Friction material, in particular for the manufacturing of a brake pad, and associated preparation method

Patent metadata

Field	Value
Publication number	US-11274721-B2
Application number	US-201615572291-A
Country	US
Kind code	B2
Filing date	May 6, 2016
Priority date	May 7, 2015
Publication date	Mar 15, 2022
Grant date	Mar 15, 2022

Abstract

An asbestos-free friction material includes inorganic and/or organic and/or metallic fibers, at least one binder, at least one friction modifier or lubricant, at least one filler or abrasive and a carbonaceous material constituted by a microstructure. The microstructure is in the form of flakes or scales of micrometric planar dimensions and of nanometric thickness consisting of a substantially pure graphene mono- or multilayers, preferably pre-blended with at least part of the organic binder.

First claim

The invention claimed is:

1. An asbestos-free friction material in a vehicle braking element, the vehicle braking element comprising a heat-pressed block of the asbestos-free friction material glued to a metal support, the asbestos-free friction material comprising:
inorganic and/or organic and/or metallic fibers consisting of between 15-30 percent of the total volume of the asbestos-free friction material;
at least one organic thermosetting binder, wherein the at least one organic thermosetting binder is one or a combination of a phenolic resin, a melamine resin and an epoxy resin, wherein the at least one organic thermosetting binder optionally comprises an inorganic binder;
the at least one organic thermosetting binder being between 2-50 percent of the total volume of the asbestos-free friction material;
at least one friction modifier or lubricant including a carbonaceous material; and
at least one filler or abrasive,
wherein the at least one friction modifier may include the at least one filler,
wherein the carbonaceous material is constituted in part by a microstructure in flakes or scales of micrometric planar dimensions and of nanometric thickness consisting of substantially pure graphene mono- or multilayers, in which the total amount of substantially pure graphene present is between 0.1 and 12% by volume of the total volume of the asbestos-free friction material, and wherein the substantially pure graphene is present in the form of a solid semi-finished product in which the entire amount of substantially pure graphene had been initially mixed with at least a part of the at least one organic thermosetting binder in a hot blending step between a set of hot rollers at a temperature lower than the curing temperature of the at least one organic thermosetting binder, but higher than the melting temperature of the at least one organic thermosetting binder to create a fluid state for enabling the substantially pure graphene to be mixed with the at least one organic thermosetting binder which had then been cooled to form a solid semi-finished product that was ground and sieved into a powder form having a particle distribution between 5 and 500 microns prior to mixing with the remaining components of the asbestos-free friction material and in which the substantially pure graphene had been evenly dispersed within a matrix formed by part of the at least one organic thermosetting binder and in which the substantially pure graphene consists of carbon having a weight percentage of greater than 98 percent, oxygen having a weight percentage of less than 0.6 percent, and sulfur having a weight percentage of less than 0.2 percent, wherein the asbestos-free friction material is free of graphite and wherein the asbestos-free friction material has been heat pressed into the block under pressure for adhesion to the metal support of the braking element.

2. The asbestos-free friction material according to claim 1 , wherein the carbonaceous material consists at least in part of substantially pure graphene flakes or scales having lateral dimensions of between 1 and 50 microns and a thickness of between 0.142 nm and 40 nm, evenly dispersed within the matrix formed by the at least one organic thermosetting binder.

3. The asbestos-free friction material according to claim 1 , wherein the carbonaceous material consists at least in part of substantially pure graphene flakes or scales having lateral dimensions smaller than 10 microns and a thickness smaller than 4 nm, evenly dispersed within the matrix formed by the at least one organic thermosetting binder.

4. The asbestos-free friction material according to claim 1 , wherein the asbestos-free friction material is free of copper or copper alloys and/or fibers of copper or copper alloys.

5. The asbestos-free friction material according to claim 1 , in which the carbonaceous material includes substantially pure graphene in an amount between 1 and 5% by volume of the total volume of the asbestos-free friction material.

6. A braking system including an element to be braked consisting of a disc or brake drum made of a cast iron or steel and at least one braking element consisting of a brake pad or brake shoe suitable to cooperate by means of friction with the element to be braked, wherein the braking element has a friction layer or block which is intended to cooperate with the element to be braked, which friction layer or block has been made of the asbestos-free friction material according to claim 1 .

7. A method for making a block or layer of asbestos-free friction material comprising:
mixing respective component materials of the asbestos-free friction material comprising:
inorganic and/or organic and/or metallic fibers consisting of between 15-30 percent of the total volume of the asbestos-free friction material;
at least one organic thermosetting binder, wherein the at least one organic thermosetting binder is one or a combination of a phenolic resin, a melamine resin and an epoxy resin, wherein the at least one organic thermosetting binder optionally comprises an inorganic binder;
the at least one organic thermosetting binder being between 2-50 percent of the total volume of the asbestos-free friction material;
at least one friction modifier or lubricant including a carbonaceous material; and
at least one filler or abrasive, wherein the at least one friction modifier may include the at least one filler;

blending, together with one or more of said component materials, a carbonaceous material constituted by a microstructure in flakes or scales of micrometric planar dimensions and of nanometric thickness consisting of a substantially pure graphene monolayer or multilayers in an amount comprised between 0.1 and 12% by volume on the total volume of the entire asbestos-free friction material,
wherein the asbestos-free friction material is free of graphite, and wherein the substantially pure graphene consists of carbon with a weight percentage of greater than 98 percent, oxygen having a weight percentage of less than 0.6 percent, and sulfur having a weight percentage of less than 0.2 percent.

8. The method according to claim 7 , wherein the substantially pure graphene having has lateral dimensions of between 1 and 50 microns and a thickness of between 0.142 and 40 nm.

9. The method according to claim 7 , further comprising:
mixing together the component materials of the asbestos-free friction material in order to obtain a raw mixture; and
pressing the raw mixture under pressure in order to obtain a block or layer of asbestos-free friction material; the mixing step comprising:
a) a first step of blending at high temperature and by a first mixer of a roller that is open to atmospheric pressure, at least part of the at least one organic thermosetting binder and at least part of the substantially pure graphene, operating at a temperature lower than the polymerization temperature of the at least one organic thermosetting binder but greater than, or equal to, the softening temperature of the at least one organic thermosetting binder, in order to obtain a solid semi-finished product in the shape of chips or ribbon or sheet;
b) a step of grinding the solid semi-finished product containing the substantially pure graphene in order to reduce the solid semi-finished product to a powder; and
c) a second blending step wherein the powder obtained by grinding the solid semi-finished product is mixed with the remaining materials comprising the asbestos-free friction material.

10. A braking system including an element to be braked consisting of a disc or brake drum made of a cast iron or steel and at least one braking element consisting of a brake pad or brake shoe suitable to cooperate by means of frict

Assignees

• Itt Italia Srl

Inventors

• Sin Xicola Agustin
• Martinotto Luca
• Galimberti Paolo

Classifications

• F16D2200/0082

  Production methods therefor · CPC title

• F16D69/026 Primary

  containing fibres · CPC title

• F16D2200/0065

  Inorganic, e.g. non-asbestos mineral fibres · CPC title

• F16D2200/0069

  being characterised by their size · CPC title

• F16D2200/0021

  Steel · CPC title