JP4201789B2 - Porous material, method for producing the same, and method for producing composite metal material - Google Patents

Description

The present invention is a porous material, a method of manufacturing the same, a method of manufacturing a composite metal 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 metal can permeate 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, 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-2005-23419

Therefore, an object of the present invention is to provide a porous material that can efficiently use carbon nanofibers and is homogeneous throughout, and a method for producing the same. Another object of the present invention is to provide a method for producing carbon nanofibers uniformly dispersed composite metallic materials.

The method for producing a porous material according to the present invention includes the step of (a) obtaining a composite elastomer by mixing a filler and carbon nanofibers in an elastomer and dispersing the mixture by shearing force.
(B) a step of heat-treating the composite elastomer to decompose and vaporize the elastomer contained in the composite elastomer to obtain an intermediate composite material;
A step (c) of compressing the intermediate composite material to obtain a porous material;
including.

  According to the step (a) of the production method of the present invention, the filler and the carbon nanofibers can be uniformly dispersed in the elastomer by a shearing force. Further, the surface of the carbon nanofiber is activated by the free radical of the sheared elastomer attacking the surface of the carbon nanofiber. And according to the process (b) of the manufacturing method of this invention, the porous intermediate | middle composite material which has an uneven | corrugated pore is formed because an elastomer decomposes | disassembles and vaporizes by heat processing. According to step (c) of the production method of the present invention, by compressing the intermediate composite material, for example, voids (pores) of 100 μm or more are crushed to obtain a porous material with uniform pore size and uniform throughout. be able to. Further, the porous material thus obtained maintains the state in which the carbon nanofibers are dispersed together with the filler in the elastomer by the step (a), so that the porous material can be used for other purposes such as casting. Carbon nanofibers can be used efficiently by handling them in metal processing.

  The elastomer used in the present invention can have an unsaturated bond or group having an affinity for carbon nanofibers. 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, the composite elastomer is obtained by uniformly dispersing carbon nanofibers in an elastomer as a base material.

  The filler of the present invention can be a particulate filler having an average diameter of 1 to 500 μm. By using such a filler, turbulent flow is generated around the particulate filler by mixing in the step (a), and the carbon nanofibers can be more uniformly dispersed in the elastomer. In addition, when the matrix metal material is infiltrated into the porous material manufactured according to the present invention, it can be easily infiltrated by capillary action.

  The filler of the present invention can use metal particles or non-metal particles depending on the use of the porous material.

  In step (c) of the production method of the present invention, the intermediate composite material can be compressed at 2.5 MPa to 500 MPa. If the compressive force is less than 2.5 MPa, the porous material may become brittle due to insufficient strength, and the porous shape may not be maintained. On the other hand, when the compressive force exceeds 500 MPa, the pores of the porous material become too small, and the porous characteristics may not be obtained, for example, the matrix metal material does not penetrate into the porous material.

  The step (b) of the production method of the present invention includes a step (b-1) of pulverizing the intermediate composite material obtained by decomposing and vaporizing the elastomer, and the step (c) includes the step (b). The intermediate composite material crushed in can be compressed in a mold. By crushing the intermediate composite material in this way, a porous material having a desired shape can be molded. In addition, the pore size in the intermediate composite material varies, but the intermediate composite material is pulverized and compressed in a mold to obtain a porous material with uniform pore size and uniform throughout. be able to.

  The method for producing a composite metal material of the present invention includes a step (d) of infiltrating the molten matrix metal material into the porous material.

  In the porous material obtained in the step (c), the surface of the carbon nanofiber is activated, and the wettability with other substances such as metals is improved, so that the matrix metal material penetrates in the step (d). easy. The composite metal material produced according to the present invention can favorably disperse carbon nanofibers in a matrix metal material.

  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. As the raw material elastomer, an uncrosslinked product is used in the case of a rubber-based elastomer.

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

  The method for producing a porous material according to the present embodiment includes a step (a) of obtaining a composite elastomer by mixing a filler and carbon nanofibers in an elastomer and dispersing the mixture by a shearing force, and the composite elastomer. And a step (b) of obtaining an intermediate composite material by decomposing and vaporizing the elastomer contained in the composite elastomer, and a step (c) of compressing the intermediate composite material to obtain a porous material.

  Moreover, the manufacturing method of the composite metal material concerning this Embodiment has the process (d) which osmose | permeates the molten matrix metal material to the porous material obtained by the process (c).

  (I) 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 are 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. Thus, 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 body having the above conditions is crosslinked, T2n of the obtained crosslinked body 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 affinity for the radical at the end of the carbon nanofiber in at least one of the main chain, the side chain and the end chain, or generates such a radical or group. Easy to use. 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. And when the elastomer and carbon nanofibers are kneaded, the free radicals generated by breaking the molecular chains of the elastomer attack the defects of the carbon nanofibers and guess that they generate radicals on the surface of the carbon nanofibers it can.

  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. Particularly preferred are highly polar elastomers that easily generate free radicals during elastomer kneading, such as natural rubber (NR) and nitrile rubber (NBR). Even in the case of an elastomer having a low polarity, such as ethylene propylene rubber (EPDM), free radicals are generated by setting the kneading temperature to a relatively high temperature (for example, 50 to 150 ° C. in the case of EPDM). Can be used for invention.

  The elastomer of the present embodiment may be a rubber elastomer or a thermoplastic elastomer. In the case of a rubber-based elastomer, the elastomer is preferably an uncrosslinked product.

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

  The carbon nanofibers used in the present embodiment 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.

  Although the compounding quantity of carbon nanofiber can be set according to the use of a porous material, it is preferable that the composite elastomer of this Embodiment contains carbon nanofiber in the ratio of 0.01 to 50 weight%.

  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.

  These carbon nanofibers are improved in adhesion and wettability with the elastomer by performing a surface treatment in advance, for example, ion implantation treatment, sputter etching treatment, plasma treatment, etc. before being kneaded into the elastomer. be able to.

  (III) Next, the filler will be described.

  The filler used in the present embodiment disperses the carbon nanofibers more favorably in the step (a), and is also a structural material in the porous material. The filler is preferably in the form of particles having an average diameter of 1 to 500 μm, and more preferably in the form of particles of 1 to 300 μm. When the average diameter of the filler is less than 1 μm, the pore size of the porous material is reduced, so that the porosity is lowered, and the matrix metal material is less likely to penetrate into the porous material in the step (d). If the average diameter of the filler exceeds 500 μm, kneading in step (a) becomes difficult. The shape of the filler is not limited to spherical particles, but may be flat or flake shaped as long as the elastomer can generate a turbulent flow during mixing in step (a). In order to obtain a porous material, spherical particles are preferred.

  The filler is preferably metal particles or nonmetal particles, and a combination of metal particles and nonmetal particles can also be used.

  As the filler for the metal particles, aluminum, magnesium, titanium, iron, gold, silver, copper, nickel, chromium, germanium, selenium, tin, zinc, and alloys thereof can be used alone or in combination.

  When the metal particles are, for example, aluminum particles, the wettability of the aluminum particles and the molten aluminum by reducing oxides on the surface of the aluminum particles by radicals generated by thermal decomposition of the elastomer when the molten aluminum is infiltrated. Can be improved and the binding force can be strengthened. In addition, since the metal particles include aluminum particles and magnesium particles, the magnesium particles can be used as a reducing agent in the step (d) to reduce the oxide on the surface of the aluminum particles, and further facilitate the penetration of the molten aluminum. be able to. Therefore, the flow due to the permeation of the molten aluminum causes the carbon nanofibers to enter the inside of the aluminum particles whose surface is reduced. Thus, when a metal particle has an oxide on the surface like an aluminum particle, it has the above preferable effects.

  As the filler for non-metallic particles, carbon black, silicic acid particles, mineral particles and the like can be used alone or in combination.

  Carbon blacks used for non-metallic particles include reinforcing carbon blacks such as SAF, ISAF, HAF, SRF, T, GPF, FT and MT, and color carbon blacks such as HCC, HCF, LFF, MFF and RCF. Further, for example, conductive carbon black such as acetylene black and ketjen black can be used.

  As the silicic acid particles used for the non-metallic particles, hydrous silicic acid, ultrafine silica, anhydrous silicic acid or the like can be used.

  As mineral particles used for non-metallic particles, mineral powder such as porcelain, kaolin, talc, bentonite, hard clay, soft clay, calcium carbonate, magnesium hydroxide, aluminum oxide, magnesium oxide, etc. should be used. Can do.

  These non-metallic particles composed of carbon black, silicic acid particles, mineral particles, and the like are used as extenders in rubber compositions, and therefore are appropriately selected according to the use of porous materials and composite metal materials. can do.

  The amount of the filler is preferably 0.1 to 1000 parts by weight with respect to 100 parts by weight of the elastomer. If the filler is less than 0.1 parts by weight, the dispersibility of the carbon nanofiber is hardly affected. Moreover, when there are more fillers than 1000 weight part, the workability in a manufacturing process will become difficult, and also 800 weight part or less is preferable in workability.

  (IV) Next, step (a) will be described.

  In the step (a) according to the present embodiment, a filler is mixed with a filler and carbon nanofibers and dispersed by shearing force to obtain a composite elastomer.

  Step (a) can be performed using an open roll method, a closed kneading method, a multi-screw extrusion kneading method, or the like.

  In the present embodiment, as an example of mixing carbon nanofibers with an elastomer, an example using an open roll method in which thinning with a roll interval of 0.5 mm or less is used 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, for example, 1.5 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.

  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. A step of mixing the filler 50 with the elastomer 30 is performed by adding the filler 50 into the bank 32 and further rotating the first and second rolls 10 and 20. Next, when the carbon nanofibers 40 are added to the bank 32 in which the elastomer 30 and the filler 50 are mixed and the first and second rolls 10 and 20 are rotated, the elastomer, the filler, and the carbon nanofibers are rotated. Is obtained. Remove this mixture from the open roll. Further, the distance d between the first roll 10 and the second roll 20 is preferably set to 0.5 mm or less, more preferably 0.1 to 0.5 mm, and the obtained elastomer and carbon nanofibers are separated. The mixture is put into an open roll and thinned. The number of thinning is preferably about 10 times. When the surface speed of the first roll 10 is V1, and the surface speed of the second roll 20 is V2, the ratio of the surface speeds (V1 / V2) in thinness is 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.

  Due to the shearing force thus obtained, a high shearing force acts on the elastomer 30, and the aggregated carbon nanofibers 40 are separated from each other so as to be pulled out one by one to the elastomer molecules, and dispersed in the elastomer 30. The Further, since the filler 50 is introduced into the bank 32 prior to the introduction of the carbon nanofiber 40, the shearing force generated by the roll generates a turbulent flow around the filler 50, and the carbon nanofiber 40 is transformed into the elastomer 30. Can be further dispersed.

  In this step (a), in order to obtain as high a shearing force as possible, the elastomer and the carbon nanofiber are mixed at a relatively low temperature of preferably 0 to 50 ° C., more preferably 5 to 30 ° C. . When EPDM is used as the elastomer, it is desirable to perform a two-stage kneading step. In the first kneading step, in order to obtain as high a shearing force as possible, mixing of EPDM and carbon nanofibers is performed in the first step. The first temperature is 50 to 100 ° C. lower than the kneading step 2. The first temperature is preferably a first temperature of 0 to 50 ° C., more preferably 5 to 30 ° C. The dispersibility of the carbon nanofibers can be improved by setting the second temperature of the roll to a relatively high temperature of 50 to 150 ° C.

  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.

  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, particularly the chemical interaction with the carbon nanofiber, and the like. Since the dispersion is facilitated, a composite elastomer excellent in the dispersibility and dispersion stability of the carbon nanofibers (the carbon nanofibers once dispersed are difficult to reaggregate) 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.

  The step (a) is not limited to the open roll method, and the above-described closed kneading method or multi-screw extrusion kneading method can also be used. In short, in this step (a), it is only necessary to be able to separate the aggregated carbon nanofibers and to give the elastomer a shearing force that cuts the elastomer molecules to generate radicals.

  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.

  In the composite elastomer obtained by the step (a), carbon nanofibers are uniformly dispersed in the 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 composite elastomer according to the present embodiment include carbon nanofibers. It is shorter than the case of no elastomer alone.

  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 that the composite elastomer according to the present embodiment has a measurement 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.

  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) is 1000 to 4000 μs. The component fraction (fnn) of the component having the second spin-spin relaxation time is preferably less than 0.08.

  In addition, it is desirable that the composite elastomer according to the present embodiment has a measurement value obtained by the Hahn echo method using the pulse method NMR within the following range. That is, the amount of change (ΔT1) in the spin-lattice relaxation time (T1) measured at 150 ° C. of the crosslinked product per part by weight of the carbon nanofibers is preferably decreased by 1 msec or more, more preferably 2 It is preferable to decrease by ~ 15 msec.

  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 composite elastomer 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 composite elastomer of the present embodiment, the filler 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.

  (V) Next, step (b) will be described.

  In the step (b) according to the present embodiment, the composite elastomer is heat-treated, and the elastomer contained in the composite elastomer is decomposed and vaporized to obtain an intermediate composite material.

  In the step (b), for example, the composite elastomer obtained in the step (a) is heat-treated in a furnace, whereby the elastomer contained in the composite elastomer is removed by decomposition and vaporization, and the surface is activated. Porous intermediate composite materials can be produced. The intermediate composite material obtained by decomposing and vaporizing the elastomer from the composite elastomer is a porous material in which only the carbon nanofibers and the filler remain while being uniformly dispersed in the elastomer and maintaining almost the state. Such an intermediate composite material is fragile and difficult to handle while maintaining a porous state.

  FIG. 2 is a cross-sectional view schematically showing the composite elastomer 100 obtained in the step (a). FIG. 3 is a cross-sectional view schematically showing the intermediate composite material 200 obtained in the step (b). As shown in FIG. 2, the composite elastomer 100 has a filler 50 and carbon nanofibers 40 dispersed in a matrix of the elastomer 30. In the step (b), the composite elastomer 100 is disposed in a heat treatment furnace, and the inside of the heat treatment furnace is heated to a temperature at which the elastomer 30 is decomposed and vaporized, for example, 420 ° C. The elastomer 30 is decomposed by this heating, and most of the elastomer 30 is removed by decomposition and vaporization, so that an intermediate composite material 200 as shown in FIG. 3 is obtained. In the intermediate composite material 200, the portions from which the elastomer is removed become pores 60, and the filler 50 and the carbon nanofibers 40 are combined to maintain a slightly larger form than the composite elastomer 100.

  The intermediate composite material 200 is brittle because the bonding force between the filler 50 and the carbon nanofiber 40 is small. Moreover, since the pores 60 are expanded when the elastomer 30 is decomposed and vaporized, the sizes of the pores 60 vary and are not uniform.

  Various conditions can be selected for the heat treatment in step (b) depending on the type of elastomer used, but at least the heat treatment temperature is equal to or higher than the temperature at which the elastomer decomposes and vaporizes, and the filler and carbon nanofibers are The temperature is set lower than the melting temperature. The heat treatment temperature in step (b) is desirably controlled by measuring the temperature of the composite elastomer placed in the heat treatment furnace. For example, a thermocouple is embedded in the composite elastomer, and the temperature inside the composite elastomer is accurately measured.

  The heat treatment in the step (b) is preferably performed at a relatively slow heating rate (temperature increase per unit time) of the composite elastomer disposed in the heat treatment furnace. For example, when the elastomer is natural rubber (NR), the natural rubber is decomposed and removed by raising the temperature of the composite elastomer from room temperature to 420 ° C., which is a temperature at which the natural rubber is efficiently decomposed and vaporized, in 4 hours. In particular, since natural rubber begins to decompose around 300 ° C., it is preferable to slowly raise the temperature from 300 ° C. to 420 ° C. over 3 hours, for example. By gradually raising the temperature of the composite elastomer in this manner, the elastomer can be slowly decomposed and vaporized, and expansion deformation of the intermediate composite material can be suppressed.

  In the heat treatment of the step (b), carbon on the surface of the carbon nanofibers and oxygen contained in the atmosphere in the furnace or oxygen contained in the elastomer can be combined and oxidized. The surface of the carbon nanofiber is activated by the free radicals of the elastomer molecules sheared by the step (a), and can be easily combined when, for example, oxygen is present in the furnace atmosphere. The surface of the intermediate composite material thus obtained improves wettability with other substances such as metals.

  The surface structure of the intermediate composite material thus obtained is described in detail in the previously filed Japanese Patent Application No. 2004-212854, but can be analyzed by X-ray spectroscopic analysis (XPS), and also can be analyzed by EDS analysis. It can also be analyzed by (Energy Dispersive Spectrum).

  In addition, when it is desired to bind nitrogen to the surface of the carbon nanofiber instead of oxygen, the heat treatment furnace can be performed in an ammonium gas atmosphere.

  Further, as described above, the size of the pores 60 formed in the intermediate composite material 200 is not uniform, and for example, there may be pores 60 of 100 μm or more. When the matrix metal is infiltrated into the intermediate composite material 200 by the step (d) described later, the pores 60 of 100 μm or more are formed as they are as the matrix metal phase. Since such a large matrix metal phase is not reinforced by the carbon nanofibers, the overall strength of the composite metal material is lowered, which is not preferable in terms of structure. Therefore, in order to make such non-uniform pores uniform, a step (b-1) of pulverizing the intermediate composite material obtained in step (b) may be included. This is because non-uniform pores can be removed by grinding the intermediate composite material.

  In the step (b-1), after the heat treatment in the step (b), the intermediate composite material 200 is pulverized to such an extent that the carbon nanofibers 40 do not re-aggregate. The intermediate composite material 200 can be pulverized experimentally by placing the intermediate composite material 200 in a mortar and pushing it moderately with a mortar. Industrially, it is pulverized with a dry mixer such as a Proshear mixer, Eirich mixer, or Redige mixer.

  In the intermediate composite material 200 pulverized in the step (b-1), for example, pores of 100 μm or more are removed.

  (VI) Next, step (c) will be described.

  In step (c) according to the present embodiment, the intermediate composite material pulverized in step (b-1) is compressed in a mold to obtain a porous material. In the step (c), the intermediate composite material obtained in the step (b) can be compressed as it is.

  FIG. 4 is a schematic explanatory diagram of the step (c). The intermediate composite material 250 pulverized in the step (b-1) is disposed in the mold 80 and is compressed with the pressure P by the push piece 90 from above. The compressed and molded intermediate composite material 250 is knocked out from the mold 80 and taken out, and is molded into a uniform porous material 300 (shown in FIG. 5, which will be described later).

  The size of the pores in the porous material 300 is formed to a uniform size as a whole by the steps (b-1) and (c).

  In the step (c), it is preferable that the intermediate composite material is compacted so that at least the shape can be maintained when the intermediate composite material is handled in the subsequent step. It is preferable. Therefore, in the step (c), it is preferable to compress the intermediate composite material at 2.5 MPa to 500 MPa. If the compressive force is less than 2.5 MPa, the molded porous material may not be able to maintain its shape. Although depending on the material of the filler, when the compressive force exceeds 500 MPa, the pores of the molded porous material become too small, and the matrix metal material may not penetrate into the porous material in the step (d). .

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

  The porous material obtained in the step (c) can maintain the form in which the carbon nanofibers are dispersed between the fillers, and can be stored and transported while maintaining a fine porous structure. It can be handled easily.

  (VII) Next, step (d) will be described.

  FIG.5 and FIG.6 is a schematic block diagram of the apparatus explaining a process (d). FIG. 7 is a cross-sectional view schematically showing the composite metal material obtained in the step (d).

  In the step (d) according to this embodiment, the molten matrix metal material is infiltrated into the porous material 300 obtained in the step (c) to obtain the composite metal material 400. More specifically, as shown in FIG. 5, the porous material 300 previously molded in the step (c) is placed in the sealed container 1. Above the porous material 300, a mass 5 of a matrix metal material serving as a matrix of a composite metal material is disposed. Next, the porous material 300 and the matrix metal material lump 5 disposed in the container 1 are heated to a melting point or higher of the matrix metal material by a heating means (not shown) incorporated in the container 1. The heated mass 5 of the matrix metal material is melted to form a molten metal.

  The porous material 300 is appropriately compressed in the step (c), so that the porous material 300 is formed into a homogeneous porous structure as a whole, and the molten metal of the matrix metal material can permeate the entire material faster by capillary action. . The molten metal of the matrix metal material penetrates between the particulate fillers 50 by capillary action, and the molten metal of the matrix metal material is completely filled up to the inside of the porous material 300. Then, heating by the heating means of the container 1 is stopped, the molten metal of the matrix metal material that has penetrated into the porous material 300 is cooled and solidified, and the carbon nanofibers 40 and the filler 50 as shown in FIG. A composite metal material 400 uniformly dispersed in 70 can be produced. The porous material 300 used in the step (d) is preferably formed in advance using a filler having good wettability with the matrix metal material, for example, metal particles of the same metal. By doing in this way, the molten metal of a matrix metal material is easy to osmose | permeate in the porous material 300, and a homogeneous composite metal material can be obtained as a whole.

  For example, when aluminum particles (or alumina particles) are used as the filler and aluminum (or aluminum alloy) is used as the matrix metal material, the filler preferably contains a small amount of magnesium particles. Magnesium that is heated and vaporized on the surface of the aluminum particles is reduced, and the molten aluminum can permeate between the aluminum particles with improved wettability by capillary action.

  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. By bringing the inside of the container 1 close to a vacuum, a reducing agent such as magnesium particles can be easily vaporized, and the matrix metal material can be efficiently permeated. 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.

  The composite metal material obtained by the step (d) is a composite metal material including carbon nanofibers in a matrix metal material, and an amorphous peripheral phase is formed around the carbon nanofibers. This peripheral phase includes, for example, nitrogen and oxygen. When the matrix metal material is aluminum, the peripheral phase is formed as an amorphous peripheral phase including aluminum, nitrogen, and oxygen. Therefore, since the porous material according to the present embodiment forms homogeneous pores throughout, the composite metal material obtained by infiltrating the matrix metal material into the porous material has carbon nanofibers dispersed throughout. In addition, the whole is uniformly formed by the peripheral phase.

  In addition, by forming an amorphous peripheral phase around the carbon nanofibers, a composite metal material with improved wettability between the matrix metal material and the carbon nanofibers is obtained.

  The peripheral phase of the composite metal material can be observed with a field emission scanning electron microscope (FE-SEM) and examined by elemental analysis in the vicinity of the irradiation point.

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

(Examples 1 to 3, Comparative Examples 1 and 2)
(1) Preparation of sample (a) Preparation of composite elastomer First step: A predetermined amount (100 g) of natural rubber (NR) 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)) was charged and wound around a roll.
Second step: 500 parts by weight (500 g) of aluminum particles and 2 parts by weight (2 g) of magnesium particles are added to natural rubber, and then the amount of carbon nano-particles shown in Table 1 (parts by weight (phr)) is added. Fiber (in Table 1, carbon nanofiber is described as “CNT”) was added to natural rubber. At this time, the roll gap was set to 1.5 mm.
Fourth step: When the carbon nanofibers were charged, a mixture of natural rubber and carbon nanofibers was taken out 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.
In this way, composite elastomers of Example 1 and Comparative Example 1 were obtained. In Example 1 and Comparative Example 1, magnesium particles having an average particle diameter of 50 μm, pure aluminum particles having an average particle diameter of 50 μm (99.7% is aluminum), and carbon having a diameter (fiber diameter) of about 10 to 20 nm. Nanofibers were used.

(B) Production of intermediate composite material The composite elastomer (non-crosslinked) obtained in Examples 1 to 3 and Comparative Examples 1 and 2 of (a) above was decomposed and vaporized in natural rubber in a furnace containing nitrogen atmosphere containing oxygen. Heat treatment was performed at 400 ° C., which is higher than the temperature, for 1 hour to decompose and vaporize the elastomer, simultaneously oxidize the carbon nanofibers, and lower the temperature to room temperature to obtain an intermediate composite material. In this oxidation reaction, oxygen molecules obtained from a trace amount of oxygen and water vapor contained in a nitrogen atmosphere, a trace amount of oxygen and moisture contained in the elastomer, and the like were used.
The intermediate composite material obtained in this manner was placed in a mortar and pulverized with pestle until it became powdery, and the pulverized intermediate composite materials of Examples 1 to 3 and Comparative Example 2 were obtained. In Comparative Example 1, this pulverization step is not performed.

(C) Production of porous material The pulverized intermediate composite material obtained in Examples 1 to 3 and Comparative Example 2 in (b) above was placed in a mold and compression molded at 5 MPa in an atmosphere of 400 ° C. As a result, a porous material having a size of 50 × 50 × 10 mm was obtained. In Comparative Example 1, this compression step is not performed.

(D) Production of composite metal material The porous materials obtained in Examples 1 to 3 and Comparative Examples 1 and 2 of (c) above were placed in a container (furnace), and an aluminum lump (pure aluminum ingot) was obtained. Then, the temperature was raised to 580 ° C. over 2 hours in an inert gas (nitrogen containing a small amount of oxygen), and maintained at 580 ° C. for 2 hours to evaporate the magnesium particles and The surface was reduced. Thereafter, the temperature was slowly raised to a temperature higher than the melting point of aluminum (800 ° C.). The aluminum block reduced by magnesium melted and became a molten aluminum and penetrated into the porous material. After infiltrating the molten aluminum, it was allowed to cool naturally and solidified to obtain a composite metal material using aluminum as a matrix.

(2) Measurement Using Pulse Method NMR Each composite elastomer was 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 spin-spin relaxation time (T2n), the second spin-spin relaxation time (T2nn), and the second spin-spin relaxation time of the raw material elastomer alone and the composite elastomer. The rate (fnn) was determined. In addition, about the raw material elastomer simple substance, it calculated | required also about the 1st spin-spin relaxation time (T2n) of the raw material elastomer simple substance in case measurement temperature is 30 degreeC. The measurement results are shown in Table 1. The second spin-spin relaxation time (T2nn) in Examples 1 to 3 and Comparative Examples 1 and 2 was not detected. Therefore, the component fraction (fnn) of the component having the second spin-spin relaxation time was 0 (zero).

(3) Observation of composite metal material with metal microscope The composite metal material of Example 2 and Comparative Example 1 obtained in the above (d) was observed with a metal microscope. A real photograph of the composite metal material 400 of Example 2 is shown in FIG. 8, and a metal micrograph is shown in FIG. An actual photograph of the composite metal material 410 of Comparative Example 1 is shown in FIG. 10, and a metal micrograph is shown in FIG.

(4) Measurement of compressive strength For the porous materials and composite metal materials of Examples 1 to 3 and Comparative Examples 1 and 2 obtained in (d) above, a 10 × 10 mm test piece having a thickness of 5 mm The compressive strength when compressed at 01 mm / min was measured. For the compressive strength, the maximum value, the average value, and the minimum value (MPa) were measured. The results are shown in Table 1.

  From Table 1, according to Examples 1 to 3 of the present invention, the following was confirmed. That is, the spin-spin relaxation time (T2n / 150 ° C.) at 150 ° C. in the composite elastomer is shorter than that of the raw material elastomer. Further, the component fraction (fnn / 150 ° C.) in the composite elastomer is smaller than that in the case of the raw material elastomer. From these, it can be seen that the carbon nanofibers are well dispersed in the composite elastomer according to the example.

  The compressive strengths of the porous materials of Examples 1 to 3 were larger than those of Comparative Examples 1 and 2, were excellent in handling properties, and could be easily carried in the subsequent process.

  Further, in the observation of the composite metal material 400 of Example 2 with a metallographic microscope, an aluminum phase exceeding 100 μm was not observed. In the observation of the composite metal material 410 of Comparative Example 1 with a metallographic microscope, many aluminum phases 75 exceeding 100 μm were observed.

  Furthermore, the composite metal materials of Examples 1 to 3 were higher in all of the maximum value, the average value, and the minimum value of the compressive strength than the composite metal materials of Comparative Examples 1 and 2. Further, it was found that the composite metal materials of Examples 1 to 3 had a smaller variation in compressive strength than the composite metal material of Comparative Example 1, and were homogeneous throughout.

(5) Analysis of crystal structure by X-ray diffraction The composite metal materials of Examples 1 to 3 obtained in (d) above were analyzed by X-ray diffraction (XRD). Most of the components detected as crystalline components are aluminum, and it is found that the peripheral phase formed around the carbon nanofibers of the composite metal material is an amorphous phase with no crystal structure. It was.

(6) Elemental analysis by field emission scanning electron microscope Further, the composite metal materials of Examples 1 to 3 obtained in (d) above were observed with a field emission scanning electron microscope (FE-SEM), and the irradiation point Nearby elemental analysis was performed. The amorphous peripheral phase formed around the carbon nanofibers was found to have aluminum, nitrogen, and oxygen elements.

  From the above, according to the present invention, it was found that carbon nanofibers that are generally difficult to disperse in the base material can be dispersed in the porous material and the composite metal material. Moreover, according to this invention, it turned out that the aluminum phase exceeding 100 micrometers in a composite metal material can be eliminated. Furthermore, according to the present invention, it has been found that the porous material and the composite metal material are homogeneous throughout.

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 sectional drawing which shows typically the composite elastomer obtained at the process (a). It is sectional drawing which shows typically the intermediate composite material obtained at the process (b). It is a schematic explanatory drawing of the apparatus explaining a process (c). It is a schematic block diagram of the apparatus explaining a process (d). It is a schematic block diagram of the apparatus explaining a process (d). It is sectional drawing which shows typically the composite metal material obtained at the process (d). 2 is an actual photograph of the composite metal material of Example 1. 2 is a metal micrograph of the composite metal material of Example 1. FIG. 2 is an actual photograph of a composite metal material of Comparative Example 1. 3 is a metal micrograph of a composite metal material of Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Pressure-reducing means 3 Injection | pouring means 5 Aluminum lump 10 1st roll 20 2nd roll 30 Elastomer 40 Carbon nanofiber 50 Filler 60 Pore 70 Matrix metal material 75 Aluminum phase 80 Mold 90 Pushing piece 100 Composite elastomer 200 Intermediate Composite material 250 Ground intermediate composite material 300 Porous material 400 Composite metal material

Claims (12)

A step of mixing the elastomer with a filler and carbon nanofibers and dispersing the mixture by a shearing force to obtain a composite elastomer; and
(B) a step of heat-treating the composite elastomer to decompose and vaporize the elastomer contained in the composite elastomer to obtain an intermediate composite material;
A step (c) of compressing the intermediate composite material to obtain a porous material;
A method for producing a porous material, comprising: In claim 1,
The method for producing a porous material, wherein the carbon nanofiber has an average diameter of 0.5 to 500 nm. In claim 1 or 2,
The method for producing a porous material, wherein the elastomer has a molecular weight of 5,000 to 5,000,000. In any one of Claims 1 thru | or 3,
The method for producing a porous material, wherein the elastomer has at least one unsaturated bond or group having affinity for carbon nanofibers. In any of claims 1 to 4,
The method for producing a porous material, wherein the elastomer has a network component spin-spin relaxation time (T2n) of 100 to 3000 μsec in an uncrosslinked body, measured at 30 ° C. by a Hahn echo method using pulsed NMR. . In any of claims 1 to 5,
The said filler is a manufacturing method of the porous material which is a particulate filler with an average diameter of 1-500 micrometers. In any one of Claims 1 thru | or 6.
The said filler is a manufacturing method of the porous material which is a metal particle. In any one of Claims 1 thru | or 6.
The method for producing a porous material, wherein the filler is non-metallic particles. In any of claims 1 to 8,
In the step (c), the intermediate composite material is compressed at 2.5 MPa to 500 MPa. In any one of Claim 1 thru | or 9,
Including the step (b-1) of pulverizing the intermediate composite material obtained in the step (b),
In the step (c), the intermediate composite material pulverized in the step (b-1) is compressed in a mold.   The manufacturing method of a composite metal material which has the process (d) of making the melt | dissolved matrix metal material osmose | permeate the porous material obtained by the manufacturing method in any one of Claim 1 thru | or 10.   A porous material obtained by the production method according to claim 1.