JP2008207983A - Titanate nanosheet dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high concentration dispersion of a titanate nanosheet having a low amine content and an excellent transparency and its efficient manufacturing process. <P>SOLUTION: (1) The dispersion of the titanate nanosheet is obtained by mixing a dispersion of a titanate nanosheet containing an amine with an N/Ti molar ratio of more than 0.2 with an acid-hydrolyzed product of an alkoxysilane and removing the amine from the mixture. (2) The manufacturing process of the titanate nanosheet dispersion comprises mixing a dispersion of a titanate nanosheet containing an amine with an N/Ti molar ratio of more than 0.2 with an acid-hydrolyzed product of an alkoxysilane and removing the amine from the mixture. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a titanate nanosheet dispersion and an efficient production method thereof.

  Titanium oxide is widely used industrially as a raw material for ceramics and composite oxides, a photocatalytic material, and the like. There are various forms of this titanium oxide, but the titanium oxide is not a conventional anatase-type or rutile-type titania, but a nanoscale-thick sheet containing titanic acid or a salt thereof, that is, Some form titanate nanosheets. This titanic acid nanosheet is obtained by peeling layered titanic acid into a layer that is a basic unit of the crystal structure by soft chemical treatment, and the number thereof in the lateral direction with respect to the molecular level thickness (nm level). A dense and highly smooth film having a size of 100 times or more (μm level) can be formed. For this reason, for example, application to various uses such as barrier films such as ultraviolet shielding, corrosion-resistant films, dielectric thin films, and catalysts is expected.

As a method for producing a titanate nanosheet dispersion, a method for producing a titanate nanosheet dispersion called a lipid crosite type, in which a titanium-containing raw material is fired at a high temperature and a hydrochloric acid aqueous solution and a quaternary ammonium ion are further reacted (non-patent literature) 1) has been reported.
Specifically, in this method, first, a mixed powder of Cs ₂ CO ₃ : TiO ₂ (molar ratio) = 1: 5.2 is calcined at 800 ° C. for 20 hours, and Cs, which is a lipid dodecite type layered titanic acid. By synthesizing _0.7 Ti _1.825 □ _0.175 O ₄ (□ is a void) and stirring this powder in an aqueous hydrochloric acid solution of about 1 mol / L, all the Cs ions between the layers are maintained as hydrogen ions while maintaining the layered structure. In place of H _0.7 Ti _1.825 □ _0.175 O ₄ · H ₂ O. Next, a solution containing tetrabutylammonium hydroxide, which is a basic substance, is allowed to act on this, and the above-mentioned basic substance is intercalated between layers and further delaminated to obtain a titanate nanosheet dispersion.
However, in this method, it is necessary to add an amine such as tetrabutylammonium hydroxide in an amount equal to or greater than the hydrogen ion concentration (N / Ti molar ratio of 0.37 or more). In the resulting titanate nanosheet dispersion, A large amount of amines coexist and cannot be used for applications where amines cannot be mixed.

In addition, a method of obtaining a titanic acid nanosheet aqueous dispersion by reacting water with a mixed liquid of amines and titanium alkoxide (see Non-Patent Document 2) is known. However, a large amount of amines (N / Ti molar ratio of 0.4 or more) coexist in the aqueous titanate nanosheet dispersion obtained by this method.
These titanic acid nanosheet dispersions coexisting with a large amount of amines are colored over time, and, for example, when blended with polyester resins, there are problems such as causing decomposition and coloring of the resin, resulting in poor versatility. .
In the prior art, it was not possible to obtain a titanate nanosheet dispersion with a small amount of amines and excellent transparency.

Takayoshi Sasaki, “New Nanomaterial: Oxide Nanosheet Colloid”, Color Material Association, 2003, Vol. 76, No. 10, p. 391-396 T. Ohya, A. Nakayama, Y. Shibata, T. Ban, Y. Ohya, Y. Takahashi, Journal of Sol-Gel Science and Technology, Vol. 26, p 799-802 (2003)

  An object of the present invention is to provide a dispersion of titanate nanosheets having a low amine content and excellent transparency, and an efficient production method thereof.

The present inventors mixed an amine-containing titanate nanosheet dispersion with an alkoxysilane acid hydrolyzate, and then removed the amine to thereby reduce the amine content and provide a highly transparent titanate nanosheet dispersion. Found that you can get.
That is, the present invention provides the following (1) and (2).
(1) The N / Ti molar ratio obtained by removing the amines after mixing the amine-containing titanate nanosheet dispersion with an N / Ti molar ratio exceeding 0.2 and the acid hydrolyzate of alkoxysilane. The titanate nanosheet dispersion which is 0.2 or less.
(2) The N / Ti molar ratio includes a step of removing amines after mixing the amine-containing titanate nanosheet dispersion with an N / Ti molar ratio exceeding 0.2 and the acid hydrolyzate of alkoxysilane. The manufacturing method of the titanic acid nanosheet dispersion liquid which is 0.2 or less.

  According to the present invention, it is possible to provide a titanate nanosheet dispersion having a low amine content, excellent transparency, and fluidity, and an efficient production method thereof.

(Titanate nanosheet dispersion)
The titanate nanosheet dispersion of the present invention having an N / Ti molar ratio of 0.2 or less (hereinafter sometimes simply referred to as “the present dispersion”) contains amines having an N / Ti molar ratio of more than 0.2. A dispersion obtained by mixing a titanic acid nanosheet dispersion (hereinafter sometimes simply referred to as “raw material dispersion”) and an acid hydrolyzate of alkoxysilane (hereinafter simply referred to as “intermediate dispersion”) ) To remove amines by solvent substitution or the like.

This dispersion preferably has a Si / Ti molar ratio in the dispersion of 0.001 to 10, and particularly contains a high concentration of titanic acid and a low concentration of amines, specifically TiO _2. The converted concentration can contain titanate nanosheets of 6% by mass or more, particularly 7% by mass or more, and exhibits fluidity as a liquid.
In the present invention, the N / Ti molar ratio means the molar ratio of nitrogen atoms per titanium atom in the titanate nanosheet dispersion or solid, and the nitrogen atoms are derived from amines. Moreover, Si / Ti molar ratio means the molar ratio of the silicon atom contained per titanium atom in a titanic acid nanosheet dispersion liquid or solid, and a silicon atom originates in alkoxysilane.
In the present specification, “excellent transparency” and “having fluidity” are defined as follows.
“Excellent transparency” means that the turbidity of the dispersion is 30% or less. The turbidity can be determined by the method defined in JIS K-0101.
In the present invention, “having fluidity” means that the viscosity at 25 ° C. after rotating at 60 rpm for 30 seconds using a B-type viscometer is 5000 mPa · s or less. In addition, the rotor number of the viscometer used for a viscosity measurement should be suitable for the measured viscosity.
Usually, in a solution in which titanate nanosheets are dispersed, gelation tends to occur when the amount of amines in the dispersion decreases, and when the titanate nanosheet concentration increases due to concentration, the liquid cannot be maintained. However, according to the present invention, while a high concentration of TiO ₂ in terms of the concentration 6 7 mass% or more titanate nanosheet, the viscosity of the dispersion 1000 mPa · s or less, further has the following liquidity 100 mPa · s A titanic acid nanosheet dispersion can be prepared. The lower limit of the viscosity is not less than the solvent viscosity, for example, 1 mPa · s or more.

The water content of the present dispersion is not particularly limited because it varies depending on the application, but from the viewpoint of versatility and storage stability of the present dispersion, the H ₂ O / Ti molar ratio is preferably 20 or less, more preferably 10 or less. 5 or less is more preferable, and 3 or less is particularly preferable.
The H ₂ O / Ti molar ratio means the molar ratio of water molecules per titanium atom. This water content can be determined by a conventional method such as a Karl Fischer moisture meter.
The amount of amine in the present dispersion is 0.2 or less, preferably 0.18 or less, more preferably 0.17 or less in terms of N / Ti molar ratio, from the viewpoint of versatility of the present dispersion. Moreover, Si amount in this dispersion is 0.001-10 in Si / Ti molar ratio, Preferably it is 0.005-1, More preferably, it is 0.01-0.5, Most preferably, it is 0.03. ~ 0.3.

The amount of Ti in this dispersion is determined by a conventional method such as high frequency induction plasma emission spectrometry (ICP) or fluorescent X-ray analysis, and the amount of amine is determined by a conventional method such as titration, NMR or gas chromatograph. N amount can be obtained.
The amount of Si in the dispersion can be determined from the amount of the alkoxysilane compounded, but it may be measured directly from the dispersion by a known method, and as with the amount of Ti, by the ICP method or the fluorescent X-ray method. You can ask for it.

(Titanate nanosheet)
The titanate nanosheet referred to in the present invention has an octahedral structure in which six oxygens are coordinated around titanium as a basic unit, and this unit has a molecular level thickness (nm level) spread in a two-dimensional plane. It has a sheet structure. This titanic acid nanosheet includes titanic acid nanosheets having a structure such as dititanic acid, trititanic acid, tetratitanic acid, pentatitanic acid, hexatitanic acid, and lipidocrocite type, for example, a salt of titanic acid In the form, it is considered that the following amines are contained in an N / Ti molar ratio of 0.2 or less.
It is inferred that titanate nanosheets are in a state where titanate nanosheets are dispersed separately one by one in the dispersion, and titanate nanosheet dispersion is a state in which titanate nanosheets are layered depending on the system. In addition, it is considered to include partially agglomerated materials.

Such titanate nanosheet, wavenumber Raman spectra having a respective peak in the region of 260~305cm ^-1, 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 having wave numbers of 230 to 250 cm ⁻¹ , 440 to 460 cm ⁻¹ and 600 to 620 cm ⁻¹ . These rules apply to titanate nanosheets in any of the dispersion, the raw material dispersion, and the intermediate dispersion.

(Dispersion medium)
The main component of the dispersion medium of the titanate nanosheet dispersion (the present dispersion) with a small amount of amines is preferably a water-soluble organic solvent from the viewpoint of versatility, storage stability and cost of the dispersion. Examples of the water-soluble organic solvent include alcohols having 1 to 8 carbon atoms such as methanol, ethanol, isopropanol, n-butanol, and tertiary butanol, and 3 to 3 carbon atoms such as acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. 10 polar organic solvents such as ketones. In these, C1-C6 alcohol is preferable, C1-C3 alcohol is more preferable, and methanol is especially preferable. These can be used alone or in admixture of two or more.

<Production of amine-containing titanate nanosheet dispersion>
In producing this dispersion, that is, a titanate nanosheet dispersion with a small amount of amines, a method for producing an amine-containing titanate nanosheet dispersion (raw material dispersion) having an N / Ti molar ratio exceeding 0.2 as a raw material. I will explain.
The raw material dispersion can be obtained, for example, by hydrolyzing a titanium alkoxide and / or a titanium salt (hereinafter sometimes referred to as “titanium source”) in the presence of amines. In this case, an amine-containing aqueous solution and a titanium source may be mixed, or a mixed solution of an amine and a titanium source and water may be mixed. Moreover, for example, it can be obtained by mixing titanium hydroxide obtained by hydrolysis of a titanium source with amines.

(Titanium source)
As the titanium alkoxide and / or titanium salt which is a titanium source, those which generate titanium hydroxide by hydrolysis are preferable. Here, the titanium hydroxide includes those having a composition formula represented by Ti (OH) ₂ , Ti (OH) ₃ , Ti (OH) _4, or H ₄ TiO 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 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 that coexists when producing titanium hydroxide include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth 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 them. Examples of such a solvent include alcohols 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, nickel, cobalt, manganese, and the like can coexist and be combined.

(Amines)
As the amines, at least one selected from the group consisting of primary amines, secondary amines, tertiary amines, and quaternary ammonium hydroxides is used, but preferably has a hydroxy group. Preferred are amines having 1 to 3 C1-C6 alkyl or alkenyl groups or benzyl groups.
Specifically, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, tetrapropylammonium hydroxide, butylamine, dibutylamine, tributylamine, tetrabutylammonium hydroxide, pentylamine, dipentylamine, tripentyl Preferred are amine, 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, from the viewpoint of easy distillation of amines, the boiling point at normal pressure is preferably 200 ° C. or lower, more preferably 150 ° C. or lower, and still more preferably amines having a temperature of 100 ° C. or lower. Further, secondary alkylamines and tertiary alkylamines are preferable, secondary alkylamines and tertiary alkylamines having an alkyl group having 1 to 6 carbon atoms, particularly 2 to 4 carbon atoms are more preferable, diethylamine, Triethylamine and di-n-propylamine are more preferred, and triethylamine is particularly preferred.
From the viewpoint of producing titanate nanosheets, amines having a pH of 9 or more in an aqueous solution having an amine concentration of 9 mmol / L are preferred.

In adjusting the raw material dispersion, the mixing ratio of the titanium source and amines is preferably 0.3 to 10 in terms of N / Ti molar ratio from the viewpoint of storage stability and cost of the dispersion. 5 is more preferable, and 0.4 to 2 is still more preferable.
Further, the titanium concentration in the raw material dispersion is preferably 0.01 to 15% by mass in terms of titanium oxide (TiO ₂ ), from the viewpoint of storage stability and ease of use of the present dispersion, and 0.05 to 10% by mass. % Is more preferable, and 0.05-5 mass% is still more preferable.
From the viewpoint of storage stability and cost, the pH value of the raw material dispersion is preferably 7 or more, more preferably 8 or more, and most preferably 9 or more. The pH value of is preferably 13 or less. The pH value of the present invention is measured at 25 ° C. using a pH meter, for example, according to a conventional method.

Hydrolysis of the titanium source in the presence of amines may cause white turbidity of the titanium compound, but a colorless and transparent liquid can be obtained by continuously stirring. When the titanium source is hydrolyzed in the presence of amines, the amount of water may be an amount required for titanium to decompose. The amount of water to be added is preferably 5 to 50 times the mass of the mixture of amines and titanium source, more preferably 10 to 15 times the mass.
The hydrolysis temperature of the titanium source is preferably 2 to 200 ° C, more preferably 10 to 150 ° C, and still more preferably 20 to 100 ° C, from the viewpoint of the stability of amines.
The reaction time is preferably 0.1 to 20 hours, and more preferably 1 to 10 hours.
The mixing time is preferably from 0.01 to 5 hours, more preferably from 0.02 to 2 hours, from the viewpoint of production stability and production efficiency of the dispersion. Moreover, in order to develop a layer structure, after mixing amines and a titanium source, you may perform hydrothermal synthesis further at 50-200 degreeC.

<Mixing of amine-containing titanate nanosheet dispersion and alkoxysilane acid hydrolyzate>
In order to obtain a titanate nanosheet dispersant having a low amine content and excellent transparency according to the present invention, first, a raw material dispersion having an N / Ti molar ratio of more than 0.2 obtained above is described below. An intermediate dispersion is prepared by mixing an acid hydrolyzate of alkoxysilane.
The mixing of the raw material dispersion and the alkoxysilane acid hydrolyzate is the ratio of the Si atoms in the alkoxysilane acid hydrolyzate to the Ti atoms derived from the titanium source in the raw material dispersion, that is, the Si / Ti molar ratio. And preferably 0.001 to 10, preferably 0.005 to 1, more preferably 0.01 to 0.5, and most preferably 0.06 to 0.3. This is reflected in the ratio of Si / Ti in a typical dispersion. Further, from the viewpoint of ease of production of the dispersion, etc., the mixing temperature is usually preferably from 0 to 100 ° C, more preferably from 10 to 70 ° C. The mixing time is preferably 0 to 24 hours, and more preferably 0 to 1 hour.

(Acid hydrolyzate of alkoxysilane)
The acid hydrolyzate of alkoxysilane is a necessary compound for obtaining good transparency and fluidity when removing amines from a raw material dispersion by solvent substitution.
The acid hydrolyzate of alkoxysilane can be obtained, for example, as an acid hydrolyzate solution of alkoxysilane by stirring the alkoxysilane in an acidic solution. The solvent of the acid hydrolyzate solution is preferably a water-containing organic solvent containing an amount of water necessary for hydrolyzing the alkoxysilane, and the organic solvent is preferably a solvent in which the alkoxysilane is soluble, An alcohol solvent having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, produced by decomposition is more preferable.

The pH of the acid hydrolyzate solution depends on the type and concentration of alkoxysilane, but from the viewpoint of the fluidity of the resulting titanic acid nanosheet dispersion, pH 1-7 is preferable, 2-6 is more preferable, 5 is more preferable. As the pH adjuster, an acid agent selected from inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid and oxalic acid can be used, but inorganic acids are preferable from the viewpoint of cost and the like.
The Si concentration in the acid hydrolyzate solution depends on the type of alkoxysilane, but from the viewpoint of the fluidity of the resulting titanic acid nanosheet dispersion, it is preferably 1 to 10% by mass in terms of Si, and 2 to 8%. % By mass is more preferable, and 4 to 7% by mass is still more preferable.
In addition, the hydrolysis temperature depends on the type and concentration of the alkoxysilane, but is preferably 0 to 50 ° C., and preferably 10 to 30 ° C. from the viewpoint of fluidity and ease of production of the resulting titanate nanosheet dispersion. More preferably, the hydrolysis time is preferably 0.1 to 96 hours, more preferably 1 to 48 hours, and still more preferably 3 to 36 hours.

In addition, the acid hydrolyzate of alkoxysilane is considered that the Si-O group is bonded to the surface Ti atom of the titanate nanosheet, and a part thereof may be polymerized to form a silicon compound such as polysiloxane. it is conceivable that. Therefore, the alkoxysilane may be contained in the dispersion as a polysiloxane or a silanol compound. For this reason, the amount of Si in the present dispersion means the amount of Si obtained by adding all these compounds. In addition, the hydrolysis behavior of alkoxysilane can be grasped by a conventional method such as ¹ H-NMR spectrum.

In the present invention, an aqueous dispersion of titanic acid nanosheets containing amines (for example, TiO ₂ equivalent concentration of 4% by mass, N / Ti molar ratio of 0.5) is evaporated even if the solvent is distilled off by evaporation or the like. When an acid hydrolyzate of silane is mixed, it has fluidity even at a concentration of 7% by mass or more, particularly 8% by mass or more in terms of TiO ₂ , and it becomes difficult to increase viscosity and increase viscosity or gelation. Therefore, the solvent can be easily replaced by adding and redispersing an organic solvent such as methanol to the solvent dispersion and concentrated dispersion.
By repeating this solvent distillation and redispersion step, amines are also distilled off, and a titanate nanosheet having a low amine content (N / Ti molar ratio of 0.2 or less) and excellent transparency can be obtained. In addition, a high-concentration dispersion having fluidity, specifically, a TiO ₂ equivalent concentration of 6% by mass or more, further 7% by mass or more, particularly 8% by mass or more and 30% by mass or less can be obtained. It becomes possible. The titanate nanosheet dispersion in the present invention includes a case where the amine content is 0.

The present inventors have also found that the concentration of amines in the titanate nanosheet dispersion can be reduced even when an alkoxysilane that has not been hydrolyzed or a compound obtained by hydrolyzing an alkoxysilane under alkaline conditions is used. However, in these methods, when the solvent is distilled off and concentrated in the same manner, thickening and viscosity increase or gelation occurs at a TiO ₂ equivalent concentration of about 6% by mass. In the case where no organosilicon compound such as alkoxysilane is added at all, the same titanate nanosheet dispersion is similarly distilled off and concentrated to increase the viscosity even at about 3% by mass in terms of TiO ₂ . Gelation occurs and it is difficult to reduce the amount of amine itself.
Although the mechanism of action of the alkoxysilane acid hydrolyzate that exhibits the above effects is not clear, in general, the alkoxysilane acid hydrolyzate has a positive charge. As a result, the Si-O group of the acid hydrolyzate of alkoxysilane is efficiently bonded by Ti atoms on the surface of the titanate nanosheet, so that the structure of the titanate nanosheet is stabilized (aggregation suppression), It is considered that a titanate nanosheet dispersion excellent in fluidity and transparency can be obtained. At the same time, the amines that interacted (electrostatically bonded) to the titanate nanosheet surface are desorbed from the surface, and further removed together with solvent distillation. As a result, a titanate nanosheet dispersion with a low amine content is obtained. It is thought that it is obtained.

(Alkoxysilane)
Although the kind of alkoxysilane is not particularly limited, a compound that is soluble in water and a dispersion medium used for solvent substitution is preferable. From the viewpoint of storage stability and ease of production of this dispersion, and cost, the alkoxysilane having a substituent is preferable. The number of alkoxy groups per Si atom is preferably 2 to 3, and the alkoxy group is preferably an alkoxy group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, particularly preferably a methoxy group or an ethoxy group.
From the viewpoint of the storage stability of the dispersion, the alkoxysilane substituent contains at least one selected from the group consisting of an alkyl group, an epoxy group, a phenyl group, a mercapto group, a vinyl group, and a methacryl group. preferable.

  Specific examples of the alkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, and 3-glycidoxypropyltrimethoxy. Silane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, methacryloxy Propyltrimethoxysilane, trifluoropropyltrimethoxysilane, aminopropyltrimethoxysilane, mercaptopropyltrimethoxysilane, phenyltrimethoxysilane, N-phenyl- - aminopropyltrimethoxysilane, 3-benzyl-aminopropyltrimethoxysilane, diphenyldimethoxysilane silane, dimethoxy methyl-3- (3-phenoxypropyl thio) silane coupling agents such as silane. These can be used alone or in admixture of two or more.

Among these alkoxysilanes, those containing at least one selected from the group consisting of an alkyl group, an epoxy group, and a phenyl group as a substituent are more preferable from the viewpoint of storage stability and cost of the present dispersion. Those containing an epoxy group are preferred.
Specific examples include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane. One or more selected may be mentioned.
The molecular weight of the alkoxysilane is not particularly limited, but is preferably 100 to 10,000, more preferably 150 to 1,000, and still more preferably 150 to 500 from the viewpoint of storage stability and cost of the dispersion.

<Removal of amines after mixing of alkoxysilane acid hydrolyzate>
In the titanate nanosheet dispersion of the present invention and the process for producing the same, the amine-containing titanate nanosheet dispersion having an N / Ti molar ratio of more than 0.2 and the acid hydrolyzate of alkoxysilane are mixed, and then the amines are added. It is characterized by including a removing step.
The removal of amines from the dispersion mixed with the acid hydrolyzate of alkoxysilane can be carried out by a conventional method such as evaporation of evaporation, cation exchange resin, ultrafiltration or dialysis. For example, when amines are removed by evaporation of the evaporator, the temperature during the distillation is not particularly limited, but is preferably 10 to 100 ° C., more preferably 20 to 80 ° C. from the viewpoint of storage stability of the dispersion. 30 to 60 ° C is more preferable.

If the desired titanic acid nanosheet dispersion with a small amount of amines cannot be obtained by a single distillation operation, diluting the residual liquid with a desired solvent, redispersing, and repeating the operation to distill off, A desired titanate nanosheet dispersion can be obtained. Further, by repeating this distillation-redispersion operation, the desired solvent can be substituted from water.
After diluting with a solvent, it may be redispersed and homogenized by ultrasonic irradiation or the like.

  In the following Examples and Comparative Examples, confirmation of titanate nanosheet structure by Raman spectroscopy, quantitative analysis of titanium and the like, and fluidity evaluation of titanate nanosheet dispersions were performed by the following methods. “%” Is based on mass.

<Confirmation of titanate sheet structure by Raman spectroscopy>
Using a Raman spectrometer (Nanofinder 30, manufactured by Tokyo Instrument Co., Ltd.), an argon ion laser (wavelength: 633 nm) was used as a light source, and measurement was performed at room temperature under conditions of a grating of 600 grp / mm and an integration time of 400 seconds.

<Quantitative analysis of titanium, etc.>
The Ti and Si quantitative analysis of the titanate nanosheet solid is performed using a fluorescent X-ray analysis (XRF) apparatus (manufactured by Rigaku Corporation, ZSX100E), and the C, H and N quantitative analysis is performed by a fully automatic element analyzer (Perkin). Elmer 2400II, column separation method, TCD detection). The quantitative analysis of Ti in the titanate nanosheet dispersion was performed by analyzing the dried solid of the dispersion using the fluorescent X-ray apparatus. The quantitative analysis of the amine in the titanate nanosheet dispersion was performed by the perchloric acid titration method.

<PH measurement>
A saturated potassium chloride aqueous solution (3.33 mol / L) was used as the pH electrode internal solution, and the pH at 25 ° C. was measured with a pH meter (HORIBA D-13) connected with a pH electrode (HORIBA 6367).
<Evaluation of fluidity of titanate nanosheet dispersion>
The titanate nanosheet methanol dispersion was concentrated to a TiO ₂ equivalent concentration of 8% by mass using an evaporator (50 ° C.). The viscosity (25 ° C.) of the obtained concentrated liquid was measured after rotating for 30 seconds at 60 rpm using a B-type viscometer (No. 4 rotor).

Preparation Example 1 (Preparation of acid hydrolyzate of 3-glycidoxypropyltrimethoxysilane)
Under stirring at 25 ° C., a mixed solution of 14.9 g (0.063 mol) of 3-glycidoxypropyltrimethoxysilane (hereinafter abbreviated as “GTS”) manufactured by Shin-Etsu Chemical Co., Ltd. and 7.5 g of methanol was added. By adding dropwise 5.2 g of 01N hydrochloric acid over 3 minutes and further stirring at 25 ° C. for 24 hours, an acid hydrolyzate solution (pH = 4.4) of GTS was obtained. It was confirmed by the ¹ H-NMR spectrum of the acid hydrolyzate that all of GTS was hydrolyzed.
Preparation Example 2 (Preparation of Alkaline Hydrolyzate of 3-Glycidoxypropyltrimethoxysilane)
Under stirring at 25 ° C., 5.2 g of 0.01N aqueous sodium hydroxide solution was added dropwise over 3 minutes to a mixed solution of 14.9 g (0.063 mol) of GTS and 7.5 g of methanol, and further stirred at 25 ° C. for 24 hours. As a result, an alkaline hydrolyzate solution (pH = 8.6) of GTS was obtained. From the ¹ H-NMR spectrum of the alkali hydrolyzate, it was confirmed that all of GTS was hydrolyzed.

Preparation Example 3 (Production of triethylamine-containing titanate nanosheet aqueous dispersion)
An amine aqueous solution in which 0.05 mol (5.05 g) of triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 160 g of distilled water was stirred. To this, 10 mL of 2-propanol was added to titanium tetraisopropoxide [Ti (OiPr) ₄ ] A solution in which 0.1 mol (28.42 g) was dissolved was dropped as a titanium source. The solution became cloudy with the dropwise addition, but by continuing stirring, a transparent, triethylamine-containing titanate nanosheet aqueous dispersion having a TiO ₂ equivalent concentration of 4% and an N / Ti molar ratio of 0.5 was obtained. The pH of the aqueous titanate nanosheet dispersion, which is the raw material dispersion, was 11.
Preparation Example 4 (Production of diethylamine-containing titanate nanosheet aqueous dispersion)
In Preparation Example 3, the same operation as in Preparation Example 3 was performed except that 0.05 mol (3.67 g) of diethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of 0.05 mol of triethylamine. The solution became cloudy with the dropwise addition, but by continuing stirring, a transparent, titanic acid nanosheet aqueous dispersion containing diethylamine having a TiO ₂ equivalent concentration of 4% and an N / Ti molar ratio of 0.5 was obtained. The pH of the aqueous titanate nanosheet dispersion, which is the raw material dispersion, was 11.

Example 1
To 150 g (Ti = 0.075 mol) of the triethylamine-containing titanic acid nanosheet aqueous dispersion obtained in Preparation Example 3, 150 g of methanol at room temperature and 6.6 g of the acid hydrolyzate solution of GTS obtained in Preparation Example 1 After mixing a uniform solution (Si = 0.015 mol), it was immediately concentrated using an evaporator (50 ° C.). 300 g of methanol was added to the obtained transparent concentrated liquid (TiO ₂ equivalent concentration: about 4% by mass), and after uniform mixing, the mixture was immediately concentrated again using an evaporator (50 ° C.). By repeating this methanol dilution-concentration step 20 times, a methanol dispersion (Si / Ti molar ratio = 0.2) of titanate nanosheets containing triethylamine and a GTS derivative was produced. In each concentration step, concentration was performed until the amount of the dispersion diluted with methanol was about 150 g, and in the final concentration step, the amount of the dispersion diluted with methanol was 75 g (TiO ₂ equivalent concentration 8% by mass). Concentration was performed until
The obtained high-concentration titanate nanosheet methanol dispersion was transparent and uniform and had a low viscosity. As a result of quantitative analysis, the N / Ti molar ratio was 0.11, and the H ₂ O / Ti molar ratio was 0.5. . The viscosity of this high concentration titanate nanosheet methanol dispersion was measured. The results are shown in Table 1.
The Raman spectrum confirmed the titanic acid skeleton structure.

Example 2
In Example 1, a titanate nanosheet methanol dispersion was produced in the same manner as in Example 1 except that the amount of GTS acid hydrolyzate solution added was changed to 3.3 g (Si = 0.0075 mol). The obtained high-concentration titanate nanosheet methanol dispersion was transparent, uniform and low in viscosity. The results are shown in Table 1.
Example 3
In Example 1, a titanate nanosheet methanol dispersion was produced in the same manner as in Example 1 except that the amount of the GTS acid hydrolyzate solution added was 1.6 g (Si = 0.0037 mol). The obtained high-concentration titanate nanosheet methanol dispersion was transparent, uniform and low in viscosity. The results are shown in Table 1.
Example 4
In Example 2, instead of the triethylamine-containing titanate nanosheet aqueous dispersion, the diethylamine-containing titanate nanosheet aqueous solution obtained in Preparation Example 4 was used, and the methanol dilution-concentration step was repeated 15 times. Similarly, a titanate nanosheet methanol dispersion was produced. The obtained high-concentration titanate nanosheet methanol dispersion was transparent, uniform and low in viscosity. The results are shown in Table 1.

Comparative Example 1
In Example 1, a titanate nanosheet methanol dispersion was produced in the same manner as in Example 1 except that the acid hydrolyzate of GTS was not added and the methanol dilution-concentration step was repeated 15 times. In each concentration step, concentration was performed until the amount of the dispersion diluted with methanol was about 300 g, and in the final concentration step, gelation occurred at the stage of concentration to a TiO ₂ equivalent concentration of 3% by mass. The results are shown in Table 1.
Comparative Example 2
In Example 1, instead of the acid hydrolyzate of GTS, a mixed solution of 0.63 g of 0.01 N hydrochloric acid and 0.89 g of methanol (corresponding to the amount of hydrochloric acid and methanol in the GTS acid hydrolyzate solution of Example 2) Was added in the same manner as in Example 1 except that the methanol dilution-concentration step was repeated 8 times to produce a titanate nanosheet methanol dispersion. In each concentration step, concentration was performed until the amount of the dispersion diluted with methanol was about 300 g, and in the final concentration step, gelation occurred at the stage of concentration to a TiO ₂ equivalent concentration of 3% by mass. The results are shown in Table 1.

Comparative Example 3
In Example 1, 1.78 g of GTS (Si = 0.0075 mol) was added instead of the acid hydrolyzate of GTS, and the methanol dilution-concentration step was repeated 20 times. An acid nanosheet methanol dispersion was prepared. In the final concentration step, gelation occurred at the stage of concentration to a TiO ₂ equivalent concentration of 6% by mass. The results are shown in Table 1.
Comparative Example 4
In Example 1, 3.3 g (Si = 0.0075 mol) of the GTS alkaline hydrolyzate solution of Preparation Example 2 was added instead of the GTS acid hydrolyzate, and the methanol dilution-concentration step was repeated 15 times. Except for the above, a titanate nanosheet methanol dispersion was produced in the same manner as in Example 1. In the final concentration step, gelation occurred at the stage of concentration to a TiO ₂ equivalent concentration of 6% by mass. The results are shown in Table 1.
In Table 1, TEA means triethylamine, DEA means diethylamine, and GTS means 3-glycidoxypropyltrimethoxysilane.

  The titanate nanosheet dispersion of the present invention has a low content of amines, is excellent in transparency, and has fluidity. It can be used not only as an agent, a dielectric thin film material, a catalyst, etc., but also as an additive such as a resin (for example, a polyester resin) in which amines cannot be mixed.

Claims (5)

  After mixing the amine-containing titanate nanosheet dispersion with an N / Ti molar ratio exceeding 0.2 and the acid hydrolyzate of alkoxysilane, the N / Ti molar ratio obtained by removing the amines is 0.2. A titanate nanosheet dispersion which is: The dispersion medium is an organic solvent, water content in the dispersion is 20 or less H ₂ O / Ti molar ratio, titanate nanosheet dispersion of claim 1.   The titanate nanosheet dispersion liquid according to claim 1 or 2, wherein the dispersion medium is alcohol.   The alkoxysilane contains one or more substituents selected from the group consisting of an alkyl group, an epoxy group, a phenyl group, a mercapto group, a vinyl group, and a methacryl group. The titanate nanosheet dispersion described.   After mixing the amine-containing titanate nanosheet dispersion with an N / Ti molar ratio exceeding 0.2 and the acid hydrolyzate of alkoxysilane, the step of removing amines is included, and the N / Ti molar ratio is 0.2. The manufacturing method of the titanic acid nanosheet dispersion which is the following.