Friction material composition and related friction elements

Abstract

A friction material composition and related brake pads for vehicles, particularly electric vehicles, having improved friction stability, reduced creep groan noise tendency, and reduced particle emission, and being asbestos-free, wherein the composition comprises at least one filler, at least a fibrous material, at least one binder, at least one lubricant, at least one or more abrasives, and a first carbonaceous material having a particle size distribution such that it has a D greater than at least 10 μm 50 and a second carbonaceous material having a particle size distribution such that it has a D less than at least 10 μm 50 The asbestos-free friction material composition and related brake pads comprising the same.

Description

Technical Field

[0001] Cross - reference to related applications This patent application claims the priority of Italian Patent Application No. 102022000013012 filed on June 20, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates in particular to a friction material composition suitable for the manufacture of friction layers / blocks for friction elements, such as braking elements incorporated in vehicle braking devices.

[0003] The present invention also relates to related friction elements, such as brake pads or brake shoes for vehicles, which are made of this friction material composition and are particularly suitable for electric vehicles, without limitation.

[0004] The friction material composition of the present invention belongs to the so - called NAO ("Non Asbestos Organic") type, does not contain asbestos, and does not contain copper, without limitation.

Background Art

[0005] With the rapid development of the modern transportation industry, the number of electric vehicles is increasing day by day.

[0006] Replacing combustion engines with electric motors results in much quieter vehicles. This is generating greater concern about the noise generated by other automotive components, such as brake pads incorporated in braking devices. As a result, brake pads used for electric vehicles need to maintain, and in some cases improve, braking performance in terms of friction stability, stickiness, and corrosion removal, while meeting improved NVH (noise, vibration, harshness) criteria for driving comfort.

[0007] At the same time, future mobility trends pay special attention to environmental and health damage issues and aim to reduce, for example, the emissions of particulate matter (PM10 and PM2.5) generated by braking devices.

[0008] Regarding the operating noise of braking devices, it is known that this phenomenon has a complex and multi-factorial origin, depends on the driving vibrations of the vehicle related to the inevitable assembly gaps between braking elements such as brake pads and shoes and their respective supports, and also depends on the contact phenomena occurring between the sliding parts of the braking elements and the supports during the operation of the braking device.

[0009] This contact phenomenon is called "creep groan" and produces unpleasant high-intensity and low-frequency noise at extremely low vehicle speeds. It is a classical example of self-excited braking vibration caused by the so-called "stick-slip" effect, that is, the alternation of sticking or adhesion and episodes of sliding of the brake pads on the brake disc during the subsequent braking process. As a result, the friction coefficient varies continuously between the static (stick phase) value and the dynamic (slip phase) value.

[0010] In modern vehicles such as electric vehicles, there is a strong need to eliminate or at least reduce low-frequency noise in a simple and particularly economical way.

[0011] In fact, electric vehicles are much quieter than their internal combustion engine vehicles. In particular, unlike engine-driven vehicles, electric vehicles start moving quietly due to the electric motor. Therefore, the driver and passengers are more likely to feel the above-mentioned noise and may probably feel discomfort from it. Furthermore, these types of noise may affect the living environment of residents and may become a new source of urban noise pollution.

[0012] Various solutions for reducing this phenomenon are known in the art, but they do not completely solve the problem or bring further drawbacks.

[0013] EP0959262 discloses a disc brake pad capable of removing creep groans by using a composition containing a fiber base material excluding asbestos, a binder, and a friction modifier, wherein the binder is wholly or partly made of a modified silicone resin, and in combination, the friction material composition contains 0.5 to 20% by volume of zeolite as part of the friction modifier, and the modified silicone resin is contained in the friction material composition in an amount of 3% to 30% by volume of the total composition. The modified silicone resin is obtained by reacting an oil or silicone rubber with a novolak-type phenolic resin. This results in an expensive material and difficult manufacturing.

[0014] On the other hand, WO2019120648 discloses a hybrid friction lining material and a brake pad made therefrom, in which attempts have been made to combine the positive characteristics of a steel low-friction lining material (so-called low-steel (LS) friction lining or friction lining material) and an asbestos-free organic friction lining material. In a preferred embodiment, such a hybrid friction material comprises 15 to 22% by weight, particularly 17 to 20% by weight of at least one binder, 5 to 11% by weight of organic fibers or a mixture of organic fibers, 1 to 20% by weight, particularly 8 to 14% by weight of at least one other organic compound, 0 or 8 to 16% by weight of inorganic fibers or a mixture of inorganic fibers, 10 to 40% by weight of at least one inorganic oxide, 6 to 12% by weight of at least one inorganic silicate, 13 to 15% by weight of sulfur or at least one inorganic sulfur compound, 10 to 16% by weight of carbon, or consisting essentially of carbon, particularly at least one material selected from the group consisting of natural graphite, synthetic graphite, petroleum coke, dry petroleum coke, carbon black, and any mixture thereof, 1 to 1.5% by weight of at least one filler selected from the group of inorganic hydroxides, particularly calcium hydroxide, and 0 to a maximum of 1% by weight of at least one metal, particularly iron or an iron alloy.

[0015] However, such hybrid materials result in a compromised behavior with respect to braking performance and comfort, and may not be optimal or less than optimal for many applications.

[0016] CN106015399 discloses a friction material for electric vehicle brake components. The friction material includes 25 - 30 parts by weight of carbon fiber, 10 - 15 parts by weight of aramid fiber, 40 - 50 parts by weight of nitrile rubber, 20 - 30 parts by weight of styrene - butadiene rubber, 10 - 20 parts by weight of carbon black, 5 - 12 parts by weight of composite mineral fiber, 1 - 3 parts by weight of sulfur, 1 - 4 parts by weight of vermiculite, 2 - 7 parts by weight of epoxy resin, 6 - 15 parts by weight of barium sulfate, 3 - 8 parts by weight of graphite, 0.5 - 1 part by weight of accelerator, 2 - 4 parts by weight of stabilizer, and 1 - 2 parts by weight of water. However, the brake pads containing this friction material do not show any drawbacks overcome with respect to reduction of noise and particle emissions and improvement of friction stability.

Summary of the Invention

[0017] The object of the present invention is to develop a new asbestos - free friction material composition that can overcome the disadvantages of the prior art and exhibit improved braking performance with respect to low - frequency noise and friction stability, and reduced particle emissions. In particular, the presently disclosed subject matter is intended to provide an asbestos - free friction material composition that combines improved creep groan and friction stability by reducing particle emissions by reducing material wear and optimizing heat dissipation, and by reducing the tendency of the friction block to adhere to the surface of the friction partner with which it cooperates.

[0018] Accordingly, the present invention relates to a friction material composition as defined in the appended claims.

[0019] Another object of the present invention is to provide a friction element, in particular a brake pad or a brake shoe, comprising this friction material composition.

[0020] Other features and advantages of the disclosed subject matter will become apparent, whether or not they are explicitly described, upon consideration of the following disclosure.

[0021] Accordingly, the present disclosure is directed to a friction material composition belonging to the class of friction materials called NAO (non-asbestos organic), which aims to obtain improved stick-slip behavior for the advantages of creep groan phenomenon and friction stability, and to reduce particle emission with respect to known NAO friction compositions.

[0022] Indeed, different from known NAO friction compositions, the disclosed friction material composition, in combination, has at least a first carbonaceous material having a particle size distribution such that D is higher than 10 μm 50 and at least a second carbonaceous material having a particle size distribution such that D is lower than 10 μm. 50

[0023] Due to the combination of at least the first carbonaceous material and at least the second carbonaceous material, the disclosed friction material composition leads to both a reduced stick-slip phenomenon that has a beneficial effect on both creep groan noise and friction stability, and reduced particle emission. Specifically, a friction element comprising the disclosed friction material composition makes the braking device less likely to exhibit stick-slip behavior due to the optimized porosity of the friction material that mainly improves the adhesion between the friction element and the brake disk, and reduces the negative effect of humidity on the friction coefficient.

[0024] At the same time, the reduced particle emission is due to the synergistic effect of a first carbonaceous material that reduces the friction between the brake disk and the friction element for the advantage of friction element wear, and a second carbonaceous material that dissipates the heat generated during brake application instead of accumulating it in the friction element to break the binder.

[0025] Other characteristics and advantages of the present invention will become apparent from the following description, from non-limiting examples and comparative examples, with reference to the accompanying drawings.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0027] More specifically, the disclosed asbestos-free friction material composition comprises at least one filler, at least a fibrous material, at least one binder, at least one lubricant, a D higher than 10 μm 50 and at least a first carbonaceous material having a particle size distribution such that it has, and a D lower than 10 μm 50 and at least a second carbonaceous material having a particle size distribution such that it has, as well as at least one or more abrasives.

[0028] Here and hereinafter, "particle size distribution D 50 " coincides with the value of the particle diameter at 50% in the cumulative distribution.

[0029] Preferably, a D higher than 10 μm 50At least a first carbonaceous material having is present in the disclosed composition in an amount in the range of 2 to 6% by weight, calculated based on the total weight of the friction material composition.

[0030] Preferably, D is less than 10 μm 50 At least a second carbonaceous material having is present in the disclosed composition in an amount in the range of 1 to 4% by weight, calculated based on the total weight of the friction material composition. Most preferably, the amount of at least the second carbonaceous component is 2% by weight.

[0031] The weight content ratio of the first carbonaceous material to the second carbonaceous material can be in the range of 1:1 to 6:1, preferably 2:1 to 3:1.

[0032] D higher than 10 μm 50 The first carbonaceous material having can be selected from the group consisting of graphite, petroleum coke, dry petroleum coke, carbon black, and any mixture thereof. Preferably, the first carbonaceous material having with D higher than 10 μm 50 The first carbonaceous material having is graphite.

[0033] D less than 10 μm 50 The second carbonaceous material having is selected from fillers consisting of carbon black.

[0034] Except for at least the first and at least the second carbonaceous materials, the other components of the disclosed friction material composition described above can be components used in friction materials known in the art.

[0035] In particular, at least one fibrous material can be selected from the group consisting of inorganic fibers, organic fibers, metal fibers, and any combination thereof.

[0036] Preferably, at least one fibrous material consists of organic fibers selected from the group consisting of acrylic fibers, polyaramid fibers, aramid fibers, cellulose fibers, and mixtures thereof.

[0037] Organic fibers can have the main purpose of increasing their strength under the operating conditions of brake pads / shoes that can be manufactured from the friction material composition of the present disclosure, and can preferably be included in the friction material composition of the present disclosure as part of an organic binder, without limitation.

[0038] At least one binder is preferably an organic binder and can be selected from the group consisting of phenolic resins, epoxy resins, silicone resins, modified phenolic resins, melamine resins, polyimide resins, and mixtures thereof.

[0039] At least one lubricant can preferably consist of a sulfide-based lubricant selected from the group consisting of metal sulfides of Sn, Zn, Fe, Mo, and mixtures thereof, without limitation.

[0040] A number of materials can be used as organic or inorganic fillers. Preferably, at least one filler is an inorganic filler selected from the group consisting of mineral fibers, glass fibers, rock wool, phyllosilicates (such as mica, vermiculite, talc, etc.), titanates, calcium, magnesium, potassium inorganic hydroxides, and any mixtures thereof.

[0041] At least one or more abrasives include at least one soft abrasive having a Mohs hardness of less than 7 and at least one hard abrasive having a Mohs hardness of more than 7.

[0042] The ratio of the weight content of the soft abrasive to the hard abrasive is in the range of 1:1 to 4:1, and can preferably be 2:1.

[0043] The hard abrasive (i.e., having a Mohs hardness of more than 7) preferably has a rounded shape, without limitation, and is preferably selected from the group consisting of zirconia, alumina, corundum, silicon carbide, tungsten carbide, zirconium carbide, zirconium silicate, boron nitride, and any mixtures thereof.

[0044] Soft abrasives (i.e., having a Mohs hardness of less than 7) may be selected from the group consisting of, but not limited to, magnesia, chromite, magnetite, hematite, quartz, zinc oxide, tin oxide, barium sulfate, silicates, fluorides, and any mixture thereof.

[0045] According to a preferred embodiment of the present invention, the disclosed friction composition is copper-free.

[0046] Here and hereinafter, the expression "copper-free" is to be understood to mean a content of copper and / or copper-containing materials such as copper alloys of 0.5 wt% or less than 0.5 wt%.

[0047] When at least one metal or mixture of metals is present in the disclosed friction material composition, it does not consist of copper and / or any copper alloy, but is selected in the form of powder or fiber from the group consisting of iron, steel, stainless steel, tin, zinc, and any alloy thereof.

[0048] Furthermore, the disclosed friction material composition can include an organic additive selected from the group consisting of polytetrafluoroethylene, friction dust, cashew dust, rubber (i.e., NBR, silicone rubber, SBR, etc.).

[0049] In another embodiment of the present invention, the disclosed average friction material composition is as follows (% are weight %).

[0050] Abrasive, Mohs > 7, 15 - 35% Abrasive, Mohs < 7, 30 - 60% Resin, 6 - 10% Organic additive, 4 - 8% Organic fiber, 2 - 4% Lubricant, 2 - 8% First carbonaceous material, 2 - 6% Second carbonaceous material, 1 - 4% Finally, the present invention also relates to a friction element, particularly a brake pad or shoe, having a layer of friction material made from the above-described friction material composition.

[0051] The present invention further relates to a braking device including a member to be braked composed of a brake disk or a brake drum made of cast iron or steel, and at least one braking element composed of a brake pad or a shoe designed to cooperate by friction with the member to be braked, wherein the braking member is intended to cooperate with the member to be braked and exhibits a friction layer made of the above-described friction material composition.

[0052] Exemplary embodiments for implementing the teachings of the present disclosure Examples of the present invention and comparative examples are reported herein as examples and are not intended to limit the present invention.

Example

[0053] According to Table 1 below, three formulations were prepared and designated as "Bi-Carbon 2%", "Bi-Carbon 4%", and "Mono-Carbon". The components shown in Table 1 are expressed as weight percentage values based on the total weight of the composition.

[0054] The friction material compositions according to the present invention are represented by "Bi-Carbon 2%" and "Bi-Carbon 4%" and differ in terms of the second carbonaceous material content.

[0055] The comparative friction material composition represented by "Mono-Carbon" has a composition of the standard NAO category and is substantially the same as the composition of the present invention, but does not contain a second carbonaceous material having a D 50 less than 10 μm.

[0056]

Table 1

[0057] The components shown in Table 1 were uniformly mixed with a horizontal mixer (e.g., Loedige type mixer), molded at a temperature of 160 °C under a pressure of 20 tons for 3 minutes with a mold, and then cured at a temperature in the range of 150 °C to 400 °C for 10 minutes to 10 hours, to produce two types of friction materials according to the present invention indicated as "Bi-carbon 2%" and "Bi-carbon 4%", and one type of comparative friction material indicated as "Mono-carbon" used in subsequent comparative tests. Each block of the thus obtained friction material was integrated with the same metal support made of a flat steel plate (back plate) to form a vehicle brake pad.

Example

[0058] Wear, particle emission and efficiency tests Each brake pad manufactured in the form described in Example 1 was mounted on a brake caliper with a hydraulic actuator and then connected to a dynamometer and subjected to the following tests.

[0059] Specifications of the dynamometer used: - DC motor 191 kW, - Constant torque 2000 Nm, maximum 991 rpm, - Constant power 911 - 200 rpm, - Drag torque 2000 Nm, - Maximum pressure: 200 bar, - Maximum speed: 2600 rpm, - Mechanical inertia maximum 50 kg / m 2 , - Brake suction / ventilation flow rate 1200 - 2000 m 3 / h, - 4 input analog channels for constant temperature measurement, - Friction level refinement Wear test Test results regarding the brake pad containing the friction material composition of the present invention named "Bi-carbon 2%", and the brake pad containing the comparative friction material composition named "Mono-carbon" are shown in FIG. 1.

[0060] Specifically, the results depicted at the top of Figure 1 refer to the thickness reduction (in mm) of the inner and outer brake pads resulting from 1000 braking applications at 100°C, 200 braking applications at 200°C, 500 braking applications at 350°C, and 400 and 1000 braking applications at 100°C (repetition of the first cycle). At the same time, the corresponding friction coefficient (μ) is shown.

[0061] When comparing the brake pad wear for both test sets, it can be seen that the "bi-carbon 2%" brake pads according to the present invention exhibit the lowest thickness reduction. This means that the "bi-carbon 2%" brake pads have a longer lifespan and thus result in less material reduction (and therefore less environmental pollution) and maintenance costs compared to the comparative "mono-carbon" brake pads.

[0062] Notably, the friction coefficient of the "bi-carbon 2%" brake pads is also more stable than that of the "mono-carbon" brake pads.

[0063] Confirmation of the lower wear of the "bi-carbon 2%" brake pads is obtained with respect to the amount of mass loss (in grams) depicted at the bottom of Figure 1. In fact, the "bi-carbon 2%" brake pads have the lowest mass loss compared to the "mono-carbon" brake pads.

[0064] D less than 10 μm 50 Having, the presence of the second carbonaceous material contained within the "bi-carbon 2%" brake pads of the present invention acts on the heat generated during braking applications and dissipates it instead of accumulating it within the brake pads to break the binder.

[0065] Particle emission test The mass reduced in the wear test was recovered by suction on the test bench and then analyzed with respect to the number of particles, the amount of particulate matter (PM), and the dispersion ratio (described by the number of particles with respect to the amount of PM). The first quantity was obtained using a Dekati (registered trademark) high-resolution ELPI (registered trademark) instrument. Thereby, a real-time particle number size distribution of up to 500 size classes in the range of 6 nm to 10 μm is obtained.

[0066] PM and PN are measured during the AKM test.

[0067] The amount of PM (unit: g) was obtained by using a Dekati® eFilter® device that combines a standard gravimetric filter holder and high-sensitivity real-time PM detection.

[0068] Report the particle emission test results in Table 2.

[0069]

Table 2

[0070] Notably, the reduced mass by the "bi-carbon 2%" brake pad contains a smaller number of harmful particles in the range from nanoscale-sized ultrafine particles to coarse particles with a diameter of 10 μm than those emitted by the comparative "mono-carbon" brake pad. At the same time, the amount of particulate matter emitted by the "bi-carbon 2%" brake pad during the brake test is less than that emitted by the comparative "mono-carbon" brake pad.

[0071] Efficiency test The efficiency test is carried out according to the AK-Master standard.

[0072] Figures 2 and 3 show typical reports of the results obtained from the AK-Master standard, presenting different steps and cycles for the "mono-carbon" (Figure 2) and "bi-carbon 2%" (Figure 3) brake pads, and showing important variables such as friction (μ), pressure, and temperature.

[0073] With particular reference to the FADE section in the 9th step of the AK-Master standard test, it consists of 15 consecutive brake applications at a fixed deceleration, initial, and final speeds. Specifically, - Deceleration constant: 4 m / second 2 - Initial speed: 100 km / h - Final speed: 5 km / h - End of the test minimum temperature to be reached: 550 °C Regarding the comparative "mono-carbon" brake pad (Figure 2) and the inventive "bi-carbon 2%" brake pad (Figure 3), the enclosed part of the graph related to the FADE section is particularly important. The "bi-carbon 2%" brake pad according to the invention exhibits overall nominal friction levels comparable to those of the comparative "mono-carbon" brake pad, but the Fading performance of the "bi-carbon 2%" brake pad is slightly more stable than that of the comparative "mono-carbon" brake pad throughout the entire fade section.

Example

[0074] Laboratory-scale tribometer evaluation of creep groan noise The tribometer used to test creep groan noise is equipped with an artificial climate chamber for humidity evaluation and has the following specifications.

[0075] - Rotor speed: 0.1 - 5000 rpm - Torque: 0.01 - 5 Nm - Maximum load force: 2000 N The tribometer samples are made of a 10×10 mm friction material under investigation and a cast iron disk. For each friction material, a new disk was used and measured with the tribometer.

[0076] Figure 4 shows the variation of the friction coefficient of three friction materials ("mono-carbon", "bi-carbon 2%" and "bi-carbon 4%") as a function of time under several relative humidities (20% RH, 40% RH, 60% RH, 80% RH and 90%) with a vertical force of 200 N and a disk rotation of 2 rpm. The tests were repeated three times each (Brake 1, Brake 2 and Brake 3).

[0077] From the non-resonant vibration of the friction coefficient that defines the so-called "discontinuous creep groan" band (i.e., the band of the graph surrounded by a rectangle), the number of stick-slip phenomena per test and the stick-slip amplitude can be calculated. Specifically, the stick-slip amplitude is calculated as the average of the difference between the static friction coefficient and the dynamic friction coefficient.

[0078] Figure 4 shows the amplitude stick-slip and the number of stick-slips as a function of humidity for three types of friction materials. The amplitude stick-slip and the number of stick-slips are due to the sum of three tests (Brake 1, Brake 2, and Brake 3), and the error is the standard deviation of the three.

[0079] Notably, the "bi-carbon 4%" friction material, followed by the "bi-carbon 2%" friction material, reduces the occurrence of stick-slip phenomena with respect to amplitude and frequency for the comparative "mono-carbon" brake pad.

[0080] Therefore, it is clear that the "bi-carbon 4%" and "bi-carbon 2%" brake pads according to the present invention have a creep groan noise tendency that is dramatically lower than that of the comparative "mono-carbon" brake pad.

Example

[0081] Porosity of the friction material according to the present invention Mercury porosimetry was applied to characterize the porosity of the three friction materials under investigation in terms of open porosity, pore size, and their distribution.

[0082] The results are shown in Figure 5 and summarized in Table 3.

[0083]

Table 3

[0084] Notably, the porosity of the "bi-carbon 4%" friction material according to the present invention, followed by the "bi-carbon 2%" friction material, is lower than the porosity of the comparative "mono-carbon" friction material.

[0085] The same trend applies to the average pore size. In fact, the "bi-carbon 4%" friction material according to the present invention has the lowest average pore size, followed by the "bi-carbon 2%" friction material.

[0086] Therefore, it is clear that the ultrafine second carbonaceous material that exists only in the friction material according to the present invention surprisingly contributes to reducing the porosity of the friction material.

[0087] Due to the lower porosity, the friction material according to the present invention is not very sensitive to relative humidity, and thus the stick-slip phenomenon is not very affected by humidity.

[0088] At the same time, the lower average pore size of the friction material according to the present invention improves the adhesion between the friction material surface and the disk surface, and thus further reduces the occurrence of stick-slip behavior.

[0089] From the above examples and disclosures, it is clear that the friction material composition prepared according to the present disclosure has a low creep groan noise tendency due to a reduced stick-slip phenomenon, low particle emission directly related to reduced material wear, and improved friction stability compared to the comparative composition.

[0090] All the objects of the present disclosure are therefore satisfied.

[0091] Term Although several braking devices, apparatuses, and methods have been disclosed in the context of several exemplary embodiments, those skilled in the art will understand that the scope of the present disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and / or the use of embodiments and some of their modifications and equivalent forms such as brakes, as shown for braking devices based on brake drums. The use with any structure is clearly within the scope of the present invention. The various features and aspects of the disclosed embodiments can be combined with each other or substituted in various ways to form various assemblies. The scope of the present disclosure should not be limited by the specific disclosed embodiments described herein.

[0092] Conditional language such as "can", "could", "might", or "may" generally intends to convey that some embodiments include or do not include some features, elements, and / or steps, unless specifically stated otherwise or understood otherwise within the context in which it is used. Thus, such conditional language generally does not imply that the features, elements, and / or steps are required in any one or more embodiments.

[0093] Unless otherwise stated, the terms "about", "approximately", and "substantially" herein still represent an amount close to the recited amount that performs the desired function or achieves the desired result. For example, in some embodiments, the terms "about", "approximately", and "substantially" refer to an amount within 10% of the recited amount, as the context may indicate. Similarly, the term "generally" herein represents a value, amount, or characteristic that mainly includes or tends towards a specific value, amount, or characteristic.

[0094] The present disclosure expressly contemplates that the various features and aspects of the disclosed embodiments can be combined with or substituted for each other. Accordingly, the scope of the present disclosure should not be limited by the above-described specific disclosed embodiments, but should be determined only by a fair reading of the following claims and the full scope of equivalents thereof.

Claims

1. An asbestos-free friction material composition comprising at least one fibrous material selected from the group consisting of at least one filler, inorganic fiber, organic fiber, metal fiber, and any combination thereof, at least one binder, at least one lubricant, at least one or more abrasives, and at least a first and at least a second carbonaceous material, in combination - The first carbonaceous material has a particle size distribution having a D higher than 10 μm 50 and having such a particle size distribution that - the second carbonaceous material has a particle size distribution having a D of less than 10 μm 50 such that it has a particle size distribution having a D of less than 10 μm characterized by an asbestos-free friction material composition.

2. D higher than 10 μm 50 The at least first carbonaceous material having 50 is present in an amount in the range of 2 to 6% by weight in the composition, calculated based on the total weight of the friction material composition, The asbestos-free friction material composition according to claim 1, characterized in that.

3. D less than 10 μm 50 The at least second carbonaceous material having 50 is present in an amount in the range of 1 to 4% by weight in the composition, calculated based on the total weight of the friction material composition, The asbestos-free friction material composition according to claim 1 or 2.

4. The asbestos-free friction material composition according to any one of claims 1 to 3, wherein the composition ratio of the first carbonaceous material to the second carbonaceous material is in the range of 1:1 to 6:1, preferably 2:1 to 3:

1.

5. D higher than 10 μm 50 The at least first carbonaceous material having 50 is selected from the group consisting of graphite, petroleum coke, dry petroleum coke, carbon black, and any mixture thereof, characterized in that the asbestos-free friction material composition according to any one of claims 1 to 4.

6. D higher than 10 μm 50 The asbestos-free friction material composition according to claim 5, wherein the at least first carbonaceous material having 50 is graphite.

7. D less than 10 μm 50 The at least second carbonaceous material having 50 is selected from fillers composed of carbon black, and the asbestos-free friction material composition according to any one of claims 1 to 6.

8. The asbestos-free friction material composition according to any one of claims 1 to 7, wherein the at least one fibrous material is an organic fiber selected from the group consisting of acrylic fiber, polyaramid fiber, aramid fiber, cellulose fiber, and any mixture thereof; and / or consists of inorganic or metal fiber.

9. The asbestos-free friction material composition according to any one of claims 1 to 8, wherein the at least one lubricant consists of a sulfide-based lubricant selected from the group consisting of metal sulfides of Sn, Zn, Fe, Mo, and mixtures thereof.

10. The asbestos-free friction material composition according to any one of claims 1 to 9, wherein the at least one or more abrasives has a Mohs hardness of less than 7 and comprises at least one soft abrasive selected from the group consisting of magnesia, chromite, magnetite, hematite, quartz, zinc oxide, tin oxide, barium sulfate, silicate, fluoride, and any mixture thereof.

11. The asbestos-free friction material composition according to any one of claims 1 to 10, wherein the at least one or more abrasives has a Mohs hardness of more than 7 and preferably comprises at least one hard abrasive having a rounded shape, and the hard abrasive is selected from the group consisting of zirconia, alumina, corundum, silicon carbide, tungsten carbide, zirconium carbide, zirconium silicate, boron nitride, and any mixture thereof.

12. The asbestos-free friction material composition according to claim 10 or 11, characterized in that the composition ratio of the soft abrasive and the hard abrasive is in the range of 1:1 to 4:

1.

13. The asbestos-free friction material composition according to any one of claims 1 to 12, characterized in that it does not contain copper and does not contain any copper alloy.

14. The asbestos-free friction material composition according to any one of claims 1 to 13, characterized in that it contains at least one metal selected from the group consisting of iron, steel, stainless steel, tin, zinc, and any alloy thereof, excluding copper and copper alloys, in the form of powder or fiber.

15. The asbestos-free friction material composition according to any one of claims 1 to 14, characterized in that the at least one filler is an inorganic filler selected from the group consisting of mineral fiber, glass fiber, rock wool, phyllosilicate (mica, vermiculite, talc), titanate, inorganic hydroxides of Ca, Mg, K, and any mixture thereof.

16. The asbestos-free friction material composition according to any one of claims 1 to 15, characterized in that it contains the following components in weight percentages calculated based on the total weight of the friction material composition. Abrasive, Mohs > 7, 15 - 35 Abrasive, Mohs < 7, 30 - 60 Resin, 6 - 10 Organic additive, 4 - 8 Organic fiber, 2 - 4 Lubricant, 2 - 8 First carbonaceous component, 2 - 6 Second carbonaceous component, 1 - 4

17. A friction element having a friction layer made of the friction material composition according to any one of claims 1 to 16.

18. The friction element according to claim 17, characterized in that it is a brake pad or a brake shoe.

19. A braking device including a member to be braked composed of a brake disk or a brake drum made of cast iron or steel, and at least one braking member composed of a brake pad or a brake shoe adapted to cooperate by friction with the member to be braked, wherein the braking member is intended to cooperate with the member to be braked and has a friction layer made of the friction material composition according to claims 1 - 16.

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