JP6167749B2 - Antibacterial dispersion containing fine carbon fibers - Google Patents

Description

The present invention relates to an antimicrobial suspension or dispersion containing fine carbon short fibers. More specifically, the present invention relates to an antibacterial suspension or dispersion obtained by mixing / dispersing fine carbon fibers produced by a vapor phase growth method using a catalyst in an aqueous solution in which organic substances preferred by bacteria are dissolved.

Fine carbon materials such as carbon blacks, ketjen black, fullerene, graphene, and carbon nanotubes are used in a wide range of fields such as electronics and energy due to their electrical properties and thermal conductivity. In particular, carbon nanotubes, a type of fine carbon fiber, are tube-like carbon with a diameter of 1 μm or less, and can be used in various applications due to their high conductivity, tensile strength, heat resistance, etc. based on their unique structure. Expansion is expected. Among carbon nanotubes, fine carbon fibers such as multi-walled carbon nanotubes (hereinafter referred to as MWCNT) having a diameter of 10 nm to several tens of nm are relatively inexpensive, and are used in various fields such as conductive assistants and antistatic coatings for lithium ion batteries. Practical use is expected.

In order to effectively utilize the characteristics of the fine carbon fibers, it is preferable that the fine carbon fibers are uniformly dispersed without agglomeration. However, since general MWNTs are obtained as aggregates called bundles and rope-like bundles due to mutual cohesion (van der Waals force), and aggregates in which tubes are entangled in the growth process, these aggregates It is very difficult to break the nanotubes and uniformly disperse them in the dispersion medium.

As a method for stabilizing the dispersion of carbon nanotubes (hereinafter sometimes referred to as CNT), for example, an organic polymer such as a polymer-based dispersant such as a water-soluble polymer polyvinylpyrrolidone (hereinafter referred to as PVP) was used. Methods have been proposed (Non-patent Document 1, Patent Document 1). When such water-soluble dispersants are made into aqueous solutions, heterotrophic bacteria (those that use organic matter as a carbon source) tend to grow in a suitable environment and decay rapidly, so the addition and storage of antibacterial agents Antiseptic measures by management method were necessary. However, if an antibacterial agent is added separately, it will affect the performance such as conductivity, and in the storage management place, for example, if bacterial growth is suppressed in a cold place, new equipment is required and the work is complicated. There were problems such as becoming.

On the other hand, the carbon nanotube itself is disclosed as an antibacterial substance (Patent Document 2), and the antibacterial property is enhanced by a suspension or dispersion of carbon nanotubes contained in 0.001 to 50 wt%.

JP 2005-162877 A JP 2007-33040 A

CHEMICAL PHYSICS LETTERS vol. 13 264-271 (2001)

However, in Patent Document 2, although antibacterial properties of specific CNTs are described, antibacterial properties of other CNTs are not specifically disclosed. Moreover, it does not describe the difference in antibacterial properties among various CNTs.
The present application has been made to solve this problem, and an object thereof is to obtain a fine carbon dispersion having useful antibacterial properties based on the difference in antibacterial properties among various CNTs.

As a result of extensive research, the inventors of the present invention have a bell-like structure in which a graphite net surface composed of only carbon atoms produced by a vapor phase growth method has a closed top portion and a trunk portion having an open bottom portion. Forming a structural unit, an angle θ formed by the busbar of the trunk portion and the fiber axis is smaller than 15 °, and the bell-shaped structural units are stacked by sharing 2 to 30 pieces sharing a central axis, By using the fine carbon fiber characterized in that the aggregate is formed by connecting fibers at intervals in a head-to-tail manner, the antibacterial activity value defined in JIS Z2801: 2010 To find a fine carbon dispersion with antibacterial activity value that the number of viable bacteria after 24 hours of the indicator liquid is reduced by more than two orders of magnitude compared to the control (99% or more of live bacteria die) Made possible.
That is, the present invention relates to the following matters.

1. An antibacterial dispersion containing 0.001 to 20% by weight of fine carbon fibers, wherein the fine carbon fibers are fine carbon fibers produced by a vapor phase growth method, and are composed of only carbon atoms. The graphite mesh surface forms a bell-shaped structural unit having a closed top portion and a trunk portion that is open at the bottom, and an angle θ formed between the bus bar of the trunk portion and the fiber axis is smaller than 15 °, and the bell Two to thirty structural units share a central axis to form an aggregate, and the aggregate is connected to each other at intervals in a head-to-tail manner to form fibers. Antibacterial dispersions and suspensions containing fine carbon fibers.
2. In the antibacterial dispersion liquid containing fine carbon fibers as described above, the fine carbon fibers supply a mixed gas containing CO and H ₂ onto a catalyst containing cobalt spinel oxide in which magnesium is substituted and dissolved. Thus, a graphite net surface composed only of carbon atoms is obtained by growing fine carbon fibers composed of bell-shaped structural units having a closed top and a trunk that is open at the bottom. An antibacterial dispersion and suspension containing fine carbon fibers.
3. In the antibacterial dispersion liquid containing the fine carbon fiber described in the previous period, the fine carbon fiber contains a cobalt content of 0.3% by weight or more and a magnesium content of 0.01% by weight or more. Antibacterial dispersions and suspensions containing various carbon fibers.
4). The antibacterial dispersion liquid containing fine carbon fibers as described above, wherein the dispersion liquid contains water and an aqueous dispersant, and the antibacterial dispersion liquid and suspension containing fine carbon fibers.

According to the present invention, as a result of comparing various antibacterial properties by adding various CNTs to an aqueous solution in which an organic matter preferred by bacteria is dissolved, it is a fine carbon fiber produced by a vapor phase growth method, and is composed of only carbon atoms. The net surface forms a bell-shaped structural unit having a closed top portion and a trunk portion that is open at the bottom, and an angle θ formed between the bus bar of the trunk portion and the fiber axis is smaller than 15 °, and the bell-shaped structure The unit is formed by stacking 2 to 30 units sharing the central axis to form an aggregate, and the aggregate is connected to each other in a head-to-tail manner to form a fiber. It has been found that an excellent antibacterial property can be obtained with a simple carbon fiber compared to other types of CNTs.

The present invention makes it possible to store CNT dispersions and suspensions over a long period of time, eliminates the need for sterilization during packaging, sterilization treatment and nitrogen gas replacement, and may affect conductivity. It is beneficially used in cases where antiseptic measures such as the addition of preservatives are unnecessary and storage equipment with temperature control is unnecessary. In addition, when the product is used for, for example, a surface coating film, bacterial growth during the period until drying can be suppressed.

(A) It is a figure which shows typically the minimum structural unit (bell-shaped structural unit) which comprises fine carbon fiber. (B) It is a figure which shows typically the aggregate | assembly where 2-30 bell-shaped structural units were piled up. (A) It is a figure which shows typically a mode that an aggregate | assembly connects with a space | interval and comprises a fiber. (B) It is a figure which shows typically a mode that it bent and connected, when an aggregate | assembly connects with a space | interval.

The present invention will be described in detail below.
The fine carbon fiber used in the present invention is a fine carbon fiber produced by supplying and reacting a mixed gas containing CO and H ₂ on a catalyst containing cobalt spinel oxide in which magnesium is substituted and dissolved. Something is preferable.

Further, in the fine carbon fiber used in the present invention, the graphite mesh surface composed only of carbon atoms forms a bell-shaped structural unit having a closed top and an open trunk, and the bus bar of the trunk The angle θ formed between the fiber axis and the fiber axis is smaller than 15 °, and the bell-shaped structural units are stacked by sharing 2 to 30 pieces sharing the central axis, and the aggregate is a head-to-tail style. It is preferable that the fibers are formed by connecting at intervals.

By including the above fine carbon fiber in an aqueous solution in which organic matter preferred by bacteria is dissolved, the viable count after 24 hours of the bacterial solution, which is defined as an index of antibacterial activity value by JIS Z2801: 2010, even if it is contained in a trace amount It was possible to obtain an antibacterial activity value that decreased by two orders of magnitude or more (99% or more of viable bacteria were killed) compared to the control. Although the antibacterial performance of the fine carbon fiber is not clear, it is presumed that the CNT itself has antibacterial properties and further has excellent dispersibility, so that it has a more efficient effect.

Hereinafter, the fine carbon fiber used in the present invention will be described in detail. The fine carbon fiber used in the present invention and the production method thereof are the same as those described in the republished patent WO2009 / 110570, and may be referred to as AMC manufactured by Ube Industries, Ltd. or simply AMC. “AMC” is a registered trademark.

The fine carbon fiber used in the present invention has a bell-shaped structure as shown in FIG. The temple bell is found in Japanese temples, has a relatively cylindrical body, and is different in shape from a conical Christmas bell. As shown in FIG. 1 (a), the structural unit 11 has a top portion 12 and a trunk portion 13 having an open end, like a bell, and has a rotating body shape rotated about the central axis. It has become. The structural unit 11 is formed of a graphite network surface made of only carbon atoms, and the circumferential portion of the body portion open end is the open end of the graphite network surface. In FIG. 1A, the central axis and the body portion 13 are shown as straight lines for convenience, but may not necessarily be straight lines.

The trunk portion 13 gently spreads toward the open end. As a result, the bus bar of the trunk portion 13 is slightly inclined with respect to the central axis of the bell-shaped structural unit, and the angle θ formed by both is smaller than 15 °. More preferably, 1 ° <θ <15 °, and further preferably 2 ° <θ <10 °. If θ is too large, fine fibers composed of the structural unit exhibit a fishbone-like carbon fiber-like structure, and the conductivity in the fiber axis direction is impaired. On the other hand, when θ is small, the structure is close to a cylindrical tube shape, and the frequency at which the open end of the graphite mesh surface constituting the body of the structural unit is exposed to the outer peripheral surface of the fiber becomes low, so the conductivity between adjacent fibers deteriorates. .

The fine carbon fiber used in the present invention has defects and irregular turbulence. However, if such irregularity is eliminated and the shape of the whole is captured, the body portion 13 gradually moves toward the open end side. It can be said that it has a bell-shaped structure spread out. This fine carbon fiber does not mean that θ indicates the above range in all portions, but excludes defective portions and irregular portions while capturing the structural unit 11 as a whole, Overall, it means that θ satisfies the above range. Therefore, in the measurement of θ, it is preferable to exclude the vicinity of the crown 12 where the thickness of the trunk may be irregularly changed. More specifically, for example, when the length of the bell-shaped structural unit aggregate 21 is L as shown in FIG. 1B, (1/4) L, (1/2) L and ( 3/4) θ may be measured at three points of L to obtain an average, and the value may be used as the overall θ for the structural unit 11. In addition, it is ideal to measure L with a straight line. However, since the body part 13 is often a curved line in practice, it may be closer to the actual value when measured along the curve of the body part 13. .

The shape of the top of the head is smoothly continuous with the torso and has a curved surface that protrudes upward (in the drawing). The length of the top of the head is typically about D (FIG. 1 (b)) or less and about d (FIG. 1 (b)) for explaining the bell-shaped structural unit aggregate.

Furthermore, since active nitrogen is not used as a raw material as will be described later, other atoms such as nitrogen are not included in the graphite network surface of the bell-shaped structural unit. For this reason, the crystallinity of the fiber is good.

As shown in FIG. 1 (b), the fine carbon fiber used in the present invention has a bell-shaped structural unit assembly 21 (hereinafter referred to as “bell-shaped structural unit assembly”) in which 2 to 30 such bell-shaped structural units share a central axis. It may be simply called an aggregate.) The number of stacked layers is preferably 2 to 25, and more preferably 2 to 15.

The outer diameter D of the trunk | drum of the aggregate 21 is 5-40 nm, Preferably it is 5-30 nm, More preferably, it is 5-20 nm. Since the diameter of the fine fiber formed increases as D increases, for example, in order to impart functions such as conductive performance in a composite with a polymer, a large amount of addition is required. On the other hand, when D becomes small, the diameter of the fine fibers formed becomes thin and the aggregation of the fibers becomes strong. For example, in preparing a composite with a polymer, it becomes difficult to disperse. The measurement of the trunk outer diameter D is preferably performed by measuring at three points (1/4) L, (1/2) L, and (3/4) L from the top of the aggregate. In addition, although the trunk | drum outer diameter D is shown for convenience in FIG.1 (b), the value of actual D has the preferable average value of the said 3 points | pieces.

The inner diameter d of the aggregate body is 3 to 30 nm, preferably 3 to 20 nm, more preferably 3 to 10 nm. The inner diameter d of the trunk is also measured and averaged at three points (1/4) L, (1/2) L, and (3/4) L from the top of the bell-shaped structural unit assembly. Is preferred. In addition, although the trunk | drum internal diameter d is shown in FIG.1 (b) for convenience, the actual value of d has the preferable average value of the said 3 points | pieces.

The aspect ratio (L / D) calculated from the length L of the aggregate 21 and the body outer diameter D is 2 to 150, preferably 2 to 30, more preferably 2 to 20, and further preferably 2 to 10. is there. When the aspect ratio is large, the structure of the formed fiber approaches a cylindrical tube shape, and the conductivity in the fiber axis direction of one fiber is improved. However, the open end of the graphite network surface constituting the structural unit body is a fiber. Since the frequency of exposure to the outer peripheral surface is reduced, the conductivity between adjacent fibers is deteriorated. On the other hand, when the aspect ratio is small, the open end of the graphite mesh surface constituting the structural unit body portion is more frequently exposed to the outer peripheral surface of the fiber, so that the conductivity between adjacent fibers is improved. Since many short graphite mesh surfaces are connected in the axial direction, conductivity in the fiber axial direction of one fiber is impaired.

The bell-shaped structural unit and the bell-shaped structural unit aggregate in the fine carbon fiber used in the present invention have essentially the same configuration, but have different fiber lengths as follows.

As shown in FIG. 2A, the fine carbon fiber used in the present invention is formed by further connecting the aggregates in a head-to-tail manner. The head-to-tail style means that in the configuration of fine carbon fiber, the joining portions of the adjacent aggregates are the top (Head) of one aggregate and the lower end (Tail) of the other aggregate. It means that it is formed by the combination of. Specifically, the shape of the joint portion is the top of the bell-shaped structural unit of the outermost layer of the second aggregate 21b, further inside the bell-shaped structural unit of the innermost layer, at the lower end opening of the first aggregate 21a. Is inserted, and the top of the third assembly 21c is inserted into the lower end opening of the second assembly 21b, and this is further continued to form a fiber.

Each joining part which forms one fine fiber of the fine carbon fiber used for this invention does not have structural regularity, for example, the joined part of a 1st aggregate and a 2nd aggregate The length in the fiber axis direction is not necessarily the same as the length of the joint portion of the second assembly and the third assembly. Further, as shown in FIG. 2A, the two assemblies to be joined may be connected linearly sharing the central axis, but the bell-shaped structural unit assemblies 21b and 21c in FIG. As described above, the central axis may be joined without being shared, resulting in a bent structure at the joint. The length L of the bell-shaped structural unit assembly is generally constant for each fiber. However, in the vapor phase growth method, since raw material and by-product gas components and catalyst and product solid components are mixed, in the exothermic carbon deposition reaction, a heterogeneous reaction mixture composed of the gas and solids. A temperature distribution is generated in the reactor, for example, a locally high temperature is formed depending on the flow state, and as a result, some variation in the length L may occur.

In the fine carbon fiber configured as described above, at least a part of the open end of the graphite mesh surface at the lower end of the bell-shaped structural unit is exposed on the outer peripheral surface of the fiber according to the connection interval of the aggregate. As a result, the conductivity between adjacent fibers can be improved by the jumping effect (tunnel effect) caused by the jumping out of the π electrons without impairing the conductivity in the fiber axis direction of one fiber. The structure of the fine carbon fiber as described above can be observed by a TEM image. In addition, the effect of the fine carbon fiber of the present invention is considered to have almost no influence even when the aggregate itself is bent or there is a bend in the connecting portion of the aggregate. Therefore, in the TEM image, an assembly having a shape that is relatively close to a straight line is observed to obtain each parameter relating to the structure, and the structure parameter (θ, D, d, L) for the fiber may be obtained.

In XRD based on the Gakushin method of fine carbon fibers used in the present invention, the peak half width W (unit: degree) of the 002 plane measured is in the range of 2-4. When W exceeds 4, the graphite crystallinity is low and the conductivity is low. On the other hand, when W is less than 2, the graphite crystallinity is good, but at the same time, the fiber diameter becomes large, and a large amount of addition is required to impart a function such as conductivity to the polymer.

The graphite plane distance d002 obtained by XRD measurement by the Gakushin method of fine carbon fibers used in the present invention is 0.350 nm or less, preferably 0.341 to 0.348 nm. If d002 exceeds 0.350 nm, the graphite crystallinity is lowered and the conductivity is lowered. On the other hand, the fiber of less than 0.341 nm has a low yield in production.

The ash contained in the fine carbon fiber used in the present invention is 4% by mass or less, and purification is not necessary for normal use. Usually, it is 0.3 mass% or more and 4 mass% or less, More preferably, it is 0.3 mass% or more and 3 mass% or less. The ash content is determined from the weight of the oxide remaining after burning 0.1 g or more of the fiber.

Next, the manufacturing method of the fine carbon fiber used for this invention is demonstrated.

Using a catalyst in which magnesium is replaced by a solid solution with an oxide having a spinel crystal structure of cobalt, a mixed gas containing CO and H ₂ is supplied to catalyst particles, and fine carbon fibers are produced by vapor phase growth. .

The spinel crystal structure of cobalt in which Mg is substituted and dissolved is represented by MgxCo3-xOy. Here, x is a number indicating the replacement of Co by Mg, and formally 0 <x <3. In addition, y is a number selected so that the entire expression is neutral in terms of charge, and formally represents a number of 4 or less. That is, in the spinel type oxide Co3O4 of cobalt, divalent and trivalent Co ions exist, and when the divalent and trivalent cobalt ions are represented by CoII and CoIII, respectively, the spinel type crystal structure is obtained. The cobalt oxide is represented by CoIICoIII2O4. Mg displaces both CoII and CoIII sites and forms a solid solution. When Mg substitutes and dissolves CoIII, the value of y becomes smaller than 4 in order to maintain charge neutrality. However, both x and y take values in a range where the spinel crystal structure can be maintained.

As a preferable range that can be used as a catalyst, the solid solution range of Mg has a value x of 0.5 to 1.5, and more preferably 0.7 to 1.5. When the value of x is less than 0.5, the catalyst activity is low and the amount of fine carbon fibers produced is small. When the value of x exceeds 1.5, it is difficult to prepare a spinel crystal structure.

The spinel oxide crystal structure of the catalyst can be confirmed by XRD measurement, and the crystal lattice constant a (cubic system) is in the range of 0.811 to 0.818 nm, more preferably 0.812. ~ 0.818 nm. If “a” is small, the solid solution substitution of Mg is not sufficient, and the catalytic activity is low. Also, the spinel oxide crystal having a lattice constant exceeding 0.818 nm is difficult to prepare.

The reason why such a catalyst is suitable is that as a result of substitutional solid solution of magnesium in the cobalt spinel structure oxide, a crystal structure in which cobalt is dispersed in a magnesium matrix is formed. It is presumed that the aggregation of cobalt is suppressed.

The particle size of the catalyst can be selected as appropriate. For example, the median diameter is 0.1 to 100 μm, preferably 0.1 to 10 μm.

The catalyst particles are generally used by being applied to a suitable support such as a substrate or a catalyst bed by a method such as spraying. The catalyst particles may be sprayed directly onto the substrate or the catalyst bed, but the catalyst particles may be sprayed directly, but a desired amount may be sprayed by suspending and dispersing in a dispersion medium such as ethanol.

The catalyst particles are preferably activated before reacting with the raw material gas. Activation is usually performed by heating in a gas atmosphere containing H ₂ or CO. These activation operations can be performed by diluting with an inert gas such as He or N ₂ as necessary. The temperature at which the activation is performed is preferably 400 to 600 ° C, more preferably 450 to 550 ° C.

There is no particular limitation on the reactor for the vapor phase growth method, and the reaction can be performed by a reactor such as a fixed bed reactor or a fluidized bed reactor.

A mixed gas containing CO and H ₂ is used as a source gas that becomes a carbon source for vapor phase growth.

The added concentration of H ₂ gas {H ₂ / (H ₂ + CO)} is preferably 0.1 to 30 vol%, more preferably 2 to 20 vol%. If the addition concentration is too low, a cylindrical graphitic network surface forms a carbon nanotube-like structure parallel to the fiber axis. On the other hand, if it exceeds 30 vol%, the inclination angle of the carbon-side peripheral surface of the bell-shaped structure with respect to the fiber axis becomes large, and the fish-bone shape is exhibited, leading to a decrease in conductivity in the fiber direction.

Further, the raw material gas may contain an inert gas. Examples of the inert gas include CO ₂ , N ₂ , He, Ar, and the like. The content of the inert gas is preferably such that the reaction rate is not significantly reduced, for example, 80 vol% or less, preferably 50 vol% or less. Further, waste gas such as synthesis gas or converter exhaust gas containing H ₂ and CO can be appropriately treated and used as necessary.

The reaction temperature for carrying out the vapor phase growth is preferably 400 to 650 ° C, more preferably 500 to 600 ° C. If the reaction temperature is too low, fiber growth does not proceed. On the other hand, if the reaction temperature is too high, the yield decreases. Although reaction time is not specifically limited, For example, it is 2 hours or more, and is about 12 hours or less.

The reaction pressure for carrying out the vapor phase growth is preferably normal pressure from the viewpoint of simplifying the reaction apparatus and operation, but it is carried out under pressure or reduced pressure as long as Boudard equilibrium carbon deposition proceeds. It doesn't matter.

According to the method for producing fine carbon fibers used in the present invention, the amount of fine carbon fibers produced per unit weight of the catalyst is determined according to conventional production methods such as Non-Patent Document (Carbon 2003 (41) 2949-2959 (Gadelle P. Et al.) It was shown to be significantly larger than the method described. The amount of fine carbon fiber produced by this fine carbon fiber production method is 40 times or more per unit weight of the catalyst, for example, 40 to 200 times. As a result, it is possible to produce fine carbon fibers with less impurities and ash as described above.

Although the formation process of the joint specific to the fine carbon fiber produced by the method for producing fine carbon fiber used in the present invention is not clear, from the balance between exothermic Boudouard equilibrium and heat removal by circulation of the raw material gas, Since the temperature in the vicinity of the cobalt fine particles formed from the catalyst fluctuates up and down, it is considered that carbon deposition is formed by intermittent progress. That is, [1] formation of the top of the bell-shaped structure, [2] growth of the trunk of the bell-shaped structure, [3] growth stop due to temperature rise due to heat generated in the processes [1] and [2], [4] It is presumed that the joint part peculiar to the fine carbon fiber structure is formed by repeating the four processes of cooling by the circulating gas on the catalyst fine particles.

The form of cobalt contained in the fine carbon fiber in the present invention is not particularly limited, but preferably metallic cobalt, cobalt oxide, cobalt hydroxide, cobalt carbonate and cobalt sulfate are preferred, and metallic cobalt and cobalt oxide are particularly preferred.

Although the dispersion medium in this invention is not specifically limited in the range which can disperse | distribute a fine carbon fiber, It is preferable that it is a mixed solvent which consists of any 1 type or 2 types or more of water and / or a water mixed solvent.

Examples of water and water mixed solvents include water and alcohol mixed with water (methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, benzyl alcohol, etc.), polyhydric alcohol (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 Cole monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene Glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amine-based (ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenedia , Diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone ( NEP), N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methylcaprolactam, etc.), heterocyclic systems (cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2- Imidazolidinone, γ-butyrolactone, etc.), sulfoxides (dimethylsulfoxide, etc.), sulfones (hexamethylphosphorotriamide, sulfolane, etc.), lower ketones (acetone, methyl ethyl ketone, etc.), others, tetra Dorofuran, it may be used urea, acetonitrile and the like. Among these solvents, from the viewpoints of volatility, versatility and dispersibility, water and a mixed solvent of water and alcohol or amide are preferable, and water is particularly preferably used alone.

The mixing ratio of the solvent mixed with water described above is not particularly limited, but is preferably 0 to 50% by weight.

The dispersant in the present invention is not particularly limited as long as it can be dissolved in a solvent and can stabilize the dispersion of fine carbon fibers. Anionic surfactants, cationic dispersants, amphoteric dispersants, nonionic dispersants Known dispersing agents such as can be used.

Examples of anionic dispersants include aromatic sulfonic acid surfactants (alkyl benzene sulfonates such as dodecylbenzene sulfonic acid, dodecyl phenyl ether sulfonate, etc.), monosoap anionic surfactants, ether sulfates Surfactants, phosphate surfactants, carboxylic acid surfactants and the like can be mentioned. In addition, cholic acid, oleic acid, and the like, sodium salts and ammonium salts of carboxymethyl cellulose, which is a saccharide having an anionic functional group, alginic acid, chondroitin sulfate, hyaluronic acid, and the like can also be suitably used. Cyclodextrins and the like can be used by modification with an anionic functional group. It is also possible to use the ester part of a polymer or oligomer having an ester group by hydrolyzing it into an anionic functional group.

Examples of cationic dispersants include cationic surfactants such as quaternary alkylammonium salts, alkylpyridinium salts, and alkylamine salts, and cationic groups such as polyethyleneimine, polyvinylamine, polyallylamine, polyvinylpyridine, and polyacrylamide. The compound which has is mentioned.

Examples of amphoteric dispersants include alkylbetaine surfactants (lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, propyldimethylaminoacetic acid betaine), sulfobetaine-based interfaces An activator, an amine oxide type surfactant, etc. are mentioned.

Nonionic dispersants include ethers (polyoxyethylene, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene oleyl ether, Oxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, etc.) and ester type (polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan Sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate, etc.), sorbitol, glycerin, etc. Alkyl ethers and alkyl esters of polyhydric alcohols fatty acids, surfactants such as amino alcohol fatty acid amide. In addition, cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethyl hydroxyethyl cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, etc.), polyvinyl alcohol, polyvinyl butyral, Polymeric dispersants such as polyvinyl pyrrolidone are also included.

In the present invention, the method of dispersing and mixing the fine carbon fibers, the dispersion medium, and the dispersant may be simply mixed in a suspended state, or may be subjected to a dispersion treatment, and is not particularly limited. For example, it is possible to disperse and mix by introducing fine carbon fibers into a dispersant solution in which a dispersant is dissolved in a dispersion medium and performing a dispersion treatment such as ultrasonic treatment or a stirring method. Further, after mixing the fine carbon fibers and the dispersant, a dispersion medium can be added and diluted to carry out a dispersion treatment. As the ultrasonic treatment, a bus type or probe type sonicator can be used. As a stirring method, high-speed stirring such as a homomixer or a homogenizer, a media-type wet dispersion apparatus such as an attritor, a bead mill, a sand mill, or a planetary mill, or a stirring method such as a jet mill can be used. When fine carbon fibers are dispersed at a low concentration of 1% by weight or less, ultrasonic treatment is particularly suitable. The treatment time of the ultrasonic treatment is appropriately determined depending on the addition amount of the fine carbon fiber, the type and addition amount of the fine carbon dispersant to be used, and is preferably about 10 minutes to 5 hours, and preferably 10 minutes to 3 hours. More preferred. When fine carbon fibers are dispersed at a high concentration of 1% by weight or more, treatment with a media-type wet dispersion device such as an attritor, a bead mill, a sand mill, or a planetary mill is particularly suitable. The treatment time by the media-type wet dispersion apparatus is appropriately determined depending on the treatment method, the amount of fine carbon fiber added, the type and amount of fine carbon dispersant, and a treatment of about 30 minutes to 50 hours is preferable. If the treatment time is too short, the fine carbon dispersion may be insufficient. If the treatment time is too long, fine carbon may be damaged by excessive energy.

In the fine carbon fiber dispersion of the present invention, the amount of fine carbon fibers is not particularly limited as long as the fine carbon fibers are uniformly dispersed, but generally 0.1 wt% to 20 wt%. It is appropriately selected depending on the dispersibility and application within the range. Since the fine carbon fiber dispersion of the present invention has very high dispersibility, it can be dispersed at a high concentration of 2 wt% or more, more preferably 5 wt% or more. When the concentration of the fine carbon fiber exceeds 20 wt%, the dispersion treatment becomes difficult because the viscosity of the dispersion is too high.

In the fine carbon fiber dispersion of the present invention, the addition amount of the dispersant can be appropriately determined according to the blending amount of the fine carbon fiber, the kind of the dispersant, and the use, but in general, with respect to the weight of the fine carbon fiber. If it is 10% or more and 20% or less with respect to the weight of the dispersion medium, fine carbon fibers can be sufficiently dispersed. When the amount is 10% or less with respect to the weight of the fine carbon fiber, the amount of the dispersant adsorbed on the fine carbon fiber surface and acting as a dispersant is insufficient, so that some of the fine carbon fibers are aggregated and a lot of precipitates There is a risk that a product is formed or the viscosity of the dispersion is increased. Further, if it is 20% or more with respect to the weight of the dispersion medium, it becomes difficult for a sufficient amount of the dispersant to be adsorbed on the surface of the fine carbon fiber because the molecular motion of the dispersant in the dispersion medium becomes difficult. Thus, the viscosity of the dispersant solution is too high, making mechanical dispersion difficult. When added to a coating film, a conductive assistant or other polymer as a dispersion for imparting conductivity, it is preferable to reduce the amount of the dispersant added within a range that maintains dispersibility.

The viscosity of the fine carbon fiber dispersion of the present invention is not particularly limited, but it is preferably as low as possible within the range of maintaining dispersibility, and the rotational viscosity in the measurement method described later is 50 to 500 mPa · s. It is particularly preferred that If the viscosity of the dispersion is too high, it may be difficult to apply the coating film or mix with another resin. In addition, there is a possibility that dispersion may be insufficient when mixed with another resin or active material in order to obtain a battery electrode paste, and there is a concern that the battery electrode paste has a high viscosity and adversely affects molding.

The size of the fine carbon fiber dispersed in the fine carbon fiber dispersion of the present invention is not particularly limited, but it is preferable that each fine carbon fiber is isolated and dispersed without agglomeration. The median diameter in the particle size distribution measurement (measuring instrument: LA950 manufactured by Diggaku Seisakusho) is preferably 0.1 to 5 μm, and particularly preferably 0.1 to 2 μm. When the median diameter is 3 μm or less, it is easy to show gloss when applied, and a coating film with good dispersibility can be obtained. When the median diameter is too large, the fine carbon fibers are agglomerated and cannot be isolated and dispersed, so that a coating film showing high gloss cannot be obtained.

Bacteria that are the subject of antibacterial activity of the present invention are generally also called true bacteria and bacteria, and there is no limitation on the bacterial species, but heterotrophic bacteria that use organic matter as a carbon source are preferable. Examples of bacteria include Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis, Sulfur-Reducing Bacteria, Vibrio parahaemolyticus, Salmonella, Helicobacter Examples include Helicobacter pylori and Staphylococcus aureus.

There is no limitation on the antibacterial activity of the number of bacteria that are the subject of the present invention, but it is effective at 1 to 1 billion cells / ml. As long as there is no change, it can be used semipermanently.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.
The fine carbon fibers (multi-walled carbon nanotubes) used in Examples , Reference Examples and Comparative Examples are as follows. Table 1 shows the trace element content by fluorescent X-ray (XRF) analysis (fluorescent X-ray analyzer manufactured by Spectris PANalytical: measured using model PW200). “-” In Table 1 indicates non-detection. The difference in trace elements is presumed to be based on the difference in the catalyst used during the production of fine carbon fibers. The fine carbon fibers in Reference Examples 1 to 3 and Examples 1 to 3 were AMC manufactured by Ube Industries, Ltd. As other fine carbon fibers, commercially available fine carbon fibers A and B different from AMC were used.

Comparative Example 1
10 g of carboxymethyl cellulose (manufactured by Daicel Finechem: DN400H) as a dispersant was added to 990 g of pure water and dissolved by stirring and mixing. The solution was sealed and stored in a constant temperature bath at 25 ° C. for 10 weeks. When the number of heterotrophic bacteria was measured before and after storage, it increased from 100 / ml before storage to 720000 / ml.

[Method for measuring the number of heterotrophic bacteria]
After diluting the sample 10 times with distilled water, 15-20 ml of a predetermined agar medium dissolved by heating is poured into a sterile petri dish and cooled and solidified, and a 10-fold diluted solution 0.1 ml sterile pipette is used on 3 agar plates. The solution was poured and smeared on the entire surface of the flat plate with a sterilized large rod. The culture was allowed to stand for 1 hour to dry the surface of the medium, and then the plate was turned upside down and cultured at 25 ° C. for 7 days. The number of colonies was calculated immediately after culturing, and the number of bacteria per ml of the sample was obtained by calculating the number of colonies.

Comparative Example 2
9 g of carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd .: Cellogen 5A) was added to 991 g of pure water as a dispersant and dissolved by stirring and mixing. As a result of measuring the number of heterotrophic bacteria in the same manner as in Comparative Example 1, the solution increased from 320 / ml before storage to 2200000 / ml.

Comparative Example 3
15 g of polyvinylpyrrolidone (BASF: Kollidon 25) as a dispersant was added to 985 g of pure water and dissolved by stirring and mixing. When the number of heterotrophic bacteria was measured for the solution in the same manner as in Comparative Example 1, the number was 290 / ml before storage and increased to 2100 / ml.

Reference example 1
A stainless steel 50 ml mixer mill (Lecce: MM400) dedicated pot, 60 g of 1 mmφ zirconia beads and 14.625 g of the aqueous solution used in Comparative Example 1, AMC (cobalt content 0.70 wt%) as UBE Industries, Ltd. as fine carbon fiber Then, 0.375 g of magnesium content (0.25 wt%) was added, and a dispersion of 2.5% fine carbon fiber was obtained by treatment with a mixer mill for 30 Hz-10 minutes. The number of heterotrophic bacteria was measured in the same manner as in Comparative Example 1, and no increase in the number of bacteria was observed at 10 / ml or less (not detected but due to 10-fold dilution) before and after storage.

Reference example 2
The same treatment as in Reference Example 1 was carried out except that 14.25 g of the aqueous solution used in Comparative Example 2 was changed to 0.75 g of AMC manufactured by Ube Industries Ltd. as a fine carbon fiber, and a dispersion of 5% fine carbon fiber. Got. When the number of heterotrophic bacteria was measured in the same manner as in Comparative Example 1, no increase in the number of bacteria was observed at 10 / ml or less before and after storage.

Reference example 3
The treatment was performed in the same manner as in Reference Example 2 except that the aqueous solution used in Comparative Example 3 was used to obtain a 5% fine carbon fiber dispersion. When the number of heterotrophic bacteria was measured in the same manner as in Comparative Example 1, the dispersion was 200 / ml before storage and decreased to 10 / ml or less.

Table 2 shows the breeding status of heterotrophic bacteria when the dispersions of Reference Examples 1 to 3 and Comparative Examples 1 to 3 are stored at 25 ° C.

Example 1
Stainless steel 50ml mixer mill dedicated pot 60mm 1mmφ zirconia beads, 0.925% carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd .: Serogen 5A) aqueous solution 14.625g and Ube Industries AMC (cobalt) as fine carbon fiber (Content 0.70 wt%, magnesium content 0.25 wt%) 0.375 g was added, and a 2.5% fine carbon fiber dispersion was obtained by treatment at 30 Hz for 10 minutes. The antibacterial activity value of the obtained dispersion was determined by referring to “Antimicrobial processing-antibacterial test method / antibacterial effect” defined in JIS Z 2801: 2010. there were.

[Antimicrobial activity test]
The test was conducted with reference to JIS Z 2801: 2010. In JIS Z 2801: 2010, when the antibacterial activity value obtained by the test method of the standard is 2.0 or more, it is judged that the antibacterial effect is present.
1) Preparation of test bacterial solution Escherichia coli (NBRC3972) was prepared by inoculating a stock culture on normal agar and cultivating it, and then suspending in 1/500 normal broth approximately 20 hours after passage. .
2) Inoculation of test bacteria and 0.1 ml of the culture sample was inoculated with 0.1 ml of the test bacteria solution and allowed to stand at 35 ° C. for 24 hours.
3) Washing out the test bacteria and measuring the number of viable bacteria For the control (injected distilled water) immediately after inoculation with the test bacterial solution, add 9.8 mL of SCDL medium (antibacterial agent inactivated medium) and dilute it with an agar plate culture method. Viable count was examined. The number of viable bacteria was also measured in the same manner for the control (injection distilled water) and the sample after 24 hours of culture.
4) Calculation and determination of antibacterial activity value: R = (Ut-U0)-(At-U0) = Ut-At
U0: Average logarithmic value of the number of live bacteria immediately after inoculation of unprocessed specimen
Ut: Average logarithmic value of viable cell count after 24 hours of unprocessed specimen
At: Average value of logarithm of viable cell count after 24 hours of antibacterial processed test piece

Comparative Example 5
An antibacterial activity value was obtained by carrying out a dispersion treatment and an antibacterial test in the same manner as in Example 1 except that the fine carbon fiber was changed to a commercially available fine carbon fiber A (cobalt content 0.23 wt%, magnesium content 0 wt%). It was. The antibacterial activity value of this dispersion was 1.4.

Comparative Example 6
An antibacterial activity value was obtained by carrying out a dispersion treatment and an antibacterial test in the same manner as in Example 1 except that the fine carbon fiber was changed to a commercially available fine carbon fiber B (cobalt content 0.01 wt%, magnesium content 0 wt%). It was. The antibacterial activity value of this dispersion was 0.1.

Examples 2 and 3
An antibacterial activity value was determined by carrying out an antibacterial test in the same manner as in Example 1 except that the dispersion used in Example 1 was diluted 10 times and 100 times with distilled water. The antibacterial activity value was 2.3 at 10-fold dilution (fine carbon fiber concentration = 0.25 wt%), and the antibacterial activity value was 2.3 at 100-fold dilution (fine carbon fiber concentration = 0.025 wt%). .

Comparative Examples 7 and 8
An antibacterial activity value was obtained by carrying out an antibacterial test in the same manner as in Example 1 except that the dispersion obtained in Comparative Example 5 was diluted 10 times and 100 times with distilled water. The antibacterial activity value was 1.1 at 10-fold dilution (fine carbon fiber concentration = 0.25 wt%), and the antibacterial activity value was 0.5 at 100-fold dilution (fine carbon fiber concentration = 0.025 wt%). .

Comparative Examples 9 and 10
An antibacterial activity value was determined by carrying out an antibacterial test in the same manner as in Example 1 except that the dispersion obtained in Comparative Example 6 was diluted 10-fold and 100-fold with distilled water. The antibacterial activity value was 0.4 at 10-fold dilution (fine carbon fiber concentration = 0.25 wt%), and the antibacterial activity value was −0.1 at 100-fold dilution (fine carbon fiber concentration = 0.025 wt%). It was.

The results of antibacterial activity values using Examples 1 to 3 and Comparative Examples 5 to 10 are shown in Table 2. Examples 1 to 3 , which are AMC dispersions, all have antibacterial activity values of 2.0 or more, indicating that they have antibacterial properties. On the other hand, in the dispersion using the fine carbon fibers A and B, the antibacterial activity value was 2.0 or less, and the antibacterial property was not shown.

The fine carbon fiber dispersion of the present invention is a dispersion in which fine carbon fibers are uniformly dispersed at a high concentration. The fine carbon fiber dispersion liquid of the present invention can be suitably used in fields requiring high concentration addition and fields requiring uniform dispersibility. In particular, organic polymers that are effective in stabilizing the dispersion are one of the most preferred nutrients of bacteria, and since the growth starts when the dispersant is dissolved in water, it is difficult to store for a long time after the dispersion is produced. there were. Based on the difference in antibacterial properties of various CNTs according to the present invention, the discovery of a fine carbon dispersion with useful antibacterial properties can solve these problems, such as a conductive auxiliary agent for lithium ion batteries, an antistatic coating, etc. Practical use in various fields has become possible.

Claims (3)

A antimicrobial dispersion comprising a fine carbon fiber 0.001 wt%, the fine carbon fibers, graphite-net plane consisting solely of carbon atoms, and a top portion closed, bottom open A bell-shaped structural unit having a trunk portion, and an angle θ between a busbar of the trunk portion and a fiber axis is smaller than 15 °, and two to thirty bell-shaped structural units are stacked sharing a central axis. aggregates formed Te, the aggregate, seen including the fine carbon fibers, characterized in that by connecting with a gap in Head-to-Tail manner to form a fiber,
An antibacterial dispersion having an antibacterial activity value of 2.0 or more obtained by the test method of JIS Z 2801: 2010 . 2. The antibacterial dispersion liquid containing fine carbon fibers according to claim 1 , wherein the fine carbon fibers contain a cobalt content of 0.3% by weight or more and magnesium in an amount of 0.01% by weight or more. An antibacterial dispersion containing fine carbon fibers. In the antimicrobial dispersion comprising a fine carbon fiber according to claim 1 or 2, wherein the dispersion, antimicrobial dispersion comprising a fine carbon fiber characterized by comprising water and aqueous dispersant.