JP2010090002A - Production method of monoclinic particulate bismuth oxide, ultraviolet ray shielding dispersion and production method of the same, and ultraviolet ray shielding coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide monoclinic particulate bismuth oxide having high transmissivity (transparency) to visible light and a shielding performance against long-wavelength UV rays (near UV rays), which is suitable to be used as a UV ray shielding agent, and to provide a UV ray shielding dispersion utilizing the above characteristics. <P>SOLUTION: Monoclinic particulate bismuth oxide having an average primary particle diameter of 10 nm to 100 nm are produced by adding an acidic aqueous solution of bismuth and an alkali hydroxide aqueous solution to water, hydrolyzing the bismuth in the solution while keeping the pH to 9.5 to 11.5, subjecting the produced precipitate to filtration, rinsing with water, drying and firing to obtain monoclinic bismuth oxide, and performing wet pulverizing to the obtained monoclinic bismuth oxide in the presence of a solvent and a dispersion medium. The UV ray shielding dispersion is produced by incorporating the monoclinic particulate bismuth oxide having an average primary particle diameter of 10 to 100 nm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing monoclinic fine particle bismuth oxide, and more specifically, an average having a high visible light transmittance (that is, transparency) and a long wavelength ultraviolet shielding ability suitable for use as an ultraviolet shielding agent. The present invention relates to a method for producing monoclinic fine particle bismuth oxide having a primary particle diameter of 10 to 100 nm. The present invention also provides an ultraviolet shielding dispersion containing monoclinic fine particle bismuth oxide having an average primary particle size of 10 to 100 nm, a method for producing the same, and a spreading agent added to the ultraviolet shielding dispersion. The present invention relates to an ultraviolet shielding coating composition.

Bismuth oxide (Bi ₂ O ₃ ) is used as an additive for various electronic components such as varistors, ferrite magnets, battery materials, and piezoelectric materials.

  Further, bismuth oxide is known to have an ultraviolet shielding ability like titanium dioxide and zinc oxide, and an ultraviolet shielding cosmetic containing a bismuth oxide powder has been proposed (Patent Document 1). .

  With regard to this bismuth oxide manufacturing method, especially for bismuth oxide used for varistors, ferrite magnets, battery materials, piezoelectric materials, etc., while maintaining an aqueous bismuth nitrate solution containing excess nitric acid at 30 ° C. or lower, A method of producing bismuth oxide by dripping an aqueous alkali bicarbonate solution so that the final pH is 7 to 8, washing the produced precipitate and preparing the adhering moisture, followed by calcining at 350 to 400 ° C. ( Patent Document 2), a bismuth nitrate aqueous solution and an alkali hydroxide aqueous solution are reacted, the pH is adjusted to 10.5 to 12.5, hydrogen peroxide is further added, and the generated precipitate is washed, dehydrated, A method for producing bismuth oxide powder by drying (Patent Document 3) has been proposed.

Japanese Patent No. 3441553 Japanese Patent Publication No. 5-26725 Japanese Patent No. 3928023

  However, bismuth oxide obtained so far has not found bismuth oxide having both high visible light transmittance and long-wavelength ultraviolet shielding ability when used as an ultraviolet shielding agent.

  Therefore, the present invention provides a method for producing bismuth oxide having a high visible light transmittance suitable for use as an ultraviolet shielding agent and having a long wavelength ultraviolet shielding ability, and containing the bismuth oxide. An object of the present invention is to provide an ultraviolet shielding dispersion and an ultraviolet shielding coating composition that have high transparency to visible light and that have excellent shielding ability especially against long-wavelength ultraviolet rays.

  As a result of intensive studies in view of the above circumstances, the present inventor added an acidic aqueous solution of bismuth and an aqueous alkali hydroxide solution to water to hydrolyze bismuth while maintaining the pH at 9.5 to 11.5. The resulting precipitate is filtered, washed with water, dried and calcined to obtain monoclinic bismuth oxide, and the resulting monoclinic bismuth oxide is wet pulverized in the presence of a solvent and a dispersion medium. The obtained monoclinic fine particle bismuth oxide having an average primary particle diameter of 10 to 100 nm was found to be able to solve the above problems, and based on this, the present invention was solved.

  That is, the present invention includes a method for producing monoclinic fine particle bismuth oxide having an average primary particle diameter of 10 to 100 nm, and the monoclinic fine particle bismuth oxide, and has a dry film thickness of 1 to 4 μm. The thin film has a light transmittance of 20% or less at a wavelength of 250 to 400 nm, an excellent shielding ability against long-wavelength ultraviolet light, and a light transmittance of visible light of 70% or more at a wavelength of 450 to 800 nm. A dispersion for shielding ultraviolet rays capable of forming a film having a high rate and high transparency, and a content ratio of monoclinic fine particle bismuth oxide in the dried coating film to the dispersion for ultraviolet shielding is 20 to 80 The present invention relates to an ultraviolet shielding coating composition characterized by being added so as to have a mass%. The present invention also relates to a method for directly producing an ultraviolet shielding dispersion using the method for producing monoclinic fine particle bismuth oxide. That is, this method for producing an ultraviolet shielding dispersion includes the addition of an acidic aqueous solution of bismuth and an aqueous alkali hydroxide solution in water to hydrolyze bismuth in the solution while maintaining the pH at 9.5 to 11.5. The resulting precipitate is filtered, washed with water, dried, and calcined to obtain monoclinic bismuth oxide, and the resulting monoclinic bismuth oxide is firstly averaged by wet grinding in the presence of a solvent and a dispersion medium. By obtaining monoclinic fine particle bismuth oxide having a particle diameter of 10 to 100 nm and removing monodisperse fine particle bismuth oxide having an average primary particle diameter of 10 to 100 nm, ultraviolet rays are removed. The present invention relates to a method for obtaining a shielding dispersion.

  According to the method for producing bismuth oxide of the present invention, the average primary particle size having high visible light transmittance (that is, transparency) and long-wavelength ultraviolet (near-ultraviolet) shielding ability suitable for use as an ultraviolet shielding agent. Monoclinic fine particle bismuth oxide having a thickness of 10 to 100 nm can be provided. And by including monoclinic fine particle bismuth oxide having an average primary particle diameter of 10 to 100 nm, the light transmittance of a thin film formed with a dry film thickness of 1 to 4 μm is 20% at a wavelength of 250 to 400 nm. Ultraviolet shielding capable of forming a film having excellent shielding ability against ultraviolet rays in a long wavelength region including near ultraviolet rays as described below, and having a high visible light transmittance (ie, high transparency) of 70% or more at a wavelength of 450 to 800 nm. It is possible to provide an ultraviolet shielding coating composition utilizing the characteristics of the dispersion for ultraviolet rays and the dispersion for ultraviolet shielding.

  First of all, when explaining the process from the completion of the present invention, generally, an inorganic ultraviolet shielding agent has a slight light scattering shielding ability, but most of the shielding ability is due to the band structure of the shielding agent. Based on absorption.

  In addition, in order to improve the desirable visible light transmittance in the ultraviolet screening agent, it is necessary to reduce the number of light scattering particles, and it is necessary to reduce the primary particle diameter from the geometric scattering / Mee scattering region to the Rayleigh scattering region. . In the Rayleigh scattering region, the scattered light is inversely proportional to the sixth power of the particle diameter, and light scattering is reduced. The particle size must be about 100 nm or less.

  From the viewpoints described above, fine particle titanium oxide and fine particle zinc oxide are often used as inorganic ultraviolet shielding agents, particularly in cosmetics intended for ultraviolet shielding. However, in the case of titanium oxide and zinc oxide in a fine particle state, the shielding wavelength in the near ultraviolet region is limited due to the band structure unique to the substance, and the shielding rate at 400 nm is particularly less than 50%.

  Recently, in addition to cosmetic applications, it has been increasingly used for coatings for the purpose of shielding ultraviolet rays and transmitting visible light. In these applications, for example, since photocatalytic activity generally occurs in the ultraviolet region, there is a need to more strictly shield light in the ultraviolet region in applications such as a protective film for preventing photocatalytic activity. It is getting stronger.

  The present inventor has paid attention to bismuth oxide whose band gap is lower than that of titanium oxide and zinc oxide, and has high safety and stability, and further selects a monoclinic system as a crystal form of bismuth oxide, and the monoclinic crystal By finely pulverizing the system primary bismuth oxide to an average primary particle size of 10 to 100 nm, preferably 10 to 30 nm, it has excellent shielding ability against long wavelength ultraviolet rays that could not be achieved with inorganic ultraviolet screening agents, and Monoclinic fine particle bismuth oxide having high transparency to visible light was obtained, and the present invention was completed based on this.

  It is also known from Patent Document 1 that bismuth oxide has a shielding ability at 400 nm. However, as a result of studies by the present inventors, bismuth oxide is different from other ultraviolet shielding inorganic oxides such as fine particle titanium oxide and fine particle zinc oxide, even with primary particles having a size of several hundreds of nanometers and several μm in an aggregated state. Usually it is the size of. Therefore, the dispersion of bismuth oxide produced by a general process has a problem that the transmittance in the visible light region is inferior to that of other inorganic materials for shielding ultraviolet rays.

  In the present invention, as described above, an acidic aqueous solution of bismuth and an aqueous sodium hydroxide solution are added to water to hydrolyze bismuth in the solution while maintaining the pH at 9.5 to 11.5, and the produced precipitate is filtered. , Washed, dried and then calcined in the presence of oxygen to obtain monoclinic bismuth oxide, and the monoclinic bismuth oxide in the presence of a dispersion medium such as a solvent and zirconia beads, bead mill, sand mill, By wet grinding with a wet pulverizer such as a paint conditioner until the average primary particle size is 10 to 100 nm, preferably 10 to 30 nm, fine monoclinic fine particle bismuth oxide is obtained. While maintaining excellent shielding properties in the ultraviolet region, it increases the transparency to visible light, and has excellent shielding properties in the long wavelength ultraviolet region and high visible light region. UV shielding dispersion having both permeability and is to that provided an ultraviolet-screening coating composition.

  The starting material for the monoclinic fine particle bismuth oxide is an acidic aqueous solution of bismuth. The reason why the aqueous solution is acidified is that a bismuth compound is usually difficult to dissolve completely with water alone, so that the bismuth is completely dissolved by acidification.

  When preparing an acidic aqueous solution of bismuth, as its bismuth source, for example, bismuth compounds such as bismuth sulfate, bismuth bromide, bismuth chloride, bismuth citrate, bismuth iodide, bismuth nitrate and bismuth phosphate are suitable for use. Yes. Furthermore, although what melt | dissolved metal bismuth, bismuth oxide, bismuth hydroxide, etc. in an acidic solution can be used, when setting it as the acidic solution, it is preferable to use nitrate or its solution.

  Alkali hydroxide is used for hydrolyzing an acidic aqueous solution of bismuth and maintaining the pH at 9.5 to 11.5. The alkali hydroxide includes sodium hydroxide, potassium hydroxide, water. Any lithium oxide can be used, but sodium hydroxide is particularly preferred.

  The pH for hydrolyzing an acidic aqueous solution of bismuth is 9.5 to 11.5, which is based on the following reason. When the pH is low, the production rate of bismuth hydroxide is slow, the reaction efficiency is low, and unreacted acidic ions remain, so the amount of bismuth hydroxide produced decreases, and consequently the amount of bismuth oxide produced decreases. The pH needs to be 9.5 or higher, and is particularly preferably 10 or higher.

  Also, as the pH increases, the production rate of bismuth hydroxide increases, but the crystal growth of bismuth hydroxide proceeds to become needle-like crystals, and in order to obtain the desired plate-like crystals, the pH is reduced to 11.5 or less. It is necessary to make it 11 or less.

  The temperature of the reaction solution during hydrolysis in an acidic aqueous solution of bismuth is preferably 30 to 70 ° C, more preferably 40 ° C or higher, and 60 ° C within the range, although it depends on the type of acid used. The following is more preferable. That is, the higher the temperature, the more the hydrolysis reaction proceeds. However, when the reaction temperature is higher, the crystal growth of bismuth hydroxide progresses, and the bismuth hydroxide becomes needle-like crystals that are not suitable for micronization. If the temperature is low, the hydrolysis reaction may not proceed sufficiently, so the temperature as described above is preferred.

  The concentration of bismuth in the acidic aqueous solution of bismuth is preferably 100 to 250 g / L in terms of bismuth (Bi). When the concentration of bismuth is lower than the above, production efficiency decreases, which is not preferable. When the concentration of bismuth is higher than the above, it is not preferable because aggregated particles may increase.

  The addition rate of the acidic aqueous solution of bismuth and the aqueous alkali hydroxide solution in water is to ensure that bismuth in the solution is properly hydrolyzed while maintaining the pH of the reaction solution at 9.5 to 11.5. For this purpose, it is preferable to add both of them little by little.

  Moreover, it is preferable that it is between 0.2 g / min-0.7 g / min in conversion of bismuth as an addition rate of the bismuth acidic aqueous solution in that case. When added at a higher speed than this, the aggregates of the precipitates are remarkable, and it takes time to disperse the fired product, resulting in poor productivity. In addition, when the addition rate is slower than the above, it takes time for hydrolysis and the productivity is poor.

  It is preferable to ripen for 10 minutes or more after causing the hydrolysis reaction of bismuth in the solution by adding an acidic aqueous solution of bismuth and an aqueous alkali hydroxide solution to water. It is preferable to stir the reaction solution throughout the hydrolysis reaction, including during this aging.

  The precipitate produced by the hydrolysis of bismuth in the solution is mainly composed of bismuth hydroxide. This precipitate is separated from the reaction solution by filtration, washed and dehydrated. Filtration, washing, and dehydration methods may be performed by ordinary methods, for example, filtration using a Buchner funnel or Nutsche, a dewatering method using a rotary drum type dehydrator, a filter press, or the like may be employed.

  After filtering the precipitate, it is preferable to add water again to the filtered residue to sufficiently disperse, repeat this filtration and dispersion in water, and remove the soluble salt contained in the precipitate.

  The precipitate is dehydrated and dried. This drying is performed in order to remove water adhering to bismuth hydroxide, and may be performed by an ordinary method. For example, drying with a heat dryer, vacuum drying with a vacuum dryer, or the like is employed. be able to. The drying temperature is preferably 100 ° C. or higher, which is the boiling point of water. Since the energy is consumed when the drying temperature is high, the temperature is preferably 200 ° C. or less from the economical viewpoint.

  The dried product is pulverized and fired. This baking gives a yellowish powder. This powder can be confirmed to be monoclinic bismuth oxide from the results of X-ray diffraction analysis. The firing is preferably performed at 450 to 550 ° C. for about 1.5 to 3.5 hours.

  The monoclinic bismuth oxide obtained as described above is pulverized using a wet pulverizer in the presence of a solvent and a dispersion medium, and the average primary particle diameter is reduced to 10 to 100 nm, preferably 10 to 30 nm. Is done. By isolating the obtained monoclinic fine particle bismuth oxide from a solvent or a dispersion medium and dispersing it in the solvent, the light transmittance of a thin film formed with a dry film thickness of 1 to 4 μm has a wavelength of 250 to 400 nm. It can be made into an ultraviolet shielding dispersion having a wavelength of 20% or less and 70% or more at a wavelength of 450 to 800 nm, and the obtained monoclinic fine particle bismuth oxide is used in the wet grinding process. It is possible to obtain an ultraviolet shielding dispersion similar to the above except that only the dispersion medium is not isolated. However, in order to stabilize the dispersion state of the monoclinic fine particle bismuth oxide in the dispersion for ultraviolet shielding, it is preferable that a dispersant described in detail later is present, and this dispersant is a monoclinic bismuth oxide. It can coexist with a solvent in wet dispersion.

  The monoclinic bismuth oxide obtained by wet pulverization of the monoclinic bismuth oxide as described above may be finely divided to an average primary particle size of 10 to 100 nm, preferably 10 to 30 nm. However, commercially available monoclinic bismuth oxide having a large particle diameter cannot be made into fine particles while maintaining the monoclinic system.

  Examples of the solvent used in the wet pulverization include, for example, commonly used solvents such as water, alcohols, ketones, esters, ethyl acrylate, methyl methacrylate, 1,6-hexanediol Monomers such as acrylate, trimethylolpropane triacrylate, oil agents such as linseed oil, castor oil, palm oil, olive oil, lanolin, etc., higher alcohols such as lauryl alcohol, myristyl alcohol, stearyl alcohol, stearic acid, isostearin Ester oils such as acids, higher fatty acids such as linoleic acid, isocetyl isostearate, neopentyl glycol dicaprate, isononyl isononanoate, 2-ethylhexyl palmitate, amyl acetate, butyl stearate, etc. You can use.

  Among them, highly polar solvents such as water, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol are preferable, and examples of the dispersion medium include zirconia beads, zircon beads, alumina beads, and glass beads. As the wet pulverizer, for example, a bead mill, a sand mill, a paint conditioner, or the like can be used.

  In the wet pulverization, a dispersant can be used as described above. The dispersant here refers to a compound having one or more pigment affinity groups and generally known as a pigment dispersant. Examples of the pigment affinity group include polar groups such as amino group, quaternary ammonium group, hydroxyl group, cyano group, carboxyl group, thiol group, and sulfonic acid group. This pigment affinity group may be contained in the main chain of the compound, or may be contained in the side chain or both the side chain and the main chain.

  As the dispersant, commercially available pigment dispersants can be used. For example, Solsperse 3000, Solsperse 9000, Solsperse 17000, Solsperse 20000, Solsperse 24000, Solsperse 28000, Solsperse manufactured by Nippon Lubrizol Co., Ltd. can be used. 32000, Solsparse 35100, Solsparse 36000, Solsparse 41000, Solsparse 44000, EFKA4009, EFKA4046, EFKA4047, EFKA4080, EFKA4015, EFKA4055, EFKA4055, EFKA4055, EFKA4055, EFKA4055, EFKA4055, EFKA4055, EFKA4055 The Addisper PB821, A Spur PB711, Addisper PB822, Addisper PN411, Addisper PA111, TEXAPHORUV20, TEXAPHORUV21, TEXAPHORP61, Disperbyk-101, Disperbyk-103, Disperbyk-103, Disperbyk-D, Dperbyk-D -161, Disperbyk-162, Disperbyk-163, Disperbyk-164, Disperbyk-166, Disperbyk-167, Disperbyk-168, Disperbyk-170, Disperbyk-171, Disperbyk-174, Disperbyk-174, Disperbyk-174, Disperbyk-174 Such as erbyk-190 (both trade name) and the like. These pigment dispersants may be used alone or in combination of a plurality of types, but can be used particularly preferably in a highly polar medium such as water, methyl alcohol, ethyl alcohol, propyl alcohol, and ethyl alcohol. Examples of the agent include Solsperse 41000, Solsperse 44000, Disperbyk-190, etc. (all trade names).

  The monoclinic bismuth oxide wet pulverization may be carried out under conditions suitable for each wet pulverizer, and the particle size is usually controlled by controlling the pulverization time.

  In the ultraviolet shielding dispersion of the present invention, the content of the monoclinic fine particle bismuth oxide in the ultraviolet shielding dispersion is not particularly limited, but usually about 5 to 40% by mass is suitable. In particular, 10 to 30% by mass is preferable. And when a dispersing agent is contained in the ultraviolet shielding dispersion, the amount of the dispersing agent is 5 to 30% by mass (monoclinic fine particles) as an active ingredient with respect to monoclinic fine particles of bismuth oxide. The dispersant is 5 to 30 parts by mass as an active ingredient with respect to 100 parts by mass of bismuth oxide), especially 10 to 25% by mass (the dispersant is 10 to 25 as the active ingredient with respect to 100 parts by mass of monoclinic fine particle bismuth oxide). Part by mass) is preferred. In showing the amount of the dispersant with respect to the monoclinic fine particle bismuth oxide, the expression “active ingredient” is used as described above. The dispersant is either solid or liquid, and In the case of a commercial product, a solid product may be dissolved or dispersed in a solvent.

  In the present invention, the average primary particle diameter of monoclinic fine particle bismuth oxide is required to be 10 to 100 nm, preferably 10 to 30 nm. If the diameter is smaller than the above, the monoclinic crystal, which is a crystalline form of bismuth oxide, cannot be maintained, and as a result, the ultraviolet shielding ability cannot be exhibited, and the average primary particle diameter of the monoclinic fine particle bismuth oxide If is larger than the above, since visible light scattering starts, it becomes cloudy white and the visible light transmittance is not improved. The average primary particle diameter is obtained by photographing monoclinic fine particle bismuth oxide at a magnification of 10,000 times or more using a transmission electron microscope and calculating a volume-based equivalent circle diameter using an automatic image processing apparatus. Is required.

  The ultraviolet shielding dispersion of the present invention has a light transmittance of 20% or less at a wavelength of 250 to 400 nm and a light transmittance of 70% or more at a wavelength of 450 to 800 nm. This is because of the following reason.

  First, the dry film thickness is set to 1 to 4 μm. When the film thickness is less than 1 μm, it becomes difficult to form a uniform thin film, and as a result, the ultraviolet blocking ability by monoclinic fine particle bismuth oxide is stable. In addition, when the film thickness is thicker than 4 μm, when the coating environment at the time of forming the thin film is high humidity, the thin film is likely to be whitened or cracked, so that a normal thin film can be formed. Because it becomes difficult to do. And this film thickness can be measured by the two-dimensional shape measurement of the surface three-dimensional surface roughness meter.

  And the light transmittance of the said thin film was measured on condition of wavelength range: 240-800 nm, measurement pitch: 2 nm, scan speed: 600 nm / min using Hitachi spectrophotometer U-4100, and by a base film It is obtained by performing baseline correction, and the requirement is that the light transmittance is 20% or less at a wavelength of 250 nm to 400 nm. When the light transmittance is higher than 20%, it is required for ultraviolet rays in a long wavelength region. This is because the shielding ability deteriorates, and it is particularly important that the light transmittance at a wavelength of 400 nm is 20% or less. In addition to fine particle titanium oxide and fine particle zinc oxide, orthorhombic fine particle bismuth oxide also has a wavelength. The light transmittance at 400 nm cannot be made 20% or less.

  Further, the requirement of the light transmittance of the thin film at a wavelength of 450 to 800 nm being 70% or more is that if the light transmittance is lower than 70%, the transmittance is not sufficient. In particular, it is important that the light transmittance at a wavelength of 450 nm is 70% or more. Even in the case of monoclinic bismuth oxide having an excellent ultraviolet shielding ability, the light transmittance at a wavelength of 450 nm is 70. % Or more, and only those lacking transparency can be obtained.

The monoclinic fine particle bismuth oxide can be subjected to a surface treatment with an inorganic oxide or an organic substance in order to improve dispersibility and weather resistance and suppress surface activity before wet pulverization.
As the inorganic oxide for performing the surface treatment, for example, alumina, silica, zirconia, titania and the like can be used, and as the organic substance, for example, various silanes, various silicones, fatty acids, metal soaps and the like can be used. These can be used alone or in combination of two or more for surface treatment.

The monoclinic fine particle bismuth oxide-containing ultraviolet shielding dispersion can be applied to various uses as a coating composition for the purpose of ultraviolet shielding by further adding a spreading agent. The spreading agent here refers to a component blended as a medium for facilitating adhesion of monoclinic fine particle bismuth oxide to a substrate to be coated when a coating composition is used.
When a spreading agent is used in the present invention, there are cases where an inorganic substance is mainly used and an organic substance is mainly used. Each uses differently and will be described separately.

When a material mainly composed of an inorganic substance is used as a spreading agent, outdoor durability is remarkably improved, and an unprecedented highly durable UV (ultraviolet) cut coating film can be produced.
As a substance mainly composed of this inorganic substance, a hydrolyzable silane compound is typical. Among hydrolyzable silane compounds, compounds that can be crosslinked by applying temperature, particularly using a silane coupling agent, to form a film are preferred.

  As heating temperature in this case, 200-500 degreeC is preferable, for example. That is, the film can be formed by heating at this temperature. Moreover, it is preferable to use the compound which bridge | crosslinks at 150 degreeC or more. A catalyst that promotes the reaction may be present during the crosslinking. As a specific example of the silane coupling agent to be used, tetramethoxysilane or tetraethoxysilane is preferable.

  In the case of using a substance mainly composed of an organic substance as the spreading agent, for example, a coating resin such as an acrylic resin, a polyester resin, or a urethane resin is preferable. The outdoor durability does not reach when an inorganic spreading agent is used, but even when this organic spreading agent is used, the coating composition for ultraviolet shielding of the present invention is an inorganic spreading agent. Similar to the case of using the same coating composition using fine particle titanium oxide and fine particle zinc oxide when using an adhesive, it exhibits higher transparency to visible light and excellent shielding ability against ultraviolet rays in the long wavelength range. Therefore, it is possible to form a coating film having a function of protecting the inside from ultraviolet rays for a long period of time and having very little change in appearance.

  The addition ratio in the case of adding a spreading agent is a range in which the content of monoclinic fine particle bismuth oxide in the dried coating film is 20 to 80% by mass, that is, the spreading agent is 80 to 20% by mass. The range is preferable. When the amount of the spreading agent is less than the above, the effect of blending the spreading agent is not sufficiently exhibited, and when it is more than the above, the ultraviolet shielding ability is lowered. In other words, the ultraviolet shielding coating obtained by adding the spreading agent such that the content of monoclinic fine particle bismuth oxide in the dried coating film is 20 to 80% by mass as described above. The composition retains the same light transmission characteristics as the ultraviolet shielding dispersion, and the light transmittance of the thin film formed at a dry film pressure of 1 to 4 μm has a wavelength of 250 to 250, as in the case of the ultraviolet shielding dispersion. It has a light transmission characteristic of 20% or less at 400 nm and 70% or more at a wavelength of 450 to 800 nm.

  The ultraviolet shielding dispersion and the ultraviolet shielding coating composition of the present invention obtained as described above have a high transmittance for visible light in the light transmittance of a thin film formed with a dry film thickness of 1 to 4 μm. Not only has the ability to absorb short- to medium-wavelength ultraviolet rays, but also has the ability to shield against long-wavelength ultraviolet rays that could not be achieved with conventional inorganic ultraviolet shielding agents. As a coating composition having ultraviolet absorbing ability, it can be suitably used as an industrial ultraviolet shielding agent for paints, inks, plastic sheets and plastic molded articles, or as a cosmetic ultraviolet shielding agent for sunscreen creams.

  Next, the present invention will be described more specifically with reference to examples. However, this invention is not limited only to those Examples. In the following examples and the like,% indicating the concentration of a solution or dispersion is mass% unless otherwise specified.

Example 1
66.6 g of pure water and 11.3 g of 61% nitric acid are placed in a container with an internal volume of 1 liter and mixed, and 24.3 g of bismuth nitrate pentahydrate (manufactured by Sigma Aldrich) is added to the mixture. Thus, an acidic aqueous solution of bismuth nitrate was obtained. The bismuth concentration in the aqueous acid solution of nitric acid was 134.4 g / L. Separately, a 24% aqueous sodium hydroxide solution was prepared.

  Next, 150 g of water was put into a container having an internal volume of 1 liter and heated to 50 ° C. The bismuth acid aqueous solution of bismuth and the 24% aqueous sodium hydroxide solution were added little by little while maintaining the pH of 10 to hydrolyze bismuth. Addition of the acidic aqueous solution of bismuth nitrate and the aqueous sodium hydroxide solution was carried out by dropwise addition with a roller pump. The addition speed is adjusted by adding an aqueous bismuth nitrate solution and an aqueous sodium hydroxide solution so that the pH is 10, but the rate is about 4 equivalents of sodium hydroxide per 1 equivalent of bismuth. While adding about 30 minutes. The final pH was 10.1.

  The precipitate formed by hydrolysis was filtered, washed, dried at 110 ° C. for 3 hours, and baked at 550 ° C. for 2 hours in an electric furnace.

  When the obtained fired product was pulverized and analyzed by X-ray diffraction, it was confirmed that the fired product was monoclinic bismuth oxide.

  Stirring 250 g of monoclinic bismuth oxide powder obtained as described above, 150 g of dispersant (manufactured by Nippon Lubrizol, Solsperse 44000 (trade name)) (75 g as an active ingredient), and 600 g of isopropyl alcohol in a 2000 ml vessel. Mix to make a 1 kg mixture.

This mixture was put into an ultra apex mill (trade name, Kotobuki Kogyo Co., Ltd., bead-compatible ultra-fine pulverizer, mill volume 170 ml, bead filling rate 60%, rotor peripheral speed 11.5 m / sec, slurry flow rate 50 ml / min). The solution was fed and circulated for pulverization.
As the pulverization conditions, in the first stage, a zirconia bead having a bead diameter of 0.1 mm was used for 3 hours of cyclic pulverization treatment, and the obtained primary dispersion was recovered. The second stage uses a zirconia bead having a bead diameter of 0.05 mm for this primary dispersion, and a cyclic pulverization treatment for 3 hours to obtain a monoclinic fine particle bismuth oxide dispersion. Got. In addition, when performing a wet pulverization process by the ultra apex mill (trade name), the zirconia beads filled in the pulverization are automatically separated from the monoclinic fine particle bismuth oxide dispersion after the pulverization process is completed.

  The particles in the obtained monoclinic fine particle bismuth oxide dispersion were photographed at a magnification of 50,000 times using a transmission electron microscope [JEM-1230 (trade name) manufactured by JEOL Ltd.], and imaged. Analytical flow distribution measurement software [Mounttech, Mac-View (trade name)] is used to recognize the contour of the particles with 1000 particles, the volume-based circle equivalent diameter is calculated, and the average primary particle diameter As a result, the average primary particle diameter of the monoclinic fine particle bismuth oxide was 10 nm. In addition, the average primary particle diameter of monoclinic fine particle bismuth oxide in the following examples and the like is also determined by the same method as described above.

Example 2
79 g of dilute sulfuric acid having a pH of 2.0 was placed in a container having an internal volume of 1 liter, and 20.0 g of bismuth sulfate (manufactured by Sigma-Aldrich) was added and dissolved therein to obtain an acidic aqueous solution of bismuth. The bismuth concentration in the aqueous sulfuric acid solution of bismuth was 150.0 g / L. Separately, a 24% aqueous potassium hydroxide solution was prepared.

  Next, 150 g of water was put into a container having an internal volume of 1 liter and heated to 50 ° C. The bismuth sulfuric acid aqueous solution and the 24% aqueous potassium hydroxide solution were added little by little while maintaining the pH of 10 to hydrolyze bismuth. The bismuth sulfuric acid aqueous solution and potassium hydroxide aqueous solution were added dropwise by a roller pump. The addition rate is adjusted by adding a bismuth sulfuric acid aqueous solution and a potassium hydroxide aqueous solution so that the pH is 10. However, the rate is such that potassium hydroxide is about 4 equivalents per 1 equivalent of bismuth. While adding about 30 minutes. The final pH was 10.0.

The precipitate formed by hydrolysis was filtered, washed, dried at 110 ° C. for 3 hours, and baked at 550 ° C. for 2 hours in an electric furnace. When the obtained fired product was pulverized and analyzed by X-ray diffraction, it was confirmed that the fired product was monoclinic bismuth oxide.
The obtained monoclinic bismuth oxide was subjected to wet pulverization in the same manner as in Example 1 to obtain fine particles, thereby obtaining the intended ultraviolet shielding dispersion. The average primary particle diameter of monoclinic fine particle bismuth oxide in this dispersion was 11 nm.

Example 3
The target ultraviolet shielding dispersion was obtained in the same manner as in Example 1 except that the circulation treatment time in the wet pulverization treatment was 1.5 hours for both the first stage and the second stage.
The average primary particle diameter of monoclinic fine particle bismuth oxide in this dispersion was 29 nm.

Comparative Example 1
The bismuth oxide produced in exactly the same process as in Example 1 was baked at 400 ° C. for 2 hours in an electric furnace until hydrolysis was performed and the produced precipitate was filtered, washed and dried at 110 ° C. for 3 hours. It was.
When the obtained fired product was pulverized and analyzed by X-ray diffraction, it was confirmed that the fired product was tetragonal bismuth oxide.

  The tetragonal bismuth oxide powder obtained as described above was also subjected to the same wet pulverization treatment as in Example 1 to obtain a tetragonal fine particle bismuth oxide dispersion. When the average primary particle diameter of the tetragonal fine particle bismuth oxide was measured in the same manner as in Example 1, the average primary particle diameter was 10 nm.

Comparative Example 2
Commercially available monoclinic bismuth oxide (manufactured by Sigma-Aldrich, average particle size 10 μm) was subjected to a dispersion treatment using a paint conditioner under the following conditions to prepare a monoclinic bismuth oxide dispersion.

Bethel: 200 ml, monoclinic bismuth oxide loading: 11.25 g,
Dispersant filling amount: 6.75 g, isopropyl alcohol filling amount: 27.0 g,
Zircon beads: Diameter 0.5mm (filling amount 200g)
Paint conditioner pulley rotation speed: 700 rpm, dispersion time: 2 hours

  The average primary particle diameter of monoclinic bismuth oxide in the obtained dispersion was about 500 nm.

Comparative Example 3
Using fine particle titanium oxide [MT-100HD (trade name) manufactured by Teika Co., Ltd., average primary particle size: 15 nm], a dispersion treatment was performed in the same manner as in Example 1 to obtain a fine particle titanium oxide dispersion.

Comparative Example 4
Using a fine particle zinc oxide [MZ-500 (trade name), average primary particle size: 30 nm, manufactured by Teika Co., Ltd.], a dispersion treatment was performed in the same manner as in Example 1 to obtain a fine particle zinc oxide dispersion.

  For the dispersions obtained in each of Examples 1 to 3 and Comparative Examples 1 to 4, the measurement results of the average primary particle diameter obtained from the image processing by the transmission electron micrograph described in detail in Example 1 are shown. 1 is shown collectively.

Moreover, about the dispersion obtained in each of Examples 1 to 3 and Comparative Examples 1 to 4, the bar coater no. 6 and no. 18 was applied onto a pet film and dried at room temperature to obtain thin films having a thickness of 1 μm and 4 μm, respectively.
In each thin film, the light transmittance at each wavelength of 360 nm, 400 nm, 450 nm, and 550 nm was measured as follows. That is, for the measurement, a Hitachi spectrophotometer U-4100 was used, the wavelength range was 240 to 800 nm, the measurement pitch was 2 nm, the scan speed was 600 nm / min, and the base line film was corrected. Then, the light transmittance of the thin film itself was determined by measuring the spectral transmittance, and the light transmittance of each wavelength (360 nm, 400 nm, 450 nm, 550 nm) was determined from the spectral transmittance spectrum. The results are shown in Table 2.

  As is apparent from Table 2, the ultraviolet shielding dispersions of Examples 1 to 3 have a light transmittance of 20% or less at a wavelength of 400 nm or less in the light transmittance of a thin film formed with a dry film thickness of 1 to 4 μm. In addition, it can be seen that the light transmittance is 70% or more at a wavelength of 450 nm or more.

  Next, for each of the dispersions obtained in Example 1, Comparative Example 1 and Comparative Example 2, the bar coater No. 14 was applied to a PET film so that the film thickness when dried was 2 μm, and dried at room temperature to form a thin film with a film thickness of 2 μm. The thin film was subjected to Hitachi spectrophotometer U-4100 (trade name) ) Was used to continuously measure the spectral transmittance spectrum over a wavelength range of 250 to 800 nm. The result is shown in FIG.

  As shown in FIG. 1, in the case of Example 1, the light transmittance between wavelengths of 450 to 800 nm corresponding to the visible light region was high, and the light transmittance exceeded 70% even at a wavelength of 450 nm. In the case of Comparative Example 2, the light transmittance did not reach 70% at a wavelength of 450 nm, and the transparency was low. In other words, it can be seen from FIG. 1 that even if the same bismuth oxide is used, a dispersion having high transparency to visible light cannot be obtained unless it is prepared to have a specific particle size or crystal system.

  For each of the dispersions obtained in Example 1, Comparative Example 3 and Comparative Example 4, the bar coater No. 1 was used under the same conditions as described above. 14 was used to form a thin film having a dry film thickness of 2 μm on the PET film, and the spectral transmittance spectrum was continuously measured over a range of wavelengths of 250 to 800 nm in the same manner as described above. The result is shown in FIG.

As shown in FIG. 2, in the case of Example 1, the light transmittance at a wavelength of 250 to 400 nm corresponding to the ultraviolet shielding region was low, and the light transmittance was 20% or less even at a wavelength of 400 nm corresponding to the near ultraviolet region. In the case of Comparative Example 3 using titanium oxide and Comparative Example 4 using fine particle zinc oxide, the light transmittance at a wavelength of 400 nm exceeded 20%, and the shielding ability against near ultraviolet rays was low. Monoclinic fine particle bismuth oxide is an inorganic ultraviolet shielding material, but unlike fine particle titanium oxide and fine particle zinc oxide, which have been widely used as an inorganic ultraviolet shielding material, It can be seen that a dispersion having excellent shielding ability can be obtained.

<Preparation of UV shielding coating composition>
Next, the ultraviolet shielding coating compositions of Example 4 and Example 5 were prepared using the ultraviolet shielding dispersion of Example 1 containing monoclinic fine particle bismuth oxide, and commercially available monoclinic crystals. The coating composition of Comparative Example 5 was prepared using the ultraviolet shielding dispersion of Comparative Example 2 containing a system bismuth oxide, and further Comparative Example using the ultraviolet shielding dispersion of Comparative Example 3 containing particulate titanium oxide. Six coating compositions were prepared and their properties were examined as shown below.

Example 4
For the monoclinic fine particle bismuth oxide-containing ultraviolet shielding dispersion obtained in Example 1, P / B = 4.0 (bismuth oxide / spreading agent active ingredient = 80/20: mass ratio). 8.45 g of a silane coupling agent hydrolyzed in advance as a spreading agent and 100% of a monoclinic fine particle bismuth oxide-containing ultraviolet shielding agent dispersion, aluminum acetylacetonate having a concentration of 1% active ingredient as a curing agent 3.8 g of the solution was added, and mixed and stirred with a high speed disperser to obtain a liquid ultraviolet shielding coating composition.

Example 5
Monoclinic crystals so that P / B = 0.25 (bismuth oxide / spreading agent active ingredient = 20/80: mass ratio) with respect to the monoclinic fine particle bismuth oxide-containing dispersion obtained in Example 1 An acrylic melamine resin (86.5 g) was added to 50 g of the fine particle bismuth oxide-containing ultraviolet shielding agent dispersion, and mixed and stirred with a high-speed disperser to obtain a liquid ultraviolet shielding coating composition.

Comparative Example 5
A liquid coating composition was obtained in the same manner as in Example 4 except that the commercially available monoclinic bismuth oxide-containing dispersion prepared in Comparative Example 2 was used.

Comparative Example 6
A liquid coating composition was obtained in the same manner as in Example 4 except that the fine particle titanium oxide-containing dispersion produced in Comparative Example 3 was used.

The coating compositions obtained in Examples 4 to 5 and Comparative Examples 5 to 6 were coated on a glass plate and subjected to predetermined heat treatment, and then glass coated with each inorganic oxide-containing composition was obtained.
The light transmittance of each coating glass at wavelengths of 360 nm, 400 nm, 450 nm, and 550 nm was measured in the same manner as described above. The results are shown in Table 3.

  As is apparent from Table 3, the ultraviolet shielding coating compositions of Examples 4 to 5 have a light transmittance of 20% or less at a wavelength of 400 nm in the light transmittance of a thin film formed with a dry film thickness of 4 μm or less. The light transmittance was 80% or more at 450 nm or more, and the transparency was excellent.

<Weather resistance of coating film>
Next, the ultraviolet shielding coating composition of Example 6 was prepared using the monoclinic bismuth oxide obtained in Example 1, and the coating of Comparative Example 7 was prepared using the fine particle titanium oxide of Comparative Example 3. Compositions were prepared and the weather resistance of coating films formed from these coating compositions was examined as shown below.

Example 6
Using the monoclinic bismuth oxide obtained in Example 1, the wet pulverization treatment conditions were changed as follows to prepare monoclinic fine particle bismuth oxide dispersions.
That is, 250 g of monoclinic bismuth oxide, 75 g of a dispersant (manufactured by Nippon Lubrizol Corporation, Solsperse 41000 (trade name)) (75 g as an active ingredient), and 675 g of isopropyl alcohol were stirred and mixed in 2000 ml Bethel, and a 1 kg mixture. Was prepared.

The obtained mixture is fed to the above-mentioned ultra apex mill (trade name, mill volume 170 ml, bead filling rate 60%, rotor peripheral speed 11.5 m / sec, slurry flow rate 50 ml / min), circulated and pulverized. Processed.
As the pulverization conditions, in the first stage, zirconia beads having a bead diameter of 0.1 mm were used for 3 hours of circulation treatment, and the resulting primary dispersion was recovered. In the second stage, zirconia beads having a bead diameter of 0.05 mm were used for this primary dispersion and subjected to a circulation treatment for 3 hours to obtain a monoclinic fine particle bismuth oxide dispersion. .

47.5 g of acrylic melamine resin is added to 50 g of the above monoclinic fine particle bismuth oxide dispersion, mixed and stirred with a high-speed disperser, bismuth oxide solid content / spreading agent active ingredient = 20/40 mass ratio A liquid coating composition was obtained at (P / B = 0.5).
The coating composition was applied to a bar coater no. 30 was applied, dried at room temperature for 10 minutes, and then baked at 140 ° C. for 30 minutes. The coating film thickness was 15 μm.

Comparative Example 7
A coating composition was prepared by carrying out dispersion treatment, mixing and stirring, etc., as in Example 6, except that the fine particle titanium oxide used in Comparative Example 3 was used. Application and baking were performed.

  The accelerated weathering xenon bacro (1000 hours) was performed on the coating films on the glass plates formed in Example 6 and Comparative Example 7, respectively.

Table 4 shows the color difference after battering and 20 ° gloss retention (ratio of gloss after 20 ° exposure to 20 ° initial gloss:%), respectively.
In addition, the value of the color difference after bakuro has shown the color change by bakuro, and it shows that it is what was excellent in the weather resistance, so that the value is small.
Further, the value of the 20 ° gloss retention indicates a decrease in gloss due to bakuro, and the larger the value, the better the weather resistance.

  As shown in Table 4, Example 6 containing monoclinic fine particle bismuth oxide has a smaller color difference and a higher 20 ° gloss retention and higher weather resistance than Comparative Example 7 containing fine particle titanium oxide. Had.

2 is a diagram showing spectral transmittance spectra of a thin film formed from the ultraviolet shielding dispersion of Example 1, the dispersion of Comparative Example 1, and the dispersion of Comparative Example 2. FIG. 3 is a diagram showing spectral transmittance spectra of a thin film formed from the ultraviolet shielding dispersion of Example 1, the dispersion of Comparative Example 3, and the dispersion of Comparative Example 4. FIG.

Claims (12)

  An acidic aqueous solution of bismuth and an aqueous alkali hydroxide solution are added to water to hydrolyze bismuth in the solution while maintaining the pH at 9.5 to 11.5, and the resulting precipitate is filtered, washed with water, dried and calcined. Monoclinic bismuth oxide was obtained, and the resulting monoclinic bismuth oxide was wet pulverized in the presence of a solvent and a dispersion medium to obtain monoclinic fine particles having an average primary particle size of 10 to 100 nm. A method for producing monoclinic fine particle bismuth oxide, characterized by producing bismuth oxide.   The method for producing monoclinic fine particle bismuth oxide according to claim 1, wherein the average primary particle diameter of the monoclinic fine particle bismuth oxide is 10 to 30 nm.   The light transmittance of the thin film formed in claim 1 containing monoclinic fine particle bismuth oxide having an average primary particle diameter of 10 to 100 nm and having a dry film thickness of 1 to 4 μm is 20% at a wavelength of 250 to 400 nm. It is below, and it is 70% or more in wavelength 450-800 nm, The dispersion | distribution for ultraviolet shielding characterized by the above-mentioned.   An acidic aqueous solution of bismuth and an aqueous alkali hydroxide solution are added to water to hydrolyze bismuth in the solution while maintaining the pH at 9.5 to 11.5, and the resulting precipitate is filtered, washed with water, dried and calcined. Monoclinic bismuth oxide was obtained, and the resulting monoclinic bismuth oxide was wet pulverized in the presence of a solvent and a dispersion medium to obtain monoclinic fine particles having an average primary particle size of 10 to 100 nm. By obtaining the bismuth oxide and removing the dispersion media, the light transmittance of the thin film containing the monoclinic fine particle bismuth oxide having an average primary particle diameter of 10 to 100 nm and having a dry film thickness of 1 to 4 μm is obtained. A method for producing an ultraviolet shielding dispersion, comprising producing an ultraviolet shielding dispersion which is 20% or less at a wavelength of 250 to 400 nm and 70% or more at a wavelength of 450 to 800 nm.   The method for producing an ultraviolet shielding dispersion according to claim 4, wherein the dispersant coexists in the solvent and the dispersion medium.   A spreading agent is added to the ultraviolet shielding dispersion according to any one of claims 3 to 5 so that the content of monoclinic fine particle bismuth oxide in the dried coating film is 20 to 80% by mass. A coating composition for shielding ultraviolet rays.   The ultraviolet shielding coating composition according to claim 6, wherein the spreading agent is mainly composed of an inorganic substance.   7. The ultraviolet shielding coating composition according to claim 6, wherein the spreading agent is a hydrolyzable silane compound and is a compound that crosslinks at 150 ° C. or higher in the presence of a catalyst.   The ultraviolet shielding coating composition according to claim 6, wherein the spreading agent is a silane coupling agent and is formed by heating at 200 to 500 ° C.   The coating composition for ultraviolet shielding according to claim 9, wherein the silane coupling agent is tetramethoxysilane or tetraethoxysilane.   The ultraviolet shielding coating composition according to claim 6, wherein the spreading agent is mainly composed of an organic substance.   The ultraviolet shielding coating composition according to claim 6, wherein the spreading agent is a resin for paint.

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