Composite for removing droplets having a surface tension lower than that of water, method for producing said composite, antifouling system, structure, and gas-liquid separation membrane

Abstract

To provide a complex having superior droplet removability.SOLUTION: A complex has a porous cured product that is a cured composition containing a curable silicone rubber component and a filler, and silicone oil impregnated into the porous cured product. The mass ratio of the content of the silicone oil relative to the content of the curable silicone rubber component is 0.20-0.90. The filler has a three-dimensional shape comprising a core and needle-like parts extending in different four-axis directions from the core.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to a composite, a method for manufacturing the composite, an antifouling system, and a structure. [Background technology]

[0002] As an excellent water-repellent material used for gas-liquid separation membranes and the like, Patent Document 1 describes the following: "A material obtained by curing a composition containing a curable silicone rubber component and a filler, wherein the filler has a three-dimensional shape having a core and needle-like portions extending from the core in four different axial directions, and wherein the content mass ratio r of the content of the filler to the total content of the curable silicone rubber component and the filler in the composition is 0.70 or more." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-210401 A Summary of the Invention [Problem to be solved by the invention]

[0004] The material described in Patent Document 1 has water repellency that is incomparably superior to conventional materials, and is expected to be used in gas-liquid separation membranes and the like. However, there is room for improvement in terms of the performance of removing droplets adhering to the surface, particularly droplets having a lower surface tension than water.

[0005] Therefore, an object of the present invention is to provide a composite having excellent droplet removal performance. Another object of the present invention is to provide a method for producing a composite, an antifouling system, and a structure. [Means for solving the problem]

[0006] As a result of extensive investigations aimed at achieving the above object, the present inventors have found that the above object can be achieved by the following configuration.

[0007] [1] A composite material comprising: a porous cured material obtained by curing a composition comprising a curable silicone rubber component and a filler; and a silicone oil impregnated into the porous cured material, wherein the mass ratio of the content of the silicone oil to the content of the curable silicone rubber component is 0.20 to 0.90, and the filler has a three-dimensional shape having a core and needle-like portions extending from the core in four different axial directions. [2] The composite according to [1], wherein the content mass ratio is less than 0.64. [3] The composite according to [1] or [2], wherein the content mass ratio is less than 0.61. [4] The composite according to any one of [1] to [3], wherein the content mass ratio is 0.50 or more. [5] The composite according to any one of [1] to [4], wherein the content mass ratio of the filler to the total content of the curable silicone rubber component and the filler in the composition is 0.40 to 0.99. [6] The composite according to any one of [1] to [5], wherein the curable silicone rubber component contains an organopolysiloxane having a hydrolyzable group bonded to a silicon atom. [7] The kinetic viscosity of the above silicone oil at 25°C is 1.0 x 10 0 ~1.0×10 4 mm 2 The complex according to any one of [1] to [6], wherein [8] The complex according to any one of [1] to [7], wherein the silicone oil contains dimethylpolysiloxane. [9] A method for producing a composite according to any one of [1] to [8], comprising: curing a composition containing the curable silicone rubber component and the filler to obtain a porous cured material; and impregnating the porous cured material with silicone oil.

[10] The method for producing a composite according to [9], wherein the mass ratio of the content of the silicone oil to the content of the curable silicone rubber component is 0.20 to 0.90.

[11] The method for producing a composite according to [9] or

[10] , wherein the mass ratio of the content of the filler to the total content of the curable silicone rubber component and the filler is 0.40 to 0.99.

[12] An antifouling system comprising: a composite according to any one of [1] to [8]; and a reservoir for supplying the silicone oil to the composite.

[13] A structure equipped with an antifouling system as described in

[12] . Effect of the Invention

[0008] According to the present invention, a composite having excellent droplet removal performance can be provided. The present invention also provides a method for producing a composite, an antifouling system, and a structure.

[0009] The composite of the present invention comprises a porous cured product obtained by curing a composition containing a curable silicone rubber component and a filler, and a silicone oil impregnated into the porous cured product, wherein the mass ratio of the silicone oil content to the curable silicone rubber component content (oil / rubber) is 0.20 to 0.90, and the filler is a composite having a three-dimensional shape having a core and needle-like portions extending from the core in four different axial directions.

[0010] The porous cured material has a network of numerous interconnected pores with relatively uniform particle size due to shrinkage of the curable silicone rubber during curing caused by the bulky shape of the filler. It is presumed that excellent droplet removal performance is obtained by impregnating the interconnected pores with a predetermined amount of silicone oil.

[0011] In this specification, droplet removal performance means that droplets of a fluid having a surface tension of 22.5 mN / m or more at 20°C and a surface tension lower than that of water can be caused to slide off at an inclination angle of 15° or less, preferably 10° or less, and more preferably 5° or less, in the experimental method described in the examples below.

[0012] In addition, if the oil / rubber ratio in the composite of the present invention is less than 0.64, the contact angle hysteresis is likely to be large, and as a result, better droplet removal performance is likely to be obtained. Furthermore, if the oil / rubber ratio is less than 0.64, this tendency is remarkable.

[0013] Furthermore, when the oil / rubber ratio in the composite of the present invention is 0.50 or more, the composite has a surface tension of more than 22.5 mN / m at 20°C and has a lower contact angle hysteresis for an organic solvent having a lower surface tension than water, resulting in even more excellent antifouling properties and self-cleaning properties.

[0014] Furthermore, when the mass ratio of the filler content to the total content of the curable silicone rubber component and filler in the composite of the present invention is 0.40 to 0.99, it is presumed that the pore size of the interconnected pores in the cured material will be more uniform, resulting in a composite with better droplet removal performance.

[0015] Furthermore, when the curable silicone rubber component contains an organopolysiloxane having a hydrolyzable group bonded to a silicon atom, it has excellent affinity with silicone oil, resulting in a composite having better droplet removal performance.

[0016] In addition, the kinetic viscosity of silicone oil at 25°C is 1.0×10 0 ~1.0×10 4 mm 2 / s, a composite having better droplet removal performance is obtained. This tendency is seen when the kinetic viscosity is 1.0×10 1 mm 2 / s or more, and is more pronounced at 1.0×10 2 mm2 This is even more noticeable when the ratio is 1 / s or more.

[0017] Furthermore, when the silicone oil contains dimethylpolysiloxane, a composite having better droplet removal performance is obtained.

[0018] The method for producing the composite of the present invention includes curing a composition containing a curable silicone rubber component and a filler to obtain a porous cured product, and impregnating the porous cured product with silicone oil. According to the above-mentioned production method, a composite having excellent liquid repellency can be easily produced, and the composite can also be regenerated by re-impregnating it with silicone oil.

[0019] Furthermore, when the content mass ratio of the silicone oil content to the content of the curable silicone rubber component in the composite is 0.20 to 0.90, a composite having even better droplet removal performance can be obtained.

[0020] The antifouling system of the present invention includes a composite and a reservoir for supplying silicone oil to the composite. The composite has fine communicating holes inside due to the shape of the filler, and can absorb silicone oil by capillary action. Therefore, the system including the reservoir for supplying silicone oil has excellent antifouling properties and self-repairing properties.

[0021] The structure of the present invention is a structure provided with the above-mentioned antifouling system. Since the structure is provided with the antifouling system having a self-repairing property, the structure can exhibit antifouling properties for a long period of time without maintenance. [Brief description of the drawings]

[0022] [Figure 1] FIG. 13 is a diagram showing the results of adjusting the silicone oil content depending on the rotation speed. [Diagram 2]FIG. 1 shows the static contact angle (left vertical axis) and contact angle hysteresis (right vertical axis) of water at 25° C. for test pieces in which the content of silicone oils with different kinetic viscosities was adjusted to be approximately the same (2.80 to 2.90 mg). [Diagram 3] FIG. 1 is a graph showing the relationship between the silicone oil content (right vertical axis) and the static contact angle of water (25° C., left vertical axis) in the composite. [Figure 4] FIG. 1 is a graph showing the relationship between the silicone oil content (right vertical axis) and the water contact angle hysteresis (left vertical axis) in the composite. [Diagram 5] FIG. 1 is a graph showing the relationship between the silicone oil content (right vertical axis) in the composite and the static contact angle of propylene glycol (25° C., left vertical axis). [Figure 6] FIG. 1 is a graph showing the relationship between the silicone oil content (right vertical axis) in a composite and the contact angle hysteresis of propylene glycol (left vertical axis). [Figure 7] FIG. 1 is a graph showing the relationship between the silicone oil content (right vertical axis) in the composite and the static contact angle of ethanol (25° C., left vertical axis). [Figure 8] FIG. 1 is a graph showing the relationship between the silicone oil content in the composite (right vertical axis) and the contact angle hysteresis of ethanol (25° C., left vertical axis). [Figure 9] 1 is an image showing a composite formed on a substrate and a state of water droplets dropped onto the composite. [Figure 10] A porous cured material prepared on a 300 mm x 300 mm glass substrate by the same method as in Example 2 was placed vertically with its base end held in a silicone oil reservoir filled with silicone oil, and the graph shows how silicone oil is absorbed into the porous cured material by capillary action over time. [Figure 11] 1 is a curve showing the relationship between time and the height of silicone oil rise. [Figure 12]With the base end contained in a silicone oil reservoir, the composite was rotated to apply shear force, wiped with a cloth on its surface, and sprayed with water in a shower until at least a portion of the silicone oil was lost, and then the composite was examined for self-repair. [Figure 13] FIG. 1 is a graph showing the water sliding angle and the contact angle hysteresis before and after self-repair. [Figure 14] The images show the state of the complex after it was showered with 6 L of water per minute for 6 hours (t=0), with the base end housed watertight in a silicone oil reservoir, and then 2 days (t=2 days), 6 days (t=6 days), and 12 days (t=12 days). [Figure 15] FIG. 1 is a schematic diagram of a structure including an antifouling system according to an embodiment of the present invention. [Figure 16] 1 shows the results of measuring the static contact angles of composite 5-1 and composite 5-2 with respect to water, propylene glycol, and ethanol. [Figure 17] 1 shows the results of measuring the sliding angles of composite 5-1 and composite 5-2 in water, propylene glycol, and ethanol. [Figure 18] 4 shows the results of measuring the sliding angle for various fluids. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail below. The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0024] [Complex] The composite according to the embodiment of the present invention comprises a porous cured material obtained by curing a composition containing a curable silicone rubber component and a filler, and a silicone oil impregnated into the porous cured material, the content mass ratio (oil / rubber ratio) of the silicone oil content to the content of the curable silicone rubber component is 0.20 to 0.90, and the filler has a three-dimensional shape having a core and needle-like parts extending from the core in four different axial directions. Each component contained in the composite will be described in detail below.

[0025] (Curable silicone rubber component) The curable silicone rubber component is a component that cures to become a binder for fixing the filler, and in this specification means a solid component that does not contain a solvent, and forms the matrix of the composite by curing.

[0026] The curable silicone rubber component is not particularly limited, and may be, for example, a reaction curing type silicone rubber composition. Examples of reaction curing type silicone rubber compositions include condensation type silicone rubber compositions and addition polymerization type silicone rubber compositions, and any known silicone rubber composition may be used without particular limitation.

[0027] Of these, condensation type silicone rubber compositions are preferred, and room temperature curing type silicone rubber compositions are more preferred, in that they make it easier to obtain members having superior effects according to the present invention.

[0028] A specific example of a reaction curing type silicone rubber composition is a silicone rubber composition containing an organopolysiloxane having a reactive functional group. Examples of reactive functional groups include hydroxy groups (silanol groups), alkoxy groups (alkoxysilyl groups), mercapto groups, epoxy groups, and ethylenically unsaturated groups (vinyl groups, (meth)acrylic groups, etc.).

[0029] In particular, it is preferable that the curable silicone rubber component contains an organopolysiloxane having a hydrolyzable group bonded to a silicon atom, since this allows for the production of a component having the more excellent effects of the present invention.

[0030] Organopolysiloxanes having hydrolyzable groups bonded to silicon atoms are cured by a condensation reaction, and generally suffer from greater cure shrinkage due to the elimination of water and / or alcohol during curing. When such organopolysiloxanes having hydrolyzable groups bonded to silicon atoms are used, the cure shrinkage makes it easier for fillers to come into sufficient contact with each other.

[0031] On the other hand, because the fillers have a bulky three-dimensional shape, even when the curable silicone rubber component cures and shrinks, they cannot approach each other more than a certain distance due to their three-dimensional structure; in other words, a certain distance is maintained between them, making it easier to form more uniform communicating pores.

[0032] For example, when the organopolysiloxane has alkoxysilyl groups, the curable silicone rubber composition containing the organopolysiloxane may contain a partial hydrolysate in which some of the alkoxysilyl groups are hydrolyzed, a hydrolysate in which all of the alkoxysilyl groups are hydrolyzed, and a condensate in which some of these are condensed. More specifically, the organopolysiloxane may be, for example, a diorganopolysiloxane having hydroxyl groups at both ends of the molecular chain.

[0033] The content of the curable silicone rubber component in the composite is not particularly limited, but is generally preferably 1 to 50% by mass relative to the total mass of the composite, in that a composite having a more excellent effect of the present invention can be obtained. The composite may contain one type of curable silicone rubber component alone, or may contain two or more types. When the composite contains two or more types of curable silicone rubber components, the total content is preferably within the above numerical range.

[0034] The composite contains silicone oil, which will be described in detail later. The quantitative relationship between this silicone oil and the curable silicone rubber component is such that the content mass ratio of the silicone oil to the content of the curable silicone rubber component (oil / rubber ratio) is 0.20 to 0.90, preferably 0.50 or more, more preferably 0.55 or more, 0.57 or more, 0.61 or more, 0.64 or more, 0.65 or more, 0.67 or more, and 0.69 or more in that order.

[0035] If the oil / rubber ratio is less than 0.20, the composite does not have sufficient liquid repellency against fluids with lower surface tension (e.g., ethanol, etc.), while if it exceeds 0.90, the oil component is too high, and the surface condition of the composite is likely to become uneven.

[0036] From the viewpoint of making the contact angle hysteresis smaller, the oil / rubber ratio is preferably 0.61 or more, more preferably 0.64 or more, even more preferably 0.65 or more, and particularly preferably 0.67 or more.

[0037] On the other hand, from the viewpoint that the static contact angle is likely to become larger, the contact angle is preferably 0.65 or less, more preferably 0.64 or less, more preferably less than 0.64, and even more preferably less than 0.61.

[0038] This composite exhibits excellent droplet removal performance for droplets of fluids that have a surface tension of 22.5 mN / m or more at 20° C. and that are lower than that of water. Examples of such fluids include ethanol, methanol, acetone, 1-propanol, 1-butanol, 1-hexanol, 1-octanol, benzene, toluene, aniline, dodecane, ethyl acetate, butyl acetate, ethylene glycol, propylene glycol, N,N-dimethylformamide, and glycerol.

[0039] It is speculated that the reason this composite is able to exhibit excellent droplet removal performance is because the following three conditions are satisfied:

[0040] (1) The sum of the interfacial tension between the silicone oil and the porous cured material and the surface tension of the silicone oil (energy when the silicone oil is wetting the base layer) is smaller than the sum of the interfacial tension between the porous cured material and the droplets and the surface tension of water (energy when the droplets are wetting the base layer). (2) The sum of the interfacial tension between the silicone oil and the porous cured material and the interfacial tension between the silicone oil and the droplets and the surface tension of the droplets (energy when the silicone oil wets the porous cured material and the droplets are on top) is smaller than the sum of the interfacial tension between the porous cured material and the droplets and the surface tension of water (energy when the droplets are wetting the base layer). (3) The droplets and silicone oil do not mix.

[0041] In the composite, most of the curable silicone rubber component has already cured to form a cured matrix, and therefore the oil / rubber ratio is calculated as the mass ratio of the curable silicone rubber component contained in the composition before curing to the silicone oil contained in the composite. When calculating the oil / rubber ratio from the state of the composite, the content of the curable silicone rubber component in the composition can be determined from the mass of the cured material contained in the composite, taking into account the material balance of the curing reaction, and then the calculation can be performed.

[0042] In addition, in relation to the filler described below, the mass ratio of the filler content to the total content of the curable silicone rubber component (solid content) and the filler (filler / curable silicone rubber component+filler) is preferably 0.40 to 0.99, and more preferably 0.45 to 0.80. When the mass ratio is within the above numerical range, the composite has better droplet removal performance.

[0043] In addition, the term "curable silicone rubber component" refers to the solid content. When a composite is prepared using a commercially available silicone rubber dispersion, components other than the curable silicone rubber component contained in the dispersion, such as the solvent and catalyst, are not included in the "curable silicone rubber component" as used in this specification.

[0044] Other components that may be included in the compositions, porous cured products, and composites derived from such commercially available dispersions are described below.

[0045] (filling material) The composite contains a filler having a three-dimensional shape with a core and needle-like parts extending from the core in four different axial directions. The content of the filler is not particularly limited, but is preferably 1 to 50% by mass when the total mass of the composite is taken as 100% by mass, in order to obtain a composite having better effects of the present invention.

[0046] The composite may contain one type of filler alone or two or more types in combination. When the composite contains two or more specific fillers, the total content thereof is preferably within the above range. In relation to the curable silicone rubber component already explained, the content mass ratio is 0.20 to 0.90, preferably 0.50 or more, more preferably 0.55 or more, and even more preferably 0.57 or more.

[0047] The filler is not particularly limited as long as it has a three-dimensional shape having a core and needle-like portions extending from the core in four different axial directions. However, in terms of obtaining a composite having better effects of the present invention, it is preferable that, when imagining a regular tetrahedron with the core as its center of gravity, the needle-like portions have a shape in which they extend in the directions of the four vertices of a regular tetrahedron with the core as its center of gravity.

[0048] The filler preferably has a shape similar in appearance to the three-dimensional shape of the wave-dissipating block "Tetrapod (registered trademark)" (a three-dimensional shape having a core and needle-like parts extending from the core in four different axial directions). In the case of the wave-dissipating block "Tetrapod," it is composed of four legs of a truncated cone, but the needle-like parts corresponding to the "legs" in the above filler may have sharp tips. In other words, they may be cones, pyramids, etc.

[0049] The aspect ratio of the needle-shaped portion is preferably equal to or greater than 3. Furthermore, the lengths of the four needle-shaped portions are not particularly limited, but are preferably approximately the same.

[0050] The length of the needle-like portion is not particularly limited, but the average length is preferably 1 to 50 μm, and more preferably 5 to 30 μm.

[0051] The material of the filler is not particularly limited, and examples thereof include organic substances, inorganic substances, and composites thereof. An example of the composite is a composite having a coating layer containing an organic substance on a substrate containing an inorganic substance.

[0052] Examples of inorganic substances include metal oxides such as alumina, potassium titanate, wollastonite, zinc oxide, and aluminum borate; elemental metals such as chromium, copper, iron, and nickel; inorganic oxides other than metals such as silicon carbide, graphite, and silicon nitride, and complexes of the above. Among these, the inorganic substance is preferably a metal oxide, in that a member having the more excellent effects of the present invention can be obtained, and it is particularly preferable that each of the needle-like portions is a single crystal of a metal oxide. Such fillers include Panatetra (registered trademark) zinc oxide whiskers.

[0053] (Silicone oil) The composite contains silicone oil. The form in which the composite contains silicone oil is not particularly limited, but a form in which the silicone oil permeates and is retained in the communicating pores of the porous cured product obtained by curing a composition containing a curable silicone rubber component and a filler is preferred. The porous cured product has a matrix of silicone rubber obtained by curing a curable silicone rubber component, and has a high affinity with silicone oil, so that it is easy to assume the above-mentioned holding form.

[0054] The content of silicone oil in the composite is not particularly limited as long as the oil / rubber ratio is within a predetermined range, but in order to obtain a composite having better droplet removal performance, it is generally preferable that the content is 10 to 99 mass% based on the total mass of the composite. The composite may contain one type of silicone oil alone, or may contain two or more types. When the composite contains two or more types of silicone oil, it is preferable that the total content is within the above numerical range.

[0055] The kinetic viscosity of the silicone oil at 25° C. is not particularly limited. However, from the viewpoint of obtaining a composite having a more excellent effect of the present invention, it is preferable that the kinetic viscosity is 1.0×10 0 ~1.0×10 4 mm 2 / s (cSt) is preferred. 1 mm 2 / s or more, the composite has better droplet removal performance, and the 2 mm 2 / s or more, the composite has even better droplet removal performance.

[0056] Examples of silicone oils include amino-modified silicone oil, epoxy-modified silicone oil, carboxy-modified silicone oil, carbinol-modified silicone oil, methacryl-modified silicone oil, mercapto-modified silicone oil, phenol-modified silicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, alkyl-modified silicone oil, fatty acid-modified silicone oil, alkoxy-modified silicone oil, fluorine-modified silicone oil, dimethyl silicone oil, methylphenyl silicone oil, diphenyl silicone oil, and methylhydrogen silicone oil, with dimethyl silicone oil being preferred.

[0057] (Other Ingredients) The composite may contain components other than those described above, such as a solvent and a catalyst, within the scope of the effects of the present invention.

[0058] Typically, in the process of producing a composite, the solvent may become a component of the composite in a form in which the solvent, which was a component of the composition, migrates to the composite. The content of the solvent in the composite is not particularly limited, but is preferably 0 to 30% by mass relative to the total mass of the composite, and preferably does not contain a solvent.

[0059] The solvent is not particularly limited, and water, an organic solvent, or a mixture thereof can be used. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropanol, butanol, and n-propanol; Ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; Aromatic hydrocarbons such as benzene, toluene, and xylene; Aliphatic hydrocarbons such as heptane, hexane, and octane; glycol ethers such as propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol n-butyl ether, propylene glycol n-propyl ether, and ethylene glycol n-butyl ether; Halogenated hydrocarbons such as dichloromethane, 1,1,1-trichloroethane, and methylene chloride; and the like.

[0060] Typically, the catalyst may become a component of the composite in a form in which the catalyst, which was a component of the composition, is transferred to the composite during the production process of the composite. The content of the solvent in the composite is not particularly limited, but when the content of the curable silicone rubber component is taken as 100 parts by mass, it is, for example, preferably 0.01 to 100 parts by mass, and more preferably 0.1 to 10 parts by mass. As described below, the method for producing the composite may include a step of removing the catalyst. In that case, the catalyst content in the composite is preferably less than that described above, and specifically, it is preferably 1 part by mass or less when the content of the silicone rubber component is 100 parts by mass.

[0061] The catalyst used is preferably a compound that catalyzes the condensation reaction of silanol. Examples of such compounds include tin catalysts, titanium catalysts, zirconate catalysts, and zirconium catalysts.

[0062] Specific tin catalysts include organotin compounds in which the tin valence is either +4 or +2. Specific examples of tin (IV) compounds include dibutyltin dilaurate and dimethyltin dilaurate. Tin(II) compounds include tin(II) dilaurate and stannous stearate.

[0063] Titanium catalysts include diisopropoxydi(ethoxyacetoacetyl)titanium and titanium(IV) bis(acetylacetonato)diisopropoxide.

[0064] (Method of Manufacturing the Composite) The method for producing the composite is not particularly limited, but from the viewpoint of producing the composite more simply and having the obtained composite have better droplet removal performance, a production method having the following steps in the listed order is preferred. (1) A step of curing a composition containing a curable silicone rubber component and a filler to obtain a porous cured product (curing step) (2) A step of impregnating the porous cured material with silicone oil (impregnation step)

[0065] ·Curing process The composition used in the curing step is a composition containing the curable silicone rubber and a filler as already explained, and may contain a solvent, a catalyst, and the like as necessary. The composition can be obtained by mixing the components already described, or it may be obtained by adding a predetermined amount of filler to a commercially available curable silicone rubber composition and dispersing it therein.

[0066] The mass ratio of the curable silicone rubber component and the filler in the composition is not particularly limited, but it is preferable that the filler / (curable silicone rubber component+filler) content described above is adjusted to 0.40 to 0.99.

[0067] The content of the solvent in the composition may be adjusted as appropriate depending on the viscosity of the curable silicone rubber component, the volatility of the solvent, the film-forming method, and the like, but it is preferable that the solids content of the entire composition is adjusted to be 0.01 to 0.99 mass %. The solvent used is the same as that explained as the solvent that the composite may contain, including the preferred embodiment, and therefore the explanation thereof will be omitted.

[0068] The content of the catalyst in the composition is not particularly limited, but is preferably 0.01 to 100 parts by mass, and more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the curable silicone rubber composition. The catalyst used is the same as that explained as the catalyst that may be contained in the composite, including the preferred embodiments, and therefore the explanation thereof will be omitted.

[0069] To obtain a porous cured product, the composition may be cured. To cure the composition, for example, the composition may be applied to a substrate to obtain a composition layer, and energy (typically thermal energy) may be applied to the composition layer as necessary to cure the composition. If the composition is a room temperature curing type, it may be cured by maintaining the composition at room temperature, humidifying it as necessary.

[0070] When a thick film or a block (monolith) is to be produced, a method can be used in which the composition is poured into a mold and then cured in the mold. The composition poured into the mold may be maintained under reduced pressure to degas the composition.

[0071] In addition, when the composition contains a solvent, the method may further include a step of removing the solvent from the porous cured product or the composition. The method for removing the solvent from the composition is not particularly limited, but for example, a method of removing (evaporating) the solvent in conjunction with the curing of the composition can be mentioned.

[0072] The resulting cured product is a porous cured product having interconnected pores with a sharp pore size distribution due to the bulky shape of the filler.

[0073] This step may further include a step of removing the solvent and / or catalyst from the cured product. The method for removing the catalyst is not particularly limited, but may include a method of washing the cured product with an organic solvent, etc. In addition, the method for removing the solvent is not particularly limited, but may include a method of heating the porous fallout under reduced pressure as necessary.

[0074] ·Impregnation process The method for impregnating the porous cured material with silicone oil is not particularly limited, and can be spin coating, bar coating, dip coating, screen printing, flexographic printing, nozzle coating, etc. When silicone oil is applied to the surface of the porous cured material by these methods, the applied silicone oil permeates through the communicating pores, and a composite is obtained.

[0075] (Use of the complex) This composite has excellent liquid repellency and droplet removal performance even for fluids with a surface tension lower than that of water. Therefore, it can be used as a gas-liquid separation membrane that separates such fluids from gas. A separation device including the gas-liquid separation membrane can efficiently perform gas-liquid separation (e.g., degassing) even for fluids with low surface tension.

[0076] Furthermore, when the present composite is used as a roofing or wall material for a structure, the composite has excellent droplet removal performance, and therefore the roofing or wall material can have excellent stain resistance and self-cleaning properties.

[0077] Furthermore, the liquid repellency and droplet removal performance of this composite can be easily restored by re-impregnating it with silicone oil.In addition, since this composite has interconnected pores with a sharp pore size distribution, it can absorb silicone oil by itself using capillary force.

[0078] By utilizing this property, an antifouling system can be obtained that includes a reservoir for supplying silicone oil and the above composite. By using the above antifouling system in roofing and wall materials, metal materials and wall materials that have self-repairing properties in addition to antifouling and self-cleaning properties can be obtained.

[0079] (Anti-fouling system) FIG. 15 is a schematic diagram of a structure including an antifouling system according to an embodiment of the present invention. The structure 10 is a building having a roof 12 surrounded by walls 11 on all four sides, and the composite already described is disposed on the surface of the roof 12. In addition, a silicone oil reservoir 13 for supplying silicone oil is disposed at each base end of the roof 12. Silicone oil is contained within a silicone oil reservoir 13 and is maintained in contact with the base end of roof 12.

[0080] The antifouling system according to the embodiment of the present invention has a silicone oil reservoir 13. Silicone oil is absorbed into the composite as necessary. If a part or all of the silicone oil held in the composite is removed or leaked due to some cause, the silicone oil is sucked up by capillary action, and the composite is spontaneously restored.

[0081] The above utilizes the self-repairing property of the composite. It is presumed that the self-repairing property is related to and manifests due to a combination of factors, such as the matrix of the composite being a cured product of a curable silicone rubber component, the liquid impregnated being a silicone oil that has a high affinity with the cured product, and the composite having dense interconnecting pores formed by the bulky shape of the filler and the cure shrinkage of the curable silicone rubber component. In the examples in the latter part, the self-repairing property is demonstrated by various experiments.

[0082] In addition, although the structure 10 has the composite disposed on the surface of the roof 12, the structure according to the embodiment of the present invention is not limited to the above, and the composite may be disposed in another location. For example, the composite may be disposed on the surface of the wall 11, and a reservoir may further be disposed at the proximal end of the wall.

[0083] Furthermore, the above-mentioned anti-fouling system has self-cleaning properties due to the excellent droplet removal performance of the composite. Furthermore, even if some of the silicone oil is lost by wiping off a dirty part, the silicone oil is automatically replenished from the reservoir, so that the system is maintenance-free and maintains excellent anti-fouling properties and excellent self-cleaning properties. EXAMPLES

[0084] The present invention will be described in more detail below based on examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0085] [Example 1] 80 mL of ethanol, 20 g of tetrapod-shaped zinc oxide single crystals (product name "Pana-Tetra", model number: WZ-0501, manufactured by Panasonic Corporation) serving as a filler, and 20 g of a room-temperature curing type silicone rubber component (product name "DOWSIL", model number: HC 2100, manufactured by Toray Industries, Inc.) were mixed and stirred with a magnetic stirrer to obtain a dispersion liquid. Next, a substrate (soda-lime glass, manufactured by Muto Chemical Co., Ltd., size 26 mm × 76 mm, thickness 1.2 to 1.5 mm) was immersed twice in the above dispersion (immersion speed 50 mm / s, withdrawal speed 5 mm / s) to form a composition film on the substrate.

[0086] Next, the substrate having the above composition film was left to stand overnight at room temperature to evaporate the ethanol solvent and harden the curable silicone rubber component, thereby obtaining a laminate having a porous cured layer (344 μm) on the substrate.

[0087] Next, the laminate was immersed in silicone oils with different kinetic viscosities (25°C) (product names "KF-96-10cs" (10cSt), "KF-96-100cs" (100cSt), "KF-96-1000cs" (1000cSt)) for 12 hours, then pulled out and rotated at different shear rates to adjust the amount of silicone oil impregnated. After that, the laminate was left standing vertically for 12 hours to obtain a test piece.

[0088] In the above test conditions, after the silicone oil "KF-96-100cs" was soaked, 1 cm of the composite was measured without rotating. 2 2.85mg / cm of silicone oil 2 It was found that the material was impregnated with 1 cm 2 The content of hardening silicone rubber component per unit is 4.05mg / cm 2 It was.

[0089] Figure 1 shows the results of adjusting the silicone oil content by the rotation speed. The horizontal axis is the rotation speed (rpm), and the vertical axis on the right shows the silicone oil content per unit area of ​​the composite (mg / cm 2 ) and the left vertical axis is the value without rotation (2.85 mg / cm 2 The figure represents the silicone oil content (%) in the complex when the total mass of the complex is taken as 100 mass %.

[0090] Table 1 summarizes the results of Figure 1. [Table 1]

[0091] In Table 1, "Shear rate (rpm)" indicates the rotation speed, "Oil retention (%)" indicates the silicone oil content (mass%) in each composite when the silicone oil content in the composite of Example 1 is taken as 100 mass%, and "Area oil loading (mg / cm 2 )" refers to the silicone oil content per unit area of ​​the composite (mg / cm 2 ) and "oil / rubber ratio" refers to the mass ratio of silicone oil content to the content of curable silicone rubber component. Note that in each figure, "area oil loading" is sometimes called "areal oil loading," but both have the same meaning.

[0092] FIG. 2 is a graph showing the static contact angle (left vertical axis) and contact angle hysteresis (right vertical axis) of water at 25° C. for test pieces in which the content of silicone oils with different kinetic viscosities was adjusted to be approximately the same (2.80 to 2.90 mg). From the results in Figure 2, the kinetic viscosity of silicone oil is 1.0×10 1 mm 2 / s (cSt), the contact angle hysteresis was found to be smaller, which indicates better water droplet removal performance.

[0093] (Method for measuring static contact angle) A droplet was placed on the surface of the composite formed on the glass substrate, and the static contact angle was measured. The contact angle was measured by the 2θ method using a contact angle meter (Drop master-SA-Cs1, manufactured by Kyowa Interface Science Co., Ltd.).

[0094] (Method of measuring contact angle hysteresis) The advancing / receding contact angles were measured on the surface of the composite formed on a glass substrate by the spreading / retracting method using a sessile drop. The advancing and receding contact angles were measured by the tangent method using a contact angle meter (Drop master-SA-Cs1, manufactured by Kyowa Interface Science Co., Ltd.). The difference between the obtained advancing and receding contact angles is the contact angle hysteresis (CAH). The smaller the CAH, the lower the friction with which the droplet slides off.

[0095] The following experiments were carried out using test pieces containing the silicone oil "KF-96-100cs."

[0096] Fig. 3 is a graph showing the relationship between the silicone oil content in the composite and the static contact angle of water (25°C), and Fig. 4 is a graph showing the relationship between the silicone oil content in the composite and the contact angle hysteresis of water.

[0097] 3, there is a tendency that the static contact angle of water increases as the silicone oil content decreases, and in particular, the composites having an oil / rubber ratio of less than 0.64 had a larger contact angle with water compared to the composite of Example 5. Moreover, the composite of Example 7 having an oil / rubber ratio of less than 0.61 had an even larger contact angle with water compared to the composite of Example 6.

[0098] On the other hand, the results in Figure 4 show that as the silicone oil content increases, the water contact angle hysteresis tends to decrease. The composite of Example 1, which has an oil / rubber ratio of 0.61 or more, had a smaller contact angle hysteresis with water compared to the composite of Example 7. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.64 or more, had a smaller contact angle hysteresis with water than the composite of Example 6. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.65 or more, had a smaller contact angle hysteresis with water than the composite of Example 5. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.67 or more, had a smaller contact angle hysteresis with respect to water than the composite of Example 4. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.69 or more, had a smaller contact angle hysteresis with respect to water than the composite of Example 6.

[0099] Fig. 5 is a graph showing the relationship between the silicone oil content in the composite and the static contact angle (25°C) of propylene glycol, and Fig. 6 is a graph showing the relationship between the silicone oil content in the composite and the contact angle hysteresis of propylene glycol.

[0100] 5, the composite of Example 7, which had an oil / rubber ratio of less than 0.64, had a larger contact angle with propylene glycol than the composite of Example 5. Also, the composite of Example 7, which had an oil / rubber ratio of less than 0.61, had an even larger contact angle with water than the composite of Example 6.

[0101] On the other hand, the results in Figure 6 show that as the silicone oil content increases, the contact angle hysteresis of propylene glycol tends to decrease. The composite of Example 1, which has an oil / rubber ratio of 0.61 or more, had a smaller contact angle hysteresis with propylene glycol than the composite of Example 7. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.64 or more, had a smaller contact angle hysteresis with propylene glycol than the composite of Example 6. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.65 or more, had a smaller contact angle hysteresis with propylene glycol than the composite of Example 5. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.67 or more, had a smaller contact angle hysteresis with propylene glycol than the composite of Example 4. Furthermore, the composite of Example 1, which had an oil / rubber ratio of 0.69 or more, had a smaller contact angle hysteresis with propylene glycol than the composite of Example 6.

[0102] Figure 7 shows the relationship between the silicone oil content in the composite and the static contact angle of ethanol (25°C). Figure 8 shows the relationship between the silicone oil content in the composite and the contact angle hysteresis of ethanol. The silicone oil used in both cases is "KF-96-100cs."

[0103] The results in FIG. 7 show that all of the composites have excellent liquid repellency against ethanol, and the results in FIG. 8 show that the contact angle hysteresis is also small.

[0104] [Example 2] 300 mL of ethanol, 45 g of the filler, and 5 g of a room temperature curing silicone rubber component were mixed and stirred with a magnetic stirrer to obtain a dispersion liquid. Note that the materials used were the same as those used in Example 1.

[0105] Next, the above dispersion was dropped onto various substrates described below to form a composition layer on the substrate. After that, it was kept at room temperature overnight to cure the curable silicone rubber component. Next, the above cured product was immersed in silicone oil together with the substrate and left to stand overnight to obtain a composite.

[0106] The materials of the substrates used were stainless steel, aluminum, copper, glass, polypropylene, polyvinyl chloride, polyurethane, wood, cotton, and paper.

[0107] Figure 9 shows images of the composites formed on each substrate and the state of water droplets dropped on the composites. The results in Figure 9 show that composites can be formed regardless of the substrate, and that all of the composites have excellent water repellency.

[0108] [Example 3] Fig. 10 shows the state of the porous cured material produced on a 300mm x 300mm glass substrate by the same method as in Example 2, standing vertically, and holding the base end in a silicone oil reservoir filled with silicone oil, and the state of the silicone oil being absorbed into the porous cured material by capillary action over time. Also, Fig. 11 shows the curve showing the relationship between time and the height of silicone oil rise.

[0109] Figure 10 is composed of five images, with "t=0" representing the state immediately after the base end was placed in the silicone oil reservoir, "t=2days" representing the state two days later, "t=6days" representing the state six days later, "t=14days" representing the state 14 days later, and "t=28days" representing the state 28 days later.

[0110] After two days, about 1 / 4 of the base had turned dark gray in the image, indicating that silicone oil had seeped in. After six days, the color had changed to about half, after 14 days it was about 80%, and after 28 days it had completely seeped in silicone oil.

[0111] The details can be seen in Figure 11. The horizontal axis represents time, and the vertical axis represents the height of the upper end of the part permeated with silicone oil from the base end. FIG. 11 shows that the silicone oil permeates over time, eventually permeating the entire composite.

[0112] [Example 4] Next, the self-repairing property was examined when the silicone oil was removed from at least a part of the composite.

[0113] First, 45 g of tetrapod-shaped zinc oxide (same as in Example 1), 5 g of curable silicone rubber component (before curing, same as in Example 1), and 300 mL of ethyl acetate were mixed. A stirring device ("AS ONE" RS-6DN) was used for mixing. The stirred solution was dropped onto a glass substrate (soda-lime glass, 26 mm x 76 mm) and left at room temperature overnight to obtain a porous cured material.

[0114] The resulting porous cured product was then submerged in a container filled with silicone oil and left overnight at room temperature to obtain a composite. The composite was then stood vertically to remove excess silicone oil from the surface.

[0115] Figure 12 shows the results of investigating how the composite self-repairs after at least a portion of the silicone oil is lost by rotating the composite with the base end housed in a silicone oil reservoir, applying shear force, wiping the surface with a cloth, and showering with water. The conditions for rotation, wiping, and showering are as follows:

[0116] Spinning: Mount the slide on a spin coater and spin at 6000 rpm for 1 minute. Wiping: The surface of the complex was wiped with Kimwipe (trade name). Shower: Showered with water at a flow rate of 8L / min for 2 hours.

[0117] Figure 12 shows a total of nine images, 3 columns (vertical) x 3 rows (horizontal), all of which were images of the surface of the complex taken at the same magnification. The scale bar (250 μm) is attached to the image in the first column and first row (top left corner) from the left.

[0118] The three images lined up horizontally in the first row from the top show, from the left, the composite (before treatment), the state after the substrate was rotated and subjected to shear force, and the state after self-repair after being placed in a silicone oil reservoir for 12 hours.

[0119] In addition, the three images lined up horizontally in the second row from the top show, from the left, the composite (before treatment), the state after the composite surface was wiped with a cloth, and the state after self-repair after being placed in a silicone oil reservoir for three hours.

[0120] In addition, the three images lined up horizontally in the third row from the top show, from the left, the composite (before treatment), the state after the composite surface was exposed to a shower, and the state after self-repair after being placed in a silicone oil reservoir for three hours.

[0121] FIG. 13 is a graph showing the water sliding angle and the contact angle hysteresis for each of the test pieces before and after self-repair.

[0122] The results in Figure 13 show that, compared to the state before treatment (slippery state), when the silicone oil was removed (after lubricant loss) by applying shear force (shear), wiping, or showering (shower), both the water sliding angle and the water contact angle hysteresis increased, but after self recovery, both the water sliding angle and the water contact angle hysteresis had recovered (become smaller).

[0123] In other words, the above composite exhibits excellent droplet removal performance for fluids with a surface tension lower than that of water, even in an environment where the composite is exposed to water or where part of the silicone oil on the surface is wiped off.

[0124] (Method of measuring the sliding angle) A 2 μL droplet was placed on the surface of the composite, the substrate was gradually tilted, and the sliding angle at which the droplet started to slide down was measured using a contact angle meter (Drop master-SA-Cs1, manufactured by Kyowa Interface Science Co., Ltd.).

[0125] Figure 14 shows images showing the state of the complex after it was showered with 6 L of water per minute for 6 hours (t=0), with the base end housed watertight in a silicone oil reservoir, and then 2 days (t=2 days), 6 days (t=6 days), and 12 days (t=12 days).

[0126] Immediately after showering (t = 0), the color of the composite within the box labeled "SHPO base layer exposed" in the figure was different from the surrounding area, confirming that some or all of the silicone oil had been removed. It was confirmed that this area gradually narrowed after 2 days and after 6 days. The area where the silicone oil had been removed is the area that appears whiter in the center of the images taken at t=2 and t=6. Finally, after 12 days, the silicone oil had permeated the entire surface, restoring it to the condition it was in before the shower.

[0127] [Example 5] Using the same filler, curable silicone rubber component, and silicone oil (mass ratio of 1:1:0.7) as used in Example 1, one was prepared by producing a porous cured material in the same manner as in Example 1 and then impregnating it with silicone oil to produce composite 5-1, and the other was prepared in one pot by mixing the above components, i.e., curing the curable silicone rubber component in the presence of silicone oil, to produce composite 5-2.

[0128] 16 and 17 show the static contact angles and sliding angles of the prepared composites 5-1 and 5-2 with respect to water, propylene glycol, and ethanol.

[0129] 16 and 17, solid points are the results for composite 5-1, and hollow points are the results for composite 5-2. From the above results, the composite of Example 5-1 had smaller sliding angles for water and propylene glycol.

[0130] [Example 6] For the composite of Example 1, the sliding angles for various fluids were measured in the same manner as in Example 4. Figure 18 shows the results. The results in FIG. 18 show that the composite of Example 1 can cause droplets of fluids (ethanol, methanol, acetone, dimethylformamide, ethylene glycol, and glycerol) that have a surface tension of 22.5 mN or more at 20° C. and a surface tension lower than that of water to slide down at an inclination angle of 5° or less. On the other hand, the comparative example composite, which was prepared in the same manner as the composite of Example 1 except that it was not impregnated with silicone oil, did not slide off in the cases of ethanol, methanol, acetone, dimethylformamide, ethylene glycol, and glycerol shown in FIG. 18. [Explanation of symbols]

[0131] 10: Structure 11: Wall 12: Roof 13: Silicone oil reservoir

Claims

1. The present invention comprises a porous cured material obtained by curing a composition containing a curable silicone rubber component and a filler, and a silicone oil impregnated into the porous cured material, the content mass ratio of the silicone oil to the content of the curable silicone rubber component is 0.20 to 0.90; The filler has a three-dimensional shape having a core and needle-like portions extending from the core in four different axial directions, and has a surface tension lower than that of water.

2. 2. The composite for removing droplets having a surface tension lower than that of water according to claim 1, wherein the content mass ratio is 0.50 or more and 0.90 or less.

3. 3. The composite for removing droplets having a surface tension lower than that of water according to claim 1, wherein the content mass ratio is 0.61 or more and 0.65 or less.

4. 4. The composite for removing droplets having a surface tension lower than that of water according to claim 1, wherein the content mass ratio is 0.64 or more and 0.65 or less.

5. The composite for removing droplets having a surface tension lower than that of water according to any one of claims 1 to 4, wherein the content mass ratio of the filler to the total content of the curable silicone rubber component and the filler in the composition is 0.40 to 0.

99.

6. 6. The composite for removing droplets having a surface tension lower than that of water according to claim 1, wherein the curable silicone rubber component comprises an organopolysiloxane having a hydrolyzable group bonded to a silicon atom.

7. The kinetic viscosity of the silicone oil at 25° C. is 1.0×10 ０ ~1.0 x 10 ４ mm ２ 7. The composite for removing droplets having a surface tension lower than that of water according to claim 1, wherein the surface tension is 0.1-0.25 / s.

8. 8. The droplet removal composite having a surface tension lower than that of water according to claim 1, wherein the silicone oil contains dimethylpolysiloxane.

9. A method for producing a composite for removing droplets having a surface tension lower than that of water according to any one of claims 1 to 8, comprising the steps of: curing a composition containing the curable silicone rubber component and the filler to obtain a porous cured product; and impregnating the porous cured material with silicone oil.

10. 10. The method for producing a composite for removing droplets having a surface tension lower than that of water according to claim 9, wherein the content mass ratio of the silicone oil to the content of the curable silicone rubber component is 0.20 to 0.

90.

11. A method for producing a composite for removing droplets having a surface tension lower than that of water, as described in claim 9 or 10, wherein the mass content ratio is 0.61 or more and 0.65 or less.

12. The method for producing a droplet removal composite having a surface tension lower than that of water according to any one of claims 9 to 11, wherein the content mass ratio of the filler to the total content of the curable silicone rubber component and the filler is 0.40 to 0.

99.

13. A composite for removing droplets having a surface tension lower than that of water according to any one of claims 1 to 8; a reservoir for supplying the silicone oil to the droplet removal complex having a surface tension lower than that of water.

14. A structure equipped with an anti-fouling system as described in claim 13.

15. A gas-liquid separation membrane, comprising a droplet removal composite having a surface tension lower than that of water as described in any one of claims 1 to 8, as a membrane for separating a fluid and a gas.

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