JP2020167269A - Electromagnetic wave absorbing material - Google Patents

Abstract

To provide an electromagnetic wave absorbing material, inexpensive, excellent in electromagnetic wave absorption performance, capable of being formed into a lightweight and easily processable form such as a thin sheet or a coating film.SOLUTION: The electromagnetic wave absorbing material contains flaky carbon with a thickness of 1 to 100 nm and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon. It contains 0.01 to 1.0 pts.mass of an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon with respect to 1 part by mass of the flaky carbon.SELECTED DRAWING: None

Description

The present invention relates to an electromagnetic wave absorbing material.

Metal is often used as a material that reflects electromagnetic waves. However, if it is necessary to prevent malfunction of the millimeter-wave radar for automatic operation, prevent interference between electronic circuits, prevent radiation from an electromagnetic wave source to the outside, such as a power cable, use an electromagnetic wave reflective material that reflects electromagnetic waves. However, an electromagnetic wave absorbing material that absorbs electromagnetic waves is required.

As such an electromagnetic wave absorbing material, ferrite or the like is usually used (see, for example, Patent Document 1), and since it has a large specific gravity, further weight reduction is desired. As an alternative as such an electromagnetic wave absorbing material, carbon microcoils are said to have excellent electromagnetic wave absorbing characteristics (see, for example, Patent Document 2), but they are said to have problems in strength and are expensive. is there.

Against this background, there is a demand for an electromagnetic wave absorbing material that is inexpensive, has excellent electromagnetic wave absorbing performance, is lightweight and has good workability, such as a thin sheet or a coating film.

Japanese Unexamined Patent Publication No. 2006-286729 JP-A-2009-228491

An object of the present invention is to provide an electromagnetic wave absorbing material which is inexpensive, has excellent electromagnetic wave absorbing performance, and can be formed into a lightweight and workable form such as a thin sheet or a coating film.

As a result of diligent research to achieve the above object, the present inventors have obtained a predetermined amount of flaky carbon having a thickness of 1 to 100 nm and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon. It has been found that by containing it, an electromagnetic wave absorbing material which is inexpensive, has excellent electromagnetic wave absorbing performance, and can be formed into a lightweight and processable form such as a thin sheet or a coating film can be obtained. The present inventors have further studied based on the findings and have completed the present invention. That is, the present invention includes the following configurations.

Item 1. It contains flaky carbon having a thickness of 1 to 100 nm and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, and has an affinity for the hydrophilic group and carbon with respect to 1 part by mass of the flaky carbon. An electromagnetic wave absorbing material containing 0.01 to 1.0 parts by mass of an organic compound having a highly reactive hydrophobic group.

Item 2. The hydrophilic group is a general formula (1) to (4):
[In the formula, -OH represents an alcoholic hydroxyl group or a phenolic hydroxyl group. R represents a divalent organic group. X ¹ represents a hydrogen atom, alkali metal, NH ₄ or organic ammonium. X ² represents a hydrogen atom, alkali metal, NH ₄ , organic ammonium or alkyl group. The oxygen atom of the general formula (2) is an ether bond. ]
Item 2. The electromagnetic wave absorbing material according to Item 1, which is at least one kind represented by.

Item 3. Item 2. The electromagnetic wave absorbing material according to Item 1 or 2, wherein the hydrophilic group is a phenolic hydroxyl group and / or a polyoxyethylene group.

Item 4. Item 1 to any one of Items 1 to 3, wherein the hydrophobic group is at least one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, and a polyoxyalkylene group having 3 or more carbon atoms. The electromagnetic wave absorbing material described.

Item 5. Item 2. The electromagnetic wave absorbing material according to any one of Items 1 to 4, wherein the hydrophobic group is an aryl group having two or more aromatic rings.

Item 6. Item 2. The method for producing an electromagnetic wave absorbing material according to any one of Items 1 to 5.
(1) The flaky carbon, an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, and a solvent are contained, and the hydrophilic group and carbon are contained with respect to 1 part by mass of the flaky carbon. A production method comprising a step of removing a solvent from a flaky carbon dispersion containing 0.01 to 1.0 parts by mass of an organic compound having a hydrophobic group having a high affinity.

Item 7. Item 6. The production method according to Item 6, wherein the step of removing the solvent is a step of concentrating the dispersion.

Item 8. Item 6. The production method according to Item 6, wherein the solvent is water.

Item 9. Electromagnetic wave absorption containing the electromagnetic wave absorbing material according to any one of Items 1 to 5 and at least one other material selected from the group consisting of thermosetting resin, thermoplastic resin, rubber and thermoplastic elastomer. Composition.

Item 10. Item 9. The electromagnetic wave according to Item 9, wherein the thermosetting resin is at least one selected from the group consisting of epoxy resin, thermosetting polyimide resin, phenol resin, melamine resin, unsaturated polyester resin, alkyd resin and polyurethane resin. Absorption composition.

Item 11. An electromagnetic wave absorption dispersion in which the electromagnetic wave absorption composition according to Item 9 or 10 is dispersed in an organic solvent.

Item 12. Item 9. An electromagnetic absorption sheet containing a cured product of the electromagnetic wave absorbing composition according to Item 9 or 10, wherein the other material is a thermosetting resin and / or a thermoplastic resin.

Item 13. Item 2. The electromagnetic wave absorbing sheet according to Item 12, which has a thickness of 2000 μm or less.

Item 14. An electromagnetic wave absorbing fiber material in which the electromagnetic wave absorbing material according to any one of Items 1 to 5 is supported on the surface of the fiber.

Item 15. Item 2. The electromagnetic wave absorbing fiber material according to Item 14, wherein the fiber is composed of at least one selected from the group consisting of polyamide resin, polyester resin, acrylic resin, polyolefin resin, polyurethane resin, cellulose, plant, glass and carbon. ..

Item 16. Item 12. The electromagnetic wave absorbing sheet according to Item 12 or 13, which has a surface resistivity of 10 to 10000 Ω / □ and a volume resistivity of 1 to 1000 Ωcm.

Item 17. Item 14. The electromagnetic wave absorbing fiber material according to Item 14 or 15, which has a surface resistivity of 10 to 10000 Ω / □ and a volume resistivity of 1 to 1000 Ωcm.

According to the present invention, it is possible to obtain an electromagnetic wave absorbing material which is inexpensive, has excellent electromagnetic wave absorbing performance, and can be formed into a lightweight and processable form such as a thin sheet or a coating film.

When the content of the organic compound having a hydrophobic group having a high affinity with a hydrophilic group and carbon is small (when the surface of the flaky carbon is coated with an organic compound having a hydrophobic group having a high affinity with a hydrophilic group and carbon) The configuration of the electromagnetic wave absorbing material of the present invention is shown. The present invention when the content of an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is high (when flaky carbon is dispersed in an organic compound having a hydrophobic group having a high affinity for carbon). The composition of the electromagnetic wave absorbing material is shown.

As used herein, "contains" is a concept that includes any of "comprise," "consist essentially of," and "consist of." Further, in the present specification, when the numerical range is indicated by "A to B", it means A or more and B or less.

Hereinafter, embodiments of the present invention will be described, but various modifications of the embodiments and details are possible without departing from the spirit and scope of the claims.

1. 1. Electromagnetic wave absorbing material The electromagnetic wave absorbing material of the present invention contains a flaky carbon having a thickness of 1 to 100 nm and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, and 1 part by mass of the flaky carbon. On the other hand, it contains 0.01 to 1.0 parts by mass of an organic compound having a hydrophobic group having a high affinity with the hydrophilic group and carbon.

(1-1) Flake carbon As the flake carbon, the thinner the flake carbon, the better the electromagnetic wave absorption performance, the surface resistivity and the volume resistivity are in an appropriate range, and the light weight and workability like a thin sheet or a coating film are good. It is preferable because it can be formed into a form, but its thickness is 1 to 100 nm, preferably 1 to 20 nm. Similarly, the content ratio of flaky carbon having a thickness of 1 to 10 nm is preferably 80% or more, more preferably 90% or more, assuming that the total number of flaky carbons is 100%. That is, although flaky carbon having a large thickness may be contained, the thickness of a large number of flaky carbons is preferably 10 nm or less. The thickness of the flaky carbon is measured by observation with a transmission electron microscope (TEM).

The thinner the flaky carbon, the better the electromagnetic wave absorption performance, the surface resistivity and the volume resistivity are also in an appropriate range, and it is possible to form a lightweight and workable form such as a thin sheet or a coating film. Preferably, flaky carbon having a layered structure in which 300 layers or less (that is, 1 to 300 layers) of graphene are laminated is preferable, and flaky carbon having a layered structure in which 1 to 60 layers of graphene are laminated is more preferable. Similarly, the content ratio of flaky carbon having 1 to 30 layers is preferably 80% or more, more preferably 90% or more, assuming that the total number of flaky carbons is 100%. That is, although flaky carbon having a large thickness may be contained, the thickness of a large number of flaky carbons is preferably 30 layers or less. The lamination of flaky carbon is calculated from the thickness measured by observation with a transmission electron microscope (TEM).

Since flaky carbon usually has a planar shape having many convex and concave angles, it is difficult to unconditionally specify a size other than the thickness. In the present specification, the distance between the most distant convex angles in one flaky carbon is defined as the size of the flaky carbon.

The size of such flaky carbon is preferably 20 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more. By using flaky carbon of such a size, the electromagnetic wave absorption performance is particularly excellent, the surface resistivity and volume resistivity can be easily set in an appropriate range, and it is lightweight and has good workability such as a thin sheet or a coating film. Easy to form. The larger the size of the flaky carbon, the better the electromagnetic wave absorption performance, the surface resistivity and the volume resistivity can be easily set in an appropriate range, and the form is lightweight and has good workability such as a thin sheet or a coating film. The upper limit of the size is not limited, but is usually 100 μm because it is possible and preferable. The size of flaky carbon is measured by observation with a transmission electron microscope (TEM).

In the electromagnetic wave absorbing material of the present invention, the content of flaky carbon is not particularly limited, but from the viewpoints of dispersibility in resin and solvent, electromagnetic wave absorbing performance, surface resistivity, volume resistivity, light weight, processability, etc. The total amount of the electromagnetic wave absorbing material of the present invention is 100% by mass, preferably 20 to 99.5% by mass, and more preferably 33 to 99.2% by mass.

(1-2) Organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon In the present invention, the graphene structure is maintained by using an organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon. The flaky carbon in the electromagnetic wave absorbing material of the present invention can be maintained in a uniformly dispersed state without agglomerating the flaky carbon. An organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can also function as a dispersant for uniformly dispersing flaky carbon.

The organic compound having such a hydrophilic group and a hydrophobic group having a high affinity for carbon is not particularly limited, and various organic compounds (particularly water-soluble compounds) that can function as a dispersant for flaky carbon are used. Can be used.

Among them, the hydrophobic group contained in the organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon is not particularly limited, but is an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, and a poly having 3 or more carbon atoms. An oxyalkylene group or the like is preferable. An organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can contain one or more such hydrophobic groups. When a plurality of hydrophobic groups are used, the same hydrophobic group may be used, a plurality of the same hydrophobic group may be used, or a plurality of different hydrophobic groups may be used.

The alkyl group may be a chain alkyl group or a branched chain alkyl group, but a chain alkyl group is preferable from the viewpoint of affinity with carbon. The number of carbon atoms of the alkyl group is preferably 6 or more, more preferably 8 to 28, and even more preferably 10 to 22 from the viewpoint of affinity with carbon. Examples of such an alkyl group include a hexyl group, an octyl group, a decyl group, an undecyl group, a dodecyl group (or lauryl group), a tridecyl group, a tetradecyl group (or myristyl group), a pentadecyl group, a hexadecyl group (or a cetyl group), and the like. Examples thereof include an octadecyl group and an icosyl group.

This alkyl group may or may not have a substituent. Examples of such a substituent include a cycloalkyl group, an aryl group, an aralkyl group and the like. Examples of the cycloalkyl group and the aryl group will be described later.

As the aralkyl group as the substituent of the alkyl group, an aralkyl group having 7 to 14 carbon atoms having an aryl group and an alkyl group having 1 to 6 carbon atoms, which will be described later, is preferable, and specifically, a benzyl group, a phenethyl group and the like are used. preferable.

The substituent is not limited to the above, and may have a group derived from a fluorene structure (fluorenyl group or the like). In particular, when water solubility is important, a phenyl group or the like is preferable as a substituent, and when compatibility with flaky carbon is important, a naphthyl group, a fluorenyl group or the like is preferable as a substituent.

The alkenyl group preferably has 4 or more carbon atoms, more preferably 6 to 100 carbon atoms, and even more preferably 8 to 30 carbon atoms from the viewpoint of affinity with carbon and water solubility. Examples of such an alkenyl group include an oleyl group and a linoleyl group.

This alkenyl group may or may not have a substituent. Examples of such a substituent include an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group and the like. Examples of the aralkyl group include those described above, and examples of the cycloalkyl group and the aryl group include those described below.

As the alkyl group as the substituent of the alkenyl group, an alkyl group having 1 to 6 carbon atoms is preferable, and specifically, a methyl group, an ethyl group, a propyl group, a butyl group, a tert-butyl group and the like are preferable.

The substituent is not limited to the above, and may have a group derived from a fluorene structure (fluorenyl group or the like). In particular, when water solubility is important, a phenyl group or the like is preferable as a substituent, and when compatibility with flaky carbon is important, a naphthyl group, a fluorenyl group or the like is preferable as a substituent.

As the cycloalkyl group, a cycloalkyl group having 5 to 10 carbon atoms (preferably 5 to 8, particularly 5 to 6) is preferable, and specifically, a cyclopentyl group, a cyclohexyl group and the like are preferable.

This cycloalkyl group may or may not have a substituent. Examples of such a substituent include an alkyl group, an aryl group, an aralkyl group and the like.

As the alkyl group as the substituent of the cycloalkyl group, an alkyl group having 1 to 6 carbon atoms is preferable, and specifically, a methyl group, an ethyl group, a propyl group, a butyl group, a tert-butyl group and the like are preferable.

Examples of the aryl group and the aralkyl group as the substituent of the cycloalkyl group include those exemplified above.

The substituent is not limited to the above, and may have a group derived from a fluorene structure (fluorenyl group or the like). In particular, when water solubility is important, a phenyl group or the like is preferable as a substituent, and when compatibility with flaky carbon is important, a naphthyl group, a fluorenyl group or the like is preferable as a substituent.

As the aryl group, an aryl group having 6 to 22 carbon atoms (particularly 6 to 18) is preferable, and any monocyclic aryl group, condensed ring aryl group or polycyclic aryl group can be adopted, for example, a phenyl group, a naphthyl group, etc. Examples thereof include anthrasenyl group, tetrasenyl group, phenanthrenyl group, biphenyl group, terphenyl group, fluorenyl group, acenaphthenyl group, acenaphthylenyl group, pyrenyl group, chrysenyl group, triphenylenyl group and the like. From the viewpoint of affinity with carbon, an aryl group having two or more aromatic rings (condensed aryl group and polycyclic aryl group) is preferable.

This aryl group may or may not have a substituent. Examples of such a substituent include an alkyl group, a cycloalkyl group, an aralkyl group and the like.

As the alkyl group as the substituent of the aryl group, an alkyl group having 1 to 6 carbon atoms is preferable, and specifically, a methyl group, an ethyl group, a propyl group, a butyl group, a tert-butyl group and the like are preferable.

Examples of the cycloalkyl group and the aralkyl group as the substituent of the aryl group include those exemplified above.

The substituent is not limited to the above, and may have a group derived from a fluorene structure (fluorenyl group or the like).

The polyoxyethylene group is usually hydrophilic, but the polyoxyalkylene group having 3 or more carbon atoms, such as a polyoxypropylene group and a polyoxybutylene group, becomes more hydrophobic as the degree of polymerization increases and functions as a hydrophobic group. In particular, a polyoxypropylene group having a degree of polymerization of 4 or more and a polyoxybutylene group having a degree of polymerization of 3 or more are preferable. For example, when polyoxyethylene-polyoxypropylene or polyoxyethylene-polyoxybutylene is used as an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, the polyoxypropylene group and the polyoxybutylene group are also used. Can function as a hydrophobic group.

This polyoxyalkylene group having 3 or more carbon atoms may or may not have a substituent. Examples of such a substituent include an alkyl group, a cycloalkyl group, an aralkyl group, an aryl group and the like.

As the alkyl group as a substituent of the polyoxyalkylene group having 3 or more carbon atoms, an alkyl group having 1 to 6 carbon atoms is preferable, and specifically, a methyl group, an ethyl group, a propyl group, a butyl group and a tert-butyl group. Groups and the like are preferred.

Examples of the cycloalkyl group, the aralkyl group and the aryl group as the substituent of the polyoxyalkylene group having 3 or more carbon atoms include those exemplified above.

The substituent is not limited to the above, and may have a group derived from a fluorene structure (fluorenyl group or the like). In particular, when water solubility is important, a phenyl group or the like is preferable as a substituent, and when compatibility with flaky carbon is important, a naphthyl group, a fluorenyl group or the like is preferable as a substituent.

Examples of such a hydrophobic group include an aryl group and a polyoxyalkylene group having 3 or more carbon atoms from the viewpoints of affinity with carbon, electromagnetic wave absorption performance, surface resistivity, volume resistivity, light weight, processability, and the like. Preferably, an aryl group is more preferable, and an aryl group having two or more aromatic rings (condensed aryl group and polycyclic aryl group) is further preferable. Specifically, a naphthyl group, an anthrasenyl group, a tetrasenyl group, a phenanthrenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, an acenaphthenyl group, an acenaphthylenyl group, a pyrenyl group, a chrysenyl group, a triphenylenyl group, and a polyoxypropylene having a degree of polymerization of 4 or more. A group, a polyoxybutylene group having a degree of polymerization of 3 or more, and the like are preferable.

Further, as the hydrophilic group of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, the solubility of the organic compound having a hydrophobic group having a high affinity for the hydrophilic group and carbon in water can be increased. There is no particular limitation as long as it is, but the water solubility of the organic compound having a hydrophobic group having a high affinity with the hydrophilic group and carbon, the dispersibility of flaky carbon, the electromagnetic wave absorption performance, the surface resistance, the volume resistance, and the light weight From the viewpoint of property, workability, etc., general formulas (1) to (4):
[In the formula, -OH represents an alcoholic hydroxyl group or a phenolic hydroxyl group. R represents a divalent organic group. X ¹ represents a hydrogen atom, alkali metal, NH ₄ or organic ammonium. X ² represents a hydrogen atom, alkali metal, NH ₄ , organic ammonium or alkyl group. The oxygen atom of the general formula (2) is an ether bond. ]
The hydrophilic group represented by is preferable. The organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can contain one or more such hydrophilic groups. When a plurality of hydrophilic groups are used, the same hydrophilic group may be used more than once, a plurality of types of hydrophilic groups represented by the same general formula may be used, or hydrophilicity represented by different general formulas may be used. A plurality of types of groups may be used.

In the general formula (1), -OH may be either an alcoholic hydroxyl group or a phenolic hydroxyl group. Alcohol from the viewpoints of water solubility of organic compounds having hydrophilic groups and hydrophobic groups having high affinity for carbon, dispersibility of flaky carbon, electromagnetic wave absorption performance, surface resistance, volume resistance, light weight, processability, etc. Although a sex hydroxyl group is preferable, when it contains a phenolic hydroxyl group (particularly when it contains a plurality of phenolic hydroxyl groups), it inevitably contains a benzene ring having excellent hydrophobicity, and as a whole, it has electromagnetic absorption performance and light weight. It is preferable because it is excellent in workability and the surface resistance and volume resistance can be easily set in an appropriate range.

In particular, when it has a benzenetriol structure (pyrogallol structure, hydroxyquinol structure, phloroglucinol structure, etc.), a benzenediol structure (catechol structure, resorcinol structure, hydroquinone structure, etc.), etc. (especially when it has two or more), it absorbs electromagnetic waves. It is particularly excellent in performance, light weight, workability, etc., and it is easy to set the surface resistivity and volume resistivity in an appropriate range. As the organic compound having a hydrophilic group having such a structure and a hydrophobic group having a high affinity for carbon, not only an artificially synthesized compound but also a naturally occurring polyphenol can be used.

Polyphenol is a general term for compounds also called polyphenols, and means a general term for compounds in which two or more hydrogens of aromatic hydrocarbons are substituted with hydroxyl groups, or a mixture thereof. Such polyphenols are not particularly limited, and are, for example, catechin, epicatechin, gallocatechin, epigallocatechin, catechin gallate, epicatechin gallate, gallocatechin gallate, epigallocatechin gallate, quercetin, hesperidin, tannic acid, teaflavin, etc. Examples thereof include procyanidin, leukoanthocyanidin, and rutin. Among these, water solubility of organic compounds having hydrophilic groups and hydrophobic groups having high affinity with carbon, dispersibility of flaky carbon, electromagnetic wave absorption performance, surface resistivity, volume resistivity, light weight, processability, etc. From the viewpoint, tannic acid, catechin and the like are preferable.

Since these polyphenols are present in many plants, the plants may be used as they are, or plant extracts may be used. On the other hand, polyphenol may be purified by a conventional method and used. In particular, the effects of water solubility of an organic compound having a stable hydrophilic group and a hydrophobic group having a high affinity for carbon, dispersibility of flaky carbon, electromagnetic wave absorption performance, light weight, processability, etc. can be obtained, and surface resistivity and surface resistivity and It is preferable to use a purified product (alcohol purified product or the like) because the volume resistivity can be easily set in an appropriate range.

In the general formula (2), the divalent organic group represented by R is not particularly limited, and a divalent hydrocarbon group is preferable. Examples of the divalent hydrocarbon group include an aliphatic hydrocarbon group (alkylene group (or alkylidene group), cycloalkylene group, alkylene (or alkylidene) -cycloalkylene group, bi or tricycloalkylene group, etc.), aromatic hydrocarbon. Examples thereof include a group (arylene group, alkylene (or alkylidene) -arylene group, etc.).

In the general formula (2), as the alkylene group (or alkylidene group) represented by the group R, an alkylene group is preferable, a C _1-8 alkylene group is more preferable, a C _1-4 alkylene group is further preferable, and a C _{2- A 4-} alkylene group is particularly preferable, and a C _2-3 alkylene group is most preferable. Specifically, methylene group, ethylene group, ethylidene group, trimethylene group, propylene group, propyridene group, tetramethylene group, ethylethylene group, butane-2-idene group, 1,2-dimethylethylene group, pentamethylene group, Examples thereof include a pentane-2,3-diyl group.

In the general formula (2), as the cycloalkylene group represented by the group R, a C _5-10 cycloalkylene group is preferable, and a C _5-8 cycloalkylene group is more preferable. Specifically, a cyclopentylene group, a cyclohexylene group, a methylcyclohexanelen group, a cycloheptylene group and the like can be exemplified.

In the general formula (2), as the alkylene (or alkylidene) -cycloalkylene group represented by the group R, an alkylene-cycloalkylene group is preferable, a C _1-6 alkylene-C _5-10 cycloalkylene group is more preferable, and C _{A 1-4} alkylene-C _5-8 cycloalkylene group is more preferred. Specifically, methylene-cyclohexylene group, ethylene-cyclohexylene group, ethylene-methylcyclohexylene group, ethylidene-cyclohexylene group and the like can be exemplified.

In the general formula (2), a norbornane-diyl group or the like can be specifically exemplified as the bi or tricycloalkylene group represented by the group R.

In the general formula (2), the C _6-10 arylene group is preferable as the arylene group represented by the group R. Specifically, a phenylene group, a naphthalene diyl group and the like can be exemplified.

In the general formula (2), as the alkylene (or alkylidene) -arylene group represented by the group R, an alkylene-arylene group is preferable, a C _1-6 alkylene-C _6-20 arylene group is more preferable, and C _1-4. An alkylene-C _6-10 arylene group is more preferable, and a C _1-2 alkylene-phenylene group is particularly preferable. Specifically, a methylene-phenylene group, an ethylene-phenylene group, an ethylene-methylphenylene group, an ethylidene phenylene group and the like can be exemplified.

Of these, a divalent aliphatic hydrocarbon group, particularly an alkylene group (for example, a C _1-4 alkylene group such as a methylene group or an ethylene group) is preferable.

The alkylene (or alkylidene) -cycloalkylene group and the alkylene (alkylidene) -arylene group are -Ra-Rb- (in the formula, Ra is an alkylene bonded to a separate oxygen atom in the general formula (2). A group or an alkylidene group, Rb indicates a cycloalkylene group or an arylene group).

The hydrophilic group represented by the general formula (2) is not particularly limited, and for example, -OC ₂ H ₄ O-, -OC ₃ H ₆ O-, -OCH ₂ O- and the like can be used. .. Those having a plurality of these (preferably 3 to 100) can also be preferably used, and for example, a polyoxymethylene group, a polyoxyethylene group, a polyoxypropylene group and the like can be used. In particular, when the hydrophilic group represented by the general formula (2) has a structure in which three or more are polymerized, the more carbons in R (for example, three or more carbon atoms), the lower the hydrophilicity and the more hydrophobic, so the degree of polymerization is high. -OC ₂ H ₄ O- and -OCH ₂ O-, which can maintain hydrophilicity even when increased, are preferable.

When it has such a hydrophilic group represented by the general formula (2), particularly a polyoxyalkylene group, and further a polyoxyethylene group, it is particularly excellent in electromagnetic wave absorption performance, light weight, workability, etc., and has surface resistivity and surface resistivity. The volume resistivity is also easy to be in an appropriate range.

In the general formula (3), the alkali metal represented by X ¹ is not particularly limited, and examples thereof include sodium, potassium, lithium and the like.

In the general formula (3), quaternary ammonium is preferable as the organic ammonium represented by X ¹ , and tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium and the like can be preferably used.

The hydrophilic group represented by the general formula (3) is not particularly limited, but is, for example, −SO ₃ ⁻ H ⁺ , −SO ₃ ⁻ Na ⁺ , −SO ₃ ⁻ K ⁺ , −SO ₃ ⁻ Li. ⁺ , -SO ₃ ^- NH ₄ ⁺ , -SO ₃ ^- N (CH ₃ ) ₄ ⁺ , -SO ₃ ^- N (C ₂ H ₅ ) ₄ ⁺ , -SO ₃ ^- N (C ₃ H ₇ ) ₄ ⁺ , −SO ₃ ⁻ N (C ₄ H ₉ ) ₄ ^{+ and the} like can be mentioned.

In the general formula (4), examples of the alkali metal and organic ammonium represented by X ² include those exemplified above.

In the general formula (4), the alkyl group represented by X ² may be a chain alkyl group or a branched chain alkyl group, but has carbon affinity, electromagnetic wave absorption performance, surface resistivity, volume resistivity, and the like. A chain alkyl group is preferable from the viewpoint of light weight, processability and the like. The number of carbon atoms of the alkyl group is preferably 1 to 2 from the viewpoint of affinity with carbon, electromagnetic wave absorption performance, surface resistivity, volume resistivity, light weight, workability and the like.

The hydrophilic group represented by the general formula (4) is not particularly limited, but is, for example, -COOH, -COONa, -COOK, -COOLi, -COONH ₄ , -COON (CH ₃ ) ₄ , -COON. (C ₂ H ₅ ) ₄ , -COON (C ₃ H ₇ ) ₄ ⁺ , -COON (C ₄ H ₉ ) ₄ ^{+ and the} like can be mentioned.

Among these hydrophilic groups, the water solubility of organic compounds having a hydrophilic group and a hydrophobic group having a high affinity for carbon, stability regardless of pH, dispersibility of flaky carbon, electromagnetic wave absorption performance, surface resistance, and volume resistance From the viewpoint of rate, light weight, workability and the like, the hydrophilic group represented by the general formula (1) or (2) is preferable.

However, when the water-soluble compound has a plurality of the same hydrophilic groups represented by the general formula (2), that is, has a polymerized structure, the hydrophilicity of the water-soluble compound increases as the degree of polymerization increases when the number of carbon atoms is 2 or less, but the number of carbon atoms is 3. In the above cases, the hydrophobicity may increase as the degree of polymerization increases.

Further, in the present invention, when a nonionic material (nonionic surfactant or the like) is used as the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, the HLB value thereof is the hydrophilic group and the HLB value. From the viewpoints of water solubility of an organic compound having a hydrophobic group having a high affinity with carbon, dispersibility of flaky carbon, electromagnetic wave absorption performance, surface resistance, volume resistance, light weight, processability, etc., 12 or more is preferable. 13 to 19 are more preferable. When the hydrophobic groups are the same (when the affinity with flaky carbon is about the same), the higher the HLB value is, the more preferable.

The organic compound having a hydrophilic group satisfying the above conditions and a hydrophobic group having a high affinity with carbon is not particularly limited, but an aromatic water-soluble compound may be used, or a non-aromatic water-soluble compound may be used. May be used, but aromatic water-soluble compounds are preferred. Examples of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon include polyoxyethylene lauryl ether, polyoxyethylene decyl ether, polyoxypropylene decyl ether, polyoxyethylene lauryl ether, and polyoxyethylene naphthyl ether. Polyoxypropylene lauryl ether, polyoxypropylene naphthyl ether, polyoxyethylene myristyl ether, polyoxypropylene myristyl ether, polyoxyethylene cetyl ether, polyoxypropylene cetyl ether, polyoxyethylene octylphenyl ether, polyoxypropylene octylphenyl ether, Polyoxyethylene undecylphenyl ether, polyoxypropylene undecylphenyl ether, polyoxyethylene tridecylphenyl ether, polyoxypropylene tridecylphenyl ether, polyoxyethylene pentadecylphenyl ether, polyoxypropylene pentadecylphenyl ether, polyoxy Ethylene polyoxypropylene glycol, polyoxypropylene polyglyceryl ether, sodium colate, potassium colate, sodium dodecylsulfonate, potassium dodecylsulfonate, sodium dilauroyl glutamate lysine, potassium dilauroyl glutamate lysine, decaglycerin laurate ester, n- Decyl alcohol, catechin (polyphenol derived from green tea, etc.), epicatechin, galocatechin, epigalocatechin, catechin gallate, epicatechin gallate, galocatechin gallate, epigalocatechin gallate, quercetin, hesperidin, tannic acid, theaflavin, procyanidin, leukoanthocyanidin, Rutin and the like can be mentioned.

Examples of the organic compound having such a hydrophilic group and a hydrophobic group having a high affinity for carbon include Emargen 103, Emargen 104P, Emargen 105, Emargen 106, Emargen 108, Emargen 109P, Emargen 120, Emargen 123P, and Emargen 130K. Emalgen 147, Emalgen 150, Emalgen 210P, Emalgen 220 (above, polyoxyethylene alkyl ethers manufactured by Kao Co., Ltd.), Triton X-100, Triton X-114, Triton X-305, Triton X-405 (above, Dow) Chemical company's polyoxyethylene octylphenyl ethers), Neugen EN, Neugen EN-10 (above, polyoxyethylene naphthyl ether manufactured by Daiichi Kogyo Seiyaku Kogyo Co., Ltd.), tannic acid, catechins (epicatechin, epigallocatechin gallo) Catechin, epicatechin gallate. Epigallocatechin gallate, catechin, galocatechin, catechin gallate, galocatechin gallate, etc., including polyphenols), epigallocatechin gallate, epigallocatechin gallate, persimmon astringent (including tannins), etc. can be used.

The content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon in the electromagnetic wave absorbing material of the present invention is not particularly limited, but the dispersibility of flaky carbon, electromagnetic wave absorbing performance, surface resistivity, and volume resistance. From the viewpoint of resistivity, light weight, workability, etc., the total amount of the electromagnetic wave absorbing material of the present invention is 100% by mass, preferably 0.5 to 80% by mass, and more preferably 0.8 to 67% by mass. Further, the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon in the electromagnetic wave absorbing material of the present invention is 0.01 to 1.0 part by mass with respect to 1 part by mass of flaky carbon. It is preferably 0.02 to 0.8 parts by mass. If the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon is less than 0.01 parts by mass, the surface resistivity and the volume resistivity cannot be in an appropriate range, and the electromagnetic wave absorption performance is also improved. Inferior. Further, if the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon exceeds 1.0 part by mass, it becomes difficult to make a powder, and it becomes difficult to handle such as light weight. When the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon is small, the electromagnetic wave absorbing material of the present invention has a hydrophobic group having a high affinity with the hydrophilic group and carbon on the surface of the flaky carbon. It has a structure in which an organic compound having a group is coated (Fig. 1). On the other hand, when the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is large, the electromagnetic wave absorbing material of the present invention is in the form of flakes in the organic compound having a hydrophobic group having a high affinity for carbon. It has a structure in which carbon is dispersed (Fig. 2). In either case, an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is interposed around the flaky carbon to suppress aggregation of the flaky carbon, which is particularly excellent in electromagnetic wave absorption performance and surface resistivity. The ratio and volume resistivity can be easily set in an appropriate range, and a material such as a thin sheet or a coating film that can be easily formed into a lightweight and easily processable form can be obtained.

(1-3) Other components In the electromagnetic wave absorbing material of the present invention, other components may be contained in addition to flaky carbon and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon. Examples of such other components include carbon microcoils, carbon fibers (particularly carbon nanofibers having a fiber diameter of 500 nm or less), activated charcoal, carbon black (acetylene black, oil furnace black, etc .; particularly highly conductive and specific surface area). Large Ketjen Black), glassy carbon, carbon microcoil, fullerene, biomass-based carbon materials (bagas, sorghum, wood chips, scraps, bamboo, bark, rice straw, paddy husks, coffee husks, tea husks, tea leaves, rice bran, Made from pulp waste, etc .; carbon fiber, etc. manufactured from lignin), cellulose nanofiber, boron nitride, molybdenum compound (molybdenum disulfide, organic molybdenum, etc.), tungsten disulfide, fluororesin (polytetrafluoroethylene (PTFE)) ), Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), etc.), melamine cyanurate, phthalocyanine, lead oxide, calcium fluoride, layered minerals (mica, talc, etc.), etc., do not impair the effects of the present invention. It can also be used in a range.

However, the content of other components is particularly excellent from the viewpoint of excellent electromagnetic wave absorption performance, easy to set the surface resistivity and volume resistivity in an appropriate range, and easy to form a lightweight and workable form such as a thin sheet or a coating film. Is preferably small, 0.01 to 10% by mass is preferable, and 0.02 to 5% by mass is more preferable, with the total amount of the electromagnetic wave absorbing material of the present invention being 100% by mass.

The shape of the electromagnetic wave absorbing material of the present invention is not particularly limited, and examples thereof include a coating film and a sheet.

As described above, the electromagnetic wave absorbing material of the present invention has excellent electromagnetic wave absorbing performance, can have a surface resistivity and a volume resistivity in an appropriate range, and is a lightweight and easily processable form such as a thin sheet or a coating film. It is a material that can be made into.

Such an electromagnetic wave absorbing material of the present invention includes a noise suppression sheet inside an electronic device (particularly when the electromagnetic wave source is inside to prevent electromagnetic wave emission and interference), a radio wave absorber for preventing malfunction of automatic operation, and the like. It can be used for various purposes.

2. Method for manufacturing electromagnetic wave absorbing material The electromagnetic wave absorbing material of the present invention is, for example,
(1) The flaky carbon, an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, and a solvent are contained, and the hydrophilic group and carbon are added to 1 part by mass of the flaky carbon. It can be produced by a step of removing a solvent from a flaky carbon dispersion containing 0.01 to 1.0 parts by mass of an organic compound having a hydrophobic group having a high affinity.

(2-1) Dispersion (flammed carbon dispersion)
In a dispersion containing a flake carbon, an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, and a solvent (flake carbon dispersion), the flake carbon has an affinity for the hydrophilic group and carbon. The above description can be adopted for organic compounds having a high hydrophobic group. Further, the flaky carbon dispersion may contain the above-mentioned other components, if necessary.

This flaky carbon dispersion may be formed as a dispersion liquid or as a coating film on a substrate. At this time, as the solvent used for producing the flaky carbon dispersion (flaky carbon dispersion liquid or flaky carbon coating film), the dispersibility of the flaky carbon, the electromagnetic wave absorption performance of the obtained electromagnetic wave absorbing material, and the like. From the viewpoints of surface resistivity, volume resistivity, light weight, processability, etc., it is preferable to use water as the main solvent.

The content of water in the solvent used is not particularly limited, but from the viewpoints of dispersibility of flaky carbon, electromagnetic wave absorption performance in the obtained electromagnetic wave absorbing material, surface resistivity, volume resistivity, light weight, workability, etc. With the total amount of the solvent as 100% by mass, 70% by mass or more (70 to 100% by mass) is preferable, and 75 to 100% by mass is more preferable.

In the present invention, only water may be used as the solvent, and an organic solvent may not necessarily be used, but an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can be added to water. In order to further improve the solubility, alcohols such as methanol, ethanol, 2-propanol and tert-butyl alcohol; glycols such as ethylene glycol; glycerin; and organic solvents such as 2-methoxyethanol may be used.

The content of the organic solvent in the solvent used is the solubility of an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, the dispersibility of flaky carbon, the electromagnetic wave absorption performance in the obtained electromagnetic wave absorbing material, and the surface resistivity. From the viewpoint of volume resistivity, light weight, processability, etc., the total amount of the solvent is 100% by mass, preferably 30% by mass or less (0 to 30% by mass), and more preferably 5 to 25% by mass.

In the above-mentioned flaky carbon dispersion, the content of flaky carbon is not particularly limited, but from the viewpoint of facilitating the composition of the electromagnetic wave absorbing material of the present invention, the total amount of the flaky carbon dispersion is 100% by mass and 20% by mass. The following is preferable, 0.0001 to 15% by mass is more preferable, and 0.001 to 10% by mass is further preferable. Similarly, the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is not particularly limited, but the total amount of the flaky carbon dispersion is easily obtained from the viewpoint of easily forming the composition of the electromagnetic wave absorbing material of the present invention. Is 100% by mass, 0.00001 to 40% by mass is preferable, 0.0001 to 15% by mass is more preferable, and 0.001 to 10% by mass is further preferable. Similarly, the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon in the flaky carbon dispersion is 1 part by mass of the flaky carbon from the viewpoint that the composition of the electromagnetic wave absorbing material of the present invention can be easily obtained. On the other hand, 0.01 to 1.0 parts by mass is preferable, and 0.02 to 0.8 parts by mass is more preferable. Further, the content of the solvent is not particularly limited, but from the viewpoint that the composition of the electromagnetic wave absorbing material of the present invention can be easily obtained, the total amount of the flaky carbon dispersion is 100% by mass, and 40 to 99.9998% by mass is preferable. ~ 99.998% by mass is more preferable, and 85 to 99.98% by mass is further preferable.

(2-2) Method for producing flaky carbon dispersion In the present invention, the method for producing the flaky carbon dispersion is not particularly limited, and has high affinity for flaky carbon, hydrophilic groups and carbon with respect to the solvent. An organic compound having a hydrophobic group can also be added. Specifically, flaky carbon can be added to a dispersion of an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, or a dispersion of flaky carbon having an affinity for a hydrophilic group and carbon. It is also possible to add an organic compound having a high hydrophobic group. Further, flaky carbon and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can be simultaneously added to the solvent.

However, the dispersibility of flaky carbon is further improved to make it difficult to aggregate, the electromagnetic wave absorbing performance, light weight and workability of the obtained electromagnetic wave absorbing material of the present invention are further improved, and the surface resistance and volume resistance are further moderated. From the viewpoint of adjusting to a wide range, a carbonaceous material having a layered structure between a rotating rotating disk and a disk installed substantially parallel to the rotating disk, a hydrophilic group, and a hydrophobic substance having a high affinity for carbon. A composition containing an organic compound having a group is installed, and shearing is applied to the carbonaceous material in the composition while adjusting the shortest distance between the rotating disk and the disk to be 200 μm or less. Is preferable (grinding method).

Further, the flaky carbon dispersion is subjected to a pressure treatment of 30 MPa or more on a composition containing a carbonaceous material having a layered structure and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon. It can also be preferably produced (high pressure dispersion method).

The grinding method is most preferable from the viewpoints of dispersibility of flaky carbon, electromagnetic wave absorption performance of the obtained electromagnetic wave absorbing material of the present invention, surface resistivity, volume resistivity, light weight, workability, and the like.

Conventionally, when flaky carbon is produced by a wet method, an aqueous dispersion containing an oxide of flaky carbon and an aqueous solvent has been subjected to a reduction treatment, but it is difficult to maintain the graphene structure by this method. At the same time, it was difficult to obtain a flaky carbon aqueous dispersion because the obtained flaky carbon aggregated violently. There was also a problem from the viewpoint of safety. On the other hand, in the present invention, by using an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, the flaky carbon maintaining the graphene structure is uniformly dispersed without agglomeration (flaky carbon). The flaky carbon can be obtained from the dispersion), the obtained flaky carbon is not easily destroyed, the flaky carbon can be obtained in a short time, and the lumps that have failed to be peeled off are hard to remain. At this time, the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can also function as a dispersant for uniformly dispersing flaky carbon.

Further, according to the shearing method, since the direction in which the force is applied is parallel to the plane direction of the carbonaceous material having a layered structure and the processing is performed in a narrow space, it is different from the conventional manufacturing method by high-speed stirring, ultrasonic treatment, etc. In comparison, flaky carbon with less fracture and a larger size (for example, flaky carbon with a size of 1 μm or more) can be obtained, and the peeling efficiency is good and the treatment is performed in a short time (small number of passes). In addition to being able to do so, it is difficult for thick lumps that have failed to peel off to remain.

Carbonaceous material having a layered structure The carbonaceous material having a layered structure is not particularly limited, and examples thereof include natural graphite, artificial graphite, expanded graphite, earthy graphite, and graphite oxide. As the graphite oxide, for example, graphite oxidized by one or more kinds of oxidizing agents such as sulfuric acid, nitric acid, potassium permanganate, and hydrogen peroxide can be used. For example, when graphite oxide is obtained by the Hammers method, the graphite is immersed in concentrated sulfuric acid, potassium permanganate is added to oxidize the graphite, and then the reaction product is quenched with dilute sulfuric acid and / or hydrogen peroxide. After that, by washing with distilled water or the like, oxygen atoms are bonded to carbon atoms, and oxygen atoms are introduced between the layers to obtain graphite oxide.

Among them, in the case of obtaining highly pure flaky carbon containing no heteroatoms such as oxygen, it is preferable to use graphite as a raw material, and natural graphite and expanded graphite are more preferable. When expanded graphite is used, it is preferable to use expanded graphite with less oxidation of the graphene structure. When expanded graphite is used, it may be used after being heat-treated at about 300 to 1000 ° C. for about 10 seconds to 5 hours. This makes it possible to obtain expanded graphite that has been appropriately expanded.

Further, when importance is attached to ease of production, graphite oxide may be used. By using graphite oxide, solvent molecules are easily inserted between the layers, it is easy to exfoliate only in the layer direction, and the thinning efficiency and dispersibility are improved, so that the treatment time can be shortened. is there. However, when graphite oxide is used, a reduction treatment is required later, and from the viewpoint of maintaining the graphene structure, conductivity and strength, other materials (natural graphite, artificial graphite, expanded graphite, earthy graphite) Is preferable.

On the other hand, it is also possible to use earth-like graphite in order to further improve the dispersibility. However, from the viewpoint of crystallinity, purity and structure maintenance, other materials (natural graphite, artificial graphite, expanded graphite, graphite oxide) are preferable.

Further, when the crystallinity, strength, structure maintenance and the like of the obtained flaky carbon are emphasized, artificial graphite can also be used.

In the present invention, the content of the carbonaceous material having a layered structure in the composition containing the carbonic material having a layered structure and the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is not particularly limited. The total amount of the composition used for producing the flaky carbon dispersion is 100% by mass, preferably 20% by mass or less, more preferably 0.0001 to 15% by mass, further preferably 0.001 to 10% by mass. preferable. As for the content of the carbonaceous material having a layered structure, the thinner the material, the more likely it is that flaking (delamination) occurs, so that flaky carbon can be obtained more efficiently, and the number of treatments tends to be reduced. There is a tendency that it is easy to perform shearing treatment while maintaining the viscosity appropriately. On the other hand, the higher the content of the carbonaceous material having a layered structure, the more excellent the productivity. Therefore, from the viewpoint of balancing the efficiency of flaking, viscosity, productivity, etc., it is preferable to appropriately set the content of the carbonaceous material having a layered structure. When a carbonaceous material dispersion is used, it is preferable that the content of the carbonaceous material having a layered structure in the flaky carbon dispersion is within the above range.

Organic compound having a hydrophobic group having a high affinity with a hydrophilic group and carbon As the organic compound having a hydrophobic group having a high affinity with a hydrophilic group and carbon, the above-mentioned ones can be adopted.

In the present invention, the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon in the composition used for producing the flaky carbon dispersion is not particularly limited, but the flaky carbon dispersion is not particularly limited. With the total amount of the composition used for producing the above as 100% by mass, 0.00001 to 40% by mass is preferable, 0.0001 to 15% by mass is more preferable, and 0.001 to 10% by mass is further preferable. On the other hand, in the present invention, the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon in the composition used for producing the flaky carbon dispersion is a carbonaceous material 1 having a layered structure. 0.01 to 1.0 parts by mass is preferable, and 0.02 to 0.8 parts by mass is more preferable with respect to parts by mass. As for the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, the thinner the content, the larger the content of the carbonaceous material having a relatively layered structure, and the electromagnetic wave absorbing material of the present invention obtained. The electromagnetic wave absorption performance, light weight, and workability are easily improved, the surface resistivity and volume resistivity are easily adjusted within an appropriate range, and the treatment is inexpensive. On the other hand, the higher the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, the more likely it is that flaking (delamination) occurs, so flaky carbon tends to be obtained more efficiently. As the viscosity increases, the flaking efficiency may decrease. Therefore, from the viewpoint of the balance of electromagnetic wave absorption performance, surface resistivity, volume resistivity, light weight, processability, etc. of the obtained electromagnetic wave absorbing material of the present invention, an organic having a hydrophilic group and a hydrophobic group having a high affinity with carbon. It is preferable to appropriately set the content of the compound. When a carbonaceous material dispersion is used in this production method, the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon in the carbonaceous material dispersion is within the above range. Is preferable.

Solvent In the above-mentioned method for producing a flaky carbon dispersion, as described above, a composition containing a carbonaceous material having a layered structure and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is used. , It is preferable to perform a specific treatment, but the sharding efficiency of the carbonaceous material having a layered structure, the electromagnetic wave absorption performance of the obtained electromagnetic wave absorbing material of the present invention, the surface resistance, the volume resistance, the light weight, the workability, etc. From the above viewpoint, it is preferable to perform a specific treatment on a carbonaceous material dispersion containing a carbonaceous material having a layered structure and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon.

The carbonaceous material dispersion may be formed as a dispersion liquid or as a coating film on a substrate.

At this time, the above-mentioned solvent can be adopted as the solvent used for producing the carbonaceous material dispersion (carbonaceous material dispersion liquid or carbonaceous material coating film).

In the present invention, when a specific treatment is carried out using a carbonaceous material dispersion using a solvent, the total amount of the solvent in the carbonaceous material dispersion is not particularly limited, but the carbonic material having a layered structure is fragmented. From the viewpoint of efficiency, solubility of an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, etc., the total amount of the carbonaceous material dispersion is 100% by mass, preferably 40 to 99.9998% by mass, and 63 to 99%. .998% by mass is more preferable, and 85 to 99.98% by mass is further preferable.

In the present invention, when a specific treatment is carried out using a carbonaceous material dispersion using a solvent, the carbonaceous material dispersion has a layered structure on an organic compound dispersion having a hydrophilic group and a hydrophobic group having a high affinity for carbon. A carbonaceous material having a layered structure may be charged, or an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon may be charged into the carbonaceous material dispersion having a layered structure. Further, a carbonaceous material having a layered structure and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon may be simultaneously added to the solvent.

Other Ingredients In the present invention, the composition containing a carbonaceous material having a layered structure and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon (for example, a carbonaceous material dispersion) may be used. Ingredients may be included. As a result, these other components can be contained in the finally obtained flaky carbon dispersion and the electromagnetic wave absorbing material. As such other components, those described above can be adopted and may be used as long as the effects of the present invention are not impaired. However, from the viewpoint of easily obtaining an electromagnetic wave absorbing material having particularly excellent electromagnetic wave absorbing performance, surface resistivity, volume resistivity, light weight, workability, etc., it is preferable that the content of other components is small, and the carbonaceous material is dispersed. Assuming that the total amount of the body is 100% by mass, 0.00001 to 5% by mass is preferable, and 0.0001 to 2% by mass is more preferable.

Shearing (grinding method)
In the present invention, when the grinding method is adopted, as described above, a carbonaceous material having a layered structure, a hydrophilic group and carbon are provided between the rotating rotating disk and the disk installed substantially parallel to the rotating disk. A composition containing an organic compound having a hydrophobic group having a high affinity with the above is installed, and the carbonaceous material in the composition is adjusted so that the shortest distance between the rotating disk and the disk is 200 μm or less. On the other hand, it is preferable to perform a process of applying shear. When a carbonaceous material dispersion is used, the carbonaceous material dispersion is installed between the rotating rotating disk and the disk installed substantially parallel to the rotating disk, and the rotating disk and the above-mentioned rotating disk are installed. It is preferable to perform a treatment of applying shear to the carbonaceous material in the carbonaceous material dispersion while adjusting the shortest distance from the board to 200 μm or less.

The graphene structure may not be maintained depending on the conditions because the carbonaceous material having a layered structure is atomized by the shearing treatment, but the carbonaceous material having a layered structure is efficiently sliced. It is possible to reduce the processing time. The rotating disk and the disk when performing such a shearing process are installed substantially in parallel, but they do not have to be strictly parallel. Specifically, the angle formed by the axis perpendicular to the rotating disk and the axis perpendicular to the disk is preferably 10 ° or less, and more preferably 5 ° or less. It is most preferable that the axis perpendicular to the rotating disk and the axis perpendicular to the disk are strictly parallel. The shortest distance between the two surfaces when performing such a shearing treatment is not particularly limited as long as the carbonaceous material having a layered structure can be sufficiently thinned, but is preferably 200 μm or less. ~ 50 μm is more preferable, and 2 to 30 μm is even more preferable. Although the rotating disk and the disk are installed substantially in parallel, the distance between the rotating disk and the disk may differ depending on the location. In this case, the shortest distance between the rotary disc and the disc means the distance of the shortest portion of the distance between the rotary disc and the disc. Further, it is not always necessary to leave the rotary disk and the disk apart in advance, a material to be processed may be sandwiched between the rotary disk and the disk, and the rotary disk and the disk may be brought into contact with each other. By sandwiching the carbonaceous material having a layered structure, the space between the rotating disk and the disk may be widened. Such a shearing process may be performed by using a stone mill, a vibrating mixer, a spin coater, a grinder, or the like, as long as there is a mechanism for rotating a disk-shaped object.

The sizes of the rotating disk and the disk that can be used at this time are not particularly limited, and are preferably 5 to 500 mm, more preferably 10 to 200 mm. The number of rotations of the turntable during the shearing treatment is not particularly limited, and is preferably in the range where the carbonaceous material having a layered structure can be sufficiently thinned, for example, 1000 to 10000 ppm. , 2000-5000 ppm is more preferable.

By performing such a shearing treatment, the plate and the carbonic material having a layered structure, and the carbonic material having a layered structure and the carbonic material having a layered structure are brought into contact with each other to form a layered material with respect to the carbonic material having a layered structure. Shear can be applied in the direction parallel to the graphene layer of the carbonaceous material having a structure.

By reducing the shortest distance between the rotating disk and the rotating disk in the shearing process and increasing the rotational speed of the rotating disk, the conditions can be strengthened, and a thin piece of carbonaceous material having a layered structure can be obtained. The conversion can be performed more efficiently, and the processing time can be further reduced. This shearing operation can be performed once or more, preferably three or more times.

The temperature at which the shearing treatment is performed is not particularly limited, and may be a temperature at which the carbonaceous material having a layered structure can be sufficiently thinned, and is 0 ° C. or higher, further 0 to 100 ° C., particularly 20 to 95 ° C. obtain. The temperature at which the shearing treatment is performed is preferably a condition in which the solubility of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon is high, and when the higher the temperature, the higher the solubility, the higher the temperature is, and the cloud point is formed. When a water-soluble compound is used, it is preferable to keep the temperature below the cloud point.

Before performing the above shearing treatment, a stirrer, an ultrasonic disperser, or the like is used in order to bring the carbonaceous material having a layered structure into good contact with the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon. The organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon may be blended on the surface of the carbonaceous material having a layered structure by stirring in advance before preparing the composition.

In the present invention, when graphite oxide is used as the carbonaceous material having a layered structure, it exists as an oxide of flaky carbon in the dispersion subjected to the shearing treatment. Therefore, when graphite oxide is used as the carbonaceous material having a layered structure, it is preferable to perform a reduction treatment as a post-treatment. As the reduction treatment, various methods such as chemical reduction and electrochemical reduction can be adopted, but chemical reduction is preferable. Of these, chemical reduction with a reducing agent such as hydrazine or sodium borohydride is preferable. The amount of the reducing agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass with respect to 1 part by mass of the oxide of flaky carbon. Further, if heating is performed at the time of reduction, the reduction becomes easier. The heating temperature is preferably 40 to 200 ° C, more preferably 50 to 150 ° C, and even more preferably 60 to 120 ° C. The reduction time is preferably 10 minutes to 64 hours, more preferably 30 minutes to 48 hours, still more preferably 1 to 24 hours. However, it is preferable that the graphene structure is not excessively destroyed.

According to the above-mentioned shearing treatment, the flaky carbon can be obtained as the above-mentioned flaky carbon dispersion. Since this shearing treatment contains an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, even in the flaky carbon dispersion, the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can be contained. include. Since this organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon can be adsorbed on the surface of flaky carbon and isolated and dispersed the flaky carbon in a solvent at a high concentration, the flaky carbon is dispersed. It also functions as a dispersant in the body. Further, as the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, a commercially available product can be used, which is superior to the conventional product in terms of both cost and dispersibility. Further, the organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is excellent in electromagnetic wave absorption performance, light weight, processability, etc. by remaining on the flaky carbon surface, and has surface resistivity and volume resistivity. Can be set to an appropriate range.

However, the material immediately after this shearing treatment tends to have a large content of organic compounds having a hydrophilic group and a hydrophobic group having a high affinity for carbon. In this case, the sheet or paint that absorbs electromagnetic waves is plastic. It is easy to change, and there is a possibility that workability will be a problem. Therefore, by cleaning the obtained flaky carbon dispersion, the content of the organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon is reduced, so that a sheet or paint that absorbs electromagnetic waves is blended. The degree of freedom can be increased and the workability can be improved.

Specifically, alcohols such as ethanol and 2-propanol are added to the obtained flaky carbon dispersion and filtered, and then ketones such as acetone and 2-butanone are added to the obtained cake. It is preferable to filter.

The content of the solvent that can be used at this time is not particularly limited, but the alcohol is preferably 1 to 20 parts by mass (particularly 1.5 to 10 parts by mass) with respect to 1 part by mass of the flaky carbon dispersion, and is a ketone. Is preferably 1 to 50 parts by mass (particularly 1.5 to 30 parts by mass) with respect to 1 part by mass of the above-mentioned cake.

Further, in the conventional method of performing the oxidation treatment and the reduction treatment, the plastic substrate is hydrolyzed during the reduction treatment, and the flaky carbon aggregates when the reduction treatment is performed, so that it cannot exist as a dispersion. Therefore, it was impossible to form a flaky carbon dispersion on a plastic substrate, but in the present invention, a specific organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon is contained. By performing the treatment, it is also possible to form a flaky carbon dispersion or an electromagnetic wave absorbing material on the substrate without the plastic substrate such as polyethylene terephthalate (PET) being hydrolyzed.

Pressurization treatment (high pressure dispersion method)
In the present invention, when the high-pressure dispersion method is adopted, as described above, 30 MPa is applied to a composition containing a carbonaceous material having a layered structure and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon. It is preferable to perform the above pressurization treatment.

The graphene structure may not be maintained depending on the conditions because the carbonaceous material having a layered structure is atomized by the pressure treatment, but the carbonaceous material having a layered structure can be efficiently sliced. This can be done and the processing time can be reduced. The pressure level at the time of performing such a pressure treatment is not particularly limited as long as it can sufficiently thin the carbonaceous material having a layered structure, but is preferably 30 MPa or more, preferably 50 to 400 MPa. Is more preferable, and 100 to 300 MPa is further preferable. Such pressurization treatment can be performed using a high-pressure disperser, a supercritical water preparation device, or the like. The high-pressure disperser can disperse by applying mechanical pressure, and in the supercritical water preparation device, the pressure of the system can be increased by heating water.

By such pressurization, for example,
(I) Colliding two or more of the carbonaceous material dispersions with each other.
(Ii) Collision of the carbonaceous material dispersion with a metal or ceramic material (material having high hardness such as silicon carbide or alumina).
(Iii) The carbonaceous material dispersion can be passed through a space having a cross-sectional area of 1 cm ² or less.

According to the above (i) and (ii), the pressurizing condition can be strengthened, the carbonaceous material having a layered structure can be sliced more efficiently, and the processing time can be further reduced. be able to. Further, according to the above (iii), it is possible to more appropriately thin the carbonaceous material having a layered structure while maintaining the graphene structure more appropriately. This pressurizing operation can be performed once or more, preferably 10 times or more.

The pressurizing temperature is not particularly limited and may be a temperature at which the carbonaceous material having a layered structure can be sufficiently thinned. In the cases of (i) and (ii) above, 0 to 100 ° C., particularly 20 It can be ~ 95 ° C. Further, in the case of (iii) above, 0 to 100 ° C. is preferable when mechanically applying pressure, 373 to 700 ° C. is preferable when pressure is generated by the supercritical state of water, and 380 to 450 ° C. is more preferable. preferable.

When the pressure treatment is performed, it is preferable to perform an ultrasonic dispersion treatment as a preliminary treatment (pretreatment) to atomize the carbonaceous material having a layered structure. This can have an effect of preventing clogging and the like.

The output when the ultrasonic dispersion treatment is applied is not particularly limited, but it is stronger than the usual ultrasonic dispersion treatment (about 40 to 50 W) from the viewpoint of thinning the carbonaceous material having a layered structure. Is preferable. Specifically, the output of the ultrasonic dispersion treatment is preferably 100 W or more, more preferably 300 to 20000 W, and even more preferably 400 to 18000 W.

The ultrasonic dispersion temperature is not particularly limited, and may be a temperature at which the carbonaceous material having a layered structure can be sufficiently thinned, and may be 0 to 80 ° C., particularly 10 to 70 ° C. The ultrasonic dispersion time is not particularly limited, and may be a time during which the carbonaceous material having a layered structure can be sufficiently thinned, and may be 1 to 600 minutes, particularly 3 to 120 minutes.

Further, as the pretreatment or the posttreatment of these treatments, a dispersion treatment by another dispersion device such as ordinary mechanical stirring, a dispersion treatment by an emulsifying device, and a dispersion treatment by a bead mill may be used in combination.

In the present invention, when graphite oxide is used as the carbonaceous material having a layered structure, it exists as an oxide of flaky carbon in the dispersion subjected to the pressure treatment. Therefore, when graphite oxide is used as the carbonaceous material having a layered structure, it is preferable to perform a reduction treatment as a post-treatment. As the reduction treatment, various methods such as chemical reduction and electrochemical reduction can be adopted, but chemical reduction is preferable. Of these, chemical reduction with a reducing agent such as hydrazine or sodium borohydride is preferable. The amount of the reducing agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass with respect to 1 part by mass of the oxide of flaky carbon. Further, if heating is performed at the time of reduction, the reduction becomes easier. The heating temperature is preferably 40 to 200 ° C, more preferably 50 to 150 ° C, and even more preferably 60 to 120 ° C. The reduction time is preferably 10 minutes to 64 hours, more preferably 30 minutes to 48 hours, still more preferably 1 to 24 hours. However, it is preferable that the graphene structure is not excessively destroyed.

(2-3) Method for producing electromagnetic wave absorbing material of the present invention The electromagnetic wave absorbing material of the present invention can be obtained by removing a solvent from the above-mentioned flaky carbon dispersion.

In order to remove the solvent, a method of concentrating the flaky carbon dispersion can be mentioned. In addition to drying the flaky carbon dispersion, a method of spin-coating the flaky carbon dispersion on a substrate or drying after coating, usually It can be carried out by the method of recovering the heat conductive material of the present invention by solid-liquid separation of the above. As a method for performing solid-liquid separation, for example, a method used for ordinary solid-liquid separation, for example, a method of filtering using a filter paper, a glass filter, or the like; a method of filtering after centrifugation; a vacuum filter is used. The method can be exemplified. Next, the drying method is not particularly limited, and for example, a method of drying at about 50 to 200 ° C. for about 1 to 24 hours using a warm air dryer or the like can be exemplified.

3. 3. Electromagnetic wave absorption composition The electromagnetic wave absorption composition of the present invention contains the above-mentioned electromagnetic wave absorption material of the present invention, a thermoplastic resin and / or a thermosetting resin. In particular, in the electromagnetic wave absorbing composition of the present invention, from the viewpoint of electromagnetic wave absorbing performance, surface resistivity, volume resistivity, etc., the total amount of the electromagnetic wave absorbing composition of the present invention is set to 100% by mass, and the content of flaky carbon is contained. Is preferably 1 to 30% by mass, more preferably 2 to 20% by mass. Further, in the electromagnetic wave absorbing composition of the present invention, from the viewpoint of electromagnetic wave absorbing performance, surface resistivity, volume resistivity, etc., the total amount of the electromagnetic wave absorbing composition of the present invention is set to 100% by mass, and it has an affinity with hydrophilic groups and carbon. The content of the organic compound having a highly acidic hydrophobic group is preferably 0.01 to 20% by mass, more preferably 0.02 to 10% by mass.

The electromagnetic wave absorbing material of the present invention suppresses the aggregation of flaky carbon and is easily dispersed in other materials (for example, thermoplastic resin, thermosetting resin, rubber, thermoplastic elastomer, etc.). By mixing with a material, it can be applied to nanocomposites containing flaky carbon and the like.

As such other materials, more specifically, as the thermoplastic resin, for example, a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, a polyvinyl acetate resin, and a thermoplastic polyurethane resin. , Polyfluorinated vinylidene resin, acrylonitrile-butadiene-styrene copolymer (ABS) resin, acrylonitrile-styrene copolymer (AS) resin, polymethylmethacrylate resin, polyamide resin, polyacetal resin, polycarbonate resin, polyarylate resin, polyphenylene ether Examples thereof include resins, polyethylene terephthalate resins, polybutylene terephthalates, cyclic polyolefin resins, polyphenylene sulfide resins, polyether ether ketone resins, thermoplastic polyimide resins, polyamideimide resins, and examples of the thermosetting resins include epoxy resins and thermocurable resins. Examples thereof include sex polyimide resins, phenol resins, melamine resins, unsaturated polyester resins, alkyd resins, polyurethane resins, etc. Examples of rubbers include diene rubbers (styrene / butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber, etc.) and olefins. Examples include thermoplastic rubbers (ethylene / propylene rubber, ethylene / propylene / diene rubber, etc.), acrylic rubber, butyl rubber, epichlorohydrin rubber, silicone rubber (silicone rubber, etc.), polysulfide rubber, fluororubber, etc., and thermoplastic elastomers. Examples include a thermoplastic elastomer having a polyethylene structure, a thermoplastic elastomer having a polypropylene structure, a thermoplastic elastomer having a butadiene structure (styrene / butadiene / styrene copolymer, etc.), a thermoplastic elastomer having a polyethylene terephthalate structure, and a polyamide 6 structure. Examples thereof include a thermoplastic elastomer having a polyamide 66 structure, a thermoplastic elastomer having a polyamide 66 structure, a thermoplastic elastomer having a polyamide 11 structure, and a thermoplastic elastomer having a polyamide 12 structure. These can be used alone or in combination of two or more. In addition, known or commercially available products can be used as these other materials.

In the electromagnetic wave absorption composition of the present invention, the content of the above-mentioned other materials is not particularly limited, and the total amount of the electromagnetic wave absorption composition of the present invention is 100 from the viewpoint of electromagnetic wave absorption performance, surface resistivity, volume resistivity and the like. The mass% is preferably 70 to 99% by mass, more preferably 80 to 98% by mass.

Such an electromagnetic wave absorption composition of the present invention can also be dispersed in an organic solvent to form an electromagnetic wave absorption dispersion (electromagnetic wave absorption dispersion, electromagnetic wave absorption dispersion coating film, etc.). The organic solvent that can be used at this time is not particularly limited, and is N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), glycol solvent, alcohol solvent (ethanol, 2). -Propanol, etc.), ketone solvents (acetone, 2-butanone, etc.) and the like. These solvents can be used alone or in combination of two or more. The amount of these solvents used is not particularly limited and can be the amount of the solvent. Thereby, the electromagnetic wave absorbing composition of the present invention can be easily molded into a sheet shape to obtain an electromagnetic wave absorbing sheet.

Further, when the other material contained in the electromagnetic wave absorbing composition of the present invention is a resin, the electromagnetic wave absorbing composition can be cured into a sheet shape while being cured to form an electromagnetic wave absorbing sheet. The curing method in this case can follow a conventional method.

Further, the thickness of the electromagnetic wave absorbing sheet of the present invention in the case of forming the sheet shape as described above is preferably 2000 μm or less, more preferably 10 to 1000 μm, from the viewpoint of electromagnetic wave absorption performance, light weight and the like. The thickness of the electromagnetic wave absorbing sheet is measured with a caliper.

The electromagnetic wave absorbing composition of the present invention satisfying such conditions can have a surface resistivity of 10 to 10000 Ω / □, particularly 100 to 1000 Ω / □. Further, the electromagnetic wave absorbing composition of the present invention satisfying such conditions can have a volume resistivity of 1 to 1000 Ωcm, particularly 10 to 100 Ωcm. By satisfying such conditions, the electromagnetic wave absorption composition of the present invention can particularly improve the electromagnetic wave absorption performance. The surface resistivity and volume resistivity of such an electromagnetic wave absorbing composition of the present invention are measured by a four-probe type resistivity meter.

4. Electromagnetic wave absorbing fiber material Further , the electromagnetic wave absorbing material of the present invention can be made into an electromagnetic wave absorbing fiber material by supporting it on the surface of the fiber.

Examples of the fiber that supports the electromagnetic wave absorbing material of the present invention include polyamide resin, polyester resin, acrylic resin, polyolefin resin, polyurethane resin, cellulose, plant, glass, carbon and the like. These fibers may be used alone or in combination of two or more.

Only one fiber may be used to support the electromagnetic wave absorbing material of the present invention, but from the viewpoint of absorbing electromagnetic waves more widely, a porous structure such as a mesh, a net, or a non-woven fabric (paper) in which the fibers are woven may be used. it can.

In this case, the thickness of the porous structure using fibers is preferably 10 to 100 μm, more preferably 20 to 50 μm, from the viewpoint of electromagnetic wave absorption performance, light weight and the like. The thickness of the porous structure is measured with a caliper.

In such an electromagnetic wave absorbing fiber material of the present invention, from the viewpoint of electromagnetic wave absorbing performance, surface resistivity, volume resistivity, etc., the total amount of the electromagnetic wave absorbing fiber material of the present invention is 100% by mass, and the content of flaky carbon is Is preferably 0.1 to 30% by mass, more preferably 1 to 20% by mass. Further, in the electromagnetic wave absorbing fiber material of the present invention, from the viewpoints of electromagnetic wave absorbing performance, surface resistivity, volume resistivity, water resistance, etc., the total amount of the electromagnetic wave absorbing fiber material of the present invention is 100% by mass, and the hydrophilic group and The content of the organic compound having a hydrophobic group having a high affinity with carbon is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass.

The electromagnetic wave absorbing fiber material of the present invention satisfying such conditions can have a surface resistivity of 10 to 10000 Ω / □, particularly 100 to 1000 Ω / □. Further, the electromagnetic wave absorbing fiber material of the present invention satisfying such conditions can have a volume resistivity of 1 to 1000 Ωcm, particularly 10 to 100 Ωcm. By satisfying such conditions, the electromagnetic wave absorbing fiber material of the present invention can particularly improve the electromagnetic wave absorbing performance. The surface resistivity and volume resistivity of the electromagnetic wave absorbing fiber material of the present invention are measured by a four-probe type resistivity meter.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the examples.

Example 1: Flaky carbon + polyoxyethylene naphthyl ether (carbon fiber)
500 g of artificial graphite (manufactured by Showa Denko KK), 250 g of polyoxyethylene naphthyl ether (HLB value 18) and 10000 g of water are mixed and dispersed for 5 minutes using a 600 W ultrasonic disperser, and a high-pressure disperser is used. The dispersion treatment (collision of two or more carbonaceous material dispersions with each other) was performed 100 times at 245 MPa. Moreover, TEM observation of flaky carbon was carried out, and the average number of layers was 4 layers (thickness about 1.5 nm).

The obtained dispersion is impregnated into a paper (nonwoven fabric; resistance value 20Ω / □) woven with carbon fibers and dried at 100 ° C., so that the paper on which the electromagnetic wave absorbing material is supported on the carbon fibers is made into an electromagnetic wave absorbing fiber material. Obtained as.

The thickness of the obtained electromagnetic wave absorbing fiber material was 143 μm as measured by a caliper. The surface resistivity and volume resistivity were measured with a four-probe type resistivity meter (Loresta manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The surface resistivity was 257 Ω / □, and the volume resistivity was 16.6 Ωcm. Met.

When the electromagnetic wave absorption capacity of the obtained electromagnetic wave absorbing fiber material was measured at 75 GHz by the free space method, the absorption was 17.85 dB and the reflection was 4.29 dB, indicating that the electromagnetic waves can be effectively absorbed. it can.

Comparative Example 1: None (carbon fiber)
The paper (nonwoven fabric; resistance value 20Ω / □) woven with carbon fiber, which was also used in Example 1, was used as it was. The thickness of the paper used was 210 μm as measured by calipers. When the surface resistivity and volume resistivity were measured with a four-probe type resistivity meter (Loresta manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the surface resistivity was 6.5Ω / □ and the volume resistivity was 0. It was 0.6 Ωcm. When the electromagnetic wave absorption capacity of 75 GHz was measured by the free space method on the used paper, the absorption was 1.15 dB and the reflection was 31.54 dB, so the electromagnetic waves could not be effectively absorbed and reflected. Can be understood.

Example 2: Flaky carbon + polyoxyethylene naphthyl ether (thermosetting polyimide resin)
500 g of natural graphite (manufactured by Ito Graphite Industry Co., Ltd.), 250 g of polyoxyethylene naphthyl ether (HLB value 18) and 10000 g of water were mixed and stirred to obtain a mixed solution.

This mixed solution was subjected to one shearing treatment at 1500 rpm for 30 minutes using a ceramic grinder having a radius of 300 mm. The shortest distance of the ceramic grinder was about 10 μm. Moreover, TEM observation of flaky carbon was carried out, and the average number of layers was 30 layers (thickness about 10 nm).

To the obtained dispersion, twice the mass ratio of ethanol was added and filtered, and to the obtained cake, twice the mass ratio of acetone was added and filtered. A thermal analysis of the obtained cake (electromagnetic wave absorbing material) revealed that it contained 3% by mass of polyoxyethylene naphthyl ether. Further, the obtained cake was dispersed in N-methylpyrrolidone (NMP) to obtain a 4.5% by mass NMP dispersion. As a result, a dispersion having a flaky carbon content of 4.4% by mass and a polyoxyethylene naphthyl ether of 0.14% by mass was obtained as an electromagnetic wave absorption dispersion.

This electromagnetic wave absorption dispersion and a thermosetting polyimide resin (manufactured by IST Co., Ltd., solid content 15.64% by mass, solvent NMP) are mixed so that the concentration of flaky carbon becomes 5% by mass, and 150 ° C. Dry with, heat press at 250 ° C., and use a sheet containing 5% by mass of flaky carbon, 0.15% by mass of polyoxyethylene naphthyl ether, and 94.85% by mass of thermosetting polyimide resin as an electromagnetic wave absorbing sheet. Obtained.

The thickness of the obtained electromagnetic wave absorbing sheet was 60 μm as measured by a caliper. When the surface resistivity and volume resistivity were measured with a four-probe type resistivity meter (Loresta manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the surface resistivity was 880 Ω / □ and the volume resistivity was 23.9 Ωcm. Met.

When the electromagnetic wave absorption capacity of the obtained electromagnetic wave absorbing fiber sheet was measured at 75 GHz by the free space method, the absorption was 19.5 dB and the reflection was 5.2 dB, so it was understood that the electromagnetic waves could be effectively absorbed. it can.

Comparative Example 2: None (thermosetting polyimide resin)
It was molded into a sheet under the same conditions as in Example 2 using only a thermosetting polyimide resin without using an electromagnetic absorption dispersion containing flaky carbon and polyoxyethylene naphthyl ether.

The thickness of the obtained sheet was 66 μm as measured by a caliper. In addition, I tried to measure the surface resistivity and volume resistivity with a four-probe type resistivity meter (Loresta manufactured by Mitsubishi Chemical Analytech Co., Ltd.), but the resistance was too large to measure.

When the electromagnetic wave absorbing ability of the obtained electromagnetic wave absorbing fiber sheet was measured by the free space method at 75 GHz, it was understood that the electromagnetic wave could not be absorbed because neither absorption nor reflection occurred.

In this way, by coexisting a predetermined amount of an organic compound having a hydrophilic group and a hydrophobic group having a high affinity with carbon with flaky carbon, the surface resistivity and volume resistivity are set in an appropriate range to reflect electromagnetic waves. It was possible to absorb electromagnetic waves more effectively. In the present invention, the presence of an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon on the surface of the flaky carbon appropriately hinders electrical conduction, and as a result, absorbs electromagnetic waves without reflecting them. It is probable that it was possible.

Further, since the electromagnetic wave absorbing material of the present invention can be easily dispersed in the resin material, it can be processed into a sheet shape or the like, and can be supported on a fiber material, and has excellent processability. Was there. In addition, this sheet can effectively absorb electromagnetic waves even if the thickness is reduced, and can absorb electromagnetic waves at low cost.

Claims (17)

It contains flaky carbon having a thickness of 1 to 100 nm and an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, and has an affinity for the hydrophilic group and carbon with respect to 1 part by mass of the flaky carbon. An electromagnetic wave absorbing material containing 0.01 to 1.0 parts by mass of an organic compound having a highly reactive hydrophobic group. The hydrophilic group is a general formula (1) to (4):
[In the formula, -OH represents an alcoholic hydroxyl group or a phenolic hydroxyl group. R represents a divalent organic group. X ¹ represents a hydrogen atom, alkali metal, NH ₄ or organic ammonium. X ² represents a hydrogen atom, alkali metal, NH ₄ , organic ammonium or alkyl group. The oxygen atom of the general formula (2) is an ether bond. ]
The electromagnetic wave absorbing material according to claim 1, which is at least one kind represented by. The electromagnetic wave absorbing material according to claim 1 or 2, wherein the hydrophilic group is a phenolic hydroxyl group and / or a polyoxyethylene group. Any one of claims 1 to 3, wherein the hydrophobic group is at least one selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, and a polyoxyalkylene group having 3 or more carbon atoms. The electromagnetic wave absorbing material described in. The electromagnetic wave absorbing material according to any one of claims 1 to 4, wherein the hydrophobic group is an aryl group having two or more aromatic rings. The method for producing an electromagnetic wave absorbing material according to any one of claims 1 to 5.
(1) The flaky carbon, an organic compound having a hydrophilic group and a hydrophobic group having a high affinity for carbon, and a solvent are contained, and the hydrophilic group and carbon are contained with respect to 1 part by mass of the flaky carbon. A production method comprising a step of removing a solvent from a flaky carbon dispersion containing 0.01 to 1.0 parts by mass of an organic compound having a hydrophobic group having a high affinity. The production method according to claim 6, wherein the step of removing the solvent is a step of concentrating the dispersion. The production method according to claim 6 or 7, wherein the solvent is water. An electromagnetic wave containing the electromagnetic wave absorbing material according to any one of claims 1 to 5 and at least one other material selected from the group consisting of a thermosetting resin, a thermoplastic resin, rubber and a thermoplastic elastomer. Absorption composition. The ninth aspect of claim 9, wherein the thermosetting resin is at least one selected from the group consisting of epoxy resins, thermosetting polyimide resins, phenol resins, melamine resins, unsaturated polyester resins, alkyd resins, and polyurethane resins. Electromagnetic absorption composition. An electromagnetic wave absorption dispersion in which the electromagnetic wave absorption composition according to claim 9 or 10 is dispersed in an organic solvent. An electromagnetic absorption sheet containing a cured product of the electromagnetic wave absorption composition according to claim 9 or 10, wherein the other material is a thermosetting resin and / or a thermoplastic resin. The electromagnetic wave absorbing sheet according to claim 12, which has a thickness of 2000 μm or less. An electromagnetic wave absorbing fiber material in which the electromagnetic wave absorbing material according to any one of claims 1 to 5 is supported on the surface of the fiber. The electromagnetic wave absorbing fiber according to claim 14, wherein the fiber is composed of at least one selected from the group consisting of polyamide resin, polyester resin, acrylic resin, polyolefin resin, polyurethane resin, cellulose, plant, glass and carbon. material. The electromagnetic wave absorbing sheet according to claim 12 or 13, wherein the surface resistivity is 10 to 10000 Ω / □ and the volume resistivity is 1 to 1000 Ωcm. The electromagnetic wave absorbing fiber material according to claim 14 or 15, which has a surface resistivity of 10 to 10000 Ω / □ and a volume resistivity of 1 to 1000 Ωcm.