Surface-modified inorganic oxide powder and process 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] The present 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 an organic substance, it is possible to modify the chargeability, hydrophobicity, etc. of the powder surface. The surface-modified inorganic oxide powders obtained in this manner are widely used as flowability improvers and chargeability adjusters for toners used in electrophotography, including copiers, laser printers, and plain paper facsimiles. Such surface-modified inorganic oxide powders used for toner applications are known as so-called external additives.

[0003] External additives are classified as positively or negatively chargeable depending on the chargeability of the toner. If the toner is positively chargeable, a positively chargeable external additive is used, and if the toner is negatively chargeable, a negatively chargeable external additive is used. OPC (organic photoconductor) drums are primarily used in digital color printers, color copiers, and other devices, and negatively chargeable toner is often used, which in turn requires negatively chargeable external additives. However, OPC drums have problems with durability and environmental friendliness, and amorphous silicon photoconductor drums are also used to address these issues. In systems using these drums, positively chargeable toner is used, which in turn requires positively chargeable external additives.

[0004] The surface treatment agents used for inorganic oxide powders for such applications are mainly organosilicon compounds such as dimethyldichlorosilane, hexamethyldisilazane, and silicone oil. In addition, aminosilane, amine, or the like is used in combination with these as a positive charge imparting agent, whereby silanol groups on the particle surfaces of the inorganic oxide powder are replaced with organic groups, thereby providing hydrophobicity and positive charging.

[0005] Toner is stirred in a device such as a copier and becomes electrically charged (i.e., electrified) through friction with the carrier, etc. This highly controlled chargeability allows the toner to exhibit its developing function. However, if the toner continues to be stirred in the device for a long time, the strong frictional force becomes stressful, causing the toner to deteriorate. For example, if external additives become embedded in the toner surface, they lose their function as a contact point between the toner surface and the external environment. Moreover, the mechanical stress on toner has increased in recent years, and the hardness of the toner matrix has decreased due to the softening design of the binder resin (toner matrix resin) that makes up the toner, making the external additives more likely to become embedded. For this reason, measures to prevent the embedding of external additives as described above are becoming increasingly important.

[0006] In particular, in recent years, the improvement in image quality in electrophotography has led to the advancement of smaller toner particle diameters, and in addition, the shift to higher speeds and color printing has placed greater mechanical stress on toner. Therefore, the durability of toner performance over time (control of degradation behavior) is becoming increasingly important. At the same time, however, low-temperature fixability is required for the binder resins used in toners in order to reduce print standby times and save energy. For these reasons, the use of softer, lower-melting-point components as toner base resins is becoming mainstream.

[0007] As the melting point of toner resins has been lowered, surface-treated fumed oxides have become embedded in the toner resin during long-term operation, reducing its fluidity. To improve the durability of the toner, a submicron-sized silica powder has been added to the toner surface together with the fumed oxides, and this submicron-sized silica powder exerts a spacer effect, preventing the fumed oxides from becoming embedded in the toner. This submicron-sized silica is mainly produced by the sol-gel method (see Patent Document 1, etc.).

[0008] However, silica powder produced by the sol-gel method has a problem in that it has poor charging properties, which is thought to be due in part to the high amount of water adsorbed by the particles that make up the silica powder produced by the sol-gel method.

[0009] Furthermore, the silica powder produced by the sol-gel method has a particle shape that is nearly spherical, and therefore has the problem of being easily separated from the toner surface after long-term use.

[0010] Furthermore, silica powder produced by the sol-gel method tends to retain or adsorb a large amount of water, making it difficult to obtain strong triboelectric charging properties. Therefore, in order to adjust the charge, such as in toner, the low charging properties must be improved.

[0011] In contrast, silica powder produced by the dry method or the gas phase method (hereinafter, both are collectively referred to as the "fumed method") has a particle shape that is less spherical than silica produced by the sol-gel method, and is therefore expected to suppress the problem of liberation from the toner surface, which is a problem with sol-gel silica. However, silica powder produced by the fumed method generally has a small primary particle size and is dispersed on the toner surface as particles of submicron size or less, which means that the spacer effect cannot be fully exerted. In addition, the charge characteristics are generally too high, so that the amount added and dispersibility must be precisely controlled to control the charge characteristics of the toner within an appropriate range. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-249215 Summary of the Invention [Problem to be solved by the invention]

[0013] For the reasons mentioned above, there is a strong demand for the development of external additives (particles) for toner that are submicron in size, which allows for sufficient spacer effect, yet have appropriate charging properties; however, such materials have not yet been developed.

[0014] Therefore, a main object of the present invention is to provide a powder that utilizes the excellent properties of inorganic oxide powder produced by the fumed method, while also having a good spacer effect and suitable charging properties. [Means for solving the problem]

[0015] As a result of extensive research conducted in light of the problems of the prior art, the present inventors discovered that the above object can be achieved by employing particles having specific structures and properties as external additives, and thus completed the present invention.

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

[0017] According to the present invention, it is possible to provide a powder that utilizes the excellent properties of inorganic oxide powder produced by the fumed method while also having a good spacer effect and appropriate charging properties. In particular, inorganic oxide particles produced by a dry method (fumed method or gas phase method) have unique internal pores, and by subjecting the surfaces of such particles to the surface modification specified by the present invention, the bulk density, water adsorption capacity, and other properties become unique, making it possible to provide a submicron-sized powder that has appropriate charging properties (positive charging) despite its low bulk density.

[0018] More specifically, the surface-modified inorganic oxide powder of the present invention is prepared by surface-modifying an inorganic oxide powder having internal pores with a specific organosilicon compound, thereby controlling the properties such as bulk density, hydrophobicity, water adsorption, surface area, and carbon content within certain ranges. As a result, the powder exhibits higher charging characteristics than particles produced by the sol-gel method, and is also capable of achieving sufficient cohesion to exhibit a spacer effect that cannot be obtained with silicon oxide powder produced by the conventional fumed method.

[0019] As described above, in order to solve the problems associated with surface-treated sol-gel silica produced by a wet method, the present invention has succeeded in providing a surface-modified inorganic oxide powder that combines high charging properties and low bulk density, which have been difficult to achieve with sol-gel silica, by surface-treating an inorganic oxide powder having internal pores produced by a dry method, thereby improving problems such as reduced toner fluidity that accompany toners that reduce environmental impact.

[0020] The powder of the present invention, which has these characteristics, can be particularly suitably used as an external additive for toners or powder coatings. Therefore, electrophotographic toner compositions or powder coating compositions containing the surface-modified inorganic oxide powder of the present invention, because they contain the surface-modified inorganic oxide powder with such high fixation rate and high hydrophobicity, have excellent fluidity and antistatic properties, suppress fogging or cleaning defects, and are less likely to cause adhesion of toner to the photoreceptor, resulting in less image defects. Furthermore, the composition of the present invention also provides effects such as long-term storage stability and control of developer deterioration behavior. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a particle size distribution diagram of the powder obtained in the examples. [Figure 2] FIG. 2 is a particle size distribution diagram of the powder obtained in the comparative example. [Figure 3] 10 is a schematic diagram of a method for observing toner particles with an SEM in Test Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

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

[0023] <Configuration (composition) of the powder of the present invention> The particles constituting the powder of the present invention include inorganic oxide particles and an organosilicon compound that coats the particle surface. That is, the powder has a basic structure in which an inorganic oxide particle is used as a core particle (base particle), and the surface of the core particle is partially or entirely coated with an organosilicon compound.

[0024] The inorganic oxide particles that serve as core particles are not limited to specific types, and examples thereof include, but are not limited to, silicon oxide, titanium oxide, and aluminum oxide. Among these, silicon oxide (silica) is preferably used in the present invention. These particles themselves can be publicly known or commercially available.

[0025] The particle size of the inorganic oxide particles is not limited, but usually the primary particle size is about 5 to 150 nm. The BET specific surface area of ​​the inorganic oxide is usually 30 to 400 m 2 / g, but is not limited to this.

[0026] In addition, the inorganic oxide particles are preferably produced by a fumed process, using powder. The fumed process is a well-known process, and fumed silica can be synthesized, for example, by a process including a step of introducing a silicon compound (such as silicon tetrachloride) or metallic silicon into an oxygen-hydrogen flame to cause a hydrolysis reaction. As mentioned above, such powder has a particle shape that is less spherical than silica produced by the sol-gel process, and therefore has the advantage of being able to effectively suppress liberation from the toner surface. Another advantage is that, because no solvent is used, aggregated particles are not formed during drying.

[0027] Such inorganic oxide particles produced by the fumed method may be publicly known or commercially available. For example, commercially available products shown in the examples below may also be suitably used.

[0028] As the organosilicon compound for coating the surface of the inorganic oxide particles, for example, known or commercially available compounds known as hydrophobic treatment agents can be used.

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

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

[0031] In particular, the alkylalkoxysilane compound is not particularly limited as long as it is an alkoxysilane 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 is preferably C2 to C16. If the number of carbon atoms is less than C2, the alkoxysilane may volatilize during surface treatment. If the number of carbon atoms exceeds C16, the high viscosity may cause strong aggregation, which may impair the dispersibility of the resulting powder.

[0032] In particular, as the silicone oil, in addition to polydimethylsiloxane, modified silicone oils into which alkyl groups, -OH groups, etc. have been introduced can also be used.

[0033] The viscosity range of the organosilicon compound (measured at 25°C) is not particularly limited, but is generally preferably 10 to 300 cs. If the viscosity is less than 10 cs, low-molecular-weight polysiloxanes and the like will volatilize during surface treatment, which is undesirable from the standpoints of energy efficiency and the environment. 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 the organosilicon compound in the powder of the present invention is not particularly limited as long as it is within the above-mentioned carbon content range, but it is generally about 5 to 20 parts by weight, and preferably 10 to 15 parts by weight, per 100 parts by weight of the inorganic oxide powder.

[0035] In addition, when an organosilicon compound having an amino group is included as the organosilicon compound, the content of the organosilicon compound does not include the content of the organosilicon compound having the amino group.

[0036] The positive charge imparting agent is not particularly limited as long as it can modify the inorganic oxide particles to have positive chargeability, but in the present invention, at least one of aminosilane and amino group-modified silicone oil can be preferably used. The amino group in these compounds may be any of primary, secondary, and 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. Known or commercially available aminosilanes can also be used.

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

[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 above-mentioned nitrogen content range, but it is usually about 0.5 to 30 parts by weight, and particularly 1 to 20 parts by weight, per 100 parts by weight of the inorganic oxide powder.

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

[0041] Average particle size The average particle size is usually about 0.1 to 1 μm, and preferably 0.2 to 0.8 μm. By having a particle size within this range, the function as a spacer can be effectively fulfilled. The average particle size in the present invention refers to a value (arithmetic mean diameter (volume standard)) calculated using a particle size distribution measuring device (laser diffraction scattering particle size distribution measuring device (manufactured by Horiba, Ltd.)).

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

[0043] Hydrophobicity rate The hydrophobicity is usually about 60% or more, and preferably 80% or more. It is even more preferably 97% or more, and most preferably 99% or more. The hydrophobicity in the present invention is an index showing the degree of hydrophobicity of the surface-modified inorganic oxide powder. If the hydrophobicity is less than 60%, the strong positive chargeability due to the amino groups present in the silica powder cannot be expressed, and a submicron-sized powder with excellent chargeability may not be obtained. The upper limit of the hydrophobicity is not particularly limited, but is usually 100%.

[0044] Water adsorption amount The water adsorption amount at a water vapor relative pressure of 0.8 to 0.95 is usually about 2 to 5 wt%, and preferably 2.5 to 4.0 wt%. Therefore, it can be set to, for example, 3 to 5 wt%. The water adsorption amount significantly affects charging characteristics, and by setting it within the above range, it is possible to impart appropriate charging characteristics. If the water adsorption amount is less than 2 wt%, for example, silica powder will exhibit the charging characteristics specific to fumed silica, resulting in an excessively strong positive charge. Furthermore, if the water adsorption amount exceeds 5 wt%, the retained and adsorbed water amount will be similar to that of silica produced by the sol-gel method, making it impossible to exhibit sufficient positive charging characteristics.

[0045] BET specific surface area The BET specific surface area is usually 25 to 150 m 2 / g, especially 50-150m 2 / g, and more preferably 30 to 130m 2 / g. It is more preferable that the BET specific surface area is 25m 2 If the BET specific surface area is less than 150 m / g, the aggregate particle diameter will be too large, resulting in insufficient dispersibility when dispersed in toner. 2 If the amount exceeds 1 / g, the appropriate aggregation diameter is not maintained when dispersed in the toner, and a sufficient spacer effect cannot be exhibited.

[0046] Carbon content The carbon content is typically about 0.5 to 8% by weight, preferably 0.8 to 6.0% by weight. In particular, when the surface treatment agent (hydrophobic treatment 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 indicator of the degree of fixation (fixation amount) of the organic silicon compound, which is the surface treatment agent, to the inorganic oxide powder. If the carbon content is too low, sufficient surface modification is not achieved, sufficient hydrophobicity cannot be achieved, and charging properties, dispersibility, etc. are insufficient. On the other hand, if the carbon content is too high, the organic content is too high, causing particle aggregation, resulting in insufficient fluidity and dispersibility, and even if this powder is used in toner, it will not exhibit a sufficient spacer effect.

[0047] Nitrogen content The nitrogen content is usually 0.1 to 0.75% by weight, and preferably 0.20 to 0.70% by weight. If the nitrogen content is less than 0.1% by weight, the inorganic oxide particle surface is not sufficiently modified with amino groups, making it impossible to impart sufficient positive charging. On the other hand, if the nitrogen content exceeds 0.75% by weight, aggregation of particles occurs, making it impossible to obtain sufficient fluidity and dispersibility, and even if this powder is used in toner, it will not be able to exhibit a sufficient spacer effect.

[0048] Triboelectric charge The triboelectric charge is usually about 20 to 300 μC / g, and preferably 35 to 285 μC / g. If the triboelectric charge approaches zero from 20 μC / g, it becomes difficult to impart a strong positive charging characteristic 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 triboelectric charge exceeds 300 μC / g, the strong triboelectric charge makes it difficult to control the charging 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 it can produce a powder having the above-described constitution and properties. For example, the powder can be suitably produced by a method including: (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 In the mixture preparation step, any method can be used as long as it can coat the surfaces of the particles constituting the inorganic oxide powder with an organosilicon compound, and suitable methods include, for example, a method of mixing the inorganic oxide powder with a vaporized organosilicon compound and / or a positive chargeability-imparting agent while stirring, and a method of spraying the organosilicon compound and / or a positive chargeability-imparting agent onto the inorganic oxide powder while stirring. Thus, it is preferable to mix these components while stirring.

[0051] In this case, the organosilicon compound and / or the positive charge imparting agent can be used in a state of being dissolved or dispersed in a solvent (e.g., an organic solvent 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 imparting agent used.

[0052] In the present invention, water and a catalyst (amine, etc.) can also be appropriately added to the mixture as needed.

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

[0054] The types, amounts, etc. of the organosilicon compound and the positive charge imparting agent can be the same as those explained in "1. Surface-modified inorganic oxide powder" above.

[0055] Heat Treatment Process The heat treatment temperature in the heat treatment step is not limited, but is usually preferably 100 to 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. If the heat treatment temperature is less than 100°C, the surface of the organosilicon compound may not be sufficiently modified, and the desired hydrophobicity may not be obtained.

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

[0057] The heat treatment time should be long enough to fix (adhere) the organic silane compound and the positive charge imparting agent to the surface of each particle constituting the inorganic oxide powder, and can be, for example, about 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 has all of the properties (1) to (8) described above in "1. Surface-modified inorganic oxide powder." Therefore, in addition to the excellent properties of inorganic oxide powders produced by the fumed method, it can also exhibit a good spacer effect and moderate charging properties. Therefore, the powder of the present invention can be suitably used, for example, as an additive (particularly an external additive for toner) for toners, powder coatings, etc. Therefore, the present invention also encompasses an electrophotographic toner composition or powder coating composition containing the powder of the present invention and binder resin particles (hereinafter, both are also collectively referred to as the "composition of the present invention").

[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 limitations on the composition, production 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 preferably about 0.1 to 5.0 wt%. If the content of the powder of the present invention in the composition of the present invention is less than 0.1 wt%, the effect of improving flowability or stabilizing chargeability due to the addition of the powder of the present invention may not be sufficiently obtained. On the other hand, if the content of the powder of the present invention exceeds 5.0 wt%, the powder of the present invention may act independently, which may cause problems, for example, with respect to images and cleaning properties.

[0061] In addition to the binder resin particles, the composition of the present invention may contain, as necessary, for example, a pigment, a charge control agent (charge control agent), wax, etc. These components may be the same as those in known or commercially available toner compositions. The toner type is preferably a positively charged toner, but is not otherwise particularly limited. Therefore, for example, it may be either a magnetic or non-magnetic one-component toner or a two-component toner. Furthermore, it may be either monochrome or color.

[0062] The powder of the present invention has particularly excellent spacer effect, and therefore can be suitably used as an external additive for adhesive resin particles containing a resin component that is easily softened (e.g., at least one of styrene-acrylic copolymer resin, polyester resin, epoxy resin, etc.).

[0063] In the toner composition for electrophotography 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. [Example]

[0064] The features of the present invention will be described in more detail below with reference to examples and comparative examples, but the scope of the present invention is not limited to these examples.

[0065] The components used in each of the examples and comparative examples are as follows.

[0066] (A) Silica powder (A1) Sol-gel silica The sample (BET specific surface area 30 m) produced by a known sol-gel method 2 / g) (A2) Sample A A sample with internal pores (BET specific surface area 110 m) produced by a known fumed method 2 / g) (A3) Sample B A sample with internal pores (BET specific surface area 120 m) produced by a known fumed method 2 / g) (A4) Commercially available product a Product name: AEROSIL TT600 (registered trademark) manufactured by Nippon Aerosil Co., Ltd. (fumed silica, BET specific surface area 135 m 2 / g) (A5) Sample C A sample with internal porosity (BET specific surface area 165 m) produced by a known fumed method 2 / g) (A6) Sample D A sample with internal pores (BET specific surface area 210 m) produced by a known fumed method 2 / g) (A7) Commercially available product b Product name: "AEROSIL 50" (registered trademark) manufactured by Nippon Aerosil Co., Ltd. (fumed silica, BET specific surface area 50 m 2 / g) (A8) Commercially available product c Product name: "AEROSIL 200" (registered trademark) manufactured by Nippon Aerosil Co., Ltd. (fumed silica, BET specific surface area 200 m 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 (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 (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 had internal pores and was produced by a dry method, was placed in a reactor, and alkylsilane and aminosilane B were added in predetermined amounts under stirring in a nitrogen atmosphere. With continued stirring, the mixture was heat-treated at 120°C for 120 minutes to obtain a surface-modified silica powder with internal pores.

[0071] [Example 2] As shown in Table 1, Sample A having internal voids and produced by a dry method was changed to Sample B, the surface treatment agent was changed to PDMS and aminosilane A, and the treatment temperature and time were changed as shown in Table 1. Except for this, a surface-modified silica powder having internal voids was obtained in the same manner as in Example 1.

[0072] [Example 3] As shown in Table 1, sample A was replaced with commercially available product a, the surface treatment agent was replaced with HMDS, aminosilane A, and aminosilane B, and the treatment temperature and time were changed as shown in Table 1. Except for this, a surface-modified silica powder having internal pores was obtained in the same manner as in Example 1.

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

[0074] [Example 5] As shown in Table 1, sample A was replaced with commercially available product a, the surface treatment agent was replaced with HMDS, PMDS, and aminosilane A, and the treatment temperature and time were changed as shown in Table 1. Except for this, a surface-modified silica powder having internal pores was obtained in the same manner as in Example 1.

[0075] [Example 6] As shown in Table 1, sample A was changed to sample C, the surface treatment agent was changed to PDMS, aminosilane A, and aminosilane B, and the treatment temperature and time were changed as shown in Table 1. Except for this, a surface-modified silica powder having internal pores was obtained in the same manner as in Example 1.

[0076] [Example 7] 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 Sample A was changed to Sample C, the surface treatment agent was 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, sample A was replaced with sample D, the surface treatment agent was changed to alkylsilane and aminosilane A, and the treatment temperature and time were changed as shown in Table 1. Except for this, a surface-modified silica powder having internal pores was obtained in the same manner as in Example 1.

[0078] [Example 9] As shown in Table 1, 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 shown in Table 1. Except for this, a surface-modified silica powder having internal pores was obtained in the same manner as in Example 1.

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

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

[0081] [Comparative Examples 1 to 3] As shown in Table 2, the sol-gel silica was placed in a reactor in the same manner as in Example 1, and a surface treatment agent shown in Table 2 was added thereto under stirring in a nitrogen atmosphere. With stirring continued, the mixture was heat-treated at the treatment temperature and for the time shown in Table 2 to obtain surface-treated sol-gel silica.

[0082] [Comparative Examples 4 to 6] As shown in Table 2, commercially available product b was placed in a reactor as an inorganic oxide powder in the same manner as in Example 1, and a surface treatment agent shown in Table 2 was added thereto under stirring in a nitrogen atmosphere. With stirring continued, the mixture was heat-treated at the treatment temperature and for the time shown in Table 2 to obtain surface-treated fumed silica.

[0083] [Comparative Examples 7 to 9] As shown in Table 2, commercially available product c was placed in a reactor as an inorganic oxide powder in the same manner as in Example 1, and a surface treatment agent shown in Table 2 was added thereto under stirring in a nitrogen atmosphere. With stirring being continued, the mixture was heat-treated at the treatment temperature and for the time shown in Table 2 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 an inorganic oxide powder in the same manner as in Example 1, and a surface treatment agent shown in Table 2 was added thereto under stirring in a nitrogen atmosphere. With stirring continued, the mixture was heat-treated at the treatment temperature and for the time shown in Table 2 to obtain surface-treated fumed silica.

[0085] [Comparative Example 11] As shown in Table 2, Sample B was similarly placed in a reactor, and under stirring in a nitrogen atmosphere, a surface treatment agent shown in Table 1 was added thereto. With stirring being continued, the mixture was heat-treated at the treatment temperature and for the time shown in Table 2 to obtain surface-treated fumed silica.

[0086] [Comparative Example 12] As shown in Table 2, commercially available product a was placed in a reactor in the same manner, and a surface treatment agent shown in Table 1 was added thereto under stirring in a nitrogen atmosphere. With stirring continued, the mixture was heat-treated at the treatment temperature and for the time shown 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 stirring in a nitrogen atmosphere, a surface treatment agent shown in Table 2 was added, and while continuing to stir, heat treatment was carried out at the treatment temperature and time shown in Table 2 to obtain surface-treated fumed silica.

[0088] [Comparative Example 14] As shown in Table 2, when the sample, treatment temperature, time, etc. were changed, sufficient surface treatment was not achieved and dry powder could not be obtained.

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

[0090] (1) Bulk density Place the measuring cylinder on a top-loading balance, erase the tare, add the sample to the measuring cylinder, measure the mass (mass A), and read the volume (volume B) after leaving it to stand for 2 minutes. Calculate the bulk density using the following formula: Bulk density (g / L) = (mass A / volume B) x 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, and the funnel was then capped and shaken at 90 rpm in a Turbula mixer for 10 minutes. After shaking and leaving the funnel to stand for another 10 minutes, 20-30 mL of the lower layer was removed from the funnel, and the lower layer mixture was then dispensed into a 10 mm quartz cell. Using pure water as a blank, the colorimeter measured the light transmittance (%) at a wavelength of 500 nm, which was then used as the hydrophobicity index. Higher light transmittance indicates higher hydrophobicity. This is because highly hydrophobic surface-modified inorganic oxide powders tend to float on the surface of water without dispersing, which reduces the likelihood of the water becoming cloudy and increases light transmittance.

[0092] (3) Water adsorption measurement The surface-modified silica powder was heated under vacuum at 150°C for at least two hours and thoroughly dried. After that, it was measured using a high-precision gas adsorption measuring device (product name "BELSORP-max" manufactured by Microtrac-Bell Corporation) under conditions of a 15-minute evacuation time and a pressure rise tolerance of 5,000E-1 Pa / min. The adsorption isotherm was analyzed, and the value within the water vapor relative pressure range of 0.8 to 0.95 was taken as the water adsorption amount.

[0093] (4) BET specific surface area BET{Surface area(m 2 / g)} was determined by using a fully automatic specific surface area measuring device (product name "Macsorb" manufactured by Mountec) to pretreat the sample at 100°C for 10 minutes, then determining the surface area of ​​the sample from the amount of nitrogen adsorbed and desorbed by the BET single-point method, and dividing this by the weight to determine the specific surface area.

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

[0095] (6) Frictional electrification 2 g of surface-modified silica powder and 48 g of iron powder carrier were placed in a glass container (75 mL capacity) and shaken for 10 minutes using a Turbula mixer. 0.05 g of the mixture was then sampled 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 carried out 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 carried out under dispersion conditions of circulation intensity: 10, ultrasonic intensity: 7, and ultrasonic irradiation time: 3 minutes. The range of particle size distribution within the arithmetic mean diameter was taken as the agglomerated particle diameter.

[0097] [Test Example 2] The surface-modified silica powder obtained in each example and comparative example was mixed with a commercially available positively charged polyester toner base (binding resin) powder produced by a polymerization method in a weight ratio of 99:1, and the mixture was premixed in a Henschel mixer at 600 rpm for 1 minute, followed by mixing at 3000 rpm for 30 minutes to prepare a toner sample for dispersibility evaluation. Next, the obtained toner sample was observed with a scanning electron microscope (SEM) to determine whether the toner sample particle surface was 1 μm 2 The number of surface-modified silica particles with a particle size of 0.1 μm or more adhering per unit area was counted. The results are also shown in Table 1. The measurement was carried out by arbitrarily selecting one toner base (toner particle) within the field of view of the SEM, and setting the field of view S as shown in FIG. 3 so that it was filled with the surfaces of the toner particles 10 and contained as many surface-modified silica particles 11 as possible. After counting all the surface-modified silica particles 11 within the field of view S, the number was divided by the area of ​​the field of view to obtain the number of surface-modified silica particles per unit area (1 μm 2The number of surface-modified silica particles (per particle) was calculated. In this case, any surface-modified silica particles that protrude even slightly from the field of view S were not counted.

[0098] [Test Example 3] The particle size distribution of each of the powders obtained in Examples 3, 6, and 9 and Comparative Examples 1, 5, and 8 was investigated. The particle size distribution was measured in the same manner as described above in "(7) Particle size distribution measurement." 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 of the examples satisfy all of the properties specified in the present invention. In particular, they are submicron-sized powders with appropriate charging properties (positive charging of 35 to 285 μC / g) despite having a low bulk density of 22 to 95 g / L.

Claims

1. A powder comprising particles containing fumed silica particles having internal voids, an organosilicon compound that coats the surfaces 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 the powder has 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) Water adsorption amount at a water vapor relative 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 wt.%; and (8) Triboelectric charge amount: 20 to 300 μC / g A surface-modified inorganic oxide powder exhibiting positive charging properties, characterized in that:

2. 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 ​​the fumed silica particles is 100 to 250 m ２ The surface-modified inorganic oxide powder according to claim 1, wherein the surface-modified inorganic oxide powder has a surface-modified SiO 2 content of SiO 2 / g.

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

5. 5. A toner composition or powder coating composition for electrophotography, comprising the external additive according to claim 4 and binder resin particles.

6. 2. A method for producing the surface-modified inorganic oxide powder of claim 1, comprising: (a) preparing a mixture containing 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 chargeability-imparting agent; (b) heat-treating the mixture at a temperature of 100 to 270°C A method for producing a surface-modified inorganic oxide powder, comprising:

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

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