Manufacturing method for copper and elemental free non-asbestos-organic friction material

Abstract

To provide the manufacturing method for a copper and elemental copper free NAO friction material providing an excellent fade resistance and high mechanical strength. [Means to Resolve] This manufacturing method includes the mixing step of mixing the raw friction material compounds to obtain the raw friction material mixture, the kneading step to apply the raw friction material mixture in the sealed type kneader to knead while maintaining the melting temperature of the thermosetting resin in the kneader or higher but lower than the curing temperature (temperature to start curing) under the predetermined pressure to obtain the kneaded raw friction material, the sizing step of sizing the kneaded raw friction material to obtain the raw friction material granulation article, and the hot press molding step of filling the raw friction material sized particles in the molding die to hot press molded by the press machine.

Claims

1. A manufacturing method for a copper and elemental copper free NAO (Non-Asbestos-Organic) friction material at lease including a fiber base material, a binder consisted of thermosetting resin, and a friction modifier, comprising: (1) a mixing step to mix a raw friction material compound in a mixer to obtain a raw friction material mixture; (2) a kneading step to knead the raw friction material mixture to obtain a kneaded raw friction material so as to set the raw friction material mixture in a sealed type kneader which includes a kneading chamber to store the raw friction material mixture, a compression lid to close the upper portion of the kneading chamber, a pair of rotor set in the kneading chamber and a temperature control system to control the temperature inside of the kneading chamber, and then to knead the raw friction material mixture while heating the kneading chamber to the melting temperature of the thermosetting resin or more but lower than the curing temperature (temperature to start curing), and pressurizing the inside of the kneading chamber; and (3) a hot press molding step to hot-press the kneaded raw friction material in a molding die to conduct the hot press molding to obtain the molded friction material, wherein a temperature of the kneading chamber when filing the raw friction material mixture into the sealed type kneader is elevated to 5-10 centigrade lower than the melting temperature of the thermosetting resin, the kneading step is divided into a temperature elevating kneading step in which the temperature of the kneading chamber elevates and exceeds the melting temperature of the thermosetting resin, a temperature elevating pressurizing kneading step in which the temperature of the kneading chamber elevates while pressurization takes place, and a temperature elevating decompressing kneading step in which the temperature of the kneading chamber elevates while decompression takes place, and a pressure of the compression lid in the temperature elevating step is set to be 0 MPa; a pressure of the compression lid in the temperature elevating pressurizing kneading step is set to be 0.3 MPa or higher but 1.0 MPa or lower; and a pressure of the compression lid in the temperature elevating decompressing kneading step is set to be 0 MPa.

2. The manufacturing method for the friction material according to claim 1, further comprising a sizing step between the kneading step and the hot press molding step to sizing the kneaded raw friction material to obtain the raw friction material sized particles.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a view showing one example of the manufacturing method for the friction material of this invention, showing the manufacturing method for the disc brake pad as a friction member; and

(2) FIG. 2 is a view showing one example of the manufacturing method for the friction material of the conventional art, showing the manufacturing method for the disc brake pad as a friction member.

DESCRIPTION OF EMBODIMENTS

(3) Embodiments of this invention will be explained in detail below.

(4) [Raw Friction Material]

(5) A raw friction material includes at least a fiber base material, a binder, and a friction modifier The raw friction material will be explained in detail below.

(6) (1) Fiber Base Material

(7) A fiber base material may be a nonferrous metal fiber other than a copper and a copper alloy, an organic fiber such as an aramid fiber and an acryl fiber, and an inorganic fiber such as a carbon fiber, a ceramic fiber, and a rock wool, and one or any combination of the same may be used. So as to secure a sufficient mechanical strength, the content of the fiber base material is preferably 10 weight percent or more but 40 weight percent or lower relative to an entire friction material weight and more preferably 15 weight percent or more but 30 weight percent or lower.

(8) (2) Binder

(9) The binder is made of a thermosetting resin. As the thermosetting resin, one or combination of a phenolic resin, an epoxy resin, a resin modifying the above-described resin with such as cashew oil, silicon oil, or various elastomer, and a resin dispersing the above-described resin with such as various elastomer and fluorine polymer, can be used. So as to secure the sufficient mechanical strength and wear resistance, the content of the binder is preferably 2 weight percent or more but 10 weight percent or lower relative to the entire friction material, and more preferably 4 weight percent or more but 7 weight percent or lower.

(10) (3) Friction Modifier

(11) The friction modifier can be an organic filler such as a cashew dust, a rubber dust (tire tread rubber pulverized powder), a various unvulcanized rubber particle, and a various vulcanized rubber particles, an inorganic filler such as a barium sulfate, a calcium carbonate, a calcium hydroxide, a vermiculite, mica, a silicon carbide, an alumina, a zirconium oxide, a zirconium silicate, a potassium hexatitanate, a magnetite, and a coke a lubricant such as molybdenum disulfide, a tin sulfide, a zinc sulfide, and an iron sulfide, and a nonferrous metal particle other than a copper and a copper alloy, and one or any combination of the above may be used.

(12) In the next section, the manufacturing method for the brake pad as the friction member as one example of the manufacturing method for the friction material according to this invention will be explained with reference to FIG. 1.

(13) <1> Mixing Step

(14) The raw friction material compound of the predetermined compound amount of the above-described raw friction material, for example, is filled in a mixer such as Loedige mixer and Eirich mixer to stir and mix to evenly dispersed. The raw friction material mixture after the mixing step is in powder state.

(15) <2> Kneading Step

(16) The raw friction material mixture obtained through the above mixing step is filled in a sealed type kneader including a kneading chamber, a compression lid to close an upper portion of the kneading chamber, a pair of rotors set in the kneading chamber, and a temperature control system to control the temperature in the kneading chamber and is heated for the inside of the kneading chamber to be at the melting temperature of the thermosetting resin or higher but lower than the curing temperature (temperature to start curing) and at the same time kneaded while pressurizing inside of the kneading chamber. The raw friction material mixture after the kneading step is in paste with appropriate viscosity.

(17) A significant difference between this invention and the conventional arts is the kneading step by kneading and refining the raw friction material mixture already mixed evenly under the predetermined temperature and pressure.

(18) Refining the fiber base material and the friction modifier can provide preferable wear resistance (mechanical strength) to the friction material as well as improves the heat dissipation of the friction material.

(19) The kneading step will be explained below in detail.

(20) <2.1> Kneading Effect

(21) In the kneading step, the thermosetting resin involved in the raw friction material mixture is melted immediately upon heating, and while the thermosetting resin obtained by melting the fiber base material and the friction modifier is kneaded, the fiber base material and the friction modifier are refined by applying the sufficient shearing force to the raw friction material mixture.

(22) <2.2> Kneading Temperature and Pressure

(23) The temperature and the pressure when kneading the raw friction material mixture will be explained next.

(24) In the kneading step, if melting the thermosetting resin takes too much time, the kneading time is extended and the fiber base material and the friction modifier are excessively refined, thereby resulting in the reduction of the strength of the friction material.

(25) Also, if the shearing force applied to the raw friction material is insufficient, refinement of the fiber base material and the friction modifier becomes insufficient, thereby resulting in insufficient fade resistance.

(26) In order to avoid the above-problems, the temperature of the kneading chamber when filling the raw friction material mixture into the sealed type kneader is set 5-10 centigrade lower than the melting temperature of the thermosetting resin.

(27) In addition, in the present invention, the kneading step is divided into a temperature elevation kneading step, a pressure kneading step, and a decompression kneading step, and at the same time, the pressure of the compression lid in the temperature elevation step is set to be 0 MPa; the pressure of the compression lid in the pressure kneading step is set to be 0.3 MPa or higher but 1.0 MPa or lower; and the pressure of the compression lid in the decompression kneading step is set to be 0 MPa. Adding the temperature elevation kneading step at the pressure of the compression lid of 0 MPa in the initial stage of the kneading step, the temperature of the raw friction material mixture, prior to the pressure kneading step of pressurizing the raw friction material mixture, may rise uniformly. Also, adding the decompression kneading step at the pressure of the compression lid of 0 MPa in the latter stage of the kneading step may crush small lump in the raw friction material mixture moderately. As a result, generation of the raw material lump can be suppressed, and the required time for the sizing step in the latter stage can be shorten.

(28) By kneading the raw friction material mixture as satisfying the temperature and pressure conditions, the refinement of the fiber base material and the friction modifier can be realized, and sufficient fade resistance and mechanical strength can be provided to the friction material.

(29) Here, the sealed type kneader that is appropriately used in the kneading step of this invention is such as a Wonder Kneader series of Moriyama Company Limited.

(30) <3> Sizing Step

(31) The kneaded raw friction material obtained through the kneading step may leave a raw material lump. This raw material lump may cause problems when measuring the content in the following steps, and therefore the kneaded raw friction material is filled in the mixer such as Loedige mixer and Eirich mixer to stir and mix until the raw material lump disappears. The sizing step may not be a requisite in some cases and can be skipped.

(32) <4> Hot Press Molding Step

(33) The raw friction material sized particles obtained through the sizing step is measured to be filled in a hot molding die and hot press molded by a pressing device for 1-10 minutes at 140-200 centigrade of molding temperature under the molding pressure at 20-80 MPa.

(34) When manufacturing a disc brake pad, the raw friction material sized particles and a steel back plate that is cleaned, surface treated, and applied an adhesive thereon, are superposed to be set in the hot molding die to conduct hot press molding. When manufacturing a brake lining for the drum brake, the raw friction material sizing particle only is filled in the hot molding die to conduct the hot press molding.

(35) <5> Heat Treatment Step

(36) The molded friction material is heated in a heat chamber at 180-250 centigrade for 1-5 hours, and then the curing of the thermosetting resin included in the friction material as the binder is completed.

(37) <6> Grinding Step

(38) A grinder with a grindstone is used to grind the surface of the friction material to form a friction surface.

(39) <7> Other Steps

(40) As necessary, a painting step, a paint baking step, a slit-chamfer forming step, and a scorching step may be performed.

Embodiments

(41) In the following sections, the embodiments of this invention will be explained concretely. However, the scope of this invention is not limited to the embodiments described herein.

(42) First, the manufacturing methods for the disc brake pad in the embodiments 1-6 and the Comparative Example 1-4 will be explained.

(43) (1) Mixing Step

(44) TABLE-US-00001 TABLE 1 Composition 1 Composition 2 Fiber base Material Aramid fiber 3 3 Rock wool 2 2 Binder Inorganic Phenolic resin (melting 6 0 Friction filler temperature 90 centigrade) modifier Phenolic resin (melting 0 6 temperature 100 centigrade) Zirconium oxide 23 23 Zirconium silicate 1 1 Potassium hexatitanate 20 20 Magnetite 5 5 Mica 9 9 Vermiculite 1 1 Barium sulfate 15 15 Calcium hydroxide 2 2 Coke 3 3 Organic Cashew dust 5 5 filler Rubber dust 1 1 Lubricant Artificial graphite 3 3 Zinc sulfide 1 1 Weight %

(45) Components of the raw friction material compounds shown in Table 1 are applied to be stirred for 5 minutes to obtain the raw friction material mixtures.

(46) (2) Kneading StepSizing Steps

(47) TABLE-US-00002 TABLE 2 E1 E2 E3 E4 E5 E6 CE1 CE2 CE3 CE4 CE5 Friction material composition C1 C1 C1 C2 C2 C2 C1 C1 C1 C2 C1 Kneading Kneader Adding raw 85 85 85 90 90 90 85 85 85 90 No Step Chamber friction material kneading Temperature mixture step (centigrade) Starting 110 110 110 110 110 110 110 110 110 110 pressure kneading step Ending 125 125 125 125 125 125 125 125 125 125 decompression kneading step Temperature Pressure (Mpa) 0 0 0 0 0 0 0 0 Elevation Kneading time 0.5 0.5 0.5 1.0 1.0 1.0 0.5 0.5 Kneading Step (minute) Pressure Pressure of 0.3 0.5 1.0 0.3 0.5 1.0 0.1 2.0 0.5 0.5 Kneading Step compression (Mpa) Kneading time 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 (minute) Decompression Pressure of 0 0 0 0 0 0 0 0 Kneading Step compression (Mpa) Kneading time 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 (minute) Evaluation Result Condition of GD GD GD GD GD GD BD GD BD BD N/A kneaded raw friction material Fading effect GD EX GD GD EX GD N/A BD N/A N/A BD Wear resistance GD EX GD GD EX GD N/A AV N/A N/A BD E = Embodiment CE = Comparative Example C = Composition EX = Excellent GD = Good BD = Bad Av = Average

(48) TABLE-US-00003 TABLE 3 Condition of Kneading Raw Friction Material Evaluation Method Manually checking the condition of kneaded Raw Friction Material Evaluation Standard GD no roughness of kneading and no material lump BD roughness of kneading and material lump N/A no evaluation (no kneading step)

(49) The raw friction material mixtures are stirred by the Wonder Kneader (WDS7-30, kneading capacity: 71) of Moriyama Company Limited according to the conditions in Table 2 to obtain the kneaded raw friction material. The condition of the obtained kneaded raw friction material was checked. The evaluation standard is shown in the Table 3, and the evaluation result is shown in the Table 2.

(50) The kneaded raw friction material shown in the Embodiments 1-6 and the Comparative Example 2, where the condition of the kneaded raw friction material is fine, are filled in the Loedige mixer and stirred for 5 minutes to obtain the raw friction material sized particles in the Embodiments 1-6 and the Comparative Example 2.

(51) (3) Hot Press Molding Step

(52) The raw friction material sized particles in the Embodiments 1-6 and the Comparative Example 2 are superposed on the steel back plate that is cleaned, surface treated, and applied an adhesive thereon to be set in the hot molding die to conduct the hot press molding for 5 minutes at the molding temperature of 160 centigrade under the molding pressure at 30 MPa to obtain the molded friction material.

(53) (4) Heat Treatment StepFinishing Step

(54) The molded friction material is set in the heat chamber and cured for 3 hours at 200 centigrade to be painted, baked, and grinded to make the disc brake pad in the Embodiments 1-6 and the Comparative Example 2.

(55) Next, the manufacturing method for the brake pad in the comparative example 5 will be explained.

(56) (1) Mixing Step

(57) The compositions of the raw friction material compound as in the Table 1 are added in the Loedige mixer and are stirred for 5 minutes to obtain the raw friction material mixture.

(58) (2) Pre-Forming Step

(59) The raw friction material mixture is filled in the pre-forming die and is pressure-molded for 15 seconds under the molding pressure of 30 MPa to obtain the unfinished/pre-formed friction material.

(60) (3) Hot Press Molding Step

(61) The unfinished/pre-formed friction material is superposed on the steel back plate that is cleaned, surface treated, and adhesive applied thereon to be set in the hot molding die to conduct the hot press molding for 5 minutes at the molding temperature of 160 centigrade under the molding pressure at 30 MPa to obtain the molded friction material.

(62) (4) Heat Treatment StepFinishing Step

(63) The molded friction material is set in the heat chamber and cured for 3 hours at 200 centigrade to be painted, baked, and grinded to make the disc brake pad in the Comparative Example 5.

(64) (5) Performance Comparison

(65) Relating to the disc brake pad manufactured through the above-described steps in the Embodiments 1-6 and the disc brake pad of Comparative Example 2 and 5, the fade resistance and wear resistance (mechanical strength) are evaluated.

(66) (5.1) Evaluation Method

(67) TABLE-US-00004 TABLE 4 Fade resistance Wear resistance Evaluation JASO C406 JASO C427 Method Dynamometer Test Temp.specific wear test First fade minimum Initial-brake temp.: 200 C. No. of applications: 1000 times Evaluation EX 0.25 or more Less than 0.10 mm Criterion GD 0.22 or more 0.10 mm or more less than 0.25 Less than 0.15 mm AV 0.19 or more 0.15 mm or more Less than 0.22 Less than 0.20 mm BD Less than 0.19 0.20 mm or more N/A No evaluation No evaluation (kneading condition: BD) (kneading condition: BD)

(68) Relating to the disc brake pad of the Embodiments 1-6 and the Comparative Example 2 and 5, the fade resistance and the wear resistance (mechanical strength) are evaluated. The evaluation method and standard are shown in the Table 4.

(69) (5.2) Evaluation Result

(70) The evaluation result of the fade resistance of every friction material and the wear resistance (mechanical strength) are shown in Table 2.

(71) As apparent from the evaluation result in the Table 2, the friction material manufactured through the manufacturing method of this invention has excellent fade resistance and wear resistance (high mechanical strength).