JP5798136B2 - Method for producing thermoplastic resin composition and thermoplastic resin composition - Google Patents

Description

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

  According to the method for producing a carbon fiber composite material previously proposed by the present inventors, the use of an elastomer improves the dispersibility of the carbon nanofiber, which has been considered difficult so far, and makes the carbon nanofiber 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 dispersibility of carbon nanofibers having high cohesiveness is improved by shearing force. More specifically, when the elastomer and the carbon nanofiber are mixed, the viscous elastomer penetrates into the carbon nanofiber, and a specific part of the elastomer has high activity of the carbon nanofiber due to chemical interaction. In this state, when a strong shearing force is applied to a mixture of an elastomer having high molecular mobility (elasticity) and carbon nanofibers, the carbon nanofibers are deformed as the elastomer is deformed. The fibers also moved, and the aggregated carbon nanofibers were separated and dispersed in the elastomer by the restoring force of the elastomer due to elasticity after shearing. Thus, by improving the dispersibility of the carbon nanofibers in the matrix, expensive carbon nanofibers can be used efficiently as fillers for composite materials.

  In addition, attempts have been made to produce a thermoplastic resin composition in which carbon nanofibers are combined with a thermoplastic resin.

  However, with a thermoplastic resin, it is difficult to disperse the carbon nanofibers due to elasticity like an elastomer, and many aggregates of carbon nanofibers remain in the thermoplastic resin composition. Such agglomerates of carbon nanofibers cause stress concentration in the thermoplastic resin composition, so they tend to be a starting point of fracture, and become a relatively brittle material despite being reinforced with carbon nanofibers. was there.

  Therefore, as a method for producing a thermoplastic resin composition containing carbon nanofibers, a method of further dispersing carbon nanofibers by mixing dispersion particles that promote the dispersion of carbon nanofibers into a thermoplastic resin has been proposed. (For example, refer to Patent Document 2). However, since the carbon nanofibers are uniformly dispersed throughout the carbon nanofibers, there is a reinforcing effect, but the carbon nanofiber aggregates remain. Therefore, the high ductility required for the thermoplastic resin has been lost.

  Also, carbon nanofibers are uniformly dispersed in the elastomer using 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. The manufacturing method of the thermoplastic resin composition was proposed (for example, refer patent document 3). However, most carbon nanofibers can be defibrated and dispersed in the elastomer, but it has been difficult to disperse the carbon nanofibers into the thermoplastic resin phase.

In recent years, pellets in which carbon nanofibers are blended with a thermoplastic resin have been sold (for example, see Non-Patent Document 1), but these also have a large number of aggregates of carbon nanofibers in the material, Even when ordinary molding processing was performed using the material, the agglomerates remained almost as they were in the product. When such a molded product was subjected to a tensile test, it was broken at a low strain even if the blending amount of the carbon nanofiber was very small.

JP 2005-97525 A JP 2005-336235 A JP 2007-154157 A

“PLASTICYLTMPP2001” published on the website of Nanocyl (Belgium), [December 11, 2012 search], Internet <http://www.nanocyl.com/en/Products-Solutions/Products/PLASTICYL-Carbon-Nanotubes -Conductive-Masterbatches>

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

The method for producing a thermoplastic resin composition according to the present invention includes:
A mixing step of kneading the thermoplastic resin and the carbon nanofibers at a second temperature to obtain a first mixture containing an aggregate of a plurality of carbon nanofibers in the thermoplastic resin ;
Said first mixture, and cold kneading step of kneading at a first temperature,
Including
In the dynamic viscoelasticity test of the first mixture, the first temperature is in a range up to 15 ° C. above the melting point (Tm) of the thermoplastic resin and higher than the melting point (Tm). Ri temperature range der exhibiting rubber elasticity area,
The second temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin,
The thermoplastic resin is polypropylene,
The carbon nanofiber has an average diameter of 9 nm or more and 30 nm or less,
7 parts by mass or more and 35 parts by mass or less of the carbon nanofibers with respect to 100 parts by mass of the polypropylene,
The obtained thermoplastic resin composition is characterized by having a tensile yield point according to a stress-strain curve .
In addition, the method for producing the thermoplastic resin composition according to the present invention includes:
A mixing step of kneading the thermoplastic resin and the carbon nanofibers at a second temperature to obtain a first mixture containing an aggregate of a plurality of carbon nanofibers in the thermoplastic resin;
A low temperature kneading step of kneading the first mixture at a first temperature;
Including
In the dynamic viscoelasticity test of the first mixture, the first temperature is in a range up to a temperature not lower than the melting point (Tm) of the thermoplastic resin and 15 ° C. higher than the melting point (Tm). A temperature range indicating a rubber elastic region,
The second temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin,
The thermoplastic resin is polypropylene,
The carbon nanofiber has an average diameter of more than 30 nm and 110 nm or less,
The carbon nanofibers are 15 parts by mass or more and 33.3 parts by mass or less with respect to 100 parts by mass of the polypropylene,
The obtained thermoplastic resin composition is characterized by having a tensile yield point according to a stress-strain curve.
Furthermore, the method for producing the thermoplastic resin composition according to the present invention includes:
A mixing step of kneading the thermoplastic resin and the carbon nanofibers at a second temperature to obtain a first mixture containing an aggregate of a plurality of carbon nanofibers in the thermoplastic resin;
A low temperature kneading step of kneading the first mixture at a first temperature;
Including
In the dynamic viscoelasticity test of the first mixture, the first temperature is in a range up to a temperature not lower than the melting point (Tm) of the thermoplastic resin and 15 ° C. higher than the melting point (Tm). A temperature range indicating a rubber elastic region,
The second temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin,
The thermoplastic resin is polypropylene,
The obtained thermoplastic resin composition has a tensile yield point according to a stress-strain curve, and is dynamic based on JIS K7244 at a measurement temperature of 20 to 300 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz. When the viscoelasticity test is performed, it does not flow at 300 ° C. and does not break.

  According to the method for producing a thermoplastic resin composition of the present invention, the aggregated carbon nanofibers can be loosened and dispersed in the thermoplastic resin in a separated state. Therefore, since the thermoplastic resin composition obtained by the method for producing a thermoplastic resin composition according to the present invention does not have aggregates of carbon nanofibers, the destruction due to stress concentration caused by the aggregates does not occur. It can have a high elastic modulus without sacrificing ductility.

In the method for producing a thermoplastic resin composition according to the present invention,
The thermoplastic resin is a polypropylene having a melting point (Tm) of 160 ° C.
It said first temperature, 160 ° C. or higher state, and are 180 ° C. or less,
The second temperature is, 180 ° C. or higher, can der Rukoto 300 ° C. or less.

In the method for producing a thermoplastic resin composition according to the present invention,
The thermoplastic resin is a first thermoplastic resin,
A second low-temperature kneading step for further adding a second thermoplastic resin to the second mixture obtained in the low-temperature kneading step to knead at a third temperature to obtain a third mixture;
The second thermoplastic resin is the same type of thermoplastic resin as the first thermoplastic resin,
The third temperature may be a temperature range of the first temperature.

The thermoplastic resin composition according to the present invention is:
A thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin,
There is no aggregate of carbon nanofibers,
Carbon nanofibers are dispersed throughout and separated from each other .
The thermoplastic resin is polypropylene,
The carbon nanofiber has an average diameter of 9 nm or more and 30 nm or less,
The carbon nanofiber is 5 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the polypropylene.
It has a tensile yield point in the stress-strain curve .
The thermoplastic resin composition according to the present invention is
A thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin,
There is no aggregate of carbon nanofibers,
Carbon nanofibers are dispersed throughout and separated from each other.
The thermoplastic resin is polypropylene,
The carbon nanofiber has an average diameter of more than 30 nm and 110 nm or less,
The carbon nanofiber is 5 parts by mass or more and 33.3 parts by mass or less with respect to 100 parts by mass of the polypropylene.
It has a tensile yield point in the stress-strain curve.
Furthermore, the thermoplastic resin composition according to the present invention is:
A thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin,
There is no aggregate of carbon nanofibers,
Carbon nanofibers are dispersed throughout and separated from each other.
The thermoplastic resin is polypropylene,
Having a tensile yield point in the stress-strain curve;
When a dynamic viscoelasticity test is performed based on JIS K7244 at a measurement temperature of 20 to 300 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz, it does not flow and does not break at 300 ° C. And

  According to the thermoplastic resin composition of the present invention, since there are no aggregates of carbon nanofibers, there is no breakage due to stress concentration in the aggregates, so that it has a high elastic modulus without sacrificing ductility. Can do.

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 in the sample of Comparative Examples 1-7. It is a graph which shows the DMA measurement result in the sample of the comparative example 1 and Examples 1-5. It is a graph which shows the DMA measurement result in the sample of the comparative examples 1 and 8-13. 5 is a SEM observation photograph of 250 times the frozen section of the sample of Comparative Example 4. 10 is a SEM observation photograph of 1000 times the frozen section of the sample of Comparative Example 4. 6 is a SEM observation photograph of 20000 times the frozen section of the sample of Comparative Example 4. 3 is a SEM observation photograph of 250 times the frozen section of the sample of Example 2. 4 is a SEM observation photograph of 1000 times the frozen section of the sample of Example 2. FIG. 4 is a SEM observation photograph of 20000 times the frozen section of the sample of Example 2.

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

In the method for producing a thermoplastic resin composition according to one embodiment of the present invention, a thermoplastic resin and carbon nanofibers are kneaded at a second temperature, and a plurality of carbon nanofibers are contained in the thermoplastic resin . A mixing step of obtaining a first mixture containing agglomerates , and said first mixture comprising:
Includes a low-temperature kneading step of kneading at a temperature, of, the first temperature is a the said heat melting point of the thermoplastic resin (Tm) or higher in the range of up to a temperature higher 15 ℃ than the melting point (Tm), and the Ri temperature range der exhibiting rubber elasticity region in a dynamic viscoelasticity test of the first mixture, the second temperature is the heat of the thermoplastic resin melting point (Tm) or higher, the thermoplastic resin, The carbon nanofibers have an average diameter of 9 nm or more and 30 nm or less, and the carbon nanofibers are 7 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the polypropylene. The thermoplastic resin composition is characterized by having a tensile yield point according to a stress-strain curve .
The method for producing a thermoplastic resin composition according to an embodiment of the present invention includes a method of kneading a thermoplastic resin and carbon nanofibers at a second temperature, so that a plurality of carbon nanofibers are contained in the thermoplastic resin. A mixing step of obtaining a first mixture containing fiber agglomerates; and a low-temperature kneading step of kneading the first mixture at a first temperature, wherein the first temperature is a temperature of the thermoplastic resin. A temperature range not lower than the melting point (Tm) and up to a temperature 15 ° C. higher than the melting point (Tm), and indicating a rubber elastic region in the dynamic viscoelasticity test of the first mixture, The temperature of 2 is equal to or higher than the melting point (Tm) of the thermoplastic resin, the thermoplastic resin is polypropylene, and the carbon nanofibers have an average diameter of more than 30 nm and not more than 110 nm. The carbon nanofibers are 15 parts by mass or more and 33.3 parts by mass or less with respect to 100 parts by mass of len, and the obtained thermoplastic resin composition has a tensile yield point according to a stress-strain curve. And
Furthermore, in the method for producing a thermoplastic resin composition according to one embodiment of the present invention, a thermoplastic resin and carbon nanofibers are kneaded at a second temperature, and a plurality of carbon nanofibers are contained in the thermoplastic resin. A mixing step of obtaining a first mixture containing fiber agglomerates; and a low-temperature kneading step of kneading the first mixture at a first temperature, wherein the first temperature is a temperature of the thermoplastic resin. A temperature range not lower than the melting point (Tm) and up to a temperature 15 ° C. higher than the melting point (Tm), and indicating a rubber elastic region in the dynamic viscoelasticity test of the first mixture, The temperature of 2 is equal to or higher than the melting point (Tm) of the thermoplastic resin, the thermoplastic resin is polypropylene, and the obtained thermoplastic resin composition has a tensile yield point according to a stress-strain curve, And measurement temperature 20 300 ° C., a dynamic strain ± 0.05%, when performing dynamic viscoelasticity test based on JIS K7244 at a frequency 1 Hz, at 300 ° C., does not flow, and characterized in that it does not break.

A thermoplastic resin composition according to an embodiment of the present invention is a thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin, and there is no aggregate of carbon nanofibers. The nanofibers are dispersed throughout the nanofibers, the thermoplastic resin is polypropylene, the carbon nanofibers have an average diameter of 9 nm or more and 30 nm or less, and 100 parts by mass of the polypropylene The carbon nanofiber is 5 parts by mass or more and 35 parts by mass or less, and has a tensile yield point in a stress-strain curve .
The thermoplastic resin composition according to one embodiment of the present invention is a thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin, and there is no aggregate of carbon nanofibers. The carbon nanofibers are dispersed in a state separated from each other, the thermoplastic resin is polypropylene, the carbon nanofibers have an average diameter of more than 30 nm and not more than 110 nm, and 100 parts by mass of the polypropylene On the other hand, the carbon nanofiber is 5 parts by mass or more and 33.3 parts by mass or less, and has a tensile yield point in a stress-strain curve.
Furthermore, the thermoplastic resin composition according to one embodiment of the present invention is a thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin, and there is no aggregate of carbon nanofibers. The carbon nanofibers are dispersed throughout the carbon nanofibers, the thermoplastic resin is polypropylene, has a tensile yield point in a stress-strain curve, a measurement temperature of 20 to 300 ° C., a dynamic strain of ± When a dynamic viscoelasticity test is performed based on JIS K7244 at 0.05% and a frequency of 1 Hz, it does not flow at 300 ° C. and does not break.

  A. First, the manufacturing method of the thermoplastic resin composition concerning this Embodiment is demonstrated.

  Drawing 1 is a figure showing typically the manufacturing method of the thermoplastic resin composition concerning one embodiment.

  The method for producing a thermoplastic resin composition according to the present embodiment includes a mixing step in which a thermoplastic resin and carbon nanofibers are kneaded at a second temperature to obtain a first mixture before the low-temperature kneading step. A method further comprising: This mixing step may not be necessary when a material in which carbon nanofibers are blended in advance with a thermoplastic resin, for example, a commercially available pellet-shaped material is used as the first mixture. In this case, the carbon nanofibers only need to be dispersed throughout the first mixture in the state of agglomerates.

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

  For example, a closed kneader, an extruder, or an injection molding machine can be used for mixing the carbon nanofibers with the thermoplastic resin in the mixing step. As shown in FIG. A method performed using the above 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, 0.5 mm to 1.5 mm, and are rotated forward at rotational speeds V1 and V2 in the directions indicated by the arrows. Or it rotates in reverse. The temperature of the first roll 10 and the second roll 20 can be adjusted by, for example, heating means provided therein, and is set to the second temperature.

The second temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin. The second temperature is the actual temperature of the thermoplastic resin during the mixing process, not the temperature of the processing equipment. The molding processing temperature of the thermoplastic resin is generally represented by the set temperature of the heating cylinder in the case of, for example, an extruder or an injection molding machine of the processing apparatus, but usually from the set temperature of the processing apparatus due to shear heat generation during kneading. Even the actual resin temperature becomes high. Since the second temperature in the present embodiment is a temperature during processing, it is desirable to measure the actual resin temperature as much as possible. However, if it cannot be measured, the temperature immediately after taking out the first mixture from the processing apparatus is used. It can be measured and estimated from the temperature.

  The second temperature is slightly lower in the case of processing in the mixing process using the open roll 2 than in the case of carrying out with a general molding processing apparatus of a thermoplastic resin in consideration of the winding property on the roll, for example, This can be done by setting the roll temperature to a temperature lower by 20 ° C. or more.

  When the thermoplastic resin is polypropylene, the second temperature can be not lower than the melting point, for example 160 ° C. or higher, can be 180 ° C. or higher, and can be 180 ° C. to 300 ° C., in particular. . In particular, when polypropylene is processed using the open roll 2, the roll temperature can be set to 180 ° C to 200 ° C, and further can be set to 180 ° C to 190 ° C. Although it is not common to process a thermoplastic resin with the open roll 2, in the case of the open roll 2, compared with the said other processing apparatus, from the special property that a material must be wound around a roll, When the roll temperature exceeds 200 ° C., the viscosity of the polypropylene becomes too high and processing becomes difficult. The second temperature only needs to be able to melt the thermoplastic resin and mix the carbon nanofibers. Therefore, when processing with a closed kneader, an extruder, an injection molding machine, etc., the second temperature is It can be set as the surface temperature of the resin when the set temperature of the processing apparatus is 200 ° C. to 300 ° C.

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

  However, in this state, the carbon nanofibers 80 in the first mixture are present dispersed throughout the same aggregate as the raw material. Therefore, the first mixture has a defect in the material. For example, when a tensile test or the like is performed, the elongation at break is significantly lower than that of the raw material thermoplastic resin alone.

  When the first mixture was subjected to a dynamic viscoelasticity test (hereinafter referred to as DMA test), it was found that the first mixture showed a behavior different from that of the raw thermoplastic resin. The raw material thermoplastic resin has a storage elastic modulus (E ′) that rapidly 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 when the melting point is exceeded by dispersing a predetermined amount or more of the carbon nanofibers, that is, like an elastomer. It was found that a rubber elastic region was developed.

  The method for producing a thermoplastic resin according to the present invention uses this rubber elastic region to disentangle the aggregated carbon nanofibers so as to disperse them in the thermoplastic resin. Therefore, in carrying out the present invention, a DMA test is performed in advance on a sample of the first mixture of the blend to confirm whether or not a rubber elastic region has developed, and the temperature region is used to determine thermoplasticity. A resin composition can be produced.

A-2. Low temperature kneading step The low temperature kneading step kneads the first mixture at the first temperature.

  As a 1st mixture, what was obtained by the mixing process of said A-1 can be used.

  The step of kneading the first mixture at the first temperature in the low temperature kneading step uses an apparatus for melting and molding the thermoplastic resin, for example, a closed kneader, an extruder, an injection molding machine, or the like. However, similar to the mixing step, it can be performed using an open roll 2 as shown in FIG. In this step, the roll interval d between the first roll 10 and the second roll 20 is set to, for example, 0.5 mm or less, more preferably 0 to 0.5 mm, and the first obtained in the mixing step. The mixture can be put into the open roll 2 and kneaded.

  When the surface speed of the first roll 10 is V1, and the surface speed of the second roll 20 is V2, the surface speed ratio (V1 / V2) of both in this step is 1.05 to 3.00. And can be 1.05-1.2. By using such a surface velocity ratio, a desired shear force can be obtained. The first mixture extruded from between such narrow rolls is greatly deformed by the restoring force due to the elasticity of the thermoplastic resin because the first temperature is the temperature range in which the rubber elastic region is developed. The carbon nanofibers can move greatly with the deformation of the thermoplastic resin.

  The general processing set temperature, that is, the set temperature of the processing equipment, is higher than the temperature recommended as the processing set temperature for thermoplastic resins in order to melt the thermoplastic resin sufficiently in a short time and process it quickly. It is common to process with. The thermoplastic resin is not processed near its melting point. As described above, the surface temperature of the thermoplastic resin during processing is higher than the processing set temperature. In particular, when a filler such as carbon nanofiber is blended with a thermoplastic resin, the processing set temperature is usually higher than the general processing set temperature. is there.

  However, in this embodiment, since the carbon nanofibers are moved using the resilience due to the elasticity of the thermoplastic resin in this way, the first temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin. The temperature range showing the rubbery elastic region in the DMA test of the first mixture, and in particular, as the processing temperature of the thermoplastic resin compounded with carbon nanofibers so as to give a high shearing force to the first mixture A low temperature range that has not been employed can be used.

  The first temperature is the surface temperature of the first mixture in the low-temperature kneading step, not the set temperature of the processing apparatus. As described for the second temperature, it is desirable to measure the temperature of the actual resin as much as possible for the first temperature, but if it cannot be measured, measure the temperature immediately after taking out the thermoplastic resin composition from the processing apparatus. The first temperature during processing can be estimated from the temperature. 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 taking out from the apparatus after kneading is used. The surface temperature can be measured and confirmed to be within the first temperature range.

  The first temperature is in the range up to a temperature which is equal to or higher than the melting point (Tm) of the thermoplastic resin used in this production method and 25 ° C. higher than the melting point (Tm). If the first temperature is lower than the melting point (Tm), processing is difficult. Moreover, when the first temperature exceeds 25 ° C. higher than the melting point (Tm), the carbon nanofiber aggregates cannot be loosened in the low-temperature kneading step. Even when the thermoplastic resin is polypropylene, the first temperature can be defined in the same manner. For example, when the melting point is 160 ° C., the first temperature can be 160 ° C. or higher and 180 ° C. or lower. Here, melting | fusing point (Tm) can be measured by carrying out DMA test of the thermoplastic resin used as a raw material, and is temperature which starts a flow.

Further, the first temperature may be in a range up to a melting point (Tm) or higher and 20 ° C. higher than the melting point (Tm). 15
It can range up to a high temperature.

  The low temperature kneading step can be, for example, 4 minutes to 20 minutes at the first temperature, and can be further 5 minutes to 20 minutes. By sufficiently taking the kneading time at the first temperature, the carbon nanofibers can be defibrated more reliably.

  The workability of the first mixture is lowered due to the incorporation of carbon nanofibers, and the temperature of the first mixture becomes higher than the set temperature of the apparatus due to shearing heat generated by kneading the carbon nanofibers. Therefore, in order to maintain the surface temperature of the first mixture in the first temperature range suitable for the low-temperature kneading step, if the roll is an open roll, the temperature of the first mixture is not increased by adjusting the roll temperature. The temperature must be adjusted to cool down positively. The same applies to a closed kneader, an extruder or an injection molding machine, and the surface temperature of the first mixture is brought to the first temperature range by actively adjusting the processing set temperature of the apparatus so as to cool down. It can be maintained for a certain time. For example, in the extruder, in the vicinity of supplying the material, the set temperature of the heating cylinder is set to a temperature higher than the general processing temperature, the other zones are set to a temperature lower than the first temperature, The surface temperature of the resin can be adjusted to be the first temperature.

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

  The shearing force thus obtained causes a high shearing force to act on the thermoplastic resin, so that the aggregated carbon nanofibers are separated from each other so that they are pulled out one by one into the thermoplastic resin molecule, and defibrated. And dispersed in the thermoplastic resin. In particular, the thermoplastic resin has elasticity in the first temperature range, viscosity, and chemical interaction with the carbon nanofibers due to activation of the thermoplastic resin molecules in the kneading process. Fiber can be defibrated and dispersed. And the thermoplastic resin composition excellent in the dispersibility and dispersion stability of carbon nanofiber (it is hard to re-aggregate carbon nanofiber) can be obtained.

  When the low-temperature kneading step is performed subsequent to the mixing step, a cooling step can be performed. This is because the first mixture obtained in the mixing step has a higher temperature than the first temperature in the low-temperature kneading step. The cooling step can be performed until the first mixture reaches the temperature range of the first temperature, and the first mixture is set in the first temperature range in order to facilitate introduction into the low temperature kneading step. Can be retained.

  As the first mixture, a mixture pellet obtained by mixing a commercially available thermoplastic resin and carbon nanofiber can be used. Usually, such commercially available mixture pellets are present with the carbon nanofibers agglomerated. Therefore, it can be inferred that such a commercially available mixture pellet was processed in the same manner as the mixing step of A-1.

  The method for producing the thermoplastic resin composition is such that the average diameter of the carbon nanofibers is 9 nm or more and 30 nm or less, and the thermoplastic resin can be polypropylene, and in that case, with respect to 100 parts by mass of polypropylene in the low temperature kneading step, The compounding quantity of carbon nanofiber can be 7 mass parts or more and 35 mass parts or less. In the case of carbon nanofibers having an average diameter of 9 nm or more and 30 nm or less, when the compounding amount of the carbon nanofibers with respect to 100 parts by mass of polypropylene is 7 parts by mass or more, a rubber elastic region having a melting point or more appears in the DMA test of the first mixture. be able to.

  In the method for producing a thermoplastic resin composition, the average diameter of the carbon nanofibers is more than 30 nm and not more than 110 nm, and the thermoplastic resin can be polypropylene. In that case, 100 parts by mass of polypropylene in the low temperature kneading step On the other hand, the compounding quantity of carbon nanofiber can be 15 mass parts or more and 55 mass parts or less. In the case of carbon nanofibers having an average diameter of more than 30 nm and not more than 110 nm, when the compounding amount of carbon nanofibers with respect to 100 parts by mass of polypropylene is 15 parts by mass or more, a rubber elastic region appears at the melting point or more in the DMA test of the first mixture can do.

  According to the method for producing a thermoplastic resin composition according to the present embodiment, carbon nanofibers that existed as aggregates in the thermoplastic resin can be dispersed while being separated from each other. Therefore, since the thermoplastic resin composition obtained by the method for producing a thermoplastic resin composition does not have aggregates of carbon nanofibers, fracture due to stress concentration caused by the aggregates does not occur, so the ductility is sacrificed. Without having a high elastic modulus.

A-3. Second low-temperature kneading step The method for producing a thermoplastic resin composition is such that the thermoplastic resin in the first mixture is the first thermoplastic resin, and the second mixture obtained in the low-temperature kneading step includes the second A second low-temperature kneading step of adding a thermoplastic resin and kneading at a third temperature to obtain a third mixture can be further included. The second thermoplastic resin can be the same type of thermoplastic resin as the first thermoplastic resin. Here, the same type of thermoplastic resin means that the second thermoplastic resin and the first thermoplastic resin are at least the same main constituent monomer. The third temperature can be in the same temperature range as the first temperature described in A-2. If the blending amount of the carbon nanofibers in the first mixture in A-1 is small, the rubber elastic region in the DMA test in the first mixture may not appear. In such a first mixture, the carbon nanofibers cannot be separated from each other even when the low-temperature kneading step is performed. 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 thermoplastic resin is added by performing the second low-temperature kneading step in this way. By doing, content of the carbon nanofiber in a thermoplastic resin composition can be decreased. Unless otherwise specified, the first thermoplastic resin and the second thermoplastic resin will be described below using the same kind of thermoplastic resin.

  B. Next, the raw material used for the manufacturing method of this Embodiment is demonstrated.

B-1. Thermoplastic resin As the thermoplastic resin, a thermoplastic resin having a melting point in the DMA test can be used. For example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyacetal (POM), polybutylene terephthalate ( Crystalline thermoplastic resins such as PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyimide (PI), and fluororesin (PFA) can be used. Moreover, even if it is a thermoplastic resin generally called an amorphous resin, the thermoplastic resin which shows melting | fusing point in a DMA test, for example, a polystyrene (PS), a polycarbonate (PC), etc. can be used.

B-2. Carbon nanofibers Carbon nanofibers can have an average diameter (fiber diameter) of 0.4 nm to 230 nm, and carbon nanofibers can have an average diameter (fiber diameter) of 9 nm to 110 nm, In particular, it can be 9 nm or more and 30 nm or less, or more than 30 nm and 110 nm or less. Since the carbon nanofiber has a small average diameter and a large specific surface area, the carbon nanofiber can be defibrated and dispersed throughout.
The thermoplastic resin can be effectively reinforced with a small amount of carbon nanofibers. By using carbon nanofibers having an average diameter (fiber diameter) of 0.4 nm or more and 230 nm or less, the thermoplastic resin can be reinforced. The carbon nanofibers can be oxidized, for example, in order to improve the reactivity with the thermoplastic resin on the surface thereof. In the detailed description of the present invention, the average diameter and the average length of the carbon nanofibers are, for example, 5,000 times or more from an electron microscope (the magnification can be appropriately changed depending on the size of the carbon nanofibers), and the diameters of 200 or more locations. And the length can be measured and calculated as the arithmetic average value.

  The compounding quantity of the carbon nanofiber in a thermoplastic resin composition can be mix | blended suitably according to a desired characteristic. In particular, by using the second low-temperature kneading step, 0.1 part by mass or more of carbon nanofibers can be blended with respect to 100 parts by mass of the thermoplastic resin, and by using relatively thick carbon nanofibers, for example, 100 It can mix | blend to a mass part. In addition to carbon nanofibers, the thermoplastic resin composition can be used in combination with fillers generally used for processing thermoplastic resin compositions. Here, “part by mass” indicates “phr” unless otherwise specified, and “phr” is an abbreviation for “parts per undred of resin or rubber”, and is used as an external hook for additives such as rubber and thermoplastic resin. It represents a percentage.

  Carbon nanofibers are so-called multi-walled carbon nanotubes (MWNT: multi-wall carbon nanotubes) having a cylindrical shape formed by winding one surface (graphene sheet) of graphite with a carbon hexagonal mesh surface, and an average diameter of 9 nm to 30 nm. Examples of the following carbon nanofibers include Baytubes C150P and C70P manufactured by Bayer MaterialScience, and NC-7000 manufactured by Nanosil, and carbon nanofibers having an average diameter of more than 30 nm and 110 nm or less. Examples of the fiber include NT-7 manufactured by Hodogaya Chemical Co., Ltd. A carbon material partially having a carbon nanotube structure can also be used. In addition to the name “carbon nanotube”, it may be called “graphite fibril nanotube” or “vapor-grown carbon fiber”.

Carbon nanofibers can be obtained by a vapor deposition method. Vapor growth is also called catalytic chemical vapor deposition (CCVD), which is a method of producing carbon nanofibers by gas phase pyrolysis of hydrocarbons and other gases in the presence of a metal catalyst. is there. The vapor phase growth method will be described 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 nickelcene is used as a metal catalyst, and these are used together with a carrier gas at a high temperature such as 400 ° C. It is introduced into a reaction furnace set to a reaction temperature of 1000 ° C or less and floated on a ceramic substrate such as alumina or magnesium oxide. For example, a catalyst-supporting reaction method (Substrate Reaction Method) in which carbon-containing fibers are brought into contact with a carbon-containing compound at a high temperature to form carbon nanofibers on a substrate can be used. Carbon nanofibers having an average diameter of 9 nm to 30 nm can be obtained by a catalyst-supporting reaction method, and carbon nanofibers having an average diameter of more than 30 nm and not more than 110 nm can be obtained by a floating flow reaction method. The diameter of the carbon nanofiber 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 can be 100 m ² / g or more and 350 m ² / g or less. In particular, it may be 150 m ² / g or more and 300 m ² / g or less.

  C. The thermoplastic resin composition obtained by this Embodiment is demonstrated.

  The thermoplastic resin composition according to the present embodiment is a thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin, and there is no aggregate of carbon nanofibers. , It is dispersed in the whole in a state separated from each other.

  8 to 10 are SEM observation photographs of the frozen section of a thermoplastic resin composition sample of Example 2 described later. Details of the second embodiment will be described later.

  As shown in FIGS. 8 to 10, the absence of aggregates of carbon nanofibers in the thermoplastic resin composition can be confirmed by observing an arbitrary cross section of the thermoplastic resin composition with an electron microscope. In FIG. 10, the carbon nanofibers that have been fibrillated and separated from each other are shown dispersed in the cut surface. In addition, as shown in FIGS. 5-7 which are the SEM observation photographs of the sample of the comparative example 4 (The detail of the comparative example 4 mentioned later is mentioned later) with an aggregate, it is also in a thermoplastic resin composition. The carbon nanofibers are entangled with each other as in the raw material. In particular, as shown in FIG. 7, in the aggregate, there are many hollow portions in which no resin enters between the carbon nanofibers and the carbon nanofibers. It is. The absence of such agglomerates means that the aggregated carbon nanofibers are loosened, and the carbon nanofibers are dispersed in a state separated from each other. The state which mutually isolate | separated means that it exists in the state in which a hollow part does not exist between carbon nanofibers in a thermoplastic resin composition.

  According to the thermoplastic resin composition according to the present embodiment, since there is no aggregate of carbon nanofibers, there is no breakage due to stress concentration in the aggregate, so that high elasticity is obtained without sacrificing ductility. Can have a rate.

The thermoplastic resin composition, the stress - that have a tensile yield point in strain curve. The stress-strain curve can be obtained by a tensile test. If the thermoplastic resin composition has an aggregate of carbon nanofibers, it breaks before reaching the tensile yield point in the tensile test, so that the presence or absence of the aggregate can be determined in a pseudo manner.

  In the thermoplastic resin composition, the carbon nanofibers can be 0.1 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of polypropylene, and the carbon nanofibers are 5 parts by mass or more and 60 parts by mass. Can be:

  When the average diameter of the carbon nanofiber is 9 nm or more and 30 nm or less, the thermoplastic resin composition can be 5 parts by mass or more and 40 parts by mass or less of carbon nanofibers with respect to 100 parts by mass of polypropylene. Furthermore, carbon nanofibers can be 7 parts by mass or more and 35 parts by mass or less.

  In the thermoplastic resin composition, when the average diameter of the carbon nanofibers is more than 30 nm and 110 nm or less, the carbon nanofibers can be 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of polypropylene. Furthermore, the carbon nanofibers can be 15 parts by mass or more and 55 parts by mass or less.

  The thermoplastic resin composition manufactured using the second low-temperature kneading step of A-3 is to further add a thermoplastic resin using a thermoplastic resin composition in which carbon nanofibers are already dispersed as a master batch. Thus, the blending ratio of carbon nanofibers in the thermoplastic resin composition can be reduced. Therefore, for example, the carbon nanofiber can be less than 5 parts by mass with respect to 100 parts by mass of polypropylene.

  As described above, the embodiments of the present invention have been described in detail. However, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention.

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

(1-1) Preparation of Samples of Examples 1 to 10 Mixing step: 100 parts by mass (phr) of polypropylene shown in each table was added to an open roll having a roll diameter of 6 inches (roll temperature 180 ° C. = processing set temperature) It was charged, melted and wound on a roll. The temperature of the polypropylene fabric surface at this time was 180 ° C.

  Next, multi-part carbon nanofibers (indicated in each table as “CNT-1” or “CNT-2”) shown in Table 1 were added as compounding agents. At this time, the roll gap was set to 1.5 mm. Thorough kneading was performed to disperse the multilayer carbon nanofibers, and the first mixture was taken out from the open roll. The temperature of the dough surface (second temperature) of the first mixture during the kneading is shown as “second temperature” in the “dough temperature” column in each table. As shown in each table, when the blending amount of the carbon nanofibers increased, the temperature of the first mixture increased due to shear heat generation during kneading, and the second temperature became higher than the roll temperature. The surface temperature of the dough temperature was measured with a non-contact type infrared thermometer.

  Cooling step: The first mixture was cooled until the surface temperature reached 160 ° C. to 180 ° C., and the first mixture was placed in an oven and maintained at 160 ° C. to 180 ° C.

  Low-temperature kneading step: The first mixture was put again into the open roll, and the roll gap was narrowed from 1.5 mm to 0.3 mm for kneading. During this kneading, the temperature of the roll of the first mixture was adjusted so that the temperature of the dough surface (first temperature) was measured with a non-contact infrared thermometer and maintained at 160 ° C. to 180 ° C. The temperature (first temperature) of the dough surface of the first mixture during the kneading is shown as “first temperature” in the “dough temperature” column in each table. After kneading sufficiently, 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 put in a mold and pressure-molded under vacuum to prepare a sample. In vacuum pressure molding, the mold is heated to 190 ° C., preheated for 2 minutes, then press-molded for 5 minutes while being pressurized at 23 MPa (to the mold), and the mold is moved to a cooling press to 6 MPa. And cooled to room temperature while applying pressure (to the mold).

In each table, “CNT-1” is a multi-walled carbon nanotube having an average diameter (value obtained by arithmetically averaging 200 measured values using scanning electron microscope imaging) of 15 nm, and “CNT-2”. Is a 68 nm multi-walled carbon nanotube having an average diameter (value obtained by arithmetically averaging 200 or more measured values using scanning electron microscope imaging), and “PP-1” is a polypropylene (manufactured by Nippon Polypro Co., Ltd.). Polypropylene, grade name: MG03B, MFR: 30 g / 10 min, density: 0.90 g / cm ³ , melting point 160 ° C. (melting point is the flow starting temperature measured by DMA below).

(1-2) Sample preparation of Comparative Examples 1 to 13 In Comparative Examples 2 to 13, the first mixture was obtained in the same manner as the mixing step of Examples 1 to 10, and the cooling step and the low temperature kneading step were omitted. The process was carried out to obtain a sample of the thermoplastic resin composition.

  Since the comparative example 1 is a polypropylene simple substance, the resin pellet was injected | thrown-in to the metal mold | die, the press process was performed, and the sample of the thermoplastic resin composition was obtained.

(1-3) Tensile test About the sample of an Example and a comparative example, about the test piece pierced to the dumbbell No. 1 shape of JISK-7113-1, using the tensile tester of Shimadzu Corporation autograph AG-X. , 23 ± 2 ° C., tensile speed 50 mm / min based on JIS K7127, tensile strength (TS (MPa)), elongation at break (Eb (%)) and yield point tensile stress (σy (MPa) )) Was measured. The measurement results are shown in each table.

(1-4) DMA measurement About the sample of an Example and a comparative example, about the test piece cut out into the strip shape (40x1x2 (width) mm), using the dynamic viscoelasticity tester DMS6100 made from 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 300 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz. From this test result, the storage elastic modulus (E ′) was measured at measurement temperatures of 25 ° C., 100 ° C., and 200 ° C. The storage elastic modulus is indicated by “E ′ (25 ° C.) (MPa)”, “E ′ (100 ° C.) (MPa)”, and “E ′ (200 ° C.) (MPa)” in each table. In addition, the flow start temperature (described as “flow temperature” in each table) and break temperature in the DMA test are also described in each table. In each table, a sample that did not flow up to 300 ° C. was described as “not flowing”, and a sample that did not break up to 300 ° C. was described as “not broken”.

  Moreover, although not shown in Table 1, the thermoplastic resin composition sample manufactured with the same blending amount as in Example 2 and only the temperature of the low temperature kneading step (first temperature) being 180 ° C. is the result of the tensile test. TS of 25.8 MPa, Eb of 600%, σy of 33.1 MPa, E ′ of the result of DMA test are 2.89 GPa (25 ° C.), 778 MPa (100 ° C.), 6.8 MPa (200 ° C.), It did not flow up to 300 ° C and did not break.

  Although not shown in the table, a sample produced using the same formulation as Comparative Example 2 and using the same production process as Example 1 has a TS of 27.1 MPa, Eb of 17.8%, and σy as a result of the tensile test. 30.4 MPa, E ′ of the DMA test result was 2.26 GPa (25 ° C.), 558 MPa (100 ° C.), and it flowed at 190 ° C. Although Eb was only 17.8% even though the amount of carbon nanofibers was small, it was estimated that carbon nanofiber aggregates were present.

  According to the results of the tensile tests in Tables 1 to 6, the thermoplastic resin composition samples of Examples 1 to 10 have improved tensile strength as compared with Comparative Example 1, and the effect of reinforcement by carbon nanofibers is obtained. It was. Moreover, the thermoplastic resin composition samples of Examples 1 to 10 had relatively high ductility and high yield strength without being broken before yielding as in Comparative Examples 2 to 13. Examples 1-5 are respectively compared with Comparative Examples 3-7, which are the same amount of carbon nanofibers, and Examples 6-10 are compared with Comparative Examples 9-13, which are also the same amount of carbon nanofibers. Thus, it was found that the value of breaking elongation (Eb) was increased.

  According to the results of the DMA tests in Tables 1 to 6, the thermoplastic resin composition samples of Examples 1 to 10 were compared with Comparative Examples 3 to 13 each having the same amount of carbon nanofibers. The storage elastic modulus (E ′) was improved up to (200 ° C.). Moreover, the thermoplastic resin composition sample of Examples 1-10 did not flow to 300 degreeC which is the upper limit of measurement temperature, but also improved heat resistance.

  FIG. 2 shows the temperature dependence of the storage elastic modulus (E ′) of each sample as the DMA test results of Comparative Examples 1 to 7. In FIG. 2, curves C1 to C7 correspond to Comparative Examples 1 to 7, respectively. From the curve C1 of Comparative Example 1, it was found that the melting point (Tm) of the raw material polypropylene was 160 ° C. (the manufacturer catalog value was 155 ° C.). The samples of Comparative Examples 3 to 7 have the same temperature dependence of the storage modulus of the first mixture of Examples 1 to 5.

  FIG. 3 shows the temperature dependence of the storage elastic modulus (E ′) of each sample as the DMA test results of Comparative Example 1, Examples 1 to 5 and Example 11. In FIG. 3, a curve C <b> 1 indicates Comparative Example 1, curves E <b> 1 to E <b> 5 correspond to Examples 1 to 5 respectively, and a curve E <b> 11 corresponds to Example 11. Example 11 will be described later.

  FIG. 4 shows the temperature dependence of the storage elastic modulus (E ′) of each sample as the DMA test results of Comparative Example 1 and Comparative Examples 8 to 13. In FIG. 4, a curve C1 indicates Comparative Example 1, and curves C8 to C13 correspond to Comparative Example 8 to Comparative Example 13, respectively. The samples of Comparative Examples 9 to 13 are the temperature dependence of the storage elastic modulus of the first mixtures of Examples 6 to 10.

From the results of FIGS. 2 and 4, in Comparative Examples 3 to 7 (first mixture of Examples 1 to 5),
It has been found that there is a region (hereinafter referred to as a rubber elastic region) showing rubber elasticity in which the storage elastic modulus does not change much even at a temperature of 160 ° C. or higher. In particular, a thin 18 nm multi-walled carbon nanotube (CNT-1) exhibits a rubber elastic region in a temperature range of 160 ° C. or higher when it is 7.5 parts by mass or more with respect to 100 parts by mass of polypropylene, and a relatively thick 68 nm multi-layer carbon It was found that when the nanotube (CNT-2) is 17.6 parts by mass or more with respect to 100 parts by mass of polypropylene, a rubber elastic region appears in a temperature range of 160 ° C. or more.

  From the results of FIG. 3, it was found that the thermoplastic resin composition samples of Examples 1 to 10 hardly decreased in storage elastic modulus (E ′) in the temperature range of 160 ° C. to 300 ° C.

(1-5) SEM Observation The frozen fracture sections of the samples of Comparative Examples 2 to 13 and the samples of Examples 1 to 10 were observed with a scanning electron microscope (hereinafter referred to as “SEM”).

  Many aggregates of carbon nanofibers were confirmed on the frozen fractured surfaces of the samples of Comparative Examples 2 to 13. 5 to 7 are SEM observation photographs of frozen fractured sections (250 times, 1000 times, 20000 times) of the sample of Comparative Example 4. FIG. In FIG. 5 and FIG. 6, aggregates 100 of carbon nanofibers could be observed inside the white circles. The diameter of the agglomerate 100 was about 100 μm, and it was found that the agglomerate 100 was agglomerated in a state close to the carbon nanofiber raw material as shown in FIG.

  Agglomerates of carbon nanofibers could not be confirmed on the frozen fracture surfaces of the samples of Examples 1 to 10. 8 to 9 are SEM observation photographs of frozen fractured sections (250 times, 1000 times, 20000 times) of the sample of Example 2. FIG. It was found that there was no agglomerate, and the white fibrous substance in FIG. 9 was carbon nanofibers, and the carbon nanofibers were fibrillated and dispersed throughout each other.

  Further, in the low-temperature kneading step of the example, the sample obtained with the temperature of the dough surface of the first mixture being 190 ° C., 200 ° C., and 230 ° C. observed a large number of aggregates of carbon nanofibers as in the comparative example. It was done.

(2-1) Preparation of Sample of Example 11 From the mixing step to the low-temperature kneading step, processing was performed in the same manner as in Example 2, and the thermoplastic resin composition was taken out from the open roll. The thermoplastic resin composition was further subjected to a second low temperature kneading step.

  In the second low-temperature kneading step, the thermoplastic resin composition is wound around the open roll, and 109 parts by mass (phr) of polypropylene (same as the polypropylene of Example 2) is charged again into the open roll. Kneading was performed with the gap narrowed from 1.5 mm to 0.3 mm. During the kneading, the temperature of the roll was adjusted so that the temperature of the surface of the dough of the thermoplastic resin composition was measured with a non-contact infrared thermometer and maintained at 160 ° C to 180 ° C. The fabric surface temperature (third temperature) of the thermoplastic resin composition at this time is shown as “third temperature” in the “fabric temperature” column of Table 7. After kneading sufficiently, the roll gap was changed from 0.3 mm to 1.5 mm, and the second thermoplastic resin composition was taken out from the open roll.

Pressing process: The second 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 190 ° C., preheated for 2 minutes, then press-molded for 5 minutes while being pressurized at 23 MPa (to the mold), and the mold is moved to a cooling press to 6 MPa. And cooled to room temperature while applying pressure (to the mold).

(2-2) Tensile test The sample of Example 11 was subjected to a tensile test in the same manner as in (1-3) above, and the tensile strength (TS (MPa)), elongation at break (Eb (%)), and yield point were measured. Tensile stress (σy (MPa)) was measured. The measurement results are shown in Table 7.

(2-3) DMA measurement The sample of Example 11 was subjected to a DMA test (dynamic viscoelasticity test) in the same manner as (1-4) above. The storage elastic modulus (E ′) was measured at measurement temperatures of 25 ° C., 100 ° C., and 200 ° C. In Table 7, the storage elastic modulus is indicated by “E ′ (25 ° C.) (MPa)”, “E ′ (100 ° C.) (MPa)”, and “E ′ (200 ° C.) (MPa)”. The flow temperature and break temperature in the DMA test are also shown in Table 7.

  FIG. 3 shows the DMA test result of Example 11 as a curve E11.

  From the results of Table 7, the carbon fiber composite material sample of Example 11 was maintained in the high breaking elongation (Eb) value, that is, while maintaining the state in which the carbon nanofibers were defibrated. The amount of carbon nanofiber blended was smaller than that of the sample.

(3-1) Preparation of Samples of Examples 12 to 19 The mixing step, the cooling step, the low temperature kneading step and the pressing step are processed in the same manner as in Examples 1 to 10, and the thermoplastic resin compositions of Examples 12 to 19 are used. An object sample was prepared. Tables 8 and 9 show the material composition and dough temperature during processing.

In Tables 8 and 9, “PP-2” is a polypropylene manufactured by Nippon Polypro Co., Ltd. (block copolymer polypropylene, grade name: BC03B, MFR: 30 g / 10 min, density: 0.90 g / cm ³ , melting point 160 ° C. (melting point Is a flow starting temperature measured by the following DMA)), and “PP-3” is a polypropylene manufactured by Nippon Polypro Co., Ltd. (homopolymer polypropylene, grade name: MA1B, MFR: 21 g / 10 min, density: 0.90 g / cm ³⁾ The melting point was 160 ° C. (melting point is the flow starting temperature measured by DMA below).

(3-2) Preparation of Samples of Comparative Examples 14 and 15 Since Comparative Examples 14 and 15 are polypropylene alone, resin pellets were put into a mold and a pressing process was performed to prepare a thermoplastic resin sample.

(3-3) Tensile test, DMA measurement, SEM observation The samples of Examples 12 to 19 and Comparative Examples 14 and 15 were subjected to a tensile test in the same manner as in (1-3) above, and the tensile strength (TS (MPa)). ), Elongation at break (Eb (%)) and yield point tensile stress (σy (MPa)). The measurement results are shown in Tables 8 and 9.

  The samples of Examples 12 to 19 and Comparative Examples 14 and 15 were subjected to the DMA test (dynamic viscoelasticity test) in the same manner as (1-4). The storage elastic modulus (E ') at measurement temperatures of 25 ° C, 100 ° C, and 200 ° C was measured. In Tables 8 and 9, the storage elastic modulus is indicated by “E ′ (25 ° C.) (MPa)”, “E ′ (100 ° C.) (MPa)”, and “E ′ (200 ° C.) (MPa)”. The flow temperature and break temperature in the DMA test are also shown in Tables 8 and 9.

  According to the results of the tensile tests in Tables 8 and 9, the thermoplastic resin composition samples of Examples 12 to 15 were compared with Comparative Example 14, and the thermoplastic resin composition samples of Examples 16 to 19 were compared with Comparative Example 15. In comparison, the tensile strength was improved and the effect of reinforcement by carbon nanofibers was obtained. Moreover, the thermoplastic resin composition samples of Examples 12 to 17 had relatively high ductility and high yield strength without being broken before yielding.

  According to the results of the DMA tests in Tables 8 and 9, the thermoplastic resin composition samples of Examples 12 to 15 were compared with Comparative Example 14, and the thermoplastic resin composition samples of Examples 16 to 19 were compared with Comparative Example 15. In comparison, the storage elastic modulus (E ′) was improved from room temperature to high temperature (200 ° C.). Moreover, Examples 12-19 did not flow to 300 degreeC which is the upper limit of measurement temperature, but also improved heat resistance. Although not shown in the table, as a result of a DMA test of a press-worked first mixture during the production of Examples 12 to 19, the temperature was 160 ° C. or higher as in Comparative Examples 2 to 13. However, it was confirmed that there was a region (hereinafter, referred to as a rubber elastic region) indicating that the storage elastic modulus did not change so much.

  The frozen fracture sections of Examples 12 to 19 and Comparative Examples 14 and 15 were observed with a scanning electron microscope (hereinafter referred to as “SEM”). Agglomerates of carbon nanofibers could not be confirmed on the frozen sections of the samples of Examples 12-19. As a result of SEM observation, it was found that in the samples of Examples 12 to 19, the carbon nanofibers were defibrated and dispersed throughout the sample in a separated state.

(4-1) Preparation of Samples of Examples 20 and 21 Processing from the mixing step to the low-temperature kneading step was performed in the same manner as in Examples 12 and 16, and the thermoplastic resin composition was taken out from the open roll. The thermoplastic resin composition was further subjected to a second low temperature kneading step.

In the second low-temperature kneading step, the thermoplastic resin composition is wound around the open roll, and 109 parts by mass (phr) of polypropylene (same as the polypropylene of Examples 12 and 16) is again put into the open roll. The kneading was performed with the roll gap narrowed from 1.5 mm to 0.3 mm. During the kneading, the temperature of the roll was adjusted so that the temperature of the surface of the dough of the thermoplastic resin composition was measured with a non-contact infrared thermometer and maintained at 160 ° C to 180 ° C. The fabric surface temperature (third temperature) of the thermoplastic resin composition at this time is shown as “third temperature” in the “fabric temperature” column of Table 10. After kneading sufficiently, the roll gap was changed from 0.3 mm to 1.5 mm, and the second thermoplastic resin composition was taken out from the open roll.

  Pressing process: The second 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 190 ° C., preheated for 2 minutes, then press-molded for 5 minutes while being pressurized at 23 MPa (to the mold), and the mold is moved to a cooling press to 6 MPa. And cooled to room temperature while applying pressure (to the mold).

(4-2) Tensile test, DMA measurement, SEM observation For the samples of Examples 20 and 21, a tensile test was performed in the same manner as in (1-3) above, and tensile strength (TS (MPa)), elongation at break ( Eb (%)) and yield point tensile stress (σy (MPa)) were measured. The measurement results are shown in Table 10.

  The samples of Examples 20 and 21 were subjected to the DMA test (dynamic viscoelasticity test) in the same manner as (1-4) above. The storage elastic modulus (E ') at measurement temperatures of 25 ° C, 100 ° C, and 200 ° C was measured. The storage elastic modulus is shown in Table 10 as “E ′ (25 ° C.) (MPa)”, “E ′ (100 ° C.) (MPa)”, and “E ′ (200 ° C.) (MPa)”. The flow temperature and break temperature in the DMA test are also shown in Table 10.

  From the results of Table 10, the carbon fiber composite material samples of Examples 20 and 21 are examples that maintain a high breaking elongation (Eb) value, that is, while maintaining the state in which the carbon nanofibers are defibrated. The amount of carbon nanofibers was less than that of the 12,16 samples.

The frozen fracture sections of Examples 20 and 21 were observed with a scanning electron microscope (hereinafter referred to as “SEM”). Agglomerates of carbon nanofibers could not be confirmed on the frozen sections of the samples of Examples 20 and 21. As a result of SEM observation, it was found that in the samples of Examples 20 and 21, the carbon nanofibers were defibrated and dispersed throughout in a state of being separated from each other.

  2 Open roll, 10 1st roll, 20 2nd roll, 30 thermoplastic resin, 34 bank, 80 carbon nanofiber, 100 aggregate, d interval, V1, V2 rotational speed, C1-C13 Comparative Examples 1-13 Temperature dependence curve of storage elastic modulus, E1-E5 Temperature dependence curve of storage elastic modulus of Examples 1-5

Claims (8)

A mixing step of kneading the thermoplastic resin and the carbon nanofibers at a second temperature to obtain a first mixture containing an aggregate of a plurality of carbon nanofibers in the thermoplastic resin ;
Said first mixture, and cold kneading step of kneading at a first temperature,
Including
In the dynamic viscoelasticity test of the first mixture, the first temperature is in a range up to 15 ° C. above the melting point (Tm) of the thermoplastic resin and higher than the melting point (Tm). Ri temperature range der exhibiting rubber elasticity area,
The second temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin,
The thermoplastic resin is polypropylene,
The carbon nanofiber has an average diameter of 9 nm or more and 30 nm or less,
7 parts by mass or more and 35 parts by mass or less of the carbon nanofibers with respect to 100 parts by mass of the polypropylene,
The obtained thermoplastic resin composition is a method for producing a thermoplastic resin composition having a tensile yield point according to a stress-strain curve .   A mixing step of kneading the thermoplastic resin and the carbon nanofibers at a second temperature to obtain a first mixture containing an aggregate of a plurality of carbon nanofibers in the thermoplastic resin;
  A low temperature kneading step of kneading the first mixture at a first temperature;
Including
  In the dynamic viscoelasticity test of the first mixture, the first temperature is in a range up to a temperature not lower than the melting point (Tm) of the thermoplastic resin and 15 ° C. higher than the melting point (Tm). A temperature range indicating a rubber elastic region,
  The second temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin,
  The thermoplastic resin is polypropylene,
  The carbon nanofiber has an average diameter of more than 30 nm and 110 nm or less,
  The carbon nanofibers are 15 parts by mass or more and 33.3 parts by mass or less with respect to 100 parts by mass of the polypropylene,
  The obtained thermoplastic resin composition is a method for producing a thermoplastic resin composition having a tensile yield point according to a stress-strain curve. A mixing step of kneading the thermoplastic resin and the carbon nanofibers at a second temperature to obtain a first mixture containing an aggregate of a plurality of carbon nanofibers in the thermoplastic resin;
A low temperature kneading step of kneading the first mixture at a first temperature;
Including
In the dynamic viscoelasticity test of the first mixture, the first temperature is in a range up to a temperature not lower than the melting point (Tm) of the thermoplastic resin and 15 ° C. higher than the melting point (Tm). A temperature range indicating a rubber elastic region,
The second temperature is equal to or higher than the melting point (Tm) of the thermoplastic resin,
The thermoplastic resin, Ri polypropylene der,
The obtained thermoplastic resin composition has a tensile yield point according to a stress-strain curve, and is dynamic based on JIS K7244 at a measurement temperature of 20 to 300 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz. A method for producing a thermoplastic resin composition that does not flow and does not break at 300 ° C. when a viscoelasticity test is performed . In any one of Claims 1-3 ,
The thermoplastic resin is a polypropylene having a melting point (Tm) of 160 ° C.
Said first temperature, 160 ° C. or higher state, and are 1 75 ° C. or less,
The second temperature is, 180 ° C. or higher, 300 ° C. Ru der hereinafter method for producing a thermoplastic resin composition. In claim 1 or 2 ,
The thermoplastic resin is a first thermoplastic resin,
A second low-temperature kneading step for further adding a second thermoplastic resin to the second mixture obtained in the low-temperature kneading step to knead at a third temperature to obtain a third mixture;
The second thermoplastic resin is the same type of thermoplastic resin as the first thermoplastic resin,
The method for producing a thermoplastic resin composition, wherein the third temperature is a temperature range of the first temperature. A thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin,
There is no aggregate of carbon nanofibers,
Carbon nanofibers are dispersed throughout and separated from each other .
The thermoplastic resin is polypropylene,
The carbon nanofiber has an average diameter of 9 nm or more and 30 nm or less,
The carbon nanofiber is 5 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the polypropylene.
A thermoplastic resin composition having a tensile yield point in a stress-strain curve . A thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin,
There is no aggregate of carbon nanofibers,
Carbon nanofibers are dispersed throughout and separated from each other.
The thermoplastic resin is polypropylene,
The carbon nanofiber has an average diameter of more than 30 nm and 110 nm or less,
The carbon nanofiber is 5 parts by mass or more and 33.3 parts by mass or less with respect to 100 parts by mass of the polypropylene.
A thermoplastic resin composition having a tensile yield point in a stress-strain curve . A thermoplastic resin composition in which carbon nanofibers are dispersed in a thermoplastic resin,
There is no aggregate of carbon nanofibers,
Carbon nanofibers are dispersed throughout and separated from each other.
The thermoplastic resin, Ri polypropylene der,
Having a tensile yield point in the stress-strain curve;
Thermoplasticity that does not flow and does not break at 300 ° C. when a dynamic viscoelasticity test is performed based on JIS K7244 at a measurement temperature of 20 to 300 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz . Resin composition.