Polyvinyl alcohol structure prepared using heterogeneous saponification induced by external stimulus, and preparation method therefor

Abstract

The present invention relates to a polyvinyl alcohol structure prepared using heterogeneous saponification induced by an external stimulus, and a preparation method therefor, and, more specifically, to a method for preparing a polyvinyl alcohol structure by using heterogeneous saponification, in which an external stimulus, such as acoustic pressure, is directly or indirectly applied, under tension, to a PVA precursor structure so as to be converted into a PVA structure. Compared to a conventional method, vibration caused by the acoustic pressure increases saponification speed by saponification promotion and smooth circulation, forms nano-sized curves on the surface of the PVA structure resulting from conversion by the reaction, so as to improve specific surface area, thereby increasing water resistance, and can adjust the degree of saponification according to the characteristics of the application field.

Description

Polyvinyl alcohol structure produced by heterogeneous saponification reaction caused by external stimulation and method for producing the same

[0001] The present invention relates to a polyvinyl alcohol structure produced by a heterogeneous saponification reaction and a method for producing the same, and more specifically, to a polyvinyl alcohol structure produced by a heterogeneous saponification reaction caused by an external stimulus under tension and a method for producing the same.

[0002]

[0003] Chemical vapor deposition (CVD) is a deposition method typically used to manufacture high-quality, high-performance solid materials under vacuum. It is a technique frequently used in the semiconductor industry to produce thin films, and it is applied to synthesize polymers and fabricate structures such as films and nanoparticles through gas-phase polymerization.

[0004] Gas-phase polymerization refers to a synthesis process in which gaseous monomers of organic and organometallic compounds are activated and bonded upon contact with reaction catalysts or oxidizing agents, thereby undergoing polymerization. It follows a mechanism in which gaseous monomers are activated and grow into polymers through a self-assembly process, characterized by the fact that it does not require solvents or complex purification processes. In this regard, Korean Registered Patent Publication No. 10-2605269 discloses a method for producing olefinic polymers with excellent physical properties by improving upon the problems that occur during conventional gas-phase polymerization, thereby maintaining high catalytic activity, and preventing polymer aggregation caused by localized over-reaction. Furthermore, recently, gas-phase reactions are being applied in various ways, such as surface modification of structures in the vapor phase, in addition to polymerization. Reactions carried out in the gas phase have the significant advantage of being able to proceed using only a minimal amount of reaction medium.

[0005] Generally, Poly(vinyl alcohol) (PVA) cannot be synthesized by direct polymerization of monomers due to enol-keto tautomerism of vinyl alcohol monomers. Instead, it can be obtained by first synthesizing a Poly(vinyl ester) polymer by polymerizing vinyl ester monomers such as vinyl acetate or vinyl pivalate, and then dissolving the polymer in a solvent and carrying out a homogeneous saponification reaction under a catalyst (strong acid or strong alkali).

[0006] Polyvinyl alcohol (PVA), a hydrophilic polymer, has relatively low viscosity compared to other polymers, is non-toxic, and possesses excellent mechanical properties; when applied as structures such as fibers or films, it exhibits high tensile strength, tensile modulus, wear resistance, alkali resistance, oxygen barrier properties, and biocompatibility.

[0007] However, in order to maintain the excellent physical properties of PVA, not only the degree of saponification and molecular weight but also the stereoregularity must be large. As these characteristics increase, hydrophilicity becomes stronger, and due to strong hydrogen bonding of the OH group, the number and size of polymer crystals are limited during structure formation, which has limitations in improving mechanical properties.

[0008] In order to improve these problems and enhance physical properties, the inventors have successfully manufactured PVA using PVAc in the form of particles, films, fibers, and nano nonwoven fabrics by a heterogeneous saponification method in which a structure is first prepared from a precursor, and then the structure is immersed in the saponification solution without being dissolved in the saponification solution to carry out a saponification reaction from the surface to the interior of the precursor structure in a heterogeneous phase. (Korean Registered Patent Publication No. 10-1577911 [Film], Korean Registered Patent Publication No. 10-1577911 [Nano Nonwoven Fabric], Korean Registered Patent Publication No. 10-1577911 [Particle], Korean Registered Patent Publication No. 10-1861038 [Fiber], and numerous other registered patents held.) On the other hand, conventional methods are homogeneous saponification reactions in which chemical structure conversion occurs at the molecular level, so the reaction rate is fast, but it is difficult to control the saponification. However, heterogeneous liquid-phase saponification allows for easy control of the degree of saponification because the reaction proceeds from the surface of the precursor structure, but it suffers from the problem of a slow reaction rate. Additionally, structures such as nano nonwovens have the disadvantage of being difficult to maintain their shape after the reaction.

[0009] Therefore, there is a need for in-depth research on a saponification system that can prepare precursor structures like conventional heterogeneous saponification reactions, easily control the degree of saponification within the structures, maintain the structural shapes of various structures after the heterogeneous reaction is complete, and increase the reaction rate compared to existing systems.

[0010]

[0011] The present invention was devised to solve the above problems, and the objective of the present invention is to provide a method for manufacturing a polyvinyl alcohol structure by heterogeneous saponification under tension and external stimulation, which improves upon the problems of the existing heterogeneous saponification reaction method by taking into account prior research results showing that a PVA structure can be converted by a saponification reaction by an immersion method on a heterogeneous surface, the fact that surface modification is possible in recent vapor deposition, and the fact that the reaction rate is accelerated by external stimulation.

[0012] In addition, the PVA structure converted by the heterogeneous immersion method attempted by the inventors has the problem that, although the degree of saponification is easy to control, the reaction rate is slow compared to the reaction carried out in the conventional homogeneous phase because it is carried out from the surface, and some of the structures after the reaction are difficult to maintain their structural shape. Therefore, the purpose is to provide a heterogeneous saponification system that can convert various structures of PVA precursors into PVA structures by applying a heterogeneous saponification system, selecting either a non-immersion or immersion method within the heterogeneous saponification system according to the type of structure to proceed with the reaction, and increasing the reaction rate by applying an acoustic pressure of 1 kHz directly to the sample or indirectly to the solution, thereby improving the problem of the conventional slow reaction rate. In particular, when the reaction is carried out in the non-immersion method, since it is carried out in a circulating manner in the vapor phase, the reaction can proceed with a minimum amount of solvent, thereby not only maintaining the shape of the structure after the reaction but also increasing the efficiency of the reaction.

[0013] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below.

[0014]

[0015] To achieve the above objective, the present invention provides a method for manufacturing a polyvinyl alcohol structure comprising the steps of: preparing a PVA precursor solution by mixing a poly(vinyl alcohol) (PVA) precursor with a solvent (S1); stabilizing the prepared PVA precursor solution (S2); manufacturing a structure of the PVA precursor from the stabilized PVA precursor solution (S3); selecting a saponification reaction method according to the structure of the PVA precursor and preparing a saponification solution according to the selected saponification reaction method (S4); reacting the structure of the PVA precursor with the prepared saponification solution according to the selected saponification reaction method to produce a PVA structure (S5); and washing and drying the PVA structure (S6); wherein, in the step of manufacturing the PVA structure (S5), an external stimulus is applied to the structure of the PVA precursor to promote the saponification reaction.

[0016] The above external stimuli may include one or more of acoustic pressure, vibration, ultrasound, heat, and UV.

[0017] The above polyvinyl alcohol (PVA) precursor may include one or more of polyvinyl acetate, polyvinyl pivalate, polyvinyl butyrate, polyvinyl trifluoroacetate, polyvinyl trichloroacetate, polyvinyl propionate, and copolymers or blends thereof.

[0018] The step (S1) of preparing a PVA precursor solution by mixing a poly(vinyl alcohol), PVA precursor with the above solvent may include: a step of dispersing a dispersant in a solvent by ultrasound at 400 to 500 W and 20 to 40 minutes; and a step of preparing a PVA precursor solution by adding a PVA precursor having a molecular weight of 300,000 to 350,000 to the solvent in which the dispersant is dispersed and dissolving it at 30 to 50 ℃ and 4 to 6 hours.

[0019] The above saponification reaction method can be carried out by selecting either a non-immersion or immersion method depending on the shape of the PVA structure.

[0020] The above non-immersion method involves applying tension to the structure of the PVA precursor to fix it, then vaporizing the saponification solution and reacting it at 80 to 120°C for 2 to 120 hours, and performing the saponification reaction by directly generating an acoustic pressure of 500 Hz to 10 kHz on the PVA structure; the above immersion method involves applying tension to the structure of the PVA precursor to fix it, then immersing it in the saponification solution and reacting it at 40 to 60°C for 5 to 120 hours, and performing the saponification reaction by indirectly generating an acoustic pressure of 500 Hz to 20 kHz on the PVA structure.

[0021] In addition, the present invention provides a polyvinyl alcohol structure characterized by being manufactured according to the above-described manufacturing method.

[0022] The above polyvinyl alcohol structure includes nano-sized ridges formed on the surface, and the nano-sized ridges may have a depth of 10 nm to 3 μm.

[0023]

[0024] By means of the solution to the above problem, the method for manufacturing a polyvinyl alcohol structure by a heterogeneous saponification reaction by external stimulation according to the present invention allows for the selection of a reaction method depending on the type of structure, and can further accelerate the reaction rate of the heterogeneous saponification reaction compared to the existing method by directly applying acoustic pressure to the PVA structure during the reaction under tension or indirectly applying it to the reaction medium. In particular, in the case of the non-immersion method, not only is the reaction rate accelerated, but since the reaction is carried out in a circulating manner in the vapor phase, the reaction can be carried out with a minimum amount of solvent, and structures that are difficult to maintain their shape after the reaction by the immersion method can also maintain their shape. Therefore, it can be applied in various ways to the manufacture of PVA structures, thereby reducing the cost of the final product and increasing productivity.

[0025] In addition, since the method for manufacturing a polyvinyl alcohol structure by a heterogeneous saponification reaction by external stimulation according to the present invention is carried out on a heterogeneous surface, the degree of saponification can be adjusted to suit the performance and characteristics of the desired field, thereby allowing for improved performance and optimal performance of the final product applied in various fields such as food packaging materials, wearables, and adhesives.

[0026] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0027]

[0028] Figure 1 shows a flowchart of a typical PVA structure manufacturing process.

[0029] Figure 2 shows the types of reaction methods that can be selected in a heterogeneous saponification reaction caused by external stimuli.

[0030] Figure 3 is a flowchart of a method for manufacturing a PVA structure by a heterogeneous saponification reaction by external stimulation.

[0031]

[0032] The terms used in this invention have been selected based on currently widely used general terms, taking into account their functions within the invention; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should be defined not merely by their names, but based on their meanings and the overall content of the invention.

[0033] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0034] When a part of a specification is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0035] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0036]

[0037] In the context of this specification, "polyvinyl alcohol" and "PVA" are synonyms and the two terms may be substituted for each other. In the context of this specification, "precursor" of polyvinyl alcohol or PVA refers to a substance in which a functional group can be partially or entirely converted from an ester group to a hydroxyl group by a saponification reaction. Accordingly, the polyvinyl alcohol precursor includes all substances that can be converted into polyvinyl alcohol through a saponification reaction and is not particularly limited.

[0038] In addition, in the context of this specification, "saponification solution," etc., means a solution capable of carrying out the saponification reaction, and the saponification reaction may proceed by hydrolysis, and the saponification solution may include a substance capable of carrying out hydrolysis and may further include a dispersant or a swelling agent.

[0039] In addition, in the context of this specification, "dispersant" refers to a substance that prevents aggregation, and "swelling agent" refers to a substance that causes swelling to increase in volume; therefore, any substance having such functions is not particularly limited in type.

[0040]

[0041] PVA structures are generally produced through a manufacturing process as shown in Fig. 1. The produced PVA is a hydrophilic polymer with OH groups, and due to strong hydrogen bonding during structure formation, the limited number and size of polymer crystals lead to a low degree of crystallinity, which limits the improvement of mechanical properties. Accordingly, the inventors attempted to synthesize PVA structures by a heterogeneous reaction on a PVA precursor structure rather than a conventional homogeneous reaction. Except for the slower reaction rate compared to conventional methods, the morphological and structural characteristics of the structure are excellent. However, due to the slow reaction rate, commercialization is limited despite the various excellent properties.

[0042] The present invention relates to a method for manufacturing a polyvinyl alcohol structure by a heterogeneous saponification reaction by external stimulation, which allows the reaction to be carried out by selecting the structure shape of a PVA precursor within a heterogeneous saponification system as shown in FIG. 2 in order to solve the problems of the prior art. Here, the saponification reaction is classified into non-immersion and immersion types according to the shape of the structure as previously mentioned, and proceeds at that stage as the selected reaction. In the case of the non-immersion type, external stimulation is directly applied to the structure to cause molecular vibration within the structure, thereby accelerating the reaction rate under gaseous conditions, which may be slower than the immersion type. Since a minimum amount of saponification solution is circulated in the vapor phase, the reaction efficiency can be increased, and it has the advantage of enabling the reaction of a structure where it was difficult to maintain the structure shape in the conventional immersion type reaction after the reaction. In the case of the immersion type, external stimulation is indirectly applied to the solution while the structure is immersed in the solution to cause molecular vibration in the solution and the structure, thereby accelerating the reaction more than the heterogeneous saponification reaction carried out in the conventional liquid phase.

[0043]

[0044] The present invention will be described in detail below.

[0045]

[0046] FIG. 3 is a flowchart of a method for manufacturing a polyvinyl alcohol (PVA) structure according to the present invention. The present invention provides a method for manufacturing a polyvinyl alcohol structure comprising the steps of: mixing a poly(vinyl alcohol), PVA precursor with a solvent to prepare a PVA precursor solution (S1); stabilizing the prepared PVA precursor solution (S2); manufacturing a PVA precursor structure from the stabilized PVA precursor solution (S3); selecting a saponification reaction method according to the PVA precursor structure and preparing a saponification solution according to the selected saponification reaction method (S4); reacting the PVA precursor structure with the prepared saponification solution by the selected saponification reaction method to produce a PVA structure (S5); and washing and drying the PVA structure (S6); wherein, in the step of manufacturing the PVA structure (S5), an external stimulus is applied to the PVA precursor structure to promote the saponification reaction.

[0047] The present invention relates to a method for manufacturing a PVA structure by promoting a saponification reaction by directly or indirectly applying an external stimulus to a PVA (Poly(vinyl alcohol)) precursor structure under tension according to the thickness of the structure. By exposing the PVA precursor structure to a saponification solution in a non-immersion or immersion manner, the ester groups of the PVA precursor structure are converted to hydroxyl groups on the structure, and the rate of the saponification reaction can be improved by promoting the reaction through the generation of shaking or vibration at the molecular level of the structure by the external stimulus. Furthermore, the invention relates to a method for manufacturing a polyvinyl alcohol structure through a heterogeneous saponification reaction caused by an external stimulus, in which nano-sized ridges are formed and surface modification occurs after saponification conversion, thereby improving water resistance and increasing the specific surface area.

[0048] The above external stimulus may include one or more of acoustic pressure, vibration, ultrasound, heat, and UV. Preferably, it may be acoustic pressure, but is not limited thereto. When the above external stimulus is applied directly or indirectly to the structure of the PVA precursor, molecular-level vibration may be generated to accelerate the saponification reaction. When the above external stimulus is acoustic pressure, the frequency range may be 500 Hz to 20 kHz as it is amplitude-modulated.

[0049] First, a step (S1) of preparing a PVA precursor solution by mixing a poly(vinyl alcohol), PVA precursor with a solvent can be performed.

[0050] The above polyvinyl alcohol (PVA) precursor may include one or more of polyvinyl acetate, polyvinyl pivalate, polyvinyl butyrate, polyvinyl trifluoroacetate, polyvinyl trichloroacetate, polyvinyl propionate, and copolymers or blends thereof.

[0051] The above solvent may include one or more of benzene, toluene, methanol, ethanol, o-xylene, m-xylene, trichloromethane, trichloroethylene, 1,4-dioxane, cyclohexanone, butanol, methyl ethyl ketone, pentyl acetate, ethyl acetate, chloroform, acetone, acetophenone, dimethylformamide, and dimethyl sulfoxide.

[0052] The step (S1) of preparing the above PVA precursor solution may include: a step of dispersing a dispersant in a solvent at 400 to 500 W and 20 to 40 minutes using ultrasound; and a step of preparing a PVA precursor solution by adding a PVA precursor having a molecular weight of 300,000 to 350,000 to the solvent in which the dispersant is dispersed and dissolving it at 30 to 50 ℃ and 4 to 6 hours.

[0053] The above dispersant may include one or more of sodium sulfate, sodium sulfite, calcium sulfate, and magnesium sulfate.

[0054] The above dispersant can be mixed in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polyvinyl alcohol (PVA) precursor.

[0055] The above PVA precursor may be included in an amount of 8 to 20 parts by weight per 100 parts by weight of the above PVA precursor solution.

[0056] Next, a step (S2) of stabilizing the above-mentioned prepared PVA precursor solution can be performed.

[0057] The step of stabilizing the above PVA precursor solution can be performed by leaving the above PVA precursor solution at room temperature for 0.5 to 5 hours. By stabilizing the above PVA precursor solution at room temperature, defects in the structure such as the formation of bubbles can be prevented, and a structure with a uniform matrix can be formed.

[0058] Next, a step (S3) of manufacturing a structure of the PVA precursor from the stabilized PVA precursor solution can be performed.

[0059] The step of manufacturing the structure of the above-mentioned PVA precursor is a step of manufacturing the structure to match the shape required for application in a field of application, and the method of molding the structure is not particularly limited. The method of molding the above-mentioned PVA precursor solution may be one or more of the following: electrospinning, electrospinning, centrifugal spinning, ultra-high-speed centrifugal spinning, meltblown method, polymerization method, casting method, spin coating method, and knife coating method.

[0060] The structure of the PVA precursor produced by the above molding method may be in the form of a film, sheet, nonwoven fabric, membrane, nanofiber and its structure, fiber, sponge, nanoparticle, and micron particle.

[0061] More specifically, nanofiber structures (e.g., nanononwovens) can be manufactured by centrifugal spinning and electrospinning, nanoparticles and micron particles by electrospinning and polymerization, films and thin films by casting, knife coating, spin coating, and CVD (Chemical Vapor Deposition), and other nonwovens by meltblown methods, so the molding method for forming the structure may include one or more of these.

[0062] The structure of the above PVA precursor can be prepared by volatilizing the solvent contained in the PVA precursor solution at 30 to 80°C for 3 to 24 hours after the PVA precursor solution is spread on a non-adhesive surface.

[0063] Next, a step (S4) of selecting a saponification reaction method according to the structure of the PVA precursor and preparing a saponification solution according to the selected saponification reaction method can be performed.

[0064] Depending on the shape of the structure of the above-mentioned PVA precursor, the structure may be dissolved in the reaction medium, allowing for the selection of a heterogeneous saponification reaction method. For structures where it is difficult to maintain their shape during the reaction and subsequent drying process by the immersion method, the reaction is carried out by the non-immersion method. For the remaining structures, the structure is immersed in the solution by the immersion method, and the swollen structure can then be reacted by the reaction medium. Additionally, the step of preparing the saponification solution may vary depending on the selected reaction method. In the case of the immersion method, the reaction is carried out by immersion in the saponification solution, and the saponification solution can typically be prepared and used at a weight ratio of about 10 times the polymer content. In the case of the non-immersion method, since the reaction takes place in a gaseous state after vaporization, only a minimal amount of solvent is required, and the reaction can be carried out by preparing and using a weight ratio of about 1 to 2 times the polymer content.

[0065] The above saponification solution may include one or more of a swelling agent, a catalyst, and distilled water.

[0066] The above swelling agent may further include one or more of methanol, ethanol, propanol, ethylene glycol, propylene glycol, tetrahydrofuran, dimethyl sulfoxide, benzene, and acetone.

[0067] In general, saponification reactions can be promoted by acids or bases. Accordingly, in one embodiment of the present invention, the saponification solution may use an acid or a base as a catalyst, wherein the acid may include one or more of hydrochloric acid and nitric acid, and the base may include one or more of sodium chloride, sodium hydroxide, and potassium hydroxide, but is not limited thereto as long as it is a substance capable of promoting the saponification reaction.

[0068] When proceeding with the reaction of the above saponification solution in a non-immersion or immersion manner, one or more of sodium sulfate, sodium sulfite, calcium sulfate, and magnesium sulfate may be further included as dispersants added to the PVA precursor solution to inhibit the shape transformation of the above PVA precursor structure.

[0069] According to one embodiment of the present invention, the saponification solution may include one or more of methanol, sodium hydroxide, and distilled water in the case of a non-immersion type, and may include one or more of methanol, sodium hydroxide, sodium sulfite, and distilled water in the case of an immersion type, but is not limited thereto.

[0070] Next, a step (S5) of preparing a PVA structure can be performed by reacting the structure of the PVA precursor with the selected saponification reaction method using the prepared saponification solution. The step (S5) of preparing the PVA structure is a step that allows for controlling the degree of saponification and morphological characteristics to suit the characteristics required for application in a field of application, and consists of reacting the structure of the PVA precursor with the PVA structure in part or in whole.

[0071] The above saponification reaction method can be carried out by selecting either a non-immersion or an immersion method. More specifically, in the non-immersion method, tension is applied to fix the structure of the PVA precursor, then the saponification solution is vaporized and reacted at 80 to 120°C for 2 to 120 hours, and an acoustic pressure of 500 Hz to 10 kHz is directly applied to the PVA structure to perform the saponification reaction, and in the immersion method, tension is applied to fix the structure of the PVA precursor, then the structure is immersed in the saponification solution and reacted at 40 to 60°C for 5 to 120 hours, and an acoustic pressure of 500 Hz to 20 kHz is indirectly applied to the PVA structure to perform the saponification reaction. Preferably, the non-immersion type can perform the saponification reaction by applying tension to the structure of the PVA precursor to fix it, then vaporizing the saponification solution and reacting it at 90 to 110°C for 2 to 10 hours, and directly generating an acoustic pressure of 500 Hz to 10 kHz on the PVA structure, and the immersion type can perform the saponification reaction by applying tension to the structure of the PVA precursor to fix it, then immersing it in the saponification solution and reacting it at 45 to 55°C for 20 to 100 hours, and indirectly generating an acoustic pressure of 500 Hz to 20 kHz on the PVA structure.

[0072] The method of transmitting external stimuli may vary depending on the above saponification reaction method. More specifically, in the case of the non-immersion type, the external stimulus is applied directly to the structure to induce molecular vibration within the structure and promote the reaction, and in the case of the immersion type, the external stimulus is applied indirectly to the saponification solution to induce molecular vibration in both the solution and the structure and accelerate the reaction; the method is characterized by including one or more of these methods when carrying out the reaction.

[0073] When the above saponification reaction proceeds, tension can be applied to minimize shrinkage of the PVA structure, ensure a uniform reaction, and improve the reaction speed so that the reaction proceeds from the surface upon external stimulation.

[0074] Next, a step (S6) of washing and drying the PVA structure can be performed. This step consists of washing to remove impurities remaining on the PVA structure after the reaction is finished and drying the structure after washing.

[0075] The step (S6) of washing and drying the above PVA structure may involve washing the above PVA structure with distilled water and drying it at 25 to 30 ℃.

[0076] In addition, the present invention provides a polyvinyl alcohol structure characterized by being manufactured according to the above-described manufacturing method.

[0077] The above polyvinyl alcohol structure includes nano-sized ridges formed on the surface, and the nano-sized ridges may have a depth of 10 nm to 3 μm.

[0078] According to one embodiment of the present invention, the polyvinyl alcohol structure includes the nano-sized bends, thereby increasing the specific surface area of ​​the polyvinyl alcohol structure and increasing water resistance.

[0079] In addition, according to one embodiment of the present invention, the degree of saponification of the converted PVA structure may be 30 to 99.99% depending on the concentration of the reaction medium, the reaction time, and the type and intensity of the external stimulus.

[0080]

[0081] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0082]

[0083] A comparative example was conducted to compare the change in reaction rate caused by external stimuli through the following examples. In the case of the comparative example, non-immersion and immersion heterogeneous saponification experiments were performed without external stimuli under the conditions conducted by the researcher.

[0084] The following manufacturing examples are prepared by each preparing a 9:1 copolymer solution of polyvinyl acetate and polyvinyl acetate / polyvinyl pivalate dissolved in acetone containing 1% sodium sulfate, and then, under the conditions for manufacturing a structure, manufacturing examples 1 and 2 relate to the manufacture of nanofiber structures for non-immersion application, and manufacturing examples 3 and 4 relate to the manufacture of films.

[0085] Poly(vinyl acetate) (PVAc) used in the following examples was prepared directly through suspension polymerization with a molecular weight of approximately 313,000 and a PDI of 3.30. Additionally, P(VAc-VPi) 9:1, a polyvinyl ester copolymer used as a PVA precursor, was prepared directly through suspension copolymerization with a molecular weight / PDI of 3.31. Sodium hydroxide with 99% purity, methanol with 99.8% purity, acetone with 99.5% purity, and sodium sulfate were products from Duksan Chelmical, and deionized water was used throughout the entire process. The prepared solution was stabilized at room temperature to prevent structural defects, such as bubbles, from forming.

[0086] In addition, the following manufacturing examples are intended for the application of both reaction methods classified within the system; for the non-immersion method, a nanofiber structure was prepared from the precursor solution, and for the immersion method, a film was prepared. The reason for selecting a nanofiber structure for the non-immersion method is, as mentioned earlier, that when the researcher proceeded with a heterogeneous saponification reaction using the conventional immersion method, the deformation of the structure shape due to fusion between structures led to limitations in application fields. To improve this, an acoustic pressure of 500 Hz to 10 kHz was directly applied to the structure to induce molecular vibration within the structure, thereby accelerating the reaction rate under gaseous conditions, which may be slower than the immersion method, and to exhibit surface characteristics while maintaining the structure shape when reacting with a minimum amount of saponification solution in a circulating manner in the vapor phase. On the other hand, in order to improve the limited industrial application of the immersion method due to the slow reaction, an acoustic pressure of 500 Hz to 10 kHz is applied to a film immersed in a solution to indirectly cause vibrations in the molecules of the solution and structure, thereby promoting the heterogeneous saponification reaction that proceeded in the liquid phase.

[0087] First, sodium sulfate at a content of 1% relative to the polymer was dispersed in acetone using ultrasound at 450W for 30 min. Subsequently, 10g each of Poly(vinyl acetate) (PVAc) with a molecular weight of approximately 313,000 and a PDI of 3.30, and P(VAc-VPi) with a molecular weight of approximately 330,000 and a PDI of 3.31 were added to the acetone and sufficiently dissolved at 40℃ for 5h to prepare 10wt.% polymer solutions for each condition. In addition, the prepared solutions were stabilized at room temperature to prevent structural defects caused by bubbles, etc.

[0088]

[0089] Preparation Example 1: Preparation of a pure polyvinyl acetate nanofiber structure by electrospinning

[0090] A prepared 10 wt.% pure polyvinyl acetate solution was injected into a syringe to produce a pure polyvinyl acetate nanofiber structure by electrospinning under conditions of voltage: 15 kV, TCD: 15 cm, injection rate: 0.1 mL / h, and an additional drying process was performed at 30°C for 3 hours to completely dry the internal solvent.

[0091]

[0092] Preparation Example 2: Preparation of Polyvinyl Acetate / Polyvinyl Pivalate (9:1) Nanofiber Structures by Electrospinning

[0093] A prepared 10 wt.% polyvinyl acetate / polyvinyl pivalate (9:1) solution was injected into a syringe to produce a polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure by electrospinning under conditions of voltage: 15 kV, TCD: 15 cm, injection rate: 0.1 mL / h, and an additional drying process was performed at 30°C for 3 hours to completely dry the internal solvent.

[0094]

[0095] Preparation Example 3: Preparation of a pure polyvinyl acetate film by solution casting method

[0096] A pure polyvinyl acetate film was prepared by casting a prepared 10 wt.% pure polyvinyl acetate solution into a Teflon mold by the solution casting method and drying it at 30°C for 6 hours.

[0097]

[0098] Preparation Example 4: Preparation of a polyvinyl acetate / polyvinyl pivalate (9:1) film by solution casting method

[0099] A polyvinyl acetate / polyvinyl pivalate (9:1) film was prepared by casting the prepared 10 wt.% polyvinyl acetate / polyvinyl pivalate solution into a Teflon mold by the solution casting method and drying it at 30°C for 6 hours.

[0100] Table 1 below summarizes the manufacturing conditions for the above manufacturing example.

[0101] ProcessConditionConcentration of PVA Precursor Solution10wt.%Sonication of Na2SO4 / Acetone450W, 30minTemperature of PVA Precursor Solution40℃Process time of PVA Precursor Solution5hStabilization time of PVA Precursor Solution1hTemperature of Solution casting or nanofiber structure25~30℃Process time of Solution casting or nanofiber structure6hVoltage of Electrospinning15kVTCD of Electrospinning15cmFlow Rate of Electrospinning0.1mL / h

[0102] In the following example, an experiment was conducted to produce a polyvinyl alcohol structure by carrying out a saponification reaction of the system-specific polyvinyl acetate and polyvinyl acetate / polyvinyl pivalate structures prepared in the above preparation example using a heterogeneous saponification system.

[0103]

[0104] In Examples 1 to 4, polyvinyl acetate and polyvinyl acetate / polyvinyl pivalate nanofiber structures prepared under different conditions in Preparation Examples 1 to 2 were subjected to a heterogeneous saponification reaction by a non-immersion method. Since the non-immersion method involves vaporization and the reaction taking place in a gaseous state, only a minimum amount of saponification solution is required. The solution is prepared at a weight ratio of approximately 1 to 2 times the polymer content. Based on the weight of the prepared nanofiber structures, distilled water, sodium hydroxide, and methanol were added sequentially in a ratio of 1:0.1:0.1 to prepare the saponification solution. When adding the compounds sequentially, a 30-minute interval was maintained between additions to control the temperature of the solution due to the exothermic reaction during the addition process. Afterward, tension was applied to the structure to fix it with a force such that the structure of the polyvinyl acetate / polyvinyl pivalate nano nonwoven fabric according to the copolymerization ratio was not destroyed, and the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. Then, to ensure smooth vapor circulation, an acoustic pressure of 1 kHz was directly applied to the structure under a circulation device to accelerate the reaction by causing molecular vibration within the structure, thereby synthesizing a PVA structure for 3 to 6 hours.

[0105] In Examples 5 to 8, polyvinyl acetate and polyvinyl acetate / polyvinyl pivalate films prepared under different conditions in Preparation Examples 3 to 4 were subjected to a heterogeneous saponification reaction by an immersion method. Since the reaction is carried out by immersion, the saponification solution is prepared in a weight ratio of approximately 10 times the polymer content, as sufficient saponification solution is required to fully immerse the structure. Based on the weight of the film being prepared, distilled water, sodium hydroxide, and methanol were added sequentially in a ratio of 10:1:1 to prepare the saponification solution. Similar to the non-immersion method, the addition was carried out with a 30-minute interval between additions to control the temperature of the solution increasing due to the exothermic reaction during the addition process. Subsequently, tension was applied to polyvinyl acetate / polyvinyl pivalate films immersed in a saponification solution according to copolymerization ratios, and an acoustic pressure of 10 kHz was indirectly applied to the solution to induce molecular vibration in both the solution and the structure, thereby promoting the reaction and synthesizing PVA structures under conditions of 36 to 72 hours.

[0106] In addition, to remove impurities from the saponification solution remaining in the polyvinyl alcohol structure prepared through Examples 1 to 8, the structure was immersed in distilled water and subjected to a washing process, and then dried at 25 to 30°C to prevent severe shrinkage of the structure during drying and to maintain the shape of the structure.

[0107]

[0108] Example 1: Preparation of polyvinyl alcohol nanofiber structures through non-immersion heterogeneous saponification reaction of pure polyvinyl acetate nanofiber structures

[0109] 2g of the pure polyvinyl acetate nanofiber structure of Preparation Example 1, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2mL of distilled water, 0.2g of NaOH, and 0.2g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the pure polyvinyl acetate nanofiber structure to fix it in place without destroying the structure, and the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. Then, to ensure smooth vapor circulation, an acoustic pressure of 1 kHz was applied directly to the structure under a circulation device, and a non-immersion saponification reaction was performed for 3 hours to produce a polyvinyl alcohol nanofiber structure.

[0110]

[0111] Example 2: Preparation of polyvinyl alcohol nanofiber structures through non-immersion heterogeneous saponification reaction of pure polyvinyl acetate nanofiber structures

[0112] 2g of the pure polyvinyl acetate nanofiber structure of Preparation Example 1, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2mL of distilled water, 0.2g of NaOH, and 0.2g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the pure polyvinyl acetate nanofiber structure to fix it in place without destroying the structure, and then the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. To ensure smooth vapor circulation, an acoustic pressure of 1 kHz was applied directly to the structure under a circulation device, and a non-immersion saponification reaction was performed for 6 hours to produce a polyvinyl alcohol nanofiber structure.

[0113]

[0114] Example 3: Preparation of polyvinyl alcohol nanofiber structures via non-immersion heterogeneous saponification reaction of polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structures

[0115] 2g of the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure of Preparation Example 2, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2mL of distilled water, 0.2g of NaOH, and 0.2g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure to fix it without destroying the structure, and then the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. To ensure smooth vapor circulation, an acoustic pressure of 1 kHz was applied directly to the structure under a circulation device, and a non-immersion saponification reaction was performed for 3 hours to produce a polyvinyl alcohol nanofiber structure.

[0116]

[0117] Example 4: Preparation of polyvinyl alcohol nanofiber structures via non-immersion heterogeneous saponification reaction of polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structures

[0118] 2g of the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure of Preparation Example 2, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2mL of distilled water, 0.2g of NaOH, and 0.2g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure to fix it without destroying the structure, and then the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. A non-immersion saponification reaction was performed for 6 hours under a circulation device to generate an acoustic pressure of 1 kHz directly on the structure to ensure smooth vapor circulation, thereby producing a polyvinyl alcohol nanofiber structure.

[0119]

[0120] Example 5: Preparation of a polyvinyl alcohol film through an immersion-type heterogeneous saponification reaction of a pure polyvinyl acetate film

[0121] 2g of the pure polyvinyl acetate film of Preparation Example 5, prepared by the solution casting method, was obtained, and for the saponification process, a saponification solution was prepared by gently stirring 20mL of distilled water, 2g of NaOH, and 2g of MeOH relative to the weight of the structure. First, tension was applied to the structure of the pure polyvinyl acetate film to fix it without destroying the structure, then it was immersed in the saponification solution and sufficiently submerged. The reaction was carried out at 50°C, and an acoustic pressure of 10kHz was indirectly applied to the solution to perform an immersion-type saponification reaction for 36 hours to produce a polyvinyl alcohol film.

[0122]

[0123] Example 6: Preparation of a polyvinyl alcohol film through an immersion-type heterogeneous saponification reaction of a pure polyvinyl acetate film

[0124] 2g of the pure polyvinyl acetate film of Preparation Example 5, prepared by the solution casting method, was obtained, and for the saponification process, a saponification solution was prepared by gently stirring 20mL of distilled water, 2g of NaOH, and 2g of MeOH relative to the weight of the structure. First, tension was applied to the structure of the pure polyvinyl acetate film to fix it without destroying the structure, then it was immersed in the saponification solution and sufficiently submerged. The reaction was carried out at 50°C, and an acoustic pressure of 10kHz was indirectly applied to the solution to perform an immersion-type saponification reaction for 72 hours to produce a polyvinyl alcohol film.

[0125]

[0126] Example 7: Preparation of a polyvinyl alcohol film via immersion heterogeneous saponification reaction of a polyvinyl acetate / polyvinyl pivalate (9:1) film

[0127] 2g of the polyvinyl acetate / polyvinyl pivalate (9:1) film of Preparation Example 6, prepared by the solution casting method, was obtained, and for the saponification process, a saponification solution was prepared by gently stirring 20mL of distilled water, 2g of NaOH, and 2g of MeOH relative to the weight of the structure. First, tension was applied to the structure of the polyvinyl acetate / polyvinyl pivalate (9:1) film to fix it without destroying the structure, then it was immersed in the saponification solution and sufficiently submerged. The reaction was carried out at 50°C, and an acoustic pressure of 10kHz was indirectly applied to the solution to perform an immersion-type saponification reaction for 36 hours to produce a polyvinyl alcohol film.

[0128]

[0129] Example 8: Preparation of a polyvinyl alcohol film by immersion heterogeneous saponification reaction of a polyvinyl acetate / polyvinyl pivalate (9:1) film

[0130] 2g of the polyvinyl acetate / polyvinyl pivalate (9:1) film of Preparation Example 6, prepared by the solution casting method, was obtained, and for the saponification process, a saponification solution was prepared by gently stirring 20mL of distilled water, 2g of NaOH, and 2g of MeOH relative to the weight of the structure. First, tension was applied to the structure of the polyvinyl acetate / polyvinyl pivalate (9:1) film to fix it without destroying the structure, then it was immersed in the saponification solution and sufficiently submerged. The reaction was carried out at 50°C, and an acoustic pressure of 10kHz was indirectly applied to the solution to perform an immersion-type saponification reaction for 72 hours to produce a polyvinyl alcohol film.

[0131]

[0132] Table 2 below summarizes the saponification conditions of the above examples.

[0133] Classification Saponification Reaction Time Copolymer Ratio Temperature Saponification Solution (Weight Ratio) (H2O:NaOH:MeOH)PVAcPVPi Example 1 3 100 100 1 : 0.1 : 0.1 Example 2 6 100 100 1 : 0.1 : 0.1 Example 3 3 9 1100 1 : 0.1 : 0.1 Example 4 6 9 1100 1 : 0.1 : 0.1 Example 5 3 6 100 50 10 : 1 : 1 Example 6 7 2 100 50 10 : 1 : 1 Example 7 3 6 9 150 10 : 1 : 1 Example 8 7 2 9 150 10 : 1 : 1

[0134] The following comparative example is intended to observe the saponification reaction rate depending on the presence or absence of external stimulation, and the experiment was conducted under the same conditions as the example without applying external stimulation.

[0135]

[0136] Comparative Example 1: Preparation of polyvinyl alcohol nanofiber structures through non-immersion heterogeneous saponification reaction of pure polyvinyl acetate nanofiber structures

[0137] 2g of the pure polyvinyl acetate nanofiber structure of Preparation Example 1, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2mL of distilled water, 0.2g of NaOH, and 0.2g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the pure polyvinyl acetate nanofiber structure to fix it in place without destroying the structure, and then the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. A non-immersion saponification reaction was performed for 3 hours under a circulation device to ensure smooth vapor circulation, thereby producing a polyvinyl alcohol nanofiber structure.

[0138]

[0139] Comparative Example 2: Preparation of polyvinyl alcohol nanofiber structures through non-immersion heterogeneous saponification reaction of pure polyvinyl acetate nanofiber structures

[0140] 2g of the pure polyvinyl acetate nanofiber structure of Preparation Example 1, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2mL of distilled water, 0.2g of NaOH, and 0.2g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the pure polyvinyl acetate nanofiber structure to fix it in place without destroying the structure, and then the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. A non-immersion saponification reaction was performed for 6 hours under a circulation device to ensure smooth vapor circulation, thereby producing a polyvinyl alcohol nanofiber structure.

[0141]

[0142] Comparative Example 3: Preparation of polyvinyl alcohol nanofiber structures via non-immersion heterogeneous saponification reaction of polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structures

[0143] 2 g of the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure of Preparation Example 2, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2 mL of distilled water, 0.2 g of NaOH, and 0.2 g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure to fix it in place with a force that would not destroy the structure, and then the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. A non-immersion saponification reaction was performed for 3 hours under a circulation device to ensure smooth vapor circulation, thereby producing a polyvinyl alcohol nanofiber structure.

[0144]

[0145] Comparative Example 4: Preparation of polyvinyl alcohol nanofiber structures via non-immersion heterogeneous saponification reaction of polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structures

[0146] 2 g of the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure of Preparation Example 2, prepared by electrospinning, was obtained, and a saponification solution was prepared by gently stirring 2 mL of distilled water, 0.2 g of NaOH, and 0.2 g of MeOH relative to the weight of the structure for the saponification process. First, tension was applied to the polyvinyl acetate / polyvinyl pivalate (9:1) nanofiber structure to fix it without destroying the structure, and then the reaction was carried out at 100°C under conditions where the saponification solution could vaporize. A non-immersion saponification reaction was performed for 6 hours under a circulation device to ensure smooth vapor circulation, thereby producing a polyvinyl alcohol nanofiber structure.

[0147]

[0148] Comparative Example 5: Preparation of a polyvinyl alcohol film through an immersion-type heterogeneous saponification reaction of a pure polyvinyl acetate film

[0149] 2g of the pure polyvinyl acetate film of Preparation Example 3, prepared by the solution casting method, was obtained, and for the saponification process, a saponification solution was prepared by gently stirring 20mL of distilled water, 2g of NaOH, and 2g of MeOH relative to the weight of the structure. First, the structure was fixed by applying tension to the pure polyvinyl acetate film with a force sufficient not to destroy the structure, then it was immersed in the saponification solution and sufficiently submerged, and the reaction was carried out for 36 hours at 50°C to produce a polyvinyl alcohol film through an immersion-type saponification reaction.

[0150]

[0151] Comparative Example 6: Preparation of a polyvinyl alcohol film through an immersion-type heterogeneous saponification reaction of a pure polyvinyl acetate film

[0152] 2g of the pure polyvinyl acetate film of Preparation Example 3, prepared by the solution casting method, was obtained, and for the saponification process, a saponification solution was prepared by gently stirring 20mL of distilled water, 2g of NaOH, and 2g of MeOH relative to the weight of the structure. First, the structure was fixed by applying tension to the pure polyvinyl acetate film with a force sufficient not to destroy the structure, then it was immersed in the saponification solution and sufficiently submerged, and the reaction was carried out for 72 hours at 50°C to produce a polyvinyl alcohol film through an immersion-type saponification reaction.

[0153]

[0154] Comparative Example 7: Preparation of a polyvinyl alcohol film via immersion heterogeneous saponification reaction of a polyvinyl acetate / polyvinyl pivalate (9:1) film

[0155] 2g of the polyvinyl acetate / polyvinyl pivalate (9:1) film of Preparation Example 4, prepared by the solution casting method, was obtained, and for the saponification process, 20mL of distilled water, 2g of NaOH, and 2g of MeOH were gently stirred relative to the weight of the structure to prepare a saponification solution. First, tension was applied to the structure of the polyvinyl acetate / polyvinyl pivalate (9:1) film with a force such that the structure would not be destroyed, and then the film was immersed in the saponification solution and sufficiently submerged. The reaction was carried out for 36 hours at 50°C to produce a polyvinyl alcohol film through an immersion-type saponification reaction.

[0156]

[0157] Comparative Example 8: Preparation of a polyvinyl alcohol film through an immersion heterogeneous saponification reaction of a polyvinyl acetate / polyvinyl pivalate (9:1) film

[0158] 2g of the polyvinyl acetate / polyvinyl pivalate (9:1) film of Preparation Example 4, prepared by the solution casting method, was obtained, and for the saponification process, 20mL of distilled water, 2g of NaOH, and 2g of MeOH were gently stirred relative to the weight of the structure to prepare a saponification solution. First, tension was applied to the structure of the polyvinyl acetate / polyvinyl pivalate (9:1) film with a force such that the structure would not be destroyed, and then the film was placed in the saponification solution and sufficiently immersed. The reaction was carried out for 72 hours at 50°C to produce a polyvinyl alcohol film through an immersion-type saponification reaction.

[0159]

[0160] Experimental Example 1: Measurement of Degree of Saponification

[0161] 1 The degree of saponification of polyvinyl alcohol structures produced during heterogeneous saponification reactions with and without external stimulation in Examples 1 to 8 and Comparative Examples 1 to 8 was measured using H-NMR analysis and gravimetric methods. Table 3 below summarizes the degree of saponification under conditions for the Examples and Comparative Examples.

[0162] Classification Structure Type Saponification Time Degree of Saponification External Stimulation Non-immersion Type Example 1 Nano Nonwoven Fabric 362.8% ○ Comparative Example 1 Nano Nonwoven Fabric 334.6% X Example 2 Nano Nonwoven Fabric 690.7% ○ Comparative Example 2 Nano Nonwoven Fabric 646.3% X Example 3 Nano Nonwoven Fabric 356.1% ○ Comparative Example 3 Nano Nonwoven Fabric 330.9% X Example 4 Nano Nonwoven Fabric 681.0% ○ Comparative Example 4 Nano Nonwoven Fabric 641.4% X Immersion Type Example 5 Film 3672.6% ○ Comparative Example 5 Film 3654.3% X Example 6 Film 7299.9% ○ Comparative Example 6 Film 7271.8% X Example 7 Film 3661.2% ○ Comparative Example 7 Film 364 4.1%X Example 8 Film 728 4.0%○ Comparative Example 8 Film 726 0.5%X

[0163]

[0164] Specific embodiments of the present invention have been examined so far. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the claims, not by the foregoing description, and all variations within the scope of equivalents should be interpreted as being included in the present invention.

Claims

1. A step (S1) of preparing a PVA precursor solution by mixing a poly(vinyl alcohol), PVA precursor with a solvent; Step (S2) of stabilizing the above-mentioned PVA precursor solution; Step (S3) of preparing a structure of a PVA precursor from the above stabilized PVA precursor solution; A step (S4) of selecting a saponification reaction method according to the structure of the above PVA precursor and preparing a saponification solution according to the selected saponification reaction method; Step (S5) of preparing a PVA structure by reacting the structure of the PVA precursor with the selected saponification reaction method using the saponification solution prepared above; and The method includes the step (S6) of washing and drying the above PVA structure, and A method for manufacturing a polyvinyl alcohol structure characterized by applying an external stimulus to the structure of the PVA precursor to promote a saponification reaction in the step (S5) of manufacturing the PVA structure.

2. In Paragraph 1, A method for manufacturing a polyvinyl alcohol structure characterized in that the above external stimulus includes one or more of acoustic pressure, vibration, ultrasound, heat, and UV.

3. In Paragraph 1, A method for manufacturing a polyvinyl alcohol structure characterized in that the above-mentioned polyvinyl alcohol (PVA) precursor comprises one or more of polyvinyl acetate, polyvinyl pivalate, polyvinyl butyrate, polyvinyl trifluoroacetate, polyvinyl trichloroacetate, polyvinyl propionate, and copolymers or blends thereof.

4. In Paragraph 1, The step (S1) of preparing a PVA precursor solution by mixing a poly(vinyl alcohol) (PVA) precursor with the above solvent is, A step of dispersing a dispersant in a solvent using ultrasound under conditions of 400 to 500 W and 20 to 40 minutes; and A method for manufacturing a polyvinyl alcohol structure, characterized by comprising the step of preparing a PVA precursor solution by adding a PVA precursor having a molecular weight of 300,000 to 350,000 to a solvent in which the above-mentioned dispersant is dispersed and dissolving it under conditions of 30 to 50 ℃ for 4 to 6 hours.

5. In Paragraph 1, A method for manufacturing a polyvinyl alcohol structure, characterized in that the above saponification reaction method is selected from a non-immersion or immersion method depending on the shape of the PVA structure.

6. In Paragraph 5, The above non-immersion method fixes the structure of the PVA precursor by applying tension, then vaporizes the saponification solution and reacts it at 80 to 120°C for 2 to 120 hours, and performs the saponification reaction by directly generating an acoustic pressure of 500 Hz to 10 kHz on the PVA structure. A method for manufacturing a polyvinyl alcohol structure, characterized by applying tension to the structure of the PVA precursor to fix it, then immersing it in the saponification solution to react at 40 to 60°C for 5 to 120 hours, and indirectly generating an acoustic pressure of 500 Hz to 20 kHz on the PVA structure to perform the saponification reaction.

7. A polyvinyl alcohol structure characterized by being manufactured according to the manufacturing method of claim 1.

8. In Paragraph 7, The polyvinyl alcohol structure comprises nano-sized ridges formed on its surface, wherein the nano-sized ridges have a depth of 10 nm to 3 μm.

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