JP2010285578A - Friction material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a friction material having high strength characteristics using carbon fibers. <P>SOLUTION: The friction material includes: at least a fiber substrate; a binder; and a friction modifier. In the friction material, the carbon fibers in which functional groups are pre-introduced are treated with an organometallic coupling agent and are contained as the fiber substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a friction material, and more particularly to a friction material used for automobiles, railway vehicles, industrial machines, etc., and more specifically to brake pads, brake linings, etc. used in the above-mentioned applications. It is.

Glass fiber, ceramic fiber, rock wool, potassium titanate fiber and other inorganic fibers, steel fibers, copper fibers, brass fibers and other hemp, cotton, rayon, aromatic polyamide fibers The fiber base material which combined organic fiber, such as these suitably, is examined. Carbon fiber is also used as one of them.
At present, carbon fibers have poor adhesion to a binder as a matrix due to surface characteristics, structural reinforcement is not sufficiently satisfactory, and use is limited from the viewpoint of wear resistance.
Patent Document 1 discloses a non-asbestos friction material containing a friction modifier, a thermosetting resin, and surface-oxidized carbon fiber, and provides a friction material having a high coefficient of friction and excellent wear resistance. There is a statement to that effect.
In the future, the use of carbon fiber is expected to become indispensable for weight reduction of brakes, and further improvement in strength is required.

Japanese Patent Publication No. 7-23739

  An object of the present invention is to provide a friction material having high strength characteristics using carbon fibers.

  The friction material of the present invention is a friction material including at least a fiber base material, a binding material, and a friction modifier, and the fiber base material is obtained by treating carbon fiber previously introduced with a functional group with an organometallic coupling agent. including.

  INDUSTRIAL APPLICABILITY The present invention can provide a friction material with high strength characteristics that can be expected to expand the blending design by utilizing carbon fibers and can be connected to efforts to reduce the weight with respect to environmental trends.

In the present invention, the carbon fiber treated with the organometallic coupling agent has a functional group introduced in advance. The functional group is not particularly limited as long as it can react with the organometallic coupling agent, and examples thereof include a carboxyl group, a carbonyl group, and a phenolic hydroxyl group.
The means for introducing the functional group into the carbon fiber is not particularly limited, but a carbon fiber treated with an inorganic acid is preferable. Examples of inorganic acids include sulfuric acid, nitric acid, and combinations thereof.
The treatment with the inorganic acid facilitates the formation of the organometallic coupling agent film by introducing the functional group onto the surface of the carbon fiber, and further, the organometallic coupling agent and the binder as a matrix are combined. This is because adhesion can be enhanced.

The carbon fiber preferably has a fiber diameter of 1 to 50 μm and a fiber length of 10 to 1000 μm, more preferably a fiber diameter of 3 to 10 μm and a fiber length of 50 to 500 μm. The carbon fiber referred to here includes those having a functional group introduced beforehand and untreated carbon fiber having no functional group.
The carbon fiber having a functional group previously introduced is preferably blended in an amount of 3 to 20% by mass, more preferably 5 to 10% by mass, based on the entire friction material.
By satisfying the size and blending amount of the carbon fiber into which the functional group is introduced, the above effect of the present invention is more effectively exhibited.

  Examples of the carbon fibers used in the present invention include PAN-based fibers, novoloid fibers, pitches and the like carbonized at high temperatures. As the PAN system, a homopolymer or copolymer of acrylonitrile or a mixed polymer of these polymers is used, and monomers that can be copolymerized include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (Meth) acrylates such as (meth) acrylate, butyl (meth) acrylate and hexyl (meth) acrylate, vinyl halides such as vinyl chloride, vinyl bromide and vinylidene chloride, (meth) acrylic acid and itaconic acid , Acids such as crotonic acid and their salts, maleic imide, phenylmaleimide, (meth) acrylamide, styrene, α-methylstyrene, vinyl acetate, sodium styrenesulfonate, sodium allylsulfonate, sodium β-styrenesulfonate , Sulfone groups such as sodium metaallyl sulfonate 1 or more types of polymerizable unsaturated monomers containing a pyridine group such as 2-vinylpyridine, 2-methyl-5-vinylpyridine and the like, but are not limited thereto. It is not something. (Meth) acrylic acid means one or two selected from acrylic acid and methacrylic acid. (Meth) acrylate is the same as above. Examples of the novoloid fiber include a fiber obtained by forming a phenol resin into a fiber and then performing a crosslinking treatment to make the molecular structure three-dimensional.

  As the organometallic coupling agent used in the present invention, in the molecule, a metal atom, a hydrolyzable group that is bonded to the metal atom and can be bonded to the functional group of the carbon fiber, and is bonded to the metal atom, Any coupling agent having a hydrophobic organic functional group having an affinity for a binder may be used, and examples thereof include silane coupling agents, titanate coupling agents, aluminum coupling agents, and zirconium coupling agents. It is done. Specific examples of the silane coupling agent include phenyltriethoxysilane, methacryloxypropylsilane, mercaptopropyltrimethoxysilane, aminopropyltriethoxysilane, aminosilane, vinylsilane, epoxysilane, and chlorosilane. These silane coupling agents may be used alone or in combination of two or more.

The fiber base material used in the present invention may be only carbon fibers having a functional group introduced in advance, but may be used in combination with other fiber base materials. The fiber base material that can be used in combination may be organic or inorganic. Examples of the organic base include aromatic polyamide (aramid) fiber and polyacrylic fiber. Examples of the inorganic base include copper and steel. Metal fibers, potassium titanate fibers, Al ₂ O ₃ —SiO ₂ ceramic fibers, glass fibers, ordinary carbon fibers, rock wool, and the like, each of which is used alone or in combination of two or more.

  Examples of the binder used in the present invention include thermosetting resins such as phenol resins (including various modified phenol resins such as straight phenol resins and rubbers), melamine resins, epoxy resins, and polyimide resins. The binder is usually used in an amount of 5 to 15% by mass, preferably 8 to 10% by mass, based on the entire friction material.

  Examples of the friction modifier used in the present invention include metal oxides such as alumina, silica, magnesia, zirconia, chromium oxide, and molybdenum dioxide, organic materials such as synthetic rubber and cashew resin, metals such as copper, aluminum, and zinc, Examples thereof include minerals such as vermiculite and mica, salts of barium sulfate, zirconium silicate, potassium titanate, calcium carbonate and the like, and graphite, which can be used alone or in combination of two or more. These are used as powders, and various particle sizes are selected.

The friction material of the present invention can be produced by blending the above components, preforming the blend according to a normal production method, and performing treatments such as thermoforming, heating, and polishing.
A brake pad provided with the friction material is formed into a predetermined shape by a sheet metal press, subjected to a degreasing treatment and a primer treatment, and a pressure plate coated with an adhesive, and a preform of the friction material, In the thermoforming process, it can be manufactured by a process of thermoforming at a predetermined temperature and pressure, fixing both members together, performing after-curing, and finally finishing.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to only these examples.

Examples 1 and 2
(Carbon fiber surface treatment)
After immersing 50 g of PAN-based carbon fiber (fiber diameter (diameter): 10 to 50 μm, fiber length: 500 to 1000 μm) in a mixed acid of 800 g of concentrated sulfuric acid and 50 g of concentrated nitric acid at room temperature for 24 hours, the solution is filtered to obtain a residue. It was. The residue was put into 10 liters of a 1 mass% phenyltriethoxysilane aqueous solution and stirred for 1 hour, and then the solution was filtered to obtain carbon fibers coated with phenyltriethoxysilane. There was no change in the fiber diameter and fiber length.
(Production of friction material)
A friction material mixture having a composition (mass%) shown in Table 1 was uniformly mixed with a mixer to obtain a friction material mixture. Subsequently, the friction material mixture was preformed at room temperature and 30 MPa. Next, the preform and a pressure plate pre-applied with an adhesive were set in a thermoforming mold and subjected to heat and pressure molding at 150 ° C. and 40 MPa for 5 minutes. The obtained thermoformed body was heat-treated at 220 ° C. for 3 hours to obtain a friction material.
Comparative Examples 1 and 2
In Example 1, a friction material was produced in the same manner as in Examples 1 and 2 except that untreated carbon fiber was used instead of the silane coupling agent-treated carbon fiber and Table 1 was followed.

The performance of the obtained friction material was evaluated by the following.
(Shear strength test)
The disk pad full size shear strength test was performed at normal temperature and high temperature (300 ° C.) according to JASO C444-78. The results are shown in Table 2.

  From the above table, it was proved that the strength at normal temperature and high temperature has high mechanical properties from the results of Examples 1 and 2.

Claims (4)

  A friction material comprising at least a fiber base material, a binding material, and a friction modifier, wherein the fiber base material is obtained by treating carbon fibers previously introduced with functional groups with an organic metal coupling agent.   The friction material according to claim 1, wherein the carbon fiber into which the functional group is introduced is obtained by treating carbon fiber with an inorganic acid.   The friction material according to claim 1 or 2, wherein the carbon fiber into which the functional group is introduced has a fiber diameter of 1 to 50 µm and a fiber length of 10 to 1000 µm.   The friction material according to any one of claims 1 to 3, wherein the carbon fiber into which the functional group is introduced is blended in an amount of 3 to 20 mass% with respect to the entire friction material.