JP7135851B2 - Water-repellent film-forming composition and water-repellent film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water-repellent film-forming composition and a water-repellent film for forming a water-repellent film on a substrate.

Rainwater or tap water falls on the outer walls and glass of buildings, the bodies of automobiles, mirrors in bathrooms, etc. on a daily basis, leaving water droplets on their surfaces. Since various inorganic salts, microorganisms, and the like are dissolved in rainwater, tap water, and the like, when the water droplets dry, they cause water stains, mold, and the like, which spoils the appearance. In addition, the adhesion of water droplets to the surface of glass or mirror itself affects the transmittance and reflectance of light, thereby reducing visibility.

Therefore, studies have been conducted to suppress adhesion of water droplets by forming a water-repellent film on the surface of solid materials such as metals, ceramics, glass, and resins. Materials having water-repellent surfaces in this way are used in various fields such as glass for buildings and vehicles, bodies for automobiles and trains, cover glass for solar panels, mirrors for bathrooms and panels around kitchens. By doing so, it is possible to improve the appearance and reduce or eliminate the trouble of maintenance.

A solid surface having a contact angle of more than 90° with respect to water is said to be water-repellent. Therefore, it is important to improve water droplet falling property in addition to water repellency.

When the contact angle of a solid surface to water is 150° or more, it is called "super water-repellent." Both become favorable, and the surface becomes excellent in antifouling property. Various methods have been proposed for forming a film exhibiting superhydrophobicity by imitating these plants and combining minute unevenness and a reduction in surface free energy.

For example, in Patent Document 1, a treatment liquid containing a metal alkoxide polycondensate, metal oxide fine particles, and a silane compound having a fluoroalkyl group or an alkyl group is applied to the surface of a substrate, dried, and heated. A method for modifying the surface of the material has been proposed. Specifically, aggregates of metal oxide fine particles are immobilized on a metal oxide matrix, and the surface has a fine uneven structure in which fluoroalkyl groups or alkyl groups exhibiting water repellency are exposed, and a large number of openings are formed on the surface. is a method of forming a porous metal oxide layer having pores of .

Patent Document 2 discloses a super water-repellent film-coated article in which a base material surface is coated with a super water-repellent film. A super water-repellent film-coated article has been proposed in which a part and a non-existing part are mixed, and the projections form unevenness on the film surface of the part where the projections are present.
Specifically, three-dimensionally bonded colloidal silica, an alkylalkoxysilane, and an alkylalkoxysilane containing fluorine are mixed, an acid catalyst containing water is added, and the water-repellent material and the silicon oxide fine particles coexist. A hydrolyzed/condensed product is prepared and used as a dispersion liquid for water repellent treatment, applied to glass by a flow coating method, and allowed to dry naturally to prepare a super water repellent glass substrate.

Patent Document 3 discloses a super water-repellent substrate comprising a substrate, a base film having fine irregularities formed on the surface of the substrate, and a water-repellent coating film formed on the fine irregularities of the base film, A super water-repellent substrate has been proposed in which the surface shape of the water-repellent coating is composed of particulate projections and columnar projections which are higher than the particulate projections when measured from the surface of the substrate.
Specifically, a solution of decamethylcyclopentasiloxane of tetrachlorosilane was prepared as a coating liquid for forming an uneven base film, which is a base film containing silica as a main component. A siloxane solution is prepared as a water repellent agent. Then, the coating liquid for forming the uneven base film is applied to the surface of the windshield glass for automobiles by the flow coating method, and the water-repellent agent is further applied and allowed to stand, and then washed with ethanol to remove the water-repellent agent from the surface. After completely rinsing it off, it is dried naturally to prepare a water-repellent windshield glass.

Patent Document 4 proposes an article coated with a film containing silicon oxide as a main component and having fine irregularities on the surface, wherein the fine irregularities are composed of fine projections and columnar projections. ing. As a production method thereof, it has been reported that a coating having the above-described fine uneven structure can be formed by applying a coating solution in which tetrachlorosilane is dissolved in a solvent containing silicone oil as a main component. Furthermore, as an application example, a decamethylcyclopentasiloxane solution of heptadecafluorooctyltrichlorosilane is applied to the coating film having the fine concave-convex structure by a flow coating method, allowed to stand still, and then washed with ethanol to remove excess silane solution. was completely washed away and dried naturally to obtain a water-repellent glass.

Patent Document 5 discloses a method comprising a base material and a water-repellent transparent coating on the surface of the base material, wherein the water-repellent transparent coating comprises an inorganic oxide fine particle layer containing inorganic oxide fine particles and an overcoat on the inorganic oxide fine particle layer. The surface of the water-repellent transparent coating has an uneven structure, and the average height of the protrusions, the average distance between the protrusions (pitch width), and the ratio of the average height to the average distance between the protrusions are specified. A base material with a water-repellent transparent film has been proposed in which the surface of the projections of the uneven structure is defined by a range and further has fine unevenness.

As a method for preparing the substrate in Patent Document 5, for example, tetraethoxysilane and water are added to (A) a methanol dispersion of alumina fine particles having a specific average particle length and average particle width, and these are reacted. Alumina fine particles are surface-treated and diluted with a solvent to obtain a surface-treated alumina fine particle dispersion, and the surface-treated alumina fine particle dispersion is coated on a substrate and cured to form an inorganic oxide fine particle layer. and (B) a coating solution for forming an overcoat layer, which is prepared by hydrolyzing tridecafluorooctyltrimethoxysilane in alcohol by reacting it with water using an acid catalyst and diluting it with a solvent to adjust the concentration. is applied onto the inorganic oxide fine particle layer and cured by heating to obtain a substrate with a water-repellent transparent film. Further, it is possible to form a primer layer on the substrate before the step (A) and to form a binder layer on the inorganic oxide fine particle layer between the steps (A) and (B). It is proposed to be preferred.

JP-A-11-172455 JP 2005-343016 A WO2003/039856 JP-A-2004-137137 JP 2014-124913 A

However, in the method of Patent Document 1, the molecular weight of the silane compound used for forming the water-repellent film is small. The silane compound may volatilize and be lost from the water-repellent coating.

In the case of Patent Documents 2 and 5, alkoxysilanes are used as the material for forming the water-repellent film. ing. Since a hydrolysis catalyst such as nitric acid or hydrochloric acid is also a condensation catalyst at the same time, hydrolysis and condensation of the alkoxysilanes proceed simultaneously in the coating solution. Therefore, the coating liquid is not necessarily stable, and insoluble solids may precipitate during storage.

In the case of Patent Documents 3 and 4 as well, in the process of forming a water-repellent film, chlorosilanes, which have extremely high reactivity with moisture and substrates, are used as materials, so the stability of the coating solution during storage is high. low.

The present invention has been made in view of the above circumstances, and is chemically stable, has good storage stability, can be used repeatedly, and is easily reproducible. An object of the present invention is to provide a composition for forming a water-repellent film capable of forming a super-water-repellent film.

The present inventors have made intensive studies to achieve the above objects, and as a result, have found that the above problems can be solved by using a polysilazane having a specific structure, leading to the present invention.

（式中、Ｒはそれぞれ同一でも異なっていてもよく、フッ素置換されていてもよい炭素数３～２０の一価炭化水素基を表す。Ｒ^a及びＲ^bはそれぞれ同一でも異なっていてもよく、フッ素置換されていてもよい炭素数１～２０の一価炭化水素基を表す。ｍは１～１００の整数であり、ｎ及びｐはそれぞれ０～１００の整数である。ただし、ｍ、ｎ及びｐの和は４～３００の整数である。）
〔３〕
（ｂ）金属酸化物ナノ粒子が、上記一般式（１）で表されるポリシラザンによって表面処理されていることによりケイ素原子を介してフッ素置換されていてもよい炭素数３～２０の一価炭化水素基を表面に有するものである〔２〕に記載の撥水性被膜形成用組成物。
〔４〕
（ｂ）金属酸化物ナノ粒子が、シリカである〔１〕～〔３〕のいずれかに記載の撥水性被膜形成用組成物。
〔５〕
（ａ）フッ素置換されていてもよい炭素数３～２０の一価炭化水素基がケイ素原子に結合したポリシラザン及び
（ｂ）表面未処理の金属酸化物ナノ粒子、表面にフッ素置換されていてもよい炭素数１～２０の一価炭化水素基を有する金属酸化物ナノ粒子又は表面にアルキルシリル基若しくはアルコキシシリル基を有する金属酸化物ナノ粒子
を含む撥水性被膜。 That is, the present invention provides the following water-repellent film-forming composition and water-repellent film.
[1]
A composition for forming a water-repellent film, comprising the following components (a), (b) and (c).
(a) a polysilazane in which a monovalent hydrocarbon group having 3 to 20 carbon atoms which may be fluorine-substituted is bonded to a silicon atom;
(b) Surface-untreated metal oxide nanoparticles, metal oxide nanoparticles having an optionally fluorine-substituted monovalent hydrocarbon group of 1 to 20 carbon atoms on the surface, or alkylsilyl groups or alkoxysilyl groups on the surface and (c) an aprotic solvent [2]
The composition for forming a water-repellent film according to [1], wherein the component (a) is a polysilazane represented by the following general formula (1).

(In the formula, each R may be the same or different and represents an optionally fluorine-substituted monovalent hydrocarbon group having 3 to 20 carbon atoms. R ^a and R ^b may be the same or different. , represents an optionally fluorine-substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, m is an integer of 1 to 100, and n and p are each an integer of 0 to 100, provided that m, n and the sum of p is an integer from 4 to 300.)
[3]
(b) Metal oxide nanoparticles are surface-treated with polysilazane represented by the above general formula (1), thereby monovalent carbonization having 3 to 20 carbon atoms which may be fluorine-substituted via silicon atoms. The composition for forming a water-repellent film according to [2], which has hydrogen groups on its surface.
[4]
(b) The composition for forming a water-repellent film according to any one of [1] to [3], wherein the metal oxide nanoparticles are silica.
[5]
(a) a polysilazane in which a monovalent hydrocarbon group having 3 to 20 carbon atoms, which may be optionally fluorine-substituted, is bonded to a silicon atom; and (b) surface-untreated metal oxide nanoparticles, the surface of which may be fluorine-substituted. A water-repellent film containing metal oxide nanoparticles having a good monovalent hydrocarbon group having 1 to 20 carbon atoms or metal oxide nanoparticles having an alkylsilyl group or an alkoxysilyl group on the surface.

According to the present invention, a composition for forming a water-repellent film has good storage stability, can be used repeatedly, and can easily form a water-repellent film, especially a super water-repellent film, with good reproducibility. can be obtained. In addition, by using the composition of the present invention, it is possible to obtain a coating having excellent water repellency and water drop resistance and durability.

The composition for forming a water-repellent film of the present invention is
(a) a polysilazane in which a monovalent hydrocarbon group having 3 to 20 carbon atoms which may be fluorine-substituted is bonded to a silicon atom;
(b) Surface-untreated metal oxide nanoparticles, metal oxide nanoparticles having an optionally fluorine-substituted monovalent hydrocarbon group of 1 to 20 carbon atoms on the surface, or alkylsilyl groups or alkoxysilyl groups on the surface and (c) an aprotic solvent.
Each component will be described in detail below.

<(a) Polysilazane>
Polysilazane is a polymer compound having a structure in which silicon atoms and nitrogen atoms are alternately arranged. For example, commercially available perhydropolysilazane is polysilazane in which hydrogen atoms are bonded without organic substituents on silicon atoms, and is a material that exhibits hydrophilicity when a film is formed. On the other hand, since the polysilazane used in the present invention has a monovalent hydrocarbon group with 3 to 20 carbon atoms bonded to the silicon atom, it is possible to form a film with low surface free energy and water repellency. indicates In addition, the surface free energy of the film can be further reduced by substituting fluorine for the monovalent hydrocarbon group.

（式中、Ｒはそれぞれ同一でも異なっていてもよく、フッ素置換されていてもよい炭素数３～２０の一価炭化水素基を表す。Ｒ^a及びＲ^bはそれぞれ同一でも異なっていてもよく、フッ素置換されていてもよい炭素数１～２０の一価炭化水素基を表す。ｍは１～１００の整数であり、ｎ及びｐはそれぞれ０～１００の整数である。ただし、ｍ、ｎ及びｐの和は４～３００の整数である。） Polysilazane used in the present invention is preferably polysilazane represented by the following general formula (1).

(In the formula, each R may be the same or different and represents an optionally fluorine-substituted monovalent hydrocarbon group having 3 to 20 carbon atoms. R ^a and R ^b may be the same or different. , represents an optionally fluorine-substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, m is an integer of 1 to 100, and n and p are each an integer of 0 to 100, provided that m, n and the sum of p is an integer from 4 to 300.)

In the above general formula (1), each R may be the same or different and may be fluorine-substituted. represents a valent hydrocarbon group. Substituent R includes propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group and heptadecyl group. , Octadecyl group, nonadecyl group, linear aliphatic saturated hydrocarbon groups such as eicosyl group; isopropyl group, isobutyl group, 2-butyl group, tert-butyl group, isopentyl group, 2-pentyl group, 3-pentyl group, tert -Branched chain aliphatic saturated hydrocarbon groups such as pentyl group, isohexyl group, 2-ethylhexyl group and isooctyl group; saturated hydrocarbon group; aromatic hydrocarbon group such as phenyl group, tolyl group, xylyl group and mesityl group; aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group and phenylbutyl group; fluorine-substituted aliphatic hydrocarbon groups such as fluoropropyl group, nonafluorohexyl group, tridecafluorooctyl group, heptadecafluorodecyl group; pentafluorophenyl group, 3,5-difluorophenyl group, 3-fluorophenyl group, 4 -fluorophenyl group, 3-trifluoromethylphenyl group, 3,5-bis(trifluoromethyl)phenyl group and other fluorine-substituted aromatic hydrocarbon groups; pentafluorophenylethyl group, pentafluorophenylpropyl group, pentafluorophenyl butyl group, 3,4,5-trifluorophenylpropyl group, 2,4-difluorophenylpropyl group, 3,4-difluorophenylpropyl group, 3,5-difluorophenylpropyl group, 2-fluorophenylethyl group, 2 -fluorophenylpropyl group, 3-fluorophenylethyl group, 3-fluorophenylpropyl group, 4-fluorophenylethyl group, 4-fluorophenylpropyl group, 4-(trifluoromethyl)phenylpropyl group, 3,5-bis Examples thereof include fluorine-substituted aralkyl groups such as (trifluoromethyl)phenylpropyl group. Among these, from the viewpoint of lowering the surface free energy of the film, linear or branched aliphatic saturated monovalent hydrocarbon groups, aliphatic unsaturated monovalent hydrocarbon groups, fluorine-substituted aliphatic saturated monovalent hydrocarbon groups is preferred.

In the above general formula (1), R ^a and R ^b may be the same or different, and may be fluorine-substituted with 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 carbon atom. represents a monovalent hydrocarbon group of ∼5. Examples of the substituents R ^a and R ^b include, in addition to the substituents exemplified for the substituent R, an alkyl group such as a methyl group and an ethyl group, an aliphatic unsaturated monovalent hydrocarbon group such as a vinyl group, and the like. is mentioned. Although the surface free energy of the film increases when these substituents have a low carbon number, it is possible to adjust the solubility and viscosity of the polysilazane to appropriate ranges by introducing these substituents as necessary. can be done.

The polysilazane represented by general formula (1) may not necessarily contain repeating units having substituents ^Ra and ^Rb . However, by having these repeating units, physical properties such as molecular weight, solubility and viscosity of polysilazane can be adjusted within appropriate ranges.

In the above general formula (1), m is an integer of 1-100, preferably 4-50, and n and p are each an integer of 0-100, preferably 0-50. However, the sum of m, n and p is 4-300, preferably 4-100, more preferably 4-50. That is, the polysilazane represented by general formula (1) always contains a repeating unit having a substituent R. Thereby, the surface free energy can be lowered when a coating is formed using the composition of the present invention.

The ratio of m, n and p is not limited, but the ratio of m/(m+n+p) is preferably 0.01-1, more preferably 0.1-1, and still more preferably 0.25-1. If this ratio is less than 0.01, the effect of the substituent R on the surface free energy of the film will be small, and a water-repellent film may not be obtained. , the properties of the film may not be stable.

The weight average molecular weight of polysilazane in terms of polystyrene measured by gel permeation chromatography (hereinafter referred to as "GPC") is preferably 300 to 30,000, more preferably 500 to 10,000. The GPC measurement conditions are as described later.

The amount of component (a) in the composition of the present invention is preferably 0.001 to 50% by mass, more preferably 0.01 to 30% by mass, and still more preferably 0.01 to 10% of the total composition. % by mass. If it is less than 0.001% by mass, the film may become too thin and sufficient water repellency may not be obtained, and if it exceeds 50% by mass, the viscosity of the composition may become too high. As will be described later, when the present composition is prepared while surface-treating component (b) with component (a), the theoretical amount of component (a) to be added depends on the specific surface area and amount of component (b). However, even in that case, it is preferably within the above range.

<(b) Metal oxide nanoparticles>
Metal oxide nanoparticles used in the present invention include silica, alumina, titania, zirconia, zinc oxide, tin oxide, cerium oxide, copper oxide, chromium oxide, cobalt oxide, iron oxide, manganese oxide, nickel oxide, and the like. Examples include nanoparticles containing one or more selected metal oxides. Among these, nanoparticles containing one or more metal oxides selected from silica, alumina, titania, zirconia, zinc oxide, tin oxide, and cerium oxide are preferred, and include silica, alumina, titania, and zirconia. Particular preference is given to fine particles. It is most preferred to use fumed silica, fine particles consisting essentially of silica.

The average primary particle size of the metal oxide nanoparticles is preferably 5 to 200 nm in diameter, more preferably 10 to 150 nm in diameter, still more preferably 10 to 50 nm in diameter. If the particle diameter is less than 5 nm, the film may not have an effective unevenness, while if the particle diameter exceeds 200 nm, the transparency of the film may be impaired. In addition, in the present invention, the value of the average primary particle size is a value measured by a scanning electron microscope (SEM).

In the case of fumed silica, the average primary particle size correlates with the value of the specific surface area that can be measured by the BET method. For example, if the specific surface area is 50 m ² /g, the average primary particle size is about 30 nm, if the specific surface area is 200 m ² /g, the average primary particle size is about 12 nm, and if the specific surface area is 300 m ² /g, the average primary particle size is The particle size is about 7 nm. When fumed silica is used, its specific surface area is preferably 30-500 m ² /g, more preferably 50-350 m ² /g.

Component (b) is a metal oxide nanoparticle whose surface is untreated, or a metal oxide that has been hydrophobized in advance and has a monovalent hydrocarbon group of 1 to 20 carbon atoms that may be fluorine-substituted on its surface. Nanoparticles may also be used. Metal oxide nanoparticles that have been hydrophobized in advance include, for example, metal oxide nanoparticles commercially available under the trade names Aerosil R805, Aerooxide T805, Aerooxide NKT90, Aerooxide AluC805 (manufactured by Nippon Aerosil Co., Ltd.), and the like. , methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, eicosyl group, etc. 1 to 20, preferably 1 to 10 alkyl groups, those having the same substituents as described for R ^a and R ^b of the compound of formula (1), trade names Aerosil R972, Aerosil R974, Aerosil R976, Aerosil RX50, Aerosil RX200, Aerosil RX300, Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd.), HDKH15, HDKH20, HDKH30 (manufactured by Asahi Kasei Wacker Silicone) and other dialkylsilyl groups such as dimethylsilyl groups, trimethylsilyl groups, and triethylsilyl groups , a tert-butyldimethylsilyl group, a triisobutylsilyl group, a triisopropylsilyl group, and the like, which are preferably surface-treated with a trialkylsilyl group having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms. can.

Also, as the component (b), metal oxide nanoparticles having alkoxysilyl groups on the surface of the metal oxide nanoparticles may be used. When alkoxysilyl groups are present on the surface of the metal oxide nanoparticles, the alkoxysilyl groups on the surface of the metal oxide nanoparticles and the polysilazane of component (a) above form covalent bonds through a hydrolytic condensation reaction. increased durability.

As the alkoxysilyl group, the number of carbon atoms in the alkyl group of the alkoxy group is preferably 1 to 6, more preferably 1 to 3. Specifically, trimethoxysilyl, triethoxysilyl, tripropoxy Trialkoxysilyl groups such as silyl group, triisopropoxysilyl group, diisopropoxymethoxysilyl group and dimethoxyisopropoxysilyl group; dialkoxysilyl groups such as dimethoxymethylsilyl group and diethoxymethylsilyl group; methoxydimethylsilyl group; monoalkoxysilyl groups such as ethoxydimethylsilyl group, isopropoxydimethylsilyl group, methoxydiethylsilyl group, methoxydipropylsilyl group, methoxydiisopropylsilyl group;

There are various methods for introducing alkoxysilyl groups to the surface of metal oxide nanoparticles, but a method of reacting hydroxyl groups on the surfaces of untreated metal oxide nanoparticles with an alkoxysilylating agent is preferred. The alkoxysilylating agent includes alkoxysilanes such as tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane and methyltriethoxysilane, and alkoxysilane oligomers such as tetramethoxysilane oligomer, tetraethoxysilane oligomer and methyltrimethoxysilane oligomer. alkoxyhalosilanes such as chlorotrimethoxysilane, chlorotriethoxysilane, chlorodimethoxymethylsilane and chlorodiethoxymethylsilane; alkoxysilazanes such as trimethoxysilyldimethylamine and trimethoxysilyldiethylamine; 1-trimethoxysilyloxy-1 -methoxypropene, 1-trimethoxysilyloxy-1-ethoxypropene, 1-trimethoxysilyloxy-1-butoxypropene, 1-trimethoxysilyloxy-1-methoxy-2-methylpropene, 1-triethoxysilyloxy -1-ethoxypropene, 1-dimethoxymethylsilyloxy-1-methoxypropene, 1-dimethoxymethylsilyloxy-1-ethoxypropene, 1-dimethoxymethylsilyloxy-1-octyloxypropene, 1-diethoxymethylsilyloxy -Alkoxysilyl ketene acetals such as 1-methoxypropene, 1-diethoxymethylsilyloxy-1-ethoxypropene, 1-methoxydimethylsilyloxy-1-methoxypropene, 1-methoxydimethylsilyloxy-1-ethoxypropene, etc. mentioned. Among them, alkoxysilylketene acetals are preferred because they are neutral alkoxysilylating agents and can easily remove by-products.

From the viewpoint of the dispersibility of the metal oxide nanoparticles, the amount of the alkoxysilyl group introduced is preferably 0.1 to 1, where the saturated introduction amount with respect to the metal oxide nanoparticles used as the component (b) is 1. , more preferably in the range of 0.3 to 1, more preferably in the range of 0.5 to 1.
To determine the saturated introduction amount of alkoxysilyl groups, for example, surface-untreated metal oxide nanoparticles and the above alkoxysilylating agent are mixed at a constant ratio, and the consumed amount (or residual amount) of the alkoxysilylating agent is determined. ) can be determined by gas chromatography. The amount of alkoxysilyl groups introduced when the alkoxysilylating agent is not consumed even though it is in contact with the metal oxide nanoparticles is the saturated introduction amount.

When the surface of the metal oxide nanoparticles is alkoxysilylated using the above alkoxysilylating agent, the alkoxysilylating agent and the metal oxide nanoparticles may be brought into contact with each other in the presence or absence of a solvent. .
The solvent that can be used is not particularly limited as long as it is an aprotic solvent that does not react with the alkoxysilylating agent. Hydrogen solvent: Hydrocarbon mixed solvent such as isoparaffin solvent and naphthene solvent: Ketone such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Nitrile such as acetonitrile, propionitrile and benzonitrile; Dimethylformamide, dimethylacetamide, N-methylpyrrolidone amides such as; ether solvents such as diethyl ether, dipropyl ether, diisopropyl ether, tetrahydrofuran, cyclopentyl methyl ether, dibutyl ether, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether; ethyl acetate, propyl acetate, acetic acid Ester solvents such as isopropyl, butyl acetate, isobutyl acetate, methoxyethyl acetate, and hexyl acetate, and the like are included. One of these solvents can be used alone, or two or more of them can be used in combination. Alkoxysilylation can also be carried out without a solvent by using an excessive amount of a liquid alkoxysilylating agent.

In addition, the silanol remaining in the untreated metal oxide nanoparticles or the metal oxide nanoparticles having a monovalent hydrocarbon group, an alkylsilyl group, or an alkoxysilyl group is surface-treated with polysilazane as the component (a). Therefore, it is possible to use one in which a substituent R, R ^a , or R ^b is introduced on the surface via a silicon atom. This improves the compatibility with polysilazane of the component (a).

When untreated metal oxide nanoparticles are surface-treated with polysilazane as the component (a), the amount of polysilazane to be blended is determined by the following formula (I): The minimum area to be added) can be calculated, and the minimum addition amount of polysilazane calculated by the following formula (II) can be used as a guideline. However, especially when the substituent of polysilazane is bulky, the surface treatment may be completed even if the addition amount is less than the calculated minimum addition amount. In the present invention, the amount of polysilazane to be added when surface-treating the metal oxide nanoparticles with polysilazane is preferably at least the minimum addition amount, and more preferably, from the viewpoint of obtaining good water repellency and water drop resistance. It is 1.3 times or more, more preferably 2 times or more.

The method of surface-treating the metal oxide nanoparticles with polysilazane is not particularly limited, and the metal oxide nanoparticles may be mixed with polysilazane and surface-treated by a known method. It is preferable to use a method of dispersing the metal oxide nanoparticles in the solvent (c) described below, and then adding and mixing the polysilazane.

The amount of component (b) in the composition of the present invention is preferably changed depending on the type of polysilazane of component (a), preferably 0.001 to 30% by mass of the entire composition, more preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass. If it exceeds 30% by mass, the viscosity of the composition becomes too high and the composition may not be uniform. If it is less than 0.001% by mass, the film may become too thin and sufficient water repellency may not be obtained.

<(c) Aprotic Solvent>
As will be described later, the composition for forming a water-repellent film of the present invention can be used to form a film on a substrate by various coating methods. A solvent is added to the composition.

Solvents that can be used are not particularly limited as long as they are aprotic solvents that do not react with the polysilazane represented by general formula (1). Examples include hexane, heptane, octane, isooctane, nonane, decane, toluene, xylene, Hydrocarbon solvents such as mesitylene; hydrocarbon mixed solvents such as isoparaffin solvents and naphthene solvents; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; nitriles such as acetonitrile, propionitrile and benzonitrile; amides such as N-methylpyrrolidone; ether solvents such as diethyl ether, dipropyl ether, diisopropyl ether, tetrahydrofuran, cyclopentyl methyl ether, dibutyl ether, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether; ethyl acetate, Examples thereof include ester solvents such as propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, methoxyethyl acetate, and hexyl acetate. These solvents can be used singly or in combination of two or more.

The amount of the component (c) solvent blended in the composition for forming a water-repellent film of the present invention is arbitrarily changed according to the viscosity of the component (a) polysilazane, the coating method, and the required film thickness. However, it is preferably 10 to 99.9% by mass, more preferably 30 to 99.5% by mass, still more preferably 50 to 99.5% by mass of the entire composition. If it is less than 10% by mass, the viscosity of the composition becomes too high, and the solubility (dispersibility) of components (a) and (b) may become insufficient. If it exceeds 99.9% by mass, the film may become too thin and sufficient water repellency may not be obtained.

<Other ingredients>
The composition of the present invention may contain additives such as pigments, dyes, dispersants, viscosity modifiers, leveling agents, etc., and organic groups on the surface, as long as the amount is small enough not to impair the effects of the present invention. It may contain metal oxide nanoparticles other than the component (b) that does not have

<Composition for forming a water-repellent film>
The composition for forming a water-repellent film of the present invention is prepared by mixing components (a), (b), (c) and, if necessary, other components, and adding components (a) and (b) to (c ) are obtained by dissolving or dispersing them in a solvent. Any mixing method can be used, and for example, a mixing device such as a stirrer or various mixers can be used. A method of applying ultrasonic waves is also effective.

When untreated metal oxide nanoparticles or metal oxide nanoparticles having a monovalent hydrocarbon group, alkylsilyl group or alkoxysilyl group on the surface are used after being surface-treated with component (a) polysilazane, , After surface treatment in advance, the remaining component (a), surface-treated metal oxide nanoparticles, and component (c) may be mixed, or a sufficient amount of component (a) and untreated or metal oxide nanoparticles having a monovalent hydrocarbon group, an alkylsilyl group or an alkoxysilyl group on the surface are mixed with the component (c), and the composition is obtained by performing surface treatment while mixing and dispersing. can be

The composition for forming a water-repellent film of the present invention thus obtained is a uniform solution or dispersion containing no precipitates or gels, and is chemically stable, so that it decomposes polysilazanes such as water and methanol. As long as protic compounds are not mixed, insoluble matter will not be irreversibly generated to result in a heterogeneous mixture. Therefore, it can be used for a long period of time without any change in performance. In addition, since polysilazane acts as a hygroscopic agent, deterioration of the composition can be prevented even when a small amount of moisture is mixed.

<Base material>
The composition for forming a water-repellent film of the present invention can be used for various substrates because the component (a), polysilazane, has excellent adhesion to substrate surfaces. For example, it is possible to form the water-repellent film of the present invention by applying it to a base material such as metal, resin, glass, ceramics, or a composite material thereof.

<Application method>
As a method for applying the composition for forming a water-repellent film of the present invention, it is necessary to use a method that allows the composition to uniformly wet the substrate surface. Specific methods include, for example, a flow coating method, a dip coating method, a curtain coating method, a spin coating method, a spray coating method and a bar coating method. An appropriate coating method may be selected according to the type and shape of the substrate and the required film thickness.

<Water repellent coating>
The water-repellent coating of the present invention can be obtained in a simple manner by applying the composition for forming a water-repellent coating of the present invention to the surface of a substrate and then removing the aprotic solvent as the component (c). can. As a method for removing the solvent, volatilization under normal pressure or reduced pressure is generally used. At this time, it is also possible to shorten the time by heating.

Part or all of the polysilazane can be converted to polysiloxane by applying water to the film surface during or after removing the aprotic solvent. This operation is preferable because it improves the durability of the coating. As a method for applying water, any method can be used, such as standing in an environment where water vapor exists at about 10 to 95% RH, immersing in water, or the like.

The thickness of the water-repellent film of the present invention is arbitrary, but generally the average thickness is preferably 10 nm to 50 μm, more preferably 50 nm to 10 μm. If the thickness is less than 10 nm, the film may be too thin to obtain sufficient water repellency. If it exceeds 50 μm, cracks may occur when the solvent is removed.

The water-repellent film of the present invention has both high water repellency and water drop resistance. The contact angle with water, which is an index of the water repellency of the film, is typically 150° or more, indicating super water repellency, and is preferably 160° or more. In addition, the falling angle of water (the angle at which the droplet starts to fall), which is an index of the falling property of the water droplet, varies depending on the size of the water droplet, but is typically 5° or less, preferably 3° or less, It is more preferably 1° or less. In addition, a film having a contact angle of 160° or more is preferable because the speed at which water falls is high.

Synthesis examples, examples of the present invention, and comparative examples are described below, but the present invention is not limited to these examples.

[Synthesis Example 1] Synthesis of octylpolysilazane The inside of a 1 L four-necked glass flask equipped with a stirrer, a gas feed tube, a thermometer, and a reflux condenser was replaced with nitrogen, and nitrogen gas was introduced into the open end of the upper part of the reflux condenser. 309.6 g (1.25 mol) of octyltrichlorosilane and 500 mL of toluene were charged and stirred to obtain a homogeneous solution. While stirring the contents at room temperature, ammonia gas was fed into the solution through the feed tube at a rate of about 0.62 mol/hour. Ammonia feed was continued for 7.1 hours while cooling the contents so that the temperature did not exceed 40°C. After that, the feed of ammonia was stopped, and nitrogen gas was blown through the feed pipe at a rate of 0.5 L/min for 6 hours to purge excess ammonia gas. The resulting white solid was separated by filtration through a membrane filter to obtain a colorless and transparent solution. This solution was concentrated under reduced pressure and vacuum-dried at room temperature to obtain 142.8 g of cloudy oily octylpolysilazane.

The polystyrene equivalent molecular weight by GPC was 2,420 for the weight average molecular weight and 1,900 for the number average molecular weight. In addition, the measurement conditions of GPC are as follows.
[GPC conditions]
Apparatus: Prominence GPC system (manufactured by Shimadzu Corporation)
Column: LF-404 (4.6 mm × 250 mm) (manufactured by Shodex) × 2
Eluent: Tetrahydrofuran (THF)
Flow rate: 0.35ml/min
Detector: RI
Column constant temperature bath temperature: 40°C
Reference material: polystyrene

When infrared absorption spectrum (FT-IR) was measured, 893 cm ^-1 (Si—N—Si), 1152 cm ^-1 (NH), 2853 cm ^-1 , 2920 cm ^-1 (CH), 3384 cm ^-1 Absorption was observed at (N—H), supporting the production of the desired octylpolysilazane.

[Synthesis Example 2] Synthesis of decylpolysilazane Decylpolysilazane was obtained as a white oil in the same manner as in Synthesis Example 1, except that 344.6 g (1.25 mol) of decyltrichlorosilane was used instead of octyltrichlorosilane. .
The weight average molecular weight and the number average molecular weight by GPC were 2,970 and 2,230, respectively.

[Synthesis Example 3] Synthesis of hexylpolysilazane In the same manner as in Synthesis Example 1 except that 272.5 g (1.25 mol) of hexyltrichlorosilane was used instead of octyltrichlorosilane and 750 mL of toluene was used, hexylpolysilazane was prepared. Obtained as a white oil.
The weight average molecular weight by GPC was 1,250, and the number average molecular weight was 1,130.

[Synthesis Example 4] Synthesis of propylpolysilazane Same as Synthesis Example 1 except that 221.9 g (1.25 mol) of propyltrichlorosilane was used instead of octyltrichlorosilane, and 1125 mL of cyclopentylmethyl ether was used instead of toluene. On drying, the propylpolysilazane was obtained as a white oil.
The weight average molecular weight by GPC was 890, and the number average molecular weight was 770.

[Synthesis Example 5] Synthesis of (tridecafluorooctyl)(trifluoropropyl)polysilazane The inside of a 300 mL four-necked glass flask equipped with a stirrer, gas feed tube, thermometer and reflux condenser was replaced with nitrogen, 3,3,4,4,5,5,6,6,7,7,8,8,8-trideca was added while nitrogen gas was passed through the open end of the upper portion of the reflux condenser to prevent air from entering. 54.2 g (112.5 mmol) of fluorooctyltrichlorosilane and 8.68 g (37.5 mmol) of 3,3,3-trifluoropropyltrichlorosilane and 135 mL of cyclopentyl methyl ether were charged and stirred to form a uniform solution. Obtained. While stirring the contents at room temperature, ammonia gas was fed into the solution through a feed tube at a rate of about 124 millimoles/hour. Ammonia feed was continued for 4.8 hours while cooling the contents so that the temperature did not exceed 40°C. After that, the feed of ammonia was stopped, and nitrogen gas was blown through the feed pipe at a rate of 0.15 L/min for 6 hours to purge excess ammonia gas. The resulting white solid was separated by filtration through a membrane filter to obtain a colorless and transparent solution. This solution was concentrated under reduced pressure and vacuum-dried at room temperature to obtain 39.3 g of a cloudy oil.

The polystyrene equivalent molecular weight by GPC was 2,750 for the weight average molecular weight and 2,500 for the number average molecular weight.
When infrared absorption spectrum (FT-IR) was measured, 898 cm ^-1 (Si-N-Si), 1141 cm ^-1 (C-F), 1183 cm ^-1 (N-H), 2946 cm ^-1 (C-H ), absorption was observed at 3394 cm ⁻¹ (N—H), supporting the formation of the desired (tridecafluorooctyl)(trifluoropropyl)polysilazane.

[Synthesis Example 6] Synthesis of tridecafluorooctylpolysilazane The inside of a 200 mL four-necked glass flask equipped with a stirrer, gas feed tube, thermometer, and reflux condenser was purged with nitrogen, and the open end of the upper part of the reflux condenser was replaced with nitrogen. 48.2 g of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltrichlorosilane was passed through with nitrogen gas to prevent contamination with outside air. (100 mmol) and 90 mL of meta-xylene hexafluoride were charged and stirred to obtain a uniform solution. While stirring the contents at room temperature, ammonia gas was fed into the solution through a feed tube at a rate of about 79 millimoles/hour. Ammonia feed was continued for 5.5 hours while cooling the contents so that the temperature did not exceed 40°C. After that, the feed of ammonia was stopped, and nitrogen gas was blown through the feed pipe at a rate of 0.15 L/min for 2 hours to purge excess ammonia gas. The resulting white solid was separated by filtration through a membrane filter to obtain a colorless and transparent solution. This solution was concentrated under reduced pressure and vacuum-dried at room temperature to obtain 25.4 g of a cloudy oily substance.

The polystyrene equivalent molecular weight by GPC was 2,840 for the weight average molecular weight and 2,680 for the number average molecular weight.
When the infrared absorption spectrum (FT-IR) was measured, 932 cm ^-1 (Si-N-Si), 1141 cm ^-1 (C-F), 1182 cm ^-1 (N-H), 2945 cm ^-1 (C-H ), absorption was observed at 3394 cm ^-1 (N--H), supporting the production of the desired tridecafluorooctylpolysilazane.

[Synthesis Example 7] Synthesis of hexyl(dimethyl)polysilazane The inside of a 500 mL four-necked glass flask equipped with a stirrer, gas feed tube, thermometer, and reflux condenser was purged with nitrogen, and the open end of the upper part of the reflux condenser was replaced with nitrogen. 32.9 g (150 millimoles) of hexyltrichlorosilane, 6.5 g (50 millimoles) of dimethyldichlorosilane, and 165 mL of toluene as a solvent were charged and stirred to uniform A clear solution was obtained. While stirring the contents at room temperature, ammonia gas was fed into the solution through a feed tube at a rate of about 150 millimoles/hour. Ammonia feed was continued for 6 hours while cooling the contents so that the temperature did not exceed 40°C. After that, the feed of ammonia was stopped, and nitrogen gas was blown through the feed pipe at a rate of 0.15 L/min for 2 hours to purge excess ammonia gas. The resulting white solid was separated by filtration through a membrane filter to obtain a colorless and transparent solution. This solution was concentrated under reduced pressure and vacuum dried at room temperature to obtain 18.9 g of a colorless oil.

The polystyrene equivalent molecular weight by GPC was 1574 in weight average molecular weight and 1144 in number average molecular weight.
Measurement of infrared absorption spectrum (FT-IR) revealed 900 cm ^-1 , 1153 cm ^-1 , (Si—N—Si), 1459 cm ^-1 , 2853 cm ^-1 (C—H), 3389 cm ^-1 (N—H ) was observed, supporting the formation of the desired polysilazane.

[Synthesis Example 8] Preparation of silica particle dispersion having trimethoxysilyl groups on the surface Fumed silica (specific surface area: 205 m ² /g, trade name: Rheolosil QS-102, manufactured by Tosoh Corporation) was added to a glass container with a resin cap5. 00 g was weighed, 56.25 g of cyclopentyl methyl ether and 1.25 g of 1-trimethoxysilyloxy-1-ethoxypropene were added, and the mixture was irradiated with ultrasonic waves for 1 hour with occasional shaking to uniformly disperse the fumed silica. A white translucent and stable dispersion was obtained, and GC measurement of the dispersion showed that 1-trimethoxysilyloxy-1-ethoxypropene disappeared and that a volatile compound having a trimethoxysilyl group was produced. Therefore, it was determined that a trimethoxysilyl group had been introduced onto the silica surface.

[Example 1]
Weigh 2 g of fumed silica (specific surface area: 205 m ² /g, product name: Rheolosil QS-102, manufactured by Tosoh) in a glass container with a resin cap, add 77 g of cyclopentyl methyl ether and 20 g of dipropylene glycol dimethyl ether, and leave for more than 30 minutes. Sonication was applied to disperse the fumed silica. 1 g of the octylpolysilazane obtained in Synthesis Example 1 was added, and ultrasonic waves were applied for an additional 15 minutes to obtain a translucent white composition for forming a water-repellent film. This composition was stable for more than one month at room temperature under closed conditions.

Next, this composition was used as a coating liquid and coated on a soda glass substrate (manufactured by Matsunami Glass Co., Ltd.) using a bar coater so that the film thickness after drying was about 1 μm. Thereafter, the solvent was volatilized from the coating film in an environment of 25° C. and 50% RH to form a water-repellent film on the glass substrate.

<Evaluation of water-repellent coating>
Using a contact angle meter (DMs-401) manufactured by Kyowa Interface Science for the formed water-repellent film, the contact angle (10 μL) and the falling angle (20 μL) of pure water on the film surface under the conditions of 25 ° C. and 50% RH. was measured, the contact angle was 163° and the sliding angle was 1°. It was found that a water-repellent film was formed which exhibits super water-repellency and is extremely resistant to water droplets falling off.

Next, the soda glass substrate on which the water-repellent film was formed as described above was immersed in pure water at 25°C for 1 hour, and then the contact angle and the falling angle were measured. Met.

Further, the glass substrate was washed with warm water using a dishwasher NP-TCM4 (manufactured by Panasonic) for 1 hour, and then the contact angle and the falling angle were measured. rice field. It was judged that a durable water-repellent film was formed without any deterioration in performance due to washing with water.
Table 1 shows the measurement results of the compounding amount, stability, film thickness, contact angle and sliding angle of the composition.

[Example 2]
A composition for forming a water-repellent film was obtained in the same manner as in Example 1, except that the coating film thickness by the bar coater was changed to the film thickness shown in Table 1.
When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 1, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed. Table 1 shows the measurement results of the compounding amount, stability, film thickness, contact angle and sliding angle of the composition.

[Example 3]
A composition for forming a water-repellent film was obtained in the same manner as in Example 1, except that the amounts of fumed silica and octylpolysilazane added were 1.5 g each.
When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 1, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed. Table 1 shows the measurement results of the compounding amount, stability, film thickness, contact angle and sliding angle of the composition.

[Comparative Example 1]
A composition for forming a water-repellent film was obtained in the same manner as in Example 1, except that the amounts of fumed silica and octylpolysilazane added were changed as shown in Table 1.
A water-repellent film was formed on the same glass substrate as in Example 1 using the obtained composition. Table 1 shows the measurement results of the compounding amount, stability, film thickness, contact angle and sliding angle of the composition.
The coating film obtained in Comparative Example 1, in which no fumed silica is added, does not become super water-repellent.

[Examples 4-6]
A composition for forming a water-repellent film was obtained in the same manner as in Example 1, except that the type of polysilazane to be added was changed to those shown in Table 2.
When the obtained composition was used to form a water-repellent film on the same glass substrate as in Example 1, the water-repellent film exhibited super water-repellency and had excellent water drop resistance. Table 2 shows the measurement results of the blending amount, stability, film thickness, contact angle and sliding angle of the composition.

[Example 7]
0.9 g of hydrophobic fumed silica surface-modified with a trimethylsilyl group (specific surface area: 145 m ² /g, trade name: Aerosil RX200, manufactured by Nippon Aerosil Co., Ltd.) was weighed into a glass container with a resin cap, and 30% of cyclopentyl methyl ether was added. .8 g and 8.0 g of dipropylene glycol dimethyl ether were added and mixed for 1 minute with a rotation/revolution mixer to disperse the surface-modified fumed silica. 0.3 g of the octylpolysilazane obtained in Synthesis Example 1 was added and mixed for another 5 minutes using a rotation/revolution mixer to obtain a translucent white water-repellent film-forming composition. This composition was stable for more than one month at room temperature under closed conditions.

Next, this composition was used as a coating liquid and coated on a soda glass substrate (manufactured by Matsunami Glass Co., Ltd.) using a bar coater so that the film thickness after drying was about 1 μm. Thereafter, the solvent was volatilized from the coating film in an environment of 25° C. and 50% RH to form a water-repellent film on the glass substrate.

<Evaluation of water-repellent coating>
Using a contact angle meter (DMs-401) manufactured by Kyowa Interface Science for the formed water-repellent film, the contact angle (10 μL) and the falling angle (20 μL) of pure water on the film surface under the conditions of 25 ° C. and 50% RH. was measured, the contact angle was 163° and the sliding angle was 1°. It was found that a water-repellent film was formed which exhibits super water-repellency and is extremely resistant to water droplets falling off.

[Example 8]
A composition for forming a water-repellent film was obtained in the same manner as in Example 7 except that the polysilazane to be added was changed to the (tridecafluorooctyl)(trifluoropropyl)polysilazane obtained in Synthesis Example 5.
When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 7, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed.

[Example 9]
A composition for forming a water-repellent film was prepared in the same manner as in Example 7, except that the polysilazane to be added was changed to the tridecafluorooctylpolysilazane obtained in Synthesis Example 6, and 38.8 g of meta-xylene hexafluoride was used as the solvent. got
When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 7, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed.

Table 3 shows the measurement results of the blending amount, stability, film thickness, contact angle and sliding angle of the compositions of Examples 7-9.

[Example 10]
0.18 g of fumed silica (specific surface area: 205 m ² /g, product name: Rheolosil QS-102, manufactured by Tosoh) was weighed into a glass container with a resin cap, followed by 6.10 g of cyclopentyl methyl ether and 1.60 g of dipropylene glycol dimethyl ether. . Subsequently, a 50% by mass cyclopentyl methyl ether solution containing 0.06 g of the octylpolysilazane obtained in Synthesis Example 1 was added, and the mixture was further irradiated with ultrasonic waves for 15 minutes to obtain a translucent white water-repellent film-forming composition. Obtained. This composition was stable for more than one month at room temperature under closed conditions. The method of preparing the composition of this example is described as Method A.

Next, this composition was used as a coating liquid and coated on a soda glass substrate (manufactured by Matsunami Glass Co., Ltd.) using a bar coater so that the film thickness after drying was about 1 μm. Thereafter, the solvent was volatilized from the coating film in an environment of 25° C. and 50% RH to form a water-repellent film on the glass substrate.

<Evaluation of water-repellent coating>
Using a contact angle meter (DMs-401) manufactured by Kyowa Interface Science for the formed water-repellent film, the contact angle (10 μL) and the falling angle (20 μL) of pure water on the film surface under the conditions of 25 ° C. and 50% RH. was measured, the contact angle was 161° and the sliding angle was 1°. It was found that a water-repellent film was formed which exhibits super water-repellency and is extremely resistant to water droplets falling off.

Further, the glass substrate was washed with hot water using a dishwasher NP-TCM4 (manufactured by Panasonic) for 1 hour, and then the contact angle and the falling angle were measured. rice field. It was judged that a durable water-repellent film was formed without any deterioration in performance due to washing with water.

Further, when the total light transmittance and haze of the soda glass substrate on which the water-repellent film was formed by the above method were measured using a haze meter (HZ-V3) manufactured by Suga Test Instruments, the total light transmittance was 92.7%. The haze was 0.8%, indicating that the film had high transparency.
Table 4 shows the blending amount of the composition and the measurement results of contact angle, falling angle, total light transmittance and haze.

[Examples 11 to 13]
A composition for forming a water-repellent film was obtained by Method A in the same manner as in Example 10, except that the amount of the composition was changed as shown in Table 4.
When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 10, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed. Table 4 shows the blending amount of the composition and the measurement results of contact angle, falling angle, total light transmittance and haze.

[Comparative Example 2]
A composition for forming a water-repellent film was obtained with the composition shown in Table 4 without adding fumed silica and 1-trimethoxysilyloxy-1-ethoxypropene.
A water-repellent film was formed on the same glass substrate as in Example 10 using the resulting composition. Table 4 shows the measurement results of the blending amount of the composition, the contact angle and the falling angle.
In Comparative Example 2, in which no fumed silica was added, a water-repellent coating film was obtained, but the coating film did not become super water-repellent.

※１ 組成物中のシクロペンチルメチルエーテル全量

*1 Total amount of cyclopentyl methyl ether in the composition

[Example 14]
1.50 g of the silica particle dispersion having a trimethoxysilyl group obtained in Synthesis Example 8 was weighed into a glass container with a resin cap, and 4.62 g of cyclopentyl methyl ether, 1.02 g of dipropylene glycol dimethyl ether, and Synthesis Example 1 were added. A 25% by mass dipropylene glycol dimethyl ether solution containing 0.06 g of the octylpolysilazane obtained in 1. was added and mixed for 1 minute to obtain a translucent white water-repellent film-forming composition. This composition was stable for more than one month at room temperature under closed conditions. The method of preparing the composition of this example is described as Method B.

When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 10, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed. Table 5 shows the blending amount of the composition and the measurement results of contact angle, falling angle, total light transmittance and haze.

[Example 15]
A composition for forming a water-repellent film was obtained by method B in the same manner as in Example 14, except that the amount of the composition was changed as shown in Table 5.
When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 14, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed. Table 5 shows the blending amount of the composition and the measurement results of contact angle, falling angle, total light transmittance and haze.

※２ 合成例８で用いたフュームドシリカと１－トリメトキシシリルオキシ－１－エトキシプロペンとしての配合量
※３ 組成物中のジプロピレングリコールジメチルエーテル全量

*2 Amount of fumed silica and 1-trimethoxysilyloxy-1-ethoxypropene used in Synthesis Example 8 *3 Total amount of dipropylene glycol dimethyl ether in the composition

[Examples 16-18]
A composition for forming a water-repellent film was obtained by Method A or Method B in the same manner as in Example 10 or Example 14, except that the type of polysilazane to be added and the amount of the composition were changed as shown in Table 6. .
When the obtained composition was used to form a water-repellent coating on the same glass substrate as in Example 1, a water-repellent coating exhibiting super water-repellency and having extremely good drop-off properties was formed. Table 6 shows the blending amount of the composition and the measurement results of contact angle, falling angle, total light transmittance and haze.

※１ 組成物中のシクロペンチルメチルエーテル全量
※３ 組成物中のジプロピレングリコールジメチルエーテル全量

*1 Total amount of cyclopentyl methyl ether in the composition *3 Total amount of dipropylene glycol dimethyl ether in the composition

Claims (5)

A composition for forming a water-repellent film, comprising the following components (a), (b) and (c).
(a) a polysilazane represented by the following general formula (1) ;

(In the formula, each R may be the same or different and represents a monovalent hydrocarbon group having 3 to 20 carbon atoms. R ^a and R ^b may each be the same or different and represents a monovalent hydrocarbon group, m is an integer of 1 to 100, n and p are each an integer of 0 to 100, provided that the sum of m, n and p is an integer of 4 to 300.)
(b) Surface-untreated metal oxide nanoparticles, metal oxide nanoparticles having an optionally fluorine-substituted monovalent hydrocarbon group of 1 to 20 carbon atoms on the surface, or alkylsilyl groups or alkoxysilyl groups on the surface and (c) an aprotic solvent The blending amount of components (a) to (c) is 0.001 to 50% by mass of component (a), 0.001 to 30% by mass of component (b), and 10 to 99% of component (c), based on the total composition. The composition for forming a water-repellent film according to claim 1, which is a mixture of components (a) to (c) having a content of 0.9% by mass. (b) The metal oxide nanoparticles are surface-treated with the polysilazane represented by the general formula (1), so that they have monovalent hydrocarbon groups with 3 to 20 carbon atoms on their surface via silicon atoms. 3. The composition for forming a water-repellent film according to claim 1 or 2, which is a (b) The composition for forming a water-repellent film according to any one of claims 1 to 3, wherein the metal oxide nanoparticles are silica. (a) a polysilazane represented by the following general formula (1) and

(In the formula, each R may be the same or different and represents a monovalent hydrocarbon group having 3 to 20 carbon atoms. R ^a and R ^b may each be the same or different and represents a monovalent hydrocarbon group, m is an integer of 1 to 100, n and p are each an integer of 0 to 100, provided that the sum of m, n and p is an integer of 4 to 300.)
(b) Surface-untreated metal oxide nanoparticles, metal oxide nanoparticles having an optionally fluorine-substituted monovalent hydrocarbon group of 1 to 20 carbon atoms on the surface, or alkylsilyl groups or alkoxysilyl groups on the surface A water-repellent coating containing metal oxide nanoparticles having