JP2014024732A - Ultraviolet-shielding material and method for manufacturing ultraviolet-shielding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet-shielding material having, despite having an excellent ultraviolet-shielding effect, an excellent dispersibility within an aqueous solvent and an excellent transparency.SOLUTION: In a case where titanium oxide nanotubes whose tube lengths are longer than 150 nm and shorter than 1000 nm are dispersed within an aqueous solvent based on the manufacture thereof by a method comprising: a synthesis step of synthesizing titanium oxide nanotubes from titanium oxide by means of hydrothermal synthesis; an agitation step of agitating the titanium oxide nanotubes synthesized at the synthesis step and beads in a state where the titanium oxide nanotubes and the beads are being mixed; and an ultrasonic treatment step of irradiating ultrasound onto the titanium oxide nanotubes; it becomes possible to provide an ultraviolet-shielding material exhibiting sufficient dispersibility within the aqueous solvent and capable of simultaneously realizing an advanced ultraviolet-shielding effect and transparency.

Description

  The present invention relates to an ultraviolet shielding material and an ultraviolet shielding material manufacturing method.

  In recent years, there has been a demand for shielding ultraviolet rays in various fields. Ultraviolet rays are also contained in sunlight, and if irradiated to the human body, it may cause sunburn, spots, etc., and may cause skin aging. The possibility of becoming is also pointed out. Further, when ultraviolet rays are irradiated not only on the human body but also on paper, plastics, rubber, etc. for a long time, it may cause discoloration or deterioration due to the energy of the ultraviolet rays.

  On the other hand, various ultraviolet shielding materials that shield ultraviolet rays are known. As an ultraviolet shielding material, for example, titanium oxide and zinc oxide are known. By covering the surface of the target object with titanium oxide or zinc oxide, the target object is prevented from being irradiated with the ultraviolet light by being reflected and scattered.

  However, when titanium oxide is used as an ultraviolet shielding material, there is a problem that a strong redox ability is developed due to a photocatalytic effect generated when titanium oxide absorbs light, and the surrounding organic substances are decomposed. . For this reason, for example, when it is applied to the skin as cosmetics, etc., it can be expected to have an ultraviolet shielding effect, but it has been pointed out that it may cause aging such as the occurrence of melanin and stains. There is a problem that it is difficult. In addition, when applied to the surface of an object as a coating agent, etc., titanium oxide is expected to block UV rays, while the oxidation / reduction ability of titanium oxide decomposes organic substances on the surface of the coating material and the object. However, there is a problem that the expected deterioration prevention effect cannot be obtained.

  Titanium oxide and zinc oxide have a white color as is apparent from the fact that they are used as pigments. For this reason, the cosmetics and coating agent using a titanium oxide become white, and there exists a subject that it cannot be set as a transparent cosmetics and coating agent.

  While an ultraviolet shielding material for protecting an object from ultraviolet rays has been eagerly desired, the present inventors can use it suitably as an ultraviolet absorbing material by forming a self-organized film on the surface of the titanium oxide nanotube. A functional material that can be produced has been invented (Patent Document 1). In the functional material described in this document, the photocatalytic activity of titanium oxide is suppressed by forming a self-organized film on the surface of the titanium oxide nanotube. Thus, the possibility that a titanium oxide nanotube can be used as a shielding material by forming a self-organized film on the surface of the titanium oxide nanotube was shown.

JP 2009-208988 A

  However, when titanium oxide nanotubes or titanium oxide nanotubes having a self-organized film are dissolved in water, they have very high cohesiveness. This is due to the three-dimensional nature of titanium oxide nanotubes in the shape of a tube and the chemical nature of the ability of hydroxyl groups to bond easily in water due to the presence of numerous hydroxyl groups on the surface of titanium oxide nanotubes. It is believed that there is. In Patent Document 1, the hydroxyl groups existing on the surface of the titanium oxide nanotubes are covered with the self-organized film to prevent the hydroxyl groups from being bonded to each other, but this is not sufficient. In fact, Patent Document 1 disperses the modified titanium oxide nanotubes in water at a concentration of 1180 ppm and unmodified titanium oxide nanotubes at a concentration of 3440 ppm, respectively. .

  In order to use titanium oxide nanotubes as an ultraviolet shielding material, the above-described concentration is insufficient. For this reason, development of a titanium oxide nanotube that can be sufficiently dispersed in an aqueous solvent even at a high concentration has been eagerly desired. On the other hand, since titanium oxide has a white color, it becomes white when the concentration is high. For this reason, since the high ultraviolet-ray shielding effect is calculated | required, development of the ultraviolet-ray shielding material which satisfy | fills two requirements of disperse | distributing at high concentration and maintaining transparency also at high concentration is eagerly desired.

  The present invention has been made in view of such a problem, and provides an ultraviolet shielding material having excellent dispersibility in an aqueous solvent and excellent transparency while having an excellent ultraviolet shielding effect. The main purpose.

  In order to achieve the main object described above, the inventors have synthesized a synthesis step of synthesizing titanium oxide nanotubes from titanium oxide by hydrothermal synthesis, and a mixture of the titanium oxide nanotubes synthesized in the synthesis step and beads. The tube length is greater than 150 nanometers by being manufactured by a method including a stirring step of stirring the titanium oxide nanotubes and the beads and an ultrasonic treatment step of irradiating the titanium oxide nanotubes with ultrasonic waves. By dispersing titanium oxide nanotubes shorter than nanometers in an aqueous solvent, an ultraviolet shielding material having sufficient dispersibility in an aqueous solvent and having both a high ultraviolet shielding effect and transparency can be found. It came to be completed.

That is, the ultraviolet shielding material of the present invention is
A synthesis step of synthesizing titanium oxide nanotubes from titanium oxide by hydrothermal synthesis;
A stirring step of stirring the titanium oxide nanotubes and the beads in a state where the titanium oxide nanotubes and beads synthesized in the synthesis step are mixed; and
An ultrasonic treatment step of irradiating the titanium oxide nanotube with ultrasonic waves;
A titanium oxide nanotube having a tube length greater than 150 nanometers and shorter than 1000 nanometers is dispersed in an aqueous solvent.
UV shielding material.

In the ultraviolet shielding material of the present invention, the synthesis step may be a synthesis step in which the synthesis is performed in an alkaline atmosphere and under a pressure higher than normal pressure. Here, the alkaline atmosphere preferably has a pH of 13 or more. At this time, the pH is preferably 13 or more with sodium hydroxide of 10 mol / dm ³ (hereinafter referred to as “M”) or more, and more preferably 13 or more with sodium hydroxide of 15 M or more. The pressure higher than the normal pressure is preferably 0.2 to 0.6 megapascal, more preferably 0.25 to 0.35 megapascal. By setting the pressure at the time of hydrothermal synthesis to a pressure of 0.2 megapascals or more, the titanium oxide can be sufficiently made into a nanotube shape. By doing so, sufficient transparency can be maintained when dissolved in an aqueous solvent while maintaining the ultraviolet shielding effect.

  The ultraviolet shielding material of the present invention may further include a neutralization step of neutralizing until the pH of the suspension in which the titanium oxide nanotubes are suspended becomes a neutral region. At this time, the neutral region is preferably pH 7.0 or more and 8.0 or less, and more preferably pH 7.0. Since the titanium oxide nanotubes are in an alkali salt state by a synthesis step performed in an alkaline atmosphere, neutralization until the pH is 7.0 or more and 8.0 or less improves the solubility and dispersibility in an aqueous solvent. be able to. Further, by neutralizing to pH 7.0, the quality can be kept constant and the solubility and dispersibility can be further improved.

  The ultraviolet shielding material of the present invention may further include a filtration step of filtering using a filter of 0.1 to 50 micrometers after the ultrasonic treatment step. At this time, the diameter of the filter is more preferably from 0.3 to 20 micrometers, and more preferably from 0.5 to 10 micrometers. Aggregates formed by agglomeration of nanotube-shaped titanium oxide usually have a size of 50 micrometers or more. Therefore, the aggregate of titanium oxide nanotubes can be efficiently removed by setting the filter diameter to 50 micrometers or less. Therefore, when it is dissolved in an aqueous solvent, it is preferable because sufficient transparency can be maintained. If the diameter is 20 micrometers or less, it is more preferable because transparency can be further increased. It is preferable to use a meter or less because the transparency can be further increased. On the other hand, this transparency can achieve the same effect even with a filter having a diameter of 0.1 μm or less. However, since a long time is required for the filtration step, the transparency is short while ensuring sufficient transparency. In order to obtain the ultraviolet shielding material with time, it may be 0.1 micrometers or more, more preferably 0.3 micrometers, and more preferably 0.5 micrometers or more.

  In the ultraviolet shielding material of the present invention, the ultrasonic wave irradiated in the ultrasonic treatment step preferably has a frequency of 15 kHz to 30 kHz, and preferably 20 kHz to 30 kHz. At this time, the amplitude is preferably 5 micrometers or more and 50 micrometers or less, and more preferably 20 micrometers or more and 50 micrometers or less. This is because when the frequency and amplitude of the ultrasonic waves are set within this range, a large amount of cavitation occurs, and the collision energy between the nanoparticles due to the shock wave resulting from the collapse increases.

  In the ultraviolet shielding material of the present invention, the bead is preferably 0.3 mm or more and 1.0 mm or less, and more preferably 0.3 mm or more and 0.5 mm or less. At this time, the ratio of the beads filled in the dispersion step is preferably 50% or more and 90% or less, and more preferably 70% or more and 80% or less with respect to the volume of the stirring region. Rather than separation by a special separation method using centrifugation or the like, a bead diameter of 0.3 mm or more, which can be separated by a screen conventionally known as a reliable method, is preferable. Further, it is more preferably 0.5 mm or less capable of uniformly applying a shearing force to the nanoparticles, and a thickness larger than 1.0 mm is not preferable because the shearing force cannot be applied uniformly.

  In the ultraviolet shielding material of the present invention, the hardness of the beads is preferably a Mohs hardness of 7 or more and 10 or less, and more preferably 8 or more and 9 or less. When the Mohs hardness of the beads is less than 7, it is not preferable because the titanium oxide nanotubes cannot be made sufficiently fine and the length in the tube direction may become long.

  In the ultraviolet shielding material of the present invention, the titanium oxide nanotubes may be obtained by modifying the surface of the titanium oxide nanotubes with a coupling agent having a hydrophilic functional group. In this case, the photocatalytic activity of titanium oxide can be suppressed by covering the surface of the titanium oxide nanotube with the coupling agent. At this time, the coupling agent is preferably a silane coupling agent, and more preferably a coupling agent having a hydrophilic functional group. This is because by using a coupling agent having a hydrophilic functional group, it is possible to increase the affinity for an aqueous solvent and disperse it uniformly.

The TEM image figure which shows an example of TNT. The TEM image figure which shows an example of IS-TNT. The graph which shows the change of the visible light transmittance | permeability of TNT for every ultraviolet irradiation time. The graph which shows the change of the visible light transmittance | permeability of IS-TNT for every ultraviolet irradiation time. The graph which shows the difference in the cut rate of TNT by the presence or absence of filtration. The graph which shows the difference in the cut rate of IS-TNT by the presence or absence of filtration.

  Next, an embodiment of an ultraviolet shielding material that is an example of an embodiment of the present invention will be described in detail. Since this ultraviolet shielding material mainly contains titanium oxide nanotubes (hereinafter referred to as “TNT”) or imidazole silane-modified titanium oxide nanotubes (hereinafter referred to as “IS-TNT”), After describing the method for preparing TNT, the method for preparing IS-TNT will be described.

(Hydrothermal synthesis treatment)
This TNT is prepared by hydrothermal synthesis using titanium oxide as a starting material. Specifically, titanium oxide is added to an aqueous solution of sodium hydroxide of 10 M or more and 20 M or less, and the pressure is maintained at a temperature of 110 ° C. or higher and 180 ° C. or lower and a pressure of 0.2 megapascal or higher and 0.6 megapascal or lower. Hydrothermal synthesis was performed for a time of 100 hours or less. The hydrothermal synthesis temperature may be 120 ° C. or higher and 180 ° C. or lower, 140 ° C. or higher and 180 ° C. or lower, or 155 ° C. or higher and 170 ° C. or lower. By doing so, a titanium oxide nanotube having a high dispersibility in an aqueous solvent and a tube length larger than 150 nanometers and shorter than 1000 nanometers can be obtained. The tube length can be appropriately prepared by changing the pressure and temperature of the hydrothermal synthesis treatment. For example, the tube length may be a titanium oxide nanotube having a tube length larger than 150 nanometers and shorter than 500 nanometers, The tube length may be a titanium oxide nanotube having a tube length greater than 150 nanometers and shorter than 250 nanometers, or may be a titanium oxide nanotube having a tube length of 200 nanometers.

(Neutralization treatment)
An acid was added to the synthesized product obtained by hydrothermal synthesis until the pH of the solution became a neutral region, and then washed with water. After washing with water and drying at 100 ° C. for 2 hours, a white powder (hereinafter referred to as “Sample 1”) was obtained. At this time, the neutral region is preferably pH 7.0 or more and 8.0 or less, and more preferably pH 7.0. By doing so, the solubility and dispersibility in an aqueous solvent can be improved, and the quality of the resulting synthesized product can be kept constant.

(Preparation process)
Next, Sample 1 was suspended in water and prepared so that the concentration would be 1 wt% to 7 wt% to obtain a suspension. A small amount of a dispersant is added to this suspension, and the dispersion beads and sample 1 are mixed together. The suspension is dispersed together with ultrasonic irradiation, and a highly transparent suspension (hereinafter referred to as “sample 2”). .) Thus, by applying vibration by ultrasonic waves and physical impact by beads, nanotube-shaped titanium oxide contained in the sample 2 can be prepared in a desired shape.

  The concentration at which the sample 1 is suspended in water is preferably 1 wt% to 7 wt%, and more preferably 2 wt% to 4 wt%. Sample 1 is mainly composed of nanotube-shaped titanium oxide, and the nanotube-shaped titanium oxide synthesized under highly alkaline conditions has hydroxyl groups exposed on the surface, so that the hydroxyl groups tend to interact with each other. By making it high concentration, it becomes easy to aggregate each other. Therefore, by setting the concentration suspended in water to 7 wt% or less, the possibility that the materials 1 aggregate and form aggregates can be reduced, and by setting the concentration to 4 wt% or less, the aggregates The possibility of forming can be further reduced.

  As the dispersant used here, for example, sodium tripolyphosphate can be used, and the addition amount of the dispersant can be appropriately determined according to the kind of the additive and the concentration of the sample 1. Moreover, it is not necessary to add a dispersing agent.

  The Mohs hardness of the beads used here is preferably 7 or more and 10 or less, and more preferably 8 or more and 9 or less. Specifically, for example, garnet, quartz, silicon, beryllium, zirconium, osmium, topaz, tungsten carbide, corundum, alumina, silicon carbide, diamond and the like are preferable. When the Mohs hardness of the beads is less than 7, it is not preferable because the titanium oxide nanotubes cannot be made sufficiently fine.

  The diameter of the beads used here is preferably 0.3 mm or more and 1.0 mm or less, and more preferably 0.3 mm or more and 0.5 mm or less. At this time, the ratio of beads to be filled is preferably 50% or more and 90% or less, and more preferably 70% or more and 80% or less with respect to the volume of the stirring region. A diameter of 0.3 mm or more, which is a bead diameter separable by a screen known as a reliable method, is preferable, and 0.5 mm or less, which can uniformly apply a shearing force to nanoparticles, is preferable. . On the other hand, if it is larger than 1.0 mm, it is not preferable because a shearing force cannot be applied uniformly.

  The ultrasonic wave irradiated here preferably has a frequency of 15 kHz to 30 kHz, and preferably 20 kHz to 30 kHz. At this time, the amplitude is preferably 5 micrometers or more and 50 micrometers or less, and more preferably 20 micrometers or more and 50 micrometers or less. This is because when the frequency and amplitude of the ultrasonic waves are set within this range, a large amount of cavitation occurs, and the collision energy between the nanoparticles due to the shock wave resulting from the collapse increases.

(Filtering process)
Sample 2 obtained in the dispersing step was filtered using a membrane filter (pore diameter 0.7 μm) to obtain a filtrate (hereinafter referred to as “sample 3”). Since the sample 3 in a state where the particle size is aggregated to 0.7 μm or more is removed, the sample 3 having a particle size of less than 0.7 μm is selected. Since the titanium oxide contained in the sample 3 has a nanotube shape, specifically, the nanotube length is considered to be less than 0.7 micrometers. Thus, when the length of the tube is less than 0.7 micrometers, aggregation is reduced in advance when dissolved in an aqueous solvent, and excellent dispersibility is obtained. As an example of the nanotube-shaped titanium oxide (TNT) thus obtained, an image obtained by photographing the TNT with a transmission electron microscope is shown in FIG. 1 as a TEM image. As can be seen from FIG. 1, the titanium oxide that had been in the form of particle diameter before the treatment has been changed to a nanotube shape.

(Surface modification process)
Next, an ultraviolet shielding material whose surface is modified with a silane coupling agent will be described. Here, IS-TNT is obtained by surface-modifying TNT prepared in the above-described synthesis process with a silane coupling agent, and the preparation method of TNT before surface modification is the same as the TNT synthesis process. Then, explanation is omitted.

  A silane coupling agent was added to a suspension obtained by suspending TNT prepared in the same manner as in the synthesis step described above in an organic solvent, and then stirred at 100 to 150 ° C. for 12 to 24 hours.

  The silane coupling agent used here is an organosilicon compound having both a functional group reactively bonded to an organic material and a functional group reactively bonded to an inorganic material in the molecule, one organic functional group per silicon atom and 2 to 3 It is a compound that has a structure having a hydrolyzable group that reacts with an inorganic substance, whereby the surface of the inorganic substance can be modified.

As such a silane coupling agent, for example, RSiX ₃ (X: a hydrolyzable group bonded to a silicon atom, an alkoxy group, an acetoxy group, a chloro atom, etc .; R: an organic functional group, an epoxy group in this part , Vinyl groups, amino groups, and other functional materials that can react with organic materials can be introduced). Specific compounds include methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, methyltripropoxysilane, ethyltripropoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxysilane. , N-propyltripropoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, isopropyltripropoxysilane, methyltributoxysilane, ethyltributoxysilane, n-propylbutoxysilane, isopropylbutoxysilane, phenyltrimethoxysilane, phenyltri Ethoxysilane, phenyltripropoxysilane, phenyltributoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, -Those having an alkyl side chain such as octadecyltrimethoxysilane and n-octyltriethoxysilane, and epoxy at the terminal such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane A group having a vinyl group such as allyltriethoxysilane, allyltrimethoxysilane, trichlorovinylsilane, triethoxyvinylsilane, vinyltrimethoxysilane, 3- (2-aminoethylamino) propyltriethoxysilane, 3- Those having an amino group such as (2-aminoethylamino) propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopro Examples having various functional groups such as rutriethoxysilane, 3- (triethoxysilyl) propyl isocyanate, 3- (triethoxysilyl) propyl methacrylate, chloromethyltriethoxysilane, trifluoropropyltrimethoxysilane, and imidazolesilane It is done.

  Among such silane coupling agents, for example, 3- (2-aminoethylamino) propyltriethoxysilane, 3- (2-aminoethylamino) propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- Aminopropyltrimethoxysilane, 3-mercaptotriethoxysilane, 3-mercaptotrimethoxysilane and the like having a hydrophilic functional group at the terminal are preferable. For example, imidazolesilane, 2,3-dihydroxypropyltriethoxysilane, 2, Those having a highly hydrophilic functional group such as a hydroxyl group or an imidazolium group at the terminal, such as 3-dihydroxypropyltrimethoxysilane, 3-imidazoliumpropyltriethoxysilane, and 3-imidazoliumpropyltrimethoxysilane are more preferable. Moreover, since imidazole silane has both a hydroxyl group and an imidazolium group at the terminal, it is more preferable in that it has a functional group having high hydrophilicity.

  As the reaction accelerator used here, for example, a tertiary amine such as triethylamine, tributylamine, diisopropylethylamine or the like may be used. By adding a reaction accelerator, reaction time can be shortened and productivity can be improved.

(Purification process)
The solution containing the surface-modified TNT thus obtained was naturally cooled to room temperature, and then centrifuged to obtain the resulting precipitate fraction. This precipitate fraction was suspended again in dehydrated toluene, stirred at 125 ° C. for about 6 hours, and then centrifuged again to obtain a precipitate fraction. This precipitated fraction was washed three times with hexane and then dried at 100 ° C. for about 16 hours to obtain a surface-modified TNT. The washing method with hexane was performed by resuspending the precipitate fraction in hexane and then centrifuging to obtain the precipitate fraction.

  The surface-modified TNT thus obtained was centrifuged, and the resulting precipitate fraction was resuspended in dehydrated toluene and stirred at room temperature for about 6 hours. Subsequently, the mixture was further centrifuged, and the resulting precipitate fraction was washed three times with hexane. The resulting precipitate fraction was collected and dried in a hot air dryer at 120 ° C. for 2 hours for surface modification. Was purified to obtain TNT with surface modification. As an example of the surface-modified TNT thus obtained, an image obtained by photographing the surface-modified TNT with imidazole silane with a transmission electron microscope is shown in FIG. As is apparent from FIG. 2, the nanotube shape is maintained even in the state where the surface is modified with imidazole silane.

(Preparation of each sample)
Anatase-type titanium oxide was added to a 10M sodium hydroxide aqueous solution at a mass ratio of 10: 1, and hydrothermal synthesis was performed at a temperature of 150 ° C. for 20 hours. The reaction product thus obtained was neutralized, washed with water, and dried at 100 ° for 2 hours to obtain a white powder.

  This white powder was suspended in water so as to be 3 wt%, and placed in a nanosonic mill (model: NSM-0.1C) manufactured by Inoue Seisakusho Co., Ltd. to be dispersed to obtain Sample 1. The sample put into the nanosonic mill is mixed with beads in the apparatus and irradiated with ultrasonic waves, and the white powder is uniformly dispersed in water.

  Subsequently, filtration was performed using a membrane filter manufactured by Loki Techno Co., Ltd. (product number: 20L-SLF-007XS) to obtain a filtrate (sample 2).

  Anatase-type titanium oxide was added to a 10M sodium hydroxide aqueous solution at a mass ratio of 10: 1, and hydrothermal synthesis was performed at a temperature of 150 ° C. for 20 hours. The reaction product thus obtained was neutralized, washed with water, and dried at 100 ° for 2 hours to obtain a white powder.

  To a suspension obtained by suspending 30 g of this white powder in an organic solvent, 25 ml of imidazole silane (manufactured by JX Nippon Mining & Metals Co., Ltd., trade name: imidazole silane IS-3000) and 0.4 ml of triethylamine are added. While maintaining at 125 ° C., the mixture was stirred for about 16 hours using a magnetic stirrer or the like. Subsequently, after naturally cooling to room temperature, centrifugation was performed to obtain the resulting precipitate fraction. This precipitate fraction was suspended again in dehydrated toluene, stirred at 125 ° C. for about 6 hours, and then centrifuged again to obtain a precipitate fraction. This precipitate fraction was washed three times with hexane and then dried at 100 ° C. for about 16 hours to obtain IS-TNT. The washing method with hexane was performed by resuspending the precipitate fraction in hexane and then centrifuging to obtain the precipitate fraction.

  The IS-TNT thus obtained was centrifuged, and the resulting precipitate fraction was resuspended in dehydrated toluene and stirred at room temperature for about 6 hours. Subsequently, the mixture was further centrifuged, and the resulting precipitate fraction was washed with hexane three times. The obtained precipitate fraction was collected and dried in a warm air dryer at 120 ° C. for 2 hours to obtain IS- TNT was purified to obtain IS-TNT with surface modification.

  The IS-TNT thus obtained was suspended in water at 3 wt%, and placed in a nanosonic mill (model: NSM-0.1C) manufactured by Inoue Seisakusho Co., Ltd. for dispersion to obtain sample 3. It was.

  Subsequently, filtration was performed using a membrane filter manufactured by Loki Techno Co., Ltd. to obtain a filtrate (sample 4).

(Evaluation of visible light transmittance of each sample)
Samples 1 to 4 and anatase titanium oxide thus obtained were each added to a resin (DIC Co., Ltd., Boncoat CF-6240) at a ratio of 0.16 wt%, so that the film thickness was 60 micrometers. It was applied to a quartz plate.

  Subsequently, after each quartz plate was immersed in water, an ultraviolet lamp (sterilization lamp GL-6 manufactured by Toshiba Lighting & Technology Co., Ltd.) was irradiated for 6 hours from a distance of 3 cm and dried at 37 ° C. for 12 hours. Spectroscopic measurement was performed, and the transmittance after 6 hours was measured. Similarly, measurement was performed every 6 hours for 66 hours. From this measurement result, the visible light transmittance is calculated according to the method of JIS R 3106, and the relationship between the visible light transmittance and the ultraviolet irradiation time is shown in FIGS. 3 and 4 are graphs showing the relationship between the visible light transmittance and the ultraviolet irradiation time. 3 shows titanium oxide (solid line), blank (dotted line), sample 1 (one-dot chain line), and sample 2 (two-dot chain line). FIG. 4 shows titanium oxide (solid line) and blank ( A dotted line), a sample 3 (one-dot chain line), and a sample 4 (two-dot chain line) are shown. The vertical axis represents the visible light transmittance, and the horizontal axis represents the ultraviolet irradiation time.

  As apparent from FIGS. 3 and 4, the visible light transmittances of the sample 3 and the sample 4 are higher than the visible light transmittances of the sample 1 and the sample 2. From this, it can be said that the transmittance of IS-TNT is higher than that of TNT regardless of the presence or absence of filtration. In other words, it can be said that the quartz plate coated with IS-TNT has higher transparency than TNT. From this, it can be said that by modifying the surface of TNT with imidazole silane, a decrease in transparency can be suppressed as compared with TNT. This is because by modifying the surface of TNT with imidazole silane, it is possible to cover the hydroxyl groups present on the surface of TNT, and therefore it is possible to suppress aggregation due to the interaction between the hydroxyl groups. They are thinking. As a result, it is considered that it was possible to prevent the formation of aggregates and to prevent the transparency from being lowered due to relatively large aggregates.

  Moreover, comparing the visible light transmittance after 6 hours and the visible light transmittance after 62 hours of each sample, compared with the change in the visible light transmittance of Sample 1 and Sample 2 (see FIG. 3), The change in the visible light transmittance of sample 3 and sample 4 (see FIG. 4) is small. From this, even if it is a case where ultraviolet rays are irradiated for a long time, compared with TNT, it can be said that IS-TNT has a small decrease in visible light transmittance. In other words, it can be said that the transparency of the quartz plate coated with IS-TNT is kept higher than that of TNT. From this, it can be said that by modifying the surface of TNT with imidazole silane, a decrease in transparency can be suppressed as compared with TNT. This is because by modifying the surface of TNT with imidazole silane, a self-assembled film can be formed on the surface of TNT, so that it is possible to suppress degradation (whitening) of the surrounding resin due to the photoactive action of titanium oxide. The inventors think that this is because they have been able to. As a result, it is considered that the resin can be prevented from deteriorating and the transparency can be prevented from deteriorating due to the deterioration of the resin.

Here, the amount of ultraviolet rays irradiated with the ultraviolet lamp is evaluated. The intensity of ultraviolet rays when irradiating an ultraviolet lamp (sterilization lamp GL-6, manufactured by Toshiba Lighting & Technology Corporation) from a distance of 5 cm is 19 μW / cm ² , so the intensity of ultraviolet rays when irradiated with a distance of 5 cm Is 7600 W / cm ² , which corresponds to 76 J / m ² s. Therefore, the energy per hour corresponds to 273, 6 kJ / m ² s. On the other hand, it is known that the daily integrated amount in the irradiation intensity of UV-B which was observed at a fixed point in Himeji City, Hyogo Prefecture is 13.61795 J / m ² sday. Therefore, the energy per hour of this ultraviolet lamp is approximately 2.008 days in Himeji City, Hyogo Prefecture.

(Evaluation of cut rate of each sample)
Next, regarding samples 1 to 4, the relationship between the concentration of TNT (or IS-TNT) and the cut rate is shown in FIGS. Here, the “cut rate” is a numerical value obtained by integrating the transmittance at a wavelength of 280 to 370 nanometers, and the sample of each concentration of TNT (or IS-TNT) is TNT (or IS-TNT). This is a value indicating the ratio of the concentration compared to the case where the concentration is 0. Specifically, the absorbance at a wavelength of 280 nm to 370 nm at each concentration of TNT (or IS-TNT) Is obtained by subtracting from the value of 100 the value obtained by dividing the integral value of γ by the integral value of absorbance at wavelengths of 280 to 370 nanometers that do not include TNT (or IS-TNT). The larger the cut rate represented by this equation, the more the wavelength from 280 nanometers to 370 meters (that is, the wavelength in the region corresponding to the ultraviolet rays reaching the ground surface) is blocked.

  First, FIG. 5 shows the change in the cut rate at each density of sample 1 (solid line) and sample 2 (dotted line). Here, FIG. 6 is a graph showing the change in the cut rate at each concentration of Sample 1 and Sample 2, where the vertical axis indicates the cut rate and the horizontal axis indicates the concentration of titanium oxide. As can be seen from FIG. 5, in order to obtain a cut rate of 20%, the sample 1 requires a titanium oxide concentration of about 0.4 wt%, whereas the sample 2 is about 0.05 wt% and 20%. A cut rate of can be obtained. From this, it is clear that Sample 2 can obtain a cut rate of 20% or more even when the concentration is lower than Sample 1. In other words, it can be said that it has a high ultraviolet shielding effect even at a low concentration. This is considered to be because the aggregate having a low ultraviolet shielding effect could be removed by filtration.

  Next, FIG. 6 shows changes in the cut rate at the respective concentrations of Sample 3 and Sample 4. FIG. Here, FIG. 6 is a graph showing changes in the cut rate at each concentration of sample 3 (dotted line) and sample 4 (solid line), where the vertical axis shows the cut rate and the horizontal axis shows the titanium oxide concentration. . As is clear from FIG. 6, the cut rate of both sample 3 and sample 4 is greatly increased at the titanium oxide concentration of about 0.05 wt%. From this, it is clear that the sample 3 and the sample 4 require a titanium oxide concentration of 0.05 wt% or more in order to obtain a sufficient ultraviolet shielding effect. Further, when comparing the sample 3 and the sample 4, the sample 4 has a higher cut rate than the sample 3 regardless of the concentration. From this, it can be said that sample 4 has a higher ultraviolet shielding effect than sample 3. This is considered to be because the aggregate having a low ultraviolet shielding effect could be removed by filtration.

(Change in transparency of each sample)
Finally, with respect to Samples 1 to 4, it was visually confirmed at which concentration the coating film became cloudy. As a result, sample 1 was not cloudy at 0.099 wt% or less, but was cloudy at 0.119 wt% or more. Sample 2 was not cloudy at 0.102 wt% or less, but was cloudy at 0.255 wt% or more. Sample 3 was not cloudy at 0.063 or less, but clouded at 0.071 wt% or more. Sample 4 was not cloudy at 0.16 wt% or less, but was cloudy at 0.4 wt% or more. In addition, when a similar experiment was performed using anatase-type titanium oxide as a comparison target, white turbidity was already confirmed at 0.04 wt%, and transparency could not be ensured. From this, it can be said that even if the concentration is higher, it does not become cloudy by performing the filtration when compared with TNT as to whether or not the filtration has been performed. Moreover, when it compares by IS-TNT about whether it filtered, it can be said that it does not become cloudy by a higher density | concentration by filtering. From the above, it is possible to disperse a large amount of TNT or IS-TNT without being clouded by performing filtration on both TNT and IS-TNT. As the added amount of TNT or IS-TNT increases, the ultraviolet shielding effect increases, so it can be said that a high ultraviolet shielding effect was obtained while maintaining transparency.

Claims (14)

A synthesis step of synthesizing titanium oxide nanotubes from titanium oxide by hydrothermal synthesis;
A stirring step of stirring the titanium oxide nanotubes and the beads in a state where the titanium oxide nanotubes and beads synthesized in the synthesis step are mixed; and
An ultrasonic treatment step of irradiating the titanium oxide nanotube with ultrasonic waves;
A titanium oxide nanotube having a tube length greater than 150 nanometers and shorter than 1000 nanometers is dispersed in an aqueous solvent.
UV shielding material. The synthesis step is a synthesis step in which the pH is 13 or more and synthesis is performed under a pressure higher than normal pressure.
The ultraviolet shielding material according to claim 1. In the synthesis step, the pH is maintained at 13 or more with 15 mol / dm ³ or more of sodium hydroxide,
The ultraviolet shielding material according to claim 1 or 2. The pressure greater than the normal pressure is a pressure of 0.2 megapascals or more and 0.6 megapascals or less.
The ultraviolet shielding material according to claim 1. In the ultraviolet shielding material according to any one of claims 1 to 4,
A neutralization step of neutralizing the suspension of the titanium oxide nanotubes in a neutral region after the synthesis step;
UV shielding material. The ultraviolet shielding material further includes a filtration step of filtering using a filter having a diameter of 0.1 to 10 micrometers after the ultrasonic treatment step.
The ultraviolet shielding material according to claim 1. The ultrasonic treatment step is a step of irradiating the titanium oxide nanotube with ultrasonic waves having a vibration frequency of 15 kHz to 30 kHz and an amplitude of 5 μm to 50 μm.
The ultraviolet shielding material according to claim 1. The beads are beads having a range of 0.1 mm to 1.0 mm,
The dispersion step is a step of filling and stirring the beads so as to have a ratio of 50% to 90% with respect to the volume of the stirring region.
The ultraviolet shielding material according to claim 1. The bead has a Mohs hardness of 7 to 10,
The ultraviolet shielding material according to claim 1. The titanium oxide nanotube is obtained by modifying the surface of the titanium oxide nanotube with a coupling agent having a hydrophilic functional group.
The ultraviolet shielding material according to claim 1. The coupling agent is a silane coupling agent.
The ultraviolet shielding material according to claim 10. The silane coupling agent has both an imidazolium group and a hydroxyl group,
The ultraviolet shielding material according to claim 11. The silane coupling agent includes imidazole silane,
The ultraviolet shielding material according to claim 11. A synthesis step of synthesizing titanium oxide nanotubes from titanium oxide by hydrothermal synthesis;
A stirring step of stirring the titanium oxide nanotubes and the beads in a state where the titanium oxide nanotubes and beads synthesized in the synthesis step are mixed; and
An ultrasonic treatment step of irradiating the titanium oxide nanotube with ultrasonic waves;
By including
Titanium oxide nanotubes having a tube length larger than 150 nanometers and shorter than 1000 nanometers are dispersed in an aqueous solvent,
Manufacturing method of UV shielding material.