JP2012025596A - Method for producing agglomerated silica microparticle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing agglomerated silica microparticles which have general characteristics as an external additive such as the ability to enhance the fluidity, caking resistance, fixability, and cleanability of a toner, further have, especially high dispersibility, low aggregation tendency, and exhibit good adsorption on a toner surface.SOLUTION: There is provided a method for producing agglomerated silica microparticles each composed of at least two agglomerated primary particles, which method for producing agglomerated silica microparticles comprises (A) a step of forming core particles of hydrophilic silica microparticles by subjecting a compound represented by general formula (1): Si(OR)to hydrolysis and condensation, (B) a step of forming core particle agglomerates by adding an agglomeration promoting additive thereto, and (C) a step of forming agglomerated silica microparticles by further adding the compound represented by general formula (1) to the system and subjecting it to hydrolysis and condensation to grow and agglomerate the core particle agglomerates.

Description

  The present invention relates to associative silica fine particles, particularly hydrophobic associative silica fine particles having high dispersibility and low agglomeration properties, and good adsorption to the toner surface, and more specifically, an external toner for electrostatic image development. The present invention relates to an associated silica fine particle that can be suitably used as an additive.

  Dry developers used in electrophotography and the like can be roughly classified into a one-component developer using a toner itself in which a colorant is dispersed in a binder resin and a two-component developer in which a carrier is mixed with the toner. When performing a copying operation using these developers, in order to have process compatibility, the developer needs to be excellent in fluidity, caking resistance, fixing properties, charging properties, cleaning properties, and the like. . For this reason, inorganic fine particles are often added to the toner in order to improve the fluidity, caking resistance, fixability, and cleaning properties of the developer.

  When inorganic fine particles are added to the toner for such a purpose, it is necessary to mix the external additive and the toner using a mixer, and to adhere to the toner surface while unpacking the aggregates of the external additive. However, even if the external additive is adhered to the toner surface using a mixer, there is still an external additive that does not adhere to the toner surface but is free, or the external additive adhered to the toner surface The toner may be detached from the toner surface due to mechanical / mechanical stress, rubbing, or the like. The free external additive thus released moves to the surface of the photoconductor together with the toner when the toner is developed on the surface of the photoconductor, and remains on the surface of the photoconductor after transfer, and adheres to the surface of the photoconductor without being cleaned. Often accumulating.

  Thus, if these free external additives accumulate on the surface of the photoreceptor, they can cause image quality defects on the copy (filming, etc.) or cause damage to the photoreceptor surface and shorten the life of the photoreceptor. This is a problem. Further, since the free external additives are accumulated on the surface of the photoreceptor, there is a problem that these free external additives spill out from the surface of the photoreceptor of the developing device during development and contaminate the inside of the copying machine. Furthermore, if these free external additives adhere to the carrier surface in the developer, the charge transfer between the carrier and the toner is hindered, and as a result, the chargeability of the toner may be reduced. is there. Therefore, while improving the fluidity, caking resistance, fixing property, and cleaning property of the toner, the external additive has high dispersibility and low cohesion, good adsorption to the toner surface, and hardly generates free external additives. Development of was desired.

  In order to solve the above problems, use of fumed silica as an inorganic external additive has been reported (see, for example, Patent Document 1). However, the complex particle structure of fumed silica has a problem that the fluidity-imparting effect expected for the external additive is insufficient. It has also been reported that spherical fused silica is used as an external additive for toner (for example, see Patent Document 2). However, since spherical fused silica is spherical, adhesion to the toner surface is poor. Therefore, the problem has not been solved.

JP 2002-116575 A JP 2002-154820 A

  The present invention has been made to solve the above problems, and has the general characteristics of an external additive that enhances the fluidity, anti-caking property, fixing property, and cleaning property of the toner, and is particularly high in dispersibility and low It is an object of the present invention to provide a method for producing associated silica fine particles having a cohesive property and good adsorption to the toner surface.

In order to solve the above problems, in the present invention,
A method for producing associated silica fine particles in which two or more primary particles having an average particle diameter in the range of 5 to 500 nm are associated,
(A) General formula (1): Si (OR ¹ ) ₄ (1)
(Wherein, R ¹ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
At least one compound selected from the group consisting of a tetrafunctional silane compound and a partial hydrolysis-condensation product of the tetrafunctional silane compound in a mixed medium of a hydrophilic organic solvent and water in the presence of a basic substance. A step of hydrolyzing and condensing to produce core particles of hydrophilic silica fine particles;
(B) adding an association promoting additive into the system to associate the core particles to form a core particle aggregate;
(C) At least one compound among the tetrafunctional silane compound represented by the general formula (1) and a partial hydrolysis condensation product of the tetrafunctional silane compound is further added to the system, followed by hydrolysis and condensation. There is provided a method for producing associated silica fine particles, characterized by comprising a step of reacting, and growing and associating the core particle aggregates to form associated silica fine particles.

Thus, (A) a step of generating a core particle of hydrophilic silica fine particles composed of SiO ₂ units, (B) a step of generating a core particle aggregate, and (C) a step of generating an associated silica fine particle, the associated silica fine particle is formed. Can be manufactured. The associated silica fine particles obtained in this way have the general properties of external additives that enhance the fluidity, caking resistance, fixability, and cleaning properties of the toner, as well as high dispersibility and low aggregation. The associated silica fine particles are excellently adsorbed on the toner surface.

  The association promoting additive may be any of salts, polyfunctional compounds, and condensation catalysts. Further, tetraalkylammonium hydroxide compounds are preferable for salts, aminoalcohols, diamines, and glycols are preferable for polyfunctional compounds, and Ti, Zr, Zn, and Al based organometallics are used for condensation catalysts. Compound complexes are preferred.

  Thus, by using any one of salts, polyfunctional compounds, and condensation catalysts as the association promoting additive, the primary particles are simply aggregated into a spherical shape or aggregated into a lump shape in a normal form. Instead of particles, two or more primary particles can associate to produce associated silica fine particles having a chain, fiber, or other irregular shape. Further, by appropriately selecting an association promoting additive, the primary particles in the associated silica fine particles are associated with each other by two primary particles, three or more chains, and three In addition to those that are associated at a point, those that are associated with four in a planar or tetrapot form, those that are associated with five or more particles, and various associations in which these associated silica fine particle groups are bonded together Silica fine particles can be produced.

Furthermore, the hydrophilic organic solvent is
Formula (2): R ² OH (2)
(Wherein R ² is a monovalent hydrocarbon group having 1 to 6 carbon atoms)
It is preferable to use an alcohol solvent represented by

  Thus, by using the hydrophilic organic solvent as the alcohol solvent represented by the general formula (2), the tetrafunctional compound represented by the general formula (1) in the step of generating the core particles of the hydrophilic silica fine particles (A). The hydrolytic silane compound and the partial hydrolysis-condensation product of the tetrafunctional silane compound and these hydrolysis products can be dissolved well, and the hydrolysis and condensation reaction can proceed well. Further, the particle diameter of the associated silica fine particles produced can be controlled by appropriately selecting the number of carbon atoms of 1 to 6 in the alcohol, has high dispersibility and low cohesion, and good adsorption on the toner surface. Associative silica fine particles can be obtained.

  The basic substance is preferably ammonia.

  Thus, by using ammonia as a basic substance, the reaction conditions suitable for the hydrolysis and condensation reaction can be satisfied, and the hydrolysis and condensation reaction can proceed favorably.

Further, after the step (C) of producing the associated silica fine particles,
(D) removing the hydrophilic organic solvent from the mixed medium and adding water to obtain an aqueous dispersion of the hydrophilic associated silica fine particles;
(E) R ³ SiO _3/2 units on the surface of the hydrophilic associative silica fine particles in the aqueous dispersion (wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) And the step of generating primary hydrophobic associative silica fine particles,
(F) Furthermore, R ⁴ ₃ SiO _1/2 units (wherein R ⁴ is the same or different, substituted or unsubstituted, 1 to 6 carbon atoms) on the surface of the primary hydrophobic associative silica fine particles. It is preferable that the associated silica fine particles are produced from the step of introducing a secondary hydrophobic associative silica fine particle by introducing a monovalent hydrocarbon group).

  Thus, (C) after the step of producing the associated silica fine particles, (D) a step of obtaining an aqueous dispersion of the hydrophilic associative silica fine particles, (E) a step of producing the primary hydrophobic associated silica fine particles, and (F) Hydrophobic associative silica fine particles can be produced by performing a step of generating secondary hydrophobic associative silica fine particles. The hydrophobic associative silica fine particles thus obtained have the general properties of external additives that improve the fluidity, caking resistance, fixability, and cleaning properties of the toner, as well as better high dispersibility, lower Aggregated silica particles having aggregating property and good adsorption to the toner surface are obtained.

Further, in the step (E), for the associated silica fine particles,
General formula (3): R ³ Si (OR ⁵ ) ₃ (3)
(Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms. is there)
R ³ SiO _3/2 unit (formula) is added to the surface of the hydrophilic associative silica fine particles by adding a trifunctional silane compound represented by the formula, a partial hydrolysis condensation product of the trifunctional silane compound, or a mixture thereof. R ³ is the same as described above) is preferably introduced to obtain an aqueous dispersion of the first hydrophobic associative silica fine particles.

Thus, in the step (E), the trifunctional silane compound represented by the general formula (3), the partial hydrolysis condensation product of the trifunctional silane compound or a mixture thereof is added to the associated silica fine particles. By adding, R ³ SiO _3/2 units (wherein R ³ is the same as above) can be easily introduced onto the surface of the hydrophilic associative silica fine particles. Thereby, since the hydrolyzable group is introduced while making the surface of the associated silica fine particles hydrophobic, the hydrolysis condensation reaction in the subsequent step (F) of generating the secondary hydrophobic associative silica fine particles can be favorably progressed. it can.

Further, after the step (C) of producing the associated silica fine particles,
(D) removing the hydrophilic organic solvent from the mixed medium and adding water to obtain an aqueous dispersion of the hydrophilic associated silica fine particles;
(E) R ³ SiO _3/2 units on the surface of the hydrophilic associative silica fine particles in the aqueous dispersion (wherein R ³ is the same as above and is substituted or unsubstituted and has 1 to 20 carbon atoms) A monovalent hydrocarbon group) to produce primary hydrophobic associated silica fine particles,
(F ′) Further, the dispersion medium of the aqueous dispersion of the primary hydrophobic association silica fine particles is replaced with a ketone solvent to obtain a ketone solvent dispersion of the primary hydrophobic association silica fine particles. For the ketone-based solvent dispersion of the next hydrophobically associated silica fine particles,
General formula (4): R ⁴ ₃ SiNHSiR ⁴ ₃ (4)
(Wherein R ⁴ is the same or different, substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms)
Or a silazane compound represented by
General formula (5): R ⁴ ₃ SiX (5)
(Wherein X is an OH group or a hydrolyzable group)
Or a mixture of the silazane compound and the monofunctional silane compound is added to triorganosilylate the reactive groups remaining on the surface of the first hydrophobic associative silica fine particles, By introducing R ⁴ ₃ SiO _1/2 unit (wherein R ⁴ is the same as above) to the surface of the secondary hydrophobic associating silica fine particles, the secondary hydrophobic associating silica fine particles can be generated. preferable.

Thus, (C) after the step of producing the associated silica fine particles, (D) a step of obtaining an aqueous dispersion of the hydrophilic associative silica fine particles, (E) a step of producing the primary hydrophobic associated silica fine particles, and (F ′) Dispersing the dispersion medium of the aqueous dispersion of primary hydrophobic associative silica fine particles with a ketone solvent to obtain a ketone solvent dispersion of primary hydrophobic associative silica fine particles, Silazane compound represented by general formula (4), monofunctional silane compound represented by general formula (5), or silazane compound and monofunctional silane compound with respect to a ketone-based solvent dispersion of fine associative silica fine particles And a mixture of R ⁴ ₃ SiO _1/2 units (wherein R ⁴ is the same as above) is introduced to the surface of the primary hydrophobic associating silica fine particles, and the secondary hydrophobic associating silica fine particles are introduced. The process of generating , It can be produced meeting silica fine particles. The hydrophobic associative silica fine particles thus obtained have the general properties of external additives that improve the fluidity, caking resistance, fixability, and cleaning properties of the toner, as well as better high dispersibility, lower Aggregated silica particles having aggregating property and good adsorption to the toner surface are obtained.

Further, in the step (E), for the associated silica fine particles,
General formula (3): R ³ Si (OR ⁵ ) ₃ (3)
(Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms. is there)
R ³ SiO _3/2 unit (formula) is added to the surface of the hydrophilic associative silica fine particles by adding a trifunctional silane compound represented by the formula, a partial hydrolysis condensation product of the trifunctional silane compound, or a mixture thereof. R ³ is the same as described above) is preferably introduced to obtain an aqueous dispersion of the first hydrophobic associated silica fine particles.

Thus, in the step (E), the trifunctional silane compound represented by the general formula (3), the partial hydrolysis condensation product of the trifunctional silane compound or a mixture thereof is added to the associated silica fine particles. By adding, R ³ SiO _3/2 units (wherein R ³ is the same as above) can be easily introduced onto the surface of the hydrophilic associative silica fine particles. As a result, the hydrolyzable group is introduced while making the surface of the associated silica fine particles hydrophobic, so that the hydrolytic condensation reaction in the subsequent step (F ′) of generating the secondary hydrophobic associated silica fine particles can proceed well. Can do.

  Furthermore, the ketone solvent is preferably methyl isobutyl ketone.

  Thus, by using methyl isobutyl ketone as the ketone solvent, primary hydrophobic associative silica fine particles, silazane compound represented by general formula (4), monofunctional silane compound represented by general formula (5) The mixture of the silazane compound and the monofunctional silane compound and the resulting secondary hydrophobic associative silica fine particles can be dissolved well, and the hydrolysis and condensation reaction can proceed well.

  Further, it is possible to provide a toner external additive for developing an electrostatic charge image comprising hydrophobic associated silica fine particles produced by the method for producing the associated silica fine particles.

  Thus, the hydrophobic associative silica fine particles produced by the above-described method for producing associative silica fine particles have the general characteristics of external additives that improve the fluidity, caking resistance, fixability, and cleaning properties of the toner. In particular, it is an associated silica fine particle having high dispersibility and low agglomeration properties and good adsorption to the toner surface, and therefore can be suitably used as an external toner additive for developing electrostatic images.

  As described above, according to the present invention, the toner has the general properties of an external additive that enhances the fluidity, caking resistance, fixability, and cleaning properties of the toner, and has particularly high dispersibility and low cohesion. In addition, associated silica fine particles having good adsorption to the toner surface can be produced. In particular, the toner external additive for developing an electrostatic charge image using the hydrophobic associative silica fine particles produced by the production method of the present invention is an external additive that improves the fluidity, caking resistance, fixing property and cleaning property of the toner. In addition to the general characteristics of the above, it has high dispersibility and low cohesion, and is an irregularly shaped particle in which silica particles are associated. It is an external additive that hardly causes image quality defects (filming, etc.). By using this toner external additive, high image quality can be expected by applying it to the development of electrostatic images in electrophotography, electrostatic recording, and the like.

It is a schematic diagram which shows that a primary particle | grain associates and it becomes a chain | strand shape, a fiber form, and other forms.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
As described above, while having the general properties of external additives that improve the fluidity, caking resistance, fixing properties, and cleaning properties of the toner, it has high dispersibility and low cohesion, and is adsorbed on the toner surface. Therefore, it has been desired to develop an external additive that is excellent in resistance and hardly generates a free external additive.

  As a result of diligent studies to achieve the above object, the present inventor is a general external additive that improves adsorption to toner and improves toner fluidity, caking resistance, fixability, and cleaning properties. It was found that the size and shape of the silica fine particles are important for producing an external additive having characteristics, and various shapes and sizes can be used as long as the associated silica fine particle production method is prepared using an association promoting additive. The associated silica fine particles produced by the production method are found to have high dispersibility and low agglomeration and are well adsorbed to the toner surface, and the associated silica fine particles are copied. It was found that the above image quality defects (filming, etc.) are less likely to occur, and further, the associated silica fine particles which are released from the toner surface and are not easily released to become free external additives are obtained by electrophotography, static By applying the development of the electrostatic image on the recording method or the like, image quality has completed the present invention found that can be expected. This will be described in detail below.

The present invention
A method for producing associated silica fine particles in which two or more primary particles having an average particle diameter in the range of 5 to 500 nm are associated,
(A) General formula (1): Si (OR ¹ ) ₄ (1)
(Wherein, R ¹ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
At least one compound selected from the group consisting of a tetrafunctional silane compound and a partial hydrolysis-condensation product of the tetrafunctional silane compound in a mixed medium of a hydrophilic organic solvent and water in the presence of a basic substance. A step of hydrolyzing and condensing to produce core particles of hydrophilic silica fine particles;
(B) adding an association promoting additive into the system to associate the core particles to form a core particle aggregate;
(C) At least one compound among the tetrafunctional silane compound represented by the general formula (1) and a partial hydrolysis condensation product of the tetrafunctional silane compound is further added to the system, followed by hydrolysis and condensation. There is provided a method for producing associated silica fine particles, characterized by comprising a step of reacting, and growing and associating the core particle aggregates to form associated silica fine particles.

<Method for producing general synthetic silica fine particles>
Synthetic silica fine particles are produced by combustion method silica obtained by burning a silane compound (that is, fumed silica), deflagration silica obtained by explosively burning metal silicon powder, sodium silicate and mineral acid. Wet silica obtained by the neutralization reaction of the above (the one synthesized under alkaline conditions is precipitated silica, the one synthesized under acidic conditions is gel silica), the sol-gel silica obtained by hydrolysis of hydrocarbyloxysilane (so-called (Stober method). Among these, the present invention relates to sol-gel silica, and is a method for producing associated silica fine particles by improving the sol-gel method.

<Characteristics of associated silica fine particles produced by the production method of the present invention>
First, the characteristics of the associated silica fine particles of the present invention will be described in detail. The associated silica fine particles in the present invention are not particles in a normal form in which primary particles are aggregated into a spherical shape or agglomerated into a lump, but two or more primary particles are associated to form a chain. , Refers to particles in the form of fibers and other irregular shapes. As an association mode of the primary particles in the associated silica fine particles, two primary particles are associated, three or more are associated in a chain, three are associated at three points, four are planar or In addition to those associated in a tetrapot type, those in which five or more particles are associated in the same manner, associated silica fine particles in which these associated silica fine particle groups are bonded to each other can also be exemplified (see FIG. 1). In this way, two or more primary particles are aggregated to form a chain, a fiber, or other irregularly shaped particles, and the primary particles are aggregated into a spherical shape or aggregated into a lump. It is advantageous in terms of the shape of the adhesion surface and the adhesion area from the normal form particles to the toner surface. In addition, the primary particle here refers to the particle | grains which are the minimum unit in the particle | grains which form powder.

  The associated silica fine particles that can be produced by the production method of the present invention include two or more primary particles, preferably 2 to 20 primary particles, particularly preferably 3 to 10 primary particles, which are associated with each other. It is configured. The primary particles constituting the associated silica fine particles do not necessarily have to be spherical, and may be oval, dice, or rod-shaped, but the primary particles are preferably spherical in consideration of the use of external additives. Moreover, the particle diameters of the primary particles may be different from each other, and the diameter of the associated portion may be approximately the same as the particle diameter of the primary particles, that is, there may be no constriction.

  The average particle diameter of the primary particles is in the range of 5 to 500 nm, preferably 20 to 100 nm. When the average particle size is less than 5 nm, the particle group obtained by agglomeration of primary particles tends to be agglomerated, resulting in insufficient developer fluidity, caking resistance, fixability, etc. When the average particle diameter exceeds 500 nm, the particles are too large, causing problems such as deterioration or abrasion of the photoreceptor and a decrease in adhesion of the fine particles to the toner.

  The powder of the associated silica fine particles produced by the production method of the present invention contains fine particles composed only of the associated silica fine particles and the primary particles. The number of primary particles constituting the associated silica fine particles is 5 to 100% with respect to the number of all primary particles in the powder of the associated silica fine particles produced by the production method of the present invention. It is preferable to be in the range of 10 to 80%.

  The ratio of the primary particles constituting the associated silica fine particles is determined by taking a transmission electron micrograph of the associated silica fine particles, and for all particles in an arbitrary area, the total number of primary particles and the number of particles consisting of only primary particles It can be obtained by counting each value, calculating a value obtained by subtracting the number of primary particles from the total number of primary particles, and dividing the value by the total number of primary particles. The number of particles is preferably measured in an area where the total number of primary particles is about 300. Here, “particle diameter” means a volume-based median diameter.

<Method for Producing Associated Silica Fine Particles According to the Present Invention>
Next, the method for producing associated silica fine particles of the present invention will be described in detail.
The method for producing associated silica fine particles according to the present invention is a method for producing associated silica fine particles in which two or more primary particles having an average particle diameter in the range of 5 to 500 nm are associated with each other,
(A) General formula (1): Si (OR ¹ ) ₄ (1)
(Wherein, R ¹ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
At least one compound selected from the group consisting of a tetrafunctional silane compound and a partial hydrolysis-condensation product of the tetrafunctional silane compound in a mixed medium of a hydrophilic organic solvent and water in the presence of a basic substance. A step of hydrolyzing and condensing to produce core particles of hydrophilic silica fine particles;
(B) adding an association promoting additive into the system to associate the core particles to form a core particle aggregate;
(C) At least one compound among the tetrafunctional silane compound represented by the general formula (1) and a partial hydrolysis condensation product of the tetrafunctional silane compound is further added to the system, followed by hydrolysis and condensation. And producing the associated silica fine particles by reacting them to grow and associate the core particle aggregates. Hereinafter, each process will be described.

(A) Nuclear particle generation step of hydrophilic associative silica fine particles General formula (1): Si (OR ¹ ) ₄ (1)
(Wherein, R ¹ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
At least one compound selected from the group consisting of a tetrafunctional silane compound and a partial hydrolysis-condensation product of the tetrafunctional silane compound in a mixed medium of a hydrophilic organic solvent and water in the presence of a basic substance. This is a step of generating core particles of hydrophilic spherical silica fine particles by hydrolysis and condensation reaction.

R ¹ is a monovalent hydrocarbon group having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably a monovalent hydrocarbon group having 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ¹ include a methyl group, an ethyl group, a propyl group, a butyl group, and a phenyl group, preferably a methyl group, an ethyl group, a propyl group, and a butyl group, and particularly preferably Examples thereof include a methyl group and an ethyl group.

  Examples of the tetrafunctional silane compound represented by the general formula (1) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, tetraphenoxysilane, and the like. Silane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, particularly preferably tetramethoxysilane and tetraethoxysilane. Examples of the partial hydrolysis-condensation product of the tetrafunctional silane compound represented by the general formula (1) include methyl silicate and ethyl silicate.

The hydrophilic organic solvent is not particularly limited as long as it dissolves the tetrafunctional silane compound represented by the general formula (1), a partial hydrolysis-condensation product of the tetrafunctional silane compound, water, and nuclear fine particles. E.g., alcohols, methyl cellosolve, ethyl cellosolve, buticellosolve, cellosolves such as cellosolve acetate, acetone, ketones such as methyl ethyl ketone, ethers such as dioxane, tetrahydrofuran, etc., preferably alcohols, cellosolves, especially Preferably, alcohols are used. As alcohols,
Formula (2): R ² OH (2)
(Wherein R ² is a monovalent hydrocarbon group having 1 to 6 carbon atoms)
The alcohol shown by is mentioned.

In the general formula (2), R ² is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, particularly preferably a monovalent hydrocarbon having 1 to 2 carbon atoms. It is a group. Examples of the monovalent hydrocarbon group represented by R ² include an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group, preferably a methyl group, an ethyl group, a propyl group, and an isopropyl group. Preferably a methyl group and an ethyl group are mentioned.

  Examples of the alcohol represented by the general formula (2) include methanol, ethanol, propanol, isopropanol, butanol and the like, preferably methanol and ethanol. When the number of carbon atoms in the alcohol increases, the particle diameter of the associated silica fine particles generated from the (A) process to the entire (C) process increases. Therefore, the type of alcohol can be selected according to the particle size of the target associated silica fine particles.

  Examples of the basic substance include ammonia and di-lower alkylamines such as dimethylamine and diethylamine, preferably ammonia and diethylamine, particularly preferably ammonia. These basic substances can be mixed in a medium by dissolving a required amount in water and then mixing the obtained aqueous solution (basic) with the hydrophilic organic solvent.

The amount of water used in the hydrolysis reaction during the formation of the core particles in the step (A) is the amount of the tetrafunctional silane compound of the general formula (1) used in the step (A) and the partial hydrolysis of the tetrafunctional silane compound. It is preferably 0.5 to 5 equivalents relative to the number of moles of the functional group R ^{1 in} the decomposition condensation product or a mixture thereof, and the ratio of water to the hydrophilic organic solvent is 1 equivalent of the hydrophilic organic solvent. In some cases, the weight ratio is preferably 0.1 to 10 equivalents, and the amount of the basic substance is the functional silane compound of the general formula (1) used in the step (A) and the partial hydrolysis of the tetrafunctional silane compound. The amount is preferably 0.01 to 1 equivalent relative to the number of moles of the functional group R ^{1 in} the decomposition condensation product or a mixture thereof. Thus, by appropriately selecting the amount of water, the ratio of water to the hydrophilic organic solvent, and the amount of basic substance, the size and shape of the core particles can be controlled according to the purpose.

(B) A step of adding an association promoting additive into the system (A) An additive that promotes association is added to the mixed medium containing the hydrophilic spherical silica core particles prepared in the system by the step (A). This is a step of generating a nuclear particle aggregate.

  Examples of effective additives for associating silica particles include polyfunctional compounds, condensation catalysts, and salts.

  Examples of the polyfunctional compound include amino alcohols, diamines, glycols and the like. Specific examples of amino alcohols include monoethanolamine, isopropanolamine, diethanolamine, N-methyldiethanolamine, 2-dimethylaminoethanol, and 2-diethylaminoethanol. Examples of diamines include ethylenediamine and tetramethylethylenediamine. Illustrative examples of glycols include diethylene glycol, trimethylene glycol, tetramethylene glycol, 1,6-hexanediol, and diethylene glycol. These may be one kind or a mixture of two or more kinds.

  Examples of the condensation catalyst include Ti, Zr, Zn, and Al-based organometallic compound complexes. Specifically, titanium di-n-butoxide (bis 2,4-pentadionate), zirconium 2,4-pentadionate, zinc 2,4-pentadionate, aluminum (III) 2,4-pentadionate Etc., and one kind or a mixture of two or more kinds may be used. Moreover, you may use what hydrolyzed these.

  Examples of the salts include tetraalkylammonium hydroxide. The alkyl group of the tetraalkylammonium hydroxide preferably has 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms. Specifically, it is preferably selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, or a mixture thereof.

  By interposing these association promoting additives, the association of the core particles is promoted, the core particle aggregate is easily generated efficiently, and the form of the association can be adjusted according to the purpose.

The addition amount of the association promoting additive is preferably 3 to 150 parts by mass with respect to 100 parts by mass of SiO _{2 of the} silica core particles. More preferably, it is 5-100 mass parts. If the amount is 3 parts by mass or more, the association rate is good and preferable. Moreover, if this amount is 150 parts by mass or less, it is preferable because aggregation of particles can be suppressed and adverse effects on charging characteristics when used as an external additive can be suppressed.

(C) Step of growing and associating core particle aggregates (B) After adding an association promoting additive in step (B), the tetrafunctional silane compound represented by the general formula (1) and the tetrafunctional silane compound In this process, at least one compound of the partial hydrolysis-condensation product is further added to cause hydrolysis and condensation reaction to grow and associate the core particle aggregate larger.

  In the hydrolysis reaction during the growth of the associated silica fine particles, the amount of the tetrafunctional silane compound represented by the general formula (1), the partial hydrolysis-condensation product of the tetrafunctional silane compound, or a mixture thereof is (A) 99.5 to the amount of the tetrafunctional silane compound represented by the general formula (1), the partial hydrolysis-condensation product of the tetrafunctional silane compound, or a mixture thereof used for preparing the core particles in the process. 70.0 mol% is preferable, More preferably, it is 95.0-85.0 mol%. If this amount is 99.5 mol% or less, it is preferable because too much silica is deposited on the core particle aggregate, and it can be grown in an associated form. Moreover, if this amount is 70.0 mol% or more, the associated silica fine particles are easily grown, which is preferable.

The amount of water used at this time is about 0.1 with respect to the number of moles of R ^{1 in} the tetrafunctional silane compound of the general formula (1), the partial hydrolysis condensation product of the tetrafunctional silane compound, or a mixture thereof. The ratio of water to the hydrophilic organic solvent is preferably 5 to 5 equivalents, and preferably 0.5 to 10 equivalents by weight when the hydrophilic organic solvent is 1 equivalent. Is preferably 0.01 to 1 equivalent with respect to the number of moles of R ¹ in the functional silane compound of the general formula (1), the partial hydrolysis condensation product of the tetrafunctional silane compound, or a mixture thereof. . Thus, by optimizing the amount of water, the ratio of water to the hydrophilic organic solvent, and the amount of the basic substance, the size and shape of the associated silica fine particles can be controlled according to the purpose.

  As described above, the steps (A) to (C) enable not only the formation of the core particles, the formation of the core particle aggregates, the growth and the association of the core particle aggregates, but also the controlled particle size and shape. In addition, it is possible to provide a method for producing associated silica fine particles, in which the associated silica fine particles in which the primary particles are associated can be obtained, and the size and shape of the associated silica fine particles can be controlled according to the purpose.

Further, after the step (C) of producing the associated silica fine particles,
(D) removing the hydrophilic organic solvent from the mixed medium and adding water to obtain an aqueous dispersion of the hydrophilic associated silica fine particles;
(E) R ³ SiO _3/2 units on the surface of the hydrophilic associative silica fine particles in the aqueous dispersion (wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) And the step of generating primary hydrophobic associative silica fine particles,
(F) Furthermore, R ⁴ ₃ SiO _1/2 units (wherein R ⁴ is the same or different, substituted or unsubstituted, 1 to 6 carbon atoms) on the surface of the primary hydrophobic associative silica fine particles. A monovalent hydrocarbon group) to produce secondary silica-associated silica fine particles, thereby producing associated silica fine particles, thereby improving toner fluidity, caking resistance, fixing properties, and cleaning properties. In addition to the general characteristics of the external additive, hydrophobic associated silica fine particles having better high dispersibility and low agglomeration and good adsorption to the toner surface can be obtained. Hereinafter, each process of hydrophobization will be described in detail.

(D) Step of obtaining an aqueous dispersion of hydrophilic associative silica fine particles (C) This is a step of adding water after removing the hydrophilic organic solvent from the mixed medium of the hydrophilic associative silica fine particle dispersion in the step (C). The operation of removing the hydrophilic organic solvent from the mixed medium in step (C) and adding water is, for example, an operation of adding water to the hydrophilic associative silica fine particle dispersion and distilling off the hydrophilic organic solvent (necessary This operation can be repeated accordingly.

  The total amount of water added at this time is based on the amount of the hydrophilic organic solvent used and the total amount of alcohol generated by hydrolysis and condensation reaction from step (A) to step (C). On a mass basis, the amount is preferably more than twice, more preferably 2.5 to 3.5 times, particularly preferably 3 times.

  The hydrophilic associative silica fine particles in the aqueous dispersion thus obtained are subjected to a first-stage hydrophobization treatment in the subsequent step (E).

  The water dispersion obtained by removing the hydrophilic organic solvent from the mixed medium and adding water may have a water content of 90% by mass or more. That is, the aqueous dispersion obtained by removing the hydrophilic organic solvent from the mixed medium and adding water may contain the hydrophilic organic solvent. In the above process, if the water content in the aqueous dispersion is 90% by mass or more, the hydrocarbyloxy group is sufficiently hydrolyzed because the amount of water in the dispersion is large, and the remaining hydrocarbyl in the silica fine particles. The oxy group content is preferably reduced.

(E) Step of generating primary hydrophobic associative silica fine particles (surface hydrophobization treatment step of hydrophilic associative silica fine particles)
(D) R ³ SiO _3/2 units on the surface of the hydrophilic associative silica fine particles in the aqueous dispersion in the step (wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) In order to produce primary hydrophobic association silica fine particles. That is, it is a step of performing a first-stage hydrophobization treatment.

In the surface hydrophobization treatment step of generating primary hydrophobic associative silica fine particles from the hydrophilic associative silica fine particles, for example, the hydrophilic associative silica fine particles in the aqueous dispersion having a water content of 90% by mass or more are used. for,
General formula (3): R ³ Si (OR ⁵ ) ₃ (3)
(Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms. is there)
In trifunctional silane compound represented or by adding the three partial hydrolysis-condensation product of silane compounds or mixtures thereof, hydrophilic associations silica surface R ³ SiO _3/2 units of microparticles (in the formula , R ³ is the same as described above) to obtain an aqueous dispersion of primary hydrophobic associative silica fine particles. Thus, the surface of the hydrophilic associative silica fine particles is subjected to a hydrolytic condensation reaction using the trifunctional silane compound represented by the general formula (3), the partial hydrolytic condensation product of the trifunctional silane compound, or a mixture thereof. Thus, the first-stage hydrophobization treatment can be efficiently performed.

In the general formula (3), R ³ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms, more preferably a monovalent hydrocarbon having 1 to 4 carbon atoms. It is a group. Examples of the monovalent hydrocarbon group represented by R ³ include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, and a hexyl group, a phenyl group, and the like. It is a methyl group. Further, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atom, chlorine atom, bromine atom, preferably fluorine atom.

In the general formula (3), R ⁵ is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms, particularly preferably 1 to 2 carbon atoms. . Examples of the monovalent hydrocarbon group represented by R ⁵ include an alkyl group such as a methyl group, an ethyl group, a propyl group, and a butyl group, preferably a methyl group, an ethyl group, and a propyl group, and particularly preferably a methyl group. And ethyl group.

  Examples of the trifunctional silane compound represented by the general formula (3) or a partial hydrolysis-condensation product thereof or a mixture thereof include, for example, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, trifluoropropyltrimethoxysilane, heptadecafluorodecyl Examples include trialkoxysilane such as trimethoxysilane, and methyltrimethoxysilane and methyltriethoxysilane are particularly preferable.

The addition amount of the trifunctional silane compound represented by the general formula (3), the partial hydrolysis-condensation product of the trifunctional silane compound or a mixture thereof is determined by the SiO ₂ of the hydrophilic associating silica fine particles in the aqueous dispersion. The amount is preferably 0.001 to 1 mol, more preferably 0.01 to 0.1 mol, and particularly preferably 0.01 to 0.05 mol per 1 mol of the unit.

(F) Step of generating secondary hydrophobic associative silica fine particles (surface triorganosilylation treatment step of hydrophobic associative silica fine particles)
(E) R ⁴ ₃ SiO _1/2 units (wherein R ⁴ is the same or different, substituted or unsubstituted, 1 to 6 carbon atoms) on the surface of the primary hydrophobic associative silica fine particles obtained in the step (E) Is a monovalent hydrocarbon group) to produce secondary hydrophobic associative silica fine particles. That is, it is a step of performing the second stage hydrophobization treatment.

In the surface triorganosilylation treatment of the hydrophobic associated silica fine particles, for example,
(F ′) The dispersion medium of the aqueous dispersion of the primary hydrophobic associative silica fine particles is replaced with a ketone solvent to obtain a ketone solvent dispersion of the primary hydrophobic associative silica fine particles. In the associative silica fine particle ketone solvent dispersion,
General formula (4): R ⁴ ₃ SiNHSiR ⁴ ₃ (4)
(Wherein R ⁴ is the same or different, substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms)
Or a silazane compound represented by
General formula (5): R ⁴ ₃ SiX (5)
(Wherein X is an OH group or a hydrolyzable group)
Or a mixture of the silazane compound and the monofunctional silane compound is added to triorganosilylate the reactive groups remaining on the surface of the primary hydrophobic associating silica fine particles to form a primary hydrophobic group. The secondary hydrophobic associative silica fine particles are preferably produced by introducing R ⁴ ₃ SiO _1/2 units (wherein R ⁴ is the same as above) into the surface of the associative silica fine particles. Thus, the primary hydrophobic associative silica fine particles using the silazane compound represented by the general formula (4), the monofunctional silane compound represented by the general formula (5) or a mixture of the silazane compound and the monofunctional silane compound. By modifying the surface by hydrolysis condensation reaction, the second-stage hydrophobic treatment can be efficiently performed.

In the general formulas (4) and (5), R ⁴ is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. It is a monovalent hydrocarbon group. The monovalent hydrocarbon group represented by R ⁴ is, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group, preferably a methyl group, an ethyl group, or a propyl group, particularly preferably , Methyl group, and ethyl group. Further, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atom, chlorine atom, bromine atom, preferably fluorine atom.

  X is an OH group or a hydrolyzable group. Examples of the hydrolyzable group represented by X include a halogen atom such as a chlorine atom, an alkoxy group such as a methoxy group and an ethoxy group, an amino group, an acetoxy group, and propionyloxy. An acyloxy group such as a group, preferably an alkoxy group and an amino group, particularly preferably an alkoxy group.

  In order to replace the dispersion medium of the associative silica fine particle aqueous dispersion or the mixed solvent dispersion with the ketone solvent from the aqueous dispersion, the ketone solvent is added to the dispersion, and water or a hydrophilic organic solvent is added from the dispersion. Can be carried out by distilling off (repeating this operation as necessary).

  The amount of the ketone solvent added at this time is 0.5 to 5 times, preferably 2 to 5 times, particularly preferably 3 by mass ratio with respect to the hydrophilic associative silica fine particles used in the step (D). ~ 4 times the amount. Examples of the ketone solvent include methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, and preferably methyl isobutyl ketone.

  Examples of the silazane compound represented by the general formula (4) include hexamethyldisilazane and hexaethyldisilazane, preferably hexamethyldisilazane. Examples of the monofunctional silane compound represented by the general formula (5) include monosilanol compounds such as trimethylsilanol and triethylsilanol, monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane, and monoalkoxy such as trimethylmethoxysilane and trimethylethoxysilane. Examples thereof include monoaminosilanes such as silane, trimethylsilyldimethylamine and trimethylsilyldiethylamine, and monoacyloxysilanes such as trimethylacetoxysilane, preferably trimethylsilanol, trimethylmethoxysilane and trimethylsilyldiethylamine, particularly preferably trimethylsilanol and trimethylmethoxysilane.

The amount of the silazane compound represented by the general formula (4), the monofunctional silane compound represented by (5) or the mixture of the silazane compound and the monofunctional silane compound is the amount of the hydrophilic associative silica fine particles used in the step (D). It can be 0.05-0.5 mol with respect to SiO ₂ units to 1 mol, preferably 0.1 to 0.3 mol, particularly preferably 0.15 to 0.25 mol.

  From the steps (A) to (F) or (F ′), hydrophobic associated silica fine particles can be efficiently obtained. The thus obtained hydrophobic associative silica fine particles may be obtained as a powder by a conventional method such as drying, or an organic compound is added after the hydrolysis condensation reaction in the step (F) or (F ′). It may be obtained as a dispersion. The thus obtained powder or dispersion of hydrophobic associated silica fine particles can be suitably used as, for example, a toner external additive.

  For example, in the case where the associated silica fine particles are taken out for use that does not require a high degree of hydrophobizing treatment by the step (F) or the step (F ′) from the step (D) as described above, the step (C) Subsequently, the surface of the hydrophilic associative silica fine particles may be hydrophobized by adding a silylating agent or the like.

<Toner external additive comprising hydrophobic associative silica fine particles>
Provided is a toner external additive for developing an electrostatic charge image, which is composed of hydrophobic associated silica fine particles produced by the steps (A) to (F) or (F ′). The blending amount of the toner external additive composed of the associated silica fine particles with respect to the toner is usually 0.01 to 20 parts by weight, preferably 0.1 to 5 parts by weight, particularly preferably 1 to 100 parts by weight of the toner. ˜2 parts by mass. If the blending amount is more than 0.01 parts by mass, the adhesion amount to the toner can be ensured and a sufficient fluidity imparting effect can be obtained. If the blending amount is less than 20 parts by mass, the chargeability of the toner is not adversely affected.

  The associating state of the associated silica fine particles on the surface of the toner particles may be merely mechanically adhered using a mixer or may be loosely fixed. Further, the attached associated silica fine particles may cover the entire surface of the toner particles or only a part thereof. Further, the associated silica fine particles may partially form aggregates and cover the surface of the toner particles, but are preferably covered in a state of single layer particles.

  Examples of the toner particles to which the associated silica fine particles of the present invention can be applied include known toner particles containing a binder resin and a colorant as main components, and a charge control agent or the like is further added as necessary. It may be.

  The toner to which the toner external additive composed of the associated silica fine particles of the present invention is added is used for developing an electrostatic image used for developing an electrostatic image by, for example, electrophotography or electrostatic recording. used. The toner can be used as a one-component developer, but it can also be used as a two-component developer by mixing it with a carrier. When used as a two-component developer, the toner external coating may not be added to the toner particles in advance, but may be added when the toner and the carrier are mixed to cover the surface of the toner. As the carrier, known ones, for example, ferrite, iron powder, etc., or those coated on the surface with resin can be used.

  The toner external additive comprising hydrophobic associative silica fine particles according to the present invention has the general characteristics of an external additive that enhances the fluidity, caking resistance, fixing property, and cleaning property of the toner, and also has a particularly high dispersibility, low Adhesive to the toner surface is good because it is an irregularly shaped particle that has aggregating properties, and is less likely to be detached and released from the toner surface, causing image quality defects on the copy (filming, Other than the above, the toner external additive enables high image quality.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

<Example 1>
In a 1 liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer, 208 g of methanol, 13.8 g of water, and 16.6 g of 28 mass% aqueous ammonia were mixed. This solution was adjusted to 35 ° C., and 20 g (0.13 mol) of tetramethoxysilane and 15 g of 5.4 mass% aqueous ammonia were simultaneously added while stirring, and both were added dropwise over 20 minutes. Thereafter, the mixture was stirred for 30 minutes while maintaining 35 ° C. to produce core particles. Thereto was added 3.9 g (0.065 mol) of ethylenediamine as an association promoting additive. Thereafter, 367.9 g (2.4 mol) of tetramethoxysilane and 124.4 g of 5.4 mass% ammonia water started to be dripped simultaneously, tetramethoxysilane was dripped over 4 hours, and ammonia water was dripped over 3 hours. did. Even after the completion of the dropwise addition, the suspension was further stirred for 0.5 hours to carry out hydrolysis to obtain a suspension of hydrophilic associative silica fine particles. Next, an ester adapter and a condenser tube were attached to the glass reactor, the suspension was heated to 60 to 70 ° C. to distill off 400 g of methanol, and then 400 g of water was added. Next, the suspension was set to 100 ° C., 100 g of methanol water was distilled off and 100 g of water was added three times, and 100 g of methanol water was further distilled off to obtain an aqueous suspension of hydrophilic associated silica fine particles. To the obtained aqueous suspension, 3.9 g (0.029 mol) of methyltrimethoxysilane was added dropwise at room temperature over 0.5 hours, and stirring was continued for 12 hours after the addition. Thus, the surface of the associated silica fine particles was subjected to a first-stage hydrophobization treatment to obtain a first hydrophobic associative silica fine particle aqueous dispersion. After adding 480 g of methyl isobutyl ketone to the obtained dispersion, 598 g of water was distilled off over 5 hours by heating the dispersion to 80 to 110 ° C. After adding 50 g (0.31 mol) of hexamethyldisilazane to the obtained dispersion at room temperature, this dispersion is heated to 110 ° C. and reacted for 3 hours, whereby the silica fine particles in the dispersion are trimethylsilylated. Turned into. In this way, a secondary hydrophobic associative silica fine particle aqueous dispersion was obtained by subjecting the associated silica fine particle surface to a second-stage hydrophobization treatment. Next, the solvent in the dispersion was distilled off at 80 ° C. under reduced pressure (6650 Pa) to obtain 158 g of hydrophobic associated silica fine particles as powder.

  The final hydrophobic associative silica fine particles obtained were measured according to the following measurement methods. The obtained results are shown in Table 1.

Measurement method 1: Measurement of particle diameter of silica fine particles Silica fine particles were added to methanol so as to be 0.5% by mass and subjected to ultrasonic waves for 10 minutes to disperse the silica fine particles. The particle size distribution of the silica fine particles treated in this way was measured with a laser diffraction / scattering particle size distribution analyzer (trade name: LA910, manufactured by Horiba, Ltd.), and the volume-based median diameter was defined as the particle size. The median diameter is a particle diameter corresponding to 50% cumulative when the particle size distribution is expressed as a cumulative distribution.

Measurement Method 2: Shape Measurement of Silica Fine Particles Hydrophobic spherical silica fine particles were observed with a scanning electron microscope (manufactured by Hitachi, trade name: S-4700, magnification: 100,000 times) to confirm the shape.

Measurement Method 3: Primary Particle Shape and Particle Size A photograph of silica fine particles was taken with a transmission electron microscope (trade name: HF-3300, manufactured by Hitachi, Ltd.). In the photograph, the shape and particle size of primary particles were observed and measured for all particles in an arbitrary area, and the number of bonded primary particles was measured for associated silica fine particles. These measurements were made on an area where the total number of primary particles was about 300.

Measurement method 4: Measurement of the number of bonds of primary particles in the associated silica fine particles and measurement of the shape of the associated silica fine particles A photograph of the associated silica fine particles was taken with a transmission electron microscope (trade name: HF-3300, manufactured by Hitachi, Ltd.). I took a picture. In the photograph, the number of primary particle bonds and the shape of the associated silica fine particles were measured for all particles in an arbitrary area. These measurements were made on an area where the total number of primary particles was about 300.

Measurement method 5: Measurement of the association ratio of primary particles constituting the associated silica fine particles A photograph of the silica fine particles was taken with a transmission electron microscope (trade name: HF-3300, manufactured by Hitachi, Ltd.). In the photograph, for all particles in an arbitrary area, the total number of primary particles and the number of particles consisting only of primary particles were counted, respectively, and the number of particles consisting only of primary particles was subtracted from the total number of primary particles. The value was calculated, and the ratio of the primary particles constituting the associated silica fine particles was determined by dividing the value by the total number of primary particles. The number of particles was measured in an area where the total number of primary particles was about 300.

[Preparation of external additive mixed toner]
By melt-kneading, pulverizing and classifying 96 parts by mass of a polyester resin having a glass transition temperature Tg of 60 ° C. and a softening point of 110 ° C. and 4 parts by mass of a colorant (manufactured by Sumitomo Color Co., Ltd., trade name: Carmine 6BC) A toner having an average particle diameter of 7 μm was obtained. 40 g of this toner was mixed with 1 g of the hydrophobic associative silica fine particles by a sample mill to obtain an external additive mixed toner. Using this, the toner fluidity was measured according to the following measurement method 7. The results obtained are shown in Table 2.

Measurement method 6: Measurement of toner fluidity The toner fluidity was measured using a powder fluidity analyzer FT-4 (manufactured by Sysmex Corporation). The measurement principle of this apparatus will be described. A cylindrical container placed vertically is filled with powder, and while rotating two rotating blades (blades) provided at the tip of a vertical shaft rod in the powder, a certain distance (from height H1) Down to H2. By measuring the force received from the powder separately for the torque component and the load component, the respective work (energy) associated with the blade descending from H1 to H2 is obtained, and then the total energy of both Find the amount. The smaller the total energy amount measured in this way, the better the fluidity of the powder, so it can be used as an index of powder fluidity.

  The fluidity of the toner can be measured according to the above measurement principle by measuring the powder fluidity in the stability test, flow rate test, aeration test, and compression test having different measurement conditions described in detail below. . As will be described below, the container and blade to be used are properly used according to each test.

container:
In the stability, flow rate and ventilation tests, a glass cylindrical container having a volume of 120 ml, an inner diameter of 80 mm, and a length of 60 mm was used. In the compression test, a glass cylindrical container having a volume of 25 ml, an inner diameter of 25 mm, and a length of 52.5 mm was used. It is comprised so that air can be introduce | transduced from the lower part of a container.

blade:
Two stainless steel shaft rods are vertically mounted in the center of the cylindrical container so as to be horizontally opposed to each other. A blade with a diameter of 48 mm is used for a container with a volume of 120 ml, and a blade with a diameter of 23.5 ml is used for a container with a volume of 25 ml.

  Length from H1 to H2: 50 mm for a container with a volume of 120 ml and 47.5 mm for a container with a volume of 25 ml.

Stability test:
As described above, the powder flow characteristics when the powder filled in the measurement container is caused to flow from a stationary state are observed. The total energy amount is measured seven times continuously under the condition that the rotational speed of the blade tip is 100 mm / sec. Table 2 shows the total amount of energy for the seventh time (referred to as basic fluidity energy because it is the most stable state). The smaller the value, the higher the stability.

Flow rate test:
The powder flow characteristics with respect to the change of flow velocity are observed. Table 2 shows the total energy amount when the rotational speed of the blade tip was measured at 10 mm / sec. The smaller the value, the higher the fluidity.

Ventilation test:
Check the powder flow characteristics according to the air flow rate. The rotational speed of the blade tip is set to 100 mm / sec, the amount of air introduced from the lower part of the container is increased in steps of 0.1 mm / sec from 0 mm / sec, and measured separately in six steps from 0.5 mm / sec. Table 2 shows the total energy amount at the minimum air flow rate (0 mm / sec) and the maximum air flow rate (0.5 mm / sec). The smaller the value, the higher the powder fluidity when air is involved.

Compression test:
The powder flow characteristics with respect to compression are observed. After applying a weight to the powder through a piston and compressing it by applying pressure at 10 N, the rotational speed of the blade tip was measured at 100 mm / sec to obtain the total energy amount. The results are shown in Table 2. The smaller the powder, the higher the powder fluidity when the powder is compressed.

[Developer preparation]
5 parts by weight of the external additive mixed toner prepared above and 95 parts by weight of a carrier coated with a polymer obtained by polyblending a perfluoroalkyl acrylate resin and an acrylic resin on a ferrite core having an average particle diameter of 85 μm are mixed. Was prepared. Using this developer, the toner charge amount, toner adhesion to the photoreceptor, and cleaning properties were measured in accordance with the following measurement methods 7, 8, and 9, and the results obtained are shown in Table 2.

Measurement method 7: Measurement of toner charge amount The developer is left for 1 day under conditions of high temperature and high humidity (30 ° C., 90% RH (relative humidity)) or low temperature and low humidity (10 ° C., 15% RH). The mixture was mixed for 30 seconds with a shaker to perform tribocharging. The charge amount of each sample was measured using a blow-off powder charge amount measuring device (trade name: TB-200, manufactured by Toshiba Chemical Corporation) under the same conditions. By determining the difference in toner charge amount under the above two conditions, the environmental dependency of the toner was evaluated.

Measurement Method 8: Measurement of Toner Adhesion to Photoreceptor The above developer was placed in a two-component modified developer equipped with an organic photoreceptor, and a print test of 30000 sheets was performed. The adhesion of toner to the photoreceptor can be detected as white spots in all solid images. The degree of white spots was evaluated according to the following criteria.
10 or more white spots / cm2: 1 to 9 white spots / cm2: 0 white spots / cm2: None

Measurement method 9: Cleaning performance Cleaning performance was evaluated by visually confirming the occurrence of scratches on the surface of the latent image carrier and the sticking of residual toner and the effect on the output image after the actual machine evaluation was completed.
A: Not generated.
○: Slight scratches are observed, but there is no effect on the image.
Δ: Residual toner and scratches are observed, but the influence on the image is small.
×: Residual toner is considerably large, and vertical stripe-like image defects occur.
× ×: Residual toner adheres and many image defects occur.

<Example 2>
In Example 1, 162 g of hydrophobic associative silica fine particles were obtained as a dry powder except that the association promoting additive ethylenediamine was changed to 5.8 g (0.065 mol) of 2-dimethylaminoethanol. Measurement was performed in the same manner as in Example 1 using the hydrophobic-associated silica fine particles. The results are shown in Tables 1 and 2.

<Example 3>
In the same manner as in Example 1, except that the association promoting additive ethylenediamine was changed to 1.95 g (0.0043 mol) of a 20% aqueous solution of tetramethylammonium hydroxide, 159 g of hydrophobic associated silica fine particles were obtained as a dry powder. . Measurement was performed in the same manner as in Example 1 using the hydrophobic-associated silica fine particles. The results are shown in Tables 1 and 2.

<Example 4>
In Example 1, the same as that of Example 1, except that ethylenediamine as an association promoting additive was obtained by hydrolyzing titanium di-n-butoxide (bis-2,4-pentadionate) with an excess of aqueous ammonia to obtain 1.95 g of a 20% aqueous methanol solution. Thus, 163 g of hydrophobic associative silica fine particles were obtained as a dry powder. Measurement was performed in the same manner as in Example 1 using the hydrophobic-associated silica fine particles. The results are shown in Tables 1 and 2.

<Example 5>
In a 1 liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer, 208 g of methanol, 13.8 g of water, and 16.6 g of 28 mass% aqueous ammonia were mixed. This solution was adjusted to 35 ° C., and 20 g (0.13 mol) of tetramethoxysilane and 15 g of 5.4 mass% aqueous ammonia were simultaneously added while stirring, and both were added dropwise over 20 minutes. Thereafter, the mixture was stirred for 30 minutes while maintaining 35 ° C. to produce core particles. Thereto, 1.95 g (0.0043 mol) of a 20% aqueous solution of tetramethylammonium hydroxide was added as an association promoting additive. Thereafter, 367.9 g (2.4 mol) of tetramethoxysilane and 124.4 g of 5.4 mass% ammonia water started to be dripped simultaneously, tetramethoxysilane was dripped over 4 hours, and ammonia water was dripped over 3 hours. did. Even after the completion of the dropwise addition, the suspension was further stirred for 0.5 hours to carry out hydrolysis to obtain a suspension of hydrophilic associative silica fine particles. Next, an ester adapter and a condenser tube were attached to the glass reactor, the suspension was heated to 60 to 70 ° C. to distill off 400 g of methanol, and then 400 g of water was added. Next, 100 g of methanol water was distilled off until the suspension reached 100 ° C., and 100 g of water was added three times. Further, 100 g of methanol water was distilled off to obtain an aqueous suspension of hydrophilic associated silica fine particles. To the obtained aqueous suspension, 3.9 g (0.029 mol) of methyltrimethoxysilane was added dropwise at room temperature over 0.5 hours, and stirring was continued for 12 hours after the addition. Thus, the surface of the silica fine particles was subjected to a first-stage hydrophobization treatment to obtain a first hydrophobic associative silica fine particle aqueous dispersion. After adding 50 g (0.31 mol) of hexamethyldisilazane to the obtained dispersion at room temperature, this dispersion is heated to 98 ° C. and reacted for 3 hours, whereby the silica fine particles in the dispersion are trimethylsilylated. Turned into. Next, the solvent in the dispersion was distilled off at 80 ° C. under reduced pressure (6650 Pa) to obtain 160 g of hydrophobic associated silica fine particles as powder. Measurement was carried out in the same manner as in Example 1 using the final hydrophobic associative silica fine particles obtained. The obtained results are shown in Tables 1 and 2.

<Example 6>
[Synthesis of hydrophobic-associated silica fine particles]
In a 1 liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer, 208 g of methanol, 13.8 g of water, and 16.6 g of 28 mass% aqueous ammonia were mixed. This solution was adjusted to 35 ° C., and 20 g (0.13 mol) of tetramethoxysilane and 15 g of 5.4 mass% aqueous ammonia were simultaneously added while stirring, and both were added dropwise over 20 minutes. Thereafter, the mixture was stirred for 30 minutes while maintaining 35 ° C. to produce core particles. Thereto, 1.95 g (0.0043 mol) of a 20% aqueous solution of tetramethylammonium hydroxide was added as an association promoting additive. Thereafter, 367.9 g (2.4 mol) of tetramethoxysilane and 124.4 g of 5.4 mass% ammonia water started to be dripped simultaneously, tetramethoxysilane was dripped over 4 hours, and ammonia water was dripped over 3 hours. did. Even after the completion of the dropwise addition, the suspension was further stirred for 0.5 hours to carry out hydrolysis to obtain a suspension of hydrophilic associative silica fine particles. Next, after adding 50 g (0.31 mol) of hexamethyldisilazane to the obtained dispersion at room temperature, this dispersion is heated to 110 ° C. and reacted for 3 hours, whereby silica fine particles in the dispersion are obtained. Was trimethylsilylated. Subsequently, the solvent in this dispersion was distilled off at 61 ° C. under reduced pressure (6650 Pa) to obtain 159 g of hydrophobic associated silica fine particles as powder. Measurement was carried out in the same manner as in Example 1 using the final hydrophobic associative silica fine particles obtained. The obtained results are shown in Tables 1 and 2.

<Comparative Example 1>
In the same manner as in Example 1, except that the association promoting additive was not used, 159 g of hydrophobic associative silica fine particles were obtained as a dry powder. Measurement was performed in the same manner as in Example 1 using the hydrophobic-associated silica fine particles. The results are shown in Tables 1 and 2.

<Comparative example 2>
In Example 1, 160 g of hydrophobic associative silica fine particles were added in the same manner except that ethylenediamine as an association promoting additive was not added after nucleation, but was charged in advance before nucleation, nucleated and grown. Obtained as a dry powder. Measurement was performed in the same manner as in Example 1 using the hydrophobic-associated silica fine particles. The results are shown in Tables 1 and 2.

<Comparative Example 3>
In a 1 liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer, 208 g of methanol, 13.8 g of water, and 16.6 g of 28 mass% aqueous ammonia were mixed. The solution was adjusted to 35 ° C., and while stirring, 387.9 g (2.55 mol) of tetramethoxysilane and 139.4 g of 5.4% by mass ammonia water were begun simultaneously. Ammonia water was added dropwise over 4 hours. Even after the completion of the dropwise addition, the suspension was further stirred for 0.5 hours to carry out hydrolysis to obtain a suspension of hydrophilic associative silica fine particles. Next, an ester adapter and a condenser tube were attached to the glass reactor, the suspension was heated to 60 to 70 ° C. to distill off 400 g of methanol, and then 400 g of water was added. Next, 100 g of methanol water was distilled off and the addition of 100 g of water was repeated three times until the suspension reached 100 ° C., and then 100 g of methanol water was distilled off to obtain an aqueous suspension of hydrophilic associated silica fine particles. To the resulting aqueous suspension, 3.9 g (0.029 mol) of methyltrimethoxysilane was added dropwise at room temperature over 0.5 hours, and stirring was continued for 12 hours after the addition. Thus, the surface of the silica fine particles was subjected to a first-stage hydrophobization treatment to obtain a first hydrophobic associative silica fine particle aqueous dispersion. After adding 480 g of methyl isobutyl ketone to the obtained dispersion, 598 g of water was distilled off over 5 hours by heating the dispersion to 80 to 110 ° C. After adding 50 g (0.31 mol) of hexamethyldisilazane to the obtained dispersion at room temperature, this dispersion is heated to 110 ° C. and reacted for 3 hours, whereby silica fine particles in the dispersion are obtained. Trimethylsilylated. Next, the solvent in this dispersion was distilled off at 80 ° C. under reduced pressure (6650 Pa) to obtain 163 g of hydrophobic silica fine particles as a powder. Evaluation was performed in the same manner as in Example 1 using the hydrophobic silica fine particles. The results are shown in Tables 1 and 2.

１）７回目
２）ブレードスピード １０ｍｍ／ｓ
３）通気量 ０ｍｍ／ｓ
４）通気量 ０．５ｍｍ／ｓ
５）加圧 １０Ｎ

1) 7th time 2) Blade speed 10mm / s
3) Aeration rate 0mm / s
4) Aeration rate 0.5mm / s
5) Pressurization 10N

  As shown in Comparative Examples 1, 2, and 3, the silica fine particles produced without performing the step (B) of the present invention or without performing the steps (B) and (C) do not become associated silica fine particles. In Table 1 and Comparative Example 1 where the steps (B) were not performed, the powder flowability was inferior in the stability test, flow rate test, and aeration test, the toner adhesion and cleaning properties were poor, and the association promoting additive was added early. In Comparative Example 2, the powder flowability is inferior in the stability test, flow rate test, aeration test, and compression test, and the toner adhesion and cleaning properties are poor. Further, in Comparative Example 3 in which the steps (B) and (C) are not performed, the stability is stable. In the property test, it was revealed that the powder fluidity was inferior and the toner adhesion and cleaning properties were poor. On the other hand, as shown in the Examples, the associated silica fine particles produced by the steps (A) to (F) to (F ′) of the present invention are used in the stability test, flow rate test, aeration test, and compression test. It was revealed that the body fluidity was excellent and the toner adhesion and cleaning properties were excellent.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Claims (13)

A method for producing associated silica fine particles in which two or more primary particles having an average particle diameter in the range of 5 to 500 nm are associated,
(A) General formula (1): Si (OR ¹ ) ₄ (1)
(Wherein, R ¹ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms)
At least one compound selected from the group consisting of a tetrafunctional silane compound and a partial hydrolysis-condensation product of the tetrafunctional silane compound in a mixed medium of a hydrophilic organic solvent and water in the presence of a basic substance. A step of hydrolyzing and condensing to produce core particles of hydrophilic silica fine particles;
(B) adding an association promoting additive into the system to associate the core particles to form a core particle aggregate;
(C) At least one compound among the tetrafunctional silane compound represented by the general formula (1) and a partial hydrolysis condensation product of the tetrafunctional silane compound is further added to the system, followed by hydrolysis and condensation. A method for producing an associated silica fine particle, comprising a step of reacting to produce an associated silica fine particle by growing and associating the core particle aggregate.   The method for producing associating silica fine particles according to claim 1, wherein the association promoting additive is any one of salts, a polyfunctional compound, and a condensation catalyst.   3. The method for producing associated silica fine particles according to claim 1, wherein the association promoting additive is a salt composed of a tetraalkylammonium hydroxide compound.   The method for producing associated silica fine particles according to claim 1 or 2, wherein the association promoting additive is a polyfunctional compound selected from amino alcohols, diamines, and glycols.   The method for producing associated silica fine particles according to claim 1 or 2, wherein the association promoting additive is a condensation catalyst selected from Ti, Zr, Zn, and Al-based organometallic compound complexes. The hydrophilic organic solvent is
Formula (2): R ² OH (2)
(Wherein R ² is a monovalent hydrocarbon group having 1 to 6 carbon atoms)
The method for producing associated silica fine particles according to any one of claims 1 to 5, wherein the alcohol solvent is represented by the formula:   The method for producing associated silica fine particles according to any one of claims 1 to 6, wherein the basic substance is ammonia. After the step of producing (C) the associated silica fine particles according to any one of claims 1 to 7,
(D) removing the hydrophilic organic solvent from the mixed medium and adding water to obtain an aqueous dispersion of the hydrophilic associated silica fine particles;
(E) R ³ SiO _3/2 units on the surface of the hydrophilic associative silica fine particles in the aqueous dispersion (wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) And the step of generating primary hydrophobic associative silica fine particles,
(F) Furthermore, R ⁴ ₃ SiO _1/2 units (wherein R ⁴ is the same or different, substituted or unsubstituted, 1 to 6 carbon atoms) on the surface of the primary hydrophobic associative silica fine particles. A process for producing secondary hydrophobic associative silica fine particles, which is a monovalent hydrocarbon group). In the step (E), for the associated silica fine particles,
General formula (3): R ³ Si (OR ⁵ ) ₃ (3)
(Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms. is there)
R ³ SiO _3/2 unit (formula) is added to the surface of the hydrophilic associative silica fine particles by adding a trifunctional silane compound represented by the formula, a partial hydrolysis condensation product of the trifunctional silane compound, or a mixture thereof. 9. The method for producing associated silica fine particles according to claim 8, wherein R ³ is the same as above, and an aqueous dispersion of the first hydrophobic associative silica fine particles is obtained. After the step of producing (C) the associated silica fine particles according to any one of claims 1 to 7,
(D) removing the hydrophilic organic solvent from the mixed medium and adding water to obtain an aqueous dispersion of the hydrophilic associated silica fine particles;
(E) R ³ SiO _3/2 units (wherein R ³ substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms is bonded to the surface of the hydrophilic associative silica fine particles in the aqueous dispersion. A) to produce primary hydrophobic association silica fine particles,
(F ′) Further, the dispersion medium of the aqueous dispersion of the primary hydrophobic association silica fine particles is replaced with a ketone solvent to obtain a ketone solvent dispersion of the primary hydrophobic association silica fine particles. For the ketone-based solvent dispersion of the next hydrophobically associated silica fine particles,
General formula (4): R ⁴ ₃ SiNHSiR ⁴ ₃ (4)
(Wherein R ⁴ is the same or different, substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms)
Or a silazane compound represented by
General formula (5): R ⁴ ₃ SiX (5)
(Wherein X is an OH group or a hydrolyzable group)
Or a mixture of the silazane compound and the monofunctional silane compound is added to triorganosilylate the reactive groups remaining on the surface of the first hydrophobic associative silica fine particles, Introducing the R ⁴ ₃ SiO _1/2 unit (wherein R ⁴ is the same as above) to the surface of the secondary hydrophobic associative silica fine particles to form the secondary hydrophobic associative silica fine particles. A method for producing associated silica fine particles. In the step (E), for the associated silica fine particles,
General formula (3): R ³ Si (OR ⁵ ) ₃ (3)
(Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms. is there)
R ³ SiO _3/2 unit (formula) is added to the surface of the hydrophilic associative silica fine particles by adding a trifunctional silane compound represented by the formula, a partial hydrolysis condensation product of the trifunctional silane compound, or a mixture thereof. 11. The method for producing associated silica fine particles according to claim 10, wherein R ³ is the same as above, to obtain an aqueous dispersion of the first hydrophobic associative silica fine particles.   The method for producing associated silica fine particles according to claim 10 or 11, wherein the ketone solvent is methyl isobutyl ketone.   An external toner additive for developing an electrostatic charge image, comprising hydrophobic associated silica fine particles produced by the method for producing associated silica fine particles according to any one of claims 8 to 12.

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