JPH0680405A - Hydrophobic metallic oxide powder - Google Patents

Abstract

PURPOSE:To improve the hydrophobizing ratio by coating metallic oxide powder such as SiO2, Al2O3 or TiO2 with an organopolysiloxane and a polyalkyleneimine. CONSTITUTION:A treating agent is prepared by diluting an aqueous solution of a polyalkyleneimine such as polyethyleneimine at about 30% concentration and a polyorganopolysiloxane in an amount of 5-150wt.% based on the polyalkyleneimine component with an adequate amount of a solvent such as n-propanol. Metallic oxide powder such as SiO2, Al2O3 or TiO2 having >=50m<2>/g specific surface area is then charged into a container, stirred and dispersed in an N2 atmosphere at ambient temperature. The treating agent in an amount so as to provide <=20wt.% polyalkyleneimine component based on the metallic oxide powder is subsequently sprayed and added thereto under stirred conditions and the obtained mixture is heated at 100-250 deg.C for a prescribed time and then allowed to cool to afford the objective metallic oxide having >=60% hydrophobizing ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophobic metal oxide powder used for improving powder fluidity.

[0002]

2. Description of the Related Art The so-called hydrophobic metal oxide powder obtained by hydrophobizing the surface of the metal oxide powder with an organic substance is used in electrophotography, electrostatic recording, etc.
It is widely used as an agent for improving cleaning properties.
In these applications, the triboelectrification property of the metal oxide powder itself to the carrier iron or iron oxide is one of the important properties, and its hydrophobicity and triboelectrification property are simultaneously controlled by various treatment agents. ing. Among them, as a method of reducing the negative chargeability or imparting the positive chargeability, a method of treating the surface of the powder with an amine-based organic compound is generally used. However, when a low molecular weight compound such as a quaternary ammonium salt is used as the amine-based organic compound, the reproducibility of the obtained charge amount is low because the bondability with the surface is low, and the environment is particularly susceptible to moisture. Such problems are likely to occur.
On the other hand, when treated with an amino group-substituted silane coupling agent or an amino-modified polysiloxane, these treatment agents are firmly fixed chemically or physically on the surface of the metal oxide powder, so that they are effectively positively treated. The chargeability can be obtained. However, these treatment agents are relatively expensive and it is difficult to finely control the charge amount because there are few types of products on the market.

On the other hand, polyalkyleneimine is an inexpensive organic compound having a high molecular weight and is expected as a material for improving the above problems of the treating agent. However, when the metal oxide powder is actually treated only with polyalkyleneimine, it is difficult to perform uniform surface treatment because the polyalkyleneimine has a low affinity for the metal oxide surface, and the polyalkyleneimine itself is hydrophilic. Therefore, the metal oxide powder cannot be rendered hydrophobic.
Therefore, the obtained powder is not suitable for the above applications.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a metal oxide powder having a controlled charge amount and a sufficient hydrophobicity by using an inexpensive material, polyalkyleneimine.

[0005]

[Means for Solving the Problems] [Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above problems and obtain a desired hydrophobic metal oxide powder, and as a result, organopolysiloxane was changed to polyalkyleneimine. By carrying out the surface treatment of the metal oxide powder at the same time, it was found that a metal oxide powder having a controlled charge amount and sufficient hydrophobicity was obtained, and the object of the present invention was achieved. . That is, the organopolysiloxane imparts high hydrophobicity to the metal oxide powder, and at the same time, the polyalkyleneimine is strongly bonded to the metal oxide powder surface via the organopolysiloxane having high physical adhesion. The surface of the metal oxide powder was made hydrophobic by the organopolysiloxane at the same time that the positive chargeability was imparted, and the above results were obtained.

A feature of the present invention is to provide a metal oxide powder treated with an organopolysiloxane and a polyalkyleneimine. In a preferred embodiment of the present invention, a metal oxide powder which is treated with the above compound and has a hydrophobicity of 60% or more measured by a transmittance method, in particular, the metal oxide is silica, alumina or There is provided the above metal oxide powder which is titania. The present invention will be described in more detail below.

The organopolysiloxane used in the present invention is not particularly limited except that it imparts sufficient hydrophobicity to the metal oxide surface, but in practice, those having a methyl group, a phenyl group or a hydro group as a substituent are used. From the viewpoint of processing operation, preferably 10 cs to 10,000
It is preferable to use one having a viscosity of about 0 cs. Currently commercially available materials include Shin-Etsu Silicone KF-96,
KF-99, KF-56; SH200, SH510, SH1107 and the like manufactured by Toray Dow Corning Silicone Co., Ltd. are exemplified. The polyalkyleneimine used in the present invention is generally used for industrial applications such as polyethyleneimine and polypropyleneimine (average molecular weight: several hundred to
It is about 100,000), and it is most preferable in practice to use a polyethyleneimine aqueous solution having a concentration of about 30%. The metal oxide powder used in the present invention can be selected according to the application, but silica, alumina or titania is particularly preferable for applications such as fluidity improvement.
The particle size can also be selected according to the use, but those having a specific surface area of 50 m ² / g or more are particularly preferable for the above use. The metal oxide may be a complex oxide or a mixture.

The amount of the treating agent suitable for obtaining the hydrophobic metal oxide powder targeted by the present invention depends on the kind of the metal oxide powder to be treated, the specific surface area and the kind of the treating agent, and is particularly specified. Not done. However, since excessive use of polyalkyleneimine causes a decrease in hydrophobicity, polyalkyleneimine is usually not more than 20% by weight without water, and particularly preferably 12% with respect to the weight of the metal oxide powder to be treated. It is desirable to use an amount of less than or equal to%. For the purpose of immobilizing the polyalkyleneimine, the organopolysiloxane is preferably used in an amount of 5 to 150%, particularly preferably 50 to 100%, based on the weight of the polyalkyleneimine not containing water.

The method of measuring the triboelectric charge amount on iron is specified in the literature, for example, "Coloring Material" 55 [9] 630-636.1982. The transmittance method is a method for experimentally obtaining the hydrophobicity of the treated metal oxide powder, and comprises the following steps. 1.0 g of the treated metal oxide powder and 100 ml of water are put in a separating funnel for extraction and shaken vigorously for 5 minutes. Then 1
Let stand for a minute and withdraw a small amount of suspension from the bottom of the separatory funnel. The transmittance of this liquid for light of 550 nm is represented by the transmittance of pure water as 100%, and the value is defined as the hydrophobicity of the metal oxide. As the value of the hydrophobicity ratio thus measured is higher, the hygroscopicity of the metal oxide powder is reduced, the change in the charge amount of the toner due to the humidity is reduced, and the effect of preventing aggregation is increased. High value, but practically 60%
Above, it is desirable to have a value of 70% or more.

A conventionally known method is applied to the treatment of the metal oxide powder used in the present invention. That is, organopolysiloxane and polyalkyleneimine are added dropwise or sprayed to the metal oxide powder to be treated while mechanically stirring it sufficiently. It is also possible to use a solvent such as alcohol, ketone or hydrocarbon as a diluent depending on the viscosity of the polyalkyleneimine and the organopolysiloxane used. After adding the treating agent, the temperature is in the range of 100 to 250 ° C., particularly preferably 1 under a nitrogen stream.
The reaction is completed by heating at a temperature in the range of 30 to 170 ° C and the solvent is removed. Further, depending on the kind of the metal oxide powder, when the dry treatment as described above is difficult, it is possible to perform the treatment under a wet condition using a considerable amount of a solvent.

[0011]

EFFECT OF THE INVENTION In the hydrophobic metal oxide powder constituted by the present invention, the polyalkyleneimine is more firmly fixed on the surface of the metal oxide powder by using the organopolysiloxane together with the polyalkyleneimine. As a result, it has the following features. Higher positive chargeability can be obtained and reproducibility is higher than in the case where no organopolysiloxane is used. In addition, stability against moisture etc. has also been improved. further,
The hydrophobic metal oxide powder obtained by the present invention can control the charge amount by changing the amount of the treating agent used, and is expected to be applied to a wide range of applications.

[0012]

DETAILED DESCRIPTION OF THE INVENTION 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 at all.

[Example 1] Heat-dried silica powder ("Aerosil # 130" specific surface area 13 manufactured by Nippon Aerosil Co., Ltd.)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Dimethyl polysiloxane (Shin-Etsu Chemical Co., Ltd. "KF-96" (50cs)) 1.00 g n-propanol 5.0 ml After spraying, stir for 5 minutes at room temperature. After that, external heating was performed under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The same operation was repeated to obtain a total of 5 lots of hydrophobic silica powder. The maximum value and the minimum value of the hydrophobicity of these powders by the transmittance method and the triboelectrification amount with respect to iron were 94%, 86% and 109 μC / g, 98 μC / g, respectively.

[Examples 2 to 9] In Example 1, the results when the composition or kind of the treating agent was changed are summarized in Table 1. The hydrophobization rate and the triboelectric charge amount showed the maximum value and the minimum value in 5 lots as in the case of Example 1.

[0015]

[Table 1] Examples 1 to 9 Measured amount of treating agent used Example Polyethylene Organopoly Hydrophobicity Charge amount Nimine ^* a Siloxane (%) (μC / g) (g) (g) (maximum value / minimum value) ( Maximum / minimum) 1 20 10 ^* b 94/86 109/79 2 10 10 ^* b 96/92 71/54 3 5 10 ^* b 96/91 43/12 4 2 5 ^* b 98/92 -74 / -120 5 2 10 ^* b 91/84 -194 / -250 6 10 10 ^* c 96/92 83/43 7 20 10 ^* c 84/78 138/95 8 10 5 ^* d 81/70 99/63 9 20 10 ^* d 82/69 94/77 ^* a: Polyethyleneimine 30% aqueous solution weight ^* b: Shin-Etsu Silicone KF-96 (50cs) ^* c: Shin-Etsu Silicone KF-99 ^* d: Shin-Etsu Silicone KF -56

[Comparative Example 1] Heat-dried silica powder ("Aerosil # 130" manufactured by Nippon Aerosil Co., Ltd. specific surface area 13)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g n-Propanol 5.0 ml After the spraying was completed, the mixture was further stirred at room temperature for 5 minutes, and then externally heated under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. This powder is hydrophilic and its triboelectric charge on iron is 2
It was 3 μC / g.

[Example 10] Heat-dried alumina powder ("Aluminum oxide C" manufactured by Nippon Aerosil Co., Ltd.)
10 g of a specific surface area of 90 m ² / g) was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Dimethyl polysiloxane (Shin-Etsu Chemical Co., Ltd. "KF-96" (50cs)) 1.00 g n-propanol 5.0 ml After spraying, stir for 5 minutes at room temperature. After that, external heating was performed under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The same operation was repeated to obtain a total of 5 lots of hydrophobic alumina powder. The maximum value and the minimum value of the hydrophobicity of these powders by the transmittance method and the triboelectrification amount with respect to iron were 82%, 63% and 99 μC / g, 42 μC / g, respectively.

[Example 12] Heat-dried titania powder ("Titanium oxide P2" manufactured by Nippon Aerosil Co., Ltd.)
10 g of 5 "specific surface area 80 m ² / g) was charged into a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Dimethyl polysiloxane (Shin-Etsu Chemical Co., Ltd. "KF-96" (50cs)) 1.00 g Acetone 5.0 ml After spraying was completed, the mixture was stirred at room temperature for 5 minutes, and then nitrogen. External heating was performed under a stream of air. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The same operation was repeated to obtain a total of 5 lots of hydrophobic titania powder. The maximum value and the minimum value of the hydrophobicity of these powders by the transmittance method and the triboelectrification amount with respect to iron were 70%, 63% and 54 μC / g, 23 μC / g, respectively.

Claims (3)

[Claims] 1. A metal oxide powder having a coating of organopolysiloxane and polyalkyleneimine. 2. The metal oxide powder according to claim 1, wherein the hydrophobization ratio measured by the transmittance method shows a value of 60% or more. 3. The metal oxide powder according to claim 1, wherein the metal oxide is silica, alumina or titania.