JPWO2020050150A1 - Structure - Google Patents

Abstract

It has a membrane containing cellulose nanofibers and a plurality of closed spaces composed of these membranes, has a large abundance ratio of spaces, and is difficult for unnecessary components to be mixed into the fluid held inside, and contains cellulose nanofibers. A structure including a membrane and a plurality of closed spaces composed of the membrane, wherein the content of the surfactant is less than 10 parts by mass with respect to 100 parts by mass of the cellulose nanofibers.

Description

The present invention relates to a structure containing cellulose nanofibers.

Attempts have been made to use cellulose nanofibers (CNFs) for various purposes, and as one of them, a porous body made of CNF has been proposed (see, for example, Patent Document 1). As a method for producing a porous body of CNF, a method including a step of freeze-drying a water slurry in which CNF is uniformly dispersed at a low temperature is widely known. The porous body obtained by freeze-drying has a so-called open cell structure, and is expected to be used as an adsorbent, a heat insulating material, a sound absorbing material, and the like.

Japanese Unexamined Patent Publication No. 2010-215872

In order to promote the use of CNF and further expand its use, a structure containing CNF having a new structure that cannot be obtained by a conventional manufacturing method is required. For example, there is a need for a structure suitable for use in which a fluid is held inside the structure and the fluid is taken out of the structure when needed. A structure suitable for such an application is required to be able to hold as much fluid as possible inside the structure and to prevent unnecessary components from being mixed in the fluid held inside.

The present invention comprises a membrane containing cellulose nanofibers and a plurality of closed spaces composed of the membranes, the presence ratio of the spaces is large, and unnecessary components are less likely to be mixed into the fluid held inside. The challenge is to provide.

As a result of diligent studies to solve the above problems, the present inventors have a structure having a plurality of closed spaces composed of a membrane containing cellulose nanofibers and having a surfactant content of a predetermined value or less. The present invention has been completed by finding that the above problems can be solved.
That is, the present invention provides the following [1] to [12].
[1] A structure including a membrane containing cellulose nanofibers and a plurality of closed spaces composed of the membranes, wherein the content of the surfactant is 10 parts by mass with respect to 100 parts by mass of the cellulose nanofibers. A structure that is less than a part.
[2] The structure according to the above [1], wherein a set of adjacent closed spaces among the plurality of closed spaces share at least one membrane.
[3] The structure according to the above [1] or [2], wherein the average thickness of the film containing the cellulose nanofibers is 10 nm to 2000 nm.
[4] The structure according to any one of the above [1] to [3], wherein the bulk density of the structure is 0.001 to 1.4 g / cm ^3.
[5] The structure according to any one of the above [1] to [4], wherein the structure has a sheet shape.
[6] The structure according to the above [5], wherein the structure has a thickness of 0.5 to 300 μm.
[7] In the cross section of the structure in the thickness direction, the maximum length of the closed space in the thickness direction of the structure is a, and the maximum length of the closed space in the plane direction is b. The structure according to the above [5] or [6], wherein the average of b / a of the plurality of closed spaces is larger than 1.
[8] The structure according to any one of the above [1] to [7], wherein the cellulose nanofibers are plant-derived cellulose nanofibers.
[9] The above-mentioned [1] to [8], wherein the content of the polysaccharide other than the cellulose nanofibers is less than 10 parts by mass with respect to 100 parts by mass of the cellulose nanofibers. Structure.
[10] The structure according to any one of the above [1] to [9], wherein the average diameter (thickness) of the cellulose nanofibers is 1 to 1000 nm.
[11] The structure according to any one of the above [1] to [10], wherein the average fiber length of the cellulose nanofibers is 0.01 to 10 μm.
[12] A structure with a support, wherein the structure according to any one of the above [1] to [11] is provided on the support.

According to the present invention, a membrane containing cellulose nanofibers and a plurality of closed spaces composed of the membranes are provided, the abundance ratio of the spaces is large, and unnecessary components are less likely to be mixed into the fluid held inside. Structures can be provided.

It is a schematic diagram which shows the structure of the sheet-like structure which is one Embodiment of the structure of this invention. 1 (A) is a partial cross-sectional view of a sheet-like structure in the thickness direction, FIG. 1 (B) is an enlarged view of a part of FIG. 1 (A), and FIG. 1 (C) is. It is a figure explaining the size of a closed space. It is a schematic side view which shows the appearance that the composition was applied on the support. 6 is an SEM image of a cross section of the sheet-like structure produced in Example 6 in the thickness direction.

<Structure of structure>
The structure according to the embodiment of the present invention is a structure including a membrane containing cellulose nanofibers (CNF) and a plurality of closed spaces composed of the membrane, and the content of the surfactant is CNF100. It is less than 10 parts by mass with respect to parts by mass.
As used herein, the term "closed space composed of a membrane containing CNF" means a closed space surrounded by a membrane containing CNF in all directions such as above, below, and sideways. As will be described later, the film containing CNF is a dense film but has fine voids. Therefore, if the space surrounded by the membrane containing CNF does not lead to an opening having a size exceeding the fine voids, it corresponds to "a closed space composed of a membrane containing CNF".

The shape of the structure is not particularly limited, and can be any shape, for example, by putting the composition described later in a molding mold and drying it. A preferred embodiment of the structure of the present invention is a sheet-like structure. The sheet-like structure can be easily produced in large quantities by applying the composition described below to the support and drying it, and can be used for a wide range of purposes. Hereinafter, the structure according to the embodiment of the present invention will be specifically described with reference to the sheet-like structure as an example. Note that FIGS. 1 and 2 used in the following description are schematic views and are exaggerated for ease of understanding. The number and size of the enclosed spaces, the thickness of the structure, and the like are also schematically shown, and these are not limited by the drawings.

FIG. 1A is a schematic partial cross-sectional view of a sheet-like structure according to an embodiment of the structure of the present invention in the thickness direction. As shown in FIG. 1A, a layer 31 provided on the support 40 and having a plurality of closed spaces 33 composed of a membrane 35 containing a CNF constitutes a sheet-like structure. Then, the layer 31 which is a sheet-like structure and the support 40 form a sheet-like structure 50 with a support. As will be described later, the support 40 may not be provided. When there is no support 40, it becomes a single sheet-like structure 31.
The CNF-containing film 35 formed by the manufacturing method described later is considered to be a network-like or fibrous dense film formed by arranging or entwining a plurality of CNFs. Therefore, for example, the sheet-like structure 31 or the sheet-like structure 50 with a support can be applied to a product that holds a fluid in a closed space 33 surrounded by a membrane 35 containing a CNF. Such a product (hereinafter, sometimes referred to as a "fluid holding product") can apply pressure to cleave the structure and supply the fluid to the outside when necessary.
Further, since the membrane 35 containing the CNF is a dense membrane of the CNF, it has a certain strength without thickening the membrane, and can form a closed space capable of holding the fluid inside. can. Therefore, an element other than the film containing CNF, such as a binder component, is not always required inside the structure, and the abundance ratio of the space in the structure can be increased.
Further, the membrane containing CNF has a large number of minute voids and can allow a fluid such as a gas or a liquid to permeate little by little. Therefore, for example, the sheet-like structure 31 and the sheet-like structure 50 with a support are also used in products in which the fluid is held in the closed space 33 and the fluid is gradually discharged to the outside through the membrane 35 containing the CNF. Can be applied. Hereinafter, the property of gradually releasing fluid to the outside through a membrane is referred to as sustained release property.
In addition, the conventional production method using freeze-drying has a complicated process, and the obtained porous body has a so-called open cell structure. A porous body having such an open cell structure is not suitable for holding a fluid, and it is difficult to apply it to the above-mentioned products for holding a fluid or products having a sustained release property.

Since the above structure does not contain a surfactant or contains a small amount of the surfactant, when the fluid is held in the closed space, the surfactant elutes into the fluid or the fluid is transferred to the structure. It is possible to prevent the surfactant from being released together with the fluid when it is taken out to the outside. Further, the presence of the surfactant makes it easy to prevent the physical properties of the structure from becoming unstable, for example, from deteriorating the structure or reducing the strength of the structure. Therefore, the structure according to the embodiment of the present invention is suitable for a fluid holding product or a product having sustained release property as described above. A method for producing the above-mentioned structure having a plurality of closed spaces composed of a membrane containing CNF, which does not contain a surfactant or has a low content of a surfactant, will be described later.

The upper limit of the content of the surfactant is less than 10 parts by mass, preferably less than 1 part by mass, more preferably less than 0.1 parts by mass, and further preferably less than 0.01 parts by mass with respect to 100 parts by mass of CNF. Particularly preferably less than 0.001 part by mass, most preferably 0 part by mass. As a method for measuring the content of the surfactant in the structure, the surfactant is extracted with a solvent, and the chemical composition is identified by a high performance liquid chromatograph mass spectrometer (LC-MS), a nuclear magnetic resonance apparatus (NMR), or the like. And a method of performing quantification. In addition, energy dispersive X-ray analysis (EDX) or infrared spectroscopy (IR) can also be used as the identification means. In the case of EDX, the composition may be directly observed and analyzed.

Further, in the above structure, polysaccharides other than CNF may be contained, but in the above-mentioned fluid holding products and products having sustained release property, unnecessary components are mixed in the fluid released to the outside. From the viewpoint of prevention, the content thereof is preferably less than 10 parts by mass, more preferably less than 1 part by mass, still more preferably less than 0.1 parts by mass, still more preferably 0, based on 100 parts by mass of the total amount of CNF. It is less than 0.01 parts by mass, particularly preferably 0 parts by mass. Polysaccharides can also be identified and quantified in the same procedure as surfactants.

FIG. 1B is an enlarged view of the portion surrounded by the alternate long and short dash line in FIG. 1A. As shown in FIG. 1B, in the sheet-like structure 31 and the sheet-like structure 50 with a support, the membrane 35a containing the CNF is shared between the pair of adjacent closed spaces 33a and 33b. There is. In a preferred embodiment of the structure of the present invention, a pair of adjacent closed spaces among a plurality of closed spaces, such as the sheet-shaped structure 31 and the sheet-shaped structure 50 with a support, form at least one membrane. Share.
In the cross section of the film containing CNF, a boundary formed along the film containing CNF may be observed. In the sheet-like structure of the present embodiment, the film containing CNF may include such a boundary. It is presumed that the boundary reflects the difference in the existence state of CNF before it becomes a sheet-like structure, but the presence or absence of this boundary does not particularly affect the characteristics of the sheet-like structure.

[Maximum ferret diameter in closed space]
Since the closed space can have various shapes, the size of the closed space is represented by the maximum ferret diameter in the present specification (the size of the closed space does not include the thickness of the membrane including CNF). In the structure according to the embodiment of the present invention, it is preferable that the average of the maximum ferret diameters of the plurality of closed spaces is 1 μm to 60 μm. The average lower limit of the maximum ferret diameter of the plurality of closed spaces is more preferably 5 μm or more, further preferably 10 μm or more, still more preferably 15 μm or more, and particularly preferably 20 μm or more. The average upper limit of the maximum ferret diameter of the plurality of closed spaces is more preferably 55 μm or less, further preferably 50 μm or less, even more preferably 45 μm or less, particularly preferably 40 μm or less, and most preferably 35 μm or less.
Here, the "maximum ferret diameter" of a certain figure means the maximum distance of the figure sandwiched between two parallel lines. In the present specification, a figure corresponding to the closed space is specified in the cut surface when a structure having a plurality of closed spaces composed of a film containing CNF is cut, and two parallel lines are used for this figure. The maximum ferret diameter of the closed space is calculated by measuring the maximum distance between them.
The cut surface for calculating the maximum ferret diameter of the closed space may be appropriately selected so as to include as much closed space as possible so that the average of the maximum ferret diameter can be calculated. For example, the sheet-like structure 31 or the support In the sheet-like structure 50 with a body, as shown in FIG. 1A, the maximum ferret diameter of the closed space is calculated in the cross section in the thickness direction thereof. To give a more specific example, the direction inclined with respect to the plane of the sheet-like structure 31 and the sheet-like structure 50 with the support existing in the region surrounded by the broken line in FIG. 1 (A). In the case of the closed space 33 having the maximum opening width, as shown in FIG. 1C, the maximum ferret diameter df of the closed space 33 corresponds to the maximum opening width.
In the present specification, the "average of the maximum ferret diameters of the plurality of closed spaces" is the average value of the maximum ferret diameters of the plurality of closed spaces on an arbitrary cut surface of the structure. In the present specification, in the above cross section of the structure, any 36 closed spaces are selected, the maximum ferret diameter of each is measured, and the average value thereof is referred to as "the average of the maximum ferret diameters of a plurality of closed spaces". do.

In the structure according to the embodiment of the present invention, the average of the maximum ferret diameters of the plurality of closed spaces in the cross section of the structure is in the above-mentioned range, and the size of the closed spaces is small. Therefore, a large number of films containing CNF are present inside the structure, and the strength of the structure can be increased. Therefore, it becomes easy to obtain a structure having excellent shape retention against pressure and the like. Further, as a result of increasing the strength of the structure, when the structure is applied to the above-mentioned fluid holding product or product having sustained release property, it is also advantageous for holding the fluid in the closed space for a long time. work. Furthermore, since the size of the closed space is small, the fluid can be individually held in many closed spaces, the holding property of the fluid can be improved, and the sustained release performance can be improved (the fluid takes a longer time). Can be released).
Further, as shown in FIGS. 1 (A) and 1 (B), the strength of the structure is increased by sharing the membrane with a plurality of closed spaces, so that the membrane having self-retention without adding a binder component ( A self-supporting film) can be produced. This free-standing membrane does not necessarily require a binder component, and for example, the space for holding a fluid can be increased as compared with a capsule in which a plurality of capsules having an internal space are bound with a binder.

The size of the closed space in the structure can be adjusted, for example, by changing the size of the particles having an outer shell containing CNF in the composition described later. Thereby, the maximum ferret diameter of the closed space can be adjusted, and the average of the maximum ferret diameters of the plurality of closed spaces can be set within the above-mentioned numerical range.

[Shape of closed space]
The shape of the closed space is arbitrary, but when a structure is manufactured by using the manufacturing method described later, a set of adjacent closed spaces form a membrane containing CNF as described above due to the manufacturing method. Each closed space has a polyhedral shape surrounded by a plurality of flat membranes in order to facilitate a shared structure. Therefore, at least one cut surface having a polygonal shape as shown in FIG. 1 can be formed for each closed space.
Further, in a preferred embodiment of the structure of the present invention, as shown in FIG. 1C, in a cross section in the thickness direction thereof, such as the sheet-like structure 31 and the sheet-like structure 50 with a support. , The maximum length of the closed space of the structure in the thickness direction (in other words, the distance from the lowermost position to the uppermost position of the plane of the membrane containing CNF on the closed space side) is a, the closed space of the structure. When the maximum length in the plane direction (in other words, the distance from one end to the other end of the surface of the membrane containing CNF on the closed space side in the plane direction) is b, b / a of a plurality of closed spaces. Is preferably greater than 1, more preferably greater than 1.5, and even more preferably greater than 2. When the average of b / a of the plurality of closed spaces is larger than 1, the closed spaces generally have a shape extending in the plane direction of the structure, so that a large number of closed spaces can be provided without thickening the structure. .. Further, during drying in the step (2-3) described later, the closed space extending in the plane direction is easily formed by the weight of the membrane containing CNF, so that the structure can be easily manufactured. The average of b / a of the plurality of closed spaces is preferably 10 or less, more preferably 8 or less, still more preferably 6 or less, and particularly preferably 5 or less, from the viewpoint of ease of manufacture and maintenance of strength of the structure. .. In the present specification, in the above-mentioned cross section of the structure, any 36 closed spaces are selected, each a and b are measured, b / a is calculated, and the average value thereof is set to "a plurality of closed spaces. The average of b / a ”.

[Average thickness of membrane containing CNF]
The average thickness of the film containing CNF is preferably 10 nm or more, more preferably 50 nm or more, further preferably 75 nm or more, and preferably 2000 nm or less, more preferably 1750 nm or less, still more preferably 1500 nm or less, further. It is preferably 1250 nm or less. By setting the average thickness of the membrane containing CNF to 2000 nm or less, when the structure is applied to a fluid holding product, pressure is applied to cleave the structure and the fluid can be easily supplied to the outside. Further, when the structure is applied to a product having sustained release properties, the fluid in the closed space is easily released. Further, by setting the average thickness of the membrane to 10 nm or more, the strength of the entire structure can be increased, and the fluid can be easily held in the closed space for a long time.
The average thickness of the film containing CNF was determined by observing the cross section of each structure using a scanning electron microscope (SEM) and arbitrarily selecting 36 closed spaces from the obtained magnified image. One arbitrary side that constitutes the polygon corresponding to the space is specified, and the thickness dm (indicated by two triangular marks and a leader line in FIG. 1C) at the substantially center of the side is measured, and those sides are measured. It is obtained by calculating the average value.
The thickness dm of the film containing CNF can be adjusted, for example, by making the diameter (thickness) and fiber length of CNF different. By increasing the diameter (thickness) of the CNF or shortening the fiber length of the CNF, the film containing the CNF can be thickened. On the contrary, by reducing the diameter (thickness) of the CNF or increasing the fiber length of the CNF, the film containing the CNF can be thinned.

[Bulk density of structure]
The bulk density of the structure is preferably 0.001 g / cm ³ or more, more preferably 0.005 g / cm ³ or more, more preferably 0.0075 g / cm ³ or higher, more preferably at 0.01 g / cm ³ or more Also, preferably 1.40 g / cm ³ or less, more preferably 1.20 g / cm ³ or less, still more preferably 0.920 g / cm ³ or less, still more preferably 0.800 g / cm ³ or less, still more preferably. It is 0.600 g / cm ³ or less, more preferably 0.500 g / cm ³ or less. When the bulk density is 0.001 g / cm ³ or more, the minimum necessary strength can be given to the structure, and for example, the strength that does not collapse even when rolled into a roll can be given. Further, when the bulk density is 1.40 g / cm ³ or less, it becomes easy to hold a large amount of fluid in the closed space.
In the present specification, the bulk density of a structure is calculated by dividing the mass of the structure by the volume of the entire structure including the closed space. When a layer containing CNF is formed on the support as shown in FIG. 1, the thickness and mass of the support may be measured in advance and subtracted before calculation.
The bulk density of the structure can be adjusted, for example, by varying the diameter of the particles having an outer shell containing CNF in the composition. That is, the bulk density decreases as the diameter of the particles having the outer shell containing CNF in the composition increases, and the bulk density increases as the diameter of the particles having the outer shell containing CNF decreases. The diameter of the particles having an outer shell containing CNF in the composition can be adjusted by changing the type and blending ratio of the organic solvent or changing the stirring conditions.

[Structure thickness]
When the structure is sheet-shaped or strip-shaped, the thickness L (see FIG. 1 (A)) of the structure excluding the support is preferably 0.5 μm or more, more preferably 1.0 μm or more, still more preferably 1.0 μm or more. 3.5 μm or more, more preferably 5.0 μm or more, particularly preferably 7.5 μm or more, and preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, still more preferably 75 μm or less. Particularly preferably, it is 50 μm or less. When the thickness of the structure is 300 μm or less, it is possible to avoid a long drying time and poor drying, and as a result, the variation in the shape and size of the closed space is suppressed, and the structure is formed. It is easy to prevent problems such as deterioration of the quality. Further, when the thickness of the structure is 0.5 μm or more, it is easy to prevent the strength of the structure from being insufficient and the amount of fluid that can be held in the closed space from being reduced.
When the structure has a sheet shape or a strip shape, the area of the structure and the size in the longitudinal direction are not particularly limited, and any size can be used as long as the manufacturing equipment can be prepared. Even when the structure has a shape other than a sheet shape or a strip shape, for example, a lump shape, the maximum diameter of the structure is preferably 1 mm or more, more preferably 5 mm or more, from the same viewpoint as described above. It is more preferably 1 cm or more, further preferably 2.5 cm or more, particularly preferably 5 cm or more, and preferably 5 m or less, more preferably 3 m or less, still more preferably 1 m or less, still more preferably 50 cm or less, particularly preferably. It should be 10 cm or less.

[Cellulose nanofibers (CNF) and other ingredients]
As the material and shape of the CNF constituting the structure, those described in CNF blended in the composition described later are directly applicable. In addition, polysaccharides other than CNF and other components (excluding components such as organic solvents that are allowed to exist in the closed space for the purpose of sustained release) that can be contained in the structure are also components to be blended in the composition described later. Is true as it is. Therefore, detailed description of these will be omitted here.

[Support]
In one aspect of the present invention, the structure includes a support, such as the sheet-like structure 50 with a support. When the support is provided, the structure and the support may be integrated, or the structure may be separated from the support after the structure is formed. That is, a sheet-like structure may be formed on a holding body that is temporarily used, such as a release material.
In the former case, the surface of the support to which the composition is applied is preferably subjected to an easy-adhesion treatment. As the easy-adhesion treatment, for example, corona discharge treatment, plasma treatment, ozone treatment and the like can be used. Further, for example, an easy-adhesion layer can be provided by using an acrylic resin, an ester resin, a urethane resin, or the like. In the latter case, one in which a release layer is formed on the surface to which the composition is applied may be used, or one in which the entire support is made of a material that easily peels off the structure may be used.
The support is appropriately selected according to the application of the sheet-like structure, and is, for example, a paper base material such as high-quality paper, art paper, coated paper, and glassin paper; a thermoplastic resin such as polyethylene is laminated on these paper base materials. Laminated paper; Metal foils such as aluminum foil, copper foil and iron foil; Porous materials such as non-woven fabrics: Polyethylene resin such as polyethylene resin and polypropylene resin, polyester resin such as polybutylene terephthalate resin and polyethylene terephthalate resin, acetate resin, Examples thereof include a resin film or sheet containing one or more kinds of resins such as ABS resin, polystyrene resin, vinyl chloride resin and the like.
The support may be a single-layer film or sheet, or may be a multi-layer film or sheet which is a laminated body of two or more layers.
Further, the resin film or sheet may be unstretched, or may be stretched in a uniaxial direction or a biaxial direction such as vertical or horizontal.
Further, the resin film or sheet may contain an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a slip agent, an anti-blocking agent, a coloring agent and the like in addition to the above-mentioned resin.
The thickness of the support is appropriately selected depending on the use of the sheet-like structure, but is preferably 10 μm or more, more preferably 15 μm or more, still more preferably 20 μm or more, and preferably 250 μm or less, more preferably. Is 200 μm or less, more preferably 150 μm or less.

<Manufacturing method of structure>
A structure having a plurality of closed spaces composed of a membrane containing CNF can be produced by a production method having the following steps (1) and (2) as one aspect.
-Step (1): A step of preparing a composition by adding an organic solvent to the aqueous dispersion of CNF.
Step (2): A step of applying the composition onto a support to form a coating film, and drying the coating film to form a sheet-like structure.

Hereinafter, the step (1) may be referred to as a “step of preparing the composition”, and the step (2) may be referred to as a “step of obtaining a structure”. Step (2) is a step of supplying the composition to one surface of the support (step (2-1)) and a step of applying the composition to the support (step (2-2)) as described below. ), The step of drying the composition applied on the support (step (2-3)) is included.

FIG. 2 shows one process during the manufacturing process, and is a schematic view showing how the composition is applied onto the support. The composition prepared in step (1) contains particles having an outer shell containing CNF, and in steps (2-1) to (2-2), this composition is applied onto the support. At that time, as shown in FIG. 2, the composition 30 contains particles 32 having an outer shell containing CNF and a medium 34 mainly composed of water. Further, the particles 32 contain a liquid or air mainly composed of an organic solvent, or both of them. After that, in the step (2-3), water and the organic solvent were removed by drying, and as shown in FIG. 1 (A), a layer (that is, a sheet) in which a large number of closed spaces by the membrane containing CNF were formed. The structure) 31 is formed on the support 40.
When the sheet-like structure 31 or the sheet-like structure 50 with a support is applied to the above-mentioned fluid holding product or product having sustained release property, the sheet-like structure is immersed in a specific liquid to form a closed space. The above liquid can be sealed therein, or a specific type of gas can be sealed in a closed space under a specific gas atmosphere in a sheet-like structure. Further, these fluids may be included in the closed space during the manufacturing process of the sheet-like structure. For example, a specific type of organic solvent (for example, an organic solvent having a boiling point higher than the drying temperature) is previously added to the composition so as to remain in the closed space 33 even after drying in the step (2-3). You may. Further, the fluid may be sealed in the closed space by preparing the composition in an atmosphere filled with a specific type of gas.

[Step (1): Step of preparing the composition]
In the step (1), it is preferable to supply the organic solvent little by little to the aqueous dispersion while stirring the aqueous dispersion.
With CNF uniformly dispersed in water, an organic solvent is further added, and this organic solvent is also uniformly dispersed, so that the interface between water and the organic solvent can be achieved without using a dispersant such as a surfactant. CNFs gather at the surface to form particles having an outer shell containing the CNFs. The process of forming particles having an outer shell containing CNF in the composition is not limited to this, but one of them is presumed to be due to the following mechanism. That is, since CNF is an amphipathic insoluble material, it is present at the interface between the water used for emulsification and the organic solvent to create an energetically stable state. In addition, since CNF is insoluble and film-forming, it forms an irreversible independent phase as a result of localization to the interface. In this way, it is considered that particles having an outer shell containing CNF are formed in the composition.
When an organic solvent is added to a uniformly dispersed aqueous dispersion containing CNF, the particles generated by localizing the CNF at the interface are considered to have relatively high stability. Therefore, it is unlikely that changes to large-diameter capsules will occur due to the bonding of the produced capsules, and it is considered that the aqueous dispersion to which the organic solvent is added is sufficiently agitated to obtain particles having a small diameter and uniform diameter. .. It is also conceivable that the air is stably held by being entrained in the aqueous dispersion by stirring and being surrounded and fixed by a plurality of stable particles generated earlier (this is fixed). Air is also thought to become bubbles after drying). As a result, it is considered that the particles do not disappear for several months or more and are stably present in the entire composition unless excessive stimulation is applied or a constant or higher pressure is intentionally applied.

In the step (1), from the viewpoint of preventing the organic solvent from being phase-separated from water without forming particles having an outer shell containing CNF, with respect to 100 parts by mass of the total amount of the aqueous dispersion. The amount of the organic solvent added every 10 seconds is preferably 0.1 part by mass or more, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, particularly preferably 5 parts by mass or more, and preferably 20 parts by mass. The organic solvent is added so as to be 10 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 7 parts by mass or less. The organic solvent may be continuously supplied, or the organic solvent may be supplied intermittently. In any case, by stirring while adding a limited amount of the organic solvent to the aqueous dispersion, the organic solvent is uniformly dispersed in the aqueous dispersion, and as a result, the particles having an outer shell containing CNF are good. Can be generated in.

In the step (1), it is preferable to add the organic solvent while stirring the aqueous dispersion using a stirring device equipped with stirring blades such as a homodisper, a mixer, and a paddle blade. By bringing the stirring blade into contact with the aqueous dispersion and stirring the particles, particles having an outer shell containing CNF can be efficiently generated.

The stirring speed (rotational speed) when stirring the aqueous dispersion is preferably 500 rpm or more, more preferably 1000 rpm or more, from the viewpoint of suppressing the aggregation of CNF and reducing the variation in the shape and size of the formed particles. It is more preferably 1500 rpm or more, still more preferably 2000 rpm or more, and preferably 5000 rpm or less, more preferably 4500 rpm or less, still more preferably 4000 rpm or less, still more preferably 3500 rpm or less, and particularly preferably 3000 rpm or less.

The stirring time is preferably 3 minutes or longer, more preferably 5 minutes or longer, still more preferably 10 minutes or longer, from the viewpoint of making the shape and size of the particles having the outer shell containing CNF uniform. Further, the upper limit of the stirring time is preferably 180 minutes or less, more preferably 180 minutes or less, from the viewpoint of preventing the production time from becoming too long and avoiding variations in the shape and size of the particles having an outer shell containing CNF. It is 120 minutes or less, more preferably 60 minutes or less, even more preferably 40 minutes or less, and particularly preferably 20 minutes or less. The stirring time refers to the time from the addition of the organic solvent (C) to the end of stirring. In order to sufficiently disperse the organic solvent (C) and promote the formation of particles, even after the addition of the required amount of the organic solvent (C) is completed, stirring is performed until the above time elapses from the start of the addition of the organic solvent (C). It is desirable to continue.

The temperature of the aqueous dispersion is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, still more preferably 15 ° C., from the viewpoint of suppressing aggregation of CNF and reducing variations in the shape and size of the formed particles. From the viewpoint of suppressing volatilization of the added organic solvent, the temperature is preferably 45 ° C. or lower, more preferably 40 ° C. or lower, and further preferably 35 ° C. or lower.

The step (1) is preferably carried out at 80 kPa or more, more preferably 90 kPa or more, further preferably 95 kPa or more, and preferably 120 kPa or less, more preferably 110 kPa or less, further preferably 105 kPa or less, and particularly preferably large. Perform under atmospheric pressure. By preparing the composition under conditions close to atmospheric pressure, the composition can be prepared in a short time, and the production equipment can be simplified. Further, the step (1) may be performed in an atmosphere of air or an inert gas. In an air atmosphere, the manufacturing equipment can be simplified, and in an inert gas atmosphere, deactivation of the composition can be easily suppressed. When the sheet-like structure is applied to the above-mentioned product in which the fluid is slowly released, the composition is prepared in an atmosphere of a specific type of gas so that the gas is enclosed in the generated particles. You may.
These temperature conditions, pressure conditions, and atmosphere conditions also apply to the steps (2-1) and (2-2) described later.

[Composition obtained in step (1) and constituent material of composition]
The composition prepared by the step (1) is a mixture of CNF (A), water (B), and an organic solvent (C), and is a particle having an outer shell containing CNF (A). Contains. Hereinafter, CNF (A), water (B), and organic solvent (C) may be collectively referred to as "components (A) to (C)".
In the above composition, at least a part of the organic solvent (C) is in a state of being incorporated into the particles, specifically, a state of being contained in the particles and forming an outer shell of the particles. It is preferable that at least one of the states is adsorbed on the CNF (A).
Here, "a state in which the organic solvent (C) is encapsulated in the particles" means that the particles form hollow particles from an outer shell containing CNF (A), and the organic solvent is formed in the hollow portion of the hollow particles. It means a state in which (C) is taken in. At this time, the organic solvent (C) is separated from the outside of the hollow particles by the outer shell constituting the hollow particles.
In the composition of one aspect of the present invention, the particles contain the organic solvent (C), and the CNF (A) constituting the outer shell of the particles is adsorbed with the organic solvent (C). It may be in the state of being. In the present specification, "the outer shell composed of CNF (A) adsorbs the organic solvent (C)" means that the organic solvent (C) is contained in the network structure of the outer shell composed of CNF (A). It means that it exists.

In the composition of one aspect of the present invention, the organic solvent (C) that is not incorporated into the particles may be present.

(Average particle size of particles having an outer shell containing CNF in the composition)
In order to make the average of the maximum ferret diameters of the closed space of the structure within the above-mentioned numerical range, it is necessary to set the average particle size of the particles having the outer shell containing CNF in the composition to an appropriate range. preferable.
The average particle size of the particles contained in the composition of one aspect of the present invention is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 7 μm or more, still more preferably 10 μm or more, and particularly preferably 15 μm or more. Also, it is preferably 60 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 30 μm or less.
When the average particle size of the particles is 1 μm or more, it becomes easy to suppress the aggregation of the particles, and it becomes easy to prevent the closed space of the structure from becoming too small.
Further, when the average particle size of the particles is 60 μm or less, it becomes easy to suppress the floating of the particles.

Further, the standard deviation of the particles with respect to the average particle size contained in the composition of one aspect of the present invention is such that the above-mentioned fluid is held in the structure and the fluid is brought out by cleaving the structure when necessary. In the application for supplying, from the viewpoint of stabilizing the amount of fluid released, it is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 15 μm or less, still more preferably 12 μm or less, and usually 1 μm or more.
In the present specification, the average particle size of the particles and the standard deviation with respect to the average particle size are obtained from an image obtained when the target composition is observed with a digital microscope at a magnification of 500 to 1000 times. Can be calculated.
That is, the average value of the particle diameters (outer diameters) of 36 arbitrarily selected particles among the particles projected on the image can be defined as the above-mentioned "average particle diameter". Further, the "standard deviation with respect to the average particle size" can be calculated from the value of the particle size of each of the 36 particles. The standard deviation is the standard deviation of the population, and in the above calculation, the standard deviation is calculated for all 36 particle size values.

The viscosity of the composition used in one aspect of the present invention at 23 ° C. and 50 rpm is preferably 500 mPa · s or more from the viewpoints of ease of removal from the container, ease of stirring, inhibition of sedimentation, and the like. , More preferably 1000 mPa · s or more, further preferably 1200 mPa · s or more, preferably 20000 mPa · s or less, more preferably 15000 mPa · s or less, still more preferably 12000 mPa · s or less.
In the step (2-2) described later, in order to enable the composition to be satisfactorily applied to the support, the viscosity of the composition is within the above numerical range at the temperature at which the composition is applied to the support. It is preferable to select the material so as to be.

Further, the TI value (viscosity at 5 rpm / viscosity at 50 rpm) of the composition used in one embodiment of the present invention indicates storage stability, inhibitory property of sedimentation when stored in a container, and From the viewpoint of ease of removal from the container, it is preferably 1.2 or more, more preferably 2 or more, still more preferably 3 or more, still more preferably 4 or more, and preferably 20 or less, more preferably. It is 15 or less, more preferably 10 or less, and even more preferably 8 or less.
Further, in the present specification, the viscosity of the composition means a value measured using a B-type viscometer in accordance with JIS Z 8803: 2011.

The pH of the composition used in one embodiment of the present invention is preferably 4 or more, more preferably 5 or more, still more preferably 6 from the viewpoint that the particles to be formed are stable and the dispersed state can be easily maintained in the composition. It is more than that, preferably 10 or less, more preferably 9 or less, still more preferably 8 or less.

The composition used in one aspect of the present invention may contain components other than the above components (A) to (C).
However, in the composition of one aspect of the present invention, the total content of CNF (A), water (B) and the organic solvent (C) is preferably 60 with respect to the total amount (100% by mass) of the composition. It is mass% or more, more preferably 65% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, and preferably 100% by mass or less.

The concentration of the active ingredient of the composition used in one embodiment of the present invention is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, still more preferably 0.7% by mass or more, based on the total amount (100% by mass) of the composition. Is 1.0% by mass or more, more preferably 1.5% by mass or more, and preferably 50% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, still more preferably. Is 10% by mass or less.
In addition, in this specification, an "active ingredient" refers to a component contained in a composition excluding water (B) and an organic solvent (C).

The particles having an outer shell containing CNF (A) and incorporating the organic solvent (C) include the amount of CNF (A) to be blended, the blending amount ratio of CNF (A) to the organic solvent (C), and the organic. It can be formed by appropriately preparing the type of solvent (C) and the like.

In the composition used in one embodiment of the present invention, as described later, the particles are mixed by adding an organic solvent (C) to an aqueous dispersion in which CNF (A) is dispersed in water (B). The composition is prepared to form. In a more preferred embodiment, the composition is formed by blending an organic solvent (C), which is a water-insoluble solvent, with an aqueous dispersion in which CNF (A) is dispersed in water (B) to form the particles. To prepare. In a more preferable embodiment, the organic solvent (C) having ^{a Hansen solubility parameter distance Ra of 5.80 MPa 1/2} or less is added to the aqueous dispersion in which CNF (A) is dispersed in water (B). , The composition is prepared to form the particles.
In addition to the above, the shape (diameter, fiber length, aspect ratio) of CNF (A), the blending amount of water (B) and the organic solvent (C), and the blending of water (B) and the organic solvent (C). The composition can be prepared so as to facilitate the formation of the particles by appropriately setting the amount ratio and the like.

(Cellulose Nanofiber (CNF) (A))
Examples of the raw material of CNF (A) used in one embodiment of the present invention include wood-derived kraft pulp or sulfite pulp; powdered cellulose obtained by crushing kraft pulp or sulfite pulp with a high-pressure homogenizer, a mill, or the like; powdered cellulose as an acid. Microcrystalline cellulose powder purified by chemical treatment such as hydrolysis; Bast fiber pulp such as Kozo, Ganbari, Sansho; Cellulose-based raw material derived from plants such as cotton pulp, Kenaf, hemp, rice, bacas, bamboo; etc. Examples include cellulosic materials. Since the plant-derived CNF has a high crystallinity, a linear structure, and a large aspect ratio, the strength of the outer shell can be increased and it is easily available.

If a large amount of lignin remains in these raw materials, the oxidation reaction of the raw materials may be inhibited. Therefore, cellulosic raw materials obtained by removing lignin from these raw materials are preferable.
Further, it is also possible to use the above-mentioned cellulosic raw material finely divided by a disperser such as a high-speed rotary type, a colloid mill type, a high-pressure type, a roll mill type, an ultrasonic type, or a wet high-pressure or ultra-high pressure homogenizer.

Further, these cellulosic raw materials may be chemically modified and / or physically modified to enhance their functionality. Here, as chemical modifications, addition of a functional group by acetylation, carboxylation, carboxysolation, esterification, cyanoethylation, acetalization, etherification, arylation, alkylation, acryloylation, isocyanatement, etc. In addition, inorganic substances such as silicates and titanates may be compounded or coated by a chemical reaction, a solgel method, or the like.
In addition, as physical modification, a metal or ceramic raw material is vapor-deposited, ion-plated, sputtering or other physical vapor deposition method (PVD method), chemical vapor deposition method (CVD method), electroless plating, electrolytic plating or other plating method, etc. Surface coating can be mentioned.
In addition, these modification treatments may be performed either at the time of defibration of the cellulosic raw material or before and after defibration.

The above-mentioned cellulosic raw material can be made into CNF by defibrating it into nanofibers.
As a specific method, there is a method of preparing a dispersion liquid in which a cellulosic raw material is dispersed in a dispersion medium such as water, and then applying a shearing force to the cellulosic raw material to prepare a dispersion liquid containing CNF. Be done.
As a method of applying a shearing force to a cellulosic raw material, after adding the cellulosic raw material to a dispersion medium such as water, a device such as a high-speed rotary type, a colloid mill type, a high pressure type, a roll mill type, or an ultrasonic type is used. The method of preparation is preferred.
At this time, the pressure applied to the dispersion is preferably 50 MPa or more, more preferably 100 MPa or more, still more preferably 140 MPa or more.
From the viewpoint of applying a strong shearing force to the cellulosic raw material under such high pressure, it is preferable to use a wet high pressure or ultrahigh pressure homogenizer.

The average diameter (thickness) of the CNF used in one aspect of the present invention is preferably 1.0 nm or more, more preferably 1.0 nm or more, from the viewpoint of facilitating the formation of the particles and improving the film strength of the formed particles. 1.5 nm or more, more preferably 2.0 nm or more, still more preferably 2.5 nm or more, and preferably 1000 nm or less, more preferably 500 nm or less, still more preferably 200 nm or less, still more preferably 100 nm or less. be.

The average fiber length of CNF used in one aspect of the present invention is preferably 0.01 μm or more, more preferably 0.1 μm, from the viewpoint of facilitating the formation of the particles and improving the film strength of the formed particles. Above, more preferably 0.2 μm or more, still more preferably 0.3 μm or more, preferably 10 μm or less, more preferably 7.0 μm or less, still more preferably 5.0 μm or less, still more preferably 2.5 μm or less. Is.

The average aspect ratio of CNF (A) used in one aspect of the present invention is preferably 5 or more, more preferably 10 or more, from the viewpoint of facilitating the formation of the particles and improving the film strength of the formed particles. It is more preferably 15 or more, preferably 10000 or less, more preferably 5000 or less, still more preferably 3000 or less, still more preferably 1000 or less, and particularly preferably 500 or less.

The "aspect ratio" is the ratio of the length to the thickness of the target CNF [length / thickness], and the "length" of the CNF is between the two most distant points of the CNF. Refers to the distance.
If a part of the target CNF comes into contact with another CNF and it is difficult to determine the "length", measure the length of only the part of the target CNF whose thickness can be measured. , The aspect ratio of the relevant portion may be in the above range.
The diameter (thickness) and fiber length of CNF (A) can be measured using a transmission electron microscope. The average diameter (thickness) and fiber length of CNF (A) can be obtained by measuring the diameter (thickness) and fiber length of a plurality of arbitrarily selected CNFs and calculating the average value of each. can get. The average aspect ratio of CNF (A) can be calculated using the average diameter (thickness) thus obtained and the average fiber length. The diameter (thickness), fiber length, average value thereof, and average aspect ratio of CNF (A) can be specifically calculated by the method shown in Examples.

In the production method of the present embodiment, excessive stress is not applied to the CNF when preparing the composition, so that the fiber diameter and fiber length of the CNF before compounding are almost the same even in the sheet-like structure. Be maintained. Therefore, the numerical ranges for the fiber diameter, fiber length, and aspect ratio of the CNF described above include the CNF before the composition is prepared, the CNF after the composition is prepared, and the structure prepared by using the composition described later. This applies as is to any of the CNFs in.

(Content of CNF in composition)
In the composition used in one aspect of the present invention, the blending amount of CNF (A) facilitates the formation of the particles with respect to the total amount (100% by mass) of the composition, and the film strength of the formed particles. From the viewpoint of improving, it is preferably 0.7% by mass or more, more preferably 0.8% by mass or more, still more preferably 1.0% by mass or more, still more preferably 1.2% by mass or more, and also. From the viewpoint of appropriately adjusting the viscosity of the composition so as to facilitate the formation of the particles, the composition is preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 7% by mass or less, still more preferably 5. It is mass% or less, particularly preferably 3 mass% or less.

(Water (B))
In the composition used in one aspect of the present invention, most of the water (B) is either adsorbed on the outer shell of the particles or is present outside the particles.
However, a part of water (B) may be encapsulated inside the particles together with the organic solvent (C).

In the composition used in one aspect of the present invention, from the viewpoint of preparing a composition having an appropriate viscosity and facilitating the formation of the particles, the blending amount of water (B) is the total amount (100 mass) of the composition. %), More preferably 15% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, still more preferably 60% by mass or more, and preferably 99% by mass or less. It is preferably 98.7% by mass or less, more preferably 98.5% by mass or less.

In the composition used in one aspect of the present invention, from the viewpoint of preparing a composition having an appropriate viscosity and facilitating the formation of the particles, the mixing ratio of water (B) with respect to 100 parts by mass of CNF (A) is It is preferably 500 parts by mass or more, more preferably 1000 parts by mass or more, still more preferably 2000 parts by mass or more, still more preferably 3000 parts by mass or more, and preferably 20000 parts by mass or less, more preferably 15000 parts by mass or more. Hereinafter, it is more preferably 10,000 parts by mass or less.

(Water dispersion)
As the aqueous dispersion containing CNF and water, as described above, the dispersion obtained by dispersing the cellulosic raw material in water and then applying a shearing force to the cellulosic raw material can be used as it is as the aqueous dispersion. can. A commercially available aqueous dispersion of CNF can also be used.
The pH of the aqueous dispersion is preferably 4 or more, more preferably 5 or more, and further, from the viewpoint of suppressing the aggregation of CNF (A) in the aqueous dispersion and reducing the variation in the shape and size of the formed particles. It is preferably 6 or more, preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less.

(Organic solvent (C))
The organic solvent (C) is water-insoluble from the viewpoint that it forms an independent phase with respect to water when mixed with water, and can be temporarily emulsified by being added to water and stirred. It is preferable to use a system solvent. By using a water-insoluble solvent, it is possible to generate particles having an outer shell containing CNF without using a dispersant such as a surfactant.

（前記式中、δＤは、前記有機溶剤のハンセン溶解度パラメータの分散成分、
δＰは、前記有機溶剤のハンセン溶解度パラメータの極性成分、
δＨは、前記有機溶剤のハンセン溶解度パラメータの水素結合成分を示す。）The organic solvent (C) more preferably has a Hansen solubility parameter distance Ra of 5.80 MPa ^1/2 or less at 25 ° C., which is represented by the following formula (1).

(In the above formula, δD is a dispersion component of the Hansen solubility parameter of the organic solvent.
δP is a polar component of the Hansen solubility parameter of the organic solvent.
δH indicates the hydrogen bond component of the Hansen solubility parameter of the organic solvent. )

As for the Hansen solubility parameter, the solubility parameter introduced by Hildebrand is divided into three components, δD (dispersion component), δP (polar component), and δH (hydrogen bond component) by Hansen. It is shown in the dimensional space.
The values of δD, δP, and δH are unique values for each organic solvent and are values calculated from a specific calculation.
More specifically, the definition and calculation method of the Hansen solubility parameter are as described in "Hansen Solubility Parameters: A Users Handbook (Charles M. Hansen, CRC Press, 2007)".
Further, in the present specification, the values of δD, δP, and δH are included in the database "Hansen Solubility Parameters in Practice (HSPiP) Version 4.1.03" (written by Steven Abbott, Charles M. Hansen, Hiroshi Yamamoto). The value of was used.

The present inventors have noticed that the easiness of forming the particles differs depending on the type of the organic solvent (C) to be blended.
Then, when the Hansen solubility parameter of each organic solvent is plotted in a three-dimensional space, the organic solvent used when the particles are formed is densely distributed in a certain region in the three-dimensional space. I understand.
Therefore, when the largest sphere (interaction sphere) was drawn so that all the plots of the organic solvent in which the particles were formed were included inside and the plot of the organic solvent in which the particles were not formed was outside. The radius of the sphere was "5.80 MPa ^1/2 ".
The distance Ra calculated from the formula (1) means the distance between the plot of the target organic solvent and the center of the sphere in the three-dimensional space of the Hansen solubility parameter. That is, when the distance Ra is "5.80 MPa ^1/2 " or less, which is the radius of the sphere, the plot of the target organic solvent is located inside the sphere, and the particles are likely to be formed. It can be judged that it is a solvent.

The values of δD, δP, and δH of typical organic solvents used in Examples and Comparative Examples described later, and the distance Ra calculated from the above formula (1) (all units are "MPa ^1/2 "". ) Is shown in Table 1.

As shown in Table 1, the organic solvent (C) having a distance Ra of 5.80 MPa ^1/2 or less is heptane, n-hexadecane, methyl ethyl ketone, and n-dodecane. As shown in Examples described later, it was obtained that the particles were easily formed when these organic solvents were used.
In view of this result, it is presumed that the particles are likely to be formed if the organic solvent (C) ^{has a distance Ra of 5.80 MPa 1/2} or less, even if it is other than the organic solvent shown in Table 1.
The values of δD, δP, and δH of organic solvents other than those shown in Table 1 can be calculated from the molecular structure of the organic solvent, or δD, δP, and δP as shown in Table 1. The value of δH can also be calculated by conducting an experiment on the solubility in an organic solvent known from various documents and the like.

The organic solvent (C) may be used alone or as a mixed solvent in which two or more kinds are used in combination.
When the organic solvent (C) is a mixed solvent, the values of the three components (δD, δP, δH) of the Hansen solubility parameter of the weighted average are obtained from the mixing ratio (volume ratio) of the mixed solvent and calculated from the above formula (1). The distance Ra ^{is preferably 5.80 MPa 1/2} or less.
Therefore, even in organic solvents distance Ra of 5.80MPa ^1/2 than by itself, a distance Ra and a 5.80MPa ^1/2 or less other organic solvents, and mixed with a suitable volume ratio, the distance Ra It is also possible to obtain the organic solvent (C) in which the particles are easily formed by using a mixed solvent prepared so as to have a ^{value of 5.80 MPa 1/2 or less.}
That is, when it is desired to obtain a composition containing particles incorporating an organic solvent having a distance Ra of more ^{than 5.80 MPa 1/2} by itself, it is considered that the preparation can be facilitated by using the above-mentioned mixed solvent. ..

By using the organic solvent (C) having a distance Ra of 5.80 MPa ^1/2 or less, it is considered that the particles are more easily formed than when other organic solvents are used, but the particles are formed. Whether or not this is possible also depends on the blending amounts of CNF (A), water (B) and organic solvent (C), the shape of CNF (A), and the selection of modifying groups.
Therefore, the organic solvent (C) having a distance Ra of 5.80 MPa ^1/2 or less is used, and the items described in the items of each component of the present specification are appropriately considered so that the particles can be formed more easily. It is preferable to prepare in.

The organic solvent (C) used in one aspect of the present invention preferably contains an organic solvent (C1) having less than 20 carbon atoms.
The organic solvent (C1) having less than 20 carbon atoms is easily incorporated into CNF (A), and the particles are easily formed.
That is, in an organic solvent having a large number of carbon atoms, the molecules of the organic solvent tend to gather together, and since the viscosity is high, it becomes difficult to form particles close to a true sphere. As a result, it is considered that such an organic solvent is not incorporated into the cellulose nanofibers (A) and remains on the outside of the particles in a large proportion.

From the above viewpoint, the blending ratio of the organic solvent (C1) in the organic solvent (C) is preferably 20% by mass or more, more preferably 35% by mass or more, based on the total amount (100% by mass) of the organic solvent (C). , More preferably 50% by mass or more, and even more preferably 70% by mass or more.

In the composition used in one aspect of the present invention, from the viewpoint of facilitating the formation of the particles, the blending amount of the organic solvent (C) is preferably 0.05 with respect to the total amount (100% by mass) of the composition. By mass% or more, more preferably 0.1% by mass or more, still more preferably 0.5% by mass or more, still more preferably 0.8% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or more. It is mass% or less, more preferably 45% by mass or less, still more preferably 42% by mass or less, still more preferably 40% by mass or less, and particularly preferably 38% by mass or less.

(Content of organic solvent in composition)
In the composition used in one aspect of the present invention, the blending ratio of the organic solvent (C) with respect to 100 parts by mass of CNF (A) is preferably 1 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of facilitating the formation of the particles. 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 50 parts by mass or more, still more preferably 75 parts by mass or more, still more preferably 90 parts by mass or more, and preferably 6000 parts by mass or less. It is preferably 4500 parts by mass or less, more preferably 4000 parts by mass or less, and even more preferably 3500 parts by mass or less.

(Ratio of water and organic solvent)
In the composition used in one aspect of the present invention, from the viewpoint of facilitating the formation of the particles, the blending amount ratio [(B) / (C)] of water (B) and the organic solvent (C) is a mass ratio. It is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 1.0 or more, still more preferably 1.5 or more, and preferably 1000 or less, more preferably 700 or less, still more preferable. Is 500 or less, more preferably 300 or less, and particularly preferably 100 or less.

(Other ingredients)
The composition used in one aspect of the present invention may contain components other than the components (A) to (C) as long as the effects of the present invention are not impaired.
Such other components are appropriately selected depending on the use of the composition, and examples thereof include colorants, antioxidants, pH adjusters, and sweeteners.

In the composition used for producing the structure according to the embodiment of the present invention, the content of the surfactant in the structure is such that the content of the surfactant is less than 10 parts by mass with respect to 100 parts by mass of CNF. Is.
When a composition containing a surfactant is used in an application that comes into contact with the human body, the surfactant also serves as a penetrant and an irritating irritant, especially for users with sensitive skin. In addition, the composition containing a surfactant may affect the stability of the physical properties of the composition. Furthermore, when the structure is applied to the above-mentioned fluid holding products and products that release the fluid slowly, there is a risk that a surfactant may be mixed in the fluid released by the cleavage of the structure or the fluid released through the membrane, or the interface. The activator may affect the stability of the physical properties of the structure and impair the fluid retention.
Therefore, in the composition of one aspect of the present invention, the smaller the content of the surfactant, the more preferable.
From the above viewpoint, in the composition used in one aspect of the present invention, the content of the surfactant is preferably less than 10 parts by mass, more preferably less than 1 part by mass, based on 100 parts by mass of the total amount of CNF (A). , More preferably less than 0.1 parts by mass, even more preferably less than 0.01 parts by mass, particularly preferably less than 0.001 parts by mass, most preferably 0 parts by mass. By adjusting the content of the surfactant in the composition in this way, the content of the surfactant in the structure can be within the above-mentioned range.

Further, in the composition used in one aspect of the present invention, a polysaccharide other than CNF (A) may be contained, but the thermal stability of the particles is improved and the particles are easily formed. From the viewpoint, the smaller the content of the polysaccharide, the more preferable.
From the above viewpoint, in the composition used in one embodiment of the present invention, the content of the polysaccharide other than CNF (A) is preferably less than 10 parts by mass, more preferably less than 100 parts by mass, based on 100 parts by mass of the total amount of CNF (A). Is less than 1 part by mass, more preferably less than 0.1 part by mass, still more preferably less than 0.01 part by mass, and particularly preferably 0 part by mass. By adjusting the content of the polysaccharide other than CNF (A) in the composition in this way, the content of the polysaccharide other than CNF (A) in the structure can be within the above-mentioned range.

[Step (2)]
In the step (2), the composition is applied onto the support to form a coating film, and the coating film is dried to form a sheet-like structure. In the step (2), from the viewpoint of avoiding excessive stress on the particles having the outer shell containing CNF in the composition prepared in the step (1), it is preferable that the composition is first placed on the support. (Step (2-1)), and then the composition on the support is spread evenly and applied (Step (2-2)).
(Step (2-1): Step of supplying the composition to one surface of the support)
In step (2-1), for example, a composition containing particles having an outer shell containing CNF is formed by tilting the container containing the composition and gradually moving the composition from the container to the support by its own weight. Is supplied on the support. Further, the above composition may be supplied onto the support by using a pump or the like.
The temperature condition, pressure condition, and atmosphere condition in the step (2-1) may be set in the same manner as described in the step (1).

(Step (2-2): Step of applying the composition to the support (Step (2-2)))
In the step (2-2), the composition supplied on the support in the step (2-1) is applied onto the support using a coating device. In one embodiment, the applicator is moved relative to the support along a direction along the plane of the support to apply the composition to the support (step (2-2)).
Here, the coating gap when forming the coating film forms a sufficient number of closed spaces composed of a film containing CNF in a good shape, and takes a long time to dry or heats at a relatively high temperature. From the viewpoint of preventing some particles in the composition after coating from breaking or disappearing as a result of the need for, preferably 30 μm or more, more preferably 100 μm or more, still more preferably 150 μm or more. It is more preferably 200 μm or more, preferably 1250 μm or less, more preferably 1000 μm or less, still more preferably 750 μm or less, and even more preferably 500 μm or less.

Examples of the coating method of the composition include spin coating method, spray coating method, bar coating method, knife coating method, roll coating method, roll knife coating method, blade coating method, die coating method, gravure coating method, and air knife coating method. , Dip coat method and the like. Of these, the knife coating method and the gravure coating method are preferable.
In step (2-2), a jig capable of forming a gap larger than the diameter of the particles in the composition is used from the viewpoint of preventing the particles having the outer shell containing CNF from being broken by coating. Is preferable. In this case, the gap formed by the jig is preferably 1.5 times or more, more preferably 5 times or more, still more preferably 7.5 times or more, still more preferably, the diameter of the particles having an outer shell containing CNF. Is 9 times or more, preferably 62.5 times or less, more preferably 50 times or less, still more preferably 37.5 times or less, still more preferably 25 times or less.

In the step (2-2), from the viewpoint of preventing the volatilization of the organic solvent, the composition is applied in an environment where the temperature of the composition is preferably 45 ° C. or lower, more preferably 40 ° C. or lower, and further preferably 35 ° C. or lower. I do. Further, from the viewpoint of preventing the composition from becoming too viscous to form a uniform coating layer and damaging the particles having an outer shell containing CNF, the temperature is preferably 5 ° C. or higher, more preferably 10. The coating is performed in an environment of ° C. or higher, more preferably 15 ° C. or higher.
The pressure condition and the atmosphere condition in the step (2-2) may be set in the same manner as described in the step (1).

It is also possible to use a coating device such as a die coater to supply the composition to the support and apply the composition at the same time (that is, perform the step (2-1) and the step (2-2) at the same time). However, in this case, it is preferable to adjust the injection conditions and the like so that excessive stress is not applied to the particles having the outer shell containing CNF in the composition.

(Step (2-3): Step of drying the composition applied on the support)
In the step (2-3), the layer of the composition applied on the support is dried by heating or the like to form a layer having a plurality of closed spaces composed of a film containing CNF. Specifically, the layer of the composition applied on the support is dried by a heater or the like, and water or an organic solvent is evaporated from the composition, including those incorporated inside the particles. A layer having a plurality of closed spaces composed of a membrane containing CNF is formed.
The mechanism by which the closed space composed of the membrane containing CNF is formed in the step (2-3) is not necessarily limited to this, but is presumed as follows. That is, in the process of volatilizing water and the organic solvent from the layer of the composition, some of the particles stick to each other or some of the particles move to a more stable position between the particles. The gap gradually disappears, while the CNF collected at the interface between the organic solvent and water is stably present, so that the film containing the CNF is not destroyed and a dense closed space is finally formed. It is presumed.

In the step (2-3), the temperature is preferably 90 ° C. or higher, more preferably 100 ° C. or higher, further preferably 110 ° C. or higher, and preferably 150 ° C. or lower, more preferably 140 ° C. or lower, still more preferably 130 ° C. or higher. Dry at ° C or below. By drying at 90 ° C. or higher, water and the organic solvent are quickly removed, and it becomes easy to form a well-shaped closed space. By drying at 150 ° C. or lower, it becomes easy to prevent the shape and size of the closed space from becoming uneven and the support from being deformed.
The pressure condition and the atmosphere condition in the step (2-3) may be set in the same manner as described in the step (1).

In the step (2-3), from the viewpoint of preventing the water and the organic solvent from remaining without being removed and the shape of the closed space from being deformed, it is preferably 10 seconds or longer, more preferably 30 seconds or longer, still more preferable. Is dried over 1 minute or more, more preferably 5 minutes or more, still more preferably 10 minutes or more, preferably 2 hours or less, more preferably 1 hour or less, still more preferably 30 minutes or less.

When the above structure is produced by the above-mentioned production method, a composition containing particles having an outer shell containing CNF can be produced without using a dispersant such as a surfactant. By using this composition, , The CNF content in the structure can be increased. Therefore, when the structure of the present embodiment is applied to the above-mentioned fluid holding product or product having sustained release property, a large amount of fluid can be held inside the structure and is discharged to the outside. It becomes easier to prevent unnecessary components from being mixed into the fluid.

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples. The physical property values in the following production examples and examples are values measured by the following methods.

<Average diameter (thickness) of CNF, average length, average aspect ratio>
Using a transmission electron microscope (manufactured by Carl Zeiss, product name "LEO912"), the diameter (thickness) and length of 10 arbitrarily selected CNFs were measured, and the average value of the 10 CNFs was used as the target. The "average diameter (thickness)" and "average length" of the CNFs are used. In addition, "average length / average diameter (thickness)" was used as the average aspect ratio.
<Aqueous dispersion, pH of composition>
Two-point calibration of pH 4.01 standard solution and pH 6.86 standard solution using a compact pH meter (manufactured by HORIBA Advanced Techno Co., Ltd., product name "LAQUAtwin pH-22B") in an environment of 23 ° C. and 50% relative humidity. After that, a sample was dropped so as to cover the entire plane sensor for measurement.

(Example 1)
1. 1. Preparation of Composition 1 In the preparation of the composition 1, the following commercially available aqueous dispersion (1) containing CNF was used.
-Aqueous dispersion (1) Product name "BiNFi-s AMa10002", manufactured by Sugino Machine Limited. An aqueous dispersion containing 2% by mass of a machine-treated CNF having an average diameter (thickness) of 76.8 nm, an average length of 1.4 μm, and an average aspect ratio of 18.2.
The aqueous dispersion (1) contained 4900 parts by mass of water with respect to 100 parts by mass of CNF, and the pH of the aqueous dispersion (1) was 7.0.
Water dispersion (1) 5000.0 parts by mass (CNF 100.0 parts by mass) is put into a container, and an ultra-high-speed multi-stirring system (manufactured by Primix Corporation, product name "Lab Solution (registered trademark)", stirring blade: Using a homodisper (manufactured by the same company, wing diameter 35 mm), the aqueous dispersion at 23 ° C. was stirred at a rotation speed of 3000 rpm. After the start of stirring, n-dodecane was added at a rate of 5 parts by mass every 10 seconds to 100 parts by mass of the total amount of the aqueous dispersion. To 5000.0 parts by mass of the aqueous dispersion (CNF 100.0 parts by mass), the addition of n-dodecane was continued until the amount of n-dodecane reached 100 parts by mass, and the stirring was terminated 10 minutes after the start of stirring. A composition 1 containing particles having an outer shell containing CNF was prepared. No surfactant was used in the preparation of composition 1.

2. Preparation of Sheet-like Structure 1 The composition 1 is gently placed on the easy-adhesion layer surface of a polyethylene terephthalate film having a thickness of 50 μm (Cosmo Shine (registered trademark) manufactured by Toyobo Co., Ltd., product number “A4100”, thickness: 50 μm). Then, the composition 1 was applied to the above film using an applicator (coating gap: 254 μm (10 mil)). Further, the sheet-like structure 1 was prepared by heating at 120 ° C. for 10 minutes and drying.
All the steps from the preparation of the composition 1 to the coating were carried out in an air atmosphere under atmospheric pressure and at 23 ° C. Then, the sheet-like structure 1 was prepared by heating at 120 ° C. for 10 minutes and drying.

(Examples 2 to 5)
A composition containing particles having an outer shell containing CNF in the same procedure as in Example 1 except that the total amount of n-dodecane added was changed to 500 parts by mass, 1000 parts by mass, 2000 parts by mass, and 3000 parts by mass, respectively. Items 2 to 5 were prepared. Then, the sheet-like structures 2 to 5 were prepared by the same procedure as in Example 1 except that the compositions 2 to 5 were used instead of the composition 1, respectively.

(Example 6)
The composition 1 was applied to the easy-adhesion layer surface of the polyethylene terephthalate film in the same procedure as in Example 1 except that the coating gap of the applicator was changed to 762 μm (30 mil). Further, the sheet-like structure 6 was produced by the same procedure as in Example 5 except that the drying time was changed to 20 minutes.

(Examples 7 to 9)
An outer shell containing CNF was used in the same procedure as in Example 1 except that 100 parts by mass of methyl ethyl ketone (MEK), 100 parts by mass of heptane, and 100 parts by mass of n-hexadecane were used instead of 100 parts by mass of n-dodecane. Compositions 7-9 containing particles comprising the above were prepared. Then, sheet-like structures 7 to 9 were prepared in the same procedure as in Example 1 except that the compositions 7 to 9 were used instead of the composition 1, respectively.

(Example 10)
A composition 10 containing particles having an outer shell containing CNF was prepared in the same procedure as in Example 1 except that the total amount of n-dodecane added was changed to 10 parts by mass. Then, the sheet-like structure 10 was produced by the same procedure as in Example 1 except that the composition 10 was used instead of the composition 1.

(Example 11)
1. 1. Preparation of Composition 11 In the preparation of the composition 11, the following commercially available aqueous dispersion (2) containing CNF was used.
-Aqueous dispersion (2): Product name "TEMPO Oxidized CNF", manufactured by Nippon Paper Industries, Ltd. An aqueous dispersion containing 1% by mass of chemically treated cellulose nanofibers having an average diameter (thickness) of 3.8 nm, an average length of 0.7 μm, and an average aspect ratio of 184.
The aqueous dispersion (2) contained 9900 parts by mass of water with respect to 100 parts by mass of the cellulose nanofibers, and the pH of the aqueous dispersion (2) was 7.0.
Water dispersion (2) 5000.0 parts by mass (CNF 100.0 parts by mass) is put into a container, and an ultra-high-speed multi-stirring system (manufactured by Primix Corporation, product name "Lab Solution (registered trademark)", stirring blade: Using a homodisper (manufactured by the same company, wing diameter 35 mm), the aqueous dispersion at 23 ° C. was stirred at a rotation speed of 3000 rpm. After the start of stirring, n-dodecane was added every 10 seconds at a rate of 5 parts by mass. To 5000.0 parts by mass of the aqueous dispersion (CNF 100.0 parts by mass), the addition of n-dodecane was continued until the amount of n-dodecane reached 100 parts by mass, and the stirring was terminated 10 minutes after the start of stirring. A composition 11 containing particles having an outer shell containing CNF was prepared.

2. Preparation of Sheet-like Structure 11 The composition 11 is gently placed on the easy-adhesion layer surface of a polyethylene terephthalate film having a thickness of 50 μm (Cosmo Shine (registered trademark) manufactured by Toyobo Co., Ltd., product number “A4100”, thickness: 50 μm). Then, the composition 10 was applied to the film using an applicator (coating gap: 254 μm (10 mil)), and further heated at 120 ° C. for 10 minutes and dried to prepare a sheet-like structure 11.
All the steps from the preparation of the composition 11 to the coating were carried out in an air atmosphere under atmospheric pressure and at 23 ° C. Then, the sheet-like structure 11 was prepared by heating at 120 ° C. for 10 minutes and drying.

(Example 12)
A composition 12 containing particles having an outer shell containing CNF was prepared in the same procedure as in Example 11 except that the total amount of n-dodecane added was changed to 3000 parts by mass. Then, the sheet-like structure 12 was produced by the same procedure as in Example 11 except that the composition 12 was used instead of the composition 11.

(Example 13)
A composition 13 containing particles having an outer shell containing CNF was prepared in the same procedure as in Example 11 except that 200 parts by mass of n-hexadecane was used instead of 100 parts by mass of n-dodecane. Then, the sheet-like structure 13 was produced by the same procedure as in Example 11 except that the composition 13 was used instead of the composition 11.

(Comparative Example 1)
The composition C1 was prepared in the same procedure as in Example 1 except that 100 parts by mass of n-dodecane was not added. The stirring time was 10 minutes as in Example 1. Then, the sheet-like structure C1 was produced by the same procedure as in Example 1 except that the composition C1 was used instead of the composition 1.

(Comparative Examples 2 to 5)
The composition was composed in the same procedure as in Example 1 except that 100 parts by mass of hexane, 100 parts by mass of dimethyl sulfoxide (DMSO), 100 parts by mass of aniline, and 100 parts by mass of ethanol were used instead of 100 parts by mass of n-dodecane. Objects C2 to C5 were prepared. Then, sheet-like structures C2 to C5 were prepared in the same procedure as in Example 1 except that the compositions C2 to C5 were used instead of the composition 1, respectively.
Table 2 summarizes each component and the like of the compositions prepared in Examples and Comparative Examples.

The compositions 1 to 13, C1 to C5, and the sheet-like structures 1 to 13, C1 to C5 were measured and evaluated by the following procedure. The results are shown in Table 3.

<Presence or absence of closed space>
Each sheet-like structure was cut in the thickness direction. Then, each cut surface was observed by SEM to confirm whether or not a hollow closed space was formed. FIG. 3 shows an example of an SEM image of a cross section of the sheet-like structure 6 in the thickness direction.

<Average thickness of membrane containing CNF>
Using a scanning electron microscope (SEM) (S-4700 type manufactured by Hitachi, Ltd.), observe the cut surface of each sheet-like structure, and arbitrarily select 36 closed spaces from the obtained enlarged image. , One arbitrary side constituting each was specified, and the thickness at the center of the side was measured. By calculating the average value thereof, the average thickness of the membrane containing CNF in the plurality of closed spaces was used.

<Maximum ferret diameter of the closed space of the structure and its average>
By observing the cut surface of each sheet-like structure by SEM, 36 closed spaces are arbitrarily selected from the obtained SEM images, the maximum ferret diameter of each is measured, and the average value thereof is calculated. The average maximum ferret diameter was used.
<B / a>
The cut surface of each sheet-like structure was observed by SEM, and 36 closed spaces were arbitrarily selected from the obtained SEM images, and for each, the maximum length a in the thickness direction of the structure and the maximum length a of the structure were obtained. The maximum length b in the plane direction was measured to obtain the value of b / a, and the average value thereof was calculated to obtain the value of b / a.

<Structure thickness and bulk density>
The mass and thickness of the sheet-like structure with the support were measured by the following procedure. Then, using these, the bulk density of the sheet-like structure without a support was calculated.
Mass: After cutting a sheet-like structure with a support to a size of 100 mm × 100 mm, the mass is measured and the mass of the known support is reduced to reduce the mass of the sheet-like structure without a support. Calculated.
Thickness: The thickness of the sheet-like structure without the support is measured by measuring the thickness of the entire sheet-like structure including the support using a constant pressure film thickness meter and reducing the thickness of the known base material. (Corresponding to the reference numeral L in FIG. 1 (A)) was calculated.

<Presence / absence of surfactant>
The raw materials used for preparing the sheets and the prepared sheets were extracted using a solvent, and IR analysis of those extracts was performed. As a result, no new peak was observed in any of the samples, and it was confirmed that no surfactant was contained.

As is clear from Table 3, in Examples 1 to 13, particles having an outer shell containing CNF could be generated in the composition without using a dispersant such as a surfactant. Further, in Examples 1 to 13, the composition is applied to the support and dried to obtain a sheet-like structure having a large number of closed spaces composed of a membrane containing CNF and having self-retaining property. Was done. FIG. 3 is an SEM image of a cross section of the sheet-like structure 1 produced in Example 6 in the thickness direction. It was confirmed that all of the sheet-like structures 1 to 13 have a structure in which a pair of adjacent closed spaces share a membrane containing a CNF, similar to the closed space shown in the SEM image of FIG. bottom. In the sheet-like structures of Examples 1 to 13, the average maximum ferret diameter of the closed space was in the range of 1 to 60 μm, and a small diameter closed space could be formed. Since the sheet-like structures 1 to 13 do not contain a surfactant, even when the fluid is held inside the closed space, the surfactant may be mixed in the fluid or the surfactant may be released to the outside together with the fluid. There is no fear. In addition, the presence of the surfactant does not cause the physical properties of the structure to become unstable.

As is clear from Examples 1 to 5 and 9, by adjusting the amount of the organic solvent used, the average maximum ferret diameter of the closed space, the thickness of the membrane containing CNF, the thickness of the structure, b / a It can be seen that the value of and the bulk density of the structure can be changed. Further, it can be seen that the smaller the thickness of the film containing CNF in the sheet-like structure, the thicker the sheet-like structure and the smaller the bulk density of the sheet-like structure. When the size of the particles containing the CNF-containing outer shell contained in the composition is relatively small, the influence of the thickness of the capsule outer shell per volume of the inner space of the capsule is larger than that in the large-diameter capsule. Therefore, as the film thickness of the outer shell of the capsule varies, the size of the space inside the particles also changes more greatly, and the average of the maximum ferret diameters of the closed space in the finally obtained structure, the average of the maximum ferret diameter of the closed space, and the membrane containing CNF. It is presumed that it affects the thickness and the value of b / a. This suggests that since the capsule has a relatively small diameter, it is possible to control the porosity when it becomes a structure to some extent by adjusting the thickness of the outer shell of the capsule.
Further, as is clear from Examples 1 and 7 to 9, the size of the particles having an outer shell containing CNF contained in the composition can be changed by changing the type of the organic solvent. I understand.

Further, as is clear from Examples 5 and 6, when the composition is applied, the gap of the applicator is changed to change the thickness of the applied composition, so that the average of the maximum ferret diameter of the closed space and the average of the maximum ferret diameter of the closed space are changed. It can be seen that the thickness of the structure can be significantly changed with almost no change in the thickness of the film containing CNF.
Further, as is clear from Examples 11 to 13, it can be seen that even when the type of CNF is changed, the same tendency as described above is exhibited (that is, by changing the type and the amount of the organic solvent added, the blockage occurs. The average maximum ferret diameter in space, the thickness of the membrane containing the CNF, the thickness of the structure, the value of b / a, and the bulk density of the structure can be varied).

On the other hand, in Comparative Examples 1 to 5, particles having an outer shell containing CNF could not be generated in the composition, and as a result, a closed space composed of a film containing CNF was formed in the structure. I couldn't.

The sheet-like structure obtained by the production method of the present invention has a plurality of closed spaces composed of membranes containing CNF, has a large proportion of the space existing in the structure, and is a fluid held inside the structure. The structure can be made so that unnecessary components are not easily mixed. Therefore, for example, a fluid is held inside the closed space, and when necessary, a pressure is applied to cleave a part of the structure to supply the fluid to the outside, or the fluid is held in the closed space. It can be used as a sustained release structure capable of gradually releasing a fluid. Further, it can be used as a heat insulating material, an adsorbent, a sound absorbing material, an insulating material, a base material for a flexible printed wiring board, a packaging material, and the like. Further, when the structure is strongly pressed with a finger, the closed space is compressed and broken, and a pressing mark including a fingerprint remains on the surface of the structure, so that the structure can also be used as a trace recording material.

30: Composition 31: Layer having a plurality of closed spaces (sheet-like structure)
32: Particles having an outer shell containing CNF 33, 33a, 33b: Closed space 34: Water-based medium 35: Membrane containing CNF 35a: Membrane shared by a set of adjacent closed spaces 40: Support 40a: Coating surface 50: Sheet-like structure with support a: Maximum length in the thickness direction of the structure in the closed space b: Maximum length in the plane direction of the structure in the closed space df: Maximum ferret of the closed space Diameter dm: Thickness of the membrane containing CNF L: Thickness of the layer having a plurality of closed spaces

Claims (12)

A structure including a membrane containing cellulose nanofibers and a plurality of closed spaces composed of the membranes, wherein the content of the surfactant is less than 10 parts by mass with respect to 100 parts by mass of the cellulose nanofibers. There is a structure. The structure according to claim 1, wherein a set of adjacent closed spaces among the plurality of closed spaces share at least one membrane. The structure according to claim 1 or 2, wherein the average thickness of the film containing the cellulose nanofibers is 10 nm to 2000 nm. The structure according to any one of claims 1 to ³ , wherein the bulk density of the structure is 0.001 to 1.4 g / cm 3. The structure according to any one of claims 1 to 4, wherein the structure has a sheet shape. The structure according to claim 5, wherein the structure has a thickness of 0.5 to 300 μm. In the cross section in the thickness direction of the structure, when the maximum length of the closed space in the thickness direction of the structure is a and the maximum length of the closed space in the plane direction is b, the above. The structure according to claim 5 or 6, wherein the average of b / a of the plurality of closed spaces is greater than 1. The structure according to any one of claims 1 to 7, wherein the cellulose nanofibers are plant-derived cellulose nanofibers. The structure according to any one of claims 1 to 8, wherein the content of the polysaccharide other than the cellulose nanofibers is less than 10 parts by mass with respect to 100 parts by mass of the cellulose nanofibers. The structure according to any one of claims 1 to 9, wherein the average diameter (thickness) of the cellulose nanofibers is 1 to 1000 nm. The structure according to any one of claims 1 to 10, wherein the average fiber length of the cellulose nanofibers is 0.01 to 10 μm. A structure with a support, wherein the structure according to any one of claims 1 to 11 is provided on the support.

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