Powder comprising titanium compound particles having silicon compound layer and titanium-niobium oxide layer, and method for producing the same

Abstract

To provide a powder which can impart a large negative charge to the surface of a charge control target through addition, mixing, or application.SOLUTION: The present invention provides a powder comprising particles wherein a number-based median diameter of primary particles is 0.05 μm or more and 0.50 μm or less, wherein the particles have a silicon compound layer as the outermost surface, a titanium-niobium oxide layer as the second layer, and a titanium compound as the core.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a powder composed of particles consisting of a silicon compound layer on the outermost surface, a titanium niobium oxide layer in the second layer, and a titanium compound in the center, and a method for producing the same. More specifically, the present invention relates to the above-mentioned powder suitable for use in adjusting the charging generated on the surfaces of paints, functional powders, films, fibers, resins, plastics, papers, etc., and a method for producing the same.

Background Art

[0002] Powders composed of conductive metal oxides and paints, fibers, plastics, papers, etc. containing the same are used for preventing charging and removing static electricity due to the conductivity of the metal oxides.

[0003] For example, in Japanese Patent Application Laid-Open No. 2002-339235 (Patent Document 1), a method for producing a fabric excellent in antistatic properties is disclosed by performing a low-temperature plasma treatment on a fabric woven by arranging conductive synthetic fibers in which titanium oxide fine particles coated with carbon black or stannic oxide are dispersed at regular intervals. Further, in Japanese Patent Application Laid-Open No. 2010-59588 (Patent Document 2), a polyester-based composite fiber excellent in color development property is proposed, which consists of a non-conductive layer and a conductive layer, and the conductive layer is a thermoplastic polymer containing titanium oxide particles having a conductive film. Since the inside of the fiber of the polyester-based composite fiber disclosed in Patent Document 2 is a conductive layer, it has an effect of suppressing static electricity.

[0004] These conductive metal oxides and paints, fibers, plastics, papers, etc. containing the same aim to prevent charging on their surfaces or remove the generated static electricity. However, in recent years, the opportunities to utilize static electricity in industries such as electrostatic dust collection and electrostatic coating have increased, and it has become necessary not only to simply remove the charged electric charges but also to control the amount of charged electric charges.

[0005] The applicant of the present application has disclosed a charge control powder of a titanium niobium oxide system having titanium dioxide as core particles and a coating layer of niobium-doped titanium dioxide on the surface of the core particles (Japanese Patent Application Laid-Open No. 2018-141058) (Patent Document 3). By adding or applying this charge control powder to an object, the charge on the surface of the object can be adjusted to be negative.

[0006] Examples in Patent Document 3 disclose powders having a charge amount measured by the method described in Patent Document 3 ranging from -35.0 μC / g to -22.9 μC / g. As the industries utilizing static electricity further develop in the future, it is assumed that materials with various charging characteristics will be combined and used. For example, a material that can adjust the surface of an object to a larger negative charge amount compared to the powder described in Patent Document 3 is considered to be useful in the industry.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a powder and a method for producing the same, which can impart a large negative charge to the surface of each of charge control objects such as paints, functional powders, films, fibers, resins, plastics, and papers by adding, mixing, or applying the powder.

Means for Solving the Problems

[0009] As a result of intensive studies to achieve the above object, the present inventors have found that a powder composed of particles having a median diameter of 0.05 μm or more and 0.50 μm or less based on the number of primary particles, having a silicon compound layer on its outermost surface, a titanium niobium oxide layer on the second layer, and a titanium compound at the center, can impart a large negative charge to the surface of an object.

[0010] Specific embodiments of the present invention are not limited to these, but are as follows. [Aspect 1] A powder composed of particles having a median diameter of 0.05 μm or more and 0.50 μm or less based on the number of primary particles, and composed of particles having a silicon compound layer on the outermost surface, a titanium niobium oxide layer on the second layer, and a titanium compound at the center. [Aspect 2] The powder of Aspect 1, wherein the silicon compound layer contains at least C, O, and Si. [Aspect 3] The powder of Aspect 2, wherein the content of C is 1.0 g / kg or more and 30.0 g / kg, and the content of Si is 0.2 g / kg or more and 32.0 g / kg or less. [Aspect 4] The powder according to any one of Aspects 1 to 3, wherein the content of Nb is 1.4 g / kg or more and 40.0 g / kg or less. [Aspect 5] The powder according to any one of Aspects 1 to 4, wherein the silicon compound is derived from a silane coupling agent. [Aspect 6] The powder according to any one of Aspects 1 to 5, wherein the amount of charge generated by friction with the iron powder carrier evaluated by the method described in the examples is -45 μC / g or a negative charge having an absolute value larger than this. [Aspect 7] A step of wet-coating the titanium compound with titanium niobium hydroxide, After the coating treatment, a step of firing to form a titanium niobium oxide layer on the surface of the titanium compound, After forming the titanium niobium oxide layer, a step of surface-treating with a silicon compound is included. A method for producing the powder according to any one of Aspects 1 to 6. [Aspect 8] Any one of the powders of Embodiments 1 to 6 used as a powder for charge adjustment.

Advantages of the Invention

[0011] According to the present invention, a powder composed of particles having a median diameter based on the number of primary particles of 0.05 μm or more and 0.50 μm or less, with a silicon compound layer on the outermost surface, a titanium niobium oxide layer as the second layer, and a titanium compound at the center, is filled in a charge adjustment target such as a paint, a functional powder, a film, a fiber, a resin, a plastic, or paper, or adhered to the surface. Further, by adjusting the filling amount or the adhesion amount of the powder, it is possible to adjust the charge amount of the target, and furthermore, the charge amount can be set to a large negative value.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0013] The powder of the present invention is composed of particles having a median diameter of 0.05 μm or more and 0.50 μm or less based on the number of primary particles, wherein the outermost surface is a silicon compound layer, the second layer is a titanium niobium oxide layer, and the core is a titanium compound. "Powder" refers to an aggregate of particles. In the case of "a powder composed of particles having a median diameter of 0.05 μm or more and 0.50 μm or less based on the number of primary particles, and consisting of a silicon compound layer on the outermost surface, a titanium niobium oxide layer in the second layer, and a titanium compound in the core", it means that most of the particles constituting the powder are "particles having a median diameter of 0.05 μm or more and 0.50 μm or less based on the number of primary particles, and consisting of a silicon compound layer on the outermost surface, a titanium niobium oxide layer in the second layer, and a titanium compound in the core" (referred to as the said particles), or the proportion of the said particles in the composition of individual particles is large. Specifically, it refers to those in which the proportion of the said particles in the powder is 900 g / kg or more, preferably 950 g / kg or more.

[0014] The powder of the present invention has a median diameter of 0.05 μm or more and 0.50 μm or less based on the number of primary particles. If the diameter is 0.05 μm or more, charging can be effectively retained from the viewpoint of the amount of electricity that individual particles can hold. If the diameter is 0.50 μm or less, it is possible to uniformly distribute the powder on the object. The lower limit is preferably 0.06 μm or more, and the upper limit is preferably 0.40 μm or less. The specific measurement method of the said diameter will be described in the Examples section.

[0015] The particles constituting the powder of the present invention have a silicon compound layer on their outermost surface. The silicon compound layer preferably is a layer containing carbon (C), oxygen (O), and silicon (Si). The silicon compound layer can be formed by treating (coating) the surface of the particles with a silicon compound such as silicone oil or a silane coupling agent. In particular, it is preferably a layer obtained by treating with a silane coupling agent. The silicon compound layer preferably has a C content of 1.0 g / kg or more and 30.0 g / kg or less, and an Si content of 0.2 g / kg or more and 32.0 g / kg or less. If the C content is 1.0 g / kg or more and the Si content is 0.2 g / kg or more, a large negative charge amount is easily obtained. On the other hand, if the C content is 30.0 g / kg or less and the Si content is 32.0 g / kg or less, the dispersibility is likely to be good when the powder is mixed with an object such as a resin or a paint. Also, from the viewpoint of cost, the C content and the Si content are preferably the minimum amounts to obtain the necessary properties. Preferably, the lower limit of the C content is 2.0 g / kg or more, the lower limit of the Si content is 0.4 g / kg or more, the upper limit of the C content is 28.0 g / kg or less, and the upper limit of the Si content is 20.0 g / kg or less.

[0016] The particles constituting the powder of the present invention have a second layer made of titanium niobium oxide. The titanium niobium oxide layer can be provided, for example, on the surface of core titanium compound particles by the method described later. The thickness of the second layer of titanium niobium oxide is preferably 2 nm or more and 100 nm or less. If the thickness of the second layer is 2 nm or more, it becomes easier to effectively retain charge from the viewpoint of the amount of electricity retained by the second layer, and if the thickness of the second layer is 100 nm or less, it becomes easier to obtain stable charge performance. The upper limit is preferably 50 nm or less, more preferably 40 nm or less, and still more preferably 25 nm or less. The lower limit is preferably 3 nm or more.

[0017] The niobium (Nb) content in the powder of the present invention is preferably 1.4 g / kg or more and 40.0 g / kg or less. If the Nb content is 1.4 g / kg or more, the charge characteristics are likely to be good, and if the Nb content is 40.0 g / kg or less, the Nb2 O 5 Since no single phase of 5 appears, the charge distribution tends to be uniform and it becomes easier to obtain stable charging performance. The lower limit is more preferably 3.0 g / kg or more, and the upper limit is more preferably 37.0 g / kg or less, still more preferably 35.0 g / kg or less.

[0018] The particles constituting the powder of the present invention have a titanium compound as a core material at the center. Examples of the titanium compound that can be used as the core material generally include titanium oxyhydroxide and titanium dioxide represented by the chemical formula TiO 2-n / 2 (OH) n (where n is greater than 0 and less than 4), and titanium dioxide is preferred. As the titanium dioxide, for example, rutile-type titanium dioxide, anatase-type titanium dioxide, and titanium dioxide which is a mixed crystal of anatase type and rutile type can be used. Particularly preferred is anatase-type titanium dioxide. When a titanium compound surface-treated with Al 2 O 3 or SiO 2 is used as the core material, it becomes difficult to provide the second layer. Therefore, it is preferable to use a non-surface-treated titanium compound as the core material. The median diameter of the core material is not particularly limited, but the lower limit is preferably 0.04 μm or more, more preferably 0.05 μm or more. The upper limit is preferably 0.48 μm or less, more preferably 0.40 μm or less, still more preferably 0.35 μm or less.

[0019] The powder of the present invention preferably has a large negative charge amount. For example, the charge amount E S generated by friction with the iron powder carrier evaluated by the method described in the examples is preferably -45 μC / g or a negative value with an absolute value larger than this. More preferably, the absolute value is -50 μC / g or a negative value with an absolute value larger than this, still more preferably the absolute value is -60 μC / g or a negative value with an absolute value larger than this. Also, the charge amount E SThe minimum value (the negative value with the largest absolute value) is not limited, but is about -120 μC / g, more preferably about -100 μC / g. In the case of powders composed of conventional titanium compounds and titanium niobium complex oxides, the charge amount E S obtained by this evaluation method was about -45 μC / g to -30 μC / g. In contrast, the powder of the present invention tends to exhibit a large negative charge amount.

[0020] Also, it is preferable that the negative charge amount of the powder of the present invention increases significantly after the treatment (surface treatment) for forming the outermost silicon compound layer compared to before the surface treatment. Specifically, when the charge amount of the powder before the surface treatment is E 0 (μC / g), then E s -E 0 is a negative value with an absolute value greater than or equal to -20 μC / g, and it is preferable that E s / E 0 is 1.30 or more. By forming a silicon compound layer on the surface of particles having a titanium niobium oxide layer on a titanium compound, a larger negative charge can be realized compared to the case of forming a silicon compound layer on the surface of titanium compound particles not having a titanium niobium oxide layer. E s / E 0 is more preferably 1.45 or more, and still more preferably 1.60 or more.

[0021] The powder of the present invention preferably has a relatively large resistance. The powder specific resistance is preferably 5×10 6 Ω·cm or more and 5×10 11 Ω·cm or less. If the powder specific resistance is 5×10 6 Ω·cm or more, it can be used in a wide range of industrial fields that utilize static electricity, and if it is 5×10 11 Ω·cm or less, it becomes easy to inject charges into the particles. The lower limit is more preferably 1×10 7 Ω·cm or more, still more preferably 2×10 8 Ω·cm or more, even more preferably 1×10 9 Ω·cm or more, and the upper limit is more preferably 1×10 11 Ω·cm or less. Also, for the same reason, the surface resistance is preferably 1×10 11 Ω / sq or more. The upper limit is not particularly limited, but as a rough guide, it is 1×10 12 Ω / sq. The lower limit is preferably 2×10 11 Ω / sq or more. There has never been a material that can adjust negative charging and has a high resistance.

[0022] The powder of the present invention has a specific surface area S determined by the BET method 1 of 3 m 2 / g or more and 40 m 2 / g or less, which is preferable. When the specific surface area S 1 is 3 m 2 / g or more, it becomes easier to effectively adjust the charging, and when it is 40 m 2 / g or less, aggregation hardly occurs when dispersing in the object. The upper limit is preferably 30 m 2 / g or less, and the lower limit is more preferably 5 m 2 / g or more.

[0023] The powder of the present invention preferably has a specific surface area S determined by the BET method 1 that is not too large compared to the theoretical specific surface area calculated from the above-described median diameter. Although the detailed principle is unknown, particles with excessive irregularities tend to have difficulty increasing the negative charge amount. When the specific surface area calculated from the median diameter is S 2 , when S 1 / S 2 is 1.20 or less, it is preferable. More preferably, it is 1.09 or less, and even more preferably, it is 1.04 or less. The lower limit of S 1 / S 2 is not particularly limited, but as a rough guide, it is 0.50 or more.

[0024] The powder of the present invention preferably has a high degree of hydrophobicity. Specifically, when evaluated by the method described in the examples, it preferably exhibits a degree of hydrophobicity of "450 g / kg - 475 g / kg" or greater, that is, the powder does not settle even when the methanol concentration in the methanol aqueous solution is 450 g / kg or more. If the degree of hydrophobicity is "450 g / kg - 475 g / kg" or greater, moisture adsorption is less likely to occur, and it becomes easier to maintain the charging characteristics over a long period. The lower limit is more preferably "475 g / kg - 500 g / kg" or greater, even more preferably "500 g / kg - 525 g / kg" or greater. The upper limit is not particularly limited, but as a guideline, it is "800 g / kg - 825 g / kg".

[0025] The powder of the present invention can be produced, for example, but not limited thereto, by a production method including a step of wet-coating titanium compound particles with titanium niobium hydroxide, a step of firing after the coating treatment to form a titanium niobium oxide layer on the surface of the titanium compound particles, and a step of surface-treating with a silicon compound after forming the titanium niobium oxide layer. More specifically, for example, but not limited thereto, it can be prepared by a production method comprising the following steps A to G. A: A step of dispersing the powder of the titanium compound serving as the core material in water to obtain a suspension of the core material. B: A step of dissolving a titanium source and a niobium source in an acid to obtain an acidic mixture. C: A step of adding the acidic mixture obtained in step B and an alkaline solution to the suspension obtained in step A, neutralizing the acidic mixture of the titanium source and the niobium source with the alkaline solution, and precipitating titanium and niobium hydroxides on at least a part of the surface of the core material. D: A step of removing water-soluble salts and performing solid-liquid separation from the suspension obtained in step C. E: A step of firing the solid content obtained in step D. F: A step of pulverizing the fired body obtained in step E. G: A step of surface-treating the powder obtained in step F with a silicon compound. H: A step of pulverizing the powder obtained in step G. Hereinafter, an example of the production method of the powder of the present invention will be described.

[0026] As the titanium compound serving as the core material, as described above, generally, the chemical formula is TiO 2-n / 2 (OH) n (where n is greater than 0 and less than 4), titanium oxyhydroxide, rutile-type titanium dioxide, anatase-type titanium dioxide, and titanium dioxide which is a mixed crystal of anatase-type and rutile-type can be used. Particularly preferably, anatase-type titanium dioxide is used. Al 2 O 3 or SiO 2 When titanium dioxide surface-treated with is used as the core material, it becomes difficult to form the subsequent second layer of titanium niobium oxide. Therefore, it is preferable to use non-surface-treated titanium dioxide as the core material.

[0027] As the titanium source used for forming the second layer of titanium niobium oxide, titanium salts such as titanium sulfate and titanium chloride can be preferably used. As the niobium source, niobium salts such as niobium pentachloride, niobium hydroxide, niobium pentoxide, and niobium oxyhydroxide can be preferably used. Salts that dissolve in acid are preferable for both the titanium source and the niobium source. The titanium source and the niobium source may be in solid form or an aqueous solution dissolved in acid may be used. When an aqueous solution is used, part of the dissolution operation described later may be omitted. In terms of handling and price, it is preferable to use an aqueous solution of titanium sulfate as the titanium source.

[0028] [Step A: Suspension of Core Material] The core material is dispersed in water to obtain a suspension of the core material. The core material is preferably dispersed so as to have a concentration of 30 g / L or more and 200 g / L or less with respect to water. The suspension is stirred and held to prevent sedimentation.

[0029] [Step B: Acidic Mixed Solution of Titanium Source and Niobium Source] The titanium source and the niobium source are made into an acidic aqueous solution and mixed. For dissolving the titanium source and the niobium source, it is preferable to use hydrochloric acid or sulfuric acid, but an aqueous solution of nitric acid or other acids may also be used. For example, niobium chloride is dissolved in hydrochloric acid to obtain a solution with a concentration of 30 g / kg in terms of elemental niobium Nb, and then mixed with an aqueous titanium sulfate solution to prepare an acidic mixed solution of the titanium source and the niobium source. Also, for example, niobium hydroxide and niobium pentoxide can be dissolved in concentrated sulfuric acid and mixed with an aqueous titanium sulfate solution to prepare an acidic mixed solution of the titanium source and the niobium source.

[0030] [Step C: Neutralization] In Step C, while stirring the suspension of the core material, it is maintained at 55°C or higher and 85°C or lower, and an acidic mixed solution of the titanium source and the niobium source and an alkaline solution are added, and the acidic mixed solution of the titanium source and the niobium source is neutralized with the alkaline solution to precipitate hydroxides of titanium and niobium on at least a part of the surface of the core material. The lower limit of the holding temperature is preferably 60°C or higher, and the upper limit is preferably 80°C or lower. When the suspension obtained in Step C is subjected to solid-liquid separation and the dried sample is observed with a transmission electron microscope, it is preferable that 90% or more of the core material surface is covered with hydroxides of titanium and niobium. The pH of the suspension when the acidic mixed solution and the alkaline solution are added is preferably in the range of 1.0 or higher and 6.0 or lower. The lower limit is more preferably 2.0 or higher, and the upper limit is more preferably 4.0 or lower. If the pH of the suspension is 1.0 or higher, most of the core material surface is covered, and if the pH is 6.0 or lower, formation of particles of only the titanium-niobium mixture can be prevented, so the characteristics of the obtained powder are stable and the particle size distribution becomes smaller. Further, by setting the pH to 6.0 or lower, the sodium content of the obtained powder can be suppressed, and the powder specific resistance and surface resistance can be maintained within an appropriate range. The pH is preferably maintained at a constant value within the above range. In order to maintain the pH at a constant value, it is preferable to add the acidic mixed solution of the titanium source and the niobium source and the alkaline solution simultaneously. The alkaline solution added for neutralization is not particularly limited, but one or more selected from sodium hydroxide, potassium hydroxide, sodium carbonate, and aqueous ammonia can be preferably used. Further, ammonia gas may be blown in. Sodium hydroxide is advantageous in terms of cost. It is preferable to keep the temperature constant during neutralization. After adding the acidic mixture and the alkaline solution, optionally, the suspension may be aged by holding it at a predetermined pH and a predetermined temperature for a certain period of time. The temperature and pH at this time are not particularly limited. As an example, the pH is 4.0 or more and 6.5 or less, and the temperature is 50°C or more and 85°C or less. The holding time is not particularly limited, but about 10 minutes to 2 hours is preferable.

[0031] [Step D: Removal of water-soluble salts and solid-liquid separation] In Step D, it is preferable to perform repeated washing using an aqueous solvent with a low impurity content typified by pure water to remove water-soluble salts so that the remaining amount of water-soluble salts in the suspension obtained in Step C is minimized. For the washing during the removal of water-soluble salts, methods using a filter press, a decantation method, etc. can be arbitrarily used. After removing the water-soluble salts, solid-liquid separation is performed to obtain a solid content. The obtained solid content may be optionally dried. The temperature and time during drying are not particularly limited, but for example, it is 90°C or more and 150°C or less for 1 hour or more and 24 hours or less.

[0032] [Step E: Firing] The firing temperature is preferably 250°C or higher and 900°C or lower. The firing atmosphere is not particularly limited, and firing can be carried out in an atmosphere with an oxygen concentration higher than that of the atmosphere, an air atmosphere, an atmosphere with an oxygen concentration reduced from that of the atmosphere, a non-oxidizing atmosphere of nitrogen gas, or a reducing atmosphere of hydrogen gas. By firing in an atmosphere where oxygen is present, the particle surface can be oxidized, or by firing in a non-oxidizing atmosphere or a reducing atmosphere, the particle surface can be reduced. The atmosphere can be changed to perform two-stage firing or firing in three or more stages, and the atmosphere and temperature of the second stage or subsequent stages of firing can be appropriately changed according to the degree of progress of surface oxidation of the particles. By adjusting the progress of surface oxidation or reduction, characteristics such as the resistance, charging performance, and color tone of the fired powder can be adjusted. In particular, the powder resistance tends to increase as surface oxidation progresses and decrease as reduction progresses. Therefore, by changing the atmosphere for firing, a powder resistance suitable for the application can be achieved. The firing time, holding time, and flow rate of the atmosphere gas can be appropriately adjusted according to the desired characteristics of the powder, as well as the size of the furnace used and the input amount of the solid content. For example, but not limited to this, it is preferable to perform the first-stage firing at a temperature of 250°C or higher and 780°C or lower in a non-oxidizing atmosphere or a reducing atmosphere, and then perform the second-stage firing at a temperature of 250°C or higher and 500°C or lower in an air atmosphere.

[0033] [Process F: Primary grinding] The obtained fired body may be appropriately ground. As the grinding method, known methods such as a roller mill, a jet mill, and a container-driven mill can be used without limitation, and it can be ground with a general-purpose grinder. The grinding method is determined in consideration of the particle size, the ratio of coarse particles in the ground product, the cost, and the like.

[0034] [Process G: Surface treatment] Next, in order to adjust the charging characteristics, surface treatment is performed using a silicon compound. The surface treatment can be carried out by either a dry method in which a surface treatment agent, which is a silicon compound, or its hydrolyzate is dropped onto the powder, or a wet method in which the powder is dispersed in a solvent to form a suspension and the surface treatment agent is added to the suspension. Either method is possible. As the surface treatment agent, silicon compounds such as silicone oil and silane coupling agents can be used, and by this, the negative charge amount of the powder can be increased. In particular, a silane coupling agent is preferable because it strongly binds to the surface of the second layer of titanium niobium oxide. A silane coupling agent usually has a structure in which a hydrolyzable group (-OR) and an organic functional group are bonded to a silicon atom. As the silane coupling agent, those having 1 or more and 10 or less carbon atoms in the organic functional group directly bonded to the silicon atom are preferable. The lower limit is more preferably 3 or more carbon atoms, and the upper limit is more preferably 8 or less carbon atoms. The carbon number of the hydrolyzable group is not particularly limited. The organic functional group is preferably an alkyl group having 3 or more and 8 or less carbon atoms. Typically, n-propyltrimethoxysilane, n-octyltriethoxysilane, and i-butyltrimethoxysilane can be mentioned. Depending on the application, i-butyltrimethoxysilane is preferable because a powder with a high degree of hydrophobicity can be obtained even with a small addition amount. Also, n-octyltriethoxysilane is useful particularly when a powder with a larger powder specific resistance is preferably obtained because a powder with a larger powder specific resistance can be obtained. Also, when performing surface treatment using a silane coupling agent, in either the dry method or the wet method, it is preferable to bring water into contact with the silane coupling agent to promote the hydrolysis of the silane coupling agent because the bond becomes stronger. Two or more types of surface treatment agents may be used in combination.

[0035] The surface treatment by the dry method can be carried out in a simple process, and since there is no need for filtration or moisture removal, it is excellent in terms of cost and environmental load. Specifically, it can be carried out by putting the powder obtained in step F into a powder mixer such as a Henschel mixer or a coffee mill, and dropping the surface treatment agent or its hydrolyzate from the upper part of the mixer. After dropping, continue to stir the powder to spread the surface treatment agent uniformly throughout. It is preferable to take out the powder and transfer it to, for example, a stainless steel or hollow vat, cover it, and put it into an oven heated to 90 °C for 1 h of heat treatment. Generally, when using a silane coupling agent, it is preferable to add one in which hydrolysis has proceeded in advance.

[0036] The surface treatment by the wet method is preferable in that a more uniform treatment can be realized throughout the powder. As an example, the powder obtained in step F is redispersed with pure water to form a suspension with a concentration of 50 g / L or more and 800 g / L or less, the liquid temperature is adjusted to 30 °C or more and 90 °C or less, more preferably 40 °C or more and 80 °C or less, and further the pH of the suspension is adjusted to 1.0 or more and 5.0 or less. While stirring the suspension, drop the surface treatment agent or its hydrolyzate into the suspension and continue stirring for 24 h. Then, for example, solid-liquid separation is carried out with a Buchner funnel, the cake is put into a vat, and it is preferably dried at 90 °C or more and 170 °C or less with a hot air circulation dryer or an oven. If the drying temperature is lower than this, there is a risk that the adhesion between the powder and the surface treatment agent will be insufficient, and if it is higher, there is a risk that the surface treatment agent will decompose. The lower limit of the concentration of the powder in the suspension is more preferably 50 g / kg or more, and the upper limit is more preferably 500 g / kg or less. Also, the upper limit of the pH is preferably 3.0 or less.

[0037] It is also possible to use a medium other than water, and alcohol or an oil-based medium may be used. Generally, when using a silane coupling agent, when using an aqueous medium, hydrolysis of the silane coupling agent tends to proceed, so uniform treatment is possible and a powder with a larger degree of hydrophobicity can be obtained, which is preferable. The surface treatment method can be selected according to the application, cost, and equipment. Generally, the dry method is suitable when a certain degree of non-uniformity in the characteristics between powder particles is acceptable, and the wet method is suitable when more precise control of the surface state is desired.

[0038] [Step H: Secondary grinding] The powder obtained in Step G can be ground with a known grinder. For example, when obtaining a powder suitable for the applications described later, although not limited thereto, a jet mill, a vibration mill, or a hammer mill is suitable.

[0039] [Applications] The powder of the present invention can be used as a charge control powder. The charge control powder refers to those having the function of continuously maintaining the charge amount of an object at a certain amount for a certain time or more in scenes where static electricity is actively utilized in the industry, excluding those in which the function is achieved by replacing with a conductor typified by iron powder. Therefore, it does not include those that simply adjust the resistance value or function as a path for charges. The "certain amount" of the charge to be maintained is not particularly limited, but as a guideline, it refers to -500 μC / g to 500 μC / g, more preferably -200 μC / g to 200 μC / g, and even more preferably -50 μC / g to -120 μC / g. The "certain time" for maintaining the charge is also not particularly limited, and it may be any time that holds the charge longer than the moment when electricity passes through. As a guideline, it is 1 second or more. Specific applications include the drive and control of electronic devices typified by electrostatic induction motors, electrostatic coating, and electrostatic dust collection. It can also be widely used in fields such as agriculture and medicine, such as pollen spraying and medical devices that pass a weak current through the human body. The methods of utilizing static electricity in the industry can be roughly classified into three categories: methods that utilize the charge itself, methods that use static electricity to disperse and scatter powders and others, and methods that adsorb powders and others. Although not particularly limited, it is desirable to use the powder of the present invention as a charge control powder used in the first two methods. The object is not particularly limited, and as described above, it can be used for paints, functional powders, films, fibers, resins, plastics, paper, and various other materials. Since the powder resistance can be adjusted in the firing process, a resistance corresponding to the application can be realized. In particular, since the charge control powder of the present invention has a large negative charge amount, an equivalent charge amount can be achieved with a smaller amount than before in applications that require a negative charge. It is also possible to generate a large amount of static electricity by contacting a material with a large positive charge amount.

[0040] The powder of the present invention can also be used for applications other than the powder for charge control. For example, it can also be used as an antistatic agent by combining it with a material that is also likely to be negatively charged. Further, it can also be used for applications that impart conductivity to an object. The powder of the present invention has a hydrophobic surface and, since it is an inorganic substance, it also has excellent properties such as weather resistance and water resistance, and can be used in various situations.

Examples

[0041] The present invention will be described in more detail with the following examples and comparative examples. The examples listed below are merely for illustration and do not limit the scope of the invention. In the stirring operations described in the examples and comparative examples, the rotation speed is appropriately adjusted in consideration of the properties related to the behavior of the liquid during stirring, such as the liquid volume, the viscosity of the liquid, and the shape of the container, so that the entire liquid is uniformly mixed and splashing does not occur around. Also, when the same effect can be obtained using products from any company as long as they are general commercially available products such as hydrochloric acid and aqueous sodium hydroxide solution, the company names of the manufacturers and sellers are omitted.

[0042] The method for evaluating the physical properties in the present invention will be described. [Median diameter] It was measured using a transmission electron microscope JEM-1400plus manufactured by JEOL Ltd. The observation magnification was set to 30,000 times, and when the particles were too small to be observed, it was set to 50,000 times and magnified 2 times at the time of printing. The diameters were measured for 200 particles, and the median diameter based on the number was calculated. In this specification, the "median diameter based on the number" may also be simply referred to as the "particle diameter".

[0043] [C content] The C content of the sample was measured using a carbon-sulfur simultaneous measurement device CS230 manufactured by LECO Corporation.

[0044] [Si content · Nb content] After firing the sample at 500 °C for 30 min, using a Rigaku multi-element simultaneous X-ray fluorescence analyzer Simultix (registered trademark) 15, in accordance with JIS K 0119:2008, the count values of each element were measured, and the Si content and Nb content were calculated by quantitative calculation using fundamental parameters.

[0045] [Powder charge amount] 0.050 g of the sample and 4.950 g of iron powder carrier were mixed, placed in a polyethylene bottle with a diameter of 40 mm and a height of 85 mm, shaken for 1 min with a Paint Shaker 5110 manufactured by Red Devil to cause friction, then 0.500 g of the mixture of iron powder carrier and sample was taken, placed in a Faraday cage, and the charge amount a (μC) was measured with a blow-off type powder charge amount measuring device TB-200 manufactured by Toshiba Chemical. The mass of the Faraday cage before and after blowing was measured, and the mass b (g) of the charged sample was calculated. Also, the powder charge amount C (μC / g) was calculated from the following formula. C = -a / b

[0046] [Specific surface area S by BET method 1 Using a Gemini (registered trademark) VII 2390 manufactured by MICROMERITICS INSTRUMENT CO., the specific surface area was measured by the BET single-point method. Let the obtained specific surface area be S 1 .

[0047] [Specific surface area S calculated from the median diameter 2 Assuming the median diameter is r μm, the specific surface area S 2 is calculated by the following formula. S 2 = 4×π×[((r / 2) / 10 6 )] 2 / {4 / 3×π×[((r / 2) / 10 6 )] 3 × particle density (g / m 3 )} In the examples and comparative examples described later, anatase-type titanium dioxide (particle density 3.90×10 6 g / m 3 ) and niobium pentoxide (particle density 4.47×10​​6 g / m 3 Since the particles are composed of [the above], the following values were used as the particle density in the above formula, respectively. Examples excluding Example 8 and Comparative Examples 1 and 2: 3.92×10 6 g / m 3 Example 8: 3.93×10 6 g / m 3 Comparative Examples 3 and 4: 3.90×10 6 g / m 3

[0048] [Degree of hydrophobicity] The sample passed through a sieve with a mesh size of 1 mm was used for measurement, and the measurement was carried out within 5 minutes after passing through the sieve. Methanol aqueous solutions with methanol concentrations ranging from 25 g / kg to 975 g / kg and methanol contents differing by 25 g / kg were prepared and 5 ml of each was placed in a 25-ml test tube. The measurement sample was gently dropped into the test tubes in order of increasing methanol concentration. If continuous sedimentation of the powder was observed from 5 seconds to 1 minute after dropping, it was regarded as sedimentation. As a result, for example, if there was no sedimentation at a methanol concentration of 600 g / kg and sedimentation occurred at a methanol concentration of 625 g / kg, it was recorded as "600 g / kg - 625 g / kg" or "600 - 625". If sedimentation occurred at a methanol concentration of 0 g / kg, it was recorded as "0". The higher the methanol concentration at which sedimentation is first observed, the greater the degree of hydrophobicity.

[0049] [Apparent resistivity of powder] Hirester (registered trademark) - UXMCP-HT800 manufactured by Nitto Seiko Analytic Co., Ltd. was used. With an iron electrode inserted into the lower part of a hollow tube coated with a fluororesin, 1.0 g of the sample was placed inside the tube. An iron electrode was also inserted into the upper part of a vinyl chloride hollow tube, and after sandwiching the upper and lower electrodes with an insulating plate, a pressure of 7.0 kg / cm 2 was applied with a press, and the resistance value r (Ω) at 1 minute after application of the pressure was measured. For the iron electrodes and the sample in the state immediately after pressing, the total height I (cm) was measured. When the total height of the two iron electrodes was L (cm), the apparent resistivity of the powder R (Ω·cm) was calculated by the following formula. R = {r × π × (2.54 / 2) 2} / (I - L)

[0050] [Surface resistance] 7.0 g of the sample was dissolved in 6.0 g of an acrylic resin (ACRYDIC (registered trademark) A - 168 manufactured by DIC Corporation), and further dissolved in 8.8 g of reagent - grade toluene manufactured by Sigma - Aldrich and 8.8 g of SAJ - grade xylene manufactured by Sigma - Aldrich. 120 g of YTZ (registered trademark) balls Φ0.3 mm manufactured by Nikkato Corporation were added, and the paste mixed at 4000 rpm for 2 h using a Dispermat was applied onto a PET film with a thickness of 6 mils (0.1524 mm) using a film applicator to form a coating film. After the coating film was allowed to stand at room temperature until the surface was completely dry, the surface resistance of the coating film was evaluated using a Hirester (registered trademark) - UXMCP - HT800 manufactured by Nitto Seiko Analytic Co., Ltd.

[0051] [Thickness of the titanium niobium oxide layer (second layer)] The thickness of the titanium niobium oxide layer was determined by the following calculation. Let the amount of the titanium source (in terms of TiO 2 conversion) from the titanium niobium mixed solution per 1.0 g of the core material be a (g), and the amount of the niobium source (in terms of Nb conversion) be b (g), and the BET specific surface area of the core material be S 1 (m 2 / g). Then, the layer thickness d (nm) is calculated by the following formula. In the examples and comparative examples of this case, the difference between the amount of niobium calculated from the addition amount and the Nb content described later was small, and no turbidity was observed when the titanium source leaked into the liquid during the formation of the second layer. From this, it can be considered that all of the added titanium source and niobium source became the titanium niobium oxide layer. d = [a / titanium oxide density (g / m 3 ) + {b × (132.91 / 92.91)} / niobium oxide density (g / m 3 )] × 10 9 / S 1 In the examples described later, the titanium oxide density is the density of anatase - type titanium dioxide TiO 2 which is 3.90 × 10 6 g / m 3using the density of niobium oxide, which is the density of niobium pentoxide Nb 2 O 5 which is 4.47×10 6 g / m 3 .

[0052] [Example 1] Niobium(IV) hydroxide was dissolved in concentrated sulfuric acid and mixed with an aqueous titanium sulfate solution to prepare an acidic mixed solution of a titanium source and a niobium source (hereinafter referred to as "titanium-niobium mixed solution"). Anatase titanium dioxide powder with a median primary particle diameter of 0.06 μm (specific surface area 26 m 2 / g) was dispersed in water at a concentration of 52 g / L to form a suspension, and the temperature was raised while stirring. After reaching 70 °C, while maintaining the pH at 2.5, a titanium-niobium mixed solution containing 1189 g / kg as TiO 2 and 36.9 g / kg as Nb and an aqueous sodium hydroxide solution were simultaneously added with respect to the mass of titanium dioxide serving as the core material. After the addition was completed, an aqueous sodium hydroxide solution was added to adjust the pH of the reaction solution to 5.5, and the mixture was aged by holding at 70 °C for 0.5 h. Next, it was diluted 6-fold with pure water and washed by decantation until the amount of sulfate ions was 2 g / kg or less, and then solid-liquid separation was performed using a Buchner funnel. The washed solid content was dried in a dryer at 110 °C for 12 h. The dried solid content was calcined in nitrogen gas at 725 °C for 2 h and pulverized with a TASM-1 type sample mill manufactured by Tokyo Atomizer Co., Ltd. The obtained powder was designated as Precursor 1.

[0053] Precursor 1 was redispersed in pure water to a concentration of 300 g / L, the liquid temperature was adjusted to 60 °C, the pH was adjusted to 2.5 with hydrochloric acid at a concentration of 175 g / kg, and then n-propyltrimethoxysilane was added as a surface treatment agent to Precursor 1 at 35 g / kg, and the mixture was stirred for 24 h. After solid-liquid separation using a Buchner funnel, it was dried at 110 °C for 15 h using a dryer. The dried product was pulverized with a TASM-1 type sample mill manufactured by Tokyo Atomizer Co., Ltd. to obtain a powder. The manufacturing conditions of the powder are shown in Table 1. In addition, the evaluation results of various physical properties of the powder are shown in Table 2.

[0054] [Example 2] A powder was obtained in the same procedure as in Example 1, except that the addition amount of the surface treatment agent was 38 g / kg based on Precursor 1. The evaluation results are shown in Table 2.

[0055] [Example 3] 1.8 g of n-propyltrimethoxysilane, 0.9 g of a solution obtained by adding acetic acid to pure water to adjust the pH to 3.3, and 0.5 g of methanol were mixed and stirred for 1 h. After stirring, it was confirmed that the solution became transparent, and n-propyltrimethoxysilane hydrolysis solution 1 was obtained. 40 g of Precursor 1 was put into a sample mill SK-M10 manufactured by Kyoritsu Riko Co., Ltd., and the entire amount of n-propyltrimethoxysilane hydrolysis solution 1 was added to Precursor 1 and stirred for 3 min. The addition amount of n-propyltrimethoxysilane based on Precursor 1 is 45 g / kg. The obtained powder was put into a stainless steel vat, covered, and heat-treated at 90 °C for 1 h. The heat-treated product was pulverized with a TASM-1 type sample mill manufactured by Tokyo Atomizer Manufacturing Co., Ltd. to obtain a powder. The evaluation results are shown in Table 2.

[0056] [Example 4] Precursor 1 was rediluted with pure water to a concentration of 500 g / L, the liquid temperature was adjusted to 80 °C, the pH was adjusted to 2.5 with hydrochloric acid at a concentration of 175 g / kg, and then 50 g / kg of n-propyltrimethoxysilane was added as a surface treatment agent based on Precursor 1 and stirred for 24 h. The operations after solid-liquid separation were carried out in the same manner as in Example 1 to obtain a powder. The evaluation results are shown in Table 2.

[0057] [Example 5] The type of the surface treatment agent was i-butyltrimethoxysilane. 1.6 g of i-butyltrimethoxysilane, 0.8 g of a solution obtained by adding acetic acid to pure water to adjust the pH to 3.3, and 0.4 g of methanol were mixed and stirred for 1 h. After stirring, it was confirmed that the solution became transparent, and i-butyltrimethoxysilane hydrolysis solution 1 was obtained. A powder was obtained in the same procedure as in Example 3, except that i-butyltrimethoxysilane hydrolysis solution 1 was used. The addition amount of i-butyltrimethoxysilane based on Precursor 1 is 40 g / kg. The evaluation results are shown in Table 2.

[0058] [Example 6] The type of the surface treatment agent was n-octyltriethoxysilane. 3.2 g of n-octyltriethoxysilane, 1.6 g of a solution obtained by adding acetic acid to pure water to adjust the pH to 3.3, and 0.8 g of methanol were mixed and stirred for 1 h. After the stirring, it was confirmed that the solution became transparent, and n-octyltriethoxysilane hydrolysis solution 1 was obtained. A powder was obtained in the same procedure as in Example 3 except that n-octyltriethoxysilane hydrolysis solution 1 was used. The addition amount of n-octyltriethoxysilane to the precursor 1 was 80 g / kg. The evaluation results are shown in Table 2.

[0059] [Example 7] The type of the surface treatment agent was n-octyltriethoxysilane. 3.5 g of n-octyltriethoxysilane, 1.8 g of a solution obtained by adding acetic acid to pure water to adjust the pH to 3.3, and 0.9 g of methanol were mixed and stirred for 1 h. After the stirring, it was confirmed that the solution became transparent, and n-octyltriethoxysilane hydrolysis solution 2 was obtained. A powder was obtained in the same procedure as in Example 6 except that n-octyltriethoxysilane hydrolysis solution 2 was used. The addition amount of n-octyltriethoxysilane to the precursor 1 was 88 g / kg. The evaluation results are shown in Table 2.

[0060] [Example 8] A precursor before surface treatment (precursor 2) was obtained in the same method as the precursor 1 except that the amount of the niobium source added to the suspension at 70 °C and pH 2.5 was 72.5 g / kg as Nb based on the mass of titanium dioxide as the core material. A powder was obtained in the same method as in Example 1 except that precursor 2 was used. The evaluation results are shown in Table 2.

[0061] [Example 9] An untreated product of anatase-type titanium dioxide powder with a median diameter of primary particles of 0.17 μm (specific surface area 9 m 2 / g) was dispersed in water at a concentration of 130 g / L to form a suspension, and the temperature was raised while stirring. After reaching 70 °C, while maintaining the pH at 2.5, TiO based on the mass of titanium dioxide as the core material2 A titanium-niobium mixed solution containing 337 g / kg of Ti and 20.6 g / kg of Nb and an aqueous sodium hydroxide solution were added simultaneously. After the addition was completed, an aqueous sodium hydroxide solution was added to adjust the pH of the reaction solution to 5.5, and it was aged by holding at 70 °C for 0.5 h. Then, it was washed by decantation until the amount of adsorbed sulfate ions became 2 g / kg or less, and solid-liquid separation was performed using a Buchner funnel. The solid content after washing was dried in a dryer at 110 °C for 12 h. The dried solid content was calcined in nitrogen gas at 750 °C for 2 h, and further calcined in air at 450 °C for 2 h. Then, it was pulverized using a TASM-1 type sample mill manufactured by Tokyo Atomizer Co., Ltd. to obtain a powder. This was used as precursor 3. A powder was obtained in the same manner as in Example 4 except that precursor 3 was used and the addition amount of n-propyltrimethoxysilane was 15 g / kg based on the precursor. The evaluation results are shown in Table 2.

[0062] [Example 10] A powder was obtained in the same manner as in Example 9 except that the temperature of the liquid obtained by recycling the precursor was set to 60 °C and the addition amount of n-propyltrimethoxysilane was 25 g / kg based on precursor 3. The evaluation results are shown in Table 2.

[0063] [Example 11] 1.8 g of n-propyltrimethoxysilane, 4.9 g of ethanol, and 0.5 g of pure water were mixed and stirred for 1 h to obtain an n-propyltrimethoxysilane hydrolysis solution 2. A powder was obtained in the same procedure as in Example 3 except that the n-propyltrimethoxysilane hydrolysis solution 2 was used. The addition amount of n-propyltrimethoxysilane based on precursor 1 is 45 g / kg.

[0064] [Comparative Example 1] Precursor 1 was used as Comparative Example 1. The evaluation results are shown in Table 2.

[0065] [Comparative Example 2] Precursor 3 was used as Comparative Example 2. The evaluation results are shown in Table 2.

[0066] [Comparative Example 3] Anatase titanium dioxide powder with a median diameter of primary particles of 0.17 μm was used as Comparative Example 3. The evaluation results are shown in Table 2.

[0067] [Comparative Example 4] 0.7 g of i-butyltrimethoxysilane, 0.4 g of a solution obtained by adding acetic acid to pure water to adjust the pH to 3.3, and 0.2 g of methanol were stirred and held for 1 h. After stirring and holding, it was confirmed that the liquid became transparent, and i-butyltrimethoxysilane hydrolysis solution 2 was obtained. Powders of Comparative Example 3 were used instead of the precursor 1, and powders were obtained in the same manner as in Example 5 except that i-butyltrimethoxysilane hydrolysis solution 2 was used. The addition amount of i-butyltrimethoxysilane to the powder of Comparative Example 3 was 18 g / kg. The evaluation results are shown in Table 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] All the powders of the present invention have a negative charge amount, have a negative charge amount with an absolute value larger than -45 μC / g, and have a titanium niobium oxide layer but no silicon compound layer (Comparative Examples 1 and 2), or powders having only a silicon compound layer imparted to titanium dioxide (Comparative Example 4). The negative charge amount is larger. Also, through a series of operations of forming a titanium niobium oxide layer and further performing a silane coupling agent treatment, the increase in the negative charge amount is larger than the sum of the negative charge amounts increased by each of the individual operations of forming the titanium niobium oxide layer and the silane coupling agent treatment (Examples 9 and 10 compared with Comparative Examples 2, 3, and 4). Therefore, it can be seen that it is excellent in the ability to largely adjust the charge amount negatively when filled in charge adjustment objects such as paints, functional powders, films, fibers, resins, plastics, and papers. Also, the degree of hydrophobicity, the specific resistance of the powder, and the surface resistance are large, and it can be used for a wide range of applications.

Claims

1. A powder comprising particles composed of a silicon compound layer on the outermost surface, a titanium niobium oxide layer as the second layer, and a central titanium compound, wherein the median diameter based on the number of primary particles is 0.05 μm or more and 0.50 μm or less.

2. The powder according to claim 1, wherein the silicon compound layer contains at least C, O, and Si.

3. The powder according to claim 2, wherein the content of C is 1.0 g / kg or more and 30.0 g / kg or less, and the content of Si is 0.2 g / kg or more and 32.0 g / kg or less.

4. The powder according to any one of claims 1 to 3, wherein the content of Nb is 1.4 g / kg or more and 40.0 g / kg or less.

5. The powder according to any one of claims 1 to 3, wherein the silicon compound is derived from a silane coupling agent.

6. The powder according to any one of claims 1 to 3, wherein the amount of charge generated by friction with an iron powder carrier evaluated by the method described in the examples is -45 μC / g or a negative charge with an absolute value greater than this.

7. A step of wet-coating a titanium compound with titanium niobium hydroxide, a step of firing after the coating treatment to form a titanium niobium oxide layer on the surface of the titanium compound, and a step of surface-treating with a silicon compound after forming the titanium niobium oxide layer are included. A method for producing the powder according to any one of claims 1 to 3.

8. The powder according to any one of claims 1 to 3, which is used as a charge control powder.

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