JP2011246547A - White pigment comprising surface-coated barium titanate particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated white pigment not deteriorating a resin even to a resin member requiring extremely high light resistance and heat resistance, and having extremely suppressed photocatalyst activity and heat catalyst activity.SOLUTION: The white pigment comprises barium titanate, whose surface is coated with an inorganic oxide containing at least one kind of element selected from Si, Al and Zr.

Description

  The present invention relates to a white pigment composed of barium titanate particles suitable for a thermoplastic resin composition requiring high light resistance and high heat resistance, and use thereof.

  Titanium dioxide pigment has a high refractive index of visible light, and is used as a white pigment in a wide range of fields such as paints, inks, plastics and paper. On the other hand, titanium dioxide has high photocatalytic activity and thermal catalytic activity, and also has a property of promoting the decomposition and deterioration of the organic resin component blended therein. For this reason, titanium dioxide pigments used in fields that require a high degree of light resistance and heat resistance are generally coated with an inorganic oxide such as silicon oxide, zirconium oxide, or aluminum oxide on the particle surface to provide light resistance or heat resistance. There is a technique for imparting a property (see, for example, Patent Document 1). However, in recent years, a resin in which a white pigment is kneaded with a light reflecting member such as a solar cell back sheet or an LED reflector has been used, and a solar cell back sheet has been light-resistant for several decades. LED light reflectors are required to have high light resistance and heat resistance that can withstand the exposure of energy from powerful light emitting elements, and conventional light resistance and heat resistance imparting techniques are not capable of suppressing catalyst activity. It has become enough.

  On the other hand, barium titanate is a white pigment that does not absorb in the visible light wavelength range, and its refractive index is as high as titanium dioxide. However, in the past, only the high dielectric constant was noticed and it was generally used as an electronic material such as a material of a multilayer ceramic capacitor. On the other hand, its use focusing on its optical characteristics is extremely rare. Patent Document 2 describes a technique for subjecting barium titanate particles to organosilane surface treatment as a means for improving resin dispersibility. However, a technique for subjecting barium titanate particles to surface treatment with an inorganic oxide has not been performed so far.

JP-A-9-48931 JP 2007-51225 A

  An object of the present invention is to provide a photocatalytic activity and a thermal catalyst that do not deteriorate the resin even for light-reflective resin members that require extremely high light resistance and heat resistance, such as solar cell backsheets and LED reflectors. It is an object of the present invention to provide a white pigment subjected to a surface coating treatment in which the activity is extremely suppressed.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, the photocatalytic activity and the thermal catalytic activity are further suppressed by using barium titanate as a raw material whose photocatalytic activity and thermal catalytic activity are much lower than those of titanium dioxide. For this reason, the present inventors have found that the white pigment subjected to the surface coating treatment does not deteriorate the light-reflective resin member by exposure to high energy heat or light, and have completed the present invention.

That is, the present invention relates to the following inventions.
1. A white pigment made of barium titanate surface-coated with an inorganic oxide containing at least one element selected from Si, Al, and Zr.
2. 2. The white pigment as described in 1 above, wherein the inorganic oxide is combined with the barium titanate particles in terms of anhydride and the surface coating is 0.1 to 5% by weight.
3. 3. The white pigment as described in 2 above, wherein the surface of the barium titanate particles is 0.5 to 3% by weight of inorganic oxide in terms of anhydride.
4). A thermoplastic resin composition containing 1 to 400 parts by weight of the white pigment described in any one of 1 to 3 above with respect to 100 parts by weight of the thermoplastic resin.
5). 5. A light-reflecting resin member obtained by molding the thermoplastic resin composition as described in 4 above.

  According to the present invention, a photocatalytic activity, a thermal catalyst that does not deteriorate the resin even for a light-reflective resin member that requires extremely high light resistance and heat resistance such as a back sheet of a solar cell and a reflector of an LED. It is possible to provide a white pigment which has been subjected to a surface coating treatment and whose activity is extremely suppressed.

2 is an electron micrograph of surface-coated barium titanate particles obtained in Example 1. FIG.

The barium titanate serving as the substrate in the present invention may be synthesized by any of the solid phase method, hydrothermal method, oxalate coprecipitation method, and sol-gel method, and its composition is BaTiO ₃ . The particle diameter is not particularly limited, but if the primary particle diameter is large, the mechanical properties of the resin are reduced, and if the primary particle diameter is small, the light reflectivity and the scattering ability are reduced, so that the resin dispersibility, light reflectivity, In order to satisfy both of the light scattering properties, particles of 0.1 to 1.5 μm are preferable, and particles of 0.2 to 1.2 μm are more preferable.

  The inorganic oxide containing at least one element selected from Si, Al and Zr coated on the surface of the substrate may be either an anhydride or a hydrate, and the thickness of the surface coating layer should be 1 to 100 nm. Is preferred. The coating amount is preferably 0.1 to 5% by weight in terms of anhydride with respect to the barium titanate particles. When the inorganic oxide coated on the substrate surface is small, the surface of the barium titanate particles cannot be covered, and the activity suppression of the photocatalyst and the thermal catalyst becomes insufficient. Moreover, when there are many inorganic oxides coat | covered by the base | substrate surface, the light reflectivity and scattering ability will fall. In order to achieve both suppression of the activity of the photocatalyst and thermal catalyst, light reflectivity, and light scattering property, the total content is more preferably 0.5 to 3% by weight.

  The surface-coated barium titanate particles according to the present invention are obtained by dispersing the raw material barium titanate particles in water to form an aqueous slurry, and the following surface treatment agent is added to the aqueous slurry to form a coating layer on the surface of the barium titanate particles. And after drying, it can obtain by baking and grinding | pulverizing as needed. As the surface treatment agent, sodium silicate, silicon tetrachloride and the like are used as the silicon source, and as the aluminum source, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride and the like are used, and as the zirconium source, Zirconium sulfate, zirconium oxychloride, zirconium oxynitrate and the like are used.

  The surface coating on the barium titanate particles according to the present invention can be performed, for example, as follows. That is, the surface treatment agent and the neutralizing agent are simultaneously added to the aqueous slurry containing the barium titanate particles, or the neutralizing agent is added after the surface treatment agent is added, or a predetermined amount of the neutralizing agent is added. Then, a known method such as a method of adding the surface treatment agent can be used. At this time, the pH of the aqueous slurry containing the surface-coated barium titanate is adjusted to about 6-8. Moreover, since barium elutes from the barium titanate particles when the pH is 5 or less, the reaction is performed so that the pH does not become 5 or less. The aqueous slurry during the reaction may be appropriately heated. Examples of neutralizers include inorganic acids such as sulfuric acid and hydrochloric acid, acidic compounds such as organic acids such as acetic acid and formic acid, basic compounds such as hydroxides or carbonates of alkali metals or alkaline earth metals, and ammonium compounds. Well-known ones can be used.

  Next, the water slurry is filtered with a filter press, a rotary press, or the like, washed with water to wash away remaining salts, and then dried with a band dryer, a spray dryer or the like to obtain a dried product. It is also possible to control the surface hydroxyl groups of the particles to an appropriate amount by baking the obtained dried product at a higher temperature. For heating and firing, a known firing device such as a rotary kiln or a tunnel kiln can be used.

  The dried or fired product thus obtained may be dry pulverized as it is, or may be re-dispersed in water and wet pulverized as a slurry, followed by filtration, washing and drying, followed by dry pulverization. May be. For dry pulverization, devices such as impact pulverizers such as hammer mills and pin mills, grinding pulverizers such as pulverizers, and airflow pulverizers such as jet mills can be used. Etc. can be used.

According to the present invention, when the dried or fired product is pulverized, an appropriate organic treating agent may be used as necessary for the purpose of further improving the affinity with the organic resin component. Examples of such organic treatment agents include polyhydric alcohols, alkanolamines, silicone oils, silane coupling agents, and titanium coupling agents. The amount of the organic treating agent is preferably in the range of 0.01 to 5% by weight with respect to the barium titanate particles.
The thermoplastic resin composition according to the present invention contains 1 to 400 parts by weight, preferably 2 to 200 parts by weight, of the surface-coated barium titanate particles described above with respect to 100 parts by weight of the thermoplastic resin.

  The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polystyrene resins, polyamide resins, polycarbonate resins, polyurethane resins, and fluorine resins. Examples thereof include resins and ABS resins. If necessary, additives such as stabilizers, antioxidants, ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, pigments, fillers and the like may be included. And can be obtained by melt kneading at an appropriate temperature according to the thermoplastic resin used. As a means for mixing, for example, a Henschel mixer, a tumbler mixer, or the like can be used. As a melt-kneading means, a single screw extruder, a twin screw extruder, a Banbury mixer, a roll, or the like can be used. .

  Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1
Using barium titanate particles having an average particle size of 0.5 μm obtained by the oxalate coprecipitation method, an aqueous slurry having a barium titanate concentration of 200 g / liter was obtained. While stirring 10 liters of this slurry, sodium aluminate corresponding to 1% by weight in terms of Al ₂ O ₃ was added to the barium titanate particles, and then sulfuric acid (1 N) was added to adjust the pH to 6.5. After the addition, the mixture was aged by stirring for 60 minutes to form an aluminum hydroxide coating layer. Then, using a suction filter, it was filtered and washed, separated into solid and liquid, and the obtained filter cake was dried at 150 ° C. and pulverized with a hammer mill, so that the surface coating composed of 1% by weight of Al ₂ O ₃ was obtained. Barium titanate particles having the following were obtained.

Example 2
Surface-coated barium titanate particles were obtained in the same manner as in Example 1 except that 3% by weight of Al ₂ O ₃ was coated on the barium titanate.

Example 3
Surface-coated barium titanate particles were obtained in the same manner as in Example 1 except that a surface coating of 5% by weight of Al ₂ O ₃ was applied to barium titanate.

Example 4
Surface-coated barium titanate particles were obtained in the same manner as in Example 1 except that the obtained filter cake was dried at 150 ° C. and then baked at 500 ° C.

Example 5
Using barium titanate particles having an average particle size of 0.5 μm obtained by the oxalate coprecipitation method, an aqueous slurry having a barium titanate concentration of 200 g / liter was obtained. While stirring 10 liters of this slurry, while maintaining the pH at 7, an aqueous solution of zirconium sulfate corresponding to 1% by weight in terms of ZrO ₂ with respect to the barium titanate particles and an aqueous sodium hydroxide solution (1 N) for 60 minutes Added simultaneously. Thereafter, the mixture was aged by stirring for 60 minutes to form a zirconium hydroxide coating layer. Then, using a suction filter, it is filtered and washed, separated into solid and liquid, and the obtained filter cake is dried at 150 ° C. and pulverized with a hammer mill to have a surface coating composed of 1% by weight of ZrO _2. Barium titanate particles were obtained.

Example 6
Using barium titanate particles having an average particle size of 0.5 μm obtained by the oxalate coprecipitation method, an aqueous slurry having a barium titanate concentration of 200 g / liter was obtained. While stirring 10 liters of this slurry, sodium silicate equivalent to 1% by weight in terms of SiO ₂ was added to the barium titanate particles, and then sulfuric acid (1 N) was added over 60 minutes so that the pH was 6.5. And then aged for 60 minutes to form a hydrous silica coating layer. Then, using a suction filter, it is filtered and washed, separated into solid and liquid, and the obtained filter cake is dried at 150 ° C. and ground with a hammer mill to have a surface coating composed of 1% by weight of SiO _2. Barium titanate particles were obtained.

Example 7
Using barium titanate particles having an average particle size of 0.5 μm obtained by the oxalate coprecipitation method, an aqueous slurry having a barium titanate concentration of 200 g / liter was obtained. While stirring 10 liters of this slurry, maintaining the pH at 7, an aqueous solution of aluminum sulfate corresponding to 1% by weight in terms of Al ₂ O _{3 with} respect to barium titanate particles and ZrO _{2 in} terms of barium titanate particles Then, an aqueous solution of zirconium sulfate corresponding to 1% by weight and an aqueous sodium hydroxide solution (1 N) were simultaneously added over 60 minutes. Thereafter, the mixture was aged by stirring for 60 minutes to form a coating layer composed of a composite of aluminum hydroxide and zirconium hydroxide. Then, using a suction filter, it is filtered and washed, separated into solid and liquid, and the obtained filter cake is dried at 150 ° C. and pulverized with a hammer mill, so that 1% by weight of Al ₂ O ₃ and ZrO ₂ 1 Barium titanate particles having a surface coating consisting of a weight percent composite were obtained.

Example 8
Using barium titanate particles having an average particle size of 0.5 μm obtained by the oxalate coprecipitation method, an aqueous slurry having a barium titanate concentration of 200 g / liter was obtained. While stirring 10 liters of this slurry, sodium silicate equivalent to 1% by weight in terms of SiO ₂ was added to the barium titanate particles, and then sulfuric acid (1 N) was added over 60 minutes so that the pH was 6.5. And then aged for 60 minutes to form a hydrous silica coating layer. Subsequently, while stirring the slurry and maintaining the pH at 7, an aqueous solution of zirconium sulfate corresponding to 1% by weight in terms of ZrO ₂ with respect to the barium titanate particles and an aqueous sodium hydroxide solution (1 N) were added. It was added simultaneously over a period of minutes. Thereafter, the mixture was aged by stirring for 60 minutes to form a zirconium hydroxide coating layer. Subsequently, sodium aluminate corresponding to 1 wt% in terms of Al ₂ O ₃ was added to the barium titanate particles while stirring the slurry, and then sulfuric acid (1 N) was added so that the pH became 6.5. After adding over 60 minutes, the mixture was stirred and aged for 60 minutes to form an aluminum hydroxide coating layer. Then, using a suction filter, it is filtered and washed, separated into solid and liquid, and the obtained filter cake is dried at 150 ° C. and pulverized with a hammer mill, so that SiO ₂ 1% by weight and ZrO ₂ 1% by weight. And barium titanate particles having a three-layer surface coating consisting of 1% by weight of Al ₂ O ₃ .

Comparative Example 1
Surface-coated barium titanate particles were obtained in the same manner as in Example 1 except that 0.05% by weight of Al ₂ O ₃ was coated on the barium titanate.

Comparative Example 2
Surface-coated barium titanate particles were obtained in the same manner as in Example 1 except that 7% by weight of Al ₂ O ₃ was coated on the barium titanate.

Comparative Example 3
The barium titanate particles having an average particle diameter of 0.5 μm obtained by the oxalate coprecipitation method were used as they were without being subjected to surface coating.

Comparative Example 4
The anatase-type titanium dioxide particles having an average particle diameter of 0.4 μm obtained by the sulfuric acid method were used as they were without being subjected to surface coating.

Comparative Example 5
Anatase-type titanium dioxide particles having an average particle diameter of 0.4 μm obtained by the sulfuric acid method were used to obtain an aqueous slurry having a titanium dioxide concentration of 200 g / liter. While stirring 10 liters of the slurry, sodium aluminate corresponding to 5% by weight in terms of Al ₂ O ₃ was added to the titanium dioxide particles, and then sulfuric acid (1 N) was added for 60 minutes so that the pH was 6.5. Then, the mixture was aged by stirring for 60 minutes to form an aluminum hydroxide coating layer. Then, using a suction filter, it is filtered and washed, separated into solid and liquid, and the obtained filter cake is dried at 150 ° C. and pulverized with a hammer mill to form a surface coating consisting of 5% by weight of Al ₂ O _3. Titanium dioxide particles having

Comparative Example 6
For the barium titanate particles having an average particle diameter of 0.5 μm obtained by the oxalate coprecipitation method, 5% by weight of acrylic silane [KBM-5103 manufactured by Shin-Etsu Silicone Co., Ltd.] in terms of SiO _{2 is} used as a surface treatment agent. The pigment was mixed. The structure of acrylic silane is represented by CH ₂ ═CHCOOC ₃ H ₆ Si (OCH ₃ ) ₃ .

  Resin sheets were prepared using the white pigments obtained in the above Examples and Comparative Examples, and their light resistance and heat resistance were evaluated. Light resistance and heat resistance were evaluated by the following methods, respectively. The results are shown in Table 1.

(Light resistance evaluation)
200 g of white pigment and 800 g of polyethylene terephthalate resin [MA-2101 manufactured by Unitika Co., Ltd.] were mixed, kneaded at 270 ° C. using two rolls, and then formed into a 1 mm thick sheet. This sheet was irradiated with ultraviolet rays using an ultraviolet irradiation device [CS30L-1-3 manufactured by GS Yuasa Corporation], and a difference Δb between an initial b value and a b value after 20 minutes of ultraviolet irradiation time was determined by a color difference meter. [Nippon Denshoku Industries Co., Ltd. product ND-300A] was measured. The results are shown in Table 1. The smaller the value of Δb, the smaller the degree of discoloration of the sheet, that is, the better the light resistance.

(Heat resistance evaluation)
200 g of white pigment and 800 g of polyethylene terephthalate resin [MA-2101 manufactured by Unitika Co., Ltd.] were mixed, kneaded at 270 ° C. using two rolls, and then formed into a 1 mm thick sheet. The sheet was heat-treated at 210 ° C., and the difference Δb between the initial b value and the b value after 48 hours of heat treatment was measured with a color difference meter [ND-300A manufactured by Nippon Denshoku Industries Co., Ltd.]. The results are shown in Table 1. The smaller the value of Δb, the smaller the degree of discoloration of the sheet, that is, the better the heat resistance.

(Light reflectivity evaluation)
200 g of white pigment and 800 g of polyethylene terephthalate resin [MA-2101 manufactured by Unitika Co., Ltd.] were mixed, kneaded at 270 ° C. using two rolls, and then formed into a 1 mm thick sheet. The L value of this sheet was measured with a color difference meter [ND-300A manufactured by Nippon Denshoku Industries Co., Ltd.]. The results are shown in Table 1. It shows that it is excellent in light reflectivity, so that the value of L value is large.

  As shown in Table 1, when surface coating treatment of less than 0.1% by weight is performed on barium titanate particles, the surface activity is not sufficiently suppressed, and the resulting resin sheet is inferior in both light resistance and heat resistance. (Comparative Example 1) When the surface coating treatment was performed exceeding 5% by weight, the light reflectivity was lowered (Comparative Example 2). Further, when the surface coating treatment is not performed on both the barium titanate particles and the titanium dioxide particles, the surface activity is not suppressed, so that the obtained resin sheets are inferior in both light resistance and heat resistance (Comparative Example 3 and Comparative Example 4). Moreover, in the case of titanium dioxide particles, even if 5% by weight of the surface coating treatment is performed, the surface activity is not sufficiently suppressed, and the resulting resin sheet is inferior in both light resistance and heat resistance (Comparative Example 5). Moreover, even if the organosilane surface treatment was performed on the barium titanate particles, the surface activity was not suppressed, and the resulting resin sheet was inferior in both light resistance and heat resistance (Comparative Example 6).

Claims (5)

  A white pigment made of barium titanate surface-coated with an inorganic oxide containing at least one element selected from Si, Al, and Zr.   The white pigment according to claim 1, wherein 0.1 to 5% by weight of an inorganic oxide is coated on the barium titanate particles in terms of anhydride.   The white pigment according to claim 2, wherein 0.5 to 3% by weight of an inorganic oxide is coated on the barium titanate particles in terms of anhydride.   The thermoplastic resin composition which contains 1-400 weight part of white pigments in any one of Claims 1-3 with respect to 100 weight part of thermoplastic resins. A light-reflective resin member obtained by molding the thermoplastic resin composition according to claim 4.

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