JP6235217B2 - Friction material - Google Patents

Description

  The present invention relates to a brake friction material used in automobiles, railway vehicles, industrial machines and the like.

  Friction materials used for brakes such as disc brakes and drum brakes used in automobiles, etc., or clutches, are generally friction adjusting materials that impart a frictional action and adjust the friction performance, and fibers that provide a reinforcing action. It is made of a base material and a material such as a binder that integrates these to give strength. The friction material is in frictional engagement with its counterpart material and plays the role of changing kinetic energy into heat energy, so it requires excellent heat resistance, wear resistance, high friction coefficient, stability of friction coefficient, Furthermore, it is also required that squealing is difficult to occur (squeal characteristics).

  In addition, in order to improve the mechanical strength and heat resistance of the friction material, it is known to add metal fibers or metal particles to the friction material. In Patent Document 1, a non-asbestos-based friction material obtained by molding and curing a friction material composition containing steel fibers as a main component, a binder, and a filler as a main component, petroleum coke having an average particle diameter of 50 to 150 μm. And a friction material containing hard inorganic particles having an average particle diameter of 5 to 30 μm is disclosed. Patent Document 2 discloses a friction material including a high melting point metal powder, a low melting point metal powder having a melting point of 420 ° C. or lower lower than the high melting point metal powder, and a metal sulfide powder.

  Further, in recent years, it has been suggested that friction materials containing copper components such as copper and copper alloys may contaminate the environment because copper is contained in wear powder generated during braking. Therefore, there is a demand for a friction material that does not contain a copper component in order to maintain high performance as a friction material and not adversely affect the environment.

As a friction material with a small amount of copper component, in Patent Document 3, the content of copper and the content of metals other than copper and copper alloy are set to a certain level or less, a specific amount of acrylic elastomer-dispersed phenol resin as a binder, and inorganic filling A friction material having a specific amount of Ca (OH) ₂ and / or CaO as an essential component as an agent is disclosed.

Japanese Patent Application Laid-Open No. 2004-155843 JP-A-4-304284 International Publication No. 2012/066965

  The friction material is required to have wear resistance and shear failure during braking, but the friction material described in Patent Document 1 uses steel fibers, so when used in large quantities Further, the attacking property against the mating material such as the rotor is increased, and as a result, the wear resistance of the friction material may be deteriorated. Moreover, since the friction material described in Patent Document 2 is a powder of tin or zinc used as a low melting point metal, there is a possibility that a sufficient reinforcing effect cannot be obtained. Moreover, the friction material described in Patent Document 3 has room for improvement in terms of wear resistance and shear strength.

  Accordingly, an object of the present invention is to provide a friction material that has a low environmental load and is excellent in wear resistance and shear strength.

  As a result of intensive studies to achieve the above object, the present inventors have determined that the friction material containing the non-whisker-like titanic acid compound and the low-melting-point metal fiber does not contain a copper component, and wear resistance of the friction material. The present inventors have found that the shear strength can be satisfied and have completed the present invention.

That is, the present invention relates to the following (1) to (3).
(1) A friction material including a fiber base material, a friction modifier, and a binding material, the friction material including a non-whisker-like titanate compound and a low-melting-point metal fiber, and not including a copper component.
(2) The friction material according to (1), wherein the low-melting-point metal fiber is at least one of aluminum and zinc.
(3) The friction material according to (1) or (2), wherein the non-whisker-like titanate compound is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, and magnesium potassium titanate.

  The friction material according to the present invention does not require a copper component that may adversely affect the environment, can improve the wear resistance of the friction material, and can obtain sufficient shear strength.

  The friction material according to the present invention contains a low melting point metal fiber. Here, the low melting point metal means a metal having a melting point of 1000 ° C. or lower. Since the temperature of the friction material surface during braking is 1000 ° C. or less, a coating can be formed on the surface of a mating material such as a rotor if the metal has a low melting point. As a result, it is possible to obtain a friction material that has low attack on the counterpart material and excellent wear resistance. Examples of the low melting point metal include aluminum, tin, and zinc, and aluminum and zinc are more preferable from the viewpoint of heat resistance.

  Moreover, in this invention, the shear strength of a friction material can be improved by including this low melting metal in a fiber state. It is considered that this is because fibers are likely to be entangled unlike powder, and as a result, a reinforcing effect can be imparted to the friction material. As a fiber, it is preferable that an average fiber length is 1-10 mm and an average fiber diameter is 10-500 micrometers from a viewpoint of improving a reinforcement effect.

  The content of the low melting point metal fiber is preferably 0.2 to 7.0% by mass, more preferably 1.0 to 5.0% by mass in the entire friction material. If it is the range which requires content, it is preferable from a viewpoint of a reinforcement effect.

  The friction material according to the present invention further contains a non-whisker-like titanate compound. Thereby, it can be set as the friction material excellent in abrasion resistance. Here, the non-whisker shape means that it is not a needle-like shape (whisker shape) having an aspect ratio of 3 or more and a fiber diameter of 6 μm or less. Examples of the shape include flakes and particles. It is preferable that a non-whisker-like titanic acid compound is contained from the viewpoint that an effect excellent in wear resistance can be exhibited.

  Non-whisker-like titanate compounds (hereinafter also referred to as “titanate compounds”) include potassium titanate, lithium titanate, lithium potassium titanate, sodium titanate, calcium titanate, magnesium titanate, magnesium titanate. Although potassium, barium titanate, etc. are mentioned, potassium titanate, lithium potassium titanate, and magnesium potassium titanate are more preferable from the point that abrasion resistance improves. These may be used alone or in combination of two or more.

The non-whisker-like potassium titanate (hereinafter sometimes simply referred to as “potassium titanate”) used in the present invention is potassium titanate (K ₂ O · 6TiO ₂ ), potassium potassium titanate (K ₂ O · 8TiO ₂ ) is preferred.

  Examples of the shape of potassium titanate include a layer shape, a particle shape, a plate shape, and a column shape. Among these, a particle shape is preferable from the viewpoint of wear resistance.

Moreover, it is preferable from the point of abrasion resistance that the shape of potassium titanate has a some convex part shape. Here, having a plurality of convex shapes means that the shape projected onto the plane of potassium titanate can take a shape having convex portions in two or more directions, unlike at least normal polygons, circles, ellipses and the like. It means that there is. Specifically, the convex portion refers to a portion corresponding to a portion protruding with respect to a photo (projection drawing) taken with an optical or electron microscope or the like by applying a polygon, a circle, an ellipse or the like (basic figure). Specific three-dimensional shapes of potassium titanate having a plurality of convex shapes include a boomerang shape, a cross shape, an amoeba shape, various animal and plant parts (for example, hands, horns, leaves, etc.) or their entire shapes, or those And similar shapes, confetti, and the like.
Among these, potassium titanate is more preferably in the form of particles having a plurality of convex portions. As such potassium titanate, for example, potassium titanate described in International Publication No. 2008/123046 can be used.

  The shape of the non-whisker-like lithium potassium titanate (hereinafter sometimes simply referred to as “lithium potassium titanate”) used in the present invention is preferably a layered shape, a columnar shape, a plate-like shape, etc. It is preferable that it is lamellar.

The molecular formula of the lithium titanate potassium x = 0.5 to 0.7 in _{K x Li y Ti z O w} , y = 0.27, z = 1.73, w = 3.85~3.95 , etc. Can be used.

  The shape of the non-whisker-like magnesium potassium titanate (hereinafter sometimes simply referred to as “magnesium potassium titanate”) used in the present invention is preferably a layered shape, a columnar shape, a plate-like shape, etc. It is preferable that it is lamellar.

The molecular formula of magnesium potassium titanate _K x1 _Mg y1 _Ti z1 _{O w1} at x1 = 0.2~0.7, y1 = 0.4, z1 = 1.6, such as w1 = from 3.7 to 3.95 Can be used.

  The average particle diameter of the non-whisker-like titanic acid compound may be 1 to 100 μm, and in particular, 1 to 20 μm is preferable from the viewpoint of wear resistance. The average particle diameter is a value measured by a laser diffraction particle size distribution meter.

  Further, the non-whisker-like titanic acid compound may be subjected to a surface treatment with a silane coupling agent or the like from the viewpoint of improving the strength of the friction material.

  In the present invention, the total content of the non-whisker-like titanate compound is preferably in the range of 1 to 40% by mass with respect to the entire friction material from the viewpoint of reducing the friction material (pad) wear, and 5 to 35. The mass% is more preferable.

In addition to the above components, the friction material according to the present invention includes a fiber base material, a friction modifier, and a binder.
However, the friction material of the present invention does not contain a copper component. Note that the phrase “not containing a copper component” means that the copper component is not contained as an effective component for expressing a function such as wear resistance. For example, an impurity inevitably slightly contained in the friction material It does not mean that the copper component is not included.

  For the fiber base material included in the friction material according to the present invention, a commonly used fiber base material can be used in a commonly used amount, and specifically, organic fiber, inorganic fiber, and metal fiber are used. However, copper fibers and bronze fibers containing copper components are not used.

Examples of organic fibers include aromatic polyamide (aramid) fibers and flame-resistant acrylic fibers. Examples of inorganic fibers include ceramic fibers such as potassium titanate fibers and alumina fibers, biosoluble inorganic fibers, glass fibers, and carbon fibers. A fiber, rock wool, etc. are used, and steel fiber is used as a metal fiber, for example. These may be used alone or in combination of two or more. Further, the fiber base material in the friction material is used in the entire friction material, preferably 1 to 40% by mass, more preferably 5 to 25% by mass. In addition, content of said low melting-point metal fiber is not included in this content.
Among these, biosoluble inorganic fibers are preferable as inorganic fibers because they have little influence on the human body. Such bio-soluble inorganic _fibers, SiO 2 -CaO-MgO-based fibers and _{SiO 2 -CaO-MgO-Al 2} O 3 _fibers, biosoluble ceramic fibers or living body such as SiO 2 -MgO-SrO based fiber Examples include soluble rock wool.

  The biosoluble inorganic fiber preferably has a fiber diameter of 0.1 to 20 μm and a fiber length of 100 to 5000 μm.

  In addition, the surface of the biosoluble inorganic fiber may be surface-treated with a silane coupling agent or the like from the viewpoint of improving the strength of the friction material.

  In the friction adjusting material included in the friction material of the present invention, an inorganic filler, an organic filler, an abrasive, a solid lubricant, and the like can be appropriately mixed.

Examples of the inorganic filler include inorganic materials such as barium sulfate, calcium carbonate, calcium hydroxide, vermiculite, and mica, and metal powders such as aluminum, tin, and zinc, in addition to the non-whisker-like titanate compound. These may be used alone or in combination of two or more.
In the present invention, the inorganic filler is used in the entire friction material, preferably 1 to 60% by mass, more preferably 1 to 50% by mass.

Examples of the organic filler include various rubber powders (raw rubber powder, tire powder, etc.), cashew dust, melamine dust and the like. These may be used alone or in combination of two or more.
In the present invention, the organic filler is used in the entire friction material, preferably 1 to 15% by mass, more preferably 1 to 10% by mass.

Examples of the abrasive include alumina, silica, magnesia, zirconia, zirconium silicate, chromium oxide, triiron tetroxide (Fe ₃ O ₄ ), and chromite. These may be used alone or in combination of two or more.
In the present invention, the abrasive is used in the entire friction material, preferably 5 to 30% by mass, more preferably 10 to 30% by mass.

Examples of the solid lubricant include graphite (graphite), antimony trisulfide, molybdenum disulfide, tin sulfide, polytetrafluoroethylene (PTFE), and the like. The particle size of graphite is preferably 1 to 1000 μm. These may be used alone or in combination of two or more.
In the present invention, the solid lubricant is used in the entire friction material, preferably 1 to 20% by mass, and more preferably 3 to 15% by mass.

As the binder contained in the friction material according to the present invention, various commonly used binders can be used. Specific examples include thermosetting resins such as straight phenol resins, various modified phenol resins such as elastomers, melamine resins, epoxy resins, and polyimide resins. Examples of the elastomer-modified phenol resin include acrylic rubber-modified phenol resin, silicone rubber-modified phenol resin, and NBR rubber-modified phenol resin. In addition, these binders can be used individually or in combination of 2 or more types.
Moreover, the binder in the friction material is preferably 5 to 20% by mass, more preferably 5 to 15% by mass in the entire friction material.

As a specific aspect of the manufacturing method of the friction material according to the present invention, it can be performed by a known manufacturing process, for example, the above-mentioned components are blended, and the blend is preformed, thermoformed, according to a normal production method, A friction material can be produced through processes such as heating and polishing.
A general process in manufacturing a brake pad provided with a friction material is shown below.
(A) forming a pressure plate into a predetermined shape by a sheet metal press;
(B) a step of subjecting the pressure plate to a degreasing treatment, a chemical conversion treatment and a primer treatment;
(C) a step of blending raw materials such as a fiber base material, a friction modifier, and a binder, sufficiently homogenizing by stirring, and molding at a predetermined pressure at room temperature to prepare a preform,
(D) a thermoforming process in which the preform and the pressure plate coated with an adhesive are fixed together by applying a predetermined temperature and pressure;
(E) A step of performing after-curing and finally performing finishing treatment such as polishing, surface baking, and painting.

  EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples.

(raw materials)
Potassium titanate 1 (potassium titanate having a plurality of convex shapes): TERRACESS JP (manufactured by Otsuka Chemical Co., Ltd.)
Potassium titanate 2 (plate-like potassium titanate): TERRACESS TF-S (manufactured by Otsuka Chemical Co., Ltd.)
Lithium potassium titanate (non-whisker-like lithium potassium titanate): TERRACESS L-SS (manufactured by Otsuka Chemical Co., Ltd.)
Magnesium potassium titanate (non-whiskered magnesium potassium titanate): TERRASESS PS (manufactured by Otsuka Chemical Co., Ltd.)
Biosoluble inorganic fiber: Biostar 600/70 (manufactured by ITM Co., Ltd.)

(Examples 1-15 and Comparative Examples 1-3)
(Production of friction material)
After mixing the fiber base material, the friction modifier, and the binder at a blending ratio shown in Table 1 using a mixer, the mixture is put into a preforming mold and preformed by pressurization at room temperature for 10 seconds at 20 MPa. Was made. Next, the preform was put into a thermoforming mold, a metal plate (pressure plate) previously coated with an adhesive was layered thereon, and heat pressing was performed at 150 ° C. and 40 MPa for 5 minutes. The obtained heat and pressure molded body is heat-treated at 220 ° C. for 3 hours, polished, surface-baked and painted to a predetermined thickness (friction material thickness 11 mm, pressure plate thickness 6 mm). Obtained.

(Friction test)
About the friction material obtained by the said method, according to JASO-C427 using the Dynamo testing machine, the abrasion loss of the friction material equivalent to 1000 times of brakings with a brake temperature of 100 degreeC was evaluated. The results are shown in Table 1.
The evaluation criteria were “A” when the wear amount was less than 0.1 mm, “B” when 0.1 to 0.2 mm, and “B” when it exceeded 0.2 mm.

(Shear strength)
The shear strength of the friction material was measured according to JIS D4422 (adhesion area: 50 cm ² ). The measured value was calculated by dividing the stress at the time of shear fracture by the area of the friction material and calculating the shear force (N / cm ² ) per unit area. The results are shown in Table 1.
Evaluation criteria of the case of more than ^{580N / cm 2 ◎, 530~580N /} cm 2 to ○, was 400 N / cm ² or more 530n / cm ² less than the △.

  Friction materials A to O of Examples 1 to 15 include a non-whisker-like titanate compound and a low-melting-point metal fiber, an aluminum fiber or a zinc fiber, and a friction material Q that does not contain a low-melting-point metal fiber. It was found that the shear strength was improved as compared with (Comparative Example 2). Moreover, even if it did not contain a copper component, the shear strength equivalent to the friction material P was shown by containing the same amount of low melting metal fibers as the friction material P (comparative example 1) containing the conventional copper fiber. . On the other hand, as compared with the friction material Q (Comparative Example 2) and the friction material R (Comparative Example 3) that do not contain a non-whisker-like titanate compound, it was found that the friction materials A to O were excellent in wear resistance. Therefore, according to the present invention, a friction material excellent in wear resistance and shear strength can be obtained by containing the non-whisker-like titanate compound and the low melting point metal fiber.

The present invention provides a friction material having excellent wear resistance and shear strength without using a copper component.
The friction material according to the present invention can be suitably used for disk pads, brake linings, clutch facings and the like of automobiles, railway vehicles, various industrial machines and the like without imposing a burden on the environment.

Claims (4)

A friction material comprising a fiber base material, a friction modifier and a binder, comprising a non-whisker-like titanic acid compound and a low-melting-point metal fiber having a melting point of 1000 ° C. or less, and containing the low-melting-point metal fiber A friction material having an amount of 1.0 to 7.0% by mass and containing no copper component.   The friction material according to claim 1, wherein the low-melting-point metal fiber is at least one of aluminum and zinc.   The friction material according to claim 1 or 2, wherein the non-whisker-like titanate compound is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, and magnesium potassium titanate.   The friction material according to any one of claims 1 to 3, wherein the low-melting-point metal fiber has an average fiber length of 1 to 10 mm and an average fiber diameter of 10 to 500 µm.