Hydrophilic polymer composites and surface treatment agents using the same

Abstract

To provide a hydrophilic polymer composite capable of forming a modified film with high adhesion and hydrophilicity to a substrate and excellent transparency, and a surface treatment agent using the same. Also, to provide a surface treatment agent that can form a modified film in a more practical temperature range from room temperature to around 150°C. [Solution] A hydrophilic polymer composite obtained by carrying out a sol-gel reaction of an alkoxysilane in the presence of a hydrophilic polymer containing hydroxyethylcellulose, 2-hydroxypropylmethylcellulose, or chitosan and an organic phosphonic acid.

Description

Technical Field

[0001] The present invention relates to a hydrophilic polymer composite and a surface treatment agent using the same.

Background Art

[0002] Surface modifiers for imparting hydrophilicity to the surfaces of various substrates such as glass, metal, fiber, paper, wood, plastic, synthetic resin, and ceramics are expected to be applied in various fields as materials that can exhibit various functions such as antifogging properties and antibacterial activity in the formed modified film. However, since the modified film exhibits hydrophilicity, there are problems such as solubilization in a hydrophilic atmosphere or in the presence of water and easy peeling.

[0003] Therefore, the development of a surface treatment agent capable of forming a modified film having excellent adhesion to a substrate even in a hydrophilic atmosphere is strongly desired. Especially from the perspective of realizing a sustainable energy society these days, instead of using polymers that rely on petrochemistry, the development of polymer composites using polymer materials such as cellulose and chitosan, which are carbon-neutral polymers, has become an important research issue.

[0004] From such a perspective, reports have been made on hydrophilic surface treatment agents using natural-derived polymer materials. For example, there is a report in which a hydrophilic surface treatment agent containing a sodium salt and an ammonium salt of a cellulose derivative: carboxymethyl cellulose, which is a natural material, N-methylolacrylamide, polyacrylic acid, and a zirconium compound is applied to the surface of an aluminum plate, and then a film is formed by heat curing at 240°C (see Patent Document 1).

[0005] Furthermore, surface modification of aluminum plates using a hydrophilic surface treatment composition prepared by solubilizing chitosan, an insoluble dietary fiber of animal origin obtained by alkaline decomposition of chitin contained in crustaceans such as crabs and shrimp, with citric acid, and then adding polyacrylic acid, has been reported, and it has been disclosed that the resulting modified film exhibits hydrophilicity and antibacterial / antifungal properties (see Patent Document 2). Similarly, surface modification of aluminum plates using a composition obtained by adding a perfluoroalkylene oxide adduct to an aqueous chitosan solution obtained by solubilizing chitosan with acetic acid has been reported. This composition is heated and cured at 230°C to form a modified film exhibiting hydrophilicity and antibacterial properties, and it has been disclosed that the surface-modified aluminum plate can be used as a fin for a heat exchanger (see Patent Document 3). Furthermore, surface modification of aluminum plates using an aqueous solution composition obtained by dissolving glycerylated chitosan, obtained by the reaction of chitosan and glycidyl alcohol, and 1,2,3,4-butanetetracarboxylic acid in an aqueous medium has been reported. The modified film formed by heat-curing this composition at 200°C exhibits hydrophilicity and can be applied as a fin material for air conditioners (see, for example, Patent Document 4).

[0006] To impart highly practical hydrophilicity to a surface modified by a hydrophilic surface treatment agent using naturally derived polymer materials, as disclosed in the above-mentioned Patent Documents 1 to 4, it is necessary to add a new substrate such as polyacrylic acid or perfluoroalkyl ethylene oxide, which are hydrophilic polymers, and the curing temperature must also be high, at 200°C or higher. Furthermore, there is little information regarding the appearance (transparency, etc.) of the resulting modified film, and there is a strong desire for the development of a hydrophilic surface treatment agent using naturally derived polymer materials that can form a surface modified film more practically and easily.

[0007] Furthermore, it has been reported that organic phosphonic acids are useful as metal oxide surface treatment agents (see, for example, Non-Patent Document 1), and that they can impart rust-preventive function (e.g., Patent Document 5) and lubricity function (e.g., Patent Document 6) to the modified film. In addition, due to the phosphonic acid groups, it is possible to impart high adhesion to glass, stainless steel, aluminum, etc. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 2520308 [Patent Document 2] Japanese Patent Application Publication No. 11-293149 [Patent Document 3] Patent No. 3419864 [Patent Document 4] Japanese Patent Publication No. 2002-105241 [Patent Document 5] Japanese Patent Publication No. 2010-70805 [Patent Document 6] Special Publication No. 2023-529705 [Non-patent literature]

[0009] [Non-Patent Document 1] Dojin News, No. 146 (2013) [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention aims to solve the above-mentioned problems and provides a hydrophilic polymer composite capable of forming a modified film with high adhesion and hydrophilicity to a substrate and excellent transparency, as well as a surface treatment agent using the same. It also aims to provide a surface treatment agent capable of forming a modified film within a more practical temperature range, from room temperature to around 150°C. [Means for solving the problem]

[0011] As a result of diligent research, the inventors of the present invention have found that by using a hydrophilic polymer composite obtained by performing a sol-gel reaction of an alkoxysilane in the presence of a hydrophilic polymer containing a cellulose derivative or chitosan and an organic phosphonic acid, a modified film can be formed in a temperature range from room temperature to around 150°C. Furthermore, the formed modified film exhibits excellent adhesion to various substrates and also has excellent transparency, thus completing the present invention.

[0012] In other words, the present invention is a hydrophilic polymer composite obtained by carrying out a sol-gel reaction of an alkoxysilane in the presence of a hydrophilic polymer containing hydroxyethylcellulose, 2-hydroxypropylmethylcellulose, or chitosan, and an organic phosphonic acid. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a hydrophilic polymer composite that can form a modified film with high adhesion and hydrophilicity to a substrate and excellent transparency, as well as a surface treatment agent using the same. Furthermore, it is possible to provide a surface treatment agent that can form a modified film in a more practical temperature range from room temperature to around 150°C. [Modes for carrying out the invention]

[0014] The present invention will be described below based on its preferred embodiments. The hydrophilic polymer composite of the present invention is obtained by carrying out a sol-gel reaction of an alkoxysilane in the presence of a hydrophilic polymer and an organic phosphonic acid. Therefore, it is presumed that the hydrophilic polymer composite of the present invention has a very complex structure in which a hydrophilic polymer and an organic phosphonic acid are dispersed in a highly crosslinked polysiloxane structure generated by the sol-gel reaction of an alkoxysilane. However, appropriate measurement and analysis means for identifying such a structure have not been established. Therefore, it is impossible or practically infeasible to directly identify the hydrophilic polymer composite of the present invention based on its structure or properties, and it can only be identified by the manufacturing method.

[0015] The hydrophilic polymers used in the present invention include cellulose derivatives such as hydroxyethyl cellulose and 2-hydroxypropyl methyl cellulose, or chitosan.

[0016] Hydroxyethyl cellulose is a polysaccharide polymer in which glucose is polymerized, and is obtained by modifying cellulose, a sustainable raw material source, with hydroxyethyl groups. In the present invention, industrially available products can be used as they are, and as commercially available products, for example, SANHEC T series LT manufactured by Sankyo Co., Ltd. can be used.

[0017] 2-Hydroxypropyl methyl cellulose is synthesized by mixing cellulose with water and a large excess of sodium hydroxide in a slurry state to form alkali cellulose, and then allowing propylene oxide to act thereon. In the present invention, industrially available products can be used as they are, and as commercially available products, for example, Methocel (registered trademark) 60SH-50, 9OSH-100 manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

[0018] Chitosan can be directly obtained as an industrial product, and for example, Kimica Chitosan manufactured by Kimica Corporation can be used.

[0019] In the present invention, in addition to hydroxyethyl cellulose, 2-hydroxypropyl methyl cellulose or chitosan as the hydrophilic polymer, polyvinyl alcohol may be used. By using polyvinyl alcohol, the transparency of the resulting modified film can be further enhanced. Polyvinyl alcohol is directly available as an industrial product, and for example, LM-10HD manufactured by Kuraray Co., Ltd. can be used.

[0020] Examples of the organic phosphonic acid used in the present invention include 2-phosphonobutane 1,2,4-tricarboxylic acid, sodium 2-phosphonobutane 1,2,4-tricarboxylate, and hydroxyethylidene diphosphonic acid. For these, commercially available products such as Krest PH-430, Krest PH-435, and Krest PH-210 manufactured by Kirest Co., Ltd. can be used.

[0021] Examples of the alkoxysilane used in the present invention include tetraethoxysilane and methyltriethoxysilane. Commercially available products can be used for these.

[0022] The hydrophilic polymer composite of the present invention may contain an organic antibacterial agent. Examples of the organic antibacterial agent include hinoki oil, hinokitiol, cetylpyridinium chloride, and hibitane.

[0023] The hydrophilic polymer composite of the present invention can be prepared by adding an organic phosphonic acid and an alkoxysilane to an aqueous solution of the hydrophilic polymer, further adding an organic antibacterial agent as necessary, and performing sol-gel by stirring at room temperature to form a composite.

[0024] Hydroxyethyl cellulose and 2-hydroxypropyl methyl cellulose are soluble in water, and in the present invention, it is preferable to prepare and use an aqueous solution of 0.1 to 5.0%. If it is less than 0.1%, the film thickness of the resulting modified film decreases and it is not practical. If it is 5.0% or more, the transparency of the resulting modified film tends to decrease, which is not preferable.

[0025] Chitosan is insoluble in water on its own, but an aqueous solution can be prepared by dispersing it in water and then adding an acid such as acetic acid. In this invention, it is preferable to prepare and use an aqueous solution of 0.1 to 5.0%. Below 0.1%, the thickness of the resulting modified film decreases, making it impractical, and above 5.0%, the transparency of the resulting modified film tends to decrease, which is undesirable. When using acetic acid, the amount to add is preferably in the range of 0.1 to 3.0 ml per 10 ml of aqueous dispersion containing 0.1 g of chitosan powder. Below 0.1 ml, the solubility of chitosan decreases, and above 3.0 ml, the solution becomes impractical due to discoloration and odor caused by the acetic acid.

[0026] Polyvinyl alcohol can be prepared by directly adding polyvinyl alcohol powder to water to create an aqueous solution. In this invention, it is preferable to prepare and use an aqueous solution of 0.1 to 5.0%. Outside this range, the film-forming properties of the resulting water-soluble polymer composite will decrease. Furthermore, using 1 to 20 ml of the polyvinyl alcohol aqueous solution per 10 ml of hydroxyethylcellulose, 2-hydroxypropylmethylcellulose, or chitosan aqueous solution is effective in achieving high film-forming functionality.

[0027] A hydrophilic polymer composite solution obtained by composite formation can be applied to the surface of a degreased glass plate, aluminum plate, or stainless steel plate to form a coating film, which is then cured to form a modified coating film. The coating film can be formed by application methods such as roll coating, bar coating, spraying, or dipping.

[0028] The hydrophilic polymer composite of the present invention can form a modified film by drying at room temperature without heating, but it is preferable to heat-cur it in order to efficiently form the modified film. The heating time depends on the temperature, but in the temperature range of 100 to 150°C, it is possible to form a modified film in 5 minutes to 2 hours, in the temperature range of room temperature to 100°C it is preferable to heat and leave it for several hours, and in the temperature range of 50 to 100°C it is possible to form a modified film in 5 minutes to 2 hours.

[0029] The hydrophilic polymer composite of the present invention is formed by combining a hydrophilic polymer with an organic phosphonic acid such as 2-phosphonobutane 1,2,4-tricarboxylic acid or its sodium salt, and performing a sol-gel reaction with an alkoxysilane in their presence. This allows for improved adhesion to various substrates. Furthermore, it is possible to form a modified film at relatively low temperatures, from room temperature to around 150°C. In addition, substrates such as cypress oil, hinokitiol, cetylpyridinium chloride, and hibitane can be efficiently encapsulated within the hydrophilic polymer composite, allowing the functions derived from these substrates to be expressed on the modified film surface over a long period of time.

[0030] The modified film formed using the hydrophilic polymer composite of the present invention exhibits high hydrophilicity, and when applied to surface modification of glass or plastics, it can impart anti-fogging properties to the modified film surface. Therefore, it can be applied to glass used in building materials, vehicles, and bathrooms where ensuring visibility is important, as well as transparent materials such as various lenses and eyeglasses, and reflective materials such as mirrors. In particular, aluminum and its alloys surface-modified using the hydrophilic polymer composite of the present invention can be applied to heat exchange fin materials. Because these modified metal surfaces exhibit high hydrophilicity, water droplets do not form, and they have excellent water resistance even when wet. Furthermore, due to the organic phosphonic acid units encapsulated within the hydrophilic polymer composite, it has rust prevention, high corrosion resistance, and lubricity, and can maintain high hydrophilicity without being contaminated by attached lubricating oil, and has the characteristic of not producing mold or other microorganisms for a long period of time. [Examples]

[0031] The present invention will be described in detail below with reference to examples and comparative examples.

[0032] [Example 1] Chitosan (CHI: Kimika Chitosan, manufactured by Kimika Co., Ltd.) powder was added to 5.0 g of distilled water to obtain a 3.0% aqueous dispersion. Next, 5 ml of acetic acid was added at room temperature and stirred for 30 minutes to obtain a homogeneous solution in which the CHI was dissolved. To this homogeneous solution, 5.0 g of 2.0% aqueous polyvinyl alcohol (PVA), 1.0 g of methyltriethoxysilane (MTEOS, manufactured by Tokyo Chemical Industry Co., Ltd.), and 1.0 ml of 2-propanol (IPA) solution containing 0.04 g of 2-phosphonobutane 1,2,4-tricarboxylic acid (PH-430, manufactured by Kirest Co., Ltd.) were added, and the mixture was stirred at room temperature for 90 minutes to obtain a hydrophilic polymer composite solution. Using the obtained hydrophilic polymer composite solution, a degreased glass slide (S1126, manufactured by Matsunami Glass Co., Ltd.: 26 mm × 76 mm × 0.8~1.0 mm) was coated by the dip method, and then heated and cured in a constant temperature oven set to 80°C for 120 minutes to form a modified film on the glass slide surface. The film thickness, appearance, odor, water resistance, contact angle, and adhesion of the obtained modified film were evaluated using the methods described below, and the evaluation results are shown in Table 6.

[0033] <film thickness> The measurement was taken at room temperature using a paint thickness gauge (MonotaRO Co., Ltd. paint thickness gauge for both ferrous and non-ferrous metals). <Exterior> The evaluation was conducted visually. The evaluation criteria are as follows: ◎: A colorless, transparent film is formed. ○: A thin, cloudy film has formed in some areas. ×: A cloudy white film has formed throughout. <Odor> The evaluation was conducted by directly smelling the samples. The evaluation criteria were as follows: ◎: You can smell the scent of cypress wood. ○: I can barely detect any odor. △: There is a clear odor (unpleasant smell). <Water resistance> Pure water was dropped onto the surface of the modified film, and after 10 minutes, the water droplets were removed and the surface appearance was observed. The evaluation criteria were as follows: ◎: No change was observed at all. ○: Swelling due to water was observed. ×: Created by a void. <Contact angle> 5 μL of pure water was dropped onto the surface of the modified film, and the contact angle was measured at room temperature using a contact angle meter (SImage mini11 Portable contact angle meter, manufactured by Excima Corporation). The evaluation criteria were as follows. ◎: Less than 20° ○: 20° or more and less than 30° △: 30° or more and less than 40° ×: 40° or more <Adhesion> A 7mm diameter steel ball was placed on the surface of the modified coating via four sheets of tissue paper. A 100g load was applied to the steel ball, and it was rubbed back and forth 100 times. The condition of the modified coating was then visually observed. The evaluation criteria are as follows. A rating of △ indicates that the coating has a level of abrasion resistance and adhesion that is acceptable for practical use. ○: No change. △: Slightly scratched off. ×: The modified film has peeled off, exposing the substrate.

[0034] [Example 2] A modified film was formed on the surface of a glass slide using the same method as in Example 1, except that the curing temperature conditions were changed from 80°C for 120 minutes to room temperature for 12 hours. The same evaluation was then performed. The evaluation results are shown in Table 6.

[0035] [Example 3] Hydroxyethylcellulose (HEC: SANHEC T-series LT, manufactured by Sansho Co., Ltd.) powder was added to distilled water and stirred at room temperature for 3 hours to prepare 11.0 g of a 9.0% HEC aqueous solution. To this HEC aqueous solution, 5.5 ml each of a 2-propanol solution containing 1.1 g of PH-430, 0.2 g of MTEOS, and 0.11 g of Hiba oil (natural Aomori Hiba oil, manufactured by the Aomori Prefectural Forestry Cooperative Federation) was added and stirred at room temperature for 90 minutes to obtain a hydrophilic polymer composite solution. Using the obtained hydrophilic polymer composite solution, a modified film was formed on the surface of a glass slide in the same manner as in Example 1, and the same evaluation was performed. The evaluation results are shown in Table 6.

[0036] [Examples 4-24] Hydrophilic polymer composite solutions were obtained using the materials shown in Tables 1-5 by the same method as in Example 1 or Example 3. Specifically, 2-hydroxypropyl methylcellulose (HPMC) was 90SH-100 or 60-SH-50 manufactured by Shin-Etsu Chemical Co., Ltd., while tetraethoxysilane (TEOS) and hibitane were manufactured by Tokyo Chemical Industry Co., Ltd. Furthermore, hydroxyethylidene diphosphonic acid (PH-210) was Kirest PH-210 manufactured by Kirest Corporation. Using the obtained hydrophilic polymer composite solution, a modified film was formed on the surface of a glass slide in the same manner as in Example 1, and the same evaluation was performed. The evaluation results are shown in Table 6.

[0037] [Example 25] Using the hydrophilic polymer composite solution obtained in Example 1, a modified film was formed on the surface of a stainless steel plate (SUS304, manufactured by Taiyu Kikai Co., Ltd., 80mm x 30mm x 0.5mm) using the same method as in Example 1, and the same evaluation was performed. The evaluation results are shown in Table 6.

[0038] [Example 26] Using the hydrophilic polymer composite solution obtained in Example 18, a modified film was formed on the surface of an aluminum plate (AS ONE Corporation Test Piece Aluminum Plate A1050P: 150mm x 70mm x 0.8mm) in the same manner as in Example 1, and the same evaluation was performed. The evaluation results are shown in Table 6.

[0039] [Example 27] Using the hydrophilic polymer composite solution obtained in Example 19, a modified film was formed on the surface of an aluminum plate (AS ONE Corporation Test Piece Aluminum Plate A1050P: 150mm x 70mm x 0.8mm) using the same method as in Example 1, and the same evaluation was performed. The evaluation results are shown in Table 6.

[0040] [Example 28] Using the hydrophilic polymer composite solution obtained in Example 4, a modified film was formed on the surface of a stainless steel plate (SUS304, manufactured by Taiyu Kikai Co., Ltd., 80mm x 30mm x 0.5mm) using the same method as in Example 1, and the same evaluation was performed. The evaluation results are shown in Table 6.

[0041] [Table 1]

[0042] [Table 2]

[0043] [Table 3]

[0044] [Table 4]

[0045] [Table 5]

[0046] [Table 6]

[0047] [Comparative Example 1] A modified film was formed on the glass slide surface in the same manner as in Example 9, except that MTEOS and PH-430 were not used. The resulting film was yellow with some cloudy areas, indicating solubilization of the modified film surface by water droplets.

[0048] [Comparative Example 2] A modified film was formed on the surface of the glass slide using the same method as in Example 9, except that PH-430 was not used. The resulting modified film was yellow in color, with some cloudy areas, and deflection was observed.

[0049] From a comparison of Examples 1-28 with Comparative Examples 1 and 2, it can be seen that using an alkoxysilane such as MTEOS in combination with an organic phosphonic acid such as PH-430 is effective in obtaining a modified coating that is colorless, transparent, and has excellent adhesion and water resistance.

Claims

1. A hydrophilic polymer composite obtained by carrying out a sol-gel reaction of an alkoxysilane in the presence of a hydrophilic polymer containing hydroxyethylcellulose, 2-hydroxypropylmethylcellulose, or chitosan, and an organic phosphonic acid.

2. The hydrophilic polymer composite according to claim 1, wherein the hydrophilic polymer contains polyvinyl alcohol.

3. The hydrophilic polymer composite according to claim 1, wherein the organic phosphonic acid is 2-phosphonobutane 1,2,4-tricarboxylic acid, 2-phosphonobutane 1,2,4-tricarboxylic acid sodium salt, or hydroxyethylidene diphosphonic acid.

4. The hydrophilic polymer composite according to claim 1, wherein the alkoxysilane is tetraethoxysilane or methyltriethoxysilane.

5. The hydrophilic polymer composite according to claim 1, comprising an organic antibacterial agent selected from the group consisting of cypress oil, hinokitiol, cetylpyridinium chloride, and hibitane.

6. A surface treatment agent comprising a hydrophilic polymer composite according to any one of claims 1 to 5.

7. The surface treatment agent according to claim 6, for use in surface treatment of a material selected from the group consisting of glass, metal, fiber, paper, wood, plastic, synthetic resin, and ceramics.

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