Preparation method of intramolecular complex antioxidant

Abstract

The invention discloses a preparation method of an intramolecular complex antioxidant, which comprises the following steps: (1) carrying out oxidative coupling reaction on 4-mercaptobenzoic acid under the action of an oxidant to generate an intermediate I; (2) carrying out an amide substitution reaction on the intermediate I and p-phenylenediamine to produce an intermediate II; and (3) carrying out a mercaptoamine condensation reaction on the intermediate II and 4-sulfydryl-2, 6-dialkylphenol under the action of a catalyst to obtain the intramolecular composite antioxidant. According to the preparation method of the intramolecular composite antioxidant, p-4-mercaptobenzoic acid, p-phenylenediamine and 4-mercapto-2, 6-dialkylphenol are used as raw materials, and the intramolecular composite antioxidant is synthesized through an oxidative coupling reaction, an amide substitution reaction and a mercaptoamine condensation reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis and relates to a method for preparing an antioxidant, in particular to a method for preparing an intramolecular composite antioxidant. Background Art

[0002] Polyolefin materials are widely used in various fields such as production and life due to their excellent mechanical properties and chemical inertness. In recent years, the polymer material industry has developed rapidly, especially the gap in high-end products has continued to increase, such as high-end polyethylene pipe materials, highly transparent medical resin poly-4-methyl-1-pentene and high-end polybutene-1 pipe materials. However, during its processing and use, it is inevitably affected by light, heat, oxygen, mechanical shearing and heavy metal ions, causing it to age and degrade, until it loses its commercial value and use value. For most polyolefin materials, adding antioxidants to improve their antioxidant properties is a simple and effective way. According to the different mechanisms of action of antioxidants, antioxidants mainly include two categories: primary antioxidants and auxiliary antioxidants. The primary antioxidants terminate free radical chain reactions by providing hydrogen protons or capturing free radicals to generate inert products, thereby inhibiting chain growth reactions. Commonly used primary antioxidants are hindered phenols and aromatic secondary amines. Auxiliary antioxidants terminate oxidation reactions by decomposing the hydroperoxides produced by chain growth reactions. Commonly used auxiliary antioxidants are phosphites and thioethers. Since the primary antioxidants and auxiliary antioxidants have different mechanisms of action, they are usually mixed and added to polyolefin materials to produce antioxidant synergistic effects, thereby having better antioxidant effects.

[0003] Since antioxidants with a single function cannot meet the various performance requirements of high-end polyolefin materials, and composite antioxidants have low cost, good comprehensive performance, short development cycle, and multiple additives fully exerting synergistic effects, they can meet the various performance requirements of high-end polyolefin materials. Therefore, multifunctional and compound antioxidants have become one of the main trends in the development of antioxidants. Intermolecular composite antioxidants are made by mixing the main antioxidant and the auxiliary antioxidant in a certain proportion. This type of composite antioxidant has a high-efficiency antioxidant effect, allowing various antioxidants to complement each other and synergistically exert antioxidant properties. However, there are few reports on intramolecular composite antioxidants.

[0004] Chinese patent CN102516157B reports a hindered phenol / hindered amine molecular composite antioxidant, which first uses 3,5-dialkyl-4-hydroxybenzoic acid and dichlorothionyl to undergo substitution reaction to prepare an antioxidant intermediate, and then the antioxidant intermediate is subjected to amidation reaction with N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine, and then an acid binding agent is added, and the reaction is continued. After the reaction is completed, the hindered phenol / hindered amine intramolecular composite antioxidant is obtained. And it is added to polyamide resin, and it is found in long-term aging tests that the new antioxidant can significantly delay the degradation of polyamide resin. However, the antioxidant structure provided by this technology only contains hindered phenol units as the main antioxidant, so it does not play a synergistic role of the main and auxiliary antioxidants in terms of the mechanism of action.

[0005] Chinese patent CN201910752684.3 reports a hindered phenol and amide intramolecular composite bifunctional antioxidant and its synthesis method. The antioxidant is first made into an ethylenediamine dendritic molecular skeleton by ethylenediamine, methanol, and methyl acrylate, and then the end group of the ethylenediamine dendritic molecular skeleton is sealed with DtBHP to obtain the antioxidant. The antioxidant terminates the chain reaction by capturing the generated free radicals and forming relatively stable free radicals by itself. It can directly, effectively and quickly capture free radicals and has high antioxidant capacity. However, the hindered phenol and amine active units contained in the antioxidant structure of this technology are both main antioxidants, so the synergistic effect of the main and auxiliary antioxidants is not achieved in terms of the mechanism of action.

[0006] Chinese patent CN 108164750 B Hindered amine antioxidant and polyethylene material, the invention discloses a hindered amine antioxidant and polyethylene material, the hindered amine antioxidant of the invention has good compatibility with polymers, good anti-migration and anti-solvent extraction performance, can be applied to the anti-aging of various polymer materials, and the hindered amine antioxidant is lighter in color and not easy to color. However, the amine antioxidant provided by the technology is a typical primary antioxidant, which can only terminate free radicals by providing hydrogen protons, and cannot eliminate the hydroperoxides generated during the reaction. Hydroperoxides will further trigger the occurrence of oxidation reactions, so the antioxidant effect is limited. Summary of the invention

[0007] In order to solve the problem that the main antioxidant can only play an antioxidant role by providing hydrogen protons to terminate free radicals, and the auxiliary antioxidant can only play an antioxidant role by decomposing hydroperoxides, and the auxiliary antioxidant cannot be used alone, the present invention provides a method for preparing an intramolecular composite antioxidant, using 4-mercaptobenzoic acid, p-phenylenediamine and 4-mercapto-2,6-dialkylphenol as raw materials, and synthesizing the intramolecular composite antioxidant through oxidative coupling reaction, amide substitution reaction and thiamine condensation reaction. The antioxidant contains both the phenolic hydroxyl group of the main antioxidant and the thioether group of the auxiliary antioxidant, and can realize the synergistic effect of the main and auxiliary antioxidants in the molecule, that is, it can quickly terminate the free radical chain reaction and decompose the hydroperoxides produced by the chain reaction, and has a very excellent antioxidant effect, which can effectively improve the antioxidant effect of the antioxidant. At the same time, there are multiple rigid benzene ring structures and non-hydrolyzable connecting groups in the molecular structure. It is not easy to hydrolyze and thermally decompose into small molecules during processing and use. The antioxidant has better stability and is applied to high-end polyolefin materials, especially poly-4-methyl-1-pentene materials, with a very excellent antioxidant effect.

[0008] To achieve the above object, the present invention provides a method for preparing an intramolecular composite antioxidant, the preparation method comprising the following steps:

[0009] (1) 4-Mercaptobenzoic acid undergoes oxidative coupling reaction under the action of an oxidant to generate intermediate I;

[0010] (2) Intermediate I undergoes an amide substitution reaction with p-phenylenediamine to produce intermediate II;

[0011] (3) Intermediate II reacts with 4-mercapto-2,6-dialkylphenol under the action of a catalyst to undergo a thiolamine condensation reaction to obtain an intramolecular composite antioxidant. The reaction formula of the preparation method is as follows: Figure 1 shown.

[0012] The preparation method of the intramolecular composite antioxidant of the present invention comprises the following steps: the reaction of step (1) is to add an oxidant to 4-mercaptobenzoic acid for reaction, and the reaction is carried out in an alkaline condition and in a solvent; the oxidant is selected from an aqueous solution of iodine or an aqueous solution of hydrogen peroxide; the molar amount of the oxidant is 0.8-1.5 times the molar amount of 4-mercaptobenzoic acid; the alkaline condition is to add one of ethylamine, ethylenediamine, dimethylamine and 4-methylaminopyridine, wherein the molar amount of the alkaline substance is 1-2 times the molar amount of 4-mercaptobenzoic acid; the solvent is selected from one of a mixture of dichloromethane and water, a methanol aqueous solution or a mixture of acetone and water, and the mass of the solvent is 20-50 times the total mass of the reactants.

[0013] The method for preparing the intramolecular composite antioxidant of the present invention is preferably that in the reaction of step (1), the molar amount of the oxidant is 1-1.2 times the molar amount of 4-mercaptobenzoic acid, and the molar amount of the alkaline substance is 1.4-1.6 times the molar amount of 4-mercaptobenzoic acid.

[0014] In the method for preparing the intramolecular composite antioxidant of the present invention, the reaction temperature of step (1) is 0-50°C, and the reaction time is 1-6h. Preferably, the reaction temperature is room temperature-30°C, and the reaction time is 2-4h.

[0015] The preparation method of the intramolecular composite antioxidant of the present invention comprises the following steps: the reaction of step (2) is carried out under the protection of an inert gas, the intermediate I is reacted under the action of an alkaline catalyst and a non-polar solvent; the molar amount of the p-phenylenediamine is 2-5 times the molar amount of the intermediate I; the molar amount of the alkaline catalyst is 0.02-0.4 times the molar amount of the intermediate I; the mass of the non-polar solvent is 5-9 times the total mass of the intermediate I and the p-phenylenediamine; the alkaline catalyst is selected from one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, triethanolamine and N,N-diisopropylethylamine; and the non-polar solvent is selected from at least one of benzene, toluene and ethylbenzene.

[0016] In the method for preparing the intramolecular composite antioxidant of the present invention, preferably, the molar amount of the p-phenylenediamine is 3-4 times the molar amount of the intermediate I; the molar amount of the alkaline catalyst is 0.15-0.2 times the molar amount of the intermediate I.

[0017] The preparation method of the intramolecular composite antioxidant of the present invention comprises the following steps: the p-phenylenediamine solution is dripped into the intermediate I for reaction, the reaction temperature is 80-140°C, the reaction time is 4-12h, preferably, the reaction temperature is 90-100°C, and the reaction time is 6-8h.

[0018] The method for preparing an intramolecular composite antioxidant of the present invention comprises the following steps: the reaction in step (3) is carried out under the protection of an inert gas, and the intermediate II and 4-mercapto-2,6-dialkylphenol undergo a condensation reaction under the action of a catalyst, pyridine; the molar amount of the pyridine is 0.05-0.12 times the molar amount of the intermediate II; and the molar amount of the 4-mercapto-2,6-dialkylphenol is 2-5 times the molar amount of the intermediate II.

[0019] In the method for preparing the intramolecular composite antioxidant of the present invention, preferably, the molar amount of the pyridine is 0.08-0.10 times the molar amount of the intermediate II; the molar amount of the 4-mercapto-2,6-dialkylphenol is 3-4 times the molar amount of the intermediate II.

[0020] The preparation method of the intramolecular composite antioxidant of the present invention comprises the following steps: step (3) is to drip 4-mercapto-2,6-dialkylphenol solution into intermediate II for reaction, the reaction temperature is 80-140°C, the reaction time is 5-10h, preferably, the reaction temperature is 90-110°C, and the reaction time is 6-8h.

[0021] The intramolecular composite antioxidant obtained by the preparation method of the present invention has the following structure:

[0022]

[0023] Wherein, R1, R2, R3, R4 are independently selected from hydrogen or alkyl, and R5 is selected from the following general formula:

[0024]

[0025] Wherein, R6, R7, R8, and R9 are independently selected from hydrogen or alkyl, R 10 , R 11 Independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl.

[0026] The intramolecular composite antioxidant obtained by the preparation method of the present invention, wherein R1, R2, R3 and R4 are independently selected from hydrogen, methyl, ethyl, n-propyl and isopropyl.

[0027] The intramolecular composite antioxidant obtained by the preparation method of the present invention, wherein R6, R7, R8 and R9 are independently selected from hydrogen, methyl, ethyl, n-propyl and isopropyl.

[0028] The intramolecular composite antioxidant obtained by the preparation method of the present invention preferably has the following general formula:

[0029]

[0030] The above-synthesized antioxidant is added to the poly-4-methyl-1-pentene material, extruded and granulated by a twin-screw extruder, and the oxidation induction period and mechanical properties are tested. The addition amount is 0.1%-1wt% of the mass of the poly-4-methyl-1-pentene material, and the extrusion temperature is 250-270°C.

[0031] The present invention has at least the following beneficial effects:

[0032] (1) The intramolecular composite antioxidant involved in the present invention is synthesized from 4-mercaptobenzoic acid, p-phenylenediamine and 4-mercapto-2,6-dialkylphenol as raw materials through oxidative coupling reaction, amidation substitution reaction and thiolamine condensation reaction. The reaction conditions are mild, the process is simple, and the raw materials are easily available.

[0033] (2) The intramolecular composite antioxidant molecule introduces a thioether bond into the main antioxidant such as hindered phenol, so that the antioxidant can not only terminate free radicals by providing hydrogen protons, but also react with hydroperoxides to achieve the dual role of main and auxiliary antioxidants. In addition, the introduced thioether bond is located at the para position of the phenolic hydroxyl group. Due to the electron-withdrawing effect, the electron cloud density at the position where the para position of the benzene ring is connected to the phenolic hydroxyl group is reduced, thereby making it easier for the hydrogen on the phenolic hydroxyl group to leave, resulting in a free radical termination reaction. Therefore, the antioxidant effect is significantly enhanced, and the mechanical properties and oxidation induction period of the polyolefin material can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The reaction formula is for the preparation method of the intramolecular composite antioxidant.

[0035] Figure 2 This is the H-NMR spectrum of the intramolecular composite antioxidant obtained in Example 1.

[0036] Figure 3 This is the mass spectrum of the intramolecular composite antioxidant obtained in Example 1.

[0037] Figure 4 This is the H-NMR spectrum of the intramolecular composite antioxidant obtained in Example 2.

[0038] Figure 5 This is the H-NMR spectrum of the intramolecular composite antioxidant obtained in Example 4.

[0039] Figure 6 This is the mass spectrum of the intramolecular composite antioxidant obtained in Example 4.

[0040] Figure 7 This is the H-NMR spectrum of the intramolecular composite antioxidant obtained in Example 8.

[0041] Figure 8 This is the mass spectrum of the intramolecular composite antioxidant obtained in Example 8. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described in detail below through specific embodiments.

[0043] Embodiment 1:

[0044] The preparation process of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment is as follows:

[0045] The preparation route is as follows:

[0046]

[0047] a. Synthesis of Intermediate I: Accurately weigh 100 mL of 0.1 mol / L 4-mercaptobenzoic acid methanol solution, add 0.015 mol of ethylenediamine, slowly dropwise add 22 mL of 0.5 mol / L iodine aqueous solution while stirring at room temperature, and react for 3 hours at constant room temperature. Add NH4Cl aqueous solution to the reaction mixture, filter and wash with water 2-3 times to obtain Intermediate I, with a yield of 94.1%.

[0048] b. Synthesis of intermediate II: Accurately weigh 100 mL of 0.1 mol / L toluene solution of intermediate I, add 0.002 mol of catalyst 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide under nitrogen protection, slowly add 80 mL of 0.5 mol / L toluene solution of p-phenylenediamine at 0°C, heat to 100°C and react for 8 hours after the addition is completed, remove toluene by distillation under reduced pressure to obtain a crude product, and purify the crude product by silica gel column chromatography. The volume ratio of petroleum ether:ethyl acetate used as the eluent is 10:1 to obtain intermediate II with a yield of 90.7%.

[0049] c. Synthesis of intramolecular composite antioxidant A1: accurately weigh 100 mL of 0.1 mol / L intermediate II toluene solution, add 0.001 mol of pyridine under nitrogen protection, slowly drop 80 mL of 0.5 mol / L 4-mercapto-2,6-di-tert-butylphenol toluene solution at 25°C while stirring, heat to 110°C and react for 7 hours, concentrate the reaction mixture under vacuum, dissolve the crude product in a mixed solvent of ethyl acetate and tetrahydrofuran, wash with the solution, and chromatograph the obtained organic phase. The volume ratio of petroleum ether:ethyl acetate used as the eluent is 6:1, and the intramolecular composite antioxidant A1 is obtained with a yield of 84.9%.

[0050] The intramolecular composite antioxidant A1 synthesized in this example was analyzed by nuclear magnetic resonance spectroscopy and mass spectrometry. The results are as follows: Figure 2 ,and Figure 3 As shown. Figure 2 It can be seen that the characterization data of the intramolecular composite antioxidant are: 1 H NMR(CD3Cl,400MHz): δ(ppm)1.35(s,C(CH3)3,36H),9.15(s,NH,2H),5.35(s,OH,2H),7.26(s ,OH-Ar-H,4H),7.39(d,OH-Ar-S-Ar-H,4H),8.05(d,O=C-Ar-H,4H),7.86-7.89(t,Ar-H,8H). Figure 3 It can be seen that m / z=928.4 is the molecular ion peak of the intramolecular composite antioxidant A1.

[0051] Embodiment 2:

[0052] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A2 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2,6-diisobutylphenol, and the yield of step c is 81.7%.

[0053] The structural formula of intramolecular composite antioxidant A2 is as follows:

[0054]

[0055] The intramolecular composite antioxidant A2 synthesized in this example was analyzed by nuclear magnetic resonance spectroscopy, and the results are as follows: Figure 4 shown. 1 H NMR (CD3Cl, 400MHz): δ (ppm) 9.15 (s, NH, 2H), 5.35 (s, OH, 2H), 0.91 (d, CH3, 24H), 1.82 (m, CH, 4H), 2.54 (d, C H2,8H),7.11(s,OH-Ar-H,4H),7.39(d,OH-Ar-S-Ar-H,4H),8.05(d,O=C-Ar-H,4H),7.86-7.89(t,Ar-H,8H).

[0056] Embodiment 3:

[0057] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A3 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2,6-di-n-butylphenol, and the yield of step c is 88.4%.

[0058] The structural formula of intramolecular composite antioxidant A3 is as follows:

[0059]

[0060] Embodiment 4:

[0061] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A4 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2,6-diisopropylphenol, and the yield of step c is 84.8%.

[0062] The structural formula of intramolecular composite antioxidant A4 is as follows:

[0063]

[0064] The intramolecular composite antioxidant A4 synthesized in this example was analyzed by nuclear magnetic resonance spectroscopy and mass spectrometry. The results are as follows: Figure 5 and Figure 6 shown. 1 H NMR (CD3Cl, 400MHz): δ (ppm) 1.20 (d, CH3, 24H), 3.05 (m, CH, 2H), 9.15 (s, NH, 2H), 5.35 (s, OH, 2H), 7 .12(s,OH-Ar-H,4H),7.39(d,OH-Ar-S-Ar-H,4H),8.05(d,O=C-Ar-H,4H),7.86-7.89(t,Ar-H,8H). Figure 6 It can be seen that m / z=872.7 is the molecular ion peak of the intramolecular composite antioxidant A4.

[0065] Embodiment 5:

[0066] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A5 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2,6-di-n-propylphenol, and the yield of step c is 80.9%.

[0067] The structural formula of intramolecular composite antioxidant A5 is as follows:

[0068]

[0069] Embodiment 6:

[0070] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A6 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2,6-diethylphenol, and the yield of step c is 90.7%.

[0071] The structural formula of intramolecular composite antioxidant A6 is as follows:

[0072]

[0073] Embodiment 7:

[0074] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A7 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2,6-dimethylphenol, and the yield of step c is 92.4%.

[0075] The structural formula of intramolecular composite antioxidant A7 is as follows:

[0076]

[0077] Embodiment 8:

[0078] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A8 in this example are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2-methyl-6-tert-butylphenol, and the yield of step c is 86.1%.

[0079] The structural formula of intramolecular composite antioxidant A8 is as follows:

[0080]

[0081] The intramolecular composite antioxidant A8 synthesized in this example was analyzed by nuclear magnetic resonance spectroscopy and mass spectrometry. The results are as follows: Figure 7 ,and Figure 8 As shown. Figure 7 It can be seen that the characterization data of intramolecular composite antioxidant A8 are: 1 H NMR(CD3Cl,400MHz): δ(ppm)1.35(s,C(CH3)3,18H),2.15(s,CH3,6H),9.15(s,NH,2H),5.35(s,OH,2H),7.03(s,O H-Ar-H,2H),7.27(s,OH-Ar-H,2H),7.39(d,OH-Ar-S-Ar-H,4H),8.05(d,O=C-Ar-H,4H),7.86-7.89(t,Ar-H,8H). Figure 8 It can be seen that m / z=845.9 is the molecular ion peak of the intramolecular composite antioxidant A8.

[0082] Embodiment 9:

[0083] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A9 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2-ethyl-6-tert-butylphenol, and the yield of step c is 84.9%.

[0084] The structural formula of intramolecular composite antioxidant A9 is as follows:

[0085]

[0086] Embodiment 10:

[0087] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A10 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that 4-mercapto-2,6-di-tert-butylphenol in step c is replaced by 4-mercapto-2-isopropyl-6-tert-butylphenol, and the yield of step c is 80.7%.

[0088] The structural formula of intramolecular composite antioxidant A10 is as follows:

[0089]

[0090] Embodiment 11:

[0091] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the aqueous solution of the catalyst iodine in step a is replaced by an aqueous solution of hydrogen peroxide, and the yield of step a is 83.7%, the catalyst 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in step b is replaced by triethanolamine, and the yield of step b is 74.6%, and the amount of pyridine in step c is 0.0005 mol, and the yield of step c is 71.4%.

[0092] Embodiment 12:

[0093] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the ethylenediamine in step a is replaced by ethylamine, and the yield of step a is 90.8%, the catalyst 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in step b is replaced by N,N-diisopropylethylamine, and the yield of step b is 93.4%, and the amount of pyridine in step c is 0.0012 mol, and the yield of step c is 90.7%.

[0094] Embodiment 13:

[0095] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the ethylenediamine in step a is replaced by dimethylamine, the yield of step a is 80.7%, the amount of p-phenylenediamine in step b is 40 mL, the yield of step b is 75.8%, and the amount of pyridine in step c is 0.0012 mol, and the yield of step c is 85.0%.

[0096] Embodiment 14:

[0097] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the ethylenediamine in step a is replaced by 4-methylaminopyridine, the yield of step a is 93.7%, the amount of p-phenylenediamine in step b is 100 mL, the yield of step b is 91.5%, and the reaction temperature in step c is 80° C., the yield of step c is 71.4%.

[0098] Embodiment 15:

[0099] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the amount of the iodine aqueous solution in step a is 16 mL, and the yield of step a is 81.7%, the amount of the catalyst 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in step b is 0.001 mol, and the yield of step b is 75.9%, and the reaction temperature in step c is 140° C., and the yield of step c is 84.2%.

[0100] Embodiment 16:

[0101] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the amount of the iodine aqueous solution in step a is 30 mL, and the yield of step a is 89.0%, the amount of the catalyst 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in step b is 0.004 mol, and the yield of step b is 92.1%, and the amount of 4-mercapto-2,6-di-tert-butylphenol in step c is 40 mL, and the yield of step c is 68.4%.

[0102] Embodiment 17:

[0103] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the amount of ethylenediamine used in step a is 0.01 mol, and the yield of step a is 80.7%, the reaction temperature in step b is 80°C, and the yield of step b is 74.9%, and the amount of 4-mercapto-2,6-di-tert-butylphenol used in step c is 100 mL, and the yield of step c is 85.2%.

[0104] Embodiment 18:

[0105] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the amount of ethylenediamine used in step a is 0.02 mol, the yield of step a is 90.2%, the reaction temperature of step b is 140°C, the yield of step b is 85.3%, the reaction time of step c is 5 h, and the yield of step c is 68.3%.

[0106] Embodiment 19:

[0107] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the reaction temperature of step a is 0°C, the yield of step a is 62.7%, the reaction time of step b is 4h, the yield of step b is 72.7%, the reaction time of step c is 10h, and the yield of step c is 85.0%.

[0108] Embodiment 20:

[0109] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the reaction temperature of step a is 50°C, the yield of step a is 72.8%, the reaction time of step b is 12h, and the yield of step b is 91.1%.

[0110] Embodiment 21:

[0111] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this example are basically the same as the preparation steps of the intramolecular composite antioxidant described in Example 1, except that the reaction time of step a is 1 h, and the yield of step a is 64.4%.

[0112] Embodiment 22:

[0113] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this example are basically the same as the preparation steps of the intramolecular composite antioxidant described in Example 1, except that the reaction time of step a is 6 hours and the yield of step a is 93.7%.

[0114] Embodiment 23:

[0115] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the methanol solution of 4-mercaptobenzoic acid in step a is replaced by a dichloromethane solution of 4-mercaptobenzoic acid, and the yield of step a is 90.4%.

[0116] Embodiment 24:

[0117] The preparation steps of the antioxidant intermediate and the intramolecular composite antioxidant A1 of this embodiment are basically the same as the preparation steps of the intramolecular composite antioxidant recorded in Example 1, except that the methanol solution of 4-mercaptobenzoic acid in step a is replaced by an acetone solution of 4-mercaptobenzoic acid, and the yield of step a is 85.7%.

[0118] Embodiment 25:

[0119] In the granulation section of the poly 4-methyl-1-pentene material, 0.1wt% of the antioxidants A1-A10 prepared in Examples 1-10 were added thereto, and the material was extruded, drawn and granulated by a twin-screw extruder at an extrusion temperature of 260°C. Then, the oxidation induction period and mechanical properties of the poly 4-methyl-1-pentene material were tested, and the test results are shown in Table 1. Comparative Example 1:

[0120] In the granulation section of the poly-4-methyl-1-pentene material, 0.1wt% of 2,6-di-tert-butyl-4-methylphenol was added thereto, and the material was extruded, drawn and granulated by a twin-screw extruder at an extrusion temperature of 260°C. The oxidation induction period and mechanical properties of the poly-4-methyl-1-pentene material were then tested. The test results are shown in Table 1.

[0121] Comparative Example 2:

[0122] In the granulation section of the poly-4-methyl-1-pentene material, 0.1wt% of didodecanol thiodipropionate was added thereto, and the material was extruded, drawn and granulated by a twin-screw extruder at an extrusion temperature of 260°C. Then, the oxidation induction period and mechanical properties of the poly-4-methyl-1-pentene material were tested. The test results are shown in Table 1.

[0123] Table 1 Analysis and test results of poly 4-methyl-1-pentene materials

[0124]

[0125] It can be seen from the data in Table 1 that the intramolecular composite antioxidants A1-A10 prepared by the present invention can effectively improve the mechanical properties and oxidation induction period of polyolefin materials, and antioxidants A1 and A10 have the best antioxidant effects. At the same time, the intramolecular composite antioxidants synthesized by the present invention are compared with commercial hindered phenol and thioether antioxidants, and the antioxidant effect of the intramolecular composite antioxidants synthesized by the present invention is significantly better than that of the commercial antioxidants.

[0126] In summary, the preparation method of the intramolecular composite antioxidant of the present invention uses p-4-mercaptobenzoic acid, p-phenylenediamine and 4-mercapto-2,6-dialkylphenol as raw materials, and synthesizes the intramolecular composite antioxidant through oxidative coupling reaction, amide substitution reaction and thiolamine condensation reaction. The antioxidant contains both the phenolic hydroxyl group of the main antioxidant and the thioether group of the auxiliary antioxidant, which can achieve the synergistic effect of the main and auxiliary antioxidants in the molecule, that is, quickly terminate the free radical chain reaction, and decompose the hydroperoxides produced by the chain reaction, and has a very excellent antioxidant effect. The raw materials of the synthesis process of the present invention are easy to obtain, the operation is simple, and it is easy to implement. The synthetic product is applied to high-end resins such as polybutene-1 and poly-4-methyl-1-pentene, which can effectively improve the antioxidant properties of the material, and has important guiding significance for the development and use of high-end resin additives.

[0127] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an intramolecular composite antioxidant, characterized in that: The steps include: (1) 4-Mercaptobenzoic acid undergoes oxidative coupling reaction under the action of an oxidant to generate intermediate I; (2) Intermediate I undergoes an amide substitution reaction with p-phenylenediamine to produce intermediate II; (3) Intermediate II reacts with 4-mercapto-2,6-dialkylphenol in the presence of a catalyst to undergo a thiolamine condensation reaction to obtain an intramolecular composite antioxidant.

2. The preparation method according to claim 1, characterized in that: The reaction of step (1) is to add an oxidant to 4-mercaptobenzoic acid for reaction, and the reaction is carried out under alkaline conditions and in a solvent; the oxidant is selected from an aqueous solution of iodine or an aqueous solution of hydrogen peroxide; the molar amount of the oxidant is 0.8-1.5 times the molar amount of 4-mercaptobenzoic acid; the alkaline condition is to add one of ethylamine, ethylenediamine, dimethylamine and 4-methylaminopyridine, wherein the molar amount of the alkaline substance is 1-2 times the molar amount of 4-mercaptobenzoic acid; the solvent is selected from a mixture of dichloromethane and water, a methanol aqueous solution or a mixture of acetone and water, and the mass of the solvent is 20-50 times the total mass of the reactants.

3. The preparation method according to claim 1, characterized in that: The reaction temperature of step (1) is 0-50°C, and the reaction time is 1-6h.

4. The preparation method according to claim 1, characterized in that: The reaction of step (2) is carried out under the protection of inert gas, and the intermediate I reacts under the action of an alkaline catalyst and a non-polar solvent; the molar amount of the p-phenylenediamine is 2-5 times the molar amount of the intermediate I; the molar amount of the alkaline catalyst is 0.02-0.4 times the molar amount of the intermediate I; the mass of the non-polar solvent is 5-9 times the total mass of the intermediate I and p-phenylenediamine; the alkaline catalyst is selected from one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, triethanolamine, and N,N-diisopropylethylamine; and the non-polar solvent is selected from at least one of benzene, toluene, and ethylbenzene.

5. The preparation method according to claim 4, characterized in that: The molar amount of the p-phenylenediamine is 3-4 times that of the intermediate I; the molar amount of the alkaline catalyst is 0.15-0.2 times that of the intermediate I.

6. The preparation method according to claim 1, characterized in that: The step (2) is to drop the p-phenylenediamine solution into the intermediate I for reaction, the reaction temperature is 80-140° C., and the reaction time is 4-12 hours.

7. The preparation method according to claim 1, characterized in that: The reaction in step (3) is carried out under the protection of an inert gas, and the intermediate II and 4-mercapto-2,6-dialkylphenol undergo a condensation reaction under the action of a catalyst, pyridine; the molar amount of the pyridine is 0.05-0.12 times the molar amount of the intermediate II; the molar amount of the 4-mercapto-2,6-dialkylphenol is 2-5 times the molar amount of the intermediate II.

8. The preparation method according to claim 7, characterized in that: The molar amount of the pyridine is 0.08-0.10 times that of the intermediate II; the molar amount of the 4-mercapto-2,6-dialkylphenol is 3-4 times that of the intermediate II.

9. The preparation method according to claim 1, characterized in that: The step (3) is to drip the 4-mercapto-2,6-dialkylphenol solution into the intermediate II for reaction, the reaction temperature is 80-140° C., and the reaction time is 5-10 hours.

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