JP2001040332A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a friction material that can exhibit a frictional coefficient and a shearing strength higher than those of the conventional in spite of the use of an organic paper base material. SOLUTION: Provided is a friction material consisting of a paper base material comprising a fibrous material and an organically modified inorganic binder impregnated into the base material, wherein the binder contains at least two metallic elements including at least a tetravalent metallic element, and the metallic elements are bonded to each other through organic chains having a chain length of 0.5-2.5 nm. The material can exhibit improved shearing strength because of its three-dimensional network densified by the organic chains and can exhibit a high frictional coefficient because of its flexibility realized by the organic chains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used for clutch facing of a power transmission system of an automobile, an industrial machine, a railway vehicle, and the like, and a method of manufacturing the same. The friction material of the present invention is particularly useful as a wet friction material used in oil.

[0002]

2. Description of the Related Art Wet clutch facing, etc.
For example, as disclosed in Japanese Patent Publication No. 58-47345, etc., an organic fiber as a base material, various friction modifiers are blended therein, and a binder made of a thermosetting resin such as a phenol resin is impregnated and solidified. Paper-based friction materials are widely used.

However, in the above-mentioned friction material, since both the paper-like base material and the binder are organic,
There is a problem that the heat resistance is low and the friction coefficient is small, and various measures have been taken to solve this problem.

As a countermeasure, for example, in clutch facing, the number of friction plates is increased or the area is increased. However, if you take such measures,
The wet clutch structure is complicated and large-scale, resulting in large energy loss and high cost.

[0005] On the other hand, attempts have been made to apply, for example, a copper-based sintered friction material to a wet clutch. If such a sintered friction material can be used, heat resistance and pressure resistance can be satisfied even if the number of friction plates is small and the area is small, and the above problem can be solved.

Japanese Patent Application Laid-Open No. H7-197016 discloses a wet friction material using a silicone resin having a siloxane bond and an organic group as a binder. Such a silicone resin is flexible and flexible due to a siloxane bond. Therefore, the friction material using the silicone resin as a binder has an increased contact area with a mating material and can secure a high torque capacity. Further, since the distortion characteristics of the friction material become appropriate, the friction coefficient is stabilized.

[0007]

However, many sintered metal-based friction materials often have a friction coefficient smaller than that of organic friction materials, and have a low friction characteristic for a recent high performance automobile wet clutch. It was not enough. Also, JP-A-7-
In the friction material disclosed in 197016 publication, the friction coefficient is
There was a problem that it was too low, less than 0.2, and the abrasion resistance was not sufficient.

The present invention has been made in view of such circumstances, and has as its object to secure a large friction coefficient by using an organic paper-like base material.

[0009]

A feature of the friction material of the present invention that solves the above-mentioned problems is that the friction material comprises a paper-like base made of a fibrous material and an organic-inorganic binder impregnated in the base. The organic-inorganic binder contains at least two kinds of metal elements including at least a tetravalent metal element,
The metal elements are linked together by organic chains having a chain length of 0.5-2.5 nm.

In the above-mentioned friction material of the present invention, it is desirable that the two or more kinds of metal elements contained in the organic-inorganic binder have different valences from each other. Further, as described in claim 3, the organic chain preferably contains a bond or a group selected from an ether bond, a chlorine group, an epoxy group, and an amino group. As described in claim 4, the tetravalent metal element is Desirably, it is silicon. Further, it is desirable that the other metal element other than the tetravalent metal element is aluminum.

Further, in the friction material of the present invention, it is desirable that the organic-inorganic binder is impregnated in the entire friction material by 30 to 45% by weight.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the friction material of the present invention, a fibrous material constituting a paper-like base material is bound by an organic-inorganic binder containing two or more kinds of metal elements including at least a tetravalent metal element. Therefore, an organic-inorganic binder is exposed on the surface of the base material. Therefore, at the time of friction, the friction characteristics of the organic / inorganic binder are developed and the boundary friction coefficient becomes large, so that a larger friction coefficient can be obtained as compared with the case where an organic binder such as a phenol resin is used.

Since two or more metal elements including at least a tetravalent metal element are contained, a higher friction coefficient and higher wear resistance are ensured. Although the reason for this is not clear, other metal elements are introduced into the space mainly composed of one metal element, so that an appropriate twist is generated in the molecule and internal stress occurs. This is considered to increase the skeletal strength of the binder.

In the friction material of the present invention, in the organic-inorganic binder, the metal elements are bonded to each other by an organic chain, and the chain length of the organic chain is 0.5 to 2.5 nm. This results in a friction material having particularly excellent strength such as shear strength. If the chain length of the organic chain is out of this range, the strength is undesirably reduced.

When an organic-inorganic binder in which metal elements are bonded to each other by an organic chain is used, by setting the chain length in an appropriate range as described above, strength such as shear strength is improved. This is considered because the three-dimensional network becomes dense. However, when the three-dimensional network becomes dense, the flexibility of the friction material decreases, and the friction coefficient may decrease.

Therefore, it is desirable that the organic chain binding the metal element contains a bond or a group selected from an ether bond, a chlorine group, an epoxy group and an amino group. Thereby, the flexibility of the friction material is improved, and the friction coefficient can be increased while maintaining high strength. Also in this case, the chain length of the organic chain is desirably 0.5 to 2.5 nm.

It is further desirable that the metal elements containing at least a tetravalent metal element have different valences. That is, for example, it is desirable to include a tetravalent metal element and a trivalent metal element, or to include a tetravalent metal element and a divalent metal element. Thereby, the coefficient of friction is further increased, and the wear resistance is further improved.

It is preferable that the binder contains a silicone resin. By including a soft silicone resin, the flexibility is improved, and the coefficient of friction can be further increased by increasing the contact area. The mixing amount of silicone resin
When the total of the inorganic binder and the silicone resin is 100 parts by weight, the range is preferably 5 to 70 parts by weight. When the amount of silicone resin is larger than this, the coefficient of friction decreases,
If the amount is less than this, the effect of the addition is difficult to be exhibited.

As the tetravalent metal element, silicon (Si),
Titanium (Ti) is exemplified. Examples of the trivalent metal element include aluminum (Al), gallium (Ga), and iron (Fe). As the divalent metal, magnesium (Mg),
Examples include calcium (Ca) and barium (Ba).
In some cases, a monovalent metal element such as potassium (K) and sodium (Na) may be used. 4
If Si is used as the trivalent metal and Al is used as the trivalent metal,
Particularly favorable friction characteristics are obtained.

It is preferable that the trivalent metal element is contained in the range of 0.1 to 5% based on the total number of atoms of the metal element in the binder. Even if the amount of the trivalent metal element is smaller or larger than this range, the wear resistance is reduced. When the content is within this range, the wear resistance is significantly improved.

It is preferable that the divalent metal element is contained in the range of 0.2 to 10% based on the total number of atoms of the metal element in the binder. Even if the amount of the trivalent metal element is smaller or larger than this range, the wear resistance is reduced. When the content is within this range, the wear resistance is significantly improved.

As the organic-inorganic binder, an oxide formed from the above-mentioned metal-substituted alkoxide by an sol-gel method can be used. Further, alkoxides of the above metals may be mixed.

Examples of the fibrous material constituting the paper-like base material include glass fiber, rock wool, potassium titanate fiber, ceramic fiber, silica fiber, silica-alumina fiber, kaolin fiber, bauxite fiber, canonoid fiber, and boron fiber. , Magnesia fiber, inorganic fiber such as metal fiber, linter pulp, wood pulp, synthetic pulp, polyester fiber, polyamide fiber, polyimide fiber, polyvinyl alcohol modified fiber, polyvinyl chloride fiber, polypropylene fiber, polybenzimidazole fiber, One or more organic fibers such as acrylic fibers, carbon fibers, phenol fibers, nylon fibers, and cellulose fibers can be used.

The friction material of the present invention includes, for example, barium sulfate, calcium carbonate, magnesium carbonate, silicon carbide, boron carbide, titanium carbide, silicon nitride, boron nitride,
Various friction modifiers and fillers such as alumina, silica, zirconia, cashew dust, rubber dust, diatomaceous earth, talc, kaolin, magnesium oxide, molybdenum disulfide, nitrile rubber, acrylonitrile / butadiene rubber, styrene butadiene rubber, silicon rubber, fluorine rubber, etc. Agent
One or more of them may be added and mixed in an appropriate amount.

The amount of the organic-inorganic binder impregnated is preferably in the range of 30 to 45% by weight based on the whole friction material. When the impregnation amount of the organic-inorganic binder is too small, the bonding strength of the fibers in the paper-like base material is reduced and the durability is reduced,
If the amount is too large, the friction characteristics deteriorate. Further, by setting the amount of impregnation in this range, the effect of improving the shear strength is also exerted.

In producing the friction material of the present invention, for example, a metal alkoxide and an organic group-substituted metal alkoxide are hydrolyzed to first prepare a sol solution. As metal alkoxides, use alkoxides such as silicon (Si), titanium (Ti), aluminum (Al), gallium (Ga), iron (Fe), magnesium (Mg), calcium (Ca), and barium (Ba). Can be. Further, as the organic group-substituted metal alkoxide, those in which a part of the alkoxyl group of the above-described metal alkoxide is substituted with an alkyl group can be used. Further, it is preferable to use, as the organic group-substituted metal alkoxide, one containing a bond or a group selected from an ether bond, a chlorine group, an epoxy group and an amino group.

In the alkoxide used, at least 4
It includes a metal alkoxide of a valent metal element or a metal alkoxide substituted with an organic group, and desirably further includes a metal alkoxide or a metal alkoxide of an organic group substituted with a different kind of metal element. More preferably, it contains a metal alkoxide of at least a tetravalent metal element or an organic group-substituted metal alkoxide, and desirably further contains a metal alkoxide or an organic group-substituted metal alkoxide of a different valence metal element.

The weight ratio of the metal alkoxide to the organic group-substituted metal alkoxide is preferably in the range of metal alkoxide: organic group-substituted metal alkoxide = 3: 7 to 0:10. If the amount of the metal alkoxide exceeds this range, the flexibility of the friction material decreases, and the friction coefficient decreases due to the decrease in the contact area.

This step can be carried out by adding water to an alcohol solution of at least one of the metal alkoxide and the organic group-substituted metal alkoxide, thereby producing a hydroxide sol solution. Note that it is desirable to improve the reactivity by adding an acid or an alkali or by heating.

In this step, it is desirable that the sol solution further contains a silicone resin containing an organic group in a siloxane skeleton. With this configuration, since a part of the binder of the friction material from which the soft silicone resin is obtained is formed, the flexibility is improved and the friction coefficient can be further increased.

Next, the prepared sol solution is impregnated into a paper-like substrate made of a fibrous material, and an impregnated substrate in which a hydroxide sol is impregnated between fibers is prepared. When using various friction modifiers and the like, they may be mixed in the prepared sol solution, or may be mixed with a fibrous material to form a paper-like base material and contained in the base material. Good. In some cases, after the sol solution is impregnated into the base material, the sol solution may be sprinkled onto the base material surface and adhered.

The paper-like substrate used here is desirably subjected to a hydroxyl group introduction treatment. Due to the introduced hydroxyl groups, the bonding strength between the paper-like base material and the binder is greatly improved, and the friction characteristics are further improved.

As the hydroxyl group introduction treatment, for example, there is a method of treating with an acid. As the acid, any of an inorganic acid and an organic acid can be used, but it is preferable to use an organic acid such as acetic acid and oxalic acid. When an organic acid is used, an acid component remaining at the time of calcination described below is decomposed and disappears, so that the effect on friction characteristics can be ignored.

The acid treatment can be easily carried out by immersing the paper-like substrate in an acid solution or spraying an acid solution on the paper-like substrate to impregnate the paper-like substrate.

Other methods for introducing a hydroxyl group include a method of treating in an alkaline aqueous solution such as an aqueous sodium hydroxide solution, a method of treating in boiling water, and a supercritical steam treatment. Since a hydroxyl group can be introduced into the binder, the bonding strength with the binder is greatly improved, and the friction characteristics are further improved.

When the hydroxyl group introduction treatment is performed on the paper-like base material, the affinity between the metal hydroxide to be formed and the paper-like base material is increased, and the hydroxyl group of the metal hydroxide and the paper-like base material are increased. Are considered to be oriented so as to be close to each other.

Then, by drying and baking the impregnated base material, the hydroxide sol becomes an oxide gel and firmly binds the fibers of the base material. When a large amount of the organic group-substituted metal alkoxide is used, the organic group is oriented so as to be close to the organic fiber of the base material at the time of impregnation, and is more strongly bonded to the organic fiber, so that the strength is further improved. The organic group also has the effect of improving flexibility and increasing the coefficient of friction.

When the hydroxyl group introduction treatment has been performed on the paper-like base material in advance, the metal hydroxide and the fiber are oriented so as to be close to each other, and the oxide gel and the fiber are firmly bonded to each other. improves.

The firing is preferably performed at 150 to 300 ° C. for 0.5 to 1.0 hour. If the firing temperature is lower than this or the firing time is shorter than this, it is difficult to form an oxide gel, and sufficient strength cannot be obtained. On the other hand, if the firing temperature is higher or the firing time is longer than this, organic substances are decomposed and the frictional characteristics are reduced.

The calcination is preferably performed in an atmosphere containing ammonia. Thereby, it is considered that the metal element in the sol is partially nitrided, and the coefficient of friction further increases. The effect can be obtained if a small amount of ammonia is contained, but the maximum effect is obtained if about 10% by volume is contained in the atmospheric air.

The calcination is preferably performed under supercritical conditions.
The supercritical condition is a condition in which the organic matter contained in the base material and the sol is in a state immediately before vaporization, and is a state in which molecular motion is extremely active. The temperature at which the supercritical state is established by pressurization increases, and molecular motion becomes more active. Therefore, high temperature and high pressure conditions are set. In other words, by using high-temperature, high-pressure supercritical conditions, it is possible to improve the reactivity while preventing the decomposition of organic substances, to suppress the remaining unreacted portions, and to stably produce a friction material having a large friction coefficient. Becomes possible.

[0042]

The present invention will be specifically described below with reference to examples and comparative examples.

Comparative Example 1 (1) First Step In a glass container, 27.6 g of ethanol and methyltriethoxy were added.
Silane (CH_ThreeSi (OC_TwoH_Five) _Three) 18g and ethyl acetate
Weigh 0.15 g of Luminium diisopropylate and mix
And stirred for 10 minutes. Then, while stirring this solution
20 g of 0.05N hydrochloric acid aqueous solution was added dropwise, and the mixture was further stirred for 24 hours.
Thus, a sol solution was prepared. (2) Second step A paper-like substrate made of linter pulp is prepared, and the above sol is prepared.
The entire amount of the solution was impregnated to obtain an impregnated substrate. (3) Third step The obtained impregnated base material is dried at room temperature for one hour, and then dried in air.
The wet friction material of Comparative Example 1 was fired at 00 ° C. for 1 hour.
Prepared.

The wet friction material does not contain an organic-inorganic binder in which metal elements are bonded by organic chains.

Comparative Example 2 Methyltriethoxysilane 18
Instead of g, the organic group-substituted metal alkoxide represented by the composition formula of Cl (CH ₂ ) Si (OC ₂ H ₅ ) ₃ is substituted with methyltriethoxysilane at a molar ratio of 0.3 g 18 g A friction material of Comparative Example 2 was prepared in the same manner as in Comparative Example 1 except that No. was used.

The wet friction material contains an organic-inorganic binder in which a metal element is bound by an organic chain, and the chain length of the organic chain is calculated to be 0.18 nm.

Comparative Example 3 Methyltriethoxysilane 18
Instead of g, an organic group-substituted metal alkoxide represented by a composition formula of Cl (CH ₂ ) ₂ Si (OC ₂ H ₅ ) ₃ is substituted with methyltriethoxysilane at a molar ratio of 0.3. A friction material of Comparative Example 3 was prepared in the same manner as Comparative Example 1 except that 18 g was used.

The wet friction material contains an organic-inorganic binder in which a metal element is bound by an organic chain, and the chain length of the organic chain is calculated to be 0.35 nm.

(Examples 1 to 5, Comparative Example 4) Instead of 18 g of methyltriethoxysilane, an organic group-substituted metal alkoxide represented by a composition formula of Cl (CH ₂ ) _n Si (OC ₂ H ₅ ) ₃ was used. Was replaced with methyltriethoxysilane at a molar ratio of 0.3 to obtain 18 g of the friction materials of Examples 1 to 5 and Comparative Example 4 in the same manner as Comparative Example 1.
Examples 1 to 5 and Comparative Example 4 differ in the value of n in the composition formula as shown in Table 1. And Examples 1 to 5
And the wet friction material of Comparative Example 4 contains an organic-inorganic binder in which a metal element is bound by an organic chain, and the chain length of the organic chain is 0.51 to 2.45 nm in Examples 1 to 5, and Comparative Example 4 Is calculated to be 0.35 nm.

Example 6 Methyltriethoxysilane 18
Instead of g, 3 glycidoxypropyltrimethoxysilane is added in a molar ratio of 0.3 to methyltriethoxysilane.
Comparative Example 1 except that 18 g was used instead of
In the same manner as in the above, a friction material of Example 6 was prepared.

The wet friction material contains an organic-inorganic binder in which a metal element is bonded by an organic chain, and the chain length of the organic chain is calculated to be 1.2 nm.

Example 7 Methyltriethoxysilane 18
The friction material of Example 7 was prepared in the same manner as in Comparative Example 1 except that 18 g obtained by substituting 3 aminopropyltrimethoxysilane with methyltriethoxysilane at a molar ratio of 0.3 was used instead of g. Was prepared.

The wet friction material contains an organic-inorganic binder in which a metal element is bonded by an organic chain, and the chain length of the organic chain is calculated to be 0.6 nm.

(Test / Evaluation) The friction coefficient of each of the above wet friction materials in oil at 120 ° C. was measured.
A ferrous material was used as the mating material, with a surface pressure of 10 kg / cm ² and a pressure of 0.
The friction coefficients at 01 m / sec, 0.5 m / sec, 1.0 m / sec and 1.5 m / sec were measured, respectively. Further, the shear strength was measured.
Table 1 shows the results.

[0055]

[Table 1]

The friction materials of Comparative Examples 1, 2, 3, and 4 have a problem that the friction coefficient is high but the shear strength is low.
However, in the friction materials of Examples 1 to 5, it was found that the shear strength was significantly improved as compared with the comparative example, and the n value of the organic chain was preferably in the range of 3 to 15, and the organic chain having a chain length of 0.5 to 2.5 nm was preferred. It is clear that it is preferable to use an organic-inorganic binder in which a metal element is bonded by a chain.

However, in the friction materials of Examples 1 to 5, since the three-dimensional network is dense, it is recognized that the friction coefficient is lower than that of the comparative example.

Therefore, in the friction material of Example 6, an ether bond is introduced into the organic group. This indicates that intramolecular rotation is possible, so that the flexibility is improved, and the friction coefficient is slightly increased while having high shear strength. In addition, even when an amino group is introduced into an organic group as in the friction material of Example 7, the effect of bonding between metal elements and improving strength is recognized.

Example 8 27.6 ethanol was added to a glass container.
g and, methyltriethoxysilane _{(CH 3 Si (OC 2 H} 5) 3) 9
g and 3 glycidoxypropyltrimethoxysilane in 9
g and 0.15 g of ethyl acetate aluminum diisopropylate were weighed and stirred for 10 minutes. Thereafter, while stirring this solution, 20 parts by weight of a 0.05 N aqueous hydrochloric acid solution was added dropwise, and further stirred for 24 hours to prepare a sol solution.

Next, a paper base material comprising 20% by weight of cellulose fibers and 80% by weight of aramid fibers and prepared by a fourdrinier paper machine is prepared and cut into a predetermined shape. About 50% by weight, about 40% by weight after impregnation
And about 20% by weight to obtain an impregnated base material. The impregnation amount was adjusted by adding ethanol to the sol solution to adjust the sol concentration.

Each of the obtained impregnated substrates was dried by ventilation, and then fired at 100 ° C. for 1 hour in the atmosphere.

Each of the obtained dried substrates was compression molded at 180 ° C. for 10 minutes to obtain a wet friction material having a predetermined shape. This wet friction material contains an organic-inorganic binder in which metal elements are bonded by organic chains, and the chain length of the organic chains is 1.2 nm.
Is calculated.

The same kind of these three types of wet friction materials are adhered to both sides of a metal plate using an adhesive.
The sample was heated at 80 ° C. for 30 minutes and adhered to the test. The test was performed five times for each of the three levels of wet friction materials having different organic and inorganic binder impregnation amounts. <Test / Evaluation> In the test, a friction coefficient was measured under the conditions shown in Table 2 using a SAE # 2 friction tester. The shear strength was measured by a tensile tester. Further, using a SAE # 2 friction tester under the conditions shown in Table 3, the slip speed was 0.05 m / s.
Was measured and the friction coefficient at a sliding velocity of 0.5 m / s was measured to determine the μ-V slope. The respective results are shown in FIGS.

Note that the μ-V slope is a slip velocity of 0.05 m / s.
Means the ratio of the friction coefficient at a sliding velocity of 0.5 m / s to the friction coefficient at .mu.-V slope of 1 indicates a flat friction property, greater than 1 indicates a positive slope friction property, and less than 1 If it shows a negative gradient friction characteristic. The dynamic coefficient of friction is desirably higher than the static coefficient of friction.
When the μ-V slope is smaller than 1, the closer to 1, the more preferable, and the more preferable, is 1 or more.

[0065]

[Table 2]

[0066]

[Table 3]

From the results of FIGS. 1 to 3, the higher the resin ratio (the impregnation ratio of the organic / inorganic binder), the better the μ-V slope, but the coefficient of friction and the shear strength are maximized when the resin ratio is around 40% by weight. The organic-inorganic binder impregnation amount is 30-45
Obviously, a weight percent range is preferred.

[0068]

According to the friction material of the present invention, a large friction coefficient can be ensured by using an organic paper-like base material. This eliminates the necessity of stacking a large number of sheets as in the related art, and avoids a problem that the wet clutch structure becomes complicated and large-scale and energy loss increases. Also, the cost is reduced. Further, the wear resistance is improved, and the shear strength is also significantly improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a resin ratio and a friction coefficient of a friction material according to Example 8 of the present invention.

FIG. 2 is a graph showing a relationship between a resin ratio and a shear strength of a friction material of Example 8 of the present invention.

FIG. 3 shows the resin ratio and μ-V of the friction material of Example 8 of the present invention.
It is a graph which shows the relationship with inclination.

Continued on the front page (72) Inventor Shoji Nakanishi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hideo Kamiya 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation F-term ( Reference) 3J058 BA76 EA36 FA01 FA11 FA21 GA17 GA49 GA54 GA57 GA68 GA93 GA94

Claims (6)

[Claims] 1. A friction material comprising a paper-like substrate made of a fibrous material and an organic-inorganic binder impregnated in the substrate, wherein the organic-inorganic binder has at least 4
A friction material comprising two or more kinds of metal elements including a valence metal element, wherein the metal elements are connected to each other by an organic chain having a chain length of 0.5 to 2.5 nm. 2. An organic-inorganic binder containing 2
2. The friction material according to claim 1, wherein the at least one kind of metal element has a different valence from each other. 3. The friction material according to claim 1, wherein the organic chain includes a bond or a group selected from an ether bond, a chlorine group, an epoxy group, and an amino group. 4. The friction material according to claim 1, wherein the tetravalent metal element is silicon. 5. The friction material according to claim 1, wherein the metal element other than the tetravalent metal element is aluminum. 6. The friction material according to claim 1, wherein the organic-inorganic binder is impregnated in the friction material by 30 to 45% by weight.