Composite, resin composition, and production method for composite

Abstract

One embodiment of a composite according to the present disclosure contains carbon nanotubes and a dispersant, wherein if the carbon nanotube content with respect to 100 mass% of the composite is represented by X and the proportion of the carbon nanotubes as calculated from images of fractured samples of the composite is represented by Y, X and Y satisfy the relationship 0.5X ≤ Y ≤ 0.8X in at least 80% of the images.

Description

Composite, resin composition, and method for producing the composite

[0001] The present disclosure relates to a composite, a resin composition, and a method for producing the composite.

[0002] Carbon nanotubes are generally used by kneading with resin, but it is known that carbon nanotubes are difficult to disperse in resin. If carbon nanotubes aggregate or are unevenly distributed in resin, the physical properties of the resin will not be sufficiently improved. For example, Patent Document 1 discloses a solid carbon nanotube composition that allows carbon nanotubes to be added to resin at high concentrations, the solid carbon nanotube composition being obtained by kneading 30 to 70% by weight of carbon nanotubes with 30 to 70% by weight of silicone oil having a silicon-oxygen bond repeat number of 3 to 100,000.

[0003] Japanese Patent Application Laid-Open No. 2007-231219

[0004] However, even when the carbon nanotube composition described in Patent Document 1 is kneaded with a resin, the carbon nanotubes aggregate or are unevenly distributed, and the physical properties of the resin are not sufficiently improved in some cases. Therefore, the present disclosure aims to provide a composite in which the carbon nanotubes have good dispersibility when kneaded with a resin and the resin composition has excellent mechanical properties, a method for producing the composite, and a resin composition containing the composite.

[0005] One aspect of the composite of the present disclosure includes carbon nanotubes and a dispersant, and the content of carbon nanotubes relative to 100% by mass of the composite is represented by X (mass%). A sample of the composite is broken, and images of the broken samples obtained by breaking the composite are obtained using a scanning electron microscope (SEM). The images include the boundary between the broken portion of the broken sample and the space outside the composite, and each image has a continuous boundary line length of 0.6 μm to 2.1 μm. When the ratio of the length of the portion derived from carbon nanotubes with a thickness of 0.1 μm or less at a height of 0.2 μm from the boundary to the boundary line length is represented by Y (%), X and Y satisfy the following formula (1) in at least 80% of the images taken so that the total length of the boundary lines is 7.0 μm to 9.0 μm. 0.5X≦Y≦0.8X (1)

[0006] According to the present disclosure, it is possible to provide a composite in which the carbon nanotubes have good dispersibility when kneaded with a resin and the resin composition has excellent mechanical properties, a method for producing the composite, and a resin composition containing the composite.

[0007] Fig. 1 shows SEM images 1 to 7 of the fractured portion of the composite film of Example 1. Fig. 2 shows SEM images c1 to c7 of the fractured portion of the composite of Comparative Example 1.

[0008] In this specification, a numerical range A to B means not less than A and not more than B. In this specification, when the units of the numerical values ​​written before and after "to" indicating a numerical range are the same, the unit of the numerical value written before "to" may be omitted.

[0009] In this specification, carbon nanotubes are also referred to as "CNTs," and carbon nanotube forests are also referred to as "CNT forests."

[0010] [Composite] <Carbon Nanotubes> The composite of the present disclosure contains carbon nanotubes (CNTs).

[0011] CNTs can be produced using conventionally known methods, such as thermal chemical vapor deposition (thermal CVD), plasma CVD, laser ablation, arc discharge, or combustion.

[0012] The average length of the CNTs is preferably 10 to 1000 μm, more preferably 30 to 800 μm, and even more preferably 50 to 500 μm. The average length of the CNTs can be adjusted, for example, by adjusting the time for which the CVD method is performed, i.e., the CNT growth time. The average diameter of the CNTs is preferably 1 to 50 nm, more preferably 3 to 30 nm, and even more preferably 5 to 15 nm. The average diameter of the CNTs can be adjusted, for example, by adjusting the thickness of the catalyst layer and the type of catalyst, as described below.

[0013] The average length and average diameter of CNTs are measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, 10 images of CNTs are obtained using an SEM or TEM. Ten length measurement points are randomly selected and measured for each of the 10 images, resulting in a total of 100 length measurements. The average length of the CNTs is then determined by arithmetically averaging the 100 length measurements. Additionally, ten diameter measurement points are randomly selected and measured for each of the 10 images, resulting in a total of 100 diameter measurements. The average diameter of the CNTs is then determined by arithmetically averaging the 100 diameter measurements.

[0014] The carbon purity of the CNT is preferably 95.0 to 99.999%. The lower limit of the carbon purity of the CNT is preferably 96.0%, more preferably 97.0%, even more preferably 98.0%, still more preferably 99.0%, and particularly preferably 99.8%. The upper limit of the carbon purity of the CNT may be, for example, 99.99% or 99.9%. The carbon purity of the CNT can be determined, for example, by elemental analysis using fluorescent X-rays.

[0015] The crystallinity of CNTs can be evaluated, for example, by Raman spectroscopy. In the evaluation of crystallinity by Raman spectroscopy, the value of the D / G ratio is used as an index. The D / G ratio is the value of the D / G ratio at 1580 cm in the Raman spectrum measured by Raman spectroscopy. -1 The G band peak intensity appearing near 1360 cm -1 The D / G ratio is the ratio of the peak intensity of the D band appearing near the center of the carbon nanotube. The smaller the D / G ratio, the higher the crystallinity of the carbon nanotube. The D / G ratio is preferably 0.5 to 1.0, and more preferably 0.6 to 0.8.

[0016] The carbon purity and crystallinity of the CNTs can be adjusted, for example, by adjusting the thickness of the buffer layer in the catalyst substrate described below, the type of material used for the buffer layer, the thickness of the catalyst layer, the type of catalyst, the type and flow rate of the raw material gas in the CVD method, and the temperature and pressure in the reaction chamber.

[0017] The CNT may be a single-walled carbon nanotube or a multi-walled carbon nanotube with two or more walls. The CNT is preferably a multi-walled carbon nanotube. The number of walls of the multi-walled carbon nanotube is not particularly limited, but is preferably 2 to 20.

[0018] The composite of the present disclosure can be produced, for example, using CNT powder and a dispersant. CNT powder refers to a powder containing multiple CNTs. CNT powder can be obtained from a CNT forest by scraping CNTs off a substrate using a scraper or the like.

[0019] A CNT forest is an aggregate of CNTs arranged on a substrate and aligned perpendicular to the surface of the substrate.

[0020] CNT forests can be obtained, for example, by chemical vapor deposition (CVD) using a catalyst substrate comprising a substrate and a catalyst layer provided on the substrate. CVD involves placing the catalyst substrate in a reaction chamber, supplying raw material gas into the chamber, and growing CNTs on the surface of the catalyst layer. Thermal CVD is preferred as the CVD method.

[0021] Examples of the substrate include a silicon substrate, an alumina substrate, a magnesium oxide substrate, a glass substrate, a sapphire substrate, and a stainless steel substrate.

[0022] The catalyst layer can be formed by depositing catalyst particles on the substrate, for example, by sputtering. Examples of catalysts include metals, specifically iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo), gold (Au), and alloys containing at least one metal selected from the group consisting of these. Examples of alloys include iron alloys, nickel alloys, and cobalt alloys. The catalyst may also be a metal precursor, such as a metal oxide or a metal compound. Examples of metal oxides include iron oxide, nickel oxide, and cobalt oxide. Examples of metal compounds include iron chloride. When a precursor is used, it must be converted to a metal by, for example, heating the precursor before performing the CVD method.

[0023] The catalyst substrate may further include a buffer layer between the substrate and the catalyst layer. Materials used for the buffer layer include, for example, silica (SiO), alumina (AlO), silicon nitride (SiN), zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO). The buffer layer can be formed, for example, by sputtering.

[0024] The sputtering for forming the catalyst layer and the sputtering for forming the buffer layer can be performed using known apparatus and conditions depending on the target of sputtering. The pressure condition for sputtering is preferably about 0.01 to 10 Pa, more preferably about 0.1 to 1 Pa.

[0025] The source gas may be a carbon-containing source gas, such as a hydrocarbon, a sulfur-containing organic gas, a phosphorus-containing organic gas, carbon monoxide, or an alcohol. Examples of hydrocarbons include alkane compounds such as methane and ethane, alkene compounds such as ethylene and butadiene, alkyne compounds such as acetylene, aryl hydrocarbon compounds such as benzene, toluene, and styrene, aromatic hydrocarbons with condensed rings such as indene, naphthalene, and phenanthrene, cycloalkane compounds such as cyclopropane and cyclohexane, cycloolefin compounds such as cyclopentene, and alicyclic hydrocarbon compounds with condensed rings such as steroids. Examples of alcohols include methanol and ethanol. From the viewpoint of the carbon purity of the resulting CNTs, the source gas is preferably a hydrocarbon.

[0026] A carrier gas, which is a gas that carries the source gas, may be supplied to the reaction chamber together with the source gas. Examples of the carrier gas include helium, neon, argon, nitrogen, and hydrogen.

[0027] The temperature in the reaction chamber in the CVD method is preferably 600 to 850°C, more preferably 650 to 800°C, from the viewpoints of the growth rate of CNTs and the carbon purity of the resulting CNTs. The pressure in the reaction chamber in the CVD method is preferably atmospheric pressure, from the viewpoints of the growth rate of CNTs and the carbon purity. The pressure in the reaction chamber may be reduced or increased from atmospheric pressure depending on other conditions when the CVD method is carried out.

[0028] The average length and average diameter of the CNTs in the CNT forest are, for example, similar to the average length and average diameter of the CNTs described above, respectively.

[0029] <Dispersant> The composite of the present disclosure contains a dispersant. Examples of dispersants include liquid polymers, unvulcanized rubber, thermoplastic elastomers, surfactants, and resin-type dispersants. Examples of liquid polymers include silicone oil, polyalkylene glycols, polyglycols, polycarbonate polyols, polyester polyols, and polyether polyols. Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. These may be used alone or in combination of two or more.

[0030] Examples of anionic surfactants include fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfates, alkylaryl sulfonates, alkylnaphthalenesulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkylphosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalenesulfonate-formalin condensates, polyoxyethylene alkylphosphate sulfonates, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters. Specific examples include sodium dodecylbenzenesulfonate, sodium laurate sulfate, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene nonylphenyl ether sulfate, and the sodium salt of β-naphthalenesulfonate-formalin condensates.

[0031] Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Specific examples include stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, dimethyldioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl pyridinium disulfate, cetyl pyridinium bromide, 4-alkylmercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyl triethyl ammonium chloride. Examples of amphoteric surfactants include aminocarboxylates.

[0032] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers. Specific examples include polyoxyethylene lauryl ethers, sorbitan fatty acid esters, and polyoxyethylene octylphenyl ether.

[0033] Examples of resin-type dispersants include fluorine-based resins, cellulose derivatives, polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, hydrogenated nitrile butadiene rubber, and polyacrylonitrile polymers. Examples of cellulose derivatives include cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethylhydroxyethyl cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, and carboxymethyl cellulose.

[0034] From the viewpoint of dispersibility of CNTs in the resulting resin composition, the dispersant is preferably a silicone-based dispersant. Examples of silicone-based dispersants include silicone oil. Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, methylhydrogen silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxy-modified silicone oil, carbinol-modified silicone oil, polyether-modified silicone oil, alkyl-modified silicone oil, and fluorine-modified silicone oil. The silicone-based dispersant is preferably dimethyl silicone oil. From the viewpoint of dispersibility of CNTs in the resulting resin composition, the mass ratio of the carbon nanotube content to the dispersant content (carbon nanotubes:dispersant) in the composite is preferably 1:0.5 to 1:10, more preferably 1:0.7 to 1:7, and even more preferably 1:1 to 1:5.

[0035] <Other Components> The composite of the present disclosure may further contain components other than CNTs and dispersants (hereinafter also referred to as "other components"). Examples of other components include fibrous fillers, powdered fillers, and resin additives. Examples of fibrous fillers include carbon fibers, organic fibers, metal fibers, and glass fibers. Examples of resin additives include antioxidants, heat stabilizers, light stabilizers, weather stabilizers, hydrolysis inhibitors, plasticizers, colorants, flame retardants, foaming agents, nucleating agents, pigments, lubricants, and spreading agents. One or more of the other components may be used.

[0036] The composite is preferably formed substantially from carbon nanotubes and a dispersant, where "substantially" means that the total content of the carbon nanotubes and the dispersant is 90% by mass or more, preferably 95% by mass or more, and more preferably 99% by mass or more, relative to 100% by mass of the composite.

[0037] <Form of the Composite> The composite is, for example, in the form of a continuous film. A film-like composite is also referred to as a "composite film." Examples of the shape of the composite film include a rectangular shape, a square shape, a trapezoid shape, a parallelogram shape, a diamond shape, a kite shape, an ellipse shape, a circle shape, and an irregular shape. When a composite is obtained using a three-roll roll as described below, the shape of the composite may be, for example, an irregular, long shape. A long composite may be, for example, folded. The thickness of the composite film is preferably 10 nm to 2.0 mm, more preferably 100 nm to 100 μm, and even more preferably 1 μm to 30 μm, from the viewpoint of being able to easily tear the composite film by hand or the like for image analysis as described below.

[0038] <Image analysis of composite> The carbon nanotube content relative to 100% by mass of the composite is designated as X (mass%). When a composite sample is broken and an image of the broken sample, including the boundary between the broken portion of the broken sample and the space outside the composite and in which the length of the continuous boundary line is 0.6 μm or more and 2.1 μm or less per image, is obtained using a scanning electron microscope (SEM), the ratio of the length of the portion derived from carbon nanotubes with a thickness of 0.1 μm or less at a height of 0.2 μm from the boundary to the length of the boundary line is designated as Y (%). Of multiple images taken so that the total length of the boundary line is 7.0 μm or more and 9.0 μm or less, X and Y satisfy the following formula (1) in at least 80% of the images: 0.5X≦Y≦0.8X (1)

[0039] X can be calculated from the amount of carbon nanotubes blended when the composite is produced.

[0040] To obtain an image using an SEM, a fractured sample is prepared by fractured the composite sample. The composite sample is, for example, a composite having a shape that can be torn by hand. An example of the composite sample is a composite film. The fractured sample refers to a sample having a fractured portion generated by fracture of the composite sample. An example of a method for fracture of the composite sample is a method of tearing the sample by hand.

[0041] Obtaining an image of a broken sample using an SEM means observing the broken portion with an SEM and obtaining an SEM image so that the broken portion and the space outside the composite at least 0.2 μm above the broken portion are reflected, and the length of the continuous boundary line between the broken portion and the space outside the composite is 0.6 μm or more and 2.1 μm or less. A method for calculating the length of the boundary line will be described later. When the composite sample is a composite film, the SEM observation is performed in a direction in which the composite film is viewed in plan so that the broken portion and the space outside the composite at least 0.2 μm above the broken portion are reflected. "Viewing the composite film in plan" means viewing the planar composite film from its normal direction.

[0042] The magnification of the SEM observation determines the correspondence relationship between one pixel in the SEM image and the length of the actual space. From the viewpoint of resolution, etc., the magnification of the SEM observation is preferably set so that one pixel in the obtained image corresponds to 1 to 20 nm of the actual space, and more preferably so that one pixel corresponds to 1 to 10 nm of the actual space. Using the SEM, multiple images are obtained so that the total length of the boundary lines is 7.0 μm or more and 9.0 μm or less.

[0043] The boundary between the fractured portion and the space outside the composite is identified, for example, as follows. More specifically, this is done by the method described in the Examples. First, each SEM image obtained for the fractured sample is grayscaled into 256 levels (0 to 255). Grayscaling is performed, for example, by applying an appropriate filter to the SEM image. Next, the maximum and minimum pixel values ​​in each SEM image are examined, and the SEM image is normalized by subtracting the minimum pixel value in the SEM image from the pixel value of each pixel, dividing the result by the difference between the maximum and minimum values ​​(pixel value range), and multiplying by 255.

[0044] Next, the normalized SEM image is positioned so that the composite is located at the bottom of the image and the space outside the composite is located at the top of the image, and the pixel values ​​of each pixel are observed along the vertical direction. Among the combinations of pixels where the difference in pixel values ​​(pixel values ​​in the normalized image) between adjacent pixels in the vertical direction is 30 or more, the pixel (point) located below is recorded. The above operation is performed across the entire range in the horizontal direction (vertical direction of the vertical direction) within the SEM image, and a set A consisting of the above points is created. The above points are connected to create a provisional boundary line.

[0045] For each point belonging to set A, a moving average of five points, including that point, two adjacent points to the left, and two adjacent points to the right, is calculated, and set A' consisting of the moving average points is created. If two adjacent points in set A are far apart in the vertical direction, the point farther away from the moving average point is deleted from set A, and set B is created. The points in set B are connected to form the boundary between the fracture and the space outside the composite.

[0046] Y is calculated, for example, as follows. More specifically, it is calculated by the method described in the Examples. First, the length of the boundary line between the fracture identified above and the space outside the composite is measured in terms of the number of pixels, and then the length of the boundary line in the actual space is calculated taking into account the correspondence between one pixel and the length of the actual space. Next, a pixel corresponding to the space outside the composite 0.2 μm above the boundary is identified, and the pixel values ​​of the pixel are observed in the left-right direction. A region D from the point where the pixel value increases by 7 or more gradations (a point brighter by 7 or more gradations) to the point where the pixel value decreases by 7 or more gradations (a point darker by 7 or more gradations) is examined and recorded. In this case, the region may be examined toward the right or toward the left. The above operation is performed over the entire range in the left-right direction within the SEM image to determine all of the above regions.

[0047] The length of each region is measured in terms of the number of pixels, and then the actual length of the space is calculated, and regions D' where the actual length of the space is 0.1 μm or less are extracted from all of the regions D. The lengths of all the extracted regions D' are summed up and divided by the length of the boundary line to calculate Y.

[0048] Y can be adjusted by adjusting the type of kneader and kneading conditions when kneading the carbon nanotubes and dispersant, such as the kneading time, and, when a three-roll kneader is used, the roll rotation speed and the distance between the rolls.

[0049] X and Y satisfy the following formula (1) in 80% or more of the images among a plurality of images taken so that the total length of the boundary lines is 7.0 μm or more and 9.0 μm or less: 0.5X≦Y≦0.8X (1)

[0050] Y falling within the range of formula (1) above means that the CNTs are well dispersed within the composite, with little aggregation or uneven distribution. When formula (1) is satisfied in 80% or more of the multiple images, it can be confirmed that the CNTs are uniformly dispersed within the composite. Uniform dispersion of the CNTs within the composite indicates good dispersibility of the CNTs in the resin composition produced by kneading the composite with a resin.

[0051] The above formula (1) is preferably formula (1'), and more preferably formula (1''). 0.505X≦Y≦0.75X (1') 0.51X≦Y≦0.72X (1'')

[0052] Of the plurality of images, X and Y preferably satisfy the above formula (1) in 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably all of the images.

[0053] By capturing multiple images in which the length of continuous boundary lines contained in each image is 0.6 μm or more and 2.1 μm or less, and the total length of the boundary lines is 7.0 μm or more and 9.0 μm or less, measurement errors due to uneven distribution of CNTs in the composite sample can be reduced.

[0054] <Method for Producing Composite> An example of a method for producing the composite is a method having a step of kneading CNT and a dispersant with a three-roll mill so that X and Y satisfy the formula (1). In the step of kneading CNT and a dispersant with a three-roll mill, the CNT and the dispersant may be added to the three-roll mill simultaneously or alternately. A mixture of CNT and a dispersant may also be added to the three-roll mill in advance.

[0055] In the step of kneading the CNT and dispersant with a three-roll mill, the kneading is preferably continued for more than 10 minutes after the CNT and dispersant have been added to the three-roll mill, more preferably for 20 minutes or more, even more preferably for 30 minutes or more, and particularly preferably for 45 minutes or more. The kneading time after the CNT and dispersant have been added to the three-roll mill is, for example, 3 hours or less.

[0056] The rotation speed of the three-roll mill is preferably 50 to 1000 rpm, more preferably 100 to 900 rpm, and even more preferably 150 to 800 rpm. The gap between the feed roll and the intermediate roll in the three-roll mill is preferably 5 to 200 μm, more preferably 7 to 150 μm, and even more preferably 10 to 100 μm. The gap between the intermediate roll and the finishing roll in the three-roll mill is preferably 5 to 200 μm, more preferably 7 to 150 μm, and even more preferably 10 to 100 μm.

[0057] In the process of kneading CNTs and a dispersant using a three-roll mill, it is preferable to narrow the gap between the feed roll and the intermediate roll in the three-roll mill at regular intervals. Narrowing the gap between the feed roll and the intermediate roll at regular intervals may be performed multiple times. When narrowing the gap between the feed roll and the intermediate roll at regular intervals is performed multiple times, the gap at the start and end may be different for each time. Furthermore, the gap between the feed roll and the intermediate roll may be widened after being narrowed once.

[0058] [Resin Composition] The resin composition of the present disclosure contains the above-described composite and a resin. Examples of the resin include a thermoplastic resin and a thermosetting resin. One type of resin may be used, or two or more types may be used.

[0059] Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, unsaturated group-containing (meth)acrylic resins, vinyl ester resins, urethane resins, (meth)acrylic urethane resins, phenolic resins, melamine resins, urea resins, diallyl phthalate resins, cyanate ester resins, alkyd resins, and thermosetting polyimide resins.

[0060] Examples of thermoplastic resins include polyolefins, polyvinyl chloride, polyvinylidene chloride, styrene-based resins, (meth)acrylic resins, polyesters, polyamides, thermoplastic polyimides, polycarbonates, polyacetals, polyphenylene ethers, and polyphenylene sulfides.

[0061] Examples of polyolefins include high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, polypropylene, and ethylene-propylene copolymer. Examples of styrene-based resins include polystyrene, styrene-maleic anhydride copolymer, AS resin, and ABS resin.

[0062] Examples of polyesters include polyethylene terephthalate and polybutylene terephthalate. Examples of polyamides include aliphatic polyamides and semi-aromatic polyamides. Examples of aliphatic polyamides include polyamide 6, polyamide 66, polyamide 610, polyamide 11, and polyamide 12. Examples of semi-aromatic polyamides include terephthalic acid-based polyamides such as polyamide 6T and polyamide 9T.

[0063] The resin is preferably at least one resin selected from thermoplastic resins and thermosetting resins, more preferably a thermoplastic resin, and even more preferably a polyolefin or polyamide.

[0064] The resin composition may contain other components that may be contained in the composite. The resin composition may also contain an inorganic filler. When the resin composition contains an inorganic filler, the mechanical properties of the resin composition are improved. Examples of inorganic fillers include alumina, aluminum hydroxide, zirconium hydroxide, barium hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, magnesium sulfate, titanium oxide, tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, calcium oxide, magnesium oxide, zinc oxide, molybdenum oxide, antimony oxide, nickel oxide, calcium silicate, beryllia, calcium titanate, silicon carbide, silicon nitride, aluminum nitride, boron nitride, titanium white, zinc borate, and boron nitride. metal compounds such as aluminum oxide; talc; clay; mica; metal oxides and metal nitrides such as glass fiber, kaolin, hydrotalcite, wollastonite, xonotlite, calcium hydrogen phosphate, calcium phosphate, glass flake, hydrated glass, and sepiolite; hydrated metal compounds; silica-based fillers such as fused crushed silica, fused spherical silica, crystalline silica, amorphous silica, secondary agglomerated silica, finely divided silica, hollow silica, and porous silica; nitride-based fillers and carbon-based fillers such as silicon carbide, silicon nitride, titanium carbide, and diamond.

[0065] The resin composition can be produced, for example, by melt-kneading the composite, a resin, and, if necessary, an inorganic filler and other components. Melt-kneading is performed using, for example, a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, or a roll mill. When the resin composition contains an inorganic filler or other components, the composite, the resin, and the inorganic filler or other components may be fed into a twin-screw extruder or the like to melt-knead, or the resin and the inorganic filler or other components may be mixed in advance to produce a mixture, and then the composite and the mixture may be fed into a twin-screw extruder or the like to melt-knead. After melt-kneading, the resin composition may be pelletized.

[0066] The content of CNTs in the resin composition is preferably 0.01 to 10 mass%, more preferably 0.01 to 5 mass%, even more preferably 0.05 to 1 mass%, and particularly preferably 0.05 to 0.5 mass%, relative to 100 mass% of the resin composition. When the resin composition contains an inorganic filler, the content of the inorganic filler is preferably 1 to 30 mass%, more preferably 5 to 25 mass%, and even more preferably 10 to 20 mass%, relative to 100 mass% of the resin composition.

[0067] [Molded Article] The resin composition can be molded by various known methods. Examples of molding methods include extrusion molding, press molding, injection molding, calendar molding, and blow molding. The molded article can be used as, for example, automobile parts, vehicle parts other than automobiles, ship parts, aviation or space parts, sporting goods, home appliance parts, communication equipment parts, electrical parts, electronic parts, medical equipment parts, machine parts, power tool parts, building materials, civil engineering parts, agricultural materials, food containers, or films.

[0068] The composite can be used to produce a resin composition with good CNT dispersibility, and a molded article with excellent mechanical properties can be produced using such a resin composition.

[0069] The present disclosure relates to, for example, the following items [1] to [8]. [1] A composite comprising carbon nanotubes and a dispersant, wherein X (mass%) denotes the content of the carbon nanotubes relative to 100 mass% of the composite, and when images of a fractured sample obtained by fracture of the composite, including a boundary between the fractured portion of the fractured sample and a space outside the composite and in which the length of a continuous boundary line per image is 0.6 μm to 2.1 μm, are obtained using a scanning electron microscope (SEM), and Y (%) denotes the ratio of the length of a portion derived from carbon nanotubes having a thickness of 0.1 μm or less at a height of 0.2 μm from the boundary to the length of the boundary line, the composite satisfies the following formula (1) in at least 80% of the images taken so that the total length of the boundary lines is 7.0 μm to 9.0 μm: 0.5X≦Y≦0.8X (1).

[0070] [2] The composite according to [1], wherein the mass ratio of the carbon nanotube content to the dispersant content (carbon nanotube:dispersant) is 1:0.5 to 1:10.

[0071] [3] The composite according to [1] or [2], wherein the dispersant is a silicone-based dispersant.

[0072] [4] The composite according to any one of [1] to [3], which is in the form of a film.

[0073] [5] A resin composition comprising the composite according to any one of [1] to [4] and a resin.

[0074] [6] The resin composition according to [5], wherein the resin is at least one resin selected from a thermoplastic resin and a thermosetting resin.

[0075] [7] The resin composition according to [5] or [6], further comprising an inorganic filler.

[0076] [8] A method for producing a composite containing carbon nanotubes and a dispersant, comprising a step of kneading the carbon nanotubes and the dispersant using a triple roll mill, wherein X (mass%) represents the content of the carbon nanotubes relative to 100 mass% of the composite, and when images of broken samples obtained by breaking a sample of the composite are obtained using a scanning electron microscope (SEM), the images include a boundary between the broken portion of the broken sample and a space outside the composite, and each image has a continuous boundary line length of 0.6 μm to 2.1 μm. When Y (%) represents the ratio of the length of a portion derived from carbon nanotubes having a thickness of 0.1 μm or less at a height of 0.2 μm from the boundary to the length of the boundary line, X and Y satisfy the following formula (1) in at least 80% of the images taken so that the total length of the boundary lines is 7.0 μm to 9.0 μm. 0.5X≦Y≦0.8X (1)

[0077] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[0078] [Production Example 1] (Production of Carbon Nanotube Forest) A wafer coated with a catalyst for carbon nanotube growth was prepared, and vertically aligned carbon nanotubes were grown from the catalyst by chemical vapor deposition to produce a vertically aligned carbon nanotube forest oriented perpendicular to the wafer. The carbon nanotubes constituting the carbon nanotube forest were multi-walled carbon nanotubes, each with an average length of 250 μm, an average diameter of 6 to 10 nm, a carbon purity of 99.8% or more, and a crystallinity (D / G ratio) of 0.6 to 0.8.

[0079] (Production of Carbon Nanotubes) Approximately 0.6 g of the carbon nanotube forest formed on the wafer was scraped off from the wafer using a scraper to obtain carbon nanotube powder. The same procedure was repeated to prepare 10 g of carbon nanotube powder for each of the examples and comparative examples.

[0080] Example 1 Preparation of Composite 10 g of the carbon nanotube powder and 20 g of silicone oil (Shin-Etsu Silicone, KF-96-1,000CS, dimethyl silicone oil) were mixed by alternately adding small amounts between the feed roll and the middle roll of a three-roll mill (ZYTR-80E, manufactured by Shenzhen Zhongyi Technology Co., Ltd.) until the entire amount was added over 20 minutes. The three-roll mill was set so that the gap between the feed roll and the middle roll was 50 μm, the gap between the middle roll and the finishing roll was 74 μm, and the rotation speed was 300 rpm.

[0081] During kneading, when the kneaded material came out onto the doctor plate, it was repeatedly returned to between the feed roll and the intermediate roll, and the silicone oil was used to make the kneaded material into powder-like carbon nanotubes. After kneading for about 20 minutes, in order to further improve the cohesion, the gap between the feed roll and the intermediate roll was set to 40 μm, and kneading was continued for another 20 minutes.

[0082] In order to eliminate uneven kneading and to remove the entire kneaded material from the rolls at once, the gap between the feed roll and the intermediate roll was set to 15 μm, and the gap between the intermediate roll and the finishing roll was set to 15 μm, so that almost all of the kneaded material in the rolls came out onto the doctor plate.

[0083] After removing the entire kneaded material, the kneaded material was again introduced between the feed roll and the intermediate roll and kneaded. During kneading, the gap between the feed roll and the intermediate roll was narrowed by 10 μm from 70 μm to 30 μm approximately every 5 minutes. The gap between the intermediate roll and the finishing roll was 15 μm. Thereafter, the gap between the feed roll and the intermediate roll was widened from 30 μm to 50 μm, and the kneading state was confirmed by visually checking for unevenness in the black of the kneaded material. Thereafter, kneading was performed again. During kneading, the gap between the feed roll and the intermediate roll was narrowed by 10 μm from 50 μm to 30 μm approximately every 5 minutes.

[0084] Finally, a continuous, uniform black composite film was obtained. The time required from the start of adding the carbon nanotube powder and silicone oil to the three-roll mill to obtaining the composite film was approximately 80 minutes. The resulting composite film could be easily broken into smaller pieces by external force.

[0085] (Obtaining SEM Images) The composite film obtained in Example 1 was torn by hand to expose a fractured portion. The exposed fractured portion was subjected to SEM observation at an acceleration voltage of 20 kV and a magnification of 5000 times. The SEM observation was performed in a direction in which the composite film was viewed in plan. Seven SEM images were obtained so that the fractured surface areas included in each image did not overlap.

[0086] A filter (0.2126*red+0.7152*green+0.0722*blue) was applied to the obtained SEM images to obtain 256 grayscale levels (0 to 255), SEM images 1 to 7. One pixel in the obtained SEM images corresponded to a 4 nm square area in the complex and the space outside the complex.

[0087] (Identification of the boundary between the fractured portion and the space outside the composite) In each of the obtained SEM images 1 to 7, the boundary between the fractured portion of the composite and the space outside the composite was identified by the following procedures (1) to (9).

[0088] (1) The SEM image was normalized by examining the maximum and minimum pixel values ​​in the SEM image, subtracting the minimum pixel value in the SEM image from the pixel value of each pixel, dividing by the difference between the maximum and minimum values ​​(pixel value range), and multiplying by 255. When the pixel value of a pixel corresponding to a character portion such as a scale bar present in the SEM image was the maximum value, the normalization was performed using only pixels other than the character portion.

[0089] (2) Because the space outside the composite can be visually distinguished from the composite, the SEM image normalized in (1) above was positioned so that the composite was located at the bottom of the image and the space outside the composite was located at the top of the image. In the image positioned in this way, the up-down direction was the y-axis direction, the left-right direction was the x-axis direction, the right direction was the positive x-axis direction, the up direction was the positive y-axis direction, and the vertex at the bottom left of the image was the origin.

[0090] (3) Let x = t be the position t pixels from the origin in the positive x-axis direction, and y = s be the position s pixels from the origin in the y-axis direction. A certain t was selected, and the pixel values ​​along the y-axis direction at x = t in the image normalized in (1) above (pixel values ​​in the image normalized in (1) above) were observed. Among pixel combinations where the difference in grayscale pixel values ​​between adjacent pixels above and below in the y-axis direction was 30 or more, the coordinates of the lower pixel were defined as (t, m), and the coordinates of the pixel adjacent above it were defined as (t, m+1), and the lower pixel (t, m) was recorded as point (M). Note that if there were multiple points (M) for each x-coordinate t, all points were recorded.

[0091] (4) The above t is moved and the above operation (3) is performed for all x. A set of the points (M) obtained by this is created, and the point (M) with the smallest y coordinate among the points with the same x coordinate in the set is defined as point (m), and its coordinates are (t, m t ) was decided. t means the above y coordinate at x=t.

[0092] (5) The set consisting of the points (m) obtained in (4) above was designated as set A. The points (m) belonging to set A were connected to create a provisional boundary line.

[0093] (6) Select one point from the points (m) belonging to set A and set its coordinates as (p, m p ) was selected. Among the points (m) belonging to set A, two points with the first and second closest x coordinates in the positive x-axis direction and two points with the first and second closest x coordinates in the negative x-axis direction were selected relative to the selected point. The moving average (m) of the y coordinates of a total of five points consisting of the selected point and these four points was calculated. p ') and the coordinates are (p, m p If p is near the maximum or minimum value in the x-axis direction and the two points in the positive x-axis direction or the two points in the negative x-axis direction do not exist, then m p ' is m p The same operation was performed on all points (m) belonging to set A to create set A' consisting of points (m'). The number of points (m) belonging to set A is the same as the number of points (m') belonging to set A'.

[0094] (7) Select one point from the points (m) belonging to set A and set its coordinates as (p, m p ) is set. In addition, among the points (m) belonging to set A, the coordinates of the point whose x coordinate is greater than p and closest to p are set as (p+q, m p+q ) was decided. p and m p+q If the difference between p -m p ') and the absolute value of (m p+q -m p+q The absolute value of (m p -m p If the absolute value of (p, m p ) from set A, and (m p+q -m p+q If the absolute value of (p+q, m p+q ) were deleted from set A. The same operation was performed on all points (m) belonging to set A, and the resulting set was set B. Set B is a set from which some points that make up set A have been deleted.

[0095] (8) Move x=n from the minimum value of the x coordinate of the points belonging to set B created in (7) above to the maximum value of the x coordinate. If n=0 is moved and there is no point of x=n in set B, select the coordinate of the point belonging to set B whose x coordinate is less than n and closest to n as (n0, m n0 ), among the points belonging to set B, the coordinates whose x coordinates are greater than n and closest to n are (n1, m n1 ) and the y coordinate when the x coordinate on the line segment connecting those two points is n is m n As such, (n, m n ) was added to set B. The set obtained in this way was set C. All points belonging to set B obtained in (7) also belong to set C.

[0096] (9) Set C obtained in (8) above was used as the boundary between the fractured portion of the composite and the space outside the composite.

[0097] (Calculation of Y) Y was calculated using the following steps (1) to (4). (1) The length of the boundary line between the fractured portion identified above and the space outside the composite was measured in terms of the number of pixels. Next, the actual length of the space was determined based on the pixel-converted length of the boundary line. (2) At each x coordinate in the SEM image, pixels 50 pixels above the boundary were identified. These pixels correspond to the space outside the composite at a height of 0.2 μm from the boundary. (3) The pixel values ​​of the pixels were observed in the positive direction of the x axis, and the region D from the point where the pixel value increased by 7 or more gradations (a point brighter by 7 or more gradations) to the point where the pixel value decreased by 7 or more gradations (a point darker by 7 or more gradations) was examined. All of the above regions D were determined from the minimum to maximum value of the x coordinate, and the length of each region was measured in terms of the number of pixels. Next, the actual length of the space was determined based on the pixel-converted length of each region. (4) From all of the above regions D, regions D' whose length (actual spatial length) was 0.1 μm or less were extracted, and the lengths of all the extracted regions D' were summed up. The total length was divided by the length of the boundary line to calculate Y.

[0098] For SEM images 1 to 7 of the composite film obtained in Example 1, the length (μm) of the boundary line and the proportion Y of the portion derived from carbon nanotubes with a thickness of 0.1 μm or less were determined. The results are shown in Table 1. Y refers to the proportion of the length of the portion derived from carbon nanotubes with a thickness of 0.1 μm or less that exists in the space outside the composite at a height of 0.2 μm from the boundary, relative to the length of the boundary line. Specifically, Y refers to the proportion of the length of the region that is located 50 pixels above the boundary and is 7 or more levels brighter than the length of the boundary line.

[0099]

[0100] From Table 1, it can be seen that X and Y satisfied the above formulas (1), (1'), and (1'') in all of the observed SEM images 1 to 7. Furthermore, the total length of the boundary line in the observed SEM images 1 to 7 was 8.78 μm.

[0101] Comparative Example 1 (Preparation of Composite) Using the same method as in Example 1, 10 g of the carbon nanotube powder and 20 g of silicone oil (Shin-Etsu Silicones, KF-96-1,000CS, dimethyl silicone oil) were added alternately in small amounts to a three-roll mill and kneaded until the entire amount was added over 20 minutes. After the entire amount was added, the kneading was continued for an additional 10 minutes without changing the kneading conditions, yielding a uniform black composite. The resulting composite was in the form of multiple thin flakes, had a dry texture, and could be broken down even more easily by external force than the composite of Example 1.

[0102] SEM images c1 to c7 with 256 grayscale levels were obtained in the same manner as in Example 1, and then the boundary between the fractured portion and the space outside the composite was identified, the length of the boundary line was calculated, and Y was calculated in the same manner as in Example 1.

[0103]

[0104] From Table 2, among SEM images c1 to c7, in SEM images c2 and c4 to c7, X and Y did not satisfy the above formulas (1), (1'), and (1'').

[0105] [Example 2] (Preparation of resin composition) Polypropylene (J106MG, manufactured by Prime Polymer) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10% by mass relative to 100% by mass of the resin composition, thereby obtaining pellets of the resin composition.

[0106] [Examples 3 and 4] (Preparation of Resin Composition) Polypropylene (J704UG, manufactured by Prime Polymer) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10% by mass or 0.30% by mass relative to 100% by mass of the resin composition, thereby obtaining pellets of the resin composition.

[0107] [Examples 5 and 6] (Preparation of Resin Composition) Polypropylene (manufactured by Nippon Polypropylene, BC4BSW) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10 mass % or 0.30 mass % relative to 100 mass % of the resin composition, thereby obtaining pellets of the resin composition.

[0108] [Example 7] (Preparation of resin composition) A mixture of polypropylene and talc (85% by mass of polypropylene, 15% by mass of talc) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10% by mass relative to 100% by mass of the resin composition, thereby obtaining pellets of the resin composition.

[0109] [Examples 8 to 9] (Preparation of Resin Composition) Polyamide (nylon 6 (manufactured by LIBORON, N150-300)) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10 mass % or 0.30 mass % relative to 100 mass % of the resin composition, thereby obtaining pellets of the resin composition.

[0110] [Examples 10 and 11] (Preparation of Resin Composition) Polyamide (nylon 6 (Toray, S133)) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10 mass % or 0.30 mass % relative to 100 mass % of the resin composition, thereby obtaining pellets of the resin composition.

[0111] [Example 12] (Preparation of resin composition) Polyamide (nylon 12 (a8925, manufactured by Polyplaevonik)) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10% by mass relative to 100% by mass of the resin composition, thereby obtaining pellets of the resin composition.

[0112] [Examples 13 to 14] (Preparation of Resin Composition) Polyethylene (7700M, manufactured by Prime Polymer) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10% by mass or 0.30% by mass relative to 100% by mass of the resin composition, thereby obtaining pellets of the resin composition.

[0113] [Example 15] (Preparation of resin composition) Recycled polypropylene (a mixture of four types of waste polypropylene after use as automobile parts) and the composite obtained in Example 1 were melt-kneaded using a twin-screw extruder so that the proportion of carbon nanotubes was 0.10 mass% relative to 100 mass% of the resin composition, thereby obtaining pellets of the resin composition.

[0114] Comparative Examples 2 to 10 In Examples 2 to 15, resin pellets were obtained in the same manner as in each Example, except that the composite obtained in Example 1 was not used.

[0115] [Tensile test] The obtained pellets were injection molded using an injection molding machine (Toyo Machinery & Metal Co., Ltd., PLASTARSi-100V (injection device: F200HC)) (Examples 2, 3, 4, 5, 6, 7, 15, Comparative Examples 2, 3, 4, 5, 10: cylinder temperature: 230 ° C., mold temperature: 50 ° C.) (Examples 8, 9, 10, 11, Comparative Examples 6, 7: cylinder temperature: 260 ° C., mold temperature: 40 ° C.) (Examples 12, 13, 14, Comparative Examples 8, 9: cylinder temperature: 210 ° C., mold temperature: 35 ° C.) to prepare dumbbell-shaped test pieces (tensile test pieces) in accordance with JIS K7162 1994. Using the dumbbell-shaped test pieces, tensile tests were performed to evaluate the tensile modulus (MPa), tensile strength (MPa), and breaking strain (%).

[0116] [Bending test] The obtained pellets were injection molded using an injection molding machine (Toyo Machinery & Metal Co., Ltd., PLASTARSi-100V (injection device: F200HC)) (Examples 2, 3, 4, 5, 6, 7, 15, Comparative Examples 2, 3, 4, 5, 10, cylinder temperature: 230 ° C., mold temperature: 50 ° C.) (Examples 8, 9, 10, 11, Comparative Examples 6, 7, cylinder temperature: 260 ° C., mold temperature: 40 ° C.) (Examples 12, 13, 14, Comparative Examples 8, 9, cylinder temperature: 210 ° C., mold temperature: 35 ° C.) by (Examples 12, 13, 14, Comparative Examples 8, 9, Cylinder temperature: 210 ° C., mold temperature: 35 ° C.) Cut out test pieces (bending test pieces) were prepared in accordance with JIS K7162 IBA (ISO527-2). A bending test was performed on the cut out test pieces in accordance with ISO178 to evaluate the bending modulus (MPa).

[0117] [Charpy impact strength] The obtained pellets were injection molded using an injection molding machine (Toyo Machinery & Metal Co., Ltd., PLASTARSi-100V (injection device: F200HC)) (Examples 2, 3, 4, 5, 6, 7, 15, Comparative Examples 2, 3, 4, 5, 10, cylinder temperature: 230 ° C., mold temperature: 50 ° C.) (Examples 8, 9, 10, 11, Comparative Examples 6, 7, cylinder temperature: 260 ° C., mold temperature: 40 ° C.) (Examples 12, 13, 14, Comparative Examples 8, 9, cylinder temperature: 210 ° C., mold temperature: 35 ° C.) to prepare a notched multipurpose test piece (Charpy impact test piece) in accordance with JIS K7111. Charpy impact strength (kJ / m ２ The evaluation results are shown in Tables 3 to 5.

[0118]

[0119]

[0120]

[0121] The symbol "-" in the table means that the corresponding physical property has not been measured.

[0122] From Tables 3 to 5, it was confirmed that the resin composition containing the composite of the present disclosure exhibited significant improvements in mechanical properties. However, when the composite obtained in Example 1 was replaced with the composite obtained in Comparative Example 1, no significant improvements in mechanical properties were observed.

Claims

1. A composite comprising carbon nanotubes and a dispersant, wherein X (mass%) is the content of the carbon nanotubes relative to 100 mass% of the composite, and when images of a fractured sample obtained by fracture of the composite, including the boundary between the fractured portion of the fractured sample and the space outside the composite and in which the length of a continuous boundary line per image is 0.6 μm to 2.1 μm, are obtained using a scanning electron microscope (SEM), and Y (%) is the ratio of the length of a portion derived from carbon nanotubes with a thickness of 0.1 μm or less at a height of 0.2 μm from the boundary to the length of the boundary line, the composite satisfies the following formula (1) in at least 80% of the images taken so that the total length of the boundary lines is 7.0 μm to 9.0 μm. 0.5X≦Y≦0.8X (1) 2. The composite according to claim 1, wherein the mass ratio of the carbon nanotube content to the dispersant content (carbon nanotube:dispersant) is 1:0.5 to 1:

10.

3. The composite of claim 1, wherein the dispersant is a silicone-based dispersant.

4. The composite of claim 1, which is in the form of a film.

5. A resin composition comprising the composite of claim 1 and a resin.

6. The resin composition according to claim 5, wherein the resin is at least one resin selected from the group consisting of thermoplastic resins and thermosetting resins.

7. The resin composition according to claim 5, further comprising an inorganic filler.

8. A method for producing a composite containing carbon nanotubes and a dispersant, comprising a step of kneading the carbon nanotubes and the dispersant using a triple roll mill, wherein X (mass%) denotes the content of the carbon nanotubes relative to 100 mass% of the composite, and when images of broken samples obtained by breaking a sample of the composite are obtained using a scanning electron microscope (SEM), the images include the boundary between the broken portion of the broken sample and the space outside the composite, and each image has a continuous boundary line length of 0.6 μm to 2.1 μm, and the ratio of the length of a portion derived from carbon nanotubes with a thickness of 0.1 μm or less at a height of 0.2 μm from the boundary to the boundary line length is denoted as Y (%), and the multiple images are taken so that the total length of the boundary lines is 7.0 μm to 9.0 μm, and in at least 80% of the images, X and Y satisfy the following formula (1): 0.5X≦Y≦0.8X (1)

Images