JP7053015B2 - Method for manufacturing carbon nanotube composite resin molded product - Google Patents

Description

The present invention relates to a method for producing a carbon nanotube composite resin molded body, and more particularly to a method for producing a carbon nanotube composite resin molded body in which carbon nanotubes are blended in a resin body at a predetermined concentration and in a uniform state.

Carbon nanotubes are materials having a high aspect ratio of several nanometers to several hundreds of nanometers in diameter, in which a sheet composed of carbon atoms is formed into a single-layer or multi-layered coaxial tubular.
In addition, carbon nanotubes have high electrical conductivity, thermal conductivity, elastic modulus, etc., and by mixing them with a matrix of resin or metal to form a molded body (carbon nanotube composite resin molded body), the strength and conductivity of the matrix Is known to improve.

As a method for producing a resin molded product containing the carbon nanotubes, that is, a carbon nanotube composite resin molded product, the resin powder 3 and the carbon nanotubes 1 are mixed to form composite particles 7 as shown in FIG. 12 (a). A method is known in which, after molding into a predetermined shape, heat molding is performed as shown in FIG. 12 (b).

However, in the above method, the carbon nanotubes 1 are present on the interface between the adjacent resin powders 3, and as shown in FIGS. 13 and 14, the dispersed state of the carbon nanotubes 1 in the molded product is not uniform. 13 is a schematic view showing the cross section, and FIG. 114 is a photograph of the cross section taken by a transmission electron microscope (TEM).
Further, when the concentration of the carbon nanotubes is increased, the carbon nanotubes 1 are more aggregated between the resin powders 3 and uniform strength cannot be obtained, which causes a problem that the strength of the molded body is further lowered.

Further, as another method for producing the carbon nanotube composite resin molded product, for example, as shown in Patent Document 1 (Japanese Unexamined Patent Publication No. 2008-900133), the liquefied precursor and the carbon nanotube are mixed and applied. A method of reacting (drying) has been proposed.

However, in the above method, even if the carbon nanotubes can be dispersed in the precursor solution, it is difficult to prevent the carbon nanotubes from reaggregating in the drying step.
Further, although the resin film and the resin layer can be formed by the coating process, there is a problem that it is difficult to produce a molded body having a thick three-dimensional shape (3D shape).

Further, as a solution to the problem of reducing the strength of the molded product, Patent Document 2 (Japanese Patent Laid-Open No. 2015-508437) describes the first composition containing a conductive nanofiller such as a carbon nanotube and a thermoplastic polymer. Is mixed with an uncured thermosetting resin precursor and a curing agent, and it has been proposed to form a composite by reaction molding.
According to this method, since the resin containing the precursor and the nanofiller are mixed and reaction-molded, the properties such as the strength of the resin matrix can be improved.

Japanese Unexamined Patent Publication No. 2008-900133 Japanese Patent Publication No. 2015-508437

By the way, in the invention disclosed in Patent Document 2, as described above, since the resin containing the precursor and the nanofiller are mixed and reaction-molded, the characteristics of the resin matrix can be improved. ..
However, during reaction molding, as shown in FIGS. 13 and 14, carbon nanotubes aggregate between the particles of the resin precursor, and there is a problem that it is difficult to uniformly disperse the carbon nanotubes in the molded product.

The present inventors have diligently studied the blending of carbon nanotubes in a carbon nanotube composite resin molded body in a higher concentration and uniformly dispersed state, and have developed a method for producing a carbon nanotube composite resin molded body having high strength. I came up with the idea and completed the present invention.

An object of the present invention is to provide a method for producing a carbon nanotube composite resin molded body in which carbon nanotubes are blended in a resin body having a higher concentration and a uniform dispersion state.

In order to solve the above-mentioned problems, the method for manufacturing a carbon nanotube composite resin molded body according to the present invention is a method for manufacturing a carbon nanotube composite resin molded body in which a plurality of carbon nanotubes are blended in the resin body. A step of mixing carbon nanotubes with a resin precursor to generate resin-coated carbon nanotube particles by a reprecipitation method, and molding and heating the produced resin-coated carbon nanotube particles, the resin coating the carbon nanotubes is chemically obtained. It is characterized by comprising a step of obtaining a molded body in which carbon nanotubes are dispersed in the resin body by forming a resin body by a reaction.
According to such a configuration, it is possible to obtain a carbon nanotube composite resin molded body in which carbon nanotubes are blended in a resin body at a predetermined concentration and in a uniformly dispersed state.
That is, by using this production method, the carbon nanotube composite resin molded product of the present invention can be obtained.

Here, after the step of producing the resin-coated carbon nanotube particles, a step of adding an abrasive grain and an additional substance composed of ceramics or a fine powdered metallic substance of metal to the resin-coated carbon nanotube particles is performed, and then a step is performed. A method for manufacturing a carbon nanotube composite resin molded product, wherein the molded product is obtained. The ratio is preferably 10 to 70 vol%.

Further, in the step of mixing carbon nanotubes with the resin precursor and producing resin-coated carbon nanotube particles by the reprecipitation method, the concentration of carbon nanotubes in the molded body is controlled by the thickness of the resin layer covering the carbon nanotubes. It is desirable to do.
Further, it is desirable that the resin body is a polyimide resin or a phenol resin.
When the resin body is a polyimide resin, it is preferable in that it has excellent heat resistance. Further, in the case of a phenol resin, it is preferable because it is excellent in normal temperature strength.
In addition, the resin of the resin-coated carbon nanotube is polyamic acid as a precursor, the imidization rate of the polyamic acid is 80% or less, and the carboxyl group and the imino group in the resin react by heating, resulting in imidization. It is desirable to proceed and mold the polyimide resin.
Further, the resin layer is a resin containing a novolak-type phenol resin and a curing agent that produces formaldehyde, and is a metinol group generated by the novolak-type phenol resin and the formaldehyde, and the reactive group undergoes a dehydration reaction by heating. It is desirable to cross-link and cure with.
Further, it is desirable that the resin layer is a resol type phenol resin, the reactive group is a methinol group, and the reactive group is crosslinked and cured by a dehydration reaction by heating.

Here, the molded product obtained by the step of obtaining the molded product has a carbon nanotube concentration of 74.0 vol% or less and 1 μm in an arbitrary cross section. ² It is desirable that the coefficient of variation of the area of carbon nanotubes in the above is 0.1 or less.
Such a carbon nanotube composite resin molded body has high strength, and also has high elastic modulus, high heat resistance, and high heat dissipation due to the high concentration of carbon nanotubes.

In the range where the concentration of the carbon nanotubes is 74.0 vol% or less, the elastic modulus and the heat dissipation property are improved by increasing the concentration of the carbon nanotubes.
If the concentration of the carbon nanotubes is 74.0 vol% or more, theoretically, voids are generated and the packing density cannot be obtained, which is not preferable. On the other hand, the lower limit of the concentration of the carbon nanotubes is not particularly limited, but is preferably 0.72 vol% or more.
Further, the strength is improved by increasing the concentration of carbon nanotubes when the concentration is less than 15.1 vol%, but decreases when the concentration of the carbon nanotubes exceeds 15.1 vol%. However, since it still has sufficient strength, it can be said that the molded product has excellent properties in terms of high elastic modulus, high heat resistance, and high heat dissipation in the concentration range of the carbon nanotubes.
Further, the molded product obtained by the step of obtaining the molded product has an arbitrary cross section of 1 μm. ² It is characterized in that the coefficient of variation obtained by dividing the standard deviation of the area of the carbon nanotubes in the above by the average value is 0.1 or less.
1 μm in arbitrary cross section ² When the coefficient of variation of the area of the carbon nanotubes in the above is more than 0.1, the strength is low and it is not preferable because the carbon nanotubes are localized or the carbon nanotubes are not uniformly dispersed.

Further, the concentration of carbon nanotubes is 0.72 vol% or more and 74.0 vol% or less, and 1 μm in an arbitrary cross section. ² When the fluctuation coefficient of the area of the carbon nanotubes in the above is 0.1 or less, the carbon nanotube composite resin molded body having a maximum bending stress of at least 120 MPa can be obtained, and carbon having a flexural modulus of at least 4000 MPa can be obtained. It can be a nanotube composite resin molded body. Also, the thermal diffusivity is at least 3x10. ^-3 cm ² It can be a carbon nanotube composite resin molded product of / s or more.

According to the present invention, it is possible to obtain a method for producing a carbon nanotube composite resin molded body in which carbon nanotubes are blended in a resin body at a higher concentration and in a uniformly dispersed state.

FIG. 1 is a diagram schematically showing a cross section of the carbon nanotube composite resin molded product obtained by the present invention. FIG. 2 is a transmission electron microscope (TEM) photograph of the cross section of the carbon nanotube composite resin molded body obtained by the present invention. FIG. 3 is a schematic view showing resin-coated carbon nanotube particles used in the present invention. FIG. 4 is a transmission electron microscope (SEM) photograph of resin-coated carbon nanotube particles. 5 (a) is a cross-sectional view taken along the axial direction of one of the plurality of resin-coated carbon nanotubes forming the resin-coated carbon nanotube particles of FIG. 3, and FIG. 5 (b) is a radial direction. It is a cross-sectional view of. 6 (a) and 6 (b) are diagrams for explaining a method for manufacturing a carbon nanotube composite resin molded product according to the present invention. FIG. 7 is a graph showing the results of the maximum bending stress of Examples and Comparative Examples of the present invention. FIG. 8 is a graph showing the results of the maximum bending stress and flexural modulus of the examples having different carbon nanotube concentrations of the present invention. FIG. 9 is a graph showing the results of the maximum bending stress in the case of a carbon nanotube composite polyimide resin (7.34 vol%) reaction-molded from resin-coated carbon nanotubes in which the imidization ratio of the resin portion is changed. FIG. 10 is a graph showing the results of high temperature wear resistance to alumina spheres at a sample temperature of 300 ° C. in Examples and Comparative Examples of the present invention. FIG. 11 is a graph showing the results of the thermal diffusivity with respect to the carbon nanotube concentration of the embodiment of the present invention. 12 (a) and 12 (b) are diagrams for explaining a method for manufacturing a conventional carbon nanotube composite resin molded product. FIG. 13 is a diagram schematically showing a cross section of a conventional carbon nanotube composite resin molded product. FIG. 14 is a transmission electron microscope (TEM) photograph of a conventional carbon nanotube composite resin molded body in which a cross section is observed.

Hereinafter, embodiments of a method for manufacturing a carbon nanotube composite resin molded product according to the present invention will be described with reference to the drawings.

(Carbon nanotube composite resin molded body)
As shown in FIGS. 1 and 2, the carbon nanotube composite resin molded body 100 contains a large number of carbon nanotubes 1 in a resin body 3 such as polyimide.

In the present invention, in the carbon nanotube composite resin molded body 100, the concentration of carbon nanotubes is 74.0 vol% or less, and the coefficient of variation of the area of carbon nanotubes at 1 μm ² in an arbitrary cross section is 0.1 or less. It has characteristics.
That is, in the carbon nanotube composite resin molded body 100, the concentration of the carbon nanotube 1 in the resin body 3 is 74.0 vol% or less.

As the concentration of the carbon nanotube 1 in the carbon nanotube composite resin molded body 100 increases, it has excellent properties such as electrical conductivity, thermal conductivity, and elastic modulus.
However, if the concentration of the carbon nanotube 1 in the resin body 3 is too high, it is theoretically difficult to fill the carbon nanotubes 1 and voids are formed, which is not preferable.
Therefore, in the carbon nanotube composite resin molded body 100 according to the present invention, the concentration of carbon nanotubes is 74.0 vol% or less.
On the other hand, the lower limit of the concentration of the carbon nanotubes is not particularly limited, but in the experiments of the present inventors, a predetermined effect can be obtained even when the concentration of the carbon nanotubes is 0.72 vol%. , Preferably, the concentration of carbon nanotubes is 0.72 vol% or more.

The carbon nanotubes used in the carbon nanotube composite resin molded body 100 have a length of several μm to several tens of μm and a diameter of several nm to several hundred nm. Then, in the carbon nanotube composite resin molded body 100, carbon nanotube particles in which the carbon nanotubes are coated with a resin are used.

Further, even when the concentration of the carbon nanotubes is 0.72 vol% or more and 74.0 vol% or less, if the carbon nanotubes are unevenly distributed, the predetermined strength and heat resistance cannot be obtained.
Therefore, as one index of the dispersion of carbon nanotubes, it is specified by the coefficient of variation of the area of carbon nanotubes at 1 μm ² in an arbitrary cross section.
That is, in the carbon nanotube composite resin molded body 100, when the coefficient of variation of the area of the carbon nanotubes at 1 μm ² in an arbitrary cross section is 0.1 or less, the carbon nanotubes are uniformly dispersed, and the carbon nanotubes have a predetermined strength and heat resistance. You can get sex.

Here, the coefficient of variation of the area of the carbon nanotube is defined by setting, for example, an observation region of 100 μm × 100 μm on an arbitrary cross section, and dividing the region into a region of 1 μm ² (1 μm × 1 μm). The area of the carbon nanotube in the region was obtained, and the standard deviation of the area was divided by the average value to obtain the coefficient of variation.
The smaller the coefficient of variation is, the smaller the variation in the area of carbon nanotubes per unit area is, which means that the carbon nanotubes are uniformly blended.
Therefore, the coefficient of variation of the area of the carbon nanotubes is preferably smaller, and when the coefficient of variation exceeds 0.1, the carbon nanotubes are not uniformly dispersed, so that the strength and heat resistance are low, which is preferable. not.

Further, the carbon nanotube composite resin molded body 100 in which the concentration of carbon nanotubes is 0.72 vol% or more and 74.0 vol% or less, and the variation coefficient of the area of carbon nanotubes at 1 μm ² in an arbitrary cross section is 0.1 or less. The maximum bending strength is at least 120 MPa, and the flexural modulus is at least 4000 MPa.
As described above, the maximum bending strength is at least 120 MPa, the flexural modulus is at least 4000 MPa, and the high-concentration carbon nanotubes have heat dissipation and high heat resistance, so that the machine such as an aircraft or an automobile has high heat resistance. It can be used as a resin molded body for element parts.

Further, to the carbon nanotube composite resin molded body 100 according to the present invention, if necessary, diamond or cBN abrasive grains as an additional substance, or ceramic powder or metal powder (for example, silicon carbide, copper, nickel, etc.) is added. May be good.
For example, by adding abrasive grains or metal powder, the carbon nanotube composite resin molded body 100 can be used as a grindstone for grinding or polishing.

(Resin-coated carbon nanotube particles)
Next, the structure of the resin-coated carbon nanotube particles necessary for manufacturing the carbon nanotube composite resin molded body 100 will be described.
As shown in FIGS. 3 and 4, the resin-coated carbon nanotube particles 6 are formed by connecting a plurality of resin-coated carbon nanotubes 5 with the resin layers 2 on the surface thereof. As shown in the figure, voids 4 are formed between the plurality of connected resin-coated carbon nanotubes 5.

As shown in FIGS. 5A and 5B, each of the resin-coated carbon nanotubes 5 constituting the resin-coated carbon nanotube particles 6 has a carbon nanotube 1 as a base material (for example, a diameter of 10 nm and a length of 1.5 μm). Is coated with the resin layer 2 having a reactive group.
The resin layer 2 is, for example, a resin (precursor) containing a polyamic acid, and the imidization ratio is preferably 80% or less.

Further, it is desirable that the diameter B of the resin-coated carbon nanotube 5 including the resin layer 2 has a size of 1.1 to 30 times the diameter A of the carbon nanotube 1, but this ratio is the carbon in the molded body. Affects the concentration of nanotubes.
In other words, the concentration of the carbon nanotube 1 in the molded body can be adjusted by the thickness of the resin layer 2 with respect to the carbon nanotube 1 substrate.
That is, when the concentration of the carbon nanotubes is increased, the thickness of the resin layer 2 covering the carbon nanotubes 1 is formed thinner, and when the concentration is decreased, the thickness of the resin layer 2 covering the carbon nanotubes 1 is formed. It may be formed so that the thickness is thicker.
If the concentration of the carbon nanotubes is increased, the strength, elastic modulus, heat dissipation and heat resistance of the molded product can be further increased.

(Manufacturing method of resin-coated carbon nanotube particles)
Next, a method for producing the resin-coated carbon nanotube particles 6 will be described.
The resin-coated carbon nanotube particles 6 can be produced by a method in which a large number of carbon nanotubes 1 are mixed with a polyamic acid solution which is a precursor of polyimide and reprecipitated.
Specifically, carbon nanotubes (Nanocyl NC7000) and varnish polyamic acid (U-Varnish A manufactured by Ube Kosan) are mixed in an arbitrary ratio. The mixed solution is dropped into a poor solvent, reprecipitated, and then suction-filtered to obtain a polyamic acid-coated CNT of an arbitrary coating amount, that is, resin-coated carbon nanotube particles 6.

(Manufacturing method of carbon nanotube composite resin molded product)
Subsequently, a method for manufacturing the carbon nanotube composite resin molded body 100 will be described using the resin-coated carbon nanotube particles 6.
First, as shown in FIG. 6A, the resin-coated carbon nanotube particles 6 are prepared in a required amount, and if there is an additional substance in the required amount, the additional substance is mixed to form a mixture.
At this time, as the additional substance, for example, abrasive grains such as diamond or cBN, or ceramic powder or metal powder (for example, silicon carbide, copper, nickel) may be added. The mixing ratio of the abrasive grains with the additional substance in the resin body 3 is preferably about 12.5 to 37.5 vol% of the whole, and the ratio of the fine powder of ceramics or metal to the portion excluding the abrasive grains is preferably 10 to 70 vol%.

If there is an additional substance, specifically, it is mixed using a rocking mill, a planetary ball mill, a rotation / revolution mixer, a mortar and the like. When the mixture is used as a liquid phase, an organic solvent is used as a medium, and the mixture is mixed using a rotary or ultrasonic stirring device to dry and remove the organic solvent.
When there is no additional substance (only for the resin-coated carbon nanotube particles 6), the carbon nanotube particles 6 are molded into a predetermined shape by a vacuum hot press device without mixing.

Next, the mixture in a liquid phase or solid phase state is packed in a mold, and reaction molding is performed under a reduced pressure of several Pa or less using a vacuum hot press device. In the case of polyamic acid coating, the reaction temperature is kept warm until the fluctuation of the degree of vacuum subsides, and then the temperature is raised to 380 ° C. and heated for several hours. In the absence of additional substances, a press pressure of about 20 to 50 MPa is sufficient. If there is an additional substance, a press pressure of about 200 MPa may be required if the amount added is large.
The resin layer 2 of the heated resin-coated carbon nanotube particles 6 is made into polyimide by a chemical reaction, and the resin layers 2 are connected to each other between the adjacent resin-coated carbon nanotube particles 6.

Here, as shown in FIG. 3, since the resin-coated carbon nanotube particles 6 contain a plurality of carbon nanotubes 1, the resin layer 2 of the particles 6 is made into polyimide by a chemical reaction. That is, the carboxyl group and the imino group in the resin react with each other by heating, and imidization proceeds to form the polyimide resin. At this time, since the carbon nanotubes are coated with the resin as described above, aggregation is suppressed. The resin layer 2 of the resin-coated carbon nanotube particles 6 is made into polyimide by a chemical reaction while maintaining a uniform dispersion state.
As a result, as shown in FIG. 6B, it is possible to obtain a molded product 100 in which the carbon nanotubes 1 are uniformly dispersed at a high concentration.
Although the resin-coated carbon nanotube particles 6 are shown in a spherical shape in FIG. 6, the resin-coated carbon nanotube particles 6 are actually formed in an entangled shape as shown in FIG.

As described above, according to the embodiment of the present invention, a required amount of resin-coated carbon nanotube particles 6 coated with carbon nanotubes 1 with a polyimide precursor is mixed, molded, and then chemically reacted by heating to carbon. The nanotube composite resin molded body 100 can be obtained.

By obtaining such a manufacturing process, the concentration of the carbon nanotube 1 is 0.72 vol% or more and 74.0 vol% or less, and the variation coefficient of the area of the carbon nanotube at 1 μm ² in an arbitrary cross section is 0.1 or less. A certain carbon nanotube composite resin molded body 100 can be obtained.

In the above embodiment, the polyimide precursor has been described as an example of the resin for coating the carbon nanotube 1, but the present invention is not limited to this example.
For example, a phenol resin may be used as the resin. For example, the resin layer is a resin containing a novolak-type phenol resin and a curing agent that produces formaldehyde (for example, hexamethylenetetramine), and is a metinol group produced by the novolak-type phenol resin and the formaldehyde. The phenolic group may be cross-linked and cured by a dehydration reaction by heating.
Alternatively, the resin layer may be a resol-type phenol resin, the reactive group may be a methinol group, and the reactive group may be cross-linked and cured by a dehydration reaction by heating.

The method for producing the carbon nanotube composite resin molded product according to the present invention will be further described based on Examples. In this example, the performance was verified by producing the carbon nanotube composite resin molded product shown in the embodiment.

(Experiment 1)
In Experiment 1, the effect of the concentration (vol%) of carbon nanotubes in the resin body on the bending strength (MPa) of the molded body was verified. The bending strength was measured by a three-point bending test.
As the carbon nanotubes, those having an average length of 1.5 μm and a diameter of about 10 nm were used, and resin-coated carbon nanotubes produced by a method of mixing a large number of carbon nanotubes with a polyamic acid solution which is a precursor of polyimide and reprecipitating them. Particles were used.

Then, using a vacuum hot press device (not shown), the mixture was heated at 380 ° C. for several hours under a reduced pressure of several Pa to obtain a carbon nanotube composite resin molded product.

Here, in Example 1, the concentration of carbon nanotubes was 2.16 vol%, in Example 2, the concentration of carbon nanotubes was 7.34 vol%, and in Example 3, the concentration of carbon nanotubes was 15.1 vol%.
The concentration of the carbon nanotubes was changed by changing the thickness of the resin coating of the resin-coated carbon nanotube particles. The imidization rate of the polyamic acid, which is the coating resin at this time, was 23.5%.

Further, as a comparative example, a resin powder and carbon nanotubes were mixed in a solid phase, and after molding, a carbon nanotube composite resin molded body was obtained by heat molding.
Specifically, MP5 manufactured by Nippon Coke was used as a mixer, polyimide powder having an imidization ratio of almost 100% (UIP-R manufactured by Ube Corporation) was mixed with carbon nanotubes, and carbon nanotubes were adhered to the surface of the polyimide powder. Composite particles were formed. Then, the composite particles were filled in a mold and molded by vacuum hot pressing at a temperature of about 400 ° C. and a pressing pressure of about 200 MPa.
The concentration of the carbon nanotubes of Comparative Example 1 was 7.34 vol%, and the concentration of the carbon nanotubes of Comparative Example 2 was 2.16 vol%.
The concentration of carbon nanotubes was changed depending on the amount of carbon nanotubes charged into the mixer.

Then, a cross section is formed on the carbon nanotube composite resin molded bodies of Examples 1 to 3 and Comparative Examples 1 and 2, and an observation region of 100 μm × 100 μm is set, and the region is set to a region of 1 μm ² (1 μm × 1 μm). After classification, the area of carbon nanotubes in each of the divided regions was obtained, and the coefficient of variation of the area was obtained.
As a result, the coefficient of variation of Example 1, Example 2, and Example 3 was 0.1 or less, and the coefficient of variation of Comparative Example 1 and Comparative Example 2 was about 1.1.
As a result, it was confirmed that the carbon nanotubes were uniformly dispersed in Examples 1 to 3 as compared with Comparative Examples 1 and 2.

Next, bending strength tests were performed on the carbon nanotube composite resin molded bodies of Examples 1 to 3 and Comparative Examples 1 and 2. The shape of the test piece was 10 mm in length, 40 mm in width, and 1.8 mm in thickness.
The results are shown in the bar graph of FIG. In the graph of FIG. 7, the vertical axis is the maximum bending stress (MPa).
As shown in this graph, for example, when the concentration of carbon nanotubes is 2.16 vol%, the strength of the result of Example 1 is improved by about 302% with respect to the result of Comparative Example 2. Further, when the concentration of the carbon nanotubes was 7.34 vol%, the strength of the result of Example 2 was improved by about 572% with respect to the result of Comparative Example 1.
From this result, it was confirmed that in the comparative example, the strength decreased as the carbon nanotube concentration increased, whereas in the example, the strength increased as the carbon nanotube concentration increased.
Further, the result of Example 3 in which the concentration of carbon nanotubes was 15.1 vol% obtained a higher bending stress than the result of Examples 1 and 2.

(Experiment 2)
In Experiment 2, the effects on the maximum bending stress (MPa) and flexural modulus (MPa) of the molded body were verified by variously changing the concentration (vol%) of carbon nanotubes in the resin body.
In each of Examples 4 to 10, resin-coated carbon nanotube particles are produced by a reprecipitation method in the same manner as in Examples 1 to 3, and a predetermined amount of resin-coated carbon nanotube particles are heated for reaction molding. A carbon nanotube composite resin molded body was obtained.
At this time, the concentration of the carbon nanotubes in Example 4 was 0.72 vol%, the concentration of the carbon nanotubes in Example 5 was 2.16 vol%, and the concentration of the carbon nanotubes in Example 6 was 3.62 vol%. The concentration of the carbon nanotubes in Example 7 was 7.34 vol%, the concentration of the carbon nanotubes in Example 8 was 15.1%, and the concentration of the carbon nanotubes in Example 9 was 41.6 vol%. The concentration of carbon nanotubes was 74.0 vol%.

Then, in Examples 4 to 10, the coefficient of variation of the area of the carbon nanotubes was obtained by the same method as in Examples 1 to 3.
As a result, the coefficient of variation of Examples 4 to 10 was 0.1 or less.
As a result, it was confirmed that the carbon nanotubes were uniformly dispersed in Examples 4 to 10 as compared with Comparative Examples 1 and 2.

Next, the maximum bending stress (MPa) and the flexural modulus (MPa) were tested on the carbon nanotube composite resin molded bodies of Examples 4 to 10. The shape of the test piece was 10 mm in length, 40 mm in width, and 1.8 mm in thickness.
The results of Experiment 2 “Effect of concentration of carbon nanotubes” are shown in the graph of FIG.

In the graph of FIG. 8, when the coefficient of variation of the area of the carbon nanotubes is in the range of 0.1 or less and the carbon nanotubes are well dispersed, the maximum bending elasticity is reached until the carbon nanotube concentration reaches 74.0%. There was a tendency for the rate to increase.
Further, the maximum bending stress increases up to 15.1 vol% of the carbon nanotube concentration and reaches 237 MPa. It was found that when the carbon nanotube concentrations were 41.6 vol% and 74.0 vol%, the maximum bending stress was lower than that at the concentration of 15.1 vol%, but the bending stress was 120 MPa or more.
That is, like the carbon nanotube composite resin molded body of the present invention, the fluctuation coefficient of the area of the carbon nanotube is within the range of 0.1 or less, and by having the carbon nanotube with a high concentration, the maximum bending stress and the bending elasticity It was confirmed that the rate improved.

(Experiment 3)
In Experiment 3, the effect of the imidization ratio of the resin portion of the resin-coated carbon nanotube particles on the maximum bending stress in the molded product was verified.
In the examples of this experiment, the concentration of carbon nanotubes was fixed at 7.34 vol%, and the imidization rate of the resin of the resin-coated carbon nanotubes was 23.5% in Example 11 and 49.1% in Example 12. In Example 13, it was 78.8%, and in Example 14, it was 100%. Then, in each example, a predetermined amount of resin-coated carbon nanotube particles were heated and reaction-molded to obtain a carbon nanotube composite resin molded body.

The imidization ratio in Examples 11 to 14 was controlled by the heat treatment temperature of the resin-coated carbon nanotubes. The imidization rate was defined as follows. That is, using a Fourier transform infrared spectrophotometer, the single reflection ATR method (Ge prism, range: 4000 to 650 cm ^-1 , resolution: 4 cm ^-1 , total number: 16 times, processing: ATR correction → BL correction (4000 cm) Absorbance was measured by ^-1 and 1800 cm ^-1 (corrected at 2 points))). Further, the absorbance ratio (1775 cm ^-1 / 1500 cm ^-1 ) when 1820 cm ^-1 was used as the base (Abs = 0) was calculated and used as the imidization ratio.
Further, the absorbance ratio of the sample treated at 500 ° C. for 1 hour was defined as an imidization rate of 100%, and 1775 cm ^-1 / 1500 cm ^-1 = 0 was defined as an imidization rate of 0%.

The results of this experiment 3 are shown in the graph of FIG. In the graph of FIG. 12, the vertical axis is the maximum bending stress (MPa) and the horizontal axis is the imidization ratio (%).
As shown in the graph of FIG. 9, the maximum bending stress was 200 MPa or more up to the imidization rate of 80%, but the maximum bending stress was significantly reduced at the imidization rate of 100%. This is thought to be due to the weak bond between the resins because the imidization rate is high and no reaction occurs during molding.

(Experiment 4)
In Experiment 4, the high-temperature friction resistance of the carbon nanotube composite resin molded product of the present invention was verified.
In Example 15, a predetermined amount of resin-coated carbon nanotube particles were heated and reaction-molded to obtain a carbon nanotube composite polyimide resin molded body having a carbon nanotube concentration of 1.04 vol%.
In Comparative Example 3, carbon nanotubes (NC7000 manufactured by Nanocil, diameter about 10 nm, average length 1.5 μm) and polyimide powder (UIP-R manufactured by Ube Corporation) were mixed using MP5 manufactured by Nippon Coke as a mixer, and the polyimide powder was mixed. Composite particles with carbon nanotubes attached to the surface were formed. Then, a molded product was obtained by heat molding under the same conditions as in Comparative Example 1.

In Example 15 and Comparative Example 3, high-temperature ball-on-disc tests using alumina spheres were carried out, respectively. The test conditions were an alumina sphere diameter of 6 mm, a test load of 900 gf, a rotation speed of 47.1 m / min, a total number of rotations of 15,000, no lubricating liquid, and a sample temperature of 300 ° C.
FIG. 10 is a bar graph showing the results of Experiment 4. In the graph of FIG. 10, the vertical axis is the wear volume (mm ³ ).
As shown in the graph of FIG. 10, in Comparative Example 3, the wear volume was 1.4 mm ³ , and in Example 15, the wear volume was 0.25 mm ³ . That is, as compared with Comparative Example 3, in Example 15, the wear volume was significantly reduced due to the effect of the composite of carbon nanotubes and the reaction molding (the wear volume of Example 15 was about 17% of that of Comparative Example 3). From this, the high temperature friction resistance of the carbon nanotube composite resin molded product of the present invention was shown.

(Experiment 5)
In Experiment 5, the effect of the carbon nanotube concentration in the carbon nanotube composite resin molded product of the present invention on the thermal diffusivity (cm ² / s) was verified.
Examples are the thermal diffusivity of the carbon nanotube composite resin molded article of Examples 5, 7, 9, and 10 (carbon nanotube concentrations 2.16 vol%, 7.34 vol%, 41.6 vol%, 74.0 vol%, respectively). The rate (cm ² / s) was determined.
As Comparative Example 4, only polyimide powder (UIR-P manufactured by Ube Corporation) was press-molded by a vacuum hot press device to obtain a molded body having a carbon nanotube concentration of 0 vol%, and its thermal diffusivity was determined.

FIG. 11 shows the results of Experiment 5. In the graph of FIG. 11, the horizontal axis is the carbon nanotube content (vol%), and the vertical axis is the thermal diffusivity (× 10 ^-3 cm ² / s).
As shown in this graph, it can be confirmed that the thermal diffusivity increases with the carbon nanotube concentration. At the carbon nanotube concentration of 74.0 vol% in Example 10, the thermal diffusivity reaches 4.54 × 10 ^-3 cm ² / s. Since Comparative Example 4 (carbon nanotube concentration 0 vol%) has a thermal diffusivity of 2.364 × 10 ^-3 cm ² / s, Example 10 has a heat dissipation property of about 1.92 times that of Comparative Example 4. Was confirmed to improve.

The carbon nanotube composite resin molded body according to the present invention can be widely used as a resin molded body for machine element parts such as aircraft and automobiles, and a resin molded body for jigs for processing such as grinding and polishing.

1 Carbon nanotube 2 Resin layer (precursor)
3 Resin body 4 Voids 5 Resin-coated carbon nanotubes 6 Resin-coated carbon nanotube particles 100 Carbon nanotube composite resin molded body

Claims (10)

It is a method for manufacturing a carbon nanotube composite resin molded body in which a plurality of carbon nanotubes are blended in a resin body.
The process of mixing carbon nanotubes with the resin precursor and producing resin-coated carbon nanotube particles by the reprecipitation method.
The produced resin-coated carbon nanotube particles are molded and heated to form a resin body by a chemical reaction of the resin covering the carbon nanotubes, whereby a molded body in which the carbon nanotubes are dispersed in the resin body is obtained. Process and
A method for producing a carbon nanotube composite resin molded product. After the step of producing the resin-coated carbon nanotube particles,
A step of adding an abrasive grain and an additional substance composed of ceramics or a fine metal substance of metal to the resin-coated carbon nanotube particles is performed.
After that, it is a method of manufacturing a carbon nanotube composite resin molded product in which the step of obtaining the molded product is performed.
The carbon nanotube composite according to claim 1, wherein the abrasive grains are 12.5 to 37.5 vol% of the whole, and the ratio of fine powder of ceramics or metal to the portion excluding the abrasive grains is 10 to 70 vol%. A method for manufacturing a resin molded product. In the process of mixing carbon nanotubes with the resin precursor and producing resin-coated carbon nanotube particles by the reprecipitation method.
The method for producing a carbon nanotube composite resin molded body according to claim 1 or 2, wherein the concentration of the carbon nanotubes in the molded body is controlled by the thickness of the resin layer covering the carbon nanotubes. The method for producing a carbon nanotube composite resin molded body according to any one of claims 1 to 3, wherein the resin body is a polyimide resin or a phenol resin. The resin of the resin-coated carbon nanotube is polyamic acid as a precursor, the imidization rate of the polyamic acid is 80% or less, the carboxyl group and the imino group in the resin react by heating, imidization proceeds, and polyimide The method for producing a carbon nanotube composite resin molded body according to any one of claims 1 to 4, wherein the resin is molded. The resin layer is a resin containing a novolak-type phenol resin and a curing agent that produces formaldehyde, is a metinol group generated by the novolak-type phenol resin and the formaldehyde, and the reactive group is crosslinked by a dehydration reaction by heating. The method for producing a carbon nanotube composite resin molded body according to any one of claims 1 to 4, which is characterized by being cured. The present invention according to any one of claims 1 to 4, wherein the resin layer is a resol type phenol resin, the reactive group is a methinol group, and the reactive group is crosslinked and cured by a dehydration reaction by heating. The method for producing a carbon nanotube composite resin molded body described. The molded product obtained by the step of obtaining the molded product has a carbon nanotube concentration of 74.0 vol% or less and 1 μm in an arbitrary cross section. ² The method for producing a carbon nanotube composite resin molded body according to any one of claims 1 to 4, wherein the coefficient of variation of the area of the carbon nanotubes in the above is 0.1 or less. The carbon according to claim 8, wherein the molded product obtained by the step of obtaining the molded product has a concentration of the carbon nanotubes of 0.72 vol% or more and a maximum bending stress of at least 120 MPa. A method for manufacturing a nanotube composite resin molded product. The carbon according to claim 8, wherein the molded product obtained by the step of obtaining the molded product has a concentration of the carbon nanotubes of 0.72 vol% or more and a flexural modulus of at least 4000 MPa. A method for manufacturing an nanotube composite resin molded product.

Images