WO2014104125A1

WO2014104125A1 - Friction material and method for producing same

Info

Publication number: WO2014104125A1
Application number: PCT/JP2013/084736
Authority: WO
Inventors: 北原康利; 岡山勝弥; 今井淳司
Original assignee: 株式会社アドヴィックス; 住友ベークライト株式会社
Priority date: 2012-12-25
Filing date: 2013-12-25
Publication date: 2014-07-03
Also published as: JP2014125504A

Abstract

Provided is a friction material which suppresses pseudo polymerization of a phenol resin and has favorable properties even when molded with a normal temperature pressing method. This friction material is produced by a friction material source which comprises a fiber base, a friction adjusting material, a filler, a wetting agent and a plurality of types of phenol resins with different hydroxyl equivalents, as a binder.

Description

Friction material and manufacturing method thereof

The present invention relates to a friction material used for, for example, a disc brake pad of a vehicle or the like and a method for manufacturing the friction material.

Friction materials used for brake pads, brake shoes, etc. for vehicles are generally powdered friction material raw materials mixed with fiber base material, friction modifier, filler, wetting agent, binder, etc. It is manufactured by pressing with a press. Production methods using a press include a hot press method in which a friction material material is heated and compacted to form, and a normal temperature press method in which a friction material material is compacted and molded at room temperature without being heated.

In order to produce the friction material raw material by the room temperature press method, a wetting agent such as water is usually mixed in the friction material raw material at a ratio of 3 wt% to 6 wt%. In addition, when manufactured by the hot press method, the friction material raw material contains inevitable water such as moisture contained in each component of the friction material raw material at a maximum of about 2% by weight.

In any of the above-described methods, in order to ensure the rust resistance performance of the friction material, calcium hydroxide as a filler is blended with the friction material material to make the friction material alkaline.

Furthermore, in the friction material material, there is a phenol resin as a binder in addition to water and calcium hydroxide. A part of calcium hydroxide elutes in water and becomes calcium ions. Calcium ions bind to oxygen instead of hydrogen of the hydroxyl group of the phenol resin, and ionize the phenol resin. When the ionized phenol resin is present alone, the friction material material has a high fluidity, so that the moldability is enhanced. As a result, even when the friction material is molded by the normal temperature press method, it can be compacted with an appropriate porosity, for example, to obtain a friction material having good performance, similar to the case of molding by the hot press method. it can.

However, the ionized phenol resin is altered during the mixing of the friction material, and as a result, the viscosity of the friction material may increase rapidly. In particular, the higher the moisture content, the faster the resin is denatured. For example, in the case of a friction material material for a hot press method, when the ratio of moisture in the friction material material is 1% by weight or more, the rate of alteration is increased, and this phenomenon appears remarkably.

This cause will be described with reference to FIG. As shown in FIG. 1, when a part of calcium hydroxide elutes into water and is ionized during mixing, the phenol resin binds to the eluted calcium ions with hydroxyl groups as reaction sites. A phenol resin having a small hydroxyl equivalent has many reaction points and a phenol resin having a large hydroxyl equivalent has few reaction points. A phenol resin having a large number of reaction points and a small hydroxyl equivalent is more likely to bind to calcium ions than a phenol resin having a large hydroxyl equivalent. Calcium ion has two bonds, so it can bind to two phenolic resin molecules. By connecting two phenolic resin molecules, pseudo-crosslinking is formed between the phenolic resins, and the phenolic resin is chelated. To do.

In the friction material raw material containing only a phenolic resin having a small hydroxyl equivalent weight, the phenolic resin has many reaction points, so that the once chelated phenolic resin has many hydroxyl groups that are not yet bonded to calcium ions. These hydroxyl groups bind to other calcium ions. And when a phenol resin couple | bonds one after another via a calcium ion and chelate repeats, the apparent molecular weight of a phenol resin becomes large and it becomes pseudo-polymerization. This is the alteration of the phenolic resin. It is considered that the viscosity of the friction material raw material increases due to the alteration of the phenol resin.

When the viscosity of the friction material raw material increases during mixing, a part of the friction material raw material may adhere to the inner wall or mixing blade of the mixer and the yield may deteriorate. Furthermore, since the fluidity of the friction material is lowered, the pot life (the time that can be formed by pressing after mixing the friction material) is shortened, and the moldability is also deteriorated.

In addition, it is conceivable to dry the friction material to reduce the water content and prevent the entire production line from becoming a dry environment in order to prevent an increase in viscosity. There is concern about the deterioration of handling.

As conventional manufacturing methods for solving such problems, for example, those disclosed in

Patent Documents

1 and 2 are known. In order to prevent the deterioration of the phenol resin, in Patent Document 1, the phenol resin is encapsulated in gelatin and microencapsulated, and in Patent Document 2, calcium hydroxide is coated with a water-repellent stearic acid compound. Calcium hydroxide is prevented from dissolving in water.

Japanese Patent Laid-Open No. 3-177482 (see FIG. 1) JP-A-3-210338 (refer to the claims)

However, in the manufacturing method of Patent Document 1, it is necessary to separately perform microencapsulation of phenol resin, and in the manufacturing method of Patent Document 2, it is necessary to separately perform a process of coating with calcium hydroxide. For this reason, in any of the manufacturing methods, there remains room for improvement in terms of improving work efficiency.

Also, gelatin added to encapsulate phenol resin and stearic acid compound added to coat calcium hydroxide may adversely affect the friction performance of the friction material.

In view of the above problems, an object of the present invention is to obtain a friction material that suppresses pseudo-polymerization of a phenol resin and has good characteristics even when molded by a room temperature press method.

In order to solve the above-mentioned problems, the friction material according to the present invention is characterized in that the friction material material includes a fiber base material, a friction modifier, a filler, a wetting agent, and a plurality of types of phenol resins having different hydroxyl equivalents as a binder. It is a point manufactured by.

As described above, in the friction material raw material in which a plurality of types of phenol resins having different hydroxyl equivalents, that is, a phenol resin having a small hydroxyl equivalent and a phenol resin having a large hydroxyl equivalent are mixed and mixed, the phenol resin is chelated by calcium ions as described above. However, in the case of a phenol resin having a large hydroxyl equivalent, the number of hydroxyl groups not bonded to calcium ions remains small. Therefore, chelation is not promoted any more and the pseudo-polymerization of the phenol resin is suppressed. In addition, when one of the calcium ion bonds is not bonded to another phenol resin, that is, when there is a surplus of calcium ion bonds, the phenol resin bonded to calcium ions remains in an ionized state. is doing.

As described above, in the friction material raw material in which a plurality of types of phenol resins having different hydroxyl equivalents are blended, pseudo-polymerization is suppressed, and the chelated phenol resin exists in an ionized state, so that it has high fluidity. Can be maintained. Thereby, even when the friction material is formed by the room temperature press method, the same high density of the friction material can be achieved as when the friction material is formed by the hot press method. Moreover, since it has a pore size distribution equivalent to that of the friction material formed by the hot press method, it is possible to improve the wear resistance as compared with the friction material formed by the conventional room temperature press method. Therefore, according to this characteristic configuration, it is not necessary to separately perform processes such as the conventional microencapsulation of phenol resin and coating with calcium hydroxide, and the friction material can be manufactured at a lower cost.

In the friction material according to the present invention, the product of the mixing ratio of the phenol resin and the hydroxyl group equivalent of the phenol resin is calculated for each of a plurality of types of the phenol resins, and the sum of the calculated products is calculated as a plurality of types. The hydroxyl equivalent when divided by the total blending ratio of the phenol resin is preferably 112 to 155 g / eq.

If a plurality of types of phenol resins having different hydroxyl equivalents are used so as to have such hydroxyl equivalents, pseudo-polymerization can be suppressed without impeding ionization of the phenol resins. As a result, a friction material having good performance can be produced not only in the hot press method but also in the room temperature press method.

In the friction material according to the present invention, it is preferable that the hydroxyl group equivalent of the phenol resin having the largest hydroxyl group equivalent among the plurality of types of phenol resins is 135 g / eq or more.

A phenolic resin with a large hydroxyl equivalent has few reaction points. By adding such a phenolic resin, the pseudo-polymerization of the phenolic resin is suppressed, and a friction material having good characteristics even in a room temperature press method is obtained. be able to.

In the friction material according to the present invention, the plurality of types of phenol resins are two types, and the content ratio of the phenol resin having the larger hydroxyl equivalent and the phenol resin having the smaller hydroxyl equivalent is from 2:16 to It is preferable to be in the range of 2: 1.

When the compounding ratio of the phenol resin having a large hydroxyl equivalent is small, the pseudo-polymerization of the phenol resin proceeds and the viscosity of the friction material raw material increases. In addition, if the compounding ratio of the phenol resin with a large hydroxyl equivalent is large, the pseudo-polymerization is suppressed, but there are not enough reaction points of the phenol resin, and the curing reaction of the phenol resin by heat treatment does not proceed, so that sufficient strength is obtained. I can't. With such a blending ratio, it is possible to obtain a friction material having good characteristics even in the room temperature press method by suppressing pseudo-polymerization without hindering the ionization of the phenol resin.

In the friction material according to the present invention, it is preferable that the blending ratio of the phenol resin having a larger hydroxyl equivalent is 1 to 20% by weight with respect to the entire friction material material.

If the blending ratio of the phenol resin having a large hydroxyl equivalent is set in this way, it is possible to obtain a friction material having good characteristics even in the room temperature press method by suppressing pseudo-polymerization without hindering ionization of the phenol resin. .

In the friction material according to the present invention, it is preferable that the phenol resin having a larger hydroxyl equivalent is an aralkyl-modified phenol resin.

Since the aralkyl-modified phenol resin has a hydroxyl group equivalent of 170 to 180 g / eq, mixing with a straight type phenol resin having a hydroxyl group equivalent of 105 g / eq suppresses pseudo-polymerization without disturbing the ionization of the phenol resin. A friction material having good characteristics can be obtained even in the press method.

The characteristics of the method for producing a friction material according to the present invention include a mixing step of stirring a fiber base material, a friction modifier, a filler, a wetting agent, and a friction material raw material containing a plurality of types of phenol resins having different hydroxyl equivalents as binders. And a forming step of forming the mixed powder obtained in the mixing step into a desired shape.

With such a feature, although the phenol resin having a different hydroxyl equivalent is pseudo-crosslinked to the hydroxyl group of the phenol resin that becomes the chelating base point (reaction point), further pseudo-polymerization is suppressed, and the phenol resin is altered. Is suppressed. Therefore, high fluidity can be maintained even when left for a long time in the state where the mixing step is completed, and a friction material can be formed by a room temperature press method (molding step) even after being left for a long time. The friction material formed in this way has achieved the same high density of the friction material as in the case of forming the friction material by the hot press method. In addition, the friction material formed by the normal temperature press method of the friction material having such characteristics has the same pore size distribution as the friction material formed by the hot press method, so the friction material formed by the conventional normal temperature press method The wear resistance can be improved as compared with.

It is explanatory drawing showing the process of pseudo-polymerization of a phenol resin. It is a flowchart when manufacturing the friction material which concerns on this embodiment with a normal temperature press construction method. It is a flowchart when manufacturing the friction material which concerns on this embodiment with a hot press construction method. It is a figure showing the composition and performance evaluation of the Example and comparative example of a friction material which concern on this embodiment.

1. Hereinafter, embodiments of the present invention will be described in detail. The friction material according to the present embodiment can be applied to, for example, a disc brake pad of a vehicle or the like, but is not limited thereto. In addition, it can apply to what can apply conventionally well-known friction materials, such as a brake shoe, for example. The manufactured friction material can be integrated with a plate-like member such as a metal plate as a back plate and used as a brake pad.

The friction material raw material according to the present embodiment refers to all materials that are mixed in manufacturing the friction material. The friction material raw material includes a fiber base material, a friction adjusting material, a filler, a wetting agent, a binder, etc., which will be described later. good. Hereinafter, in the present specification, a mixture of friction material raw materials for a normal temperature press method is referred to as a mixed powder for a normal temperature press method, and a mixture of friction material materials for a hot press method is referred to as a mixed powder for a hot press method. Shall.

Examples of fiber base materials that can be used as fiber components include organic fibers such as aramid fibers, cellulose fibers, acrylic fibers, and carbon fibers, glass fibers, rock wool, ceramic fibers, potassium titanate fibers, and wallast. Examples thereof include inorganic fibers such as knight, and metal fibers such as copper, stainless steel, and brass. These can be used alone or in combination of two or more. The blending ratio of the fiber base material is not particularly limited, but may be added so as to be about 3 to 5% by weight of the friction material raw material.

In the case of a mixed powder for a normal temperature press method, these fiber base materials may be added to the friction material raw material in a state of being pre-hydrated. It is preferable to use an organic fiber as a fiber base (hereinafter also referred to as a water-containing fiber) to be hydrated. Since the amount of water sprayed can be reduced by adding the water-containing fiber to the friction material material, it is possible to make it difficult for the sprayed water to adhere to the inner wall of the mixer. As a result, it is possible to prevent the friction material raw material from being easily attached to the inner wall of the mixer, and to prevent the occurrence of inconvenience that the yield of the friction material is deteriorated and the labor is required for cleaning the mixer. Further, when water-containing fibers are added and stirred during the mixing step, it becomes easier for water to penetrate into the entire friction material material than when water is sprayed separately, and therefore the friction material material can be more uniformly mixed. As a result, it is possible to produce a friction material that can further suppress the generation of dust and is excellent in homogeneity with little segregation.

Examples of friction modifiers include friction dust such as cashew dust and rubber dust, calcium carbonate, barium sulfate, magnesium oxide, graphite, mica, zircon, molybdenum disulfide, ceramic, copper powder, brass powder, zinc powder, aluminum powder, foam Examples include vermiculite. These can be used alone or in combination of two or more. The blending ratio of the friction modifier is not particularly limited, but it is preferable to add the friction modifier so as to be about 3 to 30% by weight of the friction material. In addition, these friction modifiers originally contain moisture although they are in a small amount.

Calcium hydroxide (slaked lime) is used as the filler. Calcium hydroxide is blended as a pH adjusting material in the friction material raw material, for example, as a countermeasure against rust adhesion to the brake disc rotor, thereby making the friction material alkaline. The blending ratio of calcium hydroxide is not particularly limited, but may be added so as to be about 2% to 25% by weight of the friction material raw material.

水 Preferably water is used as the wetting agent for the mixed powder for the room temperature press method. The mixing ratio of water is not particularly limited, but it is preferable to add it so as to be about 2 to 7% by weight of the friction material raw material. When water-containing fibers are used as the fiber base material, the total amount of water contained in the water-containing fibers and water supplied by spraying, etc. should be 2% to 7% by weight of the friction material material. Good. Moreover, you may comprise so that all the water added to a friction material raw material may be supplied with a water-containing fiber at this time.

For example, a surfactant or a viscosity imparting agent may be added to the water. If a surfactant is added to water, each component of the friction material raw material can be more reliably mixed by the surface active action of the added surfactant when the friction material raw material is mixed. The surfactant may be either ionic or nonionic. As the surfactant, known ones such as sodium alkyl sulfate ester, polyoxyethylene alkyl ether, alkylamine oxide can be used. These can be used alone or in combination of two or more. The blending ratio of the surfactant is not particularly limited, but may be added so as to be about 0.2% to 0.5% by weight of the friction material material.

Further, if a viscosity imparting agent is added to water, viscosity can be imparted to water, so that it is possible to reliably prevent the working environment from deteriorating due to generation of dust of the friction material, for example, during the mixing step. Moreover, the strength of the friction material can be improved by adding a viscosity imparting agent. As the viscosity imparting agent, polyethylene oxide, sodium polyacrylate, methyl cellulose, a mixture thereof, and the like can be used. These can be used alone or in combination of two or more. The blending ratio of the viscosity-imparting agent is not particularly limited, but may be added so as to be about 0.2% to 0.5% by weight of the friction material material.

Although it is not necessary to add a specific wetting agent to the mixed powder for the hot press method, moisture contained in each component of the friction material and raw materials that easily segregate in the mixing process (for example, dusts and metal fibers) ) Is preliminarily treated with a viscous aqueous solution, and unavoidable moisture such as moisture contained in total is contained in a maximum of about 2% by weight.

As the binder, a phenol resin is preferably used. The feature of the friction material in this embodiment is that two types of phenol resins having different hydroxyl equivalents are used as the phenol resin. One is a general straight type phenol resin, and the hydroxyl equivalent is 105 g / eq. The other is an aralkyl-modified phenol resin having a hydroxyl equivalent weight of 170 to 180 g / eq. The blending ratio of the aralkyl-modified phenol resin is preferably about 1 to 20% by weight of the friction material material. The blending ratio of the aralkyl-modified phenol resin and the straight type phenol resin is preferably in the range of 2:16 to 2: 1. The total hydroxyl equivalent of the two types of phenolic resins mixed at such a mixing ratio is 112 to 155 g / eq.

The total hydroxyl equivalent of the two types of phenol resins described above is determined as follows. First, the product of the blending ratio of the aralkyl-modified phenol resin and the hydroxyl equivalent of the aralkyl-modified phenol resin is calculated, and the product of the blending ratio of the straight type phenol resin and the hydroxyl equivalent of the straight type phenol resin is calculated. And the sum of each calculated product is calculated | required, and what remove | divided the sum by the total mixture ratio of the aralkyl modified phenol resin and straight type phenol resin becomes a total hydroxyl equivalent. This is a so-called weighted average. When this is used, the total hydroxyl equivalent becomes the smallest when the hydroxyl equivalent of the aralkyl-modified phenol resin is 170 g / eq and the blending ratio of the aralkyl-modified phenol resin to the straight type phenol resin is 2:16. At this time, the total hydroxyl equivalent is 112 g / eq. On the contrary, the total hydroxyl equivalent becomes the largest when the hydroxyl equivalent of the aralkyl-modified phenol resin is 180 g / eq and the blending ratio of the aralkyl-modified phenol resin and the straight type phenol resin is 2: 1. At this time, the total hydroxyl equivalent is 155 g / eq. Thus, it is desirable that two kinds of phenol resins are mixed, and the total hydroxyl equivalent is 112 to 155 g / eq, and the total hydroxyl equivalent is within this range.

In the friction material raw material in which straight type phenol resin and aralkyl-modified phenol resin are mixed, even if the phenol resin is chelated by calcium ions, in the case of aralkyl-modified phenol resin, the number of hydroxyl groups not bonded to calcium ions There is little remaining. Therefore, chelation is not promoted any more and the pseudo-polymerization of the phenol resin is suppressed. In addition, when one of the calcium ion bonds is not bonded to another phenol resin, that is, when there is a surplus of calcium ion bonds, the phenol resin bonded to calcium ions remains in an ionized state. is doing.

In this way, in the friction material raw material in which the straight type phenol resin and the aralkyl-modified phenol resin are mixed and blended, pseudo-polymerization is suppressed, and the chelated phenol resin exists in an ionized state. High fluidity can be maintained. Thereby, even when the friction material is formed by the room temperature press method, the same high density of the friction material can be achieved as when the friction material is formed by the hot press method. Moreover, since it has a pore size distribution equivalent to that of the friction material formed by the hot press method, it is possible to improve the wear resistance as compared with the friction material formed by the conventional room temperature press method.

However, the higher the proportion of aralkyl-modified phenolic resin, the better. When the blending ratio of the aralkyl-modified phenol resin is too large, the reaction points of the phenol resin to be bonded are insufficient, and the curing reaction of the phenol resin by heat treatment does not proceed, so that sufficient strength cannot be obtained. Therefore, the blending ratio of the aralkyl-modified phenol resin and the blending ratio with the straight type phenol resin are preferably in the above-described ranges.

In this embodiment, an aralkyl-modified phenol resin is used as a phenol resin having a higher hydroxyl equivalent, but the present invention is not limited to this. If the above-mentioned blending ratio, blending ratio, and total hydroxyl equivalent are satisfied, the hydroxyl equivalent is within the range of 135 to 180 g / eq, such as cashew-modified phenolic resin (hydroxyl equivalent: 135 to 145 g / eq). Some other phenolic resin may be used.

In this embodiment, two types of phenolic resins having different hydroxyl equivalents were used. However, as long as the above-described blending ratio, blending ratio, and total hydroxyl equivalents were satisfied, friction was performed using three or more phenolic resins. A material may be formed.

2. Next, a method for manufacturing the friction material according to the present embodiment will be described. The manufacturing method of the friction material according to the present embodiment includes a mixing step of stirring the friction material raw material, and a forming step of forming the mixed powder obtained in the mixing step into a desired shape. It can be applied to both the construction method and the hot press construction method. Hereinafter, it explains in detail using a drawing.

(Normal temperature press method)
FIG. 2 shows a flow diagram when the friction material according to the present embodiment is manufactured by a room temperature press method. As shown in FIG. 2, first, each of the above-mentioned fiber base material, friction modifier, filler (calcium hydroxide), wetting agent (water), friction material raw material including a binder (phenol resin) and the like are weighed. At this time, the aralkyl-modified phenol resin and the straight type phenol resin are preliminarily mixed at a blending ratio within the above range. Next, these weighed friction material materials are put into a mixer such as a Henschel mixer or a Redige mixer, and mixed at room temperature for about 10 minutes, for example, to produce a mixed powder for a room temperature press method (mixing step). At this time, mixing may be performed while cooling by a known cooling means so that the mixer does not increase in temperature.

It should be noted that the water may be added all at once after the mixing is completed, for example, or may be divided several times or continuously in small amounts. Further, the friction material material may be granulated when water is added to the friction material material and mixed.

For the back plate (metal plate, etc.), after applying an appropriate surface treatment, an adhesive is applied to the side on which the prepared mixed powder for a normal temperature press method is placed and dried.

Next, a predetermined amount of the mixed powder for room temperature press method is placed on the dried back plate, and room temperature press is performed (molding process). At this time, the molding pressure may be 50 to 200 MPa (preferably 100 MPa), and the molding time may be 5 to 60 seconds (preferably 15 seconds).

Next, a clamping process (for example, 180 ° C., 1 MPa, 10 minutes) is performed. Thereafter, heat treatment is performed at 150 to 250 ° C. for 5 to 180 minutes (preferably 230 ° C. for 3 hours), and various processes such as polishing and lot marking are performed.

(Hot press method)
Here, the steps different from the room temperature press method described above will be mainly described. FIG. 3 shows a flow chart when the friction material according to this embodiment is manufactured by the hot press method. As shown in FIG. 3, first, each of the above-mentioned fiber base material, friction adjusting material, filler (calcium hydroxide), friction material raw material including a binder (phenol resin) and the like are weighed. At this time, the aralkyl-modified phenol resin and the straight type phenol resin are preliminarily mixed at a blending ratio within the above range. Next, these weighed friction material materials are put into a mixer such as a Henschel mixer or a Redige mixer, and mixed at room temperature for about 10 minutes, for example, to produce a mixed powder for the hot press method (mixing step). At this time, mixing may be performed while cooling by a known cooling means so that the mixer does not increase in temperature.

In the hot press method, after the friction material raw material is weighed, if necessary, a raw material that easily segregates in the mixing step (for example, dusts or metal fibers) may be pretreated with a viscous aqueous solution. good.

Next, a predetermined amount of the mixed powder for the hot press method is weighed and preliminarily molded (normal temperature, 10 MPa), and then placed on the back plate and hot pressed (molding step). For the back plate, as in the case of the room temperature press method, after applying an appropriate surface treatment, an adhesive is applied to the side on which the mixed powder for the hot press method after the pre-forming is placed and dried. Use what you let.

When performing hot pressing, the molding temperature is 140 ° C. to 200 ° C. (preferably 160 ° C.), the molding pressure is 10 MPa to 30 MPa (preferably 20 MPa), and the molding time is 3 minutes to 15 minutes (preferably 10 minutes). ) Thereafter, heat treatment is performed at 150 to 250 ° C. for 5 to 180 minutes (preferably 230 ° C. for 3 hours), and various processes such as polishing and lot marking are performed. In the hot press method, it is not necessary to perform a clamping process.

Next, examples of the friction material according to the present embodiment will be described. Each component of the friction material raw material for room temperature press and hot press was weighed at a blending ratio shown in “mixed powder blending” in FIG. The high-ortho type phenolic resin has the property of preventing red color change of the resin, and the hydroxyl equivalent is equivalent to the straight type phenol resin. .

Then, in order to confirm the pot life property of the mixed powder, a friction material was formed by a normal temperature press method and a hot press method immediately after mixing (after 0 hours), 8 hours after mixing, and 24 hours after mixing, respectively. Molding process). About the mixed powder for room temperature press method, after pressing at the molding temperature of room temperature, molding pressure of 100 MPa, molding time of 15 seconds, press with a clamp (temperature 180 ° C, pressure 1 MPa, time 10 minutes), and finally heat treatment (Temperature 230 ° C., time 3 hours) was cured to obtain a friction material. The mixed powder for the hot press method was pressed under the conditions of a molding temperature of 160 ° C., a molding pressure of 20 MPa, and a molding time of 10 minutes, and then heat treated (temperature 230 ° C., time 3 hours) and cured to obtain a friction material. . Each of the friction materials thus obtained was evaluated for porosity measurement (formability), friction performance, and wear performance.

In the porosity measurement, when the porosity was 8.0 to 12.0, it was determined to have a good porosity. Generally, the friction material is worn when pressed against the brake disc, and the wear powder is taken into and discharged from the pores, so that the friction performance can be maintained without any wear powder remaining on the surface of the friction material. However, it does not mean that the porosity is high. The larger the porosity, that is, the greater the number of pores, the softer the friction material, so that the friction performance is improved, but the wear amount is increased and the wear performance is lowered. On the contrary, the smaller the porosity, that is, the smaller the number of pores, the harder the friction material becomes. Therefore, when pressed against the brake disc, the surface contact becomes worse and the friction performance is lowered, but the wear performance is improved. Therefore, it is important for the performance of the friction material that the porosity is within an appropriate range in consideration of the balance between the friction performance and the wear performance. In the friction performance evaluation, it was carried out according to JASO C406, and an average friction coefficient at a general use temperature (100 ° C.) was measured. When the average friction coefficient was larger than 0.35, it was determined that the film had good friction performance. In the wear performance evaluation, when the wear amount of Comparative Example 1 (thermoformed product) was 1.0, the wear amount was determined to be good when the wear amount was less than 1.2. In addition, as a comprehensive determination of Examples 1 to 6, in the example in which there is no item determined as defective, “◯” indicates that the friction material has good performance, and there is one item determined as defective. As for the examples, “△” as having a slightly good performance as a friction material, and “×” as having no good performance as a friction material for an example in which two or more items were judged as defective. Each was judged. In FIG. 4, defective items are shaded.

As shown in FIG. 4, in any friction material, the porosity tends to increase with time. In Comparative Example 1 and Comparative Example 2 in which only a straight type phenolic resin is blended and no aralkyl-modified phenolic resin is blended, the porosity is 12 after 24 hours of Comparative Example 1 and after 8 hours and 24 hours of Comparative Example 2. More than 0.0, deviating from the good range. The friction performance was good, exceeding 0.35 in both pot life examples of Comparative Example 1 and Comparative Example 2, and the friction performance improved as the porosity increased. On the other hand, the wear performance was poor at 1.2 or more after 24 hours of Comparative Example 1 and after 8 hours and 24 hours of Comparative Example 2. Thus, it can be seen that the friction material containing only the straight type phenolic resin cannot obtain good performance.

On the contrary, in Example 6 (room temperature press-molded product) in which only the aralkyl-modified phenol resin is blended, since the fluidity is too good and almost no pores are formed even when molded, the one immediately after mixing has a porosity of 5. 7. Even after 24 hours from mixing, the molded product was poor with a porosity of 7.9. The friction performance was poor after 0 and 8 hours, but the wear performance was good even after 24 hours. In Example 6, since there are five items determined to be defective, the overall determination is “x”. Thus, it is understood that good performance cannot be obtained with a friction material formed from a friction material material containing only an aralkyl-modified phenol resin.

In Examples 1 to 5, aralkyl-modified phenol resin and any one of straight type phenol resin and high ortho type phenol resin are blended. As shown in FIG. 4, the blending ratio of the aralkyl-modified phenol resin is 1 to 6% by weight, and the blending ratio of the aralkyl-modified phenol resin and the straight type phenol resin or the high-ortho type phenol resin is as in Example 1 and Example 3. 2: 4, 2:16 in Example 2, 2: 2 in Example 4, and 2: 1 in Example 5, all satisfy the above-described requirements.

In Examples 1 to 5, the moldability was in a favorable range. The friction performance was poor only after 0 hours of Example 5, and the rest was good. The wear performance was poor only after 24 hours of Example 2 and the rest was good. In summary, in Example 1, Example 3, and Example 4, since there were no items determined to be defective, the overall determination was “◯”. In Example 2 and Example 5, since there is one item determined to be defective, the overall determination is “Δ”. As described above, the friction material formed from the friction material containing aralkyl-modified phenol resin and either straight type phenol resin or high-ortho type phenol resin is good in terms of porosity, friction performance, and wear performance. You can see that the performance is good.

The present invention can be used for, for example, a friction material used for a disc brake pad of a vehicle or the like and a manufacturing method thereof.

Claims

A friction material manufactured from a friction material material containing a fiber base material, a friction modifier, a filler, a wetting agent, and a plurality of types of phenol resins having different hydroxyl equivalents as binders.
Calculate the product of the blending ratio of the phenolic resin and the hydroxyl group equivalent of the phenolic resin for each of the plurality of types of phenolic resins, and divide the sum of the calculated products by the total blending ratio of the plurality of types of the phenolic resins. The friction material according to claim 1, wherein the hydroxyl equivalent weight is 112 to 155 g / eq.
The friction material according to claim 1 or 2, wherein the hydroxyl group equivalent of the phenol resin having the largest hydroxyl group equivalent among the plurality of types of phenol resins is 135 g / eq or more.
The plural types of the phenolic resin are composed of two types,
The content ratio of the phenol resin having a larger hydroxyl equivalent and the phenol resin having a smaller hydroxyl equivalent is in the range of 2:16 to 2: 1. Friction material.
The friction material according to claim 4, wherein a blending ratio of the phenol resin having a larger hydroxyl equivalent is 1 to 20% by weight with respect to the whole friction material raw material.
The friction material according to claim 4 or 5, wherein the phenol resin having a larger hydroxyl equivalent is an aralkyl-modified phenol resin.
A mixing step of stirring a friction material material containing a fibrous base material, a friction modifier, a filler, a wetting agent, and a plurality of types of phenol resins having different hydroxyl equivalents as a binder;
A method for producing a friction material, comprising: a molding step of molding the mixed powder obtained in the mixing step into a desired shape.