Surface treatment agent and member

Abstract

To provide a surface treatment agent capable of imparting both hydrophilicity and favorable water sliding properties to a member.SOLUTION: There is provided a surface treatment agent which contains an alkoxysilane containing a polyethylene glycol chain (A) and an alkoxysilane containing an alkyl group (B), wherein the ethylene glycol structural unit number of the alkoxysilane containing a polyethylene glycol chain (A) is 21 or more and 25 or less, the carbon number of the alkyl group of the alkoxysilane containing an alkyl group (B) is 16 or more and 18 or less and the molar ratio (A / B) of the alkoxysilane containing a polyethylene glycol chain (A) to the alkoxysilane containing an alkyl group (B) is 1.0 or more and 3.0 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a surface treatment agent and a component. [Background technology]

[0002] Conventionally, techniques for imparting hydrophilic properties to component surfaces have been known. For example, when a heat exchanger such as an air conditioner is operating in cooling mode, water vapor in the atmosphere condenses on the fin material surface, forming droplets. These droplets cause clogging between the fin materials, which reduces heat exchange efficiency. By imparting hydrophilic properties to the fin material surface, it is possible to prevent the droplets from forming bridges between the fin materials.

[0003] Although a member that is only given hydrophilic properties can suppress the formation of bridges, it has the problem of being difficult to remove droplets. Therefore, a technology has been proposed that gives the surface of a member both hydrophilic properties and water-slip properties (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2024-032373 Summary of the Invention [Problem to be solved by the invention]

[0005] The technique disclosed in Patent Document 1 leaves room for further improvement in terms of imparting both hydrophilicity and favorable water sliding properties to a member.

[0006] The present disclosure has been made in view of the above, and has an object to provide a surface treatment agent that can impart both hydrophilicity and favorable water-sliding properties to a member. [Means for solving the problem]

[0007] The present disclosure relates to a surface treatment agent comprising a polyethylene glycol chain-containing alkoxysilane (A) and an alkyl group-containing alkoxysilane (B), wherein the number of ethylene glycol structural units in the polyethylene glycol chain-containing alkoxysilane (A) is 21 or more and 25 or less, the number of carbon atoms in the alkyl group of the alkyl group-containing alkoxysilane (B) is 16 or more and 18 or less, and the molar ratio (A / B) of the polyethylene glycol chain-containing alkoxysilane (A) to the alkyl group-containing alkoxysilane (B) is 1.0 or more and 3.0 or less. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a surface treatment agent that can impart both hydrophilicity and favorable water sliding properties to a member. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Surface treatment agent> The surface treatment agent according to this embodiment contains a polyethylene glycol chain-containing alkoxysilane (A) and an alkyl group-containing alkoxysilane (B).

[0010] (Polyethylene glycol chain-containing alkoxysilane (A)) The polyethylene glycol chain-containing alkoxysilane (A) imparts desirable hydrophilicity to the surface of a component by being contained in a surface treatment agent. The polyethylene glycol chain-containing alkoxysilane (A) is a silane compound having a polyethylene glycol chain and an alkoxy group. The number of ethylene glycol structural units in the polyethylene glycol chain-containing alkoxysilane (A) is 21 or more and 25 or less.

[0011] The polyethylene glycol chain-containing alkoxysilane (A) has, for example, the structure shown in the following formula (1).

[0012] [ka]

[0013] In the above formula (1), the number of ethylene glycol structural units represented by n is 21 or more and 25 or less. This allows the surface of the component to be imparted with desirable hydrophilicity. If the number of ethylene glycol structural units is less than 21, the hydrophilicity of the formed film may be insufficient. If the number of ethylene glycol structural units exceeds 25, the cost of the surface treatment agent increases and handling becomes difficult. The polyethylene glycol chain-containing alkoxysilane (A) may be a mixture of multiple compounds having different numbers of ethylene glycol structural units.

[0014] In the above formula (1), R1 each independently represents an alkoxy group having 1 to 5 carbon atoms. R1 is, for example, a methoxy group. Note that the alkoxy group may be in a hydrolyzed state in the surface treatment agent, as described below.

[0015] In the above formula (1), R2 represents a substituted or unsubstituted hydrocarbon group, such as alkylene groups such as methylene, ethylene, propylene, isopropylene, butylene, hexylene, 2-ethylhexylene, nonylene, and cyclohexylene.

[0016] In the above formula (1), R3 represents an alkyl group having 1 to 5 carbon atoms.

[0017] (Alkyl-containing alkoxysilane (B)) The alkyl group-containing alkoxysilane (B) imparts desirable water-slip properties to the surface of a component by being contained in a surface treatment agent. The alkyl group-containing alkoxysilane (B) is a silane compound having an alkyl group and an alkoxy group. The number of carbon atoms in the alkyl group-containing alkoxysilane (B) is 16 or more and 18 or less.

[0018] The alkyl group-containing alkoxysilane (B) has, for example, a structure shown in the following formula (2).

[0019] [ka]

[0020] In the above formula (2), R5 is an alkoxy group having the same meaning as R1 in formula (1). The alkoxy group may be in a hydrolyzed state in the surface treatment agent, as described below.

[0021] In the above formula (2), R4 is a linear or branched alkyl group having 16 to 18 carbon atoms. This allows for desirable water sliding properties to be imparted to the surface of the component. If the number of carbon atoms is less than 16, the sliding angle of the formed coating may not be small. If the number of carbon atoms exceeds 18, the cost of the surface treatment agent increases and handling becomes difficult. The alkyl group-containing alkoxysilane (B) may be a mixture of multiple compounds having R4 with different carbon numbers.

[0022] In the surface treatment agent according to this embodiment, the molar ratio (A / B) of the polyethylene glycol chain-containing alkoxysilane (A) to the alkyl group-containing alkoxysilane (B) is 1.0 or more and 3.0 or less, thereby imparting both hydrophilicity and favorable water-sliding properties to the member.

[0023] (Other ingredients) The surface treatment agent according to the present embodiment may contain components other than the polyethylene glycol chain-containing alkoxysilane (A) and the alkyl group-containing alkoxysilane (B) as long as the effects of the present disclosure are not impaired. Examples of such components include a solvent, a catalyst, and an additive.

[0024] The solvent is not particularly limited as long as it can dissolve the polyethylene glycol chain-containing alkoxysilane (A) and the alkyl group-containing alkoxysilane (B). As the solvent, an aromatic hydrocarbon solvent such as toluene is preferably used, and saturated hydrocarbon solvents, alcohol solvents, ether solvents, ketone solvents, ester solvents, amide solvents, etc. may also be used.

[0025] The catalyst may be one that acts as a catalyst for hydrolyzing the alkoxy groups of the polyethylene glycol chain-containing alkoxysilane (A) and the alkyl group-containing alkoxysilane (B). Examples of the catalyst include acidic compounds such as hydrochloric acid, nitric acid, and acetic acid, basic compounds such as ammonia and amines, and organometallic compounds having a metal element as the central metal.

[0026] Examples of the additives include antioxidants, anti-rust agents, ultraviolet absorbers, light stabilizers, anti-fungal agents, antibacterial agents, anti-biofouling agents, deodorizers, pigments, flame retardants, and antistatic agents.

[0027] <Method for preparing surface treatment agent> Examples of methods for preparing the surface treatment agent according to the above embodiment include a method in which the polyethylene glycol chain-containing alkoxysilane (A) and the alkyl group-containing alkoxysilane (B) are each dissolved in a solvent such as toluene, a hydrolysis catalyst such as hydrochloric acid is added to hydrolyze the alkoxy groups of each silane into hydroxyl groups (silanol groups), and the respective solutions are mixed so that the molar ratio (A / B) is 1.0 or more and 3.0 or less; and a method in which the polyethylene glycol chain-containing alkoxysilane (A) and the alkyl group-containing alkoxysilane (B) are dissolved in a solvent such as toluene so that the molar ratio (A / B) is 1.0 or more and 3.0 or less, and a hydrolysis catalyst such as hydrochloric acid is added to hydrolyze the alkoxy groups of each silane into hydroxyl groups (silanol groups).

[0028] <Surface treatment method> The method for treating the surface of a component using the surface treatment agent according to the above embodiment includes a contacting step of bringing the surface treatment agent into contact with the surface of the component, and a drying step of drying the surface of the component to form a coating.

[0029] In the contacting step, the specific method is not particularly limited, and examples thereof include a dipping method, a spraying method, a spin coating method, and a bar coater method.

[0030] The drying step volatilizes the solvent and the alcohol produced by hydrolysis from the surface treatment agent applied to the surface of the component, forming a dry film on the surface of the component. The drying temperature and time can be appropriately set depending on the type of solvent and the alcohol produced by hydrolysis.

[0031] The surface treatment method according to this embodiment may optionally include other steps than those described above, such as steps of washing the surface of the component with water, degreasing, pretreating, or chemical conversion treating the surface.

[0032] <Surface treatment materials> The material of the member to be surface-treated with the surface treatment agent according to the above embodiment is not particularly limited, but examples thereof include silicon, glass, metal, metal oxide, silicon nitride, and resin. Examples of resins include thermoplastic resins such as acrylic resin, polycarbonate resin, polyester resin, styrene resin, acrylic-styrene copolymer resin, cellulose resin, polyolefin resin, and polyvinyl alcohol, and thermosetting resins such as phenol resin, urea resin, melamine resin, epoxy resin, unsaturated polyester, silicone resin, and urethane resin.

[0033] The surface-treated member surface-treated with the surface treatment agent according to the embodiment has a film derived from the surface treatment agent on its surface. The surface-treated member may be used in applications requiring both hydrophilicity and water-slip properties, such as water-shedding and self-cleaning properties, but is not limited thereto, such as a fin material for a heat exchanger.

[0034] (contact angle) The contact angle of water droplets on the surface of the surface-treated member according to this embodiment (static contact angle with water) is preferably 40° or less. A contact angle of 40° or less is an indicator that the surface of the surface-treated member has been given desirable hydrophilic properties. For example, when the surface-treated member is a fin material for a heat exchanger, a contact angle of 40° or less can prevent droplets from forming bridges between the fin materials. More preferably, the contact angle is 36° or less.

[0035] (slip angle) The sliding angle of a water droplet (sliding angle relative to water) on the surface of the surface-treated member according to this embodiment is preferably less than 10°. The sliding angle is measured by dropping a droplet on a horizontal surface of the member, gradually tilting the member, and measuring the inclination angle of the member when the droplet begins to slide (sliding method). A sliding angle of less than 10° is an indicator that the surface of the surface-treated member has been imparted with favorable water-shedding properties. A sliding angle of less than 10° can improve the removability of water droplets from the member surface. The sliding angle is more preferably 7° or less.

[0036] (hysteresis) The difference (hysteresis) between the advancing angle and receding angle (the advancing angle relative to water) of a water droplet on the surface of the surface-treated member according to this embodiment is preferably 4.5° or less. The advancing angle is measured as the contact angle at which the three-phase contact line advances when a droplet in contact with a solid surface is expanded. The receding angle is measured as the contact angle at which the three-phase contact line retreats when a droplet in contact with a solid surface is sucked in. A hysteresis of 4.5° or less is an indicator that the surface of the surface-treated member has been imparted with favorable water-slip properties. A hysteresis of 4.5° or less can improve the removability of water droplets from the member surface. The hysteresis is more preferably 4° or less.

[0037] The preferred embodiments of the present disclosure have been described above. The present disclosure is not limited to the above embodiments, and can be modified within the scope of the present disclosure. [Example]

[0038] Examples of the present disclosure will be described below, but the present disclosure is not limited to these examples.

[0039] [Preparation of surface treatment agent] Example 1 A solution was prepared by adding 2.30 μmol of Si-PEG21-25 as a polyethylene glycol chain-containing alkoxysilane (A) (PEG silane (A)) and 4 μL of concentrated HCl to 5 mL of anhydrous toluene. A solution was prepared by adding 2.30 μmol of Si-C18 as an alkyl group-containing alkoxysilane (B) (alkylsilane (B)) and 4 μL of concentrated HCl to 5 mL of anhydrous toluene. The above two solutions were mixed and stirred to obtain a hydrophilic, water-slipping surface treatment agent.

[0040] Other Examples and Comparative Examples A surface treatment agent was obtained in the same manner as in Example 1, except that the PEG silane (A) and alkyl silane (B) were changed to the formulation shown in Table 1. The details of the abbreviations shown in Table 1 are as follows.

[0041] (PEG silane (A), both manufactured by Gelest) Si-PEG21-25: [[3-methoxypoly(ethyleneoxy)21-25]propyl]trimethoxysilane Si-PEG6-9: [[3-methoxypoly(ethyleneoxy)6-9]propyl]trimethoxysilane The notations "21-25" and "6-9" above mean that the compounds are mixtures of compounds with 21-25 and 6-9 ethylene glycol structural unit numbers, respectively. The molecular weights of these raw materials were calculated as the average molecular weights of the respective numbers of ethylene glycol structural units contained. For example, the molecular weight of Si-PEG21-25 was calculated as the average molecular weight of structures with 21, 22, 23, 24, and 25 ethylene glycol structural units.

[0042] (Alkylsilane (B), both manufactured by TCI) Si-C12: Dodecyltrimethoxysilane Si-C16: Hexadecyltrimethoxysilane Si-C18: Octadecyltrimethoxysilane

[0043] [Surface treatment method for components] The silicon substrates used as components were ultrasonically cleaned in acetone, ethanol, and pure water, successively, for 5 minutes each, and then dried by blowing nitrogen. The silicon substrates were then subjected to UV ozone treatment for 20 minutes. The silicon substrates were then washed with ultrapure water and dried on a hot plate at 110°C until the water droplets disappeared. They were then immediately immersed in the surface treatment agents prepared above according to each of the Examples and Comparative Examples. After 18 hours, they were removed from the surface treatment agents and washed with anhydrous toluene. Furthermore, the silicon substrates were ultrasonically cleaned in ethanol and water, successively, for 5 minutes each, dried by blowing nitrogen, and then dried on a hot plate at 120°C, thereby obtaining surface-treated silicon substrates according to each of the Examples and Comparative Examples.

[0044] <Evaluation> (Contact angle measurement) Using an automatic contact angle meter (DMo-602, manufactured by Kyowa Interface Science Co., Ltd.), a 10 μL droplet of pure water (water droplet) was dropped onto the surface-treated silicon substrate of each Example and Comparative Example, and the angle between the liquid surface of the stationary droplet and the solid surface was measured. The results are shown in Table 1.

[0045] (Advance angle, receding angle, hysteresis measurement) Using an automatic contact angle meter (DMo-602, Kyowa Interface Science Co., Ltd.), a 10 μL droplet of pure water was dropped onto a surface-treated silicon substrate. 3 seconds after the droplet landed, the sample substrate stage was continuously tilted at a rate of 1° / sec. When the three-phase contact line continuously moved 0.1 mm or more in both the advancing and retreating directions, the contact angle on the forward side of the movement at the start of the movement was defined as the advancing angle, and the contact angle on the rear side of the movement was defined as the receding angle. Hysteresis was calculated by subtracting the receding angle from the advancing angle. In Comparative Example 5, no movement of the three-phase contact line was observed with a 10 μL droplet, so measurements were taken with a 20 μL droplet.

[0046] (Sliding angle measurement) Using an automatic contact angle meter (DMo-602, Kyowa Interface Science Co., Ltd.), a 10 μL droplet of pure water was dropped onto the surface-treated silicon substrate, and the substrate surface was gradually tilted as described above. The inclination angle of the substrate surface required for the droplet to begin to slide down was taken as the sliding angle.

[0047] [Table 1]

[0048] As shown in Table 1, it is clear that the surface treatment agents according to the respective examples can impart both hydrophilicity and favorable water-sliding properties to the silicon substrate (member).

[0049] Preferred aspects of the present disclosure are listed below.

[0050] [1] A surface treatment agent comprising a polyethylene glycol chain-containing alkoxysilane (A) and an alkyl group-containing alkoxysilane (B), wherein the number of ethylene glycol structural units in the polyethylene glycol chain-containing alkoxysilane (A) is 21 to 25, the number of carbon atoms in the alkyl group of the alkyl group-containing alkoxysilane (B) is 16 to 18, and the molar ratio (A / B) of the polyethylene glycol chain-containing alkoxysilane (A) to the alkyl group-containing alkoxysilane (B) is 1.0 to 3.0.

[0051] [2] A surface-treated member having a coating film derived from the surface treatment agent according to [1] on its surface.

[0052] [3] The member according to [2], wherein the material of the member is at least one selected from the group consisting of silicon, glass, metal, metal oxide, silicon nitride, and resin.

[0053] [4] The member according to [2] or [3], which is used as a fin material for a heat exchanger.

[0054] [5] The member according to any one of [2] to [4], wherein the difference between the advancing angle and the receding angle of the water droplet (hysteresis) is 4.5° or less.

[0055] [6] The member according to any one of [2] to [5], wherein the sliding angle of a water droplet measured by a sliding method is less than 10°.

[0056] [7] The member according to any one of [2] to [6], which has a water droplet contact angle of 40° or less.

Claims

1. A surface treatment agent comprising a polyethylene glycol chain-containing alkoxysilane (A) and an alkyl group-containing alkoxysilane (B), the number of ethylene glycol structural units in the polyethylene glycol chain-containing alkoxysilane (A) is 21 or more and 25 or less, the alkyl group of the alkyl group-containing alkoxysilane (B) has 16 or more and 18 or less carbon atoms, The surface treatment agent, wherein the molar ratio (A / B) of the polyethylene glycol chain-containing alkoxysilane (A) to the alkyl group-containing alkoxysilane (B) is 1.0 or more and 3.0 or less.

2. A surface-treated member having a coating film derived from the surface treatment agent according to claim 1 on its surface.

3. 3. The member according to claim 2, wherein the material of the member is at least one selected from the group consisting of silicon, glass, metal, metal oxide, silicon nitride, and resin.

4. The member according to claim 3, which is used as a fin material for a heat exchanger.

5. 3. The element of claim 2, wherein the difference between the advancing and receding angles of the water droplet (hysteresis) is 4.5 degrees or less.

6. 3. The member of claim 2, wherein the sliding angle of a water droplet is less than 10 degrees as measured by a sliding method.

7. 3. The member according to claim 2, wherein the contact angle of a water droplet is 40° or less.

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