阅读说明：本技术 聚金属氧烷、组合物、固化膜、构件、电子部件、纤维、陶瓷成型用粘合剂、固化膜的制造方法和纤维的制造方法 (Polymetaloxane, composition, cured film, member, electronic component, fiber, adhesive for ceramic molding, method for producing cured film, and method for producing fiber ) 是由 鸣户真之 诹访充史 鸭川政雄 于 2019-03-22 设计创作，主要内容包括：作为本发明的一个方式的聚金属氧烷具有下述通式(1)所示的结构单元,(通式(1)中,R<Sup>1</Sup>是氢原子或碳原子数1~10的烷基；R<Sup>2</Sup>和R<Sup>3</Sup>各自独立地是氢原子、碳原子数1~12的烷基、碳原子数5~12的脂环式烷基、碳原子数6~30的芳族基或碳原子数1~12的酰基；R<Sup>2</Sup>和R<Sup>3</Sup>任选经由碳-碳饱和键或碳-碳不饱和键连结而形成环结构；a是0或1的整数；M表示选自Al、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、Zr、Nb、Mo、Ru、Rh、Pd、Ag、In、Sn、Sb、Hf、Ta、W、Re、Os、Ir、Pt、Au、Tl和Bi中的金属原子；m是表示金属原子M的价数的整数；b是1~(m-2)的整数)。<Image he="107" wi="197" file="DEST_PATH_IMAGE002.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(A polyoxometalate which is one embodiment of the present invention has a structural unit represented by the following general formula (1) (general formula (1) wherein R is 1 Is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; r 2 And R 3 Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, an aromatic group having 6 to 30 carbon atoms or an acyl group having 1 to 12 carbon atoms; r 2 And R 3 Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure; a is an integer of 0 or 1; m represents a metal atom selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Sb, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl and Bi; m is an integer representing the valence of the metal atom M; b is an integer of 1 to (m-2).)

1. A polyoxometalate which is characterized by having a structural unit represented by the following general formula (1),

in the general formula (1), R¹Is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; r²And R³Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, an aromatic group having 6 to 30 carbon atoms, or an acyl group having 1 to 12 carbon atoms; r²And R³Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure; the integer a is an integer of 0 or 1; the metal atom M represents a metal atom selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Sb, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl and Bi; the integer M is an integer representing the valence of the metal atom M; the integer b is an integer of 1 to (m-2).

2. The polyoxometalate according to claim 1, wherein the structural unit represented by the general formula (1) is a structural unit represented by the general formula (2),

in the general formula (2), R⁴Is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, an aromatic group having 6 to 30 carbon atoms, or an acyl group having 1 to 12 carbon atoms; r⁵And R⁴Independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, or an aromatic group having 6 to 30 carbon atoms; r⁴And R⁵Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure.

3. The polyoxometalate according to claim 1, wherein the structural unit represented by the general formula (1) is a structural unit represented by the following general formula (3);

in the general formula (3), R⁶And R⁷Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, or an aromatic group having 6 to 30 carbon atoms; r⁶And R⁷Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure.

4. A multimetal siloxane as claimed in any of claims 1 to 3, wherein the integer a is 1.

5. The polyoxometalate according to any one of claims 1 to 4, wherein the metal atom M comprises 1 or more metal atoms selected from the group consisting of Al, Ti, Zr and Sn.

6. A composition comprising the polyoxometalate of any one of claims 1 to 5.

7. The composition of claim 6, further comprising a compound containing a metal element.

8. A cured film comprising the polyoxometalate of any one of claims 1 to 5.

9. A cured film comprising the composition according to claim 6 or 7.

10. A method for producing a cured film, comprising a heating step of heating the polyoxometalate of any one of claims 1 to 5 or the composition of claim 6 or 7.

11. A member comprising the cured film according to claim 8 or 9.

12. An electronic component comprising the member according to claim 11.

13. A fiber comprising the polyoxometalate of any one of claims 1 to 5.

14. Fiber comprising the composition of claim 6 or 7.

15. A method for producing a fiber, comprising a spinning step of spinning the polyoxometalate of any one of claims 1 to 5 or the composition of claim 6 or 7 to obtain a fiber.

16. The method of manufacturing a fiber according to claim 15, comprising a calcination step of calcining the fiber obtained by the spinning step.

17. An adhesive for ceramic molded bodies, characterized by comprising the polyoxometalates according to any one of claims 1 to 5.

Technical Field

The present invention relates to a polyoxometalate, a composition, a cured film, a member, an electronic component, a fiber, a binder for ceramic molding, a method for producing a cured film, and a method for producing a fiber.

Background

Films containing metal oxides have properties such as high heat resistance and high refractive index, and are expected to exhibit useful properties in various applications. As a method for forming such a film, a method of forming a film of titanium oxide or zirconium oxide by a vapor phase method such as Chemical Vapor Deposition (CVD) is known. However, the film formation rate by a vapor phase method such as CVD is slow, and it is difficult to obtain a film thickness that can be industrially used.

On the other hand, a method of obtaining a thin film having a high refractive index by applying a solution of a polyoxometalate having a metal-oxygen-metal atomic bond in the main chain and curing the solution has been proposed. Such a polyoxometalate can be obtained by hydrolyzing a metal alkoxide and polycondensing the metal alkoxide. However, in general, if a metal alkoxide is hydrolyzed, its hydrolyzate is aggregated and is not dissolved in a solvent. Therefore, a polyoxometalate which stably exists in a uniform state in a solution and can form a uniform cured film is required.

In the past, techniques have been reported in which hydrolysis is performed under special conditions with great attention, thereby preventing precipitation and gelation due to aggregation of the hydrolysate (see, for example, patent documents 1 to 2). In addition, a polyoxometalate which is stably present in a uniform state in a solution by introducing a specific substituent into a side chain of a polymer has been reported (see, for example, patent document 3).

Disclosure of Invention

Problems to be solved by the invention

However, as a method for hydrolyzing a metal alkoxide in a solvent, in the method described in patent document 1, if water is added at a temperature lower than 70 ℃ or if the amount of water added is increased, there is a problem that precipitation due to aggregation of a hydrolysate occurs. Further, since the hydrolysis rate is low, a large amount of alkoxy groups remain in the obtained titano-xane, and hydrolysis of alkoxy groups occurs due to moisture in the air at the time of forming a coating film, and the alkoxy groups are detached. Therefore, the above-mentioned titanosiloxane has a problem that cracks are generated and a uniform film cannot be formed.

In the method described in patent document 2, if the amount of water added is increased, precipitation occurs due to aggregation of the hydrolyzat, and therefore, a high molecular weight polyoxometalate cannot be obtained, and there is a problem that cracks are generated at the time of forming a coating film, and a uniform cured film cannot be formed.

In the method described in patent document 3, a polyoxometalate which can stably exist in a uniform state in a solution is obtained by using a specific group such as a trialkylsiloxy group as a side chain. Such a polyoxometalate is obtained by using, as a starting material, a compound obtained by reacting a trialkylsilyl alcohol with a metal alkoxide. However, trialkylsilyloxols are expensive, and therefore have a problem that a large cost is required for industrially stable supply of the polyoxometalates.

The present invention has been made in view of the above problems, and an object thereof is to provide a high molecular weight polyoxometalate which can be stably present in a uniform state in a solvent and can be stably supplied industrially.

Means for solving the problems

In order to solve the above problems and achieve the object, a polyoxometalate according to the present invention is characterized by having a structural unit represented by the following general formula (1),

[ chemical formula 1]

(in the general formula (1), R¹Is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; r²And R³Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, an aromatic group having 6 to 30 carbon atoms, or an acyl group having 1 to 12 carbon atoms; r²And R³Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure; the integer a is an integer of 0 or 1; the metal atom M represents a metal atom selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Sb, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl and Bi; the integer M is an integer representing the valence of the metal atom M; the integer b is an integer of 1 to (m-2).

Further, the polyoxometalates according to the present invention are characterized in that, in the above invention, the structural unit represented by the above general formula (1) is a structural unit represented by the following general formula (2),

[ chemical formula 2]

(in the general formula (2), R⁴Is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, an aromatic group having 6 to 30 carbon atoms, or an acyl group having 1 to 12 carbon atoms; r⁵And R⁴Independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, or an aromatic group having 6 to 30 carbon atoms; r⁴And R⁵Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure).

Further, the polyoxometalates according to the present invention are characterized in that, in the above invention, the structural unit represented by the above general formula (1) is a structural unit represented by the following general formula (3),

[ chemical formula 3]

(in the general formula (3), R⁶And R⁷Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, or an aromatic group having 6 to 30 carbon atoms; r⁶And R⁷Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure).

In the present invention, the polyoxometalate is characterized in that the integer a is 1.

In the present invention, the polyoxometalate is characterized in that the metal atom M contains 1 or more kinds of metal atoms selected from Al, Ti, Zr and Sn.

The composition according to the present invention is characterized by containing the polyoxometalate according to any one of the above inventions.

The composition according to the present invention is characterized in that the composition further contains a compound containing a metal element in the above invention.

The cured film according to the present invention is characterized by containing the polyoxometalate according to any one of the above inventions.

The cured film according to the present invention is characterized by containing the composition according to any one of the above inventions.

The method for producing a cured film according to the present invention is characterized by comprising a heating step of heating the polyoxometalate or the composition according to any one of the above inventions.

The member according to the present invention is characterized by comprising the cured film according to any one of the above inventions.

The electronic component according to the present invention is characterized by including the member according to the above invention.

The fiber according to the present invention is characterized by containing the polyoxometalate according to any one of the above inventions.

The fiber according to the present invention is characterized by containing the composition according to any one of the above inventions.

The method for producing a fiber according to the present invention is characterized by comprising a spinning step of spinning the polyoxometalate or the composition according to any one of the above inventions to obtain a fiber.

The method for producing a fiber according to the present invention is characterized by including a calcination step of calcining the fiber obtained by the spinning step.

The adhesive for ceramic molded bodies according to the present invention is characterized by containing the polyoxometalates according to any one of the above inventions.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a polyoxometalate which can be stably present in a uniform state in a solvent and can be supplied industrially stably. Further, according to the polyoxometalate of the present invention, an effect is achieved that a cured film having a high refractive index can be provided.

Detailed Description

The following describes in detail embodiments for carrying out the present invention. However, the present invention is not limited to the following embodiments, and can be carried out by variously changing the embodiments depending on the purpose and the application.

(Polymetalaxane)

The polyoxometalates according to the embodiment of the present invention have a structural unit represented by the following general formula (1).

[ chemical formula 4]

In the general formula (1), R¹Is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. R²And R³Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, an aromatic group having 6 to 30 carbon atoms, or an acyl group having 1 to 12 carbon atoms. R²And R³Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure. The integer a is an integer of 0 or 1. The metal atom M represents a metal atom selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Sb, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl and Bi. The integer M is an integer representing the valence of the metal atom M. The integer b is an integer of 1 to (m-2).

Examples of the alkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.

Examples of the alicyclic alkyl group having 5 to 12 carbon atoms include cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl.

Examples of the aromatic group having 6 to 30 carbon atoms include a phenyl group, a phenoxy group, a benzyl group, a phenylethyl group, a naphthyl group, and the like.

Examples of the acyl group having 1 to 12 carbon atoms include a formyl group, an acetyl group, a trifluoroacetyl group, a phenylacetyl group, a propionyl group, a benzoyl group, and the like.

As R²And R³Examples of the ring structure formed by bonding via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond include a pyrrolidine structure, a piperidine structure, a lactam structure, a succinimide structure, a phthalimide structure, and a maleimide structure.

The polyoxometalates having a structural unit represented by the general formula (1) have R²R³N(O)_aThe compatibility with other components is obviously improved. Therefore, the polyoxometalates are stably present in the solvent. Further, the polyoxometalates having the structural unit represented by the general formula (1) have R²R³N(O)_aThe condensation stress of the polyoxometalate due to heating is relieved in the step of forming a cured film described later. Therefore, by using this polyoxometalate, a homogeneous cured film in which cracks are less likely to occur can be obtained.

As R²R³N(O)_aSpecific examples of the group include dimethylamino group, diethylamino group, dipropylamino group, diisopropylamino group, dibutylamino group, diisobutylamino group, di-sec-butylamino group, di-tert-butylamino group, dicyclohexylamino group, diphenylamino group, methylphenylamino group, ethylphenylamino group, propylphenylamino group, dinaphthylamino group, methylnaphthylamino group, ethylnaphthylamino group, propylnaphthylamino group, pyrrolidinyl group, piperidinyl group, 2,6, 6-tetramethylpiperidinyl group and the like.

Further, as R²R³N(O)_aSpecific examples of the group include diethylaminooxy group, dibenzylaminooxy group, 2-azaadamantyloxy group; formamido, formanilide, acetamide, acetanilide, trifluoroacetamide, 2, 2-trifluoroacetylanilide, benzamido, benzanilide, pyrrolidinonyl, piperidinonyl; n-acetamidyloxy, N-octanoylaminoxy, N-benzoylaminoxy, N-benzoyl-N-phenylaminooxy, N-naphthalene-1-carboxamidoyloxy, N-salicylamidooxy, α - (p-butoxyphenyl) -N-acetamidyloxy and the like.

Further, as R²R³N(O)_aSpecific examples of the group include a succinimide group, 2-ethyl-2-methylsuccinimide group, 1, 2-cyclohexanedimethylene imide group, cis-4-cyclohexene-1, 2-dicarboximide group, 1, 8-naphthalenedicarboxylic imide group, phthalimide group, 4-aminophthalimide group, 4-bromophthalimide group, 4-nitrophthalimide group, 3,4,5, 6-tetrachlorophthalimide group, 1,2,3, 4-cyclobutanetetracarboxylic acid diimine group, 1,4,5, 8-naphthalenetetracarboxylic acid diimine group, pyromellitic acid diimine group, 3-tetramethyleneglutarimide group, glutarimide group, maleimido group, 3-dimethylglutarimide group, 4-bromophthalimide group, and the like, 3-ethyl-3-methylglutarylimide, bistrifluoroacetamido, and the like.

Further, as R²R³N(O)_aSpecific examples of the group include N-succinimidyloxy, N-phthalimidyloxy, N- (4-nitrophthalimidoyl) oxy, N- (5-norbornene-2, 3-dicarboximidoyl) oxy, N-oxysulfosuccinimide sodium group, N- (N '-hydroxytetracycline-tetramimidoyl) oxy, N- (1, 8-naphthalimide) oxy, N- (N' -hydroxy-1, 2,3, 4-cyclobutane-tetracarboximidoyl) oxy and the like.

In the polyoxometalate according to the embodiment of the present invention, the structural unit represented by the general formula (1) is preferably a structural unit represented by the following general formula (2).

[ chemical formula 5]

In the general formula (2), R⁴Is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, an aromatic group having 6 to 30 carbon atoms, or an acyl group having 1 to 12 carbon atoms. R⁵And R⁴Independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, or an aromatic group having 6 to 30 carbon atoms. R⁴And R⁵Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bondA ring structure.

The polyoxometalate having the structural unit represented by the general formula (2) has a carbonyl group to stabilize a hydroxyl group in the polyoxometalate. Therefore, the compatibility and stability of the polyoxometalate with the solvent are further improved.

In the polyoxometalate according to the embodiment of the present invention, the structural unit represented by the general formula (1) is more preferably a structural unit represented by the following general formula (3).

[ chemical formula 6]

In the general formula (3), R⁶And R⁷Each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alicyclic alkyl group having 5 to 12 carbon atoms, or an aromatic group having 6 to 30 carbon atoms. R⁶And R⁷Optionally linked via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond to form a ring structure.

The polyoxometalate having the structural unit represented by the general formula (3) has more carbonyl groups than the polyoxometalate having the structural unit represented by the general formula (2), and thus, the hydroxyl group in the polyoxometalate is further stabilized. Therefore, the compatibility and stability of the polyoxometalate with the solvent are further improved.

From the viewpoint of stability at the time of hydrolysis and polycondensation in the production of a polyoxometalate, R⁶And R⁷Preferably via a carbon-carbon saturated bond or a carbon-carbon unsaturated bond, to form a ring structure.

The integer a in the general formula (1) is preferably 1 from the viewpoint of solubility of the polyoxometalate in the solvent. That is, as preferred R²R³N(O)_aExamples of the group include an N-succinimidyloxy group, an N-phthalimidyloxy group, an N- (4-nitrophthalimido) oxy group, an N- (5-norbornene-2, 3-dicarboximido) oxy group, an N-oxysulfosuccinimide sodium group, an N- (N '-hydroxytetracylimido) oxy group, an N- (1, 8-naphthalimido) oxy group, and an N- (N' -hydroxy-1, 2,3, 4-cyclobutanetetracarboxydiimido) oxy group.

In the general formula (1), R²R³N(O)_aThe content of the group is preferably 1 mol% or more and 250 mol% or less, more preferably 10 mol% or more and 200 mol% or less, when represented by the ratio of the number of moles of nitrogen atom (N) to the number of moles of metal atom M of the polyoxometalate (the number of moles of nitrogen atom/the number of moles of metal atom M). By reacting R in a polyoxometalate²R³N(O)_aWhen the content of the base is in the above range, the compatibility of the polyoxometalate with other components is further improved. Therefore, the polyoxometalate is further stably present in the solvent.

R in polyoxometalates²R³N(O)_aThe content of the base was determined by the following method. In this method, first, a polymetallic siloxane is filled in an NMR tube, and NMR measurement corresponding to a metal atom M is performed using a nuclear magnetic resonance apparatus (NMR). From this, the molar concentration of the metal atom M was determined. For example, if the metal atom M is a titanium atom (Ti), by⁴⁹Ti-NMR was measured to determine the molar concentration of titanium atoms. Then, by carrying out¹⁵N-NMR determination by reaction with N (O)_aThe peak corresponding to M, and R is obtained²R³N(O)_aMolar concentration of nitrogen atoms of radicals. By dividing the molar concentration of the nitrogen atom by the molar concentration of the metal atom M, R in the polyoxometalate can be determined²R³N(O)_aThe content of the base.

The polyoxometalate according to the embodiment of the present invention has the structural unit represented by the general formula (1), and thus a cured film mainly composed of a resin having a metal atom with a high electron density in the main chain can be formed. Therefore, the density of the metal atoms in the cured film can be increased, and thus a high refractive index of the cured film can be easily obtained. Further, the polyoxometalate according to the embodiment of the present invention has the structural unit represented by the general formula (1) and thus forms a dielectric having no free electrons, and thus can obtain high heat resistance.

In the general formula (1), the metal atom M preferably contains 1 or more kinds of metal atoms selected from the group consisting of Al, Ti, Zr and Sn. By using these metal atoms, the polyoxometalates can have a high refractive index. The metal atom M is more preferably Ti or Zr. In the general formula (1), the integer m is preferably 3 or more and 5 or less.

The lower limit of the weight average molecular weight of the polyoxometalate is preferably 500 or more, more preferably 1,000 or more, and still more preferably 10,000 or more. The upper limit of the weight average molecular weight is preferably 3,000,000 or less, more preferably 1,500,000 or less, and still more preferably 1,000,000 or less. When the weight average molecular weight is in the above range, the coating properties of the polyoxometalate become good. Further, the weight average molecular weight is not less than the lower limit, and thus the physical properties of a cured film described later are improved, and a cured film particularly excellent in crack resistance is obtained.

The weight average molecular weight in the present invention refers to a value in terms of polystyrene measured by Gel Permeation Chromatography (GPC). The weight average molecular weight of the polyoxometalates was determined by the following method. In this method, first, a sample solution is prepared by dissolving a polyoxometalate in an eluting solvent so as to reach 0.2 wt%. Next, the sample solution is injected into a column filled with a porous gel and an elution solvent. The elution time was analyzed by detecting the column eluate with a differential refractive index detector, and the weight average molecular weight of the polyoxometalates was determined. As the elution solvent, a solvent capable of dissolving the polyoxometalate at a concentration of 0.2wt% was selected. In particular, in the presence of a solution of the polyoxometalate in 0.02mol/dm³In the case of a solution of lithium chloride and N-methyl-2-pyrrolidone according to (1), the solution is used as an elution solvent.

(method for producing Polymetaloxane)

Next, a method for producing a polyoxometalate according to an embodiment of the present invention will be described. In the present invention, the method for producing the polyoxometalates having the structural unit represented by the general formula (1) is not particularly limited. In this production method, it is preferable that the metal alkoxide represented by the following general formula (4) is hydrolyzed, partially condensed and polymerized to produce the polyoxometalate. Here, the partial condensation means that not all of M — OH of the hydrolysate is condensed, but a part of M — OH remains in the obtained polyoxometalate. As long as the general condensation conditions described later are satisfied, M-OH moieties generally remain. The amount of residual M-OH is not particularly limited.

[ chemical formula 7]

In the general formula (4), R⁸Represents R²R³N(O)_aAnd (4) a base. R⁹Is an alkyl group having 1 to 10 carbon atoms. R⁸And R⁹When there are a plurality of them, each may be the same or different. The metal atom M represents a metal atom selected from the group consisting of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Sb, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl and Bi. The integer M is an integer representing the valence of the metal atom M. The integer n is an integer of 1 to (m-1).

In general, when water is added to a metal alkoxide, the metal hydroxide obtained by hydrolyzing all alkoxy groups in a molecule is produced because the hydrolysis of alkoxy groups is high. The metal hydroxide is aggregated in the solution and is insoluble in the solvent, and thus precipitated.

On the other hand, in the metal alkoxide represented by the general formula (4), R²R³N(O)_aThe hydrolyzability of the radical is relatively low compared to the alkoxy radical. Therefore, the alkoxy group can be selectively hydrolyzed by adding water to the metal alkoxide. The resulting hydrolyzed form R²R³N(O)_aSince the groups are stabilized by steric hindrance and intramolecular hydrogen bonding, they do not aggregate in a solution. As a result, a uniform solution of the hydrolysate was obtained. Therefore, the hydrolysis rate of the metal alkoxide can be improved as compared with the conventional technique. Therefore, by hydrolyzing and polycondensing the metal alkoxide represented by the general formula (4), a high molecular weight polyoxometalate, particularly a polyoxometalate having a weight average molecular weight of more than 10,000, can be obtained.

In the present invention, R is⁸The metal alkoxide (2) is not particularly limited to the one represented by the general formula (4). For example, in the case where the metal atom M is Ti, it is said to have one R⁸Metal alkoxide of (2), canExamples thereof include trimethoxy (N-succinimidyloxy) titanium, triethoxy (N-succinimidyloxy) titanium, tripropoxy (N-succinimidyloxy) titanium, triisopropoxy (N-succinimidyloxy) titanium, tributoxy (N-succinimidyloxy) titanium, triisobutoxy (N-succinimidyloxy) titanium, tri-sec-butoxy (N-succinimidyloxy) titanium, tri-tert-butoxy (N-succinimidyloxy) titanium, tricyclohexyl (N-succinimidyloxy) titanium, and triphenoxy (N-succinimidyloxy) titanium.

In addition, as having one R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyl group with an N-phthalimidyl group in the above-mentioned respective alkoxides, for example, triisopropoxy (N-phthalimidyl) titanium and tributoxy (N-phthalimidyl) titanium.

In addition, as having one R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyl group with an N- (4-nitrophthalimidoyl) oxy group in the above-mentioned respective alkoxide, for example, triisopropoxy (N- (4-nitrophthalimidoyl) oxy) titanium, tributoxy (N- (4-nitrophthalimidoyl) oxy) titanium, and the like.

In addition, as having one R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyl oxy group with an N- (5-norbornene-2, 3-dicarboximidyl) oxy group in the above respective alkoxide salts, for example, triisopropoxy (N- (5-norbornene-2, 3-dicarboximidyl) oxy) titanium and tributoxy (N- (5-norbornene-2, 3-dicarboximidyl) oxy) titanium.

In addition, as having one R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyl group with an N- (1, 8-naphthalimido) oxy group in the above-mentioned respective alkoxide, for example, triisopropoxy (N- (1, 8-naphthalimido) oxy) titanium, tributoxy (N- (1, 8-naphthalimido) oxy) titanium, and the like.

Further, as having two R⁸The metal alkoxide of (2) includes dimethoxybis (N-succinimidyl)Oxy) titanium, diethoxybis (N-succinimidyloxy) titanium, dipropoxybis (N-succinimidyloxy) titanium, diisopropoxybis (N-succinimidyloxy) titanium, dibutoxybis (N-succinimidyloxy) titanium, diisobutyoxybis (N-succinimidyloxy) titanium, di-sec-butoxybis (N-succinimidyloxy) titanium, di-tert-butoxybis (N-succinimidyloxy) titanium, dicyclohexyloxybis (N-succinimidyloxy) titanium, diphenoxybis (N-succinimidyloxy) titanium, and the like.

Further, as having two R⁸Examples of the metal alkoxide of (a) include those obtained by replacing N-succinimidyloxy with N-phthalimidyloxy in the above-mentioned groups, for example, diisopropoxybis (N-phthalimidyloxy) titanium, dibutoxybis (N-phthalimidyloxy) titanium, and the like.

Further, as having two R⁸Examples of the metal alkoxide of (a) include those obtained by replacing N-succinimidyloxy with N- (4-nitrophthalimidoyl) oxy in the above groups, for example, diisopropoxybis (N- (4-nitrophthalimidoyl) oxy) titanium, dibutoxybis (N- (4-nitrophthalimidoyl) oxy) titanium and the like.

Further, as having two R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyloxy group with an N- (5-norbornene-2, 3-dicarboximidyloxy) group in the above groups, for example, diisopropoxybis (N- (5-norbornene-2, 3-dicarboximidyloxy) titanium, dibutoxybis (N- (5-norbornene-2, 3-dicarboximidyloxy) titanium, and the like.

Further, as having two R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyloxy group with an N- (1, 8-naphthalimido) oxy group in the above groups, for example, diisopropoxybis (N- (1, 8-naphthalimido) oxy) titanium, dibutoxybis (N- (1, 8-naphthalimido) oxy) titanium, and the like.

On the other hand, when the metal atom M is Zr, R is defined as having⁸The metal alkoxide of (2) may be mentionedExamples of the alkoxide include those obtained by replacing titanium with zirconium, for example, tri-N-propoxy (N-succinimidyloxy) zirconium, tri-N-propoxy (N-phthalimidyloxy) zirconium, tri-N-propoxy (N- (4-nitrophthalimidoyloxy) zirconium, tri-N-propoxy (N- (5-norbornene-2, 3-dicarboximidoyl) oxy) zirconium, tri-N-propoxy (N- (1, 8-naphthalimido) oxy) zirconium, di-N-propoxy bis (N-succinimidyloxy) zirconium, di-N-propoxy bis (N-phthalimidyloxy) zirconium, di-N-propoxy bis (N- (4-nitrophthalimidoyl) oxy) zirconium, and di-N-propoxy bis (N- (5-norbornene-2), 3-dicarboximidyl) oxy) zirconium, di-N-propoxybis (N- (1, 8-naphthalimido) oxy) zirconium, and the like.

On the other hand, when the metal atom M is Al, it is said to have R⁸Examples of the metal alkoxide of (a) include dimethoxy (N-succinimidyloxy) aluminum, diethoxy (N-succinimidyloxy) aluminum, dipropoxy (N-succinimidyloxy) aluminum, diisopropyloxy (N-succinimidyloxy) aluminum, dibutoxy (N-succinimidyloxy) aluminum, diisobutyoxy (N-succinimidyloxy) aluminum, di-sec-butoxy (N-succinimidyloxy) aluminum, di-tert-butoxy (N-succinimidyloxy) aluminum, dicyclohexyloxy (N-succinimidyloxy) aluminum, and diphenoxy (N-succinimidyloxy) aluminum.

Further, as having R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyl group with an N-phthalimidyl group in the above-mentioned respective alkoxide, for example, di-sec-butoxy (N-phthalimidyl) aluminum.

Further, as having R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyl group with an N- (4-nitrophthalimidoyl) oxy group in the respective alkoxide, for example, di-sec-butoxy (N- (4-nitrophthalimidoyl) oxy) aluminum, and the like.

Further, as having R⁸The metal alkoxide of (2) includes, for example, the alkoxides mentioned above in which N-succinimidyloxy is replaced by N- (5-norbornene-2, 3-)Dicarboximide) oxy, for example, di-sec-butoxy (N- (5-norbornene-2, 3-dicarboximide) oxy) aluminum.

Further, as having R⁸Examples of the metal alkoxide of (a) include those obtained by replacing an N-succinimidyl group with an N- (1, 8-naphthalimido) oxy group in the respective alkoxide, for example, di-sec-butoxy (N- (1, 8-naphthalimido) oxy) aluminum, and the like.

In the hydrolysis, partial condensation and polymerization of the metal alkoxide, a general method can be used. For example, the hydrolysis reaction condition is preferably a reaction condition in which water is added to a metal alkoxide in a solvent for 1 to 180 minutes, and then the reaction is carried out at room temperature to 110 ℃ for 1 to 180 minutes. By performing hydrolysis under such reaction conditions, a vigorous reaction of the hydrolysis can be suppressed. In addition, the reaction temperature of the hydrolysis is preferably 30-150 ℃. In the hydrolysis of the metal alkoxide, a catalyst may be added as necessary.

In addition, as the reaction conditions for the partial condensation and polymerization of the metal alkoxide, it is preferable that after the metal hydroxide is obtained by the hydrolysis reaction of the metal alkoxide, the reaction solution is directly heated at 50 to 180 ℃ for 1 to 100 hours. In addition, the reaction solution may be heated again in order to increase the polymerization degree of the polyoxometalate, or a catalyst may be added to the reaction solution. Further, after the hydrolysis reaction of the metal alkoxide, an appropriate amount of the alcohol or the like produced may be distilled off and removed by at least one of heating and reduced pressure, and thereafter an arbitrary solvent may be added, as required.

The solvent is not particularly limited, and an amide solvent, an ester solvent, an alcohol solvent, an ether solvent, a ketone solvent, dimethyl sulfoxide, or the like can be suitably used.

Specific examples of the amide solvent include N, N-dimethylformamide, N-dimethylacetamide, N-dimethylisobutyramide, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, and N, N-dimethylpropyleneurea.

Specific examples of the ester-based solvent include γ -butyrolactone, -valerolactone, propylene carbonate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, propylene glycol monomethyl ether acetate, 3-methoxy-1-butyl acetate, 3-methyl-3-methoxy-1-butyl acetate, ethyl acetoacetate, and cyclohexanol acetate.

Specific examples of the alcohol-based solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, 3-hydroxy-3-methyl-2-butanone, 5-hydroxy-2-pentanone, 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol), ethyl lactate, butyl lactate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monomethyl ether, 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol, ethylene glycol, and propylene glycol.

Specific examples of the ether solvent include diethyl ether, diisopropyl ether, di-n-butyl ether, diphenyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, dipropylene glycol dimethyl ether, and the like.

Specific examples of the ketone solvent include methyl isobutyl ketone, diisopropyl ketone, diisobutyl ketone, acetylacetone, cyclopentanone, cyclohexanone, cycloheptanone, and dicyclohexylketone.

More preferred solvents are aprotic polar solvents. By using an aprotic polar solvent, a high molecular weight polyoxometalate which is stable in a solvent can be obtained. Among the aprotic polar solvents, N-dimethylformamide, N-dimethylacetamide, N-dimethylisobutyramide, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, N-dimethylpropyleneurea, γ -butyrolactone, -valerolactone, propylene carbonate, dimethyl sulfoxide, and the like are more preferable.

Further, the hydrolysis rate of the metal alkoxide can be adjusted by adjusting the amount of water to be added in the hydrolysis reaction of the metal alkoxide. The amount of water added is preferably 0.1 to 2 moles per 1 mole of the alkoxy group.

The catalyst to be added as needed in the hydrolysis reaction of the metal alkoxide is not particularly limited, and an acid catalyst or a base catalyst is preferably used. Specific examples of the acid catalyst include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, acetic acid, difluoroacetic acid, formic acid, polycarboxylic acid or an acid anhydride thereof, and an ion exchange resin. Specific examples of the base catalyst include diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, triethylamine, tripropylamine, tributylamine, triisobutylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, diethanolamine, triethanolamine, dicyclohexylamine, dicyclohexylmethylamine, 2,6, 6-tetramethylpiperidine, sodium hydroxide, potassium hydroxide, an alkoxysilane having an amino group, an ion exchange resin, and the like.

More preferred catalysts are base catalysts. By using a base catalyst, a particularly high molecular weight polyoxometalate can be obtained. Among the alkali catalysts, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dioctylamine, triethylamine, tripropylamine, tributylamine, triisobutylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, diethanolamine, triethanolamine, dicyclohexylamine, dicyclohexylmethylamine, 2,6, 6-tetramethylpiperidine are particularly preferable.

In addition, from the viewpoint of storage stability of the composition, it is preferable that the solution of the polyoxometalate after hydrolysis, partial condensation and polymerization does not contain the above-mentioned catalyst, and the catalyst may be removed as necessary. The method for removing the catalyst is not particularly limited, and at least one of water washing and treatment with an ion exchange resin is preferable from the viewpoints of ease of operation and removability. The water washing refers to a method of removing the catalyst by diluting the polyoxometalate solution with an appropriate hydrophobic solvent and then concentrating an organic layer obtained by washing several times with water by an evaporator or the like. The treatment with an ion exchange resin refers to a method of removing a catalyst by bringing a solution of a polyoxometalate into contact with an appropriate ion exchange resin.

(composition of Polymetaloxane)

The polyoxometalate according to the embodiment of the present invention may be mixed with a solvent and other necessary components to prepare a composition. That is, the composition according to the embodiment of the present invention contains at least the above-mentioned polyoxometalates.

In the present invention, when the polyoxometalate is used in the preparation of a composition, it is preferable to dilute the polyoxometalate with a solvent to adjust the solid content concentration. The solvent is not particularly limited, and the same solvent as used for the synthesis of the polyoxometalate is preferably used. The solid content concentration of the solution containing the polyoxometalate is preferably 0.1 to 50 wt%. By setting the solid content concentration in this range, the control of the thickness of the coating film of the polyoxometalate becomes favorable.

When the solid content concentration of the polyoxometalate solution is adjusted, other components may be added to the solution. Examples of the other components include a metal element-containing compound, a surfactant, a silane coupling agent, and the like. That is, the composition according to the embodiment of the present invention preferably further contains other components such as a compound containing a metal element in addition to the above-mentioned polyoxometalate.

The metal element-containing compound is preferably used to improve chemical resistance of the cured film. The polyoxometalates form a crosslinked structure with each other by the compound containing the metal element. Thus, a more dense cured film of the polyoxometalate and the composition thereof can be obtained. The compound containing the metal element may remain in the cured film.

As an example of the metal element-containing compound, an organometallic complex is preferable. Specifically, examples of the organic metal complex include mono-sec-butoxydiisopropoxyaluminum, sec-butoxyaluminum, ethyldiisopropoxyaluminum acetoacetate, aluminum bis (ethylacetate), alkylalcetyldiisopropoxyaluminum (アルキルアセトアルミニウムジイソプロピレート), aluminum bis (ethylacetoacetate), aluminum bis (acetylacetonate), aluminum tris (acetoacetate), zirconium bis (ethylacetoacetate), titanium bis (acetoacetate), titanium tetra-n-butoxide, a condensate (oligomer) of titanium tetra-n-butoxide, and a condensate (oligomer) of titanium tetra-isopropoxide.

The content of the metal element-containing compound in the composition is preferably 0.1 part by weight or more and 50 parts by weight or less, and more preferably 1 part by weight or more and 20 parts by weight or less, based on 100 parts by weight of the total amount of the polyoxometalate.

The surfactant is preferably used to improve the uniformity of film thickness when coating the polyoxometalate and the composition thereof. The surfactant may remain in the cured film.

The kind of the surfactant is not particularly limited. For example, as the surfactant, a fluorine-based surfactant such as "メガファック (registered trademark)" F142D, F172, F173, F183, F445, F470, F475, and F477 (manufactured by Dainippon ink chemical Co., Ltd.), NBX-15, FTX-218, and DFX-18 (manufactured by ネオス), a silicone-based surfactant such as BYK-333, BYK-301, BYK-331, BYK-345, and BYK-307 (manufactured by ビックケミージャパン), a polyalkylene oxide-based surfactant, a poly (meth) acrylate-based surfactant, and the like can be used. As the surfactant, 2 or more of these may be used.

The content of the surfactant in the composition is preferably 0.001 parts by weight or more and 10 parts by weight or less, and more preferably 0.01 parts by weight or more and 1 part by weight or less, based on 100 parts by weight of the polyoxometalate.

The silane coupling agent is preferably used to improve adhesion to the substrate. The silane coupling agent is not particularly limited. For example, as the silane coupling agent, vinyldimethoxysilane, vinyldiethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyldimethoxysilane, 3-glycidoxypropyldimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyldimethoxysilane, 3-acryloxypropyldimethoxysilane, 3-aminopropyldimethoxysilane, 3-aminopropyldiethoxysilane, 3-diethoxysilyl-N- (1, 3-dimethyl-butylidene) propylamine, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethoxysilane, 3-isocyanatopropyldiethoxysilane, 3-epoxydiethoxysilane, 2-epoxycyclohexyl) ethyldimethoxysilane, 3-glycidoxypropyldimethoxysilane, and the like can be used, Diphenyldimethoxysilane, dimethylsilanol, diphenylsilandiol, and the like.

The content of the silane coupling agent in the composition is preferably 0.1 part by weight or more and 50 parts by weight or less, and more preferably 1 part by weight or more and 20 parts by weight or less, based on 100 parts by weight of the polyoxometalate.

(cured film and method for producing the same)

The cured film according to an embodiment of the present invention contains the above-mentioned polyoxometalate or a composition containing the above-mentioned polyoxometalate. In the method for producing a cured film according to an embodiment of the present invention, the polyoxometalate or the composition containing the polyoxometalate may be applied to a substrate and heated to form a cured film. That is, the method for producing a cured film includes at least a heating step of heating the above-mentioned polyoxometalate or the composition thereof. The cured film obtained in this way is a cured film mainly composed of a resin having a metal atom with a high electron density in the main chain, and therefore the density of the metal atom in the cured film can be increased, and a high refractive index can be easily obtained. In addition, since the cured film forms a dielectric having no free electrons, high heat resistance can be obtained.

The substrate to which the polyoxometalate or the composition thereof is applied is not particularly limited, and examples thereof include a silicon wafer, a sapphire wafer, glass, an optical film, and the like. Examples of the glass include alkali glass, alkali-free glass, thermally strengthened glass, and chemically strengthened glass. Examples of the optical film include films made of an acrylic resin, a polyester resin, polycarbonate, polyarylate, polyethersulfone, polypropylene, polyethylene, polyimide, or a cycloolefin polymer.

Specifically, a method for producing a cured film according to an embodiment of the present invention includes: a coating step of coating the above-mentioned polyoxometalate or a composition thereof on a substrate, and the above-mentioned heating step. In the coating step, a known method can be used as a coating method for coating the above-mentioned polyoxometalate or the composition thereof on a substrate. Examples of the apparatus used for coating include a full-surface coating apparatus such as spin coating, dip coating, curtain flow coating, spray coating, or slit coating, and a printing apparatus such as screen printing, roll coating, micro-gravure coating, or ink jet.

In addition, in this coating step, after the polyoxometalate or the composition thereof is coated on the substrate, heating (pre-baking) may be performed using a heating device such as a hot plate or an oven, if necessary. The pre-baking is preferably carried out at the temperature range of 50-150 ℃ for 30 seconds-30 minutes, and the coating film on the substrate is made into a pre-baking film. By performing the pre-baking, the coating film can be formed with good film thickness uniformity. The thickness of the coating film after prebaking is preferably 0.1 μm to 15 μm.

After the coating step, a heating step of heating the polyoxometalate or the composition thereof on the substrate to obtain a cured film is performed. In the heating step, the coating film or the pre-baking film obtained in the coating step is heated (cured) at a temperature ranging from 150 ℃ to 450 ℃ for about 30 seconds to 2 hours by using a heating device such as a heating plate or an oven. Thus, a cured film containing the polyoxometalate or the composition thereof can be obtained. The thickness of the cured film is preferably 0.1 μm or more and 15 μm or less.

The cured film obtained as described above preferably has a refractive index of 1.58 or more and 2.20 or less at a wavelength of 550nm, and more preferably has a refractive index of 1.65 or more and 2.10 or less.

The refractive index of the cured film can be measured by the following method. For example, in the method of measuring the refractive index, a spectroscopic ellipsometer is used to measure a change in the polarization state of reflected light from the cured film and the substrate, and a spectrum of a phase difference and an amplitude reflectance from incident light is obtained. The dielectric function of the calculation model is fitted in a manner close to the obtained spectrum, thereby obtaining a refractive index spectrum. The refractive index value at a wavelength of 550nm was read from the obtained refractive index spectrum, thereby obtaining the refractive index of the cured film.

(use of cured film)

The cured film according to the embodiment of the present invention has excellent refractive index and insulation properties, and is therefore suitable for use as a member of an electronic component such as a solid-state imaging device or a display. The member refers to a part of an article that assembles the electronic component. That is, the member according to the embodiment of the present invention includes a cured film containing the above-described polyoxometalate or the composition thereof. The electronic component according to the embodiment of the present invention includes such a cured film. Examples of the member of the solid-state imaging device include a light-collecting lens, an optical waveguide for connecting the light-collecting lens and the photosensor section, and an antireflection film. Examples of the members of the display include a refractive index matching material, a planarization material, and an insulating protective material.

(fiber use)

Fibers can be produced by spinning a solution of the polyoxometalate or the composition thereof according to the embodiment of the present invention. That is, the fibers according to the embodiment of the present invention contain the above-mentioned polyoxometalates or the compositions containing the above-mentioned polyoxometalates. The fiber obtained in this manner can be made into a metal oxide fiber by calcination.

Fibers containing metal oxides have properties such as high heat resistance, high strength, and surface activity, and are expected to have useful properties in various applications. Such fibers (metal oxide fibers) are generally produced by a melt fiberization process. This method is as follows. For example, in this method, first, a metal oxide raw material is mixed with a low-melting-point compound such as silica. Subsequently, the mixture was melted by passing through a high-temperature furnace, and the melt was taken out in a fine stream. The fine flow is blown with high-pressure air or subjected to centrifugal force to rapidly cool the fine flow, thereby producing metal oxide fibers. However, in the melt fiberization method, if the concentration of the metal oxide raw material is high, the melting temperature is high, and therefore it is difficult to obtain a metal oxide fiber containing a metal oxide at a high concentration (hereinafter, appropriately referred to simply as a high-concentration metal oxide fiber).

As a method for obtaining a metal oxide fiber having a high concentration, a method of preparing a fibrous precursor using a spinning solution containing a metal oxide raw material and a thickener and heat-spinning the precursor is generally known. However, in such a method, voids and cracks are generated when the thickener is burned off during the calcination, and as a result, the strength of the obtained metal oxide fiber is insufficient.

The polyoxometalates and compositions thereof according to embodiments of the present invention can be processed in a solution state, and thus spinning can be performed without the need for a melting step in the above melt fiberization process. Further, the above-mentioned polyoxometalates and compositions thereof do not require a thickener in spinning, and therefore, dense metal oxide fibers can be obtained. Therefore, a metal oxide fiber having characteristics such as high heat resistance, high strength, and surface activity can be easily obtained.

(method for producing fiber)

The method for producing a fiber according to an embodiment of the present invention includes at least a spinning step of spinning the above-described polyoxometalate or the composition thereof to obtain a fiber. In this spinning step, a known method can be used for spinning a solution of the polyoxometalate or the composition thereof. Examples of the spinning method include a dry spinning method, a wet spinning method, a dry-wet spinning method, and an electrospinning method. Hereinafter, "polyoxometalates or compositions thereof" are simply referred to as "compositions and the like" as appropriate.

The dry spinning method is a method of filling a composition or the like, extruding the composition or the like into an atmosphere by loading the composition from a spinneret having fine holes, and evaporating an organic solvent to form filaments. In this method, after filling the composition or the like, the viscosity can be reduced during heating and extrusion. Further, the evaporation rate of the organic solvent can be controlled by extruding the composition or the like in a heated atmosphere. After extruding the composition or the like, the filaments may be drawn by passing them through rotating rolls and high-speed air streams.

Wet spinning is a method of extruding a composition or the like from a spinneret having fine holes into a coagulation bath by loading, and removing an organic solvent to form filaments. As the coagulation bath, water and a polar solvent are preferably used. The dry-wet spinning is a method of extruding the composition or the like into an atmosphere, immersing the composition in a coagulation bath, and removing the organic solvent to obtain filaments.

The electrospinning method is a method in which a high voltage is applied to a nozzle filled with a composition or the like, whereby electric charges are accumulated on droplets at the tip of the nozzle, the droplets are widened by repelling each other, and a solution stream is drawn, thereby performing spinning. In this method, filaments having a small diameter can be obtained. Therefore, if the electrospinning method is used, a fine filament having a diameter of several tens of nm to several μm can be obtained.

Among these, as the spinning method in the spinning step in the present invention, a dry spinning method or an electrospinning method is particularly preferably used.

In the spinning step of the present invention, the fiber obtained by spinning may be subjected to a drying treatment, a steam treatment, a hot water treatment, or a combination thereof as necessary before the fiber is calcined.

By calcining the fiber obtained by spinning in the above-mentioned spinning step, the crosslinking reaction proceeds and the organic component such as an organic group is removed, and a metal oxide fiber having excellent strength can be obtained. That is, the method for producing a fiber according to the embodiment of the present invention includes the spinning step and the calcination step of calcining the fiber obtained in the spinning step, when producing the metal compound fiber. In this calcination step, the temperature of calcination is not particularly limited, and is preferably 200 ℃ to 2000 ℃, and more preferably 400 ℃ to 1500 ℃. The calcination method is not particularly limited. Examples of the calcination method include a method of calcination in an air atmosphere; a method of calcining in an inert atmosphere such as nitrogen or argon; a method of calcination in vacuum, and the like.

In the calcination step in the present invention, the obtained metal oxide fiber may be further calcined in a reducing atmosphere such as hydrogen. In addition, in this calcination step, calcination may be performed while applying tension to the fiber obtained by spinning or the metal oxide fiber.

By this method, a continuous and dense metal oxide fiber having an average fiber diameter of 0.01 μm or more and 1000 μm or less can be obtained. The average fiber diameter of the metal oxide fibers is preferably 0.01 μm or more and 1000 μm or less, and more preferably 0.10 μm or more and 200 μm or less. When the average fiber diameter is within the above range, the metal oxide fiber can be produced into a homogeneous fiber without cracks.

The average fiber diameter of the obtained metal oxide fiber was determined by the following method. For example, an adhesive tape is stuck to a cardboard sheet, and a single fiber having a measured fiber diameter is horizontally adhered thereto to prepare a single fiber test piece. The single fiber test piece was observed from above with an electron microscope, and the width of the image was defined as the fiber diameter. The fiber diameter was measured 3 times along the length and recorded as the average. This operation was performed for 20 randomly selected single fibers, and the obtained fiber diameters were averaged and referred to as an average fiber diameter.

Fibers such as metal oxide fibers obtained by spinning a solution of the polyoxometalate or the composition thereof according to the embodiment of the present invention and calcining the fibers obtained by the spinning can be used as composite materials such as photocatalysts, heat insulating materials, heat emitting materials, and fiber-reinforced plastics (FRP). For example, the photocatalyst can be used for a water and seed purification filter or the like. As heat insulating materials and heat releasing materials, they are used in electric furnaces, nuclear fuel rod sheaths, engine turbines for aircraft, heat exchangers, and the like.

(use of Binder for ceramic Molding)

The polyoxometalates according to the embodiment of the present invention are suitably used as an adhesive for ceramic molded bodies. That is, the binder for ceramic molded bodies according to the embodiment of the present invention contains the above-mentioned polyoxometalates. The binder for ceramic molded bodies is a binder for making a ceramic raw material powder containing metal oxide particles and a sintering aid into a moldable paste. A ceramic produced using the polyoxometalate in the binder for a ceramic molded body according to the embodiment of the present invention as a binder can be used as an electronic component. More specifically, the polyoxometalate in the binder for a ceramic molded body can be used as an inorganic binder for producing a green sheet. The green sheet produced by such a method is suitably used for producing electronic components such as multilayer capacitors and ceramic substrates.

Generally, a green sheet is obtained by forming a paste composition containing a ceramic raw material powder, a binder and a solvent into a paper or a sheet and drying the formed sheet. The green sheet is processed and seeded to produce a large number of electronic components.

However, when the binder used in the production of the green sheet is an organic polymer, there is a problem that the electrical characteristics of the electronic component are degraded due to the residual ash content during firing. Further, the green sheet has a problem that the volume shrinkage of the green sheet increases due to decomposition of an organic component during sintering, and as a result, cracks and warpage occur in the green sheet.

In contrast, the polyoxometalates according to the embodiments of the present invention are inorganic polymers having a bond of a metal atom-oxygen atom-metal atom in the main chain. Therefore, when the polyoxometalate is used as a binder, the residual ash content during sintering can be greatly reduced. Further, since the polyoxometalate forms a metal oxide after firing, volume shrinkage of the green sheet can be suppressed.