JP4815380B2 - Method for producing titanic acid nanosheet dispersion - Google Patents

Description

  The present invention relates to a method for producing a titanate nanosheet dispersion, a titanate nanosheet dispersion, and a titanate nanosheet solid.

  Titanium oxide is widely used industrially as a raw material for ceramics and composite oxides, as 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.
In addition, titanium hydroxide and amines are brought into contact with each other to produce a layered titanate no sheet having a titanium source / amine molar ratio of 0.1 to 2 (see Patent Document 1), and titanium alkoxide and tetrabutyl. An organic solvent dispersion of a layered titanate nanosheet obtained by reacting with a quaternary phosphonium hydroxide such as phosphonium hydroxide (see Patent Document 2) is known.
These titanate nanosheet dispersions in which these amines and phosphoniums coexist are colored over time, and, for example, when blended with a polyester resin, there are problems such as causing decomposition and coloration of the resin.

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) JP 2006-182588 A JP 2006-206426 A

  It is an object of the present invention to provide a method for producing a titanate nanosheet dispersion having a low content of amines and / or phosphoniums and having excellent transparency, a dispersion of titanate nanosheets, and a titanate nanosheet solid. To do.

The present inventors efficiently remove amines and the like from titanate nanosheets by bringing the titanate nanosheet dispersion containing amines and / or phosphoniums into contact with a cation exchange resin, and amines and / or phosphoniums. It has been found that a titanate nanosheet dispersion with a low content of alkenyl can be obtained.
That is, the present invention provides the following (1) to (5).
(1) A method for producing a titanate nanosheet dispersion comprising a step of bringing a titanate nanosheet dispersion containing amines and / or phosphoniums into contact with a cation exchange resin.
(2) The manufacturing method of a titanic acid nanosheet dispersion which has following process I-III.
Step I: Titanium alkoxide and / or titanium salt with one or more amines selected from primary amine, secondary amine, tertiary amine and quaternary ammonium hydroxide, and / or quaternary Step of obtaining titanic acid nanosheet dispersion containing amines and / or quaternary phosphonium hydroxide by hydrolysis in the presence of phosphonium hydroxide Step II: The dispersion obtained in Step I Step of mixing the dispersion improver Step III: Step of bringing the dispersion obtained in Step II into contact with the cation exchange resin (3) N / Ti molar ratio in the dispersion obtained by the production method of (2) And a titanate nanosheet dispersion, each having a P / Ti molar ratio of less than 0.1.
(4) A titanate nanosheet dispersion containing amines and / or phosphoniums, wherein the N / Ti molar ratio and the P / Ti molar ratio in the dispersion are both less than 0.1. Dispersion.
(5) A titanate nanosheet solid obtained by removing a dispersion medium from the titanate nanosheet dispersion liquid of (3) or (4).

  According to the present invention, the content of amines and / or phosphoniums is small, an efficient method for producing a titanate nanosheet dispersion having excellent transparency, and a dispersion of titanate nanosheets, particularly amines and phosphoniums. A neutral or acidic dispersion of titanic acid nanosheets and a solid titanate nanosheet can be provided.

Conventionally, titanate nanosheets, for example, obtained lepicrosite-type layered titanic acid by firing from titanium oxide and cesium salt, treated with hydrochloric acid and a large amount of quaternary ammonium hydroxide, and delaminated as a dispersion. Or a titanium alkoxide and / or a titanium salt (hereinafter sometimes referred to as “titanium source”) with amines and / or phosphoniums (hereinafter sometimes collectively referred to as “amines and the like”). Is obtained by hydrolysis in the presence of. In this case, a large amount of amines and the like are used to produce a stable titanate nanosheet dispersion, but amines and the like cause discoloration and can be removed to prepare a transparent dispersion. preferable. However, removal of amines and the like takes time, and the removal effect is not sufficient. The present inventors have found that amines and the like can be removed efficiently and effectively by using a cation exchange resin.
That is, the method for producing a titanate nanosheet dispersion of the present invention includes a step of bringing a titanate nanosheet dispersion containing amines and / or phosphoniums into contact with a cation exchange resin. The components and steps used in the present invention are described below.

(Titanate nanosheet dispersion stock solution)
In the present specification, a titanate nanosheet dispersion immediately after preparation containing a large amount of amines and phosphoniums is referred to as a “titanate nanosheet dispersion stock solution”.
(Titanium source)
When preparing a titanic acid nanosheet in a solution, what produces | generates a titanium hydroxide by a hydrolysis as a titanium source is preferable, and a titanium alkoxide and / or a titanium salt can be mentioned. 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, one or more selected from the group consisting of primary amines, secondary amines, tertiary amines, and quaternary ammonium hydroxides are used, preferably having 1 to 10 carbon atoms. Amines having an alkyl group or an alkenyl group are preferred.
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 less, more preferably 150 ° C. or less, and still more preferably 100 ° C. or less. 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 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.

(Phosphoniums)
Phosphoniums refer to compounds in which hydrogen bonded to the phosphorus atom of an inorganic phosphonium compound is substituted with an alkyl group, phenyl group, or the like, and quaternary phosphonium hydroxides are preferred.
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 quaternary phosphonium hydroxide 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.

(Preparation of titanate nanosheet dispersion stock solution)
In preparing the titanate nanosheet dispersion stock solution, an aqueous solution such as amines and a titanium source may be mixed, or a mixture of amines 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.
From the viewpoint of storage stability and cost of the dispersion, the mixing ratio of the titanium source and the amines and / or phosphoniums is determined as N / P and Ti constituting the amines, phosphonium and titanium sources as N / At least one of the Ti molar ratio and the P / Ti molar ratio is preferably 0.3 to 10, more preferably 0.3 to 5, and still more preferably 0.4 to 2.
In addition, the titanium concentration of the titanate nanosheet dispersion stock solution is preferably 0.01 to 15% by mass, more preferably 0.05 to 10% by mass in terms of titanium oxide (TiO ₂ ), from the viewpoint of storage stability and ease of use. Preferably, 0.05-5 mass% is still more preferable.

Hydrolysis of the titanium source in the presence of amines or the like 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 or the like, 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, phosphoniums and titanium source.
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 and the like.
The reaction time of the titanium source and amines is preferably 0.1 to 20 hours, and more preferably 1 to 10 hours. The mixing time is preferably 0.01 to 5 hours, more preferably 0.02 to 2 hours.

(Titanate nanosheet)
The titanate nanosheet of 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 (for example, 0.3 to 0) spread in a two-dimensional plane. .8 nm) with a sheet structure (e.g. 2-10 nm in length). 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 and the like are contained at a ratio of 0.1 or less in terms of amines / Ti molar ratio.
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 .

(Dispersion medium)
The main component of the dispersion medium of the titanate nanosheet dispersion (dispersion stock solution and dispersion of the present invention) is preferably water or 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, a C1-C6 alcohol is more preferable and methanol is especially preferable. These can be used alone or in admixture of two or more.

(Contact treatment of titanate nanosheet dispersion containing amines and cation exchange resin)
There is no restriction | limiting in particular as a cation exchange resin, A commercial item can be used. From the viewpoint of the removal efficiency of amines and the like, a strongly acidic cation exchange resin is preferable. For example, Amberlite 120B (H ⁺ type) manufactured by Organo Corporation can be used.
The contact treatment with the cation exchange resin can be performed by a conventional method such as a batch method or a column method. The temperature and time of the cation exchange resin treatment can be appropriately determined so as to obtain a desired amine amount and the like, but from the viewpoint of ease of production of the present dispersion, the treatment temperature is preferably 10 to 80 ° C, and 20 ° C. ~ 40 ° C is more preferred. The treatment time is preferably within 24 hours, more preferably 0.5 to 5 hours.
The amount of the cation exchange resin used in the batch method can be appropriately determined so as to be the amount of the desired amines, etc., but from the viewpoint of ease of production of the present dispersion, the amines in the intermediate dispersion 1-10 equivalent is preferable with respect to quantity, and 1-5 equivalent is more preferable.
You may process by making a titanic acid nanosheet dispersion | distribution stock solution contact a cation exchange resin directly. However, amines and the like are compounds that suppress the aggregation, precipitation, gelation, etc. of the titanate nanosheet dispersion and stably disperse titanate nanosheets. There is a risk of problems such as precipitation and gelation. Therefore, before the contact with the cation exchange resin, it is preferable to add a dispersion improver that improves the dispersibility of the titanate nanosheet to suppress the adverse effects due to the removal of amines and the like.

The present invention also discloses a method for producing a titanate nanosheet dispersion having the following steps I to III.
Step I: One or more amines selected from the group consisting of primary amines, secondary amines, tertiary amines and quaternary ammonium hydroxides, and / or titanium alkoxides and / or titanium salts, and / or Step of obtaining titanic acid nanosheet dispersion liquid (titanate nanosheet dispersion stock solution) containing amines and / or quaternary phosphonium hydroxide by hydrolysis in the presence of quaternary phosphonium hydroxide Step II : Step of mixing the dispersion obtained in Step I and the dispersion improver Step III: Step of bringing the dispersion obtained in Step II into contact with the cation exchange resin

The preparation method of titanic acid nanosheet dispersion liquid (titanic acid nanosheet dispersion stock solution) in Step I and the contact treatment with the cation exchange resin in Step III are as described above.
The present invention is further characterized by having a step of adding and mixing a dispersion improver prior to contacting the cation exchange resin in Step II.
In addition, you may add the process I 'which removes amines to such an extent that aggregation, precipitation, or gelatinization does not occur between the process I and the process II. Specifically, step I ′ may be added in which the solvent in the dispersion is removed and concentrated, and the “concentration-dilution” combination of diluting the resulting concentrate with a new solvent is performed one or more times. . Similarly, Step II ′ may be added between Step II and Step III, in which the combination of concentration and dilution of the dispersion is performed once or more, and the solvent of the dispersion is removed to form a titanic acid solid. Thereafter, Step II ″ in which the solid is redispersed or dissolved in a solvent may be added. In the present invention, the removal efficiency of amines and the like by the cation exchange resin in Step III can be maximized by adding at least one of Step II ′ and Step II ″.

(Dispersion improver)
In the present invention, the dispersion improver is a compound that improves the dispersibility of titanate nanosheets and exhibits an action of suppressing aggregation, precipitation, gelation, and the like of titanate nanosheets. The dispersion improver is an important compound for thoroughly removing amines and the like by treating with a cation exchange resin from the titanate nanosheet dispersion stock solution.
For example, an aqueous dispersion of titanic acid nanosheets containing diethylamine as an amine or the like (for example, TiO ₂ equivalent concentration: mass 1%, amines etc./Ti molar ratio 0.5) can be dispersed even if treated with a cation exchange resin. Precipitation does not occur in the presence of the improver. As a result, a transparent and uniform dispersion of titanic acid nanosheets with a low content of amines and the like (amines and the like / Ti molar ratio 0.1 or less) can be obtained.
On the other hand, in the absence of a dispersion improver, when the same titanate nanosheet dispersion is treated with a cation exchange resin in the same manner, precipitation occurs even at a TiO ₂ equivalent concentration of about 1% by mass, and this is further dried to form a powder. Even so, amines and the like cannot be completely removed.

Although the action mechanism of the dispersion improver is not clear, the functional group such as silanol group, hydroxyl group, carboxyl group, etc. of the dispersion improver interacts (bonds) with the surface Ti atoms of the titanate nanosheet, thereby allowing titanic acid. It is presumed that by stabilizing the nanosheet structure (inhibiting aggregation), a stable titanate nanosheet dispersion was obtained even if the content of amines and the like was reduced by treatment with a cation exchange resin.
The mixing temperature of the titanate nanosheet dispersion stock solution and the dispersion improver is preferably from 0 to 100 ° C, more preferably from 10 to 70 ° C, more preferably from 20 to 40 ° C, from the viewpoint of ease of production and dispersibility of the present dispersion. preferable. The mixing time is preferably 0 to 24 hours, more preferably 1 to 12 hours.
From the viewpoint of productivity and dispersion stability of this dispersion, the concentration of the dispersion (intermediate dispersion) in Step III after Step II is preferably 0.1 to 40% in terms of TiO ₂ weight, and 1 to 20 % Is more preferable.

  The dispersion improver may be an organic compound or an inorganic compound, but from the viewpoint of improving the dispersibility of the resulting titanate nanosheet dispersion, a compound that is soluble in the dispersion solvent is preferable, and interaction (bonding, distribution) is preferable on the titanate nanosheet surface. Preferred are compounds that have the same structure, electrostatic interaction, etc.). Specifically, one or more selected from the group consisting of (a) hydroxycarboxylic acid, (b) alkoxysilane, (c) polyol, chlorosilane, polycarboxylic acid, and diketone is preferable, and (a) hydroxycarboxylic acid, ( One or more selected from the group consisting of b) alkoxysilane and (c) polyol are more preferred.

(A) Hydroxycarboxylic acid is a carboxylic acid having a hydroxyl group. Hydroxycarboxylic acids having one hydroxyl group include glycolic acid (monobasic acid), lactic acid (monobasic acid), mandelic acid (monobasic acid), malic acid (dibasic acid), and citric acid (tribasic acid). Etc. Examples of the hydroxycarboxylic acid having two hydroxyl groups include glyceric acid (monobasic acid) and tartaric acid (dibasic acid). From the viewpoint of dispersibility of the present dispersion, a water-soluble hydroxycarboxylic acid is preferable, and at least one selected from the group consisting of glycolic acid, lactic acid, mandelic acid, malic acid, citric acid, glyceric acid and tartaric acid is preferable. Acid is particularly preferred.
Mixing of titanic acid nanosheet dispersion stock solution and hydroxycarboxylic acid is performed by mixing the ratio of hydroxycarboxylic acid to Ti atoms derived from the titanium source in the titanate nanosheet dispersion stock solution, that is, the hydroxycarboxylic acid / Ti molar ratio is 0.01-10. The ratio is preferably 0.05 to 1, more preferably 0.1 to 0.5, and this is reflected in the final hydroxycarboxylic acid / Ti ratio in the present dispersion. .

(B) The number of alkoxy groups per Si atom of the alkoxysilane is preferably 2 to 3, and the alkoxy group is preferably one having 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms, particularly methoxy group or ethoxy group. Groups are preferred.
From the viewpoint of storage stability of the dispersion, the alkoxysilane substituent is preferably at least one selected from the group consisting of alkyl groups, epoxy groups, phenyl groups, mercapto groups, vinyl groups, and methacryl groups. From the viewpoint of storage stability of the liquid, cost, and the like, one or more selected from the group consisting of an alkyl group, an epoxy group, and a phenyl group are more 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.
Preferred examples thereof include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, phenyltrimethoxy One or more types selected from the group consisting of silane and diphenyldimethoxysilane are listed.
These can be used alone or in admixture of two or more.

The molecular weight of the alkoxysilane is not particularly limited, but is preferably 100 to 10,000, more preferably 120 to 1000, and still more preferably 150 to 500 from the viewpoint of storage stability and cost of the dispersion.
Mixing of titanic acid nanosheet dispersion stock solution and alkoxysilane is a ratio of Si atoms in alkoxysilane to Ti atoms derived from titanium source in titanate nanosheet dispersion stock solution, ie, Si / Ti in molar ratio, 0.001 to 50, preferably 0.005 to 10, more preferably 0.01 to 1, most preferably 0.05 to 0.5. This is the final Si content in the dispersion. This is reflected in the ratio of / Ti.
Alkoxysilane is presumed that the Si—O group produced by hydrolysis is bonded to the surface Ti atom of the titanate nanosheet, while a part thereof is polymerized to form a silicon compound such as polysiloxane. There is a possibility. Accordingly, the dispersion may contain alkoxysilane as polysiloxane or silanol compound. For this reason, the Si amount of this dispersion is the total Si amount of all these compounds.

(C) From the viewpoint of the storage stability of the dispersion, the polyol preferably has 2 to 20 alcohol functional groups per molecule, and the ratio of carbon to alcohol functional groups is 1 to 20. 1,2-polyol and 1,3-polyol are preferred.
The molecular weight of the polyol is not particularly limited, but is preferably 60 to 10,000, more preferably 60 to 1,500, and preferably 2 to 50 carbon atoms from the viewpoint of storage stability and cost of the dispersion.
Specific examples of the polyol include 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, , 3-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,2-cyclohexanediol, catechol, 3-butene-1,2-diol, glycerin, glyceryl ether, polyvinyl alcohol, polyethylene glycol, Water-soluble polyols such as polypropylene glycol are listed. These can be used alone or in admixture of two or more.

Among these, from the viewpoint of storage stability of the dispersion, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butane In addition to diol, 1,2-pentanediol, and 1,3-pentanediol, water-soluble diols such as polyethylene glycol and polypropylene glycol having a molecular weight of 300 to 1,200 are more preferable. In particular, 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and polyethylene glycol having a molecular weight of 300 to 1,000 are more preferable.
The blending amount of the polyol is not particularly limited, but from the viewpoint of storage stability and ease of production of the present dispersion, 0.1 to 10 is preferable as the polyol / Ti molar ratio, 0.3 to 3 is more preferable, and 0 4 to 2.5 is more preferable.

  As described above, according to the present invention, a dispersion improver is added to a titanate nanosheet dispersion stock solution containing amines or the like as necessary to improve the dispersibility of titanate nanosheets, and then contact the cation exchange resin. By making it, it is excellent in transparency and can reduce amines etc. to the very low level which is not in the past. Such a dispersion is a titanate nanosheet dispersion obtained by any of the above-described production methods, and the N / Ti molar ratio and the P / Ti molar ratio in the dispersion are both less than 0.1. When neither amines nor phosphoniums are blended in the production process, the molar ratio derived from the compound not blended is naturally zero. In the present invention, a stable dispersion having an N / Ti molar ratio and a P / Ti molar ratio of about 0.04 can be obtained. The lower limit is not particularly limited, but is 0.005 or more when the compound is blended in the production process from the viewpoint of productivity.

The titanate nanosheet dispersion of the present invention is neutral or acidic at 25 ° C., and the pH at 25 ° C. of the dispersion having a concentration of 1% in terms of TiO ₂ weight is preferably 1 to 7.5, more preferably 2 -7, more preferably 2.5-6.5. The neutral to acidic titanic acid nanosheet dispersion liquid can be combined with a base material having poor alkali resistance, and is excellent in versatility.
In addition, when an inorganic-organic nanocomposite material is produced by adding a titanate nanosheet dispersion liquid to a polyester-based resin or the like, when an alkaline titanate nanosheet dispersion liquid is blended, the storage stability of the blended composition and the composite obtained Although there is a possibility that the physical properties of the material molded body may be reduced, the addition of a neutral or acidic titanic acid nanosheet dispersion is unlikely to cause such inconvenience.
The method using the cation exchange resin of the present invention is suitable for acidifying a dispersion, can reduce the amount of amine, and in acidification by adding a conventional acid agent (hydrochloric acid, sulfuric acid, etc.) While the transparency tends to decrease, the method of the present invention is advantageous in maintaining transparency. Accordingly, the titanate nanosheet dispersion of the present invention is a neutral or acidic, highly transparent and stable dispersant without substantially adding an acid other than a dispersion improver (hydroxycarboxylic acid or the like). be able to.
Here, “excellent in transparency” means that the turbidity of a dispersion having a TiO ₂ weight conversion concentration of 1% is 30% or less. Turbidity can be determined by the method defined in JIS K-0101.
The pH is measured by the method described in the examples. The amount of Ti in this dispersion is determined by conventional methods such as high-frequency induction plasma emission spectrometry (ICP) and fluorescent X-ray analysis, and the amount of amine is determined by titration, NMR, gas chromatography, liquid chromatography, etc. It can be determined by conventional methods.

  In addition, in the production method of the present invention, after adding a dispersion improver to titanic acid nanosheet dispersion liquid (titanate nanosheet dispersion stock solution) containing amines and the like, the dispersion medium is increased, and then the dispersion medium is removed by heating or the like. A step of removing amines may be added by repeating the operation of concentrating and the operation of diluting again adding the dispersion medium to the concentrated dispersion medium. After the dispersion improver is added, the solid that has been completely removed by removing the solvent may be dispersed again in the solvent. By performing these operations, amines can be reduced. The cation exchange resin can be used before and after that. As the solvent, those listed above for the dispersion medium can be used, and an organic solvent such as methanol may be substituted depending on the intended use, or an aqueous solution may be used.

(Titanate nanosheet solid)
The solid titanate nanosheet of the present invention can be obtained by removing the dispersion medium from the dispersion obtained above.
By the way, the dispersion without performing the contact treatment with the cation exchange resin, that is, the titanate nanosheet dispersion obtained by removing the dispersion medium from the titanate nanosheet dispersion undiluted solution is electrostatically interacting with the titanate nanosheet. Inferred amines are considered to form a layered structure intercalated between titanate nanosheets. Therefore, by simply removing the dispersion medium from the titanate nanosheet dispersion stock solution, the obtained titanate nanosheet solid has a layered structure, but a large amount of amines and the like remain in the solid. However, when the contact treatment with the cation exchange resin in the present invention is performed, amines of the titanate nanosheet solid can be reduced, especially in the case of the dispersant obtained through steps I to III using a dispersion improver. In addition, it is possible to obtain a titanic acid nanosheet solid in which amines and the like are greatly reduced.
As a method for removing the dispersion medium, a conventional method such as a method of evaporating by heating or reduced pressure is employed. The heat drying temperature is preferably 200 ° C. or lower, and more preferably 150 ° C. or lower.
The drying time may be appropriately set depending on the desired degree of drying, but is usually preferably 1 to 72 hours, and more preferably 5 to 24 hours.

The titanate nanosheet solid of the present invention can be in various forms such as powder, granule, glass, and gel, but is preferably powder from the viewpoint of ease of use and ease of production.
The content of titanate nanosheets in the nanosheet solid is preferably 30 to 99% by mass, more preferably 50 to 95% by mass, and more preferably 60 to 90% by mass in terms of TiO ₂ concentration, from the viewpoint of the performance expression of titanate nanosheets. Is more preferable.
From the viewpoint of versatility, the N / Ti molar ratio and the P / Ti molar ratio are preferably 0.1 or less, more preferably 0.08 or less, and the content of amines and the like contained in the solid is preferably 0.0. 05 or less is particularly preferable, and the lower limit thereof is not particularly limited, but either is 0.005 or more from the viewpoint of productivity. In particular, it is preferable to use only amines. The nanosheet solid can coexist with elements and compounds other than titanate nanosheets within a range not impairing performance. When a dispersion improver is used, the titanate nanosheet solid contains a dispersion improver.
The qualitative analysis and quantitative analysis of each component in the nanosheet solid are powder X-ray diffraction (XRD), Raman spectrum method, IR spectrum method, NMR spectrum method, ultraviolet-visible absorption spectrum method, and fluorescent X-ray analysis method. (XRF), a composition analysis such as a combustion method, and a conventional method such as a titration method.

In the following examples and comparative examples, confirmation of the titanate nanosheet structure by Raman spectroscopy, confirmation of the layered structure of the titanium compound by powder X-ray diffraction (XRD), quantitative analysis of titanium and the like, and pH measurement are as follows. Done by the method. “%” 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.
<Confirmation of layered structure of titanium compound by powder X-ray diffraction (XRD)>
Using a powder X-ray diffractometer (Rigaku Electric Co., Ltd., RINT2500VPC, light source: Cu-Kα, tube voltage: 40 kV, tube current: 120 mA), scan range of 2θ = 4-60 °, scan interval 0.01 °, scan The measurement was performed at room temperature under the conditions of a speed of 10 ° / min, a divergence length limiting slit of 10 mm, a divergence slit of 1 °, a light receiving slit of 0.3 mm, and an automatic scattering slit. 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.
<Quantitative analysis>
Ti and Si quantitative analysis of titanate nanosheet solid is performed using a fluorescent X-ray analysis (XRF) apparatus (manufactured by Rigaku Corporation, ZSX100E), and C, H, N, and P quantitative analysis are fully automatic element analyzers. (Perkin Elmer 2400II, column separation method, TCD detection). In addition, 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. Quantitative analysis of amines and the like in the titanate nanosheet dispersion was performed by the perchloric acid titration method.
<PH measurement>
Using a pH meter (Horiba, Ltd., “D-13”, pH electrode “6367”), the pH electrode internal solution was saturated potassium chloride aqueous solution (3.33 mol / L), and the pH was 25 ° C. Was measured. When the dispersion solvent of this dispersion was an organic solvent, the pH of the dispersion diluted twice with water was measured.

Preparation Example 1 <Preparation of titanic acid nanosheet dispersion stock solution>
An amine aqueous solution in which 0.2 mol (15 g) of diethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 640 g of distilled water was stirred, and titanium tetraisopropoxide [Ti (OiPr) ₄ ] (Wa) was stirred at room temperature. 0.4 mol (114 g) manufactured by Kojun Pharmaceutical Co., Ltd. was added dropwise. The solution became cloudy with the dropwise addition, but by continuing stirring, a transparent titanate nanosheet dispersion containing diethylamine having a TiO ₂ equivalent concentration of 4%, an N / Ti molar ratio of 0.5, and a pH of 11 was obtained.

Example 1
<Preparation of citric acid mixed intermediate dispersion>
Diethylamine-containing titanate nanosheet aqueous dispersion obtained in Preparation Example 1 (titanic acid nanosheet dispersion stock solution) 768 g (Ti = 0.4 mol), stirring, room temperature, distilled water 200 g, anhydrous citric acid (Wako Pure Chemical Industries, Ltd.) An aqueous solution in which 0.067 mol (13 g) was dissolved was added dropwise over 2 hours and further stirred at room temperature for 2 hours. The colorless and transparent aqueous dispersion obtained was put into a Teflon (registered trademark) vat and dried at 100 ° C. for 8 hours using an electric dryer to obtain a pale yellow powder.
As a result of quantitative analysis of the obtained dry powder, TiO ₂ equivalent concentration 50%, diethylamine 17%, citric acid 21%, moisture 12%, N / Ti molar ratio was 0.37, and citric acid / Ti molar ratio was 0.00. 17. 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 having an interplanar spacing of 1.9 nm were observed. It was confirmed that. The Raman spectrum confirmed the titanic acid skeleton structure.
The obtained dry powder was redispersed in water at room temperature to prepare a pale yellow transparent intermediate dispersion having a TiO ₂ equivalent concentration of 5%.
<Cation exchange resin treatment>
Stirring to 80 g (Ti = 0.05 mol) of the intermediate dispersion having a TiO ₂ conversion concentration of 5% obtained above, at room temperature, strongly acidic cation exchange resin (Amberlite 120B (H ⁺ type) manufactured by Organo Corporation), 8.4 g of total exchange capacity 4.4 mg equivalent / g dry resin) (2 equivalents with respect to the amount of amine in the intermediate dispersion) was added, and after stirring for 1 hour, the cation exchange resin was removed by decantation to obtain titanium. An aqueous dispersion of acid nanosheets was obtained.
The obtained aqueous dispersion of titanate nanosheets was transparent and uniform, and was confirmed to have a titanate skeleton structure by Raman spectrum. As a result of quantitative analysis, the TiO ₂ equivalent concentration was 5.4%, the diethylamine concentration was 0.2%, and the N / Ti molar ratio was 0.04. The pH of the aqueous dispersion having a TiO ₂ equivalent concentration of 1% at 25 ° C. was 3.0.
This aqueous dispersion of titanate nanosheets was placed in a Teflon (registered trademark) vat and dried at 110 ° C. for 8 hours using an electric dryer to obtain a white powder. As a result of quantitative analysis of the obtained dry powder, the TiO ₂ equivalent concentration was 62%, the amines / Ti molar ratio was 0.04, and the citric acid / Ti molar ratio was 0.17. 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 having an interplanar spacing of 1.9 nm were observed. It was confirmed that. The Raman spectrum confirmed the titanic acid skeleton structure. The results are shown in Table 1.

Comparative Example 1
In Example 1, a titanate nanosheet aqueous dispersion and a powdered solid thereof were produced in the same manner as in Example 1 except that the cation exchange resin treatment was not performed. The titanate nanosheet dispersion and the powdered solid were both confirmed to have a titanate skeleton structure by Raman spectrum. The results are shown in Table 1.

Example 2
In Example 1, after preparing powder in the process of adjusting the intermediate dispersion, methanol was used in the same manner as in Example 1 except that methanol was used instead of water as a solvent to be dispersed during redispersion. A dispersion and its powdered solid were produced. The methanol dispersion of the obtained titanate nanosheet was transparent and uniform, and was confirmed to have a titanate skeleton structure by Raman spectrum. The results are shown in Table 1.

Example 3
<Synthesis of phenyltrimethoxysilane mixed intermediate dispersion>
Diethylamine-containing titanate nanosheet aqueous dispersion (titanate nanosheet dispersion stock solution) 30 g (Ti = 0.015 mol), 100 g of methanol and phenyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.30 g (0.0015) at room temperature Mol) was uniformly mixed and immediately concentrated using an evaporator (50 ° C.). 100 g of methanol was added to the obtained transparent concentrated liquid, and after uniform mixing, the mixture was immediately concentrated again using an evaporator (50 ° C.). By repeating this methanol dilution-concentration step 17 times, a methanol dispersion of titanate nanosheets containing diethylamine and a phenylsilane compound was produced. In each concentration step, concentration was performed until the amount of the dispersion diluted with methanol was 20 to 25 g.
The methanol dispersion of the obtained titanic acid nanosheet was transparent and uniform, and as a result of quantitative analysis, the TiO ₂ equivalent concentration was 4.2%, the moisture was 0.16%, the N / Ti molar ratio was 0.16, and H ₂ O The / Ti molar ratio was 0.19. The pH of the methanol-water mixed dispersion having a concentration of 1% in terms of TiO ₂ at 25 ° C. was 8.0.
The obtained methanol dispersion was diluted with methanol to prepare an intermediate dispersion having a TiO ₂ equivalent concentration of 2.3%.
<Cation exchange resin treatment>
Stirring the intermediate dispersion 80 g (Ti = 0.023 mol) of TiO ₂ conversion concentration 2.3% obtained above at room temperature, strongly acidic cation exchange resin (Amberlite 120B (H ⁺ type, manufactured by Organo Corporation) ), Total exchange capacity 4.4 mg equivalent / g dry resin) 3.6 g (4 equivalents relative to the amount of amine in the intermediate dispersion) was added, and after stirring for 1 hour, the cation exchange resin was removed by decantation. A methanol dispersion of titanate nanosheets was obtained. A Raman spectrum confirmed the titanic acid skeleton structure. Moreover, titanic acid nanosheet powder was obtained by drying the titanic acid nanosheet methanol dispersion obtained in the same manner as in Example 1. The results are shown in Table 1.

Example 4
<Synthesis of 1,2-butanediol mixed intermediate dispersion>
Diethylamine-containing titanate nanosheet aqueous dispersion (titanate nanosheet dispersion stock solution) 30 g (Ti = 0.015 mol), 100 g of methanol and 1,2-butanediol (Wako Pure Chemical Industries, Ltd.) 2.70 g at room temperature (0.03 mol) was homogeneously mixed and immediately concentrated using an evaporator (50 ° C.). 100 g of methanol was added to the obtained transparent concentrated liquid, and after uniform mixing, the mixture was immediately concentrated again using an evaporator (50 ° C.). By repeating this methanol dilution-concentration step 11 times, a methanol dispersion of titanic acid nanosheets containing diethylamine and 1,2-butanediol was produced. In each concentration step, concentration was performed until the amount of the dispersion diluted with methanol was 20 to 25 g.
The methanol dispersion of the obtained titanic acid nanosheet was transparent and uniform, and as a result of quantitative analysis, the TiO ₂ equivalent concentration was 4.0%, the moisture was 0.4%, the N / Ti molar ratio was 0.15, and H ₂ O. The / Ti molar ratio was 0.44. The pH of the methanol-water mixed dispersion having a concentration of 1% in terms of TiO ₂ at 25 ° C. was 8.0.
The obtained methanol dispersion was diluted with methanol to prepare an intermediate dispersion having a TiO ₂ equivalent concentration of 2.0%.
<Cation exchange resin treatment>
Stirring to 80 g (Ti = 0.02 mol) of the intermediate dispersion having a TiO ₂ conversion concentration of 2.0% obtained above, at room temperature, a strongly acidic cation exchange resin (Amberlite 120B (H ⁺ type, manufactured by Organo Corporation) ), Total exchange capacity 4.4 mg equivalent / g dry resin) 3.4 g (4 equivalents with respect to the amount of amine in the intermediate dispersion) was added and after stirring for 1 hour, the cation exchange resin was removed by decantation. A methanol dispersion of titanate nanosheets was obtained. Moreover, titanic acid nanosheet powder was obtained by drying the titanic acid nanosheet methanol dispersion obtained in the same manner as in Example 1. The results are shown in Table 1.

Example 5
Distilled water (120 g) was added to 40 g of diethylamine-containing titanate nanosheet aqueous dispersion (titanate nanosheet dispersion stock solution) to prepare a transparent uniform diethylamine-containing titanate nanosheet aqueous dispersion having a TiO ₂ equivalent concentration of 1%. This aqueous dispersion was stirred in 160 g (Ti = 0.02 mol), and at room temperature, strongly acidic cation exchange resin (Amberlite 120B (H ⁺ type), total exchange capacity 4.4 mg equivalent / g dry resin, manufactured by Organo Corporation ) 2.3 g (1 equivalent to the amount of amine in the titanate nanosheet dispersion stock solution) was added, and after stirring for 1 hour, the cation exchange resin was removed by decantation to obtain an aqueous dispersion of titanate nanosheets. . The obtained titanate nanosheet aqueous dispersion was placed in a Teflon (registered trademark) vat and dried at 100 ° C. for 8 hours using an electric dryer to obtain titanate nanosheet powder. The results are shown in Table 1.

  From Table 1, it can be seen that according to the method of the present invention, amines and the like are removed by the cation exchange resin. Furthermore, after treating the titanate nanosheet dispersion undiluted solution with a dispersion improver, a cation exchange resin is contacted to obtain a dispersion of an excellent titanate nanosheet having an N / Ti molar ratio of less than 0.1. It is possible to efficiently obtain a titanic acid nanosheet solid with reduced amines. However, if the cation exchange resin treatment is not performed (Comparative Example 1), it can be seen that even when the dispersion improver is mixed, neither the N / Ti molar ratio nor the P / Ti molar ratio is less than 0.1.

  Since the titanate nanosheet dispersion of the present invention and the solid thereof have a low content of amines, etc., coating agents for functional films (barrier films such as UV shielding, corrosion resistant films, etc.), dielectric thin film materials, catalysts, etc. In addition, it can also be used as an additive such as a resin (for example, polyester-based resin) that cannot be mixed with amines.

Claims (9)

A method for producing a titanate nanosheet dispersion comprising a step of bringing a titanate nanosheet dispersion containing amines into contact with a cation exchange resin.   The manufacturing method of the titanic acid nanosheet dispersion liquid of Claim 1 including the process of adding a dispersion | distribution improvement agent to a dispersion liquid before the process made to contact cation exchange resin. The manufacturing method of a titanic acid nanosheet dispersion which has the following process I-III.
Step I: a titanium alkoxide and / or titanium salts, primary amine, secondary amine, hydrolyzed in the presence of one or more amines selected from tertiary amines and quaternary ammonium hydroxides it makes the process step II to obtain a titanate nanosheet dispersion containing amines: step process mixed with the resulting dispersion and the dispersion-improving agent in the step I III: dispersion and the cation exchange obtained in step II Process of contacting with resin   The method for producing a titanate nanosheet dispersion according to claim 2 or 3, wherein the dispersion improver is one or more selected from the group consisting of hydroxycarboxylic acid, alkoxysilane, and polyol. A titanic acid nanosheet dispersion, wherein the N / Ti molar ratio in the dispersion obtained by the production method according to claim 1 is less than 0.19 . A titanic acid nanosheet dispersion, wherein the N / Ti molar ratio in the dispersion is less than 0.1, obtained by the production method according to claim 2. A titanate nanosheet dispersion containing amines, N / Ti molar ratio in the dispersion is less than 0.19, titanate nanosheet dispersion. The titanate nanosheet dispersion according to any one of claims 5 to 7 , wherein the titanate nanosheet dispersion is neutral or acidic. Titanate nanosheet dispersion according to any one of claims 5-8 obtained by removing the dispersion medium, titanate nanosheet solid.