Method for producing polymer compounds

Abstract

A method for producing a polymer, the method comprising a step in which a starting material for the polymer is introduced into the inside of a porous object and a step in which the starting material is polymerized in voids within the porous object.

Description

Cross - reference to related applications

[0001] This application is based on Japanese Patent Application No. 2020 - 085490 filed on May 14, 2020, claims the benefit of its priority, and all the contents of that patent application are incorporated herein by reference.

Technical Field

[0002] This disclosure relates to a manufacturing technology of polymer compounds, and particularly relates to a method for manufacturing polymer compounds, a porous body usable in the manufacturing method, and particles of polymer compounds.

Background Art

[0003] Polymer microparticles are used in various applications in a wide range of fields such as the material field of cosmetics and paints, as well as the information field and the medical field (for example, see Patent Document 1). Among them, those with a diameter of 100 nm or less are called nano - particles, and further applications are expected due to their unique properties. For example, since the particle size of nano - particles is much smaller than the wavelength of visible light (380 nm - 800 nm), the dispersion liquid of nano - particles has high transparency. Utilizing this property, it is expected to apply nano - particles to the rheology control of paints and the like.

[0004] Nano - particles are produced, for example, by an emulsion polymerization method or a soap - free emulsion polymerization method. In the emulsion polymerization method, monomers are polymerized in the presence of a surfactant, so the particle surface is protected by an electric double layer, and aggregation of particles is unlikely to occur. Therefore, nano - particles with a particle diameter of 100 nm or less can be synthesized.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, surfactants, which are used in large quantities in emulsion polymerization, are difficult to decompose, making treatment difficult with the activated sludge method, a major industrial wastewater treatment method. Soap-free emulsion polymerization does not use surfactants, but it is difficult to synthesize nanoparticles with a particle size of 100 nm or less.

[0007] This disclosure is made in view of these challenges, and its purpose is to improve the technology for producing polymer compound particles. [Means for solving the problem]

[0008] To solve the above problems, one aspect of this disclosure is a method for producing a polymer compound. This method comprises the steps of introducing raw materials for a polymer compound into the interior of a porous body and polymerizing the raw materials in the pores inside the porous body.

[0009] Another aspect of this disclosure is a porous body, which contains particles of a polymer compound in its internal pores.

[0010] Another aspect of this disclosure is a polymer compound particle, which has a particle size of 100 nm or less and does not contain a surfactant on its surface. [Effects of the Invention]

[0011] According to this disclosure, it is possible to improve the technology for producing polymer compound particles. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows the three-dimensional network structure of a methylcellulose gel. [Figure 2] This figure shows the synthesis procedure for nanoparticles. [Figure 3] This figure shows SEM images of nanoparticles synthesized under the experimental conditions shown in Table 1. [Figure 4]It is a figure showing a SEM image of the network of the methylcellulose gel prepared under the experimental conditions shown in Table 3. [Figure 5] It is a figure showing the relationship between the network size of methylcellulose used as a reaction field and the average particle diameter of the synthesized nanoparticles. [Figure 6] It is a figure schematically showing the state of water in the gel. [Figure 7] It is a figure showing the three-dimensional network structure of the melamine foam. [Figure 8] It is a figure showing the synthesis procedure of the nanoparticles. [Figure 9] It is a figure schematically showing the method of introducing styrene into the melamine foam. [Figure 10] It is a figure showing a SEM image of the nanoparticles synthesized under the experimental conditions shown in Table 4. [Figure 11] It is a figure showing a SEM image of the nanoparticles synthesized under the experimental conditions shown in Table 4. [Figure 12] It is a figure showing the information of the area where the average particle diameter was measured in Example 2-2. [Figure 13] It is a figure showing the average particle diameter of the nanoparticles measured for each area shown in Figure 12. [Figure 14] It is a figure showing the state of the colored styrene infiltrated into the melamine foam. [Figure 15] It is a figure showing the relationship between the polymerization temperature and the average particle diameter of the nanoparticles. [Figure 16] It is a figure showing the state of the dispersion liquid of each sample. [Figure 17] It is a figure showing SEM images of C-8 and C-4. [Figure 18] It is a figure showing an optical micrograph of the methylcellulose filled with glass beads. [Figure 19] It is a figure showing the relationship between the porosity of the methylcellulose and the average particle diameter of the nanoparticles. [Figure 20] It is a figure showing the state of methylene blue diffused in the methylcellulose. [Figure 21]This figure shows SEM images of benzyl methacrylate nanoparticles synthesized by the soap-free emulsion polymerization method and the manufacturing method according to the embodiment. [Figure 22] This figure shows SEM images of methyl methacrylate nanoparticles synthesized by the soap-free emulsion polymerization method and the manufacturing method according to the embodiment. [Figure 23] This figure shows SEM images of styrene nanoparticles synthesized by emulsion polymerization and the manufacturing method according to the embodiment. [Modes for carrying out the invention]

[0013] As an embodiment of this disclosure, a technique for producing nanoparticles of polymer compounds using voids inside a porous material as a reaction field will be described.

[0014] The method for producing a polymer compound according to the embodiment of this disclosure comprises the steps of introducing a raw material for a polymer compound into the interior of a porous body and polymerizing the raw material in the pores inside the porous body. In soap-free emulsion polymerization, it is thought that particles grow by the repeated aggregation of particle nuclei, but in the method of this embodiment, the aggregation of particle nuclei can be suppressed by the three-dimensional network structure of the porous body. As a result, nanoparticles can be produced without using surfactants, thereby reducing the burden on the environment.

[0015] The polymer compound may be any compound that can be synthesized by polymerizing monomers or oligomers. The polymer compound may be a thermoplastic resin such as polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, or polyvinyl acetate; an engineering plastic such as polyamide, polyethylene terephthalate, polycarbonate, or polyphenylene ether; a super engineering plastic such as polyphenylene sulfide, polytetrafluoroethylene, polysulfone, polyethersulfone, polyetheretherketone, or polyamideimide; or a thermosetting resin such as phenolic resin, epoxy resin, melamine resin, urea resin, or polyurethane.

[0016] The raw materials for the polymer compound may be monomers, oligomers, or mixtures thereof.

[0017] The porous material may be any porous material having pores inside into which raw materials for polymer compounds can be introduced. The porous material may be a foam made of, for example, melamine resin, urethane resin, phenolic resin, urea resin, acrylic resin, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, or ethylene vinyl acetate copolymer. In particular, melamine resin foam has excellent impact resistance and heat resistance, and since nanoparticles synthesized in the internal pores can be easily extracted simply by squeezing the foam, it can be repeatedly used as a reaction site for nanoparticles. The porous material may also be a gel of polysaccharides such as starch, cellulose, methylcellulose, agarose, pectin, or curdlan, or a gel of protein such as whey or gelatin. Even with gels such as starch, nanoparticles can be easily extracted by decomposing the porous material with enzymes or the like. Whey is obtained as a byproduct in the processing of dairy products, and much of it is discarded as is. By utilizing such unused waste, nanoparticles can be manufactured inexpensively while minimizing the burden on the environment. Furthermore, even when nanoparticles are used in the medical field, the impact on living organisms can be minimized. The porous body, structure 10, may be formed by a 3D printer using any technique such as material extrusion deposition (FDM), material jetting, binder jetting, solid light sintering (SLS), or stereolithography. In this case, the size of the pores can be adjusted more precisely and easily, so the particle size or particle size distribution of the polymer compound to be manufactured can be controlled more precisely and easily. For example, a large number of nanoparticles with uniform particle size can be manufactured at once. When nanoparticles are manufactured by introducing raw materials of a polymer compound from outside the porous body formed by a 3D printer into the pores inside the porous body, channels for the diffusion of the raw materials may be formed inside the porous body. In this case, in order to prevent nanoparticles formed in adjacent pores from aggregating through the channels, the diameter, shape, and arrangement of the pores and channels may be designed according to the type of polymer compound, its aggregating properties, the rate, time, and temperature of the polymerization reaction.

[0018] The size of the pores inside the porous material may be adjusted according to the particle size of the nanoparticles being manufactured. The smaller the particle size of the nanoparticles being manufactured, the smaller the pore size may be adjusted. The size of the pores inside the porous material may also be adjusted according to the type or cohesiveness of the polymer compound. The higher the cohesiveness of the polymer compound, the smaller the pore size may be adjusted.

[0019] When using foam as the porous material, the size of the pores may be adjusted by adjusting at least one of the following: the type and amount of foaming agent and foaming aid used in foam formation, the foaming method, and the foaming temperature. Alternatively, the porosity of the porous material may be reduced by introducing a filler into the porous material before polymerizing the raw materials of the polymer compound inside the porous material. The filler may be, for example, beads made of a material that does not chemically react with the raw materials of the polymer compound and the foam, such as glass, ceramics, carbon materials, resins, metals, or compounds. At least one of the type, amount, and particle size of the filler may be adjusted according to the particle size of the polymer compound to be manufactured. For example, the smaller the particle size of the polymer compound to be manufactured, the larger the amount or particle size of the filler may be adjusted. Also, the higher the cohesiveness of the polymer compound, the larger the amount or particle size of the filler may be adjusted. If the available particle sizes for the selected type of filler are limited, the amount of filler may be adjusted according to the particle size of the available filler. For example, the porosity of the foam to achieve the particle size of the polymer compound to be manufactured may be calculated based on the particle size of the filler used, and the amount of filler to achieve the calculated porosity may be determined. Furthermore, the type of filler may be selected according to the type of foam, the type of polymer compound to be manufactured, and the manufacturing cost, and the amount and particle size of the filler may be adjusted according to the selected type of filler.

[0020] When using gels such as polysaccharides or proteins as porous materials, the size of the pores may be adjusted by adjusting at least one of the types and concentrations of the polysaccharides or proteins that constitute the dispersed phase of the gel. As shown in the examples described later, generally, increasing the concentration of polysaccharides or proteins reduces the size of the pores, while decreasing the concentration increases the size of the pores. At least one of the types and concentrations of the dispersed phase of the gel may be adjusted according to the particle size of the polymer compound to be produced. For example, the smaller the particle size of the polymer compound to be produced, the higher the concentration of the dispersed phase of the gel may be adjusted. Also, the higher the cohesiveness of the polymer compound, the higher the gel concentration may be adjusted. Based on the molecular weight of the dispersed phase used, the porosity of the gel required to achieve the particle size of the polymer compound to be produced may be calculated, and the amount of dispersed phase required to achieve the calculated porosity may be determined. Furthermore, the type of dispersed phase may be selected according to the type of polymer compound to be produced, the production cost, the type and amount of the dispersion medium, etc., and the concentration of the dispersed phase may be adjusted according to the selected type of dispersed phase.

[0021] The step of polymerizing the raw materials may include a step of heating the porous body. Depending on the particle size of the polymer compound to be produced, at least one of the polymerization time and temperature of the raw materials may be adjusted. As shown in the examples described later, generally, increasing the polymerization temperature of the raw materials results in a larger particle size of the polymer compound. For example, the smaller the particle size of the polymer compound to be produced, the lower the heating temperature when polymerizing the raw materials may be adjusted. Also, the higher the cohesiveness of the polymer compound, the lower the heating temperature when polymerizing the raw materials may be adjusted, or the shorter the heating time may be adjusted.

[0022] As described above, the particle size of the polymer compound to be manufactured can be adjusted by at least one of the following: the size of the pores in the porous material, the polymerization time of the polymer compound raw materials, and the temperature. The particle size of the polymer compound to be manufactured may be adjusted by any one of the above, or by any two or three combinations thereof. For example, the particle size of the polymer compound to be manufactured may be reduced by adjusting the size of the pores in the porous material and adjusting the polymerization temperature of the polymer compound raw materials to a lower level. Alternatively, the particle size of the polymer compound to be manufactured may be reduced by adjusting the size of the pores in the porous material and adjusting the polymerization time of the polymer compound raw materials to a shorter level. There may be certain constraints on the heating temperature and heating time depending on the polymerization reaction rate and manufacturing cost of the polymer compound to be manufactured. For example, if the heating temperature is too low, the polymerization reaction rate will be slow, the manufacturing of the polymer compound will take a long time, and the manufacturing efficiency may be low. Also, if the heating time is too short, the raw materials may not diffuse sufficiently into the interior of the porous material, which may result in low manufacturing efficiency. Even in such cases, by adjusting the size of the pores in the porous material, it is possible to appropriately adjust the particle size of the polymer compound to be manufactured while maintaining high manufacturing efficiency.

[0023] The raw material may be introduced from the side of the porous body that is heated. This allows the raw material to diffuse efficiently into the interior of the porous body, enabling the production of polymer compound particles. The raw material may also be introduced by spreading it across the surface of the porous body that is heated. This allows the raw material to diffuse even more efficiently into the interior of the porous body, enabling the production of polymer compound particles. In the step of heating the porous body, the porous body may be heated at a temperature at which the rate at which the raw material volatilizes is approximately the same as the rate at which the raw material polymerizes. This allows the raw material to polymerize inside the porous body before it volatilizes to the outside of the porous body, thus enabling the production of polymer compound particles efficiently. The temperature at which the porous body is heated may be such that the rate at which the raw material volatilizes is 1 or more times the rate at which the raw material polymerizes, but 2 or less, 5 or less, 10 or less, 20 or less, 50 or less, or 100 or less.

[0024] Particles produced by the manufacturing method of this disclosure may be removed from the porous body and used. When a foam is used as the porous body, the internal particles can be removed by squeezing the foam. When a gel is used as the porous body, the internal particles can be removed by adding enzymes or solvents to decompose or dissolve the gel, or by solving the gel and then centrifuging it.

[0025] Porous materials can also be used as containers for storing manufactured particles. When particles are removed from a porous material for storage, there is a possibility that they may aggregate with adjacent particles during storage. By storing the particles together with the porous material, while the particles remain in the internal pores, the aggregation of particles can be suppressed.

[0026] The porous body according to the embodiments of this disclosure contains polymer compound particles in its internal pores. The porous body may be a foam or a gel. The particle size may be 100 nm or less. The particle size may be 95 nm or less, 90 nm or less, 85 nm or less, 80 nm or less, 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, or 30 nm or less. The particle size may also be the average particle diameter measured by analyzing an SEM image of the particle with image analysis software.

[0027] The polymer compound particles according to the embodiments of this disclosure have a particle size of 100 nm or less and do not contain surfactants on their surface. This makes it possible to provide nanoparticles with a low environmental impact. Furthermore, even when the nanoparticles are used in the medical field, the impact on living organisms can be minimized. The particle size may be 95 nm or less, 90 nm or less, 85 nm or less, 80 nm or less, 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, or 30 nm or less. The particle size may also be the average particle diameter measured by analyzing the SEM image of the particles with image analysis software.

[0028] [Example 1: Synthesis of nanoparticles using a polysaccharide gel as a reaction field] Nanoparticles were synthesized using methylcellulose (MC, molecular weight: 211,000, DS (number of hydroxyl groups substituted with methoxy groups per unit glucose ring): 1.8) and curdlan (CUD, molecular weight: 81,000) as porous materials.

[0029] When methylcellulose dissolves in cold water, it forms a colorless, transparent, viscous sol. When heated, hydrophobic aggregates begin to form around 42.5°C, increasing the viscosity. As the temperature rises, the aggregates grow and the bonding forces become stronger, and at approximately 60°C, it turns white and gels. Figure 1 shows the three-dimensional network structure of methylcellulose gel. The methylcellulose gel retains moisture within its network structure. Methylcellulose undergoes a sol-gel transition in response to temperature changes. Once gelled, it can be returned to a fluid sol by cooling.

[0030] Curdlan is a nearly linear β1,3-glucan synthesized from glucose by the microorganism Agrobacterium. It is insoluble in water at room temperature and most organic solvents, but soluble in strongly basic aqueous solutions such as NaOH solution. When curdlan is dispersed in water and heated, the dispersion gels. Curdlan is known to exist as a triple helix, single helix, or single chain depending on the temperature. Two types of gels can be created by the change in structure between these states. First, the dispersion becomes soluble in water at around 70°C. If cooled to around 40°C, a thermoreversible gel (lowset gel) is formed. If heated above 70°C to 85°C or higher, a thermoreversible gel (highset gel) is formed. In this example, since gelation in the heated state is required, the mixture was heated to 85°C to form a thermoreversible gel, which was then returned to a sol by dissolving it in NaOH solution.

[0031] Styrene (St) was used as the monomer for the polymer compound; 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044), potassium peroxodisulfate (KPS), and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086) were used as initiators; and distilled water was used as the reaction solvent. The distilled water was prepared using a pure water production device (Auto Still® WG250, manufactured by Yamato Scientific Co., Ltd.) and degassed by passing nitrogen through it for a sufficient time before use to prevent dissolved oxygen from interfering with radical polymerization.

[0032] Figure 2 shows the synthesis procedure for nanoparticles. A 30 mL screw-cap tube was used as the reaction vessel. In the experiment using methylcellulose, distilled water and styrene monomer were first emulsiond using a Free Micro Mixer (FMM), and then methylcellulose and an initiator were dissolved. In the experiment using curdlan, distilled water, curdlan, and styrene monomer were first treated with an emulsifier, and then the initiator was dissolved. Heating was carried out on a magnetic stirrer with a hot plate (RCH-1000, manufactured by Tokyo Rikakikai Co., Ltd.) at a reaction temperature of 70°C for 6 hours without stirring. After the reaction, the methylcellulose gel was cooled to room temperature and returned to a sol, and then the particles were separated by centrifugation. The curdlan gel was dissolved by adding an aqueous NaOH solution, and then the particles were separated by centrifugation.

[0033] [Measurement of average particle size and average mesh size] The particle and gel networks were observed using a scanning electron microscope (FE-SEM; JSM-7500F, JEOL Ltd.). Particle SEM samples were prepared by dropping a colloidal solution onto a mica flake with the surface layer peeled off using cellophane tape, vacuum drying, and then depositing a 10 nm thick osmium coating using an osmium coater (OPC60A, Philgen Co., Ltd.). Network SEM samples were prepared by creating a gel, freezing it with liquid nitrogen, and then freeze-drying it using a freeze-dryer (EYELA FREEZE DRYER FD-1000, Tokyo Rikakikai Co., Ltd.). After drying, the sample pieces were fixed to carbon tape, and then a 10 nm thick osmium coating was deposited. SEM images were analyzed using particle analysis software (Asahi Kasei Engineering Corporation). The CV value was calculated using the following formula. CV value [%] = (standard deviation) / (average particle size) × 100 The zeta potential was measured using a zeta potential measuring device (Zetasaizer Nano ZS, manufactured by Malvern Panalytical Ltd.).

[0034] [Example 1-1: Effects of initiator and gel type on particles] Multiple nanoparticles with different initiators and gel types were synthesized. Table 1 shows the experimental conditions in Example 1-1. [Table 1]

[0035] Figure 3 shows SEM images of nanoparticles synthesized under the experimental conditions shown in Table 1. Table 2 shows the physical properties of nanoparticles synthesized under the experimental conditions shown in Table 1. [Table 2]

[0036] The average particle size of the nanoparticles synthesized using gel was smaller than that of nanoparticle A-1 synthesized without gel, all being 100 nm or less. This is thought to be because the lack of fluidity in the gel suppressed Brownian motion of the particles within it, hindering aggregation and growth. Nanoparticles A-2 and A-3, synthesized using methylcellulose, were able to be synthesized with an average particle size of 50 nm or less.

[0037] [Examples 1-2: Effect of gel concentration on particles] Nanoparticles were synthesized using multiple gels with different concentrations of dispersed phase as reaction fields. Table 3 shows the experimental conditions in Examples 1-2. [Table 3]

[0038] Figure 4 shows an SEM image of the methylcellulose gel network prepared under the experimental conditions shown in Table 3. Figure 5 shows the relationship between the methylcellulose network size used as the reaction field and the average particle size of the synthesized nanoparticles. The gel network size was calculated by measuring the longitudinal distance of the network at 150 points using the linear distance measurement function of particle analysis software and calculating the average.

[0039] As can be seen from Figures 4 and 5, increasing the concentration of methylcellulose reduced the mesh size. As the mesh size decreased, the average particle size of the nanoparticles also decreased, and a correlation was observed between the two. B-1 showed the greatest variation in average particle size, which is thought to be due to heterogeneity in the reaction system caused by the large variation in the mesh size of the methylcellulose. As the concentration of methylcellulose increased, the distribution of nanoparticle sizes also became more uniform.

[0040] To consider the reason why the gel's mesh size contributed to the average particle size of nanoparticles, we consider the state of water inside the polysaccharide gel. Figure 6 schematically shows the state of water in the gel. Water in the gel can be broadly classified into bound water, intermediate water, and free water. Bound water is strongly oriented and interacts with the polysaccharide chains by hydrogen bonds, and is unable to move freely. Intermediate water is located outside of this and is subject to weak interactions. Free water is at a distance from the polysaccharide chains and can move freely without interaction, but its outflow from the tissue is hindered, and it has lost its fluidity. Thus, many reports indicate that the mobility of water is restricted compared to pure water or dilute aqueous solutions, as it is bound not only by interactions with the hydrophilic groups of the polymer chains but also by the mesh, hindering its free thermal motion as a liquid. In other words, as the mesh size decreases, the amount of bound water increases, the proportion of free water decreases, and the mobility decreases, thus suppressing Brownian motion of particles. This is thought to hinder particle aggregation and inhibit particle growth.

[0041] [Example 2: Synthesis of nanoparticles using foam as a reaction field] Nanoparticles were synthesized using melamine foam (MF: manufactured by Wako Co., Ltd.) as a porous material. Melamine foam is obtained by foam molding melamine resin and is used in abrasive sponges for cleaning tools and soundproofing materials. Melamine resin can be obtained by polycondensation of melamine and formaldehyde. Figure 7 shows the three-dimensional network structure of melamine foam. Melamine foam has a network structure of 100 μm or more and has excellent impact resistance and heat resistance.

[0042] Figure 8 shows the synthesis procedure for nanoparticles. In Example 2-1, a φ40 × 18 [mm] melamine foam was used as the porous material for the reaction field, while in Examples 2-2 and 2-3, a φ30 × 15 [mm] melamine foam was used as the porous material for the reaction field. Distilled water in which potassium peroxodisulfate (KPS) was dissolved as an initiator and styrene (St) as a monomer for the polymer compound were impregnated into the melamine foam. The mixture was then placed in a glass petri dish, sealed with a silicone film, and heated on a hot plate to carry out polymerization. In all experiments, the polymerization time was 24 hours. After polymerization, the particles were extracted by squeezing the melamine foam.

[0043] [Example 2-1: Method for introducing raw materials into the reaction field] Nanoparticles were synthesized by introducing the raw material styrene into melamine foam, which served as the reaction site, using several different methods. Figure 9 schematically shows the method of introducing styrene into melamine foam. Table 4 shows the experimental conditions in Example 2-1. [Table 4]

[0044] Figures 10 and 11 show SEM images of nanoparticles synthesized under the experimental conditions shown in Table 4. Table 5 shows the physical properties of nanoparticles synthesized under the experimental conditions shown in Table 4. [Table 5]

[0045] In A-1, where styrene was introduced as an emulsion into melamine foam, several aggregates resembling linked particles were observed. It is thought that the emulsion that did not completely dissolve in water polymerized like an adhesive. In A-2, where styrene was introduced directly into the center of the melamine foam, particles with excellent dispersibility were produced. However, as shown in Figure 11(a), many large clumps were also present. It is thought that the styrene that did not completely diffuse into the water polymerized as is. In A-3, where styrene was introduced directly into the bottom of the melamine foam, particles with excellent dispersibility were also produced. In A-3, no clumps like those in A-2 were observed. It is thought that because the styrene was present on the heated surface, it completely diffused into the water due to the heat. However, the CV value in A-3 was large. This is thought to be due to differences in styrene concentration depending on the location, resulting in variations in particle size. Also, judging from the comparison of SEM images, it appears that A-3 had a larger number of particles than A-2. In A-3, as shown in Figure 11(b), parts with a neat arrangement were also observed. Based on the above, it is considered best to introduce the styrene so that it is in contact with the heating surface.

[0046] [Example 2-2: Particle size distribution for each area of ​​the reaction field] Styrene was dropped onto the heated surface of melamine foam to carry out polymerization, and particles were collected from each area of ​​the melamine foam to measure the particle size distribution. Table 6 shows the experimental conditions in Example 2-2. Figure 12 shows information on the areas where the average particle size was measured in Example 2-2. [Table 6]

[0047] Figure 13 shows the average particle size of nanoparticles measured for each area shown in Figure 12. Table 7 shows the CV values ​​of the nanoparticle sizes measured for each area. [Table 7]

[0048] Area 1, where styrene was introduced, produced the largest particles and had the highest coefficient of variation (CV). As the particle size moved radially away from the center, the average particle size decreased, and in Area 4, particles smaller than 100 nm were synthesized, resulting in monodisperse particles with a CV of 10 or less. In Areas 5 and 6, which were separated by height, particles smaller than 100 nm were obtained, and both were monodisperse with a CV of 10 or less.

[0049] Monomer diffusion is thought to consist of two main types: diffusion driven primarily by a concentration gradient, and diffusion caused by the volatilization of monomers due to heat. Diffusion due to a concentration gradient diffuses monomers three-dimensionally in both the radial and vertical directions. Diffusion due to heat occurs because heating is applied from below, causing monomers introduced to the heated surface to volatilize from below and diffuse upwards. Therefore, it is thought that only concentration diffusion acts in the radial direction, while both concentration and thermal diffusion act in the vertical direction. Due to this difference, monomers diffused more effectively in the vertical direction than in the radial direction, resulting in particles with a smaller CV value and greater monodispersity.

[0050] To further investigate the results of Example 2-2, styrene was colored with quinizalin to determine whether concentration diffusion or thermal diffusion was dominant. Figure 14 shows the colored styrene impregnated into melamine foam. The colored styrene was introduced into the entire bottom surface or only the center of the melamine foam, placed in a glass petri dish, sealed with a silicone film, and heated or left to stand for 2 hours. Figure 14(a) shows the state after introducing the colored styrene into the bottom surface of the melamine foam, Figure 14(b) shows the state after heating the bottom surface for 2 hours from the state in Figure 14(a), and Figure 14(c) shows the state after leaving it to stand for 2 hours from the state in Figure 14(a). Figure 14(d) shows the state after introducing the colored styrene into the center of the bottom surface of the melamine foam, Figure 14(e) shows the state after heating the bottom surface for 2 hours from the state in Figure 14(d), and Figure 14(f) shows the state after leaving it to stand for 2 hours from the state in Figure 14(d). Figure 14(g) shows the state of the silicon film in the condition shown in Figure 14(b) after heating for 2 hours, and Figure 14(h) shows the state of the silicon film in the condition shown in Figure 14(c) after standing for 2 hours.

[0051] As shown in Figure 14, a clear difference was observed between heating and standing. The heated sample was lighter in color than when it was first introduced, suggesting that styrene had evaporated. The precipitation of quinizalin as a powder also confirmed that styrene had evaporated. The sample left standing without heating showed no difference from the initial state even after 2 hours. From these findings, it is thought that monomer diffusion is mainly controlled by heat. Therefore, it is preferable to introduce styrene by spreading it uniformly on the heated surface. Furthermore, as shown in Figure 14, a difference was also observed between the heated and unheated samples in the silicone film used as a sealing lid. Quinizarin was attached to the silicone film of the heated sample, and it was stained a light orange color. From this, it was confirmed that heating allowed the styrene to reach the top surface of the melamine foam.

[0052] [Examples 2-3: Effect of polymerization temperature on particles] To investigate the effect of polymerization temperature on nanoparticles, monomers were polymerized at various temperatures to synthesize nanoparticles. Table 8 shows the experimental conditions in Examples 2-3. [Table 8]

[0053] Figure 15 shows the relationship between polymerization temperature and the average particle size of nanoparticles. Table 9 shows the physical properties of nanoparticles synthesized under the experimental conditions shown in Table 8. Figure 16 shows the appearance of the dispersions of each sample. Figure 17 shows SEM images of C-8 and C-4. [Table 9]

[0054] As shown in Figure 15, a positive correlation was found between polymerization temperature and average particle size. The average particle size of the sample polymerized using melamine foam was smaller than that of the sample polymerized at the same temperature without using melamine foam. This is thought to be because the three-dimensional network structure of melamine foam suppresses Brownian motion, preventing aggregation of particles during the growth process. As shown in Figure 16, for C-1 to C-4, which were polymerized without melamine foam, a dense white dispersion was obtained as the temperature increased. No particles were produced in C-1, possibly due to the low temperature. For C-5 to C-8, which were polymerized using melamine foam, a dense white dispersion was also obtained as the temperature increased. For C-8, almost no particles were obtained, and as shown in Figure 17(a), non-particle material was obtained. Even in C-4, which was polymerized at the same temperature, some crystals like those shown in Figure 17(b) were obtained, suggesting that potassium crystals derived from the initiator precipitate when polymerization is performed at 90°C. The reason particles were not formed in C-8 is thought to be that the high temperature caused the styrene to volatilize quickly, reaching the surface of the melamine foam before it could be used in polymerization, and adhering to the silicone film as oil droplets. From this, it can be concluded that the optimal polymerization temperature is the temperature at which the rate of monomer volatilization and the rate at which it is consumed by the polymerization reaction are approximately the same. For example, in this embodiment, the optimal polymerization temperature is 70-80°C. Furthermore, comparing C-1 and C-5, particles were synthesized when melamine foam was used, even though the temperature was the same. Considering that the specific heat of melamine foam is 669.4 [J / kg·K] and the specific heat of water is 4184 [J / kg·K], it is thought that in C-5, the melamine foam, which was spread throughout the entire system, heated up first due to its lower specific heat, and continued to warm the entire system, resulting in particle synthesis.

[0055] [Example 2-4: Effect of porosity on particles] To confirm the effect of the porosity of the porous material, which serves as the reaction site, on the nanoparticles, nanoparticles were synthesized in melamine foam in which the mesh size was controlled by filling with glass beads. Table 10 shows the experimental conditions in Examples 2-4. [Table 10]

[0056] Figure 18 shows an optical microscope image of melamine foam filled with glass beads. Figure 19 shows the relationship between the porosity of the melamine foam and the average particle size of the nanoparticles. Table 11 shows the physical properties of the nanoparticles synthesized under the experimental conditions shown in Table 10. The mesh size of the melamine foam was evaluated by the porosity of the melamine foam after filling with glass beads. The porosity of the melamine foam was calculated using the following formula. The porosity of melamine foam [%] = (saturation water supply [g]) / (density of water [g / cm³]) 3 ]) × (Volume of melamine foam [cm³ 3 ]))×100 [Table 11]

[0057] As shown in Figure 19, it was found that using melamine foam as a polymerization site resulted in a smaller average particle size compared to when it was not used. Furthermore, it was revealed that the average particle size decreased as the porosity of the melamine foam decreased. According to Newton's law of viscosity, the flow velocity of a fluid can be considered to be zero at the contact surface with a solid material, and in that vicinity, water cannot move freely (bound water). It is thought that the bound water in melamine foam is strongly oriented by hydrogen bonds, similar to the bound water in the gel mentioned above. Filling with glass beads reduces the confining space and increases the specific surface area. As a result, the proportion of free water decreases, and the movement of water molecules is suppressed, thus weakening the Brownian motion of the particles. Therefore, it is thought that the aggregation of particles is suppressed and growth is inhibited.

[0058] To confirm that diffusion due to Brownian motion within melamine foam is suppressed by filling it with glass beads, a methylene blue aqueous solution was diffused into the melamine foam. The size of the melamine foam used was 5 mm (length) x 20 mm (width) x 40 mm (height). Figure 20 shows the diffusion of methylene blue into the melamine foam. The porosity of the melamine foam on the left is 90%, and the porosity of the melamine foam on the right is 60%. As shown in Figure 20, the diffusion rate of the melamine foam with 60% porosity, which was filled with glass beads, was significantly slower than that of the melamine foam with 90% porosity. In addition, a concentration gradient was observed in the melamine foam with 90% porosity, while little concentration gradient was observed in the melamine foam with 60% porosity. This indicates that the diffusion rate within melamine foam can be significantly suppressed by filling it with glass beads. In other words, it is thought that filling with glass beads suppresses Brownian motion of particles, suppresses particle aggregation, and inhibits growth, resulting in a smaller particle size.

[0059] [Example 3-1: Synthesis of benzyl methacrylate nanoparticles] Nanoparticles were synthesized in the same manner as in Example 2, using benzyl methacrylate (BMA) as the monomer of the polymer compound, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044), potassium peroxodisulfate (KPS), and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086) as initiators, distilled water as the reaction solvent, and melamine foam as the reaction field.

[0060] Figure 21(a) shows an SEM image of benzyl methacrylate nanoparticles synthesized by soap-free emulsion polymerization using a batch reactor. The average particle size of the nanoparticles was 322 nm. Figure 21(b) shows an SEM image of benzyl methacrylate nanoparticles synthesized using melamine foam as the polymerization site. The average particle size of the nanoparticles was 55 nm. This demonstrates that the average particle size of nanoparticles can be reduced by synthesizing them using melamine foam as the polymerization site.

[0061] [Example 3-2: Synthesis of methyl methacrylate nanoparticles] Nanoparticles were synthesized in the same manner as in Example 2, using methyl methacrylate (MMA) as the monomer of the polymer compound, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044), potassium peroxodisulfate (KPS), and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086) as initiators, distilled water as the reaction solvent, and a batch reactor or melamine foam as the reaction field.

[0062] Figure 22(a) shows an SEM image of methyl methacrylate nanoparticles synthesized by soap-free emulsion polymerization using a batch reactor. The average particle size of the nanoparticles was 109 nm. Figure 22(b) shows an SEM image of methyl methacrylate nanoparticles synthesized using melamine foam as the polymerization site. The average particle size of the nanoparticles was 76 nm. This demonstrates that the average particle size of nanoparticles can be reduced by synthesizing them using melamine foam as the polymerization site.

[0063] [Example 4: Synthesis of nanoparticles of styrene with surfactant added] Styrene (St) was used as the monomer for the polymer compound; 10 mmol / l sodium dodecyl sulfate (SDS) was used as the surfactant; 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044), potassium peroxodisulfate (KPS), and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086) were used as initiators; distilled water was used as the reaction solvent; and a batch reactor or melamine foam was used as the reaction site. First, distilled water, surfactant, and initiator were introduced into the melamine foam to form surfactant micelles in the pores of the melamine foam. Subsequently, the monomer was introduced into the interior from the bottom of the melamine foam while heating the bottom surface of the melamine foam.

[0064] Figure 23(a) shows an SEM image of styrene nanoparticles synthesized by emulsion polymerization using a batch reactor. The average particle size of the nanoparticles was 32 nm. Figure 23(b) shows an SEM image of styrene nanoparticles synthesized using melamine foam on which SDS micelles were formed as the polymerization site. The average particle size of the nanoparticles was 23 nm. This demonstrates that the average particle size of nanoparticles can be reduced by synthesizing nanoparticles using emulsion polymerization with melamine foam as the polymerization site.

[0065] The present disclosure has been explained above based on examples. These examples are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure. [Industrial applicability]

[0066] Polymer microparticles produced by the manufacturing method disclosed herein can be used in a wide range of applications in various fields, including materials fields such as cosmetics and paints, information technology fields, and medical fields. For example, in cosmetics, by immobilizing titanium dioxide on nylon particles, it is possible to improve spreadability and adhesion without impairing the UV protection effect. In paints, it can be used to improve rheology. In the information technology field, it can be used as an electrically conductive polymer as a switching element or as a self-temperature regulator. In the medical field, it can be applied as a drug delivery system in which a drug is supported on the particles and delivered to the target site.

Claims

1. The steps include introducing raw materials and fillers (in no particular order) of a polymer compound into the interior of a porous body, The steps include: polymerizing the raw material in the pores inside the porous body at 60 to 80°C to produce particles of the polymer compound with a particle size of 100 nm or less, corresponding to the size of the pores; Equipped with, The porous body is melamine foam, The aforementioned raw material is styrene or methyl methacrylate. The filler is a bead made of glass, ceramics, carbon material, resin, or metal. A method for producing polymer compounds.

2. Depending on the particle size of the polymer compound to be manufactured, at least one of the type, amount, and particle size of the filler is adjusted. A method for producing a polymer compound according to claim 1.

3. The steps include introducing raw materials and fillers (in no particular order) of a polymer compound into the interior of a porous body, The steps include polymerizing the raw material in the pores inside the porous body at 60 to 80°C, Equipped with, Depending on the particle size of the polymer compound to be manufactured, at least one of the type, amount, and particle size of the filler is adjusted. The porous body is melamine foam, The aforementioned raw material is styrene or methyl methacrylate. The particle size of the polymer compound is 100 nm or less. The filler is a bead made of glass, ceramics, carbon material, resin, or metal. A method for producing polymer compounds.

4. The smaller the particle size of the polymer compound being manufactured, the greater the adjustment of at least one of the filler's quantity and particle size. A method for producing a polymer compound according to claim 2 or 3.

5. Depending on the particle size of the polymer compound to be manufactured, at least one of the following is adjusted: the size of the pores, the time for polymerization of the raw materials, and the temperature. A method for producing a polymer compound according to any one of claims 1 to 4.

6. The step of polymerizing the raw materials includes the step of heating the porous body, The raw material is introduced from the side of the porous body that is heated. A method for producing a polymer compound according to any one of claims 1 to 5.

7. The raw material is introduced by spreading it over the heated surface of the porous body. A method for producing a polymer compound according to claim 6.

8. In the step of heating the porous body, the porous body is heated at a temperature such that the rate at which the raw material volatilizes and the rate at which the raw material polymerizes are approximately the same. A method for producing a polymer compound according to claim 6 or 7.

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