HK1223390B

HK1223390B - Composite reinforcing material and the method of preparation

Info

Publication number: HK1223390B
Application number: HK16111473.5A
Authority: HK
Inventors: 长谷川正治; 神谷渚
Original assignee: 石墨烯平台株式会社
Priority date: 2014-09-09
Filing date: 2015-03-19
Publication date: 2018-07-06

Abstract

The present invention provides composite reinforcement raw materials with excellent mechanical strength.A composite reinforcement raw material characterized by dispersing at least graphene like graphite obtained by peeling off a graphite based carbon raw material and a reinforcement raw material in a base material. The graphite based carbon raw material has a rhombohedral graphite layer (3R) and a hexagonal graphite layer (2H), and the ratio Rate (3R) defined by the following equation (1) obtained by X-ray diffraction of the rhombohedral graphite layer (3R) and the hexagonal graphite layer (2H) is 31% or more.Rate (3R)=P3/(P3+P4) × 100oooo (Formula 1) In Formula 1, P3 is the peak intensity of the (101) plane obtained by X-ray diffraction of the rhombohedral graphite layer (3R), and P4 is the peak intensity of the (101) plane obtained by X-ray diffraction of the hexagonal graphite layer (2H).

Description

Composite reinforced raw material and manufacturing method thereof

Technical Field

The invention relates to a composite reinforced raw material and a manufacturing method thereof.

Background

In recent years, the addition of various nanomaterials has been studied in various fields for the purpose of size reduction and weight reduction. In particular, in terms of environmental and resource problems, carbon materials such as graphene, CNT (carbon nanotube), fullerene and the like have attracted attention as non-metallic nanomaterials, and resin composite reinforcing materials in which a reinforcing material (filler) is dispersed in a resin have been proposed in order to improve the physical properties (tensile strength, elastic modulus, and the like) of the resin.

For example, a resin composite reinforced material in which a carbon material such as exfoliated graphite is added to a thermoplastic resin such as polyolefin is disclosed (patent document 1). Further, composite reinforcing materials in which flaked graphite and an inorganic filler are added to improve physical properties (tensile modulus, rigidity, and impact resistance) are disclosed (patent documents 2 and 3).

Among them, graphene is superior to other carbon materials in terms of mass productivity, handling properties, and the like, and is expected in various fields, but in order to sufficiently obtain a physical property improvement effect when a reinforcing material such as graphene is kneaded with a resin, it is necessary to uniformly disperse the reinforcing material.

In order to obtain high-quality graphene with a small number of graphite layers, the following methods have been studied: a method in which natural graphite is subjected to weak ultrasonic waves in a solvent (NMP) for a long time (7 to 10 hours), large lumps precipitated at the bottom are removed, and then the supernatant is subjected to centrifugal separation and concentration to obtain a graphene dispersion in which graphite materials are dispersed at about 0.5g/L, wherein the graphite materials have a monolayer (flake) of 20% or more, 2 or 3 layers of flakes of 40% or more, and 10 or more layers of flakes of less than 40% (patent document 4).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2010-254822 ([0032] - [0038])

Patent document 2: japanese patent laid-open publication No. 2014-201676 ([0048] - [0064])

Patent document 3: japanese patent laid-open No. 2014-210916 ([0043])

Patent document 4: international publication No. 2014/064432 (page 19, lines 4-9)

Patent document 5: japanese patent laid-open publication No. 2013-79348 ([0083])

Patent document 6: japanese patent laid-open No. 2009-114435 ([0044])

Non-patent document

Non-patent document 1: structural changes associated with graphite grinding; the method comprises the following steps: the long branches of the rice-Yuandao, the Maidao and the thin Sichuan are healthy and defective; 1973, 2 months and 1 day (Accept)

Non-patent document 2: the change in probability P1, PABA, and PABC associated with the carbon heat treatment; the method comprises the following steps: ji, Shifu Zhengming and Daorhidao; 1966, 9, 16 th month (accepted)

Non-patent document 3: spectroscopic and X-ray differentiation students on fluidized rhombohedrial graphics from the easter n Ghats Mobile Belt, India; G.Parthasarath, Current Science, Vol.90, No.7,10April 2006

Non-patent document 4: classification and respective structural features of the solid carbon material; kawasaki jin of famous ancient house industrial university

Disclosure of Invention

Problems to be solved by the invention

However, in the methods disclosed in patent documents 1, 2, and 3, commercially available exfoliated graphite is used, and the exfoliated graphite is aggregated and cannot be dispersed by kneading alone, and the effects of exfoliated graphite cannot be sufficiently obtained. Further, even when the graphite material obtained by the method disclosed in patent document 4 (the single-layer sheet is 20% or more, the 2-layer or 3-layer sheet is 40% or more, and the 10-layer or more sheet is less than 40%) is mixed in a solvent, the amount of graphene dispersed in the solvent is small, and only a thin graphene dispersion liquid can be obtained. Further, it is also conceivable to collect and concentrate the supernatant, but when the step of collecting and concentrating the supernatant is repeated, the treatment takes time, and the production efficiency of the graphene dispersion is poor. It is considered that even when natural graphite is subjected to ultrasonic treatment for a long period of time as disclosed in patent document 4, only weak portions of the surface are exfoliated, and most of the others do not contribute to exfoliation, and there is a problem that the amount of exfoliated graphene is small.

In addition, in order to improve mechanical strength, a reinforcing material is usually added to a base material such as a polymer, but depending on the amount of the reinforcing material added, the original properties (appearance) of the polymer may be affected (patent document 5).

In the above patent documents 2 and 3, a reinforcing material is added to improve physical properties contributing to rigidity (hardness) such as elastic modulus and impact resistance. The same results were obtained in example 5 (invention not disclosed in the present application).

In addition, in order to improve the tensile strength (tensile strength), a reinforcing material is added (for example, patent document 1). In order to improve the tensile strength, a tape-shaped material such as carbon fiber, glass fiber, or cellulose fiber is generally suitable as a reinforcing material (filler). Further, in order to make it difficult to pull out the strip-shaped material from the base material, it has also been proposed to increase the tensile yield stress by using a compatibilizing agent (patent document 6). However, it is found that the mechanical strength such as tensile strength cannot be sufficiently improved by simply adding a tape-shaped material. This is considered to be because the strip-shaped material is pulled out together with the base material because the base material is flexible.

As described above, even when natural graphite is treated as it is, the amount of exfoliated graphene is generally small, which is a problem. However, as a result of intensive studies, a graphite-based carbon material (graphene precursor) which can be easily exfoliated into graphene and has a high concentration or high dispersion is obtained by subjecting graphite as a material to a predetermined treatment. The graphene precursor is partially or completely exfoliated by ultrasonic waves, stirring, and kneading, and a mixture "graphene-like graphite" from the graphene precursor to graphene is obtained. The graphene-like graphite is not limited because the size, thickness, and the like vary depending on the amount of the added graphene precursor, the process time, and the like, but is preferably further flaked. That is, graphite that is easily exfoliated/dispersed into graphene-like graphite by a conventional stirring, kneading process or apparatus is a graphite-based carbon material (graphene precursor).

By dispersing such graphene-like graphite in a matrix material in a small amount together with a reinforcing material, mechanical strength such as flexural modulus, compressive strength, tensile strength, young's modulus, and the like can be improved, and the composite reinforcing material can be produced without significantly changing the production method from the conventional method.

The present invention has been made in view of such a problem, and an object thereof is to provide a composite reinforcement material having excellent mechanical strength and a method for producing the same.

Further, it is an object to provide a composite reinforcement material that exhibits desired properties even when the amount of graphene-like graphite dispersed/blended in a base material is small.

Further, the object is to provide a composite reinforcement material having excellent mechanical strength by using a conventional production process.

Means for solving the problems

In order to solve the above problems, a method for producing a composite reinforcing material according to the present invention includes a step of kneading at least a graphite-based carbon material and a reinforcing material in a matrix,

the graphite-based carbon material has a rhombohedral graphite layer (3R) and a hexagonal graphite layer (2H), and the ratio Rate (3R) of the rhombohedral graphite layer (3R) to the hexagonal graphite layer (2H) defined by the following (formula 1) obtained by X-ray diffraction is 31% or more.

Rate (3R) ═ P3/(P3+ P4). times.100. cndot. (formula 1)

In the formula 1, the reaction mixture is,

p3 represents the peak intensity of the (101) plane of the rhombohedral graphite layer (3R) obtained by X-ray diffraction,

p4 is the peak intensity of the (101) plane of the hexagonal graphite layer (2H) obtained by the X-ray diffraction method.

Thus, the graphene-like graphite is peeled off from the graphite-based carbon material, and a large amount of the thin graphene-like graphite is dispersed in the base material.

Here, the number of the first and second electrodes,

the graphene-like graphite is a mixture of the graphite-based carbon material and graphene, which is obtained by peeling off a part or all of the graphite-based carbon material,

the graphene is a flaky or flaky graphene having an average size of 100nm or more and having 10 or less layers.

Further, the reinforcing material is a band-shaped, linear or flake-shaped fine particle.

Further, the fine particles are characterized in that the aspect ratio is 5 or more.

Further, the weight ratio of the graphite-based carbon material to the reinforcing material is 1/100 or more and less than 10.

Further, the composite reinforcing material is characterized in that at least a graphite-based carbon material and a reinforcing material are kneaded in a matrix and a part or all of the graphite-based carbon material is exfoliated to obtain a composite reinforcing material,

Rate (3R) ═ P3/(P3+ P4). times.100. cndot. (formula 1)

In the formula 1, the reaction mixture is,

According to this feature, the composite material is excellent in mechanical strength. This is presumably because the function of increasing the elastic modulus of the matrix material itself by dispersing the graphene-like graphite in the matrix material and the function of making the reinforcing material less likely to be pulled out are exerted in cooperation. The mechanical strength includes flexural modulus, compressive strength, tensile strength, young's modulus, and the like, and for example, the tensile strength is excellent.

Further, the composite reinforcing material is characterized in that at least graphene-like graphite obtained by exfoliation from a graphite-based carbon material and a reinforcing material are dispersed in a matrix,

Rate (3R) ═ P3/(P3+ P4). times.100. cndot. (formula 1)

In the formula 1, the reaction mixture is,

p4 represents the peak intensity of the (101) plane of the hexagonal graphite layer (2H) by X-ray diffraction,

Characterized in that the reinforcing material is a band-like, linear or flaky fine particle.

According to this feature, since the graphene-like graphite exists around the fine particles, the reinforcing function of the fine particles can be sufficiently exhibited.

Characterized in that the aspect ratio of the fine particles is 5 or more.

This feature enables the reinforcing function of the fine particles to be more fully exerted.

Wherein the weight ratio of the sum of the graphite-based carbon material and the graphene-like graphite to the reinforcing material is 1/100 or more and less than 10.

This feature makes it possible to sufficiently exert the reinforcing function of the reinforcing material.

Wherein the base material is a polymer.

This feature makes it possible to obtain a composite reinforcement material having excellent mechanical strength.

Characterized in that the base material is an inorganic material.

The molding material is characterized by using the composite reinforcing material.

This feature makes it possible to obtain a modeling material for 3D printing or the like that has excellent mechanical strength.

Drawings

Fig. 1 is a diagram showing a crystal structure of graphite, and fig. 1 (a) is a crystal structure of hexagonal crystal, and fig. 1 (b) is a crystal structure of rhombohedral crystal.

Fig. 2 is a diagram showing an X-ray diffraction pattern of a typical natural graphite.

Fig. 3 is a diagram illustrating a manufacturing apparatus a using a jet mill (jet mill) and plasma in example 1.

Fig. 4 is a diagram illustrating a manufacturing apparatus B using a ball mill and a magnetron in example 1, fig. 4 (a) is a diagram illustrating a state in which the graphite-based carbon material (precursor) is pulverized, and fig. 4 (B) is a diagram illustrating a state in which the graphite-based carbon material (precursor) is collected.

Fig. 5 is a diagram showing an X-ray diffraction pattern of the graphite-based carbon material of sample 5 produced by production apparatus B in example 1.

Fig. 6 is a diagram showing an X-ray diffraction pattern of a graphite-based carbon material of sample 6 produced by production apparatus a in example 1.

Fig. 7 is a diagram showing an X-ray diffraction pattern of the graphite-based carbon material of sample 1 of the comparative example.

Fig. 8 is a diagram showing a dispersion liquid production apparatus for producing a dispersion liquid using a graphite-based carbon material as a precursor.

Fig. 9 is a diagram showing the dispersion state of the dispersion liquid prepared by using the graphite-based carbon material of sample 1 representing the comparative example and sample 5 produced by the production apparatus B of example 1.

Fig. 10 is a TEM image of the graphite-based carbon material (graphene) dispersed in the dispersion liquid.

Fig. 11 is a diagram showing the distribution state of the graphite-based carbon material dispersed in the dispersion liquid prepared using the graphite-based carbon material (precursor) of sample 5, fig. 11 (a) is a diagram showing the distribution of the average size, and fig. 11 (b) is a diagram showing the distribution of the number of layers.

Fig. 12 is a diagram showing a distribution state of a graphite-based carbon material dispersed in a dispersion liquid prepared using a graphite-based carbon material representing sample 1 of a comparative example, fig. 12 (a) is a diagram showing a distribution of an average size, and fig. 12 (b) is a diagram showing a distribution of the number of layers.

Fig. 13 is a graph showing the distribution of the number of layers of the graphite-based carbon material dispersed in the dispersion liquid prepared using samples 1 to 7 as precursors.

Fig. 14 is a graph showing the ratio of 10 or less layers of graphene with respect to the content of rhombohedral crystals dispersed in the dispersion.

Fig. 15 is a graph showing the distribution state of graphite when the conditions for preparing a dispersion using the graphite-based carbon material (precursor) of sample 5 were changed in example 2, fig. 15 (a) is a graph showing the distribution when ultrasonic treatment and microwave treatment were used in combination, and fig. 15 (b) is a graph showing the distribution of the number of layers when ultrasonic treatment was performed.

Fig. 16 is a graph showing the resistance value when the graphite-based carbon material of example 3 was dispersed in the conductive ink.

Fig. 17 is a graph showing the tensile strength when the graphite-based carbon material of example 4 was kneaded into a resin.

Fig. 18 is a graph showing the elastic modulus when the graphite-based carbon material of example 5 was kneaded into a resin.

Fig. 19 is a diagram showing a distribution state of a graphite-based carbon material dispersed in a dispersion liquid of N-methylpyrrolidone (NMP) for supplementary explanation of the dispersion state in example 5, fig. 19 (a) is a diagram showing a distribution state of sample 12, and fig. 19 (b) is a diagram showing a distribution state of sample 2.

Fig. 20 is a graph showing the tensile strength and flexural modulus of the test piece of example 6.

Fig. 21 is an SEM photograph (top view) of the graphene precursor.

Fig. 22 is an SEM photograph (side view) of the graphene precursor.

Fig. 23 is an SEM photograph (cross-sectional view) of the resin in which graphene-like graphite is dispersed.

Fig. 24 is a side SEM photograph (side view) of the graphene-like graphite in fig. 23.

Fig. 25 is a graph showing the tensile strength and flexural modulus of the test piece of example 7.

Fig. 26 is a graph showing the tensile strength and flexural modulus of the test piece when the shape of the reinforcing material of example 8 was changed.

Fig. 27 is a schematic diagram for explaining the shapes of the reinforcing materials of example 8, (a) for explaining the shapes of glass fibers and carbon fibers, (b) for explaining the shape of talc, and (c) for explaining the shape of silica.

Fig. 28 is a graph showing the tensile strength and flexural modulus of the test piece when the mixing ratio of the graphene precursor to the reinforcing material of example 9 was changed.

Detailed Description

The present invention focuses on the crystal structure of graphite, and first, the contents of the crystal structure will be described. Natural graphite is known to be classified into three crystal structures of hexagonal, rhombohedral, and disordered according to the manner of overlapping layers. As shown in fig. 1, hexagonal crystal has a crystal structure in which layers are stacked in the order ABABAB · and rhombohedral crystal has a crystal structure in which layers are stacked in the order ABCABCABC · and.

Natural graphite has almost no rhombohedral at the stage of extraction, but is broken at the stage of purification, and thus about 14% of rhombohedral is present in a normal natural graphite-based carbon material. It is also known that the ratio of rhombohedral crystals is about 30% even when the refining is carried out for a long time by crushing (non-patent documents 1 and 2).

Further, a method of expanding graphite by heating to form a sheet is known in addition to physical force such as crushing, but even when graphite is treated by applying heat at 1600K (about 1300 degrees celsius), the ratio of rhombohedral is about 25% (non-patent document 3). Even if heat of 3000 degrees celsius at a very high temperature is further applied, it reaches about 30% at most (non-patent document 2).

In this way, the ratio of the rhombohedral crystal can be increased by treating the natural graphite with physical force or heat, but the upper limit is about 30%.

Hexagonal crystals (2H) contained in a large amount in natural graphite are very stable, and van der waals force between layers of graphene is expressed by (formula 3) (patent document 2). By applying energy exceeding the force, graphene exfoliation occurs. Since the energy required for exfoliation is inversely proportional to the third power of the thickness, graphene is exfoliated by weak physical force such as very weak ultrasonic waves in a thick state in which a plurality of layers are stacked, but a very large energy is required for exfoliation from graphite that is thin to a certain extent. In other words, even if graphite is treated for a long time, only a weak portion of the surface is peeled off, and most of the graphite remains in an un-peeled state.

Fvdw H/(6 pi. t 3. cndot. (formula 3)

Fvdw: van der waals force

H: hamaker constant

A: surface area of graphite or graphene

t: thickness of graphite or graphene

The inventors of the present application succeeded in increasing the proportion of rhombohedral crystals (3R) to a higher level, which could be increased only to about 30% by crushing and/or heating to ultrahigh temperature treatment, by subjecting natural graphite to a predetermined treatment as shown below. As a result of the experiment/study, the following findings were obtained: when the content of the rhombohedral crystal (3R) in the graphite-based carbon material is increased, particularly when the content is 31% or more, the graphite-based carbon material is used as a precursor, and thus the material tends to be easily exfoliated into graphene, and a graphene solution or the like having a high concentration and a high degree of dispersion can be easily obtained. This is considered to be because when a force such as shearing is applied to the rhombohedral crystal (3R), strain occurs between layers, that is, the strain of the entire structure of graphite increases, and exfoliation becomes easy, without depending on van der waals forces. Therefore, in the present invention, a graphite-based carbon material from which graphene can be easily exfoliated by subjecting natural graphite to a predetermined treatment and can be highly concentrated or highly dispersed is referred to as a graphene precursor, and hereinafter, in the examples described below, a method for producing a graphene precursor by a predetermined treatment, a crystal structure of the graphene precursor, and a graphene dispersion liquid using the graphene precursor will be described in order.

Here, in the present specification, graphene refers to flaky or flake-like graphene which is a crystal having an average size of 100nm or more, not a crystallite having an average size of several nm to several tens of nm, and has 10 or less layers.

Since graphene is a crystal having an average size of 100nm or more, it is impossible to obtain graphene even when artificial graphite or carbon black, which is an amorphous (microcrystalline) carbon material other than natural graphite, is treated (non-patent document 4).

In the present specification, the graphene composite refers to a composite prepared by using a graphite-based carbon material having a Rate (3R) of 31% or more, which is a graphite-based carbon material that can be used as a graphene precursor of the present invention (for example, samples 2 to 7 in example 1 and samples 2 and 21. cndot. in example 5, which will be described later).

Examples of the composite reinforcing material and the molding material for carrying out the present invention will be described below.

Example 1

< production of graphite-based carbon Material useful as graphene precursor >

A method for obtaining a graphite-based carbon material usable as a graphene precursor by using a manufacturing apparatus a using a jet mill and plasma as shown in fig. 3 will be described. In the manufacturing apparatus a, a case where plasma is applied as a process based on an electromagnetic force and a jet mill is used as a process based on a physical force is exemplified.

In FIG. 3, the reference numeral 1 denotes a natural graphite material (flake graphite ACB-50 manufactured by the Japan graphite industry) having particles of 5mm or less; 2 is a hopper containing natural graphite material 1; 3 is a venturi nozzle for spraying the natural graphite material 1 from the hopper 2; 4, a jet mill for injecting air pressurized and delivered from the compressor 5 at eight places to cause the natural graphite material to collide with the jet flow in the chamber; reference numeral 7 denotes a plasma generating device which generates plasma in the chamber of the jet mill 4 by ejecting gas 9 such as oxygen, argon, nitrogen, or hydrogen from the container 6 from the nozzle 8 and applying a voltage to a coil 11 wound around the outer periphery of the nozzle 8 by a high voltage power supply 10, and is provided at four positions in the chamber. Reference numeral 13 denotes a pipe connecting the jet mill 4 and the dust collector 14, 14 denotes a dust collector, 15 denotes a collecting container, 16 denotes a graphite-based carbon material (graphene precursor), and 17 denotes a blower.

The following describes the manufacturing method. Conditions of the jet mill and plasma are as follows.

The conditions of the jet mill were as follows.

Pressure: 0.5MPa

Air volume: 2.8m³Per minute

Nozzle bore diameter: 12mm

Flow rate: about 410 m/s

The plasma conditions are as follows.

Output power: 15W

Voltage: 8kV

Gas species: ar (purity 99.999 vol%)

Gas flow rate: 5L/min

It is considered that the natural graphite materials 1 fed into the chamber of the jet mill 4 from the venturi nozzle 3 are accelerated to the sonic velocity or higher in the chamber, and are pulverized by the impact of collision of the natural graphite materials 1 with each other and with the wall, and at the same time, the plasma 12 discharges and excites the natural graphite materials 1 to directly act on atoms (electrons) and increase the strain of crystals to promote pulverization. When the natural graphite material 1 is formed into fine powder having a particle diameter of about 1 to 10 μm, the mass is reduced and the centrifugal force is weakened, and the fine powder is drawn out from the pipe 13 connected to the center of the chamber.

The gas mixed with the graphite-based carbon material (graphene precursor) flowing from the pipe 13 into the cylindrical container of the chamber of the dust collector 14 forms a swirling flow, the graphite-based carbon material 16 colliding with the inner wall of the container falls into the lower collection container 15, and an updraft is generated at the center of the chamber by the conical container portion below the chamber, and the gas is discharged from the blower 17 (so-called cyclone separation (cyclone) action). About 800g of a graphite-based carbon material (graphene precursor) 16 usable as a graphene precursor was obtained from 1kg of a natural graphite material 1 as a raw material by the production apparatus a in this example (recovery efficiency: about 8).

Next, a method for obtaining a graphite-based carbon material usable as a graphene precursor by using a manufacturing apparatus B using a ball mill and microwaves as shown in fig. 4 will be described. In the manufacturing apparatus B, a case where microwave is performed as a process based on electromagnetic force and a ball mill is used as a process based on physical force is exemplified.

In fig. 4 (a) and 4 (b), reference numeral 20 denotes a ball mill, 21 denotes a microwave generator (magnetron), 22 denotes a waveguide, 23 denotes a microwave inlet, 24 denotes a medium, 25 denotes a natural graphite material (flake graphite ACB-50 manufactured by the japan graphite industry) having particles of 5mm or less, 26 denotes a collection container, 27 denotes a filter, and 28 denotes a graphite-based carbon material (graphene precursor).

The following describes the manufacturing method. The conditions of the ball mill and the microwave generating apparatus are as follows.

The conditions of the ball mill are as follows.

Rotating speed: 30rpm

Medium size:

the kind of the medium: zirconia ball

And (3) crushing time: 3 hours

The conditions of the microwave generating apparatus (magnetron) are as follows.

Output power: 300W

Frequency: 2.45GHz

The irradiation method comprises the following steps: intermittent type

1kg of a natural graphite-based carbon material 25 and 800g of a medium 24 were charged into a chamber of the ball mill 20, and the chamber was sealed and treated at 30rpm for 3 hours. In this process, the chamber was irradiated with microwaves intermittently (20 seconds at intervals of 10 minutes). It is considered that the irradiation with the microwave directly acts on atoms (electrons) of the raw material to increase the strain of the crystal. After the treatment, the medium 24 is removed by the filter 27, whereby a graphite-based carbon material (precursor) 28 of about 10 μm powder can be collected in the collection container 26.

< X-ray diffraction Pattern on graphite-based carbon raw Material (precursor) >

Referring to fig. 5 to 7, the X-ray diffraction patterns and crystal structures of the graphite-based natural materials (sample 6 and sample 5) produced by the production apparatus A, B and the graphite-based natural material (sample 1: comparative example) obtained as a powder of about 10 μm by using only the ball mill of the production apparatus B will be described.

The measurement conditions of the X-ray diffraction apparatus are as follows.

Line source: CuKalpha ray

Scanning speed: 20 DEG/min

Tube voltage: 40kV

Tube current: 30mA

Each sample was described as showing peak intensities P1, P2, P3 and P4 on the surface (100) of hexagonal crystal 2H, the surface (002), the surface (101) and the surface (101) of rhombohedral crystal 3R, respectively, by X-ray diffraction (Ultima IV, a sample horizontal multi-purpose X-ray diffraction apparatus manufactured by Rigaku co., ltd.).

In recent years, so-called normalized values have been used for the measurement of X-ray diffraction patterns both at home and abroad. The sample horizontal multi-purpose X-ray diffraction apparatus Ultima IV manufactured by Rigaku corporation is an apparatus capable of measuring an X-ray diffraction pattern based on JIS R7651: 2007 "method for measuring lattice constant and crystallite size of carbon material". Note that the Rate (3R) is a ratio of diffraction intensities obtained by setting the Rate (3R) to P3/(P3+ P4) × 100, and the value of the Rate (3R) does not change even if the diffraction intensity changes. In other words, the ratio of diffraction intensities is normalized, usually to avoid identification of the substance in absolute values, which are independent of the measurement device.

As shown in fig. 5 and table 1, in the sample 5 produced by the production apparatus B which applied the ball mill treatment and the microwave treatment, the ratio of the intensities of the peak intensity P3 and the peak intensity P1 was high, and the Rate (3R) defined by (formula 1) indicating the ratio of P3 to the sum of P3 and P4 was 46%. The intensity ratio P1/P2 was 0.012.

Rate (3R) ═ P3/(P3+ P4). times.100. cndot. (formula 1)

Here, the number of the first and second electrodes,

p1 represents the peak intensity of the (100) plane of the hexagonal graphite layer (2H) by X-ray diffraction,

p2 represents the peak intensity of the (002) plane of the hexagonal graphite layer (2H) obtained by X-ray diffraction,

TABLE 1

Similarly, as shown in fig. 6 and table 2, in sample 6 produced by the production apparatus a in which the jet mill treatment and the plasma treatment were performed, the ratios of the intensities of the peak intensity P3 and the peak intensity P1 were high, and the Rate (3R) was 51%. The intensity ratio P1/P2 was 0.014.

TABLE 2

As shown in fig. 7 and table 3, the peak intensity P3 of sample 1, which is a comparative example and produced only by a ball mill, is smaller than those of samples 5 and 6, and the Rate (3R) is 23%. The intensity ratio P1/P2 was 0.008.

TABLE 3

As described above, sample 5 produced by the production apparatus B in example 1 and sample 6 produced by the production apparatus a in example 1 showed: the Rate (3R) was 46% or 51%, and was 40% or more or 50% or more as compared with the natural graphite shown in fig. 2 and sample 1 representing the comparative example.

Next, a graphene dispersion was prepared using the graphene precursor prepared as described above, and the ease of peeling of graphene was compared.

< graphene Dispersion >

A method for producing the graphene dispersion liquid will be described with reference to fig. 8. In fig. 8, a case where ultrasonic treatment and microwave treatment are used in combination in a liquid when preparing a graphene dispersion liquid is taken as an example.

(1) 0.2g of a graphite-based carbon raw material usable as a graphene precursor and 200ml of N-methylpyrrolidone (NMP) as a dispersion were charged into the beaker 40.

(2) The beaker 40 is placed in the chamber 42 of the microwave generator 43, and the ultrasonic transducer 44A of the ultrasonic horn 44 is inserted into the dispersion liquid 41 from above.

(3) The ultrasonic horn 44 was operated to continuously apply ultrasonic waves of 20kHz (100W) for 3 hours.

(4) While the ultrasonic horn 44 was operated, the microwave generator 43 was operated to intermittently apply microwaves (10 seconds per 5 minutes) at 2.45GHz (300W).

Fig. 9 shows a state in which the graphene dispersion liquid prepared as described above has elapsed for 24 hours.

It was confirmed that the graphene dispersion liquid 30 using sample 5 produced by production apparatus B was black in color as a whole, although a part of the graphene dispersion liquid was precipitated. This is considered to be because the graphite-based carbon material used as the graphene precursor is dispersed in a state of being exfoliated into graphene in many cases.

It was confirmed that most of the graphite-based carbon material precipitated in the dispersion 31 using the sample 1 representing the comparative example, and a part of the graphite-based carbon material floated in the state of a supernatant liquid. From this, it is considered that a very small portion is exfoliated into graphene and floats in the form of a supernatant.

The graphene dispersion prepared as described above was diluted at a concentration that enables observation, applied on a sample stage (TEM grid), dried, and the size and number of layers of graphene were observed from an image taken by a Transmission Electron Microscope (TEM) as shown in fig. 10. The supernatant was diluted and applied to sample 1. For example, in the case of fig. 10, the maximum length L of the sheet (flake)33 is determined to be about 600nm from fig. 10 (a), and the number of graphene layers is determined to be 6 (the region indicated by the reference numeral 34) by observing the end face of the sheet 33 and counting the number of graphene layers from fig. 10 (b). The size and number of layers of each sheet (the number of sheets is N) were measured in this manner, and the number of graphene layers and the size shown in fig. 11 and 12 were obtained.

Referring to fig. 11 (a), the particle size distribution (size distribution) of the flaky sheets contained in the graphene dispersion of sample 5(Rate (R3) 46%) produced by the production apparatus B in example 1 is a distribution having a peak of 0.5 μm. In fig. 11 (b), the number of layers is a distribution with 3 layers as a peak and 68% or less of graphene.

Referring to fig. 12, the particle size distribution (size distribution) of the flake-like flakes contained in the dispersion of sample 1 (23% Rate (R3)) of the comparative example is a distribution with a peak of 0.9 μm. The number of layers is 30 or more and the majority thereof, and 10% or less of graphene is distributed.

From the results, it is understood that when sample 5 produced by production apparatus B is used as a graphene precursor, a graphene dispersion liquid having a large amount of 10 or less layers of graphene, excellent in graphene dispersibility, and high in concentration can be obtained.

Next, referring to fig. 13, a relationship between the ratio Rate (3R) of the graphene precursor and the number of layers in the graphene dispersion liquid will be described. Samples 1, 5 and 6 in fig. 13 are the above-mentioned samples. Samples 2, 3, and 4 were produced by the production apparatus B which performed the ball mill treatment and the microwave treatment, and the graphene dispersion liquid was produced using the graphene precursor produced by making the irradiation time of the microwave shorter than that of sample 5. Sample 7 was produced by using the production apparatus a which applied the jet mill treatment and the plasma treatment, and a graphene dispersion liquid was prepared using a graphene precursor which was produced by applying plasma having an output higher than that of sample 6.

From fig. 13, the shape of the layer number distribution of samples 2 and 3 having rates (3R) of 31% and 38% is a shape close to a normal distribution having peaks around 13 layers (using the dispersions of samples 2 and 3). The number-of-layers distribution shape of samples 4 to 7 having a Rate (3R) of 40% or more is a shape of a so-called log-normal distribution having peaks in portions of several layers (thin graphene). On the other hand, sample 1 having a Rate (3R) of 23% has a peak shape in a portion where the number of layers is 30 or more (using the dispersion of sample 1). Namely, the following tendency is known: when the Rate (3R) reaches 31% or more, the layer number distribution shape differs from less than 31%, and further when the Rate (3R) reaches 40% or more, the layer number distribution shape differs from less than 40%. Further, it is understood that the ratio of 10 or less layers of graphene is 38% for the Rate (3R) of the dispersion liquid using sample 3, and 42% for the Rate (3R) of the dispersion liquid using sample 4, and that the ratio of 10 or less layers of graphene increases rapidly when the Rate (3R) is 40% or more.

From this, it is considered that graphene easily exfoliated to 10 layers or less when the Rate (3R) is 31% or more, and graphene easily exfoliated to 10 layers or less as the Rate (3R) increases to 40%, 50%, 60%. When attention is paid to the strength ratio P1/P2, the strength ratio P1/P2 is preferably in a narrow range of 0.012 to 0.016 for sample 2 to sample 7, and exceeds 0.01 which is considered to cause strain in the crystal structure and to be easily exfoliated into graphene.

Fig. 14 shows the results of comparing the Rate (3R) and the content ratio of graphene having 10 or less layers. Referring to fig. 14, it can be seen that when the Rate (3R) is 25% or more, 10 layers or less of graphene increases from near 31% (forming a slope that increases rightward), and at about 40% the 10 layers or less of graphene suddenly increases (the Rate (3R) of the dispersion using sample 3 is 38% for the Rate of 10 layers or less of graphene, while the Rate (3R) of the dispersion using sample 4 is 42% for the Rate of 10 layers or less of graphene, the Rate (3R) increases by 4%, and the Rate of 10 layers or less of graphene suddenly increases by 24%), and the total amount of 10 layers or less of graphene is 50% or more. The black squares in fig. 14 represent different samples, and include the above-mentioned samples 1 to 7 and other samples other than these samples.

Thus, when a graphene dispersion liquid is prepared using a sample having a Rate (3R) of 31% or more as a graphene precursor, the dispersion ratio of 10 or less layers of graphene starts to increase, and when a graphene dispersion liquid is prepared using a sample having a Rate (3R) of 40% or more as a graphene precursor, 50% or more of 10 or less layers of graphene are generated. That is, a graphene dispersion liquid in which graphene is highly dispersed at a high concentration can be obtained. Further, as described above, since the graphite-based carbon material (precursor) contained in the dispersion liquid is not substantially precipitated, a relatively concentrated graphene dispersion liquid can be easily obtained. By this method, a graphene dispersion liquid having a graphene concentration of more than 10% can be prepared without concentration. In particular, the Rate (3R) is more preferably 40% or more from the viewpoint of a sharp increase in the dispersion ratio of 10 or less layers of graphene to 50% or more.

From this, it is found that when the Rate (3R) is 31% or more, preferably 40% or more, and more preferably 50% or more, the ratio of the graphite-based carbon material separated into 10 or less layers and about 10 thin layers is high, and when these graphite-based carbon materials are used as the graphene precursor, a graphene dispersion liquid having excellent dispersibility of graphene and a high concentration can be obtained. As is apparent from example 5 described later, when the Rate (3R) is 31% or more, it is useful as a graphene precursor as a graphite-based carbon material.

It is not necessary to particularly limit the upper limit of the Rate (3R), but it is preferable to satisfy the intensity ratio R1/R2 of 0.01 or more at the same time, since graphene is easily separated when preparing a dispersion liquid or the like. In the case of the production method using the production apparatus A, B, the upper limit is about 70% from the viewpoint of ease of production of the graphene precursor. Further, the method of using a combination of a jet mill treatment and a plasma treatment in the manufacturing apparatus a is more preferable because a material having a high Rate (3R) can be easily obtained. Note that the Rate (3R) may be set to 31% or more by using the physical force processing and the electromagnetic force processing in combination.

Example 2

In example 1, a case where the ultrasonic treatment and the microwave treatment were used in combination when the graphene dispersion liquid was obtained was described, whereas in example 2, only the ultrasonic treatment was performed without performing the microwave treatment, and other conditions were the same as in example 1.

Fig. 15 (B) shows the distribution of the number of layers of the graphene dispersion liquid obtained by performing the ultrasonic treatment using the graphene precursor of sample 5(Rate (3R) ═ 46%) manufactured by the manufacturing apparatus B. Fig. 15 (a) is the same as the distribution shown in fig. 11 (B) of sample 5 produced by production apparatus B in example 1.

As a result, the distribution of the number of layers tended to be approximately the same, but the proportion of 10 layers or less of graphene was 64%, which was slightly lower than 68% of example 1. From this, it was found that, when the graphene dispersion liquid was prepared, it was more effective to perform both the physical force and the electromagnetic force.

Example 3

In embodiment 3, an example for the conductive ink will be described.

Ink 1, ink 3, ink 5, and ink 6 were prepared as graphene precursors at concentrations used as conductive inks in a mixed solution of water and an alcohol having 3 or less carbon atoms as a conductivity-imparting agent, using sample 1(Rate (3R) ═ 23%), sample 3(Rate (3R) ═ 38%), sample 5(Rate (3R) ═ 46%), and sample 6(Rate (3R) ═ 51%) of example 1 as graphene precursors, and the respective resistance values were compared. From this result, a result is obtained in which the resistance value decreases as the Rate (3R) increases.

Example 4

In example 4, an example of kneading into a resin will be described.

In the production of a resin sheet in which graphene is dispersed, the reason why the resin sheet containing glass fibers has very good tensile strength has been studied, and as a result, the following findings have been obtained: the addition of a compatibilizer simultaneously with the glass fibers aids in the graphitization of the precursor. Therefore, a case where a dispersant and a compatibilizer are mixed into a resin has been studied.

1 wt% of sample 5 of example 1(Rate (3R) ═ 46%) was added as a precursor directly to LLDPE (polyethylene), and kneaded with a kneader, a twin-screw kneader (extruder) or the like while applying shear (shearing force).

Since it is known that the tensile strength increases when a graphite-based carbon material in a resin undergoes graphitization and is highly dispersed, the degree of graphitization and dispersion can be relatively estimated by measuring the tensile strength of the resin. The tensile strength was measured under the condition of a test speed of 500 mm/min using a bench precision universal tester (AUTOGRAPH AGS-J) manufactured by Shimadzu corporation.

In addition, in order to compare the graphitization and dispersibility by the presence or absence of the additive, the following three comparisons (a), (b), and (c) were made.

(a) Without additives

(b) Conventional dispersant (Zinc stearate)

(c) Compatibilizer (graft-modified Polymer)

The results will be described with reference to fig. 17 showing the measurement results. In fig. 17, the circle mark is the resin material of sample 1 using the comparative example, and the square mark is the resin material of sample 5 using example 1.

In the case of (a) without adding the additive, the difference in tensile strength is small.

In the case where the dispersant is added to (b), it is found that the graphene formation of the graphene precursor of sample 5 is promoted to some extent.

When the compatibilizer is added to (c), it is found that the graphene formation of the graphene precursor of sample 5 is greatly promoted. This is considered to be because the compatibilizer not only has an effect of dispersing graphene but also acts as follows: when the graphene layer assembly is bonded to a resin and shear is applied in this state, the graphene layer assembly is torn.

The dispersant is exemplified by zinc stearate, but a dispersant having properties matching those of the compound may be selected. Examples of the dispersant include an anionic (anion) surfactant, a cationic (cation) surfactant, a zwitterionic surfactant, and a nonionic (nonion) surfactant. In particular, for graphene, anionic surfactants and nonionic surfactants are preferable. More preferably a nonionic surfactant. The nonionic surfactant is a surfactant which exhibits hydrophilicity due to hydrogen bonds with water, such as sugar chains of oxyethylene groups, hydroxyl groups, or glycosides, and does not dissociate into ions, and therefore has an advantage that it can be used in a nonpolar solvent, although it does not have strong hydrophilicity as in an ionic surfactant. And also because: by changing the chain length of the hydrophilic group, the property of the hydrophilic group can be freely changed from lipophilicity to hydrophilicity. As the anionic surfactant, an X acid salt (X acid is, for example, cholic acid, deoxycholic acid) is preferable, and for example, SDC: sodium deoxycholate, phosphate esters, and the like. The nonionic surfactant is preferably a fatty acid glyceride, a sorbitan fatty acid ester, a fatty alcohol ethoxylate, a polyoxyethylene alkylphenyl ether, an alkyl glycoside, or the like.

Example 5

In order to further verify that the graphene precursor is useful when the Rate (3R) is 31% or more as described in example 1, an example in which the graphene precursor is kneaded into a resin is used in example 5. The elastic modulus of a resin molded article using as a precursor a graphite-based carbon material of Rate (3R) shown in fig. 14 including samples 1 to 7 in example 1 will be described.

(1) The above-mentioned graphite-based carbon material as a precursor, LLDPE (20201J manufactured by Prime Polymer co., ltd.) 5 wt%, and a dispersant (nonionic surfactant) 1 wt% were mixed in ion-exchanged water, and the apparatus of fig. 8 was operated under the same conditions to obtain a graphene dispersion liquid in which the content of graphene and/or graphite-based carbon material was 5 wt%.

(2) 0.6kg of the graphene dispersion liquid obtained in (1) was immediately kneaded with 5.4kg of a resin using a kneader (WDS 7-30, pressure type kneader manufactured by Moriyama Company Ltd.) to prepare pellets. The mixing conditions are described below. The blending ratio of the resin and the dispersion liquid is selected so that the amount of the final graphene and/or graphite-based carbon material added is 0.5 wt%.

(3) Using the pellets prepared in (2), a test piece JIS K71611A type (total length 165mm, width 20mm, thickness 4mm) was prepared by an injection molding machine.

(4) Based on JIS K7161, a bench precision universal tester (AUTOGRAPH AGS-J) manufactured by shimadzu corporation was used to perform the following tests at test rates: the elastic modulus (MPa) of the test piece produced in (3) was measured under the condition of 500 mm/min.

The kneading conditions are as follows.

Mixing temperature: 135 deg.C

Rotor speed: 30rpm

Mixing time: 15 minutes

Pressurizing in the furnace: 0.3MPa 10 min after the start, and the pressure is released to the atmospheric pressure 10 min after the end

Here, in the dispersion of the graphene dispersion liquid of the above (2) into a resin, water evaporates in the atmosphere because the melting point of the resin is generally 100 ℃ or higher, but a pressure kneader may pressurize a furnace. In the furnace, the boiling point of water is increased to keep the dispersion in a liquid state, whereby an emulsion of the dispersion and the resin can be obtained. After pressurization for a predetermined time, the pressure is gradually released, the boiling point of water is lowered, and water is gradually evaporated. At this time, the graphene confined in the water remains in the resin. It is considered that the graphene-based carbon material is highly dispersed in the resin.

In addition, since the graphene-based carbon material tends to settle over time in the graphene dispersion liquid, it is preferable to obtain the graphene dispersion liquid and immediately knead the graphene dispersion liquid into a resin.

The means for obtaining the emulsion of the dispersion and the resin may be a chemical propeller, a vortex mixer, a homomixer, a high-pressure homogenizer, a hydroshear (hydro), a jet mixer, a wet jet mill, an ultrasonic generator, or the like, in addition to the pressure kneader.

As the solvent of the dispersion, 2-propanol (IPA), acetone, toluene, N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), and the like can be used in addition to water.

Table 4 shows the relationship between the Rate (3R) at a Rate (3R) of about 30% and the elastic modulus of the resin molded article. In table 4, sample 00 is a blank sample in which the precursor is not kneaded, samples 11 and 12 are samples in which the Rate (3R) is between sample 1 and sample 2, and sample 21 is a sample in which the Rate (3R) is between sample 2 and sample 3.

TABLE 4

As can be seen from fig. 18 and table 4, the difference in elastic modulus (the increase ratio of elastic modulus) with respect to sample 00 (blank) is approximately 10% or so until the Rate (3R) reaches 31%, and is approximately constant, and the difference increases abruptly to 32% with the Rate (3R) 31% being the boundary, increases monotonically to 50% between the Rate (3R) 31% and 42%, and then slightly increases and converges to 60% or so after the Rate (3R) is 42%. When the Rate (3R) is 31% or more, a resin molded article having an excellent elastic modulus can be obtained. Further, since the amount of graphene and/or graphite-based carbon material contained in the resin molded product is small such as 0.5 wt%, the influence on the properties inherent in the resin is small.

This tendency is considered to be due to: a graphite-based carbon material having a thin layer containing 10 or less layers of graphene in contact with a resin is rapidly increasing in the range of Rate (3R) 31%. Here, in example 5, the number of graphene layers could not be confirmed even when observed by TEM due to the influence of the dispersant for dispersing in water. For reference, the reason for the above increase was examined based on the layer number distribution of the graphite-based carbon material when dispersed in NMP shown in table 4. In comparison between sample 12 and sample 2, the graphene (having 10 or less layers) was 25%. On the other hand, as shown in fig. 19, the proportion of the thin layers of less than 15 layers in sample 2 is larger than that of sample 12, which is considered to be because: the surface area of the graphite-based carbon material dispersed as the precursor is large, and the area in contact with the resin is rapidly increased.

As described above, according to example 5, when the Rate (3R) is 31% or more, the graphite-based carbon material that can be used as the graphene precursor clearly shows a tendency to be separated into 10 or less layers of graphene and/or a thin layer of the graphite-based carbon material.

Example 6

In example 5, only graphene-like graphite was dispersed, and only an increase in elastic modulus was observed, but not so much increase in tensile strength.

Then, an experiment was performed in which the graphene precursor and the glass fiber manufactured by the above method were added to a resin.

< conditions >

Resin: J707G, manufactured by PP (polypropylene) Prime Polymer Co., Ltd,

A compatilizer: KAYABRID (KAYAKU AKZO CO., LTD. 006PP maleic anhydride modified PP)

Glass Fiber (GF): CENTRAL GLASS CO, LTD. manufacture of ECS03-631K (diameter 13 μm, length 3mm),

Graphite-based carbon raw material: a graphene precursor (produced by the above-described method),

Mixing machine: a tumbler mixer (SEIWA GIKEN Co., Ltd.; manufactured by Ltd.),

< mixing conditions 1: the rotating speed is 25rpm multiplied by 1 minute >),

A mixing mill: a twin-screw extruder (HYPERKTX 30 manufactured by Kohyo Steel Co., Ltd.),

< mixing conditions 1: barrel temperature 180 ℃, rotor speed 100rpm, discharge amount 8kg/h >

Test piece: JIS K7139(170 mm. times.20 mm. times.t 4mm),

A measuring device: table type precision universal tester AUTOGRAPH AGS-J manufactured by Shimadzu corporation

< Experimental procedures >

Step 1. A master batch 1 was obtained by previously mixing 40 wt% of Glass Fiber (GF), 4 wt% of a compatibilizer, and 56 wt% of a resin under mixing conditions 1 using a drum mixer, and then mixing them under mixing conditions 1 using a twin-screw extruder (extruder).

Step 2. graphene precursors 12% by weight and resins 88% by weight, which differ in the Rate (3R) shown in table 5, were previously mixed under mixing condition 1 using a drum mixer, and then kneaded under mixing condition 1 using a twin-screw extruder (extruder) to obtain a master batch 2.

Step 3, 125 wt% of the master batch, 225 wt% of the master batch, and 50 wt% of the resin were previously mixed by a drum mixer under mixing condition 1, and then kneaded by a twin-screw extruder (extruder) under mixing condition 1.

And 4, molding the material obtained by the kneading in the step 3 into a test piece by an injection molding machine, and observing a change in mechanical strength at a test speed of 500 mm/min according to JIS K7139.

In order to confirm the effect of graphene-like graphite, experiments were carried out with rates (3R) of 23% (sample 1), 31% (sample 2), 35% (sample 21), and 42% (sample 4) at the mixing ratios shown in table 5.

TABLE 5

According to Table 5 and FIG. 20, it was observed that examples 6-2, 6-3, and 6-4 were higher than those of example 6-1 and comparative examples 6-1, 6-2, and 6-3 with respect to tensile strength. In particular, the following tendency is observed: when the Rate (3R) of the graphene precursor is 31% or more, the tensile strength tends to be improved by 30% or more as compared with 0% (comparative example 6-2) (strictly speaking, the Rate (3R) ═ 0%, since the graphene precursor is not added, and the graphene precursor cannot be plotted on the same graph, and therefore 0% is the same meaning in the following description) and 23% (example 6-1) for convenience. In FIG. 20, comparative examples 6-1 and 6-3 containing no GF are not shown.

In addition, with respect to the flexural modulus, in the same manner as the tensile strength, it was observed that examples 6-2, 6-3 and 6-4 were higher than examples 6-1 and comparative examples 6-1, 6-2 and 6-3. In particular, the following tendency is observed: when the Rate (3R) of the graphene precursor is 31% or more, the flexural modulus tends to be remarkably increased by 40% or more as compared with 0% (comparative example 6-2) or 23% (example 6-1).

When a graphene precursor having a Rate (3R) of 31% or more (examples 6-2, 6-3, and 6-4) was used in combination with GF, the tensile strength and flexural modulus were increased. It is presumed that, in the case where graphene-like graphite having a thickness of 0.3 to several tens of nm and a size of several nm to 1 μm is dispersed between PPs, the elastic modulus of the PP itself is increased, and the graphene-like graphite in contact with GF which is tightly bonded to the PP by the compatibilizer and is less likely to be pulled out is subjected to a so-called wedge action, and the tensile strength and the flexural modulus are increased by the synergistic action of the increase in the elastic modulus of the PP itself and the wedge action. For example, the pile with barbs is easily pulled out even if it penetrates into a loose ground, but is difficult to pull out in a compacted ground. It is also presumed that the addition of the compatibilizing agent promotes the exfoliation of graphene-like graphite or the like from the graphite-based carbon material, and a large amount of thin graphene-like graphite exists.

When the Rate (3R) is less than 31% (example 6-1), the amount of dispersed graphene-like graphite is small, and the effect of adding the graphene precursor is not considered to be sufficiently exhibited.

When the Rate (3R) is 35% or more (examples 6-3 and 6-4), the flexural modulus and tensile strength are better than those of the case where the Rate is not more than these values. This is considered to be because the number of graphene-like graphite particles increasing the elastic modulus of PP is increased as compared with a case where the Rate (3R) is 31% (example 6-2).

For reference, a Scanning Electron Microscope (SEM) photograph of the graphene precursor is illustrated. The graphene precursor obtained in example 1 is a laminate of thin-layer graphite having a length of 7 μm and a thickness of 0.1 μm, as shown in fig. 21 and 22, for example.

Further, the graphene-like graphite dispersed in the resin can be observed by cutting a molded test piece with a precision high-speed cutter (TechCut 5 manufactured by allid) or the like and observing the cut piece with a Scanning Electron Microscope (SEM) or the like. For example, fig. 23 shows a cross section of a resin in which carbon nanotubes and graphene-like graphite are dispersed, and a linear portion is a carbon nanotube and a white spot portion is graphene-like graphite. Such graphene graphite is a laminate of thin-layer graphite having a thickness of 3.97nm, for example, as shown in fig. 24.

Example 7

An experiment was performed to obtain a resin molded article using the graphene precursor produced by the above method.

< conditions >

Resin: PA66(66 Nylon) Asahi Kasei Kogyo 1300S,

Mixing machine: a tumbler mixer (SEIWA GIKEN Co., Ltd.; manufactured by Ltd.),

< mixing conditions 1: the rotating speed is 25rpm multiplied by 1 minute >),

< mixing conditions 2: barrel temperature 280 ℃, rotor speed 200rpm, discharge amount 12kg/h >

Test piece: JIS K7139(170 mm. times.20 mm. times.t 4mm),

< Experimental procedures >

Step 1. A master batch 1 was obtained by previously mixing 40 wt% of Glass Fiber (GF), 4 wt% of a compatibilizer, and 56 wt% of a resin in a tumbler mixer under mixing conditions 1 and then kneading the mixture in a twin-screw extruder (extruder) under kneading conditions 2.

Step 2, 12 wt% of graphene precursors having different rates (3R) shown in table 6 and 88 wt% of a resin were previously mixed by a drum mixer under mixing conditions 1, and then kneaded by a twin-screw extruder (extruder) under kneading conditions 2 to obtain a master batch 2.

Step 3. mixing 137.5% by weight of the master batch, 225% by weight of the master batch, and 37.5% by weight of the resin in advance in the mixing condition 1 using a drum mixer, and then kneading them in the kneading condition 2 using a twin-screw extruder (extruder).

In order to confirm the effect of graphene-like graphite, experiments were carried out with rates (3R) of 23% (sample 1), 31% (sample 2), 35% (sample 21), and 42% (sample 4) at the mixing ratios shown in table 6.

TABLE 6

According to Table 6 and FIG. 25, it was observed that examples 7-2, 7-3, and 7-4 were higher than examples 7-1 and comparative examples 7-1, 7-2, and 7-3 with respect to tensile strength. In particular, the following tendency is observed: when the Rate (3R) of the graphene precursor is 31% or more, the tensile strength tends to be remarkably improved by 20% or more as compared with 0% (comparative example 7-2) or 23% (example 7-1). In FIG. 25, comparative examples 7-1 and 7-3 containing no GF are not shown.

In addition, with respect to the flexural modulus, in the same manner as the tensile strength, it was observed that examples 7-2, 7-3 and 7-4 were higher than examples 7-1 and comparative examples 7-1, 7-2 and 7-3. In particular, the following tendency is observed: when the Rate (3R) of the graphene precursor is 31% or more, the flexural modulus tends to be remarkably increased by 20% or more as compared with 0% (comparative example 7-2) or 23% (example 7-1).

The reason why the tensile strength and the bending modulus are improved is considered to be the same as that described in example 6.

It is observed from examples 6 and 7 that the tensile strength and flexural modulus are improved regardless of the resin as the base material when GF is added. The case where the graphene precursor is added together with GF will be described. It was observed that, in the case where the Rate (3R) was 23% as the graphene precursor (examples 6-1 and 7-1), the tensile strength and flexural modulus were slightly improved compared with the case where the graphene precursor was not added (comparative examples 6-2 and 7-2) regardless of the resin as the base material, but when the graphene precursor having the Rate (3R) of 31% or more was used as the graphene precursor, the tensile strength and flexural modulus were sharply improved (improved by 10% or more).

Example 8

Experiments were performed in which the graphene precursor and the reinforcing raw material produced by the above-described method were added to a resin.

In example 8, Glass Fibers (GF), Carbon Fibers (CF), talc, and silica were used as reinforcing materials, and the influence of the shape of the reinforcing materials was confirmed. The experimental conditions and the like other than those of the reinforcing material were the same as those of example 6.

As shown in fig. 27, GF and CF are bands and/or lines having a diameter of several tens μm and a length of several hundreds μm as a reinforcing material. Talc is typically a flake having a length of several to several tens of μm and a thickness of several hundreds of nm, and silica is a particle having a diameter of several tens of nm to several μm.

TABLE 7

As shown in table 7 and fig. 26, the example with the reinforcing material added has both improved tensile strength and flexural modulus compared to comparative example 6-1 without the reinforcing material added. When the examples (examples 6-2, 8-1, 8-2, and 8-3) to which the reinforcing material and the graphene precursor were added were compared with the examples (comparative examples 6-2, 8-1, 8-2, and 8-3) to which only the reinforcing material was added, the tensile strength and the flexural modulus were 1.4 times and 1.4 times, respectively, when the reinforcing material added together with the graphene precursor was GF (the rate of increase/decrease of example 6-2 with respect to comparative example 6-2). Similarly, CF is 1.3 times and 1.3 times, talc is 1.3 times and 1.1 times, and silica is 1.0 times and 2.0 times. From this fact, it is found that when the graphene precursor is used in combination with a reinforcing material in a ribbon, wire or sheet form, the tensile strength and flexural modulus are preferably improved by 10% or more. It is presumed that the tape-like, linear, or sheet-like nanoreinforcement material has a large surface area per unit mass due to its shape, and therefore has a high effect of improving tensile strength, can increase flexural modulus, and has good affinity with graphene-like graphite. Further, it has been found that the aspect ratio of the reinforcing material is particularly preferably 5 or more as a strip-like, linear or sheet-like shape. On the other hand, a reinforcing material having an aspect ratio of 5 or less, such as silica, has a result of increasing only the flexural modulus. The aspect ratio of the flake-like raw material may be determined by the ratio of the average thickness to the longest portion. The aspect ratio referred to herein is obtained from the average value of the diameter or thickness and the average value of the length described in the catalog of reinforcing materials and the like. In particular, when there is no product list, an arbitrary number of the samples are observed by an electron microscope such as SEM and the like, and the average value of the length and thickness is obtained.

Example 9

Next, an experiment was performed to obtain a resin molded article using the graphene precursor produced by the above method.

The experiment was performed under the conditions shown in table 8, in which the mixing ratio of the graphene precursor with the Rate (3R) of 31% to the reinforcing raw material was set. The experimental conditions and the like were the same as in example 6.

TABLE 8

As shown in table 8 and fig. 28, when the mixing ratio of the graphene precursor to the reinforcing material is greater than 1 (example 9-4), the tensile strength and the flexural modulus are substantially the same, and the characteristics are observed to be saturated. When the mixing ratio of the graphene precursors is 10 or more, the influence on the properties of the base material becomes large. On the other hand, when the mixing ratio was 1/100 (example 9-8), the tensile strength was increased by 4% or more and the flexural modulus was increased by 10% or more, as compared with comparative example 6-2 in which no graphene precursor was added. Further, it was observed that the tensile strength sharply increased at the blending ratio 1/10 (example 6-2) and the flexural modulus sharply increased at the blending ratio 1/3 (example 9-1) or more.

Accordingly, the lower limit of the mixing ratio is 1/100 or more, preferably 1/10 or more, and the upper limit is 10 or less, preferably 1 or less.

In FIG. 28, comparative example 6-1 containing no GF is not shown.

Here, in examples 6 to 9, since the graphene precursor is manufactured by using the electromagnetic force-based process and/or the physical force-based process as described above, the oxidation and reduction processes are not required. Further, since reduction treatment is not required in the production of the test piece, it is not necessary to set the temperature to a high temperature, and the production of the test piece is easy.

While the embodiments of the present invention have been described above with reference to the drawings, the specific embodiments are not limited to these embodiments, and modifications and additions within the scope not exceeding the gist of the present invention are also included in the present invention.

For example, the following materials can be mentioned as the base materials of the dispersion reinforcing material and the graphite-based carbon material. However, the proportion of the matrix material may be smaller than the reinforcing material and the graphite-based carbon material. In addition, the water may disappear by combustion, oxidation, vaporization, evaporation, or the like during use. For example, when the base material such as a coating agent is a volatile solvent, the base material is burned or carbonized like a C/C mixture.

Examples of the resin include thermoplastic resins such as Polyethylene (PE), polypropylene (PP), Polystyrene (PS), polyvinyl chloride (PVC), ABS resin (ABS), polylactic acid (PLA), acrylic resin (PMMA), polyamide/nylon (PA), Polyacetal (POM), Polycarbonate (PC), polyethylene terephthalate (PET), cyclic polyolefin (COP), Polyphenylene Sulfide (PPs), Polytetrafluoroethylene (PTFE), Polysulfone (PSF), Polyamideimide (PAI), thermoplastic Polyimide (PI), polyether ether ketone (PEEK), and Liquid Crystal Polymer (LCP). Among the synthetic resins, examples of the thermosetting resin or the ultraviolet curable resin include epoxy resin (EP), phenol resin (PF), melamine resin (MF), Polyurethane (PUR), unsaturated polyester resin (UP), examples of the conductive polymer include fibers such as PEDOT, polythiophene, polyacetylene, polyaniline, polypyrrole, fibrous nylon, polyester, acrylic resin, vinylon, polyolefin, polyurethane, rayon, and examples of the elastomer include Isoprene Rubber (IR), Butadiene Rubber (BR), Styrene Butadiene Rubber (SBR), Chloroprene Rubber (CR), nitrile rubber (NBR), polyisobutylene rubber/butyl rubber (IIR), ethylene propylene rubber (EPM/EPDM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM), epoxy rubber (CO/ECO), and the like, examples of the thermosetting resin-based elastomer include a part of urethane rubber (U), silicone rubber (Q), Fluororubber (FKM), and examples of the thermoplastic elastomer include styrene-based, olefin-based, polyvinyl chloride-based, polyurethane-based, and amide-based elastomers.

Examples of the inorganic material include concrete, ceramics, gypsum, and metal powder.

As the reinforcing material, the following can be mentioned.

Examples of the metal material include silver nanoparticles, copper nanoparticles, silver nanowires, copper nanowires, scale-like silver, scale-like copper, iron powder, zinc oxide, fibrous metals (boron, tungsten, aluminum oxide, and silicon carbide), and the like.

Examples of the carbon material include carbon black, carbon fiber, CNT, graphite, and activated carbon.

Examples of the non-metallic material other than carbon include glass fiber, nanocellulose, nanoclay (clay mineral such as montmorillonite), aramid fiber, and polyethylene fiber.

Further, as natural graphite used for producing a graphite-based carbon material used as a graphene precursor, a natural graphite material having particles of 5mm or less (flake graphite ACB-50 produced by the graphite industry of japan) is exemplified, but from the viewpoint of easy availability, natural graphite which is flake graphite and is pulverized to 5mm or less, and has a Rate (3R) of less than 25% and a strength ratio P1/P2 of less than 0.01 is preferable. With recent technological development, artificial natural graphite-like graphite (graphite in which crystals are layered) can be synthesized, and thus the raw material of graphene and graphene-like graphite is not limited to natural graphite (mineral). For applications where control of the metal content is desired, it is preferred to use high purity synthetic graphite. When the Rate (3R) is 31% or more, the artificial graphite may be obtained by a method other than the physical force-based treatment or the electromagnetic force-based treatment.

The graphene-based carbon material used as the graphene precursor is generally referred to as graphene, a graphene precursor, Graphene Nanosheets (GNPs), few-layer graphene (FLG), nanographene, and the like, but is not particularly limited.

Industrial applicability

The present invention is directed to a composite reinforced material having strength, and the application field thereof is not limited. The present invention is applicable to, for example, the following fields.

(1) Examples in which the base material is an organic material (resin, plastic)

(1-1) vehicle

Structural members such as housings and parts of aircrafts, automobiles (passenger cars, trucks, buses, etc.), ships, amusement park facilities, and the like. (the structural member is a composite resin, a modified resin, a fiber-reinforced resin, or the like)

(1-2) general-purpose article

And structural members such as housings and parts of furniture, home appliances, household goods, toys, and the like.

(1-3)3D Printer

Various molding materials such as resin filaments and UV curable resins are used in hot melt lamination molding (FDM), Stereolithography (SLA), powder fixing, powder sintering molding (SLS), and multi-jet molding (MLM, inkjet molding).

(1-4) coating agent

The resin is dispersed in an organic solvent and applied by spraying, coating or the like to coat the surface. Besides improving the strength, the paint also has the effects of water repellency, rust prevention, ultraviolet resistance and the like. The resin composition is used for surface/interior coating of buildings (such as bridge piers, buildings, walls, and roads), automobiles, aircrafts, and the like, and resin molded articles such as helmets, protectors, and the like.

(2) Examples in which the parent material is an inorganic material

Fiber-reinforced structural members such as cement (concrete, mortar), gypsum board, ceramics, and C/C mixtures (carbon fiber-reinforced carbon composites). Graphene-like graphite and a reinforcing material are dispersed using these inorganic materials as a base material.

(3) The base material being a metallic material

Structural members of aluminum, stainless steel, titanium, brass, bronze, mild steel, nickel alloys, tungsten carbide, and the like. (the structural member is a fiber-reinforced metal or the like). The graphene-like graphite and the reinforcing material are dispersed using these metal materials as a base material.

Claims

1. A method for producing a composite reinforcing material, comprising a step of kneading at least a graphite-based carbon material and a reinforcing material in a matrix,

the graphite-based carbon material has a rhombohedral graphite layer (3R) and a hexagonal graphite layer (2H), wherein the ratio Rate (3R) of the rhombohedral graphite layer (3R) to the hexagonal graphite layer (2H) defined by the following formula (1) obtained by an X-ray diffraction method is 31% or more,

rate (3R) ═ P3/(P3+ P4). times.100. cndot. (formula 1)

In the formula 1, the reaction mixture is,

the composite reinforced raw material is at least dispersed with graphene,

the graphene is a crystal having an average size of 100nm or more, and has 10 or less layers.

2. The method of manufacturing a composite reinforcement raw material according to claim 1, wherein the reinforcement raw material is a band-shaped, linear, or flake-shaped fine particle.

3. The method for producing a composite reinforcing material according to claim 2, wherein the aspect ratio of the fine particles is 5 or more.

4. The method for producing a composite reinforcing material according to claim 1 or 2, wherein the weight ratio of the graphite-based carbon material to the reinforcing material is 1/100 or more and less than 10.

5. The method of manufacturing a composite reinforcement raw material according to claim 1, wherein the base material is a polymer.

6. The method of manufacturing a composite reinforced raw material as recited in claim 5, wherein a compatibilizer is used in the step.

7. The method of manufacturing a composite reinforcement raw material according to claim 1, wherein the base material is an inorganic material.

8. A composite reinforcing material obtained by kneading at least a graphite-based carbon material and a reinforcing material in a matrix and peeling off a part or all of the graphite-based carbon material,

rate (3R) ═ P3/(P3+ P4). times.100. cndot. (formula 1)

In the formula 1, the reaction mixture is,

the composite reinforced raw material is at least dispersed with graphene,