JPH07187647A - Hydrophobic silica powder, its production and electrophotographic developer containing the same - Google Patents

Abstract

PURPOSE:To obtain a hydrophobic silica powder having sufficient hydrophobicity and positive triboelectrifying property to iron in combination and capable of stably showing the improvement effect of toner fluidity by bringing a floating silica powder into contact with a hydrophobic organosilicic compound and an amino substituted silane compound. CONSTITUTION:The desired powder is obtained by bringing the floating silica powder into contact with the hydrophobic organosilicic compound expressed by formula I or II and the amino substituted silane compound expressed by formula III. The hydrophobic silica powder is surface treated with the hydrophobic organosilicic compound expressed by formula I or II and the amino substituted silane compound expressed by formula III and has >=60% hydrophobicity measured by permeability method and positive electrifying property to iron. In the formulas, R<1> represents 3-20C alkyl, R<2> represents 1-20C alkyl, R<3> represents I, Cl, Br or alkoxyl, R<4> represents alkyl containing amino group, R<5> represents 1-20C alkyl, R<6> represents I, Cl, Br or alkoxyl, (n) represents 0, 1 or 2, (x) represents 1-3, (y) represents 0, 1 or 2, (z) represents 1-3 and (x)+(y)+(z)=4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophobic silica powder useful as a toner additive, a method for producing the same, and an electrophotographic developer containing the same.

[0002]

_2. Description of the Related Art So-called hydrophobic silica powder (hereinafter simply referred to as "hydrophobic silica"), in which an organic substance is adhered to the surface of fine silica (SiO ₂ ) powder to make it hydrophobic, is used in copying machines, laser printers, It is widely used as a toner fluidity improver in electrophotography including plain paper facsimiles. In such applications, the triboelectrification property with respect to the carrier iron or iron oxide is one of the important properties.

The toner has a polarity opposite to that of the charge of the photoconductor used for forming the electrostatic latent image. Therefore, it is desired that hydrophobic silica having the same polarity as that of the toner is used so that the charging property of the toner is not disturbed or largely changed, and the charging property is stable. Since chalcogen-based materials such as selenium, which have been mainly used as photoreceptors, have a positive polarity, negatively charged toner has been used for development, and thus negatively charged type has also been used as hydrophobic silica. . On the other hand, since recently developed photoreceptors made of organic semiconductors are generally of a negative polarity type, positively charged toner is used, and silica having a large positive charge is required.

The amount of triboelectricity of hydrophobic silica with respect to iron is
It shows a positive or negative value depending on the type of organic material used for the hydrophobic treatment. As one of methods for obtaining a silica powder having a positive chargeability, a method of treating the surface of the silica powder with an amino-substituted silane compound is known (Japanese Patent Laid-Open No. 53-22447).
No.). Since the silica powder treated with the amino-substituted silane compound is hydrophilic as it is, it is generally used to be double-treated with hexamethyldisilazane which is a hydrophobic silane compound in order to make it hydrophobic. But,
Even after double treatment with an amino-substituted silane compound and hexamethyldisilazane, the hydrophobicity of the resulting hydrophobic silica is still insufficient, and it is easily affected by the environment, especially humidity, and the charge amount is not constant. It was pointed out that there were problems such as the short life of the. Moreover, the charge amount was not sufficient.

Further, instead of hexamethyldisilazane, dimethyl silicone (also known as dimethyl polysiloxane)
Is also proposed to obtain a hydrophobic silica having a high hydrophobicity by carrying out a double treatment with an amino-substituted silane compound while maintaining a sufficient charge amount (Japanese Patent Laid-Open No. Hei 5-
No. 97423). However, the silica powder obtained by this method has a drawback that its fluidity is lower than that of the silica powder using hexamethyldisilazane.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a hydrophobic silica which has both sufficient hydrophobicity and positive triboelectricity with respect to iron and which exhibits a sufficient effect of improving toner fluidity in a stable manner. It is to provide a manufacturing method. Another object of the present invention is to provide an electrophotographic developer having stable chargeability and excellent fluidity by adding the above silica powder to a toner.

[0007]

As a result of intensive studies aimed at achieving the above object, the inventors of the present invention have found that a hydrophobic silane compound and an amino-substituted silane compound in which at least one substituent is an alkyl group having 3 or more carbon atoms. It has been found that the above object can be achieved by surface treatment of silica powder used in combination.

The gist of the present invention is to provide a transmittance method obtained by surface-treating a hydrophobic organosilicon compound represented by the general formula (1) or (2) and an amino-substituted silane compound represented by the general formula (3). It is a hydrophobic silica having a positive chargeability to iron with a hydrophobicity ratio of 60% or more measured by.

General formula (1): R ¹ Si (R ² ) _n (R ³ ) _3-n General formula (2): R ¹ (R ² ) ₂ Si NH Si R ¹ (R ² ) ₂ General formula ( 3): (R ⁴ ) _x (R ⁵ ) _y Si (R ⁶ ) _{z In the} formula, R ¹ : an alkyl group having 3 to 20 carbon atoms, R ² : an alkyl group having 1 to 20 carbon atoms, and R ³ : I , Cl, Br or an alkoxyl group,, R ^4: an alkyl group containing an amino group, R ^5: an alkyl group having 1 to 20 carbon atoms, R ^6: I, Cl, Br or an alkoxyl group,, n: 0, 1 , Or 2, x: an integer of 1 to 3, y: 0, 1, or 2, z: an integer of 1 to 3, x + y + z = 4.

According to the present invention, the silica powder in a floating state is brought into contact with the hydrophobic organosilicon compound represented by the above general formula (1) or (2) and the amino-substituted silane compound represented by the above (3). There is also provided a process for producing hydrophobic silica consisting of the above, and an electrostatic photography developer characterized by containing the hydrophobic silica.

The above general formulas (1) and (2) used in the present invention
Each of the hydrophobic organosilicon compounds represented by is a silane compound and a disilazane compound, each of which has a common characteristic of having at least one long-chain alkyl group (R ¹ group) having 3 or more carbon atoms. The presence of the alkyl group renders the compound hydrophobic. Below, this general formula (1) and
The compounds represented by (2) are collectively called hydrophobic silane compounds. When the silica powder is surface-treated with the hydrophobic silane compound having the long-chain alkyl group, the compound reacts with the powder surface to give the silica powder sufficient hydrophobicity and fluidity. The carbon number of this long-chain alkyl group is 3 or more,
It may be 20 or less, but is preferably in the range of 6 to 12 in order to impart higher hydrophobicity and fluidity. The R ² group is preferably an alkyl group having 1 to 3 carbon atoms. General formula (1) or
The following compounds are exemplified as typical examples of the compound represented by (2), but other compounds can also be used (Me = CH
₃ , Et = C ₂ H ₅ ).

C ₃ H ₇ Si (OMe) ₃ , C ₆ H ₁₃ Si (OEt) ₃ , C ₆
H ₁₃ SiCl ₃ , C ₈ H ₁₇ SiMe (OMe) ₂ , C ₈ H ₁₇ SiMeCl ₂ ,
C ₁₀ H ₂₁ Si (OMe) ₃ , C ₁₂ H ₂₅ Si (OEt) ₃ , C ₄ H ₉ SiMe
₂ NHSiMe ₂ C ₄ H ₉ .

The amino-substituted silane compound represented by the general formula (3) used in the present invention reacts with the surface of the silica powder to impart positive chargeability to iron to the silica powder. In the general formula (3), the amino group contained in the R ⁴ group may be any of primary, secondary and tertiary amino groups, and the number of amino substituents may be 1 or 2 or more. The carbon number of the R ⁴ group is not particularly limited, but is usually in the range of 1 to 20. preferable
The R ⁴ group is an aminoalkyl group, an aminoalkylaminoalkyl group, a phenylaminoalkyl group or the like. The R ⁵ group is preferably an alkyl group having 1 to 3 carbon atoms. The following compounds are exemplified as typical examples of the amino-substituted silane compound, but compounds other than these can also be used.

H ₂ N (CH ₂ ) ₃ Si (OEt) ₃ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ S
i (OMe) ₃ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ SiMe (OMe) ₃ , C ₆ H ₅ HN (C
_{H 2) 3 Si (OMe)} 3, H 2 N (CH 2) 2 NH (CH 2) 3 SiCl 3.

The silica powder used in the present invention is silica composed of fine particles called colloidal silica. The particle size of the silica powder is not particularly limited as long as it is suitable for the application in which the charging property is required, but it is generally preferable that the specific surface area is 50 m ² / g or more. The average primary particle size of a suitable silica powder is generally several nm to several hundreds nm.

The method of measuring the triboelectric charge amount on iron is described in the literature.
(Eg, coloring material, 55 [9] 630-636, 1982). Since this triboelectric charge amount changes depending on the amount of the amino-substituted silane compound used, the desired amount of charge can be obtained by adjusting the amount of triboelectric charge. When used for positively charged toner, the amount of triboelectric charge on iron is generally in the range of +20 μC / g to +700 μC / g, especially +
It is desirable to be in the range of 100 μC / g to +300 μC / g.

In the present invention, the hydrophobicity of hydrophobic silica is experimentally determined by the transmittance method. The hydrophobicity measurement by the transmittance method is performed by the following procedure. 1.0 g of the hydrophobic silica powder sample to be measured is placed in an extraction flask together with 100 mL of water, and vigorously shaken and stirred for 5 minutes. Then, it is allowed to stand for 1 minute, and a small amount of suspension is withdrawn from the bottom of the flask. The transmittance of this solution for light at 550 nm was calculated as 10% for pure water.
The value expressed as 0% is the hydrophobicity of the silica.

The higher the value of the hydrophobicity measured in this way, the lower the hygroscopicity of the silica powder, and the smaller the change in the toner charge amount with respect to humidity when added to the toner, and the more the agglomeration occurs. Highly useful because it increases the effect of prevention. Practically, if the hydrophobicity thus obtained is 60% or more, the effect of improving the fluidity of the toner is sufficient. Therefore, in the present invention, the hydrophobicity of the hydrophobic silica is 60% or more. Desirably, when the hydrophobization rate is 70% or more, even better results are obtained.

The hydrophobic silica powder of the present invention has an appropriate particle size.
(Or specific surface area) silica powder, at least one hydrophobic silane compound represented by the general formula (1) or (2) and at least one amino-substituted silane compound represented by the general formula (3) It is manufactured by surface treatment with and. This surface treatment can be carried out by various conventionally known methods, but the treatment method in which the silica powder is suspended and the above two kinds of silane compounds are brought into contact with the powder is uniform without aggregation. It is a preferred method because it gives a hydrophobic silica treated with.

Since the silica powder is a very fine particle, it can be brought into a suspended state only by mechanical stirring.
Therefore, the silica powder to be treated is mechanically sufficiently stirred to be in a floating state, and in this state, the hydrophobic silane compound and the amino-substituted silane compound are dissolved in a solvent, if necessary, or diluted with a solvent, The treatment can be carried out simultaneously or sequentially (whichever comes first) by dropping or spraying. By this treatment, the surface of silica powder is
Reacts with hydrophobic silane compounds and amino-substituted silane compounds (the hydroxyl groups on the silica surface react with the alkoxyl groups or halogen groups and amino groups in these silane compounds). At the same time, the hydrophobic silane compound and the amino-substituted silane compound bonded to the surface of the powder are treated with siloxane by the alkoxyl group or halogen contained therein reacting with a small amount of surrounding water to undergo hydrolysis.
The surface of the silica powder is partially or completely covered with a film formed from these silane compounds firmly bonded to the surface because the (Si-O) bond can crosslink to form a film. It will be. As a result, the surface properties unique to each of these silane compounds are imparted to the surface of the silica powder, and a sufficient positive charge amount for iron is exhibited, and at the same time, the surface of the silica powder is hydrophobized, that is, , Hydrophobic silica is obtained. Further, since the coating is firmly bonded to the surface of the silica powder, the hydrophobicity and the chargeability are stably maintained even under a severe environment such as high temperature and high humidity.

In order to obtain a liquid treatment liquid having a viscosity suitable for dropping or spraying, an appropriate organic solvent such as alcohol, ketone or hydrocarbon is used as a solvent depending on the properties of the hydrophobic silane compound and amino-substituted silane compound used. Alternatively, it can be used as a diluent. Further, in the obtained treatment liquid, an organic amine such as diethylamine is added as a catalyst for enhancing the reactivity of the silica powder surface with the hydrophobic silane compound and the amino-substituted silane compound, or instead of the addition of the amine. It is also possible to blow ammonia gas into the silica powder to be treated. After adding processing solution, 10
It is preferable to heat at a temperature in the range of 0 ° C. to 250 ° C. to complete the reaction and remove the solvent. Although the heating time in this case depends on the temperature, it is usually 1 including the heating time.
~ 5 hours. The above treatment is preferably performed in an atmosphere of an inert gas such as nitrogen in order to prevent the above-mentioned two kinds of silane compounds, which are treatment agents, from being oxidized.

By the above treatment, the hydrophobic silica of the present invention
(That is, the amount of the above two kinds of treating agents used to obtain a silica powder having a hydrophobicity of 60% or more as measured by the transmittance method and having a positive chargeability) is obtained. It varies depending on conditions such as the amount of positive charge, the specific surface area of the silica powder to be treated, and the type of treating agent. The required amount of the treating agent used can be easily determined by experiment. Specific surface area 13
Taking 0 m ² / g silica powder as an example, the amount of hydrophobic silane compound used is relative to the weight of the silica powder.
2.0 to 15.0% by weight, preferably about 4.0 to 10.0% by weight,
The amount of amino-substituted silane compound used is 1.0 to 15.0% by weight,
Preferably, a silica powder having a hydrophobicity of 60% or more as measured by the transmittance method in the range of about 2.0 to 10.0% by weight and having a positive chargeability can be obtained.

The ratio of the two kinds of treating agents to be used is not particularly limited as long as the hydrophobic silica having the above characteristics can be obtained by the treatment, but usually, the weight ratio of amino-substituted silane compound: hydrophobic silane compound is from 10: 3 to. It will be in the range of 3:10.

The hydrophobic silica powder of the present invention treated with the hydrophobic silane compound and the amino-substituted silane compound as described above can be added to the toner by a usual method. Toners generally contain small amounts of pigments and charge control agents in addition to the thermoplastic resin. When this toner is mixed with a carrier (usually iron powder or iron oxide powder) and other additives, the electrophotographic developer of the present invention is obtained. As long as the hydrophobic silica of the present invention is blended in the toner, the other components of this developer may be the same as conventional ones, and may be either one-component system or two-component system.

The hydrophobic silica powder of the present invention can enhance the fluidity of the toner without impairing the characteristics of the toner even if it is contained in the toner in a relatively large amount. It was also confirmed that the obtained developer is less likely to be affected by humidity and temperature, and fogging and image deterioration are less likely to occur.

The amount of the hydrophobic silica of the present invention added to the toner is not particularly limited as long as the resulting developer exhibits the above-mentioned characteristic improvement, but it is usually based on the total weight of the toner. The amount is 0.05 to 5.0% by weight, preferably 0.1 to 10% by weight.

[0027]

EXAMPLES Examples and comparative examples are shown below for the purpose of facilitating the understanding of the present invention, but these do not limit the present invention in any way. In the examples, the hydrophobicity measurement by the transmittance method was performed according to the above procedure, and the triboelectric charge amount with respect to iron was measured according to the method described in Coloring Material, 55 [9] 630-636, 1982.

Example 1 20 g of heat-dried silica powder (specific surface area 130 m ² / g) was charged into a stainless steel container,
The silica powder was treated by sequentially spraying the treating agents A and B having the following compositions at room temperature while mechanically stirring the silica powder so as to float in a nitrogen atmosphere.

Treatment agent composition A: Hydrophobic silane compound [C ₆ H ₁₃ Si (OMe) ₃ ] 1.0 g diethylamine few drops methanol 4.0 mL B: amino-substituted silane compound [H ₂ N (CH ₂ ) ₃ Si (OEt) ₃ ] 0.5 g diethylamine few drops i-propanol 4.0 mL After the spraying was completed, external heating was performed under a nitrogen stream while continuing to stir the silica powder. The temperature was raised to 220 ° C. over 50 minutes, the temperature was maintained for 4 hours, and the temperature was allowed to cool to room temperature. The hydrophobicity of the obtained hydrophobic silica by the transmittance method and the triboelectrification amount for iron were 85% and +63 μC /
It was g.

Next, 18% by weight of carbon (pigment) and 3% by weight of nigrosine (charge control agent) were dispersed in the styrene-acrylic acid copolymer resin,
After crushing, 5-10μm (average particle size 7μm) and 7.5-20μm
(Average particle size 10 μm), and a toner composed of two kinds of colored resin powders having different particle sizes was prepared.
Below, they are referred to as 7 μm toner and 10 μm toner, respectively). In 100 g of each of these two types of toner, 0.3 g of the above-mentioned hydrophobic silica was mixed with a toner of 7 μm, and 0.5 g was mixed with a toner of 10 μm, and a fluidity test was conducted using the toner to which the hydrophobic silica was added. It was

The fluidity test is carried out by using a 10 g sample of the toner to be tested.
Was placed on top of two sieves of 48 mesh (upper) and 100 mesh (lower), and sieved at a strength of 3 for 1 minute using an electromagnetic laboratory sieve shaker (Fritsch), The rate of toner that passed through the mesh sieve was evaluated. In this case, 77% for 7 μm toner and 69% for 10 μm toner
The liquidity result was obtained.

Further, 30 g of two kinds of toners containing the hydrophobic silica are mixed with 1000 g of iron oxide powder,
An electrophotographic developer was prepared. The triboelectric charge of this developer was +15 μC / g for both toners.

When this developer was put into a commercially available copying machine and subjected to a life test, no fog occurred on the image even after copying about 25,000 sheets. Higher temperature and humidity (28 ℃,
When the same test was performed under an environment of 85% RH), similarly, good images with high contrast and high contrast were obtained up to almost the same number.

Example 2 20 g of a heat-dried silica powder (specific surface area 130 m ² / g) was sprayed with a treating agent having the following composition at room temperature as in Example 1.

The treatment agent sets forming a hydrophobic silane compound _{[C 6 H 13 Si (OMe} ) 3] 1.0 g amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt) 3] 1.5 g of diethylamine few drops i- After the dropwise addition of 8.0 mL of propanol, the external heating was performed in the same manner as in Example 1. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
It was 69% and +277 μC / g.

Next, using the hydrophobic silica obtained by this treatment, two kinds of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was carried out.
%, 71% for 10 μm toner. Further, 30 g of each of these toners was mixed with 1000 g of iron oxide powder to prepare a developer for electrophotography. The triboelectric charges of this developer were both +17 μC / g. When this developer was put into a commercially available copying machine and subjected to a life test, no fog was generated on the image even after copying about 22,000 sheets. Furthermore, when the same test was performed in a high temperature and high humidity (28 ° C, 85% RH) environment, similarly good images were obtained up to almost the same number.

(Example 3) 20 g of heat-dried silica powder (specific surface area 130 m ² / g) was sprayed with treating agents A and B having the following compositions in the same manner as in Example 1 at room temperature.

The treatment agent of sets formed A: hydrophobic silane compound _{[C 10 H 21 Si (OMe} ) 3] 1.0 g of diethylamine few drops of methanol 4.0 mL B: Amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt ) ₃ ] 0.5 g diethylamine few drops i-propanol 8.0 mL After the dropping was completed, external heating was performed in the same manner as in Example 1. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
It was 84% and +101 μC / g.

Next, using the hydrophobic silica thus obtained, two types of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was conducted.
It was 67% with the toner of μm. Further, 30 g of each of these toners was mixed with 1000 g of iron oxide powder to prepare a developer for electrophotography. The triboelectric charge of this developer is +16 for both
It was μC / g. When this developer was put into a commercially available copying machine and a life test was conducted, no fog occurred in the image even after copying about 24,000 sheets. More hot and humid (28
When the same test was performed even in an environment of ℃, 85% RH), similarly good images were obtained up to almost the same number of sheets.

Example 4 To 20 g of the heat-dried silica powder (specific surface area 200 m ² / g), treating agents A and B having the following compositions were sequentially sprayed at room temperature in the same manner as in Example 1.

The treatment agent of sets formed A: hydrophobic silane compound _{[C 6 H 13 SiMe (OMe} ) 2] 2.0 g of diethylamine few drops of methanol 4.0 mL B: Amino-substituted silane compound _{[H 2 N (CH 2)} 2 NH (CH ₂ ) ₃ Si (OMe) ₃ ] 1.0 g Diethylamine Several drops Acetone 4.0 mL After the completion of dropping, external heating was performed in the same manner as in Example 1. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
It was 89% and +335 μC / g.

Next, using the hydrophobic silica obtained by this treatment, two kinds of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was carried out.
%, 67% for 10 μm toner. Further, 30 g of each of these toners was mixed with 1000 g of iron oxide powder to prepare a developer for electrophotography. The triboelectric charges of this developer were both +17 μC / g. When this developer was put into a commercially available copying machine and subjected to a life test, no fog was generated on the image even after copying about 22,000 sheets. Further, when the same test was performed even in an environment of high temperature and high humidity (28 ° C, 85% RH), similarly good images were obtained up to almost the same number.

(Example 5) To 20 g of heat-dried silica powder (specific surface area 130 m ² / g), treating agents A and B having the following compositions were sequentially sprayed at room temperature in the same manner as in Example 1.

The treatment agent of sets formed A: hydrophobic silane compound _{[C 12 H 25 Si (OEt} ) 3] 1.0 g of diethylamine few drops of ethanol 4.0 mL B: Amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt ) ₃ ] 1.0 g diethylamine several drops i-propanol 4.0 mL After completion of the dropwise addition, external heating was performed in the same manner as in Example 1. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
It was 92% and +132 μC / g.

Next, using the hydrophobic silica obtained by this treatment, two kinds of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was carried out.
%, 68% for 10 μm toner. Further, 30 g of each of these toners was mixed with 1000 g of iron oxide powder to prepare a developer for electrophotography. The triboelectric charges of this developer were both +16 μC / g. When this developer was put into a commercially available copying machine and a life test was conducted, no fog was generated on the image even after copying about 26,000 sheets. Further, when the same test was performed even in an environment of high temperature and high humidity (28 ° C, 85% RH), similarly good images were obtained up to almost the same number.

Example 6 To 20 g of the heat-dried silica powder (specific surface area 130 m ² / g), treating agents A and B having the following compositions were sprayed in that order at room temperature in the same manner as in Example 1.

The treatment agent of sets formed A: hydrophobic silane compound _{[C 3 H 7 Si (OEt} ) 3] 1.0 g of diethylamine few drops of ethanol 4.0 mL B: Amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt ) ₃ ] 1.0 g diethylamine several drops i-propanol 4.0 mL After completion of the dropwise addition, external heating was performed in the same manner as in Example 1. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
75% and +248 μC / g.

Next, using the hydrophobic silica obtained by this treatment, two types of toner having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was conducted.
%, 65% for 10 μm toner. Further, 30 g of each of these toners was mixed with 1000 g of iron oxide powder to prepare a developer for electrophotography. The triboelectric charges of this developer were both +17 μC / g. When this developer was put into a commercially available copying machine and subjected to a life test, no fog was generated on the image even after copying about 23,000 sheets. Further, when the same test was performed even in an environment of high temperature and high humidity (28 ° C, 85% RH), similarly good images were obtained up to almost the same number.

(Example 7) 20 g of heat-dried silica powder (specific surface area 130 m ² / g) was sprayed with a treating agent having the following composition at room temperature as in Example 1.

The treatment agent sets forming a hydrophobic silane compound _{[(C 6 H 13 SiMe 2} ) 2 NH] 2.0 g amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt) 3] 1.4 g of diethylamine few drops i After the dropwise addition of 8.0 mL of propanol, external heating was performed as in Example 1. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
It was 74% and +256 μC / g.

Next, using the hydrophobic silica obtained by this treatment, two kinds of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was carried out.
%, 72% for 10 μm toner. Further, 30 g of each of these toners was mixed with 1000 g of iron oxide powder to prepare a developer for electrophotography. The triboelectric charges of this developer were both +17 μC / g. When this developer was put into a commercially available copying machine and subjected to a life test, no fog was generated on the image even after copying about 23,000 sheets. Furthermore, when the same test was performed in a high temperature and high humidity (28 ° C, 85% RH) environment, similarly good images were obtained up to almost the same number.

Comparative Example 1 20 g of heat-dried silica powder (specific surface area 130 m ² / g) was sprayed at room temperature on a treating agent having the following composition as in Example 1.

[0053] processing Additives formed amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt) 3] 1.0 g of diethylamine few drops n- propanol 5.0 mL After the completion of dropwise addition, similarly to the external heating as in Example 1 performed It was The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
18% and +285 μC / g. Next, using the hydrophobic silica obtained by this treatment, two types of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was conducted.
26% for the m toner and 32% for the 10 μm toner. Furthermore, 30 g of each of these toners was added to iron oxide powder 10
It was mixed with 00 g to prepare a developer for electrophotography. The triboelectric charges of this developer were both +18 μC / g.

Since the treatment agent did not contain a hydrophobic silane compound, both the hydrophobicity of the treated silica powder and the fluidity of the toner were significantly reduced. When this developer was put into a commercially available copying machine and a life test was conducted, image fog occurred after about 5,000 copies. In the environment of high temperature and high humidity (28 ℃, 85% RH), it was further reduced, and the image was fogged after about 4,000 copies.

Comparative Example 2 20 g of heat-dried silica powder (specific surface area 130 m ² / g) was sprayed at room temperature on the treating agent having the following composition as in Example 1.

[0056] processing Additives formed amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt) 3] 1.0 g of hexamethyldisilazane 1.0 g Diethylamine a few drops n- propanol 5.0 mL After the completion of dropwise addition, as in Example 1 Similarly, external heating was performed. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
It was 44% and +348 μC / g. Next, using the hydrophobic silica obtained by this treatment, two types of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was conducted.
It was 62% for the m toner and 58% for the 10 μm toner. Furthermore, 30 g of each of these toners was added to iron oxide powder 10
It was mixed with 00 g to prepare a developer for electrophotography. The triboelectric charges of this developer were both +18 μC / g.

When hexamethyldisilazane is used according to the prior art in place of the hydrophobic silane compound used in the present invention, the fluidity is not much different from that of the present invention, but the hydrophobicity ratio is much lower than 60%, The sex was insufficient. When this developer was put in a commercially available copying machine and a life test was conducted, image fog was generated in about 10,000 copies. In the high temperature and high humidity (28 ℃, 85% RH) environment, it was further reduced, and fog was generated on the image at about 5,500 copies. It can be seen that when the hydrophobizing agent is hexamethyldisilazane, the hydrophobicity is unstable, and therefore the fluidity is significantly reduced in a hot and humid environment.

Comparative Example 3 20 g of a silica powder (specific surface area 130 m ² / g) which had been dried by heating was sprayed at room temperature with a treating agent having the following composition as in Example 1.

[0059] processing Additives formed amino-substituted silane compound _{[H 2 N (CH 2)} 3 Si (OEt) 3] 1.0 g of dimethyl polysiloxane [Shin-Etsu Chemical Co., Ltd. KF-96 (50 cs)] 1.0 g of diethylamine few drops n After the dropwise addition of 5.0 mL of propanol, external heating was performed in the same manner as in Example 1. The hydrophobization rate after treatment and the triboelectric charge on iron are respectively
It was 87% and +385 μC / g. Next, using the hydrophobic silica obtained by this treatment, two types of toners having different particle sizes were prepared in the same manner as in Example 1, and a fluidity test was conducted.
m toner was 50%, and 10 μm toner was 54%. Furthermore, 30 g of each of these toners was added to iron oxide powder 10
It was mixed with 00 g to prepare a developer for electrophotography. The triboelectric charges of this developer were both +16 μC / g.

When dimethylpolysiloxane, which is one type of silicone oil, is used in accordance with another conventional technique in place of the hydrophobic silane compound used in the present invention, the hydrophobicity is good, but the fluidity is poor. Was enough. It is speculated that the reason is that polysiloxane enhances the agglomeration of silica powder. When this developer was put into a commercially available copying machine and a life test was conducted, fog occurred on the image after about 8,000 copies. In the environment of high temperature and high humidity (28 ℃, 85% RH), it was further reduced, and the image was fogged after about 7,000 copies.

[0061]

As is clear from the above results, according to the present invention, by treating the silica powder by the combined use of the hydrophobic silane compound and the amino-substituted silane compound, an appropriate positive triboelectric charge with respect to iron is obtained, It is possible to obtain hydrophobic silica having a hydrophobicity of 60% or more measured by the transmittance method. When this treatment is carried out with the silica powder in a floating state, it is possible to obtain a uniformly treated hydrophobic silica without aggregation. The hydrophobic silica exhibits stable hydrophobicity even in a humid environment and has a high effect of improving the fluidity of the toner. When this hydrophobic silica is added to the toner for electrophotography as a fluidity improving agent to prepare an electrophotographic developer, an electrostatic charge image can be clearly developed with high contrast without fog, and at the same time as in summer in Japan. An electrophotographic developer having a stable and long-life developing property even in a humid environment can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yumi Kato 1-297, Kitabukuro-cho, Omiya City, Saitama Prefecture Central Research Laboratory, Mitsubishi Materials Corporation

Claims (3)

[Claims] 1. A hydrophobicity measured by a transmittance method, which is surface-treated with a hydrophobic organosilicon compound represented by the general formula (1) or (2) and an amino-substituted silane compound represented by the general formula (3). Hydrophobic silica powder with a conversion rate of 60% or more and a positive charge to iron. General formula (1): R ¹ Si (R ² ) _n (R ³ ) _3-n General formula (2): R ¹ (R ² ) ₂ Si NH Si R ¹ (R ² ) ₂ General formula (3): (R ⁴ ) _x (R ⁵ ) _y Si (R ⁶ ) _{z In the} formula, R ¹ : an alkyl group having 3 to 20 carbon atoms, R ² : an alkyl group having 1 to 20 carbon atoms, R ³ : I, Cl, Br or an alkoxyl group,, R ^4: an alkyl group containing an amino group, R ^5: an alkyl group having 1 to 20 carbon atoms, R ^6: I, Cl, Br or an alkoxyl group,, n: 0, 1 or 2, , X: an integer of 1 to 3, y: 0, 1, or 2, z: an integer of 1 to 3, x + y + z = 4. 2. The method for producing a hydrophobic silica powder according to claim 1, which comprises contacting a silica powder in a floating state with the hydrophobic organosilicon compound and the amino-substituted silane compound. 3. A developer for electrostatic photography, which comprises the hydrophobic silica powder according to claim 1.