Preparation method of modified diatomite for friction material filler
By modifying diatomaceous earth with nanocellulose, the problem of pore structure damage during the grinding process of diatomaceous earth was solved, the porosity and specific surface area were improved, and the noise and thermal stability of the friction material were improved.
Patent Information
- Application Number
- CN202511622117.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-06
- Publication Date
- 2026-03-03
AI Technical Summary
The nanoporous structure of diatomaceous earth is damaged during the drying, pulverizing and grinding process, which affects its surface properties and performance, resulting in poor friction noise and thermal decay performance of the friction material.
A method for modifying diatomaceous earth using nanocellulose was employed, which involved adding nanocellulose to a diatomaceous earth suspension, mixing and grinding it in a bead mill, and then introducing CO2 to adjust the pH to 7.5–8.5, thereby preparing a modified diatomaceous earth compound.
It significantly improves the porosity and specific surface area of modified diatomaceous earth, and reduces frictional noise and thermal degradation of the product.
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of fillers for friction materials, and specifically relates to a method for preparing modified diatomaceous earth. Background Technology
[0002] Fillers are an indispensable component of friction materials, including various friction modifiers and compounding agents. Their main function is to adjust the friction and wear properties of the friction material to better meet the requirements of braking and transmission functions under various working conditions. In addition, different fillers are often added to control and adjust the hardness and structural density of friction material products to improve braking noise and reduce product costs.
[0003] When a certain amount of friction particles are added to a friction material, the working interface and internal structure of the friction material change significantly. When the friction material contacts the mating parts, the braking effect is no longer achieved through a single, homogeneous interface, but through a composite friction interface composed of ordinary friction material and friction particles of different sizes. This not only maintains the stability of the friction coefficient, reduces wear rate, increases the service life of the friction material, and protects and extends the life of the mating parts, but also buffers braking energy transmission, reduces temperature rise rate, and reduces noise. Fillers include friction-reducing fillers and friction-increasing fillers. Friction-reducing fillers mainly aim to improve the stability and wear resistance of the material, reduce the friction coefficient, and reduce braking noise. They are mostly anisotropic non-metallic minerals such as graphite, vermiculite, talc, mica, and some layered metal sulfides (MoS2, Cu2S, Sb2S3, PbS, ZnS). Friction-increasing fillers in friction materials can increase the friction coefficient and improve resistance to thermal fading. Commonly used friction-enhancing fillers include barite, fluorite, vermiculite, zircon, corundum, and various rock fillers. To improve the uniform dispersion of friction-enhancing fillers in polymer matrices such as resins and rubbers and their effective bonding with the matrix material, surface modification is usually performed on the fillers. Diatomaceous earth is a biogenic siliceous sedimentary rock, mainly composed of diatom remains formed during geological evolution. Its chemical composition is mainly SiO2, but it is amorphous. It is usually white or grayish-white, with a density of 1.9–2.3 g / cm³, is lightweight and porous with a porosity of 80%–90%, a hardness of 1–1.5, and strong adsorption capacity, capable of absorbing 1.5–4 times its own weight in water. Its thermal conductivity at 200℃ and 800℃ is 0.0088–0.0158 W / (m·K) and 0.0277–0.219 W / (m·K), respectively. As a filler for friction materials, diatomaceous earth can effectively reduce friction noise and thermal degradation of products. The porous structure and surface properties of diatomaceous earth have a significant impact on reducing frictional noise and the thermal degradation of products.
[0004] The processing and purification of diatomaceous earth includes steps such as grading, washing, screening, drying, and grinding. During the drying, grinding, and pulverizing processes, the nanoporous structure of diatomaceous earth is inevitably damaged, thus affecting its surface properties. Summary of the Invention
[0005] In view of this, the purpose of the present invention is to provide a method for preparing modified diatomaceous earth for use as a filler in friction materials, wherein the porosity and specific surface area of the modified diatomaceous earth prepared by this method are significantly improved.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A method for preparing modified diatomaceous earth for use as a filler in friction materials includes the following specific steps:
[0008] S1 prepares a suspension with a solid content of 5-40% by mixing diatomaceous earth and calcium oxide in a mass ratio of 5-20:1. Nanocellulose is added under high-speed stirring conditions. The amount of nanocellulose is 1-15% based on the oven-dry diatomaceous earth.
[0009] S2 The prepared diatomaceous earth suspension containing nanocellulose was transferred into a bead mill for mixing and grinding;
[0010] After S3 grinding, CO2 is introduced into the diatomaceous earth suspension containing nanocellulose until the pH of the system reaches 7.5-8.5, thus obtaining the modified diatomaceous earth compound.
[0011] The nanocellulose is obtained by mechanically grinding pulp fibers; the pulp includes softwood pulp, hardwood pulp, bamboo pulp and other non-wood pulps.
[0012] The bead milling conditions described are a bead-to-material ratio of 8–4:1 and a linear velocity of 7–12 m / s during grinding. -1 The grinding concentration is 2-20%, and the feed flow rate is 500-2000 ml / min. -1 Grinding time: 2-4 hours.
[0013] The present invention has at least the following beneficial effects:
[0014] (1) The porosity and specific surface area of the prepared modified diatomite are significantly higher than those of the unmodified diatomite.
[0015] (2) The modified diatomaceous earth prepared can more effectively reduce friction noise and thermal degradation of products when used in friction materials. Detailed Implementation
[0016] The present invention will be further described below with reference to embodiments, which will enable those skilled in the art to have a more comprehensive understanding of the invention, but will not limit the invention in any way. All raw materials used in the following embodiments are commercially available and will not be described in detail by the inventor.
[0017] Example 1
[0018] Diatomaceous earth with an average particle size of 9.9 μm and calcium oxide were mixed at a mass ratio of 19:1. Under stirring, an appropriate amount of water was added to prepare a suspension with a solid content of 40%. After thorough dispersion, the stirring speed was increased, and nanocellulose prepared from hardwood pulp was added. The amount of nanocellulose was 5% based on the oven-dry diatomaceous earth. High-speed stirring was continued for 10 minutes to obtain a diatomaceous earth suspension containing nanocellulose. The resulting suspension was transferred to a bead mill for mixing and grinding under the following conditions: bead-to-material ratio of 4:1 and a linear velocity of 10 m / s. -1 Grinding concentration 10%, feed flow rate 1000 ml / min -1 The grinding time was 2.5 hours. After grinding, an appropriate amount of CO2 was introduced into the resulting diatomaceous earth suspension containing nanocellulose until the pH of the system reached 7.5–8.5, thus obtaining the modified diatomaceous earth compound. The porosity, specific surface area, and particle size properties of the obtained modified diatomaceous earth compound are shown in Table 1.
[0019] Example 2
[0020] Diatomaceous earth with an average particle size of 9.9 μm and calcium oxide were mixed at a mass ratio of 20:1. Under stirring, an appropriate amount of water was added to prepare a suspension with a solid content of 40%. After thorough dispersion, the stirring speed was increased, and nanocellulose prepared from hardwood pulp was added. The amount of nanocellulose was 10% based on the oven-dry diatomaceous earth. High-speed stirring was continued for 10 minutes to obtain a diatomaceous earth suspension containing nanocellulose. The resulting suspension was transferred to a bead mill for mixing and grinding under the following conditions: bead-to-material ratio of 5:1 and a linear velocity of 12 m / s. -1 The grinding concentration is 8%, and the feed flow rate is 800 ml / min. -1 The grinding time was 3.5 hours. After grinding, an appropriate amount of CO2 was introduced into the resulting diatomaceous earth suspension containing nanocellulose until the pH of the system reached 7.5–8.5, thus obtaining the modified diatomaceous earth compound. The porosity, specific surface area, and particle size properties of the obtained modified diatomaceous earth compound are shown in Table 1.
[0021] Example 3
[0022] Diatomaceous earth with an average particle size of 9.9 μm and calcium oxide were mixed at a mass ratio of 10:1. Under stirring, an appropriate amount of water was added to prepare a suspension with a solid content of 40%. After thorough dispersion, the stirring speed was increased, and nanocellulose prepared from hardwood pulp was added. The amount of nanocellulose was 5% based on the oven-dry diatomaceous earth. High-speed stirring was continued for 10 minutes to obtain a diatomaceous earth suspension containing nanocellulose. The resulting suspension was transferred to a bead mill for mixing and grinding under the following conditions: bead-to-material ratio of 5:1 and a linear velocity of 10 m / s. -1 Grinding concentration 10%, feed flow rate 1000 ml / min -1 The grinding time was 2.5 hours. After grinding, an appropriate amount of CO2 was introduced into the resulting diatomaceous earth suspension containing nanocellulose until the pH of the system reached 7.5–8.5, thus obtaining the modified diatomaceous earth compound. The porosity, specific surface area, and particle size properties of the obtained modified diatomaceous earth compound are shown in Table 1.
[0023] Table 1. Properties of Diatomite
[0024] serial number Unmodified diatomaceous earth Example 1 Example 2 Example 3 Average particle size / μm 9.91 7.28 5.34 8.33 Porosity / % 78 81 87 83 <![CDATA[Specific surface area / (m 2 / g)]]> 65 78 85 73
[0025] The present invention was implemented according to the specific embodiments described above, and all achieved the expected results.
Claims
1. A method for preparing modified diatomaceous earth for use as a filler in friction materials, characterized in that: The specific steps include the following: S1 prepares a suspension with a solid content of 5-40% by mixing diatomaceous earth and calcium oxide in a mass ratio of 5-20:
1. Nanocellulose is added under high-speed stirring conditions. The amount of nanocellulose is 1-15% based on the oven-dry diatomaceous earth. S2 The prepared diatomaceous earth suspension containing nanocellulose was transferred into a bead mill for mixing and grinding; After S3 grinding, CO2 is introduced into the diatomaceous earth suspension containing nanocellulose until the pH of the system reaches 7.5-8.5, thus obtaining the modified diatomaceous earth compound.
2. The method for preparing modified diatomaceous earth for friction material fillers according to claim 1, characterized in that... The nanocellulose is obtained by mechanically grinding pulp fibers; the pulp includes softwood pulp, hardwood pulp, bamboo pulp and other non-wood pulps.
3. The method for preparing modified diatomaceous earth for friction material fillers according to claim 1, characterized in that... The bead milling conditions described are a bead-to-material ratio of 8–4:1 and a linear velocity of 7–12 m / s during grinding. -1 The grinding concentration is 2-20%, and the feed flow rate is 500-2000 ml / min. 1 Grinding time: 2-4 hours.