Method for producing composite particles and composite particles

Abstract

To provide particles having a uniform particle size.SOLUTION: This method includes mixing an alkyl halide-based hydrophobic solvent containing a vinyl chloride-based polymer with an aqueous solvent to form a fluid dispersion, and stirring the fluid dispersion to form droplets of the hydrophobic solvent containing the vinyl chloride-based polymer in the aqueous solvent. Then, this method involves heating the fluid dispersion to evaporate the hydrophobic solvent from the droplets composed of the hydrophobic solvent containing the vinyl chloride-based polymer. As a result, it is possible to obtain vinyl chloride-based polymer particles composed of the vinyl chloride-based polymer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing vinyl chloride polymer particles, a method for producing composite particles, and composite particles. [Background technology]

[0002] Micro-sized polymer particles are in demand as functional materials in various fields, for example, as fillers, spacers, abrasives, etc. A common method for producing such polymer particles is suspension polymerization, in which a monomer and a water solvent are mechanically stirred to form a suspension, and then the monomer is polymerized to obtain polymer particles.

[0003] Cellulose nanofibers (CNFs), which are cellulose fibers defibrated to the maximum extent possible, are being explored for use in a variety of fields due to their high elasticity, high strength, low expansion, and safety. Despite their great potential, CNFs face significant challenges in nanocomposite fabrication. Plants are composed of highly hierarchical structures, and CNFs, which are molecular aggregates of cellulose, are arranged in a complex and rigid manner. Strong intermolecular hydrogen bonds pose a major obstacle to defibration and compounding with resins. CNFs possess numerous hydroxyl groups derived from cellulose molecules, making them highly hydrophilic. As defibration progresses, their specific surface area increases, amplifying the effects of hydrogen bonds. Therefore, it is extremely difficult to nano-disperse CNFs directly into hydrophobic resins and fully utilize their additive effects.

[0004] For example, Patent Document 1 proposes forming a coating layer made of cellulose fibers on the surface of an assembly of polymerizable monomers in an aqueous solvent, and polymerizing the polymerizable monomer in the assembly on which the coating layer is formed, thereby producing composite particles consisting of a coating layer made of cellulose fibers and a polymer covered by the coating layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-38949 Summary of the Invention [Problem to be solved by the invention]

[0006] The method of Patent Document 1 can only be applied to polymers that can be polymerized by suspension polymerization, which involves polymerizing polymerizable monomers in an aqueous solvent to obtain a polymer. For example, it is very difficult to obtain well-shaped polymer particles or composite particles using the method of Patent Document 1 for polyvinyl chloride, whose monomer is gaseous at room temperature.

[0007] The present invention has been proposed in view of the above-mentioned problems associated with the conventional technology in order to preferably solve these problems, and aims to provide a method for producing vinyl chloride-based polymer particles that can easily produce well-shaped vinyl chloride-based polymer particles, a method for producing composite particles containing vinyl chloride-based polymer particles and nanopolysaccharides, and composite particles containing vinyl chloride-based polymer particles and nanopolysaccharides. [Means for solving the problem]

[0008] In order to overcome the above-mentioned problems and achieve the intended object, the method for producing vinyl chloride polymer particles according to the present invention comprises the steps of: a dispersion liquid obtained by mixing an alkyl halide hydrophobic solvent containing a vinyl chloride polymer with an aqueous solvent is stirred to form droplets of the hydrophobic solvent containing the vinyl chloride polymer in the aqueous solvent; heating the dispersion to evaporate the hydrophobic solvent from the droplets; The gist of the present invention is to obtain vinyl chloride polymer particles formed from the vinyl chloride polymer.

[0009] In order to overcome the above problems and achieve the intended object, the method for producing composite particles according to the present invention comprises: A mixed solution is prepared by mixing a halogenated alkyl hydrophobic solvent containing a vinyl chloride polymer and a dispersion medium containing nanopolysaccharides, a dispersion obtained by mixing the mixed liquid and an aqueous solvent is stirred to form droplets of the mixed liquid containing the vinyl chloride polymer and the nanopolysaccharide in the aqueous solvent; heating the dispersion to evaporate the hydrophobic solvent from the droplets; The gist of the present invention is to obtain composite particles having vinyl chloride-based polymer particles formed from the vinyl chloride-based polymer and the nanopolysaccharide disposed on the vinyl chloride-based polymer particles.

[0010] In order to overcome the above problems and achieve the intended object, the composite particles according to the present invention comprise: vinyl chloride polymer particles; and nanopolysaccharides disposed at least inside the vinyl chloride polymer particles. [Effects of the Invention]

[0011] The method for producing vinyl chloride polymer particles according to the present invention can be applied to polymers that cannot be obtained by room temperature suspension polymerization, and can easily produce well-shaped vinyl chloride polymer particles. The method for producing composite particles according to the present invention can be applied to vinyl chloride polymers that cannot be obtained by room temperature suspension polymerization, and can easily produce composite particles in which nanopolysaccharides are arranged on well-shaped vinyl chloride polymer particles. The composite particles according to the present invention provide the combined function of the vinyl chloride polymer particles and the nanopolysaccharides disposed on the vinyl chloride polymer particles. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a process for producing vinyl chloride polymer particles of the present invention. [Figure 2] FIG. 1 is an explanatory diagram showing an example of a process for producing vinyl chloride polymer particles of the present invention. [Figure 3] FIG. 1 is an explanatory diagram showing an example of a process for producing composite particles of the present invention. [Figure 4] FIG. 1 is an explanatory diagram showing an example of a process for producing composite particles of the present invention. [Figure 5] FIG. 1 is an explanatory diagram showing an example of a process for producing composite particles of the present invention. [Figure 6] FIG. 1 is an explanatory diagram schematically illustrating the process of forming a composite particle of the present invention, in which a nanopolysaccharide is disposed inside a vinyl chloride-based polymer particle. [Figure 7] FIG. 1 is an explanatory diagram schematically illustrating the process of forming composite particles of the present invention, in which nanopolysaccharides are arranged on the surface of vinyl chloride polymer particles. [Figure 8] Schematic diagrams showing composite particles of the present invention: (a) nanopolysaccharides are disposed on the surface of a vinyl chloride polymer, (b) nanopolysaccharides are disposed inside a vinyl chloride polymer, and (c) nanopolysaccharides are disposed from the surface to the inside of a vinyl chloride polymer. [Figure 9] FIG. 1 is an explanatory diagram showing the mechanism of suspension polymerization. [Figure 10] This is a photograph showing that PVC is in a semi-dissolved state in methylene chloride. [Figure 11] 1 is an electron microscope photograph of vinyl chloride polymer particles of Example 1, the magnification of which is 400 times. [Figure 12] 1 is an electron microscope photograph of vinyl chloride polymer particles of Example 1, the magnification of which is 10,000 times. [Figure 13] 1 is an electron microscope photograph of vinyl chloride polymer particles of Example 1, the magnification of which is 20,000 times. [Figure 14] 1 is an electron microscope photograph of vinyl chloride polymer particles of Example 1, the magnification of which is 400 times. [Figure 15] 1 is an electron microscope photograph of vinyl chloride polymer particles of Example 1, the magnification of which is 50 times. [Figure 16] 1 is an electron microscope photograph of polyvinyl chloride raw material particles used in the vinyl chloride polymer particles of Example 1, taken at a magnification of 50 times. [Figure 17] 1 is an electron microscope photograph showing a comparison between vinyl chloride polymer particles of Example 1 and polyvinyl chloride raw material particles used in the vinyl chloride polymer particles of Example 1. [Figure 18] 1 is an electron microscope photograph of the composite particles of Example 2, taken at a magnification of 400 times. [Figure 19] 1 is an electron microscope photograph of the composite particles of Example 2, taken at a magnification of 10,000 times. [Figure 20] 1 is an electron microscope photograph of the composite particles of Example 2, at a magnification of 20,000 times. [Figure 21] 1 is an electron microscope photograph showing a cross section of a composite particle of Example 2. The magnification is 400 times. [Figure 22] 1 is an electron microscope photograph of the composite particles of Example 3, taken at a magnification of 400 times. [Figure 23] 1 is an electron microscope photograph of the composite particles of Example 3, taken at a magnification of 10,000 times. [Figure 24] 1 is an electron microscope photograph showing a cross section of a composite particle of Example 3. The magnification is 400 times. [Figure 25] 1 is an electron microscope photograph showing a cross section of a composite particle of Example 3. The magnification was 10,000 times. [Figure 26] FIG. 1 is a diagram showing infrared absorption spectra of Examples 1, 2, and 3. [Figure 27] FIG. 2 is an explanatory diagram showing a method for forming a film. [Figure 28] FIG. 1 is a diagram showing the measurement results of haze value. [Figure 29] FIG. 1 is a diagram showing the tensile strength of the films of Examples 1 to 3. [Figure 30] FIG. 1 is a schematic diagram showing a film of an example. [Figure 31] 1 is an electron microscope photograph of the composite particles of Example 6, the magnification of which is 200 times. [Figure 32] 1 is an electron microscope photograph of the composite particles of Example 6, taken at a magnification of 800 times. [Figure 33] 1 is an electron microscope photograph of the composite particles of Example 6, taken at a magnification of 20,000 times. [Figure 34]1 is an electron microscope photograph showing a cross section of a composite particle of Example 6. The magnification is 500 times. [Figure 35] 34 is an electron microscope photograph showing a cross section of a composite particle of Example 6. The squared area in FIG. 34 is enlarged and shown at a magnification of 3000 times. [Figure 36] 35 is an electron microscope photograph showing a cross section of a composite particle of Example 6. The squared area in FIG. 35 is enlarged and shown at a magnification of 50,000 times. [Figure 37] FIG. 1 shows the results of a liquid chromatogram. [Figure 38] FIG. 10 is an explanatory diagram showing the mechanism of formation of the composite particles of Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Vinyl chloride polymer particles) The vinyl chloride polymer particles (hereinafter simply referred to as PVC particles) according to the present invention can be made into micro-sized particles with an average particle size of 1 mm or less. Specifically, the average particle size of the PVC particles is preferably in the range of 5 μm to 800 μm, more preferably in the range of 10 μm to 500 μm. The PVC particles having the aforementioned average particle size are convenient when added to other materials. The average particle size in the present disclosure is measured by flow image analysis and scanning electron microscopy (SEM).

[0014] (vinyl chloride polymer) The vinyl chloride polymer of the vinyl chloride polymer particles (hereinafter simply referred to as vinyl chloride polymer) is a polymer obtained by polymerizing vinyl chloride monomer alone, or a copolymer obtained by copolymerizing vinyl chloride monomer and a monomer copolymerizable with vinyl chloride monomer (hereinafter sometimes referred to as copolymerizable monomer). The vinyl chloride polymer may be composed solely of a polymer or copolymer of a single monomer, or may be composed of a combination of multiple polymers and / or copolymers of a single monomer.

[0015] Examples of copolymerizable monomers include α-olefin monomers such as ethylene, propylene, 1-butene, 2-butene, 1-pentene, 1-hexene, 1-heptane, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4.4-dimethyl-1-hexene, 4.4-dimethyl-1-pentene, 4-ethyl-1-hexene, and 3-ethyl-1-hexene; aromatic monomers such as styrene and α-methylstyrene;Methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, propyl methacrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, di-n-butyl maleate, diisobutyl maleate, di-n-pentyl maleate, di-n-hexyl maleate, di-2-ethylhexyl maleate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, di-n-butyl fumarate, diisobutyl fumarate, di-n- Pentyl, di-n-hexyl fumarate, di-2-ethylhexyl fumarate, dimethyl itaconate, diethyl itaconate, dipropyl itaconate, di-n-butyl itaconate, diisobutyl itaconate, di-n-pentyl itaconate, di-n-hexyl itaconate, di-2-ethylhexyl itaconate, dimethyl citraconate, diethyl citraconate, dipropyl citraconate, di-n-butyl citraconate, diisobutyl citraconate, di-n-pentyl citraconate, di-n-hexyl citraconate, di-2-ethylhexyl citraconate Dimethyl mesaconic acid, diethyl mesaconic acid, dipropyl mesaconic acid, di-n-butyl mesaconic acid, diisobutyl mesaconic acid, di-n-pentyl mesaconic acid, di-n-hexyl mesaconic acid, di-2-ethylhexyl mesaconic acid, dimethyl glutaconate, diethyl glutaconate, dipropyl glutaconate, di-n-butyl glutaconate, diisobutyl glutaconate, di-n-pentyl glutaconate, di-n-hexyl glutaconate, di-2-ethylhexyl glutaconate, dimethyl allylmalonate, diethyl allylmalonate, allylmalonate ethylenically unsaturated carboxylic acid alkyl esters such as dipropyl allyl malonate, di-n-butyl allylmalonate, diisobutyl allylmalonate, di-n-pentyl allylmalonate, di-n-hexyl allylmalonate, di-2-ethylhexyl allylmalonate, dimethyl allylmalonate, diethyl allylmalonate, dipropyl allylmalonate, di-n-butyl allylmalonate, diisobutyl allylmalonate, di-n-pentyl allylmalonate, di-n-hexyl allylmalonate, and di-2-ethylhexyl allylmalonate; vinyl ester monomers such as vinyl acetate and vinyl propionate;Examples include α,β-ethylenically unsaturated monocarboxylic acid amides such as acrylamide and methacrylamide; vinyl ether monomers such as vinyl methyl ether and vinyl cetyl ether; and vinylidene compounds such as vinylidene chloride.

[0016] Specific examples of vinyl chloride polymers include polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride-polyvinylidene chloride which is a complex of polyvinyl chloride and polyvinylidene chloride, polyvinyl chloride-vinyl acetate copolymer, polyvinyl chloride-ethylene copolymer, and acrylonitrile-vinylene chloride copolymer.

[0017] (Method of producing vinyl chloride polymer particles) Next, a method for producing PVC-based particles will be described. A PVC solution is prepared by adding a vinyl chloride polymer to a hydrophobic solvent (see FIG. 1(a)). Here, in the PVC solution, the vinyl chloride polymer may be in a dissolved state in which it is completely dissolved in the hydrophobic solvent, or the vinyl chloride polymer may be in a semi-dissolved state. Here, "semi-dissolved state" refers to a state in which the vinyl chloride polymer is dispersed as fine particles in the hydrophobic solvent (colloidal state). In other words, according to the method for producing PVC-based particles of the present disclosure, PVC-based particles can be formed even when the vinyl chloride polymer is in a semi-dissolved state, in which it is not completely dissolved in the hydrophobic solvent. PVC-based particles can be easily formed from vinyl chloride polymers, which are inherently difficult to dissolve in organic solvents. Note that vinyl chloride polymers are preferably in the form of relatively fine granules or chunks for dissolution in the hydrophobic solvent; for example, crushed material crushed to a size of about several millimeters can be used.

[0018] A PVC solution is mixed with an aqueous solvent to prepare a dispersion. For example, a PVC solution in which a PVC polymer is partially or completely dissolved can be added to an aqueous solvent (see Figure 1(a)). The dispersion may contain a thickener if necessary. In this case, the viscosity of the dispersion is increased by adding a thickener to the aqueous solvent. Next, the dispersion is stirred (see Figure 1(b)), and the PVC solution in the dispersion is broken into droplets (see Figure 1(c)). The droplets formed at this time contain the PVC polymer dispersed in hydrophobic solvent domains.

[0019] Next, the dispersion is heated to evaporate the hydrophobic solvent from the droplets of PVC solution (droplets) (see Figure 2(a)). During this process, the dispersion is continuously stirred. As the hydrophobic solvent evaporates from the droplets, the remaining vinyl chloride polymer solidifies into particles, yielding PVC particles (see Figure 2(b)). The PVC particles are then recovered by necessary processing such as filtration and washing. The PVC particles may also be classified to further standardize the particle size.

[0020] (hydrophobic solvent) The hydrophobic solvent can be one that can dissolve (semi-dissolve) the vinyl chloride polymer and is not easily mixed with water (aqueous dispersion medium). Furthermore, the hydrophobic solvent can be a so-called low-boiling hydrophobic solvent that has a boiling point lower than that of water (aqueous dispersion medium). Examples of the hydrophobic solvent include alkyl halide hydrophobic organic solvents such as methylene chloride, chloroform, and ethane dichloride.

[0021] (Ratio of hydrophobic solvent to PVC) The PVC solution is preferably prepared so that the vinyl chloride polymer is in the range of 0.5 wt% to 50 wt%, more preferably 2 wt% to 20 wt%. When the proportion of the vinyl chloride polymer in the PVC solution is in this range, it is possible to achieve an appropriate viscosity. This makes it possible to stabilize the droplets formed from the PVC solution in the dispersion. Note that if the proportion of the vinyl chloride polymer in the PVC solution is low, the viscosity of the PVC solution decreases and the droplets become unstable, while if the proportion of the vinyl chloride polymer in the PVC solution is high, the viscosity of the PVC solution tends to increase, making it difficult to handle.

[0022] (aqueous solvent) The aqueous solvent may be either pure water or pure water to which additives have been added. Examples of additives include thickeners that aid in the dispersion of the PVC solution (droplets). Examples of thickeners that can be used include water-soluble polymers that can increase the viscosity of water, such as polyvinyl alcohol, starch, gelatin, chitosan-acid, polyethylene glycol, poly(meth)acrylic acid, polyacrylamide or its derivatives, and sodium carboxycellulose or its salts. The concentration of the water-soluble polymer in the aqueous dispersion medium is preferably in the range of 0.01 wt% to 50 wt%, more preferably 0.1 wt to 20 wt%. A concentration of the water-soluble polymer in the aqueous dispersion medium within this range facilitates droplet formation and stabilizes the formed droplets. Note that the lower the concentration of the water-soluble polymer in the aqueous dispersion medium, the more unstable the droplets become, while the higher the concentration of the water-soluble polymer in the aqueous dispersion medium, the more difficult it is for droplets to form during stirring. As the inorganic thickener, salts such as sodium sulfate, silica, talc, calcium carbonate, potassium carbonate, etc. may be used.

[0023] (Viscosity of dispersion) The viscosity of the dispersion is preferably in the range of 2.52 mPa·s to 725 mPa·s (when the dispersion is at 25°C). When the viscosity of the dispersion is within this range, droplets can be efficiently formed and the formed droplets can be stabilized. A low viscosity dispersion tends to make the droplets unstable, while a high viscosity dispersion tends to inhibit phase separation between the hydrophobic solvent and the aqueous solvent, making droplet formation difficult. Furthermore, increasing the viscosity of the dispersion leads to finer droplets, resulting in smaller particle sizes for the resulting PVC-based particles. A lower viscosity dispersion leads to larger droplets, resulting in larger particle sizes for the resulting PVC-based particles. Thus, the particle size of the resulting composite particles can be controlled simply by adjusting the viscosity of the dispersion.

[0024] (Ratio of PVC solution to aqueous solvent) The ratio of the PVC solution to the aqueous solvent is preferably in the range of 0.004:1 to 1:1, and more preferably in the range of 0.02:1 to 0.25:1. When the ratio of the PVC solution to the aqueous solvent is in this range, droplets can be efficiently formed in the dispersion liquid, and the recovery rate of the PVC particles can be improved. Note that, if the ratio of the PVC solution to the aqueous solvent is low, the recovery rate of the PVC particles decreases, and if the ratio of the PVC solution to the aqueous solvent is high, it tends to be difficult to form a sea (aqueous solvent domain)-island (PVC solution domain) structure.

[0025] (Stirring speed of dispersion liquid) Droplets of the PVC solution can be formed by stirring the dispersion with a stirring blade, for example, ultrasonic stirring, or a rotation-revolution stirrer, but any other method that can produce droplets is acceptable. For example, when stirring with a stirring blade, the stirring speed is preferably set in the range of 10 rpm to 20,000 rpm, more preferably in the range of 50 rpm to 3,000 rpm. Here, the faster the stirring speed, the finer the droplets become, and the smaller the particle size of the resulting PVC-based particles can be. Conversely, the slower the stirring speed, the larger the droplets become, and the larger the particle size of the resulting PVC-based particles can be. In this way, the particle size of the resulting PVC-based particles can be controlled by simply adjusting the stirring speed.

[0026] (Dispersion stirring time) The stirring time for the dispersion can be adjusted depending on the degree of droplet formation. For example, when stirring with a stirring blade, the stirring time is preferably set in the range of 3 to 24 hours, more preferably 6 to 10 hours. Here, the longer the stirring time, the finer the droplets become, and the smaller the particle size of the resulting PVC-based particles can be. Conversely, the shorter the stirring time, the larger the droplets become, and the larger the particle size of the resulting PVC-based particles can be. In this way, the particle size of the resulting PVC-based particles can be controlled by simply adjusting the stirring time.

[0027] (Heating conditions of dispersion liquid) The heating temperature of the dispersion is not particularly limited as long as it can evaporate the hydrophobic solvent from the PVC solution droplets. For example, at atmospheric pressure, the temperature is preferably below the boiling point of water, within the range of −30°C to +10°C from the boiling point of the hydrophobic solvent. If the PVC solution droplets boil excessively, the droplets tend to burst or the shape of the resulting particles tends to deteriorate. Therefore, it is preferable to heat the dispersion below the boiling point of the hydrophobic solvent. Furthermore, the pressure at which the dispersion is heated is not limited to atmospheric pressure; for example, the pressure can be reduced. By adjusting the heating conditions for the dispersion, the hydrophobic solvent can be effectively evaporated from the droplets, allowing PVC particles to be obtained efficiently.

[0028] Polyvinyl chloride particles and unsaturated vinyl copolymer particles are generally produced by a suspension polymerization method in which vinyl chloride monomer and a water solvent are polymerized while being mechanically stirred (see, for example, Japanese Patent Application Laid-Open No. 1-65160). Because vinyl chloride monomer is gaseous at room temperature, it must be prepared in a sealed autoclave reactor. Furthermore, since the end point of the polymerization reaction must be determined while monitoring the pressure drop due to the disappearance of gaseous vinyl chloride monomer, polyvinyl chloride particles are obtained, which requires a high level of equipment and is also complicated to operate.

[0029] As shown in Figure 9, in suspension polymerization, the initiator is added to the polymerization system separately from the vinyl chloride monomer. The initiator is mixed with the monomer droplets through repeated coalescence and redispersion of the monomer and initiator droplets. As the polymerization progresses, the droplets become more viscous and more prone to agglomeration. As the polymerization rate increases, the particles harden and are recovered as irregularly shaped particles. As PVC polymerizes, a single molecule grows by curling, eventually becoming particles of 20 to 30 Å. The smallest unit visible with an electron microscope in the early stages of polymerization is several hundred Å in size, likely composed of numerous 20 to 30 Å particles bonded together. Polymers with a low polymerization rate of around 4% to 6% contain particles of around 0.1 μm in size. As the polymerization progresses, these particles grow to become particles of around 1 μm to 3 μm in size. The resulting polyvinyl chloride particles are irregularly shaped because they are aggregates of multiple 1 to 3 μm primary particles. Thus, when polyvinyl chloride particles are granulated by suspension polymerization, polyvinyl chloride particles with different degrees of polymerization generated during the polymerization of vinyl chloride monomer become a non-uniform mixture (aggregates), which has the drawback of easily causing variations in particle size and distorting the shape. Furthermore, when polyvinyl chloride particles are molded into a molded product, the strength of the molded product varies greatly and the molded product is prone to have defects.

[0030] According to the method for producing PVC-based particles of the present disclosure, PVC-based particles are produced from a solid vinyl chloride polymer. This eliminates the need for equipment for gaseous vinyl chloride monomer, such as a sealed autoclave-type reactor, simplifying the production equipment. Furthermore, since no polymerization reaction is involved, the process eliminates the need for reaction control and significantly reduces the production effort. Furthermore, the resulting PVC-based particles can be uniformly spherical in shape and have a uniform particle size. Because the resulting PVC-based particles have a uniform shape, when molded from the PVC-based particles, the molded body can have uniform strength and is less likely to have defects. Furthermore, when the resulting PVC-based particles are incorporated into paint, the occurrence of uneven coating can be reduced. Furthermore, vinyl chloride polymer scraps and waste can be used as the raw vinyl chloride polymer, and new PVC-based particles can be produced by recycling the vinyl chloride polymer, contributing to the recycling of vinyl chloride polymers.

[0031] (composite particles) The composite particles according to the present invention comprise vinyl chloride polymer particles (PVC particles) and nanopolysaccharides disposed on the vinyl chloride polymer particles. In the composite particles, the chlorine atoms of the vinyl chloride polymer (vinyl chloride polymer) of the PVC particles are believed to be halogen-bonded to the nanopolysaccharide, thereby firmly holding the nanopolysaccharide to the vinyl chloride polymer. In the composite particles, the nanopolysaccharides disposed on the PVC particles maintain their fibrous shape if they are nanofibers, or their needle-like crystalline shape if they are nanocrystals. Furthermore, in the composite particles, numerous nanopolysaccharides are disposed on the PVC particles in an entangled or overlapping manner. The composite particles can be spherical or nearly spherical.

[0032] (Average particle size of composite particles) The particle size of the composite particles can be adjusted as desired as described below, but they are preferably micro-sized particles with an average particle size of 1 mm or less. Specifically, the average particle size of the composite particles is preferably in the range of 5 μm to 800 μm, and more preferably in the range of 10 μm to 500 μm. The composite particles having the aforementioned average particle size are convenient when added to other materials. The average particle size in the present disclosure is measured using a flow image analysis method and a scanning electron microscope (SEM).

[0033] (Ratio of polymer particles to nanopolysaccharides in composite particles) The ratio of nanopolysaccharide to PVC-based particles is preferably in the range of 0.0001 wt% to 20 wt%, more preferably 0.01 wt% to 5 wt%. When the ratio of nanopolysaccharide to PVC-based particles is within this range, the nanopolysaccharide can be uniformly arranged in the resulting composite particles, and the nanopolysaccharide's functions can be appropriately exerted. The lower the ratio of nanopolysaccharide to PVC-based particles, the more difficult it becomes for the composite particles to exhibit the functions specific to the nanopolysaccharide. The higher the ratio of nanopolysaccharide to polymer particles, the more difficult it becomes for the nanopolysaccharide to be uniformly distributed on the surface of the polymer particles.

[0034] (Vinyl chloride polymer particles) The PVC particles constituting the composite particles may be the same as the PVC particles made of the vinyl chloride polymer described above. As mentioned above, gaseous vinyl chloride monomer cannot be suspension polymerized at room temperature (atmospheric pressure). Therefore, a polymer that cannot be polymerized by room temperature (atmospheric pressure) suspension polymerization can be used as the polymer constituting the PVC particles of the present disclosure. Note that "cannot be polymerized by room temperature (atmospheric pressure) suspension polymerization" means that the polymer of the PVC particles constituting the composite particles cannot be suspension polymerized at 30°C or below (atmospheric pressure), and that the polymerization method of the polymer generally (industrially) is a method other than room temperature (atmospheric pressure) suspension polymerization. In the context of the PVC particles of the present disclosure, polymers obtained by polymerization methods other than room temperature suspension polymerization, such as bulk polymerization, solution polymerization, solid-state polymerization, high-temperature (high-pressure) suspension polymerization, emulsion polymerization, and mass polymerization, are granulated. Note that this does not exclude the use of polymers obtained by room temperature (atmospheric pressure) suspension polymerization as raw materials in the manufacturing method described below.

[0035] (Average particle size of PVC particles) The particle size of the PVC-based particles can be adjusted as desired, as described below, but it is preferable that the average particle size be microparticles. Since the nanopolysaccharides in the composite particles are smaller than the polymer particles, the size of the composite particles is largely determined by the size of the polymer particles. The average particle size of the PVC-based particles is preferably in the range of 5 μm to 800 μm, and more preferably in the range of 10 μm to 500 μm. Having the aforementioned average particle size, the PVC-based particles are convenient for use as a substrate for holding nanopolysaccharides.

[0036] (Characteristics of PVC particles) The vinyl chloride polymer constituting the PVC particles is preferably soluble in a hydrophobic organic solvent, such as a halogenated alkyl hydrophobic organic solvent such as methylene chloride, chloroform, or ethane dichloride.

[0037] (nanopolysaccharides) Examples of nanopolysaccharides include nanofibers or nanocrystals of cellulose, TEMPO-oxidized cellulose, chitin, chitosan, carboxymethyl cellulose, sulfated cellulose, etc. Note that either one type of nanopolysaccharide or a combination of multiple types of nanopolysaccharides may be used.

[0038] (size of nanopolysaccharide) Nanopolysaccharides that can be used include nanofibers with a fiber diameter in the range of 4 to 100 nm and a fiber length in the range of 5 to 30 μm, and nanocrystals with a crystal diameter in the range of 10 to 50 nm and a crystal length in the range of 100 to 500 nm.

[0039] (Method of manufacturing composite particles) The composite particles according to the present invention can be produced as follows: A polymer solution is prepared by adding a vinyl chloride polymer to a hydrophobic solvent (see FIG. 3(a)). Here, in the polymer solution, the polymer may be in a dissolved state in which it is completely dissolved in the hydrophobic solvent, or the polymer may be in a semi-dissolved state. Here, the "semi-dissolved state" refers to a state in which the vinyl chloride polymer is dispersed as fine particles in the hydrophobic solvent (colloidal state). In other words, according to the method for producing composite particles of the present disclosure, composite particles can be formed even when the vinyl chloride polymer is in a semi-dissolved state in which it is not completely dissolved in the hydrophobic solvent. Composite particles can be easily formed from vinyl chloride polymers, which are inherently difficult to dissolve in organic solvents. The polymer is preferably in the form of relatively fine particles or chunks in order to dissolve it in the hydrophobic solvent; for example, crushed material crushed to a size of about several millimeters can be used.

[0040] Nanopolysaccharide is added to a dispersion medium, and this dispersion medium is mixed with a polymer solution to prepare a mixed liquid (see Figure 3(a)). The mixed liquid is then mixed with an aqueous solvent to prepare a dispersion liquid (see Figure 3(b)). The dispersion liquid may contain a thickener as needed. In this case, for example, the thickener is added to the aqueous solvent to increase the viscosity of the dispersion liquid. The dispersion medium is sometimes called a nanopolysaccharide dispersion medium, and a dispersion medium containing nanopolysaccharide is sometimes called a nanopolysaccharide dispersion liquid.

[0041] The dispersion is stirred to form droplets of the mixture containing the PVC polymer and nanopolysaccharide in an aqueous solvent (see Figure 4). The dispersion is heated to evaporate the hydrophobic solvent from the droplets of the mixture (see Figure 5(a)). As the hydrophobic solvent evaporates from the droplets containing the PVC polymer and nanopolysaccharide, the remaining PVC polymer solidifies in particulate form. This results in composite particles consisting of PVC particles formed from the PVC polymer and nanopolysaccharides arranged on these PVC particles (see Figure 5(b)).

[0042] After granulation of the composite particles, washing may be performed depending on the type of dispersion medium used for the nanopolysaccharide. For example, when an amphipathic organic compound or other organic compound is used as the dispersion medium, washing may be performed with water or warm water in which the organic compound can be dissolved. Note that the temperature of the warm water used for washing must be below the melting point of the PVC-based particles that form the core of the composite particles. The composite particles are then recovered by necessary processing such as filtration. Note that the composite particles may also be classified to make the particle size uniform.

[0043] In the production of composite particles, the arrangement of nanopolysaccharides in the droplets can be controlled by adjusting the affinity between the hydrophobic solvent, the dispersion medium, and the aqueous solvent. For example, when water is used as the dispersion medium for nanopolysaccharides and methylene chloride, which has a low affinity for water, is used as the hydrophobic solvent, as shown in Figure 6, the dispersion medium containing the nanopolysaccharide undergoes phase separation in the hydrophobic solvent domain containing the PVC polymer, forming a W / O domain structure within the droplets. This results in a W / O / W domain structure between the aqueous solvent and the droplets with the W / O domain structure. This results in composite particles in which the nanopolysaccharides are located inside the PVC particles, rather than appearing on the surface of the PVC particles (see Figure 8(a)). In contrast, as shown in Figure 7, when acetone, an amphiphilic organic compound, is used as the nanopolysaccharide dispersion medium and methylene chloride, which has a relatively high affinity for acetone, is used as the hydrophobic solvent, the nanopolysaccharide dispersion medium does not undergo phase separation in the hydrophobic solvent domain containing the PVC polymer, and therefore no W / O domain structure is formed within the droplets. As a result, the nanopolysaccharide migrates from the inside to the outside of the droplets, resulting in nanopolysaccharides distributed unevenly on the droplet surface, resulting in composite particles in which the nanopolysaccharide is distributed on the surface of the PVC-based particles (see Figure 8(b)). Furthermore, when diethyl ether, which has a lower solubility in water than acetone, is used as the nanopolysaccharide dispersion medium, the nanopolysaccharide is dispersed from the droplet surface to the inside, resulting in composite particles in which the nanopolysaccharide is distributed from the outer side to the inner side of the PVC-based particles (see Figure 8(c)).

[0044] (hydrophobic solvent) The hydrophobic solvent can be one that can dissolve (semi-dissolve) the vinyl chloride polymer and is not easily mixed with water (aqueous dispersion medium). Furthermore, it is preferable to use a so-called low-boiling hydrophobic solvent, which has a boiling point lower than that of water (aqueous solvent). For example, it is preferable to use an alkyl halide hydrophobic organic solvent such as methylene chloride, chloroform, or ethane dichloride.

[0045] (Ratio of hydrophobic solvent to PVC) The PVC solution is preferably prepared so that the vinyl chloride polymer is in the range of 0.5 wt% to 50 wt%, more preferably 2 wt% to 20 wt%. When the proportion of the vinyl chloride polymer in the PVC solution is in this range, it is possible to achieve an appropriate viscosity. This makes it possible to stabilize the droplets formed from the PVC solution in the dispersion. Note that if the proportion of the vinyl chloride polymer in the PVC solution is low, the viscosity of the PVC solution decreases and the droplets become unstable, while if the proportion of the vinyl chloride polymer in the PVC solution is high, the viscosity of the PVC solution tends to increase, making it difficult to handle.

[0046] (dispersion medium) The dispersion medium for dispersing the nanopolysaccharide may be selected based on the relationship between the hydrophobic solvent and the aqueous solvent, depending on the arrangement of the nanopolysaccharide relative to the PVC particles. Note that the dispersion medium may be used alone or in combination with multiple types.

[0047] (Dispersion medium: nanopolysaccharide - encapsulated configuration) To localize nanopolysaccharides to the interior of PVC-based particles, water or an aqueous dispersion medium with low affinity for hydrophobic solvents can be selected. Using a dispersion medium that is miscible or soluble in aqueous solvents and phase-separates from the hydrophobic solvent used to disperse PVC polymers results in composite particles in which nanopolysaccharides are located inside PVC-based particles. Examples of aqueous dispersion media include water mixed with a hydrophilic medium such as methanol. In this case, phase separation from the hydrophobic solvent is prevented when the amount of hydrophilic medium added is large. For example, in the case of a water-methanol mixed dispersion medium, the ratio of water to methanol is preferably set to 3.75 or less (10 parts hydrophobic solvent (methylene chloride) 10 parts methanol 10 parts water 3.75 parts). Furthermore, nanopolysaccharides can also be localized to the interior of PVC-based particles using aqueous salts, acids, or alkalis, which are more polar than water.

[0048] (Dispersion medium: nanopolysaccharide - surface arrangement) To distribute nanopolysaccharides unevenly on the surface of PVC particles, an amphiphilic organic compound with high affinity for both hydrophobic and aqueous solvents can be selected. When a dispersion medium for dispersing nanopolysaccharides is used that is miscible or soluble in aqueous solvents and miscible with the hydrophobic solvent for dispersing PVC polymers, composite particles with nanopolysaccharides distributed on the surface of PVC particles can be obtained.

[0049] (Amphiphilic organic compounds) The amphiphilic organic compound can be a solvent that has affinity for nanopolysaccharides, dissolves in water (aqueous dispersion medium) and polymers, and is also compatible with hydrophobic organic solvents. The amphiphilic organic compound is preferably an organic solvent with a solubility of greater than 8.3 g in 100 ml of water. Specific examples of amphiphilic organic compounds include methanol, ethanol, acetone, 1-propyl alcohol, 2-propyl alcohol, 2-butanol, 2-methyl-2-propanol, 2-pentanol, 2-methyl-2-butanol, tetrahydrofuran, dioxane, ethylene glycols having ethylene glycol chains such as ethylene glycol, diethylene glycol, and triethylene glycol, propylene glycol, glycerin, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, acetonitrile, methyl ethyl ketone, sugar alcohols, phenols, acetic acid, propionic acid, butyric acid, and amines. Amphiphilic organic compounds may be used alone or in combination.

[0050] (Dispersion medium: nanopolysaccharides - arranged from the surface to the inside) To disperse nanopolysaccharides from the inside to the outside of PVC-based particles, a dispersion medium with an affinity for the hydrophobic solvent between the aqueous dispersion medium and the amphipathic dispersion medium described above can be selected. Using a dispersion medium for dispersing nanopolysaccharides that is soluble in aqueous solvents but has a relatively low solubility and is miscible with the hydrophobic solvent for dispersing PVC-based polymers can result in composite particles in which nanopolysaccharides are distributed from the outside to the inside of PVC-based particles. Specifically, a dispersion medium with a solubility of 8.3 g or less in 100 ml of water is preferred. Examples of such dispersion mediums include ethyl acetate, 1-butanol, diethyl ether, methyl propionate, and ethyl propylene.

[0051] (Ratio of dispersion medium to nanopolysaccharide) A nanopolysaccharide dispersion in which nanopolysaccharide is dispersed in a dispersion medium is preferably prepared so that the nanopolysaccharide concentration is in the range of 0.1 wt% to 20 wt%, more preferably 1.0 wt% to 10 wt%. When the proportion of nanopolysaccharide in the nanopolysaccharide dispersion is in this range, the nanopolysaccharide can be appropriately retained in the droplets, and aggregation of the nanopolysaccharide can be prevented, allowing it to be appropriately dispersed on the surface of the PVC-based particles. Note that, if the proportion of nanopolysaccharide in the nanopolysaccharide dispersion is low, the diffusion rate of the nanopolysaccharide in the droplets increases, making it difficult to retain the nanopolysaccharide on the PVC-based particles. On the other hand, if the proportion of nanopolysaccharide in the nanopolysaccharide dispersion is high, the nanopolysaccharide is more likely to aggregate, making it difficult to uniformly disperse the nanopolysaccharide on the surface of the PVC-based particles.

[0052] (Ratio of nanopolysaccharide dispersion to polymer solution) The ratio of the nanopolysaccharide dispersion to the polymer solution is preferably in the range of 1.0 vol% to 50 vol%, more preferably 5.0 vol% to 30 vol%. When the ratio of the nanopolysaccharide dispersion to the polymer solution is in this range, it is possible to ensure an appropriate amount of nanopolysaccharide supported in the composite particles and to prevent precipitation of the polymer in the polymer solution. Note that the lower the ratio of the nanopolysaccharide dispersion to the polymer solution, the lower the amount of nanopolysaccharide supported in the resulting composite particles, and the higher the ratio of the nanopolysaccharide dispersion to the polymer solution, the more likely the polymer is to precipitate in the polymer solution.

[0053] (Amount of nanopolysaccharide blended relative to vinyl chloride polymer) The amount of nanopolysaccharide blended relative to the vinyl chloride polymer is preferably in the range of 0.0001 wt% to 20 wt%, more preferably 0.01 wt% to 5 wt%. When the amount of nanopolysaccharide blended relative to the vinyl chloride polymer is within this range, the nanopolysaccharide can be uniformly arranged in the resulting composite particles, and the nanopolysaccharide's functions can be appropriately exhibited. The smaller the amount of nanopolysaccharide blended relative to the vinyl chloride polymer, the more difficult it becomes for the nanopolysaccharide's unique functions to be exhibited in the resulting composite particles. The greater the amount of nanopolysaccharide blended relative to the vinyl chloride polymer, the more likely the nanopolysaccharide to aggregate non-uniformly within the vinyl chloride polymer.

[0054] (aqueous solvent) The aqueous solvent may be either pure water or pure water to which additives have been added. Examples of additives include thickeners that aid in the dispersion of the mixed liquid (droplets). Examples of thickeners that can be used include water-soluble polymers that can increase the viscosity of water, such as polyvinyl alcohol, starch, gelatin, chitosan-acid, polyethylene glycol, poly(meth)acrylic acid, polyacrylamide or its derivatives, and sodium carboxycellulose or its salts. The concentration of the water-soluble polymer in the aqueous dispersion medium is preferably in the range of 0.01 wt% to 50 wt%, more preferably 0.1 wt to 20 wt%. A concentration of the water-soluble polymer in the aqueous dispersion medium within this range facilitates droplet formation and stabilizes the formed droplets. Note that the lower the concentration of the water-soluble polymer in the aqueous dispersion medium, the more unstable the droplets become, while the higher the concentration of the water-soluble polymer in the aqueous dispersion medium, the more difficult it is for droplets to form during stirring. As the inorganic thickener, salts such as sodium sulfate, silica, talc, calcium carbonate, potassium carbonate, etc. may be used.

[0055] (Viscosity of dispersion) The viscosity of the dispersion is preferably in the range of 2.5 mPa·s to 725 mPa·s (when the dispersion is at 25°C). When the viscosity of the dispersion is in this range, droplets can be efficiently formed and the formed droplets can be stabilized. A low viscosity dispersion tends to make the droplets unstable, while a high viscosity dispersion tends to inhibit phase separation between the hydrophobic solvent and the aqueous solvent, making droplet formation difficult. Furthermore, increasing the viscosity of the dispersion leads to finer droplets, resulting in a smaller particle size for the resulting PVC-based particles. Conversely, decreasing the viscosity of the dispersion leads to larger droplets, resulting in a larger particle size for the resulting PVC-based particles. Thus, the particle size of the resulting composite particles can be controlled simply by adjusting the viscosity of the dispersion.

[0056] (Ratio of mixed solution to aqueous solvent) The ratio of the mixed liquid to the aqueous solvent is preferably in the range of 0.004:1 to 1:1, and more preferably in the range of 0.02:1 to 0.25:1. When the ratio of the mixed liquid to the aqueous solvent is in this range, droplets can be efficiently formed in the dispersion liquid, and the recovery rate of the PVC particles can be improved. Note that if the ratio of the mixed liquid to the aqueous solvent is low, the recovery rate of the PVC particles decreases, and if the ratio of the mixed liquid to the aqueous solvent is high, it tends to be difficult to form a sea (aqueous solvent domain)-island (PVC solution domain) structure.

[0057] (Stirring speed of dispersion liquid) Droplets from the mixed liquid can be formed by stirring the dispersion with a stirring blade, for example, ultrasonic stirring, or a rotation-revolution stirrer, but any other method that can produce droplets is acceptable. For example, when stirring with a stirring blade, the stirring speed is preferably set in the range of 10 rpm to 20,000 rpm, more preferably in the range of 50 rpm to 3,000 rpm. Here, the faster the stirring speed, the finer the droplets become, and the smaller the particle size of the resulting PVC-based particles can be. Conversely, the slower the stirring speed, the larger the droplets become, and the larger the particle size of the resulting PVC-based particles can be. In this way, the particle size of the resulting composite particles can be controlled by simply adjusting the stirring speed.

[0058] (Dispersion stirring time) The stirring time for the dispersion can be adjusted depending on the degree of droplet formation. For example, when stirring with a stirring blade, the stirring time is preferably set in the range of 3 to 24 hours, more preferably 6 to 10 hours. Here, the longer the stirring time, the finer the droplets become, and the smaller the particle size of the resulting PVC-based particles can be. Conversely, the shorter the stirring time, the larger the droplets become, and the larger the particle size of the resulting PVC-based particles can be. In this way, the particle size of the resulting composite particles can be controlled by simply adjusting the stirring time.

[0059] (Heating conditions of dispersion liquid) The heating temperature of the dispersion is not particularly limited as long as it can evaporate the hydrophobic solvent from the droplets of the mixed solution (PVC solution + nanopolysaccharide dispersion). For example, at atmospheric pressure, the temperature is preferably below the boiling point of water, within the range of −30°C to +10°C above the boiling point of the hydrophobic solvent. If the droplets of the mixed solution boil excessively, they tend to burst or the shape of the resulting particles may deteriorate. Therefore, it is preferable to heat the dispersion below the boiling point of the hydrophobic solvent. Furthermore, the pressure at which the dispersion is heated is not limited to atmospheric pressure; for example, the pressure can be reduced. By adjusting the heating conditions for the dispersion, the hydrophobic solvent can be effectively evaporated from the droplets, allowing composite particles to be obtained efficiently.

[0060] By disposing nanopolysaccharides on PVC-based particles, composite particles can obtain combined functions derived from the PVC-based particles and nanopolysaccharides. When nanopolysaccharides are disposed on the surface of PVC-based particles, for example, chitosan nanofibers, cationic functions are imparted to the composite particles, while anionic cellulose nanofibers such as TEMPO-oxidized cellulose nanofibers, carboxymethyl cellulose nanofibers, and sulfated cellulose nanofibers are imparted with anionic functions. Furthermore, when nanopolysaccharides are disposed inside the PVC-based particles, the effects of the properties of the nanopolysaccharide's functional groups and the like on the composite particles can be suppressed. Furthermore, when composite particles are used to form a molded article, a molded article in which the nanopolysaccharides are uniformly dispersed can be obtained, allowing the strength-increasing effect of the nanopolysaccharides to be uniformly exerted. can.

[0061] The composite particle manufacturing method of the present invention can be applied to vinyl chloride polymers that cannot be obtained by room temperature (normal pressure) suspension polymerization, and can easily produce composite particles with nanopolysaccharides attached to the surface of vinyl chloride polymer particles. The resulting composite particles can be uniformly spherical in shape, and particles with uniform particle size can be obtained. Because the resulting composite particles have a uniform shape, when a molded article is made from the composite particles, the strength of the molded article can be made uniform, and defects and other defects in the molded article can be made less likely. Furthermore, when the resulting composite particles are incorporated into a paint, the occurrence of uneven coating can be suppressed.

[0062] The composite particles of the present invention can be used, for example, as cosmetic carriers, biochemical carriers, adsorption carriers, and plastic reinforcing fillers.

[0063] Next, the composite particles and the method for producing the same according to the present invention will be described below by way of preferred examples with reference to the accompanying drawings. [Example]

[0064] The PVC-based particles of the examples shown in Table 1 and the composite particles of the examples shown in Table 1 were prepared as follows: The composite particles of the comparative examples shown in Table 2 were prepared as follows.

[0065] Example 1 - PVC-based particles Polyvinyl chloride (PVC) raw material particles obtained by suspension polymerization were prepared (Shin-Etsu Chemical: TK-1000). A PVC-methylene chloride solution (polymer solution) was prepared so that the polyvinyl chloride (PVC) content was 6.0 wt%. As shown in Figure 10, the polymer solution became opaque due to the PVC being semi-dissolved in the methylene chloride. A dispersion was prepared by adding 150 ml of the polymer solution to 450 ml of a 1.5 wt% aqueous polyvinyl alcohol solution as an aqueous dispersion medium. The viscosity of the dispersion was 2.74 mPa·s (when the dispersion was at 40°C, 3.93 mPa·s when the dispersion was at 25°C). The dispersion obtained by dispersing the polymer solution in the aqueous polyvinyl alcohol solution was heated from room temperature to 40°C over 20 minutes, and while maintaining the temperature at 40°C, the dispersion was stirred at 300 rpm using a homogenizer (SMT Process Homogenizer PH91, Co., Ltd.) for 20 hours to form particles, thereby obtaining PVC particles consisting only of polyvinyl chloride of Example 1. Note that the same homogenizer was used in the examples and comparative examples.

[0066] Electron microscope photographs of the PVC particles of Example 1 are shown in Figures 11 to 15. Also, an electron microscope photograph of the PVC raw material particles used in Example 1 is shown in Figure 16. As shown in Figures 11, 14, and 15, it can be seen that the PVC particles of Example 1 are formed in a nearly spherical shape, and compared to the PVC raw material particles of Figure 16, they are found to be nearly circular and have a relatively uniform particle size.

[0067] (Circularity) The circularity of the PVC particles of Example 1 was compared with that of the PVC raw material particles used in Example 1. The circularity is the value obtained by dividing the perimeter calculated from the diameter of a perfect circle having the same projected area as the perimeter of an image of the particle by the perimeter of the image of the particle. Note that the circularity is "1" for a perfect circle, and the more complex the particle shape, the smaller the value. Circularity = "Perimeter calculated from the diameter of a perfect circle with the same projected area as the perimeter of the image of the particle" / "Perimeter of the image of the particle"

[0068] 17, the PVC raw material particles used in Example 1 were irregular in shape and not uniform in size, whereas the PVC particles of Example 1 were nearly spherical in shape and relatively uniform in size. It can also be seen that the PVC particles of Example 1 were nearly perfectly round with a circularity of 0.998, which is a significant improvement over the circularity of the PVC raw material particles, which was 0.924.

[0069] Example 2 20 ml of acetone was added to 10 ml of a 10.0 wt% CNF aqueous dispersion (manufactured by Chuetsu Pulp Industries Co., Ltd., product name: nanoforest, C-defibrated, bamboo-derived cellulose nanofiber dispersion), and the CNF was precipitated by centrifugation for 10 minutes (rotation speed: 5000 rpm), and the supernatant was removed. 30 ml of acetone was added to the resulting precipitate, and the mixture was dispersed again. The mixture was then centrifuged as before, and the supernatant was removed. This procedure was repeated three times, and the acetone was distilled off to obtain a CNF-acetone dispersion adjusted to the specified CNF concentration. Cellulose nanofibers may also be referred to as "CNF."

[0070] Polyvinyl chloride (PVC) raw particles obtained by suspension polymerization were prepared (Shin-Etsu Chemical: TK-1000). 32 ml of the CNF-acetone dispersion containing 15 wt% CNF was mixed with 150 ml of a PVC-methylene chloride solution containing 6.0 wt% PVC. The mixture was stirred at 5000 rpm for 2 minutes using a homogenizer to prepare a CNF-polymer solution. The weight ratio of polyvinyl chloride (PVC) to CNF (CNF nanopolysaccharide) was 100:3. The CNF-polymer solution was added to 450 ml of a 1.5 wt% aqueous polyvinyl alcohol solution as an aqueous dispersion medium. The viscosity of the dispersion was 2.74 mPa·s at 40°C (3.93 mPa·s at 25°C). The dispersion, in which the CNF-polymer solution was dispersed in an aqueous polyvinyl alcohol solution, was heated from room temperature to 40°C over 20 minutes, and while maintained at 40°C, the mixture was stirred at 300 rpm with the homogenizer for 20 hours to form particles, yielding composite particles of Example 2 in which CNF was supported on the surface of polyvinyl chloride particles. Elemental analysis of the composite particles of Example 2 revealed that they contained 2.36 wt% CNF.

[0071] Electron microscope photographs of the composite particles of Example 2 are shown in Figures 18 to 21. As shown in Figures 18 to 21, it can be seen that the surfaces of the PVC-based particles in the composite particles of Example 2 are covered with fibrous CNF, and that CNF is not disposed inside the PVC-based particles.

[0072] The interaction between cellulose and acetone was calculated using computational chemistry with wB97XD / 6-31G(d)(*), and the interaction between polyvinyl chloride and cellulose was 3.51 Kcal / mol, while the interaction between polyvinyl chloride and cellulose was a high value of 9.40 Kcal / mol. This confirms that polyvinyl chloride and cellulose adsorb through a specific interaction. Furthermore, when cellulose microparticles were packed into a column and chlorine-based compounds were injected, the retention was examined. The greater the number of chlorine atoms, the greater the retention. This is thought to be due to halogen bonding between the chlorine atoms and cellulose.

[0073] Example 3 A CNF-polymer solution was prepared by mixing 42.7 ml of the CNF-aqueous dispersion containing 0.6 wt% CNF with 250 ml of a PVC-methylene chloride solution containing 2.5 wt% polyvinyl chloride (PVC (Shin-Etsu Chemical: TK-1000)). The mixture was stirred at 5000 rpm for 2 minutes using a homogenizer. The weight ratio of polyvinyl chloride (polymer) to CNF (nanopolysaccharide) was 100:3. The CNF-polymer solution was added to 450 ml of a 1.5 wt% aqueous polyvinyl alcohol solution as an aqueous dispersion medium. The viscosity of the dispersion was 2.74 mPa·s at 40°C (3.93 mPa·s at 25°C). The dispersion, in which the CNF-polymer solution was dispersed in an aqueous polyvinyl alcohol solution, was heated from room temperature to 40°C over 20 minutes, and while maintained at 40°C, the mixture was stirred at 300 rpm with the homogenizer for 20 hours to form particles, yielding the composite particles of Example 3. Elemental analysis of the composite particles of Example 3 revealed that they contained 3.0 wt% CNF.

[0074] 22 to 25 are electron microscope photographs of the composite particles of Example 3. As shown in Figures 22 to 25, it can be seen that fibrous CNF is arranged inside the PVC-based particles of the composite particles of Example 3.

[0075] (Examples 4 and 5) Examples 4 and 5 have the same formulation as Example 2, except that the operating procedures and operating conditions are as shown in Table 1. In Example 4, 2-propanol (isopropyl alcohol) was used as the nanopolysaccharide dispersion medium, and in Example 5, 2-butanol was used as the nanopolysaccharide dispersion medium.

[0076] In Example 4, it was found that composite particles in which nanopolysaccharides were arranged on the surface of PVC-based particles could be obtained by using 2-propanol, which is miscible in both water and methylene chloride, as the nanopolysaccharide dispersion medium.In Example 5, it was found that composite particles in which nanopolysaccharides were arranged on the surface of PVC-based particles could be obtained by using 2-butanol, which is soluble in water and miscible in methylene chloride, as the nanopolysaccharide dispersion medium.

[0077] [Table 1]

[0078] (Comparative Example) Comparative Examples 1 to 6 were the same as Example 2 except that a polymer other than a vinyl chloride polymer was used as the polymer, and the formulations were as shown in Table 2, and the operating procedures and operating conditions were as shown in Table 2. In Comparative Example 1, polystyrene (PS) is used as the polymer. In Comparative Example 2, polycarbonate (PC) was used as the polymer. In Comparative Example 3, a copolymer of polyvinyl acetate (PVAM) and polyethylene (PE) is used as the polymer. In Comparative Example 4, polyvinyl acetate (PVAM) was used as the polymer. In Comparative Example 5, polymethyl methacrylate (PMMA) was used as the polymer. In Comparative Example 6, polymethyl acrylate (PMA) was used as the polymer.

[0079] (Comparative Example 7) 90 ml of a PVC-methylene chloride solution containing 6.0 wt% polyvinyl chloride (PVC) was mixed with 4.7 ml of the CNF-acetone dispersion containing 5 wt% CNF. The mixture was stirred at 300 rpm at room temperature using a homogenizer (SMT Process Homogenizer PH91, SMT Corporation) to obtain a bulk polymer. The resulting bulk polymer was pulverized using a high-speed milling machine to obtain the PVC / CNF composite irregularly crushed material of Comparative Example 3. Elemental analysis of the PVC / CNF composite irregularly crushed material of Comparative Example 7 revealed that it contained 2.36 wt% CNF. Note that the "random" nanopolysaccharide arrangement in Table 3 indicates that the nanopolysaccharides are randomly located inside and on the surface of the polymer.

[0080] [Table 2]

[0081] In Comparative Examples 1 to 6, the CNF was rejected from the polymer and could not be arranged in the polymer, and composite particles were not formed.

[0082] (nanopolysaccharide dispersion medium) The results of preparing composite particles by changing the nanopolysaccharide dispersion medium are shown in Table 3. In the examples in Table 3, the operating procedures and operating conditions were the same as in Example 2, except that the nanopolysaccharide dispersion medium was changed as shown in Table 3.

[0083] [Table 3]

[0084] As shown in Table 3, when a dispersion medium for dispersing nanopolysaccharides that is miscible or soluble in aqueous solvents and phase-separates from the hydrophobic solvent for dispersing PVC polymers is used, composite particles in which nanopolysaccharides are arranged inside the PVC particles are obtained. Furthermore, when a dispersion medium for dispersing nanopolysaccharides that is miscible or soluble in aqueous solvents and miscible with the hydrophobic solvent for dispersing PVC polymers is used, composite particles in which nanopolysaccharides are arranged on the surface of the PVC particles are obtained. When a dispersion medium for dispersing nanopolysaccharides that is soluble in aqueous solvents but has a relatively low solubility (solubility of 8.3 g or less in 100 ml of water) and is miscible with the hydrophobic solvent for dispersing PVC polymers is used, composite particles in which nanopolysaccharides are arranged from the surface to the interior of the PVC particles are obtained.

[0085] 26 shows the results of infrared absorption spectrum measurement by infrared spectroscopy for Examples 1, 2, and 3. The composite particles of Example 2 have a wavelength of 3600 cm -1 ~3200cm -1 The increase in absorbance due to CNF is evident, indicating that CNF is attached to the surface of the PVC particles.

[0086] (Creating film by compression molding) Using the particles of Examples 1 and 2 and the particles of Comparative Example 7, a film was produced as shown in FIG.

[0087] (Film example 1) A stainless steel plate (thickness: 510 μm to 520 μm, external dimensions: 10 cm × 10 cm square, frame size: 5 cm × 5 cm) was placed on the polyimide sheet, 2.0 g of the PVC-based particles of Example 1 was placed in the frame, and another polyimide sheet was placed on top of that, and pressed at 75°C and 20 MPa for 5 minutes. After the pressure was once reduced to normal pressure, the temperature was raised to 180°C, and then the pressure was raised again to 20 MPa and maintained for 3 minutes to form a film of Film Example 1.

[0088] (Film example 2) A stainless steel plate (thickness: 510 μm to 520 μm, external dimensions: 10 cm × 10 cm square, frame size: 5 cm × 5 cm) was placed on the polyimide sheet, 2.0 g of the composite particles of Example 2 was placed in the frame, and another polyimide sheet was placed on top of that, and pressed at 75°C and 20 MPa for 5 minutes. After the pressure was once reduced to normal pressure, the temperature was raised to 180°C, and then the pressure was raised again to 20 MPa and maintained for 3 minutes to form a film of Film Example 2.

[0089] (Film example 3) A stainless steel plate (thickness: 510 μm to 520 μm, external dimensions: 10 cm × 10 cm square, frame size: 5 cm × 5 cm) was placed on top of the polyimide sheet, and 2.0 g of the PVC / CNF composite irregularly crushed material from Comparative Example 7 was placed in the frame. Another polyimide sheet was placed on top of that and pressed at 75°C and 20 MPa for 5 minutes. After the pressure was temporarily reduced to normal pressure, the temperature was raised to 180°C, and then the pressure was raised again to 20 MPa and maintained for 3 minutes to form a film of Film Example 3.

[0090] (cloudy value) The haze values ​​of the films of Film Examples 1 to 3 were measured. The haze values ​​were measured using a Suga Testing Instrument (Haze Meter HZ-2P) with a light source (D65). The results are shown in Figure 28. As shown in Figure 28, it was found that the incorporation of CNF made it difficult for light to pass through.

[0091] (tensile strength) The tensile strength of the films of Film Examples 1 to 3 was measured. A dumbbell was made using a JIS No. 8 mold. Both ends were fixed by 10 mm, and conditions were set to keep the stroke constant (conditions for stretching the film by 10 mm per minute: strain 10 mm / min), and a stress-strain curve was obtained using an Autoflaf (Shimadzu Corporation: small tabletop testing machine EZ-LX).

[0092] As shown in Figure 29, the composite particles of CNF / PVC particles have a higher tensile strength than the composite irregularly crushed material. The improved tensile strength is thought to be due to the orderly arrangement of the fine particles and the orientation of the CNFs in a mesh structure, as shown in Figure 30.

[0093] Example 6 In Example 6, methylene chloride was used as the dispersion medium for dispersing CNF. 20 ml of methylene chloride was added to 10 ml of a 10.0 wt% CNF aqueous dispersion (manufactured by Chuetsu Pulp Industries Co., Ltd., product name: nanoforest, C-defibrated, bamboo-derived cellulose nanofiber dispersion), and the mixture was centrifuged for 10 minutes (rotation speed: 5000 rpm) to precipitate the CNF, and the supernatant was removed. 30 ml of methylene chloride was added to the resulting precipitate, and the mixture was dispersed again. The mixture was then centrifuged as before, and the supernatant was removed. This procedure was repeated three times, and the methylene chloride was distilled off to obtain a CNF-methylene chloride dispersion prepared to a predetermined CNF concentration.

[0094] Polyvinyl chloride (PVC) raw material particles obtained by suspension polymerization were prepared (Shin-Etsu Chemical: TK-1000). In Example 6, 3.41 g of PVC raw material particles were added to 100 ml of methylene chloride to prepare a PVC-methylene chloride solution with a polyvinyl chloride (PVC) content of 2.5 wt%. 23.5 ml of the CNF-methylene chloride dispersion containing 0.33 wt% CNF was mixed with 150 ml of the PVC-methylene chloride solution and stirred at 5000 rpm for 2 minutes using a homogenizer to prepare a CNF-polymer solution. The weight ratio of polyvinyl chloride (as the polymer) to CNF (as the nanopolysaccharide) was 100:3. The CNF-polymer solution was added to 300 ml of a 1.5 wt% polyvinyl alcohol aqueous solution as an aqueous dispersion medium. The viscosity of the dispersion was 2.74 mPa·s (40°C) (3.93 mPa·s (25°C)). The dispersion, in which the CNF-polymer solution was dispersed in the aqueous polyvinyl alcohol solution, was heated from room temperature to 40°C over 20 minutes, and while maintaining the temperature at 40°C, it was stirred at 300 rpm with the homogenizer and subjected to particle formation over 20 hours, yielding composite particles of Example 6 in which CNF was dispersed from the surface to the interior of the polyvinyl chloride particles.

[0095] [Table 4]

[0096] The composite particles of Example 6 had an average particle size of 32 μm to 106 μm and a yield of 1.836 g (53.7% yield) of particles with an average particle size of more than 106 μm, and the yield was 0.919 g (28.6% yield). Elemental analysis of the composite particles of Example 6 revealed that they contained 2.65 wt% CNF.

[0097] Electron microscope photographs of the composite particles of Example 6 are shown in Figures 31 to 36. As shown in Figures 31 to 33, it can be seen that the surfaces of the PVC-based particles in the composite particles of Example 6 are covered with fibrous CNF. Furthermore, the cross sections of the composite particles of Example 6 shown in Figures 34 to 36 reveal that CNF is present inside the PVC-based particles. In Figure 34, the areas that appear whiter than the other areas are CNF.

[0098] 31, it can be seen that the composite particles of Example 6 have a nearly spherical shape and are relatively uniform in size. The circularity of the composite particles of Example 6 was 0.98.

[0099] The presence or absence of interactions between CNF and chlorinated compounds was investigated using liquid chromatography. CNF particles with an average particle size of 30 μm were packed into a column (30 cm x 8 mm I.D.), and ethanol was used as the mobile phase. Chlorinated compounds, chloroform, dichloromethane, and dichloroethane, and a branched-chain alkane without a chloro group, 3-methylpentane, were each injected in an amount of 20 μL into a cellulose-packed column at a column temperature of 25°C. As shown in Figure 37, the peak retention times increased and tailing occurred for the chlorinated compounds, chloroform, dichloromethane, and dichloroethane, suggesting interactions between CNF and chlorinated compounds. On the other hand, no increase in peak retention time or tailing was observed for 3-methylpentane.

[0100] As shown in Figure 38, taking Example 6 as an example, in the CNF-methylene chloride dispersion, a weak interaction occurs between CNF and methylene chloride. Furthermore, in the CNF-polymer solution, there is also a weak interaction between PVC and CNF, so the CNF is uniformly mixed with PVC in the CNF-polymer solution. It is believed that when the CNF-polymer solution is added to an aqueous dispersion medium and particle-formed, the domains become stable, the particles are close to spherical, and the CNF is uniformly compounded. In this way, by using a chlorine compound as a dispersion medium, composite particles can be obtained in which nanopolysaccharides are distributed from the surface to the inside of PVC-based particles. This has the advantage of making the resulting composite particles closer to spherical.

Claims

1. A mixed solution is prepared by mixing a halogenated alkyl hydrophobic solvent containing a vinyl chloride polymer and a dispersion medium containing nanopolysaccharides, a dispersion obtained by mixing the mixed liquid and an aqueous solvent is stirred to form droplets of the mixed liquid containing the vinyl chloride polymer and the nanopolysaccharide in the aqueous solvent; heating the dispersion to evaporate the hydrophobic solvent from the droplets; and obtaining composite particles having vinyl chloride-based polymer particles formed from the vinyl chloride-based polymer and the nanopolysaccharide disposed on the vinyl chloride-based polymer particles. A method for producing composite particles, comprising:

2. 2. The method for producing composite particles according to claim 1, wherein the vinyl chloride polymer is semi-dissolved in the hydrophobic solvent.

3. 3. The method for producing composite particles according to claim 1, wherein the nanopolysaccharide is disposed on the surface of the vinyl chloride polymer particles using an amphiphilic organic compound as the dispersion medium.

4. 3. The method for producing composite particles according to claim 1, wherein the dispersion medium is an aqueous dispersion medium, and the nanopolysaccharide is disposed inside the vinyl chloride polymer particles.

5. 3. The method for producing composite particles according to claim 1, wherein a chlorine compound is used as the dispersion medium, and the nanopolysaccharide is dispersed from the surface of the vinyl chloride polymer particles to the inside thereof.

6. Polyvinyl chloride particles; and a nanopolysaccharide disposed at least inside the polyvinyl chloride particle, A composite particle characterized in that a chlorine atom of the polyvinyl chloride particle and the nanopolysaccharide are halogen-bonded.

7. The composite particle according to claim 6 , wherein the nanopolysaccharide is unevenly distributed on the surface of the polyvinyl chloride particle.

8. The composite particle according to claim 6 , wherein the nanopolysaccharide is unevenly distributed inside the polyvinyl chloride particle.

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