins, polyester resins, polyolefin resins, phenol resins, urea resins, Any one or more of resins, melamine-formaldehyde resins, silicone resins, etc.

The preferred blending amount of the above-mentioned conductive zinc oxide powder to the above-mentioned base resin differs depending on the type of base resin and the degree of conductivity required by the target conductive resin, so it cannot be generalized, but usually relative to 100 parts by mass of the base resin It is 10-300 mass parts, More preferably, it is the range of 20-150 mass parts. By the way, when the compounding amount of conductive zinc oxide powder is too small, it is difficult to connect the conductive path sufficiently, so that the conductivity becomes insufficient, and the volume resistivity of the conductive composition exceeds the level of 10 ¹¹ Ω·cm; If the amount is too high, the volume resistivity of the modified resin will be saturated at the level of 10 ³ Ω·cm and will not decrease further, thus causing waste economically.

In addition, additives that can be blended into the base resin simultaneously with the above-mentioned conductive zinc oxide powder are not particularly limited, and generally used resin blending agents can be used similarly. Examples of substances that can be blended into the base resin include, without limitation, plasticizers, anti-aging agents (antioxidants), fillers (reinforcing agents, extenders), colorants, lubricants, ultraviolet rays, etc. Absorbent, light stabilizer, antibacterial agent, flame retardant, etc.

The base resin, the above-mentioned conductive zinc oxide powder, and other additives can be kneaded using a closed kneader, kneader, mixer, etc. based on a common method, and other organic substances or inorganic conductive materials can be blended as needed. .

As molding processing of resin products, the kneaded product mixed with conductive zinc oxide powder can be molded into any shape by injection molding, extrusion molding, compression molding, blow molding, etc. based on common methods.

In addition, when the conductive zinc oxide powder of the present invention is used in a conductive or antistatic paint, it is preferable that the base resin constituting the paint contains 10 to 50 wt. %, more preferably 15 to 40% by mass of conductive zinc oxide powder. It can be dispersed uniformly in the carrier composition. There are no restrictions on the form of the coating, for example, organic solvent-based coatings, water-based coatings, slurry coatings, powder coatings, etc. are all applicable. As the type of the coating resin, any type such as a firing-curing type and a drying-curing type may be used. There is no limitation on the kind of the base resin constituting the paint, and any resin such as epoxy resin, acrylic resin, polyamide resin, polyurethane resin, polyester resin, polyolefin resin, alkyd resin, etc. can be used. one or more.

Examples of additives that can be blended into paint resins include, without limitation, plasticizers, anti-aging agents, colorants, component content agents, flow regulators, lubricants, ultraviolet absorbers, and light stabilizers. , antibacterial agent, flame retardant, etc.

Example

The following examples and comparative examples are given to describe the present invention in more detail. Of course, the present invention is not limited to the following examples, and can be appropriately modified within the scope of the meanings described above and below. included in the technical scope of the present invention.

Example 1

150 g of zinc oxide powder having an average particle diameter of 1.0 µm produced by the French method was added and dispersed in 2800 ml of distilled water at a temperature of 20°C. On the other hand, dissolve 75 grams of ammonium bicarbonate in 500 ml of water at a temperature of 20°C in advance, add the aqueous solution of ammonium bicarbonate to the above-mentioned zinc oxide dispersion, stir at the same temperature for 30 minutes, and then dissolve it at a rate of 1°C/min. Speed up to 70°C to generate basic zinc carbonate. By aging at the same temperature for 30 minutes, basic zinc carbonate crystals were grown.

Next, dissolve 14.3 grams of aluminum sulfate in 500 milliliters of distilled water and add it to the aqueous dispersion of basic zinc carbonate obtained above. After stirring for 30 minutes to disperse, the temperature of the liquid is raised to 70°C again, and then matured again for 30 minutes. minute.

After aging, the dispersion liquid was sucked and filtered, and the solid was collected by filtration, dried at 150°C or less, then calcined at 300°C for 3 hours, and then reduced and calcined at 400°C for 2 hours under a hydrogen atmosphere. The obtained fired product was pulverized with a pulverizer to obtain conductive zinc oxide powder having an average particle diameter of 3.0 micrometers.

The obtained conductive zinc oxide powder had an average primary particle diameter calculated from the specific surface area obtained by the BET method of 0.02 μm, a volume resistivity of 3000 Ω·cm, and a bulk density of 0.14 g/ml.

Fig. 1 is a drawing-substituting electron microscope photo of the obtained electroconductive zinc oxide powder (using the trade name "JSM-5200" manufactured by JEOL Ltd., the magnification is 20,000 times). Compared with zinc oxide powder, it can be clearly observed from the appearance that the primary particles are loosely assembled in an extremely loose state.

Example 2

150 g of the same zinc oxide as used in Example 1 above was added to 2800 ml of distilled water at a temperature of 20°C and dispersed. On the other hand, 75 grams of ammonium bicarbonate was dissolved in 500 ml of water at a temperature of 20°C in advance, and the aqueous ammonium bicarbonate solution was added to the above-mentioned zinc oxide dispersion, and stirred at the same temperature for 30 minutes. The speed is raised to 70°C to generate basic zinc carbonate. By aging at the same temperature for 30 minutes, basic zinc carbonate crystals were grown.

Next, dissolve 1.9 grams of gallium chloride in 500 milliliters of distilled water, and add it to the aqueous dispersion of basic zinc carbonate obtained above, stir for 30 minutes to disperse, then raise the temperature of the liquid to 70° C., and then ripen it for 30 minutes again .

After aging, the dispersion was filtered and dried in the same manner as in Example 1 above, and the dried product was calcined at 300°C for 3 hours, and then reduced and calcined at 400°C for 2 hours under a hydrogen atmosphere. The obtained fired product was pulverized with a pulverizer to obtain conductive zinc oxide powder having an average particle diameter of 2.0 micrometers.

The average primary particle diameter calculated from the specific surface area of the obtained conductive zinc oxide was 0.02 μm, the volume resistivity was 1000 Ω·cm, and the bulk density was 0.15 g/ml.

Example 3

150 g of the same zinc oxide as used in Example 1 above was added to 2800 ml of distilled water at a temperature of 20°C and dispersed. On the other hand, 75 grams of ammonium bicarbonate was dissolved in 500 ml of distilled water at a temperature of 20°C in advance, and the aqueous solution of ammonium bicarbonate was added to the above-mentioned zinc oxide dispersion. The temperature is raised to 70°C at a speed of 1 minute to generate basic zinc carbonate. By aging at the same temperature for 30 minutes, basic zinc carbonate crystals were grown.

Next, dissolve 18.43 grams of ferric chloride hexahydrate in 500 milliliters of distilled water, and add it to the aqueous dispersion of basic zinc carbonate obtained above, stir for 30 minutes to disperse, and then raise the temperature of the liquid to 70° C. , and then ripened again for 30 minutes.

After aging, the dispersion was filtered and dried in the same manner as in Example 1 above, and the dried product was fired at 300°C for 3 hours, and then fired at 400°C for 2 hours in an oxidizing atmosphere. The obtained fired product was pulverized with a pulverizer to obtain conductive zinc oxide powder having an average particle diameter of 3.0 micrometers.

The average primary particle diameter calculated from the specific surface area of the obtained conductive zinc oxide was 0.02 μm, the volume resistivity was 1×10 ⁸ Ω·cm, and the bulk density was 0.17 g/ml.

Comparative example 1

600 g of the same zinc oxide powder as that used in Example 1 above was added to 1800 ml of distilled water at a temperature of 20°C and dispersed. On the other hand, 300 g of ammonium bicarbonate was previously dissolved in 1500 ml of distilled water at a temperature of 20°C, and 57.2 g of aluminum sulfate was added thereto and uniformly dispersed. This dispersion liquid was added to the above zinc oxide dispersion liquid and stirred for 30 minutes to disperse, then the temperature was raised to 70° C. at a rate of 1° C./min to generate Al-containing basic zinc carbonate. By aging at the same temperature for 30 minutes, basic zinc carbonate crystals were grown.

After the obtained dispersion was filtered and dried in the same manner as above, it was baked at 300° C. for 3 hours, and further reduced and fired at 800° C. for 2 hours under a hydrogen atmosphere. The obtained fired product was pulverized with a pulverizer to obtain conductive zinc oxide powder having an average particle diameter of 6.0 micrometers.

The average primary particle diameter calculated from the specific surface area of the obtained conductive zinc oxide was 0.2 µm, the volume resistivity was 150 Ω·cm, and the bulk density was 0.4 g/ml.

That is, although the conductive zinc oxide powder of this comparative example has a sufficiently low volume resistivity value, the particle diameter calculated from the specific surface area is remarkably large compared with the above-mentioned Examples 1 to 3, and the bulk density is also very high.

Comparative example 2

600 g of the same zinc oxide powder as that used in Example 1 above was added to 1800 ml of distilled water at a temperature of 20°C and dispersed. On the other hand, 300 g of ammonium bicarbonate was previously dissolved in 1500 ml of distilled water at a temperature of 20°C, and 57.2 g of aluminum sulfate was added thereto and uniformly dispersed. This dispersion liquid was added to the above zinc oxide dispersion liquid and stirred for 30 minutes to disperse, then the temperature was raised to 70° C. at a rate of 1° C./min to generate Al-containing basic zinc carbonate. By aging at the same temperature for 30 minutes, basic zinc carbonate crystals were grown.

After the obtained dispersion was filtered and dried in the same manner as above, it was baked at 300° C. for 3 hours, and further reduced and fired at 400° C. for 2 hours under a hydrogen atmosphere. The obtained fired product was pulverized with a pulverizer to obtain conductive zinc oxide powder having an average particle diameter of 6.0 micrometers.

The average primary particle diameter calculated from the specific surface area of the obtained conductive zinc oxide was 0.03 μm, the volume resistivity was 300 Ω·cm, and the bulk density was 0.35 g/ml. That is, the conductive zinc oxide powder has a low volume resistivity and a small particle diameter calculated from a specific surface area, but has a high bulk density.

Fig. 2 is the accompanying drawing of the obtained conductive zinc oxide powder instead of an electron micrograph (the electron microscope used is the same as above, and the magnification is 20000 times), if compared with the conductive zinc oxide powder obtained in the above-mentioned embodiment 1, From the appearance, it can be clearly observed that the primary particles are closely integrated into one state on the plane.

Comparative example 3

Conductive zinc oxide powder was produced according to Example 1 described in the production method of conductive zinc oxide disclosed in JP-A-62-41171.

That is, dissolve 30 grams of ammonium carbonate in 500 milliliters of water. Separately, a solution obtained by dissolving 5 g of aluminum sulfate in 50 ml of water was prepared and put into the above-mentioned ammonium carbonate solution. Disperse 100 grams of the same zinc oxide powder used in the above-mentioned Example 1 in 200 milliliters of water to form a dispersion, then add the above-mentioned ammonium carbonate solution with an aqueous solution of aluminum sulfate to the dispersion, heat up to 60° C. and stir , after continuing to stir at the same temperature for 1 hour, dehydrated lumps were obtained by filtering and washing with water. After drying this lump, it baked at 800 degreeC for 60 minutes in hydrogen atmosphere, and obtained the electroconductive zinc oxide powder.

The average primary particle diameter calculated from the specific surface area of the obtained conductive zinc oxide was 0.4 µm, the volume resistivity was 30 Ω·cm, and the bulk density was 0.45 g/ml.

That is, the volume resistivity value of the conductive zinc oxide powder obtained by this method is sufficiently low, but the primary particle diameter calculated from the specific surface area is extremely large compared with the above-mentioned Examples 1 to 3, and the bulk density is also very high.

Performance test 1

In order to investigate the dispersibility of the conductive zinc oxide powder obtained in Examples 1 to 3 and Comparative Examples 1 to 3 above, the transmittance was measured by the above-mentioned dispersibility evaluation test method, and the results shown in Table 1 below were obtained. . As shown in the table, the conductive zinc oxide powder of the present invention has higher visible light transmittance and extremely low ultraviolet transmittance than the conductive zinc oxide powder obtained in Comparative Example, and has extremely excellent dispersibility.

Table 1 Transmittance (%) 550nm 350nm Example 1 10.56 0.02 Example 2 10.88 0.01 Example 3 10.55 0.02 Comparative example 1 5.33 2.11 Comparative example 2 9.13 5.29 Comparative example 3 4.25 1.89

Performance test 2

The electroconductive zinc oxide powders obtained in Examples 1 to 3 and Comparative Examples 1 to 3 above were evaluated by the following method in terms of volume resistivity for the conductivity imparting effect obtained when they were mixed into rubber.

That is, using ethylene-propylene-diene rubber (EPDM) (manufactured by JSR Corporation, trade name "EP-21") as the base rubber, and blending 100 parts by mass of the base rubber into 100 parts by mass of the above-mentioned implementation The conductive zinc oxide powders obtained in Examples and Comparative Examples were uniformly kneaded with twin rolls. After kneading, aging for a certain period of time, and then adding 1.75 parts by mass of sulfur as a vulcanizing agent and 1.0 parts by mass of a vulcanization accelerator (manufactured by Ouchi Shinko Chemical Co., Ltd., trade name "Nokusera-EP-50"), and then uniformly kneaded , formed into a 2mm thick sheet.

The obtained sheet was put into a metal mold and fixed on a vulcanizer, and a hard rubber body was obtained by vulcanizing at a pressure of 9.8 MPa and a temperature of 160° C. for 60 minutes, using Mitsubishi Oil Chemicals according to the regulations in JIS K 6911 The manufactured measuring instrument "HIRESTA-IP (100V)" measured the volume resistivity of this hard rubber body.

The results are shown in Table 2. Compared with the conventional conductive zinc oxide powder obtained in the comparative example, the electroconductive zinc oxide powder of the present invention obtained in the examples shows that the effect of lowering the volume resistivity of rubber is significantly more pronounced. .

Table 2 Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Conductive Zinc Oxide Particle size (micron) 0.02 0.02 0.02 0.2 0.03 0.40 Bulk Density (g/ml) 0.14 0.15 0.17 0.4 0.35 0.45 Volume resistivity (Ω·cm) 3000 1000 1×10 ⁸ 150 300 30 EPDM amount (parts by mass) 100 100 100 100 100 100 The blending amount of conductive zinc oxide (mass parts) 100 100 100 100 100 100 Volume resistivity of rubber (Ω·cm) 9×10 ⁷ 1×10 ⁷ 8×10 ⁸ 1×10 ¹⁵ 1×10 ¹² 1×10 ¹⁵

Performance test 3

The conductive zinc oxide powder obtained in Examples 1 to 3 and Comparative Examples 1 to 3 above was evaluated for the conductivity-imparting effect obtained by mixing it into a resin by measuring the volume resistivity shown below.

That is, using epoxy resin (manufactured by JER Corporation, trade name "1001X75") as the base resin, 4.06 g of each conductive zinc oxide powder obtained in the above-mentioned Examples and Comparative Examples was mixed with 50 g of the base resin ( Resin solid content: 75%), 5.5 gram xylenes, 5.5 gram isobutanols are blended together, to the electroconductive zinc oxide powder that obtains among the embodiment 1～3 and comparative example 2, add the dispersant that is 9% relative to powder (manufactured by Kusumoto Kasei Co., Ltd., trade name "DA-325"), and kneaded for 5 minutes at 2000 rpm using a homogenizer. After kneading, add 30 grams of epoxy resin curing agent (manufactured by JER Corporation, trade name "S002") (resin solid content: 62.5%), and mix with 1000rpm by propeller mixer for 1 minute, then use applicator (applicator) (Storage: 50) A coating film was formed and dried at 25° C. for 48 hours.

The volume resistivity of a coating film having a thickness of 0.2 mm was measured using a measuring instrument "HIRESTA-IP (100V)" manufactured by Mitsubishi Oil Chemicals in accordance with JIS K 6911.

The results are shown in Table 3. Compared with the conventional conductive zinc oxide powder obtained in the comparative example, the electroconductive zinc oxide powder of the present invention obtained in each example is more effective in reducing the volume resistivity of the paint. obvious.

table 3 Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Volume resistivity of coating film (Ω·cm) 5×10 ⁸ 2×10 ⁸ 3×10 ¹⁰ 1×10 ¹⁵ 5×10 ¹³ 1×10 ¹⁵

Possibility of industrial use

As mentioned above, the conductive zinc oxide powder of the present invention not only has an extremely fine average primary particle size, but also has a secondary aggregate that is a powder with an extremely small bulk density in which the primary particles are loosely assembled in a point contact state. The dispersion of the base material is excellent, so it can contact each other at a high frequency in the base material. Compared with the conventional conductive zinc oxide, it has an exceptionally superior conductivity-imparting effect; Volume resistivity, therefore, can be widely and effectively used as a material for imparting conductivity to various materials represented by rubber, resin, paint, and the like.

And according to the production method of the present invention, it is possible to provide conductive zinc oxide powder having the above-mentioned characteristics that cannot be obtained by conventional methods, especially low bulk density, excellent dispersibility and conductivity imparting property.

Claims (7)

1, a kind of electroconductive zinc oxide powder is characterized in that, with respect to the quality of zinc oxide, this electroconductive zinc oxide powder solid solution is by at least a element in the group of being made up of IIIB family element, IVB family element and Fe of being selected from of 0.01～10 quality %; The average primary particle diameter that this electroconductive zinc oxide powder is calculated by specific surface area is smaller or equal to 0.03 micron, and volume density is smaller or equal to 0.20 grams per milliliter, and volume specific resistance is smaller or equal to 10 ¹⁰Ω cm.

2, the manufacture method of the described electroconductive zinc oxide powder of a kind of claim 1 is characterized in that, this manufacture method is implemented following steps successively:

(I) make basic carbonate reaction and obtain the step of alkaline carbonic acid zinc in zinc oxide water-soluble serous;

(II) add the step of this alkaline carbonic acid zinc of thermomaturation;

(III) in the slaking liquid that obtains, sneak into water-soluble salt that is selected from least a element in the group of being formed by IIIB family element, IVB family element and Fe and the step of carrying out recurring;

(IV) dehydrate the step of this slaking thing;

(V) step that the dry thing that obtains is burnt till;

(VI) pulverize the step of this burned material.

3, manufacture method according to claim 2, wherein, the water-soluble serous concentration of the zinc oxide that uses in the described step (I) is smaller or equal to 10 quality %.

4, according to claim 2 or 3 described manufacture method, wherein, in described step (V), under oxidisability atmosphere gas or reductibility atmosphere gas, described dry thing is burnt till at 300～600 ℃.

5, a kind of conductive composition is characterized in that, this conductive composition contains the aforesaid right that 100 mass parts base materials and 10～300 mass parts exist with dispersion state and requires 1 described electroconductive zinc oxide powder, and volume specific resistance is 10 ³～10 ¹¹Ω cm.

6, conductive composition according to claim 5, wherein, described base material is a rubber.

7, conductive composition according to claim 5, wherein, described base material is a resin.

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