A low-ash high-quality antioxidant 1098 production process

Abstract

The application discloses a production process of low-ash high-quality antioxidant 1098, and belongs to the technical field of polymer material additives.The process uses ester 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid methyl ester and hexanediamine as reaction raw materials, selects a metal-free composite catalyst system prepared by using an organic guanidine main catalyst and a quaternary phosphonium salt main catalyst, realizes two-stage directional amidation-reaction rectification coupling continuous reaction, and then realizes purification process to obtain the antioxidant 1098 product.The application effectively avoids metal ion residues, effectively inhibits the generation of colored by-products, and realizes the technical effects of low-ash, high-whiteness, high-purity and high-yield of the product.

Description

Technical Field

[0001] This invention relates to the field of polymer material additives technology, and more particularly to antioxidant 1098, specifically a process for the stable production of low-ash, high-quality antioxidant 1098. Background Technology

[0002] Antioxidant 1098, or N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, is a high-performance hindered phenolic antioxidant. It possesses excellent anti-thermal oxidation performance, good compatibility with polar polymers such as polyamides, low volatility, and resistance to extraction. It is a core additive in the fields of polyamides, polyesters, engineering plastics, and high-end elastomers, effectively inhibiting the thermal oxidative degradation of polymer materials during high-temperature processing and long-term use, preventing the decline of mechanical properties and discoloration. With the rapid development of high-end fields such as 5G communication, optical fiber cables, medical polymers, and food contact materials, the market has placed far stringent standards on antioxidant 1098 regarding ash content control, purity stability, and whiteness, exceeding national standards, and has demanded higher requirements for the optimization and upgrading of its industrial production processes.

[0003] Currently, the mainstream industrial production route for antioxidant 1098 is the amidation condensation process. This process uses methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (referred to as the ester) and hexamethylenediamine as raw materials, and alkali metal alkoxides such as sodium methoxide and sodium ethoxide as catalysts, to prepare antioxidant 1098 through an ester-amine decondensation reaction. However, with the increasing demands for antioxidant 1098, it has been found that this process has unresolved problems.

[0004] (1) The catalysts selected are alkali metal alkoxides such as sodium methoxide and sodium ethoxide. After the reaction, a large amount of water washing is required to remove them, but metal ion residues are still unavoidable. The ash content of the product is usually above 100 ppm, which cannot meet the stringent requirements of no more than 50 ppm for high-end electronics, optical fiber, medical polymers and other fields. Some improved technologies use organotin and rare earth metal catalysts, which have the problems of high toxicity, high cost and difficulty in removing metal residues. Alkaline ionic liquid catalysts have the defects of complex preparation, difficult recovery and poor industrial adaptability.

[0005] (2) During the reaction, the phenolic hydroxyl group is easily oxidized at high temperature to generate quinone colored byproducts. At the same time, impurities such as monoamide intermediates and ester hydrolysis products are easily generated, resulting in poor whiteness and large fluctuations in purity of the product, which limits its application in light-colored / white products and highly transparent materials. Existing technologies are mostly improved by multiple recrystallization and activated carbon decolorization, which have problems such as complex process, large solvent consumption and significantly reduced product yield.

[0006] (3) The aminolysis reaction is a reversible reaction. If the byproduct methanol cannot be removed in time, it will inhibit the forward reaction, resulting in low raw material conversion rate and an increase in monosubstituted byproducts. Existing processes mostly use a single high-temperature and low-pressure reaction, which can easily cause excessive local reaction and aggravate side reactions. The product yield is usually only 85%-90%, and the industrial production cost is relatively high.

[0007] Therefore, existing technologies cannot simultaneously achieve low ash content, high whiteness, high purity, and high yield, making it difficult to meet the quality requirements of antioxidant 1098 in high-end fields. Developing a preparation process for antioxidant 1098 that can solve the above problems in one integrated way, with stable technology and suitable for industrial production, has significant market value. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention proposes a production process for low-ash, high-quality antioxidant 1098, achieving the technical effects of low ash content, high whiteness, high purity, and high yield.

[0009] The technical problem to be solved by the present invention is achieved through the following technical solution: A production process for a low-ash, high-quality antioxidant 1098 includes the following steps: S1 Raw Material Preparation: Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and hexamethylenediamine are used as reactants, with a molar ratio of ester to hexamethylenediamine of (2.08-2.15):1. A slight excess of ester ensures complete reaction of hexamethylenediamine and reduces monoamide byproducts. A metal-free composite catalyst system composed of organic guanidine compounds and quaternary phosphonium salt phase transfer catalysts is used to avoid metal ion residues from the source. Toluene is selected as the reaction solvent because its boiling point matches the reaction temperature and it can form an azeotrope with methanol, facilitating the continuous removal of methanol byproducts. S2 continuous reaction: Under nitrogen protection, a two-stage directional continuous reaction is carried out: (1) First stage low-temperature directional monoamidation: Hexamethylenediamine, composite catalytic system and part of the reaction solvent are fed into a static mixing reactor, heated to 40-55℃, and the reaction solvent solution of methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is continuously added dropwise. The feed molar ratio of methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to hexamethylenediamine is controlled to be (1.05-1.1):1. The material residence time is 30-60 min to complete the directional monoamidation reaction and obtain the monoamide intermediate reaction solution. (2) Second stage deep diamidation-reactive distillation: The monoamide intermediate reaction liquid is continuously fed into the reactive distillation column, the column bottom temperature is raised to 80-100℃, and the remaining ester methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is added to the column bottom at the same time; the reactive distillation column adopts gradient pressure reduction operation, and the vacuum degree at the top of the column is gradually reduced from atmospheric pressure to -0.09~-0.098 MPa within 30-60 min, and the by-product methanol is distilled off continuously throughout the process. The total residence time of the material in the column is 2-4 h, and the deep diamidation reaction is completed to obtain the crude reaction liquid; S3 purification post-processing: The crude reaction liquid is sequentially subjected to complexation extraction to remove the catalyst, nanofiltration for deep impurity removal, dissolution and directional crystallization, and vacuum drying to obtain the low-ash, high-quality antioxidant 1098 product, specifically including: (1) Complex extraction to remove catalyst: Cool the crude reaction liquid to 50-60℃, add a citrate-sodium dihydrogen phosphate buffer solution with pH 5.5-6.5, keep warm and stir for 15-30 min, let stand and separate the layers, remove the aqueous phase, and extract the organic phase once again with the same batch of buffer solution until the conductivity of the organic phase is ≤8 μS / cm; the guanidine group of the main catalyst is formed by the citrate-phosphate buffer solution, and the catalyst system is completely removed by one-step extraction without multiple water washing, thus avoiding product loss.

[0010] (2) Nanofiltration for deep impurity removal: The organic phase after complex extraction is fed into a polyamide nanofiltration membrane system with a molecular weight cutoff of 500 Da. The operating pressure is 1.2-1.8 MPa and the operating temperature is 40-50℃. The permeate is a clear toluene solution of the product, and the effluent is a large molecular colored impurity and trace by-products. The nanofiltration membrane accurately retains the large molecular colored impurities and trace by-products, replacing the traditional activated carbon decolorization process, avoiding product loss caused by activated carbon adsorption, and completely solving the product color problem.

[0011] (3) Directional crystallization by dissolution: The nanofiltration permeate is concentrated under reduced pressure to a solid content of 45%-55%. Hexane is continuously added to the concentrate as a solvent, and the mass ratio of toluene to hexane is controlled to be 1:(1.5-2). After stirring evenly, the temperature is gradually reduced to 5-15℃ at a rate of 0.8-1.5℃ / min. The mixture is kept at this temperature for 3-5 h to crystallize. The filter cake is obtained by filtration and washed twice with cold hexane at 0-5℃. Through gradient dissolution crystallization of the toluene-hexane binary system, the product can achieve ultra-high purity in one crystallization, without the need for multiple recrystallizations, which greatly improves the product yield.

[0012] (4) Vacuum drying: Place the filter cake in a vacuum drying oven for drying at a temperature of 85-95℃, a vacuum degree of ≤ -0.098MPa, and a drying time of 5-8 h.

[0013] In this invention, the composite catalyst system uses hindered phenol-functionalized bicyclic guanidine as the main catalyst and dihydroxy-functionalized quaternary phosphonium salt as the co-catalyst to form a bifunctional synergistic catalytic system. The main catalyst is 7-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and the co-catalyst is dihydroxyethyldimethylphosphonium bromide.

[0014] Furthermore, the main catalyst is prepared through the following steps: (1) Preparation of acylation intermediate: Using 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid as raw material, anhydrous dichloromethane was added as solvent. Under nitrogen protection, excess thionyl chloride or oxaloyl chloride was added dropwise at low temperature. 1-2 drops of N,N-dimethylformamide were added as catalyst. The reaction was stirred at room temperature for 4-6 h. After the reaction was completed, excess thionyl chloride or oxaloyl chloride and solvent dichloromethane were removed by vacuum distillation to obtain the pale yellow acylation intermediate 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, which can be used directly in the next step of the reaction without the need for catalysis. (2) Amide condensation: 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and anhydrous dichloromethane were added to a dry three-necked flask and stirred until dissolved. Triethylamine, an acid-binding agent, was added in a molar amount of 1.1-1.2 times that of TBD. Under chlorine protection and in an ice-water bath at 0°C, a dichloromethane solution of the above acyl chloride intermediate was slowly added dropwise. The molar ratio of the acyl chloride intermediate to TBD was 1:1.05. After the addition was completed, the temperature was raised to room temperature and the reaction was stirred for 8-12 h. The reaction endpoint was monitored by thin-layer chromatography (TLC). (3) Post-treatment and purification: The reaction solution was washed successively with deionized water, saturated sodium bicarbonate solution and saturated brine. The organic phase was dried with anhydrous sodium sulfate. After filtration, the crude product was concentrated under reduced pressure. The crude product was recrystallized 2-3 times with a mixed solvent of ethyl acetate and n-hexane, or purified by column chromatography. After vacuum drying, a high-purity white target product was obtained.

[0015] Furthermore, the amount of the main catalyst is 0.15%-0.4% of the total mass of the esterified methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and the amount of the co-catalyst is 0.08%-0.25% of the total mass of the esterified product.

[0016] In this invention, the reaction solvent is toluene, and its total amount is 2.5-3.5 times the total mass of the esterified methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and hexamethylenediamine.

[0017] In this invention, in step S2, the endpoint of the first low-temperature directional monoamide reaction is detected by high performance liquid chromatography, and the hexamethylenediamine residue in the system is controlled to be ≤0.05%, and the monoamide intermediate selectivity is ≥99%; the endpoint of the second deep diamide reaction is detected by high performance liquid chromatography, and the ester residue in the system is controlled to be ≤0.08%, and the monoamide intermediate residue is ≤0.1%.

[0018] In this invention, the main catalyst and the co-catalyst work together to achieve a synergistic catalytic effect, specifically: The bicyclic guanidine group of the main catalyst provides a strong basic catalytic site, which can efficiently abstract the active hydrogen of the amino group of hexamethylenediamine, enhance the nucleophilicity of the amino group, and efficiently catalyze the ester-amine aminolysis reaction. The hindered phenolic group grafted in its molecular structure is consistent with the functional group structure of the raw material ester, which can capture alkyl free radicals and peroxy free radicals generated during the reaction in situ, completely inhibit the oxidation of phenolic hydroxyl groups from the source of the reaction, and prevent the generation of colored quinone by-products. No additional polymerization inhibitors are needed, and no new impurities are introduced. The dihydroxy group of the co-catalyst acts as a hydrogen bond donor, forming a strong hydrogen bond with the carbonyl oxygen of the ester, activating the carbonyl group, significantly reducing the activation energy of the nucleophilic addition reaction, and increasing the reaction rate by more than 50%. Its quaternary phosphonium cation can form a cation-π interaction with the guanidinium group of the main catalyst, and the hydroxyl group can form a hydrogen bond with the nitrogen atom of the guanidinium group, constructing a stable hydrogen bond catalytic network, precisely controlling the reaction transition state, preferentially promoting the conversion of monoamide intermediates to diamide products, improving the selectivity of the diamide reaction to more than 99.9%, and completely solving the problem of monoamide intermediate residue; The entire catalytic system contains no metal elements, which can be completely removed by weak acid complexation extraction after the reaction, leaving no residue and achieving ultra-low ash control from the source.

[0019] In this invention, the reaction process is also specifically designed to complement the above-mentioned catalytic system: The first stage of low-temperature directional monoamidation is carried out in a static mixing reactor. The feed ratio of ester to hexamethylenediamine is precisely controlled, and the monoamidation reaction is completed at low temperature. This avoids the waste of raw materials and by-products caused by the simultaneous reaction of hexamethylenediamine and diamine. The selectivity of the monoamid intermediate is ≥99%, and the generation of by-products is eliminated from the reaction path. The second stage, deep diamidation-reactive distillation, feeds the monoamide intermediate into a reactive distillation column. While adding the remaining esters, methanol byproducts are removed by continuous distillation under reduced pressure at the top of the column. This breaks the reversible reaction equilibrium in real time, bringing the feed conversion rate close to 100%. The reaction temperature is reduced by 10-20°C compared to the traditional process, and the total reaction time is shortened by more than 60%, significantly reducing high-temperature side reactions.

[0020] Compared with the prior art, the present invention has the following advantages: (1) This application adopts a metal-free composite catalyst system, which eliminates the introduction of metal ions from the source and can stably control the ash content of the product to within 30 ppm, which is far below the national standard requirements and meets the stringent requirements of high-end electronics, optical fiber, medical polymers and other fields. At the same time, the dual-function synergistic catalytic system achieves the synergistic effect of catalysis, polymerization inhibition, activation and selective regulation by molecular design of organic guanidine and quaternary phosphonium salt, which effectively solves the problems of poor selectivity, many side reactions and large amount of catalyst used in the existing catalytic system. (2) The process of this application utilizes inert gas protection throughout, combined with low temperature and reaction, to suppress the generation of colored by-products from the reaction end. The product has Hunter whiteness L value ≥98, b value ≤0.5, melt color APHA ≤20, HPLC purity ≥99.8%, and the quality fluctuation performance between single batches is suitable for the application needs of light-colored, white, and highly transparent polymer products. (3) The production efficiency and yield of this application are greatly improved. The total reaction time of the continuous reaction process is ≤5 h, which is more than 60% shorter than the traditional process. The molar yield of the product is stable at ≥97%, which is significantly improved compared with the existing process. The solvent recovery rate is ≥97%, and the catalyst usage is only 1 / 5-1 / 3 of that of the existing organic guanidine process, which greatly reduces the production cost. (4) The process of this application is highly adaptable and easy to industrialize. The process conditions are mild and there are no harsh requirements for high temperature and high pressure. Continuous production can be achieved by modifying existing equipment. There is no fluctuation in product quality between batches. The amount of waste emissions is reduced by more than 70% compared with traditional processes. It has extremely high industrial application value. Attached Figure Description

[0021] Figure 1 This is a comparison curve of the kinetics of the aminolysis reaction under different catalytic systems in this application; Figure 2 The above are HPLC chromatograms comparing products prepared using different processes in this application. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. Example 1

[0023] This embodiment is a specific example of the application of the production process according to the present invention.

[0024] Synthesis of S1 main catalyst: In an anhydrous reaction system under nitrogen protection, 32.8 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and 17.2 g of TBD were fed. The propionic acid raw material was first reacted with thionyl chloride to obtain an acyl chloride intermediate. A TBD dichloromethane solution containing triethylamine acid binder was added dropwise at 0°C and reacted at room temperature for 10 h. After washing with water, drying, and concentrating, the reaction solution was recrystallized twice with hexane and dried under vacuum to obtain 36.7 g of the white target product 7-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]-1,5,7-triazabicyclo[4.4.0]dec-5-ene, with a yield of 78.0% and a purity of 99.2% as determined by HPLC.

[0025] S2 Raw Material Preparation: Accurately weigh 402.2 g (1.224 mol) of methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 69.7 g (0.6 mol) of hexamethylenediamine, with a total molar ratio of ester to ethylenediamine of 2.04:1, 0.8 g of main catalyst (0.2% of the esterified mass), 0.4 g of co-catalyst dihydroxyethyldimethylphosphonium bromide (0.1% of the esterified mass), and a total amount of toluene (3 times the total mass of the esterified and hexamethylenediamine) as the reaction solvent.

[0026] S3 Two-Stage Directed Amide-Reactive Distillation Coupled Reaction: Continuous Feed Reaction with Full Nitrogen Protection: The first stage of low-temperature directional monoamide oxidation: Hexamethylenediamine, the entire catalytic system, and 600 g of toluene were fed into a static mixing reactor. The temperature was raised to 50°C, and a toluene solution of 206.3 g (0.63 mol, molar ratio to hexamethylenediamine 1.05:1) of the esterified product was continuously added dropwise (toluene dosage 415.7 g). The feed rate was controlled to ensure a total residence time of 45 min. At the reaction endpoint, the residual hexamethylenediamine was 0.03%, and the selectivity of the monoamide intermediate was 99.2%, yielding the monoamide intermediate reaction solution. The second stage of deep diamidation-reactive distillation: The monoamide intermediate reaction solution was continuously fed into a reactive distillation column, and the column bottom temperature was raised to 90°C. At the same time, 195.9 g (0.594 mol) of the remaining ester was continuously added to the column bottom. The pressure was reduced at the top of the column by gradient: from atmospheric pressure to -0.05 MPa within 30 min, and then to -0.095 MPa within another 30 min. The vacuum was maintained to continuously distill off methanol. The total residence time in the column was 3 h. At the reaction endpoint, the residual ester was 0.06% and the residual monoamide intermediate was 0.08%. The reaction was stopped, and the crude reaction solution was obtained.

[0027] S4 coupling purification process Catalyst removal by complexation extraction: Cool the crude reaction solution to 55℃, add 200 mL of citrate-sodium dihydrogen phosphate buffer solution at pH 6.0, keep warm and stir for 20 min, let stand to separate the aqueous phase, and extract the organic phase once again with 100 mL of the same batch of buffer solution. The conductivity of the organic phase was measured to be 6 μS / cm, and the extraction was stopped. Nanofiltration for deep impurity removal: The extracted organic phase is fed into a polyamide nanofiltration membrane system with a molecular weight cutoff of 500 Da, operating at a pressure of 1.5 MPa and a temperature of 45°C. The permeate is collected to remove large molecular colored impurities and trace by-products. Directed crystallization by dissolution: The permeate was concentrated under reduced pressure at -0.09 MPa and 75℃ to a solid content of 50%. Hexane was continuously added to the concentrate, and the mass ratio of toluene to hexane was controlled at 1:1.8. After stirring evenly, the temperature was gradually reduced to 10℃ at a rate of 1℃ / min. The mixture was kept at this temperature for 4 h to crystallize. The filter cake was obtained by filtration and washed twice with cold hexane at 0-5℃, with a dosage of 60 g each time. Vacuum drying: The filter cake was placed in a vacuum drying oven and dried at 90℃ and -0.098 MPa for 6 h to obtain 419.1 g of antioxidant 1098 product, with a molar yield of 97.4%.

[0028] S5 Product Testing: Performance testing was conducted on the finished product. The HPLC purity was 99.92%, the ash content was 12 ppm, the Hunter whiteness L value was 99.1, the b value was 0.18, the melting color was APHA8, and the melting point was 156.5-157.0℃. All indicators far exceeded the national standard requirements. Example 2

[0029] This embodiment, through appropriate adjustments, selects the lower limit of some process parameters to form a new implementation case.

[0030] The S1 main catalyst was obtained using the method described in Example 1.

[0031] S2 raw material preparation: total mass of esterified product 410.0 g (1.248 mol), hexamethylenediamine 69.7 g (0.6 mol), total molar ratio 2.08:1, main catalyst 0.62 g (0.15% of the mass of esterified product), main catalyst 0.33 g (0.08% of the mass of esterified product), total toluene 1189.3 g (2.5 times the total mass of esterified product and hexamethylenediamine).

[0032] S3 bi-stage directional amidation-reactive distillation coupled reaction First stage: The static mixing reactor was heated to 40℃, and a toluene solution containing 209.2 g (0.636 mol, molar ratio of ester to hexamethylenediamine 1.06:1) was added dropwise. The residence time was 60 min. At the reaction endpoint, the residual hexamethylenediamine was 0.04%, and the monoamide selectivity was 99.1%. Second stage: The temperature of the bottom of the reactive distillation column is 80℃. The pressure is gradually reduced to -0.09 MPa at the top of the column within 60 min. 200.8 g of the remaining ester is added. The residence time in the column is 4 h. At the reaction endpoint, the ester residue is 0.07% and the monoamide residue is 0.09%.

[0033] S4 coupling purification process Complex extraction: The solution was cooled to 50℃ and extracted twice with a buffer solution of pH 5.5. The final organic phase conductivity was 7 μS / cm. Nanofiltration for impurity removal: operating pressure 1.2 MPa, operating temperature 40℃; Dissolution and crystallization: Concentrate to a solid content of 45%, with a toluene to n-hexane mass ratio of 1:1.5, and cool to 15℃ at a rate of 0.8℃ / min, crystallizing for 5 h; Vacuum drying: dried at 85℃ and -0.098 MPa for 8 h to obtain 417.8 g of the product, with a molar yield of 97.1%.

[0034] S5 product testing: HPLC purity 99.90%, ash content 14 ppm, Hunter whiteness L value 99.0, b value 0.20, melt color APHA10. Example 3

[0035] This embodiment, through appropriate adjustments, selects the lower limit of some process parameters to form a new implementation case.

[0036] The S1 main catalyst was obtained using the method described in Example 1.

[0037] S2 raw material preparation: total mass of esterified product 423.8 g (1.29 mol), hexamethylenediamine 69.7 g (0.6 mol), total molar ratio 2.15:1, main catalyst 1.70 g (0.4% of the mass of esterified product), main catalyst 1.06 g (0.25% of the mass of esterified product), total toluene 1727.3 g (3.5 times the total mass of esterified product and hexamethylenediamine).

[0038] S3 bi-stage directional amidation-reactive distillation coupled reaction First stage: The static mixing reactor was heated to 55℃, and a toluene solution containing 216.1 g of esterified compound (0.66 mol, molar ratio of hexamethylenediamine 1.1:1) was added dropwise. The residence time was 30 min. At the reaction endpoint, the residual hexamethylenediamine was 0.02%, and the monoamide selectivity was 99.3%. Second stage: The temperature of the bottom of the reactive distillation column is 100℃. The pressure is gradually reduced to -0.098 MPa at the top of the column within 30 min. 207.7 g of the remaining ester is added. The residence time in the column is 2 h. At the end of the reaction, the ester residue is 0.05% and the monoamide residue is 0.07%.

[0039] S4 coupling purification process Complex extraction: The solution was cooled to 60℃ and extracted twice with a buffer solution of pH 6.5. The final organic phase conductivity was 5 μS / cm. Nanofiltration for impurity removal: operating pressure 1.8 MPa, operating temperature 50℃; Dissolution and crystallization: Concentrate to a solid content of 55%, with a toluene to n-hexane mass ratio of 1:1.2, and cool to 5℃ at a rate of 1.5℃ / min, then crystallize for 3 h; Vacuum drying: dried at 95℃ and -0.098 MPa for 5 h to obtain 420.0 g of product, with a molar yield of 97.6%.

[0040] S5 product testing: HPLC purity 99.93%, ash content 10 ppm, Hunter whiteness L value 99.2, b value 0.15, melt color APHA7. Example 4

[0041] This embodiment sets up a control experiment to compare Examples 1-3 with comparative cases that include prior art, thereby verifying the technical effect of this application.

[0042] 4.1 Comparative examples include Comparative Examples 1-5. Comparative Example 1 uses a conventional sodium methoxide catalytic process; Comparative Example 2 uses a conventional TBD and tetrabutylphosphine bromide catalytic process; Comparative Example 3 uses only the main catalyst of this application, organic guanidine, without a co-catalyst; Comparative Example 4 uses only the co-catalyst dihydroxyethyldimethylphosphonium bromide, without a main catalyst; Comparative Example 5 uses conventional tetramethylguanidine (TMG) as the main catalyst, combined with the co-catalyst dihydroxyethyldimethylphosphonium bromide. The specific processes are shown below.

[0043] Comparative Example 1 S1 raw material preparation: 394.5 g (1.2 mol) of esterified product, 69.7 g (0.6 mol) of hexamethylenediamine, 3.95 g of sodium methoxide catalyst (1.0% of the esterified product mass), and 1392.6 g of toluene.

[0044] S2 reaction process: Under nitrogen protection, all raw materials are added to the reactor at once, heated to 110℃, and reacted at atmospheric pressure for 2 hours. Then the pressure is reduced to -0.09 MPa and the reaction is maintained at this temperature for 6 hours. Methanol is distilled off throughout the process. The ester residue at the reaction endpoint is 0.32%, and the monoamide residue is 0.58%.

[0045] S3 post-treatment: neutralize to pH-7 with glacial acetic acid, wash 5 times with deionized water, decolorize with 1.5% activated carbon at 80℃ for 2 h, filter, recrystallize twice with toluene, and vacuum dry to obtain 372.1 g of the finished product with a molar yield of 86.5%.

[0046] Comparative Example 2 S1 Raw material preparation: Same as S2 in Example 1, except that the main catalyst is replaced with conventional TBD 0.80 g and conventional tetrabutylphosphine bromide 0.40 g.

[0047] S2 reaction process: A distributed temperature-controlled gradient decompression intermittent process was adopted. The ester was added dropwise at 50℃ for 1.5 h, kept at 50℃ for 1.5 h, heated to 95℃, and then the pressure was reduced to -0.09 MPa for 4 h. At the reaction point, the residual ester was 0.21% and the residual monoamide was 0.35%.

[0048] S3 post-treatment: acid washing, water washing, activated carbon decolorization, and toluene-ethanol recrystallization to obtain 390.9 g of finished product with a molar yield of 90.8%.

[0049] Comparative Example 3 S1 Raw material preparation: Same as S2 in Example 1, except that 0.80 g of the main catalyst 7-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]-1,5,7-triazabicyclo[4.4.0]dec-5-ene is added, and no co-catalyst is added.

[0050] S2 reaction process: Same as the S3 two-stage continuous process in Example 1. At the end of the second stage reaction, the residual ester was 0.85% and the residual monoamide was 0.62%. After extending the reaction time to 6 h, the residual ester was 0.22% and the residual monoamide was 0.31%.

[0051] Post-processing S3: Same as S4 in Example 1, yielding 394.3 g of finished product with a molar yield of 91.6%.

[0052] Comparative Example 4 S1 Raw material preparation: Same as S2 in Example 1, except that 0.40 g of co-catalyst dihydroxyethyl dimethylphosphonium bromide is added, and no main catalyst is added.

[0053] S2 reaction process: Same as the S3 two-stage continuous process in Example 2. After 6 hours of reaction, the conversion rate of esterified product was only 12.3%, with no obvious target product generated, and the reaction could not proceed.

[0054] Comparative Example 5 S1 Raw material preparation: Same as S2 in the example, except that the main catalyst is replaced with conventional TMG 0.80 g and the co-catalyst is bis(hydroxyethyl)dimethylphosphonium bromide 0.40 g.

[0055] S2 reaction process: Same as the S3 two-stage continuous process in Example 1, with the key reaction residues being 0.42% esterified and 0.55% monoamide.

[0056] Post-processing S3: Same as S4 in Example 1, yielding 385.7 g of finished product with a molar yield of 89.6%.

[0057] 4.2 The samples obtained in Comparative Examples 1-5 were tested and compared with the test results of the products in Examples 1-3. The results are shown in the table below.

[0058] Table 1 compares the core performance indicators of finished products from different processes. Among them, Comparative Example 4 only added a co-catalyst. Without a co-catalyst, the aminolysis reaction could not proceed normally, no qualified finished product was generated, and there was no corresponding performance test data.

[0059] Table 2 Comparison of Production Efficiency and Economic Indicators of Different Process Schemes Wherein: the total reaction time is the total effective reaction time of monoamidation and deep diamidation, excluding post-treatment time; the relative emissions of wastewater, waste residue and waste solvent are calculated based on the traditional sodium methoxide process (Comparative Example 1); Comparative Example 4 has no effective reaction process and no corresponding production and economic data.

[0060] Figure 1 The figure in the middle is a comparative curve of the kinetics of the aminolysis reaction in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 5. Figure 2 The above are high-performance liquid chromatography (HPLC) chromatograms comparing the products of Example 1, Comparative Example 1, and Comparative Example 2.

[0061] In summary, the hindered phenol-functionalized bicyclic guanidine-dihydroxy functionalized quaternary phosphonium salt bifunctional synergistic catalytic system and the matching two-stage directional amidation-reactive distillation coupled continuous process employed in Examples 1-3 of this invention achieve a significant leap in both product quality and production efficiency compared to the traditional mainstream sodium methoxide process (Comparative Example 1), the conventional organic guanidine and quaternary phosphonium salt simple compounding process (Comparative Example 2), the single-component functionalized main catalyst process (Comparative Example 3), and the conventional organic guanidine and functionalized co-catalyst compounding process (Comparative Example 5). Furthermore, the reaction in Comparative Example 4 was completely impossible without the main catalyst, demonstrating the indispensable synergistic effect of the catalytic system of this invention. Regarding the core performance of the product, the antioxidant 1098 prepared by the process of this invention consistently achieves an HPLC purity of over 99.90%, with an ash content as low as 10%. The Hunter whiteness L value is ≥99.0, the yellowness b value is ≤0.20, and the melting color is as low as 7-10. All indicators are far superior to those of the comparative processes, completely solving the problems of excessive ash content, poor whiteness, and insufficient purity of traditional processes. It can fully meet the stringent application requirements of high-end electronics, optical fiber and cable, medical polymers and other fields. In terms of production efficiency and comprehensive benefits, the total reaction time of the process of this invention is as short as 2.5 h, which is more than 70% shorter than the traditional process. The product molar yield is stable at more than 97.1%, which is more than 10% higher than the traditional process. The solvent recovery rate is ≥97%, and the relative emissions of waste gas, wastewater, and solid waste can be reduced by up to 72%. At the same time, the total amount of catalyst used is kept at an extremely low level. It has multiple advantages of high efficiency, low cost and environmental protection. The comparative processes cannot simultaneously achieve high reaction selectivity, high product yield, low energy consumption and low emissions of waste gas, wastewater, and solid waste. This fully proves the excellent technical effect of the technical solution of this invention.

Claims

1. A production process for a low-ash, high-quality antioxidant 1098, characterized in that, Includes the following steps: S1 raw material preparation: Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and hexamethylenediamine were used as reaction raw materials, with a molar ratio of ester to hexamethylenediamine of (2.08-2.15):

1. A metal-free composite catalyst system composed of organic guanidine compounds and quaternary phosphonium salt phase transfer catalysts was adopted. S2 continuous reaction: Under nitrogen protection, a two-stage directional continuous reaction is carried out: (1) First stage low-temperature directional monoamidation: Hexamethylenediamine, composite catalytic system and part of the reaction solvent are fed into a static mixing reactor, heated to 40-55℃, and the reaction solvent solution of methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is continuously added dropwise. The feed molar ratio of methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to hexamethylenediamine is controlled to be (1.05-1.1):

1. The material residence time is 30-60 min to complete the directional monoamidation reaction and obtain the monoamide intermediate reaction solution. (3) Second stage deep diamidation-reactive distillation: The monoamide intermediate reaction liquid is continuously fed into the reactive distillation column, the column bottom temperature is raised to 80-100℃, and the remaining ester methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is added to the column bottom at the same time; the reactive distillation column adopts gradient pressure reduction operation, and the vacuum degree at the top of the column is gradually reduced from atmospheric pressure to -0.09~-0.098 MPa within 30-60 min, and the by-product methanol is distilled off continuously throughout the process. The total residence time of the material in the column is 2-4 h, and the deep diamidation reaction is completed to obtain the crude reaction liquid; S3 purification and post-processing: The crude reaction liquid is subjected to complexation extraction to remove the catalyst, nanofiltration for deep impurity removal, dissolution and directional crystallization, and vacuum drying steps in sequence to obtain the low-ash, high-quality antioxidant 1098 product.

2. The production process according to claim 1, characterized in that, The composite catalyst system uses hindered phenol-functionalized bicyclic guanidine as the main catalyst and dihydroxy-functionalized quaternary phosphonium salt as the co-catalyst to form a bifunctional synergistic catalytic system. The main catalyst is 7-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and the co-catalyst is dihydroxyethyldimethylphosphonium bromide.

3. The production process according to claim 2, characterized in that, The main catalyst is prepared by the following steps: (1) Preparation of acylation intermediate: Using 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid as raw material, anhydrous dichloromethane was added as solvent. Under nitrogen protection, excess thionyl chloride or oxaloyl chloride was added dropwise at low temperature. 1-2 drops of N,N-dimethylformamide were added as catalyst. The reaction was stirred at room temperature for 4-6 h. After the reaction was completed, excess thionyl chloride or oxaloyl chloride and solvent dichloromethane were removed by vacuum distillation to obtain the pale yellow acylation intermediate 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride, which can be used directly in the next step of the reaction without the need for catalysis. (2) Amide condensation: 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and anhydrous dichloromethane were added to a dry three-necked flask and stirred until dissolved. Triethylamine, an acid-binding agent, was added in a molar amount of 1.1-1.2 times that of TBD. Under chlorine protection and in an ice-water bath at 0°C, a dichloromethane solution of the above acyl chloride intermediate was slowly added dropwise. The molar ratio of the acyl chloride intermediate to TBD was 1:1.

05. After the addition was completed, the temperature was raised to room temperature and the reaction was stirred for 8-12 h. The reaction endpoint was monitored by thin-layer chromatography (TLC). (3) Post-treatment and purification: The reaction solution was washed successively with deionized water, saturated sodium bicarbonate solution and saturated brine. The organic phase was dried with anhydrous sodium sulfate. After filtration, the crude product was concentrated under reduced pressure. The crude product was recrystallized 2-3 times with a mixed solvent of ethyl acetate and n-hexane, or purified by column chromatography. After vacuum drying, a high-purity white target product was obtained.

4. The production process according to claim 2, characterized in that, The amount of the main catalyst is 0.15%-0.4% of the total mass of the esterified methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and the amount of the co-catalyst is 0.08%-0.25% of the total mass of the esterified product.

5. The production process according to claim 1, characterized in that: In step S2, the reaction solvent is toluene, and its total amount is 2.5-3.5 times the total mass of the esterified methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and hexamethylenediamine.

6. The production process according to claim 1, characterized in that: In step S2, the endpoint of the first low-temperature directional monoamidation reaction is detected by high performance liquid chromatography, and the residual hexamethylenediamine in the system is controlled to be ≤0.05%, and the selectivity of the monoamid intermediate is ≥99%. The endpoint of the second stage of deep diamidation reaction was detected by high performance liquid chromatography, and the residual esters in the system were controlled to be ≤0.08% and the residual monoamide intermediates to be ≤0.1%.

7. The production process according to claim 1, characterized in that, In step S3, the complex extraction catalyst removal is specifically performed as follows: the crude reaction liquid is cooled to 50-60℃, a citrate-sodium dihydrogen phosphate buffer solution with pH 5.5-6.5 is added, the mixture is kept warm and stirred for 15-30 min, and after standing and separating into layers, the aqueous phase is removed. The organic phase is then extracted once again with the same batch of buffer solution until the conductivity of the organic phase is ≤8 μS / cm.

8. The production process according to claim 1, characterized in that, In step S3, the nanofiltration depth removal specifically involves: the organic phase after complex extraction is fed into a polyamide nanofiltration membrane system with a molecular weight cutoff of 500 Da, the operating pressure is 1.2-1.8 MPa, the operating temperature is 40-50℃, the permeate is a clear toluene solution, and the effluent is a large molecular weight colored impurity and trace by-products.

9. The production process according to claim 1, characterized in that, In step S3, the directional crystallization by dissolution is specifically as follows: the nanofiltration permeate is concentrated under reduced pressure to a solid content of 45%-55%, and n-hexane is continuously added to the concentrate as a solvent, with the mass ratio of toluene to n-hexane controlled at 1:(1.5-2). After stirring evenly, the temperature is gradually reduced to 5-15℃ at a rate of 0.8-1.5 ℃ / min, and the mixture is kept at this temperature for 3-5 h to crystallize. The filter cake is then obtained by filtration and washed twice with cold n-hexane at 0-5℃.

10. The application of a bifunctional synergistic metal-free catalyst system in the synthesis of antioxidant 1098, characterized in that, The catalytic system uses hindered phenol-functionalized bicyclic guanidine 7-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]-1,5,7-triazabicyclo[4.4.0]dec-5-ene as the main catalyst and dihydroxyfunctionalized quaternary phosphonium salt dihydroxyethyldimethylphosphonium bromide as the co-catalyst. The amount of the main catalyst is 0.15%-0.4% of the mass of the esterified raw material, and the amount of the co-catalyst is 0.08%-0.25% of the total mass of the esterified product.

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