A high heat resistance modified phenolic resin, preparation and application thereof

Abstract

The application belongs to the technical field of functional resin, and particularly relates to a novel modified phenolic resin with high heat resistance, preparation and application thereof. The thermoplastic phenolic resin is modified by 4,4'-diaminodiphenyl methane (MDA) to improve the heat resistance of the phenolic resin. The obtained modified phenolic resin has excellent heat resistance, and when the modified phenolic resin is applied to a friction material as a binder, the wear rate of the friction material at high temperature is greatly reduced, and the service life of the friction material is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional resins, and specifically relates to a novel high-heat-resistant modified phenolic resin, its preparation method and its application. Background Art

[0002] The continuous development of industry, particularly the increasing operating conditions of various vehicles and machinery, as well as the advancement of cutting-edge technologies in aviation, aerospace, and other defense sectors, has put forward new requirements for high-performance friction materials, such as high thermal decomposition temperatures, good thermal recovery, sufficient friction coefficients, good wear resistance, and low noise levels. While phenolic resins are currently widely used in industry, traditional phenolic resins have structural weaknesses. Their heat resistance is severely compromised by the susceptibility of their phenolic hydroxyl and methylene groups to oxidation. While conventional phenolic resins offer long-term stability below 200°C, they begin to oxidize significantly above 200°C, entering a thermal decomposition phase between 340 and 360°C. At temperatures between 600 and 900°C, they release substances such as CO, CO₂, H₂O, and phenol. Furthermore, upon curing, conventional phenolic resins release water, resulting in brittleness and poor toughness. It is precisely because of the above-mentioned weaknesses of traditional unmodified phenolic resins that the development of traditional phenolic resins as high-performance materials in high-tech fields such as automobiles, aviation, and aerospace has been affected and restricted. For example, using it as a friction material for the base material of brake pads and clutch plates of luxury cars and motorcycles can no longer meet the new development requirements. Therefore, there is an urgent need to improve the heat resistance of traditional phenolic resins. Summary of the Invention

[0003] The purpose of the present invention is to provide a new type of high heat-resistant modified phenolic resin, its preparation and application in response to the above-mentioned defects. The obtained modified phenolic resin has excellent heat resistance. When the modified phenolic resin is used as a binder in friction materials, the wear rate of the friction material at high temperature is greatly reduced, and the service life of the friction material is extended.

[0004] The technical solution of the present invention is: a novel high heat-resistant modified phenolic resin, comprising a phenolic resin having the following structural formula:

[0005]

[0006] The novel high-heat-resistant modified phenolic resin is based on thermoplastic phenolic resin and is modified by 4,4'-diaminodiphenylmethane.

[0007] The structure of the thermoplastic phenolic resin is a high-para linear type.

[0008] The preparation method of the modified phenolic resin comprises the following steps: first, adding phenol, formaldehyde aqueous solution and oxalic acid into a reaction container; heating to 75-85°C and keeping the temperature constant for 1 hour; then heating to 90-95°C and keeping the temperature constant for 1 hour; then adding 4,4'-diaminodiphenylmethane, and keeping the temperature constant for 3 hours after the 4,4'-diaminodiphenylmethane is completely dissolved; after the reaction is completed, performing atmospheric distillation, heating to 160°C and performing reduced pressure distillation under a pressure of 8000 Pa to obtain the modified phenolic resin.

[0009] The molar ratio of phenol: 4,4'-diaminodiphenylmethane: formaldehyde is 1:0.5:0.7; the amount of oxalic acid used is 1% of the mass of phenol.

[0010] Application of the novel high heat-resistant modified phenolic resin in friction materials.

[0011] A friction material using the novel high-heat-resistant modified phenolic resin comprises the following raw materials: aramid fiber, copper fiber, calcium sulfate whisker, molybdenum disulfide, graphite, aluminum oxide, fly ash, barium sulfate and the high-heat-resistant modified phenolic resin.

[0012] The lengths of the aramid fibers and the copper fibers are both 100 to 300 μm.

[0013] The friction material comprises, by weight percentage, 10% aramid fiber, 10% copper fiber, 10% calcium sulfate whisker, 2% molybdenum disulfide, 10% graphite, 3% aluminum oxide, 20% fly ash, 15% modified phenolic resin, and the balance barium sulfate.

[0014] The method for preparing the friction material comprises the following steps:

[0015] (1) Material mixing: After weighing the raw materials of each component according to the ratio, mix and stir them evenly to obtain a mixed raw material;

[0016] (2) Hot pressing: The mixed raw materials are placed in a mold and hot pressed at a temperature of 145°C to 155°C and a pressure of 15 MPa to obtain a sample; the pressure is maintained for 3 to 5 minutes during the hot pressing process, and the mold is opened and air is released 2 to 3 times within 3 minutes before the pressure is maintained;

[0017] (3) Heat treatment: Place the sample obtained in step (2) in a drying oven and heat it to 180°C. Keep it at 180°C for 12 hours for heat treatment. After cooling, the finished friction material is obtained.

[0018] The beneficial effects of the present invention are as follows: the present invention uses 4,4'-diaminodiphenylmethane (MDA) to modify thermoplastic phenolic resin to improve the heat resistance of the phenolic resin. The reaction process is as follows:

[0019]

[0020] The entire modification process eliminates the need for toluene as a solvent, avoiding potential safety and environmental risks during production. Furthermore, there is no need to evaporate the toluene later, simplifying the production process. The modified phenolic resin described herein, when used as a binder in friction materials, significantly reduces the wear rate of the friction material at high temperatures and extends its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a thermogravimetric measurement diagram of the sample obtained in Example 1 at 800°C.

[0022] Figure 2 This is the thermogravimetric measurement diagram of the sample obtained in Comparative Example 1 at 800°C.

[0023] Figure 3 This is the thermogravimetric measurement diagram of the sample obtained in Comparative Example 2 at 800°C.

[0024] Figure 4 This is the infrared spectrum of the sample obtained in Example 1. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0026] Example 1

[0027] The novel high-heat-resistant modified phenolic resin is based on a high-para-linear phenolic resin and is modified by 4,4'-diaminodiphenylmethane.

[0028] First, 500 g of phenol, 253 g of a 44% formaldehyde aqueous solution, and 5 g of oxalic acid were placed in a 2000 mL reaction vessel equipped with a thermometer, a stirring device, and a reflux condenser. The temperature was raised to 80° C. and kept constant for 1 hour, and then raised to 90° C. and kept constant for 1 hour. Then, 526 g of 4,4'-diaminodiphenylmethane was slowly added, and after it was completely dissolved, the temperature was kept constant for 3 hours. After the reaction was terminated and atmospheric distillation was performed, the mixture was heated to 160° C. and then reduced pressure distillation was performed under a pressure of 8000 Pa to obtain a modified phenolic resin.

[0029] The molar ratio of phenol: 4,4'-diaminodiphenylmethane: formaldehyde is 1:0.5:0.7

[0030] Comparative Example 1

[0031] Ordinary phenolic resin: 500 g of phenol, 253 g of a 44% formaldehyde solution, and 5 g of oxalic acid were placed in a 1000 mL reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser. The mixture was heated to 80°C and held at this temperature for 1 hour, then to 90°C and held at this temperature for 4 hours. After the reaction was completed, atmospheric distillation was performed, and the mixture was heated to 160°C and then distilled under reduced pressure at 8000 Pa to obtain a phenolic resin.

[0032] Comparative Example 2

[0033] Add a certain amount of MDA: 500 g of phenol, 253 g of 44% formaldehyde aqueous solution, and 5 g of oxalic acid are placed in a 2000 mL reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser. The temperature is raised to 80°C and maintained at this temperature for 1 hour, then raised to 90°C and maintained at this temperature for 1 hour. Then, 300 g of 4,4'-diaminodiphenylmethane is slowly added. After it is completely dissolved, the temperature is kept at this temperature for 3 hours. After the reaction is terminated and atmospheric distillation is performed, the mixture is heated to 160°C and then distilled under reduced pressure at 8000 Pa to obtain a phenolic resin.

[0034] The molar ratio of phenol: 4,4'-diaminodiphenylmethane: formaldehyde is 1:0.285:0.7.

[0035] Comparative Example 3

[0036] Using thermosetting phenolic resin as the matrix: 500g of phenol, 435.2g of a 44% formaldehyde aqueous solution, and 2g of sodium hydroxide were placed in a 2000mL reaction vessel equipped with a thermometer, a stirring device, and a reflux condenser. The temperature was raised to 80°C and kept constant for 1 hour, then raised to 90°C and kept constant for 1 hour; then 300g of 4,4'-diaminodiphenylmethane was slowly added, and after it was completely dissolved, the temperature was kept for 3 hours. The reaction was terminated and vacuum distillation was performed at a pressure of 8000Pa. The resin became gelled and the experiment failed.

[0037] Table 1 shows the results of thermal gravimetric measurements of the examples and comparative examples under air. These results demonstrate that the phenolic resin modified with 4,4'-diaminodiphenylmethane exhibits significantly lower thermal gravimetric loss. The thermal gravimetric loss of the product in Example 1 is significantly lower than that of the products in Comparative Examples 1 and 2, demonstrating that the introduction and dosage of 4,4'-diaminodiphenylmethane plays a decisive role in improving the heat resistance of the phenolic resin.

[0038] Table 1: Comparison of thermal weight loss test data of samples at 600℃

[0039] resin Thermal gravimetric loss Example 1 63.21％ Comparative Example 1 97.64％ Comparative Example 2 89.16％

[0040] The friction coefficient and wear rate of the friction materials prepared using the modified phenolic resin obtained in Example 1, Comparative Example 1 and Comparative Example 2 as a binder were tested respectively. The results are shown in Table 2.

[0041] Table 2: Comparison of test data of constant speed test machine

[0042]

[0043]

[0044] pass Figure 1 、 Figure 2 and Figure 3 By comparison, it can be seen that although the degree of thermal degradation of the three resins obtained in Example 1, Comparative Example 1 and Comparative Example 2 is basically the same when the temperature is below 400°C, after exceeding 400°C, the resins obtained in Comparative Example 1 and Comparative Example 2 all show severe degradation, especially the ordinary pure thermoplastic phenolic resin obtained in Comparative Example 1, which has only 2.37% residue at 600°C.

[0045] The resin obtained by adding a certain amount of MDA in Comparative Example 2 has a residual weight of 10.84% ​​at 600°C. This shows that the addition of MDA has a certain effect on the heat resistance of the resin. However, according to the amount of MDA added in Comparative Example 2, a stable phenolic resin structure is not formed. Therefore, the heat resistance of the resin obtained in Comparative Example 2 is far inferior to that of Example 1.

[0046] Depend on Figure 1 It can be seen that the modified phenolic resin obtained in Example 1 has a residual weight of 36.79% at 600° C. According to the amount of MDA added in Example 1, the structure of MDA is introduced into the side chain of the phenolic resin, and the prepared resin is more resistant to ablation.

[0047] pass Figure 4 It can be seen that the broad absorption peak of 3330.18 is the OH stretching vibration peak, 3016 is the CH stretching vibration peak on the benzene ring, 2895 cm-1 is the antisymmetric stretching vibration peak of methylene CH, 1466 cm-1, 1508 cm-1, and 1588 cm-1 are the stretching vibration peaks of the benzene ring skeleton, 1219 cm-1 is the corresponding stretching vibration of the Ar-O ether bond, 3340 cm-1 is the antisymmetric vibration peak of the primary amino group NH, and 931 cm-1 is the characteristic absorption peak of the oxazine ring. The oxazine ring is a characteristic peak of the benzoxazine resin monomer, but the modified phenolic resin of the present invention does not have this peak.

Claims

1. A modified phenolic resin for friction material with high heat resistance, characterized in that: Phenolic resins having the following structural formula: ； The modified phenolic resin is prepared by the following steps: First, phenol, formaldehyde aqueous solution and oxalic acid are added to a reaction container; Heat to 75-85°C and keep constant temperature for 1 hour; then heat to 90-95°C and keep constant temperature for 1 hour; Then, add 4,4'-diaminodiphenylmethane and keep the temperature constant for 3 hours after it is completely dissolved; After the reaction is completed, the mixture is distilled under normal pressure, heated to 160° C. and distilled under reduced pressure at 8000 Pa to obtain a modified phenolic resin; The molar ratio of phenol: 4,4'-diaminodiphenylmethane: formaldehyde is 1:0.5:0.7; and the amount of oxalic acid used is 1% of the mass of phenol.

2. The modified phenolic resin according to claim 1, wherein Thermoplastic phenolic resin is used as the matrix and modified by 4,4'-diaminodiphenylmethane.

3. The modified phenolic resin according to claim 2, wherein The structure of the thermoplastic phenolic resin is a high-para linear type.

4. Use of the modified phenolic resin according to claim 1 in friction materials.

5. A friction material using the modified phenolic resin according to claim 1, characterized in that: The invention comprises the following raw materials: aramid fiber, copper fiber, calcium sulfate whisker, molybdenum disulfide, graphite, aluminum oxide, fly ash, barium sulfate and the modified phenolic resin.

6. The friction material according to claim 5, characterized in that: The lengths of the aramid fibers and the copper fibers are both 100 to 300 μm.

7. The friction material according to claim 5, characterized in that: Calculated by mass percentage, the raw materials include 10% aramid fiber, 10% copper fiber, 10% calcium sulfate whisker, 2% molybdenum disulfide, 10% graphite, 3% alumina, 20% fly ash, 15% modified phenolic resin, and the balance is barium sulfate.

8. A method for preparing the friction material according to claim 5, characterized in that: The following steps are involved: (1) Material mixing: weigh the raw materials according to the ratio, mix and stir evenly to obtain a mixed raw material; (2) Hot pressing: Place the mixed raw materials in a mold and hot press to obtain a sample at a temperature of 145°C to 155°C and a pressure of 15 MPa; hold the pressure for 3 to 5 minutes during the hot pressing process, and open the mold to release air 2 to 3 times within 3 minutes before holding the pressure; (3) Heat treatment: The sample obtained in step (2) is placed in a drying oven and heated to 180°C. The sample is kept at 180°C for 12 hours for heat treatment. After cooling, the finished friction material is obtained.

Images