Method for manufacturing a processed body with a water-repellent surface and processed body with a water-repellent surface

Abstract

Provided are: a method for manufacturing a machining body provided with a water-repellent surface; and a machining body provided with said water-repellent surface.　This method for manufacturing a machining body provided with a water-repellent surface, includes a step (a) for bringing a member formed from a crystalline or semi-crystalline polymer into contact with a solvent in a solvent contact region and a step (b) for taking out the member brought into contact with the solvent from the solvent contact region and drying the member. A difference of Hildebrand solubility parameter between the polymer and the solvent is less than 7.5 MPa1 / 2. The boiling point of the solvent is higher than the crystallization temperature (Tc) of the polymer. The temperature of the solvent when the member is brought into contact with the solvent is Tc±50°C of the polymer and is not more than the boiling point of the solvent, and the temperature at which the member is dried is lower than Tc of the polymer by at least 20°C.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a workpiece with a water-repellent surface and to a workpiece with a water-repellent surface. [Background technology]

[0002] The degree of wetting of an object surface by water is expressed as water repellency. For example, water repellency can be achieved by coating the surface with a hydrophobic fluorine compound or by providing the surface with micro- or nano-scale protrusions.

[0003] Lotus leaves have fine cilia on their surface, and this microstructure allows water droplets on the surface to form a spherical shape, thereby providing water repellency (the so-called "lotus effect").

[0004] When the surface of an object exhibits such water repellency, the surface of the object not only repels water but also becomes less susceptible to dirt.

[0005] The water repellency of an object surface can be explained based on static and dynamic water repellency. Static water repellency can be determined by the contact angle θ between a droplet of liquid resting on the surface of the object and the surface. The larger the contact angle, the less likely the object is to become wet, meaning the higher the water repellency. Generally, a contact angle of 90° or more is called "water repellency," and a contact angle of over 140° is called "ultra-water repellency."

[0006] Dynamic water repellency is defined by the "sliding angle," which is expressed by the angle of inclination when a droplet placed on the surface of an object slides down the inclined surface, and the contact angle hysteresis (CAH), which is expressed by the difference between the advancing angle (or advancing contact angle) and the receding angle (or receding contact angle) when the droplet slides down the inclined surface.

[0007] Contact angle hysteresis is thought to occur when the presence of microstructures on an object's surface causes the energy required for a droplet to move across the surface to become non-uniform, resulting in the creation of multiple metastable states. Therefore, contact angle hysteresis depends on the shape and size of the microstructures, and is also thought to be closely related to the behavior of the liquid as it spreads and wets the surface. The smaller the contact angle hysteresis, the higher the dynamic water repellency tends to be.

[0008] While the substrate itself may be water-repellent, there are also techniques to further improve the inherent water-repellency of the substrate. For example, there are methods for producing water-repellent surfaces based on microstructures, and more specifically, etching processes such as etching using lasers or plasma, chemical etching using treatment solutions, and surface structuring using templates are known. These processes can further improve the water-repellency of substrates.

[0009] For example, Non-Patent Document 1 describes a method for producing an ultrahydrophobic surface on a polypropylene surface. According to this method, a polypropylene specimen with a contact angle of 110° or less is first immersed in xylene at 135°C for a few seconds, forming a crystalline microstructure on the specimen surface. However, it also describes that the contact angle hysteresis CAH of the specimen surface after such treatment exceeds 30°. It then describes that a contact angle of more than 150° can be achieved by immersing the specimen in a mixture of a xylene solution of trimethoxypropylsilane (TMPSi) and TiO nanoparticles to coat it (especially Table 2). However, there is no description of the formation of a peelable surface layer on the specimen surface after treatment with xylene or a solution containing xylene.

[0010] Patent Document 1 also describes the production of an ultra-water-repellent surface by treating a thermoplastic resin with a solvent for about 1 minute to about 5 hours and then drying it at room temperature to form a hierarchical surface structure consisting of microscale and nanoscale structures.

[0011] Patent Document 1 specifically describes that treating polycarbonate with acetone results in the formation of a layer on the polycarbonate surface with a hierarchical structure consisting of a microscale spherulite structure and a nanoscale fibrous structure formed on the spherulite structure. The crystallinity of the polycarbonate surface depends on the treatment time with the solvent, and when acetone is used, it reaches a peak after about 30 minutes of treatment and remains almost unchanged thereafter (paragraph

[0016] , Figure 3).

[0012] Furthermore, it is stated that the polymer and solvent should be selected so that their solubilities are similar, and that crystallization and a hierarchical structure occur on the polymer surface when the polymer is immersed in the solvent and then the solvent is evaporated. However, in the case of the combination of polycarbonate and acetone, the difference in Hildebrand solubility parameters is 5.25 MPa. 1 / 2 Furthermore, Patent Document 1 does not disclose that a peelable surface layer is formed on the surface of the test specimen after treating the polycarbonate with acetone. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] US Patent Application Publication No. 2012 / 0142795 [Non-patent literature]

[0014] [Non-Patent Document 1] Gabriela Chagas, Thomaz C. Rangel, Marco A. Justino, Daniel E. Weibel, PREPARATION OF SUPERHYDROPHOBIC AND SUPEROLEOPHOBIC SURFACES AND THE EFFECT OF CHEMICAL HETEROGENEITY ON HYSTERESIS, The Eighth International Conference on Material Technologies and Modeling, MMT-2014 (ISBN: 978-965-91944-2-1), (July 28-August 1, 2014, Ariel, Israel) Summary of the Invention [Problem to be solved by the invention]

[0015] In view of the above circumstances, the present invention aims to provide a method for producing a water-repellent workpiece in a short time using a simple method, without using materials such as silicon compounds (e.g., trimethoxypropylsilane (TMPSi)) or titanium oxides (e.g., TiO nanoparticles) that have been known in the prior art to achieve water repellency, and to provide a workpiece with a water-repellent surface. [Means for solving the problem]

[0016] The present invention is configured as follows. [1] A method for producing a processed body having a water-repellent surface, comprising: (a) contacting a component made of a crystalline or semi-crystalline polymer with a solvent in a solvent contact area; (b) removing the member that has been contacted with the solvent from the solvent contact area and drying it; It has The difference in Hildebrand solubility parameters between the polymer and the solvent is 7.5 MPa 1 / 2 is less than the boiling point of the solvent is higher than the crystallization temperature (Tc) of the polymer; The temperature of the solvent when the member is brought into contact with the solvent is Tc of the polymer ± 50°C and is equal to or lower than the boiling point of the solvent; and The method for producing a processed body having a water-repellent surface, wherein the temperature at which the member is dried is at least 20° C. lower than the Tc of the polymer. [2] The method according to [1], wherein the polymer is selected from polyethylene (PE), polypropylene (PP), polyamide (PA), polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), syndiotactic polystyrene (SPS), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyacetal (POM), or a mixture, composite, nanocomposite, or blend of two or more of these polymers, and the polymer may be a homopolymer or a copolymer containing monomers different from those constituting the polymer. [3] The solvent may be n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, diethyl ether, cyclohexane, xylene, decalin, ethyl acetate, butyl acetate, benzene, methyl ethyl ketone, acetone, pyridine, diethylamine, butyl isobutyrate, n-butyl butyrate, butyl chloride, isobutyl ether, isobutyl formate, isodecyl acrylate, diacetone alcohol, methyl ether, tetralin, o-dichlorobenzene, acetonitrile, acrylic acid, benzyl alcohol, 1,4-butanediol, 2,3-butylene carbonate, butyrolactone, chloroacetone, methyl ether ... The method according to [1] or [2], wherein the solvent is selected from acetonitrile, diethylene glycol, diethylsulfone, ethylacetamide, ethylenediamine, formic acid, phenylhydrazine, tolylene diisocyanate, acetic acid, dimethyl sulfoxide (DMSO), nitrobenzene, phenol, o-chlorophenol, 1,1,1,3,3,3-hexafluoro-2-propanol, o-cresol, toluene, chlorobenzene, 1,2-dichlorobenzene, chloroform, 1,4-dioxane, tetrahydrofuran, N,N-dimethylformamide (DMF), a mixture of two or more of these solvents, or a mixture of these solvents with another solvent. [4] The method according to any one of [1] to [3], wherein the solvent is in a liquid phase or a gas phase. [5] The method according to any one of [1] to [4], wherein the time for contacting the component with the solvent in step (a) is at least 30 seconds. [6] The method according to any one of [1] to [5], wherein the temperature of the solvent in the solvent contact area is 90 to 160°C. [7] The method according to any one of [1] to [6], wherein the member is preheated before step (a). [8] The method according to any one of [1] to [7], wherein the drying in step (b) is carried out in multiple steps using the same or different drying means at the same or different temperatures. [9] The method according to any one of [1] to [8], wherein one or more additives selected from the group consisting of flame retardants, antioxidants, ultraviolet absorbers, stabilizers, fillers, antistatic agents, lubricants, dispersants, reinforcing agents, colorants, conductive fillers, and thermally conductive fillers are added to the polymer.

[10] The method according to any one of [1] to [9], wherein the member has a flat film, sheet or plate shape, a film, sheet or plate shape with a folded portion, or a three-dimensional shape.

[11] The method according to any one of [1] to

[10] , wherein a skin layer formed on the surface of the member is peeled off.

[12] A processed body having at least one water-repellent surface obtained by the method according to any one of [1] to

[11] .

[13] A skin layer having a water-repellent surface obtained by the method described in

[11] .

[14] A processed body comprising a crystalline or semi-crystalline polymer substrate and a crystal structure layer, wherein the crystal structure layer is composed of spherulites having an average particle size of 300 nm to 70 μm and nanostructures having an average particle size of 60 nm to 1500 nm present on the surface of the polymer substrate, and the average particle size of the nanostructures is less than the average particle size of the spherulites.

[15] The processed body according to

[14] , wherein the nanostructure is present on the surface of the spherulite.

[16] The processed body according to

[14] or

[15] , wherein the polymer substrate is a thermoplastic resin.

[17] The processed body according to any one of

[14] to

[16] , wherein the polymer substrate is a crystalline plastic.

[18] The processed body according to any one of

[14] to

[17] , wherein the polymer substrate is polypropylene (PP).

[19] The processed body according to any one of

[14] to

[18] , wherein the composition of the polymer substrate and the composition of the crystal structure layer are the same. [Effects of the Invention]

[0017] As described above, according to the method of the present invention, in producing a processed body with a water-repellent surface, it is not necessary to provide a coating with a water-repellent material different from the material constituting the processed body, such as through fluorine treatment or silane treatment. Furthermore, in producing a fine surface structure that imparts water repellency, it is not necessary to use expensive equipment and complicated processes such as etching using a laser or plasma, or to add titanium oxides such as TiO nanoparticles. Instead, a processed body with a water-repellent surface can be produced in a short time by a simple and inexpensive method of simply treating it with a solvent.

[0018] According to the present invention, the processed body obtained through steps (a) and (b) has a skin layer formed on the surface of a solvent-treated crystalline or semi-crystalline substrate, such as a crystalline or semi-crystalline polymer substrate. At the interface between the skin layer and the processed body, spherulitic structures are formed on both the surface of the processed body adjacent to the skin layer and the surface of the skin layer adjacent to the processed body, and both spherulitic structures are water-repellent. Furthermore, this spherulitic structure is a hierarchical (double-layered) crystalline structure layer in which nanocrystals or nanostructures (primary structures) with an average particle size of 60 nm to 1500 nm, preferably 150 nm to 1400 nm, are provided on the surface of spherulites (secondary structures) with an average particle size of 300 nm to 70 μm, preferably 20 μm to 70 μm. The size of the nanocrystals (average particle size) does not exceed the size of the spherulites (average particle size). The average particle sizes of the spherulites and nanocrystals are determined from scanning electron microscope (SEM) images.

[0019] This skin layer can be peeled off from the processed body immediately after steps (a) and (b), but it can also be easily peeled off after a certain period of time has passed since the production of the processed body. Therefore, in order to protect the water-repellent surface formed on the surface of the processed body, it is also possible to leave the skin layer attached to the processed body until just before the processed body is used.

[0020] On the other hand, the skin layer peeled off from the processed body also has a water-repellent surface like the processed body, and therefore can be used for the same purpose as the processed body or for a different purpose than the processed body. [Brief explanation of the drawings]

[0021] [Figure 1] 1A and 1B are diagrams illustrating one embodiment of a method for producing a workpiece with a water-repellent surface according to the present invention and the formation of a workpiece with a water-repellent surface and a skin layer according to the present invention. [Figure 2] 1A and 1B are electron microscope photographs of a processed body produced according to the present invention and the water-repellent surface (hierarchical structure) of the skin layer. DETAILED DESCRIPTION OF THE INVENTION

[0022] A method for producing a processed body having a water-repellent surface according to an embodiment of the present invention will be described in detail below.

[0023] A method for producing a processed body having a water-repellent surface includes the steps of: (a) contacting a member (polymer substrate) made of a crystalline or semi-crystalline polymer with a solvent in a solvent contact area; and (b) removing the member that has been contacted with the solvent from the solvent contact area and then drying the member. In step (a), the difference in Hildebrand solubility parameter between the polymer and the solvent is 7.5 MPa. 1 / 2 From the viewpoint of forming a surface with good water repellency, the pressure is preferably less than 7.2 MPa. 1 / 2 less than 5.25 MPa, more preferably 1 / 2 less than 5 MPa, more preferably 1 / 2 The boiling point of the solvent is higher than the crystallization temperature (Tc) of the polymer. The temperature of the solvent when the member is brought into contact with the solvent is within the Tc of the polymer ±50°C and is equal to or lower than the boiling point of the solvent. When the polymer substrate contains 80% or more polymers composed only of carbon and hydrogen or polymers composed only of carbon, hydrogen, and oxygen, it is preferable from the viewpoint of forming a good water-repellent surface that the temperature of the solvent when the member is brought into contact with the solvent is higher than the Tc of the polymer but is equal to or lower than the boiling point of the solvent. Furthermore, in step (b), the temperature at which the member is dried is at least 20°C lower than the Tc of the polymer.

[0024] [polymer] The members used in the present invention are composed of crystalline or semi-crystalline polymers, preferably crystalline polymers. Examples of such polymers include polyethylene (PE), polypropylene (PP), polyamide (PA), polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), syndiotactic polystyrene (SPS), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), and polyacetal (POM). Mixtures, composites, nanocomposites, or blends of two or more of the above polymers can also be used. From the standpoint of processability, the polymer is preferably a thermoplastic resin.

[0025] The polymer may be a homopolymer or a copolymer. Examples of polypropylene homopolymers or copolymers include TIPPLEN (R) Examples of polyethylene that can be used include H681F, H649FH, H145F, H880, K793, K597, K199, K395A, K948, R660, R359, and R959A. The polyethylene may be high-density polyethylene (HDPE) or low-density polyethylene (LDPE). High-density polyethylene is sometimes called medium-low pressure polyethylene based on its manufacturing method, and typically refers to polyethylene with a specific gravity of approximately 0.94 or higher. Low-density polyethylene is sometimes called high-pressure polyethylene based on its manufacturing method, and typically refers to polyethylene with a specific gravity of approximately 0.91 to 0.93.

[0026] As the polymer constituting the member according to the present invention, polypropylene, polyethylene, polylactic acid, and particularly polypropylene are preferably used because the final product has high water repellency.

[0027] The polymer used according to the present invention may also contain additives commonly used in the plastics field, such as flame retardants, antioxidants, UV absorbers, stabilizers, fillers, antistatic agents, lubricants, dispersants, reinforcing agents, colorants, thermally conductive fillers, and / or electrically conductive fillers. The additives listed above are merely examples, and other additives may be added to the polymer instead of or in addition to these additives.

[0028] [solvent] The solvent used to treat the member in step (a) according to the present invention has a solubility parameter (Hildebrand solubility parameter, hereinafter referred to as SP value) of the solvent and the SP value of the polymer constituting the member of 7.5 MPa or less. 1 / 2 Less than 7.2 MPa, preferably 1 / 2 less than 5.25 MPa, more preferably 1 / 2 less than 5 MPa, more preferably 1 / 2There are no particular limitations as long as the solvent satisfies the two requirements that the boiling point of the solvent is lower than the crystallization temperature (Tc) of the polymer, and that the boiling point of the solvent is higher than the crystallization temperature (Tc) of the polymer. Examples of the solvent include n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, diethyl ether, cyclohexane, xylene, decalin, ethyl acetate, butyl acetate, benzene, methyl ethyl ketone, acetone, pyridine, diethylamine, butyl isobutyrate, n-butyl butyrate, butyl chloride, isobutyl ether, isobutyl formate, isodecyl acrylate, diacetone alcohol, methyl ether, tetralin, o-dichlorobenzene, acetonitrile, acrylic acid, benzyl alcohol, 1,4-butanediol, 2,3-butylene carbonate, butyrolactone, chloroform ... Solvents that can be used include acetonitrile, diethylene glycol, diethyl sulfone, ethylacetamide, ethylenediamine, formic acid, phenylhydrazine, tolylene diisocyanate, acetic acid, dimethyl sulfoxide (DMSO), nitrobenzene, phenol, o-chlorophenol, 1,1,1,3,3,3-hexafluoro-2-propanol, o-cresol, toluene, chlorobenzene, 1,2-dichlorobenzene, chloroform, 1,4-dioxane, tetrahydrofuran, N,N-dimethylformamide (DMF), or a mixture of two or more of these solvents or a mixture of these solvents with other solvents. Among these, xylene, decalin, butyl acetate, and DMSO are preferred from the viewpoint of forming a good skin layer. Even when using a mixture of two or more of these solvents or a mixture of these solvents with other solvents, the difference in SP value between the solvent mixture and the SP value of the polymer constituting the member must be 7.5 MPa or less according to the "rule of mixtures." 1 / 2 Less than 7.2 MPa, preferably 1 / 2 less than 5.25 MPa, more preferably 1 / 2 less than 5 MPa, more preferably 1 / 2 It should be noted that the .DELTA..times ...

[0029] The SP value can be determined based on information in existing databases (see, for example, http: / / polymerdatabase.com / polymer%20physics / delta%20Table.html), or can be estimated from UV measurements of the solution, swelling index, cloud point, theoretical calculations, etc. (unit: MPa 1 / 2 ).

[0030] The SP value is a numerical estimate of the interaction of multiple substances and is a measure of the solubility of non-polar substances, such as many polymers.

[0031] From the viewpoint of further reducing the difference in SP value, when polypropylene is used as the polymer, preferred solvents are, for example, xylene, decalin, and butyl acetate. When polyethylene is used as the polymer, preferred solvents are, for example, decalin. When PVDF is used as the polymer, preferred solvents are, for example, DMSO.

[0032] The temperature of the solvent when contacting the solvent with the member is Tc of the polymer ±50°C and is equal to or lower than the boiling point of the solvent. In particular, for a resin in which the proportion of polymers composed only of carbon and hydrogen (or only carbon, hydrogen, and oxygen) among the polymer components of the resin is 80% or more, it is more preferable that the temperature of the solvent is higher than the Tc of the polymer but equal to or lower than the boiling point of the solvent. The solvent may be in either a liquid or gas phase when contacting the solvent with the member. The temperature of the solvent when contacting the member is preferably 90 to 160°C, and more preferably 110 to 150°C from the viewpoint of forming a highly releasable skin layer and a highly water-repellent surface.

[0033] [Process (a)] In step (a), the contact time between the member and the solvent in the solvent contact area is not particularly limited, but is preferably at least 30 seconds from the viewpoint of obtaining a good water-repellent surface and forming a continuous, peelable skin layer. The contact time between the member and the solvent depends on the type of polymer used, the type of solvent, and the temperature at which the member and the solvent are contacted, but is usually about 30 seconds to 10 minutes, taking into consideration the process efficiency and the formation of a layer with good water repellency.

[0034] From the viewpoint of process efficiency, it is preferable to preheat the member prior to step (a). The preheating temperature is not particularly limited, but from the viewpoint of contact between the member and the solvent in the solvent contact region, it is preferable that the preheating temperature be equal to or lower than the temperature at which the member and the solvent are brought into contact.

[0035] [Step (b)] Following step (a), the treated component is removed from the solvent contact area where the component is brought into contact with the solvent and dried. The temperature at which the treated component is dried is at least 20°C lower than the Tc of the polymer constituting the component, preferably at least 30°C lower than the Tc of the polymer constituting the component. The component can also be dried at ambient temperature or room temperature. From the viewpoint of controlling the formation of a skin layer, the drying in step (b) is preferably carried out in multiple steps using the same or different drying means at the same or different temperatures. There are no particular limitations on the number of steps, the drying means used, or the drying temperature, but it is preferred that the temperature of one or more drying steps preceding the final drying step does not exceed the temperature of the final drying step.

[0036] FIG. 1 shows a series of steps in which a sheet- or web-like member 1 is brought into contact with a solvent 3 in a solvent tank 2 (solvent contact area), the member 1 is removed from the solvent tank 2, and then subjected to drying means 4. Next, a skin layer 5 formed on the surface of the member 1 is peeled off, resulting in a processed body 6 with an ultra-water-repellent surface.

[0037] Figure 1 further shows, corresponding to the above steps, a cross section 1-1 of the member 1 before contact with the solvent, a cross section 1-2 of the member 1 on which a swollen gel layer 7 has been formed on the surface due to contact with the solvent 3 in the solvent tank 2 (solvent contact area), cross sections 1-3 and 1-4 of the member 1 after removal from the solvent tank 2 on which a skin layer 5 has been formed, and a cross section 1-5 when the skin layer 5 has been peeled off after drying to obtain the processed body 6.

[0038] The method of the present invention can be carried out in a batch mode instead of in a continuous mode as shown in Fig. 1. The method to be adopted is optional and depends on, for example, the shape of the manufacturing equipment and the components. The shape of the components is also optional and is not particularly limited as long as they can be treated by the method of the present invention.

[0039] While FIG. 1 shows a flat member, the member may have a flat shape such as a sheet, film, web, or board (also called a board or plate, generally 1 mm or more thick), or may have a three-dimensional shape (such as a shampoo bottle). The member may also be made of a flexible material that can be rolled up. According to the JIS (Japanese Industrial Standards), a film is a plastic membrane with a thickness of less than 250 μm, and a sheet is a thin plastic plate with a thickness of 250 μm or more.

[0040] [Processed body and skin layer with water-repellent surface] The method according to the present invention allows for the rapid and easy production of polymer processed products with water-repellent surfaces. Unlike conventional methods, there is no need to add a water-repellent material different from the substrate or a material for forming a water-repellent structure, such as titanium oxide nanoparticles. A polymer processed product with a water-repellent surface can be produced by drying the component in step (b), and a layer or film (skin layer) that can be peeled off from the component is formed on the component surface that came into contact with the solvent in step (a). At the interface between the skin layer and the processed product, both the surface of the processed product in contact with the skin layer and the surface of the skin layer in contact with the surface of the processed product are water-repellent. The term "skin layer" as used herein refers to a film-like, sheet-like, or web-like processed product having a two-dimensional or three-dimensional shape.

[0041] The skin layer can be left unpeeled until just before use of the processed body, for example, to protect the water-repellent surface formed on the surface of the processed body. Furthermore, the skin layer peeled off from the processed body also has a water-repellent surface similar to the processed body, and can therefore be used as a water-repellent sheet, etc. The thickness of the skin layer depends on the type of polymer and solvent used, the temperature and time when the polymer member is brought into contact with the solvent, and the time for drying the polymer member, but is typically about 10 to 200 μm. To improve light transmittance and use as a translucent member, a thickness of about 10 to 100 μm is more preferred.

[0042] The processed body produced by the method of the present invention comprises a crystalline or semi-crystalline polymer substrate and a crystal structure layer, and the crystal structure layer is composed of spherulites with an average particle size of 300 nm to 70 μm, preferably 20 μm to 70 μm, present on the surface of the polymer substrate, and nanostructures with an average particle size of 60 nm to 1500 nm, preferably 150 nm to 1400 nm. In this case, the average particle size of the nanostructures does not exceed the average particle size of the spherulites. In other words, the average particle size of the nanostructures is less than the average particle size of the spherulites. The nanostructures are preferably present on the surface of the spherulites, and the average particle size of the nanostructures present on the surface of the spherulites is less than the average particle size of the spherulites.

[0043] Therefore, according to the present invention, the composition of the polymer substrate of the processed body and the composition of the crystalline structure layer are the same.

[0044] FIG. 2 shows electron microscope photographs of the hierarchical structure of the surface of the processed body (photograph a showing the microstructure and photograph b showing the nanostructure) and the surface of the skin layer (photographs c and d showing the microstructure) obtained by the method of the present invention. These figures clearly show that a hierarchical crystalline structure consisting of spherulite-like structures (a, c, and d) as secondary structures and a nanocrystalline structure (b) as primary structure is formed on the surfaces of the processed body and the skin layer. The particle diameters of these spherulites and crystals were obtained by focusing on the outermost surfaces of these structures using an SEM, identifying at least 20 structures on the outermost surface whose diameters could be measured, and measuring the diameters of these structures using ImageJ (image processing software). The average particle diameter is the average value obtained by averaging the diameters of at least 20 structures obtained from ImageJ. The average particle diameters of the spherulites and nanostructures shown in photos a to d obtained by this method are as follows: a:21.1μm b: 48.9 μm c: 25.6 μm d:213nm [Example]

[0045] Hereinafter, the production of a processed body having a water-repellent surface according to the present invention will be described based on examples, but the present invention is not limited to the embodiments according to these examples.

[0046] [Example 1] Polypropylene homopolymer (TIPPLEN H681F, crystallization temperature Tc: 109°C, melting temperature Tm: 167°C, SP value: 16.2 MPa) 1 / 2 The sheet was placed in a solvent contact area in decalin (boiling point: 187°C, SP value: 18.00 MPa) at 150°C. 1 / 2) for a predetermined time (step (a)). Thereafter, the polypropylene sheet was removed from the solvent contact area and dried at room temperature (step (b)).

[0047] [Examples 2 to 9] The same procedure as in Example 1 was carried out using the polymers and solvents listed in Table 1 and at the processing and drying temperatures as listed in Table 1.

[0048] [Comparative Example 1] The polymer used was polypropylene homopolymer, and the solvent used was dimethyl sulfoxide (DMSO). The difference in SP value between the polymer and the solvent was 8 MPa. 1 / 2 It was super.

[0049] Comparative Example 2 Polypropylene homopolymer was used as the polymer, and acetone was used as the solvent. The temperature of the solvent in step (a) was 56°C, which is lower than the crystallization temperature of polypropylene, 109°C.

[0050] Comparative Example 3 The polymer used was polypropylene homopolymer, and the solvent used was decalin. The temperature of the solvent in step (a) was 130°C, and the drying temperature in step (b) was 100°C.

[0051] [result] The polymers used in these examples and comparative examples, their crystallization temperatures Tc, melting temperatures Tm, SP values ​​(Hildebrand solubility), and the types of solvents, their boiling points, SP values, and process conditions, as well as the structure of the crystalline structure layer on the substrate surface after treatment or on the obtained processed body and the results of water repellency, are summarized in the following Table 1. The SP values ​​of the solvents and polymers listed in Table 1 are literature values, and the crystallization temperatures Tc and melting temperatures Tm are values ​​determined by differential scanning calorimetry (DSC), respectively.

[0052] [Table 1]

[0053] The evaluation of "water repellency" in the "Results" column of Table 1 is as follows: ◎ An extremely good water-repellent surface was obtained (static water-repellent contact angle of 155° or more and dynamic water-repellent CAH of 5 or less). A good water-repellent surface (static water-repellent contact angle of 150° or more and dynamic water-repellent CAH of 5 or less) was obtained. A water-repellent surface (static water-repellent with a contact angle of 140° or more and less than 150°, or dynamic water-repellent with a CAH of more than 5 and 10 or less) was obtained. × Poor water-repellent surface (static water-repellent contact angle less than 140° and dynamic water-repellent CAH 10 or more).

[0054] CAH is the contact angle hysteresis ( C Contact A ngle H CAH represents the contact angle when the wetting spreads (expands), and is the value obtained by subtracting the receding angle from the advancing angle. The advancing angle is the contact angle when the wetting spreads (expands), and is also written as the (dynamic) advancing angle θα. The receding angle is the contact angle when the wetting contracts, and is also written as the (dynamic) receding angle θγ. A small CAH value is an indicator of good water repellency. The advancing angle and receding angle were measured using the sessile drop method, where θ is the angle formed between the solid surface and the droplet when the droplet is brought into contact with the solid surface and when the droplet is removed, as follows: 20 μL of deionized water is dropped onto or removed from the treated surface of the sample (workpiece), and the contact angle θ is measured. The contact angle θ is obtained by recording the shape of the droplet that has landed on the sample surface with a high-resolution CCD camera and measuring its angle using ImageJ software. The measurement is performed at room temperature (25°C). This measurement is performed at least five times, and the average value is used.

[0055] As shown in Table 1, in Examples 1 to 9 of the present invention, processed bodies having a peelable skin layer and a sufficiently water-repellent surface were obtained. Furthermore, in Examples 1 to 5 and 7, the skin layers were more stable than those in the other Examples.

[0056] On the other hand, the difference in SP value between the polymer and the solvent is 7.5 MPa. 1 / 2 In Comparative Example 1, where the temperature was greater than 100°C, a surface with good water repellency was not obtained, even though the other requirements of the present invention were met. In Comparative Example 2, the difference between the solvent temperature and the crystallization temperature of the polymer in step (a) was 50°C. In this Comparative Example, although the requirements of the present invention were met except for the solvent temperature, a peelable skin layer was not formed, and a sufficiently water-repellent surface was not obtained. In Comparative Example 3, the drying temperature of the member in step (b) was 100°C, which is 9°C lower than the crystallization temperature of polypropylene, 109°C. In this case, a peelable skin layer was not formed, and a sufficiently water-repellent surface was not obtained. [Industrial Applicability]

[0057] The processed body and skin layer having a water-repellent surface obtained by the novel manufacturing method of the present invention can be used, for example, in the fields of medicine and nursing care, as a water-repellent sheet for medical or nursing care sheets or surgical gowns, or as a water-repellent sheet or cover for antennas to prevent radio wave attenuation due to rain or snow.

[0058] Furthermore, by taking advantage of the water repellency of the surface, or by taking advantage of the property that dirt contained in water droplets does not adhere to the water repellent surface, or that dirt that adheres to the surface flows off together with the water droplets, the material can be used on, for example, the exterior walls of buildings, bathtubs and toilets, toilet bowls, floors, walls, ceilings, kitchen counters and sinks, furniture, home appliances, etc., to exhibit antifouling effects or self-cleaning effects.

[0059] By using the present invention as a surface material for vehicles, aircraft, and ships, fluid resistance can be reduced, improving fuel efficiency and reducing CO2 emissions.

[0060] Furthermore, the processed body and skin layer of the present invention have a microstructure or micro-irregular structure on their water-repellent surface that also has high reflectivity and scattering properties, and therefore, when used in, for example, optical components or lighting equipment, they can exhibit functions such as water repellency, anti-fouling, and reflection and scattering. [Explanation of symbols]

[0061] 1. Components 2 Solvent bath (solvent contact area) 3. Solvent 4 Drying means 5 Skin Layer 6 Processed body 7 Gel layer 1-1 Cross section of component 1 before contact with solvent 1-2 Cross section of a member on which a swollen gel layer 7 is formed 1-3 Cross section of member 1 during drying 1-4 Cross section of component 1 with skin layer 5 after drying 1-5 Cross section when the skin layer 5 is peeled off to obtain the processed body 6 a Electron micrograph of the microstructure formed in the skin layer b Electron micrograph of the nanostructure formed in the skin layer c Electron microscope image of the microstructure formed on the processed body. d Electron microscope image of the microstructure formed on the processed body

Claims

1. A method for producing a workpiece having a water-repellent surface, comprising the steps of: (a) contacting a component made of a crystalline or semi-crystalline polymer with a solvent at a solvent contact area; (b) removing the member that has been contacted with the solvent from the solvent contact area and drying it; It has The difference in Hildebrand solubility parameters between the polymer and the solvent is 7.5 MPa. １／２ is less than The temperature of the solvent when the member is brought into contact with the solvent is 125° C. or higher and is equal to or lower than the boiling point of the solvent; and The method for manufacturing a processed body having a water-repellent surface, wherein the temperature at which the member is dried is at least 20° C. lower than the Tc of the polymer.

2. 2. The method of claim 1, wherein the polymer is selected from polyethylene (PE), polypropylene (PP), polyamide (PA), polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), syndiotactic polystyrene (SPS), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyacetal (POM), or a mixture, composite, nanocomposite, or blend of two or more of these polymers, and the polymer may be a homopolymer or a copolymer comprising monomers different from those constituting the polymer.

3. The solvent may be n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, diethyl ether, cyclohexane, xylene, decalin, ethyl acetate, butyl acetate, benzene, methyl ethyl ketone, acetone, pyridine, diethylamine, butyl isobutyrate, n-butyl butyrate, butyl chloride, isobutyl ether, isobutyl formate, isodecyl acrylate, diacetone alcohol, methyl ether, tetralin, o-dichlorobenzene, acetonitrile, acrylic acid, benzyl alcohol, 1,4-butanediol, 2,3-butylene carbonate, butyrolactone, chloroacetone, methyl ether ...

3. The method according to claim 1, wherein the solvent is selected from the group consisting of toluene, ...

4. 4. The method of claim 1, wherein the solvent is in the liquid or gas phase.

5. 5. The method according to claim 1, wherein the time for contacting the member with the solvent in step (a) is at least 30 seconds.

6. 6. The method of any one of claims 1 to 5, wherein the temperature of the solvent in the solvent contact area is in the range of 90 to 160°C.

7. 7. The method of claim 1, wherein the member is preheated prior to step (a).

8. 8. The method according to claim 1, wherein the drying in step (b) is carried out in multiple steps using the same or different drying means at the same or different temperatures.

9. 9. The method of claim 1, wherein the polymer further comprises one or more additives selected from the group consisting of flame retardants, antioxidants, ultraviolet absorbers, stabilizers, fillers, antistatic agents, lubricants, dispersants, reinforcing agents, colorants, electrically conductive fillers, and thermally conductive fillers.

10. The method according to any one of claims 1 to 9, wherein the member has a flat film, sheet or plate shape, a film, sheet or plate shape having a folded portion, or a three-dimensional shape.

11. The method according to claim 1 , further comprising peeling off a skin layer formed on the surface of the member.

12. 12. A processed body having at least one water-repellent surface, obtained by the method according to any one of claims 1 to 11.

13. A skin layer having a water-repellent surface obtained by the method according to claim 11.

14. A processed body comprising a crystalline or semi-crystalline polymer substrate and a crystal structure layer, wherein the crystal structure layer is composed of spherulites having an average particle size of 20 μm to 70 μm and nanostructures having an average particle size of 60 nm to 1500 nm, which are present on the surface of the polymer substrate, and the average particle size of the nanostructures is less than the average particle size of the spherulites.

15. The workpiece of claim 14 , wherein the nanostructures are present on surfaces of the spherulites.

16. The processed body according to claim 14 or 15, wherein the polymer substrate is a thermoplastic resin.

17. 17. The workpiece according to any one of claims 14 to 16, wherein the polymer substrate is a crystalline plastic.

18. 18. The workpiece according to any one of claims 14 to 17, wherein the polymer substrate is polypropylene (PP).

19. 19. The processed body according to claim 14, wherein the composition of the polymer substrate and the composition of the crystalline structure layer are the same.

Images