Preparation method of low-chroma 2.4. 6-tri (dimethylaminomethyl) phenol and obtained product

Abstract

The invention discloses a preparation method of low-chromaticity 2.4. 6-tri (dimethylaminomethyl) phenol and an obtained product, and the preparation method of low-chromaticity 2.4. 6-tri (dimethylaminomethyl) phenol comprises the following steps: mixing liquid dimethylamine, liquid phenol and a formaldehyde aqueous solution, carrying out a liquid phase reaction, after the reaction is completed, carrying out heating aging, then carrying out standing layering, and discharging a lower-layer aqueous phase, so as to obtain the low-chromaticity 2.4. 6-tri (dimethylaminomethyl) phenol. And adding an acidic auxiliary agent into the retained organic phase, and heating again to remove moisture in the product to obtain 2.4. 6-tri (dimethylaminomethyl) phenol. The 2.4. 6-tri (dimethylaminomethyl) phenol prepared by the preparation method is low in product chroma, low in unit consumption, high in yield, stable in structure, simple, convenient and easy to operate, and suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, and more specifically, to a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol and the resulting product. Background Technology

[0002] 2,4,6-Tris(dimethylaminomethyl)phenol is a core additive in the epoxy resin and polyurethane fields, and its technological evolution has always revolved around "high efficiency, greenness, and functionalization." The traditional Mannich reaction has significantly improved product quality and environmental friendliness through raw material substitution, catalyst improvement, and purification technology upgrades. In the future, with the growth in demand from new energy, high-end manufacturing, and other fields, 2,4,6-tris(dimethylaminomethyl)phenol will develop towards high purity, low color, and customization. The synthesis of 2,4,6-tris(dimethylaminomethyl)phenol still adopts the classic Mannich process, and its reaction equation is shown in Formula I:

[0003] Currently, there are three main process routes for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol. The first involves adding a boron-containing reducing agent (such as sodium borohydride or potassium borocyanide) after production to remove quinone-based colored impurities generated during synthesis through a reduction reaction. This method increases the production process, requiring heating and stirring after adding the reducing agent, thus increasing batch production time and energy consumption. The second method uses paraformaldehyde depolymerization to replace formaldehyde aqueous solution in the production of 2,4,6-tris(dimethylaminomethyl)phenol, reducing the water content and minimizing side reactions. The main challenge in this process is the introduction of paraformaldehyde depolymerization. During depolymerization, the temperature needs to be increased and the reaction time extended. Additionally, incompletely depolymerized monomers may participate in the reaction, generating other byproducts and affecting product purity. Third, gaseous dimethylamine directly participates in the reaction, avoiding the moisture and impurities introduced by formaldehyde aqueous solution in the traditional process, reducing side reactions and color generation. This scheme has been applied to the production process of 2,4,6-tris(dimethylaminomethyl)phenol, which has improved the process using dimethylamine aqueous solution to a certain extent and reduced the impact of moisture on the color of 2,4,6-tris(dimethylaminomethyl)phenol. However, it has not solved the key problem of producing low-color 2,4,6-tris(dimethylaminomethyl)phenol. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol and the resulting product.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] This invention provides a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol, comprising: mixing liquid dimethylamine, liquid phenol and formaldehyde aqueous solution, and reacting them in a liquid phase to obtain 2,4,6-tris(dimethylaminomethyl)phenol.

[0007] The present invention also provides a 2,4,6-tris(dimethylaminomethyl)phenol prepared according to the preparation method described above, wherein the 2,4,6-tris(dimethylaminomethyl)phenol product contains ≥90% 2,6-tris(dimethylaminomethyl)phenol, has a moisture content ≤0.5wt%, an amine value of 610-635mgKOH / g, and a color APHA ≤50.

[0008] The present invention has the following beneficial effects: This invention provides a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol and the resulting product. The method involves mixing liquid dimethylamine, liquid phenol, and an aqueous formaldehyde solution, followed by a liquid-phase reaction to obtain 2,4,6-tris(dimethylaminomethyl)phenol. The 2,4,6-tris(dimethylaminomethyl)phenol prepared by this method has fewer side reactions. Furthermore, an acidic auxiliary agent is added before dehydration, and ions affecting color are removed during the dehydration process, resulting in the obtained 2,4,6-tris(dimethylaminomethyl)phenol. The prepared product has the advantages of low color and high yield, stable product structure, low unit consumption, and is simple and easy to operate, making it suitable for industrial applications. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0010] The following is a detailed description of a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol and the resulting product provided by the present invention.

[0011] In a first aspect, the present invention provides a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol, comprising: mixing liquid dimethylamine, liquid phenol and an aqueous formaldehyde solution, and reacting them in a liquid phase to obtain 2,4,6-tris(dimethylaminomethyl)phenol.

[0012] 2,4,6-Tris(dimethylaminomethyl)phenol (DMP-30) is a commonly used tertiary amine epoxy resin curing accelerator. DMP-30 is readily soluble in water, and the tertiary amine group (-N(CH3)2) in its molecule is weakly basic, easily reacting slightly with moisture and carbon dioxide in the air (generating trace amounts of amine salts or bicarbonates), thus affecting the performance of epoxy resins and hindering their use as curing accelerators. Therefore, the preparation method of 2,4,6-tris(dimethylaminomethyl)phenol provided by this invention uses a mixture of liquid dimethylamine, liquid phenol, and formaldehyde aqueous solution for a liquid-phase reaction. On the one hand, using pure liquid materials of liquid dimethylamine and liquid phenol as raw materials can improve the batch feed coefficient, minimize the "side effects" caused by moisture in the raw materials, and ensure more uniform mass transfer in the liquid-phase reaction, thereby increasing the yield of 2,4,6-tris(dimethylaminomethyl)phenol. On the other hand, the raw materials used in this invention are all liquid, and the materials can be added through pipelines, avoiding contact between operators and materials and improving safety.

[0013] In some alternative embodiments, the formaldehyde in the liquid dimethylamine or formaldehyde aqueous solution is in a feed molar ratio of (2.8:1) to (3.15:1) of the liquid phenol.

[0014] In some alternative embodiments, the reaction pressure is atmospheric pressure or slightly positive pressure, and the slightly positive pressure is maintained at 0.01-0.05 MPa, and the reaction temperature is 58-70°C.

[0015] The method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol provided by this invention involves a liquid-phase reaction at atmospheric pressure or slightly positive pressure. Maintaining slightly positive pressure ensures a nitrogen environment during the reaction, preventing oxygen from intervening and generating byproducts. Nitrogen can be introduced when the reactor pressure is low. Simultaneously, the reaction temperature is controlled at 58-70℃. Formaldehyde readily undergoes self-polymerization at high temperatures, generating methanol, formic acid, or other long-chain organic compounds. Excess formaldehyde easily leads to the formation of phenolic resin in the system. The formation of these byproducts all deepen the color of the product. Therefore, controlling the appropriate ratio of reactants, reaction temperature, and pressure is essential.

[0016] In some optional embodiments, the process includes the following steps: adding liquid dimethylamine and liquid phenol sequentially to a reactor, mixing them thoroughly, heating the mixture to the reaction temperature, and then adding an aqueous formaldehyde solution to carry out a liquid-phase reaction.

[0017] In some optional embodiments, the following steps are included: adding the liquid dimethylamine into the reactor, maintaining the reactor temperature at no less than 42°C, starting stirring after the liquid dimethylamine feeding is completed, then adding liquid phenol, mixing evenly, raising the temperature to the reaction temperature, and then adding the formaldehyde aqueous solution to carry out the liquid phase reaction; Preferably, the stirring frequency of the reactor is controlled at 20-50 Hz, and the stirring current is 20-40 A; Preferably, the formaldehyde aqueous solution is added to the reactor by dripping, wherein the mass concentration of the formaldehyde aqueous solution is 37%, and the feeding rate is 1500-3500 kg / h; Preferably, the formaldehyde aqueous solution is added dropwise via a bottom-inserted tube; Preferably, the feed flow rate of the liquid dimethylamine is controlled at 5000-8000 kg / h, and the feeding is completed within 10-30 minutes; the feed flow rate of the liquid phenol is controlled at 4000-6000 kg / h; and the feed flow rate of the formaldehyde aqueous solution is controlled at 1500-3500 kg / h. The feed amounts of the liquid dimethylamine and formaldehyde aqueous solution are based on the amount of liquid phenol used and can be adjusted within 50-100% load.

[0018] This invention provides a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol. The feeding process involves adding liquid dimethylamine, liquid phenol, and an aqueous formaldehyde solution as follows: Liquid dimethylamine is added to a reactor, maintaining the reactor temperature at no less than 42°C. This temperature ensures the added liquid phenol remains liquid and does not solidify. After the liquid dimethylamine is added, stirring is started, followed by the addition of liquid phenol, and stirring continues until the two are uniformly mixed. During mixing, phenol is easily oxidized, causing the solution to change color. Furthermore, the added liquid phenol reacts with the liquid dimethylamine in an exothermic reaction. Increased temperature can also easily lead to side reactions of phenol. Therefore, under controllable temperature conditions, the faster the liquid phenol is fed, the better. After the liquid dimethylamine and liquid phenol are uniformly mixed, the reactor temperature is raised to the reaction temperature. An aqueous formaldehyde solution is then added dropwise, preferably through a submersible tube, to ensure rapid reaction of the formaldehyde upon entering the system and prevent prolonged residence time that could generate byproducts affecting the product's color.

[0019] In some alternative embodiments, after the feeding is completed, the reaction is continued at a constant temperature for 0.5-1 hour, and then the reactor temperature is raised to 80-100°C and kept at that temperature for aging for 0.5-1 hour.

[0020] In some optional embodiments, the process further includes: after the aging process is completed, stopping the stirring, maintaining the aging temperature and allowing the phase to separate, then separating the lower aqueous phase and retaining the organic phase in the reactor.

[0021] In some optional embodiments, the method further includes adding an acidic additive to the organic phase within the reactor to remove colorimetric ions therein; Preferably, the acidic auxiliary agent includes one or more of sulfuric acid, carbonic acid, phosphoric acid, and nitric acid; Preferably, the acidic additive is diluted 3-10 times with water before application, and the water used for dilution is selected from distilled water or purified water; Preferably, the amount of acid additive added is 0.01-1‰ of the amount of phenol added.

[0022] The method for preparing 2,4,6-tris(dimethylaminomethyl)phenol provided by this invention employs appropriate steps and conditions to control the occurrence of side reactions in the non-reactive stage, thereby reducing the generation of the following byproducts: colored quinones / polyquinones generated by high-temperature oxidation of the phenolic hydroxyl group; dark polymers generated by high-temperature degradation and side reactions of the tertiary amino group (-N(CH3)2); dark phenolic resin impurities generated by high-temperature self-polymerization / re-condensation of excess formaldehyde; and carbonaceous dark impurities generated by localized carbonization at extreme high temperatures, thus producing a low-color product. It is worth noting that since most of the conveying pipelines and feeders used in industrial production are made of metal, colored iron ions generated by the dissolution of metallic iron will inevitably be introduced into the solution. Adding acidic substances can complex with these iron ions, thereby eliminating the color development problem caused by the introduction of metal ions, resulting in a higher quality 2,4,6-tris(dimethylaminomethyl)phenol that meets the high-end market demand.

[0023] In some optional embodiments, the process further includes: after adding the acidic additive, restarting the stirring of the reactor and continuing to heat up for dehydration treatment; Preferably, the stirring frequency of the reactor is controlled at 20-50 Hz, and the stirring current is 20-40 A; Preferably, the initial stage of dehydration is performed under normal pressure, while the later stage is performed under reduced pressure vacuum dehydration. Preferably, the dehydration temperature is controlled at 100-130℃, and the dehydration time is controlled at 30-90 minutes; Preferably, samples should be taken for testing during the dehydration process, and the temperature should be rapidly reduced to 30-60℃ after the moisture content is deemed acceptable; Preferably, after dehydration is complete, the negative pressure in the system needs to be broken to collect the generated 2,4,6-tris(dimethylaminomethyl)phenol.

[0024] It is worth noting that in the preparation method of 2,4,6-tris(dimethylaminomethyl)phenol provided by this invention, after the liquid-phase reaction is completed, the product undergoes aging at elevated temperature and separation by settling. An acidic substance is then added to the organic phase for decolorization, followed by continued heating for direct dehydration. Since 2,4,6-tris(dimethylaminomethyl)phenol is prone to discoloration at high temperatures, dehydration temperatures above 130°C will generate byproducts resulting in a darker product color. Conversely, low temperatures will reduce reactivity, prolong reaction time, and increase energy consumption. Therefore, controlling the dehydration temperature between 100-130°C is optimal. Compared to transferring the product to a distillation column for distillation after the reaction, the dehydration and product collection steps in this invention are simpler, minimizing the time delays and product contamination / oxidation caused by product transfer. The time from feeding to product collection is approximately 7-8 hours, while the time for product transfer and vacuum distillation is approximately 30-32 hours, significantly shortening processing time and improving efficiency and quality.

[0025] In some alternative embodiments, the process includes the following steps: adding liquid dimethylamine to a reactor, maintaining the reactor temperature at no less than 42°C, starting the reactor with stirring, adding phenol to the reactor, raising the temperature to the reaction temperature, adding formaldehyde dropwise through a submersible line, aging the reactor after the reaction is complete, stopping the stirring to separate the phases, transferring the lower aqueous phase, adding an auxiliary agent to the organic phase remaining in the reactor to remove the coloring substances, raising the temperature to dehydrate, and preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol.

[0026] As can be seen from the above, the preparation method of low-color 2,4,6-tris(dimethylaminomethyl)phenol provided by the present invention includes: providing liquid dimethylamine, liquid phenol, and an aqueous solution of formaldehyde; adding the above raw materials into a reactor; and proceeding through the following three stages: a reaction stage, a decolorization stage, and a dehydration stage. Controlling the feeding sequence, feeding amount, and reaction temperature in the reaction stage can reduce the generation of byproducts affecting the product color. After the reaction stage is completed, after undergoing heating aging and phase separation treatment, the product enters the decolorization stage, where an acidic substance is added to the organic phase retained after phase separation treatment to remove trace metal ions brought by the dissolution of the metal pipeline. Then, the product is stirred and heated again to enter the dehydration stage. Initially, dehydration is performed at atmospheric pressure, which removes most of the water from the 2,4,6-tris(dimethylaminomethyl)phenol. Then, vacuum dehydration is performed under vacuum conditions to further remove the remaining small amount of water. After the dehydration stage, the negative pressure in the reactor is broken, and the product is collected. The entire reaction can be carried out in the reactor where the initial feed is added. There is no need to add a reducing agent or transfer the product to a distillation tower for distillation and recovery after the reaction is completed. This is because the raw materials used in this invention include liquid dimethylamine, liquid phenol, and formaldehyde aqueous solution, which contain little water. During the entire reaction process, by controlling the synthesis conditions, the generated 2,4,6-tris(dimethylaminomethyl)phenol has high purity and low color. It is only necessary to simply remove the color-developing ions in the product and remove the small amount of water contained therein to obtain 2,4,6-tris(dimethylaminomethyl)phenol with good performance in all aspects.

[0027] Secondly, the present invention also provides a 2,4,6-tris(dimethylaminomethyl)phenol prepared according to the preparation method described above, wherein the 2,4,6-tris(dimethylaminomethyl)phenol product contains ≥90% 2,6-tris(dimethylaminomethyl)phenol, has a moisture content ≤0.5wt%, an amine value of 610-635mgKOH / g, and a color APHA ≤50.

[0028] The following detailed description, in conjunction with embodiments, illustrates a method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol and the resulting product provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0029] In the following examples and comparative examples, the feeding process is as follows: liquid dimethylamine is added to the reactor, the reactor temperature is maintained at no less than 42°C, stirring is started after the liquid dimethylamine feeding is completed, then liquid phenol is added, mixed evenly, the temperature is raised to the reaction temperature, and then the formaldehyde aqueous solution is added to carry out the reaction. In industrial production, controlling the temperature during the reaction process to not exceed the required reaction temperature can achieve the relevant reaction without the occurrence of a large number of side reactions.

[0030] Example 1 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. During the later stages of dehydration, the reactor is evacuated under reduced pressure for further dehydration. After dehydration, cool the reactor and collect the product through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥90%, amine value 615mgKOH / g, and color APHA ≤50.

[0031] Example 2 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% purity). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 130-135℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤ 0.15 wt%, main product content ≥ 90%, amine value 617 mg KOH / g, and color APHA ≤ 200.

[0032] Example 3 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3.2:1. After the reactor is purged with nitrogen and the purging is successful, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 122 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 60-65℃. After the reaction is complete, the aging temperature is 90-95℃, and the aging time is 0.5 h. After the aging process is complete, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, leaving the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 130-135℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥90%, amine value 622mgKOH / g, and color APHA ≤150.

[0033] Example 4 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 2.7:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 145 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥70%, amine value 605mgKOH / g, and color APHA ≤50.

[0034] Example 5 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 80-85℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥85%, amine value 612mgKOH / g, and color APHA ≤150.

[0035] Example 6 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% purity). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 50-55℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥70%, amine value 609mgKOH / g, and color APHA ≤100.

[0036] Example 7 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 70-75℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥80%, amine value 610mgKOH / g, and color APHA ≤200.

[0037] Example 8 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 150 kg per hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥85%, amine value 613mgKOH / g, and color APHA ≤100.

[0038] Example 9 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% purity). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 400 kg / hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥85%, amine value 612mgKOH / g, and color APHA ≤100.

[0039] Example 10 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After the reactor is purged with nitrogen and the purging is successful, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 2 hours. After the aging process, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, leaving the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥90%, amine value 615mgKOH / g, and color APHA ≤200.

[0040] Example 11 A method for preparing low-color 2,4,6-tris(dimethylaminomethyl)phenol includes the following steps: Prepare raw materials: dimethylamine (liquid), phenol, and formaldehyde aqueous solution (37% concentration). Control the molar ratio of dimethylamine, formaldehyde, and phenol to be 3:1. After purging the reactor with nitrogen, start the feed pump. The feed rates are: dimethylamine 187 kg, 37% formaldehyde aqueous solution 338 kg, phenol 130 kg, and formaldehyde aqueous solution 200 kg / hour. Control the reaction temperature at 60-65℃. After the reaction, the aging temperature is 90-95℃, and the aging time is 0.5 hours. After aging, stop stirring and maintain the aging temperature to allow for static stratification. After phase separation, separate the lower aqueous phase, retaining the organic phase in the reactor. Add 10 ml of acidic additive (diluted 5 times with water) to the reactor, restart stirring at 50 Hz, and continue heating to 105-110℃ for dehydration. Cool the product and collect it through a filter. The finished product specifications are as follows: moisture content ≤0.3wt%, main product content ≥90%, amine value 615mgKOH / g, color APHA ≤50, long material transfer time, and many impurities in the filter.

[0041] Comparative Example 1 Similar to the steps in Example 1, the only difference is that the dehydration temperature during the preparation process is 135°C, and the results are: finished product moisture ≤0.15wt%, main product content ≥90%, amine value 617mgKOH / g, and color APHA ≤200.

[0042] Comparative Example 2 Similar to the steps in Example 1, the only difference is that the feed molar ratio in the preparation process is 3.2:1, and the results are: finished product moisture ≤0.3wt%, main product content ≥90%, amine value 622mgKOH / g, and color APHA ≤150.

[0043] Comparative Example 3 Similar to the steps in Example 1, the only difference is that the feed molar ratio in the preparation process is 2.7:1, and the results are: finished product moisture ≤0.3wt%, main product content ≥70%, amine value 605mgKOH / g, and color APHA ≤50.

[0044] Comparative Example 4 Similar to the steps in Example 1, the only difference is that the aging temperature during the preparation process is 80-85℃, and the results are: finished product moisture ≤0.3wt%, main product content ≥85%, amine value 612mgKOH / g, and color APHA ≤150.

[0045] Comparative Example 5 Similar to the steps in Example 1, the only difference is that the reaction temperature during the preparation process is 50-55℃, and the results are: finished product moisture ≤0.3wt%, main product content ≥70%, amine value 609mgKOH / g, and color APHA ≤100.

[0046] Comparative Example 6 Similar to the steps in Example 1, the only difference is that the reaction temperature during the preparation process is 70-75℃, and the results are: finished product moisture ≤0.3wt%, main product content ≥80%, amine value 610mgKOH / g, and color APHA ≤200.

[0047] Comparative Example 7 Similar to the steps in Example 1, the only difference is that the 37% formaldehyde aqueous solution was added at a rate of 150 kg / h during the preparation process. The results were: finished product moisture ≤ 0.3 wt%, main product content ≥ 85%, amine value 613 mg KOH / g, and color APHA ≤ 100.

[0048] Comparative Example 8 Similar to the steps in Example 1, the only difference is that the 37% formaldehyde aqueous solution was added at a rate of 400 kg / h during the preparation process. The results were: finished product moisture ≤ 0.3 wt%, main product content ≥ 85%, amine value 612 mg KOH / g, and color APHA ≤ 100.

[0049] Comparative Example 9 Similar to the steps in Example 1, the only difference is that the aging time during the preparation process is 2 hours, and the results are: finished product moisture ≤ 0.3 wt%, main product content ≥ 90%, amine value 615 mg KOH / g, and color APHA ≤ 200.

[0050] Comparative Example 10 Similar to the steps in Example 1, the only difference is that the amount of acidic additive added during the preparation process is 30ml. The results are: finished product moisture ≤0.3wt%, main product content ≥90%, amine value 615mgKOH / g, color APHA≤50, long material transfer time, and many impurities in the filter.

[0051] The experimental results above show that: in the embodiments of this invention, 2,4,6-tris(dimethylaminomethyl)phenol was prepared by liquid-phase reaction of dimethylamine, phenol, and formaldehyde. The optimal reaction temperature was 60-65℃, the optimal feed ratio was 3.0:1, the optimal dropping rate of 37% formaldehyde aqueous solution was 200 kg / h, the optimal aging temperature was 90-95℃, the optimal aging time was 0.5 h, the optimal amount of additive was 10 ml, and the optimal dehydration temperature was 105-110℃. In Comparative Example 1, the dehydration temperature was higher than the target value, resulting in the formation of byproducts at high temperatures and high color. In Comparative Example 2, the molar ratio of dimethylamine to formaldehyde aqueous solution was higher than the target value, and the excess formaldehyde polymerized at high temperatures to form phenolic resin and other impurities, resulting in a dark product color and high amine value. In Comparative Example 3, the molar ratio of dimethylamine to formaldehyde aqueous solution was lower than the target value. Due to insufficient addition, not all trisubstituted products were formed, resulting in lower main product content and amine value than normal. In Comparative Example 4, the aging temperature was lower than the target value. At this temperature, the reactivity was low, and some formaldehyde did not fully participate in the reaction, generating other impurities, resulting in high product color and low amine value. In Comparative Example 5, the reaction temperature was lower than the target value, and the raw materials did not participate in the reaction at the optimal reaction temperature, resulting in incomplete reaction. Furthermore, other impurities were generated during dehydration, leading to low main product content, low amine value, and high color. In Comparative Example 6, the reaction temperature was higher than the target value. Due to the high temperature, side reactions increased, resulting in low main product content and high color. In Comparative Example 7, the formaldehyde dropping rate was lower than the target value, and the dropping time was long, leading to a long residence time of the material in the system and high product color. In Comparative Example 8, the formaldehyde dropping rate was higher than the target value, resulting in excess formaldehyde entering the system. Some of the unreacted formaldehyde reacted with phenol to form phenolic resin, reducing the main product content and increasing the product speed. In Comparative Example 9, the aging time was higher than the target value, and the product remained in the reaction system at high temperatures for a long time, generating byproduct quinones that affected the product color. In Comparative Example 10, the amount of acid additives added was higher than the target value. The product had more solid impurities during the material transfer process, the transfer time was longer, and the filter bags inside the filter needed to be replaced frequently, which increased the production cost.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for the preparation of low color 2.4.6-tris(dimethylaminomethyl)phenol, characterized in that, It comprises: mixing liquid dimethylamine, liquid phenol and aqueous formaldehyde solution, and preparing 2.4.6-tris(dimethylaminomethyl)phenol through liquid phase reaction.

2. The production method according to claim 1, characterized by, The feed molar ratio of the liquid dimethylamine or the formaldehyde in the aqueous formaldehyde solution to the liquid phenol is (2.8:1)-(3.15:1).

3. The preparation method according to claim 1, characterized in that, The reaction pressure is normal pressure or micro-positive pressure, and the micro-positive pressure is maintained at 0.01-0.05 Mpa, and the reaction temperature is 58-70 DEG C.

4. The production method according to any one of claims 1 to 3, characterized by, It comprises the following steps: The liquid dimethylamine and the liquid phenol are added into the reactor in sequence, and after being uniformly mixed, the temperature is raised to the reaction temperature, and then the aqueous formaldehyde solution is added to perform liquid phase reaction.

5. The production method according to claim 4, characterized by, It comprises the following steps: the liquid dimethylamine is added into the reactor, the temperature of the reactor is maintained at not less than 42 DEG C, after the liquid dimethylamine is added, the stirring is started, then the liquid phenol is added, after being uniformly mixed, the temperature is raised to the reaction temperature, and then the aqueous formaldehyde solution is added to perform liquid phase reaction; Preferably, the stirring frequency of the reactor is controlled to be 20-50 HZ, and the stirring current is 20-40 A; Preferably, the aqueous formaldehyde solution is added into the reactor in a dropwise manner, wherein the mass concentration of the aqueous formaldehyde solution is 37%, and the feeding speed is 1500-3500 kg / h; Preferably, the dropwise manner of the aqueous formaldehyde solution is bottom insertion liquid dropwise adding; Preferably, the feeding flow of the liquid dimethylamine is controlled to be 5000-8000 kg / h, the feeding is completed within 10-30 min, the feeding flow of the liquid phenol is controlled to be 4000-6000 kg / h, and the feeding flow of the aqueous formaldehyde solution is controlled to be 1500-3500 kg / h, and the feeding amount of the liquid dimethylamine and the aqueous formaldehyde solution can be adjusted within 50-100% load based on the amount of the liquid phenol.

6. The preparation method according to claim 5, characterized in that, After the feeding is completed, the reaction is continued for 0.5-1 h, and then the temperature of the reactor is raised to 80-100 DEG C to maintain aging for 0.5-1 h.

7. The production method according to claim 4, characterized by, It further comprises: After the aging is completed, the stirring is stopped, the aging temperature is maintained to stand and separate, then the lower water phase is separated out, and the organic phase is reserved in the reactor.

8. The production method according to claim 7, characterized by, It further comprises: An acidic auxiliary agent is added into the organic phase in the reactor to remove the chromogenic ions therein; Preferably, the acidic auxiliary agent comprises one or more of sulfuric acid, carbonic acid, phosphoric acid and nitric acid; Preferably, the acidic auxiliary agent is diluted 3-10 times with water before application, and the dilution water is selected from distilled water or pure water; Preferably, the addition amount of the acidic auxiliary agent is 0.01-1‰ of the addition amount of the phenol.

9. The production method according to claim 8, characterized by, It further comprises: After the acidic auxiliary agent is added, the stirring of the reactor is restarted, and the dehydration treatment is continued; Preferably, the stirring frequency of the reactor is controlled to be 20-50 HZ, and the stirring current is 20-40 A; Preferably, the early stage of dehydration is normal pressure dehydration, and the later stage of dehydration is vacuum dehydration under reduced pressure; Preferably, the dehydration temperature is controlled to be 100-130 DEG C, and the dehydration time is controlled to be 30-90 min; Preferably, during the dehydration process, the sample should be detected, and after the moisture is qualified, the temperature is rapidly reduced to 30-60 DEG C; Preferably, after the dehydration is completed, the system needs to be broken to negative pressure, and the generated 2.4.6-tris (dimethylaminomethyl) phenol is collected.

10. Low color 2.4.6-tris(dimethylaminomethyl)phenol produced according to the production process of any one of claims 1 to 9, characterized in that The 2.4.6-tris (dimethylaminomethyl) phenol content in the 2.4.6-tris (dimethylaminomethyl) phenol product is ≥90%, the moisture content is ≤0.5wt%, the amine value is 610-635mgKOH / g, and the color APHA is ≤50.

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