JP4503086B2 - Superhydrophobic powder, structure having superhydrophobic surface using the same, and production method thereof - Google Patents

Description

  The present invention has a basic structure of an aggregate of silica-based nanofibers, a superhydrophobic powder in which a hydrophobic group is chemically bonded to silica, and a structure having a superhydrophobic surface using the same , And their manufacturing method.

  It is defined as superhydrophobic when a water droplet contacts with a solid surface and the contact angle of the water droplet is 150 ° or more. The range where the contact angle is 70 to 150 ° is defined as hydrophobic. In general, hydrophobicity is expressed by covering a surface with molecular residues having a low surface tension, but superhydrophobicity is difficult to express only with molecular residues having a low surface tension.

  On the other hand, many organisms in the natural world show superhydrophobicity. For example, leaves such as lotus, rice and cabbage have super hydrophobicity (super water repellency) that completely repels water droplets. For example, it is known that the superhydrophobicity of a lotus leaf is closely related to the surface structure of the leaf. That is, the surface layer is formed while the nanofibers are spread over the entire surface, and micron-sized protrusions such as nanofiber aggregates are formed on the outermost surface layer at a certain distance. It is known that hydrophobic wax exists on the surface. This suggests that the control of the surface roughness, that is, the surface structure / shape in the nano-dimension is the most important for developing the superhydrophobicity.

  The structural principle of superhydrophobic expression, also referred to as the effect of lotus, has become a guideline for the development of many artificial lotus-like structural design methods. I came. For example, it has been reported that the contact angle is increased to 170 ° or more by regularly arranging the carbon nanotubes on the surface of the substrate (see, for example, Non-Patent Document 1). In addition, it has been reported that polypyrrole nanofibers are grown on a platinum-coated silicon surface by an electrochemical process to increase the surface contact angle to 170 ° or more (for example, see Non-Patent Document 2). In addition, after forming a zinc oxide nanocrystal seeds film on the surface of the glass substrate at a temperature of 400 ° C. or higher, an infinite number of rod-shaped zinc oxide nanofibers are grown on the glass substrate surface. It is expressed (see, for example, Non-Patent Document 3).

  As a simple method, for example, a certain poor solvent is added to a solution of polypropylene, and it is cast on the surface of a substrate, and the temperature is adjusted, thereby forming a network structure composed of polypropylene nanoparticles, and thereby a contact angle. Has been reported to be increased to 160 ° (for example, see Non-Patent Document 4). In addition, a glass composed of oxides of silicon, boron, and sodium has a phase separation structure, and it is further etched by chemical treatment to induce a concavo-convex structure on the surface, and finally a fluorine compound is applied to the surface. Superhydrophobicity can be expressed by reacting (see, for example, Patent Document 1). Furthermore, after producing a laminated film of polyarylamine and polyacrylic acid, the surface is treated with a chemical method to induce a surface porous structure, and silica nanoparticles are fixed thereon, and finally a fluorinated alkyl. It is also known to construct a superhydrophobic boundary surface by hydrophobizing with a silane coupling agent having a group (see, for example, Patent Document 2).

  Many known documents frequently discuss superhydrophobic films and methods for producing them, but they often correspond to techniques for processing roughness on the surface of a substrate (ie, roughness). The processing process tends to be complicated and the cost is high. Further, in the case of a superhydrophobic surface based on an organic polymer, the cost is low, but the solvent resistance and corrosion resistance of the obtained superhydrophobic surface are low, which causes a practical problem.

Research on making the powder itself superhydrophobic (superhydrophobic) or using the superhydrophobic powder to form a superhydrophobic film is extremely rare, but a recent example For example, it has been found that a powder of iron oxide (α-Fe ₂ 0 ₃ ) having a size of 2-3 μm exhibits superhydrophobicity by having a petal structure on the surface. (For example, refer nonpatent literature 5). However, the technique proposed in Non-Patent Document 5 has a narrow application range and is not based on an industrially simple technique.

  On the other hand, as a superhydrophobic powder in nature, it is understood that, for example, the feet of amembo correspond to an aggregate of superhydrophobic powder. The structure of the leg of Amembo is super-hydrophobic, and by adding the buoyancy and surface tension of the water generated due to it, the body more than 25 times the weight of the leg can be floated on the water surface. By adding elasticity, the Amoebo can run so as to fly over the water surface (see, for example, Non-Patent Document 6). The development of superhydrophobic powder has high industrial utility value, especially if it can be synthesized by a simple manufacturing method using a large amount of silicon compounds existing in nature as a raw material. This is a highly anticipated issue.

Sun et al. , Acc. Chem. Res. 2005, 38, 644-652. Li et al. , J .; Mater. Chem. , 2008, 18, 2276-2280 Feng et al. , J .; Am. Chem. Soc. , 2004, 126, 62-63 Erbil et al. , Science, 2003, 299, 1377-1380 Cao et al. , Appl. Phys. Lett. , 2007, 91. 034102 Gao et al. , Nature 2004, 432, 36 Special table 2008-508181 US Patent Application Publication No. 2006/029808

  The problem to be solved by the present invention is to make the powder containing silica as a main component itself superhydrophobic. More specifically, a superhydrophobic powder characterized in that a hydrophobic group is bonded to an aggregate of organic-inorganic composite nanofibers in which a polymer filament having a linear polyethyleneimine skeleton is coated with silica. And providing a simple method for producing the powder. Furthermore, a hydrophobic group is bonded to an aggregate of nanofibers mainly composed of silica obtained by removing a polymer having a linear polyethyleneimine skeleton from the organic-inorganic composite nanofiber by baking. Is to provide a superhydrophobic powder characterized by the above and a simple method for producing the powder.

  Furthermore, it is providing the structure which has the superhydrophobic surface using said superhydrophobic powder, and its manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor is present on the surface of an aggregate of organic-inorganic composite nanofibers in which an organic polymer and an inorganic silica are combined on the nanometer order. It has been found that a powder exhibiting superhydrophobicity can be obtained by hydrophobizing silica, and the present invention has been completed.

  That is, the present invention is a superhydrophobic powder containing an association of organic-inorganic composite nanofibers, wherein the nanofibers are polymer filaments having a linear polyethyleneimine skeleton, and hydrophobic groups are bonded. The present invention provides a superhydrophobic powder characterized by being coated with silica, and a simple production method thereof.

  Furthermore, the present invention provides a superhydrophobic powder characterized in that a hydrophobic group is bonded to the silica of the nanofiber aggregate containing silica as a main constituent, and a method for producing the same.

  Furthermore, the present invention provides a structure having a superhydrophobic surface obtained by fixing the superhydrophobic powder obtained above on a solid substrate and a method for producing the structure.

  The superhydrophobic powder of the present invention can convert any solid surface to superhydrophobic by applying it to the surface of a base material of any material and shape. This can be applied to protective films for metals, metal oxides, fibers, wood, paper, leather, and plastics that can rust, rot, and get dirty with water. More specifically, structures such as buildings, car bodies, ship bodies, container structures, packages, glass products, pottery products (toilet bowls, entire bathrooms), pools, water pipes, electric wires, light bulbs, various carvers, etc. It can be applied to the protective film. Furthermore, it can also be applied to the surface coating of household electrical appliances such as refrigerators, microwave ovens and washing machines, and electrical appliances for communication such as personal computers, televisions and mobile phones. It can also be applied to energy conversion-related fuel cell devices.

  The present inventors have already used a crystalline aggregate in which a polymer having a linear polyethyleneimine skeleton grows in an aqueous medium in a self-organizing manner as a reaction field, and hydrolyzes alkoxysilane on the surface of the aggregate in a solution. A silica-containing nanostructure (powder) having a complex shape with nanofibers as a basic unit and a method for producing them were provided by decomposing condensation and precipitating silica (JP 2005-264421, JP 2005-336440, JP-A-2006-063097, and JP-A-2007-051056.)

  The basic principle of this technique is to spontaneously grow a crystalline aggregate of a linear polyethyleneimine skeleton-containing polymer in a solution. Once a crystalline aggregate is formed, the crystalline aggregate is simply A silica source is mixed in the dispersion liquid, so that the deposition of silica only on the surface of the crystalline aggregate is naturally left (so-called sol-gel reaction). The silica-containing nanostructure obtained in this way basically has nanofabric as a unit for structure formation, and since the shape of the entire structure is induced by the spatial arrangement of these units, there are many nano-level gaps, It is a powder with a large surface area.

  Such a powder is very similar to the basic structure necessary for developing superhydrophobicity in nature, that is, nanofibers gather to form a micrometer dimension. Therefore, it is considered that superhydrophobicity can be expressed by modifying the powder surface with a chemical residue having a low surface tension.

  Based on this concept, the present inventors have developed a silica-containing nanostructure on the order of micrometer (a silica-containing nanostructure) having a basic structure of a nanofiber derived from a polymer having a linear polyethyleneimine skeleton. It was found that the powder itself can be made superhydrophobic by bonding a hydrophobic group to the powder surface, which is a structure consisting of basic units in the metric order. Hereinafter, the present invention will be described in detail.

  In the present application, a filament is a polymer chain formed by crystallization of a plurality of linear polyethyleneimine skeleton portions in a polymer chain having a linear polyethyleneimine skeleton used in the present invention in the presence of water molecules. Are associated with each other and grow into a fibrous form. When a sol-gel reaction occurs on the surface of the filament, an organic-inorganic composite nanofiber in which the filament is coated with silica is formed. During this reaction, a plurality of organic-inorganic nanofibers are bonded or aggregated by silica. As a result, a silica-containing nanostructure (powder) that is an aggregate of organic-inorganic nanofibers is formed.

[Polymer (A) having linear polyethyleneimine skeleton (a)]
The polymer (A) having a linear polyethyleneimine skeleton (a) used in the present invention may be a homopolymer having a linear, star or comb structure, but may be a copolymer having other repeating units. There may be. In the case of a copolymer, the molar ratio of the linear polyethyleneimine skeleton (a) in the polymer (A) is preferably 20% or more from the viewpoint of forming a stable filament. It is more preferable that it is a block copolymer in which the number of repeating units in (a) is 10 or more.

  As the polymer (A) having the linear polyethyleneimine skeleton (a), the higher the ability to form a crystalline aggregate, the more preferable. Therefore, it is preferable that the molecular weight corresponding to the linear polyethyleneimine skeleton (a) portion is in the range of 500 to 1,000,000, whether it is a homopolymer or a copolymer. The polymer (A) having the linear polyethyleneimine skeleton (a) can be obtained from a commercially available product or a synthesis method already disclosed by the present inventors (see the above-mentioned patent document).

[Silica (B)]
The superhydrophobic powder provided by the present invention is a group of organic-inorganic composite nanofibers (I) in which the filament of the polymer (A) having the linear polyethyleneimine skeleton (a) is coated with silica (B). The basic structure of the aggregate or the aggregate of nanofibers (II) mainly composed of silica (B) obtained by removing the polymer (A) from the aggregate of the organic-inorganic composite nanofibers (I) by calcination And

  The silica (B) is obtained by a sol-gel reaction on the filament surface in the presence of the filament of the polymer (A). As a silica source necessary for the formation of the silica (B), for example, alkoxysilane , Water glass, hexafluorosilicon ammonium and the like can be used.

  As the alkoxysilanes, tetramethoxysilane, oligomers of methoxysilane condensates, tetraethoxysilane, oligomers of ethoxysilane condensates can be suitably used. Further, alkyl-substituted alkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, iso-propyltrimethoxysilane, iso-propyltriethoxysilane, etc., 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycid Xylpropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptotriethoxysilane, 3,3 -Trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, p -Chloromethylphenyltrimethoxysilane, p-chloromethylphenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane and the like can be used alone or in combination.

  In addition, other silica metal compounds may be mixed with the silica source. For example, tetrabutoxytitanium, tetraisopropoxytitanium, or an aqueous solution of titanium bis (ammonium lactate) dihydroxide stable in an aqueous medium, an aqueous solution of titanium bis (lactate), a propanol / water mixture of titanium bis (lactate), titanium (ethyl) Acetoacetate) diisopropoxide, titanium sulfate, hexafluorotitanium ammonium and the like can be used.

[Metal ions]
Metal ions can be stably taken into the organic-inorganic composite nanofiber (I), and therefore a superhydrophobic powder containing metal ions can be obtained.

  Since the linear polyethyleneimine skeleton (a) in the polymer (A) has a strong coordination ability to metal ions, the metal ions coordinate with the ethyleneimine units in the skeleton to form metal ion complexes. Form. The metal ion complex is obtained by coordination of a metal ion to an ethyleneimine unit. Unlike a process such as ionic bonding, the metal ion is coordinated to an ethyleneimine unit regardless of whether the metal ion is a cation or an anion. Can form a complex. Accordingly, the metal species of the metal ion is not limited as long as it can coordinate with the ethyleneimine unit in the polymer (A), and is not limited to alkali metal, alkaline earth metal, transition metal, metalloid, lanthanum metal, poly Any of metal compounds such as oxometalates may be used, and they may be used alone or in combination.

Examples of the alkali metal include Li, Na, K, Cs and the like, and examples of counter ions of the alkali metal ions include Cl, Br, I, NO ₃ , SO ₄ , PO ₄ , ClO ₄ , PF ₆ , Examples thereof include BF ₄ and F ₃ CSO ₃ .

  Examples of the alkaline earth metal include Mg, Ba, and Ca.

As a transition metal-based metal ion, even if it is a transition metal cation (M ^{n +} ), an acid group anion (MO _x ⁿ⁻ ) composed of a bond with oxygen, or an anion composed of a halogen bond ( ML _x ⁿ⁻ ) can also be suitably used. In the present specification, the transition metal refers to Sc, Y in Group 3 of the periodic table, and transition metal elements in Groups 4 to 12 in the 4th to 6th periods.

Examples of transition metal cations include cations of various transition metals (M ^{n +} ), such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ru, Rh, Pd, and Ag. , Cd, W, Os, Ir, Pt, Au, Hg, monovalent, divalent, trivalent or tetravalent cations. The counter anion of these metal cations may be any of Cl, NO ₃ , SO ₄ , polyoxometalates anions, or organic anions of carboxylic acids. However, for those that are easily reduced by the ethyleneimine skeleton, such as Ag, Au, and Pt, it is preferable to prepare an ionic complex by suppressing the reduction reaction, for example, by adjusting the pH to acidic conditions.

Examples of the transition metal anion include various transition metal anions (MO _x ⁿ⁻ ) such as MnO ₄ , MoO ₄ , ReO ₄ , WO ₃ , RuO ₄ , CoO ₄ , CrO ₄ , VO ₃ , NiO ₄ , UO _2. Anions and the like.

  As the metal ion in the present invention, a metal compound of polyoxometalates in which the transition metal anion is fixed in silica (B) through a metal cation coordinated to an ethyleneimine unit in the polymer (A). It may be a form. Specific examples of the polyoxometalates include molybdate, tungstate and vanadate in combination with a transition metal cation.

Furthermore, anions (ML _x ⁿ⁻ ) containing various metals, such as AuCl ₄ , PtCl ₆ , RhCl ₄ , ReF ₆ , NiF ₆ , CuF ₆ , RuCl ₆ , In ₂ Cl _6, etc. The coordinated anion can also be suitably used for forming an ion complex.

  Further, examples of the metalloid ions include ions of Al, Ga, In, Tl, Ge, Sn, Pb, Sb, and Bi. Among them, ions of Al, Ga, In, Sn, Pb, and Tl are preferable.

  Examples of the lanthanum metal ions include trivalent cations such as La, Eu, Gd, Yb, and Eu.

[Metal nanoparticles]
As described above, in the present invention, metal ions can be taken into the organic-inorganic composite nanofiber (I). Accordingly, among these metal ions, metal ions that are easily reduced by a reduction reaction can be converted into metal nanoparticles, whereby a superhydrophobic powder containing metal nanoparticles can be obtained.

  Examples of the metal species of the metal nanoparticles include copper, silver, gold, platinum, palladium, manganese, nickel, rhodium, cobalt, ruthenium, rhenium, molybdenum, iron, and the like. The particles may be one kind or two or more kinds. Among these metal species, silver, gold, platinum, and palladium are particularly preferable because the metal ions are spontaneously reduced at room temperature or in a heated state after being coordinated to the ethyleneimine unit.

  The size of the metal nanoparticles in the superhydrophobic powder can be controlled in the range of 1 to 20 nm. Moreover, a metal nanoparticle can be fixed to the inside of an organic inorganic composite nanofiber (I) of a polymer (A) and silica (B), or an outer surface.

[Organic dye molecules]
The linear polyethyleneimine skeleton (a) in the polymer (A) is physically bonded with a compound having an amino group, a hydroxy group, a carboxylic acid group, a sulfonic acid group, or a phosphoric acid group, and hydrogen bonds and / or electrostatic attraction. A bonded structure can be constructed. Therefore, it is possible to contain organic dye molecules having these functional groups in the superhydrophobic powder.

  As the organic dye molecule, a monofunctional acidic compound or a bifunctional or higher polyfunctional acidic compound can be suitably used.

  Specifically, for example, aromatic acids such as tetraphenylporphyrin tetracarboxylic acid and pyrene dicarboxylic acid, naphthalene disulfonic acid, pyrene disulfonic acid, pyrene tetrasulfonic acid, anthraquinone disulfonic acid, tetraphenyl porphyrin tetrasulfonic acid, phthalocyanine tetra Aromatic or aliphatic sulfonic acids such as sulfonic acid and pipes (PIPES), acid yellow, acid blue, acid red, direct blue, direct yellow, direct red series azo dyes and the like can be mentioned. In addition, a dye having a xanthene skeleton, for example, rhodamine, erythrosine, and eosin dyes can be used.

[Organic inorganic composite nanofiber (I)]
In the present invention, the size of the organic-inorganic composite nanofiber (I) is the molecular weight and shape of the polymer (A) to be used, the content of the linear polyethyleneimine skeleton (a), and the type and use ratio of the silica source to be used. In particular, the organic-inorganic composite nanofiber (I) having a thickness of 10 to 100 nm and an aspect ratio of 10 or more can be easily produced.

  The content of the polymer (A) in the organic-inorganic composite nanofiber (I) can be adjusted to 5 to 30% by mass, and the polymer (A) is included as a filament shape as described above.

The organic-inorganic composite nanofibers (I) are randomly arranged in a three-dimensional space during the production process (during sol-gel reaction) to form an aggregate (silica-containing nanostructure) having a size of 2 to 100 μm. The surface area of the powder composed of such an aggregate is in the range of 50 to ²⁰⁰ m ² / g.

  The method for producing the organic-inorganic composite nanofiber (I) and the aggregate thereof may be any method described in the patent literature already provided by the present inventors.

[Nanofibers (II) mainly composed of silica]
When the aggregate of the organic-inorganic composite nanofiber (I) described above is heated and fired, the polymer (B) contained therein is removed while maintaining the shape, and the nanofiber (II) containing silica as the main constituent (II) ) Can be obtained. Here, silica as a main constituent means that, for example, the polymer (A) or the carbon atom in the organic dye molecule used in combination is carbonized and contained, or the metal ion or metal is not baked. When nanoparticles are used in combination, metal atoms may be contained, but the shape of the nanofiber is formed by silica (B), and the content of silica (B) is Usually, it is 90 mass% or more, preferably 95 mass%.

  The baking temperature should just be 500 degreeC or more, and baking time can be suitably set with temperature. The temperature may be 1 hour at a temperature higher than 500 ° C., and it is desired to calcinate for 2 hours or more near 500 ° C.

The structure of the aggregate obtained by firing is the same as before firing, and the nanofiber (II) has a thickness of 10 to 100 nm and an aspect ratio of 10 or more. The nanofiber of this thickness is random in a three-dimensional space. The aggregate formed by the arrangement still maintains a size of 2 to 100 μm. The specific surface area of the powder obtained after firing is larger than that before firing, and is generally 100 to 400 m ² / g.

[Hydrophobic treatment]
In the present invention, the surface of the nanofiber (I) or nanofiber (II) aggregate must be modified with a hydrophobic group (X) in order to obtain a superhydrophobic powder. The modification can be easily performed by contact with a compound having a hydrophobic group (X).

  Examples of the hydrophobic group (X) include an alkyl group having 1 to 22 carbon atoms and an aromatic group which may have a substituent (as the substituent, an alkyl group having 1 to 22 carbon atoms, a fluorinated group). And hydrophobic groups such as alkyl groups and partially fluorinated alkyl groups), fluorinated alkyl groups having 1 to 22 carbon atoms, and partially fluorinated alkyl groups having 1 to 22 carbon atoms.

  In order to efficiently introduce the hydrophobic group (X) into the silica (B) on the surface of the nanofiber (I) or the nanofiber (II) aggregate, the hydrophobic group (X) has the hydrophobic group (X). The silane coupling agent (x) is preferably used alone or in combination for contact. At this time, by adjusting the contact amount with the silane coupling agent (x) having the hydrophobic group (X), the obtained powder can be adjusted to be hydrophobic to superhydrophobic.

  Examples of the silane coupling agent (x) include methyltrimethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, and iso-propyltrimethoxy. Examples include alkyltrimethoxysilanes or alkyltrichlorosilanes having 1 to 22 carbon atoms in the alkyl group such as silane, iso-propyltriethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane and the like.

  Further, as having a fluorine atom effective for lowering the surface tension, a (partially) silane coupling agent having a fluorinated alkyl group, such as 3,3,3-trifluoropropyltrimethoxysilane, tridecafluoro-1, 1,2,2-tetrahydrooctyl) trichlorosilane and the like can also be used.

  Moreover, as a silane coupling agent having an aromatic group, phenyltrimethoxysilane, phenyltriethoxysilane, p-chloromethylphenyltrimethoxysilane, p-chloromethylphenyltriethoxysilane, and the like can be taken up.

[Introduction of reactive functional groups]
The superhydrophobic powder of the present invention can be fixed on a solid substrate of any shape / material to obtain a structure having a superhydrophobic surface. At this time, the method for fixing the powder on the solid substrate is not particularly limited, but is a method in which the powder is dispersed in a polymer solution or silica sol as described later, and the dispersion is applied and dried. However, it is simple and industrially useful.

  At this time, in order to more easily fix the superhydrophobic powder of the present invention, it is preferable to introduce a reactive functional group (Y) into the superhydrophobic powder. The introduction of the reactive functional group (Y) is the same method as the introduction of the hydrophobic group (X), that is, the method by contact with the silane coupling agent (y) having the reactive functional group (Y). Is preferred.

  Examples of the silane coupling agent (y) having a reactive functional group (Y) include γ-methacryloylpropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltri Methoxysilane, γ- (2-hydroxylethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ- (2-hydroxylethyl) aminopropyltriethoxysilane, γ- (2- Aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldiethoxysilane, γ- (2-hydroxylethyl) aminopropylmethyldimethoxysilane, γ- (2-hydroxylethyl) aminopropylmethyldi Ethoxysilane or γ- ( N, N-di-2-hydroxylethyl) aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane or Has (meth) acryloyl group, glycidyl group, amino group, hydroxy group, mercapto group, such as γ- (N-phenyl) aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptophenyltrimethoxysilane The silane coupling agent may be mentioned, and may be used alone or in combination of two or more.

  The introduction ratio of the reactive functional group (Y) is not particularly limited, but from the viewpoint of balancing the point of being easily fixed on the solid substrate and maintaining superhydrophobicity, the silica (B) It is preferable that the molar ratio (X) / (X + Y) of the hydrophobic group (X) bonded to the reactive functional group (Y) is in the range of 0.2-1.

[Production method of superhydrophobic powder]
In the method for producing a superhydrophobic powder of the present invention, the organic-inorganic composite nanofiber (I) aggregate or nanofiber (II) aggregate is dispersed in a solvent, and a silane having a hydrophobic group (X) Mix with a solution of a coupling agent (x) or a solution containing a silane coupling agent (x) having a hydrophobic group (X) and a silane coupling agent (y) having a reactive functional group (Y). Is the method.

  Silane coupling agent (x) having hydrophobic group (X) and silane coupling agent (y) having reactive functional group (Y) are solvents such as chloroform, methylene chloride, cyclohexanone, xylene, toluene, ethanol and methanol. It can be dissolved in These solvents can be used alone or in combination.

  In the said solution, if the total density | concentration of silane coupling agent (x) and (y) is 1-5 mass%, it can use suitably, especially it mixes with the ethanol solution of 1-5 mass% ammonia water. More preferably, it is used. The volume ratio when mixing is preferably 5 to 10 times the amount of the ammonia water ethanol solution with respect to the solution of the silane coupling agent.

  When a silane coupling agent (x) having a hydrophobic group (X) and a silane coupling agent (y) having a reactive functional group (Y) are used, they are introduced into the resulting superhydrophobic powder. In order to make the molar ratio of the hydrophobic group (X) and the reactive functional group (Y) within the above-mentioned preferable range, the molar ratio (x) / (x + y) is preferably in the range of 0.2-1.

  By mixing a dispersion of a powder composed of an aggregate of nanofibers (I) or (II) with the above mixed solution, Si—O— is added to silica (B) having a silane coupling agent silane on the surface of the aggregate. Introduced by Si bonding, a superhydrophobic powder can be obtained.

  When using the aggregate | assembly which consists of organic-inorganic composite nanofiber (I) in which polymer (A) is contained in powder, it is preferable that the time mixed with the said solution is 10 to 24 hours. In addition, in the case of using a powder that is an aggregate composed of nanofiber (II) not containing polymer (A), the hydrophobic group (X) can be easily introduced if the mixing time is 2 hours or longer. it can.

  The superhydrophobic powder obtained by the above method has no water wettability and can only float on the water surface as a powder even when dispersed in water. This is completely different from completely sinking in water before the introduction of the hydrophobic residue (X).

[Superhydrophobic surface using super water-repellent powder]
A structure having a superhydrophobic surface can be obtained by bonding and fixing the superhydrophobic powder of the present invention to the surface of a solid substrate. Adhesion fixation is easily achieved by mixing the powder with a polymer solution, silica sol solution, or commercially available paint, adhesive, etc., applying the mixture to the surface of the substrate, and drying it as necessary. it can.

  The superhydrophobic surface is a state in which the superhydrophobic powder is fixed to the coating surface. That is, it is characterized in that a polymer or silica sol or the like forms a continuous film as a binder, and structures derived from the superhydrophobic powder of the present invention are distributed at regular intervals on the surface of the continuous film.

  The polymer that can be used in the binder layer is not particularly limited as long as it is a hydrophobic polymer. Examples of the hydrophobic polymer include polystyrene, polyvinyl chloride, polymethacrylate, polyacrylate, polycarbonate, polyester, and epoxy resin.

  For example, when using a superhydrophobic powder having a glycidyl group or an amino group as the reactive functional group (Y), the epoxy resin can be used as a binder resin to firmly fix the resultant coating film surface. It becomes possible. Moreover, when using the superhydrophobic powder which has a (meth) acryloyl group, it can fix firmly by UV hardening by using together the monomer which has a (meth) acryloyl group. In addition, it is possible to obtain a highly stable structure having a superhydrophobic surface by selecting a binder resin according to the type of reactive functional group (Y) introduced on the surface of the superhydrophobic powder. Become.

  Furthermore, as the binder layer, silica sol, metal oxide sol or the like dispersed in alcohol can be used. In this case, methanol, ethanol, isopropanol, etc. can be taken up as alcohols.

  Moreover, as a binder layer of the said coating film, a commercially available coating material or a commercially available adhesive agent can also be used normally.

  The contact angle of the superhydrophobic surface obtained above can be varied in the range of 150-179 °. The higher the density of superhydrophobic powder on the surface, the better the contact angle. In order to obtain a surface having a target hydrophobicity level lower than this, for example, a contact angle of 70 to 150 ° which is a general hydrophobicity level, the use ratio of the superhydrophobic powder of the present invention is decreased. Of course, the density of the powder may be lowered.

  The solid substrate can be selected according to the material used for the binder layer, and examples thereof include glass, metal, metal oxide, wood, paper, fiber, plastic, rubber, leather, etc. There is no particular limitation, and any shape that can be applied with a polymer solution or silica sol may be used.

  The method for fixing and adhering the superhydrophobic powder to the surface of the solid substrate is not particularly limited, and the coating liquid containing the powder is appropriately applied by a usual coating method such as a spin coater, bar coater, brushing, spray or the like. What is necessary is just to apply.

  Further, in accordance with the properties of the binder layer forming the coating film, the film obtained by coating can be cured by a process such as UV curing, heat curing, or natural drying.

  The superhydrophobic powder of the present invention is easily wetted by organic solvents other than water and can be easily dispersed. Accordingly, the medium that can dissolve or disperse the binder may be any solvent other than water, and a mixed medium of an organic solvent and water can also be used.

  In the coating liquid for surface preparation, the ratio of the binder constituent part and the superhydrophobic powder part may be in the range of binder / powder = 60/50 to 99/1 (mass ratio), and the composition ratio. In this range, the solid content concentration of the coating liquid can be appropriately determined.

  In particular, when preparing a hydrophobic surface, the superhydrophobic powder must be exposed to the surface of the coating film. Therefore, it is desirable that the thickness of the coating film is within a certain range, for example, 0.1 to 20 μm. The thinner the coating film, the more the powder will protrude on the surface of the coating film, and the contact angle of water can be increased.

  In addition, the horizontal distance between the powders exposed on the coating film surface is an important structural element for the expression of superhydrophobicity of the entire film. Superhydrophobicity can be sufficiently expressed if the horizontal distance between the powder structures is 1 to 20 μm, but the contact angle of water can be increased to about 150 ° even if the distance is longer than that, depending on the intended use. It is preferable to adjust.

  Hereinafter, the present invention will be described in more detail with reference to examples. Unless otherwise specified, “%” represents “mass%”.

[Shape analysis of nanofiber aggregates and powders by scanning electron microscope]
The isolated and dried aggregates and powders were fixed to a sample support with a double-sided tape, and observed with a surface observation apparatus VE-9800 manufactured by Keyence.

[Contact angle measurement]
The contact angle was measured with an automatic contact angle meter Contact Angle System OCA (manufactured by Dataphysics).

Synthesis example 1
[Preparation of Powder 1 Composed of Aggregates of Organic-Inorganic Composite Nanofiber (I)]
Powders having different shapes were produced by the methods disclosed in patent documents (Japanese Patent Application Laid-Open Nos. 2005-264421, 2005-336440, 2006-063097, and 2007-051056).

<Synthesis of linear polyethyleneimine (P5K)>
5 g of commercially available polyethyloxazoline (number average molecular weight 500,000, average polymerization degree 5,000, manufactured by Aldrich) was dissolved in 20 mL of 5 M aqueous hydrochloric acid solution. The solution was heated to 90 ° C. in an oil bath and stirred at that temperature for 10 hours. Acetone 50 mL was added to the reaction solution to completely precipitate the polymer, which was filtered and washed three times with methanol to obtain a white polyethyleneimine powder. When the obtained powder was identified by ¹ H-NMR (heavy water), peaks 1.2 ppm (CH ₃ ) and 2.3 ppm (CH ₂ ) derived from the side chain ethyl group of polyethyloxazoline completely disappeared. It was confirmed that That is, it was shown that polyethyloxazoline was completely hydrolyzed and converted to polyethyleneimine.

  The powder was dissolved in 5 mL of distilled water, and 50 mL of 15% aqueous ammonia was added dropwise to the solution while stirring. The mixture was allowed to stand overnight, the precipitated powder was filtered, and the powder was washed 3 times with cold water. The washed powder was dried in a desiccator at room temperature (25 ° C.) to obtain linear polyethyleneimine (P5K). The yield was 4.5 g (containing crystallization water). In polyethyleneimine obtained by hydrolysis of polyoxazoline, only the side chain reacts and the main chain does not change. Therefore, the polymerization degree of P5K is the same as 5,000 before hydrolysis.

<Synthesis of organic-inorganic composite nanofiber (I) aggregate>
A certain amount of P5K was mixed in distilled water, heated to 90 ° C. to obtain a clear solution, and then prepared into a total 3% aqueous solution. The aqueous solution was naturally cooled at room temperature to obtain a pure white P5K aggregate solution. While stirring, 70 mL of an ethanol solution (volume concentration 50%) of TMOS (tetramethoxysilane) was added to 100 mL of the aggregated body solution, and stirring was continued at room temperature for 1 hour. The deposited precipitate was filtered, washed with ethanol three times, and dried under heating at 40 ° C. to obtain 15 g of powder. FIG. 1 shows an SEM photograph of the obtained powder. It was confirmed to be an assembly of nanofibers.

From the thermogravimetric loss analysis (TG / DTA6300 made by SII Nano Technology Inc.) of the powder thus obtained, it was confirmed that the polymer content was 7%. In addition, the specific surface area was measured (Flow Sorb II 2300 manufactured by Micrometrics), and as a result, it was 105 m ² / g.

Synthesis example 2
[Preparation of Powder 2 Consisting of Nanofiber (II) Containing Silica as Main Component]
15 g of the powder 15 obtained in Synthesis Example 1 was heated in an electric furnace at 600 ° C. for 2 hours under air introduction conditions to remove polyethyleneimine contained in the powder 1 to obtain a white powder 2. The specific surface area was 187 m ² / g. FIG. 2 shows an SEM photograph of powder (II). It was suggested that there was no change in the nanofiber structure after firing.

Example 1
[Synthesis of superhydrophobic powder 1]
50 mL of 2% ammonia in ethanol and 5 mL of 20% decyltrimethoxysilane (DTMS) in chloroform were mixed, 0.5 g of Powder 1 was added to the mixture, and the mixture was stirred at room temperature for 24 hours. After filtering the reaction solution, the obtained powder was washed with ethanol three times. The dried powder did not sink at all in the water and floated on the water surface. This was completely different from the tendency of the powder 1 before hydrophobization treatment to completely sink in water.

  After the obtained powder was adhered to a double-sided tape to form a surface made of powder, the contact angle of water was measured, and the contact angle of water was 177.5 °. It was strongly suggested that the membrane state of the powder was superhydrophobic. This is designated as superhydrophobic powder 1.

Example 2
[Synthesis of super water-repellent powder 2]
50 mL of an ethanol solution of 2% ammonia and 5 mL of a chloroform solution of 20 wt% decyltrimethoxysilane (DTMS) were mixed, 0.5 g of powder 2 was added to the mixture, and the mixture was stirred at room temperature for 24 hours. After filtering the reaction solution, the obtained powder was washed with ethanol three times. The thermogravimetric loss of the powder after drying (between 150 and 800 ° C.) was 8.4%. This corresponds to the amount of organic residues due to introduction of the silane coupling agent. This powder did not sink at all in the water and floated on the water surface. This was completely different from the fact that the powder 2 before the hydrophobization treatment tended to completely sink in water. FIG. 3 shows an SEM photograph of the powder.

  After the obtained powder was adhered to a double-sided tape to form a surface made of powder, the contact angle of water was measured, and the contact angle of water exceeded 179 °. It was strongly suggested that the membrane state of the powder was superhydrophobic. This is designated as superhydrophobic powder 2.

Example 3
[Synthesis of super water-repellent powder 3]
Mix 50 mL of ethanol solution of 2% ammonia and 5 mL of chloroform solution containing 6% silane coupling agent [5% decyltrimethoxysilane (DTMS) and 1% aminopropyltrimethoxysilane (ATMS)]. 0.5 g of the powder 2 was added to the mixture and stirred at room temperature for 24 hours. After filtering the reaction solution, the obtained powder was washed with ethanol three times. The thermogravimetric loss of the powder after drying (between 150 and 800 ° C.) was 7.5%. The powder floated on the surface of the water without sinking at all.

  After the obtained powder was adhered to a double-sided tape to form a surface made of powder, the contact angle of water was measured, and the contact angle of water was 168 °. It was strongly suggested that the membrane state of the powder was superhydrophobic. This is designated as superhydrophobic powder 3.

Example 4
[Synthesis of super water-repellent powder 4]
Mix 50 mL of 2% ammonia in ethanol and 5 mL of chloroform solution containing 6% silane coupling agent [5% decyltrimethoxysilane (DTMS) and 1% methacryloylpropyltrimethoxysilane (ATMS)] 0.5 g of the powder 2 was added to the mixture and stirred at room temperature for 24 hours. After filtering the reaction solution, the obtained powder was washed with ethanol three times. The thermogravimetric loss of the powder after drying (between 150 and 800 ° C.) was 8.3%. The dried powder did not sink at all in the water and floated on the water surface.

  After the obtained powder was adhered to a double-sided tape to form a surface made of powder, the contact angle of water was measured, and the contact angle of water was 176 °. It was strongly suggested that the membrane state of the powder was superhydrophobic. This is designated as superhydrophobic powder 4.

Example 5
[Superhydrophobic membrane on filter paper using superhydrophobic powder 2 (dipping method)]
A commercially available polystyrene (manufactured by Aldrich, Mw = 45,000) was used to prepare a 1% toluene solution. 10 mg of the powder 2 was added to 0.5 mL of the solution and dispersed uniformly, and then the filter paper was immersed in the dispersion for 15 minutes. After removing the filter paper and drying at room temperature, water drops were dropped on the filter paper, but the water drops blew completely. The contact angle was 165.5 °. FIG. 4 shows the contact image with the coating film.

Example 6
[Superhydrophobic membrane on filter paper using superhydrophobic powder 2 (brush method)]
The same dispersion used in Example 5 was brushed on the filter paper. When the surface contact angle was measured after drying it at room temperature, the contact angle was 178 °. The filter paper did not get wet.

Example 7
[Superhydrophobic film on glass using superhydrophobic powder 2 (casting method)]
A dispersion similar to that in Example 5 was cast on a glass slide using a bar coater. The cast film thus obtained was dried at room temperature and then the surface contact angle was measured. The contact angle was 179.6 ° (15 μL water droplets) (FIG. 5).

  This glass surface was observed by SEM (FIG. 6). From the SEM photograph image, it can be seen that the particles derived from the powder spread on the film surface in a fixed state. From the enlarged image, it can be seen that the powder is dispersed at intervals of 5 μm or more.

Example 8
[Superhydrophobic membrane on wood using superhydrophobic powder 2 (brush method)]
The same dispersion used in Example 5 was brushed onto a wooden board that had not been surface-treated. After drying it at room temperature and dropping water drops, the water was completely repelled and the wood surface did not get wet.

Example 9
[Superhydrophobic film on cowhide using superhydrophobic powder 2 (dipping method)]
A commercially available polymethyl methacrylate (manufactured by Aldrich, Mw = 120,000, manufacturer, product number) was used to prepare a 1% chloroform solution. In 0.5 mL of the solution, 10 mg of the powder 2 was added and uniformly dispersed, and then the cut-off of cowhide not surface-treated was immersed in the dispersion for 1 hour. After removing the cowhide and drying at room temperature, water droplets were dropped on it, but the water droplets completely repelled and the wettability was lost.

Example 10
[Superhydrophobic film (brush method) on stainless steel plate using superhydrophobic powder 2]
The same dispersion used in Example 9 was applied to a stainless steel petri dish (Takizawa Rika, 50 × 50 × 0.6 mm) with a brush. After drying it at room temperature and dropping water drops, the water was completely repelled and the metal surface did not get wet.

Example 11
[Superhydrophobic membrane on the inner wall of glass tube using superhydrophobic powder 2 (dipping method)]
The same dispersion used in Example 9 was sucked into a glass pipette (inner diameter 6 mm, length 8 cm), held for 2 hours, and then the liquid was extruded. After the glass pipette was dried at room temperature, water was sucked into the glass pipette and the test was performed to push out the water again. No water droplets adhered to the glass wall, and the absorbed water could be completely transferred to another container without reducing its weight.

  For comparison, when an untreated glass pipette was used, it was confirmed that water droplets adhered to the wall whenever water was pushed out after sucking out water.

2 is a scanning electron micrograph of the silica powder obtained in Synthesis Example 1. The powder is a bundle structure composed of nanofibers. 4 is a scanning electron micrograph of the fired silica powder obtained in Synthesis Example 2. FIG. Even after firing, a bundle structure composed of nanofibers is maintained. 2 is a scanning electron micrograph of superhydrophobic powder 2 obtained in Example 2. FIG. It is a contact image of the superhydrophobic film | membrane (upper figure) on the filter paper in Example 5, and the water droplet formed on the film | membrane surface. 7 is a contact image of water droplets formed on the surface of a film produced in Example 7. 6 is a scanning electron micrograph of the film surface produced in Example 7. FIG. The left figure is a photograph in a large area range, and the right figure is an enlarged photograph of a portion surrounded by a circle in the left figure.

Claims (11)

A powder composed of an association of an organic-inorganic composite nanofiber (I) in which a filament of a polymer (A) having a linear polyethyleneimine skeleton (a) is coated with silica (B) is dispersed in a solvent. A method for producing a superhydrophobic powder , comprising: a step of mixing a silane coupling agent (x) having a hydrophobic group (X) in a liquid; and a step of drying . (1) firing an aggregate of organic-inorganic composite nanofibers (I) in which a filament of a polymer (A) having a linear polyethyleneimine skeleton (a) is coated with silica (B);
(2) A powder composed of an aggregate of nanofibers (II) containing silica (B) obtained in (1) as a main constituent is dispersed in a solvent, and the dispersion has a hydrophobic group (X). A step of mixing the silane coupling agent (x), a step of drying,
A process for producing a superhydrophobic powder characterized by comprising: The superhydrophobic powder production according to claim 1 or 2, wherein the silane coupling agent (y) having a reactive functional group (Y) is used in combination with the silane coupling agent (x) having a hydrophobic group (X). Method. The use ratio of the silane coupling agent (x) having the hydrophobic group (X) and the silane coupling agent (y) having the reactive functional group (Y) is represented by (x) / (x + y). The method for producing a superhydrophobic powder according to claim 3, wherein the molar ratio is in the range of 0.2 to 1. The hydrophobic group (X) may have an alkyl group having 1 to 22 carbon atoms, a fluorinated alkyl group having 1 to 22 carbon atoms, a partially fluorinated alkyl group having 1 to 22 carbon atoms, or a substituent. A good aromatic group (wherein the substituent is an alkyl group having 1 to 22 carbon atoms, a fluorinated alkyl group having 1 to 22 carbon atoms, or a partially fluorinated alkyl group having 1 to 22 carbon atoms). The manufacturing method of the super-hydrophobic powder in any one of 1-4. The method for producing a superhydrophobic powder according to any one of claims 1 to 5, wherein the reactive functional group (Y) is a (meth) acryloyl group, a glycidyl group, an amino group, a hydroxy group, or a mercapto group. . The thickness of the organic-inorganic composite nanofiber (I) is 10 to 100 nm, the aspect ratio is 10 or more, and the size of the aggregate of the organic-inorganic composite nanofiber (I) is in the range of 2 to 100 μm. Item 7. A method for producing a superhydrophobic powder according to any one of Items 1 to 6. Any wherein the thickness of the nanofiber (II) is 10 to 100 nm, and an aspect ratio of 10 or more and the size of the aggregates of the nanofibers (II) is according to claim 2-6 in the range of 2~100μm A method for producing the superhydrophobic powder according to claim 1. A superhydrophobic powder obtained by the production method according to claim 1. A structure having a superhydrophobic surface, wherein the superhydrophobic powder according to claim 9 is fixed to a solid substrate. A method for producing a structure having a superhydrophobic surface, wherein the superhydrophobic powder according to claim 9 is dispersed in a polymer solution or silica sol, and the dispersion is applied and dried.