Block of friction material for equipping a brake pad, and brake pad and method of manufacturing a brake pad

Abstract

A friction block or layer made of an asbestos-free friction material, the friction material comprising inorganic and / or organic and / or metal fibers, at least a binder, at least a friction modifier or lubricant, and at least a filler or abrasive as constituent materials, wherein the asbestos-free friction material further comprises a hydrophobic wax as an additional constituent material or additive, the hydrophobic wax preferably being present in 0.5% to 5% by volume, the asbestos-free friction material block or layer being hydrophobic, the hydrophobicity being defined as the absorption time of droplets formed from 20 + / - 5 pL of distilled water within the friction material being greater than 60 minutes, such that the force required to separate the friction block or layer from a metal surface to which it has been electrochemically bonded is less than 15 Nw.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102020000021919, filed on September 17, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to friction blocks made of friction materials designed to equip brake pads, wherein the friction material may have a formulation that allows for a reduction or elimination of the tendency of the friction block to press against the surface of its cooperating friction partner (a phenomenon referred to as "static friction"). This disclosure generally relates to friction blocks for brake pads, and to related brake pads designed to cooperate with the surfaces of a vehicle's disc brakes to brake the vehicle. This disclosure also generally relates to related methods. Background Technology

[0004] It is well known that, especially under harsh operating and / or environmental conditions, such as frequent off-road driving and / or driving on muddy roads or routes exposed to saline air or acid rain, one or more brake pads in a vehicle in use may “stick” to the associated brake disc, which is made of cast iron or steel. This is generally due to corrosion, which affects the brake disc and causes corrosion products to combine with the friction material of the brake pads during braking, resulting in the brake pads inadvertently adhering to the brake disc (an adhesion that is temporarily maintained even when the vehicle's brakes are deactivated). This adhesion phenomenon is known in the English technical term “stiction,” which is derived from the abbreviation and combination of the terms “static” and “friction,” i.e., “static friction.”

[0005] Clearly, static friction or sticking in vehicles in use involves various drawbacks, such as jolts / tensions during braking and subsequent release, increased energy consumption, and, in extreme cases, damage to the friction material of the brake pads, leading to vehicle malfunction and / or premature replacement of the brake pads. Therefore, static friction is well-known in the brake pad industry and also affects vehicles that are constantly traveling on paved roads when exposed to wet weather conditions. Summary of the Invention

[0006] The purpose of this disclosure is to provide embodiments of friction blocks or layers made of friction materials, wherein the friction materials have a formulation that allows for a reduction or elimination of the tendency of the friction blocks to press against the surfaces of the friction pairs that cooperate with them.

[0007] In particular, the purpose of this disclosure is to provide an embodiment of a friction block that is integral with or integrated into a brake pad designed to cooperate with a brake disc made of steel or cast iron in use.

[0008] Therefore, as defined in the appended claims, this disclosure relates to embodiments of friction blocks or layers made of friction materials formulated in a manner that reduces or eliminates the tendency of friction blocks to press against the surfaces of their friction pairs.

[0009] Generally, friction blocks or layers can be part of a brake pad for a vehicle and designed to cooperate with a brake disc made of steel or cast iron in use, or part of a clutch disc for a vehicle or any other application.

[0010] This disclosure also relates to embodiments of brake pads equipped with or having such friction blocks or layers as integrated components.

[0011] This disclosure also relates to a method for manufacturing brake pads for vehicles, said brake pads having a reduced tendency to press against the friction surface of the associated brake disc or not having a tendency to press against the friction surface of the associated brake disc, that is, having a reduced tendency to static friction or not having a tendency to static friction, especially in wet weather.

[0012] EP3507587 (incorporated herein by reference in its entirety) discloses a method for studying and determining the physicochemical conditions for adhesion between a first mechanical element and a second mechanical element, comprising a vehicle braking element and a braking element, respectively, the method comprising the following steps:

[0013] - A first mechanical element is connected to a first support and a second mechanical element is connected to a second support. The first and second supports are positioned relative to each other and are axially movable relative to each other. The second support faces the first support such that the second mechanical element is completely embedded in the second support except for its first surface. The first surface is not covered by the second support and is arranged to be flush with the front end of the second support facing the first support and the first mechanical element connected thereto.

[0014] - Electrically connect the second mechanical component to an insulated wire, the insulated wire protruding from the second support member in a fluid-sealed manner;

[0015] - By applying a first predetermined force, the first surface of the second mechanical element is adhered to and then pressed against the first mechanical element, thereby pushing the second support member toward the first support member to realize the static friction unit, which includes the first mechanical element and the second mechanical element, as well as the first support member and the second support member;

[0016] - The first mechanical element and the second mechanical element, along with the first support and the second support, together with at least one counter electrode and a reference electrode, are immersed in an electrolyte to form an electrochemical cell, wherein the second mechanical element constitutes the working electrode;

[0017] - Connect the insulated wires, counter electrode, and reference electrode electrically to the potentiometer and / or current generator;

[0018] - Electrochemical testing is performed by a potentiometer and / or a current generator, wherein a gradually varying potential is applied between the working electrode and the reference electrode and / or a gradually varying current path is established between the counter electrode and the working electrode, thereby causing corrosion between the second mechanical element and the first mechanical element.

[0019] - The current through the electrolyte between the second mechanical element and the counter electrode is detected by means of a potential generator / current generator or another instrument based on the applied potential, or conversely, the potential established between the second mechanical element and the reference electrode is detected based on a predetermined current set on the potential generator / current generator.

[0020] In this way, the "static friction" between the braking element (brake pad) and the element to be braked (brake disc) of the vehicle under investigation was quickly obtained "artificially" under controlled conditions. The force required to separate the braking element from the brake disc was then measured, and its value provided an accurate estimate of the nature of the static friction phenomenon that had occurred. Attached Figure Description

[0021] Preferred, but not limiting, embodiments will now be described in more detail with reference to several practical examples of their implementation and the accompanying drawings. These examples are intended only to disclose features that are part of this disclosure in a non-exhaustive and non-limiting manner, as illustrated in the accompanying drawings:

[0022] - Figure 1 This is a graph showing the results of a series of experiments conducted on different friction materials according to the procedures discussed in EP3507587;

[0023] - Figure 2 This is a graph showing the results of experiments conducted on the same friction materials with and without additional components (additives) according to the steps discussed in EP3507587;

[0024] - Figure 3 The figure shows the results of braking tests conducted on a vehicle under different braking conditions using brake pads made of the same friction material containing or not containing other components (additives) of this disclosure.

[0025] - Figure 4A , Figure 4B , Figure 4C and Figure 5A , Figure 5B , Figure 5C The results of the AK Master standard test on brake pads are shown. The brake pads are of the same type and size and are provided with friction material blocks having the same composition but not and not respectively incorporated with other component materials or "additives" according to this disclosure.

[0026] - Figure 6 An exemplary non-limiting embodiment of a brake pad manufactured according to the present disclosure is shown, wherein various test areas for checking the hydrophobicity of its friction material are highlighted;

[0027] - Figure 7 and Figure 8 A practical example of implementing a test method for determining the hydrophobicity of brake pads manufactured according to this disclosure is shown; and

[0028] - Figure 9 A flowchart is provided to illustrate a method for manufacturing a friction material according to the embodiments described herein. Detailed Implementation

[0029] In some embodiments, friction blocks or layers made of asbestos-free friction materials, specifically designed to be provided as part of the vehicle brake pads as an integral part, contain inorganic and / or organic and / or metal fibers, at least a binder, at least a friction modifier or lubricant, and at least a filler or abrasive as constituent materials.

[0030] Materials belonging to the above general categories are well known in the field of brakes and are selected according to known standards to obtain specific properties, such as wear resistance, stable coefficient of friction during braking, fade, and limited use of brake fluid.

[0031] Exemplary embodiments of the fiber component may include, but are not limited to: inorganic fibers, such as glass fiber, rock wool, wollastonite, sepiolite, attapulgite; and / or metal fibers, such as stainless steel and zinc; and organic fibers, such as carbon fiber, aramid fiber, polyimide fiber, polyamide fiber, phenolic fiber, cellulose fiber, and acrylic fiber or PAN (polyacrylonitrile). This fiber base component may be used in short fiber or powder form.

[0032] Many materials known in the art can be used as organic or inorganic fillers. Exemplary embodiments include, but are not limited to, calcium carbonate precipitate, barium sulfate, magnesium oxide, calcium hydroxide, calcium fluoride, quicklime, talc, molybdenum trioxide, zirconium silicate, iron oxide, mica, iron sulfide, silica, vermiculite, rubber powder (rubber powder and granules), nitrile rubber powder (vulcanized product), metal powder (excluding copper and its alloys), and acrylic rubber powder (vulcanized product). These materials can be used alone or in combination of both or more thereof. Based on the total composition of the friction material, the loading of such filler is preferably 2% to 40% by volume.

[0033] Exemplary embodiments of suitable adhesives include, but are not limited to, phenolic resins, melamine resins, and epoxy resins; various modified phenolic resins, such as epoxy-modified phenolic resins, oil-modified phenolic resins, alkylbenzene-modified phenolic resins, and acrylonitrile butadiene rubber (NBR). Any one of these compounds or a combination of two or more thereof can be used. Based on the total composition of the friction material, the adhesive is included in an amount preferably from 2% to 30% by volume.

[0034] Exemplary embodiments of friction modifiers may include, but are not limited to, 0% to 10% (or about 0% to about 10%) of solid lubricants, such as tin sulfides like SnS and SnS2, cashew nut powder, rubber powder (crushed rubber powder), various non-vulcanized rubber particles, various vulcanized rubber particles, inorganic fillers such as barium sulfate, calcium carbonate, calcium hydroxide, vermiculite and / or mica, abrasives such as silicon carbide, alumina, zirconium silicate, lubricants such as molybdenum disulfide, tin sulfides as described above, zinc sulfide, iron and non-ferrous metal sulfides, metal particles other than copper and copper alloys, and / or combinations of all of the above.

[0035] In some embodiments, graphite and / or coke may also advantageously be included in the composition. Graphite (and / or coke) may be added in appropriately selected amounts, preferably from 2% to 15% by volume of the total composition of the friction material. Embodiments of friction materials suitable for use in this disclosure include those known as non-asbestos-organic (NAO) friction materials.

[0036] Graphite (and / or coke) may be added in an appropriate amount, which may be 2% to 15% by volume (or about 2% to about 15% by volume) of the total composition of the friction material.

[0037] The fibers can be used in the form of short fibers or powder. In some embodiments, the fibers can have a total fiber length of 0.5 mm to 1.5 mm (or about 0.5 mm to about 1.5 mm) and a fiber diameter of 40 micrometers to 150 micrometers, although specific dimensions are not limiting.

[0038] Based on the overall composition of the friction material, the amount of filler can range from 2% to 40% by volume.

[0039] Based on the overall composition of the friction material, the binder may be included in an amount ranging from 2% to 30% by volume.

[0040] Exemplary embodiments of suitable abrasives may be subdivided into mild abrasives, medium abrasives, and high-strength abrasives, and may include any or more of the flowing materials. The following list should not be considered exhaustive or in any way limiting:

[0041] • Mild abrasives (Mohs hardness 1 to 3): Talc, calcium hydroxide, potassium titanate, mica, kaolin

[0042] Medium abrasives (Mohs hardness 4 to 6): Barium sulfate, magnesium oxide, calcium fluoride, calcium carbonate, wollastonite, calcium silicate, iron oxide, silicon dioxide, chromite, zinc oxide

[0043] • High-strength abrasives (Mohs hardness 7 to 9): silicon carbide, zirconium sand (zirconia), zirconium silicate, zirconium oxide, corundum, alumina, mullite.

[0044] The ratio of abrasive to lubricant is 3 to 10. In some embodiments, this ratio may be equal to 6 (or about 6).

[0045] The friction material composition according to this disclosure may comprise aramid fibers, with the ratio of binder to aramid fibers being from 0.5 vol% to 8 vol% (or from about 0.5 vol% to about 8 vol%). In some embodiments, this ratio may be equal to 5 (or about 5).

[0046] According to embodiments of this disclosure, the asbestos-free friction material further comprises a hydrophobic wax as an additional component or additive. The relative amount of the hydrophobic wax to the other components is selected based on the chemical properties and amounts of the other components of the asbestos-free friction material, such that the asbestos-free friction material block or layer is hydrophobic after formation. The hydrophobicity is defined by the method described below as the absorption time of a droplet formed from 20 + / - 5 μL of distilled water within the friction material being greater than 60 minutes.

[0047] According to the embodiments of this disclosure, the asbestos-free friction material includes a hydrophobic wax as an additional component or additive, preferably in the form of a solid powder with a melting point above 110°C and chemically stable under high temperature and pressure.

[0048] Chemical stability means that the wax molecules do not undergo decomposition. "High temperature and pressure" refers to several hundred degrees Celsius and kg / cm², respectively. 2 Temperature and pressure on the order of magnitude.

[0049] According to embodiments of this disclosure, the asbestos-free friction material includes a hydrophobic wax as an additional constituent material or additive, said hydrophobic wax being selected from the non-limiting group consisting of: polyethylene (PE) wax, high-density PE (HDPE) wax, polypropylene wax, micronized PE wax, oxidized PE wax, polytetrafluoroethylene (PTFE) modified polyethylene wax, micronized amide wax, micronized polypropylene wax, and specialty waxes (adhesive wax, modified PE wax, PTFE textured powder).

[0050] The hydrophobic wax may be present in the asbestos-free friction material in an amount of 0.5% to 5% (or about 0.5% to about 5%) by volume, based on the total amount of the friction material. In some embodiments, the wax may be in an amount of 1.0% to 2.0% (or about 1.0% to about 2.0% by volume).

[0051] According to any of the above possible embodiments, the asbestos-free friction material friction block or layer may not have a tendency to press against the surface of its friction pair or has a low tendency to press against the surface of its friction pair when the friction material block or layer is integral part of / included in the brake pad, the friction pair is typically a vehicle brake disc. Specifically, according to the embodiment of the test described in detail in this disclosure, the friction material block or layer is electrochemically pressed onto the metal surface by pushing it against a metal surface of steel, iron, or cast iron, and then electrochemical corrosion is induced thereon. According to this test, any embodiment of the friction material block or layer according to this disclosure may exhibit a separation force of less than 15 (or about 15) Newtons from the metal surface, indicating a low tendency to static friction or no tendency to static friction.

[0052] Asbestos-free friction material blocks or layers may be incorporated into vehicle brake pads designed to cooperate with vehicle brake discs made of iron, steel, or cast iron in use, although specific materials are not limiting.

[0053] When an asbestos-free friction material block or layer contains 0.5 vol% to 5 vol% of a hydrophobic wax with a melting point above 110°C as its component material, the resulting friction pair present in the vehicle brake pads and vehicle brake discs does not experience static friction or experiences very limited static friction during use. This allows the two friction pairs to easily separate with low forces (e.g., less than 15 Newtons).

[0054] The hydrophobic wax will be selected from the group consisting of: polyethylene wax, HDPE wax, polypropylene wax, micronized PE wax, oxidized PE wax, PTFE-modified polyethylene wax, micronized amide wax, micronized polypropylene wax, and specialty waxes (adhesive wax, modified PE wax, PTFE textured powder), in an amount that gives the brake pads a reduced or no tendency to static friction, especially in humid weather.

[0055] This disclosure also relates to the use of a hydrophobic wax in an asbestos-free friction material comprising inorganic and / or organic and / or metal fibers, at least a binder, at least a friction modifier or lubricant, and at least a filler or abrasive as additional component materials, wherein the hydrophobic wax is contained in the asbestos-free friction material in an amount of 0.5% to 5% (or about 0.5% to about 5%) by volume based on the total volume of the friction material, and causes the asbestos-free friction material to exhibit a reduced tendency to static friction or no tendency to static friction, especially in humid weather.

[0056] This disclosure also relates to a method for manufacturing brake pads for vehicles, said brake pads having a reduced tendency to press against or not press against the friction surface of the associated brake disc, i.e., a reduced tendency to static friction or no tendency to static friction, especially in wet weather. The method includes the following steps:

[0057] i) - Prepare test quantities of asbestos-free friction materials, especially NAO-type friction materials, by mixing together various component materials comprising inorganic and / or organic and / or metal fibers, at least a binder, at least a friction modifier or lubricant, and at least a filler or abrasive.

[0058] ii) - Add a predetermined amount of hydrophobic wax as an additional component material in step i) to mix with the component material in step i);

[0059] iii) - To form a liner, a solid block or layer of the asbestos-free friction material containing the hydrophobic wax is formed by pressing and heating the mixed component materials in a mold;

[0060] iv) Perform a hydrophobicity test on the liner, the hydrophobicity test including measuring the adsorption time of droplets formed from 20 + / - 5 μL of distilled water on the liner;

[0061] v) Repeat steps i) to iv) using different predetermined amounts of the hydrophobic wax;

[0062] vi) - Industrially producing brake pads using an asbestos-free friction material containing the hydrophobic wax, the asbestos-free friction material having the same chemical composition as those tested friction materials produced by the preceding steps i) to v), and exhibiting a water droplet adsorption time greater than 60 minutes as in step iv).

[0063] This disclosure also relates to a method for manufacturing brake pads for vehicles, the brake pads having a reduced tendency to press against the friction surface of the associated brake disc or not having a tendency to press against the friction surface of the associated brake disc, that is, having a reduced tendency to static friction or not having a tendency to static friction, especially in wet weather, the method comprising the following steps:

[0064] i) - Prepare asbestos-free friction materials, especially NAO-type friction materials, by mixing together various component materials comprising inorganic and / or organic and / or metal fibers, at least a binder, at least a friction modifier or lubricant, and at least a filler or abrasive.

[0065] ii) - In step i), a certain amount of hydrophobic wax is added as an additional component material to be mixed with the component material in step i). The hydrophobic wax is selected from the group consisting of: polyethylene (PE) wax, high-density PE (HDPE) wax, polypropylene wax, micronized PE wax, oxidized PE wax, polytetrafluoroethylene (PTFE) modified polyethylene wax, micronized amide wax, micronized polypropylene wax, specialty waxes (adhesive wax, modified PE wax, PTFE texture powder), and the hydrophobic wax is added in an amount of 0.5% to 5% (or about 0.5% to about 5%) by volume based on the total amount of friction material, and preferably in an amount of 1.0% to 2.0% (or about 1.0% to about 2.0%) by volume to the asbestos-free friction material.

[0066] iii) - A solid block or layer of the asbestos-free friction material containing the hydrophobic wax is formed by pressing and heating the mixed component materials in a mold to form a liner.

[0067] Possible and non-limiting embodiments of brake pads manufactured according to this disclosure are as follows: Figure 6 The image is shown schematically.

[0068] Figure 6 The diagram shows a top view from above the brake pad 1, which includes a metal support or "base plate" 2 and at least one cured friction material pad, block, or layer 3. The base plate is made of an ferrous material (typically iron or steel), but may also be made of a light alloy such as an age-hardening Al alloy.

[0069] In the non-limiting example shown, the brake pad 1 has two friction material blocks or pads 3 arranged side by side and integrally formed with the base plate 2, for example, co-molded on the base plate 2 or bonded to the base plate 2 after curing. Of course, in some embodiments, there may be a single friction material block or pad (or layer) integral with the base plate and large enough to cover almost the entire surface 4 of the base plate 3, which faces the element to be braked in use, such as a known but not shown brake disc.

[0070] exist Figure 6 In the design, brake pad 1 displays test points numbered 10 to 15, highlighted by small circles. At least two test points, points 10 and 11, are arranged near or at the center of brake pad 1, while the remaining test points are evenly distributed on both friction material blocks or pads 3, preferably near or at their respective opposite regions 16 of the blocks or pads 3. Figure 6 The middle part is highlighted as a dashed ellipse.

[0071] As will be described in more detail below, points 10 to 15 are used in a hydrophobicity test developed by the applicant's technicians to test the adsorption time of distilled water droplets in the friction material block or pad 3, since, as will be seen, this measurement may be related to the tendency of the brake pad 1 to undergo static friction phenomena, i.e., the tendency to press against the surface of the friction pair of the brake pad (i.e. the friction surface of the brake disc) during use.

[0072] Figure 7 The product shown is as described and substantially corresponds to the one produced. Figure 6 The photograph of the actual brake pad 1 is shown only schematically, and the test points used therein are shown as small circles and numbered 1 to 6.

[0073] Figure 8 During the hydrophobicity test Figure 7 A photograph of the brake pads, as will be seen in more detail in the working embodiment.

[0074] Figure 9 This is a flowchart describing a method for manufacturing a friction material according to the embodiments described herein. The multiple steps of the method briefly disclosed above are shown as sequentially arranged boxes, with explanations of what happens in each step inserted in each box.

[0075] This disclosure will now be completed through the following non-limiting examples of operational practices.

[0076] Example 1

[0077] Friction materials with different compositions were prepared. All of these friction materials were NAO Cu-free and asbestos-free.

[0078] Table 1 shows the general composition of the prepared friction materials, where the constituent materials shown can be mixed together in different combinations.

[0079] Table 1

[0080]

[0081] (1) Silica powder coated with siloxane

[0082] In Table 1, for mild, medium, and high-strength abrasives, select one or more of the following materials:

[0083] • Mild abrasives (Mohs hardness 1 to 3): talc, calcium hydroxide, potassium titanate, mica, kaolin;

[0084] Medium abrasives (Mohs hardness 4 to 6): barium sulfate, magnesium oxide, calcium fluoride, calcium carbonate, wollastonite, calcium silicate, iron oxide, silicon dioxide, chromite, zinc oxide;

[0085] • High-strength abrasives (Mohs hardness 7 to 9): silicon carbide, zirconium sand (zirconia), zirconium silicate, zirconium oxide, corundum, alumina, mullite.

[0086] Starting with the general effective components listed in Table 1, friction material compositions are prepared in test quantities, molded into liner blocks, and subjected to static friction tests as described in EP3507587, the contents of which are incorporated herein by reference in their entirety.

[0087] Test results Figure 1 The chart shows the force required to separate the examined friction material liner from the fragments of the commercial brake disc.

[0088] Friction material composition #4 contains a hydrophobic additive to combat the creep groan phenomenon as described in WO 2019 / 171325. Friction material #2 corresponds to a known composition known to be substantially free of static friction. Composition #1 contains a hydrophobic wax. Finally, composition #3 corresponds to a known composition known to be substantially subjected to static friction.

[0089] The hydrophobic waxes tested are included in the following non-limiting and non-exhaustive list:

[0090] Polyethylene wax

[0091] HDPE wax

[0092] Polypropylene wax

[0093] Micronized PE wax

[0094] Oxidized PE wax

[0095] PTFE-modified polyethylene wax

[0096] Micronized amide wax

[0097] Micronized polypropylene wax

[0098] Specialty waxes (adhesive waxes, modified PE waxes, PTFE-based powders)

[0099] As can be seen, all compositions containing hydrophobic waxes (the results of different hydrophobic waxes are completely additive) exhibit a separation force of less than 15 Newtons, corresponding to a low risk of static friction, and typically even less than 10, meaning a near-zero risk of static friction. As will be described later, further testing on actual brake pads mounted on automobiles and subjected to braking has demonstrated that a separation force value of 15 to 30 corresponds to a real risk of static friction in the sense that static friction may occur under specific and / or harsh environmental conditions (i.e., humidity, temperature, contaminants, salt, etc.) and braking dynamics conditions (high-temperature clamping, etc.). Values ​​above 30 correspond to severe static friction that is certain to occur under less harsh or specific environmental and / or braking dynamics conditions.

[0100] Example 2

[0101] Other friction material compositions are prepared as shown in Table 2 below.

[0102] Material #1 in Table 2 is the same as Material #1 in Table 1, containing 2.0 vol% polyethylene wax, hereinafter also referred to as "Composition W", while Material #5 in Table 2 corresponds to the same composition as Material #1 but without wax, and the content of medium abrasive is increased by 2 vol% to compensate.

[0103] Table 2

[0104]

[0105] (1) Silica powder coated with siloxane

[0106] Materials #1 and #5 from Table 2 were molded onto the same metal substrate / support and cured in a conventional manner to form identical brake pads. The only difference was that composition #5 did not contain hydrophobic wax and was used as a reference, while the corresponding composition W tested contained 2.0% by volume of commercial polyethylene wax in place of a corresponding amount of medium abrasive.

[0107] The brake liner is pressed at a temperature of 60°C to 200°C and a pressure of 150 kg / cm² to 1800 kg / cm² for a duration of 3 to 10 minutes, or the mixture is pre-formed in a mold and then pressed at a temperature of 130°C to 180°C and a pressure of 150 kg / cm² to 500 kg / cm² (14.7 MPa to 49 MPa) for a duration of 3 to 10 minutes.

[0108] The resulting pressed products are typically post-cured by heat treatment at 150°C to 400°C for 10 minutes to 10 hours, followed by spraying or powder coating, drying in an oven, and possibly machining to produce the final product.

[0109] The effective braking area of ​​each individual brake pad is 26.8 cm². 2 .

[0110] Example 3

[0111] The brake pads thus obtained using friction material compositions #5 and W were subjected to the following tests:

[0112] A- Hydrophobicity test (water adsorption test)

[0113] The following operations were performed on each brake pad that constituted the test sample:

[0114] ■ Blow up and clean the raised surfaces of the brake pads (the surfaces intended to contact the brake disc);

[0115] ■ Dry the sample at 105℃ for 2 hours;

[0116] ■ Cool the sample to a temperature of 10°C to 30°C;

[0117] ■ Apply 20 + / - 5 μL of distilled water to the same point on the brake pad;

[0118] ■ The time period required to measure complete absorption;

[0119] To obtain reliable measurements independent of the potential anisotropy of the molded friction material, the tests are performed at multiple points on the brake pad, for example... Figure 6 Points 10 to 15 are shown schematically in the diagram. Additionally, refer to... Figure 7 The overall value of hydrophobicity expressed in minutes is not calculated as a pure arithmetic mean between measurements corresponding to different test points, but is calculated in the following manner, as well as... Figure 7 As shown:

[0120] ■Data 1: The average between point 1 and point 2

[0121] ■Data 2: The average between point 3 and point 4

[0122] ■Data 3: The average of Data 1 and Data 2

[0123] Average adsorption time: given as the average of the measurements at points 5 and 6 and the value at data 3.

[0124] The results are reported in Table 3:

[0125] Table 3

[0126] Material Water droplet absorption time (minutes) Reference - Wax-free 42 wax 72

[0127] Figure 8 The test is shown at a moment in time where a droplet of distilled water has been poured onto the friction material block of the brake pad. As can be seen, the water droplet forms an angle with the surface of the friction material block or pad; the measurement of this angle is typically considered a unit of measurement for hydrophobicity. However, in this case, the hydrophobicity being measured is not at the surface, but rather the overall hydrophobicity of the friction material block or pad; therefore, the "conventional" unit of measurement would be inappropriate. Consequently, the test described in detail above has been developed, and its ease of implementation and reliability have been proven.

[0128] Example 4

[0129] Some brake pads obtained using friction material compositions #5 and W were subjected to static friction tests according to EP3507587. The results are shown in... Figure 2 And in Table 4 below:

[0130] Table 4

[0131] Material Static friction (N) Reference - No wax 21 wax 13

[0132] As can be seen, the test results are consistent with... Figure 1 The test results reported in the Chinese report were completely consistent. Adding only 2% of the hydrophobic wax to a specific composition resulted in separation forces ranging from 21 to 13, indicating a transition from a static friction risk state to a very low risk state.

[0133] For simplicity, other experiments, not reported in detail, showed that adding higher or lower amounts of wax or changing the type of wax reduced the separation force value to below 10. Figure 1 As shown in the image.

[0134] Example 5

[0135] Some brake pads obtained using friction material compositions #5 and W were subjected to vehicle testing according to the following scheme:

[0136] ■ Install new discs and linings on the vehicle

[0137] ■ Perform 10 braking and stopping applications from 50 km / h to 0 km / h to break in the vehicle.

[0138] ■ Spray 2 liters of water onto each wheel, keeping the wheels rotating during spraying.

[0139] ■Measure the torque with a torque wrench after parking for 6 nights.

[0140] ■ Conduct 50 braking applications (from 50 km / h to 0 km / h) in urban traffic without replacing brake pads and brake rotors.

[0141] ■ Repeat steps 4 and 5, then perform a break-in period in urban traffic; verify that the disc surface is free of corrosion.

[0142] The report on torque verification using a torque wrench is in Figure 3 In this context, it is expressed in Nm (Newtons per meter).

[0143] As can be seen, even taking into account random variations in different experiments, the torque value measured for a brake pad with a friction material block or pad containing hydrophobic wax in its composition is significantly lower than the torque value of a brake pad with a friction material block of the same composition but without wax.

[0144] Example 6

[0145] Some brake pads obtained by friction material compositions #5 and W were subjected to various standard AK-Master tests according to SAE J2522.

[0146] For brake pads made of friction materials without wax, in Figure 4A , Figure 4B , Figure 4C The diagram shows a summary and important figure of the tests conducted, while for brake pads made of the same composition but containing 2% hydrophobic wax, in Figure 5A , Figure 5B , Figure 5C The diagram shows a summary and important figures of the tests conducted.

[0147] As can be immediately understood, brake pads containing hydrophobic wax and those without exhibit similar braking behavior. This confirms that adding hydrophobic wax to standard friction materials does not impair their braking performance.

[0148] Wear on the brake pads and brake discs was also assessed, expressed as the difference in component weight before and after the AK-Master test. The results are reported in Tables 5 and 6 below.

[0149] Table 5 – Unwaxed

[0150]

[0151] Table 6 – Wax

[0152]

[0153] As can be seen, the wear of brake pads made with friction materials containing hydrophobic wax is reduced significantly, while the wear of the disc, even if higher, is not significant due to the considerable mass of the disc.

[0154] in conclusion

[0155] It is evident from the above working examples and disclosures that, when compared to the same friction material composition but without hydrophobic wax, simply adding or even reducing the amount of one of the hydrophobic waxes disclosed herein in any possible friction material composition always tends to reduce or eliminate static friction.

[0156] Friction materials containing hydrophobic additives different from waxes (such as those according to WO 2019 / 171325, which are incorporated herein by reference in their entirety) generally have a lower tendency to static friction, but not enough to significantly reduce the risk of static friction, especially when the additives are used in conjunction with friction materials (which do not contain any additives) that exhibit severe static friction in use.

[0157] Since silica powder coated with siloxane is not chemically incompatible with any hydrophobic wax, these two additives (for creep flutter and for static friction) can be used together in the same friction material composition.

[0158] Therefore, the full purpose of this disclosure has been achieved.

[0159] certain terms

[0160] While certain braking devices, systems, and methods have been disclosed in the context of some example embodiments, those skilled in the art will understand that the scope of this disclosure extends to other alternative embodiments and / or uses of the embodiments, as well as certain modifications and equivalents thereof. Use of any structure is clearly within the scope of this invention. Various features and aspects of the disclosed embodiments can be combined or substituted with each other to form different assembly modes. The scope of this disclosure should not be limited to the specific disclosed embodiments described herein.

[0161] Some features described in the context of different implementations in this disclosure may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations. Furthermore, although features may function in certain combinations as described above, in some cases, one or more features of the claimed combination may be removed from that combination, and the combination may be claimed as any sub-combination or any variation of the sub-combination.

[0162] Unless otherwise specifically stated or otherwise understood in the context in which they are used, conditional language such as “may,” “can,” “may,” or “may” is generally intended to convey that certain embodiments include or exclude certain features, elements, and / or steps. Therefore, such conditional language is generally not intended to imply that one or more embodiments require features, elements, and / or steps in any way.

[0163] Unless otherwise specifically stated, connective language such as the phrase “at least one of X, Y, and Z” is otherwise understood, depending on the context, to generally convey that an item, term, etc., can be X, Y, or Z. Therefore, such connective language is not generally intended to imply that some implementation requires the presence of at least one of X, at least one of Y, and at least one of Z.

[0164] Unless otherwise stated, the terms “approximately,” “about,” and “substantially” as used herein mean an amount that is close to the stated amount but still performs the desired function or achieves the desired result. For example, in some embodiments, as the context may determine, the terms “approximately,” “about,” and “substantially” may refer to an amount less than or equal to 10% of the stated amount. The term “generally” as used herein means a value, amount, or characteristic that primarily comprises or tends to a particular value, amount, or characteristic. As an example, in some embodiments, as the context may determine, the term “generally parallel” may refer to a deviation from perfect parallelism of less than or equal to 20 degrees.

[0165] Several embodiments have been described in conjunction with the accompanying drawings. The drawings are drawn to scale, but such scale should not be limiting, as dimensions and scales other than those shown are taken into account and are within the scope of the disclosed invention. Distances, angles, etc., are merely illustrative and do not necessarily have an exact relationship to the actual dimensions and layout of the illustrated apparatus. Components may be added, removed, and / or rearranged. Furthermore, any particular feature, aspect, method, characteristic, feature, quality, attribute, element, etc., disclosed herein in conjunction with multiple embodiments can be used in all other embodiments set forth herein. Moreover, it will be appreciated that any method described herein can be implemented using any apparatus suitable for performing the stated steps.

[0166] Summarize

[0167] Several illustrative embodiments of braking devices, systems, and methods have been disclosed. While the machines, systems, and methods have been disclosed in the context of these embodiments, this disclosure extends the specifically disclosed embodiments to other alternative embodiments and / or other uses of the embodiments, as well as certain modifications and equivalents thereof. This disclosure expressly contemplates that various features and aspects of the disclosed embodiments can be combined or substituted with each other. Therefore, the scope of this disclosure should not be limited to the specific disclosed embodiments described above, but should be determined only through a reasonable interpretation of the full scope of the appended claims and their equivalents.

Claims

1. A friction block or layer made of an asbestos-free friction material, designed to be provided as integral part of a vehicle brake pad, said asbestos-free friction material comprising inorganic and / or organic fibers, binders, friction modifiers, and fillers as constituent materials, wherein said asbestos-free friction material further comprises a hydrophobic wax as an additional constituent material or additive, characterized in that, The relative amount of the hydrophobic wax is selected based on the chemical properties and amounts of the other constituent materials of the asbestos-free friction material, thereby making the asbestos-free friction material block or layer hydrophobic. The hydrophobicity is defined as the absorption time of a droplet formed from 20 + / - 5 μL of distilled water within the friction material being greater than 60 minutes. This results in the asbestos-free friction material block or layer having no tendency to press against the surface of its friction pair or having a low tendency to press against the surface of its friction pair. After electrochemically pressing the friction material block or layer against the metal surface of steel or iron by pushing it against the metal surface and causing corrosion thereon, the friction block or layer exhibits a separation force of less than 15 Newtons from the metal surface.

2. The friction block or layer made of asbestos-free friction material according to claim 1, characterized in that, The friction modifier is a lubricant, and the filler is an abrasive.

3. The friction block or layer made of asbestos-free friction material according to claim 1, characterized in that, The metal surface is a cast iron metal surface.

4. The friction block or layer made of asbestos-free friction material according to claim 1, characterized in that, The hydrophobic wax is in the form of a solid powder with a melting point above 110°C and is chemically stable under high temperature and pressure.

5. A friction block or layer made of asbestos-free friction material according to any one of claims 1 to 3, characterized in that, The hydrophobic wax is selected from the following components: polyethylene wax, modified PE wax, micronized amide wax, polypropylene wax, and PTFE textured powder.

6. The friction block or layer made of asbestos-free friction material according to claim 5, characterized in that, The hydrophobic wax is selected from the following components: PTFE-modified polyethylene wax, HDPE wax, micronized PE wax, oxidized PE wax, and micronized polypropylene wax.

7. The friction block or layer made of asbestos-free friction material according to claim 5, characterized in that, The hydrophobic wax is selected from adhesive waxes.

8. A friction block or layer made of asbestos-free friction material according to any one of claims 1 to 3, characterized in that, The hydrophobic wax is present in the asbestos-free friction material in an amount of 0.5% to 5% by volume, calculated based on the total amount of the friction material.

9. The friction block or layer made of asbestos-free friction material according to claim 8, characterized in that, The hydrophobic wax is present in the asbestos-free friction material in an amount of 1.0 vol% to 2.0 vol%.

10. A vehicle brake pad designed to cooperate with a vehicle brake disc made of iron or steel during use, said vehicle brake pad comprising a non-asbestos friction material block or layer operatively associated with said vehicle brake disc during use, said non-asbestos friction material block or layer comprising 0.5 vol% to 5 vol% of a hydrophobic wax with a melting point above 110°C as one of its component materials, characterized in that, The hydrophobic wax enables the asbestos-free friction material block or layer to have no tendency to press against the surface of the vehicle brake disc or to have a low tendency to press against the surface of the vehicle brake disc. After being electrochemically pressed against the metal surface by pushing the friction material block or layer against the metal surface of steel or iron and causing corrosion thereon, the friction material block or layer exhibits a separation force of less than 15 Newtons from the metal surface, so that the brake disc has a reduced or zero tendency to static friction even in wet weather.

11. The vehicle brake pad according to claim 10, wherein the hydrophobic wax is selected from the following components: polyethylene wax, modified PE wax, polypropylene wax, micronized amide wax, and PTFE textured powder.

12. The vehicle brake pad according to claim 10, wherein the vehicle brake disc is made of cast iron, and the metal surface is a cast iron metal surface.

13. The vehicle brake pad according to claim 11, wherein the hydrophobic wax is selected from the following components: PTFE-modified polyethylene wax, HDPE wax, micronized PE wax, oxidized PE wax, and micronized polypropylene wax.

14. The vehicle brake pad according to claim 11, wherein the hydrophobic wax is selected from adhesive waxes.

15. Use of a hydrophobic wax in an asbestos-free friction material comprising inorganic and / or organic fibers, binders, friction modifiers, and fillers as additional component materials, wherein the hydrophobic wax is contained in the asbestos-free friction material in an amount of 0.5% to 5% by volume of the total volume of the friction material, wherein the hydrophobic wax is selected such that the asbestos-free friction material exhibits reduced or no tendency to static friction even in humid weather, and wherein the hydrophobic wax is selected such that after the asbestos-free friction material has been pressed against a steel or iron metal surface and corroded thereon to electrochemically bond to the metal surface, the asbestos-free friction material exhibits a separation force of less than 15 Newtons from the metal surface.

16. The use according to claim 15, wherein the friction modifier is a lubricant and the filler is an abrasive.

17. The use according to claim 15, wherein the metal surface is a cast iron metal surface.

18. A method of manufacturing a brake pad for a vehicle, the brake pad having a reduced tendency to press against or not press against the friction surface of an associated brake disc, i.e., having a reduced tendency to static friction or not having a static friction tendency even in wet weather, the method comprising the steps of: i) - Prepare non-asbestos organic friction materials by mixing together various component materials containing inorganic and / or organic fibers, binders, friction modifiers and fillers. ii) - In step i), a certain amount of hydrophobic wax is added as an additional component material to be mixed with the component material in step i). The hydrophobic wax is selected from the following components: polyethylene wax, modified PE wax, polypropylene wax, micronized amide wax, PTFE texture powder, and the hydrophobic wax is added to the asbestos-free friction material in an amount of 0.5% to 5% by volume based on the total amount of the friction material. iii) - A solid block or layer of the asbestos-free friction material containing the hydrophobic wax is formed by pressing and heating the mixed component materials in a mold to form a liner, wherein the solid block or layer exhibits a separation force of less than 15 Newtons from the metal surface after being electrochemically pressed onto the metal surface by pushing the solid block or layer of the asbestos-free friction material against the metal surface of steel or iron and causing corrosion thereon.

19. The method of claim 18, wherein the metal surface is a cast iron metal surface.

20. The method of claim 18, wherein the hydrophobic wax is selected from the following components: polytetrafluoroethylene modified polyethylene wax, HDPE wax, micronized PE wax, oxidized PE wax, and micronized polypropylene wax.

21. The method of claim 18, wherein the hydrophobic wax is selected from adhesive waxes.

22. The method of claim 18, wherein the hydrophobic wax is added to the asbestos-free friction material in an amount of 1.0 vol% to 2.0 vol% based on the total amount of the friction material.

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