JP3437667B2 - White conductive powder and conductive resin composition using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a white conductive powder having excellent conductive properties and excellent stability over time,
Mainly used in antistatic paints, fibers, resins, rubbers, films, etc. Also provided are white electroconductive powders which are applied to charge control agents for toners for electrophotography, resistance control agents for photosensitive drums, image recording materials, electrostatic recording papers, electrode materials and the like.

[0002]

2. Description of the Related Art Currently known conductive powder is a single particle type having a uniform structure such as tin oxide powder containing antimony, and selected inorganic powder is used as a base powder and the powder surface is It is classified into a so-called conductive layer coating type in which a conductive layer is coated. In particular, the latter conductive layer-covered conductive powder used a base powder selection to reduce the addition amount by reducing the specific gravity, and used the shape of plate-shaped or needle-shaped particles, compared to the single particle type. It has the features that the efficiency of the conductive performance can be improved, and that it can be used as a conductive powder for transparent films by utilizing the refractive index and particle size of the base powder, and for a conductive coating having a high hiding power. In recent years, the amount of its use has been increasing, and it is expected to expand to new applications. Among the conductive layer coating types, in the field where high conductivity performance is required, the tin oxide type tin oxide containing antimony is used. Things are the mainstream.

However, since the problem of toxicity of antimony has been particularly noticed in Europe and the like, it has become necessary to develop an antimony-less type that does not contain antimony. Therefore, a conductive powder coated with indium oxide containing tin oxide is considered, and is disclosed in JP-A-61-14161.
8, JP-A-60-253112 and JP-A-5-26
No. 2526 and the like were disclosed, but these did not satisfy the conductive performance because the coating of the conductive powder on the base powder was not uniform, and were not sufficient in terms of stability of the conductive performance with time.

Therefore, in Japanese Patent Laid-Open No. 6-338213,
Disclosed is that the conductive layer is uniformly coated on the substrate powder,
Although the conductive performance was satisfactory, it was still insufficient in terms of stability over time.

Next, although there are many precedent cases in which a coupling agent is surface-treated, there is no one in which an indium-tin-based conductive layer-covering type conductive powder is used as the object to be treated, and it is a feature of the present invention. None have improved the deterioration of the conductive performance over time due to the properties of certain indium.

[0006]

DISCLOSURE OF THE INVENTION The present invention is based on indium
The tin-based conductive layer-covered conductive powder has excellent conductivity with an initial powder specific resistance of 100 Ω · cm or less, preferably 50 Ω · cm or less, and has stability over time that is important as a practical material, that is, , 10 Ω · cm or less per month at 50 ° C., preferably 5 Ω · cm
And the powder resistivity is 100 Ω · c even after aging.
It is intended to provide a white electroconductive powder having an excellent electroconductivity while maintaining m or less.

From the standpoint of industrially using the conductive powder, it is considered that it is desired that the powder has not only the conductive performance according to the intended use but also the deterioration with time. In particular, indium-tin-based conductive powders have excellent conductive performance, but on the other hand, there are some properties peculiar to indium that are inevitable over time, and it has been a problem to improve them.

[0008]

Means for Solving the Problems The inventors of the present invention have prepared a conductive layer coating type conductive powder comprising a white inorganic pigment as a base powder, the surface of which is coated with an indium-tin based conductive layer.
The present invention has been completed as a result of intensive studies to develop a powder having excellent electric conductivity and excellent stability over time.

That is, the present invention is characterized in that a white inorganic pigment is used as a base powder, and the surface of the powder is coated with a conductive layer of an indium-tin type conductive layer, and the powder is subjected to a surface treatment with a coupling agent. To provide a powdery powder.

The white conductive powder according to the present invention is selected from silane-based, titanate-based, zirconate-based, aluminate-based, and zirco-aluminate-based, with respect to the indium-tin-based conductive layer-coated conductive powder. The specific surface area of the indium-tin conductive layer coating type conductive powder of the object to be treated is 0.03 to 0.4 per 1 m ² / g.
The weight%, preferably 0.05 to 0.35% by weight, can be obtained by coating with a mixer such as a Henschel mixer. When the amount treated is 0.03% by weight or less, the effect of improving stability over time is obtained. In addition, if the treatment amount is 0.4% by weight or more, it is wasteful in terms of cost, and rather, the coupling treatment layer becomes an insulating layer and the conductivity is deteriorated, which is not preferable. Further, when coating with a Henschel mixer, it is preferable to keep the temperature of the apparatus at 60 to 80 ° C. for more uniform coating.

The indium-tin-based conductive layer coating type conductive powder which is the object to be processed has a sufficient conductive property of the conductive layer itself, and the conductive layer is uniformly coated on the base powder. Is important and not evenly coated,
Since the surface of the uncoated base powder blocks the conduction path, a low resistance conductive powder cannot be obtained. The coating amount of indium and tin for having the good conductive performance is
Relative to the substrate of the inorganic pigment, 5 to 200 wt% as an In ₂ O _3, preferably 8-150% by weight, as SnO ₂ 5
˜240 wt%, preferably 8-173 wt%.

The white inorganic pigment as the base of the white conductive powder is any commercially available titanium dioxide, aluminum oxide, silicon dioxide, zinc oxide, barium sulfate, zirconium oxide, alkali metal titanate or muscovite. Can be used. Explaining in more detail using titanium dioxide as an example, there is no limitation on the size of particles, and any shape such as spherical or needle-like, and further as a crystalline form, anatase type, rutile type and amorphous The thing of can also be used. Although the present invention emphasizes white color,
It can also be applied to various colored pigments such as iron oxide.

The detailed description of the manufacturing method of the present invention will be continued.

In the case of a conductive layer-covering type conductive powder, when the conductive layer is poorly adhered to the base powder, the powder specific resistance increases even at room temperature, and the initial value is, for example, a few days. It may be 2 to 3 times. It is considered that this is due to the indium oxide ultrafine particles containing tin oxide, which are free without being deposited. However, even in the best coating state, due to the conductive mechanism of the tin oxide-containing indium oxide semiconductor, there is a slight increase in the specific resistance even at room temperature.
Under a heated or humidified environment, the specific resistance of powder is unavoidably increased. Industrially, assuming the environment in which it is actually used, we believe that a material that does not impair the original conductive performance at high temperatures is required, and we have conducted research to ensure that it does not change over time. Overlaid.

As a countermeasure, basically, it is sufficient to block the contact with oxygen and water, so that a method of surface-treating the surface of the conductive powder can be considered, but in order to maintain the characteristics of the conductive performance. Is not preferable because the surface treatment will form an insulating layer that blocks the conduction path.

As a result of repeated research on various methods, the present inventors have found that an appropriate amount of silane-based, titanate-based, zirconate-based, or aluminate-based conductive powder coated with an indium-tin-based conductive layer is used. It was unexpected, not to mention that it was unexpectedly excellent in stability over time by treating with a coupling agent of a zircoaluminate type and a coupling agent of a zircoaluminate type. It was found that the treatment of No. 1 reduces the powder specific resistance and improves the conductivity. Furthermore, the effect of lowering the powder specific resistance value by the treatment of the coupling agent is effective even for those whose conductivity performance has already deteriorated over time, and an appropriate amount of coupling agent is added to the conductive powder that has deteriorated over time. It was found that the treatment also had an effect of recovering the level before the passage of time.

Next, the improving effects of the present invention will be specifically listed.

First, regarding the indium-tin-based conductive layer coating type conductive powder which is the object to be processed, the initial value of 100Ω is observed when the change in the powder specific resistance when left at 50 ° C. for one month is observed.・ Even if it has excellent conductivity of less than or equal to cm, it will be several hundred to several thousand Ω · cm after the passage of time.
Even a conductive powder having a high conductivity performance region of Ω · cm or less may become 100 Ω · cm or more after aging and may no longer be a material that imparts high conductivity. On the other hand, a silane coupling agent having 30 or less carbon atoms, preferably 21 or less carbon atoms, and more preferably 2 to 13 carbon atoms is added to the indium-tin conductive layer coating type conductive powder. , The specific surface area of which is 0.03 to 0.4% by weight, preferably 0.05 to 0.35% by weight per 1 m ² / g, so that the powder specific resistance is reduced by one digit as compared with that before the treatment. In addition, the increase in powder resistivity was suppressed to 10 Ω · cm or less even when stored at 50 ° C., and high conductivity performance could be maintained even when placed at high temperature. Also, among the coupling agents to be coated, in the case of a silane-based,
Coupling agent in which carbon, a vinyl group having a double bond between carbons, a methacrylo group or an epoxy group having a ring oxygen group is present in the molecule is more effective than a saturated type,
Further, the one having a mercapto group also tended to show an excellent effect. In the titanate system, those containing P, N or S in the functional group were particularly effective. Two or more of these coupling agents can be used in combination depending on the application.

The present invention will be described in more detail with reference to examples. The following examples are provided for illustration only and the scope of the invention is not limited thereby.

[0020]

[Production Example 1 of white conductive powder] Rutile titanium dioxide (KR-310 manufactured by Titanium Industry Co., Ltd., specific surface area 7 m ² / g) was used as a base powder, and 200 g of this base powder was dispersed in pure water to obtain 2 liters. It was made into a water suspension and kept warm at 70 ° C. Stannic chloride _{(SnCl 4 · 5H 2 O)} 23.2g
Was dissolved in 200 ml of 2N hydrochloric acid and a 12 wt% aqueous ammonia solution was added to the suspension so that the pH of the suspension was 6 to 7.
Was added in parallel for about 90 minutes so as to maintain the temperature at 1. Subsequently, separately prepared indium chloride (InCl ₃ ) 73.4
g and stannic chloride (SnCl ₄ .5H ₂ O) 10.8
An indium-stannic acid solution having g dissolved in 900 ml of 2N hydrochloric acid and a 12 wt% aqueous ammonia solution were added in parallel over about 2 hours so as to maintain the pH of the suspension at 6 to 7. The suspension is then filtered, washed and washed at 120 ° C for 10
Allowed to dry for hours. This dried product was subjected to a heat treatment at 550 ° C. for 1 hour in a nitrogen gas stream (2 liters / minute), and an indium-tin-based conductive layer-coated conductive powder having a specific surface area of 9.5 m ² / g. (Conductive powder A) was obtained.

[0021]

[Production Example 2 of white conductive powder] Production Example 1 except that the base powder is aluminum oxide (specific surface area 6.8 m ² / g)
In the same manner as in (1) above, an indium-tin-based conductive layer-covered conductive powder (conductive powder B) having a specific surface area of 11.8 m ² / g was obtained.

[0022]

[Production Example 3 of white conductive powder] Anatase type ultrafine particle titanium dioxide (specific surface area 40 m ² / g) was used as the base powder, and stannic acid solution was stannic chloride (SnCl ₄ .5H ₂ O) 53.1.
g dissolved in 400 ml of 2N hydrochloric acid, and indium-stannic acid solution added to indium chloride (InCl
₃ ) 212.8 g and stannic chloride (SnCl ₄ .5H ₂
O) was performed in the same manner as in Production Example 1 except that 31.3 g was dissolved in 1330 ml of 2N hydrochloric acid,
An indium-tin conductive layer coating type conductive powder (conductive powder C) having a specific surface area of 48.3 m ² / g was obtained.

[0023]

Example 1 2000 g of the conductive powder A of Production Example 1 was mixed with
The mixture was placed in a Henschel mixer heated to 0 to 80 ° C., and 70 g of γ-glycidoxypropyltriethoxysilane as a coupling agent was added over about 15 minutes while stirring at a low speed. After the addition was completed, the mixture was stirred at a high speed for 10 minutes and heat-treated at 100 ° C. to obtain a white conductive powder.

[0024]

Example 2 A white conductive powder was obtained in the same manner as in Example 1, except that 40 g of vinyltriethoxysilane was used as the coupling agent.

[0025]

Example 3 In Example 1, the coupling agent was n-
White conductive powder was obtained in the same manner except that 40 g of propanol and 20 g of isopropyltridodecylbenzenesulfonyl titanate were mixed.

[0026]

Example 4 A white conductive powder was prepared in the same manner as in Example 1, except that the object to be treated was the conductive powder B of Production Example 2 and the coupling agent was γ-mercaptopropyltrimethoxysilane 40 g. Got

[0027]

Example 5 In Example 4, the coupling agent was γ-
A white conductive powder was obtained in the same manner except that 60 g of methacryloxypropyltrimethoxysilane was used.

[0028]

Example 6 In Example 4, the coupling agent was γ-
A white conductive powder was obtained in the same manner except that 10 g of aminopropyltriethoxysilane was used.

[0029]

Example 7 In Example 4, the coupling agent was n-
A white conductive powder was obtained in the same manner except that 40 g of hexane and 20 g of isopropyltriisostearoyl titanate were mixed.

[0030]

Example 8 A white conductive powder was obtained in the same manner as in Example 1, except that the object to be treated was the conductive powder C of Production Example 3 and the coupling agent was 300 g of vinyltriethoxysilane.

[0031]

[Comparative Example 1] A conductive powder B which has not been treated with the coupling agent of Production Example 2.

[0032]

Comparative Example 2 In Example 6, the amount of coupling agent was 3
A white conductive powder was obtained in the same manner except that the amount was g.

[0033]

Comparative Example 3 In Example 6, the amount of coupling agent was 1
A white conductive powder was obtained in the same manner except that the amount was 40 g.

The measurement results of the samples obtained in Examples 1 to 8 and Comparative Examples 1 to 3 are shown in Table 1. The measured values described in Examples and Comparative Examples are the values measured in the following manner.

(1) Evaluation of Powder Resistivity A sample powder was compression-molded at 280 Kg / cm ² , and its electric resistance value was measured using a universal bridge manufactured by Yokogawa Hewlett-Packard Company and converted into a specific resistance.

(2) Change with time The sample powder was put in an oven at 50 ° C. and the specific resistance of the powder was measured after one month. The value obtained by subtracting the powder specific resistance value before the aging from the powder specific resistance value after the lapse of time was expressed as the change value with time.

[0037]

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09C 3/08 C09C 3/08 H01B 1/00 H01B 1/00 (72) Inventor Takashi Harada At 1978 Kogushi, Ube City, Yamaguchi Prefecture 25 Within Titan Kogyo Co., Ltd. (56) Reference JP-A-1-261469 (JP, A) JP-A-63-215704 (JP, A) JP-A-6-338213 (JP, A) JP-A-7- 14430 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09C 3/12 C08K 9/02 C08K 9/04 C08L 101/00 C09C 3/06 C09C 3/08 H01B 1/00

Claims (3)

(57) [Claims] 1. A substrate particle is coated with an indium-tin-based conductive layer, and a coupling agent layer is further formed thereon, and the coupling agent layer has a specific surface area of 1 m ² / m ² . 0.03 to 0.4% by weight per gram of white conductive powder having excellent conductive performance and improved stability over time. 2. The coupling agent is one or more selected from the group consisting of a silane type, a titanate type, a zirconate type, an aluminate type and a zircoaluminate type. The white conductive powder according to claim 1. 3. A conductive resin composition obtained by blending the white conductive powder according to claim 1 or 2 with a resin component.