JP2006126468A - Near-infrared ray shielding agent and resin composition containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a white near infrared ray shielding agent which has superior to shielding performance of near-infrared rays and also superior concealing properties and which can be used as a pigment. <P>SOLUTION: This near-infrared ray shielding agent contains as an effective component acicular titanium dioxide the single particle of which has 1.5-6 μm average major axis and 0.2-0.8 μm average minor axis. The acicular titanium dioxide can be obtained, by hydrolyzing a hydrolyzable titanium compound in a liquid phase in the presence of a seed crystal of acicular titanium dioxide, to obtain a hydrolysis product and heating/firing the hydrolysis product at 900-1,200°C, in the presence of a firing agent containing an alkali metal compound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a near-infrared shielding agent containing rod-shaped titanium dioxide as an active ingredient.

  In recent years, there has been a strong demand for energy saving, in particular, reduction of power consumption, from the viewpoints of the environment such as air pollution and global warming and from the viewpoint of effective use of resources. In Japan, the use of air conditioners, coolers, refrigerators, etc. in summer is a factor that increases power consumption. For this reason, the technique which suppresses the absorption of the near infrared rays (heat ray) contained in sunlight by coating the outer wall of a building with the paint containing a near-infrared shielding agent, and suppresses the temperature rise in a building is proposed. . As such a near-infrared shielding agent, a near-infrared reflective composite pigment in which a white pigment is coated and colored with a near-infrared reflective and / or transparent dye (see Patent Document 1) is known. Moreover, as a white pigment excellent in near-infrared shielding ability, a large particle diameter titanium dioxide (refer nonpatent literature 1) with an average particle diameter of 0.4-1.5 micrometers is known.

JP 2002-249676 A (page 2) Kenji Yamamoto, “Development of Titanium Oxide for Near-Infrared Shielding”, Convertech, Processing Technology Research Association, July 2004, No. 376 P95-97

  Titanium dioxide described in Non-Patent Document 1 has an excellent near-infrared shielding ability because it is set to an average particle diameter in the above range suitable for reflecting near-infrared rays. However, the reflectance in the visible light region is lower than that of ordinary pigment-grade titanium oxide (average particle size is 0.2 to 0.4 μm), and thus it is difficult to use in applications that require high concealment properties. . The present invention provides a white near-infrared shielding agent that is excellent in near-infrared shielding ability, has excellent concealment properties, and can be used as a pigment.

  As a result of intensive studies to solve these problems, the present inventors have made the shape of the titanium oxide particles into a rod shape having an average major axis diameter and an average minor axis diameter in a specific range, and thereby the near infrared ray. The present invention has been completed by finding that the shielding ability and the hidden payability can be compatible.

  That is, the present invention contains rod-shaped titanium dioxide having an average major axis diameter of a single particle in a range of 1.5 to 6 μm and an average minor axis diameter in a range of 0.2 to 0.8 μm as an active ingredient. It is a near infrared shielding agent.

  The near-infrared shielding agent of the present invention has an excellent near-infrared shielding ability and a concealing property, and a resin composition blended therewith, as a near-infrared shielding material, protects a substrate from near-infrared rays, Or it can use for uses, such as suppression of the temperature rise in a structure.

  The present invention is a near-infrared shielding agent, in which the average long axis diameter of a single particle is in the range of 1.5 to 6 μm and the average short axis diameter is in the range of 0.2 to 0.8 μm. Is contained as an active ingredient. In rod-like titanium dioxide, it is presumed that the near-infrared shielding ability is strongly influenced by the long axis diameter, and the visible light scattering is strongly influenced by the short axis diameter. For this reason, in the present invention, the long axis diameter of the rod-like titanium dioxide is set to the above-described range optimal for near-infrared shielding ability, and the short-axis diameter is set to the above-mentioned range optimal for scattering of visible light. The balance of payability is at a high level. A more preferable range of the average major axis diameter is 1.5 to 4 μm, and a range of the average minor axis diameter is 0.2 to 0.5. Particularly, those having an axial ratio in the range of 3 to 15 are preferable because the balance between the near-infrared shielding ability and the hidden payability is excellent, and the range of 5 to 10 is more preferable.

  There is no restriction | limiting in particular in the crystal form of the rod-shaped titanium dioxide used by this invention, Either a rutile type or an anatase type can be used. However, the rutile type is preferable because it has a high reflectance of light having a long wavelength and is excellent in weather resistance and light resistance for a resin composition.

  The surface of the rod-shaped titanium dioxide may have a coating layer of a known inorganic compound or organic compound, or a combination thereof may be coated. In general, an inorganic compound coating is known to improve productivity and weather resistance, and an organic compound coating is known to improve affinity with a resin component. The coating amount of the inorganic compound varies depending on the use, but is preferably in the range of 0.1 to 10% by weight when used in a coating composition and 0.05 to 5% by weight in the case of a plastic composition. A preferable coating amount of the organic compound is usually in the range of 0.01 to 5% by weight, and a more preferable range is 0.05 to 2% by weight.

  Examples of inorganic compounds that can be used for surface coating include oxides such as aluminum, silicon, zirconium, tin, titanium, and antimony, hydroxides, hydrated oxides, and phosphates. One of these is coated. In addition, two or more kinds of coatings may be laminated, or two or more kinds of inorganic compounds may be mixed and coated to be used in combination. The inorganic compound coating layer may be a porous layer or a dense layer, and is not particularly limited.

  Examples of organic compounds that can be used for surface coating include polyhydric alcohols, alkanolamines or derivatives thereof, organosilicon compounds, higher fatty acids or metal salts thereof, and organometallic compounds. Specifically, for example, (1) as polyhydric alcohol, trimethylolethane, tripropanolethane, pentaerythritol, etc., (2) as alkanolamine, triethylamine, tripropylamine, etc., as derivatives thereof Organic acid salts, etc. (3) As organosilicon compounds, (a) polysiloxanes (dimethylpolysiloxane, methylhydrogenpolysiloxane, etc.), (b) organosilanes (alkylsilane, phenylsilane, etc.) (4) Higher fatty acids include stearic acid and lauric acid, and metal salts thereof include magnesium salts and zinc salts. (5) Examples of organometallic compounds include titanium Coupling agents, aluminum coupling agents, zirconium coupling agents. These can be coated alone or in combination of two or more.

  Next, the present invention is a method for producing rod-like titanium dioxide, comprising hydrolyzing a hydrolyzable titanium compound in the liquid phase in the presence of rod-like titanium dioxide nucleus crystals to obtain a hydrolysis product, The hydrolysis product is heated and fired at a temperature in the range of 900 to 1200 ° C. in the presence of a baking treatment agent containing a compound. The rod-like titanium dioxide of the present invention is a known method, for example, a method of heating and firing a mixture of a titanium source, an alkali metal salt, and an oxylin compound in the presence of rod-like titanium dioxide nucleus crystals disclosed in Japanese Patent Publication No. 6-24977. Can also be obtained. However, in the method described in Japanese Patent Publication No. 6-24977, the long axis is easy to grow as compared to the short axis. When the short axis is increased, the long axis is further increased. It is difficult to obtain. On the other hand, in the method of the present invention, the long axis is less likely to grow than the short axis. Therefore, the average long axis diameter of single particles is in the range of 1.5 to 6 μm, and the average short axis diameter is 0.2. Desirable rod-shaped particles in the range of ˜0.8 μm are particularly preferable because those having an axial ratio in the range of 3 to 15 and preferably in the range of 5 to 10 are easily obtained. The hydrolyzed product is considered to be the hydrous titanium oxide (or titanium hydroxide) produced by hydrolysis of the hydrolyzable titanium compound deposited on the surface of the nucleus crystal.

  First, a rod-like titanium dioxide nucleus crystal is added to the hydrolyzable titanium compound solution, or a hydrolyzable titanium compound solution is added to the rod-like titanium dioxide nucleus crystal slurry, and then hydrolyzable in the liquid phase. The titanium compound is hydrolyzed to produce a hydrolysis product. For hydrolysis, heat hydrolysis, neutralization hydrolysis, or the like can be used, but since a neutralizing agent is not required, industrially heat hydrolysis is preferable. Heat hydrolysis is preferably performed at a temperature of 50 ° C. or higher because hydrolysis is likely to proceed, and more preferably 80 ° C. or higher. There is no particular upper limit to the temperature of the heat hydrolysis, but a temperature lower than 100 ° C. is preferable because the hydrolysis can be performed under normal pressure. The neutralization hydrolysis is preferably carried out when the pH is in the range of 5.5 to 9, since the hydrolysis easily proceeds, and more preferably in the range of 6 to 8. Neutralizing agents include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide and calcium hydroxide, alkali metal or alkaline earth metal carbonates such as sodium carbonate and potassium carbonate, ammonia Ammonium compounds such as ammonium carbonate and ammonium nitrate can be used.

  The rod-shaped titanium dioxide nucleus crystals to be used are selected in accordance with the major axis diameter and minor axis diameter of the rod-shaped titanium dioxide used for the intended near-infrared shielding agent. The short axis diameter of the rod-shaped titanium dioxide nucleus crystal is selected to be smaller than the target. However, in the production method of the present invention, the major axis diameter is slightly larger than the target because the major axis shrinks after heating and firing. May be. For example, the average major axis diameter of single particles as nuclei is in the range of 1 to 10 μm, the average minor axis diameter is in the range of 0.05 to 0.6 μm, and preferably the axial ratio is in the range of 8 to 25. It can be appropriately selected from a certain one. In order to obtain rod-like titanium dioxide nucleus crystals, a known method, for example, a method of heating and firing a mixture of a titanium source, an alkali metal salt, and an oxylin compound can be used. Alternatively, commercially available rod-like titanium dioxide, for example, FTL-100, FTL-200, FTL-300 (all manufactured by Ishihara Sangyo Co., Ltd.) and the like can also be used. When the rod-like titanium dioxide nucleus crystal is used in the range of 0.5 to 30% by weight with respect to the hydrolyzable titanium compound, the desired rod-like particles are easily obtained, and the range of 1 to 15% by weight is more preferred.

As the hydrolyzable titanium compound, for example, titanyl sulfate (TiOSO ₄ ), titanium tetrachloride, titanium alkoxide or the like can be used, and it is preferable to use titanyl sulfate or titanium tetrachloride in terms of cost. Titanyl sulfate can be obtained, for example, by reacting a titanium component and sulfuric acid while dissolving a titanium-containing ore such as illuminite ore and titanium slag with sulfuric acid in a so-called sulfuric acid method manufacturing process. Titanium tetrachloride is obtained by reacting titanium-containing ore and chlorine gas at a temperature of about 1000 ° C. in the presence of a reducing agent such as coke in a so-called chlorine process.

The baking treatment agent containing an alkali metal compound has an effect of promoting rod-like formation of titanium dioxide at the time of heating and baking. Examples of the alkali metal compound include a sodium compound, a potassium compound, a lithium compound, and the like. One or more selected from these can be used. Among them, the combined use of a sodium compound and a potassium compound is preferable because the effect of promoting rod formation is high. Sodium hydroxide, sodium chloride, sodium carbonate, etc. can be used as the sodium compound, potassium hydroxide, potassium chloride, etc. can be used as the potassium compound, and lithium hydroxide, lithium chloride, etc. can be used as the lithium compound. The amount used is 0.1 to 1.5% by weight in terms of Na ₂ O and 0.1 in terms of K ₂ O with respect to the total amount of titanium converted to TiO ₂ contained in the hydrolysis product. The range of ˜1.5% by weight and the range of 0.1 to 1.5% by weight in terms of Li ₂ O are preferable. More preferable ranges are 0.1 to 1% by weight in terms of Na ₂ O, 0.2 to 1.2% by weight in terms of K ₂ O, and 0.2 to 1.2% by weight in terms of Li ₂ O. is there.

In order to produce rutile rod-like titanium dioxide, preferably, rod-like titanium dioxide nuclei having a rutile crystal structure are used, and an aluminum compound and / or a phosphorus compound is contained in the baking treatment agent. It is preferable because a rutile crystal can be stably generated. Examples of the aluminum compound include aluminum oxide, aluminum chloride, and aluminum sulfate, and examples of the phosphorus compound include orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, and salts thereof. Aluminum compounds, the amount of phosphorus compound with respect to the total amount of titanium in terms of TiO ₂ contained in the hydrolysis product, in the range of 0.1 to 1.5 wt% in terms _{of Al} 2 _{O 3, P} 2 O The range of 0.1 to 1.5% by weight in terms of ₅ is preferable, and the range of 0.2 to 1.2% by weight in terms of Al ₂ O ₃ is 0.2 to 1.2% in terms of P ₂ O _5. % Range is more preferred. Moreover, as a compound which stabilizes a rutile type crystal, a magnesium compound, a zinc compound, etc. can also be used other than an aluminum compound and a phosphorus compound, for example. The preferred amount varies depending on the compound, but if it is a magnesium compound, it is in the range of 0.005 to 0.1% by weight as MgO with respect to the TiO ₂ converted value, and the more preferred range is 0.01 to 0.00. 05% by weight. As the magnesium compound, magnesium chloride, magnesium carbonate, magnesium sulfate or the like can be used.

  There is no particular limitation on the method for heating and baking the hydrolysis product in the presence of the baking treatment agent, but it is preferable to add and mix the baking treatment agent to the slurry of the hydrolysis product because it can be uniformly mixed. After mixing these compounds with the slurry, the slurry is dehydrated as necessary and subjected to the next heating and firing step.

  In the case of obtaining rutile rod-like titanium dioxide, the rutile crystal is further stabilized, so that the hydrolyzed product may be heated and fired in the presence of further rutile microparticle nuclei. As the method, in addition to the rod-shaped titanium dioxide nuclei crystal in the hydrolyzable titanium compound solution, further the rutile type fine particle nuclei are added for hydrolysis, or rutile is added to the slurry of the hydrolysis product. It is preferable that the hydrolyzed product contains rutile type fine nuclei by adding and mixing type fine nuclei. Rutile type fine nuclei can be prepared by a known method, for example, a method of neutralizing titanyl sulfate with sodium carbonate, a method of reacting hydrous titanium oxide with sodium hydroxide, and then treating with hydrochloric acid. .

  The hydrolysis product is heated and fired at a temperature in the range of 900 to 1200 ° C. in the presence of a baking treatment agent containing an alkali metal compound to obtain the rod-like titanium dioxide of the present invention. If the heating and firing temperature is lower than the above range, the particles do not become rods in a desired shape, and even if the temperature is higher than the above range, no further effect can be obtained, and the durability of the heating and firing furnace is lowered in the long term. Therefore, firing at 950 to 1150 ° C. is more economical and more preferable. Known devices such as a rotary kiln and a tunnel kiln can be used for the heating and firing furnace.

  When the rod-like titanium dioxide is coated with an inorganic compound, the obtained rod-like particles are dispersed in a liquid medium such as water to form a slurry, and preferably after further wet pulverization, a solution of the target inorganic compound salt is prepared. In addition, an acidic compound or a basic compound may be added, or a salt of an inorganic compound and an acidic compound or a basic compound may be added simultaneously to cause a neutralization reaction, thereby depositing the inorganic compound on the particle surface. The coating of the organic compound is usually performed by dry pulverizing the obtained rod-shaped titanium dioxide and then mixing it with an organic compound using a high-speed stirrer such as a Henschel mixer or a super mixer, or the rod-shaped titanium dioxide in a dry pulverizer And so-called dry treatment, in which pulverization and mixing / coating treatment are performed simultaneously, are applied. When coating an organic compound that reacts with and strongly binds to the surface of titanium dioxide, such as organosilanes, so-called wet processing is performed by adding an organic compound to the slurry after wet grinding or after coating with an inorganic compound. Can also be applied.

  After the predetermined rod-like titanium dioxide is obtained, wet grinding, dehydration / washing, drying, and dry grinding may be performed by a known method. For wet grinding, vertical sand mill, horizontal sand mill, etc., for drying, band type heater, batch type heater, etc., for dry grinding, hammer mill, pin mill etc. impact crusher, crusher etc. grinding crusher, jet Equipment such as an airflow crusher such as a mill or a snail mill, or a spray dryer can be used.

  Furthermore, this invention is a resin composition characterized by including the said near-infrared shielding agent and a resin component. There is no restriction | limiting in particular in a resin component, Well-known resin components, such as a coating material, ink, plastics, paper, can be selected suitably. Since the resin composition of the present invention has an excellent concealing property, it can be applied in the same manner as a resin composition such as ordinary paints, inks, plastics and paper. At the same time, since it has an excellent near-infrared shielding ability, for example, by applying the coating composition or ink composition of the present invention, or by applying the plastic composition or paper composition of the present invention, A protective film can be formed on the surface of the material to protect the substrate from near infrared rays. Alternatively, an increase in the internal temperature of the structure can be reduced by forming such a protective film on the surface of the structure or using the plastic composition of the present invention as a base material of the structure. Although the compounding quantity of the near-infrared shielding agent in a resin composition changes with uses, if it is a resin composition for coatings or a resin composition for ink, for example, the near-infrared shielding agent 0.5 with respect to 1 weight part of resin components. If 10 parts by weight is a resin composition for plastics, 0.05 to 2 parts by weight of a near-infrared shielding agent is preferable with respect to 1 part by weight of the resin component.

  If it is a resin composition for paint, examples of the resin component to be used include alkyd resins, acrylic resins, polyester resins, epoxy resins, amino resins, fluorine resins, modified silicone resins, urethane resins, Vinyl resin etc. are mentioned and can be selected suitably. These resin components for paint are not particularly limited, such as an organic solvent-soluble type, a water-soluble type, and an emulsion type, and the curing method is not limited such as a heat curing type, a room temperature curing type, an ultraviolet curing type, and an electron beam curing type. The paint fat composition of the present invention contains an organic solvent such as alcohols, esters, ethers, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, water or a mixed solvent thereof as a solvent. The solvent may be selected according to suitability with the resin component. In addition, colorants such as organic pigments, inorganic pigments, dyes, extenders, surfactants, plasticizers, curing aids, dryers, antifoaming agents, thickeners, emulsifiers, flow regulators, depending on the purpose Various additives such as anti-skinning agents, anti-color separation agents, ultraviolet absorbers and anti-mold agents, fillers and the like may be contained. Or it can also be set as the two-component coating material which uses a hardening | curing agent, a hardening adjuvant, and a curable resin component separately as a hardening liquid, and mixes with a coating material at the time of coating.

  As the resin component used in the plastics resin composition, for example, thermoplastic resins such as general-purpose plastics and engineering plastics, thermosetting resins, and the like can be used. The above can be used as an alloy. Specifically, as general-purpose plastics, polyolefin resin (polyethylene, polypropylene, etc.), polyvinyl chloride resin, ABS resin, polystyrene resin, methacrylic resin, polyvinylidene chloride resin, etc., as engineering plastics, polycarbonate resin, Thermoplastic polyester resins, polyamide resins, polyacetal resins, modified polyphenylene ethers, fluororesins, etc., and thermosetting resins include epoxy resins, phenol resins, unsaturated polyester resins, polyurethane resins, melamine resins, silicone resins, etc. . Depending on the application, reinforcing materials such as glass fibers known to those skilled in the art, and various additives such as stabilizers, dispersants, lubricants, antioxidants, ultraviolet absorbers and fillers may be added.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1
(1) Preparation of rod-like titanium dioxide particles To a titanyl sulfate solution, a commercially available rutile rod-like titanium dioxide (FTL-100: manufactured by Ishihara Sangyo Co., Ltd., average major axis diameter 1.68 μm, average minor axis diameter 0.13 μm). As nuclei crystals, 5 wt% was added to and mixed with titanyl sulfate, and heated at a temperature of 99 ° C. for 4 hours to hydrolyze titanyl sulfate to produce a hydrolysis product. The total amount of titanium converted to TiO ₂ contained in the hydrolysis product was 1000 g. Aluminum sulfate corresponding to 0.2 wt% in terms of Al ₂ O ₃ , sodium carbonate corresponding to 0.5 wt% in terms of Na ₂ O, K ₂ , based on the total titanium content in the hydrolysis product slurry Potassium hydroxide corresponding to 0.5% by weight in terms of O and orthophosphoric acid corresponding to 0.2% by weight in terms of P ₂ O ₅ were added, mixed, and dehydrated. The obtained dehydrated cake was heated and fired at 1050 ° C. using an electric furnace to obtain rutile rod-like titanium dioxide particles. The obtained rod-like titanium dioxide particles were made into an aqueous slurry having a TiO ₂ concentration of 300 g / liter, and an aqueous sodium hydroxide solution was added to disperse the pH to 11.0. Classification was performed at.

(2) Surface coating After maintaining the temperature of 1000 ml of the classified slurry at 60 ° C. and adding sulfuric acid to adjust the pH to 9 with stirring, an aqueous sodium aluminate solution (300 g / liter as Al ₂ O ₃₎ ) 20 ml was added over 20 minutes while adjusting the pH to 8-9 with sulfuric acid. Next, the pH was adjusted to 7, and then aging was performed for 30 minutes to coat 2% by weight of aluminum oxide hydrate as Al ₂ O ₃ . Then, it filtered with the suction filter, washed with water, and dried at 120 degreeC for 20 hours, Then, it grind | pulverized with the jet mill and obtained the near-infrared shielding agent of this invention. (Sample A)

Comparative Example 1
To the hydrous titanium oxide equivalent to 1000 g as TiO ₂ , the aluminum sulfate equivalent to 0.05% by weight in terms of Al ₂ O ₃ and 0.2% by weight in terms of Na ₂ O to TiO ₂ in the hydrous titanium oxide. Corresponding sodium carbonate, potassium hydroxide equivalent to 0.15% by weight in terms of K ₂ O, and orthophosphoric acid equivalent to 0.2% by weight in terms of P ₂ O ₅ are added, and the electric furnace is used at 1100 ° C. By heating and baking, spherical particles of rutile titanium dioxide were obtained. Wet pulverization, surface coating, classification, solid-liquid separation, washing, drying, and dry pulverization were performed in the same manner as in Example 1 to obtain a comparative sample. (Sample B)

Comparative Example 2
A commercially available pigment grade rutile type titanium dioxide (CR-50: manufactured by Ishihara Sangyo Co., Ltd.) is used as Comparative Example 2. (Sample C)

Evaluation 1: Evaluation of average particle diameter For the samples (A to C) obtained in Example 1 and Comparative Examples 1 and 2, using a particle analyzer (manufactured by Carl Zeiss), the average major axis diameter and the average minor axis Diameter, axial ratio and average particle size were measured by electron microscopy. The average major axis diameter and the average minor axis diameter are calculated from the 50% cumulative value of about 1000 particles by calculating the cylinder equivalent volume from the major axis diameter and minor axis diameter for one primary particle of titanium oxide. It is. The axial ratio means average major axis diameter / average minor axis diameter. The results are shown in Table 1.

Evaluation 2: Evaluation of hidden payability Using the samples (A to C) obtained in Example 1 and Comparative Examples 1 and 2, each component of the formulation 1 shown in Table 2 and 80 g of glass beads were made of glass having a capacity of 225 cc. After preparing into a container and dispersing for 20 minutes using a paint conditioner (manufactured by Red Devil) to prepare a dispersion, in Formulation 2 shown in Table 3, 1 part by weight of a titanium dioxide pigment with respect to 1 part by weight of a resin component, The coating material had a solid content volume concentration of 46%. Next, it was coated on black and white chart paper using a # 30 bar coater and baked at 110 ° C. for 40 minutes to form a coating film. The reflectance on the black ground (Y _B value) and the reflectance on the white ground (Y _W value) of the coating applied on the black and white chart paper were measured using a color computer (SM-7 type: manufactured by Suga Test Instruments). The concealment rate ( _CR value) was calculated according to the following formula 1. The results are shown in Table 4. Having a high C _R value is excellent in hiding property. The near-infrared shielding agent of the present invention has a concealing property substantially equal to that of conventional pigment grade titanium dioxide.
Formula 1: Concealment rate (C _R ) = (Y _B / Y _W ) × 100 (%)

Evaluation 3: Evaluation of near-infrared shielding ability The coating materials of Example 1 and Comparative Examples 1 and 2 used in Evaluation 2 were applied onto a PET film using a # 60 bar coater, and baked at 110 ° C. for 40 minutes. Turned into. The reflectance of the coating film was measured using a spectrophotometer (V-570 type: manufactured by JASCO Corporation) in the wavelength range of 500 to 2000 nm. The results are shown in Table 5. It can be seen that the near-infrared shielding agent of the present invention has a high reflectance in the near-infrared region (wavelength range of 800 to 3000 nm) and has an excellent near-infrared shielding ability. For reference, the paint is diluted with a mixed solvent of xylene and n-butanol (weight ratio 4: 1) to give a solid content volume concentration of 21.2%, and applied with a # 30 bar coater. Then, the reflectance of this coating film was measured with a spectrophotometer in the wavelength range of 500 to 2500 nm. The results are shown in Table 6. It can be seen that the near-infrared shielding agent of the present invention has an excellent near-infrared shielding ability because of its low transmittance in the near-infrared region.

  The present invention is useful as a near-infrared shielding agent. The rod-like titanium dioxide obtained by the production method of the present invention is also useful as a catalyst, a reinforcing material, a conductive material base, and the like.

2 is an electron micrograph showing the particle shape of sample A. FIG. 3 is an electron micrograph showing the particle shape of Sample B. FIG.

Claims (10)

A near-infrared shielding agent containing rod-like titanium dioxide having an average major axis diameter of 1.5 to 6 μm and an average minor axis diameter of 0.2 to 0.8 μm as an active ingredient. The near-infrared shielding agent according to claim 1, wherein the average axial ratio of the rod-shaped titanium dioxide is in the range of 3 to 15. The near-infrared shielding agent according to claim 1, wherein the crystal form of the rod-like titanium dioxide is a rutile type. A hydrolyzable titanium compound is hydrolyzed in the liquid phase in the presence of rod-shaped titanium dioxide nuclei to obtain a hydrolysis product, and then the hydrolysis product is 900 in the presence of a baking treatment agent containing an alkali metal compound. A method for producing rod-like titanium dioxide, characterized by heating and firing at a temperature in the range of ˜1200 ° C. The method for producing rod-shaped titanium dioxide according to claim 4, wherein the hydrolyzable titanium compound is at least one selected from titanyl sulfate and titanium tetrachloride. The method for producing rod-shaped titanium dioxide according to claim 4, wherein the alkali metal compound is a sodium compound and a potassium compound. The method for producing a rod-like titanium dioxide according to claim 4, further comprising an aluminum compound and / or a phosphorus compound as the baking treatment agent. The method for producing a rod-like titanium dioxide according to claim 4, wherein the crystal form of the rod-like titanium dioxide nucleus crystal is a rutile type. A resin composition comprising the near-ultraviolet shielding agent according to claim 1 and a resin component. The resin composition according to claim 9, wherein the resin component is a coating resin or a plastics resin.

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