JP2011032317A - Coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition excellent in dispersion stability and a coating film excellent in feel of whiteness, hardness, and adhesion. <P>SOLUTION: (1) The coating composition contains titanate nanoparticles (A) of which the primary particle has a major axis length of 10-1,000 nm, a resin (B) for coating, and a solvent (C). (2) The coating film is formed when the coating composition is applied to a substrate and dried. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coating composition containing titanic acid nanoparticles and a coating film comprising the same.

  Titanium oxide is widely used industrially as raw materials such as ceramics and composite oxides, photocatalysts, white pigments, high refractive index materials, dye-sensitized solar cell electrode materials, resin fillers, and the like.

For example, Patent Document 1 discloses that a lamellar titanate having an average major axis of 5 to 30 μm and an average thickness of 0.5 to 300 nm, which is obtained by acid treatment of a layered titanate and then causing an organic basic compound to act to swell or peel the interlayer. A glittering paint obtained by mixing an aqueous dispersion of titanic acid and a resin emulsion is disclosed. In Patent Document 1, it is said that a coating film containing flaky titanic acid has better design properties such as silky feeling than a white coating film containing anatase type or rutile type titanium oxide. Since the average major axis of the titanic acid is large, the dispersion stability in the paint and the hardness of the coating film are insufficient. In particular, in organic coatings, flocculated titanic acid, which is a hydrophilic surface, is remarkably agglomerated and the dispersion stability of flaky titanic acid in the coating is poor, so it is possible to obtain a coating film with excellent design and hardness. Have difficulty.
Patent Document 2 discloses a coating agent for optical equipment containing a titanate nanosheet. This titanic acid nanosheet has a particle diameter of substantially less than 10 nm, and the dispersion stability of the titanic acid nanosheet in the coating agent is good, but the coating film obtained from this coating agent is transparent and poor in design . Moreover, it is difficult to say that the coating film containing the titanate nanosheet has sufficient film hardness and adhesion.

JP 2006-257179 A JP 2007-199656 A

  An object of the present invention is to provide a coating composition excellent in dispersion stability and a coating film excellent in whiteness, hardness and adhesion.

The present inventors have used a titanic acid nanoparticle in which the major axis length of primary particles is in the range of 10 to 1000 nm as a white pigment, thereby achieving a coating composition having excellent dispersion stability, whiteness, hardness, and adhesion. It was found that an excellent coating film can be obtained.
That is, the present invention provides the following (1) and (2).
(1) A coating composition containing titanic acid nanoparticles (A) having a major axis length of primary particles of 10 to 1000 nm, a coating resin (B), and a solvent (C).
(2) A coating film formed by applying the coating composition of (1) to a substrate and drying.

  According to the present invention, by using titanic acid nanoparticles having a primary particle major axis length of 10 to 1000 nm as a white pigment, a coating composition having excellent dispersion stability, and excellent whiteness, hardness, and adhesion are obtained. A coated film can be provided.

2 is a transmission electron microscope (TEM) photograph showing spindle-shaped titanate nanoparticles obtained in Example 1. FIG.

The coating composition of the present invention contains titanic acid nanoparticles (A) whose primary particles have a major axis length of 10 to 1000 nm, a coating resin (B), and a solvent (C). The coating film is characterized in that the coating composition is applied to a substrate and dried.
Hereinafter, each component etc. which are used for the coating composition of this invention are demonstrated.

[Titanate nanoparticles (A)]
(Shape of titanate nanoparticles)
The major axis length of the primary particles of titanic acid nanoparticles (A) contained in the coating composition and coating film of the present invention is 10 to 1000 nm, and the dispersion stability, handling property and coating film performance of the coating composition. From the viewpoint of expression, it is preferably 20 to 500 nm, more preferably 30 to 200 nm, and still more preferably 30 to 100 nm.
Further, the ratio of (major axis length / minor axis length) of the primary particles of titanic acid nanoparticles (A) is preferably 3 to 20, more preferably 5 to 15, and still more preferably 8 from the same viewpoint as described above. ~ 12.
Here, the major axis length of titanate nanoparticles (A) means the maximum length in the major axis direction of the primary particles of titanate nanoparticles (A), and the minor axis length means the major axis direction. It means the maximum length of the primary particles of titanate nanoparticles in the direction perpendicular to it. The major axis length and minor axis length of the primary particles are values obtained from a transmission electron microscope (TEM) photograph.

The shape of the primary particles of the titanic acid nanoparticles (A) is spherical, flat (sheet-like), fibrous (whisker-like), rod-like (rod-like), indefinite shape, etc., and is not particularly limited. From the viewpoint of dispersion stability, handling properties, and performance of the coating film, a sheet shape, a whisker shape, and a rod shape are preferable, a sheet shape and a rod shape are more preferable, and a rod shape is more preferable.
The shape of the rod may be the same shape as the center of the particle and both ends of the particle, such as a cylindrical shape, or the shape where the center of the particle swells from both ends of the particle, such as a spindle shape. However, a spindle shape is preferable from the viewpoint of dispersion stability of the coating composition, handling properties, and expression of coating film performance.
The shape of the sheet is not particularly limited, but the thickness of the sheet is preferably 0.5 to 100 nm from the viewpoint of ease of production of titanate nanoparticles, dispersion stability of the coating composition, handling properties, and expression of coating film performance. 0.5 to 10 nm is more preferable.

(Crystal structure of titanate nanoparticles)
The titanic acid nanoparticles (A) used in the present invention have a crystal structure of titanic acid such as trititanic acid, tetratitanic acid, pentatitanic acid, hexatitanic acid, or lipidocrocite-type titanic acid. The crystal structure of these titanic acids has an octahedral structure in which six oxygens are coordinated around titanium as a basic unit, and this unit has a molecular level thickness (for example, 0.3 to 0.8 nm). The titanate nanoparticles (A) are present in the form of a salt with this titanate sheet and amines, phosphoniums, etc., and the amines, phosphoniums, etc. are contained between the titanate sheets, It is considered that a layered structure composed of amines, phosphoniums and the like is formed.
Titanate nanoparticles used in the present invention (A) is wavenumber Raman spectrum 260～305Cm ^-1, has a peak of each from the crystal structure of the titanate in the area of 440～490Cm ^-1 and 650～1000Cm ^-1 . Incidentally, the conventional anatase titania which is a typical titanium oxide, wavenumber in Raman spectrum 140~160cm ^-1, 390~410cm ^-1, have a peak in the region of 510～520Cm ^-1 and 630～650Cm ^-1 Rutile-type titania has peaks in the Raman spectrum with wave numbers of 230 to 250 cm ⁻¹ , 440 to 460 cm ⁻¹ and 600 to 620 cm ⁻¹ .

The titanic acid nanoparticles (A) used in the present invention have an XRD peak derived from a layered structure in the range of d = 1 to 5 nm of the powder X-ray diffraction (XRD) pattern from the viewpoint of structural stability and expression of coating film performance. Is preferable, and it is more preferable that an XRD peak is observed in the range of d = 1 to 3 nm.
The titanate nanoparticles (A) used in the present invention have an absorption rise wavelength in the ultraviolet-visible absorption spectrum on the shorter wavelength side (320 nm) than anatase type (380 nm) or rutile type (410 nm) titanium oxide, It is preferable that the amount of absorption of ultraviolet light is small. If it absorbs less ultraviolet light than anatase or rutile titanium oxide, the photocatalytic activity is low, and even when mixed and combined with an organic matrix such as a resin or solvent, the organic matrix is unlikely to decompose or deteriorate photocatalytically. It is. That is, it becomes possible to produce a coating composition and a coating film excellent in light resistance.

(Method for producing titanic acid nanoparticles)
The method for producing titanic acid nanoparticles (A) used in the present invention is not particularly limited. For example, titanic acid nucleation using sol-gel method, titanic acid nanoparticle production method by particle growth (hereinafter referred to as bottom-up method), and micron-sized alkali titanate obtained by firing titanium-containing raw material at high temperature Examples thereof include a titanic acid nanoparticle production method (hereinafter referred to as a top-down method) by pulverizing and atomizing a metal salt powder in a solution containing amines and / or phosphoniums after protonation. From the viewpoint of ease of production of titanic acid nanoparticles, cost, the resulting coating composition, and the performance of the coating film, the bottom-up method is more preferable.

<Method for producing titanic acid nanoparticles by bottom-up method>
In the production of titanic acid nanoparticles (A) used in the present invention by the bottom-up method, a method comprising first producing a titanic acid nanosheet aqueous dispersion and replacing the water in the aqueous dispersion with a solvent. Therefore, it can manufacture efficiently.
(1) Production of titanic acid nanosheet aqueous dispersion In the present invention, the production method of titanic acid nanosheet aqueous dispersion is not particularly limited, but titanium alkoxide and / or titanium salt (hereinafter collectively referred to as “titanium source”). Is also hydrolyzed in the presence of amines and / or phosphoniums and subjected to a condensation reaction to produce a titanate nanosheet dispersion stock solution, and the obtained titanate nanosheet dispersion stock solution is subjected to hydrothermal treatment, A method of obtaining an aqueous dispersion of titanate nanosheets by increasing the particle size and crystallinity of titanate nanosheets by hydrothermal treatment with seed crystals added is preferred.

(Titanium source)
In the said method, as a titanium source, what produces | generates a titanium hydroxide by a hydrolysis reaction is preferable, and a titanium alkoxide and / or a titanium salt are more preferable. Here, the titanium hydroxide includes those having a composition formula represented by Ti (OH) ₂ , Ti (OH) ₃ , or Ti (OH) ₄ .
The titanium alkoxide is preferably a titanium alkoxide having an alkoxide having 1 to 6 carbon atoms, preferably 2 to 4 carbon atoms. Specific examples include titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide and the like. . These can be used alone or in admixture of two or more.
Among these, titanium tetraalkoxide is particularly preferable, and titanium tetraisopropoxide is more preferable from the viewpoint of general availability and handling.

Examples of the titanium salt include titanium chloride such as titanium tetrachloride, titanium trichloride, and titanium dichloride, titanium sulfate, titanyl sulfate, and titanyl nitrate. These can be used alone or in admixture of two or more. Among these, titanium tetrachloride, titanium sulfate, and titanyl sulfate are more preferable from the viewpoint of general availability and handleability.
The titanium salt produces titanium hydroxide by mixing with water or by heating after mixing with water, and in that case, an alkali may be further allowed to coexist. Examples of the alkali to be coexisted when producing titanium hydroxide include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide. Furthermore, ammonia and the above amines can also be used as an alkali.
Among these, alkali metal hydroxides, ammonia, and amines are more preferable from the viewpoint of easy availability and handling. The amount of alkali added is preferably such that the pH of the aqueous titanium salt solution is 2 or more, more preferably 4 or more.

The titanium source may be dissolved in water and / or a solvent highly compatible with the titanium source. Examples of the solvent include aliphatic alcohols having 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, and isopentyl alcohol.
In addition to titanium, other elements such as vanadium, niobium, tantalum, zirconium, aluminum, iron, cobalt, nickel, manganese, and the like can be combined to form a composite.

(Amines)
As the amines, one or more selected from the group consisting of primary amines, secondary amines, tertiary amines, and quaternary ammonium hydroxides are used, but preferably one or more carbon atoms. Preferred are amines having an alkyl group or alkenyl group having 1 to 5 carbon atoms.
Preferable examples of amines include ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, tetrapropylammonium hydroxide, butylamine, dibutylamine, tributylamine, tetrabutylammonium hydroxide, pentylamine, dipentylamine , Tripentylamine, hexylamine, dihexylamine, trihexylamine, dimethylhexylamine, dimethylbenzylamine, dimethyloctylamine and the like. In addition, substituted amines such as monoethanolamine, diethanolamine, and triethanolamine can also be used. These can be used alone or in admixture of two or more.
Among these, quaternary ammonium hydroxide is more preferable, and tetrabutylammonium hydroxide is particularly preferable from the viewpoint of the structural stability and manufacturability of the titanate nanosheet.
The amine is preferably an amine having a pH of 9 or more in an aqueous solution having an amine concentration of 9 mmol / L from the viewpoint of production of titanate nanosheets.

(Phosphoniums)
As the phosphoniums, quaternary phosphonium hydroxides are preferable. The quaternary phosphonium hydroxide refers to a compound in which the 4-atom hydrogen bonded to the phosphorus atom of the inorganic phosphonium compound is substituted with an alkyl group, a phenyl group or the like.
The quaternary phosphonium hydroxide includes an alkyl group having 2 to 8 carbon atoms such as tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, tetrabutylphosphonium hydroxide, tetrapentylphosphonium hydroxide, and tetrahexylphosphonium hydroxide. Tetraalkylphosphonium hydroxide, tetraphenylphosphonium hydroxide, ethyltriphenylphosphonium hydroxide, butyltriphenylphosphonium hydroxide, pentyltriphenylphosphonium hydroxide, 2-dimethylaminoethyltriphenylphosphonium hydroxide, methoxymethyltriphenylphosphonium And triphenylphosphonium hydroxide such as hydroxide.
Among these, one or more selected from tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, tetrabutylphosphonium hydroxide, and tetrapentylphosphonium hydroxide are preferable.
The phosphonium is preferably a quaternary phosphonium hydroxide having a pH of 9 or more in an aqueous solution having a quaternary phosphonium hydroxide concentration of 9 mmol / L from the viewpoint of producing titanate nanosheets.

(Production of titanate nanosheet dispersion stock solution)
The titanate nanosheet dispersion stock solution can be obtained by hydrolyzing and condensing a titanium source in the presence of the amines and / or phosphoniums (hereinafter collectively referred to as “amines etc.”). it can.
The amount of water added in the hydrolysis may be more than the amount necessary for obtaining titanium hydroxide. Usually, the mass of 3-50 times is preferable with respect to the mass of a titanium source, and the mass of 5-15 times is more preferable. The temperature and time of the hydrolysis and condensation reaction can be appropriately selected according to the titanium alkoxide and / or titanium salt used.
Although the manufacturing method of titanic acid nanosheet dispersion | distribution stock solution containing amines etc. is not specifically limited, According to the 1st method and the 2nd method shown below, it can manufacture efficiently.

[First method]
The first method is a method of mixing an aqueous solution such as amines with a titanium source.
The aqueous solution of amines and the like may contain an organic solvent in order to facilitate dissolution of amines and the like. As such an organic solvent, an aliphatic alcohol having 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, and isopentyl alcohol is preferable.
When mixing the aqueous solution containing amines and the titanium source, the mixing ratio of the titanium source and the amines is preferably such that the molar ratio of (amines / Ti / Ti) is 0.2 to 5, 3 to 3 is more preferable, and 0.4 to 1 is still more preferable. By increasing the ratio of amines and the like to the titanium source when producing the titanate nanosheet, a transparent titanate nanosheet dispersion stock solution can be obtained even with a lower polarity organic solvent. Here, the molar ratio of (amines etc./Ti) means the molar ratio of amines or titanium quaternary phosphonium hydroxide molecules in the titanate nanosheet aqueous dispersion, respectively. .
The titanium concentration in the mixed liquid of the aqueous solution containing amines and the titanium source is preferably 0.01 to 15% by mass, more preferably 0.1 to 10% by mass in terms of titanium oxide (TiO ₂ ). 8 mass% is still more preferable.

When the aqueous solution containing amines and the titanium source are mixed, the titanium compound may become cloudy. By continuously stirring, a colorless transparent to light yellow liquid can be obtained.
The temperature at which the titanium source is mixed is not particularly limited. Although nanosheets of titanic acid containing amines and the like are produced at 2 to 200 ° C, 10 to 150 ° C is more preferable and 20 to 100 ° C is more preferable from the viewpoint of the stability of the long-chain amine. The reaction time is preferably 0.1 to 20 hours, and more preferably 1 to 10 hours.

[Second method]
The second method is a method of preparing a titanic acid nanosheet dispersion stock solution by mixing amines and a titanium source in advance and then mixing water. The amines and the like may contain the same organic solvent as in the first method.
When water is added to the mixture of amines and the titanium source, the amount of water may be an amount necessary for titanium to decompose. The amount of water to be added is preferably 5 to 50 times, more preferably 10 to 15 times the mass of the mixture of amines and the titanium source. Although the temperature which adds water is not specifically limited, 2-200 degreeC is preferable and 20-100 degreeC is more preferable. Moreover, 0.01-5 hours are preferable and the dripping time of water is more preferable 0.02-2 hours. Furthermore, it is preferable to perform aging for 0.1 to 20 hours after the addition of water.
The concentration of titanium titanate nanosheet aqueous dispersion containing the amine and the like is preferably 0.01 to 15% by weight of titanium oxide (TiO ₂₎ in terms of, more preferably 0.1 to 10 mass%, 1-8 More preferred is mass%.

(Production of titanic acid nanosheet aqueous dispersion)
The titanate nanosheet aqueous dispersion is obtained by hydrothermally treating the titanate nanosheet dispersion stock solution (hereinafter also simply referred to as “dispersion stock solution”) obtained by the above-described method, or hydrothermally treating the titanate nanosheet dispersion stock solution. The dispersion liquid in which part or all of the seed crystals obtained are hydrothermally treated (b), and the lipidocrosite-type layered titanate nanosheet obtained by firing the titanium-containing raw material at a high temperature is mixed with an aqueous hydrochloric acid solution. It can be suitably produced by the method (c) of hydrothermally treating a dispersion containing 1 part of seed crystals obtained by exfoliation in a sheet form with a solution containing amines and / or phosphoniums.
The particle diameter of titanate nanosheets can be grown by hydrothermally treating the titanate nanosheet dispersion stock solution. Here, the hydrothermal treatment means that the dispersion stock solution in the method (a) or the dispersion stock solution after addition of the seed crystals in the method (b) and (c) is aged by applying temperature and pressure. It is considered that when both the temperature and pressure are applied and the titanate nanosheet particles in the dispersion stock solution are aged, the titanate nanosheet particles undergo dissolution / precipitation reaction, the particles grow, and the particle size increases.

(1) Hydrothermal treatment method of titanate nanosheet-dispersed stock solution The hydrothermal treatment temperature in the method (a) is preferably 75 to 200 ° C, more preferably 95 to 150 ° C, and further preferably 100 to 130 ° C. If the temperature is too high, the titanate nanosheets containing amines and the like may undergo crystal transition to anatase-type titanium oxide, and if the temperature is too low, control for increasing the particle size may not be performed efficiently.
The pressure of the hydrothermal treatment varies depending on the solvent to be used, but is 0.8 MPa or more, preferably 1 MPa or more, and the upper limit is preferably about 1.5 MPa or less.
Although the treatment time varies depending on the solvent, pressure and temperature, it is usually 0.5 hours or more, preferably 1 hour or more. The particle size grows as the treatment time becomes longer, but when it takes too much time, it transitions to the anatase type. Therefore, the upper limit of the processing time is usually 24 hours or less, preferably 12 hours or less.

About pH (25 degreeC) of the dispersion | distribution stock solution at the time of hydrothermal treatment performs about 10-13 which is the pH range at the time of a titanic acid nanosheet synthesis | combination. When the pH of the dispersion stock solution is less than 10, crystals are likely to be transferred to anatase during hydrothermal treatment, and when the pH exceeds 13, the particle size control may be difficult.
Agitation of the dispersion stock solution during the hydrothermal treatment may be performed without stirring as long as the titanate nanosheet particles do not settle, but it is preferable to stir in consideration of thermal conductivity. There is no particular upper or lower limit for the stirring speed, but it is sufficient that the hydrothermal treatment apparatus is not burdened.
In addition, as a factor affecting the particle diameter of titanate nanosheets, there is titanic acid concentration in the dispersion stock solution, and the titanic acid concentration in the dispersion stock solution is preferably 0.1 to 15% by mass, more preferably, in terms of TiO _2. It is 0.5-10 mass%, Most preferably, it is 1-8 mass%.

(2) Method of adding seed crystal and hydrothermally treating In order to further increase the particle size of titanate nanosheet, method (b) using seed crystal titanate nanosheet is preferred. That is, the titanium source nanosheet dispersion stock solution obtained by hydrolyzing and condensing a titanium source in the presence of amines and / or phosphoniums has a step of hydrothermal treatment in the presence of seed crystal titanate nanosheets. The method is preferred. In addition, the dispersion | distribution stock solution in this case may be the dispersion | distribution stock solution prepared by the method different from the titanic acid nanosheet dispersion liquid which performs a hydrothermal treatment in order to prepare a seed-crystal titanate nanosheet.

(Seed crystal titanate nanosheet)
The seed crystal titanate nanosheets are those that increase the particle size of titanate nanosheets or grow titanate nanosheets. In particular, when preparing a titanate nanosheet having a volume-based average particle diameter of 5 nm or more, it is preferable to use a seed crystal. As seed crystal titanate nanosheets, (i) a titanate nanosheet dispersion once hydrothermally treated to improve crystallinity, or (ii) a lipid crocite type obtained by firing a titanium-containing raw material at a high temperature A layered titanate nanosheet that has been exfoliated in a sheet form with a hydrochloric acid aqueous solution and a solution containing amines and / or phosphoniums can be used in the form of a dispersion. In the case of (ii), it is preferable to use a seed crystal obtained by removing excess titanic acid by centrifugation.

(Preparation of seed crystal titanate nanosheet)
As a method for preparing the seed crystal titanate nanosheet, (i) a method of hydrothermally treating the titanate nanosheet dispersion is preferable. The titanate nanosheet dispersion can be hydrothermally treated to grow titanate nanosheets. However, when the seed crystal particle size becomes too large, the titanate nanosheet dispersion is easily transferred to the anatase type. In order to suppress this, it is preferable to use a method in which the seed crystal titanate nanosheet is added to the titanate nanosheet dispersion.
The titanate nanosheet dispersion used for preparing the seed crystal has a molar ratio of (amines etc./Ti) of preferably 0.2 to 5, more preferably 0.3 to 3, and still more preferably 0. .4 to 1. The TiO ₂ concentration in the dispersion is preferably 0.1 to 15% by mass, more preferably 0.5 to 10%, and further preferably 1 to 8%. Therefore, the TiO ₂ concentration in the seed crystal titanate nanosheet dispersion obtained has the same numerical value.
The temperature of the hydrothermal treatment for preparing the seed crystal is preferably 75 to 200 ° C, more preferably 100 to 150 ° C. If the temperature is too high, the crystals are transferred to anatase, and if the temperature is too low, the crystallinity may not be improved. The hydrothermal treatment time is preferably 0.5 to 24 hours, more preferably 1 to 12 hours.
In order to increase the particle diameter of the seed crystal, the treatment may be performed for a long time when the hydrothermal treatment temperature is low and for a short time when the hydrothermal treatment temperature is high, but the above time is preferable in view of efficient production. As other hydrothermal treatment conditions, the hydrothermal treatment conditions described above can be used.

(Hydrothermal treatment of titanate nanosheet dispersion stock solution)
When the seed crystal obtained by the above method is added to the dispersion stock solution and then hydrothermally treated to produce the titanate nanosheet aqueous dispersion, the seed crystal titanium is usually used to increase the particle size of the titanate nanosheet. The ratio of the acid nanosheet may be increased, but in order to sufficiently grow the particle size, the TiO ₂ concentration in the dispersion stock solution and the seed crystal titanate nanosheet dispersion is preferably 0.1% by mass or more, and the crystal transition From the viewpoint of suppressing the TiO ₂ concentration in the dispersion stock solution and in the seed crystal titanate nanosheet dispersion liquid, 15% by mass or less is preferable. From this viewpoint, the TiO ₂ concentration in the dispersion stock solution and the seed crystal titanate nanosheet dispersion is preferably 0.1 to 15% by mass, more preferably 0.5 to 10%, and still more preferably 1 to 8%. is there. The molar ratio of (amines etc./Ti) in the dispersion stock solution and the seed crystal titanate nanosheet dispersion is preferably 0.2 to 5, more preferably 0.3 to 3, and still more preferably 0.4. ~ 1.
The seed crystal titanate nanosheet is preferably added to and mixed with the titanate nanosheet dispersion stock solution in the form of a dispersion. The amount of seed crystal titanate nanosheets added is preferably such that the ratio of (amount of seed crystal titanate nanosheets / total amount of titanate nanosheets and seed crystal titanate nanosheets contained in the dispersion stock solution) is TiO ₂ equivalent concentration. It is preferable to adjust to the range which becomes -100 mass%, More preferably, it is 50-100 mass%, More preferably, it becomes 100 mass%.
The conditions of the hydrothermal treatment of the dispersion stock solution after adding the seed crystals can be performed under the same conditions (paragraphs [0022] to [0023]) as in the method (a). That is, hydrothermal treatment can be performed under conditions of a temperature of 75 to 200 ° C., a pressure of 0.8 to 1.5 MPa, a pH of 10 to 13 (25 ° C.), and a treatment time of 0.5 to 24 hours.

(Confirmation of titanate nanosheet in titanate nanosheet aqueous dispersion)
The formation of titanate nanosheets can be confirmed by Raman spectroscopy, ultraviolet-visible absorption spectrum, transmission electron microscope (TEM) observation, and the like.
It is presumed that a titanate sheet containing amines or the like is formed in the titanate nanosheet aqueous dispersion. This uses an argon ion laser (wavelength 488 nm) as a light source, and in the measurement of a transmission Raman spectrum under the conditions of a laser output of 100 to 600 mW and an integration time of 30 to 300 seconds, the wave number is 260 to 305 cm ⁻¹ , 440 to 490 cm ^{−. This is because} peaks were respectively obtained in the regions of ¹ and 650 to 1000 cm ⁻¹ and the structures of the titanium atom and the titanate sheet were derived.
In the ultraviolet-visible absorption spectrum of the titanate nanosheet containing amines, the rising wavelength of the absorption spectrum is found at 320 nm. On the other hand, the rising wavelength of the absorption spectrum is observed at 380 nm for anatase type titania and at 410 nm for rutile type titania.
Moreover, a layered structure can be confirmed by drying a titanate nanosheet aqueous dispersion and performing X-ray diffraction. It has been confirmed that the layer spacing increases as the cation size of the amines increases, and it is considered that the amines are present between the layers.

(Production of titanic acid nanoparticles)
The titanic acid nanoparticles (A) contained in the coating composition of the present invention and the coating film are obtained by a method including a solvent substitution step of substituting water in the titanic acid nanosheet aqueous dispersion obtained by the above method with a solvent. Manufactured.
By replacing the water in the aqueous titanate nanosheet dispersion with a solvent, the dispersibility of the titanate nanosheet is improved, and titanate nanoparticles having a predetermined major axis length can be efficiently obtained. The reason for the formation of titanate nanorods is not always clear, but when the water adsorbed on the titanate nanosheet surface is removed, shape change is induced due to aggregation, fusion, rearrangement, etc. of titanate nanosheet particles. It is thought that it was done. It is considered that the solvent promotes the removal of adsorbed water on the titanate nanosheet surface and contributes to the stabilization of the shape of the produced titanate nanorods.

The method for solvent replacement is not particularly limited, and can be carried out continuously or batchwise under normal pressure or reduced pressure. For example, (i) a method of repeating the operation of adding a solvent and redispersing after concentrating the aqueous dispersion of titanate nanosheets using an evaporator, (ii) while continuously dropping the substitution solvent into the aqueous dispersion of titanate nanosheets, Solvent replacement can be performed by conventional methods such as a method of continuously distilling off the solvent, (iii) a method of once drying the aqueous dispersion of titanic acid nanosheets and then redispersing in the solvent. Among these, the methods (i) and (ii) are preferable from the viewpoints of ease of production, and the performance expression of the coating composition and the coating film.
In the case of concentrating and distilling off the solvent, the solvent may be heated, but from the viewpoint of production cost of titanate nanorods and expression of the performance, the temperature for heating is preferably 20 to 100 ° C, more preferably 40 to 80 ° C. . From the same viewpoint, the TiO ₂ equivalent concentration of the dispersion at the time of solvent substitution is preferably 0.1 to 15% by mass, and more preferably 1 to 8% by mass.

Here, the solvent used for solvent substitution is not particularly limited, but an organic solvent azeotroped with water is preferable from the viewpoint of ease of production. In addition, an organic solvent having good compatibility with the coating resin is preferable from the viewpoint of performance of the coating composition and the coating film. Such organic solvents include alcohols, ethers, ketones, esters, aromatic hydrocarbons and the like.
Examples of the alcohol include ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, n-pentanol, 2-pentanol, 4-methyl-1-butanol, 2-methoxyethanol, n-hexanol, n -C2-C8 aliphatic alcohols, such as heptanol, n-octanol, 2-octanol, etc., C4-C7 heterocyclic alcohols, such as furfuryl alcohol, phenol, benzyl alcohol, etc. Group alcohol and the like.

Examples of ethers include dibutyl ether, tetrahydrofuran, and dioxane. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and diethyl ketone. Examples of esters include 5- to 6-membered ring lactones such as γ-butyrolactone. Is mentioned.
Moreover, as aromatic hydrocarbon, C6-C12 aromatic hydrocarbons, such as toluene, ethylbenzene, m-xylene, and naphthalene, are mentioned.
In these, C2-C5 aliphatic alcohols, such as n-propanol, 2-propanol, n-butanol, 2-butanol, etc., C2-C5 aliphatic alcohol, toluene, ethylbenzene, m-xylene, naphthalene, etc. Group hydrocarbons are preferred, and n-butanol is particularly preferred.

<Method for producing titanic acid nanoparticles by top-down method>
In the production of the titanate nanoparticles (A) used in the present invention by the top-down method, first, after protonating a micron-sized alkali metal titanate powder obtained by firing a titanium-containing raw material at a high temperature, amines and / or Alternatively, according to a method including a solvent substitution step of pulverizing and atomizing in an aqueous dispersion containing phosphoniums and substituting the water in the aqueous dispersion with a solvent, it can be efficiently produced.
Protonation of a micron-sized alkali metal titanate powder obtained by high-temperature firing of a titanium-containing raw material can be performed by a conventional method described in Patent Document 1 and the like.
A method of pulverizing and atomizing the obtained protonated product in an aqueous dispersion containing amines and / or phosphoniums is not particularly limited, and can be efficiently performed by, for example, wet pulverization using a ball mill.

The wet pulverization conditions are not particularly limited, but from the viewpoints of manufacturability, productivity, etc., the mixing ratio of the titanium source and the amines is a molar ratio of (amines etc./Ti), preferably 0. It is desirable to carry out in the range of 2 to 5, more preferably 0.3 to 3, and still more preferably 0.4 to 1. Here, the molar ratio of (amines etc./Ti) means the molar ratio of amines or titanium quaternary phosphonium hydroxide molecules per titanium atom in the aqueous titanate dispersion. Further, the concentration of titanic acid in the dispersion is preferably 0.01 to 15% by mass, more preferably 0.1 to 10% by mass, more preferably 0.1 to 10% by mass in terms of TiO ₂ from the viewpoints of manufacturability and productivity. Preferably it is 1-8 mass%. When using a ball mill, a zirconia ball having a diameter of 1 to 10 mm is preferable.
The titanic acid nanoparticles (A) used in the present invention are produced by a method including a solvent substitution step of substituting water in the titanic acid aqueous dispersion obtained by the above method with a solvent.

[Resin for paints (B)]
The coating composition and coating film of the present invention contain a coating resin (B). The coating resin (B) is not particularly limited, and may be a thermoplastic resin or a thermosetting resin, but a thermosetting resin is preferred from the viewpoint of the performance of the coating film. For example, urethane resin, vinyl resin, acrylic resin, polystyrene resin, alkyd resin, melamine resin, epoxy resin, polyester resin, amide resin, imide resin, silicon resin, urea resin, aniline resin, polycarbonate resin, etc. These may be used in combination. Although depending on the use of the coating film and the usage environment, urethane-based resins, acrylic resins, polystyrene-based resins, alkyd-based resins, melamine resins, and epoxy resins are preferable from the viewpoint of expressing the performance of the coating film.

The content of the coating resin (B) in the coating composition of the present invention is not particularly limited, but from the viewpoint of dispersion stability of the coating composition, performance of the coating film, and ease of manufacture, the resin in the coating composition. As a mass fraction, 5-70 mass% is preferable, and 10-60 mass% is more preferable. Further, the mass ratio [(A) / (B)] of the titanic acid nanoparticles (A) in terms of TiO ₂ and the coating resin (B) is not particularly limited, but the dispersion stability of the coating composition, the coating film From the viewpoint of performance development, 0.05 to 0.5 is preferable, and 0.1 to 0.3 is more preferable.

[Solvent (C)]
The solvent (C) in the coating composition of the present invention is not particularly limited, but from the viewpoints of dispersion stability of the coating composition, performance of the coating film, and ease of production, alcohol, ether, ketone, ester, aromatic carbonization Hydrogen, chain hydrocarbon, mixed hydrocarbon and the like are preferable.
Examples of alcohol include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, n-pentanol, 2-pentanol, 4-methyl-1-butanol, 2-methoxyethanol, and n-hexanol. N-heptanol, n-octanol, 2-octanol, diacetone alcohol, ethyl cellosolve, butyl cellosolve, etc., C1-10, preferably C2-8, more preferably C2-5 aliphatic alcohol, Examples thereof include heterocyclic alcohols having 4 to 7 carbon atoms such as furfuryl alcohol, and aromatic alcohols having 6 to 10 carbon atoms such as phenol and benzyl alcohol.
Examples of the ether include dibutyl ether, tetrahydrofuran, dioxane and the like.

Examples of the ketone include acetone, methyl ethyl ketone, methyl isobutyl ketone, and diethyl ketone. Examples of the ester include 5 to 6-membered ring lactones such as ethyl acetate, butyl acetate, isobutyl acetate, and γ-butyrolactone.
Examples of the aromatic hydrocarbon include aromatic hydrocarbons having 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms such as toluene, ethylbenzene, m-xylene, and naphthalene. Examples of chain hydrocarbons include n-hexane, n-octane, n-decane, gasoline, mineral spirit, white kerosene, and examples of mixed hydrocarbons include swazole.
Among these, aliphatic alcohols having 2 to 5 carbon atoms such as n-propanol, 2-propanol, n-butanol and 2-butanol, ketones such as methyl isobutyl ketone, esters such as butyl acetate and isobutyl acetate, toluene, C6-C10 aromatic hydrocarbons, such as ethylbenzene, m-xylene, naphthalene, etc. are more preferable.
These solvents (C) can be used alone or in admixture of two or more. From the viewpoint of dispersion stability of the coating composition and expression of the performance of the coating film, two or more of the solvents are mixed and used. Preferably, a solvent containing alcohol is preferable.

[Coating composition]
The coating composition of the present invention contains titanic acid nanoparticles (A), a coating resin (B), and a solvent (C). The coating composition of the present invention is preferably a white or yellowish white uniform suspension, and more preferably maintains uniformity even after being allowed to stand for several hours.
[Coating]
The coating film of this invention contains the titanic acid nanoparticle (A) whose major axis length of a primary particle is 10-1000 nm, and resin (B) for coating materials.
Moreover, the coating film of this invention is formed by apply | coating the said coating composition to a board | substrate, and drying. There is no restriction | limiting in particular in the board | substrate used, The board | substrate which consists of glass, a metal (aluminum, stainless steel, etc.), ceramics (an insulator, a tile, etc.), a heat resistant polymer material, etc. is mentioned.
The coating composition is applied to the substrate and then dried. By heating in the drying step, the drying time can be shortened and the hardness of the formed coating film can be improved. The heating temperature is preferably 40 to 300 ° C, more preferably 100 to 150 ° C, and the heating time is preferably 30 seconds to 2 hours, more preferably 5 to 60 minutes.
The thickness of the coating film varies depending on applications, etc., but is usually 40 μm or less, preferably 30 μm or less from the viewpoint of film productivity and performance, and from the viewpoint of increasing hardness, it is usually 1 μm or more, preferably 2 μm or more. is there.
The coating film of the present invention is excellent in whiteness and depends on the film thickness, but the haze value is preferably 1 to 50%, more preferably 2 to 10%, and further preferably 3 to 8%. The coating film of the present invention is excellent in hardness and adhesion, and the pencil hardness is preferably 3B or more, more preferably B or more, and the adhesion is preferably 0 in the 100 square cross-cut test. In addition, the physical property of a coating film can be evaluated by the conventional method as described in an Example, for example.

Structure confirmation and morphology observation of titanate nanoparticles obtained in the following production examples were performed by the following methods.
(1) Confirmation of titanic acid structure by Raman spectroscopy Using a Raman spectrometer (Nanofinder 30 manufactured by Tokyo Instruments Co., Ltd.), an argon ion laser (wavelength 633 nm) as a light source, a grating 600 grp / mm, an integration time 400 The Raman spectrum was measured at room temperature under the condition of seconds.
(2) Confirmation of layered structure by powder X-ray diffraction method (XRD) Using a powder X-ray diffractometer (manufactured by Rigaku Corporation, RINT 2500 VPC, light source: Cu-Kα, tube voltage: 40 kV, tube current: 120 mA), In the range of 2θ = 4-60 °, scanning interval 0.01 °, scanning speed 10 ° / min, divergence length limit slit 10 mm, divergence slit 1 °, light receiving slit 0.3 mm, scattering slit automatic condition at room temperature Powder X-ray diffraction measurement was performed. In the range of 2θ = 2 to 10 °, the scanning interval is 0.01 °, the scanning speed is 1 ° / min, the divergence length limit slit is 10 mm, the divergence slit is 1/2 °, the light receiving slit is 0.15 mm, and the scattering slit is automatic. Measured at room temperature.

(3) Measurement of absorption edge wavelength by ultraviolet-visible absorption spectrum A TiO ₂ equivalent concentration 4 × 10 ⁻⁴ mass% titanate nanoparticle dispersion is placed in a quartz cell having an optical path length of 1 cm, and an ultraviolet-visible absorption spectrophotometer ( The ultraviolet-visible absorption spectrum was measured using Shimadzu Corporation's SolidSpec-3700), and the absorption rising wavelength was defined as the absorption edge wavelength.
(4) Particle morphology observation with a transmission electron microscope (TEM) A titanic acid nanoparticle dispersion liquid having a TiO ₂ equivalent concentration of 0.04% by mass was dropped on a TEM grid and dried at room temperature to prepare a sample prepared by a transmission electron microscope ( Using JEM-2100, manufactured by JEOL Ltd., the particle morphology was observed at a magnification of 50,000 to 100,000.
The maximum length of the primary particles of titanic acid nanoparticles in the major axis direction was measured as the major axis length, and the maximum length of the primary particles in the direction perpendicular to the major axis direction was measured as the minor axis length.
(5) Particle morphology observation by scanning electron microscope (SEM) About a micron-sized titanic acid sample, it is 1000 to 10,000 times using a field emission scanning electron microscope (S-4000, manufactured by Hitachi, Ltd.). The particle morphology was observed at magnification.

Production Example 1
(1) Production of titanate nanosheet dispersion stock solution To a solution of 153 g of tetrabutylammonium hydroxide (10 mass% aqueous solution, manufactured by Wako Pure Chemical Industries, Ltd.) dissolved in 42 g of distilled water, 2-propanol (sum) A solution in which 33.6 g of titanium tetraisopropoxide [Ti (OiPr) ₄ ] (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 7.8 g was added dropwise over 5 minutes. The solution became cloudy with the dropwise addition, but by continuing stirring, a transparent titanate nanosheet dispersion stock solution containing titanate nanosheets (TiO ₂ equivalent concentration: 4% by mass, amines / Ti (molar ratio) = 0. 5) was obtained.
As a result of measuring the obtained titanic acid nanosheet with the Raman spectroscopic measurement device, it was confirmed that it had a titanic acid structure. In the XRD pattern, no peaks of crystalline compounds such as anatase type and rutile type were observed, and only peaks derived from a layered structure having a surface spacing of 1.7 nm were observed. Therefore, the titanate nanosheet solid had a layered structure. It was confirmed that there was.
As a result of TEM observation, the obtained titanic acid nanosheet was 5 nm tabular primary particles, and as a result of ultraviolet-visible absorption spectrum measurement, the absorption edge wavelength was 320 nm.
(2) Production of seed crystal titanate nanosheet 80 g of titanate nanosheet dispersion stock solution obtained in (1) above was charged into a 100 mL autoclave (Teflon (DuPont, registered trademark) lining) and hydrothermally treated at 110 ° C. for 6 hours. Then, a transparent dispersion of the seed crystal titanate nanosheet (TiO ₂ equivalent concentration: 4 mass%, amines / Ti (molar ratio) = 0.5) was obtained.

(3) Hydrothermal treatment 80 g of the seed crystal titanate nanosheet dispersion obtained in (2) above was charged into a 100 mL autoclave (Teflon (DuPont, registered trademark) lining) and hydrothermally treated at 110 ° C. for 6 hours. It was. The obtained titanic acid nanosheet aqueous dispersion was white colloidal.
As a result of measuring the obtained titanic acid nanosheet with the Raman spectroscopic measurement device, it was confirmed that it had a titanic acid structure. In the XRD pattern, no peaks of crystalline compounds such as anatase type and rutile type were observed, and only peaks derived from a layered structure having a surface spacing of 1.7 nm were observed. Therefore, the titanate nanosheet solid had a layered structure. It was confirmed that there was.
As a result of TEM observation, the obtained titanic acid nanosheet was a 20 nm tabular primary particle, and as a result of ultraviolet-visible absorption spectrum measurement, the absorption edge wavelength was 320 nm.

(4) Solvent replacement 50 g of n-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed with 50 g of the aqueous titanate nanosheet dispersion obtained in (3) above. This dispersion was concentrated twice using an evaporator (60 ° C.). Titanic acid is obtained by adding 50 g of n-butanol to the obtained transparent concentrated liquid (TiO ₂ equivalent concentration: 4% by mass) and mixing the mixture uniformly, and then concentrating again twice using an evaporator (60 ° C.). A nanorod n-butanol dispersion (white turbidity, TiO ₂ equivalent concentration: 4% by mass, amines / Ti (molar ratio) = 0.5, moisture: 0.9% by mass) was obtained.
As a result of measuring the obtained titanate nanorods with the Raman spectrometer, it was confirmed to have a titanate structure. Moreover, in the XRD pattern, no peaks of crystalline compounds such as anatase type and rutile type were observed, and only peaks derived from a layered structure having a surface spacing of 1.7 nm were observed. Therefore, the titanate nanorod solid had a layered structure. It was confirmed that there was.
As a result of TEM observation, the obtained primary particles of titanate nanorods are spindle-shaped nanorods having a major axis length of 60 nm, a minor axis length of 6 nm, and a ratio of (major axis length / minor axis length) of 10; As a result of measuring the visible absorption spectrum, the absorption edge wavelength was 320 nm. FIG. 1 shows the obtained TEM photograph.

Production Example 2
Rutile type titanium oxide (manufactured by Teika, MT-500B) and cesium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed in a mortar with a TiO ₂ / Cs ₂ CO ₃ molar ratio = 5.3, and then an electric furnace ( Firing was carried out at 800 ° C. for 30 minutes (temperature rising: 2 hours, temperature falling: 2 hours) using a super burn manufactured by Motoyama. The obtained white solid was pulverized and then calcined at 800 ° C. for 40 hours (temperature increase: 2 hours, temperature decrease: 2 hours) to produce a lipid crosite type cesium titanate.
Protonated lepidochrosite titanic acid is produced by repeating the steps of 5 g of the obtained lipidocrosite type cesium titanate powder in 500 g of 1 mol / L hydrochloric acid aqueous solution at room temperature for one day, followed by filtration and washing three times. did.
5 mm of an aqueous dispersion obtained by dispersing the obtained protonated lipidocrosite type titanic acid powder in a tetrabutylammonium hydroxide aqueous solution so that the concentration in terms of TiO ₂ weight is 4% by weight and the N / Ti atomic ratio is 0.5. A ball milling was performed for 3 days using a zirconia-diameter ball to produce a tetrabutylammoniumated lipidocrosite type titanic acid aqueous dispersion.
50 g of n-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed with 50 g of this tetrabutylammoniumated lipidocrosite type titanic acid aqueous dispersion. This dispersion was concentrated twice using an evaporator (60 ° C.). After adding 50 g of butanol to the resulting white turbid concentrated liquid (TiO ₂ equivalent concentration: 4% by mass) and mixing uniformly, titanic acid nanoparticles are obtained by concentration twice again using an evaporator (60 ° C.). An n-butanol dispersion (white turbidity, TiO ₂ equivalent concentration: 4% by mass, amines / Ti (molar ratio) = 0.5, moisture: 0.2% by mass) was obtained.
As a result of measuring the obtained titanic acid nanoparticles with the Raman spectrometer, it was confirmed that the titanic acid structure was a titanic acid structure. In addition, in the XRD pattern, no peaks of crystalline compounds such as anatase type and rutile type were observed, and only peaks derived from a layered structure with an interplanar spacing of 1.8 nm were observed. It was confirmed that.
As a result of TEM observation, the primary particles of the obtained titanic acid nanoparticles are tabular nanoparticles having a major axis length of 300 nm, a minor axis length of 300 nm, and a ratio of (major axis length / minor axis length) of 1, As a result of measuring the ultraviolet-visible absorption spectrum, the absorption edge wavelength was 320 nm.

Production Example 3
Rutile type titanium oxide (manufactured by Teika, MT-500B) and cesium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed in a mortar with a TiO ₂ / Cs ₂ CO ₃ molar ratio = 5.3, and then an electric furnace ( Firing was carried out at 800 ° C. for 30 minutes (temperature rising: 2 hours, temperature falling: 2 hours) using a super burn manufactured by Motoyama. The obtained white solid was pulverized and then calcined at 800 ° C. for 40 hours (temperature increase: 2 hours, temperature decrease: 2 hours) to produce a lipid crosite type cesium titanate.
Protonated lepidochrosite titanic acid is produced by repeating the steps of 5 g of the obtained lipidocrosite type cesium titanate powder in 500 g of 1 mol / L hydrochloric acid aqueous solution at room temperature for one day, followed by filtration and washing three times. did.
To 50 g of an aqueous dispersion in which the obtained protonated lipidocrosite type titanic acid powder was dispersed in a tetrabutylammonium hydroxide aqueous solution so that the concentration was 4 wt% in terms of TiO ₂ and the N / Ti atomic ratio was 0.5. 50 g of n-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed. This dispersion was concentrated twice using an evaporator (60 ° C.). After adding 50 g of butanol to the resulting white turbid concentrate (TiO ₂ equivalent concentration: 4% by mass) and mixing it uniformly, it is concentrated twice again using an evaporator (60 ° C.) to obtain micron-size titanic acid. N-butanol dispersion (white turbidity, TiO ₂ equivalent concentration: 4% by mass, amines / Ti (molar ratio) = 0.5, moisture: 0.2% by mass) was obtained.
As a result of measuring the obtained micron-sized titanic acid with the Raman spectrometer, it was confirmed that it had a titanic acid structure. In addition, in the XRD pattern, no peaks of crystalline compounds such as anatase type and rutile type were observed, and only peaks derived from a layered structure with an interplanar spacing of 1.8 nm were observed. It was confirmed that.
As a result of SEM observation, the obtained primary particles of micron-sized titanic acid have a plate shape with a major axis length of 10000 nm, a minor axis length of 10,000 nm, and a ratio of (major axis length / minor axis length) of 1, and UV-visible. As a result of the absorption spectrum measurement, the absorption edge wavelength was 320 nm.

Production Example 4
50 g of n-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed with 50 g of the titanic acid nanosheet dispersion stock solution obtained in Production Example 1 (1). This dispersion was concentrated twice using an evaporator (60 ° C.). Titanic acid is obtained by adding 50 g of n-butanol to the obtained transparent concentrated liquid (TiO ₂ equivalent concentration: 4% by mass) and mixing the mixture uniformly, and then concentrating again twice using an evaporator (60 ° C.). An n-butanol dispersion of nanosheets (light white, TiO ₂ equivalent concentration: 4% by mass, amines / Ti (molar ratio) = 0.5, moisture: 0.3% by mass) was obtained.
As a result of measuring the obtained titanic acid nanosheet with the Raman spectroscopic measurement device, it was confirmed that it had a titanic acid structure. Moreover, in the XRD pattern, no peaks of crystalline compounds such as anatase type and rutile type were observed, and only peaks derived from a layered structure with a surface spacing of 1.8 nm were observed. Therefore, the titanate nanosheet solid had a layered structure. It was confirmed that there was.
As a result of TEM observation, the primary particles of the titanate nanosheet obtained were flat nanosheets having a major axis length of 5 nm, a minor axis length of 5 nm, and a ratio of (major axis length / minor axis length) of 1, and ultraviolet- As a result of measuring the visible absorption spectrum, the absorption edge wavelength was 320 nm.

Example 1
5 g of n-butanol dispersion of titanate nanorods obtained in Production Example 1 and 2.8 g of urethane-based paint (manufactured by Kansai Paint, Retan PG Multi-One Pack Clear, solid content concentration: 36% by mass) are mixed, and yellowish white uniform Preparation of suspension-containing titanate nanorod-containing coating composition [TiO ₂ equivalent mass of titanate nanoparticles (A) and coating resin (B) mass ratio [(A) / (B)] = 0.2] did. After this titanate nanorod-containing coating composition is formed on a glass substrate (Matsunami Glass Industrial Co., Ltd., S9111, 76 × 52 mm) by bar coating (film thickness 20 μm), it is cured at 120 ° C. for 30 minutes to obtain a white color. A coating film containing titanate nanorods was prepared.
Example 2
Using the n-butanol dispersion of titanic acid nanoparticles obtained in Production Example 2, a coating composition and a coating film were produced in the same manner as in Example 1.
Comparative Examples 1 and 2
Using the n-butanol dispersion of micron-size titanic acid or titanic acid nanosheet obtained in Production Example 3 (Comparative Example 1) or Production Example 4 (Comparative Example 2), in the same manner as in Example 1, a coating composition A coating film was prepared.

The coating composition and the coating film were evaluated by the following methods. The results are shown in Table 1.
(1) Dispersion stability of coating composition The state of the coating composition after standing for 3 hours at room temperature was visually evaluated.
◎: Transparent or uniform suspension ○: Slightly non-uniform suspension ×: Partial precipitation (2) Transparency of coating film (haze)
The transparency of the coating film was evaluated by a haze value (%) using a haze meter (manufactured by Murakami Color Research Laboratory, Inc., reflection transmission meter HR-150).
(3) Whiteness of coating film The whiteness of the film was visually evaluated.
◯: With white feeling ×: Without white feeling (4) Pencil hardness The hardness of the coating film was evaluated by the JIS K-5400 pencil hardness method.
(5) Adhesiveness of coating film The adhesiveness of the coating film to the substrate was evaluated by the cross-cut tape method of JIS K-5400. Using a cutter knife, 100 grids (1 mm width) were made on the coating film, and cellophane tape (manufactured by Nichiban) was applied to the grids, and then the number of peeled off pieces was counted.

  From Table 1, it can be seen that the coating compositions of Examples 1 and 2 are excellent in dispersion stability, and the coating film is excellent in transparency (haze), whiteness, hardness, and adhesion. In particular, in Example 1 using a coating composition containing titanic acid nanorod particles having a ratio of (major axis length / minor axis length) (L / D) of 3 to 20, the coating composition as compared with Example 2 The dispersion stability of the product is extremely excellent, and the hardness of the coating film is also excellent.

Claims (6)

  A coating composition containing titanic acid nanoparticles (A) having a major axis length of primary particles of 10 to 1000 nm, a coating resin (B), and a solvent (C).   The coating composition according to claim 1, wherein the ratio of (major axis length / minor axis length) of primary particles of titanic acid nanoparticles (A) is 3 to 20. The mass ratio [(A) / (B)] of the TiO ₂ conversion mass of titanic acid nanoparticles (A) and the resin for coating (B) is 0.05 to 0.5. Paint composition.   The coating composition in any one of Claims 1-3 whose solvent (C) contains alcohol.   The coating film formed by apply | coating the coating composition in any one of Claims 1-4 to a board | substrate, and drying.   A coating film containing titanic acid nanoparticles (A) having a major axis length of primary particles of 10 to 1000 nm and a coating resin (B).