Surface treatment agents

Abstract

To provide a surface treatment agent that can readily exhibit a high hydrophilization effect on a target surface, and can also sufficiently maintain the hydrophilization effect, and a surface treatment method using the surface treatment agent.SOLUTION: The present invention provides [1] a surface treatment agent that comprises betaine group-containing inorganic particles A containing betaine groups on their surfaces through covalent bonds, with the betaine group-containing inorganic particles A having a volume average particle diameter DA of 800 nm or less, and [2] a surface treatment method that comprises the step of applying the surface treatment agent set forth in [1] to a target surface, causing the betaine group-containing inorganic particles A to adhere to the target surface.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a surface treatment agent and a surface treatment method using the surface treatment agent. [Background technology]

[0002] Inorganic particles have been investigated for their potential applications in a wide range of industrial fields due to their many functionalities. For example, U.S. Patent No. 5,949,999 describes that modifying abrasive nanoparticles with multiple chemically bonded zwitterionic functional groups confers stability to the nanoparticles in solution, prevents aggregation and adhesion under a wide range of conditions, and provides abrasive nanoparticles that exhibit minimal adhesion to surfaces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2007 / 146680 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, methods for modifying solid surfaces, such as hydrophilization and water-repellent treatment, have been known to control the wettability of solid surfaces. Among these, hydrophilization treatment of solid surfaces reduces the contact angle of the solid surface with water, making the solid surface more water-wettable. This is expected to facilitate the removal of dirt when cleaning the treated solid surface, and to prevent the re-adhesion of dirt. It is also expected to provide anti-fogging properties for glass, mirrors, etc., anti-static properties for plastics, anti-frosting properties for aluminum fins of heat exchangers, and anti-fouling properties for bathtub and toilet surfaces. Therefore, it is used in various industrial fields. However, the performance of surface treatment agents that can easily perform hydrophilization treatment on various materials is still insufficient, and further performance improvements are desired. An object of the present invention is to provide a surface treatment agent that can easily impart a high hydrophilic effect to a target surface and can maintain the hydrophilic effect well, and a surface treatment method that uses the surface treatment agent. [Means for solving the problem]

[0005] The present inventors have found that the above-mentioned problems can be solved by a surface treatment agent containing betaine group-containing inorganic particles that have betaine groups on their surfaces via covalent bonds, and the volume average particle diameter of the betaine group-containing inorganic particles is within a predetermined range. That is, the present invention provides the following [1] and [2]. [1] A betaine group-containing inorganic particle A having a betaine group on the surface thereof via a covalent bond, and the volume average particle diameter D of the betaine group-containing inorganic particle A A A surface treatment agent having a wavelength of 800 nm or less. [2] A surface treatment method, comprising the steps of applying the surface treatment agent according to [1] above to a target surface and adhering betaine group-containing inorganic particles A to the target surface. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a surface treatment agent that can easily impart a high hydrophilic effect to a target surface and can well maintain the hydrophilic effect, and a surface treatment method that uses the surface treatment agent. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Surface treatment agent] The surface treatment agent of the present invention contains betaine group-containing inorganic particles A (hereinafter also simply referred to as "betaine group-containing inorganic particles A") having betaine groups on the surface via covalent bonds, and the volume average particle diameter D of the betaine group-containing inorganic particles A A is less than 800 nm. In this specification, the inorganic particles that constitute the betaine group-containing inorganic particles A are referred to as "inorganic particles (a)," and the inorganic particles used in producing the betaine group-containing inorganic particles A are referred to as "raw inorganic particles (a')."

[0008] In the present invention, the betaine group-containing inorganic particles A have betaine groups on their surfaces via covalent bonds, and preferably have a plurality of betaine groups on their surfaces via covalent bonds. In the present invention, the term "betaine group" refers to a functional group having a cationic moiety and an anionic moiety, and the functional group as a whole does not have an electric charge. The cationic moiety of the betaine group is a positively charged atomic group, preferably a cationic group. In the present invention, the term "cationic group" refers to a cationic group or a group that can be ionized to become a cationic group. Examples of cationic groups include primary amino groups, secondary amino groups, tertiary amino groups, and quaternary ammonium groups. Among these, the cationic moiety of the betaine group is preferably a quaternary ammonium group from the viewpoint of enhancing the hydrophilic effect. The anionic portion of the betaine group is a negatively charged atomic group, preferably an anionic group. In the present invention, the term "anionic group" refers to an anionic group or a group that can be ionized to become an anionic group. The anionic group is a carboxyl group (-COOM 1 ), sulfonic acid group (-SO3M 1 ), phosphate group (-OPO3M 1 2) and the like. In the above chemical formula, M 1 represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium.

[0009] The surface treatment agent of the present invention is preferably used for the surface treatment of a solid surface as the target surface, and is preferably used as a surface hydrophilization treatment agent that imparts a hydrophilic effect to the target surface. As used herein, the term "solid surface" refers to the interface between a solid and the atmosphere. The solid is not particularly limited, and examples thereof include synthetic resins such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), polycarbonate (PC), polyurethane (PU), acrylonitrile / butadiene / styrene copolymer (ABS), polyamide (PA), melamine resin, and FRP; natural fibers such as cotton, silk, and wool; synthetic fibers such as polyester, nylon, and rayon; metals such as aluminum, stainless steel (SUS), and brass; glass, pottery, porcelain, enamel, tile, ceramics, wood, skin, hair, nails, and teeth. The shape of the solid surface is not particularly limited. Among these, the solid surface is preferably a hard surface, a skin surface, or a hair surface, and more preferably a hydrophobic hard surface, a skin surface, or a hair surface. As used herein, a "hydrophobic surface" refers to a surface having a contact angle of 70° or more, and a "hydrophilic surface" refers to a surface having a contact angle of less than 70°. The contact angle can be measured by a method for measuring static contact angles. The static contact angle can be measured by placing a measurement sample on the stage of a fully automatic contact angle measuring meter "DM-701" (manufactured by Kyowa Interface Science Co., Ltd.), adhering 1 μL of ultrapure water to the sample, and determining the static contact angle after 5 seconds using the θ / 2 method. The hydrophobic hard surface is preferably one or more selected from synthetic resins, metals, and ceramics.

[0010] According to the present invention, it is possible to easily impart a high hydrophilic effect to a target surface and to maintain the hydrophilic effect well. The reason for this effect is not clear, but it is thought to be as follows. The betaine group-containing inorganic particles contained in the surface treatment agent of the present invention have betaine groups on their surfaces via covalent bonds, and it is believed that the betaine groups can impart a high hydrophilic effect to the target surface. Here, the force exerted per particle of the betaine group-containing inorganic particles is mainly contributed by the van der Waals force between the betaine group-containing inorganic particles and the target surface, taking into account the surface roughness of the target surface, and the external force applied to the betaine group-containing inorganic particles when applied to the target surface. Since the betaine group-containing inorganic particles have a volume average particle diameter of 800 nm or less, the van der Waals force between the betaine group-containing inorganic particles and the target surface is dominant over the external force applied to the betaine group-containing inorganic particles, and the betaine group-containing inorganic particles can be uniformly attached to the target surface, which is thought to further enhance the hydrophilic effect of the betaine groups and maintain the hydrophilic effect well. Furthermore, even when water droplets are moving during cleaning or application, the van der Waals forces between the betaine group-containing inorganic particles and the target surface are dominant over the external forces applied to the betaine group-containing inorganic particles, and therefore it is thought that the betaine group-containing inorganic particles can be maintained in a state where they are uniformly attached to the target surface, and the hydrophilization effect can be maintained satisfactorily. Therefore, due to the imparting of a high hydrophilic effect and the good maintenance of the hydrophilic effect, it is believed that, when applied to a target surface, the present invention can also impart an anti-adhesion property that suppresses the adhesion of dirt to the target surface, i.e., anti-fouling property, and easy cleanability that allows dirt to be easily removed by washing even if it does adhere.

[0011] <Betaine group-containing inorganic particles A> (Inorganic particles (a)) Examples of the inorganic particles (a) constituting the betaine group-containing inorganic particles A include particles containing a metal, a metal oxide, or a semiconductor material. Examples of metals constituting the inorganic particles (a) include gold, silver, cobalt, copper, aluminum, nickel, platinum, lead, palladium, and iron. Examples of metal oxides constituting the inorganic particles (a) include silicon oxide, aluminum oxide, titanium (IV) oxide, zirconium (IV) oxide, yttrium (III) oxide, iron oxide, cobalt oxide, cerium (IV) oxide, samarium (III) oxide, gadolinium (III) oxide, dysprosium (III) oxide, holmium (III) oxide, and erbium (III) oxide. Examples of semiconductor materials constituting the inorganic particles (a) include cadmium selenide, cadmium tellurium, cadmium sulfide, zinc sulfide, zinc selenide, lead sulfide, lead selenide, gallium arsenide, gallium phosphide, indium phosphide, and indium arsenide.

[0012] From the viewpoints of uniformly adhering the betaine group-containing inorganic particles to the target surface, enhancing the hydrophilic effect imparted to the target surface, and maintaining the hydrophilic effect well, the inorganic particles (a) are preferably inorganic particles containing one or more selected from silica (SiO2), alumina (Al2O3), titania (TiO2), zirconia (ZrO2), ceria (CeO2), calcium carbonate, garnet, nanodiamond, and silicate, more preferably inorganic particles having a silica surface layer, and even more preferably silica particles. When inorganic particle (a) is a particle containing components other than silica, from the viewpoint of introducing betaine group, the inorganic particle (a) is preferably an inorganic particle having a silica surface layer.The inorganic particle having a silica surface layer is preferably a core-shell particle.In this case, the core contains components other than silica, and the shell contains silica. The core constituting the core-shell particle may be made of a metal, a metal oxide, or a semiconductor material other than the silica mentioned above. When the inorganic particles (a) are silica particles, the silica particles may contain inorganic elements other than Si, such as Al, but the silica (SiO2) content in the silica particles is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 99 mass% or more, and preferably 100 mass% or less.

[0013] (betaine group) The betaine groups present on the surface of the betaine group-containing inorganic particles A are preferably sulfobetaine groups, phosphobetaine groups, or carbobetaine groups, from the viewpoint of enhancing the hydrophilic effect imparted to the target surface and maintaining the hydrophilic effect in a good condition, and are more preferably represented by the following formula (1): The betaine group may be of one type or of two or more types.

[0014] [ka] [In formula (1), R 1 is an alkylene group having 1 to 4 carbon atoms, or -Y 1 -OPO3 - -Y 2 - indicates Y 1 and Y 2 are the same or different and represent alkylene groups having 1 to 4 carbon atoms, R 2 and R 3 are the same or different and represent groups necessary to form a hydrocarbon group having from 1 to 4 carbon atoms, or a saturated or unsaturated nitrogen-containing heterocyclic group (preferably a 5- to 8-membered heterocyclic group), X 1 is R 1 When is an alkylene group having 1 to 4 carbon atoms, R 7 SO3 - , or R 7 COO - indicates R 7 represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxyl group, and X 1 is R 1 Ga-Y 1 -OPO3 - -Y 2 - represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms; * indicates a binding site.

[0015] From the viewpoint of enhancing the hydrophilic effect imparted to the target surface and maintaining the hydrophilic effect in a good condition, the betaine group is preferably introduced onto the surface of the inorganic particle (a) via a betaine group-containing silane compound (b) represented by the following formula (2) (hereinafter, also simply referred to as "betaine group-containing silane compound (b)"). [ka] [In formula (2), R 4 ~R 6 each independently represents an alkoxy group having 1 to 5 carbon atoms, a halogen atom, or an alkyl group having 1 to 5 carbon atoms; R 4 ~R 6 At least one of is an alkoxy group or a halogen atom. R 1 ~R 3 , X 1 is the same as the above formula (1).

[0016] In the formulas (1) and (2), R 1 ~R 3 , X 1 Specific examples or preferred embodiments of the above are as follows, from the viewpoint of enhancing the hydrophilic effect imparted to the target surface. R 1 is preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms, and even more preferably an alkylene group having 3 carbon atoms. R 2 and R 3 is preferably a methyl group or an ethyl group, more preferably a methyl group. X 1 is R 1 When is an alkylene group having 1 to 4 carbon atoms, R 7 SO3 - , or R 7 COO - and preferably R 7 SO3 - R 7represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxyl group, is preferably an alkylene group having 1 to 3 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, is more preferably an alkylene group having 1 to 3 carbon atoms, is even more preferably an alkylene group having 2 or 3 carbon atoms, and is still more preferably an alkylene group having 3 carbon atoms. X 1 is R 1 Ga-Y 1 -OPO3 - -Y 2 When it is -, it is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, preferably a hydrocarbon group having 1 to 4 carbon atoms, and more preferably a methyl group. In formula (2), R 4 ~R 6 are each independently preferably an alkoxy group having 1 to 5 carbon atoms or a halogen atom, more preferably an alkoxy group having 1 or 2 carbon atoms, and even more preferably a methoxy group, from the viewpoint of introducing a betaine group to enhance the hydrophilic effect imparted to the target surface, and from the viewpoint of maintaining the hydrophilic effect in a good condition.

[0017] Among these, from the viewpoint of enhancing the hydrophilic effect imparted to the target surface and maintaining the hydrophilic effect well, the betaine group is preferably at least one selected from sulfobetaine groups such as an N-(3-sulfopropyl)-N,N-dimethylammonium betaine group; phosphobetaine groups such as phosphorylcholine; and carbobetaine groups such as an N-carboxymethyl-N,N-dimethylammonium betaine group and an N-carboxymethyl-N,N-dimethylammonium betaine group, more preferably at least one selected from a sulfobetaine group and a phosphobetaine group, even more preferably a sulfobetaine group, and still more preferably an N-(3-sulfopropyl)-N,N-dimethylammonium betaine group.

[0018] An example of a method for producing the betaine group-containing silane compound (b) is a method in which a silane compound represented by the following formula (2') is betained with a betaining agent.

[0019] [ka] [In formula (2'), R 1 ~R 6 is the same as the formula (2) above, and the preferred embodiments are also the same as the formula (2).

[0020] As the betaining agent, a compound represented by the following formula (2'-2) or a compound represented by the following formula (2'-3) can be reacted to betaine, and among these, the compound represented by the following formula (2'-2) is preferred.

[0021] [ka] [In formula (2'-2), n is 1 or 2, preferably 1.]

[0022] ZR 7 -SO3M 2 (2'-3) [In formula (2'-3), Z is Cl or Br, preferably Cl; R 7 is an alkylene group having 2 to 4 carbon atoms which may have a hydroxyl group, preferably a 2-hydroxypropylene group; M 2 indicates Na or K.]

[0023] [Production of Betaine Group-Containing Inorganic Particles A] The method for producing the betaine group-containing inorganic particles A according to the present invention includes, for example, contacting the raw inorganic particles (a') with the betaine group-containing silane compound (b) to introduce the betaine group through a silane coupling reaction. Examples of the raw inorganic particles (a') include particles containing metals, metal oxides, or semiconductor materials. Examples of the metals, metal oxides, and semiconductor materials constituting the raw inorganic particles (a') include those exemplified for the inorganic particles (a) described above. From the viewpoints of uniformly adhering the betaine group-containing inorganic particles to the target surface, enhancing the hydrophilic effect imparted to the target surface, and maintaining the hydrophilic effect well, the raw inorganic particles (a') are preferably inorganic particles containing one or more selected from silica (SiO2), alumina (Al2O3), titania (TiO2), zirconia (ZrO2), ceria (CeO2), calcium carbonate, garnet, nanodiamond, and silicate, more preferably inorganic particles having a silica surface layer, even more preferably silica particles, and even more preferably hydrophilic silica particles. In this specification, "hydrophilic silica particles" refers to silica particles having silanol (-SiOH) groups on their surfaces (i.e., surface-untreated silica particles whose surfaces have not been hydrophobized). Also, "hydrophobic silica particles" refers to surface-hydrophobized silica particles whose surfaces have been hydrophobized with alkylsilane or the like.

[0024] Volume average particle diameter D of raw inorganic particles (a') a' From the viewpoints of uniformly adhering the betaine group-containing inorganic particles to the target surface, enhancing the hydrophilic effect imparted to the target surface, and maintaining the hydrophilic effect in a good condition, the volume average particle diameter D is preferably 800 nm or less, more preferably 700 nm or less, even more preferably 600 nm or less, still more preferably 500 nm or less, and is preferably 30 nm or more, more preferably 50 nm or more, even more preferably 70 nm or more, and still more preferably 100 nm or more. a' is measured by the method described in the Examples. When the raw inorganic particles (a') are silica particles, the specific surface area of ​​the silica particles is preferably 50 m 2 / g or more, more preferably 100m 2 / g or more, more preferably 150m 2 / g or more, and preferably 500m 2 / g or less, more preferably 400m 2 / g or less, more preferably 300m 2 / g or less. The specific surface area is a BET specific surface area measured in accordance with JIS Z 8830:2013. Commercially available silica particles used as the raw inorganic particles (a') include hydrophilic silica particles such as AEROSIL 200 and 300 (trade names, manufactured by Nippon Aerosil Co., Ltd.).

[0025] In particular, when the raw inorganic particles (a') are particles having a silica surface layer or silica particles, a condensation reaction between the silanol (-SiOH) groups generated by hydrolysis of the betaine group-containing silane compound (b) and the hydroxyl groups (-OH) present on the surface of the raw inorganic particles (a') can be carried out to obtain betaine group-containing inorganic particles A having betaine groups on the surface of the inorganic particles (a) via covalent bonds. In the silane coupling reaction, it is preferable to use an acid catalyst from the viewpoint of promoting the hydrolysis of the betaine group-containing silane compound (b). The acid catalyst is preferably an organic acid, such as formic acid, acetic acid, lactic acid, malic acid, citric acid, tartaric acid, succinic acid, adipic acid, fumaric acid, or benzoic acid.

[0026] Specifically, a preferred method for producing the betaine group-containing inorganic particles A is to add the acid catalyst to an aqueous solution of the betaine group-containing silane compound (b), stir and mix the mixture, add the raw material inorganic particles (a'), and heat and dry the resulting suspension under reduced pressure to carry out the silane coupling reaction. The amount of the raw inorganic particles (a') in the suspension is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and is preferably 30% by mass or less, more preferably 10% by mass or less. The amount of the betaine group-containing silane compound (b) to be blended is not particularly limited as long as it is an amount sufficient to react with the hydroxyl groups present on the surface of the raw inorganic particles (a'). The amount of the betaine group-containing silane compound (b) to be blended is determined based on the volume average particle diameter D of the raw inorganic particles (a'). a' It is preferable to adjust the specific surface area. Examples of the medium for the suspension include water, ethanol, methanol, isopropanol, n-butanol, dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, tetrahydrofuran, acetonitrile, acetone, etc. Among these, the medium for the suspension preferably contains water, from the viewpoint of promoting the hydrolysis and condensation reaction of the betaine group-containing silane compound (b). The amount of water in the suspension is preferably 80% by mass or more, more preferably 90% by mass or more, and preferably 99.9% by mass or less, more preferably 99% by mass or less.

[0027] The temperature of the silane coupling reaction is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 30°C or higher, still more preferably 70°C or higher, even more preferably 90°C or higher, and preferably 150°C or lower, more preferably 130°C or lower, even more preferably 110°C or lower. The time for the silane coupling reaction is preferably 10 minutes or more, more preferably 30 minutes or more, even more preferably 1 hour or more, even more preferably 3 hours or more, even more preferably 6 hours or more, even more preferably 12 hours or more, and preferably 36 hours or less, more preferably 30 hours or less. After the silane coupling reaction, it is preferable to obtain betaine group-containing inorganic particles A by washing the obtained crude product with water and drying it in order to remove unreacted betaine group-containing silane compound (b) and the like.

[0028] Volume average particle diameter D of betaine group-containing inorganic particles A A From the viewpoints of uniformly adhering the betaine group-containing inorganic particles to the target surface, enhancing the hydrophilic effect imparted to the target surface, and maintaining the hydrophilic effect in a good condition, the volume average particle diameter D is 800 nm or less, preferably 500 nm or less, more preferably 300 nm or less, even more preferably 250 nm or less, still more preferably 200 nm or less, and is preferably 30 nm or more, more preferably 50 nm or more, even more preferably 70 nm or more, and still more preferably 100 nm or more. Ais measured by the method described in the Examples.

[0029] The content of betaine groups in the betaine group-containing inorganic particles A according to the present invention is set to 1 nm on the surface of the betaine group-containing inorganic particles A from the viewpoint of enhancing the hydrophilic effect imparted to the target surface by the betaine groups and maintaining the hydrophilic effect well. 2 The number of betaine groups per particle is preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.7 or more, and preferably 1.0 or less. When the betaine groups are sulfobetaine groups, the content of betaine groups in the betaine group-containing inorganic particles A can be calculated using the specific surface area of ​​the betaine group-containing inorganic particles A and the content (mmol / g) of sulfobetaine groups in the betaine group-containing inorganic particles A. Here, the specific surface area of ​​the betaine group-containing inorganic particles A is the BET specific surface area measured in accordance with JIS Z 8830:2013, and the content (mmol / g) of sulfobetaine groups in the betaine group-containing inorganic particles A is calculated by the method described in the Examples.

[0030] The content or blending amount of the betaine group-containing inorganic particles A in the surface treatment agent of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 99% by mass or more, and preferably 100% by mass or less, from the viewpoint of enhancing the hydrophilic effect imparted to the target surface and maintaining the hydrophilic effect in a good condition.

[0031] (Other ingredients) The surface treatment agent of the present invention can be used as it is without diluting it with a solvent or the like, but it can also be used by appropriately blending it with commonly used solvents, oils, and additives depending on the form or purpose of use. The surface treatment agent of the present invention may contain or be blended with additives to the extent that the effects of the present invention are not impaired. Examples of such additives include dyes, organic pigments, inorganic pigments, UV scattering agents, UV absorbers, fragrances, cosmetic ingredients, medicinal ingredients, pH adjusters, viscosity adjusters, moisturizers, antioxidants, bactericides, and preservatives. These may be used alone or in combination of two or more.

[0032] The form of use of the surface treatment agent of the present invention is not particularly limited. Examples of the form of use include any form such as powder, mist, liquid, foam, paste, and cream, but the liquid, paste, or cream form is preferred, and the liquid form is more preferred.

[0033] [Surface treatment method] The surface treatment method of the present invention includes the steps of applying the surface treatment agent to a target surface and attaching betaine group-containing inorganic particles A to the target surface, from the viewpoint of simply enhancing the hydrophilic effect imparted to the target surface and maintaining the hydrophilic effect in a good condition. The target surface in the method of the present invention is as described above. The method of applying the surface treatment agent to the target surface is not particularly limited and can be selected appropriately depending on the shape of the target surface. When the surface treatment agent is in liquid, foam, paste, or cream form, it can usually be applied by immersion, coating, spraying, or the like. The spraying or coating method can be selected appropriately depending on the size (area) of the target surface, etc. After spraying, it may be thinly spread using a sponge or the like. From the viewpoint of ease of workability, the ambient temperature when the surface treatment agent is applied to the target surface is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and is preferably 50°C or lower, more preferably 40°C or lower, even more preferably 30°C or lower. The amount of the surface treatment agent applied to the target surface is preferably 0.01 mg / cm as the amount of betaine group-containing inorganic particles A to be applied, from the viewpoints of uniformly adhering the betaine group-containing inorganic particles to the target surface, enhancing the hydrophilic effect imparted to the target surface, and maintaining the hydrophilic effect in a good condition. 2More preferably, 0.03 mg / cm 2 More preferably, 0.05 mg / cm 2 More preferably, 0.07 mg / cm 2 More preferably, 0.1 mg / cm 2 and from the viewpoint of appearance and feel, it is preferably 5 mg / cm 2 Less than 3 mg / cm, more preferably 2 More preferably, 1 mg / cm or less 2 or less, even more preferably 0.8 mg / cm 2 or less, even more preferably 0.5 mg / cm 2 More preferably, 0.3 mg / cm or less 2 The following is the result.

[0034] In the present invention, from the viewpoint of enhancing the hydrophilic effect imparted to the target surface, the static contact angle of the treated surface after applying the surface treatment agent to the target surface is preferably 50° or less, more preferably 40° or less, even more preferably 30° or less, still more preferably 20° or less, and even more preferably 15° or less, and although there is no particular lower limit, it is preferably 0° or more. The static contact angle can be measured by the method described in the examples.

[0035] On the other hand, in the present invention, the advancing contact angle of the treated surface after applying the surface treatment agent to the target surface is preferably 50° or less, more preferably 40° or less, even more preferably 30° or less, still more preferably 20° or less, and even more preferably 15° or less, and although there is no particular lower limit, it is preferably 0° or more. The advancing contact angle can be measured by the method described in the Examples. The advancing contact angle is known as the dynamic change in contact angle when a water droplet moves on a solid surface, such as during cleaning or coating. The advancing contact angle is usually defined as the contact angle when the water droplet moves forward on the interface. Details of this definition can be found in "Fundamentals and Applications of Wetting," edited by Meguro Kenjiro and Esumi Kunio (Realize Science and Engineering Center, 1989), and "Measurement and Evaluation Techniques for Interfaces of Different Materials," edited by Ishii Yoshio (Techno System, 2012, pp. 35-37). In the present invention, when the advancing contact angle is within the above range, the hydrophilic effect can be exhibited satisfactorily even in a state where water droplets are moving, such as during cleaning or application.

[0036] The surface treatment agent is preferably applied to the skin surface as the target surface. Since the skin surface is composed of skin ridges and skin grooves, when applied to the skin surface, the surface treatment agent generally tends to flow from the skin ridges to the skin grooves, making it difficult for the surface treatment agent to adhere to the skin ridges. However, in the present invention, the van der Waals force between the betaine group-containing inorganic particles and the target surface is dominant over the external force applied to the betaine group-containing inorganic particles A. Therefore, when applied to the skin, the flow of the betaine group-containing inorganic particles A from the skin ridges to the skin grooves can be suppressed, and the betaine group-containing inorganic particles A can be sufficiently adhered to the skin ridges, thereby imparting a high hydrophilic effect to the skin surface, maintaining the hydrophilic effect well, and further improving ease of washing. That is, the surface treatment agent is preferably used in a surface treatment method in which it is applied to the skin surface to impart antifouling properties (adhesion prevention properties) that inhibit adhesion of dirt to the skin or easy cleanability that allows dirt to be easily removed by washing even if it does adhere to the skin. From this perspective, when applied to the skin surface, the surface treatment agent can also be used as a material for imparting an antifouling effect or easy cleanability to topical skin preparations, skin cosmetics, etc., and is preferably used as a topical skin preparation. Here, "applying to the skin surface" includes not only directly applying the surface treatment agent to the skin surface with the hands, etc., but also adhering the surface treatment agent to the skin surface by spraying or the like.

[0037] The surface treatment agent is preferably applied to the hair surface as the target surface. When the target surface is the hair surface, a high hydrophilizing effect can be imparted to the hair surface, thereby imparting effects such as improving the water absorption of the hair surface, preventing static electricity on the hair surface, and preventing bedhead. In other words, the surface treatment agent is preferably used as a hair hydrophilization treatment agent that is applied to the hair surface to impart a hydrophilizing effect. When applied to the hair surface, the composition can be incorporated into hair cosmetics such as hair cleansers such as shampoos, conditioners, treatments, and hair dyes. The formulation of the hair cosmetics is not particularly limited, and can be any formulation such as a liquid, foam, paste, or cream. Among these formulations, the hair cosmetics are preferably in liquid form. Specific methods for applying the surface treatment agent to the hair surface include, for example, when the surface treatment agent is incorporated into a hair cleanser such as shampoo, applying the hair cleanser to the hair, lathering the hair, and then rinsing it off with water; when the surface treatment agent is incorporated into a hair cosmetic such as a conditioner, treatment, or hair dye, applying the hair cosmetic to the hair, leaving it for about 0.1 to 5 minutes as necessary, and then rinsing it off with water. These steps can easily and quickly impart a hydrophilic effect to the hair surface, and can impart effects such as improved water absorption of the hair surface, anti-static properties to the hair surface, and prevention of bedhead. [Example]

[0038] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Various measurements were carried out by the following methods.

[0039] [Volume average particle diameter D a' and volume average particle diameter D A Measurement of A 0.3% by mass ethanol dispersion of the raw inorganic particles (a') or the betaine group-containing inorganic particles A was prepared as a measurement sample. Approximately 1 mL of the prepared measurement sample was placed in a square cell with an optical path length of 10 mm, and the particle diameter was measured using a light scattering device "Zetasizer Nano ZS" (manufactured by Malvern Panalytical). The volume average particle diameter D a' or volume average particle diameter D A asked for.

[0040] [Sulfobetaine group content of betaine group-containing inorganic particles A] 100 mg of betaine-group-containing inorganic particles A were weighed, mixed with 10 mL of sulfuric acid and one tablet of the decomposition accelerator "Kjeldahl Tablet" (Merck). The decomposition was carried out using a Kjeldahl decomposition apparatus "K-432" (BUCHI) at 250°C for 30 minutes, then at 300°C for 30 minutes, and finally at 420°C for 80 minutes. After the decomposition reaction was complete, 30 mL of ion-exchanged water was added to the sample. Using an automatic Kjeldahl distillation and titration apparatus "K-370" (BUCHI), the solution was made alkaline by adding 40 mL of 30% by weight sodium hydroxide solution. The ammonia liberated by the distillation process was collected in a 1% by weight boric acid solution. The collected solution was titrated with 0.005 mol / L sulfuric acid to determine the nitrogen content (mass%) of 100 mg of betaine-group-containing inorganic particles A. From the obtained nitrogen content, the content of sulfobetaine groups in the betaine group-containing inorganic particles A (hereinafter referred to as "sulfobetaine group content") was calculated according to the following formula (I).

[0041]

number

[0042] (Production of betaine group-containing silane compound (b)) Manufacturing Example 1-1 A 200 mL three-neck flask was charged with 20.7 g of N,N-dimethyl-3-(trimethoxysilyl)propylamine (Tokyo Chemical Industry Co., Ltd.) and 75 mL of 1,2-dichloroethane. A condenser was attached to the top of the flask, and the flask was immersed in an oil bath. While stirring with a magnetic stirrer, 12.2 g of 1,3-propane sultone (Kanto Chemical Co., Inc.) was added dropwise over approximately 20 minutes at a temperature of 50°C or less. After the addition was complete, the solution in the flask was heated to reflux for approximately 3 hours to carry out the reaction. After the reaction was complete, the solvent was distilled off from the reaction solution to obtain a white solid. The resulting white solid was washed with 1,2-dichloroethane and dried under reduced pressure at 50°C for 24 hours to obtain 3-(N,N-dimethyl(3-(trimethoxysilyl)propyl)ammonio)propane-1-sulfonate as the betaine group-containing silane compound (b).

[0043] (Production of betaine group-containing inorganic particles A) Manufacturing Example 1 In a 2,000 mL beaker, 10.0 g of adipic acid, 10.0 g of 3-(N,N-dimethyl(3-(trimethoxysilyl)propyl)ammonio)propane-1-sulfonate obtained in Production Example 1-1 as the betaine group-containing silane compound (b), and 1,000 mL of water were added and stirred at room temperature for 48 hours. Next, hydrophilic silica particles "AEROSIL 200" (manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter: 460 nm, specific surface area: 200±25 m) were added as raw inorganic particles (a') to the beaker. 2 10.0 g of HCl (10.0 g / g) was added and stirred at room temperature for 30 minutes to obtain a suspension. The resulting suspension was then centrifuged (processing conditions: 3000 rpm, 10 min) using a centrifuge, "H-28F" (manufactured by Kokusan Co., Ltd.). The supernatant was then removed by decantation, and the mixture was dried under reduced pressure at 100°C for 24 hours to carry out a silane coupling reaction, thereby obtaining a crude product. The resulting crude product was then washed with ion-exchanged water and dried again under reduced pressure at 100°C for 24 hours in a nitrogen atmosphere to obtain sulfobetaine group-containing silica particles A1. The volume average particle diameter of the sulfobetaine group-containing silica particles A1 was 150 nm. Based on the volume average particle diameter of the hydrophilic silica particles used as the raw inorganic particles (a') and the volume average particle diameter of the resulting sulfobetaine group-containing silica particles A1, it is inferred that aggregates of hydrophilic silica particles were dispersed during the production of the sulfobetaine group-containing silica particles A1. The content of sulfobetaine groups in the betaine group-containing silica particles A1 is within 1 nm of the surface. 2 The sulfobetaine group content of the betaine group-containing silica particles A1 was calculated from the BET specific surface area measured in accordance with JIS Z 8830:2013 and the sulfobetaine group content calculated from the formula (I) above.

[0044] Comparative Examples 1 and 2 Sulfobetaine group-containing silica particles AC1 and sulfobetaine group-containing silica particles AC2 were obtained in the same manner as in Production Example 1, except that the raw inorganic particles (a') were changed to silica particles "Hipressica SS N3N" (manufactured by Ube Exsymo Co., Ltd., volume average particle diameter: 1,000 nm) in Comparative Production Example 1 and to silica particles "Hipressica TS N3N" (manufactured by Ube Exsymo Co., Ltd., volume average particle diameter: 10,000 nm) in Comparative Production Example 2. The volume average particle diameter of the sulfobetaine group-containing silica particles AC1 was 1,000 nm, and the volume average particle diameter of the sulfobetaine group-containing silica particles AC2 was 10,000 nm.

[0045] Example 1-1, Comparative Examples 1-1 to 1-2, and Reference Example 1-1 An ethanol dispersion of the betaine group-containing inorganic particles A shown in Table 1 (surface treatment agent content: 7% by mass) was prepared as a surface treatment agent, and the dispersion was applied to white artificial leather, a polyethylene (PE) substrate, and a hair tress using the methods described below, and evaluations were carried out. The results are shown in Table 1. In Comparative Examples 1-1 and 1-2, the surface treatment agent used was silica particles shown in Table 1. Details of the silica particles shown in Table 1 are as follows. Hydrophobic silica particles: Product name "AEROSILRX200", manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter 590 nm, specific surface area 200 ± 25 m 2 / g Hydrophilic silica particles: Trade name "AEROSIL200", manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter 460 nm, specific surface area 200 ± 25 m 2 / g In Reference Example 1-1, the same evaluation was carried out using untreated white artificial leather, a PE substrate, and a hair tress as evaluation samples, without using the ethanol dispersion of betaine group-containing inorganic particles A.

[0046] (Evaluation of hydrophilic effect) [Measurement of static contact angle] The ethanol dispersion of the betaine group-containing inorganic particles A was applied to a white artificial leather "Laforet S2923" (manufactured by Okamoto Shinwa Co., Ltd.) (70 mm x 120 mm) and a polyethylene (PE) substrate (manufactured by Engineering Test Service Co., Ltd.) (25 mm x 75 mm) at a concentration of 2 mg / cm. 2 (adhesion amount of betaine group-containing inorganic particles A: 0.14 mg / cm 2 The resulting evaluation samples were then placed on the stage of a fully automatic contact angle measuring instrument (Kyowa Interface Science Co., Ltd., "DM-701"), and 1 μL of ultrapure water was applied to the samples. The static contact angle after 5 seconds was determined by the θ / 2 method. The smaller the static contact angle, the higher the hydrophilicity and the greater the hydrophilization effect. [Measurement of Advancing Contact Angle] The ethanol dispersion of the betaine group-containing inorganic particles A was applied to a white artificial leather "Laforet S2923" (manufactured by Okamoto Shinwa Co., Ltd.) (70 mm x 120 mm) at a concentration of 2 mg / cm. 2 (adhesion amount of betaine group-containing inorganic particles A: 0.14 mg / cm 2 ) and left to dry at room temperature for 15 minutes to obtain each evaluation sample. Next, the advancing contact angle of the obtained evaluation sample was measured by the expansion / contraction method using a fully automatic contact angle meter ("DM-701" manufactured by Kyowa Interface Science Co., Ltd.) The measurement was carried out using ultrapure water at 25°C. The initial volume of ultrapure water was 50 μL, and ultrapure water was injected into this droplet at a rate of 0.58 μL / s. The advancing contact angle was determined by calculating the average contact angle when the edge of the droplet (contact line) began to move forward due to the injection of ultrapure water. The smaller the advancing contact angle, the higher the hydrophilicity when the droplet moves on a solid surface during cleaning or coating, indicating that the hydrophilic effect can be maintained.

[0047] (Evaluation of ease of cleaning) The ethanol dispersion of the betaine group-containing inorganic particles A was applied to a white artificial leather "Laforet S2923" (manufactured by Okamoto Shinwa Co., Ltd.) (30 mm x 30 mm) at a concentration of 2 mg / cm. 2(adhesion amount of betaine group-containing inorganic particles A: 0.14 mg / cm 2 ) and left to dry at room temperature for 15 minutes to obtain each evaluation sample. Next, 100 mL of oleic acid colored oil red was applied to the surface treated with the surface treatment agent of the obtained evaluation sample, and after rinsing with ion-exchanged water for 30 seconds, the evaluation sample was immersed in a solution obtained by mixing 10 mL of hexane and 0.07 g of decane, and ultrasonic treatment was performed by irradiating the sample with ultrasonic waves for 10 minutes using an ultrasonic irradiation device (manufactured by Sharp Manufacturing Systems Co., Ltd., model "UT-206") under conditions of an output of 200 W and an oscillation frequency of 37 kHz, thereby obtaining a solution in which the oleic acid attached to the evaluation sample had been eluted. Next, 1 mL of trimethylsilylation agent "TMSI-H" (GL Sciences Inc.) was added to 2 mL of this solution, mixed, and allowed to stand for 5 minutes, after which the solid content was removed by filtration. The obtained filtrate was quantitatively analyzed by gas chromatography (GC) under the following measurement conditions, and the residual percentage of oleic acid was calculated using the following formula. The lower the residual percentage of oleic acid, the better the ease of cleaning. Residual rate of oleic acid (%) = [(amount of oleic acid determined by GC) / (amount of oleic acid applied to the evaluation sample)] × 100 [Measurement conditions] Equipment: Agilent "HP6890" Detector: FID method, 350℃ Column: FronteerLAB "Ultra-Alloy-1" (inner diameter 0.25 mm x length 30 m x film thickness 0.15 μm) Flow rate: 0.8 mL / min (gas: helium) Injection volume: 2μL Split ratio: 50:1 Inlet temperature: 300℃ Column temperature conditions: 60°C (2 min) → 10°C / min → 350°C (2 min)

[0048] (Evaluation of hair surface water absorption) 0.2 g of the ethanol dispersion of the betaine group-containing inorganic particles A was applied to a hair tress (manufactured by Beaulux Co., Ltd., product number: BM-B15) weighing 2 g and having a length of 15 cm, and the tress was left to dry at room temperature for 15 minutes to obtain each evaluation sample. 0.3 g of ion-exchanged water was dropped onto the obtained evaluation sample, and the time until the sample absorbed water (hereinafter also referred to as "water absorption time") was measured to evaluate the water absorbency. The shorter the water absorption time, the better the water absorbency and the higher the hydrophilicity.

[0049] [Table 1]

[0050] From Table 1, it can be seen that Example 1-1 has a smaller static contact angle value and can impart a high hydrophilic effect to the target surface compared to Reference Example 1-1, whether the target surface is artificial leather or a PE substrate. Furthermore, it can be seen that Example 1-1 has a smaller static contact angle value, a higher degree of hydrophilicity, and an excellent hydrophilic effect compared to Comparative Examples 1-1 and 1-2. Example 1-1 has a smaller advancing contact angle than Reference Example 1-1, and it is clear that a high hydrophilic effect can be maintained even in states where water droplets move, such as in cleaning, application, etc. Furthermore, Example 1-1 has a smaller advancing contact angle than Comparative Examples 1-1 and 1-2, and it is clear that the degree of hydrophilicity is high even in states where water droplets move, such as in cleaning, application, etc., and that the high hydrophilic effect can be maintained well. Example 1-1 has a lower residual oleic acid rate than Reference Example 1-1, and can impart easy cleaning properties to the target surface. Furthermore, Example 1-1 has a lower residual oleic acid rate than Comparative Examples 1-1 and 1-2, and is therefore superior in easy cleaning properties. It is clear that Example 1-1 has a shorter hair absorption time and can impart water absorbency (hydrophilicity) to the hair surface than Reference Example 1-1. It is also clear that Example 1-1 has a shorter hair absorption time and can impart water absorbency (hydrophilicity) to the hair surface than Comparative Examples 1-1 and 1-2.

[0051] Example 2-1, Comparative Examples 2-1 to 2-2, and Reference Example 2-1 An ethanol dispersion of the betaine group-containing inorganic particles A shown in Table 2 was prepared as a surface treatment agent (amount of surface treatment agent: 7% by mass). The obtained ethanol dispersion of the betaine group-containing inorganic particles A was applied at a concentration of 2 mg / cm to an artificial skin model "Bio Skin" (manufactured by Beaulux Co., Ltd., product number: Skin Model No. 10C (20s) #Biocolor) (φ50 mm × 5T mm) as a skin replica sample. 2 (adhesion amount of betaine group-containing inorganic particles A: 0.14 mg / cm 2 ) and left to dry at room temperature for 15 minutes to obtain evaluation samples. The static contact angle of the obtained evaluation samples was measured as described above to evaluate the hydrophilization effect. In Reference Example 2-1, the static contact angle was measured in the same manner using the untreated artificial skin model as an evaluation sample without using the ethanol dispersion of betaine group-containing inorganic particles A. The results are shown in Table 2.

[0052] [Table 2]

[0053] From Table 2, it can be seen that Example 2-1 has a smaller static contact angle value and can impart a higher hydrophilic effect than Reference Example 2-1. Furthermore, it can be seen that Example 2-1 has a smaller static contact angle value and a higher degree of hydrophilicity than Comparative Examples 2-1 and 2-2, and is therefore superior in hydrophilic effect. [Industrial Applicability]

[0054] According to the present invention, a high hydrophilic effect can be easily imparted to a target surface and the hydrophilic effect can be well maintained, and therefore the surface treatment agent of the present invention is useful as a surface hydrophilization treatment agent. Furthermore, when the target surface is a skin surface, the surface treatment agent can also impart excellent washability to the skin surface, and therefore the surface treatment agent is useful, for example, as a skin topical agent. Furthermore, when the target surface is a hair surface, the surface treatment agent can improve the water absorption (hydrophilicity) of the hair surface, and therefore the surface treatment agent is also useful as a hair hydrophilization treatment agent.

Claims

1. The betaine group-containing inorganic particles A have betaine groups on their surfaces via covalent bonds, and the volume average particle diameter D of the betaine group-containing inorganic particles A is A A surface treatment agent for use in treating a skin surface or a hair surface, wherein the particle size is more than 100 nm and not more than 800 nm.

2. 2. The surface treatment agent according to claim 1, wherein the inorganic particles constituting the betaine group-containing inorganic particles A are silica particles.

3. The surface treatment agent according to claim 2, wherein the silica (SiO 2 ) content in the silica particles is 90% by mass or more and 100% by mass or less.

4. The surface treatment agent according to any one of claims 1 to 3, wherein the betaine group is a sulfobetaine group.

5. The surface treatment agent according to claim 1, wherein the betaine group is an N-(3-sulfopropyl)-N,N-dimethylammonium betaine group.

6. A method for treating a skin or hair surface, comprising the steps of applying the surface treatment agent according to any one of claims 1 to 5 to a skin or hair surface of a subject, and attaching betaine group-containing inorganic particles A to the skin or hair surface of the subject.

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