Disc brake pad friction material and preparation process thereof

Abstract

The invention discloses a disc brake pad friction material and a preparation process thereof, and relates to the technical field of brake pads. The friction material is prepared from the following raw materials in parts by weight: 10 to 14 parts of phenolic resin, 10 to 12 parts of modified nitrile rubber, 1.5 to 2.5 parts of hexamethylenetetramine, 1 to 2 parts of calcium stearate, 0.5 to 1 part of magnesium oxide, 0.3 to 0.5 part of aluminum oxide, 2 to 4 parts of self-healing microcapsules, 5 to 7 parts of diatomite, 20 to 24g of barium sulfate, 21 to 25 parts of kaolin, 10 to 12 parts of calcium carbonate and 5 to 7 parts of graphite. The synthesized modified nitrile rubber is obtained by introducing a POSS structure, hydroxyl and hindered phenol into nitrile rubber, and the synthesized self-healing microcapsule is obtained by introducing dehydroabietic acid and a polysiloxane chain into the wall material of the microcapsule, namely the surface of urea-formaldehyde resin. The friction material is high in oxidation resistance, high temperature resistance, water resistance and self-healing capacity and has stable tribological performance.

Description

Technical Field

[0001] The invention relates to the technical field of brake pads, and in particular to a disc brake pad friction material and a preparation process thereof. Background Art

[0002] Disc brake pads are a component of the disc brake system. They are fixed to the tires of the vehicle and rotate at the same speed. They work with the caliper to brake the vehicle. Like most brake pad friction materials, disc brake pad friction materials are also multi-component composite materials composed of multiple components, mainly including reinforcing materials, adhesives, fillers, and friction performance modifiers. The performance of the brake friction material will also be affected by the different proportions of each component and the raw materials.

[0003] At present, thermosetting phenolic resin is still the main body of the matrix of friction materials, that is, the binder. Therefore, the toughness of thermosetting phenolic resin has a significant impact on the overall performance of friction materials. In the prior art, nitrile rubber is used in friction materials because it has good fluidity and can significantly improve the toughness of thermosetting phenolic resin. However, the high temperature resistance of nitrile rubber cannot meet the use in the high temperature environment of the braking process. The high temperature and high humidity environment will also cause the antioxidant effect of nitrile rubber to decrease. Therefore, the high temperature resistance and antioxidant properties of nitrile rubber need to be improved.

[0004] During the use of disc brake pads, under the action of normal load and tangential force, stress concentration is likely to occur at the interface of the friction material, resulting in microcracks that expand rapidly, causing the deterioration of friction and wear performance, thereby affecting the use of the friction material. Previous studies have added microcapsules made of urea-formaldehyde resin as the wall material and a repair agent as the core material, and the wall material coated with the core material to the friction material to enhance the self-healing ability of the friction material. However, urea-formaldehyde resin has poor water resistance and is not resistant to high temperatures. When in a humid and high-temperature environment, urea-formaldehyde resin is limited in its use in friction materials.

[0005] Therefore, it is necessary to find a suitable modification method to improve the high temperature resistance and oxidation resistance of nitrile rubber, and to enhance the water resistance and high temperature resistance of the wall material of the self-healing microcapsule, namely urea-formaldehyde resin, so as to obtain a disc brake pad friction material with excellent performance. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a disc brake pad friction material and a preparation process thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions: A disc brake pad friction material, comprising the following raw materials in parts by weight: 10-14 parts of phenolic resin, 10-12 parts of modified nitrile rubber, 1.5-2.5 parts of hexamethylenetetramine, 1-2 parts of calcium stearate, 0.5-1 parts of magnesium oxide, 0.3-0.5 parts of aluminum oxide, 2-4 parts of self-healing microcapsules, 5-7 parts of diatomaceous earth, 20-24g of barium sulfate, 21-25 parts of kaolin, 10-12 parts of calcium carbonate, and 5-7 parts of graphite; The preparation of the disc brake pad friction material comprises the following steps: Phenolic resin, modified nitrile rubber, hexamethylenetetramine, calcium stearate, magnesium oxide, aluminum oxide, self-healing microcapsules, diatomaceous earth, barium sulfate, kaolin, calcium carbonate and graphite are placed in a pulverizer for pulverization and mixing to obtain a mixture; the mixture is then roll-refined on a roll mill to obtain a roll-refined material; the roll-refined material is then pulverized and placed in a vulcanizer for hot pressing and then cured to obtain a disc brake pad friction material; Furthermore, the temperature of the hot pressing molding is 155-165°C and the pressure is 10-12MPa; the curing conditions are firstly heating to 120°C and keeping it for 3-3.5h, then heating to 140°C and keeping it for 3-3.5h, then heating to 160°C and keeping it for 3-3.5h, and finally heating to 180°C and keeping it for 4-4.5h; The modified nitrile rubber is prepared by the following steps: Step A1: In a protective gas atmosphere, add carboxylated nitrile rubber to toluene, heat to 45-50° C., add pyridine, start stirring, then add γ-glycidyloxysilylpropylsesquioxane, stir and react for 8-10 hours, then heat to 110-120° C., stir for 1-2 hours, and obtain an alcohol hydroxyl product; Further, the amount ratio of carboxylated nitrile rubber, toluene, pyridine and γ-glycidyl ether silyl propyl sesquioxane is 20-25 g: 160-170 mL: 0.1-0.2 mol: 49-51 g; During the reaction of step A1, the carboxyl group of the carboxylated nitrile rubber reacts with the epoxy group of γ-glycidyloxysilylpropylsesquioxane to form an alcohol hydroxyl product; Step A2: Add the alcohol hydroxyl product to toluene, start stirring, then add sodium hydroxide solution, stir for 5-10 minutes, then dropwise add epichlorohydrin, stir and react at room temperature for 6-7 hours to obtain an epoxy product; Further, the usage ratio of alcohol hydroxyl product, toluene, sodium hydroxide solution and epichlorohydrin is 35-40g:100-120mL:5-10mL:0.1-0.2mol, and the mass fraction of sodium hydroxide solution is 5-10%; During the reaction of step A2, the hydroxyl group in the alcoholic hydroxyl product reacts with epichlorohydrin to generate an epoxy product; Step A3: In a protective gas atmosphere, add 3,5-di-tert-butyl-4-hydroxybenzoic acid to toluene, heat to 40-45° C., add pyridine, start stirring, then add the epoxy product, stir and react for 9-11 hours, then heat to 100-110° C., stir for 1.5-2 hours, and obtain modified nitrile rubber; Further, the usage ratio of 3,5-di-tert-butyl-4-hydroxybenzoic acid, toluene, pyridine and epoxidation product is 0.1-0.2 mol: 150-160 mL: 0.1-0.15 mol: 42-45 g; During the reaction of step A3, the carboxyl group of 3,5-di-tert-butyl-4-hydroxybenzoic acid undergoes a ring-opening reaction with the epoxy group of the epoxy product to generate a modified nitrile rubber containing polysilsesquioxane (POSS), hindered phenol, and alcoholic hydroxyl groups.

[0008] The preparation of the self-healing microcapsule comprises the following steps: Step B1: drying the microcapsules at 80-90° C. for 6-8 hours to obtain dried microcapsules for standby use; adding a silane coupling agent to deionized water, then adding an acetic acid solution, stirring for 10-15 minutes, adjusting the pH to neutral, adding the dried microcapsules, heating to 80-85° C., stirring for 1-1.5 hours, washing with ethanol and filtering, and then drying at 40-50° C. for 24-26 hours to obtain silane coupling agent modified microcapsules; Furthermore, the dosage ratio of silane coupling agent, deionized water, acetic acid solution and dried microcapsules is 5-6g:90-100mL:10-20mL:10-12g, the silane coupling agent is 10-alkenyl undecyl trimethoxysilane, the mass fraction of acetic acid solution is 30-40%, and the volume fraction of ethanol is 95%; the preparation of microcapsules refers to the preparation process of microcapsules in the preparation content of sample 1.2 of the paper "Preparation and Performance Study of Fluorosilane Modified Microcapsule Composite Materials"; During the reaction of step B1, the silanol obtained after the hydrolysis of the silane coupling agent is used to treat the surface of the wall material of the microcapsule and grafted with the surface of the microcapsule to obtain a silane coupling agent-modified microcapsule containing a carbon-carbon double bond on the surface; Step B2: adding the silane coupling agent modified microcapsules into dichloromethane, stirring for 30-40 minutes, then adding 3-chloroperoxybenzoic acid, stirring and reacting at room temperature for 5-6 hours to obtain the epoxy product 1; Further, the dosage ratio of the silane coupling agent modified microcapsules, dichloromethane, and 3-chloroperoxybenzoic acid is 5-6 g: 70-80 mL: 20-23 g; During the reaction of step B2, the carbon-carbon double bonds on the surface of the microcapsules modified by the silane coupling agent are oxidized into epoxy groups to obtain epoxy product 1; Step B3: In a protective gas atmosphere, add dehydroabietic acid to toluene, heat to 50-60°C, add pyridine, start stirring, then add the epoxy product 1, stir and react for 10-12h, then heat to 110-120°C, stir for 1-2h to obtain a hydroxyl product; Further, the usage ratio of dehydroabietic acid, toluene, pyridine and epoxidation product 1 is 34-36 g: 140-150 mL: 0.1-0.15 mol: 6-8 g; During the reaction of step B3, the carboxyl group of dehydroabietic acid reacts with the epoxy group of the epoxy product 1 to form a hydroxyl product; Step B4: Add the carboxyl-terminated polysiloxane to DMF, add dichlorothionyl under stirring, reflux and stir at 50-60° C. for 4-5 hours to obtain an acyl chloride product; stir and mix the hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide to obtain a mixed solution 1; add the acyl chloride product to dimethyl sulfoxide to obtain a mixed solution 2, slowly drop the mixed solution 2 into the mixed solution 1 in an ice-water bath, after the dropwise addition is completed, heat to 40-45° C., stir and react at a constant temperature for 8-10 hours, then heat to 100-110° C., continue stirring for 1-2 hours, and distill under reduced pressure to obtain self-healing microcapsules; Further, the amount ratio of the carboxyl-terminated polysiloxane, DMF, and dichlorothionyl is 40-42 g: 55-65 mL: 1.2-1.5 g; the amount ratio of the hydroxyl product, pyridine, triethylamine, and dimethyl sulfoxide is 12-14 g: 9-11 mL: 15-20 mL: 40-50 mL; the amount ratio of the acyl chloride product and dimethyl sulfoxide is 43-45 g: 90-100 mL; the amount ratio of the mixed solution 1 and the mixed solution 2 is 85-95 mL: 100-110 mL; the carboxyl-terminated polysiloxane is a carboxypropyl-terminated polydimethylsiloxane; During the reaction of step B4, the carboxyl group of the carboxyl-terminated polysiloxane reacts with thionyl chloride to generate an acyl chloride product; the acyl chloride product reacts with the alcoholic hydroxyl group of the hydroxyl product to generate a self-healing microcapsule containing polysiloxane chains on the surface.

[0009] Beneficial effects of the invention: The invention discloses a disc brake pad friction material, comprising the following raw materials: phenolic resin, modified nitrile rubber, hexamethylenetetramine, calcium stearate, magnesium oxide, aluminum oxide, self-healing microcapsules, diatomaceous earth, barium sulfate, kaolin, calcium carbonate and graphite.

[0010] The synthesized modified nitrile rubber is obtained by introducing POSS structure, hindered phenol and hydroxyl group into nitrile rubber; the hydroxyl group causes hydrogen bond cross-linking between the modified nitrile rubber and the phenolic resin, the modified nitrile rubber has good compatibility with the phenolic resin, can better toughen the phenolic resin and improve the impact strength and wear rate of the friction material; the POSS structure has strong structural stability and high temperature resistance, and the hindered phenol can quickly terminate the free radical oxidation reaction of the friction material caused by light, heat and oxygen, so the high temperature resistance and oxidation resistance of the modified nitrile rubber are significantly improved, thereby significantly improving the high temperature resistance and oxidation resistance of the friction material.

[0011] The synthesized self-healing microcapsules are obtained by introducing dehydroabietic acid and polysiloxane chains into the wall material surface of microcapsules whose wall material is urea-formaldehyde resin and core material is epoxy resin. With the friction sliding process, the cracks generated by the friction material expand and cause the microcapsules to rupture. The core material epoxy resin is released to the crack surface by capillary action, so that the fractured surfaces are adhered together, thereby repairing the cracks, reducing the wear rate, and improving the stability of the tribological properties of the material; dehydroabietic acid is one of the derivatives of rosin. Due to the tricyclic diterpene structure in its molecule, it has strong hydrophobicity, improves the water resistance of the wall material urea-formaldehyde resin, and makes the self-healing microcapsules more suitable for the use of brake pad friction materials. The Si-C bond and Si-O-Si bond energy in the polysiloxane chain are relatively high, the fracture energy consumption is large, and the thermal stability is good. Therefore, the self-healing microcapsules with better water resistance and high temperature resistance synthesized by the present invention can reduce the wear rate of the friction material. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] Example 1

[0014] A modified nitrile rubber, the preparation of which comprises the following steps: Step A1: In a nitrogen atmosphere, add carboxylated nitrile rubber to toluene, heat to 45°C, add pyridine, start stirring, then add γ-glycidyloxysilylpropylsesquioxane, stir and react for 8 hours, then heat to 110°C, stir for 1 hour, and obtain an alcohol hydroxyl product; the amount ratio of carboxylated nitrile rubber, toluene, pyridine and γ-glycidyloxysilylpropylsesquioxane is 20g:160mL:0.1mol:49g, and the model of the carboxylated nitrile rubber is 1072CG; Step A2: add the alcoholic hydroxyl product to toluene, start stirring, then add sodium hydroxide solution, stir for 5 minutes, then drop epichlorohydrin, stir and react at room temperature for 6 hours to obtain an epoxy product; the amount ratio of the alcoholic hydroxyl product, toluene, sodium hydroxide solution and epichlorohydrin is 35g:100mL:5mL:0.1mol, and the mass fraction of the sodium hydroxide solution is 5%; Step A3: In a nitrogen atmosphere, add 3,5-di-tert-butyl-4-hydroxybenzoic acid to toluene, heat to 40°C, add pyridine, start stirring, then add the epoxy product, stir and react for 9 hours, then heat to 100°C, stir for 1.5 hours to obtain modified nitrile rubber; the amount ratio of 3,5-di-tert-butyl-4-hydroxybenzoic acid, toluene, pyridine and epoxy product is 0.1 mol: 150 mL: 0.1 mol: 42 g.

[0015] Example 2

[0016] A modified nitrile rubber, the preparation of which comprises the following steps: Step A1: In a nitrogen atmosphere, add carboxylated nitrile rubber to toluene, heat to 48°C, add pyridine, start stirring, then add γ-glycidyloxysilylpropylsesquioxane, stir and react for 9 hours, then heat to 115°C, stir for 1.5 hours, and obtain an alcohol hydroxyl product; the amount ratio of carboxylated nitrile rubber, toluene, pyridine and γ-glycidyloxysilylpropylsesquioxane is 23g:165mL:0.15mol:50g, and the model of the carboxylated nitrile rubber is 1072CG; Step A2: add the alcoholic hydroxyl product to toluene, start stirring, then add sodium hydroxide solution, stir for 8 minutes, then dropwise add epichlorohydrin, stir and react at room temperature for 6.5 hours to obtain an epoxy product; the amount ratio of the alcoholic hydroxyl product, toluene, sodium hydroxide solution and epichlorohydrin is 37g:110mL:8mL:0.15mol, and the mass fraction of the sodium hydroxide solution is 8%; Step A3: In a nitrogen atmosphere, add 3,5-di-tert-butyl-4-hydroxybenzoic acid to toluene, heat to 43°C, add pyridine, start stirring, add the epoxy product, stir and react for 10 hours, then heat to 105°C, stir for 1.8 hours to obtain modified nitrile rubber; the amount ratio of 3,5-di-tert-butyl-4-hydroxybenzoic acid, toluene, pyridine and epoxy product is 0.15 mol: 155 mL: 0.13 mol: 43.5 g.

[0017] Example 3

[0018] A modified nitrile rubber, the preparation of which comprises the following steps: Step A1: In a nitrogen atmosphere, add carboxylated nitrile rubber to toluene, heat to 50°C, add pyridine, start stirring, then add γ-glycidyloxysilylpropylsesquioxane, stir and react for 10 hours, then heat to 120°C, stir for 2 hours, and obtain an alcohol hydroxyl product; the amount ratio of carboxylated nitrile rubber, toluene, pyridine and γ-glycidyloxysilylpropylsesquioxane is 25g:170mL:0.2mol:51g, and the model of the carboxylated nitrile rubber is 1072CG; Step A2: adding the alcoholic hydroxyl product to toluene, stirring, adding sodium hydroxide solution, stirring for 10 minutes, and then dropping epichlorohydrin, stirring and reacting at room temperature for 7 hours to obtain an epoxy product; the amount ratio of the alcoholic hydroxyl product, toluene, sodium hydroxide solution and epichlorohydrin is 40g:120mL:10mL:0.2mol, and the mass fraction of the sodium hydroxide solution is 10%; Step A3: In a nitrogen atmosphere, add 3,5-di-tert-butyl-4-hydroxybenzoic acid to toluene, heat to 45°C, add pyridine, start stirring, add the epoxy product, stir and react for 11 hours, then heat to 110°C, stir for 2 hours to obtain modified nitrile rubber; the amount ratio of 3,5-di-tert-butyl-4-hydroxybenzoic acid, toluene, pyridine and epoxy product is 0.2 mol:160 mL:0.15 mol:45 g.

[0019] Example 4

[0020] A self-healing microcapsule, the preparation of which comprises the following steps: Step B1: Dry the microcapsules at 80°C for 6 hours to obtain dried microcapsules for standby use; add a silane coupling agent to deionized water, then add an acetic acid solution, stir for 10 minutes, adjust the pH to neutral, add the dried microcapsules, heat to 80°C, stir for reaction for 1 hour, wash with ethanol and filter, and then dry at 40°C for 24 hours to obtain silane coupling agent modified microcapsules; the amount ratio of silane coupling agent, deionized water, acetic acid solution, and dried microcapsules is 5g:90mL:10mL:10g, the silane coupling agent is 10-alkenyl undecyl trimethoxysilane, and the mass fraction of the acetic acid solution is 30%; the preparation of the microcapsules refers to the preparation process of the microcapsules in the sample preparation content of Item 1.2 of the paper "Preparation and Performance Study of Fluorosilane Modified Microcapsule Composite Materials"; Step B2: adding the silane coupling agent modified microcapsules to dichloromethane, stirring for 35 minutes, then adding 3-chloroperoxybenzoic acid, stirring and reacting at room temperature for 5 hours to obtain the epoxy product 1; the amount ratio of the silane coupling agent modified microcapsules, dichloromethane, and 3-chloroperoxybenzoic acid is 5g:70mL:20g; Step B3: In a nitrogen atmosphere, dehydroabietic acid was added to toluene, the temperature was raised to 50°C, pyridine was added, stirring was started, and then the epoxy product 1 was added, stirring was carried out for 10 hours, and then the temperature was raised to 110°C, and stirring was carried out for 1 hour to obtain a hydroxyl product; the amount ratio of dehydroabietic acid, toluene, pyridine and epoxy product 1 was 34g:140mL:0.1mol:6g; Step B4: Add the carboxyl-terminated polysiloxane to DMF, add dichlorothionyl under stirring, and reflux and stir at 50°C for 4 hours to obtain an acyl chloride product; stir and mix the hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide to obtain a mixed solution 1; add the acyl chloride product to dimethyl sulfoxide to obtain a mixed solution 2, and slowly drop the mixed solution 2 into the mixed solution 1 in an ice-water bath. After the dropwise addition is completed, the temperature is raised to 40°C, and the reaction is stirred at a constant temperature for 8 hours, and then the temperature is raised to 100°C and the stirring is continued for 1 hour. , and distill under reduced pressure to obtain self-healing microcapsules; the amount ratio of carboxyl-terminated polysiloxane, DMF, and dichlorothionyl is 40g:55mL:1.2g; the amount ratio of hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide is 12g:9mL:15mL:40mL; the amount ratio of acyl chloride product and dimethyl sulfoxide is 43g:90mL; the amount ratio of mixed solution 1 and mixed solution 2 is 85mL:100mL; the carboxyl-terminated polysiloxane is carboxypropyl-terminated polydimethylsiloxane.

[0021] Example 5

[0022] A self-healing microcapsule, the preparation of which comprises the following steps: Step B1: Dry the microcapsules at 85°C for 7 hours to obtain dried microcapsules for standby use; add a silane coupling agent to deionized water, then add an acetic acid solution, stir for 13 minutes, adjust the pH to neutral, add the dried microcapsules, heat to 83°C, stir for reaction for 1.3 hours, wash with ethanol and filter, and then dry at 45°C for 25 hours to obtain silane coupling agent modified microcapsules; the amount ratio of silane coupling agent, deionized water, acetic acid solution, and dried microcapsules is 5.5g:95mL:15mL:11g, the silane coupling agent is 10-alkenyl undecyl trimethoxysilane, and the mass fraction of the acetic acid solution is 35%; the preparation of microcapsules refers to the preparation process of microcapsules in the sample preparation content of Item 1.2 of the paper "Preparation and Performance Study of Fluorosilane Modified Microcapsule Composite Materials"; Step B2: adding the silane coupling agent modified microcapsules to dichloromethane, stirring for 35 minutes, then adding 3-chloroperoxybenzoic acid, stirring and reacting at room temperature for 5.5 hours to obtain the epoxy product 1; the amount ratio of the silane coupling agent modified microcapsules, dichloromethane, and 3-chloroperoxybenzoic acid is 5.5g:75mL:21.5g; Step B3: In a nitrogen atmosphere, dehydroabietic acid was added to toluene, the temperature was raised to 55°C, pyridine was added, stirring was started, and then the epoxy product 1 was added, stirring was carried out for 11 hours, and then the temperature was raised to 115°C, and stirring was carried out for 1.5 hours to obtain a hydroxyl product; the amount ratio of dehydroabietic acid, toluene, pyridine and epoxy product 1 was 35g:145mL:0.13mol:7g; Step B4: Add the carboxyl-terminated polysiloxane to DMF, add dichlorothionyl under stirring, and reflux and stir at 55°C for 4.5 hours to obtain an acyl chloride product; stir and mix the hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide to obtain a mixed solution 1; add the acyl chloride product to dimethyl sulfoxide to obtain a mixed solution 2, and slowly drop the mixed solution 2 into the mixed solution 1 in an ice-water bath. After the dropwise addition is completed, the temperature is raised to 43°C, and the reaction is stirred at a constant temperature for 9 hours, and then the temperature is raised to 105°C and stirred for 1.5 h, and distill under reduced pressure to obtain self-healing microcapsules; the amount ratio of terminal carboxyl polysiloxane, DMF, and dichlorothionyl is 41g:60mL:1.3g; the amount ratio of hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide is 13g:10mL:18mL:45mL; the amount ratio of acyl chloride product and dimethyl sulfoxide is 44g:95mL; the amount ratio of mixed solution 1 and mixed solution 2 is 90mL:105mL; the terminal carboxyl polysiloxane is carboxypropyl-terminated polydimethylsiloxane.

[0023] Example 6

[0024] A self-healing microcapsule, the preparation of which comprises the following steps: Step B1: Dry the microcapsules at 90°C for 8 hours to obtain dried microcapsules for standby use; add a silane coupling agent to deionized water, then add an acetic acid solution, stir for 15 minutes, adjust the pH to neutral, add the dried microcapsules, heat to 85°C, stir for 1.5 hours, wash with ethanol and filter, and then dry at 50°C for 26 hours to obtain silane coupling agent modified microcapsules; the amount ratio of silane coupling agent, deionized water, acetic acid solution, and dried microcapsules is 6g:100mL:20mL:12g, the silane coupling agent is 10-alkenyl undecyl trimethoxysilane, and the mass fraction of the acetic acid solution is 40%; the preparation of microcapsules refers to the preparation process of microcapsules in the sample preparation content of Item 1.2 of the paper "Preparation and Performance Study of Fluorosilane Modified Microcapsule Composite Materials"; Step B2: adding the silane coupling agent modified microcapsules to dichloromethane, stirring for 40 minutes, then adding 3-chloroperoxybenzoic acid, stirring and reacting at room temperature for 6 hours to obtain the epoxy product 1; the amount ratio of the silane coupling agent modified microcapsules, dichloromethane, and 3-chloroperoxybenzoic acid is 6g:80mL:23g; Step B3: In a nitrogen atmosphere, dehydroabietic acid was added to toluene, the temperature was raised to 60°C, pyridine was added, stirring was started, and then the epoxy product 1 was added, stirring was carried out for 12 hours, and then the temperature was raised to 120°C, and stirring was carried out for 2 hours to obtain a hydroxyl product; the amount ratio of dehydroabietic acid, toluene, pyridine and epoxy product 1 was 36g:150mL:0.15mol:8g; Step B4: Add the carboxyl-terminated polysiloxane to DMF, add dichlorothionyl under stirring, and reflux and stir at 60°C for 5 hours to obtain an acyl chloride product; stir and mix the hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide to obtain a mixed solution 1; add the acyl chloride product to dimethyl sulfoxide to obtain a mixed solution 2, slowly drop the mixed solution 2 into the mixed solution 1 in an ice-water bath, and after the dropwise addition is completed, heat to 45°C, stir and react at a constant temperature for 10 hours, and then heat to 110°C and continue stirring for 2 hours. Self-healing microcapsules are obtained by distillation under reduced pressure; the amount ratio of carboxyl-terminated polysiloxane, DMF and dichlorothionyl is 42g:65mL:1.5g; the amount ratio of hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide is 14g:11mL:20mL:50mL; the amount ratio of acyl chloride product and dimethyl sulfoxide is 45g:100mL; the amount ratio of mixed solution 1 and mixed solution 2 is 95mL:110mL; the carboxyl-terminated polysiloxane is carboxypropyl-terminated polydimethylsiloxane.

[0025] Example 7

[0026] A disc brake pad friction material, comprising the following raw materials in parts by weight: 10 parts of phenolic resin, 10 parts of modified nitrile rubber, 1.5 parts of hexamethylenetetramine, 1 part of calcium stearate, 0.5 parts of magnesium oxide, 0.3 parts of aluminum oxide, 2 parts of self-healing microcapsules, 5 parts of diatomaceous earth, 20 g of barium sulfate, 21 parts of kaolin, 10 parts of calcium carbonate, and 5 parts of graphite; The preparation of the disc brake pad friction material comprises the following steps: Phenolic resin, modified nitrile rubber obtained in Example 1, hexamethylenetetramine, calcium stearate, magnesium oxide, aluminum oxide, self-healing microcapsules obtained in Example 4, diatomaceous earth, barium sulfate, kaolin, calcium carbonate and graphite are placed in a pulverizer for pulverization and mixing to obtain a mixture; the mixture is then roll-refined on a roller mill to obtain a roll-refined material; the roll-refined material is pulverized and placed in a vulcanizer for hot pressing, and then cured to obtain a disc brake pad friction material; the hot pressing molding temperature is 155°C and the pressure is 10MPa; the curing conditions are first heated to 120°C and kept warm for 3 hours, then continued to heat up to 140°C and kept warm for 3 hours, then heated to 160°C and kept warm for 3 hours, and finally heated to 180°C and kept warm for 4 hours.

[0027] Example 8

[0028] A disc brake pad friction material, comprising the following raw materials in parts by weight: 12 parts of phenolic resin, 11 parts of modified nitrile rubber, 2.0 parts of hexamethylenetetramine, 1.5 parts of calcium stearate, 0.8 parts of magnesium oxide, 0.4 parts of aluminum oxide, 3 parts of self-healing microcapsules, 6 parts of diatomaceous earth, 22 g of barium sulfate, 23 parts of kaolin, 11 parts of calcium carbonate, and 6 parts of graphite; The preparation of the disc brake pad friction material comprises the following steps: Phenolic resin, modified nitrile rubber obtained in Example 2, hexamethylenetetramine, calcium stearate, magnesium oxide, aluminum oxide, self-healing microcapsules obtained in Example 5, diatomaceous earth, barium sulfate, kaolin, calcium carbonate and graphite are placed in a pulverizer for pulverization and mixing to obtain a mixture; the mixture is then roll-refined on a roller mill to obtain a roll-refined material; the roll-refined material is pulverized and placed in a vulcanizer for hot pressing, and then cured to obtain a disc brake pad friction material; the hot pressing molding temperature is 160°C and the pressure is 11MPa; the curing conditions are first heated to 120°C and kept warm for 3.3h, then continued to heat to 140°C and kept warm for 3.3h, then heated to 160°C and kept warm for 3.3h, and finally heated to 180°C and kept warm for 4.3h.

[0029] Example 9

[0030] A disc brake pad friction material, comprising the following raw materials in parts by weight: 14 parts of phenolic resin, 12 parts of modified nitrile rubber, 2.5 parts of hexamethylenetetramine, 2 parts of calcium stearate, 1 part of magnesium oxide, 0.5 parts of aluminum oxide, 4 parts of self-healing microcapsules, 7 parts of diatomaceous earth, 24 g of barium sulfate, 25 parts of kaolin, 12 parts of calcium carbonate, and 7 parts of graphite; The preparation of the disc brake pad friction material comprises the following steps: Phenolic resin, modified nitrile rubber obtained in Example 3, hexamethylenetetramine, calcium stearate, magnesium oxide, aluminum oxide, self-healing microcapsules obtained in Example 6, diatomaceous earth, barium sulfate, kaolin, calcium carbonate and graphite are placed in a pulverizer for pulverization and mixing to obtain a mixture; the mixture is then roll-refined on a roller mill to obtain a roll-refined material; the roll-refined material is pulverized and placed in a vulcanizer for hot pressing, and then cured to obtain a disc brake pad friction material; the hot pressing molding temperature is 165°C and the pressure is 12MPa; the curing conditions are first heated to 120°C and kept warm for 3.5 hours, then continued to heat up to 140°C and kept warm for 3.5 hours, then heated to 160°C and kept warm for 3.5 hours, and finally heated to 180°C and kept warm for 4.5 hours.

[0031] Comparative Example 1 Compared with Example 9, the modified nitrile rubber is replaced by the alcohol hydroxyl product obtained in step A1, that is, only the POSS structure is introduced without introducing hindered phenol, to prepare a disc brake pad friction material.

[0032] Comparative Example 2 Compared with Example 9, the modified nitrile rubber was replaced with substance 1, that is, the POSS structure was not introduced, and only hindered phenol was introduced to prepare a disc brake pad friction material; Preparation process of substance 1: In a nitrogen atmosphere, 3,5-di-tert-butyl-4-hydroxybenzoic acid is added to toluene, the temperature is raised to 60°C, pyridine is added, stirring is started, and then end-epoxy liquid nitrile rubber is added, stirring and reacting for 12 hours, and then the temperature is raised to 120°C and stirred for 2 hours to obtain substance 1; the amount ratio of 3,5-di-tert-butyl-4-hydroxybenzoic acid, toluene, pyridine and end-epoxy liquid nitrile rubber is 28g:110mL:0.15mol:6g, and the model of the end-epoxy liquid nitrile rubber is TL910.

[0033] Comparative Example 3 Compared with Example 9, the self-healing microcapsules were replaced with the hydroxyl product in step B3, that is, polysiloxane chains were not introduced into the wall material, and the rest was exactly the same as Example 9 to obtain a disc brake pad friction material.

[0034] Comparative Example 4 Compared with Example 9, the dehydroabietic acid in step B3 was replaced with the hydroxyl product 1 obtained by carboxypropyl-terminated polydimethylsiloxane to replace the self-healing microcapsules, that is, dehydroabietic acid was not introduced into the wall material. The rest was exactly the same as Example 9 to obtain a disc brake pad friction material.

[0035] The disc brake pad friction material prepared by the present invention is further tested for its effect, and the test results are as follows.

[0036] To test the disc brake pad friction material prepared by the present invention, the impact strength was tested according to GB / T1043.1-2008, the volume wear rate was determined according to GB5763-2008; the friction coefficient of the brake pad friction material was determined according to GB / T34007-2017; the brake pad friction material was placed in a strength of 1000W / m 2 After irradiating the friction material under ultraviolet light for 200 hours, the friction coefficient after photo-oxidation treatment was measured; after placing the friction material at 350°C for 24 hours, the friction coefficient and volume wear rate after high temperature treatment were measured; after soaking the friction material in distilled water at room temperature for 24 hours, the volume wear rate after soaking was measured; the above test results are recorded in Table 1; Table 1: Test results

[0037] According to the data in Table 1, the disc brake pad friction material of the present invention has excellent impact strength, low volume wear rate and stable friction coefficient, high temperature resistance, oxidation resistance, water resistance and strong self-healing ability. Compared with Example 1, Example 9 shows that the introduction of POSS structure without hindered phenol causes the modified nitrile rubber to be oxidatively degraded after photooxidation treatment, and the friction coefficient of the friction material decreases. Compared with Example 2, Example 9 shows that the introduction of hindered phenol without POSS structure causes the high temperature resistance of the modified nitrile rubber to decrease, and the volume wear rate of the friction material increases more after high temperature treatment. Compared with Example 3, Example 9 shows that the polysiloxane chain is not introduced into the wall material of the self-healing microcapsule, and the high temperature resistance of the self-healing microcapsule decreases, resulting in an increase in the volume wear rate after high temperature treatment, and a decrease in the self-healing ability of the friction material. Compared with Example 4, Example 9 shows that the dehydrogenated rosin acid is not introduced into the wall material of the self-healing microcapsule, resulting in a decrease in the water resistance of the self-healing microcapsule, resulting in an increase in the volume wear rate after water immersion, and a decrease in the self-healing ability of the friction material.

[0038] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A disc brake pad friction material, characterized in that: The invention comprises the following raw materials in parts by weight: 10-14 parts of phenolic resin, 10-12 parts of modified nitrile rubber, 1.5-2.5 parts of hexamethylenetetramine, 1-2 parts of calcium stearate, 0.5-1 parts of magnesium oxide, 0.3-0.5 parts of aluminum oxide, 2-4 parts of self-healing microcapsules, 5-7 parts of diatomaceous earth, 20-24g of barium sulfate, 21-25 parts of kaolin, 10-12 parts of calcium carbonate and 5-7 parts of graphite; The modified nitrile rubber is prepared by the following steps: Step A1: In a protective gas atmosphere, add carboxylated nitrile rubber to toluene, heat to 45-50° C., add pyridine, start stirring, then add γ-glycidyloxysilylpropylsesquioxane, stir and react for 8-10 hours, then heat to 110-120° C., stir for 1-2 hours, and obtain an alcohol hydroxyl product; Step A2: Add the alcohol hydroxyl product to toluene, start stirring, then add sodium hydroxide solution, stir for 5-10 minutes, then dropwise add epichlorohydrin, stir and react at room temperature for 6-7 hours to obtain an epoxy product; Step A3: In a protective gas atmosphere, add 3,5-di-tert-butyl-4-hydroxybenzoic acid to toluene, heat to 40-45°C, add pyridine, start stirring, then add the epoxy product, stir and react for 9-11h, then heat to 100-110°C, stir for 1.5-2h, and obtain modified nitrile rubber.

2. The disc brake pad friction material according to claim 1, characterized in that: In step A1, the usage ratio of carboxylated nitrile rubber, toluene, pyridine and γ-glycidyl ether silyl propyl sesquioxane is 20-25 g: 160-170 mL: 0.1-0.2 mol: 49-51 g.

3. The disc brake pad friction material according to claim 1, characterized in that: In step A2, the usage ratio of alcohol hydroxyl product, toluene, sodium hydroxide solution and epichlorohydrin is 35-40g:100-120mL:5-10mL:0.1-0.2mol, and the mass fraction of sodium hydroxide solution is 5-10%.

4. The disc brake pad friction material according to claim 1, characterized in that: In step A3, the usage ratio of 3,5-di-tert-butyl-4-hydroxybenzoic acid, toluene, pyridine and epoxidation product is 0.1-0.2 mol: 150-160 mL: 0.1-0.15 mol: 42-45 g.

5. The disc brake pad friction material according to claim 1, characterized in that: The preparation of the self-healing microcapsule comprises the following steps: Step B1: drying the microcapsules at 80-90° C. for 6-8 hours to obtain dried microcapsules for standby use; adding a silane coupling agent to deionized water, then adding an acetic acid solution, stirring for 10-15 minutes, adjusting the pH to neutral, adding the dried microcapsules, heating to 80-85° C., stirring for 1-1.5 hours, washing with ethanol and filtering, and then drying at 40-50° C. for 24-26 hours to obtain silane coupling agent modified microcapsules; Step B2: adding the silane coupling agent modified microcapsules into dichloromethane, stirring for 30-40 minutes, then adding 3-chloroperoxybenzoic acid, stirring and reacting at room temperature for 5-6 hours to obtain the epoxy product 1; Step B3: In a protective gas atmosphere, add dehydroabietic acid to toluene, heat to 50-60°C, add pyridine, start stirring, then add the epoxy product 1, stir and react for 10-12h, then heat to 110-120°C, stir for 1-2h to obtain a hydroxyl product; Step B4: Add the carboxyl-terminated polysiloxane to DMF, add thionyl chloride under stirring, and reflux and stir at 50-60° C. for 4-5 hours to obtain an acyl chloride product; The hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide are stirred and mixed to obtain a mixed solution 1; the acyl chloride product is added to dimethyl sulfoxide to obtain a mixed solution 2, and the mixed solution 2 is slowly added dropwise to the mixed solution 1 in an ice water bath. After the addition is completed, the temperature is raised to 40-45°C, and the reaction is stirred at a constant temperature for 8-10 hours, and then the temperature is raised to 100-110°C, and the stirring is continued for 1-2 hours, and the self-healing microcapsules are obtained by distillation under reduced pressure.

6. The disc brake pad friction material according to claim 5, characterized in that: In step B1, the dosage ratio of the silane coupling agent, deionized water, acetic acid solution, and dried microcapsules is 5-6 g: 90-100 mL: 10-20 mL: 10-12 g, the silane coupling agent is 10-alkenyl undecyl trimethoxy silane, the mass fraction of the acetic acid solution is 30-40%, and the volume fraction of ethanol is 95%.

7. The disc brake pad friction material according to claim 5, characterized in that: In step B2, the usage ratio of silane coupling agent modified microcapsules, dichloromethane, and 3-chloroperoxybenzoic acid is 5-6 g: 70-80 mL: 20-23 g; in step B3, the usage ratio of dehydroabietic acid, toluene, pyridine, and epoxy product 1 is 34-36 g: 140-150 mL: 0.1-0.15 mol: 6-8 g.

8. The disc brake pad friction material according to claim 5, characterized in that: In step B4, the amount ratio of carboxyl-terminated polysiloxane, DMF and dichlorothionyl is 40-42 g: 55-65 mL: 1.2-1.5 g; the amount ratio of hydroxyl product, pyridine, triethylamine and dimethyl sulfoxide is 12-14 g: 9-11 mL: 15-20 mL: 40-50 mL; the amount ratio of acyl chloride product and dimethyl sulfoxide is 43-45 g: 90-100 mL; the amount ratio of mixed solution 1 and mixed solution 2 is 85-95 mL: 100-110 mL; the carboxyl-terminated polysiloxane is carboxypropyl-terminated polydimethylsiloxane.

9. A process for preparing the friction material for a disc brake pad according to any one of claims 1 to 8, characterized in that: The steps include: Phenolic resin, modified nitrile rubber, hexamethylenetetramine, calcium stearate, magnesium oxide, aluminum oxide, self-healing microcapsules, diatomaceous earth, barium sulfate, kaolin, calcium carbonate and graphite are placed in a pulverizer for pulverization and mixing to obtain a mixture; the mixture is then roll-refined on a roll mill to obtain a roll-refined material; the roll-refined material is then pulverized and placed in a vulcanizer for hot pressing, and then cured to obtain a disc brake pad friction material.

10. The process for preparing the friction material of a disc brake pad according to claim 9, characterized in that: The temperature of the hot pressing molding is 155-165°C and the pressure is 10-12MPa; the curing conditions are first heating to 120°C and keeping warm for 3-3.5h, then heating to 140°C and keeping warm for 3-3.5h, then heating to 160°C and keeping warm for 3-3.5h, and finally heating to 180°C and keeping warm for 4-4.5h.

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