JP2019181398A - Microcapsule coating, microcapsule formulation, and method for producing microcapsule formulation - Google Patents

Abstract

To provide: a microcapsule coating that can become one expanding the use of a cellulose nanofiber; a microcapsule formulation; and a method for producing the same.SOLUTION: The microcapsule formulation of the present invention comprises a core particle and a microcapsule coating surrounding the core particle, and in which the microcapsule coating contains a cellulose nanofiber to which a styrene-based compound is added. The microcapsule formulation of the present invention can be produced, for example, by adding a styrene-based compound to a cellulose nanofiber to produce a coating material, and mixing and decompressing the coating material and core particles in the presence of a supercritical fluid or a subcritical fluid.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a microcapsule coating, a microcapsule formulation, and a method for producing a microcapsule formulation, and more particularly, to a microcapsule coating, a microcapsule formulation, and a method for producing a microcapsule formulation that contain cellulose nanofibers as a coating component. .

  In Japan, where material resources such as metals and fossil fuels are scarce, we have relied on imports for many materials. The situation has not changed, and it is indispensable for future industrial development to secure resources that can be harvested in the country and are industrially useful.

  In recent years, cellulose nanofiber (CNF) has been attracting attention as a new material that satisfies the conditions (Non-patent Document 1). Cellulose nanofibers are made of plant fibers such as pulp, and there are many merits for Japan, where about 70% of the country is forests, such as easy procurement of raw materials, recyclability, and low environmental impact.

  Cellulose nanofibers have excellent properties that are said to be 5 times the strength of steel and 1/5 the weight, and a wide range of industries from upstream to downstream in Japan, namely paper industry, chemical industry, textile industry. It has been proposed as a material related to the automobile industry, IT industry, food industry, medical industry, molding processing industry, etc. (Non-patent Document 2), and applied research has already been promoted. For example, cellulose nanofibers, in addition to automotive parts and display components for electronic terminals, use the property of thixotropy to increase the number of sunscreen components and ballpoint pens that prevent stickiness on the skin after application. It is also used as a sticking agent and is expected to be applied to a wider range of fields.

  On the other hand, cellulose nanofibers are not sufficiently applied in technical fields such as pharmaceuticals and agricultural chemicals. In a broader technical field including these technical fields, it is desired to further expand the use of cellulose nanofibers.

Tetsuo Kondo, “New Development of Cellulose Nanofiber Technology”, Journal of the Wood Society, 2008, Vol. 54, no. 3, p. 107-115 Hiroyuki Yano, “Manufacture and utilization of cellulose nanofiber”, Journal of Functional Papers, 2010, No. 49, p. 15-20

  An object of the present invention is to provide a microcapsule film and a microcapsule formulation, and a method for producing the same, which can be one of the applications to expand cellulose nanofibers. is there.

  The present invention is a microcapsule film containing cellulose nanofibers to which a styrenic compound is added.

  In one embodiment, the styrenic compound has the following formula (I):

(Wherein R ¹ is a hydrogen atom or a methyl group, and R ² is a hydrogen atom, a halogen atom, a carboxyl group, an optionally branched C ₁ -C ₄ alkyl group, and an optionally branched group. It is a compound selected from the group consisting of good C ₁ -C ₄ alkoxy groups.

  In a further embodiment, the styrenic compound is a styrene monomer.

  The present invention is also a microcapsule formulation comprising core particles and the above microcapsule film surrounding the core particles.

The present invention is also a method for producing a microcapsule formulation,
Adding a styrenic compound to cellulose nanofibers to obtain a coating material; and mixing and microencapsulating the coating material and core particles in the presence of a supercritical fluid or a subcritical fluid;
A method comprising

  In one embodiment, the styrenic compound has the following formula (I):

(Wherein R ¹ is a hydrogen atom or a methyl group, and R ² is a hydrogen atom, a halogen atom, a carboxyl group, an optionally branched C ₁ -C ₄ alkyl group, and an optionally branched group. It is a compound selected from the group consisting of good C ₁ -C ₄ alkoxy groups.

  In a further embodiment, the styrenic compound is a styrene monomer.

  In one embodiment, the cellulose nanofiber is a cellulose material treated with a TEMPO catalyst.

  According to the present invention, a preparation coated with cellulose nanofibers can be efficiently provided without exposing the core particles. The cellulose nanofiber constituting the preparation of the present invention is a material that can be produced in Japan and can be regenerated. For this reason, it is not necessary to depend on overseas resources for manufacturing, and the influence of environmental load can be reduced.

It is a schematic diagram of the experimental apparatus used for preparation of the microcapsule formulation under supercritical fluid performed in Examples 1-2 and Comparative Examples 1-2. It is a graph showing the FT-IR spectrum about the solid particle E1 obtained in Example 1, the solid particle E2 obtained in Example 2, and the silica balloon used in Examples 1 and 2. It is a photograph which shows the SEM image of the silica balloon single used in Example 1 grade | etc.,. 2 is a photograph showing an SEM image of solid particles E1 obtained in Example 1. FIG. 2 is a photograph showing an SEM image of solid particles E2 obtained in Example 2. FIG. 4 is a photograph showing an SEM image of solid particles CE1 obtained in Comparative Example 1. 6 is a photograph showing an SEM image of solid particles CE2 obtained in Comparative Example 2.

  Hereinafter, the present invention will be described in detail.

(Microcapsule formulation and microcapsule coating)
The microcapsule formulation of the present invention includes core particles and a microcapsule film surrounding the core particles.

  In the present invention, the microcapsule film contains cellulose nanofibers to which a styrenic compound is added.

  Cellulose nanofiber (CNF) is a fibrous structure derived from plants. Many plants have a cell wall as the extracellular matrix. The cell wall is composed of, for example, approximately 50% by mass of cellulose, 20% by mass to 30% by mass of hemicellulose, and 20% by mass to 30% by mass of lignin based on mass. Cellulose nanofibers are obtained by isolating cellulose from such a cellulose material by removing hemicellulose and lignin through, for example, high-temperature treatment using steam in an alkaline solution, and further subjecting to a predetermined chemical or physical treatment. Can be obtained by solving bonds and entanglements between cellulose molecules. In one embodiment, the cellulose nanofibers are composed of cellulose fibers having a diameter of 1 nm to 100 nm and having an aspect ratio of 100 or more.

  Cellulose materials used as raw materials for cellulose nanofibers include, for example, trees obtained by natural or industrial afforestation; wood, wheat straw, rice straw, corn core / foliage, and bagasse obtained as industrial waste; and these Combinations are listed.

  Such cellulose materials are processed into cellulose nanofibers using various methods known to those skilled in the art. As an example of a method for obtaining cellulose nanofibers from cellulose material, cellulose fiber pulp is charged into a tank having a nozzle together with water, and the pulp and water are jetted from the nozzle at high pressure to collide cellulose fibers in the pulp. And pulverization method (ACC (Aqueous Counter Collation) method; using TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) catalyst), present at C6 position of cellulose molecule contained in cellulose material A method of refining cellulose fibers contained in the material by oxidizing its primary alcohol by utilizing its charge repulsion; and a microorganism using a microorganism derived from the genus Trichoderma or an enzyme produced by the microorganism Water addition In the present invention, the reaction can proceed at room temperature and atmospheric pressure, and no special and large production facilities are required, and the catalyst itself is recovered and reused. For the reason that it is possible, it is preferable to use cellulose nanofibers obtained by using a method of refining cellulose fibers contained in a cellulose material using the TEMPO catalyst.

  The styrenic compound is an oleophilic compound that can be graft-polymerized with the cellulose constituting the cellulose nanofiber as a backbone polymer by addition.

  Examples of such styrenic compounds include the following formula (I):

(Wherein R ¹ is a hydrogen atom or a methyl group, and R ² is a hydrogen atom, a halogen atom, a carboxyl group, an optionally branched C ₁ -C ₄ alkyl group, and an optionally branched group. And a compound selected from the group consisting of good C _{1 to} C ₄ alkoxy groups. Examples of the halogen atom that can constitute R ² in the formula (I) include a fluorine atom, a chlorine atom, and a bromine atom.

  Specific examples of the styrene compound represented by the formula (I) include styrene (monomer), m-chlorostyrene, p-chlorostyrene, p-methoxystyrene, m-tert-butoxystyrene, and p-vinyl. Examples include benzoic acid, p-methyl-α-methylstyrene, and 1-ethynyl-4-fluorobenzene. Since the dispersibility of the cellulose fiber which comprises a cellulose nanofiber can be improved effectively, it is preferable that styrene (monomer) is added to the cellulose nanofiber.

  In the present invention, the microcapsule film preferably has a film thickness of 0.001 to 100 μm, more preferably 0.01 to 50 μm. When the film thickness of the microcapsule film is less than 0.001 μm, it may be difficult to completely surround the core particles described later. When the film thickness of the microcapsule film exceeds 50 μm, the film becomes too strong, and when the microcapsule preparation is used for a desired application, it may be difficult to discharge the film from the film to the outside of the core particles.

  The core particle is a substance having a specific function, action effect, and the like desired for the microcapsule formulation, and is composed of a solid, a liquid, and a mixture thereof containing one or more active ingredients Or the particle group. Examples of core particles include, but are not necessarily limited to, drug substances and / or components (eg, calcium carbonate) for pharmaceuticals or agrochemicals; active ingredients for cosmetics or health foods; food materials that constitute general foods; Chemical materials used in the printing field, the electronic field, and the like.

  The core particles may also contain components other than the above active ingredients. Examples of other components that can be contained in the core particles include excipients, stabilizers, preservatives, buffers, pH adjusters, antioxidants, disintegrants, corrigents, suspending agents, emulsifiers, wear Flavor, Solubilizer, Colorant, Thickener, Strengthening Agent, Bactericide, Bleaching Agent, Acidulant, Coloring Agent, Enzyme, Seasoning, Sweetener, Thickening Stabilizer, Fragrance, Antifungal Agent, Preservative , Swelling agents, gelling agents, pastes, bittering agents, brighteners, gum bases, yeast powder, cane, binders, antifoaming agents, extraction solvents, coagulants, shelf life improvers, mold release agents, and filter aids Agents, and combinations thereof. Content of the said other component in a core particle is not specifically limited, Arbitrary content may be selected by those skilled in the art.

  Although the average particle diameter of the core particle which comprises the microcapsule formulation of this invention is not necessarily limited, For example, they are 0.05 micrometer-1000 micrometers, More preferably, they are 1 micrometer-100 micrometers. When the average particle diameter of the core particles is outside the above range, it may be difficult for the microcapsule coating with the cellulose nanofibers to surround the core particles substantially uniformly.

  The microcapsule preparation of the present invention utilizes the excellent properties (for example, high strength and high elastic modulus) of the cellulose nanofiber itself constituting the microcapsule film, for example, pharmaceuticals, agricultural chemicals, cosmetics, foods, printing, It can be used for microcapsule preparations in various fields such as electronic chemicals.

(Method for producing microcapsule preparation)
Next, the manufacturing method of the microcapsule formulation of this invention is demonstrated.

  In the production method of the present invention, first, a coating material is produced by adding a styrene compound to cellulose nanofibers.

  In the present invention, as described above, the cellulose nanofiber is refined into a cellulose material (for example, not only a dried plant body but also a crude cellulose nanofiber) by using a TEMPO catalyst to refine the cellulose fiber (that is, It is preferable that the cellulose nanofibers obtained have been subjected to a high dispersion treatment. When the cellulose material is processed using a TEMPO catalyst, the amount used is not necessarily limited, but is preferably 0.01 parts by mass to 10 parts by mass, more preferably 0.1 parts by mass with respect to 100 parts by mass of the cellulose material. Up to 5 parts by weight of TEMPO catalyst can be used. When the amount of the TEMPO catalyst used is less than 0.01 parts by mass with respect to 100 parts by mass of the cellulose material, the TEMPO catalyst with respect to the cellulose material acts non-uniformly to obtain cellulose nanofibers in which the cellulose fibers are uniformly refined. May be difficult. When the amount of the TEMPO catalyst used exceeds 10 parts by mass with respect to 100 parts by mass of the cellulose material, there is almost no change in the obtained cellulose nanofibers, but rather overall productivity in that many TEMPO catalysts are used. May be reduced.

  In the present invention, the styrene compound may be used in a proportion of preferably 100 parts by mass to 10000 parts by mass, more preferably 500 parts by mass to 1000 parts by mass with respect to 100 parts by mass of the cellulose nanofiber. When the amount of the styrene compound used is less than 100 parts by mass with respect to 100 parts by mass of the cellulose nanofibers, the amount of the styrene compound added to the cellulose nanofibers is too small, and the microcapsule coating is more uniform with respect to the core particles. May be difficult to form. When the amount of the styrene compound used exceeds 100 parts by mass with respect to 100 parts by mass of the cellulose nanofibers, radical polymerization of the styrene compounds proceeds, and the amount added to the cellulose nanofibers and the microcapsules to be formed are further increased. There may be no substantial change in the coating.

  The addition of styrenic compounds to cellulose nanofibers can be performed using methods well known to those skilled in the art. The addition is performed, for example, by graft polymerization of a styrene compound to cellulose (trunk polymer) constituting cellulose nanofibers using diammonium cerium (IV) nitrate as an initiator. Conditions required for this graft polymerization can be appropriately selected by those skilled in the art.

  Thus, the coating material used as the raw material of a microcapsule film is produced using a cellulose nanofiber and a styrene-type compound.

  In the present invention, the coating material and the core particles are then mixed in the presence of a supercritical fluid or a subcritical fluid and microencapsulated.

  Every substance has a critical point that is the upper limit of gas-liquid coexistence. A state beyond the critical point is called a supercritical state.

A supercritical fluid that can be used in the present invention refers to a fluid in this supercritical state. Supercritical fluids are dense fluid above the critical point and the critical pressure, preferably have a density of ^{200kg / m 3 ~900kg / m 3} , preferably ¹⁰ -5 Pa · s ^{to 10} -4 Pa - a viscosity of seconds, preferably ¹⁰ -8 ^{m 2} / s to ^10-7 m ² / has a diffusion coefficient of seconds, and / or preferably ^{10 -3 W / m 2 · K~10} -1 A fluid having a thermal conductivity of W / m ² · K.

On the other hand, the subcritical fluid that can be used in the present invention is in a state slightly lower than the high-temperature and high-pressure state of the supercritical fluid, specifically, in a liquid state at a pressure lower than the vapor pressure curve in a temperature range lower than the critical temperature. a certain fluid preferably has a density of ^{500kg / m 3 ~1100kg / m 3} , preferably having a viscosity of ¹⁰ -4 Pa · s ^{to 10} -3 Pa · sec, preferably ¹⁰ -10 ^{m 2} / sec to ^10-9 m has a diffusion coefficient of ² / s, and / or preferably a fluid having a thermal conductivity of 0.08W / m · K~0.10W / m · K.

  Examples of substances constituting such a supercritical fluid or subcritical fluid include carbon dioxide, water, methane, ethane, propane, ethylene, propylene, methanol, ethanol, and acetone, and combinations thereof. In the present invention, carbon dioxide set to a supercritical state or a mixture of carbon dioxide and ethanol set to a supercritical state is used because the coating material can be efficiently dissolved. Is preferred. When using a mixture of carbon dioxide and ethanol set to a supercritical state, the composition of carbon dioxide and ethanol in the mixture is preferably a concentration of 0.001 to 0.5 in terms of molar fraction, and more preferably Is a concentration of 0.001 to 0.1.

  In the presence of this supercritical fluid, the coating material and core particles are mixed. Then, the mixed coating material and core particles are injected at a stroke under a low pressure environment (for example, normal pressure) through the nozzle or gradually reduced in pressure to induce phase separation between the coating agent and the core material. Thus, a microcapsule preparation in which the outer periphery of the core particle is microencapsulated with a coating material (that is, covered with a microcapsule film) can be obtained. In the present invention, because the more uniform microcapsule film can be produced, the mixed coating material and core particles are gradually decompressed in the presence of the supercritical fluid, and the coating agent and the core material It is preferable to induce micro-encapsulation by inducing phase separation.

  In this way, a microcapsule preparation containing cellulose nanofibers to which a styrenic compound is added and in which core particles are surrounded by a microcapsule coating can be produced.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited to these Examples.

(Reference Example 1: High dispersion of cellulose nanofibers)
In order to produce a microcapsule film described later, the cellulose nanofiber (CNF) used was highly dispersed.

  To a 100 mL beaker, add 50 mL of softwood pulp (manufactured by Chuetsu Pulp Co., Ltd .; purity 1.03%), 0.008 g of TENPO catalyst (manufactured by ACROS ORGANICS; purity 96%), and 0.05 g of sodium bromide. To 100 mL with ultrapure water. To the obtained solution, 0.65 mmol of sodium hypochlorite pentahydrate was added to start the oxidation reaction, and the mixture was stirred at room temperature at 500 rpm for 24 hours. During this reaction, in order to prevent a decrease in pH in the reaction solution, the pH is measured with a pH meter (desk type pH meter SK-650PH manufactured by Sato Keiki Seisakusho Co., Ltd.), and 0.1 M sodium hydroxide is appropriately used. An aqueous solution was added to maintain the pH at approximately 10.

  Thereafter, the reaction product was separated by filtration, washed with ultrapure water, and dried to obtain highly dispersed cellulose nanofibers (0.4340 g).

(Example 1: Production of microcapsule preparation)
To a 50 mL Erlenmeyer flask, 0.01 g of highly dispersed cellulose nanofiber prepared in Reference Example 1 was added, and 10 mL of styrene monomer (purity 99.0%) and 2.5 mmol / L diammonium cerium nitrate ( IV) (catalyst; purity 99.5% or more) was added.

  Next, this flask was placed in a constant temperature water bath at 50 ° C., and the inside of the flask was replaced with nitrogen for about 10 minutes. After nitrogen substitution, while maintaining the temperature of the thermostatic water bath at 50 ° C., sales were expanded at 500 rpm and reacted for 100 minutes. After completion of the reaction, the solid in the flask was separated to remove unreacted styrene and the catalyst, thereby obtaining cellulose nanofibers added with styrene (hereinafter referred to as “styrene-added CNF”).

  Using the styrene-added CNF thus obtained, the following operation was performed under the supercritical fluid in the experimental apparatus 1 shown in FIG.

  In a high-pressure cell 10 having a volume of 50 mL, 0.010 g of silica balloon (core particle; average particle size 9.8 μm), 2.5 mL of styrene-added CNF, and 2.5 mL of ethanol were charged, and valves 13 and 15 were connected. In a closed state, the valves 12 and 14 were opened, carbon dioxide (purity 99.9% or more) was supplied from the cylinder 11 to the high-pressure cell 10, and left for a while until the pressure in the high-pressure cell 10 reached the operating pressure. Meanwhile, the inside of the high-pressure cell 10 was stirred with a magnetic stirrer 17. After confirming that the operating pressure was reached, the valves 12 and 14 were closed, and the stirring in the high-pressure cell 10 was continued to disperse the reactant 18 in the pressurized carbon dioxide (supercritical fluid). This state was left for about 30 minutes. Then, the valve 15 was opened and the pressure in the high-pressure cell 10 was reduced at 0.067 MPa / min to promote phase separation between the styrene-added CNF in the reaction product 18 and the silica balloon. After the atmospheric pressure was reached, the high-pressure cell 10 was opened, and the solid particles E1 (silica-T-CNF-styrene) remaining inside were recovered.

(Example 2: Production of microcapsule preparation)
Instead of the highly dispersed cellulose nanofiber prepared in Reference Example 1 (cellulose nanofiber treated with a TEMPO catalyst), 0.01 g of softwood pulp (manufactured by Chuetsu Pulp Co., Ltd .; purity: 1.03%) was used as it was. Except for this, styrene was added in the same manner as in Example 1, and the operation was performed under supercritical fluid in the experimental apparatus 1 shown in FIG. E2 (silica-CNF-styrene) was recovered.

(Comparative Example 1)
Instead of the highly dispersed cellulose nanofiber prepared in Reference Example 1 (cellulose nanofiber treated with a TEMPO catalyst), 0.01 g of softwood pulp (manufactured by Chuetsu Pulp Co., Ltd .; purity 1.03%) was used as it was. 1 and except that the styrene monomer was not added, the same operation as in Example 1 was carried out under the supercritical fluid in the experimental apparatus 1 shown in FIG. The solid particles CE1 (silica-CNF) remaining inside were recovered.

(Comparative Example 2)
FIG. 1 shows the same procedure as in Example 1 except that the styrene monomer was not added to the highly dispersed cellulose nanofiber prepared in Reference Example 1 (cellulose nanofiber treated with a TEMPO catalyst). The operation under the supercritical fluid in the experimental apparatus 1 was performed and the pressure was changed to atmospheric pressure, and then the solid particles CE2 (silica-T-CNF) remaining in the high-pressure cell 10 were recovered.

(Surface analysis of the obtained solid)
The solid particles E1 obtained in Example 1 (silica-T-CNF-styrene), the solid particles E2 obtained in Example 2 (silica-CNF-styrene), and the silica balloon used in Examples 1 and 2 ( That is, for each of the core particles not covered with the microcapsule film alone, each of them was measured by ATR method (total reflection measurement method) using a Fourier transform infrared spectrophotometer (FT-IR 470-Plus manufactured by JASCO Corporation). The surface condition of the particles was measured. The obtained results are shown in FIG.

  As shown in FIG. 2, each of the solid particles E1 (silica-T-CNF-styrene) obtained in Example 1, the solid particles E2 (silica-CNF-styrene) obtained in Example 2, and the silica balloons In the IR spectrum, a remarkable difference could be observed around 3300 nm. This difference near 3300 nm is due to OH stretching vibration, which is considered to be derived from many hydroxyl groups present in cellulose contained in each particle.

  Here, referring to FIG. 2, it is shown that the solid particles E1 and E2 of Examples 1 and 2 using the coating material containing cellulose nanofibers have a peak near 3300 nm as compared with the silica balloon. It can be seen that a large amount of cellulose, that is, cellulose nanofibers are distributed as the microcapsule film on the surface of the solid particles.

(Observation of surface state of solid particles by SEM)
Silica balloon used in Example 1 or the like (that is, core particles alone not covered with a microcapsule film), solid particles E1 obtained in Example 1 (silica-T-CNF-styrene), obtained in Example 2 Surface of the obtained solid particles E2 (silica-CNF-styrene), the solid particles CE1 obtained in Comparative Example 1 (silica-CNF), and the solid particles CE2 obtained in Comparative Example 2 (silica-T-CNF) The state was observed with a scanning electron microscope (SEM) (JSM-6060 manufactured by JEOL Ltd.). The obtained results are shown in FIGS.

  As is apparent from FIGS. 3 to 7, the solid particles E1 (FIG. 4) obtained in Example 1 are more cellulose on the outer surface of the silica balloon than in the case of the silica balloon alone (FIG. 3). The pieces adhered and a substantially uniform film was formed as a whole. Moreover, when FIG. 4 is compared with FIG. 5, in the solid particle E2 (FIG. 5) obtained in Example 2, a somewhat large cellulose piece is adhered, and cellulose nanofibers treated with a TENPO catalyst were used. The solid particles E1 (FIG. 4) of Example 1 formed a more uniform film than the solid particles E2 (FIG. 5) of Example 2 that were not treated with the TENPO catalyst.

  On the other hand, the solid particles CE1 (FIG. 6) of Comparative Example 1 using cellulose nanofibers that were not treated with the TENPO catalyst and not added with styrene were prominent compared to the case of silica balloon alone (FIG. 3). No significant difference was observed, and almost no cellulose film was formed on the silica balloon. Further, in the solid particles CE2 (FIG. 7) of Comparative Example 2 using cellulose nanofibers that were treated with the TENPO catalyst but not added with styrene, large cellulose pieces were formed on the outer periphery of the silica balloon. The surface state of the coating was extremely uneven.

  From the above, it can be seen that by adding styrene to cellulose nanofibers, a microcapsule preparation in which a good film is formed on a silica balloon can be produced. Further, it can be seen that the cellulose nanofibers can be obtained in a microcapsule formulation having a more uniform film by being preliminarily dispersed through a TENPO catalyst.

  The microcapsule preparation of the present invention is useful in various fields such as pharmaceuticals, agricultural chemicals, cosmetics, foods, printing, and electronic chemicals.

1 Experimental apparatus 10 High-pressure cell 11 Cylinder 12, 13, 14, 15 Valve 17 Magnetic stirrer 18 Reactant

Claims (8)

  A microcapsule film containing cellulose nanofibers to which a styrenic compound is added. The styrenic compound has the following formula (I):
(Wherein R ¹ is a hydrogen atom or a methyl group, and R ² is a hydrogen atom, a halogen atom, a carboxyl group, an optionally branched C ₁ -C ₄ alkyl group, and an optionally branched group. The microcapsule film according to claim 1, which is a compound represented by a group selected from the group consisting of good C _{1 to} C ₄ alkoxy groups.   The microcapsule film according to claim 2, wherein the styrenic compound is a styrene monomer.   A microcapsule preparation comprising core particles and the microcapsule coating according to any one of claims 1 to 3 surrounding the core particles. A method for producing a microcapsule formulation comprising:
Adding a styrenic compound to cellulose nanofibers to obtain a coating material; and mixing and microencapsulating the coating material and core particles in the presence of a supercritical fluid or a subcritical fluid;
Including the method. The styrenic compound has the following formula (I):
(Wherein R ¹ is a hydrogen atom or a methyl group, and R ² is a hydrogen atom, a halogen atom, a carboxyl group, an optionally branched C ₁ -C ₄ alkyl group, and an optionally branched group. The method according to claim 5, which is a compound represented by a group selected from the group consisting of good C _{1 to} C ₄ alkoxy groups.   The method according to claim 6, wherein the styrenic compound is a styrene monomer.   The method according to any one of claims 5 to 7, wherein the cellulose nanofiber is obtained by treating a cellulose material with a TEMPO catalyst.