Composite inorganic oxide powder, powder coating composition containing the composite inorganic oxide powder, electrophotographic toner composition containing the composite inorganic oxide powder, method for producing the composite inorganic oxide powder

Abstract

To provide a composite inorganic oxide powder that has negative chargeability sufficient to be used as a charge modifier, and demonstrates excellent environmental stability and electrification rising properties.SOLUTION: A composite inorganic oxide powder has gas phase-method composite inorganic oxide particles containing alumina and silica. The gas phase method composite inorganic oxide particles have an alumina content of 0.2 mass% or more and 20 mass% or less. The composite inorganic oxide powder has a volume resistivity of 1.0×1011 Ωcm or more and 9.0×1014 Ωcm or less in accordance with JIS K 6911.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composite inorganic oxide powder added as an external additive to electrophotographic toner, powder coating, etc. for the purpose of improving the fluidity of powder, adjusting the charge amount, etc., a method for producing the same, and a powder coating composition and an electrophotographic toner composition containing the composite inorganic oxide powder. In particular, the present invention relates to a composite inorganic oxide powder and a method for producing the same, which are excellent in the stability of the charge amount and the charge rising characteristics under high temperature and high humidity or low temperature and low humidity environments, and can achieve rapid printing and good image quality, and a powder coating composition and an electrophotographic toner composition containing the composite inorganic oxide powder.

Background Art

[0002] In the electrophotographic method used in laser printers, copiers, etc., generally, a charging process of charging a photoreceptor, an exposure process of forming an electrostatic latent image by irradiating a laser beam based on image data on the charged photoreceptor, a developing process of attaching a charged toner to the photoreceptor to form a mirror image of the image on the photoreceptor, a transfer process of transferring the toner on the photoreceptor to a medium such as paper, and a fixing process of fixing the toner on the medium by heating and pressure are performed to carry out printing.

[0003] In the above electrophotographic method, since an image is formed by electrostatic force, in the process of charging the toner by triboelectrification, it is necessary that the charge is of a desired strength, and the difference in the charge amount due to differences in conditions such as high temperature and high humidity, low temperature and low humidity is small, which is directly related to the image quality. Therefore, for the purpose of adjusting the charge amount of the toner, conventionally, metal and inorganic oxide powders such as silica, titania, and alumina have been added as external additives. In addition, with the recent miniaturization and high-speedization of printing devices, rapid charging is required for the toner. For electrophotographic toner, surface-treated products of inorganic oxides such as silica, titania, and alumina and organic fine particles are widely used for the purpose of improving fluidity and adjusting the charge amount.

[0004] Specifically, in order to obtain fluidity and stable chargeability, an external additive of hydrophobized small-particle silica is used. As a result, although the fluidity is improved, there is a problem that the charge amount is easily affected by severe environmental changes such as high temperature and high humidity, and low temperature and low humidity conditions.

[0005] Therefore, in order to reduce the influence of the charge amount accompanying severe environmental changes, it has been proposed to use small-particle silica hydrophobized with highly hydrophobic silicone oil as an external additive (Patent Document 1). However, the external additive of Patent Document 1 has a problem that the fluidity and charge rising of the toner deteriorate.

[0006] On the other hand, in order to reduce the influence of the charge amount accompanying severe environmental changes, it has also been proposed to use an external additive such as titania (Patent Documents 2 and 3). However, in Patent Documents 2 and 3, although the influence of the charge amount accompanying environmental changes can be reduced, problems such as complication of the formulation, member contamination by titania, and in recent years, safety problems such as concerns about the carcinogenicity of titania have occurred.

[0007] In recent years, development has been progressing towards high-speed printing and miniaturization of printing devices. For this purpose, it is required to stably maintain the triboelectric charge value of the toner more efficiently in a shorter time. In addition, since the difference between the charge value of the toner under high temperature and high humidity and the charge value of the toner under low temperature and low humidity is directly related to the image quality, reducing these differences has been continuously required together with the stability of the charge value.

[0008] As one method for improving these problems, a silica-alumina composite oxide has been proposed (Patent Document 4). In Patent Document 4, although an improvement in environmental stability due to a high ratio of alumina is observed, there is a need for improvement in terms of fluidity and charge rising characteristics.

[0009] Furthermore, a method for producing an external additive for toner by attaching alumina to the surface of silica has been proposed (Patent Document 5). However, the silica powder with alumina attached produced in Patent Document 5 has a problem that its charge amount is about -100 to -120 μC / g, which is too negatively charged to be used as a charge control agent. Furthermore, the production method of Patent Document 5 requires a two-step production process, and has problems such as a complicated production process.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0011] The inventors of the present invention have intensively studied the above problems, and newly found that when a composite inorganic oxide powder produced by a vapor phase decomposition method containing alumina in a predetermined range ratio shows a volume resistivity in a predetermined range, it satisfies environmental stability and charge rising characteristics, and thus arrived at the present invention. That is, an object of the present invention is to provide a composite inorganic oxide powder having a negative charge property to such an extent that it can be used as a charge control agent, and having good environmental stability and charge rising characteristics, a method for producing the composite inorganic oxide powder, a powder coating composition containing the composite inorganic oxide powder, and an electrophotographic toner composition containing the composite inorganic oxide powder.

Means for Solving the Problems

[0012] The gist of the constitution of the present invention is as follows. [1] A composite inorganic oxide powder having gas-phase composite inorganic oxide particles containing alumina and silica, wherein the alumina content of the gas-phase composite inorganic oxide particles is 0.2% by mass or more and 20% by mass or less, and the volume resistivity of the composite inorganic oxide powder conforming to JIS K 6911 is 1.0×10 11 Ω·cm or more and 9.0×10 14 Ω·cm or less. [2] The composite inorganic oxide powder according to [1], wherein the gas-phase composite inorganic oxide particles are surface-treated with an organosilicon compound. [3] The composite inorganic oxide powder according to [1] or [2], having a degree of hydrophobicity of 50% or more. [4] The composite inorganic oxide powder according to [2], having a carbon content of 0.5% by mass or more and 11.0% by mass or less. [5] The composite inorganic oxide powder according to [2] or [4], wherein the gas-phase composite inorganic oxide particles are surface-treated with 3.0 parts by mass or more and 40 parts by mass or less of the organosilicon compound with respect to 100 parts by mass of the gas-phase composite inorganic oxide particles. [6] The organosilicon compound is represented by the following general formula (1) R 5 n SiR 6 (4-n) (1) (In the formula, R 5 represents a hydrocarbon group having 1 to 18 carbon atoms, R 6 represents a hydrocarbon group having 1 to 18 carbon atoms, a chlorine atom, a hydroxy group or an alkoxy group having 1 to 3 carbon atoms, and n represents an integer of 1 to 3.) The composite inorganic oxide powder according to [2], [4] or [5], which is an organosilicon compound, hexamethyldisilazane and / or silicone oil. [7] The organosilicon compound is represented by the following general formula (2)

Chemical formula

[10] A powder coating composition containing the composite inorganic oxide powder according to any one of [1] to [9].

[11] An electrophotographic toner composition containing the composite inorganic oxide powder according to any one of [1] to [9].

[12] A gas-phase method composite inorganic oxide particle preparation step of introducing a silica raw material and an alumina raw material into a flame and obtaining gas-phase method composite inorganic oxide particles having an alumina content of 0.2% by mass or more and 20% by mass or less by gas-phase decomposition, An organosilicon compound supply step of applying an organosilicon compound to the surface of the gas-phase method composite inorganic oxide particles, A heating step of heating the gas-phase method composite inorganic oxide particles to which the organosilicon compound has been applied at a heating temperature of 100°C or more and 370°C or less for a heating time of 15 minutes or more and 350 minutes or less, A method for producing a composite inorganic oxide powder including the above steps.

Advantages of the Invention

[0013] The composite inorganic oxide powder of the present invention has a negative chargeability to such an extent that it can be used as a charge control agent, and has good environmental stability and charge rising characteristics.

[0014] The present invention relates to a composite inorganic oxide powder having gas-phase composite inorganic oxide particles containing alumina and silica, the gas-phase composite inorganic oxide particles having an alumina content of 0.2% by mass or more and 20% by mass or less, and preferably, the surface of the gas-phase composite inorganic oxide particles is modified with an organosilicon compound which is a hydrophobizing agent. Also preferably, the degree of hydrophobicity of the composite inorganic oxide powder is 50% or more. The gas-phase composite inorganic oxide particles having an alumina content of 0.2% by mass or more and 20% by mass or less contain an appropriate amount of alumina on the surface of the gas-phase composite inorganic oxide particles while maintaining good fluidity derived from silica, and thus, an alumina having a volume resistivity lower than that of silica can provide an effect of preventing excessive charging due to charge leakage. The gas-phase composite inorganic oxide particles having an alumina content of 0.2% by mass or more and 20% by mass or less suppress excessive charging caused by surface-treated silica, for example, and are adjusted to an appropriate charge amount.

[0015] In addition, the gas-phase composite inorganic oxide particles having an alumina content of 0.2% by mass or more and 20% by mass or less have a relatively small amount of alumina particles existing adjacent to silica particles, and charge transfer occurs between the alumina particles and the silica particles. As a result, it is considered that the composite inorganic oxide powder of the present invention exhibits good charge rising characteristics.

Best Mode for Carrying Out the Invention

[0016] First, the composite inorganic oxide powder of the present invention will be described in detail below. The composite inorganic oxide powder of the present invention is a composite inorganic oxide powder having gas-phase composite inorganic oxide particles containing alumina and silica, the alumina content of the gas-phase composite inorganic oxide particles being 0.2% by mass or more and 20% by mass or less, and the volume resistivity of the composite inorganic oxide powder conforming to JIS K 6911 being 1.0×10 11 Ω·cm or more and 9.0×10 14 Ω·cm or less. The gas-phase composite inorganic oxide particles are composite inorganic oxide powders produced by a gas-phase method.

[0017] The composite inorganic oxide powder having the above alumina content and volume resistivity has a negative chargeability to such an extent that it can be used as a charge control agent, and exhibits good environmental stability and charge rising characteristics. Specifically, the composite inorganic oxide powder of the present invention has an environmental variation ratio of 0.48 or more as environmental stability. When the environmental variation ratio of the composite inorganic oxide powder is less than 0.48, the difference in the charge amount between high temperature and high humidity and low temperature and low humidity becomes large, and when the composite inorganic oxide powder is added to the toner component, quality problems such as image defects are likely to occur. The charge rising characteristic of the composite inorganic oxide powder is 0.36 or more. When the charge rising characteristic of the composite inorganic oxide powder is less than 0.36, there is a problem that it takes a long time until printing becomes possible when the composite inorganic oxide powder is added to the toner component. The measurement methods of the "environmental variation ratio" and the "charge rising characteristic" will be described later.

[0018] The vapor-phase composite inorganic oxide particles having an alumina content of 0.2% by mass or more and 20% by mass or less are not particularly limited in their component composition as long as they contain silica and 0.2% by mass or more and 20% by mass or less of alumina in 100% by mass of the vapor-phase composite inorganic oxide particles, but vapor-phase composite inorganic oxide particles composed of silica and 0.2% by mass or more and 20% by mass or less of alumina are preferable. The vapor-phase composite inorganic oxide particles composed of silica and 0.2% by mass or more and 20% by mass or less of alumina contain 0.2% by mass or more and 20% by mass or less of alumina and 80% by mass or more and 99.8% by mass or less of silica in 100% by mass of the vapor-phase composite inorganic oxide particles.

[0019] The alumina content of the gas-phase composite inorganic oxide particles is not particularly limited as long as it is 0.2% by mass or more and 20% by mass or less. However, from the viewpoint of further improving the environmental stability of the charge amount and the charge rising characteristics, the lower limit value is preferably 0.3% by mass, more preferably 0.5% by mass, and particularly preferably 0.8% by mass. On the other hand, from the viewpoint of further improving the environmental stability of the charge amount and the charge rising characteristics, the upper limit value of the alumina content is preferably 18% by mass, more preferably 15% by mass, and particularly preferably 10% by mass. In the gas-phase composite inorganic oxide particles, when the alumina content is less than 0.2% by mass, the properties as a composite inorganic oxide are not exhibited and it shows behavior similar to silica. When it exceeds 20% by mass, the properties as a composite inorganic oxide are not exhibited and it is strongly affected by alumina. As a result, the negative chargeability becomes very weak.

[0020] The volume resistivity of the composite inorganic oxide powder of the present invention conforms to JIS K 6911 and is 1.0×10 11 Ω·cm or more and 9.0×10 14 Ω·cm or less. The volume resistivity of the composite inorganic oxide powder is not particularly limited as long as it is 1.0×10 11 Ω·cm or more and 9.0×10 14 Ω·cm or less. However, the lower limit value is preferably 5.0×10 11 Ω·cm and particularly preferably 1.0×10 12 Ω·cm from the viewpoint of reliably maintaining the charge amount. On the other hand, the upper limit value of the volume resistivity of the composite inorganic oxide powder is preferably 5.0×10 14 Ω·cm and particularly preferably 1.0×10 14 Ω·cm from the viewpoint of obtaining an appropriate negative chargeability as an external additive such as toner. When the volume resistivity is less than 1.0×10 11 Ω·cm, it becomes difficult to maintain an appropriate charge amount. When the volume resistivity exceeds 9.0×10 14 Ω·cm, there is a problem that the negative chargeability becomes too strong.

[0021] Note that the volume resistivity of the gas-phase silica particles becomes 1.0×10 15 Ω·cm or more, and an appropriate negative chargeability cannot be obtained. Also, the volume resistivity of the gas-phase alumina particles is 1.0×10 8It becomes less than Ω·cm, and the desired charge amount cannot be obtained. Even silica alone produced by the sol-gel method has a volume resistivity of 1.0×10 15 Ω·cm or more.

[0022] The BET specific surface area of the gas-phase composite inorganic oxide particles with an alumina content of 0.2 mass% or more and 20 mass% or less is not particularly limited. However, from the viewpoint of achieving a good balance between fluidity and suppression of burial in toner particles, it is preferably 10 to 500 m 2 / g, particularly preferably 20 to 400 m 2 / g. When the composite inorganic oxide powder of the present invention is added to toner, the absolute value of the charge amount becomes larger as the specific surface area is smaller and the coating rate on the toner is higher. Also, physical properties such as excellent environmental stability and charge rise characteristics are not greatly affected by the specific surface area. However, in an actual electrophotographic process, although a high specific surface area, that is, the smaller the particle diameter of the composite inorganic oxide powder, the easier it is to be buried in toner particles, the effect of improving fluidity is high. On the other hand, the larger the particle diameter of the composite inorganic oxide powder, the lower the fluidity of the toner, but the burial in toner particles tends to be suppressed. Therefore, gas-phase composite inorganic oxide particles with an appropriate specific surface area can be selected according to the physical properties required for the composite inorganic oxide powder. Also, regarding the charge amount of the composite inorganic oxide powder, when the same weight of the composite inorganic oxide powder is added to toner, the smaller particle diameter, that is, the gas-phase composite inorganic oxide particles with a larger specific surface area, show stronger negative chargeability. Therefore, an appropriate particle diameter and addition amount can be selected as appropriate according to the physical properties required for the composite inorganic oxide powder.

[0023] Also, the degree of hydrophobicity of the composite inorganic oxide powder of the present invention is not particularly limited. However, from the viewpoint of surely improving environmental stability, the degree of hydrophobicity is preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more. The degree of hydrophobicity means the degree of hydrophobicity measured with a spectrophotometer for the light transmittance of a mixture of the composite inorganic oxide powder and pure water, as described later.

[0024] In the composite inorganic oxide powder of the present invention, the vapor-phase method composite inorganic oxide particles may be surface-treated with an organosilicon compound. That is, the vapor-phase method composite inorganic oxide particles may be surface-modified with an organosilicon compound. In this case, the organosilicon compound functions as a surface modifier for the vapor-phase method composite inorganic oxide particles. When the surface of the vapor-phase method composite inorganic oxide particles is modified with an organosilicon compound, the surface of the vapor-phase method composite inorganic oxide particles is sufficiently hydrophobized, that is, sufficient hydrophobicity is imparted to the composite inorganic oxide powder. When the surface of the vapor-phase method composite inorganic oxide particles is sufficiently hydrophobized, the composite inorganic oxide powder has a high moisture adsorption inhibition effect and more reliably exhibits good environmental stability and charge rising characteristics.

[0025] As an aspect of the surface modification of the vapor-phase method composite inorganic oxide particles, for example, a part or the whole of the surface of the vapor-phase method composite inorganic oxide particles may be coated with a layer of an organosilicon compound. In this case, the vapor-phase method composite inorganic oxide particles are core particles and the organosilicon compound forms a shell, and the composite inorganic oxide powder has a core-shell structure.

[0026] Examples of the organosilicon compound that functions as a surface modifier include the following general formula (1) R 5 n SiR 6 (4-n) (1) (In the formula, R 5 represents a hydrocarbon group having 1 to 18 carbon atoms, R 6 represents a hydrocarbon group having 1 to 18 carbon atoms, a chlorine atom, a hydroxy group or an alkoxy group having 1 to 3 carbon atoms, preferably an alkoxy group having 1 to 2 carbon atoms, and n represents an integer of 1 to 3.) Examples of the organosilicon compound represented by the formula include those represented by the formula. R 5 in the general formula (1) does not contain heteroatoms such as nitrogen, oxygen, and phosphorus, and is an alkyl group containing only carbon and hydrogen. If the organosilicon compound of the general formula (1) has nitrogen in its chemical structure, it may have an adverse effect on the charge amount characteristics. Further, if the organosilicon compound of the general formula (1) has oxygen in its chemical structure, sufficient hydrophobicity may not be obtained. R 6The alkoxy group has 1 to 3 carbon atoms. When the carbon number is 4 or more, surface modification requires a long time due to a decrease in reactivity. Furthermore, an organosilicon compound having an alkoxy group with 4 or more carbon atoms is generally difficult to obtain industrially.

[0027] Among the organosilicon compounds represented by the general formula (1), examples of the organosilicon compound that functions as a surface modifier include the following general formula (2)

Chemical formula

[0028] Examples of the organosilicon compound that functions as a surface modifier also include hexamethyldisilazane and the like.

[0029] Examples of the organosilicon compound that functions as a surface modifier also include silicone oil. The kinematic viscosity of the silicone oil at 25 °C is, for example, 0.65 mm 2 / s to 10000 mm 2 / s and the like. When performing uniform surface modification on silicone oil, it is necessary to dissolve the silicone oil in an appropriate solvent. When the kinematic viscosity of the silicone oil exceeds 10,000 mm 2 / s, a large excess amount of solvent is required for surface modification. This causes problems such as complication of the process and cost increase, and furthermore, when volatilizing the solvent, it is easy to cause aggregation of the composite inorganic oxide powder.

[0030] In the present invention, the method of reacting the gas-phase composite inorganic oxide particles with the surface modifier is not particularly limited. As a general example, a normal surface modification method can be used. As a specific example, a method of evaporating the surface modifier and bringing it into contact with the gas-phase composite inorganic oxide particles, a method of spraying the surface modifier onto the surface of the gas-phase composite inorganic oxide particles by spraying or the like while flowing the gas-phase composite inorganic oxide particles (dry contact method), a method of dissolving the surface modifier in a predetermined solvent and dispersing the gas-phase composite inorganic oxide particles in the solvent in which the surface modifier is dissolved, etc. can be mentioned. Among these, the dry contact method is suitable in terms of preventing aggregation of the composite inorganic oxide powder and performing uniform treatment.

[0031] The carbon content of the surface-modified gas-phase composite inorganic oxide particles (that is, the composite inorganic oxide powder obtained by hydrophobizing the gas-phase composite inorganic oxide particles) in the present invention is not particularly limited. However, from the viewpoint of ensuring appropriate environmental stability and chargeability while preventing adsorption of moisture and the like, it is preferably 0.5% by mass or more and 11.0% by mass or less. When the carbon content of the composite inorganic oxide powder obtained by hydrophobizing the gas-phase composite inorganic oxide particles is less than 0.5% by mass, it indicates that the surface coating by the surface modifier is small, and there is a tendency that appropriate environmental stability and chargeability cannot be surely obtained. On the other hand, when the carbon content of the composite inorganic oxide powder obtained by hydrophobizing the gas-phase composite inorganic oxide particles exceeds 11.0% by weight, it indicates that a large amount of the surface modifier that did not react due to the presence of an excessive surface modifier exists on the surface of the gas-phase composite inorganic oxide particles, and there is a possibility that moisture is adsorbed on the surface modifier that did not react, or the surface modifier that did not react contaminates other members.

[0032] The amount of the organosilicon compound, which is a surface modifier used for the surface treatment of the gas-phase composite inorganic oxide particles, is preferably 3.0 parts by mass or more and 40 parts by mass or less, more preferably 5.0 parts by mass or more and 35 parts by mass or less, with respect to 100 parts by mass of the gas-phase composite inorganic oxide particles, in order to surely obtain appropriate environmental stability and chargeability while preventing adsorption of moisture and the like.

[0033] In addition, the average primary particle diameter of the composite inorganic oxide powder in the present invention is not particularly limited, but its lower limit value is preferably 7.0 nm, more preferably 10 nm, in order to surely prevent the particles from being easily buried in the toner particles and losing stable charging behavior. On the other hand, the upper limit value of the average primary particle diameter of the composite inorganic oxide powder is preferably 100 nm, more preferably 80 nm, in order to surely prevent the particles from being unable to be appropriately buried in the toner particles and detaching from the toner particles and losing stable charging behavior.

[0034] Next, a method for producing the composite inorganic oxide powder of the present invention will be described. Here, a method for producing the composite inorganic oxide powder obtained by the hydrophobization treatment of the gas-phase composite inorganic oxide particles will be described.

[0035] The method for producing the composite inorganic oxide powder of the present invention includes a step of preparing gas-phase composite inorganic oxide particles having an alumina content of 0.2% by mass or more and 20% by mass or less by introducing a silica raw material and an alumina raw material into a flame and subjecting them to a gas-phase decomposition method, a step of supplying an organosilicon compound, which is a surface modifier, to the surface of the gas-phase composite inorganic oxide particles, a reaction step of reacting the gas-phase composite inorganic oxide particles with the organosilicon compound, which is a surface modifier, and a heating step of heating the gas-phase composite inorganic oxide particles to which the organosilicon compound has been supplied and reacted with the organosilicon compound at a heating temperature of 100°C or more and 370°C or less for a heating time of 15 minutes or more and 350 minutes or less.

[0036] In the production of the composite inorganic oxide powder of the present invention, in the above heating step, in an inert gas atmosphere, the vapor-phase composite inorganic oxide particles are heat-treated at a heat treatment temperature of 100°C or higher and 370°C or lower, preferably 100°C or higher and 350°C or lower, particularly preferably 150°C or higher and 250°C or lower, and a heating time of 15 minutes or longer and 350 minutes or shorter, preferably 15 minutes or longer and 300 minutes or shorter, particularly preferably 30 minutes or longer and 120 minutes or shorter. The inert gas is not particularly limited, but it is necessary to use a gas that does not contain oxygen, such as nitrogen, helium, or argon. The reason for setting an inert gas atmosphere is to prevent combustion due to the reaction between the surface modifier and oxygen during heating. Also, setting an inert gas atmosphere is to prevent problems such as discoloration of the modified composite inorganic oxide powder due to surface oxidation caused by the presence of oxygen.

[0037] When the heat treatment temperature in the above heating step is less than 100°C, there is a problem that the reaction does not proceed sufficiently and a predetermined degree of hydrophobicity cannot be obtained. On the other hand, when the heat treatment temperature exceeds 370°C, decomposition of the surface modifier occurs, and there is a problem that discoloration occurs in the composite inorganic oxide powder obtained by surface modification. When the heating time in the above heating step is less than 15 minutes, the reaction does not proceed sufficiently, and there is a possibility that the solvent and by-products remain in the obtained composite inorganic oxide powder. On the other hand, even when the heating time in the above heating step exceeds 350 minutes, no significant difference in characteristics is observed compared to the case where it is 350 minutes or less, and it is preferable to carry out the process within the range of 350 minutes or less from the viewpoints of production time, production cost, etc.

[0038] Next, the measurement methods for various physical properties of the composite inorganic oxide powder of the present invention will be described below.

[0039] 〔Measurement of alumina content〕 Elemental analysis of the vapor-phase composite inorganic oxide particles is performed using an energy-dispersive X-ray fluorescence analyzer to measure the alumina content.

[0040] 〔Measurement of degree of hydrophobicity〕 Weigh 1 g of the composite inorganic oxide powder into a 200 mL separatory funnel, add 100 mL of pure water thereto, stopper it, shake it at 90 rpm for 10 minutes using a Turbler mixer, and then let it stand for 10 minutes. After standing, collect the lower-layer mixed solution into a 10 mm quartz cell, and using pure water as a blank, measure the transmittance of light with a wavelength of 500 nm using a spectrophotometer, and take this value as the degree of hydrophobization.

[0041] 〔Measurement of volume resistivity (JIS K 6911)〕 Put 0.5 g of the composite inorganic oxide powder into the powder probe unit of a powder resistance measurement system (Mitsubishi Chemical Analytech Co., Ltd.: MCP-PD51 type), and measure the volume resistivity using a resistivity measuring device (trade name: High Rester UX) manufactured by Mitsubishi Chemical Analytech Co., Ltd. under a pressure of 5 kN.

[0042] 〔Measurement of charge amount〕 Stir and mix 1 g of the composite inorganic oxide powder and 100 g of a negatively charged toner using a mixer to obtain a toner composition. Put 2 g of this toner composition and 48 g of iron powder carrier into a glass container (75 ml capacity), and let it stand for 40 hours or more under HH environment and LL environment. Here, the HH environment means an atmosphere of temperature 32.5°C and humidity 80%, and the LL environment means an atmosphere of temperature 10°C and humidity 10%. Shake the sample prepared under the above conditions using a Turbler mixer, collect 0.05 g of the mixture of the toner composition and the iron powder carrier, and take the value after blowing it off for 10 seconds using a suction blow-off type Q / m meter (trade name: MODEL230TO) manufactured by Trek Japan Co., Ltd. as the charge amount of the toner composition.

[0043] 〔Evaluation of environmental stability (environmental variation ratio)〕 Take the ratio of the charge amount under HH environment to that under LL environment (HH / LL) as the environmental variation ratio, and consider those with an environmental variation ratio of 0.48 or more to have a small environmental difference and excellent environmental stability.

[0044] 〔Evaluation of charge rising characteristics〕 The value obtained by dividing the value when shaking for 1 minute with a turbular mixer under the LL environment of the above charge amount by the value when shaking for 30 minutes is defined as the value of charge rise. The closer the value of charge rise is to 1, the more it indicates that sufficient charging is achieved in a short shaking time. Those with a charge rise numerical value of 0.36 or more were regarded as having excellent charge rise characteristics.

[0045] 〔Measurement of carbon content〕 The carbon content of the composite inorganic oxide powder obtained by surface treatment with a surface modifier can be measured under the following conditions using a carbon analyzer (manufactured by Sumika Chemical Analysis Service, Ltd., trade name: SUMIGRAPH NC - 22). Detector conditions: "INJ / DET" = 100 °C, "COL" = 70 °C Gas flow rate: O 2 = 350 ml / min, He = 80 ml / min

[0046] 〔Measurement of average primary particle size〕 It was determined by analyzing the images taken with a transmission electron microscope. Specifically, 50 images were taken by changing the field of view, and the average primary particle size of 2500 composite inorganic oxide powders was analyzed by image analysis and calculated by number average.

[0047] The composite inorganic oxide powder of the present invention can be used as an external additive for powder coatings or an external additive for electrophotographic toners.

[0048] By using the composite inorganic oxide powder of the present invention as an external additive for powder coatings, a powder coating composition containing the composite inorganic oxide powder of the present invention can be obtained. Further, by using the composite inorganic oxide powder of the present invention as an external additive for electrophotographic toners, an electrophotographic toner composition containing the composite inorganic oxide powder of the present invention can be obtained.

[0049] Hereinafter, a method for manufacturing an electrophotographic toner composition containing the composite inorganic oxide powder of the present invention will be described.

[0050] In the production of the electrophotographic toner composition of the present invention, the addition amount of the composite inorganic oxide powder of the present invention may be any addition amount as long as a desired property improvement effect can be obtained, and is not particularly limited. However, it is preferable that the composite inorganic oxide powder of the present invention is contained in the electrophotographic toner composition in an amount of 0.1% by mass to 6.0% by mass. If the content of the composite inorganic oxide powder of the present invention in the electrophotographic toner composition is less than 0.1% by mass, various effects related to charging due to the addition of this composite inorganic oxide powder cannot be sufficiently obtained. On the other hand, if the content of the composite inorganic oxide powder exceeds 6.0% by mass, it will desorb from the toner surface and the composite inorganic oxide powder will exist alone, causing problems in image characteristics and cleaning characteristics.

[0051] The content S (% by mass) of the composite inorganic oxide powder of the present invention in the electrophotographic toner composition is preferably in the range of R / 40 ≦ S ≦ R / 7, more preferably in the range of R / 25 ≦ S ≦ R / 15, and particularly preferably S = R / 20, with respect to the average primary particle diameter R (nm) of the raw material powder.

[0052] Generally, the electrophotographic toner composition contains, in addition to a thermoplastic resin, a small amount of a pigment, a charge control agent, and other external additives. In the present invention, as long as the above composite inorganic oxide powder is blended, other components may be the same as those in the prior art, and either a magnetic or non-magnetic one-component toner or a two-component toner may be used. Also, either a negatively charged toner or a positively charged toner may be used, and either a monochrome or color toner may be used.

[0053] In the production of the electrophotographic toner composition of the present invention, the composite inorganic oxide powder of the present invention as an external additive is not limited to being used alone, and may be used in combination with other metal oxide particles or the like according to the purpose. For example, the above composite inorganic oxide powder can be used in combination with other surface-modified dry silica fine particles, surface-modified dry titanium oxide fine particles, or modified wet titanium oxide fine particles.

Examples

[0054] Next, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments as long as it does not exceed the gist thereof.

[0055] <Example 1> The production of the composite inorganic oxide was carried out as follows. As a production apparatus for gas-phase composite inorganic oxide particles, a flame tube, a double-walled raw material supply tube that vertically extends above the flame tube and supplies hydrogen, air, gaseous SiCl 4 and gaseous AlCl 3 to the flame tube, and an air supply tube that obliquely extends above the flame tube and additionally supplies air (a known production apparatus described in Example 1 of European Patent No. 0585544) were used. Using the above production apparatus, nuclear hydrogen or reactive hydrogen 1.4 Nm 3 / h, air 5.5 Nm 3 / h and pre-evaporated gaseous SiCl 4 3.60 kg / h were mixed together. Into this hot mixture at about 200 °C, additionally pre-evaporated gaseous AlCl 3 0.04 kg / h was additionally supplied. The obtained mixture was burned in the flame tube, and at that time, additionally 12 Nm 3 / h of air was supplied into these flame tubes. The powder generated after passing through the flame tube was separated from the hydrochloric acid-containing gas in a filter or a cyclone. The gas-phase composite inorganic oxide particles obtained by treating the adhering hydrochloric acid residue at a high temperature were separated from the filter or the cyclone. The gas-phase composite inorganic oxide particles had the following analysis data.

[0056] BET specific surface area 40 m 2 / g, pH value of 4 mass% dispersion 4.5, bulk density 50 g / l, composition of gas-phase composite inorganic oxide particles Al 2 O 3 1 mass%, SiO 2 99 mass%.

[0057] Using the gas-phase composite inorganic oxide particles thus obtained as the raw material powder, isobutyltrimethoxysilane (trade name "Dynasylan (trademark registered) IBTMO" manufactured by Evonik Industries AG) was used as the surface modifier. 100 parts by mass of the gas-phase composite inorganic oxide particles were placed in a reaction vessel, and under a nitrogen atmosphere, the gas-phase composite inorganic oxide particles were made into a fluidized state by stirring, and 5 parts by mass of the surface modifier was sprayed. While continuing stirring, the temperature was raised from room temperature to 150 °C and held at 150 °C for 30 minutes. Then, by cooling, a composite inorganic oxide powder, which is the surface-modified gas-phase composite inorganic oxide particles, was obtained. Regarding the composite inorganic oxide powder thus obtained, the average primary particle diameter, carbon content, volume resistivity, and degree of hydrophobization (hydrophobicity ratio) were measured by the above-described measurement methods.

[0058] Also, 1 part by mass of the composite inorganic oxide powder thus obtained was added to 100 parts by mass of a toner containing polyester to obtain a toner composition. Regarding the obtained toner composition, the environmental stability (environmental variation ratio), which is the charge amount under predetermined conditions, and the charge-up characteristics were evaluated by the above-described measurement methods.

[0059] The measurement results of the above items are shown in Table 1.

[0060] <Example 2> A composite inorganic oxide powder was obtained by performing the same treatment as in Example 1 except that the addition amount of the surface modifier was 10 parts by mass.

[0061] <Example 3> The BET specific surface area of the gas-phase composite inorganic oxide particles was 80 m 2 / g, and the same treatment as in Example 1 was performed except that the amount of the surface modifier was 10 parts by mass.

[0062] <Example 4> The BET specific surface area of the gas-phase composite inorganic oxide particles was 80 m 2 / g, and the same treatment as in Example 1 was performed except that the amount of the surface modifier was 20 parts by mass.

[0063] <Example 5> The BET specific surface area of the gas-phase composite inorganic oxide particles was 170 m 2 / g, and the same treatment as in Example 1 was carried out except that the amount of the surface modifier was 15 parts by mass.

[0064] <Example 6> The BET specific surface area of the gas-phase composite inorganic oxide particles was 170 m 2 / g, and the same treatment as in Example 1 was carried out except that the amount of the surface modifier was 30 parts by mass and the treatment temperature was 200 °C.

[0065] <Example 7> The alumina component in the gas-phase composite inorganic oxide particles was 0.3% by mass, and the BET specific surface area was 110 m 2 / g, and the same treatment as in Example 1 was carried out except that the amount of the surface modifier was 12 parts by mass and the treatment time was 60 minutes.

[0066] <Example 8> The alumina component in the gas-phase composite inorganic oxide particles was 0.3% by mass, and the BET specific surface area was 110 m 2 / g, and the same treatment as in Example 1 was carried out except that the amount of the surface modifier was 24 parts by mass.

[0067] <Example 9> The BET specific surface area of the gas-phase composite inorganic oxide particles was 200 m 2 / g, and the same treatment as in Example 1 was carried out except that 25 parts by mass of hexadecyltrimethoxysilane (trade name "Dynasylan (registered trademark) 9116" manufactured by Evonik Industries AG) was used as the surface modifier and the treatment temperature was 200 °C.

[0068] <Example 10> The alumina component in the gas-phase composite inorganic oxide particles was 5% by mass, and the BET specific surface area was 200 m 2 / g, and the same treatment as in Example 1 was carried out except that 25 parts by mass of hexadecyltrimethoxysilane (trade name "Dynasylan (registered trademark) 9116" manufactured by Evonik Industries AG) was used as the surface modifier.

[0069] <Example 11> The alumina component in the gas-phase composite inorganic oxide particles is 7% by mass, and the BET specific surface area is 200 m 2 / g. The same treatment as in Example 1 was carried out except that 25 parts by mass of hexadecyltrimethoxysilane (trade name “Dynasylan (registered trademark) 9116” manufactured by Evonik Industries AG) was used as a surface modifier.

[0070] <Example 12> The BET specific surface area of the gas-phase composite inorganic oxide particles is 170 m 2 / g. The same treatment as in Example 1 was carried out except that 25 parts by mass of hexadecyltrimethoxysilane (trade name “Dynasylan (registered trademark) 9116” manufactured by Evonik Industries AG) was used as a surface modifier.

[0071] <Example 13> The BET specific surface area of the gas-phase composite inorganic oxide particles is 170 m 2 / g. The same treatment as in Example 1 was carried out except that 25 parts by mass of hexamethyldisilazane (trade name “Dynasylan (registered trademark) HMDS” manufactured by Evonik Industries AG) was used as a surface modifier.

[0072] <Example 14> The alumina component in the gas-phase composite inorganic oxide particles is 18% by mass, and the BET specific surface area is 170 m 2 / g. The same treatment as in Example 1 was carried out except that 15 parts by mass of silicone oil (polydimethylsiloxane; trade name “KF96-50cs” manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a surface modifier and the treatment time was 20 minutes.

[0073] <Example 15> The alumina component in the gas-phase composite inorganic oxide particles is 5% by mass, and the BET specific surface area is 80 m 2 / g, and the same treatment as in Example 1 was carried out except that 15 parts by mass of isobutyltrimethoxysilane (trade name "Dynasylan® IBTMO" manufactured by Evonik Industries AG) was used as a surface modifier, the treatment temperature was 120 °C, and the treatment time was 300 minutes.

[0074] <Example 16> The alumina component in the gas-phase composite inorganic oxide particles is 5% by mass, and the BET specific surface area is 80 m 2 / g, and the same treatment as in Example 1 was carried out except that 10 parts by mass of silicone oil (polydimethylsiloxane; trade name "KF96-50cs" manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a surface modifier, the treatment temperature was 320 °C, and the treatment time was 20 minutes.

[0075] <Comparative Example 1> The same treatment as in Example 1 was carried out except that the treatment time was 10 minutes.

[0076] <Comparative Example 2> Fumed silica powder (trade name "AEROSIL® 200" manufactured by Nippon Aerosil Co., Ltd.) was used in place of the gas-phase composite inorganic oxide particles in the raw material powder, and the same treatment as in Example 1 was carried out except that 40 parts by mass of hexadecyltrimethoxysilane (trade name "Dynasylan® 9116" manufactured by Evonik Industries AG) was used and the treatment time was 200 minutes.

[0077] <Comparative Example 3> Fumed silica powder (trade name "AEROSIL® 200" manufactured by Nippon Aerosil Co., Ltd.) was used in place of the gas-phase composite inorganic oxide particles in the raw material powder, and the same treatment as in Example 1 was carried out except that 20 parts by mass of silicone oil (polydimethylsiloxane; trade name "KF96-50cs" manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a surface modifier, the treatment temperature was 300 °C, and the treatment time was 300 minutes.

[0078] <Comparative Example 4> Instead of the gas-phase composite inorganic oxide particles, fumed alumina powder (trade name "AEROXIDE® AluC" manufactured by Evonik Industries AG) was used for the raw material powder, 13 parts by mass of octyltrimethoxysilane (trade name "Dynasylan® OCTMO" manufactured by Evonik Industries AG) was used as a surface modifier, and the same treatment as in Example 1 was performed except that the treatment time was 130 minutes.

[0079] <Comparative Example 5> Instead of the gas-phase composite inorganic oxide particles, fumed titania powder (trade name "AEROXIDE® TiO 2 P90" manufactured by Nippon Aerosil Co., Ltd.) was used for the raw material powder, 15 parts by mass of isobutyltrimethoxysilane (trade name "Dynasylan® IBTMO" manufactured by Evonik Industries AG) was used as a surface modifier, and the same treatment as in Example 1 was performed except that the treatment time was 150 minutes.

[0080] <Comparative Example 6> The same treatment as in Example 1 was performed except that the treatment temperature was 400°C and the treatment time was 120 minutes.

[0081] <Comparative Example 7> The same treatment as in Example 1 was performed except that the treatment temperature was 80°C and the treatment time was 150 minutes.

[0082] <Comparative Example 8> 20 parts by mass of silicone oil (polydimethylsiloxane; trade name "KF96-50cs" manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a surface modifier, and the same treatment as in Example 1 was performed except that the treatment temperature was 80°C and the treatment time was 10 minutes.

[0083] The treatment conditions described in the above Examples and Comparative Examples are summarized in Table 1 below, the correspondence table of surface modifiers is summarized in Table 2 below, and the physical property data and application characteristics are summarized in Table 3 below.

[0084]

Table 1

[0085]

Table 2

[0086]

Table 3

[0087] From the above Tables 1 and 3, by comparing the examples with Comparative Examples 1, 6, 7, and 8, the composite inorganic oxide powder of the example in which the gas-phase composite inorganic oxide particles were treated under appropriate heating conditions showed good environmental variation ratio (i.e., environmental stability) and good charge-up characteristics. Also, in the examples, the volume resistivity was 1.0×10 11 Ω·cm or more and 9.0×10 14 Ω·cm or less, and it was found that an appropriate charge amount could be obtained. On the other hand, in Comparative Examples 1, 6, and 7, the volume resistivity was less than 1.0×10 11 Ω·cm, and it was not possible to achieve both good environmental variation ratio (i.e., environmental stability) and good charge-up characteristics.

[0088] From the comparison between the examples and Comparative Examples 2, 3, and 4, when fumed silica and fumed alumina were used instead of the gas-phase composite inorganic oxide particles, the volume resistivity was less than 1.0×10 11 Ω·cm or the volume resistivity was 1.0×10 15 Ω·cm or more, and it was found that an appropriate charge amount could not be obtained. Also, in Comparative Examples 2, 3, and 4, although a good environmental variation ratio was obtained, it was confirmed that the charge-up characteristics tended to be somewhat inferior.

[0089] Also, from Comparative Example 5, when fumed titania was used instead of the gas-phase composite inorganic oxide particles, good results were shown for the environmental variation ratio and the charge-up characteristics, but the volume resistivity was less than 1.0×10 11 Ω·cm, and it was found that an appropriate charge amount could not be obtained.

Industrial Applicability

[0090] Since the composite inorganic oxide powder of the present invention can maintain an appropriate charge amount and has good environmental stability and good charge rising characteristics, it can be used, for example, in the field of external additives for powder coatings or external additives for electrophotographic toners. In particular, it has high utility value in the fields of high-speed printing and miniaturized printing devices.

Claims

1. A composite inorganic oxide powder having gas-phase composite inorganic oxide particles containing alumina and silica, The alumina content of the gas-phase composite inorganic oxide particles is 5% by mass or more and 10% by mass or less, and the volume resistivity of the composite inorganic oxide powder conforming to JIS K 6911 is 1.0×10 １１ Ω·cm or more and 9.0×10 １４ Ω·cm or less, and wherein the gas-phase composite inorganic oxide particles are surface-treated with an organosilicon compound.

2. The composite inorganic oxide powder according to Claim 1, having a degree of hydrophobicity of 50% or more.

3. The composite inorganic oxide powder according to Claim 1, having a carbon content of 0.5% by mass or more and 11.0% by mass or less.

4. The composite inorganic oxide powder according to Claim 1 or 3, wherein the gas-phase composite inorganic oxide particles are surface-treated with 3.0 parts by mass or more and 40 parts by mass or less of the organosilicon compound based on 100 parts by mass of the gas-phase composite inorganic oxide particles.

5. The organosilicon compound has the following general formula (1) R ５ ｎ SiR ６ （４－ｎ） (1) (wherein, R ５ represents a hydrocarbon group having 1 to 18 carbon atoms, and R ６ represents a hydrocarbon group having 1 to 18 carbon atoms, a chlorine atom, a hydroxy group or an alkoxy group having 1 to 3 carbon atoms, and n represents an integer of 1 to 3.) The composite inorganic oxide powder according to claim 1, 3 or 4, which is an organosilicon compound, hexamethyldisilazane and / or silicone oil.

6. The organosilicon compound has the following general formula (2) 【Chemical 1】 (wherein R １ represents a hydrocarbon group having 1 to 18 carbon atoms, and R ２ , R ３ and R ４ each independently represent a chlorine atom, a hydroxy group or an alkoxy group having 1 to 3 carbon atoms.). The composite inorganic oxide powder according to claim 1, 3 or 4, which is an organosilicon compound, hexamethyldisilazane and / or silicone oil represented by the formula.

7. The composite inorganic oxide powder according to any one of Claims 1 to 6, having an average primary particle diameter of 7.0 nm or more and 100 nm or less.

8. The composite inorganic oxide powder according to any one of Claims 1 to 7, which is used as an external additive for a powder coating or an external additive for an electrophotographic toner.

9. A powder coating composition containing the composite inorganic oxide powder according to any one of Claims 1 to 8.

10. An electrophotographic toner composition containing the composite inorganic oxide powder according to any one of Claims 1 to 8.

11. A gas-phase composite inorganic oxide particle preparation step of introducing a silica raw material and an alumina raw material into a flame and obtaining gas-phase composite inorganic oxide particles having an alumina content of 5% by mass or more and 10% by mass or less by a gas-phase decomposition method, an organosilicon compound supply step of applying an organosilicon compound to the surface of the gas-phase composite inorganic oxide particles, and a heating step of heating the gas-phase composite inorganic oxide particles to which the organosilicon compound has been applied at a heating temperature of 100°C or more and 370°C or less for a heating time of 15 minutes or more and 350 minutes or less. A method for producing a composite inorganic oxide powder, comprising:

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