Hindered phenol antioxidant as well as preparation method and application thereof
By optimizing the reaction conditions of 3,5-dimethylphenol and α-methylstyrene, 2-isopropylbenzene-3,5-dimethylphenol was prepared, solving the problems of easy volatility and antioxidant efficacy decay of p-cumylphenol and achieving stable application in high-temperature environments.
Patent Information
- Application Number
- CN202511853969.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-04-03
AI Technical Summary
In the existing technology, the synthesized p-cumylphenol has a small molecular weight, is easily volatile, and lacks stabilizing substituents, resulting in rapid decay of antioxidant efficacy and making it difficult to apply effectively in high-temperature environments.
2-Isopropylbenzene-3,5-dimethylphenol was prepared by reacting 3,5-dimethylphenol with α-methylstyrene in the presence of a catalyst. The reaction conditions were optimized by controlling the molar ratio, temperature, time, and catalyst dosage to improve the molecular weight and stability.
The prepared 2-isopropylbenzene-3,5-dimethylphenol has a large molecular weight, good antioxidant and high temperature resistance, and is suitable for plastics, synthetic rubber and industrial coatings, improving the thermal stability and antioxidant properties of materials.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of organic synthesis technology, and specifically relates to a hindered phenolic antioxidant, its preparation method, and its application. Background Technology
[0002] p-Cuiylphenol is an important organic compound with the chemical formula C15H16O and a molecular weight of 212. Its applications are mainly concentrated in the chemical and materials fields. As a hindered phenolic antioxidant, it can effectively prevent or slow down oxidation reactions and is widely used in plastics, synthetic rubber, and industrial coatings to improve the thermal stability and oxidation resistance of materials.
[0003] Currently, the main method for synthesizing p-cumylphenol is the condensation reaction of phenol and α-methylstyrene under the catalysis of a cation exchange resin. However, due to its relatively small molecular weight, it is prone to volatility, leading to the loss of effective components, especially in high-temperature or long-term use environments; secondly, it lacks stabilizing substituents, making it difficult to continuously scavenge free radicals through multiple pathways, resulting in a rapid decline in antioxidant efficacy.
[0004] Therefore, there is a need to develop a hindered phenolic antioxidant that has better antioxidant and high-temperature resistance than p-cumylphenol. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a hindered phenolic antioxidant, its preparation method and application. The hindered phenolic antioxidant has a larger molecular weight than p-cumylphenol, which satisfies the requirements of stabilizing substituents and retaining the antioxidant and high temperature resistance of hydroxyl groups, and has good application prospects.
[0006] This invention provides a hindered phenolic antioxidant, wherein the hindered phenolic antioxidant is 2-isopropylbenzene-3,5-dimethylphenol.
[0007] This invention also provides a method for preparing hindered phenolic antioxidants, comprising the following steps:
[0008] 3,5-Dimethylphenol and solvent were added to a reactor containing a catalyst, and then α-methylstyrene was added to react, wherein the molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1-2. The reaction product was cooled to obtain a solution of 2-isopropylbenzene-3,5-dimethylphenol. The solvent and unreacted raw materials were then removed by water washing, alkali washing, and vacuum distillation. Finally, 2-isopropylbenzene-3,5-dimethylphenol was obtained by recrystallization.
[0009] Preferably, the solvent is an inert solvent such as dichloroethane or toluene to improve reaction efficiency, and the mass ratio of the solvent to the 3,5-dimethylphenol is 1:1.
[0010] Preferably, the catalyst is one of p-toluenesulfonic acid, an acidic molecular sieve, and Lewis acid; the amount of the catalyst is 0.5wt%-2wt% of the total material.
[0011] Preferably, the reaction temperature is 60-100℃ and the reaction time is 4-6 hours.
[0012] Furthermore, 3,5-dimethylphenol and solvent are added from the top feed inlet of the reactor, followed by the slow addition of α-methylstyrene. Then, with the stirring of the reactor, 3,5-dimethylphenol and α-methylstyrene can fully contact the catalyst.
[0013] This invention also provides the application of hindered phenolic antioxidants in plastics, synthetic rubber, and industrial coatings.
[0014] The reaction formula for 2-isopropylbenzene-3,5-dimethylphenol of this invention is shown below:
[0015] .
[0016] Beneficial effects
[0017] The hindered phenolic antioxidant of this invention has a larger molecular weight than p-cumylphenol, which satisfies the requirements of stabilizing substituents while retaining the antioxidant and high-temperature resistance of hydroxyl groups, and has good application prospects. Detailed Implementation
[0018] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0019] Unless otherwise specified, all reagents used in the following examples are commercially available.
[0020] Example 1
[0021] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0022] Example 2
[0023] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0024] Example 3
[0025] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.5) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0026] Example 4
[0027] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:2) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0028] Example 5
[0029] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in a single batch. The reaction temperature was controlled at 85°C, and the reaction time was 5 hours. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0030] Example 6
[0031] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 60°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0032] Example 7
[0033] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 70°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0034] Example 8
[0035] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 90°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0036] Example 9
[0037] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 100°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0038] Example 10
[0039] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 4 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0040] Example 11
[0041] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 6 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0042] Example 12
[0043] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 0.5 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0044] Example 13
[0045] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.5 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0046] Example 14
[0047] 3,5-Dimethylphenol and an equal mass of toluene solution were added to a reactor containing 2 wt% p-toluenesulfonic acid. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0048] Example 15
[0049] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2 wt% AlCl3 of the total material. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85°C and the reaction time at 5 h. The fraction collected at 195-220°C was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0050] Example 16
[0051] 3,5-Dimethylphenol and an equal mass of toluene were added to a reactor containing 1.2% H2SO4 molecular sieves. Then, α-methylstyrene (molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1.3) was slowly added in two batches, with the reaction temperature controlled at 85℃ and the reaction time at 5 h. The fraction collected at 195-220℃ was then washed with water, alkali, and distilled under reduced pressure. This fraction was then recrystallized from petroleum ether to obtain a high-purity 2-isopropylbenzene-3,5-dimethylphenol product.
[0052] Comparative Example 1
[0053] By replacing 3,5-dimethylphenol in Example 1 with phenol, a high-purity p-cumylphenol product was prepared by reaction.
[0054] Comparative Example 2
[0055] High-purity 2-isopropylbenzene-4-methylphenol was prepared by replacing 3,5-dimethylphenol with p-cresol in Example 1.
[0056] Comparative Example 3
[0057] High-purity 4-isopropylbenzene-2,4,6-trimethylphenol was prepared by replacing 3,5-dimethylphenol in Example 1 with 2,4,6-trimethylphenol.
[0058] Table 1
[0059]
[0060] Table 1 shows that a molar ratio of α-methylstyrene to 3,5-dimethylphenol of 1:1.3 results in higher product purity and is more economical. When the proportion of 3,5-dimethylphenol is less than or equal to 1, some will form a dimer of 2,6-diisopropylbenzene-3,5-dimethylphenol, affecting purity. Although excessive 3,5-dimethylphenol inhibits dimer formation and increases product purity, it is not economical. Therefore, a molar ratio of 1:1.3 is preferred.
[0061] Table 2
[0062]
[0063] As shown in Table 2, the addition of α-methylstyrene in batches can effectively increase the yield of the product, reduce the formation of dimers, and increase the yield of 2-isopropylbenzene-3,5-dimethylphenol.
[0064] Table 3
[0065]
[0066] As shown in Table 3, the reaction rate can be increased when the temperature rises, but the yield of 2-isopropylbenzene-3,5-dimethylphenol will first increase and then decrease, and the dimer will also increase accordingly. Therefore, the optimal temperature is 85℃.
[0067] Table 4
[0068]
[0069] As shown in Table 4, the reaction time affects the product yield. However, after a certain period of time, the reaction becomes extremely slow. For economic reasons, a reaction time of about 5 hours is preferred.
[0070] Table 5
[0071]
[0072] As shown in Table 5, the reaction yield increases with the increase of the catalyst proportion. However, excessive catalyst can promote the formation of dimers, affecting the yield of 2-isopropylbenzene-3,5-dimethylphenol. Therefore, a catalyst content of 1.2% of the total material is more appropriate.
[0073] Table 6
[0074]
[0075] As shown in Table 6, p-toluenesulfonic acid is the optimal catalyst.
[0076] In summary, the best product benefits were obtained by slowly adding α-methylstyrene (the molar ratio of α-methylstyrene to 3,5-dimethylphenol is 1:1.3) in two batches with a total material content of 1.2 wt% p-toluenesulfonic acid catalyst, controlling the reaction temperature at 85℃ and the reaction time at 5 h.
[0077] The antioxidant and high-temperature resistance properties of the three products from Example 1, Comparative Example 1, and Comparative Example 2 were tested. Due to steric hindrance, the methyl group of trimethylphenol in Comparative Example 3 inhibited the electrophilic substitution of the benzene ring, resulting in the formation of byproducts and very low product yield and purity, so it was not considered.
[0078] Table 7
[0079]
[0080] As shown in Table 7, 3,5-dimethylphenol has superior performance compared to other phenols.
[0081] As shown in Table 7, 2-isopropylbenzene-3,5-dimethylphenol, prepared by the reaction of 3,5-dimethylphenol and α-methylstyrene, has better antioxidant and high-temperature resistance than p-cumylphenol. In addition, during the experiment, it was found that 2-isopropylbenzene-3,5-dimethylphenol is also superior to p-cumylphenol in terms of compatibility with resin.
[0082] The above content is a further detailed description of the technical solution provided in conjunction with the preferred embodiments of the present invention. It should not be considered that the specific implementation of the present invention is limited to the above description. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.
Claims
1. A hindered phenolic antioxidant, characterized in that, The hindered phenolic antioxidant is 2-isopropylbenzene-3,5-dimethylphenol.
2. A method for preparing a hindered phenolic antioxidant, characterized in that, Includes the following steps: 3,5-Dimethylphenol and solvent were added to a reactor containing a catalyst, and then α-methylstyrene was added to react, wherein the molar ratio of α-methylstyrene to 3,5-dimethylphenol was 1:1-2. The reaction product was cooled to obtain a solution of 2-isopropylbenzene-3,5-dimethylphenol. The solvent and unreacted raw materials were then removed by water washing, alkali washing, and vacuum distillation. Finally, 2-isopropylbenzene-3,5-dimethylphenol was obtained by recrystallization.
3. The preparation method according to claim 2, characterized in that, The solvent is dichloroethane or toluene, and the mass ratio of the solvent to the 3,5-dimethylphenol is 1:
1.
4. The preparation method according to claim 2, characterized in that, The catalyst is one of p-toluenesulfonic acid, an acidic molecular sieve, and Lewis acid; the amount of the catalyst used is 0.5wt%-2wt% of the total material.
5. The preparation method according to claim 2, characterized in that, The reaction temperature is 60-100℃, and the reaction time is 4-6 hours.
6. The application of the hindered phenolic antioxidant as described in claim 1 in plastics, synthetic rubber and industrial coatings.