JP2005023419A - Carbon fiber composite material and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon fiber composite metallic material containing uniformly dispersed carbon nanofibers, to provide a method for producing the same, and to provide a metallic molding. <P>SOLUTION: The method for producing the carbon fiber composite metallic material comprises the step (a) of mixing a carbon fiber composite material with a metallic material in a fluid state and subsequent step (b) of cooling and solidifying the mixture obtained in the step (a). The carbon fiber composite material comprises an elastomer and carbon nanofibers dispersed in the elastomer. The elastomer has unsaturated bonds or groups having an affinity for the carbon nanofibers. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a carbon fiber composite metal material, a method for producing the same, and a metal molded article using the carbon fiber composite metal material.

  In recent years, composite materials using carbon nanofibers have attracted attention. Such a composite material is expected to improve mechanical strength and the like by including carbon nanofibers. However, since carbon nanofibers have strong cohesiveness with each other, it is very difficult to uniformly disperse the carbon nanofibers in the base material of the composite material. 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.

  For example, when carbon nanofibers and metal powder are mechanically mixed using a stirring means such as a ball mill as a means for compounding carbon nanofibers with metal, the carbon nanofibers are entangled with each other. It is not possible to obtain a carbon fiber composite metal material that is unevenly distributed and in which carbon nanofibers are uniformly dispersed. Further, in such a method, the carbon nanofibers are broken into pieces by mechanical shearing force, and it is difficult to sufficiently exhibit the function as a fiber.

  Therefore, an object of the present invention is to provide a carbon fiber composite metal material in which carbon nanofibers are uniformly dispersed while maintaining a good fiber state, a manufacturing method thereof, and a metal molded product.

The method for producing a carbon fiber composite metal material according to the present invention includes:
A step (a) of mixing a carbon fiber composite material and a metal material in a fluid state;
After the step (a), cooling and solidifying the mixture obtained in the step (a), and
The carbon fiber composite material includes an elastomer and carbon nanofibers dispersed in the elastomer.

  According to the production method of the present invention, it is possible to obtain a carbon fiber composite metal material in which carbon nanofibers are uniformly dispersed while maintaining a good fiber state.

  In the present invention, in the step (a), the metal material may be a thixotropic fluid or a molten state.

  In the present invention, the step of removing the elastomer may be included before the step (b).

  In the present invention, the step (a) and the step (b) can be performed by a casting method.

  In the present invention, the metal material may be one selected from aluminum, magnesium, and an alloy containing at least one of these.

  The elastomer of the carbon fiber composite material used in the present invention may have an unsaturated bond or group having an affinity for the carbon nanofiber. By using such an elastomer, the unsaturated bond or group of the elastomer is bonded to the active portion of the carbon nanofiber, particularly the radical at the end of the carbon nanofiber, thereby weakening the cohesive force of the carbon nanofiber. Dispersibility can be increased. As a result, in the carbon fiber composite material, carbon nanofibers are uniformly dispersed in an elastomer as a base material.

  The elastomer may be a rubber elastomer or a thermoplastic elastomer. In the case of a rubber-based elastomer, the elastomer may be either a crosslinked body or an uncrosslinked body. As the raw material elastomer, an uncrosslinked product is used in the case of a rubber-based elastomer.

  The carbon fiber composite material has a first spin-spin relaxation time (T2n) of 100 to 3000 μsec in an uncrosslinked body, measured at 150 ° C. by a Hahn echo method using pulsed NMR, The spin-spin relaxation time (T2nn) may be 1000 to 10,000 μs, and the component fraction (fnn) of the component having the second spin-spin relaxation time may be less than 0.2.

  The carbon fiber composite material has a first spin-spin relaxation time (T2n) of 100 to 2000 μsec measured in a crosslinked product at 150 ° C. by a Hahn echo method using pulse NMR, The spin-spin relaxation time (T2nn) may not exist or may be 1000 to 5000 μs, and the component fraction (fnn) of the component having the second spin-spin relaxation time may be less than 0.2. .

  The carbon fiber composite material has such characteristics, and carbon nanofibers are uniformly dispersed in an elastomer as a base material.

  In the production method of the present invention, by mixing the carbon fiber composite material in which the carbon nanofibers are already uniformly dispersed and the metal material in a fluid state, the carbon nanofibers are separated from each other without being entangled, A uniformly dispersed carbon fiber composite metal material can be obtained. Further, in the present invention, since the carbon fiber composite material and the metal material in a fluid state are mixed, a strong shearing force is applied to the carbon nanofibers as in the case of stirring the carbon nanofibers and the metal powder with a ball mill. Since it does not act directly, the carbon nanofibers are not broken and the fiber state can be maintained well. As a result, it is possible to obtain a carbon fiber composite metal material that can sufficiently exhibit properties such as a reinforcing function of carbon nanofibers.

  The metal molded product according to the present invention can be obtained by molding the carbon fiber composite metal material according to the present invention. The metal molded article of the present invention is excellent in mechanical strength such as rigidity, particularly rigidity at high temperatures, by containing carbon nanofibers in a good dispersion state. Further, since the metal molded product of the present invention has high mechanical strength, the molded product can be made thin, and the size and weight can be reduced. As a molding method of the metal molded product of the present invention, a known molding method such as a casting method, a forging method, an injection method, a sintering method, or the like can be used.

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

  The method for producing a carbon fiber composite metal material according to the present embodiment includes a step (a) of mixing a carbon fiber composite material and a metal material in a fluid state, and the step (a) after the step (a). And (b) a step of cooling and solidifying the obtained mixture. The carbon fiber composite material includes an elastomer and carbon nanofibers dispersed in the elastomer.

  First, steps (a) and (b) will be described.

  The carbon fiber composite material used in the step (a) is one in which carbon nanofibers are uniformly dispersed in an elastomer, as will be described in detail later. In addition, the metal material is in a fluid state, and can be a thixotropic fluid or a molten state. The carbon fiber composite material is mixed with the dissolved metal material, for example, in a casting method. The timing of mixing the carbon fiber composite material with such a metal material is set in consideration of the temperature, viscosity, etc. of the metal material.

  Before the step (b) of solidifying the mixture formed in the step (a), the carbon fiber composite elastomer can be removed. The method and timing for removing the elastomer are not particularly limited. As a method for removing the elastomer, for example, the elastomer can be decomposed by heat of the dissolved metal material. At this time, only the elastomer can be decomposed and removed at a temperature at which the carbon nanofibers are not decomposed by heat.

  In the step (a), when the carbon fiber composite material is mixed in the molten metal (molten metal), it is desirable that the molten metal is stirred to create a downward flow. This flow can prevent the carbon nanofibers having a small specific gravity from floating above the melt.

  The elastomer molecules in the carbon fiber composite material added to the molten metal are immediately decomposed and removed while burning. The molten metal enters the space from which the elastomer molecules have been removed, preventing the carbon nanofibers from aggregating. When the elastomer molecules are removed by combustion and decomposition, a reducing atmosphere is formed to reduce oxidation of the molten metal and prevent oxidative decomposition of the carbon nanofibers.

  When using thixotropic fluid, it is performed as follows. For example, when the temperature of the metal melted at 700 ° C. is gradually lowered to 500 ° C. to 550 ° C. with vigorous stirring, spherical dendritic crystals are formed where normal dendrite crystals grow, and the liquid phase surrounds them. In such a solid-liquid phase coexistence state, thixotropy is exhibited. In the thixotropic state, a large resistance (viscosity) to stirring is generated, the dispersion of the added carbon fiber composite material is improved, and the carbon nanofibers can be prevented from floating when the elastomer molecules are removed.

  Carbon nanofibers undergo oxidative decomposition at 500 ° C. to 600 ° C. in an oxygen atmosphere. However, it does not decompose up to about 900 ° C. in an inert atmosphere or a reducing atmosphere where oxygen is not present. Therefore, steps (a) and (b) are performed in an inert atmosphere such as nitrogen or argon, or in a reducing atmosphere in which a small amount of hydrogen is mixed in these inert atmospheres to prevent the molten metal from being oxidized, and defects such as nests are removed. In addition to preventing, oxidative degradation of the carbon nanofibers can be prevented.

  In the step (b), the molten metal containing the carbon nanofibers obtained in the step (a) can be poured into a mold and cooled to make an ingot.

  Using this ingot as a raw material, the most general gravity casting, various casting methods such as squeeze casting and centrifugal casting, as well as molding methods such as forging to obtain a shape by applying high pressure with a press, injection molding such as casting into a die at high pressure Can be obtained.

  In the step (b), it is also possible to directly cast using the molten metal obtained in the step (a). In this case, a desired shape can be obtained not only by gravity casting, squeeze casting, and centrifugal casting, but also by thixocasting from a thixo state. Moreover, the injection molding which inject | pours the molten metal obtained at the process (a) into a type | mold at high pressure is also possible.

  In this way, various forms of metal molded articles in which carbon nanofibers are dispersed can be obtained. This metal molded article is excellent in mechanical strength such as rigidity, particularly rigidity at high temperatures. In addition, since the metal molded product has high mechanical strength, the molded product can be thinned, and the size and weight can be reduced.

  In the present embodiment, the metal material is not particularly limited, but one kind selected from aluminum, magnesium, and an alloy containing at least one of them can be used. In particular, aluminum or an aluminum alloy can be used as the metal material.

  Next, the carbon fiber composite material will be described.

  (A) First, the elastomer will be described.

  In the carbon fiber composite material used in the present embodiment, the elastomer has an unsaturated bond or group having an affinity for carbon nanofibers. When the unsaturated bond or group of the elastomer is bonded to an active portion of the carbon nanofiber, particularly a radical at the end of the carbon nanofiber, the cohesive force of the carbon nanofiber can be weakened and the dispersibility can be increased. As a result, in the carbon fiber composite material, carbon nanofibers are uniformly dispersed in the elastomer as the base material.

  For example, the elastomer desirably has characteristics such as having a certain molecular length and flexibility in addition to having high affinity with the carbon nanofibers. The carbon fiber composite material can be obtained by dispersing carbon nanofibers in an elastomer by a shearing force.

  The elastomer preferably has a molecular weight of 5,000 to 5,000,000, more preferably 20,000 to 3,000,000. When the molecular weight of the elastomer is within this range, the elastomer molecules are entangled with each other and connected to each other. Therefore, the elastomer easily invades the aggregated carbon nanofibers, and thus has a great effect of separating the carbon nanofibers. If the molecular weight of the elastomer is less 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. If the molecular weight of the elastomer is greater than 5 million, the elastomer becomes too hard and processing becomes difficult.

  The elastomer preferably has a network component spin-spin relaxation time (T2n / 30 ° C.) of 100 to 3000 μsec, more preferably 200, measured at 30 ° C. by the Hahn echo method using pulsed NMR. Or 1000 μs. 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. Accordingly, when the elastomer and the carbon nanofiber are mixed, the elastomer can easily enter the gap 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 tends to flow like a liquid, and it becomes difficult to disperse the carbon nanofibers.

  The elastomer preferably has a spin-spin relaxation time (T2n) of the network component of 100 to 2000 μsec in the crosslinked product, measured at 30 ° C. by the Hahn echo method using pulsed NMR. The reason is the same as that of the uncrosslinked product described above. That is, when an uncrosslinked product having the above conditions is crosslinked by the production method of the present invention, T2n of the obtained crosslinked product is approximately within the above range.

  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, and relaxation A second component having a longer spin-spin relaxation time (T2nn) 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. Further, 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. 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 elastomer has an unsaturated bond or group having an affinity for carbon nanofibers, particularly a radical at its terminal, in at least one of the main chain, side chain and terminal chain, or such a radical or group has Easy to generate. Such unsaturated bonds or groups include double bonds, triple bonds, 瘰 / f, carbonyl groups, carboxyl groups, hydroxyl groups, amino groups, nitrile groups, ketone groups, amide groups, epoxy groups, ester groups, vinyl groups, halogens. It can be at least one selected from functional groups such as groups, urethane groups, burette groups, allophanate groups and urea groups.

  Carbon nanofibers are usually composed of a 6-membered ring with carbon atoms on the side, and the tip is closed by introducing a 5-membered ring, but the tip is structurally impossible, so in practice, Defects are easily generated, and it is easy to generate radicals and functional groups at the portions. In the present embodiment, at least one of the main chain, side chain, and terminal chain of the elastomer has an unsaturated bond or group having high affinity (reactivity or polarity) with the radical of the carbon nanofiber, so that the elastomer and carbon Nanofibers can be combined. This makes it possible to easily disperse the carbon nanofibers by overcoming the cohesive force.

  Elastomers include natural rubber (NR), epoxidized natural rubber (ENR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene propylene rubber (EPR, EPDM), and butyl rubber (IIR). ), Chlorobutyl rubber (CIIR), acrylic rubber (ACM), silicone rubber (Q), fluoro rubber (FKM), butadiene rubber (BR), epoxidized butadiene rubber (EBR), epichlorohydrin rubber (CO, CEO), urethane rubber (U), elastomers such as polysulfide rubber (T); olefin (TPO), polyvinyl chloride (TPVC), polyester (TPEE), polyurethane (TPU), polyamide (TPEA), styrene (SBS) ), Etc., thermoplastic elastomer ; And it can be a mixture thereof.

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

  The carbon nanofibers preferably have an average diameter of 0.5 to 500 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. When a carbon fiber composite material is used as a raw material for a metal composite material, carbon nanofibers can be included at a ratio of 0.01 to 50% by weight with respect to the carbon fiber composite material. The carbon fiber composite material can be used as a so-called master batch as a carbon nanofiber supply source when carbon nanofibers are mixed with a metal material.

  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 on the 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 surface treatment such as ion implantation treatment, sputter etching treatment, and plasma treatment in advance before being kneaded with the elastomer.

  (C) Next, a method for obtaining a carbon fiber composite material by dispersing carbon nanofibers in an elastomer by a shearing force will be described.

  As an example of a method for obtaining a carbon fiber composite material by dispersing carbon nanofibers in an elastomer by a shearing force, an example using an open roll method with a roll interval of 0.5 mm or less will be described.

  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 elastomer and the amount of carbon nanofibers.

  In this step, in order to obtain as high a shearing force as possible, the elastomer and the 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 nanofibers 40 are added to the bank 32, and the first and second rolls 10 and 20 are further rotated to mix the elastomer 30 and the carbon nanofibers 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, since the elastomer has the above-described characteristics, that is, the molecular morphology (molecular length) of the elastomer, molecular motion, and chemical interaction with the carbon nanofiber, it facilitates the dispersion of the carbon nanofiber. Thus, it is possible to obtain a carbon fiber composite material excellent in dispersibility and dispersion stability (the carbon nanofibers are difficult to reaggregate). More specifically, when an elastomer and carbon nanofibers are mixed, an elastomer with a moderately long molecular length and high molecular mobility penetrates into the carbon nanofibers, and a specific part of the elastomer is chemically It binds to the highly active part of the carbon nanofiber by interaction. In this state, if a strong shearing force acts on the mixture of the elastomer and carbon nanofibers, the carbon nanofibers move as the elastomer moves, and the aggregated carbon nanofibers are separated and dispersed in the elastomer. Will be. The carbon nanofibers once dispersed are prevented from reaggregating due to chemical interaction with the elastomer, and can have good dispersion stability.

  The method for dispersing carbon nanofibers in the elastomer by a shearing force is not limited to the above open roll method, and a closed kneading method or a multiaxial extrusion kneading method can also be used. In short, in this step, it is sufficient that a shearing force capable of separating the aggregated carbon nanofibers can be given to the elastomer.

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

  In the mixing / dispersing step of the elastomer and the carbon nanofiber, or following the mixing / dispersing step, a compounding agent usually used in processing of the 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 crosslinking agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization retarder, a softening agent, a plasticizer, a curing agent, a reinforcing agent, a filler, an antiaging agent, and a coloring agent. it can.

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

  In the carbon fiber composite material, carbon nanofibers are uniformly dispersed in an elastomer as a base material. This can be said to be a state where the elastomer is restrained by the carbon nanofibers. In this state, the mobility of the 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 are the same as those of the elastomer alone that does not include carbon nanofibers. Shorter than the case. Note that the spin-lattice relaxation time (T1) in the crosslinked body changes in proportion to the amount of carbon nanofibers mixed.

  In addition, in the state where the elastomer molecules are constrained by the carbon nanofibers, it is considered that the non-network component (non-network chain component) decreases for the following reason. In other words, when the molecular mobility of the elastomer decreases as a whole due to carbon nanofibers, the non-network component becomes more difficult to move, making it easier to behave like the network component, and the non-network component ( It is considered that the non-network component is reduced due to the fact that the terminal chain is easy to move and is easily adsorbed to the active site of the carbon nanofiber. Therefore, the component fraction (fnn) of the component having the second spin-spin relaxation time is smaller than that in the case of an elastomer alone that does not include carbon nanofibers.

  From the above, it is desirable for the carbon fiber composite material to have a measured value obtained by the Hahn echo method using pulsed NMR in the following range.

  That is, in the uncrosslinked product, the first spin-spin relaxation time (T2n) measured at 150 ° C. is 100 to 3000 μsec, and the second spin-spin relaxation time (T2nn) is 1000 to 10,000 μsec. Furthermore, the component fraction (fnn) of the component having the second spin-spin relaxation time is preferably less than 0.2.

  In the crosslinked product, the first spin-spin relaxation time (T2n) measured at 150 ° C. is 100 to 2000 μs, and the second spin-spin relaxation time (T2nn) does not exist or is 1000 to 5000 μs. Second, and the component fraction (fnn) of the component having the second spin-spin relaxation time is preferably less than 0.2.

  The spin-lattice relaxation time (T1) measured by the Hahn-echo method using pulsed NMR is a measure representing the molecular mobility of a substance together with the spin-spin relaxation time (T2). 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.

  In the carbon fiber composite material, the flow temperature in the temperature dependence measurement of dynamic viscoelasticity is preferably 20 ° C. or more higher than the flow temperature of the raw material elastomer alone. In the carbon fiber composite material, carbon nanofibers are well dispersed in the elastomer. This can be said to be a state where the elastomer is restrained by the carbon nanofibers as described above. In this state, the elastomer has a smaller molecular motion than the case where it does not contain carbon nanofibers, resulting in a decrease in fluidity. By having such flow temperature characteristics, the carbon fiber composite material has a low temperature dependency of dynamic viscoelasticity, and as a result, has excellent heat resistance.

  Carbon nanofibers usually have the property of being entangled with each other and difficult to disperse in a medium. However, in the present embodiment, when the carbon fiber composite material is used as a raw material for the metal composite material, the carbon nanofibers are already dispersed in the elastomer, so that the carbon fiber composite material and the metal material are mixed. The carbon nanofibers can be easily dispersed in the metal material.

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

(1) Preparation of carbon fiber composite material samples (Experimental Examples 1-6, Comparative Experimental Examples 1-3)
First, the sample of the carbon fiber composite material used for an Example was obtained. Specifically, a sample was obtained by kneading a predetermined amount of carbon nanofibers with the polymer material shown in Table 1 by the open roll method. As the sample, an uncrosslinked sample and a crosslinked sample were prepared by the following method.

(A) Preparation of uncrosslinked sample 1) A 6-inch open roll (roll temperature: 10 to 20 ° C.) was charged with a predetermined amount (100 g) of a polymer substance (100 parts by weight (phr)) shown in Table 1, It was wound around a roll.

  2) Carbon nanofibers (described as “CNT” in Table 1) in an amount (parts by weight) shown in Table 1 with respect to the polymer material were added to the polymer material. At this time, the roll gap was set to 1.5 mm.

  3) When the carbon nanofibers were added, the mixture of the polymer substance and the carbon nanofibers was taken out from the roll.

  4) 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.

  5) The roll was set to a predetermined gap (1.1 mm), and the thinned mixture was charged and dispensed.

  In this way, uncrosslinked samples of Experimental Examples 1 to 6 and Comparative Experimental Examples 2 and 3 were obtained.

  As the polymer plasticizer of Comparative Experimental Example 1, liquid 2-diethylhexyl phthalate (molecular weight: 391) was used. As Comparative Experimental Example 2, ethyl cellulose which is a thermoplastic resin was used. Further, as Comparative Experimental Example 3, an uncrosslinked sample of a polymer material (EPDM) containing no carbon nanofibers was obtained in the same manner except that carbon nanofibers were not mixed in the above steps 1) to 5).

(B) Production of crosslinked sample 1) to 4) were performed in the same manner as the uncrosslinked sample.

  5) A roll was set at a predetermined gap (1.1 mm), a thinned mixture was charged, and a predetermined amount of a crosslinking agent (2 parts by weight) was further charged. The mixture was then dispensed.

6) A sample cut into a mold size was set in a mold and subjected to press crosslinking at 175 ° C. and 100 kgf / cm ² for 20 minutes.

  In this way, crosslinked samples of Experimental Examples 1 to 5 and Comparative Experimental Example 3 were obtained. In Experimental Example 6, SBS (styrene-butadiene-styrene thermoplastic elastomer) is used as the raw material elastomer, and no crosslinking is performed. In Comparative Experimental Example 1, a liquid polymer material is used and crosslinking is not performed. In Comparative Experimental Example 2, a thermoplastic resin is used, and no crosslinking is performed.

(2) Measurement Using Pulse Method NMR Each uncrosslinked sample and crosslinked sample were measured by the Hahn echo method 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. By this measurement, the component content of the component having the first and second spin-spin relaxation times (T2n, T2nn) and the second spin-spin relaxation time for the uncrosslinked sample and the crosslinked sample of the raw material elastomer alone and the composite material. The rate (fnn) was determined. The measurement results are shown in Table 1. Further, the first and second spin-spin relaxation times (T2n, T2nn) of the uncrosslinked sample at the measurement temperature of 30 ° C. were measured, and the results are also shown in Table 1. For the crosslinked sample of the composite material, the amount of change in spin-lattice relaxation time (ΔT1) converted per 1% by volume of carbon nanofibers was determined. The measurement results are shown in Table 1.

(3) Measurement of E ′ (dynamic storage modulus), TB (tensile strength) and EB (cut elongation) E ′, TB and EB were measured according to JIS K 6521-1993 for the crosslinked sample of the composite material. These results are shown in Table 1. Since Comparative Experimental Example 1 was a liquid, these characteristics could not be measured. Comparative Experimental Example 2 is a non-crosslinked product, and in Table 1, these numerical values are marked with *.

(4) Measurement of flow temperature About the raw material elastomer simple substance and the uncrosslinked sample of a composite material, the flow temperature was measured by the dynamic viscoelasticity measurement (JIS K 6394). Specifically, the flow temperature was determined by applying a sine vibration (± 0.1% or less) to a sample having a width of 5 mm, a length of 40 mm, and a thickness of 1 mm, and measuring the stress and phase difference δ generated thereby. At this time, the temperature was changed from −70 ° C. to 150 ° C. at a rate of temperature increase of 2 ° C./min. The results are shown in Table 1. In Table 1, the case where no sample flow phenomenon was observed up to 150 ° C. was described as “150 ° C. or higher”.

  From Table 1, according to Experimental Examples 1 to 6 of the present invention, the following was confirmed. That is, the spin-spin relaxation time (T2n and T2nn / 150 ° C.) at 150 ° C. in the composite materials containing carbon nanofibers (uncrosslinked sample and crosslinked sample) is compared with that of the raw material elastomer alone not containing carbon nanofibers. Short. In addition, the component fraction (fnn / 150 ° C.) in the composite material containing carbon nanofibers (uncrosslinked sample and crosslinked sample) is smaller than that of an elastomer alone not containing carbon nanofibers. Furthermore, the spin-lattice relaxation time (T1) in the crosslinked sample containing carbon nanofibers is lower by a change amount (ΔT1) than in the case of the raw material elastomer not containing carbon nanofibers. From these, it can be seen that the carbon nanofibers are well dispersed in the carbon fiber composite material according to the experimental example.

  This can be clearly understood by comparing Experimental Examples 1 and 2 with Comparative Experimental Example 3. That is, in Comparative Experimental Example 3 that does not include carbon nanofibers, the spin-spin relaxation time (T2n and T2nn / 150 ° C.) of the uncrosslinked sample is not much different from that of the raw material elastomer alone. On the other hand, in Experimental Examples 1 and 2 of the present invention, the spin-spin relaxation time (T2n and T2nn / 150 ° C.) of the uncrosslinked sample is considerably shorter than that of the raw material elastomer alone. And in Experimental example 2 with a large carbon nanofiber content, the spin-spin relaxation time (T2nn / 150 ° C.) of the uncrosslinked sample was not detected. Thus, it was confirmed that in the uncrosslinked sample, Experimental Examples 1 and 2 were significantly different from Comparative Experimental Example 3 in terms of T2n and T2nn. The same was confirmed for the component fraction (fnn / 150 ° C.).

  For the crosslinked sample, it was confirmed that the spin-spin relaxation time (T2n and T2nn / 150 ° C.) was shorter than that of the raw material elastomer alone. In particular, in Experimental Example 2 in which the content of carbon nanofibers was large, the spin-spin relaxation time (T2nn / 150 ° C.) of the crosslinked sample was not detected. From this, it was confirmed that in the crosslinked sample, Experimental Examples 1 and 2 were significantly different from Comparative Experimental Example 3 in terms of T2n and T2nn. The same was confirmed for the component fraction (fnn / 150 ° C.). Further, the amount of change in spin-lattice relaxation time (ΔT1) converted per 1% by volume of carbon nanofibers showed a large value, and it was confirmed that the molecular mobility was lower than that of the raw material elastomer alone. It was.

  Also, from the results of E ′, TB and EB using the crosslinked sample, by including carbon nanofibers, the dynamic storage elastic modulus and tensile strength are improved while maintaining the cut elongation according to the experimental example of the present invention. In addition, it was confirmed that the carbon nanofibers can provide a significant reinforcing effect. This can be clearly understood by comparing Experimental Examples 1 and 2 with Comparative Experimental Example 3 that does not include carbon nanofibers. In particular, in Experimental Example 2 where the proportion of carbon nanofibers is large, it can be seen that the dynamic storage elastic modulus and tensile strength are remarkably improved.

  Furthermore, since the flow temperature in the composite material containing carbon nanofibers (uncrosslinked sample) is 20 ° C. or higher compared to the case of an elastomer alone not containing carbon nanofibers, the temperature dependence of dynamic viscoelasticity is small, It turns out that it has the outstanding heat resistance.

  In Comparative Experimental Example 1, the carbon nanofibers could not be dispersed because the molecular weight of the elastomer was too small. In Comparative Experimental Example 1, the spin-spin relaxation time and the characteristics E ′, TB, and EB could not be measured.

  In Comparative Experimental Example 2, since the first spin-spin relaxation time (T2n) at 30 ° C. of the raw material elastomer was too small, it was confirmed that the carbon nanofibers could not be sufficiently dispersed. Also, since the spin-spin relaxation time (T2nn) at 150 ° C. is too large, the molecular mobility is too high to apply a shearing force to the sample, and it is also difficult to disperse the carbon nanofibers. Was confirmed.

  In Comparative Experimental Example 3, since no carbon nanofibers were included, no reinforcing effect was observed.

  Furthermore, the image by SEM (Scanning Electron Microscopy) was calculated | required about the crosslinked sample of the composite material obtained in Experimental example 4. FIG. This SEM image is shown in FIG. The photographing conditions in this case were an acceleration voltage of 3.0 kV and a magnification of 10.0 k. From FIG. 2, it was confirmed that the carbon nanofibers were uniformly dispersed in the elastomer base material made of NBR without being entangled with each other. In FIG. 2, the whitish line-shaped part is a carbon nanofiber.

  For reference, an SEM image of raw material carbon nanofibers before mixing is shown in FIG. The SEM imaging conditions were an acceleration voltage of 3.0 kV and a magnification of 10.0 k. From the SEM image of FIG. 3, it can be seen that the raw carbon nanofibers are entangled with each other.

  From the above, according to this experimental example, it became clear that carbon nanofibers which are generally very difficult to disperse into the base material are uniformly dispersed in the elastomer while maintaining a good fiber state.

(5) Production of carbon fiber composite metal material (Example 1)
Using the carbon fiber composite material obtained in the above experimental example, the carbon fiber composite metal material according to the example was obtained by the following method.

  In a nitrogen atmosphere, the temperature was gradually lowered to 500 ° C. to 550 ° C. while vigorously stirring aluminum dissolved at 700 ° C. At this time, the aluminum fluid exhibited thixotropy. To this aluminum fluid, the carbon fiber composite material obtained in Experimental Example 4 of (1) above was added, and the aluminum fluid was stirred. Furthermore, this aluminum fluid was poured into a mold and cooled to prepare a carbon fiber composite metal material. When the cross section of this carbon fiber composite metal material was examined with an electron microscope, it was confirmed that the carbon nanofibers were dispersed.

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. It is a figure which shows the SEM image of the carbon fiber composite material obtained by the experiment example. It is a figure which shows the SEM image of raw material carbon nanofiber.

Explanation of symbols

10 first roll 20 second roll 30 elastomer 40 carbon nanofiber

Claims (18)

A step (a) of mixing a carbon fiber composite material and a metal material in a fluid state;
After the step (a), the step (b) of cooling and solidifying the mixture obtained in the step (a),
The said carbon fiber composite material is a manufacturing method of a carbon fiber composite metal material containing an elastomer and the carbon nanofiber disperse | distributed to this elastomer. In claim 1,
In the step (a),
The method for producing a carbon fiber composite metal material, wherein the metal material is a thixotropic fluid. In claim 1,
In the step (a),
The method for producing a carbon fiber composite metal material, wherein the metal material is in a molten state. In any of claims 1 to 3,
The manufacturing method of a carbon fiber composite metal material including the process by which the said elastomer is removed before the said process (b). In any of claims 1 to 4,
The said process (a) and process (b) are the manufacturing methods of a carbon fiber composite metal material performed by the casting method. In any of claims 1 to 5,
The method for producing a carbon fiber composite metal material, wherein the metal material is one selected from aluminum, magnesium, and an alloy containing at least one of them. In any one of Claims 1 thru | or 6.
The method for producing a carbon fiber composite metal material, wherein the elastomer has an unsaturated bond or group having an affinity for the carbon nanofiber. In any one of Claims 1 thru | or 7,
The method for producing a carbon fiber composite metal material, wherein the elastomer has a molecular weight of 5,000 to 5,000,000. In any of claims 1 to 8,
The elastomer has at least one of a main chain, a side chain and a terminal chain, a double bond, a triple bond, an α hydrogen, a carbonyl group, a carboxyl group, a hydroxyl group, an amino group, a nitrile group, a ketone group, an amide group, an epoxy group, A method for producing a carbon fiber composite metal material having at least one selected from functional groups such as ester groups, vinyl groups, halogen groups, urethane groups, burette groups, allophanate groups, and urea groups. In any one of Claim 1 thru | or 9,
The elastomer is a carbon fiber composite metal material having a spin-spin relaxation time (T2n) of a network component of 100 to 3000 μsec in an uncrosslinked body measured at 30 ° C. by a Hahn echo method using pulse NMR. Production method. In any one of Claim 1 thru | or 9,
The elastomer is a carbon fiber composite metal material having a network component spin-spin relaxation time (T2n) of 100 to 2000 μs measured in a crosslinked product at 30 ° C. by a Hahn echo method using pulsed NMR. Method. In any one of Claims 1 thru | or 11,
The carbon fiber composite material has a first spin-spin relaxation time (T2n) of 100 to 3000 μsec in an uncrosslinked body, measured at 150 ° C. by a Hahn echo method using pulsed NMR, The spin-spin relaxation time (T2nn) does not exist or is 1000 to 10000 μsec, and the component fraction (fnn) of the component having the second spin-spin relaxation time is less than 0.2. A method for producing a metal material. In any one of Claims 1 thru | or 11,
The carbon fiber composite material has a first spin-spin relaxation time (T2n) of 100 to 2000 μsec in the crosslinked body measured at 150 ° C. by a Hahn echo method using pulsed NMR, and a second spin A carbon fiber composite metal in which the spin relaxation time (T2nn) does not exist or is 1000 to 5000 μs, and the component fraction (fnn) of the component having the second spin-spin relaxation time is less than 0.2 Material manufacturing method. In any one of Claims 1 thru | or 13.
The method for producing a carbon fiber composite metal material, wherein the flow temperature in the uncrosslinked elastomer is 20 ° C. or more higher than the flow temperature of the elastomer alone. In any one of Claims 1 thru | or 14.
The carbon nanofiber is a method for producing a carbon fiber composite metal material having an average diameter of 0.5 to 500 nm.   A carbon fiber composite metal material obtained by the production method according to claim 1.   A carbon fiber composite metal material comprising carbon nanofibers dispersed in a metal base material so as not to be entangled with each other.   The metal molded product formed using the carbon fiber composite metal material of Claim 16 or 17.