JP4222048B2 - Carbon nanotube-containing resin composite, method for producing the same, and highly elastic film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carbon nanotube-containing resin composite having a high elastic modulus, a method for producing the same, and a high elastic film made of the resin composite.
[0002]
[Prior art]
Addition of fillers to resins has been widely used as a technique for improving mechanical properties such as tensile strength and elastic modulus and obtaining resin composites having desired properties. As such a reinforcing filler, a fibrous or acicular filler is used as a reinforcing filler. For example, a fibrous filler such as glass fiber, carbon fiber, or aramid fiber is wollastonite. Zonotolite etc. are known.
[0003]
The properties required as a filler for reinforcing the resin include: 1. high strength and elastic modulus; 2. The density is small. 3. Small variation in size; Examples thereof include good adhesiveness with a resin.
[0004]
In recent years, nanotubes have been attracting attention as promising fibrous fillers among the above 1 to 3. Nanotubes are tube-like molecules formed by a network of chemical bonds, and carbon nanotubes (hereinafter referred to as CNTs) in which graphite-type carbon forms a tube-like network are typical. Discovery has also been reported for BCN nanotubes and BN nanotubes, some or all of which have been replaced with boron (B) or nitrogen (N). In addition, it has been reported that CNT can be subjected to chemical modification relatively easily, such as the ability to introduce a carboxyl group into the defective part of the graphite structure or the end part of the nanotube by performing acid treatment. Yes. For example, chemically modified CNTs in which various functional groups are introduced by esterification or amidation using this carboxyl group as an anchor, and fluorinated CNTs in which a graphite structure is fluorinated are known.
[0005]
A nanotube has a length of about several tens of nanometers to several tens of micrometers, whereas a diameter of about 1 to 50 nm is very fine and elongated, and has a form with a large aspect ratio. Further, the density is small because of the tube shape. In particular, CNT has a high elasticity and high strength compared to any existing material, and has useful properties such as the structure does not change up to high temperatures, so structural materials and resin composites with excellent mechanical properties. Application development is underway.
[0006]
Some examples of resin composites using CNTs as a reinforcing filler for resin have been reported so far. For example, Non-Patent Document 1 describes a manufacturing method in which CNTs are dispersed using polymethyl methacrylate (PMMA) as a matrix resin. In this method, uniform dispersion of CNTs is required unless the process is repeated several hundred times or more. This is a very complicated and inefficient method. In addition, this document describes that the elastic modulus is increased by a fiber that has been stretched after dispersing CNT, but it is considered that only the effect of dispersing CNT can be evaluated. Extrapolation of the elastic modulus value from the data of the same document shows little improvement.
[0007]
[Non-Patent Document 1]
“Chemical Physics Letters”, Vol. 330, 2000, p. 219.
[Problems to be solved by the invention]
As described above, in the conventional method, the interaction between the matrix resin and the CNT in the CNT-containing resin composite is generally small. Therefore, it is difficult to sufficiently reflect the excellent mechanical properties inherent in the CNT in the resin composite. There was a problem that there was.
[0009]
Therefore, an object of the present invention is to provide a CNT-containing resin composite having improved mechanical properties, particularly an elastic modulus , as compared with a matrix resin alone, in order to solve the above-mentioned problems.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to produce a CNT-containing high modulus resin composite, the present inventors have selected a conjugated polymer having a strong interaction with a matrix resin having a specific chemical structure, and the conjugated polymer is used as a CNT polymer. By producing a CNT-containing resin composite by uniformly dispersing in the matrix resin with the surface covered, it is possible to reflect the excellent mechanical properties of CNT in the resin composite and improve the mechanical properties, particularly the elastic modulus. We have found out that we can do it and have reached the present invention.
[0011]
That is, the present invention is a resin composite in which a single-layer and / or multi-layer CNT coated with a polythiophene polymer is dispersed in a resin having a side chain structure, and a functional group is introduced into the CNT. CNT-containing resin composite composition fraction in the resin is 1 wt% or less than 0.01 wt%, resulting polythiophene polymers in the process and the process for coating a polythiophene-based polymer to the CNT which functional groups are introduced A method for producing a CNT-containing resin composite comprising a step of mixing and dispersing CNTs coated with a resin in a side chain structure or the resin solution, and a highly elastic film comprising the CNT-containing resin composite.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The CNT-containing resin composite of the present invention and the production method thereof will be specifically described below.
[0013]
The CNT constituting the CNT-containing resin composite of the present invention is a single-layer and / or multilayer CNT, and the CNT needs to be coated with a conjugated polymer. The conjugated polymer covering the CNT is preferably a conjugated polymer that is a polymer having a strong interaction with the CNT, and that having a strong interaction with the resin having a side chain structure that is a matrix resin. Specifically, a linear conjugated polymer is preferred as one having a strong interaction with CNT. Examples of the linear conjugated polymer include a polythiophene polymer, a polypyrrole polymer, a polyaniline polymer, a polyacetylene polymer, a polyphenylene polymer, and a polyphenylene vinylene polymer. Polythiophene polymer and polypyrrole polymer are those in which monomer units are connected at the 2nd and 5th positions of the thiophene ring and pyrrole ring, respectively, and in the case of polyphenylene polymer, poly-p-phenylene in which the phenylene group is connected at the para position. In the case of a polymer or polyphenylene vinylene polymer, a poly-p-phenylene vinylene polymer in which a phenylene group and a vinylene group are linked at the para position is preferable.
[0014]
Among the linear conjugated polymers, a polythiophene polymer is used in the present invention . Here, the polythiophene polymer is a polymer having a structure with a side chain attached to a polymer having a polythiophene structure skeleton, and because it becomes soluble in a solvent due to the effect of this side chain, it is easy to handle and molded. Excellent in workability and workability. Specific examples include poly-3-alkylthiophene (alkyl group) such as poly-3-methylthiophene, poly-3-butylthiophene, poly-3-hexylthiophene, poly-3-octylthiophene, and poly-3-dodecylthiophene. The number of carbons in the group is not particularly limited, but preferably 1-12), poly-3-alkoxythiophene such as poly-3-methoxythiophene, poly-3-ethoxythiophene, poly-3-dodecyloxythiophene (carbon of alkoxy group) The number is not particularly limited, but preferably 1 to 12), poly-3-alkoxy-4-alkylthiophene (alkoxy) such as poly-3-methoxy-4-methylthiophene, poly-3-dodecyloxy-4-methylthiophene, etc. The carbon number of the group and the alkyl group is not particularly limited, but preferably 1 to 12), poly-3 Preferable examples include poly-3-thioalkylthiophene such as thiohexylthiophene and poly-3-thiododecylthiophene (the number of carbon atoms of the alkyl group is not particularly limited, but preferably 1 to 12). Can be used. Among these, poly-3-alkylthiophene and poly-3-alkoxythiophene are preferable, and poly-3-hexylthiophene is particularly preferable as the former. A preferred molecular weight is 800 to 100,000 in terms of weight average molecular weight. Further, the polymer need not necessarily have a high molecular weight, and may be an oligomer composed of a linear conjugated system.
[0015]
In the present invention, CNT having a functional group introduced is used. CNTs with various chemical modifications, or BCN nanotubes or BN nanotubes in which some or all of the carbon atoms of CNTs are replaced with boron (B) or nitrogen (N) may be used.
[0016]
Specific examples of the functional group introduced into the chemically modified CNT include at least one of a carboxyl group, a hydroxyl group, an amide group, an ester group, a thioester group, a halogen group, and the like. Absent.
[0017]
The CNT is produced by an arc discharge method, a chemical vapor deposition method (CVD method), a laser ablation method, or the like. The CNT used in the present invention may be obtained by any method. In addition, a single-walled CNT in which a single carbon film (graphene sheet) is wound in a cylindrical shape, a double-walled CNT in which two graphene sheets are wound in a concentric shape, and a plurality of graphene sheets Are multi-layered CNTs wound concentrically, and each of them can be used alone or in the present invention.
[0018]
In the CNT-containing resin composite of the present invention, the matrix resin in which the CNTs are dispersed needs to be a resin having a side chain structure. Specific examples of the resin having a side chain structure include vinyl resins such as polystyrene, polyacrylonitrile, and polyvinyl acetate, and acrylic resins such as polymethyl methacrylate, and polystyrene and polymethyl methacrylate are particularly preferable. It is not limited to these, Resins other than those listed above, for example, thermoplastic resins such as nylon-based and polyester-based main chain structures, thermosetting resins such as epoxy-based, melamine-based, polyimide-based, etc. Or a copolymer resin composed of a vinyl monomer and an acrylic monomer even if it has a side chain structure, the elastic modulus is 15% compared to the matrix resin alone. It can be set as the CNT containing resin composite of this invention improved above.
[0019]
In general, when the amount of filler added to the resin composite is increased, the elastic modulus of the resin composite increases and is usually used at a filler concentration of several percent or more. However, in the present invention, the amount of filler CNT is 0.01 to 1% by weight with respect to the resin having a side chain structure, and the elastic modulus of the resin can be increased with a slight addition amount of 1% by weight or less. Is also a feature of the present invention. By being in this range, it is possible to improve the characteristics of the CNT while taking advantage of the characteristics of the matrix resin. If the amount of CNT is less than 0.01% by weight, the elastic modulus is not sufficiently improved, and if it exceeds 1% by weight, uniform dispersion of CNT tends to be difficult.
[0020]
Moreover, when it is necessary to consider coloring property in consideration of optical characteristics, it is preferably 0.01 to 0.5% by weight. By being in this range, it is difficult to visually confirm the CNT, and the transmittance of the film / film is not lowered so much.
[0021]
Next, an example of a method for producing the CNT-containing resin composite of the present invention will be described. The CNT-containing resin composite of the present invention has, for example, a step of coating a polythiophene polymer on a CNT introduced with a functional group , and a CNT coated with the polythiophene polymer obtained in the above step has a side chain structure. It can be manufactured through a step of mixing and dispersing in a resin or resin solution.
[0022]
In the step of coating the polythiophene polymer on the CNTs introduced with functional groups , for example, the following method can be used. That is, (A) a method of adding and mixing CNTs having functional groups introduced into a molten polythiophene polymer, and (B) dissolving a polythiophene polymer in a solvent and introducing functional groups therein. the method of mixing by adding CNT was a method of mixing by adding polythiophene-based polymer at which had been preliminarily dispersed in such previously ultrasonically CNT that has been introduced (C) functional group in a solvent, (D ) A method in which a polythiophene polymer and a CNT having a functional group introduced therein are put in a solvent, and this mixed system is irradiated with ultrasonic waves and mixed. In the present invention, any method may be used alone, or any method may be combined. Among them, a method of putting a polythiophene polymer and a CNT having a functional group introduced into the solvent (D) and irradiating the mixed system with ultrasonic waves is preferable.
[0023]
When the CNTs are covered with a polythiophene polymer, the van der Waals interaction acting between the CNTs is relaxed and highly dispersed in the solvent.
[0024]
Next, a process of mixing and dispersing CNTs coated with a polythiophene polymer in a resin having a side chain structure or the resin solution will be described. When mixing and dispersing CNTs coated with a polythiophene polymer, (1) a method of adding a CNT to a polythiophene polymer and using the mixture of the dispersed polythiophene polymer and CNT as it is, (2) a polythiophene polymer For example, there is a method of using a polymer and CNT mixture after removing excess polythiophene polymer by filtering the CNTs with a filter having a pore size of about 0.1 μm. Even in the case of using the latter (2) filtration method, the polythiophene polymer has a strong interaction with CNT, and thus covers the surface of CNT. It can be confirmed by various elemental analysis and surface analysis devices that the surface of CNT is covered with a polythiophene polymer.
[0025]
The procedure for mixing and dispersing includes (i) a method of redispersing CNT covered with a polythiophene polymer in a solvent and dissolving a resin having a side chain structure therein, and (ii) a resin solution having a side chain structure. There are a method of adding and dispersing CNT covered with a polythiophene polymer, and (iii) a method of adding and dispersing directly to a resin having a liquid side chain structure. Examples of the mixing / dispersing means include stirring, ultrasonic treatment, vibration dispersion, kneading and the like, and it is necessary to select the means according to the concentration and viscosity. For example, as a dispersion method by stirring, a flask or a container with a lid can be rotated, or a device in which a screw type or brush type stirring blade rotates at high speed can be used. As a dispersion method by ultrasonic treatment, a container containing a CNT covered with a resin having a side chain structure and a polythiophene polymer is placed in a tank of an ultrasonic cleaner, or an ultrasonic vibrator is attached to the ultrasonic vibrator. There are methods such as placing them in containers. As a dispersion method by kneading, a bead mill device, a ball mill device, a three-roller, or the like using ceramic fine particles can be used. In the method for producing a CNT-containing resin composite of the present invention, it is preferable to perform ultrasonic treatment after stirring and mixing, but is not limited thereto. Thus, by dispersing the CNT covered with the polythiophene polymer in the resin having a side chain structure which is a matrix resin, a CNT-containing resin composite having a polythiophene polymer layer between the CNT and the matrix resin is obtained. Obtainable.
[0026]
In addition, as a solvent used in the manufacturing method of the CNT-containing resin composite of the present invention, methanol, ethanol, butanol, toluene, xylene, o-chlorophenol, acetone, ethyl acetate, ethylene glycol, chloroform, chlorobenzene, dimethylformamide, Examples include, but are not limited to, dimethyl sulfoxide, N-methylpyrrolidone, γ-butyrolactone, 1,1,1,3,3,3-hexafluoro-2-propanol, and a solvent is selected as necessary. be able to.
[0027]
By processing the CNT-containing resin composite thus obtained, it can be applied to various structural materials represented by plates, functional materials such as optical resins, and composite materials with other materials such as metal materials. .
[0028]
Since the CNT-containing resin composite of the present invention has a characteristic of having high elasticity, high-elasticity plastic products such as high-elasticity films and high-elasticity fibers are manufactured by molding suitable for the resin having a side chain structure which is a matrix resin. In particular, it can be preferably used as a highly elastic film.
[0029]
Specific methods of film forming include, for example, casting molding in which a CNT-containing resin composite or resin composite solution in a fluidized state is poured into a mold or surface to solidify, and heat-softening the CNT-containing resin composite using an extruder. Extrusion molding extruding, inflation molding in which a molten resin composite is extruded from an annular hole to form a cylindrical film, calendar molding in which a CNT-containing resin composite is rolled between two heated rolls, and the like.
[0030]
In addition, spinning methods for fiber production include melt spinning for spinning a molten resin composite into a cooling chamber, dry spinning for spinning a liquid in which a CNT-containing resin composite is dispersed in a volatile solvent into a drying chamber, solvent Examples include wet spinning in which a liquid in which a CNT-containing resin composite is dispersed is spun into a solution containing a non-solvent, but the molding method of the CNT-containing resin composite of the present invention is not limited to these, It can be processed into a film or fiber by molding in consideration of the matrix resin material used, the solubility of the resin composite, and the required properties of the product.
[0031]
【Example】
Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to these examples.
[0032]
Reference example 1
First, 3 mg of single-walled CNT (hereinafter referred to as SWCNT) (manufactured by CNI, purity 95%) is added to 30 mL of chloroform, and 3 mg of poly-3-hexylthiophene (manufactured by Aldrich, molecular weight: Mw 20000) is added as a conjugated polymer. The mixture was ultrasonically stirred for 30 minutes at an output of 250 W using an ultrasonic homogenizer (VCX-500 manufactured by SONICS) while cooling with ice to obtain a SWCNT dispersion.
[0033]
To 0.5 mL of the obtained SWCNT dispersion, a matrix resin solution in which 50 mg of polymethyl methacrylate (hereinafter referred to as PMMA) (“SUMIPEX” manufactured by Sumitomo Chemical Co., Ltd., molecular weight: Mw 500,000) was dissolved in 4.5 mL of chloroform was added. The SWCNT-containing PMMA paste was obtained by ultrasonically stirring for 30 minutes using an ultrasonic cleaner (US-2 manufactured by Inoue Seieido Co., Ltd., output 120 W, 2.6 L).
[0034]
Next, 1 mL of the obtained paste is dropped onto a 50 mm square glass substrate with an adhesive tape having a thickness of 100 μm on the periphery, and a blade coater (manufactured by RK Print-Coat Instruments) is moved at a speed of 30 mm / sec. After forming a uniform coating surface by the above method, the entire substrate is placed in an oven at 50 ° C. for 5 minutes, and finally the solvent is removed with a vacuum dryer for 2 hours to prepare a coating film having a thickness of 20 μm. A PMMA film containing 1 wt% was obtained.
[0035]
Next, the tensile elastic modulus of the PMMA film obtained in the same manner as described above, except that the SWCNT containing 0.1 wt% of SWCNT and SWCNT are not contained, is measured using a wide area dynamic viscoelasticity measuring device (DVE- manufactured by Rheology Co., Ltd.). It measured in the temperature range of -20-100 degreeC using V4 FT rheospectr (FIG. 1). The former has a tensile modulus (E ′) at 20 ° C. of 4.21 GPa, which is very small compared to the elastic modulus of 2.25 GPa of the PMMA film, which is the latter matrix resin, even though the SWCNT content is extremely small. Increased by 87% .
[0036]
Reference example 2
A matrix resin solution prepared by dissolving 50 mg of polystyrene (manufactured by Wako Pure Chemical Industries, Ltd., degree of polymerization: about 3000) in 4.5 mL of chloroform was added to 0.5 mL of the SWCNT dispersion liquid similar to Reference Example 1, and the same as in Reference Example 1 SWCNT-containing polystyrene paste was obtained by ultrasonically stirring for 30 minutes using an ultrasonic cleaner. Using the paste, a coating film having a thickness of 10 μm was prepared by the same method as described above.
[0037]
This SWCNT0.1 except that it does not contain a% by weight content of polystyrene film and the SWCNT was measured in the same manner the tensile modulus as in Reference Example 1 at 20 ° C. of polystyrene film obtained in the same manner as the above-described method, tensile former Although the elastic modulus is 3.16 GPa and the content of SWCNT is extremely small, the tensile modulus (E ′) at 20 ° C. of the polystyrene film as the latter matrix resin is 32 as compared with 2.39 GPa. % Increase.
[0038]
Example 1
First, 50 mg of SWCNT was put into 200 mL of a mixed acid having a volume ratio of 3: 1 sulfuric acid (manufactured by Wako Pure Chemical Industries, Ltd., purity 95% or more) and nitric acid (manufactured by Wako Pure Chemical Industries, Ltd., density 1.38), After ultrasonically stirring for 10 hours using an ultrasonic cleaner, the mixture of this mixed acid and SWCNT is filtered through a polytetrafluoroethylene (PTFE) membrane filter (Millipore Corporation, filter type: JH) to remove carboxyl groups. The introduced SWCNT (hereinafter referred to as c-SWCNT) was filtered off.
[0039]
Using 3 mg of the obtained c-SWCNT and 3 mg of poly-3-hexylthiophene as a conjugated polymer in the same manner as in Reference Example 1, a dispersion using 30 mL of chloroform as a solvent was obtained. A matrix resin solution in which 50 mg of PMMA is dissolved in 4.5 mL of chloroform is added to 0.5 mL of this dispersion, and the PMMA paste containing c-SWCNT is stirred by ultrasonically using the same ultrasonic cleaner as in Reference Example 1 for 30 minutes. In the same manner as in Reference Example 1, a 0.1% by weight c-SWCNT-containing PMMA film was obtained.
[0040]
The tensile elastic modulus at 20 ° C. of the PMMA film containing 0.1% by weight of c-SWCNT was measured in the same manner as in Reference Example 1, and found to be 3.65 GPa. The tensile elastic modulus at 20 ° C. of the PMMA film as the matrix resin ( E ′) 62% increase compared to 2.25 GPa.
[0041]
Comparative Example 1
Except not using a conjugated polymer, operation similar to the said reference example 1 was performed, and SWCNT0.1 weight% containing PMMA film | membrane was obtained. When the tensile elastic modulus of this film was measured with a wide-range dynamic viscoelasticity measuring apparatus in the same manner as in Reference Example 1, the tensile elastic modulus at 20 ° C. was 2.44 GPa, similar to the elastic modulus of the PMMA film as the matrix resin. Met.
[0042]
Comparative Example 2
The same operation as in Reference Example 1 was performed except that 6-nylon, which is a resin having no side chain structure, was used as a matrix resin to obtain a 6-nylon membrane containing 0.1% by weight of SWCNT. The tensile elastic modulus of this film was measured with a wide-range dynamic viscoelasticity measuring apparatus in the same manner as in Reference Example 1. The tensile elastic modulus at 20 ° C. was 2.40 GPa, and it was the same as the above method except that it did not contain SWCNT. The elastic modulus of the 6-nylon film obtained in this way increased only by about 5.7% from 2.27 GPa.
[0043]
【The invention's effect】
According to the present invention, by dispersing CNT coated with a conjugated polymer in a specific matrix resin, both the CNT and the matrix resin are strongly bonded via the conjugated polymer without going through complicated steps. Since the CNT can be uniformly dispersed in the matrix resin, the characteristics of the CNT can be effectively exhibited even with a small CNT addition amount, and the elastic modulus of the resin composite can be dramatically improved. Further, a highly elastic film can be obtained from the resin composite.
[Brief description of the drawings]
FIG. 1 is a graph showing temperature characteristics of tensile elastic modulus of each PMMA film obtained in Example 1. FIG.

Claims (8)

A resin composite in which single-walled and / or multi-walled carbon nanotubes coated with a polythiophene polymer are dispersed in a resin having a side chain structure, wherein a functional group is introduced into the carbon nanotube, A carbon nanotube-containing resin composite having a composition fraction of 0.01% by weight or more and 1% by weight or less. Polythiophene-based polymer is a poly-3-alkylthiophene, poly-3-alkoxy thiophene, poly-3-at least one kind of claim 1 carbon nanotube-containing resin composite according thio alkylthiophene. The carbon nanotube-containing resin composite according to claim 1, wherein the resin having a side chain structure is at least one of a vinyl resin and an acrylic resin. The carbon nanotube-containing resin composite according to claim 3 , wherein the vinyl resin is polystyrene. The carbon nanotube-containing resin composite according to claim 3 , wherein the acrylic resin is polymethyl methacrylate. Functional group is a carboxyl group, a hydroxyl group, an amide group, an ester group, thioester group, at least one carbon nanotube-containing resin composite according to claim 1, wherein the halogen groups. Coating a polythiophene-based polymer to the carbon nanotubes which functional groups are introduced step, the step of mixing and dispersing the carbon nanotubes obtained were coated with polythiophene-based polymer in the step resin or the resin solution having a side chain structure The manufacturing method of the carbon nanotube containing resin composite of Claim 1 containing this. A highly elastic film comprising the carbon nanotube-containing resin composite according to any one of claims 1 to 6 .

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