JP2008222730A - Friction material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a friction material excellent in high temperature characteristics. <P>SOLUTION: This friction material 2 contains a reinforcing fiber, filler, rubber composition and binder resin. The rubber composition is provided by dispersing carbon nanofibers having 0.5 to 500 nm mean diameter uniformly in a matrix of an ethylene-propylene rubber, showing 1,000 to 3,000 μsec first spin-spin relaxation time (T2n) in a non-cross-linked material measured by a Hahn echo method by using a pulse method NMR at 150°C and having <0.2 component fraction (fnn) of a component having a second spin-spin relaxation time (T2nn). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a friction material excellent in high temperature characteristics.

  For friction materials used for disc brake pads, drum brake shoes, clutch facings for clutches, etc. of automobiles and other vehicles, thermosetting phenol resin is used as a matrix (base material), and inorganic and organic fibers. A friction material containing a reinforcing fiber such as a filler and a filler containing vulcanized rubber powder is known (see, for example, Patent Document 1). Examples of the vulcanized rubber powder used as the filler include silicone rubber (Q), fluoro rubber (FKM), ethylene-propylene rubber (EPDM), and nitrile rubber (NBR). Nitrile rubber is generally used. It was. Nitrile rubber in the friction material increases the coefficient of friction by making the contact between the friction material and the disc rotor uniform, for example, due to its flexibility, and for example, the noise of the disc brake due to its damping characteristic (loss tangent (tan δ)). Was reduced. However, although nitrile rubber is excellent in damping characteristics and dynamic elastic modulus near room temperature, the damping characteristics (loss tangent (tan δ)) at a high temperature, for example, 120 ° C. or higher are low, and the deterioration start temperature is relatively low. Therefore, for example, when the friction material becomes high temperature due to continuous braking of the disc brake, the dynamic elastic modulus and damping characteristics of the nitrile rubber contained in the friction material decrease, the friction coefficient of the friction material decreases, Uneven wear sometimes occurred. Furthermore, since the peak temperature of loss tangent (tan δ) at low temperatures of nitrile rubber is about −20 ° C., friction damping materials using nitrile rubber have lower vibration damping performance at temperatures lower than −20 ° C., for example, disc brakes. Then there was a cry. Ethylene-propylene rubber is superior in anti-vibration performance at low temperatures than nitrile rubber, but has not been practically used as a friction material.

  Further, a friction material containing a thermosetting resin as a matrix and carbon nanofibers as a filler has been proposed (see, for example, Patent Document 2). However, carbon nanofibers are expensive, and their use as fillers for improving the mechanical strength of friction materials has not yet progressed. In particular, the carbon nanofibers easily aggregate and are difficult to uniformly disperse in the resin matrix. As a result, a sufficient effect cannot be obtained as a whole unless the blending ratio of the carbon nanofibers is increased.

According to the carbon fiber composite material manufacturing method previously proposed by the present inventors, it is possible to improve the dispersibility of carbon nanofibers, which has been considered difficult so far, and to uniformly disperse the carbon nanofibers in the elastomer. (For example, see Patent Document 3). According to such a method for producing a carbon fiber composite material, an elastomer and carbon nanofibers are kneaded, and dispersibility of carbon nanofibers having high cohesiveness is improved by shearing force. More specifically, when the elastomer and the carbon nanofiber are mixed, the viscous elastomer penetrates into the carbon nanofiber, and a specific part of the elastomer has a high activity of the carbon nanofiber due to chemical interaction. In this state, when a strong shearing force is applied to a mixture of an elastomer having high molecular mobility (elasticity) and carbon nanofibers, the carbon nanofibers are deformed as the elastomer is deformed. The fibers also moved, and the aggregated carbon nanofibers were separated and dispersed in the elastomer by the restoring force of the elastomer due to elasticity after shearing. Thus, by improving the dispersibility of the carbon nanofibers in the matrix, expensive carbon nanofibers can be efficiently used as fillers for composite materials.
JP 2005-336340 A JP 2004-217828 A JP 2005-97525 A

  An object of the present invention is to provide a friction material having excellent high temperature characteristics.

The friction material according to the present invention is
A friction material comprising a reinforcing fiber, a filler, a rubber composition, and a binder resin,
In the rubber composition, carbon nanofibers having an average diameter of 0.5 to 500 nm are uniformly dispersed in ethylene-propylene rubber as a matrix, and measured at 150 ° C. by a Hahn echo method using pulsed NMR, non-crosslinked The first spin-spin relaxation time (T2n) in the body is 1000 to 3000 μs, and the component fraction (fnn) of the component having the second spin-spin relaxation time (T2nn) is less than 0.2. .

  According to the friction material of the present invention, since T2n and fnn of the rubber composition are in such a range, the carbon nanofibers are uniformly dispersed in the ethylene-propylene rubber, thereby deteriorating the rubber composition. The onset temperature is high and therefore the rubber composition can maintain excellent damping properties and high dynamic modulus even at high temperatures. As a result, the friction material according to the present invention has a high coefficient of friction at high temperatures, and can reduce squeal at high temperatures due to contact with the friction target member. Moreover, according to the friction material concerning this invention, the amount of wear can be reduced by the uniform contact with a to-be-rubbed member.

  In the friction material according to the present invention, the rubber composition may be a non-crosslinked body.

  In the friction material according to the present invention, the rubber composition may be a crosslinked body.

  In the friction material according to the present invention, the rubber composition may include 5 to 100 parts by weight of the carbon nanofibers with respect to 100 parts by weight of the ethylene-propylene rubber.

  In the friction material according to the present invention, the rubber composition may include 40 to 80 parts by weight of carbon black and 5 to 20 parts by weight of the carbon nanofibers with respect to 100 parts by weight of the ethylene-propylene rubber. it can.

  In the friction material according to the present invention, the rubber composition may have a loss tangent (tan δ) at 200 ° C. of 0.05 to 1.00.

  In the friction material according to the present invention, the rubber composition may have a dynamic elastic modulus (E ′) at 200 ° C. of 7 MPa to 1000 MPa.

  In the friction material according to the present invention, the rubber composition may have a deterioration start temperature of 160 ° C. to 300 ° C. in thermomechanical analysis.

  In the friction material according to the present invention, the rubber composition may have a loss tangent (tan δ) peak temperature in the vicinity of the glass transition point of the ethylene-propylene rubber of −30 ° C. to −60 ° C.

  In the friction material according to the present invention, the binder resin may be a phenol resin.

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

  FIG. 1 is a front view showing a pad 1 using a friction material 2 according to the present embodiment. FIG. 2 is a partially cutaway plan view showing the pad 1 using the friction material 2 according to the present embodiment. FIG. 3 is a rear view of the pad 1 using the friction material 2 according to the present embodiment. FIG. 4 is a longitudinal sectional view showing an example of a disc brake 10 used for a vehicle brake.

  The friction material 2 according to the present embodiment is a friction material including a reinforcing fiber, a filler, a rubber composition, and a binder resin, and the rubber composition is made of ethylene-propylene rubber as a matrix. First spin-spin relaxation time (T2n) in a non-crosslinked body in which carbon nanofibers having an average diameter of 0.5 to 500 nm are uniformly dispersed and measured at 150 ° C. by the Hahn echo method using pulsed NMR Is 1000 to 3000 μs, and the component fraction (fnn) of the component having the second spin-spin relaxation time (T2nn) is less than 0.2.

(pad)
As shown in FIG. 4, the structure of the disc brake 10 used in an automobile or the like is transmitted to the hydraulic chamber 14 of the caliper body 11 by, for example, hydraulic pressure by a hydraulic device, presses the piston 12, and the pressing force presses the pad. The first and first friction members 2 and 2 are pressed so as to sandwich the disk-shaped disk rotor 13, and the rotation of the disk rotor 13 is braked by the friction action. As shown in FIGS. 1 to 3, the pad 1 of the disc brake 10 includes a metal back plate 3 (hereinafter referred to as “plate 3”) pressed against the caliper body 11 and the piston 12 via the shim plate 5. The friction material 2 is configured to generate a frictional force in contact with the disk rotor 13. The friction material 2 has a flat surface 21 that comes into contact with the disk rotor 13, and a part of the friction material 2 enters the two binding holes 4, 4 formed in the plate 3, so that the friction material 2 is firmly bonded to the plate 3. It is worn. The type of the disc brake 10 is not limited to the pin slide type as in the present embodiment, but may be an opposed type disc brake in which pistons are arranged on both sides of the disc rotor, and the number of pistons and the shape of the shim plate are also the same. The present invention is not limited to the embodiment. In the present embodiment, the friction material 2 used for the pad 1 of the disc brake 10 has been described. However, the friction material 2 can be applied to, for example, a friction material for a shoe of a drum brake (not shown) or a clutch facing for a clutch. is there.

(Reinforcing fiber, filler, binder resin)
Conventionally used materials can be appropriately selected and used as the reinforcing fibers and fillers to be mixed with the binder resin. Examples of such reinforcing fibers include inorganic fibers such as alumina fibers, glass fibers, rock wool, potassium titanate fibers, ceramic fibers, silica fibers, kaolin fibers, bauxite fibers, cananoid fibers, boron fibers, magnesia fibers, and metal fibers. Organic fibers such as fiber, polyester fiber, polyamide fiber, polyimide fiber, polyvinyl alcohol modified fiber, polyvinyl chloride fiber, polypropylene fiber, polybenzimidazole fiber, acrylic fiber, carbon fiber, phenol fiber, nylon fiber, and cellulose fiber One or two or more selected from the above can be used in combination. Examples of the filler include organic fillers such as cashew dust and melamine dust, carbon black, barium sulfate, calcium carbonate, magnesium carbonate, silicon carbide, boron carbide, titanium carbide, silicon nitride, boron nitride, alumina, and silica. Inorganic fillers such as zirconia, graphite, talc and metal powder, lubricants, and pH adjusters can be used alone or in combination.

  The binder resin that is the binder of the reinforcing fiber and filler of the friction material 2 according to the present embodiment is preferably a thermosetting phenol resin, but other curable resins such as unsaturated polyester resins, epoxy resins, Resins such as vinyl ester resins, alkyd resins, acrylic resins, melamine resins, xylene resins, guanamine resins, diallyl phthalate resins, allyl ester resins, furan resins, imide resins, urethane resins, and urea resins can be used. Specific examples of the phenol resin include a resol type phenol resin and a novolac type phenol resin, and a novolac type phenol resin is preferable. Such a phenol resin may be modified or unmodified. Binder resin can be used individually by 1 type or in mixture of 2 or more types. In particular, in a field where airtightness is required, it is preferable to select a resin that does not generate gas in the curing reaction, such as a combination of an epoxy resin and a phenol resin. By using these resins, it is possible to obtain a molded product having high airtightness without voids in the cured product.

(Rubber composition)
The rubber composition is a non-crosslinked product in which carbon nanofibers having an average diameter of 0.5 to 500 nm are uniformly dispersed in ethylene-propylene rubber as a matrix and measured at 150 ° C. by the Hahn echo method using pulsed NMR. The first spin-spin relaxation time (T2n) is 1000 to 3000 μs, and the component fraction (fnn) of the component having the second spin-spin relaxation time (T2nn) is less than 0.2. The rubber composition can be blended with the friction material in the form of a non-crosslinked body. The rubber composition can be crosslinked and blended with the friction material. The rubber composition has a first spin-spin relaxation time (T2n) of 500 to 2000 μs measured in a crosslinked product at 150 ° C. by a Hahn echo method using pulsed NMR, and a second spin-spin. The component fraction (fnn) of the component having the relaxation time (T2nn) is preferably less than 0.2.

  T2n and fnn of the rubber composition can represent that the carbon nanofibers are uniformly dispersed in the ethylene-propylene rubber as the matrix. That is, it can be said that the fact that the carbon nanofibers are uniformly dispersed in the ethylene-propylene rubber is a state in which the ethylene-propylene rubber is restrained by the carbon nanofibers. In this state, the mobility of the ethylene-propylene rubber 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 rubber composition according to the present embodiment are the same as those of the carbon nanofiber. It becomes shorter than the case of the ethylene-propylene rubber which does not contain, and becomes shorter especially when the carbon nanofibers are uniformly dispersed. In addition, the spin-lattice relaxation time (T1) in the crosslinked body changes in proportion to the mixing amount of the carbon nanofibers.

  In the state where the ethylene-propylene rubber molecules are constrained by the carbon nanofibers, it is considered that the non-network component (non-network chain component) decreases for the following reason. That is, when the molecular mobility of ethylene-propylene rubber is reduced overall by carbon nanofibers, the non-network component cannot easily move, and the behavior becomes the same as that of the network component. Since the network component (terminal chain) is easy to move, the non-network component is considered to decrease due to the fact that the network component (terminal chain) 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 (T2nn) is smaller than that of the ethylene-propylene rubber alone not including the carbon nanofibers. Since the component fraction (fn) of the component having the first spin-spin relaxation time (T2n) is fn + fnn = 1, the component fraction (fn) is larger than that of the ethylene-propylene rubber alone not including the carbon nanofiber.

  From the above, in the rubber composition according to the present embodiment, the carbon nanofibers are uniformly dispersed when the measurement value obtained by the Hahn echo method using the pulse method NMR is in the above range. Recognize.

  The spin-lattice relaxation time (T1) measured by the inversion recovery 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 ethylene-propylene rubber, the lower the molecular mobility, and the harder the ethylene-propylene rubber, and the longer the spin-lattice relaxation time, the higher the molecular mobility. Propylene rubber is soft.

The rubber composition preferably has a loss tangent (tan δ) at 200 ° C. of 0.05 to 1.00, more preferably 0.05 to 0.5. Loss tangent (tan δ) is determined by performing a dynamic viscoelasticity test, dynamic shear modulus (E ′, unit is dyn / cm ² ) and dynamic loss modulus (E ″, unit is dyn / cm ² ) And calculating the loss tangent (tan δ = E ″ / E ′). When the loss tangent (tan δ) at 200 ° C. is 0.05 or more, a rubber composition having high damping characteristics in a high temperature region (200 ° C.) can be obtained.

  The rubber composition preferably has a dynamic elastic modulus (E ′) at 200 ° C. of 7 MPa to 1000 MPa, more preferably 7 MPa to 300 MPa.

  The rubber composition preferably has a deterioration start temperature of 160 ° C. to 300 ° C., more preferably 200 ° C. to 300 ° C. in thermomechanical analysis. The deterioration start temperature in the thermomechanical analysis is a temperature at which a deterioration phenomenon including softening deterioration (expansion) and hardening deterioration (shrinkage) starts. From the characteristic graph of the temperature-linear expansion coefficient differential value obtained by the thermomechanical analysis. It is obtained by measuring the temperature at which the deterioration phenomenon has started. It is desirable that the deterioration start temperature of the rubber composition is high, since the deterioration of the rubber composition does not start even at a high temperature, so that the maximum temperature at which the friction material 2 can be used increases. The rubber composition can be said to be in a state where the ethylene-propylene rubber is restrained by the carbon nanofibers because the carbon nanofibers are well dispersed in the ethylene-propylene rubber. Therefore, the ethylene-propylene rubber has a smaller molecular motion than the case where carbon nanofibers are not included, and as a result, the deterioration start temperature moves to the high temperature side.

  The rubber composition preferably has a loss tangent (tan δ) peak temperature in the vicinity of the glass transition point of ethylene-propylene rubber of −30 ° C. to −60 ° C. The peak temperature of the loss tangent (tan δ) of the rubber composition in the region near the glass transition point (Tg) of the ethylene-propylene rubber is too hard in the region lower than this peak temperature, and the cushioning property is lost. Therefore, it is a use limit temperature as a rubber composition, and can be called a minimum use temperature.

(Method for producing rubber composition)
As a method for producing the rubber composition according to the present embodiment, ethylene-propylene rubber and carbon nanofibers are supplied to a known mixer such as an open roll, a single or twin screw extruder, a Banbury mixer, a kneader. And a kneading method. The filler other than carbon nanofibers such as carbon black is preferably supplied to the mixer before supplying the carbon nanofibers.

  The step of kneading the ethylene-propylene rubber, the carbon black, and the carbon nanofiber includes the first kneading step of kneading the ethylene-propylene rubber, the carbon black, and the carbon nanofiber at a first temperature; A second kneading step of kneading the mixture obtained in the kneading step at a second temperature, and a third kneading step of passing through the mixture obtained in the second kneading step. In the present embodiment, an example in which a closed kneading method is used as the first kneading step and the second kneading step and an open roll method is used as the third kneading step will be described.

  FIG. 5 is a diagram schematically showing a method for producing a rubber composition using a closed kneader 30 using two rotors. FIG. 6 is a diagram schematically showing a third kneading step (thinning) of the rubber composition by the open roll machine 40. In FIG. 5, the closed kneader 30 includes a first rotor 31 and a second rotor 32. The 1st rotor 31 and the 2nd rotor 32 are arrange | positioned at predetermined intervals, and can knead ethylene-propylene rubber by rotating. In the example shown in the figure, the first rotor 31 and the second rotor 32 are rotated at a predetermined speed ratio in opposite directions (for example, directions indicated by arrows in the drawing). A desired shear force can be obtained depending on the speed between the first rotor 31 and the second rotor 32, the distance between the first and second rotors 31 and 32, and the inner wall of the chamber 36, and the like. The shearing force in this step is appropriately set depending on the type of ethylene-propylene rubber and the amounts of carbon black and carbon nanofibers.

(Mixing process)
First, ethylene-propylene rubber 37 is introduced from the material supply port 34 of the closed kneader 30 and the first and second rotors 31 and 32 are rotated. Further, the carbon black 39 and the carbon nanofibers 38 are added to the chamber 36, and the first and second rotors 31 and 32 are further rotated to mix the ethylene-propylene rubber 37 and the carbon nanofibers 38. Is called.

(First kneading step)
Next, a first kneading step is performed in which the mixture obtained by adding the carbon nanofibers 38 to the ethylene-propylene rubber 37 is further kneaded by rotating the first and second rotors 31 and 32 at a predetermined speed ratio. . In the first kneading step, in order to obtain as high a shearing force as possible, mixing of the ethylene-propylene rubber and the carbon nanofiber is performed at a first temperature that is 50 to 100 ° C. lower than that in the second kneading step. The first temperature is preferably a first temperature of 0 to 50 ° C., more preferably 5 to 30 ° C. When the first temperature is lower than 0 ° C., kneading is difficult, and when the first temperature is higher than 50 ° C., high shearing force cannot be obtained, so that the carbon nanofibers are dispersed throughout the ethylene-propylene rubber. I can't let you. The first temperature may be set according to the temperature of the chamber 36, the temperature of the first and second rotors 31 and 32, or control of the speed ratio while measuring the temperature of the mixture. Various temperature controls may be performed. In addition, when the first kneading step is performed in the same closed kneader 30 following the above-described mixing step, the first temperature may be set in advance.

  When non-polar EPDM (ethylene-propylene-diene copolymer rubber) is used as the ethylene-propylene rubber 37, the carbon-nanofibers 38 are formed in the entire ethylene-propylene rubber 37 while leaving an agglomerate by the first kneading step. To disperse.

(Second kneading step)
Furthermore, the mixture obtained by the first kneading step is put into another closed kneader 30 to perform the second kneading step. In the second kneading step, the molecules of the ethylene-propylene rubber 37 are cut to generate radicals, so that the kneading is performed at a second temperature that is 50 to 100 ° C. higher than the first temperature. The closed kneading machine 30 used in the second kneading step is heated to the second temperature by a heater built in the rotor or a heater built in the chamber, and the first kneading machine 30 is higher than the first temperature. The second kneading step can be performed at a temperature of 2. Although 2nd temperature can be suitably selected according to the kind of ethylene-propylene rubber used, 50-150 degreeC is preferable. When the second temperature is lower than 50 ° C., radicals are hardly generated in the ethylene-propylene rubber molecules, and the aggregates of the carbon nanofibers cannot be unwound. On the other hand, when the second temperature is higher than 150 ° C., the molecular weight of the ethylene-propylene rubber is excessively decreased, which is not preferable because the elastic modulus is decreased.

  The second kneading time can be appropriately set by setting the second temperature, setting the rotor interval, the rotation speed, or the like. In the present embodiment, the effect can be obtained with a kneading time of about 10 minutes or more. By performing the second kneading step in this way, the ethylene-propylene rubber 37 molecules are cut to generate radicals, and the carbon nanofibers 38 are easily bonded to the ethylene-propylene rubber molecule radicals.

(Third kneading step)
Then, the mixture 46 obtained by the second kneading step is further charged into the open roll machine 40 set to the first temperature, and a plurality of third kneading steps (thinning steps) are performed as shown in FIG. Repeat 10 times, for example, and dispense. The roll interval d (nip) between the first roll 42 and the second roll 44 is set to 0 to 0.5 mm, for example, 0.3 mm, where the shearing force is larger than that in the first and second kneading steps. The temperature is set to the same third temperature of 0 to 50 ° C., more preferably 5 to 30 ° C. as in the first kneading step. Assuming that the surface speed of the first roll 42 is V1 and the surface speed of the second roll 44 is V2, the ratio of the surface speeds (V1 / V2) between the thin rolls 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. The thin rubber composition is rolled with a roll and dispensed into a sheet. The third kneading step is a finishing dispersion step for further uniformly dispersing the carbon nanofibers 38 in the ethylene-propylene rubber 37, and is effective when more uniform dispersibility is required. By the third kneading step (thinning step), the ethylene-propylene rubber 37 in which radicals are generated acts so as to pull out the carbon nanofibers 38 one by one, and the carbon nanofibers 38 can be further dispersed. In addition, a crosslinking agent can be added in the third kneading step to uniformly disperse the crosslinking agent.

  In this way, by performing the first kneading step at the first temperature, the carbon nanofibers can be dispersed throughout the ethylene-propylene rubber with a high shearing force, and further the second kneading step at the second temperature. And the third kneading step allow the carbon nanofiber aggregates to be released by the radicals of the ethylene-propylene rubber molecules. Accordingly, a non-polar ethylene-propylene rubber such as EPDM can disperse the carbon nanofibers as a whole and produce a rubber composition free from aggregates of carbon nanofibers. In particular, since the ethylene-propylene rubber 37 has elasticity, viscosity, and chemical interaction with the carbon nanofibers 38, the carbon nanofibers 38 can be easily dispersed. Further, in the first to third kneading steps, shear force acts in the direction of separating the individual carbon nanofibers due to various complicated flows such as the turbulent flow of the elastomer generated around the carbon black 39. It will be. Accordingly, the carbon nanofibers move in the respective flow directions of the elastomer molecules bonded individually by chemical interaction, and thus are uniformly dispersed in the elastomer. And the rubber composition excellent in the dispersibility and dispersion stability of carbon nanofiber 38 (it is hard to re-aggregate carbon nanofiber) can be obtained.

  More specifically, when ethylene-propylene rubber and carbon nanofibers are mixed with an open roll, viscous ethylene-propylene rubber penetrates into the carbon nanofibers, and a specific portion of the ethylene-propylene rubber is It binds to the highly active part of carbon nanofibers by chemical interaction. Next, when a strong shearing force acts on the ethylene-propylene rubber, the carbon nanofibers move with the movement of the ethylene-propylene rubber molecules, and further aggregate due to the restoring force of the ethylene-propylene rubber due to elasticity after shearing. The carbon nanofibers are separated and dispersed in the ethylene-propylene rubber. According to this embodiment, when the rubber composition is extruded from between narrow rolls, the rubber composition is deformed thicker than the roll interval by the restoring force due to the elasticity of the ethylene-propylene rubber. The deformation can be presumed to cause the rubber composition on which a strong shear force has been applied to flow more complicatedly and to disperse the carbon nanofibers in the ethylene-propylene rubber. And once disperse | distributed carbon nanofiber is prevented from reaggregating by the chemical interaction with ethylene-propylene rubber, and it can have favorable dispersion stability.

  In the first and second kneading steps in which carbon nanofibers are dispersed in ethylene-propylene rubber by shearing force, it is preferable to use a closed kneader from the viewpoint of workability, but other kneaders such as an open roll method. May be used. As the closed kneader, a tangential type or meshing type such as a Banbury mixer, a kneader, or a Brabender can be adopted. The first, second, and third kneading steps are not limited to the above-described closed kneading method and open roll method, and can be performed by a multi-screw extrusion kneading method (for example, a twin-screw extruder). The kneader can be selected in combination as appropriate according to the production amount. In particular, the open roll method in the third kneading step is preferable because it can measure and manage not only the roll temperature but also the actual temperature of the mixture.

  The rubber composition is produced by mixing a cross-linking agent in the rubber composition dispensed during the first to third kneading steps or after passing through the third kneading step, and crosslinking to form a rubber composition of a cross-linked product. You may use as a product, and you may shape | mold into a friction material with a non-crosslinked body without making it bridge | crosslink. Since the rubber composition is in the form of a sheet obtained by the open roll method, it is preferable that the rubber composition be pulverized into particles so that it can be easily mixed with the particulate filler. As a method for making the rubber composition into particles, a known method can be adopted, for example, roll pulverization by a shearing force of a roll or cut pulverization by a cutting blade, and the rubber composition is cooled or frozen in advance. You may grind | pulverize.

  In the method for producing a rubber composition according to the present embodiment, a compounding agent that is usually used in the processing of ethylene-propylene 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. These compounding agents may be added to the ethylene-propylene rubber, for example, before the carbon nanofibers in the kneader, or may be added during the first to third kneading steps.

  In the method for producing a rubber composition according to the present embodiment, carbon nanofibers are directly mixed with ethylene-propylene rubber having rubber elasticity. However, the present invention is not limited to this, and the following method is adopted. You can also. First, before mixing the carbon nanofibers, the ethylene-propylene rubber is masticated to lower the molecular weight of the ethylene-propylene rubber. When the molecular weight of ethylene-propylene rubber decreases due to mastication, the viscosity decreases, so that it easily penetrates into the voids of the aggregated carbon nanofibers. The ethylene-propylene rubber used as the raw material has a first spin-spin relaxation time (T2n) of the network component in the uncrosslinked body of 100 to 3000 μsec as measured at 30 ° C. by the Hahn echo method using pulsed NMR. is there. The raw material ethylene-propylene rubber is masticated to reduce the molecular weight of the ethylene-propylene rubber, and a liquid ethylene-propylene rubber having a first spin-spin relaxation time (T2n) exceeding 3000 μsec is obtained. The first spin-spin relaxation time (T2n) of the liquid ethylene-propylene rubber after mastication is the first spin-spin relaxation time (T2n) of the raw ethylene-propylene rubber before mastication. It is preferable that it is 5 to 30 times. This mastication is different from general mastication in which ethylene-propylene rubber is kept in a solid state, and by applying a strong shearing force, for example, by an open roll method, the ethylene-propylene rubber molecules are cut and the molecular weight is remarkably reduced. Until the liquid state is reached until it shows a flow unsuitable for kneading. For example, when the open roll method is used, this mastication is performed at a roll temperature of 20 ° C. (minimum mastication time: 60 minutes) to 150 ° C. (minimum mastication time of 10 minutes). Carbon black and carbon nanofibers are put into ethylene-propylene rubber that has been masticated at 0.0 mm and in a liquid state. However, since ethylene-propylene rubber is liquid and its elasticity is remarkably reduced, the aggregated carbon nanofibers are not very dispersed even when kneaded in a state where the free radicals of the ethylene-propylene rubber and the carbon nanofibers are combined.

  Therefore, the molecular weight of the ethylene-propylene rubber in the mixture obtained by kneading the liquid ethylene-propylene rubber and the carbon nanofibers is increased, and the elasticity of the ethylene-propylene rubber is recovered, thereby mixing the rubber-like elastic body. After that, the carbon nanofibers are uniformly dispersed in the ethylene-propylene rubber by performing the above-described thinning of the open roll method or the like. A mixture of rubber-like elastic bodies having an increased molecular weight of ethylene-propylene rubber has a first spin-spin relaxation time (T2n) of 3000 μsec as measured by the Hahn echo method at 30 ° C. using pulsed NMR. It is as follows. The first spin-spin relaxation time (T2n) of the rubber-like elastic mixture having an increased molecular weight of ethylene-propylene rubber is the first spin-spin relaxation time of the raw material ethylene-propylene rubber before mastication. It is preferably 0.5 to 10 times (T2n). The elasticity of the rubber-like elastic mixture can be expressed by the molecular form (observable by molecular weight) and molecular mobility (observable by T2n) of ethylene-propylene rubber. The step of increasing the molecular weight of the ethylene-propylene rubber is preferably performed for 10 hours to 100 hours by placing the mixture in a heating furnace set to a heat treatment, for example, 40 ° C. to 100 ° C. By such a heat treatment, the molecular chain is extended by the bonding of free radicals of ethylene-propylene rubber present in the mixture, and the molecular weight is increased. In addition, when the molecular weight of the ethylene-propylene rubber is increased in a short time, a small amount of the crosslinking agent, for example, 1/2 or less of an appropriate amount of the crosslinking agent is mixed, and the mixture is subjected to heat treatment (for example, annealing treatment). In addition, the molecular weight can be increased in a short time by the crosslinking reaction. When the molecular weight of the ethylene-propylene rubber is increased by a crosslinking reaction, it is preferable to set the amount of the crosslinking agent, the heating time, and the heating temperature to such an extent that kneading is not difficult in the subsequent steps.

  According to the manufacturing method of the rubber composition described here, the carbon nanofibers are more uniformly dispersed in the ethylene-propylene rubber by reducing the viscosity of the ethylene-propylene rubber before introducing the carbon nanofibers. Can be made. More specifically, the agglomerated carbon is obtained by using liquid ethylene-propylene rubber having a low molecular weight rather than mixing carbon nanofibers with ethylene-propylene rubber having a large molecular weight as in the production method described above. It is easy to penetrate into the voids of the nanofibers, and the carbon nanofibers can be more uniformly dispersed in the thinning process. In addition, free radicals of ethylene-propylene rubber produced in large quantities by molecular cutting of ethylene-propylene rubber can be bonded more firmly to the surface of carbon nanofibers, so that carbon nanofibers are evenly dispersed. Can be made. Therefore, according to the manufacturing method described here, the same performance can be obtained even with a smaller amount of carbon nanofibers than in the previous manufacturing method, and economical efficiency is improved by saving expensive carbon nanofibers.

(Ethylene-propylene rubber)
It is preferable to use EPDM (ethylene-propylene-diene copolymer) as the ethylene-propylene rubber as a matrix raw material of the rubber composition. Further, the ethylene-propylene rubber according to the present embodiment contains a third component such as ethylidene norbornene in order to obtain heat resistance and cold resistance, and the copolymerization ratio of ethylene and propylene is 45% to 45% in terms of ethylene content. 80% EPDM is preferred. The average molecular weight of the ethylene-propylene rubber is usually desirably 50,000 or more, more preferably 70,000 or more, and particularly preferably about 100,000 to 500,000. When the molecular weight of the ethylene-propylene rubber is within this range, the ethylene-propylene rubber molecules are entangled with each other and are connected to each other. Great effect to separate fibers. If the molecular weight of the ethylene-propylene rubber is smaller than 5000, the ethylene-propylene rubber 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 the process described above. It is not preferable. On the other hand, if the molecular weight of the ethylene-propylene rubber is larger than 5,000,000, the ethylene-propylene rubber becomes too hard and difficult to process, which is not preferable.

  The ethylene-propylene rubber preferably has a spin-spin relaxation time (T2n / 30 ° C.) of the network component in the uncrosslinked body of 100 to 3000 μsec, as measured at 30 ° C. by the Hahn echo method using pulse NMR. Preferably it is 200-1000 microseconds. By having a spin-spin relaxation time (T2n / 30 ° C.) in the above range, the ethylene-propylene rubber can be flexible and have sufficiently high molecular mobility, that is, suitable for dispersing the carbon nanofibers. It will have elasticity. In addition, since elastomer has viscosity, when ethylene-propylene rubber and carbon nanofiber are mixed, ethylene-propylene rubber can easily penetrate into the gaps between carbon nanofibers due to high molecular motion. it can. When the spin-spin relaxation time (T2n / 30 ° C.) is shorter than 100 μsec, the ethylene-propylene rubber cannot have sufficient molecular mobility. Also, if the spin-spin relaxation time (T2n / 30 ° C.) is longer than 3000 μsec, the ethylene-propylene rubber tends to flow like a liquid and has low elasticity, so that it becomes difficult to disperse the carbon nanofibers as they are. .

  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 ethylene-propylene rubber is measured by the Hahn-echo method using pulsed NMR, the first component having the first spin-spin relaxation time (T2n) having a short relaxation time And a second component having a second spin-spin relaxation time (T2nn) having a longer relaxation time. 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 ethylene-propylene rubber. Further, it can be said that the longer the first spin-spin relaxation time, the higher the molecular mobility and the softer the ethylene-propylene rubber.

  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 ethylene-propylene rubber according to the present invention has a moderate spin-spin relaxation time (T2), the Hahn echo method is most suitable. In general, the solid echo method and the 90 ° pulse method are suitable for short T2 measurement, the Hahn echo method is suitable for medium T2 measurement, and the CPMG method is suitable for long T2 measurement.

(Carbon nanofiber)
The carbon nanofibers preferably have an average diameter of 0.5 to 500 nm and an average diameter of 0.5 to 100 nm. The carbon nanofibers preferably have an average length of 0.01 to 1000 μm. The compounding amount of the carbon nanofiber can be set as appropriate depending on the amount of the rubber composition blended in the friction material and the high temperature characteristics required of the friction material. It is preferable to contain 100 parts by weight in order to obtain excellent high temperature characteristics of the friction material. In particular, by adding carbon black as a reinforcing agent to the rubber composition, excellent high temperature characteristics of the friction material can be obtained even if the amount of carbon nanofibers is reduced, with respect to 100 parts by weight of ethylene-propylene rubber. When carbon black is mixed in an amount of 40 to 80 parts by weight, the carbon nanofiber is preferably contained in an amount of 5 to 20 parts by weight.

  Examples of carbon nanofibers include so-called carbon nanotubes. Carbon nanotubes are single-walled carbon nanotubes (single-walled carbon nanotubes: SWNT) in which one sheet of graphite having a carbon hexagonal mesh surface is wound in one layer, and double-walled carbon nanotubes (double-walled carbon nanotubes: DWNT) in two layers. Multi-walled carbon nanotubes (MWNT: multiwall carbon nanotubes) wound in three or more layers are used as appropriate. 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”. Carbon nanofibers that have been graphitized at about 2300 ° C. to 3200 ° C. with a graphitization catalyst such as boron, boron carbide, beryllium, aluminum, and silicon may be used.

  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 are subjected to surface treatment, for example, ion implantation treatment, sputter etching treatment, plasma treatment, etc. in advance before being kneaded with ethylene-propylene rubber, thereby adhering or wetting with ethylene-propylene rubber. Can improve sex.

(Friction material manufacturing method)
The method for manufacturing the friction material 2 according to the present embodiment is not particularly limited, but is formed into a desired shape using a generally known molding method such as compression molding, transfer molding, injection molding, or injection compression molding. And can be cured by heating. A method for manufacturing the friction material 2 according to the present embodiment will be described in detail with reference to FIGS. FIG. 7 is a process diagram showing a manufacturing process of the friction material 2 according to the embodiment of the present invention. FIG. 8 is an explanatory diagram for explaining a temporary forming process for manufacturing the friction material 2 according to the embodiment of the present invention. FIG. 9 is an explanatory diagram for explaining a heating / pressurizing process for manufacturing the friction material 2 according to the embodiment of the present invention.

  The friction material 2 according to the present embodiment can be manufactured by the manufacturing process shown in FIG. In this manufacturing process, first, after forming the binding holes 4 and 4 in the metal plate 3, various surface treatments are performed, and then drying is performed. For such surface treatment, a degreasing process for degreasing the plate 3, a shot processing process for increasing the binding strength between the friction material 2 and the plate 3 by injecting granular materials toward the surface of the plate 3, For example, an adhesive application step of applying a thermosetting adhesive to the plate 3 to the surface of the plate 3 is included. On the other hand, the friction material 2 is molded in a separate process from the processing process of the plate 3. In forming the friction material 2, the raw materials of the friction material 2 are mixed, and then, a predetermined amount is measured and temporarily molded to form a plate-like temporary molded body. At this time, the raw material of the friction material 2 used as the raw material includes the above-described reinforcing fiber, filler, rubber composition, and binder resin.

  As shown in FIG. 8, the raw material of the friction material 2 (reinforcing fiber, filler particles, rubber composition particles, binder resin) sufficiently mixed in advance by a mixer is temporarily formed on a mounting table 54. The mold 52 is filled. And the raw material of the friction material 2 is pressed with the press die 50, and temporary molding is performed, and the temporary molded body 65 is obtained.

  As shown in FIG. 9, the temporary molded body 65 obtained by the temporary molding is formed into the friction material 2 integrated with the plate 3 by being heated and pressure-molded by a press machine. In the heating and pressure molding, first, a temporary molded body 65 is placed in a mold 62 on a mounting table 64 of a press machine, and the plate 3 is set at a predetermined position on the temporary molded body 65. The molded body 65 is heated while being pressed. By this heating and pressure molding, the binder resin blended in the raw material of the temporary molded body 65 is dissolved and fluidized, and then cured to firmly bond the raw materials of the temporary molded body 65 together with the surface of the plate 3. Both are firmly bound to form the friction material 2. The friction material 2 obtained by performing such heating and pressure molding is fired in an oven for several hours in order to make the binding between the friction material 2 and the plate 3 even more complete. . The friction material that has undergone the firing process becomes a product (pad 1) through a groove processing for forming a groove in the friction material 2, a polishing process for polishing the surface of the friction material 2, a post-processing process such as painting, and the like.

  The amount of the rubber composition blended in the friction material 2 can be adjusted as appropriate depending on the high temperature characteristics required of the friction material 2, but in order to improve the high temperature characteristics of the friction material 2, 2 to 10 wt% It is preferable to include.

  The friction material 2 has an excellent damping characteristic and a high dynamic elastic modulus even at high temperatures, so that the friction material 2 has a high friction coefficient at high temperatures and can reduce squeal at high temperatures due to contact with the friction target member. it can. Moreover, according to the friction material concerning this invention, the amount of wear can be reduced by the uniform contact with a to-be-rubbed member.

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

(1) Preparation of samples of Examples 1 to 8 and Comparative Examples 1 and 2 (a) A predetermined amount (100 g) of ethylene-propylene shown in Table 1 in a Brabender (chamber setting temperature 20 ° C.) of a closed kneader Rubber (100 parts by weight (phr)) was charged.
(B) The amount of carbon black shown in Table 1 (parts by weight (phr)) was added to the ethylene-propylene rubber, and then the carbon nanofibers were added to the ethylene-propylene rubber.
(C) When the carbon nanofibers were charged, a mixture (kneading) step of a mixture of ethylene-propylene rubber, carbon black and carbon nanofibers was performed and taken out from the rotor.
(D) The mixture obtained in (c) above was charged into the rotor of a closed kneader having a set temperature of 20 ° C., and the first kneading step was performed for 10 minutes, and the mixture was taken out from the rotor.
(E) The mixture obtained in the above (d) was put into a closed kneader set at 100 ° C., subjected to the second kneading step for 10 minutes, and taken out from the closed kneader.
(F) The mixture obtained in the above (e) is put into a 6 inch open roll having a roll temperature of 20 ° C. with a roll interval (nip) as narrow as 0.3 mm, and thinned 10 times (third kneading step). did. This thinned mixture was rolled to about 1.1 mm thickness and dispensed. The dispensed rubber composition was press-molded at 90 ° C. for 5 minutes, and each was molded into a sheet-like uncrosslinked rubber composition sample having a thickness of 1 mm. Moreover, an organic peroxide and a co-crosslinking agent were blended in the dispensed rubber composition, mixed with an open roll, and the roll gap was dispensed at 1.1 mm. The extracted rubber composition was press-crosslinked at 175 ° C. for 20 minutes, and the crosslinked rubber composition samples of Examples 1 to 4, 6 to 8 and Comparative Examples 1 and 2 were molded.

  This rubber composition sample is mixed with the reinforcing fibers, particulate filler and binder resin shown in Table 1, and is heated and pressure-molded by a press machine to form a friction material. And the friction material obtained by shape | molding was further baked, and the friction material of Examples 1-8 and Comparative Examples 1 and 2 was obtained.

  In Table 1, the binder resin as the raw material of the friction material is particulate “phenol resin”, the reinforcing fibers are “aramid fiber” and “inorganic fiber”, and the filler is particulate “cashew dust”, “metal material”, “ They were “inorganic material”, “lubricant” and “pH adjuster”. In Table 1, “EPDM” as a raw material of the rubber composition is ethylene-propylene rubber (EPDM: ethylene-propylene-diene copolymer rubber) (EP103AF) manufactured by JSR, “NBR” is a nitrile rubber of medium to high nitrile, “ “MWNT13” is a vapor-grown multiwall carbon nanotube having an average diameter of about 13 nm, “MWNT100” is a vapor-grown multiwall carbon nanotube having an average diameter of about 100 nm, and “HAF” is a HAF grade carbon black. It was. In Table 1, “Friction material blending ratio” is expressed in weight%, and “Rubber composition blending ratio” is expressed in parts by weight (phr).

(2) Measurement using pulsed method NMR About the raw material rubbers of Examples 1 to 8 and Comparative Examples 1 and 2 and rubber composition samples of each non-crosslinked body, measurement was performed by the Hahn echo method using pulsed 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. As shown in parentheses in Table 1, the measurement temperatures were 30 ° C. and 150 ° C. By this measurement, the first spin-spin relaxation time (T2n / 30 ° C.) of the raw rubber, the first spin-spin relaxation time (T2n / 150 ° C.) and the second spin for each uncrosslinked rubber composition sample. -The component fraction (fnn / 150 ° C) of the component having the spin relaxation time (T2nn / 150 ° C) was determined. The measurement results are shown in Table 1.

(3) Thermomechanical analysis (TMA)
Tests in which the crosslinked rubber composition samples of Examples 1 to 4, 6 to 8 and Comparative Examples 1 and 2 and the uncrosslinked rubber composition sample of Example 5 were cut into 1.5 mm × 1.0 mm × 10 mm For the piece, using a thermomechanical analyzer manufactured by SII (TMA-SS6100), the side long load is 25 KPa, the measurement temperature is −100 to 300 ° C., the heating rate is 3 ° C./min, and the linear expansion coefficient in the atmosphere is obtained. The deterioration start temperature (° C.) at which softening deterioration or hardening deterioration starts was measured from the temperature change characteristic of the obtained linear expansion coefficient. More specifically, the deterioration start temperature is a crosslinking type in that the linear expansion coefficient is extremely increased in the temperature (° C.)-Differential linear expansion coefficient (ppm / K) graph of each rubber composition sample. It was judged that the chain-breaking type softening deterioration (expansion) had started at the point where the hardening deterioration (shrinkage) or the linear expansion coefficient was extremely reduced, and was set as the deterioration start temperature. These results are shown in Table 1.

(4) Dynamic Viscoelasticity Test The crosslinked rubber composition samples of Examples 1 to 4, 6 to 8 and Comparative Examples 1 and 2 and the uncrosslinked rubber composition sample of Example 5 were formed into strips (40 × 1 × 5 (width) mm), using a dynamic viscoelasticity tester DMS6100 manufactured by SII, distance between chucks 20 mm, measurement temperature −100 to 300 ° C., dynamic strain ± 0.05 %, A dynamic viscoelasticity test was performed based on JIS K6394 at a frequency of 10 Hz, and a dynamic elastic modulus (E ′, unit is MPa) and loss tangent (tan δ) were measured. Table 1 shows the measurement results of the dynamic elastic modulus (E ′) at the measurement temperatures of 30 ° C. and 200 ° C. Table 1 shows the measurement results of loss tangent (tan δ) at measurement temperatures of −10 ° C., 30 ° C., and 200 ° C. Furthermore, Table 1 shows the peak temperature of the loss tangent (tan δ) in the region near the glass transition point (Tg) as the lowest usable temperature (° C.). The minimum use temperature is the limit temperature for use as a rubber composition because the rubber composition becomes too hard in the region lower than this temperature and loses cushioning properties.

(5) Fade test A load cell is subjected to a fade test in which the friction materials of Examples 1 to 8 and Comparative Examples 1 and 2 are pressed against a rotating FC250 (graphite cast iron, specific gravity 7.2) disk rotor for braking under the following test conditions. It carried out using.
(Test conditions)
Vehicle speed: (initial speed) 60 km / h-(final speed) 0 km / h
Deceleration: 0.4G
Braking interval: 20 sec
Table 1 shows the maximum temperature (° C.) of the disc rotor in the 24th fade test, the friction coefficient (μ) in the 24th fade test, and the total wear amount (mm) of the friction material in the fade test. The temperature of the disk rotor is a temperature measured while the disk rotor is stopped, and the friction coefficient is the highest value during braking. Further, FIG. 10 shows a graph of the number of braking times-the maximum disk rotor temperature in the fade tests of Examples 2 and 4 and Comparative Example 2, and FIG. 11 shows a graph of the number of braking times-the maximum value of the friction coefficient. In FIG. 10, the number of braking times in Example 2—the disk rotor temperature (° C.) characteristic is A, the number of braking times in Example 4—the disk rotor temperature (° C.) characteristic is B, the number of braking times in Comparative Example 2—the disk rotor temperature (° C. ) Characteristics are indicated by C. In FIG. 11, the braking frequency-friction coefficient (μ) characteristic of Example 2 is D, the braking frequency-friction coefficient (μ) characteristic of Example 4 is E, and the braking frequency-friction coefficient (μ) characteristic of Comparative Example 2 is Eq. Indicated by F.

表１から、本発明の実施例１〜８によれば、以下のことが確認された。すなわち、本発明の実施例１〜８のゴム組成物サンプルの劣化開始温度は、比較例１、２のゴム組成物サンプルの劣化開始温度よりも高く、１６０℃以上であった。また、本発明の実施例１〜８のゴム組成物サンプルによれば、２００℃における動的弾性率（Ｅ’）が７ＭＰａ以上であり、高温においても高い剛性を維持していることがわかった。なお、比較例１，２のゴム組成物サンプルは、劣化開始温度が１１５℃及び１５５℃であったので、２００℃では軟化して測定できなかった。本発明の実施例１〜８によれば、常温（３０℃）における動的弾性率（Ｅ’）が４０ＭＰａ以上で比較例１，２よりも高く、常温（３０℃）においても高い剛性を有していた。したがって、実施例１〜８の摩擦材は、低温から高温まで高い動的弾性率を維持したゴム組成物を含むため高摩擦係数を維持することができる。図１０に示すように、制動回数が増えるとディスクロータの温度も上昇し、ディスクロータに接触する摩擦材の温度も上昇する。しかしながら、図１１に示すように、摩擦材の温度が上昇しても、比較例２の摩擦材サンプルの低い摩擦係数に比べ、実施例２，４の摩擦材サンプルは高い摩擦係数を維持したままほとんど変化が無かった。

From Table 1, according to Examples 1 to 8 of the present invention, the following was confirmed. That is, the deterioration start temperature of the rubber composition samples of Examples 1 to 8 of the present invention was higher than the deterioration start temperature of the rubber composition samples of Comparative Examples 1 and 2, and was 160 ° C. or higher. Moreover, according to the rubber composition samples of Examples 1 to 8 of the present invention, it was found that the dynamic elastic modulus (E ′) at 200 ° C. is 7 MPa or more and maintains high rigidity even at high temperatures. . Since the rubber composition samples of Comparative Examples 1 and 2 had degradation start temperatures of 115 ° C. and 155 ° C., they were softened at 200 ° C. and could not be measured. According to Examples 1 to 8 of the present invention, the dynamic elastic modulus (E ′) at room temperature (30 ° C.) is 40 MPa or higher, higher than those of Comparative Examples 1 and 2, and has high rigidity at room temperature (30 ° C.). Was. Therefore, since the friction material of Examples 1-8 contains the rubber composition which maintained the high dynamic elastic modulus from low temperature to high temperature, it can maintain a high friction coefficient. As shown in FIG. 10, when the number of times of braking increases, the temperature of the disk rotor also increases, and the temperature of the friction material that contacts the disk rotor also increases. However, as shown in FIG. 11, even when the temperature of the friction material is increased, the friction material samples of Examples 2 and 4 maintain a high friction coefficient as compared with the low friction coefficient of the friction material sample of Comparative Example 2. There was little change.

  Furthermore, according to Examples 1 to 8 of the present invention, the loss tangent (tan δ) at 200 ° C. was 0.05 or more, and it was found that high damping characteristics were maintained particularly at high temperatures. In addition, the rubber compositions of Comparative Examples 1 and 2 had deterioration initiation temperatures of 115 ° C. and 155 ° C., and therefore were softened at 200 ° C. and could not be measured. According to Examples 1 to 8 of the present invention, the minimum operating temperature is −30 ° C. to −60 ° C., the loss tangent (tan δ) at a low temperature (−10 ° C.) is 0.08 or more, and normal temperature (30 (° C.), the loss tangent (tan δ) was 0.09 or more and a relatively high attenuation characteristic was obtained. Therefore, since the friction material of Examples 1-8 contains the rubber composition which has the damping characteristic excellent from low temperature to high temperature, the squeal in a brake can be reduced in the wide range from low temperature to high temperature, for example.

  Moreover, according to the friction material of Examples 1-8 of this invention, compared with the friction material of the comparative examples 1 and 2, there was little abrasion amount. In Example 4 and Example 6 of the present invention, the composition of the rubber composition was the same, and the content ratio of the rubber composition in the friction material was different, but there was no significant difference in the friction coefficient and the wear amount.

It is a front view of the pad for disc brakes concerning one embodiment of the present invention. 1 is a partially cutaway plan view of a pad for a disc brake according to an embodiment of the present invention. It is a rear view of the pad for disc brakes concerning one embodiment of the present invention. It is a longitudinal section showing the structure of the disc brake concerning one embodiment of the present invention. It is a figure which shows typically the manufacturing method of the rubber composition by a closed kneading machine. It is a figure which shows typically the 3rd kneading | mixing process (thinning) of the rubber composition by an open roll machine. It is process drawing which shows the manufacturing process of the friction material concerning one embodiment of this invention. It is explanatory drawing for demonstrating the temporary forming process which manufactures the friction material concerning one embodiment of this invention. It is explanatory drawing for demonstrating the heating and pressurizing process which manufactures the friction material concerning one embodiment of this invention. It is a figure which shows the frequency | count of braking by the fade test of Example 2, 4 and the comparative example 2-disk rotor temperature (degreeC). It is a figure which shows the frequency | count of braking-friction coefficient (micro) by the fade test of Example 2, 4 and the comparative example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pad 2 Friction material 3 Plate 5 Shim board 10 Disc brake 11 Caliper body 12 Piston 13 Disc rotor 14 Hydraulic chamber 30 Sealing kneading machine 37 Ethylene-propylene rubber 38 Carbon nanofiber 40 Open roll machine V1 The surface of the first roll Speed V2 Surface speed A of the second roll A Number of times of braking in Example 2-Disk rotor temperature (° C) characteristic B Number of times of braking in Example 4-Disk rotor temperature (° C) characteristic C Number of times of braking in Comparative Example 2-Disk rotor temperature (° C.) Characteristic D Number of times of braking in Example 2-friction coefficient characteristic E Number of times of braking in Example 4-friction coefficient characteristic F Number of times of braking in Comparative Example 2-friction coefficient characteristic

Claims (10)

A friction material comprising a reinforcing fiber, a filler, a rubber composition, and a binder resin,
In the rubber composition, carbon nanofibers having an average diameter of 0.5 to 500 nm are uniformly dispersed in ethylene-propylene rubber as a matrix, and measured at 150 ° C. by a Hahn echo method using pulsed NMR, non-crosslinked The first spin-spin relaxation time (T2n) in the body is 1000 to 3000 μs, and the component fraction (fnn) of the component having the second spin-spin relaxation time (T2nn) is less than 0.2. , Friction material. In claim 1,
The rubber composition is a friction material which is a non-crosslinked body. In claim 1,
The rubber composition is a friction material which is a crosslinked body. In any one of Claims 1-3,
The rubber composition is a friction material including 5 to 100 parts by weight of the carbon nanofibers with respect to 100 parts by weight of the ethylene-propylene rubber. In claim 4,
The rubber composition is a friction material including 40 to 80 parts by weight of carbon black and 5 to 20 parts by weight of the carbon nanofibers with respect to 100 parts by weight of the ethylene-propylene rubber. In any one of Claims 1-5,
The rubber composition is a friction material having a loss tangent (tan δ) at 200 ° C. of 0.05 to 1.00. In any one of Claims 1-5,
The rubber composition is a friction material having a dynamic elastic modulus (E ′) at 200 ° C. of 7 MPa to 1000 MPa. In any one of Claims 1-5,
The rubber composition is a friction material having a deterioration start temperature in a thermomechanical analysis of 160 ° C to 300 ° C. In claim 8,
The rubber composition is a friction material in which a peak temperature of a loss tangent (tan δ) in the vicinity of a glass transition point of the ethylene-propylene rubber is −30 ° C. to −60 ° C. In any one of Claims 1-9,
The binder resin is a friction material, which is a phenol resin.

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