Surface-modified carbon nanotubes, methods for producing the same, and dispersion compositions of surface-modified carbon nanotubes

Abstract

To provide surface-modified carbon nanotubes that can be uniformly and easily dispersed in various organic solvents. [Solution] The modified component comprises a block polymer having a portion derived from a cellulose derivative into which polymerizable functional groups are introduced, and a vinyl polymer portion derived from a vinyl monomer in which vinyl monomers are graft-polymerized onto the polymerizable functional groups, and a carbon nanotube, wherein the average number of moles of the polymerizable functional groups is 1 to 8 relative to the number of moles calculated from the number-average molecular weight of the cellulose derivative, and the portion derived from the cellulose derivative of the modified component is adsorbed onto the surface of the carbon nanotube by interaction.

Description

Technical Field

[0001] The present invention relates to a surface-modified carbon nanotube in which an organic polymer compound is adsorbed on the surface of a carbon nanotube, a method for producing the same, and a surface-modified carbon nanotube dispersion.

Background Art

[0002] In recent years, nanocarbons represented by carbon nanotubes have attracted attention as materials having excellent conductivity and thermal conductivity. Carbon nanotubes have a structure in which six-membered rings are continuously bonded and have extremely high conductivity and thermal conductivity characteristics.

[0003] In order to exhibit high conductivity with a small addition amount, it is necessary to densely disperse carbon nanotubes to form an efficient conductive network. However, carbon nanotubes have high hydrophobicity and aggregate due to strong van der Waals forces, so it is extremely difficult to disperse them well.

[0004] Patent Document 1 describes a method of dispersing carbon nanotubes in N-methylpyrrolidone using an acrylic polymer and an amine compound. Patent Document 2 describes a method of dispersing carbon nanotubes in an organic solvent using a dispersant for a carbon material containing an acrylic copolymer containing a nitrogen atom. Patent Document 3 describes a method of dispersing carbon nanotubes in an organic solvent using a cationic polymer dispersant. Patent Document 4 describes a method of dispersing carbon nanotubes in an organic solvent using a cellulose derivative. Patent Document 5 proposes a polymer-coated carbon nanotube in which ethyl cellulose is coated on the surface of a carbon nanotube. Patent Document 6 describes a carbon nanotube in which an acidic group is introduced by performing acid treatment.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, the dispersibility of carbon nanotubes using the conventional dispersants described above is still insufficient, and further improvement is needed. Furthermore, when functional groups are introduced to the surface of carbon nanotubes by acid treatment or other methods to improve dispersibility, the extremely high electrical and thermal conductivity of the carbon nanotubes mentioned above is impaired. The object of the present invention is to provide carbon nanotubes that can be uniformly and easily dispersed in various organic solvents. [Means for solving the problem]

[0007] To solve the above problems, the present invention has the following configuration. In other words, the surface-modified carbon nanotube comprises a modified component consisting of a block polymer having a portion derived from a cellulose derivative into which polymerizable functional groups are introduced, and a portion derived from a vinyl monomer in which vinyl monomers are graft-polymerized onto the polymerizable functional groups, wherein the average number of moles of the polymerizable functional groups is 1 to 8 relative to the number of moles calculated from the number-average molecular weight of the cellulose derivative, and the portion derived from the cellulose derivative of the modified component is adsorbed onto the surface of the carbon nanotube by interaction.

[0008] Furthermore, the present invention provides a method for producing surface-modified carbon nanotubes, comprising: step 1) reacting a cellulose derivative with an organic compound having polymerizable functional groups to introduce polymerizable functional groups; step 2) dispersing the product from step 1) and carbon nanotubes in a solvent to obtain a composite composition (CNT-CeD) in which the product from step 1) is adsorbed onto the surface of the carbon nanotubes; and step 3) adding a vinyl monomer to the reaction solution from step 2) to graft polymerize the vinyl monomer onto the polymerizable functional groups to obtain surface-modified carbon nanotubes (CNT-CeD / Ac). [Effects of the Invention]

[0009] According to the present invention, it is possible to provide surface-modified carbon nanotubes and surface-modified carbon nanotube dispersions that can be dispersed in various organic solvents by a simple method. [Modes for carrying out the invention]

[0010] The "surface-modified carbon nanotube" of the present invention consists of a structure in which a polymer having a graft polymer structure of a vinyl polymer and a cellulose derivative is adsorbed onto various carbon nanotubes. These structures can be fabricated in various ways. One method involves creating a cellulose derivative (generally high molecular weight) into which polymerizable functional groups are introduced, and then using this to graft polymerize vinyl monomers to produce block polymers of the cellulose derivative and vinyl polymer. These block polymers are then adsorbed onto carbon nanotubes in solution to obtain surface-modified carbon nanotubes. Another method involves pre-adsorbing the aforementioned cellulose derivative with polymerizable functional groups onto carbon nanotubes in solution to create a dispersion solution. Subsequently, vinyl monomers are mixed in to perform graft polymerization, and the vinyl polymer is blocked onto the cellulose derivative with polymerizable functional groups adsorbed on the surface of the carbon nanotubes (the product being a block polymer) to obtain surface-modified carbon nanotubes. In this specification, "block polymer" refers to a polymer in which different polymer chains are bonded together. In the following text, "carbon nanotube" will be abbreviated as "CNT". The following describes in detail preferred embodiments of the structure of surface-modified carbon nanotubes according to the present invention and their manufacturing method. However, the scope of the present invention is not limited to these descriptions, and modifications may be made as appropriate without impairing the spirit of the invention, in addition to the examples given below.

[0011] [Method for producing surface-modified carbon nanotubes (CNTs) (1)] The present invention will be explained through a method for producing surface-modified CNTs by first producing the modifying components, which are constituent elements of the CNTs, from cellulose derivatives and then adsorbing them onto CNTs.

[0012] <Carbon nanotubes (CNTs)> The carbon nanotubes (CNTs) that can be used in this invention are not particularly limited, and those with a short diameter of 0.1 to 300 nm and an aspect ratio of 10 or more can be used, such as multi-walled carbon nanotubes (MWCNTs) having a multilayer structure, such as double-walled CNTs having a two-layer structure, and single-walled carbon nanotubes (SWCNTs) having a single-layer structure. Furthermore, they can be manufactured by any method, for example, by arc discharge, laser evaporation, CVD, etc. Commercially available SWCNTs include the TUBALL® series from OCSiAl and the ZEONANO® SG101 series from Zeon Nanotechnology Co., Ltd. Commercially available MWCNTs include the VGCF® series from Resonaq Corporation and the Baytubes® series from Bayer AG. The CNTs used in this invention may be of one type only, or two or more types may be used in combination. Various types of carbon nanotubes (CNTs), including conductive and semiconducting types, are known and can be selected appropriately depending on the application. For conductive applications and as conductive additives for batteries, SWCNTs or MWCNTs, which exclude the semiconducting component, are preferably used. For thermal conductivity applications, all types of CNTs, including semiconducting ones, can be used.

[0013] <Cellulose derivatives> The "cellulose derivative" of the present invention refers to a cellulose in which some of the hydroxyl groups are replaced with organic groups. The method of hydroxyl group substitution is not particularly limited, but examples include alkyl etherification, hydroxyalkyl etherification, and esterification of the hydroxyl groups. Only one cellulose derivative may be used, or two or more may be used in combination.

[0014] As the cellulose derivative, conventionally known cellulose derivatives can be used. Specifically, examples include methylcellulose, ethylcellulose, propylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, cellulose acetate (acetylcellulose, diacetylcellulose, triacetylcellulose, etc.), cellulose acetate propionate, cellulose acetate butyrate, and nitrocellulose. Among these, ethylcellulose, cellulose acetate butyrate, and cellulose acetate propionate are preferred from the viewpoint of high solubility in organic solvents, ease of grafting vinyl polymers, and availability.

[0015] The number-average molecular weight of the cellulose derivative is preferably selected from the range of 1,000 to 50,000. When the molecular weight is within this range, the CNTs are easily wetted and spread in the dispersion solvent, and the CNTs are well dispersed. In this specification, when "molecular weight" is mentioned, it refers to the number-average molecular weight (Mn) unless otherwise specified.

[0016] These conventionally well-known cellulose derivatives usually have unmodified hydroxyl groups. By utilizing these unmodified hydroxyl groups, polymerizable functional groups such as polymerizable unsaturated groups and thiol (mercapto) groups can be introduced. By introducing polymerizable functional groups in this way, vinyl polymers can be easily grafted and block polymerized by the polymerization of vinyl monomers described later.

[0017] <Introduction of Polymerizable Functional Groups into Cellulose Derivatives> The introduction of the above polymerizable functional groups can be carried out, for example, by adding an isocyanate-based (meth)acrylate compound such as Karenz MOI or Karenz AOI manufactured by Resonac Co., Ltd. to the above-mentioned conventionally well-known cellulose derivatives, adding an anhydride such as (meth)acrylic anhydride or maleic anhydride, using a condensing agent such as carbodiimide to add (meth)acrylic acid, etc., reacting (meth)acrylic acid chloride with an organic acid having a thiol group, etc.

[0018] Examples of organic compounds having polymerizable functional groups (hereinafter, may be simply referred to as organic compounds) include (meth)acrylic acid, maleic acid, crotonic acid, butenetricarboxylic acid, 4-ethenylbenzoic acid, succinic acid mono(2-(meth)acryloyloxyethyl), phthalic acid mono2-((meth)acryloyloxyethyl), 6-acrylamidohexanoic acid, 4-carboxystyrene, ω-carboxy-polycaprolactone mono(meth)acrylate, 2-carboxyethyl (meth)acrylate, mercaptoacetic acid, 3-mercaptopropionic acid, 6-mercaptohexanoic acid, 4-mercaptobenzoic acid, Karenz MOI manufactured by Resonac Co., Ltd., Karenz AOI, etc. The above expression of meta(acrylic) includes both methacrylate and acrylate.

[0019] In addition, as the organic compound to be introduced, it is desirable that it is an organic compound having 3 to 20 carbon atoms other than the polymerizable functional group. Although the mechanism is unclear, by introducing these organic compounds into the cellulose derivative, the dispersibility of the surface-modified CNT can be further enhanced.

[0020] The reactions for introducing the above organic compounds into cellulose derivatives are esterification, urethane formation, and etherification reactions. Conventional known methods and reaction conditions can be used in these reactions. Typically, the reactions are carried out using solutions dissolved in various organic solvents. Aprotic solvents are preferred as reaction solvents for this reaction, and aprotic solvents such as ethyl acetate, propyl acetate, butyl acetate, tetrahydrofuran, dioxane, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and pyridine can be used alone or in combination. Among these, ethyl acetate, propyl acetate, butyl acetate, and toluene are preferred.

[0021] To elaborate on the esterification reaction, it can be carried out using a condensing agent, for example. Examples of condensing agents include carbodiimide, diphenyl phosphate adide, 1-hydroxybenzotriazole, and BPO chemicals. One type of condensing agent may be used, or two or more may be used in combination. Among these, carbodiimide is preferable because of its versatility and reactivity, and because the reaction can proceed under low temperature conditions and without being affected by moisture in the reaction environment. Examples of carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide, and N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide methiozide. Among these, dicyclohexylcarbodiimide and diisopropylcarbodiimide are preferred from the viewpoint of availability. Furthermore, when using carbodiimide, it is also preferable to use a reaction accelerator such as dimethylaminopyridine or triethylamine as a base in the range of 0.01 mol% to 100 mol% relative to the carbodiimide.

[0022] The urethane reaction can be carried out, for example, using a reaction catalyst. Examples of reaction catalysts include amine compounds such as dioctyltin dilaurate, dibutyltin dilaurate, zinc naphthenate, PMDETA (N,N,N",N"-pentamethyldiethylenetriamine), N,N-dimethylcyclohexylamine, N-methyldicyclohexylamine, N,N,N',N'-tetramethylpropylenediamine, N,N,N',N'-tetramethylhexamethylenediamine, N-methylmorpholine, N-ethylmorpholine, N,N-dimethylethanolamine, and N,N-diethylethanolamine.

[0023] Etherification reactions can be efficiently carried out by using alkali metal hydroxides such as KOH and NaOH, or alkali metal hydrides such as NaH and KH, as reaction catalysts.

[0024] The reaction temperature between cellulose derivatives and organic compounds is, for example, around 0 to 100°C. The amount of polymerizable functional groups introduced can be measured by NMR analysis, IR analysis, or mass spectrometry. When carbodiimide is used as a coupling agent, urea may be formed as a byproduct and may become insoluble, but purification by filtration or reprecipitation may be performed as needed.

[0025] The amount of polymerizable functional groups introduced into the cellulose derivative can be adjusted during the reaction by adjusting the number of moles of the organic compound having polymerizable functional groups relative to the number of moles of the cellulose derivative, or by adding an appropriate amount of condensing agent or reaction catalyst to the organic compound. The amount of condensing agent or reaction catalyst can be appropriately changed depending on the type of organic compound, condensing agent, and reaction catalyst. Although this is only one condition, the organic compound can be quantitatively introduced into the cellulose derivative by adding an equimolar amount of condensing agent and about 0.1 moles of reaction accelerator to the organic compound.

[0026] The average number of moles of polymerizable functional groups introduced into the cellulose derivative must be between 1 and 8 for every 1 mole calculated from the number-average molecular weight of the cellulose derivative. If the average number of moles of polymerizable functional groups is less than 1, the dispersion of CNTs will be insufficient. On the other hand, if the average number of moles of polymerizable functional groups exceeds 8, there is a risk of gelation during graft polymerization or side reactions that hinder the formation of good surface-modified CNTs. In order to set the average number of moles of polymerizable functional groups between 1 and 8, the selection of reaction conditions when introducing polymerizable functional groups into the cellulose derivative is important.

[0027] <Vinyl polymer> Grafting vinyl polymers onto cellulose derivatives can be carried out, for example, by polymerizing vinyl monomers in the presence of cellulose derivatives into which polymerizable unsaturated groups or thiol groups have been introduced, as described above. Graft chains of vinyl polymers are formed using the polymerizable functional groups, such as polymerizable unsaturated groups or thiol groups, as starting points.

[0028] In the polymerization described above, vinyl monomers used include alkyl groups with 1 to 20 carbon atoms such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, as well as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glyceryl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate with 1 to 30 repeating units, and methoxypolypropylene glycol (meth)acrylate with 1 to 30 repeating units. Glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl succinic acid, glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl methacrylate, 2-(meth)acryloyloxyethyl acid phosphate, styrene, styrene derivatives, (meth)acrylic acid, (meth)acrylamide, N-phenylmaleimide, N-cyclo Examples include hexylmaleimide, maleic anhydride, (meth)acrylonitrile, N-vinylpyrrolidone, silicone-based (meth)acrylates (JNC products, trade names Cylaprene "FM-0711", "FM-0721", "FM-0725", etc.; Shin-Etsu Chemical Co., Ltd. products, "X-22-174DX", "X-22-2426", "X-22-2475", etc.), and fluorine-substituted (meth)acrylates (various fluorine-substituted alkyl (meth)acrylates from Daikin Industries, Ltd., etc.). These vinyl monomers may be used individually or in combination of two or more.

[0029] Furthermore, crosslinkable polyfunctional monomers may be added as needed. For example, polyfunctional monomers such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, tricyclodecanol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tri-tetra(meth)acrylate can be used, as well as those containing epoxy groups such as glycidyl(meth)acrylate, β-methylglycidyl(meth)acrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate, 3,4-epoxycyclohexylethyl(meth)acrylate, 3,4-epoxycyclohexylpropyl(meth)acrylate, allylglycidyl ether, and divinylbenzene can be used.

[0030] It is presumed that the grafted vinyl polymer chains spread out upon solvation in the solvent, and that their steric effect suppresses the proximity of CNTs to each other, thereby contributing to the dispersion stability of the CNTs. The mass ratio of the cellulose derivative to which the polymerizable functional group is introduced to the vinyl polymer is preferably in the range of 95:5 to 5:95. When the mass ratio is within this range, the steric hindrance of the grafted chains works effectively, and the CNTs can be easily dispersed.

[0031] The properties of the resulting vinyl polymer change depending on the selection of the vinyl monomers mentioned above, and in particular, the dispersion performance of surface-modified CNTs in organic solvents and resins changes. Generally speaking, the Solubility Parameter (SP) value is used as an indicator of affinity with the organic solvent or resin to be dispersed. It is desirable to design the product so that the SP values ​​of the grafted vinyl polymer and the target of dispersion are close.

[0032] It is also desirable to select vinyl monomers that have interactions with the material to be dispersed (especially resins). These interactions include hydrophobic interactions such as alkyl groups, hydrogen bonds such as hydroxyl groups, amino groups, carboxyl groups, and amide groups, and conjugated system interactions such as π-π due to aromatic rings. This can be achieved by using vinyl monomers with such functional groups. Furthermore, it is possible to introduce reactive groups into the generated vinyl polymer and form bonds with the resin to be dispersed. One method for this is copolymerizing vinyl monomers containing epoxy groups, such as glycidyl (meth)acrylate and 3,4-epoxycyclohexylmethyl (meth)acrylate. Another method is to introduce polymerizable (meth)acrylate groups, vinyl groups, allyl groups, etc., through chemical reactions using functional groups in the generated vinyl polymer, such as hydroxyl groups and carboxyl groups. The introduction of such reactive groups can be achieved by addition reactions using isocyanate group-containing (meth)acrylates such as Karenz MO-I and AO-I (manufactured by Showa Denko), glycidyl (meth)acrylate, and 3,4-epoxycyclohexylmethyl (meth)acrylate.

[0033] In the present invention, the vinyl polymer may have an electrostatic group. Having an electrostatic group in the vinyl polymer allows for higher concentration dispersion of CNTs. This is because the presence of an electrostatic group in the vinyl polymer causes moderate electrostatic repulsion between the vinyl polymers, further suppressing the proximity of CNTs. Examples of such electrostatic groups include amino groups, quaternary ammonium groups, acidic groups, and their salts. Quaternary ammonium groups can be realized by using vinyl monomers containing quaternary ammonium groups, or by polymerizing various monomers containing secondary or tertiary amino groups as one component, and then reacting them with alkyl halogen compounds or the like to achieve quaternary formation. Acidic groups and their salts can be realized by polymerizing vinyl monomers containing acids such as carboxyl groups, phosphate groups, and sulfonic acid groups as one component, and then reacting them with various base compounds, such as metal hydroxides, various amines, and various ammonium hydroxides. Furthermore, for charging groups, it is desirable to use large molecular sizes, so-called soft salts, that exhibit excellent charging properties even in low dielectric constant organic solvents.

[0034] In the polymerization described above, it is not necessary for all vinyl polymers formed from vinyl monomers to be grafted (chemically bonded) to cellulose derivatives. Polymers produced by the homopolymerization of vinyl monomers may also be included. Furthermore, vinyl polymers that are not chemically bonded to such cellulose derivatives can be removed by known purification methods such as precipitation separation or filtration.

[0035] (Polymerization solvent) In this specification, the solvent used in the polymerization reaction is referred to as the polymerization solvent. In the polymerization of vinyl monomers into cellulose derivatives having polymerizable functional groups, general organic solvents can be used. The reaction solvent used when introducing the polymerizable functional groups can be used as the polymerization solvent, or a different organic solvent may be used. Examples include ethyl acetate, propyl acetate, butyl acetate, tetrahydrofuran, dioxane, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethyl alcohol, isopropyl alcohol, butyl alcohol, benzyl alcohol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethyl lactate, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate (butyl carbitol acetate), diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol ethyl methyl One or a mixture of diethylene glycol ether, diethylene glycol isopropyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol dimethyl ether, propylene glycol diacetate, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol dibutyl ether, tripropylene glycol dimethyl ether, dihydroterpineol acetate, terpineol, dihydroterpineol, dihydroterpineol acetate, pyridine, etc. can be used.

[0036] (Polymerization initiator) The polymerization initiator referred to here is a chemical substance used to graft vinyl monomers onto polymerizable functional groups. There are many types of polymerization initiators, including ionic polymerization initiators and radical polymerization initiators, but the choice is not particularly limited, and conventionally known ones can be used. However, it is preferable to appropriately select a radical polymerization initiator that has high efficiency. The radicals generated from the radical polymerization initiator are quickly captured by the polymerizable functional groups introduced into the cellulose derivative and the vinyl monomers, and a block polymer is efficiently formed.

[0037] Specifically, examples include azo-based and peroxide-based radical polymerization initiators such as 2,2'-azobis-(2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis-(cyclohexane-1-carbonnitrile), lauryl peroxide, benzoyl peroxide, di-t-butyl peroxide, and t-butylperoxy-2-ethylhexanoate.

[0038] Furthermore, redox initiators, which combine a polymerization initiator with a reducing agent, can also be used. These polymerization initiators may be used individually or in appropriate mixtures of two or more types. The amount of polymerization initiator used is not particularly limited, but it should be appropriately selected from a range of 0.1 to 10% of the total mass of monomers during polymerization. The polymerization time and temperature should also be appropriately selected from the range of general radical polymerization conditions. As described above, the modified components used in the present invention can be obtained.

[0039] In the present invention, it is necessary to set the average number of polymerizable functional groups to 1 to 8 relative to the number of moles calculated from the Mn of the cellulose derivative. In other words, depending on the combination of cellulose derivatives and vinyl monomers, if the average number of moles of polymerizable functional groups is less than 1, surface-modified CNTs with good dispersibility cannot be obtained. If it is greater than 8, the reaction solution gels or side reactions occur that hinder the formation of good surface-modified CNTs.

[0040] By sequentially carrying out the reaction using the raw materials described above, a modified component is obtained, which consists of a block polymer having a portion derived from a cellulose derivative into which polymerizable functional groups have been introduced, and a vinyl polymer portion derived from a vinyl monomer in which vinyl monomers have been graft-polymerized onto the polymerizable functional groups. Next, a method for obtaining surface-modified CNTs from the modified component and CNTs will be described.

[0041] Surface-modified CNTs can be obtained by weighing out appropriate masses of the aforementioned modifying components and CNTs, adding them to an adsorption solvent (a solvent used to adsorb modifying components onto CNTs), and dispersing them using an optimal dispersion apparatus. The preferred mass ratio of CNTs to modifying components is in the range of 100:1 to 1:100.

[0042] For adsorption, dispersion devices such as ultrasonic homogenizers, high-pressure homogenizers, ball mills, bead mills, jet mills, dissolvers, paint shakers, motor-driven stirring blades, and magnetic stirrers can be used.

[0043] The adsorption solvent used when adsorbing the modifying components onto the surface of CNTs includes ethyl acetate, butyl acetate, tetrahydrofuran, dioxane, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethyl alcohol, isopropyl alcohol, butyl alcohol, benzyl alcohol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethyl lactate, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate (butyl carbitol acetate), diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, and diethylene One or a mixture of the following can be used: diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol dimethyl ether, propylene glycol diacetate, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol dibutyl ether, tripropylene glycol dimethyl ether, dihydroterpineol acetate, terpineol, dihydroterpineol, and dihydroterpineol acetate. Among these, N-methylpyrrolidone is preferred due to its ease of adsorption, but other adsorption solvents may also be used by optimizing the dispersion apparatus and dispersion conditions.

[0044] Through the above operation, surface-modified CNTs are obtained in which the modifying components are adsorbed onto the CNTs. At first glance, hydrophobic CNTs and hydrophilic cellulose derivatives having hydroxyl groups may seem to have low affinity, but although the detailed mechanism is unknown, it is presumed that some kind of interaction acts between the cellulose derivative portion and the CNTs, causing adsorption, and thus contributing to an excellent dispersion effect. Furthermore, in the surface-modified CNTs of the present invention, the adsorbed modifying components quickly solvate in the dispersion solvent and spread, promoting the dispersion of the CNTs, and thus exhibiting good dispersibility even with relatively gentle stirring forces. Therefore, it is possible to improve upon the problems of conventional technology, such as the cutting of CNT fibers and deterioration of the surface.

[0045] Furthermore, although the above manufacturing method involves dispersion in an organic solvent, surface-modified CNTs can also be obtained as a dried product by removing the organic solvent after dispersion. In this case, it is also preferable to wash the surface-modified CNTs to remove unreacted monomers, etc. The washing solvent is not particularly limited, but one example is deionized water.

[0046] (Method for producing surface-modified CNTs (2) Method for producing surface-modified CNTs according to the present invention) Up to this point, in order to explain the structure of the surface-modified CNTs of the present invention, we have described the manufacturing process following the steps of obtaining a modification component from a cellulose derivative as a raw material, and then obtaining surface-modified CNTs from the obtained modification component and CNTs. However, by employing the method for producing surface-modified CNTs of the present invention as described below, surface-modified CNTs can be obtained efficiently with fewer by-products. The method for producing surface-modified CNTs of the present invention is described below.

[0047] The present invention provides a method for producing surface-modified CNTs, comprising: step 1) reacting a cellulose derivative with an organic compound having polymerizable functional groups to introduce polymerizable functional groups; step 2) dispersing the product from step 1) and CNTs in a solvent to obtain a composite composition (CNT-CeD) in which the product from step 1) is adsorbed onto the surface of the CNTs; and step 3) adding a vinyl monomer to the reaction solution from step 2) to graft polymerize the vinyl monomer onto the polymerizable functional groups to obtain surface-modified CNTs (CNT-CeD / Ac). Details of each step are described below.

[0048] <Process 1> Step 1 is a step in which a polymerizable functional group is introduced into a cellulose derivative by reacting it with an organic compound having a polymerizable functional group in a reaction solvent. The reaction conditions, chemical substances used, and reaction solvent are the same as those described in manufacturing method (1).

[0049] <Process 2> Step 2 involves dispersing the product from Step 1 and CNTs in an adsorption solvent to obtain a composite composition (CNT-CeD) in which the product from Step 1 is adsorbed onto the surface of the CNTs. For example, a (CNT-CeD) dispersion is prepared by processing the adsorption solvent shown in the composition production example of the manufacturing method (1) above, the polymerizable functional group-introduced cellulose derivative which is the product of step 1, and CNTs in a dispersion device. The mixing and dispersion device can be at least one selected from the ultrasonic homogenizer, high-pressure homogenizer, ball mill, bead mill, jet mill, desolver, paint shaker, motor-driven stirring blade, magnetic stirrer, etc. The preferred mass ratio of CNTs to the cellulose derivative into which polymerizable functional groups are introduced is in the range of 0.001 to 10 parts by mass per 1 part by mass of CNTs.

[0050] The stirring speed or output of each dispersion device during dispersion, the processing time, and the temperature conditions should be determined appropriately considering the type of adsorbent solvent, the concentration of each component, etc. Additives may be added as long as the adsorption of CNTs and cellulose derivatives into which polymerizable functional groups have been introduced is not significantly impaired. For example, by adding a small amount (approximately 0.1 to 10% by mass) of another CNT dispersion composition or surfactant that is compatible with the cellulose derivative, adsorption processing can be performed at a low output.

[0051] <Process 3> Step 3 is a step in which a vinyl monomer and a polymerization initiator are added to a solution in which the CNT-CeD prepared in Step 2 is dispersed, and the vinyl monomer is graft polymerized onto the polymerizable functional groups of CNT-CeD to obtain surface-modified CNTs (CNT-CeD / Ac). The chemical substances used in the polymerization reaction are the same as those used in manufacturing method (1). For example, a vinyl monomer composition (containing at least one monomer, a radical polymerization initiator, and other solvents) can be added dropwise to the (CNT-CeD) dispersion, and after thoroughly removing oxygen from the reaction system by purging with an inert gas such as nitrogen, the vinyl monomer can be polymerized and grafted by heating or other means. The radicals generated from the radical polymerization initiator are rapidly captured by the polymerizable functional groups introduced into the cellulose derivative and the vinyl monomer, thereby efficiently forming a block polymer.

[0052] The preferred monomer concentration in the polymerization reaction is selected within the range of 1 to 50% by mass relative to the total mass of the polymerization solution. By setting the monomer concentration within this range, a high polymerization reaction rate can be achieved without the risk of gelation. The amount of polymerization initiator used is not particularly limited, but it should be appropriately selected from a range of 0.1 to 10% by mass relative to the total mass of monomers during polymerization. The polymerization time and temperature should also be appropriately selected from the general range of conditions for radical polymerization. The vinyl monomer may be mixed in step 2, or it may be added beforehand when preparing the (CNT-CeD) dispersion. The polymerization temperature and time can be set appropriately according to the polymerization start temperature and reactivity of the vinyl monomer, but for example, it can be 50 to 110°C for 2 to 24 hours.

[0053] The mass ratio of the cellulose derivative to which the polymerizable functional group is introduced to the vinyl polymer is preferably in the range of 95:5 to 5:95. When the mass ratio is within this range, the steric hindrance of the graft chain works effectively, making it possible to obtain surface-modified CNTs that can be easily dispersed in various solvents.

[0054] <Other processes> The manufacturing method according to the present invention may include steps other than steps 1 to 3 described above. For example, by adding steps such as filtration, washing with a solvent, and drying after step 2, the by-products of step 2 can be removed. To perform filtration efficiently, it is also preferable to add a filter adjusting agent such as ion-exchanged water to appropriately aggregate the surface-modified CNTs.

[0055] The surface-modified CNTs of the present invention are not limited to those produced by the method for producing surface-modified CNTs of the present invention described above. However, the method for producing surface-modified CNTs of the present invention makes it less likely for gelation to occur when grafting vinyl polymers onto the polymerizable functional groups of cellulose derivatives, allowing for the production of surface-modified CNTs with a wide range of designs. Although the mechanism is unknown, it is presumed that thickening or gelation during the reaction is suppressed by introducing polymerizable functional groups into a cellulose derivative, then adsorbing the product onto CNTs to obtain CNT-CeD, and then grafting vinyl polymers onto the polymerizable functional groups of this CNT-CeD.

[0056] [Surface modified CNT dispersion composition] The surface-modified CNT dispersion composition of the present invention is obtained by dispersing the surface-modified CNTs in a dispersion solvent. The dispersion solvent is not particularly limited, and the reaction solvents described in the above-mentioned production method may be used as is, but for example, ester solvents (ethyl acetate, butyl acetate, etc.), ketone solvents (methyl isobutyl ketone, cyclohexanone, etc.), hydrocarbon solvents (hexane, n-decane, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.), low-polarity alcohol solvents (terpineol, dihydroterpineol, etc.), ether solvents (dimethyl ether, diethyl ether, etc.), halogen solvents (dichloroethane, trichloromethane, etc.), amide solvents (dimethylformamide, dimethylacetamide, etc.), N-methylpyrrolidone, etc. can be preferably used.

[0057] As described above, the organic solvent used when producing the surface-modified CNTs may be the dispersion composition of the dispersion, or the organic solvent may be removed, and the purified and dried surface-modified CNTs may be redispersed in another organic solvent. The dispersion apparatus for redispersion may be at least one selected from the ultrasonic homogenizer, high-pressure homogenizer, ball mill, bead mill, jet mill, desolver, paint shaker, motor-driven stirring blade, magnetic stirrer, etc.

[0058] The surface-modified CNT dispersion composition of the present invention may contain various resins, functional materials, particles, plasticizers, dyes, and stabilizers, to the extent that they do not impair the properties. Examples include curing resin precursors such as acrylic resins, styrene resins, polyester resins, fluororesins, various epoxy resins, and various acrylic monomers; carbon-based materials other than CNTs, such as carbon, graphite, graphene, carbon nanohorns, and fullerenes; cellulose-based materials, such as cellulose nanofibers and cellulose nanocrystals; metal particles, ceramic particles, viscosity modifiers, storage stabilizers, various polymerization initiators, curing agents, photosensitive materials, conductive materials, thermally conductive materials, dyes, and the like.

[0059] The amounts of these additives are not particularly limited and can be changed as appropriate depending on the application. For example, they can be appropriately selected from a range of 0.001 to 90% by mass relative to the total mass of the surface-modified CNT dispersion composition.

[0060] Furthermore, a CNT-dispersed resin composition can also be prepared by redispersing the surface-modified CNTs in the vinyl monomer or epoxy resin, polymerizing or curing them using the polymerization initiator or curing agent, or simply dispersing them in the resin and then removing the organic solvent.

[0061] Furthermore, the CNT dispersion composition of the present invention has a wide range of applications as a solvent-containing solution or varnish-like composition, and is also a useful material that can be widely applied as a solvent-free coating film, film, or various components with different thicknesses and shapes.

[0062] Furthermore, the surface-modified CNTs and CNT dispersion compositions of the present invention possess excellent dispersibility and dispersion stability, making them easy to adjust viscosity and giving them superior electrical and thermal conductivity. They are useful for a wide range of applications as conductivity-imparting additives in batteries, conductive inks, transparent conductive films, and thermal conductive materials with high thermal conductivity. [Examples]

[0063] The following examples and comparative examples illustrate the surface-modified carbon nanotubes (CNTs), surface-modified CNT dispersion compositions, and methods for producing the same according to the present invention. However, the present invention is not limited to these examples. The samples (chemicals) used are as follows: <Cellulose derivatives> STD4: Etocel STD-4 manufactured by Dow Chemical (Mn: 14,000) STD10: Etocel STD-10 manufactured by Dow Chemical (Mn: 25,000) STD20: Etocel STD-20 manufactured by Dow Chemical (Mn: 40,000) STD45: Etocel STD-45 manufactured by Dow Chemical (Mn: 56,000) STD100: Etocell STD-100 manufactured by Dow Chemical (Mn: 75,000) CAB: Eastman CAB553-0.4 (Mn: 26,000) CAP: Eastman CAP504-0.2 (Mn: 18,000) <Condensing agent> DIC: N-N'-diisopropylcarbodiimide manufactured by Tokyo Chemical Industry Co., Ltd. <Reaction accelerator> DMAP: 4-dimethylaminopyridine manufactured by Tokyo Chemical Industry Co., Ltd. <Organic compounds> AA: Acrylic acid manufactured by Tokyo Chemical Industry Co., Ltd. MAA: Methacrylic acid manufactured by Tokyo Chemical Industry Co., Ltd. SA: Mono(2-methacryloyloxyethyl) succinate manufactured by Sigma-Aldrich A-SA: Mono(2-acryloyloxyethyl) succinate manufactured by Sigma-Aldrich MMP: Mono-2-(methacryloyloxy)ethyl phthalate, manufactured by Tokyo Chemical Industry Co., Ltd. MPA: Mercaptopropionic acid manufactured by Tokyo Chemical Industry Co., Ltd. MOI: Resonac Corporation's Kalens MOI <cnt> CNT: Single-walled carbon nanotubes manufactured by Sigma-Aldrich. <Vinyl monomers> MMA: Methyl methacrylate manufactured by Tokyo Chemical Industry Co., Ltd. iBMA: Isobutyl methacrylate manufactured by Tokyo Chemical Industry Co., Ltd. EHMA: 2-ethylhexyl methacrylate manufactured by Tokyo Chemical Industry Co., Ltd. BzMA: Benzyl methacrylate 2, manufactured by Tokyo Chemical Industry Co., Ltd. DMA: 2-(dimethylamino)ethyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd. <Polymerization initiator> Perocta-O: 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate manufactured by NOF Corporation <Other> t-BuBr: 2-bromo-2-methylpropane manufactured by Tokyo Chemical Industry Co., Ltd. Polymethyl methacrylate: Methyl methacrylate polymer manufactured by Tokyo Chemical Industry Co., Ltd.

[0064] [Solution of cellulose derivative into which polymerizable functional groups have been introduced] <Synthesis Examples 1-17> Based on the methods described in Japanese Patent Publication No. 6742791 and Japanese Patent Publication No. 7061795, a cellulose derivative solution in which polymerizable functional groups were introduced was prepared by dissolving a cellulose derivative, an organic compound, DIC, and DMAP in ethyl acetate to a concentration of 15% by mass of the cellulose derivative, and heating and stirring at 40°C for 5 hours to react the organic compound with the cellulose derivative.

[0065] Small samples were taken from the cellulose derivative solution into which the polymerizable functional groups had been introduced, reprecipitated and purified with heptane, dried, and subjected to NMR analysis to determine the average number of moles of the introduced polymerizable functional groups. Furthermore, the Mn content of the cellulose derivative solution was measured using the method described below. Details are shown in Table 1.

[0066] <Synthesis Example 18> 100 parts by mass of STD10 and 565 parts by mass of ethyl acetate were added to a reaction vessel and mixed to prepare a solution in which ethylcellulose was uniformly dissolved in ethyl acetate. Furthermore, molecular sieves were added to remove as much water as possible for dehydration. To the above solution, 3.41 parts by mass of an organic compound and 0.03 parts by mass of dioctyltin dilaurate were added, and the mixture was reacted at 60°C for 5 hours to react the MOI with ethylcellulose, thereby preparing cellulose derivative solution B-8 in which polymerizable functional groups were introduced. Small samples were taken from the cellulose derivative solution into which the polymerizable functional groups were introduced, dried, and subjected to NMR analysis, revealing that an average of 5 moles of polymerizable functional groups were introduced.

[0067] (Measurement of non-volatile content) Approximately 0.3 g of a cellulose derivative solution into which polymerizable functional groups have been introduced was accurately weighed, and the non-volatile content was calculated from the mass before and after heat treatment at 100°C for 5 hours. The non-volatile content is calculated using the following formula. Non-volatile content (mass%) = {(mass after heat treatment) / (mass before heat treatment)} × 100

[0068] (Measurement of number-average molecular weight) Using tetrahydrofuran as the mobile phase, analysis was performed by gel permeation chromatography (GPC) to determine the Mn content in terms of polystyrene.

[0069] [Table 1]

[0070] [Production of surface-modified CNTs by manufacturing method (1)] <Example 1> To achieve a mass ratio of polymerizable functional groups to vinyl polymer (hereinafter referred to as the CeD / Ac ratio) of cellulose derivative solution B-2 with polymerizable functional groups (20 parts by mass of the polymerizable functional group-containing cellulose derivative in the solution), 20 parts by mass of EHMA, 0.8 parts by mass of perocta-O, and 118 parts by mass of ethyl acetate as the polymerization solvent, the mixture was placed in a reaction vessel and mixed, and the reaction vessel was thoroughly purged with nitrogen gas. By heating and stirring at 75°C for 8 hours, modified component 1 was prepared in which the vinyl polymer was grafted onto the polymerizable functional groups of the cellulose derivative. 0.02 parts by mass of CNTs, 0.67 parts by mass of the above reaction solution (0.10 parts by mass of modification component 1 in the solution), and 20 parts by mass of N-methylpyrrolidone as an adsorption solvent were placed in a polypropylene container. This solution was treated with an ultrasonic dispersion device at 40 μm for 1 minute to obtain a CNT-CeD / Ac dispersion in which the CNTs were wetted and spread in the adsorption solvent due to the interaction of modification component 1. The obtained CNT-CeD / Ac dispersion was added to 200 parts by mass of deionized water, and the moderately aggregated CNT-CeD / Ac was filtered and dried to obtain surface-modified CNT1-1.

[0071] <Example 2> Modified component 2 and surface-modified CNT1-2 were obtained in the same manner as in Example 1, except that the cellulose derivative solution B-2 into which polymerizable functional groups were introduced was 173 parts by mass, EHMA was 13 parts by mass, and ethyl acetate was 80 parts by mass.

[0072] <Example 3> Modified component 3 and surface-modified CNT1-3 were obtained in the same manner as in Example 1, except that the cellulose derivative solution B-2 into which polymerizable functional groups were introduced was 84 parts by mass, EHMA was 27 parts by mass, and ethyl acetate was 209 parts by mass.

[0073] [Production of surface-modified CNTs by manufacturing method (2)] <Example 4> 0.02 parts by mass of CNTs, 0.32 parts by mass of solution A-1 of a cellulose derivative into which polymerizable functional groups have been introduced (0.05 parts by mass of the cellulose derivative into which polymerizable functional groups have been introduced in the solution), and 1 part by mass of MMA, a vinyl monomer, were placed in a polypropylene container together with 19 parts by mass of N-methylpyrrolidone, an adsorption solvent. This solution was treated with an ultrasonic dispersion device (US-300AT, manufactured by Nippon Seiki Co., Ltd.) at 40 μm for 1 minute to obtain a CNT-CeD dispersion in which the CNTs were wetted and spread out on the adsorption solvent due to the interaction of the cellulose derivative into which polymerizable functional groups have been introduced. 0.02 parts by mass of perocta-O was added to the obtained CNT-CeD dispersion, and the mixture was incubated at 75°C for 6 hours under magnetic stirring to obtain a CNT-CeD / Ac dispersion. The obtained CNT-CeD / Ac dispersion was added to 200 parts by mass of deionized water, and the moderately aggregated CNT-CeD / Ac was recovered by filtration and washed with deionized water. The washed CNT-CeD / Ac was dried at 40°C to obtain surface-modified CNTs 1-4.

[0074] (Calculation of the mass ratio of CNTs / cellulose derivatives with polymerizable functional groups / vinyl polymers) Unreacted monomers and some acrylic homopolymers are removed by filtration and washing. The mass ratio (hereinafter referred to as mass ratio) of CNTs / cellulose derivatives with polymerizable functional groups / vinyl polymers in the obtained surface-modified CNTs was calculated from the measurement results of TG / DTA analysis under a nitrogen atmosphere using Seiko Instruments Inc.'s "EXSTAR TG / DTA6200".

[0075] <Examples 5-27> Surface-modified CNTs 1-5 to 1-27 were obtained in the same manner as in Example 1, except that the polymerizable functional group-introduced cellulose derivative solution and vinyl monomer used were as shown in Table 2. The mass ratio was calculated from the TG / DTA measurement results.

[0076] <Example 28> Surface-modified CNT1-28 was obtained in the same manner as in Example 1, except that the cellulose derivative solution to which polymerizable functional groups were introduced was B-2, and the vinyl monomers were 0.90 parts by mass of MMA and 0.10 parts by mass of DMA.

[0077] <Example 29> 0.02 parts by mass of CNTs, 0.31 parts by mass of cellulose derivative solution B-2 with polymerizable functional groups introduced, 0.9 parts by mass of vinyl monomer MMA, and 0.10 parts by mass of SA were placed in a polypropylene container along with 19 parts by mass of N-methylpyrrolidone as a dispersion medium. This solution was treated with an ultrasonic dispersant at 40 μm for 1 minute to obtain a CNT-CeD dispersion in which the CNTs were wetted and spread on the adsorbent solvent by the interaction of the cellulose derivative with polymerizable functional groups introduced. 0.02 parts by mass of perocta-O was added to the obtained CNT-CeD dispersion, and the mixture was kept warm at 75°C for 6 hours under magnetic stirring to obtain a CNT-CeD / Ac dispersion. After air cooling to room temperature, 0.060 parts by mass of t-BuBr was added and stirred for 30 minutes to quaternize the SA. Surface-modified CNTs 1-29 were obtained by adding the obtained CNT-CeD / Ac dispersion to 200 parts by mass of deionized water, and filtering and drying the moderately aggregated CNT-CeD / Ac.

[0078] [Surface modified CNT dispersion composition] <Example 30> 0.3 parts by mass of surface-modified CNT1-27 (mass ratio 1 / 2.5 / 6) prepared in Example 27 was weighed into a screw-cap tube, and 1.2 parts by mass of polymethyl methacrylate and 13.5 parts by mass of butyl acetate were mixed with it. The mixture was then stirred at room temperature for 30 seconds using an ultrasonic dispersion device to prepare a surface-modified CNT dispersion composition. This was applied to a PET film and dried at 120°C for 30 minutes to form a resin layer containing CNTs with a dry film thickness of approximately 10 μm. Using a Rolester GP probe manufactured by Mitsubishi Chemical Corporation, the surface resistance of the prepared dried coating film was measured at 20°C by applying the probe to the surface, and the result was 6.7 × 10⁻⁶. 6 The impedance was Ω / □, indicating sufficient conductivity.

[0079] <Comparative Example 1> 0.02 parts by mass of CNTs and 0.05 parts by mass of STD10 were placed in a polypropylene container along with 19 parts by mass of N-methylpyrrolidone, which was used as a dispersion medium. This solution was treated with an ultrasonic dispersion device at 40 μm for 1 minute to obtain a dispersion in which the CNTs were wetted and spread out in the adsorbent solvent due to the interaction of STD10. The above dispersion was added to 200 parts by mass of deionized water, allowed to coagulate appropriately, recovered by filtration, and washed with deionized water. The washed surface-modified CNTs were dried at 40°C to obtain surface-modified CNT2-1 modified with STD10. The obtained surface-modified CNT2-1 was found to be composed of CNT / STD10 = 1 / 2.5 in TG / DTA analysis under a nitrogen atmosphere, indicating that STD10 was almost quantitatively adsorbed onto the carbon nanotubes.

[0080] <Comparative Example 2> Cellulose derivative solution B-0 was prepared in the same manner as in Synthesis Example 1, except that STD10 was used as the cellulose derivative and MAA as the organic compound, and the molar ratio of [STD10]:[MAA]:[DIC]:[DMAP] was 1:0.8:0.8:0.08. NMR analysis confirmed an average molar number of polymerizable functional groups of 0.8, and GPC analysis confirmed a manganese content of 26,000. Furthermore, surface-modified CNT2-2 was obtained in the same manner as in Example 1, except that the cellulose derivative solution to which the polymerizable functional group was introduced was designated as B-0.

[0081] <Comparative Example 3> Cellulose derivative solution A-3 with polymerizable functional groups was prepared in the same manner as in Synthesis Example 1, except that STD4 was used as the cellulose derivative and MAA as the organic compound, and the molar ratio of [STD4]:[MAA]:[DIC]:[DMAP] was 1:10:10:1.0. NMR analysis confirmed that the average number of polymerizable functional groups was 10, and GPC analysis confirmed that the Mn content was 20,000. Furthermore, surface-modified CNT2-3 was obtained in the same manner as in Example 1, except that the cellulose derivative solution into which the polymerizable functional group was introduced was designated as A-3.

[0082] <Comparative Example 4> Cellulose derivative solution B-9 with polymerizable functional groups was prepared in the same manner as in Synthesis Example 1, except that STD10 was used as the cellulose derivative and MAA as the organic compound, and the molar ratio of [STD10]:[MAA]:[DIC]:[DMAP] was 1:10:10:1.0. NMR analysis confirmed that the average number of polymerizable functional groups was 10, and GPC analysis confirmed that the Mn content was 32,000. Furthermore, surface-modified CNT2-4 was obtained in the same manner as in Example 1, except that the cellulose derivative solution to which the polymerizable functional group was introduced was designated as B-9.

[0083] <Comparative Example 5> Cellulose derivative solution C-3, into which polymerizable functional groups were introduced, was prepared in the same manner as in Synthesis Example 1, except that STD20 was used as the cellulose derivative and MAA as the organic compound, and the molar ratio of [STD20]:[MAA]:[DIC]:[DMAP] was 1:10:10:1.0. NMR analysis confirmed that the average number of polymerizable functional groups was 10, and GPC analysis confirmed that the Mn content was 46,000. Furthermore, surface-modified CNT2-5 was obtained in the same manner as in Example 1, except that the cellulose derivative solution to which the polymerizable functional group was introduced was designated as C-3.

[0084] [Table 2]

[0085] [Evaluation of the dispersibility of surface-modified CNTs 1-4] The surface-modified CNTs in Examples 1-3 and Comparative Example 1 were diluted with n-heptane to a mass% concentration of 0.1% of the CNTs in the solvent, and then treated with an ultrasonic dispersion device at room temperature for 30 seconds. The liquid's appearance and microscopic observation using an Olympus BX53M microscope were performed, and the results were evaluated according to the following criteria. The results are summarized in Table 3. (Evaluation Criteria) 4. No aggregates were observed visually, and virtually no fibrous material was detected under a microscope. Compared to the 3:1 ratio, sufficient dispersibility was observed, but slight aggregates were visible to the naked eye, and microscopic observation revealed that the CNTs were not sufficiently wetted and spread in the solvent, with some fibrous material measuring several tens of micrometers being visible. Compared to a 2:1 ratio, sufficient dispersibility is observed, but aggregates can be seen visually, and large unfibrillated material measuring several hundred micrometers can be observed under a microscope. 1: The carbon nanotubes (CNTs) do not mix with the solvent at all and immediately settle and separate.

[0086] [Table 3]

[0087] [Evaluation of the dispersibility of surface-modified CNTs 5-33] For the surface-modified CNTs in Examples 4-27 and Comparative Examples 1-5, they were diluted with a dispersion solvent to a mass% concentration of 0.1% of the CNTs in the solvent, and then treated with an ultrasonic dispersion device at room temperature for 30 seconds. The liquid was examined visually and under a microscope, and evaluated according to the above evaluation criteria. The results are summarized in Table 4.

[0088] [Table 4]

[0089] [Evaluation of the dispersibility of surface-modified CNTs 34-35] For the surface-modified CNTs in Examples 28-29, they were diluted with a dispersion solvent to a CNT concentration of 0.3%, treated with an ultrasonic dispersion device at room temperature for 1 minute, and evaluated according to the evaluation criteria described above. The results are summarized in Table 5.

[0090] [Table 5]

[0091] [Discussion of Results] In dispersion evaluations 1-3, it was confirmed that surface-modified CNTs prepared by manufacturing method (1) dispersed well in n-heptane. On the other hand, in dispersion evaluation 4, it was confirmed that surface-modified CNTs modified with STD10 did not disperse at all in n-heptane. From this, it can be said that the modifying component of the present invention contributes significantly to the dispersion of CNTs, and in particular, the steric hindrance of the vinyl polymer portion plays an important role.

[0092] In dispersion evaluations 5-22, it was confirmed that surface-modified CNTs prepared by manufacturing method (2) dispersed well in ethyl acetate. Furthermore, dispersion evaluations 5-16 and 21-22, where the Mn of the cellulose derivative was 50,000 or less, showed particularly good dispersibility. Among these, dispersion evaluations 10-14, using specific organic compounds, showed extremely good dispersibility.

[0093] On the other hand, in dispersion evaluations 29-32, the CNTs did not disperse at all in ethyl acetate, and settled immediately after stirring was stopped. Since the CNTs did not disperse at all in dispersion evaluation 29, which was modified only with STD10, it can be said that the steric hindrance of the vinyl polymer portion of the present invention plays an important role, similar to the case of manufacturing method (1). Furthermore, when the average number of moles of polymerizable functional groups is not in the range of 1 to 8, the steric hindrance of the vinyl polymer portion does not work, and the dispersibility is significantly reduced. Since the dispersibility did not improve at all even when the Mn of the cellulose derivative was changed, it can be said that adjusting the average number of moles of polymerizable functional groups is extremely important.

[0094] In dispersion evaluations 23-25, it was confirmed that surface-modified CNTs disperse in various solvents. In dispersion evaluations 26-28, it was confirmed that surface-modified CNTs with different mass ratios disperse uniformly.

[0095] Furthermore, by introducing specific functional groups into the vinyl polymer-derived portion, CNTs can be dispersed at high concentrations. Examples of this are shown in dispersion evaluations 34-35.

[0096] Furthermore, manufacturing method (2) tends to be less prone to gelation even when the number of moles introduced is increased, which broadens the range of design possibilities, and therefore may be more suitable than manufacturing method (1) depending on the composition. [Industrial applicability]

[0097] By using the surface-modified CNTs of the present invention, carbon materials can be easily and uniformly dispersed in organic solvents. The CNT dispersion composition of the present invention is useful as a constituent material for paints, inks, resists, adhesives, resin molded products, etc., exhibiting properties such as high conductivity and high thermal conductivity, and is suitable for various applications such as battery materials, conductive films, electronic component materials, IC chip covers, electromagnetic shielding, automotive components, and robot parts.< / cnt>

Claims

1. A surface-modified carbon nanotube comprising a carbon nanotube and a modified component comprising a block polymer having a cellulose derivative-derived portion consisting of a cellulose derivative into which polymerizable functional groups have been introduced, and a vinyl polymer portion derived from a vinyl monomer in which vinyl monomers have been graft-polymerized onto the polymerizable functional groups, wherein the average number of moles of the polymerizable functional groups is 1 to 8 relative to the number of moles calculated from the number-average molecular weight of the cellulose derivative, and the cellulose derivative-derived portion of the modified component is adsorbed onto the surface of the carbon nanotube by interaction.

2. The surface-modified carbon nanotube according to claim 1, wherein the number-average molecular weight of the cellulose derivative into which the polymerizable functional group is introduced is 1,000 to 50,000.

3. The surface-modified carbon nanotube according to claim 1, wherein the mass ratio of the cellulose derivative to which the polymerizable functional group is introduced to the vinyl polymer portion is in the range of 95:5 to 5:

95.

4. The surface-modified carbon nanotube according to claim 1, characterized in that the vinyl polymer portion has a charging group selected from an amino group, a quaternary ammonium group, an acid group, and a salt thereof.

5. Step 1) A step of introducing polymerizable functional groups by reacting a cellulose derivative with an organic compound having polymerizable functional groups, Step 2) Disperse the product from Step 1) and carbon nanotubes in an adsorption solvent to obtain a composite composition (CNT-CeD) in which the product from Step 1) is adsorbed on the surface of the carbon nanotubes. Step 3) Adding a vinyl monomer to the reaction solution from Step 2) and graft polymerizing the vinyl monomer onto the polymerizable functional group to obtain surface-modified carbon nanotubes (CNT-CeD / Ac). A method for producing surface-modified carbon nanotubes, characterized by including the following:

6. A surface-modified carbon nanotube according to any one of claims 1 to 4 is dispersed in a dispersion solvent. A dispersion composition of surface-modified carbon nanotubes.

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