Method for manufacturing nanofibers through solution blow spinning

Abstract

The present invention relates to a method for manufacturing nanofibers through solution blow spinning (SBS). When nanofibers are manufactured through the solution blow spinning process, the production rate per hour is significantly improved. Furthermore, nanofibers manufactured by the method using the biodegradable polymer Polybutylene Succinate (PBS) have excellent oil-water separation and oil adsorption capabilities, which can be utilized in various fields.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing nanofibers through solution blow spinning (SBS), and more specifically, to a method for manufacturing polybutylene succinate (PBS) nanofibers through solution blow spinning, a composition for oil-water separation comprising the nanofibers, an oil adsorbent composition, and a composition for a membrane filter. Background Technology

[0003] Nanofibers have a lower density and a very large surface area compared to conventional fibers. Additionally, due to their micropores, only fine particles can pass through, and surface roughness can make hydrophilic materials hydrophobic depending on the raw materials. Conventional nanofibers are manufactured via an electrospinning process, but this method has a low hourly production rate and requires relatively expensive equipment.

[0004] Meanwhile, it is known that an average of 263 marine pollution spills occurred annually between 2011 and 2020, with an average of 554.04 kL of pollutants spilled, of which 301.58 kL was collected. Additionally, the average daily wastewater discharge volume from wastewater discharge facilities was reported to have increased from 2011 to 2019. Currently, oil adsorbents used in marine pollution spills and wastewater discharge include zeolites, activated carbon, and polypropylene nonwoven fabrics. However, the above oil adsorbents have disadvantages, such as high unit costs or difficulties in recycling or disposal.

[0005] Polybutylene succinate (PBS) is a polyester-based thermoplastic polymer and a biodegradable polymer. Polybutylene succinate (PBS) is primarily produced through the esterification of succinic acid using succinic acid and 1,4-butandiol, and it decomposes into water and carbon dioxide by microorganisms after use. Currently, Polybutylene succinate (PBS) is used in various industrial fields, such as packaging films, disposable products, and agricultural mulching films.

[0007] Accordingly, the inventors made diligent efforts to develop a nanofiber manufacturing method that is improved in terms of economic, productive, and environmental aspects compared to existing technology. As a result, they confirmed that when nanofibers are manufactured through a solution blow spinning (SBS) process, the hourly production rate is significantly improved, and that the water-oil separation ability and oil adsorption ability of the nanofibers manufactured by the above method using the biodegradable polymer Polybutylene Succinate (PBS) are excellent, thereby completing the present invention. The problem to be solved

[0009] The objective of the present invention is to provide a method for manufacturing nanofibers through solution spinning. means of solving the problem

[0011] To achieve the above objective, the present invention provides a method for manufacturing nanofibers comprising the following steps.

[0012] (a) a step of preparing a spinning solution by dissolving a polymer in a solvent; and

[0013] (b) A step of manufacturing nanofibers by solution spinning the above spinning solution.

[0014] The present invention may further include a step of removing moisture from the polymer prior to step (a).

[0015] In the present invention, the polymer of step (a) may be characterized as being one or more selected from the group consisting of Polybutylene succinate (PBS), Polylactic acid (PLA), Polybutylene adipate terephthalate (PBAT), and Polyethylene (PE).

[0016] In the present invention, the solvent of step (a) may be characterized as being one or more volatile solvents selected from the group consisting of chloroform, tetrahydrofuran (THF), and formic acid.

[0017] In the present invention, the polymer of step (a) may be characterized as being in an amount of 3 to 9 parts by weight based on 100 parts by weight of the spinning solution.

[0018] In the present invention, step (b) may be characterized by extruding the spinning solution at a rate of 100 mL / h to 500 mL / h.

[0020] The present invention also provides nanofibers manufactured by the above method.

[0021] In the present invention, the average diameter of the nanofiber may be 10 nm to 500 nm.

[0023] The present invention also provides a composition for separating oil and water comprising the nanofiber as an active ingredient.

[0024] In the present invention, the composition may be characterized by separating one or more selected from the group consisting of soybean oil, cottonseed oil, gasoline, light oil, crude oil, and sunflower seed oil from one or more selected from the group consisting of water, methanol, and ethanol.

[0026] The present invention also provides an oil adsorption composition comprising the nanofiber as an active ingredient.

[0027] In the present invention, the oil may be characterized as being one or more selected from the group consisting of soybean oil, cottonseed oil, gasoline, diesel oil, crude oil, and sunflower seed oil.

[0029] The present invention also provides a composition for a membrane filter comprising the nanofiber as an active ingredient. Effects of the invention

[0031] The nanofiber manufacturing method according to the present invention utilizes solution spinning to significantly improve the production yield of nanofibers compared to the conventional nanofiber manufacturing method using electrospinning, and is economical as the process can be simplified and streamlined. Production costs can also be significantly reduced compared to the electrospinning process, which uses expensive equipment.

[0032] In addition, Polybutylene succinate (PBS) nanofibers produced by the above method can be utilized in various fields due to their excellent oil-water separation ability and oil adsorption ability.

[0033] Furthermore, Polybutylene succinate (PBS) is a biodegradable polymer that is easy to dispose of, so it has advantages in terms of the environment. Brief explanation of the drawing

[0035] Figure 1 is a schematic diagram of a method for producing polybutylene succinate (PBS) nanofibers through solution spinning. Figure 2 is a schematic diagram of the entire experiment. Figure 3 relates to the viscosity measurement results (Figure 3A) and specific viscosity measurement results (Figure 3B) according to polybutylene succinate (PBS) concentration. As a result of confirming the possibility of nanofiber formation, beads or films were formed in the dilute region, beads and nanofibers were mixed in the semi-dilute region, and nanofibers were formed in the entanglement region (Figure 3B). Figure 4 shows SEM images of nanofibers prepared according to polybutylene succinate (PBS) concentrations. The polybutylene succinate (PBS) concentrations were 1% (Fig. 4A), 3% (Fig. 4B), 5% (Fig. 4C), 7% (Fig. 4D), and 9% (Fig. 4E), respectively, and the SEM images were shown magnified to (i) 5.00Kx, (ii) 10.00Kx, and (iii) 50.00Kx, respectively. Figure 5 shows the distribution of nanofiber diameters (Figures 5A, 5B, 5C, and 5D) and the hourly production yield according to PBS concentration (Figure 5E). Figure 6 shows the FT-IR spectrum (Figure 6A) and gel chromatography spectrum and molecular weight (Figure 6B) in the form of a pellet and nanofiber. Figure 7A shows the results of comparing the productivity of electrospinning and solution spinning according to PBS concentration, and Figure 7B shows the results of comparing the productivity of nanofiber manufacturing processes. In addition, Figures 7C to 7F show the results of confirming the folding potential of the nanofibers. Figure 8 relates to water and oil contact angle experiments for various forms of PBS. Figure 8A shows the contact angle of a PBS fiber to water, Figure 8B shows the contact angle of a PBS film to water, Figure 8C shows the contact angle of a PBS nanofiber to water, Figure 8D shows the contact angle of a PBS fiber to oil, Figure 8E shows the contact angle of a PBS film to oil, and Figure 8F shows the contact angle of a PBS nanofiber to oil. Additionally, Figure 8G is a photograph of water and oil droplets in the vertical direction. Figure 9 shows the results of measuring the water contact angle of nanofibers per hour. Figure 10 relates to photographs of the adsorption before, during, and after of different types of oil (Figure 10A), the measurement results of the adsorption amount of nanofibers by different types of oil (Figure 10B), the comparison results of the adsorption amount by different types of oil (Figure 10C), the measurement results of the desorption ability of nanofibers according to the solvent after oil adsorption (Figure 10D), and the oil adsorption efficiency per number of reuses (Figure 10E). Figure 11 shows the results of measuring Flux (permeability) according to the type of oil for each nanofiber (Figure 11A) and the results of oil-water separation according to the type of nanofiber (Figure 11B). Figure 12 shows a schematic diagram of an oil-water emulsion separation experiment (Figure 12A), oil-water emulsion separation efficiency according to the type of nanofiber (Figure 12B), a photograph of oil-water emulsion separation using nanofibers (Figure 12C), a photograph, microscope image, and particle size of the emulsion before separation (Figures 12D-F), and a photograph, microscope image, and particle size of the emulsion after separation (Figures 12G-I). Figure 13 relates to the evaluation of the degradability of nanofibers. It shows the results of the hydrolysis of nanofibers using 1M sodium hydroxide (Figure 13A), a schematic diagram of the nanofiber hydrolysis mechanism (Figure 13B), and images of the nanofiber degradation and a graph of the degradation rate in a composting environment (Figure 13C). In Figure 13C, MCC represents microcrystalline cellulose. Figures 14A and 14B show graphs of the degradation and degradation rate of nanofibers at pH 4 and 7. The nanofibers did not degrade at pH 4 and 7. Additionally, Figure 14 shows SEM images after drying following immersion in a pH 4 environment and SEM images after drying following immersion in a pH 7 environment. Specific details for implementing the invention

[0036] The present invention will be described in detail below.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a skilled expert in the art to which this invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0040] Nanofibers have a lower density and a very large surface area compared to conventional fibers. Additionally, due to their micropores, only fine particles can pass through, and surface roughness can make hydrophilic materials hydrophobic depending on the raw materials. Conventional nanofibers are generally manufactured via an electrospinning process, but this method has a low hourly production rate and requires relatively expensive equipment.

[0041] Accordingly, the present invention manufactured polybutylene succinate (PBS) nanofibers using a solution blow spinning (SBS) process instead of the electrospinning process commonly used to manufacture PBS nanofibers. When a polymer is dissolved in a solvent and then spun under high air pressure, the volatile solvent evaporates, and only the polymer accumulates irregularly in a collector to form a nonwoven fabric. It was confirmed that when PBS nanofibers are manufactured using the above solution blow spinning process, the production yield per hour increases by approximately 5 to 7 times compared to when they are manufactured using the electrospinning process.

[0042] Furthermore, the morphology of the PBS nanofibers prepared by the above method was analyzed using a scanning electron microscope, and the hydrophobicity and lipophilicity of the nanofibers were confirmed through contact angle measurements. In addition, the present invention was completed by confirming the excellent oil-water separation ability, oil adsorption ability, desorption ability, and biodegradability of the PBS nanofibers.

[0044] Accordingly, the present invention relates to a method for manufacturing nanofibers comprising the following steps in one aspect.

[0045] (a) a step of preparing a spinning solution by dissolving a polymer in a solvent; and

[0046] (b) A step of manufacturing nanofibers by solution spinning the above spinning solution.

[0047] The present invention may further include, but is not limited to, a step of removing moisture from the polymer prior to step (a).

[0048] In the present invention, the polymer of step (a) may be characterized as being one or more selected from the group consisting of Polybutylene succinate (PBS), Polylactic acid (PLA), Polybutylene adipate terephthalate (PBAT) and Polyethylene (PE), but is not limited thereto.

[0049] The above Polybutylene succinate (PBS), Polylactic acid (PLA), Polybutylene adipate terephthalate (PBAT), and Polyethylene (PE) are biodegradable polymers, and Polyethylene is a non-degradable polymer.

[0050] In the present invention, the solvent of step (a) may be characterized as being one or more volatile solvents selected from the group consisting of chloroform, tetrahydrofuran (THF), and formic acid, but is not limited thereto.

[0051] In the present invention, when the polymer of step (a) is Polybutylene succinate (PBS), the solvent of step (a) may be chloroform, but is not limited thereto.

[0052] In the present invention, the polymer in step (a) may be characterized as being in an amount of 3 to 9 parts by weight, preferably 3.5 to 8.5 parts by weight, more preferably 4 to 8 parts by weight, based on 100 parts by weight of the spinning solution, but is not limited thereto; however, if a polymer with a concentration outside the above range is used, it may have a negative effect on the productivity of the nanofiber.

[0053] In the present invention, step (b) may be characterized by spinning the spinning solution at a rate of 100 mL / h to 500 mL / h, preferably 200 mL / h to 400 mL / h, but is not limited thereto; however, spinning the solution at a rate outside the above range may have a negative effect on the productivity of the nanofiber.

[0054] In the present invention, the distance between the collector and the spinning nozzle and the air pressure may affect the diameter of the nanofiber, but are not limited thereto.

[0056] The present invention relates to nanofibers manufactured by the above method in another aspect.

[0057] In the present invention, the average diameter of the nanofiber may be characterized as being 10 nm to 500 nm, preferably 44 nm to 229 nm, but is not limited thereto.

[0059] In another aspect, the present invention relates to a composition for separating oil and water comprising the above-mentioned nanofiber as an active ingredient.

[0060] In the present invention, the composition may be characterized by separating one or more selected from the group consisting of soybean oil, cottonseed oil, gasoline, light oil, crude oil, and sunflower oil from one or more selected from the group consisting of water, methanol, and ethanol, but is not limited thereto.

[0062] In another aspect, the present invention relates to an oil adsorption composition comprising the above-mentioned nanofiber as an active ingredient.

[0063] In the present invention, the oil may be characterized as being one or more selected from the group consisting of soybean oil, cottonseed oil, gasoline, light oil, crude oil, and sunflower seed oil, but is not limited thereto.

[0065] In another aspect, the present invention relates to a composition for a membrane filter comprising the nanofiber as an active ingredient.

[0067] The present invention will be described in more detail below through examples. These examples are intended solely to illustrate the present invention, and it is obvious to those skilled in the art that the scope of the present invention is not to be interpreted as being limited by these examples.

[0069] [Example]

[0070] Preparation of Polybutylene Succinate (PBS) Solution

[0071] To remove moisture from the raw material Polybutylene succinate (PBS) (Anko Bioplastics Co., Ltd., Wonju, South Korea), it was dried in a 60°C oven for 24 hours, and then the moisture-removed PBS was added to the solvent Chloroform (ACS reagent, Sigma-Aldrich, Seoul, South Korea) at a weight ratio of 1 to 9% and dissolved using a magnetic stirrer for 24 hours.

[0073] Fabrication of PBS nanofibers using solution spinning

[0074] The above PBS solution was placed into the paint cup of an airbrush (Beetlebug, Seoul, South Korea), and fibers were spun by applying air at a pressure of 50 psi after placing the airbrush at a distance of 30 cm from the collector (Fig. 1). During the spinning process, the solvent in the solution evaporates, and only the polymer adheres to the surface of the collector. PBS nanofibers were obtained through the above solution spinning.

[0076] SEM image analysis results of nanofibers according to PBS concentration

[0077] The spinning efficiency and morphological characteristics of the polymer vary depending on the polymer concentration. The morphological characteristics of nanofibers prepared at different PBS concentrations were analyzed using a scanning electron microscope (SEM) (Carl Zeiss, UK).

[0078] In the dilute region (low concentration), polymers were formed in the form of beads or films; in the semi-dilute region, a mixture of beads and nanofibers was formed; and in the entanglement region, nanofibers were formed (Fig. 3). However, at high concentrations, the fiber thickness did not meet the nanofiber criteria, or the nozzle became clogged. Through SEM images, it was confirmed that when the PBS concentration was 1%, the material exhibited a film form rather than a fiber form (Fig. 4). This is believed to be because the polymer concentration was not sufficient to form a fiber. Nanofibers began to appear when the PBS concentration was 3% or higher; however, at a PBS concentration of 3%, the amount of spun fibers was small, making collection by the collector difficult, and the fibers tore during the collection process. At PBS concentrations of 5% and 7%, the nanofibers maintained their shape without tearing during collection, allowing for easy acquisition. At a PBS concentration of 9%, the high polymer concentration caused nozzle clogging.

[0080] Analysis results of nanofiber diameter and productivity according to PBS concentration

[0081] Based on SEM images, the diameter of the fibers was measured according to PBS concentration. The average fiber diameter was approximately 44 nm at a PBS concentration of 3%, 129 nm at 5%, 130 nm at 7%, and 229 nm at 9% (Figs. 5A to D). The thickness of the fibers increased significantly in dependence on PBS concentration, and the deviation also increased.

[0082] Fiber productivity was measured by converting the production per minute into production per hour (Fig. 5E). As the PBS concentration increased, the production volume also showed an increasing trend, but it was observed that the production volume decreased sharply when the PBS concentration was 9%. This is believed to be due to the high viscosity of the polymer solution causing nozzle clogging.

[0084] Comparison of nanofiber productivity between electrospinning and solution spinning

[0085] The production yields by PBS concentration were compared in the electrospinning and solution spinning processes.

[0086] As a result, trace amounts of nanofibers were detected at 3% PBS in the solution spinning process, and at 5% and 7% PBS, the production of nanofibers increased by approximately 5-6 times compared to the electrospinning process (Fig. 7). However, at 9% PBS in the solution spinning process, a smaller amount of nanofibers was detected than in the electrospinning process. This is believed to be due to nozzle clogging caused by high viscosity in the solution spinning process.

[0088] Contact angle analysis results of PBS nanofibers

[0089] To verify the hydrophobicity of the nanofibers, water and oil contact angle experiments were conducted on various forms of PBS. PBS fibers and films were used as controls.

[0090] As a result, it was confirmed that the contact angle of the PBS nanofibers produced by solution spinning was superior to that of other forms (PBS fibers, PBS films) (Fig. 8), which is believed to be due to surface roughness. A height difference in the nanometer range is created on the surface, and an air layer is trapped on the surface, resulting in hydrophobicity.

[0092] Oil adsorption experiment results of PBS nanofibers

[0093] The lipophilicity of PBS nanofibers can be utilized for oil adsorbents and for the separation of oil-water emulsions. To evaluate the oil adsorption capacity of PBS nanofibers, a total of four types of oil were used: soybean oil (Haepyo, South Korea), cottonseed oil (Sigma-Aldrich, Seoul, South Korea), gasoline, and diesel (purchased from a local gas station). To facilitate the distinction between water and oil, water was stained with methylene blue (Sigma-Aldrich, Seoul, South Korea), and oil was stained with Sudan IV (Sigma-Aldrich, Seoul, South Korea).

[0094] It was confirmed that PBS nanofibers selectively adsorb oil (Fig. 10A). As a result of comparing the adsorption performance by type of oil (Fig. 10B), low adsorption performance was observed for gasoline. It is believed that this low adsorption capacity is due to the volatility of gasoline. Due to the high volatility of gasoline, it was confirmed that the weight decreased even during actual measurement.

[0095] In addition, the adsorption capacity of PBS nanofibers varies depending on the viscosity of the oil. In the desorption efficiency experiment, water, methanol, and ethanol were used, and methods were employed in which the sample was immersed and then physically squeezed, or in which the sample was immersed and then desorbed using a vortex.

[0096] As a result, it was confirmed that the method using vortex after immersion in ethanol was the most efficient, and the desorption efficiency was approximately 98% regardless of the type of oil (Fig. 10D).

[0097] In the reuse performance evaluation, it was confirmed that the adsorption efficiency decreased with the number of reuses (Fig. 10E). This is believed to be due to damage to the fibers during the adsorption-desorption process and unremoved oil between the pores of the nanofibers.

[0099] Results of oil-water emulsion separation experiment using PBS nanofibers

[0100] In an experiment to evaluate the oil-water emulsion separation performance of nanofibers, a surfactant (Span 80) (Duksan Pharmaceutical, Ansan-si, South Korea) was added to a 100:1 oil / water solution to prepare an emulsion, and then the nanofibers were placed in the neck of a funnel and the emulsion was poured in to evaluate the oil / water separation in the emulsion (Fig. 12A).

[0101] As a result, it was confirmed that the milky white emulsion changed to its original transparent color (Fig. 12C). When the droplets were examined using a stereomicroscope (lv100, Nikon, Japan), the droplets were visible before separation but could not be seen after separation, confirming that only oil could be selectively adsorbed from the emulsion.

[0102] In addition, as a method to measure separation efficiency, moisture was measured using a moisture meter (MB120, OHAUS, USA), and as a result, it was confirmed that the separation efficiency was maintained at 98% even after 5 reuses.

[0103] Furthermore, since oil-water separation is possible even under gravity conditions without a separate pressurization device, PBS nanofibers selectively allow only oil to pass through, effectively suppressing water penetration. The flux of PBS nanofibers during oil-water emulsion separation is 181.9 Lm -2 h -1 It was found to be at a level similar to that of non-degradable plastic-based nanofibers produced by conventional electrospinning.

[0105] Analysis results of the degradation of PBS nanofibers

[0106] As a method to evaluate the degradation performance of PBS nanofibers, hydrolysis and biodegradability in a composting environment were evaluated.

[0107] Hydrolysis evaluation was performed by immersing PBS nanofibers in a 1M sodium hydroxide solution and conducting a decomposition experiment at a temperature of 58°C. The decomposition rate was measured by preparing samples corresponding to each time point and weighing them at each time interval (Fig. 13B). As a result, it was confirmed that the PBS nanofibers decompose within 8 hours (Figs. 13A and B).

[0108] In the biodegradation experiment, laboratory-prepared compost was used, and the decomposition rate of the nanofibers was measured using carbon dioxide after burying the nanofibers in the compost. As a result, it was confirmed that about 50% of the nanofibers decomposed after about 30 days of burial in the compost (Fig. 13C).

[0109] Polymer hydrolysis is influenced by various factors such as the molecular structure, crystallinity, and morphological characteristics of the polymer. In general, hydrophilic, amorphous, and polymeric materials with high specific surface areas are more susceptible to hydrolysis. The hydrolytic degradation behavior of PBS nanofibers prepared by the solution spinning process was evaluated in buffer media of various concentrations (pH 4, pH 7, and pH 10) for up to 12 hours.

[0110] As a result, the nanofibers were well maintained at pH 4 and 7, and no significant degradation was observed, nor were they degraded (Fig. 14). On the other hand, under alkaline conditions of pH 10, morphological breakdown of the PBS nanofibers occurred over time, and after 8 hours, all PBS nanofibers were hydrolyzed (Fig. 14).

Claims

Claim 1 A method for manufacturing reusable oil-adsorbing nanofibers comprising: (a) a step of preparing a spinning solution by dissolving polybutylene succinate (PBS) in chloroform; and (b) a step of producing nanofibers by solution spinning the spinning solution, excluding electrospinning, wherein the PBS is 5 to 7 parts by weight based on 100 parts by weight of the spinning solution. Claim 2 A method according to claim 1, further comprising a step of removing moisture from the PBS prior to step (a). Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 A method according to claim 1, characterized in that, in step (b), the spinning solution is spun at a rate of 100 mL / h to 500 mL / h. Claim 7 Reusable oil-adsorbing nanofibers manufactured by the method of any one of paragraphs 1, 2 and 6. Claim 8 A nanofiber according to claim 7, characterized in that the average diameter of the nanofiber is 10 nm to 500 nm. Claim 9 A composition for oil-water separation comprising the nanofiber of claim 7 as an active ingredient. Claim 10 A composition for separating oil and water according to claim 9, characterized in that the composition separates one or more selected from the group consisting of soybean oil, cottonseed oil, gasoline, light oil, crude oil, and sunflower oil from one or more selected from the group consisting of water, methanol, and ethanol. Claim 11 An oil adsorption composition comprising the nanofiber of claim 7 as an active ingredient. Claim 12 An oil adsorption composition according to claim 11, characterized in that the oil is one or more selected from the group consisting of soybean oil, cottonseed oil, gasoline, light oil, crude oil, and sunflower seed oil. Claim 13 A composition for a membrane filter comprising the nanofiber of claim 7 as an active ingredient.

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