JP2008138725A - Shim for disc brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shim for a disk brake capable of providing excellent damping characteristics at high temperatures by uniformly dispersing carbon nano fiber. <P>SOLUTION: This shim 76 for the disk brake comprises a sheet metal 76a and a rubber part 76b formed on at least one of the surfaces of the sheet metal 76a. In the rubber part 76b, the carbon nano fiber with an averaged diameter of 0.5 to 500 nm is dispersed on a nitrile rubber, the first spin-spin relaxation time T2n of a non-bridged body measured at 150°C by the Haln-echo method using a pulse method NMR is 100 to 3,000 μsec, and the component fraction fnn having the second spin-spin relaxation time T2nn is less than 0.2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disc brake shim plate that prevents squeal that occurs when a disc brake is operated.

  An example of a disc brake used for a vehicle brake is shown in FIG. A disc brake shim plate (hereinafter, simply referred to as a shim plate) 76 such as a metal plate is disposed between the pad 70 and the piston 62 in order to prevent an abnormal noise called squeal that occurs when the disc brake is braked. Has been. The vehicle disc brake 50 has a caliper body 60 supported on the vehicle body side, and the caliper body 60 has an action portion 60a in which a hydraulic chamber 64 is formed through a disk-like disc rotor 52, and an action. And a reaction portion 60b disposed to face the portion 60a. A piston 62 is disposed in the hydraulic pressure chamber 64, and the brake fluid is kept fluid tight by the piston seal 63.

  A pair of pads 70, 70 that can be pressed against the pressure contact surface (side surface) of the disk rotor 52 are disposed between the action portion 60 a and the reaction portion 60 b. In the pad 70, a lining material 72 is integrally provided on a surface of the metal back plate 74 on the disk rotor 52 side. Therefore, when the disc brake 50 applies hydraulic pressure to the hydraulic chamber 64 from the outside, the piston 62 moves in the direction of arrow B in FIG. 6 and the piston 70 side (inner side) pad 70 is moved to the disc rotor 52. The caliper body 60 is pressed against one pressure contact surface 52a, and at the same time, the caliper body 60 slides in the direction of arrow C in FIG. 6 via a slide pin (not shown), and the outer pad 70 is moved to the other side of the disc rotor 52 by the reaction portion 60b. A braking force is generated by pressing against the pressure contact surface 52b. At this time, a sliding loss due to friction occurs between the pad 70 and the disk rotor 52, and a braking force is obtained by the loss. However, the friction between the pad 70 and the disk rotor 52 is always in braking. A fine vibration occurs between the two. It is considered that this vibration resonates with the disc rotor 52, the caliper body 60, etc., and makes an abnormal noise of the disc brake 50 to generate a squeal.

  In order to prevent such squeal, the disc brake 50 has a shim plate 76 interposed between the pad 70 and the piston 62 on the action part 60a side, and between the pad 70 and the reaction part 60b on the reaction part 60b side. A shim plate 76 is interposed (see, for example, Patent Document 1). Such a shim plate 76 is attached to the back plate 74 by a plurality of locking pieces 76c and, as shown in FIG. 7, for example, a thin stainless steel metal plate 76a and vulcanized and bonded to both surfaces of the metal plate 76a. And a sheet-like rubber portion 76x in which a reinforcing fiber and a filler such as magnesium oxide are mixed with a synthetic rubber such as nitrile rubber (NBR: acrylonitrile-butadiene rubber). Examples of the rubber material used for the rubber portion 76x include nitrile rubber (NBR), styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), etc., but generally glass transition Nitrile rubber (NBR) having a high point (Tg) and excellent damping characteristics (loss tangent (tan δ)) has been used.

  However, the shim plate having a rubber part using nitrile rubber (NBR) has a low damping characteristic (loss tangent (tan δ)) at a high temperature, for example, 120 ° C. or higher, and a low deterioration start temperature. For this reason, squealing is likely to occur when the disc brake becomes hot, and the damping characteristics are lowered due to deterioration of the rubber part due to the high temperature, so that the life of the shim plate is relatively short compared to other parts of the disc brake.

In general, carbon nanofibers are fillers that are difficult to disperse in a matrix. 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 2). 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 used efficiently as fillers for composite materials.
JP-A-6-94057 JP 2005-97525 A

  An object of the present invention is to provide a shim plate for a disc brake having excellent damping characteristics at high temperature by uniformly dispersing carbon nanofibers.

The disc brake shim plate according to the present invention is:
A disc brake shim plate that generates a braking force by pressing a pad containing a lining material against a disk-shaped disc rotor,
A metal plate, and a rubber part formed on at least one surface of the metal plate,
The rubber part has a first spin-in-crosslinked body in which carbon nanofibers having an average diameter of 0.5 to 500 nm are dispersed in nitrile rubber and measured at 150 ° C. by a Hahn echo method using pulse NMR. The spin relaxation time (T2n) is 100 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 shim plate for a disc brake according to the present invention, since T2n and fnn are in such a range, the carbon nanofibers are uniformly dispersed in the nitrile rubber of the rubber portion, and thereby the deterioration start temperature is reduced. Therefore, it can have excellent damping characteristics even at high temperatures. According to the disc brake shim plate of the present invention, even when nitrile rubber is used for the rubber part, the rigidity and damping characteristics at high temperatures can be maintained, and the occurrence of squeal can be effectively suppressed even when used at high temperatures. it can. Further, even when the disc brake becomes high temperature, the deterioration start temperature is high and the heat resistance is excellent, so that the rubber portion of the shim plate is hardly deteriorated and the life of the shim plate can be extended. Further, according to the shim plate of the present invention, even if it is a non-crosslinked body, it is possible to obtain a damping characteristic close to that of the crosslinked body, so that it can be used as a non-crosslinked shim plate. Kneaded and reused (recycled).

Further, a shim plate for a disc brake according to the present invention,
A disc brake shim plate that generates a braking force by pressing a pad containing a lining material against a disk-shaped disc rotor,
A metal plate, and a rubber part formed on at least one surface of the metal plate,
The rubber part is a first spin-spin in a crosslinked body in which carbon nanofibers having an average diameter of 0.5 to 500 nm are dispersed in nitrile rubber and measured at 150 ° C. by a Hahn echo method using pulsed NMR. The relaxation time (T2n) is 100 to 2000 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 shim plate for a disc brake according to the present invention, since T2n and fnn are in such a range, the carbon nanofibers are uniformly dispersed in the nitrile rubber of the rubber portion, and thereby the deterioration start temperature is reduced. Therefore, it can have excellent damping characteristics even at high temperatures. According to the disc brake shim plate of the present invention, even when nitrile rubber is used for the rubber part, the rigidity and damping characteristics at high temperatures can be maintained, and the occurrence of squeal can be effectively suppressed even when used at high temperatures. it can. Further, even when the disc brake becomes high temperature, the deterioration start temperature is high and the heat resistance is excellent, so that the rubber portion of the shim plate is hardly deteriorated and the life of the shim plate can be extended.

In the shim plate for a disc brake according to the present invention,
The rubber part may have a loss tangent (tan δ) at 200 ° C. of 0.05 to 1.00.

In the shim plate for a disc brake according to the present invention,
The rubber part may have a dynamic elastic modulus (E ′) at 200 ° C. of 10 MPa to 1000 MPa.

In the shim plate according to the present invention,
The rubber part may have a deterioration start temperature in a thermomechanical analysis of 160 ° C to 300 ° C.

In the shim plate for a disc brake according to the present invention,
The rubber part may be formed on both surfaces of the metal plate.

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

  FIG. 1 is a front view showing an assembled state of shim plates and pads according to the present embodiment. FIG. 2 is a III-III ′ longitudinal sectional view of the shim plate of FIG. 1. 3 is a partially enlarged longitudinal sectional view of the shim plate of FIG.

  The shim plate 76 according to the present embodiment can be used, for example, in a disk brake 50 of a vehicle that generates a braking force by pressing a pad 70 including a lining material 72 shown in FIG. 6 against a disk-shaped disk rotor 52. The disc brake 50 has a shim plate 76 interposed between the pad 70 and the piston 62 on the action portion 60a side, and a shim plate 76 interposed between the pad 70 and the reaction portion 60b on the reaction portion 60b side. Prevent 50 squeals. As shown in FIG. 1, the shim plate 76 is assembled to the disc brake 50 shown in FIG. 6 in a state where the shim plate 76 is attached to the back plate 74 of the pad 70 by a plurality of locking pieces 76c. As shown in FIGS. 2 and 3, the shim plate 76 is, for example, a thin stainless steel metal plate 76a and a nitrile rubber (NBR) vulcanized and bonded to both surfaces of the metal plate 76a in a sheet shape reinforced with carbon nanofibers. Rubber part 76b. In the present embodiment, the rubber portions 76b are formed on both surfaces of the metal plate 76a. However, the rubber portions 76b may be formed only on at least one surface of the metal plate 76a. A plurality of, for example, two 76 may be mounted on the back plate 74. Further, the type of the disc brake 50 is not limited to the pin slide type of the present embodiment, but may be an opposed type disc brake in which pistons are arranged on both sides of the disc rotor. The form is not limited.

  The rubber part 36 is a non-crosslinked body, and the first spin-spin relaxation time (T2n) measured at 150 ° C. by the Hahn echo method using pulsed NMR is 100 to 3000 μs, and the second spin- The component fraction (fnn) of the component having the spin relaxation time (T2nn) is less than 0.2. In addition, the rubber part 36 is a crosslinked body, and the first spin-spin relaxation time (T2n) measured at 150 ° C. by the Hahn echo method using pulsed NMR is 100 to 2000 μs, and the second spin -The component fraction (fnn) of the component having the spin relaxation time (T2nn) is less than 0.2.

  T2n and fnn of the rubber part 76b can represent that the carbon nanofibers are uniformly dispersed in the nitrile rubber as the matrix. That is, the fact that the carbon nanofibers are uniformly dispersed in the nitrile rubber can be said to be a state where the nitrile rubber is restrained by the carbon nanofibers. In this state, the mobility of the nitrile 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 portion 76b according to the present embodiment are the same as those of the carbon nanofiber. It becomes shorter than the case of the nitrile 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.

  Further, in the state where the nitrile 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. In other words, when the molecular mobility of nitrile rubber is generally reduced by carbon nanofibers, the non-network component becomes more difficult to move, making it easier to behave the same as the network component. Since the (end chain) is easy to move, the non-network component is considered to decrease because it is easily adsorbed to the active site of the carbon nanofiber. Therefore, the component fraction (fnn) of the component having the second spin-spin relaxation time (T2nn) is smaller than that of a nitrile rubber alone not containing 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 a nitrile rubber alone not including carbon nanofibers.

  From the above, in the rubber part 76b according to the present embodiment, the carbon nanofibers are uniformly dispersed because 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 nitrile rubber, the lower the molecular mobility, the harder the nitrile rubber, and the longer the spin-lattice relaxation time, the higher the molecular mobility, and the softer the nitrile rubber. .

The rubber portion 76b 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, the rubber portion 76b having high damping characteristics in the high temperature region (200 ° C.) can be obtained.

  The rubber portion 76b preferably has a dynamic elastic modulus (E ′) at 200 ° C. of 10 MPa to 1000 MPa, and more preferably 10 MPa to 100 MPa.

  The rubber portion 76b preferably has a deterioration start temperature in a thermomechanical analysis of 160 ° C to 300 ° C, more preferably 200 ° C to 300 ° C. 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 part 76b is high, since the deterioration of the rubber part 76b does not start even at a high temperature, so that the maximum temperature at which the shim plate 76 can be used increases. The rubber portion 76b can be said to be in a state where the nitrile rubber is restrained by the carbon nanofibers because the carbon nanofibers are well dispersed in the nitrile rubber. Therefore, the nitrile rubber has a smaller molecular motion than the case where the carbon nanofiber is not included, and as a result, the deterioration start temperature moves to the high temperature side.

Next, the manufacturing method of the rubber composition which comprises the rubber part 76b is demonstrated.
FIG. 4 is a diagram schematically showing a method for producing a rubber composition by the open roll method.

  The nitrile rubber used as a raw material has a first spin-spin relaxation time (T2n) of a network component of 100 to 3000 μsec in a non-crosslinked body, as measured at 30 ° C. by a Hahn echo method using pulsed NMR. As shown in FIG. 4, the first roll 10 and the second roll 20 are arranged at a predetermined interval d, for example, 0.5 mm to 1.0 mm, and the rotational speed in the direction indicated by the arrow in FIG. It rotates by V1 and V2 by forward rotation or reverse rotation. First, the nitrile rubber 30 wound around the first roll 20 is masticated, and the nitrile rubber molecular chain is appropriately cut to generate free radicals. Carbon nanofibers usually have a six-membered ring of carbon atoms and a closed end with a five-membered ring introduced at the tip. Since it is easy to generate and it is easy to produce | generate a radical and a functional group in the part, it will be in the state in which the free radical of a nitrile rubber will be easy to be combined with carbon nanofiber by mastication.

  Next, carbon nanofibers 40 having an average diameter of 0.5 to 500 nm are put into a bank 34 of nitrile rubber 30 wound around the first roll 20 and kneaded. The step of mixing the nitrile rubber 30 and the carbon nanofiber 40 is not limited to the open roll method, and a closed kneading method or a multiaxial extrusion kneading method can also be used.

  Further, the roll interval d between the first roll 10 and the second roll 20 is preferably set to 0.5 mm or less, more preferably 0 to 0.5 mm, and the mixture is put into an open roll and thinned. Repeat several times. The number of thinning is preferably about 5 to 10 times, for example. 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. The thin rubber composition is rolled with a roll and dispensed into a sheet. In this thinning process, in order to obtain as high a shearing force as possible, the roll temperature is preferably set to a relatively low temperature of 0 to 50 ° C, more preferably 5 to 30 ° C. The temperature is also preferably adjusted to 0 to 50 ° C. Due to the shearing force thus obtained, a high shearing force acts on the nitrile rubber 30 and the aggregated carbon nanofibers 40 are separated from each other so that they are pulled out one by one into the nitrile rubber molecule. Distributed in. In particular, since the nitrile rubber 30 has elasticity, viscosity, and chemical interaction with the carbon nanofibers 40, the carbon nanofibers 40 can be easily dispersed. And the rubber composition excellent in the dispersibility and dispersion stability of carbon nanofiber 40 (it is hard to re-aggregate carbon nanofiber) can be obtained.

  More specifically, when nitrile rubber and carbon nanofibers are mixed with an open roll, viscous nitrile rubber penetrates into the carbon nanofibers, and a specific part of the nitrile rubber is carbonized by chemical interaction. It binds to the highly active part of the nanofiber. Next, when a strong shearing force acts on the nitrile rubber, the carbon nanofibers move as the nitrile rubber molecules move, and the aggregated carbon nanofibers are separated by the restoring force of the nitrile rubber due to the elasticity after shearing. And dispersed in the nitrile 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 nitrile 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 nitrile rubber. The carbon nanofibers once dispersed are prevented from reaggregating due to chemical interaction with the nitrile rubber, and can have good dispersion stability.

  The step of dispersing the carbon nanofibers in the nitrile rubber by a shearing force is not limited to the open roll method, and a closed kneading method or a multiaxial extrusion kneading method can also be used. In short, in this step, it is sufficient that a shear force capable of separating the aggregated carbon nanofibers can be applied to the nitrile rubber. In particular, the open roll method is preferable because it can measure and manage not only the roll temperature but also the actual temperature of the mixture.

  As a method for producing a rubber composition, a rubber composition of a crosslinked body may be obtained by mixing a cross-linking agent with the dispensed rubber composition after thinning and cross-linking. The rubber composition may be molded without being crosslinked. The rubber composition may remain in the form of a sheet obtained by the open roll method, or a rubber molding process generally employed for the obtained rubber composition, for example, an injection molding method, a transfer molding method, a press molding method, an extrusion method. You may shape | mold into a desired shape, for example, a sheet form, by a shaping | molding method, a calendar processing method, etc.

  In the method for producing a rubber composition according to the present embodiment, a compounding agent usually used for processing nitrile 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 can be added to the nitrile rubber before the carbon nanofibers in the open roll, for example.

  The rubber composition thus obtained may be overlapped on the metal plate 76a and bonded by cross-linking adhesion or the like to form the rubber portion 76b. Alternatively, the rubber composition is dissolved in a solvent and spray coating, roller coating, dipping is performed. The rubber portion 76b may be formed by applying and heat treatment.

  Nitrile rubber can be abbreviated as NBR, and can be used in a relatively wide range as long as it is an acrylonitrile-butadiene copolymer synthetic rubber having rubber-like elasticity at room temperature. Nitrile rubber can change its physical properties by including the amount of acrylonitrile in about 15-50%, for example, low nitrile less than 24%, medium nitrile 24-30%, medium high nitrile 30-36%, high nitrile 36 It can be classified by the amount of nitrile such that it exceeds ˜42% and exceeds nitrile 42%. The average molecular weight of the nitrile rubber is usually desirably 50,000 or more, more preferably 70,000 or more, and particularly preferably about 100,000 to 500,000.

  The carbon nanofibers preferably have an average diameter of 0.5 to 500 nm, and more preferably an average diameter of 0.5 to 100 nm. The carbon nanofibers preferably have an average length of 0.01 to 1000 μm. The compounding quantity of carbon nanofiber is not specifically limited, It can set suitably according to a use, the kind or quantity of another compounding agent, etc.

  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. Carbon nanofibers are improved in adhesion and wettability with nitrile rubber by performing surface treatment, for example, ion implantation treatment, sputter etching treatment, plasma treatment, etc. in advance before being kneaded with nitrile rubber. be able to.

  In the method for manufacturing the rubber part of the shim plate according to the present embodiment, carbon nanofibers are directly mixed with nitrile 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 nitrile rubber is masticated to reduce the molecular weight of the nitrile rubber. Since the viscosity of nitrile rubber decreases when the molecular weight decreases due to mastication, the nitrile rubber easily penetrates into the voids of the aggregated carbon nanofibers. The raw material nitrile rubber is a rubber-like material in which the first spin-spin relaxation time (T2n) of the network component in the uncrosslinked product is 100 to 3000 μsec, measured at 30 ° C. by the Hahn echo method using pulsed NMR. It is an elastic body. This raw material nitrile rubber is masticated to reduce the molecular weight of the nitrile rubber, and a liquid nitrile rubber having a first spin-spin relaxation time (T2n) exceeding 3000 μsec is obtained. The first spin-spin relaxation time (T2n) of the liquid nitrile rubber after mastication is 5 to 30 of the first spin-spin relaxation time (T2n) of the raw material nitrile rubber before mastication. It is preferable that it is double. This kneading is different from the general kneading performed in a state where the nitrile rubber is in a solid state. By applying a strong shearing force, for example, by an open roll method, the molecules of the nitrile rubber are cut and the molecular weight is significantly reduced. It is performed until it becomes a liquid state until it shows an unsuitable flow. 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 10 minutes), and the roll interval d is, for example, 0.1 mm to 1 mm. At 0.0 mm, carbon nanofibers are put into a nitrile rubber that is masticated and liquid. However, since nitrile rubber is liquid and has a remarkably reduced elasticity, the aggregated carbon nanofibers are not very dispersed even when kneaded in a state where the free radicals of nitrile rubber and carbon nanofibers are combined.

  Therefore, after increasing the molecular weight of the nitrile rubber in the mixture obtained by kneading the liquid nitrile rubber and the carbon nanofibers to restore the elasticity of the nitrile rubber to obtain a mixture of the rubber-like elastic body, The carbon nanofibers are uniformly dispersed in the nitrile rubber by performing the open roll method thinning described in the above. A mixture of rubber-like elastic bodies having an increased molecular weight of nitrile rubber has a first spin-spin relaxation time (T2n) of 3000 μsec or less as measured by a Hahn echo method at 30 ° C. using pulse NMR. is there. Also, the first spin-spin relaxation time (T2n) of the rubber-like elastic mixture having an increased molecular weight of the nitrile rubber is equal to the first spin-spin relaxation time (T2n) of the raw material nitrile rubber before mastication. It is preferably 0.5 to 10 times. The elasticity of the mixture of rubber-like elastic bodies can be expressed by the molecular form of nitrile rubber (observable by molecular weight) and molecular mobility (observable by T2n). The step of increasing the molecular weight of the nitrile 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 heat treatment, the molecular chain is extended by the bonding of free radicals of the nitrile rubber present in the mixture, and the molecular weight is increased. In addition, when the molecular weight of the nitrile rubber is increased in a short time, a small amount of a crosslinking agent, for example, ½ or less of an appropriate amount of the crosslinking agent is mixed, and the mixture is heated (for example, annealed) to be crosslinked. The molecular weight can be increased in a short time by the reaction. When the molecular weight of the nitrile rubber is increased by a crosslinking reaction, it is preferable to set the blending 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 part of the shim plate described here, the carbon nanofibers can be dispersed more uniformly in the nitrile rubber than before by reducing the viscosity of the nitrile rubber before introducing the carbon nanofibers. Can do. More specifically, the agglomeration of carbon nanofibers aggregated by using liquid nitrile rubber having a reduced molecular weight rather than mixing carbon nanofibers with nitrile rubber having a large molecular weight as in the production method described above. The carbon nanofibers can be more uniformly dispersed in the thin process. Moreover, since free radicals of nitrile rubber produced in large quantities by molecular cutting of nitrile rubber can be more firmly bonded to the surface of carbon nanofibers, carbon nanofibers can be evenly dispersed. . 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.

  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 6 and Comparative Examples 1 to 6 A 6-inch open roll (roll temperature: 10 to 20 ° C., roll interval: 1.5 mm) and predetermined amounts of nitrile rubber shown in Tables 1 and 2 (100 parts by weight (phr)) is added, wound on a roll, masticated for 5 minutes, and then the amount of carbon nanofiber shown in Table 1 or the amount of carbon black shown in Table 2 is added and the mixture is opened. Removed from roll. And the roll space | interval was narrowed from 1.5 mm to 0.3 mm, the mixture was again thrown into the open roll, and thinning was repeated 5 times. At this time, the surface speed ratio of the two rolls was set to 1.1. Further, the rubber composition obtained through thinning was set by setting the roll gap to 1.1 mm 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. In addition, among the rubber compositions thus dispensed, peroxides were blended as crosslinking agents in the rubber compositions of Examples 1, 3 to 6 and Comparative Examples 1 to 6, mixed with an open roll, and the roll gap was 1 Dispensing at 1 mm. The extracted rubber composition was press-crosslinked at 175 ° C. for 20 minutes, and the crosslinked rubber composition samples of Examples 1, 3-6 and Comparative Examples 1-6 were molded.

  In Tables 1 and 2, “NBR (high nitrile)”, “NBR (medium / high nitrile)”, and “NBR (low nitrile)” were used as the raw material nitrile rubber. In Tables 1 and 2, “MWNT13” is a vapor-grown multi-wall carbon nanotube having an average diameter of about 13 nm, and “MWNT100” is a vapor-grown multi-wall carbon nanotube having an average diameter of about 100 nm. “HAF” is HAF grade carbon black.

(2) Measurement Using Pulse Method NMR The uncrosslinked rubber composition samples of Examples 1 to 6 and Comparative Examples 1 to 6 were measured by the Hahn echo method using pulse method NMR. This measurement was performed using “JMN-MU25” manufactured by JEOL Ltd. The measurement was performed under the conditions of the observation nucleus of ¹ H, the resonance frequency of 25 MHz, and the 90 ° pulse width of 2 μsec. The Pi was changed in various ways using the pulse sequence of the Hahn-echo method (90 ° x-Pi-180 ° x). The decay curve was measured. Further, the sample was measured by inserting it into a sample tube up to an appropriate range of the magnetic field. Measurement temperatures were 30 ° C. and 150 ° C. as shown in parentheses in Tables 1 and 2. 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-spin relaxation time (T2nn / The component fraction (fnn / 150 ° C.) of the component having 150 ° C. was determined. The measurement results are shown in Tables 1 and 2.

(3) Thermomechanical analysis (TMA)
About the test piece which cut out the rubber composition sample of the crosslinked body of Examples 1, 3-6 and Comparative Examples 1-6 and the rubber composition sample of the non-crosslinked body of Example 2 into 1.5 mm x 1.0 mm x 10 mm Using a thermomechanical analyzer (TMASS) manufactured by SII, the linear expansion coefficient was measured at a side long load of 25 KPa, a measurement temperature of −80 to 350 ° C., and a temperature increase rate of 2 ° C./min. The deterioration start temperature at which softening deterioration or hardening deterioration starts was measured from the temperature change characteristic of the expansion coefficient. These results are shown in Tables 1 and 2. The deterioration start temperature will be described for Example 4 and Comparative Examples 3 and 4 with reference to FIG. FIG. 5 shows temperature (° C.)-Differential linear expansion coefficient showing the temperature change of the differential linear expansion coefficient of Example 4 (X in the figure), Comparative Example 3 (Y in the figure) and Comparative Example 4 (Z in the figure). It is a graph of (ppm / K). In Example 4 (X), it is a bridge-type curing deterioration (shrinkage), and it is judged that the deterioration has started at the point where the linear expansion coefficient is extremely changed in FIG. It was temperature. Further, Comparative Example 3 (Y) and Comparative Example 4 (Z) are chain-breaking type softening deterioration (expansion), and the deterioration starts at the point where the linear expansion coefficient changes extremely in FIG. Therefore, 127 ° C. and 152 ° C. were set as the deterioration start temperatures.

(4) Dynamic Viscoelasticity Test The crosslinked rubber composition samples of Examples 1 and 3 to 6 and Comparative Examples 1 to 6 and the non-crosslinked rubber composition sample of Example 2 were strip-shaped (40 × 1 × 5 (width) mm), using a dynamic viscoelasticity tester DMS6100 manufactured by SII, the distance between chucks is 20 mm, the measurement temperature is −100 to 300 ° C., the dynamic strain is ± 0.05%, A dynamic viscoelasticity test was performed at a frequency of 10 Hz based on JIS K6394, and a dynamic elastic modulus (E ′, unit is MPa) and a loss tangent (tan δ) were measured. Tables 1 and 2 show the measurement results of the dynamic elastic modulus (E ′) at the measurement temperatures of 30 ° C. and 200 ° C. Tables 1 and 2 show measurement results of loss tangent (tan δ) at measurement temperatures of −10 ° C., 30 ° C., and 200 ° C. Further, Table 1 and Table 2 show the peak temperature of loss tangent (tan δ) in the region near the glass transition point (Tg) as the lowest usable temperature (° C.). The minimum use temperature is a limit temperature for use as a rubber composition for a shim plate because the rubber composition becomes too hard in a region lower than this temperature and loses cushioning properties.

表１及び表２から、本発明の実施例１〜６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１〜６のゴム組成物サンプルの劣化開始温度は、比較例１〜６のゴム組成物サンプルの劣化開始温度よりも高く、２００℃以上であった。したがって、実施例１〜６のゴム組成物をシム板のゴム部として用いた場合、シム板の使用可能な最高温度を２００℃以上に設定することができる。

From Table 1 and Table 2, according to Examples 1 to 6 of the present invention, the following was confirmed. That is, the deterioration start temperature of the rubber composition samples of Examples 1 to 6 of the present invention was higher than the deterioration start temperature of the rubber composition samples of Comparative Examples 1 to 6, and was 200 ° C. or higher. Therefore, when the rubber compositions of Examples 1 to 6 are used as the rubber part of the shim plate, the maximum usable temperature of the shim plate can be set to 200 ° C. or higher.

  Moreover, according to Examples 1-6 of this invention, it turned out that the dynamic elastic modulus (E ') in 200 degreeC is 10 Mpa or more, and maintains high rigidity also at high temperature. In addition, since the deterioration start temperature was 123 degreeC-152 degreeC, the rubber composition of Comparative Examples 1-6 was softened at 200 degreeC, and could not be measured. According to Examples 1 to 6 of the present invention, the dynamic elastic modulus (E ′) at room temperature (30 ° C.) is 25 MPa or higher, higher than those of Comparative Examples 1 to 6, and has high rigidity at room temperature (30 ° C.). Was.

  Furthermore, according to Examples 1 to 6 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, since the deterioration start temperature was 123 degreeC-152 degreeC, the rubber composition of Comparative Examples 1-6 was softened at 200 degreeC, and could not be measured. According to Examples 1 to 6 of the present invention, the loss tangent (tan δ) at low temperature (−10 ° C.) is 0.2 or more, and the loss tangent (tan δ) is 0.1 or more even at room temperature (30 ° C.). It had a relatively high attenuation characteristic.

  Moreover, according to Examples 1-6 of this invention, the minimum use temperature measured by the dynamic viscoelasticity test is -10 degrees C or less, and it is flexible at low temperature and can be used as a rubber part for shim boards. I understood it.

It is a front view which shows the assembly | attachment state of the pad and shim board of this Embodiment. FIG. 3 is a III-III ′ longitudinal sectional view of the shim plate of FIG. 1. FIG. 3 is a partially enlarged longitudinal sectional view of the shim plate of FIG. 2. It is a figure which shows typically the manufacturing method of the rubber composition by an open roll method. It is a figure which shows the temperature (degreeC) -differential linear expansion coefficient (ppm / K) of Example 4, Comparative Example 3, and Comparative Example 4. It is a longitudinal cross-sectional view which shows an example of the disc brake used for the brake of a vehicle. It is a longitudinal cross-sectional view of a shim board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st roll 20 2nd roll 30 Nitrile rubber 40 Carbon nanofiber 50 Disc brake 52 Disc rotor 60 Caliper body 60a Action part 60b Reaction part 62 Piston 64 Hydraulic chamber 70 Pad 72 Lining material 74 Back plate 76 Shim plate 76a Metal plate 76b Rubber portion 76c Locking piece d Roll interval V1 First roll surface speed V2 Second roll surface speed X Temperature-differential linear expansion coefficient characteristic Y of Example 4 Temperature-differential linear expansion of Comparative Example 3 Coefficient characteristic Z Temperature-differential linear expansion coefficient characteristic of Comparative Example 4

Claims (6)

A disc brake shim plate that generates a braking force by pressing a pad containing a lining material against a disk-shaped disc rotor,
A metal plate, and a rubber part formed on at least one surface of the metal plate,
The rubber part has a first spin-in-crosslinked body in which carbon nanofibers having an average diameter of 0.5 to 500 nm are dispersed in nitrile rubber and measured at 150 ° C. by a Hahn echo method using pulse NMR. A disk brake shim plate having a spin relaxation time (T2n) of 100 to 3000 μs and a component fraction (fnn) of a component having a second spin-spin relaxation time (T2nn) of less than 0.2. A disc brake shim plate that generates a braking force by pressing a pad containing a lining material against a disk-shaped disc rotor,
A metal plate, and a rubber part formed on at least one surface of the metal plate,
The rubber part is a first spin-spin in a crosslinked body in which carbon nanofibers having an average diameter of 0.5 to 500 nm are dispersed in nitrile rubber and measured at 150 ° C. by a Hahn echo method using pulsed NMR. A shim plate for a disc brake having a relaxation time (T2n) of 100 to 2000 μs and a component fraction (fnn) of a component having a second spin-spin relaxation time (T2nn) of less than 0.2. In claim 1 or 2,
The rubber part is a shim plate for a disc brake having a loss tangent (tan δ) at 200 ° C. of 0.05 to 1.00. In claim 1 or 2,
The rubber part is a shim plate for a disc brake having a dynamic elastic modulus (E ′) at 200 ° C. of 10 MPa to 1000 MPa. In claim 1 or 2,
The rubber part is a shim plate for a disc brake having a deterioration start temperature of 160 ° C. to 300 ° C. in a thermomechanical analysis. In any one of Claims 1-5,
The rubber part is a shim plate for a disc brake formed on both surfaces of the metal plate.

Images