JP2013209509A - Water-repellent structure and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-repellent structure that has antifouling properties and antibiotic properties while having elevated durability of an advanced water repellency state.SOLUTION: A water-repellent structure comprises a monolith structure body that has a co-continuous structure in which voids and a skeleton that forms the voids are connected like a three-dimensional network, wherein pores are disposed on a surface of the skeleton, a water repellency filler of liquid or gel is filled in the inside of the voids. Moreover, a method of manufacturing a water-repellent structure is characterized in that pores are formed to a surface of the skeleton in the monolith structure body that has a co-continuous structure in which voids and the skeleton that forms the voids are connected like a three-dimensional network, and the water repellency filler of liquid or gel is filled into the voids.

Description

  The present invention relates to a water-repellent structure having antifouling properties and antibacterial properties while having high durability in a highly water-repellent state and a method for producing the same.

  It is known that a water-repellent surface having a high contact angle can be produced by combining surface roughness with low surface energy. There are various manufacturing methods.

  The super-water-repellent surface can significantly reduce the contact area between the surface and water, which can suppress the progress of chemical reaction through water, formation of local batteries, short circuit of electric lines, or formation of hydrogen bonds. it can. For this reason, a high effect can be expected for various purposes such as prevention of raindrops on the solid surface, prevention of dirt, rust prevention, electrical insulation, and releasability.

  The highly water-repellent surface described here is a surface having a contact angle of 120 ° or more that cannot be realized on a smooth surface. And the scope of application includes exteriors of vehicles such as automobiles and bullet trains, ship bottom paint, outdoor lights, kitchens and kitchenware, bathrooms and toilets and their equipment, fishing nets, buoys, dental supplies, electrical equipment, residential floors and exteriors, Entrance doors and knobs, roofs, pools and poolsides, bridge piers, gates, posts, benches, towers, antennas, electric wires, garages, tents, umbrellas, raincoats, sports equipment and sports clothing, helmets, shoes and bags and other leather products , Outdoor loudspeakers such as cameras, video, paper, speakers, audio equipment, curtains, carpets, oiling nozzles for gas stations, chemical plants such as refineries, metal tools, nails, screws, buckets, etc. It extends to.

  However, the highly water-repellent surface is realized by a combination of a fine surface structure and low surface energy, so even if a hard material is used for the base material that forms the surface structure, durability against abrasion etc. is ensured. Was the most difficult.

  As an improvement measure, a highly water-repellent surface using an organic monolith structure as disclosed in Patent Document 1 has been realized. An organic monolith structure is a co-continuous structure (spinodal) in which voids (0.1 to 10 μm) and skeletons constituting the voids are connected. Therefore, even if the lump is cut in any direction, it has a certain uneven structure. Become the surface. Further, the monolith structure has a double pore structure in which pores having a diameter of several tens of nanometers exist on the skeleton surface and / or inside the skeleton. The organic monolith structure has a concavo-convex structure sufficient to exhibit high water repellency when surface modification is performed to make the skeleton water-repellent.

  In addition, the material design guideline that mimics the “self-healing function” by the metabolism of living organisms has been realized, and a material that maintains a high water repellency that maintains an uneven structure by constantly exposing a fresh surface has been realized. For example, porous cross-linked polymer resins used for separation and purification media and packing materials for column chromatography are attracting attention as a separation medium having an integral structure that exhibits separation performance by a thin skeleton (see Patent Document 2), and is partially practical. Has led to This is a porous body having a three-dimensional network skeleton of a cured epoxy resin, and the three-dimensional network structure is a co-continuous structure of a cured epoxy resin having a columnar shape. Resins that can be used at that time were styrene, methacrylate and acrylate in addition to the epoxy resin.

  Conventionally, many water-repellent surfaces have realized a highly water-repellent surface by entraining air (gas) into a fine surface structure (Patent Document 1). There is also a report that a highly water-repellent surface with good tumbling properties is formed by installing a fluorine-based solution in the gap between the structures (Non-Patent Document 1).

JP 2011-162672 A JP 2009-269948 A

Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity, Nature, 477, 443 (2011).

  As described in the prior art, many examples of production of highly water-repellent surfaces have been reported, but it has been extremely limited until practical use. For example, a highly water-repellent surface using an organic monolith structure disclosed in Patent Document 1 has improved durability (particularly abrasion resistance), but water and oil drops are insufficiently tumbled. Therefore, the antifouling property was insufficient.

  At that time, there has been a measure to arrange a liquid having a low surface tension in the structure, but it is necessary to suppress evaporation in consideration of the vapor pressure. In addition, the physical retention of the liquid (retention against washing away by a water flow or the like) was required.

  In addition, the photocatalyst has an antibacterial property due to its strong redox power, but it could not always exert its power when used on a site where dirt is regularly attached.

  Then, the subject of this invention is providing the water-repellent structure which has antifouling property and antibacterial property, having high durability of a highly water-repellent state.

  In order to solve the above problems, the water-repellent structure according to the present invention comprises a monolith structure having a co-continuous structure in which voids and a skeleton forming the voids are connected in a three-dimensional network, Fine pores are formed on the surface, and liquid or gel-like water repellent filler is filled in the voids.

  Since the monolith structure has a co-continuous structure (spinodal) in which voids and a skeleton that forms the voids are connected, a certain uneven structure is exposed on the surface even if cut along any direction. Therefore, even when the surface is peeled off while applying strong friction, it is possible to always maintain the uneven structure necessary for forming a highly water-repellent surface. The porosity of the monolith structure is preferably 60 to 80%. Furthermore, in order to suppress evaporation and fluidity of the water repellent filler filled in the pores, it is preferable that pores of several tens of nm are formed on the skeleton of the monolith structure. As a specific example of the monolith structure, for example, a monolith structure made of a cured epoxy resin as described in Patent Document 2 can be used.

  According to such a water-repellent structure of the present invention, the liquid of the monolith structure is filled with a liquid or gel-like water-repellent filler having a low surface energy. -A highly water-repellent surface with significantly improved antibacterial properties can be formed in a large area.

  In such a water-repellent structure, it is preferable that the water-repellent filler is a fluorine-based water-repellent filler containing fluorine. The water repellent filler preferably has a low surface tension in order to realize water repellency and oil repellency, and preferably has a low vapor pressure in order to prevent volatilization after impregnation. Specific examples of the water-repellent filler having such physical properties include fluorine-based water-repellent fillers such as perfluorocarbon, perfluoropolyether oil having a linear structure, and fluorine-based inert liquid. In particular, by using an inert liquid in which water and oil are difficult to dissolve, the antifouling property can be drastically improved.

  Moreover, it is preferable that a fluorine-containing resin containing fluorine is disposed on the surface and / or inside of the skeleton. By disposing the fluoropolymer resin or the like on the skeleton portion by coating or the like, the water repellency of the skeleton portion exposed to the outside is improved, and high water repellency is realized as the entire water-repellent structure according to the present invention. Such a fluororesin may be contained by being kneaded into the inside of the skeleton, or may be coated on the surface of the skeleton. In order to develop high water repellency, for example, polytetrafluoroethylene can be used as the fluororesin.

  Moreover, it is preferable that the photocatalyst is arrange | positioned on the surface or the inside of the said frame | skeleton. By doing in this way, it becomes possible for photocatalysts, such as titanium dioxide and a visible light response type photocatalyst, to decompose | disassemble the stain | pollution | contamination of a frame | skeleton surface. In particular, when the monolith structure is an organic monolith structure made of an organic material, a fresh surface always appears due to the self-etching action that gradually decomposes the monolith structure. As a result, high durability is maintained by adding a “self-repair function by metabolism”.

  Here, the self-etching action means an action of promoting an organic matter decomposition reaction that is exhibited when a photocatalyst such as titanium dioxide is irradiated with ultraviolet rays. When an appropriate amount of a photocatalyst is added to the internal structure or the surface of the organic monolith structure, and the organic monolith structure is irradiated with ultraviolet rays, the organic monolith structure is decomposed in order from the surface. In addition, a fresh monolithic structure is always exposed on the surface by washing the decomposition products with rainwater during rainfall, so that high water repellency can be maintained over a long period of time.

  In such a water-repellent structure of the present invention, the photocatalyst preferably occupies 10% or less of the monolith structure by volume. Although the photocatalyst has a self-etching action for decomposing the monolith structure, it is advantageous to secure a certain amount of the exposed area of the monolith structure in order to give the water-repellent structure itself sufficient water repellency. Specifically, if the photocatalyst occupies 10% or less of the monolith structure, sufficient water repellency is exhibited.

  In order to solve the above problems, the method for producing a water-repellent structure according to the present invention provides a monolith structure having a co-continuous structure in which voids and a skeleton forming the voids are connected in a three-dimensional network. The method comprises forming pores on the surface of the skeleton and filling the voids with a liquid or gel water-repellent filler.

  According to such a method for producing a water-repellent structure according to the present invention, a liquid or gel-like water-repellent filler having a low surface energy is filled in the voids of the monolith structure. A highly water-repellent surface with significantly improved antifouling and antibacterial properties can be formed in a large area. The larger the number of pores on the surface of the skeleton, the better. For example, when cross-sectional observation is performed with a scanning electron microscope, one or more in a 1 μm × 1 μm region, and further 1 in a 0.1 μm × 0.1 μm region. It is desirable that there are more than one.

  According to the water-repellent structure according to the present invention, since the liquid or gel-like water-repellent filler is filled in the voids of the monolith structure exhibiting high water repellency, water or oil enters the voids. As a result, it is possible to provide a water repellent structure that is highly durable and excellent in antifouling properties and antibacterial properties.

  In addition, the water-repellent structure that can suppress evaporation and physically hold the liquid (holding against water flow, etc.) by limiting the fluidity of the water-repellent filler with gelation and / or pores on the surface of the skeleton. Can be provided.

It is a schematic sectional drawing which shows the co-continuous structure of the organic monolith structure in the water-repellent structure which concerns on one embodiment of this invention. 1 shows a method for measuring the falling angle of a solid surface, (A) is when the solid surface of a water-repellent structure formed by impregnating the organic monolith structure of FIG. 1 with a fluorocarbon solution is inclined at an inclination angle of 2 °. (B) is a front view when the solid surface of the organic monolith structure of FIG. 1 is inclined at an inclination angle of 90 °. It is a fall characteristic figure of a water drop in the solid surface of Drawing 2 (A) and Drawing 2 (B). It is an enlarged view of the frame | skeleton part when the cross section of the organic monolith structure which comprises the water-repellent structure which concerns on one embodiment of this invention is observed with a scanning electron microscope.

(Method for producing monolith structure)
An organic monolith structure having a co-continuous structure (spinodal) in which a void and a skeleton constituting the void are connected to a substrate is prepared. This is a chemically stable viscoelastic body, and the pore diameter of the voids can be controlled to some extent (see Patent Document 2), and is obtained by polymerizing an epoxy monomer. The pore diameter is not particularly limited, but is preferably 200 nm to 10 μm, more preferably 500 nm to 1 μm. In addition, the pore diameter on the skeleton surface is sufficiently smaller than each skeleton diameter, but it is desirable that the number of pores is large. In order to add a self-healing function using a self-etching function that decomposes the monolith structure from the light-irradiated surface using the photocatalytic oxidative decomposition reaction and always maintains the uneven structure equivalent to the initial state, the monolithic titanium dioxide photocatalyst is monolithic. It is installed inside the structure and / or on the surface (see Patent Document 1). When installed inside the monolith structure (FIG. 1), a titanium dioxide photocatalyst is added to the monomer in a volume ratio of 0.01 to 95% by mass when the monolith structure is produced. For a wall material or the like that is moderately contaminated, a skeleton is formed at 5% by mass or less, and desirably it is added in a range of 1.5 to 0.5% by mass. In order to attach importance to the maintenance of high water repellency, for example, 30 to 65% by mass of polytetrafluoroethylene may be incorporated into the skeleton. When emphasizing antibacterial properties, a skeleton is formed at 50% by mass or more, and desirably it is added in the range of 50 to 80% by mass. In either case, the particle size of the photocatalyst such as titanium dioxide is not particularly limited, but a particle size sufficiently smaller than the pore size of the voids of the monolith structure is appropriate, and is preferably several tens of nm or less. Finally, the monolith structure to which the titanium dioxide photocatalyst is added is impregnated with a water-repellent polymer (silicon-based / fluorine-based) dissolved in 0.0001 to 40% by mass in an organic solvent to perform surface modification.

(Liquid or gel to fill)
The liquid or gel to be filled preferably has a low surface tension (to bring about water and oil repellency) and a low vapor pressure (to prevent volatilization after impregnation). Things can be used.

・ Perfluorocarbon alone or multiple perfluorocarbon liquids (C6F14, etc.)
・ Fluorine-based inert liquid (Surface tension = 12-18mN / m @ 25 ℃: Sumitomo 3M Forolinate)
・ Fluorine-based inert liquid (Surface tension = 16mN / m @ 25 ℃: Mitsubishi Materials Inert Liquid)
・ Fluorine oil (Surface tension = 17.7 to 19.1mN/m@25℃: Daikin Inert Liquid)
・ Perfluoropolyether oil with linear structure ・ Silicone oil (Surface tension = 19-22mN / m @ 25 ℃: Shin-Etsu Silicone)

In addition to the above specific examples, liquids or gels can be applied such that the surface energy of the water repellent structure is 12 to 45 mJ / m ² by impregnating the monolith structure. This numerical range of the surface energy is calculated by measuring the contact angle of two polar and nonpolar liquid droplets in accordance with the Owens and Wendt method. An example of the actually measured surface energy value of the water repellent structure obtained by impregnating the organic monolith structure with a predetermined liquid is 37.6 mJ / m ² .

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, these Examples do not restrict | limit this invention.

(Contact angle)
FIG. 1 is a schematic cross-sectional view showing a co-continuous structure of an organic monolith structure in a water-repellent structure according to an embodiment of the present invention. In FIG. 1, an organic monolith structure 1 has a co-continuous structure in which a skeleton 2 (outlined portion) and voids 3 (portions with a lattice pattern) are connected in a three-dimensional network, Have pores 4 formed. When a TiO ₂ photocatalyst and PTFE are placed in the organic monolith structure 1 (in the skeleton 2) and a droplet is dropped on a solid surface impregnated with a fluorocarbon solvent, the contact angle is approximately 140 ° or more. It was.

(Dropability of droplets)
FIG. 2 shows a method for measuring the falling angle of the solid surface. FIG. 2A is a front view when the solid surface of a water-repellent structure obtained by impregnating the organic monolith structure of FIG. 1 with a fluorocarbon solution is inclined at an inclination angle of 2 °. FIG. 2B is a front view when the solid surface of the organic monolith structure of FIG. 1 is inclined at an inclination angle of 90 °. In the example (FIG. 2A), the sliding angle was measured as 2 °, and in the comparative example (FIG. 2B), the sliding angle was measured as “none”. Here, the falling angle refers to an angle at which a 30 μL water droplet dropped on the surface of the water-repellent structure starts to fall when the inclination slowly increases. In FIG. 3, 30 μL of water droplets are dropped on the solid surface of FIG. 2A (Example) and the solid surface of FIG. 2B (Comparative Example) so that the inclination angle of the solid surface becomes 35 °. An example of the fall characteristics when tilted to. 2 to 3, it can be seen that in the example, the falling angle is overwhelmingly smaller than in the comparative example, and the falling speed (= falling distance / elapsed time) is large.

  FIG. 4 is an enlarged view of a skeleton portion when a cross-section of the organic monolith structure constituting the water-repellent structure according to one embodiment of the present invention is observed with a scanning electron microscope. According to FIG. 4, it is observed that a skeleton having a columnar diameter of 100 nm to 10 μm and a void 3 having a diameter of 200 nm to 10 μm are present in the organic monolith structure. On the surface of the skeleton, pores 4 having a pore diameter of several tens of nm (mode in normal distribution) are present everywhere. The number of pores can be controlled at the production stage of the monolith structure.

(Colorability)
Brilliant Blue FCF or New Coccine is further mixed in a mixture of thermoplastic epoxy monomer and curing agent, TiO2 photocatalyst, and polytetrafluoroethylene particles, and allowed to stand for 24 hours in a 75 ° C temperature environment for phase separation. Thus, it is possible to produce a colored monolith structure. When the colored color is immersed in water for about 24 hours, the color fading hardly occurs.

  The water-repellent structure according to the present invention can be used for building materials and other various materials that require a functional surface with high water / oil repellency, high droplet sliding property, high durability, and high antifouling property. It is.

1 Organic Monolith Structure 2 Skeleton 3 Void 4 Pore

Claims (12)

  A monolith structure having a co-continuous structure in which voids and a skeleton that forms the voids are connected in a three-dimensional network, pores are formed on the surface of the skeleton, and a liquid or gel-like structure is formed in the voids. A water repellent structure characterized by being filled with a water repellent filler.   The water-repellent structure according to claim 1, wherein the water-repellent filler is a fluorine-based water-repellent filler containing fluorine.   The water-repellent structure according to claim 1 or 2, wherein a fluorine-containing resin containing fluorine is disposed on the surface of the skeleton.   The water-repellent structure according to claim 3, wherein the surface of the skeleton is coated with the fluororesin.   The water-repellent structure according to claim 3 or 4, wherein the fluororesin is also contained in the skeleton.   The water-repellent structure according to any one of claims 3 to 5, wherein the fluororesin is made of polytetrafluoroethylene.   The water-repellent structure according to any one of claims 1 to 6, wherein a photocatalyst is disposed on the surface and / or inside of the skeleton.   The water-repellent structure according to claim 7, wherein the photocatalyst is made of titanium oxide.   The water repellent structure according to claim 7 or 8, wherein the photocatalyst is a visible light responsive photocatalyst.   The water repellent structure according to any one of claims 7 to 9, wherein the photocatalyst occupies 10% or less of the monolith structure by volume ratio.   The water-repellent structure according to any one of claims 1 to 10, wherein the monolith structure is an organic monolith structure made of a cured epoxy resin. In a monolith structure having a co-continuous structure in which voids and a skeleton forming the voids are connected in a three-dimensional network, pores are formed on the surface of the skeleton, and liquid or gel-like water-repellent filling is provided in the voids. A method for producing a water-repellent structure, comprising filling a material.

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