Surface-modified inorganic oxide powder and its manufacturing method

Abstract

To provide a surface-modified inorganic oxide powder which has high hydrophobicity and has high fluidity in which the charge amount is controlled within a predetermined range.SOLUTION: There is provided a surface-modified inorganic oxide powder which is a powder comprising particles containing inorganic oxide particles and a layer containing a reactive silicone oil and a non-reactive silicone oil formed on the particle surface, wherein (1) the carbon content (wt.%) in the powder is 3.0 to 8.0 wt.%, (2) a value obtained by dividing the carbon content by the specific surface area of the inorganic oxide particles is 1.6 to 3.4%, (3) the hydrophobicity rate is 50% or more, (3) the charge amount is -170 to -310 μC / g and (4) the free oil content is 3 wt.% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a 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] Conventionally, organic silicon compounds such as dimethyldichlorosilane, hexamethyldisilazane, and silicone oil have been used as surface treatment agents for inorganic oxide powders. Surface treatment with these organic silicon compounds is carried out to hydrophobize the silica fine particle surface by substituting silanol groups with organic groups, for example.

[0004] Among these organosilicon compounds, silicone oil is used to treat the surface of inorganic oxide powders, and products with silicone oil exhibit sufficient hydrophobicity, and when used as an external toner additive, they exhibit good cleaning properties, so silicone oil is known as a good surface treatment agent. For this reason, external additives using non-reactive silicone oil as a surface treatment agent have also been proposed (for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2014-162681 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0006] However, when silicone oil-treated products are used, there is a problem in that the fluidity of the toner powder to which it is externally added is significantly impaired compared to toner powders that use external additives that have been surface-treated with other surface treatment agents (such as hexamethyldisilane).

[0007] Furthermore, when silicone oil is used as a surface treatment agent, the chargeability tends to be highly negative, making it difficult to control the chargeability.

[0008] Therefore, a main object of the present invention is to provide a surface-modified inorganic oxide powder that is highly hydrophobic, has high flowability, and has a charge amount controlled within a predetermined range. [Means for solving the problem]

[0009] As a result of extensive research into the problems of the prior art, the inventors discovered that the above object can be achieved by applying a specific silicone oil to an inorganic oxide powder so as to achieve a specific fixation rate, and thus completed the present invention.

[0010] That is, the present invention relates to the following surface-modified inorganic oxide powder and a method for producing the same. 1. A powder comprising particles including inorganic oxide particles and a layer containing reactive silicone oil and non-reactive silicone oil formed on the surface of the particles, (1) The carbon content (wt%) in the powder is 3.0 to 8.0 wt%, (2) the value obtained by dividing the carbon content by the specific surface area of ​​the inorganic oxide particles is 1.6 to 3.4%; (3) The hydrophobicity rate is 50% or more, (3) The charge amount is -170 to -310 μC / g, (4) The free oil content is 3% by weight or less. A surface-modified inorganic oxide powder characterized by: 2. The surface-modified inorganic oxide powder according to item 1, wherein the inorganic oxide powder is fumed silica. 3. The surface-treated inorganic oxide powder according to item 1 or 2, wherein the value of the fluidity energy value measured by a dry fluidity evaluation method when added to a toner divided by the energy value before addition is 0.25 or less. 4. The surface-modified inorganic oxide powder according to any one of items 1 to 3, wherein the reactive silicone oil has OH groups at both ends of the main chain consisting of siloxane bonds and has a kinematic viscosity of 10 to 200 cs. 5. The surface-modified inorganic oxide powder according to any one of items 1 to 4, wherein the non-reactive silicone oil has a kinematic viscosity of 10 to 200 cs. 6. The surface-modified inorganic oxide powder according to any one of items 1 to 5, wherein the weight ratio of the non-reactive silicone oil to the reactive silicone oil is 1:0.2 to 1:4.0. 7. An external additive for toner or powder coating, comprising the surface-modified inorganic oxide powder according to any one of items 1 to 6. 8. A toner composition or a powder coating composition for electrophotography, comprising the external additive according to item 7 and binder resin particles. 9. A method for producing a surface-modified inorganic oxide powder, comprising: (a) preparing a mixture containing an inorganic oxide powder, a reactive silicone oil, and a non-reactive silicone oil; (b) heat-treating the mixture at a temperature of 80 to 380°C A method for producing a surface-modified inorganic oxide powder, comprising: 10. A method for producing a surface-modified inorganic oxide powder, comprising: (a) preparing a first mixture containing an inorganic oxide powder and a reactive silicone oil; (b) heat-treating the first mixture at a temperature of 80 to 380°C; (c) preparing a second mixture comprising the heat-treated first mixture and a non-reactive silicone oil; (d) heat-treating the second mixture at a temperature of 80 to 380°C; A method for producing a surface-modified inorganic oxide powder, comprising: 11. A method for producing a surface-modified inorganic oxide powder, comprising: (a) preparing a first mixture comprising an inorganic oxide powder and a non-reactive silicone oil; (b) heat-treating the first mixture at a temperature of 80 to 380°C; (c) preparing a second mixture comprising the heat-treated first mixture and a reactive silicone oil; (d) heat-treating the second mixture at a temperature of 80 to 380°C; A method for producing a surface-modified inorganic oxide powder, comprising: [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a surface-modified inorganic oxide powder that is highly hydrophobic, has high fluidity, and has an amount of charge controlled within a predetermined range.

[0012] In particular, the surface-modified inorganic oxide powder of the present invention has specific physical properties due to its surface treatment with both reactive and non-reactive silicone oils, making it industrially more advantageous than conventional products treated only with non-reactive silicone oils as a surface-modified inorganic oxide powder added to powder materials such as powder coatings, electrophotographic toners, and cosmetics for the purposes of improving flowability, preventing caking, and adjusting charge. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1. Surface-modified inorganic oxide powder The surface-modified inorganic oxide powder of the present invention (powder of the present invention) is a powder comprising particles including inorganic oxide particles and a layer containing reactive silicone oil and non-reactive silicone oil formed on the surface of the particles, (1) The carbon content (wt%) in the powder is 3.0 to 8.0 wt%, (2) The carbon content is calculated based on the specific surface area (m 2 / g) is 1.6 to 3.4%, (3) The hydrophobicity rate is 50% or more, (3) The charge amount is -170 to -310 μC / g, (4) The free oil content is 3% by weight or less. It is characterized by:

[0014] <Configuration (composition) of the powder of the present invention> The particles constituting the powder of the present invention include inorganic oxide particles and a layer containing reactive silicone oil and non-reactive silicone oil formed on the surface of the particles (hereinafter also referred to as a "silicone oil layer"). That is, the basic structure is a structure (coated particle) in which an inorganic oxide particle is used as a core particle (base particle), and part or all of its surface is coated with a silicone oil-containing layer.

[0015] The inorganic oxide particles that become the core particles are not limited to their type, and examples thereof include, but are not limited to, silicon oxide, titanium oxide, and aluminum oxide. Among these, silicon oxide (silica) (particularly fumed silica) is preferably used in the present invention. These may be used alone or in combination of two or more. These particles themselves may be publicly known or commercially available.

[0016] The particle size of the inorganic oxide particles is not limited, but can usually be selected appropriately from a range of primary particle diameters of about 5 to 150 nm depending on the range of the average particle size of the desired surface-modified inorganic oxide powder.

[0017] In addition, inorganic oxide particles have a specific surface area of ​​100 to 500 m2 as determined by the nitrogen adsorption method (BET). 2 / g, especially 110~400m 2 / g. If the BET specific surface area is too small, the effect as a fluidizing agent will be reduced when added to electrophotographic toner. On the other hand, if the BET specific surface area is too large, the agent will quickly sink into the toner when added to electrophotographic toner, resulting in significant deterioration of performance over time.

[0018] The inorganic oxide particles are preferably produced by a fumed process, using powder. The fumed process is a well-known process that can synthesize silica, for example, by introducing a silicon compound (such as silicon tetrachloride) or metallic silicon into an oxygen-hydrogen flame to cause a hydrolysis reaction. This type of powder has a particle shape that is less spherical than silica produced by a sol-gel process, for example, and therefore has the advantage of being able to effectively prevent separation from the toner surface. Another advantage is that no solvent is used, making it less likely for aggregated particles to form during drying.

[0019] For such inorganic oxide particles produced by the fumed method, commercially available products can be used, for example, the commercially available products shown in the examples below can also be suitably used.

[0020] The silicone oil layer that coats the surface of inorganic oxide particles contains reactive silicone oil and non-reactive silicone oil. In the present invention, the silicone oil layer includes any of the following layer configurations: a) inorganic oxide particles / (a mixed layer containing reactive silicone oil and non-reactive silicone oil), b) inorganic oxide particles / a layer containing reactive silicone oil / a layer containing non-reactive silicone oil, c) inorganic oxide particles / a layer containing non-reactive silicone oil / a layer containing reactive silicone oil, etc.

[0021] The reactive silicone oil is a silicone oil having functional groups at both ends, one end, and at least one side chain of the main chain formed by siloxane bonds. In the present invention, the use of the reactive silicone oil can increase the reactivity of the silicone oil with inorganic oxide particles and increase the fixing rate. The proportion of the reactive silicone oil in the layer can be, for example, about 90 to 100% by weight, but is not limited thereto.

[0022] The main chain (main skeleton) consisting of the siloxane bond is not particularly limited, but poly(dimethylsiloxane) can be particularly preferably used. The functional group is not particularly limited, and examples thereof include at least one of a hydrogen atom, a hydroxyl group, an amino group, a carbinol group, an epoxy group, and a carboxyl group.

[0023] Therefore, modified silicone oils such as amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, methacrylic-modified silicone oil, mercapto-modified silicone oil, phenol-modified silicone oil, both-terminal silanol dimethyl oil, one-terminal reactive modified silicone oil, heterofunctional group-modified silicone oil, polyether-modified silicone oil, higher fatty acid ester-modified silicone oil, hydrophilic special modified silicone oil, higher alkoxy-modified silicone oil, higher fatty acid-containing modified silicone oil, and fluorine-modified silicone oil can be suitably used.

[0024] Among these, reactive silicone oils having at least one type of hydroxyl group as a functional group are preferred, since they can react with OH groups on the surface of inorganic oxide particles to form "Si-O-Si" bonds. By using reactive silicone oils having hydroxyl groups, Si-OH on the particle surface of inorganic oxide particles can react with Si-OH of the reactive silicone oil to form Si-O-Si bonds.

[0025] In particular, in the present invention, at least one of dimethyl oil having silanol groups at both ends and dimethyl hydrogen polysilicone can be preferably used. Therefore, as the dimethyl oil having silanol groups at both ends, for example, a reactive silicone oil represented by the following formula (1) can be preferably used.

[0026] [ka] (However, R 1represents an organic group other than a methyl group. m represents an integer of 1 or more. n represents an integer of 0 or 1 or more. m+n≧1 is satisfied. The above repeating units -(Si(CH3)2-O)- and -(SiR 1 The (CH3)-O)- may be in any of the bond forms of an alternating copolymer, a random copolymer, or a block copolymer.

[0027] As shown in the above formula, a reactive silicone oil can be used that has a siloxane bond -(Si-O)- as a repeating unit and has hydroxyl groups at both ends of the main chain consisting of at least siloxane bonds. Therefore, for example, in the above general formula, a reactive silicone oil that has hydroxyl groups at both ends of a polydimethylsiloxane structure in which m is 1 or more and n is 0 can be preferably used. In other words, a structure in which at least one hydroxyl group is bonded to the silicon atoms at both ends can be preferably used.

[0028] As the dimethylhydrogen polysilicone, for example, a reactive silicone oil having hydrogen atoms in the side chains of the polysiloxane structure, as shown in the following formula (2), can be suitably used.

[0029] [ka] (wherein m represents an integer of 0 or 1 or more, and n represents an integer of 1 or more, satisfying m+n≧1. The repeating units -(Si(CH3)2-O)- and -(SiH(CH3)-O)- may be bonded in any form of an alternating copolymer, a random copolymer, or a block copolymer.)

[0030] These reactive silicone oils may be publicly known or commercially available, and may be used alone or in combination of two or more.

[0031] The kinematic viscosity (measured at 25°C) (hereinafter referred to as "viscosity") of the reactive silicone oil is not particularly limited, but is usually preferably 30 to 100 cs. If the viscosity is less than 30 cs, the low-molecular-weight reactive silicone oil will volatilize during heat treatment, making it difficult to perform sufficient surface treatment, and is also undesirable from an environmental standpoint. On the other hand, if the viscosity exceeds 100 cs, the reactive silicone oil may promote aggregation of the inorganic oxide particles, significantly impairing fluidity.

[0032] The molecular weight range of the reactive silicone oil may be any range as long as it satisfies the above viscosity range, and may be, for example, in the range of about 3000 to 7500, but is not limited to this.

[0033] The content of reactive silicone oil is not particularly limited as long as it is within the above carbon content range, but is generally preferably about 1 to 45 parts by weight per 100 parts by weight of inorganic oxide powder, more preferably 2 to 40 parts by weight, and most preferably 5 to 38 parts by weight. If the content of reactive silicone oil is too low, it is impossible to obtain a surface-modified inorganic oxide powder with a high hydrophobicity. On the other hand, if the content of reactive silicone oil is too high, particle aggregation may occur, which may impair fluidity.

[0034] The non-reactive silicone oil may be any oil that does not have a reactive functional group, and examples thereof include dimethyl silicone oil and the R 1 Examples of non-reactive silicone oils include silicone oils in which the alkyl group is an alkyl group other than a methyl group, an aralkyl group, a polyether group, a fluoroalkyl group, an ester group, a phenyl group, etc. These non-reactive silicone oils themselves can be publicly known or commercially available. In addition, one or more types of non-reactive silicone oils can be used.

[0035] The viscosity of the non-reactive silicone oil (measured at 25°C) is not particularly limited, but is usually preferably 5 to 300 cs. If the viscosity is less than 5 cs, the low-molecular-weight silicone oil will volatilize during heat treatment, making it difficult to perform sufficient surface treatment, and is also undesirable from an environmental standpoint. On the other hand, if the viscosity exceeds 300 cs, the silicone oil may promote aggregation of the inorganic oxide particles, significantly impairing fluidity.

[0036] The molecular weight range of the non-reactive silicone oil may be any range as long as it satisfies the above viscosity range, and may be, for example, in the range of about 850 to 16,000, but is not limited to this.

[0037] The content of the non-reactive silicone oil is not particularly limited as long as it is within the above-mentioned carbon content range, but is generally preferably about 2 to 40 parts by weight per 100 parts by weight of the inorganic oxide powder, more preferably 5 to 30 parts by weight, and most preferably 10 to 25 parts by weight. If the content of the non-reactive silicone oil is too low, it is impossible to obtain a surface-modified inorganic oxide powder with a high hydrophobicity. On the other hand, if the content of the non-reactive silicone oil is too high, particle aggregation may occur, resulting in a loss of fluidity.

[0038] The ratio of non-reactive silicone oil to reactive silicone oil is not particularly limited, but it is particularly desirable that the weight ratio of non-reactive silicone oil to reactive silicone oil is 1:0.2 to 1:4.0. By setting such a ratio, higher fluidity can be obtained and the chargeability can be more reliably controlled within a predetermined range.

[0039] <Characteristics of the powder of the present invention> The characteristics of the powder of the present invention are as follows: (1) The carbon content (wt%) in the powder is 3.0 to 8.0 wt%, (2) The carbon content is calculated based on the specific surface area (m 2 / g) (carbon value) is 1.6 to 3.4%, (3) The hydrophobicity rate is 50% or more, (3) The charge amount is -170 to -310 μC / g, (4) The free oil content is 3% by weight or less. It is characterized by:

[0040] As described above, the carbon content is usually 3.0 to 8.0% by weight, and preferably 3.2 to 7.0% by weight. In the present invention, the carbon content is an index showing the fixed amount of the surface treatment agent, and a carbon content within the above range indicates that the desired surface treatment has been performed.

[0041] The carbon value in the powder of the present invention is usually 1.6 to 3.4%, as described above. If the carbon value is less than 1.6%, the amount of organic matter present on the surface is insufficient to coat the surface of the inorganic powder, and sufficient hydrophobicity or fluidity cannot be achieved. On the other hand, if the carbon value exceeds 3.4%, the amount of organic matter coating the surface becomes excessive, adversely affecting fluidity. Regarding the method of calculating the carbon value, for example, when the carbon content (carbon amount) is 4.6 wt.% and the specific surface area of ​​the inorganic oxide particles is 200 m, 2 / g, it can be calculated as [4.6 / 200]×100=2.3%.

[0042] The hydrophobicity is usually 50% or more, and preferably 55 to 99%. If the hydrophobicity is less than 50%, sufficient chargeability may not be obtained under high temperature and high humidity conditions.

[0043] The charge amount is usually about -170 to -310 μC / g, and preferably 185 to 280 μC / g. If the charge amount approaches zero below -170 μC / g, when the powder is added to a toner, it becomes difficult to impart stable charge characteristics to the toner, and it becomes difficult to control the toner within a predetermined charge amount range. On the other hand, if the charge amount becomes more negative than -310 μC / g, it also becomes difficult to impart stable charge characteristics to the toner to which it is added.

[0044] The free oil content in the powder of the present invention is usually 3% by weight or less. If the free oil content exceeds 3% by weight, sufficient fluidity may not be obtained.

[0045] Furthermore, an index of the ability of the powder of the present invention to impart fluidity to toners and the like is a ratio based on the energy value measured by a powder rheometer. That is, the fluidity energy value measured by a dry fluidity evaluation method when the powder of the present invention is added to toner divided by the energy value before addition is preferably 0.25 or less. By keeping this value 0.25 or less, even higher fluidity can be imparted to toner products to which the powder of the present invention is externally added.

[0046] The average particle size of the powder of the present invention is not particularly limited, but is usually about 5 nm to 18 nm. Therefore, it can be, for example, 6 to 17 nm. The average particle size in the present invention refers to the arithmetic mean value of particle sizes of 1,000 particles randomly selected by observation with a transmission electron microscope (TEM).

[0047] 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-mentioned constitution and properties, but it is preferable to carry out the method by any one of the following first to third methods.

[0048] (1) First method The first method is a method for producing a surface-modified inorganic oxide powder, (a) a step of preparing a mixture containing an inorganic oxide powder, a reactive silicone oil, and a non-reactive silicone oil (mixture preparation step); (b) a step of heat-treating the mixture at a temperature of 80 to 380°C (heat-treatment step) The method is characterized by comprising:

[0049] Mixture preparation process The mixture preparation step is not limited to any method as long as it can coat the surface of each particle constituting the inorganic oxide powder with reactive silicone oil. For example, a method of mixing inorganic oxide powder with vaporized reactive silicone oil and non-reactive silicone oil under stirring, or a method of spraying reactive silicone oil and non-reactive silicone oil onto inorganic oxide powder under stirring, etc. can be suitably employed.

[0050] In this case, the reactive silicone oil or non-reactive silicone oil can be diluted with water or an organic solvent before blending. The organic solvent can be appropriately selected depending on the type of reactive silicone oil or non-reactive silicone oil used, and examples thereof include hexane, toluene, alcohol (aliphatic alcohols having 1 to 8 carbon atoms, such as methanol, ethanol, and propanol), and acetone. The concentration when diluted is not limited, and can be, for example, about 5 to 70% by weight.

[0051] 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.

[0052] The type, amount, etc. of the reactive or non-reactive silicone oil may be the same as those explained in "1. Surface-modified inorganic oxide powder" above.

[0053] Heat Treatment Process The heat treatment temperature in the heat treatment step is not limited, but is usually preferably 80 to 380°C (particularly 280 to 380°C). If the heat treatment temperature exceeds 380°C, partial decomposition of the reactive silicone oil or non-reactive silicone oil occurs, which is undesirable in terms of thermal energy and the environment. On the other hand, if the heat treatment temperature is less than 150°C, the reactive silicone oil or non-reactive silicone oil may not be sufficiently fixed to the inorganic oxide powder, the amount of free oil may increase, and hydrophobicity or fluidity may be reduced.

[0054] 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.

[0055] The heat treatment time should be long enough to fix (adhere) the reactive silicone oil and non-reactive silicone oil to the surface of each particle constituting the inorganic oxide powder, and can be, for example, about 5 to 120 minutes, but is not limited to this.

[0056] (2) Second method The second method is a method for producing a surface-modified inorganic oxide powder, comprising the steps of: (a) preparing a first mixture containing an inorganic oxide powder and a reactive silicone oil; (b) heat-treating the first mixture at a temperature of 80 to 380°C; (c) preparing a second mixture comprising the heat-treated first mixture and a non-reactive silicone oil; (d) heat-treating the second mixture at a temperature of 80 to 380°C; The method is characterized by comprising:

[0057] In the second method, the inorganic oxide powder is first surface-treated with reactive silicone oil and then surface-treated with non-reactive silicone oil.Other than that, the same conditions as in the first method can be used.

[0058] (3) Third method The third method is a method for producing a surface-modified inorganic oxide powder, comprising the steps of: (a) preparing a first mixture comprising an inorganic oxide powder and a non-reactive silicone oil; (b) heat-treating the first mixture at a temperature of 80 to 380°C; (c) preparing a second mixture comprising the heat-treated first mixture and a reactive silicone oil; (d) heat-treating the second mixture at a temperature of 80 to 380°C; The method is characterized by comprising:

[0059] The third method is a method in which the inorganic oxide powder is first surface-treated with a non-reactive silicone oil and then surface-treated with a reactive silicone oil, but other than that, the same conditions as in the first method can be used.

[0060] 3. Use of the powder of the present invention The powder of the present invention can be used as, for example, a flowability improver or a chargeability adjuster in toners used in electrophotography, including copiers, laser printers, and plain paper facsimiles, as well as in powder coatings and cosmetics. In particular, the powder of the present invention can be suitably used as an external additive for toners. Therefore, the present invention also encompasses an electrophotographic toner composition or a 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").

[0061] 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.

[0062] 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 be about 0.01 to 5.0 wt%. If the content of the surface-modified inorganic oxide powder of the present invention in the composition of the present invention is less than 0.01 wt%, the effect of improving flowability or stabilizing chargeability due to the addition of the surface-modified inorganic oxide powder may not be sufficiently obtained. Furthermore, if the content of the surface-modified inorganic oxide powder exceeds 5.0 wt%, the surface-modified inorganic oxide powder may act independently, which may cause problems, for example, with respect to images and cleaning properties.

[0063] The composition of the present invention may contain, in addition to the binder resin particles, for example, pigments, charge control agents (charge control agents), waxes, etc. These components may be the same as those in known or commercially available toner compositions. Furthermore, the toner type is preferably a negatively charged toner. Other aspects are not 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.

[0064] The powder of the present invention can be suitably used as an external additive (external toner additive) for binder resin particles containing at least one of styrene-acrylic copolymer resin, polyester resin, epoxy resin, and the like.

[0065] In the 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 intended use, etc. 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]

[0066] 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.

[0067] The specifications of the fumed silica, reactive silicone oil and non-reactive silicone oil used in each of the examples and comparative examples are as follows:

[0068] <Fumed silica> Fumed silica 380: AEROSIL (registered trademark) 380 (BET specific surface area 380 m) manufactured by Nippon Aerosil Co., Ltd. 2 / g) Fumed silica 300: AEROSIL® 300 (BET specific surface area 300 m), manufactured by Nippon Aerosil Co., Ltd. 2 / g) Fumed silica 200: AEROSIL (registered trademark) 200 (BET specific surface area 200 m), manufactured by Nippon Aerosil Co., Ltd. 2 / g) Fumed silica 130: AEROSIL (registered trademark) 130 (BET specific surface area 130 m), manufactured by Nippon Aerosil Co., Ltd. 2 / g)

[0069] <Reactive silicone oil> DMO-SiOH(A): Reactive silicone oil (viscosity 30cs) with hydroxyl groups at both ends of poly(dimethylsiloxane) DMO-SiOH(B): Reactive silicone oil (viscosity 40cs) with hydroxyl groups at both ends of poly(dimethylsiloxane) DMO-SiOH(C): Reactive silicone oil (viscosity 60cs) with hydroxyl groups at both ends of poly(dimethylsiloxane)

[0070] <Non-reactive silicone oil> PDMS (100cs): Polydimethylsiloxane (viscosity 100cs) PDMS (50cs): Polydimethylsiloxane (viscosity 50cs) PDMS (20cs): Polydimethylsiloxane (viscosity 20cs)

[0071] [Examples 1 to 6] 100 parts by weight of the fumed silica shown in Table 1 was placed in a reactor, and under stirring in a nitrogen gas atmosphere, reactive silicone oil or non-reactive silicone oil shown in Table 1 diluted with hexane was added in the manner and amount shown in Table 1, and surface treatment was carried out while continuing stirring. Finally, in order to break up loose agglomerates of the surface-treated silica, it was crushed using a sample mill (manufactured by Nara Machinery Works, Ltd.). In this way, surface-treated fumed silica was obtained. In Table 1, the "treatment method" symbol A indicates the first method, symbol B indicates the second method, and symbol C indicates the third method. Also, in Table 1, "surface treatment condition 1" indicates the first treatment condition in the two-stage surface treatment, and "surface treatment condition 2" indicates the second treatment condition in the two-stage surface treatment.

[0072] [Comparative Examples 1 to 5] Surface-treated fumed silica was prepared in the same manner as in Example 1, except that the conditions shown in Table 1 were used.

[0073] [Test Example 1] The surface-treated fumed silica obtained in each of the Examples and Comparative Examples was measured for free oil content, hydrophobicity, charge amount, and flowability. The results are shown in Table 1. The average particle size of each surface-treated fumed silica powder was 5 nm or more and 18 nm or less.

[0074] The free oil content, hydrophobicity, charge amount and flowability of the surface-treated fumed silica powder were measured as follows.

[0075] (1) Amount of free oil and carbon Using a BUCHI Soxhlet extraction apparatus, 0.5 g of surface-treated fumed silica powder was placed in a cylindrical filter paper with a diameter of 28 mm, and the free oil on the surface-treated fumed silica was extracted using hexane as the extraction solvent under the conditions of an extraction time of 60 minutes and a rinse time of 30 minutes. The amount of carbon on the surface-treated fumed silica after the oil was extracted and removed was measured, and the difference between the amount of carbon on the surface-treated fumed silica before extraction and the amount of carbon after extraction was determined to be the amount of free oil. The carbon content of the surface-treated fumed silica was measured using a carbon-in-metal decomposition device (EMIA-110) manufactured by Horiba, Ltd.

[0076] (2) Hydrophobicity 1 g of surface-treated fumed silica powder was weighed into a 200 mL separatory funnel, 100 mL of pure water was added, the funnel was capped, and the mixture was shaken for 10 minutes using a Turbula mixer. After shaking, the funnel was left to stand for 10 minutes. After standing, 20-30 mL of the lower layer was removed from the funnel, and the mixture was then dispensed into a 10 mm quartz cell. The colorimeter was then run using pure water as a blank, and the transmittance of light at a wavelength of 500 nm was determined as the hydrophobicity. Higher light transmittance indicates higher hydrophobicity. This is because highly hydrophobic surface-treated fumed silica tends to float on the surface of the water without dispersing, making the water less likely to become cloudy and resulting in higher light transmittance.

[0077] (3) Liquidity Using a Henschel mixer, 1 g of the surface-treated fumed silica powder of the Examples and Comparative Examples was externally added to 99 g of toner (negatively charged styrene acrylic toner base (binding resin, average particle size 6 μm) powder, and then an air permeability test of the toner sample was performed using a powder rheometer. The total energy value was measured 13 times for each sample, the first time without air permeation and the second and subsequent times with air permeation at a linear velocity of 0.04 mm / s. The total energy value of the 13th measurement was then evaluated as fluidity. A smaller energy value indicates higher fluidity.

[0078] (4) Charge amount A sample containing 100 parts by weight of carrier (reduced iron powder) and 0.2 parts by weight of surface-treated fumed silica was mixed in a turbulator mixer for a certain period of time to be triboelectrically charged, and then the charge amount (triboelectric charge amount) was measured using a blow-off powder charge amount measuring device under conditions of a temperature of 20°C and a humidity of 45% RH.

[0079] [Table 1]

[0080] As is clear from the results in Table 1, the powders of the examples satisfy all of the properties specified in the present invention, and are both highly hydrophobic and fluid.

Claims

1. A powder comprising particles including inorganic oxide particles and a layer containing reactive silicone oil and non-reactive silicone oil formed on the surface of the inorganic oxide particles, (1) The carbon content (wt%) in the powder is 3.0 to 7.0 wt%; (2) The carbon content is calculated based on the specific surface area (m ２ / g) is 1.6 to 3.4%, (3) The hydrophobicity rate is 50% or more, (4) The charge amount is −170 to −310 μC / g, (5) The free oil content is 3% by weight or less, (6) The reactive silicone oil has OH groups at both ends of a main chain formed of a siloxane bond. A surface-modified inorganic oxide powder characterized by:

2. 2. The surface-modified inorganic oxide powder of claim 1, wherein the inorganic oxide particles are fumed silica.

3. The inorganic oxide particles have a specific surface area of ​​100 to 500 m2 as determined by the nitrogen adsorption method (BET). ２ The surface-modified inorganic oxide powder according to claim 1 or 2, wherein the surface modifier is a 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. A toner composition or powder coating composition for electrophotography comprising the external additive of 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 an inorganic oxide powder, a reactive silicone oil having OH groups at both ends of a main chain formed by a siloxane bond and having a kinematic viscosity of 30 to 100 cs, and a non-reactive silicone oil having a kinematic viscosity of 5 to 300 cs; (b) heat-treating the mixture at a temperature of 80 to 380°C A method for producing a surface-modified inorganic oxide powder, comprising:

7. 2. A method for producing the surface-modified inorganic oxide powder of claim 1, comprising: (a) preparing a first mixture containing an inorganic oxide powder and a reactive silicone oil having OH groups at both ends of a main chain formed by a siloxane bond and having a kinematic viscosity of 30 to 100 cs; (b) heat-treating the first mixture at a temperature of 80 to 380°C; (c) preparing a second mixture comprising the heat-treated first mixture and a non-reactive silicone oil having a kinematic viscosity of 5 to 300 cs; (d) heat treating the second mixture at a temperature of 80 to 380°C; A method for producing a surface-modified inorganic oxide powder, comprising:

8. 2. A method for producing the surface-modified inorganic oxide powder of claim 1, comprising: (a) preparing a first mixture containing an inorganic oxide powder and a non-reactive silicone oil having a kinematic viscosity of 5 to 300 cs; (b) heat-treating the first mixture at a temperature of 80 to 380°C; (c) preparing a second mixture containing the heat-treated first mixture and a reactive silicone oil having OH groups at both ends of a main chain formed by a siloxane bond and having a kinematic viscosity of 30 to 100 cs; (d) heat treating the second mixture at a temperature of 80 to 380°C; A method for producing a surface-modified inorganic oxide powder, comprising:

9. The method according to any one of claims 6 to 8, wherein the weight ratio of the non-reactive silicone oil to the reactive silicone oil is 1:0.2 to 1:4.0.

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