JP2024027834A - Composite particle and method for producing composite particle - Google Patents

Abstract

To provide a composite particle that can be stably produced with high purification efficiency and good dispersibility, and a method for producing a composite particle.SOLUTION: A composite particle includes microfibers 2 and a core particle 3 including at least one polymer. The microfibers 2 are joined to the surface of the core particle 3. The microfibers 2 have a median size of 0.01 μm or more and 10 μm or less. The microfibers 2 are ion-modified fibers with ionic functional groups. The introduction level of the ionic functional groups is 1.3 mmol/g or more and 5.0 mmol/g or less relative to the dry mass of the microfibers 2. The composite particle 1 has an average particle size of 0.1 μm or more and 50 μm or less and an average circularity of 0.8 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to composite particles and a method for producing composite particles.

In recent years, active efforts have been made to miniaturize cellulose fibers in wood until at least one side of their structure is on the order of nanometers, and to use them as new functional materials.

For example, Patent Document 1 discloses that micronized cellulose fibers, that is, cellulose nanofibers (hereinafter also referred to as "CNF") can be obtained by repeatedly subjecting wood cellulose to mechanical treatment using a blender or a grinder. There is. It is described that CNF obtained by this method has a minor axis diameter of 10 to 50 nm and a major axis diameter of 1 μm to 10 mm. This CNF is one-fifth lighter than steel, more than five times stronger, and has a huge specific surface area of more than 250 m ² /g, so it is expected to be used as a filler for reinforcing resins and as an adsorbent. ing.

In the production of CNF, active attempts are being made to chemically process the cellulose fibers in wood so that they can be easily made fine, and then to make them fine using a low-energy mechanical process similar to that used in a household mixer. The chemical treatment method described above is not particularly limited, but a method of introducing ionic functional groups into cellulose fibers to facilitate micronization is preferred. By introducing ionic functional groups into the cellulose fibers, the solvent can easily penetrate between the cellulose microfibril structures due to the osmotic pressure effect, and the energy required to refine the cellulose raw material can be significantly reduced.

The method of introducing the ionic functional group is not particularly limited, but for example, Non-Patent Document 1 discloses a method of selectively phosphoricating the surface of cellulose fine fibers using phosphoric esterifying treatment. has been done. Patent Document 2 discloses carboxymethylation of cellulose by reacting it with monochloroacetic acid or sodium monochloroacetate in a highly concentrated alkaline aqueous solution. Carboxy groups may be introduced by directly reacting a carboxylic acid anhydride compound such as maleic acid or phthalic acid gasified in an autoclave with cellulose.

In addition, a method of selectively oxidizing the surface of cellulose fine fibers using 2,2,6,6-tetramethylpiperidinyl-1-oxy radical (TEMPO), which is a relatively stable N-oxyl compound, as a catalyst. It has also been reported (for example, see Patent Document 3). The oxidation reaction using TEMPO as a catalyst (TEMPO oxidation reaction) allows environmentally friendly chemical reformation that proceeds in an aqueous system at room temperature and pressure. When the TEMPO oxidation reaction is applied to cellulose in wood, the reaction does not proceed inside the crystal, and only the alcoholic primary carbons possessed by the cellulose molecular chains on the surface of the crystal can be selectively converted into carboxy groups. .

Cellulose single nanofibers (hereinafter also referred to as CSNF) are dispersed into individual cellulose microfibril units in a solvent due to the osmotic pressure effect accompanying the ionization of carboxy groups selectively introduced to the crystal surface by TEMPO oxidation. ) is obtained. CSNF exhibits high dispersion stability derived from the carboxy groups on the surface. Wood-derived CSNF obtained from wood by the TEMPO oxidation reaction is a structure with a high aspect ratio of around 3 nm in short axis diameter and several tens of nm to several μm in long axis diameter, and its aqueous dispersion and molded body is reported to have high transparency.
Patent Document 4 describes that a laminated film obtained by coating and drying a CSNF dispersion has gas barrier properties.

Furthermore, consideration is being given to imparting further functionality to CNF or CSNF. For example, it is possible to impart further functionality using the carboxy group on the surface of CSNF.
For example, Patent Document 5 discloses a composite in which metal nanoparticles are supported on CSNF (metal nanoparticle-supported CSNF) by reducing and precipitating metal with metal ions adsorbed to the carboxy groups on the surface of CSNF. has been done. Patent Document 5 discloses an example in which metal nanoparticle-supported CSNF is used as a catalyst, and the catalytic activity is improved by making it possible to stabilize the dispersion of metal nanoparticles in a state with a high specific surface area. has been reported.

Patent Document 6 discloses an example in which a target substance is adsorbed onto CNF having an anionic functional group and used as an immunoassay composition, an immunoassay diagnostic agent, and an immunoassay device, and utilizes the characteristics of CNF. Applications are being considered. Furthermore, Non-Patent Document 2 discloses that a cationic dye is adsorbed onto CNF having an anionic functional group.

On the other hand, a problem facing the practical application of CNF is that the solid content concentration of the resulting CNF dispersion is as low as about 0.1 to 5%. For example, when attempting to transport a micronized cellulose dispersion, transportation costs increase because it is transported along with a large amount of solvent, which greatly affects business viability. In addition, when used as an additive for reinforcing resins, there are problems such as poor addition efficiency due to low solid content concentration, and difficulty in compounding if water, which is a solvent, is not compatible with the resin. be. Furthermore, when distributed in a moist state, there is a risk of spoilage, so measures such as refrigerated storage and preservative treatment are required, which causes an increase in costs.

However, if the solvent of the finely divided cellulose dispersion is simply removed by heat drying, etc., the finely divided cellulose will aggregate, become keratinized, or form a film, and when used as an additive, the expected function will not be achieved. It may not be expressed stably. Furthermore, since the solid content concentration of CNF is low, the process of removing the solvent by drying itself requires a large amount of energy, which poses a hurdle to business viability.

As described above, handling CNF in the form of a dispersion itself has become an issue for business feasibility, and it is strongly desired to provide a new mode in which CNF can be easily handled.

As a new aspect in which CNF can be easily handled, Patent Document 7 describes composite particles that include a coating layer made of cellulose fibers and a polymer covered with the coating layer. In this composite particle, since the cellulose fiber and the polymer are integrated, they can be easily separated and distributed as a powder. The redispersibility of the powder is also good.

Japanese Patent Application Publication No. 2010-216021 International Publication No. 2014/088072 Japanese Patent Application Publication No. 2008-001728 International Publication No. 2013/042654 International Publication No. 2010/095574 International Publication No. 2019/235318 JP 2019-38949 Publication

Noguchi Y, Homma I, Matsubara Y. Complete nanofibrillation of cellulose prepared by phosphorylation. Cellulose. 2017;24:129 5.10.1007/s10570-017-1191-3 Shigefusa Yamakata (1970), Fluorescent spectroscopic analysis of acridine orange-stained cells, Journal of the Japanese Society of Clinical Cytology, Vol. 9, No. 2, p. 164-169.

However, since the cellulose fiber of Patent Document 7 has a high aspect ratio and high viscosity, it may be difficult to purify composite particles. Even if recovery is possible depending on the purification method and conditions, the yield of the purified recovered product may decrease, and free cellulose fibers may be recovered in the purified recovered product, so the resulting composite particles may be bridged with each other, resulting in composite particles In some cases, the dispersibility of Furthermore, composite particles that are not perfectly spherical are sometimes produced among composite particles obtained using cellulose fibers having a long fiber length.

Acridine orange, which is a fluorescent dye described in Non-Patent Document 2, emits green fluorescence with a short wavelength when it is a single molecule, but when the dye molecules associate with each other, it emits red light with a long wavelength. As described above, fluorescent dyes cannot exhibit stable fluorescence emission due to association or aggregation, and the fluorescence emission wavelength may change. In addition, there are cases where it cannot be used depending on its solubility in the solvent.

In view of the above circumstances, the object of the present invention is to provide composite particles and a method for producing composite particles that can be stably produced with high purification efficiency and good dispersibility.
Furthermore, a further object of the present invention is to provide composite particles and a method for producing composite particles in which a functional material such as a fluorescent dye can be stably introduced.

As a result of extensive studies, the present inventors found that by using fine fibers with a shorter fiber length, free fine fibers can be sufficiently removed through filtration or centrifugation, purification efficiency can be further improved, and the use of various solvents can be improved. It has been found that dispersibility can be further improved and composite particles can be produced more stably. Furthermore, the present inventors have discovered that functional materials such as fluorescent dyes can be stably introduced into composite particles, leading to the completion of the present invention.

That is, the present invention has the following aspects.
[1] Composite particles having fine fibers and core particles containing at least one kind of polymer,
the fine fibers are bonded to the surface of the core particle,
The median diameter of the fine fibers is 0.01 μm or more and 10 μm or less,
The fine fibers are ion-modified fibers having ionic functional groups,
The amount of the ionic functional group introduced is 1.3 mmol/g or more and 5.0 mmol/g or less based on the dry mass of the fine fibers,
The average particle size is 0.1 μm or more and 50 μm or less,
Composite particles having an average circularity of 0.8 or more.
[2] The viscosity at 25° C. of the aqueous dispersion containing 0.5% by mass of the fine fibers as a solid content is 2 mPa·s or more and 1000 mPa·s or less at a shear rate of 1 ^{s −1} , and The composite particle according to [1], wherein the pressure is 5 mPa·s or more and 100 mPa·s or less.
[3] The composite particle according to [1] or [2], wherein the fine fibers are one or more types selected from cellulose nanofibers and chitin nanofibers.
[4] The composite particle according to any one of [1] to [3], wherein the ionic functional group is one or more selected from a carboxy group, a phosphoric acid group, and a sulfo group.
[5] The composite particle according to any one of [1] to [4], wherein the content of the ionic functional group is 0.1 μmol/g or more and 100 μmol/g or less based on the dry mass of the composite particle.
[6] The composite particles according to any one of [1] to [5], having a solid content of 80% by mass or more.
[7] The composite particle according to any one of [1] to [6], wherein the polymer has a benzene ring structure at least in part.
[8] The composite particle according to any one of [1] to [7], wherein the polymer is a biodegradable polymer.
[9] Part or all of the ionic functional group is modified by a reaction that combines with one or more functional materials selected from anionic functional materials and cationic functional materials, [1 ] to [8]. The composite particle according to any one of [8].
[10] The composite particle according to [9], wherein the functional material is a fluorescent dye.
[11] The fluorescent dye is a fluorescent dye having one or more selected from a cyanine skeleton, a xanthene skeleton, an oxazine skeleton, an acridine skeleton, a diphenylmethane skeleton, a thiazole skeleton, an indole skeleton, an ethidium skeleton, and a propidium skeleton, [10] Composite particles described in.
[12] The composite particle according to [10] or [11], wherein the amount of the fluorescent dye bound is 0.1 μmol/g or more and 100 μmol/g or less based on the dry mass of the composite particle.

[13] A step of subjecting the fiber raw material to shortening treatment to obtain shortened fibers;
defibrating one or more selected from the fiber raw material and the shortened fiber in a solvent to obtain a fine fiber dispersion in which fine fibers are dispersed;
adding droplets containing a core particle precursor to the fine fiber dispersion and coating the surface of the droplets with the fine fibers;
solidifying the core particle precursor to obtain a core particle, and obtaining a composite particle in which the surface of the core particle is coated with the fine fiber;
A method for producing composite particles, comprising:
[14] The composite particle according to [13], further comprising a step of introducing an ionic functional group into one or more selected from the fiber raw material, the shortened fiber, and the fine fiber to obtain an ion-modified fiber. Production method.
[15] The method for producing composite particles according to [14], wherein the ion-modified fibers are brought into contact with a functional material-containing liquid containing a functional material to obtain composite particles with the functional material bound to the surface.
[16] The method for producing composite particles according to [15], wherein the functional material is a fluorescent dye.

According to the composite particles and the method for producing composite particles of the present invention, composite particles can be stably produced with high purification efficiency and good dispersibility.

FIG. 1 is a schematic diagram showing composite particles according to an embodiment of the present invention. It is a figure showing an example of the manufacturing method of the composite particle concerning one embodiment of the present invention. It is a graph showing particle size distribution of fine fibers concerning one embodiment of the present invention. 1 is a graph showing viscosity characteristics of fine fibers according to an embodiment of the present invention. 1 is a scanning electron microscope (SEM) image of composite particles of Example 1. 1 is a scanning electron microscope (SEM) image of composite particles of Example 1. 3 is a fluorescence microscopy image of composite particles of Example 20. 3 is a fluorescence microscope image of composite particles of Comparative Example 4.

Embodiments of the present invention will be described below with reference to the drawings. However, in each figure described below, mutually corresponding parts are given the same reference numerals, and explanations of overlapping parts will be omitted as appropriate. Further, this embodiment is an example of a configuration for embodying the technical idea of the present invention, and the material, shape, structure, arrangement, dimensions, etc. of each part are not specified as described below. The technical idea of the present invention can be modified in various ways within the technical scope defined by the claims.

≪Composite particles≫
The composite particles of the present invention have fine fibers and core particles containing at least one type of polymer.
The fine fibers are ion-modified fibers having ionic functional groups and are bonded to the surface of the core particle.

As shown in FIG. 1(a), the composite particle 1 of this embodiment has fine fibers 2 and core particles 3. The fine fibers 2 are bonded to the surface of the core particles 3.
In the composite particle 1, fine fibers 2 are formed as a coating layer (fibrous layer) 20 that covers the surface of the core particle 3.
The composite particle 1 has a core particle 3 and fine fibers 2 that are bonded to the surface of the core particle 3 and are inseparable.

As shown in FIG. 1(b), in the composite particle 1A, the functional material 4 is bonded to the composite particle 1.
The composite particles 1A are modified by a reaction in which part or all of the ionic functional groups are bonded to one or more functional materials 4 selected from anionic functional materials and cationic functional materials.

The fine fibers 2 are bonded to the surface of the core particle 3 and are inseparable. "Inseparable" here means that composite particles 1 or composite particles 1A are purified by centrifuging the dispersion containing composite particles 1 or composite particles 1A, removing the supernatant, and then redispersing by adding a solvent. Even after repeating the washing operation or the washing operation with a solvent by filtration washing using a membrane filter, the core particles 3 and the fine fibers 2 do not separate, and the core particles 3 are covered with the fine fibers 2. means that the condition is maintained.

The coating state can be confirmed by observing the surface of composite particle 1 or composite particle 1A using a scanning electron microscope (SEM).
Although the bonding mechanism between the fine fibers 2 and the core particles 3 in the composite particles 1 is not certain, it is believed that this is because the composite particles 1 are produced using an O/W type emulsion stabilized by the fine fibers 2 as a template. Conceivable. This is because the fine fibers 2 physically form the core particles 3 in order to solidify the core particle precursors to form the core particles 3 while the fine fibers 2 are in contact with the core particle precursors inside the emulsion droplets. It is presumed that the core particles 3 and the fine fibers 2 are immobilized on the surface and eventually become inseparable.
It is thought that the functional material-bound fibers in which the functional material 4 is bonded to the fine fibers 2 and the core particles 3 become inseparable by the same mechanism.
Here, the O/W emulsion is also called an oil-in-water emulsion, in which water is the continuous phase and oil is dispersed therein as oil droplets (oil particles). .

Although not particularly limited, when composite particles 1 are produced using an O/W type emulsion stabilized by the fine fibers 2 as a template, the O/W type emulsion is stabilized, so a true spherical shape derived from the O/W type emulsion is obtained. Composite particles 1 can be obtained. Specifically, it is preferable that the coating layer 20 made of the fine fibers 2 is formed on the surface of the spherical core particles 3 with a relatively uniform thickness. When the fine fibers 2 are short fibers, the thickness of the coating layer 20 becomes more uniform.

The particle size of the composite particles 1 can be confirmed by observation using an optical microscope or the like. The average particle diameter can be calculated by measuring the diameter (or major axis) of 100 randomly selected composite particles 1 and calculating the arithmetic mean. The average particle diameter of the composite particles 1 is 0.1 μm or more and 50 μm or less, preferably 0.5 μm or more and 30 μm or less, and more preferably 1 μm or more and 20 μm or less. When the average particle diameter of the composite particles 1 is equal to or larger than the above lower limit, purification of the composite particles 1 becomes easy. When the average particle diameter of the composite particles 1 is equal to or less than the above upper limit, variations in the particle diameter of the composite particles 1 can be reduced, and the composite particles 1 can be stably produced.
The average particle size of the composite particles 1A is the same as the average particle size of the composite particles 1.
In this way, by using the fine fibers 2, fine composite particles 1 with small variations in particle size can be obtained.

The composite particles 1 are preferably spherical, particularly perfectly spherical. By using the fine fibers 2, a stable O/W type Pickering emulsion is formed, and thereby true spherical composite particles 1 can be obtained. When the fine fibers 2 are short fibers, a stable Pickering emulsion can be formed and composite particles 1 with high sphericity can be obtained. When the composite particles 1 are perfectly spherical, aggregation is suppressed and dispersibility in various liquid media and resins is improved.
The index of sphericity can be evaluated from the average circularity measured by an image analysis type particle size distribution analyzer. The average circularity of the composite particles 1 is 0.8 or more, preferably 0.85 or more, and more preferably 0.9 or more. When the average circularity of the composite particles 1 is equal to or greater than the above lower limit, the composite particles 1 can be stably manufactured. In addition, when the average circularity of the composite particles 1 is equal to or greater than the above lower limit value, a smooth feeling of use can be easily obtained. The upper limit of the average circularity of the composite particles 1 is not particularly limited, but is ideally 1.0.
The average circularity can be calculated as the arithmetic mean value of the circularity of 1000 or more particles measured using an image analysis type particle size distribution analyzer. It is preferable to use the average circularity as an index of the sphericity. Note that when the area of the composite particle 1 on the image is S and the perimeter is L, the circularity can be calculated using the formula "Circularity = 4πS/L ² ", and the closer the circularity is to 1, the more spherical it is. becomes higher.
The average circularity of the composite particles 1 can be adjusted by the type of polymer constituting the core particles 3, the type of fine fibers 2, the median diameter, the type and amount of ionic functional groups introduced into the fine fibers 2, and the combination thereof. can.
The shape, average circularity, and sphericity of the composite particle 1A are the same as the shape, average circularity, and sphericity of the composite particle 1.

From the viewpoint of dispersion stability, it is preferable that the fine fibers 2 form a coating layer 20 on the surface of the core particles 3. In this case, the covering layer 20 is composed of fine fibers 2. It is preferable that the coating layer 20 covers the entire surface of the core particle 3. When the fine fibers 2 are short fibers, the surface of the core particles 3 can be uniformly covered, so the stability of the Pickering emulsion is improved, true spherical composite particles 1 can be efficiently obtained, and the dispersibility is improved. improves.
The average thickness of the coating layer 20 is not particularly limited, but is preferably, for example, 0.1 nm or more and 1000 nm or less, more preferably 0.5 nm or more and 500 nm or less, and even more preferably 1.0 nm or more and 200 nm or less. When the average thickness of the coating layer 20 is at least the above lower limit, a stable Pickering emulsion can be easily formed and variations in particle size can be suppressed. In addition, when the average thickness of the coating layer 20 is equal to or greater than the above lower limit, the functional material 4 such as a fluorescent dye is easily adsorbed. When the average thickness of the coating layer 20 is less than or equal to the above upper limit value, separation of the fine fibers 2 from the surface of the core particles 3 can be suppressed.
Here, "Pickering emulsion" refers to an emulsion stabilized by solid particles adsorbed at the liquid/liquid interface.
The average thickness of the coating layer 20 is determined by observation using a scanning electron microscope (SEM) or the like. Specifically, the composite particles 1 fixed with embedding resin are cut with a microtome and subjected to SEM observation. It can be calculated by measuring the thickness of the coating layer 20 in a cross-sectional image of the composite particle 1 in the image observed by SEM at 100 random locations on the image and taking the average value.
The average thickness of the coating layer 20 can be adjusted by the type of polymer constituting the core particle 3, the type of fine fiber 2, the median diameter, the type and amount of the ionic functional group introduced into the fine fiber 2, and a combination thereof. .
The average thickness of the coating layer 20 of the composite particles 1A is the same as the average thickness of the composite particles 1.

It is preferable that the composite particles 1 are uniformly coated with a coating layer 20 having a relatively uniform thickness. When the fine fibers 2 are short fibers, the thickness of the coating layer 20 becomes uniform. When the thickness of the coating layer 20 is uniform, the dispersion stability is high and the functional material 4 is easily adsorbed.
The uniformity of the thickness of the coating layer 20 can be evaluated by the coefficient of variation obtained by dividing the standard deviation of the thickness by the average thickness. The coefficient of variation of the thickness of the coating layer 20 is preferably 0.5 or less, more preferably 0.4 or less.
The coefficient of variation of the thickness of the coating layer 20 of the composite particle 1A is the same as that of the composite particle 1.

The ionic functional groups (content of ionic functional groups) present on the surface of the composite particles 1 are preferably 0.1 μmol or more and 100 μmol or less, more preferably 0.5 μmol or more and 50 μmol or less per 1 g of dry mass of the composite particles 1. By using fine fibers 2 with a short fiber length, composite particles 1 having a sufficient amount of ionic functional groups on the surface of the composite particles 1 can be obtained, so that the dispersibility of the composite particles 1 and the adsorption of the functional material 4 can be improved. improves. When the ionic functional groups present on the surface of the composite particles 1 are at least the above lower limit, composite particles 1 with a uniform particle size distribution are likely to be obtained. In addition, if the ionic functional groups present on the surface of the composite particles 1 are at least the above lower limit, the dispersibility of the composite particles 1 can be further improved. In addition, the functional material 4 such as a fluorescent dye can be easily adsorbed to the extent that association and aggregation can be suppressed, and the functionality such as the fluorescence emission intensity of the composite particles 1A to which the functional material 4 is bound can be further enhanced.
The content of ionic functional groups in the composite particles 1A is similar to the content of ionic functional groups in the composite particles 1.

The content of ionic functional groups in the composite particles 1 can be measured by electrical conductivity titration using a dispersion of the composite particles 1. After uniformly dispersing 1 g of composite particles 1 in 99 g of ion-exchanged water, hydrochloric acid is added to adjust the pH to 2.0 or less, and the mixture is stirred for about 1 hour. Using an automatic titration device (product name: AUT-701, manufactured by DKK Toa Co., Ltd.), 1 mmol/L sodium hydroxide aqueous solution was injected at 0.05 mL/30 seconds, and the conductivity and pH value were measured every minute. and continue measuring until pH11. From the obtained conductivity curve, the titration amount of sodium hydroxide is determined, and the content of ionic functional groups is calculated.

The solid content percentage of the composite particles 1 is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass. When the solid content percentage of the composite particles 1 is equal to or higher than the above lower limit, the transportation cost can be reduced and the dispersibility in the hydrophobic resin becomes good.
The solid content percentage of the composite particles 1 is determined by dividing the mass of the composite particles 1 after drying the composite particles 1 at a temperature of 120° C. for 1 hour by the mass before drying.
The solid content percentage of the composite particles 1A is the same as that of the composite particles 1.

In the composite particle 1, the surface of a core particle 3 is coated with short-length fine fibers 2 having ionic functional groups. Therefore, a stable emulsion can be formed, with small variations in particle diameter, a true spherical shape, and better dispersibility.
Moreover, since the fine fibers 2 have ionic functional groups, they can adsorb one or more functional materials 4 selected from anionic functional materials and cationic functional materials.

Part or all of the ionic functional groups are preferably modified by a reaction that combines with one or more functional materials 4 selected from anionic functional materials and cationic functional materials. Since some or all of the ionic functional groups are modified by a reaction that combines with the functional material 4, functionality can be imparted to the composite particles 1.

Examples of functional materials 4 include colorants (fluorescent dyes, redox dyes, etc.), oil absorbers, light shielding agents (ultraviolet absorbers, ultraviolet scattering agents, etc.), antibacterial agents, antioxidants, antiperspirants, and deodorants. Foaming agents, antistatic agents, binders, bleaching agents, chelating agents, deodorizing ingredients, fragrances, fragrances, anti-dandruff active substances, emollients, insect repellents, preservatives, natural extracts, beauty ingredients, pH regulators, Examples include vitamins, amino acids, hormones, oily raw materials including fats and waxes, surfactants, and inorganic particles (titanium oxide, silica, clay, etc.).
As the functional material 4, a coloring agent is preferable, and a fluorescent dye is more preferable.

The anionic functional material is a functional material having an anionic functional group. Examples of the anionic functional group include, but are not limited to, a carboxy group, a phosphoric acid group, a sulfo group, and the like.
A cationic functional material is a functional material having a cationic functional group. Examples of the cationic functional group include an amino group, an onium group, a hydrazinium group, a phosphonium group, an oxonium group, a sulfonium group, a diazenium group, and a diazonium group.

Examples of the skeleton of fluorescent dyes include cyanine (HITCI, etc.), xanthene (Rhodamine 6G, Rhodamine B, etc.), oxazine (Nile Blue, etc.), coumarin (4-MU, etc.), quinoline (Carbostyryl 165, etc.), stilbene ( stilbene 1, etc.), oxazole (POPOP, etc.), para-oligophenylene (p-triphenyl, etc.), acridine (acridine, acridine orange, etc.), diallylmethane (auramine, etc.), thiazole (Thioflavin T, etc.), indole (DAPI dihydrochloride, etc.) Salts), ethidium (ethidium bromide, etc.), propidium (propidium bromide, etc.), tetrapyrrole (chlorophyll, etc.), dipyrromethene (BODIPY, etc.), naphthalene, anthracene, pyrene, perylene, etc. can be used.
Among them, it is preferable to use dyes having a cyanine skeleton, a xanthene skeleton, an oxazine skeleton, an acridine skeleton, a diallylmethane skeleton (diphenylmethane skeleton), a thiazole skeleton, an indole skeleton, an ethidium skeleton, and a propidium skeleton from the viewpoint of solubility in hydrophilic solvents. .
Furthermore, since dyes having a xanthene skeleton, oxazine skeleton, acridine skeleton, thiazole skeleton, indole skeleton, ethidium skeleton, or propidium skeleton tend to associate, adsorption to the fine fibers 2 tends to exhibit an association suppressing effect.

Examples of the cationic fluorescent dye include rhodamine 6G, rhodamine B, rhodamine 123, Nile blue, acridine orange, auramine, DAPI dihydrochloride, ethidium bromide, and ethidium bromide.
Examples of anionic fluorescent dyes include merocyanine I, merocyanine 540, pyranine, and fluorescein.
In addition, one type of fluorescent dye may be used alone, or two or more types may be used in combination. Further, a cationic fluorescent dye and an anionic fluorescent dye may be used in combination within a range that can suppress association and aggregation.
The skeleton of the fluorescent dye adsorbed on the fine fibers 2 can be analyzed by methods such as infrared spectroscopy (IR) and gas chromatography-mass spectrometry (GC/MS).

Examples of redox dyes include methylene blue and indigo carmine.

<Fine fiber>
The fine fiber 2 of this embodiment is an ion-modified fiber having an ionic functional group with a median diameter of 0.01 μm or more and 10 μm or less.
The amount of ionic functional groups introduced into the fine fibers 2 is from 1.3 mmol/g to 5.0 mmol/g based on the dry mass of the fine fibers 2.

It is preferable that the fine fibers 2 have a fiber shape derived from a microfibril structure. Specifically, the fine fibers 2 are fibrous and have a number average minor axis diameter of 1 nm or more and 1000 nm or less, a number average major axis diameter of 50 nm or more and 50 μm or less, and a number average major axis diameter of 1 nm or more and 1000 nm or less, and a number average major axis diameter of 50 nm or more and 50 μm or less. It is preferable that the diameter is 5 times or more.
When the number average minor axis diameter is equal to or greater than the above lower limit, a rigid fiber structure can be obtained, emulsion stability is improved, and composite particles 1 with small particle size variations can be obtained. Furthermore, when the functional material 4 is adsorbed onto the composite particles 1, association or aggregation of the molecules of the functional material 4 can be suppressed, making it possible to more reliably impart functionality to the composite particles 1. When the number average minor axis diameter is below the above upper limit value, the fine fibers 2 can uniformly cover the droplets of the emulsion of the core particle precursor, and a stable Pickering emulsion can be formed. Therefore, it is possible to obtain truly spherical composite particles 1 with small variations in particle size.
The number average major axis diameter is preferably 5 times or more the number average minor axis diameter. When the number average major axis diameter is equal to or larger than the above lower limit value, the particle size and shape of the composite particles 1 and 1A of composite particles can be more easily controlled.
The number average major axis diameter of the fine fibers 2 is preferably 50 nm or more and 1000 nm or less, more preferably 50 nm or more and 800 nm or less, and even more preferably 100 nm or more and 500 nm or less. When the number average major axis diameter of the fine fibers 2 is below the above upper limit value, when producing the composite particles 1, the free fine fibers 2 and the composite particles 1 are sufficiently separated, and the composite particles 1 can be produced in high yield. It can be collected at In particular, when the number average major axis diameter of the fine fibers 2 is 500 nm or less, the composite particles 1 can be stably produced and efficiently recovered.
The number average minor axis diameter and number average major axis diameter of the fine fibers 2 are determined by the method described in Examples.

The median diameter of the fine fibers 2 is 0.01 μm or more and 10 μm or less, preferably 0.03 μm or more and 5 μm or less, and more preferably 0.05 μm or more and 1.0 μm or less. When the median diameter of the fine fibers 2 is equal to or larger than the above lower limit, the stability of the emulsion is good because the fine fibers 2 have a rigid fiber structure, and composite particles 1 with small variations in particle size can be obtained. When the median diameter of the fine fibers 2 is equal to or less than the above upper limit, the fiber length of the fine fibers 2 is sufficiently short to uniformly cover the droplets of the emulsion of the core particle precursor, forming a stable Pickering emulsion. can. Therefore, it is possible to obtain perfectly spherical composite particles 1 with small variations in particle size. Further, when producing the composite particles 1, the free fine fibers 2 and the composite particles 1 can be sufficiently separated, and the composite particles 1 can be recovered at a high yield.
Here, the "median diameter of fine fibers" refers to the median diameter (or diameter) based on the number of diameters (or long diameters) when fine fibers are likened to spheres when measured using a laser diffraction/scattering particle size distribution analyzer. (diameter when the cumulative number of particles is 50%).
The median diameter of the fine fibers 2 is determined by the method described in Examples.

The material of the fine fibers 2 is not particularly limited, and may be organic or inorganic. As the organic substance, an organic polymer can be used. Examples of the organic polymer include acrylic polymers, epoxy polymers, ester polymers, amino polymers, silicone polymers, fluorine polymers, and urethane polymers. Examples include polymers.
The organic polymer may be a natural polymer or a synthetic polymer.

Examples of natural polymers include polysaccharides produced by plants (cellulose, starch, alginic acid, etc.), polysaccharides produced by animals (chitin, chitosan, hyaluronic acid, etc.), proteins (collagen, gelatin, albumin, etc.), and polysaccharides produced by microorganisms. Examples include polyesters (poly(3-hydroxyalkanoate)) and polysaccharides (hyaluronic acid, etc.).

Examples of synthetic polymers include aliphatic polyesters, polyols, and polycarbonates.
Examples of fatty acid polyesters include glycol-dicarboxylic acid polycondensation systems (polyethylene succinate, polybutylene succinate, etc.), polylactides (polyglycolic acid, polylactic acid, etc.), polylactones (β-caprolactone, ε-caprolactone, etc.) and others (polybutylene terephthalate, adipate, etc.).
Examples of the polyol include polyvinyl alcohol.
Examples of the polycarbonate include polyester carbonate.

Although not particularly limited, the organic polymer is preferably a biodegradable polymer.
Examples of biodegradable polymers include, in addition to the above-mentioned natural polymers, polyacid anhydrides, polycyanoacrylates, polyorthoesters, polyphosphazenes, and the like.
Among the biodegradable polymers, it is preferable to use natural polymers such as cellulose, chitin, and chitosan. Since cellulose, chitin, and chitosan can uniformly introduce ionic functional groups, the functional material 4 can be uniformly adsorbed, and the functional material 4 can be more stably introduced into the composite particles 1.

An inorganic polymer is a polymer compound that does not contain carbon, and examples of the inorganic polymer include silicon dioxide, polysiloxane, polyphosphazene, and polysilane.

Among these, the fine fibers 2 are preferably one or more selected from cellulose nanofibers and chitin nanofibers. One or more selected from cellulose nanofibers and chitin nanofibers can uniformly introduce ionic functional groups onto the fiber surface, so they have good dispersibility and a high emulsion stabilizing effect. Further, the functional material 4 such as a fluorescent dye is uniformly adsorbed, and the functional material 4 can be more stably introduced into the composite particle 1. Furthermore, when a fluorescent dye is applied as the functional material 4, the fluorescent dye is uniformly adsorbed to the fine fibers 2, so that stable fluorescence can be exhibited.

Cellulose nanofibers (CNFs) are fibers made of cellulose or cellulose derivatives and having a number average minor axis diameter of 1 nm or more and 1000 nm or less.
Cellulose nanofibers are fine fibers that can be obtained by pulverizing cellulose raw materials obtained from wood etc. into ultrafine fibers, and are safe and biodegradable.

Chitin nanofibers (chitin NF) are fibers with a number average minor axis diameter of 1 nm or more and 1000 nm or less, which are made of one or more types selected from chitin and chitosan, and one or more types of derivatives selected from chitin and chitosan.
Chitin nanofibers are fine fibers that can be obtained by grinding one or more raw materials selected from chitin and chitosan collected from crab shells etc. into ultrafine fibers, and are safe, biodegradable, and have antibacterial properties. have
Therefore, since safety confirmation is not necessary, it becomes much easier to develop the product in applications where the product is taken into the body, such as food, medical care, medicine, and personal care.

The fine fibers 2 have a cationic functional group, an anionic functional group, or both of these as ionic functional groups. By having the ionic functional group, the fine fibers 2 can stabilize the emulsion during production of the composite particles 1, and can efficiently obtain the composite particles 1A with small variation in particle size.
Furthermore, the functional material 4 such as a fluorescent dye can be adsorbed onto the fine fibers 2 while suppressing aggregation and association. In particular, when a fluorescent dye is applied as the functional material 4, if the fiber raw material used as the raw material for the fine fibers 2 has an ionic functional group only on the crystal surface, the distance between the molecules of the fluorescent dye is maintained, resulting in stable fluorescence. Shows luminescence.
When the fine fibers 2 have anionic functional groups, they can adsorb cationic functional materials. When the fine fibers 2 have cationic functional groups, they can adsorb anionic functional materials.

Examples of the anionic functional group include, but are not limited to, a carboxy group, a phosphoric acid group, a sulfo group, and the like. Among these, carboxy groups and phosphoric acid groups are preferred, and carboxy groups are more preferred because they can be easily introduced selectively onto the cellulose crystal surface.
Examples of the cationic functional group include an amino group, an onium group, a hydrazinium group, a phosphonium group, an oxonium group, a sulfonium group, a diazenium group, and a diazonium group.

Among these, it is preferable to use cellulose single nanofibers (hereinafter also referred to as CSNF, TEMPO-oxidized cellulose nanofibers, and TEMPO-oxidized CNF) in which carboxyl groups are selectively introduced to the crystal surface of the fiber raw material by TEMPO oxidation.
In TEMPO-oxidized CNF, the hydroxyl group (OH group) at the C6 position on the crystal surface of the fiber raw material is selectively oxidized, so only the OH group on the crystal surface is oxidized, and the distance between the carboxy groups is constant and short. The shaft diameter is uniform. Therefore, it is possible to form a stable emulsion, have small variations in particle size, have a uniform thickness of the coating layer 20, and obtain perfectly spherical composite particles 1. Furthermore, when a fluorescent dye is used as the functional material 4, the distance between molecules of the fluorescent dye can be made uniform, and stable fluorescence emission is exhibited.

The amount of ionic functional groups introduced into the fine fibers 2 is 1.3 mmol/g or more and 5.0 mmol/g or less, and 1.5 mmol/g or more and 4.0 mmol/g or less based on the dry mass of the fine fibers 2. It is preferably 1.7 mmol/g or more and 3.5 mmol/g or less, and even more preferably 2.0 mmol/g or more and 3.0 mmol/g or less. When the content of ionic functional groups is at least the above lower limit, fine fibers 2 with a small median diameter can be obtained. In addition, when the content of the ionic functional group is equal to or higher than the above lower limit, the dispersibility of the fine fibers 2 is improved, so that it is easy to purify the composite particles 1 and the free fine fibers 2 in the production of the composite particles 1. Therefore, it is possible to stably obtain true spherical composite particles 1 with small variations in particle size. Furthermore, when a fluorescent dye is used as the functional material 4, the amount of fluorescent dye adsorbed can be increased, and the intensity of fluorescence emission can be further increased. When the content of ionic functional groups is below the above upper limit, a rigid fiber structure can be maintained, so emulsion stability is improved and composite particles 1 with small particle size variations can be obtained. When a fluorescent dye is used as the functional material 4, aggregation of molecules of the fluorescent dye can be suppressed, and changes in fluorescence emission can be suppressed.
Here, the dry mass of the fine fibers 2 means the mass after drying the fine fibers 2 at a temperature of 120° C. for 1 hour.
The content of ionic functional groups is determined by electrical conductivity titration.

When the fine fibers 2 are cellulose nanofibers, the crystal structure of the cellulose nanofibers is preferably cellulose I type from the viewpoint of the strength of the fine fibers 2 and the dimensional stability during heating.
The degree of crystallinity of cellulose nanofibers is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. When the crystallinity of the cellulose nanofibers is equal to or higher than the above lower limit, the strength of the fine fibers 2 and the dimensional stability during heating are maintained, so that highly stable composite particles 1 can be obtained.
The crystallinity of cellulose nanofibers can be determined using a sample horizontal rotating anticathode multipurpose X-ray diffractometer (XRD).

The viscosity at 25°C of an aqueous dispersion containing 0.5% by mass of fine fibers 2 (hereinafter also referred to as "viscosity of fine fibers 2") is 2 mPa·s or more and 1000 mPa·s at a shear rate of 1 s ^-1 . It is preferably 5 mPa·s or more and 100 mPa·s or less when the shear rate is 100 s ⁻¹ . More preferably, it is 5 mPa·s or more and 800 mPa·s or less when the shear rate is 1 s ⁻¹ , and 10 mPa·s or more and 80 mPa·s or less when the shear rate is 100 ^{s −1} . When the viscosity of the fine fibers 2 is equal to or higher than the above lower limit, since the fine fibers 2 have a rigid fiber structure, a stable Pickering emulsion can be formed, and composite particles 1 with small particle size variations can be obtained. When the viscosity of the fine fibers 2 is below the above upper limit, purification by filtration or centrifugation becomes easy, and the composite particles 1 can be recovered from the free fine fibers 2 with good yield.
The viscosity of the fine fibers 2 is determined by measuring the rheology of an aqueous dispersion of the fine fibers 2 with pure water adjusted to a solid content of 0.5% by mass using a rheometer (manufactured by TA Instruments, AR2000ex) at an inclination angle. Evaluate by measuring steady viscoelasticity with a 1° cone plate. The temperature of the measuring section is adjusted to 25° C., and the shear viscosity is continuously measured at shear rates from 0.01 s ⁻¹ to 1000 s ⁻¹ while holding each speed for 30 seconds. After increasing the shear rate from 0.01 s ^-1 to 1000 s ^-1 , and then decreasing the shear rate from 1000 s ^-1 to 0.01 s ^-1 , the shear viscosity at 1 s ^-1 and 100 s ^-1 is finely calculated. Let it be the viscosity of fiber 2.

<Core particle>
Core particles 3 contain at least one polymer. The polymer may be an organic polymer or an inorganic polymer. As the polymer, a known polymer can be used, and a polymer obtained by polymerizing a polymerizable monomer by a known method may be used. Examples of the polymer include acrylic polymers, epoxy polymers, ester polymers, amino polymers, silicone polymers, fluorine polymers, and urethane polymers.
Among these, it is preferable that the polymer contained in the core particles 3 has a benzene ring structure at least in part. Since a polymer having a benzene ring structure emits fluorescence, when a fluorescent dye is applied as the functional material 4, the core particles 3 emit light together with the fluorescent dye, and can exhibit characteristic light emission.

The polymer contained in the core particles 3 is preferably a biodegradable polymer. As used herein, the term "biodegradable polymer" refers to a polymer that decomposes and disappears in the earth's environment such as soil or seawater, or a polymer that decomposes and disappears within a living body.
In general, polymers are degraded in soil or seawater by enzymes possessed by microorganisms, whereas in living organisms they are degraded by physicochemical hydrolysis without the need for enzymes. Polymer decomposition means that the polymer becomes lower in molecular weight or water-soluble and loses its shape. Decomposition of the polymer is not particularly limited, but occurs by hydrolysis of the main chain, side chains, crosslinking points, oxidative decomposition of the main chain, and the like.
Examples of biodegradable polymers include naturally occurring natural polymers and synthetic polymers.

Examples of natural polymers include polysaccharides produced by plants (cellulose, starch, alginic acid, etc.), polysaccharides produced by animals (chitin, chitosan, hyaluronic acid, etc.), proteins (collagen, gelatin, albumin, etc.), and polysaccharides produced by microorganisms. Examples include polyesters (poly(3-hydroxyalkanoate)) and polysaccharides (hyaluronic acid, etc.).

Examples of synthetic polymers include aliphatic polyesters, polyols, and polycarbonates.
Examples of fatty acid polyesters include glycol-dicarboxylic acid polycondensation systems (polyethylene succinate, polybutylene succinate, etc.), polylactides (polyglycolic acid, polylactic acid, etc.), polylactones (β-caprolactone, ε-caprolactone, etc.) and others (polybutylene terephthalate, adipate, etc.).
Examples of the polyol include polyvinyl alcohol.
Examples of the polycarbonate include polyester carbonate.
Other biodegradable synthetic polymers include polyacid anhydrides, polycyanoacrylates, polyorthoesters, and polyphosphazenes.

The core particles 3 may contain other components such as functional components in addition to the polymer. Other ingredients include, for example, colorants (fluorescent dyes, redox dyes, etc.), oil absorbers, light shielding agents (ultraviolet absorbers, ultraviolet scattering agents, etc.), antibacterial agents, antioxidants, antiperspirants, and antifoaming agents. agents, antistatic agents, binders, bleaching agents, chelating agents, deodorizing ingredients, fragrances, fragrances, insect repellents, preservatives, natural extracts, pH adjusters, oil-based raw materials including fats and waxes, and surfactants. and inorganic particles (titanium oxide, silica, clay, etc.).
The above-mentioned functional component may be in any form of solid, gas, or liquid. The content of the functional component in the composite particles 1 is not particularly limited, and is preferably within a range that allows the composite particles 1 to stably maintain their shape. The content of the functional component is preferably 0.001 parts by mass or more and 80 parts by mass or less when composite particle 1 is 100 parts by mass.

Among these, the functional component is preferably a coloring agent, and more preferably a fluorescent dye. Since the core particle 3 contains the fluorescent dye, it emits fluorescent light together with the fluorescent dye on the surface of the composite particle 1, so that it can exhibit characteristic light emission and is suitable for use in preventing counterfeiting. The fluorescent dye is not particularly limited as long as it emits fluorescence, but it is preferably dissolved or dispersed in the core particle precursor described below. By dissolving and dispersing the fluorescent dye in the core particle precursor, the fluorescent dye can be efficiently encapsulated in the core particle 3. Note that the fluorescent dye may be of the same type as the fluorescent dye on the surface of the composite particle 1, or may be of a different type.

The average particle size of the core particles 3 is determined by subtracting the average thickness of the coating layer 20 from the average particle size of the composite particles 1.
In the case of the composite particles 1A, the average particle size of the core particles 3 is determined by subtracting the average thickness of the coating layer 20 from the average particle size of the composite particles 1A.

In the composite particles 1, it is preferable that the functional material 4 is adsorbed to the ionic functional groups of the fine fibers 2.
As shown in FIG. 1(b), in the composite particles 1A of this embodiment, some or all of the ionic functional groups of the fine fibers 2 are selected from anionic functional materials and cationic functional materials. It is modified by a reaction that combines with one or more functional materials 4.
The functional material 4 forms a pair with the ionic functional group of the fine fiber 2 and is adsorbed by ionic bonding. Among the ionic functional groups, the functional groups to which the functional material 4 is adsorbed are modified by a reaction that combines with the functional material 4.
Here, "modified" means that the ionic functional group is electrically neutral.

As the functional material 4, a coloring agent is preferable, and a fluorescent dye is more preferable.
Fluorescent dyes are dyes that emit fluorescence and become excited by absorbing light energy such as ultraviolet light, visible light, or infrared light due to excitation light, and emit fluorescence when returning to the ground state.
The fluorescent dye of this embodiment is a fluorescent dye that ion-adsorbs to the fine fibers 2, and is a cationic or anionic fluorescent dye. Although not particularly limited, in order to adsorb the fluorescent dye by adding and mixing the fluorescent dye to the dispersion liquid of the fine fibers 2, it is preferable that the fluorescent dye is dissolved in a hydrophilic solvent.

An anionic fluorescent dye is a fluorescent dye having an anionic functional group. Examples of the anionic functional group include, but are not limited to, a carboxy group, a phosphoric acid group, a sulfo group, and the like.
A cationic fluorescent dye is a fluorescent dye having a cationic functional group. Examples of the cationic functional group include an amino group, an onium group, a hydrazinium group, a phosphonium group, an oxonium group, a sulfonium group, a diazenium group, and a diazonium group.

Examples of the skeleton of fluorescent dyes include cyanine (HITCI, etc.), xanthene (Rhodamine 6G, Rhodamine B, etc.), oxazine (Nile Blue, etc.), coumarin (4-MU, etc.), quinoline (Carbostyryl 165, etc.), stilbene ( stilbene 1, etc.), oxazole (POPOP, etc.), para-oligophenylene (p-triphenyl, etc.), acridine (acridine, acridine orange, etc.), diallylmethane (auramine, etc.), thiazole (Thioflavin T, etc.), indole (DAPI dihydrochloride, etc.) Salts), ethidium (ethidium bromide, etc.), propidium (propidium bromide, etc.), tetrapyrrole (chlorophyll, etc.), dipyrromethene (BODIPY, etc.), naphthalene, anthracene, pyrene, perylene, etc. can be used.
Among them, it is preferable to use dyes having a cyanine skeleton, a xanthene skeleton, an oxazine skeleton, an acridine skeleton, a diallylmethane skeleton (diphenylmethane skeleton), a thiazole skeleton, an indole skeleton, an ethidium skeleton, and a propidium skeleton from the viewpoint of solubility in hydrophilic solvents. .
Furthermore, since dyes having a xanthene skeleton, oxazine skeleton, acridine skeleton, thiazole skeleton, indole skeleton, ethidium skeleton, or propidium skeleton tend to associate, adsorption to the fine fibers 2 tends to exhibit an association-suppressing effect.

Examples of the cationic fluorescent dye include rhodamine 6G, rhodamine B, rhodamine 123, Nile blue, acridine orange, auramine, DAPI dihydrochloride, ethidium bromide, and ethidium bromide.
Examples of anionic fluorescent dyes include merocyanine I, merocyanine 540, pyranine, and fluorescein.
In addition, one type of fluorescent dye may be used alone, or two or more types may be used in combination. Further, a cationic fluorescent dye and an anionic fluorescent dye may be used in combination within a range that can suppress association and aggregation.
The skeleton of the fluorescent dye adsorbed on the composite particles 1 is obtained by removing the component from which the fluorescent dye has been removed from the composite particles 1 using a method such as infrared spectroscopy (IR) or gas chromatography-mass spectrometry (GC/MS). can be analyzed.

The wavelength of excitation light for the fluorescent dye (excitation wavelength) is not particularly limited, but it may be excited with light of any wavelength among ultraviolet light (UV), visible light, and infrared light. The emission wavelength of the fluorescent dye is not particularly limited either, and it is preferable that the fluorescent dye emits UV, visible light, or infrared light.

Fluorescence emission derived from a fluorescent dye can be evaluated using, for example, fluorescence microscopy or a fluorescence spectrum measuring device.
In the fluorescence microscopy observation, for example, a stereoscopic microscope system SZX16 (manufactured by Olympus Corporation) is used with a black background and an eyepiece x 1 (1x) and an objective lens x 10 (10x). Fluorescence observation can be evaluated using SZX2-FGFP (GFP filter) and SZX2-FUV (UV filter). Observations are made in a color range of 100 to 255 under the GFP filter condition and 0 to 125 under the UV filter condition, and evaluation is performed while covering the stereoscopic microscope system with paper or the like to prevent outside light from entering. The fine fibers 2 modified with fluorescent dyes are called fluorescent dye-adsorbed fibers. Observation of fluorescent dye-adsorbed fibers can be evaluated by placing a sample on a glass slide.
Fluorescence spectrum measurement can be evaluated using a fiber-type compact optical spectrometer USB2000+ (manufactured by Ocean Optics). A sample of fluorescent dye-adsorbed fiber is placed on a glass slide, and the fluorescence spectrum is measured when irradiated with a light source. As a light source, a light source of a stereoscopic microscope system SZX16 (manufactured by Olympus Corporation) that has passed through a GFP filter can be used, and measurement can be performed while preventing external light from entering.

Normally, association or aggregation of fluorescent dyes causes a change in fluorescence wavelength or a decrease in fluorescence intensity. By adsorbing the fluorescent dye to the fine fibers 2 of the composite particles 1, the association of the dye is suppressed, and the wavelength of fluorescence emission can be suppressed from becoming longer.
For example, the maximum fluorescence wavelength of an aqueous solution of 10 μM rhodamine 6G is 560 nm, whereas the maximum fluorescence wavelength of a single fluorescent dye solid reagent becomes a longer wavelength of 670 nm due to the association of the fluorescent dyes. When the fluorescent dye is adsorbed to the fine fibers 2 of the composite particles 1, association and aggregation of the fluorescent dye is suppressed, and the fluorescence wavelength can be prevented from becoming longer, and the maximum fluorescence wavelength becomes 580 nm.
Assuming that the maximum fluorescence wavelength derived from the fluorescent dye of the composite particles 1A of the present embodiment is λ1, the maximum fluorescence wavelength of the dye solid alone is λ2, and the maximum fluorescence wavelength of the 10 μM aqueous solution of the fluorescent dye is λ3, then 50 nm≦(λ2-λ1) ” is preferable. When used as a single solid dye, association and aggregation of fluorescent dyes are likely to occur. In the composite particles 1A, it is preferable that (λ2-λ1) be equal to or greater than the lower limit value, since association and aggregation of the fluorescent dye can be further suppressed.
Further, it is preferable that the relational expression for the maximum fluorescence wavelength is "-100 nm≦(λ3-λ1)≦100 nm." In a 10 μM fluorescent dye aqueous solution, the fluorescent dye exists as a single molecule. In the composite particles 1A, it is preferable that (λ3-λ1) be within the above numerical range, since association of fluorescent dyes can be further suppressed.
As a method for calculating λ1 derived from the fluorescent dye in the composite particles 1A, there is a method of subtracting the value of the fluorescence intensity of the composite particles 1 on which no fluorescent dye has been adsorbed from the value of the fluorescence intensity of the composite particles 1A on which the fluorescent dye has been adsorbed. Can be mentioned.

The amount of the fluorescent dye adsorbed on the surface of the composite particle 1 (the amount of fluorescent dye adsorbed) is preferably 0.01 μmol or more and 100.0 μmol or less, more preferably 0.05 μmol or more and 50.0 μmol or less per 1 g of dry mass of the composite particle 1. preferable. When the amount of fluorescent dye adsorbed is at least the above lower limit, sufficient fluorescence can be exhibited. When the amount of fluorescent dye adsorbed is below the above upper limit value, association and aggregation between fluorescent dye molecules can be suppressed, and changes in fluorescence emission wavelength can be suppressed.

The amount of fluorescent dye bound (the amount of fluorescent dye adsorbed) is determined by the following method.
The composite particles 1A are immersed in an acidic aqueous solution or an alkaline aqueous solution to remove the adsorbed fluorescent dye. The amount of desorbed fluorescent dye is determined from the absorbance. The amount of fluorescent dye determined from the absorbance is defined as the amount of fluorescent dye adsorbed (the amount of bound fluorescent dye).
For example, if the ionic functional group is an anionic functional group, 1% by mass of composite particles 1A is added to hydrochloric acid having a pH of 2.0 or less, and the mixture is left to stand for 1 hour or more while stirring. Thereafter, it is separated into a solid component and a liquid component by centrifugation or filtration. The absorbance of the separated liquid component is measured to determine the amount of fluorescent dye desorbed by the acid. The amount of fluorescent dye desorbed by the acid is defined as the amount of fluorescent dye adsorbed.
The amount of fluorescent dye desorbed by the acid is determined by the following procedure.
Using pure water as a reference, the absorbance of a fluorescent dye aqueous solution with a known concentration is measured in advance, and the molar extinction coefficient of the fluorescent dye is calculated from Beer-Lambert's law expressed by the following formula (i).
A=-log ₁₀ (I ₁ /I ₀ )=εcl...(i)
In equation (i), A is the absorbance, _I0 is the intensity of light before entering the medium (irradiance), _I1 is the intensity of light after passing through the medium of length l, ε is the molar extinction coefficient, c represents the molar concentration of the medium.
From the absorbance A of the separated liquid component and the molar extinction coefficient ε of the fluorescent dye, the molar concentration c of the fluorescent dye in the separated liquid component, that is, the amount of the fluorescent dye desorbed by the acid is determined.

The fine fibers 2 in the composite particle 1A are the same as the fine fibers 2 in the composite particle 1.

The adsorption amount (bond amount) of the fluorescent dye in the fine fibers 2 of the composite particles 1A is not particularly limited, but is preferably 0.1 mol/g or more and 4.0 mmol/g or less, and 0.1 mol/g or more and 4.0 mmol/g or less based on the dry mass of the fine fibers 2. More preferably, the amount is .2 mmol/g or more and 3.0 mmol/g or less. When the amount of fluorescent dye bound is at least the above lower limit, sufficient fluorescence can be exhibited. When the binding amount of the fluorescent dye is below the above upper limit, the distance between the molecules of the fluorescent dye can be maintained appropriately, association or aggregation can be suppressed, and shift of fluorescence emission and weakening of fluorescence emission can be suppressed. .

The amount of fluorescent dye bound in the fluorescent dye-adsorbed fiber is determined by the following method.
The fluorescent dye-adsorbing fiber is immersed in an acidic or alkaline aqueous solution to remove the adsorbed fluorescent dye. The amount of desorbed fluorescent dye is determined from the absorbance. The amount of fluorescent dye determined from the absorbance is defined as the amount of fluorescent dye adsorbed (the amount of bound fluorescent dye).
For example, if the ionic functional group is an anionic functional group, 0.1% by mass of the fluorescent dye-adsorbing fiber is added to hydrochloric acid having a pH of 2.0 or lower, and the mixture is left for 1 hour or more while stirring. Thereafter, the solid and liquid components are separated. The absorbance of the separated liquid component is measured to determine the amount of fluorescent dye desorbed by the acid. The amount of fluorescent dye desorbed by the acid is defined as the amount of fluorescent dye adsorbed.
The amount of fluorescent dye desorbed by the acid is determined by the following procedure.
Using pure water as a reference, the absorbance of an aqueous fluorescent dye solution with a known concentration is measured in advance, and the molar extinction coefficient of the fluorescent dye is calculated from Beer-Lambert's law expressed by the following formula (i).
A=-log ₁₀ (I ₁ /I ₀ )=εcl...(i)
In equation (i), A is the absorbance, _I0 is the intensity of light before entering the medium (irradiance), _I1 is the intensity of light after passing through the medium of length l, ε is the molar extinction coefficient, c represents the molar concentration of the medium.
From the absorbance A of the separated liquid component and the molar extinction coefficient ε of the fluorescent dye, the molar concentration c of the fluorescent dye in the separated liquid component, that is, the amount of the fluorescent dye desorbed by the acid is determined.

The adsorption amount (adsorption rate) of the fluorescent dye to the ionic functional groups of the fine fibers 2 is not particularly limited, but when the amount of ionic functional groups is 100 mol%, it is preferably 0.1 mol% or more and 95 mol% or less, and 1 mol% or more. It is more preferably 90 mol%, and even more preferably 2 mol% or more and 50 mol% or less. When the adsorption rate of the fluorescent dye to the ionic functional group is equal to or higher than the above lower limit, sufficient fluorescence can be exhibited. When the adsorption rate of the fluorescent dye to the ionic functional group is below the above upper limit, the distance between the molecules of the fluorescent dye can be maintained at an appropriate level, association or aggregation can be suppressed, and the shift of fluorescence emission and fluorescence emission are weak. You can suppress what happens.
The adsorption rate of the fluorescent dye to the ionic functional group is determined by dividing the amount of the fluorescent dye bound by the content of the ionic functional group.

≪Method for manufacturing composite particles≫
The method for producing the composite particles of the present invention is not particularly limited, and any known method can be used. For example, using a chemical preparation method or a physicochemical preparation method, a composite particle 1 having a core particle 3 formed of a material containing a polymer and a fine fiber 2 bonded to the surface of the core particle 3 is manufactured. do.
Examples of chemical preparation methods include polymerization granulation methods (emulsion polymerization method, suspension polymerization method, seed polymerization method, radiation polymerization method, etc.) in which particles are formed from polymerizable monomers during the polymerization process.
Examples of physicochemical preparation methods include, for example, dispersion granulation methods (spray drying method, in-liquid curing method, solvent evaporation method, phase separation method, solvent dispersion cooling method, etc.) in which particles are formed from a polymer solution formed into microdroplets. can be mentioned.
Composite particles 1A can be manufactured by adsorbing functional material 4 to fine fibers 2 on the surface of composite particles 1.

For example, an O/W Pickering emulsion using fine fibers 2 is formed, the core particle precursor inside the droplet is solidified, and fiber-coated particles (composite By producing particles 1), it is possible to obtain composite particles 1 in which core particles 3 and fine fibers 2 are bonded and inseparable.
By using the fine fibers 2, stable droplets can be formed without using additives such as surfactants, so that true spherical composite particles 1 with a small particle size distribution can be obtained.
In addition, the fine fibers 2 present on the surface of the composite particles 1 are hydrophilic, have a high specific surface area, and have good dispersibility, so the functional material 4 is efficiently adsorbed on the surface of the composite particles 1, and Material 4 becomes difficult to detach.
The core particle precursor may be anything that can be solidified to form the core particles 3, and examples thereof include polymerizable monomers, molten polymers, dissolved polymers, and the like.
The method for solidifying the core particle precursor is not particularly limited, and the core particle precursor can be solidified by polymerizing a polymerizable monomer, solidifying a molten polymer, removing a solvent from a dissolved polymer, etc. .

Hereinafter, the method for manufacturing composite particles 1 and composite particles 1A of this embodiment will be described in detail with reference to the drawings.

Composite particles 1 and composite particles 1A of this embodiment can be manufactured by the manufacturing method shown in FIG. 2. As shown in FIG. 2, the method for manufacturing composite particles 1 of this embodiment includes a first step, a second step, a third step, and a fourth step. Moreover, the manufacturing method of composite particle 1A of this embodiment has the 1st process, the 2nd process, the 3rd process, and the 4th process in the manufacturing method of the composite particle 1, and the 5th process after the 4th process.

<First step>
In the first step (step 1), as shown in FIG. 2(a), the fiber raw material is subjected to short fiber processing to obtain a dispersion of short fibers, and the fiber raw material and short fibers are mixed in a hydrophilic solvent 7. This is a step of defibrating one or more types of synthetic fibers to obtain a dispersion of fine fibers 2.

As the fiber raw material, a cellulose raw material and one or more raw materials selected from chitin and chitosan (hereinafter also referred to as "chitin/chitosan raw material") can be used.
The type and crystal structure of cellulose that can be used as a cellulose raw material are not particularly limited. Specifically, raw materials consisting of cellulose type I crystals include, in addition to wood-based natural cellulose, non-wood-based natural celluloses such as cotton linters, bamboo, hemp, bagasse, kenaf, bacterial cellulose, ascidian cellulose, and valonia cellulose. can be used. Furthermore, regenerated cellulose typified by rayon fibers and cupra fibers made of cellulose type II crystals can also be used. From the viewpoint of ease of material procurement, it is preferable to use wood-based natural cellulose as the raw material. The wood-based natural cellulose is not particularly limited, and those commonly used in the production of cellulose nanofibers, such as softwood pulp, hardwood pulp, and waste paper pulp, can be used. As the wood-based natural cellulose, softwood pulp is preferred because it can be easily purified and refined.

Chitin/chitosan raw materials include, for example, crustaceans such as crabs and shrimp, insects, arthropods such as spiders, and linear structural polysaccharides that support and protect the bodies of animals, such as the tendons of squid. It will be done. Chitin/chitosan raw materials are crystalline (there are parts where molecules are arranged regularly), and some of them are bound to proteins. Chitin is a polysaccharide whose main constituent sugar is N-acetylglucosamine. When chitin/chitosan raw materials are isolated and purified, there is almost no purified chitin that consists of 100% N-acetylglucosamine, and one or more chitins selected from chitin and chitosan containing glucosamine as a component are obtained.
For example, a raw material obtained by crushing dry red king crab shell into pieces of about 5 mm or a raw material obtained by crushing wet shell of a squid into pieces about 1 cm can be used as the chitin/chitosan raw material.
It is preferable to refine the chitin/chitosan raw material in advance.
One or more types selected from cellulose nanofibers and chitin nanofibers can be produced from cellulose raw materials and chitin/chitosan raw materials.

First, the fiber raw material is dispersed in a solvent to form a suspension. The concentration of the fiber raw material in the suspension is preferably 0.1% by mass or more and less than 10% by mass. When the concentration of the fiber raw material in the suspension is equal to or higher than the above lower limit, it is possible to prevent excessive solvent from impairing productivity. When the concentration of the fiber raw material in the suspension is less than the above upper limit value, it is easy to reduce variations in the particle diameters of the composite particles 1 and the composite particles 1A. In addition, when the concentration of the fiber raw material in the suspension is less than the above upper limit, when obtaining fine fibers, it is possible to suppress the suspension from rapidly thickening due to the defibration of the fiber raw material, and to obtain a uniform Defibration processing can be performed more easily.

As the solvent used for preparing the suspension, it is preferable to use hydrophilic solvent 7.
The hydrophilic solvent 7 is not particularly limited, and includes water; alcohols such as methanol, ethanol, and isopropanol; cyclic ethers such as tetrahydrofuran; and mixtures thereof.
The suspension preferably contains 50% by mass or more of water. When the proportion of water in the suspension is 50% by mass or more, the dispersion of the fine fibers 2 is inhibited in the process of obtaining the fine fibers 2 by subjecting one or more selected from fiber raw materials and fibers to shortening treatment. This can be suppressed. Further, as the solvent other than water, the above-mentioned hydrophilic solvent 7 is preferable.

In the first step, the pH of the suspension may be adjusted, if necessary, in order to improve the dispersibility of the fiber raw material, the produced short fibers, and the fine fibers 2. Examples of the alkaline aqueous solution used for pH adjustment include a sodium hydroxide aqueous solution, a lithium hydroxide aqueous solution, a potassium hydroxide aqueous solution, an ammonia aqueous solution, an organic alkali aqueous solution, and the like. Examples of the organic alkali aqueous solution include a tetramethylammonium hydroxide aqueous solution, a tetraethylammonium hydroxide aqueous solution, a tetrabutylammonium hydroxide aqueous solution, a benzyltrimethylammonium hydroxide aqueous solution, and the like. As the alkaline aqueous solution used for pH adjustment, a sodium hydroxide aqueous solution is preferable because it is easy to adjust the pH and is excellent in terms of cost.

The fiber raw material is subjected to a shortening process to shorten the long axis diameter (fiber length) of the fine fibers 2. By performing the shortening treatment, the long axis diameter of the fiber raw material is shortened, and fine fibers 2 having a small median diameter and low viscosity can be obtained. Therefore, the process of purifying the composite particles 1 is facilitated, and it is possible to recover perfectly spherical composite particles 1 with high yield, high purity, and small variation in particle size.

The shortening treatment includes chemical treatment and physical treatment. Both chemical and physical shortening treatments reduce the molecular weight of the fiber raw material while maintaining the surface structure, resulting in fine fibers with a short major axis diameter (fiber length) and low viscosity2. can be manufactured. Therefore, it is possible to easily cover the entire minute droplet 6 containing the core particle precursor, form a stable Pickering emulsion, and obtain true spherical composite particles 1 with small variation in particle size. can.

Chemical treatment uses reagents and enzymes to decompose fibers using chemical reactions and convert them into low-molecular-weight fibers. Although not particularly limited, at least one of enzymatic oxidation treatment, acid hydrolysis treatment, and alkali treatment is preferable.

Examples of the physical treatment include microwave irradiation treatment, laser irradiation treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, gamma ray irradiation treatment, hydroxy (OH) radical treatment, and the like. Among these, at least one of ultraviolet irradiation treatment, electron beam irradiation treatment, gamma ray irradiation treatment, and OH radical treatment is preferable.

By performing the shortening treatment, the viscosity of the 0.5% by mass aqueous dispersion at 25°C is 2 mPa·s or more and 1000 mPa·s or less when the shear rate is 1 s ^-1 , and 2 mPa when the shear rate is 100 s ^-1 . - It is possible to obtain fine fibers 2 having a pressure of not less than s and not more than 100 mPa·s. Therefore, it is possible to easily purify the composite particles 1 with high yield and to produce composite particles 1 with small variations in particle size.

The shortening treatment may be performed before or after introducing ionic functional groups into the fiber raw material. Furthermore, shortening treatment may be performed while introducing ionic functional groups. Although not particularly limited, it is preferable to perform a shortening treatment after introducing an ionic functional group into the fiber raw material.

The type of enzyme used in the enzymatic oxidation treatment is not particularly limited, but when the fiber raw material is a cellulose raw material, cellulase is preferred. Examples of cellulases include cellobiohydrolase, glucanase, and β-glucosidase.
These enzymes may be used alone or in combination of two or more.

In the enzymatic oxidation treatment, an enzyme is added to an aqueous dispersion containing fiber raw materials, held for a certain period of time, and stirred if necessary, so that the enzyme is adsorbed onto the fibers and acts on the dispersion. The enzymatic oxidation treatment promotes hydrolysis of the fibers, shortens the major axis diameter of the fiber raw material, and provides fine fibers 2 with low viscosity and a short major axis diameter. The progress of the hydrolysis reaction by enzymatic oxidation treatment can be controlled by the amount of enzyme used, enzyme oxidation treatment temperature, pH, reaction time, etc., and it is preferable to carry out the shortening treatment within a range where the structure of the crystal surface does not change.

The amount of enzyme used is preferably 0.005 to 20% by mass, more preferably 0.1 to 10% by mass, based on 100% by mass of the fiber raw material. When the amount of enzyme used is at least the above lower limit, the hydrolysis reaction can be promoted. When the amount of enzyme used is below the above upper limit, it is possible to suppress short fiber formation and low viscosity due to the progress of the hydrolysis reaction, suppress changes in the surface structure of the fibers, and make it easier to create a stable Pickering emulsion. Can be formed.
The treatment temperature in the enzymatic oxidation treatment is preferably 4 to 70°C, more preferably 10 to 50°C, from the viewpoint of promoting the enzyme reaction.
The pH in the enzymatic oxidation treatment is preferably 3.0 to 12.0, more preferably 4.0 to 10.0, from the viewpoint of promoting the enzyme reaction.
The treatment time in the enzymatic oxidation treatment is preferably, for example, 0.5 to 48 hours.

The fiber raw material may be subjected to acid hydrolysis treatment. For example, cellulose is reduced in molecular weight by acid hydrolysis. By reducing the molecular weight of the fiber raw material through acid hydrolysis treatment, fine fibers 2 with a short major axis diameter and low viscosity can be obtained. The conditions for the acid hydrolysis treatment are not particularly limited, as long as they act on the amorphous portion of the fibers and do not destroy the fiber surface structure. As the acid used in the acid hydrolysis treatment, known acids can also be used. For example, sulfuric acid, hydrochloric acid, and nitric acid can be used.

The amount of acid added is preferably 0.05 to 10% by mass based on the dry mass of the fiber raw material. When the amount of acid added is at least the above lower limit, hydrolysis can be promoted. When the amount of acid added is below the above upper limit, excessive reaction can be suppressed, collapse of the structure of the fiber surface can be suppressed, and a stable Pickering emulsion can be formed more easily.
The progress of acid hydrolysis treatment can be controlled by pH, temperature, and treatment time.
The pH in the acid hydrolysis treatment is preferably 1.5 to 5.0.
The temperature in the acid hydrolysis treatment is preferably 10 to 120°C.
The treatment time in the acid hydrolysis treatment is preferably 0.5 to 20 hours.
After the acid hydrolysis treatment, it is preferable to add an alkali such as sodium hydroxide for neutralization before the fibrillation treatment.

By performing hydrolysis in an alkaline solution, preferably under conditions of pH 7.5 to pH 14, the fibers are shortened and low-viscosity fine fibers 2 can be obtained (alkali treatment).

The solid content concentration of the fiber raw material in the alkali treatment is preferably 0.1 to 30% by mass based on 100% by mass of the alkaline solution. The alkali used in the alkali treatment is preferably water-soluble. As the alkali, for example, hydroxides of alkali metals or alkaline earth metals can be used, and among them, it is preferable to use sodium hydroxide. Progress of molecular weight reduction in alkali treatment can be controlled by pH, temperature, and time.
The temperature in the alkali treatment is preferably 30 to 150°C.
The treatment time in the alkali treatment is preferably 0.25 to 20 hours.

In the alkaline treatment, an oxidizing agent or a reducing agent may be used as an auxiliary agent. The oxidizing agent and reducing agent are not particularly limited, but examples of the oxidizing agent include oxygen, ozone, hydrogen peroxide, and hypochlorite. Examples of the reducing agent include sodium borohydride and chlorous acid.

In an alkaline solution with pH 7.5 to pH 14, carboxyl groups exist in the amorphous region of the fiber raw material that has been oxidized using an N-oxyl compound, and the hydrogen at the C6 position where this carboxyl group exists is charged by the carboxy group. is lacking. Hydrogen at the C6 position is easily abstracted by hydroxide ions under alkaline conditions, and cleavage of the glycosidic bond proceeds by β-elimination. In this way, by subjecting the fiber raw material to alkaline conditions, short fibers and lower viscosity occur. By using an oxidizing agent or a reducing agent, the double bonds generated during β-elimination can be removed by oxidation or reduction, so that coloring of the fine fibers 2 can be suppressed.

As a physical treatment, short fine fibers 2 can be obtained by irradiating with electron beams or gamma rays. Generally, when an organic compound is irradiated with electron beams or gamma rays, it is possible to promote modification or decomposition of the material depending on the irradiation dose. When irradiated with electron beams or gamma rays, bonds between atoms are broken and radicals are generated. The generated radicals may cause molecular cleavage or new covalent bonds may be formed by recombination. When the fiber raw material is a natural polymer such as cellulose, decomposition progresses predominately and the molecular weight is reduced, so that fine fibers 2 with low viscosity can be obtained.

When shortening the fiber by electron beam irradiation or gamma ray irradiation, if the organic compound contains water, the water-containing state promotes decomposition behavior. While water irradiated with electron beams or gamma rays may accelerate the decomposition of materials due to radicals, the presence of water may block electron beam irradiation or gamma ray irradiation and reduce decomposition efficiency. The moisture content of the fiber raw material is preferably 5% by mass or more and 90% by mass or less. When the water content of the fiber raw material is equal to or higher than the above lower limit, aggregation of the fiber raw material can be suppressed, the subsequent dispersion treatment becomes easier, and the handling after treatment becomes easier. When the moisture content of the fiber raw material is below the above upper limit value, the shielding effect of electron beam irradiation and gamma ray irradiation can be suppressed, and the decomposition efficiency of the fiber raw material can be further improved.

The electron beam irradiation method is not particularly limited, and known methods such as curtain type, scan type, and plasma discharge type can be used. Cobalt-60 can be used as a source of gamma rays. The irradiation amount is not particularly limited, but is preferably 10 kGy or more and 1000 kGy or less. If it is less than 10 kGy, the decomposition ability is insufficient, and if it is more than 1000 kGy, only the decomposition efficiency equivalent to 1000 kGy can be obtained, resulting in excessive irradiation energy.

Since gamma rays have a very high ability to penetrate substances, the irradiation surface is not particularly limited, and the irradiation may be performed from any surface. Regarding electron beams, the ability to penetrate materials varies depending on the accelerating voltage, and the higher the accelerating voltage, the higher the ability of electron beams to penetrate materials. In the case of water, the electron beam has a penetrating ability of about 8 mm when the acceleration voltage is 2 MeV. Therefore, it is necessary to consider the surface to be irradiated with the electron beam depending on the form of the material. The acceleration voltage is preferably 0.1 MeV to 10 MeV. If it is lower than 0.1 MeV, the electron beam transmission ability is low, so that the electron beam irradiation effect is limited only to the vicinity of the material surface. On the other hand, an apparatus having an accelerating voltage higher than 10 MeV requires a large scale of equipment and is not practical.

When treating fiber raw materials with electron beams or gamma rays, in a state where the electron beams or gamma rays can decompose fibers, water contained in the material to be treated may evaporate excessively during the treatment process, or fibers may be destroyed. The packaging material for packaging the fibers is not particularly limited as long as it does not adversely affect the fibers due to decomposition products generated by irradiation with electron beams or gamma rays. For example, it is preferable to cover the fiber raw material with aluminum foil and treat it with electron beams or gamma rays. By irradiating with electron beams or gamma rays, it is possible to process at a high solid content concentration without using chemicals, etc., and it does not require complicated operations, so it is a highly productive method.

Ultraviolet rays are a type of electromagnetic waves (light), and are generally a general term for electromagnetic waves in the range of 100 nm to 400 nm. The energy of electromagnetic waves is expressed as E=1/5.2·N·h·c/λ (kcal/mol). Here, h is Planck's constant (6.626×10 ⁻²⁷ erg・sec), c is the speed of light (2.998×10 ¹⁰ cm/sec), λ is the wavelength (cm), and N is Avogadro's constant (6.02 ×10 ²³ /mol). Ultraviolet light, for example, light in the ultraviolet range such as 172 nm, 185 nm, and 254 nm, has a higher energy than most chemical bonds and can break bonds.

Oxygen (O ₂ ) in the atmosphere absorbs 185 nm ultraviolet rays to produce ozone (O ₃ ), and the generated O ₃ further absorbs 254 nm ultra violet rays and reacts with O ₂ to form oxygen element radicals ( Generates active oxygen). These active oxygen species have strong oxidizing power, and organic compounds are cleaved and become excited, reacting with the active oxygen species, producing low-molecular compounds with hydrophilic groups such as carbonyl and carboxyl groups, and CO ₂ and H ₂ O.
Alternatively, OH radicals with high oxidizing power may be generated by directly irradiating water with ultraviolet rays of 185 nm. The reaction between 254 nm ultraviolet rays and an oxidizing agent (O ₃ , hydrogen peroxide, etc.) generates OH radicals, which can also decompose fiber raw materials.

For the above-mentioned reasons, when the fiber raw material is irradiated with ultraviolet rays, the molecular weight of the fiber raw material becomes low, and the obtained fine fibers 2 become short fibers. The wavelength of ultraviolet light is 100 to 400 nm. In particular, ultraviolet rays with a wavelength of 130 to 270 nm are suitable because they cause the fiber raw materials to become lower in molecular weight. The ultraviolet irradiation conditions are not particularly limited and can be set so as to obtain fine fibers 2 with a desired long axis diameter and viscosity.

As the ultraviolet radiation source, an ultraviolet irradiation lamp such as a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, etc. can be used. Low-pressure mercury lamps are preferred because they emit two intense spectra at 185 nm and 254 nm. One type of these radiation sources may be used, or a plurality of radiation sources may be used. The shape of the lamp may be a straight tube type, a U type, an M type, a square type, etc., and is not particularly limited. Further, the oxygen concentration may be lowered during ultraviolet irradiation, and nitrogen can be used as the inert gas introduced for this purpose.

The method of ultraviolet irradiation treatment is not particularly limited, and can be adjusted so that the viscosity characteristics can be within a desired range.
The ultraviolet irradiation treatment determines the long axis diameter and viscosity of the fine fibers 2 obtained by changing the ultraviolet irradiation time, the energy amount of ultraviolet irradiation, the moisture content of the fiber raw material, and introducing an inert gas such as air or nitrogen into the device. Characteristics can be controlled. The ultraviolet irradiation treatment is preferably carried out in the presence of an auxiliary agent such as oxygen, ozone, peroxide, etc. because the photooxidation efficiency can be increased.

Hydroxy (OH) radical treatment is a treatment in which OH radicals are generated by a known method to reduce the molecular weight of fiber raw materials. Since OH radicals with a high oxidative decomposition potential can cleave C--C bonds in organic compounds, the fiber raw material can be reduced in molecular weight, and fine fibers 2 with short major axis diameters and low viscosity can be obtained.
The method for generating OH radicals is not particularly limited, and it is common to use physicochemical treatment methods such as ozone, hydrogen peroxide, and ultraviolet rays in combination. For example, a method using O ₃ (Japanese Unexamined Patent Publication No. 2010-235681) and a method using a combination of ultraviolet rays and an oxidizing agent are known. In particular, it is preferable to directly generate OH radicals by discharging because the efficiency of generating OH radicals is high.

A common method for using O ₃ is to generate O ₃ by electric discharge and generate OH radicals during the process in which dissolved O ₃ dissolved in treated water is decomposed by H ₂ O ₂ or ultraviolet rays. The method for generating O ₃ is not particularly limited, but a method using ultraviolet rays, an electrolytic method, a radiation irradiation method, a method of generating by electric discharge, etc. are used. In the method using ultraviolet light, O ₂ in the atmosphere absorbs 185 nm ultraviolet light to generate ozone (O ₃ ). The electrolytic method generally uses an aqueous solution of sulfuric acid or hydrochloric acid as an electrolytic solution, and generates ozone by electrolysis. The radiation irradiation method relies on the ionizing effect of radiation, and applies the fact that ozone is generated by introducing air into the high-energy region of the radiation. Examples of methods for generating O ₃ by discharge include a silent discharge method, a corona discharge method, and a composite discharge method that combines several discharge methods.

As the method using ultraviolet rays, it is preferable to irradiate the oxidizing agent with ultraviolet rays to generate OH radicals with stronger oxidizing power. Although not particularly limited, H ₂ O, O ₃ , H ₂ O ₂ , hypochlorite, and photocatalyst are generally used as the oxidizing agent.

The method of generating OH radicals by discharge only needs to generate OH radicals, and other radical species may be generated. Although not particularly limited, it is preferable to use plasma discharge or corona discharge because the efficiency of generating OH radicals is high. An example of a device for generating OH radicals is a device consisting of a dispersion of fiber raw materials, a hollow cylindrical pin electrode placed above the dispersion, and a high voltage pulse power source for applying a high voltage to the pin electrode. Can be mentioned. When a high voltage is applied to the pin electrode, corona discharge occurs at the extreme end of the electrode. Due to the discharge, a dissociation reaction of water (H ₂ O) molecules and oxygen molecules (O ₂ ) occurs internally due to electron collision, and OH radicals are generated. The OH radicals move through the gas space, dissolve in the treated water, react with the fiber raw material in the water, and undergo decomposition treatment. The atmosphere during discharge is not particularly limited, but generally O ₂ , N ₂ , air, or a mixture thereof can be used.

The degree of treatment in the OH radical treatment can be adjusted by adjusting the solid content concentration, pH, temperature, treatment time, etc. of the fiber raw material. In the OH radical treatment, the moisture content of the fiber raw material is preferably 5% or more. If it is less than 5%, the agglomeration of the fiber raw material becomes too strong, making it difficult to handle it after processing, such as making subsequent dispersion processing difficult.

Although the temperature of the fiber raw material in the OH radical treatment is not particularly limited, it is preferably 10° C. or higher in terms of reaction efficiency. Further, the temperature is preferably 80° C. or lower because the solid content concentration during treatment is less likely to change and the structure of the fiber surface is less likely to collapse. Although the pH is not particularly limited, it is preferable to carry out the reaction between pH 2.0 and pH 12.0. The amount of O ₃ generated, the amount of oxidizing agent added, the amount of ultraviolet ray irradiation, etc. are not particularly limited, and are adjusted as appropriate so that the degree of low molecularization of the fiber and the obtained fine fibers 2 have the desired long axis diameter and viscosity characteristics. can. In order to carry out the reaction efficiently and uniformly, it is preferable to use a stirrer, a device capable of controlling temperature, and pH.

The chemical treatment or physical treatment may be performed before or after the introduction of the ionic functional group, after the shortening treatment, during the introduction of the ionic functional group, or during the shortening treatment. Furthermore, the same process may be performed multiple times, different types of processes may be performed sequentially, or multiple processes may be performed simultaneously.

Ionic functional groups are introduced into the fiber raw materials through chemical modification. The ionic functional group may be introduced into the fiber raw material in advance and then defibrated, or the ionic functional group may be introduced after the fiber raw material is defibrated. Further, an ionic functional group may be introduced before the fiber shortening treatment, or an ionic functional group may be introduced after the fiber shortening treatment.
If an ionic functional group is introduced into the crystal surface of the fiber raw material, emulsion stability will be improved, and variations in particle diameters of composite particles 1 and composite particles 1A can be easily reduced. Furthermore, functional materials 4 such as fluorescent dyes can be adsorbed via the ionic functional groups of the fine fibers 2 present on the surface of the composite particles 1.
Furthermore, if an ionic functional group is introduced into the crystal surface of the fiber raw material or short fiber, the solvent will easily penetrate between the crystals of the fiber raw material or short fiber due to the osmotic pressure effect. The fibrous fibers are easily refined, and a dispersion of fine fibers 2 (fine fiber dispersion) can be efficiently obtained.

The type of ionic functional group introduced into the crystal surface of the fiber raw material is not particularly limited. Note that the ionic functional group may be introduced before the shortening treatment or may be introduced into the shortened fiber. Moreover, it may be introduced before defibration or after defibration.
Examples of the ionic functional group include anionic functional groups and cationic functional groups.
The type and method of introduction of the anionic functional group are not particularly limited, but carboxy groups and phosphoric acid groups are preferred. When the fiber raw material is a cellulose raw material, a carboxy group is preferred because it can be easily introduced selectively onto the cellulose crystal surface.
The type and introduction method of the cationic functional group are not particularly limited either. Examples of the cationic functional group include an amino group, an onium group, a hydrazinium group, a phosphonium group, an oxonium group, a sulfonium group, a diazenium group, and a diazonium group. For example, as a method for introducing amino groups, there is a method in which chitin/chitosan raw materials are purified and amino groups are introduced by partial deacetylation treatment.

The amount of ionic functional group introduced is 1.3 mmol/g or more and 5.0 mmol/g or less, and 1.5 mmol/g or more and 4. It is preferably 0 mmol/g or less, more preferably 1.7 mmol/g or more and 3.5 mmol/g or less, and even more preferably 2.0 mmol/g or more and 3.0 mmol/g or less. When the content of ionic functional groups is at least the above lower limit, fine fibers 2 with a small median diameter can be obtained. In addition, when the content of ionic functional groups is equal to or higher than the above lower limit, the dispersibility of the fine fibers 2 will improve, making it easier to purify the composite particles 1 and the free fine fibers 2, and reducing the variation in particle size. Small, perfectly spherical composite particles 1 can be obtained efficiently. Further, when a fluorescent dye is used as the functional material 4, the amount of fluorescent dye adsorbed can be increased, and the intensity of fluorescence emission can be further increased. When the content of ionic functional groups is below the above upper limit, a rigid fiber structure can be maintained, so emulsion stability is improved and composite particles 1 with small particle size variations can be obtained. Furthermore, when a fluorescent dye is used as the functional material 4, aggregation of molecules of the fluorescent dye can be suppressed, and changes in fluorescence emission can be suppressed.
Here, the dry mass of the fiber raw material, short fibers, or fine fibers 2 means the mass after drying the fiber raw material, short fibers, or fine fibers 2 at a temperature of 120° C. for 1 hour.
The content of ionic functional groups is determined by electrical conductivity titration.

The method for introducing a carboxy group into the crystal surface of the fiber raw material, shortened fiber, or fine fiber 2 is not particularly limited. Specifically, for example, there is a method in which carboxymethylation is carried out by reacting cellulose with monochloroacetic acid or sodium monochloroacetate in a highly concentrated alkaline aqueous solution. Alternatively, a carboxy group may be introduced by directly reacting a gasified carboxylic acid anhydride compound such as maleic acid or phthalic acid with cellulose in an autoclave. Furthermore, a method using a co-oxidizing agent may be used under relatively mild aqueous conditions in the presence of a compound with high selectivity for oxidation of alcoholic primary carbon while maintaining the structure as much as possible. Examples of compounds with high selectivity for oxidation of alcoholic primary carbon include N-oxyl compounds such as TEMPO.
Oxidation using an N-oxyl compound is more preferable in terms of selectivity of the carboxyl group introduction site and reduction of environmental impact. In the method using a co-oxidizing agent in the presence of an N-oxyl compound, the hydroxyl group at the C6 position present on the crystal surface is selectively oxidized, so that carboxy groups are regularly introduced.

Examples of N-oxyl compounds include TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl radical), 2,2,6,6-tetramethyl-4-hydroxypiperidinyl-1-oxyl , 4-methoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-ethoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetamido-2,2,6 , 6-tetramethylpiperidine-N-oxyl and the like. Among them, TEMPO, which has high reactivity, is preferred.
The amount of the N-oxyl compound to be used may be a catalytic amount and is not particularly limited. Usually, it is preferably 0.01% by mass or more and 5.0% by mass or less based on the solid content of the wood-based natural cellulose (fiber raw material) to be oxidized.

Examples of oxidation methods using N-oxyl compounds include a method in which wood-based natural cellulose is dispersed in water and oxidized in the presence of an N-oxyl compound. At this time, it is preferable to use a co-oxidizing agent together with the N-oxyl compound. In this case, in the reaction system, the N-oxyl compound is sequentially oxidized by a co-oxidizing agent to produce an oxoammonium salt, and the oxoammonium salt oxidizes cellulose. According to this oxidation treatment, the oxidation reaction proceeds smoothly even under mild conditions, and the efficiency of introducing carboxy groups is improved. When the oxidation treatment is performed under mild conditions, it is easier to maintain the crystal structure of cellulose.
Examples of mild conditions include conditions in which the reaction is carried out at a temperature of 20 to 60°C.

Co-oxidants that can promote the oxidation reaction include, for example, halogens, hypohalous acid, halous acids, perhalogen acids, or salts thereof, halogen oxides, nitrogen oxides, peroxides, etc. Any oxidizing agent, if any, can be used. In terms of availability and reactivity, hypohalous acid or a salt thereof is preferred, and sodium hypochlorite is more preferred.
The amount of the co-oxidant used is not particularly limited and may be an amount that can promote the oxidation reaction. Usually, it is about 1 to 200% by mass based on the solid content of the wood-based natural cellulose to be oxidized.

At least one compound selected from the group consisting of bromides and iodides may be further used together with the N-oxyl compound and the co-oxidizing agent. This allows the oxidation reaction to proceed more smoothly and improves the efficiency of introducing carboxy groups. As such a compound, for example, sodium bromide and lithium bromide are preferable, and sodium bromide is more preferable in terms of cost and stability.
The amount of the above compound to be used may be an amount that can promote the oxidation reaction, and is not particularly limited. Usually, it is about 1 to 50% by mass based on the solid content of the wood-based natural cellulose to be oxidized.

The reaction temperature of the oxidation reaction is preferably 4°C or more and 80°C or less, more preferably 10°C or more and 70°C or less. When the reaction temperature of the oxidation reaction is equal to or higher than the above lower limit, the reactivity of the reagent can be increased and the reaction time can be shortened. When the reaction temperature of the oxidation reaction is below the above upper limit, side reactions can be suppressed and the highly crystalline and rigid fiber structure of cellulose nanofibers can be maintained.

The reaction time of the oxidation treatment can be appropriately set in consideration of the reaction temperature, the desired amount of carboxy groups, etc., and is usually 10 minutes or more and 5 hours or less, although it is not particularly limited.

The pH of the reaction system during the oxidation reaction is not particularly limited, but is preferably 9 or more and 11 or less. When the pH is 9 or higher, the reaction can proceed efficiently. When the pH is 11 or less, side reactions can be suppressed, and decomposition of the fiber raw material, short fibers, or fine fibers 2 can be suppressed.
In addition, in the oxidation treatment, as the oxidation progresses, the pH in the system decreases due to the generation of carboxy groups, etc., so it is preferable to maintain the pH of the reaction system at 9 or more and 11 or less during the oxidation treatment. . As a method for maintaining the pH of the reaction system at 9 or more and 11 or less, a method of adding an alkaline aqueous solution according to the decrease in pH can be mentioned.

Examples of the alkaline aqueous solution include a sodium hydroxide aqueous solution, a lithium hydroxide aqueous solution, a potassium hydroxide aqueous solution, an ammonia aqueous solution, an organic alkali aqueous solution, and the like. Examples of the organic alkali aqueous solution include a tetramethylammonium hydroxide aqueous solution, a tetraethylammonium hydroxide aqueous solution, a tetrabutylammonium hydroxide aqueous solution, a benzyltrimethylammonium hydroxide aqueous solution, and the like. As the alkaline aqueous solution, a sodium hydroxide aqueous solution is preferred because it is easy to adjust the pH and is cost effective.

The oxidation reaction caused by the N-oxyl compound can be stopped by adding alcohol to the reaction system. At this time, it is preferable to maintain the pH of the reaction system within the above range.
The alcohol to be added is preferably a low molecular weight alcohol such as methanol, ethanol, or propanol in order to quickly complete the reaction, and ethanol is more preferred in view of the safety of by-products produced by the reaction.

The reaction solution after oxidation treatment may be subjected to fibrillation treatment as it is, but in order to remove coloring and impurities such as N-oxyl compounds, the oxidized cellulose contained in the reaction solution is recovered and washed with a cleaning solution. It is preferable.

Oxidized cellulose can be recovered by a known method such as filtration using a glass filter or a nylon mesh with a pore size of 20 μm.
Methods for recovering cellulose after oxidation treatment include (a) filtration with carboxy groups forming salts, and (b) adding acid to the reaction solution to make the system acidic and removing carboxyl groups. Examples include a method of separating by filtration as an acid, and a method of (c) adding an organic solvent to aggregate and then filtering.
Among these, the method (b) of recovering the carboxylic acid as a carboxylic acid is preferable from the viewpoints of handling properties, recovery efficiency, and waste liquid treatment. In addition, when replacing a counter ion in the counter ion replacement step described below, the generation of by-products can be suppressed and the replacement efficiency is excellent if the counter ion does not contain a metal ion, so (b) it is recovered as a carboxylic acid. The method is preferred.

The metal ion content in cellulose after the oxidation reaction can be investigated using various analytical methods. For example, it can be simply investigated by the EPMA method using an electron beam microanalyzer or elemental analysis using fluorescent X-ray analysis. can. When the salt is recovered using a method of filtering it while forming it, the metal ion content is 5 wt% or more, whereas when it is recovered using a method of filtering it as a carboxylic acid, the metal ion content is 5 wt% or more. It becomes 1wt% or less.

Furthermore, the recovered cellulose can be purified by repeated washing to remove the catalyst and by-products. At this time, the amount of remaining metal ions and salts can be reduced by repeating washing with a washing liquid adjusted to an acidic condition of pH 3 or less using hydrochloric acid or the like, and then repeating washing with pure water.

Next, the counterion replacement step is carried out by adding an alkali to the suspension of the fiber raw material, shortened fibers, or fine fibers 2 into which carboxy groups have been introduced. The amount of alkali added is preferably 0.8 equivalent or more and 2 equivalents or less based on the carboxy group introduced into the fiber raw material, short fiber, or fine fiber 2. In particular, it is more preferable that the amount is 1 equivalent or more and 1.8 equivalents or less because counterions can be exchanged without adding an excessive amount of alkali. Although it is possible to disperse the fiber raw material, short fibers, or fine fibers 2 to some extent even if the amount is less than 0.8 equivalent, the dispersion treatment requires a long time and high energy, and the fiber diameter of the obtained fibers is also limited by this method. morphologies, and the homogeneity of the dispersion decreases. On the other hand, if the amount exceeds 2 equivalents, it is not preferable because it may be decomposed by an excessive amount of alkali or the affinity for the dispersion medium may decrease.

In the counterion replacement step, it is preferable to adjust the pH of the suspension of the fiber raw material, shortened fibers, or fine fibers 2 to a range of pH 4 or more and pH 12 or less using an alkali. In particular, the pH is set to be alkaline at pH 7 or higher and pH 12 or lower to form a carboxylic acid salt with the added alkali. As a result, charge repulsion between carboxyl groups is likely to occur, thereby improving dispersibility and making it easier to obtain a fine fiber dispersion. Here, even if the pH is less than 4, it is possible to disperse the fiber raw material, short fibers, or fine fibers 2 by mechanical dispersion treatment, but for the same reason as when the amount of alkali added is too small, the fine fiber dispersion homogeneity decreases. On the other hand, if the pH exceeds 12, the peeling reaction of fiber raw materials, shortened fibers, or fine fibers 2 during dispersion treatment, lowering of the molecular weight due to alkaline hydrolysis, and yellowing of the fine fiber dispersion due to the formation of terminal aldehydes and double bonds. is promoted, resulting in a decrease in mechanical strength and homogeneity.

The alkali for adjusting the pH of the suspension is one or more selected from sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, onium compounds, and amines (hereinafter also referred to as "onium compounds/amines"). Aqueous solutions can be used.
By using the onium compound/amine, the stability of the emulsion droplets described below can be controlled, and composite particles 1 can be obtained in high yield.

The onium compound in this embodiment has a cation structure shown in the following structural formula (1).

In structural formula (1), M is a nitrogen atom, a phosphorus atom, or a sulfur atom, and R1, R2, R3, and R4 are a hydrogen atom, a hydrocarbon group, or a hydrocarbon group containing a heteroatom. It is.

For example, when M is a nitrogen atom and R1, R2, R3 and R4 are all hydrogen atoms, the onium compound is an ammonium ion. If three of R1, R2, R3, and R4 are hydrogen atoms, it will be a primary amine, if two, it will be a secondary amine, if one, it will be a tertiary amine, and if there are zero, it will be a quaternary amine, All are onium compounds in this embodiment.
Examples of the hydrocarbon group containing a heteroatom include an alkyl group, an alkylene group, an oxyalkylene group, an aralkyl group, an aryl group, and an aromatic group. R1, R2, R3, and R4 may form a ring.

In structural formula (1), examples of quaternary ammonium compounds (quaternary ammonium salts) in which M is a nitrogen atom include tetraethylammonium hydroxide (TEAH), tetraethylammonium chloride, and tetrabutylammonium hydroxide (TBAH). ), tetrabutylammonium chloride, didecyldimethylammonium chloride, lauryltrimethylammonium chloride, dilauryldimethyl chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, cetyltrimethylammonium chloride, alkylbenzyldimethylammonium chloride, coconut amine, etc. Can be mentioned.
In particular, it is preferable to use didecyldimethylammonium chloride, cetyltrimethylammonium chloride, and alkylbenzyldimethylammonium chloride because they can impart antibacterial properties.

In structural formula (1), examples of the quaternary phosphonium compound (quaternary phosphonium salt) in which M is a phosphorus atom include tetramethylphosphonium hydroxide, tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, and tetrabutyl. Examples include phosphonium hydroxide, benzyltrimethylphosphonium hydroxide, benzyltriethylphosphonium hydroxide, hexadecyltrimethylphosphonium hydroxide, and the like.

The counter ion of the cationic structure of the onium compound is not particularly limited, but in consideration of the adverse effects of metal ions and the dispersibility in the dispersion medium, it is preferable that the counter ion is a hydroxide ion. In addition to the onium compound, an inorganic alkali containing metal salts such as alkali metals and alkaline earth metals may be added.

The primary amine, secondary amine, and tertiary amine in this embodiment have structures shown in the following structural formulas (2), (3), and (4), respectively. Note that the structures when these are ionized to become ammonium ions are (2)', (3)', and (4)', respectively.

In the above structural formula, R ¹ to R ⁶ are either a hydrocarbon group or a hydrocarbon group containing a hetero atom.

Examples of the primary amine include methylamine, ethylamine, propylamine, butylamine, hexylamine, 2-ethylhexylamine, n-octylamine, dodecylamine, stearylamine, and oleylamine.
Examples of the secondary amine include dimethylamine, diethylamine, dipropylamine, dibutylamine, dihexylamine, and dioctylamine.
Examples of the tertiary amine include trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, trihexylamine, and the like.

A suspension obtained using an anionic fiber raw material, short fibers or fine fibers 2, and an onium compound/amine has lower energy than when using an inorganic alkali having a metal ion as a counterion. Dispersion treatment can be carried out in a short time, and the final fine fiber dispersion obtained has high homogeneity. This is because when using an onium compound/amine, the ionic diameter of the counter ion of the anionic moiety of the fiber raw material, shortened fiber, or fine fiber 2 is larger, which has the effect of separating the fine fibers 2 from each other in the dispersion medium. This is thought to be because it is larger. Furthermore, if the fine fiber dispersion contains an onium compound/amine, the viscosity and thixotropy of the fine fiber dispersion can be lowered compared to inorganic alkalis, which is advantageous in ease of dispersion treatment and subsequent handling. Further, the fine fibers 2 that have interacted with the onium compound/amine through ionic bonding have reduced hydrophilicity due to steric repulsion or hydrophobic action based on one or more ions selected from onium ions and ammonium ions. This increases the affinity of the liquid core particle precursor to the emulsion droplets in the second step (step 2), which will be described later, and improves the stability of the droplets 6.

By defibrating the fiber raw material or short fibers in which one or more ions selected from onium ions and ammonium ions are bonded as countercations, fine fibers in which one or more ions selected from onium cations and amines are bonded as countercations are defibrated. fine fibers 2 can be obtained. The fine fibers 2 in which one or more selected from onium cations and amines are bonded as counter cations have high emulsion stability, and can form a stable O/W type Pickering emulsion regardless of the type of core particle precursor. Composite particles 1 with small variations in particle diameter can be obtained in high yield using various core resins.
Further, the ionized state of an onium compound is referred to as an onium ion or an onium cation. Moreover, the amine referred to here includes ammonium ions that are partially or completely ionized. From now on, one or more ions selected from onium cations and amines, and one or more ions selected from onium cations and ammonium ions will be referred to as "onium cations (or onium ions)/amines" and "onium ions," respectively. Also referred to as "onium cation (or onium ion)/ammonium ion".

The average bonding amount of onium ions/ammonium ions in the fiber raw material or short fiber is preferably 0.02 mmol/g or more, and 0.2 mmol per 1 g of dry mass of the fiber raw material or short fiber from the viewpoint of emulsion stability. /g or more is more preferable. Further, the average bonding amount of onium ions/ammonium ions in the fiber raw material or fine fiber 2 is preferably 3 mmol/g or less, more preferably 2.5 mmol/g or less, and 2 mmol/g or less per 1 g of dry mass of the fiber raw material or fine fiber 2. /g or less is more preferable. Two or more arbitrary types of onium ions/ammonium ions may be bonded to the fiber raw material or short fibers at the same time, and in this case, the average bonding amount of onium ions/ammonium ions is the total amount of introduced modifying groups. is preferably within the above range. The average binding amount (mmol/g) of onium ions/ammonium ions can be measured by a known method. For example, it can be calculated by titration, IR measurement, etc.

When a part of the surface of the fiber raw material or short fiber is made hydrophobic by bonding onium ions/ammonium ions, the contact angle of the membrane prepared using the fine fiber 2 with respect to water is particularly Although not limited, the angle is preferably 45° or more, and more preferably 50° or more. For example, the contact angle can be determined by pouring a 0.5% by mass aqueous dispersion of fine fiber 2 into a 5cm x 5cm container, drying it at a temperature of 30°C and humidity of 80%, and then drying it in a nitrogen atmosphere. It can be measured by dropping 2 μl of pure water using a contact angle meter (manufactured by Kyowa Interface Science, PCA-1).

A cationic substance other than onium ions/ammonium ions may be bonded as a counter ion to the anionic functional group of the fiber raw material or short fiber. Examples of the cationic substance include, but are not particularly limited to, metal ions such as alkali metals such as sodium ions, potassium ions, and lithium ions, and alkaline earth metals such as magnesium ions and calcium ions. The counter ion of the anionic functional group is preferably an alkali metal ion such as sodium ion, potassium ion, lithium ion, etc. from the viewpoint of dispersion stability of the fiber raw material or short fiber.
From the viewpoint of dispersion stability and emulsion stability of the fine fibers 2, the bonding equivalent of cationic substances other than onium ions/ammonium ions should be 0.02 mmol/g or more per 1 g of dry mass of the fiber raw material or short fibers. Preferably, 0.2 mmol/g or more is more preferable. In addition, the bonding equivalent of the cationic substance other than onium ion/ammonium ion is preferably 3 mmol/g or less, more preferably 2.5 mmol/g or less, and 2 mmol/g per 1 g of dry mass of the fiber raw material or short fiber. The following are more preferred. Two or more arbitrary cationic substances may be introduced into the fiber raw material or short fiber at the same time. The average binding amount (mmol/g) of a cationic substance can be measured by a known method. For example, when the cationic substance is a metal ion, the average bond amount of the cationic substance can be measured by EPMA method using an electron beam microanalyzer, X-ray fluorescence analysis, elemental analysis by ICP emission spectrometry, etc.

As a method for obtaining a dispersion of fine fibers 2 by defibrating a fiber raw material or short fibers, a dispersion of fine fibers 2 can be obtained by defibrating the fiber raw material or short fibers in a solvent. The ion denaturation treatment may be performed either before or after defibration, and the defibration treatment may be performed either before or after ion modification. For example, after introducing an ionic functional group into a fiber raw material or short fiber in a solvent, defibration can be performed. The ionic functional group may be introduced after the fiber raw material or short fibers are defibrated.

Methods for defibrating the fiber raw material or short fibers by physically defibrating the suspension include, but are not particularly limited to, high-pressure homogenizers, ultra-high-pressure homogenizers, ball mills, roll mills, cutter mills, planetary mills, Mechanical treatments include jet mills, attritors, grinders, juicer mixers, homomixers, ultrasonic homogenizers, nanogenizers, and underwater counter-impact. By performing such a physical defibration treatment, the fibers in the suspension of the fiber raw material or short fibers using the hydrophilic solvent 7 as a solvent are made fine, and at least one side of the structure is on the order of nanometers. A dispersion of fine fibers 2 can be obtained. Further, the number average minor axis diameter and the number average major axis diameter of the obtained fine fibers 2 can be adjusted by the time and number of times of the physical defibration treatment at this time.

In the above manner, a dispersion of fine fibers 2 (fine fiber dispersion) whose structure is finely divided until at least one side is on the order of nanometers is obtained. The obtained dispersion can be used as a stabilizer for the O/W emulsion described later, either as it is or after dilution, concentration, etc.

The dispersion of fine fibers 2 may contain other components other than those used for pH adjustment, if necessary, within a range that does not impair the effects of the present invention. The other components mentioned above are not particularly limited, and can be appropriately selected from known additives depending on the use of the composite particles 1 or the composite particles 1A. Specifically, organic silane compounds such as alkoxysilane or their hydrolysates, inorganic layered compounds, inorganic acicular minerals, antifoaming agents, inorganic particles, organic particles, lubricants, antioxidants, antistatic agents, Ultraviolet absorbers, stabilizers, magnetic materials, orientation promoters, plasticizers, crosslinking agents, pharmaceuticals, agricultural chemicals, fragrances, adhesives, enzymes, colorants, deodorants, metals, metal oxides, inorganic oxides, preservatives , antibacterial agents, natural extracts, surfactants, etc.

<Second process>
In the second step (step 2), as shown in FIG. 2(b), droplets 6 containing core particle precursors are added to the dispersion of fine fibers 2, dispersed, and the surface of the droplets 6 is made into fine particles. This is the step of covering with fiber 2.
By including the second step, the manufacturing method of this embodiment can coat the surface of the droplet 6 containing the core particle precursor with the fine fibers 2 and stabilize it as an emulsion.

Specifically, a liquid containing a core particle precursor is added to the dispersion of fine fibers 2 obtained in the first step, dispersed as droplets 6 in the dispersion of fine fibers 2, and the surface of the droplets 6 is is coated with fine fibers 2 to produce an O/W emulsion stabilized by the fine fibers 2. The O/W type emulsion stabilized by the fine fibers 2 is called an emulsion liquid.

The method for producing the O/W emulsion is not particularly limited, but general emulsification treatments, such as various homogenizer treatments and mechanical stirring treatments, can be used. Specifically, high-pressure homogenizers, ultra-high-pressure homogenizers, all-purpose homogenizers, ball mills, roll mills, cutter mills, planetary mills, jet mills, attritors, grinders, juicer mixers, homomixers, ultrasonic homogenizers, nanogenizers, underwater opposing collisions, and paints. Mechanical treatment such as a shaker may be used. Further, a combination of a plurality of mechanical treatments may be used.

For example, when using an ultrasonic homogenizer, a core particle precursor-containing liquid is added to the dispersion of the fine fibers 2 to form a mixed solvent, and the tip of the ultrasonic homogenizer is inserted into the mixed solvent to perform ultrasonic treatment. Although the processing conditions of the ultrasonic homogenizer are not particularly limited, for example, the frequency is preferably 20 kHz or more, and the output is preferably 10 W/cm ² or more. The processing time is not particularly limited, and is preferably about 10 seconds to 1 hour, for example.

By the above-mentioned ultrasonic treatment, the droplets 6 containing the core particle precursor are dispersed in the dispersion of the fine fibers 2, and emulsification progresses. Furthermore, by selectively adsorbing the fine fibers 2 to the liquid/liquid interface between the droplets 6 and the dispersion of the fine fibers 2, the droplets 6 are covered with the fine fibers 2, resulting in a stable structure as an O/W emulsion. form. An emulsion that is stabilized by adsorption of solid matter at the liquid/liquid interface is academically referred to as a "Pickering emulsion." As mentioned above, the mechanism by which the Pickering emulsion is formed by the fine fibers 2 is not clear. However, when the fine fibers 2 are cellulose, cellulose has hydrophilic sites derived from hydroxyl groups and hydrophobic sites derived from hydrocarbon groups in its molecular structure, and thus exhibits amphipathic properties. It is thought that the fine fibers 2 are adsorbed at the liquid/liquid interface between the hydrophobic monomer and the hydrophilic solvent due to the above.

The O/W emulsion structure can be confirmed by optical microscopic observation or the like. Although the particle size of the O/W emulsion is not particularly limited, since the Pickering emulsion serves as a template for the composite particles 1, it is preferable that the average particle size is 0.1 μm or more and 50 μm or less. The average particle size can be calculated by randomly measuring the diameters of 100 emulsions and taking the average value.

In the O/W emulsion structure, the thickness of the coating layer 20 (fibrous layer) formed on the surface of the droplet 6 is not particularly limited, but is preferably, for example, 3 nm or more and 1000 nm or less. The particle size in the emulsion structure is not particularly limited, but is approximately the same as the particle size of composite particles 1 obtained in the third step and composite particles 1A obtained in the fifth step. The thickness of the coating layer 20 can be measured using, for example, cryo-TEM.

In the second step, the mass ratio of the fine fiber 2 dispersion to the core particle precursor-containing liquid is not particularly limited, but 1 mass of the core particle precursor-containing liquid is added to 100 parts by mass of the fine fiber 2 dispersion. The amount is preferably 50 parts by mass or more. When the mass of the core particle precursor-containing liquid is equal to or greater than the above lower limit, the yield of composite particles 1 and composite particles 1A is improved. When the mass of the core particle precursor-containing liquid is less than or equal to the above upper limit, it becomes easier to uniformly cover the droplets 6 with the fine fibers 2, and the particle size can be more easily controlled. In addition, when the mass of the core particle precursor-containing liquid is less than or equal to the above upper limit, it becomes easier to adsorb the functional material 4 .

The core particle precursor-containing liquid only needs to contain the core particle precursor and form an O/W emulsion, and is preferably hydrophobic in order to stably form an O/W emulsion.
The core particle precursor is a precursor that solidifies to form the core particles 3 by chemical change or physicochemical change. The core particle precursor is not particularly limited as long as it can form droplets 6 stably. As the core particle precursor, for example, a polymerizable monomer (monomer), a molten polymer, or a dissolved polymer can be used.

The types of polymerizable monomers that can be used in the second step include polymer monomers that have a polymerizable functional group in their structure, are liquid at room temperature, and are compatible with water. First, it is not particularly limited as long as it can form a polymer (high molecular weight polymer) through a polymerization reaction. The polymerizable monomer has at least one polymerizable functional group. A polymerizable monomer having one polymerizable functional group is also referred to as a monofunctional monomer. Furthermore, a polymerizable monomer having two or more polymerizable functional groups is also referred to as a polyfunctional monomer. The type of polymerizable monomer is not particularly limited, but examples thereof include (meth)acrylic monomers, vinyl monomers, and the like. Furthermore, it is also possible to use a polymerizable monomer having a cyclic ether structure such as an epoxy group or an oxetane structure (for example, ε-caprolactone, etc.). Among these, it is preferable to use a monomer having a benzene ring structure because the core particles 3 exhibit fluorescence.
Note that the expression "(meth)acrylate" indicates that one or both of "acrylate" and "methacrylate" are included.

Examples of monofunctional (meth)acrylic monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl. (meth)acrylate, t-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate , isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate Acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphoric acid (meth)acrylate, ethylene oxide modified phosphoric acid (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide modified phenoxy (meth)acrylate , propylene oxide modified phenoxy (meth)acrylate, nonylphenol (meth)acrylate, ethylene oxide modified nonylphenol (meth)acrylate, propylene oxide modified nonylphenol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, Methoxypropylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl hydrogen phthalate, 2-( meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetra Fluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, monovalent mono(meth)acrylate derived from 2-adamantane and adamantane diol. Examples include adamantane derivative mono(meth)acrylates such as adamantyl acrylate.

Examples of difunctional (meth)acrylic monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, and nonanediol di(meth)acrylate. ) acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate (meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, etc. ) acrylate, etc.

Examples of trifunctional or higher-functional (meth)acrylic monomers include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and tris(2- Tri(meth)acrylates such as hydroxyethyl) isocyanurate tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate Trifunctional (meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane Polyfunctional (meth)acrylate compounds with four or more functionalities such as penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane hexa(meth)acrylate, and some of these (meth)acrylates with alkyl groups or Examples include polyfunctional (meth)acrylate compounds substituted with ε-caprolactone.

As the monofunctional vinyl monomer, liquid monomers that are incompatible with water at room temperature are preferred, such as vinyl ether, vinyl ester, and aromatic vinyl (especially styrene and styrene) monomers.
Examples of (meth)acrylates among monofunctional vinyl monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, t-butyl (meth)acrylate, diethylaminoethyl (meth)acrylate, hepta Examples include fluorodecyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and the like.
In addition, monofunctional aromatic vinyl monomers include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, isopropenyltoluene, isobutyltoluene, tert-butylstyrene, vinyl Examples include naphthalene, vinylbiphenyl, 1,1-diphenylethylene and the like.

Examples of the polyfunctional vinyl monomer include polyfunctional groups having an unsaturated bond such as divinylbenzene. A liquid that is incompatible with water at room temperature is preferred.
Specifically, the polyfunctional vinyl monomers include:
(1) Divinyls such as divinylbenzene, 1,2,4-trivinylbenzene, 1,3,5-trivinylbenzene,
(2) Ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexamethylene glycol dimethacrylate , dimethacrylates such as neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2-bis(4-methacryloxydiethoxyphenyl)propane,
(3) trimethacrylates such as trimethylolpropane trimethacrylate and triethylolethane trimethacrylate;
(4) Ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, 1,3-dipropylene glycol diacrylate, 1,4-dibutylene glycol diacrylate, 1,6-hexylene glycol Diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, polypropylene glycol diacrylate, 2,2-bis(4-acryloxypropoxyphenyl)propane, 2,2-bis(4-acryloxydiethoxyphenyl)propane Diacrylates such as
(5) triacrylates such as trimethylolpropane triacrylate and triethylolethane triacrylate;
(6) Tetraacrylates such as tetramethylolmethanetetraacrylate,
(7) Other examples include tetramethylene bis(ethyl fumarate), hexamethylene bis(acrylamide), triallyl cyanurate, triallyl isocyanurate, and the like.
Specifically, the functional styrenic monomers include divinylbenzene, trivinylbenzene, divinyltoluene, divinylnaphthalene, divinylxylene, divinylbiphenyl, bis(vinylphenyl)methane, bis(vinylphenyl)ethane, and bis(vinylphenyl). ) propane, bis(vinylphenyl)butane, etc.
In particular, a functional styrenic monomer is preferable because it has a benzene ring structure and can yield core particles 3 that exhibit fluorescence.

In addition to these, polyether resins, polyester resins, polyurethane resins, epoxy resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, etc. having at least one polymerizable functional group can be used. However, the material thereof is not particularly limited.

The above polymerizable monomers may be used alone or in combination of two or more.

Furthermore, a polymerization initiator may be added to the polymerizable monomer. General polymerization initiators include radical initiators such as organic peroxides and azo polymerization initiators.

Examples of the organic peroxide include peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxycarbonate, and peroxyester.

Examples of the azo polymerization initiator include 2,2-azobis(isobutyronitrile) (AIBN), 2,2-azobis(2-methylbutyronitrile) (AMBN), 2,2-azobis(2,4 -dimethylvaleronitrile) (ADVN), 1,1-azobis(1-cyclohexanecarbonitrile) (ACHN), dimethyl-2,2-azobisisobutyrate (MAIB), 4,4-azobis(4-cyanovalerian) acid) (ACVA), 1,1-azobis(1-acetoxy-1-phenylethane), 2,2-azobis(2-methylbutyramide), 2,2-azobis(4-methoxy-2,4-dimethyl valeronitrile), 2,2-azobis(2-methylamidinopropane) dihydrochloride, 2,2-azobis[2-(2-imidazolin-2-yl)propane], 2,2-azobis[2-methyl- N-(2-hydroxyethyl)propionamide], 2,2-azobis(2,4,4-trimethylpentane), 2-cyano-2-propylazoformamide, 2,2-azobis(N-butyl-2- methylpropionamide), 2,2-azobis(N-cyclohexyl-2-methylpropionamide), and the like.

In the second step, if a core particle precursor containing liquid containing a polymerizable monomer and a polymerization initiator is used, the polymerization initiator will be included in the droplets 6 of the O/W emulsion, so in the third step described below. , the polymerization reaction progresses more easily when the monomer inside the droplet 6 is polymerized.

The mass ratio of the polymerizable monomer to the polymerization initiator in the second step is not particularly limited, but, for example, it is preferable that the amount of the polymerizable initiator is 0.1 part by mass or more with respect to 100 parts by mass of the polymerizable monomer. When the mass of the polymerizable monomer is at least the above lower limit, the polymerization reaction will proceed sufficiently, and the yield of composite particles 1 and furthermore, composite particles 1A can be further increased. The upper limit of the content of the polymerization initiator is not particularly limited, but is, for example, 10 parts by mass per 100 parts by mass of the polymerizable monomer.

The core particle precursor-containing liquid may contain a solvent. From the viewpoint of stabilizing the emulsion, it is preferable to use an organic solvent as the solvent. Examples of organic solvents include toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), isophorone, cellosolve acetate, Solvesso (registered trademark) 100, trichlene (trichloroethylene), hexane, chloroform, Dichloromethane, dichloroethane, isooctane, nonane, etc. can be used.

The mass ratio of the polymerizable monomer to the solvent in the second step is not particularly limited, but, for example, it is preferable that the solvent is 80 parts by mass or less with respect to 100 parts by mass of the polymerizable monomer.

It is preferable that the polymer for obtaining the dissolved polymer is difficult to dissolve in the hydrophilic solvent 7. When the polymer is dissolved in the hydrophilic solvent 7, a stable emulsion cannot be formed.
Examples of the polymer for obtaining the dissolved polymer include the following. Cellulose acetate derivatives such as cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate, polysaccharides such as chitin and chitosan, polylactic acids such as polylactic acid, and copolymers of lactic acid and other hydroxycarboxylic acids. Dibasic acid polyesters such as polybutylene succinate, polyethylene succinate, and polybutylene adipate. Polycaprolactones such as polycaprolactone and a copolymer of caprolactone and hydroxycarboxylic acid. Polyhydroxybutyrates such as polyhydroxybutyrate and copolymers of polyhydroxybutyrate and hydroxycarboxylic acid. Aliphatic polyesters such as polyhydroxybutyric acid and copolymers of polyhydroxybutyric acid and other hydroxycarboxylic acids. Polyamino acids, polyester polycarbonates, natural resins such as rosin, etc. These may be used alone or in combination of two or more.

A dissolved polymer can be obtained by dissolving the above polymer in a solvent. As the solvent for dissolving the polymer, it is preferable to use a solvent that has low compatibility with the dispersion liquid of the fine fibers 2. When the solubility in the hydrophilic solvent 7 is high, the solvent easily dissolves from the droplet 6 phase into the hydrophilic solvent 7 phase, making emulsion formation difficult. Further, the solvent preferably has a boiling point of 90°C or lower. When the boiling point is higher than 90° C., the hydrophilic solvent 7 of the dispersion of the fine fibers 2 evaporates before the solvent, making it difficult to obtain the composite particles 1. Examples of the solvent for dissolving the above polymer include benzene, toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), isophorone, cellosolve acetate, Solvesso (registered trademark) 100, trichlene, and hexane. , chloroform, dichloromethane, dichloroethane, isooctane, nonane, etc. can be used.

The mass ratio of the polymer and the solvent in which the polymer is dissolved is not particularly limited, and for example, the mass of the solvent is preferably 0.005 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the polymer, More preferably 0.1 parts by mass or more and 80 parts by mass or less.

Examples of methods for obtaining a molten polymer include a method in which a polymer that is solid at room temperature is melted into a liquid. The molten polymer is added to the dispersion of the fine fibers 2 which has been heated to a temperature at which the molten state can be maintained while being subjected to mechanical treatment using the aforementioned ultrasonic homogenizer, etc., thereby forming molten polymer droplets in the dispersion. It is preferable to stabilize it as an O/W type emulsion.

As the molten polymer, one having low solubility in the hydrophilic solvent 7 of the fine fibers 2 is preferable. When the solubility in the hydrophilic solvent 7 is high, the polymer easily dissolves from the molten polymer droplet phase 6 into the hydrophilic solvent phase 7, making emulsion formation difficult. Moreover, it is preferable that the melting point of the molten polymer is 90° C. or lower. If the melting point is higher than 90° C., the hydrophilic solvent 7 in the dispersion of the fine fibers 2 will evaporate, making it difficult to form an emulsion.

Examples of polymers used in the molten polymer include pentaerythritol tetrastearate, pentaerythritol distearate, pentaerythritol tristearate, batyl stearate, stearyl stearate, myristyl myristate, cetyl palmitate, ethylene glycol distearate, and behenyl alcohol. , microcrystalline wax, paraffin wax, hydrocarbon wax, fatty acid alkyl ester, polyol fatty acid ester, mixture of fatty acid ester and wax, mixture of fatty acid ester, glycerin monopalmitate (stearic acid monoglyceride), glycerin mono-distearate (glycerin stearate) ), glycerin monoacetomonostearate (glycerin fatty acid ester), succinic acid aliphatic monoglyceride (glycerin fatty acid ester), citric acid saturated aliphatic monoglyceride, sorbitan monostearate, sorbitan fatty acid ester, sorbitan tribehenate, propylene glycol Monobehenate (propylene glycol fatty acid ester), stearate of pentaerythritol adipate polymer, pentaerythritol tetrastearate, dipentaerythritol hexastearate, stearyl citrate, pentaerythritol fatty acid ester, glycerin fatty acid ester, ultra-light colored rosin, rosin Containing diol, ultra-light colored rosin metal salt, hydrogenated petroleum resin, rosin ester, hydrogenated rosin ester, special rosin ester, novolak, crystalline polyα-olefin, polyalkylene glycol, polyalkylene glycol ester, polyoxyalkylene ether, polylactic acid , polylactic acids such as copolymers of lactic acid and other hydroxycarboxylic acids; dibasic acid polyesters such as polybutylene succinate, polyethylene succinate, and polybutylene adipate; polycaprolactone, copolymers of caprolactone and hydroxycarboxylic acids; Polycaprolactones such as polymers; Polyhydroxybutyrates such as polyhydroxybutyrate, copolymers of polyhydroxybutyrate and hydroxycarboxylic acids; Polyhydroxybutyrates, copolymers of polyhydroxybutyrate and other hydroxycarboxylic acids; Aliphatic polyesters such as polymers; polyamino acids, polyester polycarbonates, natural resins such as rosin, etc. can be used.

The droplet 6 may contain a functional component other than the polymerization initiator in advance. Specifically, colorants (fluorescent dyes, redox dyes, etc.), oil absorbers, light shielding agents (ultraviolet absorbers, ultraviolet scattering agents, etc.), antibacterial agents, antioxidants, antiperspirants, antifoaming agents, and electrostatic charges. Preventive agents, binders, bleaching agents, chelating agents, deodorants, fragrances, fragrances, anti-dandruff active substances, emollients, insect repellents, preservatives, natural extracts, beauty ingredients, pH regulators, vitamins, amino acids, Examples include hormones, oily raw materials such as fats and oils and waxes, surfactants, inorganic particles (titanium oxide, silica, clay, etc.), enzymes, and the like.
When the polymerizable monomer contains in advance a functional component other than the polymerization initiator, the above-mentioned functional component can be contained inside the core particle 3 when formed as the composite particle 1, and it can be used for various purposes. It becomes possible to express the corresponding functions.
Among these, it is preferable to include a fluorescent dye. In the composite particles 1A in which a fluorescent dye is adsorbed as the functional material 4, when the fluorescent dye is contained inside the core particles 3, characteristic fluorescence is generated by the fluorescent dye on the surface of the composite particle 1A and the fluorescence of the core particles 3. Can exhibit luminescence. Note that the fluorescent dye inside the core particle 3 may be the same type as the fluorescent dye on the surface of the composite particle 1A, or may be a different type.

It is preferable that the functional component is easily dissolved or dispersed in the droplet 6 and difficult to be dissolved or dispersed in the hydrophilic solvent 7. By dissolving or dispersing the functional component in the droplets 6, when an O/W emulsion is formed, the functional component can be easily encapsulated in the droplets 6 of the emulsion, and the composite particles 1 and Composite particles 1A can be obtained efficiently. Furthermore, it is possible to increase the amount of functional ingredients included.

It is also possible to form the droplets 6 by using a polymerizable monomer, a dissolved polymer, and a molten polymer in combination as the core particle precursor to form an emulsion. Furthermore, when a biodegradable polymer (resin) is selected as the polymer type of the core particles 3 of the composite particles 1, the resulting composite particles 1 are composed of the core particles 3 made of biodegradable polymers and the fine fibers 2. It is also possible to provide highly environmentally friendly composite particles 1 having a biodegradable material.

<3rd process>
In the third step (step 3), as shown in FIG. 2(c), the core particle precursor inside the droplet 6 is solidified to obtain composite particles 1 in which the surface of the core particle 3 is coated with fine fibers 2. It is a process.

There are no particular limitations on the method of solidifying the core particle precursor. When a polymerizable monomer is used as a core particle precursor, it can be solidified by polymerizing the polymerizable monomer. When a dissolved polymer is used as the core particle precursor, the polymer can be solidified by removing the solvent by diffusing the solvent inside the droplet 6 into the hydrophilic solvent 7 or by evaporating the solvent. When a molten polymer is used as a core particle precursor, the molten polymer can be solidified by cooling and solidifying.

For example, an O/W emulsion in which droplets 6 containing a polymerizable monomer as a core particle precursor and a polymerization initiator are coated with fine fibers 2 and stabilized is heated while stirring to polymerize the polymerizable monomer, Solidify the core particle precursor. The stirring method is not particularly limited, and any known method can be used. Specifically, a disperser or a stirrer can be used. Alternatively, only heat treatment may be performed without stirring.
The temperature conditions during heating can be appropriately set depending on the type of polymerizable monomer and the type of polymerization initiator, but preferably 20°C or more and 150°C or less. If the temperature during heating is less than 20°C, the reaction rate of polymerization will decrease, which is not preferable, and if it exceeds 150°C, the fine fibers 2 may be modified, which is not preferable. The time for the polymerization reaction can be appropriately set depending on the type of polymerizable monomer and the type of polymerization initiator, but is usually about 1 hour to 24 hours. Further, the polymerization reaction may be carried out by ultraviolet irradiation treatment, which is a type of electromagnetic wave. In addition to electromagnetic waves, particle beams such as electron beams may also be used.

Specifically, the method for evaporating the solvent of the dissolved polymer includes a method of evaporating and removing the solvent by heating and/or drying under reduced pressure. If the boiling point of the solvent is lower than that of water, it is possible to selectively remove the solvent. Although not particularly limited, the solvent can be efficiently removed by heating under reduced pressure conditions. The heating temperature is preferably 20° C. or more and 100° C. or less, and the pressure is preferably 600 mmHg or more and 750 mmHg or less.

As a method of diffusing the solvent of the dissolved polymer, specifically, a method of diffusing the solvent inside the droplets 6 by further adding a solvent or a salt to the O/W emulsion liquid can be mentioned. As the solvent with low solubility in the hydrophilic solvent 7 diffuses into the hydrophilic solvent 7 phase over time, the dissolved polymer can be precipitated and solidified as particles.

Examples of the method of solidifying the molten polymer include a method of solidifying the molten polymer by cooling an O/W emulsion liquid.

<4th step>
The fourth step (step 4) is a step of refining the composite particles 1 from the composite particles 1 and the dispersion of free fine fibers 2, as shown in FIG. 2(d).

Through the above steps, composite particles 1 in which core particles 3 are covered with fine fibers 2 can be produced. In addition, immediately after the composite particles 1 are generated, a large amount of water and free fine fibers 2 that do not contribute to the formation of the coating layer 20 are mixed in the dispersion of the composite particles 1. Therefore, by collecting and refining the composite particles 1 in the fourth step, the powder of the composite particles 1 can be recovered. Since the fine fibers 2 in the present invention have a short major axis diameter and a low viscosity, they can be easily purified and the composite particles 1 can be recovered with a high yield.

Examples of recovery and purification methods include washing by centrifugation and washing by filtration. For example, the dispersion of the composite particles 1 after the third step is subjected to centrifugation or filtration, the free fine fibers 2 are separated, the composite particles 1 are recovered, and the composite particles 1 are purified. Subsequently, a hydrophilic solvent is added to redisperse the composite particles 1, and the free fine fibers 2 are separated by centrifugation or filtration again, and the composite particles 1 are collected, the fine fibers 2 are separated, and the composite particles 1 are separated. can be purified. Furthermore, by repeating washing using an organic solvent instead of a hydrophilic solvent and washing using a hydrophilic solvent and washing using an organic solvent, not only the free fine fibers 2 but also the remaining particles in the core particles 3 were removed. Monomers can be purified.

The hydrophilic solvent used to purify and wash the composite particles 1 is not particularly limited, but pure water, phosphate buffer, etc. can be used. As the organic solvent, an organic solvent that dissolves the monomer remaining in the core particles 3 but does not dissolve the polymer of the core particles 3 can be used. Although not particularly limited, alcohols such as ethanol and methanol can be used.

The solid content concentration in the dispersion containing the composite particles 1 during purification is not particularly limited, but is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less. Similarly, in the redispersion liquid, it is preferable that the solid content concentration of the composite particles 1 is 5% by mass or more and 50% by mass or less. When the solid content concentration of the composite particles 1 is purified or redispersed at the above-mentioned lower limit or higher, efficient purification is possible, and when it is at or below the above-mentioned upper limit, sufficient washing is possible.

The pH of the hydrophilic solvent used for purification is not particularly limited as long as the free fine fibers 2 do not aggregate. For example, when the ionic functional group of the fine fibers 2 is a carboxy group, the pH is preferably 4.0 or more and 8.0 or less. If the pH is less than 4.0, the carboxy group becomes COOH (acid type), the fine fibers 2 aggregate, and it becomes difficult to separate them from the composite particles 1.

The temperature of the redispersion liquid during purification is not particularly limited, but is preferably 4°C or higher and 40°C or lower, more preferably 10°C or higher and 30°C or lower. When the temperature of the redispersion liquid is equal to or higher than the above lower limit, free fine fibers 2 can be dispersed without agglomerating, and purification can be performed efficiently. When the temperature of the redispersion liquid is below the above upper limit, the organic solvent used for purification is difficult to volatilize, and the workability of purification becomes good.

As a washing method using centrifugation, known methods such as a fractional precipitation method, a density gradient sedimentation velocity method, and a density gradient equilibrium method can be used. Among these, it is preferable to use a fractional precipitation method. Specifically, the composite particles 1 can be recovered by sedimenting the composite particles 1 by centrifugation and removing the supernatant containing the free fine fibers 2 by decantation to separate the free fine fibers 2. . Further, the composite particles 1 can be washed by adding a hydrophilic solvent, redispersing the composite particles 1, precipitating the composite particles 1 again by centrifugation, and removing the supernatant.
Examples of the centrifuge include a batch type centrifuge, an automatic discharge type centrifuge, a nozzle type centrifuge, and a hand washing type centrifuge.

The centrifugal acceleration in centrifugation is preferably 5000 x g or more and 500000 x g or less. More preferably, it is 10,000×g or more and 100,000×g or less. When the centrifugal acceleration is equal to or higher than the above lower limit value, the composite particles 1 can be efficiently sedimented and the composite particles 1 can be recovered. When the centrifugal acceleration is below the above upper limit value, the composite particles 1 can be precipitated and purified without free fine fibers 2 being precipitated. Furthermore, the composite particles 1, which are precipitates, can be prevented from forming into lumps, and can be easily redispersed.
The processing time in centrifugation (also referred to as centrifugation time) is preferably 1 minute or more and 60 minutes or less, more preferably 3 minutes or more and 30 minutes or less, and even more preferably 5 minutes or more and 10 minutes or less. When the centrifugation time is equal to or longer than the above lower limit, the composite particles 1 can be sufficiently sedimented and the composite particles 1 can be recovered with a good yield. When the centrifugation time is equal to or less than the above upper limit, the composite particles 1 can be purified without sedimentation of free fine fibers 2.
The processing temperature in centrifugation (also referred to as centrifugation temperature) is preferably 4°C or higher and 40°C or lower. When the centrifugation temperature is 4° C. or higher, an increase in the viscosity of the fine fibers 2 can be suppressed, and when it is 40° C. or lower, deterioration of the fine fibers 2 can be suppressed.

Since the fine fibers 2 have a small median diameter, the viscosity of the dispersion containing the composite particles 1 obtained in the third step is low, and the composite particles 1 tend to settle. Further, since the fine fibers 2 have a small median diameter, sedimentation of the fine fibers 2 themselves can be suppressed, and the composite particles 1 and free fine fibers 2 can be efficiently separated.

Known methods can also be used for filtration and washing. By filtration, the fine fibers 2 and the solvent can pass through the filter medium, and the composite particles 1 can be collected on the filter medium. Furthermore, the composite particles 1 can be washed by supplying a hydrophilic solvent to the filtration device, redispersing the composite particles 1, and filtering again. In filtration, it is preferable to supply a hydrophilic solvent to the filtration device because it can prevent the composite particles 1 from forming into lumps and facilitate redispersion.
Examples of the filtration method include natural filtration, vacuum filtration, pressure filtration, and centrifugal filtration.

The filter medium is not particularly limited, and known filter media such as cellulose, glass fiber, membrane filter, filter plate, sintered filter, cotton plug, and celite can be used. Among these, it is preferable to use a membrane filter because the composite particles 1 can be easily recovered. Further, since the fine fibers 2 and the hydrophilic solvent 7 used in preparing the composite particles 1 are hydrophilic, it is preferable to use a hydrophilic filter medium.
For example, using a polytetrafluoroethylene (PTFE) membrane filter with a pore size of 5 μm, suction filtration is repeated with water and methanol, and finally the residual solvent is further removed from the paste remaining on the membrane filter to recover composite particles 1. can do.

The pore diameter of the filter medium is not particularly limited, but is preferably 0.45 μm or more and 20 μm or less, more preferably 1 μm or more and 15 μm or less, and even more preferably 5 μm or more and 10 μm or less. When the pore size of the filter medium is equal to or larger than the above lower limit value, the fine fibers 2 can easily pass through the filter medium, and the composite particles 1 can be easily purified. When the pore size of the filter medium is below the above upper limit value, the composite particles 1 can be recovered at a high yield without passing through the filter medium.
Normally, fine fibers have a high viscosity and a high aspect ratio, so it is difficult to filter them without passing through a filter medium. However, if the fine fibers 2 of this embodiment have a small median diameter, they can pass through the filter medium and separate the free fine fibers 2 and composite particles 1 by filtration.

<5th step>
In the fifth step (step 5), as shown in FIG. 2(e), the composite particles 1 are impregnated with a functional material-containing liquid containing the functional material 4 to bond the functional material 4 to the composite particles 1. It is a process. Through this step, composite particles 1A (particles in which the surface of the core particle 3 is coated with the fine fibers 2 and the functional material 4 is adsorbed on the surface) are obtained.
Specifically, the composite particles 1 obtained in the fourth step are dispersed in a solvent, the functional material 4 is added and mixed, and the functional material 4 is adsorbed onto the composite particles 1 through ionic bonding.

The method of adding the functional material 4 to the dispersion of the composite particles 1 is not particularly limited, but may include adding a functional material-containing liquid in which the functional material 4 is previously dispersed in a solvent to the dispersion of the composite particles 1. An example is a method of stirring. The temperature of the dispersion liquid of the composite particles 1 when adsorbing the functional material 4 is preferably 5° C. or more and 50° C. or less.

When binding the functional material 4, by removing the counter ion of the ionic functional group of the composite particle 1 in advance, the functional material 4 can be efficiently adsorbed. Specifically, it is preferable to adjust the pH using an acid such as hydrochloric acid or an alkali, and then remove excess salt before adsorbing the functional material 4. It is preferable to impregnate and wash the composite particles 1 using an acidic solution such as hydrochloric acid or an alkaline solution. The counter ions of the fine fibers 2 can be removed by impregnating and washing the composite particles 1 with an acidic solution or an alkaline solution.
When the fine fibers 2 have anionic functional groups, counterions can be removed by, for example, impregnating the composite particles 1 with hydrochloric acid at pH 2.0 and then washing them multiple times with pure water or dilute acid. For washing, the above-mentioned centrifugation or filtration can be used. When the anionic functional group is a carboxy group, the functional material 4 can be efficiently adsorbed to the carboxy group by changing the carboxy group from a sodium salt type (COO ⁻ Na ⁺ ) to an acid type (COOH).
When the ionic functional group is cationic, the functional material 4 can be adsorbed after the pH is made alkaline using an alkali and excess salt is removed.

The solid content concentration of the composite particles 1 in the dispersion of the composite particles 1 (composite particle dispersion) when binding the functional material 4 is not particularly limited, but is preferably 0.1% by mass or more and 20% by mass or less, for example. . When the solid content concentration of the composite particles 1 is equal to or higher than the above lower limit value, the adsorption efficiency of the functional material 4 can be further improved. When the solid content concentration of the composite particles 1 is below the above upper limit value, it is easy to stir and it is easy to uniformly adsorb the functional material 4.
Here, the solid content concentration of the dispersion of the composite particles 1 is determined by dividing the dry mass of the composite particles 1 by the total mass of the dispersion of the composite particles 1.

The temperature of the dispersion liquid of the composite particles 1 when adsorbing the functional material 4 is preferably 5° C. or more and 50° C. or less.

The concentration of the functional material 4 in the functional material-containing liquid is not particularly limited, but is preferably, for example, 1 μM or more and 1 M or less. When the concentration of the functional material 4 is equal to or higher than the above lower limit value, the adsorption efficiency of the functional material 4 to the fine fibers 2 on the surface of the composite particle 1 can be further increased. When the concentration of the functional material 4 is below the above upper limit value, the solubility of the functional material 4 is increased, and the functional material 4 is easily adsorbed uniformly on the fine fibers 2 on the surface of the composite particle 1.

The adsorption amount of the functional material 4 adsorbed on the composite particles 1 is preferably 0.01 μmol or more and 100 μmol or less, more preferably 0.05 μmol or more and 50 μmol or less per 1 g of dry mass of the composite particles 1. When the adsorption amount of the functional material 4 is at least the above lower limit, functionality can be sufficiently imparted. When the adsorption amount of the functional material 4 is below the above upper limit value, association and aggregation between the molecules of the functional material 4 can be suppressed. Therefore, when a fluorescent dye is used as the functional material 4, changes in the fluorescence emission wavelength can be suppressed.
By using fine fibers 2 with a small median diameter, the fine fibers 2 uniformly cover the surface of the core particles 3, so the amount of ionic functional groups on the surface of the composite particles 1 increases, and the functional materials 4 associate and aggregate. It is possible to increase the amount of adsorption of the functional material 4 within the range where it does not.

The adsorption amount of the functional material 4 to the fine fibers 2 is not particularly limited, but for example, it is preferably 0.01 mmol/g or more and 3.0 mmol/g or less, and 0.1 mmol/g per 1 g of dry mass of the fine fibers 2. More preferably, the amount is in the range of g to 2.0 mmol/g. When the adsorption amount of the functional material 4 is at least the above lower limit, functionality can be sufficiently imparted. When the adsorption amount of the functional material 4 is below the above upper limit value, the distance between the molecules of the functional material 4 can be maintained appropriately, and association or aggregation can be suppressed. Therefore, when a fluorescent dye is used as the functional material 4, it is possible to suppress a shift in fluorescence emission and a weakening of fluorescence emission.

The amount of ions adsorbed by the functional material 4 to the ionic functional groups of the composite particles 1 is not particularly limited, but when the amount of ionic functional groups is 100 mol%, it is preferably 0.1 mol% or more and 95 mol% or less, and 1 mol%. More preferably, the content is 90 mol% or less. When the adsorption amount of the functional material 4 is at least the above lower limit, functionality can be sufficiently imparted. When the adsorption amount of the functional material 4 is below the upper limit value, the intermolecular distance of the functional material 4 can be maintained, and association and aggregation of the functional material 4 can be suppressed. Therefore, when a fluorescent dye is applied as the functional material 4, it is possible to suppress the weakening of fluorescence emission and the shift of the fluorescence emission wavelength.
Note that the amount of ionic functional groups present in the composite particles 1 can be evaluated by electrical conductivity titration. The amount of ion adsorption of the functional material 4 on the composite particles 1A can be determined by immersing the composite particles 1 in acid or alkali to desorb the functional material 4, and measuring the absorbance of the desorbed functional material 4. The amount can be calculated and evaluated.

According to the above first step, second step, third step, fourth step, and fifth step, composite particles 1A in which functional material 4 is bonded to composite particles 1 can be obtained.

(dry)
Dry powders of composite particles 1 and composite particles 1A are obtained by removing the solvent remaining in composite particles 1 after purification in the fourth step or composite particles 1A after functional material adsorption in the fifth step by drying. be able to.
The method for removing the residual solvent is not particularly limited, and can be carried out by air drying, heat drying using an oven, or the like. The dry solid material containing composite particles 1 and composite particles 1A thus obtained does not form a film or aggregate, but is obtained as a fine-textured powder.

The solid content percentage of the composite particles 1 and the composite particles 1A after drying is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass. When the solid content percentage of the composite particles 1 and 1A of the composite particles is equal to or higher than the above lower limit, the transportation cost can be reduced and the dispersibility in the hydrophobic resin becomes good.
The solid content percentage of composite particles 1 and composite particles 1A is determined by dividing the mass of composite particles 1 and composite particles 1A after drying them at a temperature of 120° C. for 1 hour by the mass before drying.

≪Molded object≫
The composite particles 1 and 1A of the present embodiment may be used as a powder, or may be contained in a molded body.
The molded product is not particularly limited, and includes, for example, a film-like molded product, a sheet-like molded product, a card-like molded product, a block-like molded product, and the like.

The method for manufacturing the molded article of this embodiment is not particularly limited, and any known method can be used.
For example, a resin containing one or more selected from the fine fibers 2 and composite particles 1 of this embodiment is molded by extrusion molding, injection molding, blow molding, vacuum molding, pressure molding, press molding, etc. to form a molded body. There are several ways to obtain it.
As the resin, known resins such as thermoplastic resins, thermosetting resins, and ultraviolet curing resins can be used.

One or more selected from Composite Particles 1 and Composite Particles 1A may be mixed with resin or paper and molded, and one or more selected from Composite Particles 1 and Composite Particles 1A may be mixed with resin or paper by coating. It is also possible to form a layer containing more than one species.

A problem facing the practical use of fine fibers is that the solid content concentration of the resulting fine fiber dispersion is as low as about 0.1 to 5% by mass. Therefore, when attempting to transport a dispersion of fine fibers, transporting a large amount of solvent is equivalent to transporting a large amount of solvent, leading to an increase in transport costs and significantly impairing business viability (problem of excess solvent). By compositing fine fibers and resin, fine fibers can be transported as solids, and there is no need to disperse them in a large amount of solvent. Problems can be solved. However, in compositing fine fibers and resin, the process of separating free fine fibers and composite resin is complicated. Further, even if separation is possible, the yield may be low, and the purified and recovered portion may contain free fine fibers, resulting in reduced dispersibility. Furthermore, if the long axis diameter of the fine fibers is long, the fine fibers may not be able to sufficiently cover the emulsion droplets, resulting in an increase in the particle size of the composite particles.

According to the composite particles 1 of the present invention, it is possible to efficiently refine and recover true spherical composite particles 1 of resin and fine fibers 2 with small variations in particle size with a small number of purification times. In addition, composite particles 1A having a new type of fine fibers 2 that can be produced by a simple method can be provided. According to the composite particles 1A of the present invention, association and aggregation between four functional material molecules can be suppressed, and desorption of the functional material 4 can be suppressed. Therefore, when a fluorescent dye is used as the functional material 4, it emits stable fluorescence. As a result, stable fluorescence wavelength and fluorescence emission intensity can be maintained. Furthermore, when the core particles 3 emit fluorescence, it is possible to provide composite particles 1A that emit two types of fluorescence due to the core particles 3 and the fluorescent dyes on the surface, and a method for producing the same.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to the present embodiments, and may include design changes without departing from the gist of the present invention.
Further, the components shown in the above-described embodiments can be configured by appropriately combining them.

The present invention will be explained in more detail below using Examples, but the present invention is not limited to these Examples.
In each of the following examples, "%" indicates mass % (w/w%) unless otherwise specified.

[Example 1]
<First step: Step of obtaining fine fiber dispersion (cellulose nanofiber aqueous dispersion)>
(TEMPO oxidation of wood cellulose)
70g of softwood kraft pulp was suspended in 3500g of distilled water, and 0.7g of TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyradical) and 7g of sodium bromide were dissolved in 350g of distilled water. The solution was added and cooled to 20°C. 450 g of an aqueous sodium hypochlorite solution having a concentration of 2 mol/L and a density of 1.15 g/mL was added dropwise thereto to start an oxidation reaction. The temperature in the system was always kept at 40° C., and the pH during the reaction was kept at 10 by adding a 0.5N aqueous sodium hydroxide solution. When the total amount of sodium hydroxide added to the mass of cellulose (softwood kraft pulp) reached 3.5 mmol/g, about 100 mL of ethanol was added to stop the reaction. Thereafter, filtration and washing with distilled water was repeated using a glass filter to obtain oxidized pulp (oxidized cellulose) (oxidation step).

(Defibration treatment of oxidized cellulose)
1 g of oxidized cellulose obtained by the above TEMPO oxidation was dispersed in 99.0 g of distilled water, and subjected to short fiber treatment for 30 minutes with a juicer mixer. liquid) was obtained.

<Second step: Step of producing O/W emulsion>
Next, 1 g of 2,2-azobis(2,4-dimethylvaleronitrile) (hereinafter also referred to as ADVN), which is a polymerization initiator, is added to 10 g of divinylbenzene (hereinafter also referred to as DVB), which is a polymerizable monomer. was dissolved to obtain a polymerizable monomer mixture. When the entire amount of the polymerizable monomer mixture was added to 40 g of the fine fiber dispersion, the polymerizable monomer mixture and the fine fiber dispersion were each separated into two phases.

Next, the shaft of an ultrasonic homogenizer was inserted from the liquid level of the upper phase of the mixed liquid separated into two phases, and ultrasonic homogenizer treatment was performed for 3 minutes at a frequency of 24 kHz and an output of 400 W. The appearance of the mixed solution after treatment with an ultrasonic homogenizer was that of a cloudy emulsion. When a drop of the mixed solution was placed on a slide glass, sealed with a cover glass, and observed under an optical microscope, countless emulsion droplets of several micrometers were formed, and it was confirmed that the dispersion was stabilized as an O/W emulsion. It was done.

<Third step: Step of solidifying the core particle precursor>
The entire amount of the O/W type emulsion dispersion obtained in the second step was placed in a water bath at 70° C. and treated for 8 hours while stirring with a stirrer to carry out a polymerization reaction. After treatment for 8 hours, the dispersion was cooled to room temperature (25°C). There was no change in the appearance of the dispersion before and after the polymerization reaction.

<4th step: Purification step>
The obtained dispersion liquid was diluted 10 times with pure water and filtered using a PTFE membrane filter with a pore size of 5.0 μm to collect composite particles (recovery of composite particles).

The collected composite particles were redispersed in 100 g of pure water and filtered under reduced pressure using a PTFE membrane filter with a pore size of 5.0 μm to wash the composite particles (first filtration and washing).

The washed composite particles were redispersed in 100 g of methanol and filtered using a PTFE membrane filter with a pore size of 5.0 μm to wash the composite particles (second filtration and washing).

The composite particles washed twice were redispersed in 100 g of pure water and filtered under reduced pressure using a PTFE membrane filter with a pore size of 5.0 μm to wash the composite particles (third filtration and washing).

(drying process)
The purified and recovered product after washing three times was redispersed in pure water at a solid content concentration of 1%, and the particle size was evaluated using a particle size distribution analyzer (NANOTRAC UPA-EX150, manufactured by Nikkiso Co., Ltd.). Next, the purified and recovered product was air-dried and further subjected to vacuum drying treatment at room temperature of 25° C. for 24 hours to obtain fine-textured white dry powder (composite particles).

[Example 2]
In Example 1, the cellulose raw material was subjected to alkali treatment. In the alkali treatment, oxidized cellulose is dispersed in an aqueous sodium hydroxide solution with a pH of 9.0 to a solid content of 10% by mass, left at 30°C for 1 hour with stirring, neutralized with acid, and washed with water. I went there.
In addition, in the oxidation step of Example 1, the temperature in the system was set to 20°C, and when the amount of sodium hydroxide reached 3.0 mmol/g based on the mass of cellulose, an excess amount of ethanol was added to stop the reaction. It was stopped.
Fine fibers and composite particles were produced under the same conditions as in Example 1 except for the above.

[Example 3]
In Example 2, the oxidized cellulose after the oxidation step was subjected to electron beam irradiation treatment without being subjected to alkali treatment. The electron beam irradiation treatment was performed by wrapping the oxidized cellulose in aluminum foil and irradiating it with an electron beam at an acceleration voltage of 2 MeV and an irradiation dose of 50 kGy using an electron beam irradiation device.
Fine fibers and composite particles were produced under the same conditions as in Example 2 except for the above.

[Example 4]
Fine fibers and composite particles were produced under the same conditions as in Example 1, except that the temperature inside the oxidation process system was maintained at 30° C. and pH 12.0.

[Example 5]
In Example 2, enzyme treatment was performed instead of alkali treatment. Enzyme treatment was performed as follows. The dispersion of the cellulose raw material was adjusted to a pH of 7.0, 1.0% by mass, and a temperature of 25° C. while stirring, and Sucrase C (Mitsubishi Chemical Foods, Inc.) was added and reacted for 1 hour. Thereafter, the cellulase was inactivated by heating to 95°C.
Fine fibers and composite particles were produced under the same conditions as in Example 2 except for the above.

[Example 6]
In Example 2, the alkali treatment was not performed, but the acid hydrolysis treatment was performed after the oxidation step. The oxidized cellulose obtained in the oxidation step was prepared to a concentration of 1% by mass, hydrochloric acid was added so that the pH became 3.0, and acid hydrolysis treatment was performed at 80° C. for 3 hours. The oxidized cellulose fibers subjected to acid hydrolysis treatment were washed with water and neutralized with an aqueous sodium hydroxide solution.
Fine fibers and composite particles were produced in the same manner as in Example 2 except for the above.

[Example 7]
In Example 2, the alkali treatment was not performed and the ultraviolet irradiation treatment was performed after the oxidation step. The oxidized cellulose was 10% by mass and subjected to ultraviolet irradiation treatment using a xenon lamp at 3.6 kV 100 times.
Fine fibers and composite particles were produced in the same manner as in Example 2 except for the above.

[Example 8]
In Example 2, alkali treatment was not performed, and hydrogen peroxide treatment was performed after the oxidation step. Oxidized cellulose was prepared at pH 7.0 and 1% by mass, hydrogen peroxide was added at 0.5% by mass based on the oxidized cellulose fibers, sodium hydroxide was further added to bring the pH to 11, and the mixture was heated to 70°C. After reacting for 3 hours, the mixture was filtered and washed with water.
Fine fibers and composite particles were produced in the same manner as in Example 2 except for the above.

[Example 9]
In Example 2, OH radical treatment was performed without alkali treatment. The oxidized cellulose after the oxidation step was adjusted to pH 7.0 and 1% by mass, and treated with OH radicals at 10 W for 30 minutes in an oxygen atmosphere.
Fine fibers and composite particles were produced in the same manner as in Example 2 except for the above.

[Example 10]
The same procedure as Example 1 was performed except that in the oxidation step, when the amount of sodium hydroxide reached 6.0 mmol/g based on the mass of cellulose, an excessive amount of ethanol was added to stop the reaction. Fine fibers and composite particles were produced in the same manner.

[Example 11]
In Example 1, fine fibers and composite particles were produced under the same conditions as in Example 1, except that the temperature in the system during the oxidation step was maintained at 60°C.

[Example 12]
Example 2 except that, instead of TEMPO oxidation, a CM-modified CNF dispersion obtained by performing carboxymethylation (CM-conversion) treatment according to Patent Document 2 cited as a prior art document was used. Fine fibers and composite particles were produced under the same conditions as in Example 2.

[Example 13]
Example 2 except that, instead of TEMPO oxidation, a phosphoric acid esterified CNF dispersion obtained by performing a phosphoric acid esterification treatment according to Non-Patent Document 1 cited as a prior art document was used. Fine fibers and composite particles were produced under the same conditions as in Example 2.

[Example 14]
Example 1 was the same as in Example 1, except that instead of TEMPO oxidation, a chitin nanofiber (hereinafter also referred to as chitin NF) dispersion obtained by the method described in JP-A-2010-180309 was used. Fine fibers and composite particles were produced under the following conditions.

Production of chitin NF was performed as follows.
One or more raw materials selected from chitin and chitosan (hereinafter also referred to as "chitin/chitosan raw materials") were defibrated in a solvent to obtain a finely divided chitin dispersion. Specifically, a dispersion of micronized chitin was prepared through the following steps: (1) purification and partial deacetylation treatment of chitin/chitosan raw materials, (2) soaking treatment, and (3) fibrillation treatment.

(1-1) Purification of chitin/chitosan raw material First, dry king crab shells crushed into pieces of about 5 mm are used as chitin/chitosan raw materials. Soaked for a day.
Next, in order to demineralize the defatted raw material, it was treated with 1M hydrochloric acid for 3 hours. The treated raw material was treated overnight with a nitrogen-purged 10% aqueous sodium hydroxide solution to deproteinize it. Thereafter, the treated raw material was bleached by immersing it in a 0.3% aqueous sodium chlorite solution and stirring for 4 hours using a magnetic stirrer in an oil bath set at 70°C. After repeating a series of treatments of demineralization, deproteinization, and bleaching four times, the defatted raw material was washed with a 1M aqueous sodium hydroxide solution to deproninate the amino groups on the surface, and then washed with water.

(1-2) Partial deacetylation of purified chitin The purified chitin raw material obtained by performing the above purification treatment on the chitin/chitosan raw material was immersed in a 33% sodium hydroxide aqueous solution kept at 90°C for 4 hours to partially deacetylate it. Acetylation treatment was performed. Thereafter, the partially deacetylated raw material was thoroughly washed by filtration and water washing until the filtrate became neutral. The purified chitin raw material had a lower degree of N-acetylation due to partial deacetylation, making it suitable for making into nanofibers. The chitin contained in the purified chitin raw material partially became a chitosan structure as a result of deacetylation.

(2) Soaking treatment Next, water was added to the purified chitin obtained above to prepare a purified chitin aqueous dispersion having a solid content concentration of 0.1%. Thereafter, an aqueous dispersion sample was prepared in which the pH was adjusted to 3.3 by adding acetic acid to the above aqueous dispersion.

(3) Defibration treatment Next, the obtained 0.25% purified chitin aqueous dispersion sample was defibrated for 1 minute using a household mixer, and then defibrated for 1 minute using an ultrasonic homogenizer.
Through the above treatments (1) to (3), fine fibers and a fine fiber dispersion using purified chitin as a raw material were obtained.

[Examples 15 to 18]
In Example 1, tetrabutylammonium chloride (TBACl) was added in an amount equimolar to the carboxyl group of cellulose nanofibers, and the counter ions were converted to tetrabutylammonium (TBA) ions before fibrillation. Instead, fine fibers and composite particles according to Examples 15 to 18 were produced in the same manner as in Example 1, except that the following monomers and oligomers were used as core particle precursors.
- Example 15: Monofunctional acrylate isobornyl methacrylate (IB-X).
- Example 16: Monofunctional acrylate isobornyl acrylate (IB-XA).
- Example 17: p-methylstyrene (p-MeSt), a monofunctional vinyl monomer.
- Example 18: Bifunctional urethane acrylate oligomer (UA4200, manufactured by Shin Nakamura Chemical Industry Co., Ltd.).

[Example 19]
<First step: Step of obtaining fine fiber dispersion (cellulose nanofiber aqueous dispersion)>
A fine fiber dispersion (cellulose nanofiber aqueous dispersion) was obtained under the same conditions as in Example 1.

<Second step: Step of producing O/W emulsion>
Next, 10 g of poly-ε-caprolactone (PCL, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was dissolved in 200 g of ethyl acetate to prepare a dissolved polymer.
When the entire amount of the dissolved polymer was added to 500 g of a fine fiber dispersion having a solid content of 0.5% by mass, the dissolved polymer and the fine fiber dispersion were each separated into two phases.

Next, in the same manner as in the second step of Example 1, the upper layer of the liquid mixture separated into two phases was subjected to ultrasonic homogenization using an ultrasonic homogenizer. Using an optical microscope, it was confirmed that countless emulsion droplets of about 1 to several tens of micrometers were generated, and the dispersion was stabilized as an O/W emulsion.

<Third step: Step of solidifying the core particle precursor>
The O/W emulsion was dried under reduced pressure of 700 mmHg at 40° C. for 3 hours to completely volatilize ethyl acetate. There was no change in the appearance of the dispersion before and after volatilization of ethyl acetate.
When the obtained dispersion was washed under the same conditions as in Example 1, spherical composite particles with a particle diameter of about 1 to several tens of μm were obtained. When the recovered material was dried under the same conditions as in Example 1, a white dry powder with fine texture was obtained.

[Comparative example 1]
In Example 1, the oxidation reaction was carried out for 4 hours in the oxidation step, and when the amount of sodium hydroxide reached 3.0 mmol/g based on the mass of cellulose, an excessive amount of ethanol was added to stop the reaction. Fine fibers and composite particles were produced under the same conditions as in Example 1 except for the above.

[Comparative example 2]
In Example 1, the oxidation reaction was carried out for 2 hours in the oxidation step, and when the amount of sodium hydroxide reached 1.5 mmol/g based on the mass of cellulose, an excessive amount of ethanol was added to stop the reaction. Fine fibers and composite particles were produced under the same conditions as in Example 1 except for the above.

[Comparative example 3]
In Example 1, an attempt was made to produce fine fibers and composite particles under the same conditions as in Example 1, except that a carboxymethyl cellulose (hereinafter also referred to as CMC) aqueous solution was used instead of the TEMPO-oxidized CNF dispersion. Each evaluation was carried out.

<Evaluation method for fine fibers>
Regarding the fine fibers obtained in each example, the amount of introduced ionic functional groups, the degree of crystallinity, the number average diameter of short axes (number average short axis diameter), the number average diameter of long axes (number average long axis diameter), ), light transmittance and rheology were measured and calculated as follows.

(Measurement of amount of ionic functional group introduced)
The amount of ionic functional groups introduced into the fine fibers before dispersion treatment was calculated using the following method.
0.2 g of fine fibers in terms of dry mass was placed in a beaker, and 80 mL of ion-exchanged water was added. Thereto, 5 mL of 0.01 mol/L sodium chloride aqueous solution was added, and while stirring, 0.1 mol/L hydrochloric acid was added to adjust the pH of the whole to 2.8.
Using an automatic titration device (trade name: AUT-701, manufactured by DKK Toa), 0.1 mol/L sodium hydroxide aqueous solution was injected at 0.05 mL/30 seconds, and the conductivity was measured every 30 seconds. The pH value was measured and continued until pH 11.
From the obtained conductivity curve, the titration amount of sodium hydroxide was determined, and the amount (mmol/g) of the ionic functional group (carboxy group) introduced was calculated.
When the ionic functional group was a cationic group, electrical conductivity titration was performed under alkaline conditions by injecting hydrochloric acid. 0.2 g of fine fibers before dispersion treatment in terms of dry mass was placed in a beaker, and 80 mL of ion-exchanged water was added. While stirring, 0.1 mol/L aqueous sodium hydroxide solution was added thereto to adjust the pH of the whole to 8.
Using an automatic titrator (trade name: AUT-701, manufactured by DKK Toa), 0.1 mol/L hydrochloric acid was injected at 0.05 mL/30 seconds, and the conductivity and pH value were measured every 30 seconds. Measurement was continued until pH 2.0.
From the obtained conductivity curve, the titration amount of hydrochloric acid was determined, and the amount (mmol/g) of the ionic functional group (amino group) introduced was calculated.

(Calculation of crystallinity)
The crystallinity of the fine fibers obtained in each example was calculated by the following method.
Regarding fine fibers (TEMPO oxidized cellulose), using a sample horizontal multipurpose X-ray diffraction device (product name: Ultima III, manufactured by Rigaku), under the conditions of X-ray output: (40 kV, 40 mA), 5° ≦ 2θ ≦ 35° The X-ray diffraction pattern was measured in the range of . Since the obtained X-ray diffraction pattern is derived from the cellulose type I crystal structure, the crystallinity of the fine fibers was calculated using the following formula (I) and the method shown below.
Crystallinity (%) = [(I22.6-I18.5)/I22.6] x 100...(I)
However, I22.6 is the diffraction intensity of the lattice plane (002 plane) (diffraction angle 2θ = 22.6°) in X-ray diffraction, and I18.5 is the diffraction intensity of the amorphous part (diffraction angle 2θ = 18.5°). Indicates strength.

(Calculation of number average axis diameter of short axis and long axis of fine fibers)
The number average axis diameter of the short axis and long axis of the fine fibers was calculated by the following method.
First, the fine fiber dispersion was diluted to 0.001%, and then 20 μL each was cast onto a mica plate and air-dried. After drying, the shape of the fine fibers was observed in DFM mode using an atomic force microscope (trade name: AFM5400L, manufactured by Hitachi High-Technologies).
The number-average short-axis diameter (number-average short-axis diameter) of the fine fibers was determined by measuring the short-axis diameter (fiber width) of 100 fibers from an image observed using an atomic force microscope, and determining the average value thereof. The number average long axis diameter (number average long axis diameter) of the long axes of the fine fibers was determined by measuring the long axis diameters (fiber length) of 100 fibers from an image observed using an atomic force microscope, and was determined as the average value.

(Measurement of light transmittance of fine fiber dispersion)
The light transmittance (transmittance) of an aqueous dispersion containing 0.5% fine fibers in solid content was measured by the following method.
One side of the quartz sample cell was filled with water as a reference, and the other side was filled with a fine fiber dispersion to prevent air bubbles from entering. The light transmittance at wavelengths from 220 nm to 800 nm at an optical path length of 1 cm was measured using a spectrophotometer (trade name: NRS-1000, manufactured by JASCO Corporation). Table 1 shows the light transmittance at a wavelength of 660 nm.

(Measurement of particle size distribution)
Using a laser diffraction/scattering type particle size distribution meter SALD-7100H (manufactured by Shimadzu Corporation), the fine fiber dispersion was dropped into a flow cell, and the particle size distribution was measured when the scattered light intensity became stable. The results of Example 1 and Comparative Example 1 are shown in FIG. As shown in FIG. 3(a), the median diameter of the fine fibers of Example 1 was 0.083 μm. As shown in FIG. 3(b), the median diameter of the fine fibers of Comparative Example 1 was 34 μm. Here, the "median diameter of fine fibers" refers to the median diameter (or diameter) based on the number of diameters (or long diameters) when fine fibers are likened to spheres when measured using a laser diffraction/scattering particle size distribution analyzer. (diameter when the cumulative number of particles is 50%).

(Rheology measurement)
The rheology of a fine fiber dispersion having a solid content concentration of 0.5% was measured using a rheometer (trade name: AR2000ex, manufactured by TA Instruments) using a cone plate with an inclination angle of 1°.
The temperature of the measuring part was adjusted to 25°C, and in the steady viscoelasticity measurement, the shear rate was continuously increased from 0.01 s ^-1 to 1000 s ^-1 every 30 seconds, and then from 1000 s ^-1 to 0.01 s ^-1. The shear viscosity was measured while the shear rate was continuously lowered every 30 seconds. The results of Example 1 and Comparative Example 1 at shear rates of 0.1 s ^-1 to 1000 s ^-1 are shown in FIG. 4 . Further, Table 1 shows the shear viscosity when the shear rate was 1 s ^-1 and 100 s ^-1 .

As shown in FIG. 4, the shear viscosity of the fine fiber dispersion decreased as the shear rate increased. As is clear from this result, the fine fiber dispersion exhibited thixotropic properties.

As shown in the light transmittance in Table 1, the fine fiber dispersion exhibited high transparency. Further, the number average minor axis diameter of the fine fibers (TEMPO oxidized CNF) contained in the fine fiber dispersion of Example 1 was 3 nm, and the number average major axis diameter was 558 nm.

<Evaluation method of composite particles>
The dry powders (composite particles) obtained in each example were evaluated as follows.

(yield)
The mass of the obtained dry powder was measured and the yield was calculated. The yield was calculated using the following formula.
Yield (%) = Mass of dry powder (g) / Mass of charged core particle precursor (g) x 100
Table 1 shows the results of calculating the yield of composite particles for each example.

(Average circularity)
As an indicator of whether the shape of the composite particles was truly spherical, the average circularity was evaluated using an image analysis type particle size distribution analyzer PITA-04 (Seishin Enterprise). The obtained dry powder was dispersed in pure water, and the circularity of 3000 particles was measured using an image analysis type particle size distribution meter, and the average circularity was calculated as the arithmetic mean value of the circularity. When the area of the sample on the image is S and the perimeter is L, the circularity can be calculated by the formula "circularity=4πS/L ² ", and the closer the circularity is to 1, the higher the sphericity is.
Table 1 shows the results of calculating the average circularity of the composite particles of each example.

(Shape observation using scanning electron microscope, average particle size, maximum particle size)
The obtained dry powder was observed using a scanning electron microscope (SEM). The SEM image is shown in FIG. By performing a polymerization reaction using the O/W type emulsion droplets as a template, it was confirmed that countless true spherical particles were formed due to the shape of the emulsion droplets.
Furthermore, as shown in FIGS. 6(a) and 6(b), it was confirmed that the surfaces of the composite particles were uniformly covered with fine fibers having a width of several nm. Despite repeated washing by filtration, the surfaces of the particles were equally and uniformly covered with fine fibers, indicating that the core particles and fine fibers were bonded and inseparable.
In addition, the particle diameters of 100 composite particles randomly extracted from the SEM images were measured, and the average particle diameter and maximum particle diameter were evaluated. The results are shown in Table 1.

(Possibility of refining)
In the fourth step, the dispersion obtained in the first to third steps was diluted 10 times with pure water and filtered using a PTFE membrane filter (hereinafter also simply referred to as "filter") with a pore size of 5.0 μm. . The feasibility of purification was evaluated based on the following evaluation criteria. The results are shown in Table 1.
"Evaluation criteria"
○: The entire amount of the dispersion liquid can be filtered without clogging the filter.
×: The filter was clogged and the entire amount of the dispersion liquid could not be filtered.

(Evaluation of dispersibility)
The dry powder obtained in each example was added to pure water or acetone at a concentration of 1% by mass, stirred with a stirrer for 24 hours to disperse, and then dropped onto a slide glass, covered with a cover glass, and subjected to an optical microscope. The presence or absence of aggregates was confirmed. Dispersibility was evaluated based on the following evaluation criteria. The results are shown in Table 1.
"Evaluation criteria"
○: No aggregates in pure water and acetone.
×: Aggregates were present in pure water or acetone.

The evaluation results of Examples 1 to 19 and Comparative Examples 1 to 3 are summarized in Table 1. In Table 1, "-" indicates that the evaluation was not performed.

As shown in Table 1, Example 1 to which the present invention was applied had a short fiber length, so the median diameter was small as shown in FIG. 3, and the fine fibers had a low viscosity as shown in FIG. 4. When this fine fiber dispersion was filtered using a membrane filter, the entire amount of the dispersion could be filtered without clogging the filter. As a result of drying the collected material on the filter and calculating the yield of the collected material, the yield was as high as 80% or more. When the obtained particles were observed by SEM, as shown in FIGS. 5 and 6, they were true spherical particles covered with fine fibers, and the variation in particle size was small. When the average circularity was evaluated using a particle size distribution meter, the average circularity was 0.8 or more, suggesting that the particles were perfectly spherical. Moreover, the dispersibility in pure water and acetone was good.

In Examples 1 to 11, it was possible to obtain low-viscosity fine fibers with ionic functional groups and a small median diameter regardless of the shortening treatment method. When a Pickering emulsion of DVB monomer droplets was formed using the fine fibers and the polymerized dispersion was filtered under reduced pressure, the entire amount of the dispersion could be filtered without clogging the filter. In addition, it was possible to produce composite particles that were perfectly spherical, had small variations in particle diameter, and had good dispersibility at a high yield.

In Examples 12 to 14, fine fibers with a small median diameter and low viscosity could be obtained regardless of the type of ionic functional group of the fine fibers or the type of raw material. Using these fine fibers, it is possible to filter the entire amount of the dispersion without clogging the filter during vacuum filtration in the purification process, and it is possible to achieve high yield, perfect spherical shape, small variation in particle size, and good dispersibility. Composite particles could be produced.

In Examples 15 to 19, it was possible to produce composite particles in which the surface of the core particle was coated with fine fibers, regardless of the type of polymer in the core particle. When this dispersion of composite particles and fine fibers was filtered under reduced pressure, it was possible to filter the dispersion without clogging the filter, and it was found that the dispersion was spherical in high yield, had small variations in particle size, and had good dispersibility. Composite particles could be produced.

On the other hand, in Comparative Examples 1 and 2, which used TEMPO-oxidized CNF (fine fibers), which had a large median diameter and high viscosity because they were not subjected to shortening treatment, stable DVB monomer droplets were obtained using fine fibers. A Pickering emulsion could be formed. However, when attempting to purify the dispersion after polymerizing the monomers, the filter became clogged and the entire amount of the dispersion could not be filtered. Since the obtained recovered material was collected together with free fine fibers, when dried, the fine fibers were bridged across a plurality of particles, resulting in poor dispersibility.
In Comparative Example 3 using a non-fibrous polymer CMC, the emulsion of DVB monomer collapsed during polymerization. Although purification was possible, it was not possible to obtain truly spherical particles with small variation in particle size, and the dispersibility was low.

[Example 20]
In Example 1, the following procedure was carried out after the composite particle purification step.

(Acid cleaning process)
The obtained composite particles were dispersed in 0.01M (pH 2.0) hydrochloric acid, stirred for 1 hour, filtered through a PTFE membrane filter with a pore size of 0.45 μm, and washed three times with pure water to remove the carboxy groups from acid. Composite particles of type (-COOH) were obtained.

<Fifth step: Functional material (fluorescent dye) adsorption step>
After adding 0.1 g of composite particles to 5 mL of an aqueous solution of 10 mM fluorescent dye (acridine orange (AO) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)) and stirring, the mixture was left overnight. Thereafter, particles were separated by filtration using a PTFE membrane filter with a pore size of 0.45 μm.

(Washing process and drying process)
The process of adding 5.0 ml of 0.01 M phosphate buffer (pH 7.0) to disperse the particles and filtering through a PTFE membrane filter with a pore size of 0.45 μm was repeated four times (washing process) to remove excess fluorescent dye. was removed and dried at room temperature (25°C) (drying step). In this way, fluorescent dye-adsorbed composite particles in which a fluorescent dye was adsorbed on the surface of the composite particles were obtained through a washing step and a drying step.

[Example 21]
In Example 20, fluorescent dye adsorption composite particles were produced under the same conditions as in Example 20, except that Rhodamine 6G (Rh6G) (manufactured by Tokyo Kasei Kogyo Co., Ltd.) aqueous solution was used instead of the AO aqueous solution.

[Example 22]
Fluorescent dye adsorption was carried out under the same conditions as in Example 20, except that 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) (manufactured by Sigma Aldrich) was used instead of the AO aqueous solution. Composite particles were produced.

[Example 23]
In Example 20, fluorescent dye adsorption composite particles were produced under the same conditions as in Example 20, except that Thioflavin T (TT) (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was used instead of the AO aqueous solution.

[Example 24]
Example 20 except that in place of TEMPO oxidation, a phosphoric acid esterified CNF dispersion obtained by performing a phosphoric acid esterification treatment according to Non-Patent Document 1 cited as a prior art document was used. Fluorescent dye-adsorbing composite particles were produced under the same conditions as described above.

[Example 25]
In Example 20, the chitin NF dispersion liquid described in Example 14 obtained by the method described in JP-A-2010-180309 was used instead of TEMPO oxidation. The composite particles obtained from chitin NF were base-washed using an aqueous sodium hydroxide solution instead of acid-washing using hydrochloric acid. Fluorescent dye adsorption composite particles were produced under the same conditions as in Example 20, except that an aqueous solution of pyranine (Py) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was used instead of the AO aqueous solution in Example 20.

[Example 26]
In Example 20, tetrabutylammonium chloride (TBACl) was added in an amount equimolar to the carboxyl group of cellulose nanofibers, and the counter ions were made into tetrabutylammonium (TBA) ions before fibrillation, and divinylbenzene (DVB) Fluorescent dye-adsorbed composite particles were produced in the same manner as in Example 20, except that IB-X monomer was used as the core particle precursor in the same manner as in Example 15.

[Example 27]
In Example 20, fluorescent dye adsorption composite particles were produced under the same conditions as in Example 20, except that the acid washing step was not performed.

[Example 28]
In Example 20, the functional material adsorption step was carried out as follows.

<Fifth step: Functional material (antibacterial agent) adsorption step>
After adding 0.1 g of composite particles to 5 mL of a 10 mM aqueous solution of an antibacterial agent (benzalkonium chloride (BAC) (manufactured by Tokyo Chemical Industry Co., Ltd.)) and stirring, the mixture was left overnight. Thereafter, particles were separated by filtration using a PTFE membrane filter with a pore size of 0.45 μm.

(Washing process and drying process)
The process of adding 5.0 ml of 0.01 M phosphate buffer (pH 7.0) to disperse the particles and filtering through a PTFE membrane filter with a pore size of 0.45 μm is repeated four times (washing process) to remove excess antibacterial agent. was removed and dried at room temperature (25°C) (drying step). In this manner, antibacterial agent-adsorbing composite particles with an antibacterial agent adsorbed on the surface of the composite particles were obtained through a washing process and a drying process.

[Comparative example 4]
The following evaluations were performed on the AO solid reagent alone (solid, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.).

[Comparative example 5]
In Example 1, particles were prepared under the same conditions as in Example 1, except that a CMC aqueous solution was used instead of the TEMPO-oxidized CNF dispersion, and the following evaluations were performed.

<Evaluation method of fluorescent dye adsorption composite particles (or antibacterial agent adsorption composite particles)>
(Evaluation of dispersibility)
The fluorescent dye-adsorbed composite particles (or antibacterial agent-adsorbed composite particles) obtained in each example were purified under the same conditions as described in Example 1 to obtain dry powder. The obtained dry powder was added to pure water or acetone at a concentration of 1% by mass, stirred with a stirrer for 24 hours to disperse, then dropped onto a slide glass, covered with a cover glass, and observed for aggregation under an optical microscope. I checked to see if something was present. Dispersibility was evaluated based on the following evaluation criteria.
"Evaluation criteria"
○: No aggregates in pure water and acetone.
×: Aggregates were present in pure water or acetone.

(Evaluation of fluorescence emission intensity)
The dry powder obtained in each example or the dye solid reagent used for adsorption (hereinafter also referred to as "sample") was observed using a fluorescence microscope. Using a stereoscopic microscope system SZX16 (manufactured by Olympus Corporation), fluorescence observation of the sample mounted on a slide glass was performed using a black base and an eyepiece x 1 (1x) and an objective lens x 10 (10x). Fluorescence observation is performed using a GFP filter (excitation: 450 nm to 500 nm, emission: 500 nm or more) or a UV filter (excitation: 300 nm to 400 nm, emission: 400 nm or more), and paper is used to prevent light from external fluorescent lamps from entering. The stereo microscope system was covered and evaluated. Under the GFP filter condition, observation was made in the tonal range of histograms 100 to 255, and in the UV filter condition, observation was made in the tonal range of histograms 0 to 125, with an exposure time of 1000 ms. The presence or absence of fluorescence was confirmed, and the fluorescence intensity was evaluated based on the following evaluation criteria.
"Evaluation criteria"
○: Fluorescence is present.
×: No fluorescence emission.

(Evaluation of fluorescence wavelength)
The fluorescence spectrum of each sample was measured using a fluorescence spectrum measuring device. A sample placed on a slide glass was irradiated with a light source passed through a GFP filter of a stereoscopic microscope system SZX16 (manufactured by Olympus), and the fluorescence spectrum was measured using a fiber-type compact optical spectrometer USB2000+ (manufactured by Ocean Optics). The fluorescence spectrum was measured by using a black base for the stereomicroscope system and covering the stereomicroscope system with a blackout curtain to prevent light from an external fluorescent lamp from entering.
The maximum fluorescence wavelength derived from the fluorescent dye of the measured sample was defined as λ1, the maximum fluorescence wavelength of the fluorescent dye solid reagent alone was defined as λ2, and the maximum fluorescence wavelength of the 10 μM fluorescent dye aqueous solution was defined as λ3. When calculating λ1 derived from a fluorescent dye from a sample, the value of fluorescence intensity of a sample not adsorbing a fluorescent dye was subtracted from the value of fluorescence intensity of a sample adsorbing a fluorescent dye. (λ2-λ1) and (λ3-λ1) of each sample were calculated, respectively, and it was confirmed whether the following formulas (II) and (III) were satisfied. Fluorescence wavelength was evaluated based on the following evaluation criteria.
50nm≦(λ2-λ1)...(II)
-100nm≦λ3-λ1≦100nm...(III)
"Evaluation criteria"
○: Satisfies the relationship of formula (II) and formula (III).
x: The relationship of formula (II) or formula (III) is not satisfied.

(Evaluation of antibacterial properties)
One platinum loop of Escherichia coli NBRC3972 stored in a refrigerated ordinary agar (NA) slant medium was scraped off, transferred to a new NA slant medium, and cultured at 35° C. for 22 hours. One platinum loop of the cultured E. coli was transplanted into a sterilized Mueller-Hinton broth (MHB) medium and cultured at 35°C for 19 hours. This was used as a sample for pour culture, and the number of E. coli contained in the bacterial solution was estimated. In addition, a portion of the sample was diluted 100 times with sterilized MHB medium.
The sample was weighed into a screw tube bottle, 1 mL of sterilized MHB medium was added, and the screw tube bottle was placed in an ultrasonic cleaning bath and stirred for 3 minutes. 10 μL of the bacterial solution was inoculated into a screw tube bottle to prepare a test solution, and this test solution was cultured at 35° C. for 28 hours. After culturing for 28 hours, 9 mL of soybean casein digest (SCDLP) medium supplemented with lecithin polysorbate 80 was added to each screw tube bottle and allowed to stand for 30 minutes. This was diluted 10 times the test solution, further diluted appropriately with phosphate buffered saline (PBS), and cultured in agar medium for 24 hours. The number of E. coli was estimated from the number of E. coli colonies after pour culture, and the minimum concentration at which no colonies were observed was defined as the minimum bactericidal concentration (MBC), and the antibacterial properties were evaluated based on the following evaluation criteria.
"Evaluation criteria"
○: MBC is 32 ppm (mass basis) or less.
×: MBC exceeds 32 ppm (mass basis).

The evaluation results of Examples 20 to 28 and Comparative Examples 4 to 5 are summarized in Table 2. In Table 2, "-" indicates that the component is not contained or the evaluation thereof was not performed.

The results of fluorescence observation in Example 20 are shown in FIG.
As in Example 20, when AO, which is a fluorescent dye, was adsorbed onto the composite particles of Example 1, fluorescence emission was confirmed under the GFP filter condition as shown in Figure 7(a), indicating that sufficient fluorescence emission was observed. It was intense. Example 20 exhibited green fluorescence originating from AO.
Further, as shown in FIG. 7(b), when fluorescence was observed under UV filter conditions, fluorescence of the core particles was confirmed. The fluorescence emission of the core particle was blue originating from the benzene ring.
As a result of measuring the fluorescence spectrum of the sample of Example 20, the maximum fluorescence wavelength (λ1) derived from the fluorescent dye was 600 nm or less.

On the other hand, when the AO solid reagent of Comparative Example 4 was observed alone under GFP filter conditions, fluorescence was observed as shown in FIG. 8. The fluorescence emission of Comparative Example 1 was red. When the fluorescence spectrum of the sample of Comparative Example 1 was measured, the maximum fluorescence wavelength (λ2) was 700 nm, and the maximum fluorescence wavelength of the sample of Example 20 was 50 nm or more shorter than that of the AO solid reagent alone. In addition, the maximum fluorescence wavelength (λ3) of a 10 μM AO aqueous solution is 530 nm, and the difference from the maximum fluorescence wavelength of the sample of Example 20 is 100 nm or less, and in Example 20, association and aggregation of fluorescent dyes are suppressed. It was suggested that it was possible.

As shown in Table 2, in Examples 20 to 26, association and aggregation of fluorescent dyes were suppressed, and sufficient fluorescence was obtained regardless of the type of fine fibers, the type of ionic functional group, the core particle, and the type of fluorescent dye. It was possible to obtain fluorescent dye-adsorbed composite particles that had luminescent intensity and suppressed the shift of fluorescent luminescence.
As in Example 27, the fluorescent dye could be adsorbed without acid washing. This composite particle also had good dispersibility, had sufficient fluorescence intensity, and was able to suppress the shift of fluorescence.
The antibacterial properties of the composite particles of Example 28 were evaluated as "○", and it was confirmed that the composite particles had antibacterial properties.

On the other hand, Comparative Example 4, which does not contain fine fibers, showed sufficient fluorescence emission intensity as shown in FIG. The wavelength was longer than 100 nm, suggesting that the fluorescent dye was associated with the fluorescent dye.
In Comparative Example 5, which used a non-fibrous polymer with an ionic functional group, fluorescence emission was confirmed, but the maximum fluorescence wavelength was shifted to a longer wavelength by more than 100 nm with respect to a 10 μM dye aqueous solution. It was suggested that they were meeting.

According to the composite particles of the present invention, it is possible to solve the problem of too much solvent in fine fibers such as cellulose nanofibers and chitin nanofibers, and to provide composite particles having a new type of fine fibers that can be produced by a simple method. Can be done.
By using fine fibers, stable droplets are formed without the use of additives such as surfactants, so it is possible to obtain true spherical composite particles with a small particle size distribution.
By using fine fibers with short fiber length, emulsion droplets can be sufficiently covered and a stable Pickering emulsion can be formed, so that true spherical composite particles with small variation in particle size can be obtained.
In addition, by using short, low-viscosity fine fibers, purification efficiency is improved and free fine fibers can be sufficiently removed, suppressing cross-linking between particles and improving dispersibility in various solvents. Composite particles with improved properties can be provided. This is expected to lead to applications in cosmetics, security materials, and the like.
Cellulose nanofibers and chitin nanofibers are fine fibers made of biodegradable polymers. Therefore, by making the core particle also of a material containing a biodegradable polymer, it is possible to provide a composite particle that can reduce the burden on the environment and solve the microplastic problem.
According to the composite particles (fluorescent dye-adsorbing composite particles) of the present invention, by preventing the association and aggregation of fluorescent dyes, it is possible to stably exhibit the original fluorescence of fluorescent dye molecules. Therefore, a molded article containing fluorescent dye-adsorbing composite particles can be used as a security member for preventing counterfeiting and the like.

1,1A Composite particle 2 Fine fiber 3 Core particle 4 Functional material 6 Droplet 7 Hydrophilic solvent 20 Covering layer (fibrous layer)

Claims (16)

A composite particle having fine fibers and a core particle containing at least one polymer,
the fine fibers are bonded to the surface of the core particle,
The median diameter of the fine fibers is 0.01 μm or more and 10 μm or less,
The fine fibers are ion-modified fibers having ionic functional groups,
The amount of the ionic functional group introduced is 1.3 mmol/g or more and 5.0 mmol/g or less based on the dry mass of the fine fibers,
The average particle size is 0.1 μm or more and 50 μm or less,
Composite particles having an average circularity of 0.8 or more. The viscosity at 25° C. of the aqueous dispersion containing 0.5% by mass of the fine fibers as a solid content is 2 mPa·s or more and 1000 mPa·s or less when the shear rate is 1 s ⁻¹ , and 5 mPa·s when the shear rate is 100 s ⁻¹ . The composite particle according to claim 1, having a pressure of not less than 100 mPa·s and not more than 100 mPa·s. The composite particle according to claim 1 or 2, wherein the fine fibers are one or more types selected from cellulose nanofibers and chitin nanofibers. The composite particle according to claim 1 or 2, wherein the ionic functional group is one or more selected from a carboxy group, a phosphoric acid group, and a sulfo group. The composite particle according to claim 1 or 2, wherein the content of the ionic functional group is 0.1 μmol/g or more and 100 μmol/g or less based on the dry mass of the composite particle. The composite particles according to claim 1 or 2, having a solid content of 80% by mass or more. The composite particle according to claim 1 or 2, wherein the polymer has a benzene ring structure at least in part. Composite particles according to claim 1 or 2, wherein the polymer is a biodegradable polymer. 2. Part or all of the ionic functional group has been modified by a reaction that combines with one or more functional materials selected from anionic functional materials and cationic functional materials. Composite particles described in. The composite particle according to claim 9, wherein the functional material is a fluorescent dye. 11. The fluorescent dye according to claim 10, wherein the fluorescent dye has one or more selected from a cyanine skeleton, a xanthene skeleton, an oxazine skeleton, an acridine skeleton, a diphenylmethane skeleton, a thiazole skeleton, an indole skeleton, an ethidium skeleton, and a propidium skeleton. composite particles. The composite particle according to claim 11, wherein the amount of the fluorescent dye bound is 0.1 μmol/g or more and 100 μmol/g or less based on the dry mass of the composite particle. A step of subjecting the fiber raw material to shortening treatment to obtain shortened fibers;
defibrating one or more selected from the fiber raw material and the shortened fiber in a solvent to obtain a fine fiber dispersion in which fine fibers are dispersed;
adding droplets containing a core particle precursor to the fine fiber dispersion and coating the surface of the droplets with the fine fibers;
solidifying the core particle precursor to obtain a core particle, and obtaining a composite particle in which the surface of the core particle is coated with the fine fiber;
A method for producing composite particles, comprising: 14. The method for producing composite particles according to claim 13, further comprising the step of introducing an ionic functional group into one or more selected from the fiber raw material, the shortened fiber, and the fine fiber to obtain an ion-modified fiber. 15. The method for producing composite particles according to claim 14, wherein the ion-modified fibers are brought into contact with a functional material-containing liquid containing a functional material to obtain composite particles with the functional material bonded to the surface. The method for producing composite particles according to claim 15, wherein the functional material is a fluorescent dye.

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