Friction material compositions 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 of related applications This patent application claims priority to Italian Patent Application No. 102022000013012, filed on 20 June 2022, the entire disclosure thereof is incorporated herein by reference.

[0002] The present invention relates in particular to friction material compositions suitable for manufacturing friction layers / blocks for friction elements, such as braking elements incorporated into vehicle braking systems.

[0003] The present invention also relates to related friction elements, such as brake pads or brake shoes for vehicles, made from this friction material composition and particularly suitable for electric vehicles, but not limited to them.

[0004] The friction material composition of the present invention belongs to the so-called NAO ("Non Asbestos Organic") type, and does not contain asbestos, and is not limited to copper. [Background technology]

[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 engines results in much quieter vehicles. This is leading to greater concern about noise generated by other automotive components, such as brake pads integrated into the braking system. As a result, brake pads used for electric vehicles require improved NVH (noise, vibration, and harshness) standards for driving comfort, while maintaining, and in some cases improving, braking performance in terms of friction stability, stiction, and corrosion resistance.

[0007] At the same time, future mobility trends will pay special attention to environmental and health hazards, aiming to reduce the release of particulate matter (PM10 and PM2.5) generated by braking systems, for example.

[0008] Regarding the operating noise of braking systems, it is known that this phenomenon has a complex and multi-factor origin, and that it depends on the vehicle's drive vibrations related to the unavoidable assembly gap between braking elements such as brake pads and shoes and their respective supports, as well as on the contact phenomenon that occurs between the sliding parts of the braking elements and the supports during the operation of the braking system.

[0009] This contact phenomenon is called "creep-grown" and produces an unpleasant high-intensity, low-frequency noise at very low vehicle speeds. It is a classic example of self-excited braking vibration caused by the so-called "stick-slip" effect, that is, by alternating episodes of sticking or adhesion and the subsequent slipping of the brake pads on the brake disc during the braking process, resulting in the coefficient of friction fluctuating continuously between static (stick phase) and dynamic (slip phase) values.

[0010] Modern vehicles, such as electric vehicles, have a strong need to eliminate, or at least reduce, low-frequency noise in a simple and especially economical way.

[0011] In fact, electric vehicles are far quieter than their internal combustion engine counterparts. In particular, unlike engine-driven vehicles, electric vehicles start up quietly due to their electric motors. Therefore, drivers and passengers are more likely to perceive the aforementioned noises and may find them unpleasant. Furthermore, these types of noises can affect the living environment of residents and could become a new source of noise pollution in cities.

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

[0013] EP0959262 discloses a disc brake pad capable of removing creepgrown using a composition comprising a fibrous base material excluding asbestos, a binder, and a friction modifier, wherein the binder is made up of all or part of a modified silicone resin, and in combination, the friction material composition contains 0.5 to 20 volume percent 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 volume percent of the total composition. The modified silicone resin is obtained by reacting oil or silicone rubber with a novolac-type phenolic resin. This results in an expensive material and makes manufacturing difficult.

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

[0015] However, such hybrid materials can result in compromised behavior in terms of braking performance and comfort, making them unsuitable or below optimal for many applications.

[0016] CN106015399 discloses a friction material for electric vehicle brake components. The friction material comprises 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, brake pads containing this friction material have not shown any improvement in reducing noise and particulate emission or improving frictional stability. [Overview of the project]

[0017] The object of the present invention is to develop a novel 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 frictional stability, and reduced particle emission. In particular, the subject matter disclosed herein is intended to provide an asbestos-free friction material composition that combines improved creep growth and frictional stability by reducing particle emission through reduced material wear and optimized heat dissipation, thereby reducing the tendency of friction blocks to adhere to the surface of their cooperating friction partners.

[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, particularly a brake pad or 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] Thus, the present disclosure relates to a friction material composition belonging to the friction material class called NAO (non-asbestos organic), which aims to obtain improved stick-slip behavior for the advantages of creep groan phenomenon and friction stability, as well as to reduce particle emission with respect to known NAO friction compositions.

[0022] In fact, 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 good effect on both creep groan noise and friction stability, and reduced particle emission. Specifically, a friction element including the disclosed friction material composition makes a 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 due to the advantage of friction element wear, and a second carbonaceous material that dissipates the heat generated during braking 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, and by reference to the accompanying drawings.

Brief Description of the Drawings

[0026] [Figure 1] This figure shows the results of wear tests conducted on friction elements made from two types of friction material compositions: one made from the friction material composition according to the present invention and the other from the comparative friction material composition. [Figure 2] This figure shows a report of the results obtained from the AK-Master test for friction elements made with comparative friction material compositions. [Figure 3] This figure shows a report of the results obtained from the AK-Master test for friction elements made with the friction material composition according to the present invention. [Figure 4] This figure shows the results of a creep-grown test for two friction elements made with friction material compositions according to two different embodiments of the present invention, and one friction element made with a comparative friction material composition. [Figure 5] This figure shows the porosity evaluation of two friction elements made from friction material compositions according to two different embodiments of the present invention, and one friction element made from a comparative friction material composition. [Modes for carrying out the invention]

[0027] In more detail, the disclosed asbestos-free friction material composition comprises at least one filler, at least one fibrous material, at least one binder, at least one lubricant, and D23 50 A first carbonaceous material having a particle size distribution such as and a D lower than 10 μm 50 The material comprises at least a second carbonaceous material having a particle size distribution such as, and at least one or more abrasives.

[0028] Here and below, "Particle size distribution D" 50 This corresponds to the particle diameter value at 50% of the cumulative distribution.

[0029] Preferably, D is greater 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 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, 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. [[ID=​​​​​Organic fibers can be included in the friction material composition of this disclosure, preferably as part of an organic binder, for the primary purpose of increasing the strength of the brake pads / shoes produced from the friction material composition of this disclosure under operating conditions.

[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 may be a sulfide-based lubricant selected from the group consisting of metal sulfides of Sn, Zn, Fe, Mo, and mixtures thereof, although this is not limited to the group.

[0040] Numerous 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, and talc), titanates, inorganic hydroxides of calcium, magnesium, and potassium, and any mixture 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 greater than 7.

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

[0043] The hard abrasive (i.e., having a Mohs hardness greater than 7) is preferably rounded in shape, but is not limited to it, and is preferably selected from the group consisting of zirconia, alumina, corundum, silicon carbide, tungsten carbide, zirconium carbide, zirconium silicate, boron nitride, and any mixture thereof.

[0044] The soft abrasive (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, silicate, fluoride, and any mixture thereof.

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

[0046] Hereafter, the expression “copper-free” shall be understood to mean the content of copper and / or copper alloys or other copper-containing materials at a rate of 0.5% by weight or less.

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

[0048] Furthermore, the disclosed friction material composition may include organic additives selected from the group consisting of polytetrafluoroethylene, friction dust, cashew dust, and 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 (% is by weight):

[0050] Abrasive: Mohs > 7, 15-35% Abrasive: Mohs < 7, 30-60% Resin 6-10% Organic additives 4-8% Organic fibers 2-4% Lubricant 2-8% Primary carbonaceous material: 2-6% Second carbonaceous material: 1-4% Finally, the present invention also relates to friction elements, particularly brake pads or shoes, that exhibit a layer of friction material made from the above-described friction material composition.

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

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

[0053] Three formulations were prepared and labeled as "Bi-Carbon 2%", "Bi-Carbon 4%", and "Mono-Carbon" according to Table 1 below. The components shown in Table 1 are expressed as weight percentages relative to the total weight of the composition.

[0054] The friction material compositions according to the present invention are indicated as "2% bicarbon" and "4% bicarbon," which differ in their content of the second carbonaceous material.

[0055] The comparative friction material composition indicated as "mono-carbon" has a composition in the standard NAO category and is substantially identical to the composition of the present invention, but with a D of less than 10 μm. 50 It does not contain a second carbonaceous material having the following characteristics.

[0056] [Table 1]

[0057] The components shown in Table 1 are uniformly mixed in a horizontal mixer (e.g., a Loedige mixer), molded in a mold under a pressure of 20 tons at a temperature of 160°C for 3 minutes, 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, labeled "2% bicarbonate" and "4% bicarbonate," as well as one type of comparative friction material labeled "monocarbon" for use in subsequent comparative tests. Each block of the thus obtained friction material is then integrated with the same metal support made of a flat steel plate (backing plate) to form a vehicle brake pad. [Examples]

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

[0059] Specifications of the dynamometer used: - DC motor 191kW, - Constant torque 2000Nm, maximum 991rpm, - Constant power 911~200rpm, - Drag torque 2000Nm, - Maximum pressure: 200 bar, - Maximum speed: 2600rpm, - Mechanical inertia: Maximum 50 kg / m 2 , - Brake suction / ventilation flow rate 1200~2000m 3 / time, - Four input analog channels for constant temperature measurement. - Friction level refinement Abrasion test Figure 1 shows the test results for brake pads containing the friction material composition of the present invention, named "B-Carbon 2%", and brake pads containing a comparative friction material composition named "Mono-Carbon".

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

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

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

[0063] The lower wear of the "bi-carbon 2%" brake pads is confirmed in terms of 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 The presence of a second carbonaceous material contained within the "B-Carbon 2%" brake pad of the present invention means that the heat generated during braking acts on the brake pad, causing it to dissipate rather than accumulate and destroy the binder.

[0065] Particle emission test The mass lost during the abrasion test was recovered by suction on the test stand, and then analyzed for particle number, particulate matter (PM) amount, and dispersion ratio (expressed as the number of particles relative to the amount of PM). The first quantity was obtained using a Dekati® high-resolution ELPI® instrument. This allows for real-time particle number size distributions up to the 500-size class in the range of 6 nm to 10 μm.

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

[0067] The amount of PM (in grams) was obtained using a Dekati® eFilter® instrument, which combines a standard gravimetric filter holder with high-sensitivity real-time PM detection.

[0068] The results of the particle emission test are reported in Table 2.

[0069] [Table 2]

[0070] Notably, the mass reduction achieved by the "B-Carbon 2%" brake pads included fewer harmful particles ranging from nanoscale ultrafine particles to coarse particles with a diameter of 10 μm than those released by the comparative "Mono-Carbon" brake pads. Simultaneously, the amount of particulate matter released by the "B-Carbon 2%" brake pads during the brake test was less than that released by the comparative "Mono-Carbon" brake pads.

[0071] Efficiency testing Efficiency testing will be conducted according to the AK-Master standard.

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

[0073] Referring specifically to the FADE section in the ninth step of the AK-Master standard test, it consists of fixed deceleration and 15 consecutive brake applications at initial and final speeds. Specifically, - Deceleration constant: 4m / sec 2 - Initial speed: 100km / h - Final speed: 5km / h - Minimum test temperature to be reached: 550℃ For the comparative "mono-carbon" brake pad (Figure 2) and the present invention's "bi-carbon 2%" brake pad (Figure 3), the enclosed portion of the graph related to the FADE section is particularly important. The "bi-carbon 2%" brake pad according to the present invention exhibits an overall nominal friction level comparable to 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 along the entire fade section. [Examples]

[0074] Evaluation of creepgrown noise using a laboratory-scale friction meter. The friction meter used to test creepgrown noise is equipped with an artificial climate chamber for humidity evaluation and has the following specifications:

[0075] - Rotor speed: 0.1~5000rpm - Torque: 0.01~5Nm - Maximum load force: 2000N The friction meter samples were prepared using 10 x 10 mm friction material and cast iron discs under investigation. For each friction material, a new disc was used and measurements were taken with the friction meter.

[0076] Figure 4 shows the variation in the coefficient of friction of three types of friction materials ("mono-carbon," "bi-carbon 2%," and "bi-carbon 4%") as a function of time under a vertical force of 200 N and a disk rotation of 2 rpm at several relative humidity levels (20% RH, 40% RH, 60% RH, 80% RH, and 90% RH). Each test was repeated three times (Brake 1, Brake 2, and Brake 3).

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

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

[0079] Notably, the "4% bicarbonate" friction material, followed by the "2% bicarbonate" friction material, reduces the occurrence of stick-slip phenomena in terms of amplitude and frequency compared to comparative "monocarbon" brake pads.

[0080] Therefore, it is clear that the "4% bicarbonate" and "2% bicarbonate" brake pads according to the present invention have a dramatically lower creep-grown noise tendency than the comparative "monocarbon" brake pads. [Examples]

[0081] Porosity of friction material according to the present invention Using mercury porosimetry, the porosity of the three friction materials under investigation was characterized 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 that of the comparative "mono-carbon" friction material.

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

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

[0087] Due to its lower porosity, the friction material according to the present invention is less sensitive to relative humidity, and therefore the stick-slip phenomenon is less adversely affected by humidity.

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

[0089] From the above examples and disclosures, it is clear that friction material compositions prepared in accordance with this disclosure have a tendency toward low creep-grown noise due to reduced stick-slip phenomena, lower particle emission directly related to reduced material wear, and improved friction stability compared to comparative compositions.

[0090] All the purposes of this disclosure are therefore fulfilled.

[0091] term While 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 this disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments, and / or the use of several modifications and equivalent forms thereof, such as brakes, is shown for brake drum-based braking devices. Any use involving any of these structures is clearly within the scope of the invention. Various features and aspects of the disclosed embodiments can be combined or substituted with one another to form various types of assemblies. The scope of this disclosure should not be limited by the specific embodiments disclosed herein.

[0092] Conditional language such as “can,” “could,” “might,” or “may” is generally intended to convey that some embodiments include or do not include certain features, elements, and / or steps, unless otherwise specifically stated or understood in the context in which they are used. Therefore, such conditional language does not generally imply that any feature, element, and / or step is required in any one or more embodiments.

[0093] Unless otherwise stated, the terms “about,” “about,” and “substantially” in this specification refer to an amount close to the stated amount that still performs the desired function or achieves the desired result. For example, in some embodiments, as the context may indicate, the terms “about,” “about,” and “substantially” refer to an amount that is within 10% or less of the stated amount. Similarly, the term “generally” in this specification refers to a value, quantity, or characteristic that primarily includes, or tends toward, a particular value, quantity, or characteristic.

[0094] This disclosure expressly intends that various features and aspects of the disclosed embodiments can be combined or substituted for one another. Therefore, the scope of this disclosure should not be limited by the specific disclosed embodiments described above, but should be determined solely by an impartial reading of the subsequent claims and the entire scope of equivalent forms. The invention described in the original claims of this application is listed below. [1] An asbestos-free friction material composition comprising at least one filler, at least a fibrous material selected from the group consisting of inorganic fibers, organic fibers, metal fibers, and any combination thereof, at least one binder, at least one lubricant, at least one or more abrasives, and at least first and at least second carbonaceous materials, In combination - The first carbonaceous material has a diameter greater than 10 μm. 50 Having a particle size distribution such as, - The second carbonaceous material has a diameter of less than 10 μm. 50 Having a particle size distribution such as An asbestos-free friction material composition characterized by the following. [2] D higher than 10 μm 50 The asbestos-free friction material composition according to [1], characterized in that the at least first carbonaceous material having is present in the composition in an amount in the range of 2 to 6% by weight, calculated with respect to the total weight of the friction material composition. [3] D less than 10 μm 50 The asbestos-free friction material composition according to [1] or [2], characterized in that the at least second carbonaceous material having is present in the composition in an amount ranging from 1 to 4% by weight, calculated relative to the total weight of the friction material composition. [4] The asbestos-free friction material composition according to any one of [1] to [3], characterized in that 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 asbestos-free friction material composition according to any one of [1] to [4], characterized in that the at least first carbonaceous material having is selected from the group consisting of graphite, petroleum coke, dry petroleum coke, carbon black, and any mixture thereof. [6] D higher than 10 μm 50 The asbestos-free friction material composition according to [5], characterized in that the at least first carbonaceous material having is graphite. [7] D less than 10 μm 50 The asbestos-free friction material composition according to any one of [1] to [6], characterized in that the at least second carbonaceous material having is selected from a filler made of carbon black. [8] The asbestos-free friction material composition according to any one of [1] to [7], characterized in that the at least one fibrous material consists of organic fibers selected from the group consisting of acrylic fibers, polyaramid fibers, aramid fibers, cellulose fibers, and any mixture thereof; and / or inorganic or metallic fibers. [9] The asbestos-free friction material composition according to any one of [1] to [8], characterized in that the at least one lubricant is 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 [1] to [9], characterized in that the at least one or more abrasives 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, having a Mohs hardness of less than 7.

[11] The asbestos-free friction material composition according to any one of [1] to

[10] , characterized in that the at least one or more abrasives comprises at least one hard abrasive having a Mohs hardness greater than 7 and preferably having a rounded shape, wherein 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

[10] or

[11] , characterized in that the composition ratio of the soft abrasive to the hard abrasive is in the range of 1:1 to 4:1.

[13] An asbestos-free friction material composition according to any one of [1] to

[12] , characterized in that it does not contain copper and does not contain any copper alloys.

[14] The asbestos-free friction material composition according to any one of [1] to

[13] , characterized by comprising at least one metal selected from the group consisting of iron, steel, stainless steel, tin, zinc, and all alloys thereof, excluding copper and copper alloys, in the form of powder or fibers.

[15] The asbestos-free friction material composition according to any one of [1] to

[14] , characterized in that the at least one filler is an inorganic filler selected from the group consisting of mineral fibers, glass fibers, 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 [1] to

[15] , characterized in that it contains the following components in a weight percentage 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 additives 4-8 Organic fibers 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 a friction material composition described in any one of the items [1] to

[16] .

[18] The friction element according to

[17] , characterized in that it is a brake pad or brake shoe.

[19] A braking device comprising a member to be braked, comprising a brake disc or brake drum made of cast iron or steel, and at least one braking member comprising a brake pad or brake shoe adapted to cooperate with the member to be braked by friction, wherein the braking member has a friction layer made of a friction material composition described in [1] to

[16] , which is intended to cooperate with the member to be braked.

Claims

1. An asbestos-free friction material composition comprising at least one filler, at least a fibrous material selected from the group consisting of inorganic fibers, organic fibers, metal fibers, and any combination thereof, at least one binder, at least one lubricant, at least one or more abrasives, and at least first and at least second carbonaceous materials, In combination - The first carbonaceous material has a particle size distribution such that it has a D50 greater than 10 μm, - The second carbonaceous material has a particle size distribution such that it has a D50 of less than 10 μm. The at least second carbonaceous material having a D50 of less than 10 μm is selected from a filler made of carbon black. An asbestos-free friction material composition characterized by the following.

2. The asbestos-free friction material composition according to claim 1, characterized in that at least the first carbonaceous material having a D50 greater than 10 μm is present in the composition in an amount in the range of 2 to 6% by weight, calculated relative to the total weight of the friction material composition.

3. The asbestos-free friction material composition according to claim 1, characterized in that at least the second carbonaceous material having a D50 of less than 10 μm is present in the composition in an amount in the range of 1 to 4% by weight, calculated with respect to the total weight of the friction material composition.

4. The asbestos-free friction material composition according to claim 1, characterized in that the composition ratio of the first carbonaceous material to the second carbonaceous material is in the range of 1:1 to 6:

1.

5. The asbestos-free friction material composition according to claim 1, characterized in that the at least first carbonaceous material having a D50 greater than 10 μm is selected from the group consisting of graphite, petroleum coke, dry petroleum coke, carbon black, and any mixture thereof.

6. The asbestos-free friction material composition according to claim 5, characterized in that the at least first carbonaceous material having a D50 greater than 10 μm is graphite.

7. The asbestos-free friction material composition according to claim 1, characterized in that the at least one fibrous material comprises an organic fiber selected from the group consisting of acrylic fibers, polyaramid fibers, aramid fibers, cellulose fibers, and any mixture thereof; and / or an inorganic or metallic fiber.

8. The asbestos-free friction material composition according to claim 1, characterized in that the at least one lubricant comprises a sulfide-based lubricant selected from the group consisting of metal sulfides of Sn, Zn, Fe, and Mo, and mixtures thereof.

9. The asbestos-free friction material composition according to claim 1, characterized in that the at least one or more abrasives include 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, having a Mohs hardness of less than 7.

10. The asbestos-free friction material composition according to claim 9, characterized in that the at least one or more abrasives include at least one hard abrasive having a Mohs hardness of 7 or greater, 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.

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

1.

12. The asbestos-free friction material composition according to claim 1, characterized in that it does not contain copper and does not contain any copper alloys.

13. The asbestos-free friction material composition according to claim 1, characterized by containing at least one metal selected from the group consisting of iron, steel, stainless steel, tin, zinc, and all alloys thereof, excluding copper and copper alloys, in the form of powder or fibers.

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

15. The asbestos-free friction material composition according to claim 1, characterized in that it contains the following components in a weight percentage calculated based on the total weight of the friction material composition. Abrasive: Mohs > 7, 15-35 Abrasives Mohs <7 30-60 Resin 6-10 Organic additives 4-8 Organic fibers 2-4 Lubricant 2-8 First carbonaceous component 2-6 Second carbonaceous component 1-4

16. A friction element having a friction layer made of the friction material composition described in any one of claims 1 to 15.

17. The friction element according to claim 16, characterized in that it is a brake pad or a brake shoe.

18. A braking device comprising a member to be braked, comprising a brake disc or brake drum made of cast iron or steel, and at least one braking member comprising a brake pad or brake shoe adapted to cooperate with the member to be braked by friction, wherein the braking member has a friction layer made of a friction material composition according to any one of claims 1 to 15, which is intended to cooperate with the member to be braked.

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