JP2008184582A - Friction material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a friction material which is improved in heat resistance and mechanical strength and is satisfactory in the stable fade resistance and abrasion resistance, also in a high load range, in the case of a composition with a flame retardant comprising a nitrogen compounds such as a melamine polyphosphate, etc. <P>SOLUTION: The friction material comprises at least a base material fiber, a friction conditioning material and a binder, wherein a complex friction dust containing at least one of nitrogen acid-based compounds composed of a basic nitrogen compound and a flame retardant inorganic acid is compounded in resin dust. The complex friction dust preferably, contains 5-15 vol.%. of the nitrogen acid-based compounds composed of the basic nitrogen compound and the flame retardant inorganic acid, and the complex friction dust has 50-500 μm of the average particle diameter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a friction material used for brake pads, brake linings, clutch facings, etc. for automobiles, industrial vehicles, railway vehicles, and the like. More specifically, it has high wear resistance and fading resistance at high speed, and is a problem of squealing. On the other hand, it relates to a good friction material.

  Conventionally, friction materials such as clutch facings and brake linings of automobiles are required to have heat resistance and wear resistance, and improvement of automobile performance has been required to improve effectiveness at high speed, and improve fading and friction characteristics. ing. Conventionally, countermeasures have been taken by using hard materials such as abrasives for effectiveness and fading characteristics and using lubricants such as graphite and molybdenum disulfide for friction characteristics. However, with such an improvement method, it is very difficult to balance because of contradictory contents.

  Therefore, in order to satisfy various properties, the friction material is manufactured by blending various composite materials. The main blending materials include fiber base materials, resin binders, and binding to these fiber base materials. There are various fillers that are dispersed and filled in a matrix with the material. And as a fiber base material, inorganic fiber, such as glass fiber, organic fiber, such as aramid fiber, metal fiber, such as steel fiber, etc. are used, and thermosetting resin, such as phenol resin, is used as a resin binder. Alternatively, a cross-linkable rubber is used, and further, as a filler, a filler such as barium sulfate, a solid lubricant, a friction modifier, or other additives are used.

  For example, in order to improve wear resistance and maintain lubricity at high temperatures, friction materials containing antimony compounds such as antimony oxide and antimony sulfide have been proposed as flame retardants for binders. However, although antimony compounds are effective in wear resistance, they are not very effective in fade resistance, and there is a problem that squeal becomes worse when the amount is increased in order to further improve the wear resistance. In recent years, development of friction materials that do not use antimony has been desired mainly in Europe and the United States due to environmental hygiene considerations.

In “Patent Document 1”, a nitrogen compound selected from the flame retardants melamine, benzoguanamine, acetoguanamine, and ethylenediamine, and phosphoric acid, polyphosphoric acid, sulfuric acid, sulfamic acid, boric acid, oxalic acid, phthalic acid, and cyanuric acid are selected. A friction material containing 0.5 to 20% by mass of a flame retardant, which is a nitrogen acid-based compound containing nitrogen composed of a nitrogen compound and an acid, not containing antimony composed of an acid, is described. . Specific examples of the flame retardant include melamine sulfate, melamine polyphosphate, and ammonium polyphosphate. However, a friction material that satisfies both the fade characteristics and the wear resistance has not yet been found.
JP 2002-173667 A

Recently, with high performance and long-term guarantee of automobiles, friction materials such as clutch facings for automobiles can be applied under a wide range of conditions from light load, medium load to high load, and have a long life. It is strongly desired.
However, a friction material is formed by mixing a flame retardant, which is a nitrogen acid-based compound containing nitrogen composed of a nitrogen compound and an acid as described in "Patent Document 1," with other compounding materials including resin dust. Then, although it is excellent in the stability of friction characteristics in light and medium loads, and in wear resistance, the friction coefficient μ decreases in the high load area due to insufficient heat resistance of the resin dust itself. There was a problem that wear resistance also deteriorated.
Accordingly, an object of the present invention is to provide a friction material that satisfies stable fade characteristics and wear resistance even in a high load region by increasing the heat resistance of the resin dust, and has no environmental pollution.

A resin dust, a basic nitrogen compound, and a nitrogen acid compound composed of a flame retardant inorganic acid are mixed well in advance, and the nitrogen acid compound is coated with the resin dust, for example, to thereby add the nitrogen acid compound. A friction material having both fading characteristics and wear resistance can be provided by adding it to other compounding materials and molding the friction material after making it contained in resin dust as friction dust.
The present invention has solved the above-mentioned problems by the following means: (1) In a friction material using at least a base fiber, a friction modifier, and a binder, a basic nitrogen compound and a flame retardant in resin dust A friction material comprising a compounded friction dust containing at least one nitrogen acid compound composed of an inorganic acid.
(2) The friction material according to (1), wherein the combined friction dust contains 5 to 15 vol% of a nitrogen acid compound composed of a basic nitrogen compound and a flame retardant inorganic acid. .
(3) The friction material according to (1) or (2), wherein the composite friction dust has an average particle size of 50 to 500 μm.
(4) The above-described (1) to (1), wherein the nitrogen acid compound comprising the basic nitrogen compound and the flame retardant inorganic acid contains at least one of melamine sulfate, melamine polyphosphate, or ammonium polyphosphate. The friction material according to any one of (3).

The friction material of the present invention can maintain the flame retardant effect of the friction material and suppress the deterioration of the organic material by using the friction dust obtained by combining the resin dust with the flame retardant composition. This makes it possible to achieve both μ at high load and wear resistance.
In addition, according to the present invention, it is possible to improve the effect at high speed, the fading, and the improvement of the friction characteristics without substantially deteriorating the contradictory characteristics. Further, it is possible to provide a friction material having strength even after receiving a strong heat history.

The present invention is described in detail below.
In the present invention, resin dust such as cashew dust and furfural modified cashew dust is blended with a composite friction dust containing at least one kind of a nitrogen compound based on a basic nitrogen compound and a flame retardant inorganic acid. Achieved by the featured friction material.
In the nitrogen acid-based compound containing a basic nitrogen compound and a flame retardant inorganic acid used in the present invention, examples of the basic nitrogen compound as a raw material include melamine, ammonium, benzoguanamine, acetoguanamine, ethylenediamine, and amino group. It can be selected from a substituted imidazole, a triazole substituted with an amino group, and preferably a nitrogen compound having an amino group. The flame retardant inorganic acid can be selected from phosphoric acid, polyphosphoric acid, pyrophosphoric acid, sulfuric acid, sulfamic acid, boric acid, oxalic acid, phthalic acid, cyanuric acid and the like.
Specific examples of nitric acid compounds containing basic nitrogen compounds and flame retardant inorganic acids (having the properties of flame retardant compositions) include melamine sulfate, melamine polyphosphate, ammonium polyphosphate, melamine pyrophosphate, etc. Can be mentioned.

Melamine polyphosphate is a compound in which polyphosphate and melamine are bound in various different ratios. In addition, when polyphosphoric acid is partially bonded to other nitrogen-containing compounds such as ammonia, amide, ethylenediamine, or metals such as aluminum, magnesium, calcium, etc., the portion bonded to melamine exceeds 50%. The case can be defined as melamine phosphate. However, it is usually preferable to use a highly pure compound as melamine polyphosphate.
Examples of the melamine polyphosphate that can be used in the present invention include MPP-A (manufactured by Sanwa Chemical Co., Ltd.), PMP-100 (manufactured by Nissan Chemical Co., Ltd.) and the like as trade names. A mixture of two or more types is used.

  Melamine pyrophosphate is a compound in which pyrophosphate (a dehydration-condensed dimer of phosphoric acid) and melamine are combined at various different ratios. Similarly to melamine phosphate, it may be bound to other nitrogen-containing compounds such as ammonia, amide and ethylenediamine or metals such as aluminum, magnesium and calcium as long as it is less than 50%. As melamine pyrophosphate, for example, Planeron (registered trademark) NP (manufactured by Mitsui Chemicals) or the like can be used as a trade name.

Ammonium polyphosphate is a compound in which polyphosphoric acid (dehydration condensate of phosphoric acid trimer or higher) and ammonia are combined. Ammonium polyphosphate can also be used without any particular limitation on the degree of condensation of polyphosphoric acid and the primary structure of the molecule such as chain or cyclic. Further, 100% of the phosphoric acid unit structure does not bind to ammonia and may be partially substituted with other residues, for example, nitrogen-containing compounds such as amide and ethylenediamine, or metals such as aluminum, magnesium and calcium. .
Sumisafe (registered trademark) P (manufactured by Sumitomo Chemical Co., Ltd.), Sumisafe (registered trademark) PM (manufactured by Sumitomo Chemical Co., Ltd.), Terage (registered trademark) C60 (manufactured by Chisso Corporation), nonen PR-62 (manufactured by Maruhishi Oil Chemical Co., Ltd.) (Manufactured by Kogyo Co., Ltd.) are available as commercial products, and these can be used alone or in combination of two or more.

  Examples of the resin dust include cashew dust (including modified cashew resin), natural resin dust such as natural rubber, and phenol resin dust (including modified phenol resin).

The addition amount of the nitrogen acid compound contained in the composite material (friction dust) combined with the resin dust of the present invention and the nitrogen acid compound is in a range of 3 vol% or more and less than 20 vol% in volume ratio, Considering fade characteristics and cost, 5 vol% or more and 15 vol% or less is preferable. If the ratio of the flame retardant composition is too high, a large amount of gas is generated at the time of heating / pressing molding and heat treatment to reduce productivity, and conversely, if too low, the strength of the friction dust is reduced. The particle size of the friction dust is preferably 50 μm or more and 500 μm or less because the kneading work is facilitated. When the particle size is less than 50 μm, dust is likely to be generated, and when it exceeds 500 μm, segregation is likely to occur.
The composite friction dust used in the present invention is prepared by mixing and stirring the resin dust and the nitrogen acid compound at 150 to 250 ° C., and cooling and pulverizing them. Then, it mix | blends with another member and shape | molds a friction material.

  The friction material used in the present invention is molded by blending a base fiber, a binder, a friction modifier, a filler, and the like. As a base fiber, what is used for the conventional friction material can be used. For example, rock wool, glass fiber, silicate fiber, alumina fiber, carbon fiber, potassium titanate fiber and other inorganic fibers, steel fiber, copper fiber, brass fiber, bronze fiber and other metal fibers, hemp, cotton, aromatic polyamide fiber Organic fibers such as phenol fibers can be used. Of these, one or a combination of two or more can be used. The usage-amount of a base fiber is 5-50 volume% normally with respect to friction material whole quantity.

  Examples of the binder include thermosetting resins such as phenol resins, urea resins, melamine resins, epoxy resins, or modified resins thereof. Among these, a thermosetting phenol resin is preferable. The amount of the binder used is preferably 5 to 25% by volume with respect to the total amount of the friction material. Examples of the filler include calcium carbonate, barium sulfate, calcium hydroxide, aluminum powder, copper powder, graphite, molybdenum disulfide, cashew dust, rubber dust, mica, vermiculite, etc. Two or more types appropriately combined can be used. The amount of the filler used is preferably 20 to 60% by volume with respect to the total amount of the friction material.

Although the friction material of the present invention can be manufactured by a usual method, it can be specifically manufactured as follows.
The above-mentioned friction material is uniformly mixed with a blender or the like, and the resulting powder mixture is heated and pressure-molded (specifically, a mold in which a pressure plate is set after preforming the powder mixture in a mold) And then heated and pressurized to form an integral part with the pressure plate, then after-curing), and the powder mixture is uniformly mixed and wetted in the presence of a solvent (wetting agent). There is a wet method of heating and pressure forming, and any method is possible.

  Although it does not specifically limit as a wetting agent used in a wet method, Preferably the caking aggregation agent which consists of a water-alcohol mixed solvent is used. Specifically, while the above-described blending components are dry-mixed, a caking flocculant composed of a water-alcohol mixed solvent is added to and mixed with this to wet the powder mixture and to impart viscosity to the wet mixture. And then granulating the wet mixture to form granules and drying to dry granules. By using such a mixed solvent, the granule moves during granulation or during drying, even if a step of drying after shaping the wet mixture into granules in advance for the purpose of avoiding dust in the drying step, It is not destroyed by vibration. The obtained dried granule is heated and pressurized in a mold set with a pressure plate, integrally molded with the pressure plate, and further subjected to after-curing to obtain a friction material. As molding conditions in this case, known conditions can be employed.

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

Examples a to f, comparative examples g to j
(Manufacture of friction materials)
First, in a furfural-modified cashew dust which is a kind of resin dust, a nitrogen acid compound composed of a basic nitrogen compound and a flame-retardant inorganic acid was mixed well. Thereafter, cooling and pulverization were performed to create a composite friction dust.
In the friction material using phenol resin as binder resin (binding material resin), aramid fiber as base material, graphite as lubricant, barium sulfate, calcium carbonate as filler, zirconium oxide as abrasive, each material is listed in Table 3. After sufficiently uniformly mixing with a blender at the indicated ratio, the powdery mixture was put into a preforming mold and pressed at room temperature at a pressure of about 7.2 MPa for about 5 seconds to form a preformed product. Next, it was set in a thermoforming mold together with a pressure plate whose surface was previously coated with a phenol resin adhesive, and thermoformed at a pressure of 13 MPa and a temperature of 160 ° C. for 5 minutes. This was further heat-treated at 200 ° C. for 5 hours to obtain a friction material.

  In addition, in order to determine the addition amount and particle size of the composite friction dust suitable for the performance and workability of the friction material, mixing resin dust and melamine sulfate based on the formulation of Example a shown in Table 3 A composite friction dust having different particle diameters was prepared by reacting at different ratios to be combined, cooling and pulverizing, and a preliminary test sample of a friction material was prepared by a conventional method. These samples were tested together with the friction material performance test for the samples of the following examples. Among these, the characteristics with respect to the content of the composite friction dust are shown in Table 1, and the relationship between the average particle diameter of the composite friction dust and the segregation state at the time of blending or the ease of generation of dust is shown in Table 2.

As can be seen from the results in Table 1, the content of the combined friction dust is preferably 5 to 15 vol% in terms of fade characteristics and cost. The average particle size of the friction dust is preferably 50 to 500 μm in consideration of segregation and dust.
Table 3 shows the formulation of Examples af and Comparative Examples gj. From the results of Table 1, in the case of using one kind of nitrogen acid compound, the content of the composite friction dust is 10 vol%, and Examples d, e and f using two kinds of nitrogen acid compound are used. In this case, 5 vol% of each composite friction dust was contained. The average particle size is 100 μm.
About each brake friction material shown in Table 3, the performance evaluation by a test piece was implemented, and the result shown in Table 4 was obtained.

(1) Test piece friction test The test conditions basically conform to JASO C 406. The difference is that a 1/5 scale tester is used, the vehicle classification is P1, and in the normal temperature effect test in the second effect test, 200 km / h is added to the initial braking speed, and the high temperature effect in the second fade recovery test. The test etc. and the test below the 4th regrind were cut.
“Efficacy” in Table 4 shows the coefficient of friction at a deceleration of 2.94 m / s ² in 2) normal temperature efficacy test of e) second efficacy test. “Fade Min.μ” represents i) the lowest coefficient of friction in 2) the fade test of the first fade recovery test. “Wear” represents the total wear after the above test.

The test results were evaluated as follows.
<Fade Resistance> As shown in Table 4, Examples a to f of the present invention using composite friction dust were more effective than Comparative Examples g to j.
<Abrasion resistance> With regard to the abrasion resistance, Examples a to f had a remarkable effect.
<Effectiveness at high speed> The effect of the friction material of the present invention is obvious when measured at 200 km / h.

  According to the present invention, a friction material free from environmental pollution and having both fade characteristics and wear resistance has been put to practical use. Therefore, the friction material of the present invention is particularly useful for brake pads, brake linings, clutch facings and the like used for industrial machines, railway vehicles, luggage vehicles, passenger cars and the like.

Claims (4)

  In a friction material using at least a base fiber, a friction modifier, and a binder, the resin dust contains at least one kind of a nitrogen acid compound composed of a basic nitrogen compound and a flame-retardant inorganic acid. A friction material characterized in that it contains blended friction dust.   The friction material according to claim 1, wherein the combined friction dust contains 5 to 15 vol% of a nitrogen acid compound composed of a basic nitrogen compound and a flame retardant inorganic acid.   The friction material according to claim 1 or 2, wherein the composite friction dust has an average particle size of 50 to 500 µm.   The nitrogenous acid compound comprising the basic nitrogen compound and the flame retardant inorganic acid contains at least one of melamine sulfate, melamine polyphosphate, or ammonium polyphosphate. The friction material as described in any one of Claims.