JP4201794B2 - Porous composite material and method for producing the same, and method for producing the composite material - Google Patents

Description

The present invention, porous composite materials and methods of manufacturing the same, a method of manufacturing a composite materials.

  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.

  In addition, as a method for casting a metal composite material, magnesium vapor is allowed to permeate and disperse in a porous molded body made of oxide ceramics, and at the same time, nitrogen gas is introduced so that the molten metal penetrates into the porous molded body. A casting method has been proposed (see, for example, Patent Document 1).

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. Therefore, in order to efficiently use expensive carbon nanofibers, a method for producing a carbon fiber composite metal material using a carbon fiber composite material in which an elastomer and carbon nanofiber are mixed has been proposed (for example, Patent Document 2). reference).
JP-A-10-183269 JP-A-2005-97534

Therefore, an object of the present invention is to provide a porous composite material in which carbon nanofibers are dispersed and a method for producing the same. Another object of the present invention is to provide a method for producing a composite materials of the carbon nanofibers are uniformly dispersed.

The method for producing a porous composite material according to the present invention includes:
(A) a step of mixing a first particle, a second particle, and a carbon nanofiber with an elastomer and dispersing the mixture by a shearing force to obtain a carbon fiber composite material;
(B) a step of heat-treating the carbon fiber composite material to decompose and vaporize an elastomer contained in the carbon fiber composite material to obtain an intermediate composite material;
Pressing the intermediate composite material to obtain a porous composite material (c);
Including
The second particles have a hardness higher than that of the first particles, and a weight ratio in the carbon fiber composite material is smaller than that of the first particles.

  The porous composite material concerning this invention is obtained by the said manufacturing method.

  According to step (a) of the production method of the present invention, carbon nanofibers are dispersed in an elastomer by a shearing force, and a porous composite material in which carbon nanofibers are uniformly dispersed is obtained by steps (b) and (c). be able to. The intermediate composite material obtained by the step (b) has a variation in the size of pores formed by decomposing and vaporizing the elastomer, but the step (c) crushes voids (voids) of 100 μm or more, for example. A porous composite material having a uniform size and uniform throughout can be obtained. Moreover, since the second particles have a higher hardness than the first particles, an appropriate porous structure can be maintained without crushing the gaps between the particles by pressurization in the step (c). it can. In addition, since the second particles have a smaller weight ratio in the carbon fiber composite material than the first particles, the second particles have less influence on the material properties of the porous composite material. Further, the porous composite material in which the carbon nanofibers are uniformly dispersed and the pore size is uniform can be easily used for general metal processing, for example, processing such as a non-pressure infiltration method.

In the method for producing a porous composite material according to the present invention,
The hardness of the second particles can be 2 to 150 times the hardness of the first particles.

In the method for producing a porous composite material according to the present invention,
The weight ratio of the second particles to the first particles can be 0.1 wt% to 10 wt%.

In the method for producing a porous composite material according to the present invention,
The blending amount of the first particles and the second particles can be 300 to 600 parts by weight with respect to 100 parts by weight of the elastomer.

In the method for producing a porous composite material according to the present invention,
The first particles have an average particle size larger than the average diameter of the carbon nanofibers,
The second particles may have an average particle size that is greater than the average particle size of the first particles.

In the method for producing a porous composite material according to the present invention,
The first particles are aluminum;
The second particles can be alumina.

In the method for producing a porous composite material according to the present invention,
The elastomer may have an unsaturated bond or group having affinity for carbon nanofibers.

The method for producing a composite material according to the present invention includes:
A molten matrix material is infiltrated into the porous composite material.

  According to such a method for producing a composite material, a composite material in which carbon nanofibers are uniformly dispersed can be obtained by using a porous composite material in which carbon nanofibers are dispersed as described above. In addition, according to such a manufacturing method, the porous composite material is formed of only the matrix material that has penetrated the porous composite material because the pore size does not vary due to the pressurization in the step (c). There are no large streak defects of 100 μm or more. Moreover, since the pores of the porous composite material can be maintained in a porous structure without being crushed by the step (c) by including the second particles, the molten metal can easily penetrate into the porous composite material. Can be made.

  Further, in the composite material obtained in this way, the matrix material is uniformly filled between the particles of the first particles, and the carbon nanofibers are well dispersed. Thus, the composite material has mechanical properties that are homogeneous throughout.

  The elastomer in the present invention may be either a rubber-based 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, but an uncrosslinked body is preferable in order to easily decompose and vaporize the elastomer in the step (b).

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

  In the method for producing a porous composite material according to the present embodiment, a first fiber, a second particle, and a carbon nanofiber are mixed in an elastomer and dispersed by a shearing force. A step (a) of obtaining a carbon fiber composite material, a step (b) of obtaining an intermediate composite material by decomposing and vaporizing an elastomer contained in the carbon fiber composite material, and pressurizing the intermediate composite material. And (c) obtaining a porous composite material, wherein the second particles have a higher hardness than the first particles, and the weight ratio in the carbon fiber composite material is Smaller than the first particle.

  The porous composite material according to the present embodiment is obtained by the manufacturing method.

  In the method for manufacturing a composite material according to the present embodiment, a molten metal material is infiltrated into the porous composite material.

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

(A) First, the elastomer will be described.
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 elastomer according to the present invention has a medium 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, α hydrogen, carbonyl groups, carboxyl groups, hydroxyl groups, amino groups, nitrile groups, ketone groups, amide groups, epoxy groups, ester groups, vinyl groups, halogen groups. , Urethane groups, burette groups, allophanate groups, and urea groups.

  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, 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), fluorine 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. According to the research of the present inventors, it has been found that it is difficult to disperse carbon nanofibers particularly in ethylene propylene rubber (EPR, EPDM).

(B) Next, the first particles and the second particles will be described.
The first particles are used as raw materials for producing the composite material, and are mixed and dispersed in the elastomer, so that the carbon nanofibers are more favorably dispersed when the carbon nanofibers are mixed. Is. The first particle is a main constituent material in the porous composite material and the composite material, and can be appropriately selected according to the application. As the first particles, aluminum (hardness: HV27), magnesium (hardness: HV35), titanium (hardness: HV150), iron (hardness: HV300), gold (hardness: HV80), silver (hardness: HV80), copper (Hardness: HV100), nickel (hardness: HV100), selenium (hardness: HV30), tin (hardness: HV10), zinc (hardness: HV70) (including these alloys) alone or in combination Can be used.

  The second particles have a higher hardness than the first particles, and the weight percentage in the carbon fiber composite material is smaller than the first particles. Since the hardness of the second particles is higher than the hardness of the first particles, the pore size of the entire porous composite material is maintained while maintaining appropriate pores of the porous composite material even after the step (c). Therefore, the porous composite material can be homogenized. The hardness of the second particles is preferably 2 to 150 times, more preferably 25 to 90 times the hardness of the first particles. If the hardness of the second particles is less than twice the hardness of the first particles, the second particles are also compressed and deformed together with the first particles by the pressurization in the step (c), and there is an empty space between the first particles. The hole cannot be maintained. In addition, it is industrially difficult to select the type of particles such that the hardness of the second particles exceeds 150 times the hardness of the first particles, since they are generally expensive. Here, the hardness indicates the Vickers hardness (HV) of the metal constituting each particle.

The second particle may be an alloy of the same metal having a high hardness if the first particle is a pure metal, or a ceramic having a higher hardness, such as alumina (Al ₂ O ₃ ) (hardness: HV1800). , Zirconia (ZrO ₂ ) (hardness: HV1300), magnesia (MgO) (hardness: HV1000), mullite (3Al ₂ O ₃ · 2SiO ₂ ) (hardness: HV900), zircon (ZrSiO ₄ ) (hardness: HV1500), etc. Oxide ceramics, silicon nitride (Si ₂ N ₂ ) (hardness: HV1400), aluminum nitride (AlN) (hardness: HV1000), titanium nitride (TiN) (hardness: HV2200), zirconium nitride (ZrN) (hardness: HV2000 ), Nitride ceramics such as tantalum nitride (TaN) (hardness: HV2000), silicon carbide (SiC) (hardness: HV2200), titanium carbide (TiC) (hardness: HV3200), boron carbide (B ₄ C) (hardness: HV3300), tungsten carbide (WC) (hardness: HV2400) and other carbide-based ceramics, composite oxides and mixtures thereof can be appropriately selected according to the application. In particular, it is preferable to use alumina particles or silicon carbide particles. If the first particles are aluminum, alumina is preferable as the second particles, and silicon carbide is preferable if the first particles are silicon.

  The second particles only need to be able to maintain dense vacancies even after the step (c). Therefore, the compounding amount of the second particles is preferably about the level of impurities in the porous composite material or the composite material. It is preferable that the quality of the composite material or the physical properties of the composite material is not significantly affected. It is preferable that the weight ratio of the 2nd particle with respect to the 1st particle mix | blended in a process (a) is 0.1 to 10 weight%, for example. When the weight ratio of the second particles to the first particles is less than 0.1% by weight, the pores are crushed by the pressurization in the step (c), and the matrix material cannot easily penetrate. Further, when the weight ratio of the second particles to the first particles is more than 10% by weight, the influence on the physical properties of the porous composite material and the composite material is increased, which is not preferable.

  It is preferable that the first particles have an average particle size larger than the average diameter of the carbon nanofibers, and the second particles have an average particle size larger than the average particle size of the first particles. When the average particle size of the first particles is larger than the average particle size of the carbon nanofibers, the dispersibility of the carbon nanofibers can be improved in the step (a). By making the average particle size of the second particles larger than the average particle size of the first particles, the stress due to the pressurization in the step (c) can be relaxed, and the entire porous composite material can be homogenized. . For example, the average particle size of the first particles is preferably 10 μm to 100 μm, and the average particle size of the second particles is preferably 0.1 μm to 100 μm. Further, the shape of the first particle and the second particle is not limited to the spherical particle shape, and the pore size may be uniform between the particles of the first particle in the case of the porous composite material.

(C) Next, the carbon nanofiber will be described.
The carbon nanofibers preferably have an average diameter of 0.5 to 500 nm, and more preferably 0.5 to 30 nm in order to improve the strength of the composite material. Furthermore, the carbon nanofibers may be straight fibers or curved fibers.

  The compounding quantity of carbon nanofiber is not specifically limited, It can set according to a use. In the carbon fiber composite material of the present embodiment, a crosslinked elastomer, an uncrosslinked elastomer or a thermoplastic elastomer can be used as it is as an elastomeric material. The carbon fiber composite material of the present embodiment can contain carbon nanofibers in a proportion of 0.01 to 50% by weight. The porous composite material obtained by decomposing and vaporizing the elastomer of the carbon fiber composite material can be used as a so-called master batch as a supply source of carbon nanofibers when the matrix material is infiltrated.

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

(D) Next, the step (a) of obtaining a carbon fiber composite material by mixing the first particles, the second particles, and the carbon nanofibers in the elastomer and dispersing them by a shearing force will be described. .
In this embodiment, an example using an open roll method with a roll interval of 0.5 mm or less will be described as the step (a).

  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 1.0 mm or less, more preferably 0.1 to 0.5 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) of both is preferably 1.05 to 3.00, It is preferably 1.05 to 1.2. By using such a surface velocity ratio, a desired shear force can be obtained. First, when the elastomer 30 is wound around the second roll 20 while 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. By adding the first particles 41 and the second particles 42 in the bank 32 and further rotating the first and second rolls 10 and 20, the elastomer 30, the first particles 41, and the second particles are rotated. The step of mixing the particles 42 is performed. Next, the carbon nanofibers 40 are added to the bank 32 in which the elastomer 30 and the first particles 41 and the second particles 42 are mixed, and the first and second rolls 10 and 20 are rotated. Further, the distance between the first and second rolls 10 and 20 is 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. Further, since the first particles 41 and the second particles 42 are in the form of particles, the shearing force generated by the roll is turbulent flow around the first particles 41 and the second particles 42 dispersed in the elastomer. Is generated. The carbon nanofibers are further dispersed in the elastomer 30 by this complicated flow. Note that if the elastomer 30 and the carbon nanofiber 40 are mixed before the first particle 41 and the second particle 42 are mixed, the movement of the elastomer 30 is restrained by the carbon nanofiber 40. It becomes difficult to mix the particles and the second particles. Therefore, it is preferable to perform a step of mixing the first particles 41 and the second particles 42 before adding the carbon nanofibers 40 to the elastomer 30.

  In addition, in this step (a), for example, magnesium particles are added in a small amount, for example, about 10 parts by weight with respect to 100 parts by weight of the elastomer as metal particles that act as a reducing agent in the step of infiltrating the molten metal of the matrix material into the porous composite material. It is preferable to mix.

  The blending amount of the first particles 41 and the second particles 42 is preferably 300 to 600 parts by weight with respect to 100 parts by weight of the elastomer. If the blending amount of the first particles 41 and the second particles 42 is less than 300 parts by weight, the amount of the elastomer to be decomposed and vaporized is too much, and the productivity is unfavorable. If the blending amount of the first particles 41 and the second particles 42 is more than 600 parts by weight, the processing in the step (a) becomes difficult, which is not preferable.

  Further, in this step (a), free radicals are generated in the elastomer sheared by the shearing force, and the free radicals attack the surface of the carbon nanofibers, thereby activating the surface of the carbon nanofibers. For example, when natural rubber (NR) is used as an elastomer, each natural rubber (NR) molecule is cut while being kneaded by a roll, and has a smaller molecular weight than before being put into an open roll. Radicals are generated in the natural rubber (NR) molecules thus cut, and the radicals attack the surface of the carbon nanofibers during kneading, so that the surface of the carbon nanofibers is activated. The activated carbon nanofibers are bonded to oxygen in the atmosphere and the wettability with a matrix material such as aluminum is improved.

  Further, in this step (a), in order to obtain as high a shearing force as possible, the mixing of the elastomer and the carbon nanofiber is preferably performed at a relatively low 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. The distance d between the first and second rolls 10 and 20 is set wider than the average particle diameter of the first particles 41 and the second particles 42 even in the narrowest state, so that the carbon nanofibers in the elastomer 30 are set. The dispersion of 40 can be performed satisfactorily.

  At this time, the elastomer of the present embodiment has the characteristics described above, that is, the molecular morphology (molecular length) of the elastomer, the molecular motion, the chemical interaction with the carbon nanofiber, and the like. Therefore, a carbon fiber composite material excellent in dispersibility and dispersion stability (hardness of re-aggregation of carbon nanofibers) can be obtained. More specifically, when an elastomer and carbon nanofibers are mixed, an elastomer having a reasonably long molecular length and high molecular mobility penetrates into the carbon nanofibers, and a specific portion of the elastomer is chemically interlinked. It binds to the highly active part of the carbon nanofiber by action. 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.

  In addition, since a predetermined amount of the first particles are contained in the elastomer, the individual carbon nanofibers are separated from each other by various complicated flows such as the turbulent flow of the elastomer generated around the first particles. Shear force will also work in the direction of pulling apart. Therefore, even in the case of carbon nanofibers having a diameter of about 30 nm or less or curved carbon-like carbon nanofibers, they move in the respective flow directions of the individual elastomer molecules bonded by chemical interaction. Will be distributed.

  The step of dispersing the carbon nanofibers in the elastomer by a shearing force is not limited to the open roll method, and a closed kneading method or a multi-screw 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.

  The carbon fiber composite material obtained by the step (a) of dispersing the first particles, the second particles, and the carbon nanofibers in the elastomer described above and mixing them is crosslinked with a crosslinking agent and molded, or It can be molded without crosslinking. As a molding method at this time, for example, a compression molding process or an extrusion molding process can be employed. In the compression molding step, a carbon fiber composite material in which carbon nanofibers are dispersed is molded in a pressurized state for a predetermined time (for example, 20 minutes) in a molding die having a desired shape set at a predetermined temperature (for example, 175 ° C.). Process.

  In the step of mixing / dispersing the elastomer and the carbon nanofiber, or subsequently, 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.

(E) 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 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 according to the present embodiment are the carbon nanofibers. It becomes shorter than the case of the elastomer simple substance which does not contain. In particular, when carbon nanofibers are mixed in an elastomer containing metal particles, the second spin-spin relaxation time (T2nn) is shorter than in the case of an elastomer containing carbon nanofibers. In addition, the spin-lattice relaxation time (T1) in the crosslinked body changes in proportion to the mixing amount of the carbon nanofibers.

  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. In particular, when carbon nanofibers are mixed with an elastomer including first particles and second particles, the component content of the component having the second spin-spin relaxation time is further increased than that of an elastomer including carbon nanofibers. The rate (fnn) becomes small.

  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, 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) does not exist or 1000 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 according to the present embodiment, 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 of the present embodiment, the first and second particles and the 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 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.

  Carbon nanofibers usually have the property of being entangled with each other and difficult to disperse in a medium. However, when the porous composite material obtained by decomposing and vaporizing the elastomer of the carbon fiber composite material of the present embodiment is used as a raw material for a metal composite material, for example, the carbon nanofibers are already dispersed in the elastomer, By mixing this raw material and a matrix material such as metal, the carbon nanofibers can be easily dispersed in the matrix material. In addition, since the surface of the carbon nanofiber is activated or reacts with oxygen or the like to improve the wettability with the metal, the matrix material of the composite material has good wettability.

(F) Next, the step (b) of obtaining an intermediate composite material by heat-treating the carbon fiber composite material to decompose and vaporize the elastomer contained in the carbon fiber composite material will be described.
In the step (b), the carbon fiber composite material is heat-treated to decompose and vaporize the elastomer, thereby obtaining an intermediate composite material in which the carbon nanofibers are dispersed around the first particles and the second particles.

  Various conditions can be selected for such heat treatment depending on the type of elastomer used. Step (b) is preferably heat-treated in an inert gas atmosphere at a temperature equal to or higher than the decomposition vaporization temperature of the elastomer and lower than the melting point of the first particles. As the inert gas, nitrogen, nitrogen containing 5% or less of oxygen, argon, or the like can be used. The inert gas atmosphere is used because the carbon nanofibers are oxidatively decomposed (burned) when the heat treatment in the step (b) is performed in the air.

  A carbon fiber composite material is placed in a heat treatment furnace in an inert gas atmosphere, and the inside of the furnace is heated to a temperature higher than the temperature at which the elastomer is decomposed and vaporized. By this heating, the elastomer is decomposed and vaporized, and an intermediate composite material in which carbon nanofibers are dispersed around the first particles and the second particles is manufactured.

  When the elastomer is, for example, natural rubber (NR) and the first particles are, for example, aluminum particles, the heat treatment temperature in step (b) is preferably 300 to 650 ° C. If the heat treatment temperature is 300 ° C. or higher, natural rubber is decomposed and decomposed and vaporized, and if the heat treatment temperature is 650 ° C. or lower, an intermediate composite material can be obtained without melting aluminum particles. In addition, although heat processing time becomes short, so that heat processing temperature is high, in order for an elastomer to decompose | disassemble and vaporize, it is 1 minute-100 hours.

  The intermediate composite material obtained in this way has carbon nanofibers dispersed between the first particles and the second particles. Since the wettability between the carbon nanofibers and the first particles is good, the carbon nanofibers are dispersed around the first particles in a state close to the state dispersed in the elastomer. However, the intermediate composite material thus obtained has relatively large pores that widen the interval between the first particles when the elastomer is decomposed and vaporized, and the pores between the first particles are not uniform. Absent.

(G) Next, the step (c) in which the intermediate composite material is pressurized to obtain a porous composite material will be described.
In step (c), the intermediate composite material obtained in step (b) is compressed in a mold to obtain a porous material. By the pressurization in the step (c), relatively large pores, for example, pores of 100 μm or more are removed from the intermediate composite material, and a porous composite material in which the pore sizes between the first particles are uniform is obtained.

  FIG. 2 is a schematic explanatory diagram of the step (c). The intermediate composite material 250 obtained in the step (b) is disposed in the mold 80 and is pressurized with the pressure P by the push piece 90 from above. The intermediate composite material 250 is pressurized, compressed, knocked out of the mold 80 and taken out, and formed into a porous composite material that is uniform throughout.

  FIG. 3 is a schematic diagram illustrating the structure of the porous composite material 300. As shown in FIG. 3, in the porous composite material 300, the first particles 41 and the second particles 42 are brought into close contact with each other by the pressurization in the step (c), and the first particles 41 and the second particles 42 are interposed. The size of the holes 46 formed in the above is almost uniform. This is considered because the second particles having high hardness are randomly arranged in the intermediate composite material 250 to relieve stress due to pressurization and maintain the shape with an appropriate porous structure. .

  FIG. 4 is a reference schematic diagram for explaining the structure of the porous composite material (reference example) 310 when the second particle is not present in the intermediate composite material. As shown in FIG. 4, pressure is not easily applied in the central portion of the porous composite material 310 and in the direction from the center toward the corner portion of the porous composite material, and a relatively large streaky void 48 of, for example, 100 μm or more is formed. It is easy to be done. The large pores 48 form a phase of only the matrix material that is not reinforced when the matrix material penetrates, and affects physical properties such as strength of the composite material. In addition, the first particles 41 may be crushed by pressure, and the pores 46 formed between the first particles 41 may be reduced, making it difficult for the matrix material to penetrate. Therefore, as described above with reference to FIG. 3, the second particles having higher hardness than the first particles play an important role.

  In the step (c), when the intermediate composite material is handled in a subsequent step, it is preferable that the intermediate composite material is pressed to such an extent that the shape can be maintained. preferable. Therefore, in the step (c), it is preferable to pressurize the intermediate composite material at 0.5 MPa to 10 MPa. If the applied pressure is less than 0.5 MPa, the molded porous material may not be able to maintain its shape. Although depending on the material of the filler, when the applied pressure exceeds 10 MPa, the pores of the molded porous material become too small and the matrix material may not penetrate into the porous material.

  Moreover, it is preferable to perform a process (c) in heat processing atmosphere so that 1st particle | grains may couple | bond together easily. The temperature of the heat treatment atmosphere can be appropriately selected depending on the type of the first particles to be used. For example, when aluminum particles are used, the step (c) is preferably performed in an atmosphere of about 400 ° C.

  The porous composite material obtained in the step (c) can maintain a form in which the carbon nanofibers are dispersed between the first particles, and further maintain a fine porous structure. It can be handled easily during storage and transportation.

(H) Finally, a manufacturing method for obtaining a composite material using a porous composite material will be described.
In the manufacturing method for obtaining a composite material in the present embodiment, a composite material in which carbon nanofibers are dispersed can be obtained by infiltrating the molten metal of the matrix material into the porous composite material obtained in the step (c). . In the present embodiment, a step of casting using a so-called non-pressure infiltration method for infiltrating a molten metal into a porous composite material will be described in detail with reference to FIGS. 5 and 6.

  5 and 6 are schematic configuration diagrams of an apparatus for producing a composite material by a non-pressure infiltration method. In FIG. 5, a porous composite material 300 molded in advance is placed in a sealed container 1. A mass 5 of matrix material is disposed above the porous composite material 300. Next, the porous composite material 300 and the matrix material lump 5 arranged in the container 1 are heated to the melting point of the matrix material or higher by a heating means (not shown) incorporated in the container 1. The heated mass 5 of the matrix material melts into a molten metal and penetrates into the pores in the porous composite material 300.

  In the porous composite material 300 of the present embodiment, the appropriate pore size is uniformly formed throughout the pressurizing step of step (c), so that the molten metal can permeate through the entire capillaries earlier by capillary action. Can do. Prior to the main permeation step, for example, in step (a), the inside of the container 1 may be reduced by adding magnesium particles to the porous composite material 300 and mixing them. When, for example, aluminum is used as the first particles and the matrix material, the wettability is improved by reducing the aluminum, and the molten metal permeates between the first particles by a capillary phenomenon to completely reach the inside of the porous composite material. Is filled with molten aluminum. And the heating by the heating means of the container 1 is stopped, the molten metal is cooled and solidified, and the composite material 400 in which the carbon nanofibers are uniformly dispersed can be manufactured. The matrix material according to the present embodiment penetrates into the pores 46 formed between the first particles and is used as a binding material that bonds the first particles. Therefore, it is preferable that the porous composite material 300 used in the main infiltration step is molded in advance using the first particles of the same material as the molten matrix material used in the infiltration step. By doing so, it is possible to obtain a homogeneous composite material in which the molten metal and the first particles are easily mixed. Matrix materials include metal particles such as aluminum, magnesium, titanium, iron, gold, silver, copper, nickel, chromium, germanium, selenium, tin, zinc, and alloys thereof, and non-metal particles such as ceramics, glass, and silicon Can be used alone or in combination.

  Further, before the container 1 is heated, the inside of the container 1 may be degassed by the decompression means 2 connected to the container 1, for example, a vacuum pump. Furthermore, nitrogen gas may be introduced into the container 1 from an inert gas injection means 3 connected to the container 1, for example, a nitrogen gas cylinder.

  In the above-described embodiment, the non-pressure infiltration method has been described. However, the infiltration method is not limited to this, and for example, a pressure infiltration method in which pressure is applied by an atmospheric pressure such as an inert gas can be used.

  As described above, since the surface of the carbon nanofiber in the porous composite material is activated, the wettability with the matrix material is improved, and the composite material has a uniform variation in mechanical properties and is homogeneous. Can be obtained. Moreover, since the porous composite material has relatively large pores removed by the step (c), the composite material does not have a large phase formed only of the matrix material, and is homogeneous throughout. In addition, the porous structure does not collapse greatly due to the pressurization in the step (c) due to the small amount of high hardness second particles contained in the intermediate composite material, and the molten metal of the matrix material is evenly distributed throughout the porous composite material. Can penetrate. Therefore, the composite material according to the present embodiment has almost no voids due to poor penetration of the molten metal, and is homogeneous throughout.

Examples of the present invention will be described below, but the present invention is not limited thereto.
(Examples 1-4, Comparative Example 1)
(1) Preparation of sample (a) Preparation of carbon fiber composite material First step: A predetermined amount (100 g) of natural rubber shown in Table 1 on an open roll having a roll diameter of 6 inches (roll temperature: 10 to 20 ° C.) 100 parts by weight (phr) (indicated in Table 1 as “NR”) was added and wound around a roll.
Second step: The amount (parts by weight) of the first particles, the second particles, and the reducing agent shown in Table 1 with respect to the natural rubber was added to the natural rubber. At this time, the roll gap was set to 1.5 mm.
Third step: Next, carbon nanofibers (described as “CNT13” in Table 1) in an amount (parts by weight) shown in Table 1 were added to natural rubber. At this time, the roll gap was set to 1.5 mm.
Fourth step: When the carbon nanofibers were charged, the mixture was removed from the roll.
Fifth step: 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.
Sixth step: The roll was set to a predetermined gap (1.1 mm), and the thinned mixture was charged and dispensed.

Thus, the uncrosslinked carbon fiber composite material samples of Examples 1 to 4 and Comparative Example 1 were obtained. In addition, pure aluminum particles (99.7% is aluminum, hardness: HV27) having an average particle diameter of 30 μm as aluminum powder of the first particles, multi-wall carbon nanofibers having an average diameter (fiber diameter) of about 13 nm, and reduction As the agent, magnesium particles having an average particle diameter of 50 μm were used. As the second particles, alumina powder A as alumina particles having an average particle diameter of 0.4 μm (Al ₂ O ₃ , hardness: HV1800) and alumina powder B as alumina particles having an average particle diameter of 30 μm (Al ₂ O ₃₎ , Hardness: HV1800) and silicon carbide particles having an average particle size of 30 μm (SiC, hardness: HV2200) as silicon carbide powder.

(B) Preparation of intermediate composite material The carbon fiber composite material obtained in (a) above is heat-treated for 2 hours at a temperature equal to or higher than the decomposition vaporization temperature of the elastomer (500 ° C.) in a nitrogen atmosphere furnace to decompose and vaporize the elastomer. An intermediate composite material was obtained.

(C) Production of porous composite material The intermediate composite material obtained in the above (b) was placed in a molding die and pressed from above with a compressive stress of about 5 MPa as a load P on a punch in an atmosphere of 400 ° C. Compression molding was performed to obtain a porous composite material having a size of 50 × 50 × 10 mm.

(D) Preparation of composite material The porous composite material obtained in the above (c) was obtained as a composite material by a non-pressure permeation method. More specifically, the porous composite material obtained in the above (c) is placed in a container (furnace), an aluminum lump (pure aluminum ingot) as a matrix material is placed thereon, and an inert gas (nitrogen) It heated to the temperature (800 degreeC) more than melting | fusing point of aluminum in atmosphere. The aluminum lump melted to become a molten aluminum, and the molten metal penetrated so as to fill the pores of the porous composite material. After infiltrating the molten aluminum, it was naturally cooled and solidified to obtain a composite material.

(2) Observation with a microscope Table 1 shows the observation results of the composite material samples of Examples 1 to 4 and Comparative Example 1 with an electron microscope (SEM) and a metallographic microscope. In Table 1, samples in which carbon nanofiber aggregation was not observed in the composite material with an electron microscope are described as “good” in the column of the CNT dispersion state, and aluminum streaks (width of 100 μm or more) were observed with a metal microscope. Samples that were not observed were described as “None” in the column of aluminum streaks, and samples that were observed as aluminum streaks were described as “Yes”. FIG. 7 is a photograph of the cut surface of the composite material sample of Example 1, and FIG. 8 is a photograph of the cut surface of the composite material sample of Comparative Example 1. The white streaks in FIG. 8 are aluminum streaks A. The aluminum streaks identified here were found to be a single phase of aluminum by elemental analysis using EDS or XPS.

(3) Measurement of compression strength About the composite material sample, the maximum value, the minimum value, and the average value of compression strength (MPa) were measured. The measurement of the compressive yield strength was 0.2% yield strength (σ0.2) when a 10 × 10 × 5 (thickness) mm sample was compressed at 0.01 mm / min. The results are shown in Table 1.

(4) 100 samples of 10 × 10 × 10 (thickness) mm were cut out from the non-defective rate composite material sample, and the specific gravity was measured. When the specific gravity of the sample was less than 2.6, the product was judged as a defective product, and when the specific gravity was 2.6 or more, it was judged as a non-defective product. The yield rate (%) for each composite material sample was calculated, and the results are shown in Table 1.

  From Table 1, according to Examples 1 to 4 of the present invention, the following was confirmed. That is, in the composite material containing the second particles, since aluminum streaks were not observed, it was found that relatively large pores could be removed by the step (c). Further, in the observation of the composite material of Comparative Example 1 not including the second particles, aluminum streaks were observed. The composite materials of Examples 1 to 4 and Comparative Example 1 were good with almost no aggregation of carbon nanofibers observed.

  Furthermore, the compressive yield strength of the composite materials of Examples 1 to 4 is larger than the compressive yield value of the composite material of Comparative Example 1 in all of the maximum value, the minimum value, and the average value. This composite material was found to be homogeneous throughout with reduced variations in mechanical properties. Moreover, since the non-defective rate (%) of the composite materials of Examples 1 to 4 was about twice that of Comparative Example 1 and was close to 100%, it was found that industrial production was possible.

  From the above, according to the present invention, carbon nanofibers that are generally difficult to disperse into the base material can be uniformly dispersed in the elastomer, and the composite material can be efficiently produced by including the second particles. It became clear. Moreover, according to this invention, it turned out that the composite material which has a homogeneous mechanical property as a whole is 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. It is a schematic explanatory drawing of the process (c) of this Embodiment. It is a schematic diagram explaining the structure of the porous composite material of this Embodiment It is a reference schematic diagram explaining the structure of the porous composite material which does not use a 2nd particle | grain. It is a schematic block diagram of the apparatus which manufactures a composite material by the non-pressurization osmosis | permeation method. It is a schematic block diagram of the apparatus which manufactures a composite material by the non-pressurization osmosis | permeation method. 2 is a photograph taken of a cut surface of a composite material sample of Example 1. FIG. 3 is a photograph of a cut surface of a composite material sample of Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Pressure-reducing means 3 Injection | pouring means 5 Mass 10 of matrix materials 1st roll 20 2nd roll 30 Elastomer 40 Carbon nanofiber 41 1st particle 42 2nd particle 46 Hole 48 Large hole 80 Mold 90 Pushing piece 250 Intermediate composite material 300 Porous composite material 310 Porous composite material (reference example)
400 Composite material A Aluminum streaks

Claims (10)

(A) a step of mixing a first particle, a second particle, and a carbon nanofiber with an elastomer and dispersing the mixture by a shearing force to obtain a carbon fiber composite material;
(B) a step of heat-treating the carbon fiber composite material to decompose and vaporize an elastomer contained in the carbon fiber composite material to obtain an intermediate composite material;
Pressing the intermediate composite material to obtain a porous composite material (c);
Including
The method for producing a porous composite material, wherein the second particles have a hardness higher than that of the first particles, and a weight ratio in the carbon fiber composite material is smaller than that of the first particles. In claim 1,
The method for producing a porous composite material, wherein the hardness of the second particles is 2 to 150 times the hardness of the first particles. In claim 1 or 2,
The method for producing a porous composite material, wherein a weight ratio of the second particles to the first particles is 0.1 wt% to 10 wt%. In any one of Claims 1-3,
The compounding amount of the first particles and the second particles is 300 parts by weight to 600 parts by weight with respect to 100 parts by weight of the elastomer. In any one of Claims 1-4,
The first particles have an average particle size larger than the average diameter of the carbon nanofibers,
The method for producing a porous composite material, wherein the second particles have an average particle size larger than an average particle size of the first particles. In any one of Claims 1-5,
The first particles are aluminum;
The method for producing a porous composite material, wherein the second particles are alumina. In any one of Claims 1-6,
The method for producing a porous composite material, wherein the elastomer has an unsaturated bond or group having affinity for carbon nanofibers.   A method for producing a composite material, wherein a melt of a matrix material is infiltrated into the porous composite material obtained in any one of claims 1 to 7. In claim 8,
The method for producing a composite material, wherein the matrix material is aluminum.   The porous composite material obtained by the manufacturing method in any one of Claims 1-7.