JP2013129801A - Method of producing friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a friction material with excellent friction performance more efficiently, while preventing viscosity from rapidly increasing during mixture of a raw material for the friction material, the raw material containing a phenolic resin, calcium hydroxide and water.SOLUTION: A method of producing a friction material includes: a mixing step of stirring a raw material for the friction material, the raw material containing a phenolic resin, calcium hydroxide, water, and a chelating agent; and a forming step of forming mixed powder obtained through the mixing step in a desired shape.

Description

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

  One of the requirements for manufacturing friction materials used in brake pads, brake shoes, etc. of vehicles, etc., at room temperature is to be able to press the mixed friction material material (powder) at room temperature. . Therefore, a wetting agent such as water is usually added to the friction material raw material at a ratio of 3 wt% to 6 wt%.

  Even when the friction material is manufactured by the hot press method, the mixed friction material raw material (powder) contains about 2% by weight of unavoidable moisture such as water contained in each component of the friction material raw material.

  In any of the above-described methods, the friction material is made alkaline by adding calcium hydroxide to the friction material raw material in order to ensure the rust resistance performance of the friction material.

  On the other hand, in the friction material raw material, in addition to water and calcium hydroxide, if a phenol resin coexists as a binder, the phenol resin is denatured during mixing, and the viscosity of the friction material raw material increases rapidly. There is. In particular, in the case of a friction material material for the hot press method, this phenomenon appears remarkably when the amount of water in the friction material material becomes 1% by weight or more.

  As shown in FIG. 1, when a part of calcium hydroxide elutes in water and is ionized during mixing, the calcium ion acts on the phenol resin to chelate, and a pseudo-crosslink is formed between the phenol resins. This is thought to be due to the progress of pseudo-polymerization of phenol resins.

When the viscosity of the friction material raw material increases rapidly, 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 material is lowered and the pot life (potential time) is shortened, the moldability is also deteriorated.
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 modification of the phenol resin, in Patent Document 1, the phenol resin is encapsulated in gelatin and microencapsulated, and in Patent Document 2, by coating calcium hydroxide 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)

  In the manufacturing method of Patent Document 1, it is necessary to separately perform microencapsulation of a phenol resin, and also 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.

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

  Accordingly, an object of the present invention is to more efficiently produce a friction material with good friction performance while suppressing a sudden increase in viscosity at the time of mixing a friction material material containing a phenol resin, calcium hydroxide, and water. .

  The first characteristic configuration of the method for producing a friction material according to the present invention includes a mixing step of stirring a friction material material containing phenol resin, calcium hydroxide, water, and a chelating agent, and a mixed powder obtained in the mixing step. And a forming step of forming the desired shape into a desired shape.

[Action and effect]
According to this structure, as shown in FIG. 2, a part of calcium ion of calcium hydroxide eluted in water is trapped by the chelating agent. For this reason, chelation of calcium ions shown in FIG. 1 is suppressed, and it is difficult to form pseudo-crosslinks between the phenol resins, and the pseudo-polymerization of the phenol resin is suppressed.
That is, by simply adding a chelating agent to the friction material, it is possible to suppress an abrupt increase in viscosity when mixing the friction material material containing phenol resin, calcium hydroxide and water, resulting in poor yield and pot life. Shortening can be prevented.
Therefore, according to this configuration, it is not necessary to separately perform processes such as the conventional microencapsulation of phenol resin and calcium hydroxide coating, and the friction material can be manufactured more efficiently.

  A second characteristic configuration is that the chelating agent is ethylenediamine or ethylenediaminetetraacetic acid.

[Action and effect]
If ethylenediamine or ethylenediaminetetraacetic acid is used as a chelating agent, calcium ions can be reliably captured even in a small amount. For this reason, since the content of the chelating agent in the friction material is small, it is easy to configure so as not to affect the friction performance of the friction material.

  A third characteristic configuration is that the chelating agent is contained at 1% by weight or less in the moisture contained in the friction material material.

[Action and effect]
According to this configuration, it is possible to manufacture a friction material having friction performance almost the same as a friction material that does not contain a chelating agent.

It is explanatory drawing of the chelation reaction of a phenol resin. It is a figure which shows the chelation state of ethylenediaminetetraacetic acid (EDTA) (M is a metal ion). It is a flowchart of the normal temperature press construction method based on the Example of this invention. It is a flowchart of the hot press construction method based on the Example of this invention. It is a figure which shows the composition and performance evaluation of the Example and comparative example of this invention.

Embodiments of the present invention will be described below.
The friction material manufactured by the manufacturing method of the friction material of the present invention can be applied to a disc brake pad of a vehicle or the like, for example, 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 manufacturing method of the friction material of the present invention 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 any hot press method.

  The friction material raw material refers to all materials mixed in manufacturing the friction material. The friction material raw materials include fiber base materials, friction modifiers, fillers, wetting agents, binders, chelating agents, etc., which will be described later. It may be included. Hereinafter, in the present specification, a mixture of friction material raw materials for a room 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 include inorganic fibers such as aramid fibers, cellulose fibers, acrylic fibers, and carbon fibers, glass fibers, rock wool, ceramic fibers, and potassium titanate fibers. Examples thereof include metal fibers such as fiber, 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 wt% to 5 wt% of the friction material raw material.

  In the case of the mixed powder for the room temperature press method, these fiber base materials may be added to the friction material raw material in a pre-hydrated state. It is preferable to use a water-containing organic fiber as the water-containing fiber. Since the amount of water to be sprayed can be reduced by adding water-containing fibers 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, the friction material material becomes difficult to adhere to the inner wall of the mixer, and it is possible to prevent the occurrence of inconvenience that the yield of the friction material is deteriorated and that 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, and therefore the friction material material is more easily 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, molybdenum disulfide, ceramic, copper powder, brass powder, zinc powder, aluminum powder, and foamed vermiculite. It is done. These can be used alone or in combination of two or more. The blending ratio of the friction modifier is not particularly limited, but may be added so as to be about 3% to 30% by weight of the friction material raw material.

  As the filler, calcium hydroxide (slaked lime) is used. Calcium hydroxide is blended as a pH adjuster in the friction material material, for example, as a countermeasure against rust adhesion with the brake disc rotor. 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.

  As the wetting agent of the mixed powder for the room temperature press method, water is preferably used. The blending ratio of water is not particularly limited, but may be added so as to be about 3% to 6% 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 the amount of water supplied by spraying is 3% to 6% by weight of the friction material raw material. Good. At this time, you may comprise so that all the water added to a friction material raw material may be supplied with a water-containing fiber.

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, and 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 wt% to 0.5 wt%.
In addition, if a viscosity imparting agent is added to water, viscosity can be imparted to water, so that it is possible to reliably prevent, for example, dust from the friction material from being generated during the mixing step and the working environment from deteriorating. 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 wt% to 0.5 wt%.

  Although it is not necessary to add a specific wetting agent to the mixed powder for the hot press method, the moisture contained in each component of the friction material and the raw material that easily segregates in the mixing process (for example, dusts, metal fibers, etc.) ) 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. As the phenol resin, a novolac type phenol resin can be usually used. The blending ratio of the phenol resin is not particularly limited, but may be added so as to be about 5% by weight to 20% by weight of the friction material raw material.

  The chelating agent is not particularly limited as long as it can capture and capture calcium ions. For example, diamines such as ethylenediamine (EDA), and heterocyclic compounds such as 2,2′-bipyridyl , Β-diketones such as acetylacetone, hydroxycarboxylic acids such as citric acid, ethylenediaminetetraacetic acid (EDTA), and the like. In particular, ethylenediamine (EDA) and ethylenediaminetetraacetic acid (EDTA) bind more strongly to calcium ions and reliably capture them, so that even if a small amount is used, the rapid increase in viscosity during mixing of the friction material is effectively suppressed. This is preferable.

  The mixing ratio of the chelating agent is not particularly limited, but it may be added so as to be about 1% by weight at the maximum with respect to the water contained in the mixed powder of the friction material. Even in a small amount, the chelating material can exhibit a chelation suppressing function and extend the pot life of the mixed powder. In addition, if the amount of chelating agent added is not too much, too much will inhibit the viscous fluidity of the room temperature press method and may affect the friction performance of the friction material of the final product. It is preferably 1% by weight or less based on the moisture contained in the mixed powder of the raw material.

Hereinafter, the room temperature press method and the hot press method according to the method of manufacturing the friction material of the present invention will be described.
(Normal temperature press method)
As shown in FIG. 3, first, each of the above-mentioned fiber base material, friction modifier, filler (calcium hydroxide), wetting agent (water), binder (phenol resin), chelating agent, etc. Weigh. 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.

  In addition, for example, water may be continuously added after mixing is completed, or it 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. In addition, the chelating agent may be previously mixed in water or a phenol resin, and the addition method is not particularly limited.

  About a back board (metal plate etc.), after giving an appropriate surface treatment, an adhesive agent is apply | coated and dried on the side which mounts the produced mixed powder for normal temperature press methods.

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

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

(Hot press method)
Here, based on FIG. 4, the process different from the above-mentioned room temperature press method will be mainly described.
As shown in FIG. 4, first, each of the above-mentioned fiber base material, friction modifier, filler (calcium hydroxide), binder (phenolic resin), chelating agent, and other friction material raw materials are weighed. 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 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, a raw material that easily segregates in the mixing step (for example, dusts or metal fibers) may be pretreated with a viscous aqueous solution, if necessary. .

  Next, a predetermined amount of the mixed powder for the hot press method is weighed and preformed (normal temperature, 10 MPa), and then placed on the back plate and hot pressed (molding step). As 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 carrying out 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). ) In the hot press method, it is not necessary to perform a clamping process.

Examples of the method for producing a friction material according to the present invention 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 FIG. 5 and then put into a Redige mixer and mixed for 10 minutes (mixing step).

  After mixing, the mixed powder was discharged, and the material fixing property to the inner wall of the mixer was evaluated. The evaluation method evaluated the adhering condition by rubbing the inner wall surface of the mixer with a nylon brush. “◯” indicates that the material is not fixed, “Δ” indicates that the material is fixed, and “X” indicates that the material is fixed.

  In addition, as a pot life property of the mixed powder, the mixed powder is stored at room temperature, and the state of the powder after 8 hours and 24 hours is visually checked while it is squeezed by hand to evaluate whether there is a lump. did. The case where there was no lump was evaluated as “◯”, the case where there was a lump, “Δ”, and the case where there was a clear lump was evaluated as “x”.

  A press (molding process) was performed. The mixed powder for the hot press method was molded under the conditions of a molding temperature of 160 ° C., a molding pressure of 20 MPa, and a molding time of 10 minutes, and the pressability was evaluated. Moreover, about the mixed powder for normal temperature press construction methods, it shape | molded on the conditions of the shaping | molding pressure of 100 Mpa, and the shaping | molding time of 15 second, and evaluated pressability.

  In the case of the hot press method, the molded product was taken out from the mold, and the case where a crack occurred on the side surface of the molded product was evaluated as “x”. In the case of the room temperature press method, “◯” was given if it could be handled without any chipping when the molded product was taken out of the mold, and “X” was given if it was chipped even a little and the handling property was affected.

  Finally, the molded product was cured at 230 ° C. for 3 hours (heating step). The hot press-molded product was heat-treated in a free state, and the room temperature press-molded product was heat-treated while being pressed with a clamp (1 MPa).

  A friction performance test was performed on the friction material thus manufactured. The friction performance test was conducted according to JASO C406, and the average friction coefficient at a general use temperature (100 ° C.) was measured. If the value of the friction coefficient is 0.35 or more, it is “◯” as having good frictional force, and if it is 0.35 to 0.32, it is “△” as having normal frictional force, If it was less than 0.32, it was evaluated as “x” because it did not have sufficient frictional force. In Comparative Example 2, since a part of the mixed powder was immediately after mixing, a subsequent press, heat treatment, and friction performance test were not performed.

  As shown in FIG. 5, in Examples 1 to 8 of the present invention, good results were obtained in terms of material adhesion to the mixer, pot life, and pressability. Further, the friction materials of Examples 1 to 3 and 5 to 7 in which the addition amount of the chelating agent was 1% by weight or less had good friction performance. For the friction materials of Examples 4 and 8 in which the addition amount of the chelating agent is 1.2% by weight and 1.1% by weight, respectively, although the friction performance is somewhat inferior to the other examples, It had a normal frictional force that could be used as a brake pad or brake shoe.

  On the other hand, for Comparative Example 1 and Comparative Example 2 that do not contain a chelating agent, all the friction materials have good friction performance, but the material fixing property in the mixer, the pot life property, and the press property are the present invention. It was inferior to Examples 1-8.

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

Claims (3)

A mixing step of stirring the friction material raw material containing phenol resin, calcium hydroxide, water, chelating agent;
And a molding step of molding the mixed powder obtained in the mixing step into a desired shape.   The method for producing a friction material according to claim 1, wherein the chelating agent is ethylenediamine or ethylenediaminetetraacetic acid.   The method for producing a friction material according to claim 1 or 2, wherein the chelating agent is contained in water contained in the friction material raw material at 1 wt% or less.

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