JP4292320B2 - Non-asbestos friction material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-asbestos-based friction material suitably used for disk pads, brake linings, clutch facings, etc. for automobiles, large trucks, railway vehicles, and various industrial machines.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, friction materials have been used for braking in automobiles, large trucks, railway vehicles, and various industrial machines. The friction materials have excellent wear resistance, a high friction coefficient, and Performance such as stability, excellent fade resistance, no noise such as squeaking during brake braking, wear pieces are hard to come out, and molding is possible for a short time. It is requested.
[0003]
Above all, as a measure to reduce brake squeal, rubber modified phenolic resins such as acrylic rubber modified phenol novolac resin, which has little damping effect due to thermal history, and nitrile rubber modified phenol novolac resin, which has excellent damping characteristics at room temperature, are used as binders. Various attempts have been made to add damping properties to increase vibration damping and reduce squeal by adding rubber powder (Japanese Patent Laid-Open No. 60-184533, Japanese Patent Publication No. 60-51504). Etc.).
[0004]
However, nitrile rubber-modified novolak phenolic resin has a vibration damping performance that deteriorates due to changes over time due to thermal history, and squeal is generated. In addition, heat resistance is insufficient. There is a problem that the effectiveness of is reduced. In addition, the acrylic rubber-modified novolak phenol resin is excellent in heat resistance, but has the disadvantages of causing blisters during internal heating and pressure molding and internal cracks, resulting in poor moldability.
[0005]
As described above, all of the friction materials conventionally proposed have various problems and do not sufficiently satisfy the demand, and further improvements and improvements are desired.
[0006]
The present invention has been made in view of the above circumstances, and is a high-quality non-asbestos-based material that is resistant to thermal history and deterioration over time with respect to vibration characteristics, has less occurrence of brake squealing, and can maintain these performances over a long period of time. The object is to provide a friction material.
[0007]
Means for Solving the Problem and Embodiment of the Invention
As a result of intensive studies to achieve the above object, the present inventor has formed a non-asbestos-based friction obtained by molding and curing a composition for a friction material mainly composed of a fiber base material, a binder, and a filler. It was found that the use of a mixed resin of an acrylic rubber-modified phenol resin and a nitrile rubber-modified phenol resin as the binder in the material is effective in suppressing squeal during braking.
[0008]
That is, in a non-asbestos-based friction material formed by molding and curing a friction material composition mainly composed of a fiber base material, a binder, and a filler, acrylic rubber-modified phenol resin and nitrile rubber-modified phenol are used as the binder. By using a mixed resin with the resin, surprisingly, the advantageous properties of each resin can be effectively extracted, while the unfavorable properties can be suppressed as much as possible to prevent squeal during braking. In addition to being excellent in vibration characteristics, it is resistant to thermal history and deterioration over time, has good moldability that does not cause blisters and internal cracks, and can obtain a non-asbestos-based friction material that can effectively solve conventional problems. I found out.
[0009]
Further, in this case, it was found that when the difference obtained by subtracting the value at 50 ° C. from the value of the 100 Hz vibration damping rate (tan δ) at 300 ° C. is −0.030 or more, there is an effect of suppressing squealing. That is, conventionally, it is considered that the larger the vibration attenuation rate, the less the noise is generated, and the vibration attenuation rate of a general friction material decreases significantly when the temperature is raised. It was designed to be higher. That is, the conventional friction material has a large difference between V ₅₀ and V ₃₀₀ when comparing tan δ (V ₅₀ ) at 50 ° C. and tan δ (V ₃₀₀ ) at 300 ° C. In this case, the value of V ₃₀₀ fairly small it, if V ₃₀₀ -V ₅₀ is smaller than -0.030 often occurs, Therefore value predetermined level V ₃₀₀ even if the value of V ₃₀₀ is reduced as described above but from the value of V ₅₀ The V ₅₀ value was set high so as to maintain the above.
[0010]
However, as a result of various studies by the present inventor, rather, when the value of V ₃₀₀ −V ₅₀ is −0.030 or more, that is, when the degree of decrease of V ₃₀₀ is small and the difference from V ₅₀ is small, or V ₃₀₀ If towards the value is greater than the value of V ₅₀ (if V ₃₀₀ -V ₅₀ is positive), surprisingly, without setting a high value of V ₅₀ as in the prior art, comparable to the value of the conventional V ₃₀₀ However, it has been found that squeal is remarkably suppressed.
[0011]
It should be noted that the reason why the reduction of the vibration damping rate is effective in suppressing the squeal when the decrease in the vibration attenuation rate is small or increased is not necessarily clear, but may be as follows.
(B) When using a friction material, the friction material itself becomes various temperatures due to friction. Even if you choose something that does not sound at a certain temperature, it is possible to sound at a specific temperature, and if the sound is related to vibration attenuation in some way, it is more effective for noise when the change in vibration attenuation rate with respect to temperature change is small You can say that.
(B) If squeal is a kind of resonance, not only is the vibration damping rate high, but also the fact that the change in the vibration damping rate due to the change in conditions is small as described above is effective in maintaining the set initial performance. Yes, it may not sound as a result.
[0012]
Therefore, the present invention provides a non-asbestos-based friction material obtained by molding and curing a composition for a friction material mainly composed of a fiber base material, a binder, and a filler. A mixed resin of a nitrile rubber-modified phenol resin is used , and one of the acrylic rubber-modified phenol resin and the nitrile rubber-modified phenol resin has a ratio of an ortho bond to a para bond in a methylene bond in this resin of 1. 0.0 or more, and the other phenolic resin has a ratio of ortho bond to para bond in the methylene bond in the resin of less than 1.0, and the friction material has a 100 Hz vibration damping rate at 300 ° C. ( Hisage a non-asbestos friction material difference obtained by subtracting the value at 50 ° C. from the value of tan [delta) is equal to or is -0.012 or more To.
[0013]
Hereinafter, the present invention will be described in more detail.
The non-asbestos-based friction material of the present invention can be obtained by molding and curing a composition for a friction material mainly composed of (A) a fiber base material, (B) a binder, and (C) a filler. However, in achieving the object of the present invention, among these components, a binder is selected, that is, a mixed resin of an acrylic rubber-modified phenol resin and a nitrile rubber-modified phenol resin is used as the binder of the component (B). This is very important.
[0014]
Here, the mixed resin of the acrylic rubber-modified phenol resin and the nitrile rubber-modified phenol resin as the component (B) is obtained by adding acrylic rubber or nitrile rubber to the phenol resin and modifying it. In the present invention, the rubber modification includes not only chemical bonding between rubber and resin but also simple mixing of rubber and resin.
[0015]
The amount of modification (addition amount) in the mixed resin of the rubber component is 10% by weight or more, preferably 10 to 35% by weight, more preferably 10 to 30% by weight. In this case, it is preferable to add acrylic rubber in an amount of 20 to 35% by weight, since even if the amount of modification is large, the decrease in heat resistance is small. Further, in the case of a nitrile rubber-modified phenol resin, it is preferable to add nitrile rubber in an amount of 10 to 20% by weight because the heat resistance is lowered if the amount of modification is too large.
[0016]
The mixing ratio of the mixed resin (acrylic rubber-modified phenol resin to nitrile rubber-modified phenol resin) is 1/10 to 3/2, preferably 1/4 to 1/1 by weight. If the mixing ratio of the two is too large, the moldability may be deteriorated, causing blisters and cracks, which may impair the productivity.On the other hand, if the mixing ratio is too small, the heat resistance will be insufficient and the squeal characteristics after the heat history will be reduced. It may lead to deterioration and deterioration of efficacy stability.
[0017]
In this case, component (B) of the acrylic rubber-modified phenolic resin and nitrile rubber-modified phenolic resin, the ratio of ortho bond to para bond of methylene bonds of the phenolic resin (O / P ratio) is one of the phenol The resin has an ortho to para bond ratio of methylene bonds in the resin of 1.0 or greater, and the other phenolic resin has an ortho bond to para bond ratio of methylene bonds in the resin of less than 1.0. preferably of the nitrile rubber (acrylonitrile-butadiene rubber) modified phenolic resin, especially is, O / P ratio is 1.0 or more, preferably 1.0 to 4.5, more preferably 1.0 to 3 0.0, more preferably 1.0 to 1.5 high-orthophenol resin.
[0018]
Incidentally, O / P ratio can be determined and the absorbance of the ortho bond appearing at 730～770Cm ^-1 by an infrared absorption spectrum, the ratio between the absorbance of para bonds appearing in 800~840cm ^-1.
[0019]
The rubber-modified high-orthophenol resin is obtained by adding a rubber component in a molten state to a high-ortho-type novolak resin and modifying it.
[0020]
As the rubber component, a liquid rubber component is preferable from the viewpoint of uniform mixing with the resin and reactivity, and examples thereof include acrylonitrile butadiene rubber (NBR) and acrylic rubber. Particularly, the molecular weight is 1,000 to 30, 000, more preferably 1,000 to 10,000 liquid NBR and liquid acrylic rubber are suitable. The liquid rubber component may be a solventless liquid rubber or a rubber component dissolved in a solvent.
[0021]
In the case of liquid NBR, the modification amount (addition amount) of the rubber component is 10% by weight or more, preferably 10 to 15% by weight, based on the entire rubber-modified high-orthophenol resin. If the amount of modification of the rubber component is less than 10% by weight, the friction material is not imparted with flexibility and may be disadvantageous for the occurrence of squeal. On the other hand, if the amount exceeds 15% by weight, the friction material is effective and stable against fade. The nature may be inferior.
[0022]
The obtained rubber-modified high-orthophenol resin is molded by adding about 5 to 15% by weight of hexamine as a curing agent.
[0023]
The addition amount of the binder (B) (mixed resin of acrylic rubber-modified phenol resin and nitrile rubber-modified phenol resin) is 3 to 30% by weight, preferably 8 to 25% by weight with respect to the entire friction material composition. %, More preferably 10 to 20% by weight. If the added amount of the binder is too small, the amount of the binder is insufficient and a molded product cannot be obtained. On the other hand, if the added amount is too large, the effectiveness stability of the friction material, fade resistance, etc. may be inferior.
[0024]
As described above, the non-asbestos-based friction material of the present invention is obtained by molding and curing a friction material composition containing (A) a fiber base material, (B) a binder, and (C) a filler as main components. However, as the fiber substrate of the component (A), inorganic fibers, organic fibers and the like that are usually used for friction materials other than asbestos (asbestos) can be used. Examples of such fiber base materials include metal fibers such as iron, copper, brass, bronze, and aluminum, ceramic fibers, potassium titanate fibers, glass fibers, carbon fibers, rock wool, wollastonite, sepiolite, attapulgite, and artificial fibers. Inorganic fibers such as mineral fibers, aramid fibers, polyimide fibers, polyamide fibers, phenol fibers, cellulose, organic fibers such as cellulose fibers, etc. are used, and these are used alone or in combination of two or more. Among them, aramid fiber and glass fiber are preferable.
[0025]
The fiber base material of the component (A) is used in the form of short fibers or powders, and the amount added is 1 to 50% by weight, preferably 5 to 40% by weight, based on the entire composition for friction material. .
[0026]
As the filler of the component (C), known organic fillers and inorganic fillers usually used for friction materials can be used. Examples of inorganic fillers include molybdenum disulfide, antimony trisulfide, and calcium carbonate. , Barium sulfate, magnesium oxide, graphite, calcium hydroxide, calcium fluoride, talc, iron oxide, mica, iron sulfide, aluminum powder, copper powder, brass powder and other metal powders, vermiculite, etc. Can be used alone or in combination of two or more.
[0027]
Examples of the organic filler include cashew dust, tire liquor, rubber dust, nitrile rubber dust (vulcanized product), acrylic rubber dust (vulcanized product), etc., and one of these may be used alone or in combination of two or more. Can be used.
[0028]
The amount of the filler of the component (C) is preferably 20 to 96% by weight, more preferably 40 to 85% by weight, based on the entire friction material composition.
[0029]
The method for producing a friction material according to the present invention is to uniformly mix the above components (A) to (C) using a mixer such as a Henschel mixer, a Redige mixer, or an Eirich mixer to obtain a powder for molding. The powder is preformed in a molding die, and the preform is molded for ² to 10 minutes at a molding temperature of 130 to 200 ° C. and a molding pressure of 100 to 1000 kg / cm ² .
[0030]
Next, the obtained molded product is heat-treated (post-cured) for 2 to 48 hours at a temperature of 140 to 250 ° C., and subjected to spray coating, baking and polishing treatment as necessary to obtain a finished product.
[0031]
When manufacturing a disk pad for automobiles, etc., a preform is placed on an iron or aluminum plate that has been previously cleaned, surface-treated, and coated with an adhesive, and in this state, it is molded and heat-treated in a molding die. Can be manufactured.
[0032]
The friction material of the present invention has the above-described configuration, but the difference obtained by subtracting the value at 50 ° C. from the value of the 100 Hz vibration damping rate (tan δ) at 300 ° C. is −0.012 or more (V ₃₀₀ −V ₅₀ ≧ − 0.012 ), and by reducing the decrease in the vibration attenuation rate or increasing the vibration attenuation rate in this way, the noise suppression effect can be significantly enhanced. If the vibration attenuation rate change (V ₃₀₀ -V ₅₀ ) is smaller than −0.012 , it is disadvantageous for squealing. In this case, the preferred value of the change in the vibration damping factor is -0.012～ 0.030, more preferred value -0.012 0.025, more preferred value is -0.015～0.021, The most preferable value is ± 0.010, and it is preferable that the change in vibration damping rate is small. In addition, it is preferable that the change of the vibration damping rate between 50 ° C. and 300 ° C. is also small, and the difference from the value of tan δ at 50 ° C. is preferably in the above range.
[0033]
In the friction material of the present invention, the vibration damping factor (tan δ) at 50 ° C. is preferably 0.13 or less, more preferably 0.13 to 0.1, still more preferably 0.126 to 0.1. If the vibration attenuation rate (tan δ) at 50 ° C. is out of the above range, it may be disadvantageous for squeak.
[0034]
The vibration damping rate is a value measured by a method in accordance with JIS K 7198 (“Testing method for temperature dependence of dynamic viscoelasticity by non-resonant forced vibration method of plastic”).
[0035]
Incidentally, the vibration damping factor changes, Ru is accomplished by appropriately combining the acrylic rubber-modified phenolic resin and a nitrile rubber-modified phenolic resin.
[0036]
The non-asbestos-based friction material of the present invention is suitable for various uses such as brake linings, clutch facings, disk pads, paper clutch facings, and control wheels for automobiles, large trucks, railway vehicles, and various industrial machines.
[0037]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[0038]
[ Reference Examples 1 and 2, Comparative Examples 1 and 2]
The friction material compositions having the compositions shown in Table 1 were blended in the proportions shown in Table 1, mixed uniformly using a Redige mixer, and pre-molded by pressurizing at 100 kg / cm ² for 1 minute in a pressure mold. . The preform molding temperature 145 ° C., any and time molding under the conditions of a molding pressure 180 kg / cm ^2, then for 5 hours heat treatment at 180 ° C. (post-curing), Reference Examples 1 and 2, Comparative Example 1, 2 brake linings for heavy trucks were created.
[0039]
[Table 1]
* 1: Acrylic rubber-modified phenol novolac resin O / P ratio = 0.7, acrylic rubber modified amount 30 wt%, acrylic rubber molecular weight about 7000
* 2: Nitrile rubber-modified phenol novolac resin O / P ratio = 0.7, nitrile rubber modification amount 14% by weight, NBR molecular weight about 5000
[0040]
A test piece having a size of 55 mm (L) × 10 mm (W) × 3 mm (T) made of the composition of Reference Examples 1 and 2 and Comparative Examples 1 and 2 was prepared, and the vibration damping rate (tan δ) was determined according to the following method. It was measured. The results are shown in Table 2. The results of Reference Examples 1 and 2 and Comparative Examples 1 and 2 are shown in FIG.
[0041]
Vibration damping factor (tan δ)
About the obtained test piece, using a viscoelasticity measuring device DMS-6100 (manufactured by Seiko Denshi Kogyo Co., Ltd.), the vibration damping rate (tan δ) was measured under the conditions of a temperature range of 50 ° C. to 300 ° C. and a temperature increase rate of 4 ° C./min. It was determined by a bending excitation method in which both ends of the test piece were fixed and the central portion was vibrated (100 Hz) (based on JIS K 7198). Three test pieces were prepared from the same material, and the average value of the measurement results was defined as the tan δ value of the friction material.
[0042]
[Table 2]
From the results in Table 2, the difference between tan δ (300 ° C.-50 ° C.) was −0.030 or more compared to Comparative Examples 1 and 2, and it was confirmed that Reference Examples 1 and 2 had excellent squeal characteristics. .
[0043]
Next, regarding the brake linings for large trucks of Reference Examples 1 and 2 and Comparative Examples 1 and 2 obtained, (1) Performance test of a large truck actual vehicle JASO-404-87 equivalent to a constant volume (GVW = 20 t), and (2) Formability was carried out according to the following methods. The results are shown in Table 3.
[0044]
(1) JASO C404-87 performance test on actual heavy-duty truck equivalent to constant volume (GVW = 20t)
The brake linings for large trucks of Reference Examples 1 and 2 and Comparative Examples 1 and 2 are actually attached to the heavy trucks, and the first half (sliding together) according to the actual vehicle JASO C404-87 performance test equivalent to a constant volume (GVW = 20t). , Performance test, regular braking test, squeal test total of about 1800 times), second half (total of effectiveness test, regular braking test, squeal test about 600 times), and total squeal occurrence rate.
(2) Formability ◎: Excellent ○: Good △: Slightly inferior ×: Very inferior [0045]
[Table 3]
[0046]
From the results shown in Table 3, Comparative Example 1 uses only acrylic rubber-modified phenolic resin as a binder, and the squeaking rate is high throughout the first half to the second half, and the moldability is inferior.
In Comparative Example 2, only the nitrile rubber-modified phenol resin is used as a binder, the squeezing rate in the latter half is extremely higher than that in the first half, and the stability of the squealing performance is inferior.
On the other hand, Reference Examples 1 and 2 have good moldability, have a low squeaking rate throughout the first half and second half, and have little deterioration over time in good squealing performance.
[0047]
[ Examples 1 and 2 ]
The friction material composition having the composition shown in Table 4 was blended at the ratio shown in Table 4, and this was uniformly mixed using a Redige mixer, and pre-molded by pressurizing at 100 kg / cm ² for 1 minute in a pressure mold. . The preform is molded for an arbitrary time under conditions of a molding temperature of 145 ° C. and a molding pressure of 180 kg / cm ² , and then heat-treated (post-cured) at 180 ° C. for 5 hours to produce the friction materials of Examples 1 and 2. did.
[0048]
About each obtained friction material, the short-time moldability, squealing performance, effectiveness stability, and fade resistance were measured with the following method. The results are also shown in Table 4.
Short formability ◎: Excellent ○: Good △: Slightly inferior ×: Very inferior
Sound performance ◎: Excellent ○: Good △: Slightly inferior ×: Very inferior
Effective stability ◎: Excellent ○: Good △: Slightly inferior ×: Very inferior
Fade resistance Shows the change in coefficient of friction (μ) with temperature.
◎: Excellent ○: Good △: Slightly inferior ×: Very inferior
[Table 4]
* 3: NBR modified high-orthophenol resin O / P ratio = 1.3, NBR modified amount = 14 wt%, NBR molecular weight of about 5000
* 1: Acrylic rubber-modified phenol novolac resin O / P ratio = 0.7, acrylic rubber modified amount 30 wt%, acrylic rubber molecular weight about 7000
[0050]
A test piece having a size of 55 mm (L) × 10 mm (W) × 3 mm (T) having the composition of Examples 1 and 2 was prepared, and the vibration damping rate (tan δ) was measured in the same manner as described above. The results are shown in Table 5. The results of Examples 1 and 2 are shown in FIG.
[0051]
[Table 5]
[0052]
From the results of Tables 4 and 5 and FIG. 2, the non-asbestos-based friction material of the present invention can be molded in a short time even when a mixed resin of a rubber-modified high-orthophenol resin and a rubber-modified phenol resin is used as a binder. In addition, it has been confirmed that it has excellent squealing performance, good effect stability, and good fade resistance.
[0053]
[Reference example]
A novolak phenol resin was synthesized so as to have an O / P ratio shown in Table 6, and this was modified with NBR to prepare N to N-modified phenol resins A to G and H phenol resin.
[0054]
These phenol resins were uniformly mixed with the blends shown in Tables 7 and 8 using a Redige mixer, and pre-molded by pressurizing at 100 kg / cm ² for 1 minute in a pressure mold. The preform was molded for an arbitrary time under the conditions of a molding temperature of 145 ° C. and a molding pressure of 180 kg / cm ² , and then heat-treated (post-cured) at 180 ° C. for 5 hours to prepare a friction material.
[0055]
About each obtained friction material, the short-time moldability, squealing performance, effectiveness stability, and fade resistance were measured by the method similar to the above. The results are also shown in Tables 7 and 8.
[0056]
Further, a test piece having a size of 55 mm (L) × 10 mm (W) × 3 mm (T) was prepared, and the vibration damping rate (tan δ) was measured according to the same method as described above. The results are shown in Table 9 and FIGS.
[0057]
[Table 6]
* 4: O / P ratio is a value determined from the ratio of the absorbance of ortho bond appearing at 730～770Cm ^-1 by an infrared absorption spectrum, the absorbance of para bonds appearing in 800~840cm ^-1.
* 5: NBR (acrylonitrile butadiene rubber) Molecular weight of about 5000
[0058]
[Table 7]
[0059]
[Table 8]
[0060]
[Table 9]
* The amount of change indicates the difference between the tan δ value at 50 ° C. and the tan δ value at each temperature.
[0061]
【The invention's effect】
The non-asbestos-based friction material of the present invention is resistant to thermal history and deterioration over time with respect to vibration characteristics, has little occurrence of brake squealing, and can maintain these performances over a long period of time. It is suitable for disk pads, brake linings, clutch facings, etc. for vehicles and various industrial machines.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between measured temperature (thermal history) and tan δ in Reference Examples 1 and 2 and Comparative Examples 1 and 2.
FIG. 2 is a graph showing the relationship between measured temperature (thermal history) and tan δ in Examples 1 and 2 .
FIG. 3 Reference Example No. 1 and No. 8 is a graph showing a relationship between a measured temperature (heat history) of 8 and tan δ.
FIG. 5 and No. 10 is a graph showing the relationship between ten measured temperatures (thermal history) and tan δ.

Claims (4)

In a non-asbestos-based friction material obtained by molding and curing a friction material composition mainly composed of a fiber base material, a binder, and a filler, an acrylic rubber-modified phenol resin and a nitrile rubber-modified phenol resin as the binder A mixed resin of any one of the above acrylic rubber-modified phenol resin and nitrile rubber-modified phenol resin, the ratio of ortho bond to para bond in the methylene bond in this resin is 1.0 or more, The other phenol resin has a ratio of ortho bond to para bond in the methylene bond in this resin of less than 1.0, and 50 from the value of 100 Hz vibration damping rate (tan δ) at 300 ° C. of the friction material. A non-asbestos-based friction material, wherein a difference obtained by subtracting the value at ° C. is −0.012 or more.   The non-asbestos-based friction material according to claim 1, wherein the mixing ratio of the acrylic rubber-modified phenol resin to the nitrile rubber-modified phenol resin is 1/10 to 3/2.   The non-asbestos-based friction material according to claim 1 or 2, wherein the amount of rubber modification in the mixed resin is 10% by weight or more.   The non-asbestos-based friction material according to any one of claims 1 to 3, wherein the amount of the mixed resin added is 3 to 30% by weight of the entire friction material composition.