JP2009001830A - Method for producing carbon fiber composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber composite material containing carbon nanofibers dispersed homogeneously. <P>SOLUTION: The method for producing the carbon fiber composite material comprises a step of dispersing the carbon nanofiber 40 in an elastomer 30 by shearing force. The elastomer 30 is a styrene-based thermoplastic elastomer having an epoxy group which has the affinity to the carbon nanofiber 40. The dispersing step is carried out by using an open roll method having ≤0.5 mm roll distance (d) at 0-50°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a carbon fiber composite material.

  A method for producing a fiber-reinforced composite material using a prepreg that is a sheet-like intermediate base material in which an epoxy resin or the like is impregnated with carbon fiber is known (for example, see Patent Document 1).

  In recent years, composite materials using carbon nanofibers have attracted attention. However, since carbon nanofibers have strong cohesiveness with each other, it is very important to uniformly disperse carbon nanofibers on the base material of composite materials. It is considered difficult. Therefore, at present, it is difficult to obtain a composite material of carbon nanofibers having desired characteristics, and expensive carbon nanofibers cannot be efficiently used.

Further, thermoplastic elastomers, which are recyclable rubber materials, are attracting attention due to the recent increase in environmental movement. However, although conventional thermoplastic elastomers are more recyclable than natural rubber, synthetic rubber, etc., the cross-linked structure is physical cross-linking, so there is a problem that flow due to temperature rise and creep deformation at low temperature are large. It was.
WO96 / 02592 Publication

  Accordingly, an object of the present invention is to provide a method for producing a carbon fiber composite material in which carbon nanofibers are uniformly dispersed.

The method for producing a carbon fiber composite material according to the present invention includes a step of dispersing carbon nanofibers in an elastomer by a shearing force,
The elastomer is a styrenic thermoplastic elastomer having an epoxy group having affinity for the carbon nanofibers,
The process is performed at 0 to 50 ° C. using an open roll method with a roll interval of 0.5 mm or less.

  According to the production method of the present invention, a carbon fiber composite material having good dispersibility of carbon nanofibers and excellent dispersion stability can be obtained.

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

  The method for producing a carbon fiber composite material according to the present embodiment includes a step of dispersing carbon nanofibers in an elastomer by a shearing force, and the elastomer has styrene having an epoxy group having affinity for the carbon nanofibers. A thermoplastic elastomer, and the process is performed at 0 to 50 ° C. using an open roll method with a roll interval of 0.5 mm or less.

  It is desirable that the styrenic thermoplastic elastomer has characteristics such as having a certain molecular length and flexibility in addition to having high affinity with the carbon nanofibers. Moreover, it is desirable that the step of dispersing the carbon nanofibers in the styrenic thermoplastic elastomer with a shearing force is kneaded with a shearing force as high as possible.

  (A) First, the styrenic thermoplastic elastomer having an epoxy group will be described.

  The styrene thermoplastic elastomer having an epoxy group according to the present embodiment (hereinafter simply referred to as “the present elastomer”) preferably has a molecular weight of 5,000 to 500,000, more preferably 20,000 to 200,000. If the molecular weight of the elastomer is within this range, the elastomer molecules are entangled with each other and are connected to each other. Therefore, the elastomer easily invades the aggregated carbon nanofibers, and thus has an effect of separating the carbon nanofibers from each other. Is big. When the molecular weight of the elastomer is smaller than 5000, the elastomer molecules cannot be sufficiently entangled with each other, and the effect of dispersing the carbon nanofibers is reduced even when a shearing force is applied in a later step. On the other hand, if the molecular weight of the elastomer is greater than 500,000, the elastomer becomes too hard and processing becomes difficult.

The elastomer has a network component spin-spin relaxation time (T2n / 30 ° C.) of 30 to 100 ° C. measured by pulsed NMR using the Hahn-echo method at ¹ ° C. and the observation nucleus is preferably 100 to 3000 μsec. Preferably it is 200 to 1000 microseconds. By having a spin-spin relaxation time (T2n / 30 ° C.) in the above range, the elastomer can be flexible and have sufficiently high molecular mobility. Thus, when the present elastomer and carbon nanofibers are mixed, the present elastomer can easily enter the gaps between the carbon nanofibers due to high molecular motion. If the spin-spin relaxation time (T2n / 30 ° C.) is shorter than 100 μsec, the elastomer cannot have sufficient molecular mobility. Also, if the spin-spin relaxation time (T2n / 30 ° C.) is longer than 3000 μsec, the elastomer easily flows like a liquid, and it becomes difficult to disperse the carbon nanofibers.

  The spin-spin relaxation time obtained by the Hahn-echo method using pulsed NMR is a measure representing the molecular mobility of a substance. Specifically, when the spin-spin relaxation time of the elastomer is measured by the Hahn-echo method using pulsed NMR, a first component having a first spin-spin relaxation time (T2n) having a short relaxation time; A second component having a second spin-spin relaxation time (T2nn) having a longer relaxation time is detected. The first component corresponds to a polymer network component (skeleton molecule), and the second component corresponds to a polymer non-network component (branch and leaf component such as a terminal chain). The shorter the first spin-spin relaxation time, the lower the molecular mobility and the harder the elastomer. Moreover, it can be said that the longer the first spin-spin relaxation time, the higher the molecular mobility and the softer the elastomer.

  As a measurement method in the pulsed NMR method, the solid echo method, the CPMG method (Car Purcell, Mayboom, Gill method) or the 90 ° pulse method can be applied instead of the Hahn echo method. However, since the carbon fiber composite material according to the present invention has a moderate spin-spin relaxation time (T2), the Hahn echo method is most suitable. Further, since accurate measurement is possible even at high temperatures, the Hahn echo method is most suitable. In general, the solid echo method and the 90 ° pulse method are suitable for short T2 measurement, the Hahn echo method is suitable for medium T2 measurement, and the CPMG method is suitable for long T2 measurement.

  The styrene-based thermoplastic elastomer raw material used in the present embodiment is defined as a block polymer having polystyrene as a hard segment and a rubbery polymer such as polybutadiene, polybutylene, or polyisoprene as a soft segment.

  Moreover, it is preferable that the structural unit content of the styrene compound is usually 5 to 80% by weight, and more preferably 10 to 70% by weight in the styrene thermoplastic elastomer raw material used in the present invention.

  The molecular structure of the styrenic thermoplastic elastomer raw material used in the present invention is preferably linear. For example, it is a styrene compound-conjugated diene compound block copolymer having a structure such as ABA, BABA, ABBABA, etc. ("A" is a styrene compound) Compound, “B” is a conjugated diene compound). Moreover, you may have a polyfunctional coupling agent residue in the molecule terminal.

  This elastomer is obtained by epoxidizing the styrene thermoplastic elastomer raw material. More specifically, the present elastomer comprises a conjugated diene compound of a block copolymer comprising a polymer block mainly comprising a styrene compound and a polymer block mainly comprising a conjugated diene compound or a partially hydrogenated product thereof. This is an epoxidized double bond.

  Examples of the styrenic compound include styrene, α-methylstyrene, vinyltoluene, p-tertiary butylstyrene, divinylbenzene, p-methylstyrene, 1,1-diphenylstyrene, vinylnaphthalene, vinylanthracene, and the like. 1 type or 2 types or more can be selected from among them, and styrene is particularly preferable.

  Examples of the conjugated diene compound include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene, phenyl-1,3-butadiene. Among these, one or more can be selected, and butadiene is particularly preferable.

  Therefore, for example, when the present elastomer is a styrene-butadiene block copolymer, the epoxy group can be an epoxidized double bond of butadiene in the styrene-butadiene block copolymer.

  The manufacturing method of this elastomer may be any manufacturing method as long as it has the structure described above. For example, it can be obtained by reacting the styrenic thermoplastic elastomer used in the present embodiment with an epoxidizing agent such as hydroperoxides and peracids in an inert solvent. The “inert solvent” is used for the purpose of reducing the viscosity of the raw material and stabilizing by diluting the epoxidizing agent, and for example, hexane, cyclohexane, toluene, benzene, ethyl acetate, carbon tetrachloride, chloroform, etc. can be used. .

  In the epoxidation, a “catalyst” can be used as necessary. For example, in the case of peracids, an alkali such as sodium carbonate or an acid such as sulfuric acid can be used as a catalyst. On the other hand, in the case of hydroperoxides, a catalytic effect is obtained by using a mixture of tungstic acid and caustic soda with hydrogen peroxide, organic acid with hydrogen peroxide, or molybdenum hexacarbonyl with tertiary butyl hydroperoxide. be able to.

  Isolation of the obtained elastomer is, for example, a method of precipitating with a poor solvent, a method of pouring the elastomer into hot water with stirring and distilling off the solvent, or directly drying the solvent by heating and / or decompression. It can be performed by a method or the like.

  The epoxidation rate of the epoxidized styrenic thermoplastic elastomer in the present invention is preferably 0.01 to 10% by weight, more preferably 0.5 to 3% by weight. When the amount of the epoxy group is less than 0.01% by weight, the effect of improving the dispersibility of the carbon nanofibers is poor.

  Carbon nanofibers usually have a six-membered ring of carbon atoms and a closed end with a five-membered ring introduced at the tip. It tends to occur, and it is easy to generate radicals and functional groups in the part. In the present embodiment, since the epoxy group of the elastomer has a high affinity with the radical of the carbon nanofiber, the elastomer and the carbon nanofiber can be bonded. This makes it possible to easily disperse the carbon nanofibers by overcoming the cohesive force.

  (B) Next, the carbon nanofiber will be described.

  The carbon nanofibers preferably have an average diameter of 0.5 to 500 nm, and more preferably an average diameter of 0.5 to 100 nm. The carbon nanofibers preferably have an average length of 0.01 to 1000 μm.

  The compounding quantity of carbon nanofiber is not specifically limited, It can set according to a use. The carbon fiber composite material of this embodiment can be used as an elastomer-based material, or can be used as a raw material for a composite material of metal or resin. When the carbon fiber composite material of the present embodiment is used as a raw material for a metal or resin composite material, carbon nanofibers can be included in a proportion of 0.01 to 50% by weight. The raw material of such a metal or resin composite material can be used as a so-called master batch as a supply source of carbon nanofibers when carbon nanofibers are mixed with metal or resin.

  Examples of carbon nanofibers include so-called carbon nanotubes. Carbon nanotubes have a single-layer structure in which graphene sheets with carbon hexagonal mesh surfaces are closed in a cylindrical shape, or a multilayer structure in which these cylindrical structures are arranged in a nested manner. That is, the carbon nanotube may be composed of only a single-layer structure or a multilayer structure, and the single-layer structure and the multilayer structure may be mixed. 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”.

  Single-walled carbon nanotubes or multi-walled carbon nanotubes are manufactured to a desired size by an arc discharge method, a laser ablation method, a vapor phase growth method, or the like.

  The arc discharge method is a method of obtaining multi-walled carbon nanotubes deposited on a cathode by performing an arc discharge between electrode materials made of carbon rods in an argon or hydrogen atmosphere at a pressure slightly lower than atmospheric pressure. In addition, the single-walled carbon nanotube is obtained by mixing the carbon rod with a catalyst such as nickel / cobalt to cause arc discharge and adhering to the inner surface of the processing vessel.

  The laser ablation method melts and evaporates the carbon surface by irradiating a strong YAG laser pulsed laser beam onto a carbon surface mixed with a target catalyst such as nickel / cobalt in a rare gas (eg argon). This is a method for obtaining single-walled carbon nanotubes.

  The vapor phase growth method is a method in which hydrocarbons such as benzene and toluene are thermally decomposed in the gas phase to synthesize carbon nanotubes. More specifically, a fluid catalyst method, a zeolite supported catalyst method, and the like can be exemplified.

  The carbon nanofibers can be improved in adhesion and wettability with the elastomer by performing a surface treatment such as ion implantation treatment, sputter etching treatment, and plasma treatment in advance before being kneaded with the elastomer. .

  (C) Next, a process of dispersing carbon nanofibers in the elastomer by a shearing force will be described.

  In the present embodiment, an example using an open roll method in which a roll interval is 0.5 mm or less will be described as a step of dispersing carbon nanofibers in the elastomer by a shearing force.

  FIG. 1 is a diagram schematically showing an open roll method using two rolls. In FIG. 1, the code | symbol 10 shows a 1st roll and the code | symbol 20 shows a 2nd roll. The first roll 10 and the second roll 20 are arranged at a predetermined interval d, preferably 0.5 mm or less, more preferably 0.1 to 0.3 mm. The first and second rolls rotate in the normal direction or the reverse direction. In the illustrated example, the first roll 10 and the second roll 20 rotate in the direction indicated by the arrow. 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) is preferably 1.05 to 3.00. By using such a surface velocity ratio, a desired shear force can be obtained. The shearing force in this step is appropriately set depending on the type of the elastomer and the amount of carbon nanofibers.

  In this step, in order to obtain as high a shearing force as possible, the present elastomer and carbon nanofiber are mixed preferably at a temperature of 0 to 50 ° C., more preferably 5 to 30 ° C. When the open roll method is used, it is desirable to set the temperature of the roll to the above temperature.

  When the elastomer 30 is wound around the second roll 20 in a state where the first and second rolls 10 and 20 are rotated, a so-called bank 32 in which the elastomer is accumulated between the rolls 10 and 20 is formed. The carbon nanofiber 40 is added to the bank 32 and the first and second rolls 10 and 20 are further rotated to mix the styrenic thermoplastic elastomer 30 and the carbon nanofiber 40. Next, the distance between the first and second rolls 10 and 20 is further reduced to the distance d described above, and the first and second rolls 10 and 20 are rotated at a predetermined surface speed ratio in this state. Thereby, a high shearing force acts on the elastomer 30, and the carbon nanofibers aggregated by the shearing force are separated from each other so as to be pulled out one by one and dispersed in the elastomer 30.

  At this time, the elastomer of the present embodiment has the above-described characteristics, that is, the characteristics of the elastomer, such as molecular morphology (molecular length), molecular motion, and chemical interaction with the carbon nanofibers. Therefore, it is possible to obtain a carbon fiber composite material excellent in dispersibility and dispersion stability (hardness of re-aggregation of carbon nanofibers). More specifically, when the elastomer and carbon nanofibers are mixed, the elastomer having a reasonably long molecular length and high molecular mobility enters the carbon nanofibers, and the epoxy groups of the elastomer are chemically It binds to a functional group such as a carboxyl group or a carbonyl group formed in a highly active portion of the carbon nanofiber, for example, a defective portion of the carbon nanofiber, by mechanical interaction. In addition, radicals are generated at the ends of the elastomer molecules when the elastomer is cleaved by a shearing force generated by an open roll or the like, and the radicals react with defective portions of the carbon nanofibers. In this state, when a strong shearing force is applied to the mixture of the elastomer and carbon nanofibers, the carbon nanofibers move with the movement of the elastomer, and the aggregated carbon nanofibers are separated. Will be distributed. And once disperse | distributed carbon nanofiber is prevented from reaggregating by the chemical interaction with this elastomer, and it can have favorable dispersion stability.

  In the step of dispersing the carbon nanofibers in the elastomer by a shearing force, it is sufficient that a shearing force capable of separating the aggregated carbon nanofibers can be applied to the elastomer.

  After the step of dispersing the carbon nanofibers in the elastomer described above and mixing them (mixing / dispersing step), an extrusion step, a molding step, and the like can be performed by a known method.

  In the mixing / dispersing step of the present elastomer and the carbon nanofiber, or following the mixing / dispersing step, a compounding agent usually used in processing of an elastomer such as rubber can be added. A well-known thing can be used as a compounding agent. Examples of the compounding agent include a softening agent, a plasticizer, a curing agent, a reinforcing agent, a filler, an antiaging agent, and a coloring agent.

  (D) Next, the carbon fiber composite material obtained by the above method will be described.

  In the carbon fiber composite material of the present embodiment, carbon nanofibers are uniformly dispersed in the elastomer as a base material. This can be said to be a state where the present elastomer is restrained by carbon nanofibers. In this state, the mobility of the present elastomer molecules constrained by the carbon nanofibers is smaller than that when not constrained by the carbon nanofibers. Therefore, the first spin-spin relaxation time (T2n), the second spin-spin relaxation time (T2nn), and the spin-lattice relaxation time (T1) of the carbon fiber composite material according to the present embodiment are the carbon nanofibers. This is shorter than the case of the present elastomer alone that does not contain.

  In the state where the present elastomer molecule is constrained by carbon nanofibers, the non-network component (non-network chain component) is considered to decrease for the following reason. In other words, when the molecular mobility of the elastomer decreases as a whole due to the carbon nanofibers, the non-network component becomes more difficult to move, making it easier to behave in the same way as the network component. Since the (end chain) is easy to move, the non-network component is considered to decrease because it is easily adsorbed to the active site of the carbon nanofiber. Therefore, the component fraction (fn) of the component having the first spin-spin relaxation time is larger than that of the present elastomer alone not containing carbon nanofibers.

  From the above, it is desirable that the carbon fiber composite material according to the present embodiment has a measured value obtained by the Hahn echo method using the pulse method NMR in the following range.

That is, the first spin-spin relaxation time (T2n) measured at 150 ° C. and the observation nucleus at ¹ H is 500 to 2000 μs, and the second spin-spin relaxation time (T2nn) is 5000 to 10,000 μs. In addition, the component fraction (fn) of the component having the first spin-spin relaxation time is preferably 0.9 or more.

The first spin-spin relaxation time (T2n) measured at 250 ° C. and the observation nucleus at ¹ H is 500 to 2000 μs, and the second spin-spin relaxation time (T2nn) is 5000 to 10,000 μs. In addition, the component fraction (fn) of the component having the first spin-spin relaxation time is preferably 0.5 or more. By measuring at 250 ° C., it can be determined whether the carbon fiber composite material is not flowing at 250 ° C. If the component fraction (fn) of the component having the first spin-spin relaxation time is 0.5 or more, it can be determined that the component does not flow.

  The spin-spin relaxation time (T2) measured by the Hahn-echo method using pulsed NMR is a measure representing the molecular mobility of a substance. Specifically, the shorter the spin-lattice relaxation time of the elastomer, the lower the molecular mobility, and the harder the elastomer, and the longer the spin-lattice relaxation time, the higher the molecular mobility and the softer the elastomer. The Hahn-echo method is desirable as a method for obtaining the spin-spin relaxation time (T2) at 150 ° C. or 250 ° C. because the measurement result at high temperature can be accurately obtained.

  In the carbon fiber composite material according to the present embodiment, the flow temperature in the temperature dependence measurement of dynamic viscoelasticity is preferably higher than the flow temperature of the single elastomer as a raw material, and the flow temperature is 300 ° C. or higher. is there. In the carbon fiber composite material of the present embodiment, carbon nanofibers are well dispersed in the elastomer. This can be said to be a state where the present elastomer is restrained by the carbon nanofibers as described above. In this state, the present elastomer has a smaller molecular motion than the case where carbon nanofibers are not contained, and as a result, the fluidity is lowered. By having such a flow temperature characteristic, the carbon fiber composite material of the present embodiment has a low temperature dependency of dynamic viscoelasticity, and as a result, has excellent heat resistance.

  Conventional thermoplastic elastomers have a problem that flow due to temperature rise and creep deformation at low temperatures are large compared to rubber materials such as natural rubber and synthetic rubber because the crosslinked structure is physical crosslinking. However, the carbon fiber composite material according to the present embodiment contains the above-described high-temperature characteristics (heat resistance) and low-temperature creep resistance by containing carbon nanofibers uniformly dispersed. Therefore, the carbon fiber composite material of the present embodiment can be used in the same field as conventional natural rubber and synthetic rubber, and can provide a recyclable rubber material.

  As described above, the carbon fiber composite material of the present embodiment can be used as an elastomer-based material, or can be used as a raw material for composite materials such as metals and resins. Carbon nanofibers usually have the property of being entangled with each other and difficult to disperse in a medium. However, when the carbon fiber composite material of the present embodiment is used as a raw material for a metal or resin composite material, the carbon nanofibers are already dispersed in the elastomer, so this raw material and a medium such as a metal or resin are used. By mixing, the carbon nanofibers can be easily dispersed in the medium.

Examples of the present invention will be described below, but the present invention is not limited thereto.
(Examples 1 to 3, Comparative Examples 1 and 2)
(1) Preparation of sample A sample was obtained by kneading a predetermined amount of carbon nanofibers with a styrene-based thermoplastic elastomer (present elastomer) having an epoxy group shown in Table 1 by an open roll method.
a) A predetermined amount (100 g) of the elastomer (100 parts by weight (phr)) shown in Table 1 was put into a 6-inch open roll (roll temperature: 10 to 20 ° C.) and wound around the roll.
b) An amount (parts by weight) of carbon nanofibers (described as “CNT” in Table 1) shown in Table 1 was added to the elastomer. At this time, the roll gap was set to 1.5 mm.
c) When the carbon nanofibers were charged, the mixture of the elastomer and the carbon nanofibers was taken out from the roll.
d) The roll gap was narrowed from 1.5 mm to 0.3 mm, and the mixture was introduced to make it thin. At this time, the surface speed ratio of the two rolls was set to 1.1. Thinning was repeated 10 times.
e) The roll was set to a predetermined gap (1.1 mm), and the thinned mixture was charged and dispensed.
Thus, the sample of the carbon fiber composite material of Examples 1-3 and Comparative Examples 1 and 2 was obtained.
As Comparative Example 1, a sample of this elastomer containing no carbon nanofibers was obtained in the same manner except that carbon nanofibers were not mixed in the above steps 1) to 5). As Comparative Example 2, a styrene-butadiene block copolymer having no epoxy group (SBS manufactured by Asahi Kasei Co., Ltd., described as “SBS” in Table 1) was used in place of this elastomer.

  In this way, samples of Examples 1 to 3 and Comparative Examples 1 and 2 were obtained. In Examples 1 to 3, a styrene-butadiene block copolymer (referred to as “E-SBS” in Table 1) Epofriend manufactured by Daicel Chemical Industries, Ltd. was used as a raw material elastomer. As the Epofriend, a molecular structure of styrene-butadiene-styrene (so-called SBS), which is an epoxidized double bond of butadiene, was used. The epoxidation rate of the raw material elastomers of Examples 1 and 2 and Comparative Example 1 is 1.7% by weight (trade name: A1005), and the epoxidation rate of the raw material elastomer of Example 3 is 0.9% by weight. % (Trade name: AT501). The constituent unit content of the styrene compound of the raw material elastomers of Examples 1 to 3 and Comparative Examples 1 and 2 was 60% by weight.

(2) Measurement using pulse method NMR About each sample, the measurement by the Hahn echo method was performed using pulse method NMR. This measurement was performed using “JMN-MU25” manufactured by JEOL Ltd. The measurement was performed under the conditions of the observation nucleus of ¹ H, the resonance frequency of 25 MHz, and the 90 ° pulse width of 2 μsec. The Pi was changed in various ways using the pulse sequence of the Hahn-echo method (90 ° x-Pi-180 ° x). The decay curve was measured. Further, the sample was measured by inserting it into a sample tube up to an appropriate range of the magnetic field. The measurement temperature was 150 ° C. and 250 ° C. By this measurement, for the sample of the carbon fiber composite material and the raw material elastomer alone (Comparative Example 1), the component having the first and second spin-spin relaxation times (T2n, T2nn) and the first spin-spin relaxation time is obtained. The component fraction (fn) was determined. The measurement results are shown in Table 1. Further, the spin-spin relaxation time (T2n) of the first component of the raw material elastomer when the measurement temperature is 30 ° C. was measured, and this result is also shown in Table 1.

(3) Measurement of E ′ (dynamic storage elastic modulus) and TB (tensile strength) E ′ and TB were measured according to JIS K 6521-1993 for a sample of carbon fiber composite material. These results are shown in Table 1.

(4) Measurement of flow temperature The flow temperature of the carbon fiber composite material sample and the raw material elastomer alone (Comparative Example 1) was measured. Specifically, the flow temperature was a temperature at which E ′ measured in (3) above was 1 MPa or less. The results are shown in Table 1. In Table 1, the case where E ′ did not become 1 MPa or less up to 300 ° C. was described as “none”.

(5) Recyclability test The carbon fiber composite material is molded in a mold, and the sample of the molded carbon fiber composite material is again put into the open roll used in (1) above and kneaded back, and then in the mold. Recyclability was judged based on whether it could be remolded.

(6) Measurement of creep resistance property A 1 mm (thickness) x 3 mm (width) x 10 mm (length) sample of a carbon fiber composite material was subjected to a thermomechanical analyzer (TMA / SS6100, manufactured by SII) at 100 ° C and a load of 5 MPa. Table 1 shows the change rate (%) of the length dimension after 1 hour. The smaller the rate of change (%), the better the creep resistance.

(7) Observation of carbon nanofiber dispersion state A sample of the carbon fiber composite material was observed by SEM (Scanning Electron Microscopy) to determine whether the carbon nanofibers were dispersed. Table 1 shows the results. In Table 1, “very good” is described when the carbon nanofibers are uniformly dispersed, and “good” is described when the carbon nanofibers are dispersed almost uniformly.

From Table 1, according to Examples 1 to 3 of the present invention, the following was confirmed. That is, the spin-spin relaxation time (T2n and T2nn / 150 ° C., 250 ° C.) at 150 ° C. and 250 ° C. in the carbon fiber composite material containing carbon nanofibers is compared with that of the raw material elastomer alone not containing carbon nanofibers. Short. Moreover, the component fraction (fn / 150 degreeC, 250 degreeC) in the sample of the carbon fiber composite material containing carbon nanofiber is large compared with the case of the elastomer simple substance which does not contain carbon nanofiber (Comparative Example 1).

  This can be clearly understood by comparing Examples 1 and 2 with Comparative Example 1. That is, in Examples 1 and 2 of the present invention, the spin-spin relaxation time (T2n and T2nn / 150 ° C., 250 ° C.) of the sample of the carbon fiber composite material is considerably higher than that of the raw material elastomer alone of Comparative Example 1. It is getting shorter. And in Example 2 with a large content ratio of carbon nanofibers, it was shorter than the spin-spin relaxation time (T2nn / 150 ° C., 250 ° C.) of the sample of the carbon fiber composite material of Example 1. Therefore, in the carbon fiber composite material sample, it was confirmed that Examples 1 to 3 differed from Comparative Example 1 in terms of T2n, T2nn, and fn. Moreover, the component fraction (fn / 250 degreeC) of Examples 1-3 was 0.5 or more, and it was determined that it was not flowing.

  In addition, from the results of E ′ and TB using a sample of carbon fiber composite material, by including carbon nanofibers, the dynamic storage elastic modulus and tensile strength are improved according to the example of the present invention. It was confirmed that a significant reinforcing effect was obtained with the fiber. This can be clearly seen by comparing Examples 1 and 2 with Comparative Example 1 that does not contain carbon nanofibers. In particular, it can be seen that in Example 2 where the proportion of carbon nanofibers is large, the dynamic storage elastic modulus is improved.

  Furthermore, the flow temperature in the sample of the carbon fiber composite material containing carbon nanofibers is higher than that of the raw material elastomer alone not containing carbon nanofibers, and the flow temperature is 300 ° C. or higher. It can be seen that the temperature dependency is small and the heat resistance is excellent.

  Moreover, in the comparative example 1, since the carbon nanofiber was not included, the reinforcement effect was not recognized.

  It turned out that Examples 1-3 are excellent in creep resistance in high temperature (100 degreeC) compared with Comparative Examples 1 and 2. In Comparative Example 2, the carbon nanofibers are relatively well dispersed, but in Examples 1-3, the creep resistance at high temperatures is improved because the carbon nanofibers are more uniformly dispersed by the interaction with the carbon nanofibers due to the epoxy groups. It was confirmed. Recyclability was good for all samples.

  In addition, as a result of SEM (Scanning Electron Microscopy) observation, the samples of the carbon fiber composite materials of Examples 1 to 3 are more uniform in the state where the carbon nanofibers are separated from each other than the sample of Comparative Example 2. It was confirmed that they were dispersed.

  From the above, according to the present invention, it is clear that carbon nanofibers that are generally very difficult to disperse in the base material are uniformly dispersed in the elastomer, there is no flow at high temperature, and creep resistance at high temperature It has been found that a good thermoplastic elastomer (carbon fiber composite material) can be obtained. Therefore, it was found that a thermoplastic elastomer that is excellent in recyclability and can be used even at high temperatures can be obtained.

It is a figure which shows typically the kneading | mixing method of the elastomer and carbon nanofiber by the open roll method used in this Embodiment.

Explanation of symbols

10 first roll 20 second roll 30 elastomer 40 carbon nanofiber

Claims (7)

Including a step of dispersing carbon nanofibers in an elastomer by a shearing force,
The elastomer is a styrenic thermoplastic elastomer having an epoxy group having affinity for the carbon nanofibers,
The said process is a manufacturing method of a carbon fiber composite material performed at 0-50 degreeC using the open roll method whose roll space | interval is 0.5 mm or less. In claim 1,
The method for producing a carbon fiber composite material, wherein the styrene-based thermoplastic elastomer having an epoxy group has a molecular weight of 5000 to 500,000. In claim 1 or 2,
The styrenic thermoplastic elastomer having an epoxy group has a spin-spin relaxation time (T2n) of a network component of 100 to 3000 μsec as measured by a Hahn-echo method using pulsed NMR at 30 ° C. and an observation nucleus of ¹ H. A method for producing a carbon fiber composite material. In any of claims 1 to 3,
The styrenic thermoplastic elastomer is a styrene-butadiene block copolymer,
The said epoxy group is a manufacturing method of the carbon fiber composite material which epoxidized the double bond of butadiene among the said styrene-butadiene block copolymers. In any of claims 1 to 4,
The method for producing a carbon fiber composite material, wherein the styrenic thermoplastic elastomer has an epoxidation rate of 0.001 to 10% by weight. In any of claims 1 to 5,
The carbon nanofiber is a method for producing a carbon fiber composite material having an average diameter of 0.5 to 500 nm. In claim 1,
The open roll method is a method for producing a carbon fiber composite material in which the surface speed ratio of two rolls is 1.05 to 3.00.

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