Friction material composition for preparing brake pad and preparation method thereof

Abstract

The invention relates to the technical field of friction materials, in particular to a friction material composition for preparing a brake pad and a preparation method of the friction material composition. The friction material composition is prepared from, by mass, 8-12 parts of matrix phenolic resin, 2-6 parts of reinforcing components, 4-8 parts of sepiolite powder, 15-20 parts of metal oxide, 10-15 parts of calcium carbonate, 6-10 parts of crystalline flake graphite, 1-2 parts of zinc stearate and 1-2 parts of friction powder. According to the friction material composition for preparing the brake pad and the preparation method of the friction material composition, the problem of heat fade caused by the fact that the matrix phenolic resin serves as a single binder can be reinforced and made up through the arranged reinforcing component, the problem that the friction coefficient is reduced due to heat fade is solved, and the high-temperature stability of the friction coefficient is further improved and maintained.

Description

Technical Field

[0001] The invention relates to the technical field of friction materials, and in particular to a friction material composition for preparing a brake pad and a preparation method thereof. Background Art

[0002] Friction material is an important functional material, and the quality of each component of the friction material will affect the friction performance. The main binder of organic friction material is currently phenolic resin and its modified products. However, the following problems have been found in the use of phenolic resin as a binder for friction materials: when high temperatures are generated during braking, obvious thermal decay is likely to occur, which will lead to a significant reduction in the friction coefficient; currently, most methods of improving the thermal decay phenomenon are to add physical fillers or perform modification treatments, but the effect is not good; therefore, it is considered to develop components that can enhance the performance of phenolic resin-based friction materials, so that the friction material composition as a whole has good high temperature resistance and maintains a good friction coefficient; in view of this, we propose a friction material composition for preparing brake pads and a preparation method thereof. Summary of the invention

[0003] The purpose of the present invention is to solve the deficiencies mentioned in the above background technology and provide a friction material composition for preparing brake pads and a preparation method thereof.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: A friction material composition for preparing a brake pad, comprising a base phenolic resin as a binder, wherein the mass fractions of the components of the friction material composition are as follows: Base phenolic resin: 8-12 parts; Reinforcement component: 2-6 parts; Sepiolite powder: 4-8 parts; Metal oxide: 15-20 parts; Calcium carbonate: 10-15 parts; Flake graphite: 6-10 parts; Zinc stearate: 1-2 parts; Friction powder: 1-2 parts.

[0005] Preferably, the reinforcing component comprises polyetheretherketone resin and polyurethane elastomer in a mass ratio of 0.5-1:1, and toluene-2,4-diisocyanate accounting for 5-10% of the total mass of the polyetheretherketone resin and the polyurethane elastomer.

[0006] Preferably, the metal oxide is aluminum oxide, calcium oxide, magnesium oxide, or iron oxide.

[0007] Preferably, the bulk density of the metal oxide is set to 3.0-3.5 g / cm 3 , moisture content is not more than 3%.

[0008] A method for preparing a friction material composition for preparing a brake pad, the method comprising: preparing the friction material by sequentially adopting a granulation process and a powder hot pressing process according to the proportion of each component; the specific steps are: Step 1: Mixing: Except for the base phenolic resin, other components are mixed in a mixing barrel to obtain a mixed powder; Step 2: Preliminary granulation: spray anhydrous ethanol into the mixed powder, stir and mix to obtain preliminary granules; Step 3: Refinement, increase the stirring speed in step 2 to break the preliminary pellets into uniform pellets; Step 4: Drying: Dry at 60-80°C until the moisture content is 3-6%, and sieve to obtain particles with a particle size of 2-10 mm; Step 5: Coating and granulating: spread the base phenolic resin powder in a disc, pour the granules in step 4 into the disc and shake them to coat the surface of the phenolic resin powder, and dry them naturally in a ventilated place; Step 6: Hot pressing and curing.

[0009] Preferably, the preparation method of the reinforcing component is: mix polyetheretherketone resin, polyurethane elastomer and toluene-2,4-diisocyanate in proportion, set the temperature to 200-320°C, react for 2-6 hours to obtain a solid product, and refine it to obtain 38-75μm powder as the reinforcing component.

[0010] Preferably, the hot pressing molding is provided with: 6-12MPa pressing pressure, 10-15min holding time, 140-200°C hot pressing temperature, 130-140°C mold preheating temperature; In the hot pressing process, an intermittent exhaust process of 3-5 times of hot pressing for 10-15s and exhausting for 10-15s is provided before holding pressure.

[0011] Preferably, the specific method of the curing treatment is: placing the hot-pressed material into a heat treatment drying oven, applying an initial heat preservation of 140-150°C for 1-1.5h, heating to 160-170°C, keeping warm for 2-4h, heating to 180-200°C, keeping warm for 5-8h, and taking out after natural furnace cooling to room temperature.

[0012] Preferably, the temperature rise rate of the curing treatment is: heating to 100-120°C at 2-3°C / min, and the subsequent heating stage is set at a heating rate of 0.25-0.75°C / min.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The friction material composition for preparing brake pads and the preparation method thereof can strengthen and compensate for the thermal decay problem caused by the base phenolic resin as a single binder through the provided reinforcing component, reduce the problem of reduced friction coefficient caused by thermal decay, and are conducive to further improving and maintaining the high-temperature stability of the friction coefficient. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0015] The present invention describes the above technical solution in detail through the following embodiments: Example 1

[0016] A friction material composition for preparing a brake pad includes a base phenolic resin as a binder, and the mass fractions of the components of the friction material composition are specifically: Base phenolic resin 2123-1T: 10 parts; Reinforcement component: 5.5 parts; Sepiolite powder: 7 parts; Alumina powder: 20 parts; QT-3 calcium carbonate: 10 parts; Flake graphite-195: 8 parts; Zinc stearate: 1 part; Friction powder: 1 part.

[0017] It should be noted that the reinforcing component in this embodiment specifically includes 2.5 parts of polyetheretherketone resin, 2.5 parts of polyurethane elastomer, and 0.5 parts of toluene-2,4-diisocyanate; in this embodiment, the reinforcing component is prepared in advance and then mixed as a component of the composition to prepare the friction material; the preparation method of the reinforcing component is: mix polyetheretherketone resin, polyurethane elastomer and toluene-2,4-diisocyanate, set the temperature to 280°C, react for 6 hours to obtain a solid product, and refine and sieve out 38-75μm powder as a reinforcing component for standby use.

[0018] It is worth explaining that this part of the reinforcing component plays an important role in supplementing the performance. The polyurethane elastomer contains isocyanate groups, and the polyetheretherketone resin contains hydroxyl groups that can cross-link with isocyanate groups. The two can be cross-linked under heating conditions. The toluene-2,4-diisocyanate selected in this embodiment can be used as a curing agent to improve the molding quality on the one hand, and on the other hand, it can further provide isocyanate groups to play a reinforcing and supplementary role, so that a cross-linked structure is formed between the three; polyetheretherketone resin and polyurethane elastomer themselves have good heat resistance and mechanical properties. The reason why this embodiment does not directly mix and granulate the raw materials of the reinforcing components is that compared with the direct mixing of a single raw material, a more stable and composite molecular structure can be obtained after cross-linking, which is used to reinforce the performance of the base phenolic resin.

[0019] To be specific, in this embodiment, the base phenolic resin was purchased from Hebei Zetian Chemical and sold a phenolic resin product with the brand number 2123-1T, in which free phenol was ≤2.5% and the fineness was 200 mesh; polyetheretherketone resin was purchased from Suzhou Jutai New Materials Co., Ltd., and the polyurethane elastomer was purchased from Zhejiang Huafeng Thermoplastic Polyurethane Co., Ltd.; 2-2.5g / cm3 specification sepiolite powder was purchased from Shijiazhuang Leisheng Mineral Products Co., Ltd.; metal oxide alumina powder was purchased from Zhengzhou Xinli Wear-resistant Materials Co., Ltd. and sold 4000# specification, 3.2g / cm3 product; calcium carbonate powder was purchased from Zhejiang Qintang Calcium Industry Co., Ltd. and sold QT-3 type; flake graphite was purchased from China Graphite Group Co., Ltd. and sold 195 type; zinc stearate was purchased from Liyang Qiangsheng Chemical Co., Ltd.; and friction powder was purchased from Chemical Dasegao (Beijing) Technology Co., Ltd.

[0020] The present embodiment is a method for preparing a friction material composition for preparing a brake pad. The preparation method is: according to the proportion of each component, a granulation process and a powder hot pressing process are sequentially used to prepare the friction material; the specific steps are: Step 1: Mixing: Except for the base phenolic resin, other components are mixed in a mixing barrel to obtain a mixed powder; Step 2: Preliminary granulation: spray anhydrous ethanol accounting for 30% of the total weight of the powder into the mixed powder, stir and mix to obtain preliminary granules; Step 3: Refinement, breaking the preliminary pellets into uniform pellets; Step 4: Drying: Dry at 80°C to a moisture content of 5%, sieving, and selecting particles with a particle size of 2-10 mm; Step 5: Coating and granulating: spread the base phenolic resin powder in a disc, pour the granules in step 4 into the disc and shake them to coat the surface of the phenolic resin powder, and dry them naturally in a ventilated place; Step 6: Hot pressing: put the material from step 5 into the hot pressing mold, set the pressing pressure to 8MPa and the mold preheating temperature to 140℃, and when the temperature rises to 180℃, repeat the intermittent exhaust process of hot pressing for 10s and exhaust for 10s for 3 times, and then keep the pressure at 180℃ for 10min; Step seven: curing treatment, the material formed by hot pressing in step six is ​​placed in a JF980D heat treatment drying oven, and the temperature is controlled to rise from room temperature to 120°C at a rate of 2-3°C / min, and then to 150°C at a heating rate of 0.5°C / min, and initially kept warm for 1 hour, and then to 160°C at a heating rate of 0.5°C / min, and kept warm for 3 hours, and then to 180 at a heating rate of 0.5°C / min, and kept warm for 6 hours. After natural furnace cooling to room temperature, the friction material composition is taken out.

[0021] It should be explained that in this embodiment, an exhaust process is applied during the hot pressing molding process. Its purpose is to exhaust the gas in the material gap during the hot pressing temperature rise process, the residual volatile gas in the resin-based material, etc., to avoid the gas being unable to be discharged during the hot pressing process and affecting the molding quality.

[0022] The purpose of the curing treatment is to increase the degree of curing of the base phenolic resin and each component, eliminate the thermal stress inside the material to prevent deformation, and at the same time limit the heating rate. The heating rate should not be too fast and it is not easy to remove quickly. Quality problems such as sudden cooling deformation or sudden heating fracture need to be prevented.

[0023] Example 2

[0024] The only difference between this embodiment and embodiment 1 is that in this embodiment, the mass ratio of polyetheretherketone resin to polyurethane elastomer in the reinforcing component is set to 0.5:1, 1.25 parts of polyetheretherketone resin and 2.5 parts of polyurethane elastomer are set, and other conditions are the same.

[0025] Comparative Example 1

[0026] The difference between this comparative example and Example 1 is that in this comparative example, the reinforcing component is not prepared separately, and the raw material of the reinforcing component is directly added to the mixing in step 1, and other conditions are the same.

[0027] Comparative Example 2

[0028] The difference between this comparative example and Example 1 is that in this comparative example, no intermittent exhaust process is provided during the hot pressing forming process, and other conditions are the same.

[0029] Comparative Example 3

[0030] The only difference between this comparative example and Example 1 is that no curing treatment is applied in this comparative example, and other conditions are the same.

[0031] Comparative Example 4

[0032] The difference between this comparative example and Example 1 is that in this comparative example, no reinforcing component is added, and 15.5 parts of base phenolic resin are directly used, and other conditions are the same.

[0033] According to the above-mentioned Example 1, Example 2 and Comparative Examples 1 to 4, samples were prepared to test the friction coefficient and wear amount. The specific test method is as follows: First, each sample is run-in treated by heating with a heating tube, and the temperature is controlled below 100°C and run-in until the contact surface between the test piece and the friction disc is ≥95% before testing; (1) Friction coefficient: MMW-1A universal friction and wear testing machine was used, the pressure load was 30N, the speed was 200r / min, and the friction time was 10min; the small thrust ring specimen was made of 32GrMn steel, the dual diameter was 28mm, the measurement was repeated 5 times and the average value was taken, and the test temperature was controlled at 100℃-350℃.

[0034] (2) Wear amount: measured by the mass loss of the test block per unit time, with a turntable speed of 330 r / min, wear on the turntable for 180 min, and weighing the wear amount as a percentage of the original mass after the test is completed at 100℃-350℃.

[0035] The specific data is as follows:

[0036] From the data in the above table, it can be seen that the initial 100°C friction coefficients of Example 1 and Example 2 are similar, but as the temperature increases, the friction coefficient decay trend is greater than that of Example 1. Considering that the content of the reinforcing component will affect the thermal decay performance of the friction material, the corresponding wear rate will increase slightly. Considering that the reinforcing component is reduced, the wear resistance is affected; From the data of Comparative Examples 1 and 4, it can be seen that if the materials are directly mixed, the friction coefficient of the material will not be significantly improved compared with the use of all phenolic resins, that is, the thermal decay resistance is not fully demonstrated. Considering that the mixed materials cannot form a cross-linked structure between the reinforcing materials, the effective function is not achieved, and the friction coefficient and high wear are still poor. The friction coefficients of Comparative Examples 2 and 3 are similar, but the wear volume is significantly increased. The reason is that the preparation method easily leads to defects such as internal pores, cracks or deformation in the friction material, and the scrap rate of the finished product is high. Therefore, it is necessary to apply curing and intermittent exhaust processes.

[0037] In summary, the reinforcing component and the preparation method thereof can significantly improve the performance of the friction material, and Example 1 can be preferably used as an implementation method.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A friction material composition for preparing a brake pad, comprising a base phenolic resin as a binder, characterized in that: The specific mass fractions of the components of the friction material composition are: Base phenolic resin: 8-12 parts; Reinforcement component: 2-6 parts; Sepiolite powder: 4-8 parts; Metal oxide: 15-20 parts; Calcium carbonate: 10-15 parts; Flake graphite: 6-10 parts; Zinc stearate: 1-2 parts; Friction powder: 1-2 parts.

2. The friction material composition for preparing a brake pad according to claim 1, characterized in that: The reinforcing component comprises polyetheretherketone resin and polyurethane elastomer in a mass ratio of 0.5-1:1, and toluene-2,4-diisocyanate accounting for 5-10% of the total mass of the polyetheretherketone resin and the polyurethane elastomer.

3. The friction material composition for preparing a brake pad according to claim 2, characterized in that: The metal oxides are aluminum oxide, calcium oxide, magnesium oxide and ferric oxide.

4. The friction material composition for preparing a brake pad according to claim 3, characterized in that: The bulk density of the metal oxide is set to 3.0-3.5 g / cm 3 , moisture content is not more than 3%.

5. A method for preparing a friction material composition for preparing a brake pad, applicable to the friction material composition according to any one of claims 1 to 4, characterized in that: The preparation method is: according to the proportion of each component, the friction material is prepared by sequentially adopting the granulation process and the powder hot pressing process; the specific steps are: Step 1: Mixing: Except for the base phenolic resin, other components are mixed in a mixing barrel to obtain a mixed powder; Step 2: Preliminary granulation: spray anhydrous ethanol into the mixed powder, stir and mix to obtain preliminary granules; Step 3: Refinement, increase the stirring speed in step 2 to break the preliminary pellets into uniform pellets; Step 4: Drying: Dry at 60-80°C to a moisture content of 3-6%, sieving, and selecting particles with a particle size of 2-10 mm; Step 5: Coating and granulating: spread the base phenolic resin powder in a disc, pour the granules in step 4 into the disc and shake them to coat the surface of the phenolic resin powder, and dry them naturally in a ventilated place; Step 6: Hot pressing and curing.

6. The method for preparing a friction material composition for preparing a brake pad according to claim 5, characterized in that: The preparation method of the reinforcing component is: mix polyetheretherketone resin, polyurethane elastomer and toluene-2,4-diisocyanate in proportion, set the temperature to 200-320°C, react for 2-6 hours to obtain a solid product, and refine and take 38-75 μm powder as the reinforcing component.

7. The method for preparing a friction material composition for preparing a brake pad according to claim 5, characterized in that: The hot pressing molding is provided with: 6-12MPa pressing pressure, 10-15min holding time, 140-200℃ hot pressing temperature, 130-140℃ mold preheating temperature; In the hot pressing process, an intermittent exhaust process of 3-5 times of hot pressing for 10-15s and exhausting for 10-15s is provided before holding pressure.

8. The method for preparing a friction material composition for preparing a brake pad according to claim 5, characterized in that: The specific method of the curing treatment is: putting the hot-pressed material into a heat treatment drying oven, applying an initial heat preservation of 140-150°C for 1-1.5h, heating to 160-170°C, keeping warm for 2-4h, heating to 180-200°C, keeping warm for 5-8h, and taking it out after natural furnace cooling to room temperature.

9. The method for preparing a friction material composition for preparing a brake pad according to claim 8, characterized in that: The heating rate of the curing treatment is: heating to 100-120°C at 2-3°C / min, and the subsequent heating stage is set at a heating rate of 0.25-0.75°C / min.

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