JP2020158568A - Friction member, friction material composition, friction material and automobile - Google Patents

Abstract

To provide a friction material composition that can exhibit an excellent wear resistance when high speed braking is repeated, in a friction material composition that does not contain copper or contains a slight amount of copper, a friction member and a friction material which use the friction material composition, and an automobile equipped with the friction member or the friction material.SOLUTION: A friction member having a friction material and a back metal, in which the friction material contains magnesium oxide and titanate, and does not contain copper, or, even if containing copper, contains smaller than 0.5 mass% as a copper element, and the magnesium oxide has a maximum primary particle size of 50 μm or larger.SELECTED DRAWING: None

Description

The present invention relates to friction members, friction material compositions, friction materials and vehicles.

Generally, brakes installed in automobiles and the like are roughly classified into disc brakes and drum brakes. In the disc brake, a disc rotor that rotates integrally with the wheels during traveling is sandwiched between brake pads, and a braking force is generated by the frictional force generated at that time. A drum brake is, for example, a drum brake in which a brake lining (also called a brake shoe) is mounted inside a drum installed inside a wheel, and the braking force is exerted by crimping the brake lining from the inside to the outside. Is.
A friction material is provided on the brake pad of the disc brake (hereinafter referred to as the disc brake pad) and the brake lining of the drum brake (hereinafter referred to as the drum brake lining), and the friction material is a disc rotor, a drum, or the like. Braking is performed by rubbing against the facing material and converting the kinetic energy of the automobile or the like into heat energy. Therefore, the friction material is required to have a good friction coefficient, wear resistance (the life of the friction material is long), strength, vibration damping property (the brake squeal is unlikely to occur), and the like.

Currently, non-asbestos friction materials (hereinafter sometimes abbreviated as NAO materials) are the mainstream as friction materials, and copper (including copper alloys) and the like have been used for these NAO materials. .. However, it is suggested that the friction material containing copper contains a large amount of copper in the wear powder generated by braking, which causes pollution of rivers, lakes, the ocean, and the like. Therefore, in some parts of North America, a law was enacted prohibiting the sale of friction materials containing 5% by mass or more of copper after 2021 and 0.5% by mass or more of copper after 2023 and the installation in new cars. .. Therefore, in order to make a friction material that can be used in other countries such as the United States, it is required that it does not contain copper or that the copper content is significantly reduced.
Under such circumstances, friction materials containing no copper or having a low copper content have begun to be proposed (see, for example, Patent Document 1). The invention described in Patent Document 1 is a friction material composition containing a binder, an organic filler, an inorganic filler, and a fiber base material, and does not contain copper as an element or has a copper content of 0. It does not exceed 5% by mass, contains potassium titanate, and further contains at least one of lithium titanate and magnesium titanate, and among the potassium titanate, the lithium potassium titanate, and the potassium magnesium titanate. A friction material composition having a total of at least one type of 10 to 35% by mass and a mass reduction rate of 5 to 20% when heated at 500 ° C. in an air atmosphere. The invention described in Patent Document 1 is a transfer film (a film in which a friction material composition is transferred to the surface of a disc rotor) which is stable during light load braking while having a composition having a low environmental load and harm to the human body. It has been achieved as an object to provide a friction material composition which forms a friction material and gives a friction material which exhibits a stable friction coefficient.

JP-A-2017-002186

However, in the invention described in Patent Document 1, a stable transfer film is formed during "light load braking" and a stable coefficient of friction is exhibited, but excellent wear resistance is exhibited during "repeated high-speed braking". It is not an issue to do, and the solution to the issue is unknown.
In the conventional friction material containing copper, a copper spreading film is formed at the friction interface by braking, and the spreading film has an effect of preventing the friction material from being excessively worn when braking from a high speed state. .. However, with a friction material that does not contain copper or has a low copper content, the effect of copper cannot be substantially obtained. Therefore, in a friction material that does not contain copper or has a low copper content, " A method of exhibiting excellent abrasion resistance during repeated high-speed braking is desired.

Therefore, an object of the present invention is to provide a friction material composition which does not contain copper or has a low copper content and which can exhibit excellent wear resistance when high-speed braking is repeated. An object of the present invention is to provide a friction member and a friction material using the friction material composition, and to provide the friction member or a vehicle equipped with the friction material.

As a result of diligent research to solve the above problems, the present inventor has been excellent in repeating high-speed braking by using a friction material composition containing titanate and magnesium oxide having a predetermined size. We have found that abrasion resistance is exhibited, and have completed the present invention. The present invention has been completed based on such findings.

The present invention relates to the following [1] to [15].
[1] A friction member having a friction material and a back metal.
The friction material contains magnesium oxide and titanate, and does not contain copper, or even if it contains copper, the content of copper is less than 0.5% by mass as a copper element.
A friction member having a maximum primary particle size of magnesium oxide of 50 μm or more.
[2] The friction member according to the above [1], wherein the content of magnesium oxide in the friction material is 5 to 45% by mass.
[3] The friction member according to the above [1] or [2], wherein the content of the titanate in the friction material is 5 to 35% by mass.
[4] Any of the above [1] to [3], wherein the titanate is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, magnesium magnesium titanate and sodium titanate. The friction member described in.
[5] The friction material further contains at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the magnesium oxide and the titanate), a fiber base material and a binder. The friction member according to any one of [1] to [4].
[6] The friction member according to any one of [1] to [5] above, which is used for disc brake pads or drum brake linings.
[7] A vehicle equipped with the friction member according to any one of the above [1] to [6].
[8] A friction material composition containing magnesium oxide and titanate.
It does not contain copper, or even if it does, the copper content is less than 0.5% by mass as a copper element.
A friction material composition having a maximum primary particle size of magnesium oxide of 50 μm or more.
[9] The friction material composition according to the above [8], wherein the magnesium oxide content is 5 to 45% by mass.
[10] The friction material composition according to the above [8] or [9], wherein the content of the titanate is 5 to 35% by mass.
[11] Any of the above [8] to [10], wherein the titanate is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, magnesium magnesium titanate and sodium titanate. The friction material composition according to.
[12] Further, the above [8] to [12], further containing at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the magnesium oxide and the titanate), a fiber base material and a binder. 11] The friction material composition according to any one of.
[13] The friction material composition according to any one of the above [8] to [12], which is used for disc brake pads or drum brake linings.
[14] A friction material containing the friction material composition according to any one of the above [8] to [13].
[15] A vehicle equipped with the friction material according to the above [14].

A friction material composition that can exhibit excellent wear resistance when high-speed braking is repeated in a friction material that does not contain copper or has a low copper content, and high-speed braking using the friction material composition. It is possible to provide a friction member and a friction material having excellent wear resistance during repetition. Further, it is possible to provide the friction member or a vehicle equipped with the friction material.
When the friction material of the present invention is used as a friction material for disc brake pads, drum brake linings, etc., it has a low environmental load and is less harmful to the human body.

It is a schematic diagram which shows one aspect of the friction member. It is an SEM photograph of the (ii) 100 mesh pass product of magnesium oxide used in Example 1. It is another SEM photograph of the (ii) 100 mesh pass product of magnesium oxide used in Example 1. It is an SEM photograph of the (iii) 100-200 mesh product of magnesium oxide used in Example 2. It is an SEM photograph of the (iv) 32-100 mesh product of magnesium oxide used in Example 3.

Hereinafter, the present invention will be described in detail. However, in the following embodiments, the components are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.
In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. Further, the lower limit value and the upper limit value of the numerical range are arbitrarily combined with the lower limit value or the upper limit value of the other numerical range, respectively. Further, in the present specification, the content of each component in the friction material composition is the plurality of substances existing in the friction material composition when a plurality of substances corresponding to the respective components are present, unless otherwise specified. Means the total content of the species substance.
Further, in the present invention, "substantially 0% by mass" and "substantially free of ~ ~" are 0% by mass and have a content to the extent that there is essentially no meaning in containing them. (For example, 0.1% by mass or less, 0.05% by mass or less, etc.) is also included.
As used herein, the term "high speed" refers to a speed of 100 km / h or more (for example, 100 to 200 km / h).
The present invention also includes aspects in which the items described in the present specification are arbitrarily combined.

[Friction member]
The friction member according to one aspect of the present invention is a friction member having a friction material and a back metal.
The friction material contains magnesium oxide and titanate, and does not contain copper, or even if it contains copper, the content of copper is less than 0.5% by mass as a copper element.
It is a friction member having a maximum primary particle size of magnesium oxide of 50 μm or more.
Hereinafter, the material (friction material composition) used for the friction material will be described in detail. Each component in the friction material composition and its content are the same as each component in the friction material and its content.

[Friction material composition]
The friction material composition according to one aspect of the present invention contains magnesium oxide and titanate, and does not contain copper, or even if it contains copper, the content of copper is 0.5% by mass as a copper element. A friction material composition having a maximum primary particle size of less than 50 μm and having a maximum primary particle size of 50 μm or more.
A preferred embodiment of the friction material composition consists of the magnesium oxide and the titanate, as well as an organic filler, an inorganic filler (excluding the magnesium oxide and the titaniumate), a fiber substrate and a binder. A friction material composition containing at least one selected. A more preferred embodiment is a friction material composition containing the magnesium oxide and the titanate, as well as an organic filler, an inorganic filler (excluding the magnesium oxide and the titaniumate), a fiber base material and a binder. ..

The friction material composition preferably does not contain copper, and when copper is contained, the content of copper in the friction material composition is set to less than 0.5% by mass as a copper element, so that it can be used as abrasion powder in the environment. Even if it is released, it can be considered not to cause pollution of rivers and the like. The copper content indicates the content of copper element (Cu) contained in fibrous and powdery copper, copper alloys and copper compounds in the entire friction material composition. The content of copper in the friction material composition is more preferably 0.2% by mass or less, and further preferably 0.05% by mass or less as a copper element.

Further, from the viewpoint of avoiding deterioration of durability due to rust, it is preferable that the friction material composition of the present invention does not contain an iron-based metal, but even if an iron-based metal is contained, the friction material composition contains the iron-based metal. By setting the content of the iron-based metal to less than 0.5% by mass as the iron element, the rust resistance can be improved. The content of the iron-based metal in the friction material composition is more preferably 0.2% by mass or less, and further preferably 0.05% by mass or less as the iron element. Here, the iron-based metal is a metal containing iron as a main component and refers to general steel, and the iron content is that of iron, an iron element (Fe) contained in an iron alloy and an iron compound. The content in the entire friction material composition is shown.

The friction material composition of the present invention is classified as a NAO (Non-Asbestos-Organic) material, and is a so-called non-asbestos friction material composition (a friction material composition that does not contain asbestos, or when it is contained). Even if there is, it is a friction material composition with a very small amount of asbestos). The content of asbestos in the friction material composition is 0.2% by mass or less, which is substantially 0% by mass.

(Magnesium oxide, titanate)
The friction material composition contains titanate as well as magnesium oxide.
In the present invention, magnesium oxide having a maximum primary particle size of 50 μm or more is used as the magnesium oxide. When the maximum primary particle size of magnesium oxide is 50 μm or more, excellent wear resistance can be obtained when high-speed braking is repeated. From the same viewpoint, the maximum primary particle size of magnesium oxide is preferably 70 μm or more, more preferably 90 μm or more, still more preferably 100 μm or more, particularly preferably 130 μm or more, and most preferably 200 μm or more. The upper limit of the maximum primary particle size of magnesium oxide is not particularly limited, but is usually 1,000 μm or less, 700 μm or less, 500 μm or less, 400 μm or less, 250 μm or less. It may be as follows.

The maximum primary particle size of magnesium oxide may satisfy the above conditions, but from the viewpoint of excellent wear resistance during repeated high-speed braking, the average particle size is preferably 8 to 500 μm, and 15 to 500 μm. It is more preferably 30 to 500 μm, particularly preferably 30 to 200 μm, and most preferably 50 to 150 μm.
In the present specification, the average particle size means the value of d50 (median diameter of volume distribution, cumulative median value) measured by the method of laser diffraction particle size distribution measurement, and the same applies hereinafter.

As magnesium oxide, magnesium oxide having a particle size in a specific range can be used by using magnesium oxide that has passed through a sieve. For example, magnesium oxide (330 mesh pass product) that has passed through a 330 mesh sieve tends to be substantially free of magnesium oxide having a primary particle diameter of 50 μm or more, and is substantially free of magnesium oxide having a primary particle diameter of 50 μm or more. It is preferable that it is not included.
Magnesium oxide (200-mesh pass product) that has passed through a sieve of 200 mesh or less has a primary particle size of 50 μm or more. In particular, magnesium oxide (100-mesh pass product) that has passed through a 100-mesh sieve tends to have a primary particle diameter of 50 μm or more, 100 μm or more, and even 200 μm or more. On the other hand, for example, those that did not pass through the 200 mesh sieve tend to be difficult to include those having a diameter of 70 μm or less (particularly those having a diameter of 50 μm or less), and those that did not pass through the 100 mesh sieve have a thickness of 100 μm or less. (Especially those of 70 μm or less and those of 50 μm or less) tend to be difficult to be included.
In the present invention, magnesium oxide that has passed through a sieve of 200 mesh or less is preferable from the viewpoint of excellent wear resistance during repeated high-speed braking, and further, from the viewpoint of suppressing wear of the disc rotor, which is an object of friction, 100 Magnesium oxide that passed through a mesh sieve (100 mesh pass product), magnesium oxide that passed through a 100 mesh sieve but did not pass through a 200 mesh sieve (100-200 mesh product), passed through a 32 mesh sieve but 100 Magnesium oxide (32-100 mesh product) that did not pass through the mesh sieve is more preferable, magnesium oxide that has passed through the 100 mesh sieve (100 mesh pass product), and passed through the 100 mesh sieve but through the 200 mesh sieve. Magnesium oxide (100-200 mesh product) that was not used is more preferable.

The content of magnesium oxide is not particularly limited, but if it is contained in the friction material composition in an amount of 5% by mass or more, the friction material tends to have an excellent coefficient of friction and wear resistance during repeated high-speed braking, which is preferable. .. In addition, wear of the disc rotor or drum, which is an object of friction during high-speed braking, tends to be easily suppressed. Further, it also contributes to the reduction of the specific gravity of the friction material composition, which leads to the weight reduction of the friction material. When the content of magnesium oxide is 45% by mass or less in the friction material composition, the friction object (for example, a disc rotor) tends not to be excessively worn. From the same viewpoint, the content of magnesium oxide in the friction material composition is preferably 5 to 45% by mass, more preferably 10 to 40% by mass, still more preferably 10 to 35% by mass, and particularly preferably 15 to 30%. It is mass%.

As described above, in the conventional copper-containing friction material, a copper spreading film is formed at the friction interface by braking, and the spreading film prevents the friction material from being excessively worn when braking from a high speed state. Although there was an effect, the effect of copper cannot be substantially obtained with a friction material that does not contain copper or has a low copper content. As a method of developing excellent wear resistance during "repeated high-speed braking" in a friction material that does not contain copper or has a low copper content, the present inventor first considers heat before examining the present invention. A method of adding a large amount of highly conductive graphite to the friction material was investigated. With this method, since thermal conductivity is imparted to the friction material, the heat at the friction interface is quickly diffused, which leads to suppression of deterioration of the resin component in the friction material and improves wear resistance. This is because I thought it might be there. However, probably because the cohesive force of the friction material composition was lowered by adding a large amount of graphite, the friction coefficient was lowered by the method of simply adding a large amount of graphite. In this way, it is not easy to develop excellent wear resistance during "repeated high-speed braking" while having a stable friction coefficient in a friction material that does not contain copper or has a low copper content. Absent. However, according to the present invention, the above effect is exhibited even in a friction material that does not contain copper or has a low copper content.

When the friction material composition does not contain titanium salt, a film is not formed at the friction interface, the friction coefficient becomes unstable, and the amount of wear increases. The content of titanate in the friction material composition is preferably 5 to 35% by mass, more preferably 8 to 30% by mass, still more preferably 10 to 30% by mass, particularly preferably 10 to 25% by mass, most preferably. Is 12 to 20% by mass. By setting the content of the titanate to 5% by mass or more, the stability of the friction coefficient during repeated high-speed braking tends to be further improved. On the other hand, when the content is 35% by mass or less, the decrease in mechanical strength and wear resistance of the friction material is suppressed, the decrease in the stability of the friction coefficient due to moisture absorption is suppressed, and the friction material and the friction target are suppressed. There is a tendency that sticking due to rust between objects is suppressed.

The titanate is not particularly limited, and examples thereof include potassium titanate, lithium potassium titanate, magnesium magnesium titanate, and sodium titanate.
One of these may be used alone, or two or more thereof may be used in combination. Of these, potassium titanate is preferable from the viewpoint of wear resistance during repeated high-speed braking.

The shape of the titanate is not particularly limited, and examples thereof include fibrous, columnar, plate-like, particulate, and scaly shapes. The shape of the titanate can be analyzed, for example, by observation with a scanning electron microscope (SEM).
The titanate is not particularly limited, but for example, a titanate having an average particle diameter of 1 to 50 μm and a specific surface area of 0.5 to 10 m ² / g can be used. The specific surface area can be determined by a BET method or the like using nitrogen gas as the adsorbed gas.

Hereinafter, each component that may be further contained in the friction material composition will be described in order.
(Organic filler)
The organic filler can exhibit a function as a friction modifier for improving vibration damping property, wear resistance and the like. Here, in the present invention, the organic filler does not include those having a fiber shape (for example, organic fibers described later). As the organic filler, one type may be used alone, or two or more types may be used in combination.
As the organic filler, an organic filler generally used in a friction material composition can be used, and examples thereof include cashew particles, rubber, and melamine particles. Among these, cashew particles and rubber are preferable from the viewpoint of improving the stability and abrasion resistance of the friction coefficient and suppressing squeal.
Further, as the organic filler, cashew particles and rubber may be used in combination, or cashew particles coated with rubber may be used.

The cashew particles are obtained by crushing a cured cashew nut shell oil, and are also generally referred to as cashew dust.
Cashew particles are generally classified into brown-based, brown-black-based, black-based, and the like according to the type of curing agent used in the curing reaction. By adjusting the molecular weight and the like of the cashew particles, it is possible to easily control the heat resistance, the sound vibration property, and the film forming property on the disc rotor which is the object of friction.
From the viewpoint of dispersibility, the average particle size of the cashew particles is preferably 850 μm or less, more preferably 750 μm or less, and further preferably 600 μm or less. The lower limit of the average particle size of the cashew particles is not particularly limited, and may be 200 μm or more, 300 μm or more, or 400 μm or more.
Commercially available products can be used as the cashew particles.
One type of cashew particles may be used alone, or two or more types may be used in combination.

When the friction material composition contains an organic filler, the content thereof is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and further preferably 5 to 15% by mass with respect to the friction material composition. %. By setting the total content of the organic filler in the above range, the elastic modulus of the friction material tends to be high, and the deterioration of vibration damping property such as squeal and the deterioration of wear resistance tend to be avoided. , Deterioration of heat resistance and decrease in strength due to heat history tend to be avoided.

Examples of the rubber include rubbers usually used in friction material compositions, and examples thereof include natural rubber and synthetic rubber. Examples of the synthetic rubber include acrylonitrile-butadiene rubber (NBR), acrylic rubber, isoprene rubber, and polybutadiene rubber. (BR), styrene-butadiene rubber (SBR), silicone rubber, crushed powder of tire tread rubber and the like. One of these may be used alone, or two or more thereof may be used in combination. Among these, pulverized powder of acrylonitrile-butadiene rubber (NBR) and tire tread rubber is preferable from the viewpoint of balance between heat resistance, flexibility and manufacturing cost.
When the rubber is contained, the content thereof is preferably 1 to 30% by mass, more preferably 2 to 15% by mass, and 2 to 8% by mass with respect to the friction material composition. Is even more preferable. By setting the rubber content in the above range, the elastic modulus of the friction material tends to be high, and it is possible to avoid deterioration of vibration damping properties such as squealing, and deterioration of heat resistance and heat resistance. There is a tendency to avoid a decrease in strength due to heat history.

(Inorganic filler)
The friction material composition may contain an inorganic filler. However, the inorganic filler does not contain the magnesium oxide and the titanate to avoid duplication.
The inorganic filler can exhibit a function as a friction adjusting material for avoiding deterioration of heat resistance, wear resistance, stability of friction coefficient and the like of the friction material. Here, in the present invention, the inorganic filler does not include those having a fiber shape (for example, inorganic fibers described later). As the inorganic filler, one type may be used alone, or two or more types may be used in combination.
The inorganic filler is not particularly limited, and an inorganic filler usually used as a friction material can be used. Examples of the inorganic filler include metal sulfides such as antimony trisulfide, tin sulfide, molybdenum disulfide, bismuth sulfide, and zinc sulfide; mica, graphite, coke, calcium hydroxide, calcium oxide, sodium carbonate, calcium carbonate, and carbon dioxide. Magnesium, barium sulfate, dolomite, coke, mica, vermiculite, calcium sulfate, talc, clay, zeolite, zirconium silicate (zircone), zirconia, mullite, chromate, titanium oxide, silica, triiron tetroxide, zinc oxide, garnet, Alumina, silicon carbide; metal powders such as iron powder, cast iron powder, aluminum powder, nickel powder, tin powder, zinc powder, and alloy powder containing at least one of the metals. Although not particularly limited, the inorganic filler preferably does not contain copper, and more preferably does not contain copper or an iron-based metal, from the viewpoint of reducing environmental load and harmfulness to the human body. Among these, at least one selected from the group consisting of metal sulfide, graphite, calcium hydroxide, barium sulfate, zircon, alumina and zinc powder is preferable, and metal sulfide, graphite, calcium hydroxide, barium sulfate and zircon are preferable. , Alumina and zinc powder are more preferable in combination.

Of the above-mentioned inorganic fillers, calcium hydroxide, calcium oxide, sodium carbonate and zinc oxide are preferable from the viewpoint of suppressing the generation of rust on the friction material. However, calcium hydroxide, calcium oxide, and sodium carbonate increase the pH of the friction material, and the aramid fiber tends to be easily decomposed. Therefore, when used together with the aramid fiber, the amount used should not be too high. For example, when calcium hydroxide is contained as an inorganic filler, the content of calcium hydroxide is preferably 0.5 to 10% by mass, more preferably 0.5 to 10% by mass, based on the friction material composition. It is 1 to 8% by mass, more preferably 1 to 5% by mass.

The graphite is not particularly limited, and any known graphite, that is, natural graphite or artificial graphite can be used. The average particle size of graphite is preferably 1 to 50 μm, more preferably 2 to 40 μm, further preferably 5 to 30 μm, and particularly preferably 10 to 20 μm.
When the friction material composition contains graphite, the content thereof is preferably 2 to 20% by mass, more preferably 3 to 15% by mass, still more preferably 3 to 10% by mass, based on the friction material composition. Particularly preferably, it is 3 to 8% by mass. If it is 2% by mass or more, the thermal conductivity of the friction material can be easily improved, and if it is 20% by mass or less, the decrease in the cohesive force of the friction material composition can be suppressed, and the decrease in the friction coefficient tends to be easily suppressed. is there.

When the friction material composition contains zinc (zinc powder), the content thereof is preferably 0.5 to 10% by mass, more preferably 0.5 to 8% by mass, and further, based on the friction material composition. It is preferably 1 to 6% by mass. Since zinc is more easily oxidized than iron, it is possible to suppress the occurrence of rust within the above range without affecting the friction characteristics.
When the friction material composition contains alumina, the content thereof is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and further preferably 0. It is 5 to 3% by mass. Within the above range, it is possible to impart appropriate grindability without excessively wearing the friction object (for example, a disc rotor).
When the friction material composition contains zirconium silicate (zircon), the content thereof is preferably 1 to 15% by mass, more preferably 1 to 10% by mass, still more preferably 3 with respect to the friction material composition. ~ 8% by mass. Within the above range, it is possible to impart appropriate grindability without excessively wearing the friction object (for example, a disc rotor).
When the friction material composition contains tin sulfide, the content thereof is preferably 1 to 15% by mass, more preferably 1 to 10% by mass, and further preferably 3 to 8% by mass with respect to the friction material composition. Is. Within the above range, lubricity can be imparted without lowering the friction coefficient too much.
The friction material composition of the present invention does not have to contain zirconium oxide from the viewpoint of weight reduction and manufacturing cost, and even if it is contained, the content thereof is preferably relative to the friction material composition. It is 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less.
Barium sulfate serves as a mere filler for adjusting the volume of the friction material composition. That is, the content of barium sulfate depends on the content of other components, and the balance for adjusting the friction material composition to a predetermined amount can be replenished with barium sulfate.

As described above, when the friction material composition contains an inorganic filler, the total content of the inorganic filler, the magnesium oxide and the titanate is preferably 40 to 40 to the friction material composition. It is preferable to adjust the content to 85% by mass, more preferably 50 to 85% by mass, and even more preferably 60 to 85% by mass. Within this range, deterioration of heat resistance tends to be easily avoided.

(Fiber base material; organic fiber and inorganic fiber)
The fiber base material exhibits a reinforcing action in the friction material. The friction material composition preferably contains organic fibers as a fiber base material, and preferably contains inorganic fibers. As the fiber base material, one type may be used alone, or two or more types may be used in combination. Here, the organic fiber is a fibrous material containing an organic substance as a main component. The inorganic fiber is a fibrous material containing an inorganic substance other than a metal or a metal alloy as a main component.

-Organic fiber-
Examples of the organic fiber include hemp, cotton, aramid fiber, cellulose fiber, acrylic fiber, phenol resin fiber (having a crosslinked structure) and the like. One type of organic fiber may be used alone, or two or more types may be used in combination. As the organic fiber, an aramid fiber is preferable from the viewpoint of heat resistance. Further, from the viewpoint of improving the strength of the friction material, it is preferable to contain the fibrillated organic fiber as the organic fiber, and it is more preferable to contain the fibrillated aramid fiber. The fibrillated organic fiber is a fibrillated and fluffy organic fiber, and fibrillated aramid fiber, fibrillated acrylic fiber, fibrillated cellulose fiber and the like are commercially available. Needless to say, the friction material composition may contain other organic fibers together with the fibrillated organic fibers.
When the friction material composition contains organic fibers, particularly fibrillated organic fibers, the content thereof is preferably 1 to 8% by mass, preferably 2 to 7% by mass, based on the friction material composition. More preferably, it is 2 to 5% by mass. If it is 1% by mass or more, good shear strength, crack resistance and abrasion resistance tend to be exhibited, and if it is 8% by mass or less, it is different from the organic fiber (fibrillated organic fiber) in the friction material composition. There is a tendency that deterioration of shear strength and crack resistance due to uneven distribution of other materials can be effectively suppressed.

-Inorganic fiber-
Inorganic fibers can exhibit the effect of improving the mechanical strength and abrasion resistance of the friction material.
Examples of the inorganic fiber include glass fiber, metal fiber, mineral fiber, carbon fiber, ceramic fiber, biodegradable ceramic fiber, sepiolite (α-type sepiolite and β-type sepiolite), attapulsite, potassium titanate fiber, silica alumina fiber, and the like. At least one selected from the group consisting of flame-resistant fibers and the like can be used.

The glass fiber refers to a fiber produced by melting and spinning glass. As the glass fiber, those whose raw materials are E glass, C glass, S glass, D glass and the like can be used, and among these, glass containing E glass or S glass from the viewpoint of particularly high strength. It is preferable to use fiber. Further, in order to improve the affinity with the binder, the glass fiber whose surface is treated with aminosilane, epoxysilane or the like is preferable.

Examples of the metal fiber include fibers in the form of simple substances or alloys of metals such as aluminum, iron, zinc, tin, titanium, nickel and magnesium, and fibers containing a metal such as cast iron as a main component. Examples of alloy fibers (alloy fibers) include iron alloy fibers and aluminum alloy fibers. One type of metal fiber may be used alone, or two or more types may be used in combination. In the present invention, the friction material composition may not contain metal fibers.
From the viewpoint of improving crack resistance and abrasion resistance, copper fibers, copper alloy fibers, iron fibers and iron alloy fibers are generally preferred.
However, when copper or a copper alloy fiber is contained, the content of copper in the friction material composition is preferably less than 0.5% by mass, more preferably 0.3% by mass, as a copper element for the above-mentioned reasons. Hereinafter, the embodiment is more preferably 0.1% by mass or less, and particularly preferably substantially free of copper. Examples of the copper alloy fiber include copper fiber, brass fiber, bronze fiber and the like.
Further, when iron fiber or iron alloy fiber is contained, the content of iron in the friction material composition may be less than 0.5% by mass as an iron element from the viewpoint of suppressing deterioration of durability due to rust. It is preferably 0.3% by mass or less, more preferably 0.1% by mass or less, and particularly preferably substantially iron-free.

Examples of the mineral fiber include natural mineral fiber; blast furnace slag such as slag wool, basalt such as basalt fiber, and artificial mineral fiber melt-spun with other natural rocks as main components. Examples of the artificial mineral fiber include artificial mineral fiber containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, FeO, Na ₂ O and the like, or artificial mineral fiber containing one or more of these compounds. Can be mentioned. As the artificial mineral fiber, an artificial mineral fiber containing an aluminum element is preferable, an artificial mineral fiber containing Al ₂ O ₃ is more preferable, and an artificial mineral fiber containing Al ₂ O ₃ and SiO ₂ is further preferable.

The mineral fiber is preferably biosoluble from the viewpoint of harmfulness to the human body. The biosoluble mineral fiber referred to here is a mineral fiber having a characteristic that it is partially decomposed in a short time and discharged to the outside of the body even when it is taken into the human body. Specifically, the chemical composition is such that the total amount of alkali oxides and alkaline earth oxides (total amount of oxides of sodium, potassium, calcium, magnesium and barium) is 18% by mass or more, and (a) short-term inhalation. In vivo endurance test by exposure, the half-life of fibers over 20 μm in length is less than 10 days, (b) In-vivo endurance test by short-term intratracheal injection, half-life of fibers over 20 μm in length Is less than 40 days, (c) no significant carcinogenicity in the intraperitoneal administration test, or (d) no pathological findings or tumorigenesis associated with carcinogenicity in the long-term inhalation exposure test. A fiber satisfying any of the above (see Nota Q (exclusion of carcinogenicity) of EU Directive 97/69 / EC) is shown. Examples of such biodegradable mineral fibers include SiO _2- Al ₂ O ₃ -CaO-MgO-FeO (-K ₂ O-Na ₂ O) -based fibers, which include SiO ₂ , Al ₂ O ₃ , and CaO. , MgO, FeO, include mineral fibers containing at least two kinds in any combination is selected from _{K 2} O and Na ₂ O or the like. Examples of commercially available products include the Rolex series manufactured by LAPINUS FIBERS BV. “Roxul” includes SiO ₂ , Al ₂ O ₃ , CaO, MgO, FeO and the like, and may further include at least one selected from the group consisting of K ₂ O and Na ₂ O.

Examples of the carbon fiber include flame-resistant fiber, pitch-based carbon fiber, PAN-based carbon fiber, activated carbon fiber and the like. One type of carbon fiber may be used alone, or two or more types may be used in combination.

When the friction material composition contains a fiber base material, the content thereof is preferably 3 to 50% by mass, more preferably 3 to 30% by mass, and further preferably 3 to 20% by mass with respect to the friction material composition. %, Especially preferably 5 to 15% by mass. By setting the content of the fiber base material in the above range, the optimum porosity as a friction material can be obtained, squeal can be prevented, appropriate material strength can be obtained, wear resistance is improved, and moldability is further improved. It tends to be improved.

(Binder)
The binder has a function of binding and integrating an organic filler, an inorganic filler, a fiber base material, and the like to give a predetermined shape and strength. The binder contained in the friction material composition is not particularly limited, but a thermosetting resin generally used as a binder for the friction material can be used.
Examples of the thermosetting resin include phenol resin, modified phenol resin, elastomer-dispersed phenol resin, epoxy resin, polyimide resin, melamine resin and the like. Here, examples of the modified phenol resin include acrylic modified phenol resin, silicone modified phenol resin, cashew modified phenol resin, epoxy modified phenol resin, alkylbenzene modified phenol resin and the like. Examples of the elastomer-dispersed phenolic resin include acrylic elastomer-dispersed phenolic resin and silicone elastomer-dispersed phenolic resin.
In particular, phenolic resin, acrylic-modified phenolic resin, silicone-modified phenolic resin, and alkylbenzene-modified phenolic resin are preferable, and phenolic resin is more preferable, because they provide good heat resistance, moldability, and friction coefficient.
One type of thermosetting resin may be used alone, or two or more types may be used in combination.

When the friction material composition contains a binder, the content thereof is preferably 5 to 25% by mass, more preferably 5 to 20% by mass, still more preferably 6 to 18% by mass, based on the friction material composition. , Particularly preferably 6 to 13% by mass. By setting the content of the binder in the above range, the strength of the friction material is maintained, and the deterioration of vibration damping property such as squeal due to the high elastic modulus tends to be more easily suppressed.

(Other materials)
In addition to the above-mentioned materials, other materials may be added to the friction material composition, if necessary.
Examples of other materials include organic additives such as fluorine-based polymers such as polytetrafluoroethylene (PTFE) from the viewpoint of improving wear resistance and heat fade characteristics.
When the friction material composition contains the above-mentioned other materials, the total amount of the organic filler, the inorganic filler (including the magnesium oxide and the titanate), the fiber base material and the binder is 100. It is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, further preferably 5 parts by mass or less, particularly preferably 3 parts by mass or less, and may not contain other materials. ..

[Friction material]
The present invention also provides a friction material containing the friction material composition. The friction material may be formed only from the friction material composition of the present invention, or is a friction material having an upholstery material and an underlay material, and at least one of the upholstery material and the underlay material has the friction. It may be a friction material formed from a material composition. When the friction material is a friction material having an upholstery material and an underlaying material, the friction material composition of the present invention is preferably used for the upholstery material. The friction material having the upholstery material and the underlay material will be described with reference to FIG. 1. Since the friction material composition of the present invention exhibits excellent wear resistance when high-speed braking is repeated, the friction material is on the friction member. It is preferable to use it as the upholstery material 1. The upholstery material 1 is a friction material that serves as a friction surface of the friction member, and the underlay material 2 is a shear strength in the vicinity of the adhesive portion between the friction material and the back metal, which is interposed between the upholstery material 1 and the back metal 3. It is a layer for the purpose of improving crack resistance.

The friction material can be produced, preferably by molding the friction material composition by heat and pressure molding.
As for the friction material having the upholstery material and the underlaying material, the friction material composition for the upholstery material and the friction material composition for the underlaying material are separately separated from each other, and the radige mixer (“Radige” is a registered trademark). Mix using a mixer such as a pressurized kneader and an Erich mixer (“Erich” is a registered trademark), and premold the mixture for the upholstery material and the mixture for the underlaying material integrally with a molding die, and then premold. The obtained premolded product is molded in, for example, a molding temperature of 130 to 160 ° C. and a molding pressure of 20 to 50 MPa in 2 to 10 minutes, and the obtained molded product is heat-treated at, for example, 150 to 250 ° C. for 2 to 10 hours. Manufactured in. Further, if necessary, painting, scorch treatment, and polishing treatment may be performed. In the above steps, the preforming step may be omitted and the mixture may be directly thermoformed.

The friction material can be used as a friction material for disc brake pads of automobiles and the like, and as a friction material for drum brake linings of automobiles and the like. Further, by performing steps such as molding, processing, and pasting the friction material composition into a target shape, it can also be used as a friction material for clutch facing, electromagnetic brake, holding brake, and the like.
The friction material of the present invention exhibits excellent wear resistance when high-speed braking is repeated, and is therefore suitable as a friction material for automobiles, particularly for automobiles.

The back metal is usually used as a friction member in order to improve the mechanical strength of the friction member, and a metal, fiber reinforced plastic, or the like can be used as the material. Examples of the backing metal include iron, stainless steel, inorganic fiber reinforced plastic, carbon fiber reinforced plastic and the like. The primer layer and the adhesive layer may be those usually used for friction members such as brake pads and brake linings.

In the present invention, with respect to the friction member 6 in FIG. 1, it is also possible to provide a friction member having a shim 4 on the side of the back metal 3 opposite to the side having the underlaying material 2. The shim 4 is a spacer generally used for improving the vibration damping property of the friction member.

[car]
The present invention also provides a vehicle equipped with the friction material or friction member of the present invention. More specifically, a vehicle mounted as a friction member such as a brake pad or a brake lining is also provided. Examples of the vehicle include various automobiles including motorcycles and motorcycles, such as large automobiles, medium-sized automobiles, ordinary automobiles, large special automobiles, small special automobiles, large motorcycles and ordinary motorcycles.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by these examples.

Each friction material sample of Examples and Comparative Examples was measured according to the following method.
[Measuring method]
(1) Coefficient of friction The coefficient of friction was measured based on the Japanese Automotive Standards Organization "JASO C406", the average value of the coefficient of friction in the second efficacy test was calculated, and evaluated according to the following evaluation criteria. The coefficient of friction was measured for each of the first, fifth, and thirteenth brakes of repeated high-speed braking that decelerates from 150 km / h to 0 km / h at 0.35 m / s ² , and the average value was calculated.
(Evaluation criteria for the average value of the coefficient of friction)
A: The average value is 0.37 or more and less than 0.43.
B: The average value is 0.34 or more and less than 0.37, or 0.43 or more and less than 0.47.
C: The average value is less than 0.34 or 0.47 or more.

(2) Amount of wear (mm) of friction material and disc rotor after repeated high-speed braking
An embossed scale tester was used for the test. Braking to decelerate at 0.35 m / s ² from 150 km / h to 0 km / h was repeated 13 times, and the difference in thickness between the friction material and the disc rotor before and after the test was measured, and the amount of wear of each was determined. A micrometer was used to measure the thickness of the friction material and the disc rotor.

[Making disc brake pads]
In producing the disc brake pad, the following components of the friction material composition were prepared. Each component described in Table 1 is as follows.
(Binder)
・ Phenolic resin (organic filler)
・ NBR: Acrylonitrile-butadiene rubber ・ Crushed powder of tire tread rubber ・ Cashew particles (inorganic filler)
・ Zinc, graphite, alumina, zircon, tin sulfide, barium sulfate, calcium hydroxide, magnesium oxide:
(i) 330 mesh pass product (No particle diameter of 50 μm or more was confirmed)
(ii) 100 mesh pass product [see Figures 2 and 3]
(iii) 100-200 mesh product [see Fig. 4]
(iv) 32-100 mesh product [see Fig. 5]
・ Zirconium oxide ・ Potassium titanate (fiber base material)
・ Aramid fiber: Fibrilized aramid fiber ・ Mineral fiber

[Examples 1 to 3 and Comparative Example 1] (Production of disc brake pads)
Each component was blended according to the blending amount shown in Table 1 to obtain each friction material composition.
This friction material composition was mixed with a Ladyge (registered trademark) mixer (manufactured by Matsubo Co., Ltd., trade name: Ladyge Mixer M20) to obtain a mixture. The obtained mixture was integrally premolded with a molding press (manufactured by Oji Kikai Kogyo Co., Ltd.). The obtained premolded product is heated with an iron backing metal (manufactured by Hitachi Automotive Systems Co., Ltd.) using a molding press (manufactured by Sanki Seiko Co., Ltd.) under the conditions of a molding temperature of 145 ° C., a molding pressure of 35 MPa, and a molding time of 5 minutes. It was pressure molded. The obtained molded product was heat-treated at 200 ° C. for 4.5 hours, polished using a rotary polishing machine, and scorch-treated at 500 ° C. to obtain a disc brake pad. The disc brake pads obtained in Examples and Comparative Examples have a friction material thickness of 9.5 mm.
From the obtained disc brake pads, test pieces having a size of 20 mm × 45 mm square were produced by a cutting machine, and each measurement and evaluation was performed according to the above method. The results are shown in Table 1.

In the embodiment, it can be seen that the friction coefficient of the friction material is excellent even after repeated high-speed braking. Further, in the examples, it can be seen that the wear resistance of the friction material during repeated high-speed braking is excellent and the amount of wear of the disc rotor is small as compared with the comparative example.
In Comparative Example 1, although the friction coefficient of the friction material was excellent, the amount of wear of both the friction material and the disc rotor was large.

The friction member and friction material of the present invention are friction materials that do not contain copper or have a low copper content, have low environmental load and harm to the human body, and have a stable friction coefficient and high-speed braking. It is suitable as a friction member and a friction material for a car because it exhibits excellent wear resistance when the above steps are repeated.

1 Upholstery 2 Underlayment 3 Slush fund 4 Shim 5 Friction material 6 Friction member

Claims (15)

A friction member having a friction material and a back metal,
The friction material contains magnesium oxide and titanate, and does not contain copper, or even if it contains copper, the content of copper is less than 0.5% by mass as a copper element.
A friction member having a maximum primary particle size of magnesium oxide of 50 μm or more. The friction member according to claim 1, wherein the content of magnesium oxide in the friction material is 5 to 45% by mass. The friction member according to claim 1 or 2, wherein the content of the titanate in the friction material is 5 to 35% by mass. The friction according to any one of claims 1 to 3, wherein the titnate is at least one selected from the group consisting of potassium titanate, lithium titanate, magnesium magnesium titanate and sodium titanate. Element. Claims 1 to 1, wherein the friction material further contains at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the magnesium oxide and the titanate), a fiber substrate and a binder. The friction member according to any one of 4. The friction member according to any one of claims 1 to 5, which is for a disc brake pad or a drum brake lining. A vehicle equipped with the friction member according to any one of claims 1 to 6. A friction material composition containing magnesium oxide and titanate.
It does not contain copper, or even if it does, the copper content is less than 0.5% by mass as a copper element.
A friction material composition having a maximum primary particle size of magnesium oxide of 50 μm or more. The friction material composition according to claim 8, wherein the content of magnesium oxide is 5 to 45% by mass. The friction material composition according to claim 8 or 9, wherein the content of the titanate is 5 to 35% by mass. The friction according to any one of claims 8 to 10, wherein the titanate is at least one selected from the group consisting of potassium titanate, lithium titanate, magnesium magnesium titanate and sodium titanate. Material composition. Any one of claims 8 to 11, further comprising at least one selected from the group consisting of an organic filler, an inorganic filler (excluding the magnesium oxide and the titanate), a fiber substrate and a binder. The friction material composition according to the item. The friction material composition according to any one of claims 8 to 12, which is used for disc brake pads or drum brake linings. A friction material containing the friction material composition according to any one of claims 8 to 13. A vehicle equipped with the friction material according to claim 14.