Heat-resistant modified phenolic resin and preparation method thereof

Abstract

The invention discloses heat-resistant modified phenolic resin and a preparation method thereof, and belongs to the field of high polymer materials. Aiming at the problems of poor heat resistance and high preparation cost of the existing phenolic resin, the invention provides the preparation method of the heat-resistant modified phenolic resin, which comprises the following steps: uniformly mixing resorcinol and biphenyl dimethyl ether under an acidic condition to form a reaction system, and reacting for 7-9 hours at a first target temperature; after the reaction is completed, cooling the reaction system to a second target temperature, and adjusting the pH value of the reaction system to be neutral; removing residual resorcinol in the neutral reaction system, and washing the reaction system for a plurality of times to obtain the heat-resistant modified phenolic resin. According to the invention, a biphenyl structure with excellent comprehensive performance and resorcinol are creatively introduced into a resin skeleton, so that the finally prepared phenolic resin has good heat resistance; the reaction between resorcinol and biphenyl dimethyl ether is further promoted under the acidic condition, so that the heat resistance of the phenolic resin is further improved; preparation is simple and cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of new polymer materials, and more specifically, relates to a heat-resistant modified phenolic resin and a preparation method thereof. Background Art

[0002] Phenolic resin is a general term for resins formed by the reaction of phenols and aldehydes in the presence of a catalyst. It is the earliest industrially produced polymer material, which has good dimensional stability, flame retardancy, acid resistance, mechanical properties and heat resistance, and is widely used in electronic packaging. Among them, it is generally formed by the polycondensation of formaldehyde and phenol. The structure and functional groups of phenolic resin determine its properties. High crosslinking density and high aromatic ring content endow it with great advantages in heat resistance, electrical insulation performance, corrosion resistance and other aspects. However, high crosslinking density and high aromatic ring content also make phenolic resin brittle and have poor toughness, resulting in low impact strength and short service life of phenolic resin products, increasing the cost in the application of copper clad laminates, greatly limiting the application of phenolic resin, and the heat resistance still needs to be improved in some fields. Therefore, in order to meet the requirements of different industrial developments, it is necessary to modify phenolic resin to obtain performance improvement.

[0003] Corresponding improvements have also been made to the above problems. For example, Chinese Patent Application No. CN202410585641.1, with a publication date of August 6, 2024, discloses a heat-resistant phenolic resin for copper clad laminates and a preparation method thereof, specifically relating to the technical field of copper clad laminate resins. In the present invention, graphene oxide is successfully reduced to reduced graphene oxide, and the Si-O-Si bonds formed by the further hydrolysis and condensation of alkoxy groups form a coating on the surface of reduced graphene oxide; functionalized reduced graphene oxide has excellent heat resistance, and at the same time forms a crosslinked network with the phenolic resin matrix, and heat can be effectively transferred between the phenolic resin matrix and functionalized reduced graphene oxide that constitute the crosslinked network, improving the thermal stability, and can significantly improve the mechanical properties, friction properties and thermal stability of heat-resistant phenolic resin; the toughening modification of boron phenolic resin by introducing carboxyl-terminated nitrile rubber significantly improves the mechanical properties of boron phenolic resin. The disadvantages of this patent are as follows: there are many raw materials used, and there may be by-products, resulting in low purity of the finally prepared phenolic resin.

[0004] For another example, Chinese Patent Application No. CN202211021653.9, with a publication date of November 8, 2022, discloses a high heat-resistant phenolic resin, its synthesis method, a positive-type I-line photoresist composition prepared from the resin, and applications thereof. A synthesis method of a high heat-resistant phenolic resin includes the following steps: S1: Mix a phenolic monomer, an aldehyde monomer, a catalyst, water, and solvent a evenly, and react for a period of time at 65-95°C; S2: Cool down to 25-45°C, add alkali to neutralize until the pH value of the system is 6-7, and then wash with ultrapure water; S3: Then carry out vacuum dehydration at 85-95°C to obtain product A; S4: Mix product A, solvent a, and solvent b evenly, take the lower-layer solution after standing, and then slowly add the lower-layer solution into ultrapure water, filter by suction and dry to obtain the target product B. The deficiencies of this patent are as follows: Although the molar ratio of substances is controlled, the reaction efficiency is slow and the reaction process is not easy to control. Summary of the Invention

[0005] 1. Problems to be Solved Aiming at the problems of poor heat resistance and high preparation cost of existing phenolic resins, the present invention provides a heat-resistant modified phenolic resin and its preparation method. The present invention creatively introduces a biphenyl structure and resorcinol with excellent comprehensive properties into the resin skeleton, making the finally prepared phenolic resin have good heat resistance; and the acidic condition further promotes the reaction between resorcinol and biphenyl dimethyl ether, further improving the heat resistance of the phenolic resin; then by adjusting the system to neutrality, the occurrence of side reactions is minimized to ensure the purity of the phenolic resin; the overall preparation is simple and the cost is low.

[0006] 2. Technical Solutions To solve the above problems, the present invention adopts the following technical solutions.

[0007] A preparation method of a heat-resistant modified phenolic resin includes the following steps: S1: Mix resorcinol and biphenyl dimethyl ether evenly under acidic conditions to form a reaction system, and react at a first target temperature for 7-9 hours; S2: After the reaction is completed, cool down the reaction system to a second target temperature, and adjust the pH value of the reaction system to neutral; S3: Remove the remaining resorcinol in the neutral reaction system, and then wash the reaction system several times to obtain the heat-resistant modified phenolic resin.

[0008] Furthermore, the first target temperature in step S1 includes a first-stage heating temperature and a second-stage heating temperature; specifically, it includes the following steps: S11: Heat up the reaction system to the first-stage heating temperature and maintain it for 2 h to 3 h; and remove methanol during the heating process; and the first-stage heating temperature is 110°C to 120°C; S12: Then heat up the reaction system to the second-stage heating temperature and maintain it for 5 h to 6 h; and the second-stage heating temperature is 130°C to 140°C.

[0009] Furthermore, the heating rate of the first-stage heating temperature is greater than the heating efficiency of the second-stage heating temperature.

[0010] Furthermore, in step S1, resorcinol and biphenyl dimethyl ether react under the action of catalyst methanesulfonic acid; and the amount of substance of methanesulfonic acid is between two-thousandths and four-thousandths of the amount of substance of resorcinol.

[0011] Furthermore, in step S3, the remaining resorcinol is removed by means of high temperature and negative pressure; then the reaction system is washed with water 2 to 3 times repeatedly, and the conductivity of water is kept less than 10 us / cm; finally, heat-resistant modified phenolic resin is obtained.

[0012] A heat-resistant modified phenolic resin is prepared by using the preparation method of a heat-resistant modified phenolic resin as described in any one of the above.

[0013] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention creatively uses resorcinol and biphenyl dimethyl ether to react, introducing the biphenyl structure and resorcinol with excellent comprehensive performance into the resin skeleton, so that the finally prepared phenolic resin has good heat resistance; at the same time, resorcinol and biphenyl dimethyl ether can be more activated under acidic conditions, making it easier to undergo polycondensation reaction to form phenolic resin; and the crosslinking degree of phenolic resin is higher under acidic conditions, and the molecular structure is more compact, thereby further improving the heat resistance of the resin; by adjusting the pH value of the reaction system to neutral, on the one hand, it is convenient for subsequent removal of the remaining resorcinol and washing and other steps, further ensuring the purity of the prepared phenolic resin; on the other hand, the neutral environment helps to reduce the occurrence of side reactions, so as to obtain a phenolic resin with a more uniform structure and more stable performance; (2) In the present invention, during the reaction of resorcinol and biphenyl dimethyl ether, the temperature is raised in two stages. The main purpose of the first-stage temperature rise is to recover methanol. Since a large amount of methanol volatilizes at the initial stage of the reaction between resorcinol and biphenyl dimethyl ether, methanol recovery is carried out at this stage, which is efficient and sufficient, ensuring the recyclability of resources. As the reaction time increases and the raw materials are continuously consumed, the second temperature rise is then carried out to further promote the full occurrence of the reaction and improve the reaction efficiency. Moreover, the first-stage heating rate is greater than the second-stage heating rate, avoiding uncontrollable reactions caused by blindly rapid heating, making the whole process more flexible and controllable, and ensuring the stable progress of the reaction. (3) The present invention uses methanesulfonic acid as a catalyst to promote the reaction between resorcinol and biphenyl dimethyl ether, and the reaction system is under acidic conditions. Methanesulfonic acid shows high selectivity during the catalytic process, which can promote specific chemical reactions to occur and reduce the generation of by-products, thereby obtaining phenolic resin with higher purity. And when methanesulfonic acid is used as a catalyst, it can usually carry out under relatively mild reaction conditions, thus eliminating the need to use complex or high-cost equipment, saving costs. Moreover, the amount of methanesulfonic acid is correlated with the amount of resorcinol, avoiding insufficient catalytic action due to too little methanesulfonic acid dosage, increasing the reaction time; avoiding unnecessary side reactions that may be caused by too much methanesulfonic acid dosage, which affects the purity of the finally prepared phenolic resin. Brief Description of the Drawings

[0014] Figure 1 It is a schematic diagram of the TAG analysis result. Detailed Embodiments

[0015] The present invention will be further described below in conjunction with specific embodiments and drawings.

[0016] A preparation method of heat-resistant modified phenolic resin includes the following steps: S1: Mix resorcinol and biphenyl dimethyl ether evenly under acidic conditions to form a reaction system, and react at the first target temperature for 7 - 9 h. Specifically, based on 100 parts by weight, the weight of resorcinol is 40 - 70 parts; the weight of biphenyl dimethyl ether is 20 - 50 parts. That is to say, in a ratio with a total of 100 parts, the proportion of resorcinol should be between 40% and 70%, and the proportion of biphenyl dimethyl ether should be between 20% and 50%. Specifically, the following reaction occurs in this S1 step:

[0017] The heat resistance of the resin is achieved by synthesizing a specific structural formula through the above reactions. Specifically, in this step, biphenyl dimethyl ether and resorcinol are used to prepare phenolic resin, changing the traditional resin formed by the reaction of phenols and aldehydes in the presence of a catalyst. The biphenyl structure with excellent comprehensive properties and resorcinol are introduced into the resin skeleton, making the finally prepared phenolic resin have good heat resistance. And the acidic catalyst used makes the overall reaction system promote the reaction under acidic conditions, because the acidic conditions can activate phenolic compounds and biphenyl dimethyl ether, making the two react more easily to form phenolic resin. At the same time, under acidic conditions, the crosslinking degree of the generated phenolic resin is higher and the molecular structure is denser, thus further improving the heat resistance and other properties of the phenolic resin.

[0018] S2: After the reaction is completed, cool the reaction system to the second target temperature and adjust the pH value of the reaction system to neutral. It should be noted here that: since in step S1, in order to make resorcinol and biphenyl dimethyl ether react better and more fully, the whole system is acidic. Then after the reaction is complete, if the whole system remains acidic, it may catalyze some unnecessary side reactions such as further condensation of phenolic hydroxyl groups or degradation of the resin, thus affecting the quality and performance of the product. Therefore, this step is mainly to make the reaction system in a neutral state, and the neutral state can make the reaction system more stable and more conducive to the subsequent steps. There are various means to adjust the pH value of the reaction system to neutral, such as adding water to dilute the acidic reaction system to reach neutral, or other means known to those skilled in the art that do not affect the reaction can be used to adjust the pH of the reaction system to neutral, which will not be elaborated in detail in this application.

[0019] S3: Remove the remaining resorcinol in the neutral reaction system, and then wash the reaction system several times to obtain heat-resistant modified phenolic resin.

[0020] This step is the final step. In this step, mainly some redundant substances are removed to make the finally prepared heat-resistant modified phenolic resin have a higher purity.

[0021] The present invention creatively uses resorcinol and biphenyl dimethyl ether for reaction, introducing a biphenyl structure with excellent comprehensive properties and resorcinol into the resin skeleton. Biphenyl is a structure with high rigidity, and introducing it into the resin structure can effectively improve the heat resistance of the resin. At the same time, resorcinol also has a rigid structure. Through the reaction of two rigid structures, the resulting phenolic resin has good heat resistance. Meanwhile, under acidic conditions, resorcinol and biphenyl dimethyl ether can be more activated, making it easier to undergo a polycondensation reaction to form a phenolic resin. And under acidic conditions, the crosslinking degree of the phenolic resin is higher and the molecular structure is more compact, thus further improving the heat resistance of the resin. By adjusting the pH value of the reaction system to neutral, on the one hand, it facilitates the subsequent removal of residual resorcinol and washing steps, further ensuring the purity of the prepared phenolic resin. On the other hand, the neutral environment helps to reduce the occurrence of side reactions, thereby obtaining a phenolic resin with a more uniform structure and more stable performance.

[0022] In a specific embodiment, the first target temperature in step S1 includes a first-stage heating temperature and a second-stage heating temperature; specifically, it includes the following steps: S11: Heat the reaction system to the first-stage heating temperature and maintain it for 2 h to 3 h; and methanol is removed during the heating process; and the first-stage heating temperature is 110°C to 120°C; S12: Then heat the reaction system to the second-stage heating temperature and maintain it for 5 h to 6 h; and the second-stage heating temperature is 130°C to 140°C.

[0023] In this embodiment, the first target temperature is divided into two stages. Since a large amount of methanol is released at the initial stage of the reaction between resorcinol and biphenyl dimethyl ether, methanol can be efficiently and fully recovered during this stage, ensuring the recyclability of resources. As the reaction progresses and the raw materials are continuously consumed, a second heating is then carried out to further promote the full occurrence of the reaction and improve the reaction efficiency. Therefore, dividing it into two stages has different focuses in each stage, enabling the entire reaction to proceed smoothly and stably while also being able to recover the formaldehyde volatilized during the reaction well.

[0024] Preferably, the heating rate of the first-stage heating temperature is greater than the heating efficiency of the second-stage heating temperature. Since the second-stage heating temperature is mainly to further promote the reaction of resorcinol and dimethyl biphenyl ether and make the two react fully, rapid heating in this stage not only increases the energy consumption but also does not greatly promote the reaction. It ensures that the reaction proceeds under milder conditions, reduces the occurrence of side reactions, and improves the selectivity and purity of the product. And a slower heating rate also allows the reactant molecules to have more sufficient time to contact and collide, thereby increasing the chance of reaction and promoting the completeness of the reaction. Since the first stage is mainly to recover the volatile methanol, a higher heating rate can quickly increase the temperature of the reaction system, thereby accelerating the volatilization of methanol, achieving effective removal of methanol in a short time, facilitating the subsequent reaction. And a faster heating rate can also reduce the residence time of methanol in the reaction system and reduce the risk of unnecessary reactions with other reactants, thereby improving the recovery efficiency of methanol.

[0025] In a specific embodiment, in step S1, resorcinol and dimethyl biphenyl ether are reacted under the action of the catalyst methanesulfonic acid; and the amount of substance of methanesulfonic acid is between two-thousandths and four-thousandths of the amount of substance of resorcinol. In this embodiment, methanesulfonic acid is selected as the catalyst, making the entire reaction system react under acidic conditions. Methanesulfonic acid shows high selectivity during the catalysis process, can promote specific chemical reactions to occur, reduce the generation of by-products, and thus obtain phenolic resin with higher purity. And when methanesulfonic acid is used as the catalyst, it can usually proceed under relatively mild reaction conditions, so there is no need to use complex or high-cost equipment, saving costs. And the amount of methanesulfonic acid is related to the amount of resorcinol to avoid insufficient catalysis due to too little methanesulfonic acid, increasing the reaction time. Avoiding too much methanesulfonic acid may cause unnecessary side reactions and affect the purity of the finally prepared phenolic resin. And the influence of the catalyst on the reaction: 1. When the amount of catalyst is too large, the reaction speed is very fast, the heat release is high, and there is a safety risk in the process. The acidity of the reaction system is too strong, promoting an increase in the proportion of macromolecules and a relatively high softening point. 2. When the amount of catalyst is small, the reaction speed is very slow, and basically twice the reaction time is required. Eventually, the proportion of small molecules in the resin is relatively high, and the softening point will be slightly lower.

[0026] In a specific embodiment, in step S3, the residual resorcinol is removed by means of high temperature and negative pressure; then the reaction system is washed with water 2 - 3 times repeatedly, keeping the water conductivity less than 10 us / cm; finally, heat-resistant modified phenolic resin is obtained.

[0027] A heat-resistant modified phenolic resin is prepared by using the preparation method of a heat-resistant modified phenolic resin as described above. The prepared heat-resistant modified phenolic resin has good heat stability and can meet the application requirements of some specific fields. Moreover, the preparation process is simple, without complex procedures, and the overall cost is low.

[0028] For the convenience of further understanding the solution of the present application, the following specific examples are given: Example 1 A preparation method of a heat-resistant modified phenolic resin includes the following steps: Under a nitrogen atmosphere, the weight parts of the raw material resorcinol are 165 parts, the weight parts of diphenyl dimethyl ether are 121 parts, and the weight parts of the catalyst methanesulfonic acid are 0.38 part; Add the above-mentioned weight parts of resorcinol, diphenyl dimethyl ether, and methanesulfonic acid into a reaction vessel, then start heating to 110°C - 120°C for reaction, maintain the condensation reflux for 2 - 3 h, separate out the generated methanol, then heat up to 130 - 140°C to continue the reaction, and maintain it for 5 - 6 h. After the reaction is completed, cool down to 115°C - 125°C, then add pure water to adjust the pH of the whole reaction system to neutral, and then adopt the method of high-temperature negative pressure to remove the residual resorcinol in the reaction system, wash with water 2 - 3 times, and the conductivity of the water is less than 10 us / cm to obtain a phenolic resin monomer with a softening point of about 90 degrees, and then cool it.

[0029] Example 2 A preparation method of a heat-resistant modified phenolic resin includes the following steps: Under a nitrogen atmosphere, the weight parts of the raw material resorcinol are 165 parts, the weight parts of diphenyl dimethyl ether are 60.5 parts, and the weight parts of the catalyst methanesulfonic acid are 0.38 part; Add the above-mentioned weight parts of resorcinol, diphenyl dimethyl ether, and methanesulfonic acid into a reaction vessel, then start heating to 110°C - 120°C for reaction, maintain the condensation reflux for 2 - 3 h, separate out the generated methanol, then heat up to 130 - 140°C to continue the reaction, and maintain it for 5 - 6 h. After the reaction is completed, cool down to 115°C - 125°C, then add pure water to adjust the pH of the whole reaction system to neutral, and then adopt the method of high-temperature negative pressure to remove the residual resorcinol in the reaction system, wash with water 2 - 3 times, and the conductivity of the water is less than 10 us / cm to obtain a phenolic resin monomer with a softening point of about 71 degrees, and then cool it.

[0030] Example 3 A preparation method of heat-resistant modified phenolic resin, comprising the following steps: Under a nitrogen atmosphere, the weight parts of the raw material resorcinol are 165 parts, the weight parts of biphenyl dimethyl ether are 151 parts, and the weight parts of the catalyst methanesulfonic acid are 0.38 parts; Add the above-mentioned weight parts of resorcinol, biphenyl dimethyl ether, and methanesulfonic acid into a reaction vessel, then start heating to 110°C - 120°C for reaction, maintain condensation reflux for 2 - 3 h, separate out the methanol generated by the reaction, then heat up to 130 - 140°C to continue the reaction, and maintain for 5 - 6 h. After the reaction is completed, cool down to 115°C - 125°C, then add pure water to adjust the pH of the entire reaction system to neutral, and then use the method of high temperature and negative pressure to remove the residual resorcinol in the reaction system, wash with water 2 - 3 times, the conductivity of the water is less than 10 us / cm, to obtain a phenolic resin monomer with a softening point of about 112 degrees, and cool down.

[0031] Example 4 A preparation method of heat-resistant modified phenolic resin, comprising the following steps: Under a nitrogen atmosphere, the weight parts of the raw material resorcinol are 165 parts, the weight parts of biphenyl dimethyl ether are 121 parts, and the weight parts of the catalyst methanesulfonic acid are 0.58 parts; Add the above-mentioned weight parts of resorcinol, biphenyl dimethyl ether, and methanesulfonic acid into a reaction vessel, then start heating to 110°C - 120°C for reaction, maintain condensation reflux for 2 - 3 h, separate out the methanol generated by the reaction, then heat up to 130 - 140°C to continue the reaction, and maintain for 5 - 6 h. After the reaction is completed, cool down to 115°C - 125°C, then add pure water to adjust the pH of the entire reaction system to neutral, and then use the method of high temperature and negative pressure to remove the residual resorcinol in the reaction system, wash with water 2 - 3 times, the conductivity of the water is less than 10 us / cm, to obtain a phenolic resin monomer with a softening point of 92 degrees, and cool down.

[0032] Example 5: A preparation method of heat-resistant modified phenolic resin, comprising the following steps: Under a nitrogen atmosphere, the weight parts of the raw material resorcinol are 165 parts, the weight parts of biphenyl dimethyl ether are 121 parts, and the weight parts of the catalyst methanesulfonic acid are 0.18 parts; Add the above-mentioned weight parts of resorcinol, biphenyl dimethyl ether, and methanesulfonic acid into a reaction vessel, then start heating to 110°C - 120°C for reaction, maintain condensation reflux for 2 - 3 h, separate out the methanol generated by the reaction, then heat up to 130 - 140°C to continue the reaction, and maintain for 5 - 6 h. After the reaction is completed, cool down to 115°C - 125°C, then add pure water to adjust the pH of the entire reaction system to neutral, and then use the method of high temperature and negative pressure to remove the residual resorcinol in the reaction system, wash with water 2 - 3 times, the conductivity of the water is less than 10 us / cm, to obtain a phenolic resin monomer with a softening point of 88 degrees, and cool down.

[0033] Comparative Example 1 Under nitrogen atmosphere, the raw material phenol has 141 parts by weight, diphenyl dimethyl ether has 121 parts by weight, and the catalyst methanesulfonic acid has 0.38 parts by weight. The above parts by weight of phenol, diphenyl dimethyl ether, and methanesulfonic acid are added to the reaction vessel, and then the temperature is raised to 110°C to 120°C for reaction, and the condensation reflux is maintained for 2-3 hours. The methanol generated by the reaction is separated, and then the temperature is raised to 130°C to 140°C to continue the reaction, and maintained for 5-6 hours. After the reaction is completed, the temperature is lowered to 115°C to 125°C, and pure water is added to adjust the pH of the entire reaction system to neutral, and then the residual resorcinol in the reaction system is removed by high temperature negative pressure, and the water washing is repeated 2-3 times, and the water conductivity is less than 10us / cm to obtain a resin monomer with a softening point of about 90 degrees and cooling.

[0034] Comparative Example 2 Under nitrogen atmosphere, the raw material resorcinol has 165 parts by weight, benzaldehyde has 106 parts by weight, and methanesulfonic acid has 0.38 parts by weight. The above parts by weight of resorcinol, benzaldehyde, and methanesulfonic acid are added to the reaction vessel, and then the temperature is raised to 110°C~120°C for reaction, and the condensation reflux is maintained for 2-3h, and water is separated, and then the temperature is raised to 130°C~140°C for continued reaction and maintained for 5-6h. After the reaction is completed, the temperature is lowered to 115°C~125°C, and pure water is added to adjust the pH of the entire reaction system to neutral, and then the residual resorcinol in the reaction system is removed by high temperature and negative pressure, and the water washing is repeated 2-3 times, and the water conductivity is less than 10us / cm, and a resin monomer is obtained, and the softening point is about 90 degrees, and cooled.

[0035] The resin monomers prepared in the above-mentioned Examples 1 to 3, Comparative Examples 1 and 2 were subjected to performance tests and TGA analysis, respectively. The performance test results are shown in Table 1, and the TAG analysis results are shown in Table 1. Figure 1 As shown;

[0036] Combining Table 1 and Figure 1 It can be seen that the phenolic resin prepared by the present application and the resin generated by the reaction of conventional mature phenols and aldehydes in the presence of a catalyst have similar properties in terms of softening point, viscosity, chloride ion, etc., and the conductivity and volatile matter are slightly improved compared with the mature process, indicating that the performance of the phenolic resin prepared by the present application is relatively stable; more importantly, the residual carbon rate of the phenolic resin prepared by the present application at a high temperature of 600 degrees is much higher than that of the other two groups of comparative examples, indicating that this resin has the best heat resistance among the three samples.

[0037] The examples described in the present invention are only descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design idea of the present invention, various deformations and improvements made by those skilled in the art to the technical solutions of the present invention shall fall within the protection scope of the present invention.

Claims

1. A preparation method of a heat-resistant modified phenolic resin, characterized in that: It includes the following steps: S1: Resorcinol and biphenyl dimethyl ether are mixed evenly under acidic conditions to form a reaction system, and the reaction is carried out at the first target temperature for 7 to 9 hours; S2: After the reaction is completed, the reaction system is cooled to the second target temperature, and the pH value of the reaction system is adjusted to neutral; S3: The residual resorcinol in the neutral reaction system is removed, and then the reaction system is washed with water several times to obtain a heat-resistant modified phenolic resin.

2. The preparation method of a heat-resistant modified phenolic resin according to claim 1, characterized in that: In step S1, the first target temperature includes the first-stage heating temperature and the second-stage heating temperature; specifically, it includes the following steps: S11: The reaction system is heated to the first-stage heating temperature and maintained for 2 to 3 hours; and methanol is removed during the heating process; and the first-stage heating temperature is 110°C to 120°C; S12: Then the reaction system is heated to the second-stage heating temperature and maintained for 5 to 6 hours; and the second-stage heating temperature is 130°C to 140°C.

3. The preparation method of a heat-resistant modified phenolic resin according to claim 2, wherein: The heating rate of the first-stage heating temperature is greater than the heating efficiency of the second-stage heating temperature.

4. The preparation method of a heat-resistant modified phenolic resin according to claim 1 or 2, characterized in that: In step S1, resorcinol and biphenyl dimethyl ether react under the action of catalyst methanesulfonic acid; and the amount of substance of methanesulfonic acid is between two-thousandths and four-thousandths of the amount of substance of resorcinol.

5. The preparation method of a heat-resistant modified phenolic resin according to claim 1, characterized in that: In step S3, the residual resorcinol is removed by means of high temperature and negative pressure; then the reaction system is washed with water 2 to 3 times repeatedly, and the water conductivity is kept less than 10 us / cm; finally, a heat-resistant modified phenolic resin is obtained.

6. A heat-resistant modified phenolic resin, characterized in that: It is prepared by using the preparation method of a heat-resistant modified phenolic resin described in any one of claims 1-5 above.

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