JP6873360B2 - Thermoplastic resin composition - Google Patents

Description

The present invention relates to a thermoplastic resin composition in which carbon nanofibers are dispersed.

According to the method for producing a carbon fiber composite material previously proposed by the present inventors and others, the use of an elastomer improves the dispersibility of carbon nanofibers, which has been difficult until now, and makes the carbon nanofibers uniform in the elastomer. (See, for example, Patent Document 1).

According to such a method for producing a carbon fiber composite material, an elastomer and carbon nanofibers are kneaded, and the dispersibility of carbon nanofibers having strong cohesiveness is improved by a shearing force. More specifically, when an elastomer and carbon nanofibers are mixed, viscous elastomers penetrate each other of the carbon nanofibers, and a specific part of the elastomer has a high activity of the carbon nanofibers due to chemical interaction. When a strong shearing force acts on a mixture of an elastomer having a moderately long molecular length and high molecular motility (having elasticity) and carbon nanofibers in this state after being bonded to a portion, the carbon nanos accompany the deformation of the elastomer. The fibers also moved, and the agglomerated carbon nanofibers were separated and dispersed in the elastomer by the restoring force of the elastomer due to the elasticity after shearing.

By improving the dispersibility of carbon nanofibers in the matrix in this way, it has become possible to efficiently use expensive carbon nanofibers as a filler for composite materials.

As for the thermoplastic resin, attempts have been made to produce a thermoplastic resin composition in which carbon nanofibers are composited.

However, in a thermoplastic resin, it is difficult to disperse carbon nanofibers due to elasticity like an elastomer, and many agglomerates of carbon nanofibers remain in the thermoplastic resin composition.

Therefore, as a method for producing a thermoplastic resin composition containing carbon nanofibers, a method has been proposed in which carbon nanofibers are more dispersed by mixing the thermoplastic resin with dispersion particles that promote the dispersion of carbon nanofibers. (See, for example, Patent Document 2).

However, since the carbon nanofibers are uniformly dispersed throughout, although there is a reinforcing effect, agglomerates of carbon nanofibers remain.

Further, carbon nanofibers are uniformly dispersed in the elastomer by utilizing the elasticity of the elastomer to obtain a mixture, and then the mixture is further mixed with a thermoplastic resin and kneaded at a low temperature to disperse the carbon nanofibers. A method for producing a thermoplastic resin composition has been proposed (see, for example, Patent Document 3).

However, although most carbon nanofibers can be defibrated and dispersed in the elastomer, it has been difficult to disperse the carbon nanofibers even in the thermoplastic resin phase.

In recent years, pellets in which carbon nanofibers are blended with a thermoplastic resin have been sold (see, for example, Non-Patent Document 1), but these also still have a large number of agglomerates of carbon nanofibers in the material. Even when ordinary molding was performed using the material, the agglomerates remained in the product almost as they were.

Japanese Unexamined Patent Publication No. 2005-97525 Japanese Unexamined Patent Publication No. 2005-336235 Japanese Unexamined Patent Publication No. 2007-154157

"PLASTICYLTMPP2001" posted on the homepage of Nanocil (Belgium), [Searched on December 11, 2012], Internet <http://www.nanocyl.com/en/Products-Solutions/Products/PLASTICYL-Carbon-Nanotubes -Conductive-Masterbatches ＞

An object of the present invention is to provide a thermoplastic resin composition in which carbon nanofibers are dispersed.

The thermoplastic resin composition according to the present invention is
A thermoplastic resin composition consisting only of polyamide and carbon nanofibers dispersed in the polyamide.
The agglomerates of the carbon nanofibers are absent and
The carbon nanofibers are dispersed throughout in a state of being separated from each other.
The carbon nanofibers have an average diameter of 2 nm or more and 30 nm or less.
Wherein the polyamide 100 parts by weight, the carbon nanofibers 5.0 parts by mass or more, and wherein the Oh Rukoto 50 parts by mass or less.
In the thermoplastic resin composition according to the present invention
With respect to the polyamide 100 parts by weight, the carbon nanofibers 5.0 parts by mass or more, can be not more than 10 parts by mass.

According to the thermoplastic resin composition according to the present invention, since there is no agglomerate of carbon nanofibers, fracture due to stress concentration does not occur in the agglomerate, so that the agglomerate has a high elastic modulus without sacrificing ductility. Can be done.

It is a figure which shows typically the manufacturing method of the thermoplastic resin composition which concerns on one Embodiment. It is a graph which shows the DMA measurement result (the temperature dependence of the storage elastic modulus E') in the samples of Examples 2 and 4 and Comparative Example 1. 6 is an SEM observation photograph 2000 times the frozen fracture surface of the sample of Example 1. 6 is an SEM observation photograph 2000 times the frozen fracture surface of the sample of Example 2. It is an SEM observation photograph of 2000 times the frozen fracture surface of the sample of Reference Example 4. 6 is an SEM observation photograph 2000 times the frozen fracture surface of the sample of Example 4. It is an SEM observation photograph which is 2000 times the frozen fracture surface of the sample of Comparative Example 2. It is a figure which shows typically the manufacturing method of the thermoplastic resin composition by the biaxial kneader. It is a graph which shows the DMA measurement result (the temperature dependence of the storage elastic modulus E') in the sample of Example 5 and Comparative Example 3.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The thermoplastic resin composition according to the embodiment of the present invention is a thermoplastic resin composition consisting only of polyamide and carbon nanofibers dispersed in the polyamide, and does not have agglomerates of the carbon nanofibers. The carbon nanofibers are dispersed throughout in a state of being separated from each other, and the carbon nanofibers have an average diameter of 2 nm or more and 30 nm or less, and the carbon nanofibers are 5 in proportion to 100 parts by mass of the polyamide. 2.0 parts by mass or more, and wherein the Oh Rukoto 50 parts by mass or less.

A. First, a method for producing the thermoplastic resin composition according to the present embodiment will be described.

FIG. 1 is a diagram schematically showing a method for producing a thermoplastic resin composition according to an embodiment.

First, before the low-temperature kneading step, a mixing step of kneading polyamide and carbon nanofibers at a first temperature to obtain a first mixture will be described. In this mixing step, it can be inferred that a material in which carbon nanofibers are previously mixed with polyamide, for example, a commercially available pellet-shaped material is the first mixture produced by this mixing step. In this case, carbon nanofibers are dispersed throughout the first mixture in a state of being agglomerated.

A-1. Mixing Step In the mixing step, polyamide and carbon nanofibers are kneaded at a first temperature to obtain a first mixture.

The mixing step is a step until the planned amount of carbon nanofibers is charged into the polyamide, preferably until the operator visually recognizes that the carbon nanofibers have been mixed in the entire polyamide. It can be a process.

A-1-1. Kneader For the mixing step, for example, a kneader such as an open roll, a closed kneader, an extruder, or an injection molding machine can be used. As the open roll, a known two-roll or three-roll can be used. The closed kneader is a so-called internal mixer, and known Banbury type, kneader type and the like can be used. It is desirable that these kneaders used in the mixing step have a heating device for heating the mixture being processed.

A-1-2. First temperature The first temperature is a temperature higher than the melting point (Tm) of the polyamide. The first temperature can be 25 ° C. or higher higher than the melting point (Tm) of the polyamide. The first temperature can be 25 ° C. or higher and 70 ° C. or lower from the melting point (Tm) of the polyamide, and can be 25 ° C. or higher and 60 ° C. or lower than the melting point (Tm). The first temperature is the actual temperature of the polyamide during the mixing process, not the temperature of the processing equipment. The molding processing temperature of polyamide is generally expressed by the set temperature of the heating cylinder in the case of a processing device such as an extruder or an injection molding machine, but usually, it is actually higher than the set temperature of the processing device due to shear heat generation during kneading. The temperature of the resin becomes high. Since the first temperature in this embodiment is the temperature during processing, it is desirable to measure the actual surface temperature of the resin as much as possible, but if it cannot be measured, the resin immediately after the first mixture is taken out from the processing apparatus. The surface temperature can be measured and used as that temperature. The first temperature is not the temperature immediately after the resin is charged into the processing apparatus, but the temperature when the carbon nanofibers have been charged and mixed.

The first temperature is equal to or higher than the melting point. For example, when polyamide 12 having a melting point of 178 ° C. is used as the polyamide, the temperature can be 178 ° C. or higher, further 203 ° C. or higher, and 203 ° C. to 250 ° C. There can be. Polyamide 12 is a polyamide obtained by ring-opening polycondensation of lauryl lactam. As the commercially available polyamide 12, for example, a polyamide 12 manufactured by EMS-GRIVORY-1 (grade name: Glyramid L25 (“Grillamide” is a registered trademark), melting point 178 ° C. (DSC; ISO11357)) can be used. Further, for example, when a polyamide 66 having a melting point of 265 ° C. is used as the polyamide, the first temperature can be 265 ° C. or higher, further can be 285 ° C. or higher, and is 285 ° C. to 300 ° C. Can be done. Polyamide 66 is a polyamide synthesized by a polycondensation polymerization reaction of hexamethylenediamine and adipic acid. As the commercially available polyamide 66, for example, a polyamide 66 manufactured by Toray Industries, Inc. (grade name: Amylan (“Amylan” is a registered trademark) CM3006, melting point 265 ° C.) can be used.

When processing using an open roll, the first temperature is slightly lower in consideration of the wrapping characteristics around the roll than when processing using a general polyamide molding apparatus, for example, the roll is lowered to a temperature of 20 ° C. or more. It can be carried out by setting the temperature.

It is not common to process polyamide with an open roll, but in the case of an open roll, the viscosity of the polyamide is high due to the peculiarity that the material must be wound around the roll as compared with other processing devices. Machining becomes difficult at temperatures that are too high.

When kneading with an open roll using a polyamide having a melting point of 180 ° C., for example, the roll temperature at the time of winding can be set to 190 ° C. to 220 ° C. As the first temperature, it is sufficient that the polyamide can be melted and carbon nanofibers can be mixed. Therefore, when processing with a closed kneader, an extruder, an injection molding machine, etc., the first temperature is set by the processing device. The surface temperature of the resin can be set when the temperature is 190 ° C. to 250 ° C. When a kneader that can accurately monitor the temperature of the resin being mixed is used, it may be confirmed that the monitored temperature is within a predetermined first temperature range.

A-1--3. Open Roll As shown in FIG. 1, a method of using the two-roll open roll 2 will be described. The first roll 10 and the second roll 20 in the open roll 2 are arranged at a predetermined interval d, for example, an interval of 0.5 mm to 1.5 mm, and rotate forward at rotation speeds V1 and V2 in the directions indicated by arrows. Or it rotates in reverse. The temperature of the first roll 10 and the second roll 20 can be adjusted by, for example, an internally provided heating means, and is set to the first temperature.

As shown in FIG. 1, a plurality of carbon nanofibers 80 can be put into the bank 34 of the resin (polyamide) 30 wound around the first roll 10 and kneaded to obtain the first mixture. In the mixing step, the carbon nanofibers 80 are dispersed in the resin (polyamide) 30, and kneading is performed until, for example, there is no visual unevenness in color. As this kneading step, the same step as general kneading in which a compounding agent (carbon nanofiber or the like) is blended with polyamide can be adopted.

However, in this state, the carbon nanofibers 80 in the first mixture are dispersed and present in the same aggregate as the raw material. Therefore, the first mixture will have defects in its material, and when, for example, a tensile test is performed, the elongation at the time of cutting is significantly lower than that of the raw material polyamide alone.

When a dynamic viscoelasticity test (hereinafter referred to as a DMA test) was performed on this first mixture, it was found that the first mixture behaved differently from the raw material polyamide. The raw material polyamide has a storage elastic modulus (E') that sharply decreases near the melting point and flows. However, in the first mixture in which the carbon nanofibers 80 are mixed, the storage elastic modulus (E') hardly decreases even if the melting point is exceeded by dispersing the carbon nanofibers in a predetermined amount or more, that is, like an elastomer. It was found that a rubber elastic region was developed.

The method for producing a thermoplastic resin composition according to the present invention utilizes a temperature range near the melting point where it does not flow and this rubber elastic region developed at a temperature exceeding the melting point to aggregate carbon nanofibers. The fibers are defibrated to loosen them and dispersed in the polyamide. Therefore, in carrying out the present invention, a DMA test is performed in advance on the sample of the first mixture of the formulation to confirm whether or not the rubber elastic region is expressed, and the temperature region is used for thermoplasticity. A resin composition can be produced.

A-1-4. Biaxial kneader A biaxial kneader 50 as shown in FIG. 8 can be used instead of the open roll. FIG. 8 is a diagram schematically showing a method for producing a thermoplastic resin composition by the twin-screw kneader 50. The twin-screw kneader 50 has two conical (conical) screws 51 and 53, a return flow path 62 formed in the barrel 60, and a switching portion 64. Polyamide and carbon nanofibers are charged from the rear end side (thick side) of the screws 51 and 53, pushed out to the tip side (thin side), pass through the return flow path 62 via the switching portion 64, and return to the rear end side. It is sent and kneaded repeatedly. The switching unit 64 has a mechanism for switching between the return flow path 62 and the flow path for discharging to the outside, and in FIG. 8, a flow path is formed in the return flow path 62 from the tips of the screws 51 and 53. It is desirable that the temperature of the mixture being kneaded inside is measured by, for example, contacting the mixture with a thermocouple protruding from the flow path in the switching unit 64 to measure the actual temperature of the mixture.

Further, the twin-screw kneader 50 is preferably one having excellent accuracy and responsiveness of the processing temperature, and preferably one capable of efficiently releasing the temperature rise due to shearing heat during processing and maintaining the temperature within a desired temperature range. It is preferable that the twin-screw kneader 50 can perform not only temperature rise control by a heater but also forced temperature drop control by air blow or cooling water, for example.

A-2. Low temperature step In the low temperature step, the temperature of the first mixture is adjusted to the second temperature.

Here, the second temperature will be described.

The general machining set temperature in the mixing process, that is, the set temperature of the machining device, is higher than the recommended machining set temperature of the polyamide in order to sufficiently melt the polyamide in a short time and process it quickly. is there. Therefore, polyamide is not processed near its melting point. As described above, the surface temperature of the polyamide during processing is higher than the set processing temperature.

In particular, when a filler such as carbon nanofiber is blended in the polyamide, the processing set temperature is usually higher than the general processing set temperature. Further, when the blending amount of carbon nanofibers is increased, the temperature of the first mixture in the mixing step rises sharply due to heat generated by shearing.

Therefore, in order to carry out the low-temperature kneading step described in A-3 below using the temperature near the melting point and the elastic rubber region described in A-1-3 above, it is necessary to lower the temperature of the first mixture. is there. Since the temperature of the first mixture rises when kneading is performed, it is usually difficult to lower the temperature while continuing kneading. Therefore, in the low temperature step, after kneading, the kneader can be stopped for a predetermined time, or the first mixture can be taken out from the kneader and allowed to cool to the second temperature. Further, the first mixture can be positively cooled by using a cooling device provided with a cooling mechanism such as a fan, a spot cooler, or a chiller. Machining time can be shortened by actively cooling.

The second temperature ranges from a temperature 5 ° C. lower than the melting point (Tm) of the polyamide used in this production method to a temperature less than 25 ° C. higher than the melting point (Tm). Further, the second temperature can range from a temperature 5 ° C. lower than the melting point (Tm) of the polyamide to a temperature 20 ° C. higher than the melting point (Tm), especially from a temperature 5 ° C. lower than the melting point (Tm). It can be in the range up to a temperature 5 ° C. higher than the melting point (Tm).

From the results of the DMA test, the second temperature is a temperature near the melting point (Tm) of the processable polyamide and is in a temperature range in which it does not flow, and indicates the rubber elastic region in the DMA test of the first mixture. It is preferable to include the temperature range, but it is difficult to measure the internal temperature of the first mixture during processing. Therefore, as described in A-3 below, the second temperature is the surface temperature of the resin. Therefore, the second temperature includes a temperature slightly lower than the temperature range indicating the rubber elastic region. That is, this is to set the second temperature, which is the surface temperature of the resin, so that the internal temperature of the first mixture during processing is in the temperature range indicating the rubber elastic region. In the case of polyamide, processing is possible up to a range where the second temperature is lower than the rubber elastic region, for example, 5 ° C. lower than the melting point (Tm) .

The rubber elastic region is a flat region when a graph of temperature-storage elastic modulus is created for the DMA test result. The elastic modulus reduction rate in the flat region can be 0.005 MPa / ° C. to 0.1 MPa / ° C., and further can be 0.01 MPa / ° C. to 0.05 MPa / ° C.

At this second temperature, the carbon nanofibers can be moved by utilizing the elastic restoring force of the polyamide. The second temperature is a temperature that is not adopted as a general processing temperature of polyamide, and in particular, is a low temperature range that has not been adopted as a processing temperature of the first mixture.

If the second temperature is 25 ° C. or higher than the melting point (Tm), it is considered that the agglomerates of carbon nanofibers cannot be loosened in the low temperature kneading step. When a polyamide 12 having a melting point of 178 ° C. is used as the polyamide, the second temperature can be 173 ° C. or higher and lower than 203 ° C., and further can be 173 ° C. or higher and 198 ° C. or lower, particularly 173 ° C. or higher. , 183 ° C or lower. Further, for example, when a polyamide 66 having a melting point of 265 ° C. is used as the polyamide, the second temperature can be 260 ° C. or higher and lower than 290 ° C., and further can be 260 ° C. or higher and 285 ° C. or lower, particularly 260 ° C. It can be ℃ or more and 275 ℃ or less.

In the present invention, the "melting point (Tm)" refers to a value measured according to JIS K7121 using differential scanning calorimetry (DSC).

The first mixture, whose temperature has dropped to the second temperature, can be placed in an oven set to the second temperature, for example, and maintained at a predetermined temperature within the range of the second temperature. The temperature of the first mixture taken out from the kneader is lowered, so that the processing quality is stabilized.

Further, when a pellet containing commercially available carbon nanofibers is used as the first mixture, a reheating step is required between the mixing step and the low temperature step. The reheating step can be performed by heating above the melting temperature of the polyamide.

A-3. Low temperature kneading step In the low temperature kneading step, the first mixture is kneaded at the second temperature.

As the first mixture, the one obtained by the mixing step of A-1 can be used.

In the step of kneading the first mixture at the second temperature in the low temperature kneading step, an apparatus for melting and molding the polyamide, for example, an open roll, a closed kneader, an extruder, an injection molding machine, etc. is used. Can be done. Similar to the mixing step, a method using the open roll 2 as shown in FIG. 1 will be described. A biaxial kneader 50 as shown in FIG. 8 may be used.

In this step, the roll spacing d between the first roll 10 and the second roll 20 is set to, for example, 0.5 mm or less, more preferably 0 mm to 0.5 mm, and the first roll obtained in the mixing step is obtained. The mixture of the above can be put into the open roll 2 and kneaded.

Assuming that the surface velocity of the first roll 10 is V1 and the surface velocity of the second roll 20 is V2, the surface velocity ratio (V1 / V2) of both in this step is 1.05 to 3.00. It can be 1.05 to 1.2. By using such a surface velocity ratio, a desired high shearing force can be obtained. Since the first mixture extruded from such a narrow roll has a second temperature in a temperature range having an appropriate elasticity and an appropriate viscosity, the restoring force due to the elasticity of the polyamide is obtained. The carbon nanofibers can move greatly with the deformation of the polyamide at that time.

The second temperature is the surface temperature of the first mixture in the low temperature kneading step, not the set temperature of the processing apparatus. As explained in the first temperature, it is desirable to measure the actual surface temperature of the resin as much as possible in the second temperature, but if it cannot be measured, the surface temperature of the resin immediately after the thermoplastic resin composition is taken out from the processing apparatus is measured. It can be measured and used as the second temperature during processing from that temperature.

In the case of the open roll 2, as shown in FIG. 1, the surface temperature of the first mixture wound around the first roll 10 can be measured using a non-contact thermometer 40. The non-contact thermometer 40 may be arranged at a position other than the position immediately after passing through the nip, and is preferably above the first roll 10. Immediately after passing through the nip, the temperature of the first mixture changes rapidly and is an unstable temperature, so it is desirable to avoid it.

Further, when the surface temperature of the first mixture in the low temperature kneading step cannot be measured as in a closed kneader or an extruder, the thermoplastic resin composition immediately after being kneaded and taken out from the apparatus. It is possible to measure the surface temperature and confirm that it is within the range of the second temperature. In the case of the biaxial kneader 50 as shown in FIG. 8, it is desirable to measure the actual temperature of the mixture by, for example, a temperature sensor using a thermocouple provided in the flow path of the switching unit 64.

The low temperature kneading step can be, for example, 4 minutes to 20 minutes, and further 5 minutes to 20 minutes at the second temperature. By taking a sufficient kneading time at the second temperature, defibration of carbon nanofibers can be carried out more reliably.

The processability of the first mixture is lowered due to the inclusion of carbon nanofibers, and the temperature of the first mixture becomes even higher than the set temperature of the apparatus due to the shear heat generated by kneading the first mixture. Therefore, in order to maintain the surface temperature of the first mixture in the second temperature range suitable for the low temperature kneading step, if it is an open roll, the temperature of the roll is adjusted so that the temperature of the first mixture does not rise. The temperature must be adjusted so that it cools positively. This also applies to a closed kneader, an extruder, an injection molding machine, etc., and the surface temperature of the first mixture is kept constant in the second temperature range by adjusting the processing set temperature of the device so as to be positively cooled. Time can be maintained. For example, in an extruder, the set temperature of the heating cylinder is set to a temperature higher than the general processing temperature in the vicinity of supplying the material, the other zones are set to a temperature lower than the second temperature, and the resin being processed. The surface temperature of the can be adjusted to be the second temperature.

The thermoplastic resin composition obtained by the low-temperature kneading step can be put into a mold and press-processed, or is further processed into pellets using an extruder, for example, and is known. It can be formed into a desired shape by using a polyamide processing method.

Due to the shearing force obtained in the low-temperature kneading process, a high shearing force acts on the polyamide, and the aggregated carbon nanofibers are separated from each other so as to be pulled out one by one into the polyamide molecules, and are defibrated in the polyamide. Is distributed to. In particular, since polyamide has elasticity and viscosity in the second temperature range, carbon nanofibers can be defibrated and dispersed. Then, it is possible to obtain a thermoplastic resin composition having excellent dispersibility and dispersion stability of the carbon nanofibers (the carbon nanofibers are less likely to reaggregate).

In the method for producing a thermoplastic resin composition, the average diameter of carbon nanofibers can be 2 nm or more and 30 nm or less, and in that case, the first mixture is the blending amount of carbon nanofibers with respect to 100 parts by mass of polyamide. Can be 0.1 parts by mass or more and 50 parts by mass or less. In the case of carbon nanofibers having an average diameter of 2 nm or more and 30 nm or less, when the blending amount of carbon nanofibers with respect to 100 parts by mass of polyamide is 0.1 parts by mass or more, effects such as reinforcement by carbon nanofibers can be obtained. Further, if the blending amount of carbon nanofibers with respect to 100 parts by mass of polyamide exceeds 50 parts by mass, processing in the low temperature kneading step becomes difficult.

Further, in the first mixture, the blending amount of carbon nanofibers with respect to 100 parts by mass of polyamide can be 0.5 parts by mass or more and 20 parts by mass or less.

The average diameter of the carbon nanofibers can 9nm or more, under 30nm or less. When the average diameter of the carbon nanofibers is 9 nm or more and 30 nm or less, the first mixture can have 8 parts by mass or more and 50 parts by mass or less of carbon nanofibers with respect to 100 parts by mass of polyamide. When 8 parts by mass or more of relatively thin carbon nanofibers having an average diameter of 9 nm or more and 30 nm or less are blended, a rubber elastic region can be developed above the melting point (Tm) in the DMA test of the first mixture, and a relatively wide temperature can be developed. The low temperature kneading process can be performed in the range. In that case, the temperature range of the second temperature is a range from a temperature 5 ° C. lower than the melting point (Tm) of the polyamide to a temperature less than 25 ° C. higher than the melting point (Tm).

When the average diameter of the carbon nanofibers is 9 nm or more and 30 nm or less, the first mixture has 0.1 parts by mass or more and less than 8 parts by mass of carbon nanofibers with respect to 100 parts by mass of the polyamide. The two temperatures can range from a temperature 5 ° C. lower than the melting point (Tm) of the polyamide to a temperature 5 ° C. higher than the melting point (Tm). When relatively fine carbon nanofibers having an average diameter of 9 nm or more and 30 nm or less are blended in an amount of 0.1 part by mass or more and less than 8 parts by mass, the rubber elastic region does not appear above the melting point (Tm) in the DMA test of the first mixture. Therefore, the temperature range of the second temperature can be the temperature before the first mixture flows in the DMA test, from a temperature 5 ° C. lower than the melting point (Tm) of the polyamide to a temperature 5 ° C. higher than the melting point (Tm). Can be in the range up to.

According to the method for producing a thermoplastic resin composition according to the present embodiment, carbon nanofibers existing as agglomerates in the polyamide can be dispersed in a state of being separated from each other. Therefore, the thermoplastic resin composition obtained by the method for producing the thermoplastic resin composition does not have agglomerates of carbon nanofibers, so that the agglomerates do not cause fracture due to stress concentration, and thus the ductility is sacrificed. It is possible to have a high elastic modulus without doing so.

A-4. Second low-temperature kneading step In the method for producing the thermoplastic resin composition, the polyamide in the first mixture is the first polyamide, and the second polyamide is further added to the second mixture obtained in the low-temperature kneading step. A second low temperature kneading step of kneading at a third temperature to obtain a third mixture can be further included.

The second polyamide can be the same type of polyamide as the first polyamide. Here, the same type of polyamide means that the second polyamide and the first polyamide have at least the same main constituent monomer.

The third temperature can be in the same temperature range as the second temperature described in A-2.

As described in A-3 above, when the amount of carbon nanofibers blended in the first mixture is small or the carbon nanofibers are thick, the rubber elastic region in the DMA test in the first mixture does not appear. There is. In such a first mixture, since the second temperature of the low temperature kneading step is set within a narrow temperature range near the melting point, the difficulty of processing increases. Therefore, when it is desired to process a thermoplastic resin composition containing a relatively small amount of carbon nanofibers, an arbitrary amount of the second polyamide can be added by carrying out the second low-temperature kneading step in this way. Therefore, the content of carbon nanofibers in the thermoplastic resin composition can be reduced.

B. Raw Materials Next, the raw materials used in the production method of the present embodiment will be described.

B-1. Polyamide Polyamides include, for example, polyamide 6 (polycaprolamide, polycaprolactam), polyamide 66 (polyhexamethylene adipamide), polyamide 12 (polylaurolactam), polyamide MXD6 (polymethoxylylen adipamide), and the like. be able to.

B-2. Carbon nanofibers Carbon nanofiber is mean diameter (fiber diameter) of 30 nm or less than 2 nm, can be particularly 30nm hereinafter more 9 nm.

Since carbon nanofibers have a small average diameter and a large specific surface area, if carbon nanofibers can be defibrated and dispersed throughout, the polyamide can be effectively reinforced with a small amount of carbon nanofibers. .. Polyamide can be reinforced by using carbon nanofibers having an average diameter (fiber diameter) of 2 nm or more and 30 nm or less.

Carbon nanofibers can also be, for example, oxidized to improve their reactivity with polyamide on their surface.

In the detailed description of the present invention, the average diameter and the average length of the carbon nanofibers are 200 or more diameters from, for example, 5,000 times imaging with an electron microscope (the magnification can be appropriately changed depending on the size of the carbon nanofibers). And the length can be measured and calculated as the arithmetic mean value.

The blending amount of the carbon nanofibers in the thermoplastic resin composition can be appropriately blended according to the desired properties.

In particular, by using the second low-temperature kneading step described in A-4 above, less than 0.1 part by mass of carbon nanofibers can be blended with respect to 100 parts by mass of polyamide.

Further, in the thermoplastic resin composition, in addition to carbon nanofibers, a filler generally used for processing the thermoplastic resin composition or the like can be used together.

Here, "parts by mass" indicates "phr" unless otherwise specified, and "phr" is an abbreviation for parts per undred of resin or rubber, and is an abbreviation for external parts such as additives for rubber and thermoplastic resins. It represents a percentage.

The carbon nanofiber can be a so-called multi-walled carbon nanotube (MWNT: multi-wall carbon nanotube) having a shape in which one single surface (graphene sheet) of graphite having a carbon hexagonal mesh surface is wound to form a tubular shape.

The following carbon nanofibers 30nm average diameter of 9nm or more, for example, as possible out and the like Bayer MaterialScience by tubes (Baytubes) C150P and C70P and Nanoshiru (Nanocyl) Co. NC-7000.

Further, a carbon material having a structure of partially carbon nanotubes can also be used. In addition to the name carbon nanotube, it may be referred to as graphite fibril nanotube or vapor-grown carbon fiber.

Carbon nanofibers can be obtained by the vapor phase growth method. The vapor phase growth method is also called a catalytic vapor deposition method (CCVD), and is a method for producing carbon nanofibers by pyrolyzing a gas such as a hydrocarbon in the presence of a metal-based catalyst. is there. To explain the vapor phase growth method in more detail, for example, an organic compound such as benzene or toluene is used as a raw material, an organic transition metal compound such as ferrocene or nickel sen is used as a metal catalyst, and these are used together with a carrier gas at a high temperature such as 400 ° C. Floating Reaction Method, which is introduced into a reaction reactor set to a reaction temperature of 1000 ° C. or lower to generate carbon nanofibers in a floating state or on the reaction reactor wall, or on ceramics such as alumina and magnesium oxide in advance. A catalyst-supported reaction method (Substrate Reaction Method) or the like in which carbon nanofibers are produced on a substrate by contacting the metal-containing particles carried on the surface with a carbon-containing compound at a high temperature can be used.

The following carbon nanofibers 30nm average diameter 9nm or more as possible out to obtain the catalyst carrying reaction method.

The diameter of the carbon nanofibers can be adjusted by, for example, the size of the metal-containing particles and the reaction time. Carbon nanofibers having an average diameter of 9 nm or more and 30 nm or less can have a nitrogen adsorption specific surface area of 10 m ² / g or more and 500 m ² / g or less, and further can be 100 m ² / g or more and 350 m ² / g or less. In particular, ^{it can be 150 m 2} / g or more and 300 m ² / g or less.

C. Thermoplastic resin composition Finally, the thermoplastic resin composition obtained by the present embodiment will be described.

The thermoplastic resin composition according to the present embodiment is a thermoplastic resin composition consisting only of a polyamide and carbon nanofibers dispersed in the polyamide, and the carbon nanofibers do not have agglomerates and the carbon The nanofibers are dispersed throughout in a state of being separated from each other, and the carbon nanofibers have an average diameter of 2 nm or more and 30 nm or less, and the carbon nanofibers have 5.0 mass by mass with respect to 100 parts by mass of the polyamide. It is characterized in that it is not less than 50 parts by mass.

The absence of agglomerates of carbon nanofibers in the thermoplastic resin composition can be confirmed by observing any cross section of the thermoplastic resin composition with an electron microscope. In the electron micrograph, carbon nanofibers that have been defibrated and separated from each other appear dispersed in the fractured surface.

It should be noted that the agglomerates are hollow in which carbon nanofibers are entangled with each other like a raw material even in a thermoplastic resin composition, and particularly in the agglomerates, no resin has entered between the carbon nanofibers. There are many parts. The absence of such agglomerates means that the agglomerated carbon nanofibers are loosened and the carbon nanofibers are dispersed throughout in a state of being separated from each other. The state of being separated from each other means that there is no hollow portion between the carbon nanofibers in the thermoplastic resin composition.

According to the thermoplastic resin composition according to the present embodiment, since there is no agglomerate of carbon nanofibers, fracture due to stress concentration in the agglomerate does not occur, so that high elasticity is not sacrificed in ductility. Can have a rate.

In the thermoplastic resin composition, when the average diameter of carbon nanofibers is 2 nm or more and 30 nm or less, the amount of carbon nanofibers is 5.0 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of polyamide. Further, the thermoplastic resin composition may contain 5.0 parts by mass or more and 10 parts by mass or less of carbon nanofibers having an average diameter of 2 nm or more and 30 nm or less with respect to 100 parts by mass of polyamide.

The thermoplastic resin composition produced by using the second low-temperature kneading step of A-3 is heated by further adding polyamide using the thermoplastic resin composition in which carbon nanofibers are already dispersed as a master batch. The blending ratio of carbon nanofibers in the plastic resin composition can be reduced. Therefore, for example, the amount of carbon nanofibers can be less than 0.1 parts by mass with respect to 100 parts by mass of polyamide. In that case, the thermoplastic resin composition may contain 0.01 parts by mass or more and less than 0.1 parts by mass of carbon nanofibers with respect to 100 parts by mass of polyamide.

Further, even a thermoplastic resin composition containing 0.01 parts by mass or more and less than 8 parts by mass of carbon nanofibers having an average diameter of 9 nm or more and 30 nm or less is relatively easy to use by using the second low-temperature kneading step. Carbon nanofibers can be dispersed in a deflated state.

The thermoplastic resin composition has high yield stress, high rigidity, and excellent heat resistance. Further, as the thermoplastic resin composition, for example, a fuel tube for an automobile, a muffling gear, or the like can be molded by using injection molding or extrusion molding of a general thermoplastic resin.

As described above, the embodiments of the present invention have been described in detail, but those skilled in the art can easily understand that many modifications that do not substantially deviate from the novel matters and effects of the present invention are possible. Therefore, all such modifications are within the scope of the present invention.

Examples of the present invention will be described below, but the present invention is not limited thereto.

(A1) Test using open roll (A1-1) Preparation of samples of Examples 1 to 4 and Reference Examples 1 to 5 Mixing step: Open roll with a roll diameter of 3 inches (roll temperature 190 ° C = processing set temperature) 100 parts by mass (phr) of the polyamide shown in each table was added, melted, and wound around a roll. The temperature of the surface of the polyamide fabric at this time was 190 ° C. As the open roll, a heat roll capable of heating the roll was used.

Next, multi-walled carbon nanofibers (described as "CNT-1", "CNT-2", and "CNT-3" in each table) having parts by mass (phr) shown in Tables 1 to 4 were added as a compounding agent. .. At this time, the roll surface velocity ratio was set to 1: 1.1 to 1: 1.5, and the roll gap was set to 1.5 mm. Thorough kneading was performed to disperse the multilayer carbon nanofibers, and the first mixture was removed from the open roll. The surface temperature (first temperature) of the dough in the mixing step increased from 190 ° C. to 210 ° C. The surface temperature of the dough temperature was measured with a non-contact infrared thermometer.

Low temperature step: The first mixture was removed from the open roll, allowed to cool until the surface temperature of the first mixture reached 180 ° C., and the first mixture was placed in an oven and maintained at 180 ° C.

Low temperature kneading step: The first mixture was put into the open roll again, and kneading was performed with the roll gap narrowed from 1.5 mm to 0.3 mm. If necessary, the roll interval is 0.3 mm.
The cutback was performed while changing the range between ~ 1.5 mm. During this kneading, the roll is rolled so that the dough surface temperature (second temperature) of the first mixture is measured with a non-contact infrared thermometer and maintained at around 180 ° C (175 ° C to 185 ° C). The temperature was adjusted. In particular, in Examples 1 and 3 and Reference Examples 1 to 5 , the temperature of the roll was adjusted so that the temperature of the dough surface (second temperature) of the first mixture did not exceed 180 ° C. After sufficient kneading, the roll gap was changed from 0.3 mm to 1.5 mm, and the thermoplastic resin composition was taken out from the open roll.

Pressing process: The thermoplastic resin composition taken out from the open roll was placed in a mold and pressure-molded under vacuum to prepare a sample. In vacuum pressure molding, the mold is heated to 220 ° C to 230 ° C, preheated for 2 minutes with no load, and then press-molded for 2 minutes while pressurizing (relative to the mold), and the mold is used as a cooling press. It was moved and cooled to room temperature while pressurizing (relative to the mold) to obtain a sheet-like sample having a thickness of 0.3 mm to 0.5 mm.

In each table, "CNT-1" is a multi-layer carbon nanotube (Nanocyl) having an average diameter of 10 nm (the value obtained by arithmetically averaging the measured values of 200 or more locations using the imaging of a scanning electron microscope, and the same applies hereinafter). "CNT-2" is a multilayer carbon nanotube (manufactured by Hodoya Chemical Industry Co., Ltd., grade name: NT-7B) with an average diameter of 68 nm, and "CNT-3" is an average diameter. It is a 10 nm multilayer carbon nanotube (manufactured by SouthWest NanoTechnologies, grade name: SWeNT A), and “PA” is polyamide 12 manufactured by EMS-GRIVORY-1 (grade name: Grillamid L25 (“Grilamid” is a registered trademark), melting point. It was 178 ° C. (DSC; ISO11357)).

(A1-2) Preparation of Samples of Comparative Examples 1 and 2 Since Comparative Example 1 is a simple substance of polyamide, resin pellets were put into a mold and a pressing step was performed to obtain a sample of a thermoplastic resin composition.

In Comparative Example 2, the second temperature in the low-temperature kneading step in Example 1 was adjusted to 210 ° C., and a sample of the thermoplastic resin composition was obtained in the same manner as in the other examples.

(A2) Tensile test For the samples of Examples, Reference Examples and Comparative Examples, the test pieces punched into the dumbbell shape of JIS No. 7 were subjected to a tensile tester of Autograph AG-X manufactured by Shimadzu Corporation at 23 ± 2 ° C. , Standard line distance 10 mm, tensile speed 50 mm / min, tensile test based on JIS K7127, tensile strength (TS (MPa)), elongation at cutting (Eb (%)), yield point tensile stress (σy (σy) MPa)) and 100% modulus (σ100 (MPa)) were measured. The measurement results are shown in Tables 1 to 4.

(A3) DMA measurement For the samples of Examples, Reference Examples and Comparative Examples, the test pieces cut into strips (30 × 10 × 0.3 mm) were used with a dynamic viscoelasticity tester DMS6100 manufactured by SII. A DMA test (dynamic viscoelasticity test) was performed based on JIS K7244 at a distance between chucks of 10 mm, a measurement temperature of 20 to 300 ° C., a temperature rise pace of 1.5 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz.

From this test result, the storage elastic modulus (E') and loss tangent (tan δ) at measurement temperatures of 50 ° C., 100 ° C., 150 ° C., 173 ° C., 178 ° C., 183 ° C., 200 ° C., and 250 ° C. were measured, and Table 1 ~ Shown in Table 4. In Tables 1 to 4, the storage elastic moduli are "E'(50 ° C.) (MPa)", "E'(100 ° C.) (MPa)", "E'(150 ° C.) (MPa)", and "E'. (173 ° C) (MPa) ","E'(178 ° C) (MPa) ","E'(183 ° C) (MPa)
) ”,“ E ′ (200 ℃) (MPa) ”,“ E ′ (250 ℃) (MPa) ”,“ tan δ (50 ℃) (MPa) ”, and the loss tangent is“ tan δ (100 ℃) ”, It is shown as "tan δ (150 ° C.)", "tan δ (200 ° C.)", and "tan δ (250 ° C.)". In addition, the flow start temperature in the DMA test (described as "flow temperature" in each table) is also described in each table. In each table, the sample that did not flow up to 250 ° C. was described as "not flowing".

Further, the measurement result is shown in FIG. 2 as a graph showing the temperature dependence of the storage elastic modulus E'.

In FIG. 2, curves E3 and E9 correspond to Examples 2 and 4 , respectively, and curve C1 corresponds to Comparative Example 1.

According to the results of the tensile test in Tables 1 to 4, the following was found.

1. 1. In the thermoplastic resin composition samples of Examples 1 and 2 and Reference Example 1, the yield point tensile stress (σy) was improved, although the elongation at cutting (Eb) was lower than that of Comparative Example 1.

2. The thermoplastic resin composition sample of ginseng Reference Example 2-4, while maintaining the value elongation at break (Eb) is higher than that of Comparative Example 1, the yield tensile stress (.sigma.y) and 100% modulus (Shiguma100 ) Has improved.

3. 3. Further, the thermoplastic resin composition samples of Examples 3 and 4 and Reference Example 5 have a yield point tensile stress (σy) and 100% modulus while maintaining a high value of elongation at cutting (Eb) as compared with Comparative Example 1. (Σ100) was improved.

4. In Comparative Example 2, the fracture occurred before yielding, and both the tensile strength (TS) and the elongation at cutting (Eb) were greatly reduced. Since the defibration of the carbon nanofibers was insufficient, it is considered that the carbon nanofibers that remained agglomerated became the starting point of fracture.

According to the results of the DMA test in Tables 1 to 4 and FIG. 2, the thermoplastic resin composition samples of Examples 1 to 4 and Reference Examples 1 to 5 have a storage elastic modulus as the amount of carbon nanofibers added increases. The rate (E') has improved. The thermoplastic resin composition sample of Comparative Example 1 had a storage elastic modulus (E') of 28.6 MPa even at 183 ° C, which is 5 ° C higher than the melting point. In the thermoplastic resin composition samples of Examples 1 to 4 and Reference Examples 1 to 5 , the storage elastic modulus (E') at 50 ° C. to 150 ° C. was significantly improved as compared with Comparative Example 1. In particular, the storage elastic modulus (E') was significantly improved in Examples 1 to 4 and Reference Examples 1 and 5 using carbon nanofibers having a small average diameter. Example 1
The thermoplastic resin composition samples of Nos. 4 and Reference Examples 1 and 5 had a storage elastic modulus of 5.0 MPa or more at 173 ° C. to 183 ° C. near the melting point (Tm). Further, the thermoplastic resin composition samples of Examples 2 and 4 did not flow up to 250 ° C., which is the upper limit of the measurement temperature. As shown in FIG. 2, the thermoplastic resin composition samples of Examples 2 and 4 showed a flat region in which the storage elastic modulus (E') did not decrease even after the melting point. The elastic modulus reduction rate in this flat region was 0.023 MPa / ° C.

(A4) SEM Observation The frozen fracture sections of the samples of Examples 1, 2 and 4 , the sample of Reference Example 4 and the sample of Comparative Example 2 were observed with a scanning electron microscope (hereinafter referred to as “SEM”).

FIG. 3 is an SEM observation photograph of a frozen split cross section (2000 times) of the sample of Example 1. No agglomerates of carbon nanofibers could be confirmed on the frozen fracture surface of the sample of Example 1.

FIG. 4 is an SEM observation photograph of the frozen split cross section (2000 times) of the sample of Example 2, and FIG. 5 is an SEM observation photograph of the frozen split cross section (2000 times) of the sample of Reference Example 4. FIG. 6 is an SEM observation photograph of a frozen split cross section (2000 times) of the sample of Example 4. No agglomerates of carbon nanofibers could be confirmed in the frozen split cross sections of the samples of Examples 2 and 4 and the sample of Reference Example 4. Although the SEM observation photograph is not shown here, agglomerates of carbon nanofibers can be confirmed in the frozen split cross section in Examples 3 and Reference Examples 1 to 5 as in Examples 1, 2, 4 and Reference Example 4. There wasn't.

FIG. 7 is an SEM observation photograph of a frozen split cross section (2000 times) of the sample of Comparative Example 2. A large number of carbon nanofiber agglomerates were confirmed on the frozen fracture surface of the sample of Comparative Example 2, and carbon nanofiber agglomerates could be observed in the black circles in FIG. 7. The maximum diameter of the agglomerates in FIG. 7 was about 50 μm.

Examples 5 and 6, Reference Example 6 and Comparative Examples 3 and 4 using the polyamide 66 as the polyamide will be described below.

(B1) Test using a twin-screw kneader (B1-1) Preparation of sample of Reference Example 6 Mixing step: 100 parts by mass using a desktop twin-screw kneader MC15 manufactured by Xplore with a barrel set temperature of 295 ° C. Polyamide pellets of (phr) and carbon nanofibers of parts by mass (phr) shown in Table 5 were added, melted, and sufficiently kneaded. At this time, the temperature of the surface of the polyamide dough was 285 ° C., the kneading time was 3 minutes, the rotation speed of the screw was 90 rpm, and the stress during processing was 4000 N to 6000 N.

Low temperature kneading step: The barrel set temperature was set to 280 ° C., and the barrel was cooled to 280 ° C. by cooling with an air blow. The cooling time was 3 minutes. Kneading was performed at this temperature. At this time, the actual temperature of the first mixture was 260 ° C., the kneading time was 8 minutes, the rotation speed of the screw was 90 rpm, and the stress during processing was 5000 N to 8000 N. The actual temperature during processing of the first mixture was measured using a thermocouple in contact with the mixture at the switching section in the barrel. After sufficient kneading, the temperature was raised to 285 ° C. to extrude the strands, and the strands were extruded and cut to a predetermined length to obtain pellets of the thermoplastic resin composition from a twin-screw kneader.

Injection molding process: The thermoplastic resin composition pellets taken out from the twin-screw kneader are put into the injection molding machine and melted at 285 ° C. to form a flat plate of 50 mm × 50 mm × thickness 1 mm and JIS K7113 No. 1 1/2 dumbbell. Was injection molded.

In Example 5 , the mixing step was carried out in the same manner as in Reference Example 6 , the barrel set temperature was set to 297 ° C., and the low temperature kneading step was carried out in the same manner as in Reference Example 6. At that time, the resin temperature was 287 ° C., the kneading time was 3 minutes, the rotation speed of the screw was 90 rpm, and the stress during processing was 5000 N to 7000 N. The low temperature kneading step was set in the same manner as in Reference Example 6, and the stress during processing was 6000 N to 9000 N. Further, the temperature was raised to 287 ° C. in order to extrude the strands, and the strands were taken out from the twin-screw kneader.

In Example 6 , the mixing step was carried out in the same manner as in Reference Example 6 , the barrel set temperature was set to 297 ° C., and the low temperature kneading step was carried out in the same manner as in Reference Example 6. At that time, the resin temperature was 287 ° C., the kneading time was 3 minutes, the rotation speed of the screw was 90 rpm, and the stress during processing was 7000 N to 9200 N. In the low temperature kneading step, the barrel temperature was set to 282 ° C., and the stress during processing was 8000 N to 9400 N. Further, the temperature was raised to 287 ° C. in order to extrude the strands, and the strands were taken out from the twin-screw kneader.

In Tables 5 and 6, "CNT-4" is a multi-layer with an average diameter of 12.5 nm (the value obtained by arithmetically averaging the measured values of 200 or more points using the imaging of a scanning electron microscope, and the same applies hereinafter). It is a carbon nanotube (manufactured by KUMHO, grade name: K-Nanos-100T), and "PA" is a polyamide 66 manufactured by Toray Co., Ltd. (grade name: Amylan ("Amylan" is a registered trademark) CM3006, melting point 265 ° C. (catalog value). ))Met.

(B1-2) Preparation of Samples of Comparative Examples 3 and 4 Since Comparative Example 3 is a single polyamide 66, the injection molding step is performed by omitting the low temperature lowering step and the low temperature kneading step in the above (B1-1) to heat. A sample of the plastic resin composition was obtained.

In Comparative Example 4, the second temperature in the low-temperature kneading step in Example 5 was adjusted to 289 ° C., and a sample of the thermoplastic resin composition was obtained in the same manner as in Example 5 except for the above.

(B2) Tensile test For the samples of Examples, Reference Examples and Comparative Examples, the injection-molded JIS No. 1 1/2 dumbbell test piece was 23 ± using the Shimadzu Autograph AG-X tensile tester. Tensile tests were conducted based on JIS K7127 at 2 ° C., standard line distance 25 mm, and tensile speed 50 mm / min. Tensile strength (TS (MPa)), elongation during cutting (Eb (%)), and yield point tensile stress ( σy (MPa)) was measured. The measurement results are shown in Tables 5 and 6.

(B3) DMA measurement For the samples of Examples, Reference Examples and Comparative Examples, the test pieces cut into strips (40 × 10 × thickness 1 mm) were used with a dynamic viscoelasticity tester DMS6100 manufactured by SII. A DMA test (dynamic viscoelasticity test) was performed based on JIS K7244 at a distance between chucks of 20 mm, a measurement temperature of 20 to 380 ° C., a temperature rise pace of 1.5 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz.

From this test result, the storage elastic modulus (E') at the measurement temperature of 50 ° C., 100 ° C., 150 ° C., 200 ° C., 250 ° C., 255 ° C., 280 ° C. and the loss tangent (tan δ) at the peak at 100 ° C., 200 ° C. , Tables 5 and 6. In Tables 5 and 6, the storage elastic moduli are "E'(50 ° C.) (MPa)", "E'(100 ° C.) (MPa)", "E'(150 ° C.) (MPa)", and "E'(. It is shown as "200 ° C.) (MPa)", "E'(250 ° C.) (MPa)", "E'(255 ° C.) (MPa)", "E'(280 ° C.) (MPa)", and the loss tangent is It is shown as "tan δ (peak value)", "tan δ (100 ° C.)", and "tan δ (200 ° C.)". In addition, the flow start temperature in the DMA test (described as "flow temperature" in each table) is also described in each table. In each table, the sample that did not flow up to 380 ° C. was described as "not flowing".

Further, the measurement result is shown in FIG. 9 as a graph showing the temperature dependence of the storage elastic modulus E'.

In FIG. 9, the curve E11 corresponds to Example 5 , and the curve C3 corresponds to Comparative Example 3.

According to the results of the tensile tests in Tables 5 and 6, the following was found.

1. 1. The thermoplastic resin composition samples of Examples 5 and 6 and Reference Example 6 have lower elongation at cutting (Eb) than Comparative Example 3, but have improved tensile strength (TS) and yield point tensile stress (σy). did.

2. In Comparative Example 4, the fracture occurred before yielding, and both the tensile strength (TS) and the elongation at cutting (Eb) were greatly reduced. Since the defibration of the carbon nanofibers was insufficient, it is considered that the carbon nanofibers that remained agglomerated became the starting point of fracture.

According to the results of the DMA test in Tables 5 and 6 , the thermoplastic resin composition samples of Examples 5 and 6 and Reference Example 6 had a storage elastic modulus (E') as the amount of carbon nanofiber added increased. Improved. In the thermoplastic resin composition samples of Examples 5 and 6 and Reference Example 6 , the storage elastic modulus (E') at 50 ° C. to 255 ° C. was significantly improved as compared with Comparative Example 1. Further, the thermoplastic resin composition sample of Example 6 did not flow up to 280 ° C., which is the upper limit of the measurement temperature. As shown in FIG. 9, the thermoplastic resin composition sample of Example 6 showed a flat region in which the storage elastic modulus (E') did not decrease even after the melting point. The elastic modulus reduction rate in this flat region was 0.03 MPa / ° C.

(B4) SEM Observation The frozen fracture sections of the samples of Examples 5 and 6 and Reference Example 6 and the sample of Comparative Example 4 were observed with a scanning electron microscope (hereinafter referred to as “SEM”). In the SEM observation of the frozen split cross section (2000 times) of the samples of Examples 5 and 6 and Reference Example 6, no agglomerates of carbon nanofibers could be confirmed. A large number of agglomerates of carbon nanofibers were confirmed by SEM observation of the frozen fracture surface (2000 times) of the sample of Comparative Example 4.

2 open rolls, 10 first rolls, 20 second rolls, 30 resin (polyamide), 34 banks, 40 non-contact thermometers, 50 twin-screw kneaders, 51, 53 screws, 60 barrels, 62 return channels, 64 Switching part, 80 carbon nanofiber, d
Interval, V1, V2 Rotation speed, C1, C3 Comparative Examples 1, 3, E3, E9, E11 Examples 2, 4, 5

Claims (2)

A thermoplastic resin composition consisting only of polyamide and carbon nanofibers dispersed in the polyamide.
The agglomerates of the carbon nanofibers are absent and
The carbon nanofibers are dispersed throughout in a state of being separated from each other.
The carbon nanofibers have an average diameter of 2 nm or more and 30 nm or less.
Wherein the polyamide 100 parts by weight, the carbon nanofibers 5.0 parts by mass or more and 50 parts by mass or less, the thermoplastic resin composition. In claim 1,
With respect to the polyamide 100 parts by weight, the carbon nanofibers 5.0 parts by mass or more and 10 parts by mass or less, the thermoplastic resin composition.

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