Friction material composition and associated friction element

Abstract

The invention relates to an asbestos-free friction material composition and an associated brake pad for a vehicle. The invention relates to a friction material comprising inorganic and / or organic and / or metal fibres, at least one binder, at least one friction modifier or lubricant, at least one filler or abrasive, and at least one soluble salt of barium and / or calcium and / or aluminum and / or silver in a percentage of between 0.5% and 10% by weight. In them, barium carbonate, calcium hydroxide, aluminum triacetate and silver acetate are preferred.

Description

[0001] Cross - reference to related applications

[0002] This patent application claims the priority of Italian Patent Application No. 102022000023835, filed on November 18, 2022, the entire disclosure of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a friction material composition, which is particularly suitable for manufacturing friction layers / friction blocks for friction elements, such as brake elements to be incorporated into, for example, vehicle braking systems.

[0004] The present invention also relates to associated friction elements made of such friction material composition, such as brake pads or brake shoes for vehicles.

[0005] The friction material composition of the present invention is asbestos - free, belongs to the so - called NAO ("Non - Asbestos Organic") type, and is particularly but not exclusively copper - free. Background art

[0006] Friction materials that are asbestos - free and intended for use on vehicle brake pads / brake shoes include five categories of components: fibrous materials including inorganic fibers and / or organic fibers and / or metal fibers, binders, fillers, one or more lubricants or friction modifiers, and one or more abrasives.

[0007] The fibrous materials substituting asbestos can be either inorganic fibers such as rock fiber or rock wool, wollastonite, glass fiber, or organic fibers such as aramid fibers and carbon fibers, or can be metal fibers such as steel fibers. The binder is usually a thermosetting polymer, such as, for example, a thermosetting polymer based on phenolic resin. Various materials such as barite (barium sulfate), calcium carbonate, talc, magnesium oxide, vermiculite are used as fillers to impart sufficient strength to the friction material; usually zirconium silicate, zirconia, alumina, silicon carbide, mica can be used as abrasives; metal sulfides such as molybdenum disulfide, iron sulfide, copper, tin, graphite and / or coke can be used as friction modifiers. Other categories of materials can also be added in smaller percentages, such as, for example, rubber in the form of powder or granules, "friction powders" (well - known materials readily available on the market), other organic materials.

[0008] However, vehicle brake pads / brake shoes produced with friction materials as described above are not without drawbacks.

[0009] In particular, when in contact with water, they can release ions into the environment, which is common for vehicle components assembled on or near the wheels. In particular, when water / moisture is present, known friction materials can release free ions in the form of sulfate, sulfite, oxalate, and phosphate ions.

[0010] This release can be a major drawback. First, the release of this type of ion into the environment can cause pollution. Second, since these ions are released near the brake disc, they can be a major cause of corrosion of the disc material, which is usually made of steel or cast iron.

[0011] For example, soluble sulfate ions released from the brake lining can promote steel / cast iron corrosion because when in contact with ferrous materials, they can cause the formation of so-called "green rust" [Fe4 2+ Fe2 3+ (HO - ) 12 2+ *[SO4 2- ·2H2O] 2- The green rust compound is considered to be an intermediate in the formation of iron oxide corrosion to form iron oxyhydroxide (III) (the so-called "brown rust").

[0012] So far, there has been no known solution to eliminate the release of ions such as sulfate from the brake lining / brake shoe, unless the source of those ions is eliminated from the friction material formulation. For example, the release of sulfate ions can be eliminated by eliminating the use of sulfides in the friction material formulation. However, this solution is impractical because the elimination of sulfides will have a great negative impact on the tribological properties of the final product, such as the friction material block present on the brake lining / brake shoe.

[0013] US2015192182A1 discloses the use of modified activated carbon in the brake lining formulation, which should be able to adsorb sulfate ions in solution before the sulfate ions can chemically erode the ferrous material of the brake disc. However, since both the activated carbon used as the adsorbent and the phenolic resin used as the binder have to be chemically modified to become hydrophilic, this solution has proven to be not completely reliable and is complex and expensive to implement. Summary of the Invention

[0014] 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.

[0015] ​In particular, the presently disclosed subject matter is intended to provide an asbestos-free friction material composition which, while maintaining all common original components for having predictable braking performance, is substantially insensitive to the phenomenon of ion release when exposed to water or moisture.

[0016] Accordingly, another object of the present invention is to provide an associated braking element, in particular a brake lining or a brake shoe, which comprises such a friction material composition capable of avoiding or at least strongly reducing surface corrosion of a mating friction pair, such as a brake disc or a brake drum, during use.

[0017] Accordingly, the present invention relates to a friction material composition and an associated braking element as defined in the appended claims.

[0018] According to the present disclosure, for any friction material composition known to be subject to the phenomenon of ion release, an amount of a specifically selected water-soluble metal compound is added to the friction material standard composition itself to obtain a modified friction material composition which, when molded in a friction material block assembled to form a braking element, such as a brake lining or a brake shoe, retains all the chemical and physical properties of the corresponding standard composition, thus ensuring fully predictable braking performance, while avoiding or strongly reducing surface corrosion of its mating friction pair, since the added metal compound is chosen such that it chemically reacts with the anions released by / from one or more of the original components present in the composition, thereby directly forming a water-insoluble salt of such metal and such ions within / on the friction material block. In this way, the released ions cannot reach and erode the ferrous material of the mating friction pair.

[0019] Accordingly, the present disclosure relates to an asbestos-free friction material composition belonging to the category of friction materials known as NAO (non-asbestos organic), the asbestos-free friction material composition comprising, as its original components, at least one fibrous material, at least one filler, at least one binder, at least one lubricant and / or other friction modifiers (preferably more than one lubricant and / or friction modifier) and at least one or more abrasives, wherein the asbestos-free friction material composition further comprises at least one water-soluble metal compound capable of reacting (e.g., by means of an exchange reaction) with anions present in / released by one or more of the aforementioned original components, thereby forming a water-insoluble salt of such metal and such ions therewith.

[0020] Relative to a corresponding known NAO friction composition (i.e., having substantially the same amounts and the same component materials for all the above-mentioned generally known classes of materials), the friction material composition of the present invention thus further comprises a specific amount of a water-soluble metal compound selected from those water-soluble metal compounds whose metals are capable of forming water-insoluble salts with ions that can be released from the friction material composition itself / ions in the friction material composition itself in the presence of water and / or moisture.

[0021] In other words, the present invention consists in adding to (any) standard friction material composition one or more metal salts and / or metal hydroxides that are readily soluble in water and that are simultaneously capable of forming water-insoluble salts with sulfate ions, sulfite ions, oxalate ions, and phosphate ions that are normally present in the friction material composition and / or that may be released therefrom.

[0022] Herein and hereinafter, "readily soluble" in water means having a solubility product constant higher than 1×10 -9 as defined by Clark, Roy W., Bonicamp, Judith M. in the Journal of Chemical Education 2000 77 1558 "Solubility and Solubility Products.", i.e., a compound of K ps and, in particular, this solubility product constant must be higher than the solubility of the sulfate ion in the same solution and for the same cation.

[0023] According to a preferred embodiment, the asbestos-free friction material composition of the present disclosure comprises at least one water-soluble compound of barium and / or calcium and / or aluminum and / or silver, such as barium carbonate, calcium hydroxide, aluminum triacetate, and silver acetate.

[0024] In fact, it has surprisingly been found that such metal compounds have the ability to act as scavengers for any different ions that may be released from the friction material.

[0025] According to a most preferred embodiment, barium carbonate is used as an additional component added to any friction material composition known per se in the asbestos-free friction material composition according to the present invention, since the barium contained in BaCO3 can form insoluble salts with any one of sulfate, oxalate, and phosphate, and precipitate as BaSO4, Ba3(PO4)2, BaC2O4, and BaCrO4. In addition, barium carbonate is a safe material that is readily available and inexpensive.

[0026] In summary, the present disclosure also relates to a braking element for a vehicle, the braking element comprising a metallic support and a friction material layer or friction material block carried by the support, the friction material block being made of the asbestos-free friction material composition of the invention as disclosed above, preferably already molded on the first face of the support; and wherein the friction material block is configured to retain, in use, any ions that may be released by one or more of the component materials of the friction material composition in the form of water-insoluble metal salts captured / chelated within or on the friction material of the friction material block, such that it is not possible for these ions to reach the friction pair of the friction material block, e.g., the brake disc, where the arrival of ions at the friction pair of the friction material block may cause chemical etching of its ferrous material.

[0027] The braking element according to the present disclosure is a brake pad or brake shoe for a vehicle.

[0028] The present disclosure also extends to a braking system comprising a member to be braked constituted by a brake disc or brake drum made of cast iron or steel and at least one braking member constituted by a brake pad or brake shoe, the braking member being adapted to cooperate by friction with the member to be braked, wherein the braking member has a friction layer made of the friction material composition of the invention as disclosed above and intended to cooperate with the member to be braked. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In view of the disclosure provided below, including practical and comparative non-limiting examples that disclose its different possible and non-limiting embodiments and with reference to the drawings, further features and advantages of the disclosed subject matter, whether explicitly mentioned or not, will become apparent, in the drawings:

[0030] - Figure 1 Schematically shows the results given in the first, most significant section of the AK-Master test carried out on a brake pad produced with a test friction material according to the invention;

[0031] - Figure 2 Schematically shows Figure 1 the same first section of the same AK-Master test, but the test is carried out on a brake pad produced with a reference friction material;

[0032] - Figure 3 Schematically shows Figure 1 the results given in the fade section of the same AK-Master test, which results are obtained by using a brake pad produced with a test friction material according to the invention; and

[0033] - Figure 4 Schematically shows Figure 2Results given in the decay section of the same AK-Master test, which were obtained with brake pads produced with a reference friction material. Detailed Description

[0034] More specifically, the disclosed asbestos-free friction material composition includes, according to any known formulation of friction material compositions available on the market or commonly used to implement brake elements such as brake pads or brake shoes, at least one filler, at least one fibrous material, at least one binder, at least one lubricant / friction modifier, and at least one or more abrasives.

[0035] According to one aspect of the present invention, in addition to the standard components mentioned above, the disclosed friction material composition further includes at least one water-soluble metal compound, which is capable of chemically reacting with any ion (anion) among the ions (anions) that may be released / releasable by any other of the above-mentioned standard raw material components present in the friction material composition itself in the presence of water and / or moisture, thereby forming a water-insoluble metal salt with such an ion, and thus it may remain trapped / chelated within the friction material block formed by the currently disclosed friction material composition during use and cannot reach the friction pair (such as a brake disc) of the friction material block, and reaching the friction pair of the friction material block may cause chemical etching of its ferrous material.

[0036] In particular, the above-mentioned water-soluble metal compounds to be added to any standard friction material composition to avoid / strongly limit the ion release phenomenon include one or more metal salts and / or metal hydroxides that are readily soluble in water and are simultaneously capable of forming water-insoluble salts with sulfate ions, sulfite ions, oxalate ions, and phosphate ions that are commonly present in the friction material composition and / or may be released therefrom.

[0037] Preferably, in addition to the other standard components of the friction material, the disclosed asbestos-free friction material composition further includes at least one water-soluble compound of barium and / or calcium and / or aluminum and / or silver, such as barium carbonate, calcium hydroxide, aluminum triacetate, and silver acetate.

[0038] More preferably, in addition to the other standard components of the friction material commonly used, the disclosed asbestos-free friction material composition further includes a specific amount of barium carbonate.

[0039] At least one water-soluble metal compound that can chemically react with any ion (anion) that may be released / releasable from any standard raw material component among the standard raw material components present in the friction material composition in the presence of water and / or moisture, thereby forming a water-insoluble metal salt with these ions, is present in the friction material composition of the present invention in an amount ranging from 0.5% by weight to 10% by weight, inclusive of the extreme values of this range, based on the total weight of the friction material composition.

[0040] Preferably, in addition to the standard raw material components of the NAO friction material, the friction material composition of the present invention further comprises 0.5% to 5% by weight of barium carbonate BaCO3.

[0041] Most preferably, in addition to the standard raw material components of the NAO friction material, the friction material composition according to the present invention further comprises approximately 1% by weight of barium carbonate BaCO3.

[0042] In order to obtain a favorable chelating effect on the ions that may be released in the friction material composition, it is important that the above-mentioned one or more metal salts and / or metal hydroxides that are readily soluble in water and at the same time capable of forming water-insoluble salts with sulfate ions, sulfite ions, oxalate ions, and phosphate ions have a specific particle size and corresponding specific surface area to promote the chemical reaction of chelation of the released ions.

[0043] Therefore, in a preferred embodiment, the friction material of the present invention may contain barium carbonate in an amount ranging from 0.5% to 1% by weight, and the barium carbonate has a particle size distribution between 5 μm and 80 μm (micrometers).

[0044] In any case, the above-mentioned one or more metal salts and / or metal hydroxides that are readily soluble in water and at the same time capable of forming water-insoluble salts with sulfate ions, sulfite ions, oxalate ions, and phosphate ions included in the friction material composition of the present invention must have a particle size below 100 μm (micrometers).

[0045] In fact, experimental tests have demonstrated that a particle size distribution outside the above range and specifically above 100 micrometers has a negative impact on the solubility of the metal salts and / or metal hydroxides, thus making them less effective.

[0046] In addition to the above-mentioned one or more metal salts and / or metal hydroxides that are readily soluble in water and at the same time capable of forming water-insoluble salts with sulfate ions, sulfite ions, oxalate ions, and phosphate ions, the raw material components of the friction material according to the present invention can be any of the raw material components that are already known in the art and commonly used in friction materials.

[0047] In particular, at least one fiber material may be selected from the group consisting of: inorganic fibers, organic fibers, metal fibers, and any combination thereof.

[0048] Preferably, at least one fiber material comprises organic fibers selected from the group consisting of: polyacrylic fibers, polyaramid fibers, aromatic polyamide fibers, cellulose fibers, and mixtures thereof.

[0049] The organic fibers may preferably but non-exclusively be included as part of the organic binder in the friction material composition of the present disclosure, as they may have the primary purpose of enhancing its strength under the operating conditions of the brake pads / shoes that can be manufactured from the friction material composition of the present disclosure.

[0050] At least one binder is preferably an organic binder and may be selected from the group consisting of: phenolic resins, epoxy resins, silicone resins, modified phenolic resins, melamine resins, polyamide resins, and mixtures thereof.

[0051] At least one lubricant or friction modifier may preferably but non-exclusively include sulfide-based lubricants selected from the group consisting of: metal sulfides of Sn, Zn, Fe, Mo, and mixtures thereof.

[0052] Many materials can be used as organic fillers or inorganic fillers. Preferably, at least one filler is an inorganic filler selected from the group consisting of: mineral fibers, glass fibers, rock wool, layered silicates (such as mica, vermiculite, talc, etc.), titanates, inorganic hydroxides of calcium, magnesium, potassium, and any mixture thereof.

[0053] At least one or more abrasives include at least one soft / gentle abrasive having a Mohs hardness of less than 7 and included between 1 and 3, at least one medium abrasive having a Mohs hardness of less than 7 and included between 4 and 6, and at least one hard / strong abrasive having a Mohs hardness of 7 or higher and typically included between 7 and 9.

[0054] The hard abrasives (i.e., having a Mohs hardness higher than 7) preferably but non-exclusively have a round shape and, in any case, are preferably but non-exclusively selected from the group consisting of: silicon carbide, zircon sand, zirconium silicate, zirconia, corundum, alumina, mullite, tungsten carbide, zirconium carbide, boron nitride, and any mixture thereof.

[0055] The medium abrasives (i.e., having a Mohs hardness included between 4 and 6) are preferably but non-exclusively selected from the group consisting of: barium sulfate, magnesium oxide, calcium fluoride, calcium carbonate, wollastonite, calcium silicate, iron oxide, silica, chromite, zinc oxide, and any mixture thereof.

[0056] Soft / gentle abrasives (i.e., having a Mohs hardness between 1 and 3) can preferably but not exclusively be selected from the group consisting of talc, calcium hydroxide, potassium titanate, mica, zinc oxide, tin oxide, silicates, fluorides, and any mixtures thereof.

[0057] According to a preferred embodiment of the present invention, the disclosed friction composition can include at least one metal or mixture of metals, but does not contain copper.

[0058] Herein and hereinafter, the expression "free of copper" should be understood to imply that the content of copper and / or copper-containing materials such as copper alloys is 0.5 wt% or less than 0.5 wt%.

[0059] When present in the disclosed friction material composition, the at least one metal or mixture of metals does not include copper and / or any copper alloys, but is selected from the group consisting of iron, steel, stainless steel, tin, zinc, and any alloys thereof in powder or fiber form.

[0060] In addition, the disclosed friction material composition can include organic additives selected from the group consisting of polytetrafluoroethylene, friction powders, urushiol powders, rubbers (i.e., NBR, silicone, SBR, etc.).

[0061] In addition, the disclosed friction material composition can include carbonaceous materials such as carbon, carbon black, coke, graphite, and mixtures thereof.

[0062] In another embodiment of the present invention, the disclosed average friction material composition is as follows (% by weight):

[0063]

[0064] The present invention finally also extends to a braking element, in particular a brake lining or brake shoe, which presents a friction material layer or friction material block made of the above-described friction material composition in any known and conventional manner, for example by molding.

[0065] The present invention also extends to a braking system, which includes a member to be braked constituted by a brake disc or brake drum made of cast iron or steel and at least one braking element constituted by a brake lining or brake shoe, the braking element being designed to cooperate with the member to be braked by means of friction, wherein the braking member presents a friction layer or friction block intended to cooperate with the member to be braked and made of the friction material composition as described above.

[0066] Exemplary ways of implementing the teachings of the present disclosure

[0067] Inventive examples and comparative examples are reported herein by way of illustration and are not intended to limit the present invention.

[0068] Example 1:

[0069] Multiple samples of friction material compounds of different chemical compositions and corresponding reference samples were prepared at the percentage ratios (by weight) reported in Table 1 and according to different known NAO standard compositions.

[0070] Table 1

[0071]

[0072] All reference samples had the same chemical composition as the corresponding test samples, except for the absence of barium carbonate.

[0073] The components shown in Table 1 were uniformly mixed in a horizontal mixer (such as a Loedige-type mixer), molded onto the same metal flat support in a mold, and then cured in a conventional manner to form brake pads that were identical except for the chemical composition of the friction material.

[0074] In particular, the brake pads were pressed at a temperature between 60 °C and 200 °C under a pressure of 150 kg / cm 2 to 1800 kg / cm 2 for a duration between 3 minutes and 10 minutes, or mixed in the mold and then pressed at a temperature between 130 °C and 180 °C under a pressure of 150 kg / cm 2 to 500 kg / cm 2 for a duration of 3 minutes to 10 minutes.

[0075] Each resulting pressed product was usually post-cured by heat treatment at 150 °C to 400 °C for a duration between 10 minutes and 10 hours, and then sprayed or powder-coated and dried in an oven to produce the final product.

[0076] Example 2: Sulfate release test

[0077] The brake pads obtained in Example 1 were each individually subjected to a sulfate release test.

[0078] The test procedure was as follows:

[0079] · Collect 4 g of friction material powder;

[0080] · Boil the collected friction material powder in 100 ml of water at 90 °C in a closed system for 8 h;

[0081] · Transfer the resulting solution to a 100 ml graduated cylinder and make up to 100 ml with distilled water;

[0082] · Perform a standard SO4 chromatographic analysis on the diluted solution thus obtained.

[0083] The measurement results of the sulfate release tests performed on all the prepared samples (test samples and reference samples) gave the average values reported in Table 2 below.

[0084] Table 2

[0085] sample <![CDATA[SO4 concentration (mg / L)]]> reference friction material 120 <![CDATA[Friction material containing BaCO3]]> 4.5

[0086] As can be immediately seen from Table 2, regardless of how the composition varies within the ranges illustrated in Table 1, the addition of barium carbonate within the ranges illustrated in Table 1 always results in a significant reduction (more than 20-fold) in the release of sulfate ions from the tested friction material blocks, which is apparently due to the chemical chelation of sulfate ions by the barium carbonate salt, which converts itself into a water-insoluble salt Ba(SO4), which remains trapped in the friction material blocks rather than being released into the aqueous solution.

[0087] After the release test, chemical analysis of the residual friction material powder showed that the barium of BaCO3 had formed insoluble salts with any of sulfate, oxalate, and phosphate, and had precipitated as BaSO4, Ba3(PO4)2, BaC2O4, and BaCrO4.

[0088] Example 3:

[0089] Operating as described in Examples 1 and 2, according to the average values of the content ranges illustrated in Table 1, many identical test friction material compositions and one reference composition were prepared by replacing barium carbonate with calcium hydroxide Ca(OH)2, aluminum triacetate Al(CH3COO)3, and silver acetate CH3COOAg in the test samples, respectively.

[0090] Then ion release tests were performed on the obtained test samples and reference samples, which were operated in the same manner as described in Example 2, but looking at different ions, namely (PO4)2 3- , SO4 2- and Cl - concentrations in the aqueous solution.

[0091] Again, the final results showed that the release amounts of those ions were reduced by more than 10-fold to 15-fold relative to the reference samples.

[0092] After the release test, chemical analysis of the residual friction material powder showed that:

[0093] · Calcium hydroxide Ca(OH)2 caused the precipitation of Ca3(PO4)2 and CaSO3.

[0094] · Aluminum triacetate Al(CH3COO)3 reduced the release of phosphate, forming insoluble AlPO4.

[0095] Silver acetate, CH3COOAg, causes precipitation of AgCl, Ag3PO4, and Ag2SO3.

[0096] In summary, all of the metal compounds tested were similar in their effectiveness in significantly reducing ion release in the standard NAO friction material composition.

[0097] Example 4:

[0098] Four friction material samples were prepared using the same average values of each component listed in Table 1 and referring to the ranges shown in Table 1, but using different contents (wt%) of barium carbonate, namely: 0.5%, 1%, 2%, and 5%, in order to examine the effect of barium concentration on the scavenging of sulfate ions.

[0099] After obtaining the sample brake pads as described in Example 1 and after performing the release test as described in Example 2, the SO4 concentration in the residual aqueous solution was measured. The results are reported in Table 3 below.

[0100] Table 3

[0101]

[0102]

[0103] As can be noted, at all concentrations of barium carbonate, the addition of BaCO3 in the NAO friction material composition always significantly reduces the amount of sulfate ions released.

[0104] Surprisingly, the lowest value of the released sulfate was obtained at a concentration of 1% BaCO3, which is not only sufficient to reduce the release of SO4 ions in solution, indicating that higher concentrations (e.g., 2%, 5%) are not required, but most importantly represents a particularly favorable critical concentration.

[0105] Finally, experimental tests conducted by the Applicant's technicians have shown that the particle size distribution of the metal salts / metal hydroxides used to compare ion release phenomena is also crucial. In particular, it has been demonstrated that particle sizes above 100 microns reduce the effectiveness of the chelation of the released ions.

[0106] Example 5: Brake Performance Test

[0107] Standard AK-Master brake tests were performed on brake pads produced according to Example 1, containing (test pads) or not containing (reference pads) 1 wt% of BaCO3. Figure 1 And Figure 2 The most important part of the graphical results is shown in.

[0108] As can be readily seen by the person skilled in the art,Figure 1 and Figure 2 shows the coefficient of friction μ (maximum, intermediate, and minimum) during an efficiency test consisting of three braking sections, with ten brakings per section, as follows:

[0109] First section: 50 km / h to 0 km / h

[0110] Second section: 100 km / h to 0 km / h

[0111] Third section: 120 km / h to 0 km / h

[0112] Looking at the attached drawings, it can be understood that the goals related to standard performance have been achieved: for both materials (test material and reference material), at a deceleration of 6 m / s 2 the coefficient of friction μ remains above 0.3, and the measured wear of the brake pads is less than 1.2 mm.

[0113] Now consider Figure 3 and Figure 4 which show the fade sections of the same AK-Master test for Figure 1 and Figure 2 The same AK-Master test's fade sections for Figure 3 and Figure 4 show the variation of the coefficient of friction μ (maximum, intermediate, and minimum) with increasing temperature (upper part of the attached drawings). The different temperatures are due to performing different braking cycles. Also in this case, the coefficient of friction remains within the target value of μ > 0.25.

[0114] As can be noticed, the behavior of the two tested brake pads (test brake pad and reference brake pad) is very similar and meets all standard market requirements in all sections. This shows that the presence of BaCO3 in the friction mixture does not affect the braking performance but is very effective in solving the ion release problem.

[0115] Therefore, all the objectives of the present disclosure have been achieved.

[0116] Certain terms

[0117] Although certain braking devices, systems, and methods have been disclosed in the context of certain exemplary embodiments, those skilled in the art will understand that the scope of the present disclosure extends to other alternative embodiments and / or uses of the embodiments and certain modifications and equivalents thereof beyond the specifically disclosed embodiments, such as a brake display for a brake drum-based braking system. The use related to any structure is clearly within the scope of the present invention. The various features and aspects of the disclosed embodiments can be combined with or substituted for each other to form different modes of the components. The scope of the present disclosure should not be limited by the specifically disclosed embodiments described herein.

[0118] Unless otherwise specifically stated or understood in the context as used, conditional language such as "can", "able to", "may", or "could" generally intends to convey that certain embodiments include or do not include certain features, elements, and / or steps. Thus, such conditional language generally does not intend to imply that the features, elements, and / or steps are necessary for one or more embodiments in any way.

[0119] Unless otherwise specified, as used herein, the terms "about", "approximately", and "substantially" represent a quantity that is close to the stated quantity that still performs the desired function or achieves the desired result. For example, in some embodiments, as the context may indicate, the terms "about", "approximately", and "substantially" may refer to a quantity within a range of less than or equal to 10% of the stated quantity. Similarly, as used herein, the term "generally" represents mainly including or tending towards a particular value, quantity, or characteristic value, quantity, or characteristic.

[0120] The present disclosure expressly contemplates that the various features and aspects of the disclosed embodiments can be combined with or substituted for one another. Accordingly, the scope of the present disclosure should not be limited by the above - specifically disclosed embodiments, but should be determined only by a reasonable interpretation of the appended claims and their full scope of equivalents.

Claims

1. An asbestos-free friction material composition, the asbestos-free friction material composition comprising at least one filler, at least one fiber material, at least one binder, at least one lubricant or friction modifier, and at least one or more abrasives as its raw material components, the at least one fiber material being selected from the group consisting of inorganic fibers, organic fibers, metal fibers, and any combination thereof, characterized in that, The asbestos-free friction material composition also combinatorially includes at least one water-soluble metal compound which is capable of chemically reacting with ions that may be released / capable of being released by any of the raw material components present in the friction material composition itself in the presence of water and / or moisture, so as to form a water-insoluble metal salt with such ions.

2. The asbestos-free friction material composition according to claim 1, characterized in that, The water-soluble metal compound consists of a metal salt and / or a metal hydroxide which is readily soluble in water and at the same time capable of forming a water-insoluble salt with sulfate ions, sulfite ions, oxalate ions and phosphate ions which are usually present in the friction material composition and / or may be released by the friction material composition.

3. The asbestos-free friction material composition according to claim 1 or 2, characterized in that, The metal in the at least one water-soluble metal compound is selected from the group consisting of barium, calcium, aluminum, silver, and any combination thereof.

4. The asbestos-free friction material composition according to any one of the preceding claims, characterized in that, The at least one water-soluble metal compound includes a salt or hydroxide selected from the group consisting of barium carbonate, calcium hydroxide, aluminum triacetate and silver acetate.

5. The asbestos-free friction material composition according to any one of the preceding claims, characterized in that, The asbestos-free friction material composition contains a specific amount of barium carbonate included between 0.5% by weight and 10% by weight.

6. The asbestos-free friction material composition according to any one of the preceding claims, characterized in that, The asbestos-free friction material composition includes barium carbonate having a particle size distribution between 5 μm and 80 μm (micrometers).

7. The asbestos-free friction material composition according to claim 5 or 6, characterized in that, The asbestos-free friction material composition includes 0.5% to 5% by weight of barium carbonate BaCO₃ having a particle size distribution between 5 μm and 80 μm (micrometers).

8. The asbestos-free friction material composition according to any one of the preceding claims, characterized in that, The at least one water-soluble metal compound is present in the friction material composition in an amount included between 0.5% by weight and 10% by weight - including the extreme values of this range - calculated based on the total weight of the friction material composition, and the at least one water-soluble metal compound has a particle size below 100 μm (micrometers).

9. The asbestos-free friction material composition according to any one of the preceding claims, characterized in that, The asbestos-free friction material composition includes approximately 1% by weight of barium carbonate BaCO₃ having a particle size between 5 micrometers and 80 micrometers.

10. A braking element for a vehicle, the braking element comprising a metal support and a friction material layer or friction material block carried by the support, the friction material block being made of the asbestos-free friction material composition according to any one of the preceding claims and preferably being molded on a first surface of the support; characterized in that, The friction material block is configured to, in use, retain any ions that may be released by one or more of the component materials of the friction material composition in the form of a water-insoluble metal salt trapped / chelated within or on the friction material of the friction material block, such that it is not possible for the ions to reach the friction pair of the friction material block, such as a brake disc, and the reaching of the ions to the friction pair of the friction material block may cause chemical etching of the ferrous material of the friction pair.

11. The braking element according to claim 10, characterized in that, The braking element is a brake lining or a brake shoe.

12. A braking system, comprising a member to be braked constituted by a brake disc or brake drum made of cast iron or steel and at least one braking member constituted by a brake pad or brake shoe, the braking member being adapted to cooperate with the member to be braked by friction, characterized in that, The braking member has a friction layer made of the friction material composition according to claims 1 to 9, which is intended to cooperate with the member to be braked.

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