JP2006193649A - Carbon fiber-containing resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin molded product which contains a small amount of an extrafine carbon fiber in a nearly best dispersion state to exhibit electrical insulation or conductivity as much as possible. <P>SOLUTION: The carbon fiber-containing molded product comprises 0.05-15 pts.wt. of the extrafine carbon fiber dispersed in 100 pts.wt. of a thermoplastic resin, wherein the extrafine carbon fiber has an average aspect ratio of 20-100 and an area rate [Ar] of 0.2-5.0% as calculated from a SEM photograph, provided that the SEM photograph has preferably a maximum particle area of 5.0×10<SP>1</SP>μm<SP>2</SP>or less. The area rate äAr}: a 1 μm thick slice piece of the resin molded product is taken a photograph of at 30 magnification by a transmission electron microscope, from the image of which particles having an area of 1.23×10<SP>-1</SP>μm<SP>2</SP>or more are extracted, followed by totaling their areas to represent as a percentage äAr} in the visual field. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin molded body containing ultrafine carbon fibers. More specifically, the ultrafine carbon fibers are optimized so as to express the antistatic property or conductivity close to the maximum possible with the content of the ultrafine carbon fibers. It is related with the resin molding disperse | distributed in the dispersion state close | similar to.

  In recent years, research and development have been carried out on resin compositions and resin molded articles in which ultrafine carbon fibers are dispersed in a synthetic resin so as to exhibit antistatic properties or conductivity. As an example, a resin composition in which carbon nanotubes are dispersed in a resin, in which the proportion of 2 to 5 multilayer carbon nanotubes in the carbon nanotubes is 50% or more has been proposed ( Patent Document 1). Further, a composition comprising carbon nanotubes, a resin and a filler, wherein the carbon nanotubes are dispersed in the resin in an amount of 0.01 to 1.8% by weight without substantially entangled without forming an aggregate. The molded body has also been proposed (Patent Document 2).

However, the resin composition and the molded body thereof described in Patent Documents 1 and 2 are difficult to grasp objectively because the degree and state of dispersion of the carbon nanotubes are not numerically shown. It is unclear whether it is in a dispersion state that can exhibit antistaticity or conductivity that is close to the maximum possible, and the relationship between antistaticity or conductivity and the aspect ratio and dispersion uniformity of carbon nanotubes Since it is also unclear, there is a problem that it is difficult to obtain a resin composition and its molded body that can exhibit antistaticity or conductivity that is as close to the maximum as possible with a small amount of carbon nanotubes.
JP 2003-306607 A JP 2003-12939 A

The present invention has been made to solve the above problem, and the degree of dispersion of the ultrafine carbon fiber is quantified by the area ratio [Ar], which is a unique dispersion parameter. In addition to clarifying the relationship between the length or aspect ratio of the resin and the volume resistivity [ρ _v ], the relationship between these and the dispersion uniformity is also clarified to achieve the maximum possible control with a small fiber content. An object of the present invention is to provide a resin molded body in which ultrafine carbon fibers are dispersed in a dispersion state that is close to optimum so as to exhibit electrical conductivity or electrical conductivity.

In order to solve the above problems, a carbon fiber-containing resin molded body according to the present invention is a resin molded body in which 0.05 to 15 parts by weight of ultrafine carbon fibers are dispersed in 100 parts by weight of a thermoplastic resin, The average aspect ratio of the ultrafine carbon fiber is 20 to 100, and the area ratio [Ar] defined below is 0.2 to 5.0%.
Area ratio [Ar]: Photograph a slice of a resin molded body having a thickness of 1 μm at a magnification of 30 × with a transmission stereomicroscope, and particles having an area of 1.23 × 10 ⁻¹ μm ² or more in the image. Extracted and expressed as a percentage of the total area of the particles in the field of view.
In the present invention, the aspect ratio of the ultrafine carbon fibers dispersed in the resin molded body is a value obtained by dividing the length of the ultrafine carbon fibers dispersed one by one by the diameter in principle. When a plurality of single-walled carbon nanotubes are gathered into a bundle, and the bundles are separated and dispersed one by one, the value is obtained by dividing the length of the bundle by the diameter of the bundle. Shall.

In the carbon fiber-containing resin molded body of the present invention, it is preferable that the maximum area of the particles extracted when obtaining the area ratio [Ar] is 5.0 × 10 ¹ μm ² or less. Further, it is preferable that the ultrafine carbon fiber is a single-walled carbon nanotube or a double-walled or multi-walled carbon nanotube having a diameter of 80 nm or less and is dispersed in an amount of 0.05 to 5 parts by weight in 100 parts by weight of a thermoplastic resin. In such a resin molded body, it is preferable that the maximum area of particles extracted when determining the area ratio [Ar] is 1.0 × 10 ¹ μm ² or less. In the present invention, the standard deviation [σ] of the area ratio [Ar] obtained for a plurality of slice pieces is preferably used as a parameter for dispersion uniformity, and the standard deviation [σ] of the area ratio [Ar] is In the case of a resin molded body in which 0.05 to 5 parts by weight of the carbon nanotube is dispersed, it is preferably in the range of 0.5 to 5. The area ratio [Ar] is more preferably in the range of 0.3 to 2% in any resin molded body.

As will be described in detail later, the resin molded body in which a small amount of ultrafine carbon fiber is dispersed in a thermoplastic resin has a volume resistivity [ρ _v ] that decreases as the area ratio [Ar] decreases, and a certain area ratio. When [Ar] or less, the volume resistivity [ρ _v ] is reversed and increases. In the case of a resin molded body having an ultrafine carbon fiber content of 0.05 to 15 parts by weight with respect to 100 parts by weight of the thermoplastic resin, the minimum point of the volume resistivity [ρ _v ] has an area ratio [Ar] of 0.2. It exists in the range of -5.0%. In addition, the average fiber length of the ultrafine carbon fiber becomes shorter as the area ratio [Ar] becomes smaller, and the average aspect ratio decreases accordingly. The average aspect ratio of the ultrafine carbon fiber is 20 to 100 when the area ratio [Ar] is in the range of 0.2 to 5.0%. When the average aspect ratio is higher than this, the volume resistivity [ρ _v ] is high because there are many aggregates of ultrafine carbon fibers and the formation of the conductive path is insufficient, and when the average aspect ratio is lower than this, Although the agglomeration of carbon fibers is greatly reduced, the volume resistivity [ρ _v ] is also increased because the contact frequency of the fibers is reduced and the conductive paths are reduced. Therefore, as in the resin molded body of the present invention, 0.05 to 15 parts by weight of ultrafine carbon fibers are dispersed in 100 parts by weight of the thermoplastic resin, the average aspect ratio is 20 to 100, and the area ratio [Ar] is In the range of 0.2 to 5.0%, the volume resistivity [ρ _v ] shows a minimum value or a value close to the minimum value, and the maximum possible with the content of the ultrafine carbon fiber. It can be said that it is a molded body in which ultrafine carbon fibers are dispersed in a nearly optimal dispersion state that exhibits close antistatic properties or electrical conductivity.

  When the dispersion in the thermoplastic resin is close to the ideal state, the ultrafine carbon fiber exhibits an antistatic or conductive function even in a small amount of 0.05 to 15 parts by weight with respect to 100 parts by weight of the thermoplastic resin. Among them, the carbon nanotubes are excellent in mechanical and electrical characteristics, thermal conductivity and the like, and therefore the content (dispersion amount) can be further reduced. In particular, single-walled carbon nanotubes and 2 having a diameter of 80 nm or less. Even if the resin molded body in which the single-walled or multi-walled carbon nanotubes are dispersed is reduced to 0.05 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin, the dispersion state should be good. As a result, satisfactory antistatic or conductive properties are exhibited.

By the way, when there are particles having a large area among the particles extracted when obtaining the area ratio [Ar] of the carbon fiber-containing resin molded body, the ultrafine carbon fibers are unevenly distributed as aggregates having a large area. Therefore, it cannot be said that it is a good dispersion state, and the volume resistivity [ρ _v ] increases even if the area ratio [Ar] is in the range of 0.2 to 5.0%. The maximum allowable particle area is 5.0 × 10 ¹ μm ² , and when particles with an area larger than this are present, the dispersion of the ultrafine carbon fiber is insufficient and the volume resistivity [ρ _v ] is minimized. Since the value is not close, the maximum area of the extracted particles is preferably 5.0 × 10 ¹ μm ² or less. However, in the case of a single-walled carbon nanotube or a resin molded body in which a double-walled or multi-walled carbon nanotube having a diameter of 80 nm or less is dispersed, since the diameter of the fiber is originally small, the maximum allowable particle area is 1.0 × 10 6. ¹ [mu] m is ^2, therefore the maximum area of the particle to be extracted is preferably less than this.

The standard deviation [σ] of the area ratio [Ar] is preferably adopted as a parameter for dispersion uniformity. As described in detail later, the better the dispersion uniformity, the more the area ratio [Ar] is The smaller the value, the smaller the standard deviation [σ]. In the case of the above-mentioned resin molded body in which single-walled carbon nanotubes or two- or multi-walled carbon nanotubes having a diameter of 80 nm or less are dispersed, the standard deviation [Ar] is in the range of 0.2 to 5.0%. [sigma]] is preferably in the range of 0.5-5. When the standard deviation [σ] is larger than this, a large number of aggregates of carbon nanotubes are unevenly distributed and it is difficult to form a conductive path, so that the volume resistivity [ρ _v ] is increased and the standard deviation [σ] is smaller than this. Although the dispersion uniformity of the carbon nanotubes is greatly improved, the volume resistivity [ρ _v ] is also increased because the average aspect ratio is too low to form a conductive path. As described above, the resin molded product having the standard deviation [σ] of the area ratio [Ar] in the range of 0.5 to 5 has a good balance between the degree of dispersion uniformity of carbon nanotubes and the average aspect ratio. The ultrafine carbon fiber is dispersed in a nearly optimal dispersion state that exhibits the maximum possible antistatic property or conductivity with the content of bismuth to form a sufficient conductive path.

Further, as described later, the carbon fiber-containing resin molded body of the present invention often has a minimum value of volume resistivity [ρ _v ] in the vicinity of 1% of the area ratio [Ar]. ] Has a volume resistivity [ρ _v ] of a minimum value or a value very close to it.

  In carrying out the present invention, various known thermoplastic resins can be used as the thermoplastic resin of the material. Among them, crystalline polyphenylene sulfide and polyether ether whose viscosity is greatly reduced when heated to a temperature higher than the melting point. Olefin resins such as ketone, polyethylene and polypropylene, or ester resins such as amorphous polyethersulfone, polyetherimide, polycarbonate and crystalline or amorphous polyethylene terephthalate are preferably used. This is because these resins have a very low viscosity as described above, and therefore the dispersibility of the ultrafine carbon fibers in the low-viscosity molten resin is better than that of other thermoplastic resins. In particular, ester resins and olefin resins are more preferably used because of their low viscosity.

Carbon nanotubes, carbon nanohorns, carbon nanowires, carbon nanofibers, graphite fibrils, etc. can be used as the ultrafine carbon fibers dispersed in the above thermoplastic resin. Among them, the mechanical and electrical characteristics are excellent, and the aspect Carbon nanotubes that have a high ratio and are cut and dispersed so as to have an average aspect ratio of 20 to 100 suitable for dispersion and formation of a conductive path by kneading with a thermoplastic resin are preferably used. The carbon nanotube includes a multi-walled carbon nanotube having a plurality of cylindrically closed carbon walls having different diameters around the central axis, a double-walled carbon nanotube having two carbon walls, and a single cylinder around the central axis. There are single-walled carbon nanotubes having closed carbon walls, and multi-walled carbon nanotubes and double-walled carbon nanotubes are separated and dispersed one by one, but single-walled carbon nanotubes are difficult to separate and disperse one by one. More than ten, usually about 10 to 50, gather to form a bundle, and the bundle is separated and dispersed one by one. Particularly preferably used carbon nanotubes are two- or multi-walled carbon nanotubes having a diameter of about 5 to 80 nm , an aspect ratio of about 40 to 500, a fiber length of about 0.2 to 40 μm, and a bundle having a diameter of 0.5. The single-walled carbon nanotube has an aspect ratio of about ˜8 nm, a bundle aspect ratio of about 40 to 600, and a bundle fiber length of about 0.02 to 5 μm. When these carbon nanotubes are cut by kneading with a thermoplastic resin and have an average aspect ratio of 20 to 100, they are dispersed in a very good dispersion state to form a conductive path. Or exhibits electrical conductivity. Multi-walled carbon nanotubes having a diameter of about 80 to 200 nm and an aspect ratio of about 40 to 400 can also be used.

  The content of the ultrafine carbon fiber is 0.05 to 15 parts by weight with respect to 100 parts by weight of the thermoplastic synthetic resin. However, in the case of the single-walled carbon nanotube or the double-walled or multi-walled carbon nanotube having a diameter of 80 nm or less It is sufficient to disperse 0.05 to 5 parts by weight, and even in such a small amount, a resin molded product exhibiting good antistatic properties or conductivity can be obtained if the dispersion state is ideal.

  In addition, in order to improve the dispersibility of a carbon nanotube, you may use a dispersing agent together. Dispersants include aluminum coupling agents, titanate coupling agents, alkylammonium salt solutions of acidic polymers, tertiary amine-modified acrylic copolymers, and polymer dispersants such as polyoxyethylene and polyoxypropylene. Used.

  The resin molded body of the present invention is prepared by pre-blending 0.05 to 15 parts by weight of the above ultrafine carbon fiber with 100 parts by weight of the above thermoplastic resin and, if necessary, a small amount of a dispersant. It can be obtained by melt kneading at a temperature above the melting point of the resin while adjusting the total shear strain [γ · t] with a heated screw cylinder (screw extruder, etc.), and performing melt molding such as extrusion molding or injection molding. Is. Here, the total amount of shear strain [γ · t] is obtained by calculating the shear rate [γ] (average value) applied to the resin mixture from the screw shape of the heating screw cylinder, the extrusion discharge amount, the screw rotation speed, etc. The stagnation time [t] (average value) of the resin mixture in the screw cylinder is measured and expressed by the product of the shear rate [γ] and the stagnation time [t].

  As a screw extruder as a heating screw cylinder, a twin-screw co-rotating extruder as shown in FIG. 2 is preferably used, but a single-screw extruder, a multi-screw extruder, or the like can also be used. And as a screw, the screw of the area | region where the shear rate is low of FIG.1 (c) which mainly made the full flight progressive segment shown in FIG.1 (a), and the kneading segment shown in FIG.1 (b) are main. For example, a screw having a high shear rate, a screw having a medium shear rate in which a full flight progressive segment and a kneading segment are connected in an appropriate combination, and the like are used.

Ｄ＝押出機内壁の内径
Ｃｔ_０＝押出機内壁と押出機スクリューの最外部の隙間
θ＝押出機シリンダ内に充填されている樹脂の量を示す角度
Ｎ＝スクリューの回転数 In the case of a twin-screw co-rotating extruder, the shear rate [γ] (average value) applied to the resin mixture is determined using commercially available software (for example, twin-screw extruder quality analysis support software manufactured by YSP) As shown in FIG. 2, the material filling angle Θ can be obtained from the discharge amount, the rotation speed, the material density, and the like, and can be simply calculated based on the following basic formulas (1) to (3).

D = Inner diameter of the inner wall of the extruder Ct ₀ = Gap between the inner wall of the extruder and the extruder screw θ = An angle indicating the amount of resin filled in the extruder cylinder N = Number of rotations of the screw

In addition, the residence time [t] (average value) in the extruder of the resin mixture is, for example, that the dye is charged from the charging port of the screw extruder, and the dye is completely discharged from the screw extruder from the charging time. Until the color of the dye disappears, specimens are continuously collected, and the specimen is measured at a constant interval (for example, every 10 seconds), and the absorbance [Ab] at the maximum absorbance wavelength of the dye is measured with a spectrophotometer. Then, the retention time distribution curve is derived by plotting the value with respect to the time axis, and can be obtained based on the following equation (4).

The total shear strain [γ · t] represented by the product of the average shear rate [γ] and the average residence time [t] is closely related to the degree of dispersion of the ultrafine carbon fibers in the obtained resin molding, As the shear strain [γ · t] increases, the degree of dispersion increases and the area ratio [Ar] decreases. FIG. 3 shows a resin molded product A produced by changing the conditions in Examples and Comparative Examples described later (polycarbonate carbon nanotubes having a diameter of 10 to 20 nm and an average fiber length of about 1 μm as ultrafine carbon fibers. Is a graph showing the relationship between the area ratio [Ar] of the mass% dispersion), the total shear strain amount [γ · t], and the volume resistivity [ρ _v ], as can be seen from this graph. The logarithm of the strain amount [γ · t] and the area ratio [Ar] are substantially in inverse proportion, and the area ratio [Ar] decreases as the total shear strain amount [γ · t] increases. FIG. 6 shows a resin molded product B prepared by changing the conditions in Examples and Comparative Examples described later (single-walled carbon nanotubes having a diameter of about 8 nm and a fiber length of 0.1 to 2 μm as a bundle of ultrafine carbon fibers). FIG. 9 is a graph showing the relationship between the area ratio [Ar] of 3% by mass dispersed in a polycarbonate using the above and the total shear strain [γ · t] and volume resistivity [ρ _v ]. Resin molded product C prepared by changing conditions in Examples and Comparative Examples described later (dispersed in polycarbonate by 12% by mass using multi-walled carbon nanotubes having a diameter of 150 nm and an average fiber length of approximately 9 μm as ultrafine carbon fibers) From these graphs, it can be seen that the logarithm of the total shear strain amount [γ · t] and the area ratio [Ar] have the same relationship as described above. From this graph, the total shear strain amount [γ · t] required to obtain the resin molded product of the present invention having an area ratio [Ar] of 0.2 to 5% can be estimated. The resin molded body of the present invention can be obtained by adjusting the average shear rate [γ] and the average retention time [t] so as to obtain the shear strain amount [γ · t], and melt-kneading and molding. .

The area ratio [Ar] is as defined above, and when the degree of dispersion of the ultrafine carbon fiber is low, particles having an area of 1.23 × 10 ⁻¹ μm ² or more in the image, that is, transmission type Since there are many aggregates of ultrafine carbon fibers having a size that can be observed with a stereoscopic microscope image (for example, BX51 manufactured by ORYMPUS), the area ratio [Ar] is large. And as the degree of dispersion becomes higher, the aggregation of the ultrafine carbon fibers is dissolved and refined by shearing, and the size becomes less than 1.23 × 10 ⁻¹ μm ² which is the observation limit of the transmission stereoscopic microscope image. The area ratio [Ar] decreases. Therefore, it can be said that the smaller the area ratio [Ar], the higher the degree of dispersion.
The area ratio [Ar] of the resin molded body C was determined by extracting particles of 3 μm ² or more because many multi-walled carbon nanotubes having a diameter of about 150 nm are unevenly distributed as aggregates having a large area. Is.

When the area ratio [Ar] is large, most of the ultrafine carbon fibers are aggregated and unevenly distributed in the resin molded body, and almost no conductive path is formed by mutual contact of the ultrafine carbon fibers. [rho] _v ] is extremely high and exhibits electrical insulation. However, as the degree of dispersion increases and the area ratio [Ar] decreases, the agglomeration of ultrafine carbon fibers is dissolved and most of the fibers are dispersed to form a conductive path in contact with each other. _v ] decreases. When the area ratio is less than [Ar], the degree of dispersion is further increased, but the ultrafine carbon fibers are cut, the average fiber length becomes too short, and the average aspect ratio becomes too small. Since the formation of the conductive path due to the contact is decreased, the volume resistivity [ρ _v ] is reversed and increased. The minimum point of the volume resistivity [ρ _v ] exists in the range where the area ratio [Ar] is 0.2 to 5%.

FIG. 4 is a graph showing the relationship between the area ratio [Ar] of the resin molded body A and the average fiber length and volume resistivity [ρ _v ] of ultrafine carbon fibers (multi-walled carbon nanotubes having a diameter of 10 to 20 nm). As can be seen from the graph of FIG. 4 and the graph of FIG. 3, when the area ratio [Ar] is about 8% or more, the volume resistivity [ρ _v ] of the resin molded body A is 10 ¹⁴ Ω that cannot be measured.・ Electrically insulating at cm or more. Then, as the area ratio [Ar] decreases from about 8%, the volume resistivity [ρ _v ] also decreases, and when the area ratio [Ar] is near 1%, the volume resistivity [ρ _v ] becomes minimum, and the area ratio When [Ar] is approximately 1% or less, the volume resistivity [ρ _v ] is increased again. Since these graphs were measured for a resin molded body A having a content of ultrafine carbon fibers (multi-walled carbon nanotubes having a diameter of 10 to 20 nm) of 3% by mass, the area ratio [Ar] was 0.2 to 5%. In the range, the volume resistivity [ρ _v ] is approximately 10 ⁶ to 10 ¹¹ Ω · cm and develops antistatic properties, but when the content of the ultrafine carbon fiber increases, the graphs of FIGS. 3 and 4 , The curve showing the volume resistivity [ρ _v ] in a logarithm moves downward and to the right, the volume resistivity [ρ _v ] decreases, and the area ratio [Ar] at which the minimum point appears increases. Then it approaches 5%. When the content of the ultrafine carbon fiber decreases, the volume resistivity [ρ _v ] increases, and the area ratio [Ar] at which the minimum point appears decreases to approach 0.2%. In order to make the volume resistivity [ρ _v ] less than 10 ¹¹ Ω · cm more stably, the area ratio [Ar] is preferably set to 0.3 to 2%. The volume resistivity [ρ _v ] is about 10 ⁶ to about 10 ⁷ Ω · cm, which is extremely close to or very close to the minimum value, and exhibits sufficient antistatic performance.

FIG. 7 is a graph showing the relationship between the area ratio [Ar] of the resin molded body B and the average fiber length and volume resistivity [ρ _v ] of ultrafine carbon fibers (single-walled carbon nanotubes having a diameter of about 1 nm). FIG. 10 is a graph showing the relationship between the area ratio [Ar] of the resin molded body C and the average fiber length and volume resistivity [ρ _v ] of ultrafine carbon fibers (multi-walled carbon nanotubes having a diameter of about 150 nm). In these graphs, the volume resistivity [ρ _v ] is minimized when the area ratio [Ar] is around 1%. As can be seen from the graph of FIG. 7, in the resin molded body B, the area ratio [Ar] is in the range of 0.3 to 2%, and the volume resistivity [ρ _v ] is a value that is extremely close to the minimum value or the minimum value. From 10 ³ to about 10 ⁵ Ω · cm, antistatic or conductive properties are exhibited. On the other hand, as can be seen from the graph of FIG. 10, the resin molded body C has a volume resistivity [ρ _v ] of about 10 ⁸ to about 10 ¹³ Ω · cm even when the area ratio [Ar] is in the range of 0.3 to 2%. And higher than the resin moldings A and B. However, the volume resistivity [ρ _v ] indicates the lowest resistivity in the area ratio [Ar] in this range, and the area ratio [Ar] is also in the range of 0.3 to 2% in the resin molded body C. It can be seen that it is preferable to minimize the resistance value. As described above, the volume resistivity [ρ _v ] is greatly different between the resin molded bodies A and B and the resin molded body C. The multi-walled carbon nanotubes having a diameter of about 150 nm dispersed in the resin molded body C are resin-molded. Compared with 10 to 20 nm diameter multi-walled carbon nanotubes and single-walled carbon nanotubes dispersed in bodies A and B, the absolute number of the number per unit weight is small, so the volume resistivity is the same as that of resin molded bodies A and B. This is because a large amount of addition is required to obtain it.

Further, as can be seen from the graph of FIG. 4, the average fiber length of the ultrafine carbon fibers (multi-walled carbon nanotubes having a diameter of 10 to 20 nm) of the resin molded body A increases the degree of dispersion and the area ratio [Ar] increases. The average fiber length is 0.42 to 0.53 μm when the area ratio [Ar] is in the range of 0.2 to 5%. Accordingly, the average aspect ratio of the dispersed ultrafine carbon fibers (multi-walled carbon nanotubes having a diameter of 10 to 20 nm) is approximately 21 to 53, and the volume resistivity [ρ _v ] is substantially within the range of the average aspect ratio. 10 ⁶ to about 10 ¹¹ Ω · cm, and sufficient antistatic performance is exhibited. When the average fiber length is longer than 0.53 μm, the volume resistivity [ρ _v ] is increased because there are many aggregates of ultrafine carbon fibers and the formation of the conductive path is insufficient, and the average fiber length is shorter than 0.42 μm. In this case, although the dispersibility is improved, the contact frequency of the fibers is decreased and the conductive path is decreased, so that the volume resistivity [ρ _v ] is also increased. An average fiber length of about 0.43 to 0.5 μm and an average aspect ratio of about 22 to 50 are more preferable because the volume resistivity [ρ _v ] becomes a resin molded body A that is extremely close to or close to the minimum value. .

Also in the case of the resin molded body B, as can be seen from the graph of FIG. 7, the average fiber length (length of one bundle) of ultrafine carbon fibers (single-walled carbon nanotubes having a diameter of about 8 nm per bundle) is When the area ratio [Ar] decreases as the degree of dispersion increases and the area ratio [Ar] falls within the range of 0.2 to 5%, the average fiber length is 0.39 to 0.62 μm. Since the single-walled carbon nanotubes are dispersed in bundles having a diameter of about 8 nm, the average aspect ratio is about 40 to 75, and the volume resistivity [ρ _v ] is within the range of the average aspect ratio. It becomes approximately 10 ³ to approximately 10 ⁸ Ω · cm, and exhibits sufficient antistatic property or conductivity. In the case of the resin molded body C, as can be seen from the graph of FIG. 10, the area ratio [Ar] is in the range of 0.2 to 5%, and the ultrafine carbon fiber (multi-walled carbon nanotube having a diameter of about 150 nm) is used. ) Has an average fiber length of about 5 to 7 μm and an average aspect ratio of about 33 to 47.

As described above, the resin molded bodies A, B, and C all have an average aspect ratio of the ultrafine carbon fiber in the range of 20 to 100 in a good dispersion state where the area ratio [Ar] is 0.2 to 5%. It is in. However, even if the average aspect ratio of the ultrafine carbon fiber is in the range of 20 to 100, the dispersion uniformity is poor, and if the ultrafine carbon fiber is partially agglomerated and unevenly distributed, it is difficult to form a conductive path. The volume resistivity [ρ _v ] increases. Accordingly, the dispersion uniformity as well as the average aspect ratio of the ultrafine carbon fibers are important factors. When the standard deviation [σ] of the area ratio [Ar] obtained for a plurality of slices of the resin molded body is adopted as the dispersion uniformity parameter, the standard is the smaller the area ratio [Ar] with better dispersion uniformity. There is a relationship that the deviation [σ] becomes small.

FIG. 5 is a graph showing the relationship between the area ratio [Ar] of the resin molded body A, its standard deviation [σ], and dispersion uniformity, and the area ratio [Ar] is 0.2 to 5%. In the range, the standard deviation [σ] of the area ratio [Ar] is in the range of 0.5 to 5. When the standard deviation [σ] is greater than 5, the dispersion uniformity is poor and a large number of fine carbon fiber aggregates are unevenly distributed. When the standard deviation [σ] is less than 0.5, the dispersion uniformity is greatly increased. However, since the average fiber length becomes too short and the average aspect ratio becomes too small, a conductive path is hardly formed in any case, and the volume resistivity [ρ _v ] becomes high. On the other hand, the resin molded product A having a standard deviation [σ] of the area ratio [Ar] in the range of 0.5 to 5 has a good balance between the degree of dispersion uniformity of the ultrafine carbon fibers and the average fiber length. The ultrafine carbon fibers are dispersed in a nearly optimal dispersion state that develops an antistatic property or conductivity close to the maximum possible with the fiber content, thereby forming a sufficient conductive path. Similarly, as shown in the graph of FIG. 8, the resin molded body B also has a standard deviation [σ] of the area ratio [Ar] of 0.2 when the area ratio [Ar] is in the range of 0.2 to 5%. It is in the range of 5-5. On the other hand, as shown in the graph of FIG. 11, the resin molded body C has a standard deviation [σ] of 2 to 15 and a resin molded body A in the area ratio [Ar] of 0.2 to 5%. Greater than B. This is because, as described above, the method of obtaining the area ratio [Ar] is different. If this method of obtaining the area ratio [Ar] is obtained, sufficient dispersion uniformity can be obtained even if it is 2-15. ing. As can be seen from the graphs of FIGS. 5 and 8, it is important that the standard deviation [σ] of the area ratio [Ar] is in the range of 0.5 to 5 in order to obtain an excellent resin molded product in a dispersed state. is there.

By the way, when there are particles having a large area among the particles extracted when obtaining the area ratio [Ar] of the carbon fiber-containing resin molded body, the ultrafine carbon fibers are unevenly distributed as aggregates having a large area. Therefore, it cannot be said that the dispersion state is good, and the volume resistivity [ρ _v ] increases even if the area ratio [Ar] is in the range of 0.2 to 5.0%. The maximum allowable particle area is 5.0 × 10 ¹ μm ² , and when particles with an area larger than this are present, the dispersion of the ultrafine carbon fiber is insufficient and the volume resistivity [ρ _v ] is minimized. Since the values are not close, it is important that the maximum area of the extracted particles is 5.0 × 10 ¹ μm ² or less. However, in the case of single-walled carbon nanotubes or resin molded bodies A and B in which two- or multi-walled carbon nanotubes having a diameter of 80 nm or less are dispersed, the diameter of the fiber is originally small, so the maximum allowable particle area is 1. It is important that the maximum area of the extracted particles is less than or equal to 0 × 10 ¹ μm ² . A multi-walled carbon nanotube having a diameter of 80 nm or more has a large fiber diameter. Therefore, it is important that the maximum area of allowable particles is 5 × 10 ¹ μm ² and the maximum area is less than this.

From the above, as in the resin molded body of the present invention, 0.05 to 15 parts by weight of ultrafine carbon fibers are dispersed in 100 parts by weight of the thermoplastic resin, and the average aspect ratio of the ultrafine carbon fibers is 20 to 100. The area ratio [Ar] is 0.2 to 5%, the standard deviation [σ] of the area ratio [Ar] is 0.5 to 5, and the particles extracted when determining the area ratio [Ar] The maximum area is 5.0 × 10 ¹ μm ² or less (1.0 × 10 ¹ μm ² or less in the case of a resin molded product in which single-walled carbon nanotubes or double-walled or multi-walled carbon nanotubes having a diameter of 80 nm or less are dispersed). For some, the volume resistivity [ρ _v ] is a minimum value or a value close to a minimum value, and the dispersion state and the average that are close to the optimum, exhibiting antistaticity or conductivity close to the maximum possible with the fiber content. The ultrafine carbon fiber is dispersed with the fiber length. It can be said that that is a resin molded body. In particular, as in the resin moldings A and B, the ultrafine carbon fiber is a single-walled carbon nanotube or a double-walled or multi-walled carbon nanotube having a diameter of 80 nm or less, and 0.05% in 100 parts by weight of the thermoplastic resin. The dispersion of ˜5 parts by weight can be said to be a very preferable resin molded article because sufficient antistatic property or conductivity can be expressed with a small amount of fiber content.

  Next, more specific examples and comparative examples of the present invention will be given.

[Example 1]
As the thermoplastic resin, dried polycarbonate (Panlite K-1285 manufactured by Teijin Chemicals Ltd.) is used, and as the ultrafine carbon fiber, a multi-walled carbon nanotube (Shenzhen) having a diameter of 10 to 20 nm and an average fiber length of approximately 1 μm. 3 parts by weight of the above multi-walled carbon nanotube (hereinafter referred to as multi-walled CNT) is added to 97 parts by weight of the above-mentioned polycarbonate (hereinafter referred to as PC), and the PC and the multi-walled CNT are preliminarily mixed with a mixer. Dispersed. Then, the above pre-dispersed mixture is supplied by a quantitative feeder from the inlet of a twin-screw co-rotating extruder (with a screw having a low shear rate connected to a full flight progressive segment with a screw diameter of 25 mm). The shear rate [γ] (average value) and the residence time [t] of the mixture in the extruder so that the logarithm of the total shear strain [γ · t] is in the range of 3.2 to 4.6. By changing the (average value) and extruding while kneading and dispersing at a cylinder temperature of 270 ° C., various types of test pieces (20 × 20 ×) of the resin molded product A having different total shear strain [γ · t] 1 mm).

[Comparative Example 1]
For comparison, the shear rate [γ] (average value) and the residence time of the mixture in the extruder so that the logarithm of the total shear strain [γ · t] is less than 3.2 or exceeds 4.6. Except that [t] (average value) was changed, various types of comparative test pieces (20 × 20 × 1 mm) of the resin molded product A were obtained in the same manner as in the above-described example.

  In Example 1 and Comparative Example 1 described above, the discharge rate of the twin-screw co-rotating extruder is set to 1.7 kg / hr, and the screw rotation speed is changed within the range of 20 to 100 rpm. Is set to 60 rpm, and the discharge rate is changed within a range of 0.9 to 5.3 kg / hr, thereby changing the shear rate [γ] and the retention time [t] to change the total shear strain [γ · t ] Was adjusted. The shear rate [γ] and the retention time [t] were measured by the methods described above.

A sample having a thickness of 1 μm was cut out from the cross section of each test piece obtained in the above Examples and Comparative Examples with a microtome (RM2065 manufactured by Reica), and 30 times with a transmission stereomicroscope (BX51 manufactured by OLYMPUS). Taking a photograph (SEM photograph), using the image analysis software (Image-Pro Plus manufactured by Planetron Co.) from the image, extract particles having an area of 1.23 × 10 ⁻¹ μm ² or more in the image, The area ratio [Ar] of the particles in the field of view was determined. Further, Hiresta-UP MCP-450 manufactured by Mitsubishi Chemical Corporation was used, and the volume resistivity [ρ _v ] of each test piece was measured under the condition of a measurement time of 1 minute. Then, the logarithm of the total shear strain [γ · t], the area ratio [Ar], and the logarithm of the volume resistivity [ρ _v ] for each test piece were plotted, and the graph of FIG. 3 was created.

Moreover, about each test piece of Example 1 and Comparative Example 1 whose area ratio [Ar] is 6% or less, the PC is removed with chloroform, only the multilayer CNT is extracted, an SEM photograph is taken, and image analysis is performed from the image. Using software (Image-Pro Plus), an average length of 500 or more multi-walled CNTs was determined. Then, an average fiber length of the multi-layer CNT for each specimen, the area ratio and [Ar], by plotting the logarithm of the volume resistivity [[rho _v], and create a graph in FIG.

  Further, for five test pieces extracted from the test pieces of Example 1 and Comparative Example 1 having an area ratio [Ar] of 6% or less, between micrographs of a plurality of slice pieces cut out to obtain the area ratio [Ar]. The standard deviation [σ] of the area ratio [Ar] was determined as an index of dispersion uniformity. At that time, adjacent slice pieces were excluded, and slice pieces sufficiently separated from the size of the aggregate of the multi-walled CNTs were used for the measurement. Then, the area ratio [Ar] and its standard deviation [σ] for each test piece were plotted to create the graph of FIG.

Considerations on the graphs of FIGS. 3, 4, and 5 created based on the above-described Example 1 and Comparative Example 1 are the same as those already described, and will be omitted.
In addition, as for each test piece of Example 1, the maximum area of the particle | grains extracted when calculating | requiring an area ratio [Ar] was 1.0 * 10 < ¹ > micrometer < ² > or less.

[Example 2]
As the ultrafine carbon fiber, a single-walled carbon nanotube (manufactured by Shenzhen Nanotechport) (hereinafter referred to as single-walled CNT) having a diameter of about 1 nm and a fiber length of 0.1 to 2 μm is used, and the total shear strain [γ The shear rate [γ] (average value) and the residence time [t] (average value) of the mixture in the extruder were changed so that the logarithm of t] was in the range of 3.6 to 4.4. Except for the above, in the same manner as in Example 1, various types of test pieces (20 × 20 × 1 mm) of the resin molded body B having different total shear strain [γ · t] were obtained.

[Comparative Example 2]
For comparison, the shear rate [γ] (average value) and the residence time of the mixture in the extruder so that the logarithm of the total shear strain [γ · t] is less than 3.6 or exceeds 4.4. Except for changing [t] (average value), various types of comparative test pieces (20 × 20 × 1 mm) of the resin molded body B were obtained in the same manner as in Example 2 above.

And about each test piece of said Example 2 and Comparative Example 2, area ratio [Ar] and volume resistivity [(rho) _v ] are measured like Example 1 and Comparative Example 1, and about each test piece, The graph of FIG. 6 was created by plotting the logarithm of the total shear strain [γ · t], the area ratio [Ar], and the logarithm of the volume resistivity [ρ _v ].
Moreover, the average value of the length of single-walled CNT (one bundle) was calculated | required similarly to Example 1 and Comparative Example 1 about each test piece of Example 2 and Comparative Example 2 whose area ratio [Ar] is 6% or less. 7 was prepared by plotting the average fiber length of single-walled CNT, the area ratio [Ar], and the logarithm of volume resistivity [ρ _v ] for each test piece.
Further, for the five test pieces extracted from the test pieces of Example 2 and Comparative Example 2 having an area ratio [Ar] of 6% or less, the standard deviation of the area ratio [Ar] was obtained in the same manner as in Example 1 and Comparative Example 1. [Σ] was obtained, and the area ratio [Ar] and the standard deviation [σ] thereof for each test piece were plotted to create the graph of FIG.
In addition, as for each test piece of Example 2, the maximum area of the particle | grains extracted when calculating | requiring an area ratio [Ar] was 1.0 * 10 < ¹ > micrometer < ² > or less.

[Example 3]
As the ultrafine carbon fiber, a multi-walled carbon nanotube having a diameter of about 150 nm and a fiber length of about 9 μm [made by Showa Denko Co., Ltd.] (hereinafter referred to as multi-walled CNT 150 nmφ) is used, and the blending amount is changed to 12% by mass, The shear rate [γ] (average value) and the stagnation time [t] of the mixture in the extruder (average) so that the logarithm of the total shear strain [γ · t] is within the range of 3.25 to 3.9. In the same manner as in Example 1 except that the value) was changed, various types of test pieces (20 × 20 × 1 mm) of the resin molded product C having different total shear strain amounts [γ · t] were obtained.

[Comparative Example 3]
For comparison, the shear rate [γ] (average value) and the stagnation time of the mixture in the extruder so that the logarithm of the total shear strain [γ · t] is less than 3.25 or more than 3.9. Except having changed [t] (average value), it carried out similarly to the said Example 3, and obtained the test piece (20x20x1 mm) for a variety of comparison of the resin molding C.

And about each test piece of said Example 3 and Comparative Example 3, area ratio [Ar] and volume resistivity [(rho) _v ] are measured like Example 1 and Comparative Example 1, and about each test piece, The graph of FIG. 9 was created by plotting the logarithm of the total shear strain [γ · t], the area ratio [Ar], and the logarithm of the volume resistivity [ρ _v ]. However, the area ratio [Ar] is obtained by extracting particles of 3 μm ² or more.
Further, for each test piece of Example 3 and Comparative Example 3 having an area ratio [Ar] of 6% or less, the average value of the length of the multilayer CNT 150 nmφ was obtained in the same manner as in Example 1 and Comparative Example 1, and for each test piece. The average fiber length, the area ratio [Ar], and the logarithm of the volume resistivity [ρ _v ] were plotted to produce the graph of FIG.
Further, for five test pieces extracted from the test pieces of Example 3 and Comparative Example 3 having an area ratio [Ar] of 6% or less, the standard deviation of the area ratio [Ar] was obtained in the same manner as in Example 1 and Comparative Example 1. [Σ] was determined, and the area ratio [Ar] and the standard deviation [σ] thereof were plotted for each test piece, and the graph of FIG. 11 was created.
In addition, as for each test piece of Example 3, the maximum area of the particle | grains extracted when calculating | requiring an area ratio [Ar] was 5.0 * 10 < ¹ > micrometer < ² > or less.

  Considering the graphs of FIGS. 6, 7, and 8 created based on Example 2 and Comparative Example 2 above, and FIGS. 9, 10, and 10 created based on Example 3 and Comparative Example 3 above. The discussion on the graph of FIG. 11 is omitted because it has already been described.

The screw used for manufacture of the carbon fiber containing resin molding of this invention and its segment are illustrated, (a) is a side view and front view which show a full flight progressive segment, (b) shows a kneading segment. A side view and a front view, (c) is a side view showing a screw connected to a full flight progressive segment. It is a schematic sectional drawing of the biaxial co-rotating extruder for demonstrating how to obtain | require a shear rate [(gamma)]. Relationship between area ratio [Ar], total shear strain amount [γ · t] and volume resistivity [ρ _v ] of resin molded body A produced by changing the conditions in Example 1 and Comparative Example 1 of the present invention. It is a graph which shows. The area ratio [Ar] of the resin molding A produced by changing the conditions in Example 1 and Comparative Example 1 of the present invention, and the average fiber length and volume of ultrafine carbon fibers (multi-walled carbon nanotubes having a diameter of 10 to 20 nm) It is a graph which shows the relationship with resistivity [(rho) _v ]. It is a graph which shows the relationship between the area ratio [Ar] of the resin molding A produced by changing various conditions in Example 1 and Comparative Example 1 of the present invention, its standard deviation [σ], and dispersion uniformity. Relationship between area ratio [Ar], total shear strain amount [γ · t], and volume resistivity [ρ _v ] of resin molded body B produced by changing the conditions in Example 2 and Comparative Example 2 of the present invention. It is a graph which shows. The area ratio [Ar] of the resin molding B produced by changing the conditions in Example 2 and Comparative Example 2 of the present invention, the average fiber length and volume resistivity [ρ _{v of the} ultrafine carbon fiber (single-walled carbon nanotube) It is a graph which shows the relationship with]. It is a graph which shows the relationship between the area ratio [Ar] of the resin molding B produced by changing various conditions in Example 2 and Comparative Example 2 of the present invention, its standard deviation [σ], and dispersion uniformity. Relationship between area ratio [Ar], total shear strain [γ · t] and volume resistivity [ρ _v ] of resin molded body C produced by changing the conditions in Example 3 and Comparative Example 3 of the present invention. It is a graph which shows. The area ratio [Ar] of the resin molded body C produced by variously changing the conditions in Example 3 and Comparative Example 3 of the present invention, and the average fiber length and volume resistivity of ultrafine carbon fibers (multi-walled carbon nanotubes having a diameter of 150 nm) It is a graph which shows the relationship with [(rho) _v ]. It is a graph which shows the relationship between the area ratio [Ar] of the resin molding C produced by changing various conditions in Example 3 and Comparative Example 3 of the present invention, its standard deviation [σ], and dispersion uniformity.

Explanation of symbols

Θ Material filling angle D Inner wall inner diameter Ct ₀ Outer wall of extruder and outermost gap between extruder screw N Screw rotation speed

Claims (6)

A resin molded body in which 0.05 to 15 parts by weight of ultrafine carbon fibers are dispersed in 100 parts by weight of a thermoplastic resin, the average aspect ratio of the ultrafine carbon fibers is 20 to 100, and the area defined below Ratio [Ar] is 0.2-5.0%, The carbon fiber containing resin molding characterized by the above-mentioned.
Area ratio [Ar]: Photograph a slice of a resin molded body having a thickness of 1 μm at a magnification of 30 × with a transmission stereomicroscope, and particles having an area of 1.23 × 10 ⁻¹ μm ² or more in the image. Extracted and expressed as a percentage of the total area of the particles in the field of view. The carbon fiber-containing resin molded body according to claim 1, wherein the maximum area of particles extracted when obtaining the area ratio [Ar] is 5.0 x 10 ¹ µm ² or less.   The ultrafine carbon fiber is a single-walled carbon nanotube or a double-walled or multi-walled carbon nanotube having a diameter of 80 nm or less, and 0.05 to 5 parts by weight are dispersed in 100 parts by weight of a thermoplastic resin. Carbon fiber-containing resin molded article. The carbon fiber-containing resin molded product according to claim 3, wherein the maximum area of particles extracted when obtaining the area ratio [Ar] is 1.0 x 10 ¹ µm ² or less.   The carbon fiber-containing resin molded article according to claim 3 or 4, wherein the standard deviation [σ] of the area ratio [Ar] obtained for the plurality of slice pieces is 0.5 to 5. The carbon fiber-containing resin molded article according to any one of claims 1 to 5, wherein the area ratio [Ar] is 0.3 to 2%.

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