Surface-modified inorganic oxide powder and method for producing the same

Abstract

To provide a powder having both of a good spacer effect and proper electrostatic charge characteristics while maintaining excellent characteristics of an inorganic oxide powder by a fumed method.SOLUTION: The powder has the following physical properties: (1) a mean particle size of 0.1 to 1 μ m, (2) a bulk density of 20 to 100g / L, (3) a hydrophobicity of 60% or more, (4) a water adsorption at a water vapor relative pressure of 0.8 to 0.95 of 2 to 5%, (5) a BET specific surface area of 25 to 150m2 / g, and (6) a carbon atom content of 0.5 to 8% by weight. (7) a nitrogen content of 0.1 to 0.75% by weight, and (8) a triboelectric charge amount of 20 to 300 μ C / g SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a novel surface-modified inorganic oxide powder and a method for producing the same. [Background technology]

[0002] By treating the surface of fine inorganic oxide powders such as silica, titania, and alumina with organic matter, the electrostatic properties and hydrophobicity of the powder surface can be modified. Surface-modified inorganic oxide powders obtained in this way are widely used as fluidity improvers and electrostatic modifiers in toners used in electrophotography, including in copiers, laser printers, and plain paper facsimile machines. Such surface-modified inorganic oxide powders used in toner applications are known as external additives.

[0003] External additives are classified as positively charged or negatively charged depending on the charge properties of the toner. If the toner is positively charged, a positively charged external additive is used; if the toner is negatively charged, a negatively charged external additive is used. In drums used in digital color printers and color copiers, OPC (organic photoconductor) drums are mainly used, and these often use negatively charged toner, and consequently, negatively charged external additives are also used. However, OPC drums have problems with durability and environmental friendliness, and amorphous silicon photoconductor drums are also used to improve these issues. In systems with these drums, positively charged toner is used, and consequently, positively charged external additives are also used.

[0004] For surface treatment of inorganic oxide powders used in such applications, organosilicon compounds such as dimethyldichlorosilane, hexamethyldisilazane, and silicone oil are mainly used. In addition, by using aminosilane, amine, etc. as positive charge imparting agents, the silanol groups on the particle surface of the inorganic oxide powder are replaced with organic groups, thereby performing hydrophobic treatment and positive charging treatment.

[0005] Toner is agitated within devices such as photocopiers and becomes electrically charged (i.e., electrostatically charged) due to friction with carriers and other components. This highly controlled electrostatic charge allows it to perform its developing function. However, if toner is agitated for extended periods within the device, the strong frictional force becomes stress, leading to toner degradation. For example, if external additives become embedded in the toner surface, the toner loses its function as a point of contact with the external environment. Moreover, the mechanical stress on toner has increased in recent years, and the softening design of the binding resin (toner matrix resin) that constitutes the toner has resulted in lower hardness of the toner matrix, making external additives more susceptible to embedding. For these reasons, the importance of countermeasures against the embedding of external additives as described above is increasing.

[0006] In particular, in recent years, the increasing image quality of electrophotography has led to smaller toner particles, and coupled with higher speeds and color printing, the mechanical load on the toner has increased. Therefore, the long-term durability of toner performance (control of degradation behavior) is becoming increasingly important. At the same time, to shorten print waiting times and save energy, the binder resin used in toner is required to have low-temperature fixing properties. For these reasons, the use of softened and low-melting-point components as toner base resins is becoming mainstream.

[0007] Due to the lower melting point of toner resins, a phenomenon occurs where surface-treated fumed oxides become embedded in the toner resin during long-term operation, reducing its fluidity. To address this, submicron-sized silica powder is added to the toner surface along with the fumed oxides to improve toner durability. This submicron-sized silica powder acts as a spacer, preventing the fumed oxides from becoming embedded in the toner. Primarily, silica powder produced by the sol-gel method is used as this submicron-sized silica (see Patent Document 1, etc.).

[0008] However, silica powder produced by the sol-gel method has a problem: its electrostatic properties are weak. One possible reason for this is the high amount of adsorbed water in the particles that make up silica powder produced by the sol-gel method.

[0009] Furthermore, silica powder produced by the sol-gel method has a problem in that its particle shape is close to spherical, making it prone to detaching from the toner surface during long-term use.

[0010] Furthermore, silica powder produced by the sol-gel method tends to retain or adsorb a large amount of moisture, making it difficult to obtain strong triboelectric properties. Therefore, for materials that adjust electric charge, such as toners, its low electrostatic properties must be improved.

[0011] In contrast, silica powder produced by the dry method or gas phase method (hereinafter collectively referred to as the "fumed method") has a particle shape that deviates from spherical than silica produced by the sol-gel method, and therefore can be expected to suppress the release from the toner surface, which is a problem with the sol-gel silica mentioned above. However, generally speaking, silica powder produced by the fumed method has a small primary particle size and disperses on the toner surface as particles of submicron size or smaller, so it cannot fully exert its spacer effect, and in general its electrostatic properties are too high, so in order to control the electrostatic properties of the toner within an appropriate range, the amount added and its dispersibility must be precisely controlled. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2013-249215 [Overview of the project] [Problems that the invention aims to solve]

[0013] Due to the reasons described above, there is a strong desire to develop an external additive (particles) for toner that has a submicron size and can sufficiently obtain the spacer effect while having appropriate charging characteristics, but such materials have not yet been developed.

[0014] Therefore, the main object of the present invention is to provide a powder that combines a good spacer effect and appropriate charging characteristics while making use of the excellent characteristics of inorganic oxide powder by the fumed method.

Means for Solving the Problems

[0015] As a result of intensive research in view of the problems of the prior art, the present inventors have found that the above object can be achieved by adopting particles having specific structures and properties as external additives, and have completed the present invention.

[0016] That is, the present invention relates to the following surface-modified inorganic oxide powder and its manufacturing method. 1. A powder composed of particles containing inorganic oxide particles, an organosilicon compound covering the particle surface, and a positive charge-imparting agent, having the following physical properties: (1) Average particle size: 0.1 to 1 μm, (2) Bulk density: 20 to 100 g / L, (3) Hydrophobicity: 60% or more, (4) Moisture adsorption amount at a relative water vapor pressure of 0.8 to 0.95: 2 to 5%, (5) BET specific surface area: 25 to 150 m 2 / g, (6) Carbon content: 0.5 to 8% by weight, (7) Nitrogen content: 0.1 to 0.75% by weight and (8) Frictional charge amount: 20 to 300 μC / g A surface-modified inorganic oxide powder showing positive chargeability, characterized by the above. 2. The surface-modified inorganic oxide powder according to item 1 above, wherein the organosilicon compound is at least one of hexamethyldisilazane, polydimethylsiloxane, and alkylsilane. 3. The surface-modified inorganic oxide powder according to item 1 above, wherein the positively charge-imparting agent is at least one of an aminosilane and an amino group-modified silicone oil. 4. The surface-modified inorganic oxide powder according to item 1 above, wherein the inorganic oxide particles are fumed silica particles having a BET specific surface area of 100 to 250 m 2 / g. 5. An external additive for toner or powder coating containing the surface-modified inorganic oxide powder according to any one of items 1 to 4 above. 6. An electrophotographic toner composition or powder coating composition containing the external additive according to item 5 above and binder resin particles. 7. A method for producing a surface-modified inorganic oxide powder, comprising: (a) A step of preparing a mixture containing an inorganic oxide powder, an organosilicon compound, and a positively charge-imparting agent; (b) A step of heat-treating the mixture at a temperature of 100 to 270°C. A method for producing a surface-modified inorganic oxide powder, characterized by including the above steps. 8. The production method according to item 7 above, wherein the steps (a) and (b) are carried out under stirring.

Advantages of the Invention

[0017] According to the present invention, while making use of the excellent properties of inorganic oxide powder by the fumed method, it is possible to provide a powder having both a good spacer effect and appropriate charging properties. In particular, inorganic oxide particles produced by a dry method (fumed method or vapor phase method) have specific internal pores. By subjecting the surface of such particles to the surface modification specified in the present invention, properties such as bulk density and moisture adsorption amount become specific properties, and as a result, it is possible to provide a submicron-sized powder having an appropriate charging property (positive charging property) while having a low bulk density.

[0018] More specifically, the surface-modified inorganic oxide powder of the present invention is produced by surface-modifying an inorganic oxide powder having internal voids with a predetermined organosilicon compound. As a result, various properties such as bulk density, hydrophobicity, water adsorption capacity, surface area, and carbon content are controlled within a certain range, exhibiting higher electrostatic properties compared to particles produced by the sol-gel method, and achieving sufficient cohesiveness to exhibit a spacer effect that cannot be obtained with silicon oxide powder produced by the conventional fumed method.

[0019] As described above, the present invention aims to solve the problems associated with surface-treated sol-gel silica produced by wet methods by surface-treating an inorganic oxide powder having internal voids manufactured by a dry method. This improves problems such as reduced toner fluidity associated with toners designed to reduce environmental impact, and in particular, it has succeeded in providing a surface-modified inorganic oxide powder that combines high electrostatic properties and low bulk density, which were difficult to achieve with sol-gel silica.

[0020] The powder of the present invention, possessing these characteristics, can be suitably used as an external additive for toners or powder coatings. Therefore, an electrophotographic toner composition or powder coating composition containing the surface-modified inorganic oxide powder of the present invention, due to its high fixation rate, high hydrophobicity, etc., exhibits excellent fluidity, antistatic properties, etc., suppresses fogging or cleaning defects, and further reduces the likelihood of toner adhering to the photoreceptor, thus reducing the occurrence of image defects. In addition, the composition of the present invention can also provide effects such as long-term storage stability and control of developer degradation behavior. [Brief explanation of the drawing]

[0021] [Figure 1] This is a particle size distribution diagram of the powder obtained in the example. [Figure 2] This is a particle size distribution diagram of the powder obtained in the comparative example. [Figure 3] This is a schematic diagram of the method used to observe toner particles using a scanning electron microscope (SEM) in Test Example 2. [Modes for carrying out the invention]

[0022] 1. Surface-modified inorganic oxide powder The positively charged surface-modified inorganic oxide powder of the present invention (the powder of the present invention) is a powder comprising inorganic oxide particles, an organosilicon compound coating the surface of the particles, and a positive charge imparting agent, and has the following physical properties: (1) Average particle size: 0.1~1μm, (2) Bulk density: 20-100 g / L (3) Hydrophobicity: 60% or more, (4) Amount of water adsorption at a relative water vapor pressure of 0.8 to 0.95: 2 to 5% (5) BET specific surface area: 25~150m 2 / g, (6) Carbon content: 0.5-8% by weight, (7) Nitrogen content: 0.1 to 0.75% by weight and (8) Triboelectric charge: 20-300 μC / g It is characterized by having the following features.

[0023] <Composition of the powder of this invention> The particles constituting the powder of the present invention include inorganic oxide particles and an organosilicon compound that coats the surface of these particles. In other words, the basic structure consists of inorganic oxide particles as core particles (original material), with part or all of its surface coated with an organosilicon compound.

[0024] The inorganic oxide particles that form the core are not limited to any particular type, and examples include, but are not limited to, silicon dioxide, titanium dioxide, and aluminum dioxide. Among these, silicon dioxide (silica) can be preferably used in this invention. These particles themselves can be known or commercially available.

[0025] The particle size of inorganic oxide particles is not limited, but typically a primary particle diameter of around 5-150 nm is acceptable. Also, the BET specific surface area of ​​inorganic oxides is typically 30-400 m². 2 A value of approximately / g would suffice, but it is not limited to this.

[0026] Furthermore, it is preferable to use powder produced by the fumed method for the inorganic oxide particles. The fumed method is a known method, and fumed silica can be synthesized by a method that includes a step of introducing a silicon compound (such as silicon tetrachloride) or metallic silicon into an oxygen-hydrogen flame and causing a hydrolysis reaction. As mentioned above, such powders have a particle shape that is less spherical than silica produced by the sol-gel method, and therefore offer advantages such as effectively suppressing release from the toner surface. In addition, since no solvent is used, it also has the advantage of not generating aggregated particles during drying.

[0027] The inorganic oxide particles produced by this fumed process can be those that are known or commercially available. For example, the commercially available products shown in the examples below can be suitably used.

[0028] As the organosilicon compound used to coat the surface of the inorganic oxide particles, known or commercially available compounds, such as those known as hydrophobic treatment agents, can also be used.

[0029] More specifically, alkylsilazane compounds such as hexamethyldisilazane (HMDS), alkylalkoxysilane compounds such as dimethyldimethoxysilane, diethyldiethoxysilane, trimethylmethoxysilane, methyltrimethoxysilane, and butyltrimethoxysilane, chlorosilane compounds such as dimethyldichlorosilane and trimethylchlorosilane, as well as silicone oils such as polydimethylsiloxane (PDMS) and silicone varnishes can be used. These may be used individually or in combination of two or more.

[0030] Among these, it is preferable to use at least one of alkylsilazane compounds, alkylalkoxysilane compounds, and silicone oils in order to more reliably obtain the effects of the present invention. In particular, at least one of hexamethyldisilazane, polydimethylsiloxane, and alkylalkoxysilane is more preferable.

[0031] In particular, alkylalkoxysilane compounds are not particularly limited as long as they are alkoxysilanes having an alkyl group, and examples include trimethoxyalkoxysilane and triethoxyalkoxysilane. The number of carbon atoms (C) of the alkyl group is not particularly limited, but it is preferably C2 to C16. If it is less than C2, volatilization of the alkoxysilane may occur during surface treatment. If it is more than C16, strong aggregation may occur due to the effect of its high viscosity, and the dispersibility of the resulting powder may be impaired.

[0032] In addition to polydimethylsiloxane, modified silicone oils, such as those with added alkyl groups or -OH groups, can also be used as silicone oils.

[0033] Furthermore, the viscosity range of the organosilicon compound (measured at a temperature of 25°C) is not particularly limited, but is usually preferably between 10 and 300 cs. If the viscosity is less than 10 cs, volatilization of low molecular weight polysiloxanes, etc., occurs during surface treatment, which is undesirable from the viewpoint of energy efficiency and environmental impact. On the other hand, if the viscosity exceeds 300 cs, higher aggregation may occur, potentially impairing the dispersibility of the resulting powder.

[0034] The content of organosilicon compounds in the powder of the present invention is not particularly limited as long as it is within the above carbon content range, but generally it is about 5 to 20 parts by weight, and particularly preferably 10 to 15 parts by weight, per 100 parts by weight of inorganic oxide powder.

[0035] Furthermore, when calculating the content of organosilicon compounds, if an organosilicon compound having an amino group is included, the content of that organosilicon compound having an amino group shall not be included.

[0036] The positive charge imparting agent is not particularly limited as long as it can modify inorganic oxide particles to be positively charged, but in the present invention, at least one of aminosilane and amino group-modified silicone oil can be suitably used. The amino group in these compounds may be primary, secondary, or tertiary.

[0037] Suitable aminosilanes include amino group-containing alkoxysilanes such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. These can be known or commercially available.

[0038] As amino group-modified silicone oils, for example, silicone oils in which an amino group or an organic group containing an amino group (e.g., an aminoalkyl group) is introduced into the side chains and / or terminals of the silicone chain can be suitably used. These can be known or commercially available.

[0039] The content of the positive charge imparting agent in the powder of the present invention is not particularly limited as long as it is within the range of the nitrogen content described above, but it is usually about 0.5 to 30 parts by weight per 100 parts by weight of inorganic oxide powder, and it is particularly desirable to have 1 to 20 parts by weight.

[0040] <Characteristics of the powder of this invention> The powder of this invention has the following physical properties: (1) Average particle size: 0.1~1μm, (2) Bulk density: 20-100 g / L (3) Hydrophobicity: 60% or more, (4) Amount of water adsorption at a relative water vapor pressure of 0.8 to 0.95: 2 to 5% (5) BET specific surface area: 25~150m 2 / g, (6) Carbon content: 0.5-8% by weight, (7) Nitrogen content: 0.1 to 0.75% by weight and (8) Triboelectric charge: 20-300 μC / g It satisfies all of the following conditions.

[0041] Average particle size The average particle size is typically around 0.1 to 1 μm, preferably 0.2 to 0.8 μm. Having a particle size within this range allows the particle to effectively function as a spacer. In this invention, the average particle size refers to the value (arithmetic mean diameter (volume standard)) calculated using a particle size distribution analyzer (laser diffraction scattering particle size distribution analyzer (manufactured by Horiba, Ltd.)).

[0042] Bulk density The bulk density is typically around 20-100 g / L, preferably 50-100 g / L, and more preferably 30-80 g / L. If the bulk density is less than 20 g / L, the powder cannot be dispersed on the toner surface with an appropriate aggregate particle size, and a sufficient spacer effect cannot be achieved. Furthermore, if the bulk density exceeds 100 g / L, a large amount of equipment volume is required when mixing with the toner, which poses problems for industrial use.

[0043] Hydrophobicity The hydrophobicity is usually around 60% or higher, and particularly preferably 80% or higher. More preferably 97% or higher, and most preferably 99% or higher. In this invention, the hydrophobicity is an indicator of the degree of hydrophobicity of the surface-modified inorganic oxide powder. If the hydrophobicity is less than 60%, the strong positive charge due to the amino groups present in the silica powder cannot be exhibited, and it may not be possible to obtain a submicron-sized powder with excellent charge properties. There is no particular upper limit to the hydrophobicity, but it is usually 100%.

[0044] Moisture adsorption The moisture adsorption amount at a relative water vapor pressure of 0.8 to 0.95 is usually about 2 to 5% by weight, and particularly preferably 2.5 to 4.0% by weight. Therefore, for example, it can also be set to 3 to 5% by weight. The moisture adsorption amount greatly affects the charging characteristics, and appropriate charging properties can be imparted by setting it within the above range. When the moisture adsorption amount is less than 2% by weight, for example, silica powder exhibits the charging characteristics peculiar to fumed silica and becomes too strongly positively charged. On the other hand, when the moisture adsorption amount exceeds 5% by weight, the amount of retained and adsorbed moisture becomes close to that of silica by the sol-gel method, and sufficient positive charging properties cannot be exhibited.

[0045] BET specific surface area The BET specific surface area is usually about 25 to 150 m 2 / g, and particularly preferably about 50 to 150 m 2 / g. More preferably, it is 30 to 130 m 2 / g. When the BET specific surface area is less than 25 m 2 / g, the aggregate particle size is too large, resulting in insufficient dispersibility when dispersed in toner. When the BET specific surface area exceeds 150 m 2 / g, when dispersed in toner, the appropriate aggregate diameter cannot be maintained, and a sufficient spacer effect cannot be exhibited.

[0046] Carbon content The carbon content is usually about 0.5 to 8% by weight, preferably 0.8 to 6.0% by weight. Particularly, when the surface treatment agent (hydrophobizing agent) is HMDS, it is preferably about 0.5 to 5.0% by weight, when it is PDMS, it is preferably about 0.5 to 8.0% by weight, and when it is alkylalkoxysilane, it is preferably about 0.5 to 8.0% by weight. The carbon content is an index indicating the degree (fixed amount) of immobilization of the organic silicon compound as the surface treatment agent on the inorganic oxide powder. If the carbon content is too low, sufficient surface modification cannot be performed, and a sufficient hydrophobicity rate cannot be imparted, resulting in insufficient charging characteristics, dispersibility, etc. On the other hand, if the carbon content is too high, the content of organic substances is too high, causing particle aggregation, and sufficient fluidity and dispersibility cannot be obtained, and even when this powder is applied to toner, a sufficient spacer effect cannot be exhibited.

[0047] Nitrogen content The nitrogen content is typically 0.1 to 0.75% by weight, and particularly preferably 0.20 to 0.70% by weight. If the nitrogen content is less than 0.1% by weight, the inorganic oxide particle surface will not be sufficiently modified by amino groups, and sufficient positive charge will not be imparted. On the other hand, if the nitrogen content exceeds 0.75% by weight, aggregation of particles will occur, and sufficient fluidity and dispersibility will not be obtained, so even if this powder is applied to toner, it will not exhibit a sufficient spacer effect.

[0048] Triboelectric charge The amount of triboelectric charge is typically around 20-300 μC / g, and preferably 35-285 μC / g. If the amount of triboelectric charge approaches zero (less than 20 μC / g), it becomes difficult to impart strong positive charge characteristics to the toner when the powder is added to the toner, making it difficult to control the toner within a predetermined charge range. On the other hand, if the amount of triboelectric charge exceeds 300 μC / g, the strong amount of triboelectric charge makes it difficult to control the charge characteristics of the toner.

[0049] 2. Method for producing the powder of the present invention The method for producing the powder of the present invention is not particularly limited as long as a powder having the above-described composition and characteristics can be obtained, but it can be suitably produced by a method including, for example, (a) a step of preparing a mixture containing an inorganic oxide powder, an organosilicon compound, and a positive charge imparting agent (mixture preparation step), and (b) a step of heat-treating the mixture at a temperature of 120 to 360°C (heat treatment step).

[0050] Mixture preparation process The mixture preparation step is not limited to any method that can coat the surface of each particle constituting the inorganic oxide powder with an organosilicon compound. For example, a method of mixing the inorganic oxide powder with a vaporized organosilicon compound and / or a positive charge imparting agent under stirring, or a method of spraying the inorganic oxide powder with an organosilicon compound and / or a positive charge imparting agent under stirring can be suitably employed. Thus, it is preferable to mix these components while stirring.

[0051] In this case, the organosilicon compound and / or positive charge imparter may be used dissolved or dispersed in a solvent (e.g., organic solvents such as hexane or toluene) as needed. In this case, the concentration of each component can be appropriately set depending on the type of organosilicon compound or positive charge imparter used.

[0052] Furthermore, in this invention, water and catalysts (such as amines) can be appropriately added to the mixture as needed.

[0053] The temperature conditions in the mixture preparation process are not particularly limited and may be, for example, within the range of 10 to 40°C, but are not limited thereto. Furthermore, it is generally preferable to carry out the process in an inert gas atmosphere. For example, nitrogen gas, helium gas, argon gas, etc., can be suitably used.

[0054] The types and amounts of organosilicon compounds and positive charge imparters used can be the same as those described in "1. Surface-Modified Inorganic Oxide Powders" above.

[0055] Heat treatment process While not limited, the heat treatment temperature in the heat treatment process is generally preferably between 100 and 270°C (particularly 120 to 250°C). If the heat treatment temperature exceeds 270°C, partial decomposition of the positive charge imparting agent may occur. Conversely, if the temperature is below 100°C, sufficient surface modification of the organosilicon compound may not be achieved, potentially resulting in a failure to obtain the desired hydrophobicity.

[0056] The heat treatment atmosphere, as in the previous step, is preferably carried out in an inert gas atmosphere. For example, nitrogen gas, helium gas, argon gas, etc., can be suitably used. In particular, the previous step can be carried out in a sealed reactor, and the heat treatment step can be suitably carried out while maintaining the same atmosphere.

[0057] The heat treatment time should be sufficient to allow the organic silane compound and the positive charge imparting agent to fix (adhere) to the surface of each particle constituting the inorganic oxide powder. For example, it can be 10 to 200 minutes, but is not limited to this.

[0058] 3. Use of the powder of the present invention The powder of the present invention possesses all of the characteristics (1) to (8) shown in "1. Surface-Modified Inorganic Oxide Powder" above, and therefore, in addition to the excellent properties of inorganic oxide powder produced by the fumed method, it can exhibit both a good spacer effect and appropriate electrostatic properties. For this reason, the powder of the present invention can be suitably used as an additive (especially an external additive for toners) for toners, powder coatings, etc. Accordingly, the present invention also encompasses electrophotographic toner compositions or powder coating compositions (hereinafter, both are collectively referred to as "the composition of the present invention") that contain the powder of the present invention and binding resin particles.

[0059] The composition of the present invention contains the surface-modified inorganic oxide powder of the present invention described above, and there are no particular restrictions on its composition, manufacturing method, etc., and known compositions and methods can also be used.

[0060] The content of the powder of the present invention in the composition of the present invention is not particularly limited as long as the desired property improvement effect is obtained, but it is usually preferable that it is contained in an amount of about 0.1 to 5.0% by weight. If the content of the powder of the present invention in the composition of the present invention is less than 0.1% by weight, the improvement effect of fluidity or the stabilization effect of electrostatic properties due to the addition of the powder of the present invention may not be sufficiently obtained. Furthermore, if the content of the powder of the present invention exceeds 5.0% by weight, the amount of powder acting independently increases, which may cause problems such as image quality and cleaning properties.

[0061] In addition to binder resin particles, the composition of the present invention may optionally contain, for example, pigments, charge control agents (static control agents), waxes, etc. These components may be the same as those in known or commercially available toner compositions. Furthermore, while a positively charged toner is preferred, the toner type is not particularly limited in other respects. Therefore, for example, either a magnetic or non-magnetic one-component toner or a two-component toner may be used. Moreover, it may be either monochrome or color.

[0062] The powder of the present invention is particularly excellent in its spacer effect, and therefore can be more preferably used as an external additive for binding resin particles containing a resin component that softens easily (for example, at least one of styrene-acrylic copolymer resin, polyester resin, epoxy resin, etc.).

[0063] Furthermore, in the electrophotographic toner composition of the present invention, the powder of the present invention as an external additive is not limited to being used alone, but may be used in combination with other metal oxide fine powders depending on the purpose. For example, the surface-modified inorganic oxide powder of the present invention can be used in combination with other surface-modified dry silica fine powders, surface-modified dry titanium oxide fine powders, surface-modified wet titanium oxide fine powders, etc., as needed. [Examples]

[0064] Examples and comparative examples are shown below to give a more detailed explanation of the features of the present invention. However, the scope of the present invention is not limited to the examples.

[0065] The components used in each example and comparative example are as follows:

[0066] (A) About silica powder (A1) Sol gel silica Sample prepared by a known sol-gel method (BET specific surface area 30 m²) 2 / g) (A2) Sample A A sample with internal voids produced by a known fumed method (BET specific surface area 110 m²) 2 / g) (A3) Sample B A sample with internal voids manufactured by a known fumed method (BET specific surface area 120 m²) 2 / g) (A4) Commercial product a Product name "AEROSIL TT600" (registered trademark), manufactured by Nippon Aerosil Co., Ltd. (fumed silica, BET specific surface area 135 m²) 2 / g) (A5) Sample C A sample with internal voids manufactured by a known fumed method (BET specific surface area 165 m²) 2 / g) (A6) Sample D A sample with internal voids manufactured by a known fumed method (BET specific surface area 210 m²) 2 / g) (A7) Commercial product b Product name: "AEROSIL 50" (registered trademark), manufactured by Nippon Aerosil Co., Ltd. (Fumed silica, BET specific surface area 50 m²) 2 / g) (A8) Commercial product c Product name "AEROSIL 200" (registered trademark), manufactured by Nippon Aerosil Co., Ltd. (Fumed silica, BET specific surface area 200 m²) 2 / g)

[0067] (B) Surface treatment agents (B1) HMDS Hexamethyldisilazane (product name "Dynasilan HMDS" (registered trademark), manufactured by Evonik) (B2) PDMS • 20cs: Polydimethylsiloxane (product name "KF96-20cs", manufactured by Shin-Etsu Chemical Co., Ltd.) • 30cs: Polydimethylsiloxane (product name "KF96-30cs", manufactured by Shin-Etsu Chemical Co., Ltd.) • 50cs: Polydimethylsiloxane (product name "KF96-50cs", manufactured by Shin-Etsu Chemical Co., Ltd.) • 100cs: Polydimethylsiloxane (product name "KF96-100cs", manufactured by Shin-Etsu Chemical Co., Ltd.) • 300cs: Polydimethylsiloxane (product name "KF96-300cs", manufactured by Shin-Etsu Chemical Co., Ltd.) • 500cs: Polydimethylsiloxane (product name "KF96-500cs", manufactured by Shin-Etsu Chemical Co., Ltd.) • Amino-modified: Amino-modified polydimethylsiloxane (product name "KF96-859", manufactured by Shin-Etsu Chemical Co., Ltd.)

[0068] (B2) Alkylsilane • C1: Monomethyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) • C2: Dimethyldimethoxysilane (product name "DOWSIL Z-6329" (registered trademark), manufactured by Dow and Toyay) • C4: Isobutyltrimethoxysilane (product name "Dynasilan IBTMO", manufactured by Evonik) • C8a: Octyltrimethoxysilane (product name "Dynasilan OCTMO", manufactured by Evonik) • C8b: Octyltriethoxysilane (product name "Dynasilan OCTEO", manufactured by Evonik) • C16: Hexadecyltrimethoxysilane (product name "Dynasilan 9116", manufactured by Evonik) • C18: Octadecyltrimethoxysilane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0069] (B3) Aminosilane (positive charge imparting agent) • Aminosilane A: 3-aminopropyltriethoxysilane • Aminosilane B: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane

[0070] [Example 1] As shown in Table 1, sample A, which was produced by a dry method and had internal voids, was placed in a reactor, alkylsilane and aminosilane B were added in predetermined amounts under stirring in a nitrogen atmosphere, and the mixture was heat-treated at 120°C for 120 minutes while continuing to stir, thereby obtaining surface-modified silica powder with internal voids.

[0071] [Example 2] As shown in Table 1, a surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that Sample A, which was produced by a dry method and had internal pores, was replaced with Sample B, the surface treatment agent was changed to PDMS and aminosilane A, and the treatment temperature and time were changed as described in Table 1.

[0072] [Example 3] As shown in Table 1, surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that sample A was changed to commercially available product a, the surface treatment agents were changed to HMDS, aminosilane A and aminosilane B, and the treatment temperature and time were changed as described in Table 1.

[0073] [Example 4] As shown in Table 1, a surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that sample A was replaced with commercially available product a, the surface treatment agents were changed to alkylsilane and aminosilane A, and the treatment temperature and time were changed as described in Table 1.

[0074] [Example 5] As shown in Table 1, surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that sample A was changed to commercially available product a, the surface treatment agents were changed to HMDS, PMDS, and aminosilane A, and the treatment temperature and time were changed as described in Table 1.

[0075] [Example 6] As shown in Table 1, surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that sample A was changed to sample C, the surface treatment agents were changed to PDMS, aminosilane A, and aminosilane B, and the treatment temperature and time were changed to those listed in Table 1.

[0076] [Example 7] As shown in Table 1, surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that sample A was changed to sample C, the surface treatment agents were changed to PDMS and aminosilane B, and the treatment temperature and time were changed as shown in the table.

[0077] [Example 8] As shown in Table 1, a surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that sample A was changed to sample D, the surface treatment agents were changed to alkylsilane and aminosilane A, and the treatment temperature and time were changed as described in Table 1.

[0078] [Example 9] As shown in Table 1, a surface-modified silica powder with internal pores was obtained in the same manner as in Example 1, except that sample A was changed to sample D, the surface treatment agent was changed to PDMS and aminosilane B, and the treatment temperature and time were changed as described in Table 1.

[0079] [Example 10] As shown in Table 1, surface-modified silica powder having internal pores was obtained in the same manner as in Example 1, except that the surface treatment agents were changed to alkylsilane, aminosilane A, and aminosilane B, and the treatment temperature and time were changed as described in Table 1.

[0080] [Example 11] As shown in Table 1, a surface-modified silica powder having internal pores was obtained in the same manner as in Example 1, except that the surface treatment agents were changed to HMDS and aminosilane A, and the treatment temperature and time were also changed as described in Table 1.

[0081] [Comparative Examples 1-3] As shown in Table 2, sol-gel silica was placed in a reactor in the same manner as in Example 1, and the surface treatment agents shown in Table 2 were introduced under stirring in a nitrogen atmosphere. The surface-treated sol-gel silica was then heat-treated at the treatment temperature and time indicated in Table 2 while continuing to stir.

[0082] [Comparative Examples 4-6] As shown in Table 2, commercially available product b was placed in a reactor as inorganic oxide powder in the same manner as in Example 1. Under a nitrogen atmosphere and stirring, the surface treatment agents shown in Table 2 were introduced, and the silica was heat-treated at the treatment temperature and time indicated in Table 2 while continuing to stir, to obtain surface-treated fumed silica.

[0083] [Comparative Examples 7-9] As shown in Table 2, commercially available product c was placed in a reactor as inorganic oxide powder in the same manner as in Example 1. Under a nitrogen atmosphere and stirring, the surface treatment agents shown in Table 2 were introduced, and the silica was heat-treated at the treatment temperature and time indicated in Table 2 while continuing to stir, to obtain surface-treated fumed silica.

[0084] [Comparative Example 10] As shown in Table 2, commercially available product a was placed in a reactor as inorganic oxide powder in the same manner as in Example 1. Under a nitrogen atmosphere and stirring, the surface treatment agent shown in Table 2 was introduced, and while continuing to stir, heat treatment was performed at the treatment temperature and time described in Table 2 to obtain surface-treated fumed silica.

[0085] [Comparative Example 11] As shown in Table 2, sample B was similarly placed in the reactor, and under a nitrogen atmosphere and stirring, the surface treatment agent shown in Table 1 was introduced. While continuing to stir, the sample was heat-treated at the treatment temperature and time described in Table 2 to obtain surface-treated fumed silica.

[0086] [Comparative Example 12] As shown in Table 2, commercially available product a was similarly placed in a reactor, and under a nitrogen atmosphere and stirring, the surface treatment agent shown in Table 1 was introduced. While continuing to stir, the product was heat-treated at the treatment temperature and time described in Table 2 to obtain surface-treated fumed silica.

[0087] [Comparative Example 13] As shown in Table 2, sample C was placed in a reactor, and under a nitrogen atmosphere and stirring, the surface treatment agents shown in Table 2 were added. The sample was then heat-treated at the treatment temperature and time indicated in Table 2 while continuing to stir, to obtain surface-treated fumed silica.

[0088] [Comparative Example 14] As shown in Table 2, when the sample, processing temperature, time, etc. were changed, sufficient surface treatment was not performed, and it was not possible to obtain a dry powder.

[0089] [Test Example 1] The following physical properties were measured for the surface-modified silica powder obtained in each example and comparative example. The results are shown in Tables 1 and 2.

[0090] (1) Bulk density Place the graduated cylinder on a balance scale, remove the tare weight, place the sample in the graduated cylinder and weigh it (mass A), then read the volume after standing for 2 minutes (volume B). Calculate the bulk density using the following formula. Bulk density (g / L) = (mass A / volume B) × 1000

[0091] (2) Hydrophobicity 1 g of surface-modified silica powder was weighed into a 200 mL separatory funnel, 100 mL of pure water was added, the funnel was stoppered, and the mixture was shaken in a turbler mixer at 90 rpm for 10 minutes. After shaking, it was allowed to stand for another 10 minutes, and then 20-30 mL of the lower layer was withdrawn from the funnel. The lower layer mixture was then divided into a 10 mm quartz cell, and pure water was used as a blank. The mixture was subjected to a colorimeter test, and the light transmittance (%) at a wavelength of 500 nm was defined as the hydrophobicity. A higher light transmittance indicates higher hydrophobicity. This is because highly hydrophobic surface-modified inorganic oxide powders tend to float on the water surface without dispersing, thus reducing water turbidity and increasing light transmittance.

[0092] (3) Measurement of water adsorption Surface-modified silica powder was heated under vacuum at 150°C for more than 2 hours and thoroughly dried. Then, it was measured using a high-precision gas adsorption measurement device (product name "BELSORP-max," manufactured by Microtrac-Bel Co., Ltd.) under the conditions of an exhaust time of 15 minutes and a pressure rise allowance of 5,000E-1 Pa / min. The adsorption isotherm was analyzed, and the value within the range of 0.8 to 0.95 for relative water vapor pressure was defined as the amount of water adsorbed.

[0093] (4) BET specific surface area BET{Surface area(m 2 The specific surface area ( / g) was determined using a fully automated specific surface area analyzer (product name "Macsorb," manufactured by Mountec). After pre-treating the sample at 100°C for 10 minutes, the surface area of ​​the sample was determined from the amount of nitrogen adsorbed and desorbed using the BET one-point method, and the specific surface area was calculated by dividing it by the weight.

[0094] (5) Carbon content The carbon content was measured using a carbon analyzer (product name "SUMIGRAPH NC-22," manufactured by Sumika Analysis Center).

[0095] (6) Triboelectric charge 2 g of surface-modified silica powder and 48 g of iron powder carrier were placed in a glass container (capacity 75 mL), shaken in a turbler mixer for 10 minutes, and then 0.05 g of the mixture was taken and the amount of triboelectric charge was measured using a suction blow-off type Q / M meter (product name "MODEL 230TO", Trek Japan Co., Ltd.).

[0096] (7) Particle size distribution measurement Measurements were performed using a laser diffraction particle size distribution analyzer (product name "LA-920," manufactured by Horiba, Ltd.). Ethanol was used as the dispersion medium, and after adding the sample, measurements were taken under dispersion conditions of circulation intensity: 10, ultrasonic intensity: 7, and ultrasonic irradiation time: 3 minutes. The aggregated particle size was defined as the range of the particle size distribution within the arithmetic mean diameter.

[0097] [Test Example 2] Toner samples for dispersibility evaluation were prepared by mixing the surface-modified silica powder obtained in each example and comparative example with a commercially available positively charged polyester toner matrix (binding resin) powder manufactured by polymerization in a weight ratio of 99:1, pre-mixing at 600 rpm for 1 minute using a Henschel mixer, and then mixing at 3000 rpm for 30 minutes. Next, the obtained toner sample was observed using a scanning electron microscope (SEM) to examine the surface of the toner sample particles at 1 μm. 2 The number of surface-modified silica particles with a particle size of 0.1 μm or larger attached to a single surface was measured. The results are shown in Table 1. The measurement was performed by arbitrarily selecting one toner matrix (toner particle) within the SEM field of view, and setting the field of view S to be filled with the surface of the toner particle 10 and to include as many surface-modified silica particles 11 as possible, as shown in Figure 3. After measuring the total number of surface-modified silica particles 11 within the field of view S, the number was divided by the field of view area to obtain the number of particles per unit area (1 μm). 2The number of surface-modified silica particles (the "winning" particles) was calculated. In this case, any surface-modified silica particles that extend even slightly beyond the field of view S are not counted.

[0098] [Test Example 3] The particle size distribution of each powder obtained in Examples 3, 6, and 9, and Comparative Examples 1, 5, and 8 was investigated. The particle size distribution was determined using the same method as described in "(7) Particle Size Distribution Measurement" above. The results are shown in Figures 1 and 2.

[0099] [Table 1]

[0100] [Table 2]

[0101] As is clear from the results in Tables 1 and 2 and Figures 1 and 2, the powders in the examples satisfy all the characteristics defined in the present invention. In particular, they are submicron-sized powders with a low bulk density of 22 to 95 g / L while possessing appropriate electrostatic properties (positive charge of 35 to 285 μC / g).

Claims

1. The powder comprises fumed silica particles having internal voids, an organosilicon compound coating the surface of the particles, and a positive charge imparting agent, wherein the organosilicon compound is at least one of hexamethyldisilazane, polydimethylsiloxane, dimethyldimethoxysilane, isobutyltrimethoxysilane, octyltrimethoxysilane, and hexadecyltrimethoxysilane, and has the following physical properties: (1) Average particle size: 0.1 to 1 μm, (2) Bulk density: 20-100 g / L (3) Hydrophobicity: 60% or more, (4) Amount of water adsorption at a relative water vapor pressure of 0.8 to 0.95: 2 to 5%, (5) BET specific surface area: 25~150m² ２ / g、 (6) Carbon content: 0.5 to 8% by weight, (7) Nitrogen content: 0.1 to 0.75% by weight and (8) Triboelectric charge: 20-300 μC / g A surface-modified inorganic oxide powder exhibiting positive charge properties, characterized by the following:

2. The surface-modified inorganic oxide powder according to claim 1, wherein the positive charge imparting agent is at least one of aminosilane and amino group-modified silicone oil.

3. The BET specific surface area of ​​fumed silica particles is 100-250 m². ２ The surface-modified inorganic oxide powder according to claim 1, wherein the amount is / g.

4. An external additive for toner or powder coating, comprising the surface-modifying inorganic oxide powder described in any one of claims 1 to 3.

5. An electrophotographic toner composition or powder coating composition comprising the external additive described in claim 4 and binding resin particles.

6. A method for producing the surface-modified inorganic oxide powder described in claim 1, (a) A step of preparing a mixture comprising fumed silica particles having internal voids, an organosilicon compound having a viscosity (25°C) of 10 to 300 cs, which is at least one of hexamethyldisilazane, polydimethylsiloxane, monomethyltrimethoxysilane, dimethyldimethoxysilane, isobutyltrimethoxysilane, octyltrimethoxysilane, and hexadecyltrimethoxysilane, and a positive charge imparting agent. (b) A step of heat-treating the mixture at a temperature of 100 to 270°C. A method for producing surface-modified inorganic oxide powder, characterized by containing the following:

7. The manufacturing method according to claim 6, wherein steps (a) and (b) above are carried out under stirring.

Images