Composite flake

Abstract

This composite flake contains a binder A and a plurality of conductive materials, and has a surface area in the planar direction of 1 mm2 or less.

Description

Composite flakes

[0001] The present invention relates to composite flakes.

[0002] Communication devices such as mobile phones and smartphones enable wireless communication using electromagnetic waves, and with technological advances in this field, the frequency bands of the electromagnetic waves used have been expanding. Specifically, wireless communication systems complying with the IMT-Advanced standard established by the International Telecommunication Union (ITU) are specified, and the frequency band of first-generation mobile communication systems (1G), which was approximately 800 MHz, has been expanded to approximately 3 GHz in fourth-generation mobile communication systems (4G). Furthermore, the currently adopted fifth-generation mobile communication systems (5G) have expanded their frequency bands to the 28 GHz band in order to achieve higher speeds, larger capacity, lower latency, and multiple connections. Furthermore, development of sixth-generation mobile communication systems (6G), which use frequency bands of 100 GHz or higher, is currently underway as the next-generation communication system. While the use of electromagnetic waves in high frequency bands has attracted attention, the increasing frequency of electromagnetic waves increases the likelihood of electronic device malfunctions, communication disruptions, information leaks, and health problems, necessitating the control of electromagnetic noise (EMC). Specifically, there is a demand for the development of new materials capable of suppressing both EMI (the cause of the problem) and EMS (the cause of the problem of immunity). One approach to solving this problem is the use of electromagnetic wave control materials that can reduce the effects of electromagnetic waves from the surrounding environment. Electromagnetic wave control materials are available in a variety of forms, including semiconductor packages / modules, housings for electrical / electronic devices, adhesives for semiconductor mounting boards or cables, wallpaper for buildings such as server rooms, and clothing such as aprons for protecting the human body.

[0003] There are various types of electromagnetic wave control materials, and extensive research is being conducted on them. In recent years, attention has been focused on techniques for shielding electromagnetic waves by using materials containing conductive materials such as carbon nanotubes or graphite in binders such as resins or rubbers. For example, Patent Document 1 discloses a technique for providing a sheet with high electromagnetic wave shielding properties by drying a dispersion containing carbon nanotubes and components such as inorganic pigments and carboxymethyl cellulose. Patent Document 2 discloses a technique for providing a structure that includes surface-treated fibrous carbon nanostructures, such as carbon nanotubes, whose surfaces are treated, and has a weight per unit area within a specific range, thereby providing excellent electromagnetic wave shielding and electromagnetic wave absorption performance in the ultra-high frequency band. Patent Document 3 discloses a technique for providing an electromagnetic wave shielding sheet with excellent electromagnetic wave shielding effect by laminating two or more polymer composition layers, each layer containing a polymer substance and a conductive material, and configuring at least two of these layers as polymer composition layers with different dielectric constants.

[0004] JP 2021-161001 A International Publication No. 2018 / 066574 International Publication No. 2008 / 126690

[0005] Although studies have been conducted to improve electromagnetic wave shielding performance in Patent Documents 1 and 2 by controlling the composition in terms of the type and amount of materials contained in the molded body, and in Patent Document 3 by controlling the composition in terms of the relationship between the dielectric constant and the sheet composition, little study has been conducted in terms of the electrical resistance of the sheet, which can vary depending on the degree of contact between conductive materials, leaving room for improvement. For example, when a molded body such as a sheet having electromagnetic wave shielding performance is used as a case to protect elements such as semiconductor elements, a module can be manufactured in which the molded body is provided on a substrate to cover semiconductor elements that are susceptible to electromagnetic waves or that easily emit electromagnetic waves, thereby suppressing the penetration of electromagnetic waves into the case and the leakage of electromagnetic waves to the outside of the case. When such a case is used, the terminals of each semiconductor element are generally exposed, and if the case has high conductivity, i.e., a low electrical resistivity, there is a risk of short circuits between the terminals, making it difficult to save space.

[0006] Therefore, an object of the present invention is to provide a composite flake from which a molded article can be produced that can shield electromagnetic waves in the high frequency band while maintaining high electrical resistivity.

[0007] As a result of extensive research, the present inventors have found that the above problems can be solved by incorporating a binder and a conductive material and forming the particles into thin flakes, thereby arriving at the present invention.

[0008] That is, the present invention has the following features: [1] A binder A and a plurality of conductive materials are included, and the surface area in the planar direction is 1 mm ２[2] The composite flake according to [1], wherein the average diameter of the smallest circumscribing circle enclosing the surface shape in the planar direction is 1 μm or more and 1000 μm or less. [3] The composite flake according to [1] or [2], wherein the binder A contains cellulose nanofibers. [4] The composite flake according to [3], wherein the average fiber diameter of the cellulose nanofibers is 0.25 nm or more and 0.5 μm or less. [5] The composite flake according to any one of [1] to [4], wherein the conductive material contains at least carbon nanotubes. [6] The composite flake according to [5], wherein the length of the carbon nanotubes is 0.01 μm or more and 1000 μm or less. [7] The composite flake according to any one of [1] to [6], wherein the content of the conductive material in the composite flake is 0.010 mass % or more and 50 mass % or less. [8] The composite flake according to any one of [1] to [7], having a thickness of 0.01 μm or more and 50 μm or less. [9] A composite flake comprising cellulose nanofibers and carbon nanotubes.

[10] A liquid composition comprising the composite flake according to any one of [1] to [9] and binder B.

[11] A molded body comprising the composite flake according to any one of [1] to [9] and binder B.

[12] The molded body according to

[11] , wherein the content of the composite flake in the molded body is 1 mass % or more and 99 mass % or less.

[13] The molded body according to

[11] or

[12] , having a thickness of 20 μm or more and 5 mm or less.

[14] The molded body according to any one of

[11] to

[13] , which is an electromagnetic wave shielding sheet.

[15] The molded body according to any one of

[11] to

[14] , which is a foam.

[16] A method for producing composite flakes, comprising: a composition preparation step of obtaining a liquid composition containing binder A and a plurality of conductive materials; a freezing step of freezing the liquid composition to obtain a frozen body; and a crushing step of crushing the frozen body.

[17] The method for producing composite flakes according to

[16] , comprising, between the freezing step and the crushing step, an immersion step of immersing the frozen body in a liquid containing a component that crosslinks the binder A.

[18] The method for producing composite flakes according to

[17] , wherein the immersion step includes a step of immersing the frozen body in a liquid other than the liquid containing the component that cross-links the binder A after removing the liquid containing the component that cross-links the binder A.

[19] A method for producing a molded body, comprising a composition preparation step of obtaining a liquid composition containing the composite flakes according to any one of [1] to [9] and binder B, and a freezing step of freezing the liquid composition to obtain a frozen body.

[20] A method for producing a molded body according to

[19] , wherein the freezing step includes a immersion step of immersing the frozen body in a liquid containing a component that cross-links the binder B after the freezing step.

[21] A method for producing a molded body according to

[20] , wherein the immersion step includes a step of removing the liquid containing the component that cross-links the binder B after removing the liquid containing the component that cross-links the binder B, and then immersing the frozen body in a liquid other than the liquid containing the component that cross-links the binder B.

[0009] According to the present invention, it is possible to provide composite flakes from which a molded article can be produced that can shield electromagnetic waves in the high frequency band while maintaining high electrical resistivity.

[0010] FIG. 1 is a diagram schematically illustrating an experimental device for evaluating electromagnetic wave shielding properties. FIG. 2 is a diagram showing the results of the sheet property evaluation in Examples 1 to 4 and Comparative Example 1. FIG. 3 is a diagram showing the results of the sheet property evaluation in Examples 5 to 8 and Comparative Example 2. FIG. 4 is a diagram showing the results of the sheet property evaluation in Examples 9 to 13. FIG. 5 is a diagram showing the results of the sheet property evaluation in Comparative Examples 3 to 8. FIG. 6 is a diagram showing the results of the sheet property evaluation in Comparative Examples 9 to 11. FIG. 7 is a diagram showing the results of the sheet property evaluation in Examples 4 and 11 and Comparative Examples 1, 12 and 13.

[0011] The following describes embodiments of the present invention in detail. However, the configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the present invention. The present disclosure is not limited by the embodiments, but is limited only by the scope of the claims. In this disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, and "A to B" means A or greater and B or less. Furthermore, when a numerical range expressed as "A to B" or "A or greater and B or less" is stated in stages (e.g., in order of preference), the upper and lower limits of each numerical range can be arbitrarily combined. Furthermore, although multiple embodiments are described in this disclosure, various conditions in each embodiment may be applied to each other to the extent applicable. Furthermore, in this disclosure, the expression "A or B" can be interpreted as "at least one selected from the group consisting of A and B." Furthermore, in this disclosure, "multiple" means "two or more." The dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are merely examples. Furthermore, this embodiment will be described using drawings as appropriate, but the dimensions in the drawings are also examples. Furthermore, when "average" is used in the parameters of a conductive material, it is a value calculated as the average value of multiple conductive materials. For example, the average outer diameter of a conductive material is a value calculated by measuring the outer diameters of multiple conductive materials and averaging them. The number of measurement objects for calculating the average value is not particularly limited, and does not need to be the total number; for example, it may be 10 arbitrarily selected objects, or it may be 50 arbitrarily selected objects. The number of conductive materials in the molded body may be less than 10.

[0012] <Configuration of Molded Product> A composite flake (also simply referred to as "composite flake") according to one embodiment of the present disclosure contains a binder A and a plurality of conductive materials, and has a surface area in a planar direction of 1 mm ２ The composite flakes are as follows: In the present disclosure, a flake is a substance having a thin flaky shape, and may be any substance having a shape that is generally considered to be a flake.

[0013] Conventional conductive materials contained in EMI shielding compacts have included metal fillers, carbon nanotubes, graphite, and other materials. Using such conductive materials, especially those with nanostructures such as carbon nanotubes, can easily shield high-frequency EMI. Here, in a compact obtained by curing a composition obtained by mixing a conductive material with a binder, it is common for conductive materials to be arranged in contact with each other. When EMI is irradiated to a conductive material, a current flows through the conductive material. However, if contact occurs between the conductive materials, the electrical resistivity of the compact decreases. For example, when the compact is used in a module (semiconductor module) in which semiconductor elements are mounted on a substrate to cover them, the terminals of each semiconductor element are generally exposed. Therefore, if the compact has high conductivity, i.e., low electrical resistivity, there is a risk of short circuits between the terminals. Therefore, the present inventors conducted extensive research and developed a composite flake that exhibits excellent EMI shielding performance while maintaining (retaining) insulation properties. Because the composite flakes are a material in which a conductive material is contained in a binder, they have a higher electrical resistivity than materials that are conductive as a whole, such as metal fillers, carbon nanotubes, or graphite. Therefore, a molded article obtained using the composite flakes containing a conductive material has a higher electrical resistivity than a molded article obtained using a conductive material, such as metal fillers, carbon nanotubes, or graphite. Therefore, by using the composite flakes according to the above embodiment, a molded article that can shield high-frequency electromagnetic waves while maintaining high electrical resistivity can be produced.

[0014] Furthermore, when using conventional conductive materials, the molding conditions for the compact have often been set strict in order to improve the dispersibility of the conductive material. On the other hand, when using the composite flakes according to the above embodiment, the composite flakes, which already have the conductive material dispersed in the binder to a certain extent, are further incorporated into the binder. Therefore, a compact with high dispersibility of the conductive material can be easily obtained simply by mixing the binder and the composite flakes without any special effort. In other words, the composite flakes according to the above embodiment are advantageous in terms of production costs in producing the compact.

[0015] Furthermore, when composite flakes are used, they can be manufactured using a lightweight material such as a polymeric material as a binder together with a resin, making it easier to reduce the weight compared to conventional embodiments using metal plates. Furthermore, one of the roles of an electromagnetic wave shielding material is to prevent the reflection of electromagnetic waves incident from the side where the product to be shielded is located. However, when a metal plate is used, it is difficult to prevent reflection because electromagnetic waves are generally reflected by the metal surface. On the other hand, a molded product using composite flakes and a binder can be manufactured using a polymeric material or the like as the binder, which is easy to prevent the reflection of electromagnetic waves and also easily absorbs electromagnetic waves, making it superior in terms of electromagnetic wave shielding performance.

[0016] Conventionally, metal cases, primarily stainless steel cases, have been used as electromagnetic wave shields in semiconductor modules. Such stainless steel cases can shield external electromagnetic waves by reflecting them. While reflection can block the entry and exit of electromagnetic waves, the presence of multiple semiconductor elements within the case raises the risk of diffused reflection of electromagnetic waves emitted from the semiconductor elements, potentially causing malfunctions in adjacent semiconductor elements. Furthermore, stainless steel cases are conductive, and in order to prevent the aforementioned short circuit, they must be installed so as not to come into contact with exposed terminals, limiting their space-saving potential. When a conventional stainless steel case is replaced with the molded article according to the present embodiment, the absorber is less likely to cause diffused reflection within the case, reducing the risk of malfunction. Furthermore, due to its high resistance, it can be used in contact with exposed terminals, facilitating space savings. Furthermore, the molded article according to the present embodiment can be molded by coating or spraying, allowing it to adhere closely to multiple semiconductor elements, including their terminals, thereby achieving extreme space savings while maintaining its absorber performance.

[0017] The applications of the above composite flakes are not particularly limited, but they are suitably used for electromagnetic wave shielding sheets, etc. In the following explanation, the conditions for the configuration of the composite flakes will be explained assuming that they are contained in a molded product for an electromagnetic wave shielding sheet. However, these conditions can naturally also be applied when the composite flakes are used for applications other than electromagnetic wave shielding sheets.

[0018] The shape of the composite flakes is not particularly limited as long as they are flake-shaped. In the present disclosure, the "surface" of a composite flake is a general expression that refers to both surfaces of a flake shape having one surface and the opposite surface. For example, "the surface area of ​​a composite flake is X μm ２ "is equal to or greater than" means that the area of ​​both sides of the composite flake is X μm ２ This means that it is more than or equal to this.

[0019] The surface shape of the composite flakes is not particularly limited, and may be circular, or polygonal, such as triangular or rectangular.

[0020] The surface area of ​​the composite flakes in the planar direction is 1 mm2 in order to be able to be incorporated into molded bodies and compositions on the order of μm. ２ There are no particular limitations as long as it is less than this, but from the viewpoint of easily realizing compact size of the molded body obtained using the composite flakes, 0.5 mm ２ Preferably, it is 0.1 mm or less. ２ More preferably, it is 0.05 mm or less. ２ More preferably, it is 0.01 mm or less. ２ It is particularly preferable that the value is 0.001 mm or less. ２ It is particularly preferable that the thickness is 1 μm or less. Although there is no particular restriction on the lower limit, ２ It may be 10 μm or more ２ It may be 100 μm or more. ２ It may be more than that.

[0021] The average diameter of the smallest circumscribing circle (the smallest circle circumscribing the outer peripheral shape of the planar surface of the composite flake) surrounding the shape of the planar surface of the composite flake is not particularly limited, but from the viewpoint of easily realizing a compact size of the molded body obtained using the composite flake, it is preferably 2000 μm or less, more preferably 1000 μm or less, even more preferably 500 μm or less, and particularly preferably 200 μm or less.In addition, the lower limit is not particularly limited, but it may be 0.1 μm or more, 1 μm or more, or 10 μm or more.

[0022] The average thickness of the composite flakes is not particularly limited as long as it is on the order of μm, and may be, for example, 0.001 μm or more, 0.01 μm or more, 0.1 μm or more, 1 μm or more, 100 μm or less, 50 μm or less, 30 μm or less, or 10 μm or less.

[0023] [Conductive Material] (Configuration of Conductive Material) The conductive material has a surface area of ​​1 mm ２There are no particular limitations on the size of the material as long as it can be contained in the composite flakes described below, and examples thereof include inorganic materials, metal materials, etc. There are also no particular limitations on the shape of the material, and examples thereof include fibrous (including tubular) shapes, particulate shapes, and coil shapes.

[0024] The type of inorganic material is not particularly limited, and examples thereof include carbon materials such as carbon nanotubes or graphite, metal elements in the description of metal materials below or alloys made of a combination of the metal elements, or oxides of these metal elements or alloys (e.g., Cu ２ O, NiO, etc.), halides, or sulfides (Cu ２ Examples of the metal material include metal-containing compounds such as copper (Cu), aluminum (Al), iron (Fe), gold (Au), silver (Ag), platinum (Pt), magnesium (Mg), zinc (Zn), tungsten (W), titanium (Ti), nickel (Ni), and manganese (Mn), as well as alloys formed from combinations of these metal elements. Among these, from the viewpoints of weight reduction and biodegradability, it is preferable that the conductive material contains one or more materials selected from the group consisting of carbon nanotubes, graphite, graphene, graphene oxide, carbon black, and carbon microbeads. From the viewpoint of easily forming a conductive network with a small amount, it is particularly preferable that the conductive material contains at least carbon nanotubes. Note that, in a molded body containing composite flakes, it is undesirable for the conductive material to form a network to the extent that the volume resistivity of the entire molded body is reduced. This is because the formation of such a network can cause problems such as short circuits between the semiconductor elements described above. On the other hand, from the viewpoint of ensuring good electromagnetic wave shielding performance, it is preferable that the conductive material contained in the composite flakes form a network to some extent. In other words, for the conductive material in a molded product containing composite flakes, it is preferable that the conductive material form a network in the composite flakes, but it is not preferable that the conductive material form a network throughout the molded product.

[0025] Conditions relating to the shape of the conductive material will be explained below, and these conditions can be measured using a transmission electron microscope (TEM), a scanning electron microscope (SEM), or the like.

[0026] The average length of the conductive material, here the average length if fibrous (the length of the central axis if tubular), the average particle size if particulate, or the average length of the central axis if coiled, is not particularly limited, but from the viewpoint of facilitating the formation of a conductive network, it is preferably 0.001 μm or more, more preferably 0.01 μm or more, even more preferably 0.1 μm or more, and particularly preferably 1 μm or more, and from the viewpoint of facilitating the production of small flakes, it is preferably 10,000 μm or less, more preferably 1,000 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

[0027] When the conductive material is tubular, the average diameter in a cross section perpendicular to the axial direction (also referred to as "average fiber diameter") is not particularly limited, but from the viewpoint of facilitating the formation of a conductive network, it is preferably 0.10 nm or more, more preferably 0.25 nm or more, even more preferably 0.50 nm or more, and particularly preferably 1 nm or more, and from the viewpoint of facilitating the production of small flakes, it is preferably 10 μm or less, more preferably 0.5 μm or less, even more preferably 0.1 μm or less, and particularly preferably 0.01 μm or less.

[0028] The content of the conductive material in the composite flakes is not particularly limited, but from the viewpoint of ensuring sufficient electromagnetic wave shielding performance, it is preferably 0.005% by mass or more, more preferably 0.010% by mass or more, even more preferably 0.050% by mass or more, and particularly preferably 0.100% by mass or more, and from the viewpoint of ensuring sufficient insulation, it is preferably 75% by mass or less, more preferably 50% by mass or less, even more preferably 25% by mass or less, and particularly preferably 10% by mass or less. Note that when the composite flakes contain carbon nanotubes, the content of the conductive material can also be treated as the content of carbon nanotubes in the composite flakes.

[0029] In the composite flakes, the content of the conductive material relative to the content of binder A is not particularly limited, but from the viewpoint of ensuring sufficient electromagnetic wave shielding performance, the content of the conductive material relative to the content of binder A is preferably 0.005% by mass or more, more preferably 0.010% by mass or more, even more preferably 0.050% by mass or more, and particularly preferably 0.100% by mass or more, and may be 1% by mass or more, 3% by mass or more, or 4% by mass or more, and from the viewpoint of ensuring sufficient insulation, the content of the conductive material relative to the content of binder A is preferably 75% by mass or less, more preferably 50% by mass or less, even more preferably 25% by mass or less, and particularly preferably 10% by mass or less. Note that when the composite flakes contain carbon nanotubes, the content of the conductive material relative to the content of binder A can also be treated as the content of carbon nanotubes relative to the content of binder A.

[0030] (Characteristics of conductive material) Aspect ratio The aspect ratio of the conductive material is not particularly limited, but from the viewpoint of dispersibility, it is preferably 10 or more, more preferably 100 or more, even more preferably 250 or more, and particularly preferably 500 or more, and is preferably 100,000 or less, more preferably 50,000 or less, even more preferably 25,000 or less, and particularly preferably 10,000 or less.

[0031] [Binder A] (Configuration of Binder A) The type of binder A is not particularly limited as long as it can bond multiple conductive materials and is non-conductive. Examples include organic materials such as polymers and inorganic materials such as glass. From the viewpoint of ease of molding, organic materials are preferred, and polymer materials are more preferred. The form of binder A is not particularly limited. It may be a molten thermoplastic resin cured by cooling, a thermosetting resin or photocurable resin obtained by polymerizing a low-molecular-weight monomer by heating or light irradiation, or a fiber such as nanofiber solidified into a desired shape. In the case of a thermoplastic resin cured by cooling, a thermosetting resin cured by heating, or a low-molecular-weight monomer cured by polymerization, the conductive material tends to be unevenly distributed downward due to its own weight during the curing process. On the other hand, in the case of a fiber such as nanofiber cured into a specific shape, uneven distribution of the conductive material during the curing process is less likely to occur, and contact between the conductive materials is less likely to occur, making it easier to achieve the desired electromagnetic wave shielding performance.

[0032] When a resin is used, it may be a thermosetting resin or a thermoplastic resin, but a thermosetting resin is preferred because the electromagnetic wave shielding sheet may be exposed to high temperatures depending on its intended use. Examples of thermosetting resins include thermosetting resins and photocurable resins. Examples of thermosetting resins include thermosetting acrylic resins, unsaturated polyester resins, epoxy resins, melamine resins, phenolic resins, silicone resins, polyimide resins, and urethane resins. Examples of photocurable resins include photocurable epoxy resins, photocurable polyesters, photocurable vinyl compounds, photocurable epoxy (meth)acrylates, and photocurable urethane (meth)acrylates. Among these, unsaturated polyester resins, photocurable polyesters, epoxy resins, and photocurable epoxy resins are preferred, and epoxy resins and photocurable epoxy resins are particularly preferred from the viewpoint of heat resistance. These resins may be used alone or in combination of two or more types in any type and ratio.

[0033] The type of nanofiber material is not particularly limited, and examples thereof include cellulose, polypropylene, polyethylene terephthalate, chitin, chitosan, and aramid. Cellulose nanofibers are preferred from the viewpoint of ease of producing a foam for producing flakes. Binder A preferably contains cellulose nanofibers, but may also be cellulose nanofibers.

[0034] The average length of the nanofiber material is not particularly limited, but from the viewpoint of easily improving electromagnetic wave shielding performance by supporting the conductive material network, it is preferably 0.001 μm or more, more preferably 0.01 μm or more, even more preferably 0.1 μm or more, and particularly preferably 0.5 μm or more; and from the viewpoint of easily forming a support for the conductive material network and easily ensuring insulation, it is preferably 10,000 μm or less, more preferably 1,000 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

[0035] With regard to the nanofiber material, the average diameter in a cross section perpendicular to the axial direction (also referred to as "average fiber diameter") is not particularly limited, but from the viewpoint of easily improving electromagnetic wave shielding performance by supporting a network of conductive material, it is preferably 0.10 nm or more, more preferably 0.25 nm or more, even more preferably 0.50 nm or more, and particularly preferably 1 nm or more; and from the viewpoint of easily forming a support for the network of conductive material and easily ensuring insulation, it is preferably 10 μm or less, more preferably 0.5 μm or less, even more preferably 0.1 μm or less, and particularly preferably 0.01 μm or less.

[0036] From the viewpoint of preventing environmental pollution, the binder A is preferably a biodegradable material. Examples of biodegradable materials include cellulose, modified cellulose, chitin / chitosan, collagen, polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoate (PHA), and cellulose acetate. From the viewpoint of facilitating the formation of a conductive network, cellulose nanofibers or chitosan nanofibers are preferred.

[0037] The content of binder A in the composite flakes is not particularly limited, but from the viewpoint of ensuring sufficient electromagnetic wave shielding properties, it is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 10% by mass or more, and particularly preferably 30% by mass or more, and is usually 99.99% by mass or less, preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. Furthermore, when the composite flakes contain at least cellulose nanofibers as binder A, the content of cellulose nanofibers in the composite flakes is not particularly limited, but the conditions for the content of binder A in the composite flakes described above can be similarly adopted.

[0038] When fibers are used as binder A, the fibers may be crosslinked. That is, binder A may contain crosslinked fibers or may be crosslinked fibers. The type of crosslinking is not particularly limited, and examples thereof include crosslinking by covalent bonds and crosslinking by ionic bonds.

[0039] (Characteristics of Binder A) Refractive Index The refractive index of binder A is not particularly limited, but from the viewpoint of improving electromagnetic wave shielding properties, it is usually 1.35 or more and 1.76 or less, and preferably 1.5 or more and 1.6 or less for cellulose, or 1.55 or more and 1.61 or less for epoxy resin. The refractive index can be measured by a known method.

[0040] [Other Materials] The composite flakes may contain the above-mentioned conductive material and binder A material (other materials), such as magnetic materials, hollow-shaped powder, mica, Teflon (registered trademark) powder, SiO ２ (Silica), Al ２ O ３ (alumina), AlN, BN, antimony oxide, aluminum hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, etc. Specifically, for example, the addition of an inorganic filler can adjust the linear expansion coefficient of the composite flakes, which makes it easier to prevent warping, deflection, undulation, etc. not only of the composite flakes but also of molded articles containing the composite flakes. The content of inorganic fillers other than the conductive material in the composite flakes is not particularly limited, and may be arbitrarily contained within a range in which the effects of this embodiment can be obtained.

[0041] As described above, binder A may be crosslinked, particularly with metal ions. The composite flake may contain metal ions, including those for providing such crosslinking, and the amount thereof is not particularly limited. For example, the number of moles of metal ions per gram of composite flake may be 0.01 mmol / g or more, 0.1 mmol / g or more, or 0.2 mmol / g or more, or 100 mmol / g or less, 10 mmol / g or less, or 1 mmol / g or less.

[0042] Another embodiment of the present disclosure is a composite flake containing cellulose nanofibers and carbon nanotubes. The use of cellulose nanofibers as a binder facilitates the production of foam for flake fabrication, while the use of carbon nanotubes as a conductive material facilitates the formation of a conductive network even with a low content of conductive material. The conditions for the composite flake, including the conditions for the cellulose nanofibers and carbon nanotubes, are similarly applicable to the conditions described in the above-described embodiment.

[0043] <Method for manufacturing composite flakes> Hereinafter, embodiments relating to methods for manufacturing various molded bodies will be described, but the method for manufacturing the above-mentioned composite flakes is not limited to these methods. Furthermore, manufacturing conditions that can be mutually applied in each embodiment can be mutually applied. Furthermore, to the extent applicable, the conditions for the above-mentioned composite flakes can be applied to the conditions for the following manufacturing methods. When comparing the first and second manufacturing methods below, the second manufacturing method is preferred from the viewpoint of ease of manufacturing composite flakes on the order of μm.

[0044] <First Manufacturing Method> A first manufacturing method for composite flakes, which is another embodiment of the present disclosure (also simply referred to as the "first manufacturing method" in the description of this embodiment), is a manufacturing method for a molded body, including a composition preparation step of obtaining a liquid composition containing binder A and multiple conductive materials, and a curing step including a treatment of curing the liquid composition. The first manufacturing method may include steps other than the composition preparation step and the curing step. Furthermore, the first manufacturing method is a method that can be preferably adopted, particularly when a thermoplastic resin, a thermosetting resin, or a photocurable resin is used as binder A.

[0045] [Composition Preparation Step] The first manufacturing method includes a composition preparation step of obtaining a liquid composition containing the above-described binder A and a plurality of conductive materials. The method of obtaining the liquid composition containing the binder A and a plurality of conductive materials is not particularly limited, and examples thereof include a method of mixing the liquid binder A and a plurality of conductive materials, or a method of dissolving the binder A in a solvent to obtain a solution, and then mixing the solution with a plurality of conductive materials. The mixing method is not particularly limited, and any known method can be applied.

[0046] When a solvent is used, the type of solvent is not particularly limited as long as it can dissolve the binder A and other materials that need to be dissolved. If molding is possible without using a solvent, a solvent need not be used. A curing agent may be added depending on the type of binder A used, and known curing agents may be used appropriately depending on the binder A. The content of the curing agent in the composition may be, for example, 0.05 to 15% by mass. A polymerization initiator may also be added depending on the type of binder A used. For example, a thermal radical generator such as a peroxide, e.g., benzoyl peroxide, may be used as the thermal polymerization initiator, and a photoradical generator, a photocation generator, a photoanion generator, or the like may be used as the photopolymerization initiator.

[0047] A liquid composition according to another embodiment of the present invention is a liquid composition containing binder A and a plurality of conductive materials, and its manufacturing method is not particularly limited, but it can be obtained by the method described in the liquid composition manufacturing process. Furthermore, a molded product according to yet another embodiment of the present invention is a cured product of the above-mentioned liquid composition. The conditions for the molded product can be similarly applied to the conditions for the molded product described above.

[0048] [Curing Step] The first manufacturing method includes a curing step that includes a treatment for curing the liquid composition. The curing method is not particularly limited and can be changed appropriately depending on the type of binder A. For example, a method of curing using heat or light such as ultraviolet light can be used. Furthermore, when the binder A used is a thermoplastic resin and the composition is prepared in a melted state by applying heat, curing may be performed by leaving it to stand or cooling. The curing temperature and time vary depending on the materials used, and are not particularly limited as long as they can harden the composition. From the perspective of producing composite flakes on the order of μm, a method of curing a composition in a very thin spread state is preferred.

[0049] <Second Manufacturing Method> A second manufacturing method for a molded body, which is another embodiment of the present disclosure (also simply referred to as the "second manufacturing method" in the description of this embodiment), is a manufacturing method for composite flakes, including: a composition preparation step of obtaining a liquid composition containing binder A and multiple conductive materials; a freezing step of freezing the liquid composition to obtain a frozen body; and a pulverization step of pulverizing the frozen body. The second manufacturing method may include steps other than the composition preparation step, freezing step, and pulverization step. Furthermore, the second manufacturing method is a method that can be preferably adopted, particularly when fibers such as nanofibers are used as the binder. In this case, the obtained frozen body is not a bulk body, but a porous body such as a foam, and when the porous body is pulverized, the pulverized wall portion forming the porous body can be used as is as composite flakes.

[0050] [Composition Preparation Step] The second manufacturing method includes a composition preparation step of obtaining a liquid composition containing the above-described binder A and multiple conductive materials. The conditions for the composition preparation step in the above-described second manufacturing method can be similarly applied to this composition preparation step. However, when fibers are used as binder A, the fibers need to be dissolved in a solvent, and therefore the use of a solvent is essential.

[0051] [Freezing step] The second manufacturing method includes a freezing step in which the liquid composition is frozen to obtain a frozen body. This step aims to form a porous structure such as a foam by ice crystals growing in the dispersion. In the present disclosure, the frozen body refers to a substance derived from the composition after undergoing a freezing process. Therefore, even a substance derived from the composition in an unfrozen state after thawing is referred to as a frozen body. The method for freezing the liquid composition is not particularly limited, and examples include a method in which a container containing the liquid composition is placed in a freezer.

[0052] The shape of the frozen body is not particularly limited, but is preferably a cylindrical shape or a polygonal prism such as a square prism, a pentagonal prism, or a hexagonal prism.

[0053] The freezing temperature is not particularly limited as long as it is a temperature at which the liquid composition can be frozen, and may be, for example, −196 to 0° C., −100 to −20° C., or −60 to −30° C. The freezing time is not particularly limited as long as it is a temperature at which the liquid composition can be frozen, and may be, for example, 1 hour or more, 5 hours or more, or 10 hours or more, or 168 hours or less, 72 hours or less, or 24 hours or less.

[0054] [Immersion step] The second manufacturing method may include an immersion step between the above-mentioned freezing step and the pulverization step described below, in which the frozen body is immersed in a liquid containing a component that cross-links the binder A. This step is intended to reduce shrinkage of the volume of the frozen body in steps before or after the pulverization step described below. The method for immersing the frozen body in a liquid containing a component that cross-links the binder A is not particularly limited, and examples include a method in which the frozen body is placed in a container containing a liquid containing a component that cross-links the binder A, or a method in which a liquid containing a component that cross-links the binder A is placed in a container containing the frozen body.

[0055] The type of liquid containing a component that crosslinks binder A is not particularly limited as long as it can crosslink binder A. The type of crosslinking is also not particularly limited, and examples include crosslinking by covalent bonds and crosslinking by ionic bonds. Specific examples of the type of liquid containing a component that crosslinks binder A include polyvalent metal ion-containing liquids and acidic liquids, and more specific examples include aluminum ion-containing liquids such as aluminum nitrate, aluminum nitrate, aluminum sulfate, aluminum acetate, or aluminum chloride, copper nitrate aqueous solution, iron nitrate aqueous solution, hydrochloric acid, and acetic acid. In particular, when binder A is cellulose nanofibers, an acidic liquid is preferred, and aluminum nitrate is more preferred.

[0056] Furthermore, the immersion step may include removing a liquid (first liquid) containing a component that crosslinks binder A, and then immersing the frozen body in a liquid other than the first liquid (second liquid). This treatment is intended to prevent undesired volumetric shrinkage, which may occur if the frozen body is crushed or dried while the liquid containing the component that crosslinks binder A is attached. The method for removing the first liquid is not particularly limited, and examples include removing the first solution from a container containing the first liquid and the frozen body, or removing the frozen body from a container containing the first liquid and the frozen body. The method for immersing the frozen body in the second liquid is not particularly limited, and examples include pouring the frozen body into a container containing the second liquid, or pouring the second liquid into a container containing the frozen body.

[0057] The type of second liquid is not particularly limited as long as it is a liquid compatible with the first liquid, but examples include organic solvents with a surface tension lower than that of water, such as ethanol, acetone, hexane, or pentane. In particular, when binder A is cellulose nanofiber, a liquid such as ethanol can be used. For example, when the first liquid is water, ethanol or acetone, which are compatible with water, can be used, but hexane, which is not compatible with water, cannot be used. The replacement process with the second liquid may be performed two or more times. In this case, the replacement must be performed with a liquid that is compatible with the liquid used in the previous process. For example, when water is finally replaced with hexane, this can be performed by performing a two-step replacement, such as water → ethanol → hexane.

[0058] [Pulverization step] The second manufacturing method includes a pulverization step of pulverizing the above-described frozen body. As described above, if the pulverized material obtained in this step is in the form of flakes, it can be used as composite flakes. In particular, if the frozen body is a porous body, the wall portion forming the porous body will be in the form of flakes, and the pulverized material can be used as is as composite flakes. The pulverization method is not particularly limited, and ordinary pulverization methods such as a mixer, bead mill, ball mill, or pin mill can be applied. The pulverization conditions are not particularly limited, and pulverization can be continued until a pulverized material of the desired shape is obtained.

[0059] In the pulverization step, after the pulverization treatment, a classification treatment may be applied to classify the pulverized material into a desired size. The classification method is not particularly limited, and a sieve having a desired mesh size may be used, or a sieve shaker may be used.

[0060] [Drying step] The second manufacturing method may include a drying step of drying the frozen body after the above-mentioned freezing step, immersion step, or crushing step. This step is intended to remove volatile components contained in the frozen body, and, when the above-mentioned immersion step is employed, to promote crosslinking of the component that crosslinks the binder B. The drying method is not particularly limited, and known methods can be used, such as a method of putting the molded body into a dryer and drying it.

[0061] As long as it is possible to describe the volatile components to be removed, and in the case of employing the above-described immersion step, as long as it is possible to promote crosslinking of the components that crosslink binder A, the drying temperature and time are not particularly limited. For example, the drying temperature may be 5 to 150°C, 10 to 100°C, or 20 to 50°C, and the drying time may be 1 to 72 hours, 2 to 24 hours, or 5 to 12 hours.

[0062] <Uses of Composite Flakes> The uses of the above-described composite flakes include, for example, electromagnetic wave shielding, specifically, use as a raw material for a molded body for electromagnetic wave shielding. Another embodiment of the present invention is an electromagnetic wave shield having the above-described composite flakes. Furthermore, when the composite flakes are contained in a molded body, they can be used as a raw material for a molded body for the uses described below in the uses of the molded body.

[0063] The composite flakes can also be used as a substitute for common fillers and additives, for example, to adjust parameters such as the thermal expansion coefficient or electrical resistivity of the molded article to which they are added.

[0064] [Molded body] (Configuration of molded body) A molded body (hereinafter also simply referred to as "molded body") according to another embodiment of the present invention is a molded body containing the above-described composite flakes and binder B. The use of the molded body is not particularly limited, but it is suitably used as an electromagnetic wave shielding sheet, etc. In the following explanation, a sheet-shaped molded body, particularly an electromagnetic wave shielding sheet, will be specifically described. Hereinafter, "sheet" can be interchangeably referred to as "molded body".

[0065] The shape of the sheet is not particularly limited as long as it can be recognized as a sheet, and can be appropriately changed depending on the location where the sheet is to be installed. The sheet may be a single-layer sheet or a laminated sheet. When a laminated sheet is used, multiple sheets according to this embodiment may be stacked, or other sheets may be stacked to impart various functions. The thickness of the sheet is not particularly limited, and from the viewpoint of the recent trend toward smaller, lighter, and thinner electronic devices such as mobile phones, smartphones, and tablets, it is usually 10 μm or more, preferably 20 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more. It is also usually 10 mm or less, preferably 5 mm or less, more preferably 3 mm or less, and even more preferably 1.5 mm or less. The shape of the sheet is flat, but it may have an uneven shape within a range that can be approximately regarded as flat, or may be partially curved. Furthermore, the shape of the sheet observed from the surface may be circular or polygonal, such as triangular or rectangular.

[0066] The sheet may be a bulk body in which the composite flakes and binder B, and any other material, are densely packed, or may be a porous body (for example, a foam).

[0067] The content of the composite flakes in the sheet is not particularly limited, but from the viewpoint of ensuring sufficient electromagnetic wave shielding properties, it is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 30% by mass or more, and is usually 99.9% by mass or less, preferably 99% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The content of the composite flakes can be evaluated by thermogravimetric analysis or by isolating the constituent components by chemical treatment. Furthermore, if the composite flakes can be dissolved and removed with a liquid such as an ionic liquid, the content can be evaluated from the weight before and after removal.

[0068] The content of the conductive material in the sheet is not particularly limited, but from the viewpoint of ensuring sufficient electromagnetic wave shielding properties, it is usually 0.010% by mass or more, preferably 0.020% by mass or more, more preferably 0.030% by mass or more, and even more preferably 0.050% by mass or more. It is also usually 99.99% by mass or less, preferably 90% by mass or less, more preferably 50% by mass or less, and even more preferably 10% by mass or less. The content of the composite flakes can be evaluated by thermogravimetric analysis or by isolating the components by chemical treatment. Furthermore, if the composite flakes can be dissolved and removed using a liquid such as an ionic liquid, the content can be evaluated from the weights before and after removal. If the sheet contains carbon nanotubes, the content of the conductive material can also be treated as the content of carbon nanotubes in the sheet.

[0069] In the sheet, the content of the conductive material relative to the total content of binder A and binder B is not particularly limited, but from the viewpoint of ensuring sufficient electromagnetic wave shielding performance, the content is typically 0.010% by mass or more, preferably 0.020% by mass or more, more preferably 0.030% by mass or more, and even more preferably 0.050% by mass or more, and is typically 99.99% by mass or less, preferably 90% by mass or less, more preferably 50% by mass or less, and even more preferably 10% by mass or less, where the total content of binder A and binder B is taken as 100% by mass. Note that, when the sheet contains carbon nanotubes, the content of the conductive material relative to the total content of binder A and binder B can also be treated as the content of carbon nanotubes relative to the total content of binder A and binder B.

[0070] [Binder B] (Configuration of Binder B) The type of binder B is not particularly limited as long as it can bond multiple composite flakes and is non-conductive. Specifically, the materials described above for binder A can be used in the same manner, including within the preferred range. The type of binder B may be the same as the type of binder A, or may be different. The shape of binder A in binder B can be confirmed using a transmission electron microscope (TEM) or a scanning electron microscope (SEM), and this can be confirmed even if the types of binder B and binder A are the same.

[0071] Like binder A, binder B is preferably a biodegradable material from the viewpoint of preventing environmental pollution, etc. Examples of biodegradable materials include cellulose, modified cellulose, chitin / chitosan, collagen, polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoate (PHA), and cellulose acetate, and cellulose nanofibers or chitosan nanofibers are preferred from the viewpoint of ease of forming a conductive network.

[0072] The content of binder B in the molded body is not particularly limited, but from the viewpoint of ensuring sufficient electromagnetic wave shielding properties, it is usually 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and particularly preferably 80% by mass or more, and is usually 99.99% by mass or less, preferably 99.95% by mass or less, more preferably 99.90% by mass or less, and even more preferably 99.85% by mass or less. Furthermore, when the molded body contains at least cellulose nanofibers as binder B, the content of cellulose nanofibers (preferably cellulose nanofibers as binder B) in the molded body is not particularly limited, but the conditions for the content of binder B in the composite flakes described above can be similarly adopted.

[0073] When fibers are used as binder B, the fibers may be crosslinked with each other, as in binder A. That is, binder A may contain crosslinked fibers or may be crosslinked fibers. The type of crosslinking is not particularly limited, and examples thereof include crosslinking by covalent bonds and crosslinking by ionic bonds.

[0074] The composite flakes may be completely embedded in binder B, or may not be completely embedded (only partially embedded), i.e., a portion of the composite flakes may be exposed outside binder B.

[0075] [Other Materials] The sheet may contain materials (other materials) other than the composite flakes and binder B described above, such as magnetic materials, hollow-shaped powder, mica, Teflon (registered trademark) powder, SiO ２ (Silica), Al ２ O ３ (alumina), AlN, BN, antimony oxide, aluminum hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, etc. Specifically, for example, the addition of an inorganic filler can adjust the linear expansion coefficient of the sheet, which makes it easier to prevent the sheet from warping, sagging, undulation, etc. The content of inorganic fillers other than the conductive material in the sheet is not particularly limited, and may be arbitrarily contained within a range in which the effects of this embodiment can be obtained.

[0076] As described above, the binder B may be crosslinked, particularly with metal ions. The molded body may contain metal ions, including metal ions for providing such crosslinking, and the amount thereof is not particularly limited. For example, the number of moles of metal ions per 1 g of the molded body may be 0.01 mol / g or more, 0.1 mol / g or more, or 0.2 mol / g or more, or 100 mol / g or less, 10 mol / g or less, or 1 mol / g or less.

[0077] (Sheet characteristics) Electromagnetic wave shielding property In the present disclosure, the electromagnetic wave shielding property is evaluated by evaluating the power transmittance T(ω) using the following method. This evaluation method is based on the terahertz time-domain spectroscopy used in the transmittance measurement experiment. A schematic diagram of a terahertz time-domain spectroscopy device is shown in Figure 6. In terahertz time-domain spectroscopy, the output from one or two femtosecond lasers is generally used as pump light and probe light. The pump light acts as light that excites the terahertz wave. The probe light synchronizes the timing for measuring the terahertz wave. The electric field component of the terahertz wave in the time domain is measured by changing the arrival times of the pump light and the probe light. The electric field E after the terahertz wave has passed through the sample is ｓａｍ (t) and the electric field E after passing through air without a sample. ｒｅｆ (t) are detected. Using these values, the complex refractive index, complex dielectric constant, transmittance, power spectrum, etc. are derived. The transmittance is derived from the data obtained from the above measurements by Fourier transform. The obtained electric field waveform E ｓａｍ (t), E ｒｅｆ (t) are Fourier transformed to E ｓａｍ (ω), E ｒｅｆ Using these, the power transmittance T(ω) is expressed by the following formula (A).

[0078]

[0079] The transmittance can be measured using a terahertz spectroscopy system (for example, TAS7500TSH manufactured by Advantest Corporation).

[0080] The shielding performance L (dB) can be calculated from the power transmittance T (ω) using the following formula (B): L = 10 × Log １０(T(ω)) (B) The shielding performance L is not particularly limited, but is usually −10 dB or less, preferably −15 dB or less, and from the viewpoint of preventing malfunction of electronic devices such as computers, it is preferably −20 dB or less, more preferably −30 dB or less, even more preferably −40 dB or less, particularly preferably −60 dB or less, and most particularly preferably −80 dB or less, and although there is no need to set a lower limit, it is usually −90 dB or more. The electromagnetic wave shielding performance is expressed as −20 dB (shielding factor: 90%) when the electromagnetic wave is reduced to 1 / 10, −40 dB (shielding factor: 99%) when it is reduced to 1 / 100, −60 dB (shielding factor: 99.9%) when it is reduced to 1 / 1000, and −80 dB (shielding factor: 99.99%) when it is reduced to 1 / 10,000.

[0081] Volume Resistivity The volume resistivity of the sheet is measured by a resistivity meter (for example, Hiresta UX MCP-HT800 manufactured by Nitto Seiko Analytech Co., Ltd.) using a double ring electrode method (two-terminal method), that is, by sandwiching the molded body between a counter electrode and a double ring electrode.

[0082] The volume resistivity of the sheet that can be measured by the above method is not particularly limited. However, as described above, from the viewpoint that it is preferable that no current flows between the conductive materials, it is preferable that the volume resistivity is 10 ４ It is preferable that the resistance is Ω·cm or more, and 10 ６ It is preferable that the resistance is 10 Ω cm or more. ８ It is more preferable that the resistance is 10 Ω cm or more. １０ It is particularly preferable that the volume resistivity is Ω·cm or more. There is no particular need to set an upper limit for the volume resistivity. ２０ Ω cm or less, １８ It may be Ω·cm or less.

[0083] <Method for manufacturing a molded body> Hereinafter, various embodiments relating to the manufacturing method of a molded body will be described, but the manufacturing method of the above-mentioned molded body is not limited to these manufacturing methods. In addition, manufacturing conditions that can be mutually applied in each embodiment can be mutually applied. In addition, the conditions for the above-mentioned molded body can be applied to the conditions of the manufacturing method below to the extent applicable.

[0084] <First manufacturing method> A first manufacturing method of a molded body, which is another embodiment of the present disclosure (also simply referred to as the "first manufacturing method" in the description of this embodiment), is a manufacturing method of a molded body, including: a composition preparation step of obtaining a liquid composition containing binder B and a plurality of composite flakes; and a curing step including a treatment of curing the liquid composition. The first manufacturing method may include steps other than the composition preparation step and the curing step. Furthermore, the first manufacturing method is a method that can be preferably adopted particularly when a thermoplastic resin, a thermosetting resin, or a photocurable resin is used as binder B.

[0085] [Composition Preparation Step] The first manufacturing method includes a composition preparation step of obtaining a liquid composition containing the above-described binder B and composite flakes. The method for obtaining the liquid composition containing binder B and composite flakes is not particularly limited, and examples thereof include a method of mixing liquid binder B and composite flakes, or a method of dissolving binder B in a solvent to obtain a solution and then mixing the solution with composite flakes. The mixing method is not particularly limited, and known methods can be used.

[0086] When a solvent is used, the type of solvent is not particularly limited as long as it can dissolve the binder B and other materials that need to be dissolved, but does not dissolve the composite flakes. If molding is possible without using a solvent, a solvent need not be used. A curing agent may be added depending on the type of binder B used, and known curing agents may be used appropriately depending on the binder B. The content of the curing agent in the composition may be, for example, 0.05 to 15% by mass. A polymerization initiator may also be added depending on the type of binder B used. For example, a thermal radical generator such as a peroxide, e.g., benzoyl peroxide, may be used as the thermal polymerization initiator, and a photoradical generator, photocation generator, or photoanion generator may be used as the photopolymerization initiator.

[0087] The liquid composition according to another embodiment of the present invention is a liquid composition containing the composite flakes and binder B described above. The method for producing the liquid composition is not particularly limited, but it can be obtained by the method described in the liquid composition production process. Furthermore, the molded product according to yet another embodiment of the present invention is a cured product of the liquid composition. The conditions for the molded product described above can be applied in the same manner.

[0088] [Curing Step] The first manufacturing method includes a curing step that includes a treatment for curing the liquid composition. The curing method is not particularly limited and can be changed appropriately depending on the type of binder B. For example, a method of curing using heat or light such as ultraviolet light can be mentioned. Furthermore, when the binder B used is a thermoplastic resin and the composition is prepared in a melted state by applying heat, the curing method may be a treatment such as leaving it to stand or a cooling treatment. The curing temperature and time vary depending on the materials used, and are not particularly limited as long as they are a temperature and time that can cure the composition.

[0089] <Second Manufacturing Method> A second manufacturing method of a molded body, which is another embodiment of the present disclosure (also simply referred to as the "first manufacturing method" in the description of this embodiment), is a manufacturing method of a molded body, including a composition preparation step of obtaining a liquid composition containing the above-mentioned composite flakes and binder B, and a freezing step of freezing the liquid composition to obtain a frozen body. The second manufacturing method may include steps other than the above-mentioned composition preparation step and freezing step. Furthermore, the second manufacturing method is a method that can be preferably adopted, particularly when fibers such as nanofibers are used as binder B. In this case, the obtained molded body may not be a bulk body, but may be a porous body such as a foam.

[0090] [Composition Preparation Step] The second manufacturing method includes a composition preparation step of obtaining a liquid composition containing a plurality of the above-described composite flakes and binder B. The conditions for the composition preparation step in the above-described second manufacturing method can be similarly applied to this composition preparation step. However, when fibers are used as binder B, the fibers must be dissolved in a solvent, and therefore the use of a solvent is essential.

[0091] [Freezing step] The second manufacturing method includes a freezing step in which the liquid composition is frozen to obtain a frozen body. This step aims to form a porous structure such as a foam by ice crystals growing in the dispersion. In the present disclosure, the frozen body refers to a substance derived from the composition after undergoing a freezing process. Therefore, even a substance derived from the composition in an unfrozen state after thawing is referred to as a frozen body. The method for freezing the liquid composition is not particularly limited, and examples include a method in which a container containing the liquid composition is placed in a freezer.

[0092] The shape of the frozen body is not particularly limited, but is preferably a cylindrical shape or a polygonal prism such as a square prism, a pentagonal prism, or a hexagonal prism.

[0093] The freezing temperature is not particularly limited as long as it is a temperature at which the liquid composition can be frozen, and may be, for example, −196 to 0° C., −100 to −20° C., or −60 to −30° C. The freezing time is not particularly limited as long as it is a temperature at which the liquid composition can be frozen, and may be, for example, 1 hour or more, 5 hours or more, or 10 hours or more, or 168 hours or less, 72 hours or less, or 24 hours or less.

[0094] [Immersion step] The second manufacturing method may include an immersion step in which the frozen body is immersed in a liquid containing a component that cross-links the binder B after the freezing step. This step is intended to reduce shrinkage of the volume of the frozen body in a subsequent step. The method for immersing the frozen body in a liquid containing a component that cross-links the binder B is not particularly limited, and examples include a method in which the frozen body is placed in a container containing a liquid containing a component that cross-links the binder B, or a method in which a liquid containing a component that cross-links the binder is placed in a container containing the frozen body.

[0095] The type of liquid containing a component that crosslinks binder B is not particularly limited as long as it can crosslink binder B. The type of crosslinking is also not particularly limited, and examples include crosslinking by covalent bonds and crosslinking by ionic bonds. Specific examples of the type of liquid containing a component that crosslinks binder B include polyvalent metal ion-containing liquids and acidic liquids, and more specific examples include aluminum ion-containing liquids such as aluminum nitrate, aluminum nitrate, aluminum sulfate, aluminum acetate, or aluminum chloride, copper nitrate aqueous solution, iron nitrate aqueous solution, hydrochloric acid, and acetic acid. In particular, when the binder is cellulose nanofibers, an acidic liquid is preferred, and aluminum nitrate is more preferred.

[0096] Furthermore, the immersion step may include removing a liquid (first liquid) containing a component that crosslinks binder B, and then immersing the frozen body in a liquid other than the first liquid (second liquid). This treatment is intended to prevent undesired volumetric shrinkage, which may occur if the frozen body is dried while still attached with the liquid containing the component that crosslinks binder B. The method for removing the first liquid is not particularly limited, and examples include removing the first solution from a container containing the first liquid and the frozen body, or removing the frozen body from a container containing the first liquid and the frozen body. The method for immersing the frozen body in the second liquid is not particularly limited, and examples include pouring the frozen body into a container containing the second liquid, or pouring the second liquid into a container containing the frozen body.

[0097] The type of second liquid is not particularly limited as long as it is a liquid compatible with the first liquid, but examples include organic solvents with a surface tension lower than that of water, such as ethanol, acetone, hexane, or pentane. In particular, when the binder is cellulose nanofibers, a liquid such as ethanol can be used. For example, when the first liquid is water, ethanol or acetone, which are compatible with water, can be used, but hexane, which is not compatible with water, cannot be used. The replacement process with the second liquid may be performed two or more times. In this case, the replacement must be performed with a liquid that is compatible with the liquid used in the previous process. For example, when replacing water with hexane, this can be performed in two steps, such as water → ethanol → hexane.

[0098] [Thawing step] The second manufacturing method may include a step of thawing the frozen body. The thawing step may be included after the freezing step, and may be carried out simultaneously with the immersion step. It is preferable to carry out the thawing step after immersing the frozen body in a liquid containing a component that crosslinks the binder B, and it is also preferable to carry out the thawing step before immersing the frozen body in the second liquid. The thawing method is not particularly limited, and examples include a heating method and a method of natural thawing by leaving it.

[0099] The thawing temperature and thawing time are not particularly limited as long as they can thaw the frozen body, and can be set appropriately depending on the type of composition.

[0100] [Drying step] The second manufacturing method may include a drying step of drying the frozen body after the above-mentioned freezing step, immersion step, or thawing step. This step is intended to remove volatile components contained in the frozen body, and, when the above-mentioned immersion step is employed, to promote crosslinking of the component that crosslinks the binder B. The drying method is not particularly limited, and known methods can be used, such as a method of putting the molded body into a dryer and drying it.

[0101] As long as it is possible to describe the volatile components to be removed, and in the case of employing the above-mentioned immersion step, as long as it is possible to promote crosslinking of the component that crosslinks binder B, the drying temperature and time are not particularly limited. For example, the drying temperature may be 5 to 150°C, 10 to 100°C, or 15 to 50°C, and the drying time may be 1 to 72 hours, 5 to 54 hours, or 10 to 36 hours.

[0102] <Uses of Molded Article> Uses of the above-described molded article include electromagnetic wave shielding, and another embodiment of the present invention is an electromagnetic wave shield having the above-described molded article.

[0103] Other embodiments of the present invention include: a semiconductor module having a semiconductor device (e.g., a module in which a semiconductor element is packaged covered with a molded article, such as in an SOP, QFP, QFN, or BGA package); an electronic device or telecommunications device such as a smartphone, tablet, smart watch, smart security device, monitoring device, or smart home appliance; an automotive device such as a safety system, mobile media, communication, wireless headset, battery-powered, electric, or hybrid powertrain, or high-voltage battery system; a consumer electronic device such as a computer circuit, a wireless transmitter (including a smartphone), an electric motor, a flat panel display, or a liquid crystal display (LCD); a medical device such as a smart bed, a ventilator, a CT scan machine, or a transducer that must acquire information such as pulse rate or blood pressure and convert it into an electronic signal; an aerospace device such as an aircraft, a vehicle, an elastomeric gasket, a conductive paint, or an EMI shielding display; a system such as a railway system, a mass transit system, a high-voltage contact switching system, a signal transmission system, or a control system; or other equipment (equipment other than those described above that may have the molded article); The use of the molded article in each of the above embodiments is not particularly limited as long as the molded article is included as a component. Furthermore, each embodiment is particularly preferably used as an electromagnetic wave shielding sheet.

[0104] In particular, when used as an electromagnetic wave shielding sheet, it can be used in any application that shields electromagnetic waves. For example, by placing the electromagnetic wave shielding sheet so as to surround electronic devices that may malfunction due to electromagnetic waves, such malfunctions can be suppressed. In particular, the above-mentioned electromagnetic wave shielding sheet is superior to conventional electromagnetic wave shielding sheets in shielding electromagnetic waves in the high-frequency band, and therefore can be applied to a wider range of fields than conventional electromagnetic wave shielding sheets in that it can shield against electromagnetic waves originating from communication devices such as mobile phones and smartphones, which are being deployed at higher frequencies, particularly high frequency bands of 100 GHz or higher, in order to achieve higher speeds, larger capacities, and lower latency. Note that the above-mentioned sheet achieves a particularly strong electromagnetic wave shielding effect when the plane of the sheet is perpendicular to the direction in which electromagnetic waves arrive from outside.

[0105] The present disclosure will be described in more detail below with reference to examples, but the present disclosure should not be construed as being limited to the following examples.

[0106] <Materials used> [Binders] Binder 1: Cellulose nanofiber (cellulose nanofiber / aqueous dispersion (cellulose nanofiber content: 1% by mass), Rheocrysta I-2SX, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., length of more than 100 μm and not more than 3 mm, fiber diameter of 3 nm) Binder 2: Epoxy resin (Clear Resin V4, manufactured by Formlab) Binder 3: Carboxymethyl cellulose (CMC) (carboxymethyl cellulose sodium, Nakarai standard first class EP, manufactured by Nakarai Tesque, Inc.) Binder 4: Polyvinyl alcohol (PVA) (chemical CP, Nakarai Tesque, Inc.) [Conductive materials] Conductive material: carbon nanotubes (CNT) (CNT / aqueous dispersion (CNT content: 0.5% by mass), WPB-043, manufactured by Kusumoto Chemicals Co., Ltd., length 2 to 10 μm, fiber diameter 1.2 to 2.0 nm, aspect ratio 1,000 to 8,333)

[0107] In the tables described below, the numerical values ​​of the parameters relating to the shapes of the conductive material and flakes, etc., are all averages. Also, the "diameter of the circumscribed circle" in each table represents the average diameter of the smallest circumscribed circle that encloses the surface shape in the planar direction of the composite flake.

[0108] <Characteristics Evaluation> [Electromagnetic Shielding Performance] The electromagnetic shielding performance was evaluated by measuring the power transmittance T(ω) using a terahertz spectroscopy system (TAS7500TSH manufactured by Advantest Corporation). An aperture with a diameter of 5 mm was used. The samples to be measured were obtained by cutting each of the above sheets into a rectangular parallelepiped with a side length of 30 mm and a thickness of 1 mm. Next, the shielding performance L (dB) was calculated from the power transmittance T(ω) obtained by measurement according to the following formula (B): L = 10 × Log １０ (T(ω)) (B) The evaluation results of the electromagnetic wave shielding performance L of each sheet are shown in each table. Note that the shielding performance L shown in each table is a value evaluated at a frequency of 300 GHz.

[0109] [Volume Resistivity] The volume resistivity of the sheet was measured using a resistivity meter (Hiresta UX MCP-HT800 manufactured by Nitto Seiko Analytech Co., Ltd., upper measurement limit 10 １１ The measurement was carried out by using a double ring electrode method (two-terminal method) using a resistivity (Ω·cm) by sandwiching the molded body between an opposing electrode (registration table) and a double ring electrode (URSS probe).

[0110] Experiment A [Examples 1-4, Comparative Example 1] (Production of Composite Flakes) Binder 1 and CNT were weighed so that the amount of CNT relative to the amount of cellulose nanofiber was 6% by mass, and then mixed to obtain a mixed aqueous dispersion. The amount of cellulose nanofibers is the amount of cellulose nanofiber in the cellulose nanofiber / aqueous dispersion. The amount of CNT is the amount of CNT in the CNT / aqueous dispersion. The mixed aqueous dispersion was then filled into a cylindrical plastic container with an inner diameter of 90 mm and a height of 20 mm and frozen at -45°C for 2 hours to obtain a frozen product. The frozen product was then thawed in a 0.1 mol / L aqueous aluminum nitrate solution to prepare a hydrogel in which the cellulose nanofibers were crosslinked with aluminum ions. The obtained hydrogel was washed with distilled water to remove the aluminum nitrate. The hydrogel was then pulverized using a mixer (IFM-800DGM, manufactured by Iwatani Corporation) until the surface area of ​​the flakes reached the area shown in Table 1 (pulverization time: 1 to 20 minutes). The pulverized hydrogel was dried at 30°C for 8 hours to obtain composite flakes. The thickness of each composite flake was 4 μm. The relationship between the pulverization time using a mixer and the size of the resulting flakes was evaluated in Experiment D, which will be described later. Information on the morphology of Flakes 1 to 3 shown in Tables 1 and 2 below is also shown in Table 4, which will be described later.

[0111] (Sheet Production) Binder 1 and the above composite flakes were weighed so that the amount of CNT relative to the amount of cellulose nanofiber was the amount shown in Table 1, and these were mixed to obtain a mixed aqueous dispersion. The amount of cellulose nanofiber is the sum of the amount of cellulose nanofiber contained in the composite flakes and the amount of cellulose nanofiber in the binder used to produce the molded body. The amount of CNT is the amount of CNT in the CNT / aqueous dispersion. The mixed aqueous dispersion was then poured into a 90 mm inner diameter disposable dish and dried for one week at 10°C and 90% RH to produce a sheet having the thickness shown in Table 1. Comparative Example 1 is a sheet produced without using composite flakes. The evaluation results for electromagnetic shielding performance and volume resistivity are shown in Table 1. A graph obtained from the evaluation of electromagnetic shielding performance is shown in Figure 2. The binder content in the sheet is calculated by subtracting the CNT content shown in Table 1 from 100% by mass. In addition, in the graph of Fig. 2, the area above 0 on the vertical axis is plotted with graphs of reflectance (%), transmittance (%), and absorptance (%), and the area below 0 is plotted with a graph of shielding performance (dB). Reflectance (%), transmittance (%), and absorptance (%) are expressed as 0% or higher, and shielding performance is expressed as 0 dB or lower. This is also true for Figs. 3 to 7.

[0112] Examples 5 to 13, Comparative Example 2 (Sheet Production) Binder 2 and the above composite flakes were weighed so that the ratio of CNT to binder 2 was the amount shown in Table 1, and these were mixed to obtain a mixed solution. The mixed solution was then filled into an acrylic mold having a circular hole with a diameter of 20 mm and a thickness of approximately 1 mm, and ultraviolet light was irradiated for 1 hour using an ultraviolet irradiation device (Form Cure, manufactured by Formlab) to cure binder 2, producing a sheet (diameter 20 mm) having the thickness shown in Table 1. The evaluation results for electromagnetic wave shielding performance and volume resistivity are shown in Table 1. Graphs obtained from the evaluation of electromagnetic wave shielding performance are shown in Figures 3 and 4.

[0113] Comparative Examples 3 to 5 (Sheet Production) Binder 1 and CNT were weighed so that the ratio of CNT to cellulose nanofiber was as shown in Table 1, and these were mixed to obtain a mixed aqueous dispersion. The amount of cellulose nanofiber is the amount of cellulose nanofiber in the cellulose nanofiber / aqueous dispersion. The amount of CNT is the amount of CNT in the CNT / aqueous dispersion. The mixed aqueous dispersion was then poured into a disposable dish with an inner diameter of 90 mm and dried and cured for one week in an environment of 10°C and 90% RH. The cured sheet (diameter 90 mm) was then removed from the dish, and a sheet having the thickness shown in Table 1 was produced. The evaluation results for electromagnetic shielding performance and volume resistivity are shown in Table 1. A graph obtained from the evaluation of electromagnetic shielding performance is shown in FIG. 5.

[0114] Comparative Examples 6 to 8 (Sheet Production) Binder 3 and CNT were weighed so that the ratio of CNT to carboxymethyl cellulose was the amount shown in Table 1, and these were mixed to obtain a mixed aqueous dispersion. This CNT amount is the amount of CNT in the CNT / aqueous dispersion. Next, the mixed aqueous dispersion was filled into an acrylic mold having a circular hole with an inner diameter of 20 mm and a thickness of 1 mm. The binder was then cured by irradiating it with ultraviolet light for 1 hour using an ultraviolet irradiation device (Form Cure, manufactured by Formlab). After curing, a sheet (20 mm diameter, 1 mm thickness) was removed from the mold, and a sheet with the thickness shown in Table 1 was obtained. The evaluation results of the electromagnetic wave shielding performance and volume resistivity are shown in Table 1. Graphs obtained from the evaluation of the electromagnetic wave shielding performance are shown in Figures 5 and 6.

[0115] Comparative Examples 9 to 11 (Sheet Production) Binder 4 and CNT were weighed so that the ratio of CNT to PVA was the amount shown in Table 1, and these were mixed to obtain a mixed aqueous dispersion. This amount of CNT is the amount of CNT in the CNT / aqueous dispersion. This amount of CNT is the amount of CNT in the CNT / aqueous dispersion. Next, the mixed aqueous dispersion was poured into a disposable dish with an inner diameter of 90 mm and dried for one week in an environment of 10°C and 90% RH to obtain a sheet having the thickness shown in Table 1. The evaluation results of the electromagnetic wave shielding performance and volume resistivity are shown in Table 1. The graph obtained from the evaluation of the electromagnetic wave shielding performance is shown in FIG. 6.

[0116]

[0117] From Table 1, it is found that the binder and the conductive material are included, and the surface area in the planar direction is 1 mm ２ It can be seen that the molded body containing the composite flakes shown below can shield high-frequency electromagnetic waves while maintaining high electrical resistivity compared to a molded body not containing the composite flakes.

[0118] Experiment B [Example 11, Comparative Example 12] (Sheet Production) Binder 1 and the composite flakes produced in Experiment A were weighed so that the amount of CNT relative to the amount of cellulose nanofiber was the amount shown in Table 2. They were then mixed to obtain a mixed aqueous dispersion. The amount of cellulose nanofiber is the sum of the amount of cellulose nanofiber contained in the composite flake and the amount of cellulose nanofiber in the binder used to produce the molded article. The amount of CNT is the amount of CNT in the CNT / aqueous dispersion. The mixed aqueous dispersion was then poured into a 90 mm inner diameter petri dish and frozen at -45°C for 2 hours to obtain a frozen article. The frozen article was then thawed in a 0.1 mol / L aluminum nitrate aqueous solution to prepare a hydrogel in which the cellulose nanofibers were crosslinked with aluminum ions. The resulting hydrogel was washed with distilled water to remove the aluminum nitrate. The hydrogel was then immersed in 99% by mass ethanol to replace the water with the ethanol solvent, obtaining an alcogel. The resulting alcogel was dried at 80°C under normal pressure for 12 hours to obtain a foam sheet having the thickness shown in Table 2. Comparative Example 1 is a foam sheet produced without using composite flakes. The evaluation results for electromagnetic shielding performance and volume resistivity are shown in Table 2. The graph obtained from the evaluation of electromagnetic shielding performance is shown in Figure 7.

[0119] Comparative Example 13 (Sheet Production) Binder 1 and CNT were weighed so that the ratio of CNT to cellulose nanofiber was as shown in Table 2, and these were mixed to obtain a mixed aqueous dispersion. This amount of cellulose nanofiber is the total amount of cellulose nanofiber contained in the composite flakes and the amount of cellulose nanofiber in the binder used to produce the molded body. The amount of CNT is the amount of CNT in the CNT / aqueous dispersion. Using this mixed aqueous dispersion, a foamed sheet was obtained in the same manner as in Example 14. The evaluation results for electromagnetic wave shielding performance and volume resistivity are shown in Table 2. A graph obtained from the evaluation of electromagnetic wave shielding performance is shown in Figure 7.

[0120] [Example 4, Comparative Example 1] (Production of Sheet) Table 2 also lists the values ​​of Example 4 and Comparative Example 1 in the above-mentioned Experiment A for comparison with the above-mentioned Example 11, Comparative Examples 12 and 13. The evaluation results of the electromagnetic wave shielding performance and volume resistivity are shown in Table 2. In addition, a graph obtained from the evaluation of the electromagnetic wave shielding performance is shown in FIG.

[0121]

[0122] From Table 2, the binder and the conductive material are included, and the surface area in the planar direction is 1 mm ２ The following molded body containing composite flakes can shield high-frequency electromagnetic waves while maintaining high electrical resistivity, but by forming it into a foam, it is possible to further increase the electrical resistivity and further improve the electromagnetic wave shielding performance.

[0123] <Experiment C> [Examples 4 and 11, Comparative Example 4] (Production of Sheet) Table 3 shows the reflectance at a frequency of 300 GHz obtained in the evaluation of the electromagnetic wave shielding performance of each sheet in Examples 4 and 11 and Comparative Examples 4 and 7 described above.

[0124]

[0125] From Table 3, it can be seen that for molded articles containing composite flakes, even if the content of conductive material is the same, by forming them into a foam, the volume resistivity increases and the reflectivity is reduced, improving the electromagnetic wave shielding performance, i.e., the absorption rate can also be improved. For molded articles not containing composite flakes, even if the content of conductive material is the same, by forming them into a foam, the volume resistivity remains unchanged, but the reflectivity is reduced, improving the electromagnetic wave shielding performance, i.e., the absorption rate can also be improved.

[0126] <Experiment D> In each of the above experiments, the hydrogel was crushed using a mixer to produce composite flakes. The sizes of the multiple flakes obtained after crushing times of 1 minute, 5 minutes, and 20 minutes were evaluated, and the results of this evaluation are shown in Table 4. In Experiment D, for each crushing time, 100 composite flakes were randomly selected from the multiple composite flakes obtained, and the size evaluation was performed. The "flake surface area" and "circumscribed circle diameter" shown in Table 4 are average values. The "maximum flake area" refers to the area of ​​the largest surface among the surfaces present on the flake, and the "minimum flake area" refers to the area of ​​the smallest surface among the surfaces present on the flake. The average thickness of the composite flakes used in Experiment D was 4 μm. In Experiment D, the size evaluation was performed using 100 composite flakes randomly selected from the multiple composite flakes obtained for each crushing time. The values ​​shown in Table 4 are average values.

[0127]

Claims

1. A substrate containing binder A and a plurality of conductive materials and having a surface area of ​​1 mm ２ Below is a composite flake.

2. The composite flake of claim 1, wherein the average diameter of the smallest circumscribed circle enclosing the surface shape in the planar direction is 1 μm or more and 1000 μm or less.

3. The composite flake of claim 1 or 2, wherein the binder A comprises cellulose nanofibers.

4. The composite flake described in claim 3, wherein the average fiber diameter of the cellulose nanofibers is 0.25 nm or more and 0.5 μm or less.

5. The composite flake according to claim 1 or 2, comprising at least carbon nanotubes as said conductive material.

6. The composite flake of claim 5, wherein the carbon nanotubes have a length of 0.01 μm or more and 1000 μm or less.

7. The composite flake according to claim 1 or 2, wherein the content of the conductive material in the composite flake is 0.010 mass % or more and 50 mass % or less.

8. The composite flake of claim 1 or 2, having a thickness of 0.01 μm or more and 50 μm or less.

9. Composite flakes containing cellulose nanofibers and carbon nanotubes.

10. A liquid composition comprising the composite flakes according to claim 1 or 2 and a binder B.

11. A molded body comprising the composite flakes according to claim 1 or 2 and a binder B.

12. The molded body according to claim 11, wherein the content of the composite flakes in the molded body is 1% by mass or more and 99% by mass or less.

13. The molded article according to claim 11, having a thickness of 20 μm or more and 5 mm or less.

14. The molded article according to claim 11, which is an electromagnetic wave shielding sheet.

15. The molded article according to claim 11, which is a foam.

16. A method for producing composite flakes, comprising: a composition preparation step of obtaining a liquid composition containing a binder A and a plurality of conductive materials; a freezing step of freezing the liquid composition to obtain a frozen body; and a grinding step of grinding the frozen body.

17. A method for producing composite flakes as described in claim 16, comprising, between the freezing step and the crushing step, a dipping step of dipping the frozen body in a liquid containing a component that crosslinks the binder A.

18. A method for producing a composite flake as described in claim 17, wherein the immersion step includes a process of immersing the frozen body in a liquid other than the liquid containing a component that crosslinks the binder A after removing the liquid containing the component that crosslinks the binder A.

19. A method for producing a molded body, comprising: a composition preparation step of obtaining a liquid composition containing the composite flakes according to claim 1 or 2 and binder B; and a freezing step of freezing the liquid composition to obtain a frozen body.

20. A method for producing a molded body according to claim 19, further comprising, after the freezing step, a dipping step of dipping the frozen body in a liquid containing a component that crosslinks the binder B.

21. The method for producing a molded body according to claim 20, wherein the immersion step includes a process of immersing the frozen body in a liquid other than the liquid containing a component that crosslinks the binder B after removing the liquid.

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