JP2018012763A - Nanomaterial composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nanomaterial composition which can improve surface hardness when formed into a molded article.SOLUTION: The nanomaterial composition of the present invention contains: a dispersion medium; and cellulose nanofibers and carbon nanotubes dispersed in the dispersion medium. At least a part of the surface of the carbon nanotubes is preferably modified with a polar group. The polar group is preferably at least one selected from the group consisting of a hydroxyl group, a carbonyl group, and a carboxy group.SELECTED DRAWING: None

Description

  The present invention relates to a nanomaterial composition.

  Cellulose fiber is the basic skeletal material of all plants, and has an accumulation of over 1 trillion tons on the earth. Cellulose fiber is a fiber having a strength 5 times or more that of steel, though it is 1/5 lighter than steel. In order to further improve the mechanical strength of the cellulose fibers, cellulose nanofibers (hereinafter also referred to as “CNF”) obtained by defibrating cellulose fibers have been studied (for example, Patent Document 1). CNF is considered promising as a composite material capable of high strength and low thermal expansion in combination with a resin or the like, and various studies have been made on its structure and the like.

  When a composite material is produced by combining CNF and a resin, for example, a resin composition obtained by mixing a composition (nanomaterial composition) in which CNF is dispersed in a dispersion medium with a resin is obtained. A composite material (molded body) containing CNF and resin can be obtained by molding into a desired shape using.

JP 2011-213754 A

  However, even when a molded body containing CNF is molded by a conventional method, it is difficult to improve the surface hardness of the molded body.

  Then, in this invention, it aims at providing the nanomaterial composition which can improve the surface hardness when it is set as a molded object.

(1) The nanomaterial composition of the present invention includes a dispersion medium, and cellulose nanofibers (CNF) and carbon nanotubes (hereinafter also referred to as “CNT”) dispersed in the dispersion medium.

  According to the nanomaterial composition of the above (1), since CNF can be reinforced by interposing CNTs between CNFs when formed into a molded body, the surface hardness of the molded body can be improved.

(2) In the nanomaterial composition of (1), it is preferable that at least a part of the surface of the CNT is modified with a polar group. In the case of this configuration, since the dispersibility of CNTs in the dispersion medium can be improved, CNTs can be uniformly interposed between CNFs when formed into a molded body. Thereby, the surface hardness of a molded object can be improved uniformly.

(3) In the nanomaterial composition of (2), the polar group is preferably at least one selected from the group consisting of a hydroxyl group, a carbonyl group, and a carboxy group. In the case of this configuration, the dispersibility of CNTs in the dispersion medium can be further improved, so that the surface hardness of the molded body can be improved more uniformly. In addition, the case where the carbonyl group is modified includes not only the case where the carbonyl group is added to the CNT surface but also the case where the carbonyl group is formed by addition of an oxygen atom to the active point (defect) on the CNT surface. . In addition, the carboxy group is modified not only when a carboxy group is added to the CNT surface but also after a carbonyl group is formed by addition of an oxygen atom to an active point (defect) on the CNT surface. This includes the case where a carboxy group is formed by addition of a hydroxyl group to a carbonyl group. The same applies when at least a part of the surface of CNF described later is modified with a carboxy group.

(4) In the nanomaterial composition according to (1) to (3), the average diameter of the CNT is preferably 0.01 nm or more and 500 nm or less. By making the average diameter of CNTs 0.01 nm or more, the reinforcing effect can be enhanced. Moreover, since the dispersibility to a dispersion medium can be improved more because the average diameter of CNT shall be 500 nm or less, the surface hardness of a molded object can be improved more uniformly. The “average diameter” is an average value of the diameters of single CNTs observed with an electron microscope. For example, 10 single CNTs are arbitrarily selected with an electron microscope and the diameters of these CNTs are averaged. Value.

(5) In the nanomaterial composition according to (1) to (4), the CNT is preferably a multilayer CNT. According to this structure, since the reinforcement effect by CNT can be improved, the surface hardness of a molded object can be improved more. The “multilayer CNT” refers to a CNT having a structure in which two or more graphite layers are stacked and wound in a cylindrical shape.

(6) In the nanomaterial composition according to (1) to (5), the content of the CNT is preferably 0.01% by mass or more and 30% by mass or less. By making the content of CNT 0.01% by mass or more, the reinforcing effect can be enhanced. Moreover, since the precipitation of CNT in a dispersion medium can be suppressed by making content of CNT into 30 mass% or less, the surface hardness of a molded object can be improved uniformly.

(7) In the nanomaterial composition according to (1) to (6), at least a part of the surface of the CNF is preferably modified with a carboxy group. In the case of this configuration, since the dispersibility of CNF in the dispersion medium can be improved, a molded body in which CNF as a structural material is uniformly dispersed can be obtained. Thereby, the surface hardness of a molded object can be improved uniformly.

(8) In the nanomaterial composition of (7), it is preferable that an onium ion is further included as a counter ion of the carboxy group. In the case of this configuration, since the dispersibility of CNF in the dispersion medium can be further improved, a molded body in which CNF as a structural material is more uniformly dispersed can be obtained. Thereby, the surface hardness of a molded object can be improved more uniformly.

(9) In the nanomaterial composition of (8), the onium ion is preferably an ammonium ion. In the case of this configuration, the dispersibility of CNF in the dispersion medium can be further improved, so that a molded body in which CNF as a structural material is further uniformly dispersed can be obtained. Thereby, the surface hardness of a molded object can be improved further more uniformly.

(10) In the nanomaterial composition according to (1) to (9), it is preferable that an average fiber width of the CNF is 1 nm or more and 500 nm or less. By setting the average fiber width of CNF to 1 nm or more, the surface hardness of the molded body can be further improved. Moreover, since the precipitation of CNF in a dispersion medium can be suppressed by making the average fiber width of CNF 500 nm or less, the surface hardness of a molded object can be improved uniformly. The “average fiber width” is an average value of the single fiber widths of CNFs observed with an electron microscope. For example, 10 CNF single bodies are arbitrarily selected with an electron microscope, and the fiber widths of these CNFs are selected. Is an average value.

(11) In the nanomaterial composition according to (1) to (10), the CNF content is preferably 0.01% by mass or more and 30% by mass or less. By setting the CNF content to 0.01% by mass or more, the surface hardness of the molded body can be further improved. Moreover, since CNF precipitation in a dispersion medium can be suppressed by making content of CNF into 30 mass% or less, the surface hardness of a molded object can be improved uniformly.

(12) In the nanomaterial composition according to (1) to (11), a content ratio of the CNF to the CNT is preferably 1/10 or more and 10/1 or less by mass ratio. According to this structure, the surface hardness of a molded object can be improved more.

(13) In the nanomaterial composition according to (1) to (12), the dispersion medium may include at least one of water and an organic solvent.

(14) In the nanomaterial composition according to (13), the dispersion medium may be an alcohol.

(15) In the nanomaterial composition of (13), the dispersion medium is water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, 1-pentanol, It may be at least one selected from the group consisting of ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, styrene, ethyl acetate, toluene, xylene, methyl ethyl ketone and acetone.

  According to the nanomaterial composition of the present invention, the surface hardness when formed into a molded body can be improved.

  Hereinafter, preferred embodiments of the present invention will be described.

<Nanomaterial composition>
A nanomaterial composition according to an embodiment of the present invention includes a dispersion medium, and CNF and CNT dispersed in the dispersion medium. According to the nanomaterial composition according to the present embodiment, since the CNF can be reinforced by interposing CNTs between the CNFs when formed into a molded body, the surface hardness of the molded body can be improved. Hereinafter, the components of the nanomaterial composition according to this embodiment will be described.

(CNF)
CNF is a component that becomes a structural material of a molded body obtained by using the nanomaterial composition according to the present embodiment. Examples of cellulose fibers that are the raw materials for CNF include wood pulp such as mechanical pulp, chemical pulp, and semi-chemical pulp. Specifically, kraft wood pulp, hydrolyzed kraft wood pulp, sulfite wood pulp, etc. Bacterial cellulose, valonia cellulose, squirt cellulose, cotton cellulose, hemp cellulose, a mixture thereof, and the like can be used.

  The method for producing CNF is not particularly limited as long as CNF dispersible in a dispersion medium to be described later is obtained, and examples thereof include a method of physically and chemically treating the above exemplified raw materials (cellulose fibers). . Examples of the physical treatment method include a method of mechanically defibrating cellulose fibers. Specifically, an aqueous suspension or slurry containing cellulose fibers is refined, a high-pressure homogenizer, a grinder, uniaxial or multiaxial kneading. Examples thereof include a method of defibration by grinding or beating with a machine, a bead mill or the like.

  Further, as a method for obtaining CNF by chemical treatment of cellulose fibers, for example, N-oxyl compounds such as 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO) were used as catalysts. The method of processing a cellulose fiber using an oxidation reaction is mentioned. Oxidized cellulose obtained by this method becomes a homogeneous CNF dispersion by a mild dispersion treatment in the liquid.

  It is preferable that at least a part of the surface of CNF used in this embodiment is modified with a carboxy group. In this case, since the dispersibility of CNF in the dispersion medium can be improved, a molded body in which CNF as a structural material is uniformly dispersed can be obtained. Thereby, the surface hardness of a molded object can be improved uniformly.

  Examples of the method of modifying the surface of CNF with a carboxy group include a method of treating cellulose fibers using the above-described oxidation reaction, and specifically, a TEMPO oxidation method described in JP-A-2015-101694 is exemplified. it can.

  When using CNF in which at least a part of the surface is modified with a carboxy group, the nanomaterial composition of the present embodiment preferably further contains an onium ion as a counter ion of the carboxy group. In this case, since the dispersibility of CNF in the dispersion medium can be further improved, it is possible to obtain a molded body in which CNF as the structural material is more uniformly dispersed. Thereby, the surface hardness of a molded object can be improved more uniformly.

  Examples of the onium ions include ammonium ions, phosphonium ions, oxonium ions, sulfonium ions, fluoronium ions, chloronium ions, and the like. Among these, when ammonium ions are used, the dispersibility of CNF in the dispersion medium can be further improved, so that a molded body in which CNF as a structural material is further uniformly dispersed can be obtained. Thereby, the surface hardness of a molded object can be improved further more uniformly. As a method for introducing onium ions, a known method can be used. For example, a method described in JP-A-2015-101694 can be used.

  The average fiber width of CNF is preferably 1 nm or more and more preferably 2 nm or more from the viewpoint of further improving the surface hardness of the molded body. Further, from the viewpoint of suppressing the precipitation of CNF in the dispersion medium and improving the surface hardness of the molded body uniformly, the average fiber width of CNF is preferably 500 nm or less, and more preferably 200 nm or less.

  As content of CNF in a nanomaterial composition, 0.01 mass% or more is preferable from a viewpoint of improving the surface hardness of a molded object more, and 0.1 mass% or more is more preferable. Further, from the viewpoint of suppressing the precipitation of CNF in the dispersion medium and improving the surface hardness of the molded body uniformly, the content of CNF in the nanomaterial composition is preferably 30% by mass or less, and 10% by mass or less. Is more preferable.

(CNT)
CNT is a component that intervenes between CNFs to reinforce CNF when formed into a molded body. As long as this CNT can be dispersed in a dispersion medium described later, its production method and the like are not particularly limited, but CNT in which at least a part of the surface is modified with a polar group is preferable. According to the CNT in which at least a part of the surface is modified with a polar group, the dispersibility in the dispersion medium can be improved. Thereby, when it is set as a molded object, since CNT can be uniformly interposed between CNFs, the surface hardness of a molded object can be improved uniformly.

  The polar group is preferably at least one selected from the group consisting of a hydroxyl group, a carbonyl group, and a carboxy group. In this case, since the dispersibility of the CNTs in the dispersion medium can be further improved, the surface hardness of the molded body can be improved more uniformly.

  The method for introducing a polar group onto the surface of CNT is not particularly limited, and for example, a known method described in JP-A-2014-15387 can be employed. More specifically, first, CNT powder and sulfuric acid are mixed and stirred at a predetermined rate little by little to produce a mixed solution (step 1). Subsequently, nitric acid is mixed in the mixed solution at a predetermined ratio and stirred (step 2). Then, after heating this liquid mixture until it fully boils (process 3), heating is stopped and it cools (process 4). Subsequently, the mixed solution is diluted with an alkaline aqueous solution having a pH of 12 to 13 to adjust the pH value (step 5), and further cooled in the atmosphere (step 6). After cooling, the mixed solution is filtered to take out filtered water (step 7). And the taken-out filtered water (mixed liquid) is diluted with water (process 8). Here, step 7 and step 8 may be further repeated one or more times. Subsequently, the diluted mixed solution is centrifuged with a centrifuge (step 9), and then the supernatant is filtered while being irradiated with ultrasonic waves by an ultrasonic cleaner (step 10). Here, each of the step 9 and the step 10 may be further repeated once or more, and only one of the step 9 and the step 10 may be further repeated once or more. Subsequently, by diluting the obtained filtered water with water and adjusting it to a predetermined concentration, a dispersion of CNTs having polar groups introduced on the surface can be obtained.

  The average diameter of CNTs is preferably 0.01 nm or more, more preferably 0.1 nm or more, and even more preferably 1 nm or more from the viewpoint of enhancing the reinforcing effect. Further, from the viewpoint of further improving dispersibility in the dispersion medium, the average diameter of CNTs is preferably 500 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less.

  As the CNT used in the present embodiment, multi-layer CNT is preferable. When multi-layer CNTs are used, the reinforcing effect can be enhanced, so that the surface hardness of the molded body can be further improved.

  As content of CNT in a nanomaterial composition, 0.01 mass% or more is preferable from a viewpoint of improving a reinforcement effect, and 0.1 mass% or more is more preferable. Moreover, from the viewpoint of suppressing the precipitation of CNT in the dispersion medium and improving the surface hardness of the molded body uniformly, the content of CNT in the nanomaterial composition is preferably 30% by mass or less, and preferably 10% by mass or less. Is more preferable.

(Dispersion medium)
As the dispersion medium used in the present embodiment, those that do not react with CNF and CNT can be used, and specific examples include water, organic solvents, and mixed solvents thereof.

  Examples of the organic solvent include alcohols (methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, t-butanol, 1-pentanol, benzyl alcohol, etc.), polyhydric alcohols (Ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers ( Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol Methyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutene ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol Monophenyl ether, propylene glycol monophenyl ether, etc.), amines (ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, Tetrachi Pentamine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (2-pyrrolidone, N-methyl-2-pyrrolidone, Cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (dimethyl sulfoxide, etc.), sulfones (sulfolane, etc.), lower ketones (acetone, methyl ethyl ketone, etc.), toluene, Xylene, styrene, ethyl acetate, tetrahydrofuran, urea, acetonitrile and the like can be used. These organic solvents may be used individually by 1 type, and may be used in combination of multiple types.

(Other ingredients)
You may add other components, such as a dispersing agent, to the nanomaterial composition of this embodiment as needed. As the dispersant, water-soluble resins such as polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, and polyalkali alkali metal salts are preferable. These dispersants may be used alone or in combination of two or more.

  In addition, the nanomaterial composition of the present embodiment includes a surfactant such as an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant as other dispersants. Also good.

  Examples of the anionic surfactant include aromatic sulfonic acid surfactants (alkyl benzene sulfonates such as dodecylbenzene sulfonate, dodecyl phenyl ether sulfonate, etc.), monosoap anionic surfactants, ether sulfates. Surfactants, phosphate surfactants, carboxylic acid surfactants, and the like.

  Examples of the cationic surfactant include quaternary alkylammonium salts, alkylpyridinium salts, alkylamine salts, polyethyleneimine, polyvinylamine, polyallylamine, polyvinylpyridine, polyacrylamide and the like.

  Examples of the nonionic surfactant include ether type nonionic surfactants (polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether). , Polyoxyethylene lauryl ether, etc.), ester-based nonionic surfactants (polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, etc.) , Alkyl ethers of polyhydric alcohol fatty acids such as sorbitol and glycerin, alkyl esters of polyhydric alcohol fatty acids, amino alcohol fatty acid amides, etc. That.

  Examples of the amphoteric surfactants include alkylbetaine surfactants (such as lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, propyldimethylaminoacetic acid betaine), sulfobetaine-based surfactants. Surfactant, amine oxide type surfactant, etc. are mentioned.

  In addition to the above-mentioned components, the nanomaterial composition of the present embodiment can be used for nanomaterial compositions such as various water-soluble resins, water-dispersible resins, in vivo polymers such as proteins, and pH adjusters. It is possible to blend necessary components accordingly.

  In the nanomaterial composition of the present embodiment, the content ratio of CNF to CNT (CNF / CNT) is preferably from 1/10 to 10/1 in terms of mass ratio from the viewpoint of further improving the surface hardness of the molded body. 1/5 or more and 5/1 or less is more preferable.

  The method for producing the nanomaterial composition of the present embodiment is not particularly limited. For example, a method of dispersing powdered CNF and CNT in a dispersion medium, a method of adding powdered CNT to a CNF dispersion, and a CNT dispersion Any method may be used, such as a method of adding powdered CNF or a method of mixing a CNF dispersion and a CNT dispersion.

  The method for molding a molded body using the nanomaterial composition of the present embodiment is not particularly limited, and various molding methods can be employed depending on the purpose. For example, by mixing a nanomaterial composition and a resin to obtain a resin composition, the resin composition is used to mold the resin into a desired shape, or by applying the nanomaterial composition to a substrate or the like Examples include a method of forming a coating film containing CNF and CNT. In the latter case, the coating film corresponds to a molded body. Moreover, you may shape | mold the paper as a molded object by a well-known paper manufacturing method using a nanomaterial composition.

The nanomaterial composition of the present invention is suitable as a nanomaterial composition capable of improving the surface hardness when formed into a molded body.

Claims (15)

A dispersion medium;
A nanomaterial composition comprising cellulose nanofibers and carbon nanotubes dispersed in the dispersion medium.   The nanomaterial composition according to claim 1, wherein at least a part of the surface of the carbon nanotube is modified with a polar group.   The nanomaterial composition according to claim 2, wherein the polar group is at least one selected from the group consisting of a hydroxyl group, a carbonyl group, and a carboxy group.   The nanomaterial composition according to any one of claims 1 to 3, wherein an average diameter of the carbon nanotube is 0.01 nm or more and 500 nm or less.   The nanomaterial composition according to any one of claims 1 to 4, wherein the carbon nanotube is a multi-walled carbon nanotube.   The nanomaterial composition according to any one of claims 1 to 5, wherein a content of the carbon nanotube is 0.01 mass% or more and 30 mass% or less.   The nanomaterial composition according to any one of claims 1 to 6, wherein at least a part of the surface of the cellulose nanofiber is modified with a carboxy group.   The nanomaterial composition according to claim 7, further comprising an onium ion as a counter ion of the carboxy group.   The nanomaterial composition according to claim 8, wherein the onium ion is an ammonium ion.   The nanomaterial composition according to any one of claims 1 to 9, wherein an average fiber width of the cellulose nanofibers is 1 nm or more and 500 nm or less.   The nanomaterial composition according to any one of claims 1 to 10, wherein a content of the cellulose nanofiber is 0.01 mass% or more and 30 mass% or less.   The nanomaterial composition according to any one of claims 1 to 11, wherein a content ratio of the cellulose nanofibers to the carbon nanotubes is 1/10 or more and 10/1 or less by mass ratio.   The nanomaterial composition according to any one of claims 1 to 12, wherein the dispersion medium contains at least one of water and an organic solvent.   The nanomaterial composition according to claim 13, wherein the dispersion medium is alcohol.   The dispersion medium is water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, 1-pentanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, The nanomaterial composition according to claim 13, which is at least one selected from the group consisting of propylene glycol monoethyl ether, styrene, ethyl acetate, toluene, xylene, methyl ethyl ketone, and acetone.