JP6218133B2 - Coating agent containing ionic liquid capable of binding to substrate, coating layer and coating substrate obtained therefrom, and coating method using the same - Google Patents

Description

  The present invention relates to a novel application of an ionic liquid having a characteristic chemical structure.

  Conventionally, in order to hydrophobize the glass surface, surface treatment mainly using an organosilane coupling agent has been performed. Further, in the hydrophilization of a hydrophobic substrate such as PDMS, a plasma treatment or a chemical treatment method using a strong acid is used.

  The ionic liquid is a molten salt at room temperature, and ionic liquids having various molecular structures can be synthesized by a combination of a cationic species and an anionic species. Some ionic liquids have properties that are incompatible with water and oil, and application studies are currently being developed as special solvents in various fields (Non-patent Documents 1 and 2).

  Patent Document 1 describes a surface treatment composition containing an ionic (sexual) liquid, specifically a composition such as a detergent using the ionic liquid as an effective solvent against dirt (Claims, paragraphs). 0051). However, in Patent Document 1, it is possible to impart properties such as hydrophilicity and hydrophobicity to the base material by treating the base material having a silanol group using the ionic liquid having a hydrolyzable silyl group. There is no mention or suggestion of what can be done.

  Patent Document 2 discloses an ionic liquid having a long chain composed of a siloxane bond in an anion (which may contain a methoxy group or an ethoxy group in a side chain), and an additive, surfactant, and modifier for the ionic liquid. Or the use as a softener is described (Claims). However, the ionic liquid described in Patent Document 2 is clearly different in structure from the ionic liquid having a hydrolyzable silyl group in the cation used in the present invention. Further, Patent Document 2 does not disclose an ionic liquid having a long chain composed of a siloxane bond in an anion with specific examples, and does not describe the characteristics and applications in detail at all. Furthermore, the invention described in Patent Document 2 considers an ionic liquid having halide ions as anions, has a specific melting point or glass transition point and viscosity without containing halogen, and has improved hydrolysis stability. (Paragraphs 0006, 0007 and 0009), and the use of an ionic liquid having halide ions as anions or ionic liquids in which the halide ions are substituted with other anions is denied. doing.

  In Non-Patent Document 3, an ionic liquid having a structure in which a hydrolyzable silyl group is linked to an imidazolium cation is synthesized as a compound for immobilizing a metal catalyst such as copper on silica fine particles as a carrier. After reacting the hydrolyzable silyl group of the ionic liquid with the silanol group of the silica fine particles to bind them, the metal catalyst (chloride) is reacted to immobilize between the two imidazolium ions. It is described to do.

  Non-Patent Document 4 also synthesizes an ionic liquid similar to Non-Patent Document 3 as a compound for immobilizing palladium, which is a metal catalyst, on silica fine particles, and reacts the ionic liquid with palladium acetate to form a composite. After forming the body, it is described that it is immobilized on silica fine particles.

  However, the treatment of the silica fine particles using the ionic liquid in Non-Patent Documents 3 and 4 is for immobilizing the metal catalyst, so that the metal catalyst is always immobilized on the surface of the silica fine particles. become. In Non-Patent Documents 3 and 4, the specific ionic liquid is separated from the metal catalyst and used alone, and the base material having silica fine particles or other silanol groups is treated with hydrophilicity or parent by the action of the anion of the ionic liquid. The use of imparting oiliness is not described or suggested.

JP 2005-530910 A JP 2005-538039 A

M. J. Earle et al, Pure Appl. Chem., 72, 1391-1398 (2000) K. Shimojo et al, Anal. Chem. 76, 5039-5044 (2004) Chem. Commun., 2005, 2506-2508 Pure Appl. Chem., Vol.79, No.9, pp.1553-1559, 2007

  In the prior art, in order to control the hydrophilicity and hydrophobicity of the material surface, a hydrophilic group or a hydrophobic group has been imparted to the material surface using the method described above. However, it is difficult to maintain hydrophilicity for a long period of time by a method of imparting hydrophilicity by causing a chemical decomposition reaction to the base material by, for example, plasma treatment and generating a hydroxyl group, and the effect of the hydrophilic treatment diminishes with time. Go. Therefore, permanent surface treatment technology is required in many application fields. Further, there is a case where it is desired to change the wettability (hydrophilicity-water repellency and oleophilicity-oil repellency) of the material surface depending on the use, but the conventional technique does not have such flexibility.

  An object of the present invention is to provide means capable of imparting various wettability to a material surface and capable of stably maintaining the state.

The inventors have represented a hydrolyzable silyl group (a silyl group having a hydrolyzable group such as an alkoxy group, -SiR ¹¹ _n W _3-n contained in the general formula (I) described later as a cation substituent. An ionic liquid with a silanol group on the surface of glass or PDMS, and the ionic liquid is covalently introduced onto the surface by synthesizing it with a silanol group on the surface of glass or PDMS. succeeded in. At this time, it has been found that the wettability after the surface treatment can be greatly changed depending on the anion species used, and it is possible to prepare a surface that repels water and oil, which has not been conventionally used, and thus the present invention has been completed. It was.

  That is, this invention provides the coating agent which can be used for the surface treatment of a base material in one side surface, in order to adjust wettability. In another aspect, the present invention provides a coating layer obtained by using the coating agent that changes the wettability of a substrate and a coating base coated with the coating layer. In a further aspect, the present invention provides a method for coating a substrate using the coating agent. The present invention includes the following inventions.

  [Item 1] A coating agent comprising an ionic liquid comprising a nitrogen-containing heterocyclic cation or quaternary ammonium cation having at least one hydrolyzable silyl group and a counter anion thereof.

[Item 2] The coating according to item 1, wherein the nitrogen-containing heterocyclic cation or the quaternary ammonium cation is one in which a nitrogen atom is substituted with at least one substituent represented by the following general formula (I). Agent.
^{_{-R 10 -SiR 11 n W 3-}} n (I)
In the formula (I), n is 0, 1 or 2, R ¹⁰ is an alkylene group having 1 to 12 carbon atoms, R ¹¹ each independently represents an alkyl group having 1 to 12 carbon atoms, W is each independently -OR ¹² [wherein R ¹² represents an alkyl group having 1 to 12 carbon atoms. Or -OR ¹³ -OR ¹⁴ [wherein, R ¹³ represents an alkylene group having 1 to 12 carbon atoms, R ¹⁴ represents an alkyl group having 1 to 12 carbon atoms. ] The hydrolyzable group represented by this.

  [Item 3] The item 1 or 2, wherein the nitrogen-containing heterocyclic cation or the quaternary ammonium cation is represented by the general formula (II), (III), (IV) or (V). Coating agent.

In formula (II), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.

In Formula (III), R ¹ is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by Formula (I).

In the formula (IV), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by the formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.

In the formula (V), at least one of R ¹ , R ² , R ³ and R ⁴ has at least one hydrolyzable silyl group which may be a substituent represented by the formula (I). The other substituents are each independently a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.

[Item 4] The counter anion is Cl ⁻ , Br ⁻ , I ⁻ , CF ₃ CO ₂ ⁻ , CH ₃ CO ₂ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , PF ₆ ⁻ and (CF ₃ SO ₂ ). Item 4. The coating agent according to any one of Items 1 to 3, which is at least one selected from the group consisting of ₂ N ⁻ .

CLAIM | ITEM 5 The coating layer which changes the wettability of a base material characterized by including the film formed from the coating agent as described in any one of claim | item 1 -4.
[Item 6] A coated substrate which is coated with the coating layer according to Item 5.

[Item 7] A coating method comprising a step of bringing the coating agent according to any one of Items 1 to 4 into contact with a base material having a functional group capable of binding to the hydrolyzable silyl group.
[Item 8] The coating method according to Item 7, wherein the functional group capable of binding to the hydrolyzable silyl group is a hydroxy group.

[Item 9] The coating method according to item 7 or 8, wherein the substrate is polydimethylsiloxane (PDMS) or glass.
CLAIM | ITEM 10 The covering | coating method as described in any one of claim | item 7-9 which further includes the process of exchanging the counter anion of the ionic liquid in the said coating agent.

  [Item 11] The method according to any one of Items 7 to 10, wherein the contacting step and / or the counter-anion exchange step includes feeding the coating agent and / or the counter-anion exchange treatment liquid to a microchannel. The coating method as described.

[Item 12] The coating method according to any one of Items 7 to 11, further comprising a step of aging under heating after the contact step.
In addition, the above-mentioned invention has different categories such as, for example, the ionic liquid used as the coating agent (active ingredient thereof), the use of the ionic liquid in the preparation of the coating agent, and the use of the ionic liquid in the coating method. It is obvious to those skilled in the art that the present invention can be converted to the present invention.

  The conventional surface treatment technology only controls the hydrophilicity and hydrophobicity of the substrate surface, but the coating using the ionic liquid according to the present invention makes it neither hydrophilic nor hydrophobic, both water and oil. It is possible to provide a surface having a new wettability that is unfamiliar. For example, since PDMS swells with oil, it has not been possible to use oil for PDMS substrates (microchannels) until now, but by coating with the coating agent of the present invention, the channel wall surface It is possible to feed not only a fluid using water as a solvent but also a fluid using oil as a solvent.

  Since the ionic liquid having a predetermined structure to be blended with the coating agent of the present invention can be prepared as a liquid having a relatively low viscosity (having sufficient fluidity) at room temperature, wet coating can be applied. For example, even in places where coating is difficult by other techniques, such as the inner wall surface of a microchannel or the inner surface of another tubular structure, it can be easily and uniformly coated by feeding an ionic liquid. Moreover, since such a coating agent is stable in a solution state, there is no problem in selling it as a reagent.

  Moreover, the wettability of the substrate surface can be easily controlled simply by exchanging the anion species of the ionic liquid. The ionic liquid is covalently bonded to the substrate by a hydrolyzable silyl group possessed by the cation, and only anionic species can be exchanged afterwards without impairing the stable bond. Since there are a wide variety of ionic liquids that can be used in the present invention, the development of a coating technique that imparts specific functionality can be expected.

FIG. 1 is an observation photograph at the time of contact angle measurement with water or hexadecane in the atmosphere of a PDMS substrate (no treatment or UV treatment) conducted as an example (comparative experiment). FIG. 2 is an observation photograph at the time of contact angle measurement with water or hexadecane in the atmosphere of a PDMS substrate (ionic liquid treatment) performed as an example. FIG. 3 is a schematic diagram of a contact angle measurement experiment in a liquid of a PDMS substrate performed as an example. FIG. 4 is an observation photograph at the time of contact angle measurement in a liquid of a PDMS substrate (no treatment, UV treatment or ionic liquid treatment) performed as an example. A: Contact angle with water in hexadecane. B: Contact angle with hexadecane in water.

-Coating agent-
The coating agent of the present invention contains an ionic liquid containing a nitrogen-containing heterocyclic cation or quaternary ammonium cation having at least one hydrolyzable silyl group and a counter anion thereof. Such a coating agent may be prepared as a substance composed of the ionic liquid alone, or may be prepared as a composition containing the ionic liquid and any other components. The ionic liquid may be composed of one kind of compound alone or a mixture of two or more kinds of compounds.

<Ionic liquid>
The ionic liquid used in the present invention is a salt composed of a specific cation and its counter anion as described below. When the ionic liquid has a specific structure, such as when a hydroxyl group is present in the cation substituent, the ionic liquid (the salt) is a neutral molecule (glycerol, citric acid) capable of hydrogen bonding with it. Or a neutral proton donor or acceptor such as urea). Further, in the present invention, unlike the case where the ionic liquid is finally used as a carrier for a metal catalyst in a state of being bonded to a substrate (Non-patent Documents 3 and 4), it is necessary that a metal or a metal compound is bonded. It is desirable that no metal or metal compound is bonded.

  Ionic liquids can generally change viscosity, melting point, and other properties depending on the type of cation and its counter anion. Also in the present invention, an appropriate type of cation and its counter anion of the ionic liquid to be blended can be selected in consideration of the application of the coating agent.

(Cation)
The cation constituting the ionic liquid used in the present invention is a nitrogen-containing heterocyclic cation or a quaternary ammonium cation having at least one hydrolyzable silyl group. A hydrolyzable silyl group can be introduced as a substituent of a nitrogen atom contained in these cations.

  The nitrogen-containing heterocyclic cation and the quaternary ammonium cation (site other than the substituent having a hydrolyzable silyl group) can be selected from those constituting a known ionic liquid, and are not particularly limited. .

  The nitrogen-containing heterocyclic cation includes a cation derived from a nitrogen-containing aromatic compound and a cation derived from a nitrogen-containing alicyclic compound. Examples of cations derived from nitrogen-containing aromatic compounds include imidazolium cations (see general formula (II)), pyridinium cations (see general formula (III)), pyrazolium cations, and triazolium cations. . Examples of the cation derived from the nitrogen-containing alicyclic compound include a pyrrolidinium cation (see general formula (IV)).

  The hydrolyzable group in the hydrolyzable silyl group is not particularly limited as long as it can be bonded to the functional group of the base material through a hydrolysis reaction and a condensation reaction, and a general silane coupling agent is used. You can use what you have. Such a hydrolyzable group is preferably an alkoxy group, but may be other hydrolyzable groups such as an acyloxy group (for example, an acetoxy group).

  In order for the ionic liquid to bind to the substrate, at least one hydrolyzable silyl group is required per molecule of the ionic liquid (cation), and at least one hydrolyzable group per one hydrolyzable silyl group. is necessary. The number of hydrolyzable silyl groups per molecule of the ionic liquid (cation) and the number of hydrolyzable groups per hydrolyzable silyl group can be adjusted as appropriate while considering the binding properties with the substrate. it can. For example, an ionic liquid having one hydrolyzable silyl group having three hydrolyzable groups is suitable for use in the present invention.

Specific examples of the nitrogen-containing heterocyclic cation and the quaternary ammonium cation described above include those in which a nitrogen atom is substituted with at least one substituent represented by the following general formula (I). In formula (I), —SiR ¹¹ _n W _3-n corresponds to a portion referred to herein as a hydrolyzable silyl group, and a portion represented by W _3-n corresponds to a hydrolyzable group. For example, when W is an alkoxy group represented by —OR ¹² , the substituent represented by the general formula (I) can be referred to as a (hydrolyzable) alkoxysilyl group.

^{_{-R 10 -SiR 11 n W 3-}} n (I)
In the formula (I), n is 0, 1 or 2, R ¹⁰ is an alkylene group having 1 to 12 carbon atoms, R ¹¹ each independently represents an alkyl group having 1 to 12 carbon atoms, W is each independently -OR ¹² [wherein R ¹² represents an alkyl group having 1 to 12 carbon atoms. Or -OR ¹³ -OR ¹⁴ [wherein, R ¹³ represents an alkylene group having 1 to 12 carbon atoms, R ¹⁴ represents an alkyl group having 1 to 12 carbon atoms. ] The hydrolyzable group represented by this.

Those skilled in the art will know n, R ¹¹ and W constituting the hydrolyzable silyl group within the range of the general embodiments of the silane coupling agent, with respect to the use of the coating agent and the base material required therefor. An appropriate one can be selected in consideration of binding properties (hydrolysis rate and the like).

  n is 0, 1 or 2, but is preferably 0 or 1 (the number of hydrolyzable groups represented by 3-n is 3 or 2), and is 0 (of the hydrolyzable group). More preferably, the number is 3.

The alkylene group for R ¹⁰ may be linear or branched, and may contain an unsaturated bond, but is usually a straight chain that does not contain an unsaturated bond. The number of carbon atoms of the alkylene group is usually 1 to 12, preferably 1 to 6. For example, an ethylene group (C ₂ ) and a propylene group (C ₃ ) are preferable.

The alkyl group represented by R ¹¹ may be linear or branched and may contain an unsaturated bond, but is usually a straight chain containing no unsaturated bond. The number of carbon atoms of this alkyl group is usually 1 to 12, preferably 1 to 3. For example, a methyl group (C ₁ ) is preferable.

When W is an alkoxy group represented by —OR ¹² , the alkyl group of R ¹² may be linear or branched and may contain an unsaturated bond, but usually contains an unsaturated bond. There is no linear. The number of carbon atoms of this alkyl group is usually 1 to 12, preferably 1 to 3. For example, a methyl group (C ₁ ) and an ethyl group (C ₂ ) are preferable.

When W is an alkoxyalkoxy group represented by —OR ¹³ —OR ¹⁴ , the alkylene group represented by R ¹³ may be linear or branched, and may contain an unsaturated bond, but is usually an unsaturated group. It is a straight chain that does not contain a saturated bond. The number of carbon atoms of the alkylene group is usually 1 to 12, preferably 1 to 3, and examples thereof include a methyl group (C ₁ ) and an ethyl group (C ₂ ). On the other hand, the alkyl group of R ¹⁴ may be linear or branched, and may contain an unsaturated bond, but is usually a straight chain that does not contain an unsaturated bond. The number of carbon atoms of the alkyl group is usually 1 to 12, preferably 1 to 3, and examples thereof include a methyl group (C ₁ ). Examples of the entire group represented by OR ¹³ -OR ¹⁴ include a 2-methoxyethoxy group.

Specific examples of the nitrogen-containing heterocyclic cation and the quaternary ammonium cation as described above include those represented by the general formula (II), (III), (IV) or (V). In these cations, R ^{1 to} R ² can be a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group. It can be selected from among a variety of known ionic liquids.

In formula (II), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.

In Formula (III), R ¹ is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by Formula (I).

In the formula (IV), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by the formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.

In the formula (V), at least one of R ¹ , R ² , R ³ and R ⁴ has at least one hydrolyzable silyl group which may be a substituent represented by the formula (I). The other substituents are each independently a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.

The nitrogen-containing heterocyclic cation or quaternary ammonium cation having at least one hydrolyzable silyl group constituting the ionic liquid used in the present invention is derived from a cation represented by, for example, the formula (II) It may also include repeating structural units. For example, the ionic liquid represented by the following formula (IIa) contains a repeating unit derived from an imidazolium cation and its counter anion (X ⁻ ), and each repeating unit is similar to R ² in the formula (II). And the rightmost imidazolium cation is —R ¹⁰ —SiW ₃ (in formula (I), n = 0) as the group corresponding to R ¹ in formula (II). It has a hydrolyzable silyl group represented by. In such a long ionic liquid molecule, there are a plurality of positively charged sites (derived from the cation), and a counter anion binds to each site.

(Anion)
The anion constituting the ionic liquid used in the present invention is not particularly limited. Depending on the choice of anion, various wettability can be imparted to the substrate. Considering the use as a coating agent, an anion that can impart desired wettability (hydrophilicity-water repellency and / or lipophilicity-oil repellency) to the substrate may be used.

Specific examples of the counter anion include, for example, Cl ⁻ , Br ⁻ , I ⁻ , CF ₃ CO ₂ ⁻ , CH ₃ CO ₂ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , PF ₆ ⁻ and (CF ₃ SO _2. ) ₂ N ^- and the like.
In general, Cl ⁻ , Br ⁻ , I ⁻ , CF ₃ CO ₂ ⁻ and CH ₃ CO ₂ ⁻ are hydrophilic, PF ₆ ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ are hydrophobic, and BF _{Although 4} ⁻ and CF ₃ SO ₃ ⁻ show an intermediate tendency, wettability imparted by modifying the substrate surface in the present invention varies. For example, with respect to a PDMS substrate, Cl ⁻ as a counter anion of an ionic liquid exhibits strong hydrophilicity in both air and oil, but is extremely weak (close to untreated PDMS) oil repellency in air. On the contrary, wettability showing extremely strong oil repellency can be imparted in water. Similarly, PF ₆ ⁻ as the counter anion of the ionic liquid shows only weak hydrophilicity and weak oil repellency in the atmosphere (that is, the modification effect when compared with untreated PDMS) against the PDMS substrate. Imparting interesting wettability while exhibiting a certain hydrophilicity in oil and a certain oil repellency in water (ie, both have a certain modification effect on untreated PDMS) Can do.

(Synthesis method)
Methods for synthesizing ionic liquids used in the present invention are known (see, for example, Non-Patent Documents 1 and 2). Nitrogen-containing heterocyclic cations or quaternary ammonium cations are generally synthesized by quaternizing a nitrogen-containing heterocyclic ring or the nitrogen atom of an amine, for example, using an alkylating reagent. A nitrogen-containing heterocyclic cation or quaternary ammonium cation having a hydrolyzable silyl group is a molecule having a hydrolyzable silyl group and a reactive functional group capable of binding to the nitrogen atom during such quaternization. Can be synthesized. The ionic liquid used in the present invention can be typically synthesized by using a silane coupling agent as the quaternization molecule.

  In general, the anion derived from the reagent for quaternization becomes a counter anion of a nitrogen-containing heterocyclic cation or a quaternary ammonium cation. In the ionic liquid obtained by the above typical synthesis method, a halide ion derived from a silane coupling agent having a halogen atom as a reactive functional group is converted into a nitrogen-containing heterocyclic cation having a hydrolyzable silyl group or a quaternary cation. It becomes the counter anion of the quaternary ammonium cation.

  However, the ionic liquid used in the present invention is not limited to those obtained by the synthesis method as described above, and may be obtained by other production methods as long as it has a predetermined structure defined in the present invention. May be.

  The silane coupling agent used in the synthesis method as described above has a hydrolyzable silyl group at one end and a nitrogen-containing heterocycle or amine nitrogen atom to which a substituent is to be introduced at the other end. Any functional group may be used as long as it has a reactive functional group that can be bonded to the molecule, and a molecular chain having an appropriate length connected to these groups. As the reactive functional group, for example, a halogen group (halogen atom such as chlorine, bromine, iodine, etc.) is preferable. Silane coupling agents having such a structure (for example, 3-chloropropyltrimethoxysilane) can be purchased from Aldrich, Shin-Etsu Chemical Co., Ltd., etc. They can also be synthesized (see, for example, R. Wakabayashi et al, Angew. Chem. Int. Ed, 50, 10708-10711 (2011)).

In the synthesis method using a silane coupling agent, when a desired counter anion cannot be generated simultaneously with the generation of a cation, the counter anion can be exchanged in a further step. Such counter-anion exchange is well known for ionic liquids and can be similarly performed in the present invention. For example, the exchange to anions such as PF ⁶⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ can be performed by reacting these alkali metal salts with the synthesized ionic liquid. Anion exchange can also be performed by passing the synthesized ionic liquid through a column filled with an anion exchange resin having a desired anion.

<Optional components, etc.>
In consideration of the embodiment of the coating agent of the present invention or the coating film or coating layer formed therefrom, if necessary, a substance other than the ionic liquid may be added to the coating agent as an optional component. For example, a substance that participates in wettability with an ionic liquid, a substance that imparts characteristics other than wettability to the substrate, a substance that participates in physical properties such as the strength of the coating or coating layer, etc. can be blended as optional components Is possible.

When an optional component is used, the coating agent can be prepared by mixing it with an ionic liquid as described above by a general method.
Also, dispersion of silica fine particles surface-treated with an ionic liquid, which can be used in one embodiment of the coating layer of the present invention as will be described later, and optional components blended as necessary, for example, the treated silica fine particles. A composition containing an additive or a dispersion medium for improving the adhesion and adhesion to the substrate can also be prepared as the coating agent of the present invention. In this embodiment of the coating agent, it can be said that the ionic liquid is contained in the coating material in a state of being bonded to the silica fine particles in advance.

  The coating agent of the present invention as described above can be used to form a coating layer that changes the wettability of the substrate (thus increasing the resistance to water and / or oil) as described below.

-Coating layer and coated substrate-
The coating layer of the present invention includes a film formed from the coating agent of the present invention as described above, and can change the wettability of the substrate. Moreover, the coating base material of this invention is coat | covered with the above coating layers, and has the wettability different from the base material of an unprocessed state. These coating layers and coated substrates can be formed or manufactured using the following coating method. For example, for the explanation of the substrate, the explanation in the following coating method can be referred to.

  A coating layer may be comprised only from the film formed from the coating agent, and may be comprised with such a film and another substance. As the latter embodiment, for example, silica fine particles that have been surface-treated with an ionic liquid in advance (the ionic liquid is bonded to the surface of the silica fine particles) are prepared, and a wider plane can be formed with the treated silica fine particles. For example, the surface of the substrate having the coating may be coated. In this case, a dispersion of silica fine particles surface-treated with an ionic liquid (optional components may be further blended as necessary) corresponds to the coating agent of the present invention, and the silica fine particle treated product (individual A layer made of an ionic liquid is formed on the surface of the silica fine particles) and a layer made of an optional component blended as necessary corresponds to the coating layer of the present invention.

  The wettability of the substrate is a property generally called hydrophilicity-water repellency or lipophilicity-oil repellency. Wettability can be evaluated by contact angle with any liquid, measured in any gas or liquid, but by contact angle according to the conditions under which the coated substrate is assumed to be used. It is appropriate to do. Typically, depending on the contact angle with water or oil (for example, an organic solvent such as hexadecane) in the atmosphere, the contact angle with oil in water, or the contact angle with water in oil, Lipophilicity-oil repellency is evaluated. The wettability of the substrate may be evaluated by either hydrophilicity-water repellency or oleophilic-oil repellency, or may be evaluated by both hydrophilicity-water repellency and oleophilic-oil repellency. Good. Depending on the anionic species of the ionic liquid blended in the coating agent, the surface of the substrate can be rendered water and oil repellent.

  The degree of contact angle with water is defined as hydrophilic or water repellency, or the degree of contact angle with oil is defined as oleophilic or oleophobic. However, in general, when the contact angle is 40 ° or less, it is referred to as hydrophilic or lipophilic, and when it is 10 ° or less, it is referred to as superhydrophilic or superlipophilic, and conversely, when the contact angle is 90 ° or more. It is defined as water repellency or oil repellency, high water repellency or high oil repellency when it is 120 ° or more and less than 150 °, and super water repellency or super oil repellency when it is 150 ° or more.

  The measurement method of the contact angle is not particularly limited, and any measurement method can be employed in the user's evaluation, but the θ / 2 method (calculated contact) known as a general method. The angle is the average value of the left and right of the droplet) or the tangential method (the calculated contact angle is left and right separately, and if the value on the left and right of the droplet varies depending on the state of the solid surface, it is Can be used.

-Coating method-
The coating method of the present invention includes a step of contacting the coating agent of the present invention as described above with a base material having a functional group capable of binding to a hydrolyzable silyl group (contacting step). An aging step and an anion exchange step as described later may be included.

  The functional group that can be bonded to the hydrolyzable silyl group of the substrate is not particularly limited as long as it satisfies such a condition. An ionic liquid having an appropriate hydrolyzable silyl group may be selected according to the substrate to be surface-modified.

  A representative example of a functional group that can be bonded to a hydrolyzable silyl group is a hydroxy group. For example, when the hydrolyzable silyl group has an alkoxy group, generally a hydroxy group (silanol group) generated from the alkoxy group by a hydrolysis reaction with water in the atmosphere, and a substrate such as glass The hydroxyl group present on the surface of the silane is firmly bonded by a hydrogen bond and then a covalent bond formed by a dehydration condensation reaction.

In other words, the substrate to be surface-modified with the coating agent is not particularly limited as long as it has a functional group capable of binding to the hydrolyzable silyl group of the ionic liquid contained in the coating agent. Absent. For example, a suitable amount of hydroxy groups can be present on the surface, and polydimethylsiloxane (PDMS) and glass or silica (SiO ₂ ), which are widely used as general-purpose materials, are suitable substrates. In addition, a base material in which a general silane coupling agent such as silicon (Si) is used can be used.

  When the substrate and the coating agent are brought into contact with each other, a treatment for forming a hydroxy group on the substrate surface in advance (before the contact step) is performed in the same manner as in the case of using a general silane coupling agent. It is preferable to carry out. In general, ultraviolet treatment, plasma treatment, or the like is used as such treatment.

  The method of bringing the coating agent into contact with the substrate is not particularly limited as long as a binding reaction occurs between the hydrolyzable silyl group of the ionic liquid in the coating agent and the predetermined functional group of the substrate. Absent. For example, a general wet coating technique such as dip coating, spin coating, or spray (inkjet) coating can be used to form a film by applying a coating on the top surface of various shapes under mild conditions. Can do.

  Moreover, you may further perform the process (counter anion exchange process) of exchanging the counter anion of the ionic liquid in a coating material after a contact process. Regarding the type of anion used in this step, the reagent, the exchange method, and the like, the description described above in the section on anion relating to a predetermined ionic liquid and the section on the synthesis method can be referred to. In the counter-anion exchange step, for example, an aqueous solution of a counter-anion exchange reagent (alkali metal salt, etc.) is applied to the surface of a substrate on which a certain type of ionic liquid is already bonded, using the same wet coating technique as described above. Can be done. Such a counter anion exchange step may be performed continuously without much time after the contact step (for example, a specific anion that cannot be obtained by a single contact step using a predetermined ionic liquid). May be performed after a relatively long time after the contact process (for example, a product containing a coated substrate to which a certain ionic liquid is bound). When the counter anion is exchanged after a certain period of time has elapsed since the product was manufactured and the purchaser is ready to use it).

  As an example of a preferred embodiment of the present invention, the contact process is performed on a microchannel having a side or a diameter of about several μm to several hundreds of μm formed inside a PDMS or glass substrate, for example. A method of forming a film by bringing a coating agent into contact with the surface of the microchannel by feeding the solution. Similarly, the anion exchange step performed as necessary can also be performed by sending a counter anion exchange treatment solution (for example, an aqueous solution of an alkali metal salt of a desired anion) to the microchannel. The predetermined ionic liquid can be fed using a general means used for the microchannel, for example, a syringe pump or a peristaltic pump.

  The reaction between the predetermined ionic liquid contained in the coating agent and the substrate can be allowed to proceed under mild conditions. Usually, a silanol group generated from a hydrolyzable silyl group and a hydroxy group capable of binding thereto are obtained by contacting (for example, applying) the coating material to the substrate in a normal temperature atmosphere having a suitable humidity and reacting for a suitable time. Sufficient bonds can be formed between functional groups such as groups. If necessary, as in the case of bonding a general silane coupling agent to an inorganic material, a step or operation for accelerating the reaction or stabilizing the bond may be added. For example, a step of aging under heating may be provided after the contact step.

  [Synthesis example]

An ionic liquid was synthesized according to the above scheme (reference paper: K. Yamaguchi et al. J. Am. Chem. Soc., 127, 530-531 (2005)). That is, an equivalent amount of Compound 1 and Compound 2 were allowed to react overnight with stirring without a solvent, and a reaction product 3 was obtained in a yield of about 85%.

1. Contact angle of material surface ( based on general adhesion wetting experiment) in air (1) Untreated PDMS surface, PDMS surface treated with 1 hour, 2 hours and 3 hours UV treatment, and 3 hours UV treatment The contact angle (A) with water in the atmosphere and the contact angle (B) with hexadecane in the air were measured on the PDMS surface that was left overnight. For UV treatment, UV.TC.NA.003 (BioForce Nanosciences) was used. The contact angle was calculated by the θ / 2 method in image analysis using a contact angle measurement device after water or hexadecane was dropped on the PDMS surface. The results are shown in Table 1 and FIG.

(2) Next, regarding the PDMS surface coated with an ionic liquid having Cl ⁻ as an anion and the PDMS surface coated with an ionic liquid in which Cl ⁻ is exchanged with PF ₆ ⁻ by anion exchange treatment, water in the atmosphere is used. Contact angle (A) and contact angle (B) with hexadecane in the atmosphere. The former coating of the PDMS surface with the ionic liquid is performed by immersing the PDMS substrate in the ionic liquid obtained in the synthesis example, and then allowing the pulled PDMS substrate to stand in a constant temperature bath at 95 ° C. overnight. It was. The latter coating of the PDMS surface with the ionic liquid is performed by immersing the PDMS substrate in the ionic liquid obtained in the synthesis example, followed by immersing in a LiPF ₆ aqueous solution (concentration: 10 to 20 wt%), and then lifting the PDMS substrate. Was allowed to stand in a constant temperature bath at 95 ° C. overnight. The method for measuring the contact angle is as described above (θ / 2 method). The results are shown in Table 2 and FIG.

  First, as can be seen from the result of (1), the PDMS surface generally repels water relatively and is compatible with oils such as hexadecane. Although the hydrophilicity of the PDMS surface increases with UV treatment, the hydrophilicity decreases considerably only by placing it overnight after UV irradiation. Further, as can be seen from the results of the contact angle B in Table 1, PDMS has an affinity for oil, which represents a drawback that the conventional PDMS substrate cannot absorb oil because it exhibits oil absorption. Therefore, even if the PDMS surface is resistant to oil (oil repellency), it can be said that there is a practical merit for enabling the PDMS substrate to be adapted to oil.

  Next, as can be seen from the results of (2), it is possible to change the wettability of the PDMS surface by coating with an ionic liquid having a hydrolyzable silyl group, and the coating agent of the ionic liquid Different wettability can be imparted depending on the anion species.

When Cl ^- was used as an anion, the contact angle with water was remarkably reduced, that is, the hydrophilicity of the PDMS surface was greatly improved. This wettability was maintained in the atmosphere for 3-4 months. On the other hand, the contact angle with hexadecane (oil) also became small, and oil repellency was not shown in this experimental system. This depends on the contact angle depending on the magnitude of the interaction between the solid (PDMS) surface and air (relatively hydrophobic) and the magnitude of the interaction between the solid surface and hexadecane (oil). This is thought to be due to the fact that is born.
Therefore, the wettability of the PDMS surface in liquid (oil and water), not in the air, was evaluated in the following experiment.

2. Contact angle of material surface in solution In the experimental system shown in FIG. 3, the PDMS surface prepared in 1 (2) above and coated with an ionic liquid having Cl ⁻ as an anion, Cl ⁻ is PF ₆ ⁻ by anion exchange treatment. The contact angle (A) with water in hexadecane (0.773 g / cm ³ ) (oil) and the hexadecane in water (for PDMS surfaces coated with an ionic liquid exchanged into the water and untreated PDMS surfaces as controls) The contact angle (B) with the oil) was measured. For the measurement of the contact angle, the above-described method (θ / 2 method) or tangential method (in the case of an oil dropping experiment) was used. The results are shown in Table 3 and FIG.

As can be seen from the results of this experiment, PDMS surface exhibits a strong water repellency in oil, Cl ^- can impart high hydrophilicity by ionic liquids coating with. At this time, the oil droplets were completely unfamiliar with this surface and exhibited such oil repellency that the contact angle could not be measured. On the other hand, PF ₆ ^- by an ionic liquid coating was used to obtain an interesting result that it is possible to impart the same time constant oil repellency constant water repellency. By using a coating containing such an ionic liquid, it becomes possible to give the coating PDMS surface a property that is not compatible with water or oil in the liquid, and this is a new coating technology that has never existed before. It is considered to be.

Claims (9)

From a base material having a functional group capable of binding to a hydrolyzable silyl group, a nitrogen-containing heterocyclic cation or quaternary ammonium cation having at least one hydrolyzable silyl group, and PF ₆ ⁻ as a counter anion A coating layer containing an ionic liquid,
A coated substrate, wherein the substrate is polydimethylsiloxane (PDMS) or glass. The coated substrate according to claim 1, wherein the nitrogen-containing heterocyclic cation or the quaternary ammonium cation has a nitrogen atom substituted with at least one substituent represented by the following general formula (I).
^{_{-R 10 -SiR 11 n W 3-}} n (I)
In the formula (I), n is 0, 1 or 2, R ¹⁰ is an alkylene group having 1 to 12 carbon atoms, R ¹¹ each independently represents an alkyl group having 1 to 12 carbon atoms, W is each independently -OR ¹² [wherein R ¹² represents an alkyl group having 1 to 12 carbon atoms. Or -OR ¹³ -OR ¹⁴ [wherein, R ¹³ represents an alkylene group having 1 to 12 carbon atoms, R ¹⁴ represents an alkyl group having 1 to 12 carbon atoms. ] The hydrolyzable group represented by this. The coated substrate according to claim 1 or 2, wherein the nitrogen-containing heterocyclic cation or quaternary ammonium cation is represented by the general formula (II), (III), (IV) or (V). .
In formula (II), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.
In Formula (III), R ¹ is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by Formula (I).
In the formula (IV), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by the formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.
In the formula (V), at least one of R ¹ , R ² , R ³ and R ⁴ has at least one hydrolyzable silyl group which may be a substituent represented by the formula (I). The other substituents are each independently a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group. A coating agent containing an ionic liquid composed of a nitrogen-containing heterocyclic cation or quaternary ammonium cation having at least one hydrolyzable silyl group and PF ₆ ⁻ as a counter anion thereof is made of polydimethylsiloxane (PDMS) or The coating method characterized by including the process made to contact with the base material which consists of glass. The coating method according to claim 4, wherein the nitrogen-containing heterocyclic cation or the quaternary ammonium cation is one in which a nitrogen atom is substituted with at least one substituent represented by the following general formula (I).
^{_{-R 10 -SiR 11 n W 3-}} n (I)
In the formula (I), n is 0, 1 or 2, R ¹⁰ is an alkylene group having 1 to 12 carbon atoms, R ¹¹ each independently represents an alkyl group having 1 to 12 carbon atoms, W is each independently -OR ¹² [wherein R ¹² represents an alkyl group having 1 to 12 carbon atoms. Or -OR ¹³ -OR ¹⁴ [wherein, R ¹³ represents an alkylene group having 1 to 12 carbon atoms, R ¹⁴ represents an alkyl group having 1 to 12 carbon atoms. ] The hydrolyzable group represented by this. The coating method according to claim 4 or 5, wherein the nitrogen-containing heterocyclic cation or quaternary ammonium cation is represented by the general formula (II), (III), (IV) or (V).
In formula (II), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.
In Formula (III), R ¹ is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by Formula (I).
In the formula (IV), at least one of R ¹ and R ² is a substituent having at least one hydrolyzable silyl group, which may be a substituent represented by the formula (I), Other than the above, a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.
In the formula (V), at least one of R ¹ , R ² , R ³ and R ⁴ has at least one hydrolyzable silyl group which may be a substituent represented by the formula (I). The other substituents are each independently a linear or branched, substituted or unsubstituted alkyl group, aryl group, alkoxyalkyl group, alkylenearyl group, hydroxyalkyl group or haloalkyl group.   The coating method according to any one of claims 4 to 6, further comprising a step of exchanging a counter anion of the ionic liquid in the coating agent.   The coating according to any one of claims 4 to 7, wherein the contacting step and / or the counter-anion exchange step includes feeding the coating agent and / or the counter-anion exchange treatment liquid to a microchannel. Method.   The coating method according to any one of claims 4 to 8, further comprising a step of aging under heating after the contact step.